A NEW APPROACH FOR FINDING AN INITIAL SOLUTION NEAR TO OPTIMUM FOR THE SOLID TRANSPORTATION PROBLEMS

The solid transportation problem (STP) is a particular type of linear programming problem. This paper presented an approach for solving STP in a highly efficient and a few iterations until finding an optimal solution. The proposed method provides an initial solution near to optimum solution to the solid transportation problem close to the optimal solution. Using Lingo software, a numerical example was used to compare the solution from the proposed method to the optimal solution.      &nbsp

Nonthermal Laser-Induced Formation of Crystalline Ge Quantum Dots on Si(100)

The effects of laser-induced electronic excitations on the self-assembly of Ge quantum dots on Si (100) - (2×1) grown by pulsed laser deposition are studied. Electronic excitations due to laser irradiation of the Si substrate and the Ge film during growth are shown to decrease the roughness of films grown at a substrate temperature of ∼120 °C. At this temperature, the grown films are nonepitaxial. Electronic excitation results in the formation of an epitaxial wetting layer and crystalline Ge quantum dots at ∼260 °C, a temperature at which no crystalline quantum dots form without excitation under the same deposition conditions.© 2008 American Institute of Physics. [DOI: 10.1063/1.3041493

Melting and Solidification Study of As-Deposited and Recrystallized Bi Thin Films

Melting and solidification of as-deposited and recrystallized Bi crystallites, deposited on highly oriented 002-graphite at 423 K, were studied using reflection high-energy electron diffraction (RHEED). Films with mean thickness between 1.5 and 33 ML (monolayers) were studied. Ex situ atomic force microscopy was used to study the morphology and the size distribution of the formed nanocrystals. The as-deposited films grew in the form of three-dimensional crystallites with different shapes and sizes, while those recrystallized from the melt were formed in nearly similar shapes but different sizes. The change in the RHEED pattern with temperature was used to probe the melting and solidification of the crystallites. Melting started at temperatures below the bulk melting point of Bi, T0=544.5 K, and extended over a temperature range that depended on the size distribution of the crystallites. The as-deposited 1.5 ML film started to melt at T0-50 K and melted completely at T0-20 K. For films with higher coverage, the size distribution was observed to spread over a wider range with a larger mean value, resulting in a shift in the melting temperature range towards higher temperatures. Due to the shift in size distribution to higher values upon recrystallization, the recrystallized Bi crystallites showed a melting temperature range higher than that of the as-deposited crystallites. For the investigated conditions, all films were completely melted below or at T 0 of Bi. The characteristic film melting point, defined as the temperature at which the film melting rate with temperature is the fastest, showed a linear dependence on the reciprocal of the average crystallite radius, consistent with theoretical models. Of these models, the surface-phonon instability model best fits the obtained results. During solidification, the Bi films showed high amount of supercooling relative to T0 of Bi. The amount of liquid supercooling was found to decrease linearly with the reciprocal of the average crystallite size. © 2006 American Institute of Physics. [DOI: 10.1063/1.2208551

Activation Energy of Surface Diffusion and Terrace Width Dynamics During the Growth of in (4×3) on Si (100) - (2×1) by Femtosecond Pulsed Laser Deposition

The nucleation and growth of indium on a vicinal Si (100) - (2×1) surface at high temperature by femtosecond pulsed laser deposition was investigated by in situ reflection high energy electron diffraction (RHEED). RHEED intensity relaxation was observed for the first ∼2 ML during the growth of In (4×3) by step flow. From the temperature dependence of the rate of relaxation, an activation energy of 1.4±0.2 eV of surface diffusion was determined. The results indicate that indium small clusters diffused to terrace step edges with a diffusion frequency constant of (1.0±0.1) × 1011 s-1. The RHEED specular beam split peak spacing, which is characteristic of a vicinal surface, was analyzed with the growth temperature to obtain the average terrace width. Gradual reduction in the terrace width during growth of In (4×3) was observed with In coverage and is attributed to the detachment of In atoms from terrace edges. At a substrate temperature of 405 °C, the average terrace width decreased from 61±10 Å, which corresponds to the vicinal Si(100) surface, to an equilibrium value of 45±7 Å after deposition of ∼23 ML. Further In coverage showed a transition of the RHEED pattern from (4×3) to (1×1) and the growth of rounded In islands (average height of ∼1 nm and width of ∼25 nm), as examined by ex situ atomic force microscopy. © 2008 American Institute of Physics. [DOI: 10.1063/1.2909923

Role of spontaneous breathing trial as predictors in extubation failure in preterm infants

Background: Invasive respiratory support is associated with risk and complications including mortality and neurological impairments. Consequently, extubation of a ventilated infant should be as early as possible.Objective: This study aimed to assess the efficacy of spontaneous breathing trial as indicator for the success of extubation in mechanically ventilated preterm infants.Patients and methods: A prospective cohort study included 62 preterm born infants who were maintained on mechanical ventilation. They were divided into: (32 infants) group for whom a spontaneous breathing trial was carried out for 5 minutes. Second (30 infants) group for whom a spontaneous breathing test was carried out for 3 minutes. Then, rapid Shallow Breathing Index (RSBI) was calculated for each patient. At the end of the test, the newborns were extubated and placed on continued positive airway pressure (CPAP) or just oxygen, as needed, according to the unit’s routine protocol.Results: On multivariate logistic regression of factors associated with failure of weaning, APGAR at 5 minutes was > 6, absence of maternal PIH, birth weight > 400 gm. Pre-extubation MAP < 5.5 and preextubation PO2 > 28 were protective against failure of weaning. On the other hand, lower preextubation PCO2 was a predictor of weaning failure (increase risk of failure by about 63 times). Failure of weaning forecated in RSBI trial can predict actual failure of weaning with sensitivity of 97.9%, specificity of 73.3%, positive predictive value of 92%, negative predictive value of 91.7% and accuracy of 91.9%.Conclusion: Failure of weaning associated with lower birth weight, PO2, PCO2 and higher pre-extubation MAP. 3 minutes and 5 minutes spontaneous breathing trial (SBT) can predict actual failure of weaning with sensitivity 97.9%, specificity 73.3%

Condensation on (002) Graphite of Liquid Bismuth Far Below Its Bulk Melting Point

Condensation of thermally evaporated Bi on (002) graphite, at temperatures of 300-523K, was studied using in situ reflection high-energy electron diffraction (RHEED) and room temperature ex situ atomic force microscopy (AFM). For deposition at temperatures below 415±5K, transmission RHEED patterns of Bi appeared at an average thickness of ∼0.5 monolayer (ML). AFM images showed that the film consisted of crystallites in the shape of triangular step pyramids with step heights corresponding to single and double Bi layers in the [111] direction. This morphology indicates crystallization from the vapor. For deposition at higher temperatures, diffuse RHEED patterns appeared independent of the deposited thickness. When these films were cooled, clear transmission patterns of crystalline Bi appeared. After cooling to near room temperature, the melting and solidification behaviors of these films were investigated with RHEED. Upon subsequent heating, the topmost layers of the probed Bi crystallites started to lose long-range order at ∼10-15K below the Bi bulk melting point, T0=544.52K. When crystallized from the melt, supercooling by ∼125K below T0 was observed. These results indicate that Bi condensed on graphite in the form of supercooled liquid droplets when the graphite temperature was above 419K (T0-125). Below that temperature, Bi condensed in the solid phase. Bi films crystallized by cooling the liquid had crystal morphologies that depended on the degree of liquid supercooling. © 2005 The American Physical Society

A rare neurocutaneous syndrome and a rare association

Among the many causes of ataxia, Ataxia -telangictasia is an autosomal recessive1, multi system disease affecting the skin, nervous system & immune system. It's prevalence has been estimated at 1 to 2 per 100,000 It is a neurodegenerative disorder2 in which there is progressive cerebellar ataxia, occulocutaneous telangictasias, chronic sinopulmonary disease & high incidence of malignancy associated with variable humoral & cellular immuno deficiency. The abnormal gene has been mapped to the long arm of chromosome 11 (ATM gene)3 . Carriers has increased sensitivity to ionizing radiation4. Telangicatsias tends to develop between the ages of 3-6 years. It also affects the ears, eye lids immunologic abnormality is selective absence of IgA found in 50-80 % ,IgG may also be affected. The T cells percentage is reduced in total & T Helper (CD4) phenotype, with normal or increased percentages of the Suppressor ( CD8). Hodgkin's, non Hodgkin's lymphoma5 & leukemia6  develops in 10 % of cases6 . Other variable body tumors may occur. These patients may become critically ill and need intense care to prevent serious complications or death7. The syndrome is associated with abnormal IgA levels with a higher risk of blood malignancies like lymphoma or leukaemia, patients may have telangiectasia else were in the body specially the upper respiratory tract. The is a case report about one of this rare neuro- cutaneous syndromes which was reported in Khartoum Sudan. Consent from the parents was taken for the purpose of publication and teaching.Keywords: Ataxia telangiectasia, Sudan, Rare associatio

Atomic Hydrogen Cleaning of InP(100): Electron Yield and Surface Morphology of Negative Electron Affinity Activated Surfaces

Atomic hydrogen cleaning of the InP(100) surface has been investigated using quantitative reflection high-energy electron diffraction. The quantum efficiency of the surface when activated to negative electron affinity was correlated with surface morphology. The electron diffraction patterns showed that hydrogen cleaning is effective in removing surface contaminants, leaving a clean, ordered, and (2×4)-reconstructed surface. After activation to negative electron affinity, a quantum efficiency of ∼6% was produced in response to photoactivation at 632 nm. Secondary electron emission from the hydrogen-cleaned InP(100)-(2×4) surface was measured and correlated to the quantum efficiency. The morphology of the vicinal InP(100) surface was investigated using electron diffraction. The average terrace width and adatom-vacancy density were measured from the (00) specular beam at the out-of-phase condition. With hydrogen cleaning time, there was some reduction in the average terrace width. The surface quality was improved with hydrogen cleaning, as indicated by the increased (00) spot intensity-to-background ratio at the out-of-phase condition, and improved quantum efficiency after activation to negative electron affinity. © 2002 American Institute of Physics. [DOI: 10.1063/1.1429796

Nonuniformity in Lattice Contraction of Bismuth Nanoclusters Heated Near Its Melting Point

The structural properties of bismuth nanoclusters were investigated with transmission high-energy electron diffraction from room temperature up to 525 ± 6 K. The Bi nanoclusters were fabricated by thermal evaporation at room temperature on transmission electron microscope grids coated with an ultrathin carbon film, followed by thermal and femtosecond laser annealing. The annealed sample had an average cluster size of ∼14 nm along the minor axis and ∼16 nm along the major axis. The Debye temperature of the annealed nanoclusters was found to be 53 ± 6 K along the [012] direction and 86 ± 9 K along the [110] direction. At T = 464 ± 6 K, the diffraction intensity started to deviate from Debye-Waller behavior due to increased lattice anharmonicity. The onset of the melting of the Bi nanoclusters was T ∼ 500 ± 6 K, as measured by the reduction of the nanocluster size through the formation of a liquid shell detected by the width of the diffraction rings. The thermal expansion coefficient of the Bi (012) and (110) planes is positive up to ∼ 499 11 K. However, the expansion coefficient of the Bi (012) planes showed a transition from a positive to a negative value that occurs over the temperature range Tc ∼ 499 ± 11 K to 511 ± 8 K. For the Bi (110) planes, the thermal expansion coefficient is positive up to their melting point, which is 525 ± 6 K. © 2011 American Institute of Physics. [doi:10.1063/1.3565028

EFFECT OF ADDITIVES ON IN-VITRO RELEASE OF ORODISPERSIBLE DOSAGE FORM

Objective: The aim of this investigation was to prepare orodispersible tablets of meloxicam using various concentrations of superdisintegrants like Ac-DI-Sol, crospovidone, sodium starch glycolate by the direct compression method. Methods: Nine formulae of Meloxicam orodispersible tablets were prepared. These tablets were evaluated for their drug content, weight variation, friability, hardness, wetting time, In-vitro disintegration time and drug release.Results: All the formulation exhibited hardness between 4.21–4.55 kg/cm2. The tablets were disintegrating within 8.3 to 21.9 sec. Dissolution studies revealed that formula containing 7.5 % sodium starch glycolate showed 100% of drug release, at the end of six minutes. Among the formulated tablets, formula F9 containing 7.5 % sodium starch glycolate showed superior organoleptic properties along with excellent In-vitro disintegration time and drug release as compared to other formulae. The concentration of superdisintegrants had an effect on disintegration time and In-vitro drug dissolution whereas hardness and friability of resulting tablets were found to be independent of disintegrant concentration. It was concluded that the superdisintegrants addition technique is a useful method for preparing orodispersible tablets by the direct compression method.Â