A Multiscale Inelastic Internal State Variable Corrosion Model

We present a corrosion internal state variable (ISV) damage model based upon the integrated computational materials engineering (ICME) hierarchical multiscale paradigm. Structure-property experiments for magnesium alloys were used where the only inputs were the volume fractions of each element of the periodic table. This macroscale ISV corrosion model finds its basis in Horstemeyer's mechanical damage model, which includes three separate ISVs for damage nucleation, growth, and coalescence, as well as Walton's inclusion of corrosion, which introduces five new ISVs for pit nucleation, growth, and coalescence, along with general corrosion and intergranular corrosion. While Walton's corrosion ISVs are phenomenological in nature, herein we develop a multiscale physical basis for the corrosion ISVs. The parameters for the macroscale corrosion ISVs were garnered from the mesoscale Butler-Volmer equations. Pure magnesium with differing amounts of aluminum were used in corrosion tests to exemplify the different pitting, general corrosion, and intergranular corrosion rates, and the macroscale ISV model was calibrated with said data, in which the only inputs to the model are the volume percentages of the elements magnesium and aluminum. Although magnesium alloys were used to motivate and calibrate the model, the model is abstract enough to possibly capture other material systems as well.

Is grip strength a good marker of physical performance among community-dwelling older people?

INTRODUCTION

There is increasing interest in physical performance as it relates to both the current and future health of older people. It is often characterised using the Short Physical Performance Battery including assessment of gait speed, chair rises and standing balance. However this battery of tests may not be feasible in all clinical settings and simpler measures may be required. As muscle strength is central to physical performance, we explored whether grip strength could be used as a marker of the Short Physical Performance Battery.

OBJECTIVE

To examine associations between grip strength and components of the Short Physical Performance Battery in older community dwelling men and women.

METHODS

Grip strength measurement and the Short Physical Performance Battery were completed in 349 men and 280 women aged 63-73 years taking part in the Hertfordshire Cohort Study (HCS). Relationships between grip strength and physical performance (6m timed-up-and-go [TUG], 3m walk, chair rises and standing balance times) were analysed using linear and logistic regression, without and with adjustment for age, anthropometry, lifestyle factors and co-morbidities.

RESULTS

Among men, a kilo increase in grip strength was associated with a 0.07s (second) decrease in 6m TUG, a 0.02s decrease in 3m walk time, and a 1% decrease in chair rises time (p<0.001 for all). Among women, a kilo increase in grip strength was associated with a 0.13s decrease in 6m TUG, a 0.03s decrease in 3m walk time, and a 1% decrease in chair rises time (p<0.001). Higher grip strength was associated with better balance among men (p=0.01) but not women (p=0.57). Adjustment for age, anthropometry, lifestyle and co-morbidities did not alter these results.

CONCLUSIONS

Grip strength is a good marker of physical performance in this age group and may be more feasible than completing a short physical performance battery in some clinical settings.

Developmental influences, muscle morphology, and sarcopenia in community-dwelling older men

BACKGROUND

Sarcopenia is associated with disability, morbidity, and mortality. Lower birth weight is associated with reduced muscle mass and strength in older people, suggesting that developmental influences are important in sarcopenia. However, underlying mechanisms are unknown. Our objective was to determine whether low birth weight is associated with altered skeletal muscle morphology in older men.

METHODS

Ninety-nine men with historical records of birth weight (≤3.18 kg and ≥3.63 kg), aged 68-76 years, consented for detailed characterization of muscle, including a biopsy of the vastus lateralis. Tissue was processed for immunohistochemical studies and analyzed to determine myofibre density, area, and score.

RESULTS

Muscle fibre score (fibres kilograms per square millimeter) was significantly reduced in those with lower birth weight: 1.5 × 10(3) vs 1.7 × 10(3), p = .04 unadjusted; p = .09 adjusted for age, height, and physical activity. In addition, there was a trend for reduced myofibre density (fibres per square millimeter) in those with lower birth weight: total fibre density: 176 vs 184, type I myofibre density: 77 vs 80, and type II myofibre density: 99 vs 105. Types I and II myofibre areas (square micrometers) were larger in those with lower birth weight: type I: 4903 vs 4643 and type II: 4046 vs 3859. However, none of these differences were statistically significant.

CONCLUSIONS

This is the first study showing that lower birth weight is associated with a significant decrease in muscle fibre score, suggesting that developmental influences on muscle morphology may explain the widely reported associations between lower birth weight and sarcopenia. However, the study may have been underpowered and did not include women supporting replication in larger cohorts of older men and women.

The feasibility and acceptability of muscle biopsy in epidemiological studies: findings from the Hertfordshire Sarcopenia Study (HSS)

BACKGROUND

Sarcopenia, the loss of muscle mass and strength, is associated adversely with disability, morbidity and mortality. Epidemiological findings suggest influences operating across the life course may be important. Our aim was to ascertain the feasibility and acceptability of obtaining muscle tissue from healthy older people in order to ultimately identify cellular mechanisms underlying life course influences on sarcopenia.

METHODS

105 men with documented birth weight consented to detailed assessment of muscle mass and strength, and a biopsy of the vastus lateralis using the Weil-Blakesley conchotome. Acceptability was ascertained by questionnaire and a 100 mm pain Visual Analogue Scale (VAS). 100 mm indicated severe pain.

RESULTS

Muscle biopsy was successfully carried out in 102 out of 105 participants, mean yield 107 mg (range 20-290 mg). There were no serious wound complications. Ninety-three participants completed feedback questionnaires. The median pain VAS score during the procedure was 7 mm (Interquartile range [IQR] 1-34), 4 mm (IQR 0-16) one day after the procedure and 1mm (IQR 0-4) 7 days after the procedure. 60 (65%) participants were back to their normal levels of activity one day after the procedure. 85 (91%) found this procedure acceptable and would have the procedure again.

CONCLUSION

Muscle biopsy using a Weil-Blakesley conchotome is both feasible and acceptable in community dwelling older men participating in epidemiological research. The excellent yield of biopsy tissue will allow morphological and molecular studies of muscle to be integrated into an epidemiological study facilitating investigation of the mechanisms underpinning sarcopenia that could potentially be altered by life course influences.

Bone health and deterioration in quality of life among participants from the Hertfordshire cohort study

We utilised the Hertfordshire cohort study to examine relationships between bone density at baseline and SF-36 status 4 years later. We found deterioration in the mental health domain over follow-up in osteoporotic men (but not women) compared with other groups (relative rate ratio=5.78, 95% confidence interval (CI) 1.78-19.2).

INTRODUCTION

Osteoporosis is associated with decreased quality of life, although it has been difficult to evaluate the confounding effects of fracture and co-morbidity. Having previously shown that male osteoporotics have poorer health than counterparts with normal bone mineral density, even after adjustment for co-morbidity and prior fracture, we assessed quality of life in both groups 4 years apart.

METHODS

Four hundred and ninety-eight men and 468 women completed questionnaires detailing lifestyle factors, co-morbidities and quality of life (SF-36) before undergoing bone density measurements at the lumbar spine and total femur. At follow-up 4 years later, 322 men and 320 women were reassessed.

RESULTS

Multinomial logistic regression confirmed deterioration in mental health over follow-up in osteoporotic men compared with other groups (relative rate ratio=5.78, 95% CI 1.78-19.2). These patterns were not apparent among women.

CONCLUSIONS

Men with lower bone density at baseline had poorer quality of life some 4 years later, even after adjustment for co-morbidity and fracture. This may reflect secondary osteoporosis in men (due to alcohol or hypogonadism).

A Revised Measure of Approval Motivation and Its Relationship to Social Desirability

Existing measures of approval motivation attempt to assess this dimension of personality indirectly through evaluation of socially desirable response tendencies. The Martin-Larsen Approval Motivation (MLAM) Scale takes a more direct approach by focusing on individual differences in need for social approval. Since the original version of the MLAM scale is subject to acquiescence response bias, fully balanced and partially balanced scales were created to minimize this response style. Results indicated that the revised measures arc equivalent to the original version and that balancing affects the magnitude but not the pattern of correlates with other scales. Comparisons with the Marlowe-Crowne Social Desirability (MCSD) Scale revealed a divergent pattern of correlates with several measures of personality suggesting a basic difference between the MLAM and MCSD in their conceptualization of approval motivation.

On the Two-Dimensional Nature of the Marlowe-Crowne Social Desirability Scale

Ramanaiah, Schill, and Leung (1977) reported empirical evidence supporting Millham's (1974) hypothesis that attribution and denial are two separate components of the MC-SD scale. This paper presents the results of two studies conducted to test the hypothesis that the results obtained by Ramanaiah et al. (1977) may be attributed to method variance caused by the keying direction in the MC-SD attribution and denial subscales. The first study was concerned with the development of balanced attribution and denial scales, while the second study investigated whether the results from Ramanaiah et al., which used the original unbalanced attribution and denial scales, could be replicated with the balanced scales developed in Study I. The results strongly supported the tested hypothesis, indicating that the two subscales are measuring essentially the same construct.

The effects of aerobic exercise on metabolic risk, insulin sensitivity and intrahepatic lipid in healthy older people from the Hertfordshire Cohort Study: a randomised controlled trial

AIMS/HYPOTHESIS

We sought to determine the effect of an aerobic exercise intervention on clustered metabolic risk and related outcomes in healthy older adults in a single-centre, explanatory randomised controlled trial.

METHODS

Participants from the Hertfordshire Cohort Study (born 1931-1939) were randomly assigned to 36 supervised 1 h sessions on a cycle ergometer over 12 weeks or to a non-intervention control group. Randomisation and group allocation were conducted by the study co-ordinator, using a software programme. Those with prevalent diabetes, unstable ischaemic heart disease or poor mobility were excluded. All data were collected at our clinical research facility in Cambridge. Components of the metabolic syndrome were used to derive a standardised composite metabolic risk score (zMS) as the primary outcome. Trial status: closed to follow-up.

RESULTS

We randomised 100 participants (50 to the intervention, 50 to the control group). Mean age was 71.4 (range 67.4-76.3) years. Overall, 96% of participants attended for follow-up measures. There were no serious adverse events. Using an intention-to-treat analysis, we saw a non-significant reduction in zMS in the exercise group compared with controls (0.07 [95% CI -0.03, 0.17], p = 0.19). However, the exercise group had significantly decreased weight, waist circumference and intrahepatic lipid, with increased aerobic fitness and a 68% reduction in prevalence of abnormal glucose metabolism (OR 0.32 [95% CI 0.11-0.92], p = 0.035) compared with controls. Results were similar in per-protocol analyses.

CONCLUSIONS/INTERPRETATION

Enrolment in a supervised aerobic exercise intervention led to weight loss, increased fitness and improvements in some but not all metabolic outcomes. In appropriately screened older individuals, such interventions appear to be safe.

TRIAL REGISTRATION

Controlled-trials.com ISRCTN60986572

FUNDING

Medical Research Council.

Grip strength and cardiovascular drug use in older people: findings from the Hertfordshire Cohort Study

BACKGROUND

reduced grip strength is associated with adverse health consequences, and there is interest in identifying modifiable influences. Cardiovascular drugs are commonly used by older people, but their effect on muscle strength is unclear.

METHODS

we investigated associations between cardiovascular drug use and grip strength among 1,572 men and 1,415 women, aged 59-73, who participated in the Hertfordshire Cohort Study.

RESULTS

Forty-five percent of participants were taking a cardiovascular drug. Furosemide was associated with average decreases in grip strength of 3.15 kg (95% confidence interval [CI] 0.90, 5.39, P < 0.01) among men and 2.35 kg (95% CI 0.93, 3.77, P < 0.01) among women after adjustment for age and height. Corresponding differences for nitrates were 1.84 kg (95% CI 0.29, 3.39, P = 0.02) among men and 3.66 kg (95% CI 1.99, 5.33, P < 0.01) among women. Calcium channel blockers and fibrates were associated with reduced grip among women. Statins were not associated with grip. The associations between grip strength and nitrate use in men and nitrate and fibrate use in women were robust to additional adjustment for co-morbidity.

CONCLUSIONS

use of some cardiovascular drugs is associated with reduced grip strength in older people. These findings have potential implications for the functional ability of older people treated with these drugs.

The SF-36: a simple, effective measure of mobility-disability for epidemiological studies

BACKGROUND

Mobility disability is a major problem in older people. Numerous scales exist for the measurement of disability but often these do not permit comparisons between study groups. The physical functioning (PF) domain of the established and widely used Short Form-36 (SF-36) questionnaire asks about limitations on ten mobility activities.

OBJECTIVES

To describe prevalence of mobility disability in an elderly population, investigate the validity of the SF-36 PF score as a measure of mobility disability, and to establish age and sex specific norms for the PF score.

METHODS

We explored relationships between the SF-36 PF score and objectively measured physical performance variables among 349 men and 280 women, 59-72 years of age, who participated in the Hertfordshire Cohort Study (HCS). Normative data were derived from the Health Survey for England (HSE) 1996.

RESULTS

32% of men and 46% of women had at least some limitation in PF scale items. Poor SF-36 PF scores (lowest fifth of the gender-specific distribution) were related to: lower grip strength; longer timed-up-and-go, 3m walk, and chair rises test times in men and women; and lower quadriceps peak torque in women but not men. HSE normative data showed that median PF scores declined with increasing age in men and women.

CONCLUSION

Our results are consistent with the SF-36 PF score being a valid measure of mobility disability in epidemiological studies. This approach might be a first step towards enabling simple comparisons of prevalence of mobility disability between different studies of older people. The SF-36 PF score could usefully complement existing detailed schemes for classification of disability and it now requires validation against them.

Physical performance and physical activity in older people: are developmental influences important?

BACKGROUND

Reduced physical performance and physical activity have serious health consequences, but adult determinants do not fully explain variation in older people.

OBJECTIVE

Our objective was to investigate the relationship between early growth, physical performance and physical activity in older people.

METHODS

We studied 349 men and 280 women born 1931-1939 with known birth weight and weight at 1 year who were taking part in the Hertfordshire Cohort Study, UK. Physical performance was measured (3-m walk, chair rises and standing balance) and physical activity was assessed by questionnaire and converted to estimated energy expenditure.

RESULTS

Poor balance was associated with lower birth weight (odds ratio [OR] for poor balance per standard deviation [SD] increase in birth weight = 0.68, p=0.01) and weight at 1 year (OR for poor balance per SD increase in weight at 1 year=0.67, p=0.03) after adjustment for age and current size in men, but not in women. There were no significant positive relationships between early size and growth and the other measures of physical performance or physical activity in men or women.

CONCLUSION

Current lifestyle factors, particularly those affecting adult weight, may be more important than developmental influences on most measures of physical performance and physical activity in older people.

Cigarette smoking, birthweight and osteoporosis in adulthood: results from the hertfordshire cohort study

We looked for interaction between early environment and adult lifestyle in determination of bone mineral content (BMC) and bone mineral density (BMD) among 498 men and 468 women for whom birth records were available. Participants completed a health questionnaire, and bone densitometry (DXA) of the lumbar spine and femoral neck performed.We found no relationships between cigarette and alcohol consumption, physical activity and either BMC or BMD after adjustment for age, body mass index, dietary calcium, social class, HRT use and years since menopause. However, male current smokers in the lowest third of birth weight had lower femoral neck BMD than ex- or never smokers from the lowest birth weight third (p value for interaction term = 0.04). Similar trends were seen with femoral neck BMC and lumber spine BMC.Individuals of lower birth weight may be particularly vulnerable to the effects of bone noxious stimuli such as cigarette smoking.

Grip strength and the metabolic syndrome: findings from the Hertfordshire Cohort Study

INTRODUCTION

Sarcopenia, the loss of muscle mass and strength with age, is significantly associated with type 2 diabetes in older people.

AIM

To determine whether there is a relationship between grip strength and features of the metabolic syndrome.

DESIGN

Cross-sectional study.

METHODS

Data were collected on grip strength, fasting glucose, triglycerides and HDL cholesterol, blood pressure, waist circumference and 2 h glucose after an oral glucose tolerance test, in a population-based sample of 2677 men and women aged 59-73 years.

RESULTS

In men and women combined, a standard deviation (SD) decrease in grip strength was significantly associated with higher: fasting triglycerides (0.05 SD unit increase, 95%CI 0.02-0.09, p = 0.006); blood pressure (OR 1.13, 95%CI 1.04-1.24, p = 0.004); waist circumference (0.08 SD unit increase, 95%CI 0.06-0.10, p < 0.001); 2 h glucose (0.07 SD unit increase, 95%CI 0.03-0.11, p = 0.001) and HOMA resistance (0.05 SD unit increase, 95%CI 0.01-0.09, p = 0.008), after adjustment for gender, weight, age, walking speed, social class, smoking habit and alcohol intake. Lower grip strength was also significantly associated with increased odds of having the metabolic syndrome according to both the ATPIII (OR 1.18, 95%CI 1.07-1.30, p < 0.001) and IDF definitions (OR 1.11, 95%CI 1.01-1.22, p = 0.03).

DISCUSSION

Our findings suggest that impaired grip strength is associated with the individual features, as well as with the overall summary definitions, of the metabolic syndrome. The potential for grip strength to be used in the clinical setting needs to be explored.

Size at birth and its relation to muscle strength in young adult women

OBJECTIVE

To assess the relationship between development in utero, assessed by birth weight, and muscle strength in young adult women as assessed by grip strength.

METHODS

A total of 1563 participants aged 20-40 years in the Southampton Women's Survey had their grip strength measured during pregnancy. At recruitment to the survey the women had been asked to recall their birth weight or obtain it from their parents. For 536 women born in Southampton, birth weight was obtained from hospital records. Grip strength was related to birth weight using multiple linear regression analysis, adjusting for age, height, weight and reported physical activity.

RESULTS

Grip strength increased with age, height, weight, physical activity and birth weight. In the mutually-adjusted model, grip strength increased by 1.10 kg per kilogram of birth weight (95% CI: 0.58-1.61 kg). In women with hospital birth weight data the relationship strengthened to 1.44 kg per kilogram of birth weight (95% CI: 0.50-2.38 kg).

CONCLUSIONS

Grip strength in women in their twenties and thirties is at or approaching its peak. The association between grip strength and birth weight was remarkably similar to findings from other studies of women at younger and older ages. This indicates that in utero development has consequences for muscle strength throughout the life course, even allowing for the increase to peak muscle strength and then its decline as a woman ages.

Lipid profile, obesity and bone mineral density: the Hertfordshire Cohort Study

BACKGROUND

Body mass index (BMI) and bone mineral density (BMD) are positively correlated in several studies, but few data relate bone density, lipid profile and anthropometric measures.

AIM

To investigate these relationships in a large, well-characterized cohort of men and women (The Hertfordshire Cohort Study).

METHODS

Men (n = 465) and women (n = 448) from Hertfordshire, UK were recruited. Information was available on demographic and lifestyle factors, anthropometric measurements, body fat percentage, fasting triglycerides, cholesterol (total, HDL, LDL), apolipoprotein (a) and apolipoprotein (b); bone mineral density (BMD) was recorded at the lumbar spine and total femur.

RESULTS

BMD at the lumbar spine (males r = 0.15, p = 0.001; females r = 0.14, p = 0.003) and total femoral region (males r = 0.18, p = 0.0001; females r = 0.16, p = 0.0008) was related to serum triglyceride level, even after adjustment for waist-hip ratio, age, social class and lifestyle factors, but not if body fat percentage was substituted for waist-hip ratio in the regression model. Fasting HDL cholesterol level was related to lumbar spine BMD in women (r = -0.15, p = 0.001) and total femoral BMD in both sexes (males r = -0.15, p = 0.002; females r = -0.23, p < 0.0001); these relationships were also attenuated by adjustment for body fat percentage but not waist-hip ratio. No relationships were seen between total or LDL cholesterol with BMD.

DISCUSSION

In this cohort, relationships between lipid profile and BMD were robust to adjustment for one measure of central obesity (waist-hip ratio), but not total body fat. This broadly supports the idea that adiposity may confound the relationship between lipids and bone mass.

Is hand-held dynamometry useful for the measurement of quadriceps strength in older people? A comparison with the gold standard Bodex dynamometry

BACKGROUND

The lower limb muscle strength is an important determinant of physical function in older people. However, measurement in clinical and epidemiological settings has been limited because of the requirement for large-scale equipment. A protocol using a novel, versatile hand-held dynamometer (HHD) has been developed to measure the quadriceps strength in a supine position.

OBJECTIVE

The objective of this study was to assess the validity of this new methodology for measuring the lower limb muscle strength compared to the gold standard Biodex dynamometer.

METHODS

The supine quadriceps strength was measured twice with each of the Biodex and the HHD in 20 men and women, aged 61-81 years, on their non-dominant leg. The agreement between the peak torques obtained by Biodex and HHD was analyzed.

RESULTS

The mean peak Biodex and HHD results were 83.4 +/- (SD) 28.0 Nm and 68.9 +/- 19.6 Nm, respectively. The HHD undermeasured the quadriceps strength by an average of 14.5 Nm (95% CI 8.5, 20.6) compared to the Biodex, and this effect was most marked in the strongest participants. Nevertheless, there was a good correlation between the measures (r = 0.91, p < 0.0001). Classification of individuals into tertiles of muscle strength showed good agreement between the two methods (Kappa = 0.69, p < 0.0001).

CONCLUSIONS

Our findings suggest that the HHD using a supine positioning offers a feasible, inexpensive, and portable test of quadriceps muscle strength for use in healthy older people. It underestimates the absolute quadriceps strength compared to the Biodex particularly in stronger people, but is a useful tool for ranking muscle strength of older people in epidemiological studies. It may also be of value for quick and objective assessment of physical function in the clinical setting.

Efficient proline-catalyzed Michael additions of unmodified ketones to nitro olefins

[reaction: see text] Here we describe the proline-catalyzed Michael addition of unmodified ketones to nitro olefins. This novel reaction provides gamma-nitro ketones in modest enantioselectivity yet excellent yields.