Space Station Centrifuge: A Requirement for Life Science Research

A centrifuge with the largest diameter that can be accommodated on Space Station Freedom is required to conduct life science research in the microgravity environment of space. (This was one of the findings of a group of life scientists convened at the University of California, Davis, by Ames Research Center.) The centrifuge will be used as a research tool to understand how gravity affects biological processes; to provide an on-orbit one-g control; and to assess the efficacy of using artificial gravity to counteract the deleterious biological effect of space flight. The rationale for the recommendation and examples of using ground-based centrifugation for animal and plant acceleration studies are presented. Included are four appendixes and an extensive bibliography of hypergravity studies

Analyzing The Effectiveness Of The Gurney Method For Small Scale Fragmentation Propulsion Using Exploding Bridgewire Detonators

Explosives are common in military, mining, and construction applications where the explosive properties are understood, but mechanics of how the explosive\u27s energy fragments and throws materials are less known. Considering the type of confining material around an explosive, creates variability in fragmentation behavior due to the individual material characteristics. The most common method for assessing fragmentation behavior is the Gurney method, which eliminates any consideration of fragmenting material properties. The Gurney method assumes that, on a large scale, the inconsistencies in material are irrelevant and only the mass of the confiner need be considered. However, it is known in many fields that energy is consumed in the breaking of a material. In this paper, the detonation and resultant fragmentation propulsion of Exploding Bridgewire (EBW) detonators with the same explosive material, but different casing characteristics, is observed. The Gurney method was used to predict fragmentation velocities of the casing following detonation, which were compared to the behavior observed through high-speed video of the actual event. The EBWs were selected to provide variability in casing material, casing thickness, charge length, and charge diameter. It was found that when the amount of explosive is small, the material properties of the casing play a significant role, with 70 % of the total explosive mass lost in fragmenting PMMA EBWs and 30±3 % lost in Aluminum EBWs. There is significant energy loss to breaking the casing material that cannot be ignored on the small scale and could impact large explosives with high casing to explosive ratios

Water-Cased Kicker Charges for Use in Explosive Demolition

Demolition Projects Involving Explosives Often Incorporate Cutting Charges to Sever Columns in Conjunction with Kicker Charges that Move the Columns Out of Alignment. Traditional Kicker Charges Use Dynamite Secured to the Column above a Linear-Shaped Cutting Charge. This Study Investigates the Use of Water-Cased Kicker Charges for Use in Explosive Demolition. the Goal is to Reduce the Fragmentation of Steel Members and the Quantity of Explosive Needed Due to the Increased Density, Incompressibility, and Impedance Mismatch Water Provides. Simulations and Experimental Tests Were Utilized to Determine What Type of Charges Provide the Optimal Column Movement and Water Placement. Water Charges and Traditional Charges Were Placed on Hanging Steel Columns that Swung Freely from a Top Pivot and Analyzed for the Fragmentation and Velocity of the Column. Tests Were Recorded with High-Speed Video to Calculate Velocity and Impulse. Simulations Showed the Same Results as Experimental Tests, with Water-Cased Charges Moving the Column Faster and with More Impulse Than Traditional Charges. Experimental Testing Showed that Water-Cased Charges Moved the Column 53% Faster Than Traditional in Contact Charges While Simulations Showed that Water-Cased Charges Moved the Column 43% Faster Than Traditional in Contact Charges. Simulations Showed the Water Tamped Behind the Charge Increased Beam Velocity 32% While Water in Front of the Charge Reduced Pressure 38% through Dispersion

The implementation of chlamydia screening: a cross-sectional study in the south east of England

Background England's National Chlamydia Screening Programme (NCSP) provides opportunistic testing for under 25 year-olds in healthcare and non-healthcare settings. The authors aimed to explore relationships between coverage and positivity in relation to demographic characteristics or setting, in order to inform efficient and sustainable implementation of the NCSP. Methods The authors analysed mapped NCSP testing data from the South East region of England between April 2006 and March 2007 inclusive to population characteristics. Coverage was estimated by sex, demographic characteristics and service characteristics, and variation in positivity by setting and population group. Results Coverage in females was lower in the least deprived areas compared with the most deprived areas (OR 0.48; 95% CI 0.45 to 0.50). Testing rates were lower in 20 1324-year-olds compared with 15 1319-year-olds (OR 0.69; 95% CI 0.67 to 0.72 for females and OR 0.67; 95% CI 0.64 to 0.71 for males), but positivity was higher in older males. Females were tested most often in healthcare services, which also identified the most positives. The greatest proportions of male tests were in university (27%) and military (19%) settings which only identified a total of 11% and 13% of total male positives respectively. More chlamydia-positive males were identified through healthcare services despite fewer numbers of tests. Conclusions Testing of males focused on institutional settings where there is a low yield of positives, and limited capacity for expansion. By contrast, the testing of females, especially in urban environments, was mainly through established healthcare services. Future strategies should prioritise increasing male testing in healthcare settings

Effect Of Shock Tunnel Geometry On Shockwave And Vortex Ring Formation, Propagation, And Head On Collision

Vortex ring research primarily focuses on the formation from circular openings. Consequently, the role of tunnel geometry is less understood, despite there being numerous research studies using noncircular shock tunnels. This experimental study investigated shockwaves and vortex rings from different geometry shock tunnels from formation at the tunnel opening to head on collision with another similarly formed vortex ring using schlieren imaging and statistical analysis. The velocity of the incident shockwave was found to be consistent across all four shock tunnel geometries, which include circle, hexagon, square, and triangle of the same cross-sectional area. The velocity was 1.2 ± 0.007 Mach and was independent of the tunnel geometry. However, the velocities of the resulting vortex rings differed between the shapes, with statistical analysis indicating significant differences between the triangle and hexagon vortex velocities compared to the circle. Vortex rings from the square and circle shock tunnels were found to have statistically similar velocities. All vortex rings slowed as they traveled due to corner inversion and air drag. All shock tunnels with corners produce a wobble in the vortex rings. Vortex rings interact with opposing incident shockwaves prior to colliding with each other. Vortex velocity before and after shock-vortex interaction was measured and evaluated, showing statistically similar results. Shock-vortex interaction slows the shockwave upon interaction, while the shock-shock interaction resulted in no change in shock velocity. Although the vortex rings travel at different velocities, all head-on vortex ring collisions produce a perpendicular shockwave that travels at 1.04 ± 0.005 Mach

Investigating the relationship between HIV testing and risk behaviour in Britain: National Survey of Sexual Attitudes and Lifestyles 2000.

OBJECTIVES: To estimate the prevalence of, and identify factors associated with, HIV testing in Britain. DESIGN: A large, stratified probability sample survey of sexual attitudes and lifestyles. METHODS: A total of 12,110 16-44 year olds completed a computer-assisted face-to-face interview and self-interview. Self-reports of HIV testing, i.e. the timing, reasons for and location of testing, were included. RESULTS: A total of 32.4% of men and 31.7% of women reported ever having had an HIV test, the majority of whom were tested through blood donation. When screening for blood donation and pregnancy were excluded, 9.0% of men and 4.6% of women had had a voluntary confidential HIV test (VCT) in the past 5 years. However, one third of injecting drug users and men who have sex with men had a VCT in the past 5 years. VCT in the past 5 years was significantly associated with age, residence, ethnicity, self-perceived HIV risk, reporting greater numbers of sexual partners, new sexual partners from abroad, previous sexually transmitted infection diagnosis, and injecting non-prescribed drugs for men and women, and same-sex partners (men only). Whereas sexually transmitted disease clinics were important sites for VCT, general practice accounted for almost a quarter of VCT. CONCLUSION: HIV testing is relatively common in Britain; however, it remains largely associated with population-based blood donation and antenatal screening programmes. In contrast, VCT remains highly associated with high-risk (sexual or drug-injecting) behaviours or population sub-groups at high risk. Strategies to reduce undiagnosed prevalent HIV infection will require further normalization and wider uptake of HIV testing

The Relationship between Student Admissions Data and Six-Year Degree Completion

This study examined the six-year bachelor’s degree graduation status of freshmen (N = 1,839) entering the Dale Bumpers College of Agricultural, Food and Life Sciences (AFLS) between 2001 and 2010. The overall graduation rate was 64%, including 23% who had transferred out of AFLS. Multinomial logistic regression was used to determine if student entry data differentiated between graduates and non-graduates and between AFLS and non-AFLS graduates. High school GPA (HSGPA), first-generation status, and year of admission to the university significantly differentiated between graduates and non-graduates. Each standard deviation increase in HSGPA was associated with a 224% increase in the relative odds of graduating. Students entering each subsequent year had a 10% increase in the relative odds of graduating. Being a first-generation student decreased the relative odds of graduating by 52%. Year, major, and composite ACT score (CACT) significantly differentiated between AFLS and non-AFLS graduates. Students entering each subsequent year had a 16% increase in the relative odds of being AFLS graduates, while agriculture majors were about twice as likely to be AFLS graduates. Each standard deviation increase in CACT score was associated with a 26% decrease in the relative odds of being an AFLS graduate