37,922 research outputs found
Sensitivity of the photo-physical properties of organometallic complexes to small chemical changes
We investigate an effective model Hamiltonian for organometallic complexes
that are widely used in optoelectronic devices. The two most important
parameters in the model are , the effective exchange interaction between the
and orbitals of the ligands, and , the renormalized
energy gap between the highest occupied orbitals on the metal and on the
ligand. We find that the degree of metal-to-ligand charge transfer (MLCT)
character of the lowest triplet state is strongly dependent on the ratio
. is purely a property of the complex and can be
changed significantly by even small variations in the complex's chemistry, such
as replacing substituents on the ligands. We find that that small changes in
can cause large changes in the properties of the complex,
including the lifetime of the triplet state and the probability of injected
charges (electrons and holes) forming triplet excitations. These results give
some insight into the observed large changes in the photophysical properties of
organometallic complexes caused by small changes in the ligands.Comment: Accepted for publication in J. Chem. Phys. 14 pages, 9 figures,
Supplementary Info: 15 pages, 17 figure
In-vivo magnetic resonance imaging of hyperpolarized silicon particles
Silicon-based micro and nanoparticles have gained popularity in a wide range
of biomedical applications due to their biocompatibility and biodegradability
in-vivo, as well as a flexible surface chemistry, which allows drug loading,
functionalization and targeting. Here we report direct in-vivo imaging of
hyperpolarized 29Si nuclei in silicon microparticles by MRI. Natural physical
properties of silicon provide surface electronic states for dynamic nuclear
polarization (DNP), extremely long depolarization times, insensitivity to the
in-vivo environment or particle tumbling, and surfaces favorable for
functionalization. Potential applications to gastrointestinal, intravascular,
and tumor perfusion imaging at sub-picomolar concentrations are presented.
These results demonstrate a new background-free imaging modality applicable to
a range of inexpensive, readily available, and biocompatible Si particles.Comment: Supplemental Material include
Comparison of research framing preferences and information use of state legislators and advocates involved in cancer control, United States, 2012–2013
INTRODUCTION: Evidence-based policy plays an important role in prevention of cancer and other chronic diseases. The needs of actors involved in policy decision-making should inform knowledge translation strategies. This study examines the differences between state legislators and advocates in how they seek and use information and what their preferences are for how research information is framed. METHODS: We conducted a cross-sectional comparison of survey responses by US advocates (n = 77) and state legislators (n = 265) working on issues related to cancer control. RESULTS: Advocates differed significantly from legislators on all demographic characteristics. Advocates reported seeking and using information more frequently than legislators, though legislators used legislative research bureaus more often (0.45 point difference, P = .004). Both legislators and advocates prioritized the presentation and timeliness of research information similarly but reported different preferences for source (information bias, information relevance, delivery of information by trusted person) of research information. Several differences between advocates and legislators were modified by participant age. CONCLUSION: Our study provides insights for development of knowledge translation strategies to enhance evidence-based policy making for cancer control that are tailored to state-level legislators and advocates. Additional research efforts should evaluate the effectiveness of such knowledge translation strategies, particularly among advocates
Wang algebra: from theory to practice
Wang algebra was initiated by Ki-Tung Wang as a short-cut method for the analysis of electrical networks. It was later popularized by Duffin and has since found numerous applications in electrical engineering and graph theory. This is a semi-tutorial paper on Wang algebra, its history, and modern applications. We expand Duffin’s historic notes on Wang algebra to give a full account of Ki-Tung Wang’s life. A short proof of Wang algebra using group theory is presented. We exemplify the usefulness of Wang algebra in the design of T-coils. Bridged T-coils give a significant advantage in bandwidth, and were widely adopted in Tektronix oscilloscopes, but design details were guarded as a trade secret. The derivation presented in this paper, based on Wang algebra, is more general and simpler than those reported in literature. This novel derivation has not been shared with the public before
An easy-to-use diagnostic system development shell
The Diagnostic System Development Shell (DSDS), an expert system development shell for diagnostic systems, is described. The major objective of building the DSDS is to create a very easy to use and friendly environment for knowledge engineers and end-users. The DSDS is written in OPS5 and CommonLisp. It runs on a VAX/VMS system. A set of domain independent, generalized rules is built in the DSDS, so the users need not be concerned about building the rules. The facts are explicitly represented in a unified format. A powerful check facility which helps the user to check the errors in the created knowledge bases is provided. A judgement facility and other useful facilities are also available. A diagnostic system based on the DSDS system is question driven and can call or be called by other knowledge based systems written in OPS5 and CommonLisp. A prototype diagnostic system for diagnosing a Philips constant potential X-ray system has been built using the DSDS
Statistical interaction modeling of bovine herd behaviors
While there has been interest in modeling the group behavior of herds or flocks, much of this work has focused on simulating their collective spatial motion patterns which have not accounted for individuality in the herd and instead assume a homogenized role for all members or sub-groups of the herd. Animal behavior experts have noted that domestic animals exhibit behaviors that are indicative of social hierarchy: leader/follower type behaviors are present as well as dominance and subordination, aggression and rank order, and specific social affiliations may also exist. Both wild and domestic cattle are social species, and group behaviors are likely to be influenced by the expression of specific social interactions. In this paper, Global Positioning System coordinate fixes gathered from a herd of beef cows tracked in open fields over several days at a time are utilized to learn a model that focuses on the interactions within the herd as well as its overall movement. Using these data in this way explores the validity of existing group behavior models against actual herding behaviors. Domain knowledge, location geography and human observations, are utilized to explain the causes of these deviations from this idealized behavior
Letting Go: Conceptualizing intervention de-implementation in public health and social service settings
The discontinuation of interventions that should be stopped, or de-implementation, has emerged as a novel line of inquiry within dissemination and implementation science. As this area grows in human services research, like public health and social work, theory is needed to help guide scientific endeavors. Given the infancy of de-implementation, this conceptual narrative provides a definition and criteria for determining if an intervention should be de-implemented. We identify three criteria for identifying interventions appropriate for de-implementation: (a) interventions that are not effective or harmful, (b) interventions that are not the most effective or efficient to provide, and (c) interventions that are no longer necessary. Detailed, well-documented examples illustrate each of the criteria. We describe de-implementation frameworks, but also demonstrate how other existing implementation frameworks might be applied to de-implementation research as a supplement. Finally, we conclude with a discussion of de-implementation in the context of other stages of implementation, like sustainability and adoption; next steps for de-implementation research, especially identifying interventions appropriate for de-implementation in a systematic manner; and highlight special ethical considerations to advance the field of de-implementation research
National Register Testing at 41LT307, on CR 153 at the Navasota River, Limestone County, Texas
Archeological test excavations at 41LT307 were completed by Prewitt and Associates, Inc., in 2005 in conjunction with Texas Department of Transportation road improvements on County Road 153 in northwestern Limestone County. The site is situated on the active floodplain in Holocene alluvium adjacent to the Navasota River. Excavations revealed sparse lithic artifacts and no cultural features. No organic remains were recovered, and the age of the cultural occupation is unknown. The portion of 41LT307 inside the new right of way is considered ineligible for listing in the National Register of Historic Places or designation as a State Archeological Landmark. All artifacts were generated through a state-sponsored project and collected on state-owned property. All artifacts and records generated by this project are curated at the Texas Archeological Research Laboratory, The University of Texas at Austin
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