Advanced composite combustor structural concepts program

An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's

Drop size in a liquid pulsed sieve-plate extraction column

Peer reviewedPublisher PD

HAEMATOLOGICAL PARAMETERS IN EXOTIC COWS DURING GESTATION AND LACTATION UNDER SUBTROPICAL CONDITIONS

Seventy Holstein-Friesian and Jersey cows of different ages kept at the Livestock Experiment Station, Bhunikey (Pattoki), district Kasur, Pakistan were used for this study. These cows were divided into seven groups having 10 animals in each group. Group numbers 1 to 7 were named as pregnant heifers, pregnant lactating cows, non-pregnant dry cows, non-pregnant heifers, parturient cows, pregnant dry cows and non-pregnant lactating cows, respectively. Blood samples from all the animals were collected and haematological values were recorded, using routine haematological procedures. The highest Hb concentration (11.32 ± 0.32 gm/dl) was recorded in group-4, while the lowest (9.24 ± 0.35 gm/dl) was observed in group-7. The highest RBCs count and PCV (6.18 ± 0.47 x 106/µl and 35.51 ± 1.51%) were recorded in group-4 and the lowest (4.55 ± 0.26 x 106/µl and 29.23 ± 1.09%) values were observed in group-6. The highest MCV, MCH and MCHC (65.26 ± 1.96 fl, 23.50 ± 1.31 pg and 35.75 ± 0.99 gm/dl) were noted in group-5 and the lowest (55.16 ± 1.72 fl, 16.77 ± 1.14 pg and 30.09 ± 1.15 gm/dl) were noted in group-2. The highest ESR (7.60 ± 1.15 mm/24 hours) was recorded in group-6 and the lowest (4.89 ± 0.40 mm/24 hours) values were observed in group-5. The highest WBCs count (9.43 ± 1.15 x 103/µl) was observed in group-1 and the lowest (6.35 ± 0.72 x 103/µl) was recorded in group-5. Amongst DLC, highest (P<0.05) lymphocyte count (69.10 ± 2.55%) was observed in group-4, while lowest count (56.70 ± 5.16%) was in group-5. The differences between monocyte, neutrophil, eosinophil and basophil counts in all the groups were statistically non-significant

Ceramides: a new player in the inflammation-insulin resistance paradigm?

No abstract available

REPRODUCTIVE EFFICIENCY OF JERSEY COWS UNDER SUBTROPICAL CONDITIONS OF THE PUNJAB

Various parameters of reproductive efficiency of Jersey cows kept at the Livestock Experiment Station, Bhunikey (Pattoki), District Kasur, for the period from 1991 to 2000 were studied. The average values of age at maturity and age at first calving were 615.48 ± 8.23 and 926.48 ± 10.29 days, respectively and the differences of these parameters during different seasons of birth were statistically non-significant. The average calving to first insemination interval, service period and calving interval were 86.65 ± 1.71, 152.66 ± 4.85 and 430.15 ± 4.87 days, respectively. The differences of calving to first insemination interval among cows calved during different seasons were statistically non-significant. But the differences of calving to first insemination interval during 1st lactation were significant (P<0.05) with those of 6th, 7th and 9th lactations. Service period and calving interval in the Jersey cows calved during humid hot season were significantly (P<0.05) shorter as compared to those of cows calved during dry hot and spring seasons. Effect of parity on the service period was non-significant, but the effect of parity on the calving interval was significant (P<0.05), when the difference of calving interval during 7th and 8th lactation was compared. The average number of services per conception was 2.81 ± 0.09. The effect of parity on the number of services per conception was significant (P<0.05). The average gestation period was 277.63 ± 0.21 days. Higher gestation period was observed in cows carrying male calves than those carrying female calves (P<0.05). The frequency of calvings during winter, spring, dry hot, humid hot and autumn seasons was 19.32, 19.20, 9.79, 33.25 and 18.44 percent, respectively

Screen time is associated with adiposity and insulin resistance in children

Higher screen time is associated with type 2 diabetes (T2D) risk in adults, but the association with T2D risk markers in children is unclear. We examined associations between self-reported screen time and T2D risk markers in children. Survey of 4495 children aged 9-10 years who had fasting cardiometabolic risk marker assessments, anthropometry measurements and reported daily screen time; objective physical activity was measured in a subset of 2031 children. Compared with an hour or less screen time daily, those reporting screen time over 3 hours had higher ponderal index (1.9%, 95% CI 0.5% to 3.4%), skinfold thickness (4.5%, 0.2% to 8.8%), fat mass index (3.3%, 0.0% to 6.7%), leptin (9.2%, 1.1% to 18.0%) and insulin resistance (10.5%, 4.9% to 16.4%); associations with glucose, HbA1c, physical activity and cardiovascular risk markers were weak or absent. Associations with insulin resistance remained after adjustment for adiposity, socioeconomic markers and physical activity. Strong graded associations between screen time, adiposity and insulin resistance suggest that reducing screen time could facilitate early T2D prevention. While these observations are of considerable public health interest, evidence from randomised controlled trials is needed to suggest causality. [Abstract copyright: 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/.

Metabolic, inflammatory and haemostatic effects of a low-dose continuous combined HRT in women with type 2 diabetes: potentially safer with respect to vascular risk?

BACKGROUND Conventional hormone replacement therapy (HRT) containing conjugated equine oestrogen (CEE) and medroxyprogesterone acetate (MPA) increases triglyceride, C- reactive protein (CRP) and coagulation Factor VII concentrations, potentially explaining their increased coronary heart disease (CHD) and stroke risk. OBJECTIVE To assess the metabolic effects of a continuous combined HRT containing 1 mg oestradiol and 0.5 mg norethisterone or matching placebo. DESIGN Double-blind, randomized placebo-controlled trial. PATIENTS Fifty women with type 2 diabetes. MEASUREMENTS Classical and novel risk factors for vascular disease. RESULTS Triglyceride concentration was not altered (P = 0.31, change in active arm relative to placebo) and low-density lipoprotein (LDL) cholesterol concentration declined 13% (P = 0.018). IL-6 concentration (mean difference -1.42 pg/ml, 95% CI: -2.55 to - 0.29 IU/dl, P = 0.015), Factor VII (-32 IU/dl, -43 to -21 IU/l, P lt 0.001) and tissue plasminogen activator antigen (by 13%, P = 0.005) concentrations fell, but CRP was not significantly altered (P = 0.62). Fasting glucose (P = 0.026) also declined significantly, but there are no significant effects on HBA1c, Factor IX or APC resistance. CONCLUSIONS HRT containing 1 mg oestradiol and 0.5 mg norethisterone may avoid the adverse metabolic effects potentially implicated in the elevated CHD and stroke risk induced by conventional higher dose HRT. This type of preparation may therefore be more suitable than conventional HRT for women at elevated CHD risk such as those with type 2 diabetes. Large randomized controlled trials of such low dose preparations, powered for cardiovascular end points, are now needed