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21.
We establish the existence of traveling wave solutions for a nonlinear partial differential equation that models a logistically
growing population whose movement is governed by an advective process. Conditions are presented for which traveling wave solutions
exist and for which they are stable to small semi-finite domain perturbations. The wave is of mathematical interest because
its behavior is determined by a singular differential equation and those with small speed of propagation steepen into a shock-like
solutions. Finally, we indicate that the smoothing presence of diffusion allows wave persistence when an advective slow moving
wave may collapse.
Received: 24 November 1997 / Revised version: 13 July 1998 相似文献
22.
菌落PCR快速扩增工业酿酒酵母基因组DNA片段 总被引:2,自引:0,他引:2
针对工业酿酒酵母细胞破壁难和提取基因酵母组DNA费时长(2-3 h/样品)的问题,研究了SDS-微珠涡旋破壁的方法。以破壁液上清为模板进行菌落PCR扩增酿酒酵母南阳K基因组中铜抗性蛋白基因(cup1)片段和rDNA片段。结果表明,在不需要提取酵母基因组前提下,利用该方法能有效地扩增酵母基因组DNA片段,同时该方法也适用于对转基因酿酒酵母进行菌落PCR从而实现对转化子的准确和快速地鉴定筛选,是一种成本低和易于操作的适于处理大量样品的方法。 相似文献
23.
A. Palialexis S. Georgakarakos I. Karakassis K. Lika V. D. Valavanis 《Hydrobiologia》2011,670(1):241-266
The accurate representation of species distribution derived from sampled data is essential for management purposes and to
underpin population modelling. Additionally, the prediction of species distribution for an expanded area, beyond the sampling
area can reduce sampling costs. Here, several well-established and recently developed habitat modelling techniques are investigated
in order to identify the most suitable approach to use with presence–absence acoustic data. The fitting efficiency of the
modelling techniques are initially tested on the training dataset while their predictive capacity is evaluated using a verification
set. For the comparison among models, Receiver Operating Characteristics (ROC), Kappa statistics, correlation and confusion
matrices are used. Boosted Regression Trees (BRT) and Associative Neural Networks (ASNN), which are both within the machine
learning category, outperformed the other modelling approaches tested. 相似文献
24.
Distinct thyroid hormone-dependent expression of TrKB and p75NGFR in nonneuronal cells during the critical TH-dependent period of the cochlea 总被引:5,自引:0,他引:5
Knipper M Gestwa L Ten Cate WJ Lautermann J Brugger H Maier H Zimmermann U Rohbock K Köpschall I Wiechers B Zenner HP 《Journal of neurobiology》1999,38(3):338-356
Analyzing the thyroid hormone (TH)-dependent period of the inner ear, we observed that the presence of triiodothyronine (T3) between postnatal day 3 (P3) and P12 is sufficient for functional maturation of the auditory system. Within this short time period, an unusual transient TH-dependent expression of nonneuronal neurotrophin receptors (NT-R) trkB and p75(NGFR) was observed in correlation with neuronal and morphogenetic processes. The availability of thyroid hormone was revealed to be invariably correlated with (a) a transient expression of full-length trkB in TRalpha1-, TRalpha2- and TRbeta1-expressing hair cells concomitant to the segregation of afferent fibers and the synaptogenesis of efferent fibers; and (b) a transient expression of p75(NGFR) in TRalpha1- and TRbeta1-expressing great epithelia ridge cells in direct spatiotemporal correlation with the appearance of apoptotic cells and morphogenetic maturation of the organ. For the first time, these data suggest a TH dependency of the expression of neurotrophin receptors in nonneuronal cells. A potential role of these peculiar neurotrophin receptor expression for the conversion of the biological function of TH on innervation patterning and morphogenesis during the critical TH-dependent period of the inner ear may be considered. 相似文献
25.
Tagawa H Kizuka Y Ikeda T Itoh S Kawasaki N Kurihara H Onozato ML Tojo A Sakai T Kawasaki T Oka S 《The Journal of biological chemistry》2005,280(25):23876-23883
The HNK-1 carbohydrate, which is recognized by anti-HNK-1 antibody, is well known to be expressed predominantly in the nervous system. The characteristic structural feature of the HNK-1 carbohydrate is 3-sulfo-glucuronyl residues attached to lactosamine structures (Gal beta1-4GlcNAc) on glycoproteins and glycolipids. The biosynthesis of the HNK-1 carbohydrate is regulated mainly by two glucuronyltransferases (GlcAT-P and GlcAT-S) and a sulfotransferase. In this study, we found that GlcAT-S mRNA was expressed at higher levels in the kidney than in the brain, but that both GlcAT-P and HNK-1 sulfotransferase mRNAs, which were expressed at high levels in the brain, were not detected in the kidney. These results suggested that the HNK-1 carbohydrate without sulfate (non-sulfated HNK-1 carbohydrate) is expressed in the kidney. We substantiated this hypothesis using two different monoclonal antibodies: one (anti-HNK-1 antibody) requires sulfate on glucuronyl residues for its binding, and the other (antibody M6749) does not. Western blot analyses of mouse kidney revealed that two major bands (80 and 140 kDa) were detected with antibody M6749, but not with anti-HNK-1 antibody. The 80- and 140-kDa band materials were identified as meprin alpha and CD13/aminopeptidase N, respectively. We also confirmed the presence of the non-sulfated HNK-1 carbohydrate on N-linked oligosaccharides by multistage tandem mass spectrometry. Immunofluorescence staining with antibody M6749 revealed that the non-sulfated HNK-1 carbohydrate was expressed predominantly on the apical membranes of the proximal tubules in the cortex and was also detected in the thin ascending limb in the inner medulla. This is the first study indicating the presence of the non-sulfated HNK-1 carbohydrate being synthesized by GlcAT-S in the kidney. The results presented here constitute novel knowledge concerning the function of the HNK-1 carbohydrate. 相似文献
26.
We formulate a Dynamic Energy Budget (DEB) model for the growth and reproduction of individual organisms based on partitioning
of net production (i.e. energy acquisition rate minus maintenance rate) between growth and energy reserves. Reproduction uses
energy from reserves. The model describes both feeding and non-feeding stages, and hence is applicable to embryos (which neither
feed nor reproduce), juveniles (which feed but do not reproduce), and adults (which commonly both feed and reproduce). Embryonic
growth can have two forms depending on the assumptions for acquisition of energy from yolk. By default, when the energy acquisition
rate exceeds the maintenance rate, a fixed proportion of the resulting net production is spent on growth (increase in structural biomass), and the remaining portion is channelled to the reserves. Feeding organisms,
however, modulate their allocation of net production energy in response to their total energy content (energy in the reserves
plus energy bounded to structural biomass). In variable food environment an organism alternates between periods of growth,
no-growth, and balanced-growth. In the latter case the organism adopts an allocation strategy that keeps its total energy
constant. Under constant environmental conditions, the growth of a juvenile is always of von Bertalanffy type. Depending on
the values of model parameters there are two long-time possibilities for adults: (a) von Bertalanffy growth accompanied by
reproduction at a rate that approaches zero as the organism approaches asymptotic size, or (b) abrupt cessation of growth
at some finite time, following which, the rate of reproduction is constant. We illustrate the model's applicability in life
history theory by studying the optimum values of the energy allocation parameters for constant environment and for each of
the dynamic regimes described above.
Received: 11 May 1998 / Revised version: 18 February 2000 / Published online: 4 October 2000 相似文献
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Harini Ramalingam Sonu Kashyap Patricia Cobo-Stark Andrea Flaten Chun-Mien Chang Sachin Hajarnis Kyaw Zaw Hein Jorgo Lika Gina M. Warner Jair M. Espindola-Netto Ashwani Kumar Mohammed Kanchwala Chao Xing Eduardo N. Chini Vishal Patel 《Cell metabolism》2021,33(6):1234-1247.e7
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29.