bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-dimensional growth of lattice matched Nd-doped (Gd,Lu)2O3 films on Y2O3 by pulsed laser deposition
Authors: Gün Teoman , Kahn Andreas , İleri Bilge , Petermann Klaus , Huber Günter
Published: August 2008

This letter focuses on epitaxial growth of a 1-μm-thick lattice matched Nd-doped monocrystalline (Gd,Lu)2O3 film deposited on a {100} oriented Y2O3 substrate by pulsed laser deposition. Layer-by-layer growth indicated by in situ reflection high energy electron diffraction was observed up to film thicknesses of 100nm. The subsequent growth behavior could be explained by a multilevel growth mode. Thus, the growth mode was two-dimensional and epitaxial. Lattice matching of up to 99.3% was achieved. The evolution of the structural and topographical properties of the films was verified by ex situ x-ray diffraction analysis and atomic force microscopy, respectively.
Nonlinear characteristics of T-branch junctions: Transition from ballistic to diffusive regime
Authors: Irie H. , Diduck Q. , Margala M. , Sobolewski Roman , Feldman M. J.
Published: August 2008

Nonlinear electrical characteristics of nanostructured T-branch junctions (TBJs) made of two-dimensional electron gas in an InGaAs∕InAlAs heterostructure were studied by a systematic variation of both the device size and the operating temperature. We have found that two distinct mechanisms are responsible for the electronic transport in TBJs and their resulting nonlinear characteristics, namely, the nonlinear ballistic effect at low applied voltages and the intervalley transfer at high voltages. Detailed experimental analysis for each mechanism and their contributions with respect to the TBJ’s nanochannel length and operating temperature are discussed.
Underlying mechanism of domain-wall motions in soft magnetic thin-film nanostripes beyond the velocity-breakdown regime
Authors: Kim Sang-Koog , Lee Jun-Young , Choi Youn-Seok , Guslienko Konstantin Yu. , Lee Ki-Suk
Published: August 2008

It is known that oscillatory domain-wall (DW) motions in soft magnetic thin-film nanostripes above the Walker critical field lead to remarkable reductions in the average DW velocities. In a much-higher-field region beyond the velocity-breakdown regime, however, the DW velocities have been found to increase in response to a further increase of the applied field. We report on the physical underlying mechanism of this unexpected behavior. We associate the mechanism with the serial dynamic processes of the nucleation of vortex-antivortex pairs inside the stripe or at its edges, the nonlinear gyrotropic motions of vortices and antivortices, and their annihilation process. Moreover, this work evidences that a two-dimensional soliton model is required for adequate interpretation and understanding of DW motions in the linear- and oscillatory-DW-motion regimes as well as in the beyond-velocity-breakdown regime.
Control of the gated spectra with narrow bandwidth from a supercontinuum using ultrafast optical Kerr gate of bismuth glass
Authors: Tan Wenjiang , Liu Hui , Si Jinhai , Hou Xun
Published: August 2008

Supercontinuum generation and its application have become one of the attractive research fields in ultrafast optics. We have acquired a series of narrow bandwidth and symmetric gated spectra continuously from the chirped supercontinuum generated in a sapphire plate with a femtosecond laser, using an ultrafast optical Kerr gate (OKG) with Bi2O3–B2O3–SiO2 oxide glass as the Kerr material. Experimental results show that the gated spectra obtained using OKG of the glass have more superiorities comparing with CS2.
Effect of grain orientation on ductility in a nanocrystalline Ni–Fe alloy
Authors: LI Hongqi , Liaw Peter K. , Choo Hahn , Misra Amit
Published: August 2008

The influence of columnar grain geometry on mechanical property was studied in an electrodeposited nanocrystalline Ni–Fe alloy. The compressive results show that the strength is independent of grain orientation. However, the plastic strain increased remarkably when the loading axis is parallel to the direction of grain columns, which is due to the enhanced grain boundary and dislocation activities. The significance of the current study is that a new strategy was developed to improve the ductility of nanocrystalline materials.
Electromigration-driven motion of an elliptical inclusion
Authors: Li Z. , Chen N.
Published: August 2008

We present a rigorous analytical solution for electromigration-driven motion of an elliptical inclusion in an infinite two-dimensional conductor (here, an inclusion may imply a void). An elliptical inclusion will move at a velocity proportional to the applied electric field strength, inversely proportional to an equivalent inclusion size, and strongly affected by the shape parameter of the inclusion, but independent of rotation of the inclusion with respect to the direction of the applied electric field. For a given equivalent inclusion size, a circular inclusion will move at the lowest velocity, while a slitlike one moves quickly.
Effects of hydrogen anneals on oxygen deficient SrTiO3−x single crystals
Authors: Jalan Bharat , Engel-Herbert Roman , Mates Thomas E. , Stemmer Susanne
Published: August 2008

The influence of hydrogen gas anneals on the electrical properties of nominally undoped, oxygen-deficient SrTiO3−x single crystals was investigated. Titanium getter layers and vacuum anneals were used to obtain oxygen-deficient SrTiO3−x with a low electrical resistivity. These crystals showed an optical absorption peak at 2.92 eV and strong midinfrared absorption. Subsequent anneals at 800 °C in forming gas, which contained 10% hydrogen, returned the crystals into the insulating, transparent state. The mechanisms by which hydrogen anneals can compensate for the effects of oxygen vacancies in SrTiO3−x are discussed. The results show that forming gas anneals of stoichiometric SrTiO3 can lead to complex electrical conduction behavior.
Effect of ruthenium oxide electrode on the resistive switching of Nb-doped strontium titanate
Authors: Hasan Musarrat , Dong Rui , Choi H. J. , Lee D. S. , Seong D.-J. , Pyun M. B. , Hwang Hyunsang
Published: August 2008

We studied resistance switching characteristics of ruthenium oxide (RuOx)/niobium-doped strontium titanate (Nb:STO) contact. With increasing oxygen content of oxide electrode, the resistance window was improved. The switching speed of RuOx electrode also showed improvement compared to platinum (Pt) electrode. The RuOx film contains amorphous phase and also forms an interface oxide layer at the RuOx/Nb:STO contact, which suggests defect generation near the interface. Additionally, the interface reaction disturbs the crystalline orientation of Nb:STO. These defect sites facilitate switching properties by easy drift of current and oxygen ion and also by modulation of barrier height.
40 GHz small-signal cross-gain modulation in 1.3 μm quantum dot semiconductor optical amplifiers
Authors: Meuer C. , Kim J. , Laemmlin M. , Liebich S. , Bimberg D. , Capua A. , Eisenstein G. , Bonk R. , Vallaitis T. , Leuthold J. , Kovsh A. R. , Krestnikov I. L.
Published: August 2008

Small-signal cross-gain modulation of quantum dot based semiconductor optical amplifiers (QD SOAs), having a dot-in-a-well structure, is presented, demonstrating superiority for ultrahigh bit rate wavelength conversion. Optimization of the QD SOA high speed characteristics via bias current and optical pump power is presented and a small-signal 3 dB bandwidth exceeding 40 GHz is demonstrated. The p-doped samples investigated here enable small-signal wavelength conversion within a range of 30 nm, limited mainly by the gain bandwidth.
Remote sensing of burn severity: experience from western Canada boreal fires
Authors: Hall R. J. , Freeburn J. T. , de Groot W. J. , Pritchard J. M. , Lynham T. J. , Landry R.
Published: August 2008

The severity of a burn for post-fire ecological effects has been assessed with the composite burn index (CBI) and the differenced Normalized Burn Ratio (dNBR). This study assessed the relationship between these two variables across recently burned areas located in the western Canadian boreal, a region not extensively evaluated in previous studies. Of particular interest was to evaluate the nature of the CBI–dNBR relationship from the perspectives of modelling, the influence of fire behaviour prediction (FBP) fuel type, and how field observations could be incorporated into the burn severity mapping process. A non-linear model form best represented the relationship between these variables for the fires evaluated, and a similar statistical performance was achieved when data from all fires were pooled into a single dataset. Results from this study suggest the potential to develop a single model for application over the western region of the boreal, but further evaluation is necessary. This evaluation could include stratification by FBP fuel type due to study results that document its apparent influence on dNBR values. A new approach for burn severity mapping was introduced by defining severity thresholds through field assessment of CBI, and from which development of new models could be incorporated directly into the mapping process.
Electroconvulsive seizure and VEGF increase the proliferation of neural stem-like cells in rat hippocampus
Authors: Segi-Nishida Eri , Warner-Schmidt Jennifer L. , Duman Ronald S.
Published: August 2008

All classes of antidepressants increase hippocampal cell proliferation and neurogenesis, which contributes, in part, to the behavioral actions of these treatments. Among antidepressant treatments, electroconvulsive seizure (ECS) is the most robust stimulator of hippocampal cell proliferation and the most efficacious treatment for depression, but the cellular mechanisms underlying the actions of ECS are unknown. To address this question, we investigated the effect of ECS on proliferation of neural stem-like and/or progenitor cells in the subgranular zone of rat dentate gyrus. We define the neural differentiation cascade from stem-like cells to early neural progenitors (also referred to as quiescent and amplifying neural progenitors, respectively) by coexpression of selective cellular and mitotic activity markers. We find that at an early mitotic phase ECS increases the proliferation of quiescent progenitors and then at a later phase increases the proliferation of amplifying progenitors. We further demonstrate that vascular endothelial growth factor (VEGF) signaling is necessary for ECS induction of quiescent neural progenitor cell proliferation and is sufficient to produce this effect. These findings demonstrate that ECS and subsequent induction of VEGF stimulates the proliferation of neural stem-like cells and neural progenitor cells, thereby accounting for the superior neurogenic actions of ECS compared with chemical antidepressants.
Promoter ChIP-chip analysis in mouse testis reveals Y chromosome occupancy by HSF2
Authors: Åkerfelt Malin , Henriksson Eva , Laiho Asta , Vihervaara Anniina , Rautoma Karoliina , Kotaja Noora , Sistonen Lea
Published: August 2008

The mammalian Y chromosome is essential for spermatogenesis, which is characterized by sperm cell differentiation and chromatin condensation for acquisition of correct shape of the sperm. Deletions of the male-specific region of the mouse Y chromosome long arm (MSYq), harboring multiple copies of a few genes, lead to sperm head defects and impaired fertility. Using chromatin immunoprecipitation on promoter microarray (ChIP-chip) on mouse testis, we found a striking
in vivo
MSYq occupancy by heat shock factor 2 (HSF2), a transcription factor involved in spermatogenesis. HSF2 was also found to regulate the transcription of MSYq resident genes, whose transcriptional regulation has been unknown. Importantly, disruption of
Hsf2
caused a similar phenotype as the 2/3 deletion of MSYq, i.e., altered expression of the multicopy genes and increased mild sperm head abnormalities. Consequently, aberrant levels of chromatin packing proteins and more frequent DNA fragmentation were detected, implying that HSF2 is required for correct chromatin organization in the sperm. Our findings define a physiological role for HSF2 in the regulation of MSYq resident genes and the quality of sperm.
Structural basis for induced formation of the inflammatory mediator prostaglandin E
2
Authors: Jegerschöld Caroline , Pawelzik Sven-Christian , Purhonen Pasi , Bhakat Priyaranjan , Gheorghe Karina Roxana , Gyobu Nobuhiko , Mitsuoka Kaoru , Morgenstern Ralf , Jakobsson Per-Johan , Hebert Hans
Published: August 2008

Prostaglandins (PG) are bioactive lipids produced from arachidonic acid via the action of cyclooxygenases and terminal PG synthases. Microsomal prostaglandin E synthase 1 (MPGES1) constitutes an inducible glutathione-dependent integral membrane protein that catalyzes the oxidoreduction of cyclooxygenase derived PGH
2
into PGE
2
. MPGES1 has been implicated in a number of human diseases or pathological conditions, such as rheumatoid arthritis, fever, and pain, and is therefore regarded as a primary target for development of novel antiinflammatory drugs. To provide a structural basis for insight in the catalytic mechanism, we determined the structure of MPGES1 in complex with glutathione by electron crystallography from 2D crystals induced in the presence of phospholipids. Together with results from site-directed mutagenesis and activity measurements, we can thereby demonstrate the role of specific amino acid residues. Glutathione is found to bind in a U-shaped conformation at the interface between subunits in the protein trimer. It is exposed to a site facing the lipid bilayer, which forms the specific environment for the oxidoreduction of PGH
2
to PGE
2
after displacement of the cytoplasmic half of the N-terminal transmembrane helix. Hence, insight into the dynamic behavior of MPGES1 and homologous membrane proteins in inflammation and detoxification is provided.
Delivery of AMPA receptors to perisynaptic sites precedes the full expression of long-term potentiation
Authors: Yang Yunlei , Wang Xiao-bin , Frerking Matthew , Zhou Qiang
Published: August 2008

Trafficking of AMPA subtype glutamate receptors (AMPARs) from intracellular compartments to synapses is thought to be a major mechanism underlying the expression of long-term potentiation (LTP), a cellular substrate for learning and memory. However, it remains unclear whether the AMPAR trafficking that takes place during LTP is due to a targeted insertion of AMPARs directly into the synapse or delivery to extrasynaptic sites followed by translocation into the synapse. Here, we provide direct physiological evidence that LTP induced by a theta-burst pairing and tetanic stimulation protocols causes the rapid delivery of AMPARs to a perisynaptic site. Perisynaptic AMPARs do not normally detect synaptically released glutamate but can do so when the glial glutamate transporter EAAT1 is inhibited. AMPARs can be detected at this perisynaptic site before, but not after, the full expression of LTP. The appearance of perisynaptic AMPARs requires postsynaptic exocytosis, PKA signaling, and the C-terminal region of GluR1 subunit of AMPARs but not actin polymerization. Actin polymerization after LTP induction is required to retain AMPARs at the perisynaptic site after their appearance. Low-frequency stimulation given shortly after LTP induction leads to activity-dependent removal of perisynaptic AMPARs and suppresses the subsequent expression of LTP. These results demonstrate that AMPARs are rapidly trafficked to perisynaptic sites shortly after LTP induction and suggest that the delivery and maintenance of perisynaptic AMPARs may serve as a checkpoint in the expression of LTP.
From Words to Deeds: The Implementation of Power-Sharing Pacts in Peace Accords
Authors: Jarstad Anna K. , Nilsson Desiree
Published: August 2008

Is the implementation of power-sharing provisions the key to durable peace? This study analyzes whether the implementation of political, military, and territorial power-sharing provisions contributes to peace. We introduce a new dataset (IMPACT), which contains unique information on the implementation of power-sharing pacts in peace accords in the post—Cold War period. Based on the logic of costly signaling, we demonstrate that when the parties engage in costly concessions by implementing military and territorial provisions, peace is more likely to prevail. In contrast, the implementation of political pacts is less costly, and hence does not increase the prospects of peace.
Dilettantes, Ideologues, and the Weak: Terrorists Who Don't Kill
Authors: Asal Victor , Rethemeyer R. Karl
Published: August 2008

Why do some terrorist organizations choose not to—or fail to—kill? Of the 395 terrorist organizations operating between 1998 and 2005 only 39% had actually killed anyone. What factors account for this outcome? This article examines a series of organizational factors, including ideology, capability, and “home-base” country context, that the literature suggests are related to the decision to “go lethal.” We then test six hypotheses using data from the Memorial Institute for the Prevention of Terrorism (MIPT). Our statistical modeling suggests that ideology, capabilities, and “dilettantism” explain a significant proportion of the variation in whether an organization chooses to kill or not to kill. Leftists, anarchists, and environmentalists are far less likely to kill than those organizations inspired by religious ideologies. Larger organizations and those with more alliance ties are more likely to kill, while others are too “dilatory” and unserious about the “terrorist enterprise” to become lethal.
Acute Asthma in Primary Care
Authors: Simon Chantal
Published: August 2008

Four people per day, or one person every 7 hours, die from asthma. In 2005, asthma caused the deaths of 1318 individuals in the UK and 27 of those deaths were children. Delay in appropriate management can be fatal. Factors leading to poor outcome include doctors failing to assess severity by objective measurement, patients or relatives failing to appreciate severity and underuse of corticosteroids. It is estimated that 75% of hospital admissions and 90% of asthma deaths are preventable. It is essential that GPs know how to manage acute asthma and regard each emergency asthma consultation as acute, severe asthma until proven otherwise.
Childhood Atopic Eczema
Authors: Simon Chantal
Published: August 2008

The term eczema comes from the Greek meaning ‘to boil over’. Atopic eczema affects 15–20% of schoolchildren. It usually starts under the age of 6 months and by 1 year of age, 60% of those likely to develop eczema will have done so. It is an important condition as it has considerable impact on the quality of life of affected children. Atopic eczema is associated with other atopic conditions such as asthma and hay fever. In young children, atopic eczema may be associated with food allergy. Remission occurs by 15 years of age in 75% ( Fig. 1 ), although some children develop worsening symptoms in their teenage years and others relapse later in adulthood.
Common Injuries in General Practice
Authors: Simon Chantal
Published: August 2008

Although most people who injure themselves receive treatment at Accident & Emergency (A&E) or a Minor Injuries Unit, presentation of minor injuries to general practice, either to the GP directly or via the practice nurse, is a common occurrence. There are several reasons for this. Often patients have to wait a long time in A&E and presentation to the GP may save them time; it may be more convenient to go to the GP surgery rather than the A&E department if the A&E department is a long way away or the patient has difficulties with transport. Some patients may just prefer to see a doctor that they know and trust. In addition, many A&E departments give advice that injuries more than 2 days old should be presented to the GP rather than an A&E department. It is essential that GPs have a thorough knowledge of how to best manage these patients.
Positive roles of SAS2 in DNA replication and transcriptional silencing in yeast
Authors: Zou Yanfei , Bi Xin
Published: August 2008

Sas2p is a histone acetyltransferase implicated in the regulation of transcriptional silencing, and ORC is the six-subunit origin recognition complex involved in the initiation of DNA replication and the establishment of transcriptionally silent chromatin by silencers in yeast. We show here that SAS2 deletion (sas2Δ) exacerbates the temperature sensitivity of the ORC mutants orc2-1 and orc5-1. Moreover, sas2Δ and orc2-1 have a synthetic effect on cell cycle progression through S phase and initiation of DNA replication. These results suggest that SAS2 plays a positive role in DNA replication and cell cycle progression. We also show that sas2Δ and orc5-1 have a synthetic effect on transcriptional silencing at the HMR locus. Moreover, we demonstrate that sas2Δ reduces the silencing activities of silencers regardless of their locations and contexts, indicating that SAS2 plays a positive role in silencer function. In addition, we show that SAS2 is required for maintaining the structure of transcriptionally silent chromatin.
Incorporating the effects of changes in vegetation functioning and CO
2
on water availability in plant habitat models
Authors: Rickebusch Sophie , Thuiller Wilfried , Hickler Thomas , Araújo Miguel B , Sykes Martin T , Schweiger Oliver , Lafourcade Bruno
Published: August 2008

The direct effects of CO
2
level changes on plant water availability are usually ignored in plant habitat models. We compare traditional proxies for water availability with changes in soil water (fAWC) predicted by a process-based ecosystem model, which simulates changes in vegetation structure and functioning, including CO
2
physiological effects. We modelled current and future habitats of 108 European tree species using ensemble forecasting, comprising six habitat models, two model evaluation methods and two climate change scenarios. The fAWC models' projections are generally more conservative. Potential habitats shrink significantly less for boreo-alpine and alpine species. Changes in vegetation functioning and CO
2
on plant water availability should therefore be taken into account in plant habitat change projections.
Contemporary perspectives on the niche that can improve models of species range shifts under climate change
Authors: Morin Xavier , Lechowicz Martin J
Published: August 2008

Pioneering efforts to predict shifts in species distribution under climate change used simple models based on the correlation between contemporary environmental factors and distributions. These models make predictions at coarse spatial scales and assume the constancy of present correlations between environment and distribution. Adaptive management of climate change impacts requires models that can make more robust predictions at finer spatio-temporal scales by accounting for processes that actually affect species distribution on heterogeneous landscapes. Mechanistic models of the distribution of both species and vegetation types have begun to emerge to meet these needs. We review these developments and highlight how recent advances in our understanding of relationships among the niche concept, species diversity and community assembly point the way towards more effective models for the impacts of global change on species distribution and community diversity.
Predicting current and future biological invasions: both native and invaded ranges matter
Authors: Broennimann Olivier , Guisan Antoine
Published: August 2008

The classical approach to predicting the geographical extent of species invasions consists of training models in the native range and projecting them in distinct, potentially invasible areas. However, recent studies have demonstrated that this approach could be hampered by a change of the realized climatic niche, allowing invasive species to spread into habitats in the invaded ranges that are climatically distinct from those occupied in the native range. We propose an alternative approach that involves fitting models with pooled data from all ranges. We show that this pooled approach improves prediction of the extent of invasion of spotted knapweed (
Centaurea maculosa
) in North America on models based solely on the European native range. Furthermore, it performs equally well on models based on the invaded range, while ensuring the inclusion of areas with similar climate to the European niche, where the species is likely to spread further. We then compare projections from these models for 2080 under a severe climate warming scenario. Projections from the pooled models show fewer areas of intermediate climatic suitability than projections from the native or invaded range models, suggesting a better consensus among modelling techniques and reduced uncertainty.
Male blue monkeys alarm call in response to danger experienced by others
Authors: Papworth Sarah , Böse Anne-Sophie , Barker Jessica , Schel Anne Marijke , Zuberbühler Klaus
Published: August 2008

Male blue monkeys (
Cercopithecus mitis stuhlmanni
) of Budongo Forest, Uganda, produce two acoustically distinct alarm calls: hacks to crowned eagles (
Stephanoaetus coronatus
) and pyows to leopards (
Panthera pardus
) and a range of other disturbances. In playback experiments, males responded to leopard growls exclusively with a series of pyows and to eagle shrieks predominantly with hacks. Responses to playbacks of these alarm call series matched the responses to the corresponding predators, suggesting that the calls conveyed something about the nature of the threat. When responding to a series of hacks, indicating an eagle, males responded predominately with hacks, but produced significantly more calls if their group members were close to the playback stimulus than far away, regardless of their own position. When responding to a series of pyows, indicating a range of disturbances, males responded with pyows, but call rates were independent of the distance of other group members. The results suggest that males took into account the degree of danger experienced by other group members.
Male harassment drives females to alter habitat use and leads to segregation of the sexes
Authors: Darden Safi K , Croft Darren P
Published: August 2008

Sexual conflict is ubiquitous across taxa. It often results in male harassment of females for mating opportunities that are costly for females, in some cases reducing reproductive success and increasing mortality. One strategy that females may employ to avoid sexual harassment is to segregate spatially from males. In fact, we do find sexual segregation in habitat use in species that have high levels of sexual conflict; however, the role of sexual harassment in driving such segregation remains poorly understood. Here, we demonstrate experimentally in a population of wild Trinidadian guppies
Poecilia reticulata
that male sexual harassment drives females into habitats that they otherwise do not prefer to occupy. In support of the social factors hypothesis for sexual segregation, which states that social factors such as harassment drive sexual segregation, this female behaviour leads to segregation of the sexes. In the presence of males, females actively select areas of high predation risk, but low male presence, and thus trade off increased predation risk against reduced sexual harassment.
Severe drought and calf survival in elephants
Authors: Foley Charles , Pettorelli Nathalie , Foley Lara
Published: August 2008

Climate change in Africa is expected to lead to a higher occurrence of severe droughts in semi-arid and arid ecosystems. Understanding how animal populations react to such events is thus crucial for addressing future challenges for wildlife management and conservation. We explored how gender, age, mother's experience and family group characteristics determined calf survival in an elephant population during a severe drought in Tanzania in 1993. Young males were particularly sensitive to the drought and calf loss was higher among young mothers than among more experienced mothers. We also report high variability in calf mortality between different family groups, with family groups that remained in the National Park suffering heavy calf loss, compared with the ones that left the Park. This study highlights how severe droughts can dramatically affect early survival of large herbivores and suggests that extreme climatic events might act as a selection force on vertebrate populations, allowing only individuals with the appropriate behaviour and/or knowledge to survive.
Theoretical site-directed mutagenesis: Asp168Ala mutant of lactate dehydrogenase
Authors: Ferrer Silvia , Tuñón Iñaki , Moliner Vicent , Williams Ian H
Published: August 2008

Molecular simulations based on the use of hybrid quantum mechanics/molecular mechanics methods are able to provide detailed information about the complex enzymatic reactions and the consequences of specific mutations on the activity of the enzyme. In this work, the reduction of pyruvate to lactate catalysed by wild-type and Asp168Ala mutant lactate dehydrogenase (LDH) has been studied by means of simulations using a very flexible molecular model consisting of the full tetramer of the enzyme, together with the cofactor NADH, the substrate and solvent water molecules. Our results indicate that the Asp168Ala mutation provokes a shift in the p
K
a
value of Glu199 that becomes unprotonated at neutral pH in the mutant enzyme. This change compensates the loss of the negative charge of Asp168, rendering a still active enzyme. Thus, our methodology gives a calculated barrier height for the Asp168Ala mutant 3 kcal mol
−1
higher than that for wild-type LDH, which is in very good agreement with the experiment. The computed potential energy surfaces reveal the reaction pathways and transition structures for the wild-type and mutant enzymes. Hydride transfer is less advanced and the proton transfer is more advanced in the Asp168Ala mutant than in the wild type. This approach provides a very powerful tool for the analysis of the roles of key active-site residues.
Dynamic mechanical oscillations during metamorphosis of the monarch butterfly
Authors: Pelling Andrew E , Wilkinson Paul R , Stringer Richard , Gimzewski James K
Published: August 2008

The mechanical oscillation of the heart is fundamental during insect metamorphosis, but it is unclear how morphological changes affect its mechanical dynamics. Here, the micromechanical heartbeat with the monarch chrysalis (Danaus plexippus) during metamorphosis is compared with the structural changes observed throughin vivomagnetic resonance imaging (MRI). We employ a novel ultra-sensitive detection approach, optical beam deflection, in order to measure the microscale motions of the pupae during the course of metamorphosis. We observed very distinct mechanical contractions occurring at regular intervals, which we ascribe to the mechanical function of the heart organ. Motion was observed to occur in approximately 15 min bursts of activity with frequencies in the 0.4–1.0 Hz range separated by periods of quiescence during the first 83 per cent of development. In the final stages, the beating was found to be uninterrupted until the adult monarch butterfly emerged. Distinct stages of development were characterized by changes in frequency, amplitude, mechanical quality factor and de/repolarization times of the mechanical pulsing. The MRI revealed that the heart organ remains functionally intact throughout metamorphosis but undergoes morphological changes that are reflected in the mechanical oscillation.
The look of royalty: visual and odour signals of reproductive status in a paper wasp
Authors: Tannure-Nascimento Ivelize C , Nascimento Fabio S , Zucchi Ronaldo
Published: August 2008

Reproductive conflicts within animal societies occur when all females can potentially reproduce. In social insects, these conflicts are regulated largely by behaviour and chemical signalling. There is evidence that presence of signals, which provide direct information about the quality of the reproductive females would increase the fitness of all parties. In this study, we present an association between visual and chemical signals in the paper wasp
Polistes satan
. Our results showed that in nest-founding phase colonies, variation of visual signals is linked to relative fertility, while chemical signals are related to dominance status. In addition, experiments revealed that higher hierarchical positions were occupied by subordinates with distinct proportions of cuticular hydrocarbons and distinct visual marks. Therefore, these wasps present cues that convey reliable information of their reproductive status.
Interactions between environmental factors can hide isolation by distance patterns: a case study of
Ctenomys rionegrensis
in Uruguay
Authors: Kittlein Marcelo J , Gaggiotti Oscar E
Published: August 2008

Identifying the factors responsible for the structuring of genetic diversity is of fundamental importance for biodiversity conservation. However, arriving at such understanding is difficult owing to the many factors involved and the potential interactions between them. Here, we present an example of how such interactions can preclude us from arriving at a complete characterization of the demographic history and genetic structure of a species.
Ctenomys rionegrensis
is a species with restricted dispersal abilities and, as such, should exhibit an isolation by distance (IBD) pattern, which previous studies were unable to uncover. It was therefore concluded that this species underwent a recent population expansion. Using a novel hierarchical Bayesian method, we show that the inability to detect the IBD pattern is due to the interaction between elevation and geographical distance. We posit that populations in low areas suffer periodic floods that may reduce local population sizes, increasing genetic drift, a process that masks the effect of distance on genetic differentiation. Our results do not refute the possibility that the populations of
C. rionegrensis
underwent a recent population expansion but they indicate that an alternative scenario described by a metapopulation model at or near migration-drift equilibrium cannot be excluded either.
Molecular mechanisms of stress-induced prefrontal cortical impairment: Implications for mental illness
Authors: Hains Avis B. , Arnsten Amy F.T.
Published: August 2008

The symptoms of mental illness often involve weakened regulation of thought, emotion, and behavior by the prefrontal cortex. Exposure to stress exacerbates symptoms of mental illness and causes marked prefrontal cortical dysfunction. Studies in animals have revealed the intracellular signaling pathways activated by stress exposure that induce profound prefrontal cortical impairment: Excessive dopamine stimulation of D1 receptors impairs prefrontal function via cAMP intracellular signaling, leading to disconnection of prefrontal networks, while excessive norepinephrine stimulation of α1 receptors impairs prefrontal function via phosphatidylinositol–protein kinase C intracellular signaling. Genetic studies indicate that the genes disrupted in serious mental illness (bipolar disorder and schizophrenia) often encode for the intracellular proteins that serve as brakes on the intracellular stress pathways. For example, disrupted in schizophrenia 1 (DISC1) normally regulates cAMP levels, while regulator of G protein signaling 4 (RGS4) and diacylglycerol kinase (DGKH)—the molecule most associated with bipolar disorder— normally serve to inhibit phosphatidylinositol–protein kinase C intracellular signaling. Patients with mutations resulting in loss of adequate function of these genes likely have weaker endogenous regulation of these stress pathways. This may account for the vulnerability to stress and the severe loss of PFC regulation of behavior, thought, and affect in these illnesses. This review highlights the signaling pathways onto which genetic vulnerability and stress converge to impair PFC function and induce debilitating symptoms such as thought disorder, disinhibition, and impaired working memory.
Double dissociation of pharmacologically induced deficits in visual recognition and visual discrimination learning
Authors: Turchi Janita , Buffalari Deanne , Mishkin Mortimer
Published: August 2008

Monkeys trained in either one-trial recognition at 8- to 10-min delays or multi-trial discrimination habits with 24-h intertrial intervals received systemic cholinergic and dopaminergic antagonists, scopolamine and haloperidol, respectively, in separate sessions. Recognition memory was impaired markedly by scopolamine but not at all by haloperidol, whereas habit formation was impaired markedly by haloperidol but only minimally by scopolamine. These differential drug effects point to differences in synaptic modification induced by the two neuromodulators that parallel the contrasting properties of the two types of learning, namely, fast acquisition but weak retention of memories versus slow acquisition but durable retention of habits.
Chronic nicotine exposure induces a long-lasting and pathway-specific facilitation of LTP in the amygdala
Authors: Huang Yan-You , Kandel Eric R. , Levine Amir
Published: August 2008

Nicotine, in the form of tobacco, is the most commonly used drug of abuse. In addition to its rewarding properties, nicotine also affects many cognitive and emotional processes that involve several brain regions, including hippocampus and amygdala. Long-term changes in synaptic strength in these brain regions after drug exposure may be importantly correlated with behavioral changes induced by nicotine. Here, we study the effect of chronic oral administration of nicotine on the long-term synaptic potentiation in the amygdala, a key structure for emotional memory. We find that oral administration of nicotine for 7 d produces a significant enhancement of LTP in the amygdala. This facilitation is pathway specific: Nicotine selectively facilitates LTP in the cortical-lateral amygdala pathway, but not the thalamic-lateral and the lateral-basolateral synaptic pathway. The synaptic facilitation induced by a 7-d exposure to nicotine is long-lasting, it persists for 72 h after cessation of nicotine but decays 8 d after its cessation. In contrast, a shorter exposure of nicotine (24 h) induces only a short-lasting facilitation of synaptic plasticity that dissipates 24 and 72 h after cessation of nicotine. The facilitation of LTP in the amygdala after exposure to nicotine is mediated by removal of GABAergic inhibition, is dependent on the activation NMDA receptors, and can be prevented by blocking either α7 or β2 nACh receptors. Our results indicate that chronic exposure to nicotine can promote the induction of long-lasting modifications of synapses in a specific pathway in the amygdala.These changes in synaptic plasticity may contribute to the complex neural adaptations and behaviors caused by nicotine.
Emotional enhancement effect of memory: Removing the influence of cognitive factors
Authors: Sommer Tobias , Gläscher Jan , Moritz Steffen , Büchel Christian
Published: August 2008

According to the modulation hypothesis, arousal is the crucial factor in the emotional enhancement of memory (EEM). However, the multifactor theory of the EEM recently proposed that cognitive characteristics of emotional stimuli, e.g., relatedness and distinctiveness, also play an important role. The current study aimed to investigate the individual contribution of arousal to the neural correlates of the EEM by controlling for these additional cognitive factors. We observed the characteristic neuronal correlates of the EEM, in particular enhanced activity in the amygdala and hippocampus, which provides evidence for an arousal-driven EEM in the amygdala as proposed by the modulation hypothesis.
A case with blue gentian blues: roadside‐cutters creating neo grasslands as refugia for endangered Gentianella campestris
Authors: Huhta Ari‐Pekka , Rautio Pasi
Published: August 2008

In this paper, we report how roadside cutting affect individuals of field gentian Gentianella campestris, a highly cutting tolerant grassland herb, and if roadsides could serve as refugia for this endangered species. Injured plants produced four times more branches located close to the ground and the plants were more than two times heavier compared to the uninjured ones. No differences in final reproductive parameters between the injured and uninjured plants were observed. Unsuccessful and slow allocation of belowground resources to reproductive organs to be the reason for the overcompensation injured plants, when measured in vegetative biomass, but not in reproductive output. However, because the injured plants either fully compensated, or even overcompensated, the damage in all parameters, our results suggest that substitutive habitats, such as the roadside in question, may provide temporary safe‐sites for some species, and from these refugia they may disperse back to their original, restored habitats in the future.
Beyond Social Constructionism: A Structural Analysis of the Cultural Significance of the Child Star
Authors: O’Connor Jane
Published: August 2008

This article challenges the dominance of social constructionist theories of childhood by presenting a structural analysis of the child star as a recurrent, universal feature in the myths and legends of the world. The article argues that by conceptualising our understanding of children and childhood as being due solely to the socio‐historical context in which they live, an important dimension of childhood may be overlooked. Through looking at media stories about child stars throughout the twentieth century, this article uses a psychoanalytic Jungian framework to explore deeper similarities and patterns in cultural story telling about children over different cras and social contexts.
How Effective is Peer Education in Addressing Young People’s Sexual and Reproductive Health Needs in Developing Countries?
Authors: Price Neil , Knibbs Sarah
Published: August 2008

This review article questions the assumptions at the core of peer education interventions adopted in young people’s sexual and reproductive health programmes in developing countries. Peer education is a more complex and problematic approach than its popularity with development agencies and practitioners implies. Its rise to prominence is more indicative of the desire to find effective tools to address the HIV/AIDS pandemic, than of peer education’s proven effectiveness. The often simplistic model of social relations that underlies peer education interventions leads to the reinforcement of gendered power relations, and a failure to take account of the social dynamics of poverty. The dominant rationales for peer education are examined and contested. In spite of the mismatch between rhetoric and experience, the appeal of the approach remains powerful, stemming largely from the objective of engaging young people in health interventions in a way that increases their autonomy and capacity.
The effects of head flexion on airway seal, quality of ventilation and orogastric tube placement using the ProSeal™ laryngeal mask airway*
Authors: Xue F. S. , Mao P. , Liu H. P. , Yang Q. Y. , Li C. W. , He N. , Xu Y. C. , Liao X.
Published: August 2008

This prospective self‐controlled study was designed to evaluate the influences of head flexion on airway seal, quality of ventilation, and orogastric tube placement through the ProSeal™ laryngeal mask airway (ProSeal LMA™) in 80 anaesthetised, paralysed adult patients.

After the ProSeal LMA was inserted and the cuff pressure was set at 5.9 kPa, ventilation quality, airway seal pressure, fibreoptic positions of the cuff and the drainage tube, orogastric tube placement and efficacy of intermittent positive pressure ventilation (IPPV) were assessed in two randomly selected positions: neutral and flexed position.

When compared to the neutral head position, the head flexed significantly improved the airway seal pressure and the quality of ventilation of the ProSeal LMA (p < 0.05). Fibreoptic scores of the cuff position did not correlate with either the ability to obtain excellent or adequate ventilation through the ProSeal LMA or the ability to generate an airway seal pressure of ≥ 2 kPa. Orogastric tube placement via the drainage tube was successful on the first attempt in all patients in the neutral position compared with seven failures following three attempts in the flexed position (p < 0.05). There were no significant differences between the two head positions in the volume of air required to obtain an intracuff pressure of 5.9 kPa, fibreoptic score of the drainage tube position, and expiratory tidal volume and peak inspiratory pressure during IPPV (p > 0.05). In conclusion, head flexion improves airway seal and ventilation quality of the ProSeal LMA. However, placement of an orogastric tube via the drainage tube is impaired in the flexed position compared to the neutral position. Fibreoptic scoring of the ProSeal cuff position is not an accurate test to assess the airway seal and ventilation function.
Potency and mass of factor VIII in FVIII products
Authors: BUTENAS S. , PARHAMI‐SEREN B. , GISSEL M. T. , GOMPERTS E. D. , FASS D. N. , MANN K. G.
Published: August 2008

Summary.  Several factor (F) VIII products of different origin and structure are being used for haemophilia A treatment worldwide. The assessment of FVIII concentration in these products is done using activity assays, which are dependent upon the assay and its modifications. To evaluate FVIII products for potency and for FVIII concentration and specific activity, three activity‐based assays [activated partial thromboplastin time (APTT), intrinsic FXase and synthetic coagulation proteome] and two immunoassays (ELISA and western blotting) were used in this study with albumin‐free full‐length recombinant (r) FVIII as a standard. In all activity assays, products A and B (both contain full‐length rFVIII) at 1 U mL−1 showed potency similar to that of the 0.7 nm (1 U mL−1) rFVIII standard. Product E (contains truncated rFVIII) was less potent in the APTT (83% of standard) and product C (contains plasma FVIII) was less potent in FXase assays (66%). The ELISA immunoassay revealed that the specific activity of FVIII proteins in products A–C and E varied over a wide range (3900–13 200 U mg−1) and was higher for most lots when compared with the standard (5000 U mg−1), whereas the specific activity of product D (contains plasma FVIII) was lower than expected (3200–4800 U mg−1). (i) FVIII potency estimated in different assays gives dissimilar results; (ii) the specific activity of FVIII in various FVIII products is different and inconsistent. Thus, the administration of an equal FVIII potency in units means the administration of different amounts of FVIII protein, which may partly explain apparent discrepancies in product performance.
Impulse control and aggressive response generation as predictors of aggressive behaviour in children with mild intellectual disabilities and borderline intelligence
Authors: Van Nieuwenhuijzen M. , Orobio de Castro B. , Van Aken M. A. G. , Matthys W.
Published: August 2008

Background  A growing interest exists in mechanisms involved in behaviour problems in children with mild intellectual disabilities and borderline intelligence (MID/BI). Social problem solving difficulties have been found to be an explanatory mechanism for aggressive behaviour in these children. However, recently a discrepancy was found between automatic and reflective responding in social situations. We hypothesise that low impulse control and aggressive social problem solving strategies together may explain mechanisms involved in aggressive behaviour by children with MID/BI.

Method  In a clinical sample of 130 children with MID/BI receiving intramural treatment, main, moderating and mediating effects of impulse control and aggressive response generation on aggressive behaviour were examined by conducting hierarchical linear multiple regression analyses.

Results  Independent main effects of both impulse control and aggressive response generation on aggressive behaviour were found. Results indicated that low impulse control and aggressive response generation each explain unique variance in aggressive behaviour.

Conclusions  As this study is the first that has shown both impulse control and aggressive response generation to be important predictors for aggressive behaviour in children with MID/BI, future research should further examine the nature of relations between low impulse control and social problem solving.