测试条件对牙本质粘接强度的影响

作者考察了四种测试条件对牙本质粘接强度的影响,包括牙的新鲜程度、牙的重复使用次数、粘接部位以及拉伸负载速度。采用GP牙本质粘接材料,结果表明:粘接部位和拉伸负载速度与粘接强度没有明显的关系,牙的新鲜程度和重复使用次数与粘接强度有很大关系。牙拔出后贮存过久、使用次数越多,粘接强度超低,作粘接试件的牙的贮存期不应超过1月,且牙只能使用一次。     

The effects of 12 weeks of functional strength training on muscle strength,volume and activity upon exposure to elevated Gz forces in high-performance aircraft personnel

Background:Technological advancements in modern military and acrobatic jet planes have resulted in extraordinary psychophysiological loads being exerted upon flying personnel,including inducing neck and back pain.The purpose of this study was to examine the effects of 12 weeks of functional strength training on 1) the volume and strength of the neck and shoulder muscles and 2) muscular activity upon exposure to helmets of different masses and elevated Gz forces in a long-arm centrifuge in high-performance aircraft personnel.Methods:Eighteen participants underwent 12 weeks of functional strength training (n=12) or the control protocol(n=6) without additional strength training.Pre-and post-intervention tests included evaluations of isometric strength of the head extensor muscles,flexion,and lateral flexion and rotation,as well as magnetic resonance imaging (MRI)to measure the volume of the m.stemocleidomastoideus,m.trapezius,and deep neck muscles.Furthermore,during a long-arm centrifuge (+1.4 and +3Gz) protocol,the muscular activity levels of the m.sternocleidomastoideus,m.trapezius and m.erector spinae muscles were assessed without a flight helmet,with a helmet,and with a helmet and night vision goggles.Each participant's perception of muscular strain was noted immediately after the long-arm centrifuge protocol.Results:The maximal isometric strength in all exercises and muscle volumes increased in the training group but not the control group (P＜0.05).Relative muscle activity (％MVC) with a helmet decreased after the intervention in the training but not the control group (P=0.01).Relative muscle activity while wearing a helmet and night vision goggles was higher after intervention in the control group than in the training group (P＜0.01).The perceived muscular strain of the neck muscles induced by the long-arm centrifuge did not differ between the groups.Conclusions:Twelve weeks of functional strength training improves the maximal isometric strength and volume of neck and shoulder muscles and leads to lower relative muscle activation upon exposure to elevated Gz forces in a long-arm centrifuge.     

Psychometric properties of the Strength and Difficulties Questionnaire from five European countries

The Strength and Difficulties Questionnaire (SDQ) is a brief screening instrument for assessing emotional and behavioural problems in children and adolescents. This study examined the factor structure and validity of the self‐report original English version of the SDQ and four of its many translations (German, Cypriot Greek, Swedish, and Italian). A total of 2418 adolescents from five European countries (Germany, Cyprus, England, Sweden, Italy), ages 12 to 17 years, participated. The sample was drawn from general (school) populations. In addition to the SDQ, all participants completed the Spence Children's Anxiety Scale (SCAS), a measure of anxiety symptoms. The internal consistency and validity of the SDQ total difficulties were good for most countries. Confirmatory factor analysis showed that both five‐ and three‐factor models provided good fit for the whole sample; however, the three‐factor model fit somewhat better than the five‐factor model. The factor structure differed across countries, with the three‐factor model showing better fit indices in Cyprus, whereas the five‐factor model fitted better in Germany. Fit indices for the UK, Sweden, and Italy were poor for both models. When the reversed items were removed, the goodness‐of‐fit improved significantly for the total sample and in each country. It is therefore recommended that the reversed items be removed or re‐worded in future studies. Copyright © 2012 John Wiley & Sons, Ltd.     

山东省农村学龄前留守儿童心理健康状况及干预效果研究

目的了解山东省农村学龄前留守儿童的心理健康状况,评价干预效果,为促进学龄前留守儿童心理健康提供依据。方法采用随机整群抽样的方法,抽取山东省2个县/区的10个乡镇幼儿园共计735例儿童作为调查对象,使用长处和困难问卷(Strength and Difficulty Questionnaire,SDQ)(家长版)进行心理测量,将受试对象分为干预组和对照组,综合干预1年后,再次对受试对象进行心理状况测量。结果留守儿童在品行问题、多动问题、困难总分上的评分高于非留守儿童;综合干预1年后,留守儿童SDQ各项因子异常检出率均有下降(P0.05),监护类型为母亲和祖父母的留守儿童SDQ各项因子得分也均有下降,监护类型为外祖父母的留守儿童干预前后SDQ各项因子评分差异无统计学意义(P0.05)。结论留守儿童心理健康状况较差,适当干预可有效改善学龄前留守儿童心理健康状况;母亲和祖父母监护的留守儿童干预效果比外祖父母监护的效果好。     

Hypertrophy without increased isometric strength after weight training

Summary Eight men (20–23 years) weight trained 3 days week^–1 for 19 weeks. Training sessions consisted of six sets of a leg press exercise (simultaneous hip and knee extension and ankle plantar flexion) on a weight machine, the last three sets with the heaviest weight that could be used for 7–20 repetitions. In comparison to a control group (n = 6) only the trained group increased (P<0.01) weight lifting performance (heaviest weight lifted for one repetition, 29%), and left and right knee extensor cross-sectional area (CAT scanning and computerized planimetry, 11%, P<0.05). In contrast, training caused no increase in maximal voluntary isometric knee extension strength, electrically evoked knee extensor peak twitch torque, and knee extensor motor unit activation (interpolated twitch method). These data indicate that a moderate but significant amount of hypertrophy induced by weight training does not necessarily increase performance in an isometric strength task different from the training task but involving the same muscle group. The failure of evoked twitch torque to increase despite hypertrophy may further indicate that moderate hypertrophy in the early stage of strength training may not necessarily cause an increase in intrinsic muscle force generating capacity.     

Heightened Pelvic Floor Muscle Tone and Altered Contractility in Women With Provoked Vestibulodynia

BackgroundPelvic floor muscle (PFM) dysfunctions are reported to be involved in provoked vestibulodynia (PVD). Although heightened PFM tone has been suggested, the relative contribution of active and passive components of tone remains misunderstood. Likewise, alterations in PFM contractility have been scarcely studied.AimsTo compare PFM tone, including the relative contribution of its active and passive components, and muscular contractility in women with PVD and asymptomatic controls.MethodsFifty-six asymptomatic women and 56 women with PVD participated in the study. The PVD diagnosis was confirmed by a gynecologist based on a standardized examination.OutcomesPFM function was evaluated using a dynamometric speculum combined with surface electromyography (EMG). PFM general tone was evaluated in static conditions at different vaginal apertures and during repeated dynamic cyclic stretching. The active contribution of tone was characterized using the ratio between EMG in a static position and during stretching and the proportion of women presenting PFM activation during stretching. Contribution of the passive component was evaluated using resting forces, stiffness, and hysteresis in women sustaining a negligible EMG signal during stretching. PFM contractility, such as strength, speed of contraction, coordination, and endurance, also was assessed during voluntary isometric efforts.ResultsGreater PFM resting forces and stiffness were found in women with PVD compared with controls, indicating an increased general tone. An increased active component also was found in women with PVD because they presented a superior EMG ratio, and a larger proportion of them presented PFM activation during stretching. Higher passive properties also were found in women with PVD. Women with PVD also showed decreased strength, speed of contraction, coordination, and endurance compared with controls.Clinical ImplicationsFindings provide further evidence of the contribution of PFM alterations in the etiology of PVD. These alterations should be assessed to provide patient-centered targeted treatment options.Strengths and LimitationsThe use of a validated tool investigating PFM alterations constitutes a strength of this study. However, the study design does not allow the determination of the sequence of events in which these muscle alterations occurred—before or after the onset of PVD.ConclusionFindings support the involvement of active and passive components of PFM tone and an altered PFM contractility in women with PVD.Morin M, Binik YM, Bourbonnais D, et al. Heightened Pelvic Floor Muscle Tone and Altered Contractility in Women With Provoked Vestibulodynia. J Sex Med 2017;14:592–600.     

Is there an athlete’s artery? A comparison of brachial and femoral artery structure and function in male strength,power and endurance athletes

ObjectivesExercise places physiological demands upon the cardiovascular system, subsequently leading to adaptations in structure and function. Different exercise modalities (endurance, strength and power) lead to distinct hemodynamic demands and, possibly, different patterns of adaptation. Our aim was to assess and compare brachial and femoral artery function and structure in elite level athletes engaged in endurance, strength and power sports.Designcross sectional comparison.Methods30 male elite athletes (runners n = 10, powerlifters n = 11, weightlifters n = 9) and 23 healthy controls were recruited. Brachial and femoral arterial diameters were assessed using ultrasound. Arterial function (brachial and femoral arteries) was determined using the flow mediated dilation (FMD) technique and body composition using body mass index (BMI) and body surface area (BSA).ResultsWeightlifters had significantly larger brachial arterial diameters compared to controls (4.39 ± 0.34 vs 3.86 ± 0.42 mm, p < 0.01). As weightlifter and power athletes had significantly higher body mass, BMI and BSA, we adjusted diameter for BSA. BSA-correction ameliorated differences in brachial artery resting diameters between athletes and controls. However, BSA-corrected femoral artery diameter was significantly larger in runners compared to controls (3.51 ± 0.28 vs 3.25 ± 0.34 mm, p < 0.05). There were no differences in brachial FMD between groups. Femoral artery FMD was significantly higher in runners and weightlifters compared to controls (p < 0.05 for both groups).ConclusionsHeterogeneous, limb-specific structural and functional vascular adaptation is evident in athletes, which may be influenced by exercise modality. Further, vascular remodelling relates to differences in body shape, specifically body composition, which should be accounted for when comparing athletes.     

Midvastus approach in total knee arthroplasty: a randomized, double-blinded study on early rehabilitation

The medial parapatellar approach has become the standard technique in total knee arthroplasty (TKA). However, recent studies have reported superior results regarding functional recovery when using the midvastus approach. It was the aim of this study to evaluate the early functional outcome of both surgical techniques. In a prospective, double-blinded, randomized study, 50 patients for TKA were consecutively operated on either by the medial parapatellar or the midvastus approach. Exclusion criteria were defined as previous open knee surgery and leg deformity of more than 10° varus or valgus. TKA was performed in all patients by one surgeon using the same type of implants in both groups. Pain scores (VAS) were documented and follow-up data including quadriceps strength and proprioception were obtained 3 weeks and 6 weeks postoperatively. Both groups were comparable in preoperative demographic data. Postoperatively, patients in the midvastus group demonstrated significantly lower pain in rest (VAS: mean 2.25 vs. 3.03) and under movement (VAS: mean 2.92 vs. 3.13). Further, they showed superior isometric quadriceps strength at 3 weeks (41.4 vs. 27.6 Nm) and 6 weeks (47.6 vs. 35.5 Nm). Moreover, this group showed a superior postoperative proprioception, while the range of motion was similar in both groups. The midvastus approach offers advantages over the standard parapatellar arthrotomy, in the early rehabilitation period. No adverse effects were observed associated with this approach. Therefore, the midvastus approach should be considered as a valuable alternative in TKA.     

The repeated compression of powders

Powders were subjected to repeated compression in a tablet press, the ejection mechanism of which had been disconnected. The force detected at the upper punch was found to change with successive compressions, the magnitude of the change being dependent on the powder, the compressive force and the interval between compressions. Repeated compression also caused a change in tablet crushing strength. With compression intervals of 1.2 s, all substances showed an significant increase in strength. With longer time intervals, the increase was reduced and in some cases, a diminution in strength occurred.     

Rib structure and bending strength: An autopsy study

Mechanical rib testing and geometric analysis were explored as means of evaluating metabolic bone disease. Seventy-nine male patients were examined postmortem. Displacement rate at the loading point and patient age were important variables for which results had to be corrected. Like long bones, ribs apparently undergo progressive circumendosteal resorption with advancing age but unlike long bones, they show no evidence of continued subperiosteal apposition. Effects of selected individual diseases and of all diseases grouped by major organ system were analyzed. Most produced no discernible modification of rib volume, geometry or bending strength as quantified by modulus of rupture. Exceptions were myeloma and arthritis, where the bony material was weakened without remodeling or loss in volume.