[Exploration of detection methods for free silica with different crystal forms in dust].

Objective: To investigate the differences and applicability of free silica detection methods of different crystal forms in dust, and to provide a basis for the selection of various methods. Methods: From December 2021 to June 2022, dust samples from 20 enterprises in different industries in 18 cities in Henan Province were randomly selected as the investigation objects. X-ray diffraction (XRD) method was used to analyze the samples and classify the samples. Based on GBZ/T 192.4-2007 "Determination of Dust in the Air of Workplace-Part 4: Content of Free Silica in Dust", pyrophosphate method and infrared spectrophotometry were used for quantitative determination. The measured results were analyzed by paired sample t test to evaluate the advantages and disadvantages of the two methods and their applicable scope. Results: The XRD results of 20 dust samples could be divided into α, ß, γ crystal types and the mixed type of α and γ. There was no significant difference between pyrophosphate method and infrared spectrophotometry (P=0.180). The pyrophosphate method results of ß, γ and α, γ mixed crystalline free silica were significantly higher than those of infrared spectrophotometry, and the difference was statistically significant (P<0.001) . Conclusion: Pyrophosphate method and infrared spectrophotometry are suitable for α-type free silica, while pyrophosphate method is suitable for ß, γ and α, γ mixed crystalline free silica.

Osteocyte-specific dentin matrix protein 1 : the role of mineralization regulation in low-magnitude high-frequency vibration enhanced osteoporotic fracture healing.

AIMS: There is an increasing concern of osteoporotic fractures in the ageing population. Low-magnitude high-frequency vibration (LMHFV) was shown to significantly enhance osteoporotic fracture healing through alteration of osteocyte lacuno-canalicular network (LCN). Dentin matrix protein 1 (DMP1) in osteocytes is known to be responsible for maintaining the LCN and mineralization. This study aimed to investigate the role of osteocyte-specific DMP1 during osteoporotic fracture healing augmented by LMHFV. METHODS: A metaphyseal fracture was created in the distal femur of ovariectomy-induced osteoporotic Sprague Dawley rats. Rats were randomized to five different groups: 1) DMP1 knockdown (KD), 2) DMP1 KD + vibration (VT), 3) Scramble + VT, 4) VT, and 5) control (CT), where KD was performed by injection of short hairpin RNA (shRNA) into marrow cavity; vibration treatment was conducted at 35 Hz, 0.3 g; 20 minutes/day, five days/week). Assessments included radiography, micro-CT, dynamic histomorphometry and immunohistochemistry on DMP1, sclerostin, E11, and fibroblast growth factor 23 (FGF23). In vitro, murine long bone osteocyte-Y4 (MLO-Y4) osteocyte-like cells were randomized as in vivo groupings. DMP1 KD was performed by transfecting cells with shRNA plasmid. Assessments included immunocytochemistry on osteocyte-specific markers as above, and mineralized nodule staining. RESULTS: Healing capacities in DMP1 KD groups were impaired. Results showed that DMP1 KD significantly abolished vibration-enhanced fracture healing at week 6. DMP1 KD significantly altered the expression of osteocyte-specific markers. The lower mineralization rate in DMP1 KD groups indicated that DMP1 knockdown was associated with poor fracture healing process. CONCLUSION: The blockage of DMP1 would impair healing outcomes and negate LMHFV-induced enhancement on fracture healing. These findings reveal the importance of DMP1 in response to the mechanical signal during osteoporotic fracture healing. Cite this article: Bone Joint Res 2022;11(7):465-476.

[Application of an occupational health risk assessment method in dioctyl phthalate producing enterprise].

Objective: To find the risk assessment model of [di (2-ethylhexyl) phthalate, DEHP] fitting well for producing companies. Methods: The Cluster Sampling method was used in selecting a DEHP producing company in the occupational health and workplace environment monitoring study conducted between July and August in 2017. Data was collected by site evaluating and workplace environment monitoring. According to GBZ/T 298-2017《Technical Guidelines for Occupational Health Risk Assessment of Chemical Hazards in the Workplace》, a qualitative assessment method and a semi-quantitative comprehensive index method were chosen as the models and were compared. Results: The occupational health risk of the two methods rated 4 (high risk) and 2 (negligible risk) . Conclusion: The semi-quantitative comprehensive index method is more comprehensive and accurate when used to assess the occupational health risk caused by DEHP.

[Determination of nitrogen oxides in the air of workplace by ion chromatography].

Objective: Improvement the method of nitrogen oxide sampling, analysis and detection in workplace air. Methods: Absorption and collection with sodium carbonate-sodium bicarbonate buffer solution, analysised by ion chromatography, anion column AS23, column temperature 30 ℃. Results: The linearity of the nitrite ion in the corresponding mass concentration range 0~90.0 µg/ml was good (Nitrogen dioxide in 0~120.0 mg/m(3)) , correlation coefficient>0.999 5. The detection limit was 0.16 µg/ml, The minimum detection concentration was 0.11 mg/m(3) with the sampling volume 7.5 L. Conclusion: The method has good accuracy, high sensitivity, with directing injection and no pre-treatment, and can popularize in general laboratories, and can satisfy the determination of nitrogen oxides in the air of workplace.

[Ion Chromatography Method of Four Carboxylic Acids in Workplace Air].

Objective: To assess psychological acceptance and occupational stress of medical staff, analyze the relationship among personality, psychological acceptance and occupational stress and discuss the direct or indirect effects of personality to occupational stress. Methods: The gaseous four kinds of carboxylic acids in the workplace air were simultaneously collected by silica gel tube, and then desorbed by deionized water and eluted by ion chromatograph. The the content was detected by conductivity detector. Results: The linear relationship was good in the concentration range of about 0~140 mg/L. The correlation coefficient r>0.999, and the maximum detection limit was 4.5 µg/mL. The sampling efficiency of the four carboxylic acids ranges from 96.10%~100.27%. Through the sample added recovery experiments, the low and high content of the silicone tube samples were detected; and the range of desorption efficiency was 82.18%~100.12%; the range of precision was 0.70%~3.71%. Conclusion: This method adopts deionized water to desorb samples, and the application of ion chromatography detection have reached the requirements of《Guidelines for the establishment of occupational health standards, Part 4: Determination of chemical substances in workplace air》, which can be used in four kinds of workplace air detection of carboxylic acid compounds.

[Determination of p-Anisidine in workplace air by HPLC].

Objective: To establish an HPLC method for determining p-Anisidine in workplace air. Methods: An C(18) capillary column was used with the detection wavelength of 240 nm, the methanol solution (v/v=62:38) as mobile phase, the flow rate was 0.9 ml/min, and the injection volume was 20 µl. Results: The linear range (µg/ml) for p-Anisidine was 0~100; correlation coefficient was 0.999 7; the detection limit was 0.15 µg/ml; the average precision of RSD was 4.4%. The sampling efficiency was more than 95% using silicone tube as sampling filter. Sample can be stored at room temperature for more than 7 d. Conclusion: the method appered to be accurate, simple, sensitive and reliable, also have a high sampling efficiency, and can be usd to determine p-anisidine in workplace air simultaneously.

Shock induced reaction of Ni/Al nanopowder mixture.

Nanopowder Ni/Al mixture (mixed in Al:Ni = 2:1 stoichiometry) was shock compressed by employing single and two-stage light gas gun. The particle size of Al and Ni are 100-200 nm and 50-70 nm respectively, morphologies of Al and Ni are sphere like either. Recovered product was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. According to the XRD spectrum, the mixed powder undergo complete reaction under shock compression, reaction product consist of Ni2Al3, NiAl and corundum structure Al2O3 compound. Grain size of Ni-Al compound is less than 100 nm. With the shock pressure increasing, the ratio of Ni2Al3 decreased obviously. The corundum crystal size is 400-500 nm according to the SEM observation. The results of shock recovery experiments and analysis show that the threshold pressure for reaction of nano size powder Ni/Al mixture is much less than that of micro size powder.