bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of urocortin 1 infusion in humans with stable congestive cardiac failure
Authors: Davis Mark E. , Pemberton Christopher J. , Yandle Timothy G. , Lainchbury John G. , Rademaker Miriam T. , Nicholls M. Gary , Frampton Christopher M. , Richards A. Mark
Published: September 2005

In sheep with HF (heart failure), Ucn1 (urocortin 1) decreases total peripheral resistance and left atrial pressure, and increases cardiac output in association with attenuation of vasopressor hormone systems and enhancement of renal function. In a previous study, we demonstrated in the first human studies that infusion of Ucn1 elevates corticotropin (‘ACTH’), cortisol and ANP (atrial natriuretic peptide), and suppresses the hunger-inducing hormone ghrelin in normal subjects. In the present study, we examined the effects of Ucn1 on pituitary, adrenal and cardiovascular systems in the first Ucn1 infusion study in human HF. In human HF, it is proposed that Ucn1 would augment corticotropin and cortisol release, suppress ghrelin and reproduce the cardiorenal effects seen in animals with HF. On day 3 of a controlled metabolic diet, we studied eight male volunteers with stable HF (ejection fraction <40%; New York Heart Association Class II–III) on two occasions, 2 weeks apart, receiving 50 μg of Ucn1 or placebo intravenously over 1 h in a randomized time-matched cross-over design. Neurohormones, haemodynamics and urine indices were recorded. Ucn1 infusion increased plasma Ucn1, corticotropin (baseline, 5.9±0.9 pmol/l; and peak, 7.2±1.0 pmol/l) and cortisol (baseline, 285±42 pmol/l; and peak, 310±41 pmol/l) compared with controls (P<0.001, 0.008 and 0.047 respectively). The plasma Ucn1 half-life was 54±3 min. ANP and ghrelin were unchanged, and no haemodynamic or renal effects were seen. In conclusion, a brief intravenous infusion of 50 μg of Ucn1 stimulates corticotropin and cortisol in male volunteers with stable HF.
Real-time reverse transcription PCR (qRT-PCR) and its potential use in clinical diagnosis
Authors: Bustin Stephen A. , Mueller Reinhold
Published: September 2005

qRT-PCR (real-time reverse transcription-PCR) has become the benchmark for the detection and quantification of RNA targets and is being utilized increasingly in novel clinical diagnostic assays. Quantitative results obtained by this technology are not only more informative than qualitative data, but simplify assay standardization and quality management. qRT-PCR assays are most established for the detection of viral load and therapy monitoring, and the development of SARS (severe acute respiratory syndrome)-associated coronavirus qRT-PCR assays provide a textbook example of the value of this technology for clinical diagnostics. The widespread use of qRT-PCR assays for diagnosis and the detection of disease-specific prognostic markers in leukaemia patients provide further examples of their usefulness. Their value for the detection of disease-associated mRNA expressed by circulating tumour cells in patients with solid malignancies is far less apparent, and the clinical significance of results obtained from such tests remains unclear. This is because of conceptual reservations as well as technical limitations that can interfere with the diagnostic specificity of qRT-PCR assays. Therefore, although it is evident that qRT-PCR assay has become a useful and important technology in the clinical diagnostic laboratory, it must be used appropriately and it is essential to be aware of its limitations if it is to fulfil its potential.
Clinical, diagnostic, genetic and management issues in dementia with Lewy bodies
Authors: Boeve Bradley F.
Published: September 2005

DLB (dementia with Lewy bodies) is a syndrome associated with underlying LBD (Lewy body disease), with manifestations in the cognitive, neuropsychiatric, motor, sleep and autonomic domains. The variable symptomatology and complex array of neuronal involvement and neurotransmitter deficiencies make the diagnosis and management of patients with DLB challenging. The genetic underpinnings of DLB have only recently begun to unfold. In this review, the clinical features, diagnostic criteria, genetics and treatment issues relating to DLB will be discussed, in which a comprehensive approach to the diagnosis and management is emphasized.
Molecular genetic pathways in Parkinson's disease: a review
Authors: Jain Shushant , Wood Nicholas W. , Healy Daniel G.
Published: September 2005

Major progress has been made in the last decade in understanding the genetic basis of PD (Parkinson's disease) with five genes unequivocally associated with disease. As a result, multiple pathways have been implicated in the pathogenesis of PD, including proteasome impairment and mitochondrial dysfunction. Although Mendelian genetics has been successful in establishing a genetic predisposition for familial PD, this has not been reiterated in the sporadic form. In fact no genetic factors have been unequivocally associated with increased risk for sporadic PD. The difficulty in identifying susceptibility factors in PD has not only been because of numerous underpowered studies, but we have been unable to dissect out the genetic component in a multifactorial disease. This review aims to summarize the genetic findings within PD.
Fetal programming of appetite by exposure to a maternal low-protein diet in the rat
Authors: Bellinger Leanne , Langley-Evans Simon C.
Published: September 2005

Undernutrition in fetal life programmes risk of obesity and the metabolic syndrome in adult life. Rat studies indicate that exposure to a maternal low-protein diet throughout fetal life establishes a preference for high-fat foods. The present study aimed to assess the effect of low protein exposure during discrete 7-day periods of gestation upon feeding behaviour (full gestation 22 days). Pregnant rats were fed control or low-protein diet, with low-protein feeding targeted at day 0–7 (LPEarly), day 8–14 (LPMid) or day 15–22 (LPLate) of gestation. At 12 weeks of age, offspring were placed on a macronutrient self-selection regimen. Prenatal protein restriction programmed feeding behaviour in female, but not male, offspring. Among females, all low-protein exposed groups consumed less fat than the control group (P<0.05). Male offspring showed no changes in feeding behaviour. In males and females fed a low-fat chow diet, there were metabolic differences between the groups. LPEarly and LPLate males had greater hepatic glycogen stores than control animals. There were no differences in the size of abdominal fat depots in either male or female rats exposed to low-protein diet at any point in gestation. The data suggest that programming of feeding behaviour is likely to be gender-specific and dependent upon the timing of nutrient insult in fetal life. This work may have implications for the development of the metabolic syndrome.
A study of molecular vibrational relaxation mechanism in condensed phase based upon mixed quantum-classical molecular dynamics. II. Noncollisional mechanism for the relaxation of a polar solute in supercritical water
Authors: Sato Masahiro , Okazaki Susumu
Published: September 2005

Mixed quantum-classical molecular dynamics method has been applied to vibrational relaxation of a hydrophilic model NO in supercritical water at various densities along an isotherm above the critical temperature. The relaxation rate was determined based on Fermi’s golden rule at each state point and showed an inverse S-shaped curve as a function of bulk density. The hydration number was also calculated as a function of bulk density based on the calculated radial distribution function, which showed a good correlation with the relaxation rate. Change of the survival probability of the solute vibrational state was analyzed as a function of time together with the trajectory of the solvent water and the interaction with it. We will show that the solvent molecule resides near the solute molecule for a while and the solvent contributes to the relaxation by the random-noiselike Coulombic interaction only when it stays near the solute. After the solvent leaves the solute, it shows no contribution to the relaxation. The relaxation mechanism for this system is significantly different from the collisional one found for a nonpolar solute in nonpolar solvent in Paper I. Then, the relaxation rate is determined, on average, by the hydration number or local density of the solvent. Thus, the density dependence of the relaxation rate for the polar solute in supercritical water is apparently similar to that found for the nonpolar solute in nonpolar solvent, although the molecular process is quite different from each other.
The elimination of a hydrogen atom in Na(H2O)n
Authors: Chan Ka Wai , Siu Chi-Kit , Wong S. Y. , Liu Zhi-Feng
Published: September 2005

By a systematic examination on Na(H2O)n, with n=4–7, 9, 10, and 15, we demonstrate that a hydrogen loss reaction can be initiated by a single sodium atom with water molecules. This reaction is similar to the well-known size-dependent intracluster hydrogen loss in Mg+(H2O)n, which is isoelectronic to Na(H2O)n. However, with one less charge on Na(H2O)n than that on Mg+(H2O)n, the hydrogen loss for Na(H2O)n is characterized by a higher barrier and a more flexible solvation shell around the metal ion, although the reaction should be accessible, as the lowest barrier is around 8kcal∕mol. Interestingly, the hydroxide ion OH− produced in the process is stabilized by the solvation of H2O molecules and the formation of an ion pair Na+(H2O)4(H2O)n−l−4[OH−(H2O)l]. The activation barrier is reduced as the unpaired electron in Na(H2O)n moves to higher solvation shells with increasing cluster size, and the reaction is not switched off for larger clusters. This is in sharp contrast to the reaction for Mg+(H2O)n, in which the OH− ion is stabilized by direct coordination with Mg2+ and the reaction is switched off for n>17, as the unpaired electron moved to higher solvation shells. Such a contrast illustrates the important link between microsolvation environment and chemical reactivity in solvation clusters.
Comparison of model potentials for molecular-dynamics simulations of silica
Authors: Herzbach Daniel , Binder Kurt , Müser Martin H.
Published: September 2005

Structural, thermomechanical, and dynamic properties of pure silica SiO2 are calculated with three different model potentials, namely, the potential suggested by van Beest, Kramer, and van Santen (BKS) [Phys. Rev. Lett. 64, 1955 (1990)], the fluctuating-charge potential with a Morse stretch term for the short-range interactions proposed by Demiralp, Cagin, and Goddard (DCG)[Phys. Rev. Lett. 82, 1708 (1999)], and a polarizable force field proposed by Tangney and Scandolo (TS) [J. Chem. Phys. 117, 8898 (2002)]. The DCG potential had to be modified due to flaws in the original treatment. While BKS reproduces many thermomechanical properties of different polymorphs rather accurately, it also shows qualitatively wrong trends concerning the phononic density of states, an absence of the experimentally observed anomaly in the c∕a ratio at the quartz α–β transition, pathological instabilities in the β-cristobalite phase, and a vastly overestimated transition pressure for the stishovite I→II transition. These shortcomings are only partially remedied by the modified DCG potential but greatly improved by the TS potential. DCG and TS both reproduce a pressure-induced transition from α-quartz to quartz II, predicted theoretically based on the BKS potential.
Brownian dynamics simulations of sequence-dependent duplex denaturation in dynamically superhelical DNA
Authors: Mielke Steven P. , Grønbech-Jensen Niels , Krishnan V. V. , Fink William H. , Benham Craig J.
Published: September 2005

The topological state of DNA in vivo is dynamically regulated by a number of processes that involve interactions with bound proteins. In one such process, the tracking of RNA polymerase along the double helix during transcription, restriction of rotational motion of the polymerase and associated structures, generates waves of overtwist downstream and undertwist upstream from the site of transcription. The resulting superhelical stress is often sufficient to drive double-stranded DNA into a denatured state at locations such as promoters and origins of replication, where sequence-specific duplex opening is a prerequisite for biological function. In this way, transcription and other events that actively supercoil the DNA provide a mechanism for dynamically coupling genetic activity with regulatory and other cellular processes. Although computer modeling has provided insight into the equilibrium dynamics of DNA supercoiling, to date no model has appeared for simulating sequence-dependent DNA strand separation under the nonequilibrium conditions imposed by the dynamic introduction of torsional stress. Here, we introduce such a model and present results from an initial set of computer simulations in which the sequences of dynamically superhelical, 147 base pair DNA circles were systematically altered in order to probe the accuracy with which the model can predict location, extent, and time of stress-induced duplex denaturation. The results agree both with well-tested statistical mechanical calculations and with available experimental information. Additionally, we find that sites susceptible to denaturation show a propensity for localizing to supercoil apices, suggesting that base sequence determines locations of strand separation not only through the energetics of interstrand interactions, but also by influencing the geometry of supercoiling.
Assessment of Gaussian-3 and density-functional theories on the G3/05 test set of experimental energies
Authors: Curtiss Larry A. , Redfern Paul C. , Raghavachari Krishnan
Published: September 2005

The G3/99 test set [L. A. Curtiss, K. Raghavachari, P. C. Redfern, and J. A. Pople, J. Chem. Phys. 112, 7374 (2000)] of thermochemical data for validation of quantum chemical methods is expanded to include 78 additional energies including 14 enthalpies of formation of the first- and second-row nonhydrogen molecules, 58 energies of molecules containing the third-row elements K, Ca, and Ga–Kr, and 6 hydrogen-bonded complexes. The criterion used for selecting the additional systems is the same as before, i.e., experimental uncertainties less than ±1kcal∕mol. This new set, referred to as the G3/05 test set, has a total of 454 energies. The G3 and G3X theories are found to have mean absolute deviations of 1.13 and 1.01kcal∕mol, respectively, when applied to the G3/05 test set. Both methods have larger errors for the nonhydrogen subset of 79 species for which they have mean absolute deviations of 2.10 and 1.64kcal∕mol, respectively. On all of the other types of energies the G3 and G3X methods are very reliable. The G3/05 test set is also used to assess density-functional methods including a series of new functionals. The most accurate functional for the G3/05 test set is B98 with a mean absolute deviation of 3.33kcal∕mol, compared to 4.14kcal∕mol for B3LYP. The latter functional has especially large errors for larger molecules with a mean absolute deviation of 9kcal∕mol for molecules having 28 or more valence electrons. For smaller molecules B3LYP does as well or better than B98 and the other functionals. It is found that many of the density-functional methods have significant errors for the larger molecules in the test set.
Vibrational coupling in carboxylic acid dimers
Authors: Nandi Chayan K. , Hazra Montu K. , Chakraborty Tapas
Published: September 2005

The vibrational level splitting in the ground electronic state of carboxylic acid dimers mediated by the doubly hydrogen-bonded networks are investigated using pure and mixed dimers of benzoic acid with formic acid as molecular prototypes. Within the 0–2000-cm−1 range, the frequencies for the fundamental and combination vibrations of the two dimers are experimentally measured by using dispersed fluorescence spectroscopy in a supersonic jet expansion. Density-functional-theory calculations predict that most of the dimer vibrations are essentially in-phase and out-of-phase combinations of the monomer modes, and many of such combinations show significantly large splitting in vibrational frequencies. The infrared spectrum of the jet-cooled benzoic acid dimer, reported recently by Bakker et al. [J. Chem. Phys. 119, 11180 (2003)], has been used along with the dispersed fluorescence spectra to analyze the coupled g-u vibrational levels. Assignments of the dispersed fluorescence spectra of the mixed dimer are suggested by comparing the vibronic features with those in the homodimer spectrum and the predictions of density-functional-theory calculation. The fluorescence spectra measured by excitations of the low-lying single vibronic levels of the mixed dimer reveal that the hydrogen-bond vibrations are extensively mixed with the ring modes in the S1 surface.
The spectrum of vibration modes in soft opals
Authors: Cheng W. , Wang J. J. , Jonas U. , Steffen W. , Fytas G. , Penciu R. S. , Economou E. N.
Published: September 2005

Numerous vibrational modes of spherical submicrometer particles in fabricated soft opals are experimentally detected by Brillouin light scattering and theoretically identified by their spherical harmonics by means of single-phonon scattering-cross-section calculations. The particle size polydispersity is reflected in the line shape of the low-frequency modes, whereas lattice vibrations are probably responsible for the observed overdamped transverse mode.
Two ferromagnetic azido-bridged copper(II) complexes studied by first-principle electronic-structure calculation
Authors: Zhang Y. S. , Yao K. L. , Liu Z. L.
Published: September 2005

The electronic structures of two ferromagnetic polynuclear copper(II) complexes, derived from end-to-end azido ligand and tridentate (NNN donor) Schiff base ligand, have been studied using the full-potential linearized augmented plane-wave method based on the density-functional theory. They are [Cu(L1)(μ−1,3-N3)]n(ClO4)n (1) and [Cu(L2)(μ−1,3-N3)]n(ClO4)n (2). The result shows that the spin populations in these two complexes are mainly distributed on the equatorial planes of a square pyramidal that surround the copper(II) ions. There are large and positive spin populations on copper(II) ions, small and positive spin populations on the three nitrogen atoms of tridentate Schiff base ligand, and the two terminal nitrogen atoms of asymmetrical end-to-end azido ligand, while weak and negative spin populations on the central nitrogen atoms of asymmetrical end-to-end azido ligand. Ferromagnetic coupling through the asymmetrical azido ligand in these two complexes has been mainly attributed to the spin delocalization, also with weak spin-polarization effect.
A direct numerical simulation study of the buoyant rise of bubbles at O(100) Reynolds number
Authors: Esmaeeli Asghar , Tryggvason Grétar
Published: September 2005

Buoyancy-driven motion of bubbles is examined by direct numerical simulations. Two cases, with 48 monodispersed bubbles at two different gas∕liquid combinations, of deformable and nearly spherical bubbles, are simulated. For the nearly spherical bubbles Eo=0.5, and for the deformable ones Eo=4, and for both cases N=8000 and α=5.8%. This results in Re¯=91.5 and We¯=0.53 for the nearly spherical system and Re¯=77.6 and We¯=3 for the deformable one. The simulations show path oscillations of the bubbles in both cases and shape oscillations of the deformable bubbles. At quasi-steady-state, the distribution of the deformable bubbles is relatively uniform but the spherical bubbles are distributed nonuniformly as a result of the formation of horizontal “rafts.” For both cases, however, the probability density functions of the fluctuation velocities of the bubbles are found to be approximately Gaussian. The temporal autocorrelation functions of the fluctuation velocities show that the horizontal components become uncorrelated faster than the vertical component and the correlation time for the vertical autocorrelation for deformable bubbles is at least twice larger than that for nearly spherical ones.
Ab initio study of structural parameters and gap bowing in zinc-blende AlxGa1−xN and AlxIn1−xN alloys
Authors: Kanoun M. B. , Goumri-Said S. , Merad A. E. , Mariette H.
Published: September 2005

We present first-principles calculations of the structural and electronic properties of zinc-blende AlxGa1−xN and AlxIn1−xN alloys by application of the all-electron full-potential linearized augmented plane-wave method within density-functional theory and the local-density approximation. When the parameter x varies, both the lattice constant a and the bulk modulus B are found to vary linearly for AlxGa1−xN, while for AlxIn1−xN the lattice parameters show an upward bowing. The calculated band-gap variation for the two alloys varies nonlinearly as a function of composition x, with a strong downward bowing for AlxIn1−xN.
Semiempirical hybrid functional with improved performance in an extensive chemical assessment
Authors: Keal Thomas W. , Tozer David J.
Published: September 2005

It is demonstrated that there is still scope for improvement in the quality of conventional, semiempirical hybrid exchange-correlation functionals in density-functional theory. A new functional, denoted B97-3, is determined from a fit to eight chemical properties (316 data points). For a series of 25 chemical assessments (850 data points) including 17 assessments and 10 chemical properties absent from the fitting data, B97-3 provides the lowest or joint-lowest mean absolute error on 15 occasions, compared to 6, 5, and 4 occasions for B3LYP, PBE0, and B97-2, respectively [A. D. Becke, J. Chem. Phys. 98, 5648 (1993); M. Ernzerhof and G. E. Scuseria, J. Chem. Phys. 110, 5029 (1999); C. Adamo and V. Barone, J. Chem. Phys. 110, 6158 (1999); P. J. Wilson, T. J. Bradley, and D. J. Tozer, J. Chem. Phys. 115, 9233 (2001)]. Mean absolute errors from B97-3 are, on average, 21%, 18%, and 12% smaller than from these three functionals. The most notable improvements are obtained for classical reaction barriers, where the error reductions are 60%, 54%, and 27%.
Ferromagnetism of MnO and Mn3O4 nanowires
Authors: Na Chan Woong , Han Doo Suk , Kim Dae Sung , Park Jeunghee , Jeon Yoon Tae , Lee Gangho , Jung Myung-Hwa
Published: September 2005

Mixture of single-crystalline MnO and Mn3O4 nanowires was synthesized by thermal evaporation of MnCl2 powders. The diameter is 50–100nm, the length is about 20μm, and the growth direction is uniformly [100] for both cubic MnO and tetragonal Mn3O4 nanowires. The temperature-dependent magnetization and magnetic hysteresis curves suggest the Curie temperature of 12 and 43K for the MnO and Mn3O4 nanowires, respectively.
Design and simulation of InGaAs∕AlAsSb quantum-cascade lasers for short wavelength emission
Authors: Evans C. A. , Jovanović V. D. , Indjin D. , Ikonić Z. , Harrison P.
Published: September 2005

The design and simulation of an In0.53Ga0.47As∕Al0.56As0.44Sb quantum-cascade laser emitting in the near infrared is presented. Designed using a self-consistent rate equation solver coupled with an energy balance rate equation, the proposed laser has a calculated population inversion of ∼20% at 77K and sufficient gain to achieve room-temperature laser emission at λ∼2.8μm. Threshold currents in the range 4–8kA∕cm2 are estimated as the temperature increases from 77Kto300K. The output characteristics of the proposed laser are compared to an existing λ∼3.1μm In0.53Ga0.47As∕Al0.56As0.44Sb quantum-cascade structure presented in the literature.
Velocity fluctuations resulting from the interaction of a bubble with a vertical wall
Authors: Moctezuma M. F. , Lima-Ochoterena R. , Zenit R.
Published: September 2005

The interaction and motion of a spherical bubble with a vertical wall moving in an ideal fluid are analyzed. This case is representative of a bubble that moves at a high Reynolds number and has a small Weber number. Using potential flow theory, the velocity potential is obtained using a double expansion in spherical harmonics. The presence of the wall is approximated by considering the motion of a bubble and its virtual image. The motion equations, obtained considering an energy conservation argument, are solved numerically for a range of initial conditions. The mean and variance of the bubble velocity are calculated. In particular, the bubble velocity variance is obtained as a measure of the bubble velocity fluctuations resulting from the interaction with the wall. The predictions of this model are in good qualitative agreement with some recent experimental results.
Electric-field-aligned vertical growth and field emission properties of In2O3 nanowires
Authors: Li S. Q. , Liang Y. X. , Wang T. H.
Published: September 2005

Vertically aligned In2O3 nanowires are grown on InAs substrates by an electric field in the plasma sheath. The In2O3 nanowires are single crystalline with diameters less than 10nm. Field emission results show that the aligned In2O3 nanowires have lower turn-on and threshold electric fields than nonaligned ones. This is discussed in terms of orientation, emitter shapes, and density of the In2O3 nanowires.
Influence of indium tin oxide electrodes deposited at room temperature on the properties of organic light-emitting devices
Authors: Satoh Toshikazu , Fujikawa Hisayoshi , Taga Yasunori
Published: September 2005

The influence of indium tin oxide (ITO) electrodes deposited at room temperature (ITO-RT) on the properties of organic light-emitting devices (OLEDs) has been studied. The OLED on the ITO-RT showed an obvious shorter lifetime and higher operating voltage than that on the conventional ITO electrode deposited at 573K. The result of an in situ x-ray photoelectron spectroscopy analysis of the ITO electrode and the organic layer suggested that many of the hydroxyl groups that originate in the amorphous structure of the ITO-RT electrode oxidize the organic layer. The performance of the OLED on the ITO-RT is able to be explained by the oxidation of the organic layer.
Structural, magnetic, and electronic properties of (110)-oriented epitaxial thin films of the bilayer manganite La1.2Sr1.8Mn2O7
Authors: Takamura Yayoi , Grepstad Jostein K. , Chopdekar Rajesh V. , Suzuki Yuri , Marshall Ann F. , Zheng Hong , Mitchell John F.
Published: September 2005

We have synthesized (110)-oriented epitaxial thin films of the bilayer (n=2) manganite, La1.2Sr1.8Mn2O7, with the metallic/ferromagnetic a-b planes lying perpendicular to the substrate surface and the c-axis aligned in the plane of the film. X-ray diffraction and transmission electron microscopy confirm the alignment of the a-b planes along the [11¯0] substrate direction. The films consist primarily of the n=2 phase with a minor component of the n=1(La,Sr)2MnO4 and n=∞(La,Sr)MnO3 phases. A resistivity maximum coincides with a ferromagnet/paramagnet transition at a reduced Tc∼90K (versus 120K for bulk), indicative of the effects of epitaxial strain. The films display similar anisotropic properties to their bulk counterpart with the magnetically easy direction confined to the a-b planes and 20–200 times lower resistivity for current flowing along the a-b planes compared to the c-axis.
Spin-dependent tunneling spectroscopy in single-crystal Fe∕MgO∕Fe tunnel junctions
Authors: Ando Y. , Miyakoshi T. , Oogane M. , Miyazaki T. , Kubota H. , Ando K. , Yuasa S.
Published: September 2005

We report a detailed spin-dependent tunneling spectroscopy in single-crystal Fe(001)∕MgO(001)∕Fe(001) magnetic tunnel junctions (MTJs) that show a giant tunnel magnetoresistance effect. Spectra for antiparallel magnetic configurations show asymmetry because of extrinsic electron scatterings caused by structural defects at the barrier/electrode interfaces. Surprisingly, spectra for parallel magnetic configurations exhibit a complex oscillatory structure that has never been observed in conventional MTJs with an aluminum-oxide tunnel barrier. The complex spectra reflect the tunneling process via interface resonant states. These results provide some information that helps to elucidate the physics of spin-dependent electron tunneling and to further enhance magnetoresistance.
Dielectric dispersion of CaCu3Ti4O12 ceramics at high temperatures
Authors: Zhang J. L. , Zheng P. , Wang C. L. , Zhao M. L. , Li J. C. , Wang J. F.
Published: September 2005

Ca Cu 3 Ti 4 O 12 ceramics has been prepared by the conventional solid-state reaction method under different sintering conditions. Dielectric properties have been investigated in the temperature range of 25–350°C within the frequency range of 40Hz–10MHz. It has been found that both the dielectric constants and the grain sizes increase with the sintering time. A relaxation has been observed in the frequency range of 100Hz–100kHz, apart from the one already known in the frequency range higher than 100kHz. High-temperature dielectric dispersion shows one large low-frequency response and two Debye-type relaxations. Activation energy values of these two relaxations are 0.084 and 0.678eV, respectively. An equivalent circuit model is suggested, which well explains the dielectric dispersion.
In
Ga
As
–
Al
In
As
∕
In
P
terahertz quantum cascade laser
Authors: Ajili Lassaad , Scalari Giacomo , Hoyler Nicolas , Giovannini Marcella , Faist Jérôme
Published: September 2005

Operation of a quantum-cascade laser based on the In0.52Al0.48As–In0.53Ga0.47As∕InP material is demonstrated at a frequency of 3.6terahertz. The active region is based on a bound-to-continuum transition combined with an optical phonon extraction. The optical waveguide exploits a combination of metallic and dielectric confinement. Threshold current density of 460A∕cm2 at 10K and a maximum operating temperature of 45K are achieved.
Spin-glass behavior in CeCu2-type uranium compound U2AuGa3
Authors: Li D. X. , Yamamura T. , Nimori S. , Yubuta K. , Shiokawa Y.
Published: September 2005

We present the results of ac and dc susceptibility, magnetization, magnetic relaxation, specific heat, and electrical resistivity measurements on U2AuGa3, an orthorhombic CeCu2-type nonmagnetic atom disorder system. These data clearly indicate that U2AuGa3 undergoes a spin glass phase transition at a static freezing temperature Ts=23.6K, in spite of the lack of triangular magnetic structure. It is observed that the variation of the characteristic temperature Tir (the bifurcation point between field-cooled and zero-field-cooled susceptibilities) with applied field H for U2AuGa3 is not consistent with the “AT line,” but follows a Tir∝−H2∕5 law. The observed spin glass behavior and the formation of frustrated magnetic interactions in U2AuGa3 are discussed in a magnetic cluster model.
Investigating the Mechanism of Uranium Removal by Zerovalent Iron
Authors: Noubactep Chicgoua , Meinrath Günther , Merkel Broder J.
Published: September 2005

Environmental Context.Groundwater is the water that fills the spaces between sand, soil, and rock below the water table. It discharges into ecologically sensitive wetlands and is used as drinking water or in agriculture and industry. Inappropriate waste disposal and poor land management can contaminate groundwater and may minimize its use for decades. The common method for pumping contaminated groundwater to the surface for treatment is costly and labour intensive. Zerovalent iron is a new, more cost-effective method of groundwater remediation.
Abstract. Zerovalent iron (ZVI) has been proposed as a reactive material in permeable in situ walls for groundwater contaminated by metal pollutants. For such pollutants that interact with corrosion products, the determination of the actual mechanism of their removal is very important to predict their stability in the long term. From a study of the effects of pyrite (FeS2) and manganese nodules (MnO2) on the uranium removal potential of a selected ZVI material, a test methodology (FeS2–MnO2 method) is suggested to follow the pathway of contaminant removal by ZVI materials. An interpretation of the removal potential of ZVI for uranium in the presence of both additives corroborates coprecipitation with iron corrosion products as the initial removal mechanism for uranium.
A Two-Phase Box Model to Study Mercury Atmospheric Mechanisms
Authors: Pan Li , Carmichael Gregory R.
Published: September 2005

Environmental Context. Elemental mercury (Hg0) is converted to divalent mercury (Hg2+) in the atmosphere, largely in water droplets. The wet deposition of Hg2+ is a major concern to human health. Because it is bio-accumulated through the food chain, consumption of contaminated fish can be particularly dangerous. Currently the budgets of mercury in the atmosphere are poorly understood, due in part to uncertainties in the chemical pathways controlling the speciated forms of mercury. Improved mercury chemistry models are needed to better predict Hg2+ levels in water droplets and to estimate wet deposition of Hg2+ in order to help assess the potential health risks of mercury.
Abstract. A box model designed to investigate mercury chemical mechanisms in the atmosphere is presented. Aqueous-phase mercury oxidation–reduction, sulfite, and oxygen reactions, along with gas-phase mercury reactions are included in the model. The model is used to evaluate the key reaction steps under several atmospheric conditions. The sensitivity of the results to parameters, initial conditions, and assumptions regarding chemical mechanisms are investigated. Model simulations were performed in closed (liquid only) and two-phase (liquid/gas) systems. In the liquid phase, elemental mercury is oxidized to divalent mercury by ozone at night and by hydroxide radical and ozone during the day. Ozone is shown to play a significant role in mercury mechanisms by oxidizing elemental mercury directly and producing hydroxyl and hydroperoxyl radicals. The effects of sulfite on mercury aqueous chemistry were found to be limited due to its rapid conversion to sulfate. The results of two-phase simulations show that Hg2+ concentrations exhibit a diurnal cycle, increasing before the sunrise and decreasing before the sunset due to the aqueous-phase hydrogen–oxygen photochemistry that produces hydroxyl and hydroperoxyl radicals. Gas-phase mercury oxidation reactions significantly enhance the levels of Hg2+ in the aqueous phase, and reactions with ozone and hydroxyl radicals play the leading role. The effect of reactive chlorine on mercury chemistry can be important.
Current Perspectives in Arsenic Environmental and Biological Research
Authors: Francesconi Kevin A.
Published: September 2005

Environmental Context. Arsenic occurs in rock, fresh water and seawater. Organic arsenic compounds are found as natural constituents of many organisms and, because some, e.g. seafood, are consumed by humans, there is ongoing health interest in their arsenic content. Thio-arsenicals, a newly discovered group of arsenic compounds, may be integral to understanding the environmental behaviour of arsenic. This paper reviews recent research in arsenic environmental chemistry and discusses ideas intended to stimulate future research in this area.
Abstract. Recent results in the field of arsenic environmental and biological chemistry are presented, in particular the relevance of the discoveries to issues of human health are discussed.
Response of stream macroinvertebrates to changes in salinity and the development of a salinity index
Authors: Horrigan Nelli , Choy Satish , Marshall Jonathan , Recknagel Friedrich
Published: September 2005

Many streams and wetlands have been affected by increasing salinity, leading to significant changes in flora and fauna. The study investigates relationships between macroinvertebrate taxa and conductivity levels (µS cm−1) in Queensland stream systems. The analysed dataset contained occurrence patterns of frequently found macroinvertebrate taxa from edge (2580 samples) and riffle (1367 samples) habitats collected in spring and autumn over 8 years. Sensitivity analysis with predictive artificial neural network models and the taxon-specific mean conductivity values were used to assign a salinity sensitivity score (SSS) to each taxon (1—very tolerant, 5—tolerant, 10—sensitive). Salinity index (SI) based on the cumulative SSS was proposed as a measurement of change in macroinvertebrate communities caused by salinity increase. Changes in macroinvertebrate communities were observed at relatively low salinities, with SI rapidly decreasing to ~800–1000 µS cm−1 and decreasing further at a slower rate. Natural variability and water quality factors were ruled out as potential primary causes of the observed changes by using partial canonical correspondence analysis and subsets of the data with only good water quality.
Estimating production of gilvin from catchment leaf litter during seasonal rains
Authors: Qiu Song , McComb Arthur J. , Bell Richard W. , Davis Jenny A.
Published: September 2005

The yellow substance, gilvin, is an important component of water quality in natural waters. Quantitative study of gilvin production is difficult since gilvin is not a well defined substance. In the present study, leaf litter from four common tree species of south-western Australia were exposed to rainy weather for 183 days and leachate properties were monitored. The gilvin leaching from litter was estimated using a ‘humic acid (HA) equivalent’ concept, derived by drawing an analogy between the spectrophotometric properties of gilvin and that of humic acid. Gilvin (g440, m−1) was leached from litter primarily during the first few weeks after the commencement of the wet season. On average, 13% less gilvin was leached under ‘flooded’ conditions compared with ‘non-flooded’ conditions. Litter leaching in the presence of soil caused a significant time lag (about a month) for the peak load to occur, and reduced the total gilvin in the leachate through soil–litter interactions. Banksia menziesii leaves produced little gilvin, equivalent to 6.6% of that leached from the flooded gum. The Eucalyptus species, such as flooded gum and jarrah, common in wooded catchments in the region, appeared to be a major player producing yellow-coloured substances under annual rainfall conditions in south-western Australia.
To what extent do geographic and associated environmental variables correlate with kelp morphology across temperate Australia?
Authors: Fowler-Walker Meegan J. , Connell Sean D. , Gillanders Bronwyn M.
Published: September 2005

Intraspecific variation in morphology is common among marine algae and may allow plants to exist across a wide geography and range of environmental conditions. Morphological variation of Ecklonia radiata has been described over thousands of kilometres of the temperate Australian coastline; however, the degree to which this morphological variability is related to geographic and environmental variation is unknown. We tested the hypotheses that: (1) variation in the morphology of Ecklonia radiata, growing in both monospecific and mixed stands, is related to variation in latitude, longitude, wave exposure, temperature, depth and plant density (collectively referred to as ‘physical variables’); and (2) measures of morphological dissimilarity in E. radiata are greatest among locations that are separated by the largest geographic distances. The combined effect of the physical variables accounted for 74% of the variation in both monospecific and mixed stands. The majority of this variation was related to longitude and the remainder to wave exposure, water temperature and plant density. In monospecific stands, measures of morphological dissimilarity were consistently large between locations that were separated by the greatest geographical distances (>2500 km). The existence of such relationships may not indicate causality, but do contribute to a broad based understanding of major ecological patterns across temperate Australia’s coastline.
Hierarchical metabolomics demonstrates substantial compositional similarity between genetically modified and conventional potato crops
Authors: Catchpole Gareth S. , Beckmann Manfred , Enot David P. , Mondhe Madhav , Zywicki Britta , Taylor Janet , Hardy Nigel , Smith Aileen , King Ross D. , Kell Douglas B. , Fiehn Oliver , Draper John
Published: September 2005

There is current debate whether genetically modified (GM) plants might contain unexpected, potentially undesirable changes in overall metabolite composition. However, appropriate analytical technology and acceptable metrics of compositional similarity require development. We describe a comprehensive comparison of total metabolites in field-grown GM and conventional potato tubers using a hierarchical approach initiating with rapid metabolome “fingerprinting” to guide more detailed profiling of metabolites where significant differences are suspected. Central to this strategy are data analysis procedures able to generate validated, reproducible metrics of comparison from complex metabolome data. We show that, apart from targeted changes, these GM potatoes in this study appear substantially equivalent to traditional cultivars.
Structure and reactivity of hydroxypropylphosphonic acid epoxidase in fosfomycin biosynthesis by a cation- and flavin-dependent mechanism
Authors: McLuskey Karen , Cameron Scott , Hammerschmidt Friedrich , Hunter William N.
Published: September 2005

The biosynthesis of fosfomycin, an oxirane antibiotic in clinical use, involves a unique epoxidation catalyzed by (
S
)-2-hydroxypropylphosphonic acid epoxidase (HPPE). The reaction is essentially dehydrogenation of a secondary alcohol. A high-resolution crystallographic analysis reveals that the HPPE subunit displays a two-domain combination. The C-terminal or catalytic domain has the cupin fold that binds a divalent cation, whereas the N-terminal domain carries a helix-turn-helix motif with putative DNA-binding helices positioned 34 Å apart. The structure of HPPE serves as a model for numerous proteins, of ill-defined function, predicted to be transcription factors but carrying a cupin domain at the C terminus. Structure-reactivity analyses reveal conformational changes near the catalytic center driven by the presence or absence of ligand, that HPPE is a Zn
2+
/Fe
2+
-dependent epoxidase, proof that flavin mononucleotide is required for catalysis, and allow us to propose a simple mechanism that is compatible with previous experimental data. The participation of the redox inert Zn
2+
in the mechanism is surprising and indicates that Lewis acid properties of the metal ions are sufficient to polarize the substrate and, aided by flavin mononucleotide reduction, facilitate the epoxidation.
Sulfur accumulation in the timbers of King Henry VIII's warship
Mary Rose
: A pathway in the sulfur cycle of conservation concern
Authors: Sandström Magnus , Jalilehvand Farideh , Damian Emiliana , Fors Yvonne , Gelius Ulrik , Jones Mark , Salomé Murielle
Published: September 2005

In marine-archaeological oak timbers of the
Mary Rose
large amounts of reduced sulfur compounds abound in lignin-rich parts such as the middle lamella between the cell walls, mostly as thiols and disulfides, whereas iron sulfides and elemental sulfur occur in separate particles. Synchrotron-based x-ray microspectroscopy was used to reveal this environmentally significant accumulation of organosulfur compounds in waterlogged wood. The total concentration of sulfur in reduced forms is ≈1 mass % throughout the timbers, whereas iron fluctuates up to several mass %. Conservation methods are being developed aiming to control acid-forming oxidation processes by removing the reactive iron sulfides and stabilizing the organosulfur compounds.
Ubiquity and diversity of ammonia-oxidizing archaea in water columns and sediments of the ocean
Authors: Francis Christopher A. , Roberts Kathryn J. , Beman J. Michael , Santoro Alyson E. , Oakley Brian B.
Published: September 2005

Nitrification, the microbial oxidation of ammonia to nitrite and nitrate, occurs in a wide variety of environments and plays a central role in the global nitrogen cycle. Catalyzed by the enzyme ammonia monooxygenase, the ability to oxidize ammonia was previously thought to be restricted to a few groups within the β- and γ-Proteobacteria. However, recent metagenomic studies have revealed the existence of unique ammonia monooxygenase α-subunit (amoA) genes derived from uncultivated, nonextremophilic Crenarchaeota. Here, we report molecular evidence for the widespread presence of ammonia-oxidizing archaea (AOA) in marine water columns and sediments. Using PCR primers designed to specifically target archaealamoA, we find AOA to be pervasive in areas of the ocean that are critical for the global nitrogen cycle, including the base of the euphotic zone, suboxic water columns, and estuarine and coastal sediments. Diverse and distinct AOA communities are associated with each of these habitats, with little overlap between water columns and sediments. Within marine sediments, most AOA sequences are unique to individual sampling locations, whereas a small number of sequences are evidently cosmopolitan in distribution. Considering the abundance of nonextremophilic archaea in the ocean, our results suggest that AOA may play a significant, but previously unrecognized, role in the global nitrogen cycle.
A bacterial group II intron-encoded reverse transcriptase localizes to cellular poles
Authors: Zhao Junhua , Lambowitz Alan M.
Published: September 2005

The
Lactococcus lactis
Ll.LtrB group II intron encodes a reverse transcriptase (LtrA protein) that binds the intron RNA to promote RNA splicing and intron mobility. Here, we used LtrA–GFP fusions and immunofluorescence microscopy to show that LtrA localizes to cellular poles in
Escherichia coli
and
Lactococcus lactis
. This polar localization occurs with or without coexpression of Ll.LtrB intron RNA, is observed over a wide range of cellular growth rates and expression levels, and is independent of replication origin function. The same localization pattern was found for three nonoverlapping LtrA subsegments, possibly reflecting dependence on common redundant signals and/or protein physical properties. When coexpressed in
E. coli
, LtrA interferes with the polar localization of the
Shigella
IcsA protein, which mediates polarized actin tail assembly, suggesting competition for a common localization determinant. The polar localization of LtrA could account for the preferential insertion of the Ll.LtrB intron in the origin and terminus regions of the
E. coli
chromosome, may facilitate access to exposed DNA in these regions, and could potentially link group II intron mobility to the host DNA replication and/or cell division machinery.
Sex and estrogenic effects on coexpression of mRNAs in single ventromedial hypothalamic neurons
Authors: Devidze N. , Mong J. A. , Jasnow A. M. , Kow L.-M. , Pfaff D. W.
Published: September 2005

Regulated gene expression in single neurons can be linked to biophysical events and behavior in the case of estrogen-regulated gene expression in neurons in the ventrolateral portion of the ventromedial nucleus (VMN) of the hypothalamus. These cells are essential for lordosis behavior. What genes are coexpressed in neurons that have high levels of mRNAs for estrogen receptors (ERs)? We have been able to isolate and measure certain mRNAs from individual VMN neurons collected from rat hypothalamus. Large numbers of neurons express mRNA for ERα, but these neurons are not identical with the population of VMN neurons expressing the likely gene duplication product, ERβ. An extremely high proportion of neurons expressing either ER also coexpress mRNA for the oxytocin receptor (OTR). This fact matches the known participation of oxytocin binding and signaling in sexual and affiliative behaviors. In view of data that ER and OTR can signal through PKCs, we looked at coexpression of selected PKCs in the same individual neurons. The most discriminating analysis was for triple coexpression of ERs, OTR, and each selected PKC isoform. These patterns of triple coexpression were significantly different for male vs. female VMN neurons. Further, individual neurons expressing ERα could distribute their signaling across the various PKC isoforms differently in different cells, whereas the reverse was not true. These findings and this methodology establish the basis for systematic linkage of the brain's hormone-sensitive signaling pathways to biophysical and behavioral mechanisms in a well studied mammalian system.