Evaluation of individual and ensemble probabilistic forecasts of COVID-19 mortality in the United States

Short-term probabilistic forecasts of the trajectory of the COVID-19 pandemic in the United States have served as a visible and important communication channel between the scientific modeling community and both the general public and decision-makers. Forecasting models provide specific, quantitative, and evaluable predictions that inform short-term decisions such as healthcare staffing needs, school closures, and allocation of medical supplies. Starting in April 2020, the US COVID-19 Forecast Hub (https://covid19forecasthub.org/) collected, disseminated, and synthesized tens of millions of specific predictions from more than 90 different academic, industry, and independent research groups. A multimodel ensemble forecast that combined predictions from dozens of groups every week provided the most consistently accurate probabilistic forecasts of incident deaths due to COVID-19 at the state and national level from April 2020 through October 2021. The performance of 27 individual models that submitted complete forecasts of COVID-19 deaths consistently throughout this year showed high variability in forecast skill across time, geospatial units, and forecast horizons. Two-thirds of the models evaluated showed better accuracy than a naïve baseline model. Forecast accuracy degraded as models made predictions further into the future, with probabilistic error at a 20-wk horizon three to five times larger than when predicting at a 1-wk horizon. This project underscores the role that collaboration and active coordination between governmental public-health agencies, academic modeling teams, and industry partners can play in developing modern modeling capabilities to support local, state, and federal response to outbreaks

Association between INHA gene polymorphisms and litter size in Hainan black goats

Background The inhibin alpha (INHA) gene is one of the important genes affecting the reproductive traits of animals. Hainan black goats are the main goat breed in Hainan Island (China), whose development is limited by low reproductive performance. However, the relationship between INHA gene and the reproductive performance of Hainan black goats is still unclear. Therefore, the purpose of this work was to explore the effect of INHA gene polymorphisms on the litter size of Hainan black goats. Methods Single nucleotide polymorphisms (SNPs) of INHA were detected, and the genetic parameters and haplotype frequency of these SNPs were calculated and association analysis was performed for these SNPs with the litter size. Finally, the SNP with significant correlations to litter size was analyzed by Bioinformatics tools. Results The results showed that the litter size of individuals with the AC genotype at loci g.28317663A>C of INHA gene was significantly higher than those with the AA genotype. This SNP changed the amino acid sequence, which may affect the function of INHA protein by affecting its structure. Our results suggest that g.28317663A>C loci may serve as a potential molecular marker for improving the reproductive traits in Hainan black goats

Wavelength-tunable passively mode-locked mid-infrared Er3+-doped ZBLAN fiber laser

Abstract A passively mode-locked Er3+-doped ZBLAN fiber laser around 3 μm with a wide wavelength tuning range is proposed and demonstrated. The laser cavity was comprised of a semiconductor saturable absorber mirror and a blazed grating to provide a wavelength tunable feedback. The central wavelength of the mode-locked fiber laser can be continuously tuned from 2710 to 2820 nm. The pulse train had a maximum average power of higher than 203 mW, a repetition rate of 28.9 MHz and a pulse duration of 6.4 ps, yielding a peak power of exceeding 1.1 kW. To the best of our knowledge, this is the first demonstration of a wavelength-tunable passively mode-locked mid-infrared fiber laser at 3 μm

Design and Parameter Optimization of Conveying and Baling Devices for Ramie Cutting and Baling Machine

Conveying and baling are two important links in the mechanized harvesting of ramie, in the face of ramie cutting and baling harvesting technology research gaps, low stalk conveying rate, high breaking rate and other problems. In this paper, according to the technical requirements of ramie harvesting, we designed a conveying and baling device, the hand-held ramie cutter. First, the key mechanism of the conveying and baling device of the equipment was designed. Then, we analyzed the location of stem clogging and the reasons for the breaking problem during the conveying and baling process. The field harvesting experiments were carried out according to the principles of Box–Behnken experimental design. Taking the machine travelling speed, conveying speed and ramie raking frequency as the test factors and using the Design-Expert V8.0.6.1 to process the data, we established a regression model for each experimental factor on the conveying rate and breaking rate. The order of influence of several factors on the breaking rate is: X2 > X1 > X3; and the effects of the three factors on the conveying rate were X3 > X2 > X1. Through response surface analysis (RSA), the effects of the factors on the indicators were explained, as was the impact of the factors on the indicators. Finally, the parameter optimization was carried out with the delivery rate as the core index. The best combination of motion parameters was obtained as follows: the travelling speed was 0.37 m/s, the chain conveying speed was 1.1 m/s, and the raking frequency was 144 times/min. With the combination of parameters under the field test verification, the results show that compared with the original work quality, the stalk delivery rate increased from 85.2% to 93% (an increase of 7.8%), the stalk breaking rate fell from 31.1% to 20.4% (a decrease of 10.7%). The performance of ramie harvesting and baling was greatly improved, and we achieved relatively satisfactory results

Bending mechanics test and parameters calibration of ramie stalks

Abstract Research and development of ramie harvesting equipment is a key link to revitalize ramie industry, problems such as the tendency of stalks to tangle and clog the machine are very problematic, seriously affect the quality and fluency of the harvester. The structure of ramie stalk is complex, and the mechanical properties of each component vary greatly, collision between stalk and machine creates complex stress relationship. By building a finite element model, it is possible to analyze the stress state of the stalk during bending from a microscopic perspective, and to analyze the complex stress–strain situation within the stalk. The purpose of this paper is to establish a standard ramie stalk bending finite element model to provide a theoretical basis for the subsequent kinematics and dynamics. Firstly, material experiments were carried out on ramie straw. The structural and mechanical parameters of the straw components were obtained through measurement and calculation tests, and the force–deformation curves for straw bending were obtained. Bending finite element simulations were carried out on the basis of mechanical tests, and the parameters such as dynamic friction coefficient, wood Poisson's ratio and bast Poisson's ratio were determined by the central combination design. Then established an accurate bending finite element simulation model of ramie stalk, the accuracy of the model was verified at the end. In this paper, the key parameters of the ramie stalk model were calibrated through a combination of material tests and simulations. All parameters of the ramie stalk model were finally obtained, and the bending mechanical properties of the ramie stalk were analysed by applying finite element analysis. This bending mechanics simulation model can be used for kinematic and dynamics simulation analysis of conveying and baling to provide a theoretical basis for the structural design of the harvester. The methods explored here can be applied to other slender straw crops

Direct synthesis of controllable ultrathin heteroatoms-intercalated 2D layered materials

Abstract Two-dimensional (2D) layered materials have been studied in depth during the past two decades due to their unique structure and properties. Transition metal (TM) intercalation of layered materials have been proven as an effective way to introduce new physical properties, such as tunable 2D magnetism, but the direct growth of atomically thin heteroatoms-intercalated layered materials remains untapped. Herein, we directly synthesize various ultrathin heteroatoms-intercalated 2D layered materials (UHI-2DMs) through flux-assisted growth (FAG) approach. Eight UHI-2DMs (V1/3NbS2, Cr1/3NbS2, Mn1/3NbS2, Fe1/3NbS2, Co1/3NbS2, Co1/3NbSe2, Fe1/3TaS2, Fe1/4TaS2) were successfully synthesized. Their thickness can be reduced to the thinnest limit (bilayer 2D material with monolayer intercalated TM), and magnetic ordering can be induced in the synthesized structures. Interestingly, due to the possible anisotropy-stabilized long-range ferromagnetism in Fe1/3TaS2 with weak interlayer coupling, the layer-independent magnetic ordering temperature of Fe1/3TaS2 was revealed by magneto-transport properties. This work establishes a general method for direct synthesis of heteroatom-intercalated ultrathin 2D materials with tunable chemical and physical properties

Thickness-Tunable Growth of Composition-Controllable Two-Dimensional Fe_<i>x</i>GeTe₂

Two-dimensional (2D) magnetic materials provide an ideal platform for investigating novel magnetism and spin behavior in low-dimensional systems while being restricted by the deficiency of accurate bottom-up synthesis. To overcome this difficulty, a facile and universal flux-assisted growth (FAG) method is proposed to synthesize the multicomponent FexGeTe2 (x = 3–5) with different Fe contents and even alloyed with hetero metal atoms. This one-to-one method ensures the stoichiometry consistency from the FexGeTe2 and MyFe5–yGeTe2 (M = Co, Ni) bulk crystal precursors to the 2D nanosheets, with controllable composition. Tuning the growth temperatures can provide thickness-tunable products. Changeable magnetic properties of FexGeTe2 and alloyed CoyFe5–yGeTe2 are substantiated by the superconducting quantum interference device and reflective magnetic circular dichroism. This method generates thickness-tunable high-crystallinity FexGeTe2 samples without phase separation and exhibits a high tolerance to different substrates and a large temperature window, providing a new avenue to synthesize and explore such multicomponent 2D magnets and even the alloyed ones

Anomalous thickness dependence of Curie temperature in air-stable two-dimensional ferromagnetic 1T-CrTe2 grown by chemical vapor deposition

Here, the authors report chemical vapor deposition growth of metallic 1T-CrTe2 ultrathin crystals with controlled thickness and long-range ferromagnetic ordering, and observe a monotonic increase of the Curie temperature with decreasing thickness