2,869 research outputs found
Near-Field Direct Antenna Modulation (NFDAM) transmitter at 2.4GHz
A near-field direct antenna modulation (NFDAM) transmitter at 2.4GHz is demonstrated on a microstrip setting. The transmitter is capable of transmitting information in a direction-dependent fashion by sending the correct signal constellation only in the desired direction while leaving the signal constellation points scrambled in undesired directions. This direction-dependent constellation scrambling nature of the NFDAM systems prevents undesired receivers to correctly demodulate the signal transmitted to a desired receiver at a specific direction
Equivalence of light-front and conventional thermal field theory
ONE PHYSICS ELLIPSE, COLLEGE PK, USA, MD,
20740-384
Thermal Field Theory and Generalized Light Front Coordinates
The dependence of thermal field theory on the surface of quantization and on
the velocity of the heat bath is investigated by working in general coordinates
that are arbitrary linear combinations of the Minkowski coordinates. In the
general coordinates the metric tensor is non-diagonal. The
Kubo, Martin, Schwinger condition requires periodicity in thermal correlation
functions when the temporal variable changes by an amount
. Light front quantization fails since
, however various related quantizations are possible.Comment: 10 page
Fragment screening reveals salicylic hydroxamic acid as an inhibitor of <em>Trypanosoma brucei</em> GPI GlcNAc-PI de-N-acetylase
The zinc-metalloenzyme GlcNAc-PI de-N-acetylase is essential for the biosynthesis of mature GPI anchors and has been genetically validated in the bloodstream form of Trypanosoma brucei, which causes African sleeping sickness. We screened a focused library of zinc-binding fragments and identified salicylic hydroxamic acid as a GlcNAc-PI de-N-acetylase inhibitor with high ligand efficiency. This is the first small molecule inhibitor reported for the trypanosome GPI pathway. Investigating the structure activity relationship revealed that hydroxamic acid and 2-OH are essential for potency, and that substitution is tolerated at the 4- and 5-positions
Combined anterior segment OCT and wavefront-based autorefractor using a shared beam
We have combined an anterior segment (AS) optical coherence tomography (OCT) system and a wavefront-based aberrometer with an approach that senses ocular wavefront aberrations using the OCT beam. Temporal interlacing of the OCT and aberrometer channels allows for OCT images and refractive error measurements to be acquired continuously and in real-time. The system measures refractive error with accuracy and precision comparable to that of clinical autorefractors. The proposed approach provides a compact modular design that is suitable for integrating OCT and wavefront-based autorefraction within the optical head of the ophthalmic surgical microscope for guiding cataract surgery or table-top devices for simultaneous autorefraction and ocular biometry
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Engineered Electrodes and Electrode-Organic Interfaces for High-Efficiency Organic Photovoltaics
Organic photovoltaic (OPV) cells offer the ultimate promise of low cost, readily manufacturable, and durable solar power. While recent advances have led to cells with impressive performance levels, OPV cells have yet to break the double-digit efficiency barrier. Further gains in efficiency and durability, to that competitive with high-performance inorganic photovoltaics will require breakthroughs in transparent electrode and interfacial materials science and engineering. This project involved an integrated basic research effort carried out by an experienced and highly collaborative interdisciplinary team to address in unconventional ways, critical electrode-interfacial issues underlying OPV performance--controlling band offsets between transparent electrodes and organics, addressing current loss/leakage problems at interfaces, enhancing adhesion, interfacial stability, and device durability while minimizing cost. It synergistically combined materials and interfacial reagent synthesis, nanostructural and photovoltaic characterization, and high level quantum theory. The research foci were: 1) understanding of/development of superior transparent electrode materials and materials morphologies--i.e., better matched electronically and chemically to organic active layers, 2) understanding-based development of inorganic interfacial current-collecting/charge-blocking layers, and 3) understanding-based development of self-assembled adhesion/current-collecting/charge-blocking/cross-linking layers for high-efficiency OPV interfaces. Pursing the goal of developing the fundamental scientific understanding needed to design, fabricate, prototype and ultimately test high-efficiency OPV cells incorporating these new concepts, we achieved a record power conversion efficiency of 5.2% for an organic bulk-heterjunction solar cell
Financing Direct Democracy: Revisiting the Research on Campaign Spending and Citizen Initiatives
The conventional view in the direct democracy literature is that spending against a measure is more effective than spending in favor of a measure, but the empirical results underlying this conclusion have been questioned by recent research. We argue that the conventional finding is driven by the endogenous nature of campaign spending: initiative proponents spend more when their ballot measure is likely to fail. We address this endogeneity by using an instrumental variables approach to analyze a comprehensive dataset of ballot propositions in California from 1976 to 2004. We find that both support and opposition spending on citizen initiatives have strong, statistically significant, and countervailing effects. We confirm this finding by looking at time series data from early polling on a subset of these measures. Both analyses show that spending in favor of citizen initiatives substantially increases their chances of passage, just as opposition spending decreases this likelihood
Preparation of amino-substituted indenes and 1,4-dihydronaphthalenes using a one-pot multireaction approach: total synthesis of oxybenzo[c]phenanthridine alkaloids
Allylic trichloroacetimidates bearing a 2-vinyl or 2-allylaryl group have been designed as substrates for a one-pot, two-step multi-bond-forming process leading to the general preparation of aminoindenes and amino-substituted 1,4-dihydronaphthalenes. The synthetic utility of the privileged structures formed from this one-pot process was demonstrated with the total synthesis of four oxybenzo[c]phenanthridine alkaloids, oxychelerythrine, oxysanguinarine, oxynitidine, and oxyavicine. An intramolecular biaryl Heck coupling reaction, catalyzed using the Hermann–Beller palladacycle was used to effect the key step during the synthesis of the natural products
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