bluuebunny/crossref_metadata_2025 huggingface dataset:
Embedded cluster density functional and second-order Møller-Plesset perturbation theory study on the adsorption of N2 on the rutile (110) surface
Authors: Stodt Dorothee , Hättig Christof
Published: September 2012

The adsorption of N2 on the rutile TiO2 (110) surface in the limit of low coverage has been studied as a prototype example for the adsorption of non-polar molecules on strongly ionic oxide surfaces. We employed for this study an embedded cluster ansatz in combination with density functional theory and wavefunction methods. Both, clusters saturated with hydrogen atoms and electrostatically embedded clusters have been applied and methods and basis sets have been varied to test their reliability and accuracy for describing the electrostatic potential on the surface and its interaction with the non-polar N2 molecule. Quantum clusters consisting of up to 342 atoms have been used to converge the results with respect to the cluster size. For electrostatically embedded clusters, the convergence can considerably be enhanced by optimizing the charges for the point charge embedding. On the rutile (110) surface an accurate account of the long ranging interaction of the adsorbate with the bridging oxygen atoms is important for quantitative adsorption energies of weakly bound molecules. In addition the geometric relaxation of the surface has a marked influence on the results, whereas the basis set–dependence is small. Of all methods investigated (HF, DFT/PBE, DFT/B3LYP, MP2), only MP2 and DFT/B3LYP were able to describe the adsorption of N2 on the rutile surface properly. After including the zeropoint vibrational energy, the calculated adsorption energy is close to experimental results. The approach is thus promising for future investigations on adsorption energies and structures of non-polar molecules on ionic oxide surfaces.
Nanoscale frictional characteristics of graphene nanoribbons
Authors: Zhang Jiangnan , Lu Wei , Tour James M. , Lou Jun
Published: September 2012

We compare nanoscale frictional characteristics of three types of chemically treated graphene nanoribbons (GNRs) via atomic force microscope. Measurements in both ambient and low humidity conditions demonstrate that covalently bonded functional groups have a significant impact on the frictional response of GNRs. The measured tip-sample adhesion forces seem to support the observed friction force dependence on functionalizations, and the friction and adhesion differences could also be attributed to the surface reactivity and hydrophilicity differences induced by different chemical functionalization schemes.
Beaming of inplane elastic waves through a subwavelength channel with periodic corrugations
Authors: Takahashi Toru , Kuriyama Kouhei , Matsumoto Toshiro
Published: September 2012

We present an evidence of the beaming phenomenon regarding inplane elastic waves in the context of the enhanced acoustical transmission. Our simulations found emission of a long-range beam through a single subwavelength channel surrounded by periodic structures. The space-time spectral analysis of the inplane displacement field revealed that Rayleigh surface waves principally mediate the energy transmission that leads to the formation of beams. Consequently, we suggest a resonance condition for the beaming in terms of the ratio of the wavelength to the period of the structures. Our findings will be expected to foster the application to ultrasonic devices.
Signature of viscous flow units in apparent elastic regime of metallic glasses
Authors: Wang Z. , Wen P. , Huo L. S. , Bai H. Y. , Wang W. H.
Published: September 2012

We characterize and identify the flow units in two typical metallic glasses (MGs), which have markedly different β-relaxation behaviors and mechanical properties. The viscoelastic hysteresis loops are found in the cyclic deformation in the nominal elastic regime of the metallic glasses. We show that the hysteresis loops are related to the activation of the flow units in metallic glasses, and a model is proposed to describe the flow units. We demonstrate that the flow units are both the deformation units of the anelastic and plastic deformation behaviors and the structural origin of the β-relaxation in metallic glasses.
Effect of transportation on ostrich (Struthio camelus) weight loss and meat quality
Authors: Hoffman L. C. , Wolmarans W. J. , Smith C. , Brand T. S.
Published: September 2012

The purpose of this study was to compare the effect of different transport distances on ostrich meat quality parameters, weight loss, and dressing percentage. Twenty-four ostriches were transported for 0 (T0), 60 (T60) and 600 (T600) km before being slaughtered. There was a significant difference (P = 0.038) in the percentage liveweight loss during transport and lairage between T60 km (2.4 ± 2.185%) and T600 km (8.13 ± 1.156%), respectively. There was also a significant difference (P = 0.003) in dressing percentage (farm weight to cold carcass weight) between the two abovementioned groups (T60 = 49.77%; T600 = 46.86%). Treatments also had a significant effect (P < 0.05) on ultimate pH (pHu), with the ostriches that did not travel exhibiting the lowest average pHu (5.77 ± 0.053) and the birds that travelled 600 km having the highest average pHu (6.11 ± 0.053). No differences (P > 0.05) were found in shear force and percentage cooking loss between the treatments, although all three treatments differed significantly (P < 0.05) from each other in drip loss (T0 km = 0.40%; T60 km = 1.36%; T600 km = 0.97%). Significant differences (P < 0.05) were found for L*, b* and hue-angle colour ordinates between the three treatments, while there were no differences (P > 0.05) in a* and chroma values. A significant correlation was found between hue angle (r = 0.528; P = 0.008) and pHu. The results of this study indicate that ostrich transport distance influences liveweight loss and meat quality.
Aromatic Polycarboxylate-Tuned Assembly of Three New 2D Copper(II) Complexes Derived from a Flexible Bis(pyridylamide) Ligand
Authors: Wang Xiu-Li , Sui Fang-Fang , Lin Hong-Yan , Luan Jian , Liu Guo-Cheng
Published: September 2012

Three new 2D copper(ii) complexes [Cu(NIPH)(L)] (1), [Cu(BDC)(L)(H2O)] (2), and [Cu(HBTC)(L)]·2H2O (3) were hydrothermally synthesized by self-assembly of aromatic polycarboxylates (H2NIPH = 5-nitroisophthalic acid, H2BDC = 1,3-benzenedicarboxylic acid, H3BTC = 1,3,5-benzenetricarboxylic acid) and the flexible bis(pyridylamide) ligand L (L = N,N′-di(3-pyridyl)succinamide), and structurally characterized by single crystal X-ray diffraction, and elemental, IR, and thermogravimetric analyses. Compound 1 is a 2D coordination polymer based on tri-flexural helix chains (left-, right-handed [Cu-L]n helix chains, and left-handed Cu-NIPH helix chain). Compound 2 exhibits a 2D wavelike polymeric layer structure constructed from a 1D [Cu-L]n sinusoidal chain and a 1D [Cu-BDC]n V-like chain. Compound 3 possesses a 2D double-layer network formed from 1D [Cu-L]n zigzag chains and 1D [Cu-HBTC]2n double chains. The fluorescent properties of the three compounds and the electrochemical behaviour of compound 2-bulk-modified carbon paste electrode were also studied.
Fractional Sylvester–Gallai theorems
Authors: Barak Boaz , Dvir Zeev , Wigderson Avi , Yehudayoff Amir
Published: September 2012

We prove fractional analogs of the classical Sylvester–Gallai theorem. Our theorems translate local information about collinear triples in a set of points into global bounds on the dimension of the set. Specifically, we show that if for every points
v
in a finite set

, there are at least δ|
V
| other points
u
∈
V
for which the line through
v
,
u
contains a third point in
V
, then the
V
resides in a (13/δ
2
)-dimensional affine subspace of

. This result, which is one of several variants we study, is motivated by questions in theoretical computer science and, in particular, from the area of error correcting codes. Our proofs combine algebraic, analytic, and combinatorial arguments. A key ingredient is a new lower bound for the rank of
design
matrices, specified only by conditions on their zero/non-zero pattern.
Discovery of an orally active small-molecule irreversible inhibitor of protein disulfide isomerase for ovarian cancer treatment
Authors: Xu Shili , Butkevich Alexey N. , Yamada Roppei , Zhou Yu , Debnath Bikash , Duncan Roger , Zandi Ebrahim , Petasis Nicos A. , Neamati Nouri
Published: September 2012

Protein disulfide isomerase (PDI), an endoplasmic reticulum chaperone protein, catalyzes disulfide bond breakage, formation, and rearrangement. The effect of PDI inhibition on ovarian cancer progression is not yet clear, and there is a need for potent, selective, and safe small-molecule inhibitors of PDI. Here, we report a class of propynoic acid carbamoyl methyl amides (PACMAs) that are active against a panel of human ovarian cancer cell lines. Using fluorescent derivatives, 2D gel electrophoresis, and MS, we established that PACMA 31, one of the most active analogs, acts as an irreversible small-molecule inhibitor of PDI, forming a covalent bond with the active site cysteines of PDI. We also showed that PDI activity is essential for the survival and proliferation of human ovarian cancer cells. In vivo, PACMA 31 showed tumor targeting ability and significantly suppressed ovarian tumor growth without causing toxicity to normal tissues. These irreversible small-molecule PDI inhibitors represent an important approach for the development of targeted anticancer agents for ovarian cancer therapy, and they can also serve as useful probes for investigating the biology of PDI-implicated pathways.
O-GlcNAc cycling mutants modulate proteotoxicity in
Caenorhabditis elegans
models of human neurodegenerative diseases
Authors: Wang Peng , Lazarus Brooke D. , Forsythe Michele E. , Love Dona C. , Krause Michael W. , Hanover John A.
Published: September 2012

O-GlcNAcylation is an abundant posttranslational modification in the brain implicated in human neurodegenerative diseases. We have exploited viable null alleles of the enzymes of O-GlcNAc cycling to examine the role of O-GlcNAcylation in well-characterized
Caenorhabditis elegans
models of neurodegenerative proteotoxicity. O-GlcNAc cycling dramatically modulated the severity of the phenotype in transgenic models of tauopathy, amyloid β-peptide, and polyglutamine expansion. Intriguingly, loss of function of O-GlcNAc transferase alleviated, whereas loss of O-GlcNAcase enhanced, the phenotype of multiple neurodegenerative disease models. The O-GlcNAc cycling mutants act in part by altering DAF-16
–
dependent transcription and modulating the protein degradation machinery. These findings suggest that O-GlcNAc levels may directly influence neurodegenerative disease progression, thus making the enzymes of O-GlcNAc cycling attractive targets for neurodegenerative disease therapies.
Alternating electron and proton transfer steps in photosynthetic water oxidation
Authors: Klauss André , Haumann Michael , Dau Holger
Published: September 2012

Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel–production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese–calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the
S
2
 → 
S
3
transition of the classical
S
-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (

). The rate-determining elementary step (τ, approximately 30 µs at 20 °C) in the long-distance proton relocation toward the protein–water interface is characterized by a high activation energy (
E

a

 = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the
S
0
 → 
S
1
transition are similar (τ, approximately 100 µs;
E

a

 = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to

. By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established.
Development of promyelocytic leukemia zinc finger-expressing innate CD4 T cells requires stronger T-cell receptor signals than conventional CD4 T cells
Authors: Qiao Yu , Zhu Lingqiao , Sofi Hanief , Lapinski Philip E. , Horai Reiko , Mueller Kristen , Stritesky Gretta L. , He Xi , Teh Hung-Sia , Wiest David L. , Kappes Dietmar J. , King Philip D. , Hogquist Kristin A. , Schwartzberg Pamela L. , Sant’Angelo Derek B. , Chang Cheong-Hee
Published: September 2012

MHC class II-expressing thymocytes and thymic epithelial cells can mediate CD4 T-cell selection resulting in functionally distinct thymocyte-selected CD4 (T-CD4) and epithelial-selected CD4 (E-CD4) T cells, respectively. However, little is known about how T-cell receptor (TCR) signaling influences the development of these two CD4 T-cell subsets. To study TCR signaling for T-CD4 T-cell development, we used a GFP reporter system of Nur77 in which GFP intensity directly correlates with TCR signaling strength. T-CD4 T cells expressed higher levels of GFP than E-CD4 T cells, suggesting that T-CD4 T cells received stronger TCR signaling than E-CD4 T cells during selection. Elimination of Ras GTPase-activating protein enhanced E-CD4 but decreased T-CD4 T-cell selection efficiency, suggesting a shift to negative selection. Conversely, the absence of IL-2–inducible T-cell kinase that causes poor E-CD4 T-cell selection due to insufficient TCR signaling improved T-CD4 T-cell generation, consistent with rescue from negative selection. Strong TCR signaling during T-CD4 T-cell development correlates with the expression of the transcription factor promyelocytic leukemia zinc finger protein. However, although modulation of the signaling strength affected the efficiency of T-CD4 T-cell development during positive and negative selection, the signaling strength is not as important for the effector function of T-CD4 T cells. These findings indicate that innate T-CD4 T cells, together with invariant natural killer T cells and γδ T cells, receive strong TCR signals during their development and that signaling requirements for the development and the effector functions are distinct.
Identification of a BAHD acetyltransferase that produces protective acyl sugars in tomato trichomes
Authors: Schilmiller Anthony L. , Charbonneau Amanda L. , Last Robert L.
Published: September 2012

Glandular secreting trichomes on the surface of tomato plants and many of its relatives in the Solanaceae produce a mixture of
O
-acyl sugars that contribute to insect resistance. The majority of acyl sucroses produced by the cultivated tomato (
Solanum lycopersicum
) contain three or four short chain aliphatic acyl esters, and tetra-acyl sucroses have an acetyl group as one of the acyl chains. We previously reported overlapping
S. lycopersicum
×
Solanum pennellii
introgression lines (ILs) that fail to accumulate high levels of acetylated tetra-acyl sucroses. A survey of the annotated genes in this region of cultivated tomato chromosome 1 revealed three candidate acyltransferases that were tested for function using virus-induced gene silencing. A member of the BAHD family of acyltransferases (Solyc01g105580,
SlAT2
) was shown to encode an acetyl-CoA–dependent acyltransferase enzyme capable of acyl sucrose acetylation in vitro. RNAi suppression of
SlAT2
in transgenic
S. lycopersicum
cv. M82 resulted in reduced acyl sugar acetylation, whereas expression of the functional
S. lycopersicum
allele of
SlAT2
in the triacyl sucrose producing IL1-3 restored the ability of the IL to synthesize acetylated tetra-acyl sugars. Transgenic plants with the
SlAT2
promoter driving GFP expression showed fluorescence in tips cells of long, slender trichomes that is consistent with acyl sugar acetylation occurring in these cells.
C-terminal region of the UV-B photoreceptor UVR8 initiates signaling through interaction with the COP1 protein
Authors: Cloix Catherine , Kaiserli Eirini , Heilmann Monika , Baxter Katherine J. , Brown Bobby A. , O’Hara Andrew , Smith Brian O. , Christie John M. , Jenkins Gareth I.
Published: September 2012

UV-B light initiates photomorphogenic responses in plants.
Arabidopsis
UV RESISTANCE LOCUS8 (UVR8) specifically mediates these responses by functioning as a UV-B photoreceptor. UV-B exposure converts UVR8 from a dimer to a monomer, stimulates the rapid accumulation of UVR8 in the nucleus, where it binds to chromatin, and induces interaction of UVR8 with CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), which functions with UVR8 to control photomorphogenic UV-B responses. Although the crystal structure of UVR8 reveals the basis of photoreception, it does not show how UVR8 initiates signaling through interaction with COP1. Here we report that a region of 27 amino acids from the C terminus of UVR8 (C27) mediates the interaction with COP1. The C27 region is necessary for UVR8 function in the regulation of gene expression and hypocotyl growth suppression in
Arabidopsis
. However, UVR8 lacking C27 still undergoes UV-B–induced monomerization in both yeast and plant protein extracts, accumulates in the nucleus in response to UV-B, and interacts with chromatin at the UVR8-regulated
ELONGATED HYPOCOTYL5
(
HY5
) gene. The UV-B–dependent interaction of UVR8 and COP1 is reproduced in yeast cells and we show that C27 is both necessary and sufficient for the interaction of UVR8 with the WD40 domain of COP1. Furthermore, we show that C27 interacts in yeast with the REPRESSOR OF UV-B PHOTOMORPHOGENESIS proteins, RUP1 and RUP2, which are negative regulators of UVR8 function. Hence the C27 region has a key role in UVR8 function.
Statistical inference of the generation probability of T-cell receptors from sequence repertoires
Authors: Murugan Anand , Mora Thierry , Walczak Aleksandra M. , Callan Curtis G.
Published: September 2012

Stochastic rearrangement of germline V-, D-, and J-genes to create variable coding sequence for certain cell surface receptors is at the origin of immune system diversity. This process, known as “VDJ recombination”, is implemented via a series of stochastic molecular events involving gene choices and random nucleotide insertions between, and deletions from, genes. We use large sequence repertoires of the variable CDR3 region of human CD4+ T-cell receptor beta chains to infer the statistical properties of these basic biochemical events. Because any given CDR3 sequence can be produced in multiple ways, the probability distribution of hidden recombination events cannot be inferred directly from the observed sequences; we therefore develop a maximum likelihood inference method to achieve this end. To separate the properties of the molecular rearrangement mechanism from the effects of selection, we focus on nonproductive CDR3 sequences in T-cell DNA. We infer the joint distribution of the various generative events that occur when a new T-cell receptor gene is created. We find a rich picture of correlation (and absence thereof), providing insight into the molecular mechanisms involved. The generative event statistics are consistent between individuals, suggesting a universal biochemical process. Our probabilistic model predicts the generation probability of any specific CDR3 sequence by the primitive recombination process, allowing us to quantify the potential diversity of the T-cell repertoire and to understand why some sequences are shared between individuals. We argue that the use of formal statistical inference methods, of the kind presented in this paper, will be essential for quantitative understanding of the generation and evolution of diversity in the adaptive immune system.
Discovery of a cardiolipin synthase utilizing phosphatidylethanolamine and phosphatidylglycerol as substrates
Authors: Tan Brandon K. , Bogdanov Mikhail , Zhao Jinshi , Dowhan William , Raetz Christian R. H. , Guan Ziqiang
Published: September 2012

Depending on growth phase and culture conditions, cardiolipin (CL) makes up 5–15% of the phospholipids in
Escherichia coli
with the remainder being primarily phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). In
E. coli,
the
cls
and
ybhO
genes (renamed
clsA
and
clsB
, respectively) each encode a CL synthase (Cls) that catalyzes the condensation of two PG molecules to form CL and glycerol. However, a ∆
clsAB
mutant still makes CL in the stationary phase, indicating the existence of additional Cls. We identified a third Cls encoded by
ymdC
(renamed
clsC
). ClsC has sequence homology with ClsA and ClsB, which all belong to the phospholipase D superfamily. The ∆
clsABC
mutant lacks detectible CL regardless of growth phase or growth conditions. CL can be restored to near wild-type levels in stationary phase in the triple mutant by expressing either
clsA
or
clsB
. Expression of
clsC
alone resulted in a low level of CL in the stationary phase, which increased to near wild-type levels by coexpression of its neighboring gene,
ymdB
. CL synthesis by all Cls is increased with increasing medium osmolarity during logarithmic growth and in stationary phase. However, only ClsA contributes detectible levels of CL at low osmolarity during logarithmic growth. Mutation of the putative catalytic motif of ClsC prevents CL formation. Unlike eukaryotic Cls (that use PG and CDP-diacylglycerol as substrates) or ClsA, the combined YmdB-ClsC used PE as the phosphatidyl donor to PG to form CL, which demonstrates a third and unique mode for CL synthesis.
Prolonging the postcomplex spike pause speeds eyeblink conditioning
Authors: Maiz Jaione , Karakossian Movses H. , Pakaprot Narawut , Robleto Karla , Thompson Richard F. , Otis Thomas S.
Published: September 2012

Climbing fiber input to the cerebellum is believed to serve as a teaching signal during associative, cerebellum-dependent forms of motor learning. However, it is not understood how this neural pathway coordinates changes in cerebellar circuitry during learning. Here, we use pharmacological manipulations to prolong the postcomplex spike pause, a component of the climbing fiber signal in Purkinje neurons, and show that these manipulations enhance the rate of learning in classical eyelid conditioning. Our findings elucidate an unappreciated aspect of the climbing fiber teaching signal, and are consistent with a model in which convergent postcomplex spike pauses drive learning-related plasticity in the deep cerebellar nucleus. They also suggest a physiological mechanism that could modulate motor learning rates.
Syntacrobatics
Authors: Setton Robin , Motta Manuela
Published: September 2012

This study aimed, first, to test the widely held belief that meaning-based processing (‘deverbalisation’) results in better-quality simultaneous interpretation (SI), by the indirect method of correlating users’ quality judgments with linguistic reformulation and elaboration, and additionally, with transcript-based measures of accuracy, style and fluency. Twenty-four French SI-with-text versions of two English speeches by experts and novices were played to a panel of users from international organizations, and the transcripts independently scored by a panel of interpreters for these specific parameters. Analysis showed major errors to be a significant predictor of user quality judgments (although users did not have access to the original speeches), as well as some positive effect of lexical and cohesive elaboration, but none for restructuring per se.

 Secondly, since interpreting quality evaluation may vary between peers (the traditional judges), users, and other product-based methods, the study also explored ways of triangulating different sources — user judgments, transcript scores, and computer analysis of output text features — to learn more about the determinants of interpreting quality.
Effect of Photoperiod on Growth and Feed Efficiency of Fingerling Walleye
Authors: Harder Thomas M , Gotsch Gordon G , Summerfelt Robert C
Published: September 2012

We examined the effect of photoperiod on growth and feed efficiency of fingerling walleyes Sander vitreus cultured in a water reuse aquaculture system in northern Illinois from fall to late winter. We evaluated three photoperiod regimens over 24-h days: continuous light (24 h), 18-h light, and 12-h light. Twelve, 0.55-m3 tanks (four/treatment) were each stocked with 100 feed-trained walleyes (10.9 kg/m3; 196–203 mm total length, 61–66 g in weight). Survival over the 131-d culture interval was greater than 98.8% in all photoperiod treatments. All measures of growth were significantly slower and feeding efficiency was lower for fish in the 12 h of light treatment than for the 24-h and 18-h light treatments. Differences in performance between the 24-h and 18-h treatments were not significant, but all measures of growth and feed efficiency were higher for fish in continuous light than in the 18-h group. The findings support use of continuous, in-tank lighting for intensive culture of fingerlings walleye.
Bcl6 expression specifies the T follicular helper cell program in vivo
Authors: Liu Xindong , Yan Xiaowei , Zhong Bo , Nurieva Roza I. , Wang Aibo , Wang Xiaohu , Martin-Orozco Natalia , Wang Yihong , Chang Seon Hee , Esplugues Enric , Flavell Richard A. , Tian Qiang , Dong Chen
Published: September 2012

T follicular helper cells (Tfh cells) play a pivotal role in germinal center reactions, which require B cell lymphoma 6 (Bcl6) transcription factor. To analyze their relationships with other effector T cell lineages and their stability in vivo, we developed and analyzed a new Bcl6 reporter mouse alone or together with other lineage reporter systems. Assisted with genome-wide transcriptome analysis, we show substantial plasticity of T cell differentiation in the early phase of immune response. At this stage, CXCR5 appears to be expressed in a Bcl6-independent manner. Once Bcl6 is highly expressed, Tfh cells can persist in vivo and some of them develop into memory cells. Together, our results indicate Bcl6 as a bona fide marker for Tfh polarized program.
Autoreactive T cells bypass negative selection and respond to self-antigen stimulation during infection
Authors: Enouz Sarah , Carrié Lucie , Merkler Doron , Bevan Michael J. , Zehn Dietmar
Published: September 2012

Central and peripheral tolerance prevent autoimmunity by deleting the most aggressive CD8+ T cells but they spare cells that react weakly to tissue-restricted antigen (TRA). To reveal the functional characteristics of these spared cells, we generated a transgenic mouse expressing the TCR of a TRA-specific T cell that had escaped negative selection. Interestingly, the isolated TCR matches the affinity/avidity threshold for negatively selecting T cells, and when developing transgenic cells are exposed to their TRA in the thymus, only a fraction of them are eliminated but significant numbers enter the periphery. In contrast to high avidity cells, low avidity T cells persist in the antigen-positive periphery with no signs of anergy, unresponsiveness, or prior activation. Upon activation during an infection they cause autoimmunity and form memory cells. Unexpectedly, peptide ligands that are weaker in stimulating the transgenic T cells than the thymic threshold ligand also induce profound activation in the periphery. Thus, the peripheral T cell activation threshold during an infection is below that of negative selection for TRA. These results demonstrate the existence of a level of self-reactivity to TRA to which the thymus confers no protection and illustrate that organ damage can occur without genetic predisposition to autoimmunity.
Extraction of β‐Glucan from Oats for Soluble Dietary Fiber Quality Analysis
Authors: Doehlert Douglas C. , Simsek Senay , McMullen Michael S.
Published: September 2012

Extraction protocols for β‐glucan from oat flour were tested to determine optimal conditions for β‐glucan quality testing, which included extractability and molecular weight. We found mass yields of β‐glucan were constant at all temperatures, pH values, and flour‐to‐water ratios, as long as sufficient time and enough repeat extractions were performed and no hydrolytic enzymes were present. Extracts contained about 30–60% β‐glucan, with lower proportions associated with higher extraction temperatures in which more starch and protein were extracted. All commercial starch hydrolytic enzymes tested, even those that are considered homogenous, degraded β‐glucan apparent molecular weight as evaluated by size‐exclusion chromatography. Higher concentration β‐glucan solutions could be prepared by controlling the flour‐to‐water ratio in extractions. Eight grams of flour per 50 mL of water generated the highest native β‐glucan concentrations. Routine extractions contained 2 g of enzyme‐inactivated flour in 50 mL of water with 5mM sodium azide (as an antimicrobial), which were stirred overnight, centrifuged, and the supernatant boiled for 10 min. The polymer extracted had a molecular weight of about 2 million and was stable at room temperature for at least a month.
A role of protein degradation in memory consolidation after initial learning and extinction learning in the honeybee (Apis mellifera)
Authors: Felsenberg Johannes , Dombrowski Vincent , Eisenhardt Dorothea
Published: September 2012

Protein degradation is known to affect memory formation after extinction learning. We demonstrate here that an inhibitor of protein degradation, MG132, interferes with memory formation after extinction learning in a classical appetitive conditioning paradigm. In addition, we find an enhancement of memory formation when the same inhibitor is applied after initial learning. This result supports the idea that MG132 targets an ongoing consolidation process. Furthermore, we demonstrate that the sensitivity of memory formation after initial learning and extinction learning to MG132 depends in the same way on the number of CS-US trials and the intertrial interval applied during initial learning. This supports the idea that the learning parameters during acquisition are critical for memory formation after extinction and that protein degradation in both learning processes might be functionally linked.
Tribological behaviors of novel tri(hydroxymethyl)propane esters containing boron and nitrogen as lubricant additives in rapeseed oil
Authors: Ji Xianbing , Chen Yinxia , Wang Xiaobo , Liu Weimin
Published: September 2012

Purpose

The purpose of this paper is to study the tribological performance of tri(hydroxymethyl)propane esters containing boron and nitrogen as lubricant additives in rapeseed oil.

Design/methodology/approach

Thermal degradation tests were performed to analyze their thermal stability using a thermo‐gravimetric analyzer. Two four‐ball testers were used to measure the tribological properties of tri(hydroxymethyl)propane esters containing boron and nitrogen as lubricant additives in rapeseed oil. The worn surfaces of steel balls were investigated by scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS).

Findings

The results show that the tri(hydroxymethyl)propane esters containing boron and nitrogen have excellent thermal stability, good antiwear performance, improve the load‐carrying capacity, and possess friction‐reducing behavior especially at 98 N when they are used as additives in rapeseed oil. The results of XPS show that the adsorption and tribochemical reactions have been occurred to form a complex boundary lubrication film.

Originality/value

The paper illustrates two novel tri(hydroxymethyl)propane esters which contain B and N elements used as additives in rapeseed oil. The results are useful for further applications in advanced environment friendly lubricating oils and additives.
Investigation of oil and emulsion stability of locally prepared metalworking fluids
Authors: Al‐Sabagh Ahmed M. , Khalil Salah A. , Abdelrahman Abdellatief , Nasser Notaila M. , Noor Eldin Mahmoud R. , Mishrif Marwa R. , El‐Shafie Mohamed
Published: September 2012

Purpose

No one particular fluid has cooling and lubrication properties suitable for every metalworking application. The purpose of this paper is first, to investigate the effect of anionic and nonionic mixed emulsifier system in stabilization of cutting fluid formulations and second, to study the interaction synergism of the fulfill additives of metalworking fluids to achieve low scar diameters, high stability, anti rusting and corrosion properties.

Design/methodology/approach

A lot of set mixtures in this work were formulated to get the demand needed for soluble oil metalworking fluids. It was based on a blend of emulsifier package (anionic‐non ionic), and in order to reach acceptable manufacturing conditions, coupling agent, stabilizer, biocide, base oil and anti‐rust additives were added to the formulation. Different percentages of these components were incorporated to optimize the stability of the emulsifier system. Standard tests were carried out to evaluate the performance of oil‐in‐water (O/W) emulsions as lubricating and cooling fluids in machining operations. The evaluation was drawn in five factors; oil stability, emulsion stability, pH, anti‐rust (corrosion inhibition), biological activity and extreme pressure performance tests.

Findings

All tests achieved excellent results according to the ASTM. From the obtained results, the formula (named EPRI 950) exhibited a good performance compared with the commercial cutting fluid.

Originality/value

This work investigates the effect of anionic and nonionic mixed emulsifier system in stabilization of cutting fluid formulations; and the interaction synergism of the fulfill additives of metalworking fluids to achieve low scar diameters, high stability, anti‐rusting and corrosion properties.
Dry sliding wear behaviour of aluminium/alumina/graphite hybrid metal matrix composites
Authors: Radhika N. , Subramanian R. , Venkat Prasat S. , Anandavel B.
Published: September 2012

Purpose

Recent trends in material science show a considerable interest in the manufacturing of metal matrix composites to meet the stringent demands of lightweight, high strength and corrosion resistance. Aluminium is the popular matrix metal currently in vogue that can be reinforced with ceramic materials such as particulates to meet the desired property. The purpose of this paper is to fabricate hybrid metal matrix composites to improve the dry sliding wear resistance and to study of the effect of sliding speed, load and reinforcement (alumina and graphite) on wear properties, as well as its contact friction.

Design/methodology/approach

The present study addresses the dry sliding wear behaviour of Al‐Si10Mg alloy reinforced with 3, 6 and 9 wt% of alumina along with 3 wt% of graphite. Stir casting method was used to fabricate the composites. Mechanical properties such as hardness and tensile strength have been evaluated. A pin‐on‐disc wear test apparatus was used to evaluate the wear rate and coefficient of friction by varying the loads of 20, 30 and 40 N, sliding speeds of 1.5 m/s, 2.5 m/s and 3.5 m/s at a constant sliding distance of 2100 m.

Findings

Mechanical properties of hybrid metal matrix composites (HMMCs) have shown significant improvement. The wear rate and coefficient of friction for alloy and composites decreased with increase in sliding speed and increased with increase in applied load. Temperature rise during wearing process for monolithic alloy was larger than that of HMMCs and Al/9% Al2O3/3% Gr composite showing the minimum temperature rise.The worn surfaces of the composites were investigated using scanning electron microscope.

Practical implications

The paper shows that aluminium composites can improve strength and wear resistance.

Originality/value

HMMCs has proven to be useful in improving the dry sliding wear resistance.
External pressures affecting the adoption of employee performance management in higher education institutions
Authors: Decramer Adelien , Smolders Carine , Vanderstraeten Alex , Christiaens Johan , Desmidt Sebastian
Published: September 2012

Purpose

This paper aims to explore the relationship between external pressures and the adoption of employee performance management systems within academic units of Flemish higher education institutions. The literature on contextually based HRM and institutionalism is used to underpin the theoretical propositions.

Design/methodology/approach

A comparative case study is described to provide evidence for the theoretical arguments.

Findings

It has been suggested that academic units face a set of external pressures, which leads to different employee performance management systems. This study finds that academic units imitate their legitimacy‐based reference group and legitimacy‐driven imitation and the adoption of external employee performance management requirements distort the alignment of employee performance management systems.

Research limitations/implications

Future research could formally test the relationship between external drivers and the adoption of strategic and integrated employee performance management systems in academic units by using a survey questionnaire.

Originality/value

This theoretical argumentation uses contextually‐based human resource theory and it is explored empirically through an analysis of the specific context of Flemish academic units to explain how institutional and market pressures affect the adoption and configuration of employee performance management systems.
Importance of system and leadership in performance appraisal
Authors: Tuytens Melissa , Devos Geert
Published: September 2012

Purpose

Performance appraisal is used internationally to improve employee performance, also in the educational field. However, doubts exist about the effectiveness of performance appraisal. This study aims to contribute by expanding the knowledge about important context variables of performance appraisal in secondary education. In particular, the study aims to examine the role of both characteristics of the teacher performance appraisal system and the school leader for procedural justice and perceived feedback utility by teachers.

Design/methodology/approach

Both interviews with school leaders and a questionnaire for teachers were used to collect data in 32 schools. Path analyses (n=298) were used to test the research model.

Findings

The results indicate that teacher participation in the teacher performance appraisal system significantly influences the perceived procedural justice by teachers, which in its turn significantly influences the perceived feedback utility. The role of the school leaders is found to be extremely important. Charismatic leadership influences both directly and indirectly (through procedural justice) the perceived feedback utility by teachers.

Originality/value

This study contributes to the research field of (teacher) performance appraisal by studying empirically appraisal system characteristics and leadership characteristics that effect appraisal reactions. In this regard, this study responds to the need for more empirical research to uncover the social context of performance appraisal, especially in the field of education where there is a general skepticism towards teacher appraisal and its possible positive outcomes.
The effects of CEOs' social networks on organizational performance through knowledge and strategic flexibility
Authors: Fernández‐Pérez Virginia , Jesús García‐Morales Victor , Fernando Bustinza‐Sánchez Óscar
Published: September 2012

Purpose

This study seeks to analyze theoretically and empirically how different intermediate strategic variables related to knowledge (combinative capabilities and absorptive capacity) and strategic flexibility influence the relation between CEOs' social networks and organizational performance. To date, very little research has analyzed the direct and indirect relationships between these variables.

Design/methodology/approach

Based on the literature, a theoretical model is developed that shows the interrelations between these variables. The methodology used was LISREL analysis. The model is then tested using data from 203 Spanish organizations.

Findings

This investigation shows the influence of CEOs' social networks (larger networks with strong ties) and capabilities (combinative capabilities and absorptive capacity) on the level of strategic flexibility. It then shows the influence of their strategic flexibility level on organizational performance. It adds theoretical and empirical arguments to the importance of CEOs' social networks for the organization.

Originality/value

Today's information and knowledge society requires new CEOs who can confront a reality based on knowledge and foster strategic flexibility to achieve improvements in organizational performance. However, organizations sometimes fail to achieve sustainable competitive advantage due to their limited understanding of the relationships between these strategic variables. This paper develops a complete framework of the capturing of knowledge and information from outside the organization performed by CEOs and the process they use to assimilate, transform and use this knowledge in the organization.
Work‐life balance, travel‐to‐work, and the dual career household
Authors: Wheatley Dan
Published: September 2012

Purpose

The purpose of this paper is to reflect on the underlying conflicts associated with current work‐life balance and travel‐to‐work policies, as employed in organisations in the UK.

Design/methodology/approach

A mixed method approach is used to ascertain whether professional work‐group cultures limit the effectiveness of work‐life balance policy, and the extent to which spill‐over is present between work‐life balance and transport preferences, especially car use. These concerns are explored empirically using an in‐depth local level quantitative‐qualitative case study of Greater Nottingham (a regional employment centre in the East Midlands region of England).

Findings

The evidence presented in this paper suggests: work‐group cultures prevent employees, especially women, from achieving work‐life balance; there is spill‐over between work and non‐work activities, creating time allocation challenges, and stress, for dual career households attempting to achieve desired work‐life balance; and specific conflicts are reported in balancing work with travel‐to‐work, especially car parking.

Practical implications

The research findings suggest that transport, especially employee car parking, needs to be considered a focal point in the planning and implementation of human resource (HR) policies. Employers also need to reconsider their approach to flexible working to dissolve the negative repercussions that the “choice” to work flexibly has for the careers of highly skilled workers, especially working mothers. Increases in formalised home‐based teleworking, restructuring the gender balance in management, and positive discrimination toward certain groups offer potential routes for change.

Originality/value

This paper provides important recommendations for employers and HR managers, designing and implementing work‐life balance policies. Transport issues, presently considered largely external from the employer perspective, have central relevance.
A method for matching customer integration with operational control of service processes
Authors: Leyer Michael , Moormann Jürgen
Published: September 2012

Purpose

A major problem of operational control in the services industry is the integration of customers in the delivery process. The aim of this paper is to develop a method that allows service companies to evaluate the impact of customer integration on operational control in service processes.

Design/methodology/approach

The development of the proposed method follows a design science approach. Thus, the method is conceptualised on the basis of production, services and information systems research. A case study of loan processing in a bank serves to evaluate the applicability of the method.

Findings

As a result of this study, customer integration should be included into operational control following three steps: identification of the type of customer integration; quantification and characterisation of the impact of the integration; and identification of the appropriate mechanisms of operational control to deal with the customer integration better. The results of the case study show that customer integration has an impact on certain activities within a service process only but the results can be used to enhance operational control.

Practical implications

The method can be used by process managers of service companies to identify the impact of customer integration on operational control. Thus, decisions within operational control and consequently the overall productivity of a service process can be improved.

Originality/value

The paper delivers a new insight how customer integration and operational control can be linked in service processes. Thus, a theoretical gap in service operations literature is filled. Furthermore, the case study demonstrates how the method can be used in practice.
Employers and migration in low‐skilled services in Dublin
Authors: Rachel McPhee Siobhán
Published: September 2012

Purpose

The purpose of this paper is to analyse the role of employers as “institutional” factors in the creation of segmentation in the labour market. Industrial structure defines segments of the labour market (the employer) based on the nature of demand, and with the impact on the individual workers or groups based on their personal characteristics.

Design/methodology/approach

Empirical work is within the Dublin labour market, which experienced the largest increase in availability of migrant workers under immigration policies of the Celtic Tiger state. Focused on the sectors of catering, cleaning and security as low‐skilled service sector providers, the analysis is based on 24 semi‐structured interviews with employers selected based on a database of a cross‐section of all employers in the selected sectors in Dublin.

Findings

Semi‐structured interviews reinforce state policies as key institutional factor underlying migrant labour trends and experiences, but perspectives of the employers in low‐end service industries reveal additional insights. In addition to using migrant labour as a means of cost cutting, the daily actions of employers reveal cultural stereotyping of workers, making them an elemental component “exploiting” the trends facilitated by state immigration policies.

Originality/value

Although a large body of research on migration into Ireland during the Celtic Tiger years is available, little of it has focused on labour market processes. More broadly, in attempting to understand labour market processes and the creation of segmentation there needs to be a triangulation of processes of supply, demand and state policies; and employers are key players in shaping demand and exploiting supply trends.