A comprehensive survey of dimensionality reduction and clustering methods for single-cell and spatial transcriptomics data.

In recent years, the application of single-cell transcriptomics and spatial transcriptomics analysis techniques has become increasingly widespread. Whether dealing with single-cell transcriptomic or spatial transcriptomic data, dimensionality reduction and clustering are indispensable. Both single-cell and spatial transcriptomic data are often high-dimensional, making the analysis and visualization of such data challenging. Through dimensionality reduction, it becomes possible to visualize the data in a lower-dimensional space, allowing for the observation of relationships and differences between cell subpopulations. Clustering enables the grouping of similar cells into the same cluster, aiding in the identification of distinct cell subpopulations and revealing cellular diversity, providing guidance for downstream analyses. In this review, we systematically summarized the most widely recognized algorithms employed for the dimensionality reduction and clustering analysis of single-cell transcriptomic and spatial transcriptomic data. This endeavor provides valuable insights and ideas that can contribute to the development of novel tools in this rapidly evolving field.

[Study on the changes of demography and behavioral characteristics of drug users in Beijing].

OBJECTIVE: To understand the demography changes and behaviors in drug users. METHOD: Self-reported questionnaires was used and longitudinal investigation was conducted in one of the detoxication centers in Beijing in 1998 and 2000. Drug users were randomly chosen. RESULTS: Results showed that age of drug users tend to become younger with the numbers of drug users aged below 25, increased from 18.7% in 1998 to 28.2% in 2000. Majority of drug users remained males, but the proportion of females seemed to increase. Distribution of occupation showed that the largest increase fell among individual enterprisers, from 15.2% in 1998 to 25.9% in 2000. With educational back-ground, the proportion of lower than elementary education level, including illiterate, increased. Fifty percent of drug users were unmarried which increased from 40.8% in 1998 to 53.2% in 2000. Needle sharing was quite common, 16.5% in 1998 and 11.9% in 2000, but the decrease was not statistically significant (P > 0.05). Fifty-seven point three percent of the injecting drug users did not have constant partners to share equipments. Proportion of extra-marriage sexual practice increased from 12.5% in 1998 to 27.5% in 2000, and significant difference (Chi-square = 12.50, P < 0.001). Multiple partners in extra-married drug users was also found (mean = 2). Compared to 1998, condom use during every sexual practice increased in 2000, but 47.7% drug users still never used condom. CONCLUSION: In summary, as the quick increase of drug users, sharing of injecting equipment and high-risk sexual behavior, including multiple partners and unprotected sex, were quite common, with the possibility of HIV epidemic in drug users.