bluuebunny/crossref_metadata_2025 huggingface dataset:
On Large Delays in Multi-Server Queues with Heavy Tails
Authors: Foss Sergey , Korshunov Dmitry
Published: March 2012

We present upper and lower bounds for the tail distribution of the stationary waiting time D in the stable GI/GI/s first-come first-served (FCFS) queue. These bounds depend on the value of the traffic load ρ which is the ratio of mean service and mean interarrival times. For service times with intermediate regularly varying tail distribution the bounds are exact up to a constant, and we are able to establish a “principle of s − k big jumps” in this case (here k is the integer part of ρ), which gives the most probable way for the stationary waiting time to be large. Another corollary of the bounds obtained is to provide a new proof of necessity and sufficiency of conditions for the existence of moments of the stationary waiting time.
The Knowledge Gradient Algorithm for a General Class of Online Learning Problems
Authors: Ryzhov Ilya O. , Powell Warren B. , Frazier Peter I.
Published: March 2012

We derive a one-period look-ahead policy for finite- and infinite-horizon online optimal learning problems with Gaussian rewards. Our approach is able to handle the case where our prior beliefs about the rewards are correlated, which is not handled by traditional multiarmed bandit methods. Experiments show that our KG policy performs competitively against the best-known approximation to the optimal policy in the classic bandit problem, and it outperforms many learning policies in the correlated case.
Polymatroid Optimization, Submodularity, and Joint Replenishment Games
Authors: He Simai , Zhang Jiawei , Zhang Shuzhong
Published: March 2012

In this paper we consider the problem of maximizing a separable concave function over a polymatroid. More specifically, we study the submodularity of its optimal objective value in the parameters of the objective function. This question is interesting in its own right and is encountered in many applications. But our research has been motivated mainly by a cooperative game associated with the well-known joint replenishment model. By applying our general results on polymatroid optimization, we prove that this cooperative game is submodular (i.e., its characteristic cost function is submodular) if the joint setup cost is a normalized and nondecreasing submodular function. Furthermore, the same result holds true for a more general one-warehouse multiple retailer game, which affirmatively answers an open question posed by Anily and Haviv [Anily, S., M. Haviv. 2007. The cost allocation problem for the first order interaction joint replenishment model. Oper. Res. 55(2) 292–302].
Network Optimization Models for Resource Allocation in Developing Military Countermeasures
Authors: Golany Boaz , Kress Moshe , Penn Michal , Rothblum Uriel G.
Published: March 2012

A military arms race is characterized by an iterative development of measures and countermeasures. An attacker attempts to introduce new weapons in order to gain some advantage, whereas a defender attempts to develop countermeasures that can mitigate or even eliminate the effects of the weapons. This paper addresses the defender's decision problem: given limited resources, which countermeasures should be developed and how much should be invested in their development to minimize the damage caused by the attacker's weapons over a certain time horizon. We formulate several optimization models, corresponding to different operational settings, as constrained shortest-path problems and variants thereof. We then demonstrate the potential applicability and robustness of this approach with respect to various scenarios.
Optimizing Long-Term Production Plans in Underground and Open-Pit Copper Mines
Authors: Epstein Rafael , Goic Marcel , Weintraub Andrés , Catalán Jaime , Santibáñez Pablo , Urrutia Rodolfo , Cancino Raúl , Gaete Sergio , Aguayo Augusto , Caro Felipe
Published: March 2012

We present a methodology for long-term mine planning based on a general capacitated multicommodity network flow formulation. It considers underground and open-pit ore deposits sharing multiple downstream processing plants over a long horizon. The purpose of the model is to optimize several mines in an integrated fashion, but real size instances are hard to solve due to the combinatorial nature of the problem. We tackle this by solving the relaxation of a tight linear formulation, and we round the resulting near-integer solution with a customized procedure. The model has been implemented at Codelco, the largest copper producer in the world. Since 2001, the system has been used on a regular basis and has increased the net present value of the production plan for a single mine by 5%. Moreover, integrating multiple mines provided an additional increase of 3%. The system has allowed planners to evaluate more scenarios. In particular, the model was used to study the option of delaying by four years the conversion of Chiquicamata, Codelco's largest open-pit mine, to underground operations.
Pricing Asian Options Under a Hyper-Exponential Jump Diffusion Model
Authors: Cai Ning , Kou Steven
Published: March 2012

We obtain a closed-form solution for the double-Laplace transform of Asian options under the hyper-exponential jump diffusion model. Similar results were available previously only in the special case of the Black-Scholes model (BSM). Even in the case of the BSM, our approach is simpler as we essentially use only Itô's formula and do not need more advanced results such as those of Bessel processes and Lamperti's representation. As a by-product we also show that a well-known recursion relating to Asian options has a unique solution in a probabilistic sense. The double-Laplace transform can be inverted numerically via a two-sided Euler inversion algorithm. Numerical results indicate that our pricing method is fast, stable, and accurate; and it performs well even in the case of low volatilities.
Sequential Correlated Equilibria in Stopping Games
Authors: Heller Yuval
Published: March 2012

In many situations, such as trade in stock exchanges, agents have many opportunities to act within a short interval of time. The agents in such situations can often coordinate their actions in advance, but coordination during the game consumes too much time. An equilibrium in such situations has to be sequential in order to handle mistakes made by players. In this paper, we present a new solution concept for infinite-horizon dynamic games, which is appropriate for such situations: a sequential normal-form correlated approximate equilibrium. Under additional assumptions, we show that every such game admits this kind of equilibrium.
Synthesis and Characterization of Manganese Oxide and Investigation of its Catalytic Activities for Oxidation of Benzyl Alcohol in Liquid Phase
Authors: Ilyas Mohammad , Saeed Muhammad
Published: March 2012

Manganese oxide was prepared by mechano-chemical process in solid state and was characterized by chemical and physical techniques. Chemical techniques include determination of oxygen content while physical techniques, includes surface area and pore size analyses, particle size, XRD, FTIR and SEM analyses. The synthesized manganese oxide was shown to have octahedral layered structure. The catalytic activity of manganese oxide was studied by carrying out the oxidation of benzyl alcohol in liquid phase using n-octane as solvent at temperature (<373) and oxygen pressure of up to one atmosphere. Benzaldehyde and benzoic acid were identified as the reaction products. However, benzoic acid appeared in reaction mixture after complete conversion of benzyl alcohol to benzaldehyde. Influence of different reaction parameters like comparison of reduced and unreduced catalyst, leaching of catalyst, effect of air, oxygen and nitrogen, effect of catalyst loading, life span of catalyst, effect of time and effect of partial pressure of oxygen on the reaction performance was studied. The catalyst can easily be separated from the reaction mixture by filtration, and can be regenerated by washing with water and ethanol and drying at 323 K.
MHD Flow of an Oldroyd-B Fluid Through a Porous Channel
Authors: Hayat Tasawar , Shehzad Sabir Ali , Mustafa Meraj , Hendi Awatif
Published: March 2012

This paper discusses the hydromagnetic boundary layer flow of an Oldroyd-B fluid in a porous channel. Both suction and injection (blowing) cases are considered. Appropriate similarity transformations are invoked to convert the partial differential equations into ordinary ones. Homotopy analysis method (HAM) is used for the presentation of analytic solution of the nonlinear differential system. Graphical results provide the salient features of the embedded flow parameters which include the Reynolds number, the Deborah numbers, and the Hartman number. Comparison between the existing numerical solution in a Maxwell fluid and present deduced series solution in a limiting sense is excellent.
Fischer Tropsch Synthesis: The Promoter Effects, Operating Conditions, and Reactor Synthesis
Authors: Sarkari Majid , Fazlollahi Farhad , Atashi Hossein
Published: March 2012

The effects of K, Ce, Zn, Cs, and Rb promoters on the structure and catalytic behavior of precipitated 50%Fe/50%Mn catalyst in Fischer–Tropsch synthesis (FTS) were investigated in a fixed-bed reactor. The effects of promoter on Fischer-Tropsch iron catalysts caused an increased growth probability of hydrocarbon chains from 0.67 to 0.75 for K to Rb promoter, and the olefin/paraffin ratios increased from 0.99 to 1.36 for Rb to K-promoted catalyst. The effect on the olefin selectivity was certainly due to increased adsorption strength of CO causing an enhanced displacement of olefin. The catalysts were assessed in terms of their FTS activity and product selectivity using Anderson–Schulz–Flory (ASF) models. The effects of various reaction conditions such as flow rates, temperatures, and H2/CO feed ratios were studied and process synthesis concepts were used to investigate interactions between the optimum regions for reactor operation and the experimental results.
The US Fiscal Situation: Causes and Remedies
Authors: Lazear Edward P.
Published: March 2012

We need a rule to control the growth in government, says Edward Lazear. “Inflation plus One” would eliminate the federal budget deficit in 8 years.
The Broken Health Care System: The Real Long-Term Deficit Problem
Authors: Baker Dean
Published: March 2012

Tackling health care costs is critical – Dean Baker suggests we unleash the forces brought foreign trade in health care services and personnel. The benefits are obvious but the impediments are great.
The Effect of Education on Equity Holdings
Authors: Hryshko Dmytro , Luengo-Prado Maria , Sorensen Bent E.
Published: March 2012

We study the effect of education on equity ownership in the form of stocks or mutual funds (outside of retirement accounts). We find a causal effect of education on stockholding using the number of colleges in the county where the respondent grew up as an instrument and data from the Panel Study of Income Dynamics. The effect is particularly strong for whites from non-privileged backgrounds. We explore the channels through which education affects equity holdings using the Wisconsin Longitudinal Survey and find that, controlling for family fixed effects, increased cognition and features associated with having a white collar job appear to be the main channels.
Price-Dependent Demand in Spatial Models
Authors: Gu Yiquan , Wenzel Tobias
Published: March 2012

This paper introduces price-dependent individual demand into the circular city model of product differentiation. We show that for any finite number of firms, an unique symmetric price equilibrium exists provided that demand functions are not “too” convex. As in the case of unit demand, the number of firms under free entry decreases in the fixed cost of entry while increases in the transportation cost of consumers. However, this number is no longer always in excess of the socially optimal level. Insufficient entry occurs when the fixed and transportation costs are high.
Traditional and Virtual Shopping Trips: The Taxation of Ecommerce Reconsidered
Authors: Prinz Aloys Leo
Published: March 2012

Traditional shopping trips in the real world induce social costs of travelling whereas shopping trips in the virtual world trigger transport costs when non‐digital goods are delivered in the real world. Taking into consideration that not only the goods bought create utility but also shopping trips, it is asked whether a differentiated sales tax could be justified as an incomplete remedy for the social costs of travelling and transport when a fuel tax is not available. Employing a ‘shopping trips’ model based on the analysis of Anas' (2007) article “A unified theory of consumption, travel and trip chaining”, the consumer's decision to shop offline or online is investigated. It is shown that a fuel tax may actually internalize the variable social costs of travelling and transport. As an alternative to a fuel tax, it is analyzed whether a differentiated sales tax could also internalize at least some of the externalities. Although this seems possible it is unclear whether the benefits of such a tax rate differentiation are worth the implied hidden costs relating to distributional and fairness goals of public policy.
The Importance of Effect Measure Modification When Using Demographic Variables to Predict Evacuation
Authors: Horney Jennifer A. , MacDonald Pia D.M. , Van Willigen Marieke , Kaufman Jay S.
Published: March 2012

INTRODUCTION: Previous studies have identified a number of demographic characteristics (e.g., age, income, level of education, household composition, and race or ethnicity) that affect hurricane evacuation. However, the magnitude and direction of these associations vary widely, even when the area of landfall or the intensity of the storm is similar. We propose that the associations of demographic characteristics and hurricane evacuation are modified by psychosocial factors such as social cohesion, social capital, and social control. Additional variability may be the result of the changing prevalence of these demographic variables over time or between study locations. METHODS: Ninety census blocks in three eastern North Carolina counties affected by Hurricane Isabel were selected probability proportionate to population and seven interviews were conducted at random locations within each of the selected blocks. Risk differences (RD) and 95% confidence intervals (CI) were produced for stratified data to test for heterogeneity. RESULTS: There was statistical evidence of effect measure modification on the additive scale of the effect of home type, homeownership, age, race, gender, marital status, and having children under age 18 living at home on hurricane evacuation based on Wald p‐values of the interaction terms of ≤ 0.20 and strata‐specific RDs which crossed the null value. Social cohesion, volunteerism, property preparation, church attendance, neighbor's evacuation, and the number of local friends and family modified the RDs for the demographic characteristics. CONCLUSIONS: The associations between demographic characteristics and hurricane evacuation failure are modified by social factors. Effect measure modification on the additive scale may help explain the inconsistency of previously published results and is the appropriate measure for targeted interventions that can increase evacuation among certain groups that are missed when average risks are calculated across the population.
Citizen Participation in Post‐disaster Flood Hazard Mitigation Planning in Peterborough, Ontario, Canada
Authors: Oulahen Greg , Doberstein Brent
Published: March 2012

Citizen participation is recognized as a standard feature of democratic planning. This article examines the role of citizen participation in a post‐disaster flood hazard mitigation planning program in Peterborough. The “six strategic planning choices” outlined by Brody, Godschalk, and Burby (2003) served as an analysis framework which was applied to Peterborough's post‐disaster flood hazard mitigation program. Primary data were derived from semi‐structured key informant interviews (n=15) with senior local government officials, consultants, and community group representatives. Secondary data and direct observation were used to contextualize and extend research findings. The research revealed that post‐disaster flood hazard mitigation in Peterborough has featured strong citizen participation, and for that reason was relatively successful. However, there are at least three areas of post‐disaster planning where citizen participation could have been improved. The article concludes that the Brody, Godschalk, and Burby (2003) framework is a valuable guide for planning practice and an evaluative research tool that revealed a number of significant strengths and several weaknesses of the Peterborough flood hazard mitigation planning process.
Testing Drugs Together With Those Who Need Them
Authors: Ehni Hans‐Jörg , Wiesing Urban
Published: March 2012

Under which conditions is international biomedical research in low and middle income countries acceptable? For about 15 years there has been no agreement in the international bioethical community on how to answer this question. Strict positions ask for universal global rules including a global standard of medical care. Others are concerned that this would be too paternalistic and want to leave space for negotiations between the parties involved. We want to point out that each of the positions mentioned above can claim to meet widespread moral intuitions and to be based on widely accepted ethical principles. However, they show also important weaknesses. In order to provide evidence for this, we first outline the general context in which international biomedical research is carried out. After analyzing each position in respect to two problems, the standard of care and reasonable availability, we evaluate two paradigmatic clinical trials from the perspective of both positions. This will help us to demonstrate their weaknesses. Finally, we argue for a middle ground which can correct these weaknesses, and we will as well provide an ethical justification for this middle ground.
Why and When "Flawed" Social Network Analyses Still Yield Valid Tests of
no Contagion
Authors: VanderWeele Tyler J. , Ogburn Elizabeth L. , Tchetgen Tchetgen Eric J.
Published: March 2012

Lyons (2011) offered several critiques of the social network analyses of
Christakis and Fowler, including issues of confounding, model inconsistency,
and statistical dependence in networks. Here we show that in some settings,
social network analyses of the type employed by Christakis and Fowler will
still yield valid tests of the null of no social contagion, even though
estimates and confidence intervals may not be valid. In particular, we show
that if the alter's state is lagged by an additional period, then under the
null of no contagion, the problems of model inconsistency and statistical
dependence effectively disappear which allow for testing for contagion. Our
results clarify the setting in which even "flawed" social network analyses
are still useful for assessing social contagion and social
influence.
Tug of War? A Jurisdictional Analysis of WHO and Interpol
Authors: Lawrence Laci S.
Published: March 2012

The World Health Organization (WHO) is the premier global organization to monitor and protect global health, while the International Criminal Police Organization (Interpol) functions as an international nucleus for assistance in crime prevention and detection. In the event of a deliberate act of bioterrorism, the inevitable question is whether or not a jurisdictional “tug of war” would occur between WHO and Interpol. The following paper addresses the power, initiatives, and protocol regarding bioterrorism of both Interpol and WHO, recent collaborations between the two organizations, and a jurisdictional analysis of what may occur when the two organization work together in the aftermath of an act of bioterrorism.
Endemic Disease in Afghanistan: How an Improved Biosecurity Framework Could Alleviate the Threat to U.S. Troops
Authors: Hefferly Andrew
Published: March 2012

As it is currently structured, Afghanistans biosecurity framework is weak and offers little to no protection to US troops against the threat of either infectious disease outbreaks or a biological weapons attack by terrorists. If fact, the only legitimate biosecurity practice of the Afghanistan government is to respond to outbreaks of infectious diseases. Such responses are debilitated by a devastated infrastructure, harsh and often times impassable landscape, and non-compliance by Afghan citizens.5 As such, US troops (and, indeed, Afghan citizens) are left susceptible to these endemic diseases to a degree beyond their own control. I believe an alternative biosecurity framework could be implemented that would alleviate this threat.6 Because Afghanistan remains a decentralized and tribal society, the crux of this proposal is that biosecurity measures are to be reallocated to the local, tribal level. I will further expound in greater detail on the reasons for this proposal in section four below.
A Survey of Priorities and Impediments for a Biosecurity Code of Conduct as a Confidence Building Measure for the Biological Weapons and Toxins Convention
Authors: Sutton Victoria
Published: March 2012

The Biological and Toxins Weapons Convention (BTWC), signed in 1972, is the express sense of 162 nations that as a world community, we agree to the end of the use of biological weapons by state parties. However, the increasing numbers of biological, pharmaceutical and public health facilities, coupled with the biotechnology revolution in the latter part of the 20th century, made the development of preventative code of conduct a priority. Biosafety and biosecurity codes of conduct became a topic for consideration by the BTWC in 2005. To develop this new focus, the BTWC conference held a series of expert meetings culminating with the 2011 Review Conference.Codes of conduct encourage a community approach to formulate acceptable, effective, and reasonably related principles in order to achieve its goals. In order to achieve a collective definition of the priorities or impediments for a biosecurity code of conduct among the representatives of the States Parties, a survey was designed. The survey instrument was designed to be answered during one of the days of the regular intersessional Meetings of Experts of the BTWC on August 27, 2009. This article provides a review and assessment of results of this survey.
Introduction: Volume 2 of the Journal of Biosecurity, Biosafety & Biodefense Law
Authors: Sutton Victoria
Published: March 2012

We are pleased to publish Volume 2, of the Journal for Biosecurity, Biosafety and Biodefense Law. This volume, like the first volume, continues to raise new and important legal issues in the emerging field of biosecurity, biosafety and biodefense law.
Temporal multiplexing and shaping of few-cycle pulses with microoptical retroreflector arrays
Authors: Grunwald Ruediger , Bock Martin , Jahns Jürgen
Published: March 2012

Temporal shaping of femtosecond pulses with microoptical retroreflector arrays was studied experimentally. It was demonstrated that pulses of variable duration and multiple pulses of variable delay can easily be generated by varying the tilt angle of the compact device. The corresponding pulse characteristics were determined by second order autocorrelation measurements.
Solving the optics equation for effective LED applications
Authors: Lauret Jean-Pierre
Published: March 2012

This article provides an overview of optical design for high-power LEDs and collimating light, and it will detail all the key issues related to physics, design and manufacturing.
Pharmacokinetic interactions of selective serotonin reuptake inhibitors with other commonly prescribed drugs in the era of pharmacogenomics
Authors: Manolopoulos Vangelis G. , Ragia Georgia , Alevizopoulos Georgios
Published: March 2012

Selective serotonin reuptake inhibitors (SSRIs) are widely prescribed to treat depression and a broad range of other comorbidities. The increased use of SSRIs in patients with various comorbidities treated with different drugs engenders the risk of pharmacokinetic drug interactions via cytochrome P450 (CYP450) enzymes inhibition. In the present review, we provide an overview of documented clinically significant drug interactions between SSRIs and other drugs co-prescribed in psychiatric patients for the same or other diseases. We further discuss the significance of drug interactions in the era of pharmacogenomics to underline the need for using information on both genotype and drug interactions towards implementing better clinical outcomes through personalized medicine.
Unitals over composition algebras
Authors: Knarr Norbert , Stroppel Markus
Published: March 2012

We consider polar unitals in projective planes over composition
algebras. We prove that the little projective group of such a unital
is contained in the centralizer of the polarity defining the
unital. This yields information about the full automorphism group of
the unital;
it is contained in the automorphism group of the normal subgroup
generated by all translations of the unital. Over suitable ground fields (such as the real numbers) we obtain a
complete description of the automorphism group of the unital in
the sense that it coincides with the centralizer of the polarity. The action of a nilpotent regular normal subgroup is used to
establish isomorphisms between unitals in spaces of different
dimensions, and over different fields.
Approximations of Additive Squares in Infinite Words
Authors: Brown Tom
Published: March 2012

We show that every infinite word
Genetische und immunzytometrische Diagnostik bei der akuten myeloischen Leukämie und ihre Bedeutung für die Wahl der Therapiestrategie/Genetic and immunophenotypical diagnostics for acute myeloid leukemia and their implication on treatment strategy
Authors: Kayser Sabine , Schlenk Richard F.
Published: March 2012

Bei der akuten myeloischen Leukämie (AML) spielen zyto- und molekulargenetische Veränderungen eine zentrale Rolle in der Pathogenese, sind unverzichtbar für die diagnostische Kategorisierung, stellen die wichtigsten Faktoren für die Vorhersage des Therapieansprechens und der klinischen Prognose dar und werden zunehmend für spezifische Genotyp-adaptierte Induktions- und Konsolidierungsstrategien genutzt. Insbesondere für die AML-Entitäten Core-binding-factor AML, charakterisiert durch die t(8;21) und die inv(16)/t(16;16), und AML mit
Reference measurement procedures for the accurate determination of cell concentrations: present status and future developments/Referenzmessverfahren für die genaue Bestimmung von Zellkonzentrationen: Status und zukünftige Entwicklungen
Authors: Kammel Martin , Kummrow Andreas , Neukammer Jörg
Published: March 2012

Accurate determination of cell concentrations serves as a valuable tool to support medical diagnosis and therapy control, e.g., in haematology, immunology and transfusion medicine. Intra- and inter-laboratory comparability of measurement results is essential for patient safety. To derive the so-called “conventional quantity value” of a measurand as target value for intra- or inter-laboratory quality assurance and to establish a traceability chain to the international System of Units (SI), a primary reference measurement procedure is needed, defined as a procedure which includes a complete analysis of influence quantities and perturbing factors and a complete description of measurement uncertainties. We describe a primary reference measurement procedure for the determination of erythrocyte concentration, based on flow cytometric cell counting by impedance measurements. To correct for instrument- and sample-dependent counting loss due to random coincidences, dilution series are prepared. The reference quantity value of the cell concentration is derived by extrapolation to vanishing volume fraction of the sample in the measurement suspension. Typically, for erythrocyte and leucocyte concentrations respective uncertainties of approximately 0.75% and 2% are reached. Future developments concern the extension of the procedures validated for erythrocyte and leucocyte counting by including immunological staining and microscopic techniques.
Analysis of crystallographic and structural data of polymeric iron-alkaline metal complexes
Authors: Melnik Milan , Sundberg Markku Rafael , Uggla Rolf
Published: March 2012

The present review covers almost 100 polymeric MFe (M=Li, Na, K, Rb, and Cs) compounds. The metal atoms of group 1 as partners with iron atom build up complex polymeric chains. The iron atoms are found in the oxidation states 0, +2, and +3, of which the oxidation state +3 prevails. The coordination number of the iron atom ranges from 2 to 10 (sandwiched). The coordination sphere about the main group 1 metals varies, ranging from tetrahedral to mostly trigonal bipyramid. There are also higher coordination numbers involved, namely, from 6 to 10. The most common ligand atoms are oxygen and nitrogen. There are three compounds displaying distortion isomerism. Several relationships between structural parameters are found and discussed.
Review of the application of ionic liquids as solvents for chitin
Authors: Jaworska Malgorzata M. , Kozlecki Tomasz , Gorak Andrzej
Published: March 2012

Chitin is one of the most abundant biopolymers, but due to its high crystallinity, it is completely insoluble in most organic and inorganic solvents. Chitin is soluble only in solvents that can destroy intersheet and intrasheet H-bonds, and many of these solvents are toxic, corrosive, nondegradable, or mutagenic. Because of these drawbacks, there is a search for more environmentally friendly solvents for chitin. It has been shown that ionic liquids (ILs) can dissolve chitin at elevated temperatures (80°–110°C) or with application of microwave irradiation. The highest solubility of chitin in an IL was about 20% (1-ethyl-3-methylimidazolium acetate), whereas chitin was shown to be insoluble in 1-allyl-3-methylimidazolium chloride and 1-butyl-3-methylimidazolium formate. Dissolved chitin can be regenerated by mixing with water or methanol, where the polymer precipitates from the solution. X-ray diffraction patterns of native polymer and precipitates have been compared and only small changes in crystallinity have been observed. In addition, Fourier transform infrared spectra remained similar for both forms of chitin, native and regenerated. Presented data hold great promise for the improvement of the chemistry of chitin and open new routes for chemical and enzymatic modifications of this polymer.
Batch-foamed biodegradable polylactide acid/organic modified montmorillonite clays and polylactide/sericite powder nanocomposites
Authors: Chen Jin-Wei , Liu Jian-ling
Published: March 2012

The properties of microcellular polylactic acid (PLA)/organic modified montmorillonite (OMMT) clays and PLA/sericite powder (SP) nanocomposites were investigated and compared in terms of thermal property, rheological property, particles dispersability, and cell microstructure. The batch-foaming process uses carbon dioxide as the physical blowing agent. According to the transmission electron microscopy and X-ray diffraction characterization, fillers (i.e., OMMT and SP) have good dispersions in PLA matrices. The thermal and rheological properties of solid PLA composites are demonstrated by differential scanning calorimetry and capillary rheometer, respectively. The microcellular morphology of fractured cross-sectional surfaces is characterized by scanning electron microscope. The batch-foamed PLA composites have more uniform cells in comparison with foamed pure PLA parts due to the mineral particles.
Neuroplasticity in Cigarette Smokers Is Altered under Withdrawal and Partially Restituted by Nicotine Exposition
Authors: Grundey Jessica , Thirugnanasambandam Nivethida , Kaminsky Kim , Drees Anne , Skwirba Angela C. , Lang Nicolas , Paulus Walter , Nitsche Michael A.
Published: March 2012

Nicotine improves cognitive functions by modulating neuroplasticity and cortical excitability in nonsmoking subjects. As shown recently, the positive effect of nicotine on cognition might at least partially be caused by a focusing effect of nicotine on neuroplasticity in these subjects. Concordant to this, smokers under nicotine withdrawal show reduced cognitive abilities, which are at least partially restituted by nicotine consumption. We aimed to explore the neurophysiological foundation of these effects by exploring nonfocal and focal plasticity-inducing protocols in human smokers under nicotine withdrawal and exposition. Focal, synapse-specific plasticity was induced by paired associative stimulation (PAS), while nonfocal plasticity was induced by transcranial direct current stimulation (tDCS). Each subject (12) received placebo and nicotine patches combined with one of the stimulation protocols to the primary motor cortex. Corticospinal excitability was monitored by transcranial magnetic stimulation-induced motor-evoked potential amplitudes. In smokers during nicotine withdrawal, facilitatory plasticity induced by tDCS and PAS was abolished, but restituted by nicotine. In contrast, excitability-diminishing plasticity was not affected by nicotine withdrawal. Under nicotine, the inhibitory aftereffects of PAS were delayed and prolonged, while the tDCS-generated excitability reduction was abolished. Thus, absent facilitatory plasticity in smokers during nicotine withdrawal is restituted by nicotine, favoring the deficit-compensating hypothesis of nicotine consumption. These results might shed further light on the proposed mechanism of nicotine on cognition and attention, which might be connected to nicotine addiction and probability of relapse in smokers.
Synapsin Selectively Controls the Mobility of Resting Pool Vesicles at Hippocampal Terminals
Authors: Orenbuch Ayelet , Shalev Lee , Marra Vincenzo , Sinai Isaac , Lavy Yotam , Kahn Joy , Burden Jemima J. , Staras Kevin , Gitler Daniel
Published: March 2012

Presynaptic terminals are specialized sites for information transmission where vesicles fuse with the plasma membrane and are locally recycled. Recent work has extended this classical view, with the observation that a subset of functional vesicles is dynamically shared between adjacent terminals by lateral axonal transport. Conceptually, such transport would be expected to disrupt vesicle retention around the active zone, yet terminals are characterized by a high-density vesicle cluster, suggesting that counteracting stabilizing mechanisms must operate against this tendency. The synapsins are a family of proteins that associate with synaptic vesicles and determine vesicle numbers at the terminal, but their specific function remains controversial. Here, using multiple quantitative fluorescence-based approaches and electron microscopy, we show that synapsin is instrumental for resisting vesicle dispersion and serves as a regulatory element for controlling lateral vesicle sharing between synapses. Deleting synapsin disrupts the organization of presynaptic vesicle clusters, making their boundaries hard to define. Concurrently, the fraction of vesicles amenable to transport is increased, and more vesicles are translocated to the axon. Importantly, in neurons from synapsin knock-out mice the resting and recycling pools are equally mobile. Synapsin, when present, specifically restricts the mobility of resting pool vesicles without affecting the division of vesicles between these pools. Specific expression of synapsin IIa, the sole isoform affecting synaptic depression, rescues the knock-out phenotype. Together, our results show that synapsin is pivotal for maintaining synaptic vesicle cluster integrity and that it contributes to the regulated sharing of vesicles between terminals.
Broadening of Cortical Inhibition Mediates Developmental Sharpening of Orientation Selectivity
Authors: Li Ya-tang , Ma Wen-pei , Pan Chen-jie , Zhang Li I. , Tao Huizhong W.
Published: March 2012

Orientation selectivity (OS) of visual cortical neurons is progressively sharpened during development. However, synaptic circuit mechanisms underlying the OS sharpening remain unclear. In the current study,in vivowhole-cell voltage-clamp recordings from layer 4 excitatory neurons in the developing mouse primary visual cortex revealed changes of orientation tuning profiles of their excitatory and inhibitory inputs during a post-eye-opening period when OS of their spiking responses becomes sharpened. In addition to a parallel strengthening of excitation and inhibition during this developmental period, the orientation tuning of excitatory inputs keeps relatively constant, whereas the tuning of inhibitory inputs is broadened, and becomes significantly broader than that of excitatory inputs. Neuron modeling and dynamic-clamp recording demonstrated that this developmental broadening of the inhibitory tuning is sufficient for sharpening OS. Depriving visual experience by dark rearing impedes the normal developmental strengthening of excitation, but a similar broadening of inhibitory tuning, likely caused by a nonselective strengthening of inhibitory connections, results in the apparently normal OS sharpening in excitatory neurons. Our results thus provide the first demonstration that an inhibitory synaptic mechanism can primarily mediate the functional refinement of cortical neurons.
Deficiency of ATP13A2 Leads to Lysosomal Dysfunction, α-Synuclein Accumulation, and Neurotoxicity
Authors: Usenovic Marija , Tresse Emilie , Mazzulli Joseph R. , Taylor J. Paul , Krainc Dimitri
Published: March 2012

The autophagy-lysosomal pathway plays an important role in the clearance of long-lived proteins and dysfunctional organelles. Lysosomal dysfunction has been implicated in several neurodegenerative disorders including Parkinson's disease and related synucleinopathies that are characterized by accumulations of α-synuclein in Lewy bodies. Recent identification of mutations in genes linked to lysosomal function and neurodegeneration has offered a unique opportunity to directly examine the role of lysosomes in disease pathogenesis. Mutations in lysosomal membrane protein ATP13A2 (PARK9) cause familial Kufor–Rakeb syndrome characterized by early-onset parkinsonism, pyramidal degeneration and dementia. While previous data suggested a role of ATP13A2 in α-synuclein misfolding and toxicity, the mechanistic link has not been established. Here we report that loss of ATP13A2 in human fibroblasts from patients with Kufor–Rakeb syndrome or in mouse primary neurons leads to impaired lysosomal degradation capacity. This lysosomal dysfunction results in accumulation of α-synuclein and toxicity in primary cortical neurons. Importantly, silencing of endogenous α-synuclein attenuated the toxicity in ATP13A2-depleted neurons, suggesting that loss of ATP13A2 mediates neurotoxicity at least in part via the accumulation of α-synuclein. Our findings implicate lysosomal dysfunction in the pathogenesis of Kufor–Rakeb syndrome and suggest that upregulation of lysosomal function and downregulation of α-synuclein represent important therapeutic strategies for this disorder.
Toxic Role of K+Channel Oxidation in Mammalian Brain
Authors: Cotella Diego , Hernandez-Enriquez Berenice , Wu Xilong , Li Ruiqiong , Pan Zui , Leveille Joseph , Link Christopher D. , Oddo Salvatore , Sesti Federico
Published: March 2012

Potassium (K+) channels are essential to neuronal signaling and survival. Here we show that these proteins are targets of reactive oxygen species in mammalian brain and that their oxidation contributes to neuropathy. Thus, the KCNB1 (Kv2.1) channel, which is abundantly expressed in cortex and hippocampus, formed oligomers upon exposure to oxidizing agents. These oligomers were ∼10-fold more abundant in the brain of old than young mice. Oxidant-induced oligomerization of wild-type KCNB1 enhanced apoptosis in neuronal cells subject to oxidative insults. Consequently, a KCNB1 variant resistant to oxidation, obtained by mutating a conserved cysteine to alanine, (C73A), was neuroprotective. The fact that oxidation of KCNB1 is toxic, argues that this mechanism may contribute to neuropathy in conditions characterized by high levels of oxidative stress, such as Alzheimer's disease (AD). Accordingly, oxidation of KCNB1 channels was exacerbated in the brain of a triple transgenic mouse model of AD (3xTg-AD). The C73A variant protected neuronal cells from apoptosis induced by incubation with β-amyloid peptide (Aβ1–42). In an invertebrate model (Caenorhabditis elegans) that mimics aspects of AD, a C73A-KCNB1 homolog (C113S-KVS-1) protected specific neurons from apoptotic death induced by ectopic expression of human Aβ1–42. Together, these data underscore a novel mechanism of toxicity in neurodegenerative disease.
P2X2 and P2X5 Subunits Define a New Heteromeric Receptor with P2X7-Like Properties
Authors: Compan Vincent , Ulmann Lauriane , Stelmashenko Olga , Chemin Jean , Chaumont Séverine , Rassendren Francois
Published: March 2012

Ligand-gated ion channels are prototypic oligomeric membrane proteins whose stoichiometry determines their functional properties and subcellular localization. Deciphering the quaternary structure of such protein complexes is an arduous task and usually requires the combination of multiple approaches. ATP-gated P2X receptors are formed by the association of three subunits, but the quaternary arrangement of the seven P2X subunits at the plasma membrane remains poorly characterized. By combining bioluminescence resonance energy transfer, bifunctional fluorescence complementation and protein biochemistry, we developed an experimental approach that allows precise determination of rat P2X receptor quaternary assembly. We found that P2X5 subunits associate with P2X1, P2X2, and P2X4 subunits. We demonstrate that P2X5 and P2X2 subunits interact to form as yet uncharacterized heteromeric receptors with alternate stoichiometries, both present at the plasma membrane. P2X2/5 receptors display functional properties such as pore dilatation, membrane blebbing, and phosphatidylserine exposure that were previously thought to be characteristic hallmarks of the P2X7 receptor. In mouse, P2X2 and P2X5 subunits colocalize and physically interact in specific neuronal populations suggesting that other P2X receptors might contribute to cellular responses typically attributed to P2X7 receptor.
Validation of the Japanese Version of the Recovery Experience Questionnaire
Authors: Shimazu Akihito , Sonnentag Sabine , Kubota Kazumi , Kawakami Norito
Published: March 2012

Validation of the Japanese Version of the Recovery Experience Questionnaire: Akihito SHIMAZU, et al. Department of Mental Health, The University of Tokyo, Graduate School of Medicine—

Objectives

The aim of this study was to validate the Japanese version of the Recovery Experience Questionnaire (REQ‐J), which assesses how individuals unwind and recuperate from work during leisure time (i.e., psychological detachment, relaxation, mastery and control).

Methods

The translated and back‐translated REQ was administered via the Internet to 2,520 Japanese employees from various occupations. Exploratory and confirmatory factor analyses were conducted to evaluate factorial validity. The relationship with potential predictors and consequences of recovery experiences were investigated to evaluate construct validity. Internal consistency was examined to evaluate its reliability.

Results

A series of confirmatory factor analyses revealed that the hypothesized four‐factor model fit the data best. Construct validity was generally supported by expected correlations of recovery experiences with possible predictors and consequences. Cronbach's alpha coefficient for each of the four subscales was sufficient(0.85–0.89).

Conclusions

This study confirmed that the REQ‐J is an adequate measure of recovery experiences that can be used in the Japanese context.
Charge transport enhancement via air-mediated self-organization in polymer semiconductors
Authors: Kushida Takashi , Nagase Takashi , Naito Hiroyoshi
Published: March 2012

Air-mediated molecular ordering in self-organized polymer semiconductors of regioregular poly(3-hexylthiophene) (P3HT) and poly[(9,9′-dioctylfluorenyl-2,7-diyl)-(2,2′-bithiophene-5,5′-diyl)] (F8T2) was investigated using organic field-effect transistors (OFETs) fabricated by transfer-printing using poly(dimethylsiloxane) stamps with various surface energies. OFET measurements revealed that the charge transport in the polymer semiconductors via the air interface layer was better than that via the substrate interface layer. The results indicated that the formation of a highly ordered microstructure at the polymer/air interface through air-mediated self-organization occurs in many polymer semiconductors. This air-mediated self-organization was weaker than substrate-mediated self-organization, whose influence appeared in OFETs with thin semiconductor films.
Heat of hydration models of cementitious materials
Authors: Wang Xiao-Yong , Lee Han-Seung
Published: March 2012

Silica fume from certain metallurgical operations, granulated slag from metal industries and fly ash from the combustion of coal are industrial by-products that have been widely used as mineral admixtures in normal- and high-strength concrete. Due to the reaction between calcium hydroxide (CH) and mineral admixtures, the hydration of concrete containing mineral admixtures is much more complex compared with that of Portland cement. In this paper, the production of CH in cement hydration and its consumption due to the reaction of mineral admixtures is considered in order to develop a numerical model that simulates the hydration of concrete containing silica fume, fly ash or slag. The heat evolution rates of these admixture-blended concrete were determined by the contribution of both cement hydration and the reaction of the mineral admixtures. The proposed model was verified with experimental data on concrete with different water/cement ratios and mineral admixture substitution ratios.
Periodontal Ligament Formation Around Different Types of Dental Titanium Implants. I. The Self‐Tapping Screw Type Implant System
Authors: Warrer Kirsten , Karring Thorkild , Gotfredsen Klaus
Published: March 2012

The aim of this study was to determine if a periodontal ligament can form around self‐tapping, screw type titanium dental implants. Implants were inserted in contact with the periodontal ligament of root tips retained in the mandibular jaws of 7 monkeys. In each side of the mandible, 1 premolar and 2 molars were removed in such a manner that in approximately half the cases, the root tips were retained. Following healing, the experimental areas were examined on radiographs, and sites were selected for the insertion of the implants, so that every second implant would have a close contact to the retained root tips. Three months after placement of the implants, the animals were sacrificed, and ground sections were produced for histological analysis. The results demonstrated that newly‐formed cementum had become deposited on the implant surface in the contact area between the implant and the retained roots, whereas osseointegration was consistently found on the remaining part of the implant surface as well as on the entire surface of the implants placed without contact to the retained root tips. The study has shown that, when placed in contact with periodontal ligament tissue of retained roots, a periodontal ligament can form on self‐tapping, screw type titanium dental implants in areas where a void is present between the surrounding bone and the implant at the time of insertion. J Periodontol 1993; 64:29–34.