Search Results - (Author, Cooperation:M. Halim)

2012-05-05

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2018-11-10

Institute of Physics (IOP)

1757-8981

1757-899X

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

2018-11-23

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Geosciences

Computer Science

Medicine

Natural Sciences in General

Physics

Physics, Applied, Chemistry

1471-4159

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

We have recently shown that poly(2,5-pyridine diyl) (PPY) can be synthesized to yield a polymer with high photoluminescence quantum yield (PLQY) in the solid state, and that it is an excellent electron transport material. To explore the photophysical properties of PPY further, we have used a range of acidic "dopants" to protonate the nitrogen sites on each ring and made observations on how this affects the optical properties of the resultant protonated PPY films. In general, we find that sulphonic acids have the greatest effect, causing perturbations to both the ground-state and excited-state properties of the PPY. These changes occur with only moderate reduction of the PLQY, whereas nonsulphonic acids cause a larger reduction in PLQY without significantly affecting the ground- or excited-state energy levels. These aspects of the photophysics of PPY can be described using a simple ring torsion argument. This model can also account for the observed shifts between solution state and solid-state emission wavelengths. © 1998 American Institute of Physics.

Electronic Resource

1434-4475

3,5-Pyrazole derivatives ; Synthesis ; Aminolysis ; Pharmaceutical activity

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Zusammenfassung Die Aminolyse von 3-[2-(3,5-Dimethylpyrazolyl)]-succinanhydrid (1) führt zu5. Hydrazinhydrat reagiert mit1a zu 4-(3,5-Dimethylpyrazolyl)-1,2,4,5-tetrahydro-3,6-pyridazindion. Die Strukturen wurden mittels IR, MS,1H-NMR und13C-NMR überprüft.

Summary Aminolysis of 3-[2-(3,5-dimethylpyrazolyl)] succinic anhydride (1) leads to5. Hydrazine hydrate reacts with1a to give 4-(3,5-dimethylpyrazolyl)-1,2,4,5-tetrahydro-3,6-pyridazindione. The structures were confirmed by IR, MS,1H and13C NMR.

Electronic Resource

1434-4475

2-Methyl-3-acetylquinoxaline-1,4-dioxide ; Cinnamoylquinoxaline 1,4-dioxide ; Phenazine 5,10-dioxide

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Zusammenfassung Mehrere Phenazin-5,10-dioxide (7a–d) wurden durch Reaktion von 2-Methyl-3-acetylchinoxalin-1,4-dioxid (2) mit verschiedenen aromatischen Aldehyden oder durch direkte Cyclisierung der Chinoxalinderivate3 in basischem Milieuhergestellt. Zusätzlich wurden die Phenazinderivate8 und9–12 in einer Eintopfreaktion von substituierteno-Nitroanilinen mit verschiedenen Hydroxyverbindungen in Gegenwart von Natriumhypochloritlösung synthetisiert.

Summary Several phenazine 5,10-dioxides (7a–d) were prepared by the reaction of 2-methyl-3-acetylquinoxaline 1,4-dioxide (2) with different aromatic aldehydes or by direct cyclization of the quinoxaline cinnamoyl derivatives3 in basic medium. In addition, the phenazine derivatives8 and9–12 were synthesized by a one-pot reaction of substitutedo-nitroanilines with different hydroxy compounds in the presence of sodium hypochlorite solution.

Electronic Resource

1432-0614

Springer Online Journal Archives 1860-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Summary The morphology of two strains of Penicillium chrysogenum immobilized in calcium alginate and used in penicillin fermentation was examined. The degree and distribution of mycelial growth inside and on the surface of the beads depended on the strain, the cultivation media and the fermentation time. P. chrysogenum ATCC 12690 developed as a mycelial network inside the beads. The growth tendency of P. chrysogenum S1 in micropellets was directed to the outer surface of the beads. At the end of the production phase only a trace of mycelia and no micropellets in the center of alginate beads were observed, while the outer surface and the subsurface were completely covered with mycelia.

Electronic Resource

1420-9071

Springer Online Journal Archives 1860-2000

Biology

Medicine

Summary Compared with rats fed a normal diet, the activity of the protein inhibitor of acetyl CoA carboxylase in rat liver doubled after 48 h of fasting. Conversely, acetyl CoA carboxylase activity was diminished by nearly one half. In animals fasted and then subsequently refed a fat free diet, acetyl CoA carboxylase activity was elevated by nearly 9-fold, with a concomitant decrease in the activity of the protein inhibitor by about 9-fold as compared to fasted rats. Hence it appears that the regulatory protein inhibitor for acetyl CoA carboxylase is of physiological significance for fatty acid biosynthesis.

Electronic Resource

1573-7330

Springer Online Journal Archives 1860-2000

Medicine

Electronic Resource

1435-4373

Springer Online Journal Archives 1860-2000

Medicine

Abstract The efficacy and safety of oral fluconazole versus a polyene regimen in preventing mycoses in neutropenic patients was compared. Patients with haematological malignancy or bone marrow transplantation received as antifungal prophylaxis either fluconazole 200 mg daily or a regimen consisting of clotrimazole trouches 10 mg twice daily with mycostatin, 500,000 i.u. four times daily, benadryl and cepacol mouthwash. Ninety patients at risk for fungus infection were evaluable. Four of 42 patients (9.5 %; confidence interval 2 %–23 %) on fluconazole and 17 of 48 patients (35.4 %; confidence interval 22 %–52 %) (p〈0.01) on the clotrimazole regimen developed a clinically significant fungal infection, including 3 (7.1 %) and 11 (22.9 %) patients respectively who had severe fungal infection, mainly pulmonary aspergillosis. Death directly due to a fungal infection within 100 days of the start of prophylaxis occurred in 2 of 42 patients (4.8 %) and 9 of 48 patients (18.8 %) respectively (p〈0.06). Kaplan-Meier analysis showed that the chance of survival on fluconazole was statistically greater than for the clotrimazole regimen (p〈0.04). A decrease of candidal colonisation of the gastrointestinal and genitourinary tracts occurred only in patients receiving fluconazole. No significant toxicity occurred. A 200 mg daily dose of fluconazole given to these patients thus appears to be well tolerated and to provide a protective effect against the development of fungal infection and death from severe fungal disease.

Electronic Resource

1573-2878

Optimal control ; parameter optimization ; power systems ; load frequency control

Springer Online Journal Archives 1860-2000

Mathematics

Abstract A new approach for designing a linear regulator for the problem of load frequency control (LFC) of interconnected power systems is developed. The control is specified to be of proportional-plus-integral (P-I) form and is only a function of the measurable states. The LFC problem is formulated as a parameter optimization problem.

Electronic Resource

1573-2878

Optimal control ; parameter optimization ; power systems ; load frequency control

Springer Online Journal Archives 1860-2000

Mathematics

Abstract A new technique is described for designing an optimal controller for a system whose dynamical equations contain a backlash element. The approach is applied to the problem of load frequency control (LFC) of a single area steam power system.

Electronic Resource

1573-2878

Optimal control ; multireservoir hydroelectric power systems ; optimal release policies ; series reservoirs

Springer Online Journal Archives 1860-2000

Mathematics

Abstract The optimal monthly operating policy of a multireservoir hydroelectric power system is a stochastic nonlinear problem. This paper presents a new method for determining the optimal monthly operating policy of a power system ofn reservoirs in series on a river taking into account the stochasticity of the river flows. Functional optimization techniques and minimum-norm formulation have been used to find the optimal release policy of the system. Results for a numerical example composed of four reservoirs are presented.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

The cyclic, semicontinuous production of L-phenylacetyl carbinol (L-PAC) from a benzaldehyde substrate by Saccharomyces cerevisiae ATCC 834 immobilized in calcium alginate beads was substantially enhanced to about 4.5 g/L in a second cycle by reactivation in fresh medium for 24 h, following an earlier 24-h period of production from substrate. Intermittent feeding of benzaldehyde was employed (four doses in 3 h). In subsequent similar cycles, however, the production returned to that produced in the first cycle, viz. L-PAC concentration of 2-3 g/L in the medium. Production of L-PAC was also increased by adaptation of the cells over 200 h of exposure to the benzaldehyde substrate (compared to wild-type cells) and by continuous (as compared to intermittent) feeding of the substrate. A liter as great as 10 g/L was obtained with wild-type cells by continuous feeding of benzaldehyde over 6 h. Immobilization not only protected the cells from toxic effects of substrate but also permitted them to be used during 7 cycles of semicontinuous operation over more than 200 h.

10 Ill.

Electronic Resource

0006-3592

dextran ; dextransucrase ; Leuconostoc mesenteroides ; pore size ; Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Cells of Leuconostoc mesenteroides were immobilized within porus, stainless-steel (SS) supports and used for dextransucrase (DS) and dextran production. The pore size of the support significantly affected the dextran yields, which were greatest with average pore sizes of 2-5 μm. All immobilized-cell biocatalysts in porous stainless steel produced higher yields than free cells, with the exception of cells confined in submicrometer pores (0.5 μm). Coating supports of larger pore size (40 and 100 μm) with calcium alginate enhanced the cell-loading capacity of the supports and increased dextran and fructose yields in the cell-free broth. Controlled, fed-batch, DS production (activation), as a step preliminary to dextran production, significantly improved the subsequent dextran and fructose yields and shortened the time required to attain the maximum such yields. Scanning electron microscopy (SEM) of immobilized L. mesenteroides in stainless steel shows an irregular pattern of the microorganism inside the pores of the solid supports. Coating the porous solid supports with a cell-free calcium alginate layer led to an increase in the cell density inside the support. Cell growth inside the coated, porous stainless steel had no distinct growth form. © 1992 John Wiley & Sons, Inc.

6 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

Cells of Leuconostoc mesenteroides immobilized in calcium alginate beads were used to produce dextransucrase (DS) in three sequential cycles of semicontinuous fed-batch fermentations. Each cycle consisted of a fed-batch DS production period of 24 h followed by a batch dextran production period for another 24 h. Free, suspended cells were used in only one cycle of fed-batch DS production followed by a dextran production period. It was impractically tedious to separate and reuse free cells. Increasing sucrose feed rate from 5 to 10 g/L h led to increases of the total enzymatic activity by about 88% with immobilized cells and by about 100% with free cells. In DS fed-batch semicontinuous fermentation, total enzymatic activity produced by immobilized cells was 1.35 and 1.56 times greater than that produced by free cells with respective sucrose feeding rates of 10 and 5 g/L h. These increases in enzyme productivity with immobilized cells, however, required total overall operating times three times longer (three cycles) than with free cells (one cycle). Growing the microorganism at optimum conditions for DS production also increased the dextran yield and shortened the time of conversion of sucrose to dextran, regardless of whether the cells were free or immobilized. Moreover, during three cycles of semicontinuous operation (144 h) immobilized cells produced more than three times as much dextran as free cells during one cycle (24 h).

5 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

In fed-batch fermentation, cells of L. mesenteroides immobilized on three types of Celite were used to produce dextransucrase (DS) followed by production of dextran. A layer of calcium alginate on the porous Celite R630 particles improved their mechanical stability, increased the amount of soluble DS produced and decreased the cell leakage from the highly porous support. Enzyme production with the immobilized cell cultures was significantly affected by both pore and particle size. Immobilized cultures using Celite R648 (average particle radius of 200 μm and pore size of 0.14 μm) produced the highest total enzymatic activity, followed by Celite R633, alginate-coated Celite R630, Celite R630, and then calcium alginate beads. Culture of free cells produced about 18% more total enzymatic activity than immobilized cells in calcium alginate beads, but about 64% less than immobilized cells on Celite R630. It is expected that larger amounts of enzymatic activity than measured are immobilized inside the alginate-coated Celite R630 and calcium alginate beads due to the mass transfer limitation conferred by the dextran product formed therein. The dextran yield from conversion of sucrose to dextran and fructose with all such enzyme-enriched, immobilized-cell cultures was higher than that obtained from free-cell culture under similar conditions.

7 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

The rate and extent of microbial transformation of higher concentrations of benzaldehyde substrate to L-phenylacetyl carbinol (L-PAC) by immobilized cells of Saccharomyces cerevisiae ATCC 834 was markedly stimulated by addition of different concentrations of β-cyclodextrin (BCD) to the fermentation medium. With 0.5, 1.0, and 1.5% BCD in the fermentation medium and cumulative doses of benzaldehyde of 12 and 14 g/L, significantly higher yields of L-PAC were obtained, about one- to twofold that of the yields of the control experiments. The favorable effects of BCD were evident in spite of its presence in stoichiometric concentrations significantly lower than those of benzaldehyde. The presence of BCD also appeared to stimulate microbial growth slightly. Enhanced cellular activity was reflected by faster D-glucose consumption and faster benzaldehyde utilization in the presence of BCD.

6 Ill.

Electronic Resource

0006-3592

Chemistry ; Biochemistry and Biotechnology

Wiley InterScience Backfile Collection 1832-2000

Biology

Process Engineering, Biotechnology, Nutrition Technology

In batch fermentation Leuconostoc mesenteroides immobilized in calcium alginate beads produced a total dextransucrase activity equal to about 93% of that by free, suspended bacterial cells under comparable conditions in a bubble column reactor. Continuous sucrose feeding (5 g/L h) to the immobilized-cell culture in the airlift bioreactor increased production of enzymatic activity by about 107% compared with ordinary batch operation of this reactor. About 14% of the enzymatic activity produced by the immobilized cells appears as soluble activity in the cell-free broth compared with about 40% in case of free cells. In an airlift bioreactor, both the soluble and the intact (sorbed and entrapped) enzymatic activity produced by the immobilized bacterial cells was about 34% greater under automatic pH control, compared to that produced in a bubble column reactor with only manual pH control. During formation of dextran by intact enzyme within cells and beads, declines are observed in apparent enzymatic activity.

5 Ill.

Electronic Resource