Objective: To establish a method for determining the molecular weight and molecular weight distribution of Poly(Lactide-co-Glycolide Acid) (PLGA) using Size Exclusion Chromatography-Refractive Index-Multiangle Laser Light Scattering (SEC-RI-MALLS) and Size Exclusion Chromatography-Refractive Index (SEC-RID), and to compare the results obtained from these two methods.
Methods: For SEC-RI-MALLS, tetrahydrofuran was used as the mobile phase, Shodex GPC KF-803L was employed as the chromatographic column with a flow rate of 1 mL·min^-1, column temperature at 30 ℃, and an injection volume of 100 μL. For SEC-RID, tetrahydrofuran was also used as the mobile phase, Agilent PLgel 5 μm MIXD-D was used as the chromatographic column with a flow rate of 1 mL·min^-1, column temperature at 30 ℃, differential detector temperature at 35 ℃, and an injection volume of 20 μL. The molecular weight and molecular weight distribution were calculated using Agilent’s GPC software. The newly established methods were validated methodologically, and the molecular weight and molecular weight distribution of 13 batches of samples were determined.
Results: The precision, accuracy, stability, and repeatability tests for SEC-RI-MALLS showed RSD values of 1.35%, 1.58%, 1.53%, and 1.26%, respectively. The SEC-RID method exhibited good linearity (r=0.999 9), with RSD values for precision, accuracy, stability, and repeatability tests (n=6) of 2.05%, 1.62%, 1.30%, and 2.97%, respectively. The results obtained from SEC-RI-MALLS were lower than those from SEC-RID, and the molecular weight distribution coefficient was smaller, but the results from the paired T-test performed with the value measured by SEC-RID method and the value measured by SEC-RI-MALLS method multiplied a conversion coefficient of 1.5 showed no significant difference between the two methods.
Conclusion: Both methods are stable and reliable, and can be used for the determination of PLGA molecular weight and molecular weight distribution based on the specific situations.

Objective: To analyze the change trends in the body shape indicators and proportions of students in Harbin from 2010 to 2024, and to investigate ergonomic compatibility of functional dimensions of school desks and chairs with current student shape indicators, so as to provide a reference for revising furniture standards of desks and chairs. Methods: Between September and November of both 2010 and 2024, a combination of convenience sampling and stratified cluster random sampling was conducted across three districts in Harbin, yielding samples of 6 590 and 6 252 students, respectively. Anthropometric shape indicators cluding height, sitting height, crus length, and thigh length-and their proportional changes were compared over the 15-year period. The 2024 data were compared with current standard functional dimensions of school furniture. The statistical analysis incorporated t-test and Mann-Whitney U- test. Results: From 2010 to 2024, average height increased by 1.8 cm for boys and 1.5 cm for girls; sitting height increased by 1.5 cm for both genders; crus length increased by 0.3 cm for boys and 0.4 cm for girls; and thigh length increased by 0.5 cm for both genders. The ratios of sitting height to height, and sitting height to leg length increased by less than 0.1 . The difference between desk chair height and 1/3 sitting height ranged from 0.4-0.8 cm. Among students matched with size 0 desks and chairs, 22.0% had a desk to chair height difference less than 0, indicating that the desk to chair height difference might be insufficient for taller students. The differences between seat height and fibular height ranged from -1.4 to 1.1 cm; and the differences between seat depth and buttock popliteal length ranged from -9.8 to 3.4 cm. Among obese students, the differences between seat width and 1/2 hip circumference ranged from -20.5 to -8.7 cm, while it ranged from -12.2 to -3.8 cm among non obese students. Conclusion Current furniture standards basically satisfy hygienic requirements; however, in the case of exceptionally tall and obese students, ergonomic accommodations such as adaptive seating allocation or personalized adjustments are recommended to meet hygienic requirements.

ObjectiveTo investigate the effects of foliar fertilizer of nano-calcium carbonate and calcium nitrate tetrahydrate on the agronomic traits， carbohydrate and endogenous hormone contents of Dendrobium officinale planted for 1 year under greenhouse cultivation， in order to provide scientific basis for fertilization to improve the yield and quality of D. officinale. MethodsSingle-factor experimental design was adopted. Starting from early spring， D. officinale was treated with foliar spraying according to corresponding fertilizers. Three treatment groups were established based on different fertilizers， namely， a blank group（clear water）， a nano-calcium carbonate group（0.727 g·L^-1 nano-calcium carbonate water-soluble fertilizer）， and a calcium nitrate tetrahydrate group（1.091 g·L^-1 calcium nitrate tetrahydrate water-soluble fertilizer）. The frequency of spraying was three times per month， and the entire treatment process lasted for nine months. The effects of various treatments on the traits and relative chlorophyll content of D. officinale were dynamically monitored. Sampling was conducted at three specific time points：August 2， 2023， September 8， 2023， and November 1， 2023， respectively. The contents of glucose and mannose in D. officinale stems were determined by high performance liquid chromatography（HPLC）， the content of soluble sugars in D. officinale stems and leaves was determined by phenol method， and enzyme-linked immunosorbent assay（ELISA） was used to detect the concentrations of cytokinin and auxin. ResultsCompared with the blank group， the treatments with nano-calcium carbonate and calcium nitrate tetrahydrate could significantly increase stem length， stem node number， leaf number， and tiller number. Among them， during the harvesting period in November， the stem length and tiller number， which are indicators related to the yield of D. officinale， increased by 60.85% and 19.23% after treatment with calcium nitrate tetrahydrate， and by 32.54% and 28.85% after treatment with nano-calcium carbonate， respectively. Compared with the blank group， treatments with nano-calcium carbonate and calcium nitrate tetrahydrate could promote the accumulation of sucrose in the stems and leaves of D. officinale to varying degrees， as well as the accumulation of polysaccharides， mannose， and glucose in the stems. In addition， nano-calcium carbonate treatment also facilitated the accumulation of fructose in the stems and leaves of D. officinale. Specifically， during the harvesting period in November， polysaccharides and mannose， which were the main active ingredients in D. officinale stems， increased by 28.48% and 29.36% after treatment with calcium nitrate tetrahydrate， and by 39.91% and 82.62% after treatment with nano-calcium carbonate， respectively. In addition， compared with the blank group， the concentrations of auxin in the stems and leaves of D. officinale were significantly increased after treatment with calcium nitrate tetrahydrate（P<0.05）. Similarly， the concentrations of cytokinin and auxin in the stems of D. officinale were also elevated after treatment with nano-calcium carbonate. Correlation analysis further indicated that elongation growth and tillering of D. officinale stems after foliar spraying of nano-calcium carbonate and calcium nitrate tetrahydrate might be related to the accumulation of carbohydrates in the stems and leaves and the synergistic effect of auxin and cytokinin. ConclusionIn production practice， spraying nano-calcium carbonate and calcium nitrate tetrahydrate can promote the accumulation of cytokinin， auxin， and carbohydrate contents in the stems and leaves of D. officinale， and promote tillering and elongation growth of the stems.

AIM:To observe the clinical efficacy of 3% diquafosol sodium eye drops combined with sodium hyaluronate eye drops in the treatment of dry eyes after pterygium surgery with lacrimal insufficiency.METHODS: A total of 64 cases(64 eyes)of pterygium patients with lacrimal insufficiency were treated with pterygium resection combined with limbal stem cell transplantation, and they were given routine anti-inflammatory and infection prevention treatment postoperatively. In terms of postoperative dry eye treatment, all patients were randomly divided into two groups. The observation group was treated with 3% diquafosol sodium eye drops combined with sodium hyaluronate eye drops, and the control group was treated with sodium hyaluronate eye drops. The break-up time of tear film(BUT), fluorescein(FL), Schirmer's Ⅰ test(SⅠt), ocular surface disease index(OSDI)score, central corneal thickness(CCT)changes, adverse reactions and complications were observed and compared between the two groups at different times postoperatively.RESULTS: Both groups of pterygium patients were accompanied with mild to moderate dry eyes with insufficient tear secretion preoperatively. At 2 wk after operation, both groups showed shorter BUT and higher FL score compared with those preoperatively(P<0.05). There was no significant difference between the two groups(P>0.05). At 4 wk after operation, BUT in the observation group was prolonged, OSDI score was decreased(both P<0.05), and FL score in both groups was decreased compared with those at with 2 wk after operation(P<0.05). The observation group was better than the control group(P<0.05). At the first day after operation, the CCT of the two groups was thicker than that preoperatively(P<0.05), and there was no significant difference in SⅠt between the two groups before and after operation(P>0.05).CONCLUSION: In the treatment of dry eye after pterygium surgery with lacrimal insufficiency, 3% diquafosol sodium eye drops combined with sodium hyaluronate eye drops can effectively reduce the postoperative dry eye symptoms, and its clinical effect is better than that of sodium hyaluronate eye drops alone.

Objective: To analyze the disease burden and risk factors of colorectal cancer in Zhejiang Province from 1990 to 2019, so as to provide the basis for prevention and control of colorectal cancer. Methods: Based on data of 2019 Global Burden of Disease (GDB 2019), disease burden and risk factors of colorectal cancer in Zhejiang Province from 1990 to 2019 was assessed using years of life lost (YLL), years lived with disability (YLD), disability-adjusted life years (DALY). Results: In 2019, the YLL rate, YLD rate and DALY rate caused by colorectal cancer in Zhejiang Province were 496.15/105, 31.81/105 and 527.96/105, respectively. From 1990 to 2019, the YLL rate, YLD rate and DALY rate caused by colorectal cancer in Zhejiang Province increased by 114.90%, 482.60% and 123.38%, respectively, showing increasing trends (average annual percent change values were =2.663, 6.283 and 2.800, respectively,all P<0.05). From 1990 to 2019, the YLL rate, YLD rate and DALY rate in the age groups of 15 to 49 years, 50 to 69 years and 70 years and older showed increasing trends (all P<0.05). In 1990, the top ten risk factors for colorectal cancer in Zhejiang Province were diet low in calcium, diet low in milk, diet low in whole grains, smoking, alcohol use, low physical activity, high fasting plasma glucose, diet high in red meat, diet low in fiber and high body mass index. In 2019, the top ten risk factors for colorectal cancer in Zhejiang Province were diet low in milk, diet low in whole grains, diet low in calcium, alcohol use, diet high in red meat, high body mass index, high fasting plasma glucose, low physical activity, diet low in fiber and diet high in processed meat. Conclusions The disease burden of colorectal cancer in Zhejiang Province showed an upward trend from 1990 to 2019. The top ten risk factors for colorectal cancer remained between 1990 and 2019, while there was a slight change in ranking.