A mathematical model of an absorption tower of nitrogen oxides in nitric acid production

A mathematical model for the simulation of the steady-state operation of absorption plate tower in nitric acid production is presented. The model is deterministic and is based on mass and energy balances and chemical equilibrium between gas and liquid.

Simulation results are presented to elucidate effects of various process variables on the tower performance. In addition, the validity of the model was tested by comparing calculated results with measured values from an absorption tower producing 250 t HNO₃/d.     

Influence of buffer capacity and pH-dependent rheological properties of respiratory mucus on health effects due to acidic pollution

Respiratory mucus is found to be a barrier to the penetration of H+ ions into the surrounding tissues. These ions are captured and bound in the mucus, e.g. as H-bond cross-linkages between the molecules. They increase its viscosity, which has a bearing on the mucociliary transport, airway resistance and gas exchange. The ability to bind the H+ ions is dependent on the buffer capacity and pH value of the mucus. Persons with acid-saturated mucus (some asthmatics and bronchitics) constitute a risk group, for whom effects can be more easily triggered from the surrounding tissues than in persons with mucus of higher pH. The latter primarily react only by changes of the mucus viscosity, which has a minimum near pH = 7.4. This, together with the mucus buffer capacity, appears to constitute the basis of the health effects reported from experimental studies. A simple test for evaluating the expected sensitivity of persons to acidic pollution is described.     

The influence of Lactobacillus rhamnosus LC705 together with Propionibacterium freudenreichii ssp. shermanii JS on potentially carcinogenic bacterial activity in human colon

The bacterial enzymes beta-glucosidase, beta-glucuronidase, and urease may contribute to the development of colon cancer by generating carcinogens. A reduction in the activity of these enzymes by certain lactic acid bacteria is considered to be beneficial. This study examined fecal beta-glucosidase, beta-glucuronidase, and urease activities during administration of Lactobacillus rhamnosus LC705 (LC705) together with Propionibacterium freudenreichii ssp shermanii JS (PJS). Thirty-eight healthy men participated in this randomized, double-blind, placebo-controlled, two-period crossover study with treatment periods of 4 weeks. Subjects consumed daily bacterial or placebo capsules. Bacterial capsules contained viable LC705 and PJS (2x10(10) CFU of each strain daily). The activities of beta-glucosidase, beta-glucuronidase and urease, recovery of LC705 and PJS, and counts of total lactobacilli and propionibacteria were determined from feces. The mean fecal counts of total lactobacilli and propionibacteria as well as strains LC705 and PJS were significantly increased during the administration of bacteria (3.5-, 13-, 80- and 11-fold, respectively). beta-glucosidase activity decreased by 10% (P=0.18) and urease activity by 13% (P=0.16) during bacterial supplementation versus placebo. The change in beta-glucosidase activity was negatively correlated with the change in propionibacteria counts (R=-0.350, P=0.039), being -2.68 versus 0.94 nmol/min/mg protein in subjects with increased and unchanged/decreased propionibacteria, respectively (P=0.003). To conclude, the administration of LC705 and PJS was followed by an increase in the fecal counts of lactobacilli and propionibacteria and a decrease in the activity of beta-glucosidase with increasing counts of propionibacteria.     

The performance of levonorgestrel rod and Norplant contraceptive implants: a 5 year randomized study

A new contraceptive (LNG rod implants, Jadelle, Leiras Oy's registered trademark for rod implants) was prospectively evaluated in randomized 5 year comparison with Norplant (Population Council's registered trademark for contraceptive implants releasing levonorgestrel) capsule implants. The study involved 1198 women at seven centres. No pregnancies occurred in the first 4 years. At 5 years, the cumulative pregnancy rate was 1 per 100 users or less for each regimen. Annual discontinuation rates averaged 11-12 per 100 users (P > 0.05), corresponding to 5 year continuation rates of 55.1 for rods and 53.0 per 100 for capsules. Mean annual discontinuation rates for menstrual disturbances were 3.5 and 4.2 per 100 for rod and capsule implants respectively (P > 0.05), and mean annual removal rates for medical problems were 3.5 and 3.0 per 100 (P > 0.05) respectively. Apart from menstrual problems, headache, weight gain and acne were the principal medical reasons for removal. In proportional hazard analyses, family formation variables, age, parity and desire/non desire for another child, recorded at admission, significantly affected discontinuation rates for major decrement categories and for all reasons combined. Mean rod removal time was half that of Norplant (P < 0.01); complications of rod removal were at a lower rate. With these contraceptives indistinguishable in performance except for ease and speed of removal, LNG rod implants appear to be preferable to Norplant for use through 5 years by virtue of relative ease of removal.     

Air pollution, hygiene and health of Danish schoolchildren.

A comprehensive investigation forming part of a joint European study under the auspices of "WHO Long-Term Air Pollution Programme" uses 7-13 year old schoolchildren as the target group. The study has included social, housing, hygienic and epidemic factors as well as family smoking habits. The results indicate that, at exposure to low levels of air pollution, these factors dominate as causes for the impairment of health especially that of respiratory health.     

Link and System Level Performance of Multiuser Detection CDMA Uplink

The link level performance and the cellular systemcapacity in the uplink direction of a CDMA cellularsystem utilising multiuser detection base stationreceivers is analysed by simulation. In the receiver,parallel multistage multiuser detection is employedtogether with two-antenna diversity reception and fastclosed-loop power control. A system level simulator isbuilt to utilise the link level simulation results andto show the increase in cellular capacity obtained byusing multiuser detection. The capacity is studied inurban micro and macro-cell environments utilising thechannel models developed in the European CODITproject. The modelling of the environment specific andCDMA specific features is considered in the systemsimulator. The system level simulator is calibratedwith analytical capacity calculations.     

Method for determination and element analysis of particulate contamination in injectable solutions

A method for sampling and evaluating the chemical and physical composition of particles in injectable solutions was developed. The technique facilitates detection of the particles' sources and possible medical hazards. Particles exceeding 0.2 mum are collected on a membrane filter sized for direct application in a scanning electron microscope (SEM). The sampling device shortens the distance between filter and solution and minimizes contamination from the filter holder. Following coating of the membrane filter with gold, the particles are counted by screening at a magnification of 5,000 x in the SEM. Both unused membrane filters and filters through which a solution of 0.9% sodium chloride had been passed were analyzed. X-ray analysis of particles on the clean filter revealed silicon, aluminum (artifact from the stud) and calcium. X-ray analysis of the filter after passage of 1 liter normal saline revealed chromium, copper, iron, magnesium, manganese, aluminum (from study), calcium chlorine, sodium and silicon. Recommendations for standard procedures for particle detection in large-volume injectables are given.     

Interference considerations for the time division duplex mode ofthe UMTS Terrestrial Radio Access

The air interface of the UMTS Terrestrial Radio Access (UTRA) covers both a frequency division duplex (FDD) part for the paired bands and a time division duplex (TDD) part for the unpaired bands of the UMTS spectrum. The Universal Mobile Telecommunication System (UMTS) is the 3rd-generation mobile communication system. This paper presents an interference evaluation of the UTRA TDD. Since both uplink and downlink share the same frequency in TDD, the signals of the two transmission directions can interfere with each other. This interference can occur between two mobile stations or between two base stations within one carrier or between two operators. The interference between uplink and downlink is evaluated by system simulations. Synchronization and coordination requirements of UTRA TDD are evaluated based on the results