What affects the freezing behaviors of cement-based porous materials: The role of the unfrozen liquid-like layer

A key factor that affects freeze-thaw damages of cement-based porous materials (CBPMs) is the amount of the freezable water confined in the pores that generate large internal pressures during freezing. Taking account of an unfrozen liquid-like layer (ULLL) between ice crystals and pore wall, this paper investigates deformations of a saturated CBPM specimen under freezing with different thickness values of the ULLL. To bridge the macro strains and the local pressure exerted on the pore wall of the material, the thermodynamic equilibrium between the water and ice, and a poroelastic approach were adopted. The hydraulic pressure by volume change as phase transition takes place in the pores, the fusion pressure by energy change as ice forms and penetrates through the thin pores and the hydrothermal pressure by TEC discrepancies between the pore fluids and solid substrate dominate the internal freezing stress. The obtained results reveal that the ULLL plays an important role on the estimation of the amount of ice crystals confined in the pores, and thus influences the pore pressures and deformations of the CBPM specimen used. Appropriate model of the ULLL helps to decrease the deviations between the predicted strains and the experimental data

Morphology and thermal conductivity of model organic aerogels

The intersection volume of two independent 2-level cut Gaussian random fields is proposed to model the open-cell microstructure of organic aerogels. The experimentally measured X-ray scattering intensity, surface area and solid thermal conductivity of both polymeric and colloidal organic aerogels can be accounted for by the model.Comment: 5 pages. RevTex with 4 encapsulated figures. Higher resolution figures have been submitted for publication. To be published in Phys. Rev. E (Rapid Comm.). email, [email protected]

Self-Synchronized Universal Droop Controller

In this paper, a self-synchronization mechanism is embedded into the universal droop controller (UDC), which is applicable to inverters having an impedance angle between −π/2 rad and π/2 rad, to form a self-synchronized UDC (SUDC). Both the voltage loop and the frequency loop of the UDC are modified to facilitate the standalone and grid-connected operation of inverters. Importantly, the dedicated phase-locked-loop that is often needed for grid-connected or parallel-operated converters is removed. The inverter is able to achieve synchronization before and after connection without the need of a dedicated synchronization unit. Since the original structure of the UDC is kept in the SUDC, the properties of the UDC, such as accurate power sharing and tight output voltage regulation, are well maintained. Extensive experimental results are presented to demonstrate the performance of the proposed SUDC for a gridconnected single-phase inverter

Small‐for‐size liver transplanted into larger recipient: A model of hepatic regeneration

Orthotopic liver transplantation was performed in 60 recipient rats weighing 200 to 250 gm. Sixty rats of the same strain were used as liver donors, 30 weighing 100 to 140 gm (small for size) and the other 30 weighing 200 to 250 gm (same size). After 1, 2, 3, 4, 7 and 14 days (n = 5 each) DNA synthesis, nuclear thymidine labeling and mitoses were increased in both the small‐for‐size and same‐size groups, but significantly more in the former. These changes were maximal after 48 to 72 hr, similar to but later than the well‐known regeneration response after partial hepatectomy, which peaks at 24 hr in rats. Indirect indexes of regeneration of the transplanted livers also were measured: plasma or serum ornithine decarboxylase; insulin and glucagon serum levels; estradiol and testosterone serum levels (and their nuclear and cytosolic receptors); and transforming growth factor‐ß, c‐Ha‐ras and c‐jun mRNA expressions. With the small‐for‐size transplantation, these followed the same delayed pattern as the direct regeneration parameters. The small livers gradually increased in size over the course of 1 to 2 wk and achieved a volume equal to that of the liver originally present in the recipient. In contrast, no significant liver weight gain occurred in the transplanted livers from same‐size donors despite the evidence of regeneration by direct indexes, but not by most of the surrogate parameters, including ornithine decarboxylase. (Hepatology 1993;19:210–216). Copyright © 1994 American Association for the Study of Liver Disease

Cardiovascular health status in Chinese adults in urban areas: Analysis of the Chinese Health Examination Database 2010

Background: The American Heart Association (AHA) recently developed definitions of cardiovascular health for adults and children based on 7 cardiovascular disease risk factors or health behaviors. We applied this new construct to examine the cardiovascular health status in adult Chinese urban residents. Methods: Data of 1,012,418 subjects aged 20–65 years (55% were men; mean age, 42.4 years) who received health examination at 58 health examination centers across China was analyzed. The AHA ideal health behaviors index and ideal health factor index were evaluated among the subjects. Results: Only 0.6% of male and 2.6% of female subjects met all 7 health components, and only 39.1% of the subjects met 5 or more components of ideal cardiovascular health. The prevalence of “ideal”, “intermediate” and “poor” cardiovascular health was 1.5%, 33.9% and 64.6%, respectively. Conclusion: About two-thirds of the adult Chinese urban population has “poor” cardiovascular health. Comprehensive individual and population-based interventions must be developed to improve cardiovascular health status in China