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排序方式: 共有1349条查询结果,搜索用时 15 毫秒
41.
Francieli Tiecher Denise Carpena Coitinho Dal Molin Márcia Elisa Boscato Gomes Nicole Pagan Hasparyk Paulo José Meleragno Monteiro 《Cement and Concrete Composites》2012,34(10):1130-1140
Mesostasis material present in the interstices of volcanic rocks is the main cause of the alkali-aggregate reaction (AAR) in concretes made with these rock aggregates. Mesostasis often is referred to as volcanic glass, because it has amorphous features when analyzed by optical microscopy. However, this study demonstrates that mesostasis in the interstitials of volcanic rocks most often consists of micro to cryptocrystalline mineral phases of quartz, feldspars, and clays. Mesostasis has been identified as having different characteristics, and, thus, this new characterization calls for a re-evaluation of their influence on the reactivity of the volcanic rocks. The main purpose of this study is to correlate the characteristics of mesostasis with the AAR in mortar bars containing basalts and rhyolites. 相似文献
42.
Clara A. Ferraz Dr. Nicole G. H. Leferink Iaroslav Kosov Prof. Dr. Nigel S. Scrutton 《Chembiochem : a European journal of chemical biology》2021,22(13):2325-2334
Linalool is a monoterpenoid used as a fragrance ingredient, and is a promising source for alternative fuels. Synthetic biology offers attractive alternative production methods compared to extraction from natural sources and chemical synthesis. Linalool/nerolidol synthase (bLinS) from Streptomyces clavuligerus is a bifunctional enzyme, producing linalool as well as the sesquiterpenoid nerolidol when expressed in engineered Escherichia coli harbouring a precursor terpenoid pathway such as the mevalonate (MVA) pathway. Here we identified two residues important for substrate selection by bLinS, L72 and V214, where the introduction of bulkier residues results in variants with reduced nerolidol formation. Terpenoid production using canonical precursor pathways is usually limited by numerous and highly regulated enzymatic steps. Here we compared the canonical MVA pathway to the non-canonical isopentenol utilization (IU) pathway to produce linalool using the optimised bLinS variant. The IU pathway uses isoprenol and prenol to produce linalool in only five steps. Adjusting substrate, plasmid system, inducer concentration, and cell strain directs the flux towards monoterpenoids. Our integrated approach, combining enzyme engineering with flux control using the artificial IU pathway, resulted in high purity production of the commercially attractive monoterpenoid linalool, and will guide future efforts towards efficient optimisation of terpenoid production in engineered microbes. 相似文献
43.
We present and investigate techniques for optimizing particle dispersions in all kinds of Reynolds number flows. In particular,
we show the range of application, power and efficiency of space mapping approaches that are based on a hierarchy of models
ranging from a complex (fine, accurate, costly) to simple (coarse, rough, cheap) model. Space mapping turns out to be a reasonable
approximation to optimal control and a competitive alternative to instantaneous control regarding speed and memory demands
when dealing with complex, non-stationary problems. Moreover it allows the easy and efficient treatment of stochastic design
problems. To control random particle dynamics in a turbulent flow, we suggest a Monte-Carlo aggressive space mapping algorithm
which yields very convincing numerical results. 相似文献
44.
Nick Gravish Mateo Garcia Nicole Mazouchova Laura Levy Paul B. Umbanhowar Michael A. D. Goodisman Daniel I. Goldman 《Journal of the Royal Society Interface》2012,9(77):3312-3322
Social insects work together to complete tasks. However, different individuals within a colony may vary in task proficiency. We investigated if fire ant (Solenopsis invicta) worker body size influenced the ability to construct tunnels—a key component of subterranean nests. We monitored excavation by worker groups in a substrate of small wetted glass particles in quasi-two-dimensional arenas. Morphological and network features of the tunnel system were measured. Total tunnel area did not differ significantly between groups of large and small workers, although the tunnel area of control sized workers was significantly larger than that of large workers. Moreover, large workers created wider but shorter tunnels, with slower growth rate of tunnel number. However, edge–vertex scaling and degree distribution of the tunnel network were similar across all treatments. In all cases, the amount of excavated material was correlated with the number of active workers. Our study reveals that morphological features of excavated tunnels show modest variation when constructed by workers of varying sizes, but topological features associated with the tunnel network are conserved. These results suggest that important behavioural aspects of tunnel construction—and thus nest building—are similar among morphologically distinct members of fire ant societies. 相似文献
45.
Alistair Wood Yuval Gurfinkel Nicole Polain Wesley Lamont Sarah Lyn Rea 《International journal of molecular sciences》2021,22(9)
Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are neurodegenerative disorders that exist on a disease spectrum due to pathological, clinical and genetic overlap. In up to 97% of ALS cases and ~50% of FTLD cases, the primary pathological protein observed in affected tissues is TDP-43, which is hyperphosphorylated, ubiquitinated and cleaved. The TDP-43 is observed in aggregates that are abnormally located in the cytoplasm. The pathogenicity of TDP-43 cytoplasmic aggregates may be linked with both a loss of nuclear function and a gain of toxic functions. The cellular processes involved in ALS and FTLD disease pathogenesis include changes to RNA splicing, abnormal stress granules, mitochondrial dysfunction, impairments to axonal transport and autophagy, abnormal neuromuscular junctions, endoplasmic reticulum stress and the subsequent induction of the unfolded protein response. Here, we review and discuss the evidence for alterations to these processes that have been reported in cellular and animal models of TDP-43 proteinopathy. 相似文献
46.
A method using normal phase high performance liquid chromatography for the analysis of olefins and diolefins in cracked petroleum samples is proposed and validated in this work. A silver-impregnated silica column is used to separate olefin and diolefin species, resulting in accurate quantification of both group-types. Separations are completed using an isocratic hexane mobile phase, with no sample clean up or backflushing required. Results from the analysis of 11 model compounds are shown, as well as quantification data for four representative samples; figures of merit are also described. 相似文献
47.
48.
Dr. Johannes Broichhagen Dr. Nicole Kilian 《Chembiochem : a European journal of chemical biology》2021,22(13):2219-2236
Parasitic diseases like malaria tropica have been shaping human evolution and history since the beginning of mankind. After infection, the response of the human host ranges from asymptomatic to severe and may culminate in death. Therefore, proper examination of the parasite's biology is pivotal to deciphering unique molecular, biochemical and cell biological processes, which in turn ensure the identification of treatment strategies, such as potent drug targets and vaccine candidates. However, implementing molecular biology methods for genetic manipulation proves to be difficult for many parasite model organisms. The development of fast and straightforward applicable alternatives, for instance small-molecule probes from the field of chemical biology, is essential. In this review, we will recapitulate the highlights of previous molecular and chemical biology approaches that have already created insight and understanding of the malaria parasite Plasmodium falciparum. We discuss current developments from the field of chemical biology and explore how their application could advance research into this parasite in the future. We anticipate that the described approaches will help to close knowledge gaps in the biology of P. falciparum and we hope that researchers will be inspired to use these methods to gain knowledge – with the aim of ending this devastating disease. 相似文献
49.
Maurits Kaptein Deonne Castaneda Nicole Fernandez Clifford Nass 《Journal of Computer-Mediated Communication》2014,19(3):342-357
The feeling of connectedness experienced in computer‐mediated relationships can be explained by the similarity‐attraction effect (SAE). Though SAE is well established in psychology, the effects of some types of similarity have not yet been explored. In 2 studies, we demonstrate similarity‐attraction based on the timing of activities—“when‐similarity.” We describe a novel experimental paradigm for manifesting when‐similarity while controlling for the activities being performed (what‐similarity). Study 1 (N = 24) shows when‐similarity attraction in the evaluation of connectedness with others. Study 2 (N = 42) identifies an interaction between who‐similarity—similarity in personal backgrounds—and when‐similarity. Both studies show that real‐time computer‐mediated interaction can lead to greater feelings of connectedness between people when there is an opportunity to discover when‐similarity. 相似文献
50.