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- Fear of Developing Dementia
- This presentation is part of the faculty lecture series UNT Speaks Out on Alzheimer's disease and dementia. The presenter, Kyle Page, is a doctoral candidate in the Department of Psychology. In this presentation, he discusses his research into the fear of dementia. digital.library.unt.edu/ark:/67531/metadc152462/
- Femtosecond wave-packet dynamics in cesium dimers studied through controlled stimulated emission
- This article discusses femtosecond wave-packet dynamics in cesium dimers studied through controlled stimulated emission. Abstract: We study the dynamics of wave packets in cesium dimers using a femtosecond-controlled pump-probe technique. We implement configurations with one pulse (pump) or two pulses (pump to control) to produce vibrational wave packets on the electronic excited state. The transmission of an additional, variable-delay probe pulse is measured to monitor the time evolution of the wave packets. In the case of the pump-control-probe configuration, a superposition of two independent wave packets is observed. In order to elucidate the observed experimental data, we develop a theory based on the Liouville equation for the density matrix associated with the Franck-Condon factors. Both the numerical and analytical calculations are in good agreement with our experimental results. digital.library.unt.edu/ark:/67531/metadc103267/
- Fenología de Tayloria dubyi (Splachnaceae) en las turberas de la Reserva de Biosfera Cabo de Hornos
- This article discusses the phenology of Tayloria dubyi (Splachnaceae) in the peatlands of the Cape Horn Biosphere Reserve. Abstract: The sub-Antarctic Magellanic ecoregion harbors a high diversity of bryophytes, greater than the species richness of vascular plants. Despite this fact, phenological studies on bryophytes are lacking for this ecoregion and Chile. Based on the study of the sporophytic phase of Tayloria dubyi, an endemic moss from the sub-Antarctic Magellanic ecoregion, the authors propose a methodology for phonological studies on austral bryophytes. The authors defined five phenophases, easily distinguishable with a hand-lens, which were monthly recorded during 2007 and 2008 in populations of T. dubyi at the Omora Ethnobotanical Park and Mejillones Bay on Navarino Island (55°S) in the Cape Horn Biosphere Reserve. The sporophytic (or reproductive) phase of T. dubyi presented a clear seasonality. After growing in November, in three months (December - February) of the austral reproductive season the sporophytes mature and release their spores; by March they are already senescent T. dubyi belongs to the Splachnaceae family for which entomochory (dispersal of spores by insects, specifically Diptera) has been detected in the Northern Hemisphere. The period of spores release in T. dubyi coincides with the months of highest activity of Diptera which are potential dispersers of spores; hence, entomochory could also take place in sub-Antarctic Magellanic ecoregion. In sum, the authors' work: (i) defines a methodology for phenological studies in austral bryophytes, (ii) it records a marked seasonality ion the sporophyte phase of T. dubyi, and (iii) it proposes to evaluate in future research the occurrence of entomochory in splachnaceae species growing in the sub-Antarctic peatlands and forest ecosystems in the Southern Hemisphere. digital.library.unt.edu/ark:/67531/metadc97952/
- Field environmental philosophy and biocultural conservation at the Omora Ethnobotanical Park: Methodological approaches to broaden the ways of integrating the social component ("S") in Long-Term Socio-Ecological Research (LTSER) Sites
- This article discusses field environmental philosophy and biocultural conservation at the Omora Ethnobotanical Park. Abstract: In order to effectively address the problems derived from global environmental change, environmental scientists, citizens and decision-makers now recognize the need to integrate more fully the human or social component into ecological research. The authors propose that to achieve this integration, Long-Term Socio-Ecological Research (LTSER) networks offer an ideal platform, because such sites enable research at ecological, cultural, and political local scales, and at the same time allow addressing these issues at a global scale. However, this socio-ecological work still requires better articulation of programs developed at multiple geographic, ecological and political scales. In addition, until now the social component considered in LTSER programs has focused on economic factors, omitting ethical dimensions. A central reason for this omission is the lack of methodologies to systematically integrate ethics into LTSER programs. As a contribution to resolve this limitation, here the authors develop a methodological approach that the authors call "field environmental philosophy." It integrates ecological research and environmental ethics into biocultural education and conservation through an interrelated four-step cycle: i) interdisciplinary ecological and philosophical research, ii) composition of metaphors, and communication through simple narratives, iii) design of guided field experiences with an ecological and ethical orientation, and iv) implementation of in situ conservation areas. This cycle has been defined a posteriori, by analyzing successful experiences of biocultural research, education and conservation program at the Omora Ethnobotanical Park (OEP) in the Cape Horn Biosphere Reserve (CHBR). The Masters of Science in Subantarctic Conservation at the University of Magallanes (UMAG) adopted this cycle as a structured methodology to design theses and academic curricula for students who are creating innovative educational and ecotourism activities, such as "Ecotourism with a Hand Lens" and "Ethical Birding." To articulate the programs at multiple scales, the OEP functions at the local scale as a research center in the CHBR, at the national level as a cofounder and southernmost site of the Chilean LTSER network coordinated by the Institute of Ecology and Biodiversity (IEB), Chile, and at the coordinated by UMAG, IEB and the University of North Texas (UNT). This organization of nested units has permitted to synergistically articulate the work at local, national and international scales. Collaborative research has led to the discovery of biological and cultural diversity singularities in the remote Magellanic subantarctic ecoregion, enabled education and conservation work with multiple social actors and institutions, and has strengthened the incorporation of environmental philosophy into socio-ecological research. In this way, OEP's program is contributing to broaden the definition of the social ("S") component in LTSER, and to generate methodologies to integrate, at multiple scales, ecological and ethical dimensions into socio-ecological research, as well as biocultural education and conservation programs, which could be implemented and assessed at other LTER sites. digital.library.unt.edu/ark:/67531/metadc97961/
- Field environmental philosophy and biocultural conservation at the Omora Ethnobotanical Park: Methodological approaches to broaden the ways of integrating the social component ("S") in Long-Term Socio-Ecological Research (LTSER) Sites [Material Complementario]
- This article discusses field environmental philosophy and biocultural conservation at the Omora Ethnobotanical Park. Abstract: In order to effectively address the problems derived from global environmental change, environmental scientists, citizens and decision-makers now recognize the need to integrate more fully the human or social component into ecological research. The authors propose that to achieve this integration, Long-Term Socio-Ecological Research (LTSER) networks offer an ideal platform, because such sites enable research at ecological, cultural, and political local scales, and at the same time allow addressing these issues at a global scale. However, this socio-ecological work still requires better articulation of programs developed at multiple geographic, ecological and political scales. In addition, until now the social component considered in LTSER programs has focused on economic factors, omitting ethical dimensions. A central reason for this omission is the lack of methodologies to systematically integrate ethics into LTSER programs. As a contribution to resolve this limitation, here the authors develop a methodological approach that the authors call "field environmental philosophy." It integrates ecological research and environmental ethics into biocultural education and conservation through an interrelated four-step cycle: i) interdisciplinary ecological and philosophical research, ii) composition of metaphors, and communication through simple narratives, iii) design of guided field experiences with an ecological and ethical orientation, and iv) implementation of in situ conservation areas. This cycle has been defined a posteriori, by analyzing successful experiences of biocultural research, education and conservation program at the Omora Ethnobotanical Park (OEP) in the Cape Horn Biosphere Reserve (CHBR). The Masters of Science in Subantarctic Conservation at the University of Magallanes (UMAG) adopted this cycle as a structured methodology to design theses and academic curricula for students who are creating innovative educational and ecotourism activities, such as "Ecotourism with a Hand Lens" and "Ethical Birding." To articulate the programs at multiple scales, the OEP functions at the local scale as a research center in the CHBR, at the national level as a cofounder and southernmost site of the Chilean LTSER network coordinated by the Institute of Ecology and Biodiversity (IEB), Chile, and at the coordinated by UMAG, IEB and the University of North Texas (UNT). This organization of nested units has permitted to synergistically articulate the work at local, national and international scales. Collaborative research has led to the discovery of biological and cultural diversity singularities in the remote Magellanic subantarctic ecoregion, enabled education and conservation work with multiple social actors and institutions, and has strengthened the incorporation of environmental philosophy into socio-ecological research. In this way, OEP's program is contributing to broaden the definition of the social ("S") component in LTSER, and to generate methodologies to integrate, at multiple scales, ecological and ethical dimensions into socio-ecological research, as well as biocultural education and conservation programs, which could be implemented and assessed at other LTSER sites. digital.library.unt.edu/ark:/67531/metadc97960/
- Field Environmental Philosophy and Biocultural Conservation: The Omora Ethnobotanical Park Educational Program
- This article discusses field environmental philosophy and biocultural conservation. Abstract: Habitats (where we live), habits (how we live), and inhabitants (who we are) constitute an ecosystem unit. The biosphere is composed of a reticulate mosaic of these habitat-habit-inhabitant units, where humans (with their indigenous languages, ecological knowledge, and practices) have coevolved. Today, these diverse ecosystem units are being violently destroyed by the imposition of a single global colonial cultural model. In Cape Horn at the southern end of the Americas, educators, authorities, and decision makers do not know about the native habitats, language, and flora, and do not distinguish between Cape Horn's flora and the flora that grows in other parts of the country or the world. In contrast, indigenous people and old residents have a detailed knowledge, but they do not participate in education, and decision making. It is not Homo Sapiens in general, but bioculturally biased educators, authorities, and decision makers who need to be transformed into (educated and responsible) members and citizen of biocultural communities. The Omora Ethnobotanical Park educational program was launched to contribute to a biocultural citizenship involving three critical steps: (1) the disclosing of biocultural diversity with a "fine filter" approach that permits understanding of the cultural and ecological diversity hidden by general universal labels; (2) direct "face-to-face" encounters with human and nonhuman co-inhabitants; and (3) actions for protection of habitats and implementation of interpretative spaces that facilitate direct encounters and conservation of biocultural diversity. These steps have been implemented at local and regional scales through the creation of the Omora Ethnobotanical Park and the UNESCO Cape Horn Biosphere Reserve. digital.library.unt.edu/ark:/67531/metadc102296/
- Filosofía Ambiental de Campo y Conservación Biocultural: El Programa Educativo del Parque Etnobotánico Omora
- This article discusses field environmental philosophy and biocultural conservation. Abstract: Habitats (where we live), habits (how we live), and inhabitants (who we are) constitute an ecosystem unit. The biosphere is composed of a reticulate mosaic of these habitat-habit-inhabitant units, where humans (with their indigenous languages, ecological knowledge, and practices) have coevolved. Today, these diverse ecosystem units are being violently destroyed by the imposition of a single global colonial cultural model. In Cape Horn at the southern end of the Americas, educators, authorities, and decision makers do not know about the native habitats, language, and flora, and do not distinguish between Cape Horn's flora and the flora that grows in other parts of the country or the world. In contrast, indigenous people and old residents have a detailed knowledge, but they do not participate in education, and decision making. It is not Homo Sapiens in general, but bioculturally biased educators, authorities, and decision makers who need to be transformed into (educated and responsible) members and citizen of biocultural communities. The Omora Ethnobotanical Park educational program was launched to contribute to a biocultural citizenship involving three critical steps: (1) the disclosing of biocultural diversity with a "fine filter" approach that permits understanding of the cultural and ecological diversity hidden by general universal labels; (2) direct "face-to-face" encounters with human and nonhuman co-inhabitants; and (3) actions for protection of habitats and implementation of interpretative spaces that facilitate direct encounters and conservation of biocultural diversity. These steps have been implemented at local and regional scales through the creation of the Omora Ethnobotanical Park and the UNESCO Cape Horn Biosphere Reserve. digital.library.unt.edu/ark:/67531/metadc102297/
- Filosofía ambiental de campo y conservación biocultural en el Parque Etnobotánico Omora: Aproximaciones metodológicas para ampliar los modos de integrar el componente social ("S") en Sitios de Estudios Socio-Ecológicos a Largo Plazo (SESELP)
- This article discusses field environmental philosophy and biocultural conservation at the Omora Ethnobotanical Park. Abstract: In order to effectively address the problems derived from global environmental change, environmental scientists, citizens and decision-makers now recognize the need to integrate more fully the human or social component into ecological research. The authors propose that to achieve this integration, Long-Term Socio-Ecological Research (LTSER) networks offer an ideal platform, because such sites enable research at ecological, cultural, and political local scales, and at the same time allow addressing these issues at a global scale. However, this socio-ecological work still requires better articulation of programs developed at multiple geographic, ecological and political scales. In addition, until now the social component considered in LTSER programs has focused on economic factors, omitting ethical dimensions. A central reason for this omission is the lack of methodologies to systematically integrate ethics into LTSER programs. As a contribution to resolve this limitation, here the authors develop a methodological approach that the authors call "field environmental philosophy." It integrates ecological research and environmental ethics into biocultural education and conservation through an interrelated four-step cycle: i) interdisciplinary ecological and philosophical research, ii) composition of metaphors, and communication through simple narratives, iii) design of guided field experiences with an ecological and ethical orientation, and iv) implementation of in situ conservation areas. This cycle has been defined a posteriori, by analyzing successful experiences of biocultural research, education and conservation program at the Omora Ethnobotanical Park (OEP) in the Cape Horn Biosphere Reserve (CHBR). The Masters of Science in Subantarctic Conservation at the University of Magallanes (UMAG) adopted this cycle as a structured methodology to design theses and academic curricula for students who are creating innovative educational and ecotourism activities, such as "Ecotourism with a Hand Lens" and "Ethical Birding." To articulate the programs at multiple scales, the OEP functions at the local scale as a research center in the CHBR, at the national level as a cofounder and southernmost site of the Chilean LTSER network coordinated by the Institute of Ecology and Biodiversity (IEB), Chile, and at the coordinated by UMAG, IEB and the University of North Texas (UNT). This organization of nested units has permitted to synergistically articulate the work at local, national and international scales. Collaborative research has led to the discovery of biological and cultural diversity singularities in the remote Magellanic subantarctic ecoregion, enabled education and conservation work with multiple social actors and institutions, and has strengthened the incorporation of environmental philosophy into socio-ecological research. In this way, OEP's program is contributing to broaden the definition of the social ("S") component in LTSER, and to generate methodologies to integrate, at multiple scales, ecological and ethical dimensions into socio-ecological research, as well as biocultural education and conservation programs, which could be implemented and assessed at other LTSER sites. digital.library.unt.edu/ark:/67531/metadc97959/
- First-Principles-Based Kinetic Monte Carlo Simulation of Nitric Oxide Reduction over Platinum Nanoparticles under Lean-Burn Conditions
- This article discusses first-principles-based kinetic Monte Carlo simulation of Nitric Oxide reduction. Abstract: The kinetics for NO reduction over supported platinum under lean condition were investigated by first-principles-based kinetic Monte Carlo simulation over three-dimensional Pt nanoparticles. Model platinum nanoparticles with diameters ranging from 2.3 to 4.6 nm were constructed using a truncated octahedral cluster consisting of a two (100) facets and eight (111) facets. First-principles density functional theory (DFT) calculations were used to calculate the intrinsic kinetic parameters including the binding energies for all of the surface intermediates as well as the activation barriers and reaction energies that comprise the reaction nanoparticle. Both intra- and inter-facet diffusion of adsorbates were included to model surface diffusion effects over the particle surface. The simulation results show that under lean conditions where there is excess oxygen, NO reduction to N2 occurs solely on the (100) facets. The oxidation of NO to NO2, while much more favored on the (111) facets, can occur on both (100) and (111) facets. Only small amounts of N2O form over the (100) facets. The simulated apparent activation energies for N2 and NO2 formation over the entire particle are 45 and 42 kJ/mol, respectively. The latter is in agreement with experimentally measured value of 39 kJ/mol [Mulla, S.S., et al., Catal. Lett. 2005, 100, 267]. The effects of particle size on the activities of NO reduction to N2 and NO oxidation to NO2 depend upon the ratios of exposed surface sites. For the three-dimensional model Pt nanoparticles examined here, the fractions of the (100) terrace sites are similar while the fraction of the (111) terrace sites increases with increasing particle size. As a result, the activity for NO reduction is somewhat insensitive to the particle size which symmetrically increases the numbers of (111) and (100) facets as the size increases. NO reduction, however, increases much more dramatically when the number of the (100) sites increases over the (111) sites. NO oxidation activity, on the other hand, appears to increase with increasing particle size regardless of the symmetry or shape of the particle as the reaction occurs predominantly over the (111) sites but can also take place on the (100) terrace sites. The structure insensitivity for NO oxidation is consistent with experimental results. digital.library.unt.edu/ark:/67531/metadc71804/
- Flavin-Catalyzed Insertion of Oxygen into Rhenium-Methyl Bonds
- This article discusses flavin-catalyzed insertion of oxygen into rhenium-methyl bonds. Abstract: Flavins and related molecules catalyze organic Baeyer-Villiger reactions. Combined experimental and DFT studies indicate that these molecules also catalyze the insertion of oxygen into metal-carbon bonds through a Baeyer-Villiger-like transition state. digital.library.unt.edu/ark:/67531/metadc107791/
- A fluctuating environment as a source of periodic modulation
- This article discusses a fluctuating environment as a source of periodic modulation. Abstract: We study the intermittent fluorescence of a single molecule, jumping from the "light on" to the "light off" state, as a Poisson process modulated by a fluctuating environment. We show that the quasi-periodic and quasi-deterministic environmental fluctuations make the distribution of the times of sojourn in the "light off" state depart from the exponential form, and that their succession in time mirrors environmental dynamics. As an illustration, the authors discuss some recent experimental results, where the environmental fluctuations depend on enzymatic activity. digital.library.unt.edu/ark:/67531/metadc132981/
- Fluctuation-dissipation process without a time scale
- This article discusses fluctuation-dissipation process without a time scale. Abstract: We study the influence of a dissipation process on diffusion dynamics triggered by fluctuations with long-range correlations. We make the assumption that the perturbation process involved is of the same kind as those recently studied numerically and theoretically, with a good agreement between theory and numerical treatment. As a result of this assumption the equilibrium distribution departs from the ordinary canonical distribution. The distribution tails are truncated, the distribution border is signaled by sharp peaks, and, in the weak dissipation limit, the central distribution body becomes identical to a truncated Lévy distribution. digital.library.unt.edu/ark:/67531/metadc77161/
- Fluctuation-Dissipation Theorem for Event-Dominated Processes
- This article discusses fluctuation-dissipation theorem for event-dominated processes. Abstract: We study a system whose dynamics are driven by non-Poisson, renewal, and nonergodic events. We show that external perturbations influencing the times at which these events occur violate the standard fluctuation-dissipation prescription due to renewal aging. The fluctuation-dissipation relation of this Letter is shown to be the linear response limit of an exact expression that has been recently proposed to account for the luminescence decay in a Gibbs ensemble of semiconductor nanocrystals, with intermittent fluorescence. digital.library.unt.edu/ark:/67531/metadc40397/
- Food Habits and Racial Thinking
- This presentation is part of the faculty lecture series UNT Speaks Out on The Food We Eat. In this presentation, the author discusses race and food habits. digital.library.unt.edu/ark:/67531/metadc111278/
- Formation and characterization of ion beam assisted nanosystems in silicon
- This article discusses formation and characterization of ion beam assisted nanosystems in silicon. Abstract: Even though silicon is optically inactive, the nanoscale particle structures (e.g. SiC) in Si or silica matrices are potential candidates for light emitting solid state device applications with higher operation temperatures. The synthesis of these nanostructures involves ion implantation and subsequent thermal annealing. The film thickness and sizes of the nanostructures can be controlled by ion energy, fluence, and annealing conditions. Particle accelerator based characterization was used at different stages of formation and analysis of these nanosystems in Si. Results will be presented using infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), and photoluminescence (PL) spectroscopy. digital.library.unt.edu/ark:/67531/metadc139470/
- Foucault's Pendulum
- Front cover of the Summer 2010 issue of The Hexagon featuring Foucault's pendulum in the Panthéon of Paris, France. A large weight hangs from the ceiling over a circular table with degrees written onto its surface. A round fence with hash marks and numbers surrounds the display. Columns and a raised statue of men are visible in the background. The inside cover features a table of contents, staff list, an editorial, and a description of the front cover. digital.library.unt.edu/ark:/67531/metadc111246/
- Four-Coordinate Mo(II) as (silox)2Mo(PMe3)2 and Its W(IV) Congener (silox)2HW(ɳ2-CH2PMe2) (silox = tBu3SiO)
- This article discusses four-coordinate Mo(II). Abstract: The reduction of [(tBu3SiO)2MoCI]2 (22) provided the cyclometalated derivative, (silox)2HMoMo(k-O,C-OSitBu2CMe2CH2)(silox) (3), and alkylation of 22 with MeMgBr afforded [(tBu3SiO)2MoCH3]2 (42). The hydrogenation of 42 was ineffective, but the reduction of 22 under H2 generated [(tBu3SiO)2MoH]2 (52), and the addition of 2-butyne to 3 gave [(silox)2Mo]2 (μ:ɳ2ɳ2-C2Me2) (6), thereby implicating the existence of [(silox)2Mo]2 (12). The addition of (silox)H to Mo(NMe2)4 led to (silox)2Mo(NMe2)2 (7), but further elaboration of the core proved ineffective. The silanolysis of MoCI5 afforded (silox)2MoCI4 (8) and (silox)3 MoCI3 (9) as a mixture from which pure 8 could be isolated, and the addition of THF or PMe3 resulted in derivatives of 9 as (silox)2CI3MoL (L = THF, 10; PMe3, 11). Reductions of 11 and (silox)2WCI4 (15) in the presence of excess PMe3 provided (silox)2CI2MPMe3 (M = Mo, 12; W, 16) or (silox)2HW(ɳ2-CH2PMe2)PMe3 (14). While "(silox)2W(PMe3)2" was unstable with respect to W(IV) as 14, a reduction of 12 led to the stable Mo(II) diphosphine, (silox)2Mo(PMe3)2 (17). X-ray crystal structures of 10 (pseudo-Oh), 12 (square pyramidal), and 14 and 17 (distorted Td) are reported. Calculations address the diamagnetism of 12 and 16, and the distortion of 17 and its stability to cyclometalation in contrast to 14. digital.library.unt.edu/ark:/67531/metadc77131/
- Fractional Brownian motion as a nonstationary process: An alternative paradigm for DNA sequences
- This article discusses fractional Brownian motion as a nonstationary process. Abstract: The long-range correlations in DNA sequences are currently interpreted as an example of stationary fractional Brownian motion (FBM). First the authors show that the dynamics of a dichotomous stationary process with long-range correlations such as that used to model DNA sequences should correspond to Lévy statistics and not to FBM. To explain why, in spite of this, the statistical analysis of the data seems to be compatible with FBM, the authors notice that an initial Gaussian condition, generated by a process foreign to the mechanism establishing the long-range correlations and consequently implying a departure from the stationary condition is maintained approximately unchanged for very long times. This is so because due to the nature itself of the long-range correlation process, it takes virtually an infinite time for the system to reach the genuine stationary state. Then the authors discuss a possible generator of initial Gaussian conditions, based on a folding mechanism of the nucleic acid in the cell nucleus. The model adopted is compatible with the known biological and physical constraints, namely, it is shown to be consistent with the information of current biological literature on folding as well as with the statistical analyses of DNA sequences. digital.library.unt.edu/ark:/67531/metadc75416/
- Fractional calculus as a macroscopic manifestation of randomness
- This article discusses fractional calculus as a macroscopic manifestation of randomness. Abstract: We generalize the method of Van Hove [Physica (Amsterdam) 21, 517 (1955)] so as to deal with the case of nonordinary statistical mechanics, that being phenomena with no time-scale separation. We show that in the case of ordinary statistical mechanics, even if the adoption of the Van Hove method imposes randomness upon Hamiltonian dynamics, the resulting statistical process is described using normal calculus techniques. On the other hand, in the case where there is no time-scale separation, this generalized version of Van Hove's method not only imposes randomness upon the microscopic dynamics, but it also transmits randomness to the macroscopic level. As a result, the correct description of macroscopic dynamics has to be expressed in terms of the fractional calculus. digital.library.unt.edu/ark:/67531/metadc77121/
- From power law intermittence to macroscopic coherent regime
- This article offers discussions from power law intermittence to macroscopic coherent regime. Abstract: We address the problem of establishing which is the proper form of quantum master equation generating a survival probability identical to that corresponding to the nonergodic sequence of "light on" and "light off" fluorescence fluctuations in blinking quantum dots. We adopt a theoretical perspective based on the assumption that the abrupt transitions from the light on to light off state are the results of many collisions between system and environment, properly described by the Linkblad equation, and that between two consecutive collisions the system dynamics are frozen. This generates a quantum master equation belonging to the recently proposed class of generalized Lindblad equations, with a time convoluted structure, involving in the specific case of this paper both the unitary and the nonunitary contribution of the Lindlad equation. This is the property that under the low-frequency condition makes the new class of generalized Lindblad equation generates the required survival probability. We make the conjecture that this equation corresponds to the cooperative dynamics of many units that, in isolation, are described by the ordinary Lindblad equation. When the time scale of the unitary term of the Lindblad equation is shorter than the dephasing time, the cooperation generates a surprisingly extended macroscopic coherence. digital.library.unt.edu/ark:/67531/metadc132992/
- From self-organized to extended criticality
- This article includes discussions from self-organized to extended criticality. Abstract: We address the issue of criticality that is attracting the attention of an increasing number of neurophysiologists. Our main purpose is to establish the specific nature of some dynamical processes that although physically different, are usually termed as "critical," and we focus on those characterized by the cooperative interaction of many units. We notice that the term "criticality" has been adopted to denote both noise-induced phase transitions and Self-Organized Criticality (SOC) with no clear connection with the traditional phase transitions, namely the transformation of a thermodynamic system from one state of matter to another. We notice the recent attractive proposal of extended criticality advocated by Bailly and Longo, which is realized through a wide set of critical points rather than emerging as a singularity from a unique value of the control parameter. We study a set of cooperatively firing neurons and we show that for an extended set of interaction couplings the system exhibits a form of temporal complexity similar to that emerging at criticality from ordinary phase transitions. This extended criticality regime is characterized by three main properties: (i) In the ideal limiting case of infinitely large time period, temporal complexity corresponds to Mittag-Leffler complexity; (ii) For large values of the interaction coupling the periodic nature of the process becomes a predominant while maintaining to some extent, in the intermediate time asymptotic region, the signature of complexity; (iii) Focusing their attention on firing neuron avalanches, We find two of the popular SOC properties, namely the power indexes 2 and 1.5 respectively for time length and for the intensity of the avalanches. We derive the main conclusion that SOC emerges from extended criticality, thereby explaining the experimental observation of Plenz and Beggs: avalanches occur in time with surprisingly regularity, in apparent conflict with the temporal complexity of physical critical points. digital.library.unt.edu/ark:/67531/metadc132990/
- Function of Conserved Residues of Human Glutathione Synthetase: Implications for the ATP-grasp Enzymes
- This article discusses human glutathione synthetase. Abstract: Glutathione synthetase is an enzyme that belongs to the glutathione synthetase ATP-binding domain-like superfamily. It catalyzes the second step in the biosynthesis of glutathione from y-glutamylcysteine and glycine in an ATP-dependent manner. Glutathione synthetase has been purified and sequenced from a variety of biological sources; still, its exact mechanism is not fully understood. A variety of structural alignment methods were applied and four highly conserved residues of human glutathione synthetase (Glu-144, Asn-146, Lys-305, and Lys-364) were identified in the binding site. The function of these was studied by experimental and computational site-directed mutagenesis. The three-dimensional coordinates for several human glutathione synthetase mutant enzymes were obtained using molecular mechanics and molecular dynamics simulation techniques, starting from the reported crystal structure of human glutathione synthetase. Consistent with circular dichroism spectroscopy, the authors' results showed no major changes to overall enzyme structure upon residue mutation. However, semiempirical calculations revealed that ligand binding is affected by these mutations. The key interactions between conserved residues and ligands were detected and found to be essential for enzymatic activity. Particularly, the negatively charged Glu-144 residue plays a major role in catalysis. digital.library.unt.edu/ark:/67531/metadc75414/
- Functional and Phylogenetic Analyses of a Conserved Regulatory Program in the Phloem of Minor Veins
- This article discusses functional and phylogenetic analyses of a conserved regulatory program in the phloem of minor veins. Abstract: The minor-vein phloem of mature leaves is developmentally and physiologically distinct from the phloem in the rest of the vascular system. Phloem loading of transport sugars occurs in the minor veins, and consistent with this, galactinol synthase is expressed in the minor veins of melon (Cucumis melo) as part of the symplastic-loading mechanism that operates in this species. A galactinol synthase promoter from melon drives gene expression in the minor-vein companion cells of both transgenic tobacco (Nicotiana tabacum) and Arabidopsis. Neither of these plants use galactinol in the phloem-loading process, implying that the promoter responds to a minor-vein-specific regulatory cascade that is highly conserved across a broad range of eudicotyledons. Detailed analysis of this promoter by truncation and mutagenesis identified three closely coupled sequences that unambiguously modulate tissue specificity. These sequences cooperate in a combinatorial fashion: two promote expression throughout the vascular system of the plant, whereas the third functions to repress expression in the larger bundles. In a complementary approach, phylogenetic footprinting was used to obtain single-nucleotide resolution of conserved sites in orthologous promoters from diverse members of the Cucurbitaceae. This comparative analysis confirmed the importance of the closely coupled sites but also revealed other highly conserved sequences that may modulate promoter strength or contribute to expression patterns outside of the phloem. The conservation of this regulatory design among species that phloem load by different mechanisms supports a model for organismal development in which tissues and cell types are controlled by relatively ancient and conserved paradigms but expression of genes influencing final form and function are relatively plastic. digital.library.unt.edu/ark:/67531/metadc81378/
- Functional Assessment of the Medicago truncatula NIP/LATD Protein Demonstrates That It Is a High-Affinity Nitrate Transporter
- This article discusses a functional assessment of the Medicago truncatula NIP/LATD. Abstract: The Medicago truncatula NIP/LATD (for Numerous Infections and Polyphenolics/Lateral root-organ Defective) gene encodes a protein found in a clade of nitrate transporters within the large NRT1(PTR) family that also encodes transporters of dipeptides and tripeptides, dicarboxylates, auxin, and abscisic acid. Of the NRT1(PTR) members known to transport nitrate, most are low-affinity transporters. Here, the authors show that M. truncatula nip/latd mutants are more defective in their lateral root responses to nitrate provided at low (250 μм) concentrations than at higher (5mм) concentrations; however, nitrate uptake experiments showed no discernible differences in uptake in the mutants. Heterologous expression experiments showed that MtNIP/LATD encodes a nitrate transporter: expression in Xenopus laevis oocytes conferred upon the oocytes the ability to take up nitrate from the medium, but oocytes expressing the less severe Mtnip-3 allele were proficient in nitrate transport. M. truncatula nip/latd mutants have pleiotropic defects in nodulation and root architecture defects but not for nodulation defects. This suggests that the spectrum of activities inherent in AtNRT1.1 is different from that possessed by MtNIP/LATD, but it could also reflect stability differences of each protein in M. truncatula. Collectively, the data show that MtNIP/LATD is a high-affinity nitrate transporter and suggest that it could have another function. digital.library.unt.edu/ark:/67531/metadc130185/
- Functional Characterization of the Arabidopsis AtSUC2 Sucrose/H+ Symporter by Tissue-Specific Complementation Reveals an Essential Role in Phloem Loading But Not in Long-Distance Transport
- This article discusses functional characterization of the Arabidopsis AtSUC2 Sucrose/H+ Symporter. Abstract: AtSUC2 (At1g22710) encodes a phloem-localized sucrose (Suc)/H+ symporter necessary for efficient Suc transport from source tissues to sink tissues in Arabidopsis (Arabidopsis thaliana). AtSUC2, however, is also expressed strongly in the transport phloem, where its role is more ambiguous, and it has been implicated in mediating both efflux and retrieval to and from flanking tissues via the apoplast. To characterize the role of AtSUC2 in controlling carbon partitioning along the phloem path, AtSUC2 cDNA was expressed from tissue-specific promoters in an Atsuc2 mutant background. Suc transport in this mutant is highly compromised, as indicated by stunted growth and the accumulation of large quantities of sugar and starch in vegetative tissues. Expression of AtSUC2 cDNA from the 2-kb AtSUC2 promoter was sufficient to restore growth and carbon partitioning to nearly wild-type levels. The GALACTINOL SYNTHASE promoter of Cucumis melo (CmGAS1p) confers expression only in the minor veins of mature leaves, not in the transport phloem of larger leaf veins and stems. Mutant plants expressing AtSUC2 cDNA from CmGAS1p had intermediate growth and accumulated sugar and starch, but otherwise they had normal morphology. These characteristics support a role for AtSUC2 in retrieval but not efflux along the transport phloem and show that the only vital function of AtSUC2 in photoassimilate distribution is phloem loading. In addition, AtSUC2 mutant plants, although debilitated, do grow, and AtSUC2-independent modes of phloem transport are discussed, including an entirely symplastic pathway from mesophyll cells to sink tissues. digital.library.unt.edu/ark:/67531/metadc78290/
- Future Environmental Philosophies and Their Biocultural Conservation Interfaces
- This article discusses future environmental philosophies and their biocultural conservation interfaces. digital.library.unt.edu/ark:/67531/metadc102289/
- The Gas That Wouldn't Burn
- Article describing how Alpha Chi Sigma members were involved with the events described on a pictured Kansas historical marker relating to the discovery of helium in a deposit of natural gas. digital.library.unt.edu/ark:/67531/metadc111272/
- Geminivirus-Mediated Delivery of Florigen Promotes Determinate Growth in Aerial Organs and Uncouples Flowering from Photoperiod in Cotton
- This article discusses geminivirus-mediated delivery of florigen. Abstract: Background: Plant architecture and the timing and distribution of reproductive structures are fundamental agronomic traits shaped by patterns of determinate and indeterminate growth. Florigen, encoded by FLOWERING LOCUS T (FT) in Arabidopsis and SINGLE FLOWER TRUSS (SFT) in tomato, acts as a general growth hormone, advancing determinate growth. Domestication of upland cotton (Gossypium hirsutum) converted it from a lanky photoperiodic perennial to a highly inbred, compact day-neutral plant that is managed as an annual row-crop. This dramatic change in plant architecture provides a unique opportunity to analyze the transition from perennial to annual growth. Methodology/Principle Findings: To explore these architectural changes, the authors addressed the role of day-length upon flowering in an ancestral, perennial accession and in a domesticated variety of cotton. Using a disarmed Cotton leaf crumple virus (CLCrV) as a transient expression system, the authors delivered FT to both cotton accessions. Ectopic expression of FT in ancestral cotton mimicked the effects of day-length, promoting photoperiod-independent flowering, precocious determinate architecture, and lanceolate leaf shape. Domesticated cotton infected with FT demonstrated more synchronized fruiting and enhanced "annualization". Transient expression of FT also facilitated simple crosses between wild photoperiodic and domesticated day-neutral accessions, effectively demonstrating a mechanism to increase genetic diversity among cultivated lines of cotton. Virus was not detected in the F₁ progeny, indicating that crosses made by this approach do not harbor recombinant DNA molecules. Conclusions: These findings extend our understanding of FT as a general growth hormone that regulates shoot architecture by advancing organ-specific and age-related determinate growth. Judicious manipulation of FT could benefit cotton architecture to improve crop management. digital.library.unt.edu/ark:/67531/metadc102285/
- Gender and globalization through film: A Wiki course
- This poster discusses a learning activity with a Wiki course on gender and globalization through film. The course aims to help students understand how existing gender inequalities are challenged and furthered by processes of international development and globalization. digital.library.unt.edu/ark:/67531/metadc84135/
- Gender difference of emotional bias in sharing love
- This article accompanies a poster presentation on the gender difference of emotional bias in sharing love. Having developed a computational model for emotional response (Emotional-Gain Model) and a model for fairness (Fairness-Equity Model) that quantified emotional bias and fairness bias, the authors will address the gender difference between the perception of love. The authors employed the experimental paradigm called "ultimatum game" to elicit emotional responses to the sharing of love and money. digital.library.unt.edu/ark:/67531/metadc122154/
- O generalizare a problemei piesei de 5 lei a lui Ţiţeica
- The '5 lei coin' problem of Titeica is generalized to circles of arbitrary radii. digital.library.unt.edu/ark:/67531/metadc152461/
- Generalizarea problemei 0:59
- This note extends a certain combinatorics problem of I. Tomescu. digital.library.unt.edu/ark:/67531/metadc152440/
- Generalized anxiety modulates frontal and limbic activation in major depression
- This article discusses generalized anxiety modulates frontal and limbic activation in major depression. Abstract: Background: Anxiety is relatively common in depression and capable of modifying the severity and course of depression. Yet our understanding of how anxiety modulates frontal and limbic activation in depression is limited. Methods: The authors used functional magnetic resonance imaging and two emotional information processing tasks to examine frontal and limbic activation in ten patients with major depression and comorbid with preceding generalized anxiety (MDD/GAD) and ten non-depressed controls. Results: Consistent with prior studies on depression, MDD/GAD patients showed hypoactivation in medial and middle frontal regions, as well as in the anterior cingulate and insula. However, heightened anxiety in MDD/GAD patients was associated with increased activation in middle frontal regions and the insula and the effects varied with the type of emotional information presented. Conclusions: The authors' findings highlight frontal and limbic hypoactivation in patients with depression and comorbid anxiety and indicate that anxiety level may modulate frontal and limbic activation depending upon the emotional context. One implication of this finding is that divergent findings reported in the imaging literature on depression could reflect modulation of activation by anxiety level in response to different types of emotional information. digital.library.unt.edu/ark:/67531/metadc77158/
- Generalized Master Equation Via Aging Continuous-Time Random Walks
- This article discusses generalized master equation via aging continuous-time random walks. Abstract: We discuss the problem of the equivalence between continuous-time random walk (CTRW) and generalized master equation (GME). The walker, making instantaneous jumps from one site of the lattice to another, resides in each site for extended times. The sojourn times have a distribution density ψ(t) that is assumed to be an inverse power law with the power index μ. We assume that the Onsager principle is fulfilled, and we use this assumption to establish a complete equivalence between GME and the Montroll-Weiss CTRW.We prove that this equivalence is confined to the case where ψ(t) is an exponential. We argue that is so because the Montroll-Weiss CTRW, as recently proved by Barkai [E. Barkai, Phys. Rev. Lett. 90, 104101 (2003)], is nonstationary, thereby implying aging, while the Onsager principle is valid only in the case of fully aged systems. The case of a Poisson distribution of sojourn times is the only one with no aging associated to it, and consequently with no need to establish special initial conditions to fulfill the Onsager principle. We consider the case of a dichotomous fluctuation, and we prove that the Onsager principle is fulfilled for any form of regression to equilibrium provided that the stationary condition holds true. We set the stationary condition on both the CTRW and the GME, thereby creating a condition of total equivalence, regardless of the nature of the waiting-time distribution. As a consequence of this procedure the authors create a GME that is a bona fide master equation, in spite of being non-Markov. We note that the memory kernel of the GME affords information on the interaction between system of interest and its bath. The Poisson case yields a bath with infinitely fast fluctuations. We argue that departing from the Poisson form has the effect of creating a condition of infinite memory and that these results might be useful to shed light on the problem of how to unravel non-Markov quantum master equations. digital.library.unt.edu/ark:/67531/metadc67635/
- Generation of correlated binary sequences from white noise
- This article discusses the generation of correlated binary sequences from white noise. Abstract: We suggest a method for generation of random binary sequences of elements 0 and 1, with prescribed correlation properties. It is based on a modification of the widely used convolution method of constructing continuous random processes. Using this method, a binary sequence with a power-law decaying pair correlator can be easily generated. digital.library.unt.edu/ark:/67531/metadc103260/
- Genetic analysis of the spindle checkpoint genes san-I, mdf-2, bub-3 and the CENP-F homologues hcp-1 and hcp-2 in Caenorhabditis elegans
- This article discusses genetic analysis of the spindle checkpoint genes san-1, mdf-2, bub-3 and the CENP-F homologues hcp-1 and hcp-2 in Caenorhabditis elegans. Abstract: Background: The spindle checkpoint delays the onset of anaphase until all sister chromatids are aligned properly at the metaphase plate. To investigate the role san-1, the MAD3 homologue, has in Caenorhabditis elegans embryos, the authors used RNA interference (RNAi) to identify genes synthetic lethal with the viable san-1 (ok1580) deletion mutant. Results: The san-1 (ok1580) animal has low penetrating phenotypes including an increased incidence of males, larvae arrest, slow growth, protruding vulva, and defects in vulva morphogenesis. The authors found that the viability of san-1 (ok1580) embryos is significantly reduced when HCP-1 (CENP-F homologue) are reduced by RNAi. Interestingly, the viability of san-1 (ok1580) embryos is not significantly reduced when the paralog of HCP-1, HCP-2, is reduced. The phenotype of san-1 (ok1580); hcp-1 (RNAi) embryos includes embryonic and larval lethality, abnormal organ development, and an increase in abnormal chromosome segregation (abberrant mitotic nuclei, anaphase bridging). Several of the san-1 (ok1580); hcp-1(RNAi) animals displayed abnormal kinetochore (detected by MPM-2) and microtubule structure. The survival of mdf-2 (RNAi); hcp-1 (RNAi) embryos but not bub-3 (RNAi); hcp-1 (RNAi) embryos was also compromised. Finally, the authors found that san-1 (ok1580) and bub-3 (RNAi), but not hcp-1 (RNAi) embryos, were sensitive to anoxia, suggesting that like SAN-1, BUB-3 has a functional role as a spindle checkpoint protein. Conclusion: Together, these data suggest that in the C. elegans embryo, HCP-1 interacts with a subset of the spindle checkpoint pathway. Furthermore, the fact that san-1 (ok1580); hcp-1 (RNAi) animals had a severe viability defect whereas in the san-1 (ok1580); hcp-2 (RNAi) and san-1 (ok1580); hcp-2 (ok1757) animals the viability defect was not as severe suggesting that hcp-1 and hcp-2 are not completely redundant. digital.library.unt.edu/ark:/67531/metadc122165/
- Genetic Manipulation of a "Vacuolar" H+ -PPase: From Salt Tolerance to Yield Enhancement under Phosphorus-Deficient Soils
- This article discusses genetic manipulation of a "Vacuolar" H+ -PPase. Abstract: Plant scientists face the difficult challenge of increasing food production without further degradation of the environment. In order to protect drinking water resources and prevent the proliferation of harmful algal blooms and "dead zones" in coastal marine ecosystems, it is imperative to reduce anthropogenic nutrient inputs (Conley et al., 2009). These challenges are further compounded by the goal of utilizing agriculture to provide replacement fuels such as biodiesel and alcohol for our oil-based economy. Phosphate (Pi) is an essential macronutrient required for plant growth and development (Chen et al., 2008). Plant nutrient acquisition and partitioning depend on the H+ gradients generated by the plasma membrane H+ -ATPases (Palmgren, 2001; Fuglsang et al., 2011). In this update, the authors discuss the potential role that the type I H+ -proton- pyrophosphatase (PPase) could play in optimizing Pi use efficiency in plants. digital.library.unt.edu/ark:/67531/metadc102280/
- Genome-wide mutagenesis of Zea mays L. using RescueMu transposons
- This article discusses genome-wide mutagenesis of Zea mays L. using RescueMu transposons. Abstract: Derived from the maize Mu I transposon, RescueMu provides strategies for maize gene discovery and mutant phenotypic analysis. 9.92 Mb of gene-enriched sequences next to RescueMu insertion sites were co-assembled with expressed sequence tags and analyzed. Multiple plasmid recoveries identified probable germinal insertions and screening of RescueMu plasmid libraries identified plants containing probable germinal insertions. Although frequently recovered parental insertions and insertion hotspots reduce the efficiency of gene discovery per plasmid, RescueMu targets a large variety of genes and produces knockout mutants. digital.library.unt.edu/ark:/67531/metadc77168/
- Geographic Distribution of HIV/AIDS in Texas
- This presentation is part of the faculty lecture series UNT Speaks Out on HIV/AIDS. This presentation discusses the geographic distribution of HIV/AIDS in Texas and the associated factors. digital.library.unt.edu/ark:/67531/metadc71783/
- Global Film History: Encouraging Students to Develop Arguments that Connect Different Industries and Time Periods
- This poster discusses exploring the effectiveness of group-based blog assignments in large enrollment classes to help students learn about global film history across different industries and time periods. It looks at how the blogs fare in helping the students reflect upon the development of their learning as they see more patterns and connections through interactive and experiential exercises. digital.library.unt.edu/ark:/67531/metadc157289/
- Good Transformations: Ambiguity and the NSF's Experiment with 'Transformative' Research
- This article discusses a recent workshop on Transformative Research held at the headquarters of the U.S. National Science Foundation (NSF) in Arlington, Virginia. The authors led the two-day workshop to once again raise the question of the meaning of "transformative research" (TR). TR has come to encapsulate an increasingly central question across both U.S. and foreign science agencies: In a hypercompetitive global economy, with pressing challenges in many areas (energy, food, water, disease, etc.), how can we do a better job of picking research projects that are true game changers? digital.library.unt.edu/ark:/67531/metadc84334/
- Graft Transmission of a Floral Stimulant Derived from CONSTANS
- This article discusses graft transmission of a floral stimulant derived from CONSTANS. Abstract: Photoperiod in plants is perceived by leaves and in many species influences the transition to reproductive growth through long-distance signaling. CONSTANS (CO) is implicated as a mediator between photoperiod perception and the transition to flowering in Arabidopsis. To test the role of CO in long-distance signaling, CO was expressed from a promoter specific to the companion cells of the smallest veins of mature leaves. This expression in tissues at the inception of the phloem translocation stream was sufficient to accelerate flowering at the apical meristem under noninductive (short-day) conditions. Grafts that conjoined the vegetative stems of plants with different flower-timing phenotypes demonstrated that minor-vein expression of CO is able to substitute for photoperiod in generating a mobile flowering signal. The authors' results suggest that a CO-derived signal(s), or possibly CO itself, fits the definition of the hypothetical flowering stimulant, florigen. digital.library.unt.edu/ark:/67531/metadc81380/
- Group-Transfer Reactions of Nickel-Carbene and -Nitrene Complexes with Organoazides and Nitrous Oxide that Form New C=N, C=O, and N=N Bonds
- This article discusses group-transfer reactions of nickel-carbene and -nitrene complexes with organoazides and nitrous oxide that form new C=N, C=O, and N=N bonds. Abstract: 1-Adamantyl- and mesitylazide react with (dtbpe)Ni=CPh2 (1; dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) at ambient temperature to give the ketimines RN=CPh2 (2a, R = Mes; 2b, R = Ad) in high yield. Kinetic studies for the reaction of 1 with N3Ad yield activation parameters of ∆H‡ = +8(±1) kcal/mol and ∆S‡ = -44(±3) cal/(mol•K). Treatment of 1 with N2O at low temperature results in clean conversion to the benzophenone complex (dtbpe)Ni=NR (4a, R = Mes; 4b, R = Ad) react with N3Mes and N3Ad at ambient temperature to give the diazenes RN=NR (6a, R = Mes; 6b, R = Ad) in good yield. B3LYP/6-311+G(d) calculations support a mechanism for all three reactions that features 1,3-dipolar cycloaddition to give five-membered ring (Huisgen) intermediates, followed by N2 elimination to give the products. Calculated activation parameters for the reaction of (dhpe)Ni=CH2 (dhpe = 1,2-bis(dihydridophosphino)ethane) with N3Me compare well with the experimental values. digital.library.unt.edu/ark:/67531/metadc107794/
- GSV: a web-based genome synteny viewer for customized data
- This article discusses GSV, a web-based genome synteny viewer for customized data. Abstract: Background: The analysis of genome synteny is a common practice in comparative genomics. With the advent of DNA sequencing technologies, individual biologists can rapidly produce their genomic sequences of interest. Although web-based synteny visualization tools are convenient for biologists to use, none of the existing ones allow biologists to upload their own data for analysis. Results: The authors have developed the web-based Genome Synteny Viewer (GSV) that allows users to upload two data files for synteny visualization, the mandatory synteny file for specifying genomic positions of conserved regions and the optional genome annotation file. GSV presents two selected genomes in a single integrated view while still retaining the browsing flexibility necessary for exploring individual genomes. Users can browse and filter for genomic regions of interest, change the color or shape of each annotation track as well as re-order, hide or show the tracks dynamically. Additional features include downloadable images, immediate email notification and tracking of usage history. The entire GSV package is also light-weighted which enables easy local installation. Conclusions: GSV provides a unique option for biologists to analyze genome synteny by uploading their own data set to a web-based comparative genome browser. A web server hosting GSV is provided at http://cas.bioinfo.cas.unt.edu/gsv, and the software is also freely available for local installations. digital.library.unt.edu/ark:/67531/metadc77111/
- Helium Monument
- Front cover of the summer 2012 issue of The Hexagon, which features the Helium Monument in Amarillo, Texas. The visible portion of this monument is a metal sculpture of a helium molecule hanging from the center of a structure of metal bars. The inside cover contains a table of contents, a staff list, an editorial, and a description of the Helium Monument. digital.library.unt.edu/ark:/67531/metadc111270/
- High sensitivity measurement of implanted As in the presence of Ge in Ge(x)Si(1-x)/Si layered alloys using trace element accelerator mass spectrometry
- This article discusses high sensitivity measurement of implanted As in the presence of Ge in Ge(x)Si(1-x)/Si layered alloys using trace element accelerator mass spectrometry. Abstract: Various devices can be realized on strained GeSi/Si substrates by doping the substrate with different impurities such as As. As is an n-type dopant in both Ge and Si. As cross contamination can also arise during germanium preamorphization implantation due to inadequate mass resolution in the implanter. Thus, it is important to be able to accurately measure low-level As concentrations in the presence of Ge. Secondary ion mass spectrometry (SIMS) is the standard technique for these types of measurements but is constrained by mass interferences from molecular ions (⁷⁴GeH, ²⁹Si³⁰Si¹⁶O). The trace element accelerator mass accelerator technique allows the breakup of interfering molecules. As is measured in a GeSi matrix with sensitivity significantly better than SIMS. digital.library.unt.edu/ark:/67531/metadc146576/
- High-Valent Transition-Metal Alkylidene Complexes: Effect of Ligand and Substituent Modification
- This article discusses high-valent transition-metal alkylidene complexes. Abstract: An ab initio investigation into the effects of ligand and substituent modification on the metal-carbon double bond is reported. Prototypical group IVB (Ti, Zr, Hf) and Group VB (Nb, Ta) alkylidenes are chosen for this study. The MC/LMO/CI (multiconfiguration/localized molecular orbital/configuration interaction) procedure is used to examine the electronic structures of these complexes in terms of the prime resonance contributors to the ground-state wave function. The main conclusion drawn from this work is that the intrinsic nature of the metal-carbon double bond can typically be changed only within certain limits by modification of the electronegativity of the ligands (L) and substituents (Z). In other words, the Ta=C bond in H₃TaCCl₂ and Cl₃TaCH₂ and presumably in experimentally characterized analogues with larger ligands and substituents, e.g., Cp and neopentyl. Significant changes in the electronic structure are effected in three ways: The first way is through the introduction of a highly electropositive substituent, e.g., Li. This makes the metal-carbon bond closer to a triple bond for the Ta-alkylidenes. The second way to change the electronic structure of the alkylidenes significantly is to change the central metal atom. The heaviest members of groups IVB (Hf) and VB (Ta) are the most nucleophilic at the α-carbon. The third way in which the metal-carbon bond could be significantly altered is through the use of π-donor substituents. The introduction of π-donor substituents on Cα increases the electrophilicity of the α-carbon. digital.library.unt.edu/ark:/67531/metadc107774/
- Historic Archaeology of the Johnson and Jones Farmsteads in the Ray Roberts Lake Area: 1850-1950
- This study represents the findings of research done on the Jones and Johnson farms, "situated in Johnson Branch Park in the north-central portion of the Ray Roberts Lake area." The purpose of the study was to offset future disturbances and damages to these farmsteads, and it includes "archival investigations, architectural documentation, oral-history interviews of long-time area residents and family members, farm equipment and artifact analyses, archaeological excavations, stabilization measures, and the development of interpretative exhibits for area schools, museums, and the general public" (p. i). digital.library.unt.edu/ark:/67531/metadc29393/
- History 4263: Palestinian History
- This poster discusses a project for a UNT history course, History 4263, on Palestinian history. In the course, students explore historical foundations and interpretations of modern Palestinian history. digital.library.unt.edu/ark:/67531/metadc84142/
- The History Engine: Doing History with Digital Tools
- This article discusses the History Engine project. One of the primary goals of the History Engine project has been to design a research and writing exercise modest enough in its analytical scope and its length that it allows students to "do history" long before a senior seminar or capstone course. Another important goal, discussed in this article, is to capture this research to amass a large history archive. digital.library.unt.edu/ark:/67531/metadc36311/