This paper describes measurement of vapor-liquid equilibrium (VLE) data of methyldichlorosilane-methyltrichlorosilane-dimethyldichlorosilane system and that of the three binary systems at 101.325 kPa with a new pump-ebulliometer. The equilibrium composition of the vapor phase was calculated from pTx by indirect method. The model parameters of the liquid activity coefficient of the Wilson, NRTL, Margules and van Laar equations was corrected by the least square method. The ternary system VLE data were predicted by the Wilson equation, with the calculated boiling points showing good agreement with the experimental data.
Computer Simulation ; Gases ; chemistry ; Models, Chemical ; Phase Transition ; Pressure ; Silanes ; chemistry ; Volatilization

OBJECTIVETo employ a laser triangulation method for measuring post-gel and post-vitrification polymerization shrinkage of composite resins.

METHODSA novel experimental set-up capable of measuring real-time shrinkage strain was utilized. Total shrinkage of the five composite resins was measured. The measurements of post-gel and post-vitrification linear shrinkage as a function of the gel-point and vitrification transition point were also carried out in the study.

RESULTSGel point of the five composite resins ranged from 0.77 s to 1.59 s, while vitrification transition point ranged from 1.99 s to 6.33 s. Post-gel shrinkage ranged from 33.35 µm to 53.18 µm and post-vitrification shrinkage ranged from 16.43 µm to 30.58 µm. Total shrinkage ranged from 39.25 µm to 64.84 µm. Significant differences in the gel point and vitrification transition point among the five composite resins were found (P < 0.01). Significant differences in the post-gel shrinkage, post-vitrification shrinkage and total shrinkage among the five composite resins were found (P < 0.01). The ranking of post-gel and post-vitrification shrinkage of these composite was different from that of their total shrinkage.

CONCLUSIONSLaser triangulation method is suitable for measuring clinically significant post-gel and post-vitrification shrinkage.

Composite Resins ; chemistry ; Elasticity ; Gels ; chemistry ; Lasers ; Materials Testing ; Phase Transition ; Polymerization ; Stress, Mechanical ; Surface Properties ; Vitrification

BACKGROUND: To develop the biodegradability and thermoresponsive hydrogel, in this work we designed a pendant-functionalized, thermoresponsive, amphiphilic block copolymer. METHODS: Methoxy poly(ethylene glycol) (MPEG)-b-[poly(ε-caprolactone)-ran-poly(ε-caprolactone-3-one)-ran-polylactic acid] (MCL) and (MPEG-b-[PCL-ran-POD-ran-PLA]) [MCL-(CO)] block copolymers were prepared by ringopening polymerization of ε-caprolactone, OD and lactide monomers. The subsequent derivatization of MCL-(CO) provided MPEG-b-[PCL-ran-poly(ε-caprolactone-3-COOH)-ran-PLA] [MCL-(COOH)] with COOH pendant groups and MPEG-b-[PCL-ran-poly(ε-caprolactone-3-NH2)-ran-PLA] [MCL-(NH2)] with NH2 pendant groups. RESULTS: The measured segment ratios of MCL-(CO), MCL-(COOH), and MCL-(NH2) agreed well with the target ratios. The abundances of the COOH and NH2 groups in the MCL-(COOH) and MCL-(NH2) copolymers were determined by 1H- and 13C-nuclear magnetic resonance spectroscopy, and agreed well with the target abundances. MCL-(CO), MCL-(COOH), and MCL-(NH2) formed homogeneous, white, opaque emulsions at room temperature. Rheological analysis of the block copolymer suspensions indicated a solution-to-hydrogel phase transition as a function of temperature. The solution-to-hydrogel phase transitions and the biodegradation of MCL-(CO), MCL-(COOH), and MCL-(NH2) were affected by varying the type (ketone, COOH, or NH2) and abundance of the pendant groups. CONCLUSION: MCL-(CO), MCL-(COOH), and MCL-(NH2) with ketone, COOH, and NH2 pendant groups showed solution-to-hydrogel phase transitions and biodegradation behaviors that depended on both the type and number of pendant groups.
Emulsions ; Hydrogel ; Magnetic Resonance Spectroscopy ; Phase Transition ; Polymerization ; Polymers ; Suspensions

OBJECTIVE: Extensive neuronal death occurring in the Alzheimer's disease (AD) may be related with the apoptosis. Recent studies have suggested that regulatory failure of cell cycle appeared to be very early event of AD pathogenesis in neuronal cells as well as in peripheral lymphocytes. We compared the change of cyclin dependent kinases (Cdks), which is related with G1/S phase transition in the cell cycle, between AD patients and normal controls using peripheral lymphocytes. METHODS: We obtained Cdks from peripheral lymphocytes of 37 AD patients and 18 age-matched normal subjects. Cells in first culture were considered to be G-zero (G0) cells. We measured Cdk2, Cdk4, and Cdk6 at baseline (T0). Thereafter, we observed Cdks 24 hours later after using PHA (phytohemaglutinin) (N24). Meanwhile, we observed Cdks 24 hours later again with rapamycin treatment (T24). RESULTS: At baseline (T0), Cdk2 and Cdk6 were increased in AD patients compared to the control group (p< 0.001, p=0.038, respectively). Cdk2 was increased in AD patients more than control group after using PHA (T24, p=0.007). After rapamycin treatment for 24 hours (N24), Cdk2, Cdk4, and Cdk6 were increased in the patients compared to the controls (p=0.002, p=0.022, p=0.011, respectively). CONCLUSION: This results showed that the cell cycle regulating proteins in AD patients, which are related with G1/S phase transition, were increased in peripheral lymphocytes compared to those in normal controls. We provide the clue which demonstrate the cell cycle dysregulation in the patients with Alzheimer's disease.
Alzheimer Disease* ; Apoptosis ; Cell Cycle* ; Cyclin-Dependent Kinases ; Humans ; Lymphocytes* ; Neurons ; Phase Transition ; Sirolimus

OBJECTIVETo characterize austenite, martensite and R phase temperatures as well as transition temperature ranges of the commonly used nickel-titanium (NiTi) orthodontic arch wires selected from several manufacturers.

METHODSDifferential scanning calorimetry (DSC) method was used to study the phase transformation temperatures and the phase transition processes of 9 commonly used NiTi alloys (types: 0.406 mm, 0.406 mm x 0.559 mm).

RESULTSThe austenite finish temperatures of A, B, D NiTi wires were 22.4 CT, 21.9 degrees C, 22.5 degrees C, respectively. No phase transformation was detected during oral temperature. It indicated that these types of NiTi wires did not possess shape memory property. For C and H NiTi wires, no phase transformation was detected during the scanning temperature range, suggesting that these two types of wires did not possess shape memory either. The austenite finish temperatures of E, G and I NiTi wires were 34.3 degrees C, 36.6 degrees C, 38.5 degrees C, respectively, which were close to the oral temperature and presented as martensitic-austenitic structures at room temperature, suggesting that the NiTi wires listed above had good shape memory effect. Although F NiTi wire also showed martensitic-austenitic structures at room temperature, its austenite finish temperature (61.5 degrees C) was much higher than oral temperature.

CONCLUSIONSThe transformation phase temperatures and transformation behavior were varied among different NiTi alloys, leading to variability in shape memory effect.

Calorimetry, Differential Scanning ; Dental Alloys ; chemistry ; Materials Testing ; Orthodontic Wires ; Phase Transition ; Temperature

OBJECTIVES: The purpose of this study was to observe the change in the viscoelastic properties of thermoplasticized injectable root canal filling materials as a function of temperature and to compare the handling characteristics of these materials. MATERIALS AND METHODS: Three commercial gutta perchas and Resilon (Pentron Clinical Technologies) in a pellet form were heated in the Obtura-II system (Obtura Spartan) at 140degrees C and 200degrees C, and the extrusion temperature of the thermoplasticized materials was measured. The viscoelastic properties of the materials as a function of temperature were evaluated using a rheometer. The elastic modulus G', viscous modulus G", loss tangent tandelta, and complex viscosity eta* were determined. The phase transition temperature was determined by both the rheometer and a differential scanning calorimeter (DSC). The consistency of the materials was compared under compacting pressure at 60degrees C and 40degrees C by a squeeze test. RESULTS: The three gutta perchas had dissimilar profiles in viscoelastic properties with varying temperature. The phase transition of softened materials into solidification occurred at 40degrees C to 50degrees C, and the onset temperatures obtained by a rheometer and a DSC were similar to each other. The onset temperature of phase transition and the consistency upon compaction pressure were different among the materials (p < 0.05). Resilon had a rheologically similar pattern to the gutta perchas, and was featured between high and low-flow gutta perchas. CONCLUSIONS: The rheological characteristics of the thermoplasticized root canal filling materials changed under a cooling process. The dissimilar viscoelastic properties among the materials require different handling characteristics during an injecting and compacting procedure.
Elastic Modulus ; Gutta-Percha ; Handling (Psychology) ; Hot Temperature ; Phase Transition ; Root Canal Filling Materials ; Viscosity

The impact of metal ions on the phase behavior of phosphatidylcholine (PC) was investigated at the air/water interface by surface pressure-area (pi-A) isotherm measurements. The analysis of the pi-A isotherms showed that with the metal ionic radius decreasing, the concentration of the metal ions C increasing, and the valence of metal ions Q increasing, the amount of the corresponding curves of A0 decreases, the phase transition point would change more apparently, the collapse pressure would become larger subsequently, and the curve would be extended outside. The phenomenon could be approached when the metal ion concentration C became great enough. These experiments were identified with the rules on Langmuir films, by a variety of properties of metal ions (ion radius, ion concentration, ion valence, etc.). Among all the factors, the ionic valence showed the greatest impact on the phase changes, followed by the ion concentration, while the ionic radius influences were less on the phase-change characteristics.
Air ; Ions ; chemistry ; Membranes, Artificial ; Metals ; chemistry ; Phase Transition ; Phosphatidylcholines ; chemistry ; Surface Properties ; Water ; chemistry

BACKGROUND: Polymeric hydrogels are extensively used as promising biomaterials in a broad range of biomedical applications, including tissue engineering, regenerative medicine, and drug delivery. These materials have advantages such as structural similarity to the native extracellular matrix (ECM), multi-tunable physicochemical and biological properties, and biocompatibility. METHODS: In situ forming hydrogels show a phase transition from a solution to a gel state through various physical and chemical cross-linking reactions. These advanced hydrogel materials have been widely used for tissue regenerative medicine because of the ease of encapsulating therapeutic agents, such as cells, drugs, proteins, and genes. RESULTS: With advances in biomaterials engineering, these hydrogel materials have been utilized as either artificial cellular microenvironments to create engineered tissue constructs or as bioactive acellular matrices to stimulate the native ECM for enhanced tissue regeneration and restoration. CONCLUSION: In this review, we discuss the use of in situ cross-linkable hydrogels in tissue engineering and regenerative medicine applications. In particular, we focus on emerging technologies as a powerful therapeutic tool for tissue regenerative medicine applications.
Biocompatible Materials ; Cellular Microenvironment ; Extracellular Matrix ; Hydrogel* ; Hydrogels* ; Phase Transition ; Polymers ; Regeneration ; Regenerative Medicine* ; Tissue Engineering

OBJECTIVETo determine the rheological properties of shuanghuanglian in situ gel (SHL-gel) by using dynamic rheological experiments, in order to evaluate its gelling properties shuanghuanglian in situ gel and predict its gelling behavior in vivo.

METHODRheological parameters were determined by scanning of shear rate and frequency at different temperatures. The phase transition process from liquid to semisolid was described by testing of process heating/cooling and acute heating/cooling.

RESULTSHL-gel was Newtonian fluid under the conditions of a phase angle approaching 90 degrees at low temperature or room temperature, with its viscous characteristics dominated. It was shear-thinning pseudoplastic fluid under the conditions of a low phase angle at body temperature, with its elastic characteristics dominated. During the phase transition process, the phase angle delta was getting sharp, with exponential increase of the modulus. The gelling temperature (Tg) was at (35.38 +/- 0.05) degrees C, the phase transition temperature ranged from 33.71 to 37.01%, and phase transition time was 140 s.

CONCLUSIONThe dynamic rheological experiment characterizes the gelling properties of Shuanghuanglian in situ gel so precisely that it can be used as the basis of for in vitro evaluation and quality control of products.

Drugs, Chinese Herbal ; chemistry ; standards ; Phase Transition ; Quality Control ; Rheology ; Temperature ; Viscosity

The phase change process in cryosurgery is simulated here with finite element scheme. The calculated results are consistent with experimental results. The compared results confirm the feasibility of the enthalpy model and finite element simulation method. And the successive Freeze-thawing Circle and multi-probe cryosurgery process are further simulated and the characteristic of the thermal field and thermal gradient around cryoprobe are analyzed. The application of enthalpy mathematical model and finite element scheme provide useful simulating means for the cryosurgery and will be beneficial for the progressing and extending of the cryosurgery technology.
Computer Simulation ; Cryosurgery ; methods ; Finite Element Analysis ; Humans ; Models, Theoretical ; Phase Transition