bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationships Among Obesity, Inflammation, and Insulin Resistance in African Americans and West Africans
Authors: Doumatey Ayo P. , Lashley Kerrie S. , Huang Hanxia , Zhou Jie , Chen Guanjie , Amoah Albert , Agyenim‐Boateng Kofi , Oli Johnnie , Fasanmade Olufemi , Adebamowo Clement A. , Adeyemo Adebowale A. , Rotimi Charles N.
Published: October 2009

Several research studies in different populations indicate that inflammation may be the link between obesity and insulin resistance (IR). However, this relationship has not been adequately explored among African Americans, an ethnic group with disproportionately high rates of obesity and IR. In this study, we conducted a comparative study of the relationship among adiposity, inflammation, and IR in African Americans and West Africans, the ancestral source population for African Americans. The associations between obesity markers (BMI and waist‐to‐hip ratio (WHR)), inflammatory markers (high‐sensitivity C‐reactive protein (hsCRP), haptoglobin, interleukin (IL)‐6, and tumor necrosis factor (TNF)‐α), and IR (homeostasis model assessment of insulin resistance (HOMAIR)) were evaluated in 247 West Africans and 315 African Americans. In average, African Americans were heavier than the West Africans (by an average of 1.6 BMI units for women and 3 BMI units for men). Plasma hsCRP, haptoglobin, and IL‐6 (but not TNF‐α level) were higher in African Americans than in West Africans. In both populations, BMI was associated with markers of inflammation and with HOMAIR, and these associations remained significant after adjusting for sex and age. However, the pattern of associations between measured inflammatory markers and IR was different between the two groups. In West Africans, hsCRP was the only inflammatory marker associated with IR. In contrast, hsCRP, haptoglobin, and IL‐6 were all associated with IR in African Americans. Interestingly, none of the associations between markers of inflammation and IR remained significant after adjusting for BMI. This finding suggests that in African Americans, the relationship between inflammatory markers and IR is mediated by adiposity.
Synthesis of model morpholine derivatives with biological activities by laccase‐catalysed reactions
Authors: Hahn Veronika , Mikolasch Annett , Wende Kristian , Bartrow Hannelore , Lindequist Ulrike , Schauer Frieder
Published: October 2009

The efficient enzyme‐catalysed reaction of morpholines as model structures for bioactive compounds with para‐dihydroxylated aromatic systems was carried out using the oxidoreductase laccase and atmospheric oxygen to produce eight novel morpholine‐substituted aromatics. The laccase of Myceliophthora thermophila was used for cross‐linking morpholines containing primary or secondary amino groups with para‐dihydroxylated laccase substrates. We demonstrate that not only primary amino groups, but also secondary amino groups, are able to couple with para‐dihydroxylated aromatic systems in laccase‐catalysed reactions. The resulting model products (yields up to 80%) were isolated, structurally characterized and tested for their antibacterial, antifungal and cytotoxic activities. Four of the eight products showed low to moderate growth inhibition against several Gram‐positive and ‐negative bacterial strains and against the yeasts Candida maltosa and Candida albicans. The antibacterial and antifungal activities were determined by an agar disc diffusion test and a modified method according to the EUCAST discussion document E.Dis 7.1 [Rodríguez‐Tudela et al. (2003) Clin. Microbiol. Infect. 9, i–viii] for the evaluation of MIC (minimal inhibitory concentration). Differences in cytotoxicity against the human urinary bladder carcinoma cell line 5637 are discussed.
Mechanisms of double-strand break repair in somatic mammalian cells
Authors: Hartlerode Andrea J. , Scully Ralph
Published: October 2009

DNA chromosomal DSBs (double-strand breaks) are potentially hazardous DNA lesions, and their accurate repair is essential for the successful maintenance and propagation of genetic information. Two major pathways have evolved to repair DSBs: HR (homologous recombination) and NHEJ (non-homologous end-joining). Depending on the context in which the break is encountered, HR and NHEJ may either compete or co-operate to fix DSBs in eukaryotic cells. Defects in either pathway are strongly associated with human disease, including immunodeficiency and cancer predisposition. Here we review the current knowledge of how NHEJ and HR are controlled in somatic mammalian cells, and discuss the role of the chromatin context in regulating each pathway. We also review evidence for both co-operation and competition between the two pathways.
An allosteric transition trapped in an intermediate state of a new kinesin–inhibitor complex
Authors: Kaan Hung Yi Kristal , Ulaganathan Venkatasubramanian , Hackney David D. , Kozielski Frank
Published: October 2009

Human kinesin Eg5 plays an essential role in mitosis by separating duplicated centrosomes and establishing the bipolar spindle. Eg5 is an interesting drug target for the development of cancer chemotherapy, with seven inhibitors already in clinical trials. In the present paper, we report the crystal structure of the Eg5 motor domain complexed with a potent antimitotic inhibitor STLC (S-trityl-L-cysteine) to 2.0 Å (1 Å=0.1 nm) resolution. The Eg5–STLC complex crystallizes in space group P32 with three molecules per asymmetric unit. Two of the molecules reveal the final inhibitor-bound state of Eg5, whereby loop L5 has swung downwards to close the inhibitor-binding pocket, helix α4 has rotated by approx. 15 ° and the neck-linker has adopted a docked conformation. The third molecule, however, revealed an unprecedented intermediate state, whereby local changes at the inhibitor-binding pocket have not propagated to structural changes at the switch II cluster and neck-linker. This provides structural evidence for the sequence of drug-induced conformational changes.
Threonine at position 306 of the KAT1 potassium channel is essential for channel activity and is a target site for ABA-activated SnRK2/OST1/SnRK2.6 protein kinase
Authors: Sato Aiko , Sato Yuki , Fukao Yoichiro , Fujiwara Masayuki , Umezawa Taishi , Shinozaki Kazuo , Hibi Takao , Taniguchi Mitsutaka , Miyake Hiroshi , Goto Derek B. , Uozumi Nobuyuki
Published: October 2009

The Arabidopsis thaliana K+ channel KAT1 has been suggested to have a key role in mediating the aperture of stomata pores on the surface of plant leaves. Although the activity of KAT1 is thought to be regulated by phosphorylation, the endogenous pathway and the primary target site for this modification remained unknown. In the present study, we have demonstrated that the C-terminal region of KAT1 acts as a phosphorylation target for the Arabidopsis calcium-independent ABA (abscisic acid)-activated protein kinase SnRK2.6 (Snf1-related protein kinase 2.6). This was confirmed by LC-MS/MS (liquid chromatography tandem MS) analysis, which showed that Thr306 and Thr308 of KAT1 were modified by phosphorylation. The role of these specific residues was examined by single point mutations and measurement of KAT1 channel activities in Xenopus oocyte and yeast systems. Modification of Thr308 had minimal effect on KAT1 activity. On the other hand, modification of Thr306 reduced the K+ transport uptake activity of KAT1 in both systems, indicating that Thr306 is responsible for the functional regulation of KAT1. These results suggest that negative regulation of KAT1 activity, required for stomatal closure, probably occurs by phosphorylation of KAT1 Thr306 by the stress-activated endogenous SnRK2.6 protein kinase.
Structural and functional analysis of the intrinsic inhibitor subunit ϵ of F1-ATPase from photosynthetic organisms
Authors: Yagi Hiromasa , Konno Hiroki , Murakami-Fuse Tomoe , Isu Atsuko , Oroguchi Tomotaka , Akutsu Hideo , Ikeguchi Mitsunori , Hisabori Toru
Published: October 2009

The ε subunit, a small subunit located in the F1 domain of ATP synthase and comprising two distinct domains, an N-terminal β-sandwich structure and a C-terminal α-helical region, serves as an intrinsic inhibitor of ATP hydrolysis activity. This inhibitory function is especially important in photosynthetic organisms as the enzyme cannot synthesize ATP in the dark, but may catalyse futile ATP hydrolysis reactions. To understand the structure–function relationship of this subunit in F1 from photosynthetic organisms, we solved the NMR structure of the ε subunit of ATP synthase obtained from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1, and examined the flexibility of the C-terminal domains using molecular dynamics simulations. In addition, we revealed the significance of the C-terminal α-helical region of the ε subunit in determining the binding affinity to the complex based on the assessment of the inhibition of ATPase activity by the cyanobacterial ε subunit and the chimaeric subunits composed of the N-terminal domain from the cyanobacterium and the C-terminal domain from spinach. The differences observed in the structural and biochemical properties of chloroplast and bacterial ε subunits explains the distinctive characteristics of the ε subunits in the ATPase complex of the photosynthetic organism.
Establishment and characterization of two cell lines derived from primary cultures of Gekko japonicus cerebral cortex
Authors: Liu Mei , Gu Yun , Liu Yan , Li Jing , He Jianghong , Lin Sheyu , Gu Xiaosong
Published: October 2009

Adult Gekko japonicus is one of those vertebrates that are able to regenerate their missing or amputated tail. The most interesting feature of this animal lies in the ability of its spinal cord to regrow a functional tail. A fundamental question is whether the neuroglial cells play a different role compared with high vertebrates. Since in vitro studies using primary neuroglial cells are hampered by the limited lifespan and miscellaneous genetic background of these cells, we generated neuroglial cell lines from primary cell cultures of cerebral cortex of G. japonicus. The SV40 (simian‐virus‐40) T antigen gene was introduced into primary cell cultures. Cell cycle analysis, cell growth and proliferation, cell colony formation and contact inhibition, as well as karyotype assays were investigated. Two cell colonies, Gsn‐1 and Gsn‐3, were immunochemically characterized as glial fibrillary acidic protein and galactocerebroside‐positive respectively. Compared with parental primary cells, the Gsn cells displayed shorter population doubling time, decreased percentage of cells in the G0/G1 phase, higher cell proliferation index, and increased cell activity. In assays of colony characteristics, Gsn cells showed increased cell activity at the lower cell densities or FBS (fetal bovine serum) supplement. The karyotype of immortalized Gsn cells exhibited transformational characteristics with hyperdiploid and polyploid chromosomes. The cell lines will provide a useful in vitro model for gecko neuroglial cells and facilitate systematic studies investigating the biological functions of specific gene products related to regeneration of the central nervous system.
Cytoskeletal changes during cellular response of the A549 lung cancer cells to continuous cisplatin treatment
Authors: Szczepański Andrzej Mariusz , Grzanka Alina , Litwiniec Anna , Gackowska Lidia , Kubiszewska Izabela , Grzanka Dariusz
Published: October 2009

The cytoskeleton is a ubiquitous cellular structure that plays a crucial role in most processes of living cells. There are reports suggesting that this system not only reflects, but also contributes to many different processes, including cell death. In this study, we examined alterations of both MT and MF cytoskeletal systems related to cell death, which was induced in A549 cells by continuous cisplatin treatment. We observed that specific changes in these cytoskeletal proteins accompany cell death, while the others are associated with increased repair and cell survival. It seems that the predominant mode of cell death triggered by cisplatin was an apoptotic‐like pathway, but on the other hand, coincidence with some features of necrosis and autophagy was also demonstrated in our conditions.
Tag Clouds for Displaying Semantics: The Case of Filmscripts
Authors: Murtagh Fionn , Ganz Adam , McKie Stewart , Mothe Josiane , Englmeier Kurt
Published: October 2009

We relate tag clouds to other forms of visualization, including planar or reduced dimensionality mapping, and to Kohonen self-organizing maps. Using a modified tag cloud visualization, we incorporate other information into it, including text sequence and most pertinent words. Our notion of word pertinence goes beyond just word frequency and instead takes a word in a mathematical sense as located at the average of all of its pairwise relationships. We capture semantics through context, taken as all pairwise relationships. Our domain of application is that of filmscript analysis. The analysis of filmscripts, always important for cinema, is experiencing a major gain in importance in the context of television. Our objective in this paper is to visualize the semantics of filmscript, and beyond filmscript any other partially structured, time-ordered sequence of text segments. In particular, we develop an innovative approach to plot characterization.
A commutative algebra on degenerate CP1 and Macdonald polynomials
Authors: Feigin B. , Hashizume K. , Hoshino A. , Shiraishi J. , Yanagida S.
Published: October 2009

We introduce a unital associative algebra A associated with degenerate CP1. We show that A is a commutative algebra and whose Poincaré series is given by the number of partitions. Thereby, we can regard A as a smooth degeneration limit of the elliptic algebra introduced by Feigin and Odesskii [Int. Math. Res. Notices 11, 531 (1997)]. Then we study the commutative family of the Macdonald difference operators acting on the space of symmetric functions. A canonical basis is proposed for this family by using A and the Heisenberg representation of the commutative family studied by Shiraishi [ Commun. Math. Phys. 263, 439 (2006)]. It is found that the Ding–Iohara algebra [Lett. Math. Phys. 41, 183 (1997)] provides us with an algebraic framework for the free field construction. An elliptic deformation of our construction is discussed, showing connections with the Drinfeld quasi-Hopf twisting [Leningrad Math. J. 1, 1419 (1990)] in the sence of Babelon-Bernard–Billey [Phys. Lett. B. 375, 89 (1996)], the Ruijsenaars difference operator [Commun. Math. Phys. 110, 191 (1987)], and the operator M(q,t1,t2) of Okounkov–Pandharipande [e-print arXiv:math-ph/0411210].
Extending the detection limit of dopants for focused ion beam prepared semiconductor specimens examined by off-axis electron holography
Authors: Cooper David , Rivallin Pierrette , Hartmann Jean-Michel , Chabli Amal , Dunin-Borkowski Rafal E.
Published: October 2009

Silicon specimens containing p-n junctions have been prepared for examination by off-axis electron holography using focused ion beam (FIB) milling. FIB milling modifies the surfaces of the specimens due to gallium implantation and the creation of defects which has the effect of reducing the active dopant concentration measured during electrical characterization. Here we show that although this damage can be removed by using low temperature annealing, the presence of surface charge will modify the electrical potentials in the specimens and limit the dopant concentration that can be measured.
Development of a relaxation calorimeter for temperatures between 0.05 and 4 K
Authors: Brando M.
Published: October 2009

A detailed description of an isoperibol calorimeter for temperatures between 0.05 and 4 K is presented. The proposed setup can provide absolute values of the heat capacity C of small samples (typically 1 mg). The extremely simple design of the sample platform, based on a sapphire substrate, and the experimental setup, which makes use only of a lock-in amplifier and a temperature controller, make the construction of such a calorimeter easy and inexpensive. The thermal-relaxation method is employed, which utilizes a permanent thermal link k between the sample platform and the low-temperature bath. The temperature dependence of k(T) is shown for several platforms throughout the entire temperature range: k(T)/T is nearly constant down to 1 K, where it starts to decrease smoothly. The observed behavior is thoroughly explained by considering the thermal resistances of the platform constituents. A comparison between the values of k(T)/T for platforms based on sapphire and on silver is presented where no significant difference has been observed. Each platform can be assembled to have a particular value of k/T at 1 K. Since the sample relaxation time τ∼C/k, k(T) can be adjusted to C(T) to give a reasonably fast measuring time. Here, it is demonstrated how this calorimeter can be used in so-called single-shot refrigerators (H3e or demagnetization cryostats), where the time for a single measurement is limited. In addition, it can be used in moderate magnetic fields B≤10 T, because the platform constituents are weakly field dependent.
Hysteretic characteristics of low-field microwave absorption of a Co thin film
Authors: Lee S. J. , Tsai C. C. , Cho H. , Seo M. , Eom T. , Nam W. , Lee Y. P. , Ketterson J. B.
Published: October 2009

We have investigated the spin dynamics of a sputtered Co thin film using our broadband ferromagnetic resonance (FMR) spectrometer. From FMR spectra taken at frequencies of 4–20 GHz, we found that our Co film has a g-factor of 2.25 and a Gilbert damping factor of 4.5×108 s−1, indicating an enhanced spin-orbit interaction compared to bulk material or epitaxial films. Besides the normal FMR mode in the saturated state, we also observed the evolution of the low-field hysteretic behavior in the unsaturated state, which affects the FMR mode as the excitation frequency is lowered from 5.000 to 1.636 GHz. We found that the microwave absorption process persists in the unsaturated state for frequencies higher than 1.868 GHz such that the absorption minima occur at −12 Oe on a down-field sweep and at +12 Oe on a up-field sweep, respectively.
The influence of substrate temperature and Al mobility on the microstructural evolution of magnetron sputtered ternary Ti–Al–N thin films
Authors: Beckers M. , Höglund C. , Baehtz C. , Martins R. M. S. , Persson P. O. Å. , Hultman L. , Möller W.
Published: October 2009

Ternary Ti–Al–N films were deposited onto Al2O3 (0001) substrates by reactive cosputtering from elemental Ti and Al targets and analyzed by in situ and ex situ x-ray scattering, Rutherford backscattering spectroscopy, transmission electron microscopy, and x-ray photoemission spectroscopy. The deposition parameters were set to values that yield Ti:Al:N ratios of 2:1:1 and 4:1:3 at room temperature. 2TiAlN depositions at 675 °C result in epitaxial Ti2AlN growth with basal planes parallel to the substrate surface. Nominal 4TiAl3N depositions at 675 °C and above, however, yield domain growth of TiN and Ti2AlN due to Al loss to the vacuum. Depositions at a lower temperature of 600 °C yield films with correct 4:1:3 stoichiometry, but Ti4AlN3 formation is prevented, supposedly by insufficient adatom mobility. Instead, an incoherent Tin+1AlNn structure with random twinned stacking sequences n is obtained that exhibits both basal plane orientations parallel and nearly perpendicular to the substrate interface. X-ray photoemission spectroscopy shows that in contrast to stoichiometric nitrides the Al is metallically bonded and hence acts as twinning plane within the Tin+1AlNn stackings. Domains with perpendicular basal plane orientation overgrow those with parallel orientation in a competitive growth mode. The resulting morphology is a combination of smooth-surface parallel-basal-plane-oriented domains interrupted by repeated facetted hillocklike features with perpendicular basal plane orientation.
Phase transitions and electrical behavior of lead-free (K0.50Na0.50)NbO3 thin film
Authors: Wu Jiagang , Wang John
Published: October 2009

Lead-free (K0.50Na0.50)NbO3 (KNN) thin films with a high degree of (100) preferred orientation were deposited on the SrRuO3-buffered SrTiO3(100) substrate by off-axis radio frequency magnetron sputtering. They possess lower phase transition temperatures (To-t∼120 °C and Tc∼310 °C), as compared to those of KNN bulk ceramic (To-t∼190 °C and Tc∼400 °C). They also demonstrate enhanced ferroelectric behavior (e.g., 2Pr=24.1 μc/cm2) and fatigue endurance, together with a lower dielectric loss (tan δ∼0.017) and a lower leakage current, as compared to the bulk ceramic counterpart. Oxygen vacancies are shown to be involved in the conduction of the KNN thin film.
Silica structural changes induced by thermal treatment or ionic implantation as probed by IR reflectance spectroscopy
Authors: Bibent N. , Faivre A. , Ferru G. , Bantignies J.-L. , Peuget S.
Published: October 2009

Fourier transformed infrared microreflectance spectroscopy is used to probe and compare the consequences of thermal quenching or ionic implantation on the structure of silica. A linear change in the main structural feature associated with Si–O–Si vibration with fictive temperature (Tf) is observed up to Tf=1400 °C. Ionic implantation is shown to shift the frequency of the main IR Si–O–Si vibration toward much lower wavenumbers, for all deposited energies, indicating that a comparison can be drawn between fictive temperature and irradiation effects. Extrapolating the linear changes in the IR structural bands obtained as a function of Tf for the implanted samples, we show that two structural (νTO) and (νB) contributions are not affected by ionic implantation, as they would be by a unique very high Tf. In the case of ionic implantation, we also evidence the development of some specific structural contributions indicating a depolymerization of silica network.
Longitudinal thermal conductivity of radial nanowire heterostructures
Authors: Lü Xiang
Published: October 2009

Thermal conductivity of tubular nanowires and radial nanowire heterostructures is analytically modeled along the longitudinal direction by using Boltzmann transport equation. This work is on the basis of Dingle [Proc. R. Soc. London, Ser. A 201, 545 (1950)] and Lucas [J. Appl. Phys. 36, 1632 (1965)] formalisms on thin wires and films, respectively. To investigate the thermal conductivity dependence on the interface conditions, we have generalized Prasher’s analytical solution [Appl. Phys. Lett. 89, 063121 (2006)] to cover the case where the scattering events at the interfaces are not totally diffuse scattering. The calculation of the size-dependent thermal conductivity includes the partly diffuse and partly specular scatterings at both internal and external interfaces of the tubular nanowires. It is found that the calculated thermal conductivities are in good agreement with the numerical solution of Yang et al. [Nano Lett. 5, 1111 (2005)]. Comparison is also made with the thermal conductivity of thin films and solid nanowires with the same dimensions. Results show that the thermal conductivity of the structures can be modulated by changing the radius ratio between the shell layer and the core layer of the radial nanowire heterostructures. The obtained results may serve as a possible way for tuning the thermal conductivity in nanostructures.
Creation of storage centers in CsBr:Eu2+ needle image plates by vacuum ultraviolet radiation
Authors: Weidner M. , Batentschuk M. , Osvet A. , Winnacker A. , Tahon J. P. , Leblans P.
Published: October 2009

In this study, the photostimulated luminescence of the CsBr:Eu2+ needle image plates (NIPS) after vacuum ultraviolet (VUV) irradiation and their photoluminescence under VUV and UV excitation were investigated. It was shown that the photostimulable storage centers arise almost exclusively due to irradiation of the CsBr:Eu NIPs in the spectral lines of creation of the 4p55s anion excitons, and not in the region of interband transitions of CsBr. The explanation of the results is based mainly on the radiative and nonradiative decay of the self-localized e+Br2− excitons.
Fluorine codoping in germanium to suppress donor diffusion and deactivation
Authors: Chroneos A. , Grimes R. W. , Bracht H.
Published: October 2009

Electronic structure calculations are used to investigate the stability of fluorine-vacancy (FnVm) clusters in germanium (Ge). Using mass action analysis, it is predicted that the FnVm clusters can remediate the concentration of free V considerably. Importantly, we find that F and P codoping leads to a reduction in the concentration of donor-vacancy (DV) pairs. These pairs are responsible for the atomic transport and the formation of DnV clusters that lead to a deactivation of donor atoms. The predictions are technologically significant as they point toward an approach by which V-mediated donor diffusion and the formation of inactive DnV clusters can be suppressed. This would result in shallow and fully electrically active n-type doped regions in Ge-based electronic devices.
A comparative study of thermal behavior of iron and copper nanofluids
Authors: Sinha Kaustav , Kavlicoglu Barkan , Liu Yanming , Gordaninejad Faramarz , Graeve Olivia A.
Published: October 2009

Nanofluids consist of nanoparticles dispersed in heat transfer carrier fluid and are typically used for enhancing thermal conductivity in devices and systems. This study investigated the synthesis of iron and copper nanoparticle-based thermal fluids prepared using a two-step process. Chemical precipitation was used for the synthesis of the powders, and ultrasonic irradiation was used to disperse the nanoparticles in the carrier fluid (ethylene glycol). The size distributions of the nanopowders in the carrier fluid were determined using dynamic light scattering resulting in average particle sizes of around 500 nm. The crystallite sizes of the powders were below 20 nm. Thus, both types of nanofluids are comparable with regard to crystallite size, particle size, and morphology resulting in a direct comparison of material properties and their effect on thermal conductivity of the nanofluids. A guarded hot parallel-plate method and dynamic tests were used to compare the thermal conductivities of the nanofluids. It was shown that thermal conductivity can be enhanced by up to 70% for copper nanofluids. It was also demonstrated that for a given particle concentration, copper nanofluids are superior in thermal conductivity compared to iron nanofluids.
Strong thermal-history-dependent magnetoresistance behavior in Ni49.5Mn34.5In16
Authors: Wang B. M. , Wang L. , Liu Y. , Zhao B. C. , Zhao Y. , Yang Y. , Zhang H.
Published: October 2009

The thermal-history-dependent (THD) isothermal magnetoresistance (MR) behavior of Ni49.5Mn34.5In16 metamagnetic shape memory alloy is investigated. Irreversibility in isothermal MR is observed in reverse martensitic transformation temperature range, while an intriguing “overshooting” phenomenon is observed in forward martensitic transformation temperature range, showing a strong thermal-history dependence of MR behavior. Such a THD MR behavior can be explained in terms of phase coexistence, THD metastable phase, and magnetic-field-induced phase transition.
Simultaneous border-collision and period-doubling bifurcations
Authors: Simpson D. J. W. , Meiss J. D.
Published: October 2009

We unfold the codimension-two simultaneous occurrence of a border-collision bifurcation and a period-doubling bifurcation for a general piecewise-smooth, continuous map. We find that with sufficient nondegeneracy conditions, a locus of period-doubling bifurcations emanates nontangentially from a locus of border-collision bifurcations. The corresponding period-doubled solution undergoes a border-collision bifurcation along a curve emanating from the codimension-two point and tangent to the period-doubling locus here. In the case that the map is one-dimensional local dynamics is completely classified; in particular, we give conditions that ensure chaos.
The discovery of unexpected isomers in sodium heptamers by Born–Oppenheimer molecular dynamics
Authors: Vásquez-Pérez José Manuel , Martínez Gabriel Ulises Gamboa , Köster Andreas M. , Calaminici Patrizia
Published: October 2009

This work presents a density functional study of neutral, cationic, and anionic sodium cluster heptamers. The cluster structures were optimized with the local density approximation as well as with the generalized gradient approximation. For the neutral and cationic clusters new unexpected isomers are found closed in energy to the well known ground state structures. In the case of the neutral heptamer the new isomer was first noticed by inspection of a first-principles Born–Oppenheimer molecular dynamics (BOMD) simulations at 300 K. A structure alignment algorithm is presented which facilitates the discovery of new structures from such BOMD simulations. With this algorithm the structural evolution of the two low-lying isomers of the neutral, cationic, and anionic heptamer was analyzed at different temperatures. This work demonstrates the capability of reasonably long (∼100 ps) first-principles BOMD simulations to explore the potential energy landscape of metallic clusters.
Microwave window breakdown experiments and simulations on the UM/L-3 relativistic magnetron
Authors: Hoff B. W. , Mardahl P. J. , Gilgenbach R. M. , Haworth M. D. , French D. M. , Lau Y. Y. , Franzi M.
Published: October 2009

Experiments have been performed on the UM/L-3 (6-vane, L-band) relativistic magnetron to test a new microwave window configuration designed to limit vacuum side breakdown. In the baseline case, acrylic microwave windows were mounted between three of the waveguide coupling cavities in the anode block vacuum housing and the output waveguides. Each of the six 3 cm deep coupling cavities is separated from its corresponding anode cavity by a 1.75 cm wide aperture. In the baseline case, vacuum side window breakdown was observed to initiate at single waveguide output powers close to 20 MW. In the new window configuration, three Air Force Research Laboratory-designed, vacuum-rated directional coupler waveguide segments were mounted between the coupling cavities and the microwave windows. The inclusion of the vacuum side power couplers moved the microwave windows an additional 30 cm away from the anode apertures. Additionally, the Lucite microwave windows were replaced with polycarbonate windows and the microwave window mounts were redesigned to better maintain waveguide continuity in the region around the microwave windows. No vacuum side window breakdown was observed in the new window configuration at single waveguide output powers of 120+MW (a factor of 3 increase in measured microwave pulse duration and factor of 3 increase in measured peak power over the baseline case). Simulations were performed to investigate likely causes for the window breakdown in the original configuration. Results from these simulations have shown that in the original configuration, at typical operating voltage and magnetic field ranges, electrons emitted from the anode block microwave apertures strike the windows with a mean kinetic energy of 33 keV with a standard deviation of 14 keV. Calculations performed using electron impact angle and energy data predict a first generation secondary electron yield of 65% of the primary electron population. The effects of the primary aperture electron impacts, combined with multiplication of the secondary populations, were determined to be the likely causes of the poor microwave window performance in the original configuration.
All-solid-state repetitive semiconductor opening switch-based short pulse generator
Authors: Ding Zhenjie , Hao Qingsong , Hu Long , Su Jiancang , Liu Guozhi
Published: October 2009

The operating characteristics of a semiconductor opening switch (SOS) are determined by its pumping circuit parameters. SOS is still able to cut off the current when pumping current duration falls to the order of tens of nanoseconds and a short pulse forms simultaneously in the output load. An all-solid-state repetitive SOS-based short pulse generator (SPG100) with a three-level magnetic pulse compression unit was successfully constructed. The generator adopts magnetic pulse compression unit with metallic glass and ferrite cores, which compresses a 600 V, 10 μs primary pulse into short pulse with forward pumping current of 825 A, 60 ns and reverse pumping current of 1.3 kA, 30 ns. The current is sent to SOS in which the reverse pumping current is interrupted. The generator is capable of providing a pulse with the voltage of 120 kV and duration of 5–6 ns while output load being 125 Ω. The highest repetition rate is up to 1 kHz.
Single surface beyond Born–Oppenheimer equation for a three-state model Hamiltonian of Na3 cluster
Authors: Kumar Paul Amit , Sardar Subhankar , Sarkar Biplab , Adhikari Satrajit
Published: October 2009

When a set of three states is coupled with each other but shows negligibly weak interaction with other states of the Hilbert space, these states form a sub-Hilbert space. In case of such subspace [J. Chem. Phys. 124, 074101 (2006)], (a) the adiabatic-diabatic transformation (ADT) condition, ∇⃗A+τ⃗A=0 [Chem. Phys. Lett. 35, 112 (1975)], provides the explicit forms of the nonadiabatic coupling (NAC) elements in terms of electronic basis function angles, namely, the ADT angles, and (b) those NAC terms satisfy the so-called curl conditions [Chem. Phys. Lett. 35, 112 (1975)], which ensure the removal of the NAC elements [could be singular also at specific point(s) or along a seam in the configuration space] during the ADT to bring the diabatic representation of the nuclear Schrödinger equation with a smooth functional form of coupling elements among the electronic states. Since the diabatic to adiabatic representation of the Hamiltonian is related through the same unitary transformation (∇A+τA=0), it could be quite interesting to explore the nature of the nonadiabatic coupling terms starting from a diabatic Hamiltonian and, thereafter, to formulate the extended Born–Oppenheimer (EBO) equation for those adiabatic states transformed from diabatic ones. We consider a three-state diabatic potential matrix constructed for the excited states of Na3 cluster [J. Chem. Phys. 88, 6068 (1988)] at the pseudo-Jahn–Teller model situation, which can reproduce experimentally measured vibrationally resolved absorption lines [Surf. Sci. 156, 770 (1985)] with appropriate choice of coupling parameters, analytically calculate the nonadiabatic coupling elements along with their curls, and numerically evaluate the ADT angles to explore the nature of its nonadiabaticity. While formulating the single surface beyond the BO equation, our theoretical derivation demonstrates that the existence of zero curls of the NAC terms is a necessity. Indeed, when the energy gap between the third state (12 A1′/22 A1′) and the doubly degenerate states (22 E′/32 E′) of the model Hamiltonian for Na3 cluster is considered to be either identically or approximately zero, the curl for each NAC element naturally approaches zero, leading to a theoretically valid EBO equation. We demonstrate the numerical validity of the EBO equation by calculating the nonadiabatic effects on the photoabsorption spectrum starting with the initial wave function located on the ground electronic state and compare with the corresponding diabatic spectrum when the three states are either degenerate at a point or approaching to form three-state degeneracy at the same point. Finally, we calculate the vibrational eigenspectrum of the ground adiabatic state by using (so to say) theoretically and numerically valid EBO equation to compare with those experimentally measured and BO/geometric phase calculated spectra (Tables I-III).
NH
(
X
3
Σ
)
+
H
/
D
(
S
2
)
→
H
(
S
2
)
+
NH
/
ND
(
X
3
Σ
)
exchange reactions: State-to-state quantum scattering and applicability of statistical model
Authors: Li Zheng , Xie Daiqian , Sun Zhigang , Zhang Dong H. , Lin Shi Ying , Guo Hua
Published: October 2009

Quantum state-to-state dynamics for the NH+H/D→H+NH/ND exchange reaction is reported on an accurate ab initio potential energy surface. The differential cross section is dominated by scattering into both the forward and backward directions, while the product shows strong rotational excitation. The calculated rate constant for the NH+D reaction is in excellent agreement with experiment. The applicability of a quantum statistical model is tested against exact state-to-state quantum results. Due to strong nonreactive scattering, the statistical model significantly overestimates the integral cross section. However, it is shown that the product state distribution and differential cross sections are reasonably well reproduced by the statistical model because the reactive scattering is dominated by a complex-forming mechanism.
Radiative instability in stratified vortices
Authors: Le Dizès Stéphane , Billant Paul
Published: October 2009

This paper investigates the stability of a columnar vortex in an inviscid stratified fluid. By means of a WKBJ analysis for large axial wave number, we demonstrate that the normal modes can be stable or unstable owing to the emission of internal waves from the vortex. This phenomenon is shown to be analogous to the radioactive decay of nuclei in quantum mechanics. The destabilized character of the wave emission is shown to be associated with the presence of a critical point in the radial structure of the normal mode. The theoretical predictions for the frequency and growth rate of the normal modes are shown to be in good agreement with numerical results for two examples.
As weapons work slows, DOE labs keep busy with research
Authors: Kramer David
Published: October 2009

The laboratory-directed R&D program is a bright spot in a bleak outlook for nuclear weapons R&D.
Shear thickening in colloidal dispersions
Authors: Wagner Norman J. , Brady John F.
Published: October 2009

Shampoos, paints, cements, and soft body armor that stiffens under impact are just a few of the materials whose rheology is due to the change in viscosity that occurs when colloidal fluids experience shear stress.
Earth flyby anomalies
Authors: Nieto Michael Martin , Anderson John D.
Published: October 2009

In a reference frame fixed to the solar system’s center of mass, a satellite’s energy will change as it is deflected by a planet. But a number of satellites flying by Earth have also experienced energy changes in the Earth-centered frame—and that’s a mystery.
The two-fluid theory and second sound in liquid helium
Authors: Donnelly Russell J.
Published: October 2009

Laszlo Tisza’s contributions to our understanding of superfluid helium are often overshadowed by Lev Landau’s, but Tisza’s insights are still paying dividends—and not just for helium.
GABA uptake-dependent Ca
2+
signaling in developing olfactory bulb astrocytes
Authors: Doengi Michael , Hirnet Daniela , Coulon Philippe , Pape Hans-Christian , Deitmer Joachim W. , Lohr Christian
Published: October 2009

We studied GABAergic signaling in astrocytes of olfactory bulb slices using confocal Ca
2+
imaging and two-photon Na
+
imaging. GABA evoked Ca
2+
transients in astrocytes that persisted in the presence of GABA
A
and GABA
B
receptor antagonists, but were suppressed by inhibition of GABA uptake by SNAP 5114. Withdrawal of external Ca
2+
blocked GABA-induced Ca
2+
transients, and depletion of Ca
2+
stores with cyclopiazonic acid reduced Ca
2+
transients by approximately 90%. This indicates that the Ca
2+
transients depend on external Ca
2+
, but are mainly mediated by intracellular Ca
2+
release, conforming with Ca
2+
-induced Ca
2+
release. Inhibition of ryanodine receptors did not affect GABA-induced Ca
2+
transients, whereas the InsP
3
receptor blocker 2-APB inhibited the Ca
2+
transients. GABA also induced Na
+
increases in astrocytes, potentially reducing Na
+
/Ca
2+
exchange. To test whether reduction of Na
+
/Ca
2+
exchange induces Ca
2+
signaling, we inhibited Na
+
/Ca
2+
exchange with KB-R7943, which mimicked GABA-induced Ca
2+
transients. Endogenous GABA release from neurons, activated by stimulation of afferent axons or NMDA application, also triggered Ca
2+
transients in astrocytes. The significance of GABAergic Ca
2+
signaling in astrocytes for control of blood flow is demonstrated by SNAP 5114-sensitive constriction of blood vessels accompanying GABA uptake. The results suggest that GABAergic signaling is composed of GABA uptake-mediated Na
+
rises that reduce Na
+
/Ca
2+
exchange, thereby leading to a Ca
2+
increase sufficient to trigger Ca
2+
-induced Ca
2+
release via InsP
3
receptors. Hence, GABA transporters not only remove GABA from the extracellular space, but may also contribute to intracellular signaling and astrocyte function, such as control of blood flow.
Insulin resistance is a cellular antioxidant defense mechanism
Authors: Hoehn Kyle L. , Salmon Adam B. , Hohnen-Behrens Cordula , Turner Nigel , Hoy Andrew J. , Maghzal Ghassan J. , Stocker Roland , Van Remmen Holly , Kraegen Edward W. , Cooney Greg J. , Richardson Arlan R. , James David E.
Published: October 2009

We know a great deal about the cellular response to starvation via AMPK, but less is known about the reaction to nutrient excess. Insulin resistance may be an appropriate response to nutrient excess, but the cellular sensors that link these parameters remain poorly defined. In the present study we provide evidence that mitochondrial superoxide production is a common feature of many different models of insulin resistance in adipocytes, myotubes, and mice. In particular, insulin resistance was rapidly reversible upon exposure to agents that act as mitochondrial uncouplers, ETC inhibitors, or mitochondrial superoxide dismutase (MnSOD) mimetics. Similar effects were observed with overexpression of mitochondrial MnSOD. Furthermore, acute induction of mitochondrial superoxide production using the complex III antagonist antimycin A caused rapid attenuation of insulin action independently of changes in the canonical PI3K/Akt pathway. These results were validated in vivo in that MnSOD transgenic mice were partially protected against HFD induced insulin resistance and MnSOD+/− mice were glucose intolerant on a standard chow diet. These data place mitochondrial superoxide at the nexus between intracellular metabolism and the control of insulin action potentially defining this as a metabolic sensor of energy excess.
NF-κB activity is constitutively elevated in c-Abl null fibroblasts
Authors: Liberatore Rachel A. , Goff Stephen P. , Nunes Irene
Published: October 2009

The c-
abl
proto-oncogene encodes a nonreceptor tyrosine kinase involved in many cellular processes, including signaling from growth factor and antigen receptors, remodeling the cytoskeleton, and responding to DNA damage and oxidative stress. Many downstream pathways are affected by c-Abl. Elevated c-Abl kinase activity can inhibit NF-κB activity by stabilizing the inhibitory protein IκBα, raising the possibility that c-Abl-deficient cells might have increased NF-κB activity. We examined the levels of NF-κB activity in primary mouse embryonic fibroblasts (MEFs) derived from wild-type and c-Abl knockout mice and found that the knockout MEFs indeed exhibited elevated NF-κB activity in response to stimulation as well as constitutively elevated NF-κB activity. Thus, endogenous c-Abl is a negative regulator of basal and inducible NF-κB activity. Examination of various points of NF-κB regulation revealed that unstimulated c-Abl knockout MEFs do not exhibit an increase in IκBα degradation, p65/RelA nuclear translocation, or DNA binding of NF-κB subunits. They do, however, show reduced levels of the histone deacetylase HDAC1, a negative regulator of basal NF-κB activity. Unstimulated c-Abl knockout MEFs are less responsive to induction of NF-κB activity by trichostatin A, an HDAC inhibitor, suggesting that c-Abl might play a role in the HDAC-mediated repression of basal NF-κB activity.
Dissociation of circadian and light inhibition of melatonin release through forced desynchronization in the rat
Authors: Schwartz Michael D. , Wotus Cheryl , Liu Tiecheng , Friesen W. Otto , Borjigin Jimo , Oda Gisele A. , de la Iglesia Horacio O.
Published: October 2009

Pineal melatonin release exhibits a circadian rhythm with a tight nocturnal pattern. Melatonin synthesis is regulated by the master circadian clock within the hypothalamic suprachiasmatic nucleus (SCN) and is also directly inhibited by light. The SCN is necessary for both circadian regulation and light inhibition of melatonin synthesis and thus it has been difficult to isolate these two regulatory limbs to define the output pathways by which the SCN conveys circadian and light phase information to the pineal. A 22-h light–dark (LD) cycle forced desynchrony protocol leads to the stable dissociation of rhythmic clock gene expression within the ventrolateral SCN (vlSCN) and the dorsomedial SCN (dmSCN). In the present study, we have used this protocol to assess the pattern of melatonin release under forced desynchronization of these SCN subregions. In light of our reported patterns of clock gene expression in the forced desynchronized rat, we propose that the vlSCN oscillator entrains to the 22-h LD cycle whereas the dmSCN shows relative coordination to the light-entrained vlSCN, and that this dual-oscillator configuration accounts for the pattern of melatonin release. We present a simple mathematical model in which the relative coordination of a single oscillator within the dmSCN to a single light-entrained oscillator within the vlSCN faithfully portrays the circadian phase, duration and amplitude of melatonin release under forced desynchronization. Our results underscore the importance of the SCN′s subregional organization to both photic input processing and rhythmic output control.
Cross-generational change in /l/ in Chicano English
Authors: Van Hofwegen Janneke
Published: October 2009

The acoustic study of consonants has lagged considerably behind that of vowels. While a robust literature exists about vowel shifting, vowel quality, and the sociolinguistic significance of vowels, comparable literature is lacking for the acoustic quality of liquids. This study seeks to supplement the acoustic studies of vowels by analyzing characteristics of the liquid /l/ in its word-initial context. Traditionally, phonologists have subdivided /l/ into two allophones: dark and light, although current analysis has characterized these distinctions as gradient, not discrete. Word-initial /l/ is thought to be the canonically lightest variant of the phoneme, but cross-dialectal research has shown great acoustic variance in its phonetic realization. This case study aims to trace the phoneme through three generations of Chicano English speakers from South Texas, and to draw conclusions about how its variation among speakers and generations can shed light on other sociolinguistic phenomena, such as the persistence of substrate features from Spanish (with its characteristically light /l/s) or assimilation into mainstream American English dialects (with their characteristically dark /l/s). The study shows that there is indeed significant shift in the lightness of /l/ — independent of phonetic context — across the generations of speakers under examination. This result supports other studies that show notable assimilation with Anglo English varieties in earlier generations, but robust use of ethnically-marked phonological features among recent generations.
Writing the personal as research
Authors: Schnee Emily
Published: October 2009

Despite exponential growth in the field of narrative inquiry, personal narrative writing by research participants remains a seldom used research method. This article explores what it meant to the author, a former writing instructor, and her participants, adult college students, to use personal narrative writing by research participants as part of a larger qualitative study that examined the impact of college on adult worker education students. The author found that writing the personal was one way for adult students to begin to locate and critically interrogate their educational experiences and begin to revise their understandings of their educational journeys. This article explores the potential of personal narrative writing to engage participants in a research paradigm that moves them towards a more structural understanding of their previous educational failures and a heightened sense of their agency.