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Articles 1 - 30 of 33
Full-Text Articles in Chemistry
Exploiting Self-Assembly For Ligand-Scaffold Optimization: Substrate-Tailored Ligands For Efficient Catalytic Asymmetric Hydroboration, Shin A. Moteki, James M. Takacs
Exploiting Self-Assembly For Ligand-Scaffold Optimization: Substrate-Tailored Ligands For Efficient Catalytic Asymmetric Hydroboration, Shin A. Moteki, James M. Takacs
James Takacs Publications
A self-assembled ligand library (SAL XY) affords a wide range of R/S ratios in Rh-catalyzed asymmetric hydroboration (nbd = 2,5norbornadiene, R* is a chiral substituent). Ligand-scaffold optimization reveals “substrate-tailored” ligands that afford high regio- and enantioselectivity for a variety of ortho-substituted styrene derivatives.
Includes article (4 pp.) and supporting information (106 pp.).
Fabrication Of Pillar-Structured Thermal Neutron Detectors, Rebecca J. Nikolić, Adam M. Conway, Catherine E. Reinhardt, Robert T. Graff, Tzu Fang Wang, Nirmalendu Deo, Chin Li Cheung
Fabrication Of Pillar-Structured Thermal Neutron Detectors, Rebecca J. Nikolić, Adam M. Conway, Catherine E. Reinhardt, Robert T. Graff, Tzu Fang Wang, Nirmalendu Deo, Chin Li Cheung
Barry Chin Li Cheung Publications
Pillar detector is an innovative solid state device structure that leverages advanced semiconductor fabrication technology to produce a device for thermal neutron detection. State-of-the-art thermal neutron detectors have shortcomings in achieving simultaneously high efficiency, low operating voltage while maintaining adequate fieldability performance. By using a 3-dimensional silicon PIN diode pillar array filled with isotopic boron 10, (10B) a high efficiency device is theoretically possible. The fabricated pillar structures reported in this work are composed of 2 μm diameter silicon pillars with a 4 μm pitch and pillar heights of 6 and 12 μm. The pillar detector with a …
Tris(Dialkylamino)Aluminums: Syntheses, Characterization, Volatility Comparison, And Atomic Layer Deposition Of Alumina Thin Films, Casey R. Wade, Carter Silvernail, Chiranjib Banerjee, Axel Soulet, James Mcandrew, John A. Belot Jr.
Tris(Dialkylamino)Aluminums: Syntheses, Characterization, Volatility Comparison, And Atomic Layer Deposition Of Alumina Thin Films, Casey R. Wade, Carter Silvernail, Chiranjib Banerjee, Axel Soulet, James Mcandrew, John A. Belot Jr.
Chemistry Department: Faculty Publications
The syntheses and characterization of both tris(diethylamino)aluminum and tris(diisopropylamino)aluminum are presented in this letter. Characterization includes vapor pressure measurements and comparison of the two non-pyrophoric precursors showing them to be viable alternatives to trimethylaluminum. Ultimately, tris(diisopropyl)aluminum was successful in the atomic layer deposition of alumina thin films.
Molecules That Target Beta-Amyloid, Cliff I. Stains, Kalyani Mondal, Indraneel Ghosh
Molecules That Target Beta-Amyloid, Cliff I. Stains, Kalyani Mondal, Indraneel Ghosh
Cliff Stains Publications
The devastating effects of Alzheimer’s and related amyloidogenic diseases have inspired the synthesis and evaluation of numerous ligands to understand the molecular mechanism of the aggregation of the beta-amyloid peptide. Our review focuses on the current knowledge in this field with respect to molecules that have been demonstrated to interact with either oligomeric or fibrillar forms of the beta-amyloid peptide. We describe natural proteins, peptides, peptidomimetics, and small molecules that have been found to interfere with beta-amyloid aggregation. We also detail recent efforts in selecting molecules that target beta-amyloid isolated from antibody, protein, and peptide libraries. These new molecules will …
A Set Of Phosphatase-Inert “Molecular Rulers” To Probe For Bivalent Mannose 6-Phosphate Ligand-Receptor Interactions, Xiang Fei, Christopher M. Connelly, Richard G. Macdonald, David B. Berkowitz
A Set Of Phosphatase-Inert “Molecular Rulers” To Probe For Bivalent Mannose 6-Phosphate Ligand-Receptor Interactions, Xiang Fei, Christopher M. Connelly, Richard G. Macdonald, David B. Berkowitz
David Berkowitz Publications
A set of bivalent mannose 6-phosphonate “molecular rulers” has been synthesized to examine ligand binding to the M6P/IGF2R. The set is estimated to span a P-P distance range of 16-26 Å (MMFF energy minimization on the hydrated phosphonates). Key synthetic transformations include sugar triflate displacement for phosphonate installation and Grubbs I cross-metathesis to achieve bivalency. Relative binding affinities were tested by radioligand displacement assays versus PMP-BSA (pentamannose phosphate-bovine serum albumin). These compounds exhibit slightly higher binding affinities for the receptor (IC50’s = 3.7-5 &#;M) than the parent, monomeric mannose 6-phosphonate ligand and M6P itself (IC50 = 11.5 …
Myricetin Inhibits Escherichia Coli Dnab Helicase But Not Primase, Mark A. Griep, Sheldon Blood, Marilynn A. Larson, Scott A. Koepsell, Steven H. Hinrichs
Myricetin Inhibits Escherichia Coli Dnab Helicase But Not Primase, Mark A. Griep, Sheldon Blood, Marilynn A. Larson, Scott A. Koepsell, Steven H. Hinrichs
Mark Griep Publications
Primase and DnaB helicase play central roles during DNA replication initiation and elongation. Both enzymes are drug targets because they are essential, persistent among bacterial genomes, and have different sequences than their eukaryotic equivalents. Myricetin is a ubiquitous natural product in plants that is known to inhibit a variety of DNA polymerases, RNA polymerases, reverse transcriptases, and telomerases in addition being able to inhibit kinases and helicases. We have shown that myricetin inhibits Escherichia coli DnaB helicase according to a mechanism dominated by noncompetitive behavior with a Ki of 10.0 ± 0.5 μM. At physiological ATP concentration, myricetin inhibits …
Synthesis And Characterization Of Novel Chiral Conjugated Materials, Andrzej Rajca, Makoto Miyasaka
Synthesis And Characterization Of Novel Chiral Conjugated Materials, Andrzej Rajca, Makoto Miyasaka
Andrzej Rajca Publications
Chirality is increasingly important in the design of organic π-conjugated materials. One of the aspects of the design involves optimization of achiral properties through the introduction of chirality. In this context, the inherent three-dimensional character of chirality and the control of intermolecular interactions associated with diastereomeric recognition provide a versatile handle for the optimization of supramolecular structures, film morphology and liquid crystalline order of π-conjugated polymers and oligomers in three dimensions. These inherently achiral properties have an impact on optoelectronic coupling, which may affect the fabrication of light-emitting diodes, field effect transistors, photodiodes, photovoltaic cells, fluorescent sensors and other devices. …
Structure And Thermophysical Properties Of Single-Wall Si Nanotubes, Xinwei Wang, Zhen Huang, Tao Wang, Yuk Wai Tang, Xiao Cheng Zeng
Structure And Thermophysical Properties Of Single-Wall Si Nanotubes, Xinwei Wang, Zhen Huang, Tao Wang, Yuk Wai Tang, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
In this work, molecular dynamics (MD) simulation based on the environment-dependent interatomic potential is carried out to explore the structure, atomic energy distribution, and thermophysical properties of single-wall Si nanotubes (SWSNTs). The unique structure of SWSNTs leads to a wider range energy distribution than crystal Si (c-Si), and results in a bond order in the range of 4.8~5. The thermal conductivity of SWSNTs is much smaller than that of bulk Si, and shows significantly slower change with their characteristic size than that of Si films. Out of the three types of SWSNTs studied in this work, pentagonal SWSNTs have the …
A Strategy To Protect And Sensitize Near-Infrared Luminescent Nd3+ And Yb3+: Organic Tropolonate Ligands For The Sensitization Of Ln3+-Doped Nayf4 Nanocrystals, Jian Zhang, Chad M. Shade, Demetra A. Chengelis, Stéphane Petoud
A Strategy To Protect And Sensitize Near-Infrared Luminescent Nd3+ And Yb3+: Organic Tropolonate Ligands For The Sensitization Of Ln3+-Doped Nayf4 Nanocrystals, Jian Zhang, Chad M. Shade, Demetra A. Chengelis, Stéphane Petoud
Chemistry Department: Faculty Publications
A strategy to sensitize and protect near-infrared (NIR) emitting Nd3+ and Yb3+ is presented. Combining protection provided by the inorganic matrix of NaYF4 nanocrystals and sensitization from tropolonate ligands capped on their surface, the lanthanide cation centered luminescence was observed through the ligand excitation. The extended lanthanide luminescence lifetimes indicate the success of this strategy.
1,3-Alternate Calix[4]Arene Nitronyl Nitroxide Tetraradical And Diradical: Synthesis, X-Ray Crystallography, Paramagnetic Nmr Spectroscopy, Epr Spectroscopy, And Magnetic Studies, Andrzej Rajca, Maren Pink, Sumit Mukherjee, Suchada Rajca, Kausik Das
1,3-Alternate Calix[4]Arene Nitronyl Nitroxide Tetraradical And Diradical: Synthesis, X-Ray Crystallography, Paramagnetic Nmr Spectroscopy, Epr Spectroscopy, And Magnetic Studies, Andrzej Rajca, Maren Pink, Sumit Mukherjee, Suchada Rajca, Kausik Das
Andrzej Rajca Publications
Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and 1H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for throughbond and through-space intramolecular exchange couplings.
Includes Supplemental Data (27 pages).
Quantum Confinement Of Crystalline Silicon Nanotubes With Nonuniform Wall Thickness: Implication To Modulation Doping, Binghai Yan, Xiao Cheng Zeng, Jian Wu, Bing-Lin Gu, Wenghui Duan
Quantum Confinement Of Crystalline Silicon Nanotubes With Nonuniform Wall Thickness: Implication To Modulation Doping, Binghai Yan, Xiao Cheng Zeng, Jian Wu, Bing-Lin Gu, Wenghui Duan
Xiao Cheng Zeng Publications
First-principles calculations of crystalline silicon nanotubes (SiNTs) show that nonuniformity in wall thickness can cause sizable variation in the band gap as well as notable shift in the optical absorption spectrum. A unique quantum confinement behavior is observed: the electronic wave functions of the valence band maximum and conduction band minimum are due mainly to atoms located in the thicker side of the tube wall. This is advantageous to spatially separate the doping impurities from the conducting channel in doped SiNTs. Practically, the performance of the SiNT-based transistors may be substantially improved by selective p/n doping in the thinner side …
Thermal Stability Of Nanostructurally Stabilized Zirconium Oxide, Fereydoon Namavar, Gonghua Wang, Chin Li Cheung, Renat F. Sabirianov, Xiao Cheng Zeng, Wai Ning Mei, Jaeil Bai, Joseph R. Brewer, Hani Haider, Kevin L. Garvin
Thermal Stability Of Nanostructurally Stabilized Zirconium Oxide, Fereydoon Namavar, Gonghua Wang, Chin Li Cheung, Renat F. Sabirianov, Xiao Cheng Zeng, Wai Ning Mei, Jaeil Bai, Joseph R. Brewer, Hani Haider, Kevin L. Garvin
Xiao Cheng Zeng Publications
Nanostructurally stabilized zirconium oxide (NSZ) hard transparent films were produced without chemical stabilizers by the ion beam assisted deposition technique (IBAD). A transmission electron microscopy study of the samples produced below 150 °C revealed that these films are composed of zirconium oxide (ZrO2) nanocrystallites of diameters 7.5 ± 2.3 nm. X-ray and selected-area electron diffraction studies suggested that the as-deposited films are consistent with cubic phase ZrO2. Rutherford backscattering spectroscopy (RBS) indicated the formation of stoichiometric ZrO2. The phase identity of these optically transparent NSZ films was in agreement with cubic ZrO2, …
Ab Initio Study Of Hydrogen Adsorption On Benzenoid Linkers In Metal–Organic Framework Materials, Yi Gao, Xiao Cheng Zeng
Ab Initio Study Of Hydrogen Adsorption On Benzenoid Linkers In Metal–Organic Framework Materials, Yi Gao, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
We have computed the energies of adsorption of molecular hydrogen on a number of molecular linkers in metal–organic framework solid materials using density functional theory (DFT) and ab initio molecular orbital methods. We find that the hybrid B3LYP (Becke three-parameter Lee–Yang–Parr) DFT method gives a qualitatively incorrect prediction of the hydrogen binding with benzenoid molecular linkers. Both local-density approximation (LDA) and generalized gradient approximation (GGA) DFT methods are inaccurate in predicting the values of hydrogen binding energies, but can give a qualitatively correct prediction of the hydrogen binding. When compared to the more accurate binding- energy results based on the …
The 14N Quadrupole Coupling In Hexamethylene Triperoxide Diamine (Hmtd), John Persons, Gerard S. Harbison
The 14N Quadrupole Coupling In Hexamethylene Triperoxide Diamine (Hmtd), John Persons, Gerard S. Harbison
Gerard Harbison Publications
Using high-field NMR, we have determined the magnitude of the nuclear quadrupole interaction in hexamethylene triperoxide diamine (HMTD), the explosive allegedly used in the London bombings of July 2005. The experimental quadrupolar coupling constant, 5.334 MHz, is in good agreement with quantum chemical calculations. The predicted single zero-field transition frequency should lie in a relatively empty part of the 14N nuclear quadrupole resonance (NQR) spectrum; the spin relaxation rate is reasonably fast.
Synthesis And Structural Characterization Of Two Five Coordinate Aluminum Alkyl And Bis(Trimethylsilyl)Amino Complexes Bearing Acyclic Tetradentate Schiff Bases, C. R. Wade, B. J. Lamprecht, V. W. Day, John A. Belot
Synthesis And Structural Characterization Of Two Five Coordinate Aluminum Alkyl And Bis(Trimethylsilyl)Amino Complexes Bearing Acyclic Tetradentate Schiff Bases, C. R. Wade, B. J. Lamprecht, V. W. Day, John A. Belot
Chemistry Department: Faculty Publications
Two acyclic Schiff-base ligands, bis-5,5′-(1,3-propanediyldiimino)-2,2-dimethyl-4-hexene-3-one and bis-5,5′-(1,3-ethanediyldiimino)- 2,2-dimethyl-4-hexene-3-one, were used to complex homoleptic triethylaluminum and tris[bis(trimethylsilyl)amino]alu minum, respectively. The acid–base reactions proceeded in excellent yields with elimination of ethane or bis(trimethylsilyl)amine during in situ deprotonation of the protio Schiff-base. The colorless aluminum complexes crystallized from n-pentane and were characterized by standard methods including single crystal X-ray diffraction. Polymerization of racemic lactide, with addition of alcohol, yielded PLA with narrow polydispersities but low molecular weights.
Exohedral Silicon Fullerenes: SiNPtN/2 (20≤N≤60), Yong Pei, Yi Gao, Xiao Cheng Zeng
Exohedral Silicon Fullerenes: SiNPtN/2 (20≤N≤60), Yong Pei, Yi Gao, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Using density functional theory method we show that hollow silicon fullerene cages, SiN(20≤N≤60), can be fully stabilized by exohedrally coated platinum atoms (PtN/2), denoted as SiNPtN/2. The exohedral coating PtN/2 passivates the dangling bonds of the silicon cages, thereby making the silicon cages SiN to retain the symmetry and structure of homologous carbon fullerenes CN. In particular, the Ih symmetrical, 60-atom silicon buckminsterfullerene cage (Si60) can be fully stabilized by exohedrally coated 30 Pt atoms. Properties of SiNPtN/2 …
Topoisomerase Ii-Drug Interaction Domains: Identification Of Substituents On Etoposide That Interact With The Enzyme, Amy M. Wilstermann, Ryan P. Bender, Murrell Godfrey, Sungjo Choi, Clemens Anklin, David B. Berkowitz, Neil Osheroff, David E. Graves
Topoisomerase Ii-Drug Interaction Domains: Identification Of Substituents On Etoposide That Interact With The Enzyme, Amy M. Wilstermann, Ryan P. Bender, Murrell Godfrey, Sungjo Choi, Clemens Anklin, David B. Berkowitz, Neil Osheroff, David E. Graves
David Berkowitz Publications
Etoposide is one of the most successful chemotherapeutic agents used for the treatment of human cancers. The drug kills cells by inhibiting the ability of topoisomerase II to ligate nucleic acids that it cleaves during the double-stranded DNA passage reaction. Etoposide is composed of a polycyclic ring system (rings A–D), a glycosidic moiety at the C4 position, and a pendant ring (E–ring) at the C1 position. Although drug-enzyme contacts, as opposed to drug-DNA interactions, mediate the entry of etoposide into the topoisomerase II-drug-DNA complex, the substituents on etoposide that interact with the enzyme have not been identified. Therefore, saturation transfer …
Linear, Redox Modified Dna Probes As Electrochemical Dna Sensors, Francesco Ricci, Rebecca Lai, Kevin W. Plaxco
Linear, Redox Modified Dna Probes As Electrochemical Dna Sensors, Francesco Ricci, Rebecca Lai, Kevin W. Plaxco
Rebecca Lai Publications
We show here that hybridization-linked changes in the dynamics of a redox-modified, electrode-bound linear (as opposed to stem-loop) probe DNA produce large changes in Faradaic current, allowing for the ready detection of target oligonucleotides.
Slow Turning Reveals Enormous Quadrupolar Interactions (Streaqi), John Persons, Gerard S. Harbison
Slow Turning Reveals Enormous Quadrupolar Interactions (Streaqi), John Persons, Gerard S. Harbison
Gerard Harbison Publications
We introduce a new solid-state NMR method, which uses very slow sample rotation to visualize NMR spectra whose width exceeds feasible spectrometer bandwidths. It is based on the idea that if we reorient a tensor by a known angle about a known axis, the shifts in the NMR frequencies observed across the spectral width allow us to reconstruct the entire tensor. Called STREAQI (Slow Turning Reveals Enormous Anisotropic Quadrupolar Interactions), this method allows us to probe NMR nuclei that are intractable to current methods. To prove the concept and demonstrate its promise we have implemented the method for several 79Br …
Classification Of Chemical Substances Using Particulate Representations Of Matter: An Analysis Of Student Thinking, Marilyne Stains, Vicente Talanquer
Classification Of Chemical Substances Using Particulate Representations Of Matter: An Analysis Of Student Thinking, Marilyne Stains, Vicente Talanquer
Chemistry Department: Faculty Publications
We applied a mixed-method research design to investigate the patterns of reasoning used by novice undergraduate chemistry students to classify chemical substances as elements, compounds, or mixtures based on their particulate representations. We were interested in the identification of the representational features that students use to build a classification system, and in the characterization of the thinking processes that they follow to group substances in different classes. Students in our study used structural and chemical composition features to classify chemical substances into elements, compounds, and mixtures. Many of the students’ classification errors resulted from strong mental associations between concepts (e.g., …
Surface Properties Of Licoo2, Linio2 And Lini1-XCoXO2, Anthony W. Moses, Harry G. Garcia Flores,, Jong-Gyu Kim, Marjorie Langell
Surface Properties Of Licoo2, Linio2 And Lini1-XCoXO2, Anthony W. Moses, Harry G. Garcia Flores,, Jong-Gyu Kim, Marjorie Langell
Marjorie A. Langell Publications
The surface composition and chemical environment of LiCoO2, hexagonal LiNiO2, cubic LiNiO2, and the mixed transition metal oxide LiNi0.5Co0.5O2 have been determined by Auger electron and X-ray photoelectron spectroscopies. While the LiCoO2 surface properties can easily be extrapolated from bulk composition, the nickel-containing materials are less straightforward. Their surface concentration tends to be depleted in lithium relative to that of the bulk and shows an atypical chemical environment for the constituent elements. The Ni 2p XPS photoemission suggests a near “ NiO-like” selvedge through the XPS binding energies …
Supporting Information For "The Molecular Basis Of High-Altitude Adaptation In Deer Mice", Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman
Supporting Information For "The Molecular Basis Of High-Altitude Adaptation In Deer Mice", Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman
Hideaki Moriyama Publications
Figure S1: Variation in Site-Specific Levels of Altitudinal Differentiation across the 5′ α- Globin Gene of P. maniculatus
Figure S2: Relationship between Pairwise Linkage Disequilibrium and Distance in bp
Genbank Accession Numbers
Table S1: Amino Acid Variation in the α-Globin Genes of High- and Low-Altitude Deer Mice: Amino acid replacement polymorphisms in deer mice where the derived variant is present at a frequency of >0.100 in the high-altitude sample.
Table S2: Additional Information on Sequenced Loci: Primer sequences for nuclear loci in P. maniculatus.
The Molecular Basis Of High-Altitude Adaptation In Deer Mice, Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman
The Molecular Basis Of High-Altitude Adaptation In Deer Mice, Jay F. Storz, Stephen J. Sabatino, Federico G. Hoffmann, Eben J. Gering, Hideaki Moriyama, Nuno Ferrand, Bruno Monteiro, Michael W. Nachman
Hideaki Moriyama Publications
Elucidating genetic mechanisms of adaptation is a goal of central importance in evolutionary biology, yet few empirical studies have succeeded in documenting causal links between molecular variation and organismal fitness in natural populations. Here we report a population genetic analysis of a two-locus a-globin polymorphism that underlies physiological adaptation to high-altitude hypoxia in natural populations of deer mice, Peromyscus maniculatus. This system provides a rare opportunity to examine the molecular underpinnings of fitness-related variation in protein function that can be related to a well-defined selection pressure. We surveyed DNA sequence variation in the duplicated α -globin genes of P. maniculatus …
Doping Golden Buckyballs: Cu@Au16- And Cu@Au17- Cluster Anions, Lei-Ming Wang, Satya S. Bulusu, Hua-Jin Zhai, Xiao Cheng Zeng, Wang
Doping Golden Buckyballs: Cu@Au16- And Cu@Au17- Cluster Anions, Lei-Ming Wang, Satya S. Bulusu, Hua-Jin Zhai, Xiao Cheng Zeng, Wang
Xiao Cheng Zeng Publications
The discovery of the unique catalytic effects of gold nanoparticles on oxide substrates[1] has stimulated a flurry of research into the structures and properties of free gold nanoclusters, which may hold the key to elucidating the catalytic mechanisms of supported gold clusters. One of the most remarkable results has been the discovery of planar gold cluster anions (Aun-) of up to twelve gold atoms and the 2D to 3D transition for clusters with n larger than 12.[2]– [4] Among larger gold clusters, Au20 has been found to be a perfect tetrahedron.[5] A more recent study of …
Molecular Dynamics Of Homogeneous Nucleation In The Vapor Phase Of Lennard-Jones. Iii. Effect Of Carrier Gas Pressure, Kenji Yasuoka, Xiao Cheng Zeng
Molecular Dynamics Of Homogeneous Nucleation In The Vapor Phase Of Lennard-Jones. Iii. Effect Of Carrier Gas Pressure, Kenji Yasuoka, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
A molecular dynamics simulation of vapor phase nucleation has been performed with 40 000 Lennard-Jones particles for the target gas and 0–160 000 particles for the carrier gas. Three carrier gas models are adopted, including a soft-core model, a Lennard-Jones model, and a modified Lennard-Jones model in which the attractive interaction can be adjusted. The effect of the carrier-gas pressure is assessed through computing and comparing the rate of nucleation and cluster size distribution. It is found that the effect of the carrier-gas pressure can be strongly dependent on the carrier-gas model. A positive effect _enhancement of the nucleation rate_ …
Hydrogen Storage In Pillared Li-Dispersed Boron Carbide Nanotubes, Xiaojun Wu, Yi Gao, Xiao Cheng Zeng
Hydrogen Storage In Pillared Li-Dispersed Boron Carbide Nanotubes, Xiaojun Wu, Yi Gao, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Ab initio density-functional theory study suggests that pillared Li-dispersed boron carbide nanotubes is capable of storing hydrogen with a mass density higher than 6.0 weight% and a volumetric density higher than 45 g/L. The boron substitution in carbon nanotube greatly enhances the binding energy of Li atom to the nanotube, and this binding energy (~ 2.7 eV) is greater than the cohesive energy of lithium metal (~1.7 eV), preventing lithium from aggregation (or segregation) at high lithium doping concentration. The adsorption energy of hydrogen on the Li-dispersed boron carbide nanotube is in the range of 10 – 24 kJ/mol, suitable …
Quantized Magnetoresistance In Atomic-Size Contacts, Andrei Sokolov, Chunjuan Zhang, Evgeny Y. Tsymbal, Jody G. Redepenning, Bernard Doudin
Quantized Magnetoresistance In Atomic-Size Contacts, Andrei Sokolov, Chunjuan Zhang, Evgeny Y. Tsymbal, Jody G. Redepenning, Bernard Doudin
Jody Redepenning Publications
When the dimensions of a metallic conductor are reduced so that they become comparable to the de Broglie wavelengths of the conduction electrons, the absence of scattering results in ballistic electron transport and the conductance becomes quantized. In ferromagnetic metals, the spin angular momentum of the electrons results in spin-dependent conductance quantization and various unusual magnetoresistive phenomena. Theorists have predicted a related phenomenon known as ballistic anisotropic magnetoresistance (BAMR). Here we report the first experimental evidence for BAMR by observing a stepwise variation in the ballistic conductance of cobalt nanocontacts as the direction of an applied magnetic field is varied. …
Effect Of Surrounding Point Charges On The Density Functional Calculations Of NiXOX Clusters (X = 4–12), Evgueni B. Kadossov, Karen J. Gaskell, Marjorie Langell
Effect Of Surrounding Point Charges On The Density Functional Calculations Of NiXOX Clusters (X = 4–12), Evgueni B. Kadossov, Karen J. Gaskell, Marjorie Langell
Marjorie A. Langell Publications
Embedded NixOx clusters (x = 4–12) have been studied by the density-functional method using compensating point charges of variable magnitude to calculate the ionic charge, bulk modulus, and lattice binding energy. The computations were found to be strongly dependent on the value of the surrounding point charge array and an optimum value could be found by choosing the point charge to reproduce the experimentally observed Ni–O lattice parameter. This simple, empirical method yields a good match between computed and experimental data, and even small variation from the optimum point charge value produces significant deviation between computed …
Examination Of The New Α-(2′Z-Fluoro)Vinyl Trigger With Lysine Decarboxylase: The Absolute Stereochemistry Dictates The Reaction Course, Kannan R. Karukurichi, Roberto De La Salud-Bea, Wan Jin Jahng, David B. Berkowitz
Examination Of The New Α-(2′Z-Fluoro)Vinyl Trigger With Lysine Decarboxylase: The Absolute Stereochemistry Dictates The Reaction Course, Kannan R. Karukurichi, Roberto De La Salud-Bea, Wan Jin Jahng, David B. Berkowitz
David Berkowitz Publications
The first examination of a terminal α-fluorovinyl trigger in an amino acid decarboxylase active site is reported. To investigate the enantiospecifity of inactivation with this new AADC trigger, an enantioselective synthesis of L-α-(2′Z-fluoro)vinyllysine and its D-antipode has been developed. Control of stereochemistry is achieved through introduction of the amino acid side chain via alkylation of a chiral vinylglycine-derived dienolate. Facial selectivity is conferred by a trans-2′(β- naphthyl)-2′-propylcyclohexyl ester auxiliary, available in both antipodal forms (Comins protocol). The alkylation employs a new electrophile, N-p-methoxybenzyl-N-(2′- trimethylsilylethanesulfonyl)-4-iodobutylamine, for convergent installation of the lysine side chain. Vinyl to 2′-fluorovinyl interconversion then provides L- …
Searching For Smart Durable Coatings To Promote Bone Marrow Stromal Cell Growth While Preventing Biofilm Formation, Fereydoon Namavar, John D. Jackson, J. Graham Sharp, Ethan E. Mann, Kenneth W. Bayles, Chin Li Cheung, Connie A. Feschuk, Shailaja Varma, Hani Haider, Kevin L. Garvin
Searching For Smart Durable Coatings To Promote Bone Marrow Stromal Cell Growth While Preventing Biofilm Formation, Fereydoon Namavar, John D. Jackson, J. Graham Sharp, Ethan E. Mann, Kenneth W. Bayles, Chin Li Cheung, Connie A. Feschuk, Shailaja Varma, Hani Haider, Kevin L. Garvin
Barry Chin Li Cheung Publications
There is a great need to develop methods to regulate cellular growth in order to enhance or prevent cell proliferation, as needed, to either improve health or prevent disease. In this work we evaluated the adhesion, survival and growth of bone marrow stromal cells on the surface of several new ion beam engineered nano-crystals of ceramic hard coatings such as zirconium, titanium, tantalum and cerium oxides. Cell adhesion and growth on the ceramic coatings were compared to adhesion and growth on a nano-crystalline silver coating which is known to possess antibacterial properties. The initial results of a study to determine …