bluuebunny/crossref_metadata_2025 huggingface dataset:
How important are dispersive Alfvén waves for auroral particle acceleration?
Authors: Chaston C. C. , Carlson C. W. , McFadden J. P. , Ergun R. E. , Strangeway R. J.
Published: April 2007

The means by which charged particles are accelerated in space to form the aurora is still not fully understood. This acceleration produces earthward streaming electrons driving auroral luminosity and outward streaming ionospheric ions which populate space with terrestrial matter. With the advent of high resolution space borne field and particle instruments, dispersive Alfvén waves (DAWs) have been identified as drivers of auroral particle acceleration and it has been shown that the Alfvén wave energy observed is sufficient to power a significant fraction of auroral luminosity. Since previously it has been considered that auroral particle acceleration occurs in quasi‐steady field‐aligned currents, quantifying the amount of particle acceleration occurring in DAWs relative to the traditionally invoked processes is fundamental to our understanding of how the aurora works. We combine coincident satellite measurements of fields and particles to demonstrate that as functions of increasing auroral activity 25–39% of the total electron energy deposited in the ionosphere and 15–34% of total energetic ion outflow may be attributed to the action of DAWs. In fact in the vicinity of the polar cusps and pre‐midnight auroral oval, DAWs may provide the dominant means for powering electron and ion acceleration during active times.
Impact of transboundary transport of carbonaceous aerosols on the regional air quality in the United States: A case study of the South American wildland fire of May 1998
Authors: In Hee‐Jin , Byun Daewon W. , Park Rokjin J. , Moon Nan‐Kyoung , Kim Soontae , Zhong Sharon
Published: April 2007

The present work is an attempt to improve the performance of a regional air quality model by means of linking it with a global chemistry transport model in order to provide initial and lateral boundary conditions. The current Community Multiscale Air Quality (CMAQ) model uses a set of constant lateral background condition profiles of the pollutant species, without reflecting temporal and spatial variations at the boundaries. A modeling study of a severe biomass burning event during May 1998 in Mexico and Central America, attributable to an ENSO‐related drought, is presented. In this study, the GEOS‐Chem global model output is incorporated as the CMAQ lateral boundary and initial values through an interpolation reconciling the differences in the vertical and horizontal coordinates and the chemical species representations of the two models. Simulated daily and monthly mean aerosol concentrations were evaluated by comparing these predicted concentrations with observational data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) surface network. CMAQ, using the GEOS‐Chem output to provide the lateral boundary conditions, improves model simulation of carbonaceous aerosols, such as the elemental carbons (EC) and organic carbons (OC). The square of correlation coefficients between overall simulated versus observed monthly mean concentration of EC was 0.36 and OC was 0.72, demonstrating successful simulations of transboundary transport of aerosols. Model sensitivity simulations were performed to assess the carbonaceous emissions in the U.S. EPA's National Emissions Inventory for 1999 (NEI99) and to explore long‐range transport and local contributions of wild fire emissions as potential sources for correcting the low bias of EC simulations in CMAQ. In the simulation without the boundary influx from wildfire, the analysis shows a general net export of EC and OC from the continental United States of America, while in the simulations with the GEOS‐Chem linkage, the imported fluxes of the EC and primary OC are balanced by the export. The net fluxes of EC and OC through the southern Mexico region are equivalent to 53.7% of EC emission and 51.5% of OC emission amounts over the entire domain, which indicate that the transboundary fluxes are crucial for the proper simulation of EC and OC concentrations in this event. Secondary OC formations from gas phase precursors are equivalent to 175% of the NEI99 OC emissions over the model domain, or 55% of the OC emissions when the wildfire emission is included. Visibility degradation due to the carbonaceous aerosols from the Mexican fire resulted in an increase of the aerosol extinction coefficient by 40% over the background level in the southern United States during the May 1998 episode.
Characteristics of the recent warming of permafrost in Alaska
Authors: Osterkamp T. E.
Published: April 2007

Tentative answers are provided to questions concerning the recent warming of permafrost in Alaska, particularly those regarding timing, duration, magnitude, spatial distribution, seasonality, active layer effects, thawing, thermokarst terrain, and causes. Permafrost warmed at most sites north of the Brooks Range from the Chukchi Sea to the Alaska‐Canada border, south along a transect from Prudhoe Bay to Gulkana and at sites up to 300 km from the transect. The warming was coincident with the statewide warming of air temperatures that began in 1976/1977 and appears to have occurred statewide with some exceptions. Magnitude of the warming was 3 to 4°C for the Arctic Coastal Plain, 1 to 2°C for the Brooks Range including its northern and southern foothills, and 0.3 to 1°C south of the Yukon River. This suggests a total warming of >6°C at Prudhoe Bay during the last century. The warming was seasonal (primarily in winter) with little change in summer conditions. Consequently, active layer thicknesses did not increase and were not correlated with warming permafrost conditions. Natural thawing at the permafrost surface (∼0.1 m/yr) occurred at both a tundra and forest site. Basal thawing at one site was ∼0.04 m/yr until 2000 when it accelerated to ∼0.09 m/yr. New thermokarst terrain has been observed in interior and northern Alaska. Probable causes of the warming include increased air temperatures, snow cover effects, and combinations of these. New investigations are needed to further determine the characteristics, especially the causes, of this recent permafrost warming.
YC‐1 attenuates LPS‐induced proinflammatory responses and activation of nuclear factor‐κB in microglia
Authors: Lu D‐Y , Tang C‐H , Liou H‐C , Teng C‐M , Jeng K‐Cg , Kuo S‐C , Lee F‐Y , Fu W‐M
Published: April 2007

Background and purpose:

An inflammatory response in the central nervous system mediated by the activation of microglia is a key event in the early stages of the development of neurodegenerative diseases. LPS has been reported to cause marked microglia activation. It is very important to develop drugs that can inhibit microglia activation and neuroinflammation. Here, we investigated the inhibitory effect of YC‐1, a known activator of soluble guanylyl cyclase, against LPS‐induced inflammatory responses in microglia.

Experimental approach:

To understand the inhibitory effects of YC‐1 on LPS‐induced neuroinflammation, primary cultures of rat microglia and the microglia cell line BV‐2 were used. To examine the mechanism of action of YC‐1, LPS‐induced nitric oxide (NO) and prostaglandin E2 (PGE2) production, iNOS, COX‐2 and cytokine expression were analyzed by Griess reaction, ELISA, Western blotting and RT‐PCR, respectively. The effect of YC‐1 on LPS‐induced activation of nuclear factor kappa B (NF‐κB) was studied by NF‐κB reporter assay and immunofluorocytochemistry.

Key results:

YC‐1 inhibited LPS‐induced production of NO and PGE2 in a concentration‐dependent manner. The protein and mRNA expression of iNOS and COX‐2 in response to LPS application were also decreased by YC‐1. In addition, YC‐1 effectively reduced LPS‐induced expression of the mRNA for the proinflammatory cytokines, TNF‐α and IL‐1β. Furthermore, YC‐1 inhibited LPS‐induced NF‐κB activation in microglia.

Conclusions and implications:

YC‐1 was able to inhibit LPS‐induced iNOS and COX‐2 expression and NF‐κB activation, indicating that YC‐1 may be developed as an anti‐inflammatory neuroprotective agent.

British Journal of Pharmacology (2007) 151, 396–405; doi:10.1038/sj.bjp.0707187
Chaperoning ribonucleoprotein biogenesis in health and disease
Authors: Pellizzoni Livio
Published: April 2007

The survival motor neuron (SMN) protein is part of a macromolecular complex that functions in the biogenesis of small nuclear ribonucleoproteins (snRNPs)—the essential components of the pre‐messenger RNA splicing machinery—as well as probably other RNPs. Reduced levels of SMN expression cause the inherited motor neuron disease spinal muscular atrophy (SMA). Knowledge of the composition, interactions and functions of the SMN complex has advanced greatly in recent years. The emerging picture is that the SMN complex acts as a macromolecular chaperone of RNPs to increase the efficiency and fidelity of RNA–protein interactions in vivo, and to provide an opportunity for these interactions to be regulated. In addition, it seems that RNA metabolism deficiencies underlie SMA. Here, a dual dysfunction hypothesis is presented in which two mechanistically and temporally distinct defects—that are dependent on the extent of SMN reduction in SMA—affect the homeostasis of specific messenger RNAs encoding proteins essential for motor neuron development and function.
Proteasome proteolytic activity in skeletal muscle is increased in patients with sepsis
Authors: Klaude Maria , Fredriksson Katarina , Tjäder Inga , Hammarqvist Folke , Ahlman Bo , Rooyackers Olav , Wernerman Jan
Published: April 2007

Patients with sepsis in the ICU (intensive care unit) are characterized by skeletal muscle wasting. This leads to muscle dysfunction that also influences the respiratory capacity, resulting in prolonged mechanical ventilation. Catabolic conditions are associated with a general activation of the ubiquitin–proteasome pathway in skeletal muscle. The aim of the present study was to measure the proteasome proteolytic activity in both respiratory and leg muscles from ICU patients with sepsis and, in addition, to assess the variation of proteasome activity between individuals and between duplicate leg muscle biopsy specimens. When compared with a control group (n=10), patients with sepsis (n=10) had a 30% (P<0.05) and 45% (P<0.05) higher proteasome activity in the respiratory and leg muscles respectively. In a second experiment, ICU patients with sepsis (n=17) had a 55% (P<0.01) higher proteasome activity in the leg muscle compared with a control group (n=10). The inter-individual scatter of proteasome activity was larger between the patients with sepsis than the controls. We also observed a substantial intra-individual difference in activity between duplicate biopsies in several of the subjects. In conclusion, the proteolytic activity of the proteasome was higher in skeletal muscle from patients with sepsis and multiple organ failure compared with healthy controls. It was shown for the first time that respiratory and leg muscles were affected similarly. Furthermore, the variation in proteasome activity between individuals was more pronounced in the ICU patients for both muscle types, whereas the intra-individual variation between biopsies was similar for ICU patients and controls.
Mineralocorticoid receptor activation and cardiac fibrosis
Authors: Young Morag J. , Lam Emily Y. M. , Rickard Amanda J.
Published: April 2007

MR (mineralocorticoid receptor) activation by either administration of exogenous mineralocorticoids or by allowing endogenous glucocorticoids to activate the MR has been shown to produce oxidative stress and vascular inflammation at the earliest stages of the development of cardiac fibrosis in experimental animals. These studies suggest potential mechanisms for the benefits observed in recent large scale clinical trials investigating the cardioprotective effects of MR antagonists given in conjunction with current best practice therapy for moderate-to-severe heart failure and heart failure post-myocardial infarction. Given that few patients had elevated plasma aldosterone, novel mechanisms involved in activating the MR in the failing heart are now being investigated.
Scenarios of heterogeneous nucleation and growth studied by cell dynamics simulation
Authors: Iwamatsu Masao
Published: April 2007

The dynamics of phase transformation due to homogeneous nucleation has long been analyzed using the classic Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory. However, the dynamics of phase transformation due to heterogeneous nucleation has not been studied systematically even though it is vitally important technologically. In this report, the author studies the dynamics of heterogeneous nucleation theoretically and systematically using the phenomenological time-dependent Ginzburg-Landau (TDGL)-type model combined with the cell dynamics method. In this study the author focuses on the dynamics of phase transformation when the material is sandwiched by two supporting substrates. This model is supposed to simulate phase change storage media. Since both homogeneous and heterogeneous nucleations can occur simultaneously, the author predicts a few scenarios of phase transformation including homogeneous nucleation regime, heterogeneous nucleation regime, and the homogeneous-heterogeneous coexistence regime. These predictions are directly confirmed by numerical simulation using the TDGL model. The outcome of the study was that the KJMA formula has limited use when heterogeneous nucleation exists, but it could still give some information about the microscopic mechanism of phase transformation at various stages during phase transformation.
Molecular mechanism of transporting a polarizable iodide anion across the water-CCl4 liquid/liquid interface
Authors: Wick Collin , Dang Liem X.
Published: April 2007

The result of transferring a polarizable iodide anion across the H2O–CCl4 liquid/liquid interface was investigated in this study. The computed transfer-free energy profile or potential of mean force exhibits a minimum near the Gibbs dividing surface. These system characteristics are similar to those found in a corresponding study of iodide transfer across the H2O-vapor interface; however, the free energy minimum was lower at the H2O-vapor interface. Molecular dynamics simulations were also carried out to compare the concentrations of NaCl, NaBr, and NaI at the H2O-vapor and H2O–CCl4 interfaces. While the concentration of bromide and iodide ions were lower at the H2O–CCl4 interface when compared to the H2O-vapor interface, the chloride ion concentrations were similar at both interfaces. Analysis of the solvation structures of iodide and chloride ions revealed that the more polarizable iodide ion was less solvated than the chloride ion at the interface. This characteristic brought the iodide ion into greater contact with CCl4, resulting in repulsive interactions with CCl4 and reducing its tendency to move to the interface.
Asymmetry of domain forward switching and multilevel relaxation times of domain backswitching in antiferroelectric Pb0.99Nb0.02(Zr0.84Sn0.12Ti0.04)0.98O3 thin films
Authors: Jiang A. Q. , Lin Y. Y. , Tang T. A. , Zhang Q.
Published: April 2007

Pb 0.99 Nb 0.02 ( Zr 0.84 Sn 0.12 Ti 0.04 ) 0.98 O 3 thin films demonstrate a double hysteresis loop characteristic of antiferroelectric behavior with film thickness at above 150nm, but only one branch of the loop is present in films that are 90nm thick. The relaxation time of domain backswitching from ferroelectric into antiferroelectric is multistaged in a range of 100ns–100ms, but it is less than 100ns in the films without Sn and Nb dopants. Electrical modeling of the films composed of elementary regions with inhomogeneities of dielectric constant, conductivity, and polarization embodies the essence of charge injection for the compensation of local backswitching field of domains.
Theoretical study on intermolecular interactions between furan and dihalogen molecules XY(X,Y=F,Cl,Br)
Authors: Wang Zhao-Xu , Zhang Jing-Chang , Wu Jun-Yong , Cao Wei-Liang
Published: April 2007

Equilibrium geometries, interaction energies, atomic charge, and charge transfer for the intermolecular interactions between furan and dihalogen molecules XY(X; Y=F,Cl,Br) were studied at the MP2∕aug-cc-pVDZ level. Three types of geometry are observed in these interactions: the π-type geometry (I), in which the XY lies above the furan ring and almost perpendicularly to the C4–C5 bond of furan; the σ-type geometry (II), where the X atom is pointed toward the nonbonding electron pair (n pair) of oxygen atom in furan; and the χ-type geometry (III), describing a blueshift hydrogen bond formed between the hydrogen atom of furan and dihalogen molecules XY. The calculated interaction energies show that the π-type structures are more stable than the corresponding σ-type and χ-type structures. To study the nature of the intermolecular interactions, an energy decomposition analysis was carried out and the results indicate that both the π-type and σ-type interactions are dominantly inductive energy in nature, while dispersion energy governs the χ-type interactions.
Phase transition in disordered ferroelectric ceramic Pb0.70Ca0.30TiO3 under pressure
Authors: Chandra Amreesh , Pandey Dhananjai , Tyagi A. K. , Mukherjee G. D. , Vijayakumar V.
Published: April 2007

Pressure dependent synchrotron x-ray diffraction studies on Pb0.70Ca0.30TiO3 (PCT30) ferroelectric ceramic reveal a crossover in the nature of phase transition from first order nature observed at ambient pressures to second order at high pressures. It is shown that Ca2+ doping affects the transition temperature but does not change the transition pressure of PbTiO3 significantly. The values of bulk modulus and its pressure derivative are also given in this letter.
Threshold voltage instability of p-channel metal-oxide-semiconductor field effect transistors with hafnium based dielectrics
Authors: Zhao C. Z. , Zahid M. B. , Zhang J. F. , Groeseneken G. , Degraeve R. , De Gendt S.
Published: April 2007

Threshold voltage Vth instability is one major issue for future metal-oxide-semiconductor field effect transistors (MOSFETs) with hafnium (Hf) based gate dielectrics. Previous attention was focused on n-channel MOSFETs (nMOSFETs) and the implicit assumption is that it is not important for p-channel MOSFETs (pMOSFETs). This work shows that the Vth instability of pMOSEFTs can be higher than that of nMOSFETs for a sub-2nm nitrided Hf layer. Unlike nMOSFETs, the Vth instability of pMOSFETs is insensitive to measurement time, does not saturate as stress voltage increases, and is not controlled by carrier fluency. Using Hf silicates is less effective in suppressing it. Some speculations are given on the defect and physical processes responsible for the instability.
Liquid mixing driven motions of floating macroscopic objects
Authors: Su Ming
Published: April 2007

Dropping miscible and low-density organic solvents into water generates translational and rotational motions of floating objects including oil droplets, polymer half spheres, and model boats. The moving speed of the boat at different loads and the force produced by solvent drops are measured. In contrast to motions driven by surface tension of monolayer, the liquid mixing driven motion can be dynamically steered without restriction and continued provided the supply is maintained and the amount of water is large enough. Such motions are the result of Marangoni instability in binary liquid-liquid systems with intentionally produced concentration gradients behind the floating objects.
Comparative study of passivation mechanism of oxygen vacancy with fluorine in HfO2 and HfSiO4
Authors: Sun Qing-Qing , Chen Wei , Ding Shi-Jin , Xu Min , Lu Hong-Liang , Lindh-Rengifo Hans-Cristian , Zhang David Wei , Wang Li-Kang
Published: April 2007

It has been experimentally observed that the incorporated fluorine will greatly improve the reliability of high-permittivity gate dielectric based transistors, but the role of fluorine passivation on leakage current change through gate is still a debated issue. The authors performed first-principles calculations to study the role of fluorine in oxygen vacancies in HfO2 and HfSiO4. They found that fluorine behaves completely differently in these two gate dielectrics. Fluorine can passivate the gap states of HfO2 completely but has no effect on the passivation of oxygen vacancies in HfSiO4, which is a possible explanation to the controversy surrounding varying leakage current.
Effect of contact stiffness on wedge calibration of lateral force in atomic force microscopy
Authors: Wang Fei , Zhao Xuezeng
Published: April 2007

Quantitative friction measurement of nanomaterials in atomic force microscope requires accurate calibration method for lateral force. The effect of contact stiffness on lateral force calibration of atomic force microscope is discussed in detail and an improved calibration method is presented. The calibration factor derived from the original method increased with the applied normal load, which indicates that separate calibration should be required for every given applied normal load to keep the accuracy of friction measurement. We improve the original method by introducing the contact factor, which is derived from the contact stiffness between the tip and the sample, to the calculation of calibration factors. The improved method makes the calculation of calibration factors under different applied normal loads possible without repeating the calibration procedure. Comparative experiments on a silicon wafer have been done by both the two methods to validate the method in this article.
A novel composite is stiffer than diamond
Authors: Blau Steven K.
Published: April 2007

A crystal form that is unstable in isolation can be confined in tin to yield a material with unprecedented resistance to compression or extension.
Mechanical force may determine the final size of tissues
Authors: Day Charles
Published: April 2007

By assuming compression inhibits cell division, two independent simulations account for the growth and size of a simple model organ.
International Linear Collider gets reference design and cost estimate
Authors: Schwarzschild Bertram
Published: April 2007

But DOE warns that the design team's hope for completion of the 31-kilometer-long machine by 2019 may be too optimistic.
Defending against nuclear weapons: A 1950s proposal
Authors: Schweber Silvan S.
Published: April 2007

The discovery of strong focusing inspired Robert Wilson's ingenious idea to use mobile particle accelerators as a countermeasure against atomic weapons.
Quantum size effects in metallic nanostructures
Authors: Tringides Michael C. , Jałochowski Mieczyslaw , Bauer Ernst
Published: April 2007

Electrons confined in ultrathin metal films provide a window on the peculiar world of quantum mechanics.
Persistent maternal effects on juvenile survival in North American red squirrels
Authors: Kerr Tricia D , Boutin Stan , LaMontagne Jalene M , McAdam Andrew G , Humphries Murray M
Published: April 2007

Maternal effects can have lasting fitness consequences for offspring, but these effects are often difficult to disentangle from associated responses in offspring traits. We studied persistent maternal effects on offspring survival in North American red squirrels (
Tamiasciurus hudsonicus
) by manipulating maternal nutrition without altering the post-emergent nutritional environment experienced by offspring. This was accomplished by providing supplemental food to reproductive females over winter and during reproduction, but removing the supplemental food from the system prior to juvenile emergence. We then monitored juvenile dispersal, settlement and survival from birth to 1 year of age. Juveniles from supplemented mothers experienced persistent and magnifying survival advantages over juveniles from control mothers long after supplemental food was removed. These maternal effects on survival persisted, despite no observable effect on traits normally associated with high offspring quality, such as body size, dispersal distance or territory quality. However, supplemented mothers did provide their juveniles an early start by breeding an average of 18 days earlier than control mothers, which may explain the persistent survival advantages their juveniles experienced.
From cognitive to neural models of working memory
Authors: D'Esposito Mark
Published: April 2007

Working memory refers to the temporary retention of information that was just experienced or just retrieved from long-term memory but no longer exists in the external environment. These internal representations are short-lived, but can be stored for longer periods of time through active maintenance or rehearsal strategies, and can be subjected to various operations that manipulate the information in such a way that makes it useful for goal-directed behaviour. Empirical studies of working memory using neuroscientific techniques, such as neuronal recordings in monkeys or functional neuroimaging in humans, have advanced our knowledge of the underlying neural mechanisms of working memory. This rich dataset can be reconciled with behavioural findings derived from investigating the cognitive mechanisms underlying working memory. In this paper, I review the progress that has been made towards this effort by illustrating how investigations of the neural mechanisms underlying working memory can be influenced by cognitive models and, in turn, how cognitive models can be shaped and modified by neuroscientific data. One conclusion that arises from this research is that working memory can be viewed as neither a unitary nor a dedicated system. A network of brain regions, including the prefrontal cortex (PFC), is critical for the active maintenance of internal representations that are necessary for goal-directed behaviour. Thus, working memory is not localized to a single brain region but probably is an emergent property of the functional interactions between the PFC and the rest of the brain.
The cognitive neuroscience of constructive memory: remembering the past and imagining the future
Authors: Schacter Daniel L , Addis Donna Rose
Published: April 2007

Episodic memory is widely conceived as a fundamentally constructive, rather than reproductive, process that is prone to various kinds of errors and illusions. With a view towards examining the functions served by a constructive episodic memory system, we consider recent neuropsychological and neuroimaging studies indicating that some types of memory distortions reflect the operation of adaptive processes. An important function of a constructive episodic memory is to allow individuals to simulate or imagine future episodes, happenings and scenarios. Since the future is not an exact repetition of the past, simulation of future episodes requires a system that can draw on the past in a manner that flexibly extracts and recombines elements of previous experiences. Consistent with this
constructive episodic simulation
hypothesis, we consider cognitive, neuropsychological and neuroimaging evidence showing that there is considerable overlap in the psychological and neural processes involved in remembering the past and imagining the future.
Morphology, language and the brain: the decompositional substrate for language comprehension
Authors: Marslen-Wilson William D , Tyler Lorraine K
Published: April 2007

This paper outlines a neurocognitive approach to human language, focusing on inflectional morphology and grammatical function in English. Taking as a starting point the selective deficits for regular inflectional morphology of a group of non-fluent patients with left hemisphere damage, we argue for a core decompositional network linking left inferior frontal cortex with superior and middle temporal cortex, connected via the arcuate fasciculus. This network handles the processing of regularly inflected words (such as
joined
or
treats
), which are argued not to be stored as whole forms and which require morpho-phonological parsing in order to segment complex forms into stems and inflectional affixes. This parsing process operates early and automatically upon all potential inflected forms and is triggered by their surface phonological properties. The predictions of this model were confirmed in a further neuroimaging study, using event-related functional magnetic resonance imaging (fMRI), on unimpaired young adults. The salience of grammatical morphemes for the language system is highlighted by new research showing that similarly early and blind segmentation also operates for derivationally complex forms (such as
darkness
or
rider
). These findings are interpreted as evidence for a hidden decompositional substrate to human language processing and related to a functional architecture derived from non-human primate models.
Should I stay or should I go? How the human brain manages the trade-off between exploitation and exploration
Authors: Cohen Jonathan D , McClure Samuel M , Yu Angela J
Published: April 2007

Many large and small decisions we make in our daily lives—which ice cream to choose, what research projects to pursue, which partner to marry—require an exploration of alternatives before committing to and exploiting the benefits of a particular choice. Furthermore, many decisions require re-evaluation, and further exploration of alternatives, in the face of changing needs or circumstances. That is, often our decisions depend on a higher level choice: whether to exploit well known but possibly suboptimal alternatives or to explore risky but potentially more profitable ones. How adaptive agents choose between exploitation and exploration remains an important and open question that has received relatively limited attention in the behavioural and brain sciences. The choice could depend on a number of factors, including the familiarity of the environment, how quickly the environment is likely to change and the relative value of exploiting known sources of reward versus the cost of reducing uncertainty through exploration. There is no known generally optimal solution to the exploration versus exploitation problem, and a solution to the general case may indeed not be possible. However, there have been formal analyses of the optimal policy under constrained circumstances. There have also been specific suggestions of how humans and animals may respond to this problem under particular experimental conditions as well as proposals about the brain mechanisms involved. Here, we provide a brief review of this work, discuss how exploration and exploitation may be mediated in the brain and highlight some promising future directions for research.
The microRNA miR-124 antagonizes the anti-neural REST/SCP1 pathway during embryonic CNS development
Authors: Visvanathan Jaya , Lee Seunghee , Lee Bora , Lee Jae W. , Lee Soo-Kyung
Published: April 2007

Neuronal gene expression is tightly regulated in developing CNS. Here, we demonstrate the anti-neural function of phosphatase SCP1 (small C-terminal domain phosphatase 1) during development. We further show that the neuron-enriched microRNA miR-124 directly targets SCP1-3′ untranslated region (UTR) to suppress SCP1 expression. In developing spinal cord, expression of miR-124 and SCP1 is complementary, and miR-124 antagonism phenocopies SCP1 overexpression and vice versa. In P19 cells, miR-124 suppresses SCP1 expression and induces neurogenesis, and SCP1 counteracts this proneural activity of miR-124. Our results suggest that, during CNS development, timely down-regulation of SCP1 is critical for inducing neurogenesis, and miR-124 contributes to this process at least in part by down-regulating SCP1 expression.
HLA-B-associated transcript 3 (Bat3)/Scythe is essential for p300-mediated acetylation of p53
Authors: Sasaki Toru , Gan Eugene C. , Wakeham Andrew , Kornbluth Sally , Mak Tak W. , Okada Hitoshi
Published: April 2007

In response to DNA damage, p53 undergoes post-translational modifications (including acetylation) that are critical for its transcriptional activity. However, the mechanism by which p53 acetylation is regulated is still unclear. Here, we describe an essential role for HLA-B-associated transcript 3 (Bat3)/Scythe in controlling the acetylation of p53 required for DNA damage responses. Depletion of Bat3 from human and mouse cells markedly impairs p53-mediated transactivation of its target genes Puma and p21. Although DNA damage-induced phosphorylation, stabilization, and nuclear accumulation of p53 are not significantly affected by Bat3 depletion, p53 acetylation is almost completely abolished. Bat3 forms a complex with p300, and an increased amount of Bat3 enhances the recruitment of p53 to p300 and facilitates subsequent p53 acetylation. In contrast, Bat3-depleted cells show reduced p53–p300 complex formation and decreased p53 acetylation. Furthermore, consistent with our in vitro findings, thymocytes from Bat3-deficient mice exhibit reduced induction of puma and p21, and are resistant to DNA damage-induced apoptosis in vivo. Our data indicate that Bat3 is a novel and essential regulator of p53-mediated responses to genotoxic stress, and that Bat3 controls DNA damage-induced acetylation of p53.
Protein Interactions Captured by Chemical Cross-linking: Simple Cross-linking Screen Using Sulfo-MBS
Authors: Nadeau Owen W. , Carlson Gerald M.
Published: April 2007

INTRODUCTION

This protocol describes a method for chemical cross-linking of proteins using sulfo-MBS (m-maleimidobenzoyl-N-hydroxysulfo-succinimide ester). Optimal conditions for cross-linking can be determined rapidly for a fixed concentration of a protein complex by varying the time of cross-linking, pH of the reaction, and concentration of sulfo-MBS. Typically, these screens require only small amounts of target proteins and can be carried out in less than a day.
Collection, Dechorionation, and Preparation of Drosophila Embryos for Quantitative Microinjection: Figure 1.
Authors: Kiehart Daniel P. , Crawford Janice M. , Montague Ruth A.
Published: April 2007

INTRODUCTION

The quantitative microinjection of drugs, antibodies, toxins, and manipulated RNAs and proteins into Drosophila embryos--the “pharmacological approach”--provides a unique opportunity to analyze cellular functions in the developing embryo, and provides spatial and temporal resolution that is not readily available through genetic studies. These studies require that the observed effects reflect a dose-response relationship so that the data can be accurately interpreted. Thus, these microinjection approaches require a more refined strategy for handling embryos, and the use of appropriately designed chambers to mount and observe the embryos greatly facilitates analysis of the biological response to a given injected material. This protocol outlines the procedures for collection and preparation of Drosophila embryos for quantitative microinjection.
Staining Proteins in Gels with Coomassie Blue
Authors: Simpson Richard J.
Published: April 2007

INTRODUCTION

The most commonly used dye for visualizing proteins in SDS-PAGE gels is Coomassie Brilliant Blue R250 (CBR-250) because of its relatively high sensitivity. This protocol describes the standard CBR-250 staining method, along with a simple method for preparing stained gels for long-term storage.
Staining Frozen Mouse Embryo Sections for β-Galactosidase (lacZ) Activity
Authors: Nagy Andras , Gertsenstein Marina , Vintersten Kristina , Behringer Richard
Published: April 2007

INTRODUCTION

Frozen mouse embryo sections are stained for β-galactosidase (lacZ) activity using X-gal followed by counterstaining with Orange G.
Expatriates and corporate‐level international strategy: governing with the knowledge contract
Authors: Connelly Brian , Hitt Michael A. , DeNisi Angelo S. , Duane Ireland R.
Published: April 2007

Purpose

This paper proposes a methodology for governing expatriate assignments in the context of corporate‐level objectives.

Design/methodology/approach

The approach taken is to envisage expatriate managerial assignments within the theoretical framework of agency theory and the knowledge‐based view of the firm. The paper begins with the view that knowledge acquisition and integration is a primary goal for most expatriate assignments. The relationship between expatriate managers and multinational corporation (MNC) headquarters from an agency perspective are considered and the notion of a “knowledge contract” as a means of governing that relationship is discussed. Four corporate‐level international strategies available to MNCs (global, international, transnational, and multidomestic) are then examined and the extent of agency problems under each strategy is discussed.

Findings

The paper makes specific predictions about the type of knowledge contract that is most likely to address agency problems for each corporate strategy.

Originality/value

This research extends agency theory by introducing the knowledge contract as a means of managing agency concerns. This offers a broader range of contract alternatives, moving researchers beyond traditional agency theoretic prescriptions. The research also contributes to the literature on expatriate management by integrating assignment success with research on corporate‐level international strategy. Few authors have recognized organizational strategy as an important unit of study in international human resource management. Doing so, however, has yielded a unique set of contingency relationships that would otherwise be obscured.
Strategizing through the capability lens: sources and outcomes of integration
Authors: Bitar Jad , Hafsi Taïeb
Published: April 2007

Purpose

This paper aims to explore the concept of capabilities and where they come from as well as their impact on integration and performance.

Design/methodology/approach

The paper is presented in the form of a theoretical development and literature review.

Findings

This paper proposes a theory of capability development and discusses the conditions under which a capability is effective. In particular, for a capability to be effective both local and global coherence are required. But a capability effectiveness and coherence has an inverted U shape. It increases with coherence up to a certain threshold then decreases. As a result, the development of capability is a powerful integration mechanism that crosses levels and functions.

Research limitations/implications

This is a theoretical paper; the propositions offered have still to be empirically tested.

Practical implications

Opening up the capability black box might help managers better grasp how to develop and shape organizational capabilities that are deemed to contribute to competitive advantage (e.g. the pricing capability). First, capabilities are not to be equated with competitive advantage. They may lead to a competitive advantage only where the context is favorable. Thus consistency with the environment challenges is an important factor to watch. This suggests that managers should give attention to the relationships between what they perceive to be their capabilities and the nature of the challenges faced by the organization. Further this research might promote the development of tools to measure coherence within a context and manage appropriate levels of dissent to trigger the re‐shaping of existing capabilities or the emergence of new one.

Originality/value

The paper bridges highly theoretical questions with practical considerations.
Surface‐enhanced Raman scattering for identification of organic pigments and dyes in works of art and cultural heritage material
Authors: Chen Kui , Leona Marco , Vo‐Dinh Tuan
Published: April 2007

Purpose

Identification and characterization of organic pigments and dyes used in works of art and cultural heritage material such as prints, drawings, manuscripts, paintings, and textiles can provide important information for dating, authentication, and conservation treatment of these objects and studying art history in general. Applications of surface‐enhanced Raman scattering (SERS) for this purpose have recently attracted increasing attention of both academic scientists and museum researchers. This paper aims to review the latest development involving the emerging applications of SERS for the analysis of organic pigments and dyes used in works of art and cultural heritage material.

Design/methodology/approach

First, the importance of organic pigments and dyes in the studies of works of art and cultural heritage material and the challenges in their identification and characterization are briefly summarized. This is followed by a discussion on sampling considerations in the context of art and archaeology. Then the fundamental principle of SERS, SERS instrumentation and different types of SERS substrates are reviewed. Finally, selected examples of SERS applications to the identification of organic pigments and dyes, including the analysis of a couple of samples of artistic and archaeological interest, are presented and discussed.

Findings

The last few years have witnessed the emergence of SERS as a non‐destructive or micro‐destructive technique for the characterization of organic pigments and dyes found in artistic and archaeological objects. Spectroscopic and microscopic measurements using SERS have provided some novel information and answers to a wide variety of questions. However, SERS application to the field of art and archaeology is still in the fledging stage of development and requires closer collaboration between academic scientists and museum researchers. But the range of possible applications is broad. Future trends point to a strong need for the development of portable instruments for field applications.

Originality/value

By compiling this review, the authors hope to direct more attention toward SERS and bring together the expertise in the scientific, museum and art community to further explore the possibilities of SERS in rapid and direct identification of pigments and dyes under field conditions.
Inertial sensors for motion detection of human upper limbs
Authors: Zhou Huiyu , Hu Huosheng
Published: April 2007

Purpose

This paper seeks to present an inertial motion tracking system for monitoring movements of human upper limbs in order to support a home‐based rehabilitation scheme in which the recovery of stroke patients' motor function through repetitive exercises needs to be continuously monitored and appropriately evaluated.

Design/methodology/approach

Two inertial sensors are placed on the upper and lower arms in order to obtain acceleration and turning rates. Then the position of the upper limbs can be deduced by using the kinematical model of the upper limbs that was designed in the previous paper. The tracking system starts from inertial data acquisition and pre‐filtering, followed by a number of processes such as transformation of coordinate systems of sensor data, and kinematical modelling and optimization of position estimation.

Findings

The motion detector using the proposed kinematic model only has drifts in the measurements. Fusion of acceleration and orientation data can effectively solve the drift problem without the involvement of a Kalman filter.

Research limitations/implications

The image rendering is not undertaken when the data sampling is performed. This non‐synchronization is applied in order to avoid the breaks in the continuous sampling.

Originality/value

This new motion detector can work in different environments without significant drifts. Also, this system only deploys two inertial sensors but is able to estimate the position of the wrist, elbow and shoulder joints.
State‐wide schools' maintenance audit in Victoria, Australia: the framework and process
Authors: Smith Jim , Stewart Peter
Published: April 2007

Purpose

This article aims to provide details of the process involved in preparing a comprehensive maintenance audit of school buildings and facilities in a state government education department.

Design/methodology/approach

This paper presents the framework and logistics of the survey or audit, which relied on integrating a property management system with a consistent approach to the definition of maintenance and its costing. The use of visual illustrations of maintenance categories is a feature of the process and this study.

Findings

The work was completed in three months and drew upon the department's two computerized property management and asset systems, the physical resource management system (PRMS) and the school asset management system (SAMS). The department adopted an IT‐based approach that integrated the building element‐based maintenance items with electronic plans and a standard costing approach using hand‐held pen‐activated computers under the control of the maintenance auditors. The process of conducting the maintenance audit has resulted in the most comprehensive review and updating of all the maintenance requirements in school buildings. It has provided real and accurate costing of this work on a fair, methodical and consistent basis. The size of the final costs in each maintenance category has allowed funding to be refined, targeted and focused on many key and important areas.

Research limitations/implications

Whilst categories of different maintenance work are provided in broad terms, for confidentiality reasons the client organization would not permit the financial values of these categories to be published.

Practical implications

Examples of the categorization and analysis of maintenance items are included to illustrate and demonstrate the method of approach. Details of the extensive auditing process described provide insights for any large organization with widespread facilities and property assets to adopt a similar approach.

Originality/value

The process is an exemplar for an integrated property management and maintenance auditing system using IT and the practical skills of maintenance inspectors.
Sampling strategies of indoor air quality assessment for offices
Authors: Hui P.S. , Wong L.T. , Mui K.W.
Published: April 2007

Purpose

The aim of this paper is to propose alternative sampling schemes for indoor air quality assessments in which a balance between the sampling time required and number of sampling points chosen is allowed.

Design/methodology/approach

CO2was used as a reference to evaluate the existing and the proposed sampling schemes for average indoor pollutant concentration regarding the sampling time and sampling point density required and the probable errors induced at certain confidence levels of the measurement.

Findings

The results showed that increasing the number of sampling points would significantly reduce the corresponding sampling time required: at the same confidence level, doubling the sampling point density from 250 m2to 500 m2per measurement point would reduce the sampling time required from eight hours to three hours.

Research limitations/implications

The model parameters were determined from surveys for some typical offices in Hong Kong and therefore may require adaptation for use elsewhere.

Practical implications

A useful source of information in determining the number of sampling points chosen and the duration of the measurement needed according to the “acceptable” measurement uncertainty allowed.

Originality/value

Providing flexibility in IAQ assessment, the results would be useful to policymakers for making decisions on resources and manpower management for their respective sampling strategies while taking the uncertainties into account.