Optimization of Chemiluminescent Nitrogen Detection for Packed-Column Supercritical Fluid Chromatography with Methanol-Modified CO(2)

A chemiluminescent nitrogen detector was optimized for packed-column supercritical fluid chromatography. Methanol modifier concentrations of 15% or less, an ozone flow of 5.8 mL/min, and a decompressed CO(2) flow between 240 and 310 mL/min were found to exhibit a maximum sensitivity of 5 ng for sulfamethazine (1 ng of N). The addition of a membrane drier to the "optimized" system further decreased the minimum detectable quantity (MDQ) to 0.5 ng (0.1 ng of N). In addition, by using a microbore column (2 mm i.d.) instead of an analytical scale column, the postcolumn decompressed flow split could be eliminated, further reducing the MDQ to 0.125 ng of sulfamethazine (0.025 ng of N).     

Measurement of the thermal expansion coefficient of an all-sapphireoptical cavity

We present measurements of the frequency-temperature dependence of an all-sapphire Fabry-Perot optical cavity to be used as an optical frequency reference. Measurements were made by tracking the frequency of the cavity relative to a second high-stability cryogenic sapphire-spaced cavity-a technique with impressive resolution for measurements of the coefficient of thermal expansion (CTE). Measurements presented here cover the temperature range of 11 K to 26 K. We find that the CTE of the all-sapphire cavity for these temperatures is given by α_cavity=(7.7±0.9)×10^$ -¹³ T/sup (3.23±0.05/)     

Development of a method to measure rheological properties of carrot cell and cell-wall materials

A method for measuring the rheological properties of carrot cells and cell-wall material during typical cooking conditions has been evaluated. A Bohlin controlled-stress rheometer with a rapid heating attachment was used. Because of potential slippage and sensitivity problems with cells and cell-wall material, different geometries (parallel plate, cone and plate, and concentric cylinder) were assessed. Initial experiments were designed to determine the linear viscoelastic regions for the cell and cell-wall materials at 25°C. Samples were subjected to varying shear stresses and oscillatory frequencies. For carrot cells, linearity was observed with cone and plate geometry and with concentric cylinder geometry over a fairly wide range of stresses and frequencies. Parallel plate geometry did not give linear results. Carrot cell-wall material behaved in a linear fashion with all three geometries over similar stress and frequency ranges as carrot cells. Using the appropriate conditions of geometry, frequency and stress, the influence of heat treatments on cell and cell-wall rheology was compared. A comparison of cone and plate and concentric cylinder geometry was performed using cells and cell-wall material heated from 25 to 90°C. Cone and plate geometry showed greater changes in rheological properties during heating than concentric cylinder geometry and also allowed a greater range of heating rates. Cone and plate geometry was used in further studies. Studies on the rheological behaviour of cells during heating showed that the complex shear modulus (G^*) increased in the range 25–75°C then decreased. For cell-wall material, G^* showed a steady increase from 25 to 90°C. Further experiments demonstrated that the increase in G^* was not due to water loss during heating. The amount of cell damage during heating was measured using a conductivity meter to establish if there was a correlation between changes in G^* and cell damage.     

Characteristics of rennet–casein-based model processed cheese containing maize starch: Rheological properties,meltabilities and microstructures

The rheological properties, meltabilities and microstructural properties of rennet–casein-based model processed cheese slices containing normal maize starch, waxy maize starch and high amylose (70%) maize starch (HAMS) were investigated as a function of the ratio of starch to protein. The storage modulus (G′) increased with increasing ratio of normal maize starch to protein in the processed cheeses, whereas G′ decreased with the addition of waxy maize starch. The tan δ values at high temperature (90 °C) decreased with the addition of both normal maize starch and waxy maize starch, but normal maize starch caused a greater reduction in the tan δ values. These properties were influenced to a lesser extent in processed cheeses containing HAMS. Processed cheeses containing normal maize starch lost meltability at ratios of starch to protein > 0.16; waxy maize starch and HAMS had less influence on the meltability. The effect of starch on the properties of the processed cheeses was attributed to phase behaviours between the protein and the starch, which was shown in confocal laser scanning micrographs.     

Chylothorax: report of a case complicating ductus ligation through a median sternotomy, and review

An unusual case of chylothorax is described in a 4-year-old child after repair of a ventricular septal defect and ligation of a patent ductus arteriosus through a median sternotomy. Left chylothorax developed after a latent period of six days and was treated initially with continuous drainage and parenteral supplementation of proteins and lipids. Operative intervention with oversewing of the site of the leak in the anterior mediastinum proved necessary after three weeks. The anatomical variations of the thoracic duct are outlined to explain the occurrence of chylothorax after diverse intrathoracic operations. The physiological effects of a thoracic duct fistula and various aspects of management are reviewed.     

Autoflora in the upper respiratory tract of Apollo astronauts

The typical microbial inhabitants of the oral and nasal cavities of Apollo astronauts were identified before space flight and generally found to be similar to those previously reported for healthy male adults. Additional analyses of samples collected immediately after return of the Apollo 13, 14, 15, and 16 crew members to earth were performed to evaluate the effects of space travel on the microbial bioburden of the upper respiratory tract. In-flight cross-contamination and buildup of pathogens such as Staphylococcus aureus were noted, although significant increases in nonpathogenic species were absent. Other proposed alterations, such as dysbacteriosis (flooding of the mouth with a single species) and simplification of the autoflora, did not occur. Generally, the incidence and quantitation of each species after flight was within the preflight range, although the number of viable Haemophilus cells recovered from the mouth decreased significantly after space flight. Except for those minor alterations listed above, the aerobic and anaerobic bacterial components of the upper respiratory autoflora of Apollo astronauts was found to be stable after space flight of up to 295 h.     

Evaluation of fecal technics for the diagnosis of cat liver fluke infection

The comparative efficiency of 5 standard technics for the detection of feline liver fluke ova in feces was evaluated. The formalin-ether technic proved superior to direct smear, sugar flotation, zinc sulfate flotation, or detergent sedimentation technics. The formalin-ether technic correctly diagnosed all Platynosomum concinnum-infected cats studied, as confirmed by necropsy findings.     

Comparison of human and hamster mitochondrial transfer RNA. Physical properties and methylation status

In a comparative study, the effective of intraventricularly or intraperitoneally injected p-chloroamphetamine (p-CA) and some chloroindoles on cerebral levels of serotonin was evaluated. 5-Chloroindole depressed 5-HT levels in the brainstem and telencephalon for three days, 6-chloro-2-methylindole (6-CMI) only during the first day. 5-Chloroindazole had no effect at all. p-CA was more toxic to guinea pigs than to rats. p-CA and 5-chloro-2-methylindole (5-CMI) had no effect on cerebral 5-HT in chicks. Apparently, none of these compounds represented or was converted to a metabolite possibly responsible for the neurotoxic effects of p-CA.     

Sparganosis in the United States. Report of a case

A 20-year-old Philadelphia woman (recently moved from South Carolina) had sparganosis of her lower anterior abdominal wall. In the United States sparganosis occurs when man enters the life cycle of dog or cat tapeworms of the genus Spirometra. Most of the American cases have been reported from the southeastern United States, and the most probable source of infection is contaminated drinking water. Sporadic cases have also been seen in other parts of the country. If the pathologist is familiar with the morphology of spargana, the gross and histologic features are sufficient for identification of genus Spirometra.     

Clinical experience using a small-gauge needle for arterial puncture

The present study was undertaken to ascertain the feasibility of using a 25-gauge needle for arterial punctures. A total of 11,500 arterial punctures were performed over the past four years by this technique without any major complication. Repeated arterial punctures were well tolerated by all patients, and the necessity for indwelling arterial catheters was almost totally eliminated during this period of study.