A conjecture on the relationship of bacterial shape to motility in rod-shaped bacteria

We have calculated the optimal shape, i.e. the length-to-width ratio of a bacterial cell, that allows a bacterial cell to move most efficiently through liquid. For a cell of a given size, a minimum exists in the force required to move through any liquid when the length of the cell is approx. 3.7 times greater than the width. As this is in approximate agreement with the observed shape of bacteria such as the Enterobacteriaceae, we conjecture that the current observed shape of these bacteria may have been determined, in part, to obtain the most efficient shape for moving through liquids. It is also found that spherical cells are very inefficient in movement through liquid, while longer cells of a fixed size are still relatively efficient in moving through liquids. Since the optimal shape is independent of actual size (within large bounds), it is further proposed that hydrodynamic efficiency considerations support the proposal of constant shape over a range of sizes for rod-shaped bacteria.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73818/1/j.1574-6968.1997.tb10293.x.pd

The importance of measuring body composition in professional football players: A commentary

Professional football players are not considered to be excessively fat, but there is continuous pressure made by managers, coaches and physiotherapists to monitor player’s body composition to help reach optimal performance potential. Consequently, it is not uncommon for sport scientists to assume responsibility for monitoring and managing their players’ body composition over the playing season. As body fat is one of the main factors affecting body composition, the knowledge and understanding of whole body density and how it inluences the body could be useful to quantify the effectiveness of a prescribed training programme and/ or optimal performance potential

The Proposed U.S.-South Korea Free Trade Agreement (KORUS FTA): Provisions and Implications

On June 30, 2007, United States Trade Representative Susan Schwab and South Korean Foreign Trade Minister Kim Hyung-chong signed the proposed U.S.-South Korean Free Trade Agreement (KORUS FTA) for their respective countries. If approved, the KORUS FTA would be the largest FTA that South Korea has signed to date and would be the second largest (next to North American Free Trade Agreement NAFTA) in which the United States participates. South Korea is the seventh-largest trading partner of the United States and the United States is South Korea’s third largest trading partner. Various studies conclude that the agreement would increase bilateral trade and investment flows. The final text of the proposed KORUS FTA covers a wide range of trade and investment issues and, therefore, could have wide economic implications for both the United States and South Korea. The KORUS FTA includes issues on which the two countries achieved early agreement, such as the elimination on tariffs on trade in most manufactured goods and the partial liberalization in services trade. The agreement also includes provisions on a number of very sensitive issues, such as autos, agriculture, and trade remedies, on which agreement was reached only during the final hours of negotiations. If the agreement is to enter into force, Congress will have to approve implementation legislation. The negotiations were conducted under the trade promotion authority (TPA), also called fast-track trade authority, that the Congress granted the President under the Bipartisan Trade Promotion Act of 2002 (P.L. 107-210). The authority allows the President to enter into trade agreements that receive expedited congressional consideration (no amendments and limited debate). The White House has not indicated when it will send the draft implementing legislation to Congress. (The TPA sets no deadline for the President to do this.) While a broad swath of the U.S. business community supports the agreement, the KORUS FTA faces opposition from some groups, including some auto and steel manufacturers and labor unions. In addition, the agricultural community and some Members of Congress have withheld support for the agreement until South Korea lifts its restrictions on imports of U.S. beef. Some U.S. supporters view passage of the KORUS FTA as important to secure new opportunities in the South Korea market. Opponents claim that the KORUS FTA does not go far enough in opening up the South Korean market and is a lost opportunity to resolve long running concerns about South Korean barriers. Other observers have suggested the outcome of the KORUS FTA could have implications for the U.S.-South Korean alliance as a whole. Differences between the White House and the Democratic leadership in the Congress over the implications of the KORUS FTA have made the timing and even the likelihood of the President’s submission and the Congress’s subsequent consideration of implementing legislation uncertain. This report will be updated as events warrant

Using Tellus data to enhance targeting of volcanogenic massive sulphide mineralisation in the Tyrone Igneous Complex

The Tyrone Igneous Complex of Northern Ireland has been a target for base and precious metal exploration since the 1970s. Historic exploration was hampered by poor exposure and consequently a limited understanding of the local geology. Extensive new field mapping, utilising the high-resolution Tellus geophysical survey, coupled with U-Pb zircon geochronology and whole-rock geochemistry, has greatly improved our understanding of the complex and its potential to host volcanogenic massive sulphide (VMS) mineralisation. Targeting of Tellus and historic, geochemical and geophysical anomalies along VMS prospective stratigraphic horizons has identified new mineral occurrences and areas for further exploration. A correlation has been made with the Buchans–Robert’s Arm arc system of Newfoundland, host to numerous economic deposits

Reliability of Sprint Acceleration Performance and Three Repetition Maximum Back Squat Strength in Hurling Players

The purpose of this study was to estimate the inter-day reliability of 5, 10 and 20-meter sprint time and three repetition maximum back squat strength in male hurling players. Eighteen male hurling players volunteered to participate and performed 20- meter sprint trials and a three repetition maximum back squat strength test at each test session, on three separate occasions, a minimum of 48 hours apart. Participants performed three sprints over 20-meters, including split times at 5 and 10-meters. The three repetition back squat strength test was performed after the sprint test. The results displayed acceptable levels of reliability for sprint performance times (Intra class correlation coefficient single measure range: 0.76-0.89; Coefficient of variance range: 1.0 – 2.0%) and absolute and relative three repetition maximum back squat strength (Intra class correlation coefficient single measure: 0.98; CV 0.8%). Furthermore, sprint performance times and three repetition maximum back squat strength measures estimated feasible minimum a priori sample sizes from limits of agreement (5-meter:0.01 ± 0.08 s; 10-meter:-0.01 ± 0.12; 20-meter:-0.007 ± 0.15s; three repetition maximum (kg): 1.11 ± 4.19kg; three repetition maximum (kg/BW): 0.01 ± 0.06) random error therefore showing acceptable reliability. Sprint performance over 5, 10 and 20-meters and three repetition maximum back squat strength are reliable measures in male hurling players and can be used to estimate feasible minimum a priori sample sizes for sport science research

Neuromuscular and Bounce Drop-Jump Responses to Different Inter-Repetition Rest Intervals during A Composite Training Session in Hurling Players

The purposes of this study were to a) compare a 4-min to an 8-min rest interval between composite training (jump-sprint combination) repetitions in a single session to allow for the recovery of neuromuscular and bounce drop-jump (BDJ) performance and b) investigate if super compensation would occur after 168hrs of rest. Twelve players were randomly assigned to either a 4-min or an 8-min rest interval group. Participants first completed a BDJ test to identify individual BDJ drop heights followed by a 20m sprint test. Seventy-two hours later, a composite training session of two repetitions (three BDJs followed by a 20m sprint after a 15s rest) with either a 4-min or an 8-min rest interval was performed. A three repetition maximum (3RM) back squat strength test, a BDJ, countermovement jump (CMJ) and a sprint performance test were completed 10-mins pre- and immediately post-session, and 168 hrs post-session. CMJ force (8-min group) and BDJ (height and reactive strength index (RSI)) measures decreased significantly post-session (4-min and 8-min groups; P ≤ 0.05). Pre-session to 168 hrs post-session, relative 3RM back squat strength and 20m sprint performance increased significantly for the 4-min group only (P ≤ 0.05). In conclusion, a 4-min composite training inter-repetition rest interval leads to a significant decline in BDJ measures (RSI and jump height) which may act as fatigue markers for monitoring. However, 4-mins provides sufficient recovery during the session which, in conjunction with 168 hrs of recovery, causes super compensation in neuromuscular performance in hurling players

The Reliability of Countermovement Jump Performance and the Reactive Strength Index in Identifying Drop-Jump Drop Height in Hurling Players

The purpose of this study was to estimate the inter-day reliability of countermovement jump performance (CMJ) and the reactive strength index (RSI) in identifying drop-jump drop height in male hurling players. Eighteen male hurling players volunteered to participate. Subjects performed the CMJ and drop-jump test for RSI during the same sessions on three separate occasions a minimum of 48 hours apart. Subjects performed three CMJs and two drop-jumps from five different heights in an incremental manner (0.20, 0.30, 0.40, 0.50, 0.60 m). The results displayed acceptable levels of relative and absolute reliability for the following CMJ measures: height, velocity, force, power and average eccentric rate of force development measures (RFD). Absolute and relative peak concentric rate of force development from the CMJ test were found to have low levels of absolute reliability due to high CV% values. RSI and identified drop height from the drop-jump test displayed acceptable reliability (ICC single measure = 0.88 and 0.92 respectively; CV% = 6% and 10% respectively). Furthermore, limits of agreement random error displayed acceptable reliability for CMJ and drop-jump measures from estimated feasible minimum a priori sample sizes based upon limits of agreement. In conclusion, CMJ force-time measures (excluding peak concentric RFD measures), RSI and the identified drop height have acceptable absolute and relative reliability. For the sport science practitioner involved in hurling and for hurling players, this means that the CMJ test is reliable for kinetic and kinematic variables and the drop-jump test provides a means of developing a reactive strength profile and a means of individualizing drop height for drop-jump training

Sprint Running Performance and Technique Changes in Athletes during Periodized Training: An Elite Training Group Case Study

Purpose: To understand how training periodization influences sprint performance and key step characteristics over an extended training period in an elite sprint training group. Methods: Four sprinters were studied during five months of training. Step velocities, step lengths and step frequencies were measured from video of the maximum velocity phase of training sprints. Bootstrapped mean values were calculated for each athlete for each session and 139 within-athlete, between-session comparisons were made with a repeated measures ANOVA. Results: As training progressed, a link in the changes in velocity and step frequency was maintained. There were 71 between-session comparisons with a change in step velocity yielding at least a large effect size (>1.2), of which 73% had a correspondingly large change in step frequency in the same direction. Within-athlete mean session step length remained relatively constant throughout. Reductions in step velocity and frequency occurred during training phases of high volume lifting and running, with subsequent increases in step velocity and frequency happening during phases of low volume lifting and high intensity sprint work. Conclusions: The importance of step frequency over step length to the changes in performance within a training year was clearly evident for the sprinters studied. Understanding the magnitudes and timings of these changes in relation to the training program is important for coaches and athletes. The underpinning neuro-muscular mechanisms require further investigation, but are likely explained by an increase in force producing capability followed by an increase in the ability to produce that force rapidly

Large-effect flowering time mutations reveal conditionally adaptive paths through fitness landscapes in Arabidopsis thaliana.

Contrary to previous assumptions that most mutations are deleterious, there is increasing evidence for persistence of large-effect mutations in natural populations. A possible explanation for these observations is that mutant phenotypes and fitness may depend upon the specific environmental conditions to which a mutant is exposed. Here, we tested this hypothesis by growing large-effect flowering time mutants of Arabidopsis thaliana in multiple field sites and seasons to quantify their fitness effects in realistic natural conditions. By constructing environment-specific fitness landscapes based on flowering time and branching architecture, we observed that a subset of mutations increased fitness, but only in specific environments. These mutations increased fitness via different paths: through shifting flowering time, branching, or both. Branching was under stronger selection, but flowering time was more genetically variable, pointing to the importance of indirect selection on mutations through their pleiotropic effects on multiple phenotypes. Finally, mutations in hub genes with greater connectedness in their regulatory networks had greater effects on both phenotypes and fitness. Together, these findings indicate that large-effect mutations may persist in populations because they influence traits that are adaptive only under specific environmental conditions. Understanding their evolutionary dynamics therefore requires measuring their effects in multiple natural environments

Criterion Intervals for Pretreatment Drinking Measures in Treatment Evaluation

Drinking during a 30-day pretreatment period was found not to be representative of longer pretreatment intervals, especially in a population of seriously impaired inpatient alcoholic