gebhart/patrepeval huggingface dataset:
Synthesis and photochemistry of a carotene–porphyrin–fullerene model photosynthetic reaction center (2004)

Abstract A new photosynthetic reaction center mimic consisting of a porphyrin (P) linked to both a fullerene electron acceptor (C 60 ) and a carotenoid secondary electron donor (C) was synthesized and studied in 2‐methyltetrahydrofuran using transient spectroscopic methods. Excitation of the porphyrin is followed by photoinduced electron transfer to the fullerene (τ = 32 ps) to yield C–P ·+ –C 60 ·− . Electron transfer from the carotene to the porphyrin radical cation (τ = 125 ps) gives a final C ·+ –P–C 60 ·− state with an overall yield of 0.95. This state decays to give the carotenoid triplet state with a time constant of 57 ns. The molecular triad is highly soluble in organic solvents and readily synthesized. These qualities make the molecule a useful artificial photosynthetic reaction center for a variety of spectroscopic and photochemical investigations. Copyright © 2004 John Wiley & Sons, Ltd.
A Comparative Assessment of Different Modeling Algorithms for Estimating Leaf Nitrogen Content in Winter Wheat Using Multispectral Images from an Unmanned Aerial Vehicle (2018)

Unmanned aerial vehicle (UAV)-based remote sensing (RS) possesses the significant advantage of being able to efficiently collect images for precision agricultural applications. Although numerous methods have been proposed to monitor crop nitrogen (N) status in recent decades, just how to utilize an appropriate modeling algorithm to estimate crop leaf N content (LNC) remains poorly understood, especially based on UAV multispectral imagery. A comparative assessment of different modeling algorithms (i.e., simple and non-parametric modeling algorithms alongside the physical model retrieval method) for winter wheat LNC estimation is presented in this study. Experiments were conducted over two consecutive years and involved different winter wheat varieties, N rates, and planting densities. A five-band multispectral camera (i.e., 490 nm, 550 nm, 671 nm, 700 nm, and 800 nm) was mounted on a UAV to acquire canopy images across five critical growth stages. The results of this study showed that the best-performing vegetation index (VI) was the modified renormalized difference VI (RDVI), which had a determination coefficient (R2) of 0.73 and a root mean square error (RMSE) of 0.38. This method was also characterized by a high processing speed (0.03 s) for model calibration and validation. Among the 13 non-parametric modeling algorithms evaluated here, the random forest (RF) approach performed best, characterized by R2 and RMSE values of 0.79 and 0.33, respectively. This method also had the advantage of full optical spectrum utilization and enabled flexible, non-linear fitting with a fast processing speed (2.3 s). Compared to the other two methods assessed here, the use of a look up table (LUT)-based radiative transfer model (RTM) remained challenging with regard to LNC estimation because of low prediction accuracy (i.e., an R2 value of 0.62 and an RMSE value of 0.46) and slow processing speed. The RF approach is a fast and accurate technique for N estimation based on UAV multispectral imagery.
A novel electronically tunable active duplexer for wireless transceiver applications (2006)

In this paper, a novel electronically tunable active duplexer suitable for reconfigurable wireless transceiver applications is presented. The theory, design, and measured results of a varactor tunable active duplexer are summarized. The prototype active duplexer presented in this paper provides an electronically adjustable isolation of 20-50 dB between isolated ports and a gain of approximately 5 dB between coupled ports in the tunable range from 1.62 to 1.82 GHz in both transmit and receive modes of operations. The measured noise figure of the duplexer varied from 1.77 to 2.44 dB in the tuning range. The measured output powers at the 1-dB gain compression point and third-order intercept point, varied from 8.5 to 9.5 dBm and 20 to 29.5 dBm, respectively, in the tuning range. The design guidelines, measured S-parameters, and results of yield analysis of the duplexer are presented. The proposed duplexer can be implemented as a monolithic microwave integrated circuit
A data adaptive reprojection technique for MR angiography (1992)

Inability to detect vessel overlap and vascular loops can compromise the interpretation of magnetic resonance angiograms. A data-adaptive ray tracing (DART) technique was developed to produce the appropriate variations in signal intensity at points of vessel overlap in order to simulate the standard angiographic representation of vessels. In this technique a threshold is utilized to identify vessels in the image slices composing a 3D angiographic data set. A mask, which defines regions slightly larger than the vessel boundaries, is obtained by blurring the vessel information surviving the initial threshold. This mask is converted to binary form prior to multiplication by the original angiographic data set. Following application of an additional threshold to the masked data, line integrals through the regions defined by the mask are performed to obtain an angiographic signal proportional to the integrated vessel signal as in conventional angiography. This integrated reprojection is then uniquely combined with a maximum intensity pixel (MIP) reprojection to produce the final DART image. The application of the DART technique to 2D time-of-flight and 3D phase-contrast angiograms successfully enabled the identification of over-lapping vessels and vascular loops. DART was also found to produce less vessel narrowing than the MIP technique.
Unlocking Reactivity of TrpB: A General Biocatalytic Platform for Synthesis of Tryptophan Analogues (2017)

Derivatives of the amino acid tryptophan (Trp) serve as precursors for the chemical and biological synthesis of complex molecules with a wide range of biological properties. Trp analogues are also valuable as building blocks for medicinal chemistry and as tools for chemical biology. While the enantioselective synthesis of Trp analogues is often lengthy and requires the use of protecting groups, enzymes have the potential to synthesize such products in fewer steps and with the pristine chemo- and stereoselectivity that is a hallmark of biocatalysis. The enzyme TrpB is especially attractive because it can form Trp analogues directly from serine (Ser) and the corresponding indole analogue. However, many potentially useful substrates, including bulky or electron-deficient indoles, are poorly accepted. We have applied directed evolution to TrpB from Pyrococcus furiosus and Thermotoga maritima to generate a suite of catalysts for the synthesis of previously intractable Trp analogues. For the most challenging substrates, such as nitroindoles, the key to improving activity lay in the mutation of a universally conserved and mechanistically important residue, E104. The new catalysts express at high levels (>200 mg/L of Escherichia coli culture) and can be purified by heat treatment; they can operate up to 75 °C (where solubility is enhanced) and can synthesize enantiopure Trp analogues substituted at the 4-, 5-, 6-, and 7-positions, using Ser and readily available indole analogues as starting materials. Spectroscopic analysis shows that many of the activating mutations suppress the decomposition of the active electrophilic intermediate, an amino-acrylate, which aids in unlocking the synthetic potential of TrpB.
An Audio/Speech Watermarking Method for Copyright Protection (2015)

Protecting the copyrights of multimedia content is necessary to discourage unauthorized distribution or sharing of the content over Internet. Digital watermarking helps in protecting the copyrights while reduces the monetary loss to the content owner. Digital watermarking is the process of inserting owner or customer related unique information as a watermark into a host signal such as audio or speech or image or video without disturbing perceived quality of the host signal. One of the main characteristic of a digital watermarking is to enable accurate watermark detection even if the multimedia content undergoes some changes that may eliminate the watermark from the content. These changes include compression, rate conversion, filtering and noise addition etc. In this paper, we present a watermarking method that can be used for watermarking both audio and speech. Watermark embedding is done using singular values obtained by applying Singular Value Decomposition (SVD) on the structured Discrete Wavelet Transform (DWT) coefficients, correlation peak to side-lobe ratio (PSLR) metric is used to detect watermark from the correlation output, which is computed between the singular values obtained from the watermarked content and each watermark in the database. This method has been implemented in MATLAB and tested on various audio and speech tracks against various signal processing modifications. The experimental results prove the robustness of proposed method while satisfying the imperceptibility criteria.
Bouncing Water Droplet on a Superhydrophobic Carbon Nanotube Array (2010)

Over the past few decades, superhydrophobic materials have attaracted a lot of interests, due to their numerous practical applications. Among various superhydrophobic materials, carbon nanotube arrays have gained enormous attentions simply because of their outstanding properties. The impact dynamic of water droplet on a superhydrophobic carbon nanotube array is shown in this fluid dynamics video.
Diffraction phase microscopy with white light (2012)

We present white light diffraction phase microscopy (wDPM) as a quantitative phase imaging method that combines the single shot measurement benefit associated with off-axis methods, high temporal phase stability associated with common path geometries, and high spatial phase sensitivity due to the white light illumination. We propose a spatiotemporal filtering method that pushes the limit of the pathlength sensitivity to the subangstrom level at practical spatial and temporal bandwidths. We illustrate the utility of wDPM with measurements on red blood cell morphology and HeLa cell growth over 18 hours.
Evidence for Encapsidation of Prokaryotic Sequences during Recombinant Adeno-Associated Virus Production and Their in Vivo Persistence after Vector Delivery (2005)

Recombinant adeno-associated virus vectors (rAAV) have been successfully used for long-term gene expression in animal models and in patients. However, while the therapeutic potential of rAAV appears promising, safety issues, including contaminants found in vector stocks, must be further evaluated. We previously reported that a cis-acting replication element present within the AAV-2 p5 promoter was responsible for the encapsidation of rep-cap sequences observed during rAAV production. In that study, we also noticed that plasmid-derived prokaryotic sequences (such as the ampicillin resistance gene) could be found packaged into AAV capsids. In this report, first we confirmed and extended the latter observation by analyzing rAAV stocks produced using different procedures. Second, we demonstrated that these plasmid-derived sequences were transferred and persisted in vivo after rAAV injection into different tissues. Third, our data showed that at least some of these packaged plasmid molecules were linked to the AAV ITRs and were present in vivo in a form that could be rescued through bacterial transformation. This study highlights the need for more stringent characterization of rAAV stocks and provides useful information on the development of rAAV production methods that are able to circumvent or limit the generation of such undesirable particles.
Elimination of System-Induced Torque Pulsations in Doubly-Fed Induction Generators Via Field Reconstruction Method (2015)

Effects of system unbalance and system harmonics on the operation of doubly-fed induction generator (DFIG) used in wind energy harvesting are of great concern. This is primarily due to the fact that system unbalance and harmonics can generate unwanted torque undulations that can potentially undermine the mechanical integrity of the tower, and reduce the lifetime of the moving components that are attached to the generator shaft. This paper focuses on the development of a solution for the above problem by judicious selection of the rotor currents to actively eliminate/mitigate these undesirable vibrations. The enabling technology for optimal calculation of the rotor currents is based on the field reconstruction method (FRM). FRM is an analytical tool for the approximation of the magnetic field distribution in the middle of the air gap. Once the FRM formulation is setup, it is capable to predict the tangential/normal components of the magnetic forces. In this paper, the FRM is applied to compute the rotor phase currents in lieu of the availability of the real-time stator currents such that the resultant field will generate a smooth torque.
Note: Folded optical system for narrow forward looking probe (2014)

An optical system is described in which a laser beam makes three passes through a single graded index lens, forming a focus along the optic axis. It has important applications in endoscopic probes, where the forward looking characteristic permits the avoidance of obstacles and the narrow structure makes it minimally invasive.
LhnR and upstream operon LhnABC in <i>Agrobacterium vitis</i> regulate the induction of tobacco hypersensitive responses, grape necrosis and swarming motility (2012)

The characterization of Tn5 transposon insertional mutants of Agrobacterium vitis strain F2/5 revealed a gene encoding a predicted LysR-type transcriptional regulator, lhnR (for 'LysR-type regulator associated with HR and necrosis'), and an immediate upstream operon consisting of three open reading frames (lhnABC) required for swarming motility, surfactant production and the induction of a hypersensitive response (HR) on tobacco and necrosis on grape. The operon lhnABC is unique to A. vitis among the sequenced members in Rhizobiaceae. Mutagenesis of lhnR and lhnABC by gene disruption and complementation of ΔlhnR and ΔlhnABC confirmed their roles in the expression of these phenotypes. Mutation of lhnR resulted in complete loss of HR, swarming motility, surfactant production and reduced necrosis, whereas mutation of lhnABC resulted in loss of swarming motility, delayed and reduced HR development and reduced surfactant production and necrosis. The data from promoter-green fluorescent protein (gfp) fusions showed that lhnR suppresses the expression of lhnABC and negatively autoregulates its own expression. It was also shown that lhnABC negatively affects its own expression and positively affects the transcription of lhnR. lhnR and lhnABC constitute a regulatory circuit that coordinates the transcription level of lhnR, resulting in the expression of swarming, surfactant, HR and necrosis phenotypes.
Iterative, backscatter-analysis algorithms for increasing transmission and focusing light through highly scattering random media (2013)

Scattering hinders the passage of light through random media and consequently limits the usefulness of optical techniques for sensing and imaging. Thus, methods for increasing the transmission of light through such random media are of interest. Against this backdrop, recent theoretical and experimental advances have suggested the existence of a few highly transmitting eigen-wavefronts with transmission coefficients close to 1 in strongly backscattering random media. Here, we numerically analyze this phenomenon in 2D with fully spectrally accurate simulators and provide rigorous numerical evidence confirming the existence of these highly transmitting eigen-wavefronts in random media with periodic boundary conditions that are composed of hundreds of thousands of nonabsorbing scatterers. Motivated by bio-imaging applications in which it is not possible to measure the transmitted fields, we develop physically realizable algorithms for increasing the transmission through such random media using backscatter analysis. We show via numerical simulations that the algorithms converge rapidly, yielding a near-optimum wavefront in just a few iterations. We also develop an algorithm that combines the knowledge of these highly transmitting eigen-wavefronts obtained from backscatter analysis with intensity measurements at a point to produce a near-optimal focus with significantly fewer measurements than a method that does not utilize this information.
Design and Synthesis of Novel <i>N</i>-Hydroxy-Dihydronaphthyridinones as Potent and Orally Bioavailable HIV-1 Integrase Inhibitors (2011)

HIV-1 integrase (IN) is one of three enzymes encoded by the HIV genome and is essential for viral replication, and HIV-1 IN inhibitors have emerged as a new promising class of therapeutics. Recently, we reported the synthesis of orally bioavailable azaindole hydroxamic acids that were potent inhibitors of the HIV-1 IN enzyme. Here we disclose the design and synthesis of novel tricyclic N-hydroxy-dihydronaphthyridinones as potent, orally bioavailable HIV-1 integrase inhibitors displaying excellent ligand and lipophilic efficiencies.
Tunable-focus flat liquid-crystal diffractive lens (2010)

We demonstrate an innovative variable-focus flat liquid-crystal diffractive lens (LCDL) with 95% diffraction efficiency and millisecond switching times using a +/-2.4 V ac input. This lens is based on the electrical modulation of a 3 mum layer of nematic liquid-crystal sandwiched between a Fresnel zone electrode structure and a reference substrate. Each zone is divided into 12 subzones to digitize the phase profiles and define the phase wrapping points. The focusing power can rapidly be switched by electrically changing the number of subzones and re-establishing the wrapping points. Potential applications include zooms with no moving parts and autofocus lenses for compact imaging devices.
A Bayesian Approach to Background Modeling (2006)

Learning background statistics is an essential task for several visual surveillance applications such as incident detection and traf.c management. In this paper, we propose a new method for modeling background statistics of a dynamic scene. Each pixel is represented with layers of Gaussian distributions. Using recursive Bayesian learning, we estimate the probability distribution of mean and covariance of each Gaussian. The proposed algorithm preserves the multimodality of the background and estimates the number of necessary layers for representing each pixel. We compare our results with the Gaussian mixture background model. Experiments conducted on synthetic and video data demonstrate the superior performance of the proposed approach.
<title>Cholesterol Levels Assessed With Photon Correlation Spectroscopy</title> (1987)

The technique of quasi-elastic light scattering spectroscopy or photon correlation spectroscopy has been used to non-invasively monitor changes in the lens of the eye which could lead to lens opacification and cataract development. We have made quasi-elastic light scattering measurements from the eyes of normal and cholesterolemic rabbits. This report describes an exploratory investigation of the effects of a high cholesterol diet on the lens of the rabbit eye. The goal in making these measurements was to provide a non-invasive assessment of systemic atherosclerotic involvement in these rabbits.
New strategy for chemical modification of hyaluronic acid: Preparation of functionalized derivatives and their use in the formation of novel biocompatible hydrogels (1999)

Biodegradable materials for spatially and temporally controlled delivery of bioactive agents such as drugs, growth factors, or cytokines are key to facilitating tissue repair. We have developed a versatile method for chemical crosslinking high-molecular-weight hyaluronic acid under physiological conditions yielding biocompatible and biodegradable hydrogels. The method is based on the introduction of functional groups onto hyaluronic acid by formation of an active ester at the carboxylate of the glucuronic acid moiety and subsequent substitution with a side chain containing a nucleophilic group on one end and a (protected) functional group on the other. We have formed hyaluronic acid with amino or aldehyde functionality, and subsequently hydrogels with these hyaluronic acid derivatives and bifunctional crosslinkers or mixtures of the hyaluronic acid derivatives carrying different functionalities using active ester- or aldehyde-mediated reactions. Size analysis of the hyaluronic acid derivatives showed that the chemical modification did not lead to fragmentation of the polysaccharide. Hydrogels formed with hyaluronic acid derivatized to a varying degree and crosslinked with low- or high-molecular-weight crosslinkers were evaluated for biodegradability by digestion with hyaluronidase and for biocompatibility and ectopic bone formation by subcutaneous implantation in rats. Several hydrogel formulations showed excellent cell infiltration and chondro-osseous differentiation when loaded with bone morphogenetic protein-2 (BMP-2). Synergistic action of insulin-like growth factor-1 with BMP-2 promoted cartilage formation in this model, while addition of transforming growth factor-β and BMP-2 led to rapid replacement of the matrix by bone. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 47, 152–169, 1999.
Chiral Fiber Gratings (2004)

Chiral gratings with double helix symmetry were produced by twisting glass optical fiber with a noncircular core cross section as it passed through a miniature oven. We observed polarization-selective transmission in chiral fibers with pitches of tens of micrometers. Two modes of optical interaction were differentiated. In chirallong-period gratings, dips in transmission were observed at wavelengths associated with scattering into distinct cladding modes mediated by the chiral grating. In chiral intermediateperiod gratings, a broad scattering band was observed. These gratings can be used to produce sharp or broad polarization-selective filters.
ChemInform Abstract: Convergent Synthesis of the EFGH Ring Fragment (I) of Ciguatoxin CTX3C. (2002)

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Development of recombinant viral insecticides by expression of an insect‐specific toxin and insect‐specific enzyme in nuclear polyhedrosis viruses (1993)

As supplements to classical chemical insecticides, two approaches to develop recombinant baculovirus insecticides are described. In one approach an insect-specific toxin is expressed leading to a dramatic reduction in time to death. In the second approach an insect juvenile hormone esterase is expressed which leads to a reduction in feeding. Modifications of the wildtype esterase led to viruses which reduced the time to death as effectively as did the toxin-expressing virus. In both cases existing recombinant viruses are viewed as leads, and approaches to further improvement in the engineered viruses are suggested. Many of these approaches are based on analogy with the development of classical synthetic insecticides. Using these viruses as examples, the potential utility and limitations of recombinant viruses and other biological insecticides are discussed.