bluuebunny/crossref_metadata_2025 huggingface dataset:
Flickering dipoles in the gas phase: Structures, internal dynamics, and dipole moments of β-naphthol-H2O in its ground and excited electronic states
Authors: Fleisher Adam J. , Young Justin W. , Pratt David W. , Cembran Alessandro , Gao Jiali
Published: March 2011

Described here are the rotationally resolved S1–S0 electronic spectra of the acid–base complex cis-β-naphthol-H2O in the gas phase, both in the presence and absence of an applied electric field. The data show that the complex has a trans-linear O − H⋅⋅⋅O hydrogen bond configuration involving the −OH group of cis-β-naphthol and the oxygen lone pairs of the attached water molecule in both electronic states. The measured permanent electric dipole moments of the complex are 4.00 and 4.66 D in the S0 and S1 states, respectively. These reveal a small amount of photoinduced charge transfer between solute and solvent, as supported by density functional theory calculations and an energy decomposition analysis. The water molecule also was found to tunnel through a barrier to internal motion nearly equal in energy to kT at room temperature. The resulting large angular jumps in solvent orientation produce “flickering dipoles” that are recognized as being important to the dynamics of bulk water.
Transient surface photovoltage in n- and p-GaN as probed by x-ray photoelectron spectroscopy
Authors: Sezen Hikmet , Ozbay Ekmel , Aktas Ozgur , Suzer Sefik
Published: March 2011

Transient surface photovoltage (SPV) of n and p-GaN was measured using x-ray photoelectron spectroscopy (XPS) with a time resolution of 0.1 s. The measured SPV transients for both n- and p-GaN are ⪡0.1 s, and for the n-GaN they are not affected by flood-gun electrons. However, for the p-GaN, the transient character of the SPV is dramatically changed in the presence of flood-gun electrons. The combination of time-resolved XPS, flood gun, and laser illumination give us a new way to study the surface electronic structure and other surface properties of semiconducting materials in a chemically specific fashion.
The spatiotemporal oscillation characteristics of the dielectric wall sheath in stationary plasma thrusters
Authors: Zhang Fengkui , Yu Daren , Ding Yongjie , Li Hong
Published: March 2011

A two-dimensional particle in cell model is used to simulate the sheath oscillation in stationary plasma thrusters. The embedded secondary electron emission (SEE) submodel is based on that of Morozov but improved by considering the electron elastic reflection effect. The simulation results show that when the SEE coefficient is smaller than one due to the relative low electron temperature, one-dimensional static sheath can be found; as the electron temperature increase, the SEE coefficient approaches to one and temporal oscillation sheath appears; when the electron temperature increases so high that the SEE coefficient is beyond one, the sheath oscillates not only in time but also in space.
Surfactant mediated growth of Ti/Ni multilayers
Authors: Gupta Mukul , Amir S. M. , Gupta Ajay , Stahn Jochen
Published: March 2011

The surfactant mediated growth of Ti/Ni multilayers is studied. They were prepared using ion beam sputtering at different adatom energies. It was found that the interface roughness decreased significantly when the multilayers were sputtered with Ag as surfactant at an ion energy of 0.75 keV. On the other hand, when the ion energy was increased to 1 keV, it resulted in enhanced intermixing at the interfaces and no appreciable effect of Ag surfactant could be observed. On the basis of the obtained results, the influence of adatom energy on the surfactant mediated growth mechanism is discussed.
Heterogeneous condensation of the Lennard-Jones vapor onto a nanoscale seed particle
Authors: Inci Levent , Bowles Richard K.
Published: March 2011

The heterogeneous condensation of a Lennard-Jones vapor onto a nanoscale seed particle is studied using molecular dynamics simulations. Measuring the nucleation rate and the height of the free energy barrier using the mean first passage time method shows that the presence of a weakly interacting seed has little effect on the work of forming very small cluster embryos but accelerates the rate by lowering the barrier for larger clusters. We suggest that this results from a competition between the energetic and entropic features of cluster formation in the bulk and at the heterogeneity. As the interaction is increased, the free energy of formation is reduced for all cluster sizes. We also develop a simple phenomenological model of film formation on a small seed that captures the general features of the nucleation process for small heterogeneities. A comparison of our simulation results with the model shows that heterogeneous classical nucleation theory provides a good estimate of the critical size of the film but significantly overestimates the size of the barrier.
Fermi level pinning by integer charge transfer at electrode-organic semiconductor interfaces
Authors: Bokdam Menno , Çakır Deniz , Brocks Geert
Published: March 2011

The atomic structure of interfaces between conducting electrodes and molecular organic materials varies considerably. Yet experiments show that pinning of the Fermi level, which is observed at such interfaces, does not depend upon the structural details. In this letter, we develop a general model to explain Fermi level pinning, and formulate simple expressions for the pinning levels, based upon integer charge transfer between the conductor and the molecular layer. In particular, we show that DFT calculations give good values for the pinning levels.
Closed-form expression for the scattering coefficients at an interface between two periodic media
Authors: Śmigaj W. , Lalanne P. , Yang J. , Paul T. , Rockstuhl C. , Lederer F.
Published: March 2011

We use the Bloch-mode orthogonality to derive simple closed-form expressions for the scattering coefficients at an interface between two periodic media, a computationally-challenging electromagnetic scattering problem that can be solved only with advanced numerical tools. The derivation relies on the assumptions that the interface is illuminated by the fundamental Bloch mode and that the two media have only slightly different geometrical parameters. Through comparison with fully-vectorial three-dimensional computations, the analytical expressions are shown to be highly predictive for various geometries, including dielectric waveguides and metallic metamaterials. They can thus be used with confidence for designing and engineering stacks of periodic structures.
Near-field radiative transfer based thermal rectification using doped silicon
Authors: Basu Soumyadipta , Francoeur Mathieu
Published: March 2011

In this letter, we have designed a near-field thermal rectifier using a film and a bulk of doped silicon, with different doping levels, separated by a vacuum gap. We examine the origin of nonlinearities in thermal rectification associated with near-field heat transfer, and investigate closely the effects of varying the vacuum gap and the film thickness on rectification. For a 10 nm thick film, rectification greater than 0.5 is achieved for vacuum gaps varying from 1 nm to 50 nm with the hot and cold temperatures of the terminals of the rectifier being 400 K and 300 K, respectively. The results obtained from this study may benefit future research in thermal management and energy harvesting.
Flow control concepts for thread-based microfluidic devices
Authors: Ballerini David R. , Li Xu , Shen Wei
Published: March 2011

The emerging concept of thread-based microfluidics has shown great promise for application to inexpensive disease detection and environmental monitoring. To allow the creation of more sophisticated and functional thread-based sensor designs, the ability to better control and understand the flow of fluids in the devices is required. To meet this end, various mechanisms for controlling the flow of reagents and samples in thread-based microfluidic devices are investigated in this study. A study of fluid penetration in single threads and in twined threads provides greater practical understanding of fluid velocity and ultimate penetration for the design of devices. “Switches” which control when or where flow can occur, or allow the mixing of multiple fluids, have been successfully prototyped from multifilament threads, plastic films, and household adhesive. This advancement allows the fabrication of more functional sensory devices which can incorporate more complex detection chemistries, while maintaining low production cost and simplicity of construction.
Novel method of generating water-in-oil(W/O) droplets in a microchannel with grooved walls
Authors: Kim Jihoon , Byun Doyoung , Hong Jongin
Published: March 2011

We present a novel method of generating and retrieving droplets stored in microfluidic grooves or cavity structures. First we designed and fabricated polydimethylsiloxane microchannels with grooves on the walls and then produced a two-phase flow of oil and aqueous phases to form aqueous phase droplets in an oil state. We propose the following three mechanisms of droplet generation: the contact line on the groove wall continues moving along the wall and descends to the bottom of the cavity, confining the aqueous phase in the cavity; once the interface between the oil and aqueous phases moves into the cavity, the interface contacts the top of the neighboring groove; and a spherical droplet forms at the corner in the cavity due to surface tension. The viscosity of the oil phase and the surface tension of the interface determine whether a droplet can be generated. Then, we could adjust the velocity of the interface and the aspect ratio of the cavity to achieve the optimal conditions for generating the single droplet. We observed that the largest droplet is stably generated without a daughter droplet at typical values of free-stream velocity (10 μl/min) and groove pitch 110 μm for all three cases with different oil phases (20, 50, and 84 cP). This technique is expected to serve as a platform for droplet-based reaction systems, particularly with regard to monitoring cell behavior, in vitro expression, and possibly even micropolymerase chain reaction chambers.
Responses to historical climate change identify contemporary threats to diversity in
Dodecatheon
Authors: Oberle Brad , Schaal Barbara A.
Published: March 2011

Anthropogenic climate change may threaten many species with extinction. However, species at risk today survived global climate change in recent geological history. Describing how habitat tracking and adaptation allowed species to survive warming since the end of the Pleistocene can indicate the relative importance of dispersal and natural selection during climate change. By taking this historical perspective, we can identify how contemporary climate change could interfere with these mechanisms and threaten the most vulnerable species. We focused on a group of closely related plant species in the genus
Dodecatheon
(Primulaceae) in eastern North America. Two rare species (
Dodecatheon amethystinum
and
Dodecatheon frenchii
) that are endemic to patchy cool cliffs may be glacial relicts whose ranges constricted following the last glacial maximum. Alternatively, these species may be extreme ecotypes of a single widespread species (
Dodecatheon meadia
) that quickly adapted to microclimatic differences among habitats. We test support for these alternative scenarios by combining ecophysiological and population genetic data at a regional scale. An important ecophysiological trait distinguishes rare species from
D. meadia
, but only a few northern populations of
D. amethystinum
are genetically distinctive. These relict populations indicate that habitat tracking did occur with historical climate change. However, relatively stronger evidence for isolation by distance and admixture suggests that local adaptation and genetic introgression have been at least as important. The complex response of
Dodecatheon
to historical climate change suggests that contemporary conservation efforts should accommodate evolutionary processes, in some cases by restoring genetic connectivity between ecologically differentiated populations.
Receptor activator of NF-κB (RANK) stimulates the proliferation of epithelial cells of the epidermo-pilosebaceous unit
Authors: Duheron Vincent , Hess Estelle , Duval Monique , Decossas Marion , Castaneda Beatriz , Klöpper Jennifer E. , Amoasii Leonela , Barbaroux Jean-Baptiste , Williams Ifor R. , Yagita Hideo , Penninger Josef , Choi Yongwon , Lézot Frédéric , Groves Richard , Paus Ralf , Mueller Christopher G.
Published: March 2011

Receptor activator of NF-κB (RANK), known for controlling bone mass, has been recognized for its role in epithelial cell activation of the mammary gland. Because bone and the epidermo-pilosebaceous unit of the skin share a lifelong renewal activity where similar molecular players operate, and because mammary glands and hair follicles are both skin appendages, we have addressed the function of RANK in the hair follicle and the epidermis. Here, we show that mice deficient in RANK ligand (RANKL) are unable to initiate a new growth phase of the hair cycle and display arrested epidermal homeostasis. However, transgenic mice overexpressing RANK in the hair follicle or administration of recombinant RANKL both activate the hair cycle and epidermal growth. RANK is expressed by the hair follicle germ and bulge stem cells and the epidermal basal cells, cell types implicated in the renewal of the epidermo-pilosebaceous unit. RANK signaling is dispensable for the formation of the stem cell compartment and the inductive hair follicle mesenchyme, and the hair cycle can be rescued by
Rankl
knockout skin transplantation onto
nude
mice. RANKL is actively transcribed by the hair follicle at initiation of its growth phase, providing a mechanism for stem cell RANK engagement and hair-cycle entry. Thus, RANK–RANKL regulates hair renewal and epidermal homeostasis and provides a link between these two activities.
Homozygous mutation in
SAMHD1
gene causes cerebral vasculopathy and early onset stroke
Authors: Xin Baozhong , Jones Stephen , Puffenberger Erik G. , Hinze Claas , Bright Alicia , Tan Haiyan , Zhou Aimin , Wu Guiyun , Vargus-Adams Jilda , Agamanolis Dimitris , Wang Heng
Published: March 2011

We describe an autosomal recessive condition characterized with cerebral vasculopathy and early onset of stroke in 14 individuals in Old Order Amish. The phenotype of the condition was highly heterogeneous, ranging from severe developmental disability to normal schooling. Cerebral vasculopathy was a major hallmark of the condition with a common theme of multifocal stenoses and aneurysms in large arteries, accompanied by chronic ischemic changes, moyamoya morphology, and evidence of prior acute infarction and hemorrhage. Early signs of the disease included mild intrauterine growth restriction, infantile hypotonia, and irritability, followed by failure to thrive and short stature. Acrocyanosis, Raynaud’s phenomenon, chilblain lesions, low-pitch hoarse voice, glaucoma, migraine headache, and arthritis were frequently observed. The early onset or recurrence of strokes secondary to cerebral vasculopathy seems to always be associated with poor outcomes. The elevated erythrocyte sedimentation rate (ESR), IgG, neopterin, and TNF-α found in these patients suggested an immune disorder. Through genomewide homozygosity mapping, we localized the disease gene to chromosome (Chr) 20q11.22-q12. Candidate gene sequencing identified a homozygous mutation, c.1411–2A > G, in the
SAMHD1
gene, being associated with this condition. The mutation appeared at the splice-acceptor site of intron 12, resulted in the skipping of exon 13, and gave rise to an aberrant protein with in-frame deletion of 31 amino acids. Immunoblotting analysis showed lack of mutant SAMHD1 protein expression in affected cell lines. The function of SAMHD1 remains unclear, but the inflammatory vasculopathies of the brain found in the patients with
SAMHD1
mutation indicate its important roles in immunoregulation and cerebral vascular hemeostasis.
Compensatory network changes in the dentate gyrus restore long-term potentiation following ablation of neurogenesis in young-adult mice
Authors: Singer Benjamin H. , Gamelli Amy E. , Fuller Cynthia L. , Temme Stephanie J. , Parent Jack M. , Murphy Geoffrey G.
Published: March 2011

It is now well established that neurogenesis in the rodent subgranular zone of the hippocampal dentate gyrus continues throughout adulthood. Neuroblasts born in the dentate subgranular zone migrate into the granule cell layer, where they differentiate into neurons known as dentate granule cells. Suppression of neurogenesis by irradiation or genetic ablation has been shown to disrupt synaptic plasticity in the dentate gyrus and impair some forms of hippocampus-dependent learning and memory. Using a recently developed transgenic mouse model for suppressing neurogenesis, we sought to determine the long-term impact of ablating neurogenesis on synaptic plasticity in young-adult mice. Consistent with previous reports, we found that ablation of neurogenesis resulted in significant deficits in dentate gyrus long-term potentiation (LTP) when examined at a time proximal to the ablation. However, the observed deficits in LTP were not permanent. LTP in the dentate gyrus was restored within 6 wk and this recovery occurred in the complete absence of neurogenesis. The recovery in LTP was accompanied by prominent changes within the dentate gyrus, including an increase in the survival rate of newborn cells that were proliferating just before the ablation and a reduction in inhibitory input to the granule cells of the dentate gyrus. These findings suggest that prolonged suppression of neurogenesis in young-adult mice results in wide-ranging compensatory changes in the structure and dynamics of the dentate gyrus that function to restore plasticity.
Innate immune genes synergize to predict increased risk of chronic disease in hepatitis C virus infection
Authors: Dring Megan M. , Morrison Maria H. , McSharry Brian P. , Guinan Kieran J. , Hagan Richard ,   Irish HCV Research Consortium, O'Farrelly Cliona , Gardiner Clair M. , Courtney Gary , Crosbie Orla , Crowe John , Hegarty John , Kelleher Dermot , Lawlor Emer , Lee John , McKiernan Susan , Murray Frank , Norris Suzanne , O'Farrelly Cliona , Thornton Leila
Published: March 2011

Hepatitis C is a common infection with significant morbidity and mortality, and only a minority of patients successfully clear the infection. Identification of factors that influence disease progression in HCV infection is difficult owing to the lack of well-defined patient cohorts. However, recent evidence supports a role for the innate immune system in virus clearance. In this study, we investigated innate immune genes for their contribution to disease progression in a unique cohort of well-controlled HCV-infected patients. The Irish cohort of HCV patients is uniquely homogenous; patients were infected with a single genotype of HCV from contaminated anti-D Ig. We genotyped 543 infected patients, including 247 patients who spontaneously resolved infection, for natural killer (NK) cell-associated killer cell Ig-like receptors (KIR) genes and the recently reportedIL28B (IFNλ3)SNP. The NK cell geneKIR2DS3was significantly increased in patients with chronic infection [odds ratio (OR) 1.90, 95% confidence interval (CI) 1.25–2.90,P< 0.002]. TheIL28B“T” allele was also significantly increased in chronically infected patients (OR 7.38, 95% CI 4.93–11.07,P< 10−8). The presence of both markers synergized to significantly increase the risk of chronic infection over either factor alone (OR 20.11, 95% CI 9.05–44.68,P< 10−7). In functional experiments, we found that IL28A significantly inhibited IFN-γ production by NK cells. Thus, we demonstrate a functional link between NK cells and type 3 IFN. Our findings may contribute to the development of a prognostic test for HCV and identify therapeutic strategies for the clinical management of HCV-infected patients.
Chiral symmetry breaking by spatial confinement in tactoidal droplets of lyotropic chromonic liquid crystals
Authors: Tortora Luana , Lavrentovich Oleg D.
Published: March 2011

In many colloidal systems, an orientationally ordered nematic (N) phase emerges from the isotropic (I) melt in the form of spindle-like birefringent tactoids. In cases studied so far, the tactoids always reveal a mirror-symmetric nonchiral structure, sometimes even when the building units are chiral. We report on chiral symmetry breaking in the nematic tactoids formed in molecularly nonchiral polymer-crowded aqueous solutions of low-molecular weight disodium cromoglycate. The parity is broken by twisted packing of self-assembled molecular aggregates within the tactoids as manifested by the observed optical activity. Fluorescent confocal microscopy reveals that the chiral N tactoids are located at the boundaries of cells. We explain the chirality induction as a replacement of energetically costly splay packing of the aggregates within the curved bipolar tactoidal shape with twisted packing. The effect represents a simple pathway of macroscopic chirality induction in an organic system with no molecular chirality, as the only requirements are orientational order and curved shape of confinement.
Parasiticidal effects of peroxynitrite on ovine liver flukes in vitro
Authors: Sadeghi-Hashjin G. , Naem S.
Published: March 2011

Peroxynitrite (ONOO-) is a cytotoxic anion, produced by interaction between nitric oxide and superoxide in vivo in some inflammatory cells. This study investigated its effects on Fasciola hepatica and Dicrocoelium dendriticum isolated from ovine livers and kept in bile at room temperature. Peroxynitrite was synthesized using a quenched flow reactor and assayed spectrophotometrically. It was applied at different concentrations (10-3.5 to 10-2.3 M) to the flukes kept in bile. The viability of the peroxynitrite-treated flukes was compared with a control group (n=5–7 per group). Control F. hepatica and D. dendriticum lived for 226±11 and 208±14 min, respectively. Life times were decreased by peroxynitrite at all concentrations used (P<0.001). At the highest concentration of peroxynitrite, F. hepatica and D. dendriticum lived only for 6.1±0.4 and 4.1±4.1±0.2 min, respectively. Correlation between peroxynitrite concentration and parasite viability was significant in the case of F. hepatica (r=-0.842; P=0.0035). A single application of peroxynitrite can decrease the life span of ovine liver flukes. A failure in the activation of hepatic macrophages in infected animals may lead to a decreased production of free radicals and, thus, peroxynitrite. Such a failure is likely to deprive the body of a defence tool against multicellular parasites.
Genetic diversity within the genus Trichinella as shown by cleavage fragment length polymorphism analysis
Authors: Rombout Y.B. , Bosch S. , Mandjes B. , Homan W , van der Giessen J.W.B.
Published: March 2011

The genetic diversity within the genus Trichinella was studied using cleavage fragment length polymorphism (CFLP) analysis. The CFLP method generates specific fingerprints based on single nucleotide mutations. By this method the amplified intergenic regions of the 5S rRNA genes of the eight different genotypes of Trichinella were analysed. The CFLP pattern of T. spiralis was completely different compared with the sylvatic species T. britovi, T. nativa, T. nelsoni, and the genotypes Trichinella T5, Trichinella T6 and Trichinella T8. The T. pseudospiralis intergenic region can be differentiated by size from the other species of Trichinella.
Assortative mating in morningness–eveningness
Authors: Randler Christoph , Kretz Stefanie
Published: March 2011

Individuals differ in their morningness–eveningness preference (circadian preference); that is, some prefer morning hours for intellectual and physical activities and others prefer late afternoon or evening hours. This has been viewed as an interesting facet of personality. Assortative mating has been studied in personality research, but assortative mating in circadian preference has rarely been examined. Eighty‐four couples participated in this study. They filled in the Composite Scale of Morningness; they also supplied data about rise times and bedtimes as well as information about relationship satisfaction and duration. The results revealed a moderate positive relationship between couple partners in morningness–eveningness which persisted after correcting for age. Similarly, correlations existed between the sleep–wake variables (rise time and bedtime) on weekdays and on the weekends, the association being higher for weekends. There was no significant correlation between length of the relationship and dissimilarity in morningness–eveningness, suggesting that the above‐reported correlations reflect an initial assortment rather than convergence effects. Further, no significant correlation was found between dissimilarity in morningness–eveningness and relationship satisfaction. The results suggest that assortative mating in morningness–eveningness is likely and is probably based on an initial assortment. The likelihood to meet and mate may also be linked to chronotype. When differences in circadian preferences exist between possible partners, this reduces the likelihood that these persons meet either by accident or during work and leisure activities. Therefore, two extreme chronotypes are unlikely to meet each other because they have the smallest overlap in their preferred active time during the day due to the circadian rhythmicity.
Phosphatidylserine is a critical modulator for Akt activation
Authors: Huang Bill X. , Akbar Mohammed , Kevala Karl , Kim Hee-Yong
Published: March 2011

Akt activation relies on the binding of Akt to phosphatidylinositol-3,4,5-trisphosphate (PIP3) in the membrane. Here, we demonstrate that Akt activation requires not only PIP3 but also membrane phosphatidylserine (PS). The extent of insulin-like growth factor–induced Akt activation and downstream signaling as well as cell survival under serum starvation conditions positively correlates with plasma membrane PS levels in living cells. PS promotes Akt-PIP3 binding, participates in PIP3-induced Akt interdomain conformational changes for T308 phosphorylation, and causes an open conformation that allows for S473 phosphorylation by mTORC2. PS interacts with specific residues in the pleckstrin homology (PH) and regulatory (RD) domains of Akt. Disruption of PS–Akt interaction by mutation impairs Akt signaling and increases susceptibility to cell death. These data identify a critical function of PS for Akt activation and cell survival, particularly in conditions with limited PIP3 availability. The novel molecular interaction mechanism for Akt activation suggests potential new targets for controlling Akt-dependent cell survival and proliferation.
Herpesvirus entry mediator (TNFRSF14) regulates the persistence of T helper memory cell populations
Authors: Soroosh Pejman , Doherty Taylor A. , So Takanori , Mehta Amit Kumar , Khorram Naseem , Norris Paula S. , Scheu Stefanie , Pfeffer Klaus , Ware Carl , Croft Michael
Published: March 2011

Memory T helper cells (Th cells) play an important role in host defense against pathogens but also contribute to the pathogenesis of inflammatory disorders. We found that a soluble decoy lymphotoxin β receptor (LT-βR)–Fc, which can block tumor necrosis factor (TNF)–related ligands LIGHT (TNFSF14) and LT-αβ binding to the herpesvirus entry mediator (HVEM) and the LT-βR, inhibited the accumulation of memory Th2 cells after antigen encounter and correspondingly reduced inflammatory responses in vivo. Showing that this was a function of the receptor for LIGHT, antigen-specific memory CD4 T cells deficient in HVEM were also unable to persist, despite having a normal immediate response to recall antigen. HVEM−/− memory Th2 cells displayed reduced activity of PKB (protein kinase B; Akt), and constitutively active Akt rescued their survival and restored strong inflammation after antigen rechallenge. This was not restricted to Th2 memory cells as HVEM-deficient Th1 memory cells were also impaired in surviving after encounter with recall antigen. Furthermore, the absence of LIGHT on T cells recapitulated the defect seen with the absence of HVEM, suggesting that activated T cells communicate through LIGHT–HVEM interactions. Collectively, our results demonstrate a critical role of HVEM signals in the persistence of large pools of memory CD4 T cells.
Thermal conductivity and contact resistance of metal foams
Authors: Sadeghi E , Hsieh S , Bahrami M
Published: March 2011

Accurate information on heat transfer and temperature distribution in metal foams is necessary for design and modelling of thermal-hydraulic systems incorporating metal foams. The analysis of heat transfer requires determination of the effective thermal conductivity as well as the thermal contact resistance (TCR) associated with the interface between the metal foam and the adjacent surfaces/layers. In this study, a test bed that allows the separation of effective thermal conductivity and TCR in metal foams is described. Measurements are performed in a vacuum under varying compressive loads using ERG Duocel aluminium foam samples with different porosities and pore densities. Also, a graphical method associated with a computer code is developed to demonstrate the distribution of contact spots and estimate the real contact area at the interface. Our results show that the porosity and the effective thermal conductivity remain unchanged with the variation of compression in the range 0–2 MPa; but TCR decreases significantly with pressure due to an increase in the real contact area at the interface. Moreover, the ratio of real to nominal contact area varies between 0 and 0.013, depending upon the compressive force, porosity, pore density and surface characteristics.
Geometrical nonlinear free vibration of multi-layered graphene sheets
Authors: Wang Jinbao , He Xiaoqiao , Kitipornchai S , Zhang Hongwu
Published: March 2011

A nonlinear continuum model is developed for the nonlinear vibration analysis of multi-layered graphene sheets (MLGSs), in which the nonlinear van der Waals (vdW) interaction between any two layers is formulated explicitly. The nonlinear equations of motion are studied by the harmonic-balance methods. Based on the present model, the nonlinear stiffened amplitude–frequency relations of double-layered graphene sheets (DLGSs) are investigated in the spectral neighbourhood of lower frequencies. The influence of the vdW interaction on the vibration properties of DLGSs is well illustrated by plotting the resulting modes' shapes, in which in-phase and anti-phase vibrations of DLGSs are studied. In particular, the large-amplitude vibration which associates with the anti-phase resonant frequencies, separating DLGS into single-layered GSs, is a promising application that needs to be explored further. In contrast, the vibration modes that are associated with the resonant frequencies are nonidentical and give various vibration patterns, which indicates that MLGSs are highly suited to being used as high-frequency resonators.
High-energy neutrino astronomy: detection methods and first achievements
Authors: Baret B , Van Elewyck V
Published: March 2011

In the last century, astronomy evolved from optical observation to the multi-wavelength study of celestial objects from radio waves up to x- and γ-rays, leading to a wealth of new discoveries and opening the way to high-energy astroparticle physics. In particular, the recent success of ground-based very-high-energy γ-ray telescopes has opened a new window on the most powerful and violent objects of the Universe, giving a new insight into the physical processes at work in such sources. In the context of high-energy astronomy, neutrinos constitute a unique probe since they escape from their sources, travel undisturbed on virtually cosmological distances and are produced in high-energy hadronic processes. In particular they would allow a direct detection and unambiguous identification of the sites of acceleration of high-energy baryonic cosmic rays, which remain unknown. This report discusses the physics potential of the domain and reviews the experimental techniques relevant for the detection of high-energy (⩾TeV) neutrinos. The results obtained by the first generation of such detectors are presented, along with the perspectives opened by new projects and prototypes being currently developed.
Properties of solutions of a class of planar elliptic operators with degeneracies
Authors: da Silva P. , Meziani A.
Published: March 2011

In this paper we investigate properties of solutions of first and second order elliptic equations that degenerate along a simple closed curve in

R

2

\mathbb {R}^2

. These equations are generated by a

C

\mathbb {C}

-valued vector field

L
L

. To the vector field

L
L

, we associate the second order operator

P

=

R
e

[
L

L
¯

+
p
L
]

\mathbb {P}=\mathrm {Re}\left [L\overline {L}+p L \right ]

, where

p
p

is a

C

\mathbb {C}

-valued function. We establish a one-to-one correspondence between the solutions of the equation

P

u
=
0

\mathbb {P}u=0

and those of an associated first order equation of type

L
w
=
A
w
+
B

w
¯

Lw=Aw+B\overline {w}

.
An 𝑂̃(log²(𝑁)) time primality test for generalized Cullen numbers
Authors: Grau José , Oller-Marcén Antonio
Published: March 2011

Generalized Cullen Numbers are positive integers of the form

C
b

(
n
)
:=
n

b
n

+
1

C_b(n):=nb^n+1

. In this work we generalize some known divisibility properties of Cullen Numbers and present two primality tests for this family of integers. The first test is based in the following property of primes from this family:

n

b

n

≡
(
−
1

)

b

n^{b^{n}}\equiv (-1)^{b}

(mod

n

b
n

+
1

nb^n+1

). It is stronger and has less computational cost than Fermat’s test (to bases

b
b

and

n
n

) and than Miller-Rabin’s test (if

b
b

is odd, to base

n
n

). Pseudoprimes for this new test seem to be very scarce, only 4 pseudoprimes have been found among the many millions of Generalized Cullen Numbers tested. We also present a second, more demanding, test for which no pseudoprimes have been found. These tests lead to an algorithm, running in

O
~

(

log
2

⁡
(
N
)
)

\tilde {O}(\log ^2(N))

time, which might be very useful in the search of Generalized Cullen Primes.
Expression of an Oxalate Decarboxylase Impairs the Necrotic Effect Induced by Nep1-like Protein (NLP) of Moniliophthora perniciosa in Transgenic Tobacco
Authors: da Silva Leonardo F. , Dias Cristiano V. , Cidade Luciana C. , Mendes Juliano S. , Pirovani Carlos P. , Alvim Fátima C. , Pereira Gonçalo A. G. , Aragão Francisco J. L. , Cascardo Júlio C. M. , Costa Marcio G. C.
Published: March 2011

Oxalic acid (OA) and Nep1-like proteins (NLP) are recognized as elicitors of programmed cell death (PCD) in plants, which is crucial for the pathogenic success of necrotrophic plant pathogens and involves reactive oxygen species (ROS). To determine the importance of oxalate as a source of ROS for OA- and NLP-induced cell death, a full-length cDNA coding for an oxalate decarboxylase (FvOXDC) from the basidiomycete Flammulina velutipes, which converts OA into CO2 and formate, was overexpressed in tobacco plants. The transgenic plants contained less OA and more formic acid compared with the control plants and showed enhanced resistance to cell death induced by exogenous OA and MpNEP2, an NLP of the hemibiotrophic fungus Moniliophthora perniciosa. This resistance was correlated with the inhibition of ROS formation in the transgenic plants inoculated with OA, MpNEP2, or a combination of both PCD elicitors. Taken together, these results have established a pivotal function for oxalate as a source of ROS required for the PCD-inducing activity of OA and NLP. The results also indicate that FvOXDC represents a potentially novel source of resistance against OA- and NLP-producing pathogens such as M. perniciosa, the causal agent of witches' broom disease of cacao (Theobroma cacao L.).
Evaluation of Vineyard Weeds as Potential Hosts of Black-Foot and Petri Disease Pathogens
Authors: Agustí-Brisach C. , Gramaje D. , León M. , García-Jiménez J. , Armengol J.
Published: March 2011

Weeds were sampled in grapevine rootstock mother fields, open-root field nurseries, and commercial vineyards of Albacete, Alicante, Castellón, Murcia, and Valencia provinces in Spain between June 2009 and June 2010 and evaluated as potential hosts of black-foot and Petri disease pathogens. Isolations were conducted in the root system and internal xylem tissues for black-foot and Petri disease pathogens, respectively. Cylindrocarpon macrodidymum was successfully isolated from the roots of 15 of 19 weed families evaluated and 26 of 52 weed species. Regarding Petri disease pathogens, one isolate of Phaeomoniella chlamydospora was obtained from Convolvulus arvensis, and three isolates of Cadophora luteo-olivacea were obtained from Bidens subalternans, Plantago coronopus, and Sonchus oleraceus. Pathogenicity tests showed that Cylindrocarpon macrodidymum isolates obtained from weeds were able to induce typical black-foot disease symptoms. When inoculated in grapevines, isolates of Cadophora luteo-olivacea and Phaeomoniella chlamydospora were also shown to be pathogenic on grapevine cuttings. Our ability to recover grapevine pathogens from vineyard weeds and to demonstrate pathogenicity of recovered strains on grape suggests that these weeds may serve as a source of inoculum for infection of grapevine.
Occurrence of QoI Resistance and Detection of the G143A Mutation in Michigan Populations of Venturia inaequalis
Authors: Lesniak Kimberley E. , Proffer Tyre J. , Beckerman Janna L. , Sundin George W.
Published: March 2011

Control strategies for Venturia inaequalis rely heavily on chemical fungicides. Single-site fungicides such as the quinone-outside inhibitors (QoI) have been used in Michigan apple orchards for more than 11 years. In 2008, we sampled eight commercial orchards in the Fruit Ridge growing region of Michigan in which apple scab control failures were observed on ‘McIntosh’ apple following applications of kresoxim-methyl or trifloxystrobin. QoI resistance was assessed in 210 total isolates (a total of 17 orchards) using a spore germination assay and in 319 isolates using a polymerase chain reaction (PCR) assay to detect the G143A mutation located within the V. inaequalis cytochrome b gene (CYTB). The G143A mutation is known to confer high-level QoI resistance in plant-pathogenic fungi. QoI resistance was confirmed in 50 and 64% of the isolates tested with the spore germination and PCR assays, respectively, and there was a 97% concordance observed between the assays. In 2009, we sampled and examined an additional 1,201 V. inaequalis isolates from 64 orchards in Michigan and 86 isolates from four baseline sites in Ohio. All of these isolates were assayed for the G143A mutation and it was detected within 67 and 0% of the Michigan and Ohio isolates, respectively. Our results indicate the widespread occurrence of QoI resistance in Michigan commercial orchard populations of V. inaequalis. Loss of QoI fungicides further limits the arsenal of fungicides available to commercial apple growers for successful scab management.
Perceptions of Disease Risk: From Social Construction of Subjective Judgments to Rational Decision Making
Authors: McRoberts N. , Hall C. , Madden L. V. , Hughes G.
Published: March 2011

Many factors influence how people form risk perceptions. Farmers' perceptions of risk and levels of risk aversion impact on decision-making about such things as technology adoption and disease management practices. Irrespective of the underlying factors that affect risk perceptions, those perceptions can be summarized by variables capturing impact and uncertainty components of risk. We discuss a new framework that has the subjective probability of disease and the cost of decision errors as its central features, which might allow a better integration of social science and epidemiology, to the benefit of plant disease management. By focusing on the probability and cost (or impact) dimensions of risk, the framework integrates research from the social sciences, economics, decision theory, and epidemiology. In particular, we review some useful properties of expected regret and skill value, two measures of expected cost that are particularly useful in the evaluation of decision tools. We highlight decision-theoretic constraints on the usefulness of decision tools that may partly explain cases of failure of adoption. We extend this analysis by considering information-theoretic criteria that link model complexity and relative performance and which might explain why users reject forecasters that impose even moderate increases in the complexity of decision making despite improvements in performance or accept very simple decision tools that have relatively poor performance.
Comparison of Soil and Corn KernelAspergillus flavusPopulations: Evidence for Niche Specialization
Authors: Sweany Rebecca Ruth , Damann Kenneth Eugene , Kaller Michael Douglas
Published: March 2011

Aspergillus flavus is considered a generalist-opportunistic pathogen, but studies are beginning to show that A. flavus populations have strains specific to various hosts. The research objective was to determine whether A. flavus soil populations consist of solely saprophytic strains and strains which can be facultatively parasitic on corn. A. flavus was isolated from both corn kernels and soil within 11 Louisiana fields. Sixteen vegetative compatibility groups (VCGs) were identified among 255 soil isolates. Only 6 of the 16 VCGs were identified in the 612 corn isolates and 88% of corn isolates were in two VCGs, whereas only 5% of soil isolates belonged to the same two VCGs. Isolates were characterized for aflatoxin B1production and sclerotial size. A random subset of the isolates (99 from corn and 91 from soil) were further characterized for simple-sequence repeat (SSR) haplotype and mating type. SSR polymorphisms revealed 26 haplotypes in the corn isolates and 78 in the soil isolates, and only 1 haplotype was shared between soil and corn isolates. Corn and soil populations were highly significantly different for all variables. Differences between corn and soil populations indicate that some soil isolates are not found in corn and some isolates have become specialized to infect corn. Further understanding of A. flavus virulence is important for development of resistant hybrids and for better biological control against toxigenic A. flavus.
Biological Control of Rhizoctonia Root Rot on Bean by Phenazine- and Cyclic Lipopeptide-Producing Pseudomonas CMR12a
Authors: D'aes Jolien , Hua Gia Khuong Hoang , De Maeyer Katrien , Pannecoucque Joke , Forrez Ilse , Ongena Marc , Dietrich Lars E. P. , Thomashow Linda S. , Mavrodi Dmitri V. , Höfte Monica
Published: March 2011

Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and phenazines influenced hyphal growth. Together, results demonstrate the involvement of phenazines and CLPs during Pseudomonas CMR12a-mediated biocontrol of Rhizoctonia root rot of bean.
Roles of stress-activated protein kinases in the replication of Singapore grouper iridovirus and regulation of the inflammatory responses in grouper cells
Authors: Huang Xiaohong , Huang Youhua , OuYang Zhengliang , Cai Jia , Yan Yang , Qin Qiwei
Published: March 2011

Stress-activated protein kinases (SAPKs), including p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun N-terminal kinase (JNK), are usually activated in response to different environmental stimuli, including virus infection. In the present study, the roles of SAPKs during Singapore grouper iridovirus (SGIV) infection were investigated in fish cells. The results showed that increased phosphorylation of JNK1/2 and p38 MAPK occurred during active replication of SGIV in grouper cell cultures. Moreover, downstream effectors (c-Jun, MAPK-activated protein kinase 2, p53, activator protein 1, Myc and nuclear factor of activated T cells) were activated after SGIV infection, suggesting that SGIV replication activated the JNK and p38 MAPK signalling pathways. Notably, using specific inhibitors, it was found that viral gene transcripts, protein expression and viral titres were not affected by inhibition of p38 MAPK but were suppressed significantly by inhibiting JNK1/2 activation. In addition, transcription of grouper immune genes including interferon regulatory factor 1, interleukin-8 and tumour necrosis factor alpha (TNF-α) were regulated by JNK, whilst only TNF-α was regulated by p38 MAPK. It is proposed that the JNK pathway is important for SGIV replication and modulates the inflammatory responses during virus infection.
Cellular cap-binding proteins associate with influenza virus mRNAs
Authors: Bier Katja , York Ashley , Fodor Ervin
Published: March 2011

The influenza virus RNA polymerase synthesizes three types of RNA: genomic vRNA, anti-genomic cRNA and mRNA. Both vRNA and cRNA are bound by the viral RNA polymerase and nucleoprotein to form ribonucleoprotein complexes. Viral mRNAs are also proposed to be bound by the RNA polymerase to prevent their endonucleolytic cleavage, regulate the splicing of M1 mRNA, and facilitate translation. Here, we used standard immunoprecipitation, biochemical purification and RNA immunoprecipitation assays to investigate the association of viral and host factors with viral mRNA. We found that viral mRNA associates with the viral non-structural protein 1 (NS1), cellular poly(A)-binding protein 1 (PABP1), the 20 kDa subunit NCBP1 of the nuclear cap-binding complex (CBC), the RNA and export factor-binding protein REF/Aly and the translation initiation factor eIF4E. However, our data suggest that the RNA polymerase might not form part of the viral messenger ribonucleoprotein (mRNP) complex. We propose a model in which viral mRNAs, by associating with cellular cap-binding proteins, follow the pathways normally used by cellular mRNAs for splicing, nuclear export and translation.
A novel hantavirus detected in Yunnan red-backed vole (Eothenomys miletus) in China
Authors: Zhang Yunzhi , Yuan Junfa , Yang Xinglou , Zhou Jihua , Yang Weihong , Peng Cheng , Zhang Hai-Lin , Shi Zhengli
Published: March 2011

Rodents are the major natural reservoir of hantaviruses, which cause two main human zoonoses, haemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus pulmonary syndrome (HPS) in the Americas. Surveillance of hantaviruses in rodents plays an important role in the prevention and control of HFRS and HPS. In this study, small mammals were captured in an HFRS-endemic region, Luxi County within the Yunnan Province of China, from the autumn of 2009 to the spring of 2010, and assessed for the presence of hantaviruses. A high ratio of hantavirus infection was detected in the Yunnan red-backed vole (Eothenomys miletus). Full-length sequences of the small, middle and large segments were determined from one positive sample (designated Luxi hantavirus). Analyses of the coding sequences indicated that this virus represents a distinct hantavirus species within the hantavirus group identified from the Rodentia subfamily Arvicolinae.