The influence of resting period length on jumping performance

Pereira, G, Almeida, AG, Rodacki, ALF, Ugrinowitsch, C, Fowler, NE, Kokubun, E. The influence of resting period length on jumping performance. J Strength Cond Res 22: 1259-1264, 2008-The purpose of this study was to determine a resting interval between countermovement jumps (i.e., volleyball spikes) that allows the maintenance of maximal jumping performance. Ten male volleyball players (1.85 +/- 0.05 m, 77.2 +/- 10.6 kg, 21.6 +/- 5.3 years) performed 6 experimental jumping sessions. In the first and sixth sessions, maximal countermovement jump height was measured, followed by submaximal countermovement jumps to the point of volitional fatigue. The number of countermovement jumps was used as a reference to test the effect of rest period between volleyball spikes. From the second to fifth experimental sessions, 30 maximal volleyball spikes were performed with different resting periods (i.e., 8, 14, 17, and 20 seconds) followed by countermovement jumps. Between the 15th and 30th spikes, the blood lactate concentration and heart rate were measured. Because the performance on the first and sixth sessions was the same, no training effects were noticed. During the 8-second resting interval set, the lactate concentration increased significantly between the 15th and 30th spikes (i.e., from 3.37 +/- 1.16 mmol to 4.94 +/- 1.49 mmol); the number of countermovement jumps decreased significantly after spikes compared to those performed without a previous effort (i.e., from 23 +/- 7 jumps to 17 +/- 9 jumps); and these variables were significantly correlated (r = -0.7). On the other hand, the lactate concentration and number of countermovement jumps were stable across the other resting intervals, without a heart rate steady state. The results indicate that an adequate resting period between spikes allowed participants to achieve a lactate steady state in which the performance was maintained during the exercise. These findings show that resting intervals between 14 and 17 seconds, typical during volleyball matches, are indicated to use in volleyball spike drills due to their capacity to maintain maximal jumping performance.

Influence of concrete strength and length/diameter on the axial capacity of CFT columns

This paper presents an experimental analysis of the confinement effects in steel-concrete composite columns regarding two parameters: concrete compressive strength and column slenderness. Sixteen concrete-filled steel tubular columns with circular cross section were tested under axial loading. The tested columns were filled by concrete with compressive strengths of 30, 60. 80, and 100 MPa, and had length/diameter ratios of 3, 5, 7, and 10. The experimental values of the columns` ultimate load were compared to the predictions of 4 code provisions: the Brazilian Code NBR 8800:2008, Eurocode 4 (EN 1994-1-1:2004), AINSI/AISC 360:2005, and CAN/CSA S16-01:2001. According to the results, the load capacity of the composite columns increased with increasing concrete strength and decreased with increasing length/diameter ratio. In general, the code provisions were highly accurate in the prediction of column capacity. Among them, the Brazilian Code was the most conservative, while Eurocode 4 presented the values closest to the experimental results. (C) 2009 Elsevier Ltd. All rights reserved.

Proposal of a test specimen to evaluate the shear strength of vertical interfaces of running bond masonry walls

There is no normalized test to assess the shear strength of vertical interfaces of interconnected masonry walls. The approach used to evaluate this strength is normally indirect and often unreliable. The aim of this study is to propose a new test specimen to eliminate this deficiency. The main features of the proposed specimen are failure caused by shear stress on the vertical interface and a small number of units (blocks). The paper presents a numerical analysis based on the finite element method, with the purpose of showing the theoretical performance of the designed specimen, in terms of its geometry, boundary conditions, and loading scheme, and describes an experimental program using the specimen built with full- and third-scale clay blocks. The main conclusions are that the proposed specimen is easy to build and is appropriate to evaluate the sheaf strength of vertical interfaces of masonry walls.

A layered finite element for reinforced concrete beams with bond-slip effects

The behaviour of reinforced concrete members is affected by the slipping of steel bars inserted in the concrete matrix. A tension-stiffening effect and crack evolution occur from the beginning of slipping; thus, the assessment of those phenomena requires the introduction of a bond-slip interaction model. This work presents a beam-layered model, including the constitutive relationships of materials and their interaction, according to the CEB-FIP Model Code 1990. To eliminate the finite element sub-division procedure, a continuous slip function is imposed into the element domain. The results are continuous descriptions of bond stress in the steel-concrete interface, as well as concrete and steel stresses along the element. (C) 2007 Elsevier Ltd. All rights reserved.

Bond strength and transversal deformation aging on cement-polymer adhesive mortar

Polymer-modified mortar is widely used to set ceramic tiles used as external finishing for high rise buildings in countries such as Brazil, Israel, Singapore and Portugal, mainly because it shows better bond strength and flexibility as compared to the traditional ones. Despite this, the results in the literature already published concerning the long-term performance of those composite mortars are is not conclusive. This paper, based on a laboratory program, compared the performance over time of four commercial polymer-modified adhesive mortars exposed to a typical Brazilian outdoor aging environment and to an indoor environment in terms of mortar flexibility and the bond strength to porcelain tiles. The results show that under laboratory condition, the mortars are more flexible and have higher bond strength than under external condition, and that there is an important correlation between the transversal deformability and the bond strength. (C) 2008 Elsevier Ltd. All rights reserved.

Effect of the domain spanwise periodic length on the flow around a circular cylinder

We assess the effect of the choice of spanwise periodic length on simulations of the flow around a fixed circular cylinder. The Reynolds number is set to 400 because, at this value, both lift coefficient and shedding frequency show significant drop due to three-dimensional flow structures. From the analysis of the three-dimensionalities of the wake and of the integral quantities such as Strouhal number, RMS of lift coefficient and energy contained in the three-dimensional portion of the flow we obtain an estimate of the minimum spanwise length to satisfactorily represent the flow. Furthermore, we observe a distinct wake behavior when the spanwise length is approximately the mode B instability wavelength. (C) 2011 Elsevier Ltd. All rights reserved.

Galerkin finite element method for incompressible thermofluid flows framed within the bond graph theory

In this paper a bond graph methodology is used to model incompressible fluid flows with viscous and thermal effects. The distinctive characteristic of these flows is the role of pressure, which does not behave as a state variable but as a function that must act in such a way that the resulting velocity field has divergence zero. Velocity and entropy per unit volume are used as independent variables for a single-phase, single-component flow. Time-dependent nodal values and interpolation functions are introduced to represent the flow field, from which nodal vectors of velocity and entropy are defined as state variables. The system for momentum and continuity equations is coincident with the one obtained by using the Galerkin method for the weak formulation of the problem in finite elements. The integral incompressibility constraint is derived based on the integral conservation of mechanical energy. The weak formulation for thermal energy equation is modeled with true bond graph elements in terms of nodal vectors of temperature and entropy rates, resulting a Petrov-Galerkin method. The resulting bond graph shows the coupling between mechanical and thermal energy domains through the viscous dissipation term. All kind of boundary conditions are handled consistently and can be represented as generalized effort or flow sources. A procedure for causality assignment is derived for the resulting graph, satisfying the Second principle of Thermodynamics. (C) 2007 Elsevier B.V. All rights reserved.

Influence of egg pre-storage heating period and storage length on incubation results

This experiment aimed at evaluating the influence of different heating times of settable eggs of Cobb 500 (R) broiler breeders before submitting them to different storage periods on egg weight loss, embryo mortality, and hatchability. A total number of 1,980 eggs were distributed in a completely randomized experimental design with a 3 x 3 factorial arrangement, comprising nine treatments with 22 replicates of 10 eggs each. The following factors were analyzed: pre-storage heating periods (0, 6, 12 hours at 36.92 degrees C) and storage periods (4, 9, 14 days at 12.06 degrees C). After storage, eggs were incubated under usual conditions, and were transferred to the hatcher at 442 hours of incubation. Eggs were weighed before heating, incubation, and transference to determine weight loss. Partial hatchability was determined at 480 hours, and total hatchability at 498 hours of incubation. Embryo mortality was determined in non-hatched eggs. It was concluded that heating eggs for six hour before storage improves incubation results as it decreases incubation length and late embryo mortality, therefore its use can be indicated in commercial operations. Storing eggs for 14 days and pre-heating for 14 days and pre-heating for 12 hours severely impair incubation results, and therefore are not recommended.

Influence of egg pre-storage heating period and storage length on the digestive tract of newly-hatched broiler chicks

An experiment was carried out to evaluate the effect of different heating times of settable eggs of Cobb 500 (R) broiler breeders before submitting them to different storage periods on body weight, digestive tract organ weights, and intestinal mucosa morphology of newly-hatched chicks. Settable eggs were distributed in a completely randomized experimental design with a 3 x 3 factorial arrangement: pre-storage heating periods (0, 6, 12 hours at 36.92 degrees C) and storage periods (4, 9, 14 days at 12.06 degrees C). Body weight and relative weights of the yolk sac, heart, liver, proventriculus+gizzard, and intestinal segments were measured in chicks hatching at 480 and 498 hours of incubation. Villi height, width and perimeter, and crypt depth < im) were measured in duodenal histological sections. It was concluded that pre-storage healing for six hours of eggs stored for four or nine days increases small intestine weight of newly-hatched chicks, but does not influence the morphology of the duodenal mucosa. Pre-storage heating for 12 hours negatively influences body weight and duodenal mucosa development, and therefore this practice is not recommended. Storage length does not have consistent effect on body weight and development of the gastrointestinal tract.

Detection of the TLR4 1196C > T Polymorphism by Mismatched-Polymerase Chain Reaction Using Plasmid DNA as Internal Control in Restriction Fragment Length Polymorphism Assays

Background: Restriction fragment length polymorphism (RFLP) is a common molecular assay used for genotyping, and it requires validated quality control procedures to prevent mistyping caused by impaired endonuclease activity. We have evaluated the usefulness of a plasmid-based internal control in RFLP assays. Results: Blood samples were collected from 102 individuals with acute myocardial infarction (AMI) and 108 non-AMI individuals (controls) for DNA extraction and laboratory analyses. The 1196C> T polymorphism in the toll-like receptor 4 (TLR4) gene was amplified by mismatched-polymerase chain reaction (PCR). Amplicons and pBluescript II SK-plasmid were simultaneously digested with endonuclease HincII. Fragments were separated on 2% agarose gels. Plasmid was completely digested using up to 55.2 nmL/L DNA solutions and 1 mu L PCR product. Nevertheless, plasmid DNA with 41.4 nM or higher concentrations was incompletely digested in the presence of 7 mL PCR product. In standardized conditions, TLR4 1196C> T variant was accurately genotyped. TLR4 1196T allele frequency was similar between AMI (3.1%) and controls (2.0%, p = 0.948). TLR4 SNP was not associated with AMI in this sample population. In conclusion, the plasmid-based control is a useful approach to prevent mistyping in RFLP assays, and it is validate for genetic association studies such as TLR4 1196C> T.

Dissemination of bla(IMP-1)-carrying integron In86 among Klebsiella pneumoniae isolates harboring a new trimethoprim resistance gene dfr23

The genetic context of the bla(IMP-1) gene was evaluated in 9 Klebsiella pneumoniae isolates recovered from 2 hospitals in Sao Paulo, Brazil. All isolates harbored a copy of In86 carrying bla(Imp-1), aac(6`)-31, and aadAl. Eight strains from the same hospital also carried another class I integron harboring a new trimethoprim resistance gene (dfr23) that was chromosomally embedded. In86 was likely to be in a 30-kb nontransferable plasmid and was flanked upstream by a sequence identical to one identified in an IMP-1-producing Pseudomonas putida isolate. The bla(IMP-1)-carrying integron In86 was recently reported from nonfermentative bacilli isolated in Sao Paulo. These isolates appear to be the Source of this integron now acquired by K. pneumoniae strains from different hospitals in the same city. Metallo-beta-lactamase production is still rare among Enterobacteriaceae isolates in Brazil, but the acquisition of genetic structures carrying these mobile resistance determinants is worrisome and could lead to an increase in the prevalence of these phenotypes of resistance. (C) 2008 Elsevier Inc. All rights reserved.

In vitro Fluoride Release and Tensile Bond Strength of a Polymeric Intra-Buccal Bioadhesive

The intra-buccal polymeric bioadhesive systems that can stay adhered to the oral soft tissues for drug programmed release, with the preventive and/or therapeutic purpose has been employed for large clinical situations. A system based on hydroxypropyl methyl cellulose/Carbopol 934`/magnesium stearate (HPMC/Cp/StMg) was developed having the sodium fluoride as active principle. This kind of system was evaluated according to its resistance to the removal by means of physical test of tensile strength. Swine buccal mucosa extracted immediately after animals` sacrifice was employed as substrate for the physical trials, to obtain 16 test bodies. Artificial saliva with or without mucin was used to involve the substrate/bioadhesive system sets during the trials. Artificial salivas viscosity was determined by means of Brookfield viscometer, showing the artificial saliva with mucin 10.0 cP, and the artificial saliva without mucin 7.5 cP. The tensile strength assays showed the following averages: for the group ""artificial saliva with mucin"" - 12.89 Pa, and for the group ""without mucin"" - 12.35 Pa. Statistical analysis showed no significant difference between the assays for both artificial salivas, and it was possible to conclude that the variable mucin did not interfered with the bioadhesion process for the polymeric devices. The device was able to release fluoride in a safe, efficient and constant way up to 8 hours.

Bond strength of an adhesive system irradiated with Nd : YAG laser in dentin treated with Er : YAG laser

The purpose of this in vitro study was to verify through micro tensile bond test the bond strength of an adhesive system irradiated with Nd:YAG laser in dentine previously treated with Er:YAG laser. Twenty caries free extracted human third molars were used. The teeth were divided in four experimental groups (n = 5): (G1) control group; (G2) irradiation of the adhesive system with the Nd:YAG laser; (G3) dentin treatment with Er:YAG laser; (G4) dentin treatment with Er:YAG laser followed by the irradiation of the adhesive system with Nd:YAG laser. The Er:YAG laser fluency parameter for the dentin treatment was of 60 J/cm(2). ne adhesive system was irradiated with the Nd:YAG laser with fluency of 100 J/cm(2). Dental restorations were performed with Adper Single Bond 2/Z250. One tooth from each group was prepared for the evaluation of the adhesive interface under SEM and bond failure tests were also performed and evaluated. The statistical analysis showed statistical significant difference between the groups G1 and G3, G1 and G4, G2 and G3, and G2 and G4; and similarity between the groups G1 and G2, and G3 and G4. The adhesive failures were predominant in all the experimental groups. The SEM analysis showed an adhesive interface with features confirming the results of the mechanical tests. The Nd:YAG laser on the adhesive system did not influence the bond strength in dentin treated or not with the Er:YAG laser.

Two-stage transvaginal cervical length screening for preterm birth in twin pregnancies

Aim: To compare cervical length (CL) at 18-21 and 22-25 weeks` gestation in twin pregnancies in prediction of spontaneous preterm delivery and to examine cervical shortening. Methods: Retrospective cohort study of CL measured at 18-21 and 22-25 weeks` gestation in twin pregnancies. Results: Receiver operating characteristics (ROC) curve revealed area of 0.64 (95% CI 0.53-0.75) and 0.80 (95% CI 0.72-0.88) for measurements at 18-21 and 22-25 weeks, respectively (P <= 0.001). Sensitivities of 33.3% and 23% and negative predicting value (NPV) of 97.3% and 86.8% for delivery at <28 and <34 weeks gestation were reached for measurements at 18-21 weeks. Sensitivities of 71.4% and 38.2% and NPV of 99.1% and 91.4% for delivery at <28 and <34 weeks` gestation were reached for measurements at 22-25 weeks. Cervical length shortening analysis showed an area under ROC curve of 0.81 (95% CI 0.73-0.89) and best cut-off was at >= 2 mm/week. Sensitivities of 80% and 60.8% and NPV of 98.9% and 90.6% for delivery at <28 and <34 weeks gestation were reached. Conclusions: In twin gestations, assessment of CL at 22-25 weeks is better than assessment at 18-21 weeks to predict preterm delivery before 34 weeks. Cervical shortening at a rate of >= 2 mm/weeks between 18 and 25 weeks gestation was a good predictor of spontaneous preterm birth in this high-risk population.

Hormonal Contraceptives and the Length of Their Use Are Not Independent Risk Factors for High-Risk HPV Infections or High-Grade CIN

Aims: To evaluate the role of hormonal contraceptives as a risk factor of high-risk human papillomavirus (HR-HPV), cervical intraepithelial lesions (CIN) and cervical cancer in our multi-center population-based LAMS (Latin American Screening) study. Methods: A cohort study with >12,000 women from Brazil and Argentina using logistic regression to analyze the covariates of hormonal contraception (HOC - oral, injections, patches, implants, vaginal ring and progesterone intrauterine system) use followed by multivariate modeling for predictors of HR-HPV and CIN2+. Results: HR-HPV infection was a consistent risk factor of high-grade CIN in all three groups of women. The length of HOC use was not significantly related to high-grade squamous intraepithelial lesions (HSIL)+ Pap (p = 0.069), LSIL+ Pap (p = 0.781) or ASCUS+ (p = 0.231). The same was true with the length of HOC use and histology CIN3+ (p = 0.115) and CIN2+ (p = 0.515). Frequently, HOC users have previously shown more HPV-related lesions, as well as lower HPV prevalence if they were current smokers. But HOC use and time of usage were not independent risk factors of either HR-HPV infection or high-grade CIN using multiple logistic regressions. Conclusions: No evidence was found for an association between the use of HOC with an increased risk for HR-HPV infection or high-grade CIN in this cohort. Copyright (C) 2010 S. Karger AG, Basel