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PubMed1987

Static and dynamic response characteristics, receptive fields, and interaction with noxious input of midline medullary thermoresponsive neurons in the rat.

Thermal clamping of deep-body temperature and 16 fields covering the total truncal skin surface enabled characterization of thermal transmission neurons distributed in a midline medullary location. The total data set comprised 136 neurons from 54 female rats. Relative abundance of neuronal types was 27 to 34 to 75 for cold-responsive, warm-responsive, and thermally unresponsive neurons. Response maxima of thermoresponsive neurons to static thermal stimulation of the total truncal surface were 55 +/- 4 ips (mean +/- SE) at 5 degrees C for cold-responsive neurons and 6.0 +/- 1.6 ips at 35 degrees C for warm-responsive neurons. Dynamic thermal stimulation of the total truncal surface at rates up to +/- 1.6 degrees C/s failed to reveal a clear dynamic thermosensitivity in either cold- or warm-responsive neuronal pools. Instead, the data suggest a preferential passing of the static response relative to the dynamic response. Cutaneous thermal receptive fields were diffuse, occupying most of the truncal surface. Subparts of these fields drove thermoresponsive neurons to variable extents, suggesting convergence from unequally represented multiple cutaneous sources. Noxious stimulation at widely distributed body sites consistently augmented activity in cold-responsive neurons. A thermoregulatory rather than somatesthetic role is proposed for the midline medullary neurons studied here.

Animals↗
PubMed2006

Modeling the Entrepeñas Reservoir.

The Entrepeñas Reservoir is a monomictic reservoir located in River Tagus (Spain). The aim of this work is to establish a feasible model to predict the depth of the thermocline that is developed in the reservoir during the period of natural thermal stratification. Entrainment, eddy diffusion, inflow of external energy, and other factors are considered to calibrate the parameters of the model. The methodology involves the measure of actual temperature and electrical conductivity profiles, use of meteorological data and reservoir parameters, and selection and application of several models from the literature. The calculations and predictions are integrated to a software packet that is able to predict thermocline depth and water temperature profile during a 1-year period on a day-by-day basis. In the thermocline depth, the prediction error, on the basis of real data, is less than 6% and, in the water temperature, it is 2 degrees C.

Computer Simulation↗
PubMed2005

[Transurethral resection with saline solution: a technological achievement not yet assimilated by the urological community].

OBJECTIVES: To objectively demonstrate the advantages provided by TURP with saline solution (an adjustment made possible thanks to the technological development of new high frequency current generators), although it surprisingly has been received with scepticism in the urological community. METHODS: A first group of 51 patients (group A) underwent low hydraulic pressure TURP with a pulsed bipolar system (Gyrus Plasmakinetic, with large loop) using physiologic saline solution as irrigation. A second group of 49 patients underwent low hydraulic pressure TURP with a conventional monopolar system (Erbe 350) using glycine-ethanol solution. RESULTS: A better surgical performance was obtained in the first group, as well as a lower degree of bleeding. No intraoperative complications appear in either group. Only one case of late hematuria was registered one month after surgery in a patient of group A. CONCLUSIONS: Pulsed bipolar TURP has a minimal thermal in-depth diffusion, achieves vessel hemostasis by dessication instead of charring, has an extremely precise cutting quality, does not produce neuromuscular stimulation, and makes the use of saline solution irrigation possible. All these translate to lower tissue injury, null risk of sequelae secondary to electric current leak, a finer technique, a lower risk of accidental perforation, and the possibility of duplicate or triplicate the surgical time without risk, especially when working with low hydraulic pressure.

Aged↗
PubMed1989

[Effects of the firing temperature on the color and strength of metal bonded porcelain].

There are many reports on the optical properties of natural teeth and fused porcelain. However, only few studies have been reported on the relationship between the firing temperature, and the optical and mechanical properties of metal bonded porcelain. This is a study of the effects of the firing temperature on the optical and mechanical properties of two groups of porcelain, each of which has five kinds, opaque, body, incisal, transparent and glaze respectively. The results were as follows: 1. The chief ingredient of each porcelain was leucite (K2O . Al2O3 . 4SiO2). Some other components were metal oxides used as pigment and opaque, for regulating the recrystallization of leucite in the fused porcelain, for controlling the thermal expansion, and for diffusing in the both sides of alloy and porcelain. 2. About 40% of each porcelain powder consisted of granular powder, smaller than 10 microns in diameter. 3. Measured by using a color analyser, L, a, and b values of all opaque porcelain did not depend upon the firing temperature. L value of the other porcelain showed decrease in proportion to the increase of the firing temperature. And it slightly decreased over 900-940 degrees C. 4. The firing temperature did not affect the transparency of the opaque porcelain. The transparency of the other porcelain increased in proportion to the increase of the firing temperature. And it also showed slight increase over 900-940 degrees C. The firing temperature did not affect the Heize values of the opaque porcelain. The Heize values of the other porcelain decreased in proportion to the increase of the firing temperature. 5. The compressive and diametral tensile strength of all the porcelain increased in proportion to the increase of the firing temperature to 910-940 degrees C. However, it decreased in proportion to the increase of the firing temperature over 910-940 degrees C. 6. It was confirmed by the SEM observations, microphotographs and X-ray diffraction of the fused porcelain that fully fusing between particles occurred at the firing temperature of 910-940 degrees C. And it was also confirmed by surface roughness.

Color↗
PubMed1997

Quantitative estimation of errors in the indicator dilution measurement of extravascular lung water.

OBJECTIVE: To assess the accuracy of the diffusible indicators heavy water and thermal indicator in the measurement of extravascular lung water (EVLW). DESIGN: Cardiac output (CO), mean transit time and EVLW for the two diffusible indicators were measured. CO for indocyanine green, gravimetric EVLW and the calculated mean transit time for a diffusible indicator were used as independent reference variables. CO, mean transit time and EVLW for the two diffusible indicators were compared to the reference variables and the percentage error for each measured variable was calculated for each bolus injection. SETTING: 6 sheep with healthy lungs and 6 with pulmonary oedema in a research laboratory. INTERVENTIONS: CO was altered with positive end-expiratory pressure and dobutamine. MEASUREMENTS: All indicators were given together in a bolus through a central venous line. Indicators were detected simultaneously in the aorta, and CO, mean transit time and EVLW were measured. EVLW was measured gravimetrically (EVLWgrav) postmortem. RESULTS: In the combination of a low CO and a large distribution volume, heavy water and thermal indicator produced a large number of slow wash-out curves. These curves were abolished from further analysis. The mean errors in CO and mean transit time for heavy water were close to zero and independent of the distribution volume; the product EVLW was close to EVLWgrav. The mean error in thermodilution CO measured in the aorta was close to zero but dependent on the distribution volume. The mean error in mean transit time for the thermal indicator was 36% and dependent on the distribution volume. Their product EVLW overestimated EVLWgrav by 70%. CONCLUSIONS: The results obtained for heavy water confirmed the theoretical basis of the indicator dilution method. The mean transit time for the thermal indicator was not proportionate to its distribution volume. The magnitude of this error prevents the calculation of an anatomically defined EVLW using a catheter-mounted thermistor in the aorta.

Analysis of Variance↗
PubMed1994

A comparison of heating modes in rapid fixation techniques for electron microscopy.

Recent studies have established that microwave irradiation during aldehyde fixation of electron microscopy specimens can reduce fixation times substantially. Similar reductions in duration of histochemical and light microscopy procedures have been reported. Both thermal and non-thermal effects of microwaves have been proposed to explain these dramatic decreases in processing time. Possible thermal effects include increases in fixative diffusion and reaction rates and increased formation of glutaraldehyde monomers. Proposed non-thermal effects include preferential orientation of fixative molecules by the microwave field and other more speculative direct microwave effects. Several reported attempts to produce rapid fixation without temperature increase by cooling specimens during irradiation have produced conflicting results. If rapid fixation is a thermal effect, other heating modes in addition to microwave exposure should produce similar effects. We show that for mouse liver samples (< or = 1 mm3) comparable fixation can be obtained with microwave irradiation, conductive and convective heating in a waterbath, and resistive heating with a low-frequency (1 kHz) current passed through the fixative solution. We also show that using an efficient convective cooling method to prevent temperature increase during microwave exposure produces unsatisfactory fixation. These results are consistent with thermal mechanisms for rapid fixation.

Animals↗
PubMed2000

Research on the best chemohyperthermia technique of treatment of peritoneal carcinomatosis after complete resection.

BACKGROUND: The complete or almost complete resection of peritoneal carcinomatosis (PC) followed by intraperitoneal chemohyperthermia (IPCH) is potentially capable of curing some patients presenting with disease confined to the peritoneum. AIMS: The aim of this prospective phase I-II study was to develop an efficient IPCH procedure with good thermal homogeneity and good spatial diffusion, that would be reproducible (and thus could be standardized and exported), and to evaluate patient tolerance and its efficiency in eradicating tumor tissue. METHODS: Seven IPCH procedures were tested successively in 32 patients (up to a total of 35 IPCH). Each procedure was tested in at least 4 patients before modifications for technical reasons or due to inacceptable tolerance. Five of them were followed by early postoperative intraperitoneal chemotherapy (EPIC) lasting 4 days. Thermal homogeneity was measured with 6 thermal probes placed in different positions inside the abdominal cavity. Spatial diffusion was studied in the last patients by adding methylene blue to the IPCH liquid. The mean follow-up was 23.85 months for the series. RESULTS: From the technological point of view, we have progressively shown that procedures with closure of the abdomen are not satisfactory: it was impossible to obtain thermal homogeneity when the entire parietal wound was closed, but markedly improved when only the skin was closed. However, these "closed" procedures did not allow us to treat all surfaces at risk. The peritoneal cavity "expander" did not permit treatment of the parietal wound and an indeterminate amount of the perfusion oozed out at its periphery. The open technique with traction of the skin upwards was superior. Using different procedures successively undermined the quality of the postoperative results. Three patients (8.6%) died and morbidity (albeit minimal) occurred in 27 patients (77%) during the postoperative course. Mortality and morbidity were significantly correlated (P = 0.02) with the peritoneal index (scoring the extent of PC). The 2-year survival rate was 60% and PC did not recur in 49% of the patients. The survival rate was correlated with the extent of PC (peritoneal index greater than or below 15) (P = 0.004), and with the absence of extraperitoneal disease (P = 0.01).

Adolescent↗
PubMed1996

Coarsening Due to Thermally Induced Marangoni Convection

The growth of closely packed droplets in a decomposing butoxyethanol/water mixture is studied at reduced gravity during scaled times t* = t(D/xi2) on the order of t* = 10(6) (t, time; D, diffusion coefficient; xi, correlation length). Thermally induced Marangoni convection at the surfaces of the droplets causes an enhancement of the coarsening process.

Journal Article↗
PubMedDate not supplied

Self-localization of laser induced tumour coagulation limited by heat diffusion through active tissue.

We analyse necrosis growth due to thermal coagulation induced by laser light absorption and limited by heat diffusion into the surrounding live tissue. The tissue is assumed to contain a tumour in the undamaged tissue where the blood perfusion rate does not change during the action. By contrast, normal tissue responds strongly to an increase in the tissue temperature and the blood perfusion rate can grow by tenfold. We study in detail necrosis formation under conditions typical of a real course of thermal therapy treatment. The duration of the treatment is about 5 minutes when a necrosis domain of about 1 cm or above is formed. In particular, if the tumour size is sufficiently large, i.e. it exceeds 1 cm, and the tissue response is not too delayed, i.e. the delay time does not exceed 1 min, then there are conditions under which the relative volume of the damaged normal tissue is small in comparison with the tumour volume after the tumour is totally coagulated.

Body Temperature↗
PubMed1996

F-actin, a model polymer for semiflexible chains in dilute, semidilute, and liquid crystalline solutions.

Single actin filaments were analyzed in solutions ranging from dilute (0.2 microgram/ml), where filaments interact only with solvent, to concentrations (4.0 mg/ml) at which F-actin forms a nematic phase. A persistence length of approximately 1.8 microns and an average length of approximately 22 microns (Kaufmann et al., 1992) identify actin as a model for studying the dynamics of semiflexible polymers. In dilute solutions the filaments exhibit thermal bending undulations in addition to diffusive motion. At higher semidilute concentrations (1.4 mg/ml) three-dimensional reconstructions of confocal images of fluorescently labeled filaments in a matrix of unlabeled F-actin reveal steric interactions between filaments, which account for the viscoelastic behavior of these solutions. The restricted undulations of these labeled chains reveal the virtual tube formed around a filament by the surrounding actin. The average tube diameter scales with monomer concentration c as varies; is directly proportional to c-(0.5 +/- 0.15). The diffusion of filaments in semidilute solutions (c = (0.1-2.0) mg/ml) is dominated by diffusion along the filament contour (reptation), and constraint release by remodeling of the surrounding filaments is rare. The self-diffusion coefficient D parallel along the tube decreases linearly with the chain length for semidilute solutions. For concentrations > 2.5 mg/ml a transition occurs from an isotropic entangled phase to a coexistence between isotropic and nematic domains. Analysis of the molecular motions of filaments suggests that the filaments in the aligned domains are in thermal equilibrium and that the diffusion coefficient parallel to the director D parallel is nearly independent of filament length. We also report the novel direct observation of u-shaped defects, called hairpins, in the nematic domains.

Actins↗
PubMed1996

Blood flow cooling and ultrasonic lesion formation.

This article examines lesion formation using focused ultrasound and demonstrates how blood flow may affect lesion dimensions using a theoretical model. The effects of blood flow on temperature distributions during ultrasonic lesioning are examined for both regional cooling by the microvasculature and localized cooling due to thermally significant vessels. Regional cooling was critically assessed using two models: the Pennes bioheat transfer equation and the scalar effective thermal conductivity equation. Localized cooling was modeled by adding an advective term in the heat diffusion equation in regions enclosed by thermally significant vessels. A finite difference approach was used to solve the basic equations of heat transfer in perfused tissues in cylindrical coordinates. The extent of the lesioned tissue was determined by the accumulated thermal dose at each location. The size of the lesion was then calculated from the boundaries of the thermal isodose curves generated by the simulations. The results were compared to published in vivo lesion data in rat liver. It was shown that even for short ultrasound exposure times (approximately 8 s), blood flow may play an important role in the thermal dose distribution.

Algorithms↗
PubMed1982

Thermal effect of photolysis in 203Hg, 35S and 131I labeled mercury (II) iodide thiocyanate powders.

203Hg, 35S or 131I labeled mercury (II) iodide thiocyanate (HgISCN) powders were prepared, respectively. When the powders were exposed to sunlight, some parts of the crystals of the powders were decomposed and the decomposed atoms diffused toward crystal surface. This diffusion velocity was accelerated by thermal treatment of the darkened powders. The velocity is larger in order of 35S, 203Hg, 131I. Decomposed products consist of colloidal mercury, mercury iodide, mercury sulfide, sulfur dioxide and iodine. Mechanism of photochromism of HgISCN was discussed.

Colloids↗
PubMed2000

Large disparity between gallium and antimony self-diffusion in gallium antimonide.

The most fundamental mass transport process in solids is self-diffusion. The motion of host-lattice ('self-') atoms in solids is mediated by point defects such as vacancies or interstitial atoms, whose formation and migration enthalpies determine the kinetics of this thermally activated process. Self-diffusion studies also contribute to the understanding of the diffusion of impurities, and a quantitative understanding of self- and foreign-atom diffusion in semiconductors is central to the development of advanced electronic devices. In the past few years, self-diffusion studies have been performed successfully with isotopically controlled semiconductor heterostructures of germanium, silicon, gallium arsenide and gallium phosphide. Self-diffusion studies with isotopically controlled GaAs and GaP have been restricted to Ga self-diffusion, as only Ga has two stable isotopes, 69Ga and 71Ga. Here we report self-diffusion studies with an isotopically controlled multilayer structure of crystalline GaSb. Two stable isotopes exist for both Ga and Sb, allowing the simultaneous study of diffusion on both sublattices. Our experiments show that near the melting temperature, Ga diffuses more rapidly than Sb by over three orders of magnitude. This surprisingly large difference in atomic mobility requires a physical explanation going beyond standard diffusion models. Combining our data for Ga and Sb diffusion with related results for foreign-atom diffusion in GaSb (refs 8, 9), we conclude that the unusually slow Sb diffusion in GaSb is a consequence of reactions between defects on the Ga and Sb sublattices, which suppress the defects that are required for Sb diffusion.

Journal Article↗
PubMed1975

Effect of rotation on the diffusion-controlled rate of ligand-protein association.

The rate of binding a fairly large ligand molecule to a protein is reduced below the usual diffusion-controlled rate by the requirement of a certain rotational orientation. A simple, approximate treatment of this effect is given for special cases of spherical and ellipsoidal ligands. As the center of an ellipsoidal ligand approaches a protein surface, there is an effective repulsive potential between ligand and surface owning to restricted rotation of the ligand. The frequency factor kT/h of the Eyring rate theory is replaced in these reactions involving diffusion in solution by D/Rlambda, where D = diffusion coefficient of ligand, lambda = thermal deBroglie wavelength of ligand, and R = "capture" distance around the binding site on the protein.

Adsorption↗
PubMed2006

Molecular dynamics study of the thermodynamics and transport coefficients of hard hyperspheres in six and seven dimensions.

Molecular dynamics (MD) simulations are performed for six- and seven-dimensional hard-hypersphere fluids. The equation of state, velocity autocorrelation function, self-diffusion coefficient, shear viscosity, and thermal conductivity are determined as a function of density. The molecular dynamics results for the equation of state are found to be in excellent agreement with values obtained from theoretical approaches and previous MD simulations in seven dimensions. The short-time behavior of the velocity autocorrelation function is well described by the Enskog exponential approximation. The Enskog predictions for the self-diffusion coefficient and the viscosity agree fairly well with the simulation data at low densities, but underestimate these quantities at higher densities. Data for the thermal conductivity are in fine agreement with Enskog theory for all densities and dimensions studied.

Journal Article↗
PubMedDate not supplied

Lung thermal volume as an indicator of pulmonary extravascular water.

Double-indicator dilution methods can be used for measurement of lung water. The thermal conductivity method is based on heat as a diffusible and conductivity as a non-diffusible indicator. In the present study we correlated lung thermal volume with gravimetrical measurement of extravascular lung water after thrombin-induced microembolization in dog lungs. The embolization was accompanied by significantly increased vascular permeability and accumulation of interstitial water. Under these conditions there was a close correlation between the two methods of measuring lung water (r = 0.78, p less than 0.01).

Animals↗
PubMed2002

Synthesis and characterization of cobalt and nickel chelates of 5-dimethylaminomethyl-2-thiouracil and their evaluation as antimicrobial and anticancer agents.

A new antimetabolite of adenine, viz. 5-dimethylaminomethyl-2-thiouracil, was synthesized using the Mannich reaction. Owing to the biological importance of metalloelements in many biological processes, especially metabolic processes, cobalt(II) and nickel(II) complexes were also synthesized and examined for their antimicrobial and anticancer activities. These new compounds were characterized structurally by various techniques ranging from micro-elemental analyses to spectral analyses. Cobalt(II) complexes were found to be four coordinate, among which the bromo, iodo, and nitrato complexes were polymeric. The nickel(II) isothiocyanato complex exhibited four-coordinate geometry and the remaining nickel(II) complexes were six coordinate. Thermodynamic and kinetic parameters evaluated based on TG/DSC suggested that the initial stage of thermal decomposition follows a diffusion-controlled mechanism and the final stage a chemically controlled mechanism. Antibacterial, antifungal, and antitumor studies undertaken for the above compounds indicated structure-activity relationships. These metalloderivatives were more active than the parent compound. The order of activity was influenced by the chelate geometry and thermal stability. Activity increased with a decrease in coordination number and increase in thermal lability.

Animals↗