bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Characteristics of Tetrabutylammonium Tetrahalogenoferrates(III): X‐ray Crystal Structure of Tetrabutylammonium Tetrabromoferrate(III)
Authors: Wyrzykowski Dariusz , Kruszyński Rafał , Kłak Julia , Mroziński Jerzy , Warnke Zygmunt
Published: August 2007

The crystal and molecular structure of tetrabutylammonium tetrabromoferrate(III) was determined. The iron cation is surrounded by four bromide anions, and it adopts a slightly distorted tetrahedral coordination with two angles larger than tetrahedral, one equal to tetrahedral and one smaller than tetrahedral. In the structure there are no hydrogen bonds nor any unusual short intermolecular interactions. The compound is isostructural with its [FeBr4−nCln]− (n = 0, 1, 3, 4) analogues. Magnetic measurements of the powdered samples of [(C4H9)4N][FeBr4−nCln] gave negative values of the Weiss constants that suggest antiferromagnetic interactions transmitted within the crystal lattice.
Nd3N2SeBr: Ein neues Nitridselenidbromid des Neodyms mit $\rm ^{1}_{\infty}\{[N_{2}Nd_{3}]^{3+}\}$‐Strängen aus hochkondensierten [NNd4]9+‐Tetraedern
Authors: Lissner Falk , Schleid Thomas
Published: August 2007

Nd3N2SeBr: A New Nitride Selenide Bromide of Neodymium with $\rm ^{1}_{\infty}\{[N_{2}Nd_{3}]^{3+}\}$ Strands of Highly Condensed [NNd4]9+ Tetrahedra

The oxidation of neodymium powder with selenium and sodium azide (NaN3) in the presence of neodymium tribromide (NdBr3) yields neodymium nitride selenide bromide with the composition Nd3N2SeBr when appropriate molar ratios of the reactants are used. Additional sodium bromide (NaBr) as a flux secures fast reactions (7 d) at 900 °C in evacuated silica tubes as well as the formation of dark brown single crystals. The orthorhombic crystal structure (Pnma, Z = 4) was determined from single crystal X‐ray diffraction data (a = 1288.13(9), b = 405.22(3), c = 1206.29(8) pm). There are three crystallographically different Nd3+ cations present. Nd1 resides in eightfold coordination of four N3−, two Se2− and two Br− anions forming a square antiprism and Nd2 is coordinated by three N3−, one Se2− and three Br− in the shape of a monocapped trigonal prism. Finally, an octahedral coordination sphere of one N3−, three Se2− and two Br− anions surrounds Nd3. However, the main feature in the crystal structure comprises N3−‐centred (Nd3+)4 tetrahedra arranged as chains $\rm ^{1}_{\infty}\{[NNd_{2}]^{3+}\}$ of cis‐edge connected [NNd4]9+ units first, which are further connected via two more edges to form strands $\rm ^{1}_{\infty}\{[N_{2}Nd_{3}]^{3+}\}$ of highly condensed all‐cisoid oriented [NNd4]9+ tetrahedra. They get bundled along [010] like a hexagonal rod packing and are held together by two radiographically indistinguishable Se2− and Br− anions, which thereby also achieve the charge balance.
Dimensional Reduction in Alkali Metal Uranyl Molybdates: Synthesis and Structure of Cs2[(UO2)O(MoO4)]
Authors: Alekseev Evgeny V. , Krivovichev Sergey V. , Armbruster Thomas , Depmeier Wulf , Suleimanov Evgeny V. , Chuprunov Evgeny V. , Golubev Alexei V.
Published: August 2007

A new uranyl molybdate, Cs2[(UO2)O(MoO4)] (1), has been prepared by high‐temperature solid‐state reactions. The structure has been solved by direct methods and refined to R1 = 0.0284 for |F0| ≥4σF. The compound 1 is orthorhombic, Pca21, a = 12.018(2), b = 12.438(2), c = 17.917(3) Å, V = 2678.2(7) Å3, Z = 12. The structure of 1 is based upon one‐dimensional chains consisting of corner‐sharing UO6 and MoO4 polyhedra. The UO6 square bipyramids share cis equatorial vertices to form zigzag chains that are further stabilized by bidendate MoO4 tetrahedra. The chains have composition [(UO2)O(MoO4)]2− and are oriented parallel to the c axis. In the structure, adjacent chains form pseudo‐2D‐layers parallel to (010). The Cs+ cations are in between the pseudolayers. The composition‐structure relationships in alkali metal uranyl molybdates can be rationalized from the viewpoint of dimensional reduction using the following assumptions: (1) representation of the AxUnMomOy formula (n ≤ m) as a sum of UMoO6 (= UO2MoO4), A2O, and A2MoO4 (A = alkali metal): AxUnMomOy = kA2O + nUMoO6 + (m‐n)A2MoO4, where x = 2(k + m − n) and y = k + 2n + 4m; (2) analysis of the dimensionality of uranyl molybdate structural units and its changes upon incorporation of ionic reagents A2O and A2MoO4 into a parent framework of UO2MoO4 that consists of 3‐D array of U and Mo based polyhedra. The relationships between different compositions and structures may be visualized using the UO2MoO4–A2O–A2MoO4 compositional diagram. The observed trends of decreasing dimensionality of the uranyl molybdate units allow to specify on this diagram fields of dimensionality.
Inkommensurabel modulierte Kristallstrukturen und Phasenumwandlungen – Die Verbindungen SrPt2As2 und EuPt2As2
Authors: Imre Anette , Hellmann Andrea , Wenski Guido , Graf Jürgen , Johrendt Dirk , Mewis Albrecht
Published: August 2007

Modulated Crystal Structures and Phase Transitions – The Compounds SrPt2As2 and EuPt2As2

The new compounds SrPt2As2 (a = 4.482(1), b = 4.525(1), c = 9.869(2) Å) and EuPt2As2 (a = 4.435(2), b = 4.467(2), c = 9.784(3) Å) have been prepared by reaction of the elements at 1050 °C. Satellite reflections observed in X‐ray diffraction experiments on single crystals revealed that both compounds have modulated crystal structures at room temperature. The average structures can be derived from the CaBe2Ge2 type and described in the orthorhombic space group Pmmn (Z = 2) with splitted positions for half the Pt and As atoms. Based on the average structure of SrPt2As2, the modulated structure has been solved and refined using the (3+1)‐dimensional superspace group Pmmn(α00)0s0 and a modulation vector q = 0,62·a*. The modulation appears in the layers of the PtAs4 tetrahedra with occupational and displacive components. The other atoms are also slightly affected by the modulation. With increasing pressure, SrPt2As2 undergoes a phase transition at about 60 kbar. The crystal structure of the high pressure phase (HP‐SrPt2As2: a = 9.752(2), b = 4.398(1), c = 8.727(2) Å, β = 90.34(3)°; 66(5) kbar) is a monoclinic variant (P21/c; Z = 4) of the tetragonal CaBe2Ge2 type known from EuPt2Ge2. Band structure calculations reveal that a Peierls‐distortion within the Pt square nets is a reason for the structural instabilities in SrPt2As2. The satellite reflections of EuPt2As2 become weaker with increasing temperature and disappear above 200 °C. The high temperature phase (HT‐EuPt2As2: a = 4.464(1), c = 9.832(1) Å; 350 °C) crystallizes with the CaBe2Ge2 type (P4/nmm; Z = 2). High thermal displacement parameters of the Pt and As atoms of the PtAs4 tetrahedra cover the effects of the modulation at room temperature. Several analogous compounds were studied by X‐ray diffraction resulting in the following lattice parameters: a = 4.564(1), c = 10.021(2) Å for BaPt2As2, a = 4.603(2), c = 10.565(2) Å for SrPt2Sb2, a = 4.630(2), b = 4.683(2), c = 10.389(3) Å for EuPt2Sb2, and a = 4.458(1), c = 9.823(2) Å for SrIr2As2.
IGF‐I and INS receptor expression in the salivary glands of diabetic Nod mice submitted to long‐term insulin treatment
Authors: Caldeira Eduardo José , Cagnon Valéria Helena Alves
Published: August 2007

This work aimed to characterize the IGF‐I and INS receptor expression in the salivary glands of Nod mice, correlating to therapeutic effects of insulin treatment on these receptors. Nod mice were divided into: Groups 1 and 2 (diabetic), Groups 3 and 4 (diabetic with insulin treatment) and Group 5 (non‐diabetic). Fragments from the salivary glands were processed for immunohistochemical analysis. The results showed that the prolonged diabetic state led to a steadily increased IGF‐I receptor expression. INS receptor expression was gradually decreased. It was concluded that not only was the IGF‐I receptor expression affected by the diabetic state but also the INS receptor expression. The period of the diabetic state was directly related to changes in the expression of these receptors. In spite of the insulin treatment having recovered the glycaemic levels, the expression of INS and the IGF‐I receptors did not reach the standard level, which certainly hampered glandular function.
Relation between dose of loop diuretics and outcomes in a heart failure population: Results of the ESCAPE Trial
Authors: Hasselblad Vic , Stough Wendy Gattis , Shah Monica R. , Lokhnygina Yuliya , O'Connor Christopher M. , Califf Robert M. , Adams Kirkwood F.
Published: August 2007

Background:

We examined the relation of maximal in‐hospital diuretic dose to weight loss, changes in renal function, and mortality in hospitalised heart failure (HF) patients.

Methods:

In ESCAPE, 395 patients received diuretics in‐hospital. Weight was measured at baseline, discharge, and every other day before discharge. Weight loss was defined as the difference between baseline and last in‐hospital weight. Mortality was assessed using a log‐logistic model with non‐zero background.

Results:

Median weight loss: 2.8kg (0.7, 6.1); mean: 3.7kg (22% of values <0). Weight loss and maximum in‐hospital dose were correlated (p=0.0007). Baseline weight, length of stay, and baseline brain natriuretic peptide were significant predictors of weight loss. After adjusting for these, dose was not a significant predictor of weight loss. A strong relation between dose and mortality was seen (p=0.003), especially at >300mg/day. Dose remained a significant predictor of mortality after adjusting for baseline variables that significantly predicted mortality. Correlation between maximal dose and creatinine level change was not significant (r=0.043; p=0.412)

Conclusions:

High diuretic doses during HF hospitalisation are associated with increased mortality and poor 6‐month outcome.
Role of 3‐O‐sulfated heparan sulfate in virus‐induced polykaryocyte formation
Authors: Tiwari Vaibhav , ten Dam Gerdy B. , Yue Beatrice Y.J.T. , van Kuppevelt Toin H. , Shukla Deepak
Published: August 2007

One way herpes simplex virus type‐1 (HSV‐1) spreads in vivo is by polykaryocytes formation. Here we demonstrate that polykaryocyte production during HSV‐1 spread in cultured human corneal fibroblasts (CF) required heparan sulfate (HS) and more specifically 3‐O sulfated HS (3‐OS HS). The polykaryocyte formation heavily depended on the expression of HS on target (CF) cells but not on glycoprotein expressing effector cells. Furthermore, we provide the first visual evidence of 3‐OS HS and HSV‐1 gD colocalization during the membrane fusion process. Taken together our results provide novel insight into the significance of HS in polykaryocyte formation.
Zinc up‐regulates NF‐κB activation via phosphorylation of IκB in HUT‐78 (Th0) cells
Authors: Bao Bin , Prasad Ananda S. , Beck Frances W.J. , Sarkar Fazlul H.
Published: August 2007

Nuclear factor of κB (NF‐κB) is a major transcription factor regulating the expression of interleukin‐2 (IL‐2) and interleukin‐2 receptor‐α (IL‐2Rα) in Th1 cells. We previously demonstrated that zinc increased IL‐2 and IL‐2Rα production via NF‐κB activation in HUT‐78 (Th0) cells. However, the molecular mechanism is not well understood. In this study, we found that zinc increased phosphorylated IκB‐α, NF‐κB translocation and activation, as well as the production of IL‐2 and IL‐2Rα in wild type IκB gene transfected zinc‐sufficient HUT‐78 cells, compared to zinc‐deficient HUT‐78 cells. However, dominant negative IκB gene expression decreased these parameters in zinc‐sufficient cells, suggesting that zinc increased NF‐κB activation via IκB pathway.
Revival of apoptotic cells that display early‐stage dynamic membrane blebbing
Authors: Takashina Tomoki , Nakayama Manabu
Published: August 2007

The critical point at which apoptosis becomes irreversible and how cells attain an anti‐apoptotic state remain unknown. Here, we report that apoptotic cells undergoing early‐stage dynamic membrane blebbing revive. We examined this phenomenon in cell lines that stably express 2DED2DD, a modified FADD produced by fusing the tandem death effector domains (DEDs) and tandem death domains (DDs). Induction of apoptosis caused rapid blebbing. Eight hours later, most cells shrunk while some detached from the flask. Twenty‐four hours later, when activated caspase 3 decreased, more than half the cells revived and appeared normal, probably due to the induction of unidentified anti‐apoptotic proteins.
A role for tropical tropospheric temperature adjustment to El Niño–Southern Oscillation in the seasonality of monsoonal Indonesia precipitation predictability
Authors: Giannini A. , Robertson A. W. , Qian J.‐H.
Published: August 2007

We describe the seasonality in the variability and predictability of Indonesian monsoonal climate, dominated by the El Niño–Southern Oscillation (ENSO) phenomenon, and interpret it in light of theories of the development of the global ENSO teleconnection which explain the evolution of the response of the tropical ocean‐atmosphere to ENSO's perturbation. High predictability during the dry and transition seasons, which coincide with ENSO growth, is expected from the coherent large‐scale response to ENSO's initial perturbation. As the tropical ocean‐atmosphere equilibrates to ENSO, and ENSO itself begins to decay, its direct influence diminishes, and regional features associated with the delayed response to ENSO become more prominent. Consistent with this interpretation, in a preliminary observational analysis of station data over Jawa we find that predictability is high during the growth phase of ENSO. We also find that at these regional scales there may be more predictability than previously thought as ENSO decays. Finally, we show that a simple one‐tier prediction system, i.e., a system where the evolution of oceanic and atmospheric anomalies is internally consistent, better captures the intrinsic coupled nature of the ENSO teleconnection, compared to a two‐tier system where the ocean forces the atmosphere, but does not respond to its feedback.
Prostamides (prostaglandin‐ethanolamides) and their pharmacology
Authors: Woodward D F , Liang Y , Krauss A H‐P
Published: August 2007

The prostamides are part of a large and continually expanding series of pharmacologically unique neutral lipids. They are COX‐2 derived oxidation products of the endocannabinoid/endovanniloid anandamide. Prostamide pharmacology is unique and, as in the case of the endocannabinoids anandamide and 2‐arachidonylglycerol, bears little resemblance to that of the corresponding free acids. By virtue of its close relationship to the anti‐glaucoma drug bimatoprost, prostamide F2αhas received the greatest research attention. Prostamide F2αand bimatoprost effects appear independent of prostanoid FP receptor activation, according to a litany of agonist studies. Studies involving freshly isolated and separate feline iridial smooth muscle cells revealed that bimatoprost and FP receptor agonists stimulated different cells, without exception. This suggests the existence of receptors that preferentially recognize prostamide F2α. The recent discovery of prostamide antagonists has provided further support for prostamide receptors as discrete entities. The prototypical prostamide antagonists, AGN 204396 and 7, blocked the effects of prostamide F2αand bimatoprost but not those of PGF2αand FP receptor agonists in the feline iris. Second generation more potent prostamide antagonists, such as AGN 211334, should allow the role of prostamides in health and disease to be elucidated. From the therapeutics standpoint, the prostamide F2αanalogue bimatoprost is the most efficacious ocular hypotensive agent currently available for the treatment of glaucoma.

British Journal of Pharmacology(2008)153, 410–419; doi:10.1038/sj.bjp.0707434; published online 27 August 2007
Construction of a restriction‐endonuclease‐Eam1105I‐generated T‐vector for high‐throughput cloning and expression
Authors: Wang Baoli , Liang Hui , Liu Rui , Li Xiaoxia , Sun Bei , Zhang Rui , Guo Shanyi , Guo Gang , Zhang Jingyu , Dai Chenlin
Published: August 2007

A novel T‐vector was constructed that could be used for direct cloning and expression of PCR‐amplified cDNA. The technique was based on the insertion into the parent vector of two endonuclease‐Eam1105I restriction sequences spaced by an expression cassette of the full‐length β‐galactosidase, which helped to improve cloning efficiency and to minimize the non‐recombinant background of the T‐vector when used to clone PCR products. Moreover, this method took advantage of the reconstitution of the rarest restriction sequence of MssI to enable directional cloning. These advantages make the T‐vector suitable for high‐throughput expression and analysis.
Amplitude modulation of electron plasma oscillations in a dense electron-hole plasma
Authors: Misra Amar P. , Shukla P. K.
Published: August 2007

By using a quantum hydrodynamic model, the amplitude modulation of electron plasma oscillations (EPOs) in an unmagnetized dense electron-hole (e-h) quantum plasma is investigated. The standard reductive perturbation technique is used to derive one-dimensional nonlinear Schrödinger equation for the modulated EPO wave packet. The effects of the quantum diffraction, charged dust impurities and the effective e-h mass ratio on the propagation of linear dispersive EPOs, as well as on the modulational stability/instability of finite amplitude EPOs are examined. It is found that these parameters significantly affect the propagation of the EPOs as well as the nonlinear stability/instability domain of the wave vector, quite distinct from the classical and quantum electron-ion or electron-positron plasmas. The relevance of our investigation to semiconductor plasmas is discussed.
Wave-induced helicity current drive by helicon waves
Authors: Paul Manash Kr , Bora Dhiraj
Published: August 2007

Helicon waves are launched in a toroidal device of small aspect ratio, to form and sustain high-density plasma with 1018m−3 peak density and 12eV electron temperature. Owing to the strong poloidal asymmetry in the wave magnetic field structures, a nonresonant current is driven in plasma by the dynamo electric field, which arises due to the wave helicity injection by helicon waves. A study of the parametric dependence of plasma current driven in the electron-magnetohydrodynamic regime, at very high frequency, along with numerical estimations of nonresonant components, are presented here. The measured magnitude of plasma current is in good agreement with the estimated values. Numerical estimation, using experimentally measured variations of wave magnetic field components, clearly delineates the plasma current due to wave-induced helicity from other possible resonant or nonresonant sources in the present parameter regime.
On some solutions of Maxwell’s equations in a Schwarzschild–de Sitter black hole
Authors: Béssa Carlos H. G. , Bezerra V. B.
Published: August 2007

We determine the electrostatic potential due to a point charge in the Schwarzschild–de Sitter (SdS) space-time as well as the magnetic potential due to a radial current in this background. In these two cases, an extremal SdS black hole scenario is assumed.
Large scale and large period limits of symmetric calorons
Authors: Harland Derek
Published: August 2007

We construct SU(2) calorons, with nontrivial holonomy, instanton charge 2 and magnetic charge 0 or −1; these calorons have two constituent monopoles, with charges (2,2) or (2,1). Our calorons are U(1) symmetric and are constructed via the Nahm transform. They fall into distinct families which can be classified using representation theory. We consider large scale and large period limits of these calorons; in particular, the large scale limit may be a monopole, or a caloron with different topological charges.
Change of molecular ordering in soluble acenes via solvent annealing and its effect on field-effect mobility
Authors: Lee Wi Hyoung , Kim Do Hwan , Cho Jeong Ho , Jang Yunseok , Lim Jung Ah , Kwak Donghoon , Cho Kilwon
Published: August 2007

The increase of the molecular ordering and field-effect mobility in triethylsilylethynyl anthradithiophene (TES ADT) thin film transistors by solvent annealing was investigated. X-ray diffraction data revealed that TES ADT molecules crystallize with silyl groups on the substrate surface. After solvent annealing, spherulites were formed and the field-effect mobilities dramatically increased up to 0.43cm2∕Vs (over 100-fold) as result of maximized overlap of π electron clouds along the in-plane direction and the formation of a continuous crystal.
Electronic structure and efficient carrier injection in low-threshold T-shaped quantum-wire lasers with parallel p- and n-doping layers
Authors: Liu Shu-man , Yoshita Masahiro , Okano Makoto , Ihara Toshiyuki , Itoh Hirotake , Akiyama Hidefumi , Pfeiffer Loren N. , West Ken W. , Baldwin Kirk W.
Published: August 2007

We report on the electronic structure, efficient carrier injection, and quantitative lasing characteristics of T-shaped GaAs/AlGaAs quantum-wire-laser diodes with parallel p- and n-doping layers grown by a cleaved-edge-overgrowth method with molecular-beam epitaxy. Continuous single-mode lasing from the ground subband of the quantum wires was demonstrated between 30 and 70 K in laser diodes with high-reflectivity Au coating on both cavity facets. The lowest threshold of 0.27 mA and the highest differential quantum efficiency of 12% were achieved at 30 K. Micro-photoluminescence measurements demonstrated the high optical quality of the quantum wires with narrow linewidth of 0.9 meV and provided electronic structures of surrounding layers. Microscopic electroluminescence (EL) imaging measurements demonstrated the efficient carrier injection into the quantum wires at 30 K. These two factors, i.e., high material quality and efficient carrier injection, contribute to the low threshold current and high efficiency of the laser device. The result of EL imaging at 5 K indicates an inefficient carrier injection into the active region, which limits the operating temperature of the devices.
Efficient terahertz generation from two collinearly propagating CO2 laser pulses
Authors: Jiang Yi , Ding Yujie J.
Published: August 2007

Coherent terahertz pulses have been generated at 328.2μm (914.1GHz) by frequency-mixing two CO2 laser lines near 10μm based on collinearly phase-matched difference-frequency generation in GaSe crystals. The highest average output power was measured to be 260μW, corresponding to a peak output power of 510mW. Both the average powers and normalized conversion efficiencies have been significantly improved over the previous results. The generated terahertz pulses are expected to have the narrowest linewidth dictated by the pulse width through Fourier transform based on the characteristics of the two CO2 laser beams.
First principles phase diagram calculations for the system NaNbO3–KNbO3: Can spinodal decomposition generate relaxor ferroelectricity?
Authors: Burton B. P. , Nishimatsu Takeshi
Published: August 2007

First principles based phase diagram calculations were performed for the system (1−X) NaNbO3–(X) KNbO3. Plane wave pseudopotential calculations of formation energies were used as a basis for fitting a cluster expansion Hamiltonian, and a phase diagram was calculated. The predicted phase diagram has an unusual asymmetric miscibility gap, which suggests that it might be possible to synthesize a lead-free compositionally modulated sample with bulk composition X≈0.23; such a sample is likely to exhibit relaxor characteristics.
Improvement of output characteristics of a relativistic magnetron by creating asymmetric radio-frequency magnetic fields
Authors: Kim Hae Jin , Choi Jin Joo
Published: August 2007

Asymmetric magnetic field geometry is explored by inserting three metal tuners asymmetrically into the resonators of the A6 magnetron. The authors investigate the operating characteristics of a relativistic magnetron with asymmetrically perturbed radio-frequency (rf) magnetic fields caused by metal tuners using a three dimensional, electromagnetic particle-in-cell code MAGIC3D. By configuring perturbed rf magnetic fields, the operating characteristics of a relativistic magnetron are superior compared to those using uniform rf magnetic fields. Most significantly, by creating asymmetrically perturbed rf magnetic fields, the output power of the A6 magnetron increased by about 40% compared to the case of uniform rf magnetic fields.
Polarization engineering via staggered InGaN quantum wells for radiative efficiency enhancement of light emitting diodes
Authors: Arif Ronald A. , Ee Yik-Khoon , Tansu Nelson
Published: August 2007

Staggered InGaN quantum wells (QWs) grown by metal-organic chemical vapor deposition are demonstrated as improved active region for visible light emitters. Theoretical studies indicate that InGaN QW with step-function-like In content in the quantum well offers significantly improved radiative recombination rate and optical gain in comparison to the conventional type-I InGaN QW. Experimental results of light emitting diode (LED) structure utilizing staggered InGaN QW show good agreement with theory. Polarization band engineering via staggered InGaN quantum well allows enhancement of radiative recombination rate, leading to the improvement of photoluminescence intensity and LED output power.
Laser interferometric system for six-axis motion measurement
Authors: Zhang Zhipeng , Menq Chia-Hsiang
Published: August 2007

This article presents the development of a precision laser interferometric system, which is designed to achieve six-axis motion measurement for real-time applications. By combining the advantage of the interferometer with a retroreflector and that of the interferometer with a plane mirror reflector, the system is capable of simultaneously measuring large transverse motions along and large rotational motions about three orthogonal axes. Based on optical path analysis along with the designed kinematics of the system, a closed form relationship between the six-axis motion parameters of the object being measured and the readings of the six laser interferometers is established. It can be employed as a real-time motion sensor for various six-axis motion control stages. A prototype is implemented and integrated with a six-axis magnetic levitation stage to illustrate its resolution and measurement range.
Passivation of type-II InAs∕GaSb double heterostructure
Authors: Delaunay Pierre-Yves , Hood Andrew , Nguyen Binh Minh , Hoffman Darin , Wei Yajun , Razeghi Manijeh
Published: August 2007

Focal plane array fabrication requires a well passivated material that is resistant to aggressive processes. The authors report on the ability of type-II InAs∕GaSb superlattice heterodiodes to be more resilient than homojunctions diodes in improving sidewall resistivity through the use of various passivation techniques. The heterostructure consisting of two wide band gap (5μm) superlattice contacts and a low band gap active region (11μm) exhibits an R0A averaging of 13Ωcm2. The devices passivated with SiO2, Na2S and SiO2 or polyimide did not degrade compared to the unpassivated sample and the resistivity of the sidewalls increased to 47kΩcm.
Time resolved microphotoluminescence studies of single InP nanowires grown by low pressure metal organic chemical vapor deposition
Authors: Reitzenstein S. , Münch S. , Hofmann C. , Forchel A. , Crankshaw S. , Chuang L. C. , Moewe M. , Chang-Hasnain C.
Published: August 2007

The authors report optical studies of InP nanowires (NWs) grown by metal organic chemical vapor deposition. By means of low temperature microphotoluminescence experiments, the authors determined the optical properties of as-grown NWs. The emission of individual NWs is characterized by small linewidths as low as 2.3meV. Blueshifts of the NW emission energy between 25 and 56meV with respect to bulk InP are related to radial carrier confinement in nanowires with diameters between 15 and 50nm. Time resolved investigations reveal a low surface recombination velocity of 6×102cm∕s and indicate thermally activated nonradiative surface recombination above approximately 20K.
Puzzling differences in bismuth and lead plasmas: Evidence for the significant role of neutrals in cathodic vacuum arcs
Authors: Anders André , Yushkov Georgy Yu.
Published: August 2007

Time-dependent ion charge state measurements for Pb and Bi cathodic arc plasmas revealed unexpected differences: the mean Bi ion charge state dropped much stronger and with a longer time constant. It is shown that the differences in thermal conductivity and vapor pressure led to much higher neutral density for Bi, which in turn can cause charge exchange collisions. The results have implications beyond Pb and Bi plasmas: most importantly, they imply that the “true” ion charge states, as emitted from the cathode spots, are higher than what is generally measured and published.
Fabrication of two-dimensional photonic crystal patterns on GaN-based light-emitting diodes using thermally curable monomer-based nanoimprint lithography
Authors: Byeon Kyeong-Jae , Hwang Seon-Yong , Lee Heon
Published: August 2007

The fabrication process of photonic crystals in a p-GaN layer was established to improve the light extraction efficiency of light-emitting diodes (LEDs) by using nanoimprint lithography and inductively coupled plasma (ICP) etching process. Due to low etch selectivity of imprinted pattern, Cr mask patterns were lifted-off from the p-GaN surface and ICP etch process was followed using SiCl4-based plasma. As a result, two-dimensional pillar array patterns were uniformly fabricated on the p-GaN layer and the photoluminescence intensity of the photonic crystal patterned LED was increased by 2.6 fold compared to that of the same LED sample without photonic crystal patterns.
Bottom-gated metal-induced laterally crystallized silicon thin-film transistor with self-aligned raised source/drain
Authors: Kang Il-Suk , Han Shin-Hee , Joo Seung-Ki
Published: August 2007

A bottom-gated metal-induced laterally crystallized silicon thin-film transistor with self-aligned raised source/drain has been fabricated and characterized. In order to achieve complete alignment of the thick source/drain to the gate, a simple process of back surface exposure was employed twice. It features a thin active channel region with fewer grains, resulting in a low grain boundary trap density and a thick source/drain region with a low lateral electric field as well as a low resistance. The proposed device simultaneously improves on the turn-on and -off currents, showing good saturation characteristics and good short-channel characteristics.
High-performance and electrically stable C60 organic field-effect transistors
Authors: Zhang X.-H. , Domercq B. , Kippelen B.
Published: August 2007

The authors report on high-performance C60 organic field-effect transistors fabricated by physical vapor deposition. Electron mobility ranging from 2.7to5.0cm2∕Vs was achieved when treating the gate dielectric with divinyltetramethyldisiloxane bis(benzocyclobutene) and depositing C60 at room temperature. The transistors combine threshold voltages near zero, low subthreshold slopes (<0.7V/decade), on/off current ratios larger than 106, excellent reproducibility, and good electrical stability under prolonged continuous dc bias stress.
Differences between Early-Blind, Late-Blind, and Blindfolded-Sighted People in Haptic Spatial-Configuration Learning and Resulting Memory Traces
Authors: Postma Albert , Zuidhoek Sander , Noordzij Matthijs L , Kappers Astrid M L
Published: August 2007

The roles of visual and haptic experience in different aspects of haptic processing of objects in peripersonal space are examined. In three trials, early-blind, late-blind, and blindfolded-sighted individuals had to match ten shapes haptically to the cut-outs in a board as fast as possible. Both blind groups were much faster than the sighted in all three trials. All three groups improved considerably from trial to trial. In particular, the sighted group showed a strong improvement from the first to the second trial. While superiority of the blind remained for speeded matching after rotation of the stimulus frame, coordinate positional-memory scores in a non-speeded free-recall trial showed no significant differences between the groups. Moreover, when assessed with a verbal response, categorical spatial-memory appeared strongest in the late-blind group. The role of haptic and visual experience thus appears to depend on the task aspect tested.
Spatial distribution of commercial dredge fishing effort: application to survey design and the spatial management of a patchily distributed benthic bivalve species
Authors: Harrington Julian J. , Semmens Jayson M. , Haddon Malcolm
Published: August 2007

The patchy spatial distribution of many benthic commercial bivalve species plays an important role in determining the fishing and management strategies applied within a fishery. This study used fisher catch-return data and high resolution Vessel Monitoring System (VMS) data to determine the distribution of fishing effort within a region opened to commercial dredge fishing during the 2003 Tasmanian commercial scallop (Pecten fumatus) fishery, Australia. Fisher catch return data suggested that most (88%) of the open region was fished, however, fine-scale VMS data showed that 50% of the fishing effort occurred within 0.85% of the total area available to fishing, and 95% of the effort occurred within ~12% of the open region. The distribution of VMS inferred that the fishing effort was found to be patchy at all measured spatial scales (5 × 5 km to 250 × 250 m grid cell sizes); however, the degree of patchiness decreased with lower spatial scale cell sizes. Significant differences in the dredged benthic communities recorded within regions exposed to different concentrations of fishing intensity (heavy, moderate and low) were observed, with low and moderately fished regions containing high abundances of screwshells and their associated hermit crabs. Water depth was found to explain some of these observed differences, suggesting that the results may be the consequence of fisher behaviour over pre-existing habitat types. The observed distribution of the fishing effort and scallop beds within the Tasmanian commercial scallop, Pecten fumatus, fishery suits a closed area spatial management strategy, with the areas opened to fishing potentially being of the same scale as scallop beds (km × km).
Processes driving circulation, exchange and flushing within intermittently closing and opening lakes and lagoons
Authors: Gale Emma , Pattiaratchi Charitha , Ranasinghe Roshanka
Published: August 2007

The circulation and exchange between two intermittently closing and opening lakes and lagoons (ICOLLs) and the ocean were analysed using salinity and current meter data. Wamberal Lagoon was shallow (~2.5 m maximum depth) with a small (<1 km2) waterway area and a short opening duration (2 weeks), and Smiths Lake was deeper (~5 m maximum depth) with a larger (~11 km2) waterway area and a longer opening duration (4 months). An absence of river inflow and a restricted sill type inlet channel characterised both systems. The results showed that the smaller ICOLL exhibited a salinity structure similar to a partially or well-mixed estuary, whereas the larger ICOLL exhibited stronger separation of flow with a salt wedge-type structure. Both ICOLLs had strong current velocities in the surface water during ebb tide. The results also demonstrated that tidal effects controlled the circulation and exchange in the smaller ICOLL, whilst the wind also had a significant influence. In the larger ICOLL, subtidal effects over the fortnightly tidal cycle significantly influenced the circulation and exchange, but the influence of tide and wind effects was weaker. An analysis of the flushing for the two ICOLLs illustrated that the timescales were an order of magnitude different but comparable to the duration of opening for each ICOLL, ranging from 4 days in the smaller ICOLL (Wamberal Lagoon) to 113 days in the larger ICOLL (Smiths Lake). This research suggests that intermittent estuarine systems may be quite complex and variable within the same regional area, and consequently throughout the world.
Adaptive traits in ecology, reproduction and early life history of Sesarma meridies, an endemic stream crab from Jamaica
Authors: Anger Klaus , Torres Gabriela , Nettelmann Uwe
Published: August 2007

The endemic Jamaican freshwater crab Sesarma meridies lives in shady microhabitats on river banks, where temperature and pH are lower and ion concentrations higher than in mid-stream water. Ovigerous females were found to release up to 140 yolk-rich larvae (hatching period: 1 week; >90% at night). Larval development comprised two fully lecithotrophic zoeal stages and a feeding megalopa, which was also able to develop without food (facultative lecithotrophy). After metamorphosis in complete absence of food, juvenile crabs showed reduced body size, delayed moulting, and enhanced mortality. Endotrophic development was fuelled by internal lipid reserves; proteins were conserved as structural components of tissues and organs. Fed megalopae enhanced their protein content rather than re-stocking previously lost lipid reserves. Ecdysial biomass (CHN) losses were very low (zoeal stages: 1–2%; megalopa: 3–7%), showing an energy-saving production of thin exuviae. An extended hatching period may reduce intraspecific competition or cannibalism among juveniles; nocturnal hatching should reduce the predation on larvae. Large egg size, enhanced yolk reserves, an extended embryonic development (7 weeks at 24°C; implying a prolonged period of brood care), abbreviated and partially food-independent larval development, and reduced exuvial losses are considered as life-history adaptations to unpredictable planktonic food availability in the breeding habitat.
Contribution of adult aquatic insects to riparian prey availability along tropical forest streams
Authors: Chan Eric K. W. , Zhang Yixin , Dudgeon David
Published: August 2007

The contribution of adult aquatic insects to riparian prey availability at four sites along three hillstreams in Hong Kong was estimated during 2004–2006 dry and wet seasons using light traps deployed at different distances from the banks. The number and biomass of aquatic and terrestrial insects collected were markedly higher during the wet season. Numerically, aquatic insects (especially Chironomidae and Philopotamidae) remained a major catch component along banks throughout the year comprising 77% (range: 61–85%) of total insects. Their contribution to total biomass was higher in the wet season (mean: 50%, range: 33–62%) than during the dry season (mean: 21%, range: 8–45%). Aquatic insect abundance decreased with increasing distance from streams during both seasons: numbers at 10–20 m distance were less than 45% of those at the banks, declining to less than 13% at 80 m distance. No such decline with distance was observed for terrestrial insects, but the limited dispersal of aquatic insects meant total insect catches were highest along stream banks. Changes in biomass with distance from streams were similar to those for abundance. Adult aquatic insects may represent an important water-to-land energy subsidy for riparian predators in Hong Kong, but the magnitude varied seasonally and fell sharply with increasing distance from streams.
Refining self-reported condom use among young men at risk of HIV acquisition
Authors: Crosby Richard , DiClemente Ralph J. , Yarber William L. , Snow Gregory , Troutman Adewale
Published: August 2007

This descriptive study evaluated the validity of self-reported condom use among young African American men. Thirty percent (n = 79) of the men reported consistent condom use. After accounting for late application and/or early removal of condoms, slippage, and breakage, 26 men remained classified as consistent users. Among the 79 men initially classified as consistent condom users, 695 sexual episodes were reported as ‘condom-protected;’ however, after correcting for user error, 29.6% of the sexual episodes were actually not protected. Studies assessing self-reported condom use among young African American men should assess user errors as well as frequency of condom use.
A cost-effectiveness analysis of adding a human papillomavirus vaccine to the Australian National Cervical Cancer Screening Program
Authors: Kulasingam Shalini , Connelly Luke , Conway Elizabeth , Hocking Jane S. , Myers Evan , Regan David G. , Roder David , Ross Jayne , Wain Gerard
Published: August 2007

Background: The cost-effectiveness of adding a human papillomavirus (HPV) vaccine to the Australian National Cervical Screening Program compared to screening alone was examined. Methods: A Markov model of the natural history of HPV infection that incorporates screening and vaccination was developed. A vaccine that prevents 100% of HPV 16/18-associated disease, with a lifetime duration of efficacy and 80% coverage offered through a school program to girls aged 12 years, in conjunction with current screening was compared with screening alone using cost (in Australian dollars) per life-year (LY) saved and quality-adjusted life-year (QALY) saved. Sensitivity analyses included determining the cost-effectiveness of offering a catch-up vaccination program to 14–26-year-olds and accounting for the benefits of herd immunity. Results: Vaccination with screening compared with screening alone was associated with an incremental cost-effectiveness ratio (ICER) of $51 103 per LY and $18 735 per QALY, assuming a cost per vaccine dose of $115. Results were sensitive to assumptions about the duration of vaccine efficacy, including the need for a booster ($68 158 per LY and $24 988 per QALY) to produce lifetime immunity. Accounting for herd immunity resulted in a more attractive ICER ($36 343 per LY and $13 316 per QALY) for girls only. The cost per LY of vaccinating boys and girls was $92 052 and the cost per QALY was $33 644. The cost per LY of implementing a catch-up vaccination program ranged from $45 652 ($16 727 per QALY) for extending vaccination to 14-year-olds to $78 702 ($34 536 per QALY) for 26-year-olds. Conclusions: These results suggest that adding an HPV vaccine to Australia’s current screening regimen is a potentially cost-effective way to reduce cervical cancer and the clinical interventions that are currently associated with its prevention via screening alone.
Large-scale, saturating insertional mutagenesis of the mouse genome
Authors: Gragerov Alexander , Horie Kyoji , Pavlova Maria , Madisen Linda , Zeng Hongkui , Gragerova Galina , Rhode Alex , Dolka Io , Roth Patricia , Ebbert Amanda , Moe Stephanie , Navas Christopher , Finn Eric , Bergmann John , Vassilatis Demetrios K. , Pavlakis George N. , Gaitanaris George A.
Published: August 2007

We describe the construction of a large-scale, orderly assembly of mutant ES cells, generated with retroviral insertions and having mutational coverage in >90% of mouse genes. We also describe a method for isolating ES cell clones with mutations in specific genes of interest from this library. This approach, which combines saturating random mutagenesis with targeted selection of mutations in the genes of interest, was successfully applied to the gene families of G protein-coupled receptors (GPCRs) and nuclear receptors. Mutant mouse strains in 60 different GPCRs were generated. Applicability of the technique for the GPCR genes, which on average represent fairly small targets for insertional mutagenesis, indicates the general utility of our approach for the rest of the genome. The method also allows for increased scale and automation for the large-scale production of mutant mice, which could substantially expedite the functional characterization of the mouse genome.
Negative feedback regulation of Rac in leukocytes from mice expressing a constitutively active phosphatidylinositol 3-kinase γ
Authors: Costa Carlotta , Barberis Laura , Ambrogio Chiara , Manazza Andrea D. , Patrucco Enrico , Azzolino Ornella , Neilsen Paul O. , Ciraolo Elisa , Altruda Fiorella , Prestwich Glenn D. , Chiarle Roberto , Wymann Matthias , Ridley Anne , Hirsch Emilio
Published: August 2007

Polarization of chemotaxing cells depends on positive feedback loops that amplify shallow gradients of chemoattractants into sharp intracellular responses. In particular, reciprocal activation of phosphatidylinositol 3-kinases (PI3Ks) and small GTPases like Rac leads to accumulation, at the leading edge, of the PI3K product phosphatidylinositol 3,4,5-trisphosphate (PIP3). Mice carrying a “knockin” allele of the G protein-coupled receptor (GPCR)-activated PI3Kγ, encoding a plasma membrane-targeted protein appeared normal, but their leukocytes showed GPCR-uncoupled PIP3 accumulation.
In vivo
, the mutation increased proliferation and decreased apoptosis, leading to leukocytosis and delayed resolution of inflammation in wound healing. Mutant leukocytes showed significantly impaired directional cell migration in response to chemoattractants. Stimulated mutant macrophages did not polarize PIP3 and showed a shortened Rac activation because of enhanced PI3K-dependent activation of RacGAPs. Together with the finding that chemoattractants stimulate a PIP3-dependent GAP activation in wild-type macrophages, these results identify a molecular mechanism involving PI3K- and RacGAP-dependent negative control of Rac that limits and fine-tunes feedback loops promoting cell polarization and directional motility.
Evidence for a diffusion-controlled mechanism for fluorescence blinking of colloidal quantum dots
Authors: Pelton Matthew , Smith Glenna , Scherer Norbert F. , Marcus Rudolph A.
Published: August 2007

Fluorescence blinking in nanocrystal quantum dots is known to exhibit power-law dynamics, and several different mechanisms have been proposed to explain this behavior. We have extended the measurement of quantum-dot blinking by characterizing fluctuations in the fluorescence of single dots over time scales from microseconds to seconds. The power spectral density of these fluctuations indicates a change in the power-law statistics that occurs at a time scale of several milliseconds, providing an important constraint on possible mechanisms for the blinking. In particular, the observations are consistent with the predictions of models wherein blinking is controlled by diffusion of the energies of electron or hole trap states.
Time variability in Cenozoic reconstructions of mantle heat flow: Plate tectonic cycles and implications for Earth's thermal evolution
Authors: Loyd S. J. , Becker T. W. , Conrad C. P. , Lithgow-Bertelloni C. , Corsetti F. A.
Published: August 2007

The thermal evolution of Earth is governed by the rate of secular cooling and the amount of radiogenic heating. If mantle heat sources are known, surface heat flow at different times may be used to deduce the efficiency of convective cooling and ultimately the temporal character of plate tectonics. We estimate global heat flow from 65 Ma to the present using seafloor age reconstructions and a modified half-space cooling model, and we find that heat flow has decreased by ∼0.15% every million years during the Cenozoic. By examining geometric trends in plate reconstructions since 120 Ma, we show that the reduction in heat flow is due to a decrease in the area of ridge-proximal oceanic crust. Even accounting for uncertainties in plate reconstructions, the rate of heat flow decrease is an order of magnitude faster than estimates based on smooth, parameterized cooling models. This implies that heat flow experiences short-term fluctuations associated with plate tectonic cyclicity. Continental separation does not appear to directly control convective wavelengths, but rather indirectly affects how oceanic plate systems adjust to accommodate global heat transport. Given that today's heat flow may be unusually low, secular cooling rates estimated from present-day values will tend to underestimate the average cooling rate. Thus, a mechanism that causes less efficient tectonic heat transport at higher temperatures may be required to prevent an unreasonably hot mantle in the recent past.