Effect of Surface Forces on Subcritical Crack Growth in Glass

Data on the growth of cracks tested in aqueous solutions were interpreted in terms of surface force theory. For applied stress intensity factors greater than 0.25 MPa · m½, the position and the slope of the curves and their dependence on pH and ion concentration can be explained in terms of surface force theory, provided these forces are of a magnitude and range that are representative of those involved in the cohensive bonding of solids. Weaker forces, such as structural, double-layer, or dispersion forces, have little effect on crack growth in silica glass for K _I > 0.25 MPa · m½.     

对中国入世后洗涤剂工业形势及相关问题的分析 --国内外业界高层人士访谈

中国加入WTO后，中国洗涤用品行业面临着新的机遇与挑战，中国洗涤用品市场将面临更加激烈的竞争。由于环保的呼声越来越高，中国已开始在部分地区禁磷。中国洗涤用品工业将如何发展，其前景如何，专家的看法又如何，就这些问题本刊专访了有关人士。     

A generalized analysis of hysteresis in mercury porosimetry

Modifications in hardware, including the addition of a computer, and in operating procedures, were made to a commercial mercury porosimeter to facilitate thermal and mechanical equilibration. These modifications reduce temperature changes in the hydraulic fluid which cause an ‘apparent hysteresis’ even in the mercury-only blank. These modifications also allow the allocation of additional time for slow processes such as mercury extrusion from the porous samples analyzed in this work.Hysteresis observed between intrusion and extrusion mercury porosimetry data has been interpreted by a generalized analysis. Without specifying a particular pore shape, detailed features of sample compaction, mercury retention, and contact-angle changes can be identified by this method. The hysteresis in the mercury porosimetry data of the samples analyzed in this work are completely consistent with contact-angle hyteresis.     

The structural basis of molecular adaptation

Expression levels of fast-twitch (SERCA1), slow-twitch (SERCA2a) and "housekeeping" (SERCA2b) isoforms of the sarcoplasmic reticulum Ca(2+)-transport ATPase were monitored during regeneration of rat soleus muscles following necrosis induced by the toxin notexin at the tissue level by Western blot analysis and at the cellular level by immunocytochemical analysis. Due to necrosis, levels of muscle-specific SERCA1 and SERCA2a isoforms dropped to low levels on the third day after injection of the toxin. Subsequently, during regeneration both isoforms recovered but with a different time course. Expression of the fast type SERCA1 increased first. This type showed its most pronounced increase between day 3 and 10. Expression of the slow type SERCA2a was biphasic. After an increase to approximately one third of the control value on days 5-10, it showed its main increase up to the control level between day 10 and 21. Expression levels of the house-keeping SERCA2b isoform remained relatively constant throughout the 4 weeks of regeneration. Between day 10 and 28, when new innervation is established, SERCA2a expression spread gradually over almost all fibers whereas the number of SERCA1-expressing fibers decreased and only a limited number of fibers co-expressed SERCA1 and SERCA2a. At 4 weeks of regeneration, expression of the fast isoform was found only in 12% of the fibers, whereas the slow form was found in 98% of the fibers. In the contralateral untreated soleus muscles, 26% SERCA1-positive and 81% SERCA2a-positive fibers were observed. Immunocytochemical analysis showed that SERCA1 and SERCA2a were co-expressed with fast and slow myosin isoforms in fibers of normal muscles but in regenerated muscle only slow myosin and slow SERCA isoforms correlated. The results show that during regeneration levels of fast and slow SERCA proteins change in a similar way as their mRNAs do. However, in regenerated soleus, unlike in normal muscle, expression of slow SERCA is coregulated only with the slow myosin isoform. This finding is in agreement with the fact that the number of slow type fibers is increased in regenerated soleus.     

Correction of congenital diaphragmatic hernia in utero IX: fetuses with poor prognosis (liver herniation and low lung-to-head ratio) can be saved by fetoscopic temporary tracheal occlusion

BACKGROUND/PURPOSE: Fetuses with congenital diaphragmatic hernia (CDH) who have a "poor prognosis" with postnatal treatment now can be identified on the basis of liver herniation, early diagnosis (before 25 weeks' gestation) and a low lung-to-head ratio (LHR). Because complete in utero repair proved unsuccessful for this group, the strategy of temporary tracheal occlusion was developed to gradually enlarge the hypoplastic fetal lung. The purpose of this study is to compare the outcome of patients in the poor-prognosis group treated by one of three methods: (1) standard postnatal care, (2) fetal tracheal occlusion via open hysterotomy, and (3) the recently developed video-fetoscopic (Fetendo) technique of tracheal occlusion without hysterotomy. METHODS: In the past 3 years, 34 of 86 fetuses with an isolated left CDH met criteria for the poor-prognosis group. Thirteen families chose postnatal treatment at an extracorporeal membrane oxygenation (ECMO) center, 13 underwent open fetal tracheal occlusion, and eight underwent fetoscopic tracheal occlusion. RESULTS: The survival rate was 38% in the group treated by standard postnatal therapy, 15% in the open tracheal occlusion group, and 75% in the Fetendo group. There were less postoperative pulmonary complications noted in mothers who underwent the Fetendo procedure versus the open tracheal occlusion. All but one Fetendo clip patient had a striking physiological response demonstrated by sonographic enlargement of the small left lung that was documented postnatally by plain radiographs and its subjective appearance during repair of the CDH. In contrast, only 5 of the 13 open tracheal occlusion patients demonstrated lung growth. CONCLUSION: Fetuses with a left CDH who have liver herniation and a low LHR are at high risk of neonatal demise and appear to benefit from temporary tracheal occlusion when performed fetoscopically, but not when performed by open fetal surgery.     

Aortic root replacement: twenty years of experience

BACKGROUND: Aortic root replacement is a complex surgical procedure which has undergone major technical modifications with time. In order to assess the early and long-term outcome after aortic root replacement with this procedure, our entire experience of a two decade period was reviewed. METHODS: Between January 1979 and March 1997, 156 aortic root replacement operations were performed. One hundred and twenty five patients (80%) were male and 31 female; their mean age was 50 +/- 16 years. Diagnosis was annuloaortic ectasia in 79 patients, aortic dissection in 51 (acute 22, chronic 29), isolated aortic valve pathology in 24 and aneurysm of sinus of Valsalva in 5. Thirty nine patients had aortic root replacement using the standard "Bentall" technique, 73 using the "modified Bentall" technique, 15 using the Cabrol technique. Biologic substitutes of the aortic root were used in 29 patients (19 autografts, 4 homografts, 6 xenografts). Mean follow-up time was 41 +/- 40 months (range 1 month-18 years). RESULTS: There were 12 (7.6%) hospital deaths. Hospital mortality in elective cases was 5% (7/134) and 22% (5/22) in emergent (p = 0.01). A trend toward reduced early mortality was demonstrated in recent years. Mortality was 5% for the "modified Bentall" group, 3% for the "Biologic root" group, 10% for the "Bentall" group and 20% for the "Cabrol" group. Hospital mortality was significant higher in "Cabrol" group than in "modified Bentall" group (p = 0.04). The overall long-term survival rate was 78 +/- 4% at 5 years, 71 +/- 6% at 10 years and 51 +/- 13% at 15 years. No significant difference in survival rate nor freedom from complications was observed among patient groups. Need for reoperation and valve-related adverse events become prevalent after 10 years of follow-up. CONCLUSION: The decrease in early mortality and the satisfying late results demonstrate that aortic root replacement is a low risk surgical procedure and an effective and durable treatment. The availability of biologic substitutes for the aortic root has allowed the extension of this operation to all patient age group, with results comparable to these obtained with composite grafts.     

Stabilization of optical characteristics of DNA cholesteric liquid-crystalline dispersions

Abnormal optical properties of liquid-crystalline dispersions (phases) formed as a result of phase exclusion of double-stranded DNA and RNA from water-salt poly(ethylene glycol) solutions and X-ray parameters of these phases are compared. It is shown that the cholesteric packing of nucleic acid molecules is realized at the certain osmotic pressure of a solvent only. A comparison of the optical properties of liquid-crystalline phases (dispersions) to their X-ray parameters allows one to put forward a suggestion on various hydratation (fluctuation) regimes of the nucleic acid behaviour under the condensed phases formation and factors, influencing the mode of packing of these molecules in phases formed. It is shown as well, that immobilization of DNA cholesteric liquid-crystalline particles in the content of polymeric matrix is accompanied by the stabilization of these particles and, hence, their specific abnormal optical activity as well as by formation of particles having a structure, which corresponds to the "optically isotropic ordered liquid" without abnormal optical activity. Data on stabilization of the cholesteric structure of liquid-crystalline DNA dispersions by creation of polymeric chelate bridges between the neighbouring DNA molecules, fixed in the structure of liquid-crystalline dispersions, are shown.