Methods and variables in Electrical discharge machining of titanium alloy - A review

Titanium alloys are difficult to machine using conventional methods, therefore, nonconventional processes are often chosen in many applications. Electrical discharge machining (EDM) is one of those nonconventional processes that is used frequently for shaping titanium alloys with their respective pros and cons. However, a good understanding of this process is very difficult to achieve as research results are not properly connected and presented. Therefore, this study investigates different types of EDM processes such as, wire EDM, die-sink EDM, EDM drill and hybrid EDM used to machine titanium alloys. Machining mechanism, tool electrode, dielectric, materials removal rate (MRR), and surface integrity of all these processes are critically analysed and correlated based on the evidence accessible in literature. Machining process suffer from lower material removal rate and high tool wear while applied on titanium alloys. Formation of recast layer, heat affected zone and tool wear is common in all types of EDM processes. Additional challenge in wire EDM of titanium alloys is wire breakage under severe machining conditions. The formation of TiC and TiO₂ are noticed in recast layer depending on the type of dielectrics. Removal of debris from small holes during EDM drilling is a challenge. All these restricts the applications EDMed titanium alloys in high-tech applications such as, aerospace and biomedical areas. Most of these challenges come up due to extraordinary properties such as, low thermal conductivity, high melting point and high hardness, of titanium alloys. Though hybrid EDM has been introduced and there is some work on simulation of EDM process, further developments in EDM of this alloy is required for widening the application of this methods.

Thermal quenching sample chamber for grazing incidence small angle x-ray scattering studies of polymer films

The second generation of a sample chamber designed for in situ measurement of temperature- and time-dependent polymer film nanostructure using the method of grazing incidence small angle x-ray scattering is presented. An increased operating temperature limit (from 260 to 400 degrees C) with precise control (+/-0.1 degrees C) at fixed temperatures as well as a fourfold increase in maximum instantaneous cooling rate (up to 73 degrees C/s) relative to the first generation chamber [M. N. Groves et al, J. Appl. Crystallogr. 39, 120 (2006)] are reported. Thermal quenches from 220 to 90 degrees C are shown to be reproducible to within +/-1 degrees C of the final temperature. Experimental tests on spin-coated films of symmetric diblock styrene-butadiene copolymer demonstrate the ability to resolve the kinetics of orientation of lamellar domains parallel to the silicon substrate, distinct from the initial formation of randomly oriented lamellar domains immediately following the thermal quench.

The efficacy of exercise as a long-term antidepressant in elderly subjects: a randomized, controlled trial

BACKGROUND

Pharmacological treatment of depression in geriatric patients is often difficult. Although unsupervised exercise has been shown to benefit younger depressed patients, there is no evidence that unsupervised exercise can be used as a maintenance treatment for depression in elderly patients. Our aim was to test the feasibility and efficacy of unsupervised exercise as a long-term treatment for clinical depression in elderly patients.

METHODS

We studied 32 subjects (71.3 +/- 1.2 years of age, mean +/- SE) in a 20-week, randomized, controlled trial, with follow-up at 26 months. Subjects were community-dwelling patients with major or minor depression or dysthymia. Exercisers engaged in 10 weeks of supervised weight-lifting exercise followed by 10 weeks of unsupervised exercise. Controls attended lectures for 10 weeks. No contact was made with either group after 20 weeks until final follow-up. Blinded assessment was made with the Beck Depression Inventory (BDI), the Philadelphia Geriatric Morale Scale, and Ewart's Self Efficacy Scale at 20 weeks and with the BDI and physical activity questionnaire at 26 months.

RESULTS

Patients randomized to the exercise condition completed 18 +/- 2 sessions of unsupervised exercise during Weeks 10 to 20. The BDI was significantly reduced at both 20 weeks and 26 months of follow-up in exercisers compared with controls (p <.05-.001). At the 26-month follow-up, 33% of the exercisers were still regularly weight lifting, versus 0% of controls (p <.05).

CONCLUSIONS

Unsupervised weight-lifting exercise maintains its antidepressant effectiveness at 20 weeks in depressed elderly patients. Long-term changes in exercise behavior are possible in some patients even without supervision.

Randomized trial of progressive resistance training to counteract the myopathy of chronic heart failure

Chronic heart failure (CHF) is characterized by a skeletal muscle myopathy not optimally addressed by current treatment paradigms or aerobic exercise. Sixteen older women with CHF were compared with 80 age-matched peers without CHF and randomized to progressive resistance training or control stretching exercises for 10 wk. Women with CHF had significantly lower muscle strength (P < 0.0001) but comparable aerobic capacity to women without CHF. Exercise training was well tolerated and resulted in no changes in resting cardiac indexes in CHF patients. Strength improved by an average of 43.4 +/- 8.8% in resistance trainers vs. -1.7 +/- 2.8% in controls (P = 0.001), muscle endurance by 299 +/- 66% vs. 1 +/- 3% (P = 0.001), and 6-min walk distance by 49 +/- 14 m (13%) vs. -3 +/- 19 m (-3%) (P = 0.03). Increases in type I fiber area (9.5 +/- 16%) and citrate synthase activity (35 +/- 21%) in skeletal muscle were independently predictive of improved 6-min walk distance (r2 = 0.78; P = 0.0024). High-intensity progressive resistance training improves impaired skeletal muscle characteristics and overall exercise performance in older women with CHF. These gains are largely explained by skeletal muscle and not resting cardiac adaptations.

Etiology and modification of gait instability in older adults: a randomized controlled trial of exercise

Increased gait instability is common in older adults, even in the absence of overt disease. The goal of the present study was to quantitatively investigate the factors that contribute to gait instability and its potential reversibility in functionally impaired older adults. We studied 67 older men and women with functional impairment before and after they participated in a randomized placebo-controlled, 6-mo multimodal exercise trial. We found that 1) gait instability is multifactorial; 2) stride time variability is strongly associated with functional status and performance-based measures of function that have previously been shown to predict significant clinical outcomes such as morbidity and nursing home admission; 3) neuropsychological status and health-related quality of life play important, independent roles in gait instability; and 4) improvement in physiological capacity is associated with reduced gait instability. Although the etiology of gait instability in older persons with mild-moderate functional impairment is multifactorial, interventions designed to reduce gait instability may be effective in bringing about a more consistent and more stable walking pattern.

Artemether vs quinine therapy in Plasmodium falciparum malaria in Manipur--a preliminary report

Qinghaosu and its derivatives are rapidly effective antimalarial drugs derived from a Chinese plant (sweet worm wood). Preliminary studies suggest that these drugs may be more effective than quinine in the treatment of Plasmodium falciparum malaria. A randomised double blind trial was conducted in 52 cases of Plasmodium falciparum malaria cases. In all 26 cases were given artemether and another 26 were given quinine. There were 2 (7.5%) deaths in artemether group and 4 (15%) deaths in quinine group. The parasites were cleared more quickly from the blood in artemether group when compared to quinine group (mean-72 hrs vs 96 hrs). Resolution of fever was comparable in both artemether and quinine group (mean-84 hrs vs 78 hrs) and also the average time of recovery from coma was more earlier in artemether group (mean-60 hrs vs 72 hrs). The only side effect noticed with artemether therapy was gastrointestinal (GI) intolerance while quinine therapy was associated with myocarditis, hypotension, hypoglycemia and GI intolerance.

The effect of gender and body composition method on the apparent decline in lean mass-adjusted resting metabolic rate with age

BACKGROUND

Declining resting energy expenditure (REE) is a hallmark of normal aging, but the cause of this decline remains controversial. Some, but not all, studies have shown that the decline in REE with age is eliminated after adjustment for fat-free mass (FFM).

METHODS

We examined the effect of four body composition methods used to assess FFM (underwater weighing [UWW], bioimpedance analysis [BIA], tritium dilution, and total body potassium [TBK]) on the relationship between REE and age in 30 healthy men and 101 healthy women aged 18 to 87 years.

RESULTS

The decline in REE with age was significant in women (-80.3 kJ/d/y, p < .004) but not in men (-46.9 kJ/d/y, p = .328). After adjustment for FFM, the decline in REE with age persisted when FFM was measured by BIA, UWW, or tritium dilution, but no decline was seen when TBK was used to adjust for FFM. In both women and men, fat mass was significantly associated with REE after adjusting for age and FFM.

CONCLUSION

It is the decline in cell mass with age, detectable by TBK but not by other methods, rather than any metabolic alteration, that explains the decline in FFM-adjusted REE with age.

Biochemical and bacteriological study of urinary calculi

Biochemical and bacteriological study of urine, nidus and chemical analysis of 100 calculi from 100 patients admitted in the Regional Institute of Medical Sciences, Imphal from November, 1997 to October 1999 were done. About 47% of the cases had positive urine culture and nidus culture. Escherichia coli was the commonest bacteria isolated both in the urine and nidus of calculi. The commonest radical present in the calculi was calcium while the rarest was uric acid. The stones were composed mainly of calcium oxalate and/or phosphate followed by struvite, then mixed stone.

Association of muscle power with functional status in community-dwelling elderly women

BACKGROUND

Identification of the physiologic factors most relevant to functional independence in the elderly population is critical for the design of effective interventions. It has been suggested that muscle power may be more directly related to impaired physical performance than muscle strength in elderly persons. We tested the hypothesis that peak muscle power is closely associated with self-reported functional status in sedentary elderly community-dwelling women.

METHODS

We used baseline data that were collected as part of a 1-year randomized controlled clinical trial of a combined program of strength, power, and endurance training in 80 elderly women (mean age 74.8 +/- 5.0 years) with 3.2 +/- 1.9 chronic diseases, selected for baseline functional impairment and/or falls.

RESULTS

Functional status at baseline was related in univariate analyses to physiologic capacity, habitual physical activity level, neuropsychological status, and medical diagnoses. Leg power had the strongest univariate correlation to self-reported functional status (r = -.47, p < .0001) of any of the physiologic factors we tested. In a forward stepwise regression model, leg press power and habitual physical activity level were the only two factors that contributed independently to functional status (r = .64, p < .0001), accounting for 40% of the variance in functional status.

CONCLUSIONS

Leg power is a strong predictor of self-reported functional status in elderly women.

Insulin-like growth factor I in skeletal muscle after weight-lifting exercise in frail elders

To assess muscle remodeling and functional adaptation to exercise and diet interventions, 26 men and women aged 72-98 yr underwent a vastus lateralis biopsy before and after placebo control condition, and progressive resistance training, multinutrient supplementation, or both. Type II atrophy, Z band, and myofibril damage were present at baseline. Combined weight lifting and nutritional supplementation increased strength by 257 +/- 62% (P = 0.0001) and type II fiber area by 10.1 +/- 9.0% (P = 0.033), with a similar trend for type I fiber area (+12.8 +/- 22.2%). Exercise was associated with a 2. 5-fold increase in neonatal myosin staining (P = 0.0009) and an increase of 491 +/- 137% (P < 0.0001) in IGF-I staining. Ultrastructural damage increased by 141 +/- 59% after exercise training (P = 0.034). Strength increases were largest in those with the greatest increases in myosin, IGF-I, damage, and caloric intake during the trial. Age-related sarcopenia appears largely confined to type II muscle fibers. Frail elders respond robustly to resistance training with musculoskeletal remodeling, and significant increases in muscle area are possible with resistance training in combination with adequate energy intakes.

Combined exercise and dietary intervention to optimize body composition in aging

Concomitant losses of skeletal muscle and bone mass along with gradual accretion of adipose tissue typify usual human aging. Recent investigations have attempted to modify these processes with various combinations of dietary and exercise intervention in older adults. Complete nutritional supplements given with weight-lifting exercise have been shown to augment muscle and fat gains in healthy older men, but have merely suppressed habitual dietary intake when administered to frail sedentary elders, and have not altered body composition responses to strength training in this population. Protein supplementation at twice the RDA does not improve skeletal muscle function or increase muscle mass in healthy elderly weight lifters compared to those on a normal diet. Calcium supplementation during one year of aerobic training has an independent beneficial effect on cortical bone density at the femoral neck in postmenopausal women, whereas the exercise is associated with trabecular bone increases in the lumbar vertebrae. Hypocaloric dieting, with or without aerobic exercise, results in losses of weight, fat and lean mass in obese elderly men and women. By contrast, resistance training during hypocaloric dieting augments lean mass while further reducing fat mass. Low protein, isoenergetic diets result in muscle atrophy in older women. Current studies will determine the ability of resistance training to offset these catabolic effects on skeletal muscles of a low-protein (0.6 g/kg/day) diet prescribed for elderly with chronic renal failure. More long-term studies of efficacy and feasibility of diet and exercise combinations are needed in the aged to optimize the potential for healthful shifts in body composition.