Depth-Weighted Forecast Combination: Application to COVID-19 Cases

We develop a novel forecast combination based on the order statistics of individual predictability when many forecasts are available. To this end, we define the notion of forecast depth, which measures the size of forecast errors during the training period and provides a ranking among different forecast models. The forecast combination is in the form of a depth-weighted trimmed mean, where the group of models with the worst forecasting performance during the training period is dropped. We derive the limiting distribution of the depth-weighted forecast combination, based on which we can readily construct forecast confidence intervals. Using this novel forecast combination, we forecast the national level of new COVID-19 cases in the U.S. and compare it with other approaches including the ensemble forecast from the Centers for Disease Control and Prevention. We find that the depth-weighted forecast combination yields more accurate predictions compared with other forecast combinations

Trimmed Mean Group Estimation

This paper develops robust panel estimation in the form of trimmed mean group estimation for potentially heterogenous panel regression models. It trims outlying individuals of which the sample variances of regressors are either extremely small or large. The limiting distribution of the trimmed estimator can be obtained in a similar way to the standard mean group estimator, provided the random coefficients are conditionally homoskedastic. We consider two trimming methods. The first one is based on the order statistic of the sample variance of each regressor. The second one is based on the Mahalanobis depth of the sample variances of regressors. We apply them to the mean group estimation of the two-way fixed effects model with potentially heterogeneous slope parameters and to the common correlated effects regression, and we derive limiting distribution of each estimator. As an empirical illustration, we consider the effect of police on property crime rates using the U.S. state-level panel data

Optimum Design of Quenching Capacitor Integrated Silicon Photomultipliers for TOF-PET Application

AbstractThe prototype SiPM was designed and fabricated for MRI compatible PET using the customized CMOS process at National Nanofab Center in KAIST. The SiPM was designed to have a size of 3x3 mm2 composed of micro-cells of 65x65μm2 with a fill factor of 68%. The size of a micro-cell was determined by optimization between the photon detection efficiency (PDE) and the dynamic range for the photons of 511 keV from LYSO crystal. In the micro-cell structure, a specially designed quenching capacitor (QC) is added parallel to quenching resistor using the Metal-Insulator-Metal (MIM) process. This QC integrated SiPMs (QC-SiPM) was devised to realize rapid response of output pulses and to enhance the timing resolution of SiPM. Coincidence timing resolution of PET detectors depends on the output pulse shapes which are the convolution of the intrinsic pulse shape of scintillation crystals and the single photon pulse shape at the micro-cell in a SiPM. A quenching capacitor parallel to a quenching resistor provides a fast current path at the beginning stage of avalanche process, than reduces rising time of single photon pulse shape. In this study the rise time of the QC-SiPM signal was analyzed to be 22.5ns while that for the regular SiPM was 34.3ns

The Physico-Chemical and Microbiological Water Quality of the Artificial Lake Keumgang

This study was performed to investigate the changing encironment of Keum River after the construction of the floodgate at the mouth of Keum River. Samples were taken from the surface wateres at 3 stations near the floodgate of the artificial lake Keumgang to measure the physico-chemikcal and microbiological water qualities from May, 2001 to April, 2002. The results were as follows; water temperature ranged from 2 to 28℃, and pH values caried from 7.5 to 9.1 respectively. The dissolced oxygen contents and COD of each station varied from 7.13 to 14.10 mg l⁻¹ and from 5.2 to 9.4 mg l⁻¹resoectively. And total nitrogen and total phosphate values varied from 0.99 to 3.15 mg l⁻¹, and from 0.01 to 0.12 mg l⁻¹ during survey periods,which meant the sampling stations have set in eutrophic level The population density of heterotrophic bacteria ranged from 0.4±0.1 x 103 cfu ml⁻¹ to 3.5±0.6 x 10³cfu ml⁻¹ for during survey periods. The population densities of physiological groups of aerobic bacteria ranged from 2.0±1.0 x 10² to 1.7±0.2 x 10³ cfu ml⁻¹ for amylolytic bacteria, from 0.3±0.1 x 10² to 1.3±+0.5 x 10³ cfu ml⁻¹ for proteolytix bacteria, from 0.2±0.1 x 10³ to 4.9±1.3 x 10³ cfu ml⁻¹ for lipolytic bacteria, and from 0.2±0.1 x 10² to 2.7±0.7 x 10³ cfu ml⁻¹ for cellulolytic bacteria during survey periods, respectively. Among the measured numbers of physiological groups of bacteria, lipolytic bacteria showed the highest population density. Howecer, the numbers of amylolytic, pyoteolytic, and cellulolylic bacteria showed the similar tendency.Article信州大学山地水環境教育研究センター研究報告 2: 57-61(2004)departmental bulletin pape

Addition of Garlic or Onion before Irradiation on Lipid Oxidation, Volatiles and Sensory Characteristics of Cooked Ground Beef

Addition of 0.5% onion was effective in reducing lipid oxidation in irradiated cooked ground beef after 7 d storage. Addition of garlic or onion greatly increased the amounts of sulfur volatiles from cooked ground beef. Irradiation and storage both changed the amounts and compositions of sulfur compounds in both garlic- and onion-added cooked ground beef significantly. Although, addition of garlic and onion produced large amounts of sulfur compounds, the intensity of irradiation odor and irradiation flavor in irradiated cooked ground beef was similar to that of the nonirradiated control. Addition of garlic (0.1%) or onion (0.5%) to ground beef produced garlic/onion aroma and flavor after cooking, and the intensity was stronger with 0.1% garlic than 0.5% onion treatment. Considering the sensory results and the amounts of sulfur compounds produced in cooked ground beef with added garlic or onion, 0.5% of onion or less than 0.1% of garlic is recommended to mask or change irradiation off-odor and off-flavor

Mobile resistome of human gut and pathogen drives anthropogenic bloom of antibiotic resistance

BACKGROUND:The impact of human activities on the environmental resistome has been documented in many studies, but there remains the controversial question of whether the increased antibiotic resistance observed in anthropogenically impacted environments is just a result of contamination by resistant fecal microbes or is mediated by indigenous environmental organisms. Here, to determine exactly how anthropogenic influences shape the environmental resistome, we resolved the microbiome, resistome, and mobilome of the planktonic microbial communities along a single river, the Han, which spans a gradient of human activities. RESULTS:The bloom of antibiotic resistance genes (ARGs) was evident in the downstream regions and distinct successional dynamics of the river resistome occurred across the spatial continuum. We identified a number of widespread ARG sequences shared between the river, human gut, and pathogenic bacteria. These human-related ARGs were largely associated with mobile genetic elements rather than particular gut taxa and mainly responsible for anthropogenically driven bloom of the downstream river resistome. Furthermore, both sequence- and phenotype-based analyses revealed environmental relatives of clinically important proteobacteria as major carriers of these ARGs. CONCLUSIONS:Our results demonstrate a more nuanced view of the impact of anthropogenic activities on the river resistome: fecal contamination is present and allows the transmission of ARGs to the environmental resistome, but these mobile genes rather than resistant fecal bacteria proliferate in environmental relatives of their original hosts. Video abstract