bluuebunny/crossref_metadata_2025 huggingface dataset:
Ice flow in Greenland for the International Polar Year 2008–2009
Authors: Rignot E. , Mouginot J.
Published: May 2012

A digital representation of ice surface velocity is essential for a variety of glaciological, geologic and geophysical analyses and modeling. Here, we present a new, reference, comprehensive, high‐resolution, digital mosaic of ice motion in Greenland assembled from satellite radar interferometry data acquired during the International Polar Year 2008 to 2009 by the Envisat Advanced Synthetic‐Aperture Radar (ASAR), the Advanced Land Observation System (ALOS)'s Phase‐Array L‐band SAR (PALSAR) and the RADARSAT‐1 SAR that covers 99% of the ice sheet in area. The best mapping performance is obtained using ALOS PALSAR data due to higher levels of temporal coherence at the L‐band frequency; but C‐band frequency SAR data are less affected by the ionosphere. The ice motion map reveals various flow regimes, ranging from patterned enhanced flow into a few large glaciers in the cold, low precipitation areas of north Greenland; to diffuse, enhanced flow into numerous, narrow, fast‐moving glaciers in the warmer, high precipitation sectors of northwest and southeast Greenland. We find that the 100 fastest glaciers (v> 800 m/yr) drain 66% of the ice sheet in area, marine‐terminating glaciers drain 88% of Greenland, and basal‐sliding motion dominates internal deformation over more than 50% of the ice sheet. This view of ice sheet motion provides significant new constraints on ice flow modeling.
New particle formation at a remote site in the eastern Mediterranean
Authors: Pikridas Michael , Riipinen Ilona , Hildebrandt Lea , Kostenidou Evangelia , Manninen Hanna , Mihalopoulos Nikos , Kalivitis Nikos , Burkhart John F. , Stohl Andreas , Kulmala Markku , Pandis Spyros N.
Published: May 2012

A year (6‐April–2008 to 14‐April–2009) of particulate monitoring was conducted at a remote coastal station on the island of Crete, Greece in the eastern Mediterranean. Fifty‐eight regional new particle formation events were observed with an Air Ion Spectrometer (AIS), half of which occurred during the coldest months of the year (December–March). Particle formation was favored by air masses arriving from the west that crossed Crete or southern Greece prior to reaching the site and also by lower‐than‐average condensational sinks (CS). Aerosol composition data, which were acquired during month‐long campaigns in the summer and winter, suggest that nucleation events occurred only when particles were neutral. This is consistent with the hypothesis that a lack of NH3, during periods when particles are acidic, may limit nucleation in sulfate‐rich environments. Nucleation was not limited by the availability of SO2 alone, as nucleation events often did not take place during periods with high SO2 or H2SO4 concentrations. The above results support the hypothesis that an additional reactant (other than H2SO4) plays an important role in the formation and/or growth of new particles. Our results are consistent with NH3 being this missing reactant.
Losing balance: the origin and impact of aneuploidy in cancer
Authors: Holland Andrew J , Cleveland Don W
Published: May 2012

Most solid human tumours are aneuploid, that is, they contain an abnormal number of chromosomes. Paradoxically, however, aneuploidy has been reported to induce a stress response that suppresses cellular proliferation in vitro. Here, we review the progress in our understanding of the causes and effects of aneuploidy in cancer and discuss how, in specific contexts, aneuploidy can provide a growth advantage and facilitate cellular transformation. We also explore the emerging possibilities for targeting the cause or consequences of aneuploidy therapeutically.
Telomerase activity alterations in sequential passages of mouse embryonic stem cells
Authors: Pereira Francisco de Assis Nunes , Tavares Rubens Lene Carvalho , Camargos Aroldo Fernando , da Silva Filho Agnaldo Lopes
Published: May 2012

Telomerase is associated with cell proliferation capacity, protection and stabilization of chromosomes. TA (telomerase activity) can be detected in highly replicative cells, e.g. stem and cancer cells. Most available mESC (mouse embryonic stem cell) research is done with a few cell lines. The purpose of this study has been to evaluate the TA in different passages of newly isolated mESC. TRAP (Telomeric Repeat Amplification Protocol)‐ELISA method was used in a semi‐quantitative evaluation of TA. Three mESC lineages were investigated (CT2, CT3 and CT4) at three different passages (P13, P15 and P19). In contrast with previous studies, these mESC lines did not show the same TA throughout their passages, having initially low TA values, followed by a subsequent rise and stabilization.
Maxillary Artery Injury Associated with Subcondylar Mandible Fractures: A Novel Treatment Algorithm
Authors: Yeo Matthew S. , Goh Terence L.H. , Nallathamby Vigneswaran , Cheong Ee Cherk , Lim Thiam Chye
Published: May 2012

Mandible fractures commonly occur in patients who have sustained blunt facial trauma, and the subcondylar region is the most frequently fractured due to its intrinsic biomechanical weakness. The maxillary artery lies in close relation to the medial cortex of the subcondyle and is vulnerable to injury by the sharp edges of the fracture fragments during the initial trauma or during operative fracture reduction. Maxillary artery injuries and subcondylar fractures may be an underdiagnosed phenomenon. Yet, this is of clinical significance as the maxillary artery caliber is usually of significant caliber and may lead to substantial hemorrhage. Surgical access to the artery for hemostasis is challenging and is further compounded by small surgical incisions usually undertaken for fracture fixation, obscuring of the artery by the overlying fracture fragments, and vessel retraction following its transection. In cases where maxillary artery injury is suspected, an open surgical approach may be favored over an endoscopic one. The authors illustrate a case in which brisk hemorrhage from the maxillary artery encountered during a preauricular approach to fixation of the mandible subcondyle was successfully controlled with temporary pressure on the external carotid artery through a neck incision and direct ligation of the lacerated maxillary artery. The authors then discuss diagnosis and treatment of such maxillary artery injuries and propose a novel diagnostic and treatment algorithm.
The Use of 2.4-mm Locking Plate System in Treating Comminuted Mandibular Fracture by Firearm
Authors: Pereira Cassiano Costa Silva , Letícia dos Santos Pâmela , Jardim Ellen Cristina Gaetti , Júnior Idelmo Rangel Garcia , Shinohara Elio Hitoshi , Araujo Marcelo Marotta
Published: May 2012

Maxillofacial trauma caused by firearms has considerably increased, in which the mandibular body is the site of highest incidence of firearm projectiles. In these cases, the use of titanium plates and screws allows the early restoration of form and function of the mandible with stable and predictable results. Recently, conventional plates have been extensively used to treat comminuted mandibular fractures. Nevertheless, the conventional system presents several limitations such as screw compression against the bone interface and the necessity of precise fit of plate to the bone. To overcome such drawbacks, the locking plates have emerged. The present clinical case reported the operative treatment of mandibular fracture caused by firearm projectiles with the use of locking plate. The indications, advantages, and disadvantages of this system are presented.
Vertical Fracture of the Mandibular Posterior Ramus Border Secondary to the Stress of the Rigid Internal Fixation Material
Authors: Sencimen Metin , Gulses Aydin , Altug Hasan Ayberk
Published: May 2012

A unique case of a vertical fracture of the mandibular posterior ramus border secondary to the stress of the rigid internal fixation material is described in this study. We think that the surgeon's experience and awareness play a key role in avoidance of such a complication.
Thermoacoustic compression based on alternating to direct gas flow conversion
Authors: Sun D. M. , Wang K. , Xu Y. , Shen Q. , Zhang X. J. , Qiu L. M.
Published: May 2012

We present a remarkable thermoacoustically driven compression effect based on the conversion of gas flow from an alternating state to a direct state. The alternating gas flow is generated by the thermoacoustic effect in thermoacoustic engines, whereas direct gas flow is achieved by means of the flow rectification effect of check valves. A demonstrative thermoacoustic compressor consisting of two standing-wave thermoacoustic engines, two reservoirs, and three check valves is constructed for experimental investigation. With nitrogen as a working gas and an initial pressure of 2.4 MPa in all components, a usable pressure difference of 0.4 MPa is achieved, with the average gas pumping rate reaching 2.85 Nm3/h during the first 3 s of the compression process. The simple mechanical structure and thermally driven nature of the compressor show potential in gas compression, power generation, and refrigeration applications.
Soliton-like solutions to the ordinary Schrödinger equation within standard quantum mechanics
Authors: Zamboni-Rached Michel , Recami Erasmo
Published: May 2012

In recent times attention has been paid to the fact that (linear) wave equations admit of “soliton-like” solutions, known as localized waves or non-diffracting waves, which propagate without distortion in one direction. Such localized solutions (existing also for K-G or Dirac equations) are a priori suitable, more than gaussian's, for describing elementary particle motion. In this paper we show that, mutatis mutandis, localized solutions exist even for the ordinary (linear) Schrödinger equation within standard quantum mechanics; and we obtain both approximate and exact solutions, also setting forth for them particular examples. In the ideal case such solutions (even if localized and “decaying”) are not square-integrable, as well as plane or spherical waves: we show therefore how to obtain finite-energy solutions. At last, we briefly consider solutions for a particle moving in the presence of a potential.
Nanostructure and microripple formation on the surface of sapphire with femtosecond laser pulses
Authors: Kim Daejin , Jang Wooyoung , Kim Taehong , Moon Ayoung , Lim Ki-Soo , Lee Myeongkyu , Sohn Ik-Bu , Jeong Sungho
Published: May 2012

We have demonstrated the creation of polarization-dependent nanogratings with a period of about 250 nm on the surface of sapphire by scanning the femtosecond laser beam with appropriate irradiation conditions. Laser fluence range for nanograting self-formation was very narrow in the slow scan mode. The grating depth variation was observed with atomic force microscope image analysis. To see the composition distribution in the nanostructure, we carried out the Auger signal analysis. In addition, we found a new periodic structure with a period of a few μm and discussed the complex formation mechanism.
The mechanism and properties of bio-photon emission and absorption in protein molecules in living systems
Authors: Pang Xiao-feng
Published: May 2012

The mechanism and properties of bio-photon emission and absorption in bio-tissues were studied using Pang’s theory of bio-energy transport, in which the energy spectra of protein molecules are obtained from the discrete dynamic equation. From the energy spectra, it was determined that the protein molecules could both radiate and absorb bio-photons with wavelengths of <3 μm and 5–7 μm, consistent with the energy level transitions of the excitons. These results were consistent with the experimental data; this consisted of infrared absorption data from collagen, bovine serum albumin, the protein-like molecule acetanilide, plasma, and a person’s finger, and the laser-Raman spectra of acidity I-type collagen in the lungs of a mouse, and metabolically active Escherichia coli. We further elucidated the mechanism responsible for the non-thermal biological effects produced by the infrared light absorbed by the bio-tissues, using the above results. No temperature rise was observed; instead, the absorbed infrared light promoted the vibrations of amides as well the transport of the bio-energy from one place to other in the protein molecules, which changed their conformations. These experimental results, therefore, not only confirmed the validity of the mechanism of bio-photon emission, and the newly developed theory of bio-energy transport mentioned above, but also explained the mechanism and properties of the non-thermal biological effects produced by the absorption of infrared light by the living systems.
Transport and switching behaviors in magnetic tunnel junctions consisting of CoFeB/FeNiSiB hybrid free layers
Authors: Kim D. H. , Kim D. K. , Cho J. U. , Park S. Y. , Isogami S. , Tsunoda M. , Takahashi M. , Fullerton E. E. , Kim Y. K.
Published: May 2012

We report the efficacy of CoFeB/FeNiSiB hybrid ferromagnetic layers as free layers in magnetic tunnel junctions. A junction with a CoFeB (2.25 nm)/FeNiSiB (0.75 nm) free layer exhibited a tunneling magnetoresistance ratio and a resistance-area product value of 130% and 25 Ωμm2, respectively. The critical current density for spin transfer torque (STT) switching was 2.3 MA/cm2. This study suggests that the addition of an amorphous FeNiSiB in the free layer enhances the magnetotransport properties.
Radio-frequency superimposed direct current magnetron sputtered Ga:ZnO transparent conducting thin films
Authors: Sigdel Ajaya K. , Ndione Paul F. , Perkins John D. , Gennett Thomas , van Hest Maikel F. A. M. , Shaheen Sean E. , Ginley David S. , Berry Joseph J.
Published: May 2012

The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga2O3 (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 ± 200 S/cm, 3920 ± 600 S/cm, and 3610 ± 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in χ and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility (∼28 ± 1 cm2/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of ∼90% in the visible range.
Phonon transport in nanowire with contacts: Size and doping
Authors: Li Jing , Cheung Au Yeung Tin , Hin Kam Chan
Published: May 2012

The phonon transport in Lennard-Jones silicon wire with contacts is investigated using non-equilibrium Green’s function. With the size decreasing, the significant reduction in the number of phonon modes leads to a smaller thermal conductance density. The dopant (Ge) atoms are used to substitute the atom in the wire to study the doping effect. For thin wire, its thermal conductance is very sensitive to the location of dopants. It is also found that the interior atom substitution has more impact on the thermal conductance over surface atom; substitution near contact surface reduces thermal conductance significantly; thermal conductance is suffering a 10%–20% variation due the random distribution of dopants; 17% of Ge content is sufficient to reduce thermal conductance by 80%.
Magnetic properties and magnetocaloric effect in intermetallic compounds NdMn2−xCoxSi2
Authors: Yusuf S. M. , Halder Madhumita , Rajarajan A. K. , Nigam A. K. , Banerjee S.
Published: May 2012

We report magnetic properties and magnetocaloric effect in intermetallic compounds NdMn2−xCoxSi2 (x = 0.2, 0.4, 0.6, 0.8, and 1). dc magnetization study shows that these compounds undergo a ferromagnetic-like transition at around 45 K. Neutron diffraction study at 5 K for the x = 0.2 sample shows a canted-ferromagnetic state at lower temperature (5 K), and a collinear antiferromagnetic state at higher temperature (above ∼50 K). At 5 K, the Nd moments are aligned along the crystallographic c-axis and the Mn moments are canted to the c-axis. At higher temperatures (50, 100, 200, and 300 K), Nd sublattice does not order but Mn sublattice orders antiferromagnetically. A magnetocaloric effect (MCE) is found with a magnetic entropy change of 14.4 and 12.4 J kg−1 K−1 for the x = 0.2 and 0.4 samples, respectively, at 47.5 K under a field variation of 50 kOe. Various interesting phenomena such as metamagnetic transitions and domain wall pinning have been observed, and their role in obtaining a large MCE and an inverse MCE, respectively, has been brought out. The hysteresis (in magnetic field dependent dc magnetization study) reduces significantly at temperatures near and above the magnetic transition temperature (TC), which makes these materials important for their practical applications in magnetic refrigeration around TC.
Effect of defect bands in β-In2S3 thin films
Authors: Jayakrishnan R. , Sebastian Tina , Sudha kartha C. , Vijayakumar K. P.
Published: May 2012

Optical absorption studies in β-In2S3 thin films of band gap 2.66 eV, prepared using chemical spray pyrolysis technique, revealed presence of a defect band which could assist absorption of sub band gap photons. Extrinsic photoconductivity under excitation of 2.33 eV was observed in these films. Photoluminescence studies revealed a green emission from the films providing a recombination path to these carriers. Temperature dependence of photoconductivity showed that the states in the defect band were continuously exchanging carriers with the conduction band which caused the photocurrent to show persistent photoconductivity. Temperature dependence of photocurrent revealed existence of shallow traps located ∼24 meV below the conduction band which played vital role in controlling the photosensitivity of the films. Temporal dependence of photoconductivity revealed decay tails which were identified to be the effect of thermal release of carriers form the shallow traps.
Exciton-hole interactions in hole-doped single-walled carbon nanotubes evaluated by absorption spectral changes
Authors: Mouri Shinichiro , Matsuda Kazunari
Published: May 2012

We studied exciton–carrier interactions in hole-doped single-walled carbon nanotubes (SWNTs) through the absorption spectral changes. Broadening and blue-shifting of the exciton absorption peak in hole-doped SWNTs are observed with increasing the concentration of the p-type chemical dopant. The absorption broadening is attributed to exciton decoherence due to exciton-hole scattering. The broadening increment (∼40 meV·nm/hole) is much smaller than that of low-dimensional compound semiconductors because of restricted elastic scattering paths in SWNTs.
Screen-printing of ferrite magnetic nanoparticles produced by carbon combustion synthesis of oxides
Authors: Martirosyan Karen S. , Dannangoda Chamath , Galstyan Eduard , Litvinov Dmitri
Published: May 2012

The feasibility of screen-printing process of hard ferrite magnetic nanoparticles produced by carbon combustion synthesis of oxides (CCSO) is investigated. In CCSO, the exothermic oxidation of carbon generates a smolder thermal reaction wave that propagates through the solid reactant mixture converting it to the desired oxides. The complete conversion of hexaferrites occurs using reactant mixtures containing 11 wt. % of carbon. The BaFe12O19 and SrFe12O19 hexaferrites had hard magnetic properties with coercivity of 3 and 4.5 kOe, respectively. It was shown that the synthesized nanoparticles could be used to fabricate permanent magnet structures by consolidating them using screen-printing techniques.
Valence-band-ordering of a strain-free bulk ZnO single crystal identified by four-wave-mixing spectroscopy technique
Authors: Hazu K. , Chichibu S. F. , Adachi S. , Sota T.
Published: May 2012

Spectroscopic and temporal four-wave-mixing (FWM) measurements are carried out on a strain-free bulk ZnO single crystal, in order to clarify the valence-band-ordering. Under the collinearly polarized lights with the electric-field component parallel to the c-axis, which can excite dipole-allowed Γ1-excitons, the FWM signal appears only in the energies corresponding to the B-exciton. Under the cross-linear polarization configuration exciting both Γ5- and Γ1-excitons, the FWM signal arising from the two-photon-coherence is absent in the energies corresponding to A-exciton. Both the results indicate that Γ1-exciton state belongs exclusively to B-exciton, meaning that the valence-band ordering is Γ9-Γ7-Γ7 in order of decreasing electron energy for the present strain-free ZnO single crystal.
Development of a pulse programmer for magnetic resonance imaging using a personal computer and a high-speed digital input–output board
Authors: Hashimoto Seitaro , Kose Katsumi , Haishi Tomoyuki
Published: May 2012

We have developed a pulse programmer for magnetic resonance imaging (MRI) using a personal computer and a commercially available high-speed digital input–output board. The software for the pulse programmer was developed using C/C++ and .NET Framework 2.0 running under the Windows 7 operating system. The pulse programmer was connected to a digital MRI transceiver using a 32-bit parallel interface, and 128-bit data (16 bits × 8 words) for the pulse sequence and the digitally detected MRI signal were transferred bi-directionally every 1 μs. The performance of the pulse programmer was evaluated using a 1.0 T permanent magnet MRI system. The acquired MR images demonstrated the usefulness of the pulse programmer. Although our pulse programmer was developed for a specially designed digital MRI transceiver, our approach can be used for any MRI system if the interface for the transceiver is properly designed. Therefore, we have concluded that our approach is promising for MRI pulse programmers.
Schottky solar cells based on graphene nanoribbon/multiple silicon nanowires junctions
Authors: Xie Chao , Jie Jiansheng , Nie Biao , Yan Tianxin , Li Qiang , Lv Peng , Li Fangze , Wang Mingzheng , Wu Chunyan , Wang Li , Luo Linbao
Published: May 2012

We report the construction of Schottky solar cells based on graphene nanoribbon/multiple silicon nanowires (SiNWs) junctions. Only a few (∼10) SiNWs were involved to miniaturize the solar cell for nanoscale power source applications. It was found that doping level of the SiNWs played an important role in determining the device performance. By increasing the doping level, solar cell with open circuit voltage of 0.59 V and energy conversion efficiency of 1.47% were achieved under AM 1.5G illumination. The large effective junction area of the radial Schottky junction was responsible for the high device performance.
Millimeter wave transmission spectroscopy of gated two-dimensional hole systems
Authors: Stone K. , Du R. R. , Manfra M. J. , Pfeiffer L. N. , West K. W.
Published: May 2012

We developed a differential transmission to study cyclotron resonance of GaAs/AlxGa1−xAs two-dimensional hole samples. The technique utilizes a modulated AuPd gate isolated by a Si3 N4 dielectric from the sample, which is irradiated opposite the gate by millimeter waves ranging from 2 to 40 GHz. This technique effectively removes the background signal and yields a hole effective mass of 0.41me with a cyclotron scattering time of ∼20 ps, consistent with the previous results using different techniques.
Optical phonon lifetimes in sputtered AlN thin films
Authors: Pobedinskas P. , Ruttens B. , D’Haen J. , Haenen K.
Published: May 2012

We study the vibrational properties of AlN thin films deposited on silicon (100) substrates by the reactive DC-pulsed magnetron sputtering. The frequencies and lifetimes of the E1(TO) and A1(LO) optical phonons are calculated from Fourier transform infrared spectra using the factorized model of a damped oscillator. We analyze the structural properties by the x-ray diffraction technique to correlate the elongation of phonon lifetimes with increasing film thickness. The lifetimes of the phonon modes in AlN thin films are compared to the values in a single crystal.
Direct and charge transfer state mediated photogeneration in polymer–fullerene bulk heterojunction solar cells
Authors: Mingebach M. , Walter S. , Dyakonov V. , Deibel C.
Published: May 2012

We investigated photogeneration yield and recombination dynamics in blends of poly(3-hexyl thiophene) (P3HT) and poly[2-methoxy-5 -(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) with [6,6]-phenyl-C61butyric acid methyl ester (PC61BM) by means of temperature dependent time delayed collection field measurements. In MDMO-PPV:PC61BM, we find a strongly field dependent polaron pair dissociation which can be attributed to geminate recombination in the device. Our findings are in good agreement with field dependent photoluminescence measurements published before, supporting a scenario of polaron pair dissociation via an intermediate charge transfer state. In contrast, polaron pair dissociation in P3HT:PC61BM shows only a very weak field dependence, indicating an almost field independent polaron pair dissociation or a direct photogeneration. Furthermore, we found Langevin recombination for MDMO-PPV:PC61BM and strongly reduced Langevin recombination for P3HT:PC61BM.
Gate-controlled spin transport in a spin-diode structure
Authors: Li Yuan , Jalil Mansoor B. A. , Ghee Tan Seng
Published: May 2012

We investigate the spin transport in a spin-diode structure consisting of a quantum dot (QD) coupled to a ferromagnetic lead and a nonmagnetic (NM) lead. Electron transport through the QD system is investigated theoretically by means of the nonequilibrium Keldysh Green’s function technique. The presence of a spin bias in the NM lead induces a charge current, which shows an asymmetric “spoon-like” current-bias characteristic. The spoon-like profile can be suppressed by tuning the energy level of the QD via the gate voltage. The maximum spin-bias-induced current occurs when the tunnel couplings across the left and the right tunnel barriers are close to each other for spin-up or spin-down electrons. The effect of the tunnel couplings can thus be utilized in the design of spin-diode structures.
Characteristics of argon plasma waveguide produced by alumina capillary discharge for short wavelength laser application
Authors: Higashiguchi Takeshi , Bobrova Nadezhda , Sasorov Pavel , Sakai Shohei , Sentoku Yasuhiko , Kodama Ryosuke , Yugami Noboru
Published: May 2012

We have reported the argon (Ar) plasma waveguide produced in an alumina (Al2O3) capillary discharge and used to guide ultrashort laser pulses at intensities of the order of 1016 W/cm2. The electron density in the plasma waveguide was measured to be 1×1018 cm−3, in agreement with one-dimensional magnetrohydrodynamic (MHD) simulations. The MHD code was also used to evaluate the degree of ionization of argon (Ar) in the preformed plasma waveguide. The maximum ion charge state of Ar3+ in capillary discharge was measured and obtained in the MHD simulations. The spectrum of the propagated laser pulse in the Ar plasma waveguide was not modified and was well reproduced by a particle-in-cell simulations under initial ion charge state of Ar3+ in the preformed plasma waveguide. The optimum timing for the laser pulse injection was around 150 ns after initiation of a discharge with a peak current of 200 A.
Cyclotron resonance study in InAs/AlSb quantum well heterostructures with two occupied electronic subbands
Authors: Krishtopenko S. S. , Ikonnikov A. V. , Maremyanin A. V. , Spirin K. E. , Gavrilenko V. I. , Sadofyev Yu. G. , Goiran M. , Sadowsky M. , Vasilyev Yu. B.
Published: May 2012

We report on the cyclotron resonance (CR) study in InAs/AlSb (001) quantum well (QW) heterostructures with two occupied electronic subbands. Experimental results are compared with the CR energy calculations in the self-consistent Hartree approximation. Our theoretical approach is based on the 8-band k · p Hamiltonian and takes into account the band nonparabolicity, lattice-mismatch deformation, and spin-orbit coupling. We find out a large splitting of CR line associated with a difference in cyclotron energies in the first and second electronic subbands. The results of CR study in InAs/AlSb QW heterostructures reveal pronounced effect of the “built-in” electric field on CR spectra in the samples with two occupied electronic subbands.
OCCAM: On-line cost-function based control algorithm for microgrids
Authors: Alvarez Alvarez Eduardo , Campos López Antonio M. , Gutiérrez-Trashorras Antonio J.
Published: May 2012

This paper presents the active power dispatching of microsources, as an on-line minimization problem, including electrical and heat generation costs. The use of a new algorithm: on-line cost-function based control algorithm for microgrids (OCCAM), makes it possible to obtain similar or even better solutions than those obtained using other state of the art methods like MADS and SQP. Moreover, its execution time is about one hundred times lower than the time needed by other algorithms and it can run efficiently on-line. OCCAM is based on the same principle as the famous William Occam’s razor: “the simplest explanation is most likely the correct one”; its simplicity is the reason for its low execution time. It uses costs functions of microsources and heat savings (obtained by recovering heat from microsources in cogeneration installations) to determine the optimal solution.
Solar energy potential in Pakistan
Authors: Adnan Shahzada , Hayat Khan Azmat , Haider Sajjad , Mahmood Rashed
Published: May 2012

In view of the growing needs of energy in Pakistan, the efficient use and development of renewable energy sources has become a major issue in the country. This has brought the intention of several national and multinational companies to design and implement a major work plan for energy conservation and construction of renewable energy sources like wind mills and solar panels. Fortunately, Pakistan is among those countries in which sun warms the surface throughout the year and therefore has a strong potential for solar power generation. This study was conducted to explore those areas which are most suitable for solar energy potential using fifty eight meteorological stations covering the whole country. Angstrom equation and Hargreaves formula was used to calculate monthly solar energy potential by utilizing monthly climatical data of bright sunshine hours, mean maximum and minimum temperatures. The lowest solar radiation intensity 76.49 W/m2 observed at Cherat during December and highest 339.25 W/m2 at Gilgit. The average monthly solar radiation intensity remains 136.05 to 287.36 W/m2 in the country. The results indicate that the values of solar radiation intensity greater than 200 W/m2 were observed in the months: February to October in Sindh, March to October in almost all regions of Balochistan, April to September in NWFP, Northern Areas and Kashmir regions while March to October in Punjab. For 10 h a day, average solar radiation intensity ranges from 1500 W/m2/day to 2750 W/m2/day in Pakistan especially in southern Punjab, Sindh and Balochistan regions throughout the year. In an area of 100 m2, 45 MW to 83 MW power per month may be generated in the above mentioned regions.
Enhanced sheath heating in capacitively coupled discharges due to non-sinusoidal voltage waveforms
Authors: Lafleur T. , Boswell R. W. , Booth J. P.
Published: May 2012

Through the use of particle-in-cell simulations, we demonstrate that the power deposition in capacitively coupled discharges (in argon) can be increased by replacing sinusoidal waveforms with Gaussian-shaped voltage pulses (with a repetition frequency of 13.56 MHz). By changing the Gaussian pulse width, electron heating can be directly controlled, allowing for an increased plasma density and ion flux for the same gas pressure and geometrical operating conditions. Analysis of the power deposition profiles and electron distribution functions shows that enhanced electron-sheath heating is responsible for the increased power absorption.
High efficient antireflective down-conversion Y2O3:Bi,Yb films with pyramid preferred oriented nano-structure
Authors: Qu Ming-Hao , Wang Ru-Zhi , Zhang Ying , Li Kai-Yu , Yan Hui
Published: May 2012

The high efficient antireflective down-conversion Y2O3:Bi,Yb films with nano-structure pyramids were grown successfully on Si (100) substrates using the pulsed laser deposition (PLD). The films microstructure can be controllably tuned only by changing the oxygen pressure in PLD process. With the increasing of the oxygen pressure, the surface morphology changes from smooth surface to pyramid nano-structure, and the preferential orientation of films changes from (222) to (400). Besides, the average reflectance of the films decreases first and then increases, giving a minimum value of 15.8% at 5 Pa as the oxygen pressure increases, which is comparable to that of uniform pyramidal micro-textured surfaces with an average reflectance of 13%–15% fabricated by the complicated chemical etching method. Moreover, upon excitation of ultraviolet photon varying from 300 to 400 nm, near infrared emission of Yb3+ due to transition of the 2F5/2→2F7/2 was observed for all samples, which can be efficiently absorbed by silicon solar cell. These pyramid nano-structure down-conversion Y2O3:Bi,Yb films possess promising applications in enhancement of energy efficiency for crystalline Si solar cells by light trapping and spectrum shifting.
Multi-state resistive switching memory with secure information storage in Au/BiFe0.95Mn0.05O3/La5/8Ca3/8MnO3 heterostructure
Authors: Yao Y. P. , Liu Y. K. , Dong S. N. , Yin Y. W. , Yang S. W. , Li X. G.
Published: May 2012

The ferroelectric polarization dependent bipolar and conductive filament related unipolar resistive switching behaviors are investigated systematically in Au/BiFe0.95Mn0.05O3/La5/8Ca3/8MnO3 heterostructure. The results show that after conductive filaments are formed, the ferroelectric state previously polarized will keep almost unchanged. By combining the two resistive switching mechanisms together under appropriate programming conditions, a tri-state-like resistive switching behavior is realized, finding effective routes in designing high-density storage. According to these distinctive characteristics, a prototype memory device with secure information storage is properly designed as an example of promising applications.
The comparison of direct and indirect methods for determining the magnetocaloric parameters in the Heusler alloy Ni50Mn34.8In14.2B
Authors: Dubenko Igor , Samanta Tapas , Quetz Abdiel , Kazakov Alexander , Rodionov Igor , Mettus Denis , Prudnikov Valerii , Stadler Shane , Adams Philip , Prestigiacomo Joseph , Granovsky Alexander , Zhukov Arcady , Ali Naushad
Published: May 2012

The magnetocaloric properties of the Ni50Mn34.8In14.2B Heusler alloy have been studied by direct measurements of the adiabatic temperature change (ΔTAD(T,H)) and indirectly by magnetization (M(T,H)), differential scanning calorimetry, and specific heat (C(T,H)) measurements. The presence of a first-order ferromagnetic-paramagnetic transition has been detected for Ni50Mn34.8In14.2B at 320 K. The magnetocaloric parameters, i.e., the magnetic entropy change (ΔSM = (2.9-3.2) J/kgK) and the adiabatic temperature change (ΔTAD = (1.3-1.52) K), have been evaluated for ΔH = 1.8 T from CP(T,H) and M(T,H) data and from direct ΔTAD(T,H) measurements. The extracted magnetocaloric parameters are comparable to those of Gd.
Mechanisms contributing to central excitability changes during hearing loss
Authors: Pilati Nadia , Ison Matias J. , Barker Matthew , Mulheran Mike , Large Charles H. , Forsythe Ian D. , Matthias John , Hamann Martine
Published: May 2012

Exposure to loud sound causes cochlear damage resulting in hearing loss and tinnitus. Tinnitus has been related to hyperactivity in the central auditory pathway occurring weeks after loud sound exposure. However, central excitability changes concomitant to hearing loss and preceding those periods of hyperactivity, remain poorly explored. Here we investigate mechanisms contributing to excitability changes in the dorsal cochlear nucleus (DCN) shortly after exposure to loud sound that produces hearing loss. We show that acoustic overexposure alters synaptic transmission originating from the auditory and the multisensory pathway within the DCN in different ways. A reduction in the number of myelinated auditory nerve fibers leads to a reduced maximal firing rate of DCN principal cells, which cannot be restored by increasing auditory nerve fiber recruitment. In contrast, a decreased membrane resistance of DCN granule cells (multisensory inputs) leads to a reduced maximal firing rate of DCN principal cells that is overcome when additional multisensory fibers are recruited. Furthermore, gain modulation by inhibitory synaptic transmission is disabled in both auditory and multisensory pathways. These cellular mechanisms that contribute to decreased cellular excitability in the central auditory pathway are likely to represent early neurobiological markers of hearing loss and may suggest interventions to delay or stop the development of hyperactivity that has been associated with tinnitus.
Density-dependent fitness benefits in quorum-sensing bacterial populations
Authors: Darch Sophie E. , West Stuart A. , Winzer Klaus , Diggle Stephen P.
Published: May 2012

It has been argued that bacteria communicate using small diffusible signal molecules to coordinate, among other things, the production of factors that are secreted outside of the cells in a process known as quorum sensing (QS). The underlying assumption made to explain QS is that the secretion of these extracellular factors is more beneficial at higher cell densities. However, this fundamental assumption has never been tested experimentally. Here, we directly test this by independently manipulating population density and the induction and response to the QS signal, using the opportunistic pathogen
Pseudomonas aeruginosa
as a model organism. We found that the benefit of QS was relatively greater at higher population densities, and that this was because of more efficient use of QS-dependent extracellular “public goods.” In contrast, the benefit of producing “private goods,” which are retained within the cell, does not vary with cell density. Overall, these results support the idea that QS is used to coordinate the switching on of social behaviors at high densities when such behaviors are more efficient and will provide the greatest benefit.
Autophagy inhibitor Lys05 has single-agent antitumor activity and reproduces the phenotype of a genetic autophagy deficiency
Authors: McAfee Quentin , Zhang Zhihui , Samanta Arabinda , Levi Samuel M. , Ma Xiao-Hong , Piao Shengfu , Lynch John P. , Uehara Takeshi , Sepulveda Antonia R. , Davis Lisa E. , Winkler Jeffrey D. , Amaravadi Ravi K.
Published: May 2012

Autophagy is a lysosome-dependent degradative process that protects cancer cells from multiple stresses. In preclinical models, autophagy inhibition with chloroquine (CQ) derivatives augments the efficacy of many anticancer therapies, but CQ has limited activity as a single agent. Clinical trials are underway combining anticancer agents with hydroxychloroquine (HCQ), but concentrations of HCQ required to inhibit autophagy are not consistently achievable in the clinic. We report the synthesis and characterization of bisaminoquinoline autophagy inhibitors that potently inhibit autophagy and impair tumor growth in vivo. The structural motifs that are necessary for improved autophagy inhibition compared with CQ include the presence of two aminoquinoline rings and a triamine linker and C-7 chlorine. The lead compound, Lys01, is a 10-fold more potent autophagy inhibitor than HCQ. Compared with HCQ, Lys05, a water-soluble salt of Lys01, more potently accumulates within and deacidifies the lysosome, resulting in impaired autophagy and tumor growth. At the highest dose administered, some mice develop Paneth cell dysfunction that resembles the intestinal phenotype of mice and humans with genetic defects in the autophagy gene
ATG16L1
, providing in vivo evidence that Lys05 targets autophagy. Unlike HCQ, significant single-agent antitumor activity is observed without toxicity in mice treated with lower doses of Lys05, establishing the therapeutic potential of this compound in cancer.
Mimicking the electron transfer chain in photosystem II with a molecular triad thermodynamically capable of water oxidation
Authors: Megiatto Jackson D. , Antoniuk-Pablant Antaeres , Sherman Benjamin D. , Kodis Gerdenis , Gervaldo Miguel , Moore Thomas A. , Moore Ana L. , Gust Devens
Published: May 2012

In the photosynthetic photosystem II, electrons are transferred from the manganese-containing oxygen evolving complex (OEC) to the oxidized primary electron-donor chlorophyll P680
•+
by a proton-coupled electron transfer process involving a tyrosine-histidine pair. Proton transfer from the tyrosine phenolic group to a histidine nitrogen positions the redox potential of the tyrosine between those of P680
•+
and the OEC. We report the synthesis and time-resolved spectroscopic study of a molecular triad that models this electron transfer. The triad consists of a high-potential porphyrin bearing two pentafluorophenyl groups (PF
10
), a tetracyanoporphyrin electron acceptor (TCNP), and a benzimidazole-phenol secondary electron-donor (Bi-PhOH). Excitation of PF
10
in benzonitrile is followed by singlet energy transfer to TCNP (
τ
 = 41 ps), whose excited state decays by photoinduced electron transfer (
τ
 = 830 ps) to yield

. A second electron transfer reaction follows (
τ
 < 12 ps), giving a final state postulated as BiH
+
-PhO
•
-PF
10
-TCNP
•-
, in which the phenolic proton now resides on benzimidazole. This final state decays with a time constant of 3.8 μs. The triad thus functionally mimics the electron transfers involving the tyrosine-histidine pair in PSII. The final charge-separated state is thermodynamically capable of water oxidation, and its long lifetime suggests the possibility of coupling systems such as this system to water oxidation catalysts for use in artificial photosynthetic fuel production.
Replacing the first-generation dentition in pufferfish with a unique beak
Authors: Fraser Gareth J. , Britz Ralf , Hall Andie , Johanson Zerina , Smith Moya M.
Published: May 2012

Teleost fishes comprise approximately half of all living vertebrates. The extreme range of diversity in teleosts is remarkable, especially, extensive morphological variation in their jaws and dentition. Some of the most unusual dentitions are found among members of the highly derived teleost order Tetraodontiformes, which includes triggerfishes, boxfishes, ocean sunfishes, and pufferfishes. Adult pufferfishes (Tetraodontidae) exhibit a distinctive parrot-like beaked jaw, forming a cutting edge, unlike in any other group of teleosts. Here we show that despite novelty in the structure and development of this “beak,” it is initiated by formation of separate first-generation teeth that line the embryonic pufferfish jaw, with timing of development and gene expression patterns conserved from the last common ancestor of osteichthyans. Most of these first-generation larval teeth are lost in development. Continuous tooth replacement proceeds in only four parasymphyseal teeth, as sequentially stacked, multigenerational, jaw-length dentine bands, before development of the functional beak. These data suggest that dental novelties, such as the pufferfish beak, can develop later in ontogeny through modified continuous tooth addition and replacement. We conclude that even highly derived morphological structures like the pufferfish beak form via a conserved developmental bauplan capable of modification during ontogeny by subtle respecification of the developmental module.
Metopic suture of Taung (
Australopithecus africanus
) and its implications for hominin brain evolution
Authors: Falk Dean , Zollikofer Christoph P. E. , Morimoto Naoki , Ponce de León Marcia S.
Published: May 2012

The type specimen for
Australopithecus africanus
(Taung) includes a natural endocast that reproduces most of the external morphology of the right cerebral hemisphere and a fragment of fossilized face that articulates with the endocast. Despite the fact that Taung died between 3 and 4 y of age, the endocast reproduces a small triangular-shaped remnant of the anterior fontanelle, from which a clear metopic suture (MS) courses rostrally along the midline [Hrdlička A (1925)
Am J Phys Anthropol
8:379–392]. Here we describe and interpret this feature of Taung in light of comparative fossil and actualistic data on the timing of MS closure. In great apes, the MS normally fuses shortly after birth, such that unfused MS similar to Taung’s are rare. In humans, however, MS fuses well after birth, and partially or unfused MS are frequent. In gracile fossil adult hominins that lived between ∼3.0 and 1.5 million y ago, MS are also relatively frequent, indicating that the modern human-like pattern of late MS fusion may have become adaptive during early hominin evolution. Selective pressures favoring delayed fusion might have resulted from three aspects of perinatal ontogeny: (
i
) the difficulty of giving birth to large-headed neonates through birth canals that were reconfigured for bipedalism (the “obstetric dilemma”), (
ii
) high early postnatal brain growth rates, and (
iii
) reorganization and expansion of the frontal neocortex. Overall, our data indicate that hominin brain evolution occurred within a complex network of fetopelvic constraints, which required modification of frontal neurocranial ossification patterns.
A common X-linked inborn error of carnitine biosynthesis may be a risk factor for nondysmorphic autism
Authors: Celestino-Soper Patrícia B. S. , Violante Sara , Crawford Emily L. , Luo Rui , Lionel Anath C. , Delaby Elsa , Cai Guiqing , Sadikovic Bekim , Lee Kwanghyuk , Lo Charlene , Gao Kun , Person Richard E. , Moss Timothy J. , German Jennifer R. , Huang Ni , Shinawi Marwan , Treadwell-Deering Diane , Szatmari Peter , Roberts Wendy , Fernandez Bridget , Schroer Richard J. , Stevenson Roger E. , Buxbaum Joseph D. , Betancur Catalina , Scherer Stephen W. , Sanders Stephan J. , Geschwind Daniel H. , Sutcliffe James S. , Hurles Matthew E. , Wanders Ronald J. A. , Shaw Chad A. , Leal Suzanne M. , Cook Edwin H. , Goin-Kochel Robin P. , Vaz Frédéric M. , Beaudet Arthur L.
Published: May 2012

We recently reported a deletion of exon 2 of the trimethyllysine hydroxylase epsilon (TMLHE) gene in a proband with autism.TMLHEmaps to the X chromosome and encodes the first enzyme in carnitine biosynthesis, 6-N-trimethyllysine dioxygenase. Deletion of exon 2 ofTMLHEcauses enzyme deficiency, resulting in increased substrate concentration (6-N-trimethyllysine) and decreased product levels (3-hydroxy-6-N-trimethyllysine and γ-butyrobetaine) in plasma and urine.TMLHEdeficiency is common in control males (24 in 8,787 or 1 in 366) and was not significantly increased in frequency in probands from simplex autism families (9 in 2,904 or 1 in 323). However, it was 2.82-fold more frequent in probands from male-male multiplex autism families compared with controls (7 in 909 or 1 in 130;P= 0.023). Additionally, six of seven autistic male siblings of probands in male-male multiplex families had the deletion, suggesting thatTMLHEdeficiency is a risk factor for autism (metaanalysis Z-score = 2.90 andP= 0.0037), although with low penetrance (2–4%). These data suggest that dysregulation of carnitine metabolism may be important in nondysmorphic autism; that abnormalities of carnitine intake, loss, transport, or synthesis may be important in a larger fraction of nondysmorphic autism cases; and that the carnitine pathway may provide a novel target for therapy or prevention of autism.