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31.
基于J2ME与WebService架构的无线Internet应用研究 总被引:2,自引:0,他引:2
吕燕 《北京工商大学学报(自然科学版)》2004,22(6):56-59
对比了J2ME与WAP,阐述了基于J2ME与WebService架构的无线Internet应用开发模式,并应用此架构设计了面向手机、PDA等无线手持设备的实时航班查询系统. 相似文献
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33.
Duyilemi C. Ajonijebu Oualid Abboussi Vivienne A. Russell Musa V. Mabandla William M. U. Daniels 《Cellular and molecular life sciences : CMLS》2017,74(15):2735-2747
The detrimental effects of drug abuse are apparently not limited to individuals but may also impact the vulnerability of their progenies to develop addictive behaviours. Epigenetic signatures, early life experience and environmental factors, converge to influence gene expression patterns in addiction phenotypes and consequently may serve as mediators of behavioural trait transmission between generations. The majority of studies investigating the role of epigenetics in addiction do not consider the influence of social interactions. This shortcoming in current experimental approaches necessitates developing social models that reflect the addictive behaviour in a free-living social environment. Furthermore, this review also reports on the advancement of interventions for drug addiction and takes into account the emerging roles of histone deacetylase (HDAC) inhibitors in the etiology of drug addiction and that HDAC may be a potential therapeutic target at nucleosomal level to improve treatment outcomes. 相似文献
34.
Julhash U. Kazi Rohit A. Chougule Tianfeng Li Xianwei Su Sausan A. Moharram Kaja Rupar Alissa Marhäll Mohiuddin Gazi Jianmin Sun Hui Zhao Lars Rönnstrand 《Cellular and molecular life sciences : CMLS》2017,74(14):2679-2688
The type III receptor tyrosine kinase FLT3 is frequently mutated in acute myeloid leukemia. Oncogenic FLT3 mutants display constitutive activity leading to aberrant cell proliferation and survival. Phosphorylation on several critical tyrosine residues is known to be essential for FLT3 signaling. Among these tyrosine residues, Y842 is located in the so-called activation loop. The position of this tyrosine residue is well conserved in all receptor tyrosine kinases. It has been reported that phosphorylation of the activation loop tyrosine is critical for catalytic activity for some but not all receptor tyrosine kinases. The role of Y842 residue in FLT3 signaling has not yet been studied. In this report, we show that Y842 is not important for FLT3 activation or ubiquitination but plays a critical role in regulating signaling downstream of the receptor as well as controlling receptor stability. We found that mutation of Y842 in the FLT3-ITD oncogenic mutant background reduced cell viability and increased apoptosis. Furthermore, the introduction of the Y842 mutation in the FLT3-ITD background led to a dramatic reduction in in vitro colony forming capacity. Additionally, mice injected with cells expressing FLT3-ITD/Y842F displayed a significant delay in tumor formation, compared to FLT3-ITD expressing cells. Microarray analysis comparing gene expression regulated by FLT3-ITD versus FLT3-ITD/Y842F demonstrated that mutation of Y842 causes suppression of anti-apoptotic genes. Furthermore, we showed that cells expressing FLT3-ITD/Y842F display impaired activity of the RAS/ERK pathway due to reduced interaction between FLT3 and SHP2 leading to reduced SHP2 activation. Thus, we suggest that Y842 is critical for FLT3-mediated RAS/ERK signaling and cellular transformation. 相似文献
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Stomata consist of a pair of guard cells that mediate gas and water-vapour exchange between plants and the atmosphere. Stomatal precursor cells-meristemoids-possess a transient stem-cell-like property and undergo several rounds of asymmetric divisions before further differentiation. Here we report that the Arabidopsis thaliana basic helix-loop-helix (bHLH) protein MUTE is a key switch for meristemoid fate transition. In the absence of MUTE, meristemoids abort after excessive asymmetric divisions and fail to differentiate stomata. Constitutive overexpression of MUTE directs the entire epidermis to adopt guard cell identity. MUTE has two paralogues: FAMA, a regulator of guard cell morphogenesis, and SPEECHLESS (SPCH). We show that SPCH directs the first asymmetric division that initiates stomatal lineage. Together, SPCH, MUTE and FAMA bHLH proteins control stomatal development at three consecutive steps: initiation, meristemoid differentiation and guard cell morphogenesis. Our findings highlight the roles of closely related bHLHs in cell type differentiation in plants and animals. 相似文献
37.
Riebesell U Schulz KG Bellerby RG Botros M Fritsche P Meyerhöfer M Neill C Nondal G Oschlies A Wohlers J Zöllner E 《Nature》2007,450(7169):545-548
The oceans have absorbed nearly half of the fossil-fuel carbon dioxide (CO2) emitted into the atmosphere since pre-industrial times, causing a measurable reduction in seawater pH and carbonate saturation. If CO2 emissions continue to rise at current rates, upper-ocean pH will decrease to levels lower than have existed for tens of millions of years and, critically, at a rate of change 100 times greater than at any time over this period. Recent studies have shown effects of ocean acidification on a variety of marine life forms, in particular calcifying organisms. Consequences at the community to ecosystem level, in contrast, are largely unknown. Here we show that dissolved inorganic carbon consumption of a natural plankton community maintained in mesocosm enclosures at initial CO2 partial pressures of 350, 700 and 1,050 microatm increases with rising CO2. The community consumed up to 39% more dissolved inorganic carbon at increased CO2 partial pressures compared to present levels, whereas nutrient uptake remained the same. The stoichiometry of carbon to nitrogen drawdown increased from 6.0 at low CO2 to 8.0 at high CO2, thus exceeding the Redfield carbon:nitrogen ratio of 6.6 in today's ocean. This excess carbon consumption was associated with higher loss of organic carbon from the upper layer of the stratified mesocosms. If applicable to the natural environment, the observed responses have implications for a variety of marine biological and biogeochemical processes, and underscore the importance of biologically driven feedbacks in the ocean to global change. 相似文献
38.
The scanning tunnelling microscope (STM) relies on localized electron tunnelling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical systems--ranging from semiconductors to superconductors to atomic and molecular nanosystems. A severe limitation in scanning tunnelling microscopy is the low temporal resolution, originating from the diminished high-frequency response of the tunnel current readout circuitry. Here we overcome this limitation by measuring the reflection from a resonant inductor-capacitor circuit in which the tunnel junction is embedded, and demonstrate electronic bandwidths as high as 10 MHz. This approximately 100-fold bandwidth improvement on the state of the art translates into fast surface topography as well as delicate measurements in mesoscopic electronics and mechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM have allowed us to perform thermometry at the nanometre scale. Furthermore, we have detected high-frequency mechanical motion with a sensitivity approaching approximately 15 fm Hz(-1/2). This sensitivity is on par with the highest available from nanoscale optical and electrical displacement detection techniques, and the radio-frequency STM is expected to be capable of quantum-limited position measurements. 相似文献
39.
Genome sequence and analysis of the tuber crop potato 总被引:11,自引:0,他引:11
Potato Genome Sequencing Consortium Xu X Pan S Cheng S Zhang B Mu D Ni P Zhang G Yang S Li R Wang J Orjeda G Guzman F Torres M Lozano R Ponce O Martinez D De la Cruz G Chakrabarti SK Patil VU Skryabin KG Kuznetsov BB Ravin NV Kolganova TV Beletsky AV Mardanov AV Di Genova A Bolser DM Martin DM Li G Yang Y Kuang H Hu Q Xiong X Bishop GJ Sagredo B Mejía N Zagorski W Gromadka R Gawor J Szczesny P Huang S Zhang Z Liang C He J Li Y He Y Xu J Zhang Y Xie B Du Y Qu D Bonierbale M Ghislain M 《Nature》2011,475(7355):189-195
Potato (Solanum tuberosum L.) is the world's most important non-grain food crop and is central to global food security. It is clonally propagated, highly heterozygous, autotetraploid, and suffers acute inbreeding depression. Here we use a homozygous doubled-monoploid potato clone to sequence and assemble 86% of the 844-megabase genome. We predict 39,031 protein-coding genes and present evidence for at least two genome duplication events indicative of a palaeopolyploid origin. As the first genome sequence of an asterid, the potato genome reveals 2,642 genes specific to this large angiosperm clade. We also sequenced a heterozygous diploid clone and show that gene presence/absence variants and other potentially deleterious mutations occur frequently and are a likely cause of inbreeding depression. Gene family expansion, tissue-specific expression and recruitment of genes to new pathways contributed to the evolution of tuber development. The potato genome sequence provides a platform for genetic improvement of this vital crop. 相似文献
40.
Lee X Goulden ML Hollinger DY Barr A Black TA Bohrer G Bracho R Drake B Goldstein A Gu L Katul G Kolb T Law BE Margolis H Meyers T Monson R Munger W Oren R Paw U KT Richardson AD Schmid HP Staebler R Wofsy S Zhao L 《Nature》2011,479(7373):384-387
Deforestation in mid- to high latitudes is hypothesized to have the potential to cool the Earth's surface by altering biophysical processes. In climate models of continental-scale land clearing, the cooling is triggered by increases in surface albedo and is reinforced by a land albedo-sea ice feedback. This feedback is crucial in the model predictions; without it other biophysical processes may overwhelm the albedo effect to generate warming instead. Ongoing land-use activities, such as land management for climate mitigation, are occurring at local scales (hectares) presumably too small to generate the feedback, and it is not known whether the intrinsic biophysical mechanism on its own can change the surface temperature in a consistent manner. Nor has the effect of deforestation on climate been demonstrated over large areas from direct observations. Here we show that surface air temperature is lower in open land than in nearby forested land. The effect is 0.85 ± 0.44 K (mean ± one standard deviation) northwards of 45° N and 0.21 ± 0.53 K southwards. Below 35° N there is weak evidence that deforestation leads to warming. Results are based on comparisons of temperature at forested eddy covariance towers in the USA and Canada and, as a proxy for small areas of cleared land, nearby surface weather stations. Night-time temperature changes unrelated to changes in surface albedo are an important contributor to the overall cooling effect. The observed latitudinal dependence is consistent with theoretical expectation of changes in energy loss from convection and radiation across latitudes in both the daytime and night-time phase of the diurnal cycle, the latter of which remains uncertain in climate models. 相似文献