bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence and impact of sexually transmitted infections in pregnant women in central Ethiopia
Authors: Schönfeld Andreas , Feldt Torsten , Tufa Tafese B , Orth Hans M , Fuchs André , Mesfun Million G , Pfäfflin Frieder , Nordmann Tamara , Breuer Matthias , Hampl Monika , Häussinger Dieter
Published: August 2017

Human immunodeficiency virus (HIV) continues to be a major global public health issue and omnipresent sexually transmitted infections (STIs) increase the risk of HIV acquisition. Moreover, STIs and HIV in pregnant women can harm the unborn child. In this study, we systematically investigated the prevalence of HIV, relevant STIs and vaginal group B streptococcus colonization among pregnant women presenting at Asella Teaching Hospital in central Ethiopia and their effect on perinatal mortality. A follow-up was performed six weeks after delivery. A total of 580 women were included, of which 26.6% tested positive for at least one pathogen ( Chlamydia trachomatis 9.8%, trichomoniasis 5.3%, hepatitis B 5.3%, gonorrhoea 4.3%, group B streptococcus 2.4%, syphilis 2.2%, HIV 2.1%). None of the HIV infections were previously undiagnosed, indicating effective HIV screening activities in the region. Follow-up data were available for 473 (81.6%) children, of which 37 (7.8%) were stillborn or died within the first six weeks of life. Infection with Trichomonas vaginalis and recruitment at obstetric ward (versus antenatal care) were associated with mortality. High prevalence of STIs in pregnant women and their impact on the unborn child demonstrate the need for screening and treatment programmes in order to prevent perinatal mortality.
Characteristics Associated With Migration Among Older Women and Men in Rural Malawi
Authors: Kendall Jacob , Anglewicz Philip
Published: August 2017

The older population in sub-Saharan Africa is growing rapidly, but little is known about the migration patterns of older individuals in this setting. In this article, we identify the determinants of migration for older individuals in a rural African setting. To do so, we use rare longitudinal data with information for older individuals both before and after migration. We first identify premigration factors associated with moving in the future and then identify differences in characteristics between migrants and nonmigrants after migration. In addition to basic sociodemographic information, we examine differences between migrants and nonmigrants in land ownership, number of lifetime marriages, number of living offspring, previous migration experience, household size, social and religious participation, and religious affiliation. Results show that (a) migration in older age is related to marriage, health and HIV status, household size, and religion; (b) older women who are HIV-positive are more likely to move, and older men with better physical health are more likely to move; (c) older female migrants have worse postmigration physical health; and (d) the relationship between health and migration for older men disappears after migration.
Description and Evaluation of the Implementation of a Weight-Based, Nurse-Driven Heparin Nomogram in a Tertiary Academic Medical Center
Authors: Schurr James W , Stevens Craig A , Bane Anne , Luppi Carol , Culbreth Sarah E. , Miller Amy Leigh , Connors Jean M. , Sylvester Katelyn W.
Published: August 2017

Weight-based, nurse-driven heparin nomograms are reported in the medical literature to improve the time it takes to reach a minimum threshold for anticoagulation without compromising patient safety in specific indications or patient populations. This is the first report in the literature of an institution-wide protocol implementation and evaluation of effectiveness with simultaneous transition to an electronic health record. The purpose of implementing this practice change at our institution was to standardize practice, improve time to reach therapeutic anticoagulation, and improve patient safety. We conducted a retrospective analysis utilizing a pre/postimplementation design to compare outcomes. The primary end point evaluated was the time to reach minimum threshold value for therapeutic anticoagulation. Additionally, we assessed the percentage of patients who reached minimum threshold therapeutic anticoagulation within 24 hours, the percentage of patients with a critically supratherapeutic activated partial thromboplastin time (aPTT) value (≥120 seconds) during therapy, and a description of heparin titration for the first 4 aPTT results with nomogram use. Overall time to therapeutic anticoagulation decreased from a mean 18.7 to 11.7 hours (hazard ratio [HR] 1.59; 95% confidence interval 1.22-2.08; P < .0005). Percentage of patients receiving therapeutic anticoagulation within 24 hours increased from 74.4 to 88.5 (odds ratio [OR 2.97, P = .002) and the percentage of patients with an aPTT ≥120 seconds remained constant at 49.9 versus 46.8 (OR 0.92, P = .73). This practice change reduced time to therapeutic anticoagulation without an increase in the proportion of patients with a critically supratherapeutic aPTT at our institution.
Mobile Social Media and the News: Where Heutagogy Enables Journalism Education
Authors: Mulrennan Danielle
Published: August 2017

Journalism schools are under pressure to look beyond traditional teaching methods to prepare students for the post-Internet, rapidly evolving news landscape. Heutagogy is a net-centric teaching method in which learners are highly autonomous and self-determined. In this article, Participatory Action Research theory was applied within a heutagogical framework to the redevelopment of a social media course for journalism students at AUT University, New Zealand. The findings form the basis of recommendations across the wider journalism curriculum, and there are also implications for other areas of communication studies, public relations, and online or broadcast media.
Definitions of Evaluation Use and Misuse, Evaluation Influence, and Factors Affecting Use
Authors: Alkin Marvin C. , King Jean A.
Published: August 2017

The second article in this series on the history of evaluation use has three sections. The first and longest develops a functional definition of the term use, noting that a thorough definition of evaluation use includes the initial stimulus (i.e., evaluation findings or process), the user, the way people use the information, the aspect of the program considered, and the purpose. It then defines evaluation use’s unethical companion, misuse, detailing the distinction between the two. The second section briefly discusses a broadened concept of evaluation impact that expands to include evaluation influence. Finally, the third section summarizes the factors that research has shown to be related to evaluation use.
Reflective practices at the Security Council: Children and armed conflict and the three United Nations
Authors: Bode Ingvild
Published: August 2017

The United Nations Security Council passed its first resolution on children in armed conflict in 1999, making it one of the oldest examples of Security Council engagement with a thematic mandate and leading to the creation of a dedicated working group in 2005. Existing theoretical accounts of the Security Council cannot account for the developing substance of the children and armed conflict agenda as they are macro-oriented and focus exclusively on states. I argue that Security Council decision-making on thematic mandates is a productive process whose outcomes are created by and through practices of actors across the three United Nations: member states (the first United Nations), United Nations officials (the second United Nations) and non-governmental organizations (the third United Nations). In presenting a practice-based, micro-oriented analysis of the children and armed conflict agenda, the article aims to deliver on the empirical promise of practice theories in International Relations. I make two contributions to practice-based understandings: first, I argue that actors across the three United Nations engage in reflective practices of a strategic or tactical nature to manage, arrange or create space in Security Council decision-making. Portraying practices as reflective rather than as only based on tacit knowledge highlights how actors may creatively adapt their practices to social situations. Second, I argue that particular individuals from the three United Nations are more likely to become recognized as competent performers of practices because of their personality, understood as plural socialization experiences. This adds varied individual agency to practice theories that, despite their micro-level interests, have focused on how agency is relationally constituted.
Income elasticity of demand for tourism at Fulufjället National Park
Authors: Fredman Peter , Wikström Daniel
Published: August 2017

National Parks are significant markers in the tourism attraction system and represent an important supply of recreation opportunities for the clients of the nature-based tourism industry. In this study, we analyze income elasticities among visitors from two major nationalities at Fulufjället National Park (FNP)—a cross-boundary park between Sweden and Norway—to see if this tourism product is a luxury or not. Modeling demand with a Tobit model, we find that visiting this National Park is close to a luxury, but results also show that elasticities differ across both income and nationality: FNP is more likely to be a luxury good among low-income Germans and high-income Swedes. The article concludes with a discussion on policy and management implications from these results.
Dancing with danger: ethnographic safety, male bravado and gang research in Colombia
Authors: Baird Adam
Published: August 2017

This article considers the dilemmas and challenges of conducting fieldwork with youth gang members in Medellín, Colombia. It draws upon the author’s experiences to develop the notion of ‘ethnographic safety’, where researchers learn to perceive and avert danger by gaining a ‘feel for the rules of the game’ (Bourdieu, 1992) in violent communities; it problematizes the role that the researcher’s gender and ‘male bravado’ played in accessing and interviewing gang members; considers the ethical conundrums of building rapport with criminal subjects; and discusses the challenges of working in complex, chronically violent communities where there are no simple dichotomies between victims and perpetrators of violence.
Newly arrived migrant students in German schools: Exclusive and inclusive structures and practices
Authors: Terhart Henrike , von Dewitz Nora
Published: August 2017

Newly arrived migrant students in German schools are currently the centre of attention. In 2015 and 2016 the incoming number of migrant children and adolescents of school-age has risen. Schools, the education administration as well as politics need to take action with regard to this. In the on-going debate on new immigrant students in school, German media and the public focus have been predominantly on asylum seekers from conflict zones such as Syria or Afghanistan. For schools, the increasing number of newcomers with no or little proficiency of German currently poses a challenge, even though new immigrant students at school are not a new phenomenon, but rather a permanent one. From a theoretical point of view, social participation can be discussed within the division of inclusion and exclusion. In this article we examine the potential of a theoretical framework of social inclusion and exclusion in the case of new immigrant students and establish a connection between the organisation of schooling and practices in class. The analysis of a scene of multilingual classroom interaction, held in a separate class for newcomers only, shows how a complex interplay of including and excluding effects structure the situation of newly arrived migrant students.
Reevaluating collegiality: Relationality, learning communities, and possibilities
Authors: Chang Mary K
Published: August 2017

Researchers normatively view faculty or professional learning communities as effective methods for sharing teaching approaches. Such a view overlooks the potential impacts the groups can have more broadly on higher educational communities. In this article, three studies about university-affiliated faculty learning communities are considered from a relational perspective. Confucian relationality, which envisions people as interdependent, considers the development of collegiality that emerges from the communities as a form of personal cultivation and highlights the process-oriented aspects of the studies considered, insinuating the importance of quality interactions, commitment, and reciprocity. In particular, a relational view suggests that learning communities may enrich collegial relationships and generate collaborative projects, and other unimagined possibilities, in ways that affect institutions beyond the contexts of the communities. This work challenges scholars to consider how a relational theoretical framework situates collegiality in the context of research about university-affiliated faculty learning communities as an important achievement.
An Examination of the Influence of Implicit Theories, Attribution Styles, and Performance Cues on Questionnaire Measures of Leadership
Authors: Martinko Mark J. , Randolph-Seng Brandon , Shen Winny , Brees Jeremy R. , Mahoney Kevin T. , Kessler Stacey R.
Published: August 2017

We examined the direct and interactive effects of respondents’ implicit leadership theories (ILTs), attribution styles, and performance cues on leadership perceptions. After first assessing respondents’ implicit leadership theories and attribution styles, the participants were randomly assigned to one of nine performance cue conditions ([leader performance: low vs. average vs. high] × [follower performance: low vs. average vs. high]), observed the same leader’s behavior via video, and rated the leader by completing three leadership questionnaires. The results supported the notion that these three components of information have both direct and interactive effects on leadership perceptions as measured by the questionnaires. The three components of information accounted for about 10% of the variance in the three questionnaires. The results contribute to theories of information processing by demonstrating how ILTs, attribution styles, and performance cues interact to predict leadership perceptions. Implications regarding the meaningfulness, construct validity, and utility of leadership scales are discussed.
Pregnancy and myeloproliferative neoplasms : A retrospective monocentric cohort
Authors: Puyade Mathieu , Cayssials Emilie , Pierre Fabrice , Pourrat Olivier
Published: August 2017

Background

The most frequent myeloproliferative neoplasms are essential thrombocythemia and chronic myelogenous leukemia, which usually manifests with thrombocytosis. Only essential thrombocythemia is associated with morbidity during pregnancy (recurrent miscarriages, intrauterine fetal death, small for gestational age and preeclampsia). The aim of this paper is to describe outcomes of pregnancy in women with myeloproliferative neoplasms seen at a single academic institution.

Methods

Data were collected retrospectively from 2002 to 2015. Descriptive analyses were performed.

Results

Eighteen pregnancies in 13 patients and 17 births were identified. One patient had recurrent miscarriages. There were two intrauterine fetal deaths, three small for gestational age linked to vascular placenta pathology and one preeclampsia. All of these mothers harbored JAK2V617F mutation. Two out of three patients with small for gestational age developed a venous thrombosis in the two years following delivery.

Conclusion

Thrombocytosis associated with myeloproliferative neoplasms should be considered as a risk factor for maternal and fetal complications.
Whole-exome sequencing for RH genotyping and alloimmunization risk in children with sickle cell anemia
Authors: Chou Stella T. , Flanagan Jonathan M. , Vege Sunitha , Luban Naomi L. C. , Brown R. Clark , Ware Russell E. , Westhoff Connie M.
Published: August 2017

Key Points

WES can be applied for precise RH genotyping, detection of new or uncommon variants, and determination of RHD zygosity. An altered RH genotype is a risk factor for Rh alloimmunization in patients with sickle cell anemia.
Mortality in pulmonary arterial hypertension: prediction by the 2015 European pulmonary hypertension guidelines risk stratification model
Authors: Hoeper Marius M. , Kramer Tilmann , Pan Zixuan , Eichstaedt Christina A. , Spiesshoefer Jens , Benjamin Nicola , Olsson Karen M. , Meyer Katrin , Vizza Carmine Dario , Vonk-Noordegraaf Anton , Distler Oliver , Opitz Christian , Gibbs J. Simon R. , Delcroix Marion , Ghofrani H. Ardeschir , Huscher Doerte , Pittrow David , Rosenkranz Stephan , Grünig Ekkehard
Published: August 2017

The 2015 European pulmonary hypertension (PH) guidelines propose a risk stratification strategy for patients with pulmonary arterial hypertension (PAH). Low-, intermediate- and high-risk strata are defined by estimated 1-year mortality risks of <5%, 5–10% and >10%, respectively. This risk assessment strategy awaits validation.

We analysed data from patients with newly diagnosed PAH enrolled into COMPERA (Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension), a European-based PH registry. An abbreviated version of the risk assessment strategy proposed by the European PH guidelines was applied, using the following variables: World Health Organization functional class, 6-min walking distance, brain natriuretic peptide or its N-terminal fragment, right atrial pressure, cardiac index and mixed venous oxygen saturation.

Data from 1588 patients were analysed. Mortality rates were significantly different between the three risk strata (p<0.001 for all comparisons). In the entire patient population, the observed mortality rates 1 year after diagnosis were 2.8% in the low-risk cohort (n=196), 9.9% in the intermediate-risk cohort (n=1116) and 21.2% in the high-risk cohort (n=276). In addition, the risk assessment strategy proved valid at follow-up and in major PAH subgroups.

An abbreviated version of the risk assessment strategy proposed by the current European PH guidelines provides accurate mortality estimates in patients with PAH.
The emerging role of transient receptor potential channels in chronic lung disease
Authors: Belvisi Maria G. , Birrell Mark A.
Published: August 2017

Chronic lung diseases such as asthma, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis are a major and increasing global health burden with a high unmet need. Drug discovery efforts in this area have been largely disappointing and so new therapeutic targets are needed. Transient receptor potential ion channels are emerging as possible therapeutic targets, given their widespread expression in the lung, their role in the modulation of inflammatory and structural changes and in the production of respiratory symptoms, such as bronchospasm and cough, seen in chronic lung disease.
Oestrogen inhibition reverses pulmonary arterial hypertension and associated metabolic defects
Authors: Chen Xinping , Austin Eric D. , Talati Megha , Fessel Joshua P. , Farber-Eger Eric H. , Brittain Evan L. , Hemnes Anna R. , Loyd James E. , West James
Published: August 2017

Increased oestrogen is a strong epidemiological risk factor for development of pulmonary arterial hypertension (PAH) in patients, associated with metabolic defects. In addition, oestrogens drive penetrance in mice carrying mutations in bone morphogenetic protein receptor type II (BMPR2), the cause of most heritable PAH. The goal of the present study was to determine whether inhibition of oestrogens was effective in the treatment of PAH in these mice.

The oestrogen inhibitors fulvestrant and anastrozole were used in a prevention and treatment paradigm in BMPR2 mutant mice, and tamoxifen was used for treatment. In addition, BMPR2 mutant mice were crossed onto oestrogen receptor (ESR)1 and ESR2 knockout backgrounds to assess receptor specificity. Haemodynamic and metabolic outcomes were measured.

Oestrogen inhibition both prevented and treated PAH in BMPR2 mutant mice. This was associated with reduction in metabolic defects including oxidised lipid formation, insulin resistance and rescue of peroxisome proliferator-activated receptor-γ and CD36. The effect was mediated primarily through ESR2, but partially through ESR1.

Our data suggest that trials of oestrogen inhibition in human PAH are warranted, and may improve pulmonary vascular disease through amelioration of metabolic defects. Although fulvestrant and anastrozole were more effective than tamoxifen, tamoxifen may be useful in premenopausal females, because of a reduced risk of induction of menopause.
Patina in the construction of the poetic bronze image: science of materials, art and philosophy
Authors: Silva Claudia , Vélez Gabriel , Colorado Henry A.
Published: August 2017

Bronze has been positioned as the medium par excellence for sculptural production bearing the aesthetic, symbolic and poetic values that have propitiated the construction of a metallurgical archetype, which has its genesis in its physicochemical, metallurgical and mechanical properties. Of these properties, the formation of the patina is the one that contributes most to the construction of its poetic image, since it is the one that, along with the form, suddenly appears before the spectators, directly affecting their perception of the work. To exemplify this, we analyze the patina of the sculpture La Piedad by Bernardo Vieco using SEM–EDX and XRD. The results show a non-protective patina that, added to the other factors of deterioration of the work, contribute to the drama of the scene that is represented, taking it from pain and impotence before the death of a loved one, to a state of hopelessness and apathy embodied in a bronze that deteriorates over time with environmental factors and neglect in the protection and conservation of the work.
FGF21 Is an Insulin-Dependent Postprandial Hormone in Adult Humans
Authors: Samms Ricardo J , Lewis Jo E , Norton Luke , Stephens Francis B , Gaffney Christopher J , Butterfield Tony , Smith Dennis P , Cheng Christine C , Perfield James W , Adams Andrew C , Ebling Francis J P , Tsintzas Kostas
Published: August 2017

Context

Fibroblast growth factor 21 (FGF21) secretion has been shown to respond directly to carbohydrate consumption, with glucose, fructose, and sucrose all reported to increase plasma levels of FGF21 in rodents and humans. However, carbohydrate consumption also results in secretion of insulin.

Objective

The aim of this study was to examine the combined and independent effects of hyperglycemia and hyperinsulinemia on total and bioactive FGF21 in the postprandial period in humans, and determine whether this effect is attenuated in conditions of altered insulin secretion and action.

Methods

Circulating glucose, insulin, total and bioactive FGF21, and fibroblast activation protein were measured in adults with and without type 2 diabetes (T2D) following an oral glucose tolerance test (OGTT), and under a series of insulin and glucose clamp conditions and following high-fat diet in healthy adults.

Results

Circulating total and bioactive FGF21 levels responded acutely to OGTT, and their ratio was attenuated in T2D patients with reduced postprandial insulin response. The clamp studies revealed that insulin but not glucose accounts for the postprandial rise in FGF21. Finally, there was an attenuated rise in FGF21 in response to a high-fat dietary intervention that is known to alter insulin-stimulated substrate utilization in metabolically active tissues.

Conclusions

Insulin rather than glucose per se increases total and bioactive FGF21 in the postprandial period in adult humans. Understanding the impact of T2D on bioactive FGF21 will have a significant effect upon the efficacy of therapeutic agents designed to target the FGF21 pathway.
Reduction in Operating Room Plasma Waste After Evidence-Based Quality Improvement Initiative
Authors: Meyer Matthew J. , Dzik Walter H. , Levine Wilton C.
Published: August 2017

Anesthesiologists request units of plasma in anticipation of transfusion. The amount of plasma transfused intraoperatively is less than that issued (requested, thawed, and sent). We presented institutional-specific data on plasma usage including anesthesiologist-specific ratios of plasma issued-to-transfused. In month-to-month comparisons from the year before the presentation (June–December 2015) to 7 months after (June–December 2016), plasma issued to the operating room was reduced from 434.9 ± 81 to 327.3 ± 65 units, a change of 107.6 units per month (95% confidence interval [CI], 22–193); plasma discarded by the blood bank was reduced from 109.7 ± 48 units to 69.1 ± 9 units, a change of 40.6 units per month (95% CI, 0.2–81); and plasma transfused went from 188.4 ± 42 units to 160.7 ± 52 units, a nonsignificant change of 27.7 units per month (95% CI, −27 to 83).
Does the human immune system ever really become “senescent”?
Authors: Pawelec Graham
Published: August 2017

Like all somatic tissues, the human immune system changes with age. This is believed to result in an increased frequency of, and susceptibility to, infectious disease and to contribute to a wide range of non-communicable age-associated diseases in later life, especially cancer, cardiovascular disease, and autoimmunity. The majority of studies addressing immune ageing has been cross-sectional, but limited longitudinal studies are contributing to a better understanding of age-associated changes, as opposed to differences, and their clinical relevance. However, intriguing differences are emerging that implicate highly context-dependent immune ageing processes, mitigating against current generalisations concerning human immunosenescence and indicating the necessity for detailed comparisons of different populations, even those that would appear quite similar at first glance.
Mutual investments between GCC and CIS countries
Authors: Нагимова  , Nagimova Al'mira
Published: August 2017

This new book of an expert on the Arab capital markets Almira Nagimova explores the cross-border capital flows between the Gulf Cooperation Council and the Commonwealth of Independent States. This timely work not only reflects on the many recent cross-border deals, but also explains emerging trends.
Three sections cover: stages and prerequisites of an investment activity between GCC and CIS countries, types of the Arab investors and their investment strategies with the special focus on the sovereign wealth funds; analysis of more than 200 cross-border merger and acquisition and greenfield deals that have taken place from 1991 till 2016; the recent developments of the legal basis of investment collaboration, the performance of participants and the results of bilateral investment events.
The book provides an in-depth look at the current state of mutual investment process and prospective areas of cooperation between countries, including the prospects for Islamic finance in Russia and the CIS. It also answers key questions related to stakeholders, total value and dynamics, industrial and geographical breakdowns of deals, and more.
Self-Rated Health among youth and its associations with physical activity outside school, BMI and television time in an urban municipality of Portugal
Authors: Mota Jorge , Duncan Michael , Barros Mauro , Farias Júnior José , Ribeiro José , Carvalho Joana , Pizarro Andreia , Santos Maria
Published: August 2017

This study examined associations of physical activity (PA) outside school, Body mass index (BMI) and Television time (TVT) with SRH among youth. 1121 adolescents, aged from 10-18 years old participated in this cross-sectional study. PA was obtained through a questionnaire developed by Telama et al. (1997)1. TVT was accessed by asking the participant how many hours/day did they watch tv in the preceding week. Cole et al. (2000)2 cut points for BMI [weight (kg)/ height2 (m)] were used as an indicator of children’s nutritional status. Associations of self-reported PA, TVT and BMI to SRH were assessed by gender, using Chi Squared and multivariate logistic regression controlling for mothers’ education level. High levels of physical activity (boys: OR 2.43, 95% CI 1.24 to 4.78; girls: OR 2.02, 95% CI 1.26 to 3.24) were significantly associated with better SRH in adolescents. Obese/overweight boys were less likely to report positive SRH (OR 0.41, 95% CI 0.20 to 0.81) compared to their normal-weight peers. TVT in both genders and being overweight/obese in girls was not significantly associated with SRH. Results suggest that positive SRH is associated with PA levels, in both boys and girls, and with better nutritional status in boys.
Breast cancer: relation between quality of life and physical activity level
Authors: Ribovski Marina , Guimarães Adriana Coutinho de Azevedo , Boing Leonessa , Sperandio Fabiana Flores , Dias Mirella , Reis Nycolle Martins
Published: August 2017

The objective was to investigate the relation between quality of life and physical activity level in women with breast cancer undergoing treatment at the Oncologic Research Center (CEPON). A total of 158 women (56±9 years) answered a structured questionnaire, at a standardized interview, about sociodemographic and clinical information; economic situation (IBGE – Instituto Brasileiro de Geografia e Estatística); physical activity (IPAQ – International Physical Activity Questionnaire); and quality of life (QLQ-C30 – Quality of Life Questionnaire; QLQ-BR23). Most of the women was not sufficiently active (71.5%) and reported better global quality of life, with a score of 73±25. There was a significant difference on the functional scale for the items physical function (p=0.007) and role performance (p=0.048), with better quality of life values for active women, as well as on the symptom scale for the items loss of appetite (p=0.005) and pain (p=0.040). There was a positive association between total physical activity and quality of life in physical function (r=0.23; p=0.01) and role performance (r=0.023; p=0.01) and a negative association in the symptom scale (r=-0.24; p=0.01) and item loss of appetite (r=- 0.25; p=0.01). We conclude that women with breast cancer were not sufficiently active and showed good global quality of life scores, being that the actives presented better physical function, role performance and less loss of appetite and pain.
Flow-level Convergence and Insensitivity for Multi-class Queueing Networks
Authors: Walton Neil Stuart
Published: August 2017

We consider a multi-class queueing network as a model of packet transfer in a communication network. We define a second stochastic model as a model of document transfer in a communication network where the documents transferred have a general distribution. We prove the weak convergence of the multi-class queueing process to the document transfer process. Our convergence result allows the comparison of general document size distributions, and consequently, we prove general insensitivity results for the limit queueing process. We discuss how this separation of time-scales method of proving insensitivity may be applied to other insensitive queueing systems.
Asynchronous Stochastic Approximation with Differential Inclusions
Authors: Perkins Steven , Leslie David S.
Published: August 2017

The asymptotic pseudo-trajectory approach to stochastic approximation of Benaïm, Hofbauer and Sorin is extended for asynchronous stochastic approximations with a set-valued mean field. The asynchronicity of the process is incorporated into the mean field to produce convergence results which remain similar to those of an equivalent synchronous process. In addition, this allows many of the restrictive assumptions previously associated with asynchronous stochastic approximation to be removed. The framework is extended for a coupled asynchronous stochastic approximation process with set-valued mean fields. Two-timescales arguments are used here in a similar manner to the original work in this area by Borkar. The applicability of this approach is demonstrated through learning in a Markov decision process.
Wiener-Hopf Factorizations for a Multidimensional Markov Additive Process and their Applications to Reflected Processes
Authors: Miyazawa Masakiyo , Zwart Bert
Published: August 2017

We extend the framework of Neuts’ matrix analytic approach to a reflected process generated by a discrete time multidimensional Markov additive process. This Markov additive process has a general background state space and a real vector valued additive component, and generates a multidimensional reflected process. Our major interest is to derive a closed form formula for the stationary distribution of this reflected process. To this end, we introduce a real valued level, and derive new versions of the Wiener-Hopf factorization for the Markov additive process with the multidimensional additive component. In particular, it is represented by moment generating functions, and we consider the domain for it to be valid.

Our framework is general enough to include multi-server queues and/or queueing networks as well as non-linear time series which are currently popular in financial and actuarial mathematics. Our results yield structural results for such models. As an illustration, we apply our results to extend existing results on the tail behavior of reflected processes.

A major theme of this work is to connect recent work on matrix analytic methods to classical probabilistic studies on Markov additive processes. Indeed, using purely probabilistic methods such as censoring, duality, level crossing and time-reversal (which are known in the matrix analytic methods community but date back to Arjas & Speed [2] and Pitman [29]), we extend and unify existing results in both areas.
Two-parameter Sample Path Large Deviations for Infinite-Server Queues
Authors: Blanchet Jose , Chen Xinyun , Lam Henry
Published: August 2017

Let Qλ(t, y) be the number of people present at time t with at least y units of remaining service time in an infinite server system with arrival rate equal to λ > 0. In the presence of a non-lattice renewal arrival process and assuming that the service times have a continuous distribution, we obtain a large deviations principle for Qλ(·)/λ under the topology of uniform convergence on [0, T] × [0, ∞). We illustrate our results by obtaining the most likely paths, represented as surfaces, to overflow in the setting of loss queues, and also to ruin in life insurance portfolios.
On Bid-price Controls for Network Revenue Management
Authors: Ata Barış , Akan Mustafa
Published: August 2017

We consider a network revenue management problem and advance its dual formulation. The dual formulation reveals that the (optimal) shadow price of capacity forms a nonnegative martingale. This result is proved under minimal assumptions on network topology and stochastic nature of demand, allowing an arbitrary statistical dependence structure across time and products. Next, we consider a quadratic perturbation of the network revenue management problem and show that a simple (perturbed) bid-price control is optimal for the perturbed problem; and it is ɛ-optimal for the original network revenue management problem. Finally, we consider a predictable version of this control, where the bid prices used in the current period are last updated in the previous period, and provide an upper bound on its optimality gap in terms of the (quadratic) variation of demand. Using this upper bound we show that there exists a near-optimal such control in the usual case when periods are small compared to the planning horizon provided that either demand or the incremental information arriving during each period is small. We establish the martingale property of the (near) optimal bid prices in both settings. The martingale property can have important implications in practice as it may offer a tool for monitoring the revenue management systems.
Solving the Drift Control Problem
Authors: Matoglu Melda Ormeci , Vate John Vande , Wang Huizhu
Published: August 2017

We model the problem of managing capacity in a build-to-order environment as a Brownian drift control problem. We formulate a structured linear program that models a practical discretization of the problem and exploit a strong relationship between relative value functions and dual solutions to develop a functional lower bound for the continuous problem from a dual solution to the discrete problem. Refining the discretization proves a functional strong duality for the continuous problem. The linear programming formulation is so badly scaled, however, that solving it is beyond the capabilities of standard solvers. By demonstrating the equivalence between strongly feasible bases and deterministic unichain policies, we combinatorialize the pivoting process and by exploiting the relationship between dual solutions and relative value functions, develop a mechanism for solving the LP without ever computing its coefficients. Finally, we exploit the relationship between relative value functions and dual solutions to develop a scheme analogous to column generation for refining the discretization so as to drive the gap between the discrete approximation and the continuous problem to zero quickly while keeping the LP small. Computational studies show our scheme is much faster than simply solving a regular discretization of the problem both in terms of finding a policy with a low average cost and in terms of providing a lower bound on the optimal average cost.
The Supermarket Game
Authors: Xu Jiaming , Hajek Bruce
Published: August 2017

A supermarket game is considered with N FCFS queues with unit exponential service rate and global Poisson arrival rate Nλ. Upon arrival each customer chooses a number of queues to be sampled uniformly at random and joins the least loaded sampled queue. Customers are assumed to have cost for both waiting and sampling, and they want to minimize their own expected total cost.

We study the supermarket game in a mean field model that corresponds to the limit as N converges to infinity in the sense that (i) for a fixed symmetric customer strategy, the joint equilibrium distribution of any fixed number of queues converges as N → ∞ to a product distribution determined by the mean field model and (ii) a Nash equilibrium for the mean field model is an ε-Nash equilibrium for the finite N model with N sufficiently large. It is shown that there always exists a Nash equilibrium for λ < 1 and the Nash equilibrium is unique with homogeneous waiting cost for [Formula: see text]. Furthermore, we find that the action of sampling more queues by some customers has a positive externality on the other customers in the mean field model, but can have a negative externality for finite N.
Queue-based Random-access Algorithms: Fluid Limits and Stability Issues
Authors: Ghaderi Javad , Borst Sem , Whiting Phil
Published: August 2017

We use fluid limits to explore the (in)stability properties of wireless networks with queue-based random-access algorithms. Queue-based random-access schemes are simple and inherently distributed in nature, yet provide the capability to match the optimal throughput performance of centralized scheduling mechanisms in a wide range of scenarios. Unfortunately, the type of activation rules for which throughput optimality has been established, may result in excessive queue lengths and delays. The use of more aggressive/persistent access schemes can improve the delay performance, but does not offer any universal maximum-stability guarantees.

In order to gain qualitative insight and investigate the (in)stability properties of more aggressive/persistent activation rules, we examine fluid limits where the dynamics are scaled in space and time. In some situations, the fluid limits have smooth deterministic features and maximum stability is maintained, while in other scenarios they exhibit random oscillatory characteristics, giving rise to major technical challenges. In the latter regime, more aggressive access schemes continue to provide maximum stability in some networks, but may cause instability in others. In order to prove that, we focus on a particular network example and conduct a detailed analysis of the fluid limit process for the associated Markov chain. Specifically, we develop a novel approach based on stopping time sequences to deal with the switching probabilities governing the sample paths of the fluid limit process. Simulation experiments are conducted to illustrate and validate the analytical results.
A Skill Based Parallel Service System Under FCFS-ALIS — Steady State, Overloads, and Abandonments
Authors: Adan Ivo , Weiss Gideon
Published: August 2017

We consider a queueing system with J parallel servers [Formula: see text], and with customer types 𝒞 = {a, b, …}. A bipartite graph G describes which pairs of server-customer types are compatible. We consider FCFS-ALIS policy: A server always picks the first, longest waiting compatible customer, and a customer is always assigned to the longest idle compatible server. We assume Poisson arrivals and server dependent exponential service times. We derive an explicit product-form expression for the stationary distribution of this system when service capacity is sufficient. We also calculate fluid limits of the system under overload, to show that local steady state exists. We distinguish the case of complete resource pooling when all the customers are served at the same rate by the pooled servers, and the case when the system has a unique decomposition into subsets of customer types, each of which is served at its own rate by a pooled subset of the servers. Finally, we discuss possible behavior of the system with generally distributed abandonments, under many server scaling. This paper complements and extends previous results of Kaplan, Caldentey and Weiss [18], and of Whitt and Talreja [34], as well as previous results of the authors [4, 35] on this topic.
Resource Sharing Networks: Overview and an Open Problem
Authors: Harrison J. Michael , Mandayam Chinmoy , Shah Devavrat , Yang Yang
Published: August 2017

This paper provides an overview of the resource sharing networks introduced by Massoulié and Roberts [20] to model the dynamic behavior of Internet flows. Striving to separate the model class from the applications that motivated its development, we assume no prior knowledge of communication networks. The paper also presents an open problem, along with simulation results, a formal analysis, and a selective literature review that provide context and motivation. The open problem is to devise a policy for dynamic resource allocation that achieves what we call hierarchical greedy ideal (HGI) performance in the heavy traffic limit. The existence of such a policy is suggested by formal analysis of an approximating Brownian control problem, assuming that there is “local traffic” on each processing resource.
On Queue-size Scaling for Input-Queued Switches
Authors: Shah D. , Tsitsiklis J. N. , Zhong Y.
Published: August 2017

We study the optimal scaling of the expected total queue size in an n × n input-queued switch, as a function of the number of ports n and the load factor ρ, which has been conjectured to be Θ(n/(1 − ρ)) (cf. [15]). In a recent work [16], the validity of this conjecture has been established for the regime where 1 − ρ = O(1/n2). In this paper, we make further progress in the direction of this conjecture. We provide a new class of scheduling policies under which the expected total queue size scales as O(n1.5(1 − ρ)−1 log (1/(1 − ρ))) when 1 − ρ = O(1/n). This is an improvement over the state of the art; for example, for ρ = 1 − 1/n the best known bound was O(n3), while ours is O(n2.5 log n).
Dynamic Scheduling for Parallel Server Systems in Heavy Traffic: Graphical Structure, Decoupled Workload Matrix and some Sufficient Conditions for Solvability of the Brownian Control Problem
Authors: Pesic V. , Williams R. J.
Published: August 2017

We consider a dynamic scheduling problem for parallel server systems. J. M. Harrison has proposed a scheme for using diffusion control problems to approximately solve such control problems for heavily loaded systems. This approach has been very successfully used in the special case when the diffusion control problem can be reduced to an equivalent one for a one-dimensional workload process. However, it remains a challenging open problem to make substantial progress on using Harrison’s scheme when the workload process is more than one-dimensional. Here we present some new structural results concerning the diffusion control problem for parallel server systems with arbitrary workload dimension. Specifically, we prove that a certain server-buffer graph associated with a parallel server system is a forest of trees. We then exploit this graphical structure to prove that there exists a matrix, used to define the workload process, that has a block diagonal-like structure. An important feature of this matrix is that, except when the workload is one-dimensional, this matrix is frequently different from a choice of workload matrix proposed by Harrison. We demonstrate that our workload matrix simplifies the structure of the control problem for the workload process by proving that when the original diffusion control problem has linear holding costs, the equivalent workload formulation also has a linear cost function. We also use this simplification to give sufficient conditions for a certain least control process to be an optimal control for the diffusion control problem with linear holding costs. Under these conditions, we propose a continuous review threshold-type control policy for the original parallel server system that exploits pooling of servers within trees in the server-buffer graph and uses non-basic activities connecting different trees in a critical manner. We call this partial pooling. We conjecture that this threshold policy is asymptotically optimal in the heavy traffic limit. We illustrate the solution of the diffusion control problem and our proposed threshold control policy for a three-buffer, three-server example.
Chattering and Congestion Collapse in an Overload Switching Control
Authors: Perry Ohad , Whitt Ward
Published: August 2017

Routing mechanisms for stochastic networks are often designed to produce state space collapse (SSC) in a heavy-traffic limit, i.e., to confine the limiting process to a lower-dimensional subset of its full state space. In a fluid limit, a control producing asymptotic SSC corresponds to an ideal sliding mode control that forces the fluid trajectories to a lower-dimensional sliding manifold. Within deterministic dynamical systems theory, it is well known that sliding-mode controls can cause the system to chatter back and forth along the sliding manifold due to delays in activation of the control. For the prelimit stochastic system, chattering implies fluid-scaled fluctuations that are larger than typical stochastic fluctuations.

In this paper we show that chattering can occur in the fluid limit of a controlled stochastic network when inappropriate control parameters are used. The model has two large service pools operating under the fixed-queue-ratio with activation and release thresholds (FQR-ART) overload control which we proposed in a recent paper. The FQR-ART control is designed to produce asymptotic SSC by automatically activating sharing (sending some customers from one class to the other service pool) once an overload occurs. We have previously shown that this control is effective and robust, even if the service rates are less for the other shared customers, when the control parameters are chosen properly. We now show that, if the control parameters are not chosen properly, then delays in activating and releasing the control can cause chattering with large oscillations in the fluid limit. In turn, these fluid-scaled fluctuations lead to severe congestion, even when the arrival rates are smaller than the potential total service rate in the system, a phenomenon referred to as congestion collapse. We show that the fluid limit can be a bi-stable switching system possessing a unique nontrivial periodic equilibrium, in addition to a unique stationary point.