Labour Force Participation Rates of Older Persons: An International Comparison.

ERIC Educational Resources Information Center

Clark, Robert L.; Anker, Richard

1990-01-01

Using data from 151 countries, labor force participation of older men and women was analyzed and related to economic, demographic, and policy variables. Reduced participation rates are related to increased income levels, structural changes, social security programs, and, for men, the ratio of older persons to persons of standard working age. (SK)

Labor Force Participation Rates among Working-Age Individuals with Visual Impairments

ERIC Educational Resources Information Center

Kelly, Stacy M.

2013-01-01

The present study analyzes four consecutive years of monthly labor force participation rates reported by the Current Population Survey that included nationally representative samples of the general U.S. population and nationally representative samples of the U.S. population with specifically identified disabilities. Visual impairment is one of the…

Military milk: breastfeeding rates among Australian Defence Force women who return to military service following maternity leave.

PubMed

Stewart, Kelley

2015-02-01

The breastfeeding behaviors among Australian Defence Force women have not previously been examined. Studies have shown that breastfeeding prevalence and duration are affected by maternity leave entitlements and returning to work. This study aimed to benchmark breastfeeding initiation, prevalence, and duration among a cohort of Australian Defence Force women and to compare these findings against Australian population norms. A cross-sectional survey was conducted via email in 2008 for Australian Defence Force women who had taken maternity leave in the Australian financial year of 2006/2007. Analysis of breastfeeding indicators was undertaken. Ninety-eight percent of Australian Defence Force women in this cohort initiated breastfeeding and breastfed for a median duration of 8 months, returning to work when the mean age of the child was 8.4 months. Breastfeeding prevalence did not meet 2003 Australian National Health and Medical Research Council targets by 6 months postpartum but compared favorably to the Australian population norms. Sixty-six percent of the respondents returned to work full-time, with a median breastfeeding duration of 7 months. Women who returned to work part-time had a longer median duration of 10 months. Breastfeeding rates among this cohort of Australian Defence Force women compare favorably with the general Australian population until 9 months, coinciding with returning to work after a period of maternity leave. The results support recent Australian population studies on breastfeeding and employment. © The Author(s) 2014.

Women of Hispanic Origin in the United States Labor Force. Facts on Working Women. Fact Sheet No. 85-11.

ERIC Educational Resources Information Center

Department of Labor, Washington, DC.

A four-page synposis of data on women of Hispanic origin in the labor force is presented. Data included are numbers of Hispanic women in the labor force; percentage of Hispanics among women in labor force; percentage of Hispanic women in the labor force; median ages; unemployment rate; education level; income levels; types of jobs occupied…

Women's Access to Higher Education Leadership: Cultural and Structural Barriers

ERIC Educational Resources Information Center

Ballenger, Julia

2010-01-01

The Labor Force 2008 projections reflected that the rate of growth for women in the labor force will increase at a faster rate than that of men (Fullerton, 1999). In 2008, the majority of employed women (39 percent) worked in management, professional, and related occupations (U.S. Department of Labor, 2008). Although women's participation in the…

[Women and work. Panorama in Latin America 1960-1990].

PubMed

Espinosa, G

1994-01-01

Significant increases have occurred over the past 40 years in the labor force participation of Latin American women. The changes have been caused primarily by transformations in the economic system, but also in part by changes of attitude regarding the role of women in economic development and household survival. Average female labor force participation rates are difficult to compare over time and between countries because of differing cultural patterns concerning work, use of differing concepts of productive work and labor force, and different time periods of coverage. Some common trends can be observed in labor force participation despite the data limitations. A decline occurred in overall participation rates, at least until 1980, while female participation rates increased continually over the entire period. Several factors have been suggested to explain the overall decline, among them longer school attendance by young people. The Latin American Economic Commission classified Latin American countries into four groups according to their level of economic and social modernization. The role of women in the labor market and in domestic work is associated with the level of modernization. In all four groups, female activity rates have systematically increased in all countries. The distribution of women in the different productive sectors varied in the four groups. The two most developed groups concentrate a large part of the urban population, and in these groups the increase in female economic participation has been most pronounced. Establishment of maquiladora industries has been particularly associated with growth of female labor force participation in the past 15 years. The work of maquiladoras is associated with such problems of the informal sector as poor hygiene and exploitation. The informal sector is known to have grown considerably and to have permitted survival of many families during the economic crisis of the 1980s, but sufficient data is not yet available to gauge its true size.

The participation of women in the labour force of Latin America: fertility and other factors.

PubMed

Elizaga, J C

1974-01-01

The level of labor force participation among Latin American women, when compared with participation rates for other countries, is the lowest in the world. Only 20% or less of women 10 years of age and older are economically active. This level did not change much between 1950 and 1970. Few women work in agriculture. The following factors are considered for their effect on labor force participation of urban women: marital status, education, income, and the structure and stage of development of the society. Married women have a low participation rate. More highly educated women are more likely to work, but there must be demand for their work services. As the economy of various countries has progressed, female participation in domestic services has decreased, in industry has remained constant between 1960 and 1970, and in social services has expanded. It is concluded that work participation for married women will only increase with the following changes: 1) improved educational opportunities for women; 2) structural change and modernization in the economy; and 3) reduced family fertility. Changes in the first 2 factors are more important than reduced fertility. Since 1960, only Chile and Costa Rica have had a 25% decline in fertility rates.

Epidemiologic surveillance. Annual report for Idaho National Engineering Laboratory 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1994-12-31

Epidemiologic surveillance at DOE facilities consists of regular and systematic collection, analysis, and interpretation of data on absences due to illness and injury in the work force. Its purpose is to provide an early warning system for health problems occurring among employees at participating sites. In this annual report, the 1994 morbidity data for the Idaho National Engineering Laboratory are summarized. These analyses focus on absences of 5 or more consecutive workdays occurring among workers aged 17-85 years. They are arranged in five sets of tables that present: (1) the distribution of the labor force by occupational category and paymore » status; (2) the absences per person, diagnoses per absence, and diagnosis rates for the whole work force; (3) diagnosis rates by type of disease or injury; (4) diagnosis rates by occupational category; and (5) relative risks for specific types of disease or injury by occupational category.« less

Epidemiologic surveillance. Annual report for Sandia National Laboratories 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1994-12-31

Epidemiologic surveillance at DOE facilities consists of regular and systematic collection, analysis, and interpretation of data on absences due to illness and injury in the work force. Its purpose is to provide an early warning system for health problems occurring among employees at participating sites. In this annual report, 1994 morbidity data for the Sandia National Laboratories are summarized. These analyses focus on absences of 5 or more consecutive workdays occurring among workers aged 15-76 years. They are arranged in five sets of tables that present: (1) the distribution of the labor force by occupational category and pay status; (2)more » the absences per person, diagnoses per absence, and diagnosis rates for the whole work force; (3) diagnosis rates by type of disease or injury; (4) diagnosis rates by occupational category; and (5) relative risks for specific types of disease or injury by occupational category.« less

Epidemiologic surveillance. Annual report for Savannah River Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1997-09-01

Epidemiologic surveillance at US Department of Energy (DOE) facilities consists of regular and systematic collection, analysis, and interpretation of data on absences due to illness and injury in the work force. Its purpose is to provide an early warning system for health problems occurring among employees at participating sites. In this annual report, the 1994 morbidity data for the Savannah River Site (SRS) are summarized. These analyses focus on absences of 5 or more consecutive workdays occurring among workers aged 16-75 years. They are arranged in five sets of tables that present: (1) the distribution of the labor force bymore » occupational category and salary status; (2) the absences per person, diagnoses per absences, and diagnosis rates for the whole work force; (3) diagnosis rates by type of disease or injury; (4) diagnosis rates by occupational category; and (5) relative risks for specific types of disease or injury by occupational category.« less

Early Claiming of Social Security Benefits and Labor Supply Behavior of Older Americans.

PubMed

Benítez-Silva, Hugo; Heiland, Frank

2008-12-01

The labor supply incentives provided by the early retirement rules of the United States Social Security Old Age benefits program are of growing importance as the Normal Retirement Age (NRA) increases to 67, and the labor force participation of Older Americans starts to increase. These incentives allow individuals who claim benefits before the NRA but continue to work, or return to the labor force, to increase their future rate of benefit pay by having benefits withheld. Since the adjustment of the benefit rate takes place only after the NRA is reached, benefits received before the NRA can become actuarially unfair for those who continue to work after claiming. Consistent with these incentives, estimates from bivariate models of the monthly labor force exit and claiming hazards using data from the Health and Retirement Study indicate that early claimers who do not withdraw from the labor force around the time they claim are increasingly likely to stay in the labor force.

Early Claiming of Social Security Benefits and Labor Supply Behavior of Older Americans†

PubMed Central

Benítez-Silva, Hugo; Heiland, Frank

2010-01-01

The labor supply incentives provided by the early retirement rules of the United States Social Security Old Age benefits program are of growing importance as the Normal Retirement Age (NRA) increases to 67, and the labor force participation of Older Americans starts to increase. These incentives allow individuals who claim benefits before the NRA but continue to work, or return to the labor force, to increase their future rate of benefit pay by having benefits withheld. Since the adjustment of the benefit rate takes place only after the NRA is reached, benefits received before the NRA can become actuarially unfair for those who continue to work after claiming. Consistent with these incentives, estimates from bivariate models of the monthly labor force exit and claiming hazards using data from the Health and Retirement Study indicate that early claimers who do not withdraw from the labor force around the time they claim are increasingly likely to stay in the labor force. PMID:20811509

Facing the Future: Education and Equity for Females and Males.

ERIC Educational Resources Information Center

Matthews, Martha

This publication examines the changes in the roles of women and men and what these changes mean for the future of schools--for educational quality and opportunity and for educational decision making. Women comprise more than 44% of the paid work force. It is estimated that by the year 2000, if not before, work force participation rates of women…

California's Rural Poor: Trends, Correlates, and Policies. Working Group on Farm Labor and Rural Poverty, Working Paper No. 7.

ERIC Educational Resources Information Center

Gwynn, Douglas B.; And Others

In the 1980s California poverty rates increased dramatically. Poverty rates were substantially higher in rural areas and for Hispanics, Asians, single-parent families, and children. The percentage of the labor force in poverty increased, and poverty rates were exceptionally high for the unemployed and for "discouraged workers." The…

The Road to Poverty: A Report on the Economic Status of Midlife and Older Women in America. Mother's Day Report 1988.

ERIC Educational Resources Information Center

Older Women's League, Washington, DC.

Women of all ages continue to enter the work force in greater numbers while the work force participation rate for males is declining. Women are disproportionately concentrated in low-paying, dead-end jobs. Employment discrimination continues to be a significant problem. Job interruptions necessitated by family responsibilities are a major factor…

Effects of High School Work Experience a Decade Later: Evidence from the National Longitudinal Survey.

ERIC Educational Resources Information Center

Wright, James D.; Carr, Rhoda

Using a data sample from the National Longitudinal Survey of Youth that included all youths enrolled in high school who were aged 16-19 in 1979, a study tracked the youths' labor force attachment and earnings 12 years later. The study found that students who worked while in high school show increased rates of labor force participation along with…

Educational Attainment of Workers, March 1982-83. Special Labor Force Report. Bulletin 2191.

ERIC Educational Resources Information Center

Bureau of Labor Statistics (DOL), Washington, DC.

As this report illustrates, nearly one in four adult workers today has completed college, while in 1970 just one in seven had as much formal schooling. This growth, together with the higher labor force participation rates of college graduates, has generated significant increases in the college-educated work force. Other factors include women's…

Final Environmental Assessment for the Update and Implementation of the Total Force Training Mission for Visiting Units (Operation Snowbird, Multi-Service, and Foreign Military Sales), Davis-Monthan Air Force Base, Arizona

DTIC Science & Technology

2015-05-14

elimina ources h alternative Aircraft licopters April ation Luke AFB T No Yes Yes Yes Yes Yes s to increas ver, the ai work and t...data are shown in Table 3-9. There were almost 463,000 people in the labor force in the ROI. The average 2012 unemployment rate of 7.3 percent in...the ROI/Pima County is below the 2012 average unemployment rate for Arizona (8.3 percent) and the Nation (8.1 percent). Table 3-9. Labor Force

Factors Affecting College-Going Rates in California: A Study Prospectus. Working Paper WP/06-09

ERIC Educational Resources Information Center

California Postsecondary Education Commission, 2006

2006-01-01

This working paper announces a report proposed by the California Postsecondary Education Commission to conduct a further statistical study on the factors affecting college-going rates in California. These factors would include school demographics, neighborhood characteristics, and regional labor market forces. Such a study could reveal insights…

Personnel resources in physical therapy: an analysis of supply, career patterns, and methods to enhance availability.

PubMed

Gwyer, J

1995-01-01

Describing the ever-changing supply and demand for physical therapy personnel in the United States is an intricate, complex, and profoundly significant task for the profession. In this article, a review of data relating to the supply of physical therapy personnel in the work force and their typical career patterns is presented. The estimates of the numbers of physical therapists and physical therapist assistants are discussed, as are problems associated with such estimates. Studies of career patterns of physical therapists are compared. Changes in the participation rates of women in the physical therapy work force over the last three decades are described. Career expectations, defined as both length and pattern of work-force participation, of entering physical therapy professionals are presented. Strategies to adjust the work-force participation of personnel through changes in the educational process, career patterns, and practice patterns are discussed.

A cross-bridge based model of force depression: Can a single modification address both transient and steady-state behaviors?

PubMed

Corr, David T; Herzog, Walter

2016-03-21

Force depression (FD), the reduction of isometric force following active shortening, is a phenomenon of skeletal muscle that has received significant attention in biomechanical and physiological literature, yet the mechanisms underlying FD remain unknown. Recent experiments identified a slower rate of force redevelopment with increasing amounts of steady-state FD, suggesting that FD may be caused, at least in part, by a decrease in cross-bridge binding rate (Corr and Herzog, 2005; Koppes et al., 2014). Herein, we develop a cross-bridge based model of FD in which the binding rate function, f, decreases with the mechanical work performed during shortening. This modification incorporates a direct relationship between steady-state FD and muscle mechanical work (Corr and Herzog, 2005; Herzog et al., 2000; Kosterina et al., 2008), and is consistent with a proposed mechanism attributing FD to stress-induced inhibition of cross-bridge attachments (Herzog, 1998; Maréchal and Plaghki, 1979). Thus, for an increase in mechanical work, the model should predict a slower force redevelopment (decreased attachment rate) to a more depressed steady-state force (fewer attached cross-bridges), and a reduction in contractile element stiffness (Ford et al., 1981). We hypothesized that since this modification affects the cross-bridge kinetics, a corresponding model would be able to account for both transient and steady-state FD behaviors. Comparisons to prior experiments (Corr and Herzog, 2005; Herzog et al., 2000; Kosterina et al., 2008) show that both steady-state and transient aspects of FD, as well as the relationship of FD with respect to speed and amplitude of shortening, are well captured by this model. Thus, this relatively simple cross-bridge based model of FD lends support to a mechanism involving the inhibition of cross-bridge binding, and indicates that cross-bridge kinetics may play a critical role in FD. Copyright © 2016 Elsevier Ltd. All rights reserved.

In Vivo Force Decay of Niti Closed Coil Springs

PubMed Central

Cox, Crystal; Nguyen, Tung; Koroluk, Lorne; Ko, Ching-Chang

2014-01-01

Introduction Nickel-titanium (NiTi) closed coil springs are purported to deliver constant forces over extended ranges of activation and working times. In vivo studies supporting this claim are limited. The objective of this study is to evaluate changes in force decay properties of NiTi closed coil springs after clinical use. Methods Pseudoelastic force-deflection curves for 30 NiTi coil springs (used intra-orally) and 15 matched laboratory control springs (simulated intra-oral conditions - artificial saliva, 37°C) were tested pre- and post-retrieval via Dynamic Mechanical Analysis (DMA) and the Instron machine, respectively, to evaluate amount of force loss and hysteresis change following 4, 8, or 12 weeks of working time (n=10 per group). Effect of the oral environment and clinical use on force properties were evaluated by comparing in vivo and in vitro data. Results The springs studied showed a statistically significant decrease in force (~12%) following 4 weeks of clinical use (p<0.01), with a further significant decrease (~7%) from 4–8 weeks (p=0.03) and force levels appearing to remain steady thereafter. Clinical space closure at an average rate of 0.91mm per month was still observed despite this decrease in force. In vivo and in vitro force loss data were not statistically different. Conclusions NiTi closed coil springs do not deliver constant forces when used intra-orally, but they still allow for space closure rates of ~1mm/month. PMID:24703289

The impact of working technique on physical loads - an exposure profile among newspaper editors.

PubMed

Lindegård, A; Wahlström, J; Hagberg, M; Hansson, G-A; Jonsson, P; Wigaeus Tornqvist, E

2003-05-15

The aim of this study was to investigate the possible associations between working technique, sex, symptoms and level of physical load in VDU-work. A study group of 32 employees in the editing department of a daily newspaper answered a questionnaire, about physical working conditions and symptoms from the neck and the upper extremities. Muscular load, wrist positions and computer mouse forces were measured. Working technique was assessed from an observation protocol for computer work. In addition ratings of perceived exertion and overall comfort were collected. The results showed that subjects classified as having a good working technique worked with less muscular load in the forearm (extensor carpi ulnaris p=0.03) and in the trapezius muscle on the mouse operating side (p=0.02) compared to subjects classified as having a poor working technique. Moreover there were no differences in gap frequency (number of episodes when muscle activity is below 2.5% of a reference contraction) or muscular rest (total duration of gaps) between the two working technique groups. Women in this study used more force (mean force p=0.006, peak force p=0.02) expressed as % MVC than the men when operating the computer mouse. No major differences were shown in muscular load, wrist postures, perceived exertion or perceived comfort between men and women or between cases and symptom free subjects. In conclusion a good working technique was associated with reduced muscular load in the forearm muscles and in the trapezius muscle on the mouse operating side. Moreover women used more force (mean force and peak force) than men when operating the click button (left button) of the computer mouse.

Adult mouse motor units develop almost all of their force in the subprimary range: a new all-or-none strategy for force recruitment?

PubMed

Manuel, Marin; Heckman, C J

2011-10-19

Classical studies of the mammalian neuromuscular system have shown an impressive adaptation match between the intrinsic properties of motoneurons and the contractile properties of their motor units. In these studies, the rate at which motoneurons start to fire repetitively corresponds to the rate at which individual twitches start to sum, and the firing rate increases linearly with the amount of excitation ("primary range") up to the point where the motor unit develops its maximal force. This allows for the gradation of the force produced by a motor unit by rate modulation. In adult mouse motoneurons, however, we recently described a regime of firing ("subprimary range") that appears at lower excitation than what is required for the primary range, a finding that might challenge the classical conception. To investigate the force production of mouse motor units, we simultaneously recorded, for the first time, the motoneuron discharge elicited by intracellular ramps of current and the force developed by its motor unit. We showed that the motor unit developed nearly its maximal force during the subprimary range. This was found to be the case regardless of the input resistance of the motoneuron, the contraction speed, or the tetanic force of the motor unit. Our work suggests that force modulation in small mammals mainly relies on the number of motor units that are recruited rather than on rate modulation of individual motor units.

Physical and psychosocial work environment factors and their association with health outcomes in Danish ambulance personnel – a cross-sectional study

PubMed Central

2012-01-01

Background Reviews of the literature on the health and work environment of ambulance personnel have indicated an increased risk of work-related health problems in this occupation. The aim of this study was to compare health status and exposure to different work environmental factors among ambulance personnel and the core work force in Denmark. In addition, to examine the association between physical and psychosocial work environment factors and different measures of health among ambulance personnel. Methods Data were taken from a nationwide sample of ambulance personnel and fire fighters (n = 1,691) and was compared to reference samples of the Danish work force. The questionnaire contained measures of physical and psychosocial work environment as well as measures of musculoskeletal pain, mental health, self-rated health and sleep quality. Results Ambulance personnel have half the prevalence of poor self-rated health compared to the core work force (5% vs. 10%). Levels of mental health were the same across the two samples whereas a substantially higher proportion of the ambulance personnel reported musculoskeletal pain (42% vs. 29%). The ambulance personnel had higher levels of emotional demands and meaningfulness of and commitment to work, and substantially lower levels of quantitative demands and influence at work. Only one out of ten aspects of physical work environment was consistently associated with higher levels of musculoskeletal pain. Emotional demands was the only psychosocial work factor that was associated with both poorer mental health and worse sleep quality. Conclusions Ambulance personnel have similar levels of mental health but substantially higher levels of musculoskeletal pain than the work force in general. They are more exposed to emotional demands and these demands are associated with higher levels of poor mental health and poor sleep quality. To improve work environment, attention should be paid to musculoskeletal problems and the presence of positive organizational support mechanisms that can prevent negative effects from the high levels of emotional demands. PMID:22824415

Recruitment of faster motor units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion

PubMed Central

Lee, Sabrina S. M.; de Boef Miara, Maria; Arnold, Allison S.; Biewener, Andrew A.; Wakeling, James M.

2013-01-01

SUMMARY Animals modulate the power output needed for different locomotor tasks by changing muscle forces and fascicle strain rates. To generate the necessary forces, appropriate motor units must be recruited. Faster motor units have faster activation–deactivation rates than slower motor units, and they contract at higher strain rates; therefore, recruitment of faster motor units may be advantageous for tasks that involve rapid movements or high rates of work. This study identified motor unit recruitment patterns in the gastrocnemii muscles of goats and examined whether faster motor units are recruited when locomotor speed is increased. The study also examined whether locomotor tasks that elicit faster (or slower) motor units are associated with increased (or decreased) in vivo tendon forces, force rise and relaxation rates, fascicle strains and/or strain rates. Electromyography (EMG), sonomicrometry and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of goats during level walking, trotting and galloping and during inclined walking and trotting. EMG signals were analyzed using wavelet and principal component analyses to quantify changes in the EMG frequency spectra across the different locomotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rise and relaxation rates were determined from the tendon force data. The results of this study showed that faster motor units were recruited as goats increased their locomotor speeds from level walking to galloping. Slow inclined walking elicited EMG intensities similar to those of fast level galloping but different EMG frequency spectra, indicating that recruitment of the different motor unit types depended, in part, on characteristics of the task. For the locomotor tasks and muscles analyzed here, recruitment patterns were generally associated with in vivo fascicle strain rates, EMG intensity and tendon force. Together, these data provide new evidence that changes in motor unit recruitment have an underlying mechanical basis, at least for certain locomotor tasks. PMID:22972893

Recruitment of faster motor units is associated with greater rates of fascicle strain and rapid changes in muscle force during locomotion.

PubMed

Lee, Sabrina S M; de Boef Miara, Maria; Arnold, Allison S; Biewener, Andrew A; Wakeling, James M

2013-01-15

Animals modulate the power output needed for different locomotor tasks by changing muscle forces and fascicle strain rates. To generate the necessary forces, appropriate motor units must be recruited. Faster motor units have faster activation-deactivation rates than slower motor units, and they contract at higher strain rates; therefore, recruitment of faster motor units may be advantageous for tasks that involve rapid movements or high rates of work. This study identified motor unit recruitment patterns in the gastrocnemii muscles of goats and examined whether faster motor units are recruited when locomotor speed is increased. The study also examined whether locomotor tasks that elicit faster (or slower) motor units are associated with increased (or decreased) in vivo tendon forces, force rise and relaxation rates, fascicle strains and/or strain rates. Electromyography (EMG), sonomicrometry and muscle-tendon force data were collected from the lateral and medial gastrocnemius muscles of goats during level walking, trotting and galloping and during inclined walking and trotting. EMG signals were analyzed using wavelet and principal component analyses to quantify changes in the EMG frequency spectra across the different locomotor conditions. Fascicle strain and strain rate were calculated from the sonomicrometric data, and force rise and relaxation rates were determined from the tendon force data. The results of this study showed that faster motor units were recruited as goats increased their locomotor speeds from level walking to galloping. Slow inclined walking elicited EMG intensities similar to those of fast level galloping but different EMG frequency spectra, indicating that recruitment of the different motor unit types depended, in part, on characteristics of the task. For the locomotor tasks and muscles analyzed here, recruitment patterns were generally associated with in vivo fascicle strain rates, EMG intensity and tendon force. Together, these data provide new evidence that changes in motor unit recruitment have an underlying mechanical basis, at least for certain locomotor tasks.

Chemical energetics of force development, force maintenance, and relaxation in mammalian smooth muscle

PubMed Central

1980-01-01

High-energy phosphate utilization (delta approximately P) associated with force development, force maintenance, and relaxation has been determined during single isometric tetani in the rabbit taenia coli. ATP resynthesis from glycolysis and respiration was stopped without deleterious effects on the muscle. At 18 degrees C and a muscle length of 95% l0, the resting rate of energy utilization is 1.8 +/- 0.2 nmol/g . s-1, or 0.85 +/- 0.2 mmol approximately P/mol of total creatine (Ct) . s-1, where Ct = 2.7 mumol/g wet wt. During the initial 25 s of stimulation when force is developed, the average rate of delta approximately P was -8.2 +/- 0.8 mmol/mol Ct . s-1, some four times greater than during the subsequent 35 s of force maintenance, when the rate was -2.0 +/- 0.6 mmol approximately P/mol Ct . s-1. The energy cost of force redevelopment (0 to 95% P0) after a quick release from the peak of a tetanus is very low compared with the initial force development. Therefore, the high rate of energy utilization during force development is not due only to internal work done against the series elasticity nor to any high rate of cross-bridge cycling inherently associated with force development. The high economy of force maintenance compared with other muscle types is undoubtedly due to a slower cross-bridge cycle time. The energy utilization during 45 s of relaxation was not statistically significant, and integral of Pdt/delta approximately P was higher during relaxation than during force maintenance in the stimulated muscle. PMID:6969290

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dang, Liem X.; Vo, Quynh N.; Nilsson, Mikael

We report one of the first simulations using a classical rate theory approach to predict the mechanism of the exchange process between water and aqueous uranyl ions. Using our water and ion-water polarizable force fields and molecular dynamics techniques, we computed the potentials of mean force for the uranyl ion-water pair as the function of pressures at ambient temperature. Subsequently, these simulated potentials of mean force were used to calculate rate constants using the transition rate theory; the time dependent transmission coefficients were also examined using the reactive flux method and Grote-Hynes treatments of the dynamic response of the solvent.more » The computed activation volumes using transition rate theory and the corrected rate constants are positive, thus the mechanism of this particular water-exchange is a dissociative process. We discuss our rate theory results and compare them with previously studies in which non-polarizable force fields were used. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.« less

Prediction of Bubble Diameter at Detachment from a Wall Orifice in Liquid Cross Flow Under Reduced and Normal Gravity Conditions

NASA Technical Reports Server (NTRS)

Nahra, Henry K.; Kamotani, Y.

2003-01-01

Bubble formation and detachment is an integral part of the two-phase flow science. The objective of the present work is to theoretically investigate the effects of liquid cross-flow velocity, gas flow rate embodied in the momentum flux force, and orifice diameter on bubble formation in a wall-bubble injection configuration. A two-dimensional one-stage theoretical model based on a global force balance on the bubble evolving from a wall orifice in a cross liquid flow is presented in this work. In this model, relevant forces acting on the evolving bubble are expressed in terms of the bubble center of mass coordinates and solved simultaneously. Relevant forces in low gravity included the momentum flux, shear-lift, surface tension, drag and inertia forces. Under normal gravity conditions, the buoyancy force, which is dominant under such conditions, can be added to the force balance. Two detachment criteria were applicable depending on the gas to liquid momentum force ratio. For low ratios, the time when the bubble acceleration in the direction of the detachment angle is greater or equal to zero is calculated from the bubble x and y coordinates. This time is taken as the time at which all the detaching forces that are acting on the bubble are greater or equal to the attaching forces. For high gas to liquid momentum force ratios, the time at which the y coordinate less the bubble radius equals zero is calculated. The bubble diameter is evaluated at this time as the diameter at detachment from the fact that the bubble volume is simply given by the product of the gas flow rate and time elapsed. Comparison of the model s predictions was also made with predictions from a two-dimensional normal gravity model based on Kumar-Kuloor formulation and such a comparison is presented in this work.

Amended annual report for Brookhaven National Laboratory: Epidemiologic surveillance - 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

Epidemiologic surveillance at DOE facilities consists of regular and systematic collection, analysis, and interpretation of data on absences due to illness and injury in the work force. Its purpose is to provide an early warning system for health problems occurring among employees at participating sites. Data are collected by coordinators at each site and submitted to the Epidemiologic Surveillance Data Center, located at the Oak Ridge Institute for Science and Education, where quality control procedures and analyses are carried out. Rates of absences and rates of diagnoses associated with absences are analyzed by occupation and other relevant variables. They maymore » be compared with the disease experience of different groups within the DOE work force and with populations and do not work for DOE to identify disease patterns or clusters that may be associated work activities. This report provides a final summary for BNL.« less

Annual report for Hanford Site: Epidemiologic surveillance - 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1998-01-01

Epidemiologic surveillance at U.S. Department of Energy (DOE) facilities consists of regular and systematic collection, analysis, and interpretation of data on absences due to illness and injury in the work force. Its purpose is to provide an early warning system for health problems occurring among employees at participating sites. Data are collected by coordinators at each site and submitted to the Epidemiologic Surveillance Data Center, located at the Oak Ridge Institute for Science and Education, where quality control procedures and analyses are carried out. Rates of absences and rates of diagnoses associated with absences are analyzed by occupational and othermore » relevant variables. They may be compared with the disease experience of different groups within the DOE work force and with populations that do not work for DOE to identify disease patterns or clusters that may be associated with work activities.This report provides the final summary for the Hanford Reservation.« less

Epidemiologic surveillance. Annual report for EG&G Rocky Flats

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1994-12-31

Epidemiologic surveillance at U.S. Department of Energy (DOE) facilities consists of regular and systematic collection, analysis, and interpretation of data on absences resulting from illness and injury in the work force. Its purpose is to provide an early warning system for health problems occurring among employees at participating sites. Data are collected by coordinators at each site and submitted to the Epidemiologic Surveillance Data Center, located at the Oak Ridge Institute for Science and Education, where quality control procedures and analyses are carried out. Rates of absences and rates of diagnoses associated with absences are analyzed by occupation and othermore » relevant variables. They may be compared with the disease experience of different groups within the DOE work force and with populations that do not work for DOE to identify disease patterns or clusters that may be associated with work activities. This report presents the 1994 morbidity data for the Rocky Flats plant.« less

Principles of Technology Curriculum Guide. Curriculum Development. Bulletin 1812.

ERIC Educational Resources Information Center

Louisiana State Dept. of Education, Baton Rouge. Div. of Vocational Education.

This document describes minimum competencies and suggested student activities for a seven-unit course called Principles of Technology. The instructional units are called Force, Work, Rate, Resistance, Energy, Power, and Force Transformers. The first section of the document contains information on how to use the guide, goals for industrial…

Understanding Unemployment. "Understanding Economics" Series No. 1.

ERIC Educational Resources Information Center

Holt, Geoffrey

Devised for secondary school students, the booklet explains current employment trends, policies, and issues of Canada's labor market. The book is divided into three parts. Part I discusses the labor force in terms of supply and demand, the working age population, the labor force participation rate, total employment, unemployment, and seasonal…

In-vivo force decay of nickel-titanium closed-coil springs.

PubMed

Cox, Crystal; Nguyen, Tung; Koroluk, Lorne; Ko, Ching-Chang

2014-04-01

Nickel-titanium closed-coil springs are purported to deliver constant forces over extended ranges of activation and working times. In-vivo studies supporting this claim are limited. The objective of this study was to evaluate changes in force-decay properties of nickel-titanium closed-coil springs after clinical use. Pseudoelastic force-deflection curves for 30 nickel-titanium coil springs (used intraorally) and 15 matched laboratory control springs (simulated intraoral conditions: artificial saliva, 37°C) were tested before and after retrieval via dynamic mechanical analysis and a testing machine, respectively, to evaluate the amounts of force-loss and hysteresis change after 4, 8, or 12 weeks of working time (n = 10 per group). The effects of the oral environment and clinical use on force properties were evaluated by comparing in-vivo and in-vitro data. The springs studied showed a statistically significant decrease in force (approximately 12%) after 4 weeks of clinical use (P <0.01), with a further significant decrease (approximately 7%) from 4 to 8 weeks (P = 0.03), and force levels appearing to remain steady thereafter. Clinical space closure at an average rate of 0.91 mm per month was still observed despite this decrease in force. In-vivo and in-vitro force-loss data were not statistically different. Nickel-titanium closed-coil springs do not deliver constant forces when used intraorally, but they still allow for space-closure rates of approximately 1 mm per month. Copyright © 2014 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Exploring physical exposures and identifying high-risk work tasks within the floor layer trade

PubMed Central

McGaha, Jamie; Miller, Kim; Descatha, Alexis; Welch, Laurie; Buchholz, Bryan; Evanoff, Bradley; Dale, Ann Marie

2014-01-01

Introduction Floor layers have high rates of musculoskeletal disorders yet few studies have examined their work exposures. This study used observational methods to describe physical exposures within floor laying tasks. Methods We analyzed 45 videos from 32 floor layers using Multimedia-Video Task Analysis software to determine the time in task, forces, postures, and repetitive hand movements for installation of four common flooring materials. We used the WISHA checklists to define exposure thresholds. Results Most workers (91%) met the caution threshold for one or more exposures. Workers showed high exposures in multiple body parts with variability in exposures across tasks and for different materials. Prolonged exposures were seen for kneeling, poor neck and low back postures, and intermittent but frequent hand grip forces. Conclusions Floor layers experience prolonged awkward postures and high force physical exposures in multiple body parts, which probably contribute to their high rates of musculoskeletal disorders. PMID:24274895

[Impact and forecasting of hepatitis A immunization in French armed forces, 1990-2004].

PubMed

Richard, V; Haus, R; Verret, C; Molinier, S; Hugard, L; Nicand, E; Spiegel, A; Buisson, Y

2006-10-01

Hepatitis A is a public health problem specially for migrants or travellers from industrialized countries with a low hepatitis A endemic level. French armed forces adopted an immunization strategy which first targeted overseas forces and subsequently was extended to all armed forces. In this work we studied the impact of this policy. Epidemiological surveillance data from 1990 to 2004 was analyzed by Poisson regression and exponential models of decrease used to forecast future rates. From the 826 cases of hepatitis A reported during the study period, 266 (32.2%) occurred in overseas forces and 560 (67.8%) in forces stationed in France. Three periods could be identified in the decline of annual incidence: before 1994, with an average rate of 23.2 per 100,000; from 1994 to 1998: 10.2; and after 1998: 1.2 for all French armed forces. For overseas armed forces, the average rate was 117 per 100,000 before 1994 and 17.1 from 1994 to 1998 (p<0.001). For armed forces stationed in France, the average rate was 12.2 per 100,000 before 1998 and 0.9 after (p<0.001). For overseas armed forces, models clearly described the declining incidence subsequent to targeted immunization in 1995 and for armed forces stationed in France, the decline with generalized immunization starting in 1998. The impact of immunization against hepatitis A virus was significant both in an overseas population and in a population staying in France where the risk level can be considered low due to the low endemic rate in France. These results suggest that immunization should be proposed not only for travellers but also for the general population based on real knowledge of the situation and cost-effectiveness analyses.

Tunisia.

PubMed

1987-02-01

In 1986, Tunisia's population was 7,424,000, with an annual growth rate of 2.5%. The infant mortality rate was 90/1000 and life expectancy averages 58 years. The work force of 1,810,000 is distributed as follows: agriculture, 30.5%; manufacturing, 16.5%; services, 15.0%; construction and mining, 11.4%; and other, 26.6%. The gross domestic product was US$8.35 billion in 1985, with a per capita income (1986) of $1163. The Destourian Socialist Party has been the governing party in Tunisia since independence. Tunisia is a leader in the Arab world in the promotion of equal status for women under the law and the government supports an active family planning program. Tunisia's economy depends on oil, agriculture, phosphates, worker remittances, and tourism for economic growth. In response to an economic crisis in 1985-86, measures to restructure the economy were instituted, including basic commodity price increases, limits on wage increases, import liberalization, and price control modifications. Unemployment, aggravated by a rapidly growing work force, is a major problem in Tunisia. An estimated 50% of the potential work force is unemployed or underemployed.

Labor Force Experience and Earnings: Women with Children.

ERIC Educational Resources Information Center

Levine, Victor; Moock, Peter R.

1984-01-01

Examines the influence of child-related reductions in past hours worked on current wage rate of married women with children. The study reveals that differences in "intensity" of prior work experience account for half of the sex-related wage gap. (TE)

Soldier 2020 Injury Rates/Attrition Rates Working Group Medical Recommendations

DTIC Science & Technology

2015-06-24

upon arrival and are currently being provided a multivitamin in Basic Military Training. Female Specific Issues Pregnancy ...Approximately 5% of female Soldiers are pregnant at any given time. • This calculates to ~0.75% of the total force not available due to pregnancy and postpartum...performance Pregnancy affects approximately 0.75% of the total Army force at any given time M E D I C A L R E A D I N E S S Select SLIDE MASTER to Insert

The Effect of Increasing Mass upon Locomotion

NASA Technical Reports Server (NTRS)

DeWitt, John; Hagan, Donald

2007-01-01

The purpose of this investigation was to determine if increasing body mass while maintaining bodyweight would affect ground reaction forces and joint kinetics during walking and running. It was hypothesized that performing gait with increased mass while maintaining body weight would result in greater ground reaction forces, and would affect the net joint torques and work at the ankle, knee and hip when compared to gait with normal mass and bodyweight. Vertical ground reaction force was measured for ten subjects (5M/5F) during walking (1.34 m/s) and running (3.13 m/s) on a treadmill. Subjects completed one minute of locomotion at normal mass and bodyweight and at four added mass (AM) conditions (10%, 20%, 30% and 40% of body mass) in random order. Three-dimensional joint position data were collected via videography. Walking and running were analyzed separately. The addition of mass resulted in several effects. Peak impact forces and loading rates increased during walking, but decreased during running. Peak propulsive forces decreased during walking and did not change during running. Stride time increased and hip extensor angular impulse and positive work increased as mass was added for both styles of locomotion. Work increased at a greater rate during running than walking. The adaptations to additional mass that occur during walking are different than during running. Increasing mass during exercise in microgravity may be beneficial to increasing ground reaction forces during walking and strengthening hip musculature during both walking and running. Future study in true microgravity is required to determine if the adaptations found would be similar in a weightless environment.

The One World of Working Women. Monograph No. 1.

ERIC Educational Resources Information Center

Nelson, Anne H.

Women of many nations, particularly the industrialized countries, are achieving greater opportunity and equality in the working world. The rate at which women are joining the work force has confounded all predictions and created unexpected difficulties in securing equal pay and access to jobs and training. The most direct discrimination, separate…

Heart rate detection from an electronic weighing scale.

PubMed

González-Landaeta, R; Casas, O; Pallàs-Areny, R

2008-08-01

We propose a novel technique for beat-to-beat heart rate detection based on the ballistocardiographic (BCG) force signal from a subject standing on a common electronic weighing scale. The detection relies on sensing force variations related to the blood acceleration in the aorta, works even if wearing footwear and does not require any sensors attached to the body because it uses the load cells in the scale. We have devised an approach to estimate the sensitivity and frequency response of three commercial weighing scales to assess their capability to detect the BCG force signal. Static sensitivities ranged from 490 nV V(-1) N(-1) to 1670 nV V(-1) N(-1). The frequency response depended on the subject's mass but it was broad enough for heart rate estimation. We have designed an electronic pulse detection system based on off-the-shelf integrated circuits to sense heart-beat-related force variations of about 0.24 N. The signal-to-noise ratio of the main peaks of the force signal detected was higher than 30 dB. A Bland-Altman plot was used to compare the RR time intervals estimated from the ECG and BCG force signals for 17 volunteers. The error was +/-21 ms, which makes the proposed technique suitable for short-term monitoring of the heart rate.

Trends in the Danish work environment in 1990-2000 and their associations with labor-force changes.

PubMed

Burr, Hermann; Bjorner, Jakob B; Kristensen, Tage S; Tüchsen, Finn; Bach, Elsa

2003-08-01

The aims of this study were (i) to describe the trends in the work environment in 1990-2000 among employees in Denmark and (ii) to establish whether these trends were attributable to labor-force changes. The split-panel design of the Danish Work Environment Cohort Study includes interviews with three cross-sections of 6067, 5454, and 5404 employees aged 18-59 years, each representative of the total Danish labor force in 1990, 1995 and 2000. In the cross-sections, the participation rate decreased over the period (90% in 1990, 80% in 1995, 76% in 2000). The relative differences in participation due to gender, age, and region did not change noticeably. Jobs with decreasing prevalence were clerks, cleaners, textile workers, and military personnel. Jobs with increasing prevalence were academics, computer professionals, and managers. Intense computer use, long workhours, and noise exposure increased. Job insecurity, part-time work, kneeling work posture, low job control, and skin contact with cleaning agents decreased. Labor-force changes fully explained the decline in low job control and skin contact to cleaning agents and half of the increase in long workhours, but not the other work environment changes. The work environment of Danish employees improved from 1990 to 2000, except for increases in long workhours and noise exposure. From a specific work environment intervention point of view, the development has been less encouraging because declines in low job control, as well as skin contact to cleaning agents, were explained by labor-force changes.

Stress analysis of mandibular implant overdenture with locator and bar/clip attachment: Comparative study with differences in the denture base length.

PubMed

Yoo, Jin Suk; Kwon, Kung-Rock; Noh, Kwantae; Lee, Hyeonjong; Paek, Janghyun

2017-06-01

The design of the attachment must provide an optimum stress distribution around the implant. In this study, for implant overdentures with a bar/clip attachment or a locator attachment, the stress transmitted to the implant in accordance with the change in the denture base length and the vertical pressure was measured and analyzed. Test model was created with epoxy resin. The strain gauges made a tight contact with implant surfaces. A universal testing machine was used to exert a vertical pressure on the mandibular implant overdenture and the strain rate of the implants was measured. Means and standard deviations of the maximum micro-deformation rates were determined. 1) Locator attachment: The implants on the working side generally showed higher strain than those on the non-working side. Tensile force was observed on the mesial surface of the implant on the working side, and the compressive force was applied to the buccal surface and on the surfaces of the implant on the non-working side. 2) Bar/clip attachment: The implants on the both non-working and working sides showed high strain; all surfaces except the mesial surface of the implant on the non-working side showed a compressive force. To minimize the strain on implants in mandibular implant overdentures, the attachment of the implant should be carefully selected and the denture base should be extended as much as possible.

Population and labour force growth and patterns in ASEAN countries.

PubMed

Saw, S

1988-01-01

"The paper shows that the diverse labor dimensions prevailing in the ASEAN region can be attributed to changes in the structure of the society and economy in the course of recent economic development. It observes the considerable variety in the growth of the population and its effect on the labor force in the ASEAN region.... The paper details the similarity and diversity in the level and type of labor force participation rates. A common feature shared by ASEAN countries is a general pattern in the age-specific participation rate of men. In contrast, the women, aside from participating in the labor force at a much lower level than men at almost all ages, display diverse patterns of participation over the working age range. Lastly, the distribution of the labor force according to major industrial sectors in the six ASEAN countries is presented...." excerpt

Prediction of Cutting Force in Turning Process-an Experimental Approach

NASA Astrophysics Data System (ADS)

Thangarasu, S. K.; Shankar, S.; Thomas, A. Tony; Sridhar, G.

2018-02-01

This Paper deals with a prediction of Cutting forces in a turning process. The turning process with advanced cutting tool has a several advantages over grinding such as short cycle time, process flexibility, compatible surface roughness, high material removal rate and less environment problems without the use of cutting fluid. In this a full bridge dynamometer has been used to measure the cutting forces over mild steel work piece and cemented carbide insert tool for different combination of cutting speed, feed rate and depth of cut. The experiments are planned based on taguchi design and measured cutting forces were compared with the predicted forces in order to validate the feasibility of the proposed design. The percentage contribution of each process parameter had been analyzed using Analysis of Variance (ANOVA). Both the experimental results taken from the lathe tool dynamometer and the designed full bridge dynamometer were analyzed using Taguchi design of experiment and Analysis of Variance.

45 CFR 270.5 - What factors will we use to determine a State's score on the work measures?

Code of Federal Regulations, 2010 CFR

2010-10-01

... Force Rate is composed of two equally weighted sub-measures defined as follows: (i) The Job Retention...-measures defined as follows: (i) The Increase in the Job Retention Rate means the percentage point difference between the job retention rate for the performance year and the job retention rate for the...

[Older female employees in Germany - structures of employment and perspectives of the future].

PubMed

Clemens, W

2006-02-01

This contribution presents an overview to the structures and conditions of employment of older female employees in Germany. Based on information about the labor force participation rates, rates of unemployment and occupational patterns the conditions of female employment beyond midlife are examined. Relating to the standard of living, the meaning of employment for older women is discussed. Furthermore, the effects of regulations of welfare state, i. e., pension systems, on future life of the employed women are highlighted. Further topics are the completion of working life and the transition to retirement of female employees, the issue of the future working conditions of older female employees related with demographic change und future reduction of the potential of labor force. Finally the contribution stresses the importance of a holistic approach to investigate the living and working conditions of older female employees.

Epidemiologic surveillance. [1994] amended annual report for Brookhaven National Laboratory. Revision 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1994-12-31

Epidemiologic surveillance at DOE facilities consists of regular and systematic collection, analysis, and interpretation of data on absences due to illness and injury in the work force. Its purpose is to provide an early warning system for health problems occurring among employees at participating sites. Data are collected by coordinators at each site and submitted to the Epidemiologic Surveillance Data Center, located at the Oak Ridge Institute for Science and Education, where quality control procedures and analyses are carried out. Rates of absences and rates of diagnoses associated with absences are analyzed by occupation and other relevant variables. They maymore » be compared with the disease experience of different groups within the DOE work force and with populations that do not work for DOE to identify disease patterns or clusters that may be associated with work activities. This amended annual report corrects errors in the initial release of the BNL report for 1994. In this annual report, the 1994 morbidity data for BNL are summarized.« less

Accuracy and precision of loadsol® insole force-sensors for the quantification of ground reaction force-based biomechanical running parameters.

PubMed

Seiberl, Wolfgang; Jensen, Elisabeth; Merker, Josephine; Leitel, Marco; Schwirtz, Ansgar

2018-05-29

Force plates represent the "gold standard" in measuring running kinetics to predict performance or to identify the sources of running-related injuries. As these measurements are generally limited to laboratory analyses, wireless high-quality sensors for measuring in the field are needed. This work analysed the accuracy and precision of a new wireless insole forcesensor for quantifying running-related kinetic parameters. Vertical ground reaction force (GRF) was simultaneously measured with pit-mounted force plates (1 kHz) and loadsol ® sensors (100 Hz) under unshod forefoot and rearfoot running-step conditions. GRF data collections were repeated four times, each separated by 30 min treadmill running, to test influence of extended use. A repeated-measures ANOVA was used to identify differences between measurement devices. Additionally, mean bias and Bland-Altman limits of agreement (LoA) were calculated. We found a significant difference (p < .05) in ground contact time, peak force, and force rate, while there was no difference in parameters impulse, time to peak, and negative force rate. There was no influence of time point of measurement. The mean bias of ground contact time, impulse, peak force, and time to peak ranged between 0.6% and 3.4%, demonstrating high accuracy of loadsol ® devices for these parameters. For these same parameters, the LoA analysis showed that 95% of all measurement differences between insole and force plate measurements were less than 12%, demonstrating high precision of the sensors. However, highly dynamic behaviour of GRF, such as force rate, is not yet sufficiently resolved by the insole devices, which is likely explained by the low sampling rate.

WORKING AND CARING: THE SIMULTANEOUS DECISION OF LABOR FORCE PARTICIPATION AND INFORMAL ELDERLY AND CHILD SUPPORT ACT IVITIES IN MEXICO*

PubMed Central

van Gameren, Edwin; Velandia Naranjo, Durfari

2016-01-01

We analyze factors determining women’s decisions to participate in the labor market and provide elderly care and nonfinancial support to their (grand)children. We use data from the Mexican Health and Aging Study, a survey of people aged 50 and over, applying a three-equation, reduced-form SUR model. Results suggest that care needs are the driving force behind caregiving activities. Traditional roles also appear to be relevant in the labor force participation decision: women with a closer labor market connection when they were young are more likely to work. Simulations of demographic changes illustrate potential effects for future caregiving and participation rates. PMID:26924883

Regional income inequality model based on theil index decomposition and weighted variance coeficient

NASA Astrophysics Data System (ADS)

Sitepu, H. R.; Darnius, O.; Tambunan, W. N.

2018-03-01

Regional income inequality is an important issue in the study on economic development of a certain region. Rapid economic development may not in accordance with people’s per capita income. The method of measuring the regional income inequality has been suggested by many experts. This research used Theil index and weighted variance coefficient in order to measure the regional income inequality. Regional income decomposition which becomes the productivity of work force and their participation in regional income inequality, based on Theil index, can be presented in linear relation. When the economic assumption in j sector, sectoral income value, and the rate of work force are used, the work force productivity imbalance can be decomposed to become the component in sectors and in intra-sectors. Next, weighted variation coefficient is defined in the revenue and productivity of the work force. From the quadrate of the weighted variation coefficient result, it was found that decomposition of regional revenue imbalance could be analyzed by finding out how far each component contribute to regional imbalance which, in this research, was analyzed in nine sectors of economic business.

Measured Properties of Turbulent Premixed Flames for Model Assessment, Including Burning Velocities, Stretch Rates, and Surface Densities (Postprint)

DTIC Science & Technology

2006-10-01

Engineering) Campbell D. Carter and Jeffrey M. Donbar (Aerospace Propulsion Division, Propulsion Sciences Branch (AFRL/ PRAS )) 5f. WORK UNIT NUMBER...Sciences Branch (AFRL/ PRAS ) Propulsion Directorate Air Force Research Laboratory, Air Force Materiel Command Wright-Patterson AFB, OH 45433-7251 Uni. of...M. Donbar b a Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109, USA b Air Force Research Laboratory AFRL/ PRAS , Wright

The ATP hydrolysis and phosphate release steps control the time course of force development in rabbit skeletal muscle.

PubMed

Sleep, John; Irving, Malcolm; Burton, Kevin

2005-03-15

The time course of isometric force development following photolytic release of ATP in the presence of Ca(2+) was characterized in single skinned fibres from rabbit psoas muscle. Pre-photolysis force was minimized using apyrase to remove contaminating ATP and ADP. After the initial force rise induced by ATP release, a rapid shortening ramp terminated by a step stretch to the original length was imposed, and the time course of the subsequent force redevelopment was again characterized. Force development after ATP release was accurately described by a lag phase followed by one or two exponential components. At 20 degrees C, the lag was 5.6 +/- 0.4 ms (s.e.m., n = 11), and the force rise was well fitted by a single exponential with rate constant 71 +/- 4 s(-1). Force redevelopment after shortening-restretch began from about half the plateau force level, and its single-exponential rate constant was 68 +/- 3 s(-1), very similar to that following ATP release. When fibres were activated by the addition of Ca(2+) in ATP-containing solution, force developed more slowly, and the rate constant for force redevelopment following shortening-restretch reached a maximum value of 38 +/- 4 s(-1) (n = 6) after about 6 s of activation. This lower value may be associated with progressive sarcomere disorder at elevated temperature. Force development following ATP release was much slower at 5 degrees C than at 20 degrees C. The rate constant of a single-exponential fit to the force rise was 4.3 +/- 0.4 s(-1) (n = 22), and this was again similar to that after shortening-restretch in the same activation at this temperature, 3.8 +/- 0.2 s(-1). We conclude that force development after ATP release and shortening-restretch are controlled by the same steps in the actin-myosin ATPase cycle. The present results and much previous work on mechanical-chemical coupling in muscle can be explained by a kinetic scheme in which force is generated by a rapid conformational change bracketed by two biochemical steps with similar rate constants -- ATP hydrolysis and the release of inorganic phosphate -- both of which combine to control the rate of force development.

Insights into the relation between adhesion force and chalcopyrite-bioleaching by Acidithiobacillus ferrooxidans.

PubMed

Zhu, Jianyu; Wang, Qianfen; Zhou, Shuang; Li, Qian; Gan, Min; Jiang, Hao; Qin, Wenqing; Liu, Xueduan; Hu, Yuehua; Qiu, Guanzhou

2015-02-01

This paper presents a study on the relation between bacterial adhesion force and bioleaching rate of chalcopyrite, which sheds light on the influence of interfacial interaction on bioleaching behavior. In our research, Acidithiobacillus ferrooxidans (A. ferrooxidans) were adapted to grow with FeSO4 · 7H2O, element sulfur or chalcopyrite. Then, surface properties of Acidithiobacillus ferrooxidans and chalcopyrite were analyzed by contact angle, zeta potential and Fourier transform infrared spectroscopy (FTIR). Adhesion force between bacteria and chalcopyrite was measured by atomic force microscopy (AFM). Attachment and bioleaching behaviors were also monitored. The results showed that A. ferrooxidans adapted with chalcopyrite exhibited the strongest adhesion force to chalcopyrite and the highest bioleaching rate. Culture adapted with sulfur bacteria took second place and FeSO4 · 7H2O-adapted bacteria were the lowest. Bioleaching rate and bacterial attachment capacity were positively related to bacterial adhesion force, which is affected by the nature of energy source. According to this work, the attachment of bacteria to chalcopyrite surface is one of the most important aspects that influence the bioleaching process of chalcopyrite. Copyright © 2014 Elsevier B.V. All rights reserved.

Laboratory Observations of Sand Ripple Evolution in a Small Oscillatory Flow Tunnel

NASA Astrophysics Data System (ADS)

Calantoni, J.; Palmsten, M. L.; Chu, J.; Landry, B. J.; Penko, A.

2014-12-01

The dynamics of sand ripples are vital to understanding numerous coastal processes such as sediment transport, wave attenuation, boundary layer development, and seafloor acoustic properties. Experimental work was conducted in a small oscillatory flow tunnel at the Sediment Dynamics Laboratory at the Naval Research Laboratory, Stennis Space Center. Six different monochromatic oscillatory forcings, three with velocity asymmetry and three without, were used to investigate sand ripple dynamics using a unimodal grain size distribution with D50=0.65 mm. The experiments represent an extension of previous work using bimodal grain size distributions. A DSLR camera with a 180-degree fisheye lens collected images of the sediment bed profile every 2 seconds to resolve changes in ripple geometries and migration rates resulting from the different flow conditions for over 127 hours (229,388 images). Matlab © algorithms undistorted the fisheye images and quantified the ripple geometries, wavelengths, heights, and migration rates as a function of flow forcing. The mobility number was kept nearly constant by increasing and decreasing the semi-excursion amplitude and the wave frequency, respectively. We observed distinct changes in ripple geometry and migration rate for the pair of oscillatory forcings having nearly identical mobility numbers. The results suggested that the commonly used mobility number might not be appropriate to characterize ripple geometry or migration rates.

Contributions of nanodiamond abrasives and deionized water in magnetorheological finishing of aluminum oxynitriden

NASA Astrophysics Data System (ADS)

Miao, Chunlin; Lambropoulos, John C.; Romanofsky, Henry; Shafrir, Shai N.; Jacobs, Stephen D.

2009-08-01

Magnetorheological finishing (MRF) is a sub-aperture deterministic process for fabricating high-precision optics by removing material and smoothing the surface. The goal of this work is to study the relative contribution of nanodiamonds and water in material removal for MRF of aluminum oxynitride ceramic (ALON) based upon a nonaqueous magnetorheological (MR) fluid. Removal was enhanced by a high carbonyl iron concentration and the addition of nanodiamond abrasives. Small amounts of deionized (DI) water were introduced into the nonaqueous MR fluid to further influence the material removal process. Material removal data were collected with a spot-taking machine. Drag force (Fd) and normal force (Fn) before and after adding nanodiamonds or DI water were measured with a dual load cell. Both drag force and normal force were insensitive to the addition of nanodiamonds but increased with DI water content in the nonaqueous MR fluid. Shear stress (i.e., drag force divided by spot area) was calculated, and examined as a function of nanodiamond concentration and DI water concentration. Volumetric removal rate increased with increasing shear stress, which was shown to be a result of increasing viscosity after adding nanodiamonds and DI water. This work demonstrates that removal rate for a hard ceramic with MRF can be enhanced by adding DI water into a nonaqueous MR fluid.

Intercountry comparisons of labor force trends and of related developments: an overview.

PubMed

Mincer, J

1985-01-01

This paper is a survey of analyses of women's labor force growth in 12 industrialized countries, presented at a conference in Sussex, England in 1983. The main focus is on growth of the labor force of married women from 1960-1980; trends in fertility, wages, and family instability are discussed. In all countries, wages of women were lower than wages of men, although between 1960 and 1980 labor force rates of married women rose in most of the industrialized countries. 2 factors that are associated with this growth are declines in fertility and increases in divorce rates. The 12 countries studied are: 1) Australia, 2) Britain, 3) France, 4) Germany, 5) Israel, 6) Italy, 7) Japan, 8) Netherlands, 9) Spain, 10) Sweden, 11) US, and 12) USSR. The substitution variables (wages of women or their education) have strong positive effects on labor force participation in most cases, and in most cases the positive wage elasticities exceed the negative income elasticities by a sizable margin. A summary table estimating parameters of the P-function for each country, and their predictive performance in time series, are included. From 1960-1980 the average per country growth in participation of married women was 2.84% per year. Wages of working women, in this same period grew, on average, faster than wages of men in most countries, in part due to selectivity by education in labor force growth. While growth rates of real wages across countries have a weak relation with the differential growth rates of married women's labor force, the relation is strong when country parameters are taken into account. The dominance of the "discouraged" over the "added" workers in female labor force growth appears to be upheld internationally. On the average, total fertility rate dropped from 2.42 in 1970 to 1.85 in 1980. Both fertility declines and the growth of family instability appear to represent lagged effects of longer term developments in the labor force of women. Women's wages are lower than men's wages in all countries; wage differentials narrowed in all other countries over the past 2 decades. This narrowing was due both to women's educational attainment catching up with men's, and to a positive educational selectivity of women's labor force growth during this period. Ultimately, without labor market discrimination and with equal educational attainment, the wage gap can be eliminated only when sex differences in lifetime work experience vanish.

Utility of Equations to Estimate Peak Oxygen Uptake and Work Rate From a 6-Minute Walk Test in Patients With COPD in a Clinical Setting.

PubMed

Kirkham, Amy A; Pauhl, Katherine E; Elliott, Robyn M; Scott, Jen A; Doria, Silvana C; Davidson, Hanan K; Neil-Sztramko, Sarah E; Campbell, Kristin L; Camp, Pat G

2015-01-01

To determine the utility of equations that use the 6-minute walk test (6MWT) results to estimate peak oxygen uptake ((Equation is included in full-text article.)o2) and peak work rate with chronic obstructive pulmonary disease (COPD) patients in a clinical setting. This study included a systematic review to identify published equations estimating peak (Equation is included in full-text article.)o2 and peak work rate in watts in COPD patients and a retrospective chart review of data from a hospital-based pulmonary rehabilitation program. The following variables were abstracted from the records of 42 consecutively enrolled COPD patients: measured peak (Equation is included in full-text article.)o2 and peak work rate achieved during a cycle ergometer cardiopulmonary exercise test, 6MWT distance, age, sex, weight, height, forced expiratory volume in 1 second, forced vital capacity, and lung diffusion capacity. Estimated peak (Equation is included in full-text article.)o2 and peak work rate were estimated from 6MWT distance using published equations. The error associated with using estimated peak (Equation is included in full-text article.)o2 or peak work to prescribe aerobic exercise intensities of 60% and 80% was calculated. Eleven equations from 6 studies were identified. Agreement between estimated and measured values was poor to moderate (intraclass correlation coefficients = 0.11-0.63). The error associated with using estimated peak (Equation is included in full-text article.)o2 or peak work rate to prescribe exercise intensities of 60% and 80% of measured values ranged from mean differences of 12 to 35 and 16 to 47 percentage points, respectively. There is poor to moderate agreement between measured peak (Equation is included in full-text article.)o2 and peak work rate and estimations from equations that use 6MWT distance, and the use of the estimated values for prescription of aerobic exercise intensity would result in large error. Equations estimating peak (Equation is included in full-text article.)o2 and peak work rate are of low utility for prescribing exercise intensity in pulmonary rehabilitation programs.

AN IN SILICO INVESTIGATION OF THE ENANTIOSELECTIVE METABOLISM RATES OF TRIAZOLE FUGICIDES

EPA Science Inventory

The objective of this work is to use in silico methods such as ab initio quantum and classical force-field methods to explore and develop an understanding for the enantioselective metabolism rates experimentally observed in the triazole fungicide bromuconazole. This directed stud...

Normal force and drag force in magnetorheological finishing

NASA Astrophysics Data System (ADS)

Miao, Chunlin; Shafrir, Shai N.; Lambropoulos, John C.; Jacobs, Stephen D.

2009-08-01

The material removal in magnetorheological finishing (MRF) is known to be controlled by shear stress, λ, which equals drag force, Fd, divided by spot area, As. However, it is unclear how the normal force, Fn, affects the material removal in MRF and how the measured ratio of drag force to normal force Fd/Fn, equivalent to coefficient of friction, is related to material removal. This work studies, for the first time for MRF, the normal force and the measured ratio Fd/Fn as a function of material mechanical properties. Experimental data were obtained by taking spots on a variety of materials including optical glasses and hard ceramics with a spot-taking machine (STM). Drag force and normal force were measured with a dual load cell. Drag force decreases linearly with increasing material hardness. In contrast, normal force increases with hardness for glasses, saturating at high hardness values for ceramics. Volumetric removal rate decreases with normal force across all materials. The measured ratio Fd/Fn shows a strong negative linear correlation with material hardness. Hard materials exhibit a low "coefficient of friction". The volumetric removal rate increases with the measured ratio Fd/Fn which is also correlated with shear stress, indicating that the measured ratio Fd/Fn is a useful measure of material removal in MRF.

Normal Force and Drag Force in Magnetorheological Finishing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, C.; Shafrir, S.N.; Lambropoulos, J.C.

2010-01-13

The material removal in magnetorheological finishing (MRF) is known to be controlled by shear stress, tau, which equals drag force, Fd, divided by spot area, As. However, it is unclear how the normal force, Fn, affects the material removal in MRF and how the measured ratio of drag force to normal force Fd/Fn, equivalent to coefficient of friction, is related to material removal. This work studies, for the first time for MRF, the normal force and the measured ratio Fd/Fn as a function of material mechanical properties. Experimental data were obtained by taking spots on a variety of materials includingmore » optical glasses and hard ceramics with a spot-taking machine (STM). Drag force and normal force were measured with a dual load cell. Drag force decreases linearly with increasing material hardness. In contrast, normal force increases with hardness for glasses, saturating at high hardness values for ceramics. Volumetric removal rate decreases with normal force across all materials. The measured ratio Fd/Fn shows a strong negative linear correlation with material hardness. Hard materials exhibit a low “coefficient of friction”. The volumetric removal rate increases with the measured ratio Fd/Fn which is also correlated with shear stress, indicating that the measured ratio Fd/Fn is a useful measure of material removal in MRF.« less

"Opt-Out" Rates at Motherhood across High-Education Career Paths: Selection versus Work Environment. NBER Working Paper No. 14717

ERIC Educational Resources Information Center

Herr, Jane Leber; Wolfram, Catherine

2009-01-01

This paper examines the propensity of highly educated women to exit the labor force at motherhood. We focus on systematic differences across women with various graduate degrees to analyze whether these speak to differences in the capacity to combine children with work over a variety of high-education career paths. Working with a sample of Harvard…

Principles of Technology. Final Report, Leander Independent School District.

ERIC Educational Resources Information Center

Leander Independent School District, TX.

Principles of Technology was designed as a high school course in applied science for vocational students in the 11th and 12th grades in Leander, Texas. It consists of a 2-year curriculum covering 14 units in applied physics: (1) force; (2) work; (3) rate; (4) resistance; (5) energy; (6) power; (7) force transformers; (8) momentum; (9) waves and…

Force-extension behavior of DNA in the presence of DNA-bending nucleoid associated proteins

NASA Astrophysics Data System (ADS)

Dahlke, K.; Sing, C. E.

2018-02-01

Interactions between nucleoid associated proteins (NAPs) and DNA affect DNA polymer conformation, leading to phenomena such as concentration dependent force-extension behavior. These effects, in turn, also impact the local binding behavior of the protein, such as high forces causing proteins to unbind, or proteins binding favorably to locally bent DNA. We develop a coarse-grained NAP-DNA simulation model that incorporates both force- and concentration-dependent behaviors, in order to study the interplay between NAP binding and DNA conformation. This model system includes multi-state protein binding and unbinding, motivated by prior work, but is now dependent on the local structure of the DNA, which is related to external forces acting on the DNA strand. We observe the expected qualitative binding behavior, where more proteins are bound at lower forces than at higher forces. Our model also includes NAP-induced DNA bending, which affects DNA elasticity. We see semi-quantitative matching of our simulated force-extension behavior to the reported experimental data. By using a coarse-grained simulation, we are also able to look at non-equilibrium behaviors, such as dynamic extension of a DNA strand. We stretch a DNA strand at different rates and at different NAP concentrations to observe how the time scales of the system (such as pulling time and unbinding time) work in concert. When these time scales are similar, we observe measurable rate-dependent changes in the system, which include the number of proteins bound and the force required to extend the DNA molecule. This suggests that the relative time scales of different dynamic processes play an important role in the behavior of NAP-DNA systems.

Volumetric flow rate in simulations of microfluidic devices+

NASA Astrophysics Data System (ADS)

Kovalčíková, KristÍna; Slavík, Martin; Bachratá, Katarína; Bachratý, Hynek; Bohiniková, Alžbeta

2018-06-01

In this work, we examine the volumetric flow rate of microfluidic devices. The volumetric flow rate is a parameter which is necessary to correctly set up a simulation of a real device and to check the conformity of a simulation and a laboratory experiments [1]. Instead of defining the volumetric rate at the beginning as a simulation parameter, a parameter of external force is set. The proposed hypothesis is that for a fixed set of other parameters (topology, viscosity of the liquid, …) the volumetric flow rate is linearly dependent on external force in typical ranges of fluid velocity used in our simulations. To confirm this linearity hypothesis and to find numerical limits of this approach, we test several values of the external force parameter. The tests are designed for three different topologies of simulation box and for various haematocrits. The topologies of the microfluidic devices are inspired by existing laboratory experiments [3 - 6]. The linear relationship between the external force and the volumetric flow rate is verified in orders of magnitudes similar to the values obtained from laboratory experiments. Supported by the Slovak Research and Development Agency under the contract No. APVV-15-0751 and by the Ministry of Education, Science, Research and Sport of the Slovak Republic under the contract No. VEGA 1/0643/17.

Metabolic cost of generating muscular force in human walking: insights from load-carrying and speed experiments.

PubMed

Griffin, Timothy M; Roberts, Thomas J; Kram, Rodger

2003-07-01

We sought to understand how leg muscle function determines the metabolic cost of walking. We first indirectly assessed the metabolic cost of swinging the legs and then examined the cost of generating muscular force during the stance phase. Four men and four women walked at 0.5, 1.0, 1.5, and 2.0 m/s carrying loads equal to 0, 10, 20, and 30% body mass positioned symmetrically about the waist. The net metabolic rate increased in nearly direct proportion to the external mechanical power during moderate-speed (0.5-1.5 m/s) load carrying, suggesting that the cost of swinging the legs is relatively small. The active muscle volume required to generate force on the ground and the rate of generating this force accounted for >85% of the increase in net metabolic rate across moderate speeds and most loading conditions. Although these factors explained less of the increase in metabolic rate between 1.5 and 2.0 m/s ( approximately 50%), the cost of generating force per unit volume of active muscle [i.e., the cost coefficient (k)] was similar across all conditions [k = 0.11 +/- 0.03 (SD) J/cm3]. These data indicate that, regardless of the work muscles do, the metabolic cost of walking can be largely explained by the cost of generating muscular force during the stance phase.

Quantitative assessment of the enamel machinability in tooth preparation with dental diamond burs.

PubMed

Song, Xiao-Fei; Jin, Chen-Xin; Yin, Ling

2015-01-01

Enamel cutting using dental handpieces is a critical process in tooth preparation for dental restorations and treatment but the machinability of enamel is poorly understood. This paper reports on the first quantitative assessment of the enamel machinability using computer-assisted numerical control, high-speed data acquisition, and force sensing systems. The enamel machinability in terms of cutting forces, force ratio, cutting torque, cutting speed and specific cutting energy were characterized in relation to enamel surface orientation, specific material removal rate and diamond bur grit size. The results show that enamel surface orientation, specific material removal rate and diamond bur grit size critically affected the enamel cutting capability. Cutting buccal/lingual surfaces resulted in significantly higher tangential and normal forces, torques and specific energy (p<0.05) but lower cutting speeds than occlusal surfaces (p<0.05). Increasing material removal rate for high cutting efficiencies using coarse burs yielded remarkable rises in cutting forces and torque (p<0.05) but significant reductions in cutting speed and specific cutting energy (p<0.05). In particular, great variations in cutting forces, torques and specific energy were observed at the specific material removal rate of 3mm(3)/min/mm using coarse burs, indicating the cutting limit. This work provides fundamental data and the scientific understanding of the enamel machinability for clinical dental practice. Copyright © 2014 Elsevier Ltd. All rights reserved.

Sinusoidal high-intensity exercise does not elicit ventilatory limitation in chronic obstructive pulmonary disease.

PubMed

Porszasz, Janos; Rambod, Mehdi; van der Vaart, Hester; Rossiter, Harry B; Ma, Shuyi; Kiledjian, Rafi; Casaburi, Richard

2013-06-01

During exercise at critical power (CP) in chronic obstructive pulmonary disease (COPD) patients, ventilation approaches its maximum. As a result of the slow ventilatory dynamics in COPD, ventilatory limitation during supramaximal exercise might be escaped using rapid sinusoidal forcing. Nine COPD patients [age, 60.2 ± 6.9 years; forced expiratory volume in the first second (FEV(1)), 42 ± 17% of predicted; and FEV(1)/FVC, 39 ± 12%] underwent an incremental cycle ergometer test and then four constant work rate cycle ergometer tests; tolerable duration (t(lim)) was recorded. Critical power was determined from constant work rate testing by linear regression of work rate versus 1/t(lim). Patients then completed fast (FS; 60 s period) and slow (SS; 360 s period) sinusoidally fluctuating exercise tests with mean work rate at CP and peak at 120% of peak incremental test work rate, and one additional test at CP; each for a 20 min target. The value of t(lim) did not differ between CP (19.8 ± 0.6 min) and FS (19.0 ± 2.5 min), but was shorter in SS (13.2 ± 4.2 min; P < 0.05). The sinusoidal ventilatory amplitude was minimal (37.4 ± 34.9 ml min(-1) W(-1)) during FS but much larger during SS (189.6 ± 120.4 ml min(-1) W(-1)). The total ventilatory response in SS reached 110 ± 8.0% of the incremental test peak, suggesting ventilatory limitation. Slow components in ventilation during constant work rate and FS exercises were detected in most subjects and contributed appreciably to the total response asymptote. The SS exercise was associated with higher mid-exercise lactate concentrations (5.2 ± 1.7, 7.6 ± 1.7 and 4.5 ± 1.3 mmol l(-1) in FS, SS and CP). Large-amplitude, rapid sinusoidal fluctuation in work rate yields little fluctuation in ventilation despite reaching 120% of the incremental test peak work rate. This high-intensity exercise strategy might be suitable for programmes of rehabilitative exercise training in COPD.

Effects of Geometrical and Flow Rates on the Prediction of Bottom Pressure Coefficients of Tunnel Lift Gate of Dams

NASA Astrophysics Data System (ADS)

Ameen, Sheeraz; Taher, Taha; Ahmed, Thamir M.

2018-06-01

Hydrostatics and hydrodynamics forces are generated and applied on the vertical lift tunnel gates due to the influence of a wide range of dam operating conditions. One of the most important forces is the uplift force resulting from the jet flow issuing below the gate. This force is based mainly upon many hydraulic and geometrical parameters. In this work, the uplift force is studied in terms of bottom pressure coefficient. The investigation is made paying particular attention on the effects of various three discharges and three gate lip angles on values of bottom pressure coefficients in addition to four different tunnel longitudinal slopes whose impact has not been studied in many previous works. Hydraulic model is constructed in this work for the sake of measuring all parameters required for estimating the bottom pressure coefficients, which are all examined against gate openings. The results show that the bottom pressure coefficient is related to the said variables, however, its behaviour and values are not necessary regular with variance of studied variables. The values are seen more significantly related to the flow rates and for some extent to the slopes of tunnel. An attempt by using the nonlinear regression of Statistical package of social sciences (SPSS) is made to set equations relating bottom pressure coefficient with gate openings for several angles of gate lips. The obtained equations are shown in good agreement with the selected cases of experimental results. The results are applicable for design purposes for similar geometrical and flow parameters considered in this study.

Confirmation of linear system theory prediction: Rate of change of Herrnstein's kappa as a function of response-force requirement.

PubMed

McDowell, J J; Wood, H M

1985-01-01

Four human subjects worked on all combinations of five variable-interval schedules and five reinforcer magnitudes ( cent/reinforcer) in each of two phases of the experiment. In one phase the force requirement on the operandum was low (1 or 11 N) and in the other it was high (25 or 146 N). Estimates of Herrnstein's kappa were obtained at each reinforcer magnitude. The results were: (1) response rate was more sensitive to changes in reinforcement rate at the high than at the low force requirement, (2) kappa increased from the beginning to the end of the magnitude range for all subjects at both force requirements, (3) the reciprocal of kappa was a linear function of the reciprocal of reinforcer magnitude for seven of the eight data sets, and (4) the rate of change of kappa was greater at the high than at the low force requirement by an order of magnitude or more. The second and third findings confirm predictions made by linear system theory, and replicate the results of an earlier experiment (McDowell & Wood, 1984). The fourth finding confirms a further prediction of the theory and supports the theory's interpretation of conflicting data on the constancy of Herrnstein's kappa.

Confirmation of linear system theory prediction: Rate of change of Herrnstein's κ as a function of response-force requirement

PubMed Central

McDowell, J. J; Wood, Helena M.

1985-01-01

Four human subjects worked on all combinations of five variable-interval schedules and five reinforcer magnitudes (¢/reinforcer) in each of two phases of the experiment. In one phase the force requirement on the operandum was low (1 or 11 N) and in the other it was high (25 or 146 N). Estimates of Herrnstein's κ were obtained at each reinforcer magnitude. The results were: (1) response rate was more sensitive to changes in reinforcement rate at the high than at the low force requirement, (2) κ increased from the beginning to the end of the magnitude range for all subjects at both force requirements, (3) the reciprocal of κ was a linear function of the reciprocal of reinforcer magnitude for seven of the eight data sets, and (4) the rate of change of κ was greater at the high than at the low force requirement by an order of magnitude or more. The second and third findings confirm predictions made by linear system theory, and replicate the results of an earlier experiment (McDowell & Wood, 1984). The fourth finding confirms a further prediction of the theory and supports the theory's interpretation of conflicting data on the constancy of Herrnstein's κ. PMID:16812408

Escape rate for nonequilibrium processes dominated by strong non-detailed balance force

NASA Astrophysics Data System (ADS)

Tang, Ying; Xu, Song; Ao, Ping

2018-02-01

Quantifying the escape rate from a meta-stable state is essential to understand a wide range of dynamical processes. Kramers' classical rate formula is the product of an exponential function of the potential barrier height and a pre-factor related to the friction coefficient. Although many applications of the rate formula focused on the exponential term, the prefactor can have a significant effect on the escape rate in certain parameter regions, such as the overdamped limit and the underdamped limit. There have been continuous interests to understand the effect of non-detailed balance on the escape rate; however, how the prefactor behaves under strong non-detailed balance force remains elusive. In this work, we find that the escape rate formula has a vanishing prefactor with decreasing friction strength under the strong non-detailed balance limit. We both obtain analytical solutions in specific examples and provide a derivation for more general cases. We further verify the result by simulations and propose a testable experimental system of a charged Brownian particle in electromagnetic field. Our study demonstrates that a special care is required to estimate the effect of prefactor on the escape rate when non-detailed balance force dominates.

Sick leave and its determinants in professional soldiers of the Slovenian Armed Forces.

PubMed

Selič, Polona; Petek, Davorina; Serec, Maša; Rus Makovec, Maja

2010-12-01

To assess whether demographic characteristics, self-rated health status, coping behaviors, satisfaction with important interpersonal relationships, financial situation, and current overall quality of life are determinants of sick leave duration in professional soldiers of the Slovenian Armed Forces. In 2008, 448 military personnel on active duty in the Slovenian Armed Forces were invited to participate in the study and 390 returned the completed questionnaires (response rate 87%). The questionnaires used were the self-rated health scale, sick leave scale, life satisfaction scale, Folkman-Lazarus' Ways of Coping Questionnaire, and a demographic data questionnaire. To partition the variance across a wide variety of indicators of participants' experiences, ordinal modeling procedures were used. A multivariate ordinal regression model, explaining 24% of sick leave variance, showed that the following variables significantly predicted longer sick leave duration: female sex (estimate, 1.185; 95% confidence interval [CI], 0.579-1.791), poorer self-rated health (estimate, 3.243; 95% CI, 1.755-4.731), lower satisfaction with relationships with coworkers (estimate, 1.333; 95% CI, 0.399-2.267), and lower education (estimate, 1.577; 95% CI, 0.717-2.436). The impact of age and coping mechanisms was not significant. Longer sick leave duration was found in women and respondents less satisfied with their relationships with coworkers, and these are the groups to which special attention should be awarded when planning supervision, work procedures, and gender equality policy of the Armed Forces. A good way of increasing the quality of interpersonal relationships at work would be to teach such skills in teaching programs for commanding officers.

The aging work force in Korea.

PubMed

Hong, Jungyeon; Lee, Kangsook

2012-04-01

Korea has the fastest aging population and least fertile population of all Organization Economic Cooperation and Development countries, and it is undertaking significant preparations for an aging society. So, we want to review the present status of Elderly workers' occupational disorders and preparations, which is performed by governmental, social parties. We examine the current status of Korea's aging work force, focusing on occupational disorders (injuries and diseases), and retirements, and the associated health effects. Despite the efforts and concern about Korea's aging society since the issue was first identified, Korea's limited experience in operating a national public pension system, and a mature social security system shows that the needs of Korea's aging society cannot be fully satisfied. This problem has already resulted in increasing labor employment rates and delays in retirement from the labor market. We suggest a policy for elderly workers considering various determinants that can lead to successful employment, retirement, and health promotion for the aging work force.

The impact of work-limiting disability on labor force participation.

PubMed

Webber, Douglas A; Bjelland, Melissa J

2015-03-01

According to the justification hypothesis, non-employed individuals may over-report their level of work limitation, leading to biased census/survey estimates of the prevalence of severe disabilities and the associated labor force participation rate. For researchers studying policies which impact the disabled or elderly (e.g., Supplemental Security Income, Disability Insurance, and Early Retirement), this could lead to significant bias in key parameters of interest. Using the American Community Survey, we examine the potential for both inflated and deflated reported disability status and generate a general index of disability, which can be used to reduce the bias of these self-reports in other studies. We find that at least 4.8 million individuals have left the labor force because of a work-limiting disability, at least four times greater than the impact implied by our replication of previous models. Copyright © 2013 John Wiley & Sons, Ltd.

Black Women in the Labor Force. Facts on Working Women No. 90-4.

ERIC Educational Resources Information Center

Women's Bureau (DOL), Washington, DC.

During the 1980s, the population of black women aged 16 years and older in the United States increased by 17.2%, and labor force participation for black women increased by 29%. In 1987, black women accounted for 50% of total black employment. The unemployment rate for black teenagers in 1990 was 30% (versus 10.8% for all black women). Labor force…

Wives' Relative Wages, Husbands' Paid Work Hours, and Wives' Labor-Force Exit

ERIC Educational Resources Information Center

Shafer, Emily Fitzgibbons

2011-01-01

Economic theories predict that women are more likely to exit the labor force if their partners' earnings are higher and if their own wage rate is lower. In this article, I use the National Longitudinal Survey of Youth (N = 2,254) and discrete-time event-history analysis to show that wives' relative wages are more predictive of their exit than are…

Tera-node Network Technology (Task 3) Scalable Personal Telecommunications

DTIC Science & Technology

2000-03-14

Simulation results of this work may be found in http://north.east.isi.edu/spt/ audio.html. 6. Internet Research Task Force Reliable Multicast...Adaptation, 4. Multimedia Proxy Caching, 5. Experiments with the Rate Adaptation Protocol (RAP) 6. Providing leadership and innovation to the Internet ... Research Task Force (IRTF) Reliable Multicast Research Group (RMRG) 1. End-to-end Architecture for Quality-adaptive Streaming Applications over the

Prediction of surface roughness and cutting force under MQL turning of AISI 4340 with nano fluid by using response surface methodology

NASA Astrophysics Data System (ADS)

Patole, Pralhad B.; Kulkarni, Vivek V.

2018-06-01

This paper presents an investigation into the minimum quantity lubrication mode with nano fluid during turning of alloy steel AISI 4340 work piece material with the objective of experimental model in order to predict surface roughness and cutting force and analyze effect of process parameters on machinability. Full factorial design matrix was used for experimental plan. According to design of experiment surface roughness and cutting force were measured. The relationship between the response variables and the process parameters is determined through the response surface methodology, using a quadratic regression model. Results show how much surface roughness is mainly influenced by feed rate and cutting speed. The depth of cut exhibits maximum influence on cutting force components as compared to the feed rate and cutting speed. The values predicted from the model and experimental values are very close to each other.

Contributions of Nanodiamond Abrasives and Deionized Water in Magnetorheological Finishing of Aluminum Oxynitride

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, C.; Lambropoulos, J.C.; Romanofsky, H.

2010-01-13

Magnetorheological finishing (MRF) is a sub-aperture deterministic process for fabricating high-precision optics by removing material and smoothing the surface. The goal of this work is to study the relative contribution of nanodiamonds and water in material removal for MRF of aluminum oxynitride ceramic (ALON) based upon a nonaqueous magnetorheological (MR) fluid. Removal was enhanced by a high carbonyl iron concentration and the addition of nanodiamond abrasives. Small amounts of deionized (DI) water were introduced into the nonaqueous MR fluid to further influence the material removal process. Material removal data were collected with a spot-taking machine. Drag force (Fd) and normalmore » force (Fn) before and after adding nanodiamonds or DI water were measured with a dual load cell. Both drag force and normal force were insensitive to the addition of nanodiamonds but increased with DI water content in the nonaqueous MR fluid. Shear stress (i.e., drag force divided by spot area) was calculated, and examined as a function of nanodiamond concentration and DI water concentration. Volumetric removal rate increased with increasing shear stress, which was shown to be a result of increasing viscosity after adding nanodiamonds and DI water. This work demonstrates that removal rate for a hard ceramic with MRF can be enhanced by adding DI water into a nonaqueous MR fluid.« less

Beyond the Fear Factor: Work/Family Policies in Academia--Resources or Rewards?

ERIC Educational Resources Information Center

Spalter-Roth, Roberta; Erskine, William

2005-01-01

Several decades ago, as the composition of the workforce changed and married women increased their labor-force participation rates, federal policies were designed to help employees balance work and family responsibilities. And as the gender composition of faculty in colleges and universities increasingly changed as well, a broad-based movement…

Faces and Future of the Nonmetro Workforce.

ERIC Educational Resources Information Center

Swanson, Linda L.; Butler, Margaret A.

Due largely to outmigration of young people, the nonmetropolitan United States has a lower proportion of people in the prime working ages of 20-44 than do metropolitan areas. Discouraged workers and high levels of work-preventing disabilities have contributed to lower rates of nonmetropolitan labor force participation for each age group between 20…

Large State-Level Fluctuations in Mental Retardation Classifications Related to Introduction of Renormed Intelligence Test

ERIC Educational Resources Information Center

Scullin, Matthew H.

2006-01-01

Oppositely valenced forces may be at work to influence rates of placement of children into mental retardation programs. On one hand, educational policies regarding intellectual disability and concerns about overrepresentation of minorities in special education may contribute to lower placement rates; on the other hand, more difficult intelligence…

NaCl nucleation from brine in seeded simulations: Sources of uncertainty in rate estimates.

PubMed

Zimmermann, Nils E R; Vorselaars, Bart; Espinosa, Jorge R; Quigley, David; Smith, William R; Sanz, Eduardo; Vega, Carlos; Peters, Baron

2018-06-14

This work reexamines seeded simulation results for NaCl nucleation from a supersaturated aqueous solution at 298.15 K and 1 bar pressure. We present a linear regression approach for analyzing seeded simulation data that provides both nucleation rates and uncertainty estimates. Our results show that rates obtained from seeded simulations rely critically on a precise driving force for the model system. The driving force vs. solute concentration curve need not exactly reproduce that of the real system, but it should accurately describe the thermodynamic properties of the model system. We also show that rate estimates depend strongly on the nucleus size metric. We show that the rate estimates systematically increase as more stringent local order parameters are used to count members of a cluster and provide tentative suggestions for appropriate clustering criteria.

Why Japanese workers remain in the labor force so long: lessons for the United States?

PubMed

Williamson, John B; Higo, Masa

2009-12-01

As part of the search for ways to increase labor force participation rates among older workers in the United States, it makes sense to take a close look at evidence from Japan, one of the few industrial countries with a substantially higher labor force participation rate among older workers, particularly men, than the United States. Based mainly on prior studies and original interview data, we first discuss five potential factors which help explain why Japanese workers remain in the labor force as long as they do: (1) perceived economic necessity; (2) the large fraction of workers who are self-employed; (3) a culture that puts a high value on remaining in the labor force throughout the life course; (4) the long healthy life expectancy; and (5) the government's role in facilitating the labor force participation of older workers. We suggest that the Japanese national cultural value on remaining economically productive well into old age clearly underlies the development of the government's legislative initiatives aiming to extend the working lives of older workers. We then outline three policy suggestions for those seeking to increase labor force participation rates among older U.S. workers: (1) increase the financial incentive to workers who remain in the labor force; (2) improve public programs designed to foster efforts by older workers to become self-employed; and (3) increase the extent of government efforts to link older workers to prospective employers.

Large state-level fluctuations in mental retardation classifications related to introduction of renormed intelligence test.

PubMed

Scullin, Matthew H

2006-09-01

Oppositely valenced forces may be at work to influence rates of placement of children into mental retardation programs. On one hand, educational policies regarding intellectual disability and concerns about overrepresentation of minorities in special education may contribute to lower placement rates; on the other hand, more difficult intelligence test norms may be a countervailing force, increasing placement rates. An analysis of longitudinal data on state and national level placement rates reveals that a lengthy and steep 12-year decline in students receiving mental retardation services reversed shortly after the introduction of the WISC-III in 1991. This phenomenon has relevance for death-penalty cases, because this historical pattern may affect the ability to establish whether an adult meets the developmental period onset criterion for mental retardation.

Japan's aging economics.

PubMed

Ezrati, M

1997-01-01

"Japan's population is aging faster than that of any other country in the world. The unprecedented increase in retirees relative to the size of Japan's work force will force radical change if the nation is to avoid a fiscal crisis, or worse. These seemingly innocent demographic changes will force Japan to shrink its famously high savings rate, reverse its proud trade surplus, send more industry overseas, liberalize its tightly controlled markets, and take on a more active, high-profile foreign policy. Ultimately, these changes will shift the balance of power in East Asia." excerpt

Simulation of shear thickening in attractive colloidal suspensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F.

2017-01-01

The influence of attractive forces between particles under conditions of large particle volume fraction is addressed using numerical simulations which account for hydrodynamic, Brownian, conservative and frictional contact forces. The focus is on conditions for which a significant increase in the apparent viscosity at small shear rates, and possibly the development of a yield stress, is observed. The high shear rate behavior for Brownian suspensions has been shown in recent work [R. Mari, R. Seto, J. F. Morris & M. M. Denn, PNAS, 2015, 112, 15326-15330] to be captured by the inclusion of pairwise forces of two forms, one amore » contact frictional interaction and the second a repulsive force common in stabilized colloidal dispersions. Under such conditions, shear thickening is observed when shear stress is comparable to the sum of the Brownian stress and a characteristic stress based on the combination of interparticle force with kT the thermal energy. At sufficiently large volume fraction, this shear thickening can be very abrupt. Here it is shown that when attractive interactions are present with the noted forces, the shear thickening is obscured, as the viscosity shear thins with increasing shear rate, eventually descending from an infinite value (yield stress conditions) to a plateau at large stress; this plateau is at the same level as the large-shear rate viscosity found in the shear thickened state without attractive forces. It is shown that this behavior is consistent with prior observations in shear thickening suspensions modified to be attractive through depletion flocculation [V. Gopalakrishnan & C. F. Zukoski J. Rheol., 2004, 48, 1321-1344]. The contributions of the contact, attractive, and hydrodynamics forces to the bulk stress are presented, as are the contact networks found at different attractive strengths.« less

Fractionation of Magnetic Microspheres in a Microfluidic Spiral: Interplay between Magnetic and Hydrodynamic Forces

PubMed Central

Hayden, M. E.; Häfeli, U. O.

2017-01-01

Magnetic forces and curvature-induced hydrodynamic drag have both been studied and employed in continuous microfluidic particle separation and enrichment schemes. Here we combine the two. We investigate consequences of applying an outwardly directed magnetic force to a dilute suspension of magnetic microspheres circulating in a spiral microfluidic channel. This force is realized with an array of permanent magnets arranged to produce a magnetic field with octupolar symmetry about the spiral axis. At low flow rates particles cluster around an apparent streamline of the flow near the outer wall of the turn. At high flow rates this equilibrium is disrupted by the induced secondary (Dean) flow and a new equilibrium is established near the inner wall of the turn. A model incorporating key forces involved in establishing these equilibria is described, and is used to extract quantitative information about the magnitude of local Dean drag forces from experimental data. Steady-state fractionation of suspensions by particle size under the combined influence of magnetic and hydrodynamic forces is demonstrated. Extensions of this work could lead to new continuous microscale particle sorting and enrichment processes with improved fidelity and specificity. PMID:28107472

On the theory of intensity distributions of tornadoes and other low pressure systems

NASA Astrophysics Data System (ADS)

Schielicke, Lisa; Névir, Peter

Approaching from a theoretical point of view, this work presents a theory which unifies intensity distributions of different low pressure systems, based on an energy of displacement. Resulting from a generalized Boltzmann distribution, the expression of this energy of displacement is obtained by radial integration over the forces which are in balance with the pressure gradient force in the horizontal equation of motion. A scale analysis helps to find out which balance of forces prevail. According to the prevailing balances, the expression of the energy of displacement differs for various depressions. Investigating the system at the moment of maximum intensity, the energy of displacement can be interpreted as the work that has to be done to generate and finally eliminate the pressure anomaly, respectively. By choosing the appropriate balance of forces, number-intensity (energy of displacement) distributions show exponential behavior with the same decay rate β for tornadoes and cyclones, if tropical and extra-tropical cyclones are investigated together. The decay rate is related to a characteristic (universal) scale of the energy of displacement which has approximately the value Eu = β- 1 ≈ 1000 m 2s - 2 . In consequence, while the different balances of forces cause the scales of velocity, the energy of displacement scale seems to be universal for all low pressure systems. Additionally, if intensity is expressed as lifetime minimum pressure, the number-intensity (pressure) distributions should be power law distributed. Moreover, this work points out that the choice of the physical quantity which represents the intensity is important concerning the behavior of intensity distributions. Various expressions of the intensity like velocity, kinetic energy, energy of displacement and pressure are possible, but lead to different behavior of the distributions.

Who Attends Work-Related Training Five Years after Graduation? A Comparison across European Countries

ERIC Educational Resources Information Center

Storen, Liv Anne

2013-01-01

What are the driving forces behind the unequal distribution of training after graduation among higher education graduates? Participation in lifelong learning is restricted here to work-related training. The paper aims at examining the mechanisms that cause variation in training rates, by taking into account fields of study, personal competency…

Mature-Aged Workers' Learning Needs and Motivations for Participation in Training Programs

ERIC Educational Resources Information Center

Meyers, Rebecca; Billett, Stephen; Kelly, Ann

2010-01-01

Issues arising from an ageing society, a low fertility rate and growing need for a skilled work force have seen increased government commitment to improving the participation rate of mature-aged workers. Education and training are seen as a principal strategy to increase the employability of these workers, yet participation in training is low and…

The labor force of the future.

PubMed

Norwood, J L

1987-07-01

In the decades ahead, the US labor force will reflect changes in the industrial structure, with declines in some manufacturing industries and expansion in service industries. The services sector is so diverse that the jobs within it cannot be categorized as either high wage or low wage. The service-producing sector employs 85% of professional specialty workers in the US. In general, information on compensation trends indicates that greater increases in compensation have occurred for workers in service-producing as opposed to goods-producing industries. The increase in service sector jobs has created opportunities for women to enter the labor force and, at present, 5 out of 6 women work in this sector compared to fewer than 2 out of 3 men. Productivity growth rates in the service-producing industries vary substantially and are strongly affected by the business cycle. Central to employment opportunities in the years ahead will be the effect of new technology. To date, the aggregate effect of new technology has been increased employment and higher living standards. Although retraining programs should be in place, the scenario of a huge technology-created labor surplus seems unlikely. In fact, a more likely problem is a shortage of labor resulting from earlier labor force withdrawal and demographic aging of the population. Those in the 25-54-year age group will represent a larger share of the labor force in the years ahead. In addition, blacks are expected to account for 20% of the labor force growth in the next decade. Finally, given increasing labor force participation rates among mothers, employers may have to provide more flexible work schedules, assistance with day care, and more attractive benefits packages.

Schedule of average annual equipment ownership expense

DOT National Transportation Integrated Search

2003-03-06

The "Schedule of Average Annual Equipment Ownership Expense" is designed for use on Force Account bills of Contractors performing work for the Illinois Department of Transportation and local government agencies who choose to adopt these rates. This s...

Time-resolved electric force microscopy of charge traps in polycrystalline pentacene films

NASA Astrophysics Data System (ADS)

Jaquith, Michael; Muller, Erik; Marohn, John

2006-03-01

The microscopic mechanisms by which charges trap in organic electronic materials are poorly understood. Muller and Marohn recently showed that electric force microscopy (EFM) can be used to image trapped charge in working pentacene thin-film transistors [E. M. Muller et al, Adv. Mater. 17 1410 (2005)]. We have extended their work by imaging trapped charge in pentacene films with much larger grains. In contrast to the previous study in which charge was found to trap inhomogeneously throughout the transistor gap, we find microscopic evidence for a new trapping mechanism in which charges trap predominantly at the pentacene/metal interface in large-grained devices. We have also made localized measurements of the trap growth over time by performing pulsed-gate EFM experiments. Integrated-rate kinetics data supports a charge trap mechanism which is second order in holes, e.g., holes trap in pairs, although the charge-trapping rate appears to depend on gate voltage.

Ergonomics strategies and actions for achieving productive use of an ageing work-force.

PubMed

Kumashiro, M

2000-07-01

In this report, a basic ERGOMA (Ergonomics in Industrial Management) strategy is proposed as a policy for corporate production and employment in countries where ageing populations and reduced birth rates are imminent, and a strategy related to this is proposed. Specifically, as a strategy at the company level, the results of survey studies aimed at the development of methods for determining job capacity, to enable effective use of the labour of ageing workers, were summarized. A number of the insights gained here are steps in the development of a foundational methodology for practical use, and in actual practice a number of these insights must be subjected to measurements. However, the theory and newly developed methodology described here are thought to represent significant changes from the approaches to job capacity diagnosis and assessment published in the past and from the stance towards utilization of an ageing work-force. The author is confident that this represents new progress in one of the ergonomics approach to dealing with the working environment of ageing workers and an ageing work-force in general.

Effect of Cutting Parameters on Thrust Force and Surface Roughness in Drilling of Al-2219/B4C/Gr Metal Matrix Composites

NASA Astrophysics Data System (ADS)

Ravindranath, V. M.; Basavarajappa, G. S. Shiva Shankar S.; Suresh, R.

2016-09-01

In aluminium matrix composites, reinforcement of hard ceramic particle present inside the matrix which causes tool wear, high cutting forces and poor surface finish during machining. This paper focuses on effect of cutting parameters on thrust force, surface roughness and burr height during drilling of MMCs. In the present work, discuss the influence of spindle speed and feed rate on drilling the pure base alloy (Al-2219), mono composite (Al- 2219+8% B4C) and hybrid composite (Al-2219+8%B4C+3%Gr). The composites were fabricated using liquid metallurgy route. The drilling experiments were conducted by CNC machine with TiN coated HSS tool, M42 (Cobalt grade) and carbide tools at various spindle speeds and feed rates. The thrust force, surface roughness and burr height of the drilled hole were investigated in mono composite and hybrid composite containing graphite particles, the experimental results show that the feed rate has more influence on thrust force and surface roughness. Lesser thrust force and discontinuous chips were produced during machining of hybrid composites when compared with mono and base alloy during drilling process. It is due to solid lubricant property of graphite which reduces the lesser thrust force, burr height and lower surface roughness. When machining with Carbide tool at low feed and high speeds good surface finish was obtained compared to other two types of cutting tool materials.

Wind-forced modulations in crossing sea states over infinite depth water

NASA Astrophysics Data System (ADS)

Debsarma, Suma; Senapati, Sudipta; Das, K. P.

2014-09-01

The present work is motivated by the work of Leblanc ["Amplification of nonlinear surface waves by wind," Phys. Fluids 19, 101705 (2007)] which showed that Stokes waves grow super exponentially under fair wind as a result of modulational instability. Here, we have studied the effect of wind in a situation of crossing sea states characterized by two obliquely propagating wave systems in deep water. It is found that the wind-forced uniform wave solution in crossing seas grows explosively with a super-exponential growth rate even under a steady horizontal wind flow. This is an important piece of information in the context of the formation of freak waves.

Modeling and Tool Wear in Routing of CFRP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iliescu, D.; Fernandez, A.; Gutierrez-Orrantia, M. E.

2011-01-17

This paper presents the prediction and evaluation of feed force in routing of carbon composite material. In order to extend tool life and improve quality of the machined surface, a better understanding of uncoated and coated tool behaviors is required. This work describes (1) the optimization of the geometry of multiple teeth tools minimizing the tool wear and the feed force, (2) the optimization of tool coating and (3) the development of a phenomenological model between the feed force, the routing parameters and the tool wear. The experimental results indicate that the feed rate, the cutting speed and the toolmore » wear are the most significant factors affecting the feed force. In the case of multiple teeth tools, a particular geometry with 14 teeth right helix right cut and 11 teeth left helix right cut gives the best results. A thick AlTiN coating or a diamond coating can dramatically improve the tool life while minimizing the axial force, roughness and delamination. A wear model has then been developed based on an abrasive behavior of the tool. The model links the feed rate to the tool geometry parameters (tool diameter), to the process parameters (feed rate, cutting speed and depth of cut) and to the wear. The model presented has been verified by experimental tests.« less

Mental health and the labor force participation of older workers.

PubMed

Mitchell, J M; Anderson, K H

1989-01-01

Over the past 20 years, while mortality rates have dramatically declined, the prevalence of work-related stress has increased. This phenomenon suggests that the population's physical health has improved, but mental health has deteriorated. Concomitantly, fewer older workers are participating in the labor force. Our paper, using data from the Epidemiologic Catchment Area (ECA) program, assesses whether the decline in numbers of older workers is linked to the increasing prevalence of job-related stress. Our results indicate that symptoms of poor mental health are the most important determinants of work behavior. Surprisingly, economic and demographic characteristics appear to have little impact on an individual's labor force participation status. Further research is needed, however, because the ECA data provides insufficient information to accurately assess the relative importance of both mental health and economic factors on the retirement decision.

Simulation of shear thickening in attractive colloidal suspensions.

PubMed

Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F

2017-03-01

The influence of attractive forces between particles under conditions of large particle volume fraction, ϕ, is addressed using numerical simulations which account for hydrodynamic, Brownian, conservative and frictional contact forces. The focus is on conditions for which a significant increase in the apparent viscosity at small shear rates, and possibly the development of a yield stress, is observed. The high shear rate behavior for Brownian suspensions has been shown in recent work [R. Mari, R. Seto, J. F. Morris and M. M. Denn PNAS, 2015, 112, 15326-15330] to be captured by the inclusion of pairwise forces of two forms, one a contact frictional interaction and the second a repulsive force often found in stabilized colloidal dispersions. Under such conditions, shear thickening is observed when shear stress is comparable to the sum of the Brownian stress, kT/a 3 , and a characteristic stress based on the combination of interparticle force, i.e. σ ∼ F 0 /a 2 with kT the thermal energy, F 0 the repulsive force scale and a the particle radius. At sufficiently large ϕ, this shear thickening can be very abrupt. Here it is shown that when attractive interactions are present with the noted forces, the shear thickening is obscured, as the viscosity shear thins with increasing shear rate, eventually descending from an infinite value (yield stress conditions) to a plateau at large stress; this plateau is at the same level as the large-shear rate viscosity found in the shear thickened state without attractive forces. It is shown that this behavior is consistent with prior observations in shear thickening suspensions modified to be attractive through depletion flocculation [V. Gopalakrishnan and C. F. Zukoski J. Rheol., 2004, 48, 1321-1344]. The contributions of the contact, attractive, and hydrodynamics forces to the bulk stress are presented, as are the contact networks found at different attractive strengths.

The role of biotic forces in driving macroevolution: beyond the Red Queen

PubMed Central

Voje, Kjetil L.; Holen, Øistein H.; Liow, Lee Hsiang; Stenseth, Nils Chr.

2015-01-01

A multitude of hypotheses claim that abiotic factors are the main drivers of macroevolutionary change. By contrast, Van Valen's Red Queen hypothesis is often put forward as the sole representative of the view that biotic forcing is the main evolutionary driver. This imbalance of hypotheses does not reflect our current knowledge: theoretical work demonstrates the plausibility of biotically driven long-term evolution, whereas empirical work suggests a central role for biotic forcing in macroevolution. We call for a more pluralistic view of how biotic forces may drive long-term evolution that is compatible with both phenotypic stasis in the fossil record and with non-constant extinction rates. Promising avenues of research include contrasting predictions from relevant theories within ecology and macroevolution, as well as embracing both abiotic and biotic proxies while modelling long-term evolutionary data. By fitting models describing hypotheses of biotically driven macroevolution to data, we could dissect their predictions and transcend beyond pattern description, possibly narrowing the divide between our current understanding of micro- and macroevolution. PMID:25948685

Mechanical work for step-to-step transitions is a major determinant of the metabolic cost of human walking.

PubMed

Donelan, J Maxwell; Kram, Rodger; Kuo, Arthur D

2002-12-01

In the single stance phase of walking, center of mass motion resembles that of an inverted pendulum. Theoretically, mechanical work is not necessary for producing the pendular motion, but work is needed to redirect the center of mass velocity from one pendular arc to the next during the transition between steps. A collision model predicts a rate of negative work proportional to the fourth power of step length. Positive work is required to restore the energy lost, potentially exacting a proportional metabolic cost. We tested these predictions with humans (N=9) walking over a range of step lengths (0.4-1.1 m) while keeping step frequency fixed at 1.8 Hz. We measured individual limb external mechanical work using force plates, and metabolic rate using indirect calorimetry. As predicted, average negative and positive external mechanical work rates increased with the fourth power of step length (from 1 W to 38 W; r(2)=0.96). Metabolic rate also increased with the fourth power of step length (from 7 W to 379 W; r(2)=0.95), and linearly with mechanical work rate. Mechanical work for step-to-step transitions, rather than pendular motion itself, appears to be a major determinant of the metabolic cost of walking.

How tendons buffer energy dissipation by muscle

PubMed Central

Roberts, Thomas J.; Konow, Nicolai

2013-01-01

To decelerate the body and limbs, muscles actively lengthen to dissipate energy. During rapid energy-dissipating events, tendons buffer the work done on muscle by temporarily storing elastic energy, then releasing this energy to do work on the muscle. This elastic mechanism may reduce the risk of muscle damage by reducing peak forces and lengthening rates of active muscle. PMID:23873133

Impacts from the Youth Incentive Entitlement Pilot Projects: Participation, Work, and Schooling Over the Full Program Period.

ERIC Educational Resources Information Center

Farkas, George; And Others

The Youth Incentive Entitlement Pilot Projects (YIEPP) demonstration, which was in full operation from 1978 to 1980, was established to test the efficacy of work combined with education as a remedy for high unemployment, low labor force participation, and the excessive school dropout rate of teenagers. YIEPP offered Federal minimum-wage jobs…

The Effects on the Structure of Society of the Growing Number of Women in the Work Force.

ERIC Educational Resources Information Center

Cook, Alice H.

Women's participation in the workforce is increasing, spurred by inflation, the rising level of consumer aspirations, the increasing number of families headed by women as a consequence of divorce, and the declining birth rate. However, the work women do continues to be segregated from men's and comparatively poorly paid, while women still carry…

Wearable Devices for Classification of Inadequate Posture at Work Using Neural Networks

PubMed Central

Barkallah, Eya; Freulard, Johan; Otis, Martin J. -D.; Ngomo, Suzy; Ayena, Johannes C.; Desrosiers, Christian

2017-01-01

Inadequate postures adopted by an operator at work are among the most important risk factors in Work-related Musculoskeletal Disorders (WMSDs). Although several studies have focused on inadequate posture, there is limited information on its identification in a work context. The aim of this study is to automatically differentiate between adequate and inadequate postures using two wearable devices (helmet and instrumented insole) with an inertial measurement unit (IMU) and force sensors. From the force sensors located inside the insole, the center of pressure (COP) is computed since it is considered an important parameter in the analysis of posture. In a first step, a set of 60 features is computed with a direct approach, and later reduced to eight via a hybrid feature selection. A neural network is then employed to classify the current posture of a worker, yielding a recognition rate of 90%. In a second step, an innovative graphic approach is proposed to extract three additional features for the classification. This approach represents the main contribution of this study. Combining both approaches improves the recognition rate to 95%. Our results suggest that neural network could be applied successfully for the classification of adequate and inadequate posture. PMID:28862665

The FEM Simulation on End Mill of Plastic Doors and Windows Corner Cleaning Based on Deform-3D

NASA Astrophysics Data System (ADS)

Li, Guoping; Huang, Zhenyong; Wang, Xiaohui

2017-12-01

In the plastic doors and windows corner cleaning process, the rotating speed, the feed rate and the milling cutter diameter are the main factors that affect the efficiency and quality of the of corner cleaning. In this paper, SolidWorks will be used to establish the 3D model of end mills, and use Deform-3D to research the end mill milling process. And using orthogonal experiment design method to analyze the effect of rotating speed, the feed rate and the milling cutter diameter on the axial force variation, and to get the overall trend of axial force and the selection of various parameters according to the influence of axial force change. Finally, simulate milling experiment used to get the actual axial force data to verify the reliability of the FEM simulation model. And the conclusion obtained in this paper has important theoretical value in improving the plastic doors and windows corner cleaning efficiency and quality.

Chewing Gum: Cognitive Performance, Mood, Well-Being, and Associated Physiology

PubMed Central

Allen, Andrew P.; Smith, Andrew P.

2015-01-01

Recent evidence has indicated that chewing gum can enhance attention, as well as promoting well-being and work performance. Four studies (two experiments and two intervention studies) examined the robustness of and mechanisms for these effects. Study 1 investigated the acute effect of gum on mood in the absence of task performance. Study 2 examined the effect of rate and force of chewing on mood and attention performance. Study 3 assessed the effects of chewing gum during one working day on well-being and performance, as well as postwork mood and cognitive performance. In Study 4, performance and well-being were reported throughout the workday and at the end of the day, and heart rate and cortisol were measured. Under experimental conditions, gum was associated with higher alertness regardless of whether performance tasks were completed and altered sustained attention. Rate of chewing and subjective force of chewing did not alter mood but had some limited effects on attention. Chewing gum during the workday was associated with higher productivity and fewer cognitive problems, raised cortisol levels in the morning, and did not affect heart rate. The results emphasise that chewing gum can attenuate reductions in alertness, suggesting that chewing gum enhances worker performance. PMID:26075253

Force Generation in Single Conventional Actomyosin Complexes under High Dynamic Load

PubMed Central

Takagi, Yasuharu; Homsher, Earl E.; Goldman, Yale E.; Shuman, Henry

2006-01-01

The mechanical load borne by a molecular motor affects its force, sliding distance, and its rate of energy transduction. The control of ATPase activity by the mechanical load on a muscle tunes its efficiency to the immediate task, increasing ATP hydrolysis as the power output increases at forces less than isometric (the Fenn effect) and suppressing ATP hydrolysis when the force is greater than isometric. In this work, we used a novel ‘isometric’ optical clamp to study the mechanics of myosin II molecules to detect the reaction steps that depend on the dynamic properties of the load. An actin filament suspended between two beads and held in separate optical traps is brought close to a surface that is sparsely coated with motor proteins on pedestals of silica beads. A feedback system increases the effective stiffness of the actin by clamping the force on one of the beads and moving the other bead electrooptically. Forces measured during actomyosin interactions are increased at higher effective stiffness. The results indicate that single myosin molecules transduce energy nearly as efficiently as whole muscle and that the mechanical control of the ATP hydrolysis rate is in part exerted by reversal of the force-generating actomyosin transition under high load without net utilization of ATP. PMID:16326899

Force and number of myosin motors during muscle shortening and the coupling with the release of the ATP hydrolysis products

PubMed Central

Caremani, Marco; Melli, Luca; Dolfi, Mario; Lombardi, Vincenzo; Linari, Marco

2015-01-01

The chemo-mechanical cycle of the myosin II–actin reaction in situ has been investigated in Ca2+-activated skinned fibres from rabbit psoas, by determining the number and strain (s) of myosin motors interacting during steady shortening at different velocities (V) and the effect of raising inorganic phosphate (Pi) concentration. It was found that in control conditions (no added Pi), shortening at V ≤ 350 nm s–1 per half-sarcomere, corresponding to force (T) greater than half the isometric force (T0), decreases the number of myosin motors in proportion to the reduction of T, so that s remains practically constant and similar to the T0 value independent of V. At higher V the number of motors decreases less than in proportion to T, so that s progressively decreases. Raising Pi concentration by 10 mm, which reduces T0 and the number of motors by 40–50%, does not influence the dependence on V of number and strain. A model simulation of the myosin–actin reaction in which the structural transitions responsible for the myosin working stroke and the release of the hydrolysis products are orthogonal explains the results assuming that Pi and then ADP are released with rates that increase as the motor progresses through the working stroke. The rate of ADP release from the conformation at the end of the working stroke is also strain-sensitive, further increasing by one order of magnitude within a few nanometres of negative strain. These results provide the molecular explanation of the relation between the rate of energy liberation and the load during muscle contraction. Key points Muscle contraction is due to cyclical ATP-driven working strokes in the myosin motors while attached to the actin filament. Each working stroke is accompanied by the release of the hydrolysis products, orthophosphate and ADP. The rate of myosin–actin interactions increases with the increase in shortening velocity. We used fast half-sarcomere mechanics on skinned muscle fibres to determine the relation between shortening velocity and the number and strain of myosin motors and the effect of orthophosphate concentration. A model simulation of the myosin–actin reaction explains the results assuming that orthophosphate and then ADP are released with rates that increase as the motor progresses through the working stroke. The ADP release rate further increases by one order of magnitude with the rise of negative strain in the final motor conformation. These results provide the molecular explanation of the relation between the rate of energy liberation and shortening velocity during muscle contraction. PMID:26041599

Effect of rotation rate on the forces of a rotating cylinder: Simulation and control

NASA Technical Reports Server (NTRS)

Burns, John A.; Ou, Yuh-Roung

1993-01-01

In this paper we present numerical solutions to several optimal control problems for an unsteady viscous flow. The main thrust of this work is devoted to simulation and control of an unsteady flow generated by a circular cylinder undergoing rotary motion. By treating the rotation rate as a control variable, we can formulate two optimal control problems and use a central difference/pseudospectral transform method to numerically compute the optimal control rates. Several types of rotations are considered as potential controls, and we show that a proper synchronization of forcing frequency with the natural vortex shedding frequency can greatly influence the flow. The results here indicate that using moving boundary controls for such systems may provide a feasible mechanism for flow control.

Effect of Ionic Strength and Surface Charge Density on the Kinetics of Cellulose Nanocrystal Thin Film Swelling.

PubMed

Reid, Michael S; Kedzior, Stephanie A; Villalobos, Marco; Cranston, Emily D

2017-08-01

This work explores cellulose nanocrystal (CNC) thin films (<50 nm) and particle-particle interactions by investigating film swelling in aqueous solutions with varying ionic strength (1-100 mM). CNC film hydration was monitored in situ via surface plasmon resonance, and the kinetics of liquid uptake were quantified. The contribution of electrostatic double-layer forces to film swelling was elucidated by using CNCs with different surface charges (anionic sulfate half ester groups, high and low surface charge density, and cationic trimethylammonium groups). Total water uptake in the thin films was found to be independent of ionic strength and surface chemistry, suggesting that in the aggregated state van der Waals forces dominate over double-layer forces to hold the films together. However, the rate of swelling varied significantly. The water uptake followed Fickian behavior, and the measured diffusion constants decreased with the ionic strength gradient between the film and the solution. This work highlights that nanoparticle interactions and dispersion are highly dependent on the state of particle aggregation and that the rate of water uptake in aggregates and thin films can be tailored based on surface chemistry and solution ionic strength.

Heart rate detection from an electronic weighing scale.

PubMed

González-Landaeta, R; Casas, O; Pallàs-Areny, R

2007-01-01

We propose a novel technique for heart rate detection on a subject that stands on a common electronic weighing scale. The detection relies on sensing force variations related to the blood acceleration in the aorta, works even if wearing footwear, and does not require any sensors attached to the body. We have applied our method to three different weighing scales, and estimated whether their sensitivity and frequency response suited heart rate detection. Scale sensitivities were from 490 nV/V/N to 1670 nV/V/N, all had an underdamped transient response and their dynamic gain error was below 19% at 10 Hz, which are acceptable values for heart rate estimation. We also designed a pulse detection system based on off-the-shelf integrated circuits, whose gain was about 70x10(3) and able to sense force variations about 240 mN. The signal-to-noise ratio (SNR) of the main peaks of the pulse signal detected was higher than 48 dB, which is large enough to estimate the heart rate by simple signal processing methods. To validate the method, the ECG and the force signal were simultaneously recorded on 12 volunteers. The maximal error obtained from heart rates determined from these two signals was +/-0.6 beats/minute.

Burma.

PubMed

1986-05-01

Burma's population stood at 36,392,000 in 1985, with an annual growth rate of 2%. The infant mortality rate was 96/1000 live births and life expectancy was 57 years. The literacy rate was 66%. Of the work force of 14.8 million, 66% are engaged in agriculture, 12% work in industry, 10% are in trade, and 11% are employed by the government. The government is a socialist republic. Burma's gross domestic product was US$6.5 billion in 1984-85, with an annual growth rate of 1-4% and a per capita income of $179. The government aims to establish a centrally controlled economy, although private enterprises have been allowed to operate in the agricultural sector. Economic progress has been hindered by widespread political insurgency and weak markets for export commodities.

Influence of Applying Additional Forcing Fans for the Air Distribution in Ventilation Network

NASA Astrophysics Data System (ADS)

Szlązak, Nikodem; Obracaj, Dariusz; Korzec, Marek

2016-09-01

Mining progress in underground mines cause the ongoing movement of working areas. Consequently, it becomes necessary to adapt the ventilation network of a mine to direct airflow into newly-opened districts. For economic reasons, opening new fields is often achieved via underground workings. Length of primary intake and return routes increases and also increases the total resistance of a complex ventilation network. The development of a subsurface structure can make it necessary to change the air distribution in a ventilation network. Increasing airflow into newly-opened districts is necessary. In mines where extraction does not entail gas-related hazards, there is possibility of implementing a push-pull ventilation system in order to supplement airflows to newly developed mining fields. This is achieved by installing subsurface fan stations with forcing fans at the bottom of downcast shaft. In push-pull systems with multiple main fans, it is vital to select forcing fans with characteristic curves matching those of the existing exhaust fans to prevent undesirable mutual interaction. In complex ventilation networks it is necessary to calculate distribution of airflow (especially in networks with a large number of installed fans). In the article the influence of applying additional forcing fans for the air distribution in ventilation network for underground mine were considered. There are also analysed the extent of overpressure caused by the additional forcing fan in branches of the ventilation network (the operating range of additional forcing fan). Possibilities of increasing airflow rate in working areas were conducted.

Reduction of centrifugation force in discontinuous percoll gradients increases in vitro fertilization rates without reducing bovine sperm recovery.

PubMed

Guimarães, A C G; Leivas, F G; Santos, F W; Schwengber, E B; Giotto, A B; Machado, C I U; Gonçalves, C G M; Folchini, N P; Brum, D S

2014-05-01

The objective of this study was to determine the effect of different centrifugation forces in bovine sperm separation by discontinuous Percoll gradients for in vitro fertilization IVF. The semen samples from each bull were pooled or each bull were centrifuged separately and centrifuged in discontinuous Percoll gradients (30, 60 and 90%) at different forces: F1 (9000×g), F2 (6500×g), F3 (4500×g) and F4 (2200×g), according experiment. The sperm samples were evaluated to determine the concentration, motility, vigor, morphology, reactive oxygen species (ROS), integrity of the plasma membrane, lipid peroxidation, antioxidants and embryo development were also evaluated. No difference was observed in the concentration of sperm submitted to different centrifugation forces. The total percentage of motile sperm was increased after centrifugation at F3 and F4, and the ROS production at F1 was greater than the other forces. When the bulls semen were processed individually, no significant differences were observed for the sperm quality parameters between F1 and F4, including lipid peroxidation, antioxidants, cleavage rate and average time to the first cleavage. This work demonstrated for the first time that centrifugation at 2200×g enhanced the sperm penetration and fertilization rates without reducing sperm recovery compared to the typical centrifugation force (9000×g) currently used by the commercial bovine IVF industry. Copyright © 2014 Elsevier B.V. All rights reserved.

The Status of Women of Color in the Economy: The Legacy of Being Other.

ERIC Educational Resources Information Center

Malveaux, Julianne

Black, Latina, and Asian women generally work in jobs that are less well-paying and lower on the occupational hierarchy than are the jobs held by their white counterparts. In addition, these women of color face higher unemployment rates than do white women. Whereas the entry of large numbers of white women into the work force is a fairly recent…

Assessing the Impact of Education and Marriage on Labor Market Exit Decisions of Women. Working Paper 2010-2

ERIC Educational Resources Information Center

Hotchkiss, Julie L.; Pitts, M. Melinda; Walker, Mary Beth

2010-01-01

During the late 1990s, the convergence of women's labor force participation rates to men's rates came to a halt. This paper explores the degree to which the role of education and marriage in women's labor supply decisions also changed over this time period. Specifically, this paper investigates women's decisions to exit the labor market upon the…

Design of teleoperation system with a force-reflecting real-time simulator

NASA Technical Reports Server (NTRS)

Hirata, Mitsunori; Sato, Yuichi; Nagashima, Fumio; Maruyama, Tsugito

1994-01-01

We developed a force-reflecting teleoperation system that uses a real-time graphic simulator. This system eliminates the effects of communication time delays in remote robot manipulation. The simulator provides the operator with predictive display and feedback of computed contact forces through a six-degree of freedom (6-DOF) master arm on a real-time basis. With this system, peg-in-hole tasks involving round-trip communication time delays of up to a few seconds were performed at three support levels: a real image alone, a predictive display with a real image, and a real-time graphic simulator with computed-contact-force reflection and a predictive display. The experimental results indicate the best teleoperation efficiency was achieved by using the force-reflecting simulator with two images. The shortest work time, lowest sensor maximum, and a 100 percent success rate were obtained. These results demonstrate the effectiveness of simulated-force-reflecting teleoperation efficiency.

Plantarflexor passive-elastic properties related to BMI and walking performance in older women.

PubMed

LaRoche, Dain P

2017-03-01

The objective of this study was to examine the influence of BMI on the passive-elastic properties of the ankle plantarflexors in older women. Twenty-three women, 65-80 yr, were separated into normal weight (NW, BMI <25.0kgm -2 , n=11) and overweight-obese (OW, BMI≥25.0kgm -2 , n=12) groups. Resistive torque of the ankle plantarflexors was recorded on an isokinetic dynamometer by passively moving the ankle into dorsiflexion. Stiffness, work absorption, and hysteresis were calculated across an ankle dorsiflexion angle of 10-15°. Maximal plantarflexor strength was assessed, then participants walked at maximal speed on an instrumented gait analysis treadmill while muscle activation (EMG) was recorded. Plantarflexor stiffness was 34% lower in OW (26.4±12.7Nmrad -1 ) than NW (40.0±15.7Nmrad -1 , p=0.032). Neither work absorption nor hysteresis were different between OW and NW. Stiffness per kg was positively correlated to strength (r=0.66, p<0.001), peak vertical ground reaction force during walking (r=0.72, p<0.001), weight acceptance rate of force (r=0.51, p=0.007), push-off rate of force (r=0.41, p=0.026), maximal speed (r=0.61, p=0.001), and inversely correlated to BMI (r=-0.61, p=0.001), and peak plantarflexor EMG (r=-0.40, p=0.046). Older women who are OW have low plantarflexor stiffness, which may limit propulsive forces during walking and necessitate greater muscle activation for active force generation. Copyright © 2017 Elsevier B.V. All rights reserved.

Relationships Between Countermovement Jump Ground Reaction Forces and Jump Height, Reactive Strength Index, and Jump Time.

PubMed

Barker, Leland A; Harry, John R; Mercer, John A

2018-01-01

Barker, LA, Harry, JR, and Mercer, JA. Relationships between countermovement jump ground reaction forces and jump height, reactive strength index, and jump time. J Strength Cond Res 32(1): 248-254, 2018-The purpose of this study was to determine the relationship between ground reaction force (GRF) variables to jump height, jump time, and the reactive strength index (RSI). Twenty-six, Division-I, male, soccer players performed 3 maximum effort countermovement jumps (CMJs) on a dual-force platform system that measured 3-dimensional kinetic data. The trial producing peak jump height was used for analysis. Vertical GRF (Fz) variables were divided into unloading, eccentric, amortization, and concentric phases and correlated with jump height, RSI (RSI = jump height/jump time), and jump time (from start to takeoff). Significant correlations were observed between jump height and RSI, concentric kinetic energy, peak power, concentric work, and concentric displacement. Significant correlations were observed between RSI and jump time, peak power, unload Fz, eccentric work, eccentric rate of force development (RFD), amortization Fz, amortization time, second Fz peak, average concentric Fz, and concentric displacement. Significant correlations were observed between jump time and unload Fz, eccentric work, eccentric RFD, amortization Fz, amortization time, average concentric Fz, and concentric work. In conclusion, jump height correlated with variables derived from the concentric phase only (work, power, and displacement), whereas Fz variables from the unloading, eccentric, amortization, and concentric phases correlated highly with RSI and jump time. These observations demonstrate the importance of countermovement Fz characteristics for time-sensitive CMJ performance measures. Researchers and practitioners should include RSI and jump time with jump height to improve their assessment of jump performance.

Improved pulmonary function in working divers breathing nitrox at shallow depths

NASA Technical Reports Server (NTRS)

Fitzpatrick, Daniel T.; Conkin, Johnny

2003-01-01

INTRODUCTION: There is limited data about the long-term pulmonary effects of nitrox use in divers at shallow depths. This study examined changes in pulmonary function in a cohort of working divers breathing a 46% oxygen enriched mixture while diving at depths less than 12 m. METHODS: A total of 43 working divers from the Neutral Buoyancy Laboratory (NBL), NASA-Johnson Space Center completed a questionnaire providing information on diving history prior to NBL employment, diving history outside the NBL since employment, and smoking history. Cumulative dive hours were obtained from the NBL dive-time database. Medical records were reviewed to obtain the diver's height, weight, and pulmonary function measurements from initial pre-dive, first year and third year annual medical examinations. RESULTS: The initial forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were greater than predicted, 104% and 102%, respectively. After 3 yr of diving at the NBL, both the FVC and FEV1 showed a significant (p < 0.01) increase of 6.3% and 5.5%, respectively. There were no significant changes in peak expiratory flow (PEF), forced mid-expiratory flow rate (FEF(25-75%)), and forced expiratory flow rates at 25%, 50%, and 75% of FVC expired (FEF25%, FEF50%, FEF75%). Cumulative NBL dive hours was the only contributing variable found to be significantly associated with both FVC and FEV1 at 1 and 3 yr. CONCLUSIONS: NBL divers initially belong to a select group with larger than predicted lung volumes. Regular diving with nitrox at shallow depths over a 3-yr period did not impair pulmonary function. Improvements in FVC and FEV1 were primarily due to a training effect.

Retirement patterns and bridge jobs in the 1990s.

PubMed

Quinn, J F

1999-02-01

During most of the post-World War II period, American men have been leaving the labor force at earlier and earlier ages. Evidence suggests that this trend has been under way for more than a century. However, in the mid-1980s, this trend came to an abrupt halt. Male labor force participation rates have been flat since 1985, and have actually increased over the past several years. Understanding these issues is especially important given the looming increase in the Social Security normal retirement age to 67 and the possibility of even more increases in the ages of eligibility under Social Security and Medicare reform. Because of the influx of married women into the labor market in the post-World War II period, older women's participation rates did not decline as men's did. In contrast, their rates were relatively steady, rising or falling very slowly. Since the mid-1980s, however, older women's participation rates have increased significantly. Many more older men and women are working today than the pre-1986 trends would have suggested. Many older Americans leave the labor force gradually, utilizing "bridge jobs" between employment on a full-time career job and complete labor force withdrawal. These bridge jobs are often part-time, often in a new line of work, and sometimes involve a switch from wage and salary work to self-employment. Estimates suggest that between one-third and one-half of older Americans will work on a bridge job before retiring completely, and for these workers retirement is best viewed as a process, not as a single event. These changes in retirement behavior are consistent with societal changes that have altered the relative attractiveness of work and leisure late in life. Mandatory retirement has been outlawed for most American workers. Social Security has become more age-neutral, no longer penalizing the average worker who wants to continue working after age 65. An increasing proportion of employer pension coverage has been in defined contribution plans, which do not contain the age-specific retirement incentives that many defined benefit plans do. The composition of jobs has shifted from manufacturing to service occupations. Americans are living longer and healthier lives, and many look forward to years to productive activity after age 65. These structural changes have been accompanied by an important cyclical factor: the strength of the American economy over the past decade. This has increased the demand for all types of labor, including older workers. Evidence suggests that there is more than this cyclical factor at work, however, and that new attitudes about work late in life are developing. Labor supply decisions late in life are correlated in expected ways with the individual's health (measured in several ways), age, and pension and health insurance status. Retirement patterns in America are much richer and more varied than the stereotypical one-step view of retirement suggests. Public policy is changing in ways that make continued work late in life more likely. If employers are willing to provide flexible job opportunities to meet the needs of these potential employees, then society can tap a growing pool of older, experienced, and willing workers for years to come.

Towards High-Frequency Shape Memory Alloy Actuators Incorporating Liquid Metal Energy Circuits

NASA Astrophysics Data System (ADS)

Hartl, Darren; Mingear, Jacob; Bielefeldt, Brent; Rohmer, John; Zamarripa, Jessica; Elwany, Alaa

2017-12-01

Large shape memory alloy (SMA) actuators are currently limited to applications with low cyclic actuation frequency requirements due to their generally poor heat transfer rates. This limitation can be overcome through the use of distributed body heating methods such as induction heating or by accelerated cooling methods such as forced convection in internal cooling channels. In this work, a monolithic SMA beam actuator containing liquid gallium-indium alloy-filled channels is fabricated through additive manufacturing. These liquid metal channels enable a novel multi-physical thermal control system, allowing for increased heating and cooling rates to facilitate an increased cyclic actuation frequency. Liquid metal flowing in the channels performs the dual tasks of inductively heating the surrounding SMA material and then actively cooling the SMA via forced internal fluid convection. A coupled thermoelectric model, implemented in COMSOL, predicts a possible fivefold increase in the cyclic actuation frequency due to these increased thermal transfer rates when compared to conventional SMA forms having external heating coils and being externally cooled via forced convection. The first ever experimental prototype SMA actuator of this type is described and, even at much lower flow rates, is shown to exhibit a decrease in cooling time of 40.9%.

Sliding mode-based lateral vehicle dynamics control using tyre force measurements

NASA Astrophysics Data System (ADS)

Kunnappillil Madhusudhanan, Anil; Corno, Matteo; Holweg, Edward

2015-11-01

In this work, a lateral vehicle dynamics control based on tyre force measurements is proposed. Most of the lateral vehicle dynamics control schemes are based on yaw rate whereas tyre forces are the most important variables in vehicle dynamics as tyres are the only contact points between the vehicle and road. In the proposed method, active front steering is employed to uniformly distribute the required lateral force among the front left and right tyres. The force distribution is quantified through the tyre utilisation coefficients. In order to address the nonlinearities and uncertainties of the vehicle model, a gain scheduling sliding-mode control technique is used. In addition to stabilising the lateral dynamics, the proposed controller is able to maintain maximum lateral acceleration. The proposed method is tested and validated on a multi-body vehicle simulator.

Labor market work and home care's unpaid caregivers: a systematic review of labor force participation rates, predictors of labor market withdrawal, and hours of work.

PubMed

Lilly, Meredith B; Laporte, Audrey; Coyte, Peter C

2007-12-01

As people continue to age and receive complex health care services at home, concern has arisen about the availability of family caregivers and their ability to combine employment with caregiving. This article evaluates the international research on unpaid caregivers and their labor market choices, highlighting three conclusions: first, caregivers in general are equally as likely to be in the labor force as noncaregivers; second, caregivers are more likely to work fewer hours in the labor market than noncaregivers, particularly if their caring commitments are heavy; and finally, only those heavily involved in caregiving are significantly more likely to withdraw from the labor market than noncaregivers. Policy recommendations are targeting greater access to formal care for "intensive" caregivers and developing workplace policies for employed caregivers.

[Health problems of working-age population in the Russian Federation].

PubMed

Izmerov, N F; Tikhonova, G I

2010-01-01

The paper deals with health problems of working-age population in the Russian Federation. According to foreign and domestic experts reduction of the able-bodied population and its fraction in the general population will be accompanied by ageing of labour force in the nearest two decades. Despite the growth of life expectancy in 2006-2007 demonstrated by disability, mortality and life expectancy indices for the age group of interest, its health status is considered to be critical. Mathematical simulation of mortality rates allowed for the assessment of potential years of life lost (PYLL) from leading causes of death among active working population. The data obtained provide a basis for the elaboration of medical and social programs aimed at increasing life expectancy. The most essential role in current negative tendencies in the health of active working population belongs to the deterioration of work conditions and safety at industrial enterprises coupled to low efficiency of occupational health prevention system accounting for the significantly reduced accessibility of health services. Restoration of occupational health system in Russia is of crucial importance. Experts of the Institute of Occupational Health have elaborated a draft National Action Plan designed to improve health protection of labour force in this country; its implementation would help to solve demographic problems and increase the amount and quality of labour force.

Framework for analyzing hyper-viscoelastic polymers

NASA Astrophysics Data System (ADS)

Trivedi, Akash; Siviour, Clive

2017-06-01

Hyper-viscoelastic polymers have multiple areas of application including aerospace, biomedicine, and automotive. Their mechanical responses are therefore extremely important to understand, particularly because they exhibit strong rate and temperature dependence, including a low temperature brittle transition. Relationships between the response at various strain rates and temperatures are investigated and a framework developed to predict response at rates where experiments are unfeasible. A master curve of the storage modulus's rate dependence at a reference temperature is constructed using a DMA test of the polymer. A frequency sweep spanning two decades and a temperature range from pre-glass transition to pre-melt is used. A fractional derivative model is fitted to the experimental data, and this model's parameters are used to derive stress-strain relationships at a desired strain rate. Finite element simulations with this constitutive model are used for verification with experimental data. This material is based upon work supported by the Air Force Office of Scientific Research, Air Force Materiel Command, USAF under Award No. FA9550-15-1-0448.

From bad pharma to good pharma: aligning market forces with good and trustworthy practices through accreditation, certification, and rating.

PubMed

Miller, Jennifer E

2013-01-01

This article explores whether the bioethical performance and trustworthiness of pharmaceutical companies can be improved by harnessing market forces through the use of accreditation, certification, or rating. Other industries have used such systems to define best practices, set standards, and assess and signal the quality of services, processes, and products. These systems have also informed decisions in other industries about where to invest, what to buy, where to work, and when to regulate. Similarly, accreditation, certification, and rating programs can help drug companies address stakeholder concerns in four areas: clinical trial design and management, dissemination of clinical trial results, marketing practices, and the accessibility of medicines. To illuminate processes - such as conflicts of interests and revolving-door policies - that can jeopardize the integrity of accreditation, certification, and ratings systems, the article concludes with a consideration of recent failures of credit-rating agencies and a review of the regulatory capture literature. © 2013 American Society of Law, Medicine & Ethics, Inc.

Influence of surface potential on the adhesive force of radioactive gold surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kweon, Hyojin; Yiacoumi, Sotira; Lee, Ida

2013-08-23

Radioactive particles may acquire surface potential through self-charging, and thus can behave differently from natural aerosols in atmospheric systems with respect to aggregation, deposition, resuspension, and transport to areas surrounding a radioactive source. Here, this work focuses on the adhesive force between radioactive particles and metallic surfaces, which relates to the deposition and resuspension of particles on surrounding surfaces. Scanning surface potential microscopy was employed to measure the surface potential of radioactive gold foil. Atomic force microscopy was used to investigate the adhesive force for gold that acquired surface charge either by irradiation or by application of an equivalent electricalmore » bias. Overall, the adhesive force increases with increasing surface potential or relative humidity. However, a behavior that does not follow the general trend was observed for the irradiated gold at a high decay rate. A comparison between experimental measurements and calculated values revealed that the surface potential promotes adhesion. The contribution of the electrostatic force at high levels of relative humidity was lower than the one found using theoretical calculations due to the effects caused by enhanced adsorption rate of water molecules under a high surface charge density. Lastly, the results of this study can be used to provide a better understanding of the behavior of radioactive particles in atmospheric systems.« less

Measuring tactile cues at the fingerpad for object compliances harder and softer than the skin

PubMed Central

Hauser, Steven C.; Gerling, Gregory J.

2016-01-01

Distinguishing an object’s compliance, into percepts of “softness” and “hardness,” is crucial to our ability to grasp and manipulate it. Biomechanical cues at the skin’s surface such as contact area and force rate have been thought to help encode compliance. However, no one has directly measured contact area with compliant materials, and few studies have considered compliances softer than the fingerpad. Herein, we developed a novel method to precisely measure the area in contact between compliant stimuli and the fingerpad, at given levels of force and displacement. To determine the method’s robustness, we conducted psychophysical and biomechanical experiments with human subjects. The results indicate that cues including contact area at stimulus peak force of 3 Newtons, force rate over stimulus movement and at peak force, displacement and/or time to reach peak force may help in discriminating compliances while the directional spread of contact area is less important. Between softer and harder compliances, some cues were slightly more evident, though not yet definitively. Based upon the method’s utility, the next step is to conduct broader experiments to distill the mixture of cues that encode compliance. The importance of such work lies in building haptic displays, for example, to render virtual tissues. PMID:27331072

A Finite-Element Method Model of Soft Tissue Response to Impulsive Acoustic Radiation Force

PubMed Central

Palmeri, Mark L.; Sharma, Amy C.; Bouchard, Richard R.; Nightingale, Roger W.; Nightingale, Kathryn R

2010-01-01

Several groups are studying acoustic radiation force and its ability to image the mechanical properties of tissue. Acoustic radiation force impulse (ARFI) imaging is one modality using standard diagnostic ultrasound scanners to generate localized, impulsive, acoustic radiation forces in tissue. The dynamic response of tissue is measured via conventional ultrasonic speckle-tracking methods and provides information about the mechanical properties of tissue. A finite-element method (FEM) model has been developed that simulates the dynamic response of tissues, with and without spherical inclusions, to an impulsive acoustic radiation force excitation from a linear array transducer. These FEM models were validated with calibrated phantoms. Shear wave speed, and therefore elasticity, dictates tissue relaxation following ARFI excitation, but Poisson’s ratio and density do not significantly alter tissue relaxation rates. Increased acoustic attenuation in tissue increases the relative amount of tissue displacement in the near field compared with the focal depth, but relaxation rates are not altered. Applications of this model include improving image quality, and distilling material and structural information from tissue’s dynamic response to ARFI excitation. Future work on these models includes incorporation of viscous material properties and modeling the ultrasonic tracking of displaced scatterers. PMID:16382621

Sex-Specific Labour Market Indicators: What They Show.

ERIC Educational Resources Information Center

Elder, Sara; Johnson, Lawrence Jeffrey

1999-01-01

Data indicate that women's experience in the labor market is substantially different from men's. Women work in different sectors for fewer hours; women have lower rates of education and literacy; and women are more likely to be unemployed, underemployed, or outside the labor force. (JOW)

One Step Back? Reassessing an Ideal Security State for Northeast Asia 2025

DTIC Science & Technology

2011-03-01

kept policy interest rates below 2% for three years , from December 2001 to November 2004, which made low-interest loans available to households and...three consecutive years of CA imbalances exceeding 2% of her GDP, the exchange rate will move to correct the imbalance. This market discipline works... exchange rates . Movement in the yuan is more or less determined by the policy goals of the People’s Republic of China (PRC), not by market forces. Tight

External Hand Forces Exerted by Long-Term Care Staff to Push Floor-Based Lifts: Effects of Flooring System and Resident Weight.

PubMed

Lachance, Chantelle C; Korall, Alexandra M B; Russell, Colin M; Feldman, Fabio; Robinovitch, Stephen N; Mackey, Dawn C

2016-09-01

The aim of this study was to investigate the effects of flooring type and resident weight on external hand forces required to push floor-based lifts in long-term care (LTC). Novel compliant flooring is designed to reduce fall-related injuries among LTC residents but may increase forces required for staff to perform pushing tasks. A motorized lift may offset the effect of flooring on push forces. Fourteen female LTC staff performed straight-line pushes with two floor-based lifts (conventional, motor driven) loaded with passengers of average and 90th-percentile resident weights over four flooring systems (concrete+vinyl, compliant+vinyl, concrete+carpet, compliant+carpet). Initial and sustained push forces were measured by a handlebar-mounted triaxial load cell and compared to participant-specific tolerance limits. Participants rated pushing difficulty. Novel compliant flooring increased initial and sustained push forces and subjective ratings compared to concrete flooring. Compared to the conventional lift, the motor-driven lift substantially reduced initial and sustained push forces and perceived difficulty of pushing for all four floors and both resident weights. Participants exerted forces above published tolerance limits only when using the conventional lift on the carpet conditions (concrete+carpet, compliant+carpet). With the motor-driven lift only, resident weight did not affect push forces. Novel compliant flooring increased linear push forces generated by LTC staff using floor-based lifts, but forces did not exceed tolerance limits when pushing over compliant+vinyl. The motor-driven lift substantially reduced push forces compared to the conventional lift. Results may help to address risk of work-related musculoskeletal injury, especially in locations with novel compliant flooring. © 2016, Human Factors and Ergonomics Society.

An Analysis of Reenlistment and Reserve Intentions of First-Term Enlisted Personnel.

DTIC Science & Technology

1987-06-01

organization as poor or undesirable performers quit or are forced out. This ostensibly could lead to greater effectiveness and efficiency within the organization...perceptions nemployment rate Accession rate LNlon presence 2. Work -related Factors TO performance Role clarity.Tas repetitiveness OveIti cb satisfaction...public release; * 2b ECL ASi IC.ATI ON IDOWNGRADING SCHEDULE distribuition is unlimited a PERFORMING ORGANIZATION REPORT NUMBER(S) S MONITORING

Effect of a redesigned two-wheeled container for refuse collecting on mechanical loading of low back and shoulders.

PubMed

Kuijer, P Paul F M; Hoozemans, Marco J M; Kingma, Idsart; Van Dieën, Jaap H; De Vries, Wiebe H K; Veeger, Dirk Jan; Van der Beek, Allard J; Visser, Bart; Frings-Dresen, Monique H W

2003-05-15

The objective of this study was to compare the mechanical and perceived workload when working with a redesigned two-wheeled container and working with a standard two-wheeled container for refuse collecting. The three changes in the design of the container were a displacement of the position of the centre of mass in the direction of the axis of the wheels, a slight increase in the height of the handle and a slight increase in the horizontal distance between the handle and the wheel-axis, and an increase in the diameter of the wheels. The volume of the container remained 0.240 m3. Nine refuse collectors performed some of their most frequent daily activities with both types of containers in the laboratory. Kinematics and exerted hand forces were assessed as input for detailed 3D biomechanical models of the low back and shoulder to estimate net moments at the low back and shoulders, compressive forces at the low back and contact forces at the glenohumeral joint. Also, the refuse collectors rated the ease of handling the two-wheeled containers on a five point scale. The use of the redesigned container resulted in a decrease of the exerted hand forces of 27%, decreases in the net moments at the low back and shoulders of 8% and 20%, respectively, and a decrease of 32% of the contact force at the glenohumeral joint when compared to the standard container. However, pulling an empty redesigned container on to the pavement resulted in an increase of the shoulder moment of more than 100%. No differences between container types were found for the compressive forces at the low back. Pushing and pulling with the redesigned container was rated as easier than pushing and pulling with the standard container. No differences in subjective ratings were found for the tasks of turning the container or pulling an empty container onto the pavement. It is concluded that, provided that empty containers are placed back onto the pavement as infrequently as possible, the introduction of the redesigned container could result in a reduction of the low back and shoulder load for refuse collectors.

[Demography and labor shortage. Future challenges of labor market policy].

PubMed

Fuchs, J

2013-03-01

For demographic reasons, the German labor force will decrease dramatically and it will be much older on average. However, labor demand, especially for qualified workers, is expected to remain high. This paper focuses on the possibilities of expanding the labor force by increasing the participation rates of women and older persons. Herein, the change in the labor force is decomposed with respect to population and labor participation and, moreover, the effects of higher participation rates are simulated. The decomposition and simulation scenarios are based on data published by the Institute for Employment Research. The analysis clearly reveals that the effect of a considerably higher labor participation of women and older workers will disappear over time when the working-age population shrinks more and more. In addition, individuals who are currently unemployed or out of the labor force are not skilled enough. Since it seems difficult to get more qualified workers in the short and even in the medium term, improving the conditions for women and older people to take up jobs should be tackled soon. This includes investments in education and health care.

Laboratory study of forced rotating shallow water turbulence

NASA Astrophysics Data System (ADS)

Espa, Stefania; Di Nitto, Gabriella; Cenedese, Antonio

2011-12-01

During the last three decades several authors have studied the appearance of multiple zonal jets in planetary atmospheres and in the Earths oceans. The appearance of zonal jets has been recovered in numerical simulations (Yoden & Yamada, 1993), laboratory experiments (Afanasyev & Wells, 2005; Espa et al., 2008, 2010) and in field measurements of the atmosphere of giant planets (Galperin et al., 2001). Recent studies have revealed the presence of zonation also in the Earths oceans, in fact zonal jets have been found in the outputs of Oceanic General Circulation Models-GCMs (Nakano & Hasumi, 2005) and from the analysis of satellite altimetry observations (Maximenko et al., 2005). In previous works (Espa et al., 2008, 2010) we have investigated the impact of the variation of the rotation rate and of the fluid depth on jets organization in decaying and forced regimes. In this work we show results from experiments performed in a bigger domain in which the fluid is forced continuously. The experimental set-up consists of a rotating tank (1m in diameter) where the initial distribution of vorticity has been generated via the Lorentz force in an electromagnetic cell. The latitudinal variation of the Coriolis parameter has been simulated by the parabolic profile assumed by the free surface of the rotating fluid. Flow measurements have been performed using an image analysis technique. Experiments have been performed changing the tank rotation rate and the fluid thickness. We have investigated the flow in terms of zonal and radial flow pattern, flow variability and jet scales.

Workforce Diversity: Status, Controversies, and an Interdisciplinary Approach.

ERIC Educational Resources Information Center

Bond, Meg A.; Pyle, Jean L.

Labor force participation rates, pay inequities, occupational segregation, positions in the hierarchy, interactions between diverse groups, and organizational culture all demonstrate that diversity in the workplace has not been fully achieved. Existing approaches to supporting workplace diversity have not worked, and, in many cases, have resulted…

48 CFR 52.222-9 - Apprentices and Trainees.

Code of Federal Regulations, 2010 CFR

2010-10-01

... fide apprenticeship program registered with the U.S. Department of Labor, Employment and Training Administration, Office of Apprenticeship Training, Employer, and Labor Services (OATELS) or with a State... work force under the registered program. (3) Any worker listed on a payroll at an apprentice wage rate...

Effects of work zone configurations and traffic density on performance variables and subjective workload.

PubMed

Shakouri, Mahmoud; Ikuma, Laura H; Aghazadeh, Fereydoun; Punniaraj, Karthy; Ishak, Sherif

2014-10-01

This paper investigates the effect of changing work zone configurations and traffic density on performance variables and subjective workload. Data regarding travel time, average speed, maximum percent braking force and location of lane changes were collected by using a full size driving simulator. The NASA-TLX was used to measure self-reported workload ratings during the driving task. Conventional lane merge (CLM) and joint lane merge (JLM) were modeled in a driving simulator, and thirty participants (seven female and 23 male), navigated through the two configurations with two levels of traffic density. The mean maximum braking forces was 34% lower in the JLM configuration, and drivers going through the JLM configuration remained in the closed lane longer. However, no significant differences in speed were found between the two merge configurations. The analysis of self-reported workload ratings show that participants reported 15.3% lower total workload when driving through the JLM. In conclusion, the implemented changes in the JLM make it a more favorable merge configuration in both high and low traffic densities in terms of optimizing traffic flow by increasing the time and distance cars use both lanes, and in terms of improving safety due to lower braking forces and lower reported workload. Copyright © 2014 Elsevier Ltd. All rights reserved.

Maximal strength training improves work economy, rate of force development and maximal strength more than conventional strength training.

PubMed

Heggelund, Jørn; Fimland, Marius S; Helgerud, Jan; Hoff, Jan

2013-06-01

This study compared maximal strength training (MST) with equal training volume (kg × sets × repetitions) of conventional strength training (CON) primarily with regard to work economy, and second one repetition maximum (1RM) and rate of force development (RFD) of single leg knee extension. In an intra-individual design, one leg was randomized to knee-extension MST (4 or 5RM) and the other leg to CON (3 × 10RM) three times per week for 8 weeks. MST was performed with maximal concentric mobilization of force while CON was performed with moderate velocity. Eight untrained or moderately trained men (26 ± 1 years) completed the study. The improvement in gross work economy was -0.10 ± 0.08 L min(-1) larger after MST (P = 0.011, between groups). From pre- to post-test the MST and CON improved net work economy with 31 % (P < 0.001) and 18 % (P = 0.01), respectively. Compared with CON, the improvement in 1RM and dynamic RFD was 13.7 ± 8.4 kg (P = 0.002) and 587 ± 679 N s(-1) (P = 0.044) larger after MST, whereas isometric RFD was of borderline significance 3,028 ± 3,674 N s(-1) (P = 0.053). From pre- to post-test, MST improved 1RM and isometric RFD with 50 % (P < 0.001) and 155 % (P < 0.001), respectively whereas CON improved 1RM and isometric RFD with 35 % (P < 0.001) and 83 % (P = 0.028), respectively. Anthropometric measures of quadriceps femoris muscle mass and peak oxygen uptake did not change. In conclusion, 8 weeks of MST was more effective than CON for improving work economy, 1RM and RFD in untrained and moderately trained men. The advantageous effect of MST to improve work economy could be due to larger improvements in 1RM and RFD.

Hand-rim forces and gross mechanical efficiency in asynchronous and synchronous wheelchair propulsion: a comparison.

PubMed

Lenton, J P; van der Woude, L; Fowler, N; Nicholson, G; Tolfrey, K; Goosey-Tolfrey, V

2014-03-01

To compare the force application characteristics at various push frequencies of asynchronous (ASY) and synchronous (SYN) hand-rim propulsion, 8 able-bodied participants performed a separate sub-maximal exercise test on a wheelchair roller ergometer for each propulsion mode. Each test consisted of a series of 5, 4-min exercise blocks at 1.8 m · s-1 - initially at their freely chosen frequency (FCF), followed by four counter-balanced trials at 60, 80, 120 and 140% FCF. Kinetic data was obtained using a SMARTWheel, measuring forces and moments. The gross efficiency (GE) was determined as the ratio of external work done and the total energy expended. The ASY propulsion produced higher force measures for FRES, FTAN, rate of force development & FEF (P<0.05), while there was no difference in GE values (P=0.518). In pair-matched push frequencies (ASY80:SYN60, ASY100:SYN80, ASY120:SYN100 and ASY140:SYN120), ASY propulsion forces remained significantly higher (FRES, FTAN, rate of force development & FEF P<0.05), and there was no significant effect on GE (P=0.456). Both ASY and SYN propulsion demonstrate similar trends: changes in push frequency are accompanied by changes in absolute force even without changes in the gross pattern/trend of force application, FEF or GE. Matched push frequencies continue to produce significant differences in force measures but not GE. This suggests ASY propulsion is the predominant factor in force application differences. The ASY would appear to offer a kinetic disadvantage to SYN propulsion and no physiological advantage under current testing conditions. © Georg Thieme Verlag KG Stuttgart · New York.

First-principles calculation of the polarization-dependent force driving the Eg mode in bismuth under optical excitation.

NASA Astrophysics Data System (ADS)

Murray, Eamonn; Fahy, Stephen

2014-03-01

Using first principles electronic structure methods, we calculate the induced force on the Eg (zone centre transverse optical) phonon mode in bismuth immediately after absorption of polarized light. When radiation with polarization perpendicular to the c-axis is absorbed in bismuth, the distribution of excited electrons and holes breaks the three-fold rotational symmetry and leads to a net force on the atoms in the direction perpendicular to the axis. We calculate the initial excited electronic distribution as a function of photon energy and polarization and find the resulting transverse and longitudinal forces experienced by the atoms. Using the measured, temperature-dependent rate of decay of the transverse force[2], we predict the approximate amplitude of induced atomic motion in the Eg mode as a function of temperature and optical fluence. This work is supported by Science Foundation Ireland and a Marie Curie International Incoming Fellowship.

Work disability in adults with cystic fibrosis.

PubMed

Gillen, M; Lallas, D; Brown, C; Yelin, E; Blanc, P

1995-07-01

Greater numbers of persons with cystic fibrosis (CF) reach adulthood and, therefore, actively participate in the labor force. In this study, we estimated labor force participation rates and determined risk factors for work disability among persons with CF. We recruited 49 (73%) of 67 adults followed at one of two hospital-based CF centers. We ascertained employment history and CF-attributed work disability by structured questionnaire. Independently, we reviewed medical records for demographics and illness severity indicators. We analyzed potential risk factors for work disability by logistic regression analysis. All of those studied reported past or present labor force participation, consistent with high work motivation. Complete cessation of work attributed to CF was reported by 17 (35%; 95% CI, 21 to 49%). Although 23 (47%; 95% CI, 32 to 60%) of those surveyed stated that CF had affected career choice, only nine respondents had ever received career counselling and 16 had ever discussed job choice with their physicians. After adjusting for standard measures of disease severity by multiple logistic regression, age, adult diagnosis of CF, female gender, and single marital status, analyzed as a group, provided significant additional explanatory power to a predictive model of disability risk (model chi square [4 d.f.] = 11.5, p < 0.05). Health care professionals who design interventions targeted at work disability among persons with CF should address demographic factors as well as illness severity and should assess the vocational needs of persons with CF and the potential benefit of career counselling.

Labor Market Work and Home Care's Unpaid Caregivers: A Systematic Review of Labor Force Participation Rates, Predictors of Labor Market Withdrawal, and Hours of Work

PubMed Central

Lilly, Meredith B; Laporte, Audrey; Coyte, Peter C

2007-01-01

As people continue to age and receive complex health care services at home, concern has arisen about the availability of family caregivers and their ability to combine employment with caregiving. This article evaluates the international research on unpaid caregivers and their labor market choices, highlighting three conclusions: first, caregivers in general are equally as likely to be in the labor force as noncaregivers; second, caregivers are more likely to work fewer hours in the labor market than noncaregivers, particularly if their caring commitments are heavy; and finally, only those heavily involved in caregiving are significantly more likely to withdraw from the labor market than noncaregivers. Policy recommendations are targeting greater access to formal care for “intensive” caregivers and developing workplace policies for employed caregivers. PMID:18070333

Workplace relationships impact self-rated health: A survey of Swedish municipal health care employees.

PubMed

Persson, Sophie Schön; Lindström, Petra Nilsson; Pettersson, Pär; Andersson, Ingemar

2018-05-22

The impact of positive social relationships on the health of municipal employees in the elder care sector in Sweden needs further examination. To explore the association between health and relationships among elderly care employees using a salutogenic perspective. Survey of all employees (n = 997) in special housing, home care and Disabled Support and Services in a Swedish municipality. The questionnaire, which had a salutogenic perspective, included information on self-rated health from the previously validated SHIS (Salutogenic Health Indicator Scale), psychosocial work environment and experiences, social climate, and health-promoting workplace relationships. The response rate was 69% . Results of a multivariable linear regression model showed four significant predictors of health: general work experiences, colleague belongingness and positive relationships with managers and care recipients. In another model, colleague belongingness was significantly related to satisfaction with care recipients, work, length of employment as well as general work experiences and relationships with managers. Strengthening of positive work relationships, not only between workmates but also with managers and care recipients, seems to be an essential area for employee health promotion. Colleague belongingness may be deepened by development of a positive work climate, including satisfactory work experiences, positive manager relationships and a stable work force.

Hovercraft Project Gives Learning a Lift

ERIC Educational Resources Information Center

Benini, Jim

2010-01-01

This article describes an activity for the author's Principles of Technology class in which students bring together the concepts of force, work, and rate, and show how they apply to mechanical, fluid, electrical, and thermal systems by building and flying a hovercraft. Building, testing, flying, and racing hovercrafts isn't something very many…

"Dynamic Labor Shortage" In the Offing.

ERIC Educational Resources Information Center

Olson, Lawrence

1982-01-01

The United States is on the verge of a labor shortage that is partly the result of declining birth rates. An increase in work force participation by older adults, encouraged by reversals of early retirement and other policy changes, would be advantageous to employers, workers, and the economy. (Author/SK)

26 CFR 1.401(a)(4)-0 - Table of contents.

Code of Federal Regulations, 2010 CFR

2010-04-01

...) Composition-of-work-force method. (3) Minimum-benefit method. (4) Grandfather rules for plans in existence on... allocation rates. (3) Safe harbor testing method for cash balance plans. (d) Safe-harbor testing method for...-crediting period. (e) Family aggregation rules. [Reserved] (f) Governmental plans. [Reserved] (g) Corrective...

Unified Technical Concepts. Physics for Technicians.

ERIC Educational Resources Information Center

Center for Occupational Research and Development, Inc., Waco, TX.

Unified Technical Concepts (UTC) is a modular system for teaching applied physics in two-year postsecondary programs. This UTC classroom textbook, consisting of 14 chapters, deals with physics for technicians. Addressed in the individual chapters of the guide are the following topics: force, work, rate, momentum, resistance, power, potential and…

Determination of the myosin step size from mechanical and kinetic data.

PubMed Central

Pate, E; White, H; Cooke, R

1993-01-01

During muscle contraction, work is generated when a myosin cross-bridge attaches to an actin filament and exerts a force on it through some power-stroke distance, h. At the end of this power stroke, attached myosin heads are carried into regions where they exert a negative force on the actin filament (the drag stroke) and where they are released rapidly from actin by ATP binding. Although the length of the power stroke remains controversial, average distance traversed in the drag-stroke region can be determined when one knows both rate of cross-bridge dissociation and filament-sliding velocity. At maximum contraction velocity, the average force exerted in the drag stroke must balance that exerted in the power stroke. We discuss here a simple model of cross-bridge interaction that allows one to calculate the force exerted in the drag stroke and to relate this to the power-stroke distance h traversed by cross-bridges in the positive-force region. Both the rate at which myosin can be dissociated from actin and the velocity at which an actin filament can be translated have been measured for a series of myosin isozymes and for different substrates, producing a wide range of values for each. Nonetheless, we show here that the rate of myosin dissociation from actin correlates well with the velocity of filament sliding, providing support for the simple model presented and suggesting that the power stroke is approximately 10 nm in length. PMID:8460156

Dynamics of myosin-driven skeletal muscle contraction: I. Steady-state force generation.

PubMed

Lan, Ganhui; Sun, Sean X

2005-06-01

Skeletal muscle contraction is a canonical example of motor-driven force generation. Despite the long history of research in this topic, a mechanistic explanation of the collective myosin force generation is lacking. We present a theoretical model of muscle contraction based on the conformational movements of individual myosins and experimentally measured chemical rate constants. Detailed mechanics of the myosin motor and the geometry of the sarcomere are taken into account. Two possible scenarios of force generation are examined. We find only one of the scenarios can give rise to a plausible contraction mechanism. We propose that the synchrony in muscle contraction is due to a force-dependent ADP release step. Computational results of a half sarcomere with 150 myosin heads can explain the experimentally measured force-velocity relationship and efficiency data. We predict that the number of working myosin motors increases as the load force is increased, thus showing synchrony among myosin motors during muscle contraction. We also find that titin molecules anchoring the thick filament are passive force generators in assisting muscle contraction.

Dynamics of Myosin-Driven Skeletal Muscle Contraction: I. Steady-State Force Generation

PubMed Central

Lan, Ganhui; Sun, Sean X.

2005-01-01

Skeletal muscle contraction is a canonical example of motor-driven force generation. Despite the long history of research in this topic, a mechanistic explanation of the collective myosin force generation is lacking. We present a theoretical model of muscle contraction based on the conformational movements of individual myosins and experimentally measured chemical rate constants. Detailed mechanics of the myosin motor and the geometry of the sarcomere are taken into account. Two possible scenarios of force generation are examined. We find only one of the scenarios can give rise to a plausible contraction mechanism. We propose that the synchrony in muscle contraction is due to a force-dependent ADP release step. Computational results of a half sarcomere with 150 myosin heads can explain the experimentally measured force-velocity relationship and efficiency data. We predict that the number of working myosin motors increases as the load force is increased, thus showing synchrony among myosin motors during muscle contraction. We also find that titin molecules anchoring the thick filament are passive force generators in assisting muscle contraction. PMID:15778440

Breastfeeding practices among employed Thai women in Chiang Mai.

PubMed

Yimyam, S; Morrow, M

1999-09-01

In many developing countries, labor force participation by women in the childbearing years has increased rapidly. Social and economic changes present new challenges for women attempting to combine their roles as workers and mothers. Little is known about how these challenges affect infant feeding choices. This multidisciplinary study investigated work and infant feeding decisions among 313 employed women in Chiang Mai, Thailand. Resumption of employment generally had negative affects on breastfeeding rates and duration. At 6 months postpartum, women who worked inside the home breastfed more than those working in the formal sector at jobs with inflexible hours (home, 80%; public sector, 37%; private sector, 39%). Women who were working outside the home for a long period or had shift jobs encountered many obstacles to maintaining breastfeeding, and most gave it up within 1 month after resuming employment. There is a need for multisectoral policies that address obstacles to breastfeeding among women in the paid labor force in Thailand.

What Works Clearinghouse Quick Review: "Meeting the Challenge of Combating Chronic Absenteeism: Impact of the NYC Mayor's Interagency Task Force on Chronic Absenteeism and School Attendance and Its Implications for Other Cities"

ERIC Educational Resources Information Center

What Works Clearinghouse, 2013

2013-01-01

This study examined the effectiveness of an intervention designed to reduce rates of chronic student absenteeism in New York City public schools. The study authors reported that schools participating in the intervention experienced greater reductions in rates of student chronic absenteeism than the comparison schools. Students who attended the…

Projection of Maximum Software Maintenance Manning Levels.

DTIC Science & Technology

1982-06-01

mainte- nance team development and for outyear support resource estimation, and to provide an analysis of applications of the model in areas other...by General Research Corporation of Santa Barbara, Ca., indicated that the Planning and Resource Management Information System (PARRIS) at the Air Force...determined that when the optimal input effort is applied, steps in the development would be achieved at a rate proportional to V(t). Thus the work-rate could

Increasing older persons' employment in Finland: in search of a new strategy.

PubMed

Sihto, M

1999-01-01

Using Finland as a case study, it is argued that early retirement will probably no longer be used on a large scale to reduce older-worker labor-force participation and unemployment among older workers. Instead, new strategies are needed to enhance the ability of older workers to remain productive and in the labor force, and to facilitate the reintegration of unemployed older persons back into working life. Both tasks require massive pioneering efforts. Reducing unemployment rates among older workers, particularly, requires completely new kinds of labor-market measures.

Ply-tear webbing energy absorber

NASA Technical Reports Server (NTRS)

Stevens, G. W. H.

1972-01-01

Ply-tear webbing is essentially two plain webbings that are bound together by a portion of the warps and that can be torn apart and do work by breaking the binders. Nylon webbing were woven to range in tear force from 1 to 10 kilonewtons. This force is substantially independent of speed, which was as high as 100 m/sec in some cases. A specific energy absorption of 90 J/g was achieved in the dry state. However, lower rated webbings that absorb approximately 40 J/g are recommended for use in practice where it is acceptable.

[Association between the decline in global fertility rate and the incorporation of women to the workforce].

PubMed

Stefanelli, María de Los Ángeles; Valenzuela, María Teresa; Cárcamo, Marcela; Urquidi, Cinthya; Cavada, Gabriel; San Martín P, Pamela

2016-05-01

The global fertility rate (GFR) is defined as the mean number of children that a woman could have in a hypothetical cohort, not exposed to death during the fertile period. GFR has fallen from 3.4 to 1.9 children per women in the period 1970-2010. To explore the relationship between the fall in GFR and the incorporation of women to work in the period 1960-2011. Data from the National Statistics Institute was used. GRF was calculated using specific fertility rates for each year considering women aged 15 to 49 years. Work rates were obtained from yearly vital statistics reports. Between 1960 and 2011, GRF decreased from 5.5 to 1.9 in Chile. The first inflection occurred in 1970. In the same period, female workforce increased from 22.4 to 40.2%. To motivate the participation of female work-force without decrease the GRF allowing population replacement, it is suggested the need to create new public policies with benefits and support from the state.

[Investigation on knowledge, attitude, and practice of schistosomiasis prevention and control and infection status in Armed Police Forces stationed along Yangtze River].

PubMed

Ming-Zhen, He; Yi-Qing, Xie; Yan-Li, Guo; Hong, Chen; Yong-Gen, Zou; Shi-Ying, Zhu; You, Zhang

2016-12-21

To understand the status of knowledge, attitude, and practice of schistosomiasis prevention and control and infection status in Armed Police Forces stationed along the Yangtze River, so as to provide the reference for formulating the schistosomiasis prevention and control measures in Armed Police Forces. A questionnaire survey was conducted in the Armed Police Forces along the Yangtze River in Jiangsu Province, and the investigation content included social demographic data, schistosomiasis prevention knowledge, attitude and behavior. All the subjects were examined for Schistosoma japonicum infection. Totally 376 soldiers were investigated in 2 sites. The total passing rate of schistosomiasis knowledge was 72.87%. The passing rate among different age groups had no significant difference ( χ 2 =0.26, P > 0.05). The passing rate of soldiers from endemic areas was significantly higher than that of the soldiers from non-endemic areas ( χ 2 =4.71, P < 0.05). The passing rate of officers was significantly higher than that of the soldiers ( χ 2 = 4.21, P < 0.05). The passing rate of soldiers with the education levels of junior school, high school, college, undergraduate and above increased gradually, with a significant difference ( χ 2 =8.16, P < 0.05). The soldiers with positive attitude accounted for 93.88%. Among the water contact behaviors, training accounted for 17.55% and participating in the task (such as flood fighting and water work) accounted for 86.44%. When launching, the rate of taking protective measures was 52.93%. The rate of taking protective measures in the knowledge passing group was much higher than that in the knowledge failed group ( χ 2 =10.55, P < 0.05). The stool was harmlessly treated in the two camps. Among 376 soldiers, the positive rate of blood examinations was 0.53%, but the stool examinations were all negative. The overall level of knowledge and correct behavior of schistosomiasis prevention in the Armed Police Forces along the Yangtze River still should be improved. The better health education and behavior intervention are crucial to schistosomiasis prevention in the army.

Specific cerebellar regions are related to force amplitude and rate of force development

PubMed Central

Spraker, M.B.; Corcos, D.M.; Kurani, A.S.; Prodoehl, J.; Swinnen, S.P.; Vaillancourt, D.E.

2011-01-01

The human cerebellum has been implicated in the control of a wide variety of motor control parameters, such as force amplitude, movement extent, and movement velocity. These parameters often covary in both movement and isometric force production tasks, so it is difficult to resolve whether specific regions of the cerebellum relate to specific parameters. In order to address this issue, the current study used two experiments and SUIT normalization to determine whether BOLD activation in the cerebellum scales with the amplitude or rate of change of isometric force production or both. In the first experiment, subjects produced isometric pinch-grip force over a range of force amplitudes without any constraints on the rate of force development. In the second experiment, subjects varied the rate of force production, but the target force amplitude remained constant. The data demonstrate that BOLD activation in separate sub-areas of cerebellar regions lobule VI and Crus I/II scale with both force amplitude and force rate. In addition, BOLD activation in cerebellar lobule V and vermis VI was specific to force amplitude, whereas BOLD activation in lobule VIIb was specific to force rate. Overall, cerebellar activity related to force amplitude was located superior and medial, whereas activity related to force rate was inferior and lateral. These findings suggest that specific circuitry in the cerebellum may be dedicated to specific motor control parameters such as force amplitude and force rate. PMID:21963915

The interrelation between mechanical characteristics of contracting muscle, cross-bridge internal structure, and the mechanism of chemomechanical energy transduction.

PubMed

Rosenfeld, E V

2012-09-01

The cross-bridge working stroke is regarded as a continuous (without jumps) change of myosin head internal state under the action of a force exerted within the nucleotide-binding site. Involvement of a concept of continuous cross-bridge conformation enables discussion of the nature of the force propelling muscle, and the Coulomb repulsion of like-charged adenosine triphosphate (ATP) fragments ADP(2-) and P (i) (2-) can quite naturally be considered as the source of this force. Two entirely different types of working stroke termination are considered. Along with the fluctuation mechanism, which controls the working stroke duration t (w) at isometric contraction, another interrupt mechanism is initially taken into account. It is triggered when the lever arm shift amounts to the maximal value S ≈ 11 nm, the back door opens, and P(i) crashes out. As a result, t (w) becomes inversely proportional to the velocity v of sliding filaments t (w) ≈ S/v for a wide range of values of v. Principal features of the experimentally observed dependences of force, efficiency, and rate of heat production on velocity and ATP concentration can then be reproduced by fitting a single parameter: the velocity-independent time span t (r) between the termination of the last and beginning of the next working stroke. v becomes the principal variable of the model, and the muscle force changes under external load are determined by variations in v rather than in the tension of filaments. The Boltzmann equation for an ensemble of cross-bridges is obtained, and some collective effects are discussed.

Increased work in cardiac trabeculae causes decreased mitochondrial NADH fluorescence followed by slow recovery.

PubMed Central

Brandes, R; Bers, D M

1996-01-01

The oxidative phosphorylation rate in isolated mitochondria is stimulated by increased [ADP], resulting in decreased [NADH]. In intact hearts, however, increased mechanical work has generally not been shown to cause an increase in [ADP]. Therefore, increased [NADH] has been suggested as an alternative for stimulating the phosphorylation rate. Such a rise in [NADH] could result from stimulation of various substrate dehydrogenases by increased intracellular [Ca2+] (e.g., during increased pacing frequency). We have monitored mitochondrial [NADH] in isolated rat ventricular trabeculae, using a novel fluorescence spectroscopy method where a native fluorescence signal was used to correct for motion artifacts. Work was controlled by increased pacing frequency and assessed using time-averaged force. At low-pacing rates (approximately 0.1 Hz), [NADH] immediately decreased during contraction and then slowly recovered (approximately 5 s) before the next contraction. At higher rates, [NADH] initially decreased by an amount related to pacing rate (i.e., work). However, during prolonged stimulation, [NADH] slowly (approximately 60 s) recovered to a new steady-state level below the initial level. We conclude that 1) during increased work, oxidative phosphorylation is not initially stimulated by increased mitochondrial [NADH]; and 2) increased pacing frequency slowly causes stimulation of NADH production. Images FIGURE 2 FIGURE 4 PMID:8842239

Continuous vs. intermittent work with Canadian Forces NBC clothing.

PubMed

McLellan, T M; Jacobs, I; Bain, J B

1993-07-01

This study examined the benefits of work and rest schedules on soldiers' work tolerance (WTT) while wearing various levels of nuclear, biological and chemical (NBC) defence protective clothing in a warm environment (30 degrees C and 50% R.H.). Eight unacclimatized males were assigned to exercise at either a light (walking 1.11 m.s-1 0% grade, alternating with lifting 10 kg) or heavy metabolic rate (walking 1.33 m.s-1 7.5% grade, alternating with lifting 20 kg). Subjects were tested wearing three levels of clothing protection: combat clothing (L); combats and a semi-permeable NBC overgarment with the hood down (M); combats and NBC overgarment, gloves, boots and respirator (H). For each clothing configuration, subjects were evaluated using both a "continuous" exercise protocol and an intermittent work and rest schedule. WTT was defined as the time until rectal temperature (Tre) reached 39.3 degrees C, heart rate reached 95% maximum, dizziness or nausea precluded further exercise, or 5 h had elapsed. Assuming a resting VO2 of 4 ml.kg-1 x min-1 an average metabolic rate was calculated for all trials. A decreasing hyperbolic function described the relationship between WTT and metabolic rate for M and H. These relationships facilitate quantification of appropriate work and rest schedules if the metabolic rate of a task is known.

From slavery to incarceration: social forces affecting the epidemiology of sexually transmitted diseases in the rural South.

PubMed

Thomas, James C

2006-07-01

The high rates of sexually transmitted diseases (STDs) in the southeastern United States have been shaped by historic and contemporary social forces. More than other regions of the country, the South was defined by slavery, an extremely hierarchical relationship between whites and blacks. Emancipation left much of the racial hierarchy intact with whites as farm owners and blacks as hired workers or sharecroppers. Agricultural policies that favored mechanization caused blacks to leave farm work and move into segregated towns, leading to the advent of the rural ghetto. Post-World War II mass migration, mostly by young men, to the industrial north altered the sex ratio and social capital of the southern towns left behind. The cocaine epidemic of the 1990s, followed by the high incarceration rates of the "War on Drugs," disproportionately affected low-income blacks. Each of these forces led to sexual and care-seeking behaviors that favor transmission of STDs.

Working life of women with disabilities--a review.

PubMed

Pawłowska-Cyprysiak, Karolina; Konarska, Maria

2013-01-01

The aim of this study was to present the situation of women with disabilities on the labour market. Women with disabilities suffer from social and professional discrimination. They are discriminated because of their gender and disability. The Q1 Labour Force Participation Study (2013) showed that, in Poland, labour force participation for men and women with disabilities was 29.4% and 14.7%, respectively, while the unemployment rate was 16.1% for men and 17.2% for women. Quarterly information on employment, unemployment and economic inactivity was gathered from a Labour Force Survey in the first quarter of 2013; data from the Ministry of Labour and Social Policy were also included. The participants of the survey were 15 years old or older; they were members of a sample household. The methodology was based on definitions recommended by the International Labour Office and Eurostat. It is important that women with disabilities are substantially less professionally active, while the unemployment rate for them is only slightly higher.

Time-related changes in firing rates are influenced by recruitment threshold and twitch force potentiation in the first dorsal interosseous.

PubMed

Miller, Jonathan D; Herda, Trent J; Trevino, Michael A; Sterczala, Adam J; Ciccone, Anthony B

2017-08-01

What is the central question of this study? The influences of motor unit recruitment threshold and twitch force potentiation on the changes in firing rates during steady-force muscular contractions are not well understood. What is the main finding and its importance? The behaviour of motor units during steady force was influenced by recruitment threshold, such that firing rates decreased for lower-threshold motor units but increased for higher-threshold motor units. In addition, individuals with greater changes in firing rates possessed greater twitch force potentiation. There are contradictory reports regarding changes in motor unit firing rates during steady-force contractions. Inconsistencies are likely to be the result of previous studies disregarding motor unit recruitment thresholds and not examining firing rates on a subject-by-subject basis. It is hypothesized that firing rates are manipulated by twitch force potentiation during contractions. Therefore, in this study we examined time-related changes in firing rates at steady force in relationship to motor unit recruitment threshold in the first dorsal interosseous and the influence of twitch force potentiation on such changes in young versus aged individuals. Subjects performed a 12 s steady-force contraction at 50% maximal voluntary contraction, with evoked twitches before and after the contraction to quantify potentiation. Firing rates, in relationship to recruitment thresholds, were determined at the beginning, middle and end of the steady force. There were no firing rate changes for aged individuals. For the young, firing rates decreased slightly for lower-threshold motor units but increased for higher-threshold motor units. Twitch force potentiation was greater for young than aged subjects, and changes in firing rates were correlated with twitch force potentiation. Thus, individuals with greater increases in firing rates of higher-threshold motor units and decreases in lower-threshold motor units possessed greater twitch force potentiation. Overall, changes in firing rates during brief steady-force contractions are dependent on recruitment threshold and explained in part by twitch force potentiation. Given that firing rate changes were measured in relationship to recruitment threshold, this study illustrates a more complete view of firing rate changes during steady-force contractions. © 2017 The Authors. Experimental Physiology © 2017 The Physiological Society.

Working life tables for females in Canada, 1971.

PubMed

Krishnan, P; Penning, M; Kurian, L

1981-01-01

This paper attempts to construct some working life tables (WLTs) for females in Canada, 1971. Attention is directed to methodological problems in female WLT construction, a suggested methodology, and loss due to mortality. The working life expectancy (WLE), which refers to the average number of years that a person is likely to spend in the labor force during his/her lifetime, reveals the extent of his/her contribution to the national economy. Although working life tables have been prepared for Canadian males, no attempt has been made previously to develop a WLT for the Canadian females. In some countries, such as Canada, the long census questionnaire collects additional pieces of information on labor force participation (LFP), even though the coverage is only on a part (but sizable) of the population. It is suggested that the information on "weeks worked" (Canadian Census wording) can be used to smooth out the bimodality problem in the female LFP. If a working woman works for an entire year, i.e., 52 weeks inclusive of paid holidays and vacation, she is said to contribute 1 woman year of working (or economically active) life to the economy. On the basis of this concept of a woman year of working life, all females who are working full time, part time, and not working can be considered in regard to their respective contributions of working lives to the national economy. An age limit is not indicated in the definition. The number of hours worked per day cumulated for the year and scaled down to the base of 1 woman year of working life would make the analysis more realistic. If the census data on weeks worked are tabulated by single years of age, or age groups for the female population, the average number of weeks worked specific for the various age categories can be computed. Those who are unemployed are taken as contributing zero weeks worked in the computation of the mean. Then the age specific participation rate is obtained as the percent of the average number of weeks worked by females in a given age group to the total number of weeks in a year. From these age specific rates, the probabilities of LFP at an age interval is worked out by averaging 2 consecutive age specific rates. Employing the notion of woman years of working life and utilizing the average number of weeks worked from the 1971 Census of Canada PUST data, a set of age specific participation rates for the Canadian females was developed. With these participation rates, the WLT for the Canadian females is constructed. The WLE for a female in Canada in 1971 attains a maximum of 38.7 years at age 15 and declines with increases in age. A comparison with the males showed that the female WLE was higher in the latter and lower in the early years of life.

Inertial torque during reaching directly impacts grip-force adaptation to weightless objects.

PubMed

Giard, T; Crevecoeur, F; McIntyre, J; Thonnard, J-L; Lefèvre, P

2015-11-01

A hallmark of movement control expressed by healthy humans is the ability to gradually improve motor performance through learning. In the context of object manipulation, previous work has shown that the presence of a torque load has a direct impact on grip-force control, characterized by a significantly slower grip-force adjustment across lifting movements. The origin of this slower adaptation rate remains unclear. On the one hand, information about tangential constraints during stationary holding may be difficult to extract in the presence of a torque. On the other hand, inertial torque experienced during movement may also potentially disrupt the grip-force adjustments, as the dynamical constraints clearly differ from the situation when no torque load is present. To address the influence of inertial torque loads, we instructed healthy adults to perform visually guided reaching movements in weightlessness while holding an unbalanced object relative to the grip axis. Weightlessness offered the possibility to remove gravitational constraints and isolate the effect of movement-related feedback on grip force adjustments. Grip-force adaptation rates were compared with a control group who manipulated a balanced object without any torque load and also in weightlessness. Our results clearly show that grip-force adaptation in the presence of a torque load is significantly slower, which suggests that the presence of torque loads experienced during movement may alter our internal estimates of how much force is required to hold an unbalanced object stable. This observation may explain why grasping objects around the expected location of the center of mass is such an important component of planning and control of manipulation tasks.

A comparative analysis of physiological responses at submaximal workloads during different laboratory simulations of field cycling.

PubMed

Kenny, G P; Reardon, F D; Marion, A; Thoden, J S

1995-01-01

The purpose of this study was to evaluate the relationships between heart rate (fc), oxygen consumption (VO2), peak force and average force developed at the crank in response to submaximal exercise employing a racing bicycle which was attached to an ergometer (RE), ridden on a treadmill (TC) and ridden on a 400-m track (FC). Eight male trained competitive cyclists rode at three pre-determined work intensities set at a proportion of their maximal oxygen consumption (VO2max): (1) below lactate threshold [work load that produces a VO2 which is 10% less than the lactate threshold VO2 (sub-LT)], (2) lactate threshold VO2 (LT), and (3) above lactate threshold [workload that produces a VO2 which is 10% greater than lactate threshold VO2 (supra-LT)], and equated across exercise modes on the basis of fc. Voltage signals from the crank arm were recorded as FM signals for subsequent representation of peak and average force. Open circuit VO2 measurements were done in the field by Douglas bag gas collection and in the laboratory by automated gas collection and analysis. fc was recorded with a telemeter (Polar Electro Sport Tester, PE3000). Significant differences (P < 0.05) were observed: (1) in VO2 between FC and both laboratory conditions at sub-LT intensity and LT intensities, (2) in peak force between FC and TC at sub-LT intensity, (3) in average force between FC and RE at sub-LT. No significant differences were demonstrated at supra-LT intensity for VO2. Similarly no significant differences were observed in peak and average force for either LT or supra-LT intensities. These data indicate that equating work intensities on the basis of fc measured in laboratory conditions would overestimate the VO2 which would be generated in the field and conversely, that using fc measured in the laboratory to establish field work intensity would underestimate mechanical workload experienced in the field.

Options for Department of Defense Total Workforce Supply and Demand Analysis: Potential Approaches and Available Data Sources

DTIC Science & Technology

2014-01-01

objectives. This report reviews the approaches used in the private sector and in government organizations for tackling Steps 2a and 2b of the work- force... unemployment rate). Separation rates may also reflect early retirement incentive packages offered by the company because of reduced staffing needs...depending on their objectives. Purpose This report provides a review of analytical approaches used in the pri- vate sector and in government organizations

An Update to the Budget and Economic Outlook: 2015 to 2025

DTIC Science & Technology

2015-08-01

Economic Analysis; Bureau of Labor Statistics ; Federal Reserve. Notes: Real gross domestic product is the output of the economy adjusted to remove the...the next few years, in CBO’s view, will be continued improvements in households’ creditworthiness and in the availability of credit. Delinquency rates...Budget Office; Bureau of Labor Statistics . Notes: The rate of short-term unemployment is the percentage of the labor force that has been out of work for

A Comparative Evaluation of the Effects of the Implementation of the Production Oriented Maintenance Organization (POMO) on Aircraft Maintenance

DTIC Science & Technology

1978-09-01

Division AREA & WORK UNIT NUMBERS School of Systems and Logistics’ Air Force Institute of Technology,WPAFB,OH II. CONTROLLING OFFICE NAME AND ADDRESS 12 ...STRUCTURE) ............. ................ 9) 12 . SUMMARY OF ALL ANALYSIS RESUILT,"S ........ ........ 94 vii i LIST OF FIGURES Figure Page 1. Deputy...ness Rate (Variable 4) .... ............ ... 81 12 . Graph of Data Values for Abort Rate (Variable 5 e) . ..................... 82 13. Graph of Data

Remote Sensing Characterization of Two-dimensional Wave Forcing in the Surf Zone

NASA Astrophysics Data System (ADS)

Carini, R. J.; Chickadel, C. C.; Jessup, A. T.

2016-02-01

In the surf zone, breaking waves drive longshore currents, transport sediment, shape bathymetry, and enhance air-sea gas and particle exchange. Furthermore, wave group forcing influences the generation and duration of rip currents. Wave breaking exhibits large gradients in space and time, making it challenging to measure in situ. Remote sensing technologies, specifically thermal infrared (IR) imagery, can provide detailed spatial and temporal measurements of wave breaking at the water surface. We construct two-dimensional maps of active wave breaking from IR imagery collected during the Surf Zone Optics Experiment in September 2010 at the US Army Corps of Engineers' Field Research Facility in Duck, NC. For each breaker identified in the camera's field of view, the crest-perpendicular length of the aerated breaking region (roller length) and wave direction are estimated and used to compute the wave energy dissipation rate. The resultant dissipation rate maps are analyzed over different time scales: peak wave period, infragravity wave period, and tidal wave period. For each time scale, spatial maps of wave breaking are used to characterize wave forcing in the surf zone for a variety of wave conditions. The following phenomena are examined: (1) wave dissipation rates over the bar (location of most intense breaking) have increased variance in infragravity wave frequencies, which are different from the peak frequency of the incoming wave field and different from the wave forcing variability at the shoreline, and (2) wave forcing has a wider spatial distribution during low tide than during high tide due to depth-limited breaking over the barred bathymetry. Future work will investigate the response of the variability in wave setup, longshore currents and rip currents, to the variability in wave forcing in the surf zone.

Force probe simulations of a reversibly rebinding system: Impact of pulling device stiffness

NASA Astrophysics Data System (ADS)

Jaschonek, Stefan; Diezemann, Gregor

2017-03-01

We present a detailed study of the parameter dependence of force probe molecular dynamics (FPMD) simulations. Using a well studied calix[4]arene catenane dimer as a model system, we systematically vary the pulling velocity and the stiffness of the applied external potential. This allows us to investigate how the results of pulling simulations operating in the constant velocity mode (force-ramp mode) depend on the details of the simulation setup. The system studied has the further advantage of showing reversible rebinding meaning that we can monitor the opening and the rebinding transition. Many models designed to extract kinetic information from rupture force distributions work in the limit of soft springs and all quantities are found to depend solely on the so-called loading rate, the product of spring stiffness and pulling velocity. This approximation is known to break down when stiff springs are used, a situation often encountered in molecular simulations. We find that while some quantities only depend on the loading rate, others show an explicit dependence on the spring constant used in the FPMD simulation. In particular, the force versus extension curves show an almost stiffness independent rupture force but the force jump after the rupture transition does depend roughly linearly on the value of the stiffness. The kinetic rates determined from the rupture force distributions show a dependence on the stiffness that can be understood in terms of the corresponding dependence of the characteristic forces alone. These dependencies can be understood qualitatively in terms of a harmonic model for the molecular free energy landscape. It appears that the pulling velocities employed are so large that the crossover from activated dynamics to diffusive dynamics takes place on the time scale of our simulations. We determine the effective distance of the free energy minima of the closed and the open configurations of the system from the barrier via an analysis of the hydrogen-bond network with results in accord with earlier simulations. We find that the system is quite brittle in the force regime monitored in the sense that the barrier is located near to the closed state.

Spontaneous Pneumothorax in the USAF Aircrew Population: A Retrospective Study.

DTIC Science & Technology

1986-10-01

PROGRAM PROjECT ITASK WORK UNIT i oroc Is Ai r Force Base, TFX 78235-530Dl ELEMENT NO No NO ACCESSiON NO ITiTLE (include Security Classification) incrat...Needle aspiration plus surgery Chsest tube. oxygen, and sufer ’ program. there are no firm guidelines regarding aviation rates were lower than those

Efficiency of Support Services within the Arizona Universities.

ERIC Educational Resources Information Center

Davis, George H.

One of the working papers in the final report of the Arizona Board of Regents' Task Force on Excellence, Efficiency and Competitiveness, this document discusses the efficiency of the Arizona state universities' support services. Faculty, staff, and students were asked to rate the quality, importance, and change in quality of the services provided…

Violence Directed against Teachers: Results from a National Survey

ERIC Educational Resources Information Center

Mcmahon, Susan D.; Martinez, Andrew; Espelage, Dorothy; Rose, Chad; Reddy, Linda A.; Lane, Kathleen; Anderman, Eric M.; Reynolds, Cecil R.; Jones, Abraham; Brown, Veda

2014-01-01

Teachers in U.S. schools report high rates of victimization, yet previous studies focus on select types of victimization and student perpetrators, which may underestimate the extent of the problem. This national study was based on work conducted by the American Psychological Association Classroom Violence Directed Against Teachers Task Force and…

Career Development of Foreign-Born Workers: Where Is the Career Motivation Research?

ERIC Educational Resources Information Center

Lopes, Tobin P.

2006-01-01

Immigrants and/or foreign-born workers are entering the American work-force at an increasing rate. Career motivation for these new entrants requires research attention. As this literature review shows, researchers have virtually ignored the expanding immigrant and/or foreign-born worker population. Career motivation differences among international…

Navajo Manpower Survey.

ERIC Educational Resources Information Center

Navajo Tribe, Window Rock, AZ.

The Navajo Manpower Survey for 1967, conducted on a sample of Navajos 14 years of age and older living in the Navajo Reservation area, found high rates of unemployment and underemployment for the Navajos. Some of the other findings reported are a general lack of real work experience; an indication by 70% of the labor force members that they would…

Greek University Students: A Discouraged Workforce

ERIC Educational Resources Information Center

Mihail, Dimtrios M.; Karaliopoulou, Katerina

2005-01-01

Purpose - The significance of young, well-educated workers in the Greek labour market has been largely neglected in studies addressing the issue of low participation rate in the labour force of the country. This study focuses on the reluctance of Greek students to enter the labour market and combine studies with paid work. This article reports on…

U.S. Productivity: The Challenges Ahead.

ERIC Educational Resources Information Center

Workforce Economics, 1999

1999-01-01

Despite the soaring stock market, low unemployment, and low inflation rate, the long-term prospects for U.S. economic health remain a cause for concern. Labor productivity has slowed since 1973. As a result of this slowdown, many companies are investing in work force development and new equipment to boost productivity. Long-term economic health…

Hunger and Population. Facts for Action #7.

ERIC Educational Resources Information Center

Phillips, James

The relationship between world hunger and world population is explored in this document for high school global education classes. Reasons for the high birth rates in developing nations are suggested, e.g., a poor family has many children because children are an inexpensive work force, provide extra income, and care for parents in old age. The…

Numerical and experimental analysis of the sedimentation of spherical colloidal suspensions under centrifugal force

NASA Astrophysics Data System (ADS)

Antonopoulou, Evangelia; Rohmann-Shaw, Connor F.; Sykes, Thomas C.; Cayre, Olivier J.; Hunter, Timothy N.; Jimack, Peter K.

2018-03-01

Understanding the sedimentation behaviour of colloidal suspensions is crucial in determining their stability. Since sedimentation rates are often very slow, centrifugation is used to expedite sedimentation experiments. The effect of centrifugal acceleration on sedimentation behaviour is not fully understood. Furthermore, in sedimentation models, interparticle interactions are usually omitted by using the hard-sphere assumption. This work proposes a one-dimensional model for sedimentation using an effective maximum volume fraction, with an extension for sedimentation under centrifugal force. A numerical implementation of the model using an adaptive finite difference solver is described. Experiments with silica suspensions are carried out using an analytical centrifuge. The model is shown to be a good fit with experimental data for 480 nm spherical silica, with the effects of centrifugation at 705 rpm studied. A conversion of data to Earth gravity conditions is proposed, which is shown to recover Earth gravity sedimentation rates well. This work suggests that the effective maximum volume fraction accurately captures interparticle interactions and provides insights into the effect of centrifugation on sedimentation.

On the theory of behavioral mechanics.

PubMed

Dzendolet, E

1999-12-01

The Theory of Behavioral Mechanics is the behavioral analogue of Newton's laws of motion, with the rate of responding in operant conditioning corresponding to physical velocity. In an earlier work, the basic relation between rate of responding and sessions under two FI schedules and over a range of commonly used session values had been shown to be a power function. Using that basic relation, functions for behavioral acceleration, mass, and momentum are derived here. Data from other laboratories also support the applicability of a power function to VI schedules. A particular numerical value is introduced here to be the standard reference value for the behavioral force under the VI-60-s schedule. This reference allows numerical values to be calculated for the behavioral mass and momentum of individual animals. A comparison of the numerical values of the momenta of two animals can be used to evaluate their relative resistances to change, e.g., to extinction, which is itself viewed as a continuously changing behavioral force being imposed on the animal. This overall numerical approach allows behavioral force-values to be assigned to various experimental conditions such as the evaluation of the behavioral force of a medication dosage.

Comparison of arterial potassium and ventilatory dynamics during sinusoidal work rate variation in man.

PubMed Central

Casaburi, R; Stringer, W W; Singer, E

1995-01-01

1. The mechanisms underlying the exercise hyperpnoea have been difficult to define. Recently it has been suggested that exercise ventilation (VE) changes in proportion to changes in arterial potassium concentration ([K+]a). Similar VE and [K+]a time courses following work rate changes have been cited as supporting evidence. This study compared [K+]a and VE dynamics during moderate exercise in man. 2. We observed VE and gas exchange responses in five healthy men to sinusoidal work rate variation between 25 and approximately 105 W. Tests of approximately 30 min duration were performed at sinusoidal periods of 9, 6 and 3 min and in the steady state. In each test, during two or three sine periods, arterial blood was sampled (24 per test) and analysed for [K+] and blood gases. Response amplitude and phase (relative to work rate) were determined for each variable. 3. [K+]a fluctuated in response to sinusoidal work rate forcing with mean-to-peak amplitude averaging 0.15 mmol 1(-1). However, among tests, VE amplitude and phase were not highly correlated with [K+]a (r = 0.36 and 0.67, respectively). Further, average [K+]a amplitude in the 9 and 6 min sinusoidal studies tended to exceed the steady-state amplitude, while average VE amplitude fell progressively with increasing forcing frequency. The dissimilar dynamics of [K+]a and VE seem inconsistent with a major role for [K+]a as a proportional controller of ventilation during non-steady state moderate exercise in man. 4. Among tests, VE and CO2 output (VCO2) amplitude and phase were closely correlated (r = 0.87 and 0.94, respectively). Further, arterial CO2 pressure (Pa,CO2) and arterial pH(pHa) did not fluctuate significantly in ten of twenty and thirteen of twenty studies, respectively. In tests where sinusoidal fluctuation was detected, amplitude averaged 1.1 mmHg and 0.008 units, respectively. Thus VE demonstrated a close dynamic coupling to CO2 output, with consequent tight regulation of Pa,CO2 and pHa. PMID:7666376

Cardiorespiratory parameters in draught horses before and after short term draught work pulling loads.

PubMed

Pérez, R; Recabarren, S E; Mora, G; Jara, C; Quijada, G; Hetz, E

1992-04-01

In order to establish the relationship between draught force and cardiorespiratory responses to exercise heart rate (HR), respiratory rate (RR), arterial and venous blood gases, pH, hemoglobin concentration and temperature were measured in five draught horses during rest, immediately after exercise and 30 min post-exercise under field conditions. A wagon equipped with an odometer and a hydraulic dynamometer was used for measuring distance and draught force. The wagon was loaded with 946 kg for the low load, 1,979 kg for the medium load and 2,994 kg for the high load, and drawn for a distance of 1,500 m. Draught force and load weight were linearly related. The response of the draught horse to low and medium load exercise was characterized by a moderate increase in HR, RR and temperature with no significant changes in arterial blood gases and pH. An increase in HR, RR and temperature was observed, whereas no changes in arterial PO2 and increases in venous PO2 were noticed after high load exercise. Slight increase in venous lactic acid concentration as a result of high load exercise was observed, suggesting that some anaerobic work was performed. However this was insufficient to produce changes in blood pH. The increase in metabolic requirements during the three levels of draught exercise was associated with increases in arterial hemoglobin concentration and oxygen content of blood.

Does cancer reduce labor market entry? Evidence for prime-age females.

PubMed

Moran, John R; Short, Pamela Farley

2014-06-01

Existing studies of the labor market status of cancer survivors have focused on the extent to which cancer disrupts the employment of individuals who were working when diagnosed with cancer. We examine how surviving cancer affects labor market entry and usual hours of work among females aged 28 to 54 years who were not working when first diagnosed. We find that prime-age females have employment rates 2 to 6 years after diagnosis that are 12 percentage points lower than otherwise similar women who were initially out of the labor force, full-time employment rates that are 10 percentage points lower, and usual hours of work that are 5 hours per week lower. These estimates are somewhat larger than estimates for prime-age women employed at the time of diagnosis and highlight the importance of considering nonworking females when assessing the economic and psychosocial burden of cancer.

Minimizing Isolate Catalyst Motion in Metal-Assisted Chemical Etching for Deep Trenching of Silicon Nanohole Array.

PubMed

Kong, Lingyu; Zhao, Yunshan; Dasgupta, Binayak; Ren, Yi; Hippalgaonkar, Kedar; Li, Xiuling; Chim, Wai Kin; Chiam, Sing Yang

2017-06-21

The instability of isolate catalysts during metal-assisted chemical etching is a major hindrance to achieve high aspect ratio structures in the vertical and directional etching of silicon (Si). In this work, we discussed and showed how isolate catalyst motion can be influenced and controlled by the semiconductor doping type and the oxidant concentration ratio. We propose that the triggering event in deviating isolate catalyst motion is brought about by unequal etch rates across the isolate catalyst. This triggering event is indirectly affected by the oxidant concentration ratio through the etching rates. While the triggering events are stochastic, the doping concentration of silicon offers a good control in minimizing isolate catalyst motion. The doping concentration affects the porosity at the etching front, and this directly affects the van der Waals (vdWs) forces between the metal catalyst and Si during etching. A reduction in the vdWs forces resulted in a lower bending torque that can prevent the straying of the isolate catalyst from its directional etching, in the event of unequal etch rates. The key understandings in isolate catalyst motion derived from this work allowed us to demonstrate the fabrication of large area and uniformly ordered sub-500 nm nanoholes array with an unprecedented high aspect ratio of ∼12.

Influence of structure of iron nanoparticles in aggregates on their magnetic properties

PubMed Central

2011-01-01

Zero-valent iron nanoparticles rapidly aggregate. One of the reasons is magnetic forces among the nanoparticles. Magnetic field around particles is caused by composition of the particles. Their core is formed from zero-valent iron, and shell is a layer of magnetite. The magnetic forces contribute to attractive forces among the nanoparticles and that leads to increasing of aggregation of the nanoparticles. This effect is undesirable for decreasing of remediation properties of iron particles and limited transport possibilities. The aggregation of iron nanoparticles was established for consequent processes: Brownian motion, sedimentation, velocity gradient of fluid around particles and electrostatic forces. In our previous work, an introduction of influence of magnetic forces among particles on the aggregation was presented. These forces have significant impact on the rate of aggregation. In this article, a numerical computation of magnetic forces between an aggregate and a nanoparticle and between two aggregates is shown. It is done for random position of nanoparticles in an aggregate and random or arranged directions of magnetic polarizations and for structured aggregates with arranged vectors of polarizations. Statistical computation by Monte Carlo is done, and range of dominant area of magnetic forces around particles is assessed. PMID:21917152

Can feedback analysis be used to uncover the physical origin of climate sensitivity and efficacy differences?

NASA Astrophysics Data System (ADS)

Rieger, Vanessa S.; Dietmüller, Simone; Ponater, Michael

2017-10-01

Different strengths and types of radiative forcings cause variations in the climate sensitivities and efficacies. To relate these changes to their physical origin, this study tests whether a feedback analysis is a suitable approach. For this end, we apply the partial radiative perturbation method. Combining the forward and backward calculation turns out to be indispensable to ensure the additivity of feedbacks and to yield a closed forcing-feedback-balance at top of the atmosphere. For a set of CO2-forced simulations, the climate sensitivity changes with increasing forcing. The albedo, cloud and combined water vapour and lapse rate feedback are found to be responsible for the variations in the climate sensitivity. An O3-forced simulation (induced by enhanced NOx and CO surface emissions) causes a smaller efficacy than a CO2-forced simulation with a similar magnitude of forcing. We find that the Planck, albedo and most likely the cloud feedback are responsible for this effect. Reducing the radiative forcing impedes the statistical separability of feedbacks. We additionally discuss formal inconsistencies between the common ways of comparing climate sensitivities and feedbacks. Moreover, methodical recommendations for future work are given.

Modelling of charged satellite motion in Earth's gravitational and magnetic fields

NASA Astrophysics Data System (ADS)

Abd El-Bar, S. E.; Abd El-Salam, F. A.

2018-05-01

In this work Lagrange's planetary equations for a charged satellite subjected to the Earth's gravitational and magnetic force fields are solved. The Earth's gravity, and magnetic and electric force components are obtained and expressed in terms of orbital elements. The variational equations of orbit with the considered model in Keplerian elements are derived. The solution of the problem in a fully analytical way is obtained. The temporal rate of changes of the orbital elements of the spacecraft are integrated via Lagrange's planetary equations and integrals of the normalized Keplerian motion obtained by Ahmed (Astron. J. 107(5):1900, 1994).

Art of war hidden in Kolmogorov's equations.

PubMed

Lauren, Michael K; McIntosh, Gregory C; Perry, Nigel; Moffat, James

2007-03-01

Here we discuss how Kolmogorov's work on turbulence can be used as the inspiration for a new description of battlefield dynamics. The method presented may also represent a new way of describing self-organizing dynamical systems, in place of conventional differential equation approaches. The key finding is that the rate of attrition in a battle appears to be a function of the fractal dimension of the opposing forces. It is suggested that, this being the case, the fractal dimension could be used as a surrogate to represent the organizational efficiency of one force relative to another, commonly called Command and Control.

MEMS-Based Flexible Force Sensor for Tri-Axial Catheter Contact Force Measurement

PubMed Central

Sheng, Jun; Desai, Jaydev P.

2016-01-01

Atrial fibrillation (AFib) is a significant healthcare problem caused by the uneven and rapid discharge of electrical signals from pulmonary veins (PVs). The technique of radiofrequency (RF) ablation can block these abnormal electrical signals by ablating myocardial sleeves inside PVs. Catheter contact force measurement during RF ablation can reduce the rate of AFib recurrence, since it helps to determine effective contact of the catheter with the tissue, thereby resulting in effective power delivery for ablation. This paper presents the development of a three-dimensional (3D) force sensor to provide the real-time measurement of tri-axial catheter contact force. The 3D force sensor consists of a plastic cubic bead and five flexible force sensors. Each flexible force sensor was made of a PEDOT:PSS strain gauge and a PDMS bump on a flexible PDMS substrate. Calibration results show that the fabricated sensor has a linear response in the force range required for RF ablation. To evaluate its working performance, the fabricated sensor was pressed against gelatin tissue by a micromanipulator and also integrated on a catheter tip to test it within deionized water flow. Both experiments simulated the ventricular environment and proved the validity of applying the 3D force sensor in RF ablation. PMID:28190945

Factors associated with sex work involvement among transgender women in Jamaica: a cross-sectional study.

PubMed

Logie, Carmen H; Wang, Ying; Lacombe-Duncan, Ashley; Jones, Nicolette; Ahmed, Uzma; Levermore, Kandasi; Neil, Ava; Ellis, Tyrone; Bryan, Nicolette; Marshall, Annecka; Newman, Peter A

2017-04-06

Transgender women are disproportionately impacted by HIV. Transgender women involved in sex work may experience exacerbated violence, social exclusion, and HIV vulnerabilities, in comparison with non-sex work-involved transgender women. Scant research has investigated sex work among transgender women in the Caribbean, including Jamaica, where transgender women report pervasive violence. The study objective was to examine factors associated with sex work involvement among transgender women in Jamaica. In 2015, we implemented a cross-sectional survey using modified peer-driven recruitment with transgender women in Kingston and Ocho Rios, Jamaica, in collaboration with a local community-based AIDS service organization. We conducted multivariable logistic regression analyses to identify factors associated with paid sex and transactional sex. Exchanging oral, anal or vaginal sex for money only was categorized as paid sex. Exchanging sex for survival needs (food, accommodation, transportation), drugs or alcohol, or for money along with survival needs and/or drugs/alcohol, was categorized as transactional sex. Among 137 transgender women (mean age: 24.0 [SD: 4.5]), two-thirds reported living in the Kingston area. Overall, 25.2% reported being HIV-positive. Approximately half (n = 71; 51.82%) reported any sex work involvement, this included sex in exchange for: money (n = 64; 47.06%); survival needs (n = 27; 19.85%); and drugs/alcohol (n = 6; 4.41%). In multivariable analyses, paid sex and transactional sex were both associated with: intrapersonal (depression), interpersonal (lower social support, forced sex, childhood sexual abuse, intimate partner violence, multiple partners/polyamory), and structural (transgender stigma, unemployment) factors. Participants reporting transactional sex also reported increased odds of incarceration perceived to be due to transgender identity, forced sex, homelessness, and lower resilience, in comparison with participants reporting no sex work involvement. Findings reveal high HIV infection rates among transgender women in Jamaica. Sex work-involved participants experience social and structural drivers of HIV, including violence, stigma, and unemployment. Transgender women involved in transactional sex also experience high rates of incarceration, forced sex and homelessness in comparison with non-sex workers. Taken together, these findings suggest that social ecological factors elevate HIV exposure among sex work-involved transgender women in Jamaica. Findings can inform interventions to advance human rights and HIV prevention and care cascades with transgender women in Jamaica.

Factors associated with sex work involvement among transgender women in Jamaica: a cross-sectional study

PubMed Central

Logie, Carmen H; Wang, Ying; Lacombe-Duncan, Ashley; Jones, Nicolette; Ahmed, Uzma; Levermore, Kandasi; Neil, Ava; Ellis, Tyrone; Bryan, Nicolette; Marshall, Annecka; Newman, Peter A

2017-01-01

Abstract Introduction: Transgender women are disproportionately impacted by HIV. Transgender women involved in sex work may experience exacerbated violence, social exclusion, and HIV vulnerabilities, in comparison with non-sex work-involved transgender women. Scant research has investigated sex work among transgender women in the Caribbean, including Jamaica, where transgender women report pervasive violence. The study objective was to examine factors associated with sex work involvement among transgender women in Jamaica. Methods: In 2015, we implemented a cross-sectional survey using modified peer-driven recruitment with transgender women in Kingston and Ocho Rios, Jamaica, in collaboration with a local community-based AIDS service organization. We conducted multivariable logistic regression analyses to identify factors associated with paid sex and transactional sex. Exchanging oral, anal or vaginal sex for money only was categorized as paid sex. Exchanging sex for survival needs (food, accommodation, transportation), drugs or alcohol, or for money along with survival needs and/or drugs/alcohol, was categorized as transactional sex. Results: Among 137 transgender women (mean age: 24.0 [SD: 4.5]), two-thirds reported living in the Kingston area. Overall, 25.2% reported being HIV-positive. Approximately half (n = 71; 51.82%) reported any sex work involvement, this included sex in exchange for: money (n = 64; 47.06%); survival needs (n = 27; 19.85%); and drugs/alcohol (n = 6; 4.41%). In multivariable analyses, paid sex and transactional sex were both associated with: intrapersonal (depression), interpersonal (lower social support, forced sex, childhood sexual abuse, intimate partner violence, multiple partners/polyamory), and structural (transgender stigma, unemployment) factors. Participants reporting transactional sex also reported increased odds of incarceration perceived to be due to transgender identity, forced sex, homelessness, and lower resilience, in comparison with participants reporting no sex work involvement. Conclusions: Findings reveal high HIV infection rates among transgender women in Jamaica. Sex work-involved participants experience social and structural drivers of HIV, including violence, stigma, and unemployment. Transgender women involved in transactional sex also experience high rates of incarceration, forced sex and homelessness in comparison with non-sex workers. Taken together, these findings suggest that social ecological factors elevate HIV exposure among sex work-involved transgender women in Jamaica. Findings can inform interventions to advance human rights and HIV prevention and care cascades with transgender women in Jamaica. PMID:28406598

Preventive strength training improves working ergonomics during welding.

PubMed

Krüger, Karsten; Petermann, Carmen; Pilat, Christian; Schubert, Emil; Pons-Kühnemann, Jörn; Mooren, Frank C

2015-01-01

To investigate the effect of a preventive strength training program on cardiovascular, metabolic and muscular strains during welding. Welders are one of the occupation groups which typically have to work in extended forced postures which are known to be an important reason for musculoskeletal disorders. Subjects (exercise group) accomplished a 12-week strength training program, while another group served as controls (control group). Pre and post training examinations included the measurements of the one repetition maximum and an experimental welding test. Local muscle activities were analysed by surface electromyography. Furthermore, heart rate, blood pressure, lactate and rating of perceived exertion were examined. In the exercise group, strength training lead to a significant increase of one repetition maximum in all examined muscles (p<.05). During the experimental welding test muscle activities of trunk and shoulder muscles and arm muscles were significantly reduced in the exercise group after intervention (p<.05). While no changes of neither cardiovascular nor metabolic parameters were found, subjects of the exercise group rated a significantly decreased rate of perceived exertion welding (p<.05). Effects of strength training can be translated in an improved working ergonomics and tolerance against the exposure to high physical demands at work.

Direct measurement of the mechanical work during translocation by the ribosome

DOE PAGES

Liu, Tingting; Kaplan, Ariel; Alexander, Lisa; ...

2014-08-11

A detailed understanding of tRNA/mRNA translocation requires measurement of the forces generated by the ribosome during this movement. Such measurements have so far remained elusive and, thus, little is known about the relation between force and translocation and how this reflects on its mechanism and regulation. Here, we address these questions using optical tweezers to follow translation by individual ribosomes along single mRNA molecules, against an applied force. We find that translocation rates depend exponentially on the force, with a characteristic distance close to the one-codon step, ruling out the existence of sub-steps and showing that the ribosome likely functionsmore » as a Brownian ratchet. We show that the ribosome generates ∼13 pN of force, barely sufficient to unwind the most stable structures in mRNAs, thus providing a basis for their regulatory role. Our assay opens the way to characterizing the ribosome's full mechano–chemical cycle.« less

Agricultural work exposures and pulmonary function among hired farm workers in California (the MICASA study).

PubMed

Rodriquez, Erik J; Stoecklin-Marois, Maria T; Bennett, Deborah H; Tancredi, Daniel J; Schenker, Marc B

2014-01-01

Despite California's dependence on hired farm labor, scarce research has been conducted on the respiratory health of hired farm workers. Agricultural exposures to inorganic and organic dusts can adversely affect an individual's respiratory health and differ by farm type and job task. The purpose of the present analysis was to examine associations between agricultural work exposures and pulmonary function among 450 California farm workers. Data were collected as part of the Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) study, a prospective cohort study examining occupational risk factors and health of hired farm worker families in Mendota, California. Time-weighted self-reported average (TWSRA) dust scores were calculated from assessments of past-12-month agricultural work history. Other dust exposure indicator variables included months worked in agriculture in the past 12 months and years worked in agriculture. Multiple linear regression modeled FEV1 (forced expiratory volume in 1 second), FEF(25-75%) (forced midexpiratory flow rate), FVC (forced vital capacity), FEV6, FEV1/FVC, and FEV1/FEV6 separately. Seventy-six percent of participants had worked in agriculture in the past year. In models conducted for crops and tasks separately, high TWSRA dust score was associated with better FEV6. Crop and task models showed associations between greater months worked in agriculture in the past year and better FEV1, FEF(25-75%), and FEV6. Both models also found greater years worked in agriculture to be associated with worse FEV1/FEV6. Results were generally in the opposite direction as expected given past research but not uncommon. Future research should investigate relationships between pulmonary function and agricultural dust exposure over a lifetime and changes in pulmonary function over time.

Motor unit firing rate patterns during voluntary muscle force generation: a simulation study

NASA Astrophysics Data System (ADS)

Hu, Xiaogang; Rymer, William Z.; Suresh, Nina L.

2014-04-01

Objective. Muscle force is generated by a combination of motor unit (MU) recruitment and changes in the discharge rate of active MUs. There have been two basic MU recruitment and firing rate paradigms reported in the literature, which describe the control of the MUs during force generation. The first (termed the reverse ‘onion skin’ profile), exhibits lower firing rates for lower threshold units, with higher firing rates occurring in higher threshold units. The second (termed the ‘onion skin’ profile), exhibits an inverse arrangement, with lower threshold units reaching higher firing rates. Approach. Using a simulation of the MU activity in a hand muscle, this study examined the force generation capacity and the variability of the muscle force magnitude at different excitation levels of the MU pool under these two different MU control paradigms. We sought to determine which rate/recruitment scheme was more efficient for force generation, and which scheme gave rise to the lowest force variability. Main results. We found that the force output of both firing patterns leads to graded force output at low excitation levels, and that the force generation capacity of the two different paradigms diverged around 50% excitation. In the reverse ‘onion skin’ pattern, at 100% excitation, the force output reached up to 88% of maximum force, whereas for the ‘onion skin’ pattern, the force output only reached up to 54% of maximum force at 100% excitation. The force variability was lower at the low to moderate force levels under the ‘onion skin’ paradigm than with the reverse ‘onion skin’ firing patterns, but this effect was reversed at high force levels. Significance. This study captures the influence of MU recruitment and firing rate organization on muscle force properties, and our results suggest that the different firing organizations can be beneficial at different levels of voluntary muscle force generation and perhaps for different tasks.

The New Work Force. Trends and Issues Alerts.

ERIC Educational Resources Information Center

Imel, Susan

During the last years of this century, the work force will grow more slowly, becoming older, more female, and more disadvantaged. An increasing number of minority groups and immigrants will enter the work force. Despite public demands for reform, education lags behind in preparing youth for employment. The changing work force has many implications…

Dissipation in a tidally perturbed body librating in longitude

NASA Astrophysics Data System (ADS)

Efroimsky, Michael

2018-05-01

Internal dissipation in a tidally perturbed librating body differs in several respects from the tidal dissipation in a steadily spinning rotator. First, libration changes the spectral distribution of tidal damping across the tidal modes, as compared to the case of steady spin. This changes both the tidal heating rate and the tidal torque. Second, while a non-librating rotator experiences alternating deformation only due to the potential force exerted on it by the perturber, a librating body is also subject to a toroidal force proportional to the angular acceleration. Third, while the centrifugal force in a steadily spinning body renders only a permanent deformation (which defines the oblateness when the body cools down), in a librating body this force contains two alternating components-one purely radial, another a degree-2 potential force. Both contribute to heating, as well as to the tidal torque and potential (and, thereby, to the orbital evolution). We develop a formalism needed to describe dissipation in a homogeneous terrestrial body performing small-amplitude libration in longitude. This formalism incorporates as its part a linear rheological law defining the response of the rotator's material to forcing. While the developed formalism can work with an arbitrary linear rheology, we consider a simple example of a Maxwell material. We demonstrate that, independent of the rheology, forced libration in longitude can provide a considerable and even leading-and sometimes overwhelming-input in the tidal heating. Based on the observed parameters, this input amounts to 52% in Phobos, 33% in Mimas, 23% in Enceladus, and 96% in Epimetheus. This supports the hypothesis by Makarov and Efroimsky (2014) that the additional tidal damping due to forced libration may have participated in the early heating up of some of the large moons. As one possibility, such a moon could have been chipped by collisions-whereby it acquired a higher permanent triaxiality and, therefore, a higher forced-libration magnitude and, consequently, a higher heating rate. After the moon warms up, its permanent triaxiality decreases, and so does the tidal heating rate.

Obesity does not impair walking economy across a range of speeds and grades.

PubMed

Browning, Raymond C; Reynolds, Michelle M; Board, Wayne J; Walters, Kellie A; Reiser, Raoul F

2013-05-01

Despite the popularity of walking as a form of physical activity for obese individuals, relatively little is known about how obesity affects the metabolic rate, economy, and underlying mechanical energetics of walking across a range of speeds and grades. The purpose of this study was to quantify metabolic rate, stride kinematics, and external mechanical work during level and gradient walking in obese and nonobese adults. Thirty-two obese [18 women, mass = 102.1 (15.6) kg, BMI = 33.9 (3.6) kg/m(2); mean (SD)] and 19 nonobese [10 women, mass = 64.4 (10.6) kg, BMI = 21.6 (2.0) kg/m(2)] volunteers participated in this study. We measured oxygen consumption, ground reaction forces, and lower extremity kinematics while subjects walked on a dual-belt force-measuring treadmill at 11 speeds/grades (0.50-1.75 m/s, -3° to +9°). We calculated metabolic rate, stride kinematics, and external work. Net metabolic rate (Ė net/kg, W/kg) increased with speed or grade across all individuals. Surprisingly and in contrast with previous studies, Ė net/kg was 0-6% less in obese compared with nonobese adults (P = 0.013). External work, although a primary determinant of Ė net/kg, was not affected by obesity across the range of speeds/grades used in this study. We also developed new prediction equations to estimate oxygen consumption and Ė net/kg and found that Ė net/kg was positively related to relative leg mass and step width and negatively related to double support duration. These results suggest that obesity does not impair walking economy across a range of walking speeds and grades.

Ventilatory Function in Relation to Mining Experience and Smoking in a Random Sample of Miners and Non-miners in a Witwatersrand Town1

PubMed Central

Sluis-Cremer, G. K.; Walters, L. G.; Sichel, H. S.

1967-01-01

The ventilatory capacity of a random sample of men over the age of 35 years in the town of Carletonville was estimated by the forced expiratory volume and the peak expiratory flow rate. Five hundred and sixty-two persons were working or had worked in gold-mines and 265 had never worked in gold-mines. No difference in ventilatory function was found between the miners and non-miners other than that due to the excess of chronic bronchitis in miners. PMID:6017134

Human's Capability to Discriminate Spatial Forces at the Big Toe.

PubMed

Hagengruber, Annette; Höppner, Hannes; Vogel, Jörn

2018-01-01

A key factor for reliable object manipulation is the tactile information provided by the skin of our hands. As this sensory information is so essential in our daily life it should also be provided during teleoperation of robotic devices or in the control of myoelectric prostheses. It is well-known that feeding back the tactile information to the user can lead to a more natural and intuitive control of robotic devices. However, in some applications it is difficult to use the hands as natural feedback channels since they may already be overloaded with other tasks or, e.g., in case of hand prostheses not accessible at all. Many alternatives for tactile feedback to the human hand have already been investigated. In particular, one approach shows that humans can integrate uni-directional (normal) force feedback at the toe into their sensorimotor-control loop. Extending this work, we investigate the human's capability to discriminate spatial forces at the bare front side of their toe. A state-of-the-art haptic feedback device was used to apply forces with three different amplitudes-2 N, 5 N, and 8 N-to subjects' right big toes. During the experiments, different force stimuli were presented, i.e., direction of the applied force was changed, such that tangential components occured. In total the four directions up (distal), down (proximal), left (medial), and right (lateral) were tested. The proportion of the tangential force was varied corresponding to a directional change of 5° to 25° with respect to the normal force. Given these force stimuli, the subjects' task was to identify the direction of the force change. We found the amplitude of the force as well as the proportion of tangential forces to have a significant influence on the success rate. Furthermore, the direction right showed a significantly different successrate from all other directions. The stimuli with a force amplitude of 8 N achieved success rates over 89% in all directions. The results of the user study provide evidence that the subjects were able to discriminate spatial forces at their toe within defined force amplitudes and tangential proportion.

Human's Capability to Discriminate Spatial Forces at the Big Toe

PubMed Central

Hagengruber, Annette; Höppner, Hannes; Vogel, Jörn

2018-01-01

A key factor for reliable object manipulation is the tactile information provided by the skin of our hands. As this sensory information is so essential in our daily life it should also be provided during teleoperation of robotic devices or in the control of myoelectric prostheses. It is well-known that feeding back the tactile information to the user can lead to a more natural and intuitive control of robotic devices. However, in some applications it is difficult to use the hands as natural feedback channels since they may already be overloaded with other tasks or, e.g., in case of hand prostheses not accessible at all. Many alternatives for tactile feedback to the human hand have already been investigated. In particular, one approach shows that humans can integrate uni-directional (normal) force feedback at the toe into their sensorimotor-control loop. Extending this work, we investigate the human's capability to discriminate spatial forces at the bare front side of their toe. A state-of-the-art haptic feedback device was used to apply forces with three different amplitudes—2 N, 5 N, and 8 N—to subjects' right big toes. During the experiments, different force stimuli were presented, i.e., direction of the applied force was changed, such that tangential components occured. In total the four directions up (distal), down (proximal), left (medial), and right (lateral) were tested. The proportion of the tangential force was varied corresponding to a directional change of 5° to 25° with respect to the normal force. Given these force stimuli, the subjects' task was to identify the direction of the force change. We found the amplitude of the force as well as the proportion of tangential forces to have a significant influence on the success rate. Furthermore, the direction right showed a significantly different successrate from all other directions. The stimuli with a force amplitude of 8 N achieved success rates over 89% in all directions. The results of the user study provide evidence that the subjects were able to discriminate spatial forces at their toe within defined force amplitudes and tangential proportion. PMID:29692718

Improvement of fuel injection system of locomotive diesel engine.

PubMed

Li, Minghai; Cui, Hongjiang; Wang, Juan; Guan, Ying

2009-01-01

The traditional locomotive diesels are usually designed for the performance of rated condition and much fuel will be consumed. A new plunger piston matching parts of fuel injection pump and injector nozzle matching parts were designed. The experimental results of fuel injection pump test and diesel engine show that the fuel consumption rate can be decreased a lot in the most of the working conditions. The forced lubrication is adopted for the new injector nozzle matching parts, which can reduce failure rate and increase service life. The design has been patented by Chinese State Patent Office.

Towards an Employment-Oriented Training Policy: An Agenda for Action. Discussion Paper No. 60.

ERIC Educational Resources Information Center

Kanawaty, George; Castro, Claudio de Moura

Training systems are facing three basic considerations: (1) adjustment to demographic trends such as the population explosion in developing countries, the aging of the work force in developed countries, and the increased participation of women in economic activities; (2) changing patterns of demand, such as lower rates of growth, restructuring of…

Study of the Economic and Rehabilitative Aspects of Prison Industry. Technical Tasks and Results.

ERIC Educational Resources Information Center

National Inst. of Law Enforcement and Criminal Justice (Dept. of Justice/LEAA), Washington, DC.

This volume analyzes existing and proposed correctional industries in Connecticut. First, the results of a survey made to determine the potential inmate work force for prison industry are presented as inmate profiles, descriptions of inmate and supervisor attitudes, and analyses of parolees' employment and recidivism rates. In part 2, four…

Older Workers and VET. At a Glance

ERIC Educational Resources Information Center

Dawe, Susan

2009-01-01

Australia, in common with many industrialised countries, must adjust in the coming years to an ageing population. The labour force participation rate is projected to fall and there will be a record number of older people who have retired from work. Thus, there will be fewer workers as a share of the population to generate the income needed to…

Demonization of Divorce: Prevalence Rates and Links to Postdivorce Adjustment

ERIC Educational Resources Information Center

Krumrei, Elizabeth J.; Mahoney, Annette; Pargament, Kenneth I.

2011-01-01

The meaning-making process can be crucial to individuals as they adjust to their divorce. Demonization is a negative coping response (also known as spiritual struggle) that involves appraising someone or something as related to demonic forces. Individuals may cognitively frame a divorce as the work of Satan in order to understand suffering while…

Recombination in maize is stable, predictable, and associated with genetic load: a joint study of the US and Chinese maize NAM populations

USDA-ARS?s Scientific Manuscript database

Among the fundamental evolutionary forces, recombination arguably has the largest impact on the practical work of plant breeders. Varying over 1,000-fold across the maize genome, the local meiotic recombination rate limits the resolving power of quantitative trait mapping and the precision of favora...

Long working hours and stroke among employees in the general workforce of Denmark.

PubMed

Hannerz, Harald; Albertsen, Karen; Burr, Hermann; Nielsen, Martin Lindhardt; Garde, Anne Helene; Larsen, Ann Dyreborg; Pejtersen, Jan Hyld

2018-05-01

A systematic review and meta-analysis have found that long working hours were prospectively associated with an increased risk of overall stroke. The primary aim of the present study was to test if this finding could be reproduced in a sample that has been randomly selected from the general workforce of Denmark. A secondary aim was to estimate the association for haemorrhagic and ischaemic stroke separately. Individual participant data on 20- to 64-year-old employees were drawn from the Danish Labour Force Survey, 1999-2013, and linked to data on socio-economic status (SES), migrations, hospitalisations and deaths from national registers. The participants were followed from the time of the interview until the end of 2014. Poisson regression was used to estimate age-, sex- and SES-adjusted rate ratios for stroke as a function of weekly working hours. With 35-40 working hours per week as reference, the estimated rate ratios for overall stroke were 0.97 (95% confidence interval (CI) 0.83-1.13) for 41-48 working hours, 1.10 (95% CI 0.86-1.39) for 49-54 working hours and 0.89 (95% CI 0.69-1.16) for ≥55 working hours. The estimated rate ratios per one category increase in working hours were 0.99 (95% CI 0.93-1.06) for overall stroke, 0.96 (95% CI 0.88-1.05) for ischaemic stroke and 1.15 (95% CI 1.02-1.31) for haemorrhagic stroke. Our analysis does not support the hypothesis that long working hours are associated with increased rates of overall stroke. It suggests, however, that long working hours might be associated with increased rates of haemorrhagic stroke.

Boundary effects on forced drainage through aqueous foam

NASA Astrophysics Data System (ADS)

Brannigan, G.; de Alcantara Bonfim, O. F.

2001-03-01

The flow of liquid through foam confined in vertical tubes was investigated by measuring the velocity vf of the liquid front forced down by gravity for various flow rates Q. The power law relating the velocity to flow rate of the incoming liquid (v_f ~ Q^α) was observed for tubes of various cross-sectional areas, A. The exponent α was found to vary linearly with the reciprocal of the area: α= 0.325 + 13.7 mm^2/A . This further supports the node-dominated foam drainage model, which predicts α= 1/3 in the limit of infinite cross-sectional area. This relation appears to be independent of bubble size, suggesting that using smaller foam bubbles may not alleviate boundary effects. The results of these experiments also partially explain the discrepancies in measurements of α reported in previous works.

A qualitative and quantitative survey of Forensic Medical Examiner workload in the Northumbria Police Force area October 2002-January 2003.

PubMed

Roberts, Geoffrey; Roberts, John; Patton, Hugh Fergus; Patton, Michelle; Megson, Kenneth; Murphy, Rob

2006-01-01

This force-wide study in the Northumbria Police area provides an audit of the quality and quantity of work carried out by Forensic Medical Examiners (FMEs) over a three month period. Approximately 25% of all arrests during the period of the audit resulted in a request for FME assessment of the detainee. About 79% of consultations were performed to establish fitness to detain, in which over 30% of detainees were intoxicated and over 40% addicted to drugs and/or alcohol. Over 30% of those queried for fitness to detain also required advice and occasionally prescription for medication, both for the management of addiction and the treatment of chronic illness. In comparison to prior work this study found lower rates of mental illness in alcohol and drug dependent populations (13% and 6%, respectively). It is hoped this study will provide information in respect of the specific competencies not only required by future FMEs but also nurses working with detainees within the custody suites.

Alteration by hyperoxia of ventilatory dynamics during sinusoidal work.

PubMed

Casaburi, R; Stremel, R W; Whipp, B J; Beaver, W L; Wasserman, K

1980-06-01

The effects of hyperoxia on ventilatory and gas exchange dynamics were studied utilizing sinusoidal work rate forcings. Five subjects exercised on 14 occasions on a cycle ergometer for 30 min with a sinusoidally varying work load. Tests were performed at seven frequencies of work load during air or 100% O2 inspiration. From the breath-by-breath responses to these tests, dynamic characteristics were analyzed by extracting the mean level, amplitude of oscillation, and phase lag for each six variables with digital computer techniques. Calculation of the time constant (tau) of the ventilatory responses demonstrated that ventilatory kinetics were slower during hyperoxia than during normoxia (P less than 0.025; avg 1.56 and 1.13 min, respectively). Further, for identical work rate fluctuations, end-tidal CO2 tension fluctuations were increased by hyperpoxia. Ventilation during hyperoxia is slower to respond to variations in the level of metabolically produced CO2, presumably because hyperoxia attenuates carotid body output; the arterial CO2 tension is consequently less tightly regulated.

Control of parallel manipulators using force feedback

NASA Technical Reports Server (NTRS)

Nanua, Prabjot

1994-01-01

Two control schemes are compared for parallel robotic mechanisms actuated by hydraulic cylinders. One scheme, the 'rate based scheme', uses the position and rate information only for feedback. The second scheme, the 'force based scheme' feeds back the force information also. The force control scheme is shown to improve the response over the rate control one. It is a simple constant gain control scheme better suited to parallel mechanisms. The force control scheme can be easily modified for the dynamic forces on the end effector. This paper presents the results of a computer simulation of both the rate and force control schemes. The gains in the force based scheme can be individually adjusted in all three directions, whereas the adjustment in just one direction of the rate based scheme directly affects the other two directions.

Influence of radius of cylinder HTS bulk on guidance force in a maglev vehicle system

NASA Astrophysics Data System (ADS)

Longcai, Zhang

2014-07-01

Bulk superconductors had great potential for various engineering applications, especially in a high-temperature superconducting (HTS) maglev vehicle system. In such a system, the HTS bulks were always exposed to AC external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, it was observed that the guidance force of the YBCO bulk over the NdFeB guideway used in the HTS maglev vehicle system was decayed by the application of the AC external magnetic field. In this paper, we investigated the influence of the radius of the cylinder HTS bulk exposed to an AC magnetic field perturbation on the guidance force in the maglev vehicle system. From the results, it was found that the guidance force was stronger for the bulk with bigger radius and the guidance force decay rates of the bulks were approximately equal despite of the different radius in the maglev vehicle system. Therefore, in order to obtain higher guidance force in the maglev vehicle system, we could use the cylinder HTS bulks with the bigger radius.

48 CFR 252.223-7004 - Drug-free work force.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Drug-free work force. 252... Provisions And Clauses 252.223-7004 Drug-free work force. As prescribed in 223.570-2, use the following clause: Drug-Free Work Force (SEP 1988) (a) Definitions. (1) Employee in a sensitive position, as used in...

48 CFR 252.223-7004 - Drug-free work force.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false Drug-free work force. 252... Provisions And Clauses 252.223-7004 Drug-free work force. As prescribed in 223.570-2, use the following clause: Drug-Free Work Force (SEP 1988) (a) Definitions. (1) Employee in a sensitive position, as used in...

48 CFR 252.223-7004 - Drug-free work force.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Drug-free work force. 252... Provisions And Clauses 252.223-7004 Drug-free work force. As prescribed in 223.570-2, use the following clause: Drug-Free Work Force (SEP 1988) (a) Definitions. (1) Employee in a sensitive position, as used in...

48 CFR 252.223-7004 - Drug-free work force.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Drug-free work force. 252... Provisions And Clauses 252.223-7004 Drug-free work force. As prescribed in 223.570-2, use the following clause: Drug-Free Work Force (SEP 1988) (a) Definitions. (1) Employee in a sensitive position, as used in...

48 CFR 252.223-7004 - Drug-free work force.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Drug-free work force. 252... Provisions And Clauses 252.223-7004 Drug-free work force. As prescribed in 223.570-2, use the following clause: Drug-Free Work Force (SEP 1988) (a) Definitions. (1) Employee in a sensitive position, as used in...

40 CFR 35.936-14 - Force account work.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 1 2010-07-01 2010-07-01 false Force account work. 35.936-14 Section... Force account work. (a) A grantee must secure the project officer's prior written approval for use of the force account method for (1) any step 1 or step 2 work in excess of $10,000; (2) any sewer...

Transition state theory for activated systems with driven anharmonic barriers.

PubMed

Revuelta, F; Craven, Galen T; Bartsch, Thomas; Borondo, F; Benito, R M; Hernandez, Rigoberto

2017-08-21

Classical transition state theory has been extended to address chemical reactions across barriers that are driven and anharmonic. This resolves a challenge to the naive theory that necessarily leads to recrossings and approximate rates because it relies on a fixed dividing surface. We develop both perturbative and numerical methods for the computation of a time-dependent recrossing-free dividing surface for a model anharmonic system in a solvated environment that interacts strongly with an oscillatory external field. We extend our previous work, which relied either on a harmonic approximation or on periodic force driving. We demonstrate that the reaction rate, expressed as the long-time flux of reactive trajectories, can be extracted directly from the stability exponents, namely, Lyapunov exponents, of the moving dividing surface. Comparison to numerical results demonstrates the accuracy and robustness of this approach for the computation of optimal (recrossing-free) dividing surfaces and reaction rates in systems with Markovian solvation forces. The resulting reaction rates are in strong agreement with those determined from the long-time flux of reactive trajectories.

Forecasting Foreign Currency Exchange Rates for Air Force Budgeting

DTIC Science & Technology

2015-03-26

FORECASTING FOREIGN CURRENCY EXCHANGE RATES FOR AIR FORCE BUDGETING THESIS MARCH 2015...States. AFIT-ENV-MS-15-M-178 FORECASTING FOREIGN CURRENCY EXCHANGE RATES FOR AIR FORCE BUDGETING THESIS Presented to the Faculty...FORECASTING FOREIGN CURRENCY EXCHANGE RATES FOR AIR FORCE BUDGETING Nicholas R. Gardner, BS Captain, USAF Committee Membership: Lt Col Jonathan

Somatosensory Gating Is Dependent on the Rate of Force Recruitment in the Human Orofacial System

ERIC Educational Resources Information Center

Andreatta, Richard D.; Barlow, Steven M.

2009-01-01

Purpose: Functional orofacial behaviors vary in their force endpoint and rate of recruitment. This study assessed the gating of orofacial cutaneous somatosensation during different cyclic lip force recruitment rates. Understanding how differences in the rate of force recruitment influences trigeminal system function is an important step toward…

Importance of anisotropy in detachment rates for force production and cargo transport by a team of motor proteins.

PubMed

Takshak, Anjneya; Kunwar, Ambarish

2016-05-01

Many cellular processes are driven by collective forces generated by a team consisting of multiple molecular motor proteins. One aspect that has received less attention is the detachment rate of molecular motors under mechanical force/load. While detachment rate of kinesin motors measured under backward force increases rapidly for forces beyond stall-force; this scenario is just reversed for non-yeast dynein motors where detachment rate from microtubule decreases, exhibiting a catch-bond type behavior. It has been shown recently that yeast dynein responds anisotropically to applied load, i.e. detachment rates are different under forward and backward pulling. Here, we use computational modeling to show that these anisotropic detachment rates might help yeast dynein motors to improve their collective force generation in the absence of catch-bond behavior. We further show that the travel distance of cargos would be longer if detachment rates are anisotropic. Our results suggest that anisotropic detachment rates could be an alternative strategy for motors to improve the transport properties and force production by the team. © 2016 The Protein Society.

Fertility and work-force participation: The experience of Melbourne Wives.

PubMed

Ware, H

1976-11-01

Summary Current and retrospective data on the fertility control, work-force participation intentions and practice of Melbourne wives are combined in an examination of the causal link between work-force participation and reduced family size. Stress is laid on the analysis of the interaction between work-force participation and fertility over time, taking into account the proportion of married life spent in the work-force, rather than relying exclusively on a measure of current participation, the only option available in the analysis of census-type data. The wide range of information available makes it possible to study the effects of work-force participation on wives of unimpaired fertility, as well as the different consequences of planned and unplanned participation, and of working in a variety of occupations and for a number of distinct reasons. Examination of the future fertility intentions and current contraceptive practice of the younger wives shows that working wives are not, in these respects, markedly different from their house-wife peers. Overall, the balance of the evidence indicates that in the majority of cases fertility influences work-force participation rather than the converse.

U.S. Department of Energy, Illness and Injury Surveillance Program, Worker Health Summary, 1995-2004

DOE Office of Scientific and Technical Information (OSTI.GOV)

U.S. Department of Energy, Office of Health, Safety and Security, Office of Illness and Injury Prevention Programs

The Department of Energy’s (DOE) Illness and Injury Surveillance Program has created an opportunity to assess illness and injury rates and patterns among workers at participating sites for well over a decade. The Worker Health Summary introduces an additional perspective on worker health with the introduction of analyses comparing the experience of sites in different program offices and a focus on time trends covering a decade of worker illness and injury experience. These analyses by program office suggest that illness and injury patterns among National Nuclear Security Administration (NNSA) workers diverge in many ways from those seen among Environmental Managementmore » (EM) and Science workers for reasons not yet understood. These differences will receive further investigation in future special focus studies, as will other findings of interest. With the time depth now available in our data, the Worker Health Summary reveals an additional nuance in worker health trends: changing health patterns in a specialized and skilled but aging work force. Older workers are becoming an increasing percentage of the work force, and their absence rates for diseases such as diabetes and hypertension are increasing as well. The impact of these emerging health issues, if properly addressed, can be managed to maintain or even enhance worker health and productivity. Prevention strategies designed to reduce the toll of these health conditions appear warranted, and this report gives us an indication of where to focus them. The analyses that follow reflect the Illness and Injury Surveillance Program’s continued commitment to apply a public health perspective in protecting the health of DOE’s work force.« less

Silicone based dielectric elastomer strip actuators coupled with nonlinear biasing elements for large actuation strains

NASA Astrophysics Data System (ADS)

Hau, S.; Bruch, D.; Rizzello, G.; Motzki, P.; Seelecke, S.

2018-07-01

There are two major categories of dielectric elastomer actuators (DEAs), which differ from the way in which the actuation is exploited: stack DEAs, using the thickness compression, and membrane DEAs, which exploit the expansion in area. In this work we focus on a specific type of membrane DEAs, i.e., silicone-based strip-in-plane (SIP) DEAs with screen printed electrodes. The performance of such actuators strongly depends on their geometry and on the adopted mechanical biasing system. Typically, the biasing is based on elastomer pre-stretch or on dead loads, which results in relatively low actuation strain. Biasing systems characterized by a negative rate spring have proven to significantly increase the performance of circular out-of-plane DEAs. However, this kind of biasing has never been systematically applied to silicone SIP DEAs. In this work, the biasing design based on negative rate springs is extended to strip DEAs as well, allowing to improve speed, strain, and force of the resulting actuator. At first, the DEAs are characterized under electrical and mechanical loading. Afterwards, two actuator systems are studied and compared in terms of actuation strain, force output, and actuation speed. In a first design stage, the DEA is coupled with a linear spring. Subsequently, the membrane is loaded with a combination of linear and nonlinear spring (working in a negative stiffness region). The resulting stroke output of the second systems is more than 9 times higher in comparison to the first one. An actuation strain of up to 45% (11.2 millimeter) and a force output of 0.38 Newton are measured. A maximum speed of 0.29 m s‑1 is achieved, which is about 60 times faster than the one typically measured for similar systems based on VHB.

Women and changes in the Chilean economy: some questions.

PubMed

Smiaroski, M S

1996-10-01

The author argues that a new development model that encourages greater participation of women in the work force in domestic piecework, temporary work, and subcontracting may further lead to the exploitation of women in Chile. The importance of women in economic development in Chile should be based on building skills, providing support child care services, reorienting women's education, and tax incentives. Chile over the past decade has achieved relatively stable economic growth and increased employment of women. During 1990-93 the growth of women in the work force increased at a rate of 16.8%, while men's presence increased by only 9.8%. The Chilean economy is based on a sophisticated modern sector and a labor-intensive informal sector. The Chilean model of development relies on cheap, flexible labor and a government approval of this model. Increased participation of women in the labor force is usually perceived as increased economic empowerment. A 1994 Oxfam study found that women were being forced into the labor market due to declines in family income and low wages. 46% of men and women received wages that did not cover basic necessities. The Chilean labor market is gender-stratified. Men are paid better than women for the same work. Men are in more permanent positions. Labor laws are either inadequate or violated, particularly for hours of work and overtime pay and conditions of employment and benefits. Traditional female jobs are those that rely on women's natural attributes. These unskilled attributes are rewarded with low wages. Little opportunity is provided for upgrading skills or acquiring new skills. Some women turn down advancement because of a lack of role models. Women have little opportunity to develop their self-image as workers. Poor self-images affect women's work attitudes and motivation. Some firms use competition between women to boost production. Chilean women remain in subordinate roles.

Labor-force participation patterns of older self-employed workers.

PubMed

Quinn, J F

1980-04-01

Self-employed persons work in a less constrained environment than do most wage-and-salary employees. Generally they are not subject to compulsory retirement nor are they affected by institutional rules concerning labor supply. Data from the 1969 and 1971 interviews of the Retirement History Study show that the labor supply and retirement patterns of the self-employed are distinct from those of other workers. The self-employed (espeically "career" self-employed) nearing retirement age are less likely to be out of the labor force, and those who continue in the labor force have a wider variation in the number of hours worked per year. Downward flexibility in hours (the option for gradual retirement) may be an extremely valuable aspect of self-employed status, and one wonders whether other older workers would also choose this pattern if more flexible opportunities were available. Despite these differences, labor-supply decisions of the self-employed are found to be influenced by many of the same factors that affect the rest of the workforce--health, eligibility for social security and pension benefits, the wage rate, and the flow of asset.

How Enzymes Work: A Look through the Perspective of Molecular Viscoelastic Properties

NASA Astrophysics Data System (ADS)

Qu, Hao; Zocchi, Giovanni

2013-01-01

We present nanorheology measurements on the folded state of an enzyme that show directly that the (ensemble-averaged) stress-strain relations are nonlinear and frequency dependent beyond 1-Å deformation. We argue that this frequency dependence allows for opening a nonequilibrium cycle in the force-deformation plane if the forward and backward conformational changes of the enzyme during catalysis happen at different speeds. Using a heuristic model for the experimentally established viscoelastic properties of the enzyme, we examine a number of general features of enzymatic action. We find that the proposed viscoelastic cycle is consistent with the linear decrease of the speed of motor proteins with load. We find a relation between the stall force and the maximum rate for enzymes (in general) and motors (in particular). We estimate the stall force of the motor protein kinesin from thermodynamic quantities and estimate the maximum rate of enzymes from purely mechanical quantities. We propose that the viscoelastic cycle provides a framework for considering mechanochemical coupling in enzymes on the basis of possibly universal materials properties of the folded state of proteins.

Work Force Information and Career-Technical Education. In Brief: Fast Facts for Policy and Practice No. 10.

ERIC Educational Resources Information Center

Sommers, Dixie

To prepare young people and adults for labor market success, career-technical education (CTE) practitioners must know how to find and use work force information. Recent federal legislation, including the Workforce Investment Act of 1998, underscores the importance of work force education. The nationwide work force information system makes data on…

A socioecological analysis of the determinants of national public health nutrition work force capacity: Australia as a case study.

PubMed

Hughes, Roger

2006-01-01

This article uses a socioecological analytical approach to assess the capacity of the public health nutrition work force in Australia as a prelude to work force development strategy planning. It demonstrates how the socioecological model can be used to assess and inform the development of the infrastructure required for effective public health nutrition effort. An interpretive case study method was used involving triangular analysis of quantitative and qualitative data from multiple sources including semistructured interviews with advanced-level practitioners, literature review, a cross-sectional national work force survey, and position description audit and consensus development using a Delphi study. The findings of this analysis indicate that the Australian public health nutrition work force's capacity to effectively address priority nutrition issues is limited by determinants that can be categorized as relating to human resource infrastructure, organizational and policy environments, intelligence access and use, practice improvement and learning systems, and work force preparation. This socioecological analysis supports an intelligence-based focus for work force development effort in Australia and a conceptual framework for work force capacity assessment with potential applications in other countries.

Target: Alcohol Abuse in the Hard-to-Reach Work Force. Ideas and Resources for Responding to Problems of the Hard-to-Reach Work Force.

ERIC Educational Resources Information Center

Informatics, Inc., Rockville, MD.

This guide is designed as a source of ideas and information for individuals and organizations interested in occupational alcoholism programs for the hard-to-reach work force. Following a brief overview of the problem and a report on progress in occupational alcoholism programming, a working definition of the hard-to-reach work force is offered;…

Multifrequency spectrum analysis using fully digital G Mode-Kelvin probe force microscopy.

PubMed

Collins, Liam; Belianinov, Alex; Somnath, Suhas; Rodriguez, Brian J; Balke, Nina; Kalinin, Sergei V; Jesse, Stephen

2016-03-11

Since its inception over two decades ago, Kelvin probe force microscopy (KPFM) has become the standard technique for characterizing electrostatic, electrochemical and electronic properties at the nanoscale. In this work, we present a purely digital, software-based approach to KPFM utilizing big data acquisition and analysis methods. General mode (G-Mode) KPFM works by capturing the entire photodetector data stream, typically at the sampling rate limit, followed by subsequent de-noising, analysis and compression of the cantilever response. We demonstrate that the G-Mode approach allows simultaneous multi-harmonic detection, combined with on-the-fly transfer function correction-required for quantitative CPD mapping. The KPFM approach outlined in this work significantly simplifies the technique by avoiding cumbersome instrumentation optimization steps (i.e. lock in parameters, feedback gains etc), while also retaining the flexibility to be implemented on any atomic force microscopy platform. We demonstrate the added advantages of G-Mode KPFM by allowing simultaneous mapping of CPD and capacitance gradient (C') channels as well as increased flexibility in data exploration across frequency, time, space, and noise domains. G-Mode KPFM is particularly suitable for characterizing voltage sensitive materials or for operation in conductive electrolytes, and will be useful for probing electrodynamics in photovoltaics, liquids and ionic conductors.

Multifrequency spectrum analysis using fully digital G Mode-Kelvin probe force microscopy

DOE PAGES

Collins, Liam F.; Jesse, Stephen; Belianinov, Alex; ...

2016-02-11

Since its inception over two decades ago, Kelvin probe force microscopy (KPFM) has become the standard technique for characterizing electrostatic, electrochemical and electronic properties at the nanoscale. In this work, we present a purely digital, software-based approach to KPFM utilizing big data acquisition and analysis methods. General Mode (G-Mode) KPFM, works by capturing the entire photodetector data stream, typically at the sampling rate limit, followed by subsequent de-noising, analysis and compression of the cantilever response. We demonstrate that the G-Mode approach allows simultaneous multi-harmonic detection, combined with on-the-fly transfer function correction required for quantitative CPD mapping. The KPFM approach outlinedmore » in this work significantly simplifies the technique by avoiding cumbersome instrumentation optimization steps (i.e. lock in parameters, feedback gains etc.), while also retaining the flexibility to be implemented on any atomic force microscopy platform. We demonstrate the added advantages of G-Mode KPFM by allowing simultaneous mapping of CPD and capacitance gradient (C') channels as well as increased flexibility in data exploration across frequency, time, space, and noise domains. As a result, G-Mode KPFM is particularly suitable for characterizing voltage sensitive materials or for operation in conductive electrolytes, and will be useful for probing electrodynamics in photovoltaics, liquids and ionic conductors.« less

Wear-dependent specific coefficients in a mechanistic model for turning of nickel-based superalloy with ceramic tools

NASA Astrophysics Data System (ADS)

López de Lacalle, Luis Norberto; Urbicain Pelayo, Gorka; Fernández-Valdivielso, Asier; Alvarez, Alvaro; González, Haizea

2017-09-01

Difficult to cut materials such as nickel and titanium alloys are used in the aeronautical industry, the former alloys due to its heat-resistant behavior and the latter for the low weight - high strength ratio. Ceramic tools made out alumina with reinforce SiC whiskers are a choice in turning for roughing and semifinishing workpiece stages. Wear rate is high in the machining of these alloys, and consequently cutting forces tends to increase along one operation. This paper establishes the cutting force relation between work-piece and tool in the turning of such difficult-to-cut alloys by means of a mechanistic cutting force model that considers the tool wear effect. The cutting force model demonstrates the force sensitivity to the cutting engagement parameters (ap, f) when using ceramic inserts and wear is considered. Wear is introduced through a cutting time factor, being useful in real conditions taking into account that wear quickly appears in alloys machining. A good accuracy in the cutting force model coefficients is the key issue for an accurate prediction of turning forces, which could be used as criteria for tool replacement or as input for chatter or other models.

Child maltreatment among U.S. Air Force parents deployed in support of Operation Iraqi Freedom/Operation Enduring Freedom.

PubMed

Rabenhorst, Mandy M; McCarthy, Randy J; Thomsen, Cynthia J; Milner, Joel S; Travis, Wendy J; Colasanti, Marie P

2015-02-01

This study examined child maltreatment perpetration among 99,697 active-duty U.S. Air Force parents who completed a combat deployment. Using the deploying parent as the unit of analysis, we analyzed whether child maltreatment rates increased postdeployement relative to predeployment. These analyses extend previous research that used aggregate data and extend our previous work that used data from the same period but used the victim as the unit of analysis and included only deploying parents who engaged in child maltreatment. In this study, 2% (n = 1,746) of deploying parents perpetrated child maltreatment during the study period. Although no overall differences were found in child maltreatment rates postdeployment compared to predeployment, several maltreatment-related characteristics qualified this finding. Rates for emotional abuse and mild maltreatment were lower following deployment, whereas child maltreatment rates for severe maltreatment were higher following deployment. The finding that rates of severe child maltreatment, including incidents involving alcohol use, were higher postdeployment suggests a need for additional support services for parents following their return from combat deployment, with a focus on returning parents who have an alcohol use problem. © The Author(s) 2014.

Decreasing stochasticity through enhanced seasonality in measles epidemics.

PubMed

Mantilla-Beniers, N B; Bjørnstad, O N; Grenfell, B T; Rohani, P

2010-05-06

Seasonal changes in the environment are known to be important drivers of population dynamics, giving rise to sustained population cycles. However, it is often difficult to measure the strength and shape of seasonal forces affecting populations. In recent years, statistical time-series methods have been applied to the incidence records of childhood infectious diseases in an attempt to estimate seasonal variation in transmission rates, as driven by the pattern of school terms. In turn, school-term forcing was used to show how susceptible influx rates affect the interepidemic period. In this paper, we document the response of measles dynamics to distinct shifts in the parameter regime using previously unexplored records of measles mortality from the early decades of the twentieth century. We describe temporal patterns of measles epidemics using spectral analysis techniques, and point out a marked decrease in birth rates over time. Changes in host demography alone do not, however, suffice to explain epidemiological transitions. By fitting the time-series susceptible-infected-recovered model to measles mortality data, we obtain estimates of seasonal transmission in different eras, and find that seasonality increased over time. This analysis supports theoretical work linking complex population dynamics and the balance between stochastic and deterministic forces as determined by the strength of seasonality.

Ergonomic task reduction prevents bone osteopenia in a rat model of upper extremity overuse

PubMed Central

BARBE, Mary F.; JAIN, Nisha X.; MASSICOTTE, Vicky S.; POPOFF, Steven N.; BARR-GILLESPIE, Ann E.

2015-01-01

We evaluated the effectiveness of ergonomic workload reduction of switching rats from a high repetition high force (HRHF) lever pulling task to a reduced force and reach rate task for preventing task-induced osteopenic changes in distal forelimb bones. Distal radius and ulna trabecular structure was examined in young adult rats performing one of three handle-pulling tasks for 12 wk: 1) HRHF, 2) low repetition low force (LRLF); or 3) HRHF for 4 wk and than LRLF thereafter (HRHF-to-LRLF). Results were compared to age-matched controls rats. Distal forelimb bones of 12-wk HRHF rats showed increased trabecular resorption and decreased volume, as control rats. HRHF-to-LRLF rats had similar trabecular bone quality as control rats; and decreased bone resorption (decreased trabecular bone volume and serum CTX1), increased bone formation (increased mineral apposition, bone formation rate, and serum osteocalcin), and decreased osteoclasts and inflammatory cytokines, than HRHF rats. Thus, an ergonomic intervention of HRHF-to-LRLF prevented loss of trabecular bone volume occurring with prolonged performance of a repetitive upper extremity task. These findings support the idea of reduced workload as an effective approach to management of work-related musculoskeletal disorders, and begin to define reach rate and load level boundaries for such interventions. PMID:25739896

Neuromuscular rate of force development deficit in Parkinson disease.

PubMed

Hammond, Kelley G; Pfeiffer, Ronald F; LeDoux, Mark S; Schilling, Brian K

2017-06-01

Bradykinesia and reduced neuromuscular force exist in Parkinson disease. The interpolated twitch technique has been used to evaluate central versus peripheral manifestations of neuromuscular strength in healthy, aging, and athletic populations, as well as moderate to advanced Parkinson disease, but this method has not been used in mild Parkinson disease. This study aimed to evaluate quadriceps femoris rate of force development and quantify potential central and peripheral activation deficits in individuals with Parkinson disease. Nine persons with mild Parkinson Disease (Hoehn & Yahr≤2, Unified Parkinson Disease Rating Scale total score=mean 19.1 (SD 5.0)) and eight age-matched controls were recruited in a cross-sectional investigation. Quadriceps femoris voluntary and stimulated maximal force and rate of force development were evaluated using the interpolated twitch technique. Thirteen participants satisfactorily completed the protocol. Individuals with early Parkinson disease (n=7) had significantly slower voluntary rate of force development (p=0.008; d=1.97) and rate of force development ratio (p=0.004; d=2.18) than controls (n=6). No significant differences were found between groups for all other variables. Persons with mild-to-moderate Parkinson disease display disparities in rate of force development, even without deficits in maximal force. The inability to produce force at a rate comparable to controls is likely a downstream effect of central dysfunction of the motor pathway in Parkinson disease. Copyright © 2017. Published by Elsevier Ltd.

The Calcutta metropolitan district.

PubMed

1987-01-01

11 million residents in 1450 square kilometers make the Calcutta Metropolitan District the world's most densely packed metropolis and the world's 6th largest urban agglomeration. But even though Calcutta is India's largest city, it is growing at a much slower pace than other Indian cities. Its annual growth rate between 1971 and 1981 was 2.65%, well below the 3.8% growth rate for India's urban population as a whole. Even at this relatively slow growth rate, however, Calcutta's population will still grow to 11.7 million residents in 1990 and 15.9 million in 2000. Calcutta's failure to create urban jobs quickly enough to accommodate its vast population increase has led to widespread evidence of unemployment and extreme poverty. Many in Calcutta complain that the central goverment has thwarted development and international aid to Calcutta. Industrial stagnation has slowed the area's urbanization and rural-urban migration. As greater numbers of new job seekers enter the labor force and the dropout rate diminishes due to dramatic inprovement in health, relentless pressure is put on Calcutta's already strained economy. Calcutta's job seekers will be partly absorbed by the informal sector; one study estimates that 40-50% of Calcutta's labor force is employed in the informal sector. In 1971, 6% of Calcutta's work force was employed in agriculture, 40% in manufacturing, and 54% in services. 2/3 of the population make less than $35 a month, and about 10% are officially unemployed. Despite great improvements in public works, Calcutta's slums are still India's worst. Living standards have gone down compared to India as a whole. Most of the middle class has moved to the suburbs; what is left in the central core is the rich and the poor. However, despite widening income disparities, Calcutta is still a peaceful city--especially so at a time when India is marked with so much violence.

Assessing differences in hours worked between male and female dentists: an analysis of cross-sectional national survey data from 1979 through 1999.

PubMed

Walton, Surrey M; Byck, Gayle R; Cooksey, Judith A; Kaste, Linda M

2004-05-01

Women are increasingly entering the dental work force. This study examines the impact of sex, age and other demographic characteristics on dentists' work force participation and on hours worked from 1979 through 1999. The study drew on cross-sectional data on dentists (4,209 men and 354 women) from national population surveys conducted by the U.S. Bureau of Labor Statistics from 1979 through 1999. The authors used descriptive statistics and regression analyses to examine sex differences in work force participation and in hours worked across age, as well as other factors. Work force participation was high for both men and women. Men worked more hours and worked part time less frequently; they worked more than 42 hours per week more frequently. Older dentists worked fewer hours, with a larger impact of age seen among men. Having children had a significantly greater effect on the number of hours worked per week among female dentists than among male dentists. There were significant differences in dentists' hours worked by sex and by age. The consistency of the results with past studies suggests these differences will hold in the near future. Women's entry into the dental work force has been significant and has helped maintain the supply of dentists. Sex differences in the work force should be considered in evaluating the supply of dentists and related work force policy.

Occupational Differentiation in the First Decade after High School. Report No. 259.

ERIC Educational Resources Information Center

Gottfredson, Linda S.; Brown, Vicky C.

This report charts the rate at which occupational differentiation proceeded among 3,730 young white men and the dimensions along which it proceeded. Data from the National Longitudinal Survey of the Labor Force Experience of Young Men were used to examine employment among men aged sixteen to twenty-eight in different levels and fields of work.…

Improving Productivity in the Work Force: Implications for Research and Development in Vocational Education. Occasional Paper No. 72.

ERIC Educational Resources Information Center

Sullivan, Dennis J.

Declining productivity is a major problem in the American economy. Gains in productivity, and finally, actual rates of productivity, have been declining since the late 1960s. Specific problems arising as a result of this decline in productivity are the inflationary pressures that we face as a nation, the increased regulatory environment under…

Building the Stock of College-Educated Labor. NBER Working Paper No. 11604

ERIC Educational Resources Information Center

Dynarski, Susan

2005-01-01

Half of college students drop out before completing a degree. These low rates of college completion among young people should be viewed in the context of slow future growth in the educated labor force, as the well-educated baby boomers retire and new workers are drawn from populations with historically low education levels. This paper establishes…

Predicting Tree Mortality From Diameter Growth: A Comparison of Maximum Likelihood and Bayesian Approaches

Treesearch

Peter H. Wychoff; James S. Clark

2000-01-01

Ecologists and foresters have long noted a link between tree growth rate and mortality, and recent work suggests that i&erspecific differences in low growth tolerauce is a key force shaping forest structure. Little information is available, however, on the growth-mortality relationship for most species. We present three methods for estimating growth-mortality...

The Economic Implications of Korean Unification

DTIC Science & Technology

2002-06-01

allowing unplanned activities to become legal.205 In a similar vein, state employees were forced to create their own work-arounds by increasingly...enterprises were given the option to adopt a piece-rate system for employee wages to spur labor productivity. 208...Indonesia, Vietnam has weathered the Asian economic crisis rather well. Unlike the deep recession that faced Thailand, Malaysia , Indonesia, and

An Analysis of the Air Force Working Capital Fund’s Performance and the Pricing Strategy of the Materiel Support Division

DTIC Science & Technology

2003-03-25

Leland G. “ Defense Business Operations Fund (DBOF): Problems and Promise,” Public Budgeting & Finance, 15: 38-57 (Winter 1995). 80 Kotler , Philip ...knows if they will reach their desired rate-of return or profit level ( Kotler , 2000: 466). Market-Based Pricing The strength of market-based pricing

Part-Time Work and Flexible Hours Employment.

ERIC Educational Resources Information Center

Greenwald, Carol S.

Over the last decade, part-time employment of adult women has grown twice as fast as full-time employment. The most rapid gains in labor force participation rates of women have occurred among wives under 35, and especially among those with children under 6. At the other end of the age range, part-time employment is also a very desirable option.…

A Simulation of an Income Contingent Tuition Scheme in a Transition Economy

ERIC Educational Resources Information Center

Vodopivec, Milan

2009-01-01

The paper takes advantage of exceptionally rich longitudinal data on the universe of labor force participants in Slovenia and simulates the working of an income contingent loan scheme that seeks to recover part of schooling costs. The simulations show that under the base variant (where the target cost recovery rate is 20% and the contribution rate…

Minimization of organic and metallic industrial waste via lemna minor concentration. Final report, 1 September 1991-1 December 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowers-Irons, G.L.

1992-12-30

In recent years, new strict environmental laws have required improved and cost-effective water purification methods by Air Force complexes. Naturally assisted primary units (microbiological) and secondary units (macrophyte) could bring waste treatment systems into tighter compliance. Aquatic macrophytes which have rapid growth rates and absorb large quantities of nutrients could provide a practical and economic method for more complete wastewater maintenance, hazardous waste clean-up or river, lake and ground water purification. This work has shown that Lemna minor, or Common Duckweed, can successfully and thoroughly accumulate organics and metals from Air Force wastewaters.

Quantifying force application to a newborn manikin during simulated cardiopulmonary resuscitation.

PubMed

Solevåg, Anne Lee; Cheung, Po-Yin; Li, Elliott; Aziz, Khalid; O'Reilly, Megan; Fu, Bo; Zheng, Bin; Schmölzer, Georg

2016-01-01

To assess utility of the FingerTPS™ system in measuring chest compression (CC) rate and force. Five minutes of CC was performed in a neonatal manikin without (n = 29) and with (n = 30) a metronome. The FingerTPS™ force (lbs.) was compared to pressure (mmHg) in a 50-mL normal-saline bag inside the manikin. FingerTPS™ CC rate and the time until a 20% decline from baseline force and pressure were calculated. The normal-saline pressure declined earlier than the FingerTPS™ force. Metronome use did not influence CC rate, force or pressure. The FingerTPS™ can be used to measure CC rate and force.

Increasing Running Step Rate Reduces Patellofemoral Joint Forces

PubMed Central

Lenhart, Rachel L.; Thelen, Darryl G.; Wille, Christa M.; Chumanov, Elizabeth S.; Heiderscheit, Bryan C.

2013-01-01

Purpose Increasing step rate has been shown to elicit changes in joint kinematics and kinetics during running, and has been suggested as a possible rehabilitation strategy for runners with patellofemoral pain. The purpose of this study was to determine how altering step rate affects internal muscle forces and patellofemoral joint loads, and then to determine what kinematic and kinetic factors best predict changes in joint loading. Methods We recorded whole body kinematics of 30 healthy adults running on an instrumented treadmill at three step rate conditions (90%, 100%, and 110% of preferred step rate). We then used a 3D lower extremity musculoskeletal model to estimate muscle, patellar tendon, and patellofemoral joint forces throughout the running gait cycles. Additionally, linear regression analysis allowed us to ascertain the relative influence of limb posture and external loads on patellofemoral joint force. Results Increasing step rate to 110% of preferred reduced peak patellofemoral joint force by 14%. Peak muscle forces were also altered as a result of the increased step rate with hip, knee and ankle extensor forces, and hip abductor forces all reduced in mid-stance. Compared to the 90% step rate condition, there was a concomitant increase in peak rectus femoris and hamstring loads during early and late swing, respectively, at higher step rates. Peak stance phase knee flexion decreased with increasing step rate, and was found to be the most important predictor of the reduction in patellofemoral joint loading. Conclusion Increasing step rate is an effective strategy to reduce patellofemoral joint forces and could be effective in modulating biomechanical factors that can contribute to patellofemoral pain. PMID:23917470

3 CFR - White House Task Force on Middle-Class Working Families

Code of Federal Regulations, 2010 CFR

2010-01-01

... 3 The President 1 2010-01-01 2010-01-01 false White House Task Force on Middle-Class Working... Task Force on Middle-Class Working Families Memorandum for the Heads of Executive Departments and... times. To these ends, I hereby direct the following: Section 1. White House Task Force on Middle-Class...

Dental work force strategies during a period of change and uncertainty.

PubMed

Brown, L J

2001-12-01

Both supply and demand influence the ability of the dental work force to adequately and efficiently provide dental care to a U.S. population growing in size and diversity. Major changes are occurring on both sides of the dental care market. Among factors shaping the demand for dental care are changing disease patterns, shifting population demographics, the extent and features of third-party payment, and growth of the economy and the population. The capacity of the dental work force to provide care is influenced by enhancements of productivity and numbers of dental health personnel, as well as their demographic and practice characteristics. The full impact of these changes is difficult to predict. The dentist-to-population ratio does not reflect all the factors that must be considered to develop an effective dental work force policy. Nationally, the dental work force is likely to be adequate for the next several years, but regional work force imbalances appear to exist and may get worse. Against this backdrop of change and uncertainty, future dental work force strategies should strive for short-term responsiveness while avoiding long-term inflexibility. Trends in the work force must be continually monitored. Thorough analysis is required, and action should be taken when necessary.

The series elastic shock absorber: tendon elasticity modulates energy dissipation by muscle during burst deceleration.

PubMed

Konow, Nicolai; Roberts, Thomas J

2015-04-07

During downhill running, manoeuvring, negotiation of obstacles and landings from a jump, mechanical energy is dissipated via active lengthening of limb muscles. Tendon compliance provides a 'shock-absorber' mechanism that rapidly absorbs mechanical energy and releases it more slowly as the recoil of the tendon does work to stretch muscle fascicles. By lowering the rate of muscular energy dissipation, tendon compliance likely reduces the risk of muscle injury that can result from rapid and forceful muscle lengthening. Here, we examine how muscle-tendon mechanics are modulated in response to changes in demand for energy dissipation. We measured lateral gastrocnemius (LG) muscle activity, force and fascicle length, as well as leg joint kinematics and ground-reaction force, as turkeys performed drop-landings from three heights (0.5-1.5 m centre-of-mass elevation). Negative work by the LG muscle-tendon unit during landing increased with drop height, mainly owing to greater muscle recruitment and force as drop height increased. Although muscle strain did not increase with landing height, ankle flexion increased owing to increased tendon strain at higher muscle forces. Measurements of the length-tension relationship of the muscle indicated that the muscle reached peak force at shorter and likely safer operating lengths as drop height increased. Our results indicate that tendon compliance is important to the modulation of energy dissipation by active muscle with changes in demand and may provide a mechanism for rapid adjustment of function during deceleration tasks of unpredictable intensity. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

NASA/ORNL/AFRL Project Work on EBM LSHR: Additive Manufacturing of High-Temperature Gamma-Prime Strengthened Ni-Based Superalloys

NASA Technical Reports Server (NTRS)

Sudbrack, Chantal K.; Kirka, Michael M.; Dehoff, Ryan R.; Carter, Robert W.; Semiatin, Sheldon L.; Gabb, Timothy P.

2016-01-01

Powder-bed fabrication of aerospace alloys may revolutionize production by eliminating the need for extensive machining and expensive tooling. Heated-bed electron-beam melting (EBM) offers advantages over non-heated laser additive manufacturing (AM) methods, including lower residual stress, reduced risk of contamination, slower cooling rates, and faster build times. NASA Glenn Research Center has joint project work with Oak Ridge National Lab and the Air Force Research Laboratory to explore the feasibility of fabricating advanced Ni-based gamma-prime superalloys with EBM AM.

Modulation of post-movement beta rebound by contraction force and rate of force development.

PubMed

Fry, Adam; Mullinger, Karen J; O'Neill, George C; Barratt, Eleanor L; Morris, Peter G; Bauer, Markus; Folland, Jonathan P; Brookes, Matthew J

2016-07-01

Movement induced modulation of the beta rhythm is one of the most robust neural oscillatory phenomena in the brain. In the preparation and execution phases of movement, a loss in beta amplitude is observed [movement related beta decrease (MRBD)]. This is followed by a rebound above baseline on movement cessation [post movement beta rebound (PMBR)]. These effects have been measured widely, and recent work suggests that they may have significant importance. Specifically, they have potential to form the basis of biomarkers for disease, and have been used in neuroscience applications ranging from brain computer interfaces to markers of neural plasticity. However, despite the robust nature of both MRBD and PMBR, the phenomena themselves are poorly understood. In this study, we characterise MRBD and PMBR during a carefully controlled isometric wrist flexion paradigm, isolating two fundamental movement parameters; force output, and the rate of force development (RFD). Our results show that neither altered force output nor RFD has a significant effect on MRBD. In contrast, PMBR was altered by both parameters. Higher force output results in greater PMBR amplitude, and greater RFD results in a PMBR which is higher in amplitude and shorter in duration. These findings demonstrate that careful control of movement parameters can systematically change PMBR. Further, for temporally protracted movements, the PMBR can be over 7 s in duration. This means accurate control of movement and judicious selection of paradigm parameters are critical in future clinical and basic neuroscientific studies of sensorimotor beta oscillations. Hum Brain Mapp 37:2493-2511, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Mental health of a police force: estimating prevalence of work-related depression in Australia without a direct national measure.

PubMed

Lawson, Katrina J; Rodwell, John J; Noblet, Andrew J

2012-06-01

The risk of work-related depression in Australia was estimated based on a survey of 631 police officers. Psychological wellbeing and psychological distress items were mapped onto a measure of depression to identify optimal cutoff points. Based on a sample of police officers, Australian workers, in general, are at risk of depression when general psychological wellbeing is considerably compromised. Large-scale estimation of work-related depression in the broader population of employed persons in Australia is reasonable. The relatively high prevalence of depression among police officers emphasizes the need to examine prevalence rates of depression among Australian employees.

A Study Into the Mechanism(s) for the Electroplastic Effect in Metals and Its Application to Metalworking, Processing and Fatigue

DTIC Science & Technology

1989-03-10

Regarding metal processing , exploratory studies established that electropulsing (1 105 A/cm2 , - 100 lts duration and - 2 pulses per s) reduced the force...required for 3 drawing Cu wire and enhanced the rates of recovery and recrystallization of cold worked Cu [19] and the rate of sintering of Al powder...h£~A .2 3 o9o./7-t, s A STUDY INTO THE MECHANISM(S) FOR THE ELECTROPLASTIC EFFECT IN METALS AND ITS APPLICATION TO METALWORKING, PROCESSING AND

Accurate fluid force measurement based on control surface integration

NASA Astrophysics Data System (ADS)

Lentink, David

2018-01-01

Nonintrusive 3D fluid force measurements are still challenging to conduct accurately for freely moving animals, vehicles, and deforming objects. Two techniques, 3D particle image velocimetry (PIV) and a new technique, the aerodynamic force platform (AFP), address this. Both rely on the control volume integral for momentum; whereas PIV requires numerical integration of flow fields, the AFP performs the integration mechanically based on rigid walls that form the control surface. The accuracy of both PIV and AFP measurements based on the control surface integration is thought to hinge on determining the unsteady body force associated with the acceleration of the volume of displaced fluid. Here, I introduce a set of non-dimensional error ratios to show which fluid and body parameters make the error negligible. The unsteady body force is insignificant in all conditions where the average density of the body is much greater than the density of the fluid, e.g., in gas. Whenever a strongly deforming body experiences significant buoyancy and acceleration, the error is significant. Remarkably, this error can be entirely corrected for with an exact factor provided that the body has a sufficiently homogenous density or acceleration distribution, which is common in liquids. The correction factor for omitting the unsteady body force, {{{ {ρ f}} {1 - {ρ f} ( {{ρ b}+{ρ f}} )}.{( {{{{ρ }}b}+{ρ f}} )}}} , depends only on the fluid, {ρ f}, and body, {{ρ }}b, density. Whereas these straightforward solutions work even at the liquid-gas interface in a significant number of cases, they do not work for generalized bodies undergoing buoyancy in combination with appreciable body density inhomogeneity, volume change (PIV), or volume rate-of-change (PIV and AFP). In these less common cases, the 3D body shape needs to be measured and resolved in time and space to estimate the unsteady body force. The analysis shows that accounting for the unsteady body force is straightforward to non-intrusively and accurately determine fluid force in most applications.

On the Malthusian theory of long swings.

PubMed

Waterman, A M

1987-05-01

"In the Essay on Population economic growth consists of alternating surges of population (during which real wages fall and the rate of profit rises) and capital (during which the reverse occurs). A series of temporary equilibria exists at which wages are maximal, the rate of profit minimal, and fully employed work-force in technically determined relation to fixed capital stock. Between these equilibria occur episodes of excess labour, below-maximum wages, above minimum profit-rate and capital accumulation. Malthus's 'ratios' presuppose a logarithmic production function that implies first, that the full-employment real wage will fall to subsistence; secondly, that the full-employment 'wages fund' is constant." (SUMMARY IN FRE) excerpt

Grasp Assist Device with Automatic Mode Control Logic

NASA Technical Reports Server (NTRS)

Laske, Evan (Inventor); Davis, Donald R. (Inventor); Ihrke, Chris A. (Inventor)

2018-01-01

A system includes a glove, sensors, actuator assemblies, and controller. The sensors include load sensors which measure an actual grasping force and attitude sensors which determine a glove attitude. The actuator assembly provides a grasp assist force to the glove. Respective locations of work cells in the work environment and permitted work tasks for each work cell are programmed into the controller. The controller detects the glove location and attitude. A work task is selected by the controller for the location. The controller calculates a required grasp assist force using measured actual grasping forces from the load sensors. The required grasp assist force is applied via the glove using the actuator assembly to thereby assist the operator in performing the identified work task.

The Relationship Between Propulsive Force in Tethered Swimming and 200-m Front Crawl Performance.

PubMed

Santos, Karini B; Bento, Paulo C B; Pereira, Gleber; Rodacki, André L F

2016-09-01

Santos, KB, Bento, PCB, Pereira, G, and Rodacki, ALF. The relationship between propulsive force in tethered swimming and 200-m front crawl performance. J Strength Cond Res 30(9): 2500-2507, 2016-The aims of this study were to determine whether propulsive force (peak force, mean force, impulse, and rate of force development) and stroke rate change during 2 minutes of front crawl tethered swimming and to correlate them with the stroke rate and swimming velocity in 200-m front crawl swimming. Twenty-one swimmers (21.6 ± 4.8 years, 1.78 ± 0.06 m, 71.7 ± 8.1 kg), with 200-m front crawl swimming performance equivalent to 78% of the world record (140.4 ± 10.1 seconds), were assessed during 2 minutes of maximal front crawl tethered swimming (propulsive forces and stroke rate) and 200-m front crawl swimming (stroke rate and clean velocity). Propulsive forces decreased between the beginning and the middle instants (∼20%; p ≤ 0.05) but remained stable between the middle and the end instants (∼6%; p > 0.05). The peak force was positively correlated with the clean velocity in the 200-m front crawl swimming (mean r = 0.61; p < 0.02). The stroke rates of the tethered swimming and 200-m front crawl swimming were positively correlated (r = 45; p≤ 0.01) at the middle instant. Therefore, the propulsive force and stroke rate changed throughout the 2 minutes of tethered swimming, and the peak force is the best propulsive force variable tested that correlated with 200-m front crawl swimming performance.

Trends in the growth of population and labour force in Pakistan.

PubMed

Hashmi, S S

1990-01-01

Trends in the growth of the population and labor force in Pakistan are examined and future prospects for growth of population and labor, particularly agriculture, are estimated. The definition of labor force as employed or seeking work after a short period of employment has led to a great disparity in results for women in the labor force. Past trends in population growth reflected a growth rate of 1.6% for the 1950's, and 2.4% in 1960. The population rose to 84.3 million in 1981 from 42.6 million in 1961, which intercensally was an increase of 3.6% per annum for 1961-72 and 3.1% per annum for 1972-81. The estimated rate for 1981-86 was 2.9%/year. The rural population doubled and the urban tripled. There was a net migration of 2.123 million to urban areas reported in the 1981 census. There is also evidence of a high sex ratio. Balochistan (7.1%) and Sindh (3.6%) provinces have the highest growth rates. Although the largest population is in the Punjab, the growth is the lowest at 2.7%. The population is primarily young -- 44.5% 15 years in 1981, which is the highest in the world. Under high, medium, and low levels of fertility, prospective trends are estimated for 2006 and 2031, and by sex every 5 years from 1981. Population under high fertility is expected to reach 270 million by 2031, which is 3.39 persons/hectare. The population/hectare of land under cultivation was 4.25 in 1981 and is expected to rise to 13.49 persons/hectare in 2031. 11 million acres could be brought under cultivation to reduce the ratio. However, there are ecological considerations as well as an employment problem. The dependency ratio under the high variant will decline from 76.8 persons 0-14 and 65 years/100 persons 15-64 years in 1986 to 70.3 in 2006 which is still considerably higher than other developing countries. It is suggested that replacement level fertility be attained as soon as possible. Under low fertility, replacement level can be reached by 2011 with strong political commitment. Past trends in the labor force, employment and unemployment, and employment by major industry are reported. The labor force participation rate of 29.6% in 1985 is among the lowest in the world. The age structure of the population, inadequate human resource development, and underreporting of females in the labor force account for the low rates. Population grew by 96.5% between 1961 and 81, but labor force increased 77.3% and employment 74.4%. The greatest growth was in the nonagricultural sector. Prospective trends show agricultural labor force growing from 15.1 million in 1981 to 20.2 million in 2006, which is expected to put pressure on agricultural land. Female nonagricultural sector labor force is expected to grow due to increased literacy and fertility declines.

State Workforce Policy Initiative.

ERIC Educational Resources Information Center

Public/Private Ventures, Philadelphia, PA.

Surging demand for workers, growing income inequality, and passage of welfare reforms have made work force development one of the United States' key national concerns. Public/Private Ventures has been working with various states to design work force development strategies that seek to address the concerns of many work force development specialists…

Power, muscular work, and external forces in cycling.

PubMed

de Groot, G; Welbergen, E; Clijsen, L; Clarijs, J; Cabri, J; Antonis, J

1994-01-01

Cycling performance is affected by the interaction of a number of variables, including environment, mechanical, and human factors. Engineers have focused on the development of more efficient bicycles. Kinesiologists have examined cycling performance from a human perspective. This paper summarizes only certain aspects of human ergonomics of cycling, especially those which are important for the recent current research in our departments. Power is a key to performance of physical work. During locomotion an imaginary flow of energy takes place from the metabolism to the environment, with some efficiency. The 'useful' mechanical muscle power output might be used to perform movements and to do work against the environment. The external power is defined as the sum of joint powers, each calculated as the product of the joint (net) moment and angular velocity. This definition of external power is closely related to the mean external power as applied to exercise physiology: the sum of joint powers reflects all mechanical power which in principle can be used to fulfil a certain task. In this paper, the flow of energy for cycling is traced quantitatively as far as possible. Studies on the total lower limb can give insight into the contribution of individual muscles to external power. The muscle velocity (positive or negative) is obtained from the positions and orientations of body segments and a bar linkage model of the lower limb. The muscle activity can be measured by electromyography. In this way, positive and negative work regions in individual muscles are identified. Synergy between active agonistic/antagonistic muscle groups occurs in order to deliver external power. Maximum power is influenced by body position, geometry of the bicycle and pedalling rate. This has to be interpreted in terms of the length-tension and force-velocity-power relationships of the involved muscles. Flat road and uphill cycling at different saddle-tube angles is simulated on an ergometer. The measured pedal forces (magnitude and direction) are only dependent on the intersegmental orientation of saddle tube, crank position, upper and lower leg, and foot. The changed direction of the gravitational force with respect to the saddle-tube does not interfere with the co-ordinated force production pattern. During locomotory cycling at constant speed the external power is mainly used to overcome the aerodynamic friction force. This force and the rolling resistance are determined by coasting down experiments, yielding the external power.(ABSTRACT TRUNCATED AT 400 WORDS)

New insights into the passive force enhancement in skeletal muscles.

PubMed

Lee, Eun-Jeong; Joumaa, Venus; Herzog, Walter

2007-01-01

The steady-state isometric force following active stretching of a muscle is always greater than the steady-state isometric force obtained in a purely isometric contraction at the same length. This phenomenon has been termed "residual force enhancement" and it is associated with an active and a passive component. The origin of these components remains a matter of scientific debate. The purpose of this work was to test the hypothesis that the passive component of the residual force enhancement is caused by a passive structural element. In order to achieve this purpose, single fibers (n=6) from the lumbrical muscles of frog (Rana pipiens) were isolated and attached to a force transducer and a motor that could produce computer-controlled length changes. The passive force enhancement was assessed for three experimental conditions: in a normal Ringer's solution, and after the addition of 5 and 15mM 2,3-butanedione monoxime (BDM) which inhibits force production in a dose-dependent manner. If our hypothesis was correct, one would expect the passive force enhancement to be unaffected following BDM application. However, we found that increasing concentrations of BDM decreased the isometric forces, increased the normalized residual force enhancement, and most importantly for this study, increased the passive force enhancement. Furthermore, BDM decreased the rate of force relaxation after deactivation following active stretching of fibers, passive stretching in the Ringer's and BDM conditions produced the same passive force-sarcomere length relationship, and passive force enhancement required activation and force production. These results led to the conclusion that the passive force enhancement cannot be caused by a structural component exclusively as had been assumed up to date, but must be associated, directly or indirectly, with cross-bridge attachments upon activation and the associated active force.

Technology of forced flow and once-through boiling: A survey. [pressure distribution

NASA Technical Reports Server (NTRS)

Poppendieck, H. F.; Sabin, C. M.

1975-01-01

Representative boiling heat transfer and pressure drop information obtained primarily from past NASA and AEC programs is presented which is applicable to forced flow and once-through boiler systems. The forced convection boiler has a number of advantages: little possibility of flow mal-distribution; heat transfer characteristics are usually consistent; and conductances are predictable, so that higher heat fluxes may be employed with safety (which leads to more compact, lighter weight equipment). It was found that in gas-fired systems particularly, the controlling heat transfer resistance may be on the hot side, so that increased fluxes would require extended surfaces. If in a power generation system the working fluid is very expensive, a forced flow boiler can be designed especially for small holdup volume. If the fluid is temperature sensitive, the boiling side wall temperatures can be tailored to maintain maximum heat transfer rates without overheating the fluid. The forced flow and once-through configurations may be the only type which can satisfy a specific need (such as the automotive Rankine cycle power plant design having a very short time-response boiler).

Chemical reactions induced by oscillating external fields in weak thermal environments

NASA Astrophysics Data System (ADS)

Craven, Galen T.; Bartsch, Thomas; Hernandez, Rigoberto

2015-02-01

Chemical reaction rates must increasingly be determined in systems that evolve under the control of external stimuli. In these systems, when a reactant population is induced to cross an energy barrier through forcing from a temporally varying external field, the transition state that the reaction must pass through during the transformation from reactant to product is no longer a fixed geometric structure, but is instead time-dependent. For a periodically forced model reaction, we develop a recrossing-free dividing surface that is attached to a transition state trajectory [T. Bartsch, R. Hernandez, and T. Uzer, Phys. Rev. Lett. 95, 058301 (2005)]. We have previously shown that for single-mode sinusoidal driving, the stability of the time-varying transition state directly determines the reaction rate [G. T. Craven, T. Bartsch, and R. Hernandez, J. Chem. Phys. 141, 041106 (2014)]. Here, we extend our previous work to the case of multi-mode driving waveforms. Excellent agreement is observed between the rates predicted by stability analysis and rates obtained through numerical calculation of the reactive flux. We also show that the optimal dividing surface and the resulting reaction rate for a reactive system driven by weak thermal noise can be approximated well using the transition state geometry of the underlying deterministic system. This agreement persists as long as the thermal driving strength is less than the order of that of the periodic driving. The power of this result is its simplicity. The surprising accuracy of the time-dependent noise-free geometry for obtaining transition state theory rates in chemical reactions driven by periodic fields reveals the dynamics without requiring the cost of brute-force calculations.

Sex differences in force attenuation: a clinical assessment of single-leg hop performance on a portable force plate

PubMed Central

Harrison, A D; Ford, K R; Myer, G D; Hewett, T E

2014-01-01

Objective Impaired biomechanics and neuromuscular control have been suggested as probable links to female sex bias in the onset of patellofemoral pain syndrome. There are limited objective, clinical measures for assessment of impaired biomechanics and neuromuscular control. The primary objective of this investigation was to examine sex differences in vertical ground reaction force (vGRF) and force loading rate in young athletes performing maximum, repeated vertical single-leg hops (RVSHs). The authors hypothesised that females would demonstrate greater vGRF and force loading rate than males and show interlimb differences in force attenuation. Design Cross-sectional study. Setting Paediatric sports medicine clinic. Participants 109 Healthy high school, soccer and basketball athletes. Assessment of risk factors Participants performed RVSHs for 15 seconds on a portable force plate with a sampling rate of 400 Hz (Accupower; AMTI, Watertown, Massachusetts, USA). Main outcome measurements Raw vGRF was filtered with a generalised cross-validation spline using a 50-Hz cutoff frequency and then normalised to potential energy. Force loading rate was calculated by dividing normalised vGRF by time-to-peak force. Group means were compared using analysis of variance. Results The females demonstrated significantly greater normalised vGRF (p<0.001) and force loading rate (p<0.001) during landing than their male counterparts. Neither sex demonstrated significant interlimb differences in force attenuation (p>0.05). Conclusions The female athletes may have altered force attenuation capability during RVSHs as identified by increased vGRF and force loading rate compared with the male athletes. Portable force plates may be potential tools to identify altered force attenuation in clinical settings. PMID:19858114

Working hours and all-cause mortality in relation to the EU Working Time Directive: a Danish cohort study.

PubMed

Hannerz, Harald; Soll-Johanning, Helle

2018-03-12

In keeping with the need to protect the safety and health of workers, the EU Working Time Directive stipulates that a worker's average working time for each 7-day period, including overtime, does not exceed 48 h. It has, however, not been settled whether or not the threshold at 48 working hours a week is low enough to protect against excess mortality from long work weeks. The aim of the present study was to examine all-cause mortality in relation to weekly working hours among employees in the general population of Denmark. A special attention was given to mortality rates among employees with moderately long work weeks, 41-48 h. Interview data from cohorts of 20-64 year-old employees were drawn from the Danish Labour Force Survey. The participants (N = 159 933) were followed through national registers from the end of the calendar year of the interview (1999-2013) until the end of 2014. Rate ratios (RRs) for all-cause mortality were estimated as a function of weekly working hours while controlling for age, sex, social class, night-time work and calendar year. We found 3374 deaths during an average follow-up time of 7.7 years. With 32-40 working hours a week as reference, the RRs for all-cause mortality were 0.75 (95% CI: 0.66-0.85) for 41-48 and 0.92 (0.80-1.05) for >48 h. Mortality rates in Denmark are significantly lower among employees with moderately long work weeks than they are among full-time employees without overtime work.

Women in the American economy.

PubMed

Taeuber, C M; Valdisera, V

1986-11-01

Striking changes in the economic pursuits and status of women have marked the last 2 decades: 1) more women are in the labor force than ever before, 2) they are more likely to have continuous lifetime work experience, 3) they are better educated, and 4) the law mandates greater opportunity for equal employment. Still, as a group, most women continue to work in traditionally female, low-paying occupations. This report addresses 2 questions: 1) why some economic differences between men and women have narrowed, and 2) why they still continue to narrow. Over the past few years, women have been spending more years prior to marriage supporting themselves; in marriage, they have been contributing more to the household income, and a greater number of divorced women have been rearing children alone, often with little or no financial help. Some of the highlights reported in this study are: 1) in 1985, 31.5 million women held full-time, year-round jobs; 2) younger women are increasingly delaying marriage and childbirth to attend college and establish careers; 3) over 1/2 of all children under 18 had a mother in the labor force in 1985; 4) 48% of women with babies under 1 were in the labor force in 1985 as were over 1/2 the mothers with toddlers under 3; 5) by 1995, 61.4 million women are projected to be in the labor force--a participation rate of 60%; and 6) 13% of women who worked year-round, full-time in 1984 had earnings greater than $25,000 compared with 46% of men.

Agricultural Work Force Households: How Much Do They Depend on Farming? Background for Agricultural Policy. Agriculture Information Bulletin Number 547.

ERIC Educational Resources Information Center

Cox, E. Jane; Oliveira, Victor J.

According to data from the 1985 Agricultural Work Force Survey, over 13.5 million of the 17.6 million agricultural work force household members (77 percent) lived in households headed by a farm worker. Some farm workers worked on the farm as their primary job, whereas others primarily worked off the farm. Farm work was an occasional form of…

Optofluidic droplet coalescence on a microfluidic chip

NASA Astrophysics Data System (ADS)

Jung, Jin Ho; Lee, Kyung Heon; Lee, Kang Soo; Cho, Hyunjun; Ha, Byung Hang; Destgeer, Ghulam; Sung, Hyung Jin

2013-11-01

Coalescence is the procedure that two or more droplets fuse during contact to form a larger droplet. Optofluidic droplet coalescence on a microfluidic chip was demonstrated with theoretical and experimental approaches. Droplets were produced in a T-junction geometry and their velocities and sizes were adjusted by flow rate. In order to bring them in a direct contact of coalescence, optical gradient force was used to trap the droplets. A theoretical modeling of the coalescence was derived by combining the optical force and drag force on the droplet. The analytical expression of the optical force on a sphere droplet was employed to estimate the trapping efficiency in the ray optics regime. The drag force acting on the droplet was calculated in terms of the fluid velocity, viscosity and the geometrical parameters of a microfluidic channel. The droplet coalescence was conducted in a microfluidic setup equipped with a 1064 CW laser, focusing optics, a syringe pump, a custom-made stage and a sCMOS camera. The droplets were successfully coalesced using the optical gradient force. The experimental data of coalescence were in good agreement with the prediction. This work was supported by the Creative Research Initiatives program (No.2013-003364) of the National Research Foundation of Korea (MSIP).

Vorticity dipoles and a theoretical model of a finite force at the moving contact line singularity

NASA Astrophysics Data System (ADS)

Zhang, Peter; Devoria, Adam; Mohseni, Kamran

2017-11-01

In the well known works of Moffatt (1964) and Huh & Scriven (1971), an infinite force was reported at the moving contact line (MCL) and attributed to a non-integrable stress along the fluid-solid boundary. In our recent investigation of the boundary driven wedge, a model of the MCL, we find that the classical solution theoretically predicts a finite force at the contact line if the forces applied by the two boundaries that make up the corner are taken into consideration. Mathematically, this force can be obtained by the complex contour integral of the holomorphic vorticity-pressure function given by G = μω + ip . Alternatively, this force can also be found using a carefully defined real integral that incorporates the two boundaries. Motivated by this discovery, we have found that the rate of change in circulation, viscous energy dissipation, and viscous energy flux is also finite per unit contact line length. The analysis presented demonstrates that despite a singular stress and a relatively simple geometry, the no-slip semi-infinite wedge is capable of capturing some physical quantities of interest. Furthermore, this result provides a foundation for other challenging topics such as dynamic contact angle.

Responses to applied forces and the Jarzynski equality in classical oscillator systems coupled to finite baths: an exactly solvable nondissipative nonergodic model.

PubMed

Hasegawa, Hideo

2011-07-01

Responses of small open oscillator systems to applied external forces have been studied with the use of an exactly solvable classical Caldeira-Leggett model in which a harmonic oscillator (system) is coupled to finite N-body oscillators (bath) with an identical frequency (ω(n) = ω(o) for n = 1 to N). We have derived exact expressions for positions, momenta, and energy of the system in nonequilibrium states and for work performed by applied forces. A detailed study has been made on an analytical method for canonical averages of physical quantities over the initial equilibrium state, which is much superior to numerical averages commonly adopted in simulations of small systems. The calculated energy of the system which is strongly coupled to a finite bath is fluctuating but nondissipative. It has been shown that the Jarzynski equality is valid in nondissipative nonergodic open oscillator systems regardless of the rate of applied ramp force.

40 CFR 35.936-14 - Force account work.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 1 2011-07-01 2011-07-01 false Force account work. 35.936-14 Section... ASSISTANCE STATE AND LOCAL ASSISTANCE Grants for Construction of Treatment Works-Clean Water Act § 35.936-14 Force account work. (a) A grantee must secure the project officer's prior written approval for use of...

Diversity in the Work Force. The Highlight Zone: Research @ Work No. 4.

ERIC Educational Resources Information Center

Wentling, Rose Mary

A literature review was conducted to identify critical work force diversity issues in today's changing workplace and identify ways organizations and career and technical education (CTE) practitioners can increase work force diversity. A broad, all-inclusive definition of diversity was developed that focuses on how diversity affects individuals and…

Responsive upper limb and cognitive fatigue measures during light precision work: an 8-hour simulated micro-pipetting study.

PubMed

Yung, Marcus; Wells, Richard P

2017-07-01

Many contemporary occupations are characterised by long periods of low loads. These lower force levels, which are relevant to the development of work-related musculoskeletal disorders, are usually not the focus of fatigue studies. In studies that did measure fatigue in light manual or precision work, within and between measurement responses were inconsistent. The aim of this study was to identify fatigue measures that were responsive at lower force levels (<10% MVC) over the course of an 8-h period. A complementary set of fatigue measures, reflecting both neuromuscular and cognitive mechanisms, was measured during a light precision micro-pipetting task performed by 11 participants. Nine measures were found to be significantly responsive over the 8-h period, including: ratings of perceived fatigue, postural tremor, blink frequency and critical flicker fusion frequency threshold. Common field measures, specifically electromyography RMS amplitude and maximum voluntary contractions, did not lead to extraordinary time effects. Practitioner summary: The findings provide insight towards the responsiveness of a complementary set of field usable fatigue measures at low work intensities Although commonly used measures did not reveal significant increases in fatigue, nine alternative measures were significantly responsive over the 8-h period.

Traction force microscopy of engineered cardiac tissues.

PubMed

Pasqualini, Francesco Silvio; Agarwal, Ashutosh; O'Connor, Blakely Bussie; Liu, Qihan; Sheehy, Sean P; Parker, Kevin Kit

2018-01-01

Cardiac tissue development and pathology have been shown to depend sensitively on microenvironmental mechanical factors, such as extracellular matrix stiffness, in both in vivo and in vitro systems. We present a novel quantitative approach to assess cardiac structure and function by extending the classical traction force microscopy technique to tissue-level preparations. Using this system, we investigated the relationship between contractile proficiency and metabolism in neonate rat ventricular myocytes (NRVM) cultured on gels with stiffness mimicking soft immature (1 kPa), normal healthy (13 kPa), and stiff diseased (90 kPa) cardiac microenvironments. We found that tissues engineered on the softest gels generated the least amount of stress and had the smallest work output. Conversely, cardiomyocytes in tissues engineered on healthy- and disease-mimicking gels generated significantly higher stresses, with the maximal contractile work measured in NRVM engineered on gels of normal stiffness. Interestingly, although tissues on soft gels exhibited poor stress generation and work production, their basal metabolic respiration rate was significantly more elevated than in other groups, suggesting a highly ineffective coupling between energy production and contractile work output. Our novel platform can thus be utilized to quantitatively assess the mechanotransduction pathways that initiate tissue-level structural and functional remodeling in response to substrate stiffness.

A protocol to study ex vivo mouse working heart at human-like heart rate.

PubMed

Feng, Han-Zhong; Jin, Jian-Ping

2018-01-01

Genetically modified mice are widely used as experimental models to study human heart function and diseases. However, the fast rate of normal mouse heart at 400-600bpm limits its capacity of assessing kinetic parameters that are important for the physiology and pathophysiology of human heart that beats at a much slower rate (75-180bpm). To extend the value of mouse models, we established a protocol to study ex vivo mouse working hearts at a human-like heart rate. In the presence of 300μM lidocaine to lower pacemaker and conductive activities and prevent arrhythmia, a stable rate of 120-130bpm at 37°C is achieved for ex vivo mouse working hearts. The negative effects of decreased heart rate on force-frequency dependence and lidocaine as a myocardial depressant on intracellular calcium can be compensated by using a higher but still physiological level of calcium (2.75mM) in the perfusion media. Multiple parameters were studied to compare the function at the human-like heart rate with that of ex vivo mouse working hearts at the standard rate of 480bpm. The results showed that the conditions for slower heart rate in the presence of 300μM lidocaine did not have depressing effect on left ventricular pressure development, systolic and diastolic velocities and stroke volume with maintained positive inotropic and lusitropic responses to β-adrenergic stimulation. Compared with that at 480bpm, the human-like heart rate increased ventricular filling and end diastolic volume with enhanced Frank-Starling responses. Coronary perfusion was increased from longer relaxation time and interval between beats whereas cardiac efficiency was significantly improved. Although the intrinsic differences between mouse and human heart remain, this methodology for ex vivo mouse hearts to work at human-like heart rate extends the value of using genetically modified mouse models to study cardiac function and human heart diseases. Copyright © 2017 Elsevier Ltd. All rights reserved.

An Analysis of Women's Roles under the Impact of New Technology in the Home and Office.

ERIC Educational Resources Information Center

Bruce, Margaret; Kirkup, Gill

Focusing on the ideology of the sexual division of labor with emphasis on women's roles and their work, this paper argues that social ideology dominates both the domestic and the office environment, and is perhaps the most powerful force determining the rate and direction of technological change. The argument set forth is illustrated by two case…

The effectiveness of strategies similar to the Magnet model to create positive work environments on nurse satisfaction.

PubMed

Kol, Emine; İlaslan, Emine; Turkay, Mehtap

2017-08-01

The objective of this study was to identify the satisfaction levels of nurses with positive environment initiatives and positive management strategies. In total, 235 and 259 nurses participated in the study before and after the application of the initiatives and strategies, respectively. Strategies adopted from the magnet model to create positive work environments and management styles were executed according to the forces of magnetism. Data related to satisfaction were collected twice, once before and once after the strategies to create positive working environments were implemented. The rates of working environment satisfaction in the nurses' department were 57.07% in 2011 and 69.01% in 2013. The rate of satisfaction with governance differed significantly between 2011 and 2013, especially in terms of the merit system, equity and equality, information flow between the administration and the employees, and the influence of the nursing managers on institutional decision making. This study showed that 24 months after the implementation of these strategies, nurse satisfaction with their work environment and management style increased significantly. © 2017 John Wiley & Sons Australia, Ltd.

Natural Selection and Recombination Rate Variation Shape Nucleotide Polymorphism Across the Genomes of Three Related Populus Species

PubMed Central

Wang, Jing; Street, Nathaniel R.; Scofield, Douglas G.; Ingvarsson, Pär K.

2016-01-01

A central aim of evolutionary genomics is to identify the relative roles that various evolutionary forces have played in generating and shaping genetic variation within and among species. Here we use whole-genome resequencing data to characterize and compare genome-wide patterns of nucleotide polymorphism, site frequency spectrum, and population-scaled recombination rates in three species of Populus: Populus tremula, P. tremuloides, and P. trichocarpa. We find that P. tremuloides has the highest level of genome-wide variation, skewed allele frequencies, and population-scaled recombination rates, whereas P. trichocarpa harbors the lowest. Our findings highlight multiple lines of evidence suggesting that natural selection, due to both purifying and positive selection, has widely shaped patterns of nucleotide polymorphism at linked neutral sites in all three species. Differences in effective population sizes and rates of recombination largely explain the disparate magnitudes and signatures of linked selection that we observe among species. The present work provides the first phylogenetic comparative study on a genome-wide scale in forest trees. This information will also improve our ability to understand how various evolutionary forces have interacted to influence genome evolution among related species. PMID:26721855

Natural Selection and Recombination Rate Variation Shape Nucleotide Polymorphism Across the Genomes of Three Related Populus Species.

PubMed

Wang, Jing; Street, Nathaniel R; Scofield, Douglas G; Ingvarsson, Pär K

2016-03-01

A central aim of evolutionary genomics is to identify the relative roles that various evolutionary forces have played in generating and shaping genetic variation within and among species. Here we use whole-genome resequencing data to characterize and compare genome-wide patterns of nucleotide polymorphism, site frequency spectrum, and population-scaled recombination rates in three species of Populus: Populus tremula, P. tremuloides, and P. trichocarpa. We find that P. tremuloides has the highest level of genome-wide variation, skewed allele frequencies, and population-scaled recombination rates, whereas P. trichocarpa harbors the lowest. Our findings highlight multiple lines of evidence suggesting that natural selection, due to both purifying and positive selection, has widely shaped patterns of nucleotide polymorphism at linked neutral sites in all three species. Differences in effective population sizes and rates of recombination largely explain the disparate magnitudes and signatures of linked selection that we observe among species. The present work provides the first phylogenetic comparative study on a genome-wide scale in forest trees. This information will also improve our ability to understand how various evolutionary forces have interacted to influence genome evolution among related species. Copyright © 2016 by the Genetics Society of America.

The Bahamas.

PubMed

1984-12-01

The Commonwealth of the Bahamas had a population of 228.000 in 1984, with an annual growth rate of 2%. The infant mortality rate is 20.2/1000, and life expectancy stands at 64 years for men and 70 years for women. The literacy rate is 93%, and 14 years of education is compulsory. Since independence in 1973, the Bahamas has been an independent member of the Commonwealth of Nations. Its chief of state is the British monarch, represented in the Bahamas by an appointed governor general. The Progressive Liberal Party controls the majority of the parliamentary seats. Over 75% of the population lives on either New Providence or Grand Bahama. Of the work force of 82,000, 6% is engaged in agriculture, 10% in finance and business services, 25% in the hotel and restaurant sector, and 30% is employed by government. Tourism accounts for 75% of the gross national product, which was US$1083 billion in 1979, and employs 2/3 of the labor force. The per capita income in 1982 was US$5756, and the inflation rate averages 4.1%. The goverment has been attempting to diversify the economy and attract new industries, but without much success.

Evaluation of knee joint forces during kneeling work with different kneepads.

PubMed

Xu, Hang; Jampala, Sree; Bloswick, Donald; Zhao, Jie; Merryweather, Andrew

2017-01-01

The main purpose of this study is to determine knee joint forces resulting from kneeling work with and without kneepads to quantify how different kneepads redistribute force. Eleven healthy males simulated a tile setting task to different locations during six kneepad states (five different kneepad types and without kneepad). Peak and average forces on the anatomical landmarks of both knees were obtained by custom force sensors. The results revealed that kneepad design can significantly modify the forces on the knee joint through redistribution. The Professional Gel design was preferred among the five tested kneepads which was confirmed with both force measurements and participants' responses. The extreme reaching locations induced significantly higher joint forces on left knee or right knee depending on task. The conclusion of this study is that a properly selected kneepad for specific tasks and a more neutral working posture can modify the force distribution on the knees and likely decrease the risk of knee disorders from kneeling work. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Comparison between the Second Korean Working Conditions Survey (KWCS) and the First KWCS.

PubMed

Kim, Young Sun; Park, Jungsun; Rhee, Kyung Yong; Kim, Hye Min

2015-06-01

The study was designed to assess the changes in working conditions through a comparative analysis of the characteristics of working conditions in 2006 and 2010. We performed a comparative analysis of the data related to the first Korean Working Conditions Survey (KWCS) and the second KWCS in the categories of demographic characteristics, quality of labor, exposure to hazards, and health problems. From our analysis of the demographic characteristics, we saw an increase in labor force participation rate of women and elderly people. As a result of the investigation with regards to working hours, the ratio of employees who worked for ≥ 49 hours per week was decreased and the ratio of employees who worked for ≥ 40 h/wk increased. As for exposure to hazards, exposure to tobacco smoke notably decreased in 2010 compared with 2006. With regards to health problems, there was a sharp increase in the number of people who complained of muscle pain in their arms and legs. KWCS data included many aspects of working conditions as a nationwide sample. In addition, because this is a periodic nationwide survey, the labor force, working hours, harmful factor exposure, and the change in health problems characteristics according to the flow of time could be investigated. The information comparing the main results of the first survey conducted in 2006 and the second survey conducted in 2010 obtained through this study can be used as an important base material for the establishment of the national policy.

Validity and reliability of a controlled pneumatic resistance exercise device.

PubMed

Paulus, David C; Reynolds, Michael C; Schilling, Brian K

2008-01-01

During the concentric portion of the free-weight squat exercise, accelerating the mass from rest results in a fluctuation in ground reaction force. It is characterized by an initial period of force greater than the load while accelerating from rest followed by a period of force lower than the external load during negative acceleration. During the deceleration phase, less force is exerted and muscles are loaded sub-optimally. Thus, using a reduced inertia form of resistance such as pneumatics has the capability to minimize these inertial effects as well as control the force in real time to maximize the force exerted over the exercise cycle. To improve the system response of a preliminary design, a squat device was designed with a reduced mass barbell and two smaller pneumatic cylinders. The resistance was controlled by regulating cylinder pressure such that it is capable of adjusting force within a repetition to maximize force exerted during the lift. The resistance force production of the machine was statically validated with the input voltage and output force R2 =0.9997 for at four increments of the range of motion, and the intraclass correlation coefficient (ICC) between trials at the different heights equaled 0.999. The slew rate at three forces was 749.3 N/s +/- 252.3. Dynamic human subject testing showed the desired input force correlated with average and peak ground reaction force with R2 = 0.9981 and R2 = 0.9315, respectively. The ICC between desired force and average and peak ground reaction force was 0.963. Thus, the system is able to deliver constant levels of static and dynamic force with validity and reliability. Future work will be required to develop the control strategy required for real-time control, and performance testing is required to determine its efficacy.

India's demographic snapshot, 1991.

PubMed

Bose, A

1991-12-01

Having presented the provisional results of the 1991 Census of India in tabular form, the author discusses the policy implication of the data. During the 1981-91 decade, India witnesses a 160.99 net increase in population, which brought the country's total population to an estimated 844.32 million. The annual growth rated during the decade was 2.1%. The author explains that these alarming population figures reflect the failure of the government's population program. The author warns that unless the Planning Commission develops new strategies, the upcoming 5-year plans. The author explains that the failure of family planning is due primarily to the low literacy rate -- especially the female literacy rate is 29% (and 25% among rural women). The author also discusses the problems of urbanization and the work force. During the past decade, cities grew at a somewhat slower rate than in previous decades, meaning that the absorptive capacity of the cities has gone down. Nonetheless, the urban population grew by 58 million during 10-year period. The urban infrastructure is virtually collapsing, with 30-50% of the urban population living in slums. The data also reveals the structural stagnation of the economy. The agricultural sector, which accounts for about 2/3 of the work force, registered only slight decreases during the decade, signifying a marginal shift from agriculture to nonagricultural activity. Furthermore, population growth has aggravated the unemployment problem. Finally, the author addresses the issue of the sex ratio (females/1000 males), which declined from 934 in 1981 to 929 in 1991, which indicates a continued prejudice against women.

Wetting behavior of selected crude oil/brine/rock systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1997-04-01

Of the many methods of characterizing wettability of a porous medium, the most commonly used are the Amott test and the USBM test. The Amott test does not discriminate adequately between systems that give high values of wettability index to water and are collectively described as very strongly water-wet. The USBM test does not recognize systems that achieve residual oil saturation by spontaneous imbibition. For such systems, and for any systems that exhibit significant spontaneous imbibition, measurements of imbibition rate provide a useful characterization of wettability. Methods of interpreting spontaneous imbibition data are reviewed and a new method of quantifyingmore » wettability from rate of imbibition is proposed. Capillary pressure is the driving force in spontaneous imbibition. The area under an imbibition curve is closely related to the work of displacement that results from decrease in surface free energy. Imbibition rate data can be correlated to allow for differences in interracial tension, viscosities, pore structure, and sample size. Wettability, the remaining key factor in determining the capillary driving force and the related imbibition rate, then largely determines the differences in saturation vs. scaled time curves. These curves are used to obtain pseudo imbibition capillary pressure curves; a wettability index based on relative areas under these curves is defined as the relative pseudo work of imbibition. The method is applied for two crude oil/brine/rock systems. Comparison of the method with the Amott wettability index is made for different wettability states given by differences in aging of cores with crude oil. Correlations of wettability indices with waterflood recoveries are presented.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moutinho, Helio R.; Jiang, Cun -Sheng; To, Bobby

To better understand and quantify soiling rates on solar panels, we are investigating the adhesion mechanisms between dust particles and solar glass. In this work, we report on two of the fundamental adhesion mechanisms: van der Waals and capillary adhesion forces. The adhesion was determined using force versus distance (F-z) measurements performed with an atomic force microscope (AFM). To emulate dust interacting with the front surface of a solar panel, we measured how oxidized AFM tips, SiO 2 glass spheres, and real dust particles adhered to actual solar glass. The van der Waals forces were evaluated by measurements performed withmore » zero relative humidity in a glove box, and the capillary forces were measured in a stable environment created inside the AFM enclosure with relative humidity values ranging from 18% to 80%. To simulate topographic features of the solar panels caused by factors such as cleaning and abrasion, we induced different degrees of surface roughness in the solar glass. As a result, we were able to 1) identify and quantify both the van der Waals and capillary forces, 2) establish the effects of surface roughness, relative humidity, and particle size on the adhesion mechanisms, and 3) compare adhesion forces between well-controlled particles (AFM tips and glass spheres) and real dust particles.« less

Developing an Asteroid Rotational Theory

NASA Astrophysics Data System (ADS)

Geis, Gena; Williams, Miguel; Linder, Tyler; Pakey, Donald

2018-01-01

The goal of this project is to develop a theoretical asteroid rotational theory from first principles. Starting at first principles provides a firm foundation for computer simulations which can be used to analyze multiple variables at once such as size, rotation period, tensile strength, and density. The initial theory will be presented along with early models of applying the theory to the asteroid population. Early results confirm previous work by Pravec et al. (2002) that show the majority of the asteroids larger than 200m have negligible tensile strength and have spin rates close to their critical breakup point. Additionally, results show that an object with zero tensile strength has a maximum rotational rate determined by the object’s density, not size. Therefore, an iron asteroid with a density of 8000 kg/m^3 would have a minimum spin period of 1.16h if the only forces were gravitational and centrifugal. The short-term goal is to include material forces in the simulations to determine what tensile strength will allow the high spin rates of asteroids smaller than 150m.

Inertial Particle Migration in the Presence of a Permeate Flow

NASA Astrophysics Data System (ADS)

Garcia, Mike; Singelton, Amanda; Pennathur, Sumita

2016-11-01

Tangential Flow Filtration (TFF) is a rapid and efficient method for the filtration and separation of suspensions of particles such as viruses, bacteria or cellular material. Enhancing the efficacy of TFF not only requires a detailed understanding of particle transport mechanisms, but also the interactions between these mechanisms and a porous wall. In this work, we numerically and experimentally explore the mechanisms of inertial particle migration in the presence of a permeate flow through the porous walls of a microchannel. Numerically, we develop a force balance model to understand the competition between permeate and inertial forces and the resultant consequences on the particle equilibrium location. Experimentally, we fabricated MEMS TFF devices to study the migration of 5, 10 and 15 µm fluorescent polystyrene beads in straight channels with perpendicular permeate flow rates up to 90% of the inlet flow rate. We find that the permeate flow directly influences the inertial focusing position of the particles, both as a function of downstream channel position and ratio of inlet to outlet flow rate. Comparing experiments to our model, we can identify inertial, viscous and a co-dominant regimes.

An empirical investigation of female labor-force participation, fertility, age at marriage, and wages in Korea.

PubMed

Lee, B S; Mcelwain, A M

1985-07-01

The Korean experience raises questions about the assumption that successful economic development and equitable income distribution are preconditions for rapid fertility declines. During the 1960-70 decade, the total fertility rate in Korea declined by 36% and the crude birth rate fell by 33%, in the absence of significant economic development. This paper uses data from the 1974 Korean Fertility Survey to explore the relationships between the factors responsible for this rapid fertility decline. A simultaneous equation model of fertility, age at marriage, extent of labor force participation during marriage, quality of children, and wages is developed and tested. Rather than to provide definitive measures of these interrelationships, the aim was to investigate the utility of treating several variables as being jointly determined. The results suggest that parental education affects fertility by influencing age at marriage, implying that adult education programs will have little effect on marital fertility. There was some evidence that working women whose jobs are compatible with child care have more children than nonworking women, a finding that should be considered in planning increased job opportunities for women. Urbanized women and those who work before marriage tend to marry later than their less urbanized counterparts or women who do not work prior to marriage. Finally, women who used modern methods of birth control had significantly lower fertility than nonusers of modern methods. There is concern that the Government has reduced budgetary appropriations to family planning since the goal of reducing the annual population growth rate from 3% in 1960 to 2% in 1970 was achieved. It is suggested that family planning expenditures should be deployed to areas such as urban slums that have not yet been reached by family planning programs.

The Work, the Workplace, and the Work Force of Tomorrow.

ERIC Educational Resources Information Center

Allen, Claudia

1995-01-01

Ann McLaughlin, a former secretary of labor, discusses her views on the future of the workplace. She feels that to solve the impending problem of educational deficits among the work force, employers will begin their own educational programs, improving both employee loyalty and work force mobility. Includes predictions for future growth fields.…

Interaction Forces and Aggregation Rates of Colloidal Latex Particles in the Presence of Monovalent Counterions.

PubMed

Montes Ruiz-Cabello, F Javier; Trefalt, Gregor; Oncsik, Tamas; Szilagyi, Istvan; Maroni, Plinio; Borkovec, Michal

2015-06-25

Force profiles and aggregation rates involving positively and negatively charged polystyrene latex particles are investigated in monovalent electrolyte solutions, whereby the counterions are varied within the Hofmeister series. The force measurements are carried out with the colloidal probe technique, which is based on the atomic force microscope (AFM), while the aggregation rates are measured with time-resolved multiangle light scattering. The interaction force profiles cannot be described by classical DLVO theory, but an additional attractive short-ranged force must be included. An exponential force profile with a decay length of about 0.5 nm is consistent with the measured forces. Furthermore, the Hamaker constants extracted from the measured force profiles are substantially smaller than the theoretical values calculated from dielectric spectra. The small surface roughness of the latex particles (below 1 nm) is probably responsible for this deviation. Based on the measured force profiles, the aggregation rates can be predicted without adjustable parameters. The measured absolute aggregation rates in the fast regime are somewhat lower than the calculated ones. The critical coagulation concentration (CCC) agrees well with the experiment, including the respective shifts of the CCC within the Hofmeister series. These shifts are particularly pronounced for the positively charged particles. However, the consideration of the additional attractive short-ranged force is essential to quantify these shifts correctly. In the slow regime, the calculated rates are substantially smaller than the experimental ones. This disagreement is probably related to surface charge heterogeneities.

Optimization of Wireless Transceivers under Processing Energy Constraints

NASA Astrophysics Data System (ADS)

Wang, Gaojian; Ascheid, Gerd; Wang, Yanlu; Hanay, Oner; Negra, Renato; Herrmann, Matthias; Wehn, Norbert

2017-09-01

Focus of the article is on achieving maximum data rates under a processing energy constraint. For a given amount of processing energy per information bit, the overall power consumption increases with the data rate. When targeting data rates beyond 100 Gb/s, the system's overall power consumption soon exceeds the power which can be dissipated without forced cooling. To achieve a maximum data rate under this power constraint, the processing energy per information bit must be minimized. Therefore, in this article, suitable processing efficient transmission schemes together with energy efficient architectures and their implementations are investigated in a true cross-layer approach. Target use cases are short range wireless transmitters working at carrier frequencies around 60 GHz and bandwidths between 1 GHz and 10 GHz.

Neutron-capture rates for explosive nucleosynthesis: the case of 68Ni(n, γ) 69Ni

DOE PAGES

Spyrou, Artemis; Larsen, Ann-Cecilie; Liddick, Sean N.; ...

2017-02-22

Neutron-capture reactions play an important role in heavy element nucleosynthesis, since they are the driving force for the two processes that create the vast majority of the heavy elements. When a neutron capture occurs on a short-lived nucleus, it is extremely challenging to study the reaction directly and therefore the use of indirect techniques is essential. The present work reports on such an indirect measurement that provides strong constraints on the 68Ni(n,g) 69Ni reaction rate.The commonly used reaction libraries JINA-REACLIB and BRUSLIB are in relatively good agreement with the experimental rate. The impact of the new rate on weak r-processmore » calculations is discussed.« less

Investigation of machinability characteristics on EN47 steel for cutting force and tool wear using optimization technique

NASA Astrophysics Data System (ADS)

M, Vasu; Shivananda Nayaka, H.

2018-06-01

In this experimental work dry turning process carried out on EN47 spring steel with coated tungsten carbide tool insert with 0.8 mm nose radius are optimized by using statistical technique. Experiments were conducted at three different cutting speeds (625, 796 and 1250 rpm) with three different feed rates (0.046, 0.062 and 0.093 mm/rev) and depth of cuts (0.2, 0.3 and 0.4 mm). Experiments are conducted based on full factorial design (FFD) 33 three factors and three levels. Analysis of variance is used to identify significant factor for each output response. The result reveals that feed rate is the most significant factor influencing on cutting force followed by depth of cut and cutting speed having less significance. Optimum machining condition for cutting force obtained from the statistical technique. Tool wear measurements are performed with optimum condition of Vc = 796 rpm, ap = 0.2 mm, f = 0.046 mm/rev. The minimum tool wear observed as 0.086 mm with 5 min machining. Analysis of tool wear was done by confocal microscope it was observed that tool wear increases with increasing cutting time.

Energy absorption characterization of human enamel using nanoindentation.

PubMed

He, Li Hong; Swain, Michael V

2007-05-01

Enamel is a natural composite, which has much higher toughness than its major component, crystalline hydroxyapatite. In this study, the energy absorption behavior of human sound enamel was investigated with nanoindentation techniques. A UMIS nanoindenter system as well as a Berkovich and two spherical indenters with nominal tip radii of 5 and 20 microm were used to indent enamel at different loading forces in the direction parallel to enamel prisms. Inelastic energy dissipation versus depth of indenter penetration (U%-h(p) curve) as well as a function of indentation strain (U%-epsilon curve) of enamel was determined. Enamel showed much higher energy absorption capacity than a ceramic material with equivalent modulus (fused silica). Even at the lowest forces (1 mN) for the 20 microm indenter, inelastic response was found. Additional tests done at different force loading rates illustrated that load rate has little influence on P-h response of enamel. The top surface of enamel has the plastic work of indentation of approximately 5.2 nJ/microm(3). The energy absorbing ability is influenced by the very small protein rich component that exists between the hydroxyapatite nanocrystals as well as within the sheath structure surrounding the enamel rods. Copyright 2006 Wiley Periodicals, Inc.

A Stationary One-Equation Turbulent Model with Applications in Porous Media

NASA Astrophysics Data System (ADS)

de Oliveira, H. B.; Paiva, A.

2018-06-01

A one-equation turbulent model is studied in this work in the steady-state and with homogeneous Dirichlet boundary conditions. The considered problem generalizes two distinct approaches that are being used with success in the applications to model different flows through porous media. The novelty of the problem relies on the consideration of the classical Navier-Stokes equations with a feedback forces field, whose presence in the momentum equation will affect the equation for the turbulent kinetic energy (TKE) with a new term that is known as the production and represents the rate at which TKE is transferred from the mean flow to the turbulence. By assuming suitable growth conditions on the feedback forces field and on the function that describes the rate of dissipation of the TKE, as well as on the production term, we will prove the existence of the velocity field and of the TKE. The proof of their uniqueness is made by assuming monotonicity conditions on the feedback forces field and on the turbulent dissipation function, together with a condition of Lipschitz continuity on the production term. The existence of a unique pressure, will follow by the application of a standard version of de Rham's lemma.

An Assessment of Hickam Air Force Base's Capability to Support Strategic Airlift Throughput when Operating under an Avian Flu Pandemic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brigantic, Robert T.; Campbell, James R.; Doctor, Pamela G.

Hickam Air Force Base (AFB), Hawaii provides an ideal waypoint for U.S. strategic airlift aircraft to refuel and receive other services on their way to Northeast and Southeast Asia from the continental United States. Hickam AFB also serves as a critical aerial port of debarkation (APOD) for deploying U.S. forces and equipment to more distant lands as needed. Making use of the United States Transportation Command’s Aerial Port of Debarkation Plus model, this paper examines the ability of Hickam AFB to serve in its important role as an APOD when operating under the effects of a major avian flu pandemic.more » In this regard, the major influence on Hickam AFB will be a serious degradation to the number of available personnel to service aircraft and operate Hickam AFB’s aerial port. It is noted that the results presented herein are based on simplistic attrition rate assumptions. Nonetheless, it is envisioned that this work is applicable to more realistic input attrition rates as avian flu epidemiological models are refined, as well as attrition associated with other types of contagious pandemic disease or willful biological warfare attack.« less

Computer simulations of the energy dissipation rate in a fluorescence-activated cell sorter: Implications to cells.

PubMed

Mollet, Mike; Godoy-Silva, Ruben; Berdugo, Claudia; Chalmers, Jeffrey J

2008-06-01

Fluorescence activated cell sorting, FACS, is a widely used method to sort subpopulations of cells to high purities. To achieve relatively high sorting speeds, FACS instruments operate by forcing suspended cells to flow in a single file line through a laser(s) beam(s). Subsequently, this flow stream breaks up into individual drops which can be charged and deflected into multiple collection streams. Previous work by Ma et al. (2002) and Mollet et al. (2007; Biotechnol Bioeng 98:772-788) indicates that subjecting cells to hydrodynamic forces consisting of both high extensional and shear components in micro-channels results in significant cell damage. Using the fluid dynamics software FLUENT, computer simulations of typical fluid flow through the nozzle of a BD FACSVantage indicate that hydrodynamic forces, quantified using the scalar parameter energy dissipation rate, are similar in the FACS nozzle to levels reported to create significant cell damage in micro-channels. Experimental studies in the FACSVantage, operated under the same conditions as the simulations confirmed significant cell damage in two cell lines, Chinese Hamster Ovary cells (CHO) and THP1, a human acute monocytic leukemia cell line.

Finite Element Simulations of Micro Turning of Ti-6Al-4V using PCD and Coated Carbide tools

NASA Astrophysics Data System (ADS)

Jagadesh, Thangavel; Samuel, G. L.

2017-02-01

The demand for manufacturing axi-symmetric Ti-6Al-4V implants is increasing in biomedical applications and it involves micro turning process. To understand the micro turning process, in this work, a 3D finite element model has been developed for predicting the tool chip interface temperature, cutting, thrust and axial forces. Strain gradient effect has been included in the Johnson-Cook material model to represent the flow stress of the work material. To verify the simulation results, experiments have been conducted at four different feed rates and at three different cutting speeds. Since titanium alloy has low Young's modulus, spring back effect is predominant for higher edge radius coated carbide tool which leads to the increase in the forces. Whereas, polycrystalline diamond (PCD) tool has smaller edge radius that leads to lesser forces and decrease in tool chip interface temperature due to high thermal conductivity. Tool chip interface temperature increases by increasing the cutting speed, however the increase is less for PCD tool as compared to the coated carbide tool. When uncut chip thickness decreases, there is an increase in specific cutting energy due to material strengthening effects. Surface roughness is higher for coated carbide tool due to ploughing effect when compared with PCD tool. The average prediction error of finite element model for cutting and thrust forces are 11.45 and 14.87 % respectively.

Force Generation upon T Cell Receptor Engagement

PubMed Central

Husson, Julien; Chemin, Karine; Bohineust, Armelle; Hivroz, Claire; Henry, Nelly

2011-01-01

T cells are major players of adaptive immune response in mammals. Recognition of an antigenic peptide in association with the major histocompatibility complex at the surface of an antigen presenting cell (APC) is a specific and sensitive process whose mechanism is not fully understood. The potential contribution of mechanical forces in the T cell activation process is increasingly debated, although these forces are scarcely defined and hold only limited experimental evidence. In this work, we have implemented a biomembrane force probe (BFP) setup and a model APC to explore the nature and the characteristics of the mechanical forces potentially generated upon engagement of the T cell receptor (TCR) and/or lymphocyte function-associated antigen-1 (LFA-1). We show that upon contact with a model APC coated with antibodies towards TCR-CD3, after a short latency, the T cell developed a timed sequence of pushing and pulling forces against its target. These processes were defined by their initial constant growth velocity and loading rate (force increase per unit of time). LFA-1 engagement together with TCR-CD3 reduced the growing speed during the pushing phase without triggering the same mechanical behavior when engaged alone. Intracellular Ca2+ concentration ([Ca2+]i) was monitored simultaneously to verify the cell commitment in the activation process. [Ca2+]i increased a few tens of seconds after the beginning of the pushing phase although no strong correlation appeared between the two events. The pushing phase was driven by actin polymerization. Tuning the BFP mechanical properties, we could show that the loading rate during the pulling phase increased with the target stiffness. This indicated that a mechanosensing mechanism is implemented in the early steps of the activation process. We provide here the first quantified description of force generation sequence upon local bidimensional engagement of TCR-CD3 and discuss its potential role in a T cell mechanically-regulated activation process. PMID:21572959

Force generation upon T cell receptor engagement.

PubMed

Husson, Julien; Chemin, Karine; Bohineust, Armelle; Hivroz, Claire; Henry, Nelly

2011-05-10

T cells are major players of adaptive immune response in mammals. Recognition of an antigenic peptide in association with the major histocompatibility complex at the surface of an antigen presenting cell (APC) is a specific and sensitive process whose mechanism is not fully understood. The potential contribution of mechanical forces in the T cell activation process is increasingly debated, although these forces are scarcely defined and hold only limited experimental evidence. In this work, we have implemented a biomembrane force probe (BFP) setup and a model APC to explore the nature and the characteristics of the mechanical forces potentially generated upon engagement of the T cell receptor (TCR) and/or lymphocyte function-associated antigen-1 (LFA-1). We show that upon contact with a model APC coated with antibodies towards TCR-CD3, after a short latency, the T cell developed a timed sequence of pushing and pulling forces against its target. These processes were defined by their initial constant growth velocity and loading rate (force increase per unit of time). LFA-1 engagement together with TCR-CD3 reduced the growing speed during the pushing phase without triggering the same mechanical behavior when engaged alone. Intracellular Ca(2+) concentration ([Ca(2+)](i)) was monitored simultaneously to verify the cell commitment in the activation process. [Ca(2+)](i) increased a few tens of seconds after the beginning of the pushing phase although no strong correlation appeared between the two events. The pushing phase was driven by actin polymerization. Tuning the BFP mechanical properties, we could show that the loading rate during the pulling phase increased with the target stiffness. This indicated that a mechanosensing mechanism is implemented in the early steps of the activation process. We provide here the first quantified description of force generation sequence upon local bidimensional engagement of TCR-CD3 and discuss its potential role in a T cell mechanically-regulated activation process.

World and regional labour force trends and prospects.

PubMed

Ypsilantis, J N

1974-01-01

Changes in fertility during 1970-1985 will not have any effect on the composition of the world work force until 1985 because the people who will be of working age at that time have already been born. However, fertility for this period will directly influence the size of the age group 15-30 in the year 2000. Moreover, fertility trends for this period will have an indirect effect on participation of women in the labor force. The number of people in the labor force has proportionately followed total population. Just as total population is projected to increase in the single decade 1970-1980 by an amount equal to its size in 1750, so the labor force will increase by 360 million during the 1980's (its original size in 1750). By the end of the present century the world labor force may well number some 2,6000 million, reaching 3,000 million by the year 2010; 4,000 million by 2030; 5,000 million by 2070; and stabilizing at about 5,200 million by the end of the 21st century. There will be great regional variations. Increases will range from 20-35% in Europe and the U.S.S.R. to 100-120% in South Asia, Africa, and Latin America. For East Asia and North America the increases may amount to 60% by the year 2000 and 100% by 2050. In 1970 less developed regions had 2/3 the world's labor force; by 2000 they will have 3/4. In 1970 about 20% of the labor force in more developed regions were working in agriculture while in less developed regions 2/3 were so engaged. In other terms, in more developed regions 10 farmers supported 108 persons while in less developed regions 10 farmers supported only 38. According to Food and Agriculture Organization projections, by 2000 only 3.5% of the labor force in developed regions and 43.5% in less developed regions will be in agriculture. Differences in gross national product between regions is striking. In 1970 the less developed regions contained 70% of world population, 67% of the world labor force, 87% of the world agricultural labor, and produced 15% of its wealth. There are also sharp contrasts in participation in the labor force. In less developed countries more youths and older persons are in the labor force while in developed countries more women work. By the year 2000 female activity rates in more developed regions will increase for ages 20-64 and decrease for those under 20 and over 64. This will raise female participation in the labor force to 35%. In less developed regions female participation is expected to decline. The proportion of young workers is expected to increase in less developed and decline in more developed regions; the same will be true for older workers. The dependency burden will be concentrated among the young in less developed nations; in more devel oped regions there will be larger numbers of older dependents.

Randomised crossover trial of rate feedback and force during chest compressions for paediatric cardiopulmonary resuscitation.

PubMed

Gregson, Rachael Kathleen; Cole, Tim James; Skellett, Sophie; Bagkeris, Emmanouil; Welsby, Denise; Peters, Mark John

2017-05-01

To determine the effect of visual feedback on rate of chest compressions, secondarily relating the forces used. Randomised crossover trial. Tertiary teaching hospital. Fifty trained hospital staff. A thin sensor-mat placed over the manikin's chest measured rate and force. Rescuers applied compressions to the same paediatric manikin for two sessions. During one session they received visual feedback comparing their real-time rate with published guidelines. Primary: compression rate. Secondary: compression and residual forces. Rate of chest compressions (compressions per minute (compressions per minute; cpm)) varied widely (mean (SD) 111 (13), range 89-168), with a fourfold difference in variation during session 1 between those receiving and not receiving feedback (108 (5) vs 120 (20)). The interaction of session by feedback order was highly significant, indicating that this difference in mean rate between sessions was 14 cpm less (95% CI -22 to -5, p=0.002) in those given feedback first compared with those given it second. Compression force (N) varied widely (mean (SD) 306 (94); range 142-769). Those receiving feedback second (as opposed to first) used significantly lower force (adjusted mean difference -80 (95% CI -128 to -32), p=0.002). Mean residual force (18 N, SD 12, range 0-49) was unaffected by the intervention. While visual feedback restricted excessive compression rates to within the prescribed range, applied force remained widely variable. The forces required may differ with growth, but such variation treating one manikin is alarming. Feedback technologies additionally measuring force (effort) could help to standardise and define effective treatments throughout childhood. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Development of a control algorithm for the ultrasound scanning robot (NCCUSR) using ultrasound image and force feedback.

PubMed

Kim, Yeoun Jae; Seo, Jong Hyun; Kim, Hong Rae; Kim, Kwang Gi

2017-06-01

Clinicians who frequently perform ultrasound scanning procedures often suffer from musculoskeletal disorders, arthritis, and myalgias. To minimize their occurrence and to assist clinicians, ultrasound scanning robots have been developed worldwide. Although, to date, there is still no commercially available ultrasound scanning robot, many control methods have been suggested and researched. These control algorithms are either image based or force based. If the ultrasound scanning robot control algorithm was a combination of the two algorithms, it could benefit from the advantage of each one. However, there are no existing control methods for ultrasound scanning robots that combine force control and image analysis. Therefore, in this work, a control algorithm is developed for an ultrasound scanning robot using force feedback and ultrasound image analysis. A manipulator-type ultrasound scanning robot named 'NCCUSR' is developed and a control algorithm for this robot is suggested and verified. First, conventional hybrid position-force control is implemented for the robot and the hybrid position-force control algorithm is combined with ultrasound image analysis to fully control the robot. The control method is verified using a thyroid phantom. It was found that the proposed algorithm can be applied to control the ultrasound scanning robot and experimental outcomes suggest that the images acquired using the proposed control method can yield a rating score that is equivalent to images acquired directly by the clinicians. The proposed control method can be applied to control the ultrasound scanning robot. However, more work must be completed to verify the proposed control method in order to become clinically feasible. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

48 CFR 223.570 - Drug-free work force.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Drug-free work force. 223.570 Section 223.570 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM... TECHNOLOGIES, OCCUPATIONAL SAFETY, AND DRUG-FREE WORKPLACE Drug-Free Workplace 223.570 Drug-free work force. ...

48 CFR 223.570 - Drug-free work force.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Drug-free work force. 223.570 Section 223.570 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM... TECHNOLOGIES, OCCUPATIONAL SAFETY, AND DRUG-FREE WORKPLACE Drug-Free Workplace 223.570 Drug-free work force. ...

48 CFR 223.570 - Drug-free work force.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Drug-free work force. 223.570 Section 223.570 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM... TECHNOLOGIES, OCCUPATIONAL SAFETY, AND DRUG-FREE WORKPLACE Drug-Free Workplace 223.570 Drug-free work force. ...

48 CFR 223.570 - Drug-free work force.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false Drug-free work force. 223.570 Section 223.570 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM... TECHNOLOGIES, OCCUPATIONAL SAFETY, AND DRUG-FREE WORKPLACE Drug-Free Workplace 223.570 Drug-free work force. ...

48 CFR 223.570 - Drug-free work force.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Drug-free work force. 223.570 Section 223.570 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM... TECHNOLOGIES, OCCUPATIONAL SAFETY, AND DRUG-FREE WORKPLACE Drug-Free Workplace 223.570 Drug-free work force. ...

Exploiting elasticity: Modeling the influence of neural control on mechanics and energetics of ankle muscle-tendons during human hopping.

PubMed

Robertson, Benjamin D; Sawicki, Gregory S

2014-07-21

We present a simplified Hill-type model of the human triceps surae-Achilles tendon complex working on a gravitational-inertial load during cyclic contractions (i.e. vertical hopping). Our goal was to determine the role that neural control plays in governing muscle, or contractile element (CE), and tendon, or series elastic element (SEE), mechanics and energetics within a compliant muscle-tendon unit (MTU). We constructed a 2D parameter space consisting of many combinations of stimulation frequency and magnitude (i.e. neural control strategies). We compared the performance of each control strategy by evaluating peak force and average positive mechanical power output for the system (MTU) and its respective components (CE, SEE), force-length (F-L) and -velocity (F-V) operating point of the CE during active force production, average metabolic rate for the CE, and both MTU and CE apparent efficiency. Our results suggest that frequency of stimulation plays a primary role in governing whole-MTU mechanics. These include the phasing of both activation and peak force relative to minimum MTU length, average positive power, and apparent efficiency. Stimulation amplitude was primarily responsible for governing average metabolic rate and within MTU mechanics, including peak force generation and elastic energy storage and return in the SEE. Frequency and amplitude of stimulation both played integral roles in determining CE F-L operating point, with both higher frequency and amplitude generally corresponding to lower CE strains, reduced injury risk, and elimination of the need for passive force generation in the CE parallel elastic element (PEE). Copyright © 2014 Elsevier Ltd. All rights reserved.

Modulation of post‐movement beta rebound by contraction force and rate of force development

PubMed Central

Fry, Adam; Mullinger, Karen J.; O'Neill, George C.; Barratt, Eleanor L.; Morris, Peter G.; Bauer, Markus; Folland, Jonathan P.

2016-01-01

Abstract Movement induced modulation of the beta rhythm is one of the most robust neural oscillatory phenomena in the brain. In the preparation and execution phases of movement, a loss in beta amplitude is observed [movement related beta decrease (MRBD)]. This is followed by a rebound above baseline on movement cessation [post movement beta rebound (PMBR)]. These effects have been measured widely, and recent work suggests that they may have significant importance. Specifically, they have potential to form the basis of biomarkers for disease, and have been used in neuroscience applications ranging from brain computer interfaces to markers of neural plasticity. However, despite the robust nature of both MRBD and PMBR, the phenomena themselves are poorly understood. In this study, we characterise MRBD and PMBR during a carefully controlled isometric wrist flexion paradigm, isolating two fundamental movement parameters; force output, and the rate of force development (RFD). Our results show that neither altered force output nor RFD has a significant effect on MRBD. In contrast, PMBR was altered by both parameters. Higher force output results in greater PMBR amplitude, and greater RFD results in a PMBR which is higher in amplitude and shorter in duration. These findings demonstrate that careful control of movement parameters can systematically change PMBR. Further, for temporally protracted movements, the PMBR can be over 7 s in duration. This means accurate control of movement and judicious selection of paradigm parameters are critical in future clinical and basic neuroscientific studies of sensorimotor beta oscillations. Hum Brain Mapp 37:2493–2511, 2016. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc PMID:27061243

Internal Aspects of the Skill Transfer of Manual Assembly Work

ERIC Educational Resources Information Center

Doyo, Daisuke

2009-01-01

In manual assembly work, parts are often assembled by applying force with a simple tool or by hand. A worker thus needs control the force he or she applies in working, as an appropriate level of force is requisite for minimizing work failures and improving efficiency. The object of this study is to clarify the relationship between the level of…

Employment in Perspective: Women in the Labor Force. Third Quarter 1988. Report 758.

ERIC Educational Resources Information Center

Bureau of Labor Statistics (DOL), Washington, DC.

The female share of the older work force has nearly doubled since 1950. In 1987, the 6.2 million women aged 55 and over in the labor force constituted 4 of every 10 older workers. Because young women today have a stronger work attachment than did their mothers and grandmothers, the female share of the older work force is likely to continue to…

Effects of adding whole body vibration to squat training on isometric force/time characteristics.

PubMed

Lamont, Hugh S; Cramer, Joel T; Bemben, Debra A; Shehab, Randa L; Anderson, Mark A; Bemben, Michael G

2010-01-01

Resistance training interventions aimed at increasing lower-body power and rates of force development have produced varying results. Recent studies have suggested that whole-body low-frequency vibration (WBLFV) may elicit an acute postactivation potentiation response, leading to acute improvements in power and force development. Potentially, the use of WBLFV between sets of resistance training rather than during training itself may lead to increased recruitment and synchronization of high-threshold motor units, minimize fatigue potential, and facilitate the chronic adaptation to resistance exercise. The purpose of this study was to determine the effects of applying TriPlaner, WBLFV, prior to and then intermittently between sets of Smith machine squats on short-term adaptations in explosive isometric force expression. Thirty recreationally resistance trained men aged 18-30 were randomly assigned to 1 of 3 groups: resistance training only (SQT, n = 11), resistance plus whole-body vibration (SQTV, n = 13), or active control (CON, n = 6). An isometric squat test was performed prior to and following a 6-week periodized Smith machine squat program. Whole-body low-frequency vibration was applied 180 seconds prior to the first work set (50 Hz, 2-4 mm, 30 seconds) and intermittently (50 Hz, 4-6 mm, 3 x 10 seconds, 60 seconds between exposures) within a 240-second interset rest period. Subjects were instructed to assume a quarter squat posture while positioning their feet directly under their center of mass, which was modified using a handheld goniometer to a knee angle of 135 +/- 5 degrees . Instructions were given to subjects to apply force as fast and as hard as possible for 3.5 seconds. Isometric force (N) and rates of force development (N.s(-1)) were recorded from the onset of contraction (F(0)) to time points corresponding to 30, 50, 80, 100, 150, and 250 milliseconds, as well as the peak isometric rate of force development (PISORFD), and rate of force development to initial peak in force (RFDinitial). Repeated measures analysis of variance and analysis of covariance revealed no significant group by trial interactions for isometric rate of force development (ISORFD) between 0-30, 0-50, 0-80, 0-100, 0-150, and 0-250 milliseconds and PISORFD (p > 0.05). A significant group x trial interaction was seen for RFDinitial with SQTV >CG (p = 0.04, mean difference 997.2 N.s(-1)) and SQTV >SQT (p = 0.04, mean difference 1,994.22 N.s(-1)). Significant trial by covariate interactions (week one measures for ISORFD) and main effects for trial were observed for ISORFD between 0-80, 0-100, 0-and 150 milliseconds; PISORFD; and RFDinitial (p < 0.01). A significant trial effect was seen for Finitial (%) when expressed as a relative percentage of maximal voluntary contraction (MVC) (MVC = 100%) (p = 0.015; week 1 > week 7, mean difference, 5.82%). No significant differences were seen for any other force variables from the onset of contraction to MVC between weeks 1 and 7 (p > 0.05). The data suggest that there was a significant benefit afforded by adding WBLFV to a short-term resistance training protocol with regard to "explosive" strength expression. The addition of vibration prior to and between sets of resistance exercise may be a viable alternative to vibration applied during resistance exercise when trying to improve "explosive" isometric strength.

Rates of change in natural and anthropogenic radiative forcing over the past 20,000 years

PubMed Central

Joos, Fortunat; Spahni, Renato

2008-01-01

The rate of change of climate codetermines the global warming impacts on natural and socioeconomic systems and their capabilities to adapt. Establishing past rates of climate change from temperature proxy data remains difficult given their limited spatiotemporal resolution. In contrast, past greenhouse gas radiative forcing, causing climate to change, is well known from ice cores. We compare rates of change of anthropogenic forcing with rates of natural greenhouse gas forcing since the Last Glacial Maximum and of solar and volcanic forcing of the last millennium. The smoothing of atmospheric variations by the enclosure process of air into ice is computed with a firn diffusion and enclosure model. The 20th century increase in CO2 and its radiative forcing occurred more than an order of magnitude faster than any sustained change during the past 22,000 years. The average rate of increase in the radiative forcing not just from CO2 but from the combination of CO2, CH4, and N2O is larger during the Industrial Era than during any comparable period of at least the past 16,000 years. In addition, the decadal-to-century scale rate of change in anthropogenic forcing is unusually high in the context of the natural forcing variations (solar and volcanoes) of the past millennium. Our analysis implies that global climate change, which is anthropogenic in origin, is progressing at a speed that is unprecedented at least during the last 22,000 years. PMID:18252830

3D Finite Element Modelling of Cutting Forces in Drilling Fibre Metal Laminates and Experimental Hole Quality Analysis

NASA Astrophysics Data System (ADS)

Giasin, Khaled; Ayvar-Soberanis, Sabino; French, Toby; Phadnis, Vaibhav

2017-02-01

Machining Glass fibre aluminium reinforced epoxy (GLARE) is cumbersome due to distinctively different mechanical and thermal properties of its constituents, which makes it challenging to achieve damage-free holes with the acceptable surface quality. The proposed work focuses on the study of the machinability of thin ( 2.5 mm) GLARE laminate. Drilling trials were conducted to analyse the effect of feed rate and spindle speed on the cutting forces and hole quality. The resulting hole quality metrics (surface roughness, hole size, circularity error, burr formation and delamination) were assessed using surface profilometry and optical scanning techniques. A three dimensional (3D) finite-element (FE) model of drilling GLARE laminate was also developed using ABAQUS/Explicit to help understand the mechanism of drilling GLARE. The homogenised ply-level response of GLARE laminate was considered in the FE model to predict cutting forces in the drilling process.

Generation of synthetic surface electromyography signals under fatigue conditions for varying force inputs using feedback control algorithm.

PubMed

Venugopal, G; Deepak, P; Ghosh, Diptasree M; Ramakrishnan, S

2017-11-01

Surface electromyography is a non-invasive technique used for recording the electrical activity of neuromuscular systems. These signals are random, complex and multi-component. There are several techniques to extract information about the force exerted by muscles during any activity. This work attempts to generate surface electromyography signals for various magnitudes of force under isometric non-fatigue and fatigue conditions using a feedback model. The model is based on existing current distribution, volume conductor relations, the feedback control algorithm for rate coding and generation of firing pattern. The result shows that synthetic surface electromyography signals are highly complex in both non-fatigue and fatigue conditions. Furthermore, surface electromyography signals have higher amplitude and lower frequency under fatigue condition. This model can be used to study the influence of various signal parameters under fatigue and non-fatigue conditions.

Force sensor in simulated skin and neural model mimic tactile SAI afferent spiking response to ramp and hold stimuli

PubMed Central

2012-01-01

Background The next generation of prosthetic limbs will restore sensory feedback to the nervous system by mimicking how skin mechanoreceptors, innervated by afferents, produce trains of action potentials in response to compressive stimuli. Prior work has addressed building sensors within skin substitutes for robotics, modeling skin mechanics and neural dynamics of mechanotransduction, and predicting response timing of action potentials for vibration. The effort here is unique because it accounts for skin elasticity by measuring force within simulated skin, utilizes few free model parameters for parsimony, and separates parameter fitting and model validation. Additionally, the ramp-and-hold, sustained stimuli used in this work capture the essential features of the everyday task of contacting and holding an object. Methods This systems integration effort computationally replicates the neural firing behavior for a slowly adapting type I (SAI) afferent in its temporally varying response to both intensity and rate of indentation force by combining a physical force sensor, housed in a skin-like substrate, with a mathematical model of neuronal spiking, the leaky integrate-and-fire. Comparison experiments were then conducted using ramp-and-hold stimuli on both the spiking-sensor model and mouse SAI afferents. The model parameters were iteratively fit against recorded SAI interspike intervals (ISI) before validating the model to assess its performance. Results Model-predicted spike firing compares favorably with that observed for single SAI afferents. As indentation magnitude increases (1.2, 1.3, to 1.4 mm), mean ISI decreases from 98.81 ± 24.73, 54.52 ± 6.94, to 41.11 ± 6.11 ms. Moreover, as rate of ramp-up increases, ISI during ramp-up decreases from 21.85 ± 5.33, 19.98 ± 3.10, to 15.42 ± 2.41 ms. Considering first spikes, the predicted latencies exhibited a decreasing trend as stimulus rate increased, as is observed in afferent recordings. Finally, the SAI afferent’s characteristic response of producing irregular ISIs is shown to be controllable via manipulating the output filtering from the sensor or adding stochastic noise. Conclusions This integrated engineering approach extends prior works focused upon neural dynamics and vibration. Future efforts will perfect measures of performance, such as first spike latency and irregular ISIs, and link the generation of characteristic features within trains of action potentials with current pulse waveforms that stimulate single action potentials at the peripheral afferent. PMID:22824523

Survival Analysis of US Air Force Officer Retention Rate

DTIC Science & Technology

2017-03-23

Air Force Institute of Technology AFIT Scholar Theses and Dissertations 3-23-2017 Survival Analysis of US Air Force Officer Retention Rate Courtney N...AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base, Ohio DISTRIBUTION STATEMENT A. APPROVED FOR PUBLIC RELEASE...to the Faculty Department of Operational Sciences Graduate School of Engineering and Management Air Force Institute of Technology Air University

Influence of electric field on interwell tunneling rate in quasi two dimensional organic quantum wells

NASA Astrophysics Data System (ADS)

Donovan, K. J.; Elliott, J. E.; Jeong, I. S.; Scott, K.; Wilson, E. G.

2000-11-01

The tunneling rate of photocreated charge carriers between layers in Langmuir-Blodgett multilayer structures is measured indirectly using the novel technique of bimolecular recombination quenching. The tunneling rate is demonstrated to be dependent upon the applied electrostatic potential difference between the layers. This dependence is explored in light of the Marcus theory of charge transfer. That theory was developed to describe redox reactions where the driving force is supplied by a chemical potential difference between two chemically different parts of a more complex system. In the current work the electrostatic potential replaces the chemical potential as the driving potential. The field dependence of the exciton dissociation probability is also determined.

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 3 2011-01-01 2011-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

14 CFR 151.51 - Performance of construction work: Sponsor force account.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Performance of construction work: Sponsor force account. 151.51 Section 151.51 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT... Development Projects § 151.51 Performance of construction work: Sponsor force account. (a) Before undertaking...

Honeywell's Working Parents Task Force. Final Report and Recommendations.

ERIC Educational Resources Information Center

Honeywell, Inc., Minneapolis, Minn.

This publication provides a summary of the Honeywell Working Parent Task Force's recommendations on how to solve problems experienced by working parents. The Task Force consisted of three committees: the Employment Practices Committee (EPC); the Parent Education Committee (PEC); and the Child Care Facilities Committee (CCFC). After examining a…

Workforce Education: Issues for the New Century.

ERIC Educational Resources Information Center

Pautler, Albert J., Jr.

This paper is intended to guide small groups of vocational educators in discussions regarding work force education issues for the next century. The following work force issues are suggested: the aging work force; vocational education's role in reforming K-12 education; distance education for technical education programs; the labor shortages…

78 FR 67132 - GPS Satellite Simulator Control Working Group Meeting

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-08

... DEPARTMENT OF DEFENSE Department of the Air Force GPS Satellite Simulator Control Working Group Meeting AGENCY: Space and Missile Systems Center, Global Positioning Systems (GPS) Directorate, Air Force... Control Working Group (SSCWG) meeting on 6 December 2013 from 0900-1300 PST at Los Angeles Air Force Base...

A method for estimating the rolling moment due to spin rate for arbitrary planform wings

NASA Technical Reports Server (NTRS)

Poppen, W. A., Jr.

1985-01-01

The application of aerodynamic theory for estimating the force and moments acting upon spinning airplanes is of interest. For example, strip theory has been used to generate estimates of the aerodynamic characteristics as a function of spin rate for wing-dominated configurations for angles of attack up to 90 degrees. This work, which had been limited to constant chord wings, is extended here to wings comprised of tapered segments. Comparison of the analytical predictions with rotary balance wind tunnel results shows that large discrepancies remain, particularly for those angles-of-attack greater than 40 degrees.

Experiences of forced sex among female patrons of alcohol-serving venues in a South African township.

PubMed

Watt, Melissa H; Sikkema, Kathleen J; Abler, Laurie; Velloza, Jennifer; Eaton, Lisa A; Kalichman, Seth C; Skinner, Donald; Pieterse, Desiree

2015-05-01

South Africa has among the highest rates of forced sex worldwide, and alcohol use has consistently been associated with risk of forced sex in South Africa. However, methodological challenges affect the accuracy of forced sex measurements. This study explored the assessment of forced sex among South African women attending alcohol-serving venues and identified factors associated with reporting recent forced sex. Women (n = 785) were recruited from 12 alcohol-serving venues in a peri-urban township in Cape Town. Brief self-administered surveys included questions about lifetime and recent experiences of forced sex. Surveys included a single question about forced sex and detailed questions about sex by physical force, threats, verbal persuasion, trickery, and spiked drinks. We first compared the single question about forced sex to a composite variable of forced sex as unwanted sex by physical force, threats, or spiked drinks. We then examined potential predictors of recent forced sex (demographics, drinking behavior, relationship to the venue, abuse experiences). The single question about forced sex had low sensitivity (0.38); more than half of the respondents who reported on the detailed questions that they had experienced forced sex by physical force, threats, or spiked drinks reported on the single question item that they had not experienced forced sex. Using our composite variable, 18.6% of women reported lifetime and 10.8% reported recent experiences of forced sex. In our adjusted logistic regression model, recent forced sex using the composite variable was significantly associated with hazardous drinking (OR = 1.92), living farther from the venue (OR = 1.81), recent intimate partner violence (OR = 2.53), and a history of childhood sexual abuse (OR = 4.35). The findings support the need for additional work to refine the assessment of forced sex. Efforts to prevent forced sex should target alcohol-serving venues, where norms and behaviors may present particular risks for women who frequent these settings. © The Author(s) 2014.

Noninvasive blood-flow meter using a curved cannula with zero compensation for an axial flow blood pump.

PubMed

Kosaka, Ryo; Fukuda, Kyohei; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

2013-01-01

In order to monitor the condition of a patient using a left ventricular assist system (LVAS), blood flow should be measured. However, the reliable determination of blood-flow rate has not been established. The purpose of the present study is to develop a noninvasive blood-flow meter using a curved cannula with zero compensation for an axial flow blood pump. The flow meter uses the centrifugal force generated by the flow rate in the curved cannula. Two strain gauges served as sensors. The first gauges were attached to the curved area to measure static pressure and centrifugal force, and the second gauges were attached to straight area to measure static pressure. The flow rate was determined by the differences in output from the two gauges. The zero compensation was constructed based on the consideration that the flow rate could be estimated during the initial driving condition and the ventricular suction condition without using the flow meter. A mock circulation loop was constructed in order to evaluate the measurement performance of the developed flow meter with zero compensation. As a result, the zero compensation worked effectively for the initial calibration and the zero-drift of the measured flow rate. We confirmed that the developed flow meter using a curved cannula with zero compensation was able to accurately measure the flow rate continuously and noninvasively.

Adults on the Autism Spectrum Can Benefit the Work Force: How One New Jersey Advocacy Agency Is Paving the Path to Employment

ERIC Educational Resources Information Center

Arvanitis, Hope

2008-01-01

As people nationwide recognize the merit of observing October as National Disability Employment Awareness Month, more needs to be done to help interested adults with autism spectrum disorders (ASDs) access jobs. ASDs affect 1 in 150 children nationally, and 1 in 94 in New Jersey, which has the nation's highest rate. One premier autism advocacy…

Population Representation in the Military Services: Fiscal Year 2002

DTIC Science & Technology

2004-03-01

a more streamlined force. Although much progress has been achieved with regard to gender equity, much work remains . The representation of women has...primary reason for the difference by gender is lower retention rates among enlisted women . 4-1 Chapter 4 ACTIVE COMPONENT OFFICERS The...for women . The occupational differences by gender are illustrated in Table 3.8. In FY 2002, almost half of enlisted women were in functional

The Impact of the Indonesian Financial Crisis on Children: An Analysis Using the 100 Villages Data. Innocenti Working Papers.

ERIC Educational Resources Information Center

Cameron, Lisa A.

This study examines the impact of the Asian financial crisis on children in Indonesia. Data from four rounds of the 100 Villages Survey are used to examine changes in school attendance rates, child labor force participation, and health status. These data cover over 120 households in each of 100 villages around Indonesia and were collected prior to…

Development of surface functionalized ZnO-doped LiFePO4/C composites as alternative cathode material for lithium ion batteries

NASA Astrophysics Data System (ADS)

Saroha, Rakesh; Panwar, Amrish K.; Sharma, Yogesh; Tyagi, Pawan K.; Ghosh, Sudipto

2017-02-01

Surface modified olivine-type LiFePO4/C-ZnO doped samples were synthesized using sol-gel assisted ball-milling route. In this work, the influence of ZnO-doping on the physiochemical, electrochemical and surface properties such as charge separation at solid-liquid interphase, surface force gradient, surface/ionic conductivity of pristine LiFePO4/C (LFP) has been investigated thoroughly. Synthesized samples were characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. All the synthesized samples were indexed to the orthorhombic phase with Pnma space group. Pristine LiFePO4 retain its structure for higher ZnO concentrations (i.e. 2.5 and 5.0 wt.% of LFP). Surface topography and surface force gradient measurements by EFM revealed that the kinetics of charge carriers, e-/Li+ is more in ZnO-doped LFP samples, which may be attributed to diffusion or conduction process of the charges present at the surface. Among all the synthesized samples LFP/C with 2.5 wt.% of ZnO (LFPZ2.5) displays the highest discharge capacity at all C-rates and exhibit excellent rate performance. LFPZ2.5 delivers a specific discharge capacity of 164 (±3) mAh g-1 at 0.1C rate. LFPZ2.5 shows best cycling performance as it provides a discharge capacity of 135 (±3) mAh g-1 at 1C rate and shows almost 95% capacity retention after 50 charge/discharge cycles. Energy density plot shows that LFPZ2.5 offers high energy and power density measured at high discharge rates (5C), proving its usability for hybrid vehicles application.

Fatal occupational injuries in Taiwan, 1994-2005.

PubMed

Ho, Shu-Chen; Wang, Li-Yu; Ho, Chi-Kung; Yang, Chun-Yuh

2010-04-01

This study examines the trends in rates of fatal occupational injuries in Taiwan by demographic group and occupation for 1994-2005. Data on deaths due to injuries at work from 1994 through 2005 were obtained from the Department of Health which is responsible for the death registration system in Taiwan. Employment data, which were used as the denominators of fatality rates in this study, were retrieved from the Directorate-General of Budget and Accounting Statistics 'Employment and Earnings' database. A Poisson regression model was used to examine the trends in rates of fatal occupational injuries in various occupations while controlling for demographic characteristics. Overall fatal occupational injury rates declined during the study period among all demographic groups and occupations. Adjusted annual changes in rates of fatal injuries ranged from a decrease of 13.6% a year in machine operators/related workers to a decrease of 35.9% in clerks. The annual decrement was faster for males than for females and for older workers compared to young workers. Despite declining rates, the number of fatal occupational injuries in Taiwan remains significant because of the growing work force. Future research should focus on the disparities in fatal injury trends.

Progress toward national estimates of police use of force

PubMed Central

Garner, Joel H.; Malega, Ronald W.; Maxwell, Christopher D.

2018-01-01

This research builds on three decades of effort to produce national estimates of the amount and rate of force used by law enforcement officers in the United States. Prior efforts to produce national estimates have suffered from poor and inconsistent measurements of force, small and unrepresentative samples, low survey and/or item response rates, and disparate reporting of rates of force. The present study employs data from a nationally representative survey of state and local law enforcement agencies that has a high survey response rate as well as a relatively high rate of reporting uses of force. Using data on arrests for violent offenses and the number of sworn officers to impute missing data on uses of force, we estimate a total of 337,590 use of physical force incidents among State and local law enforcement agencies during 2012 with a 95 percent confidence interval of +/- 10,470 incidents or +/- 3.1 percent. This article reports the extent to which the number and rate of force incidents vary by the type and size of law enforcement agencies. Our findings demonstrate the willingness of a large proportion of law enforcement agencies to voluntarily report the amount of force used by their officers and the relative strengths and weaknesses of the Law Enforcement Management and Administrative Statistics (LEMAS) program to produce nationally representative information about police behavior. PMID:29447295

Intramuscular fiber conduction velocity, isometric force and explosive performance.

PubMed

Methenitis, Spyridon; Terzis, Gerasimos; Zaras, Nikolaos; Stasinaki, Angeliki-Nikoletta; Karandreas, Nikolaos

2016-06-01

Conduction of electrical signals along the surface of muscle fibers is acknowledged as an essential neuromuscular component which is linked with muscle force production. However, it remains unclear whether muscle fiber conduction velocity (MFCV) is also linked with explosive performance. The aim of the present study was to investigate the relationship between vastus lateralis MFCV and countermovement jumping performance, the rate of force development and maximum isometric force. Fifteen moderately-trained young females performed countermovement jumps as well as an isometric leg press test in order to determine the rate of force development and maximum isometric force. Vastus lateralis MFCV was measured with intramuscular microelectrodes at rest on a different occasion. Maximum MFCV was significantly correlated with maximum isometric force (r = 0.66, p < 0.01), nevertheless even closer with the leg press rate of force development at 100 ms, 150 ms, 200 ms, and 250 ms (r = 0.85, r = 0.89, r = 0.91, r = 0.92, respectively, p < 0.01). Similarly, mean MFCV and type II MFCV were better correlated with the rate of force development than with maximum isometric leg press force. Lower, but significant correlations were found between mean MFCV and countermovement jump power (r = 0.65, p < 0.01). These data suggest that muscle fiber conduction velocity is better linked with the rate of force development than with isometric force, perhaps because conduction velocity is higher in the larger and fastest muscle fibers which are recognized to contribute to explosive actions.

Contact Force Compensated Thermal Stimulators for Holistic Haptic Interfaces.

PubMed

Sim, Jai Kyoung; Cho, Young-Ho

2016-05-01

We present a contact force compensated thermal stimulator that can provide a consistent tempera- ture sensation on the human skin independent of the contact force between the thermal stimulator and the skin. Previous passive thermal stimulators were not capable of providing a consistent tem- perature on the human skin even when using identical heat source voltage due to an inconsistency of the heat conduction, which changes due to the force-dependent thermal contact resistance. We propose a force-based feedback method that monitors the contact force and controls the heat source voltage according to this contact force, thus providing consistent temperature on the skin. We composed a heat circuit model equivalent to the skin heat-transfer rate as it is changed by the contact forces; we obtained the optimal voltage condition for the constant skin heat-transfer rate independent of the contact force using a numerical estimation simulation tool. Then, in the experiment, we heated real human skin at the obtained heat source voltage condition, and investigated the skin heat transfer-rate by measuring the skin temperature at various times at different levels of contact force. In the numerical estimation results, the skin heat-transfer rate for the contact forces showed a linear profile in the contact force range of 1-3 N; from this profile we obtained the voltage equation for heat source control. In the experimental study, we adjusted the heat source voltage according to the contact force based on the obtained equation. As a result, without the heat source voltage control for the contact forces, the coefficients of variation (CV) of the skin heat-transfer rate in the contact force range of 1-3 N was found to be 11.9%. On the other hand, with the heat source voltage control for the contact forces, the CV of the skin heat-transfer rate in the contact force range of 1-3 N was found to be barely 2.0%, which indicate an 83.2% improvement in consistency compared to the skin heat-transfer rate without the heat source voltage control. The present technique provides a consistent temperature sensation on the human skin independent of the body movement environment; therefore, it has high potential for use in holistic haptic interfaces that have thermal displays.

Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking.

PubMed

Jackson, Rachel W; Dembia, Christopher L; Delp, Scott L; Collins, Steven H

2017-06-01

The goal of this study was to gain insight into how ankle exoskeletons affect the behavior of the plantarflexor muscles during walking. Using data from previous experiments, we performed electromyography-driven simulations of musculoskeletal dynamics to explore how changes in exoskeleton assistance affected plantarflexor muscle-tendon mechanics, particularly for the soleus. We used a model of muscle energy consumption to estimate individual muscle metabolic rate. As average exoskeleton torque was increased, while no net exoskeleton work was provided, a reduction in tendon recoil led to an increase in positive mechanical work performed by the soleus muscle fibers. As net exoskeleton work was increased, both soleus muscle fiber force and positive mechanical work decreased. Trends in the sum of the metabolic rates of the simulated muscles correlated well with trends in experimentally observed whole-body metabolic rate ( R 2 =0.9), providing confidence in our model estimates. Our simulation results suggest that different exoskeleton behaviors can alter the functioning of the muscles and tendons acting at the assisted joint. Furthermore, our results support the idea that the series tendon helps reduce positive work done by the muscle fibers by storing and returning energy elastically. We expect the results from this study to promote the use of electromyography-driven simulations to gain insight into the operation of muscle-tendon units and to guide the design and control of assistive devices. © 2017. Published by The Company of Biologists Ltd.

A new model for force generation by skeletal muscle, incorporating work-dependent deactivation

PubMed Central

Williams, Thelma L.

2010-01-01

A model is developed to predict the force generated by active skeletal muscle when subjected to imposed patterns of lengthening and shortening, such as those that occur during normal movements. The model is based on data from isolated lamprey muscle and can predict the forces developed during swimming. The model consists of a set of ordinary differential equations, which are solved numerically. The model's first part is a simplified description of the kinetics of Ca2+ release from sarcoplasmic reticulum and binding to muscle protein filaments, in response to neural activation. The second part is based on A. V. Hill's mechanical model of muscle, consisting of elastic and contractile elements in series, the latter obeying known physiological properties. The parameters of the model are determined by fitting the appropriate mathematical solutions to data recorded from isolated lamprey muscle activated under conditions of constant length or rate of change of length. The model is then used to predict the forces developed under conditions of applied sinusoidal length changes, and the results compared with corresponding data. The most significant advance of this model is the incorporation of work-dependent deactivation, whereby a muscle that has been shortening under load generates less force after the shortening ceases than otherwise expected. In addition, the stiffness in this model is not constant but increases with increasing activation. The model yields a closer prediction to data than has been obtained before, and can thus prove an important component of investigations of the neural—mechanical—environmental interactions that occur during natural movements. PMID:20118315

Force-momentum-based self-guided Langevin dynamics: A rapid sampling method that approaches the canonical ensemble

NASA Astrophysics Data System (ADS)

Wu, Xiongwu; Brooks, Bernard R.

2011-11-01

The self-guided Langevin dynamics (SGLD) is a method to accelerate conformational searching. This method is unique in the way that it selectively enhances and suppresses molecular motions based on their frequency to accelerate conformational searching without modifying energy surfaces or raising temperatures. It has been applied to studies of many long time scale events, such as protein folding. Recent progress in the understanding of the conformational distribution in SGLD simulations makes SGLD also an accurate method for quantitative studies. The SGLD partition function provides a way to convert the SGLD conformational distribution to the canonical ensemble distribution and to calculate ensemble average properties through reweighting. Based on the SGLD partition function, this work presents a force-momentum-based self-guided Langevin dynamics (SGLDfp) simulation method to directly sample the canonical ensemble. This method includes interaction forces in its guiding force to compensate the perturbation caused by the momentum-based guiding force so that it can approximately sample the canonical ensemble. Using several example systems, we demonstrate that SGLDfp simulations can approximately maintain the canonical ensemble distribution and significantly accelerate conformational searching. With optimal parameters, SGLDfp and SGLD simulations can cross energy barriers of more than 15 kT and 20 kT, respectively, at similar rates for LD simulations to cross energy barriers of 10 kT. The SGLDfp method is size extensive and works well for large systems. For studies where preserving accessible conformational space is critical, such as free energy calculations and protein folding studies, SGLDfp is an efficient approach to search and sample the conformational space.

Intra- and Inter-Rater Reliability of the Rate of Force Development of Hip Abductor Muscles Measured by Hand-Held Dynamometer

ERIC Educational Resources Information Center

Takeda, Kazuya; Tanabe, Shigeo; Koyama, Soichiro; Nagai, Tomoko; Sakurai, Hiroaki; Kanada, Yoshikiyo; Shomoto, Koji

2018-01-01

The aim of this study was to clarify the intra- and inter-rater reliability of the rate of force development in hip abductor muscle force measurements using a hand-held dynamometer. Thirty healthy adults were separately assessed by two independent raters on two separate days. Rate of force development was calculated from the slope of the…

Work-rate-guided exercise testing in patients with incomplete spinal cord injury using a robotics-assisted tilt-table.

PubMed

Laubacher, Marco; Perret, Claudio; Hunt, Kenneth J

2015-01-01

Robotics-assisted tilt-table (RTT) technology allows neurological rehabilitation therapy to be started early thus alleviating some secondary complications of prolonged bed rest. This study assessed the feasibility of a novel work-rate-guided RTT approach for cardiopulmonary training and assessment in patients with incomplete spinal cord injury (iSCI). Three representative subjects with iSCI at three distinct stages of primary rehabilitation completed an incremental exercise test (IET) and a constant load test (CLT) on a RTT augmented with integrated leg-force and position measurement and visual work rate feedback. Feasibility assessment focused on: (i) implementation, (ii) limited efficacy testing, (iii) acceptability. (i) All subjects were able follow the work rate target profile by adapting their volitional leg effort. (ii) During the IETs, peak oxygen uptake above rest was 304, 467 and 1378 ml/min and peak heart rate (HR) was 46, 32 and 65 beats/min above rest (subjects A, B and C, respectively). During the CLTs, steady-state oxygen uptake increased by 42%, 38% and 162% and HR by 12%, 20% and 29%. (iii) All exercise tests were tolerated well. The novel work-rate guided RTT intervention is deemed feasible for cardiopulmonary training and assessment in patients with iSCI: substantial cardiopulmonary responses were observed and the approach was found to be tolerable and implementable. Implications for Rehabilitation Work-rate guided robotics-assisted tilt-table technology is deemed feasible for cardiopulmonary assessment and training in patients with incomplete spinal cord injury. Robotics-assisted tilt-tables might be a good way to start with an active rehabilitation as early as possible after a spinal cord injury. During training with robotics-assisted devices the active participation of the patients is crucial to strain the cardiopulmonary system and hence gain from the training.

Towards a Learning Workforce: A Policy Discussion Paper on Adult Learners at Work.

ERIC Educational Resources Information Center

Tuckett, Alan

There is widespread agreement in Great Britain that the work force must receive more skills training if the country is to be competitive in the future. Of special concern is the 70 percent of the work force who left school at the earliest possible opportunity, and the (overlapping) 70 percent of the work force who have not received training for a…

Single cell Enrichment with High Throughput Microfluidic Devices

NASA Astrophysics Data System (ADS)

Pakjesm Pourfard, Pedram

Microfluidics is a rapidly growing field of biomedical engineering with numerous applications such as diagnostic testing, therapeutics, and research preparation. Cell enrichment for automated diagnostic is often assayed through measurement of biochemical and biophysical markers. Although biochemical markers have been widely used, intrinsic biophysical markers, such as, Shear migration, Lift force, Dean force, and many other label-free techniques, are advantageous since they don't require costly labeling or sample preparation. However, current passive techniques for enrichment had limited adoption in clinical and cell biology research applications. They generally require low flow rate and low cell volume fraction for high efficiency. The Control increment filtration, T-shaped microfluidic device, and spiral-shaped microfluidic devices will be studied for single-cell separation from aggregates. Control increment filtration works like the tangential filter; however, cells are separated based off of same amount of flow rate passing through large space gaps. Main microchannel of T-Shaped is connected to two perpendicular side channels. Based off Shear-modulated inertial migration, this device will enable selective enrichment of cells. The spiral shaped microfluidic device depends on different Dean and lift forces acting on cells to separate them based off different sizes. The spiral geometry of the microchannel will enable dominant inertial forces and the Dean Rotation force to cause larger cells to migrate to the inner side of the microchannel. Because manipulation of microchannel dimensions correlates to the degree of cell separation, versatility in design exists. Cell mixture samples will contain cells of different sizes and therefore design strategies could be utilized to maximize the effectiveness of single-cell separation.

Battery Capacity Fading Estimation Using a Force-Based Incremental Capacity Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samad, Nassim A.; Kim, Youngki; Siegel, Jason B.

Traditionally health monitoring techniques in lithium-ion batteries rely on voltage and current measurements. A novel method of using a mechanical rather than electrical signal in the incremental capacity analysis (ICA) method is introduced in this paper. This method derives the incremental capacity curves based onmeasured force (ICF) instead of voltage (ICV). The force ismeasured on the surface of a cell under compression in a fixture that replicates a battery pack assembly and preloading. The analysis is performed on data collected from cycling encased prismatic Lithium-ion Nickel-Manganese-Cobalt Oxide (NMC) cells. For the NMC chemistry, the ICF method can complement or replacemore » the ICV method for the following reasons. The identified ICV peaks are centered around 40% of state of charge (SOC) while the peaks of the ICF method are centered around 70% of SOC indicating that the ICF can be used more often because it is more likely that an electric vehicle (EV) or a plug-in hybrid electric vehicle (PHEV) will traverse the 70% SOC range than the 40% SOC. In addition the Signal to Noise ratio (SNR) of the force signal is four times larger than the voltage signal using laboratory grade sensors. The proposed ICF method is shown to achieve 0.42% accuracy in capacity estimation during a low C-rate constant current discharge. Future work will investigate the application of the capacity estimation technique under charging and operation under high C-rates by addressing the transient behavior of force so that an online methodology for capacity estimation is developed.« less

Battery Capacity Fading Estimation Using a Force-Based Incremental Capacity Analysis

DOE PAGES

Samad, Nassim A.; Kim, Youngki; Siegel, Jason B.; ...

2016-05-27

Traditionally health monitoring techniques in lithium-ion batteries rely on voltage and current measurements. A novel method of using a mechanical rather than electrical signal in the incremental capacity analysis (ICA) method is introduced in this paper. This method derives the incremental capacity curves based onmeasured force (ICF) instead of voltage (ICV). The force ismeasured on the surface of a cell under compression in a fixture that replicates a battery pack assembly and preloading. The analysis is performed on data collected from cycling encased prismatic Lithium-ion Nickel-Manganese-Cobalt Oxide (NMC) cells. For the NMC chemistry, the ICF method can complement or replacemore » the ICV method for the following reasons. The identified ICV peaks are centered around 40% of state of charge (SOC) while the peaks of the ICF method are centered around 70% of SOC indicating that the ICF can be used more often because it is more likely that an electric vehicle (EV) or a plug-in hybrid electric vehicle (PHEV) will traverse the 70% SOC range than the 40% SOC. In addition the Signal to Noise ratio (SNR) of the force signal is four times larger than the voltage signal using laboratory grade sensors. The proposed ICF method is shown to achieve 0.42% accuracy in capacity estimation during a low C-rate constant current discharge. Future work will investigate the application of the capacity estimation technique under charging and operation under high C-rates by addressing the transient behavior of force so that an online methodology for capacity estimation is developed.« less

A Phenomenological Model of Bulk Force in a Li-Ion Battery Pack and Its Application to State of Charge Estimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohan, S; Kim, Y; Siegel, JB

A phenomenological model of the bulk force exerted by a lithium ion cell during various charge, discharge, and temperature operating conditions is developed. The measured and modeled force resembles the carbon expansion behavior associated with the phase changes during intercalation, as there are ranges of state of charge (SOC) with a gradual force increase and ranges of SOC with very small change in force. The model includes the influence of temperature on the observed force capturing the underlying thermal expansion phenomena. Moreover the model is capable of describing the changes in force during thermal transients, when internal battery heating duemore » to high C-rates or rapid changes in the ambient temperature, which create a mismatch in the temperature of the cell and the holding fixture. It is finally shown that the bulk force model can be very useful for a more accurate and robust SOC estimation based on fusing information from voltage and force (or pressure) measurements. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email oa@electrochem.org. All rights reserved.« less

Driving reconnection in sheared magnetic configurations with forced fluctuations

NASA Astrophysics Data System (ADS)

Pongkitiwanichakul, Peera; Makwana, Kirit D.; Ruffolo, David

2018-02-01

We investigate reconnection of magnetic field lines in sheared magnetic field configurations due to fluctuations driven by random forcing by means of numerical simulations. The simulations are performed with an incompressible, pseudo-spectral magnetohydrodynamics code in 2D where we take thick, resistively decaying, current-sheet like sheared magnetic configurations which do not reconnect spontaneously. We describe and test the forcing that is introduced in the momentum equation to drive fluctuations. It is found that the forcing does not change the rate of decay; however, it adds and removes energy faster in the presence of the magnetic shear structure compared to when it has decayed away. We observe that such a forcing can induce magnetic reconnection due to field line wandering leading to the formation of magnetic islands and O-points. These reconnecting field lines spread out as the current sheet decays with time. A semi-empirical formula is derived which reasonably explains the formation and spread of O-points. We find that reconnection spreads faster with stronger forcing and longer correlation time of forcing, while the wavenumber of forcing does not have a significant effect. When the field line wandering becomes large enough, the neighboring current sheets with opposite polarity start interacting, and then the magnetic field is rapidly annihilated. This work is useful to understand how forced fluctuations can drive reconnection in large scale current structures in space and astrophysical plasmas that are not susceptible to reconnection.

Marital and Family Characteristics of the Labor Force in March 1973. Special Labor Force Report No. 164.

ERIC Educational Resources Information Center

Hayghe, Howard

This Special Labor Force Report of March 1973, shows a continued decline in labor force participation rates of married men and an increase in rates of married women with young children. It also explores the trends of husbands' and wives' labor force participation, as well as labor force activity of other groups, such as women heads of families and…

Bracing of pectus carinatum: A quantitative analysis.

PubMed

Bugajski, Tomasz; Murari, Kartikeya; Lopushinsky, Steven; Schneider, Marc; Ronsky, Janet

2018-05-01

Primary treatment of pectus carinatum (PC) is performed with an external brace that compresses the protrusion. Patients are 'prescribed' a brace tightening force. However, no visual guides exist to display this force magnitude. The purpose of this study was to determine the repeatability of patients in applying their prescribed force over time and to determine whether the protrusion stiffness influences the patient-applied forces and the protrusion correction rate. Twenty-one male participants (12-17years) with chondrogladiolar PC were recruited at the time of brace fitting. Participants were evaluated on three visits: fitting, one month postfitting, and two months postfitting. Differences between prescribed force and patient-applied force were evaluated. Relationships of patient-applied force and correction rate with protrusion stiffness were assessed. Majority of individuals followed for two months (75%) had a significantly different patient-applied force (p<0.05) from their prescribed force. Protrusion stiffness had a positive relationship with patient-applied force, but no relationship with correction rate. Patients did not follow their prescribed force. Magnitudes of these differences require further investigation to determine clinical significance. Patient-applied forces were influenced by protrusion stiffness, but correction rate was not. Other factors may influence these variables, such as patient compliance. Treatment Study - Level IV. Copyright © 2018 Elsevier Inc. All rights reserved.

The Changing Work Force. Trends and Issues Alerts.

ERIC Educational Resources Information Center

Lankard, Bettina A.

Economic pressures, work force diversity, and advances in technology are changing the nature of work and organizational policy and management. A predicted decline in the annual growth in gross national product is expected to trigger a slowdown in the labor force, especially in occupations that employ workers with only a high school education.…

[Fact Sheets on Working Women].

ERIC Educational Resources Information Center

National Commission on Working Women, Washington, DC.

These four fact sheets address a number of issues relating to women in the work force. The first, "An Overview of Women in the Work Force," offers a look at the numbers of women in the labor force, the occupational categories represented by women workers, women in professional and nonprofessional occupations, and women in nontraditional…

America's Changing Work Force. Statistics in Brief.

ERIC Educational Resources Information Center

American Association of Retired Persons, Washington, DC.

This booklet provides information about the changing work force. It offers a profile of workers aged 45 and older, as well as likely changes in the work force of the future. Tables and graphs illustrate the following: profile of Americans aged 50 and older, by employment status; employment status of the civilian noninstitutional population by age…

Effects of a powered ankle-foot prosthesis on kinetic loading of the unaffected leg during level-ground walking

PubMed Central

2013-01-01

Background People with a lower-extremity amputation that use conventional passive-elastic ankle-foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-foot prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic prosthesis, people with a transtibial amputation using a powered ankle-foot prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds. Methods We analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic prosthesis and a powered ankle-foot prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance. Results Use of the powered prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet. Conclusions Use of a biomimetic powered ankle-foot prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-foot prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis. PMID:23758860

[Workplace injuries and professional mobility correlated with health problems. The potential and limitations of the ISTAT Labour Force survey--July 1999].

PubMed

Vannoni, Francesca; Mamo, C; Demaria, M; Ceccarelli, C; Costa, G

2005-01-01

Knowledge on the occupational and social factors that influence the relationship between illness, absence from work and occupational mobility is at present insufficient. To map out, by social class and occupational group, the impact of health problems on work and the distribution of accidents and morbidity associated with occupation. Using data from the National Survey of the Italian Labour Force (ISTAT, 1999), covering a sample of 200,384 subjects, prevalence odds ratios of morbidity, work injuries and change of occupation due to health problems were calculated by social class and occupation, adjusting for age and residence. The working class showed a higher risk, due to health problems, of a reduction in time worked (OR = 3.70 in men and OR = 4.10 in women), of choosing to work part-time (OR = 2.04 in men and OR = 2.27 in women), or of withdrawing from the workforce (for artisans, skilled manual workers, farmers and agricultural labourers OR = 1.63 in men and OR = 1.47 in women). This class was also at a greater disadvantage not only with respect to accident rates (OR = 1.85 in men and OR = 1.88 in women), but also with respect to the time needed for post-trauma rehabilitation and return to work (for absences of one week to one month: OR = 1.67 and 1.83 for men and women, respectively; for absences of more than one month: OR = 1.29 and OR = 1.69). Moreover, the working class, when compared to other social classes, had a higher rate of suffering from illness, physical impairment or other physical and psychological problems caused or aggravated by working activity (25% in men and 32% in women). The ISTAT National Survey provides an estimate of minor accidents with prognoses of less than three days, including those not reported to the National Institute for Insurance against Occupational Accidents and Diseases (INAIL). This allows a preliminary exploration of the relationship between health problems and occupational mobility; however, it seems necessary to collect more detailed information in order to more exhaustively explore the mechanisms which generate the inequalities observed.

Heat strain during military training activities: The dilemma of balancing force protection and operational capability.

PubMed

Hunt, Andrew P; Billing, Daniel C; Patterson, Mark J; Caldwell, Joanne N

2016-01-01

Military activities in hot environments pose 2 competing demands: the requirement to perform realistic training to develop operational capability with the necessity to protect armed forces personnel against heat-related illness. To ascertain whether work duration limits for protection against heat-related illness restrict military activities, this study examined the heat strain and risks of heat-related illness when conducting a military activity above the prescribed work duration limits. Thirty-seven soldiers conducted a march (10 km; ∼5.5 km h -1 ) carrying 41.8 ± 3.6 kg of equipment in 23.1 ± 1.8°C wet-bulb globe temperature. Body core temperature was recorded throughout and upon completion, or withdrawal, participants rated their severity of heat-related symptoms. Twenty-three soldiers completed the march in 107 ± 6.4 min (Completers); 9 were symptomatic for heat exhaustion, withdrawing after 71.6 ± 10.1 min (Symptomatic); and five were removed for body core temperature above 39.0°C (Hyperthermic) after 58.4 ± 4.5 min. Body core temperature was significantly higher in the Hyperthermic (39.03 ± 0.26°C), than Symptomatic (38.34 ± 0.44°C; P = 0.007 ) and Completers (37.94 ± 0.37°C; P<0.001 ) after 50 min. Heat-related symptom severity was significantly higher among Symptomatic (28.4 ± 11.8) compared to Completers (15.0 ± 9.8, P = 0.006 ) and Hyperthermic (13.0 ± 9.6, P = 0.029 ). The force protection provided by work duration limits may be preventing the majority of personnel from conducting activities in hot environments, thereby constraining a commander's mandate to develop an optimised military force. The dissociation between heat-related symptoms and body core temperature elevation suggests that the physiological mechanisms underpinning exhaustion during exertional heat stress should be re-examined to determine the most appropriate physiological criteria for prescribing work duration limits.

Defining Conditions for the Use of Persistent Surveillance

DTIC Science & Technology

2009-12-01

as hard as the Air Force has worked the North Dakota and Ohio delegations,’ says Colonel Charles Bartlett, head of a special Air Force task force on...UAVs…While Richard Shelby , the Republican senator from Alabama, is concerned about the impact on Redstone Arsenal, which manages much of the Army’s...UAV work, Byron Dorgan, the North Dakota Democratic senator, wants to attract more work for Grand Forks Air Force base, partly to make up for the

Results of a national survey indicating information technology skills needed by nurses at time of entry into the work force.

PubMed

McCannon, Melinda; O'Neal, Pamela V

2003-08-01

A national survey was conducted to determine the information technology skills nurse administrators consider critical for new nurses entering the work force. The sample consisted of 2,000 randomly selected members of the American Organization of Nurse Executives. Seven hundred fifty-two usable questionnaires were returned, for a response rate of 38%. The questionnaire used a 5-point Likert scale and consisted of 17 items that assessed various technology skills and demographic information. The questionnaire was developed and pilot tested with content experts to establish content validity. Descriptive analysis of the data revealed that using e-mail effectively, operating basic Windows applications, and searching databases were critical information technology skills. The most critical information technology skill involved knowing nursing-specific software, such as bedside charting and computer-activated medication dispensers. To effectively prepare nursing students with technology skills needed at the time of entry into practice, nursing faculty need to incorporate information technology skills into undergraduate nursing curricula.

Stretching of Single Polymer Chains Using the Atomic Force Microscope

NASA Astrophysics Data System (ADS)

Ortiz, C.; van der Vegte, E. W.; van Swieten, E.; Robillard, G. T.; Hadziioannou, G.

1998-03-01

A variety of macroscopic phenomenon involve "nanoscale" polymer deformation including rubber elasticity, shear yielding, strain hardening, stress relaxation, fracture, and flow. With the advent of new and improved experimental techniques, such as the atomic force microscope (AFM), the probing of physical properties of polymers has reached finer and finer scales. The development of mixed self-assembling monolayer techniques and the chemical functionalization of AFM probe tips has allowed for mechanical experiments on single polymer chains of molecular dimensions. In our experiments, mixed monolayers are prepared in which end-functionalized, flexible polymer chains of thiol-terminated poly(methacrylic acid) are covalently bonded, isolated, and randomly distributed on gold substrates. The coils are then imaged, tethered to a gold-coated AFM tip, and stretched between the tip and the substrate in a conventional force / distance experiment. An increase in the attractive force due to entropic, elastic resistance to stretching, as well as fracture of the polymer chain is observed. The effect of chain stiffness, topological constraints, strain rate, mechanical hysteresis, and stress relaxation were investigated. Force modulation techniques were also employed in order to image the viscoelastic character of the polymer chains. Parallel work includes similar studies of biological systems such as wheat gluten proteins and polypeptides.

Current deformation in the Tibetan Plateau: a stress gauge in the large-scale India-Asia collision tectonics

NASA Astrophysics Data System (ADS)

Capitanio, F. A.

2017-12-01

The quantification of the exact tectonic forces budget on Earth has remained thus far elusive. Geodetic velocities provide relevant constraints on the current dynamics of the coupling between collision and continental tectonics, however in the Tibetan plateau these support contrasting, non-unique models. Here, we compare numerical models of coupled India-Asia plate convergence, collision and continent interiors tectonics to the geodetically-constrained motions in the Tibetan Plateau to provide a quantitative assessment of the driving forces of plate tectonics in the area. The models develop a range of long-term evolutions remarkably similar to the Asian tectonics in the Cenozoic, reproducing the current large-scale motions pattern under a range of conditions. Balancing the convergent margin forces, following subduction, and the far-field forcing along the trail of the subducting continent, the geodetic rates in the Tibetan Plateau can be matched. The comparisons support the discussion on the likely processes at work, allowing inferences on the drivers of plateau formation and its role on the plate margin-interiors tectonics. More in general, the outcomes highlight the unique role of the Tibetan Plateau as a pressure gauge for the tectonic forces on Earth.

A hierarchy of models for ENSO flavors in past climates.

NASA Astrophysics Data System (ADS)

Karamperidou, C.; Xie, R.; Di Nezio, P. N.

2017-12-01

The existence of two distinct ENSO flavors versus an ENSO continuum remains an open question. Investigating the response of ENSO diversity to past climate forcings provides a framework to approach this question. Previous work using GCMs has shown that ENSO flavors may respond differentially to mid-Holocene orbital forcing, with a significant suppression of Eastern Pacific ENSO as opposed to insensitivity of Central Pacific ENSO. Here, we employ a hierarchy of models to explore the robustness of ENSO-flavor response to orbital forcing. First, we use a modified version of the Zebiak-Cane model which simulates two ENSO modes reminiscent of ENSO flavors. We find a quasi-linear response of these two modes to orbital forcing corresponding to 6ka, 111ka, and 121ka BP in terms of growth rates, frequency and spatial pattern of SST anomalies. We then employ an Earth System Model subject only to orbital forcing to show the corresponding response in the three past climates. This investigation indicates that no extratropical influences may be required to produce such quasi-linear ENSO-flavor response to orbital forcing. Aided by paleoclimate proxies, the hierarchy of models employed here presents a paleoclimate perspective to the fundamental and elusive question of the nature and origins of ENSO diversity.

Peer Ratings: Scoring Strategy Development and Reliability Demonstration on Air Force Basic Trainees. Final Report.

ERIC Educational Resources Information Center

Borman, Walter C.; Rosse, Rodney L.

As an alternative for or adjunct to paper-and-pencil tests for predicting personnel performance, the United States Air Force studied the use of peer ratings as an evaluative tool. Purpose of this study was to evaluate the psychometric characteristics of peer ratings among Air Force basic trainees. Peer ratings were obtained from more than 27,000…

Female Labor Supply and Fertility in Iran: A Comparison Between Developed, Semi Developed and Less Developed Regions.

PubMed

Emamgholipour Sefiddashti, Sara; Homaie Rad, Enayatollah; Arab, Mohamad; Bordbar, Shima

2016-02-01

Female labor supply has been changed dramatically in the recent yr. In this study, we examined the effects of development on the relationship between fertility and female labor supply. We used data of population and housing census of Iran and estimated three separate models. To do this we employed Logistic Regressions (BLR). The estimation results of our study showed that there was a negative relationship between fertility rate and female labor supply and there are some differences for this relationship in three models. When fertility rate increases, FLS would decreases. In addition, for higher fertility rates, the woman might be forced to work more because of the economic conditions of her family; and negative coefficients of the fertility rate effects on FLS would increase with a diminishing rate.

VNTR diversity in Yersinia pestis isolates from an animal challenge study reveals the potential for in vitro mutations during laboratory cultivation

USGS Publications Warehouse

Vogler, Amy J.; Nottingham, Roxanne; Busch, Joseph D.; Sahl, Jason W.; Shuey, Megan M.; Foster, Jeffrey T.; Schupp, James M.; Smith, Susan; Rocke, Tonie E.; Klein, Paul; Wagner, David M.

2016-01-01

Underlying mutation rates and other evolutionary forces shape the population structure of bacteria in nature. Although easily overlooked, similar forces are at work in the laboratory and may influence observed mutations. Here, we investigated tissue samples and Yersinia pestis isolates from a rodent laboratory challenge with strain CO92 using whole genome sequencing and multi-locus variable-number tandem repeat (VNTR) analysis (MLVA). We identified six VNTR mutations that were found to have occurred in vitro during laboratory cultivation rather than in vivo during the rodent challenge. In contrast, no single nucleotide polymorphism (SNP) mutations were observed, either in vivo or in vitro. These results were consistent with previously published mutation rates and the calculated number of Y. pestis generations that occurred during the in vitro versus the in vivo portions of the experiment. When genotyping disease outbreaks, the potential for in vitro mutations should be considered, particularly when highly variable genetic markers such as VNTRs are used.

The dynamic Virtual Fields Method on rubbers at medium and high strain rates

NASA Astrophysics Data System (ADS)

Yoon, Sung-Ho; Siviour, Clive R.

2015-09-01

Elastomeric materials are widely used for energy absorption applications, often experiencing high strain rate deformations. The mechanical characterization of rubbers at high strain rates presents several experimental difficulties, especially associated with achieving adequate signal to noise ratio and static stress equilibrium, when using a conventional technique such as the split Hopkinson pressure bar. In the present study, these problems are avoided by using the dynamic Virtual Fields Method (VFM) in which acceleration fields, clearly generated by the non-equilibrium state, are utilized as a force measurement with in the frame work of the principle of virtual work equation. In this paper, two dynamic VFM based techniques are used to characterise an EPDM rubber. These are denoted as the linear and nonlinear VFM and are developed for (respectively) medium (drop-weight) and high (gas-gun) strain-rate experiments. The use of the two VFMs combined with high-speed imaging analysed by digital imaging correlation allows the identification of the parameters of a given rubber mechanical model; in this case the Ogden model is used.

Finland.

PubMed

1986-10-01

In 1985, Finland's population stood at 4,913,300, with an annual growth rate of 0.35%. The 1984 infant mortality rate was 6.6/1000 and life expectancy was 70.4 years for males and 78.8 years for females. Finland's literacy rate approaches 100%. Of the labor force of 2,437,000, 11.5% are engaged in agriculture; 45.5% are employed in industry, commerce, and finance; 28% are in the service sector; 5.1% work for the government; and 7.6% work in the transport sector. The gross domestic product (GDP) was US$54 billion in 1985, with an annual growth rate of 2.8% and a per capita income of $1,007. Industry accounts for 28% of the GDP. An extensive social welfare system, comprising 20% of the national income, includes a variety of pension and assistance programs and a comprehensive health insurance program covering the entire Finnish population. Finland's proportional representation system of government encourages a multitude of political parties and has resulted in several coalition governments. Finland's industrial economy is based on capital investment and new technology.

O₂migration rates in [NiFe] hydrogenases. A joint approach combining free-energy calculations and kinetic modeling.

PubMed

Topin, Jérémie; Diharce, Julien; Fiorucci, Sébastien; Antonczak, Serge; Golebiowski, Jérôme

2014-01-23

Hydrogenases are promising candidates for the catalytic production of green energy by means of biological ways. The major impediment to such a production is rooted in their inhibition under aerobic conditions. In this work, we model dioxygen migration rates in mutants of a hydrogenase of Desulfovibrio fructusovorans. The approach relies on the calculation of the whole potential of mean force for O2 migration within the wild-type as well as in V74M, V74F, and V74Q mutant channels. The three free-energy barriers along the entire migration pathway are converted into chemical rates through modeling based on Transition State Theory. The use of such a model recovers the trend of O2 migration rates among the series.

[South] Yemen.

PubMed

1987-04-01

The population of Yemen stood at 2.02 million in 1984, with an annual growth rate of 2.9%. The infant mortality rate is 137/1000; life expectancy is 46 years. The literacy rate is 32%. The work force of 410,000 is distributed as follows: agriculture and fisheries, 43.8%; industry and commerce, 28%; and services, 28%. In 1984, the gross national product in Yemen was US$1130 million, with an average real growth rate of 7.4% in 1973-83. In 1978, the 3 political parties were amalgamated into the Yemen Socialist Party, which became the only legal party. Until 1982, economic policy was focused on infrastructure development and agricultural self-sufficiency; since that time, there have been efforts to discover and produce oil. Most of the people of Yemen are subsistence farmers or nomadic herders.

Statistics of work performed on a forced quantum oscillator.

PubMed

Talkner, Peter; Burada, P Sekhar; Hänggi, Peter

2008-07-01

Various aspects of the statistics of work performed by an external classical force on a quantum mechanical system are elucidated for a driven harmonic oscillator. In this special case two parameters are introduced that are sufficient to completely characterize the force protocol. Explicit results for the characteristic function of work and the corresponding probability distribution are provided and discussed for three different types of initial states of the oscillator: microcanonical, canonical, and coherent states. Depending on the choice of the initial state the probability distributions of the performed work may greatly differ. This result in particular also holds true for identical force protocols. General fluctuation and work theorems holding for microcanonical and canonical initial states are confirmed.

Mitigated-force carriage for high magnetic field environments

DOEpatents

Ludtka, Gerard M.; Ludtka, Gail M.; Wilgen, John B.; Murphy, Bart L.

2015-05-19

A carriage for high magnetic field environments includes a plurality of work-piece separators disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla for supporting and separating a plurality of work-pieces by a preselected, essentially equal spacing, so that, as a first work-piece is inserted into the magnetic field, a second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

Respiratory symptoms and lung function in furriers.

PubMed

Zuskin, E; Skuric, Z; Kanceljak, B; Pokrajac, D; Schachter, E N; Witek, T J

1988-01-01

Forty women who had been occupationally exposed in the fur coat manufacturing industry were studied. The mean age was 30 years; mean duration of exposure was 14 years. A group of 31 females who did not work in the furrier industry also was included in the study as the control group. A higher prevalence of all chronic respiratory symptoms was found among furriers when compared with controls; these differences were statistically significant for nasal catarrh (p less than 0.05) and sinusitis (p less than 0.01). Among the furriers, the highest prevalence of respiratory symptoms was recorded for chronic cough in 20 workers (50.0%), followed by sinusitis in 12 (30.0%), dyspnea in 10 (25.0%), and nasal catarrh in 8 workers (20.0%). Among the furriers, two (5.0%) had symptoms characteristic of occupational asthma. Most of the symptomatic furriers complained of acute symptoms during their work shifts. Statistically significant mean reductions in lung function over the work shift were recorded in furriers for forced vital capacity (FVC), -4.1%; one-second forced expiratory volume (FEV1), -5.2%; and flow rate at 50% vital capacity (FEF50%), -6.3%. Furriers demonstrated significantly lower mean Monday preshift measurements for FVC and flow rate at 25% (FEF25%) (p less than 0.05) when compared with those predicted. Preshift administration (by spinhaler) of 40 mg disodium cromoglycate in three workers reduced the intensity of acute respiratory symptoms and diminished the reductions in ventilatory capacity over the work shift. Data from six additional male workers demonstrated similar findings for symptoms and lung function. Our data suggest that furriers are at risk of developing both acute and chronic respiratory symptoms as well as ventilatory capacity impairment as a result of occupational exposure.

Statistical estimates of absenteeism attributable to seasonal and pandemic influenza from the Canadian Labour Force Survey

PubMed Central

2011-01-01

Background As many respiratory viruses are responsible for influenza like symptoms, accurate measures of the disease burden are not available and estimates are generally based on statistical methods. The objective of this study was to estimate absenteeism rates and hours lost due to seasonal influenza and compare these estimates with estimates of absenteeism attributable to the two H1N1 pandemic waves that occurred in 2009. Methods Key absenteeism variables were extracted from Statistics Canada's monthly labour force survey (LFS). Absenteeism and the proportion of hours lost due to own illness or disability were modelled as a function of trend, seasonality and proxy variables for influenza activity from 1998 to 2009. Results Hours lost due to the H1N1/09 pandemic strain were elevated compared to seasonal influenza, accounting for a loss of 0.2% of potential hours worked annually. In comparison, an estimated 0.08% of hours worked annually were lost due to seasonal influenza illnesses. Absenteeism rates due to influenza were estimated at 12% per year for seasonal influenza over the 1997/98 to 2008/09 seasons, and 13% for the two H1N1/09 pandemic waves. Employees who took time off due to a seasonal influenza infection took an average of 14 hours off. For the pandemic strain, the average absence was 25 hours. Conclusions This study confirms that absenteeism due to seasonal influenza has typically ranged from 5% to 20%, with higher rates associated with multiple circulating strains. Absenteeism rates for the 2009 pandemic were similar to those occurring for seasonal influenza. Employees took more time off due to the pandemic strain than was typical for seasonal influenza. PMID:21486453

Changes in technique and efficiency after high-intensity exercise in cross-country skiers.

PubMed

Åsan Grasaas, Christina; Ettema, Gertjan; Hegge, Ann Magdalen; Skovereng, Knut; Sandbakk, Øyvind

2014-01-01

This study investigated changes in technique and efficiency after high-intensity exercise to exhaustion in elite cross-country skiers. Twelve elite male skiers completed 4 min submaximal exercise before and after a high-intensity incremental test to exhaustion with the G3 skating technique on a 5% inclined roller-ski treadmill. Kinematics and kinetics were monitored by instrumented roller skis, work rate was calculated as power against roller friction and gravity, aerobic metabolic cost was determined from gas exchange, and blood lactate values indicated the anaerobic contribution. Gross efficiency was the work rate divided by aerobic metabolic rate. A recovery period of 10 min between the incremental test and the posttest was included to allow the metabolic values to return to baseline. Changes in neuromuscular fatigue in upper and lower limbs before and after the incremental test were indicated by peak power in concentric bench press and squat-jump height. From pretest to posttest, cycle length decreased and cycle rate increased by approximately 5% (P < 0.001), whereas the amount of ski forces did not change significantly. Oxygen uptake increased by 4%, and gross efficiency decreased from 15.5% ± 0.7% to 15.2% ± 0.5% from pretest to posttest (both P < .02). Correspondingly, blood lactate concentration increased from 2.4 ± 1.0 to 6.2 ± 2.5 mmol/L (P < .001). Bench-press and squat-jump performance remained unaltered. Elite cross-country skiers demonstrated a less efficient technique and shorter cycle length during submaximal roller-ski skating after high-intensity exercise. However, there were no changes in ski forces or peak power in the upper and lower limbs that could explain these differences.

Statistical estimates of absenteeism attributable to seasonal and pandemic influenza from the Canadian Labour Force Survey.

PubMed

Schanzer, Dena L; Zheng, Hui; Gilmore, Jason

2011-04-12

As many respiratory viruses are responsible for influenza like symptoms, accurate measures of the disease burden are not available and estimates are generally based on statistical methods. The objective of this study was to estimate absenteeism rates and hours lost due to seasonal influenza and compare these estimates with estimates of absenteeism attributable to the two H1N1 pandemic waves that occurred in 2009. Key absenteeism variables were extracted from Statistics Canada's monthly labour force survey (LFS). Absenteeism and the proportion of hours lost due to own illness or disability were modelled as a function of trend, seasonality and proxy variables for influenza activity from 1998 to 2009. Hours lost due to the H1N1/09 pandemic strain were elevated compared to seasonal influenza, accounting for a loss of 0.2% of potential hours worked annually. In comparison, an estimated 0.08% of hours worked annually were lost due to seasonal influenza illnesses. Absenteeism rates due to influenza were estimated at 12% per year for seasonal influenza over the 1997/98 to 2008/09 seasons, and 13% for the two H1N1/09 pandemic waves. Employees who took time off due to a seasonal influenza infection took an average of 14 hours off. For the pandemic strain, the average absence was 25 hours. This study confirms that absenteeism due to seasonal influenza has typically ranged from 5% to 20%, with higher rates associated with multiple circulating strains. Absenteeism rates for the 2009 pandemic were similar to those occurring for seasonal influenza. Employees took more time off due to the pandemic strain than was typical for seasonal influenza.

Identification of hydrodynamic forces around 3D surrogates using particle image velocimetry in a microfluidic channel

NASA Astrophysics Data System (ADS)

Afshar, Sepideh; Nath, Shubhankar; Demirci, Utkan; Hasan, Tayyaba; Scarcelli, Giuliano; Rizvi, Imran; Franco, Walfre

2018-02-01

Previous studies have demonstrated that flow-induced shear stress induces a motile and aggressive tumor phenotype in a microfluidic model of 3D ovarian cancer. However, the magnitude and distribution of the hydrodynamic forces that influence this biological modulation on the 3D cancer nodules are not known. We have developed a series of numerical and experimental tools to identify these forces within a 3D microchannel. In this work, we used particle image velocimetry (PIV) to find the velocity profile using fluorescent micro-spheres as surrogates and nano-particles as tracers, from which hydrodynamic forces can be derived. The fluid velocity is obtained by imaging the trajectory of a range of florescence nano-particles (500-800 μm) via confocal microscopy. Imaging was done at different horizontal planes and with a 50 μm bead as the surrogate. For an inlet current rate of 2 μl/s, the maximum velocity at the center of the channel was 51 μm/s. The velocity profile around the sphere was symmetric which is expected since the flow is dominated by viscous forces as opposed to inertial forces. The confocal PIV was successfully employed in finding the velocity profile in a microchannel with a nodule surrogate; therefore, it seems feasible to use PIV to investigate the hydrodynamic forces around 3D biological models.

Direct measurements of the interactions between clathrate hydrate particles and water droplets.

PubMed

Liu, Chenwei; Li, Mingzhong; Zhang, Guodong; Koh, Carolyn A

2015-08-14

Clathrate hydrate particle agglomeration is often considered to be one of the key limiting factors in plug formation. The hydrate particle-water interaction can play a critical role in describing hydrate agglomeration, yet is severely underexplored. Therefore, this work investigates the interactions between water droplets and cyclopentane hydrate particles using a micromechanical force (MMF) apparatus. Specifically, the effect of contact time, temperature/subcooling, contact area, and the addition of Sorbitane monooleate (Span 80) surfactant on the water droplet-hydrate particle interaction behavior are studied. The measurements indicate that hydrate formation during the measurement would increase the water-hydrate interaction force significantly. The results also indicate that the contact time, subcooling and concentration of cyclopentane, which determine the hydrate formation rate and hydrate amount, will affect the hydrate-water interaction force. In addition, the interaction forces also increase with the water-hydrate contact area. The addition of Span 80 surfactant induces a change in the hydrate morphology and renders the interfaces stable versus unstable (leading to coalescence), and the contact force can affect the hydrate-water interaction behavior significantly. Compared with the hydrate-hydrate cohesion force (measured in cyclopentane), the hydrate-water adhesion force is an order of magnitude larger. These new measurements can help to provide new and critical insights into the hydrate agglomeration process and potential strategies to control this process.

High-precision horizontally directed force measurements for high dead loads based on a differential electromagnetic force compensation system

NASA Astrophysics Data System (ADS)

Vasilyan, Suren; Rivero, Michel; Schleichert, Jan; Halbedel, Bernd; Fröhlich, Thomas

2016-04-01

In this paper, we present an application for realizing high-precision horizontally directed force measurements in the order of several tens of nN in combination with high dead loads of about 10 N. The set-up is developed on the basis of two identical state-of-the-art electromagnetic force compensation (EMFC) high precision balances. The measurement resolution of horizontally directed single-axis quasi-dynamic forces is 20 nN over the working range of  ±100 μN. The set-up operates in two different measurement modes: in the open-loop mode the mechanical deflection of the proportional lever is an indication of the acting force, whereas in the closed-loop mode it is the applied electric current to the coil inside the EMFC balance that compensates deflection of the lever to the offset zero position. The estimated loading frequency (cutoff frequency) of the set-up in the open-loop mode is about 0.18 Hz, in the closed-loop mode it is 0.7 Hz. One of the practical applications that the set-up is suitable for is the flow rate measurements of low electrically conducting electrolytes by applying the contactless technique of Lorentz force velocimetry. Based on a previously developed set-up which uses a single EMFC balance, experimental, theoretical and numerical analyses of the thermo-mechanical properties of the supporting structure are presented.

Performance evaluation of a six-axis generalized force-reflecting teleoperator

NASA Technical Reports Server (NTRS)

Hannaford, B.; Wood, L.; Guggisberg, B.; Mcaffee, D.; Zak, H.

1989-01-01

Work in real-time distributed computation and control has culminated in a prototype force-reflecting telemanipulation system having a dissimilar master (cable-driven, force-reflecting hand controller) and a slave (PUMA 560 robot with custom controller), an extremely high sampling rate (1000 Hz), and a low loop computation delay (5 msec). In a series of experiments with this system and five trained test operators covering over 100 hours of teleoperation, performance was measured in a series of generic and application-driven tasks with and without force feedback, and with control shared between teleoperation and local sensor referenced control. Measurements defining task performance included 100-Hz recording of six-axis force/torque information from the slave manipulator wrist, task completion time, and visual observation of predefined task errors. The task consisted of high precision peg-in-hole insertion, electrical connectors, velcro attach-de-attach, and a twist-lock multi-pin connector. Each task was repeated three times under several operating conditions: normal bilateral telemanipulation, forward position control without force feedback, and shared control. In shared control, orientation was locally servo controlled to comply with applied torques, while translation was under operator control. All performance measures improved as capability was added along a spectrum of capabilities ranging from pure position control through force-reflecting teleoperation and shared control. Performance was optimal for the bare-handed operator.

Adhesion mechanisms on solar glass: Effects of relative humidity, surface roughness, and particle shape and size

DOE PAGES

Moutinho, Helio R.; Jiang, Cun -Sheng; To, Bobby; ...

2017-07-27

To better understand and quantify soiling rates on solar panels, we are investigating the adhesion mechanisms between dust particles and solar glass. In this work, we report on two of the fundamental adhesion mechanisms: van der Waals and capillary adhesion forces. The adhesion was determined using force versus distance (F-z) measurements performed with an atomic force microscope (AFM). To emulate dust interacting with the front surface of a solar panel, we measured how oxidized AFM tips, SiO 2 glass spheres, and real dust particles adhered to actual solar glass. The van der Waals forces were evaluated by measurements performed withmore » zero relative humidity in a glove box, and the capillary forces were measured in a stable environment created inside the AFM enclosure with relative humidity values ranging from 18% to 80%. To simulate topographic features of the solar panels caused by factors such as cleaning and abrasion, we induced different degrees of surface roughness in the solar glass. As a result, we were able to 1) identify and quantify both the van der Waals and capillary forces, 2) establish the effects of surface roughness, relative humidity, and particle size on the adhesion mechanisms, and 3) compare adhesion forces between well-controlled particles (AFM tips and glass spheres) and real dust particles.« less

Working life tables, Bangladesh 1981.

PubMed

Matin, K A

1986-06-01

Data from the 1981 Bangladesh Population Census were used to construct life tables for working men and women. Bangladesh has a dependency burden of 109 dependents to 100 economically active population. Labor force participation rates in 1981 were 74.1/100 population aged 10 years and over for males and 4.3/100 population aged 10 years and over for females. The age-specific economic activity rates provided the essential link in translating life table data to working life table data. It was calculated that a newborn Bangladesh male had a working life expectancy of 37.8 years and an overall life expectancy of 50.0 years; working life expectancy peaks at 44.2 years at 10 years of age. A newborn female has a working life expectancy of 1.8 years and an overall life expectancy of 49.0 years; a maximum working life expectancy of 2.4 years is obtained at 10 years of age. In the period 1962-81, male working life expectancy registered a slight decline at all ages, while female working life expectancy increased by about 6 months for ages up to 30 years. Mortality accounts for a loss of about 10% of gross years of active life in the 10-69-year goups and 20% in the 10-79-year age group. The male working life expectancy values for Bangladesh in 1981 correspond well with those found in India in 1971, Pakistan in 1978, and Sri Lanka in 1971. However, there is wide divergency in terms of female working life expectancy values: such rates were significantly higher in Sri Lanka and India than in Bangladesh up to the age of 30 years, after which point there was little divergence.

Comparison of Cellulose Iβ Simulations with Three Carbohydrate Force Fields.

PubMed

Matthews, James F; Beckham, Gregg T; Bergenstråhle-Wohlert, Malin; Brady, John W; Himmel, Michael E; Crowley, Michael F

2012-02-14

Molecular dynamics simulations of cellulose have recently become more prevalent due to increased interest in renewable energy applications, and many atomistic and coarse-grained force fields exist that can be applied to cellulose. However, to date no systematic comparison between carbohydrate force fields has been conducted for this important system. To that end, we present a molecular dynamics simulation study of hydrated, 36-chain cellulose Iβ microfibrils at room temperature with three carbohydrate force fields (CHARMM35, GLYCAM06, and Gromos 45a4) up to the near-microsecond time scale. Our results indicate that each of these simulated microfibrils diverge from the cellulose Iβ crystal structure to varying degrees under the conditions tested. The CHARMM35 and GLYCAM06 force fields eventually result in structures similar to those observed at 500 K with the same force fields, which are consistent with the experimentally observed high-temperature behavior of cellulose I. The third force field, Gromos 45a4, produces behavior significantly different from experiment, from the other two force fields, and from previously reported simulations with this force field using shorter simulation times and constrained periodic boundary conditions. For the GLYCAM06 force field, initial hydrogen-bond conformations and choice of electrostatic scaling factors significantly affect the rate of structural divergence. Our results suggest dramatically different time scales for convergence of properties of interest, which is important in the design of computational studies and comparisons to experimental data. This study highlights that further experimental and theoretical work is required to understand the structure of small diameter cellulose microfibrils typical of plant cellulose.

Motor control differs for increasing and releasing force

PubMed Central

Park, Seoung Hoon; Kwon, MinHyuk; Solis, Danielle; Lodha, Neha

2016-01-01

Control of the motor output depends on our ability to precisely increase and release force. However, the influence of aging on force increase and release remains unknown. The purpose of this study, therefore, was to determine whether force control differs while increasing and releasing force in young and older adults. Sixteen young adults (22.5 ± 4 yr, 8 females) and 16 older adults (75.7 ± 6.4 yr, 8 females) increased and released force at a constant rate (10% maximum voluntary contraction force/s) during an ankle dorsiflexion isometric task. We recorded the force output and multiple motor unit activity from the tibialis anterior (TA) muscle and quantified the following outcomes: 1) variability of force using the SD of force; 2) mean discharge rate and variability of discharge rate of multiple motor units; and 3) power spectrum of the multiple motor units from 0–4, 4–10, 10–35, and 35–60 Hz. Participants exhibited greater force variability while releasing force, independent of age (P < 0.001). Increased force variability during force release was associated with decreased modulation of multiple motor units from 35 to 60 Hz (R2 = 0.38). Modulation of multiple motor units from 35 to 60 Hz was further correlated to the change in mean discharge rate of multiple motor units (r = 0.66) and modulation from 0 to 4 Hz (r = −0.64). In conclusion, these findings suggest that force control is altered while releasing due to an altered modulation of the motor units. PMID:26961104

Rate Dependence in Force Networks of Sheared Granular Materials

NASA Astrophysics Data System (ADS)

Hartley, Robert; Behringer, Robert P.

2003-03-01

We describe experiments that explore rate dependence in force networks of dense granular materials undergoing slow deformation by shear and by compression. The experiments were carried out using 2D photoelastic particles so that it was possible to visualize forces at the grain scale. Shear experiments were carried out in a Couette geometry with a rate Ω. Compression experiments were carried out by repetitive compaction via a piston in a rigid chamber at comparable rates to the shear experiments. Under shearing the mean stress/force grew logarithmically with Ω for at least four decades. For compression, no dependence of the mean stress on rate was observed. In related measurements, we observed relaxation of stress in static samples that had been sheared and where the shearing was abruptly stopped. Relaxation of the force network occured over time scales of days. No relaxation of the force network was observable for uniformly compressed static samples. These results are of particular interest because they provide insight into creep and failure in granular materials.

Experimental estimation of energy absorption during heel strike in human barefoot walking.

PubMed

Baines, Patricia M; Schwab, A L; van Soest, A J

2018-01-01

Metabolic energy expenditure during human gait is poorly understood. Mechanical energy loss during heel strike contributes to this energy expenditure. Previous work has estimated the energy absorption during heel strike as 0.8 J using an effective foot mass model. The aim of our study is to investigate the possibility of determining the energy absorption by more directly estimating the work done by the ground reaction force, the force-integral method. Concurrently another aim is to compare this method of direct determination of work to the method of an effective foot mass model. Participants of our experimental study were asked to walk barefoot at preferred speed. Ground reaction force and lower leg kinematics were collected at high sampling frequency (3000 Hz; 1295 Hz), with tight synchronization. The work done by the ground reaction force is 3.8 J, estimated by integrating this force over the foot-ankle deformation. The effective mass model is improved by dropping the assumption that foot-ankle deformation is maximal at the instant of the impact force peak. On theoretical grounds it is clear that in the presence of substantial damping that peak force and peak deformation do not occur simultaneously. The energy absorption results, due the vertical force only, corresponding to the force-integral method is similar to the results of the improved application of the effective mass model (2.7 J; 2.5 J). However the total work done by the ground reaction force calculated by the force-integral method is significantly higher than that of the vertical component alone. We conclude that direct estimation of the work done by the ground reaction force is possible and preferable over the use of the effective foot mass model. Assuming that energy absorbed is lost, the mechanical energy loss of heel strike is around 3.8 J for preferred walking speeds (≈ 1.3 m/s), which contributes to about 15-20% of the overall metabolic cost of transport.

Analysis of the Sediment Hydrograph of the alluvial deltas in the Apalachicola River, Florida

NASA Astrophysics Data System (ADS)

Daranpob, A.; Hagen, S.; Passeri, D.; Smar, D. E.

2011-12-01

Channel and alluvial characteristics in lowlands are the products of boundary conditions and driving forces. The boundary conditions normally include materials and land cover types, such as soil type and vegetation cover. General driving forces include discharge rate, sediment loadings, tides and waves. Deltas built up of river-transported sediment occur in depositional zones of the river mouth in flat terrains and slow currents. Total sediment load depends on two major abilities of the river, the river shear stress and capacity. The shear stress determines transport of a given sediment grain size, normally expressed as tractive force. The river capacity determines the total load or quantity of total sediments transported across a section of the river, generally expressed as the sediment loading rate. The shear stress and sediment loading rate are relatively easy to measure in the headwater and transfer zones where streams form a v-shape valley and the river begins to form defined banks compared to the deposition zone where rivers broaden across lower elevation landscapes creating alluvial forms such as deltas. Determinations of deposition and re-suspension of sediment in fluvial systems are complicated due to exerting tidal, wind, and wave forces. Cyclic forces of tides and waves repeatedly change the sediment transport and deposition rate spatially and temporally in alluvial fans. However, the influence decreases with water depth. Understanding the transport, deposition, and re-suspension of sediments in the fluvial zone would provide a better understanding of the morphology of landscape in lowland estuaries such as the Apalachicola Bay and its estuary systems. The Apalachicola River system is located in the Florida Panhandle. Shelf sedimentation process is not a strong influence in this region because it is protected by barrier islands from direct ocean forces of the Gulf of Mexico. This research explores the characteristic of suspended sediment loadings in fluvial zones of the Apalachicola River and its distributaries through field investigation and laboratory analysis of a series of total suspended solid (TSS) samples. Time-series TSS samples are collected at the alluvial zone. TSS and particle-size distribution analyses are performed to determine the TSS hydrograph and particle-size distribution of suspended solids. Relationships between the TSS hydrograph, discharge hydrograph, and tidal data provide a better understanding of the deposition and re-suspension of the fluvial system in the region. Total suspended particle-size distribution data are used to determine the deposition rate or diminishing rate of alluvial landform in the estuarine system. This dataset and analysis provide excellent information for future modeling work and wetland morphologic studies in the Apalachicola River and similar systems.

Jeans instability in collisional strongly coupled dusty plasma with radiative condensation and polarization force

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prajapati, R. P., E-mail: prajapati-iter@yahoo.co.in; Bhakta, S.; Chhajlani, R. K.

2016-05-15

The influence of dust-neutral collisions, polarization force, and electron radiative condensation is analysed on the Jeans (gravitational) instability of partially ionized strongly coupled dusty plasma (SCDP) using linear perturbation (normal mode) analysis. The Boltzmann distributed ions, dynamics of inertialess electrons, charged dust and neutral particles are considered. Using the plane wave solutions, a general dispersion relation is derived which is modified due to the presence of dust-neutral collisions, strong coupling effect, polarization force, electron radiative condensation, and Jeans dust/neutral frequencies. In the long wavelength perturbations, the Jeans instability criterion depends upon strong coupling effect, polarization interaction parameter, and thermal loss,more » but it is independent of dust-neutral collision frequency. The stability of the considered configuration is analysed using the Routh–Hurwitz criterion. The growth rates of Jeans instability are illustrated, and stabilizing influence of viscoelasticity and dust-neutral collision frequency while destabilizing effect of electron radiative condensation, polarization force, and Jeans dust-neutral frequency ratio is observed. This work is applied to understand the gravitational collapse of SCDP with dust-neutral collisions.« less

Work and power outputs determined from pedalling and flywheel friction forces during brief maximal exertion on a cycle ergometer.

PubMed

Hibi, N; Fujinaga, H; Ishii, K

1996-01-01

Work and power outputs during short-term, maximal exertion on a friction loaded cycle ergometer are usually calculated from the friction force applied to the flywheel. The inertia of the flywheel is sometimes taken into consideration, but the effects of internal resistances and other factors have been ignored. The purpose of this study was to estimate their effects by comparing work or power output determined from the force exerted on the pedals (pedalling force) with work or power output determined from the friction force and the moment of inertia of the rotational parts. A group of 22 male college students accelerated a cycle ergometer as rapidly as possible for 3 s. The total work output determined from the pedalling force (TWp) was significantly greater than that calculated from the friction force and the moment of inertia (TWf). Power output determined from the pedalling force during each pedal stroke (SPp) was also significantly greater than that calculated from the friction force and the moment of inertia. Percentage difference (% diff), defined by % diff = ¿(TWp - TWf)/TWf¿ x 100, ranged from 16.8% to 49.3% with a mean value of 30.8 (SD 9.1)%. It was observed that % diff values were higher in subjects with greater TWp or greater maximal SPp. These results would indicate that internal resistances and other factors, such as the deformation of the chain and the vibrations of the entire system, may have significant effects on the measurements of work and power outputs. The effects appear to depend on the magnitudes of pedalling force and pedal velocity.

Work in America: Implications for Families. Hearing before the Select Committee on Children, Youth, and Families. House of Representatives, Ninety-Ninth Congress, Second Session.

ERIC Educational Resources Information Center

Congress of the U.S., Washington, DC. House Select Committee on Children, Youth, and Families.

This hearing explored the value of work, and how changes in the economy and the composition of the work force have affected families. Witnesses (1) reported data on such topics as the kinds of jobs currently available, women's participation in the work force, unemployment, and labor force growth over the next decade; (2) argued that the economy is…

Hunt's 'sincere' words only strike a false note.

PubMed

Scott, Graham

2014-10-21

The first strike by NHS staff over pay in more than 30 years - and the first by members of the Royal College of Midwives in its history - will hopefully force ministers to rethink their decision to freeze pay rates for 1.3 million health service staff. Those taking part in Monday's four-hour stoppage and this week's 'work-to-rule' deserve great credit for making a sacrifice so that everyone in the NHS may benefit.

Evaluation of experimental parameters for growth of homogeneous solid solutions

NASA Astrophysics Data System (ADS)

Scheel, Hans J.; Swendsen, Robert H.

2001-12-01

In this paper, we discuss the experimental conditions required to grow large two-component crystals from homogeneous solid solutions. Building on the work of Burton, Prim, and Slichter and that of Van Erk, we are able to establish that the concentration fluctuations for diffusion-limited growth are rather insensitive to hydrodynamic fluctuations. This enables a crystal grower to take advantage of forced convection to optimize growth rates without aggravating the striation problem.

France.

PubMed

1987-09-01

In 1986, France had a population of 55,493,000, with an annual growth rate of 0.4%. The infant mortality rate stood at 8.2/1000. Of the work force of 23.8 million, 8.3% were engaged in agriculture, 45.2% were in the industry and commerce sector, and 46.5% were engaged in services. The unemployment rate stood at 10.7%. The country's gross domestic product (GDP) was US$724 billion in 1986, with an average annual growth rate of 2.0%, and per capita income averaged $13,046. France has substantial agricultural resources, a diversified modern industrial system, and a highly skilled labor force. Following the return of a socialist majority in government in 1981, several large manufacturing firms were nationalized along with much of the commercial banking sector. Initial socialist policies were stimulative, relying partly on income redistribution and partly on increased government spending. However, the resultant increase in import demand was not offset by an increased demand French exports. In 1983, an economic stabilization plan of reductions in the budget deficit, involving spending cuts, increased taxes, and tighter monetary and credit policies, was successfully implemented. Although current economic policies should promote stronger growth over the medium to long term, trade competitiveness remains weak and high unemployment is a major social problem.

Demographics, the Third Age and partial retirement: Policy proposals to accommodate the changing picture of female retirement in Canada.

PubMed

Venne, Rosemary A; Hannay, Maureen

2017-01-01

Much concern has been raised around the potential impact of the retirement of the large baby boom generation. This article specifically addresses the unique issues surrounding the retirement of female baby boomers. Demographic changes, including increased labor force participation, coupled with declining fertility rates, have resulted in a social transformation of the roles women play in society. Despite these changes, women still bear much of the caregiving responsibilities in the household, which can complicate retirement choices. This article examines female retirement in the Canadian context and presents three policy proposals to expand women's retirement choices, encourage longer-term labor force participation, and thereby extend their working lives into the Third Age.

Mitigated-force carriage for high magnetic field environments

DOEpatents

Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Murphy, Bart L

2014-05-20

A carriage for high magnetic field environments includes a first work-piece holding means for holding a first work-piece, the first work-piece holding means being disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla. The first work-piece holding means is further disposed in operable connection with a second work-piece holding means for holding a second work-piece so that, as the first work-piece is inserted into the magnetic field, the second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

Interaction of Rate of Force Development and Duration of Rate in Isometric Force.

ERIC Educational Resources Information Center

Siegel, Donald

A study attempted to determine whether force and duration parameters are programmed in an interactive or independent fashion prior to executing ballistic type isometric contractions of graded intensities. Four adult females each performed 360 trials of producing ballistic type forces representing 25, 40, 55, and 75 percent of their maximal…

Dopaminergic influence on rat tongue function and limb movement initiation.

PubMed

Ciucci, Michelle Renee; Connor, Nadine P

2009-04-01

Altering dopamine synaptic transmission can affect both cranial and limb sensorimotor function, but often to a different degree of severity. We hypothesized that haloperidol has dose-dependent but differential effects on lingual forces, lingual movement rates, and limb movement initiation. We measured average and maximal lingual force, tongue press rate and cataleptic descent time in nine Fischer 344/Brown Norway rats in varied doses of haloperidol. Decreases in lingual force and temporal parameters and increases in cataleptic descent time were related to haloperidol dose. However, they were related to a different degree as the relationships were strong between average force and tongue press rate, moderate between maximal force and tongue press rate, moderate between average force and cataleptic descent time, and weak between maximal force and cataleptic descent time. Elucidating the relationships between the cranial and limb sensorimotor systems in the context of altered dopamine synaptic transmission may assist in developing therapies for conditions such as Parkinson's disease.

Forces on nuclei moving on autoionizing molecular potential energy surfaces.

PubMed

Moiseyev, Nimrod

2017-01-14

Autoionization of molecular systems occurs in diatomic molecules and in small biochemical systems. Quantum chemistry packages enable calculation of complex potential energy surfaces (CPESs). The imaginary part of the CPES is associated with the autoionization decay rate, which is a function of the molecular structure. Molecular dynamics simulations, within the framework of the Born-Oppenheimer approximation, require the definition of a force field. The ability to calculate the forces on the nuclei in bio-systems when autoionization takes place seems to rely on an understanding of radiative damages in RNA and DNA arising from the release of slow moving electrons which have long de Broglie wavelengths. This work addresses calculation of the real forces on the nuclei moving on the CPES. By using the transformation of the time-dependent Schrödinger equation, previously used by Madelung, we proved that the classical forces on nuclei moving on the CPES correlated with the gradient of the real part of the CPES. It was proved that the force on the nuclei of the metastable molecules is time independent although the probability to detect metastable molecules exponentially decays. The classical force is obtained from the transformed Schrödinger equation when ℏ=0 and the Schrödinger equation is reduced to the classical (Newtonian) equations of motion. The forces on the nuclei regardless on what potential energy surface they move (parent CPES or product real PESs) vary in time due to the autoionization process.

Diffusion controlled initial recombination

NASA Astrophysics Data System (ADS)

Christen, T.; Büttiker, M.

1998-08-01

This work addresses nucleation rates in systems with strong initial recombination. Initial (or ``geminate'') recombination is a process where a dissociated structure (anion, vortex, kink, etc.) recombines with its twin brother (cation, antivortex, antikink) generated in the same nucleation event. Initial recombination is important if there is an asymptotically vanishing interaction force instead of a generic saddle-type activation barrier. At low temperatures, initial recombination strongly dominates homogeneous recombination. In a first part, we discuss the effect in one-, two-, and three-dimensional diffusion controlled systems with spherical symmetry. Since there is no well-defined saddle, we introduce a threshold which is to some extent arbitrary but which is restricted by physically reasonable conditions. We show that the dependence of the nucleation rate on the specific choice of this threshold is strongest for one-dimensional systems and decreases in higher dimensions. We also discuss the influence of a weak driving force, and show that the transport current is directly determined by the imbalance of the activation rate in the direction of the field and the rate against this direction. In a second part, we apply the results to the overdamped sine-Gordon system at equilibrium. It turns out that diffusive initial recombination is the essential mechanism which governs the equilibrium kink nucleation rate. We emphasize analogies between the single particle problem with initial recombination and the multidimensional kink-antikink nucleation problem.

Supplemental Oxygen During High-Intensity Exercise Training in Nonhypoxemic Chronic Obstructive Pulmonary Disease.

PubMed

Neunhäuserer, Daniel; Steidle-Kloc, Eva; Weiss, Gertraud; Kaiser, Bernhard; Niederseer, David; Hartl, Sylvia; Tschentscher, Marcus; Egger, Andreas; Schönfelder, Martin; Lamprecht, Bernd; Studnicka, Michael; Niebauer, Josef

2016-11-01

Physical exercise training is an evidence-based treatment in chronic obstructive pulmonary disease, and patients' peak work rate is associated with reduced chronic obstructive pulmonary disease mortality. We assessed whether supplemental oxygen during exercise training in nonhypoxemic patients with chronic obstructive pulmonary disease might lead to superior training outcomes, including improved peak work rate. This was a randomized, double-blind, controlled, crossover trial. Twenty-nine patients with chronic obstructive pulmonary disease (aged 63.5 ± 5.9 years; forced expiratory volume in 1 second percent predicted, 46.4 ± 8.6) completed 2 consecutive 6-week periods of endurance and strength training with progressive intensity, which was performed 3 times per week with supplemental oxygen or compressed medical air (flow via nasal cannula: 10 L/min). Each session of electrocardiography-controlled interval cycling lasted 31 minutes and consisted of a warm-up, 7 cycles of 1-minute intervals at 70% to 80% of peak work rate alternating with 2 minutes of active recovery, and final cooldown. Thereafter, patients completed 8 strength-training exercises of 1 set each with 8 to 15 repetitions to failure. Change in peak work rate was the primary study end point. The increase in peak work rate was more than twice as high when patients exercised with supplemental oxygen compared with medical air (0.16 ± 0.02 W/kg vs 0.07 ± 0.02 W/kg; P < .001), which was consistent with all other secondary study end points related to exercise capacity. The impact of oxygen on peak work rate was 39.1% of the overall training effect, whereas it had no influence on strength gain (P > .1 for all exercises). We report that supplemental oxygen in nonhypoxemic chronic obstructive pulmonary disease doubled the effect of endurance training but had no effect on strength gain. Copyright © 2016 Elsevier Inc. All rights reserved.

Labor Force

ERIC Educational Resources Information Center

Occupational Outlook Quarterly, 2012

2012-01-01

The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…

Flextime: A Modified Work Force Scheduling Technique for Selected Headquarters Air Force Logistics Command Organizations.

ERIC Educational Resources Information Center

Kimzey, Reed T.; Prince, Samuel M. O.

The thesis discusses the advantages and disadvantages of one work force scheduling technique--flextime. The authors were interested in determining if a flextime schedule could be put into effect in a governmental organization such as Headquarters Air Force Logistics Command (AFLC). The study objectives were to determine the feasibility,…

The Older Worker. Statistical Reports on Older Americans, No. 6.

ERIC Educational Resources Information Center

Chan, Teresita; Fowles, Donald G.

Trends in the labor force participation and unemployment of older workers were reviewed in a study. A declining rate of labor force participation by older men and a growth in participation by older women were noticed. Examination of labor force participation rates by race revealed a higher participation rate for minority women than for older white…

Tidal interaction of black holes and Newtonian viscous bodies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poisson, Eric

The tidal interaction of a (rotating or nonrotating) black hole with nearby bodies produces changes in its mass, angular momentum, and surface area. Similarly, tidal forces acting on a Newtonian, viscous body do work on the body, change its angular momentum, and part of the transferred gravitational energy is dissipated into heat. The equations that describe the rate of change of the black-hole mass, angular momentum, and surface area as a result of the tidal interaction are compared with the equations that describe how the tidal forces do work, torque, and produce heat in the Newtonian body. The equations aremore » strikingly similar, and unexpectedly, the correspondence between the Newtonian-body and black-hole results is revealed to hold in near-quantitative detail. The correspondence involves the combination k{sub 2}{tau} of 'Love quantities' that incorporate the details of the body's internal structure; k{sub 2} is the tidal Love number, and {tau} is the viscosity-produced delay between the action of the tidal forces and the body's reaction. The combination k{sub 2}{tau} is of order GM/c{sup 3} for a black hole of mass M; it does not vanish, in spite of the fact that k{sub 2} is known to vanish individually for a nonrotating black hole.« less

Local muscle oxygen consumption related to external and joint specific power.

PubMed

Skovereng, Knut; Ettema, Gertjan; van Beekvelt, Mireille

2016-02-01

The purpose of the present study was to examine the effects of external work rate on joint specific power and the relationship between knee extension power and vastus lateralis muscle oxygen consumption (mVO2). We measured kinematics and pedal forces and used inverse dynamics to calculate joint power for the hip, knee and ankle joints during an incremental cycling protocol performed by 21 recreational cyclists. Vastus lateralis mVO2 was estimated using near-infrared spectroscopy with an arterial occlusion. The main finding was a non-linear relationship between vastus lateralis mVO2 and external work rate that was characterised by an increase followed by a tendency for a levelling off (R(2)=0.99 and 0.94 for the quadratic and linear models respectively, p<0.05). When comparing 100W and 225W, there was a ∼43W increase in knee extension but still a ∼9% decrease in relative contribution of knee extension to external work rate resulting from a ∼47W increase in hip extension. When vastus lateralis mVO2 was related to knee extension power, the relationship was still non-linear (R(2)=0.99 and 0.97 for the quadratic and linear models respectively, p<0.05). These results demonstrate a non-linear response in mVO2 relative to a change in external work rate. Relating vastus lateralis mVO2 to knee extension power showed a better fit to a linear equation compared to external work rate, but it is not a straight line. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Effect of ageing on the force development in tetanic contractions of motor units in rat medial gastrocnemius muscle.

PubMed

Łochyński, Dawid; Kaczmarek, Dominik; Krutki, Piotr; Celichowski, Jan

2010-09-01

The purpose of this study was to determine the effect of ageing on the rate of force generation of motor units, and the mechanical efficiency of contraction produced by a doublet discharge. The study was carried out on isolated motor units of rat medial gastrocnemius muscle of young (5-10 mo) and two groups of old (24-25 and 28-30 mo) Wistar rats. Motor units were classified into the fast fatigable (FF), fast resistant (FR) and slow (S) ones. The force output and rate of force development were determined for non-doublet unfused tetanic contractions evoked by a series of a constant-rate trains of pulses and corresponding doublet contractions starting with an initial brief interpulse interval of 5 ms, and for maximal tetanic contraction. In FF motor units the rate of force development and the force produced by the doublet discharge increased transiently at the age of 24-25 mo, while in S and FR motor units this increase was observed at the age of 28-30 mo. Age-related decrease in the rate of force development of skeletal muscle cannot be attributed to a decline in efficiency of force production by functioning motor units. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

Assessment of skeletal muscle fatigue of road maintenance workers based on heart rate monitoring and myotonometry

PubMed Central

Roja, Zenija; Kalkis, Valdis; Vain, Arved; Kalkis, Henrijs; Eglite, Maija

2006-01-01

Objective This research work is dedicated to occupational health problems caused by ergonomic risks. The research object was road building industry, where workers have to work very intensively, have long work hours, are working in forced/constrained work postures and overstrain during the work specific parts of their bodies. The aim of this study was to evaluate the work heaviness degree and to estimate the muscle fatigue of workers after one week work cycle. The study group consisted of 10 road construction and maintenance workers and 10 pavers aged between 20 and 60 years. Methods Physical load were analyzed by measuring heart rate (HR), work postures (OWAS) and perceived exertion (RPE). Assessments of the muscles strain and functional state (tone) were carried out using myotonometric (MYO) measurements. The reliability of the statistical processing of heart rate monitoring and myotonometry data was determined using correlating analysis. Results This study showed that that road construction and repairing works should be considered as a hard work according to average metabolic energy consumption 8.1 ± 1.5 kcal/min; paving, in its turn, was a moderately hard work according to 7.2 ± 1.1 kcal/min. Several muscle tone levels were identified allowing subdivision of workers into three conditional categories basing on muscle tone and fatigue: I – absolute muscle relaxation and ability to relax; II – a state of equilibrium, when muscles are able to adapt to the work load and are partly able to relax; and III – muscle fatigue and increased tone. It was also found out that the increase of muscle tone and fatigue mainly depend on workers physical preparedness and length of service, and less – on their age. Conclusion We have concluded that a complex ergonomic analysis consisting of heart rate monitoring, assessment of compulsive working postures and myotonometry is appropriate to assess the work heaviness degree and can provide prognosis of occupational pathology or work-related musculoskeletal disorders for the workers under different workload conditions. These results can also be used when deciding on necessary rest time and its periodicity. PMID:16872518

Experimental and computational investigation on the flow behavior of granular particles through an inclined rotating chute

NASA Astrophysics Data System (ADS)

Shirsath, Sushil; Padding, Johan; Clercx, Herman; Kuipers, Hans

2013-11-01

In blast furnaces operated in the steel industry, particles like coke, sinter and pellets enter from a hopper and are distributed on the burden surface by a rotating chute. Such particulate flows suffer occasionally from particle segregation in chute, which hinders efficient throughflow. To obtain a more fundamental insight into these effects, monodisperse particles flowing through a rotating chute inclined at a fixed angle has been studied both with experiments and with a discrete particle model. We observe that the prevailing flow patterns depend strongly on the rotation rate of the chute. With increasing rotation rate the particles are moving increasingly to the side wall. The streamwise particle velocity is slightly reduced in the first half length of the chute due to the Coriolis force, but strongly increased in the second half due to the centrifugal forces. The particle bed height becomes a two-dimensional function of the position inside the chute, with a strong increase in bed height along the sidewall due to the Coriolis forces. It was found that the DPM model was agreed well with the experimental measurements. We will also discuss ongoing work, where we investigate the effects of binary particle mixtures with different particle size or density, different chute geometry.

The Inhibition of the Rayleigh-Taylor Instability by Rotation.

PubMed

Baldwin, Kyle A; Scase, Matthew M; Hill, Richard J A

2015-07-01

It is well-established that the Coriolis force that acts on fluid in a rotating system can act to stabilise otherwise unstable flows. Chandrasekhar considered theoretically the effect of the Coriolis force on the Rayleigh-Taylor instability, which occurs at the interface between a dense fluid lying on top of a lighter fluid under gravity, concluding that rotation alone could not stabilise this system indefinitely. Recent numerical work suggests that rotation may, nevertheless, slow the growth of the instability. Experimental verification of these results using standard techniques is problematic, owing to the practical difficulty in establishing the initial conditions. Here, we present a new experimental technique for studying the Rayleigh-Taylor instability under rotation that side-steps the problems encountered with standard techniques by using a strong magnetic field to destabilize an otherwise stable system. We find that rotation about an axis normal to the interface acts to retard the growth rate of the instability and stabilise long wavelength modes; the scale of the observed structures decreases with increasing rotation rate, asymptoting to a minimum wavelength controlled by viscosity. We present a critical rotation rate, dependent on Atwood number and the aspect ratio of the system, for stabilising the most unstable mode.

The Inhibition of the Rayleigh-Taylor Instability by Rotation

PubMed Central

Baldwin, Kyle A.; Scase, Matthew M.; Hill, Richard J. A.

2015-01-01

It is well-established that the Coriolis force that acts on fluid in a rotating system can act to stabilise otherwise unstable flows. Chandrasekhar considered theoretically the effect of the Coriolis force on the Rayleigh-Taylor instability, which occurs at the interface between a dense fluid lying on top of a lighter fluid under gravity, concluding that rotation alone could not stabilise this system indefinitely. Recent numerical work suggests that rotation may, nevertheless, slow the growth of the instability. Experimental verification of these results using standard techniques is problematic, owing to the practical difficulty in establishing the initial conditions. Here, we present a new experimental technique for studying the Rayleigh-Taylor instability under rotation that side-steps the problems encountered with standard techniques by using a strong magnetic field to destabilize an otherwise stable system. We find that rotation about an axis normal to the interface acts to retard the growth rate of the instability and stabilise long wavelength modes; the scale of the observed structures decreases with increasing rotation rate, asymptoting to a minimum wavelength controlled by viscosity. We present a critical rotation rate, dependent on Atwood number and the aspect ratio of the system, for stabilising the most unstable mode. PMID:26130005

Ergonomic evaluation of ten single-channel pipettes.

PubMed

Lichty, Monica G; Janowitz, Ira L; Rempel, David M

2011-01-01

Repetitive pipetting is a task that is associated with work-related musculoskeletal disorders of the hand and arm. The purpose of this study was to evaluate the usability and ergonomic performance of commercially available pipettes as determined by user ratings and objective measurements. Participants were laboratory technicians and scientists at the Lawrence Berkeley National Laboratory with experience performing pipetting tasks. Twenty-one experienced pipette users completed a standardized pipetting task with 5 manual and 5 electronic pipettes. After using each pipette, the user rated it for attributes of comfort and usability. Although no single pipette was rated significantly better than all of the others for every attribute tested, some significant differences were found between pipettes. The Rainin Pipet-Lite received the highest overall quality score among manual pipettes, while the Thermo Scientific Finnpipette Novus was the top-ranked electronic pipette. Features correlated with greater hand and arm comfort were lower tip ejection force, lower blowout force, and pipette balance in the hand. The findings, when considered with participant comments, provide insights into desirable pipette features and emphasize the value of user testing and the importance of the interactions between task, workplace layout, and pipette design. © 2011 - IOS Press and the authors. All rights reserved

Single Molecule Study of Force-Induced Rotation of Carbon-Carbon Double Bonds in Polymers.

PubMed

Huang, Wenmao; Zhu, Zhenshu; Wen, Jing; Wang, Xin; Qin, Meng; Cao, Yi; Ma, Haibo; Wang, Wei

2017-01-24

Carbon-carbon double bonds (C═C) are ubiquitous in natural and synthetic polymers. In bulk studies, due to limited ways to control applied force, they are thought to be mechanically inert and not to contribute to the extensibility of polymers. Here, we report a single molecule force spectroscopy study on a polymer containing C═C bonds using atomic force microscope. Surprisingly, we found that it is possible to directly observe the cis-to-trans isomerization of C═C bonds at the time scale of ∼1 ms at room temperature by applying a tensile force ∼1.7 nN. The reaction proceeds through a diradical intermediate state, as confirmed by both a free radical quenching experiment and quantum chemical modeling. The force-free activation length to convert the cis C═C bonds to the transition state is ∼0.5 Å, indicating that the reaction rate is accelerated by ∼10 9 times at the transition force. On the basis of the density functional theory optimized structure, we propose that because the pulling direction is not parallel to C═C double bonds in the polymer, stretching the polymer not only provides tension to lower the transition barrier but also provides torsion to facilitate the rotation of cis C═C bonds. This explains the apparently low transition force for such thermally "forbidden" reactions and offers an additional explanation of the "lever-arm effect" of polymer backbones on the activation force for many mechanophores. This work demonstrates the importance of precisely controlling the force direction at the nanoscale to the force-activated reactions and may have many implications on the design of stress-responsive materials.

Force spectroscopy of quadruple H-bonded dimers by AFM: dynamic bond rupture and molecular time-temperature superposition.

PubMed

Zou, Shan; Schönherr, Holger; Vancso, G Julius

2005-08-17

We report on the application of the time-temperature superposition principle to supramolecular bond-rupture forces on the single-molecule level. The construction of force-loading rate master curves using atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) experiments carried out in situ at different temperatures allows one to extend the limited range of the experimentally accessible loading rates and hence to cross from thermodynamic nonequilibrium to quasi-equilibrium states. The approach is demonstrated for quadruple H-bonded ureido-4[1H]-pyrimidinone (UPy) moieties studied by variable-temperature SMFS in organic media. The unbinding forces of single quadruple H-bonding (UPy)2 complexes, which were identified based on a polymeric spacer strategy, were found to depend on the loading rate in the range of 5 nN/s to 500 nN/s at 301 K in hexadecane. By contrast, these rupture forces were independent of the loading rate from 5 to 200 nN/s at 330 K. These results indicate that the unbinding behavior of individual supramolecular complexes can be directly probed under both thermodynamic nonequilibrium and quasi-equilibrium conditions. On the basis of the time-temperature superposition principle, a master curve was constructed for a reference temperature of 301 K, and the crossover force (from loading-rate independent to -dependent regimes) was determined as approximately 145 pN (at a loading rate of approximately 5.6 nN/s). This approach significantly broadens the accessible loading-rate range and hence provides access to fine details of potential energy landscape of supramolecular complexes based on SMFS experiments.

Review on pen-and-paper-based observational methods for assessing ergonomic risk factors of computer work.

PubMed

Rahman, Mohd Nasrull Abdol; Mohamad, Siti Shafika

2017-01-01

Computer works are associated with Musculoskeletal Disorders (MSDs). There are several methods have been developed to assess computer work risk factor related to MSDs. This review aims to give an overview of current techniques available for pen-and-paper-based observational methods in assessing ergonomic risk factors of computer work. We searched an electronic database for materials from 1992 until 2015. The selected methods were focused on computer work, pen-and-paper observational methods, office risk factors and musculoskeletal disorders. This review was developed to assess the risk factors, reliability and validity of pen-and-paper observational method associated with computer work. Two evaluators independently carried out this review. Seven observational methods used to assess exposure to office risk factor for work-related musculoskeletal disorders were identified. The risk factors involved in current techniques of pen and paper based observational tools were postures, office components, force and repetition. From the seven methods, only five methods had been tested for reliability. They were proven to be reliable and were rated as moderate to good. For the validity testing, from seven methods only four methods were tested and the results are moderate. Many observational tools already exist, but no single tool appears to cover all of the risk factors including working posture, office component, force, repetition and office environment at office workstations and computer work. Although the most important factor in developing tool is proper validation of exposure assessment techniques, the existing observational method did not test reliability and validity. Futhermore, this review could provide the researchers with ways on how to improve the pen-and-paper-based observational method for assessing ergonomic risk factors of computer work.

Biomechanical and Structural Features of CS2 Fimbriae of Enterotoxigenic Escherichia coli

PubMed Central

Mortezaei, Narges; Singh, Bhupender; Zakrisson, Johan; Bullitt, Esther; Andersson, Magnus

2015-01-01

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrhea worldwide, and infection of children in under-developed countries often leads to high mortality rates. Isolated ETEC expresses a plethora of colonization factors (fimbriae/pili), of which CFA/I and CFA/II, which are assembled via the alternate chaperone pathway (ACP), are among the most common. Fimbriae are filamentous structures whose shafts are primarily composed of helically arranged single pilin-protein subunits, with a unique biomechanical ability to unwind and rewind. A sustained ETEC infection, under adverse conditions of dynamic shear forces, is primarily attributed to this biomechanical feature of ETEC fimbriae. Recent understanding about the role of fimbriae as virulence factors points to an evolutionary adaptation of their structural and biomechanical features. In this work, we investigated the biophysical properties of CS2 fimbriae from the CFA/II group. Homology modeling of its major structural subunit, CotA, reveals structural clues related to the niche in which they are expressed. Using optical-tweezers force spectroscopy, we found that CS2 fimbriae unwind at a constant force of 10 pN and have a corner velocity (i.e., the velocity at which the force required for unwinding rises exponentially with increased speed) of 1300 nm/s. The biophysical properties of CS2 fimbriae assessed in this work classify them into a low-force unwinding group of fimbriae together with the CFA/I and CS20 fimbriae expressed by ETEC strains. The three fimbriae are expressed by ETEC, colonize in similar gut environments, and exhibit similar biophysical features, but differ in their biogenesis. Our observation suggests that the environment has a strong impact on the biophysical characteristics of fimbriae expressed by ETEC. PMID:26153701

Structure design and characteristic analysis of micro-nano probe based on six dimensional micro-force measuring principle

NASA Astrophysics Data System (ADS)

Yang, Hong-tao; Cai, Chun-mei; Fang, Chuan-zhi; Wu, Tian-feng

2013-10-01

In order to develop micro-nano probe having error self-correcting function and good rigidity structure, a new micro-nano probe system was developed based on six-dimensional micro-force measuring principle. The structure and working principle of the probe was introduced in detail. The static nonlinear decoupling method was established with BP neural network to do the static decoupling for the dimension coupling existing in each direction force measurements. The optimal parameters of BP neural network were selected and the decoupling simulation experiments were done. The maximum probe coupling rate after decoupling is 0.039% in X direction, 0.025% in Y direction and 0.027% in Z direction. The static measurement sensitivity of the probe can reach 10.76μɛ / mN in Z direction and 14.55μɛ / mN in X and Y direction. The modal analysis and harmonic response analysis under three dimensional harmonic load of the probe were done by using finite element method. The natural frequencies under different vibration modes were obtained and the working frequency of the probe was determined, which is higher than 10000 Hz . The transient response analysis of the probe was done, which indicates that the response time of the probe can reach 0.4 ms. From the above results, it is shown that the developed micro-nano probe meets triggering requirements of micro-nano probe. Three dimension measuring force can be measured precisely by the developed probe, which can be used to predict and correct the force deformation error and the touch error of the measuring ball and the measuring rod.

Energy cost and pole forces during Nordic walking under different surface conditions.

PubMed

Schiffer, Thorsten; Knicker, Axel; Dannöhl, Regine; Strüder, Heiko K

2009-03-01

The purpose of the study was to identify the effect of three different surfaces on energy consumption and the forces acting on the walking poles during ground contact in Nordic walking (NW). Thirteen female NW instructors (age = 26 +/- 4 yr, weight = 58.5 +/- 4.2 kg, height = 168.1 +/- 4.6 cm) volunteered in the study. The subjects walked a distance of 1200 m at a controlled, constant speed of 2.2 m x s(-1) on each of a concrete surface (C), an artificial athletics track (A), and a naturally grown soccer lawn (G). They used NW poles with inbuilt strain gauge force transducers to measure ground reaction forces acting along the long axes of the poles. Oxygen uptake, capillary blood lactate (La), HR, and RPE were measured before and after the tests. Impact forces, maximum forces, force rates during ground contact identified from the registered force time histories, displayed significant differences related to the surface conditions. However, force time integrals did not show surface-related differences. Relative oxygen consumption showed significant differences between NW on C and on G whereas no surface-related differences could be identified between the surface conditions for the parameters La, HR, and RPE. Our data indicate that the impulse that is generated by the poles on the subjects is identical between the varying surfaces. Because there are differences for the oxygen uptake between C and G, the main regulator for the propulsion must be the musculature of the lower extremities. The work of the upper extremities seems to be a luxury effort for Nordic walkers with a proper technique.

[Physicians' working conditions, health and working capacity].

PubMed

Elovainio, Marko; Virtanen, Marianna; Oksanen, Tuula

2017-01-01

Changes in the working environment will also influence the work of physicians. The greatest of these changes on the Finnish scale, the SOTE reform (the reform in social welfare and public health services), still lies ahead. Labor shortage, on-call duties and patient record systems providing little support to work add to the burden. In surveys related to psychosocial working conditions, physicians' greatest work load factors have been rush, forced working pace and poor communication despite the fact that, on average, they consider their working conditions to be good, frequently better than those of other professional groups, and are committed to carry on with their work until retirement age. Although psychic symptoms and sleep disturbances are common among physicians, there are fewer disability pensions due to e.g. depression among physicians than in other professional groups. Among the municipal professions, physicians have nearly the lowest rate of job absenteeism due to sickness. Challenges brought about by the changes in physician's work can be met with fair management, development of the social capital of the work community, organization of tasks and flexibility of working hours.

Collaboration between nurses and agricultural teachers to prevent adolescent agricultural injuries: the Agricultural Disability Awareness and Risk Education Model.

PubMed

Reed, Deborah B; Kidd, Pamela S

2004-01-01

Nearly 2 million children live or work on America's farms and ranches. Despite the increasing mechanization of production agriculture in the United States, children still constitute a considerable portion of the work force on farms and ranches. When adjusted for actual work exposure time, adolescent injury rates on agricultural establishments surpass those of adults (Castillo, D. N., Landen, D. D., & Layne, L. A. (1994). American Journal of Public Health, 84, 646-649). This project, headed by two public health nurses, developed and tested an agricultural safety curriculum [Agricultural Disability Awareness and Risk Education (AgDARE)] for use in high school agriculture classes. Students who participated in AgDARE scored significantly higher in farm safety attitude and intent to change work behavior than the control group. School and public health nurses, working together with agriculture teachers, may make an effective team in reducing injuries among teen agricultural workers.

Experimental evolution and the dynamics of genomic mutation rate modifiers.

PubMed

Raynes, Y; Sniegowski, P D

2014-11-01

Because genes that affect mutation rates are themselves subject to mutation, mutation rates can be influenced by natural selection and other evolutionary forces. The population genetics of mutation rate modifier alleles has been a subject of theoretical interest for many decades. Here, we review experimental contributions to our understanding of mutation rate modifier dynamics. Numerous evolution experiments have shown that mutator alleles (modifiers that elevate the genomic mutation rate) can readily rise to high frequencies via genetic hitchhiking in non-recombining microbial populations. Whereas these results certainly provide an explanatory framework for observations of sporadically high mutation rates in pathogenic microbes and in cancer lineages, it is nonetheless true that most natural populations have very low mutation rates. This raises the interesting question of how mutator hitchhiking is suppressed or its phenotypic effect reversed in natural populations. Very little experimental work has addressed this question; with this in mind, we identify some promising areas for future experimental investigation.

Women of Hispanic Origin in the Labor Force. Facts on Working Women No. 89-1 = La mujer de origen hispano en la fuerza laboral. Facts on Working Women Num. 89-1S.

ERIC Educational Resources Information Center

Women's Bureau (DOL), Washington, DC.

Data on Hispanic women in the labor force between 1978 and 1988 show the following: (1) 6.5 percent of the women in the work force in 1988 were of Hispanic origin (3.6 million); (2) the median age of Hispanic women was 26.1 years, 2-5 years younger than Black or White women; (3) 66 percent of Hispanic women participate in the labor force, a higher…

Biomechanical risk factors for carpal tunnel syndrome: a pooled study of 2474 workers

PubMed Central

Harris-Adamson, Carisa; Eisen, Ellen A; Kapellusch, Jay; Garg, Arun; Hegmann, Kurt T; Thiese, Matthew S; Dale, Ann Marie; Evanoff, Bradley; Burt, Susan; Bao, Stephen; Silverstein, Barbara; Merlino, Linda; Gerr, Fred; Rempel, David

2015-01-01

Background Between 2001 and 2010, five research groups conducted coordinated prospective studies of carpal tunnel syndrome (CTS) incidence among US workers from various industries and collected detailed subject-level exposure information with follow-up of symptoms, electrophysiological measures and job changes. Objective This analysis examined the associations between workplace biomechanical factors and incidence of dominant-hand CTS, adjusting for personal risk factors. Methods 2474 participants, without CTS or possible polyneuropathy at enrolment, were followed up to 6.5 years (5102 person-years). Individual workplace exposure measures of the dominant hand were collected for each task and included force, repetition, duty cycle and posture. Task exposures were combined across the workweek using time-weighted averaging to estimate job-level exposures. CTS case-criteria were based on symptoms and results of electrophysiological testing. HRs were estimated using Cox proportional hazard models. Results After adjustment for covariates, analyst (HR=2.17; 95% CI 1.38 to 3.43) and worker (HR=2.08; 95% CI 1.31 to 3.39) estimated peak hand force, forceful repetition rate (HR=1.84; 95% CI 1.19 to 2.86) and per cent time spent (eg, duty cycle) in forceful hand exertions (HR=2.05; 95% CI 1.34 to 3.15) were associated with increased risk of incident CTS. Associations were not observed between total hand repetition rate, per cent duration of all hand exertions, or wrist posture and incident CTS. Conclusions In this prospective multicentre study of production and service workers, measures of exposure to forceful hand exertion were associated with incident CTS after controlling for important covariates. These findings may influence the design of workplace safety programmes for preventing work-related CTS. PMID:25324489

Prediction of surface roughness in turning of Ti-6Al-4V using cutting parameters, forces and tool vibration

NASA Astrophysics Data System (ADS)

Sahu, Neelesh Kumar; Andhare, Atul B.; Andhale, Sandip; Raju Abraham, Roja

2018-04-01

Present work deals with prediction of surface roughness using cutting parameters along with in-process measured cutting force and tool vibration (acceleration) during turning of Ti-6Al-4V with cubic boron nitride (CBN) inserts. Full factorial design is used for design of experiments using cutting speed, feed rate and depth of cut as design variables. Prediction model for surface roughness is developed using response surface methodology with cutting speed, feed rate, depth of cut, resultant cutting force and acceleration as control variables. Analysis of variance (ANOVA) is performed to find out significant terms in the model. Insignificant terms are removed after performing statistical test using backward elimination approach. Effect of each control variables on surface roughness is also studied. Correlation coefficient (R2 pred) of 99.4% shows that model correctly explains the experiment results and it behaves well even when adjustment is made in factors or new factors are added or eliminated. Validation of model is done with five fresh experiments and measured forces and acceleration values. Average absolute error between RSM model and experimental measured surface roughness is found to be 10.2%. Additionally, an artificial neural network model is also developed for prediction of surface roughness. The prediction results of modified regression model are compared with ANN. It is found that RSM model and ANN (average absolute error 7.5%) are predicting roughness with more than 90% accuracy. From the results obtained it is found that including cutting force and vibration for prediction of surface roughness gives better prediction than considering only cutting parameters. Also, ANN gives better prediction over RSM models.

The Prediction of the Work of Friction Force on the Arbitrary Path

ERIC Educational Resources Information Center

Matehkolaee, Mehdi Jafari; Majidian, Kourosh

2013-01-01

In this paper we have calculated the work of friction force on the arbitrary path. In our method didn't use from energy conservative conceptions any way. The distinction of this procedure is that at least do decrease measurement on the path once. Thus we can forecast the amount of work of friction force without information about speed of…

Canine Supply for Physical Security: An Analysis of the Royal Australian Air Force Military Working Dog Program

DTIC Science & Technology

2016-03-01

PHYSICAL SECURITY: AN ANALYSIS OF THE ROYAL AUSTRALIAN AIR FORCE MILITARY WORKING DOG PROGRAM by Mark W. Powell March 2016 Thesis...AN ANALYSIS OF THE ROYAL AUSTRALIAN AIR FORCE MILITARY WORKING DOG PROGRAM 5. FUNDING NUMBERS 6. AUTHOR(S) Mark W. Powell 7. PERFORMING...increased demand on its physical security elements. Its military working dog (MWD) workforce is required to meet an inventory of 204 by end of year 2023 as

Malta.

PubMed

1985-02-01

Malta's population stood at 330,000 in 1983, with an annual growth rate of 0.5%. The infant mortality rate is 13.4/1000, and life expectancy is 73 years. 11 years of education is compulsory and the school attendance rate is 96%; the literacy rate is 90%. Malta's work force of 121,025 is distributed as follows: agriculture and fisheries, 4.5%; industry and commerce, 34.9%; services, 30.2%; and government, 22.3%. The gross national product (GNP) was estimated at US$1.04 billion in 1983 (per capita GNP, US$3162), with an annual growth rate of 3.5%. Malta lacks natural resources and a solid agricultural base, so tourism and trade are important. The government has taken steps to launch new export industries and build a more self-reliant economy. A goal is to attract export-oriented foreign direct investment that will provide needed technology and skills.

InGaN working electrodes with assisted bias generated from GaAs solar cells for efficient water splitting.

PubMed

Liu, Shu-Yen; Sheu, J K; Lin, Yu-Chuan; Chen, Yu-Tong; Tu, S J; Lee, M L; Lai, W C

2013-11-04

Hydrogen generation through water splitting by n-InGaN working electrodes with bias generated from GaAs solar cell was studied. Instead of using an external bias provided by power supply, a GaAs-based solar cell was used as the driving force to increase the rate of hydrogen production. The water-splitting system was tuned using different approaches to set the operating points to the maximum power point of the GaAs solar cell. The approaches included changing the electrolytes, varying the light intensity, and introducing the immersed ITO ohmic contacts on the working electrodes. As a result, the hybrid system comprising both InGaN-based working electrodes and GaAs solar cells operating under concentrated illumination could possibly facilitate efficient water splitting.

Comparison of Efficacy, Embolism Rate and Safety of Thrombectomy with Stent Retrievers in an Anterior Circulation Stroke Model.

PubMed

Larsen, Naomi; Oberbeck, Katharina; Lima de Miranda, Rodrigo; Trentmann, Jens; Madjidyar, Jawid; Quandt, Eckhard; Jansen, Olav

2018-06-18

 Various stent retrievers differing in stent design and mechanical properties are currently available for the treatment of ischemic stroke. We conducted this in vitro study to compare the efficacy, embolism rate, and safety of commercially available stent retrievers and prototypes.  Whole blood thrombi were produced in a Chandler loop. The thrombi were inserted into the curved M1 segment of a silicone model of the anterior cerebral circulation. Thrombectomy maneuvers were performed with six commercially available stent retrievers and 2 prototypes with different strut thickness. Wall-stent apposition, first pass recanalization rate, retraction force, and embolism rate were compared.  Devices with complete wall-stent apposition had the highest first pass recanalization rate and lowest embolism rate, but showed the highest retraction force. The prototype with thinner struts had a comparable recanalization and embolism rate, while a lower retraction force had to be applied compared to the prototype with thicker struts.  Complete wall-stent apposition facilitates a higher recanalization rate and lower embolism rate but also correlates to a higher necessary retraction force and thus possibly higher risk of endothelium damage. Stent modifications leading to a reduced retraction force do not compromise efficacy and embolism rate.   · Complete wall-stent apposition facilitates an effective thrombectomy. · Complete wall-stent apposition leads to higher retraction force and possibly greater endothelium damage. · Modifications of strut thickness do not compromise recanalization and embolism rate. · Thinner struts correlate with a lower retraction force. · Larsen N, Oberbeck K, Lima de Miranda R et al. Comparison of Efficacy, Embolism Rate and Safety of Thrombectomy with Stent Retrievers in an Anterior Circulation Stroke Model. Fortschr Röntgenstr 2018; DOI: 10.1055/a-0631-4118. © Georg Thieme Verlag KG Stuttgart · New York.

The effect of employment status on breastfeeding in the United States.

PubMed

Ryan, Alan S; Zhou, Wenjun; Arensberg, Mary Beth

2006-01-01

In the United States, more new mothers are part of the work force than ever before. This trend has implications for many child-rearing practices, including breastfeeding. Based on a national sample of new mothers (n = 228,000), this study considered the prevalence of the initiation and duration of breastfeeding to 6 months after delivery in 2003 among women who were employed full time, who worked part time, or who were not employed outside the home. Breastfeeding trends since 1984 were also considered. In 2003, at the national level, the prevalence of the initiation of breastfeeding and breastfeeding to 6 months after delivery were 66.0% and 32.8%, respectively. In the hospital, mothers who worked part time had a significantly (p <0.05) higher rate of breastfeeding (68.8%) than those who were employed full time (65.5%), or who were not employed (64.8%). Working full time had a (p <0.05) negative effect on breastfeeding duration. By 6 months after delivery, 26.1% of mothers employed full time, 36.6% of mothers working part time, and 35.0% of nonworking mothers breastfed their infant. Mothers who were not employed were more than twice as likely to breastfeed at 6 months than mothers who worked full time. Breastfeeding trends since 1984 indicated a large increase in the rate of breastfeeding at 6 months after delivery among full-time working mothers (204.5%). However, rates for these women have not yet reached those of mothers who worked part time or were not employed. To ensure that the Healthy People 2010 goals for breastfeeding are achieved (75% in the hospital and 50% at 6 months), programs designed to support working mothers who choose to breastfeed must be continued and strengthened.

Acute pulmonary function change associated with work on large dairies in California.

PubMed

Eastman, Chelsea; Schenker, Marc B; Mitchell, Diane C; Tancredi, Daniel J; Bennett, Deborah H; Mitloehner, Frank M

2013-01-01

To study whether dairy workers in California have lower baseline and greater cross-shift decrements in lung function than control employees. A cross-sectional study of 210 dairy and 47 control workers who completed questionnaires and spirometry before and after the work shift. Dairy work was associated with mean baseline differences of -0.132 L (P = 0.07) and -0.131 L (P = 0.13) in forced expiratory volume in 1 second and forced vital capacity, respectively, compared with control employees, adjusting for age, height, smoking status, and days back at work since last day off. Dairy work was associated with a mean cross-shift difference of -65.2 mL (P = 0.02) and -103.1 mL (P < 0.01) in forced expiratory volume in 1 second and forced vital capacity, respectively, adjusting for smoking status and work-shift time. Dairy work in California was associated with mild acute airway obstruction. The unclear long-term effect of dairy work in California merits further investigation.

Catch bonds govern adhesion through L-selectin at threshold shear.

PubMed

Yago, Tadayuki; Wu, Jianhua; Wey, C Diana; Klopocki, Arkadiusz G; Zhu, Cheng; McEver, Rodger P

2004-09-13

Flow-enhanced cell adhesion is an unexplained phenomenon that might result from a transport-dependent increase in on-rates or a force-dependent decrease in off-rates of adhesive bonds. L-selectin requires a threshold shear to support leukocyte rolling on P-selectin glycoprotein ligand-1 (PSGL-1) and other vascular ligands. Low forces decrease L-selectin-PSGL-1 off-rates (catch bonds), whereas higher forces increase off-rates (slip bonds). We determined that a force-dependent decrease in off-rates dictated flow-enhanced rolling of L-selectin-bearing microspheres or neutrophils on PSGL-1. Catch bonds enabled increasing force to convert short-lived tethers into longer-lived tethers, which decreased rolling velocities and increased the regularity of rolling steps as shear rose from the threshold to an optimal value. As shear increased above the optimum, transitions to slip bonds shortened tether lifetimes, which increased rolling velocities and decreased rolling regularity. Thus, force-dependent alterations of bond lifetimes govern L-selectin-dependent cell adhesion below and above the shear optimum. These findings establish the first biological function for catch bonds as a mechanism for flow-enhanced cell adhesion.

Is rate-pressure product of any use in the isolated rat heart? Assessing cardiac 'effort' and oxygen consumption in the Langendorff-perfused heart.

PubMed

Aksentijević, Dunja; Lewis, Hannah R; Shattock, Michael J

2016-02-01

What is the central question of this study? Rate-pressure product (RPP) is commonly used as an index of cardiac 'effort'. In canine and human hearts (which have a positive force-frequency relationship), RPP is linearly correlated with oxygen consumption and has therefore been widely adopted as a species-independent index of cardiac work. However, given that isolated rodent hearts demonstrate a negative force-frequency relationship, its use in this model requires validation. What is the main finding and its importance? Despite its widespread use, RPP is not correlated with oxygen consumption (or cardiac 'effort') in the Langendorff-perfused isolated rat heart. This lack of correlation was also evident when perfusions included a range of metabolic substrates, insulin or β-adrenoceptor stimulation. Langendorff perfusion of hearts isolated from rats and mice has been used extensively for physiological, pharmacological and biochemical studies. The ability to phenotype these hearts reliably is, therefore, essential. One of the commonly used indices of function is rate-pressure product (RPP); a rather ill-defined index of 'work' or, more correctly, 'effort'. Rate-pressure product, as originally described in dog or human hearts, was shown to be correlated with myocardial oxygen consumption (MV̇O2). Despite its widespread use, the application of this index to rat or mouse hearts (which, unlike the dog or human, have a negative force-frequency relationship) has not been characterized. The aim of this study was to examine the relationship between RPP and MV̇O2 in Langendorff-perfused rat hearts. Paced hearts (300-750 beats min(-1)) were perfused either with Krebs-Henseleit (KH) buffer (11 mm glucose) or with buffer supplemented with metabolic substrates and insulin. The arteriovenous oxygen consumption (MV̇O2) was recorded. Metabolic status was assessed using (31) P magnetic resonance spectroscopy and lactate efflux. Experiments were repeated in the presence of isoprenaline and in unpaced hearts where heart rate was increased by cumulative isoprenaline challenge. In KH buffer-perfused hearts, MV̇O2 increased with increasing heart rate, but given that left ventricular developed pressure decreased with increases in rate, RPP was not correlated with MV̇O2, lactate production or phosphocreatine/ATP ratio. Although the provision of substrates or β-adrenoceptor stimulation changed the shape of the RPP-MV̇O2 relationship, neither intervention resulted in a positive correlation between RPP and oxygen consumption. Rate-pressure product is therefore an unreliable index of oxygen consumption or 'cardiac effort' in the isolated rat heart. © 2015 The Authors. Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

Fluctuations in isometric muscle force can be described by one linear projection of low-frequency components of motor unit discharge rates

PubMed Central

Negro, Francesco; Holobar, Aleš; Farina, Dario

2009-01-01

The aim of the study was to investigate the relation between linear transformations of motor unit discharge rates and muscle force. Intramuscular (wire electrodes) and high-density surface EMG (13 × 5 electrode grid) were recorded from the abductor digiti minimi muscle of eight healthy men during 60 s contractions at 5%, 7.5% and 10% of the maximal force. Spike trains of a total of 222 motor units were identified from the EMG recordings with decomposition algorithms. Principal component analysis of the smoothed motor unit discharge rates indicated that one component (first common component, FCC) described 44.2 ± 7.5% of the total variability of the smoothed discharge rates when computed over the entire contraction interval and 64.3 ± 10.2% of the variability when computed over 5 s intervals. When the FCC was computed from four or more motor units per contraction, it correlated with the force produced by the muscle (62.7 ± 10.1%) by a greater degree (P < 0.001) than the smoothed discharge rates of individual motor units (41.4 ± 7.8%). The correlation between FCC and the force signal increased up to 71.8 ± 13.1% when the duration and the shape of the smoothing window for discharge rates were similar to the average motor unit twitch force. Moreover, the coefficients of variation (CoV) for the force and for the FCC signal were correlated in all subjects (R2 range = 0.14–0.56; P < 0.05) whereas the CoV for force was correlated to the interspike interval variability in only one subject (R2= 0.12; P < 0.05). Similar results were further obtained from measures on the tibialis anterior muscle of an additional eight subjects during contractions at forces up to 20% of the maximal force (e.g. FCC explained 59.8 ± 11.0% of variability of the smoothed discharge rates). In conclusion, one signal captures most of the underlying variability of the low-frequency components of motor unit discharge rates and explains large part of the fluctuations in the motor output during isometric contractions. PMID:19840996

Fluctuations in isometric muscle force can be described by one linear projection of low-frequency components of motor unit discharge rates.

PubMed

Negro, Francesco; Holobar, Ales; Farina, Dario

2009-12-15

The aim of the study was to investigate the relation between linear transformations of motor unit discharge rates and muscle force. Intramuscular (wire electrodes) and high-density surface EMG (13 x 5 electrode grid) were recorded from the abductor digiti minimi muscle of eight healthy men during 60 s contractions at 5%, 7.5% and 10% of the maximal force. Spike trains of a total of 222 motor units were identified from the EMG recordings with decomposition algorithms. Principal component analysis of the smoothed motor unit discharge rates indicated that one component (first common component, FCC) described 44.2 +/- 7.5% of the total variability of the smoothed discharge rates when computed over the entire contraction interval and 64.3 +/- 10.2% of the variability when computed over 5 s intervals. When the FCC was computed from four or more motor units per contraction, it correlated with the force produced by the muscle (62.7 +/- 10.1%) by a greater degree (P < 0.001) than the smoothed discharge rates of individual motor units (41.4 +/- 7.8%). The correlation between FCC and the force signal increased up to 71.8 +/- 13.1% when the duration and the shape of the smoothing window for discharge rates were similar to the average motor unit twitch force. Moreover, the coefficients of variation (CoV) for the force and for the FCC signal were correlated in all subjects (R(2) range = 0.14-0.56; P < 0.05) whereas the CoV for force was correlated to the interspike interval variability in only one subject (R(2) = 0.12; P < 0.05). Similar results were further obtained from measures on the tibialis anterior muscle of an additional eight subjects during contractions at forces up to 20% of the maximal force (e.g. FCC explained 59.8 +/- 11.0% of variability of the smoothed discharge rates). In conclusion, one signal captures most of the underlying variability of the low-frequency components of motor unit discharge rates and explains large part of the fluctuations in the motor output during isometric contractions.

Ratchet motion induced by a correlated stochastic force

NASA Astrophysics Data System (ADS)

Cortés, Emilio

2000-01-01

We apply a rigorous formalism we have just worked out (Cortés and Espinosa, Physica A 267 (1999) 414) about escape rates and the Hamilton-Jacobi equation, to study the ratchet motion of a Brownian particle and calculate the probability current in a periodic non-symmetric potential subject to correlated fluctuations. We are able to obtain the current behaviour as a function of the correlation time parameter and compare with other results in the literature.

Attracting the Best. How the Military Competes for Information Technology Personnel

DTIC Science & Technology

2004-01-01

home life. The option to telecommute and a flexible work schedule top the list of low-cost benefits. • The employers create diversity in culture and...rate of promotion. But in the main, the Army did not encourage reclassifying, except for low-density, hard -to-fill specialties, and reclassification...quality recruits. The Army, Navy, and Air Force were hard pressed to meet even their overall numerical targets for recruits, let alone their tar- gets for

Dynamic Rate Dependent Elastoplastic Damage Modeling of Concrete Subject to Blast Loading: Formulation and Computational Aspects

DTIC Science & Technology

1990-10-31

and ZIP Code) Dept. of Civil Fng. & Oper. Research Building 410 Princeton University Bolling AFB, D.C. 20332-6448 ?rinceton, NJ 08544 i. NAME OF FUNDING...Department of Civil Engineering & Operations Research Princeton University Princeton, N.J. 08544 31 October 1990 Final Technical Report Approved for public...release; Distribution is unlimited. I Prepared for Air Force Office of Scientific Research Building 410 Boiling AFB, D.C. 20332-6448 PREFACE This work

Air Force Physical Fitness: An Assessment of Characteristics and Programs which Affect Individual Physical Fitness.

DTIC Science & Technology

1982-09-01

34 -_..... .,.. ........ . . ....... , ::. .. m : 7"= LIST OF TABLES Table Page 2.1 Balke and Ware Correlation of Work Capacity Rating With Oxygen Intake ...it part of their duty to meet fitness standards, include antismoking and drug and a-ohol abuse drives in fitness programs, use percent body fat to...beats per minute was recorded. The researchers found that maximum oxygen intake measured in ml/kdmin was the most satisfactory means of describing

Statistical analysis of sperm sorting

NASA Astrophysics Data System (ADS)

Koh, James; Marcos, Marcos

2017-11-01

The success rate of assisted reproduction depends on the proportion of morphologically normal sperm. It is possible to use an external field for manipulation and sorting. Depending on their morphology, the extent of response varies. Due to the wide distribution in sperm morphology even among individuals, the resulting distribution of kinematic behaviour, and consequently the feasibility of sorting, should be analysed statistically. In this theoretical work, Resistive Force Theory and Slender Body Theory will be applied and compared. Full name is Marcos.

Armed Diplomacy: Why Too Much Military is Dangerous in Latin America

DTIC Science & Technology

2010-04-01

rates, suicide , and depression among members is the indicator that the forces have been stretched too thin and are lacking sufficient manpower to...behind at their home stations who have to compensate for their absence are often being overworked . At a March 1 st , 2010, press conference, the Chief...further stated that the Army had a record number of suicides in 2009 and is studying the problem to determine why mitigation efforts are not working. In

Ductile fracture mechanism of low-temperature In-48Sn alloy joint under high strain rate loading.

PubMed

Kim, Jong-Woong; Jung, Seung-Boo

2012-04-01

The failure behaviors of In-48Sn solder ball joints under various strain rate loadings were investigated with both experimental and finite element modeling study. The bonding force of In-48Sn solder on an Ni plated Cu pad increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloy. In contrast to the cases of Sn-based Pb-free solder joints, the transition of the fracture mode from a ductile mode to a brittle mode was not observed in this solder joint system due to the soft nature of the In-48Sn alloy. This result is discussed in terms of the relationship between the strain-rate of the solder alloy, the work-hardening effect and the resulting stress concentration at the interfacial regions.

Independence of motor unit recruitment and rate modulation during precision force control.

PubMed

Kamen, G; Du, D C

1999-01-01

The vertebrate motor system chiefly employs motor unit recruitment and rate coding to modulate muscle force output. In this paper, we studied how the recruitment of new motor units altered the firing rate of already-active motor units during precision force production in the first dorsal interosseous muscle. Six healthy adults performed linearly increasing isometric voluntary contractions while motor unit activity and force output were recorded. After motor unit discharges were identified, motor unit firing rates were calculated before and after the instances of new motor unit recruitment. Three procedures were applied to compute motor unit firing rate, including the mean of a fixed number of inter-spike intervals and the constant width weighted Hanning window filter method, as well as a modified boxcar technique. In contrast to previous reports, the analysis of the firing rates of over 200 motor units revealed that reduction of the active firing rates was not a common mechanism used to accommodate the twitch force produced by the recruitment of a new motor unit. Similarly, during de-recruitment there was no tendency for motor unit firing rates to increase immediately following the cessation of activity in other motor units. Considerable consistency in recruitment behavior was observed during repeated contractions. However, firing rates during repeated contractions demonstrated considerably more fluctuation. It is concluded that the neuromuscular system does not use short-term preferential motor unit disfacilitation to effect precise regulation of muscular force output.

Hierarchical control of motor units in voluntary contractions.

PubMed

De Luca, Carlo J; Contessa, Paola

2012-01-01

For the past five decades there has been wide acceptance of a relationship between the firing rate of motor units and the afterhyperpolarization of motoneurons. It has been promulgated that the higher-threshold, larger-soma, motoneurons fire faster than the lower-threshold, smaller-soma, motor units. This relationship was based on studies on anesthetized cats with electrically stimulated motoneurons. We questioned its applicability to motor unit control during voluntary contractions in humans. We found that during linearly force-increasing contractions, firing rates increased as exponential functions. At any time and force level, including at recruitment, the firing rate values were inversely related to the recruitment threshold of the motor unit. The time constants of the exponential functions were directly related to the recruitment threshold. From the Henneman size principle it follows that the characteristics of the firing rates are also related to the size of the soma. The "firing rate spectrum" presents a beautifully simple control scheme in which, at any given time or force, the firing rate value of earlier-recruited motor units is greater than that of later-recruited motor units. This hierarchical control scheme describes a mechanism that provides an effective economy of force generation for the earlier-recruited lower force-twitch motor units, and reduces the fatigue of later-recruited higher force-twitch motor units-both characteristics being well suited for generating and sustaining force during the fight-or-flight response.

Hierarchical control of motor units in voluntary contractions

PubMed Central

Contessa, Paola

2012-01-01

For the past five decades there has been wide acceptance of a relationship between the firing rate of motor units and the afterhyperpolarization of motoneurons. It has been promulgated that the higher-threshold, larger-soma, motoneurons fire faster than the lower-threshold, smaller-soma, motor units. This relationship was based on studies on anesthetized cats with electrically stimulated motoneurons. We questioned its applicability to motor unit control during voluntary contractions in humans. We found that during linearly force-increasing contractions, firing rates increased as exponential functions. At any time and force level, including at recruitment, the firing rate values were inversely related to the recruitment threshold of the motor unit. The time constants of the exponential functions were directly related to the recruitment threshold. From the Henneman size principle it follows that the characteristics of the firing rates are also related to the size of the soma. The “firing rate spectrum” presents a beautifully simple control scheme in which, at any given time or force, the firing rate value of earlier-recruited motor units is greater than that of later-recruited motor units. This hierarchical control scheme describes a mechanism that provides an effective economy of force generation for the earlier-recruited lower force-twitch motor units, and reduces the fatigue of later-recruited higher force-twitch motor units—both characteristics being well suited for generating and sustaining force during the fight-or-flight response. PMID:21975447

Comparing the risk of work-related injuries between immigrants to Canada and Canadian-born labour market participants.

PubMed

Smith, P M; Mustard, C A

2009-06-01

To examine the burden of work-related injuries among immigrants to Canada compared to Canadian-born labour force participants. Using data from the 2003 and 2005 Canadian Community Health Surveys (n = 99,115), two nationally representative population samples, we examined the risk of self-reported, activity limiting work-related injuries among immigrants with varying time periods since arrival in Canada. Models were adjusted for hours of work in the last 12 months as well as various demographic and work-related variables. Immigrant men in their first 5 years in Canada reported lower rates of activity limiting injuries compared to Canadian-born respondents. Surprisingly, the percentage of injuries that required medical attention was much higher among recent immigrants compared to Canadian-born respondents, resulting in an increased risk of activity limiting injuries requiring medical attention among immigrant men compared to Canadian-born labour force participants. No excess risk was found among female immigrants compared to Canadian-born female labour market participants. Immigrant men in their first 5 years in Canada are at increased risk of work-related injuries that require medical attention. A similar risk is not present among immigrant women. Further, given differences in the number of activity limiting injuries requiring medical attention across immigrant groups, we believe this excess risk among immigrant men may be underestimated in the current data source. Future research should attempt to fully capture the barriers faced by immigrants in obtaining safe employment, the number of injuries that are sustained by immigrants while working, and the consequences of these injuries.

Configurational forces in electronic structure calculations using Kohn-Sham density functional theory

NASA Astrophysics Data System (ADS)

Motamarri, Phani; Gavini, Vikram

2018-04-01

We derive the expressions for configurational forces in Kohn-Sham density functional theory, which correspond to the generalized variational force computed as the derivative of the Kohn-Sham energy functional with respect to the position of a material point x . These configurational forces that result from the inner variations of the Kohn-Sham energy functional provide a unified framework to compute atomic forces as well as stress tensor for geometry optimization. Importantly, owing to the variational nature of the formulation, these configurational forces inherently account for the Pulay corrections. The formulation presented in this work treats both pseudopotential and all-electron calculations in a single framework, and employs a local variational real-space formulation of Kohn-Sham density functional theory (DFT) expressed in terms of the nonorthogonal wave functions that is amenable to reduced-order scaling techniques. We demonstrate the accuracy and performance of the proposed configurational force approach on benchmark all-electron and pseudopotential calculations conducted using higher-order finite-element discretization. To this end, we examine the rates of convergence of the finite-element discretization in the computed forces and stresses for various materials systems, and, further, verify the accuracy from finite differencing the energy. Wherever applicable, we also compare the forces and stresses with those obtained from Kohn-Sham DFT calculations employing plane-wave basis (pseudopotential calculations) and Gaussian basis (all-electron calculations). Finally, we verify the accuracy of the forces on large materials systems involving a metallic aluminum nanocluster containing 666 atoms and an alkane chain containing 902 atoms, where the Kohn-Sham electronic ground state is computed using a reduced-order scaling subspace projection technique [P. Motamarri and V. Gavini, Phys. Rev. B 90, 115127 (2014), 10.1103/PhysRevB.90.115127].

Receiving treatment, labor force activity, and work performance among people with psychiatric disorders: results from a population survey.

PubMed

Waghorn, Geoffrey; Chant, David

2011-12-01

Standard treatments for psychiatric disorders such as schizophrenia, depression and anxiety disorders are generally expected to benefit individuals, employers, and the wider community through improvements in work-functioning and productivity. We repeated a previous secondary investigation of receiving treatment, labor force activity and self-reported work performance among people with ICD-10 psychiatric disorders, in comparison to people with other types of health conditions. Data were collected by the Australian Bureau of Statistics in 2003 repeating a survey administered in 1998 using representative multistage sampling strategies. The 2003 household probability sample consisted of 36,241 working age individuals. Consistent with the previous secondary investigation based on the 1998 survey administration, receiving treatment was consistently associated with non-participation in the labor force, and was negatively associated with work performance. At a population level, receiving treatment was negatively associated with labor force activity and work performance. The stability of these results in two independent surveys highlights the need to investigate the longitudinal relationships between evidence-based treatments for psychiatric conditions as applied in real-world settings, and labor force participation and work performance outcomes.

Analysis of automobile engine cylinder pressure and rotation speed from engine body vibration signal

NASA Astrophysics Data System (ADS)

Wang, Yuhua; Cheng, Xiang; Tan, Haishu

2016-01-01

In order to improve the engine vibration signal process method for the engine cylinder pressure and engine revolution speed measurement instrument, the engine cylinder pressure varying with the engine working cycle process has been regarded as the main exciting force for the engine block forced vibration. The forced vibration caused by the engine cylinder pressure presents as a low frequency waveform which varies with the cylinder pressure synchronously and steadily in time domain and presents as low frequency high energy discrete humorous spectrum lines in frequency domain. The engine cylinder pressure and the rotation speed can been extract form the measured engine block vibration signal by low-pass filtering analysis in time domain or by FFT analysis in frequency domain, the low-pass filtering analysis in time domain is not only suitable for the engine in uniform revolution condition but also suitable for the engine in uneven revolution condition. That provides a practical and convenient way to design motor revolution rate and cylinder pressure measurement instrument.

Improving Robotic Assembly of Planar High Energy Density Targets

NASA Astrophysics Data System (ADS)

Dudt, D.; Carlson, L.; Alexander, N.; Boehm, K.

2016-10-01

Increased quantities of planar assemblies for high energy density targets are needed with higher shot rates being implemented at facilities such as the National Ignition Facility and the Matter in Extreme Conditions station of the Linac Coherent Light Source. To meet this growing demand, robotics are used to reduce assembly time. This project studies how machine vision and force feedback systems can be used to improve the quantity and quality of planar target assemblies. Vision-guided robotics can identify and locate parts, reducing laborious manual loading of parts into precision pallets and associated teaching of locations. On-board automated inspection can measure part pickup offsets to correct part drop-off placement into target assemblies. Force feedback systems can detect pickup locations and apply consistent force to produce more uniform glue bond thickness, thus improving the performance of the targets. System designs and performance evaluations will be presented. Work supported in part by the US DOE under the Science Undergraduate Laboratory Internships Program (SULI) and ICF Target Fabrication DE-NA0001808.

Simulating the dynamics of the mechanochemical cycle of myosin-V

PubMed Central

Mukherjee, Shayantani; Alhadeff, Raphael; Warshel, Arieh

2017-01-01

The detailed dynamics of the cycle of myosin-V are explored by simulation approaches, examining the nature of the energy-driven motion. Our study started with Langevin dynamics (LD) simulations on a very coarse landscape with a single rate-limiting barrier and reproduced the stall force and the hand-over-hand dynamics. We then considered a more realistic landscape and used time-dependent Monte Carlo (MC) simulations that allowed trajectories long enough to reproduce the force/velocity characteristic sigmoidal correlation, while also reproducing the hand-over-hand motion. Overall, our study indicated that the notion of a downhill lever-up to lever-down process (popularly known as the powerstroke mechanism) is the result of the energetics of the complete myosin-V cycle and is not the source of directional motion or force generation on its own. The present work further emphasizes the need to use well-defined energy landscapes in studying molecular motors in general and myosin in particular. PMID:28193897

Force and work to shear green southern pine logs at slow speed

Treesearch

Peter Koch

1971-01-01

When logs of three diameter classes and two specific gravity classes were sheared with a 3/8-inch-thick knife travelling at 2 inches per minute, shearing force and work averaged greatest for dense 13.6-inch logs cut with a knife having a 45o sharpness angle (73,517 pounds; 49,838 foot-pounds). Force and work averaged at least 5.1-inch bolts of...

Chronic disease and labour force participation among older Australians.

PubMed

Schofield, Deborah J; Shrestha, Rupendra N; Passey, Megan E; Earnest, Arul; Fletcher, Susan L

2008-10-20

To examine the association between long-term health conditions and being out of the labour force among older Australians. Retrospective analysis of cross-sectional data from the Australian Bureau of Statistics 2003 Survey of Disability, Ageing and Carers for people aged 45-64 years. Rates of premature retirement associated with ill health; odds ratios of being out of the labour force associated with each long-term health condition and number of conditions; weighted population estimates; estimates of gross domestic product lost as a result. 9198 people surveyed were aged 45-64 years, 3010 of whom were not in the labour force. Of these, 1373 (45.6%) had retired because of a chronic health condition, most commonly a back problem (10.4%), or arthritis and related disorders (8.6%). When adjusted for age and sex, all conditions studied except diseases of the ear and mastoid process, other endocrine/nutritional and metabolic disorders, noise-induced deafness or hearing loss, and high cholesterol were significantly associated with being out of the labour force. Extrapolating from these results, an estimated 663 235 older Australians were not working because of ill health, reducing Australia's gross domestic product by around $14.7 billion per annum. Prevention of long-term health conditions may help older Australians remain in the labour force longer, thereby increasing revenue to fund health care for the ageing population.

Seven Important Labor Force Trends.

ERIC Educational Resources Information Center

Bailey, John A.

1982-01-01

Presents statistics on the changing human resources mix in the labor force, which vocational counselors should be aware of. Trends include higher percentages of women working, and older men and married men leaving the work force. One result is an increasing number of persons are able to retire earlier. (JAC)

Flight Evaluation of an Aircraft with Side and Center Stick Controllers and Rate-Limited Ailerons

NASA Technical Reports Server (NTRS)

Deppe, P. R.; Chalk, C. R.; Shafer, M. F.

1996-01-01

As part of an ongoing government and industry effort to study the flying qualities of aircraft with rate-limited control surface actuators, two studies were previously flown to examine an algorithm developed to reduce the tendency for pilot-induced oscillation when rate limiting occurs. This algorithm, when working properly, greatly improved the performance of the aircraft in the first study. In the second study, however, the algorithm did not initially offer as much improvement. The differences between the two studies caused concern. The study detailed in this paper was performed to determine whether the performance of the algorithm was affected by the characteristics of the cockpit controllers. Time delay and flight control system noise were also briefly evaluated. An in-flight simulator, the Calspan Learjet 25, was programmed with a low roll actuator rate limit, and the algorithm was programmed into the flight control system. Side- and center-stick controllers, force and position command signals, a rate-limited feel system, a low-frequency feel system, and a feel system damper were evaluated. The flight program consisted of four flights and 38 evaluations of test configurations. Performance of the algorithm was determined to be unaffected by using side- or center-stick controllers or force or position command signals. The rate-limited feel system performed as well as the rate-limiting algorithm but was disliked by the pilots. The low-frequency feel system and the feel system damper were ineffective. Time delay and noise were determined to degrade the performance of the algorithm.

What is the prevalence of and associations with forced labour experiences among male migrants from Dolakha, Nepal? Findings from a cross-sectional study of returnee migrants

PubMed Central

Mak, Joelle; Abramsky, Tanya; Sijapati, Bandita; Kiss, Ligia; Zimmerman, Cathy

2017-01-01

Objectives Growing numbers of people are migrating outside their country for work, and many experience precarious conditions, which have been linked to poor physical and mental health. While international dialogue on human trafficking, forced labour and slavery increases, prevalence data of such experiences remain limited. Methods Men from Dolakha, Nepal, who had ever migrated outside of Nepal for work were interviewed on their experiences, from predeparture to return (n=194). Forced labour was assessed among those who returned within the past 10 years (n=140) using the International Labour Organization's forced labour dimensions: (1) unfree recruitment; (2) work and life under duress; and (3) impossibility to leave employer. Forced labour is positive if any one of the dimensions is positive. Results Participants had worked in India (34%), Malaysia (34%) and the Gulf Cooperation Council countries (29%), working in factories (29%), as labourers/porters (15%) or in skilled employment (12%). Among more recent returnees (n=140), 44% experienced unfree recruitment, 71% work and life under duress and 14% impossibility to leave employer. Overall, 73% experienced forced labour during their most recent labour migration. Forced labour was more prevalent among those who had taken loans for their migration (PR 1.23) and slightly less prevalent among those who had migrated more than once (PR 0.87); however the proportion of those who experienced forced labour was still high (67%). Age, destination and duration of stay were associated with only certain dimensions of forced labour. Conclusion Forced labour experiences were common during recruitment and at destination. Migrant workers need better advice on assessing agencies and brokers, and on accessing services at destinations. As labour migration from Nepal is not likely to reduce in the near future, interventions and policies at both source and destinations need to better address the challenges migrants face so they can achieve safer outcomes. PMID:28801409

The mechanical forces in katydid sound production

NASA Astrophysics Data System (ADS)

Xiao, Huaping; Chiu, Cheng-Wei; Zhou, Yan; He, Xingliang; Epstein, Ben; Liang, Hong

2013-10-01

Katydids and crickets generate their characteristic calling sound by rubbing their wings together. The mechanisms of the rubbing force, however, have not been extensively studied. The change of mechanical force with external parameters (speed and applied load) in the stridulation process has not been reported. Our current study aims to investigate the mechanical forces of katydid stridulation. Four pairs of files and plectrums from a katydid, which are responsible for the katydid's sound production, were examined with a specially designed experimental configuration. Due to the asymmetric nature of the wing motion in their opening and closing, the contact between the plectrum and file resembles that of a ratchet. Multiple frequencies were generated during experimental wing rubbing so that a calling-like sound was produced. Results showed that the morphology of the plectrum/file contact has significant effects on mechanical forces induced on the wings and resulting sound production. The roles of the mechanical forces include sound generation, tone modification, and energy consumption. The findings in this work reveal the variation trend of mechanical force with sliding speed and applied load. The frequency and amplitude of the sound wave produced in tribo-test are close to those in natural condition. By mimicking the microstructure of the plectrum and file teeth, acoustic instruments with high mechanical energy conversion rate can be developed. Our results provide new approaches in the design and improvement of micro-machines for acoustic applications, as well as in hybrid robotic systems.

Biomechanical tolerance of whole lumbar spines in straightened posture subjected to axial acceleration.

PubMed

Stemper, Brian D; Chirvi, Sajal; Doan, Ninh; Baisden, Jamie L; Maiman, Dennis J; Curry, William H; Yoganandan, Narayan; Pintar, Frank A; Paskoff, Glenn; Shender, Barry S

2018-06-01

Quantification of biomechanical tolerance is necessary for injury prediction and protection of vehicular occupants. This study experimentally quantified lumbar spine axial tolerance during accelerative environments simulating a variety of military and civilian scenarios. Intact human lumbar spines (T12-L5) were dynamically loaded using a custom-built drop tower. Twenty-three specimens were tested at sub-failure and failure levels consisting of peak axial forces between 2.6 and 7.9 kN and corresponding peak accelerations between 7 and 57 g. Military aircraft ejection and helicopter crashes fall within these high axial acceleration ranges. Testing was stopped following injury detection. Both peak force and acceleration were significant (p < 0.0001) injury predictors. Injury probability curves using parametric survival analysis were created for peak acceleration and peak force. Fifty-percent probability of injury (95%CI) for force and acceleration were 4.5 (3.9-5.2 kN), and 16 (13-19 g). A majority of injuries affected the L1 spinal level. Peak axial forces and accelerations were greater for specimens that sustained multiple injuries or injuries at L2-L5 spinal levels. In general, force-based tolerance was consistent with previous shorter-segment lumbar spine testing (3-5 vertebrae), although studies incorporating isolated vertebral bodies reported higher tolerance attributable to a different injury mechanism involving structural failure of the cortical shell. This study identified novel outcomes with regard to injury patterns, wherein more violent exposures produced more injuries in the caudal lumbar spine. This caudal migration was likely attributable to increased injury tolerance at lower lumbar spinal levels and a faster inertial mass recruitment process for high rate load application. Published 2017. This article is a U.S. Government work and is in the public domain in the USA. J Orthop Res 36:1747-1756, 2018. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

The adhesion force of Notch with Delta and the rate of Notch signaling.

PubMed

Ahimou, Francois; Mok, Lee-Peng; Bardot, Boris; Wesley, Cedric

2004-12-20

Notch signaling is repeatedly used during animal development to specify cell fates. Using atomic force microscopy on live cells, chemical inhibitors, and conventional analyses, we show that the rate of Notch signaling is linked to the adhesion force between cells expressing Notch receptors and Delta ligand. Both the Notch extracellular and intracellular domains are required for the high adhesion force with Delta. This high adhesion force is lost within minutes, primarily due to the action of Presenilin on Notch. Reduced turnover or Delta pulling accelerate this loss. These data suggest that strong adhesion between Notch and Delta might serve as a booster for initiating Notch signaling at a high rate.

Estimation of longitudinal force, lateral vehicle speed and yaw rate for four-wheel independent driven electric vehicles

NASA Astrophysics Data System (ADS)

Chen, Te; Xu, Xing; Chen, Long; Jiang, Haobing; Cai, Yingfeng; Li, Yong

2018-02-01

Accurate estimation of longitudinal force, lateral vehicle speed and yaw rate is of great significance to torque allocation and stability control for four-wheel independent driven electric vehicle (4WID-EVs). A fusion method is proposed to estimate the longitudinal force, lateral vehicle speed and yaw rate for 4WID-EVs. The electric driving wheel model (EDWM) is introduced into the longitudinal force estimation, the longitudinal force observer (LFO) is designed firstly based on the adaptive high-order sliding mode observer (HSMO), and the convergence of LFO is analyzed and proved. Based on the estimated longitudinal force, an estimation strategy is then presented in which the strong tracking filter (STF) is used to estimate lateral vehicle speed and yaw rate simultaneously. Finally, co-simulation via Carsim and Matlab/Simulink is carried out to demonstrate the effectiveness of the proposed method. The performance of LFO in practice is verified by the experiment on chassis dynamometer bench.

Work/Family Interactions: Trends and Applications.

ERIC Educational Resources Information Center

Engelbrecht, JoAnn D.; Nies, Joyce I.

1988-01-01

The authors discuss five trends and how family life educators can address them. The trends are (1) women's labor force participation, (2) growth of the service sector, (3) recognition that work and family life affect each other, (4) space sharing by work and family life, and (5) aging of the work force. (CH)

A Report of the Child Labor Task Force.

ERIC Educational Resources Information Center

Oregon State Bureau of Labor and Industry, Portland.

A task force studied youth work and its impact on the health, education, and safety of 16- and 17-year-olds. The study covered such issues as the following: effects of work on school performance, work's physical and psychological effects on young people, the effects work can have on young people's preparation for lifelong work, and what steps can…

Work-Family Spillover and Daily Reports of Work and Family Stress in the Adult Labor Force.

ERIC Educational Resources Information Center

Grzywacz, Joseph G.; Almeida, David M.; McDonald, Daniel A.

2002-01-01

Data from two affiliated national surveys were used to examine distribution of work-family spillover among working adults. Analyses testing family life course hypotheses indicated self-reported negative and positive spillover between work and family were not randomly distributed within the labor force. Age was found to have a persistent…

A clinical investigation of force delivery systems for orthodontic space closure.

PubMed

Nightingale, C; Jones, S P

2003-09-01

To investigate the force retention, and rates of space closure achieved by elastomeric chain and nickel titanium coil springs. Randomized clinical trial. Eastman Dental Hospital, London and Queen Mary's University Hospital, Roehampton, 1998-2000. Twenty-two orthodontic patients, wearing the pre-adjusted edgewise appliance undergoing space closure in opposing quadrants, using sliding mechanics on 0.019 x 0.025-inch posted stainless steel archwires. Medium-spaced elastomeric chain [Durachain, OrthoCare (UK) Ltd., Bradford, UK] and 9-mm nickel titanium coil springs [OrthoCare (UK) Ltd.] were placed in opposing quadrants for 15 patients. Elastomeric chain only was used in a further seven patients. The initial forces on placement and residual forces at the subsequent visit were measured with a dial push-pull gauge [Orthocare (UK) Ltd]. Study models of eight patients were taken before and after space closure, from which measurements were made to establish mean space closure. The forces were measured in grammes and space closure in millimetres. Fifty-nine per cent (31/53) of the elastomeric sample maintained at least 50 per cent of the initial force over a time period of 1-15 weeks. No sample lost all its force, and the mean loss was 47 per cent (range: 0-76 per cent). Nickel titanium coil springs lost force rapidly over 6 weeks, following that force levels plateaued. Forty-six per cent (12/26) maintained at least 50 per cent of their initial force over a time period of 1-22 weeks, and mean force loss was 48 per cent (range: 12-68 per cent). The rate of mean weekly space closure for elastomeric chain was 0.21 mm and for nickel titanium coil springs 0.26 mm. There was no relationship between the initial force applied and rate of space closure. None of the sample failed during the study period giving a 100 per cent response rate. In clinical use, the force retention of elastomeric chain was better than previously concluded. High initial forces resulted in high force decay. Nickel titanium coil springs and elastomeric chain closed spaces at a similar rate.