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The purpose of this study was to investigate the morphology of rotator cuff muscles and shoulder isokinetic strength in adolescent baseball players. Junior high school baseball players were divided into a skilled group (SG, 6 players) and an unskilled group (USG, 6 players), according to their baseball history. The maximal anatomical cross-sectional area, and the volume of the rotator cuff muscles (supraspinatus, external rotators: infraspinatus and teres minor, and subscapularis) were mesured on both sides of their shoulders using magnetic resonance imaging. In addition, isokinetic shoulder internal and external rotation strength (180 and 300°/sec) were measured with the shoulder abducted 90° and the elbow flexed 90° on both sides. The external/internal strength ratio was also calculated. The paired and unpaired t-tests were used to analyze the difference between the throwing and nonthrowing sides and between both groups, respectively. Although the maximal cross-sectional area and the volume of each muscle in the SG tended to be greater than those in the USG on both sides of the shoulder, both groups showed significantly greater subscapularis on the throwing side, regardless of their baseball history. Concerning the shoulder strength and the strength ratio, there were no significant differences between the throwing and nonthrowing sides in each group, or between groups. However, there was a significant correlation between the maximal cross-sectional area of the external rotators and the shoulder external rotational strength (180 and 300°sec) on both sides of the shoulder. This study suggests that remakable characteristics of repetitive throwing activities were not found in the morpholgy of the rotator cuff muscles and the shoulder rotation strength in junior high school baseball players. [ABSTRACT FROM AUTHOR]

Background: Intramuscular water movement is expected to be affected by the mechanical changes of the muscle fibers. However, the effect of changes in fiber length (FL) and pennation angle (PA) on the water movement has not been sufficiently investigated in human skeletal muscles. Purpose: To determine the relationship between intramuscular water movement and the mechanical changes in human muscle fibers. Material and Methods: Axial magnetic resonance diffusion-weighted images of the right leg (eight men) were taken using a 1.5-Tesla device with the ankle joint maximally dorsiflexed and maximally plantar flexed. The apparent diffusion coefficient (ADC) values of both the dorsiflexors (the superficial and deep parts of the tibialis anterior) and the plantar flexors (medial gastrocnemius and soleus) were calculated along three orthogonal axes (S-I: superior-to-inferior, A-P: anterior-to-posterior, and R-L: right-to-left). FL and PA of both muscle groups were also calculated from longitudinal B-mode ultrasound images with the ankle joint maximally dorsiflexed and plantar flexed. Results: There was a significant increase in the ADC in superficial (P < 0.05) and deep (P < 0.05) parts of the dorsiflexors in the S-I direction when the ankle was plantar flexed and in the A-P and R-L directions when the ankle was dorsiflexed (P < 0.05). The plantar flexors showed significantly elevated ADC in the S-I direction when the ankle was dorsiflexed (P < 0.05), and in the A-P and R-L directions when the ankle was plantar flexed (P < 0.05). The dorsiflexors also showed significantly increased PA and decreased FL values when the ankle was dorsiflexed (P < 0.05). The plantar flexors displayed similar morphological changes when the ankle was plantar flexed (P < 0.05). Conclusion: Water diffusion is affected by structural changes in the long axis of the muscle fibers, namely the changes in PA and FL. [ABSTRACT FROM AUTHOR]

Background: Muscle hardening, including delayed onset muscle soreness, can be found after vigorous exercise. Some techniques for measuring muscle hardness have been proposed. Freehand ultrasound (US) elastography has been developed and applied to breast imaging. Purpose: To evaluate the feasibility of US elastography for investigating changes in muscle hardness after eccentric exercise of the elbow flexor muscles. Material and Methods: Six healthy male volunteers performed eccentric contractions of the elbow flexor muscles of their non-dominant arms. US elastography was performed by using 14-6 MHz linear array transducer combined with a stabilizer and a gel pack of reference agent. Color-coded elasticity images and the relative strain ratio of the biceps brachii muscle to the reference were obtained. To verify the US elastography measurements, a commercially available durometer was also employed. Both measurements were performed before, immediately after, and 1-4 days after exercise. The mean scores of strain ratios of the US elastography and durometer measurements were examined using repeated-measures ANOVA. Results: US elastography demonstrated significant muscle hardening and recovery after exercise (P<0.01). Muscle hardness increased up immediately after the exercise and continued to increase, peaking on day 2 post-exercise, and then decreased until day 4. The durometer indicated similar changes to US elastography. The control arms did not demonstrate any significant change. Conclusion: US elastography is feasible to measure muscle hardness and to produce a two-dimensional hardness map of the muscle. [ABSTRACT FROM AUTHOR]

This study investigated the morphology of shoulder rotator cuff muscles and shoulder function in tennis players. Ten collegiate male tennis players (tennis group: TG) and 10 adult males (control group: CG) participated in this study. The muscle length, maximal anatomical cross-sectional area, and volume of shoulder rotator cuff muscles (supraspinatus, external muscle: infraspinatus and teres minor, and subscapularis) were mainly measured in their dominant shoulders using magnetic resonance imaging. In addition, isokinetic shoulder internal/ external strength (180 and 300deg/sec) was measured with the shoulder abducted to 90° and the elbow flexed to 90° in both groups. The external/internal strength ratio was also calculated. The unpaired t-test was used to analyze the difference between both groups. The TG showed a significantly larger value than the CG in the maximal anatomical cross-sectional area of the subscapularis (p<0.01). The TG also showed significantly larger values than the CG in the muscle volumes of the subscapularis, the shoulder external muscle, and total shoulder rotator cuff muscles (p<0.01). In addition, the isokinetic shoulder strength (180 and 300deg/sec) of the TG was significantly larger than that of the CG in internal and external rotations (p<0.01). It is possible that the repetitive racket motions resulted in muscle hypertrophy of shoulder rotator cuff muscles and elevated shoulder rotational strength in tennis players. [ABSTRACT FROM AUTHOR]

The present study tried to demonstrate the feasibility of muscle fiber tracking in human skeletal muscles using a 1.5 Tesla clinical MR device. Axial diffusion tensor images were obtained from the thigh or the leg of a healthy male subject. Muscle fiber tracking was performed using the software dTV.II for diffusion tensor analysis. This study showed the feasibility of providing 3D architectures of semitendinous muscle in the thigh, and ankle dorsiflexors peroneus longus/brevis muscles, and ankle plantar flexors in the leg. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate whether the effect of Nordic Hamstrings (NH) training, a partner exercise focusing on the eccentric phase for the prevention of hamstring strain differed between individual hamstrings [biceps femoris muscle long head (BF1) and short head (BFs), semimembranosus muscle (SM), and semitendinosus muscle (ST)]. Eight male volunteers performed six weeks of NH training. Load was gradually increased by a number of sets and exercising time to resist a forward--falling motion using hamstrings. To evaluate the training effect, the maximal isometric, concentric and eccentric knee flexion torques and the EMG activities of the hamstrings during isometric knee flexions were measured before, after the three weeks and after the six weeks training period. Moreover, the muscle volume of the hamstrings and the Gracilis muscle (G) were measured before and after the training period. There was a significant increase in eccentric knee flexion torque at 30°/sec, as well as an increase in isometric knee flexion torque at 15°, 30°, 45°, 60°, and 75°. Only in the ST did the EMG value significantly increase at 15° after the first three weeks of the training. Muscle volume of the ST, BFs and G increased significantly. These results showed that the effect of NH training for six weeks was different for each hamstring and the training had a marked effect for the ST. [ABSTRACT FROM AUTHOR]

The addition of Re, Fe and Cr into Ti–50 mol.-%Ni has been carried out to improve the oxidation and mechanical properties. The mono phase consisting of TiNi with the B2 type structure was identified in micro-alloyed materials proposed on the basis of the d-electrons concept. Experimentally, TiNi alloys were melted and solidified by the cold crucible levitation melting (CCLM) method. The TiNi–(Cr, Fe, Re) alloys with high purity and without contamination from a crucible were prepared, and the homogeneous microstructure was achieved by the diffusion mixing effect of CCLM even in the as-cast alloys which contained Re and Cr with higher melting temperatures and different specific gravities. The transformation from austenite to martensite phases occurred in all alloys below or above room temperature. Some alloys had the ability of shape memory even at room temperature. Ternary alloys showed a higher flow stress level compared with the binary TiNi alloy. On the other hand, the oxidation at 1273 K was promoted by the formation of titanium oxides (TiO2) on the alloy surfaces. The oxidation resistance was improved by the formation of the continuous Cr2O3 film in TiNi–Cr alloys. The alloying effects by ternary elements (Re, Fe, Cr) in the intermetallic TiNi as well as metallic materials were explained well using two parameters used in the d-electrons concept. [ABSTRACT FROM AUTHOR]

This study investigates the relation between T2-weighted MR image and delayed onset muscle soreness. Five healthy men (Mean ± SD. age: 23.4 ± 3.2 yr: height: 172.6 ± 5.5 cm; weight: 62.8 ± 6 kg) participated in this study. All subjects performed the ankle plantar flexion exercise including eccentric contraction (12 repetitions, 5 sets). Transaxial T2-weighted images of triceps surae muscle were obtained using a 1.5 Tesla superconducting imaging system before and 24, 48, 96, and 168 hours after exercise. T2 relaxation time (T2 value) was calculated for the medial gastrocnemius on the dominant side before and after exercise. In addition, the muscle soreness level was assessed at the same time as MRI measurements. All subjects showed the muscle soreness at 24-96 hours after exercise, while only 3 subjects showed the increased tendency in T2 value after post-exercise 48 hours. Elevation of T2 value is associated with increased intramuscular water content, and thus the present study suggests that exercise-induced edema is not always a determinant factor in delayed onset muscle soreness. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The purpose of this study was to investigate the muscle recruitment variations in the dynamic ankle plantar flexion. DESIGN: A total of 17 subjects participated in this study and performed the ankle plantar flexion exercise. Magnetic resonance T2-weighted images were obtained from the calf before and immediately after exercise to calculate each T2 relaxation time in the medial and lateral gastrocnemius, soleus, tibialis posterior, flexor digitorum/hallucis longus, peroneus longus, and dorsiflexors. RESULTS: All the muscles except the dorsiflexors showed significantly increased T2 relaxation time and signal intensity on T2-weighted images after exercise. Above all, both gastrocnemius muscles showed significantly greater postexercise T2 relaxation time than the soleus, tibialis posterior, flexor digitorum/hallucis longus, and dorsiflexors. In addition, the peroneus longus had a tendency to show the greatest T2 relaxation time next to the gastrocnemius, but there was no significant difference between them. CONCLUSIONS: The present study may suggest that the gastrocnemius muscle, especially the medial side, was best recruited in the dynamic ankle plantar flexion exercise. In addition, it is possible that the peroneus longus was most recruited next to the gastrocnemius in this exercise mode. [ABSTRACT FROM AUTHOR]

PURPOSE: To investigate the effects of cooling human skeletal muscle after strenuous exercise using 31P MR spectroscopy and MR imaging. METHODS: 14 male subjects (mean age +/- SD, 23.8 +/- 2.3 yr) were randomly assigned to the normal (N = 7) or the cooling group (N = 7). All subjects performed the ankle plantar flexion exercise (12 repetitions, 5 sets). Localized 31P-spectra were collected from the medial gastrocnemius before and after exercise (immediately, 30, 60 min, 24, 48, 96, and 168 h) to determine the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) and intracellular pH. Transaxial T2-weighted MR images of the medial gastrocnemius were obtained to calculate T2 relaxation time (T2), indicative of intramuscular water level, before and after exercise (24, 48, 96, and 168 h). In addition, the muscle soreness level was assessed at the same time as 31P-spectra measurements. Fifteen-minute cold-water immersion was administered to the cooling group after exercise and initial postexercise measurements. RESULTS: The control group showed significantly increased T2 from rest at 48 h after exercise (P < 0.05), but the cooling group showed no significant change in T2 throughout this study. Both groups showed a significantly decreased intracellular pH immediately after exercise (P < 0.05). After that, the cooling group showed a significantly greater value than the value at rest or the control group at 60 min after exercise (P < 0.05). For the Pi/PCr, no significant change was observed in both groups throughout this study. The muscle soreness level significantly increased immediately and at 24-48 h after exercise in both groups (P < 0.05). CONCLUSION: The findings of this study suggest that cooling causes an increase in intracellular pH and prevents the delayed muscle edema. [ABSTRACT FROM AUTHOR]

CNx/TiNy multilayers were prepared by ion-beam sputtering and analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive X-ray (EDX). EDX results show that the atom ratios of [N]/([C] + [N] + [Ti]) in the multilayers vary from 20 at.% to 41 at.%. XPS analysis presents that the N content of the CNx layer in CNx/TiNy is about 32.18 at.%. The nature of chemical bonding of the CNx layer in CNx/TiNy was also analyzed. The X-ray and electron diffraction analyses suggest that three kinds of C3N4 phases, such as β-C3N4, graphite-C3N4 and cubic-C3N4, are embodied in the multilayers. In CNx/TiNy bilayers, a hetero-epitaxial relationships, of (1 1 2) cubic-C3N4//(1 1 13) Ti2N, and [42 3] cubic-C3N4//[1 1 0] Ti2N, was observed between cubic-C3N4 and Ti2N. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate quantitatively and non-invasively the muscle recruitment of the rotator cuff muscles in baseball pitching using MR imaging. Five healthy baseball pitchers (Mean ± SD, age; 23.2 ± 1.3 yr; height: 171.8 ± 6.72cm; weight: 68.8 ± 5.4kg) participated in this study. Subjects threw 135 pitches from the hand-made pitcher's mound in 9 innings. T2-weighted images of rotator cuff muscles were obtained using a 1.5 Tesla superconducting imaging system with an E1 shoulder coil before and Immediately after baseball pitching. T2 relaxation times (T2) before and after pitching were calculated for the supraspinatus muscle, the shoulder external rotator muscle group (the infraspinatus muscle and teres minor muscle) and the subscapularis muscle. This study revealed that T2 values in all rotator cuff muscles tended to increase immediately after baseball pitching. T2 elevation would be associated with an exercise-induced increase in intramuscular water content and he limited to those muscles which were active during the exercise. In addition, greater mean force production during exercise translated into greater increases in T2 values for the active muscles. Judging from the relative T2 elevation immediately after pitching, the present study showed that there was personal equation among the muscles exhibiting the greatest T2 value after baseball pitching. [ABSTRACT FROM AUTHOR]

Crystalline hexagonal B(N 1- x C x ) and cubic B-C-N compounds have been synthesized from a precursor produced from melamine and boric acid by application of high temperature and high pressure. The synthesized products were characterized by X-ray diffraction. The lattice parameters for the hexagonal crystal are a=2.506 Å, c=6.657 Å, and that for the cubic crystal is a=3.596 Å. The X-ray photoelectron spectra of the B-C-N compound indicate the presence of B-N, C-N, C-C, and B-C bonds, which suggests that boron, carbon, and nitrogen atoms all bond with one another and that the B-C-N crystal is a compound in which the three kinds of atoms are mixed atomically. The composition of the B-C-N compound is B 0.47 C 0.23 N 0.30 . A strong absorption band at 1000∼1120 cm -1 attributable to the cubic B-C-N phase is observed in the infrared spectrum. The photoluminescence spectrum of hexagonal B-C-N powder measured at room temperature features a broad peak centered at 374 nm, corresponding to the band-edge emission of h-B-C-N, and is similar to that of w-GaN. [ABSTRACT FROM AUTHOR]

Compacts of 7075 aluminum have been produced from rapidly solidified powders by optimizing spark sintering parameters, such as pulse discharge time, fixed maximum temperature, holding time at this temperature, and method of cooling to room temperature after the sintering. High-grade compacts can be obtained by a short process (40-50 s) consisting of heating to 773 or 873 K at a heating rate of 9.6 K/s and holding this temperature for 10 s. The rapidly cooled compacts show the same supersaturated state at room temperature as the received as-atomized powder. Compacts quenched in water just after spark sintering at 873 K for 1.2 ks show the same age-hardening behavior as solution-heat treated compacts. Compacts that are quenched in water and aged after sintering at 873 K for 1.2 ks show the same elongation and flow stress as compacts aged after solution heat treatment. Elongation data suggest that compacts produced with longer holding time at a higher temperature and rapid cooling show a large amount of main alloying elements in solid solution and sufficient promotion of sintering. [ABSTRACT FROM AUTHOR]

Abstract: Turbostratic carbon nitride was prepared by the pyrolysis of melamine and then treated with a pulse discharge for different times. It is found that after this high-temperature short-time treatment, the structures of the products have changed while the high nitrogen content has been effectively maintained. The obtained product was characterized by X-ray diffraction and infrared spectroscopy. The composition was measured by an element analyzer. An orthorhombic CN x phase has been obtained, identified by transmission electron microscopy coupled with selected area electron diffraction. High-resolution transmission electron microscopy revealed that the product has some nanocrystals having a fringe spacing of approximately 0.32 nm, which embedded in a turbostratic matrix. [Copyright &y& Elsevier]

Abstract: Rhombohedral boron carbide has been synthesized by resistance heating of B2CN in graphite. The boron carbide and graphite form a clad morphology in a eutectic product containing ∼39wt.% of carbon. Graphite with different interlayer spacing has been observed. A wide range of carbon-rich concentration for the boron carbide indicating strong carbon segregation has been detected. Precise measurements of lattice parameters and composition analysis for the boron carbides suggest that more than 20at.% of carbon may have dissolved into some sections of the rhombohedral boron carbide crystals. Positions of the extra carbon atoms in the rhombohedral structure are discussed. [Copyright &y& Elsevier]

Abstract: In order to improve high temperature properties and good aging behavior of ZK60 (Mg–6%Zn–0.6%Zr) magnesium alloy moreover, Al18B4O33 whisker reinforced composites were developed. Al18B4O33 whisker reacts with ZK60 alloy thermodynamically. In order to suppress the interfacial reaction between Al18B4O33 and molten state ZK60 matrix, as-received whiskers were surface treated chemically. Whisker surface in preform was coated in vacuum by pure magnesium vapor, and then heat-treated at atmosphere. By the chemical reaction of whisker, MgAl2O4 layer with 10–20nm in thickness was produced on the whisker and covered with whisker completely. Then, Al18B4O33/ZK60 magnesium alloy matrix composite was fabricated by squeeze casting process. As the preform with surface treated whisker is stable for molten ZK60 alloy, the interfacial reaction did not occur during fabrication process and heat treatment after fabrication. The composites have good aging behavior because of no reaction in the interface. Although the precipitation tended to occur around interface preferentially during aging, but the obvious age hardening behavior were observed. [Copyright &y& Elsevier]

Abstract: An n-type conduction of the Mn-doped β-FeSi2 phase was observed in the isothermal annealing of the α-Fe2Si5 based alloy. Investigations of microstructures and transport properties proved that n-type conduction is caused by the abundant Fe vacancies in the supersaturated β-FeSi2(Si) solution, which exists as an intermediate state in the eutectoid decomposition, α-Fe2Si5 →β-FeSi2 +Si. [Copyright &y& Elsevier]

Abstract: The microstructures of Fe2Si5 based alloys fabricated by spark plasma sintering and the subsequent heat treatment were investigated by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). The results showed that a two-phase structure consisting of β-FeSi2 and Si dispersoids was obtained by the eutectoid decomposition of α-Fe2Si5 phase during annealing. The thermoelectric properties of Fe2Si5 based alloys were also investigated as compared with the stoichiometric FeSi2 based alloys. It was found that Fe2Si5 based alloys have the same conduction mechanism with stoichiometric FeSi2 alloys doped with Mn and Co, respectively. An increase in carrier scattering caused by Si particles was observed in both Mn- and Co-doped alloys. The effect of Si dispersoids on Seebeck coefficient and electrical resistivity was discussed. Results show that the excessive Si dispersoids in Fe2Si5 based alloys could improve the transport properties of the material, especially for the Co-doped alloys. [Copyright &y& Elsevier]

Obtaining the distribution of the voltage and temperature of the punch–die–compact systems in the spark sintering process is useful for generalization of its process control. The temperatures of these systems using two kinds of powders, titanium and alumina, of a conductor and an insulator, respectively, are measured by thermocouples in the constant current discharging process. The steady state showing the constant values of temperature and relative density is achieved in this process, and the measured temperature distribution in the systems is changed depending on the kind of compacts. The voltage and temperature of the systems at the steady state are also calculated on the basis of Ohm’s and Fourier’s laws. The calculated voltage distribution or current flow in the punch and die for the titanium compact system is similar to that for the alumina compact system, although there is the minor difference of the voltage distribution between titanium and alumina compacts because of the difference in the specific resistivity of compacts. The calculated temperature distribution is changed in these systems depending on the kind of compacts, because of the difference in the amount of Joule’s heat of compacts, which agrees with the temperature distribution measured by thermocouples. It is found from the result obtained in this study that distributions in voltage and temperature can be estimated by this calculation method, regardless of a kind and shape of the punches, dies and compacts. [Copyright &y& Elsevier]

CNx precursor powders (composition: 33.76 at.% C, 49.53 at.% N and 16.71 at.% H) having a turbostratic structure were obtained by pyrolyzing melamine. Following spark discharge treatment, the precursor becomes more ordered in structure. The order was increased with increasing treatment time. Photoluminescence (PL) analysis confirmed that the spark discharge had only a slight effect on the energy band of the turbostratic CNx powder, namely a blue shift of 11 nm in the emission spectrum of the precursor. By contrast, the high-speed impact treatment clearly promoted the mass transfer between the CNx particles. [Copyright &y& Elsevier]

By the process using electric energy, two-ply sheet laminates of aluminum (A1100)–stainless steel (SUS430) have been made without the reduction in the thickness of the both sheets. The A1100–SUS430 layered sheets were finally resistance-heated at 833 K for 0.4–3.6 ks under an applied pressure of 30 MPa after the pulsed electrical discharge for 0.7 ks. The true shear strength of the joined interface shows almost the constant value of 60–68 MPa to the holding time of 1.8 ks at 833 K. The true shear strength is close to that of A1100 sheet, which means satisfactory joining is achieved. After the holding time of 2.7 ks, the true shear strength is reduced to 30 MPa, due to the creation of a continuous intermetallic compound layer. The values of the joined area fraction at the A1100–SUS430 interface are changed from 25 to 70% for the laminates resistance-heated for 0.4–3.6 ks at 833 K. Little change of the joined area fraction are shown in the laminates resistance-heated for the holding times of more than 1.8 ks. It is suggested on the basis of the result of the thermal calculation that the maximum value (70%) of the joined area fraction is due to inhomogeneity of the surface-temperature on the SUS430 side at the A1100–SUS430 interface by the heat release because the SUS430 sheets is wider than the base surface of the graphite punch. For application of the process using the electric energy in joining the metallic sheets, it is important to avoid the inhomogeneities of electric current and temperature distribution through the interface between the sheets to be joined. [Copyright &y& Elsevier]