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Hole doping MgB_2 without chemical substitution [article]

Peihong Zhang, Susumu Saito, Steven G. Louie, Marvin L. Cohen
2007 arXiv   pre-print
Structures for realizing hole-doped MgB_2 without appealing to chemical substitutions are proposed. These structures which consist of alternating MgB_2 and graphene layers have small excess energy compared to bulk graphite and MgB_2. Density functional theory based first-principles electronic structure calculations show significant charge transfer from the MgB_2 layer to graphene, resulting in effectively hole-doped MgB_2. Substantial enhancement in the density of states at the Fermi level of the proposed structure is predicted.
arXiv:cond-mat/0702625v1 fatcat:tz5gvbxoffgdrpk4tgb2tko7ue

Topological carbon materials: a new perspective [article]

Yuanping Chen, Yuee Xie, Xiaohong Yan, Marvin L. Cohen, Shengbai Zhang
2019 arXiv   pre-print
Topological Classification Material candidates 2D Dirac (Weyl) semimetal Zhang, R.-S. & Jiang, J.-W. The art of designing carbon allotropes.  ... 
arXiv:1908.10108v1 fatcat:ual7iyx745bsnf5wdbkqz47ftq

MEMO: Test Time Robustness via Adaptation and Augmentation [article]

Marvin Zhang, Sergey Levine, Chelsea Finn
2022 arXiv   pre-print
., 2021; Zhang et al., 2021) .  ...  pretrained models is not as easily accomplished for adaptation methods which require complicated or specialized training procedures and model architectures, such as TTT (Sun et al., 2020) or ARM (Zhang  ... 
arXiv:2110.09506v2 fatcat:4l7l3fwpmrgd3ewrga22m72lqy

Fermi Surface ofNaxCoO2

Peihong Zhang, Weidong Luo, Marvin L. Cohen, Steven G. Louie
2004 Physical Review Letters  
Doping evolution of the Fermi surface topology of Na_xCoO_2 is studied systematically. Both local density approximation (LDA) and local spin density approximation (LSDA) predict a large Fermi surface as well as small hole pockets for doping levels x∼ 0.5. In contrast, the hole pockets are completely absent for all doping levels within LSDA+U. More importantly, we find no violation of Luttinger's rule in this system, contrary to a recent suggestion. The measured Fermi surface of Na_0.7CoO_2 can
more » ... e explained by its half-metallic behavior and agrees with our LSDA+U calculations.
doi:10.1103/physrevlett.93.236402 pmid:15601181 fatcat:tvqotmxdcbe5xoytreb346rkwm

Targeting the ERK pathway for the treatment of Cushing's disease

Dongyun Zhang, Marvin Bergsneider, Marilene B. Wang, Anthony P. Heaney
2016 OncoTarget  
We recently demonstrated that the orphan nuclear receptor testicular receptor 4 (TR4) is a potent regulator of corticotroph tumor growth and hormone secretion. The Ras/Raf/MEK/ERK pathway is commonly overactivated in human tumors and we have demonstrated that corticotroph tumor TR4 is activated by ERK1/2-mediated phosphorylation. We evaluated effects of MEK-162, a selective, non-ATP-competitive allosteric inhibitor of MEK1/2, on murine and human in vitro and in vivo corticotroph tumor
more » ... ion and adrenocorticotrophic hormone (ACTH) secretion. MEK-162 treatment dose-dependently inhibited corticotroph tumor proliferation, induced apoptosis, reduced pro-opiomelanocortin (POMC) mRNA levels and inhibited ACTH secretion in vitro. Similar findings were obtained in human corticotroph tumor primary cultures (n = 5). These actions of MEK-162 were augmented in the presence of TR4 overexpression, suggesting that TR4 levels may serve as a predictive biomarker of MEK-162 corticotroph tumor responsiveness. Additionally, MEK-162 treatment reduced TR4 protein expression and blocked recruitment of TR4 to bind its consensus site on the POMC promoter (-854bp to -637bp), elucidating multiple mechanisms to control TR4 corticotroph tumor actions. In a murine corticotroph tumor in vivo model of Cushing's disease, MEK-162 treatment inhibited tumor growth and reduced tumorderived circulating plasma ACTH, and corticosterone levels. These results demonstrate the potent actions of MEK-162 to inhibit corticotroph tumor growth and hormone secretion in vitro and in vivo via TR4-dependent and independent mechanisms, and raise the possibility of MEK-162 as a novel therapy for Cushing's disease.
doi:10.18632/oncotarget.12381 pmid:27708250 pmcid:PMC5342466 fatcat:foupp46mgvgp7k6lbzv55rwei4

Real Time Measurement of Airplane Flutter via Distributed Acoustic Sensing

Ezzat G. Bakhoum, Cheng Zhang, Marvin H. Cheng
2020 Aerospace (Basel)  
This research group has recently used the new technology Distributed Acoustic Sensing (DAS) for the monitoring and the measurement of airplane flutter. To the authors' knowledge, this is the first such use for this new technology. Traditionally, the measurement of airplane flutter requires the mounting of a very large number of sensors on the wing being monitored, and extensive wiring must be connected to all these sensors. The new system and technology introduced in this paper dramatically
more » ... ces the hardware requirements in such an application: all the traditional sensors and wiring are replaced with one fiber optic cable with a diameter of 2 mm. An electro-optical system with the size of a desktop PC monitors simultaneously one or more of such fiber optic cables and detects/characterizes any mechanical disturbances on the cables. Theoretical and experimental results are given.
doi:10.3390/aerospace7090125 fatcat:tzvormrzdbdahkqtwzrze7dnru

Temperature Fields in the Tropical Tropopause Transition Layer

Xue Long Zhou, Marvin A. Geller, Minghua Zhang
2004 Journal of Climate  
There has been increasing recognition of the role of the tropical tropopause layer (TTL) in determining stratospheric water vapor concentrations-the TTL being a layer of transition between air showing tropospheric properties below and stratospheric properties above. This study investigates the spatial structure of temperatures in the TTL. A dehydration index based on the atmospheric region with temperatures colder than a specific reference temperature was defined to examine the TTL temperature
more » ... tructure and possible influences on stratospheric water vapor. The results indicate that dehydration regions with cold temperatures (e.g., Ͻ190 K) occur mainly over the western Pacific and are about 1.5-2.0 km in depth during Northern Hemisphere winter. The dehydration index is mainly dependent on the annual cycle of the TTL temperatures, but is strongly affected by interannual variations associated with the quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO). Dehydration regions with extremely cold temperatures and large sizes occur when cold temperature anomalies associated with the QBO arrive at the TTL in wintertime while the TTL is at the coldest phase of the annual cycle and under La Niña conditions. La Niña events have a more dramatic influence on the dehydration index than El Niño events.
doi:10.1175/1520-0442(2004)017<2901:tfittt>2.0.co;2 fatcat:brhnlnyng5azbbw2y3tf6tntvi

Theory of sodium ordering inNaxCoO2

Peihong Zhang, Rodrigo B. Capaz, Marvin L. Cohen, Steven G. Louie
2005 Physical Review B  
The ordering of Na ions in Na_xCoO_2 is investigated systematically by combining detailed density functional theory (DFT) studies with model calculations. Various ground state ordering patterns are identified, and they are in excellent agreement with avaliable experimental results. Our results suggest that the primary driving force for the Na ordering is the screened Coulomb interaction among Na ions. Possible effects of the Na ordering on the electronic structure of the CoO_2 layer are
more » ... d. We propose that the nonexistence of a charge ordered insulating state at x = 2/3 is due to the lack of a commensurate Na ordering pattern, whereas an extremely stable Na ordering at x = 0.5 enhances the charge ordering tendency, resulting in an insulating state as observed experimentally.
doi:10.1103/physrevb.71.153102 fatcat:ftpra6fqi5drjioqh73uwefewy

Simulations of the Interannual Variability of Stratospheric Water Vapor

Marvin A. Geller, Xuelong Zhou, Minghua Zhang
2002 Journal of the Atmospheric Sciences  
JOURNAL OF THE ATMOSPHERIC SCIENCES VOLUME 59 Simulations of the Interannual Variability of Stratospheric Water Vapor MARVIN A.  ...  Marvin A. Geller, Marine Sci- ence Research Center, State University of New York at Stony Brook, Stony Brook, NY 11794-5000.  ... 
doi:10.1175/1520-0469(2002)059<1076:sotivo>2.0.co;2 fatcat:yig64uvz3rbxllqphfp73mtxhm

Computational design of direct-bandgap semiconductors that lattice-match silicon

Peihong Zhang, Vincent H. Crespi, Eric Chang, Steven G. Louie, Marvin L. Cohen
2001 Nature  
The furnace temperature (middle) was set at 800 8C during growth, and the target was placed at the upstream end rather than middle of the furnace. A pulsed (8-ns, 10-Hz) Nd-YAG laser (wavelength 1,064 nm) was used to vaporize the target. Typically, growth was performed for 10 min with NWs collected at the downstream, cool end of the furnace. Electrical characterization Transport measurement on individual NWs were carried out using published procedures 11 . NWs were ®rst dispersed in ethanol,
more » ... then deposited onto oxidized silicon substrates (600 nm oxide, 1±10 Q cm resistivity), with the conductive silicon used as a back gate. Electrical contact to the NWs was de®ned using electron beam lithography (JEOL 6400). Ni/In/Au contact electrodes were thermally evaporated. Electrical transport measurements were made using a home-built system with ,1 pA noise under computer control. Junctions (n±n and p±p) were obtained by random deposition. We ®rst deposited NWs onto oxidized silicon substrates using relatively high concentrations, determined the positions of crossed NWs, and then de®ned electrodes on all four arms of the cross by electron beam lithography. Ni/In/Au electrodes were used to make contact to the NWs. p±n junctions were obtained by layer-by-layer deposition. First, a dilute solution of one type (for example, n-type) of NW was deposited on the substrate, and the positions of individual NWs were recorded. In a second step, a dilute solution of the other type (for example, p-type) of NW was deposited, and the positions of crossed n-and p-type NWs were recorded. Metal electrodes were then de®ned and transport behaviour was measured. Optoelectrical characterization EL was studied with a home-built micro-luminescence instrument 20 . PL or scattered light (514 nm, Ar-ion laser) was used to locate the position of the junction. When the junction was located, the excitation laser was shut off, and then the junction was forward biased. EL images were taken with a liquid-nitrogen-cooled CCD camera, and EL spectra were obtained by dispersing EL with a 150 lines mm -1 grating in a 300-mm spectrometer.
doi:10.1038/35051054 pmid:11343113 fatcat:n23ibe3u5vdbxbmbkc2vpeowma

GMDD: A database of GMO detection methods

Wei Dong, Litao Yang, Banghyun Kim, Gijs A. Kleter, Hans J.P. Marvin, Wanqi Liang, Dabing Zhang
2008 Journal of Biotechnology  
Since more than one hundred events of genetically modified organisms (GMOs) have been developed and approved for commercialization in global area, the GMO analysis methods are essential for the enforcement of GMO labelling regulations. Protein and nucleic acidbased detection techniques have been developed and utilized for GMOs identification and quantification. However, the information for harmonization and standardization of GMO analysis methods at global level is needed. Results: GMO
more » ... method Database (GMDD) has collected almost all the previous developed and reported GMOs detection methods, which have been grouped by different strategies (screen-, gene-, construct-, and event-specific), and also provide a user-friendly search service of the detection methods by GMO event name, exogenous gene, or protein information, etc. In this database, users can obtain the sequences of exogenous integration, which will facilitate PCR primers and probes design. Also the information on endogenous genes, certified reference materials, reference molecules, and the validation status of developed methods is included in this database. Furthermore, registered users can also submit new detection methods and sequences to this database, and the newly submitted information will be released soon after being checked. Conclusion: GMDD contains comprehensive information of GMO detection methods. The database will make the GMOs analysis much easier.
doi:10.1016/j.jbiotec.2008.07.529 fatcat:a7xrz4rihzecvhjlulz2y6hdna

Learning Deep Neural Network Policies with Continuous Memory States [article]

Marvin Zhang, Zoe McCarthy, Chelsea Finn, Sergey Levine, Pieter Abbeel
2015 arXiv   pre-print
Policy learning for partially observed control tasks requires policies that can remember salient information from past observations. In this paper, we present a method for learning policies with internal memory for high-dimensional, continuous systems, such as robotic manipulators. Our approach consists of augmenting the state and action space of the system with continuous-valued memory states that the policy can read from and write to. Learning general-purpose policies with this type of memory
more » ... representation directly is difficult, because the policy must automatically figure out the most salient information to memorize at each time step. We show that, by decomposing this policy search problem into a trajectory optimization phase and a supervised learning phase through a method called guided policy search, we can acquire policies with effective memorization and recall strategies. Intuitively, the trajectory optimization phase chooses the values of the memory states that will make it easier for the policy to produce the right action in future states, while the supervised learning phase encourages the policy to use memorization actions to produce those memory states. We evaluate our method on tasks involving continuous control in manipulation and navigation settings, and show that our method can learn complex policies that successfully complete a range of tasks that require memory.
arXiv:1507.01273v2 fatcat:e4rkh3is3vejzdrigojzihvtbe

Cost Efficiency Benchmarking for Operational Units with Multiple Cost Drivers

Marvin D. Troutt, Donald W. Gribbin, Murali Shanker, Aimao Zhang
2000 Decision Sciences  
Marvin D. Troutt Figure 1 : 1 Hypothetical two-dimensional version of the rates departments data. [Received: September 27, 1999. Accepted: October 23, 2000.] Troutt, M. D. (1993).  ... 
doi:10.1111/j.1540-5915.2000.tb00944.x fatcat:7jkrdgdcdncjrn4mc757h4voja

Multiscale Modeling of Flow Induced Thrombogenicity With Dissipative Particle Dynamics and Molecular Dynamics

Danny Bluestein, João S. Soares, Peng Zhang, Chao Gao, Seetha Pothapragada, Na Zhang, Marvin J. Slepian, Yuefan Deng
2014 Journal of Medical Devices  
doi:10.1115/1.4027347 pmid:25053978 pmcid:PMC4042554 fatcat:e3ietiwlx5fgxm5u5zgxntpwaa

Chd5 orchestrates chromatin remodelling during sperm development

Wangzhi Li, Jie Wu, Sang-Yong Kim, Ming Zhao, Stephen A. Hearn, Michael Q. Zhang, Marvin L. Meistrich, Alea A. Mills
2014 Nature Communications  
One of the most remarkable chromatin remodelling processes occurs during spermiogenesis, the post-meiotic phase of sperm development during which histones are replaced with sperm-specific protamines to repackage the genome into the highly compact chromatin structure of mature sperm. Here we identify Chromodomain helicase DNA binding protein 5 (Chd5) as a master regulator of the histone-to-protamine chromatin remodelling process. Chd5 deficiency leads to defective sperm chromatin compaction and
more » ... ale infertility in mice, mirroring the observation of low CHD5 expression in testes of infertile men. Chd5 orchestrates a cascade of molecular events required for histone removal and replacement, including histone 4 (H4) hyperacetylation, histone variant expression, nucleosome eviction and DNA damage repair. Chd5 deficiency also perturbs expression of transition proteins (Tnp1/Tnp2) and protamines (Prm1/2). These findings define Chd5 as a multi-faceted mediator of histoneto-protamine replacement and depict the cascade of molecular events underlying this process of extensive chromatin remodelling.
doi:10.1038/ncomms4812 pmid:24818823 pmcid:PMC4151132 fatcat:ui5llxzchjeyvevpbazbubvivu
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