bluuebunny/crossref_metadata_2025 huggingface dataset:
Outcomes of Catheter Ablation of Ventricular Tachycardia in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy
Authors: Philips Binu , Madhavan Srinivasa , James Cynthia , Tichnell Crystal , Murray Brittney , Dalal Darshan , Bhonsale Aditya , Nazarian Saman , Judge Daniel P. , Russell Stuart D. , Abraham Theodore , Calkins Hugh , Tandri Harikrishna
Published: April 2012

Background—

Prior studies evaluating the efficacy of catheter ablation of ventricular tachycardia (VT) among patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) have reported varied outcomes. More recently, studies have suggested that an epicardial ablation is necessary for improved outcomes after catheter ablation of VT. The overall objective of the present study was to assess the efficacy of radiofrequency catheter ablation (RFA) of VT in ARVD/C, with particular focus on newer ablation strategies, including epicardial catheter ablation.

Methods and Results—

The study population included 87 patients with ARVD/C who underwent a total of 175 RFA procedures between 1992 and 2011 at 80 different electrophysiology centers. Recurrence of VT following RFA and effect of RFA on the burden of VT were assessed. The mean age of the cohort was 38 ± 13 years. Over a mean follow-up of 88.3 ± 66 months, the overall freedom from VT of the 175 procedures was 47%, 21%, and 15%, at 1, 5, and 10 years, respectively. The cumulative freedom from VT following epicardial RFA was 64% and 45% at 1 and 5 years, respectively, which was significantly longer than endocardial RFA (
P
=0.021). Survival free of VT among procedures with 3D electroanatomic mapping was significantly longer compared to those without (
P
=0.016). Burden of VT was reduced irrespective of the ablation strategy (
P
<0.001).

Conclusions—

Although VT recurrences are common, RFA results in a significant reduction in the burden of VT in patients with ARVD/C. Further, although the use of 3D electroanatomic mapping systems and epicardial ablation strategies are associated with longer survival free of VT, recurrence rates remain considerable.
Myocardial Lesion Depth With Circular Electroporation Ablation
Authors: Wittkampf Fred H.M. , van Driel Vincent J. , van Wessel Harry , Neven Kars G.E.J. , Gründeman Paul F. , Vink Aryan , Loh Peter , Doevendans Pieter A.
Published: April 2012

Background—

Recently, we demonstrated the feasibility and safety of circular electroporation ablation in porcine pulmonary vein ostia, but the relationship between the magnitude of the application and lesion dimensions is still unknown.

Methods and Results—

An in vivo porcine study was performed on left ventricular epicardium submerged under 10 mm of blood, using devices that mimic a 20-mm-diameter 7F circular ablation catheter. Model D contained 10 separate electrodes, whereas model M consisted of 1 circular electrode. Ablations were performed at 50, 100, and 200 J with model D and at 100 J with model M. Lesion dimensions were measured after 3-week survival. All applications resulted in smooth voltage waveforms demonstrating the absence of vapor globe formation, arcing, and a pressure wave. Applications up to 100 J with model D resulted in separate lesions under the electrodes. At 200 J, continuous deep circular lesions were created despite the use of separate electrodes. There was a significant relationship between applied current and median lesion depth, with a slope of 0.17 mm/A. At 100 J, there was no difference in lesion depth or width between models D and M. The electrodes and ablation site directly after ablation showed no signs of thermal damage.

Conclusions—

In an epicardial porcine model with blood around the application site, continuous circular lesions, deep enough for electric pulmonary vein isolation, were created with a single circular 200-J application. Lesions were continuous despite the use of separate electrodes. Lesion depth increased with the magnitude of the application.
Psychotropic Medication Use in Children With Autism in the Kentucky Medicaid Population
Authors: Williams P. Gail , Woods Charles , Stevenson Michelle , Davis Deborah Winders , Radmacher Paula , Smith Michael
Published: April 2012

This study reviewed Kentucky Medicaid claims data for children with autism spectrum disorders to determine psychotropic drug (PTD) use in this population. Children with autism spectrum disorders (ICD-9 code 299.XX) in 3 different age-groups from 2005 to 2008 were identified; PTD use was defined as at least 1 prescription per year. PTD use in all age ranges was higher than in previously reported studies. High PTD use in children between 1 and 5 years is particularly of concern and may reflect perceived inadequacies of comprehensive educational/behavioral services for these children.
Eat, Play, Love
Authors: Woolford Susan J. , Sallinen Bethany J. , Schaffer Sarah , Clark Sarah J.
Published: April 2012

Background

Participants’ perceptions may be associated with the high attrition rates reported by weight management programs.

Objective

To explore participants’ perceptions of a weight management program.

Methods

Semistructured interviews were performed (spring 2010) with past participants of the Michigan Pediatric Outpatient Weight Evaluation and Reduction program. Transcripts were reviewed and themes identified.

Results

Parents (38) and adolescents (25) were interviewed separately; similar themes emerged. Theme 1: Support/encouragement—Participants emphasized the importance of a supportive environment with a positive, compassionate approach from providers. Theme 2: Exercise—Fun, achievable activities were a valued means of making exercise enjoyable and building self-efficacy. Theme 3: Nutrition—Hands on demonstrations and tangible suggestions were preferred over activities such as self-monitoring. Theme 4: Behavioral factors—Participants valued the opportunity to hear their peers’ experiences. However, individual/family sessions addressing their personal concerns were also viewed as important.

Conclusion

Beyond program content, participants valued a supportive environment emphasizing health over habitus.
Response to Intervention With Secondary School Students With Reading Difficulties
Authors: Vaughn Sharon , Fletcher Jack M.
Published: April 2012

The authors summarize evidence from a multiyear study with secondary students with reading difficulties on (a) the potential efficacy of primary-level (Tier 1), secondary-level (Tier 2), and tertiary-level (Tier 3) interventions in remediating reading difficulties with middle school students, (b) the likelihood of resolving reading disabilities with older students with intractable reading disabilities, (c) the reliability, validity, and use of screening and progress monitoring measures with middle school students, and (d) the implications of implementing response to intervention (RTI) practices at the middle school level. The authors provide guidance about prevailing questions about remediating reading difficulties with secondary students and discuss future directions for research using RTI frameworks for students at the secondary level.
When Does Feeling Moral Actually Make You a Better Person? Conceptual Abstraction Moderates Whether Past Moral Deeds Motivate Consistency or Compensatory Behavior
Authors: Conway Paul , Peetz Johanna
Published: April 2012

According to the moral licensing literature, moral self-perceptions induce compensatory behavior: People who feel moral act less prosocially than those who feel immoral. Conversely, work on moral identity indicates that moral self-perceptions motivate behavioral consistency: People who feel moral act more prosocially than those who feel less so. In three studies, the authors reconcile these propositions by demonstrating the moderating role of conceptual abstraction. In Study 1, participants who recalled performing recent (concrete) moral or immoral behavior demonstrated compensatory behavior, whereas participants who considered temporally distant (abstract) moral behavior demonstrated behavioral consistency. Study 2 confirmed that this effect was unique to moral self-perceptions. Study 3 manipulated whether participants recalled moral or immoral actions concretely or abstractly, and replicated the moderation pattern with willingness to donate real money to charity. Together, these findings suggest that concrete moral self-perceptions activate self-regulatory behavior, and abstract moral self-perceptions activate identity concerns.
Blaming for a Better Future
Authors: Bal Michèlle , van den Bos Kees
Published: April 2012

People are often encouraged to focus on the future and strive for long-term goals. This noted, the authors argue that this future orientation is associated with intolerance of personal uncertainty, as people usually cannot be certain that their efforts will pay off. To be able to tolerate personal uncertainty, people adhere strongly to the belief in a just world, paradoxically resulting in harsher reactions toward innocent victims. In three experiments, the authors show that a future orientation indeed leads to more negative evaluations of an innocent victim (Study 1), enhances intolerance of personal uncertainty (Study 2), and that experiencing personal uncertainty leads to more negative evaluations of a victim (Study 3). So, while a future orientation enables people to strive for long-term goals, it also leads them to be harsher toward innocent victims. One underlying mechanism causing these reactions is intolerance of personal uncertainty, associated with a future orientation.
The Impact of Refeeding on Blood Fatty Acids and Amino Acid Profiles in Elderly Patients
Authors: Dror Yosef , Almashanu Shlomo , Lubart Emilia , Sela Ben‐Ami , Shimoni Liron , Segal Refael
Published: April 2012

Background: Refeeding of elderly frail patients after food deprivation is commonly associated with a high mortality rate. Objective: To evaluate the effect of refeeding on metabolite fluctuation of blood carnitine fatty acids (15 compounds) and free amino acids (14 compounds). Methods: Metabolite fluctuation was followed up in an exploratory, cohort, and noninterventional study in elderly and frail patients (84.5 ± 5 years) after a long period of food deprivation. Patients in the study group were refed by enteral nutrition (EN) and were followed up during 7 days for blood metabolites (n = 27). Patients in the control group (n = 26) had been fed by EN for more than 3 months. Refeeding was initiated with 10 kcal/kg/d and gradual increases of 200 kcal/d for 3 days afterwards. Blood metabolites were assayed in a sample of 25 µL. Results: On food deprivation, the concentrations of all even monocarboxylic carnitine fatty acids were much higher in the study group than in the EN control group (P < .01). Upon refeeding, a remarkable decrease in all carnitine fatty acids was observed. In addition, significant daily fluctuations were observed for most metabolites in the study group of the refed patients as compared with the EN control group (P < .01). The highest fluctuations were observed following refeeding in the 7 patients who later died. Conclusion: A significant metabolic instability is observed on refeeding even with a slow refeeding schedule of 10 kcal/kg/d. Measurement of metabolomics parameters may be used for the evaluation of malnutrition, refeeding status, and optimization of the enteral formula.
Histomorphological Changes of Tutoplast‐Processed Fascia Lata Grafts in a Rabbit Rhinoplasty Model
Authors: Yu Myeong Sang , Park Hyeok Sung , Lee Hee Jin , Jang Yong Ju
Published: April 2012

Objectives

Tutoplast‐processed fascia lata (TPFL) is a commercially available homograft that has been successfully used as graft tissue for rhinoplasty. The present study evaluates the histomorphological changes of TPFL in a rabbit rhinoplasty model.

Study Design

Prospective study using a rabbit model.

Setting

Animal laboratory of the Asan Medical Center.

Subjects and Methods

The study used 15 New Zealand White rabbits. Each rabbit was implanted with a TPFL (experimental group) and autologous fascia lata (control group) graft of equal size into the nasal dorsum. Rabbits were killed at 1, 3, and 6 months, and the grafts were removed and microscopically assessed for fibroblast proliferation, neovascularization, inflammation, and thickness.

Results

For TPFL grafts, the degree of inflammation significantly decreased between 1 and 3 months (P =. 041). The degree of fibroblast proliferation continually increased over time. There was a mild degree of neovascularization for the TPFL graft at 1 month. The degree of neovascularization increased between 3 and 6 months (P =. 041). For the degree of inflammation, fibroblast proliferation, and neovascularization, there was no significant difference between TPFL and autologous fascia lata at 6 months. Mean thickness analysis showed that there was no significant thickness reduction in both TPFL and autologous fascia lata grafts at 6 months.

Conclusion

The TPFL grafts showed negligible resorption rates and favorable tissue reactions in the rabbit rhinoplasty model.
Social Validity Assessment in Social Competence Interventions for Preschool Children
Authors: Hurley Jennifer J.
Published: April 2012

Social competence intervention studies published from 1970 to 2008 for preschoolers were reviewed for reports of social validity assessment. Analysis of 90 studies indicated that nearly 27% ( n = 24) of studies reported at least one measure of social validity assessment for the goals ( n = 7), procedures ( n = 8), or effects ( n = 19). The methods used for these assessments were described, including information about the participants, time of assessment, and results. Trends in the rate of social validity assessment, methodological concerns, and recommendations for further social validity assessments are discussed.
Rotator Cuff Regeneration Using a Bioabsorbable Material With Bone Marrow–Derived Mesenchymal Stem Cells in a Rabbit Model
Authors: Yokoya Shin , Mochizuki Yu , Natsu Koji , Omae Hiromichi , Nagata Yoshihiko , Ochi Mitsuo
Published: April 2012

Background: Rotator cuff regeneration using tissue engineering techniques is a challenging treatment in elderly patients with irreparable rotator cuff tears.

Hypothesis: A polyglycolic acid sheet scaffold with seeded mesenchymal stem cells (MSCs) may enhance the expression of type I collagen products and increase the mechanical strength of the regenerated tendon in vivo.

Study Design: Controlled laboratory study.

Methods: A surgically created defect of infraspinatus tendons of rabbits was reconstructed with 2 different materials, a polyglycolic acid (PGA) sheet alone (PGA group) (n = 34) and a PGA sheet seeded with autologously cultured MSCs (MSC group) (n = 34). The authors created a tendon defect model without embedding any graft as the control model (control group) (n = 34). The rabbits were sacrificed at 4, 8, and 16 weeks after the operation and then were histologically evaluated. The rabbits were also biomechanically evaluated by measuring the ultimate failure loads and Young’s modulus at 4 and 16 weeks following implantation.

Results: In the MSC group, the fibrocartilage layers and Sharpey fibers were found regularly in the insertion site at 8 weeks compared with the PGA group. In control group, thin membranes with many fibroblasts arranged in an irregular pattern linked the end of the torn cuff to the bone without any Sharpey fibers and type I collagen. A large volume of type I collagen was found in comparison with type III collagen at 16 weeks in the MSC group, whereas type III collagen was more prevalent than type I in the PGA group. The tendon maturing score in the MSC group had higher values than the PGA and control groups at 8 and 16 weeks (mean values were 21.0 ± 0.89, 24.0 ± 2.53 in the MSC group; 16.7 ± 2.25, 21.3 ± 2.42 in the PGA group; and 10.2 ± 0.98, 12.2 ± 1.72 in the control group, respectively) ( P < .05). The results of the mechanical analysis revealed that the regenerated tendons in the MSC group had better tensile strength than in the PGA and control groups at 16 weeks (mean values were 3.04 ± 0.54 in the MSC group, 2.38 ± 0.63 in the PGA group, and 1.58 ± 0.13 in the control group) ( P < .05).

Conclusion: Bone marrow–derived MSCs were able to regenerate tendon-bone insertions and the tendon belly, including the production of type I collagen, and increased the mechanical strength of the regenerated rotator cuff tendon.

Clinical Relevance: Rotator cuff regeneration using MSCs is a promising treatment for massive rotator cuff defects.
Beginning Again
Authors: Ogunsiji Olayide , Wilkes Lesley , Jackson Debra , Peters Kath
Published: April 2012

Settling in a new country exposes immigrants to various health risk factors, and the existing literature alludes to immigrant women being more vulnerable than men. This article highlights some of the difficulties faced by West African women while settling into life in Australia. A qualitative design was used to explore the experiences of West African immigrant women living in Sydney, Australia. Data were collected using audiotaped face-to-face interviews, and narratives were transcribed verbatim and thematically analyzed. Twenty-one West African women participated in this study. The findings revealed the many challenges that participants faced after immigrating to their new country, and these are presented under the following themes: beginning again and experiencing loneliness and isolation. Participants encountered difficulties in developing social networks and obtaining employment, and as a result, they felt lonely and isolated. Therefore, nurses and health care professionals need to incorporate screening for precursors of emotional and social well-being issues when caring for this population.
Using Culturally Competent Community-Based Participatory Research With Older Diabetic Chinese Americans
Authors: Wang-Letzkus Ming Fang , Washington Gail , Calvillo Evelyn R. , Anderson Nancy L. R.
Published: April 2012

The purpose of this article is to share culturally competent strategies and lessons learned from a study that used a community-based participatory research (CBPR) approach with older adult diabetic Chinese Americans. This approach was essential to gain insight into the health beliefs, attitudes, and practices of selected communities. The vulnerable population conceptual model (VPCM) provided a framework for the study. The CBPR, a collaborative research approach, and the VPCM provided the basis for the development of culturally competent research strategies. Strategies and lessons learned to be particularly effective for this CBPR study included (a) developing an in-depth understanding of the community ethnic culture; (b) developing mutual respect and trust with community members and study participants; (c) appreciating and praising community partners’ knowledge, expertise, and experiences; (d) developing a sense of ownership by incorporating their needs, ideas, suggestions, and opinions and empowering study participants to make decisions concerning the study approach and wording; (e) soliciting participant feedback and clarification of study results and involving them in disseminating the study findings to their community; and (f) having fun with them and encouraging them to have fun.
Policy Struggle on Reproduction
Authors: Engeli Isabelle
Published: April 2012

How best to govern reproduction is the subject of heated controversies and policies on abortion and reproductive technologies present strong variations. Through fuzzy-set qualitative comparative analysis, the article explores the interplay of institutional settings, Christian Democratic politics, women’s movement, and Christian opposition in France and Switzerland since the 1970s. If little evidence is found for any institutional impact on policies regarding abortion and reproductive technologies, the analysis confirms the growing influence of the medical profession over reproductive issues and shows that the success of the women’s movement has been fluctuating while prolife opposition seems to have gradually lost influence.
The Impact of Air-conditioning Usage on Sick Building Syndrome during Summer in China
Authors: Cao Bin , Shang Qi , Dai Zizhu , Zhu Yingxin
Published: April 2012

The air-conditioned thermal environments can have an important impact on human health. People stay in air-conditioned environments for a long period of time would tend to present weakened thermal adaptation and have weaker ability to endure hot environment, hence increasing the risk burden caused by heat stress on their physiological regulations to cause discomfort. In this study the relationship between human health – a prevalence of Sick Building Syndrome (SBS) – and air-conditioned indoor environment in summer was analysed using field studies. The results show that the discomfort could include physiological effects affecting the nervous system, the digestive system, the respiratory system, as well as irritation to skin and mucous membranes due to exposure to conditioned air. The frequency of such feelings of discomfort was higher for subjects who are acclimatised to air-conditioned spaces than for people who are not accustomed to air-conditioning. Thus, air-conditioning can be a cause of discomfort and could affect people’s health.
‘Am I not answering your questions properly?’ Clarification, adequacy and responsiveness in semi-structured telephone and face-to-face interviews
Authors: Irvine Annie , Drew Paul , Sainsbury Roy
Published: April 2012

This article considers spoken interaction in semi-structured qualitative research interviews, comparing those that are conducted by telephone or face-to-face. It draws upon recent empirical research that illuminated some of the differences that may be observed between these two interview modes. Methodological techniques drawn from Conversation Analysis were used to conduct a systematic and transparent comparison of the interview interactions, focusing on the spoken interactional devices that researcher and interviewee employ in order to pursue and maintain a collaborative and comprehensible dialogue. The article begins with an overview of previous discussion on the interactional effects of the telephone in qualitative interviews. Here, we find that while instructional texts have traditionally advised that the telephone mode is not well-suited to the task of qualitative interviewing – primarily because the lack of face-to-face contact is said to restrict the development of rapport and a ‘natural’ encounter – researchers giving personal accounts of conducting telephone interviews tend to offer more nuanced or critical reflections on the extent to which the lack of visual cues affects the interaction in practice. Empirical findings are then presented on: formulation and completion, clarification and comprehension, acknowledgement, interviewees’ checks on the ‘adequacy’ of their talk, and the duration of interviews. Key findings were that: completion or formulation of interviewee talk by the researcher was more common in face-to-face interviews; interviewee requests for clarification were slightly more common in telephone interviews; vocalized acknowledgements given by the researcher were less frequent in telephone interviews; interviewee checks on the adequacy of their responses were more common in telephone interviews; and telephone interviews tended to be shorter than those conducted face-to-face. The article discusses possible explanations for the findings that emerge alongside consideration of some potential implications.
Resistance Training in Older Adults
Authors: Straight Chad R. , Lofgren Ingrid E. , Delmonico Matthew J.
Published: April 2012

Sarcopenia is associated with substantial health and economic consequences and is emerging as a major public health problem in the older population. The effects of sarcopenia may increase the risk for adverse health outcomes in older adults, and strategies need to be developed to maintain healthy aging. Although several intervention strategies have been proposed, resistance training (RT) has been suggested as the most effective stimulus for optimizing improvements in physical function and body composition with age. Although RT has been established as a safe and efficacious intervention for the prevention and treatment of sarcopenia, very few older adults regularly participate in RT programs. Community-based RT programs may be a feasible strategy because of their accessibility, cost-effectiveness, and lower-intensity training stimuli. However, the effects of these interventions on health outcomes in older adults have not been adequately reviewed. This report will describe the health effects associated with sarcopenia and summarize the major findings from community-based RT interventions on different health outcomes in older adults. Finally, it is suggested that all older adults who demonstrate the ability to safely participate in RT comply with the guidelines recommended by the American College of Sports Medicine.
Jet Lag in Athletes
Authors: Lee Aaron , Galvez Juan Carlos
Published: April 2012

Context: Prolonged transmeridian air travel can impart a physical and emotional burden on athletes in jet lag and travel fatigue. Jet lag may negatively affect the performance of athletes.

Study Type: Descriptive review.

Evidence Acquisition: A Medline search for articles relating to jet lag was performed (1990-present), as was a search relating to jet lag and athletes (1983-January, 2012). The results were reviewed for relevance. Eighty-nine sources were included in this descriptive review.

Results: Behavioral strategies are recommended over pharmacological strategies when traveling with athletes; pharmacological aides may be used on an individual basis. Strategic sleeping, timed exposure to bright light, and the use of melatonin are encouraged.

Conclusions: There is strong evidence that mood and cognition are adversely affected by jet lag. Some measures of individual and team performance are adversely affected as well.
An Innovative Approach to Partnership in Asthma Care
Authors: Wall-Haas Constance L.
Published: April 2012

Control of asthma symptoms is fundamental to asthma management. New asthma guidelines suggest that asthma control, for most patients, can be achieved through education aimed at improving management. This includes providing written asthma management plans from health care providers; instructions on proper inhaler use; education about early signs and symptoms of asthma, and how to respond appropriately; medication regimens that prevent misuse of medications; follow-up medical care for long-term management of asthma after any hospitalization due to asthma; and assistance with assessing and reducing exposure to environmental risk factors in patients’ home, school, and work environments. The Shared Medical Appointment (SMA) is a group appointment model that has the potential to change the management of children with asthma for the better by offering benefits to both the health care provider and the patient. The SMA for children with asthma and their caregivers is an innovative 90-minute medical appointment in which 4 to 9 patients and their parents are seen at the same time in a supportive group setting. In addition to having concerns and questions about asthma addressed, the SMA provides education on medications, monitoring symptoms, and the demonstration and distribution of devices. Supportive materials are provided and discussed and education is emphasized through open group discussion and the participation of both caregiver and child. A brief, focused medical examination is also conducted. In this study, the charts of children with asthma who attended an SMA were reviewed for specific asthma-related clinical outcomes as defined by the National Heart, Lung, and Blood Institute’s, Expert Panel Review-3 (NHLBI-EPR-3) in the 4-month period prior to attending an SMA and during the 4-month period after attending an SMA. The results showed that asthma education provided in an SMA, as compared with a usual appointment, resulted in a significant positive impact on asthma-related outcomes in meeting NHLBI-EPR-3 guidelines for asthma management.
Abnormalities in IgA and IgM are associated with treatment-resistant ITP
Authors: Arnason Jon E. , Campigotto Federico , Neuberg Donna , Bussel James B.
Published: April 2012

We hypothesized that immune dysregulation, as represented by abnormal immunoglobulin (Ig) levels, may increase immune thrombocytopenia (ITP) severity. A cross-sectional analysis was performed encompassing patients with ITP seen at the New York Presbyterian Platelet Disorder Center in the past 10 years. The subjects' Ig levels were measured, and subjects were analyzed for differences in treatment response. Subjects with an IgA level greater than median had a significantly increased chance of failing to respond to standard treatment (steroids, intravenous Ig, and intravenous anti-D) than did subjects with an IgA level lower than median (37 of 271, 14%; vs 22 of 281, 8%; P = .03) and an increased risk for bleeding (36 of 378, 10%; vs 19 of 386, 5%; P = .02). Subjects with an IgM less than 56 (lower limit of normal) failed to respond to standard treatment more often than patients with a normal IgM (12 of 67, 18%; vs 44 of 467, 9%; P = .05) with a trend toward worsened response to splenectomy (3 of 18, 17%; vs 36 of 86, 42%; P = .06). These observations suggest that immune dysregulation, as represented by elevations in IgA or decreased levels of IgM, are associated with ITP that is more resistant to treatment.
Immunostimulatory conventional dendritic cells evolve into regulatory macrophage-like cells
Authors: Diao Jun , Mikhailova Anastassia , Tang Michael , Gu Hongtao , Zhao Jun , Cattral Mark S.
Published: April 2012

Dendritic cell (DC) homeostasis in peripheral tissues reflect a balance between DC generation, migration, and death. The current model of DC ontogeny indicates that pre-cDCs are committed to become terminal conventional DCs (cDCs). Here, we report the unexpected finding that proliferating immunostimulatory CD11c+ MHC class II+ cDCs derived from pre-cDCs can lose their DC identity and generate progeny that exhibit morphologic, phenotypic, and functional characteristics of regulatory macrophages. DC-derived–macrophages (DC-d-Ms) potently suppress T-cell responses through the production of immunosuppressive molecules including nitric oxide, arginase, and IL-10. Relative deficiency of granulocyte-macrophage colony stimulating factor (GM-CSF) provided a permissive signal for DC-d-M generation. Using a transgenic mouse model that allows tracking of CD11c+ cells in vivo, we found that DC-d-M development occurs commonly in cancer, but not in lymphoid or nonlymphoid tissues under steady-state conditions. We propose that this developmental pathway serves as an alternative mechanism of regulating DC homeostasis during inflammatory processes.
Chronic HIV infection affects the expression of the 2 transcription factors required for CD8 T-cell differentiation into cytolytic effectors
Authors: Ribeiro-dos-Santos Patricia , Turnbull Emma L. , Monteiro Marta , Legrand Agnès , Conrod Karen , Baalwa Joshua , Pellegrino Pierre , Shaw George M. , Williams Ian , Borrow Persephone , Rocha Benedita
Published: April 2012

CD8 T cells lose the capacity to control HIV infection, but the extent of the impairment of CD8 T-cell functions and the mechanisms that underlie it remain controversial. Here we report an extensive ex vivo analysis of HIV-specific CD8 T cells, covering the expression of 16 different molecules involved in CD8 function or differentiation. This approach gave remarkably homogeneous readouts in different donors and showed that CD8 dysfunction in chronic HIV infection was much more severe than described previously: some Ifng transcription was observed, but most cells lost the expression of all cytolytic molecules and Eomesodermin and T-bet by chronic infection. These results reveal a cellular mechanism explaining the dysfunction of CD8 T cells during chronic HIV infection, as CD8 T cells are known to maintain some functionality when either of these transcription factors is present, but to lose all cytotoxic activity when both are not expressed. Surprisingly, they also show that chronic HIV and lymphocytic choriomeningitis virus infections have a very different impact on fundamental T-cell functions, “exhausted” lymphocytic choriomeningitis virus-specific cells losing the capacity to secrete IFN-γ but maintaining some cytotoxic activity as granzyme B and FasL are overexpressed and, while down-regulating T-bet, up-regulating Eomesodermin expression.
Sequence and structure relationships within von Willebrand factor
Authors: Zhou Yan-Feng , Eng Edward T. , Zhu Jieqing , Lu Chafen , Walz Thomas , Springer Timothy A.
Published: April 2012

In the present study, we re-annotated von Willebrand factor (VWF), assigned its entire sequence to specific modules, and related these modules to structure using electron microscopy (EM). The D domains are assemblies of smaller modules visible as lobes in EM. Modules in the D-domain assemblies include von Willebrand D, 8-cysteine, trypsin inhibitor-like, E or fibronectin type 1-like domains, and a unique D4N module in D4. The D1-D2 prodomain shows 2 large connected assemblies, each containing smaller lobes. The previous B and C regions of VWF are re-annotated as 6 tandem von Willebrand C (VWC) and VWC-like domains. These 6 VWC domains correspond to 6 elongated domains that associate in pairs at acidic pH in the stem region of VWF dimeric bouquets. This correspondence is demonstrated by binding of integrin αIIbβ3 to the fourth module seen in EM, VWC4, which bears the VWF Arg-Gly-Asp motif. The C-terminal cystine knot domain dimerizes end-to-end in a manner predicted by homology to TGF-β and orients approximately perpendicular to the VWC domains in dimeric bouquets. Homologies of domains in VWF to domains in other proteins allow many disulfide bonds to be tentatively assigned, which may have functional implications.
Determination of finite-difference weights using scaled binomial windows
Authors: Chu Chunlei , Stoffa Paul L.
Published: April 2012

The finite-difference method evaluates a derivative through a weighted summation of function values from neighboring grid nodes. Conventional finite-difference weights can be calculated either from Taylor series expansions or by Lagrange interpolation polynomials. The finite-difference method can be interpreted as a truncated convolutional counterpart of the pseudospectral method in the space domain. For this reason, we also can derive finite-difference operators by truncating the convolution series of the pseudospectral method. Various truncation windows can be employed for this purpose and they result in finite-difference operators with different dispersion properties. We found that there exists two families of scaled binomial windows that can be used to derive conventional finite-difference operators analytically. With a minor change, these scaled binomial windows can also be used to derive optimized finite-difference operators with enhanced dispersion properties.
Risk Measures from Risk-Reducing Experiments
Authors: Delquié Philippe
Published: April 2012

This paper introduces the concept of risk-reducing experiments as a basis for designing risk measures. A risk-reducing experiment provides the option to mitigate the impact of less favorable outcomes in a gamble, and the gamble's risk is measured as the increase in value brought about by such an experiment. Two examples are presented, including one based on the concept of expected value of perfect information. Both examples yield familiar risk measures, and extensions of them are discussed. A risk measure derived from a risk-reducing experiment makes explicit the sense in which the riskiness of a gamble is captured. Risk-reducing experiments offer a new approach for conceiving, or choosing among, risk measures.
Interactions Between Ageing and Risk Properties in the Analysis of Burn-in Problems
Authors: Foschi Rachele , Spizzichino Fabio
Published: April 2012

Several relevant problems in reliability can be looked at as problems of risk management and of decisions in the face of uncertainty. However, in this frame, the so-called burn-in problem can be seen as a problem of risk taking par excellence. In this paper, we in particular point out some aspects concerning interactions between the probabilistic model for lifetimes and considerations of an economic kind. As one of the features of our work, we hinge on some unexplored connections between ageing properties of a one-dimensional survival function Ḡ and risk-aversion-type properties of the function u(t) = bG(t), b > 0, when the latter is seen as a utility function.
Game Theoretical Approach for Reliable Enhanced Indexation
Authors: Lejeune Miguel A.
Published: April 2012

Enhanced indexation is a structured investment approach that combines passive and active financial management techniques. We propose an enhanced indexation model whose goal is to maximize the excess return that can be attained with high reliability, while ensuring that the relative market risk does not exceed a specified limit. We measure the relative risk with the coherent semideviation risk functional and model the asset returns as random variables. We consider that the probability distributions of the index fund and excess returns are imperfectly known and belong to a class of distributions characterized by an ellipsoidal distributional set. We provide a game theoretical formulation for the enhanced indexation problem in which we maximize the minimum excess return over all allowable probability distributions. The variance of the excess return is calculated with a computationally efficient method that avoids model specification issues. Finally, we show that the game theoretical model can be recast as a convex programming problem and discuss the results of numerical experiments.
Product and Price Competition with Satiation Effects
Authors: Caro Felipe , Martínez-de-Albéniz Victor
Published: April 2012

Consumers become satiated with a product when purchasing too much too quickly. How much is too much and how quickly is too quickly depends on the characteristics of the product relative to the time interval between consumption periods. Knowing that, consumers allocate their budget to products that generate less satiation effects. Retailers should then choose to sell products that induce minimal satiation, but usually this is operationally more costly. To study this trade-off, we provide an analytical model based on utility theory that relates customer consumption to price and satiation, in the context of multiple competing retailers. We determine the purchasing pattern over time and provide an explicit expression to determine the consumption level in steady state. We derive market shares and show that they take the form of an attraction model in which the attractiveness depends on price and product satiation. We use this to analyze the competition between firms that maximize long-term average profit. We characterize the equilibrium under three scenarios: (i) price-only competition, (ii) product-only competition, and (iii) price and product competition. The results reveal the interplay between a key marketing lever (price) and the firm's ability to offer products that generate less satiation. In particular, we show that when a firm becomes more efficient at reducing satiation, its competitor may benefit if competition is on product only, but not if it is on price and product. We also find that when satiation effects are not managed, a firm's profit may be significantly reduced while a strategic competitor can largely benefit.

This paper was accepted by Yossi Aviv, operations management.
On the Conditional Risk and Performance of Financially Distressed Stocks
Authors: O'Doherty Michael S.
Published: April 2012

Several recent articles find that stocks with high probabilities of bankruptcy or default earn anomalously low returns and negative unconditional capital asset pricing model (CAPM) alphas in the post-1980 period. I show that the conditional CAPM resolves the performance difference between high- and low-distress stocks. In particular, financially distressed stocks have relatively low exposure to market risk during bad economic times. I help to explain these findings through a theoretical model in which a levered firm's equity beta is negatively related to uncertainty about the unobserved value of its underlying assets.

This paper was accepted by Wei Xiong, finance.
Outsourcing a Two-Level Service Process
Authors: Lee Hsiao-Hui , Pinker Edieal J. , Shumsky Robert A.
Published: April 2012

This paper studies outsourcing decisions for a two-level service process in which the first level serves as a gatekeeper for a second level of experts. The objective of the system operator (the client) is to minimize the sum of staffing costs, customer waiting costs, and mistreatment costs due to unsuccessful attempts by a gatekeeper to solve the customer's problem. The client may outsource all or part of the process to a vendor, and first-best contracts exist when the client outsources only gatekeepers or experts. When the client outsources the entire system as a two-level process, a client-optimal contract may not exist unless the exogenous system parameters satisfy a particular (and unlikely) coordination condition. In addition, optimal incentive-compatible contracts exist when the vendor's structure choice (one level or two levels) can deviate from the client's preference. Finally, we numerically examine how vendor structure choice and labor cost advantages influence the client's optimal outsourcing option.

This paper was accepted by Martin Lariviere, operations management.
Firm Survival and Industry Evolution in Vertically Related Populations
Authors: de Figueiredo John M. , Silverman Brian S.
Published: April 2012

This paper examines how the density and governance of vertically related populations affect the life chances of organizations. We integrate the literatures on organizational ecology and vertical integration to develop a theory of how (1) specialized upstream industries affect downstream survival rates, (2) the prevalence of different governance forms among upstream and downstream organizations moderates this relationship, and (3) different forms of governance exert differential competitive pressures on focal organizations. We find evidence supporting our hypotheses in an empirical examination of the downstream laser printer industry and upstream laser engine industry.

This paper was accepted by Jesper Sørensen, organizations.
Exploring metal-driven stereoselectivity of glycopeptides by free-energy calculations
Authors: Pietropaolo Adriana
Published: April 2012

A formalism to quantify the chemical stereoselectivity, based on free energy of binding calculations, is here discussed. It is used to explain the stereoselectivity of two diastereoisomeric frameworks, comprising the dimer of a copper(II)-peptide core of L- and D-carnosine, respectively, each bound to two chains of D-trehalose, in which copper(II) adopts a type-II coordination geometry. The stereocenter of carnosine is varied both L and D, giving rise to two diastereoisomers. A thermodynamic cycle crossing the formation of the two enantiomeric copper(II) peptide cores was devised. A harmonic restraining potential that depends only on the bond distance was added to ensure reversibility in bond formation and dissociation, for an accurate estimate of the free energy. The calculation of the free energy of binding between D-trehalose and the two enantiomeric copper(II) peptide cores reproduces the free-energy quantities observed from stability constants and isothermal titration calorimetry (ITC) measurements. This is an example of chirality selection based on free-energy difference.
Trends And Cycles In The Net Barter Terms Of Trade For Sub-Saharan Africa's Primary Commodity Exporters
Authors: Alagidede Paul
Published: April 2012

This paper addresses terms of trade shocks in four commodity-exporting countries: Botswana, Cote d'Ivoire (Ivory Coast), Ghana and Zambia. We address both the short run cyclical fluctuations and the long run trends. The latter is important for importing countries with respect to the uncertainties associated with production and manufacturing. For exporting countries, it enables policy makers to cope with price risk in international markets. Using unobseved components models we showed that a shock to the terms of trade dissipate between 2 and 9 years, with the long run trend indicating the tendency for the net barter terms of trade to decline over time. In addition, we showed that the shorter the shocks to the terms of trade, and the longer the frequency of the shock, the more severe the accumulated long run loss in welfare and output. Hedging the downside risk of commodity price busts, commodity beneficiation among others are suggested as policy menus for smoothing the path of income and consumption.
The Saving-Investment Gap And Income Inequality: Evidence From 16 Countries
Authors: Bahmani-Oskooee Mohsen , Hegerty Scott W. , Wilmeth Harvey
Published: April 2012

Previous studies that analyzed income inequality mostly concentrated on identifying microeconomic determinants such as income, social factors (family structure, employment, or age distribution), or factor endowments; or such macroeconomic determinants as the exchange rate, economic openness or the black market premium. These studies also relied upon cross-section estimates in their assessments. In this paper, we introduce the "saving-investment" gap, which measures whether the need for financing is unmet, as another determinant of income inequality. We then apply time-series techniques in a study of 16 countries. Using the "bounds testing" cointegration method, in which variables in a given model can be stationary, non-stationary, or a combination of the two, we find varying results across countries. While these results highlight the need for further country-specific research, they indicate the benefits that external financing can provide.
Coyotes, Migration Duration, and Remittances
Authors: Ortmeyer David L. , Quinn Michael A.
Published: April 2012

The migration of Mexican immigrants to the U.S. is one of the largest bilateral migration flows in the world and remittances from these immigrants represent a crucial source of income for Mexican households. As the United States tightens controls on illegal migration, this may impact both migration durations and remittances. Tighter borders increase crossing costs, often because migrants need to pay smugglers (coyotes). Using data from the Mexican Migration Project, we find that higher crossing costs increase the probability of remitting, the remittance rate and the duration of stay as undocumented workers pay off the crossing debt. If immigrants did not incur these crossing debts then more of their earnings could be spent in the United States or by their households in Mexico on productive activities and durations in the U.S. might be lessened at the margin. This suggests some potential gain to both the U.S. and Mexican economies through expanding guest worker programs and consequently reducing the hiring of coyotes.
Rewriting the Late Pre-European History of Amazonia
Authors: Denevan William M.
Published: April 2012

El acercamiento convencional a las poblaciones amazónicas pre-europeas ha sido el de gente simple que vive en pequeños villorios autónomos, poblaciones dispersas que sobrevivieron a través del forraje y cultivos no permanentes con impacto ambiental mínimo. En décadas recientes, un Nuevo Modelo o síntesis ha ido desarrollándose e incluye sociedades regionales complejas, poblaciones localmente densas, cultivo intensivos, suelos antropogénicos fértiles y modificaciones ambientales de consideración.