Magnetic deflection of neutral sodium-doped ammonia clusters.

We describe the setup and the performance of a new pulsed Stern-Gerlach deflector and present results for small sodium-doped ammonia clusters Na(NH3)n (n = 1-4) in a molecular beam. NaNH3 shows the expected deflection of a spin ½ system, while all lager clusters show much smaller deflections. Experimental deflection ratios are compared with the values calculated from molecular dynamics simulations. The comparison reveals that intracluster spin relaxation in NaNH3 takes place on a time scale significantly longer than 200 µs. Assuming that intracluster relaxation is the cause of the reduced deflection, relaxation times seem to be on the order of 200 µs for all larger clusters Na(NH3)n (n = 2-4). Our work is a first attempt to understand the magnetic properties of isolated, weakly-bound clusters with relevance to the variety of diamagnetic and paramagnetic species expected in solvated electron systems.

Prelabour rupture of membranes at term: early induction of labour versus expectant management.

OBJECTIVES: To compare expectant management with early induction of labour in pregnant patients with prelabour rupture of membranes at term and unfavourable cervix. STUDY DESIGN: A prospective, randomised study of 154 women with prelabour rupture of membranes at term of whom 80 had been managed expectantly, and 74 had undergone oxytocin induction at a rate of 2.5 mU/min. Digital examination was not performed before oxytocin infusion, and the first was delayed until 4 h (nulliparae), or 2 h (multiparae) of regular uterine contractions. RESULTS: The mean period from rupture of membranes to delivery was significantly shorter in the induction group. The mean duration of labour was significantly shorter in the expectant group. Operative vaginal deliveries were more common in the induction group, and fetal distress was the most common cause of operative vaginal deliveries. The caesarean rates were low and similar in both groups. Maternal and neonatal infectious morbidity was similar and no difference was found in the length of hospitalisation. CONCLUSIONS: Expectant management in patients with ruptured membranes at term is safe and reduces the frequency of operative vaginal deliveries.

A reappraisal of the feedback effects of oestradiol upon luteinizing hormone surge.

The objective of this study was to assess the temporal relationships of serum oestradiol and luteinizing hormone (LH) with regard to the feedback mechanism leading to the LH surge. Daily measurements of oestradiol, LH and follicle stimulating hormone were made in 65 women with ovarian failure undergoing an evaluation of endometrial response to oral cycle stimulation. Patients received incremental oral oestradiol valerate for varying durations at the in-vitro fertilization unit of the Sheba Medical Center, Tel Hashomer, Israel. The treatment protocol involved the administration of daily oestradiol valerate, starting with 1 mg/day, followed by a daily increment of 1 mg for a total of 4, 6 and 8 days. After the last day, a daily maintenance dose of 2 mg was continued. Serum oestradiol concentrations correlated with the dose of oral oestradiol valerate. Peak oestradiol concentrations (mean +/- SEM) were 572 +/- 60, 721 +/- 42 and 797 +/- 53 pg/ml for 4, 6 and 8 days of oestradiol valerate administration respectively. Serum LH, after an initial suppression, peaked 2 days after maximal oestradiol valerate dose and 1 day after peak serum oestradiol. The magnitude of the LH peak was proportional to the duration of incremental oestradiol valerate treatment. In conclusion, the LH surge is temporally related to the cessation of serum oestradiol increase. Consequently, the occurrence of this surge can be explained by a simple negative feedback inhibition of pituitary LH release rather than by a dual negative/positive mechanism.

Screening of urinary pathogens obtained from catheterized patients for mannose-specific lectin: clinical implications.

The adherence of bacteria to the uroepithelium is mediated partially by a lectin present on the bacterial surface and can be blocked by mannose derivatives. The presence of the bacterial lectin was sought in the urine of 170 catheterized patients. Sixty-one percent of the isolated Escherichia coli, 55% of the isolated Klebsiella sp. and 11% of the isolated Proteus sp. agglutinated yeast cells and thus had lectin on their surfaces. In most instances the agglutination could be blocked by mannose. Lectin-bearing E. coli were significantly more sensitive to cephalothin and sulfamexazole-trimethoprim than the other isolates, and they were isolated from the urine of patients who were catheterized for shorter periods of time (mean 4.0 days) and who had not received antibiotics or short antibiotic courses.