bluuebunny/crossref_metadata_2025 huggingface dataset:
A ‘fertile soil’ for sustainability-related community initiatives: A new analytical framework
Authors: Sekulova Filka , Anguelovski Isabelle , Argüelles Lucia , Conill Joana
Published: August 2017

One of the unique and emerging responses to the current ecological, social, political and economic crises has been the emergence of community initiatives in a range of formulas and geographical contexts. We explore their emergence and evolution beyond the analysis of a single fixed set of factors that are expected to contribute to their initiation and growth. Upon reviewing the trajectories of various initiatives in the region of Barcelona (Spain), we argue that the metaphor of the fertile soil provides a useful framework to describe or explain the messy process of emergence and evolution of grassroots and community projects. Fertile soil is understood here as a particular quality of the social texture, characterized by richness, diversity, unknowns but also – by multiple tensions and contradictions. Yet it is not only the diversity of factors but the quality of their mutual relatedness that ‘makes’ the soil fertile for the emergence of new groups and the continuation of existing ones. Importantly, the seemingly messy social base in which community initiatives emerge is nourished by their inner and outer contradictions. Likewise, the space opened by dealing with conflicting rationalities creates the conditions for new and more resilient strategies and structures to emerge. As community initiatives get established, the ‘fertile dilemmas’ they frequently face become a key driver of their evolutionary context, contributing to the emergence of new social imaginaries and ways of producing social change.
Physically crosslinked salicylate-based poly (N-isopropylacrylamide-co-acrylic acid) hydrogels for protein delivery
Authors: Demirdirek Bahar , Uhrich Kathryn E
Published: August 2017

Physically crosslinked hydrogels were developed via solvent casting methods using a temperature-sensitive polymer, poly( N-isopropylacrylamide- co-acrylic acid), and a therapeutic polymer, salicylate-based poly(anhydride-esters), to concurrently release salicylic acid and bovine serum albumin in a sustained manner. The physical interactions between the two polymer systems were confirmed using Fourier transform infrared spectroscopy. The crosslinked polymers were porous, thus able to encapsulate bovine serum albumin (23 wt%) and then released the protein in a sustained fashion over 96 h. Concurrently, the hydrogel releases salicylic acid in a sustained manner up to 120 h. Hydrogel systems were cytocompatible at relevant therapeutic concentrations. These hydrogel systems can be used for simultaneous delivery of salicylic acid and protein to achieve synergic effects.
Amino-functionalized mesoporous silica nanoparticles as efficient carriers for anticancer drug delivery
Authors: He Yongju , Luo Liangyu , Liang Shuquan , Long Mengqiu , Xu Hui
Published: August 2017

Amino-functionalized mesoporous silica nanoparticles (MSN-NH2) were synthesized by a post-grafting method and further studied as carriers for doxorubicin hydrochloride (DOX) delivery. The morphology, structure, and property of MSN-NH2 and DOX-loaded MSN-NH2 (DOX@MSN-NH2) were studied using various techniques, such as transmission electron microscopy, Fourier transformed infrared spectroscopy, N2 adsorption–desorption isotherms, and zeta potentials. The drug loading and release profile as well as the in vitro cell cytotoxicity were detaily investigated. The results indicated that the loading content of DOX increased with the decrease of MSN-NH2/DOX mass ratio and/or the increase of amino density. DOX@MSN-NH2 exhibited a pH-dependent drug release, drug release increased as the pH value decreased. Compared with MSN-NH2, which were neglectable cytotoxicity against non-small-cell lung cancer (A549) cells, DOX@MSN-NH2 displayed remarkable cytotoxicity toward A549 cells in dose- and time-dependent manners. It was concluded that the as-synthesized MSN-NH2 could be used as promising drug carriers for cancer therapy.
Low-frequency interior noise in prop-driven aircrafts: Sources and control methodologies
Authors: Ommi Fathollah , Azimi Mohammadreza
Published: August 2017

Nowadays, noise has turned into one of the most important among the environmental factors on which industry sets down a big part of its efforts and concerns. The recognition of noise as a serious health hazard is a development of modern times. Too much noise obviously impairs our physical and mental existence and therefore it is reasonable to pursue Technology Assessment concerning noisy technologies. The conflicts of interest associated with noise that arise from the operation of airports are well known. Propeller noise is most dominant at low frequencies (below 500 Hz) where traditional passive treatments have only little effect. The many factors contributing to the sound field inside propeller aircraft have led to extensive research directed toward identifying and improving techniques for interior noise reduction.
Modification of the mandatory generation region of producers in the reactive power market by considering reactive power losses
Authors: Ahmadimanesh A , Kalantar M
Published: August 2017

In this paper, a new reactive power market structure is studied and presented. Active power flow by itself causes active and reactive losses. Considering such losses in the reactive power market without paying any costs is the main purpose of this paper. So, this study tries to improve reactive power market and create fair competition in reactive power generation through improving the market structure. For this aim, firstly a new allocation method for reactive power losses is presented, and contribution of each producer in reactive losses is calculated. In the next step, this share of losses is used for modification of the mandatory generation region of units and the new structure of reactive power market is proposed. Also, in this work, the cost payment function of synchronous generators is modified. In order to simulate and describe the proposed methods in the implementation of the reactive power market, IEEE 24 bus reliability test system is applied and the proposed methods are compared with each other and the conventional reactive power market structure. As will be shown, the total payment by ISO will be reduced by using the proposed methods.
Trade openness, labour market rigidity and economic growth: A dynamic panel data analysis
Authors: Polat Burçak , Andrés Antonio Rodríguez
Published: August 2017

The rapid liberalisation of trade policies since the 1990s has brought additional attention to the role of trade as an engine of economic growth. Although an abundant literature addresses the relationship between openness and economic growth, the real effect of trade liberalisation is still ambiguous and undetermined. Most previous studies have ignored the selection effects of strict labour regulations on international trade. The main objective of this study is to measure the role of labour regulations in moderating the contribution of trade to economic growth among 30 Organisation for Economic Co-operation and Development countries for the period 2006–2013. In doing so, we employ a one-step Generalised Method of Moments system estimation method. Our results reveal that openness to trade does not have a robust and significant effect on growth. However, the interaction of openness with strict labour regulations enhances the contributions of trade to growth.
Fundamental Elements of Transition Program Design
Authors: Karmelita Courtney
Published: August 2017

Adult learners require supports and services to help them successfully transition into taking on the demands and expectations of college students. Transition programs have grown in popularity as a means to aid adult learners as they transition to higher education. Unfortunately, previous research on adult learner participation in transition programs is limited in its scope and depth. There is a need to understand how to develop transition programs to best support adult learners. Drawing on interviews and observation, this narrative study investigates program details about the funding structure, reporting measures, and development of the researched transition program. I identify fundamental elements for effective transition program design that align with adult education and transition theory. This research also points to the importance of connecting adult learners to institutions to give them a sense of mattering to the university.
The Clinical Utility of the Heparin Neutralization Assay in the Diagnosis of Heparin-Induced Thrombocytopenia
Authors: Zheng Gang , Streiff Michael B. , Takemoto Clifford M. , Bynum Jennifer , Gelwan Elise , Jani Jayesh , Judge Danielle , Kickler Thomas S.
Published: August 2017

Heparin-induced thrombocytopenia (HIT) remains diagnostically challenging. Immunoassays including PF4/heparin enzyme-linked immunosorbent assay (ELISA) have high sensitivity but low specificity. Whether the heparin neutralization assay (HNA) improves the diagnostic accuracy of the PF4/heparin ELISA for HIT is uncertain. In this study, to assess its clinical utility and evaluate whether it improves the diagnostic accuracy for HIT, we implemented HNA in conjunction with PF4/heparin ELISA over a 1-year period. A total of 1194 patient samples were submitted to the laboratory for testing from December 2015 to November 2016. Heparin neutralization assay alone is a poor predictor for HIT, but it has high negative predictive value (NPV): Cases with %inhibition <70% are always negative for serotonin release assay. It improves the diagnostic positive predictive value (PPV) of ELISA without compromising sensitivity: ELISA optical density (OD) ≥1.4 alone has a sensitivity of 88% (14/16) and a PPV of 61% (14/23); with HNA %inhibition ≥70%, the sensitivity remains 88% (14/16) and PPV is 82% (14/17). 4Ts score correlates with ELISA OD and predicts HIT; the predictive accuracy of 4Ts score is further improved by HNA. Interestingly, HNA %inhibition of <70% correlates with low 4Ts scores. Based on its high NPV, HNA has the potential to facilitate more timely and accurate HIT diagnosis.
The role of the endoplasmic reticulum stress response following cerebral ischemia
Authors: Hadley Gina , Neuhaus Ain A , Couch Yvonne , Beard Daniel J , Adriaanse Bryan A , Vekrellis Kostas , DeLuca Gabriele C , Papadakis Michalis , Sutherland Brad A , Buchan Alastair M
Published: August 2017

Background

Cornu ammonis 3 (CA3) hippocampal neurons are resistant to global ischemia, whereas cornu ammonis (CA1) 1 neurons are vulnerable. Hamartin expression in CA3 neurons mediates this endogenous resistance via productive autophagy. Neurons lacking hamartin demonstrate exacerbated endoplasmic reticulum stress and increased cell death. We investigated endoplasmic reticulum stress responses in CA1 and CA3 regions following global cerebral ischemia, and whether pharmacological modulation of endoplasmic reticulum stress or autophagy altered neuronal viability .

Methods

In vivo: male Wistar rats underwent sham or 10 min of transient global cerebral ischemia. CA1 and CA3 areas were microdissected and endoplasmic reticulum stress protein expression quantified at 3 h and 12 h of reperfusion. In vitro: primary neuronal cultures (E18 Wistar rat embryos) were exposed to 2 h of oxygen and glucose deprivation or normoxia in the presence of an endoplasmic reticulum stress inducer (thapsigargin or tunicamycin), an endoplasmic reticulum stress inhibitor (salubrinal or 4-phenylbutyric acid), an autophagy inducer ([4′-(N-diethylamino) butyl]-2-chlorophenoxazine (10-NCP)) or autophagy inhibitor (3-methyladenine).

Results

In vivo, decreased endoplasmic reticulum stress protein expression (phospho-eIF2α and ATF4) was observed at 3 h of reperfusion in CA3 neurons following ischemia, and increased in CA1 neurons at 12 h of reperfusion. In vitro, endoplasmic reticulum stress inducers and high doses of the endoplasmic reticulum stress inhibitors also increased cell death. Both induction and inhibition of autophagy also increased cell death.

Conclusion

Endoplasmic reticulum stress is associated with neuronal cell death following ischemia. Neither reduction of endoplasmic reticulum stress nor induction of autophagy demonstrated neuroprotection in vitro, highlighting their complex role in neuronal biology following ischemia.
Giant Left Atrial Myxoma Masquerading as Cough-Syncope Syndrome
Authors: Bowman Jennifer N. , Treece Jennifer M. , Bhattad Pradnya Brijmohan , Bochis Melania , Bajaj Kailash
Published: August 2017

Left atrial myxomas are the most common type of benign primary cardiac tumor. Patients can present with generalized symptoms, such as fatigue, symptoms from obstruction of the myxoma, or even embolization of the myxoma causing distal thrombosis. We describe a case with several-month duration of syncopal episodes that occurred after coughing and with exertion. Computed tomography of the chest showed a 6.1 cm by 4.5 cm mass in the left atrium, later evaluated with an echocardiogram. Cardiothoracic surgery removed the mass, and it was determined to be an atrial myxoma. It is important for an internist to be able to diagnose an atrial myxoma because of the risks associated with embolization and even sudden death as myxoma can block blood supply from atrium to ventricle.
Confronting Negative Narratives: The Challenges of Teaching Professional Social Media Use
Authors: West Sara
Published: August 2017

Because social media skills are increasingly viewed as essential for professionals, social media is incorporated frequently in business communication courses. When students are asked to consider professional uses of social media, however, they are often unwilling to critically engage these technologies. This article continues discussions of students’ reticence due largely to negative cultural narratives that label social media as unprofessional, or that link social media only with reputation management. Using student interviews and writing from a social media writing course, I discuss challenges posed by students’ adherence to these narratives and conclude with five suggestions for implementing social media successfully.
Missiological Missteps and the Need for Theological Education in Myanmar
Authors: Curtis Steve
Published: August 2017

In the history of missions in Myanmar, a number of missiological practices and stratagems have failed to promote unity between different groups of converts and, in fact, have fostered or encouraged disunity among a people already predisposed toward isolationism. Tribal exclusivism, Western individualism, and denominational separatism have all served to extend and expand that gulf of identity, which already separates many people in Myanmar. Furthermore, a lack of proper theological education hinders unity, as a host of conflicting doctrinal systems collide among the local churches, resulting in congregants looking ever-increasingly inward for fellowship, seeking only those most similar to themselves.
The actin-binding protein profilin 2 is a novel regulator of iron homeostasis
Authors: Luscieti Sara , Galy Bruno , Gutierrez Lucia , Reinke Michael , Couso Jorge , Shvartsman Maya , Di Pascale Antonio , Witke Walter , Hentze Matthias W. , Pilo Boyl Pietro , Sanchez Mayka
Published: August 2017

Key Points

Pfn2 mRNA has a functional and conserved IRE in the 3′ untranslated region. Pfn2 knockout mice display an iron phenotype with iron accumulation in specific areas of the brain and depletion of liver iron stores.
New oncogenic subtypes in pediatric B-cell precursor acute lymphoblastic leukemia
Authors: Lilljebjörn Henrik , Fioretos Thoas
Published: August 2017

Until recently, 20% to 30% of pediatric B-cell precursor acute lymphoblastic leukemia (BCP-ALL) could not be classified into any of the established molecular subtypes. Recent molecular studies of such cases have, however, further clarified their mutational spectrum and identified new oncogenic subtypes consisting of cases with DUX4 rearrangements, ETV6-RUNX1–like gene expression, MEF2D rearrangements, and ZNF384 rearrangements. In this review, we describe these new subtypes, which account for up to 50% of previously unclassified pediatric BCP-ALL cases.
Senolytic drugs target alveolar epithelial cell function and attenuate experimental lung fibrosisex vivo
Authors: Lehmann Mareike , Korfei Martina , Mutze Kathrin , Klee Stephan , Skronska-Wasek Wioletta , Alsafadi Hani N. , Ota Chiharu , Costa Rita , Schiller Herbert B. , Lindner Michael , Wagner Darcy E. , Günther Andreas , Königshoff Melanie
Published: August 2017

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with poor prognosis and limited therapeutic options. The incidence of IPF increases with age, and ageing-related mechanisms such as cellular senescence have been proposed as pathogenic drivers. The lung alveolar epithelium represents a major site of tissue injury in IPF and senescence of this cell population is probably detrimental to lung repair. However, the potential pathomechanisms of alveolar epithelial cell senescence and the impact of senolytic drugs on senescent lung cells and fibrosis remain unknown. Here we demonstrate that lung epithelial cells exhibit increasedP16andP21expression as well as senescence-associated β-galactosidase activity in experimental and human lung fibrosis tissue and primary cells.

Primary fibrotic mouse alveolar epithelial type (AT)II cells secreted increased amounts of senescence-associated secretory phenotype (SASP) factorsin vitro, as analysed using quantitative PCR, mass spectrometry and ELISA. Importantly, pharmacological clearance of senescent cells by induction of apoptosis in fibrotic ATII cells orex vivothree-dimensional lung tissue cultures reduced SASP factors and extracellular matrix markers, while increasing alveolar epithelial markers.

These data indicate that alveolar epithelial cell senescence contributes to lung fibrosis development and that senolytic drugs may be a viable therapeutic option for IPF.
Prevalence and incidence of interstitial lung diseases in a multi-ethnic county of Greater Paris
Authors: Duchemann Boris , Annesi-Maesano Isabella , Jacobe de Naurois Camille , Sanyal Shreosi , Brillet Pierre-Yves , Brauner Michel , Kambouchner Marianne , Huynh Sophie , Naccache Jean Marc , Borie Raphael , Piquet Jacques , Mekinian Arsène , Virally Jerôme , Uzunhan Yurdagul , Cadranel Jacques , Crestani Bruno , Fain Olivier , Lhote Francois , Dhote Robin , Saidenberg-Kermanac'h Nathalie , Rosental Paul-André , Valeyre Dominique , Nunes Hilario
Published: August 2017

The objective of the study was to estimate the prevalence and incidence of interstitial lung diseases (ILDs) in Seine-Saint-Denis, a multi-ethnic county of Greater Paris, France.

Patients with ILDs were identified between January and December 2012 by using several sources; all potentially involved medical specialists from public and private hospitals, community-based pulmonologists and general practitioners, and the Social Security system. Diagnoses were validated centrally by an expert multidisciplinary discussion.

1170 ILD cases were reported (crude overall prevalence: 97.9/105and incidence: 19.4/105/year). In the 848 reviewed cases, the most prevalent diagnoses were sarcoidosis (42.6%), connective tissue diseases associated ILDs (CTDs-ILDs) (16%), idiopathic pulmonary fibrosis (IPF) (11.6%), and occupational ILDs (5.0%), which corresponded to a crude prevalence of 30.2/105for sarcoidosis, 12.1/105for CTDs-ILDs and 8.2/105for IPF. The prevalence of fibrotic idiopathic interstitial pneumonias, merging IPF, nonspecific interstitial pneumonia and cases registered with code J84.1 was 16.34/105. An adjusted multinomial model demonstrated an increased risk of sarcoidosis in North Africans and Afro-Caribbeans and of CTDs-ILDs in Afro-Caribbeans, compared to that in Europeans.

This study, with a comprehensive recruitment and stringent diagnostic criteria, emphasises the importance of secondary ILDs, particularly CTDs-ILDs and the relatively low prevalence of IPF, and confirms that sarcoidosis is a rare disease in France.
Can Radiotherapy Be Omitted in Children With Hodgkin Lymphoma Who Achieve Metabolic Remission on Interim Positron Emission Tomography? Experience of a Tertiary Care Cancer Referral Center
Authors: Totadri Sidharth , Radhakrishnan Venkatraman , Ganesan Trivadi S. , Ganesan Prasanth , Kannan Krishnarathnam , Lakshmipathy Kadur Mallaiah , Selvaluxmy Ganesarajah , Sagar Tenali Gnana
Published: August 2017

Purpose

Treating pediatric Hodgkin lymphoma (HL) involves a delicate balance between cure and reducing late toxicity. Fluorodeoxyglucose positron emission tomography (PET) combined with computed tomography (CT) identifies patients with early response to chemotherapy, for whom radiotherapy may be avoided. The role of PET-CT in upfront risk stratification and response–adapted treatment is evaluated in this study.

Methods

Patients with HL, who were younger than 18 years, were included. PET-CT was performed at baseline and after two cycles of chemotherapy. Patients were stratified into three risk groups: group 1 (stage I or II with no unfavorable features); group 2 (stage I or II with bulky disease/B symptoms); and group 3 (stage III/IV). A doxorubicin, bleomycin, vinblastine, dacarbazine–based regimen was used in early disease. A cyclophosphamide, vincristine, prednisolone, procarbazine, doxorubicin, bleomycin, vinblastine–based regimen was used in advanced disease.

Results

Forty-nine patients were included. Fifteen (31%), seven (14%), and 27 (55%) patients were included in groups 1, 2, and 3, respectively. Among 36 patients who underwent staging by PET-CT at diagnosis, seven (19%) patients were upstaged and one (3%) patient was downstaged by PET compared with CT. On the basis of negative interim PET responses, 39 (80%) patients were treated without radiotherapy. The 3-year event-free survival for the entire cohort was 91% (± 5.2%) and overall survival was 100%.

Conclusion

PET-CT is an excellent stand-alone staging modality in HL. The omission of radiotherapy can be considered in patients who achieve metabolic remission on interim PET.
Comparison of Receptor-Defined Breast Cancer Subtypes Between German and Sudanese Women: A Facility-Based Cohort Study
Authors: Sengal Asmerom Tesfamariam , Haj Mukhtar Nada Suliman , Vetter Martina , Elhaj Ahmed Mohammed , Bedri Shahinaz , Hauptmann Steffen , Thomssen Christoph , Mohamedani Ahmed Abdalla , Wickenhauser Claudia , Kantelhardt Eva Johanna
Published: August 2017

Purpose

The objective of this study was to compare tumor characteristics, biomarkers, and surrogate subtypes of breast cancer between Sudanese and German women.

Methods

Tumor characteristics and immunohistochemistry markers (estrogen receptor [ER], progesterone receptor [PR], and human epidermal growth factor receptor 2 [HER2]) were collected from the routine assessment of consecutive patients with invasive breast cancer diagnosed from 2010 to 2015 (Gezira University Pathology Laboratory, Gezira, Sudan) and from 1999 to 2013 (Breast Centre, Martin-Luther-University, Halle, Germany).

Results

A total of 2,492 patients (German [n = 1,932] and Sudanese [n = 560]) were included. Age at diagnosis ranged from 20 to 94 years. Sudanese women were, on average, 10 years younger than German women, with a mean (± standard deviation) age of 48.8 (13.5) and 58.6 (12.4) years, respectively. The Sudanese women had a higher grade, larger tumor, and more lymph node positivity compared with German women. ER-, PR-, and HER2-negative proportions were 55%, 61.8%, and 71.3%, respectively, for Sudanese women versus 22.7%, 32.3%, and 82.5%, respectively, for German women. The triple-negative subtype was more prevalent in Sudanese women (34.5%) than in German women (14.2%). The strongest factor associated with ER-negative disease was grade III (odds ratio, 19.6; 95% CI 11.6 to 33.4; P < .001). Sudanese patients were at higher risk for ER-negative breast cancer, with an odds ratio of 2.01 ( P = .001; adjusted for age, size, nodal status, histologic type, and grade). Stratified by grade, the influence of origin was observed in grade I and grade II tumors, but not in grade III tumors.

Conclusion

Sudanese women had more aggressive tumor characteristics and unfavorable prognostic biomarkers. After adjustment, Sudanese origin was still associated with hormone receptor–negative disease, especially in grade I and II tumors. These findings suggest differences in tumor biology among these ethnic groups.
A genome-wide CRISPR screen reconciles the role of N-linked glycosylation in galectin-3 transport to the cell surface
Authors: Stewart Sarah E. , Menzies Sam A. , Popa Stephanie J. , Savinykh Natalia , Petrunkina Harrison Anna , Lehner Paul J. , Moreau Kevin
Published: August 2017

Galectins are a family of lectin binding proteins expressed both intracellularly and extracellularly. Galectin-3 (Gal-3, also known as LGALS3) is expressed at the cell surface; however, Gal-3 lacks a signal sequence, and the mechanism of Gal-3 transport to the cell surface remains poorly understood. Here, using a genome-wide CRISPR/Cas9 forward genetic screen for regulators of Gal-3 cell surface localization, we identified genes encoding glycoproteins, enzymes involved in N-linked glycosylation, regulators of ER-Golgi trafficking and proteins involved in immunity. The results of this screening approach led us to address the controversial role of N-linked glycosylation in the transport of Gal-3 to the cell surface. We find that N-linked glycoprotein maturation is not required for Gal-3 transport from the cytosol to the extracellular space, but is important for cell surface binding. Additionally, secreted Gal-3 is predominantly free and not packaged into extracellular vesicles. These data support a secretion pathway independent of N-linked glycoproteins and extracellular vesicles.
Espaço Movimento: Physical exercise program as prevention strategy in supplementary care
Authors: Faria Valéria Cristina de , Pereira Isabella Carolina Silva , Carvalho Maysa Araujo , Lima Emanuel de Almeida , Miranda Robson da Silva , Pussieldi Guilherme de Azambuja , Simplício Afonso Timão
Published: August 2017

The aim of this study was to describe a program of health promotion and prevention of risks and diseases, developed by a health plan provider by means of results achieved and activities since its inception. To demonstrate the results, active and retired employees of UFV Campus Florestal and their dependents were selected, enrolled with this provider, to attend Espaço Movimento in two groups: gym (GG) and walking/running (WRG). All were submitted to anthropometric and mood profile evaluation, and a flexibility test at baseline and every six months; VO2max was assessed only for WRG. Submitted to 12 months of intervention, GG was composed of 45 participants (25 male), with mean age 46.1 ± 15.7 years. The WRG was subjected to six months of intervention, and composed of 12 participants (10 females), with mean age 42.8 ± 13.8 years. The logical model from 2013 to 2015 was used to present the activities. Results of both groups showed significant improvements in levels of physical fitness, anthropometric variables and mental health. Between the years 2013 and 2015, three annual events were offered to the community of Florestal, including a wider range of age, from children to seniors. Therefore, the proposal of the Espaço Movimento initiative seems to be innovative in the supplementary care and demonstrates effectiveness on the observed results.
Reflecting Brownian Motion in Two Dimensions: Exact Asymptotics for the Stationary Distribution
Authors: Dai J. G. , Miyazawa Masakiyo
Published: August 2017

We consider a two-dimensional semimartingale reflecting Brownian motion (SRBM) in the nonnegative quadrant. The data of the SRBM consists of a two-dimensional drift vector, a 2 × 2 positive definite covariance matrix, and a 2 × 2 reflection matrix. Assuming the SRBM is positive recurrent, we are interested in tail asymptotic of its marginal stationary distribution along each direction in the quadrant. For a given direction, the marginal tail distribution has the exact asymptotic of the form bxκ exp(−αx) as x goes to infinity, where α and b are positive constants and κ takes one of the values −3/2, −1/2, 0, or 1; both the decay rate α and the power κ can be computed explicitly from the given direction and the SRBM data.

A key tool in our proof is a relationship governing the moment generating function of the two-dimensional stationary distribution and two moment generating functions of the associated one-dimensional boundary measures. This relationship allows us to characterize the convergence domain of the two-dimensional moment generating function. For a given direction c, the line in this direction intersects the boundary of the convergence domain at one point, and that point uniquely determines the decay rate α. The one-dimensional moment generating function of the marginal distribution along direction c has a singularity at α. Using analytic extension in complex analysis, we characterize the precise nature of the singularity there. Using that characterization and complex inversion techniques, we obtain the exact asymptotic of the marginal tail distribution.
Nearly Periodic Behavior in the Overloaded G/D/s + GI Queue
Authors: Liu Yunan , Whitt Ward
Published: August 2017

Under general conditions, the number of customers in a GI/D/s + GI many-server queue at time t converges to a unique stationary distribution as t → ∞. However, simulations show that the sample paths routinely exhibit nearly periodic behavior over long time intervals when the system is overloaded and s is large, provided that the system does not start in steady state. Moreover, the precise periodic behavior observed depends critically on the initial conditions. We provide insight into the transient behavior by studying the deterministic fluid model, which arises as the many-server heavy-traffic limit. The limiting fluid model also has a unique stationary point, but that stationary point is not approached from any other initial state as t → ∞. Instead, the fluid model performance approaches one of its uncountably many periodic steady states, depending on the initial conditions. Simulation experiments confirm that the time-dependent performance of the stochastic queueing model is well approximated by the fluid model. Like the fluid model, the behavior of the queueing system can be highly sensitive to the initial conditions over long intervals of time.
Analysis of a Splitting Estimator for Rare Event Probabilities in Jackson Networks
Authors: Blanchet Jose , Leder Kevin , Shi Yixi
Published: August 2017

We consider a standard splitting algorithm for the rare-event simulation of overflow probabilities in any subset of stations in a Jackson network at level n, starting at a fixed initial position. It was shown in [8] that a subsolution to the Isaacs equation guarantees that a subexponential number of function evaluations (in n) suffices to estimate such overflow probabilities within a given relative accuracy. Our analysis here shows that in fact O(n2βV + 1) function evaluations suffice to achieve a given relative precision, where βV is the number of bottleneck stations in the subset of stations under consideration in the network. This is the first rigorous analysis that favorably compares splitting against directly computing the overflow probability of interest, which can be evaluated by solving a linear system of equations with O(nd) variables.
Second Order Corrections for the Limits of Normalized Ruin Times in the Presence of Heavy Tails
Authors: Asmussen Søren , Kortschak Dominik
Published: August 2017

In this paper we consider a compound Poisson risk model with regularly varying claim sizes. For this model in [4] an asymptotic formula for the finite time ruin probability is provided when the time is scaled by the mean excess function. In this paper we derive the rate of convergence for this finite time ruin probability when the claims are regularly varying with a finite second moment.
Optimal Paths in Large Deviations of Symmetric Reflected Brownian Motion in the Octant
Authors: Liang Ziyu , Hasenbein John J.
Published: August 2017

We study the variational problem that arises from consideration of large deviations for semimartingale reflected Brownian motion (SRBM) in [Formula: see text]. Due to the difficulty of the general problem, we consider the case in which the SRBM has rotationally symmetric parameters. In this case, we are able to obtain conditions under which the optimal solutions to the variational problem are paths that are gradual (moving through faces of strictly increasing dimension) or that spiral around the boundary of the octant. Furthermore, these results allow us to provide an example for which it can be verified that a spiral path is optimal. For rotationally symmetric SRBM’s, our results facilitate the simplification of computational methods for determining optimal solutions to variational problems and give insight into large deviations behavior of these processes.
State-independent Importance Sampling for Random Walks with Regularly Varying Increments
Authors: Murthy Karthyek R. A. , Juneja Sandeep , Blanchet Jose
Published: August 2017

We develop importance sampling based efficient simulation techniques for three commonly encountered rare event probabilities associated with random walks having i.i.d. regularly varying increments; namely, 1) the large deviation probabilities, 2) the level crossing probabilities, and 3) the level crossing probabilities within a regenerative cycle. Exponential twisting based state-independent methods, which are effective in efficiently estimating these probabilities for light-tailed increments are not applicable when the increments are heavy-tailed. To address the latter case, more complex and elegant state-dependent efficient simulation algorithms have been developed in the literature over the last few years. We propose that by suitably decomposing these rare event probabilities into a dominant and further residual components, simpler state-independent importance sampling algorithms can be devised for each component resulting in composite unbiased estimators with desirable efficiency properties. When the increments have infinite variance, there is an added complexity in estimating the level crossing probabilities as even the well known zero-variance measures have an infinite expected termination time. We adapt our algorithms so that this expectation is finite while the estimators remain strongly efficient. Numerically, the proposed estimators perform at least as well, and sometimes substantially better than the existing state-dependent estimators in the literature.
The Morphing of Fluid Queues into Markov-Modulated Brownian Motion
Authors: Latouche Guy , Nguyen Giang T.
Published: August 2017

Ramaswami showed recently that standard Brownian motion arises as the limit of a family of Markov-modulated linear fluid processes. We pursue this analysis with a fluid approximation for Markov-modulated Brownian motion. We follow a Markov-renewal approach and we prove that the stationary distribution of a Markov-modulated Brownian motion reflected at zero is the limit from the well-analyzed stationary distribution of approximating linear fluid processes. Thus, we provide a new approach for obtaining the stationary distribution of a reflected MMBM without time-reversal or solving partial differential equations. Our results open the way to the analysis of more complex Markov-modulated processes.

Key matrices in the limiting stationary distribution are shown to be solutions of a matrix-quadratic equation, and we describe how this equation can be efficiently solved.
Construction of Asymptotically Optimal Control for Crisscross Network from a Free Boundary Problem
Authors: Budhiraja Amarjit , Liu Xin , Saha Subhamay
Published: August 2017

An asymptotic framework for optimal control of multiclass stochastic processing networks, using formal diffusion approximations under suitable temporal and spatial scaling, by Brownian control problems (BCP) and their equivalent workload formulations (EWF), has been developed by Harrison (1988). This framework has been implemented in many works for constructing asymptotically optimal control policies for a broad range of stochastic network models. To date all asymptotic optimality results for such networks correspond to settings where the solution of the EWF is a reflected Brownian motion in ℝ+ or a wedge in [Formula: see text]. In this work we consider a well studied stochastic network which is perhaps the simplest example of a model with more than one dimensional workload process. In the regime considered here, the singular control problem corresponding to the EWF does not have a simple form explicit solution. However, by considering an associated free boundary problem one can give a representation for an optimal controlled process as a two dimensional reflected Brownian motion in a Lipschitz domain whose boundary is determined by the solution of the free boundary problem. Using the form of the optimal solution we propose a sequence of control policies, given in terms of suitable thresholds, for the scaled stochastic network control problems and prove that this sequence of policies is asymptotically optimal. As suggested by the solution of the EWF, the policy we propose requires a server to idle under certain conditions which are specified in terms of thresholds determined from the free boundary.
Efecto de la resolución espacial de modelos digitales de elevación en la simulación de derrames de hidrocarburos - Effect of the spatial resolution of digital elevation models in the simulation of oil spills
Authors: Daza-Leguizamón Omar Javier , Vera-López Enrique , Riaño-Cano Gladys Alcira
Published: August 2017

Las simulaciones de derrames de hidrocarburos sobre la superficie del terreno son útiles en estudios de impacto ambiental y de gestión de integridad de ductos. Para identificar y valorar los impactos causados por estos eventos, se han implementado simulaciones en programas de sistemas de información geográfica, considerando como datos de entrada las propiedades del fluido y las características del terreno. El relieve es generalmente representado mediante modelos digitales de elevación en formato de datos raster de diferentes tamaños de pixel. En este estudio se analizó el efecto de la resolución espacial de modelos digitales de elevación sobre la simulación de áreas afectadas por derrames de hidrocarburos. Se planteó un algoritmo implementado en el software libre GRASS GIS y luego se aplicó a una zona con cartografía base a diferentes escalas. La simulación se realizó para una zona montañosa en la zona central de Colombia suponiendo el trazado de un poliducto de 12 pulgadas de diámetro. Los efectos de la resolución espacial se analizaron mediante la comparación de la longitud máxima, el área y la curvatura del terreno para la zona afectada. Los resultados muestran que la extensión afectada es mayor para tamaños de pixel de 15 y 30 metros. Además, que la perdida de detalle de las características del relieve para resoluciones de 15 y 30 metros puede modificar de manera significativa tanto el área afectada, como el alcance máximo y dirección del derrame.
Créditos
Authors: Gallego Torres Patricia
Published: August 2017

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DESARROLLO DE HABILIDADES DE PENSAMIENTO CIENTÍFICO: UNA ESTRATEGIA DIDÁCTICA PARA NIÑOS DE LA ZONA ALTOS DE CAZUCÁ CON EL PROPÓSITO DE APROXIMARLOS A LA NOCIÓN DE TEMPERATURA
Authors: Quijano Urrego Stefanny Jahel , Malagón Rusby Yalile , Bautista Germán
Published: August 2017

La presente propuesta investigativa nace del trabajo de campo realizado en la Corporación Social Fe y Esperanza ubicada en Cazucá en el Barrio el Progreso. Esta propuesta ha permitido emprender una reflexión sobre la difícil situación que viven los niños por causa deldesplazamiento y las condiciones de pobreza de su entorno. La intención es llevar a esteescenario educativo una estrategia didáctica que favorezca el desarrollo de habilidades de pensamiento científico aproximándolos a la noción de temperatura. La propuesta investigativa favorece la recreación de espacios donde los niños desarrollen la capacidad de hacer preguntas, observar eventos, realizar descripciones sencillas y explicar algunos fenómenos naturales de su entorno; así mismo, es una opción para visualizar y diseñar nuevas alternativas para llevar la ciencia a los niños de estos contextos, estimulando su gusto por curiosear e indagar sobre lo que a su alrededor ocurre, explotando al máximo los espacios que para su estimulación ofrece el lugar donde habitan.
HABILIDADES DE PENSAMIENTO CIENTÍFICO: UNA ESTRATEGIA DIDÁCTICA BASADA EN TRABAJOS PRÁCTICOS
Authors: Vargas Guerrero Martha Andrea , Cifuentes Arcila María Cristina
Published: August 2017

Esta investigación se orienta a través de la pregunta: ¿Cómo contribuye una estrategia didáctica en el Desarrollo de las Habilidades de Pensamiento Científico de los niños y niñas de sexto grado que asisten al Colegio Hacienda Los Alcaparros? Dos elementos permiten justificar esta investigación: la necesidad de pensar la práctica pedagógica como un espacio de reflexión y producción de conocimiento educativo; y la necesidad de generar didácticas que se ajusten a las singularidades de las realidades escolares. Los 22 participantes de esta investigación tienen edades entre los 11 y los 13 años de edad y pertenecen a los estratos socio-económicos 5 y 6 de la ciudad de Bogotá.. El enfoque de la investigación es cualitativo-interpretativo apoyado en los planteamientos de Erickson(1989).Los resultados indican que la estrategia didáctica funcionó en la medida en que posibilitó el Desarrollo de Habilidades de Pensamiento Científico en los estudiantes, las habilidades para la gestión y evaluación de la evidencia, así como la construcción y justificación de conclusiones para una audiencia se desarrolló de manera diferencial en cada uno de los casos estudiados.
EL PÁJARO BEBEDOR COMO HERRAMIENTA PARA GENERAR APRENDIZAJE POR CONTRADICCIÓN
Authors: Vera Valcárcel Diego Fernando , Rodríguez Diego Julián
Published: August 2017

Muchos científicos han intentado violar la segunda ley de la termodinámica a partir de la construcción de una maquina que ha sido denominada de movimiento perpetuo. Una maquina hipotética que seria capaz de continuar funcionando eternamente, después de un impulso inicial, sin necesidad de energía externa adicional, teóricamente imposible de construir. Teniendo en cuenta la necesidad que existe en despertar el espíritu científico en los estudiantes, nace la posibilidad de llevar una maquina hipotética de movimiento perpetuo didáctica y divertida que genera interés en aprender de los fenómenos y conceptos físicos, llevándolos al aula para percibir lo que ocurriría sí estos no se cumplieran, a través de la formulación de preguntas como: ¿Qué pasaría si no hubiera gravedad? ¿Flotaríamos? Y generando así aprendizaje por contradicción. Por tal razón se diseñó una máquina de movimiento perpetuo que posibilitara esta contradicción, el “Drinking Bird” o pájaro bebedor resulta ser una maquina cercana a generar este movimiento y simularía de manera adecuada lo que ocurriría si no se cumpliera la segunda ley de la termodinámica llevando a comprender el fenómeno con mayor claridad, para finalmente comprobar su principio a partir de un experimento real que contradiga su definición.
LAS RELACIONES CTSA CON LA FORMACIÓN DE MAESTROS EN CONTEXTOS DE VULNERABILIDAD
Authors: Valencia Valbuena Fredy Gregorio , Giraldo Carmen
Published: August 2017

La cátedra electiva “Trabajo Pedagógico con Comunidades en Condición de Desplazamiento” adscrita al Departamento de Física, Facultad de Ciencia y Tecnología, de la Universidad Pedagógica Nacional, ha realizado la reflexión teórica y práctica frente al trabajo pedagógico con comunidades que habitan barrios periféricos del municipio de Soacha (Altos de Cazucá), lugares que evidencian la migración de la población en condición de desplazamiento (Codhes, 2009). Lo anterior ha generado que la Universidad como institución formadora de maestros, asuma la responsabilidad ética y política con los grandes problemas de la educación colombiana, y para ello contribuye con el desarrollo de un conjunto de propuestas significativas de estudiantes de varios programas curriculares a partir del ejercicio como maestro(a) en determinados escenarios de alta vulnerabilidad social, para lo cual se propone articular las disciplinas con el contexto, en la perspectiva de la formación de ciudadanos participativos para la toma de decisiones a partir de problemáticas de su entorno que contribuyen para la búsqueda de posibles alternativas de solución a partir del planteamiento de situaciones a través del diálogo, el saber escuchar, argumentar y controvertir (Caamaño, 1995), en este sentido se articula los escenarios vulnerables como posibilitadores para el trabajo en conjunto (profesores-estudiantes-comunidad) desde los aportes del enfoque ciencia, tecnología, sociedad y ambiente (CTSA).
CONCENTRADORES SOLARES EN IBEROAMERICA: UNA PERSPECTIVA PARA LA EDUACION EN COLOMBIA
Authors: Cabrera López Steffany , Calvo Correa Martha , Rodríguez Diego
Published: August 2017

La presente propuesta investigativa surge con el objetivo de promover espacios educativos que generen en las poblaciones con bajos índices de cubrimiento o sin servicio de agua potable y energía, actitudes y acciones que les permitan mejorar su calidad de vida, y mediante el uso de conceptos físico básicos de radiometría disponer a las comunidades para la apropiación de tecnologías de concentración solar; con este objeto se realizó una revisión bibliográfica en el área de energías alternativas en Iberoamérica, para evaluar la pertinencia de su réplica en nuestro contexto. Del mismo modo se contrastó estadísticamente los territorios que presentan deficiencia en los servicios básicos, respecto a regiones de alto contenido energético solar, donde se encontraron las zonas más pertinentes para la utilización de dichas herramientas tecnológicas que contribuyen a remediar las falencias anteriormente mencionadas.
Diseño y construcción de un sistema electrónico para la repulsión de Copitarsia decolora (Lepidoptera: Noctuidae), plaga de flores de corte de exportación, mediante la simulación de llamadas de ecolocación de murciélagos
Authors: Paz Penagos Hernán , Rodríguez Ramírez Marcela , González Diana , Galarza Cesar M , Torrado-León Edison
Published: August 2017

Una de las plagas interceptadas por el Servicio de Inspección de Salud de Animales y Plantas (APHIS) de Estados Unidos en las exportaciones de algunas especies de flores de corte de Colombia es Copitarsia spp. El presente estudio evaluó la respuesta evasiva de Copitarsia decolora (Lepidoptera: Noctuidae) mediante la simulación de llamadas de ecolocación de murciélagos como propuesta para el manejo en salas de poscosecha de flores, bajo condiciones controladas. Las formas de las señales de ecolocación de los murciélagos se tomaron de algunas muestras de quirópteros insectívoros y se simularon por medio del software Sound Ruler, y se determinaron los parámetros fundamentales que caracterizan las llamadas como su amplitud, frecuencia y forma, entre otros; a partir de esta caracterización, se diseñó y construyó un sistema electrónico capaz de reproducir las llamadas de ecolocación. Se probó el sistema, emitiendo la señal reproducida hacia una muestra de Copitarsia, y se observó una reacción evasiva frente a dicha señal.