Shivering in the cold: from mechanisms of fuel selection to survival

2006 ◽  
Vol 100 (5) ◽  
pp. 1702-1708 ◽  
Author(s):  
François Haman
Keyword(s):  
Future Research ◽  
Selection Mechanism ◽  
Glycogen Depletion ◽  
Human Survival ◽  
Fuel Selection ◽  
New Information ◽  
Fundamental Research ◽  
Specific Muscle ◽  
Fuel Mixtures ◽  
Shivering Thermogenesis

In cold-exposed adult humans, significant or lethal decreases in body temperature are delayed by reducing heat loss via peripheral vasoconstriction and by increasing rates of heat production via shivering thermogenesis. This brief review focuses on the mechanisms of fuel selection responsible for sustaining long-term shivering thermogenesis. It provides evidence to explain large discrepancies in fuel selection measurements among shivering studies, and it proposes links between choices in fuel selection mechanism and human survival in the cold. Over the last decades, a number of studies have quantified the contributions of carbohydrate (CHO) and lipid to total heat generation. However, the exact contributions of these fuels still remain unclear because of large differences in fuel selection measurements even at the same metabolic rate. Recent advances on the mechanisms of fuel selection during shivering provide some plausible explanations for these discrepancies between shivering studies. This new evidence indicates that muscles can sustain shivering over several hours using a variety of fuel mixtures achieved by modifying diet (changing the size of CHO reserves) or by changing muscle fiber recruitment (increasing or decreasing the recruitment of type II fibers). From a practical perspective, how does the choice of fuel selection mechanism affect human survival in the cold? Based on a glycogen-depletion model, estimates of shivering endurance show that, whereas the oxidation of widely different fuel mixtures does not improve survival time, the selective recruitment of fuel-specific muscle fibers provides a substantial advantage for cold survival. By combining fundamental research on fuel metabolism and applied strategies to improve shivering endurance, future research in this area promises to yield important new information on what limits human survival in the cold.

scholarly journals Oxidative fuel selection and shivering thermogenesis during a 12- and 24-h cold-survival simulation

2016 ◽  
Vol 120 (6) ◽  
pp. 640-648 ◽  
Author(s):  
François Haman ◽  
Olivier L. Mantha ◽  
Stephen S. Cheung ◽  
Michel B. DuCharme ◽  
Michael Taber ◽  
...  
Keyword(s):  
Cold Exposure ◽  
Muscle Glycogen ◽  
Whole Body ◽  
Muscle Recruitment ◽  
Glycogen Depletion ◽  
Total Carbohydrate ◽  
Fuel Selection ◽  
Isotopic Methods ◽  
Shivering Thermogenesis

Because the majority of cold exposure studies are constrained to short-term durations of several hours, the long-term metabolic demands of cold exposure, such as during survival situations, remain largely unknown. The present study provides the first estimates of thermogenic rate, oxidative fuel selection, and muscle recruitment during a 24-h cold-survival simulation. Using combined indirect calorimetry and electrophysiological and isotopic methods, changes in muscle glycogen, total carbohydrate, lipid, protein oxidation, muscle recruitment, and whole body thermogenic rate were determined in underfed and noncold-acclimatized men during a simulated accidental exposure to 7.5°C for 12 to 24 h. In noncold-acclimatized healthy men, cold exposure induced a decrease of ∼0.8°C in core temperature and a decrease of ∼6.1°C in mean skin temperature (range, 5.4-6.9°C). Results showed that total heat production increased by approximately 1.3- to 1.5-fold in the cold and remained constant throughout cold exposure. Interestingly, this constant rise in Ḣprod and shivering intensity was accompanied by a large modification in fuel selection that occurred between 6 and 12 h; total carbohydrate oxidation decreased by 2.4-fold, and lipid oxidation doubled progressively from baseline to 24 h. Clearly, such changes in fuel selection dramatically reduces the utilization of limited muscle glycogen reserves, thus extending the predicted time to muscle glycogen depletion to as much as 15 days rather than the previous estimates of approximately 30–40 h. Further research is needed to determine whether this would also be the case under different nutritional and/or colder conditions.

scholarly journals Multi-Period Portfolio Optimization with Investor Views under Regime Switching

2020 ◽  
Vol 14 (1) ◽  
pp. 3
Author(s):  
Razvan Oprisor ◽  
Roy Kwon
Keyword(s):  
Regime Switching ◽  
Portfolio Allocation ◽  
Ease Of Use ◽  
Future Research ◽  
Expected Return ◽  
Asset Return ◽  
Market Portfolio ◽  
New Information ◽  
Trading Model ◽  
Portfolio Managers

We propose a novel multi-period trading model that allows portfolio managers to perform optimal portfolio allocation while incorporating their interpretable investment views. This model’s significant advantage is its intuitive and reactive design that incorporates the latest asset return regimes to quantitatively solve managers’ question: how certain should one be that a given investment view is occurring? First, we describe a framework for multi-period portfolio allocation formulated as a convex optimization problem that trades off expected return, risk and transaction costs. Using a framework borrowed from model predictive control introduced by Boyd et al., we employ optimization to plan a sequence of trades using forecasts of future quantities, only the first set being executed. Multi-period trading lends itself to dynamic readjustment of the portfolio when gaining new information. Second, we use the Black-Litterman model to combine investment views specified in a simple linear combination based format with the market portfolio. A data-driven method to adjust the confidence in the manager’s views by comparing them to dynamically updated regime-switching forecasts is proposed. Our contribution is to incorporate both multi-period trading and interpretable investment views into one framework and offer a novel method of using regime-switching to determine each view’s confidence. This method replaces portfolio managers’ need to provide estimated confidence levels for their views, substituting them with a dynamic quantitative approach. The framework is reactive, tractable and tested on 15 years of daily historical data. In a numerical example, this method’s benefits are found to deliver higher excess returns for the same degree of risk in both the case when an investment view proves to be correct, but, more notably, also the case when a view proves to be incorrect. To facilitate ease of use and future research, we also developed an open-source software library that replicates our results.

scholarly journals Expression of genes SBP and leginsulin in contrasting soybean seed coats

2016 ◽  
Vol 46 (10) ◽  
pp. 1695-1700
Author(s):  
Carlos André Bahry ◽  
Paulo Dejalma Zimmer
Keyword(s):  
Gene Expression ◽  
Seed Quality ◽  
Soybean Seed ◽  
Future Research ◽  
Expression Of Genes ◽  
New Information ◽  
Soybean Genotypes ◽  
Phases Of Development ◽  
Seed Coats ◽  
Early Phases

ABSTRACT: Evaluation of differential candidate gene expression in contrasting soybean seeds is an auxiliary tool in the partial elucidation of processes involved in seeds formation, as well as it contributes to the generation of new information that can be used in future research or in the development of r genetic superior constitutions. The aim of this study was to evaluate the expression of two candidate genes, SBP and leginsulin genes, possibly involved in seed quality, in contrasting coats of four soybean genotypes. Two cultivars of yellow soybeans were used, BMX Potência RR and CD 202, and two lines of black soybean, TP and IAC. Gene expression was evaluated using qPCR in seven stages of development from seed coats for four genotypes, at 25, 30, 35, 40, 45, 50, and 55 days after anthesis. The design was completely randomized, with three replications. Data were subjected to analysis of variance and means compared by Tukey's test at 5% probability. SBP and leginsulin gene have higher expression in the early phases of development from seed coats of BMX Potência RR cultivar, followed by the IAC line. These genotypes are therefore of interest for further research involving these genes.

scholarly journals ExTaxsI: an exploration tool of biodiversity molecular data

2020 ◽  
Author(s):  
Giulia Agostinetto ◽  
Anna Sandionigi ◽  
Adam Chahed ◽  
Alberto Brusati ◽  
Elena Parladori ◽  
...  
Keyword(s):  
Molecular Data ◽  
Data Availability ◽  
Future Research ◽  
Distribution Data ◽  
Biodiversity Data ◽  
Related Information ◽  
New Information ◽  
Starting Point ◽  
Key Factor ◽  
New Research

AbstractBackgroundThe increasing availability of multi omics data is leading to continually revise estimates of existing biodiversity data. In particular, the molecular data enable to characterize novel species yet unknown and to increase the information linked to those already observed with new genomic data. For this reason, the management and visualization of existing molecular data, and their related metadata, through the implementation of easy to use IT tools have become a key point for the development of future research. The more users are able to access biodiversity related information, the greater the ability of the scientific community to expand the knowledge in this area.ResultsIn our research we have focused on the development of ExTaxsI (Exploring Taxonomies Information), an IT tool able to retrieve biodiversity data stored in NCBI databases and provide a simple and explorable visualization. Through the three case studies presented here, we have shown how an efficient organization of the data already present can lead to obtaining new information that is fundamental as a starting point for new research. Our approach was also able to highlight the limits in the distribution data availability, a key factor to consider in the experimental design phase of broad spectrum studies, such as metagenomics.ConclusionsExTaxI can easily produce explorable visualization of molecular data and its metadata, with the aim to help researchers to improve experimental designs and highlight the main gaps in the coverage of available data.

scholarly journals Single-molecule long-read sequencing reveals a conserved selection mechanism determining intact long RNA and miRNA profiles in sperm

2020 ◽  
Author(s):  
Yu H. Sun ◽  
Anqi Wang ◽  
Chi Song ◽  
Rajesh K. Srivastava ◽  
Kin Fai Au ◽  
...  
Keyword(s):  
Single Molecule ◽  
Ribosomal Proteins ◽  
Selection Process ◽  
Future Research ◽  
Selection Mechanism ◽  
Bioinformatics Pipeline ◽  
Long Reads ◽  
Evolutionarily Conserved ◽  
Long Read ◽  
Early Trauma

AbstractSperm contributes diverse RNAs to the zygote. While sperm small RNAs have been shown to be shaped by paternal environments and impact offspring phenotypes, we know little about long RNAs in sperm, including mRNAs and long non-coding RNAs. Here, by integrating PacBio single-molecule long reads with Illumina short reads, we found 2,778 sperm intact long transcript (SpILT) species in mouse. The SpILTs profile is evolutionarily conserved between rodents and primates. mRNAs encoding ribosomal proteins are enriched in SpILTs, and in mice they are sensitive to early trauma. Mouse and human SpILT profiles are determined by a post-transcriptional selection process during spermiogenesis, and are co-retained in sperm with base pair-complementary miRNAs. In sum, we have developed a bioinformatics pipeline to define intact transcripts, added SplLTs into the “sperm RNA code” for use in future research and potential diagnosis, and uncovered selection mechanism(s) controlling sperm RNA profiles.

Coping with Information Technology

2010 ◽  
pp. 516-528 ◽  
Author(s):  
Anne Beaudry
Keyword(s):  
Information Technology ◽  
Work Environment ◽  
Working Environment ◽  
Future Research ◽  
Adaptation Process ◽  
It Adoption ◽  
Is Research ◽  
New Information ◽  
Coping Theory ◽  
It Acceptance

New information technology implementations, as major modifications to existing ones, bring about changes in the work environment of individuals that trigger an important adaptation process. Extant research on the adaptation process individuals go through when a new IT is implemented in their working environment is rather limited. Furthermore, variance theories and models useful to explain IT adoption and use are not well suited to study the dynamics underlying the adaptation process. Coping theory, because it links antecedents, adaptation behaviors, and outcomes altogether, provides a rich lens through which we can study individuals’ IT-related adaptation process. A better understanding of this process will enable researchers and practitioners to understand and predict IT acceptance and related behaviors and thus to better manage them. This chapter presents coping theory, its underlying assumptions and inherent components, discusses its application, highlights the complementarities with existing models and theories currently used in IS research, and provides several avenues for future research in this area.

IT-Enabled Integration of Business Relationships in the Steel Industry Context

2006 ◽  
pp. 275-294
Author(s):  
Jari Salo
Keyword(s):  
Information Technology ◽  
Technology Integration ◽  
Steel Industry ◽  
Future Research ◽  
Business Relationships ◽  
Longitudinal Case Study ◽  
Organizational Relationships ◽  
Factors Affecting ◽  
New Information ◽  
Complex Process

Companies engage in many business relationships; however, the number is decreasing constantly, so existing relationships are increasingly valuable. The purpose of this chapter is to highlight how inter-organizational relationships can be seen as a source of competitive advantage and how, in order to survive in a hyper-competitive landscape, key relationships are integrated with new information technology solutions, such as ERP. This chapter focuses on the changes brought about by technology integration in the context of the steel industry with the help of a longitudinal case study. The chapter sheds some light on factors affecting the changes occurring in business relationships and illustrates how those alterations can be managed. It seems that information technology integration within a business relationship is a complex process that depends on characteristics of the adopted technology as well as the relationship. Subsequently, implications are discussed together with suggestions for future research. Lastly, the limitations are briefly stated.

scholarly journals GRANDPARENT CAREGIVERS: THE RELATION BETWEEN SOCIAL NETWORKS AND RESILIENCE

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S678-S679
Author(s):  
Nancy Mendoza ◽  
Christine Fruhauf
Keyword(s):  
Social Support ◽  
Social Networks ◽  
Social Network ◽  
Future Research ◽  
Grandparents Raising Grandchildren ◽  
Face To Face ◽  
Grandparent Caregivers ◽  
New Information ◽  
Multiple Challenges ◽  
Using Data

Abstract Grandparents raising grandchildren experience multiple challenges as they take on the unexpected role of caring for their grandchildren, which usually occurs under stressful and stigmatizing conditions. Many of the challenges grandparents experience are well documented in the research. Less attention is given to understanding how a grandparent caregiver’s social network changes when s/he becomes a caregiver and how her/his social network influences resilience. Thus, the purpose of this study was to use social network analysis (SNA) to examine the relation between social networks and resilience in grandparents raising their grandchildren. This was done by conducting face-to-face interviews with twenty grandparents raising grandchildren after they completed a survey measuring social support, social isolation, and resilience. The interview protocol included questions related to participants’ social network, social support, and services. Prior to the interviews, using data from the surveys participants were identified as representing one of four resilience quadrants: resilient, maladaptive, competent, and vulnerable. Qualitative analysis of grandparent’s social networks across groups indicated resilient grandparent caregivers’ networks were structured in a way that provided more opportunities for the inflow of new information and resources. Whereas the proportion of professionals in maladaptive grandparent caregivers’ networks tended to be less than for other networks. This could suggest that for grandparent caregivers, having professionals in one’s network can be beneficial. Findings from the current study provide opportunities for future research such as identifying ways to help grandparent caregivers structure their social networks to promote resilience.

Hearing Loss in Older Adulthood

2005 ◽  
Vol 14 (3) ◽  
pp. 144-148 ◽  
Author(s):  
Arthur Wingfield ◽  
Patricia A. Tun ◽  
Sandra L. McCoy
Keyword(s):  
Older Adults ◽  
Cognitive Functioning ◽  
Contextual Information ◽  
Working Memory Capacity ◽  
Cognitive Effort ◽  
Future Research ◽  
Older Adulthood ◽  
New Information ◽  
Sensory Decline ◽  
Adult Aging

Adult aging is accompanied by declines in many areas of cognitive functioning, including reduced memory for new information. Potential sources of these declines are well established and include slowed processing, diminished working-memory capacity, and a reduced ability to inhibit interference. In addition, older adults often experience sensory decline, including decreased hearing acuity for high-frequency sounds and deficits in frequency and temporal resolution. These changes add to the challenge faced by older adults in comprehension and memory for everyday rapid speech. Use of contextual information and added perceptual and cognitive effort can partially offset the deleterious effects of these sensory declines. This may, however, come at a cost to resources that might otherwise be available for “downstream” operations such as encoding the speech content in memory. We argue that future research should focus not only on sensory and cognitive functioning as separate domains but also on the dynamics of their interaction.

scholarly journals A new web-based system to improve the monitoring of snow avalanche hazard in France

2016 ◽  
Author(s):  
E. Bourova ◽  
E. Maldonado ◽  
J.-B. Leroy ◽  
R. Alouani ◽  
N. Eckert ◽  
...  
Keyword(s):  
Information System ◽  
Data Entry ◽  
Snow Avalanche ◽  
Web Based ◽  
Risk Levels ◽  
Web Technologies ◽  
New Information ◽  
Eyewitness Reports ◽  
Hazard And Risk ◽  
Fundamental Research

Abstract. Snow avalanche data in the French Alps and Pyrenees have been recorded for more than 100 years in several databases. The increasing amount of observed data required a more integrative and automated service. Here we report the comprehensive web-based Snow Avalanche Information System newly developed to this end for three important datasets: an avalanche chronicle (Enquête Permanente sur les Avalanches, EPA), an avalanche map (Carte de Localisation des Phénomènes d'Avalanche, CLPA) and a compilation of hazard and vulnerability data recorded on selected paths endangering human settlements (Sites Habités Sensibles aux Avalanches, SSA). These datasets are now integrated into a common database, enabling full interoperability between all different types of snow avalanche records: digitized geographic data, avalanche descriptive parameters, eyewitness reports, photographs, hazard and risk levels, etc. The new information system is implemented through modular components using Java-based web technologies with Spring and Hibernate frameworks. It automates the manual data entry and improves the process of information collection and sharing, enhancing user experience, data quality, and offering new outlooks to explore and exploit the huge amount of snow avalanche data available for fundamental research and more applied risk assessment.

Sign in / Sign up

Export Citation Format

Share Document