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Search Results: 1 - 10 of 14901 matches for " Christian Feller "
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Relaxed Logarithmic Barrier Function Based Model Predictive Control of Linear Systems
Christian Feller,Christian Ebenbauer
Mathematics , 2015,
Abstract: In this paper, we investigate the use of relaxed logarithmic barrier functions in the context of linear model predictive control. We present results that allow to guarantee asymptotic stability of the corresponding closed-loop system, and discuss further properties like performance and constraint satisfaction in dependence of the underlying relaxation. The proposed stabilizing MPC schemes are not necessarily based on an explicit terminal set or state constraint and allow to characterize the stabilizing control input sequence as the minimizer of a globally defined, continuously differentiable, and strongly convex function. The results are illustrated by means of a numerical example.
Dosage compensation and the global re-balancing of aneuploid genomes
Matthias Prestel, Christian Feller, Peter B Becker
Genome Biology , 2010, DOI: 10.1186/gb-2010-11-8-216
Abstract: Complex genomes are more than just the sum of their genes, but are rather complex regulatory systems in which the expression of each individual gene is a function of the activity of many other genes, so that the levels of their protein products are maintained within a narrow range. Such homeostasis favors the maintenance of the appropriate stoichiometry of subunits in multiprotein complexes or of components in signal transduction pathways, and defines the 'ground state' of a cell [1]. In diploid genomes, both alleles of a gene are usually active and this 'double dose' of each gene is figured into the equation. Thus, deviations from diploidy, such as the deletion or duplication of genes or of larger chromosomal fragments (aneuploidy), unbalance the finely tuned expression of the genome. Segmental aneuploidies of this kind can arise from failed or faulty repair of chromosomal damage due to irradiation, chemical insult or perturbation of replication, or from illegitimate recombination during meiosis. Loss or duplication of entire chromosomes (monosomy or trisomy, respectively) can arise from non-disjunction during cell division. Depending on the extent of the aneuploidy and on the genes affected, the fine balance of trans-acting factors and their chromosomal binding sites that define the gene-expression system is disturbed, and the fitness of the cell or organism challenged.Often, aneuploidies have been associated with a variety of developmental defects and malignant aberrations, such as Down syndrome or certain breast cancers (reviewed in [2,3]). The phenotypes associated with changes in gene copy number can not only be the result of the deregulation of the affected gene(s), but may also reflect trans-acting effects on other chromosomal loci or even more global alterations of the entire regulatory system. This is particularly true if genes coding for regulatory factors, such as transcription factors, are affected (reviewed in [4,5]).Genome-wide studies in different or
Sensitive and reliable detection of Kit point mutation Asp 816 to Val in pathological material
Christian K?hler, Sabine Didlaukat, Alfred C Feller, Hartmut Merz
Diagnostic Pathology , 2007, DOI: 10.1186/1746-1596-2-37
Abstract: The Kit point mutation Asp 816 to Val is heterozygous which means a problem in detection by PCR because the wild-type allele is also amplified and the number of cells which bear the point mutation is in most of the cases low. Most PCR protocols use probes to block the wild-type allele during amplification with more or less satisfying result. This is why point-mutated forward primers were designed and tested for efficiency in amplification of the mutated allele.One primer combination (A) fits the most for the introduced PCR assay. It was able just to amplify the mutated allele with high specificity from different patient's materials (FFPE or blood) of varying quality and quantity. Moreover, the sensitivity for this assay was convincing because 10 ng of DNA which bears the point mutation could be detected in a total volume of 200 ng of DNA.The PCR assay is able to deal with different materials (blood and FFPE) this means quality and quantity of DNA and can be used for high-througput screening because of its robustness. Moreover, the method is easy-to-use, not labour-intensive, and easy to realise in a standard laboratory.1,000 to 8,000 incidences of human mastocytosis are reported every year in the US [1]. Human mastocytosis is characterised by accumulation of mast cells in different organs. It is a heterogenous group of disorders which can be divided into the categories cutaneous mastocytosis (CM) and systemic mastocytosis (SM) which is commonly seen in adults by histological lesions in the bone marrow and other non-cutaneous organs [2,3]. SM can be further divided into the categories indolent systemic mastocytosis (ISM), SM with an associated clonal hematologic non-mast cell lineage disease (AHNMD), aggressive sytemic mastocytosis (ASM), and mast cell leukemia (MCL). ISM is the most common form which involves skin, bone marrow, and GI tract with good prognosis for the patient. First relations between mastocytosis and activating mutations in the receptor tyrosine kin
Efeito do manejo do solo e da matéria organica solúvel em água quente na estabilidade de agregados de um latossolo argiloso
Neves, Carmen Silvia Vieira Janeiro;Feller, Christian;Kouakoua, Ernest;
Ciência Rural , 2006, DOI: 10.1590/S0103-84782006000500010
Abstract: it was studied the aggregate stability of an oxisol maintained with vegetation of native forest; annual crops for 20 years; a citrus orchard mantained during 9 years with permanent ground cover of arachis prostrata bong. ex benth.; or permanent spontaneous vegetation (mainly gramineous) controlled by mowing (3-4 times in the rain period of rains) and tillage (once a year in the dry period); or bare soil maintained by manual weeding. the aggregate stability was determined in samples submitted or not to treatment to remove hot water soluble organic matter. the forest vegetation provided larger stability followed by the orchard submitted to the permanent covering with leguminous or gramineous plants. extraction of hot-water soluble carbon did not cause significant differences in aggregate stability, although there has been a significant correlation between hot water soluble carbon and soil aggregation.
Efeito do manejo do solo e da matéria organica solúvel em água quente na estabilidade de agregados de um latossolo argiloso
Neves Carmen Silvia Vieira Janeiro,Feller Christian,Kouakoua Ernest
Ciência Rural , 2006,
Abstract: Estudou-se a estabilidade de agregados de um latossolo vermelho distroférrico submetido às seguintes situa es: vegeta o nativa de floresta; culturas anuais por 20 anos; pomar cítrico manejado com cobertura verde permanente com a leguminosa Arachis prostrata Bong. ex Benth.; pomar com cobertura de vegeta o espontanea (predomínio de gramíneas) controlada com ro adora (3-4 vezes no período de chuvas) e uma gradagem a disco ao ano (no período seco); pomar sem vegeta o por meio de capina manual. Os tratamentos no pomar foram mantidos durante 9 anos. A estabilidade de agregados foi determinada em amostras submetidas ou n o a tratamento para retirada da matéria organica solúvel em água quente. O solo sob vegeta o de floresta teve maior quantidade de agregados estáveis, seguido do solo sob pomar com cobertura permanente de leguminosas ou gramíneas. A estabilidade dos agregados n o foi afetada pela extra o do carbono solúvel em água quente, embora tenha havido correla o positiva entre o teor de carbono solúvel em água quente e a agrega o do solo.
Pattern formation in auxin flux
Chrystel Feller,Jean-Pierre Gabriel,Christian Mazza,Florence Yerly
Quantitative Biology , 2011,
Abstract: The plant hormone auxin is fundamental for plant growth, and its spatial distribution in plant tissues is critical for plant morphogenesis. We consider a leading model of the polar auxin flux, and study in full detail the stability of the possible equilibrium configurations. We show that the critical states of the auxin transport process are composed of basic building blocks, which are isolated in a background of auxin depleted cells, and are not geometrically regular in general. The same model was considered recently through a continuous limit and a coupling to the von Karman equations, to model the interplay of biochemistry and mechanics during plant growth. Our conclusions might be of interest in this setting, since, for example, we establish the existence of Lyapunov functions for the auxin flux, proving in this way the convergence of pure transport processes toward the set of critical configurations.
Oral Squamous Cell Carcinoma: Epidemiology, Clinical Presentation and Treatment  [PDF]
Liviu Feller, Johan Lemmer
Journal of Cancer Therapy (JCT) , 2012, DOI: 10.4236/jct.2012.34037
Abstract: Squamous cell carcinoma accounts for 90% of all oral cancers. It may affect any anatomical site in the mouth, but most commonly the tongue and the floor of the mouth. It usually arises from a pre-existing potentially malignant lesion, and occasionally de novo; but in either case from within a field of precancerized epithelium. The use of tobacco and betel quid, heavy drinking of alcoholic beverages and a diet low in fresh fruits and vegetables are well known risk factors for oral squamous cell carcinoma. Important risk factors related to the carcinoma itself that are associated with a poor prognosis include large size of the tumour at the time of diagnosis, the presence of metastases in regional lymphnodes, and a deep invasive front of the tumour. Squamous cell carcinoma is managed by surgery, radiation, and chemotherapy singularly or in combination; but regardless of the treatment modality, the five-year survival rate is poor at about 50%. This can be attributed to the fact that about two-thirds of persons with oral squamous cell carcinoma already have a large lesion at the time of diagnosis.
Nível e natureza do estoque organico de latossolos sob diferentes sistemas de uso e manejo
Freitas, Pedro Luiz de;Blancaneaux, Philippe;Gavinelli, Evelyne;Larré-Larrouy, Marie-Christine;Feller, Christian;
Pesquisa Agropecuária Brasileira , 2000, DOI: 10.1590/S0100-204X2000000100018
Abstract: the important role of organic matter (om) justifies the growing interest for the identification of more efficient use and management systems for the improvement of organic stock in tropical oxisols. the objective of this work was to analyze quantitative and qualitative om stock variations and to characterize organic compartments in a clayey dark-red latosol under situations of natural savanna vegetation (cer), long-term (pal) and degraded grasslands (pad), and fallow conditions (pac). these were compared with crops under conventional plowing (ccl) and zero tillage (pd). small organic stock variation was found in surface layer of studied soils, explained by human disturbance of vegetation in cer, no residue exportation in pd and ccl, and by fallow practice in pac. particle-size fractionating, considering the compartments: plant residues (20-2,000 μm), silt-organic (2-20 μm) and clay-organic (0-2 μm), showed differences in om quality, when comparing similar environmental situations. even with very weak differences, plant residues compartment was an important indicator of organic stock evolution, allowing the characterization of grassland degradation and zero-till effect, when compared with conventional system. pd has favored c stocking in organic-clayey compartment. soils studied soils were distinct from other tropical clayey soils by the high c/n relationship found in 0-20 μm fraction.
Soil organic matter in the granulometric fractions of an oxissol under different uses and management systems/ Matéria organica nas fra es granulométricas de um latossolo vermelho distroférrico sob diferentes sistemas de uso e manejo
Carmen Silvia Vieira Janeiro Neves,Christian Feller,Marie-Christine Larré-Larrouy
Semina : Ciências Agrárias , 2005,
Abstract: Soil organic matter (SOM) is an important component of agriculture sustainability. A clayey oxisol was studied by SOM particle size fractions in a citrus orchard managed (for a 9 year period) with a) Arachis prostrata ground cover; b) spontaneous vegetation controlled by mowing and tillage; c) bare soil. Also the same soil was studied under a 20 year period of annual crops (conventional tillage) and native forest. The orchard ground covers increased the soil C and N stocks when compared to orchard bare soil and annual crops. For all situations, the largest proportion of the SOM was found in the clay fraction (0-2 mm) (35 to 48 % of the total) followed by the silt fraction (2-20mm) (13 to 30 %). Soil C stock was reduced by 33 % with annual crops and by 19 % with bare soil orchard, and was slightly higher with orchard ground covers, when compared to native forest. The carbon losses in the layer 0-10 cm were 23 to 45% comparing the native forest to the crops, being larger with annual crops for 20 years and smaller at orchard with A. prostrata ground cover. The greatest SOM losses were in the 50-2,000 mm (vegetal debris + coarse sand), and fine sand (50-200mm) fractions. The greater recuperation of SOM in the orchard with leguminous cover was in the 20-50mm fraction when compared to annual crops. A matéria organica do solo é um importante componente da sustentabilidade dos sistemas agrícolas. Efetuou-se o fracionamento granulométrico da matéria organica de um Latossolo Vermelho distroférrico argiloso, do Norte do Paraná, sob pomar de citros manejado (por nove anos) com: a) cobertura de leguminosa (Arachis prostrata); b) vegeta o espontanea, mantida por grade e ro adora; c) sem vegeta o intercalar (capinado). O mesmo solo foi estudado também sob culturas anuais (preparo convencional) por vinte anos e floresta nativa. A cobertura com leguminosa e a manuten o da vegeta o espontanea no solo do pomar aumentaram os estoques de C e N do solo em compara o ao sistema sem vegeta o intercalar e ao solo sob culturas anuais. Nos sistemas de uso e manejo avaliados, as maiores propor es dos estoques de C e N do solo encontraram-se associadas à fra o argila (0-2 mm), com 35 a 51 % do total, e à fra o silte (2-20mm), com 13 a 30 %. O estoque de carbono (em Mg C ha-1) na profundidade 0-10 cm foi reduzido em 33 %, com culturas anuais, e em 19 %, no pomar capinado, em rela o à floresta nativa; e foi ligeiramente aumentado nas condi es de pomar com cobertura vegetal. As maiores perdas de C e N ocorreram nas fra es areia grossa + resíduos vegetais (50 - 2.000mm) e ar
Microproteins (miPs) – the next big thing
Stephan Feller
Cell Communication and Signaling , 2012, DOI: 10.1186/1478-811x-10-42
Abstract: In case you do not know what they are, no need to worry: nobody does.However, with proto-genes recently entering the stage [1] it seems just a small step for mankind to assume that those dye fronts of protein gels you have been cutting off and binning for decades now harbour a plethora of precious little gems and thus an amazing potential for discovering exciting regulatory molecules that will bind to proteins etc. to regulate their conformations and activities, their binding partners, their subcellular localisation and so on.They can be expected to steer embryonic development and stem cell differentiation, to play a role in cancers and neurodegenerative diseases and should also make great leads for future drugs. Clearly, miPs are yet another Nobel Prize lurking, and begging for attention.To study them is easy: just mass spec your protein gel dye fronts to death, synthesise all found miP candidates, biotinylate them and go fishing for binding partners. Then introduce your miPs into cells using cell-penetrating shuttle peptides or transfections and watch their interaction partners misbehave in cells. Finally, do miP knock-outs and -ins in animals of your fancy and observe what happens to them. Alternatively, if you do not have access to mass spec-omics, look for short transcribed ORFs of unknown function in the genome, synthesise those ORFs as biotinylated peptides on a vast scale and then go fishing.That is all there is to it really,…so…would someone look, PLEASE.Of course, if you actually find something, we told you so, and we would want to share the glory and the financial rewards; and do not dare to simply call these newly found, super-exciting, sparkling entities merely regulatory peptides or christen them with another boring name like that, or you shall never be grand.Merry Christmas and a healthy, happy and very productive 2013 to all of you.
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