Association between community socioeconomic characteristics and access to youth flag football.

BACKGROUND: The American Academy of Pediatrics has recommended that opportunities for non-tackling American football (e.g., flag football) be expanded, given concerns about the risks of brain trauma from tackle football. This study tested the hypothesis that flag football would be more accessible in communities characterised by higher socioeconomic status residents. METHODS: In July 2017, the locations of community-based organisations offering youth flag and tackle football for youth between the ages of 6 and 13 in two US states (Georgia and Washington) were aggregated (n=440). Organisations were coded in terms of the availability of tackle and/or flag football teams for youth at each year of age between 6 and 13. Multivariate logistic regression analyses were used to assess the odds of a community-based football organisation offering flag football, by community socioeconomic and demographic characteristics. RESULTS: In both states, communities with more educated residents were more likely to offer flag football for youth aged 6-12. For example, among 6 year-olds every 10% increase in the number of adult residents with a college education was associated with 1.51 times the odds of flag football availability (95% CI 1.22 to 1.86, P<0.001). CONCLUSION: These results suggest that youth living in communities characterised by low educational attainment are less likely than other youth to have the option of a lower contact alternative to tackle football. Relying on voluntary community-level adoption of lower contact alternatives to tackle football may result in inequitable access to such sport options. This may contribute to an inequitable burden of brain trauma from youth sport.

Sperm with an abnormal hypo-osmotic swelling test--normal fertilization, normal embryo development, but implantation failure.

PURPOSE: To review the clinical importance of including the hypo-osmotic swelling (HOS) test in routine male fertility testing which in general is not evaluated by most physicians dealing with infertility. MATERIALS AND METHODS: Pregnancy rates were evaluated in patients with low HOS test scores. A low HOS test was specifically defined as having less than 50% of sperm exhibiting the normal physiologic response of tail swelling, when subjected to a hypo-osmolar solution. Pregnancy rates of patients with low HOS test were examined after intercourse, intrauterine insemination (IUI), conventional oocyte insemination, and in vitro fertilization (IVF). Patients with a low HOS test were also treated with a protein digestive enzyme chymotrypsin. Patients receiving intervention then underwent IUI, IVF with conventional oocyte insemination, or IVF with intracytoplasmic sperm injection (ICSI). Pregnancy rates of the cohort receiving intervention were then examined for comparison. RESULTS: The HOS test abnormality leads to normal fertilization but almost invariably negatively effects embryo implantation. Treatment with chymotrypsin, or performing IVF with ICSI, can overcome the toxic protein causing the embryo implantation defect. This toxic protein may be cryolabile and freezing sperm or embryos may prove to be another mode of therapy. CONCLUSIONS: The HOS abnormality may be the most reliable semen abnormality predicting failure to conceive even with IVF unless the defect is negated. Therapy is very effective. Unfortunately this test is rarely evaluated by most infertility specialists but it should be. The frequency increases with age.

Improving the chance of successful implantation - part I - embryo attachment to the endometrium and adequate trophoblast invasion.

The first in a series on improving embryo implantation is presented with emphasis on embryo attachment and trophoblast invasion. PURPOSE: To present knowledge of events needed for embryo attachment to the endometrium and subsequent trophoblast invasion and uterine remodeling leading to successful pregnancy. MATERIALS AND METHODS: Based on normal events, some practical suggestions are proposed as to possible means of improving pregnancy rates by enhancing possible embryo attachment and trophoblast invasion. RESULTS: Potential benefits of achieving adequate serum estradiol levels at peak follicular maturation, and the benefits of progesterone in the luteal phase are discussed. Also the potential benefits of purposeful endometrial injury is considered. CONCLUSIONS: Knowledge of the events leading to embryo attachment and trophoblast invasion could lead to novel research ideas helping to improve pregnancy rates in addition to proper hormone supplementation and endometrial biopsy.

Interfacial profiles in fluid/liquid systems: a description based on the storing of elastic energy.

An analytical expression for the interfacial energy is found by solving a Poisson equation and assuming a Boltzmann distribution of volume elements forming the fluid/liquid system. Interfacial phenomena are treated as a result of the response of a liquid when it makes contact with other fluid phase, in order to reach thermal and mechanical equilibrium. This model gives a quantitative description of the interface, obtaining values for its molar, force and energy density profiles. Also, our model allows the determination of the proportion of the fluids present in the interfacial zone, the values of interfacial tension and thickness. In the case of water+n-alkanes systems, the tensions are in agreement with the behavior shown by the experimental data. Finally, the values for interfacial thickness predicted from molar density profiles are lower than the range of influence of the elastic energy and elastic field.

Influence of droplet deformability on the coalescence rate of emulsions.

In this article the influence of deformation on the coalescence rates of oil-in-water (O/W) emulsions is analyzed. Calculations for doublets and many-particles systems were performed based on a Brownian dynamics algorithm. Extensional and bending energies were included in order to quantify the effect of the changes in the surface geometry on the coalescence rates. Also, the hydrodynamic resistance due to the flat film was included through a correction to the diffusion coefficient in the lubrication limit. Results of two particles calculations were compared with previous analytical evaluations of the coalescence time in absence of highly repulsive barriers [Danov, Langmuir 9, 1731 (1993)]. Lifetime of doublets was calculated as a function of the particle radius from 100 nm to 100 microm. It was found that the doublets lifetime strongly depends on the interplay between the potential of interaction between the droplets and the hydrodynamic resistance. Depending on the repulsive barrier either a monotonous increase of the lifetime with the droplet size or a maximum value is observed. Finally, the evolution of O/W emulsions with a volume fraction of phi=0.10 was studied. For these many-particle systems, the results show a sensitive dependence of the aggregation behavior on the interfacial tension. The procedure reported here allows us to include Derjaguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO forces and the film drainage velocity of many different systems.

Correction to the interfacial tension by curvature radius: differences between droplets and bubbles.

In this work we analyze the behavior of the interfacial tension with the curvature radius of the disperse phase. Following the Young-Laplace deduction of the equation relating the internal pressure with the curvature radius for a fluid confined by a spherical interface, we restate the Tolman approach [J. Chem. Phys. 1949, 108, 333] to obtain an analytical expression relating the interfacial tension with the radius. We have found small differences between our results and those of Tolman for the liquid/gas (droplets) case. However, important differences between liquid/gas (droplets) and gas/liquid (bubbles) dispersions were found. In particular, the decrease in the interfacial tension of bubbles may be expected to occur for much larger curvature radii than for the case of droplets when the curvature radius decreases. A simple relation between the Tolman's delta parameter and the interfacial width is also discussed. In our calculations we have considered dispersions of droplet of water in methane and bubbles of methane in water at T = 273.15 K.

Interfacial energy and the law of corresponding states 2: associated fluids.

A mesoscopic model for the liquid/vapor interface previously developed for nonpolar fluids [J. Phys. Chem. A 2003, 107, 875; 2003, 107, 883] is extended to the case of polar associated compounds. The interfacial energy is factorized in two terms: one corresponding to association depending on the hydrogen bonds density, the other corresponding to the nonpolar contribution. This last term is treated in the framework of the corresponding states formalism similar to the one used in the case of nonpolar fluids [J. Phys. Chem. B 2004, 108, 5951]. The model yields a generalized behavior of the association factor as a function of the dielectric constant for the treated fluids. The calculated surface tension shows a mean error of about 1% for seven compounds having different multivalent H-bond characters.

Thermodynamics of a two-dimensional unbounded self-gravitating system.

The thermodynamics of a two-dimensional self-gravitating system occupying the whole plane is considered in the mean-field approximation. First, it is proven that, if the number N of particles and the total energy E are imposed as the only external constraints, then the entropy admits the least upper bound S+(N,E)=2E/N+N ln(epi(2)) (in appropriate units). Moreover, there does exist a unique state of maximum entropy, which is characterized by a Maxwellian distribution function with a temperature T=N/2 independent of E. Next, it is shown that, if the total angular momentum J is imposed as a further constraint, the largest possible value of the entropy does not change, and there is no admissible state of maximum entropy, but in the case J=0. Finally, some inequalities satisfied by a class of so-called H functions and related generalized entropies are given.