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Reductive Elimination of Alkylamines from Low-Valent, Alkylpalladium(II) Amido Complexes
This article discusses reductive elimination of alkylamines from low-valent, alkylpalladium(II) amido complexes. A series of three-coordinate norbornylpalladium amido complexes ligated by bulky N-heterocyclic carbene (NHC) ligands were prepared that undergo reductive eliminations to form the alkyl-nitrogen bond of alkylamine products. The rates of reductive elimination reveal that complexes containing more-electron-donating amido groups react faster than those with less-electron-donating amido groups, and complexes containing more-sterically bulky amido groups undergo reductive elimination more slowly than complexes containing less-sterically bulky amido groups. Complexes ligated by more-electron-donating ancillary NHC ligands undergo reductive elimination faster than complexes ligated by less-electron-donating NHC ligands. In contrast to the reductive elimination of benzylamines from bisphosphine-ligated palladium amides, these reactions occur with retention of configuration at the alkyl group, indicating that these reductive eliminations proceed by a concerted pathway. The experimentally determined free energy barrier of 26 kcal/mol is close to the computed free energy barrier of 23.9 kcal/mol (363 K) for a concerted reductive elimination from the isolated, three-coordinate NHC-ligated palladium anilido complex. digital.library.unt.edu/ark:/67531/metadc107792/
Remote Sensing and GIS for Nonpoint Source Pollution Analysis in the City of Dallas' Eastern Watersheds
This report describes the findings of a study conducted on the Eastern Watersheds of Lake Lavon, Lake Ray Hubbard, Lake Tawakoni, Lake Palestine and Lake Fork, which are located within the Blackland Prairie, Post Oak Savannah and Pineywoods provinces. These watersheds are among nine that provide drinking water to Dallas, Texas. The study examines the potential benefit of "remote sensing and geographic information systems (GIS) for watershed management" in these five watersheds (p. iii). digital.library.unt.edu/ark:/67531/metadc29400/
Remote Sensing and GIS for Nonpoint Source Pollution Analysis in the City of Dallas' Western Watersheds
This report describes the findings of a study conducted on the watersheds of "Lake Lewisville, Lake Ray Roberts, Lake Grapevine and the Elm Fork of the Trinity River between Lake Lewisville and Frazier Dam," which are all part of the upper Trinity drainage basin (p. 31). The study examines the potential benefit of "remote sensing and geographic information systems (GIS) for watershed management" in and around Dallas, Texas (p. i). digital.library.unt.edu/ark:/67531/metadc29399/
Renewal and memory properties in the random growth of surfaces
In this article, the authors use the model of ballistic deposition as a simple way to establish cooperation among the columns of a growing surface, 'the single individual of the same society.' The authors show that cooperation generates memory properties and at same time non-Poisson renewal events. The variable generating memory can be regarded as the velocity of a particle driven by a bath with the same time scale, and the variable generating renewal processes is the corresponding diffusional coordinate. digital.library.unt.edu/ark:/67531/metadc132977/
Renewal, Modulation, and Superstatistics in Times Series
In this article, the authors consider two different approaches, to which the authors refer to as renewal and modulation, to generate time series with a nonexponential distribution of waiting times. The authors show that different time series with the same waiting time distribution are not necessarily statistically equivalent, and might generate different physical properties. Renewal generates aging and anomalous scaling, while modulation yields no significant aging and either ordinary or anomalous diffusion, according to the dynamic prescription adopted. The authors show, in fact, that the physical realization of modulation generates two classes of events. The events of the first class are determined by the persistent use of the same exponential time scale for an extended lapse of time, and consequently are numerous; the events of the second class are identified with the abrupt changes from one to another exponential prescription, and consequently are rare. The events of the second class, although rare, determine the scaling of the diffusion process, and for this reason the authors term them as crucial events. According to the prescription adopted to produce modulation, the distribution density of the time distances between two consecutive crucial events might have, or not, a diverging second moment. In the former case the resulting diffusion process, although going through a transition regime very extended in time, will eventually become anomalous. In conclusion, modulation rather than ruling out the action of renewal events, produces crucial events hidden by clouds of exponential events, thereby setting the challenge for their identification. digital.library.unt.edu/ark:/67531/metadc40400/
La Reserva De Biosfera Cabo De Hornos: Un Desafío Para La Conservación De La Biodiversidad E Implementación Del Desarrollo Sustentable En El Extremo Austral De América
This article discusses biodiversity conservation and implementation of sustainable development in southernmost South America and the new biosphere reserve in Cape Horn, located in Antarctica Chilena Province. digital.library.unt.edu/ark:/67531/metadc102292/
Resistance to impact criteria can lead to a tightening of the accountability noose
This article discusses how resistance to impact criteria can lead to a tightening of the accountability noose. Vague impact criteria are a blessing in disguise. The authors write that researchers who push against criteria that allow considerable autonomy are foolish and should learn from overseas contemporaries that a clearer definition of impact requirements is not dissimilar from a tightening of the noose. digital.library.unt.edu/ark:/67531/metadc84357/
Response of Complex Systems to Complex Perturbations: the Complexity Matching Effect
This article discusses the complexity matching effect. The dynamical emergence (and subsequent intermittent breakdown) of collective behavior in complex systems is described as a non-Poisson renewal process, characterized by a waiting-time distribution density ψ(T) for the time intervals between successfully recorded breakdowns. In the intermittent case ψ(t) ~ t-μ, with complexity index μ. The authors show that two systems can exchange information through complexity matching and present theoretical and numerical calculations describing a system with complexity index μs perturbed by a signal with complexity index μp. The analysis focuses on the non-ergodic (non-stationary) case μ ≤ 2 showing that for μs ≥ μp, the system S statistically inherits the correlation function of the perturbation P. The condition μp = μs is a resonant maximum for correlation information exchange. digital.library.unt.edu/ark:/67531/metadc132965/
Response to "A critique of Abraham and Acree's correlation for deca-1,9-diene/water partition coefficients"
This article is a response to "A critique of Abraham and Acree's correlation for deca-1,9-diene/water partition coefficients." Abstract: The manuscript responds to the critique of Nitsche and Kasting concerning our published correlation for deca-1,9-diene-water partition coefficients. Several statements made in the critique are refuded, and shown to be misrepresentations of ideas contained in our earlier paper. digital.library.unt.edu/ark:/67531/metadc152438/
Response to: Use of prior odds for missing persons identifications - author's reply
This article is in response to an authors' reply to 'Use of prior odds for missing persons identifications.' This response is to the reply by Alex Biedermann, Franco Taroni, and Pierre Margot. digital.library.unt.edu/ark:/67531/metadc122169/
Reversible Beta-Hydrogen Elimination of Three-Coordinate Iron(II) Alkyl Complexes: Mechanistic and Thermodynamic Studies
This article discusses reversible beta-hydrogen elimination of three-coordinate iron(II) alkyl complexes. High-spin organometallic complexes have not received extensive mechanistic study, despite their potential importance as unsaturated intermediates in catalytic transformations. The authors have found that, with a suitably bulky bidentate ligand, three-coordinate, high-spin alkyl complexes of iron(II) are stable. They undergo isomerization and exchange reactions of the alkyl group through β-hydride elimination and reinsertion, and the β-hydride elimination step is rate-limiting. The alkyl complexes transfer a β-hydrogen atom to C=C, C=N, and C=O double bonds and undergo deprotonation by Brønsted acids. The reversible β-hydride elimination reactions can be used to explore relative M-C bond energies. Competition experiments and density functional calculations demonstrate an enthalpic preference for alkyl isomers with iron bound to the terminal carbon of the alkyl fragment. This preference arises from steric and electronic effects. The steric preference could be overcome with a phenyl substituent, which steers iron to the benzylic position. A Hammett correlation and density functional calculations suggest that the substituent effect is attributable to resonance stabilization of partial negative charge on the alkyl ligand. digital.library.unt.edu/ark:/67531/metadc77181/
Reversing the Bricks: The Evolution of ETDs at UNT
This presentation discusses electronic theses and dissertations (ETDs). Beginning in fall 1999, UNT has required the submission of theses and dissertations in electronic format. As an early adopter of what was to become the electronic thesis and dissertation (ETD) movement in higher education, UNT encountered and overcame several challenges in the pursuit of providing greater public access to the scholarship conducted at the University. Dr. Terrell was there from the very beginning, and will share her unique perspective on how far the ETD movement has come, and what challenges remain. digital.library.unt.edu/ark:/67531/metadc32968/
[Review] A Grammar of Mongsen Ao
This book review discusses 'A Grammar of Mongsen Ao' by Alec R. Coupe. Ao is one of the approximately 20 indigenous languages of Nagaland spoken in around fifty villages in northwestern area of the state. This book reviews discusses each of the eleven chapters in the book. digital.library.unt.edu/ark:/67531/metadc83322/
[Review] Chemistry of Advanced Materials: An Overview
This book review discusses 'Chemistry of Advanced Materials: An Overview', edited by Leonard V. Interrante from Renssalaer Polytechnic Institute, and Mark J. Hampden-Smith from the University of New Mexico. digital.library.unt.edu/ark:/67531/metadc107798/
[Review] Communications and Management at Work
This book review discusses 'Communication and Management at Work' by Thomas Klikauer. The book, intended primarily for scholars of management, business, and organizational communication, invokes the theories of Kant, Habermas, Orwell, and Marx to assess at a macro level the historical and contemporary relationships between communication and control in the workplace. digital.library.unt.edu/ark:/67531/metadc38898/
[Review] Computational Inorganic and Bioinorganic Chemistry
This book review discusses 'Computational Inorganic and Bioinorganic Chemistry', edited by Edward I. Solomon from Stanford University, Robert A. Scott from the University of Georgia Athens, and R. Bruce King from the University of Georgia Athens. digital.library.unt.edu/ark:/67531/metadc107784/
[Review] Deciphering the Chemical Code: Bonding Across the Periodic Table
This book review discusses 'Deciphering the Chemical Code: Bonding Across the Periodic Table' by Nicolaos D. Epiotis from the University of Washington. The reviewer describes the work as a new theoretical framework for describing chemical bonding and gives specific information on what's covered in the book, the themes, and ideal audiences. digital.library.unt.edu/ark:/67531/metadc107796/
[Review] Infinite Nature
This book review discusses 'Infinite Nature', by R. Bruce Hull. Hull's book dissolves dichotomous positions by portraying a plurality of views about nature and relations between human communities and their environments. digital.library.unt.edu/ark:/67531/metadc97954/
[Review] Nexus of Empire: Negotiating Loyalty and Identity in the Revolutionary Borderlands
This book review discusses 'Nexus of Empire: Negotiating Loyalty and Identity in the Revolutionary Borderlands' edited by Gene Allen Smith and Sylvia L. Hilton. The book examines the individuals who inhabited the Gulf of Mexico regions, analyzing the ways in which these people defined and redefined themselves amid a world of competing loyalties. digital.library.unt.edu/ark:/67531/metadc39329/
[Review] Tempting Fate: The Ethics of Dual-Use Research
This review is of the book Tempting Fate: The Ethics of Dual-Use Research by Seumas Miller and Michael J. Selgelid. The dual-use dilemma, which Miller and Selgelid argue arises from the fact that "one and the same piece of scientific research sometimes has the potential to be used for harm as well as for good". digital.library.unt.edu/ark:/67531/metadc77221/
The Rhetoric of Democracy and War on Terror: The Case of Pakistan
This article discusses the rhetoric of democracy on the war on terror. It offers a brief analysis of United States (U.S.) policy toward Pakistan during the last days of General Pervez Husharraf's unconstitutional regime. digital.library.unt.edu/ark:/67531/metadc146590/
RICHEST - a web server for richness estimation in biological data
This article discusses RICHEST, a web server for richness estimation in biological data. Richness is defined as the number of distinct species or classes in a sample or population. Although richness estimation is an important practice, it requires mathematical and computational methods that are challenging to understand and implement. The authors have developed a web server, RICHness ESTimator (RICHEST), which implements three non-parametric statistical methods for richness estimation. Its user-friendly web interface allows users to analyze and compare their data conveniently over the web. digital.library.unt.edu/ark:/67531/metadc77159/
Riddarhyttan City Motif
First page of The Hexagon of Alpha Chi Sigma. The blue cover features a black and white drawing of a medieval knight wearing mail and a tunic with a cross motif. He is holding a shield that bears the image of a stone building with flames shooting out of the roof. The word "Riddarhyttan" appears on a banner above the knight's head. Two photographs are arranged to the left of the knight, with text and an image of a computer mouse to the right. The next page includes a table of contents, an editorial, and a list of contributors. Near the bottom of this second page is a piece labeled "On the Cover," which describes the previous page. digital.library.unt.edu/ark:/67531/metadc111192/
Ring of Fire
Front cover of the fall 2012 issue of The Hexagon, which features an image of the "ring of fire" that occurred during the annular eclipse on May 20, 2012. The photograph was taken in Brownfield, Texas a few minutes before sunset. The inside cover contains a table of contents, a staff list, an editorial, and details about the cover photograph. digital.library.unt.edu/ark:/67531/metadc130205/
The road to biocultural ethics
This article discusses the road to biocultural ethics. As a child, Ricardo Rozzi visited indigenous communities in the high Andes with his grandfather and was enchanted by their close relationship with the natural world. Later, he and his wife would return to the region to explore the traditional ecological knowledge of the world's southernmost indigenous people. digital.library.unt.edu/ark:/67531/metadc130193/
Role of Hypoxia in the Evolution and Development of the Cardiovascular System
This article discusses the role of hypoxia in the evolution and development of the cardiovascular system. How multicellular organisms obtain and use oxygen and other substrates has evolved over hundreds of millions of years in parallel with the evolution of oxygen-delivery systems. A steady supply of oxygen is critical to the existence of organisms that depend on oxygen as a primary source of fuel (i.e., those that live by aerobic metabolism). Not surprisingly, a number of mechanisms have evolved to defend against oxygen deprivation. This review highlights evolutionary and developmental aspects of O(2) delivery to allow understanding of adaptive responses to O(2) deprivation (hypoxia). First, the authors consider how the drive for more efficient oxygen delivery from the heart to the periphery may have shaped the evolution of the cardiovascular system, with particular attention to the routing of oxygenated and deoxygenated blood in the cardiac outlet. Then the authors consider the role of O(2) in the morphogenesis and the cardiovascular system of animals of increasing size and complexity. The authors conclude by suggesting areas for future research regarding the role of oxygen deprivation and oxidative stress in the normal development of the heart and vascular or in the pathogenesis of congenital heart defects. digital.library.unt.edu/ark:/67531/metadc115191/
Ruthenium(II)-Mediated Carbon-Carbon Bond Formation between Acetonitrile and Pyrrole: Combined Experimental and Computational Study
This article discusses ruthenium(II)-mediated carbon-carbon bond formation between acetonitrile and pyrrole. The reaction of TpRu(CO)(NCMe)(Me) (1) and pyrrole forms TpRu(CO) {κ2-N,N-(H)N = C(Me)(NC4H3)} (2). The formation of complex 2 involves the cleavage of the N-H bond and 2-position C-H bonds of pyrrole as well as a C-C bond forming step between pyrrole and the acetonitrile ligand of 1. Mechanistic studies indicate that the most likely reaction pathway involves initial metal-mediated N-H activation of pyrrole to produce TpRu(CO)(N-pyrrolyl)-(NCMe) (3) followed by C-C bond formation and proton transfer. Complex 3 has been independently prepared and demonstrated to convert to 2. Computational studies support the suggested selectivity for initial N-H bond cleavage in preference to C-H bond activation. digital.library.unt.edu/ark:/67531/metadc77184/
Salman Rushdie: Reading the Postcolonial Texts in the Era of Empire
This article discusses Salman Rushdie and reading the postcolonial texts in the era of empire. Using the first three novels of Salman Rushdie, this essay articulates a different conceptual framework for reading the postcolonial texts. It is a known fact that in most metropolitan readings of the global periphery, the text is made to stand in for an entire culture. Inundation, a technique introduced in this essay, ensures a more complex reading by inserting silenced knowledge and histories in our reading to challenge any reductive representations of the global periphery. An inundated text, the author suggests, becomes a better tool in teaching the complexities of the postcolony to the metropolitan audiences, while also taking the reader beyond the politics of representation. It is hoped that this essay will invite other scholars to expand on this concept (inundation), for a new mode of reading is absolutely necessary in the politically charged world of today's empire. digital.library.unt.edu/ark:/67531/metadc146589/
Scaling Breakdown: A Signature of Aging
In this article, the authors prove that the Lévy walk is characterized by bilinear scaling. This effect mirrors the existence of a form of aging that does not require the adoption of nonstationary conditions. digital.library.unt.edu/ark:/67531/metadc67630/
Scaling Detection in Time Series: Diffusion Entropy Analysis
This article discusses scaling detection in time series. The methods currently used to determine the scaling exponent of a complex dynamic process described by a time series are based on the numerical evaluation of variance. This means that all of them can be safely applied only to the case where ordinary statistical properties hold true even if strange kinetics are involved. The authors illustrate a method of statistical analysis based on the Shannon entropy of the diffusion process generated by the time series, called diffusion entropy analysis (DEA). The authors adopt artificial Gauss and Lévy time series, as prototypes of ordinary and anomalous statistics, respectively, and the authors analyze them with the DEA and four ordinary methods of analysis, some of which are very popular. The authors show that the DEA determines the correct scaling exponent even when the statistical properties, as well as the dynamic properties, are anomalous. The other four methods produce correct results in the Gauss case but fail to detect the correct scaling in the case of Lévy statistics. digital.library.unt.edu/ark:/67531/metadc67632/
Scanning tunneling microscopy of the electronic structure of chemical vapor deposited diamond films
This article discusses scanning tunneling microscopy of the electronic structure of chemical vapor deposited diamond films. Scanning tunneling microscopy has been used to characterize the electronic structure and surface morphology of diamond films grown using the hot filament and microwave plasma chemical vapor deposition techniques. The authors observe a significant difference between the current-voltage (I-V) curves for the two types of films. The I-V curves for the hot-filament grown films are characterized by a well-defined zero-current region from which a surface band gap of 4.1 eV is measured. The I-V curves for the microwave plasma grown films exhibit a rectifying behavior which can be modeled by surface band bending. The authors compare the surface density of states obtained from the I-V curves with those obtained from x-ray photoelectron and appearance potential spectroscopies. digital.library.unt.edu/ark:/67531/metadc84361/
Scanning Tunneling Microscopy Studies of Temperature-Dependent Etching of Diamond (100) by Atomic Hydrogen
In this article, the authors present a technique for obtaining atomic resolution ultrahigh vacuum scanning tunneling microscopy images of diamond (100) films by atomic hydrogen. The authors find that etching by atomic hydrogen is highly temperature dependent, resulting in a rough and pitted surface at T ≈ 200 and 500˚C, respectively. At T ≈ 1000˚C etching results in a smooth surface and is highly anisotropic, occurring predominantly in the direction of dimer rows. This observation supports recent theoretical models that propose anisotropic etching as the mechanism for the growth of smooth diamond (100) films. digital.library.unt.edu/ark:/67531/metadc84157/
Science: For Science's or Society's Sake? Owning the National Science Foundation's Broader Impacts Criterion
This article describes changes in the U.S. National Science Foundation's (NSF) merit review criteria. The authors argue that scientists are more likely to preserve their autonomy by embracing - or 'owning' - the new Broader Impacts Criterion rather than resisting it. digital.library.unt.edu/ark:/67531/metadc86186/
Selection of Ionic Liquid Solvents for Chemical Separations Based on the Abraham Model
This book chapter discusses the selection of ionic liquid solvents for chemical separations based on the Abraham model. digital.library.unt.edu/ark:/67531/metadc155624/
Selectivity and Mechanism of Hydrogen Atom Transfer by an Isolable Imidoiron (III) Complex
This article discusses the selectivity and mechanism of hydrogen atom transfer by an isolable imidoiron (III) complex. In the literature, iron-oxo complexes have been isolated and their hydrogen atom transfer (HAT) reactions have been studied in detail. Iron-imido complexes have been isolated more recently, and the community needs experimental evaluations of the mechanism of HAT from late-metal imido species. The authors report a mechanistic study of HAT by an isolable iron (III) imido complex, LᴹᵉFeNAd (Lᴹᵉ = bulky β-diketiminate ligand, 2,4-bis(2,6-diisopropylphenylimido)pentyl; Ad = 1-adamantyl). HAT is preceded by binding of tert-butylpyridine (ᵗBupy) to form a reactive four-coordinate intermediate LᴹᵉFe(NAd)(ᵗBupy), as shown by equilibrium and kinetic studies. In the HAT step, very large substrate H/D kinetic isotope effects around 100 are consistent with C-H bond cleavage. The elementary HAT rate constant is increased by electron-donating groups on the pyridine additive, and by a more polar medium. When combined with the faster rate of HAT from indene versus cyclohexadiene, this trend is consistent with H⁺ transfer character in the HAT transition state. The increase in HAT rate in the presence of ᵗBupy may be explained by a combination of electronic (weaker Fe=N π-bonding) and thermodynamic (more exothermic HAT) effects. Most importantly, HAT by these imido complexes has a strong dependence on the size of the hydrocarbon substrate. This selectivity comes from steric hindrance by the spectator ligands, a strategy that has promise for controlling the regioselectivity of these C-H bond activation reactions. digital.library.unt.edu/ark:/67531/metadc107786/
A self-adaptive burst-detection algorithm
This article accompanies a poster presentation on a self-adaptive burst-detection algorithm. A self-adaptive, time-scale invariant single-unit spike train analysis technique is introduced to detect burst firings in neurons. This burst-detection method is an adaptive algorithm that uses the characteristic firing patterns statistics within and between bursts to identify the inter-burst period, intra-burst period and burst duration. digital.library.unt.edu/ark:/67531/metadc122157/
Senda Darwin Biological Station: Long-term ecological research at the interface between science and society
This article discusses Senda Darwin Biological Station (SDBS). SDBS is a field research center immersed in the rural landscape of northern Chiloé island (42°S), where remnant patches of the original evergreen forests coexist with open pastures, secondary successional shrublands, Sphagnum bogs, Eucalyptus plantations and other anthropogenic cover types, constituting an agricultural frontier similar to other regions in Chile and Latin America. Since 1994, the authors have conducted long-term research on selected species of plants (e.g., Pilgerodendron uviferum) and animals (e.g., Aphrastura spinicauda, Dromiciops gliroides) that are considered threatened, poorly known or important for their ecological functions in local ecosystems, and on ecosystems of regional and global relevance (e.g., Sphagnum bogs, North Patagonian and Valdivian rain forests). Research has assessed the responses of species and ecosystems to anthropogenic land-use change, climate change, and the impact of management. During this period, more than 100 scientific publications in national and international journals, and 30 theses (graduate and undergraduate) have been produced by scientists and students associated with SDBS. Because of the authors' understanding of the key role that humans play in ecological processes at this agricultural frontier, since the establishment of SDBS the authors have been committed to creative research on the communication of science to society and ecological education. The integration of SDBS to the nascent Chilean network of long-term socio-ecological research will consolidate and strengthen basic and applied research to project the authors' work into the next decade. digital.library.unt.edu/ark:/67531/metadc97945/
L-shell x-ray production cross sections for light ions on Sm, Yb, and Pb
This article discusses L-shell x-ray production cross sections for light ions on Sm, Yb, and Pb. L-shell x-ray production cross sections for the Ll, Lα₁,₂, Ly₁, and Ly₂,₃₍₆₎ have been measured for ¹H, ⁴He, and ⁷Li on Yb and Pb and for ⁴He and ⁷Li on Sm. The energy ranges for the incident-ion species were 0.3 to 2.4 MeV/amu for ¹H, 0.15 to 4.4 MeV/amu for ⁴He, and 0.9 to 3.0 MeV/amu for ⁷Li. Comparisons of the Lα₁,₂, Ly₁, and Ly₂,₃₍₆₎ x-ray production cross-section data have been made to the predictions of the plane-wave Born approximation (PWBA) and the PWBA with corrections for Coulomb deflection and/or binding-energy effects. The comparisons show that for the individual x-ray production cross sections, there are problems associated with the binding-energy correction calculations for the Ly₁ and Ly₂,₃ x-ray data. Furthermore, measurements of the ration of Lα₁,₂ to Ly₂,₃ x-ray intensities do not support the use of an increased effective binding energy in the PWBA formulation. digital.library.unt.edu/ark:/67531/metadc139486/
L-shell x-ray production cross sections of Ni, Cu, Ge, As, Rb, Sr, Y, Zr, and Pd by (0.25-2.5)-MeV protons
In this article, L-shell x-ray production cross sections by ₁¹H+ ions are reported. The data are compared to the first Born approximation (plane-wave Born approximation for direct ionization and Oppenheimer-Brinkman-Kramers approximation for electron capture) and to the ECPSSR (energy-loss and Coulomb-deflection effects, perturbed stationary-state approximation with relativistic correction) theory. The energy of the protons ranged from 0.25 to 2.5 MeV in steps of 0.25 MeV. The targets used in these measurements were ₂₈Ni, ₂₉Cu, ₃₂Ge, ₃₃As, ₃₇Rb, ₃₈Sr, ₃₉Y, ₄₀Zr, and ₄₆Pd. The first Born theory generally agrees with the data found in the literature at high energies and overpredicts them below 1.5 MeV. The ECPSSR predictions are in better agreement with experimental cross sections. At 0.25 MeV the authors' data, however, are underestimated by this theory and tend to agree with the first Born approximation. digital.library.unt.edu/ark:/67531/metadc139485/
Simultaneous measurement of the average ion-induced electron emission yield and the mean charge for isotachic ions in carbon foils
This article discusses simultaneous measurement of the average ion-induced electron emission yield and the mean charge for isotachic ions in carbon foils. Knowledge of the incident ion's atomic number (Z₁) dependence of ion-induced electron emission yields can be the basis for a general understanding of ion-atom interaction phenomena and, in particular, for the design of Z₁-sensitive detectors that could be useful, for example, in the separation of isobars in accelerator mass spectrometry. The Z₁ dependence of ion-induced electron emission yields, y, has been investigating using heavy ions C³⁺, O³⁺, F³⁺, Na³⁺, Al³⁺, Si³⁺, P³⁺, S³⁺, Cl³⁺, K³⁺, Ti³⁺, Cr³⁺, Mn⁴⁺, Fe⁴⁺, Co⁴⁺, Ni⁴⁺, Cu⁴⁺, Ga⁴⁺, As⁵⁺, Br⁵⁺, Ru⁷⁺, Ag⁷⁺, Sn⁷⁺, and I⁸⁺ of identical velocity (v = 2v₀, where v₀ is the Bohr velocity) normally incident on 50 μg/cm² sputter-cleaned carbon foils. Measured yields as a function of Z₁ reveal an oscillatory behavior with pronounced maxima and minima. Contrary to previously reported yields that assumed to monotonically increasing empirical mean charge state for the exiting ion, the present work indicates the Z₁ oscillations in the experimentally measured yields, a fact masked in previous work. The strong Z₁ oscillations can only be observed by simultaneous measurement of the yield and the mean charge state. digital.library.unt.edu/ark:/67531/metadc146596/
Single-Electron Oxidation of Monomeric Copper(I) Alkyl Complexes: Evidence for Reductive Elimination through Biomolecular Formation of Alkanes
This article discusses single-electron oxidation of monomeric copper(I) alkyl complexes. Monomeric Cu(I) alkyl complexes (NHC)Cu(R) (NHC = N-heterocyclic carbene; R = Me or Et) and (dtbpe)Cu(Me) (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane) have been prepared, isolated, and characterized. Single-electron oxidation of the Cu(I) alkyl complexes upon reaction with AgOTf to form putative Cu(II) intermediates of the type [(L)Cu(R)]+ (L = NHC or dtbpe, R = Me or Et) results in the rapid production of (L)Cu(X) (X = OTf) and R2. Experimental studies suggest that the reductive elimination of R2 from Cu(II) occurs through a nonradical bimolecular mechanism. Computational studies of the Cu-Cmethyl yield bond dissocation enthalpies of [(SIPr)Cu-CH3]n+ (80 kcal/mol for n = 0 {Cu(I)} and 38 kcal/mol for n = 1 {Cu(II)}). digital.library.unt.edu/ark:/67531/metadc77186/
Site correlation, anomalous diffusion, and enhancement of the localization length
This article discusses site correlation, anomalous diffusion, and enhancement of localization length. Herein the authors study the effects on Anderson localizations of correlations in the energy distribution of the sites of a tight-binding Hamiltonian. The lattice correlations are introduced are introduced by means of classical maps generating anomalous diffusion, that have recently been found to account for the correlated disorder of "biological" lattices. The authors show that the enhancement of localization length takes place on a much wider band of energies than in the case of the random-dimer model if the random walk on the site energies of the tight-binding Hamiltonian is determined by the joint action of short- and long-range correlations. digital.library.unt.edu/ark:/67531/metadc139487/
Six-, Five-, and Four-Coordinate Ruthenium(II) Hydride Complexes Supported by N-Heterocyclic Carbene Ligands: Synthesis, Characterization, Fundamental Reactivity, and Catalytic Hydrogenation of Olefins, Aldehydes, and Ketones
This article discusses six-, five-, and four-coordinate ruthenium(II) hydride complexes. The Ru(II) hydride complex (IMes)2Ru(Cl)(H)(CO) (1) {IMes = 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene} was synthesized from [Ru(CO)2Cl2]n and free IMes. Complex 1 rapidly reacts with CO to produce the cis-dicarbonyl Ru(II) complex (IMes)2Ru(Cl)(H)(CO)2 (2). The reaction of 1 with NaBAr'4 {Ar' = 3,5-(CF3)C6H3} produces the four-coordinate Ru(II) cationic complex [(IMes)2Ru(H)(CO)][BAr'4] (4), which can be trapped by two equivalents of tert-butylisonitrile to produce [(IMes)2Ru(H)(CO)(CNtBu)2][BAr'4] (5). Experimental and computational studies suggest that complex 4 is a diamagnetic system that adopts a sawhorse structure. The hydride ligand of complex 2 is readily displaced as dihydrogen upon reaction with HCI to produce (IMes)2Ru(CI)2(CO)2 (3). Both complex 1 and 4 were found to react with D2 (30 psi) at room temperature to produce the isotopomers (IMes)2Ru(CI)(D)(CO) (1-d1) and [(IMes)2Ru(D)(CO)][BAr'4] (4-d1), respectively, with the rate of formation of 4-d1 at least 28 times faster than the conversion of 1/D2 to 1-d1. In the presence of excess D2 complex 4 reversibly incorporates deuterium into the ortho methyl groups of the IMes ligands, whereas complex 1 does not show evidence of H/D exchange with the IMes ligands. Both 1 and 4 were found to catalyze the hydrogenation of olefins, ketones, and aldehydes. digital.library.unt.edu/ark:/67531/metadc77193/
Small Molecule Elimination from Group IVB (Ti, Zr, Hf) Amido Complexes
This article discusses small molecule elimination from group IVB (Ti, Zr, Hf) amido complexes. An ab initio quantum chemical analysis of HX (X = H, CH₃, Cl, NH₂, SiH₃) elimination by group IVB (Ti, Zr, Hf) amidos (H₂(X)M - NH₂ → H₂M = NH + HX), of interest in the context of CVD precursor design, is reported. Several deductions may be drawn from the calculations. First, in the transition state (TS) for HX elimination, electropositive and electroneutral X give rise to metal-transannular hydrogen (Ht) distances only slightly longer than normal metal-terminal hydride bonds lengths, while electronegative X groups yield substantially longer MHt distances. Second, the HX elimination barrier (∆Hǂelim) is lower when HX is polarized Hδ- • Hδ+ (X = SiH₃) or nonpolar (X = H). Third, a plot of calculated ∆Hǂelim versus MHt distances in the TS. Fourth, analysis of the electronic structure along the intrinsic reaction coordinate (IRC) supports the importance of N-H•••M agostic interactions preceding N-H scission. Fifth, the IRC shows the MHt distance decreasing as Ht is transferred from N to X, reaching a minimum when the transfer is roughly half complete, and then increasing once more is HX is eliminated. These results point to the leaving group (X) playing a crucial role in tuning the bonding the energetics of the TS, and thus the rate of HX elimination. The results lead to the conclusion that materials precursors designed to enhance MHt interaction, through the intermediacy of X, in the TS and along the reaction coordinate will lead to lower activation barriers to XH elimination. digital.library.unt.edu/ark:/67531/metadc107776/
Solar Turbulence in Earth's Global and Regional Temperature Anomalies
This article presents a study of the influence of solar activity on the earth's temperature. In particular, the authors focus on the repercussion of the fluctuations of the solar irradiance on the temperature of the Northern and Southern hemispheres as well as on land and ocean regions. While solar irradiance data are not directly analyzed, the authors make use of a published solar irradiance reconstruction for long-time-scale fluctuations, and for short-time-scale fluctuations the authors hypothesize that solar irradiance and solar flare intermittency are coupled in such a way that the solar flare frequency fluctuations are stochastically equivalent to those of the solar irradiance. The analysis is based upon wavelet multiresolution techniques and scaling analysis methods for processing time series. The limitations of the correlation analysis applied to the short-time-scale fluctuations are discussed. The scaling analysis uses both the standard deviation and the entropy of the diffusion generated by the temperature signals. The joint use of these two scaling methods yields evidence of a Levy component in the temporal persistence of the temperature fluctuations within the temporal range from a few weeks to a few years. This apparent Levy persistence of the temperature fluctuations is found, by using an appropriate model, to be equivalent to the Levy scaling of the solar flare intermittency. The mean monthly temperature data sets cover the period from 1856 to 2002. digital.library.unt.edu/ark:/67531/metadc67636/
Solubility of Anthracene in Binary Solvent Mixtures Containing Dibutyl Ether
This article discusses the solubility of anthracene in binary solvent mixtures containing dibutyl ether. Abstract: Experimental solubilities are reported for anthracene in binary solvent mixtures containing dibutyl ether with n-hexane, cyclohexane, n-heptane, methylcyclohexane, n-octane, isooctane, and cyclooctane at 25 °C. Results of these measurements, combined with estimates for the excess Gibbs free energies of the binary solvents, are used to test predictive expressions derived from the nearly ideal binary solvent (NIBS) model. Expressions based on a volume fraction average of solute properties in the two pure solvents predict anthracene solubilities to within a maximum deviation of 5.1% and an overall average deviation of 2.1%. digital.library.unt.edu/ark:/67531/metadc152449/
Solubility of Phenylacetic Acid in Binary Solvent Mixtures
This article discusses the solubility of phenylacetic acid in binary solvent mixtures. Abstract: Solubilities are reported for phenylacetic acid at 25.0 °C in binary mixtures of carbon tetrachloride with cyclohexane, n-heptane, n-octane, or isooctane and mixtures of cyclohexane with n-heptane or isooctane. The results are compared to the predictions of equations developed previously for solubility in systems of purely nonspecific interactions, with phenylacetic acid considered as either monomeric or dimeric molecules in solution. The dimer model provided the more accurate predictions and described the 15-fold range of solubilities in the carbon tetrachloride + isooctane system to within a maximum deviation of 15%. digital.library.unt.edu/ark:/67531/metadc152445/
Solubility of Pyrene in Binary Solvent Mixtures Containing Cyclohexane
This article discusses solubility of pyrene in binary solvent mixtures containing cyclohexane. Abstract: Solubilities are reported for pyrene at 26.0 °C in binary mixtures of cyclohexane with n-hexane, n-heptane, n-octane, isooctane, and cyclooctane. The results of these measurements are compared to the predictions of equations developed previously for solubility in systems of nonspecific interactions. The nearly ideal binary solvent (NIBS) model predicts these solubilities with a maximum deviation of 4.8%, using as input data the solubility of pyrene in each pure solvent. The NIBS model correctly predicts a small maxima for the mole fraction solubility of pyrene in cyclohexane + n-heptane mixtures. digital.library.unt.edu/ark:/67531/metadc152448/
Solubility of Pyrene in Binary Solvent Mixtures Containing Dibutyl Ether
This article discusses the solubility of pyrene in binary solvent mixtures containing dibutyl ether. Experimental solubilities are reported for pyrene in binary solvent mixtures containing dibutyl ether with n-hexane, cyclohexane, n-heptane, methylcyclohexane, n-octane, isooctane, and tert-butylcyclohexane at 26 °C. Results of these measurements, combined with estimates for the excess Gibbs free energies of the binary solvents, are used to test predictive expressions derived from the nearly ideal binary solvent (NIBS) model. Expressions based on a volume fraction average of solute properties in the two pure solvents predict pyrene solubilities to within a maximum deviation of 10% and an overall average deviation of 3.2%. digital.library.unt.edu/ark:/67531/metadc152453/
Spatial Distribution of Solutes in Aquifer Outcrop Zones along the Brazos River, East-Central Texas
This articles discusses the spatial distribution of solutes in Aquifer outcrop zones along the Brazos River in east-central, Texas. Concentrations of several solutes - nitrate, arsenic, sulfate, boron, chloride, and bromide - along with total dissolved solids (TDS) in ten counties bordering the Brazos River in east-central, Texas were compiled, mapped, and analyzed relative to regional land use and geology. Agriculture and oil/gas production are major activities and potential sources of groundwater contamination in the study area. Data were compiled from 104 water wells with a median depth of 446 ft (136 m) in the outcrop zones of six sedimentary aquifers: Carizzo-Wilcox, Queen City, Sparta, Yegua-Jackson, Gulf Coast, and Brazos Alluvium. Only two observations surpassed the 44.3 mg/L drinking water standard for nitrate, and four observations exceeded the 10 ug/L standard for arsenic. The median chloride concentration was 53 mg/L; however, the maximum level was almost three times the secondary drinking water standard of 250 mg/L. Chloride, bromide, sulfate, and boron concentrations resembled TDS patterns, with numerous samples exceeding secondary TDS drinking water standards in the Yegua-Jackson Aquifer. Most chloride/bromide ratios were between 100 and 300. Overall, results of this study suggest that natural processes exert a primary control on solute concentrations in the above aquifers, with a potential for modest anthropogenic impacts from agriculture and oil/gas production. digital.library.unt.edu/ark:/67531/metadc152433/