bluuebunny/crossref_metadata_2025 huggingface dataset:
Solvation pressure in chloroform
Authors: Hubel H. , Faux D. A. , Jones R. B. , Dunstan D. J.
Published: May 2006

Molecular dynamics (MD) simulations of chloroform vapor and liquid at normal temperature and pressure and liquid under hydrostatic pressure are presented, giving bond lengths and vibrational frequencies as functions of pressure. The change in bond lengths between vapor and liquid at normal temperature and pressure is consistent with a pressure equivalent to the cohesive energy density (CED) of the liquid, supporting the solvation pressure model which predicts that solvated molecules or nanoparticles experience a pressure equal to the CED of the liquid. Experimental data for certain Raman frequencies of chloroform in the vapor phase, in the liquid, and in the liquid under pressure are presented and compared to MD. Results for C–Cl vibrational modes are in general agreement with the solvation pressure model whereas frequencies associated with the C–H bond are not. The results demonstrate that masking interactions exist in the real liquid that can be reduced or eliminated in simplified simulations.
Molecular dynamics simulations of binary structure H hydrogen and methyl-tert-butylether clathrate hydrates
Authors: Alavi Saman , Ripmeester J. A. , Klug D. D.
Published: May 2006

Binary structure H (sH) hydrogen and methyl-tert-butylether (MTBE) clathrate hydrates are studied with molecular dynamics simulations. Simulations on a 3×3×3sH unit cell with up to 4.7mass% hydrogen gas are run at pressures of 100bars and 2kbars at 100 and 273K. For the small and medium cages of the sH unit cell, H2 guest molecule occupancies of 0, 1 (single occupancy), and 2 (double occupancy) are considered with the MTBE molecule occupying all of the large cages. An increase of the small and medium cage occupancies from 1 to 2 leads to a jump in the unit cell volume and configurational energy. Calculations are also set up with 1∕3, 2∕3, and 8∕9 of the MTBE molecules in the large cages replaced by sets of three to six H2 molecules, and the effects on the configurational energy and volume of the simulation cell are determined. As MTBE molecules are replaced with sets of H2 guests in the large cages, the configurational energy of the unit cell increases. At the lower temperature, the energy and volume of the clathrate are not sensitive to the number of hydrogen guests in the large cages; however, at higher temperatures the repulsions among the H2 guest molecules in the large cages cause an increase in the system energy and volume.
Open-loop and closed-loop control of dissociative ionization of ethanol in intense laser fields
Authors: Yazawa Hiroki , Tanabe Takasumi , Okamoto Tatsuyoshi , Yamanaka Mio , Kannari Fumihiko , Itakura Ryuji , Yamanouchi Kaoru
Published: May 2006

The relative yield of the C–O bond breaking with respect to the C–C bond breaking in ethanol cation C2H5OH+ is maximized in intense laser fields (1013–1015W∕cm2) by open-loop and closed-loop optimization procedures. In the open-loop optimization, a train of intense laser pulses are synthesized so that the temporal separation between the first and last pulses becomes 800fs, and the number and width of the pulses within a train are systematically varied. When the duration of 800fs is filled with laser fields by increasing the number of pulses or by stretching all pulses in a triple pulse train, the relative yield of the C–O bond breaking becomes significantly large. In the closed-loop optimization using a self-learning algorithm, the four dispersion coefficients or the phases of 128 frequency components of an intense laser pulse are adopted as optimized parameters. From these optimization experiments it is revealed that the yield ratio of the C–O bond breaking is maximized as far as the total duration of the intense laser field reaches as long as ∼1ps and that the intermittent disappearance of the laser field within a pulse does not affect the relative yields of the bond breaking pathways.
Optical fiber sensors for monitoring ingress of moisture in structural concrete
Authors: Yeo T. L. , Cox M. A. C. , Boswell L. F. , Sun T. , Grattan K. T. V.
Published: May 2006

Fiber optic-based humidity sensors, fabricated using fiber Bragg gratings coated with moisture sensitive polymer, are employed in detecting and monitoring the movement of moisture through standardized cubes made from samples of different types of structural concrete. Data obtained can give information on the properties of different types of concrete and thus on the migration of dissolved salts, e.g., sodium chloride, which is important in view of their deleterious effects on reinforcement bars within concrete. To undertake the research, two such optical fiber sensors were placed at varying distances from the edge of the cube face to the inner part of the concrete sample and subjected to a constant head of water at a constant temperature. The optical fiber sensors reacted to the ingress of water by detecting the moisture migrating through the sample, indicated by a shift in the Bragg wavelength of the sensor.
Automatic spark drill for high pressure experiments
Authors: Pugh E. , Thompson H. E. , Balsod R. B. , Brown S. V.
Published: May 2006

A low cost automatic electric discharge spark drill has been developed for the preparation of gaskets for use in high pressure diamond anvil cells. The spark drill is capable of producing centered holes quickly in a wide range of metals. It makes use of a novel electrical feedback system and provides a method for accurate alignment of the cutting tool and gasket.
Relaxation dynamics and structural isomerism in Nb10 and Nb10+
Authors: Walsh T. R.
Published: May 2006

The structure, energetics, and interconversion of isomers of Nb10 and Nb10+ are studied using density functional theory with Gaussian basis sets, using guess structures derived from basin-hopping simulations with the Finnis-Sinclair [Philos. Mag. A 50, 45 (1984)] potential. These results are used as input to a master equation approach to model the relaxation of these clusters. Ionization potentials are calculated for all relevant minima, as are the infrared spectra. On the basis of these data, and known experimental results, plausible explanations are given for the biexponential reaction kinetics observed for Nb10 and Nb10+ with respect to small molecule adsorbates. In principle, this approach could be extended to investigate any midsized transition metal cluster that exhibits structural isomerism.
Reaction dynamics of V(aFJ4)+NO→VO(XΣ−4)+N studied by a crossed-beam laser-induced fluorescence technique
Authors: Ishida M. , Yamashiro R. , Matsumoto Y. , Honma Kenji
Published: May 2006

The dynamics of the reaction, V(aFJ4)+NO→VO(XΣ−4)+N was studied by using a crossed-beam technique at 16.4kJ∕mol of collision energy. The V atomic beam was generated by laser vaporization and crossed with the O2 beam at a right angle. The laser-induced fluorescence (LIF) for the transition of VO(BΠ4-XΣ4) was used to determine the rotational state distribution of the reaction product in the vibrational ground state. Almost pure V(aFJ4) beam was obtained by using the mixture of NH3 with N2 as a carrier gas. Comparing the LIF spectra of VO measured for two carrier gases, i.e., NH3∕N2 and pure N2, it was concluded that the vibrational ground state of VO(XΣ−4) is formed almost entirely from the reaction of V(aFJ4) and the contribution of the metastable V(aDJ6) is negligible. The observed rotational distribution was similar to a statistical prior prediction, and suggested that the title reaction proceeds via a long-lived intermediate, which is consistent with an electron transfer mechanism.
High throughput screening of electrocatalysts for fuel cell applications
Authors: Prochaska Mark , Jin Jing , Rochefort Dominic , Zhuang Lin , DiSalvo Francis J. , Abruña Héctor D. , van Dover R. B.
Published: May 2006

We describe methodologies for the generation and screening of combinatorial libraries of electrocatalyst materials for fuel cell applications, generated by cosputtering of three elements onto a Si substrate coated with a Ta adhesion underlayer. Screening was carried out via a fluorescence assay as well as by scanning electrochemical microscopy. Whereas the former provided rapid qualitative screening with limited spatial resolution, the latter provided high spatial resolution. The fluorescence screening method was tested on Pt, PtBi, PtPb, and PtRu nanoparticles, while both methods were tested on a film containing a Pt–Bi–Pb ternary composition spread.
Measurement of the absolute separation for atomic force microscopy measurements in the presence of adsorbed polymer
Authors: McKee Clayton T. , Mosse Wade K. J. , Ducker William A.
Published: May 2006

We demonstrate that the absolute separation between an atomic force microscope (AFM) tip and a solid substrate can be measured in the presence of an irreversibly adsorbed polymer film. The separation is obtained from the analysis of a scattered evanescent wave that is generated at the surface of the solid. By comparing our scattering measurements to conventional AFM measurements, we also show an example where a conventional AFM measurement gives the incorrect force-distance profile. We validate the measurement of separation from scattering by examining the force-separation profile in the presence of surfactant solution. This validation is possible because the tip can be used to desorb the surfactant film that forms in surfactant solution, so we are able to measure both the scattering and the cantilever deflection when the tip is in contact with the solid substrate. The main limitation of our technique now is the lack of a rigorous method for predicting the intensity of scattering from the tip in contact with a solid that is coated with a film.
Bounds on the overlap of the Hartree-Fock, optimized effective potential, and density functional approximations with the exact energy eigenstates
Authors: Thanos S. , Theophilou A. K.
Published: May 2006

In this paper, we examine the limits of accuracy of the single determinant approximations (Hartree-Fock, optimized effective potential, and density functional theory) to the exact energy eigenstates of many electron systems. We show that an approximate Slater determinant of Sz=M gives maximum accuracy for states with S=M, provided that perturbation theory for the spin up minus spin down potential is applicable. The overlap with the exact energy eigenstates with S≠M is much smaller. Therefore, for the case that the emphasis is on wave functions, one must use symmetry preserving theories, although this is at the expense of accuracy in energy.
Polarization-sensitive ultraviolet photodetectors based on M-plane GaN grown on LiAlO2 substrates
Authors: Rivera C. , Pau J. L. , Muñoz E. , Misra P. , Brandt O. , Grahn H. T. , Ploog K. H.
Published: May 2006

Polarization-sensitive photodetectors for the ultraviolet spectral range based on M-plane GaN films grown on LiAlO2 substrates have been fabricated and characterized. These detectors exploit the dichroic properties of strained, M-plane GaN films. For a 400-nm-thick film, a maximum contrast of 7.25 between the detection of light polarized perpendicular and parallel to the c-axis is reached at 363nm. Considerations for the detector design show that thin strained M-plane GaN films will enhance the polarization-sensitive bandwidth, while the maximum contrast can be obtained for relaxed thick films under weak signal detection conditions.
Real time spectroscopic ellipsometry of nanoparticle growth
Authors: Oates T. W. H.
Published: May 2006

The use of real time spectroscopic ellipsometry to study silver nanoparticle formation in a polystyrene matrix by temperature induced reduction of silver hexafluoroacetylacetonate is reported. The optical properties of the composite are modeled using Mie theory with a modified electron relaxation frequency in silver to account for particle size effects. By measuring the final particle sizes from electron microscopy, the size of the particles during growth can be inferred above a radius of 2.3nm. Below this radius the model is limited by quantum effects.
Optical properties of shuffle dislocations in silicon
Authors: Pizzini S. , Binetti S. , Le Donne A. , Marzegalli A. , Rabier J.
Published: May 2006

The radiative recombination processes in dislocated float zone silicon samples deformed under gigapascal stresses were studied by photoluminescence (PL) spectroscopy. The observed shuffle dislocations present a reconstructed core and their generation is accompanied by the introduction of point defects and point defect clusters, whose signature is evident in the PL spectra. A broad band around 1eV is the only PL feature which could be directly related to shuffle dislocations and it is explained conjecturing strain field induced gap changes, as confirmed by molecular dynamics simulations.
Photoluminescence at room temperature in disordered Ba0.50Sr0.50(Ti0.80Sn0.20)O3 thin films
Authors: Souza I. A. , Simões A. Z. , Longo E. , Varela J. A. , Pizani P. S.
Published: May 2006

Photoluminescence (PL) properties at room temperature of disordered Ba0.50Sr0.50(Ti0.80Sn0.20)O3 (BST:Sn) thin films were obtained by the polymeric precursor method. X-ray diffraction data and corresponding PL properties have been measured using the 488nm line of an argon ion laser. The PL spectra of the film annealed at 350°C for 21h are stronger than those of the film annealed at 350°C for 28h, indicating a disorganized structure. The energy band gaps of the crystalline and amorphous BST:Sn thin films were 3.35 and 2.25eV, respectively. The doped BST thin films also tend to a cubic structure, resulting from TiO6 deformations.
Fabrication by electron beam induced deposition and transmission electron microscopic characterization of sub-10-nm freestanding Pt nanowires
Authors: Frabboni S. , Gazzadi G. C. , Felisari L. , Spessot A.
Published: May 2006

We present a method to reduce the size and improve the crystal quality of freestanding nanowires grown by electron beam induced deposition from a platinum metal organic precursor in a dual beam system. By freestanding horizontal growth and subsequent electron irradiation in a transmission electron microscope, sub-10-nm polycrystalline platinum nanowires have been obtained. A combined transmission electron microscopy–electron energy loss analysis has shown that the amorphous carbon, mixed to nanocrystalline platinum in the as-deposited material, is removed from the wires during irradiation. The same treatment progressively transforms nanocrystals dispersed in the amorphous matrix in a continuous polycrystalline platinum wire.
Tunneling modes of photonic heterostructures consisting of single-negative materials
Authors: Guan Guosheng , Jiang Haitao , Li Hongqiang , Zhang Yewen , Chen Hong , Zhu Shiyao
Published: May 2006

We show theoretically that heterostructures consisting of single-negative materials can possess tunneling modes inside forbidden gaps, owing to the resonant coupling of the evanescent-wave-based interface modes. The tunneling modes appear when the heterostructure becomes nihility. They are independent of incident angles and polarizations and have zero phase delay, which can be utilized to design zero-phase-shift omnidirectional filters.
Study of tunneling currents through germanium quantum-dot single-hole and -electron transistors
Authors: Li P. W. , Kuo David M. T. , Liao W. M. , Lai W. T.
Published: May 2006

The transport properties of Ge quantum-dot (QD) single-hole and -electron transistors (SHTs/SETs) are experimentally investigated. The tunneling currents of Ge-SETs and -SHTs could be modulated by adjusting top Si layer thickness on silicon-on-insulator substrates or applying back-gate biases due to parasitic transistors effect. The Coulomb oscillation of tunneling current is stable with respect to temperature, indicating the observed current should go through the energy levels of a Ge QD but not through trap states. The k∙p method has been employed to calculate the hole energy levels of a spherical Ge QD to clarify the homogeneous oscillation current characteristic of SHTs.
Direct observation of photoinduced charge redistribution of WO3–TiO2 double layer nanocomposite films by photoassisted Kelvin force microscopy
Authors: Wang S. J. , Cheng G. , Jiang X. H. , Li Y. C. , Huang Y. B. , Du Z. L.
Published: May 2006

The microscopic photoinduced charge redistribution between heterogeneous semiconductor nanofilms of WO3 and TiO2 double layers (written as WO3–TiO2 nanocomposite films) was directly observed using Kelvin probe force microscopy (KFM) coupled with an UV light source. Under illumination the surface potential morphologies of WO3–TiO2 nanocomposite films changed from 162to592mV, which was associated with the photoinduced charge transfer between WO3 and TiO2 nanoparticles due to the energy level alignment between them. This improved technique of photoassisted KFM was presented to visualize the photoinduced charge transfer between different semiconductor nanoparticles on microscopic scale.
Site-specific dopant profiling in a scanning electron microscope using focused ion beam prepared specimens
Authors: Kazemian P. , Twitchett A. C. , Humphreys C. J. , Rodenburg C.
Published: May 2006

Site-specific dopant profiling across a silicon p-n junction has been performed in the scanning electron microscope (SEM) on samples prepared using focused ion beam (FIB) milling. The results are compared with the dopant contrast obtained after using non-site-specific cleaving and tripod polishing of specimens. FIB milling generates a damaged surface layer which reduces the dopant contrast observed in the SEM using secondary electron imaging. These results show that two dimensional dopant contrast can be observed from FIB-prepared membranes, thereby extending the application of SEM dopant profiling to the examination of complex nanometer-scale device structures for which site selection is essential.
Parity effect in superconducting aluminum single electron transistors with spatial gap profile controlled by film thickness
Authors: Yamamoto T. , Nakamura Y. , Pashkin Yu. A. , Astafiev O. , Tsai J. S.
Published: May 2006

We propose a novel method for suppression of quasiparticle poisoning in Al Coulomb blockade devices. The method is based on creation of a proper energy gap profile along the device. In contrast to the previously used techniques, the energy gap is controlled by the film thickness. Our transport measurements confirm that the quasiparticle poisoning is suppressed and clear 2e periodicity is observed only when the island is made much thinner than the leads. This result is consistent with the existing model and provides a simple method to suppress quasiparticle poisoning.
Electric-field-dependent spectroscopy of charge motion using a single-electron transistor
Authors: Brown K. R. , Sun L. , Kane B. E.
Published: May 2006

We present observations of background charge fluctuators near an Al–AlOx–Al single-electron transistor on an oxidized Si substrate. The transistor design incorporates a heavily doped substrate and top gate, which allow for independent control of the substrate and transistor island potentials. Through controlled charging of the Si∕SiO2 interface we show that the fluctuators cannot reside in the Si layer or in the tunnel barriers. Combined with the large measured signal amplitude, this implies that the defects must be located very near the oxide surface.
A quantitative study of rat uterine sympathetic innervation during pregnancy and post partum
Authors: Chávez-Genaro R. , Lombide P. , Anesetti G.
Published: May 2006

In mammals, pregnancy induces a transient and extensive degeneration of uterine sympathetic innervation. We used the models of unilateral oviduct ligation and in oculo myometrium transplant in pregnant rats to address the role of stretching forces and/or hormone milieu in the loss of sympathetic innervation. The sympathetic fibres of the uterine horn and in oculo myometrial transplants were quantified on tissue sections processed by the glyoxylic acid technique. In normal pregnant rats, the density of uterine horn innervation was significantly reduced at late pregnancy and recovery took place during post partum. The empty horn of pregnant rats showed no significant changes in density of myometrial innervation during pregnancy or post partum. In oculo myometrial transplants were organotypically reinnervated in virgin animals. When the transplants were exposed to gestational hormonal milieu, few or no fibres were observed to the end of pregnancy; however, a significant increase at post partum was observed. Results showed that both the effects of stretching and the hormone milieu derived from the fetus–placenta complex play a role as inductors of changes on sympathetic myometrial innervation during pregnancy and support the idea that immature muscular uterine fibres are more susceptible to the effects of pregnancy than those originating from adult animals.
Angiopoietin-1 and -2 mRNA and protein expression in mouse preimplantation embryos and uteri suggests a role in angiogenesis during implantation
Authors: Hess A. P. , Hirchenhain J. , Schanz A. , Talbi S. , Hamilton A. E. , Giudice L. C. , Krüssel J. S.
Published: May 2006

After attachment and migration through the endometrial epithelium, the embryo must induce angiogenesis within the endometrial stroma to successfully complete the implantation process. Growth factors have been shown to play an important role in embryo implantation and placentation. The aim of the study was to investigate the expression of angiopoietin-1 and -2 (Ang-1 and -2) mRNA and protein expression during the development of single preimplantation mouse embryos and of possible complementary expression in mouse uteri. Angiopoietin-1 mRNA was expressed throughout development in 78% of zygotes, 66% of 2-cell-embryos, 71% of 4-cell-embryos, 70% of 8-cell-embryos, 60% of morula stages, 48% of early blastocysts and 78% of late blastocysts. The number of Ang-1-expressing embryos in the early-blastocyst group was significantly different in comparison with zygotes, 4-cell-embryos, 8-cell-embryos and late blastocysts. Angiopoietin-2 mRNA and protein expression could not be detected in preimplantation embryos. Examination of the uteri revealed Ang-2 mRNA and protein expression in the oestrogen-dominated cycling phase and the progesterone-dominated mated phase, whereas Ang-1 expression was restricted to the mated phase. Herein, Ang-1 expression in preimplantation mouse embryos as well as Ang-1 and -2 expression in mouse uteri is demonstrated, suggesting a possible role for angiopoietins in the embryo–maternal dialogue of the implantation process via an enhancement of the vascular remodelling in favour of an implanting conceptus.
Effects of chronic prenatal ethanol exposure on mitochondrial glutathione and 8-iso-prostaglandin F2α concentrations in the hippocampus of the perinatal guinea pig
Authors: Green C. R. , Watts L. T. , Kobus S. M. , Henderson G. I. , Reynolds J. N. , Brien J. F.
Published: May 2006

It is hypothesised that oxidative stress is a key mechanism of ethanol neurobehavioural teratogenicity, resulting in altered endogenous antioxidant status and increased membrane lipid peroxidation in the hippocampus of chronic prenatal ethanol exposure (CPEE) offspring. To test this hypothesis, timed pregnant guinea-pigs (term, approximately gestational day (GD) 68) received chronic daily oral administration of (i) 4 g ethanol kg–1 maternal bodyweight, (ii) isocaloric sucrose with pair feeding, or (iii) water. At GD 65 (term fetus) and postnatal day (PD) 0 (neonate), individual offspring were killed, the brain was excised and the hippocampi were dissected. Glutathione (GSH) concentration was measured in the cytosolic and mitochondrial fractions of hippocampal homogenate. The occurrence of lipid peroxidation was determined by measuring the concentration of 8-iso-prostaglandin F2α (8-iso-PGF2α). There was CPEE-induced decreased brain weight and hippocampal weight at GD 65 and PD 0, decreased mitochondrial GSH concentration in the hippocampus at PD 0, with no change in mitochondrial GSH concentration at GD 65 or cytosolic GSH concentration at GD 65 or PD 0, and no change in mitochondrial or whole-homogenate 8-iso-PGF2α concentration in the hippocampus at GD 65 or PD 0. The data demonstrate that CPEE produces selective mitochondrial dysfunction in the hippocampus of the neonatal guinea-pig, involving GSH depletion.
Amplification of DNA from preserved specimens shows blowflies were preadapted for the rapid evolution of insecticide resistance
Authors: Hartley C. J. , Newcomb R. D. , Russell R. J. , Yong C. G. , Stevens J. R. , Yeates D. K. , La Salle J. , Oakeshott J. G.
Published: May 2006

Mutations of esterase 3 confer two forms of organophosphate resistance on contemporary Australasian
Lucilia cuprina
. One form, called diazinon resistance, is slightly more effective against commonly used insecticides and is now more prevalent than the other form, called malathion resistance. We report here that the single amino acid replacement associated with diazinon resistance and two replacements associated with malathion resistance also occur in esterase 3 in the sibling species
Lucilia sericata
, suggesting convergent evolution around a finite set of resistance options. We also find parallels between the species in the geographic distributions of the polymorphisms: In both cases, the diazinon-resistance change is absent or rare outside Australasia where insecticide pressure is lower, whereas the changes associated with malathion resistance are widespread. Furthermore, PCR analysis of pinned specimens of Australasian
L. cuprina
collected before the release of organophosphate insecticides reveals no cases of the diazinon-resistance change but several cases of those associated with malathion resistance. Thus, the early outbreak of resistance in this species can be explained by the preexistence of mutant alleles encoding malathion resistance. The pinned specimen analysis also shows much higher genetic diversity at the locus before organophosphate use, suggesting that the subsequent sweep of diazinon resistance in Australasia has compromised the scope for the locus to respond further to the ongoing challenge of the insecticides.
β-Amyloid infusion results in delayed and age-dependent learning deficits without role of inflammation or β-amyloid deposits
Authors: Malm Tarja , Ort Michael , Tähtivaara Leena , Jukarainen Niko , Goldsteins Gundars , Puoliväli Jukka , Nurmi Antti , Pussinen Raimo , Ahtoniemi Toni , Miettinen Taina-Kaisa , Kanninen Katja , Leskinen Suvi , Vartiainen Nina , Yrjänheikki Juha , Laatikainen Reino , Harris-White Marni E. , Koistinaho Milla , Frautschy Sally A. , Bures Jan , Koistinaho Jari
Published: May 2006

β-Amyloid (Aβ) polypeptide plays a critical role in the pathogenesis of Alzheimer's disease (AD), which is characterized by progressive decline of cognitive functions, formation of Aβ deposits and neurofibrillary tangles, and loss of neurons. Increased genetic production or direct intracerebral administration of Aβ in animal models results in Aβ deposition, gliosis, and impaired cognitive functions. Whether aging renders the brain prone to Aβ and whether inflammation is required for Aβ-induced learning deficits is unclear. We show that intraventricular infusion of Aβ
1–42
results in learning deficits in 9-month-old but not 2.5-month-old mice. Deficits that become detectable 12 weeks after the infusion are associated with a slight reduction in Cu,Zn superoxide dismutase activity but do not correlate with Aβ deposition and are not associated with gliosis. In rats, Aβ infusion induced learning deficits that were detectable 6 months after the infusion. Approximately 20% of the Aβ immunoreactivity in rats was associated with astrocytes. NMR spectrum analysis of the animals cerebrospinal fluid revealed a strong reduction trend in several metabolites in Aβ-infused rats, including lactate and myo-inositol, supporting the idea of dysfunctional astrocytes. Even a subtle increase in brain Aβ
1–42
concentration may disrupt normal metabolism of astrocytes, resulting in altered neuronal functions and age-related development of learning deficits independent of Aβ deposition and inflammation.
Cre recombinase-mediated restoration of nigrostriatal dopamine in dopamine-deficient mice reverses hypophagia and bradykinesia
Authors: Hnasko Thomas S. , Perez Francisco A. , Scouras Alex D. , Stoll Elizabeth A. , Gale Samuel D. , Luquet Serge , Phillips Paul E. M. , Kremer Eric J. , Palmiter Richard D.
Published: May 2006

A line of dopamine-deficient (DD) mice was generated to allow selective restoration of normal dopamine signaling to specific brain regions. These DD floxed stop (DDfs) mice have a nonfunctionalTyrosine hydroxylase(Th) gene because of insertion of aNeoRgene flanked by lox P sites targeted to the first intron of theThgene. DDfs mice have trace brain dopamine content, severe hypoactivity, and aphagia, and they die without intervention. However, they can be maintained by daily treatment withl-3,4-dihydroxyphenylalanine (l-dopa). Injection of a canine adenovirus (CAV-2) engineered to express Cre recombinase into the central caudate putamen restores normalThgene expression to the midbrain dopamine neurons that project there because CAV-2 efficiently transduces axon terminals and is retrogradely transported to neuronal cell bodies. Bilateral injection of Cre recombinase into the central caudate putamen restores feeding and normalizes locomotion in DDfs mice. Analysis of feeding behavior by using lickometer cages revealed that virally rescued DDfs mice are hyperphagic and have modified meal structures compared with control mice. The virally rescued DDfs mice are also hyperactive at night, have reduced motor coordination, and are thigmotactic compared with controls. These results highlight the critical role for dopamine signaling in the dorsal striatum for most dopamine-dependent behaviors but suggest that dopamine signaling in other brain regions is important to fine-tune these behaviors. This approach offers numerous advantages compared with previous models aimed at examining dopamine signaling in discrete dopaminergic circuits.
Regulation of hypermutation by activation-induced cytidine deaminase phosphorylation
Authors: McBride Kevin M. , Gazumyan Anna , Woo Eileen M. , Barreto Vasco M. , Robbiani Davide F. , Chait Brian T. , Nussenzweig Michel C.
Published: May 2006

Activation-induced cytidine deaminase (AID) initiates Ig class switch recombination and somatic hypermutation by producing U:G mismatches in DNA. These mismatches also have the potential to induce DNA damage including double-stranded breaks and chromosome translocations; therefore, strict regulation of AID is important for maintaining genomic stability. In addition to transcriptional regulation, it has been proposed that phosphorylation can also modulate AID activity. Using a combination of MS and immunochemical approaches we found that 5–15% of the AID expressed in activated B cells was phosphorylated at serine-38 (p38AID). This form of AID was enriched in the chromatin fraction in activated B cells, suggesting a role for phosphorylation in targeting AID to DNA. Consistent with this idea, serine-38 to alanine mutant AID (AIDS38A) showed diminished somatic hypermutation activity on artificial and physiological DNA targets. We conclude that a small fraction of AID is phosphorylated in activated B cells and that the modified form contributes disproportionately to hypermutation.
A Neowicksellian in a New Classical World: The Methodology of Michael Woodford's Interest and Prices
Authors: Hoover Kevin D.
Published: May 2006

Michael Woodford's Interest and Prices: Foundations of a Theory of Monetary Policy (2003) is an important book. Woodford's title is, of course, a conscious revival of Wicksell's own famous work and it points to an effort to recast the analysis of monetary policy as centered on interest rates. I believe that Woodford's theoretical orientation is essentially correct. In repairing to Wicksell, he places the monetary aggregates into a more reasonable perspective, correcting the distortions of the monetarist and Keynesian diversions with respect to money. My money is, so to speak, where my mouth is: My own textbook-in-progress is also based around an IS/interest-rate rule/AS model, in which financial markets cleared by price rather than the LM curve are emphasized. Such an approach, as Woodford notes, has become standard in central banks, but has not yet captured either core undergraduate or graduate textbooks and instruction. My task here, however, was not to praise Woodford's economics nor to trace or evaluate its Wicksellian routes, but to consider Interest and Prices from a methodological point of view.
Mr. Woodford and the Challenge of Finance
Authors: Mehrling Perry
Published: May 2006

Once one recognizes that many prices (and wages) are fairly sticky over short time intervals, the arbitrariness of the path of nominal prices (in the sense of their under-determination by real factors alone) implies that the path of real activity and the associated path of equilibrium real interest rates are equally arbitrary. It is equally possible, from a logical standpoint, to imagine allowing the central bank to determine, by arbitrary fiat, the path of aggregate real activity, or the path of real interest rates, as it is to imagine allowing it to determine the path of nominal interest rates. In practice, it is easiest for central banks to exert relatively direct control over overnight nominal interest rates, and so they generally formulate their short-run objectives (their operating target) in terms of the effect that they seek to bring about in this variable rather than in one of the others.
Wicksell after Woodford
Authors: Boianovsky Mauro , Trautwein Hans-Michael
Published: May 2006

The New Neoclassical Synthesis that Michael Woodford puts forward in his Interest and Prices (2003) is primarily a synthesis of New Classical and New Keynesian ideas. Yet Woodford presents it as an encompassing approach that goes much further back in time to integrate the pre-Keynesian macroeconomics of Knut Wickseil and his followers. Starting with the title, the book contains many references to Geldzins und Güterpreise (1898), Wicksell's landmark contribution to monetary theory which was translated as Interest and Prices in 1936. Woodford relates his concept of a “monetary policy without money” to Wicksell's concept of the pure credit system and to Wicksell's proposal to eliminate inflation by adjusting nominal interest rates to changes in the price level—an idea that has much in common with modern policy rules à la Taylor. He presents the core model of the new synthesis (in shorthand: IS + AS + Taylor rule) as a “neo-Wicksellian framework” that serves to analyze the dynamics of interest-rate gaps and output gaps (2003, chapter 4). Referring to the Wicksellians of the 1920s and 1930s (primarily Erik Lindahl, Gunnar Myrdal, and Friedrich A. Hayek), Woodford grounds his advocacy of rules to fight inflation on the potential non-neutrality of monetary policy: “[I]t is because instability of the general level of prices causes substantial real distortions—leading to inefficient variation both in aggregate employment and output and in the sectoral composition of economic activity—that price stability is important” (2003, p. 5). He thus sees his analysis of interest-rate and output gaps as “an attempt to resurrect a view” that the old Wicksellians had developed in their analyses of cumulative processes.
Comments on the Symposium onInterest and Prices
Authors: Woodford Michael
Published: May 2006

The papers prepared for this symposium cover a great deal of ground. It is a pleasure to be able to respond to them, as this provides an opportunity to try to clarify some of the aims of my book (Woodford 2003) that may have been insufficiently clear in the original work. But I shall have to restrict my attention to only a few of the most important issues raised in the various papers. I shall consider three classes of issues in particular: the methodology adopted in the book, the role of “cashless” models, and the connection between my work and the Wicksellian tradition.
Sexual Division of Labor in Adam Smith's Work
Authors: Shah Sumitra
Published: May 2006

It is a fact universally acknowledged that a woman's work is never done and often not counted. It is a fact equally universally acknowledged that most people in the economics profession are not terribly interested in such a fact. It is my purpose to explore this lack of interest by tracing it to the place of sexual division of labor in Adam Smith's work.
Rad4TopBP1, a Scaffold Protein, Plays Separate Roles in DNA Damage and Replication Checkpoints and DNA Replication
Authors: Taricani Lorena , Wang Teresa S.F.
Published: May 2006

Rad4TopBP1, a BRCT domain protein, is required for both DNA replication and checkpoint responses. Little is known about how the multiple roles of Rad4TopBP1are coordinated in maintaining genome integrity. We show here that Rad4TopBP1of fission yeast physically interacts with the checkpoint sensor proteins, the replicative DNA polymerases, and a WD-repeat protein, Crb3. We identified four novel mutants to investigate how Rad4TopBP1could have multiple roles in maintaining genomic integrity. A novel mutation in the third BRCT domain of rad4+TopBP1abolishes DNA damage checkpoint response, but not DNA replication, replication checkpoint, and cell cycle progression. This mutant protein is able to associate with all three replicative polymerases and checkpoint proteins Rad3ATR-Rad26ATRIP, Hus1, Rad9, and Rad17 but has a compromised association with Crb3. Furthermore, the damaged-induced Rad9 phosphorylation is significantly reduced in this rad4TopBP1mutant. Genetic and biochemical analyses suggest that Crb3 has a role in the maintenance of DNA damage checkpoint and influences the Rad4TopBP1damage checkpoint function. Taken together, our data suggest that Rad4TopBP1provides a scaffold to a large complex containing checkpoint and replication proteins thereby separately enforcing checkpoint responses to DNA damage and replication perturbations during the cell cycle.
ATP-binding Cassette Transporters Are Required for Efficient RNA Interference inCaenorhabditis elegans
Authors: Sundaram Prema , Echalier Benjamin , Han Wang , Hull Dawn , Timmons Lisa
Published: May 2006

RNA interference (RNAi) is a conserved gene-silencing phenomenon that can be triggered by delivery of double-stranded RNA (dsRNA) to cells and is a widely exploited technology in analyses of gene function. Although a number of proteins that facilitate RNAi have been identified, current descriptions of RNAi and interrelated mechanisms are far from complete. Here, we report that the Caenorhabditis elegans gene haf-6 is required for efficient RNAi. HAF-6 is a member of the ATP-binding cassette (ABC) transporter gene superfamily. ABC transporters use ATP to translocate small molecule substrates across the membranes in which they reside, often against a steep concentration gradient. Collectively, ABC transporters are involved in a variety of activities, including protective or barrier mechanisms that export drugs or toxins from cells, organellar biogenesis, and mechanisms that protect against viral infection. HAF-6 is expressed predominantly in the intestine and germline and is localized to intracellular reticular organelles. We further demonstrate that eight additional ABC genes from diverse subfamilies are each required for efficient RNAi in C. elegans. Thus, the ability to mount a robust RNAi response to dsRNA depends upon the deployment of two ancient systems that respond to environmental assaults: RNAi mechanisms and membrane transport systems that use ABC proteins.
Short Thyromental Distance: A Predictor of Difficult Intubation or an Indicator for Small Blade Selection?
Authors: Tripathi Mukesh , Pandey Mamta
Published: May 2006

Background

Short thyromental distance (TMD; < 5 cm) has been correlated with difficult direct laryngoscopic intubation in adult patients. The authors hypothesized that a smaller Macintosh curved blade (No. 2 MCB) would improve the predicted difficult laryngoscopy in short-TMD patients over that with a standard Macintosh curved blade (No. 3 MCB).

Methods

In a preliminary study of 11 consenting adults (7 females and 4 males), American Society of Anesthesiologists physical status I and TMD < or = 5 cm, lateral neck radiographs were recorded during laryngoscopy with a No. 2 and No. 3 MCB in sequential fashion. In a prospective clinical study, laryngoscopy and tracheal intubation were evaluated in 83 adult patients with TMD < or = 5 cm by randomly assigning them to two groups for the blade used at first intubation. Those who failed intubation with the first blade were switched to the alternate blade. In total 100 laryngoscopies and intubations were performed: the No. 2 MCB (n = 50) and the No. 3 MCB (n = 50).

Results

Lateral neck radiographs recorded at the best laryngeal view revealed that the tip of the No. 2 MCB was proximal to the hyoid body with the No. 2 MCB and distal to it with the No. 3 MCB. The intubation distance (C5 to blade tip) on neck radiographs with the No. 2 MCB was significantly greater than it was with the No. 3 MCB for similar anterior jaw displacement. In the clinical study, the laryngoscopic grade with the No. 2 blade was considered easy (median, 2B), better than the grade with the No. 3 MCB (median, 3). When the No. 2 MCB was used, external laryngeal pressure improved the laryngoscopic grade (1, full glottic view) in 46% of patients. In contrast, when the No. 3 MCB was used, pressure improved the grade in only 10% of the patients. Intubation time with the No. 2 MCB was significantly (P < 0.05) less than it was in patients with No. 3 MCB. Overall, 14 patients who failed intubation with the No. 3 MCB were switched to the No. 2 MCB, and intubation was successful with an easy laryngoscopic grade. Three patients who failed intubation with the No. 2 MCB were switched to the No. 3 MCB.

Conclusions

The predicted difficult laryngoscopy and intubation with the use of the adult No. 3 MCB in standard adult patients with a TMD < or = 5 cm is significantly easier with use of the smaller No. 2 MCB.
A Comparison of the Effect of High- and Low-dose Fentanyl on the Incidence of Postoperative Cognitive Dysfunction after Coronary Artery Bypass Surgery in the Elderly
Authors: Silbert Brendan S. , Scott David A. , Evered Lisbeth A. , Lewis Matthew S. , Kalpokas Mario , Maruff Paul , Myles Paul S. , Jamrozik Konrad
Published: May 2006

Background

Postoperative cognitive dysfunction (POCD) after coronary artery bypass graft surgery is a common complication for which, despite many clinical investigations, no definitive etiology has been found. The current use of both high- and low-dose fentanyl as anesthetic techniques allowed us to investigate the effect of fentanyl on the incidence of POCD.

Methods

Three hundred fifty patients scheduled to undergo elective coronary artery bypass graft surgery were randomized to receive either high-dose fentanyl (50 microg/kg) or low-dose fentanyl (10 mug/kg) as the basis of the anesthetic. All patients underwent neuropsychological testing before surgery and at 1 week, 3 months, and 12 months after surgery.

Results

One hundred sixty-eight patients in the low-dose group and 158 patients in the high-dose group were included in the final analysis. Neuropsychological testing was performed on 88%, 93%, and 92% of patients at 1 week, 3 months, and 12 months, respectively. There was no difference between group mean scores at any of the three testing times. Analysis of individual patients by the 20% rule did not detect any differences between groups. The one SD rule, which has fewer false-positive results, detected significantly more patients with POCD in the low-dose group than in the high-dose group at 1 week (23.6% vs. 13.7%; P = 0.03) but not at the other testing times. Patients with POCD spent an average of 1.2 days longer in the hospital than those without POCD (P = 0.021).

Conclusions

High-dose fentanyl is not associated with a difference in the incidence of POCD at 3 or 12 months after surgery. Low-dose fentanyl leads to shorter postoperative ventilation times and may be associated with a greater incidence of POCD 1 week after surgery. Early POCD is associated with an increased duration of stay in the hospital.
Malignant Hyperthermia in Japan
Authors: Ibarra M Carlos A. , Wu Shiwen , Murayama Kumiko , Minami Narihiro , Ichihara Yasuko , Kikuchi Hirosato , Noguchi Satoru , Hayashi Yukiko K. , Ochiai Ryoichi , Nishino Ichizo
Published: May 2006

Background

Malignant hyperthermia (MH) is a disorder of calcium homeostasis in skeletal muscle triggered by volatile anesthetics or succinylcholine in susceptible persons. More than 100 mutations in the ryanodine receptor type 1 gene (RYR1) have been associated with MH susceptibility, central core disease, or both. RYR1 mutations may account for up to 70% of MH-susceptible cases. The authors aimed to determine the frequency and distribution of RYR1 mutations in the Japanese MH-susceptible population.

Methods

The authors selected 58 unrelated Japanese diagnosed as MH-susceptible for having an enhanced Ca-induced Ca release rate from the sarcoplasmic reticulum on chemically skinned muscle fibers. They sequenced the entire RYR1 coding region from genomic DNA. Muscle pathology was also characterized.

Results

Seven previously reported and 26 unknown RYR1 potentially pathogenic sequence variations were identified in 33 patients (56.9%). Of these patients, 48% had cores on muscle biopsy. The mutation detection rate was higher in patients with clear enhancement of Ca-induced Ca release rate (72.4%), whereas all patients with central core disease had RYR1 mutations. Six patients harbored potentially causative compound heterozygous sequence variations.

Conclusions

Distribution and frequency of RYR1 mutations differed markedly from those of the North American and European MH-susceptible population. Comprehensive screening of the RYR1 gene is recommended for molecular investigations in MH-susceptible individuals, because many mutations are located outside the "hot spots." Based on the observed occurrence of compound heterozygous state, the prevalence of a possibly predisposing phenotype in the Japanese population might be as high as 1 in 2,000 people.