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PubMed1996

Dynamics of temperature dependent optical properties of tissue: dependence on thermally induced alteration.

Thermal damage in heated bovine myocardial tissue is assessed from measured changes in total reflection and transmission of light. Mathematical expressions, based on random walk analysis of light propagation within tissue slabs, are used to relate the diffuse reflection and transmittance to the absorption coefficient, mu a, and effective scattering coefficient, mu's, for samples of myocardial tissue which were subjected to rapid step changes in temperature. Time-dependent changes in mu's, indicate two processes, one with a fast and temperature-dependent rate the other with a slow and apparently temperature-independent rate. For final temperatures above 56.8 degrees C and for the first 500 s after the temperature change, the optical parameters are well fit by exponential forms that exhibit temperature-dependent time constants as predicted by Arrhenius reaction rate theory of thermal damage. The scattering changes are associated with an apparent activation energy, delta E, of 162 kJ/mole and a frequency constant, A, of 3 x 10(23) s-1. This method provides a means for estimating optical coefficients which are needed to assess laser tissue dosimetry.

Absorption↗
PubMed2006

Diffusion kinetics for methanol in polycrystalline ice.

Quantitative analyses of the isothermal desorption kinetics from methanol-doped H2O films on Pt(111) reveal that transport kinetics for CH3OH in polycrystalline ice are much slower than previously reported. They also indicate that MeOH displays first-order desorption kinetics with respect to its instantaneous surface concentration below 0.1 mole fraction in ice. These observations allow isothermal desorption rate measurements to be interpreted in terms of a depth profiling analysis providing one-dimensional concentration depth profiles from methanol-doped polycrystalline ice films. Using a straightforward approach to inhibit ice sublimation, transport properties are extracted from the evolution of concentration depth profiles obtained after thermal annealing of binary ice films at high temperature. Heterodiffusion coefficients for methanol in polycrystalline (cubic) ice Ic films are reported for temperatures between 145 and 195 K and for concentrations below 10(-3) mole fraction. Finally, diffusion kinetics for methanol in ice are shown to display a very strong concentration dependence that may contribute, in addition to variations in laboratory samples microstructure, to the disagreements reported in the literature regarding the transport properties of ice.

Journal Article↗
PubMed1998

Computer-aided stochastic modeling of the radiolysis of liquid water.

A computer-aided stochastic model of the radiolysis of liquid water has been developed. It is based on Monte Carlo simulation of charged-particle tracks, a random-flight method to simulate diffusion of species and the Debye-Smoluchowski theory of reactions between radicals. The model takes into account the formation of ionizations, excitations and subexcitation electrons at the physical stage. The corresponding initial yields at approximately 1 fs were found to be G(ion) = 4.37, G(exc) = 2.81 and G(e-sub) = 4.38. The energy spectrum of subexcitation electrons has been calculated. Autoionizations and dissociations of excited molecules, hole migration, electron thermalization, geminate recombination and the cage effect are considered at the physico-chemical stage. The mean thermalization distance of subexcitation electrons is 24.5 nm. The initial yields of e(aq)-, H+, OH, H, H2 and O are 4.89, 4.86, 5.96, 1.10, 0.15 and 0.15, respectively. The reactions between radicals and products as well as their diffusion are simulated at the chemical stage. The decay kinetics of the most important radicals is reported together with the time evolution of the most important reactions. The yields of the reactive radicals, e(aq)-, H+, OH, H and OH-, at 1 ps are 4.84, 4.85, 5.87, 1.09 and 0.0, respectively. The respective steady-state yields at 10 micros are 2.70, 3.58, 2.89, 1.17 and 0.79. The yields of molecular products, H2O2 and H2, are 0.73 and 0.47 at 10 micros. The concentration-dependent yields of e(aq)-, OH and H2O2 are calculated in three different aqueous solutions. The predictions of the model agree fairly well with experimental data.

Chemical Phenomena↗
PubMed1981

The structure of acid-soluble basement membrane collagen from bovine anterior lens capsule: molecular parameters and thermal gelation properties.

Basement membrane collagen was extracted from bovine anterior lens capsules with acetic acid in the presence of protease and proteinase inhibitors. This undegraded soluble basement membrane has a sedimentation coefficient S0 20,w=7.8 X 10-13 sec-1, a diffusion coefficient D020,w=5.82 X 10-8/ cm2/sec and a zero-shear intrinsic viscosity [eta] = 2200 cm3/g. These data lead to a molecular weight, Mr of 1.1 X 10(6). Electron microscopic observation indicates that the molecules are rod-like in character with a length of 300 nm. Theoretical models describing the intrinsic viscosity in terms of the distribution of mass in such an elongated molecule show that a dumbbell-like structure is the only tenable model. In this model a single 300 nm rod-like region joins two more densely packed globular regions. The globular domains contain hydroxyproline and may has collagenase sensitive regions since digestion with purified bacterial collagenase at 37 degree C for 18 h degrades these domains as well as the central triple-helical domain. The intact acid-soluble basement membrane collagen precipitates from neutral pH solutions upon warming 4 degree C stable solutions. The pH, ionic strength and concentration dependence parameters of this thermal precipitation have been examined. The basement membrane collagen precipitation appears to be dominated by end-region domain hydrophobic interactions. The end-regions are required for precipitation in contrast to the Type I procollagen situation wherein the intact end-regions inhibit thermal gelation. Electron microscopic examination of the basement membrane thermal gels shows networks of very thin filaments which may be related directly to the structure within intact basement membrane.

Amino Acids↗
PubMedDate not supplied

Multiple field hyperthermia combined with radiotherapy in advanced carcinoma of the breast.

Extensive recurrences on the chest wall of advanced carcinoma of the breast in 20 patients were treated with multiple field patchwork hyperthermia combined with radiation therapy between 1987-1991. The objective of the study was to evaluate the feasibility, tumour response and complications of treating extensive lesions with multiple, overlapping fields of hyperthermia. All lesions were diffuse encompassing up to 2900 cm2 in area with or without multiple nodules < or = 3 cm deep. All lesions had failed previous therapy with all but three failing previous radiotherapy. Hyperthermia consisted of 282 hyperthermia applicator fields and 357 hyperthermia treatments with external 915 MHz microwaves using commercially available applicators. Hyperthermia applicator fields were defined by the surface 50% SAR distribution of a particular applicator, and hyperthermia fields were abutted to cover the entire tumour bearing area. Radiation therapy consisted of 81 fields to a mean dose of 40 +/- 1 Gy (SE), 88% of fields received between 30 and 50 Gy. The equivalent dose was 42 +/- 1 Gy, based on the linear-quadratic model and alpha/beta = 25 (Fowler 1989). Overlapping hyperthermia fields were separated by an interval of at least three days. Up to four heat sessions per week were required to cover the entire tumour in a rotating fashion. The hyperthermia treatment time was 60 min. Hyperthermia treatments were continued for the duration of radiation therapy. Each hyperthermia applicator field was heated at least once. Patients were exposed to a mean of 14 +/- 3 hyperthermia applicator fields (range of 3-46 fields) and a mean of 18 +/- 3 hyperthermia treatments (range of 6-61) delivered over a mean of 7.5 +/- 0.9 weeks (range of 3-17 weeks). Each field was heated an average of 1.3 times. The tumour complete response rate was 95% with a recurrence rate of 5%. Nevertheless, the mean survival of patients with a complete response was only 10.8 +/- 1.7 months (range of 2-28 months) because of the systemic tumour burden existing outside of the treated fields in these patients. Neither complete response, local control nor survival after thermoradiotherapy correlated with the disease free interval between initial mastectomy and recurrence. There was no evidence of increased thermal damage to skin nor evidence of tumour recurrence at junctions of hyperthermia field overlap. It is concluded that recurrent advanced carcinoma of the breast presenting as extensive, diffuse lesions on the chest wall can be treated as effectively with multiple field patchwork thermoradiotherapy as can nodular lesions treated with single hyperthermia fields.

Adult↗
PubMed2001

Chromium speciation in residues after sequential extraction of a thermally treated sludge analog.

XANES fitting indicates that non-Cr2O3 form of Cr(III), transformed from CrO3 by four-hour heat application at 1100 degrees C, is the key species sorbed onto or lattice-diffused into kaolin matrices that exhibits strong leaching resistance to sequential extraction using various combined solutions including HNO3, H2O2, and HF. The EXAFS spectra are all in agreement with the XANES results. It is suggested that some Cr2O3 might have reacted with kaolin to form new compounds such as Cr2O3 x Al2O3 x 2SiO2 to account for the slight dissimilarity between the EXAFS spectra of samples and that of Cr2O3.

Chromates↗
PubMed1985

In vivo validation of the thermal-green dye technique for measuring extravascular lung water.

Assessment of extravascular lung water (EVLW) is imprecise in vivo, yet of both clinical and investigative relevance in patients with cardiac disease. Recently, a double-indicator method using thermal-green dye has been proposed as a nondestructive technique for in vivo quantification of EVLW. In our 5-yr study, indocyanine green dye was used as the intravascular indicator and heat as the diffusible indicator in 44 control dogs, 74 dogs administered intravenous oleic acid, 63 dogs in whom left atrial pressure was altered with a left atrial balloon, and 31 dogs with low-output cardiac failure (electrical shock and complete heart block). In these animals, in vivo measures of EVLW correlated closely with standard gravimetric techniques (r = 0.87, p less than .001), although the indicator dilution technique tended to underestimate actual lung water at higher volumes. In an additional 26 dogs, fluid (lactated Ringer's solution) was administered directly into a distal pulmonary airway, producing alveolar rather than interstitial edema. In these animals, as the infused volume was increased, the thermal technique underestimated consistently the actual amount of infused fluid. Nonetheless, we conclude that in most clinical and experimental situations where moderate changes in lung water are anticipated, this technique can provide reasonable estimates of extravascular fluid accumulation.

Animals↗
PubMed1996

Stress response of the rat testis: in situ hydridization and immunohistochemical analysis of heme oxygenase-1 (HSP32) induction by hyperthermia.

By using in situ hybridization and immunohistochemistry, the distribution patterns of heme oxygenase (HO)-1 (HSP32) transcript and protein were studied, and their response to thermal stress was examined. And, by using an HO-1 cDNA probe and polyclonal antibody, the levels of HO-1 mRNA and protein in normal and heat-shocked testis were quantified. The digoxigenin-labeled probe detected a strong signal for HO-1 transcript in Leydig cells, and in the Sertoli cells, spermatogonia, primary spermatocytes, and spermatids of the seminiferous tubules. In all cell types, the transcript was predominantly concentrated in the nucleus in a defined pattern. Thermal stress (42 degrees C, 20 min) did not change the cell population pattern of HO-1 transcript expression; however, it did cause distortion of the nuclear pattern and diffusion of the transcript signal in cells. Hyperthermic treatment of rats resulted in a modest (2- to 2.8-fold), time-dependent, and sustained (1-16 h) increased in testicular 1.8-kb HO-1 mRNA. Immunohistochemical analysis of normal and heat shock patterns of testicular HO-1 expression showed robust staining of Sertoli ad leydig cells after heat shock; in normal tissue, immunoreactivity was low in these cell populations. As with the transcript distribution, hyperthermia did not affect the pattern of HO-1 immunoreactivity, and the protein was not detected in spermatogenic cells under control or stress conditions. In the Leydig cells, hyperthermia led to a more than 3-fold increase in the intensity of cytoplasmic staining for HO-1 protein. Consistent with the selective expression of HO-1, the level of the single HO-1 immunoreactive protein (approximately 32 kDa) detected in total testis microsomes showed a modest (1.5-fold) increase 6 h after heat shock. Data are consistent with te suggestion that differential distribution of HO-1 protein in the germ cell line and Sertoli cells reflects differential HO-1 mRNA processing in these cell types. The increase may be essential for the catalysis of the heme moiety of denatured hemoproteins such as cytochrome P450 and hemoglobin heme and hence may protect against heme-catalyzed free radical formation. We propose that induction of HO-1 protein in Sertoli and Leydig cells may function to protect the spermatogenic cells under conditions of thermal stress.

Animals↗
PubMed1999

A method for the decrease of phenolic content in commercial canola meal using an enzyme preparation secreted by the white-rot fungus Trametes versicolor.

An enzymatic process for upgrading the quality of canola meal (CM) by decreasing its phenolic content was investigated. The new method was based on the addition of the enzyme preparation from white-rot fungus Trametes versicolor to the meal-buffer slurry. A 98% decrease in the concentration of SAE was observed after 1 h of the treatment. The following process variables were considered for optimizing the process: pH, temperature, enzyme, meal, and oxygen concentrations. It was found that: (1) the natural buffering capacity of CM resulted in a negligible effect of the pH of the buffer, which was used as the continuous phase in the process, on the extent of decrease in sinapic acid esters (SAE); (2) the system was saturated with the enzyme when its concentration was 4 nkat/mL of the continuous phase; and (3) the optimum temperature was 50 degrees C. The process could be carried out even at higher temperatures due to the protective action of CM, which resulted in an increase in the thermal stability of the enzyme. The particle size influenced the extraction of the SAE from the meal, indicating that, at lower SAE concentrations, the process became diffusion limited. This result, together with those showing no effect of the intensity of agitation, indicated that the enzymatic process can be characterized by high Biot numbers. During the enzymatic process, the molar concentration of available oxygen can become a limiting factor when it is more than four times lower than the molar concentration of phenolics in the treated meal. The new enzymatic method was compared with other methods reported in the literature for the decrease in the phenolic content of rapeseed meals. It was found that, among the methods tested, the enzymatic treatment was the most effective, followed by the lime treatment. The enzymatic process did not reduce the quality of the protein isolates prepared from the CM. After the addition of a simple acetone-washing step, the isolate from the enzymatically treated meal had even better properties. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗
PubMed1995

Relation between adiabatic and pseudoadiabatic compressibility in ultrasonic velocimetry.

A fundamental problem in measurements of the adiabatic compressibility of macromolecules in aqueous solution using sound velocity is the unknown heat exchange between the interior of the molecule and the bulk solvent. Usually only a pseudoadiabatic compressibility is measured, which is between isothermal and adiabatic compressibility. The measured compressibility might even be close to the isothermal compressibility, depending on the experimental conditions. In this paper, a model is proposed that enables the deviation of experimental conditions from the requirement of adiabatic measurements to be estimated. This model treats the macromolecule as a heat conductive sphere. Analytical solutions for the temporal and local heat diffusion are obtained. Proteins less than 100 kDa in molecular weight at a sound frequency of less than 10 MHz are found to be essentially in thermal equilibrium with the bulk solvent. In this case, for the aqueous protein solution at temperatures < or = 25 degrees C and less than 2% protein concentration, the theory predicts that the sound velocity measurement of the interior of protein is close to isothermal conditions.

Macromolecular Substances↗
PubMed2001

MR monitoring of tumour thermal therapy.

Thermal therapy of tumour including hyperthermia and thermal ablation by heat or cold delivery requires on line monitoring. Due to its temperature sensitivity, Magnetic Resonance Imaging (MRI) allows thermal mapping at the time of the treatment. The different techniques of MR temperature monitoring based on water proton resonance frequency (PRF), longitudinal relaxation time T1, diffusion coefficient and MR Spectroscopic Imaging (MRSI) are reviewed and debated. The PRF method appears the most widely used and the most efficient at high magnetic field in spite of important drawbacks. The T1 method is the easiest method of visualisation of qualitative temperature distribution and quantitative measurement seems possible in the tissue surrounding the tumour up to a temperature of 45-65 degrees C. Despite its high temperature sensitivity, application of the diffusion method in vivo is restricted due to its high motion sensitivity. The recent MRSI technique seems very promising provided acquisition times can be reduced. Results from the literature indicate that MR temperature monitoring in vivo can be achieved in vivo with a precision of about 3 degrees C in 13 s for a voxel of 16 mm3 (1.5 x 1.5 x 7 mm) in 1.5 T scanners.

Animals↗
PubMed2004

Influence of cyclodextrins on in vitro human skin absorption of the sunscreen, butyl-methoxydibenzoylmethane.

The effects of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and sulfobutylether-beta-CD (SBE7-beta-CD) on in vitro human skin penetration and retention of the sunscreen agent butyl-methoxydibenzoylmethane (BM-DBM) were investigated. The interaction between the UV filter and the cyclodextrins was studied in water by phase-solubility analysis. Solid complexes were prepared by the co-evaporation method and characterized by (1)H NMR spectroscopy, thermal analysis and powder X-ray diffraction. Solutions containing BM-DBM free or complexed with cyclodextrins were applied to excised human skin in Franz diffusion cells and the amount of sunscreen permeated after 6 h into the stratum corneum, viable epidermis, dermis and receptor fluid was assessed by HPLC. As much as 14.10-16.78% of the applied dose of BM-DBM penetrated within the skin tissue. No sunscreen was detected in the dermis and in the receiver phase. The greater proportion (84.6-95.5%) of the absorbed UV filter was localized in the stratum corneum with no significant differences between uncomplexed or complexed BM-DBM. Notable levels (2.29% of the applied dose) of the sunscreen agent accumulated in the epidermis from the preparation containing free BM-DBM. The epidermal concentration of the UV filter was markedly reduced (0.66% of the applied dose) by complexation with SBE7-beta-CD, whereas HP-beta-CD had no effect. The decreased BM-DBM retention in the epidermal region achieved by SBE7-beta-CD limits direct contact of the sunscreen and of its reactive photolytic products with the skin viable tissues.

Adult↗
PubMed2000

Analysis of local strain in aluminium interconnects by energy filtered CBED

Energy filtered convergent beam electron diffraction (CBED) was used to investigate localised strain in aluminium interconnects. The quantitative analysis of the experimental patterns is based on a multi-step evaluation procedure which is the main subject of the present paper. The improvements which were made to the analysis method aim at increasing both the automation and the accuracy. The detection of the higher order Laue zone (HOLZ) line positions is performed by means of the Hough transform. The required sub-pixel resolution can be achieved routinely and the achievable accuracy is only limited by the line width and the amount of noise in the patterns. The determination of the strain state is performed via a refinement algorithm which is based on varying the strain state in the sample coordinate system and simulating the patterns for the individual grains until a best fit with the experiment is obtained. For the simulation we have developed a new correction scheme in which the dynamical effects are treated separately for each individual HOLZ line. The results show that the main source of the observed strains is the difference in thermal expansion coefficients. The strain is substantially reduced underneath a hillock in the interconnect. Asymmetries in the strain distribution around the hillock show that the unidirectional diffusion during electromigration tests causes peak strains in areas next to the hillock which may be possible failure sites.

Journal Article↗
PubMed2001

Bacillus subtilis cells immobilised in PVA-cryogels.

Bacillus subtilis viable cells were immobilised in PVA-cryogel beads using the 'freezing-thawing' method in a two-phase (water-oil) system. Conditions providing both high thermal and mechanical stability and suitable porosity of the carrier were optimised. For monitoring and analysis of changes inside the biocatalyst beads, and for determination of diffusive properties of the carrier, an image analysis was applied. It was revealed that bacterial spores, sodium alginate and bacterial cellulose accelerated hardening of the cryogels and modified their porosity. Proteins (haemoglobin, azoalbumin, azocasein) penetrated beads of the cryogel.

Albumins↗
PubMedDate not supplied

Dissolution of Bombyx mori silk fibroin in the calcium nitrate tetrahydrate-methanol system and aspects of wet spinning of fibroin solution.

There are still several problems associated with the spinning of dialyzed silk fibroin solutions. In this work some of these problems have been examined. The calcium nitrate tetrahydrate-methanol system was used to dissolve the silk fibroin. A compositional phase diagram was constructed at various concentrations of the solvent system. Regenerated fibroin powders from undialyzed fibroin solution in several coagulants showed different conformations. Regenerated powders from several coagulants except methanol and ethanol were resoluble in water. Atomic absorption analysis revealed that the calcium cations strongly interact with fibroin molecules in dialyzed fibroin solution, which may interfere with the regeneration of a strong fiber. Kinetic studies to determine the diffusion coefficient of methanol into dialyzed and concentrated fibroin solution were reported. The properties of both original and regenerated fibroin such as solubility in water and thermal behaviors using DSC were compared. Regenerated fibroin fiber was spun by the wet spinning method. An X-ray diffractogram showed that the regeneration process decreased the crystallinity of regenerated fibroin fiber. SEM images of the surface and cross section of the regenerated fibroin fibers were discussed.

Animals↗
PubMed2006

Supercritical CO2 extraction and purification of compounds with antioxidant activity.

Supercritical fluid extraction (SCFE), based on the utilization of a fluid under supercritical conditions, is a technology suitable for extraction and purification of a variety of compounds, particularly those that have low volatility and/or are susceptible to thermal degradation. The interest in SCFE is promoted by legal limitations of conventional solvents for food and pharmaceutical uses. The physicochemical properties of supercritical CO2 (higher diffusivity, lower viscosity, and lower surface tension than conventional solvents) facilitate mass transfer and allow an environmentally friendly operation. This article presents a comprehensive compilation of data on the supercritical CO2 extraction of antioxidant compounds from vegetal materials, with particular attention to those of a phenolic nature. Aspects concerning the supercritical operation for extraction and fractionation of antioxidants compounds are considered, including equilibrium solubility of pure compounds and effects of the operational conditions on the antioxidant activity of isolated fractions. The data are compared to those reported for synthetic antioxidants and natural extracts obtained by conventional solvent extraction from vegetal matrices.

Antioxidants↗
PubMed2005

Hot recombination of photogenerated ion pairs.

The recombination dynamics of ion pairs generated upon electron transfer quenching of perylene in the first singlet excited state by tetracyanoethylene in acetonitrile is quantitatively described by the extended unified theory of photoionization/recombination. The extension incorporates the hot recombination of the ion pair passing through the level-crossing point during its diffusive motion along the reaction coordinate down to the equilibrium state. The ultrafast hot recombination vastly reduces the yield of equilibrated ion pairs subjected to subsequent thermal charge recombination and separation into free ions. The relatively successful fit of the theory to the experimentally measured kinetics of ion accumulation/recombination and free ion yield represents a firm justification of hot recombination of about 90% of primary generated ion pairs.

Journal Article↗
PubMed1983

Dynamics of heme iron in crystals of metmyoglobin and deoxymyoglobin.

The 57Fe gamma-ray resonance absorption spectra have been measured in crystals of metmyoglobin and deoxymyoglobin over a wide range of temperatures. Above a critical temperature common to both proteins (220 K), the dynamics of heme iron display a dramatic change, in that two kinds of thermal fluctuations come into play--a fast fluctuation associated with a steep decrease of the total fluctuation of characteristic time 10(-8) sec, associated with bounded diffusive motion. By using both discrete jump and continuous diffusion models, the latter based on the Brownian motion of an overdamped harmonic oscillator, the essential parameters of the iron motion (mean square displacement and jump frequency or diffusion constant) can be derived as a function of temperature. Thus, for deoxy Mb at 288 K, the mean square displacement for the fast fluctuation is about 6 X 10(-2) A2 and for the diffusive motion is 1.6 X 10(-2) A2; the diffusion constant is 4 X 10(-10) cm2/sec. The diffusive process is associated with an activation energy of about 0.75 kcal/mol. Although the same general kinds of phenomena are observed in crystals of MetMb and deoxy Mb, significant differences in behavior are found, which suggest that the main dynamical phenomenon observed reflects internal large-scale motions of the protein.

Animals↗