1,721,193 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Endoscopy for contraception.
No full textPIP:
Over the past 2 decades, endoscopic methods of tubal sterilization-- including laparoscopic, hysteroscopic, and transcervical techniques-- have been refined so as to be less aggressive. In developing countries, laparotomic, minilaparotomic, and chemical methods of tubal sterilization prevail. Hysteroscopic methods involving the injection of silicone plugs or inert devices and transcervical injections of adhesive and sclerosing substances remain largely experimental at this time. The failure rate of tubal sterilization has remained fairly constant at 0.5%, but there has been considerable progress in terms of safety and complications. The mortality rate has dropped from 4-110/100,000 cases in the early 1970s to 4-57/100,000 procedures. In the US, the mortality rate is 4.2 for surgical sterilization and 0.4 for chemical sterilization, while, in Bangladesh, these rates are 32.6 and 30.2, respectively. The greater safety of sterilization in developing countries is due, in part, to laparoscopy and the use of Falope rings or clips. Early complications requiring surgical intervention occur in 1.1% of laparotomic sterilization cases, 1.4% of minilaparotomies, and in 0.9-3.7% of laparoscopic sterilizations. The advent of microsurgical techniques has led to a drop in the ectopic pregnancy rate from 7-21% to 4-17%. In the US, 1.1% of women request sterilization reversal and 60% of such reversals result in an intrauterine pregnancy. Most successful are isthmo-isthmic and isthmo-ampullar anastomoses performed by skilled microsurgeons. The ultimate aim is to develop a noninvasive method of tubal sterilization that is fully reversible and can be performed in an outpatient setting
Body mass index and impact on semen quality of men attending an infertility clinic
No full textBackground: The reproductive consequences of lifestyle factors in men are still controversial. In this prospective study, we verified the impact of body mass index alterations on semen parameters of patients who attended an infertility clinic. Materials and Methods: Semen samples from 156 subjects aged 22 to 53 years were analyzed. Smokers were categorized as mild (≤ 10 cigarettes/day), moderate (10-20 cigarettes/day”) and heavy smokers (> 20 cigarettes/day”). Men were grouped based upon calculated body mass index values (underweight, <18.5 Kg/m2; normal, 18.5-24.9 Kg/m2; overweight, 25-29.9 Kg/m2; obese, ≥ 30 Kg/m2). The data collected included patient height and weight, semen volume, sperm concentration, percent sperm motility, percent sperm morphology (normal forms). Results: Body mass index did not significantly affect ejaculate volume and sperm concentration. Overweight and obese men showed a percentage of progressive motility (medians 20% and 10%, respectively) significantly lower than that reported in normal-weight men (median 30%; p=0.0043). Conclusion: Our results suggest that lifestyle factors as obesity could play a major role in male infertility
Sulle tracce di una metodologia sociale appresa collettivamente
No full textOrmai, sia per ragioni di competenze collettive, sia per la facilitazione comunicativa dovuta all'Web 2.0, molte procedure metodologiche sono apprese contemporaneamente in forma collettiva
- …
