Semiparametric Tensor Factor Analysis by Iteratively Projected SVD

This paper introduces a general framework of Semiparametric TEnsor FActor analysis (STEFA) that focuses on the methodology and theory of low-rank tensor decomposition with auxiliary covariates. STEFA models extend tensor factor models by incorporating instrumental covariates in the loading matrices. We propose an algorithm of Iteratively Projected SVD (IP-SVD) for the semiparametric estimations. It iteratively projects tensor data onto the linear space spanned by covariates and applies SVD on matricized tensors over each mode. We establish the convergence rates of the loading matrices and the core tensor factor. Compared with the Tucker decomposition, IP-SVD yields more accurate estimates with a faster convergence rate. Besides estimation, we show several prediction methods with newly observed covariates based on the STEFA model. On both real and synthetic tensor data, we demonstrate the efficacy of the STEFA model and the IP-SVD algorithm on both the estimation and prediction tasks.Comment: 23 pages, 6 figures, submitte

Detecting Neutrinos from Supernova Bursts in PandaX-4T

Neutrinos from core-collapse supernovae are essential for the understanding of neutrino physics and stellar evolution. The dual-phase xenon dark matter detectors can provide a way to track explosions of galactic supernovae by detecting neutrinos through coherent elastic neutrino-nucleus scatterings. In this study, a variation of progenitor masses as well as explosion models are assumed to predict the neutrino fluxes and spectra, which result in the number of expected neutrino events ranging from 6.6 to 13.7 at a distance of 10 kpc over a 10-second duration with negligible backgrounds at PandaX-4T. Two specialized triggering alarms for monitoring supernova burst neutrinos are built. The efficiency of detecting supernova explosions at various distances in the Milky Way is estimated. These alarms will be implemented in the real-time supernova monitoring system at PandaX-4T in the near future, providing the astronomical communities with supernova early warnings.Comment: 9 pages,6 figure

Search for light dark matter from atmosphere in PandaX-4T

We report a search for light dark matter produced through the cascading decay of $\eta$ mesons, which are created as a result of inelastic collisions between cosmic rays and Earth's atmosphere. We introduce a new and general framework, publicly accessible, designed to address boosted dark matter specifically, with which a full and dedicated simulation including both elastic and quasi-elastic processes of Earth attenuation effect on the dark matter particles arriving at the detector is performed. In the PandaX-4T commissioning data of 0.63 tonne$\cdot$year exposure, no significant excess over background is observed. The first constraints on the interaction between light dark matter generated in the atmosphere and nucleus through a light scalar mediator are obtained. The lowest excluded cross-section is set at $5.9 \times 10^{-37}{\rm cm^2}$ for dark matter mass of $0.1$ MeV$/c^2$ and mediator mass of 300 MeV$/c^2$. The lowest upper limit of $\eta$ to dark matter decay branching ratio is $1.6 \times 10^{-7}$

Inverser Designansatz von Molekülen in Solarzellen

Solar cells have attracted much attention due to the climate change and the energy crisis. But it is still a tremendous challenge to design break-through molecules with high cell efficiency. In contrast to the traditional “trial and error” approaches that design the molecules first and study their properties subsequently, the inverse design approach pursued in this Ph.D. project can be used in automatically identifying structures with the optimum property within a chemical space defined by a backbone and possible substituents. In the present work, this approach has been applied to optimize porphyrins in dye-sensitized solar cells and other systems for photovoltaics. The predicted optimal molecules give guidance for future molecular design. Our approach is also applied to study the role of the backbone when optimizing functional groups. The results show that for some properties, the modifications of the backbone have remarkable impacts on the properties and the optimal sets of functional groups. On the other hand, for other properties, these effects are less pronounced. Although solar cells are the motivation of our present inverse-design approaches and the current playground, in principle every conceivable property can be optimized using our inverse- design approaches. In addition, the studied systems can be almost every class of materials, even macro-molecules or monomers. Accordingly, our inverse-design approach is applicable for a wide range of systems and properties.Solarzellen werden als eine Schlüsseltechnologie für die Energiewende betrachtet, aber das Design von Molekülen, die hohe Zelleffizienzen erzielen, ist immernoch eine enorme Heraus- forderung. Im Gegensatz zu klassischen “trial and error” Designansätzen in denen Moleküle erst synthetisiert und anschließend untersucht werden, verfolgt die vorliegende Arbeit einen inversen Designansatz. Hierbei werden, für ein gegebenes chemisches System aus Gerüst und Substituenten, die Systeme mit den optimalen Eigenschaften automatisch bestimmt. In der vorliegenden Arbeit wurden Porphyrine und andere konjugierte Systeme für die Anwendung in Farbstoffsolarzellen und ähnlichen Photovoltaiksystemen untersucht. Die vorhergesagten Moleküle können als Ausgangspunkt für weitere Studien dienen. Ferner wurde der Ein- fluss des Gerüsts auf die Eigenschaften des optimalen Moleküls und seiner Substituenten untersucht. Die Ergebnisse zeigen, dass für einige Eigenschaften Gerüstmodifikationen grundlegenden Einfluss auf die Eigenschaften und Substitutionsmuster haben, andere Eigen- schaften hingegen wenig betroffen sind. Obwohl der hier eingesetzte inverse Designansatz nur für Solarzellen angewandt wurde, steht einer Anwendung für andere chemische An- wendungen wie z. B. heterogene Katalyse und Wasserstoffspeicherung nichts im Wege. Inverses Design kann auf fast alle Materialklassen von Monomeren bis zu Makromolekülen angewandt und für ein breites Feld von Eigenschaften verwendet werden.The German Research Council, National Natural Science Foundation of Chin

Fiber-Optic Vector-Magnetic-Field Sensor Based on Gold-Clad Bent Multimode Fiber and Magnetic Fluid Materials

A kind of bent multimode fiber (MMF) vector magnetic sensor based on surface plasmon resonance (SPR) was proposed. By plating gold film on the curved part of the bent multimode fiber, the surface plasmon mode (SPM) was excited via a whispering gallery mode (WGM). Fabricating the structure only required bending the fiber and plating it with gold, which perfectly ensured the integrity of the fiber and made it more robust compared with other structures. The sensor used magnetic fluid (MF) as the magnetically sensitive material. Through monitoring the shift of the surface plasmon resonance dip, the as-fabricated sensor not only had a high magnetic field intensity sensitivity of 9749 pm/mT but could also measure the direction of a magnetic field with a high sensitivity of 546.5 pm/°. The additional advantages of the proposed sensor lay in its easy fabrication and good integrity, which make it attractive in the field of vector-magnetic-field sensing

Distinct Expression Profiles and Novel Targets of MicroRNAs in Human Spermatogonia, Pachytene Spermatocytes, and Round Spermatids between OA Patients and NOA Patients

Human spermatogenesis includes three main stages, namely, the mitosis of spermatogonia, meiosis of spermatocytes, and spermiogenesis of spermatids, which are precisely regulated by epigenetic and genetic factors. Abnormality of epigenetic and genetic factors can result in aberrant spermatogenesis and eventual male infertility. However, epigenetic regulators in controlling each stage of normal and abnormal human spermatogenesis remain unknown. Here, we have revealed for the first time the distinct microRNA profiles in human spermatogonia, pachytene spermatocytes, and round spermatids between obstructive azoospermia (OA) patients and non-obstructive azoospermia (NOA) patients. Human spermatogonia, pachytene spermatocytes, and round spermatids from OA patients and NOA patients were isolated using STA-PUT velocity sedimentation and identified by numerous hallmarks for these cells. RNA deep sequencing showed that 396 microRNAs were differentially expressed in human spermatogonia between OA patients and NOA patients and 395 differentially expressed microRNAs were found in human pachytene spermatocytes between OA patients and NOA patients. Moreover, 378 microRNAs were differentially expressed in human round spermatids between OA patients and NOA patients. The differential expression of numerous microRNAs identified by RNA deep sequencing was verified by real-time PCR. Moreover, a number of novel targeting genes for microRNAs were predicted using various kinds of software and further verified by real-time PCR. This study thus sheds novel insights into epigenetic regulation of human normal spermatogenesis and the etiology of azoospermia, and it could offer new targets for molecular therapy to treat male infertility