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  • 1
    Publication Date: 2015-08-13
    Description: The plasmonic responses of silver nanoparticle grating structures of different periods made on silver halide based electron microscope film are investigated. Raster scan of the conventional scanning electron microscope (SEM) is used to carry out electron beam lithography for fabricating the plasmonic nanoparticle grating (PNG) structures. Morphological characterization of the PNG structures, carried out by the SEM and the atomic force microscope, indicates that the depth of the groove decreases with a decrease in the grating period. Elemental characterization performed by the energy dispersive spectroscopy and the x-ray diffraction shows the presence of nanoparticles of silver in the PNG grating. The optical characterization of the gratings shows that the localized surface plasmon resonance peak shifts from 366 to 378 nm and broadens with a decrease in grating period from 10 to 2.5  μ m. The surface enhanced Raman spectroscopy of the Rhodamine-6G dye coated PNG structure shows the maximum enhancement by two orders of magnitude in comparison to the randomly distributed silver nanoparticles having similar size and shape as the PNG structure.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 2
    Publication Date: 2015-05-03
    Description: We describe a simple strategy to control mRNA translation in both prokaryotic and eukaryotic cells which relies on a unique protein–RNA interaction. Specifically, we used the Pumilio/FBF (PUF) protein to repress translation by binding in between the ribosome binding site (RBS) and the start codon (in Escherichia coli ), or by binding to the 5' untranslated region of target mRNAs (in mammalian cells). The design principle is straightforward, the extent of translational repression can be tuned and the regulator is genetically encoded, enabling the construction of artificial signal cascades. We demonstrate that this approach can also be used to regulate polycistronic mRNAs; such regulation has rarely been achieved in previous reports. Since the regulator used in this study is a modular RNA-binding protein, which can be engineered to target different 8-nucleotide RNA sequences, our strategy could be used in the future to target endogenous mRNAs for regulating metabolic flows and signaling pathways in both prokaryotic and eukaryotic cells.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 3
    Publication Date: 2015-10-23
    Description: Ultraviolet photoelectron spectroscopy is carried out to measure the energy discontinuity at the interface of p -type Na-doped MgZnO (NMZO)/ n -type Ga-doped ZnO (GZO) heterojunction grown by dual ion beam sputtering. The offset values at valence band and conduction band of NMZO/GZO heterojunction are calculated to be 1.93 and −2.36 eV, respectively. The p-type conduction in NMZO film has been confirmed by Hall measurement and band structure. Moreover, the effect of Ar + ion sputtering on the valence band onset values of NMZO and GZO thin films has been investigated. This asymmetric waveguide structure formed by the lower refractive index of GZO than that of NMZO indicates that easy extraction of photons generated in GZO through the NMZO layer into free space. The asymmetric waveguide structure has potential applications to produce ZnO-based light emitters with high extraction efficiency.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 4
    Publication Date: 2016-06-16
    Description: The crystalline, electrical, morphological, optical properties and plasmonic behaviour of Ga doped MgZnO (GMZO) thin films grown at different substrate temperatures (200–600 °C) by a dual ion beam sputtering (DIBS) system are investigated. Transmittance value of more than ∼94% in 400–1000 nm region is observed for all GMZO films. The particle plasmon features can be detected in the absorption coefficient spectra of GMZO grown at 500 and 600 °C in the form of a peak at ∼4.37 eV, which corresponds to a plasmon resonance peak of nanoclusters formed in GMZO. The presence of such plasmonic features is confirmed by ultraviolet photoelectron spectroscopy measurements. The values of particle plasmon resonance energy of various nanoclusters are in the range of solar spectrum, and these can easily be tuned and excited at the desirable wavelengths while optimizing the efficiency of solar cells (SCs) by simple alteration of DIBS growth temperature. These nanoclusters are extremely promising to enhance the optical scattering and trapping of the incident light, which increases the optical path length in the absorber layer of cost-effective SCs and eventually increases its efficiency.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 5
    Publication Date: 2012-06-20
    Description: The anthrax lethal toxin (LT) enters host cells and enzymatically cleaves MAPKKs or MEKs. How these molecular events lead to death from anthrax remains poorly understood, but published reports suggest a direct effect of LT on vascular permeability. We have found that LT challenge in mice disrupts signaling through Tie-2, a tonically activated receptor tyrosine kinase in the endothelium. Genetic manipulations favoring Tie-2 activation enhanced interendothelial junctional contacts, prevented vascular leakage, and promoted survival following a lethal dose of LT. Cleavage of MEK1/2 was necessary for LT to induce endothelial barrier dysfunction, and activated Tie-2 signaled through the uncleaved fraction of MEKs to prevent LT’s effects on the endothelium. Finally, primates infected with toxin-secreting Bacillus anthracis bacilli developed a rapid and marked imbalance in the endogenous ligands that signal Tie-2, similar to that seen in LT-challenged mice. Our results show that B. anthracis LT blunts signaling through Tie-2, thereby weakening the vascular barrier and contributing to lethality of the disease. Measurement of circulating Tie-2 ligands and manipulation of Tie-2 activity may represent future prognostic and therapeutic avenues for humans exposed to B. anthracis.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 6
    Publication Date: 2010-11-26
    Description: Ghrelin is a gastric peptide hormone that stimulates weight gain in vertebrates. The biological activities of ghrelin require octanoylation of the peptide on Ser(3), an unusual posttranslational modification that is catalyzed by the enzyme ghrelin O-acyltransferase (GOAT). Here, we describe the design, synthesis, and characterization of GO-CoA-Tat, a peptide-based bisubstrate analog that antagonizes GOAT. GO-CoA-Tat potently inhibits GOAT in vitro, in cultured cells, and in mice. Intraperitoneal administration of GO-CoA-Tat improves glucose tolerance and reduces weight gain in wild-type mice but not in ghrelin-deficient mice, supporting the concept that its beneficial metabolic effects are due specifically to GOAT inhibition. In addition to serving as a research tool for mapping ghrelin actions, GO-CoA-Tat may help pave the way for clinical targeting of GOAT in metabolic diseases.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068526/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3068526/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barnett, Brad P -- Hwang, Yousang -- Taylor, Martin S -- Kirchner, Henriette -- Pfluger, Paul T -- Bernard, Vincent -- Lin, Yu-yi -- Bowers, Erin M -- Mukherjee, Chandrani -- Song, Woo-Jin -- Longo, Patti A -- Leahy, Daniel J -- Hussain, Mehboob A -- Tschop, Matthias H -- Boeke, Jef D -- Cole, Philip A -- P01 CA016519/CA/NCI NIH HHS/ -- P01 CA016519-35/CA/NCI NIH HHS/ -- P30 DK079637/DK/NIDDK NIH HHS/ -- P60 DK079637/DK/NIDDK NIH HHS/ -- P60 DK079637-05/DK/NIDDK NIH HHS/ -- R01 DK081472/DK/NIDDK NIH HHS/ -- R01 DK081472-01A1/DK/NIDDK NIH HHS/ -- R01 DK081472-02/DK/NIDDK NIH HHS/ -- R01 DK081472-03/DK/NIDDK NIH HHS/ -- R01 GM062437/GM/NIGMS NIH HHS/ -- R01 GM062437-04/GM/NIGMS NIH HHS/ -- R01 GM062437-11/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2010 Dec 17;330(6011):1689-92. doi: 10.1126/science.1196154. Epub 2010 Nov 18.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21097901" target="_blank"〉PubMed〈/a〉
    Keywords: Acylation ; Acyltransferases/*antagonists & inhibitors ; Animals ; Cell Survival/drug effects ; Drug Design ; Enzyme Inhibitors/chemical synthesis/*pharmacology/toxicity ; Ghrelin/deficiency/genetics/*metabolism ; Glucose/*metabolism ; Glucose Tolerance Test ; HeLa Cells ; Homeostasis ; Humans ; Insulin/metabolism ; Ion Channels/metabolism ; Islets of Langerhans/drug effects/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Knockout ; Mitochondrial Proteins/metabolism ; Peptides/chemical synthesis/*pharmacology/toxicity ; Weight Gain/*drug effects
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Publication Date: 2016-04-27
    Description: The valence band offset value of 2.3 ± 0.2 eV at epitaxial NiO/Al 2 O 3 heterojunction is determined from photoelectron spectroscopy experiments. Pulsed laser deposited thin film of NiO on Al 2 O 3 substrate is epitaxially grown along [111] direction with two domain structures, which are in-plane rotated by 60° with respect to each other. Observation of Pendellosung oscillations around Bragg peak confirms high interfacial and crystalline quality of NiO layer deposited on Al 2 O 3 substrate. Surface related feature in Ni 2p 3/2 core level spectra along with oxygen K-edge soft X-ray absorption spectroscopy results indicates that the initial growth of NiO on Al 2 O 3 substrate is in the form of islands, which merge to form NiO layer for the larger coverage. The value of conduction band offset is also evaluated from the measured values of band gaps of NiO and Al 2 O 3 layers. A type-I band alignment at NiO and Al 2 O 3 heterojunction is also obtained. The determined values of band offsets can be useful in heterojunction based light emitting devices.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 8
    Publication Date: 2017-07-07
    Description: The superconductor iron selenide (FeSe) is of intense interest owing to its unusual nonmagnetic nematic state and potential for high-temperature superconductivity. But its Cooper pairing mechanism has not been determined. We used Bogoliubov quasiparticle interference imaging to determine the Fermi surface geometry of the electronic bands surrounding the = (0, 0) and X = (/ a Fe , 0) points of FeSe and to measure the corresponding superconducting energy gaps. We show that both gaps are extremely anisotropic but nodeless and that they exhibit gap maxima oriented orthogonally in momentum space. Moreover, by implementing a novel technique, we demonstrate that these gaps have opposite sign with respect to each other. This complex gap configuration reveals the existence of orbital-selective Cooper pairing that, in FeSe, is based preferentially on electrons from the d yz orbitals of the iron atoms.
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
    Publication Date: 1983-02-25
    Description: There is evidence that the mammalian female genital tract is capable of responding immunologically when challenged with alloantigens. The antigenic properties of male gametes have been well delineated. However, it is only rarely that a female mammal ever responds immunologically to the male gametic antigens as a result of coitus. When a proposed mechanism of suppression of antigenicity of epididymal spermatozoa was tested experimentally, the results indicated that two proteins (uteroglobin and transglutaminase) present in the prostate may be responsible for suppressing sperm antigenicity in the rabbit.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mukherjee, D C -- Agrawal, A K -- Manjunath, R -- Mukherjee, A B -- New York, N.Y. -- Science. 1983 Feb 25;219(4587):989-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6130601" target="_blank"〉PubMed〈/a〉
    Keywords: Acyltransferases/*immunology/metabolism ; Animals ; Epididymis/immunology ; Female ; Glycoproteins/*immunology ; *Immune Tolerance ; Lymphocyte Activation ; Male ; Rabbits ; Semen/enzymology/*immunology ; Spermatozoa/*immunology ; Transglutaminases ; Uteroglobin/*immunology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 2018-04-07
    Description: Despite promising applications of two-dimensional (2D) materials, one major concern is their propensity to fail in a brittle manner, which results in a low fracture toughness causing reliability issues in practical applications. We show that this limitation can be overcome by using functionalized graphene multilayers with fracture toughness ( J integral) as high as ~39 J/m 2 , measured via a microelectromechanical systems–based in situ transmission electron microscopy technique coupled with nonlinear finite element fracture analysis. The measured fracture toughness of functionalized graphene multilayers is more than two times higher than graphene (~16 J/m 2 ). A linear fracture analysis, similar to that previously applied to other 2D materials, was also conducted and found to be inaccurate due to the nonlinear nature of the stress-strain response of functionalized graphene multilayers. A crack arresting mechanism of functionalized graphene multilayers was experimentally observed and identified as the main contributing factor for the higher fracture toughness as compared to graphene. Molecular dynamics simulations revealed that the interactions among functionalized atoms in constituent layers and distinct fracture pathways in individual layers, due to a random distribution of functionalized carbon atoms in multilayers, restrict the growth of a preexisting crack. The results inspire potential strategies for overcoming the relatively low fracture toughness of 2D materials through chemical functionalization.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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