High-Entropy Borides under Extreme Environment of Pressures and Temperatures

The high-entropy transition metal borides containing a random distribution of five or more constituent metallic elements offer novel opportunities in designing materials that show crystalline phase stability, high strength, and thermal oxidation resistance under extreme conditions. We present a comprehensive theoretical and experimental investigation of prototypical high-entropy boride (HEB) materials such as (Hf, Mo, Nb, Ta, Ti)B₂ and (Hf, Mo, Nb, Ta, Zr)B₂ under extreme environments of pressures and temperatures. The theoretical tools include modeling elastic properties by special quasi-random structures that predict a bulk modulus of 288 GPa and a shear modulus of 215 GPa at ambient conditions. HEB samples were synthesized under high pressures and high temperatures and studied to 9.5 GPa and 2273 K in a large-volume pressure cell. The thermal equation of state measurement yielded a bulk modulus of 276 GPa, in excellent agreement with theory. The measured compressive yield strength by radial X-ray diffraction technique in a diamond anvil cell was 28 GPa at a pressure of 65 GPa, which is a significant fraction of the shear modulus at high pressures. The high compressive strength and phase stability of this material under high pressures and high temperatures make it an ideal candidate for application as a structural material in nuclear and aerospace fields.     

An Experimental Model of Heat Storage in Working Firefighters

Objective. Develop experimental models to study uncompensable heat stress (UCHS) in working firefighters (FFs). Methods. FFs ingested core temperature (Tc) capsules prior to performing sequential tasks in 40°C andpersonal protective ensemble (PPE), or 18°C andno PPE. Both trials were conducted in an environmental chamber with FFs using self-contained breathing apparatus (SCBA). Results. FFs exercising in heat andPPE reproduced UCHS conditions. For every FF in both trials for whom the capsules worked, Tc was elevated, andTc_max occurred after completion of study protocol. Trials with PPE resulted in a mean maximum temperature of 38.94°C (± 0.37°C); Tc_max reached 40.4°C. Without PPE, maximum Tc averaged 37.79°C (± 0.07°C). Heat storage values ranged from 131 to 1205 kJ, averaging 578 kJ (± 151.47kJ) with PPE and210.83 kJ (± 21.77kJ) without PPE. Conclusions. An experimental model has been developed that simulates the initial phases of an interior fire attack to study the physiology of UCHS in FF. The hot environment andPPE increase maximum Tc andheat storage over that due to the exertion required to perform the tasks andmay decrease time to volitional fatigue. This model will permit controlled studies to optimize work-rest cycles, rehab conditions, andphysical conditioning of FFs.     

Impaired macrophage leishmanicidal activity at cutaneous temperature

Summary Temperature is one of the primary influences upon the pathogenesis of cutaneous leishmaniasis. In this study, we measured the temperature of murine leishmanial lesions and determined the ability of lymphokine (LK) activated macrophages to kill Leishmania major at these temperatures. The temperature of leishmanial lesions in BALB/c and C3H/HeN mice ranged from 27°C to 32°C. We found that LK activated resident or inflammatory macrophages exhibited significantly less leishmanicidal activity in vitro at temperatures closer to those measured in vivo . The decrease in microbicidal activity was not due to the enhanced growth of the parasites at lower temperatures, since impaired killing was also observed against non-replicating radiation attenuated amastigotes. Finally, the tumoricidal activity of macrophages was found to be significantly depressed at temperatures below 37°C, indicating a generalized impairment of macrophage function at these temperatures. These findings suggest that impaired macrophage microbicidal activity at cutaneous temperatures may contribute to parasite survival, and imply that healing of leishmanial lesions, as well as other cutaneous infections, may require an exceptionally potent local LK response.     

用于人体局部微循环监测的便携式近红外检测仪

近红外技术在生物医学中应用越来越广泛,已涉及到指述的诊断和治疗.本文针对更年期妇女经常出现的潮热、局部充血等症状,研发了一套用于人体局部微循环状态监测的便携式近红外检测装置,能够同步监测人体体温和局部血容量的变化.系统由便携式监护仪和配套的PC机及相应软件组成.便携式监护仪采用腰带式设计,温度测量精度为0.2℃,在人体体温区段(35～40 ℃)精度可达到0.1℃;所测血容量的变化与体温变化一致,即体温升高,局部血液循环加快,血容量增加.配套PC机及软件主要完成对监护仪的控制、数据的传输、处理、存储等任务.     

Thermal energy balance and body temperature: comparison between isolated ultrafiltration and haemodialysis at different dialysate temperatures.

BACKGROUND: Haemodynamic stability is better maintained during isolated ultrafiltration (i-UF) than during combined ultrafiltration/haemodialysis (UF + HD). This difference might be explained by differences in thermal energy balances. In this study we compared the thermal energy balance of i-UF with UF + HD at different dialysate temperatures (Td) and determined the Td at which the thermal energy balance during UF + HD is similar to the thermal energy balance during i-UF. METHODS: In the first part of the study, 10 chronic haemodialysis patients were compared during three different treatment sessions, i-UF, UF + HD at Td of 35.5 degrees C and UF + HD at Td of 37.5 degrees C. The second part of the study consisted of one session of 1 h of UF + HD (UF + HD ET-set) with a pre-set energy transfer (ET) at the same level of ET found for that particular patient during i-UF in the first part of the study. RESULTS: First part of the study: body temperature (BT) decreased significantly during i-UF (-0.25 +/- 0.25 degrees C, P<0.05) and UF + HD 35.5 degrees C (-0.24 +/- 0.18 degrees C, P<0.05) and increased significantly during UF + HD 37.5 degrees C (+0.18 +/- 0.19 degrees C, P<0.05). The differences between the change in BT during UF + HD 37.5 degrees C compared with the other treatments were significant (P<0.05). ET gave a significantly more negative value during i-UF (-30.8 +/- 3.1 W, P<0.05) than during UF + HD 35.5 degrees C (-23.6 +/- 4.1 W, P<0.05). A slightly positive ET was found during UF + HD 37.5 degrees C (+0.4 +/- 4.7 W, P=not significant). Second part of the study: there was a slight, but not significant, decrease in BT during UF + HD ET-set (-0.17 +/- 0.26 degrees C). The changes in BT did not differ significantly between i-UF and UF + HD ET-set. After 1 h of UF + HD ET-set, the mean Td was 34.75 degrees C (34.0-36.0 degrees C). The correlation between pre-dialysis BT and Td during UF + HD ET-set was significant (r=0.764, P<0.05). CONCLUSION: ET gives a more negative value during i-UF than during UF + HD 35.5 degrees C and than during UF + HD 37.5 degrees C. To obtain the same thermal ET during UF + HD as that achieved during i-UF, a mean Td of 34.75 degrees C is needed, depending on the pre-dialytic BT of the patient. The results of this study may be of relevance in relation to future clinical investigations which can elucidate whether differences in vascular response between i-UF and UF + HD are only related to differences in thermal balance.     

局部复方低温液灌洗治疗脊髓损伤的实验与临床研究

目的探索低温、低温程度及时间和药物配方对脊髓损伤的作用。方法用Ａｌｅｎ法致伤家兔成截瘫模型，观察比较早期低温灌洗组与对照组在运动能力、局部光电镜下的病理变化。结果低温灌洗对损伤之脊髓有良好保护作用，临床应用结果与动物实验相符。结论复方低温液对脊髓损伤有确切的保护作用，低温以２～４℃为宜，低温时间以２０分钟为宜     

高温对热区部队战士激素调节的影响

选择某电子对抗团战士和某坦克旅战士共64人,分别在高温、高湿等因素作用下连续作业1h(摩托小时),观察战士体内激素及电解质的变化情况。结果表明:两部队战士的心钠素、皮质醇、醛固酮水平作业前后有非常显著性以上的差异;血清K~+、Ca~(2+)浓度降低,Na~+浓度升高。以上结果表明:高温环境对战士体内激素水平影响显著,机体出现应激性改变。     

三种液冷装备致冷效果的医学研究

本文研究了在环境温度为45℃、露点温度为28℃,受试者处于运动和安静两种状态下,液冷帽、液冷背心和简易液冷服的致冷效果。结果表明,几种液冷装备均具有明显的致冷效果和显著的隔热作用。致冷效能以简易液冷服最大,其次为液冷背心和液冷帽。相反,致冷效率液冷帽最高,其次为液冷背心和简易液冷服。由于被致冷部位的解剖和生理机能的不同,致冷时生理反应并不一样。致冷躯干时,皮肤温度达稳定状态的时间比致冷头、颈部时间约长1小时,并且前者皮肤温度也较后者低4℃。     

不同气温和体力负荷下身体各部位体表温度的变化

研究了几种气温、同一活动水平以及相同气温、不同体力负荷下的各部位体表温度变化。实验结果表明:(1)进一步确认在同一气温下头颈部皮肤温度分布的不均匀性,并表明各部位受气温的影响程度也不尽相同。(2)在同一气温下头颈部及身体其它部位的皮肤温度变化并不与体力负荷程度呈特定关系,并分析了产生这一现象的原因。(3)根据下肢为主的体力负荷对全身体表温度的影响情况,认为个体调温装备的区域性流量分配比例随身体活动形式改变而改变的必要性并不很大。由此,可以减少服装设计的复杂性。     

不同湿黑球温度下军事劳动时的适宜饮水量

本文依据在不同 WGT 下进行中、重强度劳动时人体的出汗反应以及 WGT与出汗量之间的相互关系,提出比较适合于我军在热环境下劳动时使用的补水量参考值,以增强人体耐热能力,预防中暑的发生。114名健康战士在平均 WGT26.2～31.1℃下受试。实验过程分别测定了 WGT、出汗量、心率、肛温等。结果提示:(1)WGT 与出汗量、蒸发汗量之间存在着非常显著的相关关系,WGT 的变化能相应地反映热环境下劳动者的出汗及其汗液蒸发情况;(2)不同 WGT 下推算中、重强度劳动时的适宜饮水量公式分别为:(?)(L/h)=(0.09762WGT(℃)-2.01938)×80%、(?)(L/h)=(0.10342WGT(℃)-2.00330)×80%;(3)中、重强度下劳动,WGT26.0～32.0℃时的饮水量参考值为0.415～0.962L/h。