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11.
High energy laser has emerged to be an important surgical tool in medical technology. However, the application of laser energy
to drill or cut a bone is still in an experimental state. In order to estimate the adequacy of laser heating of bone surface
and at the same time minimize the damage to the bone tissue, we developed a mathematical model of the temperature distribution
in bone due to laser irradiation. The thermal analysis shows that the temperature distribution depends on several parameters,
including the density, the specific heat, and the thermal conductivity of the osseous tissue. 相似文献
12.
模糊数学方法用于职业危害因素的综合评价徐新云(湖南省劳动卫生职业病研究所,长沙410007)用模糊数学方法进行综合评价时,首先要确定评判等级,各评判因素在不同等级中的取值,以及各评判因素的权重系数三方面内容。本文将评判等级定为优、良、一般、差、很差5... 相似文献
13.
Temperature sensitive liposomes (TSL) containing adriamycin (ADM) and cytarabine (Ara-C) were prepared. ADM and Ara-C were
selected as model compounds of amphiphilic and hydrophilic drug, respectively. Encapsulation efficiency of ADM entrapped into
TSL was about twice greater than that of Ara-C. It might be due to different polarity of the drugs. Lipid compositions of
TSL had no effect on the encapsulation efficiency of drugs. Thermal behavior of TSL using a differential scanning calorimetry
(DSC) was also investigated. Phase transition temperature (Tc) of TSL was dependent on the lipid compositions of TSL.ADM broadened thermogram of TSL but Ara-C did not. However, Tc of TSL was not changed by any drug. Release rate of drugs was highly dependent on temperature. The release profile of ADM
was similar to that of Ara-C. The maximum release rate of drugs from TSL was occurred at the near Tc and observed at 39–41°C for DPPC (Dipalmitoylphosphatidylcholine) only, 52–54°C for DSPC (Distearoylphosphatidylcholine)
only, 41–43°C for DPPC and DSPC (3∶1), and 43–45°C for DPPC and DSPC (1∶1), respectively. Effect of human serum albumin (HSA)
on the release rate of ADM was investigated. HSA had no significant effect on the release of ADM below Tc. However, ADM release from TSL was increased at the near and above Tc. The HSA-induced leakage of drug may result from the interaction of liposomal constituents with HSA structure at the near
Tc. From the fact that the release profiles of ADM from freshly prepared TSL and stored TSL for 1 week at 4°C was not changed,
the TSL was considered to be stable for at least 1 week at 4°C. Based on these findings, TSL may be useful to deliver drugs
to preheated target sites due to its thermal behaviors. 相似文献
14.
M. Estryn-Behar B. Kapitaniak M. C. Paoli E. Peigne A. Masson 《International archives of occupational and environmental health》1992,64(2):131-139
Summary The aim of this study was to evaluate the level of physical capacity in a female hospital population of Paris and its suburbs. A total of 1505 women working in the selected departments filled in a questionnaire concerning their working conditions, life habits and health and also attended a medical examination. The effort test performed consisted in flexing the legs 20 times with the chest held straigt, in 40 s. The heart rates were measured for the first, the second and the third minutes of recovery (first 15 s multiplied by 4). The blood pressure was measured just after the heart rate, for the first and the third minute. Recovery indices have been constituted from the results. The respective weights of anthropometric and sociodemographic risk factors for recovery indices were studied in multiple logistic regression models. The classification enables us to consider about 25%–30% of our population as having a satisfactory physical capacity, about 26%–27% as having an acceptable capacit, and about 24%–27% as having a weak capacity. About 21% of the population presented an excessive pressure reaction and 44% a questionable pressure reaction. Our results concerning the level of physical capacity of the female nursing staff should be taken into account especially in the future planning of work loads and architectural choices, which must avoid excessive physical burdens in relation to this level. An improvement in the level of physical capacity could be envisaged as well. 相似文献
15.
16.
Karl‐Jürgen Br Stanislaw Brehm Michael Karl Boettger Gerd Wagner Silke Boettger Heinrich Sauer 《European Journal of Pain》2006,10(5):467-471
An altered perception of pain has been described for several psychiatric disorders. To date the influence of adjustment disorders (AD) on pain perception has not been described. Here, we investigated perception of experimentally induced pain in 15 patients suffering from AD (subtype with depressive symptoms) and controls matched for age and sex. Thresholds and tolerances were assessed for thermal and electrical pain on both sides of the body. We found an overall increase of pain thresholds and tolerances in AD patients as compared to controls, predominately on the right side of the body. Analogue findings have been reported for pain perception in major depressive disorder (MDD). Of the data obtained, only thermal pain threshold on the right arm correlated with the severity of depressive symptoms. Although the underlying pathology is elusive it is likely that the mechanisms for reduced pain sensitivity are comparable in MDD and AD. 相似文献
17.
He X Wolkers WF Crowe JH Swanlund DJ Bischof JC 《Annals of biomedical engineering》2004,32(10):1384-1398
The in situ thermal protein denaturation and its correlation with direct hyperthermic cell injury in Dunning AT-1 prostate tumor cells were investigated in this study. The in situ thermal protein denaturation was studied using both Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The FTIR spectra at different temperatures show changes in protein secondary structure (from alpha helix to extended beta sheet) during in situ thermal protein denaturation within AT-1 cells. Calorimetric studies using DSC show that endothermic heat release is associated with the in situ thermal protein denaturation. Furthermore, both the secondary structure changes detected by FTIR and the calorimetric changes detected by DSC were quantified and the kinetics of the overall in situ thermal protein denaturation was derived under different heating conditions. The onset temperature where the overall in situ thermal protein denaturation is first detectable was found to be scanning rate dependent (approximately 41 degrees C at 2 degrees C min(-1) and approximately 44 degrees C at 5 degrees C min(-1)). The kinetics of the overall in situ thermal protein denaturation was derived from both DSC and FTIR measurements and was fit using kinetic and statistical models. The kinetic data determined by FTIR and DSC under the same heating conditions match well with each other. The activation energy of the overall in situ thermal protein denaturation is found to be strongly dependent on the temperature range considered (the activation energy ranges from approximately 110 kJ mol(-1) between 44 and 90 degrees C to approximately 750 kJ mol(-1) between 44 and 50 degrees C). However, its dependence on heating rate is negligible. Several denaturation peaks, including a dominant one between approximately 62 and 65 degrees C, are identifiable from both the DSC and the FTIR results. To investigate directly the relationship between thermally induced cell injury and the in situ thermal protein denaturation, both acute (propidium iodide dye exclusion, assessed 3-h postthermal treatment) and chronic (clonogenics, assessed 7-day postthermal treatment) cell injury were quantified using AT-1 cells prepared under the same conditions as for the DSC protein studies. Comparisons of the results from the cell injury studies and the DSC protein denaturation studies show that the overall in situ thermal protein denaturation correlates well with both the acute and the chronic cell injury, which suggests that overall in situ thermal protein denaturation is an important mechanism of direct hyperthermic cell injury in AT-1 cells at the macromolecular level. 相似文献
18.
Wilson TE Johnson SC Petajan JH Davis SL Gappmaier E Luetkemeier MJ White AT 《European journal of applied physiology》2002,88(1-2):67-75
This study compared the effects of pre-exercise cooling with control water immersions on exercise-induced thermal loads derived
from steady-state submaximal exercise. Eight healthy male participants [mean (SEM) age 29 (1) years, maximal oxygen uptake
3.81 (0.74) l·min–1, and body surface area 1.85 (0.11) m2] took part in experiments that included 30 min of baseline data collection [ambient temperature 21.3 (0.2°C)], 30 min of
immersion in water to the level of the supra-iliac crest [water temperatures of 35.1 (0.3)°C for thermoneutral and 17.7 (0.5)°C
for precooled treatments], and 60 min of cycling exercise at 60% of maximal oxygen uptake. No significant differences were
noted during exercise in net mechanical efficiency, metabolic rate, O2 pulse, or ratings of perceived exertion between the two treatments. Precooling resulted in a significant negative body heat
storage during immersion and allowed greater heat storage during exercise. However, net body heat storage for the entire protocol
was no different between treatments. Cooling significantly lowered rectal, mean skin, and mean body temperatures as well as
more than doubling the exercise time until a 0.5°C rectal temperature increase was observed. The cooling trial significantly
delayed onset of sweating by 19.62 min and decreased sweat rate by 255 ml·h–1 compared to control. Thermal and sweat sensation scores were lower after the cooling treatment compared to control. These
data suggest that lower-body precooling is effective at decreasing body heat storage prior to exercise and decreases reliance
on heat dissipation mechanisms during exercise. Therefore, this unique, well-tolerated cooling treatment should have a broader
application than other precooling treatments.
Electronic Publication 相似文献
19.
Local thermal unpleasantness and discomfort prediction in the vicinity of thermoneutrality 总被引:2,自引:0,他引:2
This work emphasizes a better understanding of the origin of human thermal discomfort under heterogeneous but steady environments, in subjects in the vicinity of physiological and sensory thermoneutrality. The knowledge of skin temperatures allows a psychophysiological study aiming at linking the body thermal state (local and global) to thermal sensation (perceptive and affective judgements). By using two driving simulators, 345 subjects were exposed to different thermal environments, modulated by factors such as the air distribution in the automotive cockpit or the clothing insulation (winter or summer). This work shows that consideration of the local thermal state is essential for the evaluation of thermal comfort in the case of non-uniform environments. Our experimental conditions point out that the overall sensation of discomfort is quantitative, with local unpleasantness needing to be felt for a certain number of body surfaces. A local origin is suggested for cold discomfort, in opposition to the global characteristics of warm discomfort. 相似文献
20.
Mehnert P Malchaire J Kampmann B Piette A Griefahn B Gebhardt H 《European journal of applied physiology》2000,82(1-2):52-60
The prediction of the mean skin temperature used for the Required Sweat Rate index was criticised for not being valid in
conditions with high radiation and high humidity. Based on a large database provided by 9 institutes, 1999 data points obtained
using steady-state conditions, from 1399 experiments and involving 377 male subjects, were used for the development of a new
prediction model. The observed mean skin temperatures ranged from 30.7 °C to 38.6 °C. Experimental conditions included air
temperatures (T
a) between 20 and 55 °C, mean radiant temperatures (T
r) up to 145 °C, partial vapour pressures (P
a) from 0.2 to 5.3 kPa, air velocities (v
a) between 0.1 and 2 m/s, and metabolic rates (M) from 102 to 620 W. Rectal temperature (T
re) was included in the models to increase the accuracy of prediction. Separate models were derived for nude (clothing insulation,
Icl, ≤0.2 clo, where 1 clo=0.155 m2 · °C · W−1, which is equivalent to the thermal insulation of clothing necessary to maintain a resting subject in comfort in a normally
ventilated room, air movement=10 cm/s, at a temperature of 21 °C and a humidity of less than 50%) and clothed (0.6 ≤ Icl ≤ 1.0 clo) subjects using a multiple linear regression technique with re-sampling (non-parametric bootstrap). The following
expressions were obtained for nude and clothed subjects, respectively: T
sk=7.19 + 0.064T
a + 0.061T
r + 0.198P
a− 0.348v
a + 0.616T
re and T
sk=12.17 + 0.020T
a + 0.044T
r + 0.194P
a − 0.253v
a + 0.0029M + 0.513T
re. For the nude and clothed subjects, 83.3% and 81.8%, respectively, of the predicted skin temperatures were within the range
of ±1 °C of the observed skin temperatures. It is concluded that the proposed models for the prediction of the mean skin temperature
are valid for a wide range of warm and hot ambient conditions in steady-state conditions, including those of high radiation
and high humidity.
Accepted: 7 February 2000 相似文献