A Fast Algorithm for Source-Wise Round-Trip Spanners

In this paper, we study the problem of efficiently constructing source-wise round-trip spanners in weighted directed graphs. For a source vertex set $S\subseteq V$ in a digraph $G(V,E)$, an $S$-source-wise round-trip spanner of $G$ of stretch $k$ is a subgraph $H$ of $G$ such that for every $u\in S,v\in V$, the round-trip distance between $u$ and $v$ in $H$ is at most $k$ times of the original distance in $G$. We show that, for a digraph $G(V,E)$ with $n$ vertices, $m$ edges and nonnegative edge weights, an $s$-sized source vertex set $S\subseteq V$ and a positive integer $k$, there exists an algorithm, in time $O(ms^{1/k}\log^5n)$, with high probability constructing an $S$-source-wise round-trip spanner of stretch $O(k\log n)$ and size $O(ns^{1/k}\log^2n)$. Compared with the state of the art for constructing source-wise round-trip spanners, our algorithm significantly improves their construction time $\Omega(\min\{ms,n^\omega\})$ (where $\omega \in [2,2.373)$ and 2.373 is the matrix multiplication exponent) to nearly linear $O(ms^{1/k}\log^5n)$, while still keeping a spanner stretch $O(k\log n)$ and size $O(ns^{1/k}\log^2n)$, asymptotically similar to their stretch $2k+\epsilon$ and size $O((k^2/\epsilon)ns^{1/k}\log(nw))$, respectively

「回首．動情．傳承」長者生命故事計劃

嶺南大學亞太老年學研究中心獲華人永遠墳場管理委員會（「華永會」）資助為期一年的「回首．動情．傳承」長者生命故事計劃(「計劃」)。此計劃旨在讓青年人認識長者生命經驗，學習克服困難與挫折以提升抗逆力，建立正向人生觀。 近年，主流媒體經常批評年輕人的負面人生觀，例如：「躺平主義」、「享樂主義」、「犬儒心態」等，亦不時看到青年人輕生的新聞。我們曾在大學內處理過不少受情緒困擾及企圖自殺的個案，與學生深入交流後，發現他們面對着沉重的學業壓力、財政困難或複雜的家庭關係，內心充滿掙扎不安。 此計劃讓嶺大學生與長者導師進行深度的對談，透過了解長者走過的路、他們經歷過的挫折和教訓，給予年輕人生命的啟示。如果我們以旅遊比喻人生，長者就像環遊世界的資深背包客，即使大家遊覽不同的地點、觀賞過不同的風景，他們總能夠分享一些旅遊的心得，讓新手遊客走少一點冤枉路，或領悟到旅遊的樂趣和意義。長者亦可以藉由敍述人生片段回顧他們生命中的故事，學習接納過去，增加自我認同感。青年人創作生命教育書冊，將長者積極的人生觀傳給年輕一代，並藉此鼓勵其他長者豁達地度過餘年。 我們於2022年初招募嶺南大學學生接受「生命故事敍述」培訓，內容包括：本港的人口老化現象、敍述治療理論、與長者溝通的技巧及模擬實踐練習等，以裝備同學的知識和技巧。本中心再向屯門、元朗區的長者機構發邀請信，誠邀長者擔任生命導師接受訪問。 嶺大安排同學以兩人一組的小隊形式，於2022年6至7月期間前往長者中心、日間護理中心、嶺南大學或長者家中，與十二位長者進行深入訪談。訪談結束後，同學根據訪談的內容，為長者書寫他們獨特的生命故事。例如在人離鄉賤的異國環境下，努力打拼事業的Alfred；堅持不懈持續進修的淑芹和馮春林；即使沒機會求學，仍憑一雙巧手闖出一片天的譚惠；在文化大革命的漩渦中，憑着熱忱而改變命運的蘭英；還有為家人無私奉獻的鳳群、歐婆婆、雅芳及細女；離鄉別井勇闖異地的阿美和阿水；即使被家人賣去做「妹仔」，仍能以「阿Q精神」面對的諒餘。 為保障長者的私隱權益，本書內所有刊登之故事皆經過受訪者或社工審閱，部份受訪者選擇以化名的形式來分享自己的故事，我們亦移除了部份敏感的個人資料。https://commons.ln.edu.hk/apias_guide/1008/thumbnail.jp

Sex- and age-dependent association of SLC11A1 polymorphisms with tuberculosis in Chinese: a case control study

BACKGROUND: Host genetic factors are important determinants in tuberculosis (TB). The SLC11A1 (or NRAMP1) gene has been studied extensively for genetic association with TB, but with inconsistent findings. In addition, no study has yet looked into the effect of sex and age on the relationship between SLC11A1 polymorphisms and TB. METHODS: A case-control study was conducted. In total, 278 pulmonary TB patients and 282 sex- and age-matched controls without TB were recruited. All subjects were ethnic Chinese. On the basis of linkage disequilibrium pattern, three genetic markers from SLC11A1 and one from the nearby IL8RB locus were selected and examined for association with TB susceptibility. These markers were genotyped using single strand conformation polymorphism analysis or fragment analysis of amplified products. RESULTS: Statistically significant differences in allele (P = 0.0165, OR = 1.51) and genotype (P = 0.0163, OR = 1.59) frequencies of the linked markers SLC6a/b (classically called D543N and 3'UTR) of the SLC11A1 locus were found between patients and controls. With stratification by sex, positive associations were identified in the female group for both allele (P = 0.0049, OR = 2.54) and genotype (P = 0.0075, OR = 2.74) frequencies. With stratification by age, positive associations were demonstrated in the young age group (age ≤65 years) for both allele (P = 0.0047, OR = 2.52) and genotype (P = 0.0031, OR = 2.92) frequencies. All positive findings remained significant even after correction for multiple comparisons. No significant differences were noted in either the male group or the older age group. No significant differences were found for the other markers (one SLC11A1 marker and one IL8RB marker) either. CONCLUSION: This study confirmed the association between SLC11A1 and TB susceptibility and demonstrated for the first time that the association was restricted to females and the young age group

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data