ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

A 16 cm broad-beam ion source for ion-beam etching of quartz wafers : Proceedings of the 6th international conference on ion sources (1996)

Rao, Yusheng ; Li, Ming ; Qi, Bo ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Review of Scientific Instruments 67 (1996), S. 1009-1011

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ISSN: 1089-7623

Source: AIP Digital Archive

Topics: Physics , Electrical Engineering, Measurement and Control Technology

Notes: A broad-beam ion source is developed for ion-beam etching of quartz wafers, which are used in resonators with a high basic frequency of the order of magnitude of 1 GHz. The improvement of uniformity of the extracted ion beam is investigated. The double-grid multiple-aperture ion optics is adopted, in which perveance is matched by varying both the aperture diameters and spaces between grids. The configuration of the magnetic field is optimized. Measured at the target of 12 cm from the grids, the area of uniform region (nonuniformity 〈5%) is approximately equal to the area of the bored region of the grids (12 cm diam) and 1/1.78 of the cross-section area of the anode (16 cm diam). A broad beam of 100–1000 eV and 0.1–2.0 mA/cm2 is extracted from the source to fulfill the requirement of the etching process. Without any cooling system, the ion source is installed in vacuum chamber. © 1996 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1146799

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2

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Sugars act as signal molecules and osmotica to regulate the expression of α-amylase genes and metabolic activities in germinating cereal grains (1996)

Yu, Su-May ; Lee, Yi-Ching ; Fang, Su-Chiung ; [et al.]

Springer

Plant molecular biology 30 (1996), S. 1277-1289

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ISSN: 1573-5028

Keywords: α-amylase gene ; metabolic control ; osmotic control ; feedback control ; rice ; sugar signal

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The molecular mechanisms that initiate and control the metabolic activities of seed germination are largely unknown. Sugars may play important roles in regulating such metabolic activities in addition to providing an essential carbon source for the growth of young seedlings and maintaining turgor pressure for the expansion of tissues during germination. To test this hypothesis, we investigated the physiological role of sugars in the regulation of α-amylase gene expression and carbohydrate metabolism in embryo and endosperm of germinating rice seeds. RNA gel blot analysis revealed that in the embryo and aleurone cells, expression of four α-amylase genes was differentially regulated by sugars via mechanisms beyond the well-known hormonal control mechanism. In the aleurone cells, expression of these α-amylase genes was regulated by gibberellins produced in the embryo and by osmotically active sugars. In the embryo, expression of two α-amylase genes and production of gibberellins were transient, and were probably induced by depletion of sugars in the embryo upon imbibition, and suppressed by sugars influx from the endosperm as germination proceeded. The differential expression of the four α-amylase genes in the embryo and aleurone cells was probably due to their markedly different sensitivities to changes in tissue sugar levels. Our study supports a model in which sugars regulate the expression of α-amylase genes in a tissue-specific manner: via a feedback control mechanism in the embryo and via an osmotic control mechanism in the aleurone cells. An interactive loop among sugars, gibberellins, and α-amylase genes in the germinating cereal grain is proposed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00019558

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3

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On the Nature of PSE Approximation (1996)

Li, Fei ; Malik, Mujeeb R.

Springer

Theoretical and computational fluid dynamics 8 (1996), S. 253-273

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ISSN: 1432-2250

Source: Springer Online Journal Archives 1860-2000

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

Notes: Abstract The recently developed method of parabolized stability equations (PSE) offers a fast and efficient way of analyzing the spatial growth of linear and nonlinear (convective) disturbances in shear layers. For incompressible flows, the governing equations may be represented either in primitive variables or by using other formulations obtained by eliminating the pressure gradient (e.g., vorticity—streamfunction formulation). On the other hand, for compressible flows, primitive variables offer a natural and the only choice. We show that primitive-variable formulation is not well-posed due to the ellipticity introduced by the term and the marching solution eventually blows up for a sufficiently small step size. However, it is shown that this difficulty can be overcome if the minimum step size is greater than the inverse of the real part of the streamwise wave number, An alternative is to drop the term, in which case the residual ellipticity is of no consequence for marching computations with much smaller step sizes. However, the ellipticity cannot be completely removed. Results obtained with streamfunction and vorticity–velocity formulations also show that the numerical difficulties arise for a sufficiently small marching step size. This step-size restriction can be overcome by dropping the term from the governing equations. The effect of this term on solution accuracy is negligible for Blasius flow but not so for rotating-disk flow.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00639695

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4

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On the nature of PSE approximation (1996)

Li, Fei ; Malik, Mujeeb R.

Springer

Theoretical and computational fluid dynamics 8 (1996), S. 253-273

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ISSN: 1432-2250

Source: Springer Online Journal Archives 1860-2000

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

Notes: Abstract The recently developed method of parabolized stability equations (PSE) offers a fast and efficient way of analyzing the spatial growth of linear and nonlinear (convective) disturbances in shear layers. For incompressible flows, the governing equations may be represented either in primitive variables or by using other formulations obtained by eliminating the pressure gradient (e.g., vorticity-streamfunction formulation). On the other hand, for compressible flows, primitive variables offer a natural and the only choice. We show that primitive-variable formulation is not well-posed due to the ellipticity introduced by the $$\partial \hat p/\partial x$$ term and the marching solution eventually blows up for a sufficiently small step size. However, it is shown that this difficulty can be overcome if the minimum step size is greater than the inverse of the real part of the streamwise wave number, αr. An alternative is to drop the $$\partial \hat p/\partial x$$ term, in which case the residual ellipticity is of no consequence for marching computations with much smaller step sizes. However, the ellipticity cannot be completely removed. Results obtained with streamfunction and vorticity-velocity formulations also show that the numerical difficulties arise for a sufficiently small marching step size. This step-size restriction can be overcome by dropping thedα/dx term from the governing equations. The effect of this term on solution accuracy is negligible for Blasius flow but not so for rotating-disk flow.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00639695

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5

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Transgenic approaches to increase dehydration-stress tolerance in plants (1999)

Bajaj, Shavindra ; Targolli, Jayaprakash ; Liu, Li-Fei ; [et al.]

Springer

Molecular breeding 5 (1999), S. 493-503

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ISSN: 1572-9788

Keywords: dehydration stress ; detoxifying enzymes ; lea genes ; osmoprotectants ; regulatory genes ; transgenic approaches

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Plant productivity is strongly influenced by abiotic stress conditions induced by drought, high salt and low temperature. Plants respond to these conditions with an array of biochemical and physiological adaptations, at least some of which are the result of changes in gene expression. Transgenic approaches offer a powerful means of gaining valuable information to better understand the mechanisms governing stress tolerance. They also offer new opportunities to improve dehydration-stress tolerance in crops by incorporating a gene involved in stress protection into species that lack them. In this review, we discuss progress made towards understanding the molecular elements involved in dehydration-stress responses that have been used to improve salt or drought tolerance following several transgenic approaches. Further, we discuss various strategies being used to produce transgenic plants with increased tolerance to dehydration stress. These include the overproduction of enzymes responsible for biosynthesis of osmolytes, late-embryogenesis-abundant proteins and detoxification enzymes. At this time, there is a need for a careful appraisal of the genes to be selected and promoter elements to be used, because constitutive expression of these genes may not be desirable in all applications. In this context, the advantages and limitations of transgenic approaches currently being used are discussed together with the importance of using stress-inducible promoters and the introduction of multiple genes for the improvement of dehydration-stress tolerance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1009660413133

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6

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A comparison of serum-free media for the support of in vitro mitogen-induced blastogenic expansion of cytolytic lymphocytes (1991)

McVicar, Daniel W. ; Li, Fei ; McCrady, Carl W. ; [et al.]

Springer

Cytotechnology 6 (1991), S. 105-113

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ISSN: 1573-0778

Keywords: cytotoxicity ; lymphocyte proliferation ; serum-free media ; signal transduction

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology

Notes: Abstract The high cost and potential dangers of including human AB serum in incubation media used to expand lymphocyte populations in vitro for adoptive immunotherapy have stimulated efforts to develop defined media which can support both the expansion and induction of lymphocytes with tumor cytolytic activity in the absence of serum. Lymphocyte proliferation following exposure to either PHA or the combination of phorbol 12,13-dibutyrate (PDBu) and the calcium ionophore, ionomycin, was evaluated. Although the media tested, X-Vivo 10, HB-104, AIM V, and HL-1, supported the generation of comparable levels of LAK activity after 3–5 days incubation with 103 U human recombinant interleukin-2 (rIL-2)/ml, there were striking differences in the ability of each medium to support mitogenically stimulated lymphocytes in the absence of serum, with cells in AIM V and X-Vivo 10 showing the highest levels of DNA synthesis. In long-term cultures (17 days) of blood MNC stimulated by PDBu and ionomycin, X-Vivo 10 and HB-104 yielded the greatest numbers of cells. The addition of 2% AB serum greatly enhanced the ability of each medium to support cell proliferation to equivalent maximum levels. The results indicate that while all four serum-free media were suitable for lymphocyte culture and support the development of LAK activity, they differ in their capacity to support expansion of lymphocyte populations in response to polyclonal mitogenic activation. This latter characteristic should be considered before choosing a particular serum-free formulation as its constituents may affect mechanistic interpretations regarding signal transduction events.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00373027

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