ABSTRACT
Ultra-rapid cooling and rewarming rate is a critical technical approach to achieve ice-free cells during the freezing and melting process. A set of ultra-rapid solid surface freeze-thaw visualization system was developed based on a sapphire flim, and experiments on droplet freeze-thaw were carried out under different cryoprotectant components, volumes and laser energies. The results showed that the cooling rate of 1 μL mixed cryoprotectant [1.5 mol/L propylene glycol (PG) + 1.5 mol/L ethylene glycol (EG) + 0.5 mol/L trehalose (TRE)] could be 9.2×10 3 °C/min. The volume range of 1-8 μL droplets could be vitrified. After comparing the proportions of multiple cryoprotectants, the combination of equal proportion mixed permeability protectant and trehalose had the best vitrification freezing effect and more uniform crystallization characteristics. During the rewarming operation, the heating curve of glassy droplets containing gold nanoparticles was measured for the first time under the action of 400-1 200 W laser power, and the rewarming rate was up to the order of 10 6 °C/min. According to the droplet images of different power rewarming processes, the laser power range for ice-free rewarming with micron-level resolution was clarified to be 1 400-1 600 W. The work of this paper simultaneously realizes the ultra-high-speed temperature ramp-up, transient visual observation and temperature measurement of droplets, providing technical means for judging the ice free droplets during the freeze-thaw process. It is conducive to promoting the development of ultra-rapid freeze-thaw technology for biological cells and tissues.
Subject(s)
Freezing , Vitrification , Cryopreservation/methods , Trehalose , Gold , Rewarming , Metal Nanoparticles , Cryoprotective Agents , LasersABSTRACT
Objective@#To understand the characteristics of sexual partners and the influence of having multiple sexual partners on substance use among young male students man who have sex with men (MSM) in China, and to provide scientific basis for the prevention and control of HIV/AIDS among young MSM students.@*Methods@#A mixed recruitment method of snowball sampling and respondent driven sampling was used to recruit young MSM students in Beijing and Tianjin, and a questionnaire survey was conducted among 220 participants from November to December 2019. Chi-square test and generalized linear model multi-factor Logistic regression were used to analyze the influencing factors of substance use before sexual behavior.@*Results@#The average age of them was (22.39±2.57) years old, 84.5% of them were students, the average age of first sexual behavior was (18.83±2.45) years old, 44.1% of them had two or more sexual partners (including fixed sexual partners, temporary sexual partners and commercial sexual partners), 22.7% had more than one male fixed partner. After adjusting for age and education, having multiple sexual partners was risk factor for drinking alcohol before sex (aOR=2.97) or substance abuse (aOR=2.39). Having male temporary sexual partner was an risk factor in substance use before sexual behavior(OR=4.10).@*Conclusion@#The characteristics of sexual partners among young MSM students are complex, and the proportion of multiple sexual partners is high. Having fixed single sexual partner can reduce the risk of substance use before sexual behavior. AIDS prevention education for young MSM students should be further strengthened.
ABSTRACT
Objective To investigate the urinary albumin excretion of the diabetes patients and application value in the monitoring of early impairment in kidney. Methods The random urine samples from diabetes patients and controls within three days were collectod. The changes of urinary albumin excretion within day and between days were analyzed. 24-hour urine albumin was used as a standard to evaluate early kidney damage. The correlations between results of random urine albumin at the different time points and different periods were comparod. The sensitivity and specificity of random urine albumin at the different time points and different periods was evaluated and compared to deduce the best diagnostic porformance of the random urine albumin. Results There are greater variations of the levels of urinary albumin of patients with diabetes and control. After the correction with urine creatinine and urine volume the variations can be reduced (CV:49%±23% and 64%±30%). Urinary albumin excretion rate change rhythmically within the 24 h in healthy and diabetes patients. We found the best correlation between overnight ratio of urinary concentrations of albumin and creatinine (ACR) and 24-hour urinary albumin (R2 = 0.976). It was superior to urina sanguinis (R~2 = 0.900), postprandial urine (R~2 = 0.584) and random urine (R~2 =0.791). When 24 h urinary albumin was taken as the standard, receiver operating characteristic (ROC) curve analysis showed there was significant difference between male and female(male 12.8 μg/mg urine creatinine vs female 27.0 μg/mg urine creatinine),and the the cut-off value of ACR was 27.7μg/mg urine creatinine. When the smallest available negative likelihood ratio (0.011) and the greatest positive likelihood ratio (481.000) were obtained,the concentration of 13.0 μg/mg creatinine and 87.4 μg/mg creatinine were set as the cut-off value of ACR. Conclusions The correction with urinary creatinine can reduce the variation between-days compared with urine volume, but still can not completely eliminate the variability. The ACR of overnight urine has the best correlation with the 24 h urinary albumin and can replace 24 h urinary albumin. Random urine as the most convenient collecting urine samples can also replace 24-hour urinary albumin, but the gender discrepancy need to be considered. When the concentration of 13.0 μg/mg and 87.4 μg/mg was set as a random ACR exclusion value and the confirmative value, it can basically rule out and confirm the existence of microalbuminuria.