bluuebunny/crossref_metadata_2025 huggingface dataset:
GNAS1 mutational analysis in pseudohypoparathyroidism
Authors: Ahmed S. F. , Dixon P. H. , Bonthron D. T. , Stirling H. F. , Barr D. G. D. , Kelnar C. J. H. , Thakker R. V.
Published: November 2010

OBJECTIVE

Mutations of the GNAS1 gene, which is located on chromosome 20q13.11 and encodes the α‐subunit of the stimulatory GTP‐binding protein, have been identified in patients with pseudohypoparathyroidism type Ia (PHPIa) and pseudopseudohypoparathyroidism (PPHP). We have undertaken studies to determine the prevalence of GNAS1 mutations and to explore methods for their more rapid detection.

METHODS

Thirteen unrelated families (8 with PHPIa and PPHP patients, and 5 with PPHP patients only) were investigated for GNAS1 mutations in the 1050 base‐pair (bp) region spanning exons 2–13 by single‐stranded conformational polymorphism (SSCP) and DNA sequence analysis.

RESULTS

GNAS1 mutations were detected in 4 of the 8 families with PHPIa patients. These consisted of: two novel de novo missense mutations (Pro115Ser and Glu259Val) in two families and an identical 4 bp deletion of codons 189 and 190 resulting in a frameshift in two unrelated families. These results expand the spectrum of GNAS1 mutations associated with this disorder and confirm the presence of a mutational hot‐spot involving codons 189 and 190. SSCP analysis was found to be a specific and sensitive method that detected all 4 mutations. GNAS1 mutations were not detected in any of the PPHP only families.

CONCLUSIONS

The pseudohypoparathyroid disorders appear to represent a heterogeneous group with GNAS1 mutations forming the molecular aetiology in approximately 50% of pseudohypoparathyroidism type Ia families. Such mutations can be reliably identified by single‐stranded conformational polymorphism and this will help to supplement the clinical evaluation of some patients and their families, particularly as the disease may not be fully penetrant.
Corticotrophin and vasopressin responses to metoclopramide in patients with hypothalamic amenorrhoea
Authors: Seki K. , Kato T. , Sekiya S.
Published: November 2010

OBJECTIVE A dopamine (DA) antagonist, metoclopramide, stimulates ACTH secretion in some women with hypothalamic amenorrhoea (HA) but not in normal women. Metoclopramide may stimulate ACTH secretion by decreasing dopaminergic inhibition of ACTH release. Furthermore, metoclopramide stimulates AVP secretion, and AVP is a stimulator of ACTH. Therefore, AVP may also be involved in the ACTH responses to metoclopramide. The relation between AVP and ACTH responses to metoclopramide were evaluated in normal women and women with HA to obtain more insight into the role of DA in the regulation of ACTH and AVP secretion.

DESIGN ACTH, cortisol and AVP levels were measured before and after the administration of metoclopramide in 11 normal women during the early follicular phase and 12 women with HA.

MEASUREMENTS ACTH was measured by immunoradiometric assay. AVP and cortisol were measured by radioimmunoassay.

RESULTS The administration of metoclopramide significantly increased circulating levels of ACTH and cortisol in the women with HA, but not in the normal women. It increased AVP levels both in the normal women and in the women with HA. The incremental AVP response to metoclopramide was not significantly different between the two groups of women.

CONCLUSION The effect of metoclopramide on AVP secretion may not be dependent on central dopaminergic activity, and the ACTH and cortisol responses to metoclopramide in the women with hypothalamic amenorrhoea are not accounted for by the augmented AVP response to metoclopramide.
Ulinastatin in the treatment of acute pancreatitis: A multicenter clinical trial
Authors: CHEN Shi Yao , WANG Ji Yao , Shanghai Collaboration Group on Ulinastatin Clinical Trials For The
Published: November 2010

OBJECTIVE:  To assess the effectiveness of Chinese‐made ulinastatin in the treatment of patients with acute edematous pancreatitis (AEP) and acute hemorrhagic and necrotic pancreatitis (AHNP).

METHODS:  A multicenter randomized controlled clinical trial was performed. Stratified by AHNP or AEP, patients were randomly allocated into either the treatment group (with ulinastatin) or the control group (treatment with cabexate or octreotide). Clinical symptoms and signs were scored as none, mild, moderate or severe. Laboratory tests included serum amylase, liver and renal function tests, routine blood tests, serum glucose, calcium, blood pH and PaO2. Clinical results were assessed as cured, significantly effective, effective and non‐effective. All adverse effects were recorded.

RESULTS:  From April to July 2000, a total of 94 patients with acute pancreatitis were enrolled into the study (50 males; 44 females). In this patient group, there were 68 cases of mild pancreatitis and 26 cases of severe pancreatitis. The study showed that the global effective rates of ulinastatin and cabexate in treating AEP were 100%, whereas the cured rate for ulinastatin was 83.3%, which was a little higher than that for cabexate (71.4%), but this difference was not statistically significant. Clinical symptoms, such as abdominal pain and distension, almost disappeared within 3−5 days in both groups for both treatment protocols. The global effective rate of ulinastatin in treating AHNP was similar to that of octreotide (78.6 vs 81.9%; P= 0.840). The main complication in AHNP was pancreatic pseudocyst. Only one case showed increased levels of alanine aminotransferase. No adverse effects, including allergy, skin rash and decreases in the white blood cell count, were noted. No abnormalities in liver and renal function, electrolytes or routine blood tests were noted.

CONCLUSIONS:  Ulinastatin was shown to be effective in treating AEP and AHNP with few adverse effects.
Characterizing blood pressure control in individuals with Type 2 diabetes: the relationship between clinic and self‐monitored blood pressure
Authors: Mazze R. S. , Simonson G. D. , Robinson R. L. , Kendall D. M. , Idrogo M. A. , Adlis S. A. , Boyce K. S. , Dunne C. J. , Anderson R. L. , Bergenstal R. M.
Published: November 2010

Aims To determine the relationship between blood pressure (BP) measurement in the clinic and self‐monitored blood pressure (SMBP); and to evaluate the accuracy of self‐reported data in patients with Type 2 diabetes treated intensively for hypertension.

Methods Seventy subjects had baseline and 1‐week follow‐up clinic BP measured using an Omron 907® automated device. During a contemporaneous 14‐day period these subjects measured their BP at least four times each day using an Omron IC® semiautomatic portable monitor which, unknown to them, contained an onboard memory capable of storing BP with corresponding time and date.

Results There was no significant difference between mean clinic and mean self‐monitored BP. Correlations between clinic BP and SMBP were r = 0.61 (P < 0.0001) for systolic BP and r = 0.69 (P < 0.0001) for diastolic BP. Clinic BP classified 56 subjects as uncontrolled hypertension (BP ≥ 130/80 mmHg, adjusted for diabetes) and 14 subjects as controlled hypertension. Using World Health Organization‐International Society of Hypertension criteria for SMBP (≥ 125/75 mmHg), 55 cases of clinic classified uncontrolled hypertension were confirmed, resulting in 98% sensitivity. Clinic and SMBP agreed in one case of controlled hypertension, resulting in 7% specificity. For all subjects, the median percent of values exceeding SMBP criteria for controlled hypertension was systolic 92% and diastolic 70%. Self‐reporting precision averaged 89 ± 10% (range 45–100%); under‐reporting was 25 ± 16% (ranging from 0 to 56%) and over‐reporting was 12 ± 15% (ranging from 0 to 46%). The overall logbook mean was not significantly different from the downloaded data from the Omron IC® monitors.

Conclusions SMBP was able to identify 13 patients with uncontrolled hypertension who, by clinic BP measurement, had been classified as controlled.
Fine structure physical mapping of a 1·9 Mb region of chromosome 13q12
Authors: STILL I. H. , ROBERTS T. , COWELL J. K.
Published: November 2010

Ann. Hum. Genet. (1997), 61, 15–24

In this paper we described the physical map of a 1·9 Mb region in chromosome region 13q12. Although in the text we described that the motivation for this effort was to identify the breakpoint in an 8;13 translocation associated with myeloproliferative disease, none of the results presented in fact referred to that localization. However, a reference to the position of a breakpoint was given in Figure 2 and was derived from a figure constructed from early mapping data and submitted by mistake instead of the corrected figure which should not have included this information. We now know that this is not the position of the translocation breakpoint. All of the other mapping details in Figure 2 are correct. The authors regret this error and any inconvenience it may have caused.
Molecular cloning, functional characterization and genomic organization of four alternatively spliced isoforms of the human organic cation transporter 1 (hOCT1/SLC22A1)
Authors: HAYER M. , BÖNISCH H. , BRÜSS M.
Published: November 2010

Ann. Hum. Genet. (1999), 63, 473–482

Correction

The authors wish to add the following correction to this paper:

The genomic organization of the human organic cation transporter (hOCT1/SLC22A1) has recently been described by us to consist of 7 exons [Molecular cloning, functional characterization and genomic organization of four alternatively spliced isoforms of the human organic cation transporter 1(hOCT1/SLC22A1); Ann. Hum. Genet. 63: 473–482]. A reexamination revealed 11 exons instead of 7. The mistake occurred through cDNA contamination. The corrected gene structure of the hOCT1 gene is available at EMBL under the following accession numbers:

AJ243995 (Exon 1), AJ243996 (Exon 2), AJ276051 (Exon 3), AJ276052 (Exon 4), AJ276053 (Exon 5 and 6), AJ245460 (Exon 7), AJ243998 (Exon 8), AJ243999 (Exon 9 and 10) and AJ244000 (Exon 11).
Androgensubstitution des Mannes aus der Sicht des Urologen
Authors: Djavan B. , Marberger M.
Published: November 2010

Zusammenfassung: In dieser Übersicht werden Argumente dafür präsentiert, daß eine Substitutionstherapie mit Testosteron in fortgeschrittenem Lebensalter nur für hypogonadale Männer reserviert bleiben sollte, die einen PSA‐Wert unter den altersspezifischen Grenzen aufweisen (Alter 40 – 50: 2,5 ng/ml, Alter 50 – 60: 3,5 ng/ml, Alter 60 – 70: 4,5 ng/ml, Alter über 70: 6,5 ng/ml). Weiters sollte im Fall einer positiven Familienanamnese hinsichtlich eines Prostatakarzinoms und bei Patienten mit einer bioptisch histologisch verifizierten intraepithelialen Neoplasie der Prostata sowie mit einer atypischen adenomatösen Hyperplasie von einer Substitutionstherapie mit Testosteron Abstand genommen werden. Im Falle einer Entscheidung zugunsten einer Substitutionstherapie sollten aufgrund der heutigen Datenlage in 3monatlichen Abständen PSA‐Bestimmung und rektale Palpation erfolgen; bei geringstem Verdacht sollte eine Prostatabiopsie durchgeführt werden und im Falle einer präkanzerösen Veränderung die Substitutionstherapie sofort abgesetzt werden. Eine breite Anwendung der Androgen‐Substitutionstherapie kann somit nicht empfohlen werden, sie bleibt streng selektierten Patienten vorbehalten, die in Anbetracht der unsicheren Datenlage (bezüglich der Neuentstehung oder Progression eines Prostatakarzinoms) auch sorgfältig aufgeklärt werden müssen. Neuere Erkenntnisse zur genetischen Entstehung des Prostatakarzinoms sowie zum Einfluß der Androgene auf die Prostata werden künftig eine genaue Risikoabschätzung beim individuellen Patienten ermöglichen und dadurch auch eine optimierte Patientenselektion für die Androgen‐Substitution gestatten.
Design and fabrication technology for high performance electrical pumped terahertz photonic crystal band edge lasers with complete photonic band gap
Authors: Zhang Hua , Scalari Giacomo , Faist Jérôme , Dunbar L. Andrea , Houdré Romuald
Published: November 2010

We detail the design and fabrication technology of two-dimensional photonic crystal (PhC) band edge emitting quantum cascade lasers (QCLs) operating at terahertz frequencies (∼3.3 THz). The entire QCL active layer has been deeply etched to form a triangular lattice PhC, in which a complete in-plane photonic band gap for TM polarized light exists. Strong vertical optical confinement is provided by metal-metal plasmon waveguide fabricated with thermocompression bonding and planarization. Benzocyclobutene is employed as a low loss medium to planarize the PhC structure. By tailoring the top metal contact on the planarized PhC structures, electrical current injection pad can also be defined. The lasing properties can be controlled by engineering the photonic band structure. Broad band continuous single mode tuning over 30 GHz was observed; while lower current threshold density and higher operation temperature compared to Fabry–Perot (FP) asers were obtained.
Manifestation of macroscopic correlations in elementary reaction kinetics. II. Irreversible reaction A+B→C
Authors: Kipriyanov Alexander A. , Kipriyanov Alexey A. , Doktorov Alexander B.
Published: November 2010

The applicability of the Encounter Theory (ET) (the prototype of the Collision Theory) concepts for widely occurring diffusion assisted irreversible bulk reaction A+B→C (for example, radical reaction) in dilute solutions with arbitrary ratio of initial concentrations of reactants has been treated theoretically with modern many-particle method for the derivation of non-Markovian binary kinetic equations. The method shows that, just as in the reaction A+A→C considered earlier, the agreement with the Encounter Theory is observed when the familiar Integral Encounter Theory is used which is just a step in the derivation of kinetic equations in the framework of the method employed. It allows for two-particle correlations only, and fails to consider the correlation of reactant simultaneously with a partner and with a reactant in the bulk. However, the next step leading to the Modified Encounter Theory under reduction of equations to a regular form both extends the time applicability interval of ET homogeneous rate equation (as for reactions proceeding in excess of one of the reactants), and yields the inhomogeneous equation of the Generalized Encounter Theory (GET) that reveals macroscopic correlations induced by the encounters in a reservoir of free walks in full agreement with physical considerations. This means that the encounters of reactants in solution are correlated at rather large time interval of the reaction course. However, unlike the reaction A+A→C of identical reactants, the reaction A+B→C accumulation of the above macroscopic correlations (even with the initial concentrations of reactants being equal) proceeds much slower. Another distinction is that for the reaction A+A→C the long-term behavior of ET and GET kinetics is the same, while in the reaction A+B→C these kinetics behave differently. It is of interest that just taking account of the above macroscopic correlations in the reaction A+B→C (in GET) results in the universal character of the long-term behavior of the kinetics for the case of equal initial concentrations of reactants and that where one of the reactants is in excess. This is more natural from the point of view of the reaction course on the encounters of reactants in solutions.
Forcing for statistically stationary compressible isotropic turbulence
Authors: Petersen Mark R. , Livescu Daniel
Published: November 2010

Linear forcing has been proposed as a useful method for forced isotropic turbulence simulations because it is a physically realistic forcing method with a straightforward implementation in physical-space numerical codes [T. S. Lundgren, “Linearly forced isotropic turbulence,” Annual Research Briefs (Center for Turbulence Research, Stanford, CA, 2003), p. 461; C. Rosales and C. Meneveau, “Linear forcing in numerical simulations of isotropic turbulence: Physical space implementations and convergence properties,” Phys. Fluids 17, 095106 (2005)]. Here, extensions to the compressible case are discussed. It is shown that, unlike the incompressible case, separate solenoidal and dilatational parts for the forcing term are necessary for controlling the stationary state of the compressible case. In addition, the forcing coefficients can be cast in a form that allows the control of the stationary state values of the total dissipation (and thus the Kolmogorov microscale) and the ratio of dilatational to solenoidal dissipation. Linear full spectrum forcing is also compared to its low wavenumber restriction. Low wavenumber forcing achieves much larger Taylor Reynolds number at the same resolution. Thus, high Reynolds number asymptotics can be more readily probed with low wavenumber forced simulations. Since, in both cases, a solenoidal/dilatational decomposition of the velocity field is required, the simplicity of the full spectrum linear forcing implementation in physical-space numerical codes is lost. Nevertheless, low wavenumber forcing can be implemented without using a full Fourier transform, and so is computationally less demanding.
Spatial instability of coflowing liquid-gas jets in capillary flow focusing
Authors: Si Ting , Li Fang , Yin Xie-Yuan , Yin Xie-Zhen
Published: November 2010

Considering both the first nonaxisymmetric (n=1) and the axisymmetric (n=0) disturbances, a viscous spatial instability analysis of coflowing liquid-gas jets in capillary flow focusing is carried out. A detailed parametric study is performed to explore characteristics of the spatially amplified branch in a convectively unstable regime. The numerical results show that the Weber number and the velocity at the interface have significant influences on the transition between axisymmetric and nonaxisymmetric instabilities, whereas the other parameters such as the Reynolds number, the slope of the liquid velocity profile at the interface, the density ratio, and the viscosity ratio hardly change the transition. Nonaxisymmetric disturbances grow faster than axisymmetric ones for relatively high Weber numbers. Particularly, the comparison of the theoretical prediction with the experimental results reported by Si et al. [J. Fluid Mech. 629, 1 (2009)] indicates that the spatial instability analysis is in better agreement with experiments than the temporal instability analysis for moderate and high Weber numbers.
Calibrated nanoscale capacitance measurements using a scanning microwave microscope
Authors: Huber H. P. , Moertelmaier M. , Wallis T. M. , Chiang C. J. , Hochleitner M. , Imtiaz A. , Oh Y. J. , Schilcher K. , Dieudonne M. , Smoliner J. , Hinterdorfer P. , Rosner S. J. , Tanbakuchi H. , Kabos P. , Kienberger F.
Published: November 2010

A scanning microwave microscope (SMM) for spatially resolved capacitance measurements in the attofarad-to-femtofarad regime is presented. The system is based on the combination of an atomic force microscope (AFM) and a performance network analyzer (PNA). For the determination of absolute capacitance values from PNA reflection amplitudes, a calibration sample of conductive gold pads of various sizes on a SiO2 staircase structure was used. The thickness of the dielectric SiO2 staircase ranged from 10 to 200 nm. The quantitative capacitance values determined from the PNA reflection amplitude were compared to control measurements using an external capacitance bridge. Depending on the area of the gold top electrode and the SiO2 step height, the corresponding capacitance values, as measured with the SMM, ranged from 0.1 to 22 fF at a noise level of ∼2 aF and a relative accuracy of 20%. The sample capacitance could be modeled to a good degree as idealized parallel plates with the SiO2 dielectric sandwiched in between. The cantilever/sample stray capacitance was measured by lifting the tip away from the surface. By bringing the AFM tip into direct contact with the SiO2 staircase structure, the electrical footprint of the tip was determined, resulting in an effective tip radius of ∼60 nm and a tip-sample capacitance of ∼20 aF at the smallest dielectric thickness.
Binary nucleation rates for ethanol/water mixtures in supersonic Laval nozzles
Authors: Tanimura Shinobu , Dieregsweiler Uta M. , Wyslouzil Barbara E.
Published: November 2010

Although the conditions corresponding to the onset of condensation of aqueous-alcohol mixtures have been measured in supersonic nozzles [B. E. Wyslouzil et al., J. Chem. Phys. 113, 7317 (2000)], the true nucleation rates have not. Here, we propose a new analytical method to estimate the temperature, the concentrations of condensable species in both the vapor and the liquid phases, and the amount of the condensate using only the measured static pressure profiles in the nozzle. We applied the method to ethanol/water (CH3CH2OH/D2O or CH3CH2OD/D2O) mixtures and confirmed that the aerosol volume fractions derived from pressure measurements and small angle neutron scattering measurements are in very good agreement when this method is used. Combining the results from the pressure measurements with the number densities of the condensed droplets, measured either by small angle neutron or small angle x-ray scattering, we determined the first quantitative ethanol/water binary nucleation rates in the supersonic nozzle at a temperature of 229±1 K.
Relaxation rates of protons in gadolinium chelates detected with a high-Tc superconducting quantum interference device in microtesla magnetic fields
Authors: Chen Hsin-Hsien , Yang Hong-Chang , Horng Herng-Er , Hsiao Jong-Kai , Yang Shieh-Yueh , Liao Shu-Hsien , Chen Ming-Jye
Published: November 2010

A nuclear magnetic resonance and imaging system was constructed to study spin-lattice relaxation time T1, spin-spin relaxation time T2, and effective relaxation time T2∗ of gadolinium (Gd) chelates using a high-Tc superconducting quantum interference device in microtesla magnetic fields. In the presence of the magnetic contrast T2∗ is related to T2 by the relation: 1/T2∗=1/T2+γΔB+ΓGd-chelates, where γ=42.58 kHz/mT and γΔB is the relaxation rate due to the inhomogeneity field ΔB in measuring coil at the sample position and ΓGd-chelates is the intrinsic relaxation rate of Gd chelates. It is found that T1, T2, and 1/ΓGd-chelates decay exponentially as the concentration (or magnetic susceptibility) of Gd chelates increases. The Gd chelates cause a diffusive motion of nuclear spins and hence enhance the relaxation rates. Enhanced image contrast has been demonstrated in a water phantom with Gd chelates in microtesla magnetic fields.
Tetrahydrides of third-row transition elements: Spin-orbit coupling effects on the stability of rhenium tetrahydride
Authors: Koseki Shiro , Hisashima Taka-aki , Asada Toshio , Toyota Azumao , Matsunaga Nikita
Published: November 2010

The potential energy surfaces of low-lying states in rhenium tetrahydride (ReH4) were explored by using the multiconfiguration self-consistent field (MCSCF) method together with the SBKJC effective core potentials and the associated basis sets augmented by a set of f functions on rhenium atom and by a set of p functions on hydrogen atoms, followed by spin-orbit coupling (SOC) calculations to incorporate nonscalar relativistic effects. The most stable structure of ReH4 was found to have a D2d symmetry and its ground state is A42. It is found that this is lower in energy than the dissociation limit, ReH2+H2, after dynamic correlation effects are taken into account by using second-order multireference Møller–Plesset perturbation (MRMP2) calculations. This reasonably agrees with previous results reported by Andrews et al. [J. Phys. Chem. 107, 4081 (2003)]. The present investigation further revealed that the dissociation reaction of ReH4 cannot occur without electronic transition from the lowest quartet state to the lowest sextet state. This spin-forbidden transition can easily occur because of large SOC effects among low-lying states in such heavy metal-containing compounds. The minimum-energy crossing (MEX) point between the lowest quartet and sextet states is proved to be energetically and geometrically close to the transition state for the dissociation reaction on the potential energy surface of the lowest spin-mixed state. The MEX point (C2 symmetry) was estimated to be 9184 cm−1 (26.3 kcal/mol) higher than the A42 state in D2d symmetry at the MRMP2 level of theory. After inclusion of SOC effects, an energy maximum on the lowest spin-mixed state appears near the MEX point and is recognized as the transition state for the dissociation reaction to ReH2+H2. The energy barrier for the dissociation, evaluated to be MEX in the adiabatic picture, was calculated to be 5643 cm−1 (16.1 kcal/mol) on the lowest spin-mixed state when SOC effects were estimated at the MCSCF level of theory.
Equation of state of water under negative pressure
Authors: Davitt Kristina , Rolley Etienne , Caupin Frédéric , Arvengas Arnaud , Balibar Sébastien
Published: November 2010

We report on the simultaneous measurements of the speed of sound and the density in liquid water under negative pressure. Application of a focused acoustic wave to the bulk liquid is able to generate negative pressures before nucleation of the vapor phase occurs. A method for time-resolved Brillouin scattering is developed to measure the speed of sound during the passage of a 1 MHz ultrasonic wave. This is coupled with a fiber optic probe hydrophone which allows the determination of the density. Together, these methods give an ambient temperature equation of state of metastable liquid water down to the acoustic cavitation threshold. Empirical equations of state of water are based on experimental data at positive pressure; the validity of their extrapolation to negative pressures had been tested only indirectly or with very weakly metastable liquid. We provide thermodynamic data that prove the fidelity of recent equations of state down to −26 MPa. However, this raises questions regarding the nature of the cavitation threshold observed in acoustic experiments, which is far less negative than expected.
Extensive chaos in the Lorenz-96 model
Authors: Karimi A. , Paul M. R.
Published: November 2010

We explore the high-dimensional chaotic dynamics of the Lorenz-96 model by computing the variation of the fractal dimension with system parameters. The Lorenz-96 model is a continuous in time and discrete in space model first proposed by Lorenz to study fundamental issues regarding the forecasting of spatially extended chaotic systems such as the atmosphere. First, we explore the spatiotemporal chaos limit by increasing the system size while holding the magnitude of the external forcing constant. Second, we explore the strong driving limit by increasing the external forcing while holding the system size fixed. As the system size is increased for small values of the forcing we find dynamical states that alternate between periodic and chaotic dynamics. The windows of chaos are extensive, on average, with relative deviations from extensivity on the order of 20%. For intermediate values of the forcing we find chaotic dynamics for all system sizes past a critical value. The fractal dimension exhibits a maximum deviation from extensivity on the order of 5% for small changes in system size and the deviation from extensivity decreases nonmonotonically with increasing system size. The length scale describing the deviations from extensivity is consistent with the natural chaotic length scale in support of the suggestion that deviations from extensivity are due to the addition of chaotic degrees of freedom as the system size is increased. We find that each wavelength of the deviation from extensive chaos contains on the order of two chaotic degrees of freedom. As the forcing is increased, at constant system size, the dimension density grows monotonically and saturates at a value less than unity. We use this to quantify the decreasing size of chaotic degrees of freedom with increased forcing which we compare with spatial features of the patterns.
Generation of amber III-nitride based light emitting diodes by indium rich InGaN quantum dots with InGaN wetting layer and AlN encapsulation layer
Authors: Soh C. B. , Liu W. , Chua S. J. , Ang S. S. , Tan Rayson J. N. , Chow S. Y.
Published: November 2010

Indium rich InGaN nanostructures grown by metalorganic chemical vapor deposition were incorporated in InGaN/GaN quantum wells for long wavelength generation. These results were achieved by optimizing the growth temperature of the nanostructures, InGaN quantum well, the AlN capping layer and the GaN barrier layers. Before the growth of nanostructures, a thin InGaN wetting layer was included to reduce the lattice mismatch as well as to enhance the deposition of indium-rich InGaN nanostructures These individual quantum wells were each subsequently capped with an AlN layer which better preserved the In-rich phase in the nanostructures and prevented the indium interdiffusion between the InGaN/GaN heterojunctions. The AlN capping layer also reduces the effect of piezeoelectric field in the active layers of the light emitting diodes as seen from the reduction in the blueshift in the electroluminescence peaks with higher injection currents. The energy band profile of such a structure is discussed.
Effect of point defects on thermal depoling behavior of bismuth layer-structured ferroelectric ceramics
Authors: Zeng Tao , Yan Haixue , Reece Michael J.
Published: November 2010

Effect of point defects on the thermal depoling behavior of bismuth layer-structured ferroelectric Bi2WO6 (BW) and Sr2Bi4Ti5O18 (SBT) ceramics was investigated. Point defects in BW ceramics formed defect dipoles that interacted with the ferroelectric domain structure. These defect dipoles produced pinched polarization-electric field (P-E) hysteresis loops and an irreversible reduction in d33 after annealing below 200 °C. They became decoupled and randomized above 200 °C, and the d33 of BW became stable with increasing temperature from 200 °C up to its Curie point. SBT ceramics with low defect concentration showed symmetric P-E hysteresis loops and good piezoelectric stability with increasing temperature.
Polarization behavior of poly(vinylidene fluoride-trifluoroethylene) copolymer ferroelectric thin film capacitors for nonvolatile memory application in flexible electronics
Authors: Mao D. , Mejia I. , Stiegler H. , Gnade B. E. , Quevedo-Lopez M. A.
Published: November 2010

The time domain and electric field dependence of the polarization switching kinetics of poly(vinylidene fluoride-trifluoroethylene) copolymer based thin film metal-ferroelectric-metal capacitors have been characterized. At room temperature, the time required for complete switching polarization decreases from >1 s to <50 μs as the voltage is increased from 6 to 12 V, while low nonswitching polarization is maintained. In the time domain, the ferroelectric switching polarization reversal behavior for devices biased above the coercive field follows the nucleation-limited-switching model. The exponential relationship between switching time and applied electric field indicates nucleation dominated switching kinetics. Switching behavior as a function of temperature was also characterized from −60 to 100 °C in the voltage range of 6–12 V. Higher temperatures induce larger dc conductance leakage at low frequencies and increases nonswitching polarization for all the voltages studied. It is demonstrated that for certain frequencies, by controlling the switching voltage, our optimized ferroelectric thin film capacitor shows stable switching polarization in a temperature range compatible with flexible electronics applications.
Optical constants of Cu2ZnGeS4 bulk crystals
Authors: León M. , Levcenko S. , Serna R. , Gurieva G. , Nateprov A. , Merino J. M. , Friedrich E. J. , Fillat U. , Schorr S. , Arushanov E.
Published: November 2010

The dielectric functions of Cu2ZnGeS4 bulk crystals grown by the Bridgman method were measured over the energy range 1.4 to 4.7 eV at room temperature using variable angle spectroscopic ellipsometry. The observed structures in the dielectric functions were adjusted using the Adachi’s model and attributed to interband transitions E0, E1A, and E1B at Γ:(000), N(A):2π/a(0.5 0.5 0.5), and T(Z):2π/a(0 0 0.5) points of the first Brillouin zone, respectively. The model parameters (threshold energy, strength, and broadening) have been determined using the simulated annealing algorithm. The decrease in the first gap, E0, has been attributed to a higher Ge–S hybridization. The spectral dependence of the complex refractive index, the absorption coefficient, and the normal-incidence reflectivity were also derived.
Fundamental mechanisms of focused ion beam guided anodization
Authors: Tian Zhipeng , Lu Kathy , Chen Bo
Published: November 2010

This paper is focused on understanding the fundamental mechanisms of focused ion beam guided anodization and the unique capabilities of generating new patterns based on such an understanding. By designing proper interpore distance, pore arrangement, and pore shape during focused ion beam patterning, nonspherical pore shape and nonhexagonal patterns can be obtained by further anodization. The electrical field and the mechanical stress field around each focused ion beam patterned concave dictate the pore formation and growth. The oxide barrier layer thickness and shape around the focused ion beam guided pores affect new pore formation and the meshing of different size pores.
Refractive index change in ion-implanted LiNbO3 waveguides calculated from lattice damage ratio
Authors: Huang Qing , Zhao Jin-Hua , Liu Peng , Guan Jing , Wang Xue-Lin
Published: November 2010

We related the refractive index change in ion-implanted LiNbO3 crystals to the lattice damage ratio using a quadratic polynomial relationship. We used this relationship to calculate the refractive index profiles of z-cut LiNbO3 crystals implanted with oxygen ions using different energies, fluences, and annealing treatments. A highly damaged surface layer with a decreased refractive index was caused by electronic excitations in LiNbO3 crystals implanted with 4.0 MeV oxygen ions at a fluence of 2×1015 ions/cm2, which buried the optical modes inside the crystals. This relationship was also used for the estimation of the lattice damage in ion-implanted LiNbO3 crystals. It could make a quick estimate which was basically agree with the measured damage level.
Time-dependent density functional approach for the calculation of inelastic x-ray scattering spectra of molecules
Authors: Sakko Arto , Rubio Angel , Hakala Mikko , Hämäläinen Keijo
Published: November 2010

We apply time-dependent density functional theory to study the valence electron excitations of molecules and generalize the typically used time-propagation scheme and Casida’s method to calculate the full wavevector dependent response function. This allows the computational study of dipole-forbidden valence electron transitions and the dispersion of spectral weight as a function of the wavevector. The method provides a novel analysis tool for spectroscopic methods such as inelastic x-ray scattering and electron energy loss spectroscopy. We present results for benzene and CF3Cl and make a comparison with experimental results.
Surface effects on frequency analysis of nanotubes using nonlocal Timoshenko beam theory
Authors: Lee Haw-Long , Chang Win-Jin
Published: November 2010

The natural frequency of nanotubes with consideration of surface effects is studied using the nonlocal Timoshenko beam theory. This theory with long-range interactions revealing the nanoscale effect can be applied to study the vibration behavior of nanostructures. When the nonlocal effect is neglected in the analysis, the result is identical to the previous study which used a modified Timoshenko beam theory. According to the analysis, the application of the modified Timoshenko beam theory for nanotubes would lead to an underprediction of the natural frequency.
Time-resolved observation of the plasma induced by laser metal ablation in air at atmospheric pressure
Authors: Zhou Yun , Wu Benxin , Forsman Andrew
Published: November 2010

Most of the previous studies on nanosecond (ns) laser-induced plasma typically use relatively short ns laser pulses (pulse duration less than ∼30 to 50 ns). In this paper, relatively long ns laser pulses with 200 ns duration have been used, and the produced plasma during metal ablation in air at atmospheric pressure has been studied through time-resolved observation using an intensified charge-coupled device camera. Due to the much longer ns laser pulse duration, the plasma radiation intensity distribution and the plasma front propagation have different physical features from those produced by much shorter ns laser pulses. In particular, it has been observed that during the laser pulse the plasma has two high-radiation-intensity regions: one is located right above the target surface while the other is behind the expanding plasma front. The former region will disappear once the laser pulse completes. This interesting physical phenomenon has been rarely reported, and requires further experimental and modeling study to completely understand.
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laser-induced fluorescence of spin-polarized hydrogen atoms
Authors: Bougas Lykourgos , Sofikitis Dimitris , Everest Michael A. , Alexander Andrew J. , Rakitzis T. Peter
Published: November 2010

We report the measurement of the spin polarization of hydrogen (SPH) atoms by (2+1) laser-induced fluorescence, produced via the photodissociation of thermal HBr molecules with circularly polarized 193 nm light. This scheme, which involves two-photon laser excitation at 205 nm and fluorescence at 656 nm, offers an experimentally simpler polarization-detection method than the previously reported vacuum ultraviolet detection scheme, allowing the detection of SPH atoms to be performed more straightforwardly, from the photodissociation of a wide range of molecules and from a variety of collision experiments.
Defect conduction bands, localization, and temperature-dependent electron emission from Al–Al2O3–Au diodes
Authors: Hickmott T. W.
Published: November 2010

The temperature dependence of several phenomena connected with voltage-controlled negative resistance (VCNR) of Al–Al2O3–Au diodes has been measured between 200 and 300 K. These include the current-voltage (I-V) characteristics, electroluminescence (EL), and electron emission into vacuum (EM) of diodes with 12–20 nm of anodic Al2O3. There is an abrupt decrease in EM by 3 orders of magnitude as temperature decreases from 285 to 280 K. EM recovers to the same magnitude as at 300 K at ∼260 K and is nearly constant between 260 and 200 K. The lower temperature at which EM recovers depends on the anodizing electrolyte. EM is decoupled from the major conduction mechanism because the voltage for maximum current of the I-V curve and the voltage threshold for EL are nearly constant over the same temperature range. A model is proposed in which defect levels of oxygen vacancies form two defect conduction bands in amorphous Al2O3. The concentration of oxygen vacancies is estimated from measurements of polarization of Al–Al2O3–Au diodes that do not break down to form VCNR in their I-V characteristics. EM at high and low temperatures is through defect conduction bands. Suppression of EM in the intermediate temperature range is due to localization of electrons caused by the irregular potential present when defect centers in the lower defect conduction band are nearly fully occupied. EM shows a temperature dependent metal-nonmetal transition while the conduction current does not.
Direct assessment of quantum nuclear effects on hydrogen bond strength by constrained-centroid ab initio path integral molecular dynamics
Authors: Walker Brent , Michaelides Angelos
Published: November 2010

The impact of quantum nuclear effects on hydrogen (H-) bond strength has been inferred in earlier work from bond lengths obtained from path integral molecular dynamics (PIMD) simulations. To obtain a direct quantitative assessment of such effects, we use constrained-centroid PIMD simulations to calculate the free energy changes upon breaking the H-bonds in dimers of HF and water. Comparing ab initio simulations performed using PIMD and classical nucleus molecular dynamics (MD), we find smaller dissociation free energies with the PIMD method. Specifically, at 50 K, the H-bond in (HF)2 is about 30% weaker when quantum nuclear effects are included, while that in (H2O)2 is about 15% weaker. In a complementary set of simulations, we compare unconstrained PIMD and classical nucleus MD simulations to assess the influence of quantum nuclei on the structures of these systems. We find increased heavy atom distances, indicating weakening of the H-bond consistent with that observed by direct calculation of the free energies of dissociation.
An unusually large nonadiabatic error in the BNB molecule
Authors: Stanton John F.
Published: November 2010

The vibronic coupling model of Köuppel, Domcke, and Cederbaum in one dimension is introduced as a means to estimate the effects of electronic nonadiabaticity on the vibrational energy levels of molecules that exhibit vibronic coupling. For the BNB molecule, the nonadiabatic contribution to the nominal fundamental vibrational energy of the antisymmetric stretching mode is approximately −80 cm−1. The surprisingly large effect for this mode, which corresponds to an adiabatic potential that is essentially flat near the minimum due to the vibronic interaction, is contrasted with another model system that also exhibits a flat potential (precisely, a vanishing quadratic force constant) but has a significantly larger gap between interacting electronic states. For the latter case, the nonadiabatic contribution to the level energies is about two orders of magnitude smaller even though the effect on the potential is qualitatively identical. A simple analysis shows that significant nonadiabatic corrections to energy levels should occur only when the affected vibrational frequency is large enough to be of comparable magnitude to the energy gap involved in the coupling. The results provide evidence that nonadiabatic corrections should be given as much weight as issues such as high-level electron correlation, relativistic corrections, etc., in quantum chemical calculations of energy levels for radicals with close-lying and strongly coupled electronic states even in cases where conical intersections are not obviously involved. The same can be said for high-accuracy thermochemical studies, as the zero-point vibrational energy of the BNB example contains a nonadiabatic contribution of approximately −70 cm−1 (−0.9 kJ mol−1).
Temperature dependence of spin resonance in cobalt substituted NiZnCu ferrites
Authors: Lucas A. , Lebourgeois R. , Mazaleyrat F. , Labouré E.
Published: November 2010

Cobalt substitutions were investigated in Ni0.4Zn0.4Cu0.2Fe2O4 ferrites, initial complex permeability was then measured from 1 MHz to 1 GHz. It appears that cobalt substitution led to a decrease in the permeability and an increase in the μs×fr factor. As well, it gave to the permeability spectrum a sharp resonance character. We also observed a spin reorientation occurring at a temperature depending on the cobalt content. Study of the complex permeability versus temperature highlighted that the most resonant character was obtained at this temperature. This shows that cobalt contribution to second order magnetocrystalline anisotropy plays a leading role at this temperature.
Tunneling transport properties for metal-oxide-semiconductor diode consisting of ferromagnetic ZnMnO nanocrystals
Authors: Lee Sejoon , Lee Youngmin , Shon Yoon , Kim Deuk Young , Won Kang Tae
Published: November 2010

Spin-dependent tunneling properties for the metal-semiconductor-oxide diode which was fabricated using ferromagnetic ZnMnO nanocrystals and Ti-Co ferromagnet were investigated. The diode revealed current oscillation packets after tunneling-on, and the peak-to-valley current ratio of the packets showed to be dependent on the temperature-dependent magnetization of the nanocrystals; i.e., the peak-to-valley current ratio of the packets was increased with decreasing the temperature. This result is ascribed to the increased conductance fluctuation due to the increased repulsion probability between spin-polarized and unpolarized carriers because the spin-polarized carriers which are supplied from Ti-Co and are to be injected into n+-Si are transferred through the nanocrystals.
Interactions between oscillatory modes near a 2:3 resonant Hopf-Hopf bifurcation
Authors: Revel G. , Alonso D. M. , Moiola J. L.
Published: November 2010

In this paper, the dynamics near a 2:3 resonant Hopf-Hopf bifurcation is studied. The main result is the identification of a distinctive structure connecting 1:2 and 1:3 strong resonances of limit cycles. This structure is found near the Hopf-Hopf point revealing that it may be associated to the resonant case, and may provide useful information about the dynamics generated by this codimension 3 bifurcation.
Bias-dependent absorption coefficient of the absorber section in GaN-based multisection laser diodes
Authors: Scheibenzuber W. G. , Schwarz U. T. , Sulmoni L. , Carlin J.-F. , Castiglia A. , Grandjean N.
Published: November 2010

We measure the modal absorption coefficient of the InGaN quantum wells (QWs) in the absorber section of (Al,In)GaN multisection laser diodes as a function of bias voltage and photon energy using optical gain-spectroscopy. In the examined laser diodes, the modal absorption at the laser wavelength of 430 nm has a maximum of 270 cm−1 at low negative bias and decreases with increasing negative bias. We explain this behavior by comparing the measurements to absorption coefficients calculated from a band-edge profile simulation. The decrease of the absorption at large negative bias is caused by a shift in the transition energies in the quantum wells due to the quantum confined Stark effect.
Formation of epitaxial metastable NiGe2 thin film on Ge(100) by pulsed excimer laser anneal
Authors: Lim Phyllis S. Y. , Chi Dong Zhi , Lim Poh Chong , Wang Xin Cai , Chan Taw Kuei , Osipowicz Thomas , Yeo Yee-Chia
Published: November 2010

Epitaxial nickel digermanide (NiGe2), a metastable phase, was formed by laser annealing Ni on (100) germanium-on-silicon substrates. The NiGe2 formation was investigated using transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, Rutherford backscattering spectroscopy, and first-principles calculations. The formation mechanism of NiGe2 is discussed and is attributed to both the reduced interfacial energy at the NiGe2/Ge(100) interface and the kinetic aspects of the laser annealing reaction associated with phase transformation and film agglomeration.
Negative feedback regulation of UV-B–induced photomorphogenesis and stress acclimation in
Arabidopsis
Authors: Gruber Henriette , Heijde Marc , Heller Werner , Albert Andreas , Seidlitz Harald K. , Ulm Roman
Published: November 2010

Plants respond to low levels of UV-B radiation with a coordinated photomorphogenic response that allows acclimation to this environmental stress factor. The key players in this UV-B response are COP1 (an E3 ubiquitin ligase), UVR8 (a β-propeller protein), and HY5 (a bZIP transcription factor). We have shown previously that an elevated UV-B–specific response is associated with dwarf growth, indicating the importance of balancing UV-B–specific signaling. Negative regulators of this pathway are not known, however. Here, we describe two highly related WD40-repeat proteins, REPRESSOR OF UV-B PHOTOMORPHOGENESIS 1 (RUP1) and RUP2, that interact directly with UVR8 as potent repressors of UV-B signaling. Both genes were transcriptionally activated by UV-B in a COP1-, UVR8-, and HY5-dependent manner.
rup1 rup2
double mutants showed an enhanced response to UV-B and elevated UV-B tolerance after acclimation. Overexpression of
RUP2
resulted in reduced UV-B–induced photomorphogenesis and impaired acclimation, leading to hypersensitivity to UV-B stress. These results are consistent with an important regulatory role for RUP1 and RUP2, which act downstream of UVR8–COP1 in a negative feedback loop impinging on UVR8 function, balancing UV-B defense measures and plant growth.