4,023 research outputs found
Prospects for measuring coherent neutrino-nucleus elastic scattering at a stopped-pion neutrino source
Rates of coherent neutrino-nucleus elastic scattering at a high-intensity
stopped-pion neutrino source in various detector materials (relevant for novel
low-threshold detectors) are calculated. Sensitivity of a coherent
neutrino-nucleus elastic scattering experiment to new physics is also explored.Comment: 9 pages, 14 figures; minor modifications for publicatio
Force-Feedback High-Speed Atomic Force Microscope for Studying Large Biological Systems
We designed and developed a high-speed atomic force microscope (HSAFM) utilizing a force-feedback scheme for imaging large biological samples. The system collects three simultaneous images: a deflection image, a topographic image, and a force image. We demonstrated that this force-feedback HSAFM is capable of acquiring large topographic images of Escherichia coli biofilms at approximately one frame per second in air. We discuss how the self-actuating cantilever and the piezo tube follow those larger biological topographic features during the HSAFM imaging process
Imaging Stability in Force-Feedback High-Speed Atomic Force Microscopy
We studied the stability of force-feedback high-speed atomic force microscopy (HSAFM) by imaging soft, hard, and biological sample surfaces at various applied forces. The HSAFM images showed sudden topographic variations of streaky fringes with a negative applied force when collected on a soft hydrocarbon film grown on a grating sample, whereas they showed stable topographic features with positive applied forces. The instability of HSAFM images with the negative applied force was explained by the transition between contact and noncontact regimes in the force-distance curve. When the grating surface was cleaned, and thus hydrophilic by removing the hydrocarbon film, enhanced imaging stability was observed at both positive and negative applied forces. The higher adhesive interaction between the tip and the surface explains the improved imaging stability. The effects of imaging rate on the imaging stability were tested on an even softer adhesive Escherichia coli biofilm deposited onto the grating structure. The biofilm and planktonic cell structures in HSAFM images were reproducible within the force deviation less than ~0.5 nN at the imaging rate up to 0.2 s per frame, suggesting that the force-feedback HSAFM was stable for various imaging speeds in imaging softer adhesive biological samples
Co-evolution of mutagenic genome deditors and vertebrate adaptive immunity
The adaptive immune systems of all vertebrates rely on self-DNA mutating enzymes to assemble their antigen receptors in lymphocytes of their two principal lineages. In jawed vertebrates, the RAG1/2 recombinase directs V(D)J recombination of B cell and T cell receptor genes, whereas the activation-induced cytidine deaminase AID engages in their secondary modification. The recombination activating genes (RAG) 1 and 2 evolved from an ancient transposon-encoded genome modifier into a self-DNA mutator serving adaptive immunity; this was possible as a result of domestication, involving several changes in RAG1 and RAG2 proteins suppressing transposition and instead facilitating-coupled cleavage and recombination. By contrast, recent evidence supports the notion that the antigen receptors of T-like and B-like cells of jawless vertebrates, designated variable lymphocyte receptors (VLRs), are somatically assembled through a process akin to gene conversion that is believed to be dependent on the activities of distant relatives of AID, the cytidine deaminases CDA1 and CDA2, respectively. It appears, therefore, that the precursors of AID and CDAs underwent a domestication process that changed their target range from foreign nucleic acids to self-DNA; this multi-step evolutionary process ensured that the threat to host genome integrity was minimized. Here, we review recent findings illuminating the evolutionary steps associated with the domestication of the two groups of genome editors, RAG1/2 and cytidine deaminases, indicating how they became the driving forces underlying the emergence of vertebrate adaptive immune systems
Historical roots of Agile methods: where did âAgile thinkingâ come from?
The appearance of Agile methods has been the most noticeable change to software process thinking in the last fifteen years [16], but in fact many of the âAgile ideasâ have been around since 70âs or even before. Many studies and reviews have been conducted about Agile methods which ascribe their emergence as a reaction against traditional methods. In this paper, we argue that although Agile methods are new as a whole, they have strong roots in the history of software engineering. In addition to the iterative and incremental approaches that have been in use since 1957 [21], people who criticised the traditional methods suggested alternative approaches which were actually Agile ideas such as the response to change, customer involvement, and working software over documentation. The authors of this paper believe that education about the history of Agile thinking will help to develop better understanding as well as promoting the use of Agile methods. We therefore present and discuss the reasons behind the development and introduction of Agile methods, as a reaction to traditional methods, as a result of people's experience, and in particular focusing on reusing ideas from histor
The 0nbb-decay nuclear matrix elements with self-consistent short-range correlations
A self-consistent calculation of nuclear matrix elements of the neutrinoless
double beta decays (0nbb) of 76Ge, 82Se, 96Zr, 100Mo, 116Cd, 128Te, 130Te and
130Xe is presented in the framework of the renormalized quasiparticle random
phase approximation (RQRPA) and the standard QRPA. The pairing and residual
interactions as well as the two-nucleon short-range correlations are for the
first time derived from the same modern realistic nucleon-nucleon potentials,
namely from charge-dependent Bonn potential (CD-Bonn) and the Argonne V18
potential. In a comparison with the traditional approach of using the
Miller-Spencer Jastrow correlations matrix elements for the 0nbb-decay are
obtained, which are larger in magnitude. We analyze the differences among
various two-nucleon correlations including those of the unitary correlation
operator method (UCOM) and quantify the uncertainties in the calculated
0nbb-decay matrix elements.Comment: 11 pages, 5 figure
Coil-to-Bridge Transitions of Self-Assembled Water Chains Observed in a Nanoscopic Meniscus
Ten downward portions in the large oscillatory forceâdistance curve reported earlier are analyzed to understand a nanoscale water meniscus confined between a sharp probe and a flat substrate in air. The sigmoidal shape of each portion leads to the assumption that the meniscus is made up of n independent transitions of two states: one for a coil state and the other for a bridge state. The analysis reveals that each downward portion occurs due to a coil-to-bridge transition of n self-assembled water chains whose length ranges between 197 and 383 chain units. The transition provides novel insights into waterâs unique properties like high surface tension and the long-range condensation distances
Evolutionary transition from degenerate to nonredundant cytokine signaling networks supporting intrathymic T cell development
In mammals, T cell development critically depends on the IL-7 cytokine signaling pathway. Here we describe the identification of the zebrafish ortholog of mammalian IL-7 based on chromosomal localization, deduced protein sequence, and expression patterns. To examine the biological role of il7 in teleosts, we generated an il7 allele lacking most of its coding exons using CRISPR/Cas9-based mutagenesis. il7-deficient animals are viable and exhibit no obvious signs of immune disorder. With respect to intrathymic T cell development, il7 deficiency is associated with only a mild reduction of thymocyte numbers, contrasting with a more pronounced impairment of T cell development in il7r-deficient fish. Genetic interaction studies between il7 and il7r mutants, and il7 and crlf2(tslpr) mutants suggest the contribution of additional, as-yet unidentified cytokines to intrathymic T cell development. Such activities were also ascertained for other cytokines, such as il2 and il15, collectively indicating that in contrast to the situation in mammals, T cell development in the thymus of teleosts is driven by a degenerate multicomponent network of Îłc cytokines; this explains why deficiencies of single components have little detrimental effect. In contrast, the dependence on a single cytokine in the mammalian thymus has catastrophic consequences in cases of congenital deficiencies in genes affecting the IL-7 signaling pathway. We speculate that the transition from a degenerate to a nonredundant cytokine network supporting intrathymic T cell development emerged as a consequence of repurposing evolutionarily ancient constitutive cytokine pathways for regulatory functions in the mammalian peripheral immune system
The 511 keV emission from positron annihilation in the Galaxy
The first gamma-ray line originating from outside the solar system that was
ever detected is the 511 keV emission from positron annihilation in the Galaxy.
Despite 30 years of intense theoretical and observational investigation, the
main sources of positrons have not been identified up to now. Observations in
the 1990's with OSSE/CGRO showed that the emission is strongly concentrated
towards the Galactic bulge. In the 2000's, the SPI instrument aboard ESA's
INTEGRAL gamma-ray observatory allowed scientists to measure that emission
across the entire Galaxy, revealing that the bulge/disk luminosity ratio is
larger than observed in any other wavelength. This mapping prompted a number of
novel explanations, including rather "exotic ones (e.g. dark matter
annihilation). However, conventional astrophysical sources, like type Ia
supernovae, microquasars or X-ray binaries, are still plausible candidates for
a large fraction of the observed total 511 keV emission of the bulge. A closer
study of the subject reveals new layers of complexity, since positrons may
propagate far away from their production sites, making it difficult to infer
the underlying source distribution from the observed map of 511 keV emission.
However, contrary to the rather well understood propagation of high energy
(>GeV) particles of Galactic cosmic rays, understanding the propagation of low
energy (~MeV) positrons in the turbulent, magnetized interstellar medium, still
remains a formidable challenge. We review the spectral and imaging properties
of the observed 511 keV emission and we critically discuss candidate positron
sources and models of positron propagation in the Galaxy.Comment: 62 pages, 35 figures. Review paper to appear in Reviews of Modern
Physic
CHOLINE-UTILIZING MICROBLAL STRAINS FOR BIOLOGICALLY CONTROLLING FUSARIUM HEAD BLIGHT
Three choline utilizing strains of microorganisms isolated from the anthers of wheat, Aureobasidium pullulans strainAS 55.2, Arthrobacter species strain OH 221.3, and Pseudomonas species strain AS 64.4, are superior antagonists of F. graminearum. These microorganisms are effective for suppression and control of FHB in cereals, particularly in wheat and barley
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