Modeling of picosecond pulse propagation in microstripinterconnections of integrated circuits

Theoretical time-domain analyses of the dispersion and loss of square-wave and exponential pulses on microstrip transmission line interconnections on silicon integrated-circuit substrates, performed using the quasi-TEM approximation, are discussed. Geometric dispersion and conductor line width, as well as losses from conductor resistance, conductor skin effect, and substrate conductance, are considered over the frequency range from 100 MHz to 100 GHz. Results show the enormous significance of the substrate losses and demonstrate the need for substrate resistivities >10 Ω-cm for high-performance circuits. The results also show the effects of geometric dispersion for frequencies above 10 GHz, the unimportance of conductor skin-effect losses for frequencies up to 100 GHz, and the transition from a high-frequency regime where losses do not affect phase velocity to a low-frequency regime where the ratio of he conductor and substrate loss coefficients determines phase velocity     

Early prediction of prolonged ventilator dependence in thermally injured patients

BACKGROUND: Recent studies suggest that when prolonged ventilator dependence (PVD) can be predicted in trauma or intensive care unit patients, early tracheostomy may reduce hospital stay and improve utilization of resources. This study was performed to develop criteria predictive of PVD (> 14 days) in burn patients. METHODS: We reviewed burn patients aged > or =16 years admitted between 1990 and 1994 who required ventilator support for > or =3 days. Using the variables full-thickness burn size, age, inhalation injury, and worst PaO2/FiO2 on ventilator day 3, an equation predicting PVD was created using logistic regression. The equation was tested by applying it to 1995 patients. RESULTS: When a probability of >0.5 was considered predictive of PVD, the equation correctly predicted PVD in 82% of 1990 to 1994 patients (n = 110) and 90% of 1995 patients (n = 29). CONCLUSION: PVD in burn patients can be predicted using objective variables in the early postburn period. Predictions can be used to select patients for prospective studies of early tracheostomy.     

Low-molecular weight organic compositions of acid waters from vegetable oil soapstocks

Alkaline extracts (soapstocks) from canola, corn, cottonseed, peanut, soybean, and sunflower oil refining were acidified, and identities and concentrations of the low-molecular weight organic components of the resulting acid waters were determined by gas chromatography, followed by mass spectroscopy, and by high-performance liquid chromatography. The main components of each acid water sample, in order of decreasing concentration and after omitting the fermentation product lactic acid, were phosphoric acid, α-glycerophosphate, and glycerol from canola;myo-inositol, phosphoric acid, α-glycerophosphate andmyo-inositol-1-phosphate from corn; glycerol, α-glycerophosphate,myo-inositol-1-phosphate, and β-glycerophosphate from cottonseed; phosphoric acid, glycerol, andmyo-inositol from peanut; α-glycerophospho-1-myo-inositol,myo-inositol-1-phosphate, α-glycerophosphate, and glycerol from soybean; and α-glycerophosphate, glycerol,myo-inositol-1-phosphate, and β-glycerophosphate from sunflower.     

IgM anti-phenolic glycolipid-I antibody measurements from skin-smear sites: correlation with venous antibody levels and the bacterial index

Measurements of anti-phenolic glycolipid-I antibodies were made in 200 matched samples of capillary blood from the skin-smear site, venous blood collected on filter paper, and sera. A close correlation among the three samples was observed and a weaker correlation among the antibody levels and the average and skin-smear bacterial index. Capillary blood from the skin-smear site had a consistently higher level of antibodies in each sample than did the sera. The collection of capillary blood from skin-smear sites is a convenient and economical method of obtaining samples for serology and for measuring local antibody levels, and it may be more sensitive than measurements of antibodies in sera.     

A PAb240+ conformation of wild type p53 binds DNA

It is generally accepted that wild type (growth suppressing) p53 is capable of binding to a consensus DNA sequence and is in a conformation recognizable by antibody PAb246 (for murine p53), but not by antibody PAb240. Conversely, mutant forms of p53 incapable of DNA binding often assume conformations that display the PAb240, but not the PAb246 epitope. Exposure of these two epitopes on p53 is therefore believed to be mutually exclusive. We show that wild type p53 translated in vitro in rabbit reticulocyte lysate (RRL) has a PAb240 epitope that is not always cryptic, even on p53 that is bound sequence-specifically to DNA (presumably as a tetramer). All of the DNA-bound, PAb240+ p53 concurrently displays the PAb246 epitope, and both epitopes can be occupied by antibody while p53 is bound to DNA. This novel 'dual positive' conformation also exists in the absence of DNA and suggests that p53 is not necessarily inactive when the PAb240 epitope is displayed. When the C-terminal 58 amino acids of p53 containing the dimer/tetramerization domains are replaced with a heterologous dimerization domain, the resultant dimeric p53 manifests only the PAb246+/PAb240- conformation while bound to DNA. Thus, the C-terminal 58 amino acids of p53 are required for the PAb246+/PAb240+ phenotype, possibly due to tetramerization. This novel 'dual positive' p53 conformation exists in an excess of wild type p53 that has the PAb246-/PAb240+ 'mutant' conformation, suggesting that the 'mutant' conformation is not dominant negative in and of itself.     

Sulfated 17,20 beta-dihydroxy-4-pregnen-3-one functions as a potent and specific olfactory stimulant with pheromonal actions in the goldfish

This study demonstrates that in addition to using the maturational steroid hormone 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) as a potent sex pheromone, the goldfish uses its sulfated metabolite 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate (17,20 beta-P-20S). As measured by electro-olfactogram recording (EOG), the goldfish olfactory epithelium is extremely sensitive to both free and sulfated 17,20 beta-P (detection thresholds of approximately 10(-12) and 10(-11) M) but not to glucuronidated or phosphated 17,20 beta-P. Furthermore, both structure-activity and cross-adaptation studies using EOG indicated that 17,20 beta-P-20S and 17,20 beta-P are detected by different olfactory receptor sites, suggesting that these cues function as a distinguishable mixture. Finally, although the pheromonal activity of 17,20 beta-P-20S appears to be slightly less than that of 17,20 beta-P, it too stimulates gonadotropin release and sperm production in male goldfish. The precise function of 17,20 beta-P-20S remains somewhat enigmatic, however, because it does not appear to enhance the actions of 17,20 beta-P and is released by a different mechanism. In any case, our findings clearly establish that a fish olfactory system can detect particular conjugated steroidal compounds in a highly specific manner and that naturally released conjugated steroids can function as components of a pheromonal mixture.     

Factors affecting the immunogenicity of tetanus toxin fragment C expressed in Lactococcus lactis

The relative immunogenicity of tetanus toxin fragment C (TTFC) has been determined in three different strains of inbred mice when expressed in Lactococcus lactis as a membrane-anchored protein (strain UCP1054), as an intracellular protein (strain UCP1050), or as a secreted protein which is partly retained within the cell wall (strain UCP1052). Protection against toxin challenge (20 x LD50) could be obtained without the induction of anti-lactococcal antibodies. When compared in terms of the dose of expressed tetanus toxin fragment C required to elicit protection against lethal challenge the membrane-anchored form was significantly (10-20 fold) more immunogenic than the alternative forms of the protein.     

Geophagy among school children in western Kenya

A cross-sectional study was conducted among 285 school children aged 5-18 years in Nyanza Province, Western Kenya, to determine the prevalence of geophagy and the types and amounts of soil eaten. Stool samples were taken from a subsample of 53 (19%) and their silica content determined to compare the results with the reported geophagy. Geophagy was practised by 73% of the children. The prevalence decreased with age for both sexes up to age 15, then remained stable for girls between 15 and 18 years but continued to decrease for boys in that age range. Most children ate soil from the surface of termitaria; others preferred the edges of paths and gullies, material from the wall of huts, and a chalk-like, soft stone commonly found in the area. The soil was eaten dry and was occasionally ground, but not processed in other ways. All but 4 of the children practising geophagy reported to eat soil at least once daily. The median amount reported eaten was 28 g daily, ranging from 8 to 108 g. The reported amount of soil eaten daily was significantly correlated to the results of the stool silica determinations. Using the median of 1% silica of faecal wet weight as a cut-off point to distinguish geophageous children from non-geophageous, the examination of a single stool sample had a sensitivity of 76% and a specificity of 80% to detect a geophageous child compared to the interview method. The cultural context of geophagy and its potential health impact in terms of infection and nutrition need to be further investigated, and it is suggested that more school and community-based studies on geophagy in different societies should be undertaken.     

The rise and fall of the plantar response in infancy

Herniation of the stomach through the umbilicus is exceedingly rare with only one case reported in the international literature in the past 40 years. One case of a reducible gastric umbilical hernia, not diagnosed by endoscopy, is reported. Diagnosis was made by double-contrast barium examination after 5 years of symptoms and ineffective treatment. Herniation of the stomach is difficult to diagnose by endoscopy and radiological studies can be more sensitive and allow a more specific diagnosis.     

Phenylethyl esters of fatty acids for the analytical resolution of petroselinate and oleate

2-Phenylethyl esters of fatty acids were prepared readily by esterification of free fatty acids or transesterification of other lipids. Compared with methyl esters, phenylethyl esters greatly improve the resolution of oleate and petroselinate by both gas and high-performance liquid chromatography, and the ultraviolet absorption of the phenylethyl esters facilitates detection of the derivatives by high-performance liquid chromatography (HPLC) ultraviolet detectors. The fatty acid compositions of corn and soybean oil obtained by analysis of phenylethyl esters agreed with those obtained with methyl esters. The phenylethyl esters were resolved and eluted on C-18 HPLC columns with much smaller solvent volumes than those reported for other aromatic esters.