Stretching in the prevention of hamstring strains: Attitudes, beliefs and current practices among football coaches in Mauritius

Context and Objective: Hamstring strain is a common injury in football and it causes a significant amount of time lost from competition and training. Since poor flexibility is thought to predispose to muscle strain, stretching is routinely recommended during warm-up routines by coaches to prevent injuries. However, available evidence suggests that pre-exercise stretching (PES), especially static stretching, has no benefit on injury rates and may even reduce performance in explosive type activities. We designed this study to assess the attitudes, beliefs and practices of football coaches regarding stretching in the prevention of hamstring strains. Design: A cross-sectional survey. Setting: Mauritius Football Association (MFA). Participants: 26 football coaches registered with the MFA. Intervention: Questionnaires were distributed to football coaches of the MFA via sports officers. Questionnaires were then collected two weeks after distribution. Main Outcome Measures: Attitudes, beliefs and practices of football coaches regarding stretching in the prevention of ham-string strains. Results: MFA coaches held generally positive attitudes and beliefs towards stretching. 88% of coaches felt that PES is beneficial and 93% believed that PES prevents hamstring strains. The majority of coaches recommended stretching after warming up (81%) and after the training session (93%). 76% of coaches also advised stretching outside the training sessions. 96% of coaches used static stretching to stretch the hamstrings. The hamstrings were stretched on average for 4 times at each training session and the mean duration of a static stretch was 12 seconds. Conclusions: Nearly all coaches believed that PES prevents hamstring strains although evidence is limited. Some of the coaches’ beliefs and practices were not in line with current recommendations. Coaches reported that their stretching practices would be most likely influenced by scientific research. Thus there is an urgent need to devise awareness and training programmes in this area.

Effect of Stretching - Setting Treatment on Dyeing Behavior of Wool

Changes of dyeing behavior of wool after stretching - setting treatment are studied.Effects of stretching - setting on wool structure are analyzed.It is concluded that stretching - setting treatment not only reduces wool diameter and increases wool length,but also brings about low-temperature dyeing of wool.

Study on Identification and Fermentation Condition of Strain ZY-19-2 with Inhibitory Effect against Tobacco Black Shank (Phytophtora parasitica var. nicotianae Tucker)

[Objective] The paper was to identify stain ZY-19-2 with inhibitory effect against tobacco black shank （Phytophtora parasitica var.nicotianae Tucker）, and study the fermentation condition of the strain. [Method]A strain ZY-19-2 with strong inhibitory effect against P. parasitica were isolated and screened from tobacco rhizosphere soil samples, and identified according to its morphological characteristics. The chitinase production activity of the strain under different culture conditions was also studied. [Result] For stain ZY-19-2 Paecilomyces lilacinus, the optimal fermentation conditions were as follows： 1.2% colloidal chitin as carbon source, 1% peptone as nitrogen source, 0.1% Tween 80 as surfactant, initial pH of fermentation broth at 6.0, the fermentation time of 60 h, inoculum amount at 1%, shaker speed at 120 r/min. The highest enzyme activity reached 0.216 U/ml. [Conclusion]The optimization of fermentation condition of strain ZY-19-2 lay foundation for large-scale production of cheap and efficient chitinase and chitin oligosaccharides, as well as application of the strain for control of tobacco black shank.

Probiotic yeasts: Anti-inflammatory potential of various non-pathogenic strains in experimental colitis in mice

AIM: To evaluate the in vitro immunomodulation capacity of various non-pathogenic yeast strains and to investigate the ability of some of these food grade yeasts to prevent experimental colitis in mice.METHODS: In vitro immunomodulation was assessed by measuring cytokines [interleukin (IL)-12p70,IL-10,tumor necrosis factor and interferon γ] released by human peripheral blood mononuclear cells after 24 h stimulation with 6 live yeast strains (Saccharomyces ssp.) and with bacterial reference strains.A murine model of acute 2-4-6-trinitrobenzene sulfonic acid (TNBS)-colitis was next used to evaluate the distinct prophylactic protective capacities of three yeast strains compared with the performance of prednisolone treatment.RESULTS: The six yeast strains all showed similar non-discriminating anti-inflammatory potential when tested on immunocompetent cells in vitro .However,although they exhibited similar colonization patterns in vivo ,some yeast strains showed significant anti-inflammatory activities in the TNBS-induced colitis model,whereas others had weaker or no preventive effect at all,as evidenced by colitis markers (body-weight loss,macroscopic and histological scores,myeloperoxidase activities and blood inflammatory markers).CONCLUSION: A careful selection of strains is required among the biodiversity of yeasts for specific clinical studies,including applications in inflammatory bowel disease and other therapeutic uses.

Analysis of axial strain in one-dimensional loading by different models

Different phenomenological equations based on plasticity, primary creep （as a viscoplastic mechanism）, secondary creep （as another viscoplastic mechanism） and different combinations of these equations are presented and used to describe the material inelastic deformation in uniaxial test. Agreement of the models with experimental results and with the theoretical concepts and physical realities is the criterion of choosing the most appropriate formulation for uniaxial test. A model is thus proposed in which plastic deformation, primary creep and secondary creep contribute to the inelastic deformation. However, it is believed that the hardening parameter is composed of plastic and primary creep parts. Accordingly, the axial plastic strain in a uniaxial test may no longer be considered as the hardening parameter. Therefore, a proportionality concept is proposed to calculate the plastic contribution of deformation.

EFFECT OF DYNAMIC STRAIN AGING ON LOW CYCLE FATIGUE BEHAVIOUR OF 18-8 AUSTENITIC STAINLESS STEEL

Studies were made of the symmetric tensile-compressive low cycle fatigue behaviour and the influence of dynamic strain aging(DSA)pre-treatment of 18-8 austenitic stainless steel. Within the testing amplitude range of strain.±0.5 % to±1.5 %,the three processes of cyclic hardening,cyclic saturation and cyclic softening were observed.In the same amplitude of strain,the peak stress of the samples pre-treated by DSA is higher than that of solid-solu- tion and cold working pre-treatment,but no remarkable differences of the fatigue lives of them were found.TEM observation shows that the uniform and stable dislocation networks with high density form after DSA pre-treatment,which increases the cyclic peak stress.The cyclic softening results from the low dislocation density and elongated cell structure with low energy.

Carrier fringe method of moire interferometry for tiny strain measurements in micro-field

In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the specimen surface, and the strain can be deduced from the changes in carrier fringes before and after the deformation of an object. Four coherent laser beams are used to obtain the carrier fringe patterns of field U and V. Both theoretical analysis and numerical simulation indicate that the ideal accuracy of strain can be controlled within a range of ±1με. Case study of a plane extension experiment shows that the measurement accuracy of strain can be controlled within the range of ±10με. The average strain values of every row of field U and every column of field V can be obtained by using this method, and approximated strain of every pixel in the whole-field can be further acquired, and thus it is possible to measure tiny strains occurred in a micro-field. The technology in this paper can provide comprehensive information for analyzing related mechanical content in the field of MEMS.

Cloning and Expression of a Chitinase Gene from Serratia marcescens Strain C8-8

A 1 692 bp long chitinase-encoding ch/A gene was cloned from the genomic DNA of Serrat/a marcescens strain C8-8 by PCR, which was speculated to en- code a 563 aa long polypeptide chain with molecular weight of about 60.9 kD. Homolog analysis showed that the chiA gene sequence cloned from C8-8 shared the highest similarity with cMA sequences from Serrat/a maresscens strains 141 （ DQ 990373.1 ） and 14041 （ DQ 493896. 1 ）, which reached 99%. Domain analysis showed that N-termlnal （23 aa） of the chiA gene cloned from C8-8 harbored typical signal peptide sequence, while C-telminal harbored the other two domains, in- eluding the PKD region （73 aa） and chitinase catalytic region （387 aa）. The PCR fragment was digested with restriction endonucleases and cloned into plasmid pET28a. The recombinant plasmid pET＇28a-ch/A was firstly transformed into Escherichia coli DI-I5 , and then transformed into expression host E. coli DH3 to express ch/A gene. The recombinant strain DH3 chiA could produce transparent hydrolysis circles on the colloidal chitin plate induced by isopropyl-l-thiogalactopyranoside （IFrG）. SDS-PAGE electrophoresis analysis showed that, a protein with relative molecular weight of about 60 kD was expressed by the recombinant strain DH3 chiA, which was consistent with the except molecular weight. After initial purification, biological activity test showed that the recombinant expression product could hydrolyze chitin, which produced transparent hydrolysis circles on the colloidal chitin plates. Results indicated that chiA gene from Serrat/a marcescens strain C8-8 had biological functions and could be utilized as a potential biological control factor.

MODELING THE STRESS-STRAIN CURVES UNDER DYNAMIC RECRYSTALLIZATION

An analytical model for dynamic recrystallization (DRX) is studied based on the relative grain size model proposed by Sakai and Jonas, and the characteristic flow behaviors under DRX are analyzed and simulated. Introducing the variation of dynamic grain size and the heterogeneous distribution of disolo- cation densities densities under DRX,a simple method for modeling and simulating DRX processes is developed by using Laplace transformation theory. The results derived from the present model agree well with the experimental results in literatures. This simulation can reproduce a number of features in DRX flow behaviors, for example,single and multiple peak flow behaviors followed by a steady state flow, the transition between them, and so on.

NUMERICAL SIMULATION OF STRESS-STRAIN DISTRIBUTIONS FOR WELD METAL SOLIDIFICATION CRACKING IN STAINLESS STEEL

This paper analyzed the characteristics of welding solidification crack of stainless steels,and clearly re- vealed the the of the deformation in the molten - the pool and the solidification shrinkage on the stress - strain fields in the trail of molten - weld pool.Moreover, rheologic properties of the alloys in solid - liquid zone were also obtained by measuring the hading and unloading deform curves of the steels.As a result, a numerical model for simulation of stress - strain distributions of welding solidifi- cation crack was developed. On the basis of the model,the thesis simulated the driving force of solidifi- cation crack of stainless steels, that is, stress - strain fields in the trail of molten-weld pool with fi- nite element method.

Plastic Flow Modeling of Ti-5 Al-2 Sn-2 Zr-4 Mo-4 Cr Alloy at Elevated Temperatures and High Strain Rates

The true stress-sWain relationships of Ti-5A1-2Sn-2Zr-4Mo-4Cr（TC17） alloy with a wide range of strain rates were investigated by tmiaxial quasi-static and dynamic compression tests, respectively. Quasi- static compression tests were carried out with Instron 8874 test machine, while dynamic compression tests were performed with the split Hopkinson pressure bar （SHPB） which was installed with heating device and synchro- assembly system. The dynamic mechanical behaviors tests of TC17 were carded out from room temperature to 800 ℃ at intervals of 200 ℃ and at high sWain rates （5 500-1 9200 s-l）. The stress-strain curves considering temperature-sWain rate coupling actions were obtained. The Johnson-Cook constitutive model was developed through data fitting of the stress-sWain curves. The material constants in the developed constitutive model can be determined using isothermal and adiabatic stress-strain curves at different strain rates. The Johnson-Cook constitutive model provided satisfied prediction of the plastic flow stress for TC17 alloy.

循环稳态或单调态下薄片小试样应力-应变关系试验方法

针对金属薄片沙漏试样,基于能量密度等效,提出了薄片小试样的弹塑性位移-载荷关系理论方程和等效应力、等效应变理论方程,进而提出了金属薄片沙漏试样循环稳态或单调态下的等效应力-等效应变关系试验方法。本文针对40种本构关系有限元分析预设材料和6种几何尺寸的沙漏试样完成了有限元分析,针对5种合金材料和2种几何尺寸的沙漏试样进行了单调拉伸和变幅对称应变循环试验,以及标准圆棒试样拉伸和变幅对称应变循环试验。结果表明,采用本文试验方法预测的材料单轴应力-应变关系与预设本构关系密切吻合,稳态对称循环下应力-应变关系与标准圆棒试样单轴拉伸及单轴循环试验结果吻合良好。

Study on Antimicrobial and Antiviral Activities of Lysozyme From Marine Strain S-12-86 In Vitro

In this study, the in vitro antimicrobial and antiviral activities of the lysozyme from marine strain S-12-86 （LS） were investigated, The antimicrobial activity of LS was tested by minimum inhibition concentration （MIC） and minimum bactericidal concentration （MBC） method. The inhibiting effects of LS on pseudo rabies virus （PRV） in swine kidney cells （PK-15 ceils） were judged by cytopathogenic effect test （CPE）, The results showed LS had a broad antimicrobial spectrum against several standard strains including gram-positive bacteria, gram-negative bacteria, fungi, etc, The MIC of LS was 0.25-4.00 mg mL^-1 and its MBC was 0.25-8.00 mg mL^-1, respectively, Observation under the transmission electron microscope revealed that the cell wall of Candida albicans was distorted seriously, and the cytoplasm with many cavities was asymmetrical after being hydrolyzed by LS, The median cytotoxicity concentration （TC50） of LS was 100.0 μg mL^-1, the median effective concentration （EC50） was 0.46 μg mL^-1, and the selectivity index （TI = TC50/EC50） was 217. LS could inhibit PRV in PK-15 cells when it was added to cell culture medium at 0, 2, 4, 6, and 8 h after PK-15 cells had been infected by PRV. From the results, we concluded that LS had broad antimicrobial spectrum and good inhibiting effects on PRV,

体外冲击波联合伸筋膏在慢性腰肌劳损患者中的治疗效果及对IL-6、TNF-α的影响

目的探讨慢性腰肌劳损采用体外冲击波联合伸筋膏的治疗效果及对IL-6、TNF-α的影响。方法选取2020年12月至2021年11月我院收治的慢性腰肌劳损患者共计120例,根据随机摸球法分为观察组(n=60)与对照组(n=60),对照组采用伸筋膏治疗,观察组采用体外冲击波联合伸筋膏治疗,对两组临床疗效、腰痛症状评分、白细胞介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)、视觉模拟评分法(VAS)评分、Oswestry功能障碍指数的量表(ODI)评分进行比较。结果观察组(93.33%)治疗总有效率较对照组(75.00%)明显更高(P<0.05);治疗后两组腰部功能障碍、日常活动、压痛明显降低(P<0.05),观察组较对照组明显更低(P<0.05);治疗后两组IL-6、TNF-α水平均明显降低(P<0.05),观察组较对照组明显更低(P<0.05);治疗后两组VAS评分明显降低(P<0.05),观察组较对照组明显更低(P<0.05);治疗后两组ODI评分明显降低(P<0.05),观察组较对照组明显更低(P<0.05)。结论将体外冲击波联合伸筋膏应用于慢性腰肌劳损患者治疗中,可提高临床疗效,改善患者的腰痛症状,降低IL-6、TNF-α水平,改善疼痛程度及功能障碍情况。

The Effect of Unloading Positions and Times on Sheet Metal’s Stress-Strain Curve

The loading-unloading-reloading process could affect the tensile deformation of metals with the combined function of stress relaxation and work hardening, which has been reported in multiple experiments. Nevertheless, the effects of different unloading positions and unloading times have not been investigated. In this study, unloading-reloading tests on three materials (AL6061, HSLA and Q195) were conducted. The stress exhibits a rapid rise momentarily upon reloading and stabilizes afterward while the post stress-strain curve deviates up or down from the monotonic tensile curve. The ductility is enhanced by the unloading-reloading process in general. Different unloading positions and unloading times have different degrees of influence on the stretching of these metals. The effect of loading conditions on a medium manganese steel was further studied. The functions to modify the post stress-strain relationship after unloading-reloading were established.

Determination of strain criterion of Portevin-Le Chatelier effect for aluminum alloy sheets

According to the deformation state in skin stretch forming, an experiment was investigated to determine the critical strain, which make the slip line occur, and the strain criteria under different strain paths are obtained. The uniaxial tension tests of different specimens were carried out to determine the critical strains of different strain paths. Then, the slip line limited curve(SLC) is available from these critical strains. Two kinds of aluminum alloys, 2024-T3 and 2524-T3, were studied, and two SLCs are gained. The application of the SLC to an airplane skin stretch forming simulation was investigated, and the results show that the SLC can be used to control the slip lines occurring in practice.

Unveiling the planar deformation mechanisms for improved formability in pre-twinned AZ31 Mg alloy sheet at warm temperature

To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation,the stretch forming is conducted at 200℃.Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to 11.30 mm.The mechanisms for the improved formability and the deformation behaviors during the planar stretch forming are systematically investigated based on the planar stress states.The Schmid factor for deformation mechanisms are calculated,the results reveal that planar stress states extremely affect the Schmid factor for{10-12}twinning.The detwinning is activated and the prismatic slip is enhanced in the pre-twinned sheet,especially under the planar extension stress state in the outer region.Consequently,the thickness-direction strain is accommodated better.The dynamic recrystallization(DRX)type is continuous DRX(CDRX)regardless of the planar stress state.However,the CDRX degree is greater under the planar extension stress state.Some twin lattices deviate from the perfect{10-12}twinning relation due to the planar compression stress state and the CDRX.The basal texture is weakened when the planar stress state tends to change the texture components.

A retrospective investigation on the phenotype and stability of the E-protein gene in Japanese Encephalitis (JE) virus strain SA14-14-2 used live-attenuated JE vaccine

To detect retrospectively the phenotype and stability of the E-protein gene in Japanese Encephalitis （JE） virus strain SA14-14-2 used in the live-attenuated JE vaccine prepears, the viral titer was titrated by plaque formation in BHK-21 cell cultures, and the neuro-virulence of viruses was assayed in mice with body weight of 12-14 g by intracerebral inoculation. Meanwhile, the total RNA of virus gene was extracted and amplified by RT-PCR with the designed primers, and then it was purified and cloned to the expression vector pGEM-T. The recombinant plasmid was purified and sequenced. It was found that the loss of viral titer of vaccines stored in -20℃ for longer than 10 years was less than 0.5 Lg PFU/ml. No mice inoculated intracerebrally showed signs of illness or even death. The size of plagues of the vaccine virus remained to be small, and the E genes of primary virus seed SA14-14-2 and the vaccines prepared at different years （1987-2001） were unchanged, in- cluding the 8 critical amino acid sites which were different from the parent wild virus strain SA14 and the related neuro-virulence. These results indicate that the genotypic and biological characteristics of the attenuated JE virus strain SA14-14-2 and its vaccines sion noted. prepared are quite stable without any reversion noted.

High Strain Rate Induced Plasticity-increasing of Metallic Materials under Tension

The effect of strain rate on plasticity has been Investigat-ed for three metallic materials with dynamic tension tech-nique. A phenomenon of high strain induced plasticity -increasing was found for tested materials. The elongation of quenched 30CrMnSiNi2A is 14. 5% under 40 m/s loading rate which is more than two times of the 7 % un-der 0. 5 mm/min. This typic high strain rate induced plasticity - Increasing phenomenon is associated with adiabatic heating, strain twinning and suppression of strain - induced - phase transformation.

不同缺陷类型双层石墨烯旋转摩擦特性

采用分子动力学模拟方法,构建双层石墨烯旋转摩擦的原子模型,研究缺陷类型、浓度、尺寸效应、石墨烯堆叠方式等因素对其层间旋转摩擦特性的影响,并探讨应变工程的减摩效应.实验结果表明,缺陷类型和堆叠方式对石墨烯旋转摩擦特性的影响较为显著,缺陷类型的影响程度最高.当对底层石墨烯引入拉伸应变后,其旋转摩擦阻力发生衰减,且单空位缺陷与无缺陷模型的力矩递减趋势最为相似.对比研究底层石墨烯的压缩应变,发现其在一定范围内使得层间摩擦增大.本研究有助于缺陷石墨烯层间旋转摩擦特性理论的进一步完善.