bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic consequences of ileal transposition in rats with diet-induced obesity
Authors: Lourenço Paolo , Miguel Gustavo , Carlini Marcelo , Lapchick Valderez , Azevedo Joao , Azevedo Otávio , Leal Lucas , Azevedo Joao Luiz , Aguiar-Yamaguchi Gilmara , Cardia Wellington , Marigliani Bianca , Ko Gui , Neves Karina
Published: July 2011

INTRODUCTION: The clinical management of metabolic syndrome - especially diabetes mellitus type 2 - is notoriously complex due to the progressive nature of this disease. At present, there is a need for a surgical procedure that is effective for the treatment of diabetes mellitus type 2, even in non-obese individuals. The isolated ileal transposition theory could lead to an effective alternative therapy. This intervention has not yet been performed in humans, and there are no reports of its use in an experimental model of diet-induced metabolic syndrome.

OBJECTIVES:

The objective of this study is to evaluate the physiological effects of ileal transposition in rats with diet-induced metabolic syndrome. The effects of this procedure on glucose and lipid metabolism will be assessed.

METHODS:

Forty 12-week-old male rats (albino Rattus norvegicus, Wistar, 2BAW, heterogeneous) will be divided into four groups of 10 animals each: the ileal transposition group (TG) comprising animals on a hypercaloric-hyperlipidic diet; the sham group (SG) containing animals that receive the same diet and undergo the sham surgery; control group 1 (CG1), which will receive a hypercaloric-hyperlipidic diet and will not undergo surgery; and control group 2 (CG2), which will consume standard feed and will not undergo surgery. The surgeries will be performed in 20-week-old animals. Blood samples for laboratory testing will be collected from 12-week-old animals on the day of surgery and after eight postoperative weeks, following determination of the weights of the animals and the administration of anesthesia. The levels of serum glucose, insulin, triglycerides, total cholesterol and fractions, glucagon-like peptide-1, C-peptide and glycated hemoglobin will be assessed in all of the animals. The insulin tolerance test will be performed using PRISMA software, and insulin resistance will be calculated by the HOMA-IR indirect test. On specific days, two 20-week-old rats will be separated and randomly distributed in TG and SG. These animals will be followed until the eighth postoperative week. Subsequently, they will be euthanized, and the retroperitoneal and periepididymal fat deposits will be collected and weighed using a precision scale. In addition, the pancreas, liver and intestinal segments will be sent for pathological and immunohistochemical studies.
Serine biosynthesis with one carbon catabolism represents a novel pathway for ATP generation in cells using alternative glycolysis with zero net ATP production
Authors: Vazquez Alexei , Oltvai Zoltan
Published: July 2011

Recent experimental evidence indicates that some cancer cells have an alternative glycolysis pathway with net zero ATP production, implying that upregulation of glycolysis in these cells may not be related to the generation of ATP. Here we use a genome-scale model of human cell metabolism to investigate the potential metabolic alterations in cells using net zero ATP glycolysis. We uncover a novel pathway for ATP generation that involves reactions from the serine biosynthesis and one-carbon metabolism pathways. This pathway has a predicted two-fold higher flux rate in cells using net zero ATP glycolysis than those using standard glycolysis and generates twice as much ATP with significantly lower rate of lactate- but higher rate of alanine secretion. Thus, in cells using the standard- or the net zero ATP glycolysis pathways a significant portion of the glycolysis flux is always associated with ATP generation, and the ratio between the flux rates of the two pathways determines the rate of ATP generation and lactate and alanine secretion during glycolysis.
Novel regulation of PLCζ activity via its XY-linker
Authors: Nomikos Michail , Elgmati Khalil , Theodoridou Maria , Georgilis Athena , Gonzalez-Garcia J. Raul , Nounesis George , Swann Karl , Lai F. Anthony
Published: July 2011

The XY-linker region of somatic cell PLC (phospholipase)-β, -γ, -δ and -ϵ isoforms confers potent catalytic inhibition, suggesting a common auto-regulatory role. Surprisingly, the sperm PLCζ XY-linker does not mediate auto-inhibition. Unlike for somatic PLCs, the absence of the PLCζ XY-linker significantly diminishes both in vitro PIP2 (phosphatidylinositol 4,5-bisphosphate) hydrolysis and in vivo Ca2+-oscillation-inducing activity, revealing evidence for a novel PLCζ enzymatic mechanism.
Low doses of ethanol decrease the activity of the angiotensin-converting enzyme in the aorta of aging rats and rats treated with a nitric oxide synthase inhibitor and dexamethasone
Authors: Emel'yanov Maksim O. , Korystova Antonina F. , Kublik Ludmila N. , Levitman Maria Kh. , Shaposhnikova Vera V. , Korystov Yuri N.
Published: July 2011

In the present study, the activity of ACE (angiotensin-converting enzyme) in the aorta of senescent rats and rats treated with the NOS (NO synthase) inhibitor L-NAME (NG-nitro-L-arginine methyl ester) or dexamethasone and the effect of low doses of ethanol (0.2–1.2 g/kg of body weight, daily for 8–12 days) on this activity were studied. We found that ACE activity increased with age and in response to L-NAME and dexamethasone treatment. Ethanol at a dose of 0.4 g/kg of body weight per day decreased ACE activity in the aorta of aged rats and of rats treated with L-NAME or dexamethasone to the level of activity in young control rats. The optimal ethanol dose (the dose inducing a maximum decrease in ACE activity) increased with increasing doses of dexamethasone: 0.4 g/kg of body weight per day at 30 μg of dexamethasone/kg of body weight and 0.8 g/kg of body weight per day at 100 μg of dexamethasone/kg of body weight. It was also found that optimal doses of ethanol increased the number of cells in the thymus of rats treated with dexamethasone. The optimal dose of ethanol of 0.4 g/kg of body weight per day, which induced a maximum decrease in ACE activity in rat aorta, corresponded to a dose of 30 g of ethanol/day, which, according to epidemiological data, produces a maximum decrease in the incidence of cardiovascular disease in humans. In conclusion, the decrease in ACE activity in vessels may be one of the main mechanisms of the beneficial effects of low doses of ethanol on human health.
Contribution to the numerical study of turbulence in high intensity discharge lamps
Authors: Kaziz S. , Ben Ahmed R. , Helali H. , Gazzah H. , Charrada K.
Published: July 2011

We present in this paper a comparison between results obtained with a laminar and turbulent models for high-pressure mercury arc. The two models are based on the resolution of bidimensional time-dependent equations by a semi-implicit finite-element code. The numerical computation of turbulent model is solved with large eddy simulation model; this approach takes into account the various scales of turbulence by a filtering method on each scale. The results show the quantitative influence of turbulence on the flow fields and also the difference between laminar and turbulent effects on the dynamic thermal behaviour and on the characteristics of the discharge.
Haptic-STM: A human-in-the-loop interface to a scanning tunneling microscope
Authors: Perdigão Luís M. A. , Saywell Alex
Published: July 2011

The operation of a haptic device interfaced with a scanning tunneling microscope (STM) is presented here. The user moves the STM tip in three dimensions by means of a stylus attached to the haptic instrument. The tunneling current measured by the STM is converted to a vertical force, applied to the stylus and felt by the user, with the user being incorporated into the feedback loop that controls the tip-surface distance. A haptic-STM interface of this nature allows the user to feel atomic features on the surface and facilitates the tactile manipulation of the adsorbate/substrate system. The operation of this device is demonstrated via the room temperature STM imaging of C60 molecules adsorbed on an Au(111) surface in ultra-high vacuum.
Reflection and refraction of shocks on an interface with a reflected rarefaction wave
Authors: Fang Beixiang , Wang Ya-Guang , Yuan Hairong
Published: July 2011

When a shock interacts with an interface, which is a contact discontinuity in two-dimensional gas flows, there may appear a reflected rarefaction wave, a deflected contact discontinuity and a refracted supersonic shock. We show the local existence of this flow pattern near the intersection point and its stability with respect to the perturbation satisfying certain compatibility conditions of the states on both sides of the interface as well as the incident shock.
The role of excitons and trions on electron spin polarization in quantum wells
Authors: Aceituno P. , Hernández-Cabrera A.
Published: July 2011

We have studied the time evolution of the electron spin polarization under continuous photoexcitation in remotely n-doped semiconductor quantum wells. The doped region allows us to get the necessary excess of free electrons to form trions. We have considered electron resonant photoexcitation at free, exciton, and trion electron energy levels. Also, we have studied the relative effect of photoexcitation energy density and doping concentration. In order to obtain the two-dimensional density evolution of the different species, we have performed dynamic calculations through the matrix density formalism. Our results indicate that photoexcitation of free electron level leads to a higher spin polarization. Also, we have found that increasing the photoexcitation energy or diminishing the doping enhances spin polarization.
First numerical investigation of a conjecture by N. N. Nekhoroshev about stability in quasi-integrable systems
Authors: Guzzo Massimiliano , Lega Elena , Froeschlé Claude
Published: July 2011

We investigate numerically a conjecture by N. N. Nekhoroshev about the influence of a geometric property, called steepness, on the long term stability of quasi-integrable systems. In a Nekhoroshev’s 1977 paper, it is conjectured that, among the steep systems with the same number ν of frequencies, the convex ones are the most stable, and it is suggested to investigate numerically the problem. Following this suggestion, we numerically study and compare the diffusion of the actions in quasi-integrable systems with different steepness properties in a large range of variation of the perturbation parameter ɛ and different dimensions of phase space corresponding to ν = 3 and ν = 4 (ν ≤ 2 is not significant for the conjecture). For six dimensional maps (ν = 4), our numerical experiments perfectly agree with the Nekhoroshev conjecture: for both convex and non convex cases, the numerically computed diffusion coefficient D of the actions is compatible with an exponential fit, and the convex case is definitely more stable than the steep one. For four dimensional maps (ν = 3), since we find that in the steep case D(ɛ) has large oscillations around an exponential behaviour, the agreement of our numerical experiments with the conjecture is not sharp, and it is found by considering a sup over different initial conditions.
Surface acoustic wave velocity of gold films deposited on silicon substrates at different temperatures
Authors: Salas E. , Jiménez Riobóo R. J. , Prieto C. , Every A. G.
Published: July 2011

Au thin films have been deposited by DC magnetron sputtering on Si (001) substrates at different substrate temperatures, ranging from 200 K to 450 K. With increasing temperature, the expected crystallinity and morphology of the Au thin film are clearly improved, as shown by x ray diffraction, atomic force microscopy and scanning electron microscopy experiments. Parallel to this, the surface acoustic wave propagation velocity shows a clear enhancement toward the ideal values obtained from numerical simulations of a Au thin film on Si (001) substrate. Moreover, a very thin and slightly rough interlayer between the Si (001) substrate and the Au thin film is developed for temperatures above 350 K. The composition and nature of this interlayer is not known. This interlayer may be responsible for the steep change in the structural and elastic properties of the Au thin films at the higher temperatures and possibly also for an improvement of the adhesion properties of the Au on the Si (001) substrate.
Development of optical fiber Bragg grating force-reflection sensor system of medical application for safe minimally invasive robotic surgery
Authors: Song Hoseok , Kim Kiyoung , Lee Jungju
Published: July 2011

Force feedback plays a very important role in medical surgery. In minimally invasive surgery (MIS), however, the very long and stiff bars of surgical instruments greatly diminish force feedback for the surgeon. In the case of minimally invasive robotic surgery (MIRS), force feedback is totally eliminated. Previous researchers have reported that the absence of force feedback increased the average force magnitude applied to the tissue by at least 50%, and increased the peak force magnitude by at least a factor of two. Therefore, it is very important to provide force information in MIRS. Recently, many sensors are being developed for MIS and MIRS, but some obstacles to their application in actual medical surgery must be surmounted. The most critical problems are size limit and sterilizability. Optical fiber sensors are among the most suitable sensors for the surgical environment. The optical fiber Bragg grating (FBG) sensor, in particular, offers an important additional advantage over other optical fiber sensors in that it is not influenced by the intensity of the light source. In this paper, we present the initial results of a study on the application of a FBG sensor to measure reflected forces in MIRS environments and suggest the possibility of successful application to MIRS systems.
Optical cell for in situ vibrational spectroscopic measurements at high pressures and shear
Authors: Ciezak Jennifer A. , Jenkins Timothy A.
Published: July 2011

An optical cell is described for performing simultaneous static high-pressure and shear experiments. This cell design is a modification of the previously designed megabar diamond anvil cell used by Mao and Bell that allows for controlled, remote shear. With this diamond anvil cell, it is possible to use a wide range of existing experimental techniques and pressure media. The cell was validated on a sample of calcite at 5 kbar. Raman measurements show the onset of the phase transformation from calcite to aragonite at 10° of rotation.
Carrier recombination dynamics in Si doped InN thin films
Authors: Mohanta Antaryami , Jang D.-J. , Lin G.-T. , Lin Y.-T. , Tu L. W.
Published: July 2011

Time-integrated and time-resolved photoluminescence (PL) of InN thin films of different background carrier concentrations are investigated. The PL formation mechanism is attributed to the “free-to-bound” transition by analyzing the time-integrated PL spectra at different pump fluences. The dependence of the PL decay time with emission energy is investigated using a theoretical model which speculates upon the carrier localization in InN thin films. The radiative lifetime, mobility edge, and carrier localization energy are obtained from the dependence of the PL decay time on emission energy and are studied at different background carrier concentrations. The effect of intervalley scattering between the Γ1 and Γ3 valley on the radiative lifetime, mobility edge, and carrier localization energy is discussed. The longer radiative lifetime and smaller values of the mobility edge and localization energy for 3.06 eV excitation are observed than that for the 1.53 eV excitation due to the intervalley scattering process.
Quantum pinning-transition due to charge defects in ferroelectrics
Authors: Biswas Arindam , Choudhary Kamal , Bandyopadhyay A. K. , Bhattacharjee A. K. , Mandal D.
Published: July 2011

We investigate the pinning of domain walls in ferroelectrics on the basis of the two phonon bound state (TPBS) or discrete breather state due to impurity energy levels above the phonon continua in ferroelectrics such as LiNbO3 in order to show the pinning transition, which indicates the point of easiest switching. We predict, with the help of our quantum calculations, that every ferroelectric material has such a critical point of easy switching. Here we describe the quantum origin of pinning through the findings of analytical and numerical calculations, as interpreted by a TPBS concept by such impurity or nonlinearity induced modes, by plotting various TPBS parameters against the Landau coefficient and percent impurity content. This new approach might lead to many interesting applications for device manufacturing.
Explanation of commonly observed shunt currents in c-Si solar cells by means of recombination statistics beyond the Shockley-Read-Hall approximation
Authors: Steingrube Silke , Breitenstein Otwin , Ramspeck Klaus , Glunz Stefan , Schenk Andreas , Altermatt Pietro P.
Published: July 2011

The current-voltage (I–V) characteristics of industrially fabricated, crystalline silicon solar cells are often influenced by non-linear shunts that originate from localized, highly disturbed regions and cause ideality factors n > 2. We show that recombination within such locations needs model descriptions that go beyond the Shockley-Read-Hall (SRH) approximation, because the density of defects is so high that recombination does not occur via isolated, but coupled defect states. We use a variant of coupled defect level (CDL) recombination, the donor-acceptor-pair (DAP) recombination, but via deep levels (as opposed to shallow levels). With this model, we quantitatively reproduce the I–V curves of solar cells that we subjected to various degrees of cleaving, laser scribing or diamond scratching to form shunt locations in a controlled manner. The suggested model explains the transition from ideality factors n < 2 to n > 2 when going from low to high defect densities. We also explain the non-saturating reverse I–V characteristics. We show that an additional source of currents with n > 2 is SRH recombination in an inversion layer that extends from the front p-n junction to the rear contact along the cell’s edge or along a micro-crack.
A study of planar Richtmyer-Meshkov instability in fluids with Mie-Grüneisen equations of state
Authors: Ward G. M. , Pullin D. I.
Published: July 2011

We present a numerical comparison study of planar Richtmyer-Meshkov instability with the intention of exposing the role of the equation of state. Results for Richtmyer-Meshkov instability in fluids with Mie-Grüneisen equations of state derived from a linear shock-particle speed Hugoniot relationship (Jeanloz, J. Geophys. Res. 94, 5873, 1989; McQueen et al., High Velocity Impact Phenomena (1970), pp. 294–417; Menikoff and Plohr, Rev. Mod. Phys. 61(1), 75 1989) are compared to those from perfect gases under nondimensionally matched initial conditions at room temperature and pressure. The study was performed using Caltech’s Adaptive Mesh Refinement, Object-oriented C++ (AMROC) (Deiterding, Adaptive Mesh Refinement: Theory and Applications (2005), Vol. 41, pp. 361–372; Deiterding, “Parallel adaptive simulation of multi-dimensional detonation structures,” Ph.D. thesis (Brandenburgische Technische Universität Cottbus, September 2003)) framework with a low-dissipation, hybrid, center-difference, limiter patch solver (Ward and Pullin, J. Comput. Phys. 229, 2999 (2010)). Results for single and triple mode planar Richtmyer-Meshkov instability when a reflected shock wave occurs are first examined for mid-ocean ridge basalt (MORB) and molybdenum modeled by Mie-Grüneisen equations of state. The single mode case is examined for incident shock Mach numbers of 1.5 and 2.5. The planar triple mode case is studied using a single incident Mach number of 2.5 with initial corrugation wavenumbers related by k1=k2+k3. Comparison is then drawn to Richtmyer-Meshkov instability in perfect gases with matched nondimensional pressure jump across the incident shock, post-shock Atwood ratio, post-shock amplitude-to-wavelength ratio, and time nondimensionalized by Richtmyer’s linear growth time constant prediction. Differences in start-up time and growth rate oscillations are observed across equations of state. Growth rate oscillation frequency is seen to correlate directly to the oscillation frequency for the transmitted and reflected shocks. For the single mode cases, further comparison is given for vorticity distribution and corrugation centerline shortly after shock interaction. Additionally, we examine single mode Richtmyer-Meshkov instability when a reflected expansion wave is present for incident Mach numbers of 1.5 and 2.5. Comparison to perfect gas solutions in such cases yields a higher degree of similarity in start-up time and growth rate oscillations. The formation of incipient weak waves in the heavy fluid driven by waves emanating from the perturbed transmitted shock is observed when an expansion wave is reflected.
Large volume high-pressure cell for inelastic neutron scattering
Authors: Wang W. , Sokolov D. A. , Huxley A. D. , Kamenev K. V.
Published: July 2011

Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm3. The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe2.
Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source
Authors: Lord J. S. , McKenzie I. , Baker P. J. , Blundell S. J. , Cottrell S. P. , Giblin S. R. , Good J. , Hillier A. D. , Holsman B. H. , King P. J. C. , Lancaster T. , Mitchell R. , Nightingale J. B. , Owczarkowski M. , Poli S. , Pratt F. L. , Rhodes N. J. , Scheuermann R. , Salman Z.
Published: July 2011

The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.
Pheromone synthesis in a biomicroreactor coated with anti-adsorption polyelectrolyte multilayer
Authors: Dimov Nikolay , Muñoz Lourdes , Carot-Sans Gerard , Verhoeven Michel L. P. M. , Bula Wojciech P. , Kocer Gülistan , Guerrero Angel , Gardeniers Han J. G. E.
Published: July 2011

To prepare a biosynthetic module in an infochemical communication project, we designed a silicon/glass microreactor with anti-adsorption polyelectrolyte multilayer coating and immobilized alcohol acetyl transferase (atf), one of the key biosynthetic enzymes of the pheromone of Spodoptera littoralis, on agarose beads inside. The system reproduces the last step of the biosynthesis in which the precursor diene alcohol (Z,E)-9,11-tetradecadienol is transformed into the major component (Z,E)-9,11-tetradecadienyl acetate. The scope of this study was to analyze and implement a multilayer, anti-adsorption coating based on layer-by-layer deposition of polyethylenimine/dextransulfate sodium salt (PEI/DSS). The multilayers were composed of two PEI with molecular weights 750 and 1.2 kDa at pH 9.2 or 6.0. Growth, morphology, and stability of the layers were analyzed by ellipsometry and atomic force microscopy (AFM). The anti-adsorption functionality of the multilayer inside the microreactor was validated. The activity of His6-(atf) was measured by gas chromatography coupled to mass spectrometer (GC-MS).
Equivalent circuit method analysis of the influence of frequency selective surface resistance on the frequency response of metamaterial absorbers
Authors: Pang Yong-qiang , Zhou Yong-jiang , Wang Jun
Published: July 2011

A simple equivalent circuit method has been proposed to provide understanding of the absorption mechanism of a class of metamaterial absorbers. The absorbers are composed of lossy frequency selective surfaces (FSSs) over the grounded dielectric substrates. Based on the analytical method, the influence of FSS surface resistance on the frequency responses of metamaterial absorbers is discussed in detail. It is shown that wideband or narrowband absorbers can be obtained by changing the surface resistance of the FSS. The narrowband absorbers show a similar surface resistance dependence of the absorbing performance to Salisbury absorbers and the maximum bandwidth of metamaterial absorbers can be obtained with the proper surface resistance. This can serve as a guideline for the fast and efficient design of metamaterial absorbers. Finally, experimental results are presented for verifying the validity of the analytical method.
High speed two-dimensional optical beam position detector
Authors: Rutten Paul Edmond
Published: July 2011

Disclosed is the design of a high speed two-dimensional optical beam position detector which outputs the X and Y displacement and total intensity linearly. The experimental detector measures the displacement from DC to 123 MHz and the intensity of an optical spot in a similar way as a conventional quadrant photodiode detector. The design uses four discrete photodiodes and simple dedicated optics for the position decomposition which enables higher spatial accuracy and faster electronic processing than conventional detectors. Measurements of the frequency response and the spatial sensitivity demonstrate high suitability for atomic force microscopy, scanning probe data storage applications, and wideband wavefront sensing. The operation principle allows for position measurements up to 20 GHz and more in bandwidth.
Theory of multichromophoric coherent resonance energy transfer: A polaronic quantum master equation approach
Authors: Jang Seogjoo
Published: July 2011

The approach of second order time local quantum master equation in the polaron picture, which has been employed for a theory of coherent resonance energy transfer, is extended for general multichromophore systems. Explicit expressions for all the kernel and inhomogeneous terms are derived, which can be calculated by any standard numerical procedure. The theory is then applied to a model of donor-bridge-acceptor system moderately coupled to bosonic bath. The results are compared with those based on the theory of Förster's resonance energy transfer. It is shown that coherently coupled multichromophores can speed up the transfer of energy substantially and in a way insensitive to the disorder.
Thermoelectric properties of Heusler-type compound Fe2V1−xNbxAl
Authors: Xu Bin , Wang Yuanxu , Zhao Wenjie , Yan Yuli
Published: July 2011

The transport properties are calculated within the full-potential linearized augmented plane-wave method and the semi-classical Boltzmann theory on the Heusler-type compound Fe2V1−xNbxAl. The obtained Seebeck coefficients are in reasonable agreement with experimental results. The majority carriers of stoichiometric Fe2VAl are holes. When V is slightly replaced by Nb, the Seebeck coefficient becomes negative rapidly resulting in the main carrier changing from hole to electron. σ/τ of stoichiometric Fe2VAl exhibits semiconductor behavior. However, it transits into semimetal when V is replaced by Nb at low temperature and all Nb-substituted samples exhibit semiconducting behavior above 100 K. The power factor S2σ/τ of stoichiometric Fe2VAl is relative small, and it increases greatly after Nb substitution below 360 K. The low temperature power factor of Fe2V1−xNbxAl (x ≠ 0) increases dramatically due to the enhanced Seebeck coefficient.
Description and performance of a fully automatic device for the study of the sedimentation of magnetic suspensions
Authors: Iglesias G. R. , López-López M. T. , Delgado A. V. , Durán J. D. G.
Published: July 2011

In this paper we describe an experimental setup for the automatic determination of the sedimentation behavior of magnetic suspensions (i.e., disperse systems consisting on ferro- or ferri-magnetic particles in a suitable fluid) of arbitrary volume fraction of solids. The device is based on the evaluation of the inductance of a thin coil surrounding the test tube containing the sample. The inductance L is evaluated from the measurement of the resonant frequency of a parallel LC circuit constructed with the coil and a capacitor of known capacitance. The coil can be moved vertically along the tube at specified steps and time intervals, and from the knowledge of L as a function of the vertical position and time, one can get an image of the particle concentration profiles at given instants of time. The performance of the device is tested against suspensions of spherical iron particles in the micrometer size range dispersed in silicone oil, with various initial concentrations of solids. The sedimentation profiles are then compared with the predictions of existing models for the settling of disperse systems of non-interacting particles.
Implementation of pseudopotential in the G3 theory for molecules containing first-, second-, and non-transition third-row atoms
Authors: Pereira Douglas Henrique , Ramos Alex Freitas , Morgon Nelson Henrique , Custodio Rogério
Published: July 2011

Compact effective pseudopotential (CEP) is adapted in the G3 theory providing a theoretical alternative referred to as G3CEP for calculations involving the first-, second-, and non-transition third-row elements. These modifications tried to preserve as much as possible the original characteristics of G3. G3CEP was used in the study of 247 enthalpies of formation, 22 atomization energies, 104 ionization potentials, 63 electron affinities, and 10 proton affinities, resulting in the calculation of 446 species for the first-, second-, and third-row atoms. The final average total absolute deviation was of 1.29 kcal mol−1 against 1.16 kcal mol−1 from all-electron G3 for the same calculations. The CPU time has been reduced by 7% to 56%, depending on the size of the molecules and the type of atoms considered.
Sequential shrink photolithography for plastic microlens arrays
Authors: Dyer David , Shreim Samir , Jayadev Shreshta , Lew Valerie , Botvinick Elliot , Khine Michelle
Published: July 2011

Endeavoring to push the boundaries of microfabrication with shrinkable polymers, we have developed a sequential shrink photolithography process. We demonstrate the utility of this approach by rapidly fabricating plastic microlens arrays. First, we create a mask out of the children’s toy Shrinky Dinks by simply printing dots using a standard desktop printer. Upon retraction of this pre-stressed thermoplastic sheet, the dots shrink to a fraction of their original size, which we then lithographically transfer onto photoresist-coated commodity shrink wrap film. This shrink film reduces in area by 95% when briefly heated, creating smooth convex photoresist bumps down to 30 µm. Taken together, this sequential shrink process provides a complete process to create microlenses, with an almost 99% reduction in area from the original pattern size. Finally, with a lithography molding step, we emboss these bumps into optical grade plastics such as cyclic olefin copolymer for functional microlens arrays.
Gate-induced switching in single-molecule magnet MnIIICuII
Authors: Hao Hua , Zheng XiaoHong , Dai ZhenXiang , Zeng Zhi
Published: July 2011

Gate voltage effect on electronic transport through the smallest single-molecule magnet (SMM) MnCu [MnIIICuIICl(5-Br-sap)2(MeOH)] sandwiched between Au(100) electrodes is investigated by spin-polarized density functional theory calculations combined with the Keldysh nonequilibrium Green’s technique. Our study demonstrates that a certain gate voltage can induce a switching of the conductance in the equilibrium state. Under a finite bias voltage, negative differential resistance is observed in this system and can be modulated by tuning the gate voltage. More interestingly, current rectification can be achieved at a certain negative gate voltage. These effects can be understood by the responses of the benzene rings and the magnetic core to an external electrical field.
Polarization sensitive near-complete reflection from photonic crystal slab in centered rectangular lattice
Authors: Padron Simon , Ohlinger Kris , Lozano Karen , Lin Yuankun
Published: July 2011

In this study, reflective properties have been systematically calculated for two-dimensional photonic crystal slabs in centered rectangular lattices with elliptical patterns for transverse electric polarization along perpendicular x- and y-directions. The slab structures can be geometrically optimized for a near-complete reflection over a broad wavelength range. The reflection from the photonic crystal slabs is polarization selective, allowing a complete reflection for one polarization and complete transmission for the other polarization, which could be useful for a laser cavity mirror without using Brewster windows. The dependence of the reflection on the slab thickness and the structural parameters demonstrates the effect of guided-mode resonances on the reflection.
Role of strained nano-regions in the formation of subgrains in CaCu3Ti4O12
Authors: Fang Tsang-Tse , Wang Yong-Huei , Kuo Jui-Chao
Published: July 2011

Single-phase CaCu3Ti4O12 (CCTO) was synthesized by solid-state reaction. Electron backscatter diffraction, scanning electron microscopy, and atomic force microscopy were adopted to characterize the grain orientation, microstructure, and surface morphology of the CCTO samples with or without thermal etching. Bump strained nano-regions induced by the local compositional disorder at a nano-scale have been discovered, being the origin of the formation of subgrains in CCTO. The proposed mechanism for the formation of subgrains involves the formation of etched pits and subboundaries pertaining to the strained nano-regions rather than dislocation displacement. The dielectric response inside the grains of CCTO relevant to the strained nano-regions is also discussed.
Biopolymer based system doped with nonlinear optical dye as a medium for amplified spontaneous emission and lasing
Authors: Sznitko Lech , Mysliwiec Jaroslaw , Karpinski Pawel , Palewska Krystyna , Parafiniuk Kacper , Bartkiewicz Stanislaw , Rau Ileana , Kajzar Francois , Miniewicz Andrzej
Published: July 2011

In this paper, we present results of detailed studies on amplified spontaneous emission (ASE) and lasing achieved in a double-layer system consisted of a biopolymer based matrix loaded with 3-(1,1-dicyanoethenyl1)-1phenyl-4,5dihydro-1H-pyrazole organic nonlinear optical dye and photochromic polymer. The laser action was achieved via distributed feedback configuration with third order of Bragg scattering on surface relief grating generated in photochromic polymer. To excite the luminescence, we have used 6 ns pulses of Nd:YAG laser at 532 nm. The ASE and lasing thresholds were estimated to be 17 mJ/cm2 and 11 mJ/cm2, respectively.
Acoustic levitation with self-adaptive flexible reflectors
Authors: Hong Z. Y. , Xie W. J. , Wei B.
Published: July 2011

Two kinds of flexible reflectors are proposed and examined in this paper to improve the stability of single-axis acoustic levitator, especially in the case of levitating high-density and high-temperature samples. One kind is those with a deformable reflecting surface, and the other kind is those with an elastic support, both of which are self-adaptive to the change of acoustic radiation pressure. High-density materials such as iridium (density 22.6 gcm−3) are stably levitated at room temperature with a soft reflector made of colloid as well as a rigid reflector supported by a spring. In addition, the containerless melting and solidification of binary In-Bi eutectic alloy (melting point 345.8 K) and ternary Ag-Cu-Ge eutectic alloy (melting point 812 K) are successfully achieved by applying the elastically supported reflector with the assistance of a laser beam.
Doped graphene nanohole arrays for flexible transparent conductors
Authors: Liu Jianwei , Xu Guowei , Rochford Caitlin , Lu Rongtao , Wu Judy , Edwards Christina M. , Berrie Cindy L. , Chen Zhijun , Maroni Victor A.
Published: July 2011

Graphene nanohole arrays (GNAs) were fabricated using nanoimprint lithography. The improved optical transmittance of GNAs is primarily due to the reduced surface coverage of graphene from the nanohole fabrication. Importantly, the exposed edges of the nanoholes provided effective sites for chemical doping using thionyl chloride was shown to enhance the conductance by a factor of 15–18 in contrast to only 2-4 for unpatterned graphene. GNAs can provide a unique scheme for improving both optical transmittance and electrical conductivity of graphene-based transparent conductors.
Physical origin of the incubation time of self-induced GaN nanowires
Authors: Consonni V. , Trampert A. , Geelhaar L. , Riechert H.
Published: July 2011

The nucleation process of self-induced GaN nanowires grown by molecular beam epitaxy has been investigated by reflection high-energy electron diffraction measurements. It is found that stable nuclei in the form of spherical cap-shaped islands develop only after an incubation time that is strongly dependent upon the growth conditions. Its evolution with the growth temperature and gallium rate has been described within standard island nucleation theory, revealing a nucleation energy of 4.9 ± 0.1 eV and a very small nucleus critical size. The consideration of the incubation time is critical for the control of the nanowire morphology.
Formation of hollow structures through diffusive phase transition across a membrane
Authors: Pasquini Luca , Montone Amelia , Callini Elsa , Antisari Marco Vittori , Bonetti Ennio
Published: July 2011

We report on the formation of hollow structures driven by a phase transition that proceeds via diffusion through a membrane. The mechanism is demonstrated for Mg/MgO core/shell nanoparticles: When they undergo successive metal-hydride transitions at sufficiently high temperature, the core material progressively diffuses outward and evaporates, leaving a hollow shell with the original shape and thickness. This phenomenon might become a general approach to the design of materials with controlled porosity.
Spontaneous-polarization-induced heterojunction asymmetry in III-nitride semiconductors
Authors: Kuo Cheng-Tai , Chang Kai-Kuen , Shiu Hung-Wei , Lin Shih-Chieh , Chen Chia-Hao , Gwo Shangjr
Published: July 2011

We report on precise control of film crystal polarity in fully relaxed, thin InN/AlN heterojunctions grown on sapphire by plasma-assisted molecular beam epitaxy. Using these samples, we have measured asymmetric valence band offset values (0.8 ± 0.1 eV for the In/Al− and 1.8 ± 0.1 eV for the N-polar case) at polar InN/AlN heterojuncitons by synchrotron soft x-ray photoelectron spectroscopy. We confirm that the discontinuities of spontaneous polarizations at polar InN/AlN heterointerfaces lead to the large core level shift of the Al 2p peak related to the In 4d peak (1.0 eV).
Creation of arbitrary time-sequenced line spectra with an electro-optic phase modulator
Authors: Rogers C. E. , Carini J. L. , Pechkis J. A. , Gould P. L.
Published: July 2011

We use a waveguide-based electro-optic phase modulator, driven by a nanosecond-timescale arbitrary waveform generator, to produce an optical spectrum with an arbitrary pattern of peaks. A programmed sequence of linear voltage ramps, with various slopes, is applied to the modulator. The resulting phase ramps give rise to peaks whose frequency offsets relative to the carrier are equal to the slopes of the corresponding linear phase ramps. This simple extension of the serrodyne technique provides multi-line spectra with peak spacings in the 100 MHz range.
Enhancement of microwave emission in magnetic tunnel junction oscillators through in-plane field orientation
Authors: Zeng Z. M. , Upadhyaya P. , Khalili Amiri P. , Cheung K. H. , Katine J. A. , Langer J. , Wang K. L. , Jiang H. W.
Published: July 2011

We observe giant enhancement of microwave emission in MgO-based magnetic tunnel junction nano-oscillators through in-plane magnetic field orientation. At an optimal in-plane field angle, the output power reaches up to 240 nW, two orders of magnitude higher compared to the vicinity of the easy axis (∼1 nW). Moreover, in this condition, the linewidth is significantly narrowed (<100 MHz) and the additional precession modes are suppressed. Analysis of the data indicates that the optimal field angle is influenced by the field-like torque. The results demonstrate that controlling the in-plane magnetic field orientation can be an important strategy for developing high-power spin-torque oscillators.
Thermal carrier processes in bimodal-sized quantum dots with different lateral coupling strength
Authors: Zhou X. L. , Chen Y. H. , Li T. F. , Ye X. L. , Xu Bo , Wang Z. G.
Published: July 2011

In this paper, we have studied the thermal carrier process in bimodal-sized In(Ga)As/GaAs quantum dots (QDs) via temperature dependent photoluminescence (PL). The PL intensity ratio of low energy modal to high energy modal is observed to be temperature sensitive and show different trends for QDs with weak and strong lateral coupling strength, i.e., rise and drop with increasing temperature, respectively. The experimental results are explained by two competing processes: (i) carrier thermal escape from each modal to wetting layer state and (ii) direct carrier coupling between two modals. An improved carrier rate equation model is developed to further demonstrate the importance of process ii in strong lateral coupled QDs system.
Simultaneous corona poling of multiple glass layers for enhanced effective second-order optical nonlinearities
Authors: Yadav K. , Smelser C. W. , Jacob S. , Blanchetiere C. , Callender C. L. , Albert J.
Published: July 2011

Silica-based thin-film multilayers are investigated as a means to enhance the effective second-order nonlinearity induced in silica glass structures by corona poling. Structures consisting of phosphorus-doped and undoped silica glass layers exhibit second harmonic generation (SHG) that is higher by an order of magnitude compared to the SHG in bulk silica glass poled under the same conditions. When the poled structure consists of two multilayered stacks separated in space, the stacks exhibit comparable poling-induced nonlinearities. This result suggests that the poling voltage is divided between the two stacks such that simultaneous poling of multiple regions within the sample is realized.
High-transconductance graphene solution-gated field effect transistors
Authors: Hess L. H. , Hauf M. V. , Seifert M. , Speck F. , Seyller T. , Stutzmann M. , Sharp I. D. , Garrido J. A.
Published: July 2011

In this work, we report on the electronic properties of solution-gated field effect transistors (SGFETs) fabricated using large-area graphene. Devices prepared both with epitaxially grown graphene on SiC as well as with chemical vapor deposition grown graphene on Cu exhibit high transconductances, which are a consequence of the high mobility of charge carriers in graphene and the large capacitance at the graphene/water interface. The performance of graphene SGFETs, in terms of gate sensitivity, is compared to other SGFET technologies and found to be clearly superior, confirming the potential of graphene SGFETs for sensing applications in electrolytic environments.
Optical and electrical characterization of InGaBiAs for use as a mid-infrared optoelectronic material
Authors: Petropoulos J. P. , Zhong Y. , Zide J. M. O.
Published: July 2011

In0.53Ga0.47BixAs1−x films were grown on InP:Fe substrates by molecular beam epitaxy, with Bi concentrations up to x = 3.60%. Bi content in the epilayers was determined by Rutherford backscattering spectroscopy, and channeling measurements show Bi incorporating substitutionally. Unlike previous work, electrical and optical data are obtained for all samples. A redshift in peak wavelength of about 56 meV/%Bi was observed using spectrophotometry. The valence band anti-crossing model is applied, showing InyGa1−yBixAs1−x lattice-matched to InP is possible by varying the composition, with a theoretical cutoff wavelength of about 6 μm.
Broadband second harmonic generation in one-dimensional randomized nonlinear photonic crystal
Authors: Sheng Yan , Ma Dongli , Ren Mingliang , Chai Wenqiang , Li Zhiyuan , Koynov Kaloian , Krolikowski Wieslaw
Published: July 2011

We study experimentally second harmonic generation in a one-dimensional nonlinear photonic crystal with randomized inverted-domain structure. We show that the randomness enables one to realize an efficient broadband emission of high-quality second harmonic beam.
Synthesis and Dye-sensitized Solar Cell Application of Polyolefinic Aromatic Molecules with Pyrene as Surface Group
Authors: Rajakumar Perumal , Visalakshi Kathiresan , Ganesan Shanmugam , Maruthamuthu Pichai , Suthanthiraraj Samuel Austin
Published: July 2011

Synthesis of polyolefinic aromatic molecules with pyrene as the surface group, and their role as an additive in the redox couple of dye-sensitized solar cells, is described. The studies yield a promising power conversion efficiency of 5.27% with a short circuit current density of 6.50 mA cm–2, an open circuit voltage of 0.60 V, and a fill factor of 0.54 under 40 mW cm–2 simulated air mass (A.M.) 1.5 illumination. Most importantly, the photocurrent responsivity increases with an increase in the number of pyrene units on the surface.
Anticancer Prodrug Studies: Diels - Alder Chemistry of 1-Methylthio-1-(p-tolylsulfonyl)ethene
Authors: Pratt Andrew J. , Rendle Phillip M. , Steel Peter J.
Published: July 2011

The reactivity of 1-methylthio-1-(p-tolylsulfonyl)ethene (1) as a dienophile in Diels–Alder chemistry is investigated. Cycloaddition reactions were carried out with a range of pyran-2-ones and isobenzofurans. The initial Diels–Alder adducts have the potential of undergoing fragmentation in chemistry that is relevant to the design of anticancer intercalator prodrugs. The nature of the final products of the reactions provided insights into both the cycloaddition reactions and fragmentation pathways of the adducts. By comparison with a thioether group, the sulfonyl substituent of the dienophile was found to decrease the reactivity and regioselectivity of the cycloaddition chemistry and to facilitate fragmentation of the initial adducts by the elimination of p-toluenesulfinic acid.