[Investigation on noise exposure level and health status of workers in transportation equipment manufacturing industry]

Objective: To explore the noise exposure level and the health status of workers in transportation equipment manufacturing industry, and provide a scientific basis for guidance and implementation of intervention measures. Methods: From January to December in 2019, a total of 2088 noise workers from a large enterprise were selected by cluster sampling method in railway transportation equipment manufacturing, automobile manufacturing and aerospace aircraft manufacturing enterprises. The worker's noise exposure level was detected. Occupational health checkups were performed on the noise workers including electrical audiometry, blood pressure and electrocardiogram. χ(2) test and trend χ(2) test were used to analyze the data. Results: The noise exposure level of 66.9% (1396/2088) workers exceeded 85 dB (A) , and the median noise level was 87.9 (84.3-90.3) dB (A) . Among them, workers of railway transportation equipment manufacturing enterprises had the highest noise exposure level[89.9 (87.8-91.6) dB (A) ]. The detection rate of high-frequency hearing loss, abnormal blood pressure and abnormal electrocardiogram of noise workers were 15.7% (327/2088) , 18.1% (378/2088) and 6.1% (128/2088) , respectively. The differences in the detection rates of high-frequency hearing loss, abnormal blood pressure, and abnormal electrocardiogram in workers of railway transportation equipment manufacturing enterprises, automobile manufacturing enterprises, and aerospace manufacturing enterprises were statistically significant (P<0.05) . Workers of railway transportation equipment manufacturing enterprises had higher detection rates of high-frequency hearing loss (17.6%, 186/1056) . Workers of aerospace manufacturing enterprises had higher detection rates of abnormal blood pressure and abnormal electrocardiogram (26.3%, 169/642; 10.0%, 64/642) . The differences in the detection rates of high-frequency hearing loss, abnormal blood pressure and abnormal electrocardiogram of noise workers were statistically significant in different age and working age groups, and gradually increased with age and working age (P<0.05) . The difference in the detection rate of high-frequency hearing loss of noise workers was statistically significant in different noise intensity groups, and the overall trend was increasing (P<0.05) . Conclusion: The transportation equipment manufacturing industry has serious noise hazards, especially the railway transportation equipment manufacturing industry. Long-term occupational noise exposure can adversely affect workers' hearing and cardiovascular system. Enterprises should strengthen occupational health inspections, and at the same time, take personal protective measures to protect the health of workers.

Population structure and historical demography of Dipteronia dyeriana (Sapindaceae), an extremely narrow palaeoendemic plant from China: implications for conservation in a biodiversity hot spot

Inferring past demography is a central question in evolutionary and conservation biology. It is, however, sometimes challenging to disentangle their roles of contemporary versus historical processes in shaping the current patterns of genetic variation in endangered species. In this study, we used both chloroplast microsatellite (cpSSR) loci and nuclear microsatellite (nSSR) loci to assess the levels of genetic differentiation, genetic effective population size, contemporary/historical levels of gene flow and demographic history for five populations sampled across the range of Dipteronia dyeriana, an endangered palaeoendemism from Southwestern China. We found that D. dyeriana had a mixed pattern of moderate genetic diversity and high inbreeding. Bayesian clustering divided D. dyeriana populations into two nSSR genetic clusters. Coalescent-based approximate Bayesian computation analyses suggest the western and eastern groups of D. dyeriana likely persisted in a long-term refuge in Southern China since the beginning of the last glacial period, whereas increasingly colder and arid climates at the onset of the last glacial maximum might have fostered the fragmentation of D. dyeriana within refugia. Following their divergence, the western group kept relatively stable effective population size, whereas the eastern group had experienced 500-fold population expansion during the Holocene. Although clear loss of genetic diversity by human activities was not suggested, recent habitat fragmentation has led to a reduction of population connectivity and increased genetic differentiation by ongoing genetic drift in isolated populations, possibly owing to decreased population size in recent dozen years. Finally, we discussed the implications of these results on conservation policies.

[Durability of protective effect of resin-based coating material on root surface]

OBJECTIVE

To compare the durability of resin-based root-surface coating material and all-in-one self-etching adhesive on root surface in vitro.

METHODS

Human extracted premolars or molars with intact roots were selected. The cementum was removed using a periodontal scaler to expose root dentin. The root surface was coated with an acid-resistant nail varnish, leaving a window of 3 mm×3 mm on the exposed dentin.The window was covered with either PRG Barrier Coat (PRG) or Clearfil S3 Bond (CS3). After water aging for 14 d, specimens were immersed in acid buffer at pH 4.5 for 4 d and the demineralization buffer was changed every 24 h. Then the specimen was split longitudinally through the center of the 'window' and the cross-sectional surface was observed with scanning electron microscope (SEM). After fixed and dehydrated, the prepared samples were coated with platinum. The coating material, root dentin and the interface was observed by scanning electron microscope (SEM). The thickness of the coating material was measured on the SEM images. Regarding toothbrush wear test, coronal dentindisks were prepared and covered with PRG and CS3, respectively. After storage in water for 24 h, the specimen was subjected to the toothbrush wear tester for 100, 200, 300, 500, 700, 1 500 brushing cycles. A slurry of fluoride toothpaste (1:2 ratio of toothpaste and deionized water by weight) was used and the brushing load was 300 N. The surface microstructure of remaining coating material was analyzed using SEM. The wear depths were determined by a profilometer. Statistical analysis was performed with SPSS 20.0 by one-way ANOVA. The level of significance was at 0.05.

RESULTS

Application of PRG Barrier Coat produced a coating layer of (47.1±27.3) μm, while CS3 presented a thin film of (5.7±2.1) μm in thickness. The exposed dentin was hermetically sealed and no obvious gap was observed at the interface in both PRG and CS3 groups. There was no dentin demineralization observed in both groups after water aging. The wear depths of PRG and CS3 increased along with the numbers of brushing cycles. PRG wore at a significant lower pace than CS3 did (P<0.05).

CONCLUSION

PRG coating resin had similar performances as CS3 on protecting root dentin from demineralization after water aging. What's more, PRG demonstrated a higher toothbrush wear resistance than CS3. We concluded that PRG Barrier Coat contained S-PRG filler may be an effective coating material for protecting exposed root from both chemical and mechanical challenges. Further studies should be carried out to evaluate the long-term reliability of the rootsurface coating materials under the clinical setting.

[Influence of covering of auto-crosslinked sodium hyaluronate gel in combination with xenogenic acellular dermal matrix on healing of full-thickness skin defect wound in pig]

OBJECTIVE

To explore the influence of covering of auto-crosslinked sodium hyaluronate gel in combination with xenogenic acellular dermal matrix (ADM) on healing of full-thickness skin defect wound in pig.

METHODS

Totally four 10 cm×10 cm full-thickness skin defect wounds were reproduced symmetrically on both sides of spine on the back of each one of the six Chinese experimental minipigs. After autologous microskin grafting, the 4 wounds in each pig were divided into 4 groups according to the random number table, with 6 wounds in each group. Wounds in allogenic skin group (AS) were covered by full-thickness skin from one (not the recipient) of the 6 pigs; wounds in xenogenic skin group (XS) were covered by full-thickness skin of sheep; wounds in xenogenic ADM group (XA) were covered by ADM of sheep; wounds in combination group (C) were covered by ADM of sheep combined with auto-crosslinked sodium hyaluronate gel. The wounds were bound up with pressure, and the dressing was changed once every 7 days. On post surgery day (PSD) 7, 14, 21, 28, 35, and 42 when changing dressing, the condition of wounds and the exfoliation of the covering on microskin were observed, and the complete exfoliation time of the covering was recorded. On PSD 28, 35, and 42, the wound healing rate was calculated. Data were processed with one-way analysis of variance and SNK test.

RESULTS

(1) On PSD 7, no fluid appeared under the covering of wounds in groups AS and C, while plenty of fluid appeared under the covering of wounds in groups XS and XA. From PSD 14 to 35, most of the full-thickness skin of pig in group AS did not exfoliate. All the full-thickness skin of sheep in group XS exfoliated, leaving a lot of crusts on the surface of the wounds on PSD 14. Most of the ADM of sheep in group XA separated from the wound with the crusts turning dry and exfoliating on PSD 14. All the ADM of sheep exfoliated with most of the wounds healed in group C on PSD 35. On PSD 42, all the full-thickness skin of pig in group AS exfoliated, leaving most of the wounds unhealed; all the crusts exfoliated and the majority of wounds were healed in group XS and XA group; all the wounds in group C were healed. (2) Compared with that in group C[(32.7±3.3) d], the complete exfoliation time of the covering was obviously shorter in group XS[(15.2±4.8) d]and group XA[(22.2±6.3) d], with P values below 0.05, while the complete exfoliation time of the covering in group AS[(44.8±2.7) d]was obviously longer (P<0.05). (3) On PSD 28, 35, and 42, the wound healing rates in groups XS and XA[(21.2±2.6)%, (51.4±2.4)%, (89.6±2.8)%, and (23.7±3.4)%, (53.6±6.3)%, (91.3±4.9)%, respectively]were obviously lower than those in group C[(35.1±3.4)%, (62.1±6.7)%, (98.8±1.0)%, respectively, with P values below 0.05]. On PSD 42, the wound healing rate in group AS[(44.0±3.8)%]was significantly lower than the rates in the other 3 groups (with P values below 0.05).

CONCLUSIONS

Auto-crosslinked sodium hyaluronate gel combined with ADM of sheep used as covering of microskin grafts on full-thickness wound in pig can lengthen the persistence time of ADM of sheep on the wound, as well as promote wound healing.

The challenge of the so-called electron configurations of the transition metals

Quite different meanings are attached by chemists to the words element, atom, orbital, order of orbitals or configurations. This causes conceptual inconsistencies, in particular with respect to the transition-metal elements and their atoms or ions. The different meanings will here be distinguished carefully. They are analyzed on the basis of empirical atomic spectral data and quasi-relativistic density functional calculations. The latter are quite reliable for different average configuration energies of transition-metal atoms. The so-called "configurations of the chemical elements", traditionally displayed in periodic tables, are the dominant configurations of the lowest spin-orbit levels of the free atoms. They are chemically rather irrelevant. In many-electron systems the ns and np AOs are significantly below the more hydrogen-like nd ones. Even (n+1)s is below nd for all light neutral atoms from C onwards, but only up to the first elements of the respective long rows! The most common orbital order in transition-metal atoms is 3p << 3d < 4s etc. The chemically relevant configuration in group g is always d(g) instead of d(g-2) s(2). Conceptually clear reasoning eliminates apparent textbook inconsistencies between simple quantum-chemical models and the empirical facts. The empirically and theoretically well-founded Rydberg (n-deltal) rule is to be preferred instead of the historical Madelung (n+l) rule with its large number of exceptions.