Spallative ablation of dielectrics by X-ray laser

Short laser pulse in wide range of wavelengths, from infrared to X-ray, disturbs electron-ion equilibrium and rises pressure in a heated layer. The case where pulse duration $\tau_L$ is shorter than acoustic relaxation time $t_s$ is considered in the paper. It is shown that this short pulse may cause thermomechanical phenomena such as spallative ablation regardless to wavelength. While the physics of electron-ion relaxation on wavelength and various electron spectra of substances: there are spectra with an energy gap in semiconductors and dielectrics opposed to gapless continuous spectra in metals. The paper describes entire sequence of thermomechanical processes from expansion, nucleation, foaming, and nanostructuring to spallation with particular attention to spallation by X-ray pulse

Topological R4R^4 Inflation

We consider the possibility that higher-curvature corrections could drive inflation after the compactification to four dimensions. Assuming that the low-energy limit of the fundamental theory is eleven-dimensional supergravity to the lowest order, including curvature corrections and taking the descent from eleven dimensions to four via an intermediate five-dimensional theory, as favored by recent considerations of unification at some scale around $\sim 10^{16}$ GeV, we may obtain a simple model of inflation in four dimensions. The effective degrees of freedom are two scalar fields and the metric. The scalars arise as the large five-dimensional modulus and the self-interacting conformal mode of the metric. The effective potential has a local maximum in addition to the more usual minimum. However, the potential is quite flat at the top, and admits topological inflation. We show that the model can resolve cosmological problems and provide a mechanism for structure formation with very little fine tuning.Comment: 25 pages, latex, 2 eps figures, minor changes, accepted for publication in Phys. Rev.

A randomised controlled trial of antibiotic prophylaxis in elective caesarean delivery.

OBJECTIVE: To determine whether prophylactic antibiotic administration using cefoxitin at the time of elective caesarean section significantly reduces infectious morbidity. SETTING: A tertiary teaching hospital in a large urban city in South Africa. PARTICIPANTS: Women undergoing elective caesarean section. DESIGN: A prospective, double-blind randomised placebo-controlled trial. METHODS: Four hundred and eighty women undergoing elective caesarean section had cefoxitin or placebo administration after umbilical cord clamping. Postpartum complications including febrile morbidity, wound infection, endometritis, urinary tract infection, pneumonia and transient postpartum fever were recorded, as were the duration of hospital stay and the need for therapeutic antibiotics. RESULTS: Wound infection was the most common complication occurring in 13.3% and 12.5% of women in the placebo and cefoxitin groups, respectively. Prophylactic antibiotics did not decrease febrile morbidity, wound infection, endometritis, urinary tract infection and pneumonia. Women who received cefoxitin stayed on average a day less in hospital than those who received placebo (6.9 vs 7.8 days, risk difference 0.94 CI 1.57 - 0.31 days). Eleven women (4.6%) in the placebo group and eight (3.4%) in the cefoxitin group had microbiological evidence of wound infection. Staphylococcus aureus was the most common pathogen (43%) isolated. Similar proportions in both groups (6.3% placebo and 5.1% cefoxitin) required a course of therapeutic antibiotics. CONCLUSION: Antibiotic prophylaxis with cefoxitin in elective caesarean section did not reduce post-operative infectious morbidity in this double-blind randomised placebo controlled trial