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Nanoscale imaging of electric pathways in epitaxial graphene nanoribbons

2009年

作者： harold j. bruyere j..

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Nano Research 2019年第7期12卷 1697-1702页

作者： j.hannes Aproj.nz Pantelis Bampoulis Alexei A. Zakharov harold j. W. Zandvliet Christoph Tegenkamp Institut fur Physik Technische Universitat ChemnitzChemnitz 09126Germany Institutfur Festkoperphysik Leibniz Universitat HannoverHannover 30167Germany Physics of Interfaces and Nanomaterials MESA+ Institute for NanotechnologyUniversity of TwenteEnschede 7522 NHThe Netherlands MAX TV Laboratory and Lund University Lund 22100Sweden

Graphene nanoribbons (GNRs) are considered as maj.r building blocks in future carbon-based *** electronic performance of graphene nanostructures is essentially influenced and determined by their edge termination and their supporting *** particular,semi-conducting,as well as metallic GNRs,can be fabricated by choosing the proper template which is favorable for device architecture *** study highlights the impact of microscopic details of the environment of the GNRs on the charge transport in *** means of lateral force,conductive atomic force and nanoprobe measurements,we explore the charge propagation in both zig-zag and armchair GNRs epitaxially grown on SiC *** directly image transport channels on the nanoscale and identify SiC substrate steps and nano-instabilities of SiC facets as dominant charge scattering centers.

关键词： sidewall graphene nanoribbons nanoprobe conductive-AFM nanoscale transport

On the mystery of the absence of a spin-orbit gap in scanning tunneling microscopy spectra of germanene

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j.urnal of Semiconductors 2020年第8期41卷 59-62页

作者： Carolien Castenmiller harold j.W.Zandvliet Physics of Interfaces and Nanomaterials&MESA+Institute for Nanotechnology University of Twente7500AE EnschedeThe Netherlands

Germanene,the germanium analogue of graphene,shares many properties with its carbon *** materials are two-dimensional materials that host Dirac *** are,however,also a few important differences between these two materials:(1)graphene has a planar honeycomb lattice,whereas germanene’s honeycomb lattice is buckled and(2)the spin-orbit gap in germanene is predicted to be about three orders of magnitude larger than the spin-orbit gap in graphene(24 meV for germanene versus 20μeV for graphene).Surprisingly,scanning tunneling spectra recorded on germanene layers synthesized on different substrates do not show any sign of the presence of a spin-orbit *** date the exact origin of the absence of this spin-orbit gap in the scanning tunneling spectra of germanene has remained a *** this work we show that the absence of the spin-orbit gap can be explained by germanene’s exceptionally low work function of only 3.8 *** difference in work function between germanene and the scanning tunneling microscopy tip(the work functions of most commonly used STM tips are in the range of 4.5 to 5.5 eV)gives rise to an electric field in the tunnel *** electric field results in a strong suppression of the size of the spin-orbit gap.

关键词： germanene spin-orbit coupling quantum spin Hall effect two-dimensional Dirac material

Water Vapor Variability in the Tropical Western Pacific from 20-year Radiosonde Data

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Advances in Atmospheric Sciences 2001年第5期18卷 752-766页

作者： j.nhong Wang, harold L. Cole and David j. Carlson National Center for Atmospheric Research P. O, Box 3000,Boulder, CO 80307 National Center for Atmospheric Research Boulder USA

The 20-year (1976-1995) daily radinsonde data at 17 stations in the tropical western Pacific was ana- lyzed. The analysls shows that the atmosphere is more humid in a warmer climate on seasonal,inter-annual and long-term (20-year) time scales, implying a positive water vapor feedback The vertlcal structure of the long-term trends in relative humidity (RH) is distinct from that on short-term (seasonal and inter-annual) time scales, suggesting that observed water vapor changes on short time scales could not be considered as a surrogate of long-term climate change. The increasing trend of RH (3%-5% / decade) in the upper troposphere is stronger than that in the lower troposphere (1 %-2% / decade). Such verthal structure would amplify positive water vapor feedback in comparison to the common assumption of constant RH changes vertically. The empicical orthogonal function (EOF) analysis of vertical structure of RH varmtions shows distinct features of the vert1cal structure of the first three EOFs. The first three EOFs are optimal for repre- sentation of water vapor profiles and provide some hints on physical mechanisms respons1ble for observed humidity variability. Vaisala radiosondes were used at nine stations, and VIZ radiosondes used at other eight stations The Vaisala data are corrected for temperature-dependence error using the correction siheme developed by NCAR / ATD and Vaisala. The comparison of Vaisala and VIZ data shows that the VIZ-measured RHs after October 1993 have a moist bias of - 10% at RHs < 20%. During 1976-1995, several changes in- cluding both instruments and reporting practice have been made at Vaisala stations and introduce errors to long-term RH variations.

关键词： Water vapor Radiosonde

Surface morphology-optical properties relationship in thermochromic VO_(2) thin films obtained by air oxidation of vanadium nitride

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j.urnal of Materiomics 2021年第4期7卷 657-664页

作者： A.C.García-Wong D.Pilloud S.bruyere D.Mangin S.Migot j.F.Pierson F.Capon Institut j.an Lamour(UMR CNRS 7198) Universite de Lorraine54000NancyFrance

In this paper,vanadium nitride(VN)thin films have been deposited on Al substrates by reactive magnetron *** VO_(2) films have been obtained by air oxidation of VN samples performed at three temperatures(450,525 and 550℃)at various durations(lower than 50 min).X-ray diffraction and Raman spectrometry of the VN oxidized films indicate that VO_(2) and V2O5 are the only phases produced during the oxidation *** dioxide is the first oxide *** coexists with VN in a long period at 450℃ or suddenly disappears at 525 and 550℃.Whatever the temperature,V2O5 is exclusively detected after the total oxidation of *** oxide is detrimental to the thermochromic performance of *** emissivity-switching properties of the oxidized films were analyzed by infrared camera in the 7.5e13 mm *** comparison among all the samples exhibiting a thermochromic behavior shows that the maximum emissivity switch is independent of the oxidation temperature and the surface morphology of the *** results could open a new strategy in the investigation of VN oxidation as a method to obtain VO_(2),along with an insight into the correlation between surface morphology and optical properties.

关键词： Vanadium dioxide Vanadium nitride Thermochromism Optical properties Air oxidation

Context-free Grammars for Triangular Arrays

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Acta Mathematica Sinica,English Series 2015年第3期31卷 445-455页

作者： Robert X.j.HAO Larry X.W.WANG harold R.L.YANG Center for Combinatorics LPMC-TJKLC Nankai University

We consider context-free grammars of the form G = {f → f^b1＋b2＋1g^a1＋a2, g → f^b1 g^a1＋1},where ai and bi are integers sub j.ct to certain positivity conditions. Such a grammar G gives rise to triangular arrays {T（n, k）}0≤k≤n satisfying a three-term recurrence relation. Many combinatorial sequences can be generated in this way. Let Tn （x） =∑k=0^n T（n, k）x^k. Based on the differential operator with respect to G, we define a sequence of linear operators Pn such that Tn＋1（x） = Pn（Tn（x））. Applying the characterization of real stability preserving linear operators on the multivariate polynomials due to Borcea and Br？ndén, we obtain a necessary and sufficient condition for the operator Pn to be real stability preserving for any n. As a consequence, we are led to a sufficient condition for the real-rootedness of the polynomials defined by certain triangular arrays, obtained by Wang and ***, as special cases we obtain grammars that lead to identities involving the Whitney numbers and the Bessel numbers.

关键词： Context-free grammar stable polynomials real-rootedness Bessel numbers Whitneynumbers

Molecular evolution of Na^(+) channels in teleost fishes

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Integrative Zoology 2009年第1期4卷 64-74页

作者： harold H.ZAKON Manda C.j.ST Derrick j.ZWICKL Ying LU David M.HILLIS Section of Neurobiology Section of Integrative Biology The University of TexasAustinTXUSA

Voltage-dependent sodium channels are critical for electrical *** possess a single sodium channel gene;two rounds of genome duplication early in vertebrates increased the number to *** the teleost-tetrapod split,independent gene duplications in each lineage have further increased the number of sodium channel genes to 10 in tetrapods and 8 in *** we review how the occurrence of multiple sodium channel paralogs has influenced the evolutionary history of three groups of fishes:pufferfish,gymnotiform and mor-myriform electric ***(tetraodontidae)produce a neurotoxin,tetrodotoxin,that binds to and blocks the pore of sodium *** evolved resistance to their own toxins by amino acid substitutions in the pore of their sodium *** substitutions had to occur in parallel across multiple paralogs for organismal re-sistance to *** and mormyriform fishes independently evolved electric organs to generate elec-tricity for communication and obj.ct *** sodium channel genes are expressed in muscle in most *** both groups of weakly electric fishes,one gene lost its expression in muscle and became compartmen-talized in the evolutionary novel electric organ,which is a muscle *** gene then evolved at elevated rates,whereas the gene that is still expressed in muscle does not show elevated rates of *** the electric organ-expressing gene,amino acid substitutions occur in parts of the channel involved in determining how long the channel will be open or *** enhanced rate of sequence evolution of this gene likely underlies the spe-cies-level variations in the electric signal.

关键词： electric fish molecular evolution pufferfish sodium channels tetrodotoxin.

Effect of estrogen on manganese-induced toxicity on embryonic astrocytes

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Advances in Bioscience and Biotechnology 2013年第10期4卷 9-15页

作者： Tyler T. Huynh Kimberly j. Baker harold L. Komiskey Department of Biomedical Sciences Philadelphia College of Osteopathic Medicine-GA Campus Suwanee USA

Manganese (Mn) is a natural trace metal that is essential for many physiological functions in the human body. Astrocytes in the central nervous system are susceptible reservoirs for Mn accumulation. Estrogen, a steroidal hormone, has been shown to mitigate Mn-induced toxicity in cultures of postnatal astrocytes. However, differences in expression/inducibility of glutamate transporters and glutamine synthetase, transmitters, and the natural gonadal steroids and their receptors are known to occur in astrocyte cultures derived from various stages of fetal and postnatal development. Cultures of embryonic (E18) hippocampal astrocytes were examined in this study for the ability of 17 β-estradiol (E2) to protect them from Mn toxicity by up regulating gene expression of a glutamate transporter. Primary rat hippocampal astrocytes were pretreated with β-Estradiol (E2) in vitro and subsequently, Mn sulfate (MnSO4). The amount of toxic damage to the astrocytes was measured by quantifying glial fibrillary acidic protein (GFAP) with a sandwiched Enzyme-Linked Immunosorbent Assay (ELISA). ELISA analysis indicated Mn exposure at 100 μM, 300 μM, or 600 μM significantly increased GFAP levels. However, E2 concentrations at 10 nM or 30 nM significantly reduced Mn-induced GFAP concentrations at 100 μM. Cells pretreated with 10 nM or 30 nM of E2 significantly lowered GFAP levels. The Water-Soluble Tetrazolium-8 (WST-8) method was utilized to determine cell viability. The WST-8 assay showed that Mn concentrations of 100 μM, 300 μM, or 600 μM significantly reduced the dehydrogenase activity, thereby decreasing the number of viable astrocytes. Enzyme activity with 600 μM of Mn was significantly decreased when compared with 100 μM of Mn, revealing a dose-dependent effect. However, the dehydrogenase activity in cells treated with 600 μM Mn was significantly increased when pretreated with 10 nM of E2. Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) was used to measure changes in gluta

关键词： Astrocytes Estrogen Embryonic Manganese Hippocampus

Knowledge acquisition, semantic text mining, and security risks in health and biomedical informatics

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World j.urnal of Biological Chemistry 2012年第2期3卷 27-33页

作者： j.harold Pardue William T Gerthoffer School of Computer andInformation Sciences University of South Alabama Mobile AL36688 United States Department of Biochemistry and Molecu-lar Biology University of South Alabama Mobile AL 36688 United States

Computational techniques have been adopted in medi-cal and biological systems for a long time. There is no doubt that the development and application of computational methods will render great help in better understanding biomedical and biological functions. Large amounts of datasets have been produced by biomedical and biological experiments and simulations. In order for researchers to gain knowledge from origi- nal data, nontrivial transformation is necessary, which is regarded as a critical link in the chain of knowledge acquisition, sharing, and reuse. Challenges that have been encountered include: how to efficiently and effectively represent human knowledge in formal computing models, how to take advantage of semantic text mining techniques rather than traditional syntactic text mining, and how to handle security issues during the knowledge sharing and reuse. This paper summarizes the state-of-the-art in these research directions. We aim to provide readers with an introduction of maj.r computing themes to be applied to the medical and biological research.

关键词： Biomedical informatics Bioinformatics Knowledge sharing Ontology matching Heterogeneous semantics Semantic integration Semantic data mining Semantic text mining Security risk

Bax抗原在艾滋病人脑组织中的表达及其原位检测

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中华微生物学和免疫学杂志 1996年第3期16卷 187-190页

作者：唐晓鹏 haroldj.j.mes 湖南医科大学第二临床学院传染病科长沙410011 DepartmentofNeurology UniversityofRochesterMedicalCentertUSA

采用快速免疫组织化学染色方法及ＤＮＡ３- 羟基末端特异性标记技术对２３例艾滋病人及１９例非艾滋病对照病人死后脑组织标本中Ｂｃｌ－２相关Ｘ蛋白（Ｂａｘ）及细胞凋亡进行了原位检测。结果显示，艾滋病人脑组织Ｂａｘ阳性率达７３... 详细信息

采用快速免疫组织化学染色方法及ＤＮＡ３- 羟基末端特异性标记技术对２３例艾滋病人及１９例非艾滋病对照病人死后脑组织标本中Ｂｃｌ－２相关Ｘ蛋白（Ｂａｘ）及细胞凋亡进行了原位检测。结果显示，艾滋病人脑组织Ｂａｘ阳性率达７３．９％（１７／２３），而对照病人脑组织阳性率为５．３％（１／１９）。凋亡细胞与Ｂａｘ双染结果显示两者常出现在同一细胞中，均多见于巨噬细胞及神经细胞。因此，结果提示Ｂａｘ抗原在艾滋病人脑组织中高度表达，并且艾滋病与Ｂａｘ和细胞凋亡三者之间具有一定的关系。

关键词：艾滋病细胞凋亡脑免疫组化 Bax抗原