Showing papers by "King Saud University published in 1987"

First-order integer-valued autoregressive (inar(1)) process

Abstract: . A simple model for a stationary sequence of integer-valued random variables with lag-one dependence is given and is referred to as the integer-valued autoregressive of order one (INAR(1)) process. The model is suitable for counting processes in which an element of the process at time t can be either the survival of an element of the process at time t - 1 or the outcome of an innovation process. The correlation structure and the distributional properties of the INAR(1) model are similar to those of the continuous-valued AR(1) process. Several methods for estimating the parameters of the model are discussed, and the results of a simulation study for these estimation methods are presented.

Antibiotic Therapy, Endotoxin Concentration in Cerebrospinal Fluid, and Brain Edema in Experimental Escherichia coli Meningitis in Rabbits

Abstract: We investigated the effect of cefotaxime and chloramphenicol on endotoxin concentrations in cerebrospinal fluid (CSF) and on the development of brain edema in rabbits with Escherichia coli meningitis. Both antibiotics were similarly effective in reducing bacterial titers. Cefotaxime, but not chloramphenicol, induced a marked increase of endotoxin in CSF, from log10 1.5 +/- 0.8 to log10 2.8 +/- 0.7 ng/ml (P less than .01). This result was associated with an increase in brain water content (405 +/- 12 g of water/100 g of dry weight compared with 389 +/- 8 g in untreated controls; P less than .01), whereas in animals treated with chloramphenicol, brain water content was identical to controls. The cefotaxime-induced increase in endotoxin concentration and brain edema were both neutralized by polymyxin B, which binds to the lipid A moiety of endotoxin, or by a monoclonal antibody to lipid A. These results indicate that treating gram-negative bacillary meningitis with selected antibiotics induces increased endotoxin concentrations in CSF that are associated with brain edema.

Hatching weight in relation to egg weight in domestic birds

Abstract: A review of literature concerning the relationship between egg weight at setting and the corresponding weight of the young at hatching for six different species of domestic birds (chicken, turkey, ...

Capacitance Requirements for Isolated Self Excited Induction Generators

Abstract: Capacitance requirements for isolated self excitd induction generators are discussed. It is shown that numerical methods based upon the steady state as well as operational equivalent circuit give similar predicted values. An analytical method is proposed to compute, Cmin, the minimun capacitance value required for self excitation under no load conditons. It is shown that Cmin is inversely proportional to the square of the speed. Furthermore, it is inversely proportional to the maximum saturated magnetizing reactance. The theoretical results are verified experimentally for a number of test machines and a good agreement is observed between the theoretical and the experimental values. The influence of load impedance and its power factor on the terminal capacitance required to maintain self excitation under steady state is also examined and it is shown that when machine is loaded, the terminal capacitance should be several times that required at no load. Furthermore, the influence of terminal capacitor upon the maximum available output power fron isolated induction generators is also examined.

Flow through Porous Media of a Shear-thinning Liquid with Yield Stress

Abstract: Darcy's law for the laminar flow of Newtonian fluids through porous media has been modified to a more general form which will describe the flow through porous media of fluids whose flow behavior can be characterized by the Herschel-Bulkley model. The model covers the flow of homogeneous fluids with a yield value and a power law flow behavior. Experiments in packed beds of sand were carried out with solutions of paraffin wax in two oils and with a crude oil from the Peace River area of Canada. The model fitted the data well. A sensitivity analysis of the fitting parameters showed that the model fit was very sensitive to errors in the flow behavior index, n, of the Herschel-Bulkley model. A comparison of the “n” values calculated from viscometer measurements and from flow measurements agreed well. A more general Reynolds number for flow through porous media, which includes a fluid yield value, was developed. The data were fitted to a Kozeny-Carman type equation using this Reynolds number. The constant in the Kozeny-Carman equation was determined for the two packed beds studied using Newtonian oils. The data could all be represented, within the experimental error, by the relationship f* = 150/Re*. Since the mean volume to surface diameter of the packing was determined by the measurement of its permeability to a Newtonian oil, assuming C' = 150, the new definition of the Reynolds number allows the direct use of the Kozeny-Carman equation with Herschel-Bulkley type fluids.

Relationship Between Posttetanic Count and Response to Carinal Stimulation During Vecuronium-Induced Neuromuscular Blockade

Abstract: The correlation between degree of peripheral neuromuscular blockade and response to carinal stimulation was evaluated in two groups of 25 patients: one group was anaesthetized with thiopental, N2O and halothane, and the other group received thiopental, N2O and fentanyl. The degree of peripheral blockade was evaluated using train-of-four (TOF) and posttetanic twitch (PTC) stimulation of the ulnar nerve. The degree of diaphragmatic paralysis was evaluated indirectly by stimulating the carina and observing the corresponding muscular response, which was graded as severe, mild or absent. During halothane anaesthesia a PTC of 0 always indicated that no response to carinal stimulation could be elicited. On the appearance of the first response to posttetanic twitch stimulation (PTC = 1), 2% of the patients showed a mild response to carinal stimulation. At the first response to TOF stimulation, 48% of the patients reacted with a mild response. During thiopental, N2O, fentanyl anaesthesia one of 25 patients showed a mild response to carinal stimulation at a PTC of 0. When PTC was 1, 20% of the patients reacted mildly to the stimulation. At the first response to TOF stimulation, 92% showed a response to carinal stimulation; 24% of these responses were severe, necessitating intervention. It is concluded that the TOF response elicited peripherally is a late sign of neuromuscular recovery of the diaphragm, and that the method of counting posttetanic twitches is superior to the TOF response in evaluating early recovery of this muscle. Further, to ensure total diaphragmatic paralysis, the neuromuscular blockade of the peripheral muscles should be so intense that no response to posttetanic twitch stimulation (PTC = 0) can be elicited.

Adult cephalometric norms for Saudi Arabians with a comparison of values for Saudi and North American Caucasians.

Abstract: When considering orthognathic surgery for adult Saudi Arabians, there are as yet no cephalometric norms available for use during treatment planning. Lateral cephalometric radiographs were taken for...

Value of medium-thickness CT in the diagnosis of bronchiectasis

Abstract: The usefulness of CT with 4-mm-thickness cuts at 5-mm intervals in the diagnosis of bronchiectasis was studied by comparing the results of CT with those of bronchography in 323 segmental bronchi in 20 patients. No bronchiectasis was found on either study in 222 segmental bronchi. Of the 101 segmental bronchi showing bronchiectasis on bronchography, CT correctly identified bronchiectasis in 98 segments (97%). Bronchography showed cystic bronchiectasis in 35 and varicose bronchiectasis in 14 segmental bronchi, all of which were correctly identified on CT. Of the 52 segmental bronchi showing cylindrical bronchiectasis on bronchography, CT correctly identified these changes in 49 segments but failed to detect it in three. The presence of interstitial lung disease with emphysema and very localized mild bronchiectasis in one case each made the identification of cylindrical bronchiectasis difficult and caused the false-negative results. When bronchography is used as the criterion, CT with medium-thickness cuts a...

A genetic marker for rheumatic heart disease.

Abstract: The frequency of antigen types (A, B, C, and DR) in an unselected group of 25 patients with chronic rheumatic heart disease and an unselected group of 15 patients with acute rheumatic fever was compared with that in a group of 100 healthy volunteers. All patients and controls were Arabs of Saudi origin. Only the frequency of HLA-DR4 was significantly different in the controls and the patient groups--controls 12%, chronic rheumatic heart disease 72%, acute rheumatic fever 53%, both patient groups together 65% (relative risk 13.6 with 95% confidence interval 10.5-16.7). Eighty three per cent of 12 patients with mitral stenosis and 70% of seven with aortic incompetence had HLA-DR4 antigen. In 17 non-Saudi Arab patients who had acute rheumatic fever or chronic rheumatic heart disease, the frequency of HLA-DR4 was identical (65%) to that in Saudi patients. These findings may have implications for the pathogenesis of rheumatic fever and rheumatic heart disease.

Vomiting after ophthalmic surgery. Effects of intra-operative antiemetics and postoperative oral fluid restriction.

Abstract: The usefulness of intra-operative antiemetics and postoperative oral fluid restriction in the prevention of vomiting following anaesthesia for ophthalmic surgery, was studied in 200 patients. They were allocated into four groups of 50 and given either saline (as control), droperidol, metoclopramide or prochlorperazine. Oral intake was restricted postoperatively in half of the patients of each group. Anaesthesia comprised morphine and atropine premedication and a halothane, nitrous oxide and oxygen spontaneous breathing technique. No significant beneficial effects resulted from intra-operative antiemetics; vomiting incidences of 26% after saline and droperidol, 28% after metoclopramide and 14% after prochlorperazine were observed. Younger patients and females vomited most frequently. Restriction of oral fluids did not decrease the incidence of vomiting but demonstrated that approximately half of those patients who vomit do so with their first postoperative oral intake. Vomiting was observed more frequently after non intra-ocular surgery than after intra-ocular surgery (37% cf. 16%, p less than 0.01) and postoperative analgesics were required by more non intra-ocular patients than by intra-ocular patients (25% cf. 5%, p less than 0.001). Squint patients vomited most frequently (48%) and most frequently required postoperative analgesia (35%).

Medicinal plants in southwestern Saudi Arabia

Abstract: Folk medicine practiced in southwestern Saudi Arabia has helped people prevent and cure various diseases and sicknesses such as rheumatism, asthma, diabetes, stomach problems, constipation, eye and ear problems, colds, fever, measles, bladder and urinary diseases, toothache, epilepsy, and skin allergy. The most common medicinal plants found in the region belong to the Leguminosae, Labiatae, Compositae, and Euphorbiaceae.

Airborne Dust Size Analysis for Tropospheric Propagation of Millimetric Waves into Dust Storms

Abstract: This paper presents a study of five dust storms that occured in Riyadh together with their effect on millimeter-wave propagation. Meteorological parameters are given and airborne-dust's permittivity is estimated using relative humidity data. For large particles, the size distribution and its height dependence are investigated experimentally and the findings are presented as a functional relationship. Based on actual measurements and analysis, attenuation at 37 GHz is calculated using a newly derived expression in terms of optical visibility as a storm parameter. It is found that the fitted probability distributions are best described by normal or lognormal and vary with duststorm conditions. The average effective sizes and the 37-GHz attenuation decreases with the increase of antenna height following a power law.

Effectiveness and durability of repaired acrylic resin joints

Abstract: T he fracture of acrylic resin dentures is an unresolved problem in removable prosthodontics. Attempts to determine the causes of the most frequent types of denture fractures has received little attention in the literature. The midline fracture of the lower denture is the most common.’ The breakage is usually mechanical or accidental. The mechanical causes are related to faulty design and fabrication and the improper use of materials. Fracture by accident is usually the result of expelling the denture from the mouth while coughing, dropping the denture, or excessive biting force. Denture breakage is prevalent among neuropsychiatric patients, especially those who also have neuromuscular disorders such as hemiparalytic muscular dystrophy and Parkinson’s disease.’ Broken dentures are repaired with autocuring acrylic resin or heat-curing acrylic resin.3,4 There is little scientific evidence as to which method is best. The fragments of a broken denture show an increase in internal stress. This increase is due to the breaking of molecular bonds at the points of fracture. Alteration of molecular forces within each fragment results in distortion of the fractured sections, which often causes difficulty in reassembling the broken pieces.‘x4 Regardless of the reason for the breakage or the method of repair, satisfactory repairs must fulfill the following criteria: (1) the repaired structure must have adequate strength; (2) the repair must be completed as rapidly as possible for convenience of the patient; and (3) the repaired denture must retain its dimensional accuraCY. Preparation of the pieces to be joined plays a significant role in controlling the quality of the completed repair. Sharp edges of broken pieces should be rounded with a rag-wheel and pumice to help minimize the stress concentration at the joint. Ware and Docking5 found that the transverse strength of smooth rounded edged repaired joints is superior to that of joints repaired with sharp edges and corners remaining. On the other hand, Tylman and Peyton6 recommended roughening the surface of the fractured material at the joined edges. The diversity of opinion is probably related to the

Influence of Subinhibitory Concentrations of Antibiotics on Virulence of Staphylococci

Abstract: The understanding and control of infections caused by staphylococci are still far from complete, and staphylococcal infections continue to be a serious problem. The organisms possess numerous virulence factors that can act independently to induce various symptoms and lesions. Chemotherapy has changed the clinical spectrum of staphylococci but has not eradicated serious staphylococcal infections. An evaluation of the interaction of antibiotics, staphylococci, and host defense will help to identify those factors that determine the success or failure of therapy for staphylococcal infections. The activity of antibiotics is usually expressed in terms of concentrations that either inhibit or kill microorganisms in vitro or in experimental infections. Subinhibitory concentrations of antibiotics may induce changes in bacterial properties both in vitro and in vivo. An understanding of the mechanism of such changes would allow a more rational application of antibiotics that have both specific antistaphylococcal action and positive effects on host defense mechanisms.

Statistical variation of AC corona pulse amplitudes in point-to-plane air gaps

Abstract: Using a multichannel analyzer, statistical variations of corona pulse amplitudes are studied for AC corona in point-plane air gaps. It is shown that, for each half cycle, corona pulse amplitudes generally follow a Gaussian type of probability distribution when the applied voltage is near the corona inception level. However, as the applied voltage is increased, the distributions show deviations from this behavior. Typical pulse amplitude parameters such as the average value, the standard deviation, and the coefficient of variation are measured for different experimental conditions, and the results for corona under AC voltages are compared with previously obtained results for DC corona. >

Anisotropic time-dependent coupled oscillators.

Abstract: The problem of a two-dimensional anisotropic oscillator coupled through a complex parameter that oscillates at the frequency \ensuremath{\omega} is considered. The treatment has been applied to the case when \ensuremath{\omega} is not equal to the frequency difference of the oscillators. An exact solution for the Schr\"odinger wave function has been obtained. The Green's function as well as the expectation value of the energy are calculated.

Zaydi Shi ism and the asanid Sharifs of Mecca

Abstract: The sharifs of Hasanid descent, commonly referred to as the Banū Hasan, who ruled Mecca and its dependencies from the middle of the fourth century AH/tenth century AD until the early twentieth century, can be divided into three major dynastic branches, each of which bears the name of the first of its members to attain the office of emir of Mecca Thus, the first dynasty of the Hasanid sharifs of Mecca, known as the Jaʿfarids, was founded by Jaʿfar b Muhammad b al-Husayn al-Amīr, a descendant in the ninth generation of al-Hasan b ʿAlī b Abī Ṭālib, in about the year 357/968, shortly before the conquest of Egypt for the Fatimids of North Africa by their general, Jawhar, in 358/969 Control of Mecca remained in the hands of the Jaʿfarids until the last representative of the line, Shukr b Abī'l-Futūḥ, died without leaving a male heir in 453/ 1061

Intracranial tuberculomas: Diagnosis and management

Abstract: Experience with fifteen consecutive cases of intracranial tuberculomas, treated between 1981 and 1986, is summarized. Histological confirmation was obtained in twelve patients, and acid fast bacilli (AFB) were found in and cultured from the excised lesions and biopsy specimens in nine patients. Difficulties in diagnosis are discussed. A plan of management combining the operative treatment and medical therapy of the tuberculomas is outlined. The value of computerized tomography in the diagnosis and management of these patients is emphasized.

Haemoglobinopathies, thalassaemias and enzymopathies in Saudi Arabia: the present status.

Abstract: The presence of the sickle cell (Hb S) gene in Saudi Arabia was first reported by Lehmann et al. in 1963 [Nature 198, pp. 492–493]. Later, Hb S, α- and β-thalassaemia, glucose-6-phosphate dehydrogenase deficiency and other enzymopathies were shown to occur at a variable prevalence in different regions of the country. Recent studies using restriction endonucleases have revealed α-globin gene arrangement and β-globin gene polymorphism in the Saudi population. Interactions between abnormal genes are commonly encountered which often influence the clinical manifestations of sickle cell disease. In this paper, we present recent findings and discuss the status of haemoglobinopathies, thalassaemias and enzymopathies in Saudi Arabia