Experiences with functional magnetic resonance imaging at 1 tesla

Functional magnetic resonance imaging (fMRI) has been performed on a standard 1 T system using a pulse sequence developed to utilize blood oxygen level dependent (BOLD) contrast and an off-line analysis routine using correlation techniques. The sequence and the data analysis routine have been validated by reproducing the conventional hand movement paradigm studies reported by numerous other workers. Our work has then been extended to investigate cerebral foci for a tonic pain stimulus and the cortical representation of oesophageal stimulation. Both these studies relate to paradigms where the expected BOLD signal is significantly less than that encountered for motor or visual cortex paradigms. The results show good agreement with other modalities (positron emission tomography, magnetoencephalography and cortical evoked potentials). Performing fMRI at 1 T is slightly controversial. However, our successful study of demanding paradigms, using a standard clinical 1 T imaging system, has important implications for many other users operating at this field strength.     

Gut feelings about recovery after stroke: the organization and reorganization of human swallowing motor cortex

Swallowing problems can affect as many as one in three patients in the period immediately after a stroke. In some cases this can lead to serious morbidity, in particular malnutrition and pulmonary aspiration. Despite this, swallowing usually recovers completely in the vast majority of patients within weeks. This impressive propensity for recovery is likely to relate to how the area of the motor cortex concerned with swallowing is organized and then reorganized after cerebral injury. Recent studies have indicated that swallowing has a bilateral but asymmetric inter-hemisphere representation within motor and premotor cortex. Damage to the hemisphere that has the greater swallowing output appears to predispose that individual to swallowing problems. However, because there is additional substrate for swallowing in the undamaged hemisphere, the capacity for compensatory reorganization in the contralateral motor cortex might be increased, leading to a greater likelihood of recovery. Swallowing might be an excellent system for studying cortical plasticity, and might prove useful in the development of new therapies aimed at accelerating reorganization in the undamaged hemisphere after unilateral cerebral injury.     

Thermal fatigue analysis of small-satellite structure

The small-satellite thermal subsystem main function is to control temperature ranges on equipments, and payload for the orbit specified. Structure subsystem has to ensure the satellite structure integrity. Structure integrity should meet two constraints; first constraint is accepted fatigue damage due to cyclic temperature, and second one is tolerable mounting accuracy at payload and Attitude Determination and Control Subsystem (ADCS) equipments’ seats. First, thermal analysis is executed by applying finite-difference method (IDEAS) and temperature profile for satellite components case is evaluated. Then, thermal fatigue analysis is performed applying finite-element analysis (ANSYS) to calculate the resultant damage due to on-orbit cyclic stresses, and structure deformations at the payload and ADCS equipments seats.     

Preparation and characterization of some multicomponent silicate glasses and their glass–ceramics derivatives for dental applications

The chemical corrosion and UV–vis absorption and infrared absorption spectra of binary and multicomponent lithium silicate glasses and corresponding glass–ceramics were investigated. The chemical durability of the glasses and derived glass–ceramics was found to be excellent to all leaching media. The IR absorption spectra of the glass and glass–ceramic samples reveal absorption bands of characteristic groups mainly due to major silicate network besides the possible sharing of network units due to some involving oxide constituents. X-ray analysis of glass–ceramics indicates the separation of lithium disilicate phase as the main constituent beside other phases according to the specimen chemical constituents. The obvious promising investigated chemical and physical properties are correlated with the presence of multioxides such as Al₂O₃, TiO₂, MgO and ZrO₂. Transmission and reflectivity properties reveal acceptable data. The prepared glass–ceramics are recommended for dental applications.     

Long-term effects of bisphosphonates on the growing skeleton. Studies of young patients with severe osteoporosis

Osteoporosis in children and adolescents is relatively uncommon and usually secondary to identifiable causal factors. There are no generally accepted therapies for patients with no treatable underlying cause of disease. Any treatment of young patients with bone-acting compounds should be not only effective but also devoid of adverse effects on bone growth and remodeling. For many years we have been studying the effects of bisphosphonates-an effective treatment of postmenopausal osteoporosis-on the growing skeleton. We review here our experience in the treatment of young patients with osteoporosis with special emphasis on issues of skeletal safety and effectiveness, and we discuss the available literature data. We studied 12 patients aged between 10.7 and 17.2 years with symptomatic osteoporosis and multiple fractures treated with the bisphosphonates pamidronate or olpadronate for periods between 2 and 8 years continuously. Linear growth continued normally on treatment; there was even a catch-up growth in prepubertal patients, and there was no excessive suppression of bone remodeling, assessed biochemically. Bone biopsies obtained at various stages during treatment showed bone of normal lamellar structure without mineralization defects. There was an increase in calcium balance, already evident within 10 days, the level of which was maintained for at least 3 years of treatment. This was associated with progressive increases in bone mineral density along a different slope from that of healthy peers as well as correction of vertebral deformities on X-rays in patients given bisphosphonates before puberty. Treatment was well tolerated and clinical improvement was remarkable. Our studies, supported by literature data, strongly suggest that bisphosphonate therapy can be beneficial to young patients with osteoporosis for whom no other options are currently available, and justify planning controlled studies in more common conditions for which no treatment is currently available, such as osteogenesis imperfecta.     

Corrosion behavior of electroless Ni-P alloy coatings containing tungsten or nano-scattered alumina composite in 3.5% NaCl solution

The corrosion protection performance of electroless deposited nickel-phosphorus (Ni-P) alloy coatings containing tungsten (Ni-P-W) or nano-scattered alumina (Ni-P-Al₂O₃) composite coatings on low carbon steel was studied. The effect of heat treatment on the coating performance was also studied. The optimum conditions under which such coatings can provide good corrosion protection to the substrate were determined after two weeks of immersion in 3.5% NaCl solution. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance before and after heat treatment. The Ni-P-W coatings showed the highest surface resistance compared with Ni-P-Al₂O₃ and Ni-P. The surface resistance of Ni-P-W coatings was 12.0 × 10⁴ Ω cm² which is about the double of the resistance showed by Ni-P-Al₂O₃ (7.00 × 10⁴ Ω cm²) and twenty times greater than the surface resistance of Ni-P (0.78 × 10⁴ Ω cm²). XRD analysis of non-heat-treated samples revealed formation of a protective tungsten phosphide phase. Heat treatment has an adverse effect on the corrosion protection performance of tungsten and alumina composite coatings. The surface resistance decreased sharply after heat treatment.     

Overexpression of MnSOD protects against myocardial ischemia/reperfusion injury in transgenic mice

Generation of free radicals upon reperfusion has been cited as one of the major causes of ischaemia/reperfusion injury. The following series of experiments was designed to study the effect of manganese superoxide dismutase (MnSOD) overexpression in transgenic mice on ischemia/reperfusion injury. A species of 1.4 kb human MnSOD mRNA was expressed, and a 325% increase in MnSOD activity was detected in the hearts of transgenic mice with no changes in the other antioxidant enzymes or heat shock proteins. Immunocytochemical study indicated an increased labeling of MnSOD mainly in the heart mitochondria of the transgenic mice. When these hearts were perfused as Langendorff preparations for 45 min after 35 min of global ischemia, the functional recovery of the hearts, expressed as heart rate x left ventricular developed pressure, was 52 +/- 4% in the transgenic hearts as compared to 31 +/- 4% in the non-transgenic hearts. This protection was accompanied by a significant decrease in lactate dehydrogenase release from the transgenic hearts. Overexpression of MnSOD limited the infarct size in vivo in a left coronary artery ligation model. Our results demonstrate that overexpression of MnSOD renders the heart more resistant to ischemia/reperfusion injury.     

Biomechanical and physical properties of lengthened bone in a canine model

Reports on the mechanical and physical properties of lengthened bone after completion of the lengthening process remain scarce. Varied results of torsional testing of lengthened bone have been reported. Furthermore, torsional testing provides information on the shear properties of the tissue but does not reflect the elastic properties obtained from tensile, compressive, or bending tests. The present study evaluated the mechanical properties of lengthened bone at various time points, using a uniaxial tension test. Physical properties (density and ash weight) were determined as well. Results indicate that the tensile properties of the lengthened bone increase with time after the completion of lengthening, but they remain significantly weaker than controls (50%) even after 12 weeks. Density and ash weight measurements also increased with time, correlating with the increase in the tensile mechanical properties.     

Economics of off-shore/on-shore wind energy systems in Qatar

This work presents an assessment of the potential and economical feasibility of adopting off-shore/on-shore wind energy as a renewable source of energy in Qatar. An analysis is presented for the long term measured on-shore wind speed (1976–2000) at Doha International Airport. A similar analysis is presented for the measured off-shore wind speed at the Qatari Haloul Island. For the on-shore measurements, the average annual wind speed (at 20 m height) was found to be about 5.1 m/s. On the other hand, for the off-shore measurements at Haloul, the average annual wind speed was found to be about 6.0 m/s. This result indicates the suitability of utilizing small to medium-size wind turbine generators, efficiently. Such generators can be implemented for water pumping and to produce sufficient electricity to meet vital, limited needs of remote locations, such as isolated farms, which do not have access to the national electricity grid. An economical assessment is presented which takes into consideration the interest recovery factor, the lifetime of the wind energy conversion system (WECS), the investment rate and operation and maintenance costs. The results indicate that the cost of electricity generation from the wind in Qatar compares favorably to that from fossil fuel resources. The feasibility of utilizing off-shore wind turbine systems to meet the power requirements of the island of Haloul and possibly provide additional power for nearby on-shore areas is discussed.