gebhart/patrepeval huggingface dataset:
Postprocessing Techniques for Time-resolved Contrast-enhanced MR Angiography (2002)

The purpose of this study was to improve dynamic two-dimensional projection magnetic resonance digital subtraction angiography by using remasking and filtering postprocessing techniques. Four methods were evaluated in 50 patients: default mask subtraction, remasked subtraction, filtering based on the SD, and linear filtering. The results demonstrated that postprocessing techniques such as linear filtering can reduce background motion artifacts and improve arterial contrast-to-noise ratio.
Engineering Crystalline Grain of Hybrid Perovskites for High Efficiency Solar Cells and Beyond (2015)

The presentation provides the recent advances of our group in developing high efficiency organolead trihalide perovskites thin film and single crystal solar cells, and understanding how perovskite solar cells work.
Topological Plasticity of Enzymes Involved in Disulfide Bond Formation Allows Catalysis in Either the Periplasm Or the Cytoplasm (2013)

The transmembrane enzymes disulfide bond forming enzyme B (DsbB) and vitamin K epoxide reductase (VKOR) are central to oxidative protein folding in the periplasm of prokaryotes. Catalyzed formation of structural disulfide bonds in proteins also occurs in the cytoplasm of some hyperthermophilic prokaryotes through currently, poorly defined mechanisms. We aimed to determine whether DsbB and VKOR can be inverted in the membrane with retention of activity. By rational design of inversion of membrane topology, we engineered DsbB mutants that catalyze disulfide bond formation in the cytoplasm of Escherichia coli. This represents the first engineered inversion of a transmembrane protein with demonstrated conservation of activity and substrate specificity. This successful designed engineering led us to identify two naturally occurring and oppositely oriented VKOR homologues from the hyperthermophile Aeropyrum pernix that promote oxidative protein folding in the periplasm or cytoplasm, respectively, and hence defines the probable route for disulfide bond formation in the cytoplasm of hyperthermophiles. Our findings demonstrate how knowledge on the determinants of membrane protein topology can be used to de novo engineer a metabolic pathway and to unravel an intriguingly simple evolutionary scenario where a new "adaptive" cellular process is constructed by means of membrane protein topology inversion.
Rational Design of Potent Non-Nucleoside Inhibitors of HIV-1 Reverse Transcriptase (2012)

A new series of non-nucleoside reverse transcriptase inhibitors based on an imidazole-amide biarylether scaffold has been identified and shown to possess potent antiviral activity against HIV-1, including the NNRTI-resistant Y188L mutated virus. X-ray crystallography of inhibitors bound to reverse transcriptase, including a structure of the Y188L RT protein, was used extensively to help identify and optimize the key hydrogen-bonding motif. This led directly to the design of compound 43 that exhibits remarkable antiviral activity (EC50<1 nM) against a wide range of NNRTI-resistant viruses and a favorable pharmacokinetic profile across multiple species.
Description of and Results from a Novel Borehole Gravity Gradiometer (2007)

SummaryGravitec Downhole Instruments Ltd. is in the final stages of adapting its gravity gradiometer technology for deployment in the borehole environment for use in exploration as well as for time-lapse reservoir monitoring. The project, named Scorpius, is in cooperation with partners Kenda Capital and QinetiQ Ltd.Laboratory testing of the sensor has produced gravity gradient measurements. Work has also been done to forward model the effects of gravity gradient measurements in the borehole environment.
Performance Metrics, Sampling Schemes, and Detection Algorithms for Wideband Spectrum Sensing (2014)

In this paper, we study the problem of wideband spectrum sensing for cognitive radio networks by partitioning it into four fundamental elements: system modeling, performance metrics, sampling schemes, and detection algorithms. Each element can potentially couple the individual channels so that designs for wideband spectrum sensing should consider the four elements jointly. We propose the p-sparse model for the primary occupancies and study three uniform sampling schemes for wideband spectrum sensing, specifically, partial-band Nyquist sampling, sequential narrowband Nyquist sampling, and integer undersampling. We suggest new performance metrics more appropriate for wideband spectrum sensing, specifically, the probability of insufficient spectrum opportunity and the probability of excessive interference opportunity. We also develop detection algorithms that effectively tradeoff these metrics. Our results indicate that for performance metrics that couple the individual channels, multichannel detection algorithms have a significant advantage over channel-by-channel detection algorithms even for wideband Nyquist sampling. Furthermore, integer undersampling, which corresponds to the simplest sub-Nyquist sampling scheme, along with suitable detection algorithms exhibits appealing detection performance in the regime that better protects the primary system.
Sputtered amorphous Fe–Te films: Structural and electrical studies (1986)

Thin films of an iron–tellurium alloy were prepared by rf sputtering and characterized by means of x-ray diffraction and Mössbauer spectroscopy. In an immiscible range in equilibrium composition, tellurium atoms were incorporated into iron, distorting the lattice to some extent. Beyond 14 at. % of Te, an amorphous structure appeared. Judging from the metastable superstructures formed at higher substrate temperatures and the covalent nature in the bonding, the kinetic hindrance against the redistribution of the elements due to the local atomic forces during rapid quenching plays a critical role in the formation of amorphous structure in this alloy. In addition, beyond some intermetallic range around 60 at. % Te, an amorphous phase also exists in the tellurium-rich region. The thermal stability was examined by a differential scanning calorimetry; the electrical resistivity is also discussed.
Voltage dependent capacitances of organic light emitting devices. (2001)

Various structures of organic light-emitting devices (OLEDs) including electrophosphorescence were measured for their capacitances. The zero bias capacitances were in inverse proportion to the total thickness of organic layers. Positive bias voltage only affected the capacitances. It is suggested that Joule heating of organic layers caused the dependences of the capacitances on voltage. The maximal capacitances were scattered from 7 to 34nF/cm2, and in inverse proportion not only to the total thickness, but also to the single layer thickness of Alq. The similarity of these proportionality factors suggested that the dielectric constants of the hole transports and Alq were not so different, and the contribution of Alq layer was dominant for the maximal capacitance. The capacitances of OLEDs were roughly estimated from total thickness without respect to the difference of dielectric constants of whole layers.
Reversible Dimerization of Polymeric Amphiphiles Acts as a Molecular Switch of Enzymatic Degradability (2017)

Enzyme-responsive polymeric micelles have great potential as drug delivery systems due to the high selectivity and overexpression of disease-associated enzymes, which could be utilized to trigger the release of active drugs only at the target site. We previously demonstrated that enzymatic degradation rates of amphiphilic PEG-dendron hybrids could be precisely tuned by gradually increasing the hydrophobic to hydrophilic ratio. However, with the increase in hydrophobicity, the micelles rapidly became too stable and could not be degraded, as often encountered for many other amphiphilic assemblies. Here we address the challenge to balance between stability and reactivity of enzymatically degradable assemblies by utilizing reversible dimerization of diblock polymeric amphiphiles to yield jemini amphiphiles. This molecular transformation serves as a tool to control the critical micelle concentration of the amphiphiles in order to tune their micellar stability and enzymatic degradability. To demonstrate this approach, we show that simple dimerization of two polymeric amphiphiles through a single reversible disulfide bond significantly increased the stability of their micellar assemblies toward enzymatic degradation, although the hydrophilic to hydrophobic ratio was not changed. Reduction of the disulfide bond led to dedimerization of the polymeric hybrids and allowed their degradation by the activating enzyme. The generality of the approach is demonstrated by designing both esterase- and amidase-responsive micellar systems. This new molecular design can serve as a simple tool to increase the stability of polymeric micelles without impairing their enzymatic degradability.
Coherence properties of a mid-infrared frequency comb produced by a degenerate optical parametric oscillator (2011)

We show that a broadband mid-infrared frequency comb produced by a degenerate optical parametric oscillator (OPO) is stable and phase locked to the pump. Moreover, the OPO can operate in two phase and two frequency states. In this experiment, two identical OPOs were synchronously pumped by a single 70-fs fiber laser at 1560 nm and produced broadband (>1000-nm-wide) frequency combs centered at 3120 nm. We observed stable interference fringes between the outputs of the OPOs. Also, by fine-tuning the OPO cavity length, the whole frequency comb could be shifted by steps of half the repetition rate. These results prove that sub-harmonic OPOs are suitable candidates for generation of phase-locked frequency combs in mid-IR.
Fused array preforms for the fabrication of photonic crystal fibers (2004)

A new approach for the fabrication of preforms used in drawing photonic crystal fibers is described. A multi-step process is used that involves stacking a bundle of rods and tubes of dissimilar glasses, fusing the bundle, and then etching the fused bundle to remove one of the two glasses.
Conditions for optimal efficiency of PCBM-based terahertz modulators (2017)

We demonstrate the conditions for optimal modulation efficiency of active terahertz modulators based on phenyl-C61-butyric acid methyl ester (PCBM)-silicon hybrid structures. Highly efficient active control of the terahertz wave modulation was realized by controlling organic film thickness, annealing temperature, and laser excitation wavelength. Under the optimal conditions, the modulation efficiency reached nearly 100%. Charge distributions measured with a near-field scanning microwave microscanning technique corroborated the fact that the increase of photo-excited carriers due to the PCBM–silicon hybrid structure enables the enhancement of active modulation efficiency.
Design and performance of randomized schedules for time-domain wavelength interleaved networks (2009)

Time-domain wavelength interleaved networking (TWIN) is an optical mesh network architecture in which each edge node has one (or more) tunable lasers to transmit fixed-length bursts to various destinations and one (or more) burst-mode receivers capable of decoding each burst intended to it. In this architecture, the interior nodes route each burst independently and passively based on the wavelength of the burst. Network scheduling is thus a critical component that arbitrates burst transmissions from sources to destinations so that conflicts are either avoided or minimized, and wavelength division multiplexing (WDM) transport capacity is efficiently utilized. However, in access or metro networks, which lend themselves naturally to the TWIN mesh architecture, centralized network scheduling would be cumbersome. We consider a distributed mechanism that performs scheduling of bursts to further simplify TWIN mesh architectures. In one realization, each source randomly assigns non-overlapping time slots within a frame for its transmissions. In another realization, each destination grants random but non-overlapping time slots to sources for transmissions. In neither scheme is there any coordination across sources and destinations. We present an analytical formulation of these schemes and investigate their performance under two broad types of traffic: dynamic traffic and semi-dynamic traffic. For dynamic traffic, the analytical results show that for offered load close to 100 percent of capacity, there is 63 percent efficiency for the destination-based mechanism and 37 percent efficiency for the source-based mechanism. When end-to-end demands are semi dynamic, we show through simulations that the destination-based random schedules can achieve over 90 percent efficiency even for offered loads close to 100 percent. These results indicate that the proposed distributed schemes, though exceedingly simple, provide acceptable efficiency comparable to that realized by computation-intensive centralized schedulers irrespective of propagation delays and applicable to any kind of network traffic.
Attenuated reovirus displays oncolysis with reduced host toxicity (2010)

Despite containing a truncated attachment protein, AV reovirus still preferentially targets cancer cells, and compared with wild-type reovirus it shows reduced toxicity when administered to immunodeficient hosts, suggesting the potential use of AV reovirus in combination cancer therapy.
Quantifying the Deposition of Airborne Particulate Matter Pollution on Skin Using Elemental Markers (2020)

Airborne particulate matter (PM) pollution is an environmental and health concern. The health impact of PM pollution has typically focused on the respiratory system. The impact of PM pollution on skin has been largely understudied due to the lack of a quantitative method to measure the deposition on skin. This manuscript presents a method to quantify PM pollution on skin using elemental markers as a proxy for PM. Skin tape strips were collected from forehead and buttock of 100 outdoor workers in Beijing, China. Skin samples were analyzed for 19 elemental markers using inductively coupled plasma mass spectrometry. To determine the specific elemental signature of PM for the region, air samples were collected over 7 days for PM < 2.5 μm (PM<sub>2.5</sub>) and analyzed for the same 19 elements as the skin samples. An enrichment factor was calculated for each element and the potential source was evaluated. Using the elemental markers unique to PM pollution for the region, the PM concentration deposited on skin was determined to be 0.621-2.53 μg PM<sub>2.5</sub> /cm<sup>2</sup>. This method can be re-applied in different regions and the PM concentration on skin can inform future studies on the health impact of air pollution on skin.
Pulsed Heat Transfer for Thermal Maximum Power Point Tracking (2013)

This paper presents a new method for enhancing thermal energy harvesting via pulsed heat transfer. By acting as a variable thermal resistance that theoretically generates no entropy, a pulsed thermal connection allows calibration of the effective thermal resistance of an energy harvesting system. By adjusting the frequency and duty cycle of the pulsed heat transfer, the method allows an energy harvester to be continuously optimized for a variable incident heat flux. In this paper, the analysis of a generalized model shows how the pulse strategy theoretically allows any heat engine-heat sink pair to work at the same power and efficiency as a 1:1 thermal resistance-matched engine-heat sink pair of equal or greater total thermal resistance. Experiments with a mechanical thermal switch validate this model, and show how the pulse strategy can improve the efficiency of a system with equal engine and heat sink thermal resistances by over 80% with no increase in the hot-side maximum temperature, although at reduced total power. At a 1:2 engine-sink resistance ratio, the improvement can simultaneously exceed 60% in power and 15% in efficiency. The thermal pulse strategy could be implemented to improve of a variety of systems that convert thermal energy, from waste heat harvesters to the radioisotope power systems on many spacecraft. Topics: Heat transfer
Rotating Brush Seal (2002)

The proven technology of brush seals has been extended to the mitigation of problems arising from friction and wear at the bristle-rotor interface at high surface speeds. In prototype testing, the brush is mounted on, and free to rotate with the shaft, thus providing a complaint primary seal. A face seal positioned between the backing plate of the brush seal and the housing provides a secondary seal. The purpose of this paper is to demonstrate the interaction between the brush bristles and the shaft at high surface speeds as well as introduce a numerical model to simulate the bristle behavior. A test facility was constructed to study the effects of centrifugal forces on bristle deflection in a single rotating brush seal. The bristle-rotor interface was observed through a video camera, which utilized a high magnification borescope and a high frequency strobe light source. Rotational speeds of the rotor and the brush seal were measured by a magnetic and optical speed sensor, respectively. Preliminary results with speeds up to 11,000 rpm show no speed differential between the brush seal and rotor, or any instability problems associated with the brush seal. Bristle liftoff from the rotor is successfully captured on video.
WAN-optimized replication of backup datasets using stream-informed delta compression (2012)

Replicating data off site is critical for disaster recovery reasons, but the current approach of transferring tapes is cumbersome and error prone. Replicating across a wide area network (WAN) is a promising alternative, but fast network connections are expensive or impractical in many remote locations, so improved compression is needed to make WAN replication truly practical. We present a new technique for replicating backup datasets across a WAN that not only eliminates duplicate regions of files (deduplication) but also compresses similar regions of files with delta compression, which is available as a feature of EMC Data Domain systems. Our main contribution is an architecture that adds stream-informed delta compression to already existing deduplication systems and eliminates the need for new, persistent indexes. Unlike techniques based on knowing a file's version or that use a memory cache, our approach achieves delta compression across all data replicated to a server at any time in the past. From a detailed analysis of datasets and statistics from hundreds of customers using our product, we achieve an additional 2X compression from delta compression beyond deduplication and local compression, which enables customers to replicate data that would otherwise fail to complete within their backup window.
Wavelet-based feature indices as a data mining tool for hyperspectral imagery exploitation (2004)

Advances in hyperspectral sensor technology increasingly provide higher resolution and higher quality data for the accurate generation of terrain categorization/classification (TERCAT) maps. The generation of TERCAT maps from hyperspectral imagery can be accomplished using a variety of spectral pattern analysis algorithms; however, the algorithms are sometimes complex, and the training of such algorithms can be tedious. Further, hyperspectral imagery contains a voluminous amount of data with contiguous spectral bands being highly correlated. These highly correlated bands tend to provide redundant information for classification/feature extraction computations. In this paper, we introduce the use of wavelets to generate a set of Generalized Difference Feature Index (GDFI) measures, which transforms a hyperspectral image cube into a derived set of GDFI bands. A commonly known special case of the proposed GDFI approach is the Normalized Difference Vegetation Index (NDVI) measure, which seeks to emphasize vegetation in a scene. Numerous other band-ratio measures that emphasize other specific ground features can be shown to be a special case of the proposed GDFI approach. Generating a set of GDFI bands is fast and simple. However, the number of possible bands is capacious and only a few of these “generalized ratios” will be useful. Judicious data mining of the large set of GDFI bands produces a small subset of GDFI bands designed to extract specific TERCAT features. We extract/classify several terrain features and we compare our results with the results of a more sophisticated neural network feature extraction routine.
Polyaniline Nanofiber Composites with Metal Salts: Chemical Sensors for Hydrogen Sulfide (2005)

The ability to control and enhance the response of polyaniline nanofibers to molecules such as hydrogen sulfide is demonstrated through the formation of nanostructured, conducting organic/inorganic hybrid materials. Polyaniline nanofiber composites with transition-metal chlorides have remarkable responses to hydrogen sulfide that are up to four orders of magnitude greater than the corresponding unmodified nanofibers (see graph).
Surface Reflectance Estimation Using Prior Spatial and Spectral Information (2007)

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Surface Prior-Information Reflectance Estimation (SPIRE) algorithms estimate changes in spectral reflectance using imperfect prior spatial and spectral information. This paper combines spectral and spatial processing to estimate local changes in spectral reflectance between pairs of spectral images under spatially and spectrally varying multiplicative and additive noise, which arise from variations in illumination and atmospheric effects. This approach extends the spatial SPIRE algorithms that were described earlier and utilizes only a prior reflectance image cube and ensembles of typical multiplicative and additive illumination noise spectral vectors that are deduced from images cubes of similar scenes. The method minimizes the impact of environmental noise by replacing with their prior equivalents low-spatial-frequency content and low-order principal components that are known to be noisy based on prior noise spectra. This filtering and substitution process occurs in log space when minimizing the effects of multiplicative noise. Tests on Hyperspectral Digital Imagery Collection Experiment visible near-infrared–shortwave infrared data demonstrated the algorithm's superior ability to estimate absolute reflectance changes under varying illumination conditions. SPIRE performance was nearly identical to the empirical line method (ELM) ground-truth-based atmospheric compensation results and was better than the physics-based ATmospheric REMoval (ATREM) code overall, particularly, under high clouds and haze. A “Selective SPIRE” technique that chooses between combined-spatial/spectral and spectral-only SPIRE reflectance estimates was developed; it maximizes estimation performance on both changed and unchanged pixels. Minimum-distance classification experiments demonstrated Selective SPIRE's superior performance relative to both ATREM and ELM in cross-image supervised classification applications. </para>