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Biomedical subjects

S Shaheen

Publications and source records attributed to S Shaheen.

16 recordsLinked to original sources
PubMed2001

Direct measurement of the L/K ratio in (7)Be electron capture.

The ratio of L- to K-shell electron captures in light nuclei is particularly sensitive to electron overlap and exchange effects. Calculations of these effects in (7)Be disagree by more than 20%. We report a measurement of the L/K ratio in (7)Be, using a cryogenic microcalorimeter which clearly separates L- and K-shell captures. The obtained L/K ratio of 0.040(6) is less than half that of existing predictions for free (7)Be. The discrepancy is likely due to in-medium effects distorting the L-shell electron orbitals.

Journal Article↗
PubMed1997

The beginnings of chronic airflow obstruction.

Recent follow-up studies have provided convincing evidence that the foundations of chronic airflow obstruction (CAO) are laid in utero and early childhood. Men born in Hertfordshire and Derbyshire, England, were more likely to have impaired lung function at 60-70 years of age if they had been lighter at birth and if they had had lower respiratory tract infection (LRTI) in the first 2 years of life. Furthermore, they were more likely to have died from chronic obstructive pulmonary disease if they had been lighter at 1 year of age. These findings suggest that impairment of pulmonary growth in utero and early childhood, as a consequence of undernutrition and LRTI, plays an important part in the development of CAO in late adult life. This may be of particular importance for the future respiratory health of developing nations as the additive effects of smoking take hold.

Adolescent↗
PubMed1994

Asthma in Gaza refugee camp children and its relationship with house dust mites.

Three hundred asthmatic children aged 3 to 15 years, and 100 age-sex-neighborhood matched controls, were studied for environmental risk factors for asthma during 1986 to 1987. In 98% of the asthmatic patients, exposure to house dust aggravated the symptoms. In 97% of the cases, the symptoms were more severe at home; in more than 50%, the symptoms persisted throughout the year. Significantly more cigarettes were smoked in the homes of the allergic children than in the control homes. House dust samples from homes of 20 asthmatic and 20 nonasthmatic children were examined for the presence of house dust mites. Twelve species of mites were identified, of which Dermatophagoides pteronyssinus, the most prevalent (97%), was found in all samples examined. The average number of mites per gram dust was 447 in homes of children with asthma, and 399 in homes of controls. Although dust and mites seem to be the most important factors causing allergies in Gaza and most of the children are exposed to large numbers of mites in their homes, it appears that those who are genetically predisposed and who are exposed to environmental tobacco smoke are at greater risk for allergic symptoms.

Adolescent↗
PubMed1990

Bilateral mammary artery bypass and sternal dehiscence. A favorable outcome.

The efficacy of mammary artery bypass for coronary artery disease has been well established. The present retrospective series of consecutive patients was scrutinized to assess the incidence of sternal dehiscence following myocardial revascularization using the right and left internal mammary arteries. For comparison, the consecutive group of patients undergoing myocardial revascularization with unilateral internal mammary artery bypass was analyzed for similar sternal complications. In a consecutive series of patients, 277 patients underwent myocardial revascularization using the right and left internal mammary arteries for bypass. The overall operative mortality in this group of patients was 0.722 per cent. In this group there was an overall incidence of seven sternal dehiscences, both partial and complete for an incidence of 2.52 per cent. Upon analysis, it was shown that the female sex and diabetes were the conditions that most likely predisposed to the occurrence of sternal dehiscence whether partial or complete. For comparison, a consecutive group of 413 patients were analyzed for similar demographic data and results. The overall operative mortality in this group was 1.21 per cent. The overall incidence of sternal dehiscence both partial and complete, was 0.484 per cent. Both instances of sternal dehiscence occurred in diabetic patients and the data indicates, as in the bilateral internal mammary artery group, the presence of diabetes predisposed to the occurrence of this complication. The low overall incidence of sternal dehiscence in the expanded use of the mammary arteries should not deter the surgeon from aggressive use of the mammary arteries. One should use caution, however, in using bilateral mammary artery grafts in diabetics, women, and to a lesser extent, patients more than 70 years of age.

Adult↗
PubMed1990

Mycobacterium avium-intracellulare in clinical specimens: etiological factor or contaminant?

The Mycobacterium avium-intracellulare (MAI) group comprised 10.5% of all nontuberculous mycobacteria isolated in the Mycobacterium Reference Laboratory, Tel Aviv, in an 11-year study period. From the Buirej Chest Hospital in Gaza, alone, 273 strains were isolated, representing 12.1% of the specimens from that hospital, while 149 strains (0.24% of all specimens) were isolated from all other institutions. Pulmonary disease was attributed to this organism in 22 patients, 17 of whom were hospitalized (initially for tuberculosis or another lung disease) in Buirej Hospital. The water was thought to be the source of contamination, since MAI strains, similar to those found in sputum, were isolated from it. In 1985, the water system was renovated and the MAI incidence in sputum from this hospital consequently declined.

Cross Infection↗
PubMed1989

A ten-year experience in control of poliomyelitis through a combination of live and killed vaccines in two developing areas.

We describe a successful program of poliomyelitis control using a combination of killed and live polio vaccines over a 10-year period in two developing areas, the West Bank and Gaza, adjacent to a relatively developed country, Israel. During the 1970s, immunization using live trivalent oral polio vaccine (OPV) in these areas covered more than 90 percent of the infant population. Nevertheless, the incidence of paralytic polio continued to be high, with many cases occurring in fully or partially immunized persons. It was thought that this could be due to interference with OPV take by other enteroviruses present in the environment due to poor sanitary conditions in these areas. A new policy combining five doses of OPV with two doses of inactivated polio vaccine (IPV) was adopted and implemented in 1978. In the 10 years since then, immunization coverage of infants increased to an estimated 95 percent and paralytic poliomyelitis has been controlled, despite exposure to wild poliovirus from neighboring countries including an outbreak in Israel in 1988. This experience suggests that wide coverage using the combination of IPV and OPV is an effective vaccination policy that may make eradication of polio possible even in developing areas.

Disease Outbreaks↗
PubMed1988

Effect of nitroxazepine on bone marrow cells of mice.

The antidepressant drug, nitroxazepine, was tested in mice for mutagenicity in bone marrow cells by a micronucleus test. The drug was administered orally at a dose of 4.5, 9, and 13.5 mg per mouse. The results show that the drug is found to be mutagenic in mouse bone marrow cells.

Administration, Oral↗
PubMed1986

Effect of primidone in somatic and germ cells of mice.

Primidone, an anti-convulsant drug, was tested in mice for mutagenicity in somatic cells by the micronucleus test and in germ cells by the sperm-head abnormality assay. Mice were treated orally with the drug at doses of 4.37, 8.75 and 13.11 mg/mouse. The results indicate that the drug is capable of inducing mutations both in somatic and germ cells of mice.

Animals↗
PubMedDate not supplied

A new algorithm for learning in piecewise-linear neural networks.

Piecewise-linear (PWL) neural networks are widely known for their amenability to digital implementation. This paper presents a new algorithm for learning in PWL networks consisting of a single hidden layer. The approach adopted is based upon constructing a continuous PWL error function and developing an efficient algorithm to minimize it. The algorithm consists of two basic stages in searching the weight space. The first stage of the optimization algorithm is used to locate a point in the weight space representing the intersection of N linearly independent hyperplanes, with N being the number of weights in the network. The second stage is then called to use this point as a starting point in order to continue searching by moving along the single-dimension boundaries between the different linear regions of the error function, hopping from one point (representing the intersection of N hyperplanes) to another. The proposed algorithm exhibits significantly accelerated convergence, as compared to standard algorithms such as back-propagation and improved versions of it, such as the conjugate gradient algorithm. In addition, it has the distinct advantage that there are no parameters to adjust, and therefore there is no time-consuming parameters tuning step. The new algorithm is expected to find applications in function approximation, time series prediction and binary classification problems.

Algorithms↗
PubMedDate not supplied

Measles in Israel, the West Bank, and Gaza: continuing incidence and the case for a new eradication strategy.

Measles continues to occur in epidemic waves in Israel, Gaza, and the West Bank, causing morbidity and mortality. In Israel, immunization of infants against measles began in 1967, and 90% had been immunized by the mid-1980s. In Gaza and the West Bank, where immunization of infants against measles began in 1973 and 1976, respectively, the immunization rate reached 75% in the late 1970s and increased to greater than 90% in the 1980s. Measles epidemics, which previously had occurred in 5- to 7-year cycles, occurred every 2-4 years in the 1980s and affected individuals who were older than those affected in previous years. Israel's commitment to eradicating measles by 1992 will require a substantially expanded immunization program in comparison with the traditional program that requires immunization of infants alone. The benefits of several alternative immunization strategies considerably exceed their costs. A new, two-dose immunization will be needed as a minimal strategy, and a campaign for administering booster doses to school-aged children may be required as well to achieve control and eradication of measles. Measles is a serious but preventable public health problem; appropriate strategies must be devised by national and international public health officials to control the disease in developing and developed countries.

Adolescent↗