Probabilistic Estimation of Critical Flaw Sizes in the Primary Structure Welds of the Ares I-X Launch Vehicle

The primary structure of the Ares I-X Upper Stage Simulator (USS) launch vehicle is constructed of welded mild steel plates. There is some concern over the possibility of structural failure due to welding flaws. It was considered critical to quantify the impact of uncertainties in residual stress, material porosity, applied loads, and material and crack growth properties on the reliability of the welds during its pre-flight and flight. A criterion--an existing maximum size crack at the weld toe must be smaller than the maximum allowable flaw size--was established to estimate the reliability of the welds. A spectrum of maximum allowable flaw sizes was developed for different possible combinations of all of the above listed variables by performing probabilistic crack growth analyses using the ANSYS finite element analysis code in conjunction with the NASGRO crack growth code. Two alternative methods were used to account for residual stresses: (1) The mean residual stress was assumed to be 41 ksi and a limit was set on the net section flow stress during crack propagation. The critical flaw size was determined by parametrically increasing the initial flaw size and detecting if this limit was exceeded during four complete flight cycles, and (2) The mean residual stress was assumed to be 49.6 ksi (the parent material s yield strength) and the net section flow stress limit was ignored. The critical flaw size was determined by parametrically increasing the initial flaw size and detecting if catastrophic crack growth occurred during four complete flight cycles. Both surface-crack models and through-crack models were utilized to characterize cracks in the weld toe

At what time does a quantum experiment have a result?

This paper provides a general method for defining a generalized quantum observable (or POVM) that supplies properly normalized conditional probabilities for the time of occurrence (i.e., of detection). This method treats the time of occurrence as a probabilistic variable whose value is to be determined by experiment and predicted by the Born rule. This avoids the problematic assumption that a question about the time at which an event occurs must be answered through instantaneous measurements of a projector by an observer, common to both Rovelli (1998) and Oppenheim et al. (2000). I also address the interpretation of experiments purporting to demonstrate the quantum Zeno effect, used by Oppenheim et al. (2000) to justify an inherent uncertainty for measurements of times.Comment: To appear in proceedings of 2015 ETH Zurich Workshop on Time in Physic

Outcomes Following Anterior Cruciate Ligament Reconstruction with Patellar Tendon vs Hamstring Autografts: A Systematic Review of Randomized Controlled Trials with a Mean Follow-up of 15 Years

BACKGROUND: The two most common surgical treatment modalities for anterior cruciate ligament reconstruction (ACL), patellar tendon (PT) and hamstring tendon (HS) autografts, have been shown to have outcomes that are both similar and favorable; however, many of these are short or intermediate-term. The objective of this systematic review is to evaluate randomized controlled trials (RCTs) with a minimum 10-year follow-up data to compare the long-term outcomes of ACL reconstructions performed using PT and HS autografts. METHODS: This systematic review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A search of three databases (PubMed, Cochrane and EMBASE) was performed to identify RCTs with a minimum of 10-year follow-up that compared clinical and/or functional outcomes between PT and HS autografts. RESULTS: Four RCTs with a total of 299 patients were included in the study. The mean follow-up ranged from 10.2 to 17 years (mean, 14.79 years). No significant differences in knee laxity or clinical outcome scores were demonstrated in any of the studies. One study found that PT autografts were significantly more likely to have osteoarthritis identified by radiographic findings. Two studies found that patients with PT autografts reported increase kneeling pain, while none of the four studies reported a difference in anterior knee pain. There were no significant differences in graft failure rates. CONCLUSION: This review demonstrates no long-term difference in clinical or functional outcomes between PT and HS autografts. However, radiographic and subjective outcomes indicate that patients with PT autografts may experience greater kneeling pain and osteoarthritis. Therefore, orthopedic surgeons should consider patient-centric factors when discussing graft options with patients

Can Recruiting Rankings Predict the Success of NCAA Division I Football Teams? An Examination of the Relationships among Rivals and Scouts Recruiting Rankings and Jeff Sagarin End-of-Season Ratings in Collegiate Football

This is the publisher's version, also available electronically from http://www.degruyter.com.The purpose of the present study was to examine the relationships among National Collegiate Athletic Association (NCAA) Division I football teams' 2002 recruiting rankings from the Rivals (RIV) and Scouts (SCO) recruiting services and the Jeff Sagarin end-of-season performance ratings from 2002–2006. The RIV and SCO recruiting services included rankings for 100 common NCAA Division I football teams for the 2002 recruiting season. Each recruiting service included a total point system rating (TOTPTS) and average star rating (AVESTAR). The Jeff Sagarin NCAA football ratings system was chosen as an indicator of the teams' performance. Pearson product moment correlation coefficients (R) and the corresponding predictive indices (R2) were used to examine whether the 2002 RIV & SCO TOTPTS and RIV & SCO AVESTAR ratings could predict the Jeff Sagarin end-of-season ratings and total number of wins for each football team for the 2002 through 2006 seasons. In addition, R and R2 values were computed to examine whether the 2002 Jeff Sagarin end-of-season ratings and total number of wins could predict the following season's recruiting rankings (2003 RIV & SCO TOTPTS and RIV & SCO AVESTAR). The results indicated that RIV & SCO TOTPTS and AVESTAR predicted up to 45% of the variances in the end-of-season ratings and total wins. Thus, other factors (besides recruiting rankings) must be contributing to the end-of-season ratings for the 100 NCAA football teams included in this study. In addition, up to 51% of the variance in RIV & SCO AVESTAR and TOTPTS was predicted by the previous year's end-of-season ratings or total wins, which suggests that more successful seasons tend to yield better subsequent recruiting classes

Enhancing a Wnt-Telomere Feedback Loop Restores Intestinal Stem Cell Function in a Human Organotypic Model of Dyskeratosis Congenita

Patients with dyskeratosis congenita (DC) suffer from stem cell failure in highly proliferative tissues, including the intestinal epithelium. Few therapeutic options exist for this disorder, and patients are treated primarily with bone marrow transplantation to restore hematopoietic function. Here, we generate isogenic DC patient and disease allele-corrected intestinal tissue using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9-mediated gene correction in induced pluripotent stem cells and directed differentiation. We show that DC tissue has suboptimal Wnt pathway activity causing intestinal stem cell failure and that enhanced expression of the telomere-capping protein TRF2, a Wnt target gene, can alleviate DC phenotypes. Treatment with the clinically relevant Wnt agonists LiCl or CHIR99021 restored TRF2 expression and reversed gastrointestinal DC phenotypes, including organoid formation in vitro, and maturation of intestinal tissue and xenografted organoids in vivo. Thus, the isogenic DC cell model provides a platform for therapeutic discovery and identifies Wnt modulation as a potential strategy for treatment of DC patients

Acute effects of a thermogenic nutritional supplement on cycling time to exhaustion and muscular strength in college-aged men

<p>Abstract</p> <p>Background</p> <p>The purpose of the present study was to examine the acute effects of a thermogenic nutritional supplement containing caffeine, capsaicin, bioperine, and niacin on muscular strength and endurance performance.</p> <p>Methods</p> <p>Twenty recreationally-active men (mean ± SD age = 21.5 ± 1.4 years; stature = 178.2 ± 6.3 cm; mass = 76.5 ± 9.9 kg; VO_{2 PEAK}= 3.05 ± 0.59 L/min^-1) volunteered to participate in this randomized, double-blinded, placebo-controlled, cross-over study. All testing took place over a three-week period, with each of the 3 laboratory visits separated by 7 days (± 2 hours). During the initial visit, a graded exercise test was performed on a Lode Corival cycle ergometer (Lode, Groningen, Netherlands) until exhaustion (increase of 25 W every 2 min) to determine the maximum power output (W) at the VO_{2 PEAK}(Parvo Medics TrueOne^®2400 Metabolic Measurement System, Sandy, Utah). In addition, one-repetition maximum (1-RM) strength was assessed using the bench press (BP) and leg press (LP) exercises. During visits 2 and 3, the subjects were asked to consume a capsule containing either the active supplement (200 mg caffeine, 33.34 mg capsaicin, 5 mg bioperine, and 20 mg niacin) or the placebo (175 mg of calcium carbonate, 160 mg of microcrystalline cellulose, 5 mg of stearic acid, and 5 mg of magnesium stearate in an identical capsule) 30 min prior to the testing. Testing included a time-to-exhaustion (TTE) ride on a cycle ergometer at 80% of the previously-determined power output at VO_{2 PEAK}followed by 1-RM LP and BP tests.</p> <p>Results</p> <p>There were no differences (<it>p </it>> 0.05) between the active and placebo trials for BP, LP, or TTE. However, for the BP and LP scores, the baseline values (visit 1) were less than the values recorded during visits 2 and 3 (<it>p </it>≤ 0.05).</p> <p>Conclusion</p> <p>Our findings indicated that the active supplement containing caffeine, capsaicin, bioperine, and niacin did not alter muscular strength or cycling endurance when compared to a placebo trial. The lack of increases in BP and LP strength and cycle ergometry endurance elicited by this supplement may have been related to the relatively small dose of caffeine, the high intensity of exercise, the untrained status of the participants, and/or the potential for caffeine and capsaicin to increase carbohydrate oxidation.</p

Acute effects of a thermogenic nutritional supplement on cycling time to exhaustion and muscular strength in college-aged men

This is the publisher's version, also available electronically from http://www.jissn.com/content/6/1/15.The purpose of the present study was to examine the acute effects of a thermogenic nutritional supplement containing caffeine, capsaicin, bioperine, and niacin on muscular strength and endurance performance. Methods Twenty recreationally-active men (mean ± SD age = 21.5 ± 1.4 years; stature = 178.2 ± 6.3 cm; mass = 76.5 ± 9.9 kg; VO2 PEAK = 3.05 ± 0.59 L/min-1) volunteered to participate in this randomized, double-blinded, placebo-controlled, cross-over study. All testing took place over a three-week period, with each of the 3 laboratory visits separated by 7 days (± 2 hours). During the initial visit, a graded exercise test was performed on a Lode Corival cycle ergometer (Lode, Groningen, Netherlands) until exhaustion (increase of 25 W every 2 min) to determine the maximum power output (W) at the VO2 PEAK (Parvo Medics TrueOne® 2400 Metabolic Measurement System, Sandy, Utah). In addition, one-repetition maximum (1-RM) strength was assessed using the bench press (BP) and leg press (LP) exercises. During visits 2 and 3, the subjects were asked to consume a capsule containing either the active supplement (200 mg caffeine, 33.34 mg capsaicin, 5 mg bioperine, and 20 mg niacin) or the placebo (175 mg of calcium carbonate, 160 mg of microcrystalline cellulose, 5 mg of stearic acid, and 5 mg of magnesium stearate in an identical capsule) 30 min prior to the testing. Testing included a time-to-exhaustion (TTE) ride on a cycle ergometer at 80% of the previously-determined power output at VO2 PEAK followed by 1-RM LP and BP tests. Results There were no differences (p > 0.05) between the active and placebo trials for BP, LP, or TTE. However, for the BP and LP scores, the baseline values (visit 1) were less than the values recorded during visits 2 and 3 (p ≤ 0.05). Conclusion Our findings indicated that the active supplement containing caffeine, capsaicin, bioperine, and niacin did not alter muscular strength or cycling endurance when compared to a placebo trial. The lack of increases in BP and LP strength and cycle ergometry endurance elicited by this supplement may have been related to the relatively small dose of caffeine, the high intensity of exercise, the untrained status of the participants, and/or the potential for caffeine and capsaicin to increase carbohydrate oxidation