Freezing Phase Research Articles

Automatic iceball segmentation with adapted shape priors for MRI‐guided cryoablation

To develop and evaluate an automatic segmentation method that extracts the 3D configuration of the ablation zone, the iceball, from images acquired during the freezing phase of MRI-guided cryoablation. Intraprocedural images at 63 timepoints from 13 kidney tumor cryoablation procedures were examined retrospectively. The images were obtained using a 3 Tesla wide-bore MRI scanner and axial HASTE sequence. Initialized with semiautomatically localized cryoprobes, the iceball was segmented automatically at each timepoint using the graph cut (GC) technique with adapted shape priors. The average Dice Similarity Coefficients (DSC), compared with manual segmentations, were 0.88, 0.92, 0.92, 0.93, and 0.93 at 3, 6, 9, 12, and 15 min timepoints, respectively, and the average DSC of the total 63 segmentations was 0.92 ± 0.03. The proposed method improved the accuracy significantly compared with the approach without shape prior adaptation (P = 0.026). The number of probes involved in the procedure had no apparent influence on the segmentation results using our technique. The average computation time was 20 s, which was compatible with an intraprocedural setting. Our automatic iceball segmentation method demonstrated high accuracy and robustness for practical use in monitoring the progress of MRI-guided cryoablation.

MRI of adhesive capsulitis of the shoulder: Distension of the bursa in the superior subscapularis recess is a suggestive sign of the pathology

ObjectiveTo evaluate the diagnostic values of the superior subscapularis recess sign in patients with shoulder adhesive capsulitis. The sign consists in evaluating in MRI of the shoulder the presence of fluid distension of the bursa in the superior subscapularis recess. Materials and methodsWe evaluated MRI of 165 shoulders in 48 consecutive patients with a diagnosis of shoulder adhesive capsulitis in the freezing phase (group I), in 49 short-wide superior cuff tear (group II) and in 65 controls (group III) between 2010 and 2013. On the T2 weighted images, we evaluated the presence of an high intensity signal within the superior subscapularis recess, consistent with fluid distension of the bursa. ResultsThe sign was found in 43/48 patients (89.58%) with shoulder adhesive capsulitis in 3/49 (6.12%) patients with superior cuff tear and in 1/65 controls (1.53%) (p<0.001). The mean diagnostic values were: sensibility 0.91; specificity 0.96–0.98; positive predictive value 0.93–0.97; negative predictive value 0.92–0.94; likelihood ratios for an abnormal test result 15.16–60.6; likelihood ratios for a normal test result 0.086–0.095. ConclusionFor the orthopedic surgeon or the clinician, the sign is useful to confirm in MRI the clinical diagnosis of shoulder adhesive capsulitis; accordingly, the radiologist should describe and relate this sign to the pathology in the report, looking eventually for further typical sign of shoulder adhesive capsulitis.

Confined Crystallization of n-Hexadecane Located inside Microcapsules or outside Submicrometer Silica Nanospheres: A Comparison Study

Crystallization and phase transition behaviors of n-hexadecane (n-C16H34, abbreviated as C16) confined in microcapsules and n-alkane/SiO2 nanosphere composites have been investigated by the combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). As evident from the DSC measurement, the surface freezing phenomenon of C16 is enhanced in both the microcapsules and SiO2 nanosphere composites because the surface-to-volume ratio is dramatically enlarged in both kinds of confinement. It is revealed from the XRD results that the novel solid-solid phase transition is observed only in the microencapsulated C16, which crystallizes into a stable triclinic phase via a mestastable rotator phase (RI). For the C16/SiO2 composite, however, no novel rotator phase emerges during the cooling process, and C16 crystallizes into a stable triclinic phase directly from the liquid state. Heterogeneous nucleation induced by the surface freezing phase is dominant in the microencapsulated sample and contributes to the emergence of the novel rotator phase, whereas heterogeneous nucleation induced by foreign crystallization nuclei dominates the C16/SiO2 composite, leading to phase transition behaviors similar to those of bulk C16.

Influence of pH value and locust bean gum concentration on the stability of sodium caseinate-stabilized emulsions

Sodium caseinate emulsions of 20% sunflower oil in water were prepared at various pH and Locust Bean Gum concentrations (LBG). The presence of LBG was examined to assess the stabilizing properties in relation to flocculation, creaming and coalescence, in the initial emulsions as well as freeze-thawed and freeze-dried/reconstituted samples. We found the initial emulsions to be stable at pH 6.0 and 6.5, both in the absence or presence of LBG, against creaming. However we found evidence for the aggregates of emulsion droplets in the presence of LBG. Strong shear thinning behavior, even at low shear rates, and micrographs indicated that the presence of LBG may promote flocculation by mediating depletion forces between the oil droplets. However, the absence or low concentrations of LBG resulted in creaming followed by the emulsion break-up for the freeze-dried/reconstituted emulsions, particularly at lower pH. We have also detected a proliferation in the number of very small sub-micron particles in the particle size distribution, for samples containing higher concentrations of LBG, following the freeze-thaw cycle. We believe these to be LBG aggregates nucleating during the freezing phase of the process as the polysaccharide solubility declines with temperature.

Truth-Content and Phase Transitions of Random Boolean Networks with Generic Logics

One distinguishes between qualitative and Boolean models of gene regulatory networks. Qualitative models are directed graphs with signed edges according to whether an interaction is activating or inhibiting. In Boolean models each node of the network is a Boolean variable whose value depends on the values of the node's regulators according to a specific update rule. Qualitative models can be systematically converted into Boolean models via generic logics, which allow combination of activating and inhibiting influences into an update rule. Here, we investigate random Boolean networks whose update rules are generated using generic logics. We begin by studying their truth-content, which is a mean field approximation of the fraction of ones (true nodes). We prove that the asymptotic behavior of this quantity is essentially independent of the initial conditions. In numeric analyses, the truth-content exhibits a rich dynamical behavior including period-doublings leading to chaos. We define truth-stable networks as networks whose truth-contents exhibit non-chaotic dynamics. Random Boolean networks are known to exist in two phases: a frozen phase with stable short periodic dynamics and a chaotic phase characterized by long-periodic attractors sensitive to perturbations. Our results about the truth-content of random Boolean networks with generic logics allow us to derive a criterion for phase transitions in these networks. The relation between phase transitions and the concept of truth-stability is studied. In numeric analyses we find multiple, intricately shaped critical boundaries. Simulations further strengthen the significance of our mean field results. Our results nicely fit into the theory of “living at the edge of chaos,” which aims at elucidating the crucial properties of evolvable biological systems.

Dynamical singularities of glassy systems in a quantum quench

We present a prototype of behavior of glassy systems driven by quantum dynamics in a quenching protocol by analyzing the random energy model in a transverse field. We calculate several types of dynamical quantum amplitude and find a freezing transition at some critical time. The behavior is understood by the partition-function zeros in the complex temperature plane. We discuss the properties of the freezing phase as a dynamical chaotic phase, which are contrasted to those of the spin-glass phase in the static system.

Poling and Depoling Effects on Dielectric Properties and Domain Structures in Relaxor 24Pb(In1/2Nb1/2)O3–46Pb(Mg1/3Nb2/3)O3–30PbTiO3 near a Morphotropic Phase Boundary Composition

The temperature dependence of the complex relative permittivity in a relaxor ferroelectric solid solution 24Pb(In1/2Nb1/2)O3–46Pb(Mg1/3Nb2/3)O3–30PbTiO3 (PIN–PMN–PT) crystal poled and depoled was measured from room temperature to 200 °C at various frequencies. The poled sample exhibits transitions from the ferroelectric (FE) phase to the relaxor (RE) phase on heating, and after that, the depoled one exhibits those from the RE phase to the glassy freezing phase on cooling. An RE-type dielectric dispersion with a weak frequency (f) dependence was observed. Such a dielectric dispersion in the RE state was found to be based on tweed domain structures observed by polarization light microscopy (PLM) and piezoelectric force microscopy (PFM) due to the competition between the antiferroelectric (AFE) and FE coupling in the RE state. The temperature dependence of complex permittivity with resonance- and relaxor-type dielectric dispersions in the poled and depoled samples was characterized by hierarchical domain structures.

Application of automated corrosion sensors for monitoring the rate of corrosion during accelerated corrosion tests

An automated corrosion monitoring system using the electrical resistance technique was applied for assessment of the corrosivity towards carbon steel and zinc in different phases of a complex accelerated corrosion test recently introduced by VDA, an association of German car makers. It comprises salt spray, wet, dry, and freezing phases. The developed small and battery‐driven atmospheric corrosion loggers provided high sensitivity allowing for sub‐angstrom (&lt;10−10 m) measurements of corrosion depth and good accuracy. The actual corrosion rate was affected by the exposure history due to a limited rate of wetting/drying and oxygen and ion transport to the reaction interface under a layer of corrosion products. The hysteresis was particularly strong for carbon steel. Except the freezing phase, the steel corrosion rate varied in a narrow range from 0.2 to 0.6 µm/h. For zinc, the corrosion rate varied from 0.001 to 0.1 µm/h in particular phases of the cycle with the maximum in the salt spray phase. Seventy‐five percent of the metal corroded in the salt spray phase and in the following drying period representing only 13% of the total test time. The obtained data suggest that the proposed test cycle allowed for rather efficient drying of the zinc surface, which is believed to be crucial for the formation of corrosion products with certain protective ability observed also in field conditions.

Binary n-Alkane Mixtures from Total Miscibility to Phase Separation in Microcapsules: Enrichment of Shorter Component in Surface Freezing and Enhanced Stability of Rotator Phases

The crystallization behaviors of binary normal alkane (n-alkane) mixtures with a series of carbon number difference (denoted as Δn), both in the bulk state and in nearly monodisperse microcapsules, have been investigated by the combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). As revealed by the DSC data, the surface freezing temperature (denoted as T(s)) of spatially confined binary n-alkane mixtures with large Δn is lower than the calculated value due to the enrichment of shorter component in the surface freezing phase. More alkane molecules with shorter carbon chain are located on the interface between the inner shell of microcapsules and the bulk mixture, thus leading to the decrease of the average chain length of the surface freezing phase and corresponding lower T(s). Furthermore, XRD results have proved that the enhanced surface freezing phenomenon can contribute to the stabilization of the rotator phases in n-alkane mixtures and even induce the crossover of some certain rotator phase (RII) from transient to metastable. However, the decisive reason for such stabilization or crossover is attributed to the suppression of the orienting movement of alkane molecules toward their next-nearest neighbors within the layer of rotator phases.

Scanning calorimeter for microliter-scaled samples based on lithium tantalite pyroelectric bulk material

We report the design and operation of a differential scanning calorimeter (DSC) for use with either solid or liquid samples with a volume down to a few microliters. The calorimeter is based on lithium tantalite pyroelectric bulk material used to perceive the energy involved in any phase transformation process. The device consists of a pyroelectric substrate, a thermoelectric cooler and a heat dissipation system. Its effectiveness is demonstrated by scanning the freezing and melting phase shifts of water droplets, ranging from 1 to 2 μ l. The latent heat of fusion and solidification were measured to within 3% of the bulk value.

Slow-roll freezing quintessence

We examine the evolution of quintessence models with potentials satisfying (V′/V)2≪1 and V″/V≪1, in the case where the initial field velocity is nonzero. We derive an analytic approximation for the evolution of the equation of state parameter, w, for the quintessence field. We show that such models are characterized by an initial rapid freezing phase, in which the equation of state parameter w decreases with time, followed by slow thawing evolution, for which w increases with time. These models resemble constant-V models at early times but diverge at late times. Our analytic approximation gives results in excellent agreement with exact numerical evolution.

Effects of waterlogging on the soil structure of some Italian soils in relation to the GAEC cross-compliance standard Maintenance of farm channel networks and field convexity

The aim of this work is to assess the effectiveness of the cross-compliance standard Maintenance of farm channel networks and field convexity with respect to the environmental objective to maintain soil structure through appropriate measures indicated in Annex IV of REG. EC 1782/03. This GAEC standard concerns arable land and obliges the farmer to maintain the farm channel network and the convex shape of fields with a view to the management and preservation of temporary drainage ditches and permanent channels along the edges of the fields, in order to ensure their efficacy and function in draining away water. Experiments have confirmed that maintaining the farm channel networks and giving fields a convex shape has a positive effect in predisposing the soil to ideal conditions for the preservation of its structure. In particular, we have used the data of a newly conducted laboratory study on the effects of the duration of waterlogging on the stability of soil structure, as well as the results of several studies carried out in the past with the following goals: i) assessment of the effects of soil moisture various levels on the stability of the structure; ii) assessment of the effects of several wetting and drying cycles on aggregate stability; iii) determination of aggregate stability under the influence of freezing and thawing under different soil moisture conditions; iv) determination of aggregate stability with an increasing number of freeze/thaw cycles (0, 1, 3, 5, 11 cycles) at field capacity moisture. The tests during which the soil was subjected to freezing and thawing were carried out taking into account the fact that during winter waterlogged soil may freeze, leading to a structure breakdown, due to the expansion of water into the pores during the freezing phase. In general, the results showed that in soils that are sandy and rich in rock fragments, rapid moisture penetration leads to significant disaggregation phenomena compared with soils with higher silt and clay contents. The results also showed that the least extensive disaggregation of the structure occurred with three wetting/drying cycles. This behaviour was more obvious in soils with a greater silt and clay content compared with sandy loam soils. After the third wetting/drying cycle, disaggregation increased with the cycles number increasing. In particular for moisture contents of 50%, this test confirms that maintaining the farm channels efficacy has a beneficial effect on soil structure, as good draining of water, which is ensured by well-functioning ditches, prevents waterlogging and fights the dispersion of clay and silt (when the soil is dry, these two components form a surface crust that disturbs the water and gas exchange as well as plant growth). Disaggregation due to freezing and thawing is linked very closely to the matrix potential (and hence to the moisture) of the aggregates before treatment. In general it can be said that a water content between saturation and field capacity predisposes the soils to a much higher level of disaggregation compared to soil that is air-dry or at the wilting point. The tests that examined the effect of an increasing number of freeze/thaw cycles showed a logarithmic degradation of structural stability in relation to the number of cycles. However, most of the disaggregation occurred after three freeze/thaw cycles. This experiment showed that only few freeze/thaw cycles are necessary to cause a significant structural degradation of soils with high water content and with a texture ranging from loamy to clayey. The results of the studies allow us to deduce that the Standard is efficient in contributing to the preservation of the soil structure. In fact, maintaining the water drainage network in efficient conditions and giving the fields a convex shape are elements that contribute to the removal of excess water, which results in a decrease of both of the possibility of the dispersal of silt+clay microaggregates and of the risk of structural damages due to freezing and thawing.

Three-Dimensional Numerical Study on Freezing Phase Change Heat Transfer in Biological Tissue Embedded With Two Cryoprobes

Biological tissues undergo complex phase change heat transfer processes during cryosurgery, and a theoretical model is preferable to forecast this heat experience. A mathematical model for phase change heat transfer in cryosurgery was established. In this model, a fractal treelike branched network was used to describe the complicated geometrical frame of blood vessels. The temperature distribution and ice crystal growth process in biological tissue including normal tissue and tumor embedded with two cryoprobes were numerically simulated. The effects of cooling rate, initial temperature, and distance of two cryoprobes on freezing process of tissue were also studied. The results show that the ice crystal grows more rapidly in the initial freezing stage (&lt;600 s) and then slows down in the following process, and the precooling of cryoprobes has no obvious effect on freezing rate of tissue. It also can be seen that the distance of 10 mm between two cryoprobes produces an optimal freezing effect for the tumor size (20 mm × 10 mm) in the present study compared with the distances of 6 mm and 14 mm. The numerical results are significant in providing technical reference for application of cryosurgery in clinical medicine.

Shoulder adhesive capsulitis in the early freezing phase: correlations between blood exams and Constant Score

We analysed the possibility that some blood values could be considered as a prognostic index of shoulder adhesive capsulitis. Fifty-six conservatively treated patients were clinically evaluated and prospectively followed at the moment of their freezing phase. At the beginning of the disease (time 0) and after 4 months (time 1), we registered some blood parameters values and their Constant Score (CS). Differences emerged for the white blood cell count (P = 0.037) that decreased and for the CS (P < 0.00001) that increased. At time 0, no significant correlation emerged between the studied parameters and the CS. At time 1, significant inverse correlations with the CS were found for glycaemia (P = 0.007), triglycerides (P = 0.05), ESR (P = 0.017) and CRP (P = 0.013). At time 1, patients with a better shoulder function were those with a low value of glycaemia, triglycerides, ESR and CRP.

Freezing of Lennard-Jones-type fluids

We put forward an approximate method to locate the fluid-solid (freezing) phase transition in systems of classical particles interacting via a wide range of Lennard-Jones-type potentials. This method is based on the constancy of the properly normalized second derivative of the interaction potential (freezing indicator) along the freezing curve. As demonstrated recently it yields remarkably good agreement with previous numerical simulation studies of the conventional 12-6 Lennard-Jones (LJ) fluid [S.A.Khrapak, M.Chaudhuri, G.E.Morfill, Phys. Rev. B 134, 052101 (2010)]. In this paper, we test this approach using a wide range of the LJ-type potentials, including LJ n-6 and exp-6 models, and find that it remains sufficiently accurate and reliable in reproducing the corresponding freezing curves, down to the triple-point temperatures. One of the possible application of the method--estimation of the freezing conditions in complex (dusty) plasmas with "tunable" interactions--is briefly discussed.

Petroleum Hydrocarbon Biodegradation under Seasonal Freeze−Thaw Soil Temperature Regimes in Contaminated Soils from a Sub-Arctic Site

Several studies have shown that biostimulation in ex situ systems such as landfarms and biopiles can facilitate remediation of petroleum hydrocarbon contaminated soils at sub-Arctic sites during summers when temperatures are above freezing. In this study, we examine the biodegradation of semivolatile (F2: C10-C16) and nonvolatile (F3: C16-C34) petroleum hydrocarbons and microbial respiration and population dynamics at post- and presummer temperatures ranging from -5 to 14 °C. The studies were conducted in pilot-scale tanks with soils obtained from a historically contaminated sub-Arctic site in Resolution Island (RI), Canada. In aerobic, nutrient-amended, unsaturated soils, the F2 hydrocarbons decreased by 32% during the seasonal freeze-thaw phase where soils were cooled from 2 to -5 °C at a freezing rate of -0.12 °C d(-1) and then thawed from -5 to 4 °C at a thawing rate of +0.16 °C d(-1). In the unamended (control) tank, the F2 fraction only decreased by 14% during the same period. Biodegradation of individual hydrocarbon compounds in the nutrient-amended soils was also confirmed by comparing their abundance over time to that of the conserved diesel biomarker, bicyclic sesquiterpanes (BS). During this period, microbial respiration was observed, even at subzero temperatures when unfrozen liquid water was detected during the freeze-thaw period. An increase in culturable heterotrophs and 16S rDNA copy numbers was noted during the freezing phase, and the (14)C-hexadecane mineralization in soil samples obtained from the nutrient-amended tank steadily increased. Hydrocarbon degrading bacterial populations identified as Corynebacterineae- and Alkanindiges-related strains emerged during the freezing and thawing phases, respectively, indicating there were temperature-based microbial community shifts.

Synthesis of low-melting-point metallic nanoparticles with an ultrasonic nanoemulsion method

A one-step, economical nanoemulsion method has been introduced to synthesize low-melting-point metallic nanoparticles. This nanoemulsion technique exploits the extremely high shear rates generated by the ultrasonic agitation and the relatively large viscosity of the continuous phase – polyalphaolefin (PAO), to rupture the molten metal down to diameter below 100 nm. Field’s metal nanoparticles and Indium nanoparticles of respective average diameters of 15 nm and 30 nm have been obtained. The nanoparticles size and shape are determined by transmission electron microscopy (TEM). Their phase transition behavior is examined using a differential scanning calorimeter (DSC). It is found that these nanoparticles dispersed in PAO can undergo reversible, melting–freezing phase transition, and exhibit a relatively large hysteresis. The experimental results suggest that the nanoemulsion method is a viable route for mass production of low-melting nanoparticles.

Thermal infrared mapping of the freezing phase change activity of micro liquid droplet

This article is dedicated to develop an experimental approach for directly visualizing the global freezing phase change behavior of micro liquid droplets. The infrared (IR) thermograph was proposed to image the basic solidification phenomena of droplet and to acquire its temperature variations during the transient process. In particular, the volumetric recalescence event, regarded as initiation of freezing, was revealed by IR images for the first time. Preliminary results demonstrated that the involved temperature transition due to release of the latent heat can be accurately characterized by evident color break in IR images. Further, experiments were also performed simultaneously on three kinds of droplets made of pure water, dimethylsulfoxide (DMSO) and nano liquid to grasp more precise temporal and spatial temperature distribution. Types of the occurring solidification and the initial frozen volume produced from the recalescence were generally discussed. The IR monitoring method suggests a straightforward way for detecting the freezing phase change activity and its temperature evolution at micro scale.

Frost heave and phase front instability in freezing soils

Abstract The main equations and conditions at the phase transition front are presented for a generalized model of secondary frost heave in freezing fine-grained soils. The analytical criterion for the stability/instability of the freezing phase front in porous media is derived. This criterion is obtained for the occurrence of the frost heave process by using the perturbation method in a two-dimensional, coupled heat and mass transfer model. This model assumes that the non-instantaneous crystallization process takes place in the kinetic zone, and that the rate of crystallization is a function of supercooling. This corresponds to the Arrhenius form equation and agrees with experimental investigations. The perturbation analysis of the freezing front shows that the stability criterion depends upon 1) the Stefan and Peclet numbers, 2) a parameter describing the phase transition kinetics and also 3) dimensionless parameters which characterize the frost heave process. Employing Fourier synthesis, actual front shape evolution is calculated. It is seen that the front displays a periodic morphology whose scale is essentially unrelated to that of the initial (starting) perturbation. The effect of the non-instantaneous kinetics on the front shape evolution is described. As is shown in results, the kinetics has a stabilizing effect and, in this case, the perturbations grow more slowly. The theoretical stability/instability conditions as predicted from the derived criterion were found to be in agreement with experimental investigations of the formation of soil cryogenic structure in the freezing process. On the basis of the asymptotic solution the engineering approach for the calculation of the heave rate and maximal frost penetration depth values — main characteristics for design and construction in cold regions, is presented. The good agreement between calculated values and experimental data is observed.

Evaluation of cytotoxicity of two root canal filling materials by MTT assay

The aim of this study was to assess the cytotoxicity of two root filling materials GuttaFlow (GF) and gutta-percha (GP) on mouse fibroblasts cell line L-929. In this study there were four groups: GP and GF were considered as study groups and the other two were negative control groups. GP and GF were prepared according to manufacturer's instruction. L-929 fibroblast cells of mouse were passaged with trypsin (Merck, Germany) after elimination of freeze phase. Adequate trypsin was added to cells and they were prepared with 95% of cell vitality. After 24 h, 150,000 cells were put in each well. The cell and dimethyl methacrylate were used as negative and positive controls. Ten specimens from each group were brought into contact with the culture medium and were incubated under sterilised conditions 24 h later. The cytotoxicity of all samples was assessed by dimethylthiazol diphenyltetrazolium bromide test after 1 h, 24 h and 72 h. The results showed that cytotoxicity of GF was less than GP when assessed at 24 h and 72 h, but there was no significant difference at 1 h. In GF, the most and least cytotoxicity were observed at 24 h and 72 h while cytotoxicity of GP increased with time.