A Continuum Model for the Effect of Dynamic Recrystallization on the Stress⁻Strain Response.

Austenitic Stainless Steels and High-Strength Low-Alloy (HSLA) steels show significant dynamic recovery and dynamic recrystallization (DRX) during hot forming. In order to design optimal and safe hot-formed products, a good understanding and constitutive description of the material behavior is vital. A new continuum model is presented and validated on a wide range of deformation conditions including high strain rate deformation. The model is presented in rate form to allow for the prediction of material behavior in transient process conditions. The proposed model is capable of accurately describing the stress⁻strain behavior of AISI 316LN in hot forming conditions, also the high strain rate DRX-induced softening observed during hot torsion of HSLA is accurately predicted. It is shown that the increase in recrystallization rate at high strain rates observed in experiments can be captured by including the elastic energy due to the dynamic stress in the driving pressure for recrystallization. Furthermore, the predicted resulting grain sizes follow the power-law dependence with steady state stress that is often reported in literature and the evolution during hot deformation shows the expected trend.

Infrared diffractive filtering for extreme ultraviolet multilayer Bragg reflectors.

We report on the development of a hybrid mirror realized by integrating an EUV-reflecting multilayer coating with a lamellar grating substrate. This hybrid mirror acts as an efficient Bragg reflector for extreme ultraviolet (EUV) radiation at a given wavelength while simultaneously providing spectral-selective suppression of the specular reflectance for unwanted longer-wavelength radiation due to the grating phase-shift resonance. The test structures, designed to suppress infrared (IR) radiation, were fabricated by masked deposition of a Si grating substrate followed by coating of the grating with a Mo/Si multilayer. To give the proof of principle, we developed such a hybrid mirror for the specific case of reflecting 13.5 nm radiation while suppressing 10 µm light, resulting in 61% reflectance at the wavelength of 13.5 nm together with the 70 × suppression rate of the specular reflection at the wavelength of 10 µm, but the considered filtering principle can be used for a variety of applications that are based on utilization of broadband radiation sources.

Wavelength separation from extreme ultraviolet mirrors using phaseshift reflection.

A generic design and fabrication scheme of Mo/Si multilayer-grating phaseshift reflector systems is reported. Close to optimized extreme ultraviolet (EUV, λ=13.5 nm) reflectance values up to 64% are demonstrated, while the diffractive properties can be exploited in spectral filtering applications. The results can contribute to a wavelength-unspecific solution for the suppression of λ>100 nm out-of-band radiation in EUV lithography.

Is oxytocin present in platelets?

For arginine-vasopressin (AVP) it has been suggested that about 90% of the total amount present in peripheral blood is platelet-membrane bound. Oxytocin (OT) and AVP are nonapeptides which are similar in many respects. We investigated the possibility that OT might be found in platelet-rich plasma samples from patients undergoing ovarian super-stimulation for in-vitro fertilization purposes. These plasma samples were treated with acid repeated freezing/thawing and sonification in an attempt to solubilize or expose the possible bound OT. No differences between OT concentrations in platelet-rich or -poor plasma samples were found. We conclude that plasma OT is not bound or confined to platelets.

Progesterone in saliva: pitfalls and consequent implications for accuracy of the determination.

The concentration of steroid hormones in saliva is believed to reflect the concentration of free hormone in blood. Because the assay for progesterone in saliva has not been rigorously validated, we investigated some of the analytical variables involved. Saliva samples were divided into two portions. One was centrifuged and the supernate used for extraction; the other was homogenized by sonication and used as such for extraction. Progesterone concentrations in homogenized whole saliva were double or triple those in supernates. By equilibrium dialysis we established that 85% of progesterone was in the free form in supernates but only 60 to 70% in homogenized whole saliva, depending upon the phase of the cycle of the subjects. Salivary flow was stimulated by crystals of citric acid; unstimulated and stimulated saliva samples were obtained from the same person. Progesterone concentrations were significantly (p less than 0.02) higher in stimulated samples than in unstimulated ones, particularly in samples collected during the luteal phase.

Morphological effects of high dose neomycin sulphate on the small and large intestine.

The morphology of the intestinal wall and the activity of certain mucosal enzyme systems in the course of neomycin treatment were evaluated. Conventional and, to study the role of the bacterial flora, germ-free rats received 500 mg neomycin daily by stomach tube. Rats were sacrificed after seven days and small intestine (proximal and distal part) together with segments of the colon were removed and prepared for histochemistry. The colon and proximal small intestine of untreated conventional and germ-free animals did not show appreciable differences in staining activity after treatment with neomycin. Neomycin diminished both in normal and germ-free rats the activity of NAD tetrazolium reductase, succinate dehydrogenase, esterase, alkaline phosphatase and acid phosphatase in the distal small intestine. The findings of this study indicate that explanations for the beneficial effects of neomycin on hyperammonemia in liver disease should not only include the bactericidal action of neomycin but also its influence on absorption and metabolic functions of the mucosal cells.

24-hour systemic antimicrobial prophylaxis with gentamicin and metronidazole, or metronidazole alone, in elective colorectal surgery after mechanical bowel preparation with mannitol and whole gut irrigation.

In a prospective randomized trial, systemic antimicrobial prophylaxis with metronidazole and gentamicin was compared to the administration of metronidazole alone in elective colorectal surgery. In both groups, an identical mechanical large-bowel preparation was performed. In order to reduce the duration of the whole-gut irrigation, a 10% mannitol solution was administered before the irrigation procedure. Although no serious infections were observed in either group, the incidence of superficial wound infections was relatively high: 19% in the group with metronidazole and gentamicin prophylaxis and 25% in the other group. From all these wounds E. coli was isolated, and no obligate anaerobic bacteria were cultured. This high rate of wound infections is most likely caused by an overgrowth of E. coli after irrigation, due to the residues of mannitol in the colon, which serve as a nutrient for E. coli. It is concluded that mannitol should not be used in the preoperative mechanical preparation of the large bowel before elective colorectal surgery.

Follicular development during the luteal phase of the human menstrual cycle.

The aims of the present studies were to determine the number, size range, health, and steroidogenic activities of antral follicles in normal human ovaries during the luteal phase of the menstrual cycle. Steroidogenic activity was assessed from the levels of androstenedione, testosterone, and estradiol in follicular fluid and the levels of extant and FSH-stimulable aromatase activity and FSH-stimulable progestin synthesis in the granulosa cells. Data for luteal phase ovaries were compared to those obtained for ovaries from the late follicular phase. On average, 94% (range, 70-100%) of the luteal phase follicles (greater than or equal to 1 mm diameter) were atretic as assessed by oocyte viability and granulosa cell number. The largest healthy follicles during the mid- to late luteal phase were 4-4.5 mm in diameter; these contained high levels of aromatizable androgen (500-2000 ng/ml), low levels of estradiol (less than 10 ng/ml), and granulosa cells with an extant level of aromatase activity 200 times lower than that in a preovulatory follicle. Based on these biochemical criteria, healthy (luteal phase) follicles were not distinguishable from atretic follicles. Granulosa cells from the luteal phase follicles were responsive to FSH with respect to progesterone and estradiol biosynthetic activity; the aromatase system in the cells from the mid- to late luteal phase follicles was significantly more responsive to FSH than that in cells from late follicular or early luteal phase follicles (P less than 0.05). These data suggest that the number of healthy luteal phase follicles (greater than or equal to 1 mm diameter) available for subsequent preovulatory development is limited.

Alterations in granulosa cell aromatase activity accompanying preovulatory follicular development in the rat ovary with evidence that 5alpha-reduced C19 steroids inhibit the aromatase reaction in vitro.

Locally produced androgens and oestrogens are thought to be important factors in the hormonal regulation of follicular development. In the present study the relationship between follicular maturity and granulosa cell aromatase activity has been examined in vitro. Granulosa cells harvested from the largest antral follicles in adult rat ovaries produced negligible amounts of immunoreactive oestradiol when incubated for 3 h in vitro irrespective of the day of the oestrous cycle upon which they were obtained. However, the addition of aromatizable C19 steroid substrate (testosterone, androstenedione or 19-hydroxyandro-stenedione) to the incubation medium resulted in time- and concentration-dependent increases in oestradiol production which were related to the level of follicular maturity attained in vivo. By measuring oestradiol production using testosterone (10(-7) mol/l) as substrate, the aromatase activity of granulosa cells obtained on the first day of vaginal dioestrus was shown to be only a fraction (less than 5%) of that observed for cells obtained on the morning of pro-oestrus. Cells obtained on the second day of dioestrus displayed an intermediate level of activity which remained approximately five times lower than that of granulosa cells at pro-oestrus. These observations, therefore, establish the induction or activation of granulosa cell aromatase activity as a correlate of normal preovulatory follicular development. However, intrafollicular androgen/oestrogen ratios may also be influenced by quantitative and/or qualitative alterations in the C19 steroidal substrate available for the aromatase reaction. Thus, the naturally occurring non-aromatizable 5alpha-reduced androgen metabolites, 5alpha-dihydrotestosterone and 5alpha-androstanedione, proved to be potent competitive inhibitors of the granulosa cell aromatase reaction in vitro. In this respect each of these biologically active androgens was more effective than 1-enetestololactone, an established C19 steroidal aromatase inhibitor. Since C19 steroid 5alpha-reductase is known to be an ovarian enzyme, it is suggested that by affecting the androgenic/oestrogenic composition of the hormonal milieu, local alterations in the activity of this enzyme may be an additional determinant of preovulatory follicular development and function.

Growth hormone in blood sampled continuously during pentobarbitone-induced sleep in children.

Growth hormone has been estimated in blood sampled continuously in periods each lasting 30 min during the first 3-4 h of pentobarbitone-induced sleep in 69 children. With only two half-hour samples, almost the same information was obtained as with the estimation of growth hormone in all samples. In this way 95% of normally growing children showed growth hormone levels of 5 muU/ml of more. Children with growth retardation of unknown cause and overweight children showed on the average lower growth hormone levels, not rarely even below 5 muU/ml. Pituitary dwarfs all had maximum growth hormone levels of 3 muU/ml or less. Growth hormone levels during sleep may be normal in children who show negative results on provocation, while subnormal growth hormone levels during sleep have been encountered in some children with retarded growth who had a normal response upon provocation.