Comparison of muscle strength and flexibility between the preferred and non-preferred leg in English soccer players

Most soccer players have a favoured foot for kicking the ball, and it is believed that this preference may lead to an asymmetry in the strength and flexibility of the lower extremities. This study was designed to determine whether asymmetry in strength and flexibility are present in the legs of soccer players.Forty-one elite and sub-elite soccer players (age 23.4 +/- 3.8 years; height 1.81 +/- 0.06 m; body mass 81.7 +/- 9.9 kg) were studied (data are presented as mean +/- SD). The dynamic strength of knee flexors (hamstrings) and knee extensors (quadriceps) was measured using an isokinetic dynamometer at angular velocities of 1.05, 2.09, 5.23 rad/s (in a concentric mode) and 2.09 rad/s (in an eccentric mode). The concentric strength ratio (hamstrings(conc)/quadriceps(conc)) and the dynamic control ratio (hamstrings(ecc)/quadriceps(conc)) were computed. Hip joint flexibility (in flexion) was measured using a goniometer.A significant difference between the preferred and non-preferred leg was found in the knee flexors at 2.09 rad/s (119 +/- 22 versus 126 +/- 24 Nm; P < 0.05) and for the dynamic control ratio (0.79 +/- 0.13 versus 0.84 +/- 0.16 Nm; P < 0.05). In both cases the knee flexors of the preferred leg were weaker than those of the non-preferred leg. A total of 28 of the 41 players (68%) had significant musculoskeletal abnormality (imbalance >10%) in one or more specific muscle groups. No significant differences were found in flexibility of the hip joint between the preferred and non-preferred leg (P > 0.05).It is concluded that the lower strength of the knee flexor muscles of the preferred leg may be associated with the differential use of these muscle during the kicking action and thus constitutes a unique training effect associated with soccer. This in turn can lead to muscular imbalance which is generally regarded as an injury risk factor.     

Single DNA molecule detection using nanopipettes and nanoparticles

Single DNA molecules labeled with nanoparticles can be detected by blockades of ionic current as they are translocated through a nanopipette tip formed by a pulled glass capillary. The nanopipette detection technique can provide not only tools for detection and identification of single DNA and protein molecules but also deeper insight and understanding of stochastic interactions of various biomolecules with their environment.     

Small-diameter (2 mm) laparoscopy in the evaluation of liver disease

We report the case of a pathological mediopatellar plica found in the right knee of a 15-month-old infant girl. Flexion contracture of the knee was found to be 40 degrees. An arthroscopic view showed a large and thick voluminous mediopatellar plica. It was trapped between the patella and the medial femoral condyle and it was in tight contact with the medial facet of the patella at 40 degrees flexion in the knee, blocking further extension. A longitudinal groove was noted on the articular surface of the medial femoral condyle that looked as if it had another trochlea on arthroscopic view. The mediopatellar plica came into contact with the groove at 60 degrees flexion in the knee and it fitted precisely into the groove at further flexion. The pathological plica was resected arthroscopically, which resulted in approximately 10 degrees improvement in extension of the knee. Histological examination found hypertrophy and chronic nonspecific inflammation of the synovium. The patient was helped with range-of-motion exercise and quadriceps-strengthening exercise. At 27 months follow-up, the knee had gained full extension. This article reports that a pathological mediopatellar plica may develop in infants.     

A time‐dependent multiphysics,multiphase modeling framework for carbon nanotube synthesis using chemical vapor deposition

A time‐dependent multiphysics, multiphase model is proposed and fully developed here to describe carbon nanotubes (CNTs) fabrication using chemical vapor deposition (CVD). The fully integrated model accounts for chemical reaction as well as fluid, heat, and mass transport phenomena. The feed components for the CVD process are methane (CH₄), as the primary carbon source, and hydrogen (H₂). Numerous simulations are performed for a wide range of fabrication temperatures (973.15–1273.15 K) as well as different CH₄ (500–1000 sccm) and H₂ (250–750 sccm) flow rates. The effect of temperature, total flow rate, and feed mixture ratio on CNTs growth rate as well as the effect of amorphous carbon formation on the final product are calculated and compared with experimental results. The outcomes from this study provide a fundamental understanding and basis for the design of an efficient CNT fabrication process that is capable of producing a high yield of CNTs, with a minimum amount of amorphous carbon. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Effect of solar chimney inclination angle on space flow pattern and ventilation rate

The solar chimney is a simple and practical idea that is applied to enhance space natural ventilation. The chimney could be vertical or inclined. The chimney inclination angle is an important parameter that greatly affects space flow pattern and ventilation rate.In the present study, the effect of chimney inclination angle on air change per hour and indoor flow pattern was numerically and analytically investigated. A numerical simulation using Ansys, a FEM-based code, was used to predict flow pattern. Then the results were compared with published experimental measurements. A FORTRAN program was developed to iteratively solve the mathematical model that was obtained through an overall energy balance on the solar chimney.The analytical results showed that an optimum air flow rate value was achieved when the chimney inclination is between 45° and 70° for latitude of 28.4°. The numerically predicted flow pattern inside the space supports this finding. Moreover, in the present study a correlation to predict the air change per hour was developed. The correlation was tested within a solar intensity greater than or equal to 500 W/m², and chimney width from 0.1 m to 0.35 m for different inclination angles with acceptable values.     

A chromium complex under water oxidation: A conversion mechanism and a comprehensive hypothesis

Water splitting toward hydrogen production is a promising method to store energy, but water oxidation is a bottleneck for water splitting. First-row transition metal complexes have been extensively used for water-oxidation reaction. However, only one chromium complex has been applied for water-oxidation reaction until now. Thus, the reinvestigation of water-oxidation reaction by this chromium complex in detail is interesting. Herein, water-oxidation reaction by the chromium complex with diphenoxy N,N′-ethylenebis(salicylimine) (SALEN) ligand is reinvestigated using scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction studies, X-ray photoelectron spectroscopy, thermal gravimetric analysis, elemental analysis, Fourier-transform infrared spectroscopy, and electrochemical methods. All the experiments showed that the chromium complex is neither a catalyst nor a precatalyst for water-oxidation reaction. During OER, a relationship between first-row transition metal complexes and the related metal oxides has been proposed.     

Microstructure and Optical Bandgap of Cobalt Selenide Nanofilms

Semiconductors - The purpose of this research is to explore the properties of CoSe nanostructured thin films on glass substrates prepared by a chemical solution deposition method. Special attention...     

Benders Decomposition Algorithms for Two Variants of the Single Allocation Hub Location Problem

Networks and Spatial Economics - The hub location problem (HLP) is a special type of the facility location problem with numerous applications in the airline industry, postal services, and computer...     

Simulation of CNT based mass resonator sensor and investigation on the effect of vacancy defect on sensing performances

Microsystem Technologies - In this paper carbon nanotube (CNT) as a mass resonator sensor has been modelled by molecular structural mechanics approach. Then the effect of a single vacancy defect...     

Synthesis and characterization of silicone-modified vinyl acetate–acrylic emulsion copolymers

The triethoxyvinylsilane (TEVS) containing vinyl acetate (VAc)/2-ethylhexylacrylate (2-EHA) copolymers were prepared by emulsion copolymerization. The polymerization was performed with methacrylic acid (MAA) and auxiliary agents at 80 °C in the presence of ammonium peroxodisulfate (APS) as the initiator. Alkyl phenol ether sulfate and Arkupal N-300 were used as anionic and nonionic emulsifiers, respectively. The resulting copolymers were characterized by using Fourier transform infrared spectroscopy (FTIR). Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphology of copolymers was also investigated by scanning electron microscopy (SEM) and then the effects of temperature, agitation speed, initiator and silicone concentrations on the properties of the silicone-modified VAc–acrylic emulsion copolymers were discussed. The obtained copolymers have high solid content (53%) and can be used in emulsion paints as a binder. The calculations of monomer conversion versus time histories and monomer conversion indicate that by increasing the TEVS concentration, the polymerization rate and the number of polymer particles decrease, respectively.