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排序方式: 共有115条查询结果,搜索用时 218 毫秒
1.
MA Rott VC Witthuhn BA Schilke M Soranno A Ali TJ Donohue 《Canadian Metallurgical Quarterly》1993,175(2):358-366
In Rhodobacter sphaeroides, cytochrome c2 (cyt c2)-deficient mutants are photosynthetically incompetent (PS-). However, mutations which suppress the photosynthetic deficiency (spd mutations) of cyt c2 mutants increase the levels of a cyt c2 isoform, isocyt c2. To determine whether isocyt c2 was required for photosynthetic growth of Spd mutants, we used Tn5 mutagenesis to generate a PS- mutant (TP39) that lacks both cyt c2 and isocyt c2. DNA sequence analysis of wild-type DNA that restores isocyt c2 production and photosynthetic growth to TP39 indicates that it encodes the isocyt c2 structural gene, cycI. The Tn5 insertion in TP39 is approximately 1.5 kb upstream of cycI, and our results show that it is polar onto cycI. The cycI gene has been physically mapped to a region of chromosome I that is approximately 700 kb from the R. sphaeroides photosynthetic gene cluster. Construction of a defined cycI null mutant and complementation of several mutants with the cycI gene under the control of the cyt c2 promoter region indicate that an increase in the levels of isocyt c2 alone is necessary and sufficient for photosynthetic growth in the absence of cyt c2. The data are discussed in terms of the obligate role of isocyt c2 in cyt c2-independent photosynthesis of R. sphaeroides. 相似文献
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4.
Silicon - This work fully depends on the silicon nanoparticles. It is represented as SiNPs. This depends on the transparent LEDs color converters. The spectrum obtained is fully white, so it is... 相似文献
5.
L. A. Rott 《Journal of Engineering Physics and Thermophysics》1995,68(5):595-598
The irradiation effect of a particle flow on the electrodynamic properties of a conductor is discussed. It is established that a relationship exists between three energy quanta of different origin and high-temperature superconduction current.Notation
Planck constant
-
c
velocity of light
- H
magnetic intensity
- E
electric intensity
- r
radius-vector
-
m
,
H
,
E
energy quanta
-
l
g
unit length
- j
electric current
- A
vector-potential of the electromagnetic field
-
F
ik
field tensor
-
m
mass of the absorbed particle
-
velocity
-
l
H
,l
E
,l
m
length units
-
t
time
-
e
electron charge
-
k
Boltzmann constant
-
T
cr
critical temperature
Belarus State Technological University Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 5, pp. 739–742, September–October, 1995. 相似文献
6.
Subash Bommu Chinnaraj Pahala Gedara Jayathilake Jack Dawson Yasmine Ammar Jose Portoles Nicholas Jakubovics Jinju Chen 《材料科学技术学报》2021,81(22):151-161
Bacterial attachment is a complex process affected by flow conditions,imparted stresses,and the sur-face properties and structure of both the supporting material and the cell.Experiments on the initial attachment of cells of the bacterium Streptococcus gordonii (S.gordonii),an important early coloniser of dental plaque,to samples of stainless steel (SS) have been reported in this work.The primary aim motivating this study was to establish what affect,if any,the surface roughness and topology of sam-ples of SS would have on the initial attachment of cells of the bacterium S.gordonii.This material and bacterium were chosen by virtue of their relevance to dental implants and dental implant infections.Prior to bacterial attachment,surfaces become conditioned by the interfacing environment (salivary pellicle from the oral cavity for instance).For this reason,cell attachment to samples of SS pre-coated with saliva was also studied.By implementing the Extended Derjaguin Landau Verwey and Overbeek(XDLVO) theory coupled with convection-diffusion-reaction equations and the surface roughness infor-mation,a computational model was developed to help better understand the physics of cell adhesion.Surface roughness was modelled by reconstructing the surface topography using statistical parame-ters derived from atomic force microscopy (AFM) measurements.Using this computational model,the effects of roughness and surface patterns on bacterial attachment were examined quantitatively in both static and flowing fluid environments.The results have shown that rougher surfaces (within the sub-microscale) generally increase bacterial attachment in static fluid conditions which quantitatively agrees with experimental measurements.Under flow conditions,computational fluid dynamics (CFD) simula-tions predicted reduced convection-diffusion inside the channel which would act to decrease bacterial attachment.When combined with surface roughness effects,the computational model also predicted that the surface topographies discussed within this work produced a slight decrease in overall bacterial attachment.This would suggest that the attachment-preventing effects of surface patterns dominate over the adhesion-favourable sub-microscale surface roughness;hence,producing a net reduction in adhered cells.This qualitatively agreed with experimental observations reported here and quantitatively matched experimental observations for low flow rates within measurement error. 相似文献
7.
Influenza A viruses display T cell-independent polyclonal B cell-activating properties which are mediated by the B cell-superstimulatory envelope glycoprotein hemagglutinin (HA). In this report, the receptor-binding requirements for B cell activation by influenza viruses were expected. Neuraminidase treatment of resting mature B cells from BALB/c mice abrogated late (proliferation/immunoglobulin synthesis), early (up-regulation of cell surface markers, including CD25, B220, and B7-1) and very-early events (homotypic adhesion) in virus-responding B lymphocytes. Similarly, pretreatment of murine responder cells with different inhibitors of N-glycosylation (tunicamycin, deoxymannojirimycin) significantly suppressed subsequent B lymphocyte activation by HA, but not control responses to lipopolysaccharide or anti-mu. Assays with chimeric HA transfectants, expressing the loop region of epitope B (amino acids 155-160) of the globular head of H2 (high B cell-stimulatory subtype) or H3 (medium-stimulatory subtype) on the protein backbone of a low-stimulatory subtype (H1) failed to alter the B cell-stimulatory activity of the virus, suggesting that the hypervariable loop region is not crucial in determining the B cell-activating properties of the protein. Collectively, our results imply that the B cell-superstimulatory function of influenza virus HA is not mediated by a direct protein/protein interaction, but via binding of HA to terminal sialic acid residues on cell surface receptor glycoproteins. These findings identify the influenza virus HA glycoprotein as the first viral lectin with lymphocyte-activating properties. 相似文献
8.
Boneless chicken breast portions were thawed by submersion in hot water (60 °C) and compared to refrigerator thawing. Thawing in hot water was significantly quicker (2–8.5 min) than refrigerator thawing (10–15.5 h). Thawing time in hot water increased with an increase in meat thickness. Sensory panelists could not distinguish a difference between hot water versus refrigerator thawed and subsequently grilled chicken breast portions. A model for Salmonella growth predicts that thawing chicken breast at the slowest rate in this study (0.5 °C/min) would result in a lower increase in the Salmonella concentration than that expected for room temperature storage for 4 h. 相似文献
9.
Water is essential for growing food and in some areas without irrigation agricultural production would not possible. Crop
specific agricultural drought assessment requires integrated information on meteorological parameters, soil characters and
plant vegetative dynamics throughout the growing season. Meteorological, Crop Growth Simulation Model and Space based approaches
have their own inherent limitations. The main objective of this study is to examine the possibility of developing a rationally
integrated drought assessment indicator for rice–wheat productivity over Indo-Gangetic Plains in India (IGP-India). Rice(Oryza sativa)–Wheat(Triticum aestivum) (RW) system is the major cropping system of the IGP-India and occupies 10 million hectares and provides food security and
livelihoods to the people of this region. There are four major reasons for droughts in IGP-delay in the onset of monsoon/
failure of monsoon, variability of monsoon rainfall, long break in monsoon and areal difference in the persistence of monsoon.
The Rational Integrated Drought Assessment Index (RIDAI) developed here explains 72% variations in rice productivity while
it explains 94% variations of wheat productivity. Thus, this combined drought index tool captures all the drought years in
the selected study area and this tool can be useful for getting preliminary assessment of drought impact, so that the researchers
and planners can use this integrated tool for their decisions. 相似文献
10.
Guido Velten Anja S. Rott Csar Cardona Silvia Dorn 《Journal of Stored Products Research》2007,43(4):550-557
To protect stored beans from attack by Acanthoscelides obtectus and other bruchids by non-toxic means of control, it is desirable to combine mutually compatible methods in an integrated approach. A combination of an optimal level of host–plant resistance based on the natural storage protein arcelin and a larval parasitoid has been suggested as a promising two-component strategy. While a dose–response to arcelin is evident in the bruchid Zabrotes subfasciatus, the effects of different arcelin concentrations on A. obtectus are still virtually unknown, even though they might be important for the success of the proposed integrated control system. The current investigation quantified the effect of different arcelin-based resistance levels of beans on the development of A. obtectus in a series of bioassays. Our findings show that all seven tested bean lines with markedly different levels of arcelin-based resistance against Z. subfasciatus consistently prolonged development of A. obtectus. Results provide clear evidence that arcelin acts as a growth inhibitor on first instar larvae. Furthermore, arcelin affected bruchid female fitness through its effect on body mass, which was significantly reduced on all arcelin-containing bean lines. This study demonstrates that, irrespective of its relative concentration, arcelin holds the potential to affect development of A. obtectus sufficiently to support the proposed two-component integrated pest management system. 相似文献