gebhart/patrepeval huggingface dataset:
High-Energy Metal–Organic Frameworks with a Dicyanamide Linker for Hypergolic Fuels (2021)

In this study, a hypergolic linker (dicyanamide, DCA) and a high-energy nitrogen-rich ligand (1,5-diaminotetrazole, DAT) were applied to construct high-energy metal-organic frameworks (HEMOFs) with hypergolic property. Three novel metal-organic frameworks (MOFs) were synthesized via a mild method with fascinating 2D polymeric architectures, and they could ignite spontaneously upon contact with white fuming nitric acid (WFNA). The gravimetric energy densities of the three HEMOFs all exceeded 26.2 kJ·g<sup>-1</sup>. The cupric MOF exhibits the highest gravimetric and volumetric energy density of 27.5 kJ·g<sup>-1</sup> and 51.3 kJ·cm<sup>-3</sup>, respectively. By adjusting the metal cations, high-energy ligands and hypergolic linkers can improve the performance of hypergolic MOFs. This work provides a strategy for manufacturing MOFs as potential high-energy hypergolic fuels.
Algorithm for the computation of region-based image edge profile acutance (1995)

We propose an algorithm for the computation of a region-based measure of image edge profile (IEP) acutance based on graylevel variations across the boundary of an object. A procedure to calculate the acutance based on region growing and a root-mean-squared gradient measure across region boundaries has been designed and implemented. After testing the algorithm on various images, it is shown that this measure of acutance can accurately reflect changes in the appearance of objects due to blurring and sharpening operations. Using this technique, it should be possible to quantify the level of enhancement in a digital image by calculating the acutance before and after the enhancement operation. The measure should also be useful in comparing specific features or regions of interest in images produced by different imaging systems.
On the oxidation of atmospheric nitrogen in electric arcs (1906)

Kr. Birkeland, Trans. Faraday Soc., 1906, 2, 98 DOI: 10.1039/TF9060200098
RapidSmith: Do-It-Yourself CAD Tools for Xilinx FPGAs (2011)

Creating CAD tools for commercial FPGAs is a difficult task. Closed proprietary device databases and unsupported interfaces are largely to blame for the lack of CAD research found on commercial architectures versus hypothetical architectures. This paper formally introduces RapidSmith, a new set of tools and APIs that enable CAD tool creation for Xilinx FPGAs. Based on the Xilinx Design Language (XDL), RapidSmith provides a compact, yet, fast device database with hundreds of APIs that enable the creation of placers, routers and several other tools for Xilinx devices. RapidSmith alleviates several of the difficulties of using XDL and this work demonstrates the kinds of research facilitated by removing such challenges.
Dry Spinning Based Spinneret Based Tunable Engineered Parameters (STEP) Technique for Controlled and Aligned Deposition of Polymeric Nanofibers (2009)

Polymeric nanofibers are finding increasing number of applications and hold the potential to revolutionize diverse fields such as tissue engineering, smart textiles, sensors, and actuators. Aligning and producing high aspect ratio fiber arrays (length/diameter > 2 000) in the sub-micron and nanoscale diameters has been challenging due to fragility of polymeric materials, thus making it difficult to deposit them as one dimensional structures functionally interfaced with other systems. Here, we present a pseudo dry spinning technique which allows precise control on fiber diameters and further allows deposition of fiber arrays in aligned configurations. Control on fiber diameters ranging from 50-500 nm and having lengths of several millimeters is achieved by altering the polymeric solution concentration. In the dilute and semi-dilute unentangled concentration domain droplets or beaded fibers are observed to form. Smooth uniform diameter fibers are observed to form at the onset of semi-dilute entangled concentration regime. For a given molecular weight, the increase in fiber diameter with increasing solution concentration is attributed to both the increase in the entanglement density and the decrease in the radius of gyration of solvated polymer molecules. Using this technique polymeric fiber arrays in single and multiple layers are demonstrated which can be used towards developing strong textiles, biological scaffolds, and sensor networks.
Molecular organic light-emitting diodes using highly conducting polymers as anodes (2002)

Films fabricated from commercially available poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) aqueous dispersions have been widely used in many electronic and optoelectronic applications. Previous attempts to utilize them as anodes in organic light-emitting diodes (OLEDs) were not satisfactory due to their low conductivity. In this letter we report on the fabrication and characterization of an OLED device made using a highly conductive form of PEDOT:PSS as anode and demonstrate its superior performance relative to that of a similar device using the commercial conducting polymer as an anode. An external electroluminescence quantum efficiency of ∼0.73% was measured at 100 A/m2.
The second derivative of a recurrent network (1994)

The equations for the exact calculation of the second derivative of an error function with respect to the weights (Hessian matrix) of a recurrent network are presented in this paper. The second derivative of feedforward networks has proven useful for fast retraining, weight pruning, and output error estimation. However, until now, techniques based upon the Hessian could not be used for recurrent networks because no exact equations for the second derivative existed. It is the author's hope that the equations presented which allow for the exact calculation of the second derivative will prove useful in the development of new methods for designing recurrent networks.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Channel Estimation Methods Based on Volterra Kernels for MLSD in Optical Communication Systems (2010)

Maximum likelihood sequence detection (MLSD) is the most effective electrical domain equalization scheme for mitigating dispersive optical channel impairments such as chromatic dispersion or polarization-mode dispersion. Parameter estimation for MLSD is not straightforward in optical communication systems due to the square-law nature of photodiodes. We propose a simple and efficient channel parameter estimation scheme for MLSD based on Volterra kernel modeling of the nonlinear distortion of the electrical postdetection signals.
Design of Selective Thrombin Inhibitors Based on the (R)-Phe-Pro-Arg Sequence (2002)

Potent and selective inhibitors of thrombin were sought based on the (R)-Phe-Pro-Arg sequence. The objective was to generate similar binding interactions to those achieved by potent competitive inhibitors of the argatroban type, so eliminating the need for covalent interaction with the catalytic serine function, as utilized by aldehyde and boronic acid type inhibitors. Improving the S(1) subsite interaction by substitution of arginine with a 4-alkoxybenzamidine residue provided potent lead 2 (K(i) = 0.37 nM). Though an amide bond, which H-bonds to the active site, is lost, modeling indicated that a new H-bond is generated between the alkoxy oxygen atom and the catalytic Ser-195 hydroxyl group. Substitution of the benzamidine system by 1-amidinopiperidine then gave compound 4, which provided a further gain in selectivity over trypsin. However, previous work had shown that these compounds were likely to be too lipophilic (Log D +0.4 and +0.2, respectively) and to suffer rapid hepatic extraction, presumably via biliary elimination. Accordingly, both proved short-acting when administered intravenously to rats and showed poor activity when given intraduodenally. The aim was then to reduce lipophilicity below a log D of -1.2, which in a previously reported series had been effective in preventing rapid clearance. It was anticipated that compounds of this type would rely on the cation selective paracellular route of absorption from the gastrointestinal tract. Potent polar analogues with selectivity >1000 over trypsin were obtained. The best in vivo activity was shown by compound 12. However, in the final analysis, its oral bioavilability proved poor, relative to analogues with similar physicochemical properties derived from argatroban, consistent with the hypothesis that molecular shape is an additional important determinant of paracellular absorption.
Identification of Two Mammalian Reductases Involved in the Two-carbon Fatty Acyl Elongation Cascade (2003)

The de novo synthesis of fatty acids occurs in two distinct cellular compartments. Palmitate (16:0) is synthesized from acetyl-CoA and malonyl-CoA in the cytoplasm by the enzymes acetyl-CoA carboxylase 1 and fatty acid synthase. The synthesis of fatty acids longer than 16 carbons takes place in microsomes and utilizes malonyl-CoA as the carbon source. Each two-carbon addition requires four sequential reactions: condensation, reduction, dehydration, and a final reduction to form the elongated fatty acyl-CoA. The initial condensation reaction is the regulated and rate-controlling step in microsomal fatty acyl elongation. We previously reported the cDNA cloning and characterization of a murine long chain fatty acyl elongase (LCE) . Overexpression of LCE in cells resulted in the enhanced addition of two-carbon units to C12-C16 fatty acids, and evidence was provided that LCE catalyzed the initial condensation reaction of long chain fatty acid elongation. The remaining three enzymes in the elongation reaction have not been identified in mammals. Here, we report the identification and characterization of two mammalian enzymes that catalyze the 3-ketoacyl-CoA and trans-2,3-enoyl-CoA reduction reactions in long and very long chain fatty acid elongation, respectively.
FORMS: a flexible object recognition and modelling system (2002)

We briefly describe a generic statistical framework for representing the shapes of animate objects using principal component analysis and stochastic shape grammars. Such a representation scheme gives a formalism for solving the inverse problem-object recognition. Then we show: how these representations can be extracted from 2D silhouettes by a novel method for skeleton extraction and shape segmentation; how a similarity metric can be defined on this shape space; and how we can perform recognition in a bottom up/top down loop. The system is demonstrated to be stable in the presence of noise, the absence of parts, the presence of additional parts, and considerable variations in articulation and viewpoint. Successful categorization is demonstrated on a dataset of seventeen categories of animate objects.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Manufacture of hydroxylamine by reduction of nitric oxide in trickle-bed electrochemical reactors (2010)

The manufacture of hydroxylamine by electrolytic reduction of nitric oxide was experimentally investigated. The experiments were carried out in a two-compartment packed bed electrochemical reactor consisting of a cathodic bed of tungsten carbide and a lead plate anode. The compartments were separated by an anion exchange membrane which was supported by a bed of glass beads on the anode side. The reduction occurred as the nitric oxide gas and sulphuric acid electrolyte trickled down cocurrently over the tungsten carbide bed. Sulphuric acid was also circulated separately through the anode chamber. The efficiency of tungsten carbide particles for nitric oxide reduction was observed to drop between successive runs. When in operation the activity remained fairly stable for a period of twelve hours. The drop in activity between the runs appeared to be the result of surface oxidation of the particles by dissolved or free oxygen. Tungsten carbide nevertheless gave better performance than a graphite bed electrode. The operating parameters studied over the stabilized portion of the activity of fresh tungsten carbide included catholyte flowrate and composition, catholyte recycle, gas flowrate and composition, particle size, bed dimensions and reactor pressure and temperature. In typical operation at atmospheric pressure, a current efficiency of 62% and a hydroxylamine concentration of 0.03 M were obtained under a current density of 213 A m⁻² . Doubling the pressure approximately doubled the current density under which similar current efficiencies were observed. The hy-droxylamine concentration decreased sharply with increase in catholyte flowrate. Increases in gas flow-rate produced only a moderate increase in current efficiency above a certain current density. In recycling catholyte, the hydroxylamine concentration was built up almost linearly with number of passes of catholyte through the reactor without appreciable drop of current efficiency. The rate of reduction of nitric oxide to hydroxylamine appeared to be controlled by mass transfer. Appropriate mass transfer correlations for trickle-bed reactors were suitably corrected for the present system and applied to predict the theoretical limiting current densities.
Gas-coupled acoustic microscopy in the pulse-echo mode (1993)

We demonstrate the technical feasibility of a new scanning acoustic microscope (SAM) system. Unlike the traditional SAMs, which use liquids as couplants, the new system uses gases as couplants. To demonstrate that the new system can operate in the pulse-echo mode, we generated “dark-field” C-scans of the interior of solid objects at MHz frequencies. Previously, gas-coupled ultrasonic imaging was thought to be feasible only in the transmission and surface-reflection modes. In our experiments, coins encapsulated in polymethyl methacrylate (PMMA) were used as subjects. At present, 0.25 mm sub-surface lateral resolutions are attainable at 3 MHz in PMMA and even better performance should be possible at higher frequencies. To facilitate operation in the pulse-echo mode, we had to pressurize the coupling gases, typically nitrogen or argon. At present, pressures in excess of 30 atmospheres are required to reduce the absorption of ultrasound in the coupling gas, substantially increase the conversion efficiency and sensitivity of the transducers, and abate the dynamic-range and recovery-time requirements of the front-end receiver electronics. The image-formation mechanisms of gas-coupled acoustic imaging systems are impacted by the fact that sound propagates more slowly in gases than in liquids (330 m/s in air at standard pressure and temperature vs. 1480 m/s in water) and finite-amplitude saturation effects are observed at much lower sound-pressure levels in gases than in liquids
Internet of Things Architectures, Technologies, Applications, Challenges, and Future Directions for Enhanced Living Environments and Healthcare Systems: A Review (2019)

Internet of Things (IoT) is an evolution of the Internet and has been gaining increased attention from researchers in both academic and industrial environments. Successive technological enhancements make the development of intelligent systems with a high capacity for communication and data collection possible, providing several opportunities for numerous IoT applications, particularly healthcare systems. Despite all the advantages, there are still several open issues that represent the main challenges for IoT, e.g., accessibility, portability, interoperability, information security, and privacy. IoT provides important characteristics to healthcare systems, such as availability, mobility, and scalability, that offer an architectural basis for numerous high technological healthcare applications, such as real-time patient monitoring, environmental and indoor quality monitoring, and ubiquitous and pervasive information access that benefits health professionals and patients. The constant scientific innovations make it possible to develop IoT devices through countless services for sensing, data fusing, and logging capabilities that lead to several advancements for enhanced living environments (ELEs). This paper reviews the current state of the art on IoT architectures for ELEs and healthcare systems, with a focus on the technologies, applications, challenges, opportunities, open-source platforms, and operating systems. Furthermore, this document synthesizes the existing body of knowledge and identifies common threads and gaps that open up new significant and challenging future research directions.
Escalation of Pyrethroid Resistance in the Malaria Vector Anopheles funestus Induces a Loss of Efficacy of Piperonyl Butoxide–Based Insecticide-Treated Nets in Mozambique (2019)

The loss of efficacy of pyrethroid-based LLINs with and without PBO is a concern for the effectiveness of insecticide-based interventions, and action should be taken to prevent the spread of such super-resistance.
Parameter Estimation in Differential Equations: A Numerical Study of Shooting Methods (2011)

Differential equation modeling is central to applications of mathematics to science and engineering. When a particular system of equations is used in an application, it is often important to determine unknown parameters. We compare the traditional shooting method to versions of multiple shooting methods in chaotic systems with noise added and conduct numerical experiments as to the reliability and accuracy of both methods.
光年以外,告别寂寞——《盛夏光年》 (2007)

还是喜欢这样的小电影.之所以说是小电影,因为没有科技的张牙舞爪,也没有剧情的荡气回肠.只有一些剧中演员不经意的眼神,一些简单的对白,一些色彩迷人的画面,在观影结束之后却仍然定格成你的记忆.再三咀嚼.如那盛夏的果实独留芳香,值得回味.……
The Four Arabidopsis REDUCED WALL ACETYLATION Genes are Expressed in Secondary Wall-Containing Cells and Required for the Acetylation of Xylan (2011)

Xylan is one of the major polysaccharides in cellulosic biomass, and understanding the mechanisms underlying xylan biosynthesis will potentially help us design strategies to produce cellulosic biomass better suited for biofuel production. Although a number of genes have been shown to be essential for xylan biosynthesis, genes involved in the acetylation of xylan have not yet been identified. Here, we report the comprehensive genetic and functional studies of four Arabidopsis REDUCED WALL ACETYLATION (RWA) genes and demonstrate their involvement in the acetylation of xylan during secondary wall biosynthesis. It was found that the RWA genes were expressed in cells undergoing secondary wall thickening and their expression was regulated by SND1, a transcriptional master switch of secondary wall biosynthesis. The RWA proteins were shown to be localized in the Golgi, where xylan biosynthesis occurs. Analyses of a suite of single, double, triple and quadruple rwa mutants revealed a significant reduction in the secondary wall thickening and the stem mechanical strength in the quadruple rwa1/2/3/4 mutant but not in other mutants. Further chemical and structural analyses of xylan demonstrated that the rwa1/2/3/4 mutations resulted in a reduction in the amount of acetyl groups on xylan. In addition, the ratio of non-methylated to methylated glucuronic acid side chains was altered in the rwa1/2/3/4 mutant. Together, our results demonstrate that the four Arabidopsis RWA genes function redundantly in the acetylation of xylan during secondary wall biosynthesis.
GraphX: Unifying Data-Parallel and Graph-Parallel Analytics (2014)

From social networks to language modeling, the growing scale and importance of graph data has driven the development of numerous new graph-parallel systems (e.g., Pregel, GraphLab). By restricting the computation that can be expressed and introducing new techniques to partition and distribute the graph, these systems can efficiently execute iterative graph algorithms orders of magnitude faster than more general data-parallel systems. However, the same restrictions that enable the performance gains also make it difficult to express many of the important stages in a typical graph-analytics pipeline: constructing the graph, modifying its structure, or expressing computation that spans multiple graphs. As a consequence, existing graph analytics pipelines compose graph-parallel and data-parallel systems using external storage systems, leading to extensive data movement and complicated programming model. To address these challenges we introduce GraphX, a distributed graph computation framework that unifies graph-parallel and data-parallel computation. GraphX provides a small, core set of graph-parallel operators expressive enough to implement the Pregel and PowerGraph abstractions, yet simple enough to be cast in relational algebra. GraphX uses a collection of query optimization techniques such as automatic join rewrites to efficiently implement these graph-parallel operators. We evaluate GraphX on real-world graphs and workloads and demonstrate that GraphX achieves comparable performance as specialized graph computation systems, while outperforming them in end-to-end graph pipelines. Moreover, GraphX achieves a balance between expressiveness, performance, and ease of use.
Learning where to look (2002)

A theoretical account is presented on how locations of interface objects are learned and how the mechanisms underlying location learning interact with the representativeness of object labels. The account is embodied in a computational cognitive model built within the ACT-R/PM cognitive architecture [1, 2] and is supported by point-of-gaze and performance data collected in empirical research. The model interacts with the same software under the same experimental task conditions as study participants and replicates both performance and the finer-grained point-of-gaze data. Drawing from the data and model, location learning is characterized as a process that occurs as a by-product of interaction such that, without specific intent to do so, users can gradually learn the locations of the interface objects to which they attend. Characteristics of the user interface shape this learning process, however, by constraining the set of possible strategies for interaction. Locations are learned more quickly when the least-effortful strategy available in the interface explicitly requires retrieval of location knowledge
Silyl-Substituted Conjugated Dienes: Versatile Building Blocks in Organic Synthesis (1993)

Different methods for the preparation of various silyl-substituted conjugated dienes and enynes are reviewed. Dienes having a silyl group at the terminal carbon atom are prepared by Peterson-type reactions, Wittig reactions, transition metal catalyzed cross coupling reactions, and thermal decomposition of sulfolenes in addition to other procedures. Internal silyl-substituted dienes are also prepared by similar methods (e.g. transition metal catalyzed cross coupling and thermal decomposition of sulfolenes). The synthetic applications of these dienes such as Diels-Alder reactions, coupling with electrophiles and other useful reactions are discussed