9,039 research outputs found
On the viability of Escherichia coli cells lacking DNA topoisomerase I
No full textCopyright @ 2012 Stockum et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is made available through the Brunel Open Access Publishing Fund.Background: Manipulations of the DNA double helix during replication, transcription and other nucleic acid processing cause a change of DNA topology, which results in torsional stress. This stress is relaxed by DNA topoisomerases, a class of enzymes present in all domains of life. Negatively supercoiled DNA is relaxed by type IA topoisomerases that are widespread in bacteria, archaea and eukaryotes. In Escherichia coli there is conflicting data about viability of ΔtopA cells lacking topoisomerase I. Results: In this study we sought to clarify whether E. coli cells lacking topoisomerase I are viable by using a plasmid-based lethality assay that allowed us to investigate the phenotype of ΔtopA cells without the presence of any compensatory mutations. Our results show that cells lacking topoisomerase I show an extreme growth defect and cannot be cultured without the accumulation of compensatory mutations. This growth defect can be partially suppressed by overexpression of topoisomerase III, the other type IA topoisomerase in E. coli, suggesting that the accumulation of torsional stress is, at least partially, responsible for the lethality of ΔtopA cells. The absence of RNase HI strongly exacerbates the phenotype of cells lacking topoisomerase I, which supports the idea that the processing of RNA:DNA hybrids is vitally important in ΔtopA cells. However, we did not observe suppression of the ΔtopA phenotype by increasing the level of R-loop processing enzymes, such as RNase HI or RecG. Conclusions: Our data show unambiguously that E. coli cells are not viable in the absence of DNA topoisomerase I without the presence of compensatory mutations. Furthermore, our data suggest that the accumulation of R-loops is not the primary reason for the severe growth defect of cells lacking topoisomerase I, which is in contrast to the current literature. Potential reasons for this discrepancy are discussed.The Medical Research Council (grant G0800970) and The Leverhulme Trust
Meeting with the Hebrew author Elias Hurwitz
No full textWhite paper; handpainted; on the reverse of Luftwaffe uniform pattern. Digitized posters are related to the activities of Jewish displaced persons drawn from the Records of Displaced Persons Camps and Centers in Germany (RG 294.2) Italy (RG 294.3) and Austria (RG 294.4) held by YIVO Archives. Please consult the historical note for those record groups for further information.Digital ImageDigital finding aid available
Obituary announcement about author and labor activist Sh. Mendelson
No full textBrown paper; handpainted. Digitized posters are related to the activities of Jewish displaced persons drawn from the Records of Displaced Persons Camps and Centers in Germany (RG 294.2) Italy (RG 294.3) and Austria (RG 294.4) held by YIVO Archives. Please consult the historical note for those record groups for further information.Digital ImageDigital finding aid available
An Empirical Analysis of Amazon EC2 Spot Instance Features Affecting Cost-effective Resource Procurement
No full text<p>This repository contains code and data for the paper "An Empirical Analysis of Amazon EC2 Spot Instance Features Affecting Cost-effective Resource Procurement", by Cheng Wang, Qianlin Liang and Bhuvan Urgaonkar.</p>
Sweeping has no effect on renormalized turbulent viscosity
No full textWe perform renormalization group analysis (RG) of the Navier-Stokes equation in the presence of constant mean velocity field , and show that the renormalized viscosity is unaffected by , thus negating the ``sweeping effect", proposed by Kraichnan [Phys. Fluids {\bf 7}, 1723 (1964)] using random Galilean invariance. Using direct numerical simulation, we show that the correlation functions for and differ from each other, but the renormalized viscosity for the two cases are the same. Our numerical results are consistent with the RG calculations
Organic Donor‐Acceptor Cocrystals for Multiferroic Applications
No full textThe cocrystallization strategy has provided an efficient route to fulfill room temperature magnetoelectricity in single phase owing to the long-range ordered π-π stacking (donor-acceptor assembled) network, long-lived excitons (with μs lifetime), spin orders (±1/2 s pin) and charge transfer (CT) dipoles in the assembled crystal lattice. Together with the superiorities in cost-effectiveness, easy tailoring, light weight, mechanical flexibility and large-scale integration of organic materials, research direction on organic CT multiferroics has become a rising star. In this minireview, we present the recent progress in the fundamental understanding and designing of multiferroics and highlight the advance of organic CT compounds in exploring the magnetoelectronic (ME) coupling effect ranging from experimental to theoretical investigations. Moreover, the challenges existing in this area are also put forward as well as some perspectives for the future development.Ministry of Education (MOE)Accepted versionQ. Z. acknowledges financial support from AcRF Tier 1 (RG 111/17, RG 2/17, RG 113/18, RG 8/16) and Tier 2 (MOE 2017-T2-1-021 and MOE 2018-T2-1-070), Singapore
Dataset to support the journal article '2D super-resolution metrology based on superoscillatory light'
No full textThis dataset is supporting the publication by Yu Wang et al, (2024)
"2D Super-resolution Metrology Based on Superoscillatory Light" in Advanced Science.
This dataset contains data supporting the figures in the article in Excel format:
Fig. 2 data.xlsx
Fig. 3 data.xlsx
Fig. 4 data.xlsx
This work is supported by the UK Engineering and Physical Science Research Council (grants EP/T02643X/1, EP/X03495X/1, EP/X041166/1), the Royal Society (project number RG\R2\232531), the Singapore National Research Foundation (grant No. NRF-CRP23-2019-0006), the Singapore Ministry of Education (grant MOE2016-T3-1-006), and the China Scholarship Council (202006150050; Y. Wang).</span
Organic Cocrystals: Beyond Electrical Conductivities and Field‐Effect Transistors (FETs)
No full textOrganic cocrystals based on noncovalent intermolecular interactions (weak interactions) have aroused interest owing to their unpredicted and versatile chemicophysical properties and their applications. In this Minireview, we highlight recent research on organic cocrystals on reducing the aggregation-caused quenching (ACQ) effect, tuning light emission, ferroelectricity and multiferroics, optical waveguides, and stimuli-responsiveness. We also summarize the progress made in this field including revealing the structure-property relationships and developing unusual properties. Moreover, we provide a discussion on current achievements, limitations and perspectives as well as some directions and inspiration for further investigation on organic cocrystals.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)Accepted versionQ.Z. acknowledges financial support from AcRF Tier 1 (RG111/17, RG 2/17, RG 114/16, RG 8/16) and Tier 2 (MOE2017-T2-1-021 and MOE2018-T2-1-070), Singapore.Q.Z. and Z.C.acknowledge financial support from A*STAR funding (SERC 1528000048), Singapore
A non-classical synthetic strategy for organic mesocrystals
No full textMesocrystals are ordered nanoparticle superstructures, often with internal porosity, which receive much recent research interest in catalysis, energy storage, sensors, and biomedicine area. Understanding the mechanism of synthetic routes is essential for precise control of size and structure that affect the function of mesocrystals. The classical synthetic strategy of mesocrystal was formed via self-assembly of nanoparticles with a faceted inorganic core but a denser (or thicker) shell of organic molecules. However, the potential materials and synthetic handles still need to be explored to meet new applications. In this work, we develop a non-classical synthetic strategy for organic molecules, such as tetrakis (4-hydroxyphenyl) ethylene (TPE-4OH), tetrakis (4-bromophenyl) ethylene (TPE-4Br), and benzopinacole, to produce mesocrystals with composed of microrod arrays via co-solvent-induced crystal transformation. The aligned nanorods are grown epitaxially onto organic microplates, directed by small lattice mismatch between plates and rods. Thus, the present work offers general synthetic handle for establishing well-organized organic mesocrystals.Ministry of Education (MOE)Published versionThe author(s) declare that financial support was received for the research, authorship, and/or publication of this article. This work was supported by the MOE of Singapore (RG 14/13 and RG 5/16), the National Natural Science Foundation of China (No. 21673117), recruitment Program of Global Experts, Jiangsu Provincial Foundation for Specially-Appointed Professor, start-up fund at Nanjing Tech University (39837102), SICAM Fellowship from Jiangsu National Synergetic Innovation Center for Advanced Materials, and Jiangsu Science and Technology Plan (Project No. BK20211258)
An accurate spectral method for the transverse magnetic mode of Maxwell equations in Cole-Cole dispersive media
No full textIn this paper, we propose an accurate numerical means built upon a spectral-Galerkin method in spatial discretization and an enriched multi-step spectral-collocation approach in temporal direction, for the transverse magnetic mode of Maxwell equations in Cole-Cole dispersive media in two-dimensional setting. Our starting point is to derive a new model involving only one unknown field from the original model with three unknown fields: electric, magnetic fields, and the induced electric polarization (described by a global temporal convolution of the electric field). This results in a second-order integral-differential equation with a weakly singular integral kernel expressed by the Mittag-Lefler (ML) function. The most interesting but challenging issue resides in how to efficiently deal with the singularity in time induced by the ML function which is an infinite series of singular power functions with different nature. With this in mind, we introduce a spectral-Galerkin method using Fourier-like basis functions for spatial discretization, leading to a sequence of decoupled temporal integral-differential equations (IDE) with the same weakly singular kernel involving the ML function as the original two-dimensional problem. With a careful study of the regularity of IDE, we incorporate several leading singular terms into the numerical scheme and approximate much regular part of the solution. Then, we solve the IDE by a multi-step well-conditioned collocation scheme together with mapping technique to increase the accuracy and enhance the resolution. We show that such an enriched collocation method is convergent and accurate.Ministry of Education (MOE)The research of author Can Huang is supported by the National Natural Science Foundation of China (no. 11401500, 91630204, 11771363). The research of author Li-Lian Wang is partially supported by Singapore MOE AcRF Tier 1 Grant (RG 15/12) and Singapore MOE AcRF Tier 2 Grants (MOE2017-T2-2-014 and MOE2018-T2-1-059)
- …
