Search

Multicrystalline silicon (mc-Si) wafers produced by directional solidification still dominate the world market, due to the factor quality/price. The performance of solar cell depends directly to the quality of wafer and impurities distribution in mc-Si ingot. In our study we investigate the distribution of the interstitial oxygen (Oi) and substitutional carbon (Cs), from the bottom to top of the silicon ingot. During the solidification process the solid-liquid interface moves upward with an average growth velocity of 1.2 cm/h, with a slightly convex form. The determination of (Oi) and (Cs) concentrations were performed thanks to the Fourier Transform Infrared Spectrometry (FTIR) technique. The results show that oxygen concentration increases near the crucible wall to the maximum value of 6.3 × 1017 atoms/cm3, and the carbon concentration decrease from maximum value of 9.59 × 1017 atoms/cm3 in the top to the minimal value of 7.84 × 1017 atoms/cm3 in the bottom of ingot. The concentration of global carbon and oxygen in the centre and corner bricks was investigated using the Secondary Ion Mass Spectroscopy (SIMS) technique. The concentration of oxygen and carbon in the center bricks were 1.8 1018 and 2 1018 atoms/cm3, and in the corner bricks 4.6 × 1019 and 9 × 1019 atoms/cm3, respectively. These results provide quantitative information on the concentration of the light impurities in the as-grown mc-Si and allow an overview of their spatial distribution within the final ingot.

In this study, graphene oxide (GO), polyethyleneimine (PEI) and potassium hydroxide (KOH) were used to synthesize reduced graphene oxide (rGO/PEI-KOH) nanocomposite. The presence and grafting of PEI molecules on the reduced GO surface were assessed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analyses. The rGO/PEI-KOH nanocomposite was successfully applied for hexavalent chromium, Cr(VI), wastewater elimination. The resulting rGO/PEI-KOH adsorbent was found to be highly effective for Cr(VI) removal at low pH values and achieved a maximum capacity of experimental adsorption of 398.9 mg/g, which is one of the highest sorption capacity of most GO- and PEI-based adsorbents reported in the literature up to date. Studying the adsorption mechanism, the sorption isotherm revealed that the modified-Langmuir model was the best fit and Cr(VI) removal follows a pseudo-second-order kinetics, with the predominance of intraparticle diffusion during the first step of adsorption. XPS analysis indicated the presence of appreciable amount of Cr(III) on the adsorbent surface, which suggests that the adsorbed Cr(VI) ions were effectively reduced to Cr(III) on the rGO/PEI-KOH adsorbent surface (∼70% of the total adsorbed Cr). Cr(VI) adsorption and subsequent reduction to Cr(III) both contributed to the Cr(VI) removal. The results of the present study highlight the benefits of rGO/PEI-KOH like low cost, environmentally friendly, large toxic Cr(VI) ions adsorption capacity and its effective reduction to less-toxic Cr(III).

Background: Mitral valve diseases are commonly associated with pulmonary hypertension. The aim of this study was to evaluate the effect of preoperative administration of sildenafil on the outcome after mitral valve replacement in patients with pulmonary hypertension. Methods: This prospective randomized study was carried out on 67 patients who had a mitral valve replacement and associated high systolic pulmonary artery pressure more than 50 mmHg. Patients were randomized into three groups: group A (n= 20) received preoperative sildenafil for one week, group B (n=22) received sildenafil for one month, and group C (n= 25) did not receive sildenafil. All patients had transthoracic echocardiography preoperatively, one week and one month postoperatively. Results: There was no difference in preoperative and operative variables among groups. Dobutamine support was required in 15 patients (60%) in group C vs. 6 patients (30%) in group A and 5 patients (22.5%) in group B (p= 0.012). Duration of mechanical ventilation was significantly longer in group C (389.2 ± 48.79 minutes) compared to group A and B (295.5 ± 17.01 and 281.4 ± 39.44 minutes, respectively, p

Electrophoretic deposition (EPD) of graphene-based nanomaterials has become an attractive strategy for the controlled deposition of thin films onto substrates for various applications. In this work, we demonstrate that application of an electrical potential to gold interfaces immersed in an aqueous suspension of graphene oxide (GO), loaded with nickel ions and insulin produces a continuous coating of an insulin impregnated reduced graphene oxide (rGO) matrix loaded with Ni(OH) 2 nanostructures (rGO/insulin/Ni(OH) 2 ). The rGO/insulin/Ni(OH) 2 coated Au electrodes exhibit excellent electrocatalytic behaviour towards glucose oxidation in alkaline medium at +0.6 V. The sensitivity towards glucose is 18.9 ± 1.5 mA mM −1 cm −2 with a detection limit of ≈5 μM. In addition, the amount of insulin integrated into the electrophoretically deposited coating is as high as 48 μg mL −1 , making the matrix of high interest for release studies. Electrochemical triggered release of the trapped insulin is achieved upon application of a negative potential to the interface. The possibility to form multifunctional coatings by EPD, incorporating catalytic nanostructures for diagnosis as well as drugs for therapy in one-step makes this approach a competitive alternative to other surface coating strategies.

Resume Le caractere toxique des organophosphores (OP) utilises comme pesticides est tres vite exploite dans le cadre de la preparation des agents neurotoxiques. L’un des secteurs fortement explore actuellement pour se rendre compte du risque de ces produits est le developpement de nouvelles techniques de detection. Les techniques d’inhibition enzymatique ont une large contribution dans ce domaine. Dans le cadre du present travail, des OP ont ete synthetises et testes sur une enzyme, la butyrylcholinesterase (EC) extraite du serum de cheval. L’activite enzymatique est determinee a partir de la densite optique de la solution. Le suivi cinetique est effectue par spectrophotometrie UV sur ces modeles OP pris individuellement ou en melange. L’optimisation du processus a ete etablie sur la base d’un modele mathematique utilisant le plan factoriel d’experiences. Les resultats obtenus nous ont permis d’etablir une relation entre la vitesse de reaction de desactivation de la butyrylcholinesterase et le pouvoir inhibiteur des OP experimentes.

Burning rates were measured for aluminized composite propellants with different aluminum (Al) sizes(monomodal distribution) and with bimodal Al distributions containing various amounts of ultrafine Al (UFAl). Enhanced rates were found for fine Al, with the enhancement increases for reduced Al size. The fine Al also burned in an intense region very close to the propellant surface, suggesting improved heat feedback in the form of radiation and conduction. Major modification of the burning rate could be achieved with moderate amounts of UFAl. Results obtained with various fine oxidizer particle sizes and mass fractions suggest that the degree of burning-rate modification depends on the ability to ignite the UFAl, for example, with leading-edge flames, as well as the availability of oxidizer near the Al-containing regions of the propellant.

A series of 1-(benzocycloalkyl)-4-(benzamidolkyl)piperazine derivatives was prepared in order to obtain compounds with a high affinity and selectivity for 5-HT1A receptors. The modifications of aromatic substituents, the length of the alkyl chain, and the size of the ring were explored. Most of N-(1,2,3,4-tetrahydronaphthyl)-N'-(benzamidoethyl)piperazines (32-37) were bound to 5-HT1A receptors in a nanomolar range and presented a high degree of selectivity. After resolution, levorotatory enantiomers showed affinity and selectivity higher than those of dextrorotory ones for 5-HT1A sites. The agonist type activity of selected derivatives was also confirmed in vitro on the inhibition of the activation of adenylate cyclase induced by forskolin and, in vivo, on the induction of the lower lip retraction in rats.

Summary Several benzhydryloxylalkylpiperidine derivatives were prepared with the aim of obtaining new antidepressant compounds. The influence of the length of the aliphatic chain and of aromatic and piperidine ring substitutions was studied. The pharmacological activity of compounds was investigated in vivo by means of a screening comprising four pharmacological tests: antagonism of reserpine and apomorphine hypothermia; increase of yohimbine induced mortality; and antagonism of immobility in tail suspension test. An in-depth pharmacological study was performed with the more active compounds and a binding study to serotonin (5-HT), norepinephrine (NE) and dopamine (DA) reuptake sites was performed for the preferred compounds. The most active compounds [+], [−]-cis-31, 32 and 46 exhibited an interesting psychopharmacological profile after intraperitoneal administration. This profile was confirmed by the oral route for 31 and 46. In vitro, these compounds showed a non-selective inhibition of DA, NE and 5-HT uptake.

Summary A series of 1,2-benzisoxazole-3-carboxamides derived from tertiary cycloalkylamines was synthesized and evaluated for affinity for serotonergic (5-HT 3 and 5-HT 4 ) and dopaminergic (D 2 ) receptors using radioligand binding assays. The majority of compounds displayed a very weak affinity for the studied neurotransmitter receptors. Only amides containing a conformationally rigid system retained a relative 5-HT 3 receptor affinity. The presence of a quinuclidine group affected receptor interaction more favorably than the tropane framework.

Summary Several benzhydryloxylalkylpiperidine derivatives were prepared with the aim of obtaining new antidepressant compounds. The influence of the length of the aliphatic chain and of aromatic and piperidine ring substitutions was studied. The pharmacological activity of compounds was investigated in vivo by means of a screening comprising four pharmacological tests: antagonism of reserpine and apomorphine hypothermia; increase of yohimbine induced mortality; and antagonism of immobility in tail suspension test. An in-depth pharmacological study was performed with the more active compounds and a binding study to serotonin (5-HT), norepinephrine (NE) and dopamine (DA) reuptake sites was performed for the preferred compounds. The most active compounds [+], [−]-cis-31, 32 and 46 exhibited an interesting psychopharmacological profile after intraperitoneal administration. This profile was confirmed by the oral route for 31 and 46. In vitro, these compounds showed a non-selective inhibition of DA, NE and 5-HT uptake.

To find evidence of diffuse fibrosis in dilated cardiomyopathy (DCM) patients by comparing measurements on clinical late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) studies between DCM and healthy subjects.LGE-CMR and the Look-Locker images from 20 DCM patients and 17 healthy controls were analyzed. Blood signal-to-noise ratio (SNR), myocardium SNR, and blood-to-myocardium contrast-to-noise ratio (CNR) were measured on the LGE-CMR images. The optimal inversion time (TI) to null blood and myocardium was determined on the Look-Locker images. The postcontrast T(1) was estimated using a phantom study that correlated optimal TI and heart rate to T(1).The blood SNR was lower, myocardium SNR was higher, and the blood-to-myocardium CNR was lower (6.6 +/- 0.7 vs. 10.3 +/- 0.9, P = 0.004) on DCM LGE-CMR images as compared to controls. The blood-myocardium optimal TI difference (DeltaTI) was lower (38 +/- 2 msec vs. 55 +/- 3 msec, P0.001) in DCM, and the estimated blood-myocardium T(1) difference (DeltaT(1)) (116 +/- 6 msec vs. 152 +/- 8 msec, P = 0.001) was also lower.DCM patients have reduced blood-myocardium DeltaTI and DeltaT(1), and lower CNR as compared to controls, suggesting the presence of diffuse fibrosis. This may impact the interpretation of LGE data.

A preliminary experimental investigation was carried out to investigate the ignition of ultrafine aluminum (UFAl) compared to conventional sized aluminum (CSAl) particles in ammonium perchlorate (AP)-polybutadiene acrylonitrile acrylic acid (PBAN) solid propellants. To evaluate the temperature criteria for igniting UFAl, matrix samples (binder, fine AP and Al only) were prepared with various loadings of 10μm fine AP (fAP) as a means of varying the AP-binder flame temperature, and with Al coarse-to-fine ratio of 0(30μm)/20(UFAl) and 80(30μm)/20(UFAl). Preliminary results showed that UFAl sized particles ignite at lower gasphase flame temperatures than CSAl particles and that the UFAl particles tend to affect the combustion processes close to the propellant surface depending upon the availability of oxidizer. * Senior Combustion/Propulsion Engineer. AIAA Member. E mail: allandokhan@hotmail.com † ‡ Regent Professor Emeritus. Fellow Member. Associate Professor. Senior Member. E mail: jerry.seitzman@ae.gatech.edu Senior Research Engineer. INTRODUCTION In recent studies of ultra-fine aluminum (UFAl~0.1μm) in ammonium perchlorate (AP) solid propellants with bimodal AP (10μm:400μm and 82.5μm:400μm) and bimodal aluminum (Al) distribution (30μm:UFAl), the burning of UFAl was found to create a very dense aluminum burning region (ABR) directly above and some distance beyond the propellant surface (~3000-4000μm) compared to the burning of conventional sized aluminum (CSAl~12-100μm). The density of the ABR was found to be the product of the number of burning Al particles/droplets/agglomerates leaving the propellant surface per unit area (one 30μm Al particle is the mass equivalent of 10 UFAl particles), which is very dependent upon the propellant microstructure (see later). The combustion of fine Al (~3μm) and UFAl particles occur much closer behind the AP-binder flame because of their near equilibrium state with the gas flow (temperature & velocity) compared to CSAl. As a result, they ignite quickly as they pass through the flame surface and burn close behind the convoluted flame canopy. This dense luminous bright ABR was found to be responsible for a significant amount of heat feedback to the propellant surface and to the AP-binder flame array in the form of either radiation and/or conduction, which resulted in high burning rate propellants. Copyright© 2003 A. Dokhan, E. W. Price, J. M. Seitzman and R. K. Sigman. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission 1

The effect was examined of aluminum particle size and of bimodal Al particle size on the burning rate of propellants and the particle size distribution of residual product Al2O3. It is shown that major modification of the burning rate and product size can be achieved by replacement of 20% of the conventional Al by 0.1µm Al. These effects result from the presence of an intense near surface Al flame when 0.1µm fine Al is present.

Thermodynamics of free and immobilized subtilopeptidase was studied over the temperature range from 30 degrees to 80 degrees C and from 30 degrees to 90 degrees C, respectively. The apparent optimum temperature of free enzyme was 50 degrees C and of the immobilized enzyme 60 degrees C. The heat of the reaction (delta E), accompanied by the process, was calculated from the slope of the Arrhenius equation to be 56 770 cal/mole for free enzyme and 36 640 cal/mole for immobilized enzyme. The standard free energy change (delta G) and the standard entropy change (delta S) were found to be + 241 cal/mole and + 186.6 cal/mole/degree at 30 degrees C for free enzyme and + 142 cal/mole and 120.5 cal/mole/degree at 30 degrees C for immobilized enzyme. The values of these thermodynamic quantities at other temperatures were also summarized. Studying the reaction order of heat inactivation showed that free and immobilized enzyme followed a first order reaction. The energy of inactivation was found to be 18 900 cal/mole and 24 400 cal/mole for free and immobilized enzyme, respectively.