Core and surface structure and magnetic properties of mechano-synthesized LaFeO3 nanoparticles and their Eu3+-doped and Eu3+/Cr3+-co-doped variants.

The core and surface structure, and magnetism of mechano-synthesized LaFeO3 nanoparticles (30-40 nm), Eu3+-doped (La0.70Eu0.30FeO3), and Eu3+/Cr3+ co-doped (La0.70Eu0.30Fe0.95Cr0.05O3) are reported. Doping results in a transition from the O'-type to the O-type distorted structure. Traces of reactants, intermediate phases, and a small amount of Eu2+ ions were detected on the surfaces of the nanoparticles. The nanoparticles consist of antiferromagnetic cores flanked by ferromagnetic shells. The Eu3+ dopant ions enhance the magnetization values relative to those of the pristine nanoparticles and result in magnetic susceptibilities compatible with the presence of Eu3+ van Vleck paramagnetism of spin-orbit coupling constant (λ = 363 cm-1) and a low temperature Curie-Weiss like behavior associated with the minority Eu2+ ions. Anomalous temperature-dependent magnetic hardening due to competing magnetic anisotropy and magnetoelectric coupling effects together with a temperature-dependent dopant-sensitive exchange bias, caused by thermally activated spin reversals at the core of the nanoparticles, were observed.

Prevalence of Cryptosporidium species isolated from diarrheic children in Makkah, Saudi Arabia.

Cryptosporidiosis has been identified as a significant underlying cause of morbidity and mortality worldwide. Studies in high and low income countries have recognized the importance of Cryptosporidium as a cause of diarrhea. The objectives of the current study were to determine the prevalence rate and genotypes of Cryptosporidiumin in diarrheic children in Makkah Region. A total of 1,380 fecal samples were collected from children aged up to 14 years attending 3 major hospitals of Makkah between March 2015 and March 2016. Stool collected were subjected to direct microscopic examination and crypto antigen detection using ImmunoCard STAT, Cryptosporidium/Giardia rapid test. Part of each positive stool sample was kept frozen at -20ºC for molecular characterization. Initial screening by immunochromatographic detection kit revealed 23 positive cases. PCR was performed for positive cases by amplification of a piece of the gene encoding the small (18S) subunit of rRNA producing a 435-438 bp product. Cryptosporidium genotyping was performed by RFLP analysis of PCR products. Genotyping revealed 18 cases C. hominis genotype, 4 cases C. parvaum genotype and one sample failed to be amplified. The data revealed a higher incidence of the common human species C. hominis (81.8%). The detection of both C. hominis and C. parvaum genotypes point to the possibility of both anthroponotic and zoonotic transmission routes occurring in Makkah region. Further studies are needed to verify the subgenotypes of Cryptosporidium to elucidate the real transmission modes and hence plan for effective control strategies.

Exchange bias effect in partially oxidized amorphous Fe-Ni-B based metallic glass nanostructures.

The magnetic properties of amorphous Fe-Ni-B based metallic glass nanostructures were investigated. The nanostructures underwent a spin-glass transition at temperatures below 100 K and revealed an irreversible temperature following the linear de Almeida-Thouless dependence. When the nanostructures were cooled below 25 K in a magnetic field, they exhibited an exchange bias effect with enhanced coercivity. The observed onset of exchange bias is associated with the coexistence of the spin-glass phase along with the appearance of another spin-glass phase formed by oxidation of the structurally disordered surface layer, displaying a distinct training effect and cooling field dependence. The latter showed a maximum in exchange bias field and coercivity, which is probably due to competing multiple equivalent spin configurations at the boundary between the two spin-glass phases.

Self-assembly of Silver Nanoparticles and Multiwall Carbon Nanotubes on Decomposed GaAs Surfaces.

Atomic Force Microscopy complemented by Photoluminescence and Reflection High Energy Electron Diffraction has been used to study self-assembly of silver nanoparticles and multiwall carbon nanotubes on thermally decomposed GaAs (100) surfaces. It has been shown that the decomposition leads to the formation of arsenic plate-like structures. Multiwall carbon nanotubes spin coated on the decomposed surfaces were mostly found to occupy the depressions between the plates and formed boundaries. While direct casting of silver nanoparticles is found to induce microdroplets. Annealing at 300°C was observed to contract the microdroplets into combined structures consisting of silver spots surrounded by silver rings. Moreover, casting of colloidal suspension consists of multiwall carbon nanotubes and silver nanoparticles is observed to cause the formation of 2D compact islands. Depending on the multiwall carbon nanotubes diameter, GaAs/multiwall carbon nanotubes/silver system exhibited photoluminescence with varying strength. Such assembly provides a possible bottom up facile way of roughness controlled fabrication of plasmonic systems on GaAs surfaces.

The formation of nanocrystalline SrFeO(3-delta) using mechano-synthesis and subsequent sintering: structural and Mössbauer studies.

The influence of mechanical milling and subsequent sintering of a 2:1 molar mixture of SrCO3 and alpha-Fe2O3 on the formation of SrFeO(3-delta) pervoskite-related nanocrystalline particles is investigated. The structural evolution during the formation process is systematically investigated using X-ray diffraction, thermal analysis, X-ray photoelectron spectroscopy and Mössbauer spectroscopy. Pre-milling the mixture in air for 120 h leads to the incorporation of Sr2+ in the alpha-Fe2O3 crystal structure thus facilitating the formation of a 2:1 nanocrystalline mixture of SrFeO3 and SrFeO2.875 by sintering the pre-milled mixture in air at 800 degrees C (12 h). This temperature is approximately 300 degrees C lower than those at which SrFeO(3-delta) phases are synthesized by the conventional ceramic techniques. Pre-milling the precursors was found to result in a smaller oxygen deficiency (delta) relative to conventional ceramic synthesis of SrFeO(3-delta). Rietveld refinement of the X-ray diffraction shows the interatomic distances in the resulting SrFeO2.875 nanocrystalline phase to be slightly different from those of the conventionally prepared bulk leading, in turn, to a crystal structure with tilted polyhedral cationic sites. This structural distortion is related to both small-size and surface effects in the nanoparticles that have no counterparts in the corresponding bulk material. The surface structure of the attained SrFeO(3-delta) nanocrystalline particles shows a significant partial reduction of Fe4+ to Fe3+ due to ambient conditions and the presence of an appreciable amount of SrCO3 as well.

Size-dependent surface plasmon resonance in silver silica nanocomposites.

Silver silica nanocomposites were obtained by the sol-gel technique using tetraethyl orthosilicate (TEOS) and silver nitrate (AgNO(3)) as precursors. The silver nitrate concentration was varied for obtaining composites with different nanoparticle sizes. The structural and microstructural properties were determined by x-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopic (XPS) studies were done for determining the chemical states of silver in the silica matrix. For the lowest AgNO(3) concentration, monodispersed and spherical Ag crystallites, with an average diameter of 5 nm, were obtained. Grain growth and an increase in size distribution was observed for higher concentrations. The occurrence of surface plasmon resonance (SPR) bands and their evolution in the size range 5-10 nm is studied. For decreasing nanoparticle size, a redshift and broadening of the plasmon-related absorption peak was observed. The observed redshift and broadening of the SPR band was explained using modified Mie scattering theory.

Absence of deafness-associated connexin-26 (GJB2) gene mutations in the Omani population.

We have investigated the prevalence of mutations in the connexin 26 (GJB2) gene in Omani population using both PCR-RFLP and direct DNA sequencing methods. Two common GJB2 gene mutations (35delG and 167delT) were screened in 280 healthy controls and 95 deaf patients using two different PCR-RFLP methods. To investigate other GJB2 mutations, we have amplified and sequenced DNA from 51 unrelated deaf patients and 17 control subjects. None of the samples studied, either by RFLP or sequencing, revealed any deafness-associated mutations in the coding region of the GJB2 gene. These findings disagree with many reports on the GJB2 gene, describing various mutations as the cause of congenital recessive deafness. Although, an amino acid substitution (S86T) was identified by sequencing, we conclude that this change could not be associated with deafness since it was present in all the control and patient samples sequenced.

The role of platelets in the coagulopathy of heatstroke- a study of platelet aggregation in heatstroke patients during the Makkah pilgrimage (Haj) to Makkah.

Platelet aggregation was undertaken in platelet rich plasma in 34 heat-stroke patients during the Muslim pilgrimage (Haj) to Makkah; 18 were males and 16 were females; their ages ranged from 36 to 80 years (mean SD = 58 10). Platelet aggregability, on arrival at the Heatstroke Centres, was markedly inhibited in response to adrenaline, collagen, arachidonic acid and ristocetin but not to ADP. Responses to decreasing ADP doses (20.0, 2.0, 1.0 and 0.5 micromol/l) showed hyperaggregability in 12 patients, inhibited responses in 16 and normal responses in 6 patients. Aggregation responses were not significantly different when comparing patients with bleeding manifestations ( n = 10), with those without bleeding ( n = 24). Haemostatic parameters including plasma fibrinogen, ATIII and platelet count, were markedly reduced in the two patient groups who showed hyperaggrebable and depressed aggregation responses, but not in those with normal responses. These results lead us to conclude that: (1) platelet activation is a frequent feature of heatstroke; (2) in heatstroke altered aggregation responses, whether hyperaggregable or depressed, occur simultaneously with a consumption coagulopathy.

The coagulopathy of heat stroke: alterations in coagulation and fibrinolysis in heat stroke patients during the pilgrimage (Haj) to Makkah.

Haemostatic measurements were undertaken in 132 patients diagnosed with heat stroke during the pilgrimage to Makkah, in two successive summers of 1989-90. The control group comprised 49 patients, all pilgrims, with a wide range of clinical conditions, but without hyperpyrexia or deranged haemostasis. Heat stroke patients showed (i) significant prolongation of the prothrombin (PT), activated partial thromboplastin (aPTT) and thrombin times (TT) but normal reptilase time (RT); (ii) significant reduction in plasma levels of antithrombin III (AT-III), factor V, proteins C and S, plasminogen activator inhibitor (PAI) and platelet count; (iii) increase in plasma factor VIII, tissue plasminogen activator (t-PA) and serum FDP; (iv) no significant changes in plasma fibrinogen, plasminogen, alpha 2-antiplasmin and factors VII and X. Heat stroke patients were then grouped into those with and those without bleeding symptoms. Bleeders showed greater prolongation of the PT, aPTT and TT and significant reductions in fibrinogen, AT-III, factors V, VIII and X, plasminogen, alpha 2-antiplasmin and platelet count. Logistic regression and discriminant analysis showed that AT-III was the parameter associated most with heat stroke and reliable enough to predict its occurrence, whether or not bleeding occurred. The results indicate that activation of the haemostatic mechanism, consumptive in nature, regularly accompanies heat stroke and highlights the physiological role of AT-III in checking this activation process.

Electrocardiographic abnormalities in patients with heat stroke.

Serial electrocardiograms were taken in 46 Hajj Pilgrims suffering from heat stroke immediately after cooling 12 and 24 h later. The collected data were analyzed and revealed that a statistically significant number of patients with heat stroke had sinus tachycardia (43 percent, p < 0.05), conduction defect (22 percent, p < 0.046), prolonged Q-T interval (61 percent, p < 0.007), diffuse nonspecific ST-T changes (26 percent, p < 0.036), and ST-T changes (localized to the ECG leads confirming to a territory of coronary artery) consistent with myocardial ischemia (21 percent, p < 0.02). Although adverse effects of heat stroke on the heart are multifactorial, the above data indicate that heat stroke predisposes to certain risk of myocardial ischemia and conduction disturbances. This may reflect the true cardiovascular status of these heat stroke victims.

Invasive evaluation of patients with heat stroke.

Right-heart catheterization was performed in ten patients who suffered heat stroke on their pilgrimage to Mecca, Saudi Arabia. The group included seven men and three women who had mean rectal temperatures of 42.4 degrees C. Other findings included the following: heart rate (mean, 120 beats/min); cardiac output (mean, 8.2 ml/min/m2); arterial pressure (mean, 65 mm Hg); cardiac indices (mean, 4.4 ml/min/m2); right atrial pressure (mean, 6 mm Hg); pulmonary capillary wedge pressure (mean, 10 mm Hg); systemic vascular resistance (mean, 684 dyne.s.cm-5); pulmonary vascular resistance (mean, 86 dyne.s.cm-5); oxygen delivery (mean 837 ml/min/m2); oxygen consumption (mean 160 ml/min/m2); mixed venous oxygen tension (mean, 56 mm Hg); and shunt fraction (mean, 20 percent). Nine patients survived. One, who had a cardiopulmonary arrest before any treatment could be administered, died.

Non-invasive evaluation of cardiac abnormalities in heat stroke pilgrims.

Serial electrocardiograms as well as echocardiographic studies of 51 pilgrims suffering from acute heat stroke (mean rectal temperature 41.6 degrees C) were performed. All patients were examined immediately after cooling and 24 h later whenever possible. Regional wall motion abnormalities were detected in 9 cases (17.6%) while pericardial effusion was observed in 13 cases (25%) and asymmetrical septal hypertrophy was detected in 8 cases (15.6%). Other cardiac abnormalities included right ventricular dilatation and increased in left ventricular internal dimensions in 4 cases (7.8%), respectively. Thirteen cases (25.5%) had normal echocardiographic findings. Forty (78%) patients had sinus tachycardia while 8 cases (15.7%) showed atrial fibrillation with uncontrolled ventricular rate, and 3 (5.8%) had sinus bradycardia. Heat stroke electrocardiograms showed tracings demonstrating ST segment depression, compatible with ischaemia in 9 cases, while in 6 cases there were nonspecific T wave changes, whereas in another 4 cases the tracings demonstrated different conduction abnormalities. The collected data were analysed and compared to those of 43 control patients. The adverse effects of heat stroke on the heart are multifactorial requiring the utmost attention and understanding, as they reflect the patient's cardiovascular status.

Aneurysmal dilatation of the coronary arteries: diagnostic patterns and clinical significance.

In order to define the clinical features, clinical patterns and significance of aneurysmal dilatation of the coronary arteries, five cases are presented which were diagnosed by coronary angiography. Three cases presented with left ventricular dysfunction secondary to coronary arterial occlusive disease and the fourth patient presented with thromboembolic cerebrovascular disease. The fifth case presented with manifestations of acute myocardial infarction.

Are heat stroke patients fluid depleted? Importance of monitoring central venous pressure as a simple guideline for fluid therapy.

During pilgrimage season (Hajj) in Saudi Arabia 34 patients with heat stroke (HS) were centrally cannulated to assess their state of hydration and fluid requirement during cooling period. Central venous pressure (C.V.P.) measurements indicated that most victims of heat stroke had normal C.V.P. on arrival at heat stroke centres and may not be fluid depleted. Twenty-two patients (64.7%) had normal or above normal C.V.P. Twelve patients (35.3%) had zero or below zero C.V.P. Six patients (17.6%) had above 10 cmH2O (range 10-26 cmH2O) and could have developed acute congestive heat failure and pulmonary edema if they had been transfused at the standard recommended rate of 3-4 litres of fluid during an average cooling time of 1 h as has been practiced in the heat stroke centres to date. This study also showed that heat stroke patients should not be briskly transfused because the heart may be affected by heat stroke per se and an unmonitored challenge by brisk i.v. therapy during cooling (which on its own increases preload on the heart due to peripheral vasoconstriction) can lead to acute overload problems. An average of 1 litre of normal saline or Ringer's lactate (crystalloids) was sufficient to normalize C.V.P. during the cooling period and to restore an optimal state of hydration without predisposing to congestive cardiac failure and pulmonary edema--the potential to develop disastrous adult respiratory distress syndrome and disseminated intravascular coagulopathy.

Metabolite and hormonal profiles in heat stroke patients at Mecca pilgrimage.

Sera obtained during the Hajj seasons of 1985, 1986, 1987 and 1988 from 125 heat stroke patients were collected and subjected to chemical analysis which included determination of glucose, lactate, cholesterol, and triglycerides, as well as assay of T3, T4, TSH and cortisol. Hyperglycaemia and lactic acidaemia were found to be the most frequent metabolic abnormalities. The changes in cholesterol did not exhibit a specific pattern. Triglycerides were significantly elevated in only 6% of patients. Cortisol levels were very significantly elevated in precooled patients. Although the mean T3 levels remained within the normal range, the mean concentration on admission was significantly higher than the post-cooling mean. TSH and T4 levels did not show significant changes.

The morbidity and mortality pattern of Brucella endocarditis.

Six cases of well-documented Brucella endocarditis are reported. All the patients gave a history of ingestion of raw milk and/or being in contact with sheep and/or camels during herding. The diagnosis was based in each case on a history of ingestion of raw milk, high titres of Brucella antibodies, a positive blood culture and echocardiography. A combination of tetracycline, rifampicin and streptomycin was found to be effective in eradicating the Brucella organism. Two cases required aortic valve replacement, and another two required replacement of both aortic and mitral valves. One case died before any surgical intervention could be performed and one patient did not require surgery. Although it was noted that the Brucella organism attacks mainly valves which are already damaged, it may also attack and infect normal valves.

Joint mobility and mitral valve prolapse in an Arab population.

The association of joint laxity and mitral valve prolapse (MVP) has been disputed. In this study of an Arab population, the joint mobility scores of 29 subjects with MVP, 10 of whom were asymptomatic, were compared to 60 normal controls. It was found that the joint mobility score was significantly higher in both the asymptomatic and the symptomatic subjects with MVP when compared to the controls. This suggests that both mitral valve prolapse and joint laxity may be due to the same abnormality of connective tissue structure.

Association of brucella endocarditis with intracerebral haemorrhage.

We describe a case of brucella endocarditis which was strongly suspected on clinical grounds and subsequently confirmed by bacteriological, serological and echocardiographic investigations. The endocarditis, in a 42-year-old Saudi male, was complicated by intracerebral haemorrhage, presumably from a ruptured mycotic aneurysm. Although such a complication is well documented in other forms of infective endocarditis, it has not been reported in brucellosis.

Heat stroke at the Mekkah pilgrimage: clinical characteristics and course of 30 patients.

The clinical picture and the final outcome of 30 patients with heat stroke during the Mekkah pilgrimage 1404 (September 1984) were analysed. Rapid cooling by the 'evaporative method' was achieved in a mean time of 59 min (range 15-135). An initial temperature above 42 degrees C and a cooling time of more than 1 h indicated a poor prognosis. Acute hepatic failure, 'adult respiratory distress syndrome' and decerebrate convulsions were among the fatal complications occurring in three patients. In the final outcome three patients (10 per cent) died, two patients (7 per cent) recovered but developed myocardial infarction and cerebellar ataxia respectively. Twenty-five patients (83 per cent) made an uncomplicated recovery.