Numerical studies for the thermal regime of a high-speed railway tunnel considering piston action on seasonally frozen regions

piston action describes the phenomenon that air at the train nose is pushed forward by the increased pressure and air at the train rear is drawn forward by the decreased pressure when a train passes through a tunnel. The changes of pressure can affect the thermal environment inside the tunnel, and further cause frost damage. In this paper, a fluid-thermal-solid coupled numerical model considering piston action is developed. A high-speed railway tunnel in the northeast of China is taken as an example to explore the temperature distribution laws with computational fluid dynamic (CFD). Afterwards, the effects of air temperature and train velocity on temperature distribution are analyzed. The results show that the piston action can enhance the heat transfer between cold air outside the tunnel and tunnel structure, and can cause more serious frost damage especially at the entrance and exit. The temperature distribution is characterized by three zones, including disturbed zones at two sides of tunnel and undisturbed zone at tunnel middle. The freezing length is closely related to air temperature and train velocity. And also, the lengths are different at vault and rail of tunnel portal, which indicates that the anti-freezing measure should be different at these positions considering the cost. This paper can provide some reference for determining the anti-freezing fortified length of tunnels in cold regions.

Chromosome-level genome assembly of a triploid poplar Populus alba ’Berolinensis’

Related studies have provided significant insights into polyploid breeding in recent years, but limited research was focused on trees. The genomic information for the growth and response to abiotic stress in polyploidy trees is still largely unknown. Populus alba ’Berolinensis’, also named “Yinzhong poplar”, is a triploid poplar in the northeast of China. This hybrid triploid poplar is widely used as landscape ornamentals in urban areas because of its fast growth and high tolerance to abiotic stress. As an artificially synthesized male allotriploid hybrid, the three monoploid genomes of P. alba ’Berolinensis’ originated from different poplar species, so it is the desired material for studying polyploidy genomic collaboration mechanisms. Therefore, we intensively studied the allelic genomic collaboration mechanism in P. alba ’Berolinensis’. This study generated a high-quality chromosome-level genome assembly for the P. alba ’Berolinensis’ consisting of 19 allelic chromosomes. Its three monoploid chromosomes are polymorphic with an average of 42.22 variant sites per allelic gene locus. Meanwhile, we found that stress related genes such as RD22 and LEA7 exhibited structure variations. The above information has all been deployed to our polyploid genome online analysis website TreeGenomes (https://www.treegenomes.com). These polyploid genomic related resources will provide critical foundations for the molecular breeding of P. alba ’Berolinensis’ and help us uncover the allopolyploidization effects on the resistance and traits of polyploidy species deeper in the future.

Bacteriological Profile of Conjunctiva Bacterial Flora in the Northeast of China: A Hospital-Based Study

Purpose: To investigate the distribution and influencing factors of pre-operative conjunctival flora from patients undergoing penetrating ocular surgeries in northeast of China.Methods: An observational and cross-sectional study design was used. In 305 eyes of 305 patients without infective eye diseases who underwent ocular surgeries in the First Affiliated Hospital of Harbin Medical University between May 2018 and May 2019, conjunctival sac scrapings were collected on the day before surgery.Results: The mean age of participants was 60.73 ± 14.23 years, with the majority being female, married and unemployed with at least primary school education. The positive culture rate was 48.20% (147/305 eyes), and a total of 191 bacterial strains were isolated, 22.45% (33/147) positive samples had two or more strains isolated. The most commonly isolated bacteria was Staphylococcus epidermidis (64.92%), surpassing Staphylococcus aureus (5.76%). The culture positive rate of young (18-40 years) group was different between the females(26.67%) and the males(69.23%)(P = 0.024), but in middle aged group and the elderly group, the rates between the sexes were similar with increased trend. Patients visited in summer or autumn presented a higher positive rate than other seasons. The hypertensive women had a higher rate than hypertensive men(58.14% vs. 40%, X2 =5.8662，P = 0.0154). Conclusions: In northeast of China, coagulase-negative Staphylococcus were the most common pre-operative conjunctival bacteria. The hypertensive female patients, elderly patients, or operated patients in summer and autumn should pay more attention to perioperative treatment.Trial registration number：ChiCTR2100044659

Effects of irrigation and nitrogen on chlorophyll content, dry matter and nitrogen accumulation in sugar beet (Beta vulgaris L.)

A 2-year field experiment was conducted to analyze the growth conditions, physical features, yield, and nitrogen use efficiency (NUE) of sugar-beet under limited irrigation conditions in northeast of China. A cultivar H003 was used as plant materials; six treatments (C1–C6) were included: C1, no nitrogen applied, rain-fed; C2, nitrogen (120.00 kg ha−1), rain-fed; C3, no nitrogen applied, hole irrigation for seeding; C4, nitrogen (120.00 kg ha−1), hole irrigation for seeding; C5, no nitrogen applied, hole irrigation for seeding; and C6, nitrogen (120.00 kg ha−1), hole irrigation for seeding, and irrigation at foliage rapid growth stage. The irrigation supply was only 500 mL/plant once. Results showed C6 showed the highest chlorophyll content, dry matter accumulation, yield, etc. and had the best NUE among all the treatments. In conclusion, under the routine fertilization conditions of northeast of China, the cultivation measure of hole irrigation 500 mL/plant for seeding combined with irrigation 500 mL/plant at foliage rapid growth stage greatly improved sugar-beet yield and NUE.

The Spatiotemporal Transmission Dynamics of COVID-19 among Multiple Regions: A Modeling Study in China

Current explosive outbreak of COVID-19 around the world is a complex spatiotemporal process with hidden interactions between viruses and humans. This study aims at clarifying the transmission patterns and the driving mechanism that contributed to the COVID-19 epidemics across the provinces of China. Thus a new dynamical transmission model is established by ordinary differential system. The model takes into account the hidden circulation of COVID-19 virus among/within humans, which incorporates the spatial diffusion of infection by parameterizing human mobility. Theoretical analysis indicates that the basic reproduction number is a unique epidemic threshold, which can unite infectivity in each region by human mobility, and can totally determine whether COVID-19 proceeds among multiple regions. By validating the model with real epidemic data in China, it is found that (1) if without any intervention, COVID-19 would overrun China within three months, resulting in more than 1.1 billion infections; (2) high frequency of human mobility can trigger COVID-19 diffusion across each province in China, no matter where the initial infection locates; (3) travel restrictions and other non-pharmaceutical interventions must be implemented simultaneously for disease control; and (4) infection sites in central and east (rather than west and northeast) of China would easily stimulate quick diffusion of COVID-19 in the whole country.

An Iron Meteorite with Micro-Sculpted Patterns of Greek Mythology

An iron meteorite collected from the floor of Daling River, Chaoyang City, Liaoning Province, northeast of China reveals many micro images of ancient Greek mythology from different angle, showing the ideas, arts and technology of 2000-3000 years before.

Modelling Individual Tree Diameter Growth of Quercus mongolica Secondary Forest in the Northeast of China

Quercus mongolica secondary forest is widely distributed in the northeast of China, but it usually has low productivity, unstable structure, poor health, and low biodiversity. Diameter is a tree variable that is commonly used for forest growth measurement, to provide the basis for forest management decision. Two level generalized linear mixed effects individual diameter growth model were developed using data from two times surveys of 12 Q. mongolica secondary forest permanent plots that were distributed among Wangqing forest farms. Random effects of 14 tree species and 12 plots were introduced into the basic model consisting of three factors: tree size, competition of surrounding trees, and site quality. The results showed that initial diameter at breast height(DBH) was the most important variable affecting diameter growth, followed by competition, while the effect of site quality on diameter growth was not significant. Compared with the basic model, the prediction accuracy of the mixed effect model was improved by 17.69 %, where R2 reached to 0.6805, indicating that it is suitable for the individual-tree diameter growth prediction of the secondary forest of Q. mongolica.

Effects of irrigation and nitrogen on chlorophyll content, dry matter and nitrogen accumulation in sugar beet (Beta vulgaris L.)

A two-year field experiment was conducted to analyze the growth conditions, physical features, yield, and nitrogen use efficiency (NUE) of sugar-beet under limited irrigation conditions in northeast of China. A cultivar H003 was used as plant materials; six treatments (C1-C6) were included: C1, no nitrogen applied, rain-fed; C2, 120.00 kg nitrogen hm− 2, rain-fed; C3, no nitrogen applied, hole irrigation for seeding; C4, 120.00 kg nitrogen hm− 2, hole irrigation for seeding; C5, no nitrogen applied, hole irrigation for seeding; and C6, 120.00 kg nitrogen hm− 2, hole irrigation for seeding, and irrigation at foliage rapid growth stage. The irrigation supply was only 500 mL/plant once. Results showed C6 showed the highest chlorophyll content, dry matter accumulation, yield, etc. and had the best NUE among all the treatments. In conclusion, under the routine fertilization conditions of northeast of China, the cultivation measure of hole irrigation 500 mL/plant for seeding combined with irrigation 500 mL/plant at foliage rapid growth stage greatly improved sugar-beet yield and NUE.