156 research outputs found
Concrete Curing Meter:simple and reliability monitoring of water loss from a wet surface of fresh concrete
The DnaA Tale
More than 50 years have passed since the presentation of the Replicon Model which states that a positively acting initiator interacts with a specific site on a circular chromosome molecule to initiate DNA replication. Since then, the origin of chromosome replication, oriC, has been determined as a specific region that carries sequences required for binding of positively acting initiator proteins, DnaA-boxes and DnaA proteins, respectively. In this review we will give a historical overview of significant findings which have led to the very detailed knowledge we now possess about the initiation process in bacteria using Escherichia coli as the model organism, but emphasizing that virtually all bacteria have DnaA proteins that interacts with DnaA boxes to initiate chromosome replication. We will discuss the dnaA gene regulation, the special features of the dnaA gene expression, promoter strength, and translation efficiency, as well as, the DnaA protein, its concentration, its binding to DnaA-boxes, and its binding of ATP or ADP. Furthermore, we will discuss the different models for regulation of initiation which have been proposed over the years, with particular emphasis on the Initiator Titration Model
Technical Design Report for the PANDA Solenoid and Dipole Spectrometer Magnets
This document is the Technical Design Report covering the two large
spectrometer magnets of the PANDA detector set-up. It shows the conceptual
design of the magnets and their anticipated performance. It precedes the tender
and procurement of the magnets and, hence, is subject to possible modifications
arising during this process.Comment: 10 pages, 14MB, accepted by FAIR STI in May 2009, editors: Inti
Lehmann (chair), Andrea Bersani, Yuri Lobanov, Jost Luehning, Jerzy Smyrski,
Technical Coordiantor: Lars Schmitt, Bernd Lewandowski (deputy),
Spokespersons: Ulrich Wiedner, Paola Gianotti (deputy
Fiber-reinforcement and its effects on the mechanical properties of high-workability concretes manufactured with slag as aggregate and binder
The feasibility of manufacturing fiber-reinforced concretes of high workability through additions of high volumes of electric arc furnace steel slag is evaluated in this paper, using sustainable binders with ground granulated blast furnace slag and ladle furnace slag as a supplementary cementitious material. An extensive experimental plan is developed to test four (self-compacting and pumpable) concrete mixtures, some reinforced with 0.5% vol. of (metallic or synthetic) fibers, in both the fresh and the hardened state. Very specific mechanical aspects are examined, such as the evaluation of both longitudinal and transversal stress-strain compressive behavior, and the assessment of direct tensile strength through the “dog-bone” test. The results of testing this sustainable concrete design yielded suitable mechanical strengths, and good toughness, ductility and impact strength, among other properties. Good adhesion between the fibers and the cementitious matrix was also evident from the fiber pull-out test results. Finally, the overall results confirmed that the use of electric arc furnace steel slag can make a real contribution to construction-sector sustainability and that the mechanical behavior of these novel concretes meets the basic design requirements for use in real structures.Spanish Ministries MCI, AEI, EU and ERDF [RTI2018-097079-B-C31; 10.13039/501100011033; FPU17/03374]; the Junta de Castilla y León (Regional Government) and ERDF [UIC-231, BU119P17]; the Basque Government research group [IT1314-19]; Youth Employment Initiative (JCyL) and ESF [UBU05B_1274]; the University of Burgos [Y135.GI] and the University of the Basque Country [PPGA20/26]. Likewise, our thanks to CHRYSO and HORMOR for supplying the materials used in this research
Influence of surface chemistry on the transport of H atoms in a supersonic hydrogen plasma jet
Cell Size and the Initiation of DNA Replication in Bacteria
In eukaryotes, DNA replication is coupled to the cell cycle through the actions of cyclin-dependent kinases and associated factors. In bacteria, the prevailing view, based primarily from work in Escherichia coli, is that growth-dependent accumulation of the highly conserved initiator, DnaA, triggers initiation. However, the timing of initiation is unchanged in Bacillus subtilis mutants that are ∼30% smaller than wild-type cells, indicating that achievement of a particular cell size is not obligatory for initiation. Prompted by this finding, we re-examined the link between cell size and initiation in both E. coli and B. subtilis. Although changes in DNA replication have been shown to alter both E. coli and B. subtilis cell size, the converse (the effect of cell size on DNA replication) has not been explored. Here, we report that the mechanisms responsible for coordinating DNA replication with cell size vary between these two model organisms. In contrast to B. subtilis, small E. coli mutants delayed replication initiation until they achieved the size at which wild-type cells initiate. Modest increases in DnaA alleviated the delay, supporting the view that growth-dependent accumulation of DnaA is the trigger for replication initiation in E. coli. Significantly, although small E. coli and B. subtilis cells both maintained wild-type concentration of DnaA, only the E. coli mutants failed to initiate on time. Thus, rather than the concentration, the total amount of DnaA appears to be more important for initiation timing in E. coli. The difference in behavior of the two bacteria appears to lie in the mechanisms that control the activity of DnaA
Aβ oligomers peak in early stages of Alzheimer's disease preceding tau pathology
INTRODUCTION
Soluble amyloid beta (Aβ) oligomers have been suggested as initiating Aβ related neuropathologic change in Alzheimer's disease (AD) but their quantitative distribution and chronological sequence within the AD continuum remain unclear.
METHODS
A total of 526 participants in early clinical stages of AD and controls from a longitudinal cohort were neurobiologically classified for amyloid and tau pathology applying the AT(N) system. Aβ and tau oligomers in the quantified cerebrospinal fluid (CSF) were measured using surface-based fluorescence intensity distribution analysis (sFIDA) technology.
RESULTS
Across groups, highest Aβ oligomer levels were found in A+ with subjective cognitive decline and mild cognitive impairment. Aβ oligomers were significantly higher in A+T− compared to A−T− and A+T+. APOE ε4 allele carriers showed significantly higher Aβ oligomer levels. No differences in tau oligomers were detected.
DISCUSSION
The accumulation of Aβ oligomers in the CSF peaks early within the AD continuum, preceding tau pathology. Disease-modifying treatments targeting Aβ oligomers might have the highest therapeutic effect in these disease stages.
Highlights
Using surface-based fluorescence intensity distribution analysis (sFIDA) technology, we quantified Aβ oligomers in cerebrospinal fluid (CSF) samples of the DZNE-Longitudinal Cognitive Impairment and Dementia (DELCODE) cohort
Aβ oligomers were significantly elevated in mild cognitive impairment (MCI)
Amyloid-positive subjects in the subjective cognitive decline (SCD) group increased compared to the amyloid-negative control group
Interestingly, levels of Aβ oligomers decrease at advanced stages of the disease (A+T+), which might be explained by altered clearing mechanism
Physics Performance Report for PANDA: Strong Interaction Studies with Antiprotons
To study fundamental questions of hadron and nuclear physics in interactions
of antiprotons with nucleons and nuclei, the universal PANDA detector will be
built. Gluonic excitations, the physics of strange and charm quarks and nucleon
structure studies will be performed with unprecedented accuracy thereby
allowing high-precision tests of the strong interaction. The proposed PANDA
detector is a state-of-the art internal target detector at the HESR at FAIR
allowing the detection and identification of neutral and charged particles
generated within the relevant angular and energy range. This report presents a
summary of the physics accessible at PANDA and what performance can be
expected.Comment: 216 page
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