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In this study, we examined the effect of health on the elderly's labor supply in rural China based on the data of the Chinese Health and Nutrition Survey (CHNS) from 1997 to 2006. We used simultaneous equations to address the endogeneity problem of health and estimate the models with censored data of labor supply by the full information maximum likelihood estimation. We found that the failing health does not significantly decrease the elderly's labor supply in rural areas when using both the subjective (self-reported health status) and objective (hypertension diagnosed or not) health indicators. Our finding indicates the phenomenon of "ceaseless toil" for the elderly in rural China, i.e., the elderly almost work their whole life even if they are not physically capable. The results remain robust when using a two-stage limited information maximum likelihood estimation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Tan, Chang, Guo and Wu.)

Based on the data of China's outward foreign direct investment (OFDI) in energy sector to 133 countries from 2005 to 2014, this paper uses a gravity model to investigate the impact of "intimate" relations on China's OFDI locations in energy sector. We find that the "intimate" relations have significant effects on China's OFDI locations in energy sector, namely: bilateral senior leaders' visits, institutional distance, genetic distance, and immigration. Holding other factors fixed, for each one more bilateral senior leaders' visit between China and the host country, China's OFDI in energy sector for the host country will increase by 5.44%. If the genetic distance from China and host country increases by 1%, China's OFDI in energy sector will fall by 1.69%. For every 1% increase in the institutional distance between China and host country, China's energy OFDI will decrease by 1.09%. For every 1% increase in a country's immigration to China, China's energy OFDI will increase by 0.46%. Further, after distinguishing developed and developing countries, we find that compared with developed countries, "intimate" relations have greater impacts on China's energy OFDI in developing countries. Finally, based on the dominance analysis, considering China's "intimate" relations with countries along the "Belt and Road" and current locations of China's OFDI, we find that China should further expand energy investment in countries along the "Belt and Road"., Competing Interests: The authors have declared that no competing interests exist.

These studies were designed to identify the antigens of Campylobacter fetus subsp fetus that elicit vaccinal immunity. Heifers were vaccinated subcutaneously twice (42 days between vaccinations) with bacterins containing K, O, and H antigens (group A), O and H antigens (group B), or O antigen (group C) of the challenge strain. Five heifers were not vaccinated and served as controls (group D). Two weeks after heifers were given the second vaccination, the immunity of all heifers was challenge exposed by inoculating a live culture against the cervical os. Cervicovaginal mucus samples were examined by microbiological culture technique, using a selective medium, at 7- and 14-day intervals after challenge exposure. One of the six vaccinated heifers in group A became infected, as did all vaccinated heifers in groups B and C and the controls (group D). Only heifers vaccinated with bacterin containing K antigen were resistant to experimental infection with C fetus subsp fetus (P = 0.0002). Humoral antibody responses to whole-cell antigen were monitored, using a tube agglutination test, with and without treatment of the serum with 2-mercaptoethanol. An anamnestic antibody response of 2-mercaptoethanol-resistant antibody was detected in heifers in both groups A and B. An agglutination test (IGGK) was developed to measure immunoglobulin G directed against the K antigen and was used in an attempt to correlate agglutination titers with the immunity to challenge exposure. With the IGGK test, the serum agglutination titers of heifers in group A were significantly higher (P less than 0.0001) than those of heifers in group B. The results of these studies indicate that K antigen of C fetus subsp fetus elicits vaccinal immunity and that a direct correlation exists between the IGGK test and immunity on a group basis.

Fecal specimens from 136 healthy beef calves (1 day to 12 weeks of age) were examined for the presence of infectious agents known to cause enteric disease in calves. The calves were selected from 22 herds in which all calves were free of clinically apparent enteric disease. Salmonella sp, enterotoxigenic Escherichia coli, Cryptosporidium, and coronavirus were not detected in any of the calves. Three calves were infected with rotavirus and 1 calf was infected with Yersinia enterocolitica. Campylobacter-like bacteria were isolated from 50 of 130 calves, with 36 of the calves positive for C jejuni. Seemingly, clinically normal calves may be infected more often with enterotoxigenic E coli, Cryptosporidium, coronavirus, or rotavirus in herds in which some calves have enteric disease than in herds free of major enteric disease. Campylobacter jejuni was well adapted to the bovine host and was of similar prevalence in diarrheal and nondiarrheal calves. The K99 positive, nonenterotoxigenic E coli was isolated from the feces of 16 healthy calves. Information in addition to the presence of K99 antigen is useful when diagnosing enterotoxic colibacillosis in calves.

Prothrombin times, partial thromboplastin times and platelet counts were performed to determine normal values and to screen for coagulation defects of precolostral calves. The precolostral calves were in two groups: one group of a few calves was tested two years before the second larger group. The results for both groups were similar. The tests were performed on postcolostral calves and on mature cows to compare their values with those of precolostral calves. The mean values of prothrombin times and partial thromboplastin times of precolostral calves in the first group were 18.8 seconds and 54.8 seconds respectively. The mean values of prothrombin times and partial thromboplastin times of precolostral calves in the second group were 18.8 seconds and 50.8 seconds respectively. The mean platelet count was 422,400/cmm for the first group and 482,800/cmm for the second group.

Rabbits were vaccinated with the following Campylobacter fetus var. venerealis (Vibrio fetus) antigens: whole-cell (WC), autoclaved (A), boiled (B), and purified postgrowth broth (PGB). Bactericidal activity of freshly drawn heparinized blood against the organism was determined after each vaccination. In all cases bactericidal activity of the blood of vaccinated rabbits was higher than for nonvaccinated rabbits. The in vitro bactericidal activity of the blood was determined in two separate experiments. In experiment I the bactericidal activity of the blood of rabbits vaccinated with PGB antigen was the same as that of rabbits vaccinated with WC antigen and higher than that of rabbits vaccinated with A antigen after the third vaccination. In experiment II the bactericidal activity of blood of rabbits vaccinated with PGB antigen was the same as that of those vaccinated with WC antigen after the second and third vaccinations and higher than for rabbits vaccinated with A antigen after the third vaccination. Blood of rabbits vaccinated with A antigen was less bactericidal than blood of rabbits vaccinated with B antigen after the third vaccination, indicating the presence of a surface antigen destroyed by autoclaving but not by boiling. The in vivo and in vitro whole blood bactericidal tests are more sensitive for measuring the response of rabbits vaccinated with WC, B, A, or PGB antigens than is the plate agglutination test.

Bulk-cell yields were obtained from 4 Campylobacter spp incubated aerobically without the use of a special atmosphere. A button agglutination test was developed for quantitation of blood serum antibodies against C fetus subsp venerealis, C fetus subsp fetus, C jejuni, and "C hyointestinalis." The test was sensitive, and different individuals reading it usually attained the same titers. Cells of C fetus subsp venerealis, C fetus subsp fetus, and "C hyointestinalis" grown aerobically in broth made satisfactory antigens for the button test, but some cell pools of C jejuni had a tendency to autoagglutinate. Cells of C jejuni grown on blood agar had less tendency to autoagglutinate.

A method was developed for making viable counts of Campylobacter fetus (Vibrio fetus) in tube cultures using a medium containing alkaline hematin and incubation in a carbon dioxide incubator.