Activation and Deactivation of the Polymerization of Ethylene over rac‐EtInd2ZrCl2 and (nBuCp)2ZrCl2 on an Activating Silica Support

A study is carried out in order to better understand the kinetic behavior of two different metallocene precursors supported on an activating silica support, and, in particular, to attempt to reduce the significance of catalyst deactivation through the use of different alkylating agents. It is observed that it is difficult to prevent the deactivation of the rac‐EtInd₂ZrCl₂ sites on the activating support, and, furthermore, the deactivation is accompanied by the disa­ppearance of sites producing the highest‐molecular‐weight polymer. On the contrary, with the (nBuCp)₂ZrCl₂ precursor, it is possible to manipulate the addition of either tri‐isobutylaluminum (TIBA) or triethylaluminum (TEA) to significantly reduce the deactivation of the catalyst on the activating supports. Finally, the molecular‐weight distribution seems to depend much more on the intrinsic properties of the active sites than on how the active sites are treated.

     

Well‐Defined Imidazolium ABA Triblock Copolymers as Ionic‐Liquid‐Containing Electroactive Membranes

Nitroxide‐mediated polymerization (NMP) affords the synthesis of well‐defined ABA triblock copolymers with polystyrene external blocks and a charged poly(1‐methyl‐3‐(4‐vinylbenzyl)­imidazolium bis(trifluoromethane sulfonyl)imide central block. Aqueous size‐exclusion chromatography (SEC) and ¹H NMR spectroscopy studies confirm the control of the composition and block lengths for both the central and external blocks. Dynamic mechanical analysis (DMA) reveals a room temperature modulus suitable for fabricating these triblock copolymers into electroactive devices in the presence of an added ionic liquid. Dielectric relaxation spectroscopy (DRS) elucidates the ion‐transport properties of the ABA triblock copolymers with varied compositions. The ionic conductivity in these single‐ion conductors exhibits Vogel–Fulcher–Tammann (VFT) and Arrhenius temperature dependences, and electrode polarization (EP) analysis determines the number density of simultaneously conducting ions and their mobility. The actuators derived from these triblock copolymer membranes experience similar actuation speeds at an applied voltage of 4 V DC, as compared with benchmark Nafion membranes. These tailorable ABA block copolymers are promising candidates for ionic‐polymer device applications.

     

National Athletic Trainers' Association Position Statement: Preparticipation Physical Examinations and Disqualifying Conditions

Objective

To present athletic trainers with recommendations for the content and administration of the preparticipation physical examination (PPE) as well as considerations for determining safe participation in sports and identifying disqualifying conditions.

Background

Preparticipation physical examinations have been used routinely for nearly 40 years. However, considerable debate exists as to their efficacy due to the lack of standardization in the process and the lack of conformity in the information that is gathered. With the continuing rise in sports participation at all levels and the growing number of reported cases of sudden death in organized athletics, the sports medicine community should consider adopting a standardized process for conducting the PPE to protect all parties.

Recommendations

Recommendations are provided to equip the sports medicine community with the tools necessary to conduct the PPE as effectively and efficiently as possible using available scientific evidence and best practices. In addition, the recommendations will help clinicians identify those conditions that may threaten the health and safety of participants in organized sports, may require further evaluation and intervention, or may result in potential disqualification.Key Words: medical history, family history, sudden cardiac death, concussion, sickle cell trait, diabetes, heat illness, hydrationParticipation in organized US athletics continues to rise. During the 2010–2011 academic year, more than 7.6 million high school students took part in organized interscholastic sports, compared with 7.1 million in 2005–2006.¹ Similarly, an additional 444 077 National Collegiate Athletic Association student–athletes participated in intercollegiate athletics in 2010–2011, compared with 393 509 in 2005–2006.² This growth in participation has led to a concomitant rise in sudden death. Most sudden deaths have been attributed to congenital or acquired cardiovascular malformations involving male football and basketball players.^3–5 Other causes of sudden death include heat stroke, cerebral aneurysm, asthma, commotio cordis, and sickle cell trait.^4,5 As sports participation continues to increase and catastrophic death in athletes receives more attention, the medical community should consider adopting a standardized preparticipation examination (PPE) instrument that, at a minimum and to the extent possible, sets out to ensure a safe playing environment for all and to identify those conditions that might predispose an athlete to injury or sudden death.For nearly 4 decades, PPE screening has been used routinely in an attempt to identify those conditions that may place an athlete at increased risk and affect safe participation in organized sports. Few would empirically argue the potential benefits of this practice, yet considerable debate exists as to the current efficacy of the PPE, given the significant disparities that presently characterize the examination and the information gathered. Over time, the PPE has become an integral component of athletics and sports medicine programs; however, the lack of standardization in the process has created confusion. In addition, the failure to adequately define the primary objectives of the PPE has led to the consensus that, in its current form, the PPE does not address the ultimate goal of protecting the health and safety of the player.The American Medical Association Group on Science and Technology⁶ has asserted that every physician has 2 responsibilities to an athlete during the PPE: “(1) to identify those athletes who have medical conditions that place them at substantial risk for injury or sudden death and to disqualify them from participation or ensure they receive adequate medical treatment before participation and (2) to not disqualify athletes unless there is a compelling medical reason.” As the PPE has evolved over the years, it has become increasingly difficult to meet these standards given the many objectives that have been proposed for the screening instrument. Originally, the primary objectives of the PPE were to (1) detect life-threatening or disabling conditions, (2) identify those conditions that predispose the athlete to injury or disability, and (3) address legal and insurance requirements.^7,8 Today, however, those entities charged with developing and revising the PPE (eg, state high school athletic associations, medical associations, state education departments, state health departments, legislators)⁹ often have different missions, and as a result, they have sought to influence the makeup of the PPE to address their specific interests. This has led to the identification of a number of secondary objectives, including but not limited to documenting athletic eligibility, obtaining parental consent for participation and emergency treatment, and improving athlete performance.⁹ Most notably, the PPE represents the sole source of medical evaluation for 30% to 88% of children and adolescents annually^10,11 and an opportunity to identify conditions that, although not necessarily related to or requiring restriction from athletic participation, nonetheless call for additional follow-up.⁹ Some authors¹² have advocated this practice to evaluate the general health of the athlete and to provide an opening to discuss high-risk behaviors, preventive care measures, and nonathletic concerns. Others oppose this view, stating that the PPE “should not be the sole component of health care for athletes”⁶ and that the PPE can only be effective if the goals remain specific and properly directed toward the demands of sport participation.^6,13     

Comprehensive Biomarker Testing of Glycemia,Insulin Resistance,and Beta Cell Function Has Greater Sensitivity to Detect Diabetes Risk Than Fasting Glucose and HbA1c and Is Associated with Improved Glycemic Control in Clinical Practice

Blood-based biomarker testing of insulin resistance (IR) and beta cell dysfunction may identify diabetes risk earlier than current glycemia-based approaches. This retrospective cohort study assessed 1,687 US patients at risk for cardiovascular disease (CVD) under routine clinical care with a comprehensive panel of 19 biomarkers and derived factors related to IR, beta cell function, and glycemic control. The mean age was 53?±?15, 42 % were male, and 25 % had glycemic indicators consistent with prediabetes. An additional 45 % of the patients who had normal glycemic indicators were identified with IR or beta cell abnormalities. After 5.3 months of median follow-up, significantly more patients had improved than worsened their glycemic status in the prediabetic category (35 vs. 9 %; P?HbA1c values of 5.5–5.6; 56 vs. 18 %, p?相似文献   

In between: Gypsy in Drosophila melanogaster Reveals New Insights into Endogenous Retrovirus Evolution

Retroviruses are RNA viruses that are able to synthesize a DNA copy of their genome and insert it into a chromosome of the host cell. Sequencing of different eukaryote genomes has revealed the presence of many such endogenous retroviral sequences. The mechanisms by which these retroviral sequences have colonized the genome are still unknown, and the endogenous retrovirus gypsy of Drosophila melanogaster is a powerful experimental model for deciphering this process in vivo. Gypsy is expressed in a layer of somatic cells, and then transferred into the oocyte by an unknown mechanism. This critical step is the start of the endogenization process. Moreover gypsy has been shown to have infectious properties, probably due to its envelope gene acquired from a baculovirus. Recently we have also shown that gypsy maternal transmission is reduced in the presence of the endosymbiotic bacterium Wolbachia. These studies demonstrate that gypsy is a unique and powerful model for understanding the endogenization of retroviruses.     

A cross-sectional study on factors associated with health seeking behaviour of Malawians aged 15+ years in 2016

IntroductionHealth seeking behaviour (HSB) refers to actions taken by individuals who are ill in order to find appropriate remedy. Most studies on HSB have only examined one symptom or covered only a specific geographical location within a country. In this study, we used a representative sample of adults to explore the factors associated with HSB in response to 30 symptoms reported by adult Malawians in 2016.MethodsWe used the 2016 Malawi Integrated Household Survey dataset. We fitted a multilevel logistic regression model of likelihood of ‘seeking care at a health facility’ using a forward step-wise selection method, with age, sex and reported symptoms entered as a priori variables. We calculated the odds ratios (ORs) and their associated 95% confidence intervals (95% CI). We set the level of statistical significance at P < 0.05.ResultsOf 6909 adults included in the survey, 1907 (29%) reported symptoms during the 2 weeks preceding the survey. Of these, 937 (57%) sought care at a health facility. Adults in urban areas were more likely to seek health care at a health facility than those in rural areas (AOR = 1.65, 95% CI: 1.19–2.30, P = 0.003). Females had a higher likelihood of seeking care from health facilities than males (AOR = 1.26, 95% CI: 1.03–1.59, P = 0.029). Being of higher wealth status was associated with a higher likelihood of seeking care from a health facility (AOR = 1.58, 95% CI: 1.16–2.16, P = 0.004). Having fever and eye problems were associated with higher likelihood of seeking care at a health facility, while having headache, stomach ache and respiratory tract infections were associated with lower likelihood of seeking care at a health facility.ConclusionThis study has shown that there is a need to understand and address individual, socioeconomic and geographical barriers to health seeking to increase access and appropriate use of health care and fast-track progress towards Universal Health Coverage among the adult population.