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Search Results: 1 - 10 of 88184 matches for " I Youn "
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Oxygen, nitric oxide and articular cartilage
B Fermor,S E Christensen,I Youn,J M Cernanec
European Cells and Materials (ECM) , 2007,
Abstract: Molecular oxygen is required for the production of nitric oxide (NO), a pro-inflammatory mediator that is associated with osteoarthritis and rheumatoid arthritis. To date there has been little consideration of the role of oxygen tension in the regulation of nitric oxide production associated with arthritis. Oxygen tension may be particularly relevant to articular cartilage since it is avascular and therefore exists at a reduced oxygen tension. The superficial zone exists at approximately 6% O2, while the deep zone exists at less than 1% O2. Furthermore, oxygen tension can alter matrix synthesis, and the material properties of articular cartilage in vitro.The increase in nitric oxide associated with arthritis can be caused by pro-inflammatory cytokines and mechanical stress. Oxygen tension significantly alters endogenous NO production in articular cartilage, as well as the stimulation of NO in response to both mechanical loading and pro-inflammatory cytokines. Mechanical loading and pro-inflammatory cytokines also increase the production of prostaglandin E2 (PGE2). There is a complex interaction between NO and PGE2, and oxygen tension can alter this interaction. These findings suggest that the relatively low levels of oxygen within the joint may have significant influences on the metabolic activity, and inflammatory response of cartilage as compared to ambient levels. A better understanding of the role of oxygen in the production of inflammatory mediators in response to mechanical loading, or pro-inflammatory cytokines, may aid in the development of strategies for therapeutic intervention in arthritis.
Large anisotropy in the optical conductivity of YNi2B2C
S. J. Youn,B. I. Min,A. J. Freeman
Physics , 2002, DOI: 10.1103/PhysRevB.66.052512
Abstract: The optical properties of YNi$_2$B$_2$C are studied by using the first-principles full-potential linearized augmented plane wave (FLAPW) method within the local density approximation. Anisotropic behavior is obtained in the optical conductivity, even though the electronic structure shows 3D character. A large peak in $\sigma_z$ is obtained at 2.4 eV. The anisotropic optical properties are analyzed in terms of interband transitions between energy levels and found that the Ni site plays an important role. The electronic energy loss spectroscopy (EELS) spectra are also calculated to help elucidate the anisotropic properties in this system.
Itinerant ferromagnetism in half-metallic CoS_2
S. K. Kwon,S. J. Youn,B. I. Min
Physics , 2000, DOI: 10.1103/PhysRevB.62.357
Abstract: We have investigated electronic and magnetic properties of the pyrite-type CoS_2 using the linearized muffin-tin orbital (LMTO) band method. We have obtained the ferromagnetic ground state with nearly half-metallic nature. The half-metallic stability is studied by using the fixed spin moment method. The non-negligible orbital magnetic moment of Co 3d electrons is obtained as $\mu_L = 0.06 \mu_B$ in the local spin density approximation (LSDA). The calculated ratio of the orbital to spin angular momenta /< S_z > = 0.15 is consistent with experiment. The effect of the Coulomb correlation between Co 3d electrons is also explored with the LSDA + U method. The Coulomb correlation at Co sites is not so large, $U \lesssim 1$ eV, and so CoS_2 is possibly categorized as an itinerant ferromagnet. It is found that the observed electronic and magnetic behaviors of CoS_2 can be described better by the LSDA than by the LSDA + U.
A Dynamic Cournot Model with Brownian Motion  [PDF]
Hyungho Youn, Victor J. Tremblay
Theoretical Economics Letters (TEL) , 2015, DOI: 10.4236/tel.2015.51009
Abstract: In this paper we develop a stochastic version of a dynamic Cournot model. The model is dynamic because firms are slow to adjust output in response to changes in their economic environment. The model is stochastic because management may make errors in identifying the best course of action in a dynamic setting. We capture these behavioral errors with Brownian motion. The model demonstrates that the limiting output level of the game is a random variable, rather than a constant that is found in the non-stochastic case. In addition, the limiting variance in firm output is smaller with more firms. Finally, the model predicts that firm failure is more likely in smaller markets and for firms that are smaller and less efficient at managing errors.
A Comparison of Clock Synchronization in Wireless Sensor Networks
Seongwook Youn
International Journal of Distributed Sensor Networks , 2013, DOI: 10.1155/2013/532986
Abstract: The recent advances in microelectro devices have led the researchers to an area of developing a large distributed system that consist of small, wireless sensor nodes. These sensor nodes are usually equipped with sensors to perceive the environment. Synchronization is an important component of almost all distributed systems and has been studied by many researchers. There are many solutions for the classical networks, but the traditional synchronization techniques are not suitable for sensor networks because they do not consider the partitioning of the network and message delay. Additionally, limited power, computational capacity, and memory of the sensor nodes make the problem more challenging for wireless sensor networks. This paper examines the clock synchronization issues in wireless sensor networks. Energy efficiency, cost, scalability, lifetime, robustness, and precision are the main problems to be considered in design of a synchronization algorithm. There is no one single system that satisfies all these together. A comparison of different clock synchronization algorithms in wireless sensor networks with a main focus on energy efficiency, scalability, and precision properties of them will be provided here. 1. Introduction Wireless sensor networks are the networks that consist of mobile wireless computing devices, in which these devices are usually equipped with sensors to perceive the environment. Along with the recent advances in technology and the increasing demand, sensor networks are now being widely used in many applications. Wireless sensor networks have many applications including environmental monitoring, health monitoring, inventory location monitoring, and objects tracking. Features of a sensor network, such as size (number of nodes), density, and connectivity, vary depending on the application. Sensor nodes in the network are mostly mobile devices equipped with limited power and computation capabilities. Hence, a reasonable ordering of events in such environments is a challenging task. This paper examines the clock synchronization issues in ad hoc and sensor networks [1]. Clocks can be out of synchronization in two ways: shifting (clock offset or phase offset) or drifting (clock skew-oscillator’s frequency offset). In the case of shifting, they run at the same frequency, but their clock readings differ by a constant value—the offset between the clocks. In the case of drifting, they run at different frequencies. Synchronizing drifting clocks is much more costly and difficult than synchronizing two shifting clocks. Clocks of nodes may run
Transgene Silencing and Transgene-Derived siRNA Production in Tobacco Plants Homozygous for an Introduced AtMYB90 Construct
Jeff Velten, Cahid Cakir, Eunseog Youn, Junping Chen, Christopher I. Cazzonelli
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030141
Abstract: Transgenic tobacco (Nicotiana tabacum) lines were engineered to ectopically over-express AtMYB90 (PAP2), an R2–R3 Myb gene associated with regulation of anthocyanin production in Arabidopsis thaliana. Independently transformed transgenic lines, Myb27 and Myb237, accumulated large quantities of anthocyanin, generating a dark purple phenotype in nearly all tissues. After self-fertilization, some progeny of the Myb27 line displayed an unexpected pigmentation pattern, with most leaves displaying large sectors of dramatically reduced anthocyanin production. The green-sectored 27Hmo plants were all found to be homozygous for the transgene and, despite a doubled transgene dosage, to have reduced levels of AtMYB90 mRNA. The observed reduction in anthocyanin pigmentation and AtMYB90 mRNA was phenotypically identical to the patterns seen in leaves systemically silenced for the AtMYB90 transgene, and was associated with the presence of AtMYB90-derived siRNA homologous to both strands of a portion of the AtMYB90 transcribed region. Activation of transgene silencing in the Myb27 line was triggered when the 35S::AtMYB90 transgene dosage was doubled, in both Myb27 homozygotes, and in plants containing one copy of each of the independently segregating Myb27 and Myb237 transgene loci. Mapping of sequenced siRNA molecules to the Myb27 TDNA (including flanking tobacco sequences) indicated that the 3′ half of the AtMYB90 transcript is the primary target for siRNA associated silencing in both homozygous Myb27 plants and in systemically silenced tissues. The transgene within the Myb27 line was found to consist of a single, fully intact, copy of the AtMYB90 construct. Silencing appears to initiate in response to elevated levels of transgene mRNA (or an aberrant product thereof) present within a subset of leaf cells, followed by spread of the resulting small RNA to adjacent leaf tissues and subsequent amplification of siRNA production.
Differing mental health practice among general practitioners, private psychiatrists and public psychiatrists
N Younès, MC Hardy-Bayle, B Falissard, V Kovess, MP Chaillet, I Gasquet
BMC Public Health , 2005, DOI: 10.1186/1471-2458-5-104
Abstract: All GPs (n = 492), PrPs (n = 82) and PuPs (n = 78) in the South-Yvelines area in France were informed of the implementation of a local mental health program. Practitioners interested in taking part were invited to include prospectively all patients with mental health problem they saw over an 8-day period and to complete a 6-month retrospective questionnaire on their mental health practice. 180 GPs (36.6%), 45 PrPs (54.9%) and 63 PuPs (84.0%) responded.GPs and PrPs were very similar but very different from PuPs for the proportion of patients with anxious or depressive disorders (70% v. 65% v. 38%, p < .001), psychotic disorders (5% v. 7% v. 30%, p < .001), previous psychiatric hospitalization (22% v. 26 v. 61%, p < .001) and receiving disability allowance (16% v. 18% v. 52%, p < .001). GPs had fewer patients with long-standing psychiatric disorders than PrPs and PuPs (52%, 64% v. 63%, p < .001). Time-lapse between consultations was longest for GPs, intermediate for PuPs and shortest for PrPs (36 days v. 26 v. 18, p < .001). Access to care had been delayed longer for Psychiatrists (PrPs, PuPs) than for GPs (61% v. 53% v. 25%, p < .001). GPs and PuPs frequently felt a need for collaboration for their patients, PrPs rarely (42% v. 61%. v. 10%, p < .001).Satisfaction with mental health practice was low for all categories of physicians (42.6% encountered difficulties hospitalizing patients and 61.4% had patients they would prefer not to cater for). GPs more often reported unsatisfactory relationships with mental health professionals than did PrPs and PuPs (54% v. 15% v. 8%, p < .001).GP patients with mental health problems are very similar to patients of private psychiatrists; there is a lack of the collaboration felt to be necessary, because of psychiatrists' workload, and because GPs have specific needs in this respect. The "Yvelines-Sud Mental Health Network" has been created to enhance collaboration.In developed countries, mental health problems, especially anxious an
Spatial and temporal characterization of a Bessel beam produced using a conical mirror
K. B. Kuntz,B. Braverman,S. H. Youn,M. Lobino,E. M. Pessina,A. I. Lvovsky
Physics , 2008, DOI: 10.1103/PhysRevA.79.043802
Abstract: We experimentally analyze a Bessel beam produced with a conical mirror, paying particular attention to its superluminal and diffraction-free properties. We spatially characterized the beam in the radial and on-axis dimensions, and verified that the central peak does not spread over a propagation distance of 73 cm. In addition, we measured the superluminal phase and group velocities of the beam in free space. Both spatial and temporal measurements show good agreement with the theoretical predictions.
New High Temperature Diboride Superconductors: AgB2 and AuB2
S. K. Kwon,S. J. Youn,K. S. Kim,B. I. Min
Physics , 2001,
Abstract: Based on electronic structure calculations, we have found that noble metal diborides, AgB2 and AuB2, are potential candidates for conventional BCS-type high temperature superconductors. B 2p density of states dominates at the Fermi level in comparison with Ag 4d and Au 5d states. Furthermore, the electron-phonon coupling constant \lambda is much larger in AgB2 and AuB2 than in MgB2. Estimated transition temperatures for AgB2 and AuB2 are T_c = 59 K and 72 K, respectively. These are about 2 ~ 3 times higher than the estimated T_c = 27 K in MgB2 and almost comparable to those in cuprate superconductors.
Instant single-photon Fock state tomography
S. R. Huisman,Nitin Jain,S. A. Babichev,Frank Vewinger,A. N. Zhang,S. H. Youn,A. I. Lvovsky
Physics , 2009, DOI: 10.1364/OL.34.002739
Abstract: Heralded single photons are prepared at a rate of ~100 kHz via conditional measurements on polarization-nondegenerate biphotons produced in a periodically poled KTP crystal. The single-photon Fock state is characterized using high frequency pulsed optical homodyne tomography with a fidelity of (57.6 +- 0.1)%. The state preparation and detection rates allowed us to perform on-the-fly alignment of the apparatus based on real-time analysis of the quadrature measurement statistics.
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