bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue design of structures under thermomechanical loadings
Authors: CHARKALUK E. , A BIGNONNET , A CONSTANTINESCU , K DANG VAN
Published: November 2010

This paper presents a global approach to the design of structures that experience thermomechanical fatigue loading, which has been applied successfully in the case of cast‐‐iron exhaust manifolds. After a presentation of the design context in the automotive industry, the important hypotheses and choices of this approach, based on a thermal 3D computation, an elastoviscoplastic constitutive law and the dissipated energy per cycle as a damage indicator associated with a failure criterion, are first pointed out. Two particular aspects are described in more detail: the viscoplastic constitutive models, which permit a finite element analysis of complex structures and the fatigue criterion based on the dissipated energy per cycle. The FEM results associated with this damage indicator permit the construction of a design curve independent of temperature; an agreement is observed between the predicted durability and the results of isothermal as well as non isothermal tests on specimens and thermomechanical fatigue tests on real components on an engine bench. These results show that thermomechanical fatigue design of complex structures can be performed in an industrial context.
The Cunningham Fellowship: three international points of view*
Authors: Flake Donna , Verhoeven Anita , Robu Ioana
Published: November 2010

The Medical Library Association Cunningham Fellowship Program provides funds for one medical librarian per year from outside the United States or Canada to work and learn in United States or Canadian medical libraries for a period of 4 months.

An overview of the Cunningham Fellowship is presented from three different points of view—that of a Medical Library Association member who has worked closely with the Cunningham Fellowship programme, and two former Cunningham Fellows.

Anita Verhoeven, who relates her impressions of American culture, architecture and art, was the 1998 MLA Cuningham Fellow and visited 33 libraries, met 171 librarians, visited prestigious universities and attended a Medical Library Association meeting.

Ioana Robu, the 1997 Cunningham Fellow, visited 15 libraries in 13 cities during her experience. She describes the process of applying for the fellowship and assesses the impact that the 1997 Cunningham Fellowship has made on her life, her library and medical librarianship in Romania.

An overview of the Cunningham Fellowship is also given, which includes the history, the application process, the requirements of the fellowship and the time table of the fellowship.
A comparison of the coverage of clinical medicine provided by PASCAL biomed and medline
Authors: Brand‐de Heer Dieuwke L.
Published: November 2010

The bibliographic databases PASCAL biomed and medline, available both at SilverPlatter, were compared for their coverage of clinical medicine. The main objective of the study was to identify the information in PASCAL biomed that is supplementary to medline.

In PASCAL biomed and medline 10 searches were performed, all limited to publication year 1996. Search profiles in PASCAL biomed were free text only, while in medline they were mainly composed of MeSH headings, with additional free text. Search results were analysed for numbers of (relevant) references retrieved, unique and duplicate references, precision and uniqueness ratio. Also the presence of abstracts in both databases, and the abstract language and the presence of English descriptors and identifiers in PASCAL biomed were studied.

Medline contained more relevant information than PASCAL biomed on nearly all topics studied. The precision of the PASCAL biomed searches varied from 29 to 87% (median = 68%) and of the medline searches from 20 to 91% (median = 66%). The uniqueness ratio in PASCAL biomed varied from 0 to 33% (median = 20%) and in medline from 28 to 83% (median 37%).

Considering the numbers of relevant and unique references retrieved, medline performed better than PASCAL biomed. Yet a sizeable proportion of the relevant references were unique to PASCAL biomed.

Probably PASCAL biomed would have performed better if lists of descriptors had been accessible in the database, preferably with support to trace them.
Improving standards in the scientific biomedical community in Romania by using journal ranking to improve journal quality*
Authors: Robu Ioana , Marineanu Denisa , Aciu Ileana , Wood‐Lamont Sally
Published: November 2010

The paper articulates the problems of journal publication in a relatively small country such as Romania where locally (i.e. nationally) published journals include most of the national medical scientific output. The starting point was a study ordered by the Cluj University of Medicine and Pharmacy Scientific Council, for the purpose of obtaining an objectively ranked list of all current Romanian biomedical journals that could be used in the evaluation of the scientific activity of the university academic staff. Sixty‐five current biomedical journals were identified—of which more than half were new titles that had appeared over the past 5 years. None of these are included in the Science Citation Index or Journal Citation Reports (JCR). A set of criteria was used for ranking the journals: peer review, inclusion in international databases, publication time lag, language of articles and abstracts, journal specific index and domestic impact factor. The period covered, along with tools and formulas used are presented. The problems of Romanian biomedical journals as well as ways of improving publishing standards are discussed. Also emphasized is the necessity for increased awareness in the medical scholarly community and the role of the library in this respect.
Searching for high‐quality evidence to prepare patient information
Authors: Booth‐Clibborn Nina , Milne Ruairidh , Oliver Sandy
Published: November 2010

Objectives:

To help those preparing patient information by developing a search protocol for finding evidence on treatments that would maximize rigour, relevance and completeness. To apply the search protocol in one example area, ‘early breast cancer’.

Methods:

Development—a multidisciplinary group listed evidence sources and assigned them to ‘rigour of methods’ bandings and also assessed their completeness. A search protocol was made by ranking evidence sources by rigour and then by completeness. Application—the protocol was used to search for information on treatments for early breast cancer.

Results:

Eighteen evidence sources provided details of their methods. Thirteen sources were assigned to Band A (‘key source’) and two sources to Band B (‘some doubt about rigour but nevertheless useful’). The 15 Band A and B sources were ordered into a search protocol and used to identify 24 pieces of evidence about early breast cancer. Ten reviews were excluded (as irrelevant), leaving 14 useful pieces of evidence‐based information to help inform patient information.

Conclusions:

Those preparing patient information on treatments for early breast cancer would find 14 pieces of useful evidence. It remains to be seen how far these pieces of evidence would answer questions that patients might pose about treatments.
Hospitals and consumer health information in New Zealand: the role of the library
Authors: Oliver Gillian , Bidwell Pam
Published: November 2010

A research project was conducted with the primary objective of finding out what New Zealand hospitals are doing about providing consumer health information to patients, and specifically, the role played by hospital libraries. A database was compiled of all New Zealand hospitals, both public and privately funded. An individual responsible for consumer health information was identified at each hospital and a questionnaire sent directly to them. A 64% response rate was achieved, representing 196 hospitals. Fifty‐four hospitals reported having an in‐house Library or Information Centre for patients, but the materials and services provided varied widely. Results from this survey show that the provision of consumer health information in the hospital sector in New Zealand is ad hoc, and libraries are not necessarily involved.
Biomedical information @ the speed of light: implementing desktop access to publishers’ resources at the Paterson Institute for Cancer Research
Authors: Glover Steven William
Published: November 2010

Shortly after midnight every Thursday morning, a list server in Massachusetts delivers an electronic table of contents message to the Kostoris Medical Library at the Paterson Institute for Cancer Research in Manchester, UK. The messageins details of the latest edition of the New England Journal of Medicine, complete with hyperlinks to the full text of the content online. Publishers’ electronic current awareness services have been integrated into the dissemination process of the Library service to enhance the speed of communication and access to full text content. As a means of promoting electronic journal use, a system of e‐mail delivery coupled with fast Internet access has allowed a migration from paper‐based current awareness alerting to a seamless online product.
Structure prediction and targeted synthesis: A new NanN2 diazenide crystalline structure
Authors: Zhang Xiuwen , Zunger Alex , Trimarchi Giancarlo
Published: November 2010

Significant progress in theoretical and computational techniques for predicting stable crystal structures has recently begun to stimulate targeted synthesis of such predicted structures. Using a global space-group optimization (GSGO) approach that locates ground-state structures and stable stoichiometries from first-principles energy functionals by objectively starting from randomly selected lattice vectors and random atomic positions, we predict the first alkali diazenide compound NanN2, manifesting homopolar N–N bonds. The previously predicted Na3N structure manifests only heteropolar Na–N bonds and has positive formation enthalpy. It was calculated based on local Hartree–Fock relaxation of a fixed-structure type (Li3P-type) found by searching an electrostatic point-ion model. Synthesis attempts of this positive ΔH compound using activated nitrogen yielded another structure (anti-ReO3-type). The currently predicted (negative formation enthalpy) diazenide Na2N2 completes the series of previously known BaN2 and SrN2 diazenides where the metal sublattice transfers charge into the empty N2 Πg orbital. This points to a new class of alkali nitrides with fundamentally different bonding, i.e., homopolar rather than heteropolar bonds and, at the same time, illustrates some of the crucial subtleties and pitfalls involved in structure predictions versus planned synthesis. Attempts at synthesis of the stable Na2N2 predicted here will be interesting.
Numerical investigation of heat and mass transfer of an evaporating sessile drop on a horizontal surface
Authors: Ait Saada Mebrouk , Chikh Salah , Tadrist Lounès
Published: November 2010

A convection-diffusion model is developed to analyze the effect of buoyant convection in the surrounding air on the heat and mass transfer phenomena during the evaporation of a pinned water drop deposited on a horizontal substrate of large dimensions. The substrate is maintained at constant temperature which can be equal or higher than the temperature of the ambient air. The mathematical model accounts for the motion of the gas phase surrounding the drop due to thermal and solutal buoyancy effects, while only thermal diffusion is considered in the liquid phase. A quasisteady state regime is adopted because of the slow motion of the liquid-gas interface as well as the induced heat and mass transfer phenomena in both phases. The numerical results obtained with the diffusion model or the convection-diffusion model show that heat and mass transfer rates are important toward the contact line. The heat required for evaporation process is taken from the environment, both the liquid and the gas phase, and results in a small cold zone on both sides of the interface. The influence of the buoyancy in air is of greater importance in the lower part of the interface and beyond a distance of a contact radius above the droplet. A weak variation of the evaporation rate is observed on a wider range of contact angle for high wall temperatures. The diffusion model underestimates the overall evaporation rate by 8.5% for a wall temperature equal to an ambient temperature of 25 °C and by 27.3% for a wall temperature of 70 °C. Numerical calculations show that the length of the heated wall has very little effect on the evaporation process when it exceeds 25 times the contact radius.
Backward Raman compression of x-rays in metals and warm dense matters
Authors: Son S. , Ku S. , Moon Sung Joon
Published: November 2010

Experimentally observed decay rate of the long wavelength Langmuir wave in metals and dense plasmas is orders of magnitude larger than the prediction of the prevalent Landau damping theory. The discrepancy is explored, and the existence of a regime where the forward Raman scattering is stable and the backward Raman scattering is unstable is examined. The amplification of a x-ray pulse in this regime, via the backward Raman compression, is computationally demonstrated, and the optimal pulse duration and intensity is estimated.
Theory of plasmon decay in dense plasmas and warm dense matters
Authors: Son S. , Ku S. , Moon Sung Joon
Published: November 2010

The prevalent Landau damping theory for classical plasmas does not fully explain the Langmuir wave decay in dense plasmas. A dielectric function theory adapted from the condensed matter physics is extended to be applicable for the dense plasmas and warm dense matters. This theory, accounting for the Umklapp process, predicts much higher decay rates than the Landau damping theory, which results in better agreement with the available experimental data obtained from the metals. The detailed calculations are presented for the following four cases: classical plasmas, Maxwellian plasmas, degenerate quantum plasmas, and partially degenerate plasmas.
Traveling wave model for laser-guided discharges
Authors: Lampe Martin , Fernsler Richard F. , Slinker Steven P. , Gordon Daniel F.
Published: November 2010

We present an easily solvable 1D traveling wave model for laser-guided discharges. By assuming constant propagation speed u, the hydro/electrodynamic/chemistry equations are reduced to ordinary differential equations in retarded time τ. Negative discharges are shown to propagate only if u>μEb, where μ is electron mobility and Eb is the breakdown field; positive discharges propagate only if the channel preconductance exceeds ∼6×10−11 m/Ω. The axial electric field E is shown to spike up to several times Eb and then relax to ∼Eb for as long as the gas remains cold. In this streamer region, the channel conductance, current, and potential all increase linearly with τ. The transition to the leader stage, where E is much smaller, occurs in two steps: excitation of vibrational and low-lying electronic states, then gas heating. The propagation range decreases as a function of initial radius and (for given maximum voltage) of the voltage rise rate. Expansion of the hot channel is shown to increase the range.
Field-amplified sample stacking and focusing in nanofluidic channels
Authors: Sustarich Jess M. , Storey Brian D. , Pennathur Sumita
Published: November 2010

Nanofluidic technology is gaining popularity for bioanalytical applications due to advances in both nanofabrication and design. One major obstacle in the widespread adoption of such technology for bioanalytical systems is efficient detection of samples due to the inherently low analyte concentrations present in such systems. This problem is exacerbated by the push for electronic detection, which requires an even higher sensor-local sample concentration than optical detection. This paper explores one of the most common preconcentration techniques, field-amplified sample stacking, in nanofluidic systems in efforts to alleviate this obstacle. Holding the ratio of background electrolyte concentrations constant, the parameters of channel height, strength of electric field, and concentration are varied. Although in micron scale systems, these parameters have little or no effect on the final concentration enhancement achieved, nanofluidic experiments show strong dependencies on each of these parameters. Further, nanofluidic systems demonstrate an increased concentration enhancement over what is predicted and realized in microscale counterparts. Accordingly, a depth-averaged theoretical model is developed that explains these observations and furthermore predicts a novel focusing mechanism that can explain the increased concentration enhancement achieved. Specifically, when the electric double layer is sufficient in size relative to the channel height, negatively charged analyte ions are repelled from negatively charged walls, and thus prefer to inhabit the centerline of the channels. The resulting induced pressure gradients formed due to the high and low electrical conductivity fluids in the channel force the ions to move at a slower velocity in the low-conductivity region, and a faster velocity in the high-conductivity region, leading to focusing. A simple single-channel model is capable of predicting key experimental observations, while a model that incorporates the details of the fluid inlet and outlet ports allows for more detailed comparisons between model and experiment.
Time-resolved photoelectron spectroscopy of liquids
Authors: Buchner Franziska , Lübcke Andrea , Heine Nadja , Schultz Thomas
Published: November 2010

We present a novel setup for the investigation of ultrafast dynamic processes in a liquid jet using time-resolved photoelectron spectroscopy. A magnetic-bottle type spectrometer with a high collection efficiency allows the very sensitive detection of photoelectrons emitted from a 10 μm thick liquid jet. This translates into good signal/noise ratio and rapid data acquisition making femtosecond time-resolved experiments feasible. We describe the experimental setup, a detailed spectrometer characterization based on the spectroscopy of nitric oxide in the gas phase, and results from femtosecond time-resolved experiments on sodium iodide solutions. The latter experiments reveal the formation and evolution of the solvated electron and we characterize two distinct spectral components corresponding to initially thermalized and unthermalized solvated electrons. The absence of dark states in photoionization, the direct measurement of electron binding energies, and the ability to resolve dynamic processes on the femtosecond time scale make time-resolved photoelectron spectroscopy from the liquid jet a very promising method for the characterization of photochemical processes in liquids.
Mesoscopic structure prediction of nanoparticle assembly and coassembly: Theoretical foundation
Authors: Hur Kahyun , Hennig Richard G. , Escobedo Fernando A. , Wiesner Ulrich
Published: November 2010

In this work, we present a theoretical framework that unifies polymer field theory and density functional theory in order to efficiently predict ordered nanostructure formation of systems having considerable complexity in terms of molecular structures and interactions. We validate our approach by comparing its predictions with previous simulation results for model systems. We illustrate the flexibility of our approach by applying it to hybrid systems composed of block copolymers and ligand coated nanoparticles. We expect that our approach will enable the treatment of multicomponent self-assembly with a level of molecular complexity that approaches experimental systems.
Kinetic Monte Carlo study of nucleation processes on patterned surfaces
Authors: Hopp Stefan Frieder , Heuer Andreas
Published: November 2010

The properties of template-directed nucleation are studied in the transition region where full nucleation control is lost and additional nucleation beyond the prepatterned structure is observed. To get deeper insight into the microscopic mechanisms, Monte Carlo simulations were performed. In this context, the previously used continuous algorithm [F. Kalischewski, J. Zhu, and A. Heuer, Phys. Rev. B 77, 155401, (2008)] was replaced by a discrete one to reduce simulation time and to allow more detailed calculations. The applied method is based on the assumption that the molecules on the surface occupy the sites of a simple fcc lattice. It is shown that a careful mapping of the continuous Monte Carlo technique onto the discrete algorithm leads to a good reproduction of the former results by means of the latter method. Furthermore, the new method facilitates the calculation of the spatial distribution of nuclei on the surface. This provides a detailed comparison with experimental data.
Reduced dimensionality effects on phonon transport
Authors: Blair Michael W. , Bennett Bryan L. , Tornga Stephanie C. , Smith Nickolaus A. , Muenchausen Ross E.
Published: November 2010

Electron paramagnetic resonance (EPR) spectroscopy has been used to study energy transport properties of both bulk and nanophosphor (nominally 30 nm) oxyorthosilicate samples, and we were able to separate the effects of crystal disorder and relaxation lifetime broadening on the EPR linewidths. The low temperature linewidths (T<10 K) were inhomogeneously broadened and dominated by crystal disorder effects and the nanophosphors showed an order of magnitude increase in crystal disorder. Both bulk and nanophosphor samples showed significant lifetime broadening involving direct relaxation via phonons and the Orbach relaxation process. At low temperatures, the lifetimes of the bulk samples displayed the influence of the lattice-bath relaxation time as well as the spin-lattice relaxation time while the lifetimes of the nanophosphor samples were not influenced by the lattice-bath relaxation time. The results imply that reduced dimensionality in insulators does reduce the lattice-bath relaxation time, although the exact relationship cannot be confirmed by this study largely due to the nonideal nature of the materials studied.
Microwave phase detection with a magnetic tunnel junction
Authors: Fan Xin , Kim Sangcheol , Kou Xiaoming , Kolodzey James , Zhang Huaiwu , Xiao John Q.
Published: November 2010

A magnetic tunnel junction (MTJ) can detect microwave magnetic field due to the interplay between the ferromagnetic resonance and tunneling magnetoresistance. Based on the fact that the tunneling resistance change is quadratically proportional to the rf magnetic field, we have designed a mixing circuit in which two microwaves interfere, giving rising to a dc voltage containing the phase difference between the two microwaves. With ability to detect microwave intensity and phase, the MTJ-based device may be used for on-chip microwave network analyzer and spectrum analyzer.
A comprehensive model for the ultrashort visible light irradiation of semiconductors
Authors: Medvedev N. , Rethfeld B.
Published: November 2010

We present a new model describing the irradiation of semiconductors with ultrashort laser pulses. Based on the earlier developed multiple rate equation [Rethfeld, Phys. Rev. Lett. 92, 187401 (2004)], the model additionally includes the interaction of electrons with the phononic subsystem of the lattice and allows for the direct determination of the conditions for crystal damage. In contrast to commonly used approaches based on the thermodynamic description of the material, our model is applicable to nonequilibrium electronic conditions. Accounting for the dynamic changes in the optical properties of the target (i.e., reflectivity, photoabsorption coefficients), the developed model allows for a comprehensive evaluation of the damage by tracing the changes in the optical parameters, lattice heating and subsequent melting. Our model effectively describes the dynamics of the electronic subsystem and lattice heating and the results are in very good agreement with experimental measurements on the transient reflectivity and the fluence damage threshold of silicon irradiated with a femtosecond laser pulse.
An investigation of the electrical properties of metal-insulator-silicon capacitors with pyrolytic carbon electrodes
Authors: Graham A. P. , Richter K. , Jay T. , Weber W. , Knebel S. , Schröder U. , Mikolajick T.
Published: November 2010

An investigation of amorphous, pyrolytic carbon for semiconductor applications is presented. We have deposited conductive carbon films on thin silicon oxide and aluminum oxide dielectrics and structured them into metal-insulator-silicon (MIS) capacitors in order to evaluate their electrical properties. The results show that the effective oxide thickness is comparable to metal electrodes, indicating that there is no depletion region between the dielectric and the carbon. The carbon electrodes exhibit very low leakage and Fowler–Nordheim tunneling on silicon oxide and Frenkel-Poole tunneling on aluminum oxide at high fields. The electrical parameters determined from the results are comparable to those for poly-silicon.
Structure and properties of InAs/AlAs quantum dots for broadband emission
Authors: Meng X. Q. , Jin P. , Liang Z. M. , Liu F. Q. , Wang Z. G. , Zhang Z. Y.
Published: November 2010

The InAs quantum dots (QDs) on an AlAs layer are grown on GaAs substrates by molecular beam epitaxy technique. The properties of materials and optics of such QD structures have been investigated by cross sectional transmission electron microscopy and photoluminescence (PL) techniques. It is discovered that the inhomogeneous strain filed mainly exists below InAs QDs layers in the case of no wetting layer. The full width at half maximums (FWHMs) and intensities of PL emission peaks of InAs QDs are found to be closely related to the thickness of the thin AlAs layers. The InAs QDs on an eight monolayer AlAs layer, with wide FWHMs and large integral intensity of PL emission peaks, are favorable for producing broadband QD superluminescent diodes, external-cavity QD laser with large tuning range.
Generic role of the anisotropic surface free energy on the morphological evolution in a strained-heteroepitaxial solid droplet on a rigid substrate
Authors: Ogurtani Tarik Omer , Celik Aytac , Oren Ersin Emre
Published: November 2010

A systematic study based on self-consistent dynamical simulations is presented for the spontaneous evolution of an isolated thin solid droplet on a rigid substrate, which is driven by the surface drift diffusion induced by the anisotropic capillary forces (surface stiffness) and mismatch stresses. In this work, we studied the effect of surface free energy anisotropies [weak and strong (anomalous)] on the development kinetics of the “Stranski–Krastanow” island type morphologies. The anisotropic surface free energy and the surface stiffness were treated with well accepted trigonometric functions. Although, various tilt angles and anisotropy constants were considered during simulations, the main emphasis was given on the effect of rotational symmetries associated with the surface Helmholtz free energy topography in two-dimensional space. Our computer simulations revealed the formation of an extremely thin wetting layer during the development of the bell-shaped Stranski-Krastanow island through the mass accumulation at the central region of the droplet via surface drift-diffusion. For weak anisotropy constant levels, instead of singlet islanding, we observed formation of doublet islanding, separated by a shallow wetting layer, for a set of specific tilt angles, ϕ=90° and ϕ=45°, respectively, for the twofold and fourfold rotational symmetry axis. No such formation has been detected for the sixfold symmetry. In the strong (anomalous) anisotropy constant domain, we demonstrated the existence of two distinct morphological modes: (i) the complete stability of the initial Cosine-shaped droplet just above a certain anisotropy constant threshold level by spontaneous slight readjustments of the base and the height of the cluster; (ii) the Frank-van der Merwe mode of thin film formation for very large values of the anisotropy constant by the spreading and coalescence of the droplets over the substrate surface. During the course of the simulations, we continuously tracked both the morphology (i.e., the peak height, the extension of the wetting layer beyond the domain boundaries, and the triple junction contact angle) and the energetics (the global Helmholtz free energy changes associated with the total strain and surface energy variations) of the system.
High temperature electron transport properties in AlGaN/GaN heterostructures
Authors: Tokuda H. , Yamazaki J. , Kuzuhara M.
Published: November 2010

Hall electron mobility (μH) and sheet concentration (ns) in AlGaN/GaN heterostructures have been measured from 77 to 1020 K. The effect of the deposited Al2O3 layer is also investigated with varying its thickness. It is found that μH decreases monotonously with the temperature (T) and its dependence is well approximated with the function of μH=4.5×103 exp(−0.004T) in the temperatures over 350 K. The function is different from the commonly used one of μH=AT−α (α∼1.5), which indicates that the mobility is not only governed by the polar optical phonon scattering but also the deformation potential scattering plays a role. The sheet electron concentration (ns) has a weak dependence on the temperature, that is, slightly decreases with temperature in 300–570 K and increases gradually up to 1020 K. The decrease is explained by considering the reduction in the polarization (probably both spontaneous and piezoelectric) charge and the increase seems to be due to the parallel conduction through the interface between GaN buffer layer and sapphire substrate. The dependence of sheet resistance (Rsh) in AlGaN/GaN is compared with that of n-GaN. In the low temperatures, AlGaN/GaN shows a lower Rsh due to its high mobility, however, at the temperatures higher than 350 K, Rsh of AlGaN/GaN becomes higher than that of n-GaN. This result implies that AlGaN/GaN high-electron-mobility-transistors are inferior to GaN metal-semiconductor field-effect transistors in terms of higher source, drain, and channel resistances at high temperature operations, although further investigations on other performances such as output power and reliability are needed. The Al2O3 deposited AlGaN/GaN shows about 15% higher ns than without Al2O3 layer for the whole temperatures. On the contrary, μH at 77 K shows a slight decrease with Al2O3 deposition, which degree is not affected by the layer thickness. In the temperatures higher than 400 K, μH is almost the same for with and without Al2O3 layer.
Practical time-delay synchronization of a periodically modulated self-excited oscillators with uncertainties
Authors: Kakmeni F. M. Moukam , Bowong S. , Senthikumar D. V. , Kurths J.
Published: November 2010

This paper studies time-delay synchronization of a periodically modulated Duffing Van der Pol (DVP) oscillator subjected to uncertainties with emphasis on complete synchronization. A robust adaptive response system is designed to synchronize with the uncertain drive periodically modulated DVP oscillator. Adaptation laws on the upper bounds of uncertainties are proposed to guarantee the boundedness of both the synchronization error and the estimated feedback coupling gains. Numerical results are presented to check the effectiveness of the proposed synchronization scheme. The results suggest that the linear and nonlinear terms in the feedback coupling play a complementary role in increasing the synchronization regime in the parameter space of the synchronization manifold. The proposed method can be successfully applied to a large variety of physical systems.
Macromolecular crowding effects on protein–protein binding affinity and specificity
Authors: Kim Young C. , Best Robert B. , Mittal Jeetain
Published: November 2010

Macromolecular crowding in cells is recognized to have a significant impact on biological function, yet quantitative models for its effects are relatively undeveloped. The influence of crowding on protein–protein interactions is of particular interest, since these mediate many processes in the cell, including the self-assembly of larger complexes, recognition, and signaling. We use a residue-level coarse-grained model to investigate the effects of macromolecular crowding on the assembly of protein–protein complexes. Interactions between the proteins are treated using a fully transferable energy function, and interactions of protein residues with the spherical crowders are repulsive. We show that the binding free energy for two protein complexes, ubiquitin/UIM1 and cytochrome c/cytochrome c peroxidase, decreases modestly as the concentration of crowding agents increases. To obtain a quantitative description of the stabilizing effect, we map the aspherical individual proteins and protein complexes onto spheres whose radii are calculated from the crowder-excluded protein volumes. With this correspondence, we find that the change in the binding free energy due to crowding can be quantitatively described by the scaled particle theory model without any fitting parameters. The effects of a mixture of different-size crowders—as would be found in a real cell—are predicted by the same model with an additivity ansatz. We also obtain the remarkable result that crowding increases the fraction of specific complexes at the expense of nonspecific transient encounter complexes in a crowded environment. This result, due to the greater excluded volume of the nonspecific complexes, demonstrates that macromolecular crowding can have subtle functional effects beyond the relative stability of bound and unbound complexes.
One-dimensional dynamics of nearly unstable axisymmetric liquid bridges
Authors: Perales José M. , Vega José M.
Published: November 2010

A general one-dimensional model is considered that describes the dynamics of slender, axisymmetric, noncylindrical liquid bridges between two equal disks. Such model depends on two adjustable parameters and includes as particular cases the standard Lee and Cosserat models. For slender liquid bridges, the model provides sufficiently accurate results and involves much easier and faster calculations than the full three-dimensional model. In particular, viscous effects are easily accounted for. The one-dimensional model is used to derive a simple weakly nonlinear description of the dynamics near the instability limit. Small perturbations of marginal instability conditions are also considered that account for volume perturbations, nonequality of the supporting disks, and axial gravity. The analysis shows that the dynamics breaks the reflection symmetry on the midplane between the supporting disks. The weakly nonlinear evolution of the amplitude of the perturbation is given by a Duffing equation, whose coefficients are calculated in terms of the slenderness as a part of the analysis and exhibit a weak dependence on the adjustable parameters of the one-dimensional model. The amplitude equation is used to make quantitative predictions of both the (first stage of) breakage for unstable configurations and the (slow) dynamics for stable configurations.
Weak turbulence theory for reactive instability
Authors: Yoon P. H.
Published: November 2010

In the present paper, the customary weak turbulence theory is generalized to include reactive instabilities. For the sake of simplicity, the formalism assumes electrostatic perturbation propagating in one-dimensional uniform unmagnetized plasmas. By weak turbulence theory it is meant as the perturbative nonlinear theory based upon Vlasov equation, truncated at the second (or up to third) order nonlinearity and ensemble averaged. By reactive instability it is meant as the plasma instability whose growth rate is not necessarily exceedingly small. The traditional weak turbulence theory found in the literature is applicable only to weakly growing plasma instabilities whose real frequency ωk can be determined from the real part of the dispersion relation, Re ϵ(k,ωk)=0, while the growth rate may be determined by the Landau formula, γk=−Im ϵ(k,ωk)[∂ Re ϵ(k,ωk)/∂ωk]−1. This implies the assumption that |γk|⪡ωk. On the other hand, for reactive instabilities for which γk/ωk is not necessarily small, the real frequency and growth/damping rate must be determined from the complex roots of the dispersion relation, ϵ(k,ωk+iγk)=0. The present paper extends the textbook weak turbulence theory to deal with such a situation.
Hemispherical resonators with embedded nanocrystal quantum rod emitters
Authors: Haase J. , Shinohara S. , Mundra P. , Risse G. , Lyssenko V. G. , Fröb H. , Hentschel M. , Eychmüller A. , Leo K.
Published: November 2010

We report a technique to prepare hemispherical resonators on a distributed Bragg reflector (DBR). This so-called hydrophobic spreading allows the creation of hemispherical structures with diameters ranging from 5 to 50 μm. By embedding semiconductor nanocrystal quantum rods (NQRs) into these structures, we achieve a coupling of their emission into whispering-gallery modes. Although the NQR-emission is confined in three dimensions, the DBR is transparent for the excitation, allowing selective excitation of different regions of the hemisphere. Employing a two-dimensional model to approximately describe relevant modes, we are able to estimate the refractive index and diameters of the hemispheres from spectral data.
Rayleigh-instability-driven simultaneous morphological and compositional transformation from Co nanowires to CoO octahedra
Authors: Huang X. H. , Zhan Z. Y. , Wang X. , Zhang Z. , Xing G. Z. , Guo D. L. , Leusink D. P. , Zheng L. X. , Wu T.
Published: November 2010

Arrays of regularly distributed CoO nano-octahedra are obtained by annealing Co nanowires at high temperatures. Both the size and the separation distance of the nano-octahedra can be controlled by tuning the annealing temperature. These self-assembled linear arrays of CoO nanocrystals result from the synergetic combination of the morphological transformation due to the intrinsic Rayleigh instability and the phase transformation due to the cobalt oxidation.
Effects of applied electrical field on electronic structures in LaNiO3 conductive metallic oxide film: An optical spectroscopic study
Authors: Zhu J. J. , Li W. W. , Li Y. W. , Shen Y. D. , Hu Z. G. , Chu J. H.
Published: November 2010

The reflectance spectra of LaNiO3 film on silicon have been investigated in the wavelength range of 190–2650 nm (0.47–6.5 eV) under different external direct-current voltage. The Drude–Lorentz dispersion model is used to extract the optical function. The O 2p to Ni 3d electronic transition can be uniquely assigned to the energy of about 1.96 eV and decreases with decreasing applied voltage. The discrepancy from the real part of dielectric function with the applied voltage has a strong spectral dependence. The optical conductivity variation under different external voltage indicates that the electrical field can induce the modification of the carrier transport.
Three-dimensional photoacoustic imaging system in line confocal mode for breast cancer detection
Authors: Ye Fei , Yang Sihua , Xing Da
Published: November 2010

We present a three-dimensional (3-D) photoacoustic imaging system (PAIS) in line confocal mode for breast cancer detection. With the line confocal mode, the spatial resolution of the PAIS was tested to be improved about three times compared with the nonconfocal mode PAIS. Furthermore, with a flexible scanning system and no compression on the breast, the PAIS could supply a comfortable and safe diagnosis process for the patient. An ex vivo breast tumor imaging experiment was performed and the tumor was visualized by the 3-D photoacoustic image. The experimental result demonstrated that the system had great potential of application in breast cancer detection.
Ultrafast gain dynamics in InP quantum-dot optical amplifiers
Authors: Langbein Wolfgang , Cesari Valentina , Masia Francesco , Krysa Andrey B. , Borri Paola , Smowton Peter M.
Published: November 2010

We measured the gain dynamics at the ground-state transition in an electrically pumped InP/AlGaInP quantum-dot optical amplifier at room temperature by femtosecond differential transmission. The gain shows an ultrafast recovery within 200 fs, even faster than in state-of-the-art InAs/GaAs quantum-dot amplifiers. This finding, likely to be due to the less confined and more closely spaced hole levels in InP dots, is promising for optical signal processing at high bit rates. We furthermore measured the pump-induced refractive index changes and deduced a linewidth enhancement factor similar to the one in InAs/GaAs quantum dots.
Single-photon detection using magnesium diboride superconducting nanowires
Authors: Shibata H. , Takesue H. , Honjo T. , Akazaki T. , Tokura Y.
Published: November 2010

We fabricated 10 nm thick MgB2 nanowires with a width down to 100 nm using the liftoff process. The I-V characteristics of the nanowire show hysteresis and a sharp voltage jump at Ic. Though a 150 nm wide nanowire exhibits the capacity for detecting a single photon at 405 nm wavelength, the nanowire is too wide to detect a single photon at 1560 nm. A 100 nm wide nanowire exhibits the capacity for detecting single photons in the 405–1560 nm wavelength range. This indicates a possible application of MgB2 as a high-performance superconducting nanowire single-photon detector.
Electrostatic waves and instabilities in multispecies nonneutral plasmas
Authors: Dubin Daniel H. E.
Published: November 2010

This paper briefly describes waves and instabilities in a multispecies nonneutral plasma that have previously been studied only in neutral plasmas: ion sound waves, drift waves, and ion temperature gradient waves. The theory of their dispersion relations and growth rates is similar to that for neutral plasmas, but results differ in several important respects. For instance, drift waves are not necessarily unstable, the instabilities generally do not cause plasma loss, and they can be controlled (e.g., turned on or off) by manipulation of density and temperature profiles using standard experimental techniques such as centrifugal separation and laser cooling/heating. This should allow precise experimental studies of instability growth and saturation.
Electrophoretic mobility of a growing cell studied by photonic force microscope
Authors: Tonin Mario , Bálint Stefan , Mestres Pau , Martìnez Ignacio A. , Petrov Dmitri
Published: November 2010

Living cells have spatially localized charged groups such as nucleus, cell walls, and others that can move in an external electric field providing the cell electrophoretic mobility (EPM). We suggest to monitor the EPM of a single living cell during its growth using optical tweezers combined with a position detector. As an example, we studied the EPM during the yeast growth, and we observed a nonmonotonic behavior of the EPM during the cell cycle, such as that the maximal EPM was observed at the initial stage of the growth, strongly reducing when the cell cycle is near its final stage.
Improved sensitivity of terahertz detection by GaAs photoconductive antennas excited at 1560 nm
Authors: Kataoka T. , Kajikawa K. , Kitagawa J. , Kadoya Y. , Takemura Y.
Published: November 2010

The terahertz detection by photoconductive antennas (PCAs) based on low-temperature grown (LTG) GaAs with 1.5 μm pulse excitation was revisited. We found that the detection efficiency can be improved by a factor of 10 (20 dB) by reducing the excitation spot size and the gap length of the PCA, maintaining the low noise feature of the PCA on LTG GaAs. As a result, the signal-to-noise ratio higher than 50 dB was obtained at a reasonable incident power of 9.5 mW, suggesting that the scheme is promising for the detection of terahertz waves in practical time domain systems.
Comparison of electrostatic and electromagnetic simulations for very high frequency plasmas
Authors: Zhang Yu-Ru , Xu Xiang , Zhao Shu-Xia , Bogaerts A. , Wang You-Nian
Published: November 2010

A two-dimensional self-consistent fluid model combined with the full set of Maxwell equations is developed to investigate an argon capacitively coupled plasma, focusing on the electromagnetic effects on the discharge characteristics at various discharge conditions. The results indicate that there exist distinct differences in plasma characteristics calculated with the so-called electrostatic model (i.e., without taking into account the electromagnetic effects) and the electromagnetic model (which includes the electromagnetic effects), especially at very high frequencies. Indeed, when the excitation source is in the high frequency regime and the electromagnetic effects are taken into account, the plasma density increases significantly and meanwhile the ionization rate evolves to a very different distribution when the electromagnetic effects are dominant. Furthermore, the dependence of the plasma characteristics on the voltage and pressure is also investigated, at constant frequency. It is observed that when the voltage is low, the difference between these two models becomes more obvious than at higher voltages. As the pressure increases, the plasma density profiles obtained from the electromagnetic model smoothly shift from edge-peaked over uniform to a broad maximum in the center. In addition, the edge effect becomes less pronounced with increasing frequency and pressure, and the skin effect rather than the standing-wave effect becomes dominant when the voltage is high.
Polydomain configuration in epitaxial Pb0.5Sr0.5TiO3/La0.5Sr0.5CoO3 heterostructures
Authors: Plekh M. , Narkilahti J. , Levoska J. , Tyunina M.
Published: November 2010

In epitaxial heterostructures Pb0.5Sr0.5TiO3/La0.5Sr0.5CoO3/MgO(001) with a large lattice mismatch, ferroelectric domains and properties were experimentally studied. In 130 nm thick polydomain tetragonal Pb0.5Sr0.5TiO3 films, random arrays of ∼0.1–0.5 μm sized a- and c-domains are found. In vertical capacitors with Pt top electrodes, a steplike switching of polarization is observed. The results are discussed in terms of island growth and different switching mechanisms in a- and c-domains.
Stimulated emission of terahertz radiation by exciton-polariton lasers
Authors: Kavokin K. V. , Kaliteevski M. A. , Abram R. A. , Kavokin A. V. , Sharkova S. , Shelykh I. A.
Published: November 2010

We show that planar semiconductor microcavities in the strong coupling regime can be used as sources of stimulated terahertz radiation. Emitted terahertz photons would have a frequency equal to the splitting of the cavity polariton modes. The optical transition between upper and lower polariton branches is allowed due to mixing of the upper polariton state with one of the excited exciton states and is stimulated in the polariton laser regime.
Near-room temperature relaxor multiferroic
Authors: Sanchez Dilsom A. , Kumar A. , Ortega N. , Katiyar R. S. , Scott J. F.
Published: November 2010

We report the fabrication and characterization of highly oriented Pb(Zr0.53Ti0.47)0.60(Fe0.5Ta0.5)0.40O3 thin films. Dielectric spectra showed a maximum (Tm) around 350 K for 1 kHz that shifted to higher temperatures (by ∼30 K) with an increase in frequency up to 1 MHz. High dielectric dispersion below and above Tm, low dielectric loss (2%–5%), high dielectric constant (∼1380@1 kHz), ferroelectric polarization, and weak magnetic moment are observed. Real and imaginary dielectric data were fitted with a nonlinear Vogel–Fulcher equation, implying a relaxor nature. The ac conductivity shows frequency-dependent conductivity, low loss, and frequency-dependent kinks near Tm.
Impact of surfaces on the optical properties of GaAs nanowires
Authors: Demichel O. , Heiss M. , Bleuse J. , Mariette H. , Fontcuberta i Morral A.
Published: November 2010

The effect of surfaces on the optical properties of GaAs nanowires is evidenced by comparing nanowires with or without an AlGaAs capping shell as a function of the diameter. We find that the optical properties of unpassivated nanowires are governed by Fermi-level pinning, whereas, the optical properties of passivated nanowires are mainly governed by surface recombinations. Finally, we measure a surface recombination velocity of 3×103 cm s−1 one order of magnitude lower than values previously reported for {110} GaAs surfaces. These results will serve as guidance for the application of nanowires in solar cell and light emitting devices.