bluuebunny/crossref_metadata_2025 huggingface dataset:
Inviting the messy: Drawing methods and ‘children’s voices’
Authors: Eldén Sara
Published: June 2012

This article engages with the current debate in childhood research on children’s voices and representation in the research process. In this discussion, the frequent use of drawing techniques in childhood research is often highlighted as especially problematic. While agreeing that there is a need to critically examine the concept of ‘children’s voices’ and the production of ‘voices’ in research, the author argues for the possibility of and need for reflexive and creative research enabling the ‘voicing’ of others – such as children – and the possibilities of a sociological analysis of drawing methods. The argument is elaborated with a presentation and discussion of a current research project on children and care in Sweden. The author discusses two of the methods used in interviews with children – a draw-your-day exercise and concentric circles of closeness – which together help the child and the researcher narrativize practices and relationships of care that would otherwise be obscured. While the narratives that emerge cannot be viewed as providing ‘authentic’ insights into the caring situation of the child, they can be regarded as contributing to a more complex and multi-layered picture of care, which is a valuable contribution to the research field of family and interpersonal relationships.
Performance when misinformation increases with experience
Authors: Glazer Amihai
Published: June 2012

An official whose experience increases over time may overweight old information when making decisions. If the state of nature changes over time, the official’s performance eventually worsens with experience. Though a new official may initially perform worse than his predecessor, maximizing average performance requires that officials are regularly replaced.
Sound radiation from in-plane vibration of thick annular discs with a narrow radial slot
Authors: Lee Hyeongill
Published: June 2012

The vibro-acoustic characteristics of in-plane vibration in a thick annular disc containing a narrow radial slot are investigated with a hybrid approach combining numerical or experimental results with pre-developed analytical calculations. Structural eigenfunctions for in-plane vibrations of the disc are approximated as linear combinations of eigenfunctions for a uniform disc that has same material properties and geometric dimensions except for the slot. Acoustic radiations from the normal modes of the disc are calculated using a theoretical solution introduced in previous work for the uniform disc along with the results from the approximations of structural eigenfunctions. Vibration and sound radiation from the disc due to a harmonic force fixed to the disc outer surface are investigated using the mode expansion method. The effects of the circumferential distance between the radial excitation and slot on the vibro-acoustic responses are investigated using the same method. Finally, contributions of sound radiations from two split vibration modes to the overall sound radiation from the sample disc are also investigated. Based on these results, it can be concluded that the procedure suggested in this study has good accuracy in calculating the in-plane vibro-acoustic properties of a thick annular disc with a radial slot.
Biomechanical measurements of cortical screw stripping torque in human versus artificial femurs
Authors: Nicayenzi Bruce , Crookshank Meghan , Olsen Michael , Schemitsch Emil H , Bougherara Habiba , Zdero Rad
Published: June 2012

Femur fracture plates are applied using cortical bone screws. Surgeons do this manually by subjective ‘feel’ without monitoring torque. Few studies have quantified stripping torque in human bone. No studies have measured stripping torque in the artificial bones from Sawbones (Vashon, WA, USA) that are frequently used in biomechanical studies. The present aim was to measure stripping torque of cortical screws in human versus artificial femurs. Sixteen fresh-frozen human femurs and eight artificial femurs were used. Using a digital torque screwdriver, each femur had a 3.5-mm diameter unicortical screw manually inserted into the anterior midshaft until failure of the screw–bone interface. Results were normalized by cortical thickness and the screw–bone interfacial area. There were no statistical differences in human versus artificial data, respectively, for stripping torque (1741 ± 442 N.mm, 2012 ± 176 N.mm, p = 0.11), stripping torque/thickness (313 ± 59 N, 305 ± 30 N, p = 0.74), and stripping torque/area (28.5 ± 5.3 N/mm, 27.8 ± 2.8 N/mm, p = 0.74). Artificial unicortical thickness (6.6 ± 0.3 mm) was greater than human thickness (5.6 ± 1.1 mm) ( p = 0.02). For human specimens, there was a moderate linear correlation of absolute and normalized stripping torque versus standardized bone mineral density (R ≥ 0.32) and clinical T-score (R = 0.29), but not with age (R ≤ 0.29). Surgeons should be aware of the stripping torque limits for human femurs and potentially take steps to monitor these values during surgery. The artificial femurs being increasingly used in research accurately replicate human cortical properties during screw insertion. To date, this is the first series of human femurs evaluated for cortical screw stripping.
Early Learning Shapes the Memory Networks for Arithmetic
Authors: Salillas Elena , Wicha Nicole Y. Y.
Published: June 2012

Language and math are intertwined during children’s learning of arithmetic concepts, but the importance of language in adult arithmetic processing is less clear. To determine whether early learning plays a critical role in the math-language connection in adults, we tested retrieval of simple multiplication in adult bilinguals who learned arithmetic in only one language. We measured electrophysiological and behavioral responses during correctness judgments for problems presented as digits or as number words in Spanish or English. Problems presented in the language in which participants learned arithmetic elicited larger, more graded, and qualitatively different brain responses than did problems presented in participants’ other language, and these responses more closely resembled responses for digits, even when participants’ other language was more dominant. These findings suggest that the memory networks for simple multiplication are established when arithmetic concepts are first learned and are independent of language dominance in adulthood.
Fracture and effective properties of finite magnetoelectroelastic media
Authors: Wang Baolin
Published: June 2012

Magnetoelectroelastic materials are inherently brittle and prone to cracking. It is important to understand how cracks influence the magnetoelectrical coupling properties of the magnetoelectroelastic materials. This article establishes an analytical model for a finite crack in a finite magnetoelectroelastic medium. The stress, electric displacement, and magnetic induction and their intensity factors are obtained by the integral equation technique. The temperature effect is also studied. The effect of cracking on the effective thermomagnetoelectromechanical properties is discussed. In addition, crack is modeled as a notch of finite height to study the effect of the crack-face electric and magnetic boundary condition assumptions on the predicted properties of the magnetoelectroelastic medium.
Patterns of Dating Violence Across Adolescence
Authors: Martsolf Donna S. , Draucker Claire B. , Stephenson Pamela L. , Cook Christina B. , Heckman Terri A.
Published: June 2012

Adolescent dating violence (ADV) is a prevalent social and health problem associated with a number of adolescent risk behaviors and negative outcomes. The purpose of this study was to identify patterns of dating violence across adolescence. We used cross-case analysis to analyze interviews with 88 young adults (men and women aged 18 to 21) who were involved in violent dating relationships as teens. We identified four patterns of dating violence throughout adolescence. We also identified two patterns for adolescents who had only one violent relationship based on the length of the relationship–contained ADV and prolonged ADV–and two patterns for those who had multiple violent relationships based on the level of violence severity–repetitive ADV and escalating ADV. Knowledge of these four patterns can be used to guide therapeutic interactions with teens and to develop pattern-specific prevention and intervention strategies.
Views of Depressed Patients in Pakistan Concerning Their Illness, Its Causes, and Treatments
Authors: Naeem Farooq , Ayub Muhammad , Kingdon David , Gobbi Mary
Published: June 2012

Although the core symptoms of depression appear uniform across cultures, their presentations might vary from one culture to another. This interview study was part of a project to establish whether cognitive behavior therapy could be effective for the treatment of depression in a developing country. We interviewed outpatients from a university teaching hospital in Pakistan who were diagnosed as having depression. We tried to elicit their knowledge and perceptions of depression, its causes, and treatments, and their views about nonpharmacological treatments. We discovered that patients had very little knowledge of mental illnesses in general, and depression in particular. They believed that mental health problems were the result of stress or trauma, and that only medicines could help them. Patients had no knowledge of the roles of psychologists or psychotherapy. Their model of understanding mental illnesses appeared to represent a psychosocial understanding, with physical symptoms being their main concern.
The Notion of Self in the Journey Back From Addiction
Authors: Mackintosh Valerie , Knight Tess
Published: June 2012

In this study we explored how those recovering from addiction negotiated self, and the role supported accommodation played in the journey back from addiction. Transcripts from 11 in-depth interviews were analyzed by 2 coders who identified the most salient themes relevant to the self in recovery within the personal contexts of participants. The participants noted that reclaiming the self that had been lost to addiction was of primary importance to them. The recovery journey exposed a self that had reached the lowest point in life; one that was hardly recognizable; one that was undesirable. Engaging with supported accommodation provided participants with a sanctuary within which to reclaim the self, and was seen as central to their recovery.
Nonlinear magnetoelastostatics: Energy functionals and their second variations
Authors: Bustamante Roger , Ogden Ray W
Published: June 2012

Two variational principles for nonlinear magnetoelastostatics are studied, considering a magnetosensitive body completely surrounded by free space extending to infinity. The functionals depend on the deformation function as one of the independent variables, and on either the scalar magnetic potential or the magnetic vector potential as the independent magnetic variable. Alternative representations for the energy densities are given for free space, from which simple expressions for the first and second variations of the functionals are obtained.
Dried Blood Spot Analysis of Donepezil in Support of a GLP 3-month Dose-Range Finding Study in Rats
Authors: Meier-Davis Susan R. , Meng Min , Yuan Weiwei , Diehl Lisa , Arjmand Fatima M. , Lucke Rebecca M. , Huang Betsy , Wen Jianye , Shudo Jutaro , Nagata Tetsuto
Published: June 2012

Donepezil hydrochloride is a reversible acetyl cholinesterase inhibitor approved for Alzheimer disease treatment. As an alternate therapy, a donepezil hydrochloride transdermal patch is in development. Recommended nonclinical safety studies include a 3-month Good Laboratory Practice (GLP) dose-range finding (DRF) study prior to conducting the 2-year dermal carcinogenicity study in rats. Demonstration of systemic exposure is necessary to interpret the in vivo data. Previous nonclinical reports supporting oral dosing have utilized liquid chromatography tandem mass spectrometry (LC/MS/MS) to quantify donepezil concentrations in plasma. Smaller species with limited blood volumes do not allow serial sampling to derive the full pharmacokinetic profile from a single animal. Therefore, the option of another analytical method requiring decreased sample volumes is desirable as it would decrease the required number of animals while obtaining the complete profile. The dried blood spot (DBS) technique allows drug level measurement from a few microliters; however, the method is still not widely utilized in GLP studies. Because donepezil plasma levels are known by the oral route, DBS was used to bridge the previous oral data and to support a 13-week GLP DRF study for repeated topical application in rats, comparing oral administration with 4 topical formulations. The DBS method was validated and demonstrated robustness and reproducibility for application to the DRF study. The assay results were comparable to a previously reported plasma LC/MS/MS assay-derived pharmacokinetic profile and provided justification for selection of the topical formulation and dose levels for the subsequent dermal carcinogenicity study.
Impact of Pivotal Response Training Group Therapy on Stress and Empowerment in Parents of Children With Autism
Authors: Minjarez Mendy Boettcher , Mercier Emma M. , Williams Sharon E. , Hardan Antonio Y.
Published: June 2012

Parents of children with autism are increasingly being considered as primary agents of intervention for their children. The goal of this study was to evaluate whether participating in a pivotal response training (PRT) group therapy program for parents of children with autism influenced related aspects of parents’ lives, namely, their levels of stress and empowerment. Seventeen families participated in a 10-week therapy group designed to train parents to use PRT, with a specific focus on their children’s language deficits. Measures of empowerment and stress were obtained at baseline and at the end of the trial. Ratings on the Parenting Stress Index/Short Form and the Family Empowerment Scale showed significant changes from pre- to posttreatment, indicating that parents felt higher levels of empowerment and lower levels of stress after the 10-week group program. Notably, stress related to parent–child interactions was most reduced. Possible causal factors and implications are discussed.
Dominant party rule and legislative leadership in authoritarian regimes
Authors: Reuter Ora John , Turovsky Rostislav
Published: June 2012

Authoritarian dominant parties are said to ensure elite loyalty by providing elites with regularized opportunities for career advancement. This article uses data on the distribution of leadership posts in Russia’s regional legislatures (1999–2010) to conduct the first systematic test of this proposition. Loyalty to the nascent hegemonic party, United Russia, is shown to be important in determining a legislator’s chances of being promoted to a leadership position. These findings generate insight into how authoritarian institutions help maintain regime stability and provide a clearer picture of how Russia’s ruling party works.
Effect of risk orientation on cooperation and decision process in public goods dilemma
Authors: Fung Jane M. Y. , Au Wing Tung , Hu Weipeng , Shi Kan
Published: June 2012

This paper investigates the effects of risk orientation (RO) and social value orientation (SVO) on cooperation and the process of making the decision in a public goods dilemma (PGD). We found in Study 1 that risk-seeking prosocials were more cooperative than risk-averse prosocials in a simultaneous PGD. In Study 2, we found the same effect of RO on cooperation in a real-time PGD. Moreover, we found that risk-seeking prosocials, compared with their risk-averse counterparts, took less time to make decisions and observed fewer preceding cooperation choices before making their decisions. Mediation analysis confirms our model based on the change of K’ index in real-time PGD: The number of preceding cooperation choices being observed by a player mediated the effect of RO on cooperation among prosocials that risk-seekers were more cooperative than risk-averse participants. Our studies illustrate that individual differences such as RO and SVO play an important role in decision processes in PGD that subsequently affects cooperation decisions.
Social media and online political discussion: The effect of cues and informational cascades on participation in online political communities
Authors: Velasquez Alcides
Published: June 2012

This study examines, through a content analysis of the census of news stories posted in a Colombian online political community, how status cues and informational cascades shape participation in online political discussions. Specifically, it looks at how the authors’ news stories posting increase rate, the number of news story sources, the velocity at which comments to a news story start to appear, and the comment interactivity affect discussion participation. Results suggest that cues that signal expertise influence participation, while discussion among users also influences the decision of others to participate. However, the effect of these variables is stronger for some topics. Implications for the constitution of public spheres are discussed.
Does Web 3.0 come after Web 2.0? Deconstructing theoretical assumptions through practice
Authors: Barassi Veronica , Treré Emiliano
Published: June 2012

Current internet research has been influenced by application developers and computer engineers who see the development of the Web as being divided into three different stages: Web 1.0, Web 2.0 and Web 3.0. This article will argue that this understanding – although important when analysing the political economy of the Web – can have serious limitations when applied to everyday contexts and the lived experience of technologies. Drawing from the context of the Italian student movement, we show that the division between Web 1.0, Web 2.0 and Web 3.0 is often deconstructed by activists’ media practices. Therefore, we highlight the importance of developing an approach that – by focusing on practice – draws attention to the interplay between Web platforms rather than their transition. This approach, we believe, is essential to the understanding of the complex relationship between Web developments, human negotiations and everyday social contexts.
‘You are what you research’: researcher partisanship and the sociology of the ‘underdog’
Authors: Lumsden Karen
Published: June 2012

This article contributes to debates regarding the issue of researcher partisanship and bias within social research and situates it within the current trend towards reflexivity. The discussion draws upon the researcher’s experiences of conducting fieldwork with the ‘boy racer’ culture and societal groups affected by their behaviour. In this instance, the researcher unintentionally sided with the ‘underdogs’ – the ‘boy racers’. Hence, it is argued that value neutrality is an impossible goal, particularly in research of a political nature. Social researchers will inevitably ‘take sides’ whether or not they are willing to admit so. The discussion also touches upon the prevalence of media culture in ethnographic research and the dilemmas faced when making our research public at key moments.
‘If you can call it a poem’: toward a framework for the assessment of arts-based works
Authors: Lafrenière Darquise , Cox Susan M
Published: June 2012

The use of artistic forms as an alternative means for representing research findings is gaining acceptance in the research community. There are, however, important yet unresolved and even contentious issues arising from these new applications of the arts. These include concerns about the level of expertise required to effectively utilize the arts in research, the appropriateness of various methods of creating artworks and the desirability of identifying criteria for assessing arts-based contributions. Centring on the question of criteria for the creation and assessment of arts-based works, we note that there are, at present, few salient guidelines. Drawing upon our experience in conducting a pilot project employing arts-based methods of representing research findings, we propose a Guiding Arts-Based Research Assessment (GABRA) meta-framework for assessing the quality and effectiveness of utilizing the arts for knowledge dissemination. This overarching framework incorporates normative, substantive and performative aspects of arts-based methods of representing research findings.
Investigation of interior post-insulated masonry walls with wooden beam ends
Authors: Morelli Martin , Svendsen Svend
Published: June 2012

The preponderant number of multistorey buildings constructed in Denmark in the period between 1850 and 1930 were built with masonry walls incorporating wooden floor beams. Given the nature of this construction, it is supposed that significant energy savings could be achieved by simply insulating the facades of such buildings. To maintain the exterior appearance of the facade, the only possible means of installing the required insulation is placing it on the interior of the wall. However, the installation of insulation on the interior of the wall assembly reduces the overall drying potential of the wall, and this in turn may lead to increased freeze–thaw damages and moisture problems at the beam ends embedded in the masonry, when the masonry facade is subjected to driving rain. This article presents a method to investigate retrofit measures of interior-insulated masonry walls having wooden floor beams based on a failure mode and effect analysis combined with hygrothermal simulations. The method was first used to determine the potential for failure in retrofitted walls and their effects and causes, and thereafter, the expected hygrothermal performance of the retrofit measures was further investigated using both thermal and hygrothermal simulation software. The results show that the risk to incurring moisture problems at the wooden beam ends can be resolved by not insulating that portion of the wall directly above and below the floor division. Additionally, this proposed retrofit measure would reduce the heat loss of the original wall structure by half.
Clinical and prognostic role of annexin A2 in multiple myeloma
Authors: Seckinger Anja , Meiβner Tobias , Moreaux Jérôme , Depeweg Daniela , Hillengass Jens , Hose Katja , Rème Thierry , Rösen-Wolff Angela , Jauch Anna , Schnettler Reinhard , Ewerbeck Volker , Goldschmidt Hartmut , Klein Bernard , Hose Dirk
Published: June 2012

Annexin A2 (ANXA2) promotes myeloma cell growth, reduces apoptosis in myeloma cell lines, and increases osteoclast formation. ANXA2 has been described in small cohorts of samples as expressed by myeloma cells and cells of the BM microenvironment. To investigate its clinical role, we assessed 1148 samples including independent cohorts of 332 and 701 CD138-purified myeloma cell samples from previously untreated patients together with clinical prognostic factors, chromosomal aberrations, and gene expression–based high-risk scores, along with expression of ANXA2 in whole BM samples, stromal cells, osteoblasts, osteoclasts, and BM sera. ANXA2 is expressed in all normal and malignant plasma cell samples. Higher ANXA2 expression in myeloma cells is associated with significantly inferior event-free and overall survival independently of conventional prognostic factors and is associated with gene expression–determined high risk and high proliferation. Within the BM, all cell populations, including osteoblasts, osteoclasts, and stromal cells, express ANXA2. ANXA2 expression is increased significantly in myelomatous versus normal BM serum. ANXA2 exemplifies an interesting class of targetable bone-remodeling factors expressed by normal and malignant plasma cells and the BM microenvironment that have a significant impact on survival of myeloma patients.
Eyeing central neurons in vascular growth and reparative angiogenesis
Authors: Sapieha Przemyslaw
Published: June 2012

The generation of blood vessels is a highly synchronized process requiring the coordinated efforts of several vascular and nonvascular cell populations as well as a stringent orchestration by the tissue being vascularized. Stereotyped angiogenesis is vital for both developmental growth and to restore tissue metabolic supply after ischemic events. Central neurons such as those found in the brain, spinal cord, and retina are vast consumers of oxygen and nutrients and therefore require high rates of perfusion by functional vascular networks to ensure proper sensory transmission. During a metabolic mismatch, such as that occurring during a cerebrovascular infarct or in ischemic retinopathies, there is increasing evidence that central neurons have an inherent ability to influence the vascular response to injury. With a focus on the retina and retinal ischemic disorders, this review explores the ever-growing evidence suggesting that central neurons have the propensity to impact tissue vascularization and reparative angiogenesis. Moreover, it addresses the paradoxical ability of severely ischemic neurons to hinder vascular regrowth and thus segregate the most severely injured zones of nervous tissue. The topics covered here are pertinent for future therapeutic strategies because promoting and steering vascular growth may be beneficial for ischemic disorders.
Factors influencing fecundity in experimental crosses of water lotus (Nelumbo nucifera Gaertn.) cultivars
Authors: Teng Nian-Jun , Wang Yan-Li , Sun Chun-Qing , Fang Wei-Min , Chen Fa-Di
Published: June 2012

Background

Breeding programs for the water lotus (Nelumbo nucifera) are hampered by an inability to account for variation in seed set associated with crosses between different cultivars. We studied seed set in two reciprocal crosses between lotus cultivars (‘Guili’ × ‘Aijiangnan’ and ‘Molingqiuse’ × ‘Qinhuaiyanzhi') to obtain insights into factors that govern fecundity in these experimental hybrids. Pollen viability, stigma receptivity and embryo development were compared for each hybrid and reciprocal cross.

Results

Pollen viability of the individual cultivars ranged from 4.1% to 20.2%, with the highest level (>11.9%) for all cultivars observed from the earliest collected grains (05:00–06:00 a.m.). Stigmatic pollen germination peaked at 4 h after pollination and varied from 4.8 to 60.6 grains per stigma among the crosses. Production of normal embryos ranged from 7.6% to 58.8% at 1 d after pollination and from 0 to 25% by 11 d after pollination. Seed set in crosses (0.2–23.3%) was generally lower than in open-pollinated plants (8.4–26.5%). Similar to the germination results, seed set was substantially reduced in both reciprocal crosses.

Conclusions

These results suggested that poor pollen fertility, low stigma receptivity, and embryo abortion were responsible for the failure of the crosses ‘Molingqiuse’ × ‘Qinhuaiyanzhi’, ‘Qinhuaiyanzhi’ × ‘Molingqiuse’, and ‘Aijiangnan’ × ‘Guili’.
Insulin-containing lipogenic stimuli suppress mast cell degranulation potential and up-regulate lipid body biogenesis and eicosanoid secretion in a PPARγ-independent manner
Authors: Greineisen William E , Shimoda Lori M N , Maaetoft-Udsen Kristina , Turner Helen
Published: June 2012

Endocrine regulation of inflammatory potential in mast cells identifies insulin as a driving force for lipid body biogenesis and eicosanoid secretion.

Lipid bodies are most studied in adipocytes, where the lipogenic action of insulin initiates their formation. Here, we test the hypothesis that insulin may regulate lipid body content in mast cells and hence, modify their proinflammatory potential. Our data show that insulin causes lipid body accumulation in RBL2H3 and BMMCs. Lipid body accumulation in mast cells is associated with enhanced levels of leukotriene-synthesizing enzymes (LTC4S and 5-LO). Increased basal and antigen-stimulated release of LTC4 is observed in insulin-treated mast cells. Concomitantly, the insulin-containing lipogenic stimulus induces a phenotypic change in mast cells, where this enhancement in leukotriene levels is accompanied by a marked down-regulation in secretory granule content and release in response to stimulus. Mast cells exposed to insulin exhibit altered scatter and fluorescence properties, accumulating in a SSCloFSChi population that exhibits decreased BS staining and degranulation responses and is enriched in NR-positive lipid bodies and eicosanoid synthesis enzymes. Lipid body accumulation in mast cells is mechanistically distinct from the process in adipocytes; for example, it is independent of PPARγ up-regulation and does not involve significant accumulation of conjugated glycerides. Thus, chronic exposure to metabolic stimuli, such as insulin, may be a determinant of the proinflammatory potential of the mast cell.
Gestational Exposure to Bisphenol A Produces Transgenerational Changes in Behaviors and Gene Expression
Authors: Wolstenholme Jennifer T. , Edwards Michelle , Shetty Savera R. J. , Gatewood Jessica D. , Taylor Julia A. , Rissman Emilie F. , Connelly Jessica J.
Published: June 2012

Bisphenol A (BPA) is a plasticizer and an endocrine-disrupting chemical. It is present in a variety of products used daily including food containers, paper, and dental sealants and is now widely detected in human urine and blood. Exposure to BPA during development may affect brain organization and behavior, perhaps as a consequence of its actions as a steroid hormone agonist/antagonist and/or an epigenetic modifier. Here we show that BPA produces transgenerational alterations in genes and behavior. Female mice received phytoestrogen-free chow with or without BPA before mating and throughout gestation. Plasma levels of BPA in supplemented dams were in a range similar to those measured in humans. Juveniles in the first generation exposed to BPA in utero displayed fewer social interactions as compared with control mice, whereas in later generations (F2 and F4), the effect of BPA was to increase these social interactions. Brains from embryos (embryonic d 18.5) exposed to BPA had lower gene transcript levels for several estrogen receptors, oxytocin, and vasopressin as compared with controls; decreased vasopressin mRNA persisted into the F4 generation, at which time oxytocin was also reduced but only in males. Thus, exposure to a low dose of BPA, only during gestation, has immediate and long-lasting, transgenerational effects on mRNA in brain and social behaviors. Heritable effects of an endocrine-disrupting chemical have implications for complex neurological diseases and highlight the importance of considering gene-environment interactions in the etiology of complex disease.
Stein's Method and Stochastic Orderings
Authors: Daly Fraser , Lefèvre Claude , Utev Sergey
Published: June 2012

A stochastic ordering approach is applied with Stein's method for approximation by the equilibrium distribution of a birth-death process. The usual stochastic order and the more generals-convex orders are discussed. Attention is focused on Poisson and translated Poisson approximations of a sum of dependent Bernoulli random variables, for example,k-runs in independent and identically distributed Bernoulli trials. Other applications include approximation by polynomial birth-death distributions.
Increasing Hazard Rate of Mixtures for Natural Exponential Families
Authors: Bar-Lev Shaul K. , Letac Gérard
Published: June 2012

Hazard rates play an important role in various areas, e.g. reliability theory, survival analysis, biostatistics, queueing theory, and actuarial studies. Mixtures of distributions are also of great preeminence in such areas as most populations of components are indeed heterogeneous. In this study we present a sufficient condition for mixtures of two elements of the same natural exponential family (NEF) to have an increasing hazard rate. We then apply this condition to some classical NEFs having either quadratic or cubic variance functions (VFs) and others as well. Particular attention is paid to the hyperbolic cosine NEF having a quadratic VF, the Ressel NEF having a cubic VF, and the NEF generated by Kummer distributions of type 2. The application of such a sufficient condition is quite intricate and cumbersome, in particular when applied to the latter three NEFs. Various lemmas and propositions are needed to verify this condition for such NEFs. It should be pointed out, however, that our results are mainly applied to a mixture of two populations.
Closed-Form Asymptotic Sampling Distributions under the Coalescent with Recombination for an Arbitrary Number of Loci
Authors: Bhaskar Anand , Song Yun S.
Published: June 2012

Obtaining a closed-form sampling distribution for the coalescent with recombination is a challenging problem. In the case oftwoloci, a new framework based on an asymptotic series has recently been developed to derive closed-form results when the recombination rate is moderate to large. In this paper, anarbitrarynumber of loci is considered and combinatorial approaches are employed to find closed-form expressions for the first couple of terms in an asymptotic expansion of the multi-locus sampling distribution. These expressions are universal in the sense that their functional form in terms of the marginal one-locus distributions applies to all finite- and infinite-alleles models of mutation.
Approximate Sampling Formulae for General Finite-Alleles Models of Mutation
Authors: Bhaskar Anand , Kamm John A. , Song Yun S.
Published: June 2012

Many applications in genetic analyses utilize sampling distributions, which describe the probability of observing a sample of DNA sequences randomly drawn from a population. In the one-locus case with special models of mutation, such as the infinite-alleles model or the finite-alleles parent-independent mutation model, closed-form sampling distributions under the coalescent have been known for many decades. However, no exact formula is currently known for more general models of mutation that are of biological interest. In this paper, models with finitely-many alleles are considered, and an urn construction related to the coalescent is used to derive approximate closed-form sampling formulae for an arbitrary irreducible recurrent mutation model or for a reversible recurrent mutation model, depending on whether the number of distinct observed allele types is at most three or four, respectively. It is demonstrated empirically that the formulae derived here are highly accurate when the per-base mutation rate is low, which holds for many biological organisms.
On the Joint Behavior of Types of Coupons in Generalized Coupon Collection
Authors: Mahmoud Hosam M. , Smythe Robert T.
Published: June 2012

The ‘coupon collection problem’ refers to a class of occupancy problems in which j identical items are distributed, independently and at random, to n cells, with no restrictions on multiple occupancy. Identifying the cells as coupons, a coupon is ‘collected’ if the cell is occupied by one or more of the distributed items; thus, some coupons may never be collected, whereas others may be collected once or twice or more. We call the number of coupons collected exactly r times coupons of type r. The coupon collection model we consider is general, in that a random number of purchases occurs at each stage of collecting a large number of coupons; the sample sizes at each stage are independent and identically distributed according to a sampling distribution. The joint behavior of the various types is an intricate problem. In fact, there is a variety of joint central limit theorems (and other limit laws) that arise according to the interrelation between the mean, variance, and range of the sampling distribution, and of course the phase (how far we are in the collection processes). According to an appropriate combination of the mean of the sampling distribution and the number of available coupons, the phase is sublinear, linear, or superlinear. In the sublinear phase, the normalization that produces a Gaussian limit law for uncollected coupons can be used to obtain a multivariate central limit law for at most two other types — depending on the rates of growth of the mean and variance of the sampling distribution, we may have a joint central limit theorem between types 0 and 1, or between types 0, 1, and 2. In the linear phase we have a multivariate central limit theorem among the types 0, 1,…, k for any fixed k.
A Self-Normalized Central Limit Theorem for Markov Random Walks
Authors: Fuh Cheng-Der , Pang Tian-Xiao
Published: June 2012

Motivated by the study of the asymptotic normality of the least-squares estimator in the (autoregressive) AR(1) model under possibly infinite variance, in this paper we investigate a self-normalized central limit theorem for Markov random walks. That is, let {Xn,n≥ 0} be a Markov chain on a general state spaceXwith transition probabilityPand invariant measure π. Suppose that an additive componentSntakes values on the real line, and is adjoined to the chain such that {Sn,n≥ 1} is a Markov random walk. Assume thatSn= ∑k=1nξk, and that {ξn,n≥ 1} is a nondegenerate and stationary sequence under π that belongs to the domain of attraction of the normal law with zero mean and possibly infinite variance. By making use of an asymptotic variance formula ofSn/ √n, we prove a self-normalized central limit theorem forSnunder some regularity conditions. An essential idea in our proof is to bound the covariance of the Markov random walk via a sequence of weight functions, which plays a crucial role in determining the moment condition and dependence structure of the Markov random walk. As illustrations, we apply our results to the finite-state Markov chain, the AR(1) model, and the linear state space model.
Fractional Relaxation Equations and Brownian Crossing Probabilities of a Random Boundary
Authors: Beghin L.
Published: June 2012

In this paper we analyze different forms of fractional relaxation equations of order ν ∈ (0, 1), and we derive their solutions in both analytical and probabilistic forms. In particular, we show that these solutions can be expressed as random boundary crossing probabilities of various types of stochastic process, which are all related to the Brownian motion B. In the special case ν = ½, the fractional relaxation is shown to coincide with Pr{sup0≤s≤tB(s) < U} for an exponential boundary U. When we generalize the distributions of the random boundary, passing from the exponential to the gamma density, we obtain more and more complicated fractional equations.
Typical Distances in Ultrasmall Random Networks
Authors: Dereich Steffen , Mönch Christian , Mörters Peter
Published: June 2012

We show that in preferential attachment models with power-law exponent τ ∈ (2, 3) the distance between randomly chosen vertices in the giant component is asymptotically equal to (4 + o(1))log log N / (-log(τ − 2)), where N denotes the number of nodes. This is twice the value obtained for the configuration model with the same power-law exponent. The extra factor reveals the different structure of typical shortest paths in preferential attachment graphs.
Risk Measures and Multivariate Extensions of Breiman's Theorem
Authors: Fougeres Anne-Laure , Mercadier Cecile
Published: June 2012

The modeling of insurance risks has received an increasing amount of attention because of solvency capital requirements. The ruin probability has become a standard risk measure to assess regulatory capital. In this paper we focus on discrete-time models for the finite time horizon. Several results are available in the literature to calibrate the ruin probability by means of the sum of the tail probabilities of individual claim amounts. The aim of this work is to obtain asymptotics for such probabilities under multivariate regular variation and, more precisely, to derive them from extensions of Breiman's theorem. We thus present new situations where the ruin probability admits computable equivalents. We also derive asymptotics for the value at risk.
On the Residual and Inactivity Times of the Components of Used Coherent Systems
Authors: Goliforushani S. , Asadi M. , Balakrishnan N.
Published: June 2012

In the study of the reliability of technical systems in reliability engineering, coherent systems play a key role. In this paper we consider a coherent system consisting of n components with independent and identically distributed components and propose two time-dependent criteria. The first criterion is a measure of the residual lifetime of live components of a coherent system having some of the components alive when the system fails at time t. The second criterion is a time-dependent measure which enables us to investigate the inactivity times of the failed components of a coherent system still functioning though some of its components have failed. Several ageing and stochastic properties of the proposed measures are then established.
Advances in Complete Mixability
Authors: Puccetti Giovanni , Wang Bin , Wang Ruodu
Published: June 2012

The concept of complete mixability is relevant to some problems of optimal couplings with important applications in quantitative risk management. In this paper we prove new properties of the set of completely mixable distributions, including a completeness and a decomposition theorem. We also show that distributions with a concave density and radially symmetric distributions are completely mixable.
Hurst Index of Functions of Long-Range-Dependent Markov Chains
Authors: Oğuz Barlas , Anantharam Venkat
Published: June 2012

A positive recurrent, aperiodic Markov chain is said to be long-range dependent (LRD) when the indicator function of a particular state is LRD. This happens if and only if the return time distribution for that state has infinite variance. We investigate the question of whether other instantaneous functions of the Markov chain also inherit this property. We provide conditions under which the function has the same degree of long-range dependence as the chain itself. We illustrate our results through three examples in diverse fields: queueing networks, source compression, and finance.
Continuous-Time Skewed Multifractal Processes as a Model for Financial Returns
Authors: Bacry Emmanuel , Duvernet Laurent , Muzy Jean-François
Published: June 2012

We present the construction of a continuous-time stochastic process which has moments that satisfy an exact scaling relation, including odd-order moments. It is based on a natural extension of the multifractal random walk construction described in Bacry and Muzy (2003). This allows us to propose a continuous-time model for the price of a financial asset that reflects most major stylized facts observed on real data, including asymmetry and multifractal scaling.
Focal adhesion kinase is a phospho-regulated repressor of Rac and proliferation in human endothelial cells
Authors: Bryant Patrick W. , Zheng Qingxia , Pumiglia Kevin M.
Published: June 2012

Focal adhesion kinase (FAK) is critically positioned to integrate signals from the extracellular matrix and cellular adhesion. It is essential for normal vascular development and has been implicated in a wide range of cellular functions including the regulation of cell proliferation, migration, differentiation, and survival. It is currently being actively targeted therapeutically using different approaches. We have used human endothelial cells as a model system to compare the effects of inhibiting FAK through several different approaches including dominant negatives, kinase inhibitors and shRNA. We find that manipulations of FAK signaling that result in inhibition of FAK 397 phosphorylation inhibit proliferation and migration. However, abolition of FAK expression using stable (shRNA) or transient (siRNA) approaches does not interfere with these cellular functions. The ability to regulate cell proliferation by FAK manipulation is correlated with the activation status of Rac, an essential signal for the regulation of cyclin-dependent kinase inhibitors. The knockdown of FAK, while not affecting cellular proliferation or migration, dramatically interferes with vascular morphogenesis and survival, mirroring in vivo findings. We propose a novel model of FAK signaling whereby one of the multifunctional roles of FAK as a signaling protein includes FAK as a phospho-regulated repressor of Rac activation, with important implications on interpretation of research experiments and therapeutic development.
Life-long preservation of the regenerative capacity in the fin and heart in zebrafish
Authors: Itou Junji , Kawakami Hiroko , Burgoyne Tyler , Kawakami Yasuhiko
Published: June 2012

The zebrafish is a widely used model animal to study the regeneration of organs, such as the fin and heart. Their average lifetime is about 3 years, and recent studies have shown that zebrafish exhibit aging-related degeneration, suggesting the possibility that aging might affect regenerative potential. In order to investigate this possibility, we compared regeneration of the fin and heart after experimental amputation in young (6–12 month old) and old (26–36 month old) fish. Comparison of recovery rate of the caudal fin, measured every two or three days from one day post amputation until 13 days post amputation, show that fins in young and old fish regenerate at a similar rate. In the heart, myocardium regeneration and cardiomyocyte proliferation occurred similarly in the two groups. Moreover, neo-vascularization, as well as activation of fibroblast growth factor signaling, which is required for neo-vascularization, occurred similarly. The epicardial tissue is a thin layer tissue that covers the heart, and starts to express several genes immediately in response to injury. The expression of epicardial genes, such as wt1b and aldh1a2, in response to heart injury was comparable in two groups. Our results demonstrate that zebrafish preserve a life-long regenerative ability of the caudal fin and heart.
Adhesion rings surround invadopodia and promote maturation
Authors: Branch Kevin M. , Hoshino Daisuke , Weaver Alissa M.
Published: June 2012

Invasion and metastasis are aggressive cancer phenotypes that are highly related to the ability of cancer cells to degrade extracellular matrix (ECM). At the cellular level, specialized actin-rich structures called invadopodia mediate focal matrix degradation by serving as exocytic sites for ECM-degrading proteinases. Adhesion signaling is likely to be a critical regulatory input to invadopodia, but the mechanism and location of such adhesion signaling events are poorly understood. Here, we report that adhesion rings surround invadopodia shortly after formation and correlate strongly with invadopodium activity on a cell-by-cell basis. By contrast, there was little correlation of focal adhesion number or size with cellular invadopodium activity. Prevention of adhesion ring formation by inhibition of RGD-binding integrins or knockdown (KD) of integrin-linked kinase (ILK) reduced the number of ECM-degrading invadopodia and reduced recruitment of IQGAP to invadopodium actin puncta. Furthermore, live cell imaging revealed that the rate of extracellular MT1-MMP accumulation at invadopodia was greatly reduced in both integrin-inhibited and ILK-KD cells. Conversely, KD of MT1-MMP reduced invadopodium activity and dynamics but not the number of adhesion-ringed invadopodia. These results suggest a model in which adhesion rings are recruited to invadopodia shortly after formation and promote invadopodium maturation by enhancing proteinase secretion. Since adhesion rings are a defining characteristic of podosomes, similar structures formed by normal cells, our data also suggest further similarities between invadopodia and podosomes.