412 research outputs found
Anomalous insulator metal transition in boron nitride-graphene hybrid atomic layers
The study of two-dimensional (2D) electronic systems is of great fundamental
significance in physics. Atomic layers containing hybridized domains of
graphene and hexagonal boron nitride (h-BNC) constitute a new kind of
disordered 2D electronic system. Magneto-electric transport measurements
performed at low temperature in vapor phase synthesized h-BNC atomic layers
show a clear and anomalous transition from an insulating to a metallic behavior
upon cooling. The observed insulator to metal transition can be modulated by
electron and hole doping and by the application of an external magnetic field.
These results supported by ab-initio calculations suggest that this transition
in h-BNC has distinctly different characteristics when compared to other 2D
electron systems and is the result of the coexistence between two distinct
mechanisms, namely, percolation through metallic graphene networks and hopping
conduction between edge states on randomly distributed insulating h-BN domains.Comment: 9 pages, 15 figure
Harbinger II: Deployment and Evolution of Assertive Community Treatment in Michigan
Assertive Community Treatment (ACT) is now recognized as the model proven to be most successful in working with clients with long-term, severe mental illness. The first documented research replication study of ACT was Harbinger of Grand Rapids, in Kent County, Michigan. The Harbinger program influenced significant programmatic changes throughout the public mental health system in Michigan. This paper describes this evolution in community mental health locally and why these changes came about. The state-level strategy to implement replications of Harbinger is described, as well as funding and monitoring mechanisms that have now resulted in over 100 successful ACT programs in Michigan. For mental health administrators, the implications discussed include the future of ACT promotion and implementation, within the reality of a managed care framework.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44094/1/10488_2004_Article_414562.pd
Harbinger I: The Development and Evaluation of the First PACT Replication
While Assertive Community Treatment (originally known as the PACT program) is now recognized around the world as an effective model for rehabilitation of persons with severe mental illness, this was not the case 20 years ago. Harbinger of Grand Rapids, in Kent County, Michigan, was the first replication of the PACT model which sought fidelity and included an experimental design for assessing effectiveness. The design and results are presented from an initial 30-month and a follow-up 66-month evaluation of Harbinger. The 30-month evaluation showed significant differences favoring Harbinger vs. the control group on independent living, employment, and client functioning. At 66-months, there were fewer experimental-control group differences. The differences in results are analyzed in terms of design and data collection problems, changes in the treatment environment for the control group, and the longitudinal course of mental illness. The discussion focuses on next steps in ACT research, utilizing program theory to better establish the mechanisms for successful intervention models.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44093/1/10488_2004_Article_414561.pd
Trends in Metal Oxide Stability for Nanorods, Nanotubes, and Surfaces
The formation energies of nanostructures play an important role in
determining their properties, including the catalytic activity. For the case of
15 different rutile and 8 different perovskite metal oxides, we find that the
density functional theory (DFT) calculated formation energies of (2,2)
nanorods, (3,3) nanotubes, and the (110) and (100) surfaces may be described
semi-quantitatively by the fraction of metal--oxygen bonds broken and the
bonding band centers in the bulk metal oxide
Transform-domain analysis of packet delay in network nodes with QoS-aware scheduling
In order to differentiate the perceived QoS between traffic classes in heterogeneous packet networks, equipment discriminates incoming packets based on their class, particularly in the way queued packets are scheduled for further transmission. We review a common stochastic modelling framework in which scheduling mechanisms can be evaluated, especially with regard to the resulting per-class delay distribution. For this, a discrete-time single-server queue is considered with two classes of packet arrivals, either delay-sensitive (1) or delay-tolerant (2). The steady-state analysis relies on the use of well-chosen supplementary variables and is mainly done in the transform domain. Secondly, we propose and analyse a new type of scheduling mechanism that allows precise control over the amount of delay differentiation between the classes. The idea is to introduce N reserved places in the queue, intended for future arrivals of class 1
p-doped 1.3 μm InAs/GaAs quantum-dot laser with a low threshold current density and high differential efficiency
Amodification of the thickness of the low-growth- emperature component of the GaAs spacer layers in multilayer 1.3 um InAs/GaAs quantum-dot (QD) lasers has been used to significantly improve device performance. For a p-doped seven-layer device, a reduction in the thickness of this component from 15 to 2 nm results in a reduced reverse bias leakage current and an increase in the
intensity of the spontaneous emission. In addition, a significant reduction of the threshold current density and an increase of the external differential efficiency at room temperature are obtained. These improvements indicate a reduced defect density, most probably a combination of the selective elimination of a very low density of dislocated dots and a smaller number of defects in the thinner low-growth-temperature component of the GaAs spacer layer
Who is afraid of ticks and tick-borne diseases?:Results from a cross-sectional survey in Scandinavia
Quasiparticle interfacial level alignment of highly hybridized frontier levels: HO on TiO(110)
Knowledge of the frontier levels' alignment prior to photo-irradiation is
necessary to achieve a complete quantitative description of HO
photocatalysis on TiO(110). Although HO on rutile TiO(110) has been
thoroughly studied both experimentally and theoretically, a quantitative value
for the energy of the highest HO occupied levels is still lacking. For
experiment, this is due to the HO levels being obscured by hybridization
with TiO(110) levels in the difference spectra obtained via ultraviolet
photoemission spectroscopy (UPS). For theory, this is due to inherent
difficulties in properly describing many-body effects at the
HO-TiO(110) interface. Using the projected density of states (DOS) from
state-of-the-art quasiparticle (QP) , we disentangle the adsorbate and
surface contributions to the complex UPS spectra of HO on TiO(110). We
perform this separation as a function of HO coverage and dissociation on
stoichiometric and reduced surfaces. Due to hybridization with the TiO(110)
surface, the HO 3a and 1b levels are broadened into several peaks
between 5 and 1 eV below the TiO(110) valence band maximum (VBM). These
peaks have both intermolecular and interfacial bonding and antibonding
character. We find the highest occupied levels of HO adsorbed intact and
dissociated on stoichiometric TiO(110) are 1.1 and 0.9 eV below the VBM. We
also find a similar energy of 1.1 eV for the highest occupied levels of HO
when adsorbed dissociatively on a bridging O vacancy of the reduced surface. In
both cases, these energies are significantly higher (by 0.6 to 2.6 eV) than
those estimated from UPS difference spectra, which are inconclusive in this
energy region. Finally, we apply self-consistent QP (scQP1) to obtain
the ionization potential of the HO-TiO(110) interface.Comment: 12 pages, 12 figures, 1 tabl
Negative Smad Expression and Regulation in the Developing Chick Limb
The inhibitory or negative Smads, Smad6 and Smad7, block TGFβ superfamily signals of both the BMP and TGFβ classes by antagonizing the intracellular signal transduction machinery. We report the cloning of one Smad6 and two Smad7 (Smad7a and Smad7b) chick homologs and their expression and regulation in the developing limb. Smad6 and Smad7a are expressed in dynamic patterns reflecting the domains of BMP gene expression in the limb. Activation and inhibition of the BMP signaling pathway in limb mesenchyme indicates that negative Smad gene expression is regulated, at least in part, by BMP family signals
A Late Role for bmp2b in the Morphogenesis of Semicircular Canal Ducts in the Zebrafish Inner Ear
BACKGROUND:The Bone Morphogenetic Protein (BMP) genes bmp2 and bmp4 are expressed in highly conserved patterns in the developing vertebrate inner ear. It has, however, proved difficult to elucidate the function of BMPs during ear development as mutations in these genes cause early embryonic lethality. Previous studies using conditional approaches in mouse and chicken have shown that Bmp4 has a role in semicircular canal and crista development, but there is currently no direct evidence for the role of Bmp2 in the developing inner ear. METHODOLOGY/PRINCIPAL FINDINGS:We have used an RNA rescue strategy to test the role of bmp2b in the zebrafish inner ear directly. Injection of bmp2b or smad5 mRNA into homozygous mutant swirl (bmp2b(-/-)) embryos rescues the early patterning defects in these mutants and the fish survive to adulthood. As injected RNA will only last, at most, for the first few days of embryogenesis, all later development occurs in the absence of bmp2b function. Although rescued swirl adult fish are viable, they have balance defects suggestive of vestibular dysfunction. Analysis of the inner ears of these fish reveals a total absence of semicircular canal ducts, structures involved in the detection of angular motion. All other regions of the ear, including the ampullae and cristae, are present and appear normal. Early stages of otic development in rescued swirl embryos are also normal. CONCLUSIONS/SIGNIFICANCE:Our findings demonstrate a critical late role for bmp2b in the morphogenesis of semicircular canals in the zebrafish inner ear. This is the first demonstration of a developmental role for any gene during post-embryonic stages of otic morphogenesis in the zebrafish. Despite differences in the early stages of semicircular canal formation between zebrafish and amniotes, the role of Bmp2 in semicircular canal duct outgrowth is likely to be conserved between different vertebrate species
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