正常人的血液粘弹性和触变性研究

应用ＬｏｗＳｈｅａｒ４０流变仪对正常人的血液粘弹性、触变性等指标进行测定与分析，得到了全血滞后环和应力衰减曲线，发现应力的变化在突加一个切变率后并不是单纯的指数衰减，而是先经过０６ｓ左右的振荡过程，然后才开始指数衰减。弹性模量Ｇ′及耗散模量Ｇ″随振荡频率的变化在三个频点出现局部极大（极小）值，在０８Ｈｚ时Ｇ′、Ｇ″都达到谷值，应力与应变的相位差δ达到极小值，说明此振荡频率下血液的粘性分量与弹性分量之比达到最小。在０２Ｈｚ、３３Ｈｚ时Ｇ′达到谷值，Ｇ″保持上升趋势，相位差δ达到局部峰值，说明此二个振荡频率下血液的粘性分量与弹性分量之比达到最大。血液粘度的测量结果表明同心圆筒式粘度计在测量不同切变率范围（０～２００ｓ－１）的全血粘度时稳定性较锥板式差，而且在较高切变率时（１６０２００ｓ－１）数据不稳定。因此在进行一般的全血粘度测量时仍以锥板式为好。     

大马蹄蝠中脑上,下丘的功能形态学研究——氚标记的2—脱氧核糖法

用定量氚标记的２－＾３Ｈ脱氧核糖法（＾３Ｈ－２－Ｄｅｏｘｙｇｌｕｃｏｓｅ，＾３Ｈ－２－ＤＧ）和电生理学技术，研究了大马蹄蝠中脑上，下丘的听反应特征，电生理实验表明：下丘听反应的最佳频率为５９ＫＨｚ，从下丘中央核腹侧部到下丘表面，其频率从６２ＫＨｚ依次递减到３５ＫＨｚ具音频组构特点，＾３Ｈ－ＤＧ法结果表明：（１）上丘对５９ＫＨｚ６５ｄＢ５９ＫＨｚ，２０ｄＢ，２９．５ＫＨｚ，２０ｄＢ三组声刺激的反应处     

用生后精神生理学指标分析毫米波辐射对小鼠植入后胚胎生长发…

用频率３６．１１ＧＨｚ，功率密度为１．０ｍＷ／ｃｍ２的毫米波，在小鼠怀孕６－１５ｄ时进行２ｊ／ｄ的照射，胎仔出生后用精神生理学指标进行分析。结果显示，毫米波辐射可导致生后仔鼠三项反射指标形成时间明显延迟，可导致成年子鼠学习和记忆成绩降低，表现在Ｙ型电迷宫被动逃避条件反射实验中，需要较对照组鼠更多训练及次数才能达到规定标准。     

振动对小鼠体内磺胺嘧啶（SD）分布的影响

为了研究振动对生物体内物质的耗散作用，本文用药代动力学的方法在振动频率为２０Ｈｚ，加速度为１．１ｇ与５０Ｈｚ，４．４ｇ的条件下分别测试了小鼠体内血、肝与肾组织中磺胺啮咬（ＳＤ）在１至９小时内的分布，结果表明：２０Ｈｚ实验组血中ＳＤ浓度峰伍比对照组提前３小时，在振动１小时时，小鼠体内血、肝与肾组织中ＳＤ含量均比对照组高，但振动３小时至９小时内，其含量均比对照组低，从管道气栓体外模拟实验与本文的研究可得到启示：在上述频率与强度条件下，振动对生物体可能有促进血液循环的作用。     

一种抑制50Hz工频干扰的方法——基于FTF算法的自适应滤波

在长时间动态心电记录（ＨＯＬＴＥＲ）系统中５０Ｈｚ工频干扰会影响ＥＣＧ信号的质量和可诊断性，从而对ＱＲＳ复波的自动识别及节律分析产生不良影响。因此消除５０Ｈｚ工频干扰在ＥＣＧ信号予自理中占有重要地位。５０Ｈｚ工频干扰的频率和幅度是随着电网我参数的波动而变化的。从本质上讲，５０Ｈｚ工频干扰的波动过程是一种非平稳随机过程，采用固定的窄带隐波器对５０Ｈｚ工频干扰进行去除，不可能完全抑制５０Ｈｚ工频干扰，     

Er：YAG激光在皮肤外科中的应用

在应用于皮肤外科学的众多脉冲式外激光中，２９４ｍＥｒ：ＹＡＧ激光以它组织中独特的吸收性而成为最有效的磨皮方式并具有最少的热损伤。最新的高能Ｅｒ：ＹＡＧ激光可提供高达１．５Ｊ／次的输出能量和高达１５Ｈｚ的频率，使我们可以进一步研究它在皮肤手术中的临床应用。     

振动对动物体内血脂水平的影响

为了研究振动对生物体内物质的耗散作用，本文在振动频率为２０Ｈｚ，振幅为０．１ｃｍ条件下对土母鸡的腹部脂肪作局部振动。并于振动一个疗程（２小时／天，５－７ｘ）的前后分别测试了血清中总胆固醇（ＴＣ）、甘油三脂（ＴＧ）和高密度脂蛋白胆固醇（ＨＤＬ－Ｃ）等各项指标。结果表明：上述特定频率、振幅与时间的振动使实验动物体内血清中总胆固醇、高密度脂蛋白胆固时与低密度脂蛋白胆固醇（ＬＤＬ－Ｃ）显著增加；甘油三酯显著减少（Ｐ＜０．０５）。ＴＣ的变化与ＨＤＬ－Ｃ、ＬＤＬ－Ｃ的变化呈正相关；ＴＧ的变化与ＨＤＬ－Ｃ的变化呈负相关。从而证实了特定参数的振动对动物体内的脂肪代谢有明显的作用，为人体施局部伍振动减肥的可行性提供了有益的参考。     

采样率和放大器宽对心电信号波形的影响

设计了高端截止频率分别为１００Ｈｚ，３００Ｈｚ，１０００Ｈｚ的三通道放大器，用三妆同一信号，保证了信号的同源性及同时性，研究表明大放大时间常数对心电信号波形有影响，如时间常数０．１秒时，出现Ｔ波双相最为明显，放大器带宽越宽心电信号高频成分越多，但功主很小，心电信号细节主要采样频率决定，硬件带宽时之影响次之。     

采样率和放大器带宽对心电信号波形的影响

设计了高端截止频率分别为１００Ｈｚ、３００Ｈｚ、１０００Ｈｚ的三通过放大器；用三通道接同一信号，保证了信号的同源性及同时性。研究表明放大器时间常数对心电信号波形有影响，如时间常数０．１秒时，出现Ｔ波双相最为明显。放大器带宽越宽心电信号高频成分越多，但功率很小。心电信号细节主要由采样频率决定，硬件带宽对之影响次之。     

功能性消化不良胃电活动及频谱分析

功能性消化不良胃电活动及频谱分析战淑慧，柯美云，王智凤（北京协和医院消化内科）本研究观察了功能性消化不良（ＦＤ）病人的体表胃电活动的变化，探讨ＥＧＧ对研究ＦＤ的价值，并观察西沙必利对ＥＧＧ和胃排空的影响。１．对象和方法：１０名ＦＤ病人（男／女：２／８...     

多电极射频美容仪的温度场仿真实验研究

射频美容仪是国内家用美容仪市场中很受欢迎的保健产品。然而,市面上的射频美容仪产品质量参差不齐,相关参数也缺乏统一的标准规范。该研究基于有限元仿真方法和COMSOL仿真软件,构建了具有隔膜的三维皮肤模型,仿真分析、研究了不同射频美容仪的射频电压有效值、射频频率、电极高度、电极直径、电极间距、电极数量及排布等参数条件对皮肤及皮下组织温度场分布的影响,并进行了对比分析。仿真结果表明：提高电压有效值或射频频率能提高模型温度场的最大值;提高电极高度相比紧贴皮肤会降低温度场最大值并使射频美容仪下的温度分布更加均匀;增加电极直径或缩小电极间距能提高电极间的温度;不同的正负极数量会使热量集中在数量较少的电极下方。最后,该研究还完成了温度场分布随时间的实验测量及与仿真结果的比较分析。该研究较为系统、全面地仿真探讨了射频美容仪产品的各项参数条件变化对皮肤温度分布的影响规律,为溶脂技术的安全与疗效提供参考,也为射频美容仪的临床应用及产业化提供参考。     

Response of the respiratory network of mice to hyperthermia

Most mammals modulate respiratory frequency (RF) to dissipate heat (i.e., panting) and avoid heat stroke during hyperthermic conditions. During hyperthermia, the RF of intact mammals increases and then declines or ceases (apnea). It has been proposed that this RF modulation depends on the presence of higher brain structures such as the hypothalamus. However, the direct effects of hyperthermia on the respiratory neural network have not been examined. To address this issue, the respiratory neural network [i.e., ventral respiratory group (VRG)] was isolated in a brain stem preparation taken from the medulla of mice (P0 -P6). Integrated population activity, predominated by inspiratory neurons, was recorded extracellularly from VRG neurons. The bath temperature was then heated from 30 to 40 degrees C, resulting in a biphasic frequency response in VRG activity. Following an initial six- to sevenfold increase and subsequent decline, fictive RF was maintained at a frequency that was higher than baseline frequency; at 40 degrees C, the RF was maintained at about two to four times that at 30 degrees C. The inspiratory burst amplitude and duration were significantly reduced during hyperthermic conditions. An increase in RF and decrease in VRG burst amplitude and duration also occurred when heating from 37 to 40 degrees C. Fictive apnea typically occurred during cooling to the control temperature. Furthermore, changes in hypoglossal motor nucleus activity paralleled those of the VRG, suggesting that temperature modulation of the VRG is likely to have a behaviorally relevant impact on respiration. We conclude that the VRG activity itself is modulated during hyperthermia and the respiratory network is particularly sensitive to temperature changes.     

Parallel transmission RF pulse design with strict temperature constraints

RF safety in parallel transmission (pTx) is generally ensured by imposing specific absorption rate (SAR) limits during pTx RF pulse design. There is increasing interest in using temperature to ensure safety in MRI. In this work, we present a local temperature correlation matrix formalism and apply it to impose strict constraints on maximum absolute temperature in pTx RF pulse design for head and hip regions. Electromagnetic field simulations were performed on the head and hip of virtual body models. Temperature correlation matrices were calculated for four different exposure durations ranging between 6 and 24 min using simulated fields and body‐specific constants. Parallel transmission RF pulses were designed using either SAR or temperature constraints, and compared with each other and unconstrained RF pulse design in terms of excitation fidelity and safety. The use of temperature correlation matrices resulted in better excitation fidelity compared with the use of SAR in parallel transmission RF pulse design (for the 6 min exposure period, 8.8% versus 21.0% for the head and 28.0% versus 32.2% for the hip region). As RF exposure duration increases (from 6 min to 24 min), the benefit of using temperature correlation matrices on RF pulse design diminishes. However, the safety of the subject is always guaranteed (the maximum temperature was equal to 39°C). This trend was observed in both head and hip regions, where the perfusion rates are very different.     

Differential regulation of the expression of Period2 protein in the limbic forebrain and dorsomedial hypothalamus by daily limited access to highly palatable food in food-deprived and free-fed rats

Circadian clock genes are rhythmically expressed in many areas of the brain and body and are thought to underlie most endogenous circadian behaviors and physiological processes. Daily rhythms of clock gene expression throughout the brain and body are normally coordinated by the suprachiasmatic nucleus (SCN), but they are also strongly influenced by daily temporal restrictions of food availability. Here, we studied the effects of a daily restricted presentation of highly palatable complete meal replacement, chocolate Ensure Plus (Ensure) in food-deprived (restricted feeding, RF) and free-fed (restricted treat, RT) rats, on the expression of the clock protein, Period2 (PER2) in regions of the brain involved in motivational and emotional regulation; these include the oval nucleus of the bed nucleus of the stria terminalis (BNSTov), the central nucleus of the amygdala (CEA), the basolateral amygdala (BLA), the dentate gyrus (DG) and the dorsomedial hypothalamus (DMH). RF and RT rats consumed similar amounts of Ensure, but changes in the pattern of PER2 expression were seen only in the RF condition, suggesting that changes in PER2 expression in these regions are triggered by the daily alleviation of a negative metabolic state associated with RF and are independent of the positive incentive properties of the consumed substance, per se. In contrast, the expression of the immediate early gene, Fos, was increased in these regions by both RF and RT schedules, showing that signals concerning the incentive value of the consumed food reach these regions. No changes in either PER2 or Fos expression were observed in the SCN of RF or RT rats. These findings demonstrate that mechanisms leading to changes in the expression of PER2 and those affecting the induction of Fos under RF and RT are, at least in part, dissociable.     

Contributions to enhanced activity in rectus femoris in response to Lokomat-applied resistance

The application of resistance during the swing phase of locomotion is a viable approach to enhance activity in the rectus femoris (RF) in patients with neurological damage. Increased muscle activity is also accompanied by changes in joint angle and stride frequency, consequently influencing joint angular velocity, making it difficult to attribute neuromuscular changes in RF to resistance. Thus, the purpose of this study was to evaluate the effects of resistance on RF activity while constraining joint trajectories. Participants walked in three resistance conditions; 0 % (no resistance), 5 and 10 % of their maximum voluntary contraction (MVC). Visual and auditory biofeedback was provided to help participants maintain the same knee joint angle and stride frequency as during baseline walking. Lower limb joint trajectories and RF activity were recorded. Increasing the resistance, while keeping joint trajectories constant with biofeedback, independently enhanced swing phase RF activity. Therefore, the observed effects in RF are related to resistance, independent of any changes in joint angle. Considering resistance also affects stride frequency, a second experiment was conducted to evaluate the independent effects of resistance and stride frequency on RF activity. Participants walked in four combinations of resistance at 0 and 10 %MVC and natural and slow stride frequency conditions. We observed significant increases in RF activity with increased resistance and decreased stride frequency, confirming the independent contribution of resistance on RF activity as well as the independent effect of stride frequency. Resistance and stride frequency may be key parameters in gait rehabilitation strategies where either of these may be manipulated to enhance swing phase flexor muscle activity in order to maximize rehabilitation outcomes.     

Hyperthermia modulates respiratory pacemaker bursting properties

Most mammals modulate respiratory frequency (RF) to dissipate heat (e.g., panting) and avoid heat stroke during hyperthermic conditions. Respiratory neural network activity recorded in an isolated brain stem-slice preparation of mice exhibits a similar RF modulation in response to hyperthermia; fictive eupneic frequency increases while inspiratory network activity amplitude and duration are significantly reduced. Here, we study the effects of hyperthermia on the activity of synaptically isolated respiratory pacemakers to examine the possibility that these changes may account for the hyperthermic RF modulation of the respiratory network. During heating, modulation of the bursting frequency of synaptically isolated pacemakers paralleled that of population bursting recorded from the intact network, whereas nonpacemaker neurons were unaffected, suggesting that pacemaker bursting may account for the temperature-enhanced RF observed at the network level. Some respiratory neurons that were tonically active at hypothermic conditions exhibited pacemaker properties at approximately the normal body temperature of eutherian mammals (36.81 +/- 1.17 degrees C; mean +/- SD) and continued to burst at 40 degrees C. At elevated temperatures (40 degrees C), there was an enhancement of the depolarizing drive potential in synaptically isolated pacemakers, while the amplitude of integrated population activity declined. Isolated pacemaker bursting ceased at 41-42 degrees C (n = 5), which corresponds to temperatures at which hyperthermic-apnea typically occurs in vivo. We conclude that pacemaker properties may play an important role in the hyperthermic frequency modulation and apnea, while network effects may play important roles in generating other aspects of the hyperthermic response, such as the decreased amplitude of ventral respiratory group activity during hyperthermia.     

Investigation of the genotoxic effect of microwave irradiation in rat bone marrow cells: in vivo exposure

An in vivo mammalian cytogenetic test (the erythrocyte micronucleus assay) was used to investigate the extent of genetic damage in bone marrow red cells of rats exposed to radiofrequency/microwave (RF/MW) radiation. Wistar rats (n = 40) were exposed to a 2.45 GHz continuous RF/MW field for 2 h daily, 7 days a week, at a power density of 5-10 mW/cm(2). The whole body average specific absorption rate (SARs) was calculated to be 1.25 +/- 0.36 (SE) W/kg. Four subgroups were irradiated for 4, 16, 30 and 60 h. Sham-exposed controls (n = 24) were included in the study. The animals of each treated subgroup were killed on the final day of irradiation. Bone marrow smears were examined to determine the extent of genotoxicity after particular treatment times. The results were statistically evaluated using non-parametric Mann-Whitney and Kruskal-Wallis tests. In comparison with the sham-exposed subgroups, the findings of polychromatic erythrocytes (PCE) revealed significant differences (P < 0.05) for experimental days 8 and 15. The frequency of micronucleated PCEs was also significantly increased on experimental day 15 (P < 0.05). Pair-wise comparison of data obtained after 2, 8 and 30 irradiation treatments did not reveal statistically significant differences between sham-exposed and treated subgroups. Under the applied experimental conditions the findings revealed a transient effect on proliferation and maturation of erythropoietic cells in the rat bone marrow and the sporadic appearance of micronucleated immature bone marrow red cells.     

A comparative study of myocardial function and morphology during fasting/refeeding and food restriction in rats

BackgroundThis study compared the influence of fasting/refeeding cycles and food restriction on rat myocardial performance and morphology.MethodsSixty-day-old male Wistar rats were submitted to food ad libitum (C), 50% food restriction (R50), and fasting/refeeding cycles (RF) for 12 weeks. Myocardial function was evaluated under baseline conditions and after progressive increase in calcium and isoproterenol. Myocardium ultrastructure was examined in the papillary muscle.ResultsFasting/refeeding cycles maintained rat body weight and left ventricle weight between control and food-restricted rats. Under baseline conditions, the time to peak tension (TPT) was more prolonged in R50 than in RF and C rats. Furthermore, the maximum tension decline rate (?dT/dt) increased less in R50 than in RF with calcium elevation. While the R50 group showed focal changes in many muscle fibers, such as the disorganization or loss of myofilaments, polymorphic mitochondria with disrupted cristae, and irregular appearance or infolding of the plasma membrane, the RF rats displayed few alterations such as loss or disorganization of myofibrils.ConclusionFood restriction promotes myocardial dysfunction, not observed in RF rats, and higher morphological damage than with fasting/refeeding. The increase in TPT may be attributed possibly to the disorganization and loss of myofibrils; however, the mechanisms responsible for the alteration in ?dT/dt in R50 needs to be further clarified.     

Improvement of patient return electrodes in electrosurgery by experimental investigations and numerical field calculations

Numerical field calculations and experimental investigations were performed to examine the heating of the surface of human skin during the application of a new electrode design for the patient return electrode. The new electrode is characterised by an equipotential ring around the central electrode pads. A multilayer thigh model was used, to which the patient return electrode and the active electrode were connected. The simulation geometry and the dielectric tissue parameters were set according to the frequency of the current. The temperature rise at the skin surface due to the flow of current was evaluated using a two-step numerical solving procedure. The results were compared with experimental thermographical measurements that yielded a mean value of maximum temperature increase of 3.4°C and a maximum of 4.5°C in one test case. The calculated heating patterns agreed closely with the experimental results. However, the calculated mean value in ten different numerical models of the maximum temperature increase of 12.5K (using a thermodynamic solver) exceeded the experimental value owing to neglect of heat transport by blood flow and also because of the injection of a higher test current, as in the clinical tests. The implementation of a simple worst-case formula that could significantly simplify the numerical process led to a substantial overestimation of the mean value of the maximum skin temperature of 22.4K and showed only restricted applicability. The application of numerical methods confirmed the experimental assertions and led to a general understanding of the observed heating effects and hotspots. Furthermore, it was possible to demonstrate the beneficial effects of the new electrode design with an equipotential ring. These include a balanced heating pattern and the absence of hotspots.     

Erythropoietic dynamic equilibrium in rats maintained after microwave irradiation

The aim of study was to define influence of radiofrequency microwave (RF/MW) radiation on erythropoiesis in rats. The kinetics of polychromatic erythrocytes (PCEs) and micronucleated (MN) PCEs in the bone marrow (BM) and peripheral blood (PB) of rats during the intermittent subchronic experiment was followed. Rats were exposed 2h/day, 7 days/week to RF/MW of 2.45 GHz and whole-body specific absorption rate (SAR) of 1.25+/-0.36 W/kg. Control animals were included in the study. Each exposed and control group was killed on the final day of irradiation. Acridine-orange stained BM and blood smears were examined by fluorescence microscope. PCEs were obtained by inspection of 2000 BM and 1000 PB erythrocytes/slides. BMMNs and PBMNs frequency was obtained by observation of 1000 PCEs/slides. BMPCEs were increased on day 8 and 15, and PBPCEs were elevated on days 2 and 8 (p<0.05). The BMMN frequency was increased on experimental day 15, and MNPCEs in the PB was increased on day 8 (p<0.05). Findings of BM and PBPCEs or MNPCEs declined nearly to the control values until the end of the experiment. Such findings are considered to be indicators of radiation effects on BM erythropoiesis consequently reflected in the PB. Rehabilitated dynamic haemopoietc equilibrium in rats by the end of experiment indicates possibility of activation adaptation process in rats to the selected experimental conditions of subchronic RF/MW exposure.