By a novel freeze-gelcasting technique, ceramic bodies with unidirectional ordered and gradient porous structures were fabricated, using tert-butyl alcohol (TBA)/acrylamide (AM)/ alumina (Al 2 O 3 ) slurries. TBA, which can freeze below 251C and volatilize rapidly above 301C, was used as a template for forming pores. The porous structures could be controlled by the temperature conditions, resulting in special unidirectional and gradient porous structures over a long range of several millimeters. At the same time, gelation of AM was successfully introduced in this process, and played an important role in strengthening the green bodies (with compression strength over 10 MPa). Sintered Al 2 O 3 with a high porosity showed high compression mechanical properties, which contributed to the high density of ceramic walls. This technique combines the two processes of cold freezing and thermal gelation in one procedure, and is considered to be potentially useful in many applications.

Articles you may be interested inModel for the voltage and temperature dependence of the soft breakdown current in ultrathin gate oxides A physical model has been developed which complies with the experimental observation on the failure mechanism of ultrathin gate oxide breakdown during constant voltage stress. Dynamic equilibrium needs to be established between the percolation conductive path and the dielectric breakdown induced epitaxy ͑DBIE͒ formation during gate dielectric breakdown transient. The model is capable of linking the percolation model, soft breakdown, and hard breakdown to the DBIE growth for a variety of stress conditions and gate oxide thickness without involving new empirical parameters.

Objectives The purpose of this study was to determine the impact of contraception, menopause and vaginal flora on the physical and biochemical properties of cervicovaginal fluid. Study Design Vaginal swabs, cervicovaginal fluid (CVF) and cervicovaginal lavage (CVL) were collected from a total of 165 healthy asymptomatic women including: post-menopausal women (n=29), women in the proliferative (n=26) or follicular (n=27) phase, and women using the levonogestrel intrauterine device (LNG-IUD) (n=28), depomedroxyprogesterone acetate (DMPA) (n=28) or combined oral contraceptives (OCPs) (n=27). Vaginal smears were evaluated using the Nugent score. The osmolality, viscosity, density and pH of CVL samples were measured. Results CVL from postmenopausal women and women with abnormal vaginal flora was less viscous and had higher pH than premenopausal women and women with normal flora, respectively. Women using hormonal contraceptives had more viscous CVL as compared to premenopausal women not using hormonal contraceptives, but this increase in viscosity was mitigated in the presence of bacterial vaginosis. Women using DMPA had less total protein in the CVL as compared to women using the LNG-IUD, and had similar protein content when compared to postmenopausal women. Conclusion The differences in CVL protein content between DMPA and LNG-IUD suggest that type of progesterone and route of delivery impact the vaginal environment. Contraceptive hormone users had more viscous CVL than women not using contraceptives. However, the presence of bacterial vaginosis impacted both the pH and viscosity (regardless of hormonal contraceptive use), demonstrating that vaginal flora has a greater impact on the physical properties of cervicovaginal fluid than reproductive hormones.

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