Local Defects in colloidal quantum dot thin films measured via spatially resolved multi-modal optoelectronic spectroscopy.

The morphology, chemical composition, and electronic uniformity of thin-film solution-processed optoelectronics are believed to greatly affect device performance. Although scanning probe microscopies can address variations on the micrometer scale, the field of view is still limited to well under the typical device area, as well as the size of extrinsic defects introduced during fabrication. Herein, a micrometer-resolution 2D characterization method with millimeter-scale field of view is demonstrated, which simultaneously collects photoluminescence spectra, photocurrent transients, and photovoltage transients. This high-resolution morphology mapping is used to quantify the distribution and strength of the local optoelectronic property variations in colloidal quantum dot solar cells due to film defects, physical damage, and contaminants across nearly the entire test device area, and the extent to which these variations account for overall performance losses. It is found that macroscopic defects have effects that are confined to their localized areas, rarely prove fatal for device performance, and are largely not responsible for device shunting. Moreover, quantitative analysis based on statistical partitioning methods of such data is used to show how defect identification can be automated while identifying variations in underlying properties such as mobilities and recombination strengths and the mechanisms by which they govern device behavior.DMR-1807342 - National Science Foundation; Hopkins Extreme Materials InstituteAccepted manuscrip

Extending the Potential of Thin-film Optoelectronics via Optical Engineering

Optoelectronics based on nanomaterials have become a research focus in recent years, and this technology bridges the fields of solid state physics, electrical engineering and materials science. The rapid development in optoelectronic devices in the last century has both benefited from and spurred advancements in the science and engineering of pho- ton detection and manipulation, image sensing, high-efficiency and high-power-density light emission, displays, communications and renewable energy harvesting. A particu- larly promising material class for optoelectronics is colloidal nanomaterials, due to their functionality, cost -efficiency and even new physics, thanks to their exotic properties in the areas of light-matter interaction, low-dimensionality, and solution-processability which dramatically reduces the time and cost required to fabricate thin film devices, and at the same time provides wide compatibility with existing materials interfaces and device structures. This thesis focuses on exploring and assessing the capabilities of lead sulfide quantum dot-based solar cells and photodetectors. The discussion involves advances in techniques such as implementing novel photonic structures, designing and building novel characterization systems and methods, and coupling to external optical structures and components. This thesis comprises three sections. The first section focuses on the design and adap- tion of photonic structures to tailor the function and response of photovoltaics and other absorption-based optoelectronics for specific applications. in the first part, we introduce consideration of complete multi-layer thin film interference effects into the design of so- ii lar cells. By numerical calculation and optimization of the film thicknesses as well as the precise fabrication control, devices with specific target colors or optical transparency levels were achieved. In the second part, we investigate the presence of 2D photonic crystal bands in absorbing materials that can be readily incorporated into nanomaterial thin films through nanostructuring of the material. We carried out simulations and the- oretical analyses and proposed a method to realize simultaneous selectivity in the device reflection, transmission and absorption spectra that are critical for optoelectronic appli- cations. The next section focuses on designing and building a multi-modal microscopy sys- tem for thin-film optoelectronic devices, accompanied with analyses and explanation of complex experimental data. The goal of the system was to provide simultaneous 2D spatial measurements of, including but not limited to, photoluminescence spectra, time- resolved photocurrent and photovoltage responses, and a rich variety of all the possible combinations of these measurements and their associated derived quantities, collected with micrometer resolution. The multi-dimensional data helped us understand the in- tercorrelation between local defective regions in films and the entire device behavior, as well as a more comprehensive profile of mutual relationships between solar cell figures of merit. In the last section, we discuss a new implementation of miniature solar concentrator arrays for lead sulfide quantum dot solar cells. First, we design and analyze the effects of a medium concentration ratio lens-type concentrator made from polydimethylsiloxane, a flexible organosilicon polymer. The concentrators were designed and optimized with the aid of ray-tracing simulation tools to achieve the best compatibility with colloidal nanomaterial-based solar cells. Experimentally, we produced an integrated concentrator system delivering 20-fold current and power enhancements close to the theoretical pre- dictions , and also used our concentrator measurements to explain the rarely-explored carrier dynamics critical to high-power operation of thin film solar cells. Next, we de- iii sign a wide-acceptance-angle dielectric solar concentrator that can be adapted to many types of high- efficiency small-area solar cells. The design was generated using rigorous optical models that define the behaviors of light rays, and was verified with ray-tracing optical simulations to yield results for the full annual 2D time-resolved collectible power for the resulting system. Finally, we discuss strategies for further extending the possi- bilities of nanomaterial-based optoelectronics for future challenges in energy production and related applications

New Approach for Unambiguous High-Resolution Wide-Swath SAR Imaging

The high-resolution wide-swath (HRWS) SAR system uses a small antenna for transmitting waveform and multiple antennas both in elevation and azimuth for receiving echoes. It has the potential to achieve wide spatial coverage and fine azimuth resolution, while it suffers from elevation pattern loss caused by the presence of topographic height and impaired azimuth resolution caused by nonuniform sampling. A new approach for HRWS SAR imaging based on compressed sensing (CS) is introduced. The data after range compression of multiple elevation apertures are used to estimate direction of arrival (DOA) of targets via CS, and the adaptive digital beamforming in elevation is achieved accordingly, which avoids the pattern loss of scan-on-receive (SCORE) algorithm when topographic height exists. The effective phase centers of the system are nonuniformly distributed when displaced phase center antenna (DPCA) technology is adopted, which causes Doppler ambiguities under traditional SAR imaging algorithms. Azimuth reconstruction based on CS can resolve this problem via precisely modeling the nonuniform sampling. Validation with simulations and experiment in an anechoic chamber are presented

Serving Deep Learning Model in Relational Databases

Serving deep learning (DL) models on relational data has become a critical requirement across diverse commercial and scientific domains, sparking growing interest recently. In this visionary paper, we embark on a comprehensive exploration of representative architectures to address the requirement. We highlight three pivotal paradigms: The state-of-the-artDL-Centricarchitecture offloadsDL computations to dedicated DL frameworks. The potential UDF-Centric architecture encapsulates one or more tensor computations into User Defined Functions (UDFs) within the database system. The potentialRelation-Centricarchitecture aims to represent a large-scale tensor computation through relational operators. While each of these architectures demonstrates promise in specific use scenarios, we identify urgent requirements for seamless integration of these architectures and the middle ground between these architectures. We delve into the gaps that impede the integration and explore innovative strategies to close them. We present a pathway to establish a novel database system for enabling a broad class of data-intensive DL inference applications.Comment: Authors are ordered alphabetically; Jia Zou is the corresponding autho

Metabolomics of Clinical Poisoning by Aconitum Alkaloids Using Derivatization LC-MS

The root of Aconitum kusnezoffii (Caowu in Chinese, CW) is not only commonly used as a traditional Chinese medicine (TCM), but also served as a tonic in China. Due to its high toxicity, clinical poisoning cases induced by CW have frequently been reported. However, the mechanism is still unclear. In this study, Aconitum alkaloids and altered endogenous metabolites in CW poisoning patients were investigated to elucidate the possible intoxication mechanism. Eighteen alkaloids, including 6 toxic diester diterpenoid alkaloids (DDAs), were determined from the sera of patients. At the same time, 5-(diisopropylamino)amylamine (DIAAA) derivatization-ultrahigh performance liquid chromatography- quadrupole-time of flight mass spectrometry (UHPLC-Q-TOF/MS) approach was applied in the metabolomics analysis to find much more carboxyl-containing metabolites (CCMs), which are the essential components for life and critical to elucidate the mechanism of toxicity. As a result, 32 altered metabolites after poisoning were identified. Among them, hydroxyeicosatetraenoic acids (HETEs) and some dicarboxylic acids were first found to be related to Aconitum alkaloids toxicity. Finally, biological pathway analysis indicated that the significantly changed metabolites were primarily involved in amino acid metabolism, TCA cycle, fatty acid metabolism, pyruvate metabolism, arachidonic acid metabolism, sphingolipid metabolism and so on. These results can not only provide more information on the mechanism of CW intoxication but also help the clinical diagnosis of CW poisoning

Terlipressin May Decrease In-Hospital Mortality of Cirrhotic Patients with Acute Gastrointestinal Bleeding and Renal Dysfunction: A Retrospective Multicenter Observational Study

Acute gastrointestinal bleeding (GIB) rapidly reduces effective blood volume, thereby precipitating acute kidney injury (AKI). Terlipressin, which can induce splanchnic vasoconstriction and increase renal perfusion, has been recommended for acute GIB and hepatorenal syndrome in liver cirrhosis. Thus, we hypothesized that terlipressin might be beneficial for cirrhotic patients with acute GIB and renal impairment. In this Chinese multi-center study, 1644 cirrhotic patients with acute GIB were retrospectively enrolled. AKI was defined according to the International Club of Ascites (ICA) criteria. Renal dysfunction was defined as serum creatinine (sCr) > 133 μmol/L at admission and/or any time point during hospitalization. Incidence of renal impairment and in-hospital mortality were the primary end-points. The incidence of any stage ICA-AKI, ICA-AKI stages 1B, 2, and 3, and renal dysfunction in cirrhotic patients with acute GIB was 7.1%, 1.8%, and 5.0%, respectively. The in-hospital mortality was significantly increased by renal dysfunction (14.5% vs. 2.2%, P < 0.001) and ICA-AKI stages 1B, 2, and 3 (11.1% vs. 2.8%, P = 0.011), but not any stage ICA-AKI (5.7% vs. 2.7%, P = 0.083). The in-hospital mortality was significantly decreased by terlipressin in patients with renal dysfunction (3.6% vs. 20.0%, P = 0.044), but not in those with any stage ICA-AKI (4.5% vs. 6.0%, P = 0.799) or ICA-AKI stages 1B, 2, and 3 (0.0% vs. 14.3%, P = 0.326). Renal dysfunction increased the in-hospital mortality of cirrhotic patients with acute GIB. Terlipressin might decrease the in-hospital mortality of cirrhotic patients with acute GIB and renal dysfunction. NCT03846180 ( https://clinicaltrials.gov )