bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative atom probe study of Cu(In,Ga)Se2 thin-film solar cells deposited on soda-lime glass and mild steel substrates
Authors: Choi Pyuck-Pa , Cojocaru-Mirédin Oana , Wuerz Roland , Raabe Dierk
Published: December 2011

We report on a comparative study of Cu(In,Ga)Se2 solar cells deposited on soda-lime glass and mild steel substrates, using atom probe tomography in conjunction with secondary ion mass spectrometry, x-ray fluorescence, current density-voltage, and external quantum efficiency measurements. Cu(In,Ga)Se2 films deposited on soda-lime glass substrates and on steel substrates with a NaF precursor layer on top of the Mo back contact contain a significant amount of Na impurities and yield an enhanced open circuit voltage and fill factor. Using atom probe tomography, Na atoms are found to be segregated at grain boundaries and clustered in both bulk and grain boundaries. The atom probe data indicate that NaCu point defects are most likely formed at grain boundaries, reducing the number of compensating InCu point defects and thus contributing to an enhanced cell efficiency. However, for steel substrates the positive effect of Na on the cell performance is counterbalanced by the incorporation of Fe impurities into the Cu(In,Ga)Se2 film. Fe atoms are homogeneously distributed inside the grains suggesting that Fe introduces point defects in the bulk
Anti-phase domains in cubic GaN
Authors: Maria Kemper Ricarda , Schupp Thorsten , Häberlen Maik , Niendorf Thomas , Maier Hans-Jürgen , Dempewolf Anja , Bertram Frank , Christen Jürgen , Kirste Ronny , Hoffmann Axel , Lindner Jörg , Josef As Donat
Published: December 2011

The existence of anti-phase domains in cubic GaN grown on 3C-SiC/Si (001) substrates by plasma-assisted molecular beam epitaxy is reported. The influence of the 3C-SiC/Si (001) substrate morphology is studied with emphasis on the anti-phase domains (APDs). The GaN nucleation is governed by the APDs of the substrate, resulting in equal plane orientation and the same anti-phase boundaries. The presence of the APDs is independent of the GaN layer thickness. Atomic force microscopy surface analysis indicates lateral growth anisotropy of GaN facets in dependence of the APD orientation. This anisotropy can be linked to Ga and N face types of the {111} planes, similar to observations of anisotropic growth in 3C-SiC. In contrast to 3C-SiC, however, a difference in GaN phase composition for the two types of APDs can be measured by electron backscatter diffraction, μ-Raman and cathodoluminescence spectroscopy.
Modulating magnetism of ZnO:C with vacancy and substitution
Authors: Li W. Q. , Cao J. X. , Ding J. W. , Hu Xuedong
Published: December 2011

We investigate magnetic properties of C-doped ZnO (ZnO:C) systems in the presence of defects such as O and Zn vacancies and substitution of Li and Al for Zn. Specifically, we use density functional theory to calculate electronic structures, local magnetic moment, polarization energy, etc., for these material systems. We find that the magnetic moment at a C atom in ZnO:C can be suppressed by the presence of an oxygen vacancy and enhanced by the presence of a Zn vacancy, and depends sensitively on the distance between the C atom and such a vacancy. Our results provide an explanation of the experimental observation that the C-induced magnetic moment in ZnO:C varies widely, from 1.3 μB to 3.0 μB. We also show that Lithium and Aluminum implantations in ZnO:C can effectively tailor the magnetic moment and ferromagnetism, regardless of the distance between the implanted atoms and the C atoms. In particular, our results indicate that Curie temperature in a ZnO:C system can potentially be increased by Al implantation.
The effect of boundary conditions on the vibrations of armchair, zigzag, and chiral single-walled carbon nanotubes
Authors: Pine Polina , Yaish Yuval E. , Adler Joan
Published: December 2011

Single-walled carbon nanotubes (SWCNTs) have three distinct structures: armchair, zigzag, and chiral. It is known that they have different electronic properties, but the situation regarding their vibrational behavior is less clear. Doubly clamped nanotubes of all three types exhibit the same vibrational modes, and their vibrations in the directions perpendicular to the nanotube axis are degenerate. In nanotube applications, such as sensors based on nano-electro-mechanical systems, their ends are not fully clamped, thus their vibrational behavior could differ. Careful molecular dynamics simulations of SWCNTs with boundary conditions, which imitate the partly clamped experimental conditions, show that armchair, zigzag, and chiral nanotubes indeed vibrate differently. The symmetry between the two perpendicular directions is broken, and SWCNT type does influence the vibrational modes.
A two-dimensional-reference interaction site model theory for solvation structure near solid-liquid interface
Authors: Iida Kenji , Sato Hirofumi
Published: December 2011

We develop a new equation to describe solvation structure near solid-liquid interface at the atomic-level. The developed equation focuses on anisotropy of solvation structure near the interface by using two-dimensional density distribution of solvent along two directions, one of which is perpendicular to the interface and the other is parallel to the interface. As a first application of the equation, we treat a system where a solid modeled by an atomistic wall is immersed in solvent water. The preferential adsorption position of water molecules and the change of water orientation by charging the wall are discussed.
Effects of composition and compositional distribution on the electronic structure of ZnSe1−xTex ternary quantum dots
Authors: Pandey Sumeet C. , Maroudas Dimitrios
Published: December 2011

We report results of first-principles density functional theory (DFT) calculations for the electronic structure of ZnSe1−xTex ternary quantum dots (TQDs) and the effects of composition and compositional distribution on the electron density distribution, electronic density of states, and band gap. We analyze the electronic structure of five types of nanocrystal configurations, namely, pristine ZnSe and ZnTe quantum dots, as well as ZnSe/ZnTe core/shell, ZnTe/ZnSe reverse core/shell, and randomly alloyed ZnSe1−xTex TQDs. We find that the band gaps for ZnSe/ZnTe core/shell TQDs are nonlinearly dependent on the number of Te atoms in the shell, whereas presence of Te in the core of alloyed ZnSe1−xTex TQDs modifies the electronic energy levels abruptly and significantly in the limits of x → 0 and x → 1. Our results imply that distribution of Te atoms in the TQD in the form of a ZnSe/ZnTe core/shell configuration allows for optimum tunability of the band gap and wave function confinement in TQDs.
Observations of laser induced magnetization dynamics in Co/Pd multilayers with coherent x-ray scattering
Authors: Wu B. , Zhu D. , Acremann Y. , Miller T. A. , Lindenberg A. M. , Hellwig O. , Stöhr J. , Scherz A.
Published: December 2011

We report on time-resolved coherent x-ray scattering experiments of laser induced magnetization dynamics in Co/Pd multilayers with a high repetition rate optical pump x-ray probe setup. Starting from a multi-domain ground state, the magnetization is uniformly reduced after excitation by an intense 50 fs laser pulse. Using the normalized time correlation, we study the magnetization recovery on a picosecond timescale. The dynamic scattering intensity is separated into an elastic portion at length scales above 65 nm, which retains memory of the initial domain magnetization, and a fluctuating portion at smaller length scales corresponding to domain boundary motion during recovery.
Strain enhanced electron cooling in a degenerately doped semiconductor
Authors: Prest M. J. , Muhonen J. T. , Prunnila M. , Gunnarsson D. , Shah V. A. , Richardson-Bullock J. S. , Dobbie A. , Myronov M. , Morris R. J. H. , Whall T. E. , Parker E. H. C. , Leadley D. R.
Published: December 2011

Enhanced electron cooling is demonstrated in a strained-silicon/superconductor tunnel junction refrigerator of volume 40 μm3. The electron temperature is reduced from 300 mK to 174 mK, with the enhancement over an unstrained silicon control (300 mK–258 mK) being attributed to the smaller electron-phonon coupling in the strained case. Modeling and the resulting predictions of silicon-based cooler performance are presented. Further reductions in the minimum temperature are expected if the junction sub-gap leakage and tunnel resistance can be reduced. However, if only tunnel resistance is reduced, Joule heating is predicted to dominate.
High temperature thermoelectric properties of optimized InGaN
Authors: Sztein Alexander , Ohta Hiroaki , Bowers John E. , DenBaars Steven P. , Nakamura Shuji
Published: December 2011

The effects of carrier concentration, composition, and temperature on the thermoelectric properties of high quality n-type InGaN grown by metal organic chemical vapor deposition (MOCVD) were systematically investigated. The Seebeck coefficient was found to decrease and electrical conductivity increase with increasing carrier concentration, while both were found to decrease with increasing indium composition. Additionally, thermal conductivity was found to decrease by over an order of magnitude as indium composition was increased from 0 to 19%. These trends resulted in optimum carrier concentration and indium composition of 1.1×1019 cm−3 and 17%, respectively, with a room temperature ZT of 0.04. Increasing temperature resulted in a rapidly increasing ZT, reaching a maximum value of 0.34 at 875 K. This significantly improved ZT demonstrates the potential of InGaN and other III-Nitride materials for high temperature thermoelectric applications.
An empirical law for the band gaps of MgZnO nanowires
Authors: Zhang Y. G. , He H. Y. , Pan B. C.
Published: December 2011

The practice of semiconducting nanowires in the photoelectronic nano-devices requires that the band gaps of the nanowires are controllable in the process of the synthesis, where the bandgap of a semiconducting nanowire is highly dependent on its chemical components and the structural parameters. In this work, by performing theoretical calculations at the level of the density functional theory, the band gaps of the MgxZn1-xO nanowires with different contents of Mg and different structural features are extensively studied. Through correlating the calculated band gaps to both the contents of Mg and the structural parameters, we find that the bandgap of a MgxZn1-xO nanowire can be expressed by an empirical formula. Our calculations indicate that this formula is valid for the ZnO nanowires, the alloy MgZnO nanowires, as well as the ZnO/MgxZn1-xO core-shell nanowires. We anticipate that this empirical formula can serve as a guidance for designing a MgZnO nanowire with the desired bandgap in its realistic applications.
Resonant tunneling in Si/SiGe/Si structures with a single quantum well under surface passivation
Authors: Antonova I. V. , Vinokurov P. V. , Smagulova S. A. , Kagan M. S. , Ray S. K. , Kolodzey J.
Published: December 2011

Si/SiGe/Si structures with single SiGe quantum wells (QWs) of different Ge content in the SiGe layer were studied at temperatures of 80 to 300 K. The structure surfaces were passivated with organic monolayers of 1 octadecene. The passivation removed the surface-defect charge resulting in a high hole population of SiGe QWs and made it possible to observe clearly the resonant tunneling of holes through confined levels in SiGe QW. The tunneling became evident as the steps on current–voltage characteristics. The energies of confined levels found from these data are consistent with calculated ones and with energies found from DLTS measurements. It was shown that the carrier emission from QWs is mainly caused by thermally activated tunneling at low biases and direct tunneling through the confined states at high biases.
The effects of 100 nm-diameter Au nanoparticles on dye-sensitized solar cells
Authors: Nahm Changwoo , Choi Hongsik , Kim Jongmin , Jung Dae-Ryong , Kim Chohui , Moon Joonhee , Lee Byungjoo , Park Byungwoo
Published: December 2011

Gold nanoparticles of ∼100 nm in diameter were incorporated into TiO2 nanoparticles for dye-sensitized solar cells (DSSCs). At the optimum Au/TiO2 mass ratio of 0.05, the power-conversion efficiency of the DSSC improved to 3.3% from a value of 2.7% without Au, and this improvement was mainly attributed to the photocurrent density. The Au nanoparticles embedded in the nanoparticulate-TiO2 film strongly absorbed light due to the localized surface-plasmon resonance, and thereby promoted light absorption of the dye. In the DSSCs, the 100 nm-diameter Au nanoparticles generate field enhancement by surface-plasmon resonance rather than prolonged optical paths by light scattering.
Catalyst-free growth of high-optical quality GaN nanowires by metal-organic vapor phase epitaxy
Authors: Chen X. J. , Gayral B. , Sam-Giao D. , Bougerol C. , Durand C. , Eymery J.
Published: December 2011

Catalyst-free GaN wires with 100–200 nm diameters are grown on bare c-sapphire substrates by a metal-organic vapor phase epitaxy approach using both low V/III ratio and V-III precursor flows that favor a reaction-limited growth regime. The polarity control of the initial seeds allows obtaining pencil-shape wires with very sharp pyramids at their top (∼5 nm diameter). These defect-free nanowires evidence excellent structural and optical properties as shown by a sharp photoluminescence linewidth (1–3 meV at 5 K).
Multiphoton dissociative ionization of tert-pentyl bromide near 265 nm
Authors: Mao Rui , Zhang Qun , Zang Jianzheng , He Chao , Chen Min , Chen Yang
Published: December 2011

We report on the photodissociation dynamics of tert-pentyl bromide near 265 nm investigated by time-sliced velocity map imaging. The speed and angular distributions have been analyzed for both the ground-state Br(2P3/2) atom (denoted Br) and the spin–orbit excited-state Br(2P1/2) atom (denoted Br*). The speed distributions of Br and Br* atoms are all found to consist of three Gaussian components, which correlate to three independent dissociation pathways on the excited potential energy surfaces: (1) the high translational energy (ET) component from the prompt dissociation along the C–Br stretching mode, (2) the middle ET component from the repulsive mode along the C–Br stretching coupled with some bending motions, and (3) the low ET component from the repulsive mode along the C–Br stretching coupled with more bending motions. More interestingly, we have also observed the $tert{\rm - C}_{\rm 5} {\rm H}_{{\rm 11}}^ +$tert−C5H11+ ions in 263–267 nm. The near-zero kinetic energy distributions extracted from the three $tert{\rm - C}_{\rm 5} {\rm H}_{{\rm 11}}^ +$tert−C5H11+ images near 265 nm show the typical characteristics that are attributable to multiphoton dissociative ionization, suggesting the existence of a neutral superexcited state of the parent tert-pentyl bromide molecule. The contribution of bromine atoms formed in this dissociative ionization channel adds in the total relative distribution of low ET component in the Br*(Br) formation channel, which reasonably explains the abnormal distributions observed in between the middle and low ET components in the Br*(Br) formation channel.
Significantly improved minority carrier lifetime observed in a long-wavelength infrared III-V type-II superlattice comprised of InAs/InAsSb
Authors: Steenbergen E. H. , Connelly B. C. , Metcalfe G. D. , Shen H. , Wraback M. , Lubyshev D. , Qiu Y. , Fastenau J. M. , Liu A. W. K. , Elhamri S. , Cellek O. O. , Zhang Y.-H.
Published: December 2011

Time-resolved photoluminescence measurements reveal a minority carrier lifetime of >412 ns at 77 K under low excitation for a long-wavelength infrared InAs/InAs0.72Sb0.28 type-II superlattice (T2SL). This lifetime represents an order-of-magnitude increase in the minority carrier lifetime over previously reported lifetimes in long-wavelength infrared InAs/Ga1−xInxSb T2SLs. The considerably longer lifetime is attributed to a reduction of non-radiative recombination centers with the removal of Ga from the superlattice structure. This lifetime improvement may enable background limited T2SL long-wavelength infrared photodetectors at higher operating temperatures.
Phase behavior of lyotropic rigid-chain polymer liquid crystal studied by dissipative particle dynamics
Authors: Zhao Tongyang , Wang Xiaogong
Published: December 2011

The phase behavior of lyotropic rigid-chain liquid crystal polymer was studied by dissipative particle dynamics (DPD) with variations of the solution concentration and temperature. A chain of fused DPD particles was used to represent each mesogenic polymer backbone surrounded with the strongly interacted solvent molecules. The free solvent molecules were modeled as independent DPD particles, where each particle includes a lump of solvent molecules with the volume roughly equal to the solvated polymer segment. The simulation shows that smectic-B (SB), smectic-A (SA), nematic (N), and isotropic (I) phases exist within certain regions in the temperature and concentration parameter space. The temperature-dependent SB/SA, SA/N, and N/I phase transitions occur in the high concentration range. In the intermediate concentration range, the simulation shows coexistence of the anisotropic phases and isotropic phase, where the anisotropic phases can be the SB, SA, or N phases. Mole fraction and compositions of the coexisted phases are determined from the simulation, which indicates that concentration of rigid rods in isotropic phase increases as the temperature increases. By fitting the orientational distribution function of the systems, the biphasic coexistence is further confirmed. From the parameter α obtained for the simulation, the distribution of the rigid rods in the two coexistence phases is quantitatively evaluated. By using model and simulation methods developed in this work, the phase diagrams of the lyotropic rigid-chain polymer liquid crystal are obtained. Incorporating the solvent particles in the DPD simulation is critical to predict the phase coexistence and obtain the phase diagrams.
Exponential cluster synchronization of impulsive delayed genetic oscillators with external disturbances
Authors: Zhang Wenbing , Tang Yang , Fang Jian-an , Zhu Wu
Published: December 2011

This paper investigates the problem of the exponential cluster synchronization of coupled impulsive genetic oscillators with external disturbances and communication delay. Based on the Kronecker product, some new cluster synchronization criteria for coupled impulsive genetic oscillators with attenuation level are derived. The derived results are related to the impulsive strength, and the derived results also indicate that the maximal allowable bound of time delay is inversely proportional to the decay rate, the decay rate is proportional to the couple strength, the maximal allowable bound of time delay is proportional to attenuation level, and the attenuation level is inversely proportional to the couple strength. Moreover, the case when the feedback have different self-delay is also investigated. Finally, numerical examples are given to illustrate the effectiveness of the derived results.
Cotranscriptional folding kinetics of ribonucleic acid secondary structures
Authors: Zhao Peinan , Zhang Wenbing , Chen Shi-Jie
Published: December 2011

We develop a systematic helix-based computational method to predict RNA folding kinetics during transcription. In our method, the transcription is modeled as stepwise process, where each step is the transcription of a nucleotide. For each step, the kinetics algorithm predicts the population kinetics, transition pathways, folding intermediates, and the transcriptional folding products. The folding pathways, rate constants, and the conformational populations for cotranscription folding show contrastingly different features than the refolding kinetics for a fully transcribed chain. The competition between the transcription speed and rate constants for the transitions between the different nascent structures determines the RNA folding pathway and the end product of folding. For example, fast transcription favors the formation of branch-like structures than rod-like structures and chain elongation in the folding process may reduce the probability of the formation of misfolded structures. Furthermore, good theory-experiment agreements suggest that our method may provide a reliable tool for quantitative prediction for cotranscriptional RNA folding, including the kinetics for the population distribution for the whole conformational ensemble.
Room temperature lasing with high group index in metal-coated GaN nanoring
Authors: Wang Yow-Gwo , Chang Shu-Wei , Chen Cheng-Chang , Chiu Ching-Hsueh , Kuo Ming-Yen , Shih M. H. , Kuo Hao-Chung
Published: December 2011

The room temperature lasing action from a metal-coated GaN nanoring cavity was observed by optical pumping. The GaN nanoring is 7 μm in diameter and 400 nm in width. The quality factor of the cavity is approximately 860 with a threshold power density of 37.5 mJ/cm2. Such a device performance was attributed to the combination of metal-coated nanocavity with whispering-gallery modes. Moreover, the group index extracted from the experiment was 5.99 and was verified with calculations and analyses of the lasing modes as well as their characteristics. The study showed a promising way to further improve the performance of metal-coated nanolasers.
Electroluminescence from Si nanocrystal/c-Si heterojunction light-emitting diodes
Authors: Di Dawei , Perez-Wurfl Ivan , Wu Lingfeng , Huang Yidan , Marconi Alessandro , Tengattini Andrea , Anopchenko Aleksei , Pavesi Lorenzo , Conibeer Gavin
Published: December 2011

Silicon nanocrystals have shown attractive properties for photonic and photovoltaic applications. We demonstrate all-Si light-emitting diodes based on boron-doped Si nanocrystal/c-Si p-n heterojunction structure, which show electroluminescence in the visible/infrared regions. The electroluminescence spectra of these diodes can be modified by changing the quantum confining barriers from SiO2 to Si3N4. Our results are an important demonstration of electroluminescence from boron-doped Si nanocrystals—a wide band gap absorber material for third generation photovoltaics.
Robust adaptive synchronization for a general class of uncertain chaotic systems with application to Chua’s circuit
Authors: Koofigar Hamid Reza , Sheikholeslam Farid , Hosseinnia Saeed
Published: December 2011

The synchronization problem for a general class of uncertain chaotic systems is addressed. The underlying systems may be perturbed by unknown time-varying parameters, unstructured uncertainties, and external disturbances. Meanwhile, the time-varying parameters and disturbances are neither required to be periodic nor to have known bounds. Assuming the disturbances are L2 signals, an adaptive control incorporated with H∞ control technique is employed to construct a robust adaptive synchronization algorithm. Then, removing such assumption, a novel adaptive-based method is developed to achieve the goal of synchronization. In order to demonstrate the effectiveness of the proposed algorithms, such methods are applied to solve the synchronization problem of uncertain chaotic Chua’s circuits.
Not Exactly like the Phoenix—But Rising all the Same: Reconstructing Displaced Livelihoods in Post-Cleanup Harare
Authors: Kamete Amin Y
Published: December 2011

Studies of displacement often emphasise massive physical dislocation. In this paper, based on a study of displaced youth in Harare, Zimbabwe, I argue for the freeing of the concept from ‘physical uprooting’ and build a case for focusing on in situ displacement and displaced livelihoods. I consider attempts by youth to reconstitute displaced livelihoods in the wake of ‘cleansing’ by the state. I scrutinise evolving recovery tactics in the face of determined efforts by the authorities to repress the ‘filth’, demonstrating that the youth's resistance comprises a myriad of spatialised recovery strategies for dealing with spatialised repression. I argue that it is the mutation of the youth's modes of operation that have enabled them to (re)contaminate and (re)subvert the ‘purified’ spaces.
Molecular data sheds light on the classification of long-legged flies (Diptera:Dolichopodidae)
Authors: Germann Christoph , Wimmer Corinne , Bernasconi Marco Valerio
Published: December 2011

Dolichopodidae (long-legged flies) is the world’s fourth largest dipteran family, but a phylogeny based on a broad global taxon sample is still lacking. We present here a first molecular phylogenetic hypothesis for Dolichopodidae, based on 157 dolichopodid species in 68 genera and 15 subfamilies from the Old and New World, and seven empidoid species (Empididae, Hybotidae) as outgroups. Both relatively fast-evolving mitochondrial markers (COI, 12S, 16S) and a more conserved nuclear marker (18S) were used, the latter being widely employed to study the phylogeny at higher taxonomic levels. We present strong evidence for Microphorinae as sister group to Dolichopodidae sensu stricto, and for the monophyletic Parathalassiinae as part of Dolichopodidae sensu stricto. Monophyly of Achalcinae, Dolichopodinae, and Sciapodinae is supported and Stolidosomatinae are placed within Sympycninae. Diaphorinae, Medeterinae, Neurigoninae, Rhaphiinae, and Sympycninae are paraphyletic, and Hydrophorinae and Peloropeodinae polyphyletic. Our broad taxon sample allows us to gain new insights into the complex systematics of Dolichopodidae. Our results highlight several problems with the traditional classification, which have considerable consequences for the systematic status of some taxa. The poor resolution observed in deep divergences supports previous hypotheses suggesting a rapid early radiation of Dolichopodidae.
Signal transducer and activator of transcription 3 (STAT3) and survivin induction by varicella-zoster virus promote replication and skin pathogenesis
Authors: Sen Nandini , Che Xibing , Rajamani Jaya , Zerboni Leigh , Sung Phillip , Ptacek Jason , Arvin Ann M.
Published: December 2011

Varicella-zoster virus (VZV) is a human α-herpesvirus that causes varicella (chickenpox) during primary infection and zoster (shingles) upon reactivation. Like other viruses, VZV must subvert the intrinsic antiviral defenses of differentiated human cells to produce progeny virions. Accordingly, VZV inhibits the activation of the cellular transcription factors IFN regulatory factor 3 (IRF3) and signal transducers and activators of transcription 1 (STAT1), thereby downregulating antiviral factors, including IFNs. Conversely, in this study, we found that VZV triggers STAT3 phosphorylation in cells infected in vitro and in human skin xenografts in SCID mice in vivo and that STAT3 activation induces the anti-apoptotic protein survivin. Small-molecule inhibitors of STAT3 phosphorylation and survivin restrict VZV replication in vitro, and VZV infection of skin xenografts in vivo is markedly impaired by the administration of the phospho-STAT3 inhibitor S3I-201. STAT3 and survivin are required for malignant transformation caused by γ-herpesviruses, such as Kaposi's sarcoma virus. We show that STAT3 activation is also critical for VZV, a nononcogenic herpesvirus, via a survivin-dependent mechanism. Furthermore, STAT3 activation is critical for the life cycle of the virus because VZV skin infection is necessary for viral transmission and persistence in the human population. Therefore, we conclude that takeover of this major cell-signaling pathway is necessary, independent of cell transformation, for herpesvirus pathogenesis and that STAT3 activation and up-regulation of survivin is a common mechanism important for the pathogenesis of lytic as well as tumorigenic herpesviruses.
Excavating Zarathustra: Ernst Herzfeld'sArchaeological History of Iran
Authors: Jenkins Jennifer
Published: December 2011

This article analyzes the work of the German archaeologist Ernst Herzfeld (1879–1948) and its influence on the writing of Iranian national history in the 1920s and 1930s. Herzfeld's life and work illuminates the relationship between Germany and Iran and between orientalist scholarship and nationalist history in the first half of the twentieth century. Through the method of what he called “archaeological history,” Herzfeld wrote an interdisciplinary history of Iran and its Aryan foundations that contested the assumptions of decades of European orientalist scholarship.
Looking through The Two Eyes of the Earth: A Reassessment of Sasanian Rock Reliefs
Authors: Soudavar Abolala
Published: December 2011

Matthew Canepa's recent study of the cultural and political interactions between Rome and Sasanian Iran, has provided an opportunity to reassess Sasanian rock reliefs in light of the claims and counter claims between these two empires. Since victory over Romans meant a victory over an-Erān, and generated the most potent of all farrs, i.e. the Aryan farr, many rock reliefs were conceived to show its reflection on the king. What is most interesting, though, is the array of nuances that are incorporated in them to account for the differences that were particular to each situation.
Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST
Authors: Zuo G Z , Hu J S , Sun Z , Li J G , Mansfield D K , Cao B , Wu J H , Zakharov L E ,   the EAST Team
Published: December 2011

Reductions in H content and particle recycling are important for the improvement of ion cyclotron range of frequency (ICRF) minority heating efficiency and the enhancement of plasma performance of the EAST superconducting tokamak. During recent years several techniques of surface conditioning such as baking, glow discharge cleaning/ICRF discharge cleaning, surface coatings, such as boronization, siliconization and lithium coating, have all been attempted in order to reduce the H/(H+D) ratio and particle recycling in EAST. Even though boronization and siliconization were both reasonably effective methods to improve plasma performance, lithium coatings were observed to reduce the H content and particle recycling to levels low enough to allow the attainment of enhanced plasma parameters and operating modes on EAST. For example, by accomplishing lithium coating using either vacuum evaporation or the real-time injection of fine lithium powder, the H/(H+D) ratio could be routinely decreased to about 5%, which significantly improved ICRF minority heating efficiency during the autumn campaign of 2010. Due to the reduced H/(H+D) ratio and lower particle recycling, and a reduced H-mode power threshold, improved plasma confinement and the first EAST H-mode plasma were obtained. Furthermore, with increasing accumulation of deposited lithium, several new milestones of EAST performance, such as a 6.4 s-long H-mode, a 100 s-long plasma duration and a 1 MA plasma current, were achieved in the 2010 autumn campaign.
High-yield oil palm expansion spares land at the expense of forests in
the Peruvian Amazon
Authors: Gutiérrez-Vélez Víctor H , DeFries Ruth , Pinedo-Vásquez Miguel , Uriarte María , Padoch Christine , Baethgen Walter , Fernandes Katia , Lim Yili
Published: December 2011

High-yield agriculture potentially reduces pressure on forests by requiring less land
to increase production. Using satellite and field data, we assessed the area
deforested by industrial-scale high-yield oil palm expansion in the Peruvian Amazon
from 2000 to 2010, finding that 72% of new plantations expanded into forested areas.
In a focus area in the Ucayali region, we assessed deforestation for high- and
smallholder low-yield oil palm plantations. Low-yield plantations accounted for most
expansion overall (80%), but only 30% of their expansion involved forest conversion,
contrasting with 75% for high-yield expansion. High-yield expansion minimized the
total area required to achieve production but counter-intuitively at higher expense
to forests than low-yield plantations. The results show that high-yield agriculture
is an important but insufficient strategy to reduce pressure on forests. We suggest
that high-yield agriculture can be effective in sparing forests only if coupled with
incentives for agricultural expansion into already cleared lands.
The mechanisms of microtubule catastrophe and rescue: implications from analysis of a dimer-scale computational model
Authors: Margolin Gennady , Gregoretti Ivan V. , Cickovski Trevor M. , Li Chunlei , Shi Wei , Alber Mark S. , Goodson Holly V.
Published: December 2011

Microtubule (MT) dynamic instability is fundamental to many cell functions, but its mechanism remains poorly understood, in part because it is difficult to gain information about the dimer-scale events at the MT tip. To address this issue, we used a dimer-scale computational model of MT assembly that is consistent with tubulin structure and biochemistry, displays dynamic instability, and covers experimentally relevant spans of time. It allows us to correlate macroscopic behaviors (dynamic instability parameters) with microscopic structures (tip conformations) and examine protofilament structure as the tip spontaneously progresses through both catastrophe and rescue. The model's behavior suggests that several commonly held assumptions about MT dynamics should be reconsidered. Moreover, it predicts that short, interprotofilament “cracks” (laterally unbonded regions between protofilaments) exist even at the tips of growing MTs and that rapid fluctuations in the depths of these cracks influence both catastrophe and rescue. We conclude that experimentally observed microtubule behavior can best be explained by a “stochastic cap” model in which tubulin subunits hydrolyze GTP according to a first-order reaction after they are incorporated into the lattice; catastrophe and rescue result from stochastic fluctuations in the size, shape, and extent of lateral bonding of the cap.
Protein disulfide isomerases contribute differentially to the endoplasmic reticulum–associated degradation of apolipoprotein B and other substrates
Authors: Grubb Sarah , Guo Liang , Fisher Edward A. , Brodsky Jeffrey L.
Published: December 2011

ER-associated degradation (ERAD) rids the early secretory pathway of misfolded or misprocessed proteins. Some members of the protein disulfide isomerase (PDI) family appear to facilitate ERAD substrate selection and retrotranslocation, but a thorough characterization of PDIs during the degradation of diverse substrates has not been undertaken, in part because there are 20 PDI family members in mammals. PDIs can also exhibit disulfide redox, isomerization, and/or chaperone activity, but which of these activities is required for the ERAD of different substrate classes is unknown. We therefore examined the fates of unique substrates in yeast, which expresses five PDIs. Through the use of a yeast expression system for apolipoprotein B (ApoB), which is disulfide rich, we discovered that Pdi1 interacts with ApoB and facilitates degradation through its chaperone activity. In contrast, Pdi1's redox activity was required for the ERAD of CPY* (a misfolded version of carboxypeptidase Y that has five disulfide bonds). The ERAD of another substrate, the alpha subunit of the epithelial sodium channel, was Pdi1 independent. Distinct effects of mammalian PDI homologues on ApoB degradation were then observed in hepatic cells. These data indicate that PDIs contribute to the ERAD of proteins through different mechanisms and that PDI diversity is critical to recognize the spectrum of potential ERAD substrates.
Warmer temperatures reduce the vectorial capacity of malaria mosquitoes
Authors: Paaijmans Krijn P. , Blanford Simon , Chan Brian H. K. , Thomas Matthew B.
Published: December 2011

The development rate of parasites and pathogens within vectors typically increases with temperature. Accordingly, transmission intensity is generally assumed to be higher under warmer conditions. However, development is only one component of parasite/pathogen life history and there has been little research exploring the temperature sensitivity of other traits that contribute to transmission intensity. Here, using a rodent malaria, we show that vector competence (the maximum proportion of infectious mosquitoes, which implicitly includes parasite survival across the incubation period) tails off at higher temperatures, even though parasite development rate increases. We also show that the standard measure of the parasite incubation period (i.e. time until the first mosquitoes within a cohort become infectious following an infected blood-meal) is incomplete because parasite development follows a cumulative distribution, which itself varies with temperature. Including these effects in a simple model dramatically alters estimates of transmission intensity and reduces the optimum temperature for transmission. These results highlight the need to understand the interactive effects of environmental temperature on multiple host-disease life-history traits and challenge the assumptions of many current disease models that ignore this complexity.
Lettuce necrotic yellows cytorhabdovirus protein localization and interaction map, and comparison with nucleorhabdoviruses
Authors: Martin Kathleen M. , Dietzgen Ralf G. , Wang Renyuan , Goodin Michael M.
Published: December 2011

Lettuce necrotic yellows virus (LNYV), Sonchus yellow net virus (SYNV) and Potato yellow dwarf virus (PYDV) are members of the family Rhabdoviridae that infect plants. LNYV is a cytorhabdovirus that replicates in the cytoplasm, while SYNV and PYDV are nucleorhabdoviruses that replicate in the nuclei of infected cells. LNYV and SYNV share a similar genome organization with a gene order of nucleoprotein (N), phosphoprotein (P), putative movement protein (Mv), matrix protein (M), glycoprotein (G) and polymerase (L). PYDV contains an additional predicted gene of unknown function located between N and P. In order to gain insight into the associations of viral structural and non-structural proteins and the mechanisms by which they may function, we constructed protein localization and interaction maps. Subcellular localization was determined by transiently expressing the viral proteins fused to green or red fluorescent protein in leaf epidermal cells of Nicotiana benthamiana. Protein interactions were tested in planta by using bimolecular fluorescence complementation. All three viruses showed Mv to be localized at the cell periphery and the G protein to be membrane associated. Comparing the interaction maps revealed that only the N–P and M–M interactions are common to all three viruses. Associations unique to only one virus include P–M for LNYV, G–Mv for SYNV and M–Mv, M–G and N–M for PYDV. The cognate N–P proteins of all three viruses interacted and exhibited characteristic changes in localization when co-expressed.
Coating Particles with Dextran-Conjugated Fluorescent Dyes or Other Hydrophilic Compounds
Authors: Morgan Josh L. , Kerschensteiner Daniel
Published: December 2011

Imaging and reconstruction of developing neurons require cells that are labeled in a way that distinguishes them from their neighbors. This can be achieved with ballistic labeling, which refers to the delivery of a cell label by means of carrier particles (tungsten or gold) propelled from a pressurized gun. Ballistic delivery can reach many dispersed cells in one shot and can deploy a wide variety of cell markers to neurons in diverse preparations. The three most commonly used types of ballistic labels are carbocyanine dyes, dextran-conjugated fluorescent markers, and DNA plasmids. The primary advantage of ballistic labeling is that multiple dispersed cells can be labeled quickly in live or fixed tissue. This article describes a protocol for coating tungsten particles with dextran-conjugated fluorescent dyes or ion indicators. Such hydrophilic compounds conjugated to dextran are water soluble, and therefore they are excellent indicators for functional studies within living cells. This protocol was developed for labeling ganglion cells in retinal flat mounts.
Production and Harvest of Feline Immunodeficiency Virus-Based Lentiviral Vector from Cells Grown in T75 Tissue-Culture Flasks
Authors: Saenz Dyana T. , Barraza Román , Loewen Nils , Teo Wulin , Poeschla Eric M.
Published: December 2011

Feline immunodeficiency virus (FIV)-based lentiviral vectors are useful for introducing integrated transgenes into nondividing human cells. This protocol describes the production and harvesting of vector from cells grown in T75 tissue-culture flasks. The methods are for production for basic science laboratory use and in vivo experimentation. They do not meet standards for clinical-grade (good manufacturing practice [GMP]) production.
Titration of Feline Immunodeficiency Virus-Based Lentiviral Vector Preparations
Authors: Saenz Dyana T. , Barraza Román , Loewen Nils , Teo Wulin , Poeschla Eric M.
Published: December 2011

Feline immunodeficiency virus (FIV)-based lentiviral vectors are useful for introducing integrated transgenes into nondividing human cells. This protocol describes methods for measuring and calculating vector titers in transducing units (TU)/mL. Alternate methods are provided for green fluorescent protein (GFP) vectors and for β-galactosidase vectors.
Poly[di-μ-aqua-μ-1,2-bis(pyridin-4-yl)ethene-κ2N:N′-tetrakis(4-iodobenzoato-κ2O,O′)dicadmium]
Authors: Liu Dong , Li Ni-Ya
Published: December 2011

Colourless crystals of the title compound, [Cd2(C7H4IO2)4(C12H10N2)(H2O)2]n, were obtained by the self-assembly of Cd(NO3)2·4H2O, 1,2-bis(pyridin-4-yl)ethene (bpe) and 4-iodobenzoic acid (4-IBA). Each CdIIatom is seven-coordinated in a pentagonal–bipyramidal coordination environment by four carboxylate O atoms from two different 4-IBA ligands, two O atoms from two water molecules and one N atom from a bpe ligand. The CdIIcentres are bridged by the aqua molecules and bpe ligands, which lie across centres of inversion, to give a two-dimensional net. Topologically, taking the CdIIatoms as nodes and the μ-aqua and μ-bpe ligands as linkers, the two-dimensional structure can be simplified as a (6,3) network.
A triclinic polymorph ofcyclo-tetra-μ-thiosaccharinato-κ8S:S-tetrakis[(triphenylphosphane-κP)silver(I)]
Authors: Dennehy Mariana , Freire Eleonora , Baggio Ricardo
Published: December 2011

The triclinic structure of the title compound,cyclo-tetrakis(μ-1,1-dioxo-1λ6,2-benzothiazole-3-thiolato-κ2S:S)tetrakis[(triphenylphosphane-κP)silver(I)], [Ag4(C7H4NO2S2)4(C18H15P)4], is a polymorph of the previously reported monoclinic structure [Dennehy, Mandolesi, Quinzani & Jennings (2007).Z. Anorg. Allg. Chem.633, 2746–2752]. In both polymorphs, the complex lies on a crystallographic inversion centre and the bond distances are closely comparable. Some differences can be found in the interatomic angles and torsion angles involving the inner Ag4S4skeleton. The polymorphs contain essentially identical two-dimensional layers, but with different layer stacking arrangements. In the triclinic form, all layers are related by lattice translation, while in the monoclinic form they are arranged around glide planes so that adjacent layers are mirrored with respect to each other.
PbCa2[Al8O15] with a novel three-dimensional aluminate anion
Authors: Artner Christine , Weil Matthias
Published: December 2011

The asymmetric unit of the title compound, lead(II) dicalcium octaaluminate, contains one Pb, one Ca, four Al and eight O atoms, with the Pb atom and one O atom situated on mirror planes. Three Al atoms exhibit slightly distorted tetrahedral coordinations with a mean Al—O bond length of 1.76 Å. The fourth Al atom is in a considerably distorted trigonal–bipyramidal coordination with a mean Al—O bond length of 1.89 Å. One AlO4tetrahedron forms infinite chains parallel to [100]viacorner-sharing. These chains are linked by parallel chains of edge-sharing AlO5trigonal bipyramids into layersAof six-membered double rings extending parallel to (010). The second layerBis made up of the remaining two AlO4tetrahedra. These tetrahedra share corners, resulting in likewise six-membered double rings. Finally, the parallel layersAandBare linked into a three-dimensional framework by common corners. Charge compensation is achieved by the Pb2+and Ca2+cations, which are situated in the cavities of the anionic framework, and which are surrounded by seven and six O atoms, respectively, both within highly irregular coordination polyhedra.
Two succinic acid derivatives of 2-ethyl-6-methylpyridin-3-ol
Authors: Lyakhov Alexander S. , Ivashkevich Ludmila S. , Survilo Vladimir L. , Trukhachova Tatjana V.
Published: December 2011

Crystals of bis(2-ethyl-3-hydroxy-6-methylpyridinium) succinate–succinic acid (1/1), C8H12NO+·0.5C4H4O42−·0.5C4H6O4, (I), and 2-ethyl-3-hydroxy-6-methylpyridinium hydrogen succinate, C8H12NO+·C4H5O4−, (II), were obtained by reaction of 2-ethyl-6-methylpyridin-3-ol with succinic acid. The succinate anion and succinic acid molecule in (I) are located about centres of inversion. Intermolecular O—H...O, N—H...O and C—H...O hydrogen bonds are responsible for the formation of a three-dimensional network in the crystal structure of (I) and a two-dimensional network in the crystal structure of (II). Both structures are additionally stabilized by π–π interactions between symmetry-related pyridine rings, forming a rod-like cationic arrangement for (I) and cationic dimers for (II).
Magnesium chloride tetrahydrate, MgCl2·4H2O
Authors: Schmidt Horst , Hennings Erik , Voigt Wolfgang
Published: December 2011

The title compound, MgCl2·4H2O, was crystallized at 403 K and its structure determined at 200 K. The structure is built up from MgCl2(H2O)4octahedra with atransconfiguration. Each complex is situated on a crystallographic twofold axis, with the rotation axis aligned along one H2O—Mg—OH2axis. They are connected by a complex network of O—H...Cl hydrogen bonds. The structure contains two-dimensional sections that are essentially identical to those in the reported tetrahydrates of CrCl2, FeCl2, FeBr2and CoBr2, but they are stacked in a different manner in MgCl2·4H2O compared with the transition metal structures.
Biological observations on the crocodile shark Pseudocarcharias kamoharai
Authors: Dai X. J. , Zhu J. F. , Chen X. J. , Xu L. X. , Chen Y.
Published: December 2011

Sex ratios and gravid characteristics were analysed for the crocodile shark Pseudocarcharias kamoharai from the tropical eastern Pacific Ocean. Gravid females ranged from 80 to 102 cm fork length (LF). The mode litter size was four (two embryos per uterus), mean embryo length was linearly correlated with maternal length (r = 0·465, n = 32); there was no significant difference in LF between female and male embryos.
Vitamin D and its role in allergic disease
Authors: Reinholz M. , Ruzicka T. , Schauber J.
Published: December 2011

In Western countries, the incidence of atopy and allergic diseases is high and further rising. While genetic factors certainly play a role, epigenetic or even nutritional factors might also be important in the pathogenesis of allergies. Vitamin D – the ‘sunshine hormone’ – exerts profound effects on both adaptive and innate immune functions involved in the development and course of allergic diseases. As also the incidence of vitamin D insufficiency is surprisingly high in the general population, clinical and experimental studies have started to investigate if correcting vitamin D levels [measured as serum 25 hydroxy vitamin D ‐25(OH)D] is beneficial or even protective in patients with allergies or children at risk. This review highlights current data on the effects of vitamin D on the allergy‐mediating immune system and the vitamin D status in atopic patients. Furthermore, the benefits and risks of vitamin D supplementation during pregnancy, childhood and in adults with respect to the development and course of allergic disease are discussed.