Compression-induced crossovers for the ground state of classical dipole lattices on a Möbius strip.

We explore the ground-state properties of a lattice of classical dipoles spanned on the surface of a Möbius strip. The dipole equilibrium configurations depend significantly on the geometrical parameters of the Möbius strip, as well as on the lattice dimensions. As a result of the variable dipole spacing on the curved surface of the Möbius strip, the ground state can consist of multiple domains with different dipole orientations which are separated by domain-wall-like boundaries. We analyze in particular the dependence of the ground-state dipole configuration on the width of the Möbius strip and highlight two crossovers in the ground state that can be correspondingly tuned. A first crossover changes the dipole lattice from a phase which resists compression to a phase that favors it. The second crossover leads to an exchange of the topological properties of the two involved domains. We conclude with a brief summary and an outlook on more complex topologically intricate surfaces.

Driven toroidal helix as a generalization of the Kapitza pendulum.

We explore a model system consisting of a particle confined to move along a toroidal helix while being exposed to a static potential as well as a driving force due to a harmonically oscillating electric field. It is shown that in the limit of a vanishing helix radius, the governing equations of motion coincide with those of the well-known Kapitza pendulum-a classical pendulum with oscillating pivot-implying that the driven toroidal helix represents a corresponding generalization. It is shown that the two dominant static fixed points present in the Kapitza pendulum are also present for a finite helix radius. The dependence of the stability of these two fixed points on the helix radius, the driving amplitude, and the static potential are analyzed analytically. These analytical results are subsequently compared to results corresponding of numerical simulations. Additionally, the most prominent deviations of the driven helix from the Kapitza pendulum with respect to the resulting phase space are investigated and analyzed in some detail. These effects include an unusual transition to chaos and an effective directed transport due to the simultaneous presence of multiple chaotic phase space regions.

Evidence for a cultivar and a chronology from patterned wetlands in central veracruz, Mexico.

The patterning found in certain wetlands of lowland Mesoamerica has added an important element to the subsistence system that may be attributed to pre-Hispanic inhabitants of the region. The form of the remains, largely expressed in terms of surface vegetation, suggests agriculture on planting platforms, separated by canals. The physical and chemical aspects of the stratigraphy have clarified depositional environments but have not indicated agricultural horizons. Maize phytoliths at about 1 meter below the surface in two Central Veracruzan wetlands do confirm the practice of agriculture. Associated ceramics indicate wetlands agriculture was practiced by A.D. 500 and perhaps earlier.

Laser microsurgery in cell and developmental biology.

New applications of laser microbeam irradiation to cell and developmental biology include a new instrument with a tunable wavelength (217- to 800-nanometer) laser microbeam and a wide range of energies and exposure durations (down to 25 X 10(-12) second). Laser microbeams can be used for microirradiation of selected nucleolar genetic regions and for laser microdissection of mitotic and cytoplasmic organelles. They are also used to disrupt the developing neurosensory appendages of the cricket and the imaginal discs of Drosophila.

In vitro cellular effects of hematoporphyrin derivative.

Several in vitro cell systems were exposed to hematoporphyrin derivative (HPD): established lines of rat kangaroo epithelial kidney; normal mouse embryonic fibroblasts; and differentiated neonatal rat myocardial cells. The uptake of HPD (25 to 100 micrograms/ml) by individual cells occurred rapidly over a 2-hr period and leveled off by 24 hr. HPD was excreted from cells by 48 hr after exposure. However, a low level of HPD (above background) was maintained in cells for up to 4 days following cessation of exposure. Intracellular binding of HPD was to mitochondria as demonstrated by fluorescence microscopy. HPD was also shown to have a growth-inhibiting effect on rat kangaroo cells without added light. The growth effects on mouse cells were less marked.

Vasectomy and cardiovascular deaths in Korean men: a community-based case-control study.

This community-based case-control study was carried out in four cities in South Korea to examine whether vasectomy is associated with a long-term increased risk of cardiovascular death in Korean men. Our results coincide with those from epidemiological studies conducted in Western countries as well as the one study conducted in China and do not support the vasectomy--atherosclerosis hypothesis originating from animal research.

PIP: Researchers compared data on 413 35-65 year old men who died between October 1982-September 1983 with data on 413 healthy 35-65 year old men. Both cases and controls were from Seoul, Pusan, or Incheon, South Korea. Interviewers spoke only to wives as proxies of the deceased. 36 cases and 26 controls had undergone a vasectomy, but none of their counterparts had undergone a vasectomy. This paired analysis revealed a statistically nonsignificant odds ratio (OR) of 1.38. The researchers then controlled for all confounding variables while conducting a multivariate analysis. They found the adjusted OR to be 1 for vasectomy. None of the 3 underlying causes of death ORs (cerebrovascular disease, ischemic heart disease, and hypertensive disease) different significantly from unity. The leading cause of death was stroke (71.4%). Just 7% died from ischemic heart disease. Limitations of the study included problematic diagnosis of underlying causes of death, heterogeneous cardiovascular deaths, and the lack of distinction between thrombotic or hemorrhagic stroke, and small number of cases when stratified by length of exposure to vasectomy or by cause of death. Nevertheless, like other epidemiologic studies, this community-based study did not find an association between cardiovascular deaths and vasectomy, even though animal research in the late 1970s-early 1980s found that vasectomy in monkeys brought on a progression of atherosclerosis.

Effects of various psychoative drugs on the metabolism of delta-tetrahydrocannabinol by rats in vitro and in vivo.

Metabolism of 14C-tetrahydrocannabinol (14C-THC) by rat liver microsomal preparations in vitro was studied in the absence and presence of other psychoative drugs. Disappearance of 14C-THC, and changes in metabolite patterns as shown by thin layer chromatography, were studied. SKF 525-A, pentobarbital, phenobarbital and amphetamine all produced an apparently non-competitive inhibition of THC metabolism. The inhibition produced by meprobamate was at least partly competitive. Morphine and mescaline had no evident effect. SKF 525-A and the barbiturates markedly decreased the concentrations of all the major THC metabolites found in the incubation media. In contrast, none of the drugs tested in vivo, with the exception of SKF 525-A, had any effect on the biliary 14C-excretion or metabolite pattern, or on final tissue levels of 14C, when administered in doses comparable to those used for studies of interaction with THC in vivo. SKF 525-A, however, did markedly decrease the excretion of total 14C and alter the pattern of THC metabolities in the bile, and increased the final tissue 14C levels. It is concluded that in vivo interactions between THC and other psychoactive drugs are probably not explainable primarily on the basis of altered THC metabolism.

Syncope and other vasovagal reactions at interval insertion of Lippes Loop D--who is most vulnerable?

Syncope and other vasovagal reactions occasionally occur at or immediately after IUD insertion. This analysis, using an international data set comprised of interval insertions of Lippes Loop D, found that women who are primiparous (as compared to those who are multiparous), and/or those who want more children are at higher risk for vasovagal reactions and deserve more careful counseling and gentler cervical manipulation. Moderate to severe pelvic pain at insertion is closely associated with the development of vasovagal reaction. Measures to alleviate or prevent pain at insertion could reduce the incidence of vasovagal reactions.

A clinical trial of Neo Sampoon vaginal tablets and Emko foam in Alexandria, Egypt.

Results are reported for a comparative 12-month study of Neo Sampoon foaming vaginal tablets containing 60 mg of the spermicide, menfegol, and Emko vaginal foam containing an 8.0% concentration of the spermicide, nonoxynol-9. Conducted in cooperation with the Family Planning Association in Alexandria, Egypt, the trial included 349 women who were randomly allocated to use one of the two contraceptive products. The twelve-month cumulative life-table rate for accidental pregnancy (per 100 women) was 2.8 for Neo Sampoon tablet users and 2.1 for Emko foam users. The 12-month continuation rates were 77.6 and 77.2 per 100 women for the tablet and foam groups, respectively. In both groups, the majority of discontinuations from the study were for personal reasons, including lack of confidence in the method, messiness, partner's objection and a burning sensation. Few women reported a product-related complaint while using their assigned contraceptive method. The most commonly reported complaint for both methods was that use of the product led to an uncomfortable burning sensation for the woman and/or her partner. This complaint, however, was cited by less than 5% of the women in each group. Thus, a combination of low pregnancy rates, few complications and complaints and high continuation rates confirm the relative acceptability, effectiveness and short-term safety of these methods of contraception among this sample of Egyptian women.

PIP: Results are reported for a 12-month study of Neo Sampoon foaming vaginal tablets containing 60mg of the spermicide, menfegol, and EMKO vaginal foam containing an 8.0% concentration of the spermicide, nonoxynol-9. Conducted in cooperation with the Family Planning Association in Alexandria, Egypt, the trial included 349 women randomly allocated to use 1 of 2 contraceptive products. The 12-month cumulative life-table rate for accidental pregnancy (per 100 women) was 2.8 for Neo Sampoon tablet users and 2.1 for Emko foam users. The 12-month continuation rates were 77.6 and 77.2/100 women for the tablet and foam groups, respectively. In both the majority of discontinuations from the study were for personal reasons, including lack of confidence in the method, messiness, partner's objection and a burning sensation. Few women reported a product-related complaint while using their assigned contraceptive method. The most commonly reported complaint for both methods was that use of the product led to an uncomfortable burning sensation for the woman and/or her partner. This complaint, however, was cited by 5% of the women in each group. Thus, a combination of low pregnancy rates, few complications and complaints and high continuation rates confirm the relative acceptability, effectiveness and short-term safety of these methods of contraception among this sample of Egyptian women.

Pregnancy following minilaparotomy tubal sterilization--an update of an international data set.

Seventeen pregnancies were reported from an international tubal sterilization data set comprising 1,862 minilaparotomy cases between 1978 and 1984. Of these 17, seven (41.2%) were diagnosed as luteal phase pregnancies. Of the 10 pregnancies due to sterilization failure, one was an ectopic pregnancy which occurred much later (20 months poststerilization) than the intrauterine pregnancies (10 months or less). Poststerilization pregnancy risk was greater among gravid women (those undergoing sterilization at the time of abortion or soon after childbirth) than among non-gravid women (those undergoing interval sterilization). These findings are, in general, consistent with those of previous studies using a much larger data set of primarily laparoscopic sterilizations. Pregnancies occurred with every type of mechanical tubal occlusion techniques included for study (the tubal ring, the Rocket Clip, the Secuclip and the Filshie Clip), and a frequently reported reason for failure was incorrect placement of the device. No pregnancies occurred in women sterilized with the non-mechanical Pomeroy/modified Pomeroy techniques. Findings of this analysis suggest that in minilaparotomy sterilization, for the mechanical tubal occlusion techniques to be as effective as the Pomeroy/modified Pomeroy techniques, more care and skill are required for the operator.

PIP: 17 pregnancies were reported from an international tubal sterilization data set comprising 1,862 minilaparotomy cases between 1978 and 1984. Of these 17, 7 (41.2%) were diagnosed as luteal phase pregnancies. Of the 10 pregnancies due to sterilization failure, 1 was an ectopic pregnancy which occurred much later (20 months poststerilization) than the intrauterine pregnancies (10 months or less). Poststerilization pregnancy risk was greater among gravid women (those undergoing sterilization at the time of abortion or soon after childbirth) than among non-gravid women (those undergoing interval sterilization). These findings are, in general, consistent with those of previous studies using a much larger data set of primarily laparascopic sterilizations. Pregnancies occurred with every type of mechanical tubal occlusion technic included for study (the tubal ring; the Rocket Clip; the Secuclip; and the Filshie Clip), and a frequently reported reason for failure was incorrect placement of the device. No pregnancies occurred in women sterilized with the non-mechanical Pomeroy/modified Pomeroy technics. Findings of this analysis suggest that in minilaparotomy sterilization, for the mechanical tubal occlusion technics to be as effective as the Pomeroy/modified Pomeroy technics, more care and skill are required for the operation.

Severe pain at interval IUD insertion: a case-control analysis of patient risk factors.

This investigation, using a case-control analysis approach on an IUD data set from a less-developed country center, delineated four risk factors in patient characteristics that are associated with severe pain at interval IUD insertion. They are: higher education (greater than or equal to seven years), low-parity (1-2 live births), longer open interval (greater than or equal to 13 months) between the end of the last pregnancy and insertion, and non-breastfeeding at the time of insertion. Adjusted relative risks estimated by odds ratios are 2.1, 2.7, 2.7 and 5.0, respectively. For women with a combination of the above risk factors, they have a further increased (additive in nature) risk of suffering severe insertion pain. Similar analysis was also performed on a developed country center data set for which only the effect of education and parity could be studied; an odds ratio of 5.0 for nulliparity was obtained. The plausibility of these findings as well as their clinical and programmatic implications are discussed.

PIP: This investigation, using a case-control analysis approach on an intrauterine device (IUD) data set from a less-developed country center, delineated 4 risk factors in patient characteristics that are associated with severe pain at interval IUD insertion. They are: higher education ( or = 7 years) low parity (1-2 live births), longer open interval ( or = 13 months) between the end of the last pregnancy and insertion, and non-breast feeding at the time of insertion. Adjusted relative risks estimated by odds ratios are 2.1, 2.7, 2.7, and 5.0 respectively. For women with a combination of the above risk factors, they have a further increased (additive in nature) risk of suffering severe insertion pain. Similar analysis was also performed on a developed country center data set for which only the effect of education and parity could be studied; an odds ratio of 5.0 for nulliparity was obtained. Better educated women are probably less inhibited to complain of pain than less-educated women. A tighter uterine cervix and a smaller uterine cavity in women of low parity may account for IUD insertion pain. Postpartum involution of the uterus could explain pain upon insertion for women with a long open interval. These findings support the hypothesis that cervical stretching and direct endometrial pressure are probably the most important factors for IUD insertion pain.

Cross-tolerance between delta9-tetrahydrocannabinol and ethanol: the role of drug disposition.

Acute challenge doses of delta9-tetrahydrocannabinol (THC), 10.1 mg/kg, administered intragastrically by gavage (IG), or ethanol, 1.24 g/kg, IP, reduced the rotarod performance of female rats by 50%. Daily treatment of the animals with THC, 10.1 mg/kg, IG, or ethanol, 4 g/kg, IG, resulted in tolerance development to the impairing effects of the challenge doses of each drug on rotarod performance. THC-tolerant animals were cross-tolerant to the challenge dose of ethanol, but ethanol-tolerant rats did not show complete cross-tolerance to the challenge dose of THC. THC-tolerant animals initially had higher blood levels of 14C-THC than controls after IG drug administration. Following IV injection, the rates of 14C-THC disappearance were equivalent in the latter groups. 14C-THC disappearance was not altered in ethanol-tolerant animals. The rates of ethanol disappearance were not significantly modified in THC- or ethanol-tolerant animals. In conclusion, THC-tolerant female rats demonstrated cross-tolerance to ethanol as shown previously for males. Furthermore, the development of tolerance and cross-tolerance was not a function of changes in drug disappearance.

Influence of cefoperazone on ethanol and acetaldehyde metabolism in vitro.

The effect of cefoperazone on ethanol and acetaldehyde metabolism was studied in rat liver homogenates and with a purified aldehyde dehydrogenase. Rat liver homogenates were incubated with ethanol (30 mM) alone or in combination with cefoperazone (15 or 150 micrograms/g liver). Ethanol and acetaldehyde concentrations were determined at 6, 12, 18 and 24 minutes. Cefoperazone added to the incubation medium inhibited ethanol and acetaldehyde metabolism in a concentration-dependent manner. The addition of cefoperazone to rat liver homogenates incubated with acetaldehyde (300 microM), however, did not inhibit acetaldehyde disappearance for a period of 15 minutes. Purified aldehyde dehydrogenase was incubated with 300 microM acetaldehyde. When cefoperazone was added, acetaldehyde disappearance was significantly slower than without cefoperazone. The data indicate that cefoperazone inhibits ethanol metabolism in rat liver homogenates in a concentration-dependent manner. The effect of the antibiotic on acetaldehyde elimination in liver homogenate, however, depends on the concentration of acetaldehyde in the medium. The acetaldehyde dehydrogenase obtained from yeast is inhibited by cefoperazone.

Composition of pork carcasses by potassium-40 liquid scintillation detection: estimation and validation.

Liquid scintillation detection of potassium-40 was used to estimate pork carcass composition of 124 boars, barrows and gilts. Pigs were fed to five live weights (23, 45, 68, 91 and 114 kg) and 40K emissions were determined on live pigs in a whole body counter (WBC) equipped with a two-pi liquid scintillation detector. Then, pigs were slaughtered conventionally and the right side of each carcass was weighed, 40K emissions of this carcass side was determined in the WBC and total grams of potassium were calculated. The right side of each carcass was ground, sampled and analyzed for fat, protein, moisture and potassium. Fat, protein, moisture and overall potassium percentage means were 23.9 +/- 7.2, 16.5 +/- .94, 57.0 +/- 6.5 and .25 +/- .02, respectively. Whole body counter carcass potassium was highly correlated (P less than .01) to chemically determined carcass potassium (r = .70). Percentage of fat, protein and moisture prediction equations were formed by stepwise regression using the linear, quadratic and interactive effects of live animal and carcass side weight. Whole body counter live animal and carcass potassium and sex were utilized as independent variables. Carcass weight and 40K determined potassium of the carcass explained more of the variation in carcass composition than did live animal weight and 40K determined potassium of the live animal.

Yearling adjustments for pelvic area of test station bulls.

Yearling bulls (n = 3,071) located at 18 stations in Missouri, Nebraska, Virginia, and Wisconsin were measured for pelvic area, in addition to standard performance traits. Linear adjustments for age and weight were determined using covariate regression analyses. Only bulls that were 300 to 452 d of age, 325 to 640 kg, and were in consignments offering more than nine bulls per breed were included in the analyses. Because the subsets of Angus, Polled Hereford, and Simmental bulls had large numbers of observations (817, 271, and 449, respectively), individual adjustment coefficients were determined for each breed. Angus, Polled Hereford, and Simmental bulls had pelvic area adjustment regressions on age of .20, .32, and .20 cm2/d, respectively, and regressions on body weight of .15, .22, and .18 cm2/kg, respectively. Homogeneous linear responses of all breeds (11 breeds including Angus, Polled Hereford, and Simmental) were combined to form all-breed coefficients for age and weight adjustments, which were .21 cm2/d and .15 cm2/kg, respectively. Weight or age adjustments can be used to compare contemporaries for relative pelvic area differences, but both should not be used on the same bull. Although many factors contribute to dystocia, high priority should be given to identifying sires of replacement heifers of low to moderate birth weight genotype and above average pelvic area genotype.

Comparison of market hog characteristics of pigs selected by feeder pig frame size or current USDA feeder pig grade standards.

Two feeder pig grading systems were tested. Forty-five barrows were selected using current USDA Feeder Pig Grade Standards (U.S. No. 1, No. 2 and No. 3). Additionally, 45 barrows were selected using three frame sizes (large, medium and small). Pigs were slaughtered at 100, 113.5 of 127 kg live weight. Trimmed four lean cuts were separated into soft tissue, skin and bone. The skinless belly and soft tissue from the four lean cuts were ground separately and analyzed chemically. Data from each grading system were analyzed separately in a 3 X 3 factorial plan. Pigs selected using current USDA grade standards differed (P less than .05) for last rib backfat, 10th rib fat depth, longissimus muscle area, percentage of trimmed four lean cuts and USDA carcass grade. In the frame size system, pigs with large frame size had less last rib backfat, less 10th rib fat depth, longer carcasses, higher percentage of four lean cuts and superior USDA carcass grades than pigs with small frame size did (P less than .05). The Bradley and Schumann test of sensitivity showed that selection by frame size was more sensitive than current USDA grade standards for discriminating feeder pig foreleg length, body depth and ham width. In addition, selection by frame size was more sensitive than current USDA grade standards for discriminating carcass length and carcass radius length. No increase in sensitivity (P greater than .10) was noted for carcass composition or growth traits over the current USDA Feeder Pig Grade Standards.

Legislative view of research.

Congress has its own perception of research; whether it equates to reality is up to the research community. Many in Congress perceive that the research community is free-floating and is not focused on addressing the problems that face the United States today. Recent government reports have reviewed the purposes, accountability, and challenges facing the traditional research and extension system as it enters the 1990s. These reports send a strong message that the status quo will not work sufficiently in the 1990s. How does this affect agricultural research dollars? Congress, in response to its own perceptions, has strived to establish priorities by allocating resources to key projects. Whether this is in the best interest of the nation is debatable. The agricultural research community needs to establish priorities and to communicate them effectively; otherwise someone less informed in the Congress will do it.