- Nanotubes in Microwave Fields: Light Emission, Intense Heat, Outgassing, and Reconstruction
- This article discusses nanotubes in microwave fields. Single-walled carbon nanotubes (SWNTs) exhibit diverse and unique properties. Recently, a surprising feature has been the ignition of nanotubes in the presence of an ordinary camera flash. Here, the authors report that SWNTs, produced via the HiPco process, display strong microwave absorption (1.01 x 10⁻⁵ eV microwave field) with subsequent dramatic light emission, intense heat release, outgassing, and nanotube reconstruction. digital.library.unt.edu/ark:/67531/metadc84367/
- Neural correlates of derived relational responding on tests of stimulus equivalence
- This article discusses neural correlates of derived relational responding on tests of stimulus equivalence. Background: An essential component of cognition and language involves the formation of new conditional relations between stimuli based upon prior experiences. Results of investigations on transitive inference (TI) highlight a prominent role for the medial temporal lobe in maintaining associative relations among sequentially arranged stimuli (A > B > C > D > E). In this investigation, medial temporal lobe activity was assessed while subjects completed "Stimulus Equivalence" (SE) tests that required deriving conditional relations among stimuli within a class (A ≡ B ≡ C). Methods: Stimuli consisted of six consonant-vowel-consonant triads divided into two classes (A1, B1, C1; A2, B2, C2). A simultaneous matching-to-sample task and differential reinforcement were employed during pretraining to establish the conditional relations A1:B1 and B1:C1 in class 1 and A2:B2 and B2:C2 in class 2. During functional neuroimaging, recombined stimulus pairs were presented and subjects judged (yes/no) whether stimuli were related. SE tests involved presenting three different types of within-class pairs: Symmetrical (B1 A1; C1 B1; B2 A2; C2 B2), and Transitive (A1 C1; A2 C2) and Equivalence (C1 A1; C2 A2) relations separated by a nodal stimulus. Cross-class 'Foils' consisting of unrelated stimuli (e.g., A1 C2) were also presented. Results: Relative to cross-class Foils, Transitive and Equivalence relations requiring inferential judgements elicited bilateral activation in the anterior hippocampus while Symmetrical relations elicited activation in the parahippocampus. Relative to each derived relation, Foils generally elicited bilateral activation in the parahippocampus, as well as in frontal and parietal lobe regions. Conclusion: Activation observed in the hippocampus to nodal-dependent derived conditional relations (Transitive and Equivalence relations) highlights its involvement in maintaining relational structure and flexible memory expression among stimuli within a class (A ≡ B ≡ C). digital.library.unt.edu/ark:/67531/metadc77156/
- The neuroprotective properties of palmitoylethanolamine against oxidative stress in a neuronal cell line
- This article discusses the neuroprotective properties of palmitoylethanolamine against oxidative stress in a neuronal cell line. Background: N-acylethanolamines (NAEs) are lipids upregulated in response to cell and tissue injury and are involved in cytoprotection. Arachidonylethanolamide (AEA) is a well characterized NAE that is an endogenous ligand at cannabinoid and vanilloid receptors, but it exists in small quantities relative to other NAE types. The abundance of other NAE species, such as palmitoylethanolamine (PEA), together with their largely unknown function and receptors, has prompted us to examine the neuroprotective properties and mechanism of action of PEA. The authors hypothesized that PEA protects HT22 cells from oxidative stress and activates neuroprotective kinase signaling pathways. Results: Indeed PEA protected HT22 cells from oxidative stress in part by mediating an increase in phosphorylated Akt (pAkt) and ERK 1/2 immunoreactivity as well as pAkt nuclear translocation. These changes take place within a time frame consistent with neuroprotection. Furthermore, the authors determined that changes in pAkt immunoreactivity elicited by PEA were not mediated by activation of cannabinoid receptor type 2 (CB2), thus indicating a novel mechanism of action. These results establish a role for PEA as a neuroprotectant against oxidative stress, which occurs in a variety of neurodegenerative diseases. Conclusions: The results from this study reveal that PEA protects HT22 cells from oxidative stress and alters the localization and expression levels of kinases known to be involved in neuroprotection by a novel mechanism. Overall, these results identify PEA as a neuroprotectant with potential as a possible therapeutic agent in neurodegenerative diseases involving oxidative stress. digital.library.unt.edu/ark:/67531/metadc122166/
- Nikolaikirche and Apotheke zum Bären, Berlin, Germany
- Front cover of volume 100, issue 1 of The Hexagon, featuring the multistory brick and stone church, Nikolaikirche. The church's first several floors are comprised of older stone work while the upper stories use newer red brick. People and vehicles are on the street near the church, and a row of buildings can be seen in the background to the left. The magazine's logo is printed over the church's bluish roof spires. The inside cover contains a table of contents, staff credits, and an editorial. digital.library.unt.edu/ark:/67531/metadc111235/
- Non-Markovian Nonstationary Completely Positive Open-Quantum-System Dynamics
- This article discusses non-Markovian nonstationary completely positive open-quantum-system dynamics. By modeling the interaction of a system with an environment through a renewal approach, the authors demonstrate that completely positive non-Markovian dynamics may develop some unexplored nonstandard statistical properties. The renewal approach is defined by a set of disruptive events, consisting in the action of a completely positive superoperator over the system density matrix. The random time intervals between events are described by an arbitrary waiting-time distribution. The authors show that, in contrast to the Markovian case, if one performs a system preparation (measurement) at an arbitrary time, the subsequent evolution of the density-matrix evolution is modified. The nonstationary character refers to the absence of an asymptotic master equation even when the preparation is performed at arbitrary long times. In spite this property, the authors demonstrate that operator expectation values and operators correlations have the same dynamical structure, establishing the validity of a nonstationary quantum regression hypothesis. The nonstationary property of the dynamics is also analyzed through the response of the system to an external weak perturbation. digital.library.unt.edu/ark:/67531/metadc40393/
- Non-Poisson Dichotomous Noise: Higher-Order Correlation Functions and Aging
- In this article, the authors study a two-state symmetric noise, with a given waiting time distribution ψ(τ), and focus their attention on the connection between the four-time and two-time correlation functions. The transition of ψ(τ) from the exponential to the nonexponential condition yields the breakdown of the usual factorization condition of high-order correlation functions, as well as the birth of aging effects. The authors discuss the subtle connections between these two properties and establish the condition that the Liouville-like approach has to satisfy in order to produce a correct description of the resulting diffusion process. digital.library.unt.edu/ark:/67531/metadc40403/
- Non-Poisson distribution of the time distances between two consecutive clusters of earthquakes
- This article discusses non-Poisson distribution of the time distances between two consecutive clusters of earthquakes. With the help of the Diffusion Entropy technique the authors show the non-Poisson statistics of the distances between consecutive Omori's swarms of earthquakes. The authors give an analytical proof of the numerical results of an earlier paper [Mega et al., Phys. Rev. Lett. 90 (2003) 188501]. digital.library.unt.edu/ark:/67531/metadc132976/
- Nucleation of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface
- In this article, the authors report the preferential nucleation and synthesis of β-FeSi2 nanostructures at pinned step bunches on the Si(111) surface. The nanostructures are synthesized by depositing Fe on Si at room temperature and subsequent annealing. The surface topography is studied using scanning tunneling microscopy and atomic force microscopy. The size, shape and orientation of the nanostructures indicate that the phase is the semiconducting β-FeSi2 phase. digital.library.unt.edu/ark:/67531/metadc84154/
- Octahedral [TpRu(PMe3)2OR]n+ Complexes (Tp = hydridotris(pyrazolyl)borate; R = H or Ph; n = 0 or 1): Reactions at Ru(II) and Ru(III) Oxidation States with Substrates that Possess Carbon-Hydrogen Bonds
- This article discusses octahedral [TpRu(PMe3)2OR]n+ Complexes (Tp = hydridotris(pyrazolyl)borate. The Ru(II) complexes TpRu(PMe3)2OR (R = H or Ph) react with excess phenylacetylene at elevated temperatures to produce the phenylacetylide complex TpRu(PMe3)2(C≡CPh). Kinetic studies indicate that the reaction of TpRu(PMe3)2OH and phenylacetylene likely proceeds through a pathway that involves TpRu(PMe3)2OTf as a catalyst. The reaction of TpRu(PMe3)2OH with 1,4-cyclohexadiene at elevated temperature forms benzene and TpRu(PMe3)2H, while TpRu(PMe3)2OPh does not react with 1,4-cyclohexadiene even after 20 days at 80 ˚C. The paramagnetic Ru(III) complex [TpRu(PMe3)2OH][OTf] is formed upon single-electron oxidation of TpRu(PMe3)2OH with AgOTf. Reactivity studies suggest that [TpRu(PMe3)2OH][OTf] initiates reactions, including hydrogen atom abstraction, with C-H bonds that have bond dissociation energy < 80 kcal/mol. Experimentally, the O-H bond strength of the Ru(II) cation [TpRu(PMe3)2(OH2)][OTf] is estimated to be between 82 and 85 kcal/mol, while computational studies yield a BDE of 84 kcal/mol, which are in reasonable agreement with the observed reactivity of [TpRu(PMe3)2OH]+. digital.library.unt.edu/ark:/67531/metadc77187/
- Olefin Substitution in (silox)3M(olefin) (silox = tBu3SiO; M = Nb, Ta): The Role of Density of States in Second vs Third Row Transition Metal Reactivity
- This article discusses the role of density of states in second vs third row transition metal reactivity. The substitution chemistry of olefin complexes (silox)3M(ole) (silox = tBu3SiO; M = Nb (1-ole), Ta (2-ole); ole = C2H4 (as 13C2H4 or C2D4), C2H3Me, C2H3Et, cis-2-C4H8, iso-C4H8, C2H3Ph, cC5H8, cC6H10, cC7H10 (norbornene)) was investigated. For 1-ole, substitution was dissociative (∆Gǂdiss), and in combination with calculated olefin binding free energies (∆G˚bind), activation free energies for olefin association (∆Gǂassoc) to (silox)3Nb (1) were estimated. For 2-ole, substitution was not observed prior to rearrangement to alkylidenes. Instead, activation free energies for olefin association to (silox)3Ta (2) were measured, and when combined with ∆G˚bind(calcd), estimates of olefin dissociation rates from 2-ole were obtained. Despite stronger binding energies for 1-ole vs 2-ole, the dissociation of olefins from 1-ole is much faster than that from 2-ole. The association of olefins to 1 is also much faster than that to 2. Linear free energy relationships (with respect to ∆G˚bind) characterize olefin dissociation from 1-ole, but not olefin dissociation from 2-ole, and olefin association to 2, but not olefin association to 1. Calculated transition states for olefin dissocation from (HO)3M(C2H4) (M = Nb, 1´-C2H4; Ta, 2´-C2H4) are asymmetric and have orbitals consistent with either singlet or triplet states. The rearrangement of (silox)3Nb(trans-Vy,Ph-cPr) to (silox)3Nb=CHCH=CHCH2CH2Ph (3) is consistent with a diradical intermediate akin to the transtion state for substitution. The disparity between Nb and Ta in olefin substitution chemistry is rationalized on the basis of a greater density of states (DOS) for the products (i.e., (silox)3M + ole) where M = Nb, leading to intersystem crossing events that facilitate dissociation. At the crux of the DOS difference is the greater 5dz2/6s mixing for Ta vs the 4dz2/5s mixing of Nb. This rationalization is generalized to explain the nominally swifter reactivities of 4d vs 5d elements. digital.library.unt.edu/ark:/67531/metadc77142/
- Oxygen Atom Transfer Energetics: Assessment of the Effect of Method and Solvent
- This article discusses oxygen atom transfer energetics. Several density functional methods, the semiempirical methods AM1 and PM3, Hartree-Fock, and Gaussian3 theories were applied to compute the oxygen atom transfer enthalpies for 14 X/XO couples (inorganic and organic systems, charged and neutral species, light and heavy main group element containing molecules). The calculated reaction enthalpies were compared to available experimental data. The G3 method alone was found to perform within the experimental error, while the popular B3LYP and BLYP functionals provided inadequate results. Solvent effects were estimated for 19 neutral and anionic X/XO couples by using the conductor-like polarizable continuum model and several cavity models coupled with the B3LYP/6-31++G-(2d,2p) level of theory. Surprisingly, the magnitude of the aqueous solvent correction was found to vary significantly for different solute cavity models, occasionally giving larger errors than the gas-phase calculation. digital.library.unt.edu/ark:/67531/metadc77147/
- Performance of Density Functional Theory for 3d Transition Metal-Containing Complexes: Utilization of the Correlation Consistent Basis Sets
- This article discusses the performance of density functional theory for 3d transition metal-containing complexes. The performance of 44 density functionals used in conjunction with the correlation consistent basis sets (ccpVnZ where n = T and Q) has been assessed for the gas-phase enthalpies of formation at 298.15 K of 3d transition metal (TM) containing systems. Nineteen molecules were examined: ScS, VO, VO₂, Cr(CO)₆, MnS, MnCl₂, Mn(CO)₅Cl, FeCl₃, Fe(CO)₅, CoH(CO)₄, NiCl₂, Ni(CO)₄, CuH, CuF, CuCl, ZnH, ZnO, ZnCl, and Zn(CH₃)₂. Of the functionals examined, the functionals that resulted in the smallest mean absolute deviation (MAD, in parentheses, kcal molˉ¹) from experiment were B97-1(6.9), PBE1KCIS (8.1), TPSS1KCIS (9.6), B97-2(9.7), and B98(10.7). All five of these functionals include some degree of Hartree-Fock (HF) exchange. The impact of increasing the basis set from cc-pVTZ to cc-pVQZ was found to be slight for the generalized gradient approximation (GGA) and meta-GGA (MGGA) functionals studied, indicating basis set saturation at the triple-ζ level. By contrast, for most of the generalized gradient exchange (GGE), hybrid GGA (HGGA), and hybrid meta-GGA (HMGGA) functionals considered, improvements in the average MAD of 2-3 kcal molˉ¹ were seen upon progressing to a quadruple-ζ level basis set. Overall, it was found that the functionals that include Hartree-Fock exchange performed best overall, but those with greater than 40% HF exchange exhibit significantly poor performance for the prediction of enthalpies of formation for 3d TM complexes. Carbonyl-containing complexes, a mainstay in organometallic TM chemistry, are demonstrated to be exceedingly difficult to describe accurately with all but 2 of the 44 functionals considered. The most accurate functional, for both CO-containing and CO-free compounds, is B97-1/cc-pVQZ, which is shown to be capable of yielding results within 1 kcal molˉ¹ of high-level ab initio composite methodologies. digital.library.unt.edu/ark:/67531/metadc109722/
- Performance of the correlation consistent composite approach for transition states: A comparison to G3B theory
- This article discusses performance of the correlation consistent composite approach for transition states. The correlation consistent composite approach (ccCA) was applied to the prediction of reaction barrier heights (i.e., transition state energy relative to reactants and products) for a standard benchmark set of reactions comprised of both hydrogen transfer reactions and nonhydrogen transfer reactions (i.e., heavy-atom transfer, Sn2, and unimolecular reactions). The ccCA method was compared against G3B for the same set of reactions. Error metrics indicate that ccCA achieves "chemical accuracy" with a mean unsigned error (MUE) of 0.89 kcal/mol with respect to the benchmark data for barrier heights; G3B has a mean unsigned error of 1.94 kcal/mol. Further, the greater accuracy of ccCA for predicted reaction barriers is compared to other benchmarked literature methods, including density functional (BB1K, MUE=1.16 kcal/mol) and wavefunction-based [QCISD(T), MUE=1.10 kcal/mol] methods. digital.library.unt.edu/ark:/67531/metadc77196/
- Power-Law Time Distribution of Large Earthquakes
- In this article, the authors study the statistical properties of time distribution of seismicity in California by means of a new method of analysis, the diffusion entropy. The authors find that the distribution of time intervals between a large earthquake (the main shock of a given seismic sequence) and the next one does not obey Poisson statistics, as assumed by the current models. The authors prove that this distribution is an inverse power law with an exponent μ = 2.06 ± 0.01. The authors propose the long-range model, reproducing the main properties of the diffusion entropy and describing the seismic triggering mechanisms induced by large earthquakes. digital.library.unt.edu/ark:/67531/metadc67639/
- A Priori Assessment of the Stereoelectronic Profile of Phosphines and Phosphites
- This article discusses research that has demonstrated the utility of a rigorously calibrated, molecular mechanics/semiempirical quantum mechanical protocol for developing stereoelectronic (Tolman) maps for phosphine ligands. A computational analysis of alkyl and aryl phosphines in common usage suggests that these ligands are quite similar stereoelectronically. A noticeable gap int he Tolman map for common phosphines is observed for large, electron-poor phosphines. Several candidates meeting these criteria were identified, the most promising of which is P(t-C₄F₉)₃. Phosphines in which the phosphorus participates in a ring, which comprise a very small subset of reported phosphines, have very interesting stereoelectronic properties, particularly those in which the ligating phosphorus is part of a three-membered ring. In terms of steric properties, the symmetric deformation coordinate proposed by Orpen and co-workers on the basis of crystallographic studies is calculated with sufficient accuracy using PM3(tm) to allow good confidence in predictions of novel phosphines. For quantification of the electronic properties of phosphines, the authors analyzed changes in the CO stretching frequency upon changing the ancillary phosphine ligands. digital.library.unt.edu/ark:/67531/metadc107782/
- Quantitative Computational Thermochemistry of Transition Metal Species
- This article discusses quantitative computational thermochemistry of transition metal species. The correlation consistent Composite Approach (ccCA), which has been shown to achieve chemical accuracy (±1 kcal mol⁻¹) for a large benchmark set of main group and s-block metal compounds, is used to compute enthalpies of formation for a set of 17 3d transition metal species. The training set includes a variety of metals, ligands, and bonding types. Using the correlation consistent basis sets for the 3d transition metals, the authors find that gas-phase enthalpies of formation can be efficiently calculated for inorganic and organometallic molecules with ccCA. However, until the reliability of gas-phase transition metal thermochemistry is improved, both experimentally and theoretically, a large experimental training set where uncertainties are near ±1 kcal mol⁻¹ (akin to commonly used main group benchmarking sets) remains an ambitious goal. For now, an average deviation of ±3 kcal mol⁻¹ appears to be the initial goal of "chemical accuracy" for ab initio transition metal model chemistries. The ccCA is also compared to a more robust but relatively expensive composite approach primarily utilizing large basis set coupled cluster computations. For a smaller training set of eight molecules, ccCA has a mean absolute deviation (MAD) of 3.4 kcal mol⁻¹ versus the large basis set coupled-cluster-based model chemistry, which has a MAD of 3.1 kcal mol⁻¹. However, the agreement for transition metal complexes is more system dependent than observed in previous benchmark studies of composite methods and main group compounds. digital.library.unt.edu/ark:/67531/metadc107799/
- Quantum Entanglement and Entropy
- This article discusses quantum entanglement and entropy. Entanglement is the fundamental quantum property behind the now popular field of quantum transport of information. This quantum property is incompatible with the separation of a single system into two uncorrelated subsystems. Consequently, it does not require the use of an additive form of entropy. The authors discuss the problem of the choice of the most convenient entropy indicator, focusing their attention on a system of two qubits, and on a special set, denoted by ℑ. This set contains both the maximally and partially entangled states that are described by density matrices diagonal in the Bell basis set. The authors select this set for the main purpose of making their work of analysis more straightforward. As a matter of fact, the authors find that in general the conventional von Neumann entropy is not a monotonic function of the entanglement strength. This means that the von Neumann entropy is not a reliable indicator of the departure from the condition of maximum entanglement. The authors study the behavior of a form of nonadditive entropy, made popular by the 1988 work by Tsallis [J. Stat. Phys. 52, 479 (1988)]. The authors show that in the set ℑ, implying the key condition of nonvanishing entanglement, this nonadditive entropy indicator turns out to be a strictly monotonic function of the strength of the entanglement, if entropy indexes q larger than a critical value Q are adopted. The authors argue that this might be a consequence of the nonadditive nature of the Tsallis entropy, implying that the world is quantum and that uncorrelated subsystems do not exist. digital.library.unt.edu/ark:/67531/metadc67627/
- Random Growth of Interfaces as a Subordinated Process
- In this article, the authors study the random growth of surfaces from within the perspective of a single column, namely, the fluctuation of the column height around the mean value, y(τ)=h(τ)-‹h(τ)›, which is depicted as being subordinated to a standard fluctuation-dissipation process with friction y. The authors argue that the main properties of Kardar-Parisi-Zhang theory, in one dimension, are derived by identifying the distribution of return times to y(0)=0, which is a truncated inverse power law, with the distribution of subordination times. The agreement of the theoretical prediction with the numerical treatment of the (1+1)-dimensional model of ballistic deposition is remarkably good, in spite of the finite-size effects affecting this model. digital.library.unt.edu/ark:/67531/metadc67637/
- Rapid Analysis of Legume Root Nodule Development Using Confocal Microscopy
- This article discusses the rapid analysis of legume root nodule development using confocal microscopy. A rapid method for detailed analysis of nodule formation has been developed. Inoculated root tissues were stained with SYTO 13, a cell-permeant fluorescent nucleic acid-binding dye, and visualized using confocal laser scanning microscopy (CLSM). Structures with high concentrations of DNA and RNA, such as plant cell nuclei and bacteria, labeled strongly. The autofluorescent properties of cell walls made it possible to use CLSM to visualize both plant and rhizobial structures and generate a three-dimensional reconstruction of the root and invading bacteria. This method allowed clear observation of stages and structures important in nodule formation, such as rhizobial attachment to root hairs, hair deformation, infection thread ramification, nodule primordium development and nodule cell invasion. Bacteroid structures were easily were easily assessed without the need for fixation that might alter cellular integrity. Plant nodulation mutants with phenotypic differences in thread growth, cellular invasion and plant defense response were also documented. Multiple samples can be assessed using detailed microscopy without the need for extensive preparative work, labor-intensive analysis, or the generation of genetically modified samples. digital.library.unt.edu/ark:/67531/metadc40415/
- Rational Design of Macrometallocyclic Trinuclear Complexes with Superior π-Acidity and π-Basicity
- This article discusses the rational design of macrometallocyclic trinuclear complexes with superior π-acidity and π-basicity. Density functional theory (DFT) has been used to assess the π-acidity and π-basicity of metal-organic trimetallic macromolecular complexes of the type [M(µ-L)]3, where M = Cu, Ag, or Au and L = carbeniate, imidazolate, pyridiniate, pyrazolate, or triazolate. The organic compounds benzene, triazole, imidazole, pyrazole, and pyridine were also modeled, and their substituent effects were compared to those of the coinage metal trimers. Our results, based on molecular electrostatic potential surfaces and positive charge attraction energy curves, indicate that the metal-organic macromolecules show superior π-acidity and -basicity compared to their organic counterparts. Moreover, the metal-organic cyclic trimers are found to exhibit π-acidity and -basicity that can be systematically tuned both coarsely and finely by judicious variation of the bridging ligand (relative π-basicity imidazolate > pyridiniate > carbeniate > pyrazolate > triazolate), metal (relative π-basicity Au > Cu > Ag), and ligand substituents. These computational findings are thus guiding experimental efforts to rationally design novel [M(µ-L)]3 materials for applications in molecular electronic devices that include metal-organic field-effect transistors and light-emitting diodes. digital.library.unt.edu/ark:/67531/metadc83330/
- Reactions of a Ru(II) Phenyl Complex with Substrates that Possess C-N or C-O Multiple Bonds: C-C Bond Formation, N-H Bond Cleavage, and Decarbonylation Reactions
- This article discusses reactions of a Ru(II) phenyl complex. The Ru(II) phenyl complex TpRu(CO)(NCMe)(Ph) (1) (Tp = hydridotris(pyrazolyl)borate) reacts with carbodiimides to yield amidinate complexes that result from C-C bond formation between the phenyl ligand and the carbodiimide carbon. Complex 1 and N-methylacetamide react to produce benzene and the amidate complex TpRu(CO){N,O-OC(Me)N(Me)} (4). The reaction of complex 1 with C≡N(tBu)}(Ph) (5), and heating a solution of PMe3 and 5 results in the observation of an equilibrium with the product of isonitrile insertion TpRu(CO){C(Ph)=NtBu}(PMe3) (6) (∆H = +9(1) kcal/mol and ∆S = +20(3)eu). The reaction of 1 with aromatic aldehydes at elevated temperatures results in C-H activation and decarbonylation of the aldehyde to produce TpRu(CO)2(Ar) (Ar = phenyl or p-tolyl) and free benzene. DFT calculations have been incorporated to study coordination and insertion reactions of ethylene, methyleneimine, formaldehyde, HC=C=NH, and C=NH into the Ru-Ph bond of the model fragment (Tab)Ru(CO)(Ph) (Tab = tris(azo)borate). In addition, the energetics of Ru-mediated decarbonylation of formaldehyde have been calculated. digital.library.unt.edu/ark:/67531/metadc77185/
- Reactions of TpRu(CO) (NCMe) (Me) (Tp = Hydridotris(pyrazolyl)borate) with Heteroaromatic Substrates: Stoichiometric and Catalytic C-H Activation
- This article discusses reactions of TpRu(CO)(NCMe)(Me) (Tp = Hydridotris(pyrazolyl)borate) with heteroaromatic substrates. The Ru(II) complex TpRu(CO)(NCMe)(Me) (Tp = hydridotris(pyrazolyl)borate) initiates carbon-hydrogen bond activation at the 2-position of furan and thiophene to produce methane and TpRu(CO)(NCMe)(aryl) (aryl = 2-furyl or 2-thienyl). Solid-state structures have been determined for TpRu(CO)(NCMe)(2-thienyl) and [TpRu(CO)(μ-C,S-thienyl)]2. The complex TpRu(CO)(NCMe)(2-furyl) serves as a catalyst for the formation of 2-ethylfuran from ethylene and furan. DFT calculations of the C-H activation of furan by {(Tab)Ru-(CO)(Me)} (Tab = tris(azo)borate) indicate that the C-H activation sequence does not proceed through a Ru(IV) oxidative addition intermediate. digital.library.unt.edu/ark:/67531/metadc77182/
- The Reactivity Patterns of Low-Coordinate Iron-Hydride Complexes
- This article discusses the reactivity patterns of low-coordinate iron-hydride complexes. The authors report a survey of the reactivity of the first isolable iron-hydride complexes with a coordiination number less than 5. The high-spin iron(II) complexes [(β-diketiminate)Fe(μ-H)]2 react rapidly with representative cyanide, isocyanide, alkyne, N2, alkene, diazene, azide, CO2, carbodilimide, and Brønsted acid containing substrates. The reaction outcomes fall into three categories: (1) addition of Fe-H across a multiple bond of the substrate, (2) reductive elimination of H2 to form iron(I) products, and (3) protonation of the hydride to form iron(II) products. The products include imide, isocyanide, vinyl, alkyl, azide, triazenido, benzo[c]cinnoline, amidinate, formate, and hydroxo complexes. These results expand the range of known bond transformations at iron complexes. Additionally, they give insight into the elementary transformations that may be possible at the iron-molybdenum cofactor of nitrogenases, which may have hydride ligands on high-spin, low-coordinate metal atoms. digital.library.unt.edu/ark:/67531/metadc77143/
- Rediscovery of the Elements: Agricola
- Article describing the career and discoveries of Georgius Agricola. Tourist information regarding locations important to his life are visited and discussed. digital.library.unt.edu/ark:/67531/metadc111206/
- Rediscovery of the Elements: Althofen, Austria and Auer von Welsbach
- Article recounting a visit to sites related to Baron Carl Auer von Welsbach, discoverer of lutetium and ytterbium and inventor of the incandescent "Welsbach mantle." Maps and tourist information are provided regarding the Welsbach Museum in Treibach, Austria. digital.library.unt.edu/ark:/67531/metadc111184/
- Rediscovery of the Elements: Aluminum
- Article describing the history of aluminum, from its use in alum to its isolation. Tourist information is given regarding locations pertinent to aluminum. digital.library.unt.edu/ark:/67531/metadc111212/
- Rediscovery of the Elements: Carl Wilhelm Scheele
- Article describing the career and discoveries of Carl Wilhelm Scheele. Tourist information regarding locations important to Scheele's life are visited and discussed. digital.library.unt.edu/ark:/67531/metadc111204/
- Rediscovery of the Elements: Courtois and Iodine
- Article describing the history of iodine, including its discovery by Bernard Courtois while during the production of saltpeter. Tourist information regarding pertinent locations is included. digital.library.unt.edu/ark:/67531/metadc111240/
- Rediscovery of the Elements: Europium. Eugène Demarcay
- Article describing Eugène Demarcay and his discovery of europium. The authors toured Paris, France, in search of locations important to Demarcay, providing the reader with maps and historical information regarding the sites. digital.library.unt.edu/ark:/67531/metadc111194/
- Rediscovery of the Elements: Fluorine
- Article describing the isolation of elemental fluorine. Tourist information is given regarding locations pertinent to the element's history. digital.library.unt.edu/ark:/67531/metadc111213/
- Rediscovery of the Elements: Gallium
- Article describing the discovery of the element gallium. The authors travel to sites pertinent to the history of gallium, including the home and laboratory of its discoverer and the location from which it was procured. digital.library.unt.edu/ark:/67531/metadc111187/
- Rediscovery of the Elements: Germanium
- Article recounting the history of the element Germanium, including background material on mining in Germany and the isolation of Germanium by Clemens A. Winkler. Tourist information is provided regarding Winkler's laboratory and mines open to the public as museums. digital.library.unt.edu/ark:/67531/metadc111177/
- Rediscovery of the Elements: Jáchymov (Joachimsthal), Czech Republic
- Article describing Jáchymov, Czech Republic, and its relation to radon. Tourist information is included for pertinent areas. digital.library.unt.edu/ark:/67531/metadc111230/
- Rediscovery of the Elements: Johann Wolfgang Döbereiner
- Article describing the life of Johann Wolfgang Döbereiner and his attempts to systematically organize the elements. Tourist information regarding locations significant to his history is included. digital.library.unt.edu/ark:/67531/metadc111218/
- Rediscovery of the Elements: Jöns Jakob Berzelius
- Article describing the life and career of Jöns Jakob Berzelius. Tourist information regarding locations significant to his history is included. digital.library.unt.edu/ark:/67531/metadc111219/
- Rediscovery of the Elements: Joseph Priestley
- Article describing the career and discoveries of Joseph Priestley. Tourist information regarding locations important to Priestley's life are visited and discussed. digital.library.unt.edu/ark:/67531/metadc111205/
- Rediscovery of the Elements: Klaproth
- Article describing the life and career of Martin Heinrich Klaproth, including his discoveries of uranium and zirconium. Tourist information regarding locations significant to his history is included. digital.library.unt.edu/ark:/67531/metadc111225/
- Rediscovery of the Elements: Mineral Waters and Spectroscopy
- Article describing the career of Robert Bunsen and the history of spectroscopy and its use in mineral analysis. The discovery of cesium and rubidium using spectroscopy on mineral water is included. In addition, the authors offer tourist information regarding locations pertinent to Bunsen and certain mineral water springs. digital.library.unt.edu/ark:/67531/metadc111227/
- Rediscovery of the Elements: Montpellier and Bromine
- Article recounting the history of the element Bromine, including its discovery in the salt lagoons of the Montpellier region of France by Antoine-Jérome Balard. Maps of the region and of Balard's birthplace are presented. digital.library.unt.edu/ark:/67531/metadc111178/
- Rediscovery of the Elements: Paracelsus
- Article describing the career and discoveries of Phillippus Aureolus Theophrastus Paracelsus Bombastus von Hohenheim. Tourist information regarding locations important to his life are visited and discussed. digital.library.unt.edu/ark:/67531/metadc111207/
- Rediscovery of the Elements: Phlogiston and Lavoisier
- Article describing the rise and fall of the eighteenth century idea of phlogiston. Tourist information is provided regarding pertinent areas of phlogiston's history. digital.library.unt.edu/ark:/67531/metadc111203/
- Rediscovery of the Elements: Phosphoro di Bologna
- Article recounting a visit to sites related to the discovery of phosphorescent stone (barium sulfide) in Bologna, Italy. Maps with driving directions are included. digital.library.unt.edu/ark:/67531/metadc111185/
- Rediscovery of the Elements: Riddarhyttan, Sweden
- Article describing the authors' tour through Riddarhyttan, Sweden, to visit the areas where cerium and cobalt were discovered. Maps and photographs of pertinent locations are located as well as a history of the area and the elements discovered there. digital.library.unt.edu/ark:/67531/metadc111193/
- Rediscovery of the Elements: Ruthenium
- Article describing the discovery of platinum in Russia and the history of ruthenium. Tourist information regarding sites pertinent to this history are included. digital.library.unt.edu/ark:/67531/metadc111238/
- Rediscovery of the Elements: Strontium
- Article describing the history of the element strontium from its discovery in Strontian, Scotland, to its early uses in English medicine. Maps with directions and photographs of pertinent locations are included. digital.library.unt.edu/ark:/67531/metadc111186/
- Rediscovery of the Elements: Tellurium and Fata Baii (Fascebanya), Romania.
- Article describing the discovery of the element tellurium. The authors travel through Romania to visit the Transylvanian mine where tellurium was discovered. They also visit the Brukenthal Museum of Sibiu and describe the museum's mineral collection. digital.library.unt.edu/ark:/67531/metadc111174/
- Rediscovery of the Elements: The Grand Tour
- Article advertising the release of "Rediscovery of the Elements" on DVD with additional information. digital.library.unt.edu/ark:/67531/metadc111229/
- Rediscovery of the Elements: The Periodic Table
- Article recounting the history of the development of the Periodic Table. Sites pertinent to this development were visited by the authors, who provide related tourist information. digital.library.unt.edu/ark:/67531/metadc111217/
- Rediscovery of the Elements: The Platinum Metals
- Article describing the history of the platinum metals, from its discovery in the New World and subsequent experiments in Europe. Tourist information is provided regarding areas pertinent to the history of platinum. digital.library.unt.edu/ark:/67531/metadc111236/
- Rediscovery of the Elements: The Road to Karlsruhe
- Article describing the history of atomic weight and the events leading up to the Karlsruhe Congress of chemists. The authors visited several sites pertinent to these events and offer tourist information. digital.library.unt.edu/ark:/67531/metadc111216/