Electrical and optical properties of zinc oxide for scintillator applications

Zinc oxide (ZnO) is a wide-band-gap semiconductor suitable for many optical and optoelectronic applications. Among these is to use single crystal, powder, or ceramic forms of ZnO as a fast UV scintillator. In this work, the electrical and optical properties of ZnO were studied using photoluminescence, X-ray-induced luminescence, optical absorption, and Hall Effect techniques. This study included single crystal ZnO and ZnO:Ga samples grown from high-pressure-melt (HPM), seeded chemical-vapor-transport (SCVT), and hydrothermal (HYD) techniques; powder samples synthesized using both solution and solid-state processes, and purchased from different commercial sources; and ceramic samples prepared by hot-uni-axial-pressing and spark-plasma-sintering methods. Temperature-dependent PL and Hall measurements were combined to establish the luminescence origins in the n-type ZnO and ZnO:Ga single crystals. Based on a PL line-shape analysis, including band-gap renormalization, the direct (e,h) transition is the main luminescent channel in highly n-type ZnO:Ga, while FX and FX-LO recombinations are responsible for the UV PL from as-grown ZnO. An intrinsic mobility limit for n-type ZnO was established by including three major phonon-scattering mechanisms. Analysis of Hall data from single-crystal samples including both neutral- and ionized-impurity scatterings provided donor and acceptor concentrations and energy levels. High n-type single-crystal ZnO samples prepared either by Ga doping and co-doping, or by after-growth treatments, were also studied. Absorption and reflectance data were used to obtain free carrier concentrations from the Ga-doped and co-doped crystals, and it was found that several samples with n ∼ high-1018 to low-1019 cm -3 had optimum UV luminescence. Anneal treatments in reducing atmospheres increased free carrier concentrations in HPM and HYD samples, but an induced absorption band due to oxygen vacancies limited the UV emission from these samples. PL and X-ray-induced luminescence studies on powder ZnO:Ga samples demonstrated that high Ga-doping levels and H-anneal treatments can improve UV emission, while impurities such as Cu and Li enhance the lower energy visible emissions and affect the UV output. For ceramic forms of ZnO, reduction of scattering losses remains as the main challenge for improved scintillation

Exploring an LM to generate Prolog Predicates from Mathematics Questions

Recently, there has been a surge in interest in NLP driven by ChatGPT. ChatGPT, a transformer-based generative language model of substantial scale, exhibits versatility in performing various tasks based on natural language. Nevertheless, large language models often exhibit poor performance in solving mathematics questions that require reasoning. Prior research has demonstrated the effectiveness of chain-of-thought prompting in enhancing reasoning capabilities. Now, we aim to investigate whether fine-tuning a model for the generation of Prolog codes, a logic language, and subsequently passing these codes to a compiler can further improve accuracy. Consequently, we employ chain-of-thought to fine-tune LLaMA7B as a baseline model and develop other fine-tuned LLaMA7B models for the generation of Prolog code, Prolog code + chain-of-thought, and chain-of-thought + Prolog code, respectively. The results reveal that the Prolog generation model surpasses the baseline in performance, while the combination generation models do not yield significant improvements. The Prolog corpus based on GSM8K and the correspondingly finetuned Prolog generation model based on LLaMA7B are released to the research community.Comment: 6 pages, 3 figure

Analysing Railway Safety with Systems Thinking

Railway system is a socio-technical system because the operation of such system also heavily relies on the management of human activities and operating procedures in the organisation, as well as the execution of technical subsystems. Safety of these systems therefore is more than just about engineering their technical subsystems. The latest approach from systems engineering considers that an accident is due to inadequate controlled interactions in the system and is usually a dynamic event chain started from the activation of a hazard and culminated in a complex process of sequential and concurrent events until the system is eventually out of control. Meanwhile the analysis of these systems’s safety becomes much harder when simply applying the traditional techniques of safety assessment. It is because, first of all, a social-technical system consists of a lot of complex and non-linear interactions, traditional techniques show their limits when analysing complex systems. And secondly, the safety of a social-technical system requires a system perspective, which should take all the behaviours (desired and undesired but predicted) of a system as a whole in the context of its environment. To capture the information needed, the models for these analyses (i.e., fault tree and FMEA table) will become too complex to have a systemic view of each individual causal factor. In this paper, we proposed an approach based on system thinking and system dynamics to analyse the safety of a social-technical system. The case study of a tram accident is simple enough for the purpose of demonstrating its feasibility and benefits. The comparison with fault tree analysis was conducted, but it was not for the evaluation of our approach. The real evaluation comes from the extensive applications in real world

On The I/O Complexity of Dynamic Distinct Counting

In dynamic distinct counting, we want to maintain a multi-set S of integers under insertions to answer efficiently the query: how many distinct elements are there in S? In external memory, the problem admits two standard solutions. The first one maintains $S$ in a hash structure, so that the distinct count can be incrementally updated after each insertion using O(1) expected I/Os. A query is answered for free. The second one stores S in a linked list, and thus supports an insertion in O(1/B) amortized I/Os. A query can be answered in O(N/B log_{M/B} (N/B)) I/Os by sorting, where N=|S|, B is the block size, and M is the memory size. In this paper, we show that the above two naive solutions are already optimal within a polylog factor. Specifically, for any Las Vegas structure using N^{O(1)} blocks, if its expected amortized insertion cost is o(1/log B}), then it must incur Omega(N/(B log B)) expected I/Os answering a query in the worst case, under the (realistic) condition that N is a polynomial of B. This means that the problem is repugnant to update buffering: the query cost jumps from 0 dramatically to almost linearity as soon as the insertion cost drops slightly below Omega(1)

Simple and Efficient Heterogeneous Graph Neural Network

Heterogeneous graph neural networks (HGNNs) have powerful capability to embed rich structural and semantic information of a heterogeneous graph into node representations. Existing HGNNs inherit many mechanisms from graph neural networks (GNNs) over homogeneous graphs, especially the attention mechanism and the multi-layer structure. These mechanisms bring excessive complexity, but seldom work studies whether they are really effective on heterogeneous graphs. This paper conducts an in-depth and detailed study of these mechanisms and proposes Simple and Efficient Heterogeneous Graph Neural Network (SeHGNN). To easily capture structural information, SeHGNN pre-computes the neighbor aggregation using a light-weight mean aggregator, which reduces complexity by removing overused neighbor attention and avoiding repeated neighbor aggregation in every training epoch. To better utilize semantic information, SeHGNN adopts the single-layer structure with long metapaths to extend the receptive field, as well as a transformer-based semantic fusion module to fuse features from different metapaths. As a result, SeHGNN exhibits the characteristics of simple network structure, high prediction accuracy, and fast training speed. Extensive experiments on five real-world heterogeneous graphs demonstrate the superiority of SeHGNN over the state-of-the-arts on both accuracy and training speed.Comment: Accepted by AAAI 202

Insulin resistance in Chinese patients with type 2 diabetes is associated with C-reactive protein independent of abdominal obesity

<p>Abstract</p> <p>Background</p> <p>There is debate as to whether the association between C-reactive protein (CRP) and insulin resistance is independent of body fatness, particularly central obesity. Therefore, the association among CRP, insulin resistance and obesity was analyzed in Chinese patients with type 2 diabetes.</p> <p>Methods</p> <p>The study included 520 Chinese patients diagnosed with type 2 diabetes with CRP levels not exceeding 10 mg/L. The degree of insulin resistance was determined with the homeostasis model assessment of insulin resistance (HOMA-IR). The CRP levels were categorized into quartiles from the lowest to the highest concentrations (Q1-Q4).</p> <p>Results</p> <p>Body mass index (BMI) and waist circumference (WC) were both higher in Q4, Q3 and Q2 than those in Q1. HOMA-IR was higher in Q2, Q3 and Q4 than that in Q1 (Q1 vs Q4, P < 0.001; Q1 vs Q3, P < 0.001; Q1 vs Q2, P = 0.028). Log CRP was significantly correlated with log HOMA-IR (correlation coefficient: 0.230, P < 0.001) and BMI (correlation coefficient: 0.305, P < 0.001) and WC (correlation coefficient: 0.240, P < 0.001) by Spearman correlation analysis. Multiple linear regression analysis adjusting for age, gender and components of metabolic syndrome, log CRP was also independently associated with log HOMA-IR (β coefficient, 0.168; P < 0.001) and WC (β coefficient, 0.131; P = 0.006).</p> <p>Conclusion</p> <p>These findings showed that insulin resistance was associated with CRP levels independent of abdominal obesity in Chinese patients with type 2 diabetes, suggesting that abdominal obesity could only partly explain the link between subclinical inflammation and insulin resistance.</p

Genetic approach to track neural cell fate decisions using human embryonic stem cells

With their capability to undergo unlimited self-renewal and to differentiate into all cell types in the body, human embryonic stem cells (hESCs) hold great promise in human cell therapy. However, there are limited tools for easily identifying and isolating live hESC-derived cells. To track hESC-derived neural progenitor cells (NPCs), we applied homologous recombination to knock-in the mCherry gene into the Nestin locus of hESCs. This facilitated the genetic labeling of Nestin positive neural progenitor cells with mCherry. Our reporter system enables the visualization of neural induction from hESCs both in vitro (embryoid bodies) and in vivo (teratomas). This system also permits the identification of different neural subpopulations based on the intensity of our fluorescent reporter. In this context, a high level of mCherry expression showed enrichment for neural progenitors, while lower mCherry corresponded with more committed neural states. Combination of mCherry high expression with cell surface antigen staining enabled further enrichment of hESC-derived NPCs. These mCherry(+) NPCs could be expanded in culture and their differentiation resulted in a down-regulation of mCherry consistent with the loss of Nestin expression. Therefore, we have developed a fluorescent reporter system that can be used to trace neural differentiation events of hESCs

Hidden hazard weight analysis and safety assessment of fire protection in residential areas

To evaluate the current situation of fire safety in domestic high-rise residential communities, the community, which integrates high-rise residential buildings, office buildings, and shops, was deliberately selected as an example to conduct fire safety assessment. Combined with the current domestic and foreign fire safety assessment methods and practical application of the review, the establishment of the community at all levels of the evaluation index system, the use of analytic hierarchy process (AHP) for fire safety assessment of the community. Results showed that the fire hydrant system and automatic fire alarm linkage system played a decisive role in the fire safety of the community. To perfect community fire safety assessment, and reduce the plot to fire safety risk, enhance the level of community comprehensively, can not only enhance residents on fire control safety knowledge, and the exact analysis of problems existing in the community fire and handled in time, but also strengthen fire safety management, enhanced the safety awareness of the people