20 research outputs found
Minimization of Handoff Failure Probability for Next-Generation Wireless Systems
During the past few years, advances in mobile communication theory have
enabled the development and deployment of different wireless technologies,
complementary to each other. Hence, their integration can realize a unified
wireless system that has the best features of the individual networks.
Next-Generation Wireless Systems (NGWS) integrate different wireless systems,
each of which is optimized for some specific services and coverage area to
provide ubiquitous communications to the mobile users. In this paper, we
propose to enhance the handoff performance of mobile IP in wireless IP networks
by reducing the false handoff probability in the NGWS handoff management
protocol. Based on the information of false handoff probability, we analyze its
effect on mobile speed and handoff signaling delay.Comment: 16 Page
Promoters, enhancers, and transcription target RAG1 binding during V(D)J recombination
RAG1 binding to TCR gene elements is dictated by transcriptional control elements and by transcription itself; these findings provide direct confirmation of the long-held accessibility model
An Intergenic Region Shared by At4g35985 and At4g35987 in Arabidopsis Thaliana is a Tissue Specific and Stress Inducible Bidirectional Promoter Analyzed in Transgenic Arabidopsis and Tobacco Plants
On chromosome 4 in the Arabidopsis genome, two neighboring genes (calmodulin methyl transferase At4g35987 and senescence associated gene At4g35985) are located in a head-to-head divergent orientation sharing a putative bidirectional promoter. This 1258 bp intergenic region contains a number of environmental stress responsive and tissue specific cis-regulatory elements. Transcript analysis of At4g35985 and At4g35987 genes by quantitative real time PCR showed tissue specific and stress inducible expression profiles. We tested the bidirectional promoter-function of the intergenic region shared by the divergent genes At4g35985 and At4g35987 using two reporter genes (GFP and GUS) in both orientations in transient tobacco protoplast and Agro-infiltration assays, as well as in stably transformed transgenic Arabidopsis and tobacco plants. In transient assays with GFP and GUS reporter genes the At4g35985 promoter (P85) showed stronger expression (about 3.5 fold) compared to the At4g35987 promoter (P87). The tissue specific as well as stress responsive functional nature of the bidirectional promoter was evaluated in independent transgenic Arabidopsis and tobacco lines. Expression of P85 activity was detected in the midrib of leaves, leaf trichomes, apical meristemic regions, throughout the root, lateral roots and flowers. The expression of P87 was observed in leaf-tip, hydathodes, apical meristem, root tips, emerging lateral root tips, root stele region and in floral tissues. The bidirectional promoter in both orientations shows differential up-regulation (2.5 to 3 fold) under salt stress. Use of such regulatory elements of bidirectional promoters showing spatial and stress inducible promoter-functions in heterologous system might be an important tool for plant biotechnology and gene stacking applications
Amberlyst-15 catalyzed acetylation of heteroaromatics with acetic anhydride under solvent free conditions
198-200Amberlyst-15 has been
found to be an efficient reusable heteroĀgeneous catalyst for acetylation of
indole, 2-methylindole and pyrrole with acetic anhydride under solvent free
conditions
Exon Inclusion Is Dependent on Predictable Exonic Splicing Enhancers
We have previously formulated a list of approximately 2,000 RNA octamers as putative exonic splicing enhancers (PESEs) based on a statistical comparison of human exonic and nonexonic sequences (X. H. Zhang and L. A. Chasin, Genes Dev. 18:1241-1250, 2004). When inserted into a poorly spliced test exon, all eight tested octamers stimulated splicing, a result consistent with their identification as exonic splicing enhancers (ESEs). Here we present a much more stringent test of the validity of this list of PESEs. Twenty-two naturally occurring examples of nonoverlapping PESEs or PESE clusters were identified in six mammalian exons; five of the six exons tested are constitutively spliced. Each of the 22 individual PESEs or PESE clusters was disrupted by site-directed mutagenesis, usually by a single-base substitution. Eighteen of the 22 disruptions (82%) resulted in decreased splicing efficiency. In contrast, 24 control mutations had little or no effect on splicing. This high rate of success suggests that most PESEs function as ESEs in their natural context. Like most exons, these exons contain several PESEs. Since knocking out any one of several could produce a severalfold decrease in splicing efficiency, we conclude that there is little redundancy among ESEs in an exon and that they must work in concert to optimize splicing
Noontime satellite observations to evaluate clear sky latent heat flux (lE) estimates over diverse agricultural landscapes
Not AvailableA simplified evaporative fraction (L) based single-source energy balance scheme was tested with
moderate resolution ( 1 km) noontime satellite observations to evaluate clear sky latent heat flux (lE)
estimates over diverse agricultural landscapes. This approach uses two-dimensional (2D) scatter
between land surface temperature (LST) and albedo to determine L. The operational utility of this
scheme was demonstrated for estimating regional evapotranspiration and consumptive water use
during rabi (November to April) crop growing season to predict pre-harvest wheat yield (error within
15.9% of reported mean) using time series data. The existence of triangular relations between L and LAI
(leaf area index) or NDVI (normalized difference vegetation index) was found with basal line
(hypotenuse) linearly coupled with LAI or NDVI at low level of surface soil wetness. The analysis of
diurnal course of in situ L proved the validity of constant-L hypothesis over pure, uniform,
homogeneous crop canopies but showed irregular and wave-like patterns over heterogeneous, mixed
crop canopies. The root mean square error (RMSE) of noontime and daytime average lE estimates with
respect to in situ lE measurements were also smaller over homogeneous agricultural canopies (41 and
23Wm 2) with correlation coefficients (r) 0.94 and 0.96, respectively, from 135 clear sky datasets as
compared to RMSE over heterogeneous ones (59 and 28Wm 2 with r = 0.66 and 0.82, respectively from
22 datasets). The intercomparison with another L based approach (LSTāNDVI 2D scatter) showed the
supremacy of L determined from LSTāalbedo 2D scatter. The efficiency of LSTāNDVI scatter was better
during the dry down or water limited phases of crop growth only. The uncertainties of lE estimates were
attributed to errors in core radiation budget inputs, relative loss of conservativeness of L due to canopy
heterogeneity, and the inherent limitations of the single-source approach. There is further scope to
reduce present lE uncertainties by combining the new findings on L (LSTāalbedo scatter)āNDVI
triangular relations, diurnal L and two-source radiation budgetNot Availabl