bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic anisotropy in the basal plane of the rare-earth ferroborate Nd0.75Dy0.25Fe3(BO3)4
Authors: Zvyagina G. A. , Zhekov K. R. , Zvyagin A. A. , Gudim I. A. , Bilych I. V.
Published: May 2012

The magneto-acoustic behavior of the rare-earth multiferroic Nd0.75Dy0.25Fe3(BO3)4 in external magnetic fields lying in the basal plane of the crystal is studied. The data confirm the existence of a magnetic anisotropy in this plane and of magnetic phase transitions in the crystal caused by this anisotropy. H-T phase diagrams are constructed for the cases H||C2 and H⊥C2.
Reconstruction of the electron-phonon interaction function in Ta, 2H-NbSe2 and MgB2 from spectra of S–c–N microcontacts
Authors: Bobrov N. L. , Fisun V. V. , Kvitnitskaya O. E. , Chernobay V. N. , Yanson I. K.
Published: May 2012

Using Ta, 2H-NbSe2 and MgB2 as an example it is shown that it is possible to reconstruct qualitatively a function of the electron-phonon interaction from microcontact spectra in a superconducting state. The limits and the restrictions of this method are also shown. The results obtained are compared with available literature data.
Phononic and magnetic excitations in the quasi-one-dimensional Heisenberg antiferromagnet KCuF3
Authors: Gnezdilov V. , Deisenhofer J. , Lemmens P. , Wulferding D. , Afanasiev O. , Ghigna P. , Loidl A. , Yeremenko A.
Published: May 2012

The Raman-active phonons and magnetic excitations in the orbitally ordered, quasi one-dimensional Heisenberg antiferromagnet KCuF3 are studied as a function of temperature in the range between 3 and 290 K in different scattering configurations. The low-energy Eg and B1g phonon modes show an anomalous softening (∼25% and ∼13%, respectively) between room temperature and the characteristic temperature TS = 50 K. In this temperature range, a freezing-in of F− ion dynamic displacements is proposed to occur. In addition, the Eg mode at about 260 cm−1 clearly splits below TS. The width of the phonon lines above TS follows an activated behavior with an activation energy of about 50 K. Our observations clearly evidence reduction of the lattice symmetry below TS and indicate strong coupling of lattice, spin, and orbital fluctuations for T > TS. A strongly polarization dependent quasielastic scattering is observed at temperatures above TN = 39 K due to magnetic-energy fluctuations. For temperatures below TN a rich spectrum of additional modes is observed, with different lineshape, polarization and temperature dependence. We attribute them to longitudinal and transverse magnetic modes as well as to a continuum of magnetic excitations.
Kinetics of current formation in a molecular diode
Authors: Petrov E. G. , Leonov V. A. , Shevchenko Ye. V.
Published: May 2012

Using the kinetic theory of electron transport in low-dimensional molecular systems, the establishment of transient and stationary currents in a system “electrode l–molecule–electrode 2” (molecular diode) is studied at different regimes of charge transmission. Within the framework of the HOMO–LUMO molecular model, the case where an electrical current through the system is initiated either by the photoexcitation of the molecule or variation of the inter-electrode bias is analyzed. It is found that inelastic electron tunneling plays a crucial role in the evolution of the molecular electronic states and, as a result, in generating the transmission channels for the hopping (sequential) and direct (tunneling) current components. The effect of inelastic tunneling is particularly pronounced in the case of resonant electron transmission.
Quasi-periodic behavior of ion acoustic solitary waves in electron-ion quantum plasma
Authors: Sahu Biswajit , Poria Swarup , Narayan Ghosh Uday , Roychoudhury Rajkumar
Published: May 2012

The ion acoustic solitary waves are investigated in an unmagnetized electron-ion quantum plasmas. The one dimensional quantum hydrodynamic model is used to study small as well as arbitrary amplitude ion acoustic waves in quantum plasmas. It is shown that ion temperature plays a critical role in the dynamics of quantum electron ion plasma, especially for arbitrary amplitude nonlinear waves. In the small amplitude region Korteweg-de Vries equation describes the solitonic nature of the waves. However, for arbitrary amplitude waves, in the fully nonlinear regime, the system exhibits possible existence of quasi-periodic behavior for small values of ion temperature.
Long range lateral migration of intrinsic point defects in n-type 4H-SiC
Authors: Løvlie L. S. , Vines L. , Svensson B. G.
Published: May 2012

The lateral distributions of intrinsic point defects in n-type (0001) 4H-SiC have been investigated following room temperature irradiation with a focused beam of 10 keV protons. Laterally resolved deep level transient spectroscopy measurements reveal that the well-known and prominent Z1/2 and S1/2 centers display lateral diffusion lenghts on the order of 1 mm with negligible (if any) motion parallel to the direction of the c-axis. The migration occurs only in the presence of excess charge carriers generated during the proton irradiation, and no further motion takes place even under subsequent optical excitation of high intensity. Assuming one-dimensional geometry, an effective defect diffusivity in excess of 10−6 cm2/s is deduced by numerical modelling of the experimental data, corresponding to an energy barrier for migration of ∼0.2 eV. Possible mechanisms for the rapid migration, invoking charge carrier recombination as a necessary condition, are discussed, and especially, an association with the glide of partial dislocations along the (0001) basal plane is scrutinized in some detail.
Charge transport and trap characterization in individual GaSb nanowires
Authors: Xu Wei , Chin Alan , Ye Laura , Ning C. Z. , Yu Hongbin
Published: May 2012

Charge transport of unintentionally doped GaSb nanowires was studied through the fabrication and analysis of nanowire field effect transistors (FETs). In this work, both temperature dependent and voltage dependent measurements demonstrate various operating regimes, including a transition from linear current-voltage behavior at low bias to a space-charge limited current (SCLC) at large bias. Analysis of the voltage and temperature variation in the SCLC regime provided quantitative information about the trap energy distribution in the nanowires, which, after thermal annealing, has been shown to reduce from 0.26 eV to 0.12 eV. The measurements also indicate that the GaSb nanowire FETs exhibit n-type behavior, which is likely due to oxygen impurities in the nanowires.
Composition-crystallinity-property relations in Mg-M-O films
Authors: Saraiva M. , Persoons R. , Depla D.
Published: May 2012

The crystallographic properties such as texture and the level of crystallinity are important issues for the application of thin films. A fundamental understanding of the thin film growth mechanism forms the key to tune these properties. To understand the transition from crystalline-to-amorphous noticed when changing the composition of oxide thin films, Mg-M-O thin films (with M = Al, Cr, Ti, Zr, and Y) were deposited using reactive magnetron sputtering. Because substituting Mg by M yields to vacancy formation, the observed transition can be compared to the crystalline-to-liquid transition noticed in the hard sphere model, when the packing density is changed. The hardness and the bang gap of the Mg-M-O were measured. Using the packing density, it is possible to decouple the influence of the crystallinity from the influence of the composition in the hardness and band gap of the thin films.
Carrier localization and out of plane anisotropic magnetoresistance in Nd0.55−xSmxSr0.45MnO3 thin films
Authors: Srivastava M. K. , Kaur A. , Singh H. K.
Published: May 2012

The impact of carrier localization on the anisotropic magnetoresistance (AMR) has been investigated in Nd0.55−xSmxSr0.45MnO3 (x = 0.00–0.45) thin films. The substitution of smaller Sm3+ cations for larger Nd3+ reduces the average radius of the A-site of the perovskite lattice and enhances size disorder. This quenched disorder results in (1) enhanced Jahn-Teller (J-T) distortion as suggested by decrease in the out of plane lattice constant, (2) stronger carrier localization as evidenced by enhancement in the activation energy of small polaron hopping, (3) decrease in the ferromagnetic (FM) and insulator-metal transition (IMT) temperatures (TC/TIM), (4) sharpening of the IMT, (5) increase in the low field MR, and (6) large enhancement in the AMR. The AMR-T curves of all the films show a maximum just below TIM. The peak AMR measured at small magnetic field of 4.2 kOe increases from −5% for x = 0.00 to −60% for x = 0.45. The enhancement in AMR has been explained in terms of the unquenching of the orbital angular momentum of t2g3 and eg1 configuration and spin fluctuations due to stronger J-T distortion at higher values of x.
Temperature dependent distinct coupling and dispersions of heavy- and light-hole excitonic polaritons in ZnO
Authors: Zheng C. C. , Xu S. J. , Ning J. Q. , Chen Y. N. , Zhang F. , Che C. M.
Published: May 2012

Distinct coupling behavior of heavy- and light-hole excitonic polaritons in ZnO was unveiled by investigating the optical reflectance spectra of a high quality ZnO single crystal as a function of temperature both experimentally and theoretically. A resonance like coupling region was found at a temperature of around 50 K at which several relevant physical quantities such as the transverse exciton transition energy, polarizability, and damping parameters of the two kinds of excitonic polaritons were revealed to overturn. Calculated dispersions correctly reflect the nature of coupled photon and exciton and reproduce the spectral structures of the interacting polaritons.
Spatio-temporal mapping of ablated species in ultrafast laser-produced graphite plasmas
Authors: Al-Shboul K. F. , Harilal S. S. , Hassanein A.
Published: May 2012

We studied the spatial and temporal distributions of ionic, neutral, and molecular species generated by femtosecond laser produced plasma under varying ambient nitrogen gas pressures. Plasmas were generated by irradiating planar graphite targets using 40 fs pulses of 800 nm radiation from a Ti:Sapphire laser. The results show that in the presence of an ambient gas, the molecular species spatial extension and lifetime are directly correlated to the evolution of excited ions. The present studies also provide valuable insights into the evolution history of various species and their excitation during ultrafast laser ablation.
Second harmonic generation in phase matched aluminum nitride waveguides and micro-ring resonators
Authors: Pernice W. H. P. , Xiong C. , Schuck C. , Tang H. X.
Published: May 2012

We demonstrate second order optical nonlinearity in aluminum nitride on insulator substrates. Using sputter-deposited aluminum nitride thin films, we realize nanophotonic waveguides and critically coupled micro-ring resonators that simultaneously support high Q cavity resonant modes for both visible and infrared light. Using phase matched devices, we achieve efficient second-harmonic generation and produce up to 0.55 μW of visible light on the chip with a conversion efficiency of −46 dB with 22 mW input waveguide pump power. From the measured response, we obtain a second order nonlinear susceptibility (χ2) of 4.7 pm/V. Our platform provides a viable route for realizing wideband linear and nonlinear optical devices on a chip.
Transformation of a two-dimensional to one-dimensional energy profile on a spatially deformed Si0.82Ge0.18/Si0.51Ge0.49 wrinkled heterostructure
Authors: Chang Guo-En , Wu K. Y. , Cheng H. H. , Sun G. , Soref R. A.
Published: May 2012

A change in the dimensionality of an energy band in a semiconductor is done by reducing the dimension of its physical size. Here, we show that by spatially deforming a two-layer heterostructure into a wrinkled pattern, the minimum of the energy profile transforms from a two-dimensional plane at the hetero-interface into a one-dimensional path that lies along the wrinkled edge. This change alters the carrier path, causing the carriers to travel along a one-dimensional sinusoidal path, which may lead to an application. The present investigation shows that the dimensionality of the energy profile can be engineered by changing the morphology of the epilayers and provides insight into possible applications of the wrinkled pattern.
Grain boundary effects on defect production and mechanical properties of irradiated nanocrystalline SiC
Authors: Jin Enze , Niu Li-Sha , Lin Enqiang , Song Xiaoxiong
Published: May 2012

Grain boundaries (GBs) are known to play an important role in determining the mechanical and functional properties of nanocrystalline materials. In this study, we used molecular dynamics simulations to investigate the effects of damaged GBs on the mechanical properties of SiC that is irradiated by 10 keV Si atoms. The results reveal that irradiation promotes GB sliding and reduces the ability of GBs to block dislocations, which improves the deformation ability of nanocrystalline SiC. However, irradiation causes local rearrangements in disordered clusters and pinning of dislocations in the grain region, which restrains its deformation. These two mechanisms arise from the irradiation effects on GBs and grains, and these mechanisms compete in nanocrystalline SiC during irradiation. The irradiation effects on GBs dominate at low irradiation doses, and the effects on grains dominate at high doses; the result of these combined effects is a peak ductility of 0.09 dpa in nanocrystalline SiC.
Thermal modulation of birefringence observed in a crystalline molecular gyrotop
Authors: Setaka Wataru , Yamaguchi Kentaro
Published: May 2012

Recently, functional organic materials have been put into practical use. The application of molecular motions has the potential to create new molecule-based materials. For this reason, considerable attention has been focused on the chemistry and properties of molecular machines in which mechanical motions of parts of the molecules are observed. In particular, phenylene rotation in the crystalline state has been investigated using framed molecular gyrotops having a phenylene rotor encased in three long alkyl spokes. In this study, we show thermal modulation of birefringence in a crystal due to the states of dynamic equilibrium of a novel molecular gyrotop. A macrocage molecule having a bridged phenylene rotor was synthesized as a novel molecular gyrotop. Rapid rotation of the phenylene rotor of the molecular gyrotop was confirmed by solid-state
2
H NMR spectroscopy that showed changes in the optical properties of a single crystal, i.e., the thermal modulation of birefringence. These results are the first application of the dynamic states in a crystal causing an optical change. These phenomena were also confirmed by control experiments using a molecular gyrotop with a nonrotating xylene rotor. We anticipate our finding to be a starting point for the creation of a new field of material chemistry that will make use of the dynamic states of molecules.
Revealing the microscale spatial signature of dengue transmission and immunity in an urban population
Authors: Salje Henrik , Lessler Justin , Endy Timothy P. , Curriero Frank C. , Gibbons Robert V. , Nisalak Ananda , Nimmannitya Suchitra , Kalayanarooj Siripen , Jarman Richard G. , Thomas Stephen J. , Burke Donald S. , Cummings Derek A. T.
Published: May 2012

It is well-known that the distribution of immunity in a population dictates the future incidence of infectious disease, but this process is generally understood at individual or macroscales. For example, herd immunity to multiple pathogens has been observed at national and city levels. However, the effects of population immunity have not previously been shown at scales smaller than the city (e.g., neighborhoods). In particular, no study has shown long-term effects of population immunity at scales consistent with the spatial scale of person-to-person transmission. Here, we use the location of dengue patients’ homes in Bangkok with the serotype of the infecting pathogen to investigate the spatiotemporal distribution of disease risk at small spatial scales over a 5-y period. We find evidence for localized transmission at distances of under 1 km. We also observe patterns of spatiotemporal dependence consistent with the expected impacts of homotypic immunity, heterotypic immunity, and immune enhancement of disease at these distances. Our observations indicate that immunological memory of dengue serotypes occurs at the neighborhood level in this large urban setting. These methods have broad applications to studying the spatiotemporal structure of disease risk where pathogen serotype or genetic information is known.
Tafamidis, a potent and selective transthyretin kinetic stabilizer that inhibits the amyloid cascade
Authors: Bulawa Christine E. , Connelly Stephen , DeVit Michael , Wang Lan , Weigel Charlotte , Fleming James A. , Packman Jeff , Powers Evan T. , Wiseman R. Luke , Foss Theodore R. , Wilson Ian A. , Kelly Jeffery W. , Labaudinière Richard
Published: May 2012

The transthyretin amyloidoses (ATTR) are invariably fatal diseases characterized by progressive neuropathy and/or cardiomyopathy. ATTR are caused by aggregation of transthyretin (TTR), a natively tetrameric protein involved in the transport of thyroxine and the vitamin A–retinol-binding protein complex. Mutations within TTR that cause autosomal dominant forms of disease facilitate tetramer dissociation, monomer misfolding, and aggregation, although wild-type TTR can also form amyloid fibrils in elderly patients. Because tetramer dissociation is the rate-limiting step in TTR amyloidogenesis, targeted therapies have focused on small molecules that kinetically stabilize the tetramer, inhibiting TTR amyloid fibril formation. One such compound, tafamidis meglumine (Fx-1006A), has recently completed Phase II/III trials for the treatment of Transthyretin Type Familial Amyloid Polyneuropathy (TTR-FAP) and demonstrated a slowing of disease progression in patients heterozygous for the V30M TTR mutation. Herein we describe the molecular and structural basis of TTR tetramer stabilization by tafamidis. Tafamidis binds selectively and with negative cooperativity (K
d
s ∼2 nM and ∼200 nM) to the two normally unoccupied thyroxine-binding sites of the tetramer, and kinetically stabilizes TTR. Patient-derived amyloidogenic variants of TTR, including kinetically and thermodynamically less stable mutants, are also stabilized by tafamidis binding. The crystal structure of tafamidis-bound TTR suggests that binding stabilizes the weaker dimer-dimer interface against dissociation, the rate-limiting step of amyloidogenesis.
Electronic properties of nanoentities revealed by electrically driven rotation
Authors: Fan D. L. , Zhu Frank Q. , Xu Xiaobin , Cammarata Robert C. , Chien C. L.
Published: May 2012

Direct electric measurement via small contacting pads on individual quasi-one-dimensional nanoentities, such as nanowires and carbon nanotubes, are usually required to access its electronic properties. We show in this work that 1D nanoentities in suspension can be driven to rotation by AC electric fields. The chirality of the resultantrotation unambiguously reveals whether the nanoentities are metal, semiconductor, or insulator due to the dependence of the Clausius–Mossotti factor on the material conductivity and frequency. This contactless method provides rapid and parallel identification of the electrical characteristics of 1D nanoentities.
In vitro microvessels for the study of angiogenesis and thrombosis
Authors: Zheng Ying , Chen Junmei , Craven Michael , Choi Nak Won , Totorica Samuel , Diaz-Santana Anthony , Kermani Pouneh , Hempstead Barbara , Fischbach-Teschl Claudia , López José A. , Stroock Abraham D.
Published: May 2012

Microvascular networks support metabolic activity and define microenvironmental conditions within tissues in health and pathology. Recapitulation of functional microvascular structures in vitro could provide a platform for the study of complex vascular phenomena, including angiogenesis and thrombosis. We have engineered living microvascular networks in three-dimensional tissue scaffolds and demonstrated their biofunctionality in vitro. We describe the lithographic technique used to form endothelialized microfluidic vessels within a native collagen matrix; we characterize the morphology, mass transfer processes, and long-term stability of the endothelium; we elucidate the angiogenic activities of the endothelia and differential interactions with perivascular cells seeded in the collagen bulk; and we demonstrate the nonthrombotic nature of the vascular endothelium and its transition to a prothrombotic state during an inflammatory response. The success of these microvascular networks in recapitulating these phenomena points to the broad potential of this platform for the study of cardiovascular biology and pathophysiology.
Autophagy regulates
Wolbachia
populations across diverse symbiotic associations
Authors: Voronin Denis , Cook Darren A. N. , Steven Andrew , Taylor Mark J.
Published: May 2012

Wolbachia
are widespread and abundant intracellular symbionts of arthropods and filarial nematodes. Their symbiotic relationships encompass obligate mutualism, commensalism, parasitism, and pathogenicity. A consequence of these diverse associations is that
Wolbachia
encounter a wide range of host cells and intracellular immune defense mechanisms of invertebrates, which they must evade to maintain their populations and spread to new hosts. Here we show that autophagy, a conserved intracellular defense mechanism and regulator of cell homeostasis, is a major immune recognition and regulatory process that determines the size of
Wolbachia
populations. The regulation of
Wolbachia
populations by autophagy occurs across all distinct symbiotic relationships and can be manipulated either chemically or genetically to modulate the
Wolbachia
population load. The recognition and activation of host autophagy is particularly apparent in rapidly replicating strains of
Wolbachia
found in somatic tissues of
Drosophila
and filarial nematodes. In filarial nematodes, which host a mutualistic association with
Wolbachia
, the use of antibiotics such as doxycycline to eliminate
Wolbachia
has emerged as a promising approach to their treatment and control. Here we show that the activation of host nematode autophagy reduces bacterial loads to the same magnitude as antibiotic therapy; thus we identify a bactericidal mode of action targeting
Wolbachia
that can be exploited for the development of chemotherapeutic agents against onchocerciasis, lymphatic filariasis, and heartworm.
Molecular interactions in the priming complex of bacteriophage T7
Authors: Kulczyk Arkadiusz W. , Richardson Charles C.
Published: May 2012

The lagging-strand DNA polymerase requires an oligoribonucleotide, synthesized by DNA primase, to initiate the synthesis of an Okazaki fragment. In the replication system of bacteriophage T7 both DNA primase and DNA helicase activities are contained within a single protein, the bifunctional gene 4 protein (gp4). Intermolecular interactions between gp4 and T7 DNA polymerase are crucial for the stabilization of the oligoribonucleotide, its transfer to the polymerase, and its extension by DNA polymerase. We have identified conditions necessary to assemble the T7 priming complex and characterized its biophysical properties using fluorescence anisotropy. In order to reveal molecular interactions that occur during delivery of the oligoribonucleotide to DNA polymerase, we have used four genetically altered gp4 to demonstrate that both the RNA polymerase and the zinc-finger domains of DNA primase are involved in the stabilization of the priming complex and in sequence recognition in the DNA template. We find that the helicase domain of gp4 contributes to the stability of the complex by binding to the ssDNA template. The C-terminal tail of gp4 is not required for complex formation.
Anisotropic magnetoresistance in polycrystalline La0.67(Ca1−xSrx)0.33MnO3
Authors: Liu Yiwei , Yang Zhihuan , Yang Huali , Zou Tao , Xie Yali , Chen Bin , Sun Young , Zhan Qingfeng , Li Run-Wei
Published: May 2012

We investigated the anisotropic magnetoresistance (AMR) effects in polycrystalline La0.67(Ca1−x
Sr
x
)0.33MnO3. An anomalously large AMR of 19.1% was observed near the metal–insulator transition temperature (T
MI) in polycrystalline La0.67Ca0.33MnO3, but slight Sr doping could significantly depress the anomalous AMR around T
MI. By studying the temperature, magnetic field, current direction dependence of AMR and the phase transition process, it was suggested that the anisotropic spin-polarized transport and the demagnetization effect together with the metamagnetic transition around T
MI play important roles in the anomalous AMR effects in polycrystalline perovskite manganites.
CSR expansions of matrix powers in max algebra
Authors: Sergeev Sergeĭ , Schneider Hans
Published: May 2012

We study the behavior of max-algebraic powers of a reducible nonnegative matrix

A
∈

R

+

n
×
n

A\in \mathbb {R}_+^{n\times n}

. We show that for

t
≥
3

n
2

t\geq 3n^2

, the powers

A
t

A^t

can be expanded in max-algebraic sums of terms of the form

C

S
t

R

CS^tR

, where

C
C

and

R
R

are extracted from columns and rows of certain Kleene stars, and

S
S

is diagonally similar to a Boolean matrix. We study the properties of individual terms and show that all terms, for a given

t
≥
3

n
2

t\geq 3n^2

, can be found in

O
(

n
4

log
⁡
n
)

O(n^4\log n)

operations. We show that the powers have a well-defined ultimate behavior, where certain terms are totally or partially suppressed, thus leading to ultimate

C

S
t

R

CS^tR

terms and the corresponding ultimate expansion. We apply this expansion to the question whether

{

A
t

y
,

t
≥
0
}

\{A^ty,\; t\geq 0\}

is ultimately linear periodic for each starting vector

y
y

, showing that this question can also be answered in

O
(

n
4

log
⁡
n
)

O(n^4\log n)

time. We give examples illustrating our main results.
First Report of Gray Leaf Spot on Pepper Caused by Stemphylium solani in Malaysia
Authors: Nasehi A. , Kadir J. B. , Abidin M. A. Zainal , Wong M. Y. , Ashtiani F. Abed
Published: May 2012

Symptoms of gray leaf spot were first observed in June 2011 on pepper (Capsicum annuum) plants cultivated in the Cameron Highlands and Johor State, the two main regions of pepper production in Malaysia (about 1,000 ha). Disease incidence exceeded 70% in severely infected fields and greenhouses. Symptoms initially appeared as tiny (average 1.3 mm in diameter), round, orange-brown spots on the leaves, with the center of each spot turning gray to white as the disease developed, and the margin of each spot remaining dark brown. A fungus was isolated consistently from the lesions using sections of symptomatic leaf tissue surface-sterilized in 1% NaOCl for 2 min, rinsed in sterile water, dried, and plated onto PDA and V8 agar media (3). After 7 days, the fungal colonies were gray, dematiaceous conidia had formed at the end of long conidiophores (19.2 to 33.6 × 12.0 to 21.6 μm), and the conidia typically had two to six transverse and one to four longitudinal septa. Fifteen isolates were identified as Stemphylium solani on the basis of morphological criteria described by Kim et al. (3). The universal primers ITS5 and ITS4 were used to amplify the internal transcribed spacer region (ITS1, 5.8, and ITS2) of ribosomal DNA (rDNA) of a representative isolate (2). A 570 bp fragment was amplified, purified, sequenced, and identified as S. solani using a BLAST search with 100% identity to the published ITS sequence of an S. solani isolate in GenBank (1). The sequence was deposited in GenBank (Accession No. JQ736024). Pathogenicity of the fungal isolate was tested by inoculating healthy pepper leaves of cv. 152177-A. A 20-μl drop of conidial suspension (105 spores/ml) was used to inoculate each of four detached, 45-day-old pepper leaves placed on moist filter papers in petri dishes (4). Four control leaves were inoculated similarly with sterilized, distilled water. The leaves were incubated at 25°C at 95% relative humidity for 7 days. Gray leaf spot symptoms similar to those observed on the original pepper plants began to develop on leaves inoculated with the fungus after 3 days, and S. solani was consistently reisolated from the leaves. Control leaves did not develop symptoms and the fungus was not reisolated from these leaves. Pathogenicity testing was repeated with the same results. To our knowledge, this is the first report of S. solani causing gray leaf spot on pepper in Malaysia.

References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) M. P. S. Camara et al. Mycologia 94:660, 2002. (3) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (4) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002.
Resistance to Foliar Diseases in a Mini-Core Collection of Sorghum Germplasm
Authors: Sharma Rajan , Upadhyaya H. D. , Manjunatha S. V. , Rao V. P. , Thakur R. P.
Published: May 2012

Anthracnose, leaf blight, and rust are important biotic constraints to grain and forage sorghum production worldwide and are best managed through host plant resistance. A sorghum mini-core collection, consisting of 242 germplasm accessions developed from a core collection of 2,246 landrace accessions originating from 58 countries, was evaluated to identify sources of resistance to foliar diseases. The mini-core accessions were evaluated in anthracnose- and leaf-blight-screening nurseries under artificial inoculation in the rainy and late rainy seasons, respectively, during 2009 and 2010. For rust resistance, screening was done under artificial inoculation in the greenhouse as well as in the field under natural infection. In all, 13 accessions were found resistant (score ≤3.0 on a 1-to-9 scale) to anthracnose and 27 to leaf blight in both 2009 and 2010. Six accessions exhibited resistance to rust in both the greenhouse and the field. In the resistant accessions, a wide range of diversity was observed for agronomic traits such as days to 50% flowering, plant height, and grain yield/plant, and morphological characteristics such as grain or glume color, glume coverage, endosperm texture, and panicle type (ear head compactness). Three mini-core accessions (IS 473, IS 23684, and IS 23521) exhibited resistance to all three diseases. These accessions with multiple disease resistance will be useful in sorghum disease resistance breeding programs.
High-frequency electromagnetic non-destructive evaluation for high spatial resolution, using metamaterials
Authors: Grimberg Raimond , Tian Gui-Yun
Published: May 2012

This study presents a new high-frequency electromagnetic method for a non-destructive evaluation of metallic strip gratings from printed circuit boards and of some carbon-fibre-reinforced plastic composites, allowing the detection of small defects. The electromagnetic transducer is based on a metamaterial lens realized with two conical Swiss rolls, that allows the transmission and intensification of purely evanescent modes generated in the slits of metallic strip gratings and in the dielectric that insulate the carbon fibres between them. The method and the transducer used allow the localization of metallic strip interruptions whose widths are greater than 0.2 mm, the non-alignment of carbon fibres, the breaking of carbon fibres, the lack of resin or delaminations due to impact at low energies, with spatial resolution being greater than 0.1 mm.
A quantum
battle of the sexes
cellular automaton
Authors: Alonso-Sanz Ramón
Published: May 2012

The dynamics of a spatial quantum formulation of the iterated
battle of the sexes
game is studied in this work. The game is played in the cellular automata manner, i.e. with local and synchronous interaction. The effect of spatial structure is assessed in the quantum versus quantum players contest as well as in the unfair quantum versus classical players contest. The case of partial entangling is also scrutinized.
Host–parasite coevolution beyond the nestling stage? Mimicry of host fledglings by the specialist screaming cowbird
Authors: De Mársico María C. , Gantchoff Mariela G. , Reboreda Juan C.
Published: May 2012

Egg mimicry by obligate avian brood parasites and host rejection of non-mimetic eggs are well-known textbook examples of host–parasite coevolution. By contrast, reciprocal adaptations and counteradaptations beyond the egg stage in brood parasites and their hosts have received less attention. The screaming cowbird (Molothrus rufoaxillaris) is a specialist obligate brood parasite whose fledglings look identical to those of its primary host, the baywing (Agelaioides badius). Such a resemblance has been proposed as an adaptation in response to host discrimination against odd-looking young, but evidence supporting this idea is scarce. Here, we examined this hypothesis by comparing the survival rates of young screaming cowbirds and non-mimetic shiny cowbirds (Molothrus bonariensis) cross-fostered to baywing nests and quantifying the similarity in plumage colour and begging calls between host and cowbird fledglings. Shiny cowbirds suffered higher post-fledging mortality rates (83%) than screaming cowbirds (0%) owing to host rejection. Visual modelling revealed that screaming cowbirds, but not shiny cowbirds, were indistinguishable from host young in plumage colour. Similarly, screaming cowbirds matched baywings' begging calls more closely than shiny cowbirds. Our results strongly support the occurrence of host fledgling mimicry in screaming cowbirds and suggest a role of visual and vocal cues in fledgling discrimination by baywings.
Socially flexible female choice differs among populations of the Pacific field cricket: geographical variation in the interaction coefficient psi (Ψ)
Authors: Bailey Nathan W. , Zuk Marlene
Published: May 2012

Indirect genetic effects (IGEs) occur when genes expressed in one individual affect the phenotype of a conspecific. Theoretical models indicate that the evolutionary consequences of IGEs critically depend on the genetic architecture of interacting traits, and on the strength and direction of phenotypic effects arising from social interactions, which can be quantified by the interaction coefficientΨ. In the context of sexually selected traits, strong positiveΨtends to exaggerate evolutionary change, whereas negativeΨimpedes sexual trait elaboration. Despite its theoretical importance, whether and howΨvaries among geographically distinct populations is unknown. Such information is necessary to evaluate the potential for IGEs to contribute to divergence among isolated or semi-isolated populations. Here, we report substantial variation inΨfor a behavioural trait involved in sexual selection in the field cricketTeleogryllus oceanicus: female choosiness. Both the strength and direction ofΨvaried among geographically isolated populations.Ψalso changed over time. In a contemporary population of crickets from Kauai, experience of male song increased female choosiness. In contrast, experience of male song decreased choosiness in an ancestral population from the same location. This rapid change corroborates studies examining the evolvability ofΨand demonstrates how interpopulation variation in the interaction coefficient might influence sexual selection and accelerate divergence of traits influenced by IGEs that contribute to reproductive isolation in nascent species or subspecies.
The Effects of Heart and Skeletal Muscle Inflammation and Cardiomyopathy Syndrome on Creatine Kinase and Lactate Dehydrogenase Levels in Atlantic Salmon (Salmo salarL.)
Authors: Yousaf Muhammad Naveed , Powell Mark D.
Published: May 2012

Heart and skeletal muscle inflammation (HSMI) and cardiomyopathy syndrome (CMS) are putative viral cardiac diseases of Atlantic salmon. This study examined the levels and correlated the serum enzymes creatine kinase (CK) and lactate dehydrogenase (LDH) to the histopathology of clinical outbreaks of HSMI and chronic CMS in farmed Atlantic salmon. A total of 75 fish from 3 different HSMI outbreaks, 30 chronic CMS fish, and 68 fish from 3 nondiseased fish groups were used as the study population (N=173). Serum CK and LDH levels correlated significantly with the total inflammation and total necrosis scores for HSMI fish (P=0.001). However, no correlation was identified for enzyme levels and histopathology scores for chronic CMS fish. The significantly increased CK and LDH levels and their positive correlations to histopathology differentiate HSMI from CMS clinically suggesting the potential use of enzymes for screening for HSMI is promising.
Polygenic cis-regulatory adaptation in the evolution of yeast pathogenicity
Authors: Fraser Hunter B. , Levy Sasha , Chavan Arun , Shah Hiral B. , Perez J. Christian , Zhou Yiqi , Siegal Mark L. , Sinha Himanshu
Published: May 2012

The acquisition of new genes, via horizontal transfer or gene duplication/diversification, has been the dominant mechanism thus far implicated in the evolution of microbial pathogenicity. In contrast, the role of many other modes of evolution—such as changes in gene expression regulation—remains unknown. A transition to a pathogenic lifestyle has recently taken place in some lineages of the budding yeast Saccharomyces cerevisiae. Here we identify a module of physically interacting proteins involved in endocytosis that has experienced selective sweeps for multiple cis-regulatory mutations that down-regulate gene expression levels in a pathogenic yeast. To test if these adaptations affect virulence, we created a panel of single-allele knockout strains whose hemizygous state mimics the genes' adaptive down-regulations, and measured their virulence in a mammalian host. Despite having no growth advantage in standard laboratory conditions, nearly all of the strains were more virulent than their wild-type progenitor, suggesting that these adaptations likely played a role in the evolution of pathogenicity. Furthermore, genetic variants at these loci were associated with clinical origin across 88 diverse yeast strains, suggesting the adaptations may have contributed to the virulence of a wide range of clinical isolates. We also detected pleiotropic effects of these adaptations on a wide range of morphological traits, which appear to have been mitigated by compensatory mutations at other loci. These results suggest that cis-regulatory adaptation can occur at the level of physically interacting modules and that one such polygenic adaptation led to increased virulence during the evolution of a pathogenic yeast.
2-Azido-1-(4-nitrophenyl)ethanone
Authors: Yousuf Sammer , Arshad Muhammad , Butt Hafiza Madiha , Saeed Sumayya , Basha Fatima Z.
Published: May 2012

In the title compound, C8H6N4O3, the ketone [C—C(=O)—C] and nitro groups are tilted with respect to the benzene ring by 18.92 (6) and 24.11 (15)°, respectively. In the crystal, molecules are linked into interwoven chains running parallel to the [100] direction by C—H...N hydrogen bonds and weak π–π stacking interactions, with centroid–centroid separations of 3.897 (3) Å.
2-Chloroquinazolin-4(3H)-one
Authors: Cao Dong-Lei , Yan Fan-Yong , Wang Meng , Li Chu-Ying , Chen Li
Published: May 2012

In the title compound, C8H5ClN2O, the quinazoline system is approximately planar with a maximum deviation from the least-squares plane of 0.034 (2) Å. In the crystal, classical N—H...O and weak non-classical C—H...N hydrogen bonds link the molecules.
Poly[[{μ4-2,2′-[butane-1,4-diylbis(sulfanediyl)]bis(1,3,4-thiadiazole)}silver(I)] perchlorate sesquihydrate]
Authors: Li Jia-Jia , Zhu Wei-Min
Published: May 2012

In the polymeric title compound, {[Ag(C8H10N4S4)]ClO4·1.5H2O}
n
, the AgI atom has a slightly distorted trigonal-planar coordination geometry provided by three N-atom donors from the thiadiazole rings of three symmetry-related 2,2′-[butane-1,4-diylbis(sulfanediyl)]bis(1,3,4-thiadiazole) ligands. Centrosymmetrically related AgI atoms are bridged by the N–N fragments of rings, forming six-membered dinuclear metallacycles, which are further linked by the alkyl spacers of the thiadiazole ligands into a layer network extending parallel to (0-21). The crystal structure is stabilized by intermolecular O—H...O hydrogen bonds. The O atoms of the perchlorate anion and one water molecule are disordered over two sets of sites with refined occupancy ratios of 0.640 (6):0.360 (6) and 0.663 (11):0.337 (11), respectively. The second water molecule shows half-occupancy.
Poly[bis(μ6-benzene-1,3,5-tricarboxylato-κ7
O
1,O
1′:O
1′:O
3:O
3′:O
5:O
5′)tetrakis(dimethylformamide-κO)trimagnesium(II)]
Authors: Łuczyńska-Szymczak Katarzyna , Starosta Wojciech , Leciejewicz Janusz
Published: May 2012

The asymmetric unit of the polymeric title compound, [Mg3(C9H3O6)2(C3H7NO)4]
n
, contains three MgII ions bridged by carboxylate O atoms from two fully deprotonated benzene-1,3,5-tricarboxylate (BTC) trianions and four metal-coordinated dimethylformamide (DMF) molecules. One MgII ion is octahedrally coordinated by six carboxylate O atoms. The other two cations are each octahedrally coordinated by four carboxylate O atoms and two O atoms donated by two DMF molecules: in one, the DMF molecules are cis and in the other they are trans. The three MgII octahedra form clusters, which are bridged by the BTC trianions, generating a three-dimensional structure.
N,N,N′,N′-Tetramethyl-N′′,N′′-dipropylguanidinium chloride–(2Z)-2,3-diaminobut-2-enedinitrile (1/1)
Authors: Tiritiris Ioannis , Kantlehner Willi
Published: May 2012

In the crystal structure of the title compound, C11H26N3
+·Cl−·C4H4N4, the (2Z)-2,3-diaminobut-2-ene-dinitrile (Z-DAMN) molecules are connected with the chloride ions via N—H...Cl hydrogen bonds, forming ribbons running along the a axis. The guanidinium ions are located in between the ribbons formed by Z-DAMN molecules and chloride ions.
(E)-3,3,6,6-Tetramethyl-9-(2-nitrostyryl)-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione
Authors: Lee Jae Kyun , Min Sun-Joon , Cho Yong Seo , Lee Ki Soo , Cha Joo Hwan
Published: May 2012

In the title compound, C25H27NO5, each of the cyclohexenone rings adopts a half-chair conformation, whereas the six-membered pyran ring adopts a flattened boat conformation, with the O and methine C atoms deviating from the plane of the other four atoms. In the crystal, weak C—H...O hydrogen bonds link molecules into chains parallel to the c axis.
1-[(3-Nitrophenyl)(piperidin-1-yl)methyl]piperidine
Authors: Wang Zhe-Qin , Ma Yi
Published: May 2012

In the crystal structure of the title compound, C17H25N3O2, one-dimensional chains are formed via intermolecular C—H...O hydrogen bonds along the a axis.
A triclinic polymorph of bis(μ-di-tert-butylphosphanido)bis[(di-tert-butylphosphane)palladium(I)]
Authors: Breunig Jens , Lerner Hans-Wolfram , Bolte Michael
Published: May 2012

A new polymorph of the title compound, [Pd2(C8H18P)2(C8H19P)2], has been found. It belongs to the triclinic P-1 space group, whereas the known form [Leoni, Sommovigo, Pasquali, Sabatino & Braga (1992), J. Organomet. Chem.
423, 263–270] crystallizes in the monoclinic C2/c space group. The title compound features a dinuclear palladium complex with a planar central Pd2(μ-P)2 core (r.m.s. deviation = 0.003 Å). The Pd—Pd distance of 2.5988 (5) Å is within the range of a PdI—PdI bond. The molecules of both polymorphs are located on a crystallographic centre of inversion. The molecular conformations of the two polymorphs are essentially identical. The crystal packing patterns, on the other hand, are slightly different.
2-(3,4-Dimethyl-5,5-dioxo-2H,4H-pyrazolo[4,3-c][1,2]benzothiazin-2-yl)acetic acid
Authors: Aslam Sana , Siddiqui Hamid Latif , Ahmad Matloob , Zia-ur-Rehman Muhammad , Parvez Masood
Published: May 2012

In the title molecule, C13H13N3O4S, the heterocyclic thiazine ring adopts a half-chair conformation in which the S and an adjacent C atom are displaced by 0.919 (3) and 0.300 (4) Å, respectively, on the same side of the mean plane formed by the remaining ring atoms. The mean planes of the benzene and pyrazole rings are inclined at a dihedral angle of 18.32 (12)° with respect to each other. The acetate group is oriented at 80.75 (8)° with respect to the pyrazole ring. The crystal structure is stabilized by O—H...N and C—H...O hydrogen bonds, resulting in fused eight- and seven-membered rings with R
2
2(8) and R
2
2(7) graph-set motifs, respectively.
[μ-Bis(di-o-tolylphosphanyl)methane-1:2κ2
P:P′]nonacarbonyl-1κ3
C,2κ3
C,3κ3
C-[tris(2-chloroethyl) phosphite-3κP]-triangulo-triruthenium(0)
Authors: Shawkataly Omar bin , Khan Imthyaz Ahmed , Sirat Siti Syaida , Quah Ching Kheng , Fun Hoong-Kun
Published: May 2012

In the title compound, [Ru3(C6H12Cl3O3P)(C29H30P2)(CO)9], the bis(di-o-tolylphosphanyl)methane ligand bridges one Ru—Ru bond and the monodentate phosphite ligand bonds to the third Ru atom. Both ligands are equatorial with respect to the Ru3 triangle. Each Ru atom bears one equatorial and two axial terminal carbonyl ligands. The dihedral angles between the two benzene rings in the diphenylphosphanyl groups are 79.52 (10) and 69.88 (10)°. In the crystal, molecules are linked via C—H...O hydrogen bonds into chains along [100].
(5-Benzoyl-2-methyl-4-{[1-(pyridin-4-yl)-1H-1,2,3-triazol-4-yl]methoxy}-1-benzofuran-7-yl)(phenyl)methanone
Authors: Zhang Xiao-qin , Zhang Hai-Liang , Dong Zhu-Yong , Qian Qiang , Wang Yu-Guang
Published: May 2012

The crystal structure of the title compound, C31H22N4O4, features weak C—H...O interactions. The dihedral angle between the fused benzene and furan rings is 2.49 (15)°, while that between the triazole and pyridine rings is 10.23(18)°.
Di-μ-aqua-bis{diaqua[μ-4-({4-[bis(2-hydroxyethyl)amino]-6-chloro-1,3,5-triazin-2-yl}amino)benzenesulfonato]sodium(I)}
Authors: Zhang Mei , Sun Fu-Yu , Zhao Gui-Zhe , Liu Ya-Qing
Published: May 2012

In the dinuclear title compound, [Na2(C13H15ClN5O5S)2(H2O)6]
n
, two Na+ cations, disposed about a centre of inversion, are linked by two bridging water molecules. The coordination geometry is based on an O5 donor set defined by four water molecules and a 4-aminobenzenesulfonate O atom in a distorted trigonal–bipyramidal geometry. In the crystal, significant O—H...O, O—H...N and N—H...O hydrogen bonds lead to the formation of a three-dimensional architecture.
1-Methyl-2-({[(2-methylphenyl)methyl]disulfanyl}methyl)benzene
Authors: Tayamon Shahedeh , Ravoof Thahira Begum S. A. , Tahir Mohamed Ibrahim Mohamed , Crouse Karen A. , Tiekink Edward R. T.
Published: May 2012

In the title disulfide, C16H18S2, the molecule is twisted about the central S—S bond [the C—S—S—C torsion angle = 93.24 (7)°] and the dihedral angle between the benzene rings is 72.84 (7)°, indicating an almost orthogonal relationship; the methyl groups are orientated to the same side of the molecule. The crystal packing features C—H....π interactions which consolidate a three-dimensional architecture.