OBJECTIVE: The aim of this research was to evaluate the mechanical properties (MP) and degree of the phase transformation (PT) of martensitic (M-NiTi), austenitic (A-NiTi) and thermodynamic nickel-titanium wire (T-NiTi). METHODS: The samples consisted of 0.016 x 0.022 inch M-NiTi (Nitinol Classic, NC), A-NiTi (Optimalloy, OPTI) and T-NiTi (Neo-Sentalloy, NEO). Differential scanning calorimetry (DSC), three-point bending test, X-ray diffraction (XRD), and microstructure examination were used. Statistical evaluation was undertaken using ANOVA test. RESULTS: In DSC analysis, OPTI and NEO showed two peaks in the heating curves and one peak in the cooling curves. However, NC revealed one single broad and weak peak in the heating and cooling curves. Austenite finishing (Af) temperatures were 19.7degrees C for OPTI, 24.6degrees C for NEO and 52.4degrees C for NC. In the three-point bending test, residual deflection was observed for NC, OPTI and NEO. The load ranges of NC and OPTI were broader and higher than NEO. XRD and microstructure analyses showed that OPTI and NEO had a mixture of martensite and austenite at temperatures below Martensite finishing (Mf). NEO and OPTI showed improved MP and PT behavior than NC. CONCLUSIONS: The mechanical and thermal behaviors of NiTi wire cannot be completely explained by the expected degree of PT because of complicated martensite variants and independent PT induced by heat and stress.
Calorimetry, Differential Scanning ; Dental Alloys ; Heating ; Hot Temperature ; Thermodynamics ; Transition Temperature ; X-Ray Diffraction

BACKGROUND: Liquid nitrogen freezing techniques have already met with widespread success in biology and medicine as a means of long-term storage for cells and tissues. The use of cryoprotectants such as glycerol and dimethylsulphoxide to prevent ice crystal formation, with carefully controlled rates of freezing and thawing, allows both structure and viability to be retained almost indefinitely. Cryopreservation of various tissues has various controlled rates of freezing. MATERIAL AND METHOD: To find the optimal freezing curve and the chamber temperature, we approached the thermodynamic calculation of tissues in two ways. One is the direct calculation method. We should know the thermophysical characteristics of all components, latent heat of fusion, area, density and volume, etc. This kind of calculation is so sophisticated and some variables may not be determined. The other is the indirect calculation method. We performed the tissue freezing with already used freezing curve and we observed the actualfreezing curve of that tissue. And we modified the freezing curve with several steps of calculation, polynomial regression analysis, time constant calculation, thermal response calculation and inverse calculation of chamber temperature. RESULT: We applied that freezing program on mesenchymal stem cell, chondrocyte, and osteoblast. The tissue temperature decreased according to the ideal freezing curve without temperature rising. We did not find any differences in survival. The reason is postulated to be that freezing material is too small and contains cellular components. We expect the significant difference in cellular viability if the freezing curve is applied on a large scale of tissues. CONCLUSION: This program would be helpful in finding the chamber temperature for the ideal freezing curve easily.
Biology ; Chondrocytes ; Cryopreservation ; Dimethyl Sulfoxide ; Freezing* ; Glycerol ; Hot Temperature* ; Ice ; Mesenchymal Stromal Cells ; Nitrogen ; Osteoblasts ; Thermodynamics ; Transplantation, Homologous

High intensity focused ultrasound (HIFU) is a very complex transient process and can cause tissue coagulation necrosis. The cavitation and boiling behaviour of bubbles in the focal region play very important roles throughout an injury process. This paper reviews the research done by domestic and foreign scholars on behaviours of bubbles in HIFU irradiation process and summarizes in the focal region bubble cavitation and boiling generation, related detective means and relationships with hyperecho, temperature rise of the focus and injury shape.
Biophysical Phenomena ; High-Intensity Focused Ultrasound Ablation ; methods ; Humans ; Thermal Conductivity ; Thermodynamics

AIMTo study the thermal stability, decomposition process and kinetics of such purine pharmaceuticals as aciclovir (Acv), penciclovir (Pcv), and their parent substance, guanine.

METHODSUsing infrared technique, accelerating test method and thermogravimetry to investigate the thermal decomposition processes and using Coast-Redfern method, MKN method and Ozawa method to deal with the data to get kinetic functions.

RESULTSThe decomposition process and the formed products were derived, the kinetic model function was suggested by comparison of the kinetic parameters.

CONCLUSIONPcv and Acv's degrading product for the first step is guanine. The sequences of their thermal stabilities is: Pcv > Acv. The two drugs' kinetic equation of thermal decomposition is expressed as: da/dt = Ae-Ea/RT2(1-alpha)3/2.

Acyclovir ; analogs & derivatives ; chemistry ; Drug Stability ; Guanine ; chemistry ; Hot Temperature ; Kinetics ; Thermodynamics ; Thermogravimetry

The inclusion compound of amylose and salicylic acid (SA) was prepared by a sealed temperature control method, and the formation of the inclusion compound was confirmed by IR spectrum and powder X-ray diffraction. The kinetic parameters of dissociation of amylose/SA compound were studied by the nonisothermal method which was defined as a relationship between the dissociation ratio and time. The values of activation energy (Ea) and frequency factors (InA) were calculated by a nonlinear least-square method. In this study, the formation of the inclusion compound of amylose/SA was confirmed by IR spectrum powder X-ray diffraction. SA existed in a molecule form in the spiral stouction of amylose. The dissociation of amylose/SA compound was attributed to first order reaction. The values of Ea calculated by the nor-isothermal method were 21.71 and 22.41 kJ x mol(-1) at heating rate 5 and 10 degrees C x h(-1), respectively. The corresponding isothermal method value of Ea was 22.17 kJ x mol(-1); the calculated InA values were 9.32 and 10.08 at heating rate 5 and 10 degrees C x h(-1), respectively. The corresponding isothermal method lnA value was 9.26. The results were in good agreement with Ea values and lnA values by isothermal method. These results indicated that the non-isothermal method described in this study could be adequately used for the stability study of inclusion compound and was a rapid and accurate method for the determination of kinetic parameters.
Amylose ; chemistry ; Drug Stability ; Hot Temperature ; Kinetics ; Powder Diffraction ; Salicylic Acid ; chemistry ; Spectrophotometry, Infrared ; Thermodynamics

WATER HYDROXIDES INORGANIC CHEMICALS OXYGEN COMPOUNDS OXIDES TRANSITION TEMPERATURE TEMPERATURE THERMODYNAMICS PHYSICAL PHENOMENA ANGIOFIBROMA NEOPLASMS ; VASCULAR TISSUE NEOPLASMS BY HISTOLOGIC TYPE NEOPLASMS THERAPEUTICS THERAPY

In this work, the dipeptide composition of 3216 thermophilic and 4007 mesophilic protein sequences was systematically analyzed. We found that the thermophilic proteins contained more dipeptides such as EE, EK, KE, VE, EI, KI, EV, KK, VK and IE, whereas less dipeptides such as AA, LL, LA, AL, QA, QL, AQ, LT, TL and EQ. Based on this information, a statistical method for discriminating thermophilic and mesophilic proteins was developed. Our approach correctly picked up the thermophilic proteins with the accuracy of 94.0% and 89%, respectively, for the testing sets of 382 and 73 thermophilic proteins. And for the testing 325 and 73 mesophilic proteins, the accuracy was 85.2% and 89%, respectively. The influence of specific dipeptides on discrimination was also discussed.
Amino Acids ; chemistry ; Bacteria ; chemistry ; Bacterial Proteins ; chemistry ; Dipeptides ; chemistry ; Discriminant Analysis ; Hot Temperature ; Sequence Analysis, Protein ; Thermodynamics

In the surgical use of lasers in medicine, the laser light energy is transformed into heat within the tissue. As the result of this generation of heat, coagulation occurs and the tissue is carbonized and vaporized. The thermal effect depends upon the energy of the light radiation, its power and the irradiation time, the beam geometry, and the optical properties of the tissue itself, and also upon the thermal .parameters of the tissue such as its thermal conductivity and specific heat. In this experiment, to investigate the Neodymium-YAG laser effect on the bladder tissue and the extend of tissue damage at the various power and irradiation time under the same laser energy were aimed. Immediate after irradiation, the bladder tissues were fixed with formalin solution and H& E stained The extend of tissue damage was examined with light microscope. The following results were obtained: The effect of Neodymium-YAG laser irradiation on the bladder tissue was like a burn effect. Although the energy delivered to the tissue was the same, the resultant lesions created by the energy differed. The delivery of same energy in a low-power, long-duration manner made more tissue damage than a high-power, short-duration. Judging from the results of this experiment, it may be believed that a long period of irradiation time that there is sufficient time for the heat to be conducted into the surrounding tissue increases the zone of thermal damage and the coagulation necrosis.
Burns ; Carbon ; Formaldehyde ; Hot Temperature ; Lasers, Solid-State ; Necrosis ; Thermal Conductivity ; Urinary Bladder*

PURPOSE: This study was designed to better understand the mechanism of low temperature burn and to show clinical cases of low temperature burn. METHODS: The local temperature increase of electric pad was investigated at 4 different surface cooling conditions. Blocks (5x5x2 cm3) made of silicone rubber, aluminum, or urethane foam were placed on the top of the electric pad, and temperature between the blocks and electric pad was measured up to 7 hours after switching on maximally (level 7). Each block has different thermal conductivity (TC) and TC of silicone rubber (0.2 W/m.degrees C) is similar to TC of human skin (0.37 W/m.degrees C). TC of aluminum is higher and TC of urethane foam is lower than TC of human skin. Experiments were performed on two occasions with or without a blanket covering over the electric pad and blocks. RESULTS: The initial surface temperature (18degrees C) of the electric pad under the silicone rubber block was elevated to 36.5degrees C at 1 hour, 41.8degrees C at 3 hours, 44.2degrees C at 5 hours, and 45.5degrees C at 7 hours. After covering the electric pad and blocks with a blanket, the temperature of the electric pad under the silicone rubber block was elevated to 40.9degrees C at 1 hour, 51.8degrees C at 3 hours, 56.1degrees C at 5 hours and 58.1degrees C at 7 hours. Under the same conditions, surface temperatures under the urethane foam and aluminum blocks were 70.8degrees C and 50.degrees C respectively at 7 hours. CONCLUSION: The local temperature increase of electric pad was dependent on the surface cooling conditions, heating time and blanket covering over the electric pad. The surface temperature increased to 56.1degrees C at 5 hours after blanket covering over the silicone block which temperature can cause severe injuries on the human skin within a minute.
Aluminum ; Beds ; Burns* ; Heating ; Hot Temperature ; Humans ; Silicon ; Silicone Elastomers ; Silicones ; Skin ; Thermal Conductivity ; Urethane

An apparatus was designed, based on the principle of Grayson's internal calorimetry, for the determination of the choroidal blood flow with thermistor as a sensing element. Experiments with water; 10%, 20%, 30% and 50% gelatin solution; living and dead rabbit eye and enucleated human eye showed that there was a linear relationship between the thermal conductivities and the currents required to raise the heating thermistor by 1 degree. Thus it was found that the Carslaw's law could be applied in these experiments In rabbit's eyes, thermistors were introduced into the suprachoroidal space after separating the sclera from the underlying choroid. At the same time, one of the vortex veins was cut right after the vein emerge from the sclera, and the amount of blood was absorbed and weighed. The results showed that when the blood flow was in the lower range, the thermal conductivity increased abruptly. When the blood flow increased, the increase in the thermal conductivity was at a more slower rate. In the physiological range of blood flow, however, there was a linear relationship between the blood flow and the changes in the thermal conductivity.
Calorimetry ; Choroid* ; Gelatin ; Heating ; Hot Temperature ; Humans ; Jurisprudence ; Rabbits* ; Sclera ; Thermal Conductivity ; Veins ; Water