Transient response of an overcritical high-speed rotor is considered. A rapid increase of unbalance initiates a series of rotor–stator collisions succeeded by full annular rub during which a very ...high dynamic load can develop, exceeding by several times that due to separate collisions. The main reasons leading to such a potentially catastrophic response are highlighted.
It has been suggested that the relative importance of oestrogen-metabolising pathways may affect the risk of oestrogen-dependent tumours including endometrial cancer. One hypothesis is that the ...2-hydroxy pathway is protective, whereas the 16α-hydroxy pathway is harmful.
We conducted a case-control study nested within three prospective cohorts to assess whether the circulating 2-hydroxyestrone : 16α-hydroxyestrone (2-OHE1 : 16α-OHE1) ratio is inversely associated with endometrial cancer risk in postmenopausal women. A total of 179 cases and 336 controls, matching cases on cohort, age and date of blood donation, were included. Levels of 2-OHE1 and 16α-OHE1 were measured using a monoclonal antibody-based enzyme assay.
Endometrial cancer risk increased with increasing levels of both metabolites, with odds ratios in the top tertiles of 2.4 (95% CI=1.3, 4.6; P(trend)=0.007) for 2-OHE1 and 1.9 (95% CI=1.1, 3.5; P(trend)=0.03) for 16α-OHE1 in analyses adjusting for endometrial cancer risk factors. These associations were attenuated and no longer statistically significant after further adjustment for oestrone or oestradiol levels. No significant association was observed for the 2-OHE1 : 16α-OHE1 ratio.
Our results do not support the hypothesis that greater metabolism of oestrogen via the 2-OH pathway, relative to the 16α-OH pathway, protects against endometrial cancer.
Rotor—frame contact in a centrifuge installed on board a ship Grāpis, O; Ohlson, N-G; Andersons, J
Proceedings of the Institution of Mechanical Engineers. Part C, Journal of mechanical engineering science,
03/2010, Letnik:
224, Številka:
3
Journal Article
Recenzirano
Abstract
The criticality of rotor and stator contact in a large-size marine separator is studied by numerical modelling. Two plausible mechanisms leading to such contact, namely rolling of a ship in ...steady-state motion and a suddenly occurring unbalance in the rotor, are considered. It is found that contact due to sea motion may be tolerable, while sudden development of unbalance at operating speed can lead to unacceptably high contact forces. This agrees with experience of centrifugal separators operating on board of ships.
It is well established that parity and use of oral contraceptives reduce the risk of ovarian cancer, but the associations with other reproductive variables are less clear.
We examined the ...associations of oral contraceptive use and reproductive factors with ovarian cancer risk in the European Prospective Investigation into Cancer and Nutrition. Among 327,396 eligible women, 878 developed ovarian cancer over an average of 9 years. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazard models stratified by centre and age, and adjusted for smoking status, body mass index, unilateral ovariectomy, simple hysterectomy, menopausal hormone therapy, and mutually adjusted for age at menarche, age at menopause, number of full-term pregnancies and duration of oral contraceptive use.
Women who used oral contraceptives for 10 or more years had a significant 45% (HR, 0.55; 95% CI, 0.41-0.75) lower risk compared with users of 1 year or less (P-trend, <0.01). Compared with nulliparous women, parous women had a 29% (HR, 0.71; 95% CI, 0.59-0.87) lower risk, with an 8% reduction in risk for each additional pregnancy. A high age at menopause was associated with a higher risk of ovarian cancer (>52 vs ≤ 45 years: HR, 1.46; 95% CI, 1.06-1.99; P-trend, 0.02). Age at menarche, age at first full-term pregnancy, incomplete pregnancies and breastfeeding were not associated with risk.
This study shows a strong protective association of oral contraceptives and parity with ovarian cancer risk, a higher risk with a late age at menopause, and no association with other reproductive factors.
The mechanical behaviour of parts containing ER fluid can be derived, once the constitutive equation for characterising the fluid is known. An elastic-plastic material model with kinematic ...strain-hardening was selected, its parameters having been determined from a test with uniaxial loading. Four different damper designs were analysed by the finite element program
nisa. This material model displays no frequency dependence but, if required, the model may be modified to account for frequency dependence by introducing strain-rate sensitive friction. The paper describes how this is done. The application of an ER damper to a Laval rotor system was studied. The system response to stationary as well as to some transient loads was derived by a time-integration technique in Matlab. The results agree well with those obtained from a small Laval rotor test rig. One concludes that the force-displacement hysteresis loop can be predicted by FE calculation for any damper design. The loop may then be simplified so as to be described by only two parameters for ensuing transient response analysis.
A model is proposed for non-linear time-dependent materials, often referred to as materials with memory or hereditary type materials. It is applied to various types of loading: monotonous loading, ...creep and relaxation. As an example, the polymer material POM (polyoximethylene) is chosen. This material possesses strongly pronounced non-linearity, which is clearly seen in the stress–strain diagrams. The material was tested at three different loading rates, at creep conditions with three levels of stress and at relaxation conditions with three levels of strain. It is shown that the constitutive equation representing the model describes these types of loading using only one set of parameters. Determination of parameters is based on short-time experiments with constant stress rate loading. Prediction of material behaviour at long times for creep and relaxation processes can be made. Unloading is not considered in the paper but may be treated as well.
The accuracy of rubber impression materials was evaluated by taking impressions of a steel model, pouring it with stone and comparing certain measurements between steel and stone models. It is ...assumed that acceptance is achieved when the difference in measurements is within permissible limits, defined by clinical criteria. A mathematical formulation of these criteria will lead to the concept of probability of acceptance. The probability is affected when the limits are changed. The particular case of satisfying two acceptance criteria that contain variables which are not statistically independent s considered, leading to the application of the bivariate normal distribution in the evaluation of acceptance probability.
Abstract Background : The role of estrogen and progesterone in the development of endometrial cancer is well documented. Few studies have examined the association of genetic variants in sex ...hormone-related genes with endometrial cancer risk. Methods : We conducted a case-control study nested within three cohorts to examine the association of endometrial cancer risk with polymorphisms in hormone-related genes among 391 cases (92% postmenopausal at diagnosis) and 712 individually-matched controls. We also examined the association of these polymorphisms with circulating levels of sex hormones and SHBG in a cross-sectional analysis including 596 healthy postmenopausal women at blood donation (controls from this nested case-control study and from a nested case-control study of breast cancer in one of the three cohorts). Results : Adjusting for endometrial cancer risk factors, the A allele of rs4775936 in CYP19 was significantly associated (ORper allele = 1.22, 95% CI = 1.01–1.47, ptrend = 0.04), while the T allele of rs10046 was marginally associated with increased risk of endometrial cancer (ORper allele = 1.20, 95% CI = 0.99–1.45, ptrend = 0.06). PGR rs1042838 was also marginally associated with risk (ORper allele = 1.25, 95% CI = 0.96–1.61, ptrend = 0.09). No significant association was found for the other polymorphisms, i.e. CYP1B1 rs1800440 and rs1056836, UGT1A1 rs8175347, SHBG rs6259 and ESR1 rs2234693. Rs8175347 was significantly associated with postmenopausal levels of estradiol, free estradiol and estrone and rs6259 with SHBG and estradiol. Conclusion : Our findings support an association between genetic variants in CYP19 , and possibly PGR , and risk of endometrial cancer.
In a previous paper, authors proposed a constitutive equation for non-linear hereditary-type materials. This equation can be extended to take into account the influence of temperature. The model is ...capable of describing various kinds of deformation such as monotonous tension at constant loading rate, creep and relaxation. The procedure for determining parameters is described. Seven polymer materials were investigated. A comparison of calculated and experimental results was made for these materials and these types of loading.
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