Load that maximizes power output in countermovement jump

Introduction: One of the main problems faced by strength and conditioning coaches is the issue of how to objectively quantify and monitor the actual training load undertaken by athletes in order to maximize performance. It is well known that performance of explosive sports activities is largely determined by mechanical power. Objective: This study analysed the height at which maximal power output is generated and the corresponding load with which is achieved in a group of male-trained track and field athletes in the test of countermovement jump (CMJ) with extra loads (CMJEL). Methods: Fifty national level male athletes in sprinting and jumping performed a CMJ test with increasing loads up to a height of 16 cm. The relative load that maximized the mechanical power output (Pmax) was determined using a force platform and lineal encoder synchronization and estimating the power by peak power, average power and flight time in CMJ. Results: The load at which the power output no longer existed was at a height of 19.9 ± 2.35, referring to a 99.1 ± 1% of the maximum power output. The load that maximizes power output in all cases has been the load with which an athlete jump a height of approximately 20 cm. Conclusion: These results highlight the importance of considering the height achieved in CMJ with extra load instead of power because maximum power is always attained with the same height. We advise for the preferential use of the height achieved in CMJEL test, since it seems to be a valid indicative of an individual's actual neuromuscular potential providing a valid information for coaches and trainers when assessing the performance status of our athletes and to quantify and monitor training loads, measuring only the height of the jump in the exercise of CMJEL.Actividad Física y Deport

The four serotypes of dengue recognize the same putative receptors in Aedes aegypti midgut and Ae. albopictus cells

BACKGROUND: Dengue viruses (DENV) attach to the host cell surface and subsequently enter the cell by receptor-mediated endocytosis. Several primary and low affinity co-receptors for this flavivirus have been identified. However, the presence of these binding molecules on the cell surface does not necessarily render the cell susceptible to infection. Determination of which of them serve as bona fide receptors for this virus in the vector may be relevant to treating DENV infection and in designing control strategies. RESULTS: (1) Overlay protein binding assay showed two proteins with molecular masses of 80 and 67 kDa (R80 and R67). (2) Specific antibodies against these two proteins inhibited cell binding and infection. (3) Both proteins were bound by all four serotypes of dengue virus. (4) R80 and R67 were purified by affinity chromatography from Ae. aegypti mosquito midguts and from Ae albopictus C6/36 cells. (5) In addition, a protein with molecular mass of 57 kDa was purified by affinity chromatography from the midgut extracts. (6) R80 and R67 from radiolabeled surface membrane proteins of C6/36 cells were immunoprecipitated by antibodies against Ae. aegypti midgut. CONCLUSION: Our results strongly suggest that R67 and R80 are receptors for the four serotypes of dengue virus in the midgut cells of Ae. aegypti and in C6/36 Ae. albopictus cells

Electrode-dependent asymmetric conduction mechanisms in K0.5Na0.5NbO3 micro-capacitors

The ultimate performance of devices employing lead-free piezoelectrics is determined not only by the intrinsic properties of the piezo, but also by processes and materials employed to create the electric contacts. In this paper, we investigate the impact of different metallic electrodes with increasing chemical reactivity (Pt, Ni, Ti, Cr), on the asymmetric behavior of the leakage current in M/K0.5Na0.5NbO3/Pt(111) micro-capacitors, where M stands for the top metallic electrode. For all electrodes we found a marked leakage asymmetry that we ascribed to the presence of a Schottky-like rectifying junction at the M/K0.5Na0.5NbO3/Pt(111) bottom interface, while the corresponding junction at the top interface is deeply affected by the creation of oxygen vacancies due to oxygen scavenging during the growth of the top metallic electrodes, leading to an almost ohmic top contact. The leakage increases with the reactivity of the electrodes, while the asymmetry decreases, thus suggesting that the creation of the top metal/K0.5Na0.5NbO3 interface generates oxygen vacancies diffusing down to the bottom interface and impacting on the rectifying behavior of the Schottky-like junction. Noteworthy, this asymmetric conduction can reflect in an asymmetric piezoelectric and ferroelectric behavior, as a sizable portion of the applied voltage drops across the rectifying junction in reverse bias, thus hampering symmetric bipolar operation, especially in leaky materials

¿Cuál es su diagnóstico?

ResumenSe trata de un paciente masculino de 58 años de edad, procedente de área rural, que refiere dolor torácico y disfagia, asociado a disnea leve, de inicio hace varios meses. Tiene como antecedente haber presentado cáncer de esófago hace tres años, por lo cual fue operado y sometido a radioterapia; no aporta más información relacionada ni trae estudios previos. Niega otros antecedentes. El examen fisico no muestra hallazgos de importancia

ALMIDÓN DE YUCA MODIFICADO POR COPOLIMERIZACIÓN CON ACRILONITRILO

Se describe el aprovechamiento del almidón de yuca para producir copolímeros de injerto con acrilonitrilo, mediante reacción iniciada por oxidoreducción con sulfato ferroso y peróxido de hidrógeno en medio acuoso.El almidón fue utilizado tanto en forma granular como gelatinizado, haciendo un seguimiento de los efectos de proporción de mezcla de reactivos y las temperaturas del pretratamiento del almidón y del medio reaccionante.Los mejores resultados se presentaron operando con suspensiones de almidón del 8% en peo, gelatinizado a 74 ºC durante 30 minutos y utilizando relaciones en peso de 1,5 acrilonitrilo/almidón y 0,0095 Sulfato Ferroso/Almidón; igualmente una relación volúmetrica de 0,0254 Peróxido/Acrilonitrilo. La copolimerización ocurrió favorablemente a 27 ºC durante 3 horas en atmósfera de Nitrógeno.El copolímero obtenido contiene cerca del 45% en peso de poliacrilonitrilo, el cual fue posteriormente sometido a saponificación convirtiendo los grupos nitrilo a una mezcla de carboxilo y carboxamida, con lo cual el materil exhibe propiedades útiles como absorbente acuoso y como floculante de suspensiones de sólidos.Las pruebas de aplicación como absorbente indican que el copolímero saponificado tiene una capacidad de absorción de 100 mL de agua por gramo y aproximadamente 15 mL de solución de Urea al 1,94% por gramo de copolímero. AbstractStarch derived from native plant manihot esculenta was studied to obtain graft copolymers with acrylonitrile using a Ferrous-hydrogen peroxide initiation system.The effect of concentration, starch pretreatment, reactant ratios and temperature are discussed.The saponified starch-polyacrylonitrile graft copolymers were tested as absorbent products

Dissipative Dynamics of Polymer Phononic Materials

Phononic materials are artificial composites with unprecedented abilities to control acoustic waves in solids. Their performance is mainly governed by their architecture, determining frequency ranges in which wave propagation is inhibited. However, the dynamics of phononic materials also depends on the mechanical and material properties of their constituents. In the case of viscoelastic constituents, such as most polymers, it is challenging to correctly predict the actual dynamic behavior of real phononic structures. Existing studies on this topic either lack experimental evidence or are limited to specific materials and architectures in restricted frequency ranges. A general framework is developed and employed to characterize the dynamics of polymer phononic materials with different architectures made of both thermoset and thermoplastic polymers, presenting qualitatively different viscoelastic behaviors. Through a comparison of experimental results with numerical predictions, the reliability of commonly used elastic and viscoelastic material models is evaluated in broad frequency ranges. Correlations between viscous effects and the two main band-gap formation mechanisms in phononic materials are revealed, and experimentally verified guidelines on how to correctly predict their dissipative response are proposed in a computationally efficient way. Overall, this work provides comprehensive guidelines for the extension of phononics modeling to applications involving dissipative viscoelastic materials.</p

Differential expression of dnaA and dosR genes among members of the Mycobacterium tuberculosis complex under oxic and hypoxic conditions

Major differences regarding the pathology and host immune response of the Beijing and Canettii genotypes of Mycobacterium tuberculosis have been reported; however, studies on the genetic expression of these genotypes during in vitro dormancy are scarce. This study examined the expression of five cell-cycle-related genes and two dormancy-related genes in M. canettii, M. tuberculosis H37Rv, and M. tuberculosis Beijing during the Wayne model of dormancy. The results showed that under hypoxic conditions the three tuberculosis genotypes were able to transcribe genes involved in DNA replication and cellular division. In addition, dosR was found to be up-regulated in M. tuberculosis Beijing during the exponential growth phase but down-regulated under hypoxic conditions. In this genotype, the replication-related gene dnaA was also strongly down-regulated. These latter two findings suggest that, compared to M. tuberculosis H37Rv and M. canettii, the Beijing genotype has a lower capacity to synthesize dosR, hspX, and dnaA mRNAs during in vitro dormancy. [Int Microbiol 2010;13(1):9-13

Features of dengue and chikungunya infections of colombian children under 24 months of age admitted to the emergency department

We aimed to assess clinical and laboratory differences between dengue and chikungunya in children <24 months of age in a comparative study. We collected retrospective clinical and laboratory data confirmed by NS1/IgM for dengue for 19 months (1 January 2013 to 17 August 2014). Prospective data for chikungunya confirmed by real-time polymerase chain reaction were collected for 4 months (22 September 2014-14 December 2014). Sensitivity and specificity [with 95% confidence interval (CI)] were reported for each disease diagnosis. A platelet count <150 000 cells/ml at emergency admission best characterized dengue, with a sensitivity of 67% (95% CI, 53-79) and specificity of 95% (95% CI, 82-99). The algorithm developed with classification and regression tree analysis showed a sensitivity of 93% (95% CI, 68-100) and specificity of 38% (95% CI, 9-76) to diagnose dengue. Our study provides potential differential characteristics between chikungunya and dengue in young children, especially low platelet counts. © The Author [2017].Universidad Nacional de Colombia, UN Johns Hopkins University1Departamento de Epidemiologia, Hospital Infantil Napoleón Franco Pareja—La Casa del Niño, Cartagena, Colombia 2Facultad de Medicina, Universidad Nacional de Colombia, Bogotá, Colombia 3Departamento de Epidemiologia, Faculdade de Saúde Publica, Universidade de São Paulo, São Paulo, Brazil 4Facultad de Ingenería, Universidad Tecnológica de Bolívar, Cartagena, Colombia 5Facultad Ciencias Básicas y Biomédicas, Universidad Simón Bolívar, Barranquilla, Colombia 6Facultad de Medicina, Universidad de Cartagena, Cartagena, Colombia 7Instituto de Investigaciones Biologicas del Tropico, Universidad de Córdoba, Montería, Colombia 8Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA Correspondence: Angel Paternina-Caicedo, Hospital Infantil Napoleón Franco Pareja—La Casa del Niño, Bruselas Transversal 36 N. 36-33, Cartagena, Bolívar, Colombia. Tel: +1-412-3267809. E-mail or

First insights into the genetic diversity of Mycobacterium tuberculosis isolates from HIV-infected Mexican patients and mutations causing multidrug resistance

<p>Abstract</p> <p>Background</p> <p>The prevalence of infections with <it>Mycobacterium tuberculosis </it>(MTb) and nontuberculous mycobacteria (NTM) species in HIV-infected patients in Mexico is unknown. The aims of this study were to determine the frequency of MTb and NTM species in HIV-infected patients from Mexico City, to evaluate the genotypic diversity of the <it>Mycobacterium tuberculosis </it>complex strains, to determine their drug resistance profiles by colorimetric microplate Alamar Blue assay (MABA), and finally, to detect mutations present in <it>kat</it>G, <it>rpo</it>B and <it>inh</it>A genes, resulting in isoniazid (INH) and rifampin (RIF) resistance.</p> <p>Results</p> <p>Of the 67 mycobacterial strains isolated, 48 were identified as MTb, 9 as <it>M. bovis</it>, 9 as <it>M. avium </it>and 1 as <it>M. intracellulare</it>. IS<it>6110</it>-RFLP of 48 MTb strains showed 27 profiles. Spoligotyping of the 48 MTb strains yielded 21 patterns, and 9 <it>M. bovis </it>strains produced 7 patterns. Eleven new spoligotypes patterns were found. A total of 40 patterns were produced from the 48 MTb strains when MIRU-VNTR was performed. Nineteen (39.6%) MTb strains were resistant to one or more drugs. One (2.1%) multidrug-resistant (MDR) strain was identified. A novel mutation was identified in a RIF-resistant strain, GAG → TCG (Glu → Ser) at codon 469 of <it>rpo</it>B gene.</p> <p>Conclusions</p> <p>This is the first molecular analysis of mycobacteria isolated from HIV-infected patients in Mexico, which describe the prevalence of different mycobacterial species in this population. A high genetic diversity of MTb strains was identified. New spoligotypes and MIRU-VNTR patterns as well as a novel mutation associated to RIF-resistance were found. This information will facilitate the tracking of different mycobacterial species in HIV-infected individuals, and monitoring the spread of these microorganisms, leading to more appropriate measures for tuberculosis control.</p