344 research outputs found
A method of fuel testing in a CFR engine
At the present time, only a very small fraction of motor fuels produced for domestic use in the United States contain any alcohol in their blends. Soma foreign markets, notably the Philippine Islands and South American Countries use high proportions of alcohol in their motor fuel blends. Special purpose fuels in the United States which have alcohol blended with other compounds, have been used for engines from which maximum horsepower output is imperative. An example of this type of motor fuel blend might be found in the competitive motor sports involving motorcycles, stock automotive equipment, and special racing equipment.
An extensive survey of literature brought to light the lack of scientific information and basis for proper blending of alcohol blend fuel mixtures. The most apparent information in the literature was the lack of any scientific approach to the compounding of these fuels. The author considers that this lack of scientific background is due to the difficulty of providing a satisfactory testing procedure to follow in making such an evaluation.
This thesis reports the work involved in (a) preparing a suitable test engine for use in fuel research, (b) calibrating the associated equipment, (c) taking data, and (d) evaluating the resultant data in the light of the objective of the tests.
A standard ASTM-CFR single cylinder fuel research engine was used as the basic engine, with necessary modifications to achieve as near actual operating conditions as possible and still allow maximum control over all the variables. These modifications and the reasons for them are described in detail in the discussion section under the preparation of the test engine.
A piezoelectric crystal pickup was used to determine the cylinder pressures of the engine by electrically amplifying its output and using this output to drive an oscilloscope. The amplifier contained a special pressure evaluating device, and it, along with the pickup were calibrated as described in the discussion under the calibration of associated equipment.
Once the engine was prepared and the associated equipment calibrated, the taking of data was begun in a relatively straight forward manner. However, since the data was taken over a period of time but was evaluated all at one time, it was necessary to maintain rigid control over the variables and the calibrations as the data was taken. The necessary steps and precautions are described in the discussion under the section of operation and data taking --Introduction, pages 1-2
On Active Galactic Nuclei as Sources of Ultra-High Energy Cosmic Rays
We measure the correlation between sky coordinates of the Swift BAT catalogue
of active galactic nuclei with the arrival directions of the highest energy
cosmic rays detected by the Auger Observatory. The statistically complete, hard
X-ray catalogue helps to distinguish between AGN and other source candidates
that follow the distribution of local large-scale structure. The positions of
the full catalogue are marginally uncorrelated with the cosmic ray arrival
directions, but when weighted by their hard X-ray flux, AGN within 100 Mpc are
correlated at a significance level of 98 per cent. This correlation sharply
decreases for sources beyond ~100 Mpc, suggestive of a GZK suppression. We
discuss the implications for determining the mechanism that accelerates
particles to these extreme energies in excess of 10^19 eV.Comment: 5 pages, 2 figures. Accepted for publication in MNRA
The High Energy view of the Broad Line Radio Galaxy 3C 111
We present the analysis of Suzaku and XMM-Newton observations of the
broad-line radio galaxy (BLRG) 3C 111. Its high energy emission shows
variability, a harder continuum with respect to the radio quiet AGN population,
and weak reflection features. Suzaku found the source in a minimum flux level;
a comparison with the XMM-Newton data implies an increase of a factor of 2.5 in
the 0.5-10 keV flux, in the 6 months separating the two observations. The iron
K complex is detected in both datasets, with rather low equivalent width(s).
The intensity of the iron K complex does not respond to the change in continuum
flux. An ultra-fast, high-ionization outflowing gas is clearly detected in the
XIS data; the absorber is most likely unstable. Indeed, during the XMM-Newton
observation, which was 6 months after, the absorber was not detected. No clear
roll-over in the hard X-ray emission is detected, probably due to the emergence
of the jet as a dominant component in the hard X-ray band, as suggested by the
detection above ~ 100 keV with the GSO on-board Suzaku, although the present
data do not allow us to firmly constrain the relative contribution of the
different components. The fluxes observed by the gamma-ray satellites CGRO and
Fermi would be compatible with the putative jet component if peaking at
energies E ~ 100 MeV. In the X-ray band, the jet contribution to the continuum
starts to be significant only above 10 keV. If the detection of the jet
component in 3C 111 is confirmed, then its relative importance in the X-ray
energy band could explain the different observed properties in the high-energy
emission of BLRGs, which are otherwise similar in their other multiwavelength
properties. Comparison between X-ray and gamma-ray data taken at different
epochs suggests that the strong variability observed for 3C 111 is probably
driven by a change in the primary continuum.Comment: Accepted for publication in MNRAS; 15 pages, 9 figures, 5 table
Why do authoritarian regimes provide public goods? Policy communities, external shocks and ideas in China’s rural social policy making
Recent research on authoritarian regimes argues that they provide public goods in order to prevent rebellion. This essay shows that the ‘threat of rebellion’ alone cannot explain Chinese party-state policies to extend public goods to rural residents in the first decade of the twenty-first century. Drawing on theories of policy making, it argues that China’s one-party regime extended public goods to the rural population under the influence of ideas and policy options generated by policy communities of officials, researchers, international organisations and other actors. The party-state centre adopted and implemented these ideas and policy options when they provided solutions to external shocks and supported economic development goals. Explanations of policies and their outcomes in authoritarian political systems need to include not only ‘dictators’ but also other actors, and the ideas they generate
Systematic review and meta-analysis of the diagnostic accuracy of ultrasonography for deep vein thrombosis
Background
Ultrasound (US) has largely replaced contrast venography as the definitive diagnostic test for deep vein thrombosis (DVT). We aimed to derive a definitive estimate of the diagnostic accuracy of US for clinically suspected DVT and identify study-level factors that might predict accuracy.
Methods
We undertook a systematic review, meta-analysis and meta-regression of diagnostic cohort studies that compared US to contrast venography in patients with suspected DVT. We searched Medline, EMBASE, CINAHL, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Controlled Trials Register, Database of Reviews of Effectiveness, the ACP Journal Club, and citation lists (1966 to April 2004). Random effects meta-analysis was used to derive pooled estimates of sensitivity and specificity. Random effects meta-regression was used to identify study-level covariates that predicted diagnostic performance.
Results
We identified 100 cohorts comparing US to venography in patients with suspected DVT. Overall sensitivity for proximal DVT (95% confidence interval) was 94.2% (93.2 to 95.0), for distal DVT was 63.5% (59.8 to 67.0), and specificity was 93.8% (93.1 to 94.4). Duplex US had pooled sensitivity of 96.5% (95.1 to 97.6) for proximal DVT, 71.2% (64.6 to 77.2) for distal DVT and specificity of 94.0% (92.8 to 95.1). Triplex US had pooled sensitivity of 96.4% (94.4 to 97.1%) for proximal DVT, 75.2% (67.7 to 81.6) for distal DVT and specificity of 94.3% (92.5 to 95.8). Compression US alone had pooled sensitivity of 93.8 % (92.0 to 95.3%) for proximal DVT, 56.8% (49.0 to 66.4) for distal DVT and specificity of 97.8% (97.0 to 98.4). Sensitivity was higher in more recently published studies and in cohorts with higher prevalence of DVT and more proximal DVT, and was lower in cohorts that reported interpretation by a radiologist. Specificity was higher in cohorts that excluded patients with previous DVT. No studies were identified that compared repeat US to venography in all patients. Repeat US appears to have a positive yield of 1.3%, with 89% of these being confirmed by venography.
Conclusion
Combined colour-doppler US techniques have optimal sensitivity, while compression US has optimal specificity for DVT. However, all estimates are subject to substantial unexplained heterogeneity. The role of repeat scanning is very uncertain and based upon limited data
Exploring the Feasibility of Service Integration in a Low-Income Setting: A Mixed Methods Investigation into Different Models of Reproductive Health and HIV Care in Swaziland.
Integrating reproductive health (RH) with HIV care is a policy priority in high HIV prevalence settings, despite doubts surrounding its feasibility and varying evidence of effects on health outcomes. The process and outcomes of integrated RH-HIV care were investigated in Swaziland, through a comparative case study of four service models, ranging from fully integrated to fully stand-alone HIV services, selected purposively within one town. A client exit survey (n=602) measured integrated care received and unmet family planning (FP) needs. Descriptive statistics were used to assess the degree of integration per clinic and client demand for services. Logistic regression modelling was used to test the hypothesis that clients at more integrated sites had lower unmet FP needs than clients in a stand-alone site. Qualitative methods included in-depth interviews with clients and providers to explore contextual factors influencing the feasibility of integrated RH-HIV care delivery; data were analysed thematically, combining deductive and inductive approaches. Results demonstrated that clinic models were not as integrated in practice as had been claimed. Fragmentation of HIV care was common. Services accessed per provider were no higher at the more integrated clinics compared to stand-alone models (p>0.05), despite reported demand. While women at more integrated sites received more FP and pregnancy counselling than stand-alone models, they received condoms (a method of choice) less often, and there was no statistical evidence of difference in unmet FP needs by model of care. Multiple contextual factors influenced integration practices, including provider de-skilling within sub-specialist roles; norms of task-oriented routinised HIV care; perceptions of heavy client loads; imbalanced client-provider interactions hindering articulation of RH needs; and provider motivation challenges. Thus, despite institutional support, factors related to the social context of care inhibited provision of fully integrated RH-HIV services in these clinics. Programmes should move beyond simplistic training and equipment provision if integrated care interventions are to be sustained
Experience of sexual coercion and risky sexual behavior among Ugandan university students
<p>Abstract</p> <p>Background</p> <p>Growing worldwide evidence shows that the experience of sexual coercion is fairly prevalent among young people and is associated with risky sexual behavior thereafter. The causal mechanisms behind this are unclear but may be dependent on specific contextual determinants. Little is known about factors that could buffer the negative effects of coercion. The aim of this study was to assess the association between the experience of sexual coercion and risky sexual behavior among university students of both sexes in Uganda.</p> <p>Methods</p> <p>In 2005, 980 (80%) out of a total of 1,220 students enrolled in Mbarara University of Science and Technology in Uganda participated in a self-administered questionnaire covering socio-demographic and religious factors, social capital, mental health, alcohol use, and sexual behavior. A validated scale of six items was used to assess the experience of sexual coercion. Logistic regression analyses were applied to control for confounders. Potential buffering factors were analyzed by testing for effect modification.</p> <p>Results</p> <p>Fifty-nine percent of those who responded had previously had sexual intercourse. Among the male students 29.0%, and among the female students 33.1% reported having had some experience of sexual coercion. After controlling for age, gender, and educational level of household of origin, role of religion and trust in others sexual coercion was found to be statistically significantly associated with previously had sex (OR 1.6, 95% CI; 1.1-2.3), early sexual debut (OR 2.4, 95% CI; 1.5-3.7), as well as with having had a great number of sexual partners (OR 1.9, 95% CI; 1.2-3.0), but not with inconsistent condom use.</p> <p>Scoring low on an assessment of mental health problems, reporting high trust in others, or stating that religion played a major role in one's family of origin seemed to buffer the negative effect that the experience of sexual coercion had on the likelihood of having many sexual partners.</p> <p>Conclusion</p> <p>The findings of this study suggest that the experience of sexual coercion is common among youth/young adults in Uganda and is subsequently associated with risky sexual behavior in both sexes. The existence of individual and contextual factors that buffer the effects mentioned was also demonstrated. In the Ugandan context, this has implications for policy formulation and the implementation of preventive strategies for combating HIV/AIDS.</p
Editor's Choice – European Society for Vascular Surgery (ESVS) 2024 Clinical Practice Guidelines on the Management of Asymptomatic Lower Limb Peripheral Arterial Disease and Intermittent Claudication
Psychosocial and Sociodemographic Contributors to Breastfeeding Intention in First-Time Mothers
Objective
Breastfeeding has multiple benefits for women and babies. Understanding factors contributing to intention to exclusively breastfeed may allow for improving the rates in first-time mothers. The study objective was to examine factors associated with a woman’s intention to breastfeed her first child.
Methods
A secondary analysis of the prospective “Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be” (nuMoM2b) study of nulliparous women in the U.S. with singleton pregnancies was performed. Sociodemographic and psychosocial factors were analyzed for associations with breastfeeding intention.
Results
For the 6443 women with complete information about breastfeeding intention and all factors under consideration, women who intended to breastfeed (either exclusively or any breastfeeding) were more likely to be older, not black, have reached a higher level of education, have higher incomes, have a lower body mass index (BMI), and be nonsmokers. Reporting a planned pregnancy and several psychosocial measures were also associated with intention to breastfeed. In the multivariable analysis for exclusive breastfeeding, in addition to age, BMI, race, income, education, and smoking, of the psychosocial measures assessed, only women with higher hassle intensity ratios on the Pregnancy Experience Scale had lower odds of exclusive breastfeeding intention (OR 0.71, 95% CI 0.55–0.92). Other psychosocial measures were not associated with either exclusive breastfeeding or any breastfeeding after controlling for demographic characteristics.
Conclusions for Practice
Several sociodemographic factors, having a planned pregnancy, and fewer intense pregnancy hassles compared to uplifts are associated with intention to exclusively breastfeed. Identifying these factors may allow providers to identify women for focused, multilevel efforts to enhance breastfeeding rates
Severity-adjusted evaluation of liver transplantation on health outcomes in urea cycle disorders
Purpose: Liver transplantation (LTx) is performed in individuals with urea cycle disorders when medical management (MM) insufficiently prevents the occurrence of hyperammonemic events. However, there is a paucity of systematic analyses on the effects of LTx on health-related outcome parameters compared to individuals with comparable severity who are medically managed. Methods: We investigated the effects of LTx and MM on validated health-related outcome parameters, including the metabolic disease course, linear growth, and neurocognitive outcomes. Individuals were stratified into “severe” and “attenuated” categories based on the genotype-specific and validated in vitro enzyme activity. Results: LTx enabled metabolic stability by prevention of further hyperammonemic events after transplantation and was associated with a more favorable growth outcome compared with individuals remaining under MM. However, neurocognitive outcome in individuals with LTx did not differ from the medically managed counterparts as reflected by the frequency of motor abnormality and cognitive standard deviation score at last observation. Conclusion: Whereas LTx enabled metabolic stability without further need of protein restriction or nitrogen-scavenging therapy and was associated with a more favorable growth outcome, LTx—as currently performed—was not associated with improved neurocognitive outcomes compared with long-term MM in the investigated urea cycle disorders.</p
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