bluuebunny/crossref_metadata_2025 huggingface dataset:
General necessary conditions for partially observed optimal stochastic controls
Authors: Li Xunjing , Tang Shanjian
Published: April 2006

The partially observed control problem is considered for stochastic processes with control entering into the diffusion and the observation. The maximum principle is proved for the partially observable optimal control. A pure probabilistic approach is used, and the adjoint processes are characterized as solutions of related backward stochastic differential equations in finite-dimensional spaces. Most of the derivation is identified with that of the completely observable case.
Dixie cups: sampling with replacement from a finite population
Authors: Klaassen Chris A. J.
Published: April 2006

At which (random) sample size will every population element have been drawn at least m times? This special coupon collector's problem is often referred to as the Dixie cup problem. Some asymptotic properties of the Dixie cup problem with unequal sampling probabilities are described.
On redundancy allocations in systems
Authors: Singh Harshinder , Misra Neeraj
Published: April 2006

Allocation of a redundant component in a system in order to optimize, in some sense, the lifetime of the system is an important problem in reliability theory, having practical applications. Consider a series system consisting of two components (say C1 and C2), having independent random lifetimes X1 and X2, and suppose a component C having random lifetime X (independent of X1 and X2) is available for active redundancy with one of the components. Let U1 = min(max(X1, X), X2) and U2 = min(X1, max(X2, X)), so that U1 (U2) denote the lifetime of a system obtained by allocating C to C1 (C2). We consider the criterion where C1 is preferred to C2 for redundancy allocation if . Here we investigate the problem of allocating C to C1 or C2, with respect to the above criterion. We also consider the standby redundancy for series and parallel systems with respect to the above criterion. The problem of allocating an active redundant component in order that the resulting system has the smallest failure rate function is also considered and it is observed that unlike stochastic optimization, here the lifetime distribution of the redundant component also plays a role, making the problem of even active redundancy allocation more complex.
Approximations and boundary conditions for continuous-time threshold autoregressive processes
Authors: Hyndman Rob J.
Published: April 2006

Continuous-time threshold autoregressive (CTAR) processes have been developed in the past few years for modelling non-linear time series observed at irregular intervals. Several approximating processes are given here which are useful for simulation and inference. Each of the approximating processes implicitly defines conditions on the thresholds, thus providing greater understanding of the way in which boundary conditions arise.
A bivariate optimal replacement policy for a repairable system
Authors: Zhang Yuan Lin
Published: April 2006

In this paper, a repairable system consisting of one unit and a single repairman is studied. Assume that the system after repair is not as good as new. Under this assumption, a bivariate replacement policy (T, N), where T is the working age and N is the number of failures of the system is studied. The problem is to determine the optimal replacement policy (T, N)∗such that the long-run average cost per unit time is minimized. The explicit expression of the long-run average cost per unit time is derived, and the corresponding optimal replacement policy can be determined analytically or numerically. Finally, under some conditions, we show that the policy (T, N)∗ is better than policies N∗ or T∗.
On the input-output map of aG/G/1 queue
Authors: Chang Cheng-Shang
Published: April 2006

In this note, we considerG/G/1 queues with stationary and ergodic inputs. We show that if the service times are independent and identically distributed with unbounded supports, then for a given mean of interarrival times, the number of sequences (distributions) of interarrival times that induce identical distributions on interdeparture times is at most 1. As a direct consequence, among all theG/M/1 queues with stationary and ergodic inputs, theM/M/1 queue is the only queue whose departure process is identically distributed as the input process.
Fast simulation of Markov fluid models
Authors: Ridder Ad
Published: April 2006

In this paper we study continuous flow finite buffer systems with input rates modulated by Markov chains. Discrete event simulations are applied for estimating loss probabilities. The simulations are executed under a twisted version of the original probability measure (importance sampling). We present a simple rule for determining a new measure, then show that the new measure matches the ‘most likely' empirical measure that we expect from large deviations arguments, and finally prove optimality of the new measure.
Stochastic comparisons of random minima and maxima
Authors: Shaked Moshe , Wong Tityik
Published: April 2006

Let X1, X2,… be a sequence of independent random variables and let N be a positive integer-valued random variable which is independent of the Xi. In this paper we obtain some stochastic comparison results involving min {X1, X2,…, XN) and max{X1, X2,…, XN}.
Stochastic storage networks: stationarity and the feedforward case
Authors: Kella Offer
Published: April 2006

We show that for a certain storage network the backward content process is increasing, and when the net input process has stationary increments then, under natural stability conditions, the content process has a stationary version under which the cumulative lost capacities have stationary increments. Moreover, for the feedforward case, we show that under some minimal conditions, two content processes with net input processes which differ only by initial conditions can be coupled in finite time and that the difference of two content processes vanishes in the limit if the difference of the net input processes monotonically approaches a constant. As a consequence, it is shown that for the natural stability conditions, when the net input process has stationary increments, the distribution of the content process converges in total variation to a proper limit, independent of initial conditions.
Reliability analysis of M/G/1 queueing systems with server breakdowns and vacations
Authors: Li Wei , Shi Dinghua , Chao Xiuli
Published: April 2006

This note introduces reliability issues to the analysis of queueing systems. We consider an M/G/1 queue with Bernoulli vacations and server breakdowns. The server uptimes are assumed to be exponential, and the server repair times are arbitrarily distributed. Using a supplementary variable method we obtain a transient solution for both queueing and reliability measures of interest. These results provide insight into the effect of server breakdowns and repairs on system performance.
Toxicology in the Drug Discovery and Development Process
Authors: Dorato Michael A. , Buckley Lorrene A.
Published: April 2006

The primary objective of toxicology studies in the drug development process is to evaluate the safety of potential drug candidates. This is accomplished using relevant animal models and validated procedures. The ultimate goal is to translate the animal model responses into an understanding of the risk for human subjects. To this end, the toxicologist must be aware of the international guidelines for safety evaluation, as well as traditional and nontraditional toxicology models. As described in this unit, the typical toxicology profile consists of safety pharmacology, genetic toxicology, acute and subchronic toxicology, chronic toxicology, absorption, distribution, metabolism, and excretion (ADME) studies, reproductive and developmental toxicology, and an evaluation of carcinogenic potential.
Unidirectional development of CD8+ central memory T cells into protective Listeria‐specific effector memory T cells
Authors: Huster Katharina M. , Koffler Martina , Stemberger Christian , Schiemann Matthias , Wagner Hermann , Busch Dirk H.
Published: April 2006

Three distinct subsets of antigen‐experienced CD8+ T cells have been identified so far: short‐living effector T cells (TEC) and two long‐living subsets, described as central (TCM) and effector memory (TEM) T cells. The lineage relationships of these subpopulations as well as their involvement in protection have not yet been conclusively determined. We recently described a novel marker combination (CD127 and CD62L) to identify all three major CD8+ T cell subsets in mice infected with Listeria monocytogenes (L.m.). Extensive lineage relationship analyses on highly purified subpopulations after in vitro and in vivo stimulation demonstrated that TCM can develop into TEM or TEC, whereas TEM can only progress to TEC cells. Short‐living TEC never regained a TEM or TCM phenotype. These data strongly suggest a hierarchical and unidirectional order of developmental stages. In vivo priming protocols that preferentially induced one of the different CD8+ T cell subsets demonstrated that predominance of TEM (CD40 stimulation) correlated best with effective protection against L.m., whereas generation of neither TCM (by immunization with heat‐killed L.m.) nor TEC (by systemic co‐administration of CpG during primary infection) conferred substantial long‐term protective immunity. These findings have important implications for the design of more effective T cell‐based vaccines.
Managing a phased retirement program: The case of UNC
Authors: Allen Steven G. , Clark Robert L. , Ghent Linda S.
Published: April 2006

The implications of the policy choices made in setting up a phased retirement system are demonstrated by its variety of outcomes.
The costs and benefits of phased retirement
Authors: Leslie David W.
Published: April 2006

Individuals who retire have widely varying needs and differ also in their preparedness for their new conditions.
Multiphoton excited fabricated nano and micro patterned extracellular matrix proteins direct cellular morphology
Authors: Pins George D. , Bush Katie A. , Cunningham Lawrence P. , Campagnola Paul J.
Published: April 2006

We use multiphoton excited (MPE) photochemistry to fabricate patterned extracellular matrices (ECM) and to investigate the morphology of human dermal fibroblasts adhered to the resulting photocrosslinked linear structures of fibronectin (FN), fibrinogen (FG), and bovine serum albumin (BSA). These proteins were chosen to systematically investigate the roles of topography and ECM biochemistry on cell spreading, as fibroblasts bind directly to both FN and FG at RGD sites through known integrins, whereas BSA provides no comparable ECM cues for cell binding. MPE crosslinked patterns are created from parallel linear structures 600 nm in width, 200 μm in length, and spaced by either 10 or 40 μm. Immunofluorescence staining of FN and FG was used to assay the functionality of crosslinked proteins. The metrics of orientation, elongation, and cell perimeter were used to quantitate the resulting cellular behavior on the crosslinked protein patterns. These parameters all reflect statistical differences for cells on BSA, relative to the similar statistical behavior on fibronectin and fibrinogen. Cells on the BSA patterns are constrained by physical guidance and orientation between linear structures. In contrast, cells adhered on both FN and FG had a greater propensity to spread across adjacent structures, indicating the importance of cell matrix interactions. Focal adhesion staining of cells adhered to the protein structures revealed similar trends. These findings are consistent with our hypothesis that these crosslinked matrix protein structures are expected to direct cell adhesion and spreading and that the topography and ECM cues lead to different forms of guidance. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Identification of candidate antigen in Whipple's disease using a serological proteomic approach
Authors: Kowalczewska Malgorzata , Fenollar Florence , Lafitte Daniel , Raoult Didier
Published: April 2006

Whipple's disease (WD) is a chronic multisystemic infection, caused by Tropheryma whipplei, a Gram‐positive rod. Recently, a reliable method has been developed for cultivating T. whipplei in vitro. This together with the availability of complete genome sequence of T. whipplei prompted us to initiate proteome analysis of T. whipplei. The objective of the present study was to identify candidate proteins for serological diagnosis of WD. Immunoreactivities of sera collected from 18 patients with WD were compared with those of 24 control subjects who did not have WD. For this, we used 2‐DE, immunoblotting, and MS. In total, we identified 23 candidate antigenic proteins. These included a subset of six proteins, each of which was found significantly more frequently in cases as compared to their controls. The remaining 17 proteins were found exclusively in cases. The methods we used in the current study enabled us to identify candidate antigens that, in our view, might be useful for serological diagnosis of WD.
From surface science to nanoscience
Authors: von Blanckenhagen Peter
Published: April 2006

In this communication, a short summary is given of results obtained by our research group in the fields of surface science and nanoscience, thus visualizing a path from surface science to nanoscience. Copyright © 2006 John Wiley & Sons, Ltd.
Definitions of Suicidal Behavior
Authors: De Leo D. , Burgis S. , Bertolote J.M. , Kerkhof A.J.F.M. , Bille-Brahe U.
Published: April 2006

Based on the experience matured during the 15 years of the WHO/EURO Multicentre Study on Suicidal Behavior, this paper provides an excursus on main elements that characterize components for definitional needs. It describes the rationale for choosing the initial set of definitions within the study and the subsequent problems and developments. As a result, unifying terminologies are proposed.
Evidence of temperature dependence of initial adsorption sites of Ge atoms on Si(111)-7×7
Authors: Ansari Zubaida A. , Tomitori Masahiko , Arai Toyoko
Published: April 2006

Small amounts of Ge atoms are deposited on Si(111)-7×7 surfaces at room temperature (RT) and at 100°C to clarify the initial adsorption sites using scanning tunneling microscopy. At RT Ge atoms are adsorbed at high coordination B2 sites around the rest atoms, as predicted by Cho and Kaxiras [Surf. Sci. 396, L261 (1998)]. On one hand, at 100°C Ge atoms are adsorbed on corner adatom sites. With increasing Ge coverage the corner sites are gradually occupied, followed by Ge adsorption at center adatom sites, resulting in Ge cluster growth with a size of the half unit cell.
Magnetoelectric effect in magnetostrictive/piezoelectric laminate composite Terfenol-D∕LiNbO3 [(zxtw)−129°∕30°]
Authors: Yang P. , Zhao K. , Yin Y. , Wan J. G. , Zhu J. S.
Published: April 2006

A magnetoelectric (ME) laminate composite consisting of a new cut type [(zxtw)−129°∕30°] piezoelectric LiNbO3 single crystal and the magnetostrictive Tb1−xDyxFe2−y has been developed and its ME effect has been studied. Our small laminate shows a superior ME voltage coefficient (αE). A wide bandwidth of the frequency peak under a fixed magnetic bias field and a wide bandwidth of optimized magnetic bias field under a high fixed frequency were also observed. The largest value of αE is 2.31V∕cmOe at 160kHz when the magnetic bias field reaches 1.76kOe.
Migration and the Transnational Habitus: Evidence from Canada and the Philippines
Authors: Kelly Philip , Lusis Tom
Published: April 2006

The experiences and decisions of migrants frequently confound scholarly expectations. In particular, the transnational linkages maintained by migrants transcend the social scales at which they are often assumed to live, and the spaces in which their integration or assimilation is usually studied—the neighbourhood, the urban labour market, the national society. Studies of transnationalism have shown that immigrants maintain multistranded connections to their places of origin and that these continue to influence the lifeworlds both of migrants and of those they leave behind significantly. In this paper we suggest that these multistranded connections—incorporating social, cultural, and economic ties—can be usefully considered using Pierre Bourdieu's notion of the habitus as a heuristic framework for integrating the various dimensions of transmigrants' lives. Drawing on interviews in Canada and the Philippines, we demonstrate the ways in which economic, social, and cultural capital are accumulated, exchanged, converted, valued, and devalued in a transnational habitus.
Embedded Cosmopolitanism and the Politics of Obligation: The Ghanaian Diaspora and Development
Authors: Mohan Giles
Published: April 2006

The author analyses how identities and obligations operate within the spaces of transnational communities and how this affects development. Within spatially diffuse communities, identities are fluid and overlapping, as are the obligations to multiple others—be that kin, ethnic group, or nation—in different localities. The author is concerned with the institutions through which these identities are formed and obligations are fulfilled. These include families, clans, hometown associations, and religious organisations, which link people ‘abroad’ to people ‘at home’. The author understands these spaces as a form of public sphere involving a ‘deterritorialised’ citizenship, which has been termed ‘embedded cosmopolitanism’. In this way, obligations are not legally defined but operate as part of the moral universe of those concerned. The case study is based upon recent fieldwork on Ghanaians in the United Kingdom and their connections to other Ghanaians outside Ghana and to those at home. The ways in which these complex networks of affiliation operate, as well as the ways in which the state seeks to ‘capture’ support from them, and how migrants selectively redefine both ethnic identities and family boundaries, are described.
Development, Transnational Religion, and the Power of Ideas in the High Provinces of Cusco, Peru
Authors: Olson Elizabeth
Published: April 2006

I examine the enmeshment of transnationally networked religious organizations in predominantly Quechua communities in the southern Andes of Peru. I aim specifically to understand the multiple ways in which transnational religious organizations contribute to the construction of development epistemologies, or the socioeconomics of development truths. Peru has been undergoing a religious transformation similar to the rest of Latin America, with Evangelical and other non-Catholic faiths now well established in the rural highlands. Drawing on fieldwork conducted in the Provincias Altas of Cusco, Peru, I examine the histories and organizational expressions of development truths promoted by the Iglesia Surandina (the Catholic Church of the Southern Andes), and the Iglesia Evangélica Peruana (the Peruvian Evangelical Church). The ways that these epistemologies become negotiated and translated in two rural districts reinforces the importance of historical context in the formation of development epistemologies, but it also suggests that organizational structures and differences in transnational processes contribute to the acceptance of or challenge to different sets of knowledge regarding development.
Hip-Hop Gangsta or Most Deserving of Victims? Transnational Migrant Identities and the Paradox of Tibetan Racialization in the USA
Authors: Yeh Emily T , Lama Kunga T
Published: April 2006

This ethnographic paper examines the complex cultural politics of Tibetan transnational migration by examining racialized everyday practices in Tibetan communities in the San Francisco Bay Area and Boulder, Colorado. After providing an overview of Tibetan migration to the USA, we discuss migrants' contradictory insertion into American racial bipolarism. On the one hand, Tibetans' racialized class positions place them at the lower end of a spectrum of moral deserving and worth. On the other hand, the discursive practices of the transnational Tibet Movement and the traveling of Tibetan Buddhist institutions to the USA ‘whitens’ Tibetans by making them seem particularly worthy and deserving of sponsorship. After exploring the production of Tibetan migrant subjectivities through white sponsorship, we examine how the successful articulation of Tibetan identities for a transnational political struggle is a double-edged sword which has unintended, and sometimes violent consequences. These play out in various ways, including intergenerational struggles over hip-hop and internalized racism.
Retreatment with rabbit anti‐thymocyte globulin and ciclosporin for patients with relapsed or refractory severe aplastic anaemia
Authors: Scheinberg Phillip , Nunez Olga , Young Neal S.
Published: April 2006

The management of patients with severe aplastic anaemia (SAA) who do not have a matched sibling donor and fail a course of horse anti‐thymocyte globulin (h‐ATG)/ciclosporin (CsA) is uncertain. Repeated courses of ATG‐based immunosuppression are often employed; in children and increasingly in adults, alternative donor haematopoietic stem cell transplantation is an option. We analysed the success rate of retreatment with rabbit ATG (r‐ATG)/CsA in 43 patients treated at our institution in the last 5 years; 22 were refractory (20 adults; two children) to h‐ATG/CsA‐based regimens and 21 (17 adults; four children) had relapsed after h‐ATG/CsA‐based regimens. The overall response rate was 30% in patients who were refractory to h‐ATG and 65% in patients who had relapsed following h‐ATG. The 1000‐d survival in patients who responded to r‐ATG was 90% compared with 65% in non‐responders. Six patients developed a clonal haematological disorder; two were responders, two were non‐responders and in two the evolution occurred before the response could be assessed at 3 months following r‐ATG. Thirteen patients died; three were responders, six were non‐responders and four patients died prior to 3 months when response was assessed. In our study, the response rate in refractory patients was inferior to what has been previously reported.
Market Efficiency in Person‐to‐Person Betting
Authors: SMITH MICHAEL A. , PATON DAVID , WILLIAMS LEIGHTON VAUGHAN
Published: April 2006

Bookmakers have argued that person‐to‐person internet ‘betting exchanges’ represent unfair competition. In this paper we suggest that, in fact, betting exchanges have brought about significant efficiency gains by lowering transaction costs for consumers. We test this hypothesis using matched data on UK horse racing from betting exchanges and from traditional betting media. In comparison with traditional betting media, we find that betting exchanges exhibit evidence of significantly lower market biases. We also find that an information‐based model explains the well documented favourite–longshot bias more convincingly than traditional explanations based on risk preferences.
Continuous Positive Airway Pressure Reduces Subjective Daytime Sleepiness in Patients with Mild to Moderate Alzheimer's Disease with Sleep Disordered Breathing
Authors: Chong Mei S. , Ayalon Liat , Marler Matthew , Loredo Jose S. , Corey‐Bloom Jody , Palmer Barton W. , Liu Lianqi , Ancoli‐Israel Sonia
Published: April 2006

OBJECTIVES: Studies have reported that 33% to 70% of patients with Alzheimer's disease (AD) have sleep‐disordered breathing (SDB). Continuous positive airway pressure (CPAP) treatment has been shown to reduce daytime sleepiness and improve health‐related quality of life in nondemented older people with SDB. The effect of therapeutic CPAP treatment on daytime sleepiness in patients with mild‐moderate AD with SDB was assessed.

DESIGN: Randomized, double‐blind, placebo‐controlled trial.

SETTING: Patients' home and the University of California San Diego, General Clinical Research Center, J. Christian Gillin Laboratory of Sleep and Chronobiology.

PARTICIPANTS: Thirty‐nine community‐dwelling elderly patients with mild‐moderate probable AD with SDB.

INTERVENTION: Patients were randomly assigned to receive 6 weeks of therapeutic CPAP or 3 weeks of sham CPAP followed by 3 weeks of therapeutic CPAP.

MEASUREMENTS: Epworth Sleepiness Scale (ESS) was administered at baseline, 3 weeks, and 6 weeks. Changes in daytime sleepiness in subjects who received optimal therapeutic CPAP were compared with changes in the sham CPAP group.

RESULTS: Within the therapeutic CPAP group, ESS scores were reduced from 8.89 during baseline to 6.56 after 3 weeks of treatment (P=.04) and to 5.53 after 6 weeks of treatment (P=.004). In the sham CPAP group, there was no significant difference after 3 weeks of sham CPAP but a significant decrease from 7.68 to 6.47 (P=.01) after 3 weeks of therapeutic CPAP.

CONCLUSION: These data provide evidence of the effectiveness of CPAP in reducing subjective daytime sleepiness in patients with AD with SDB.
RNA Trafficking in Axons
Authors: Sotelo‐Silveira Jose R. , Calliari Aldo , Kun Alejandra , Koenig Edward , Sotelo Jose R.
Published: April 2006

A substantial number of studies over a period of four decades have indicated that axons contain mRNAs and ribosomes, and are metabolically active in synthesizing proteins locally. For the most part, little attention has been paid to these findings until recently when the concept of targeting of specific mRNAs and translation in subcellular domains in polarized cells emerged to contribute to the likelihood and acceptance of mRNA targeting to axons as well. Trans‐acting factor proteins bind to cis‐acting sequences in the untranslated region of mRNAs integrated in ribonucleoprotein (RNPs) complexes determine its targeting in neurons. In vitro studies in immature axons have shown that molecular motors proteins (kinesins and myosins) associate to RNPs suggesting they would participate in its transport to growth cones. Tau and actin mRNAs are transported as RNPs, and targeted to axons as well as ribosomes. Periaxoplasmic ribosomal plaques (PARPs), which are systematically distributed discrete peripheral ribosome‐containing, actin‐rich formations in myelinated axons, also are enriched with actin and myosin Va mRNAs and additional regulatory proteins. The localization of mRNAs in PARPs probably means that PARPs are local centers of translational activity, and that these domains are the final destination in the axon compartment for targeted macromolecular traffic originating in the cell body. The role of glial cells as a potentially complementary source of axonal mRNAs and ribosomes is discussed in light of early reports and recent ultrastructural observations related to the possibility of glial‐axon trans‐endocytosis.
Measurements of Vocal Fold Elasticity Using the Linear Skin Rheometer
Authors: Hess Markus M. , Mueller Frank , Kobler James B. , Zeitels Steven M. , Goodyer Eric
Published: April 2006

Objective: The linear skin rheometer (LSR), which measures skin visco-elasticity, was adapted for measurements of vocal fold properties. A series of studies was performed on animal and human excised larynges to determine if the LSR technique can be applied to the vocal fold. Methods: In excised larynges, small patches of mucosa were driven sinusoidally at 0.3 Hz over distances of 1–2 mm using a small probe. Forces in the order of 1 g equivalent gave optimal measurements. Stiffness and viscosity values were derived from stress/strain data. Results: The instrument was able to measure the visco-elasticity of the tissue in a repeatable manner and it could detect areas where the tissue was artificially stiffened. Two-dimensional maps of the mechanical properties of the laryngeal mucosa were obtained showing local variations in elasticity both parallel and perpendicular to the vocal fold edge. Initial studies were undertaken using animal tissue; more recently, the LSR has been successfully used to obtain similar data from human tissue. Conclusion: The LSR was been demonstrated to be capable of measuring the elastic properties of the vocal fold in a repeatable and reliable manner. Further studies will now be undertaken to obtain data from a larger sample of human tissue.
Comparison of Methods for Counting Cells in the Mouse Glomerulus
Authors: Basgen John M. , Nicholas Susanne B. , Mauer Michael , Rozen Silvia , Nyengaard Jens R.
Published: April 2006

Background: Researchers have long been interested in counting the number of cells within the glomerulus. Investigators using different techniques have yielded conflicting results. The most direct method is to count the cells in serial sections from the entire glomerulus. This Exhaustive Count method is not usually practical. The disector/fractionator method counts the number of cells in a fraction of sections. The total is estimated from the product of the cell count and the reciprocal of the fraction. The Weibel-Gomez method determines the density of cells per glomerulus, then multiplies this density by glomerular volume to obtain cell number. In this study, we compared the disector/fractionator and Weibel-Gomez methods to identify a practical alternative for the time-consuming Exhaustive Count method. Methods: Glomeruli from a normal mouse kidney were completely sectioned and images obtained. Appropriate images were used to count glomerular cell number using each method. Results: The Exhaustive Count method yielded 213 ± 22 (mean ± SD) cells/glomerulus vs. the disector/fractionator average of 211 ± 29 cells/glomerulus (p = 0.82). The Weibel-Gomez method average of 235 ± 26 cells/glomerulus was statistically different from the Exhaustive Count method (p = 0.003). Conclusion: The Weibel-Gomez produced a 10% overestimation, whereas the disector/fractionator method was unbiased and thus a good substitute for the Exhaustive Count method.
A New Parameterization of Cloud Droplet Activation Applicable to General Circulation Models
Authors: Ming Yi , Ramaswamy V. , Donner Leo J. , Phillips Vaughan T. J.
Published: April 2006

A new parameterization is proposed to link the droplet number concentration to the size distribution and chemical composition of aerosol and updraft velocity. Except for an empirical assumption of droplet growth, the parameterization is formulated almost entirely on first principles to allow for satisfactory performance under a variety of conditions. For a series of updraft velocity ranging from 0.03 to 10.0 m s−1, the droplet number concentrations predicted with the parameterization are in good agreement with the detailed parcel model simulations with an average error of −4 ± 26% (one standard deviation). The accuracy is comparable to or better than some existing parameterizations. The parameterization is able to account for the effects of droplet surface tension and mass accommodation coefficient on activation without adjusting the empirical parameter. These desirable attributes make the parameterization suitable for being used in the prognostic determination of the cloud droplet number concentration in general circulation models (GCMs).
“Already the Effect of the Whip”: Critical Theory and the Feminine Ideal
Authors: Marasco Robyn
Published: April 2006

robyn marasco is Assistant Professor of Political Science at Williams College. She recently completed her dissertation titled “Critique on the Heights of Despair: Politics, Philosophy, and the Persistence of Hope.”
Spatiotemporal dynamics of actin-rich adhesion microdomains: influence of substrate flexibility
Authors: Collin Olivier , Tracqui Philippe , Stephanou Angélique , Usson Yves , Clément-Lacroix Jocelyne , Planus Emmanuelle
Published: April 2006

In this study we analyse the formation and dynamics of specific actin-rich structures called podosomes. Podosomes are very dynamic punctual adhesion sites tightly linked to the actin cytoskeleton. Mechanical properties of substrates are emerging as important physical modulators of anchorage-dependent processes involved in the cellular response. We investigate the influence of substrate flexibility on the dynamic properties of podosomes. We used mouse NIH-3T3 fibroblasts, transfected with GFP-actin and cultured on polyacrylamide collagen-coated substrates of varying stiffness. Static and dynamic features of cell morphologies associated with an optical flow analysis of the dynamics of podosomes revealed that: (1) they have constant structural properties, i.e. their shape factor and width do not change with the substrate flexibility; (2) the lifespan of podosomes and mean minimum distance between them depend on the substrate flexibility; (3) there is a variation in the displacement speed of the rosette of podosomes. Moreover, the rosettes sometimes appear as periodically emergent F-actin structures, which suggests that a two-level self-organisation process may drive first, the formation of clusters of podosomes and second, the organisation of these clusters into oscillating rings. Such dynamic features give new perspectives regarding the potential function of podosomes as mechanosensory structures.
Phosphorylation on Ser5 increases the F-actin-binding activity of L-plastin and promotes its targeting to sites of actin assembly in cells
Authors: Janji Bassam , Giganti Adeline , De Corte Veerle , Catillon Marie , Bruyneel Erik , Lentz Delphine , Plastino Julie , Gettemans Jan , Friederich Evelyne
Published: April 2006

L-plastin, a malignant transformation-associated protein, is a member of a large family of actin filament cross-linkers. Here, we analysed how phosphorylation of L-plastin on Ser5 of the headpiece domain regulates its intracellular distribution and its interaction with F-actin in transfected cells and in in vitro assays. Phosphorylated wild-type L-plastin localised to the actin cytoskeleton in transfected Vero cells. Ser5Ala substitution reduced the capacity of L-plastin to localise with peripheral actin-rich membrane protrusions. Conversely, a Ser5Glu variant mimicking a constitutively phosphorylated state, accumulated in actin-rich regions and promoted the formation of F-actin microspikes in two cell lines. Similar to phosphorylated wild-type L-plastin, this variant remained associated with cellular F-actin in detergent-treated cells, whereas the Ser5Ala variant was almost completely extracted. When compared with non-phosphorylated protein, phosphorylated L-plastin and the Ser5Glu variant bound F-actin more efficiently in an in vitro assay. Importantly, expression of L-plastin elicited collagen invasion in HEK293T cells, in a manner dependent on Ser5 phosphorylation. Based on our findings, we propose that conversely to other calponin homology (CH)-domain family members, phosphorylation of L-plastin switches the protein from a low-activity to a high-activity state. Phosphorylated L-plastin might act as an integrator of signals controlling the assembly of the actin cytoskeleton and cell motility in a 3D-space.
The Contingent Effects of Transactive Memory: When Is It More Beneficial to Know What Others Know?
Authors: Ren Yuqing , Carley Kathleen M. , Argote Linda
Published: April 2006

Previous studies have provided evidence of the positive impact of transactive memory (TM) on group performance, such as the efficient storage and recall of knowledge and better product quality. This paper aims to unify the experimental research on TM and to extend it to more dynamic and diverse group settings. In this paper, we develop an empirically grounded computational model—ORGMEM—and apply it to explore the contingent effects of TM on group performance. The comparison between virtual experimental results and relevant laboratory experimental results demonstrates the validity of ORGMEM as a useful tool to study memory-related phenomena. Through a series of virtual experiments, we find that TM decreases group response time by facilitating knowledge retrieval processes and improves decision quality by informing task coordination and evaluation. Our results also suggest that the effects of TM are contingent upon group characteristics, such as group size and environment, as well as the dimension along which group performance is assessed. Overall, TM seems to be more beneficial to small groups using quality as the dependent variable, but more beneficial to large groups, groups in a dynamic task environment, and groups in a volatile knowledge environment using time as the dependent variable.
Safety last: risk, interactivity and video activism in contemporary Tokyo
Authors: McKnight Anne
Published: April 2006

As the debate over Japan's re-militarization and revision of the 1947 Peace Constitution continues, art and activism have challenged the increasing presence of the security state in everyday life. Art activists object to the way that ambient global risk is framed by state and media
in indigenous terms, seen as imminent and local to Japan, particularly through measures analogizing Japan's supposed threat from North Korea to the 9/11 attacks. Departing from the political modernist critique of idealism pursued as rupture and discontinuity by film-maker critics of post-war
militarism in the 1960s and 1970s, video activist/director Tsuchiya Yutaka patterns his critique of risk on properties of television - sitespecificity, genre, and form - to show how global risk is made to seem site-specific to Tokyo, yet written into narratives of risk on a global scale.
Radio Guangdong: Chinese radio discourses revisited
Authors: Maynard Laura
Published: April 2006

All radio broadcasting is live in a sense, whether the material is spontaneously generated, as in a chat show or a running commentary, or pre-recorded, as is the case with a compact disc or a tape. In all cases, it is heard on the receiver in the same moment that it is transmitted from
the studio. Before 15 December 1986, almost all Chinese radio broadcasting was either pre-recorded or consisted of prescripted continuity and time checks. But after that date a situation gradually developed in which as much as 75 per cent of speech content was spontaneous: neither pre-recorded
nor scripted word-for-word. It is this sort of radio that is commonly referred to as live in China - and this is the sense in which I shall use the word live throughout the rest of this essay. As the station that pioneered the development, Radio Guangdong is immensely proud of its position
in Chinese broadcasting history. The implications for local culture have also been immense. So great is its sense of pride and achievement in leading the major reform of broadcasting in China that, in 1999, Radio Guangdong marked its fiftieth anniversary by compiling and publishing a collection
of essays that charted and reflected its last thirteen years of broadcasting practice.
Corrections to “linear-intercept distributions do not characterize plane sets”
Authors: Mallows C. L. , Clark J. M. C.
Published: April 2006

Dr. J. Alan Steppe has kindly pointed out two serious flaws, and some others less serious, in the proof of our paper [2]. However these can all be corrected, so that the result remains valid.
Stochastic population processes in the theory of radiative transfer
Authors: Brockwell P. J.
Published: April 2006

Starting from a characterization of radiative transfer in terms of a collision rate λ and a single-collision transition probability Ψ, we study the distribution of the generalized state ζ(t) of a radiation particle at time t conditional on a specified initial state at time t= 0. The generalized state is a vector consisting of the state ω(t) at time t and the states ω1, ω2, …, ωn of the particle immediately after the collisions it experiences in the time interval (0, t]. The variable ζ(t) takes values in a population space and can be studied conveniently with the aid of a certain generating functional G. The first-collision integral equation and the backward integro-differential equation for G are derived. Simultaneous consideration of the first-collision and last-collision equations lead to a generalized reciprocity principle for G. First-passage problems are also considered. Finally a number of illustrative examples are given.
Solutions for some diffusion processes with two barriers
Authors: Sweet A. L. , Hardin J. C.
Published: April 2006

Use is often made of the Wiener and Ornstein-Uhlenbeck (O.U.) processes in various applications of stochastic processes to problems of engineering interest. These applications frequently involve the presence of barriers. Although mathematical methods for solving Kolmogorov's forward equation for the above processes have previously been discussed ([1], [2]), many solutions for problems with two barriers do not seem to be available in the literature. Instead, one finds solutions for unrestricted processes or simulation used in place of analytical solutions in various applications ([3], [4], [5]). In this paper, solutions of Kolmogorov's forward equations in the presence of constant absorbing and/or reflecting barriers are obtained by means of separation of variables. This enables one to obtain expressions for the probability density functions for first passage times when absorbing barriers are present. The solution for the O.U. process is used to obtain a result of Breiman's [6] concerning first passage times.
The joint asymptotic distribution of the k-smallest sample spacings
Authors: Weiss Lionel
Published: April 2006

Suppose Q1⋆, … Qn⋆ are independent, identically distributed random variables, each with probability density function f(x), cumulative distribution function F(x), where F(1) – F(0) = 1, f(x) is continuous in the open interval (0, 1) and continuous on the right at x = 0 and on the left at x = 1, and there exists a positive C such that f(x) > C for all x in (0, l). f(0) is defined as f(0+), f(1) is defined as f(1–).
A note on the queueing system GI/Ek/1
Authors: Finch P. D.
Published: April 2006

In this note we adopt the notation and terminology of Kingman (1966) without further comment. For the general single server queue one has

For the queueing system GI/Ek/1 it is possible to make use of the particular nature of the service time distribution to evaluate the right-hand side of Equation (1) in terms of the k roots of a certain equation. This evaluation is carried out in detail in Prabhu (1965) to which reference should be made for the technicalities involved. A similar evaluation applies to the limiting distribution

when it exists. However, the resulting expression again involves the k roots of a certain equation. In this note we draw attention to an alternative procedure which does not involve the calculation of roots. We remark that a similar, but slightly different, procedure can be used in the study of the queueing system Ek/GI/1. Details of this will be presented in a separate note.
On some problems in operations research
Authors: Samuel Ester
Published: April 2006

Consider an airplane which is at a distance t ≧ 0 from its destination (the distance being measured in time-units) and has n anti-aircraft missiles. The enemy sends its aircraft according to a Poisson process with known parameter, which by redefining the time-scale may, without loss of generality, be taken to be one. When meeting an enemy aircraft, the plane can use, simultaneously, some of its missiles, and it is assumed that the hits are independent random events with known probability 1 > 1 – q > 0. If no missile hits the enemy aircraft, the airplane is shot down with known probability 1 ≧ 1 – u > 0. The case u= 0 is of particular interest. (We have excluded the values q = 0, q = 1 and u= 1 since these yield trivial solutions.)
Study of a specialM/M/1 queue
Authors: Tambouratzis D. G.
Published: April 2006

To optimize the performance of anM/M/squeue, Moder and Phillips [1] have studied the problem in which there are alwaysn1open counters ready to offer service. The actual number of open counters increases by one, up to a maximumn2, every time the number of waiting customers exceeds a certain critical number; it decreases by one every time the queue length becomes smaller than another critical number.
Perturbation theory and finite Markov chains
Authors: Schweitzer Paul J.
Published: April 2006

A perturbation formalism is presented which shows how the stationary distribution and fundamental matrix of a Markov chain containing a single irreducible set of states change as the transition probabilities vary. Expressions are given for the partial derivatives of the stationary distribution and fundamental matrix with respect to the transition probabilities. Semi-group properties of the generators of transformations from one Markov chain to another are investigated. It is shown that a perturbation formalism exists in the multiple subchain case if and only if the change in the transition probabilities does not alter the number of, or intermix the various subchains. The formalism is presented when this condition is satisfied.
Labelling experiments and phase-age distributions for multiphase branching processes
Authors: Brockwell P. J. , Kuo W. H.
Published: April 2006

A supercritical age-dependent branching process is considered in which the lifespan of each individual is composed of four phases whose durations have joint probability density f(x1, x2, x3, x4). Starting with a single individual of age zero at time zero we consider the asymptotic behaviour as t→ ∞ of the random variable Z(4) (a0,…, an, t) defined as the number of individuals in phase 4 at time t for which the elapsed phase durations Y01,…, Y04,…, Yi1,…, Yi4,…, Yn4 of the individual itself and its first n ancestors satisfy the inequalities Yij ≦ aij, i = 0,…, n, j = 1,…, 4. The application of the results to the analysis of cell-labelling experiments is described. Finally we state an analogous result which defines (conditional on eventual non-extinction of the population) the asymptotic joint distribution of the phase and elapsed phase durations of an individual drawn at random from the population and the phase durations of its ancestors.
Decidability of α (pk) > 0 for some k
Authors: Madsen Richard W.
Published: April 2006

Paz (1963), (1971) has shown that for an n × n stochastic matrix P the property that some power of P has a positive ergodic coefficient is decidable. In particular he shows that α (Pk) > 0 for some k, only if it is positive for k = ½n(n – 1). However he states that it is not known whether this bound is sharp. In this paper a sharp bound is given, namely k =½(n – 1)2 + ½ or ½(n − 1)2 + 1 depending on whether n is even or odd. The proof of this is based on some results from number theory.
A stochastic general epidemic in m sub-populations
Authors: Billard L.
Published: April 2006

Epidemic models have generally assumed that the population mixes homogeneously. More realistic models can be obtained by dividing the population into sub-populations within which mixing is homogeneous but between which mixing is heterogeneous. We consider such a model for the general epidemic process and present a formulation which permits inroads to be made towards obtaining explicit solutions to the state probabilities.
An Erdös-Rényi strong law for sample quantiles
Authors: Book Stephen A. , Truax Donald R.
Published: April 2006

From a random sampleX1,X2, …,XNthere can be constructedN – K+ 1 successive sample means of the formfor 0 ≦n≦N−K, whereErdös and Rényi (1970) studied the maximum Σ(N,K) of theseN – K +1 sample means. Under appropriate conditions, they showed that for a wide interval of λ's there exist constants C(λ), depending only on λ and the distribution from which the sample was selected, such that Σ(N, [C(λ) logN])→ λ a.s. asN→∞. In the present article, analogous results are developed for the maximum of theN–K+ 1 successive sample medians and, more generally, for all sample quantiles.
Random collision processes with transition probabilities belonging to the same type of distribution
Authors: Nishimura Shōichi
Published: April 2006

By analogy with statistical mechanics we consider a random collision process with discrete time wand continuous states x ∈ [0, ∞). We assume three conditions (i), (ii) and (iii), which can be applied to Kac's model of a Maxwellian gas, and show that the sequence of probability distributions converges to a probability distribution using their moments.