The Traveling Salesman Problem Under Squared Euclidean Distances

Let $P$ be a set of points in $\mathbb{R}^d$, and let $\alpha \ge 1$ be a real number. We define the distance between two points $p,q\in P$ as $|pq|^{\alpha}$, where $|pq|$ denotes the standard Euclidean distance between $p$ and $q$. We denote the traveling salesman problem under this distance function by TSP($d,\alpha$). We design a 5-approximation algorithm for TSP(2,2) and generalize this result to obtain an approximation factor of $3^{\alpha-1}+\sqrt{6}^{\alpha}/3$ for $d=2$ and all $\alpha\ge2$. We also study the variant Rev-TSP of the problem where the traveling salesman is allowed to revisit points. We present a polynomial-time approximation scheme for Rev-TSP$(2,\alpha)$ with $\alpha\ge2$, and we show that Rev-TSP$(d, \alpha)$ is APX-hard if $d\ge3$ and $\alpha>1$. The APX-hardness proof carries over to TSP$(d, \alpha)$ for the same parameter ranges.Comment: 12 pages, 4 figures. (v2) Minor linguistic change

Conversational contexts:Investigating the dynamics of relationships between clients and professionals in child welfare

The effectiveness of interventions has become an important object of scientificstudy in child welfare and often a prerequisite for funding of child welfare programmes. Many studies on the effectiveness of interventions aimed at supporting families at risk and behavioural change of youth have suggested that features of the relationship between professional and client, and the characteristics of the professional, are decisive for the interventions’ effectiveness. There are, however, few studies of what is important in terms of relational skills, personal characteristics or communication strategies. In this special issue, we focus on the dynamics of relationships between child welfare workers and clients (i.e. young people and/or their parents) by using direct observation and close analysis of naturally occurring processes. The contributions to this special issue have a ‘bottom up’ and a ‘top down approach’ in analysing relationships. The first part uses a ‘bottom up’ approach and reports on conversations between youth and family treatment parents in treatment homes. Using a ‘top down’ approach, the second part specifically focuses on Motivational Interviewing skills of care professionals in their interactions with youth. The third part covers the interactions between parents and professionals in the context of child protection using a ‘bottom up’ approach

MSCDA: Multi-level Semantic-guided Contrast Improves Unsupervised Domain Adaptation for Breast MRI Segmentation in Small Datasets

Deep learning (DL) applied to breast tissue segmentation in magnetic resonance imaging (MRI) has received increased attention in the last decade, however, the domain shift which arises from different vendors, acquisition protocols, and biological heterogeneity, remains an important but challenging obstacle on the path towards clinical implementation. In this paper, we propose a novel Multi-level Semantic-guided Contrastive Domain Adaptation (MSCDA) framework to address this issue in an unsupervised manner. Our approach incorporates self-training with contrastive learning to align feature representations between domains. In particular, we extend the contrastive loss by incorporating pixel-to-pixel, pixel-to-centroid, and centroid-to-centroid contrasts to better exploit the underlying semantic information of the image at different levels. To resolve the data imbalance problem, we utilize a category-wise cross-domain sampling strategy to sample anchors from target images and build a hybrid memory bank to store samples from source images. We have validated MSCDA with a challenging task of cross-domain breast MRI segmentation between datasets of healthy volunteers and invasive breast cancer patients. Extensive experiments show that MSCDA effectively improves the model's feature alignment capabilities between domains, outperforming state-of-the-art methods. Furthermore, the framework is shown to be label-efficient, achieving good performance with a smaller source dataset. The code is publicly available at \url{https://github.com/ShengKuangCN/MSCDA}.Comment: 17 pages, 8 figure

Identification of asthma associated microRNAs in bronchial biopsies

Background Changes in microRNA (miRNA) expression can contribute to the pathogenesis of many diseases, including asthma. We aimed to identify miRNAs that are differentially expressed between asthma patients and healthy controls, and explore their association with clinical and inflammatory parameters of asthma. Methods Differentially expressed miRNAs were determined by small RNA sequencing on bronchial biopsies of 79 asthma patients and 82 healthy controls using linear regression models. Differentially expressed miRNAs were associated with clinical and inflammatory asthma features. Potential miRNA-mRNA interactions were analysed using mRNA data available from the same bronchial biopsies, and enrichment of pathways was identified with Enrichr and g:Profiler. Results In total, 78 differentially expressed miRNAs were identified in bronchial biopsies of asthma patients compared with controls, of which 60 remained differentially expressed after controlling for smoking and inhaled corticosteroid treatment. We identified several asthma-associated miRNAs, including miR-125b-5p and miR-223-3p, based on a significant association with multiple clinical and inflammatory asthma features and their negative correlation with genes associated with the presence of asthma. The most enriched biological pathway(s) affected by miR-125b-5p and miR-223-3p were inflammatory response and cilium assembly/organisation. Of interest, we identified that lower expression of miR-26a-5p was linked to more severe eosinophilic inflammation as measured in blood, sputum as well as bronchial biopsies. Conclusion Collectively, we identified miR-125b-5p, miR-223-3p and miR-26a-5p as potential regulators that could contribute to the pathogenesis of asthma

Ubicación y peso de Micelio de Sclerotinia sclerotiorum para producir infeccion en lechuga (Lactuca sativa)

p.85-88El objetivo del presente trabajo es evaluar la distancia crítica para la inoculación del micelio de Sclerotinia sclerotiorum al cuello de la planta de lechuga (Lactuca sativa) y el peso del mismo para producir infección y caída de las plántulas en cámara de cultivo. La mayor cantidad de plantas caídas se obtuvo con 0,7 y 2,8 grs de inoculo (masa miceliar) ubicado junto al cuello de la planta. Estos resultados pueden ser de utilidad para estudios acerca del control cultural, químico o biológico de la podredumbre ocasionada por S. sclerotiorum en lechuga

Determinants of SARS-CoV-2 receptor gene expression in upper and lower airways

The recent outbreak of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), has led to a worldwide pandemic. One week after initial symptoms develop, a subset of patients progresses to severe disease, with high mortality and limited treatment options. To design novel interventions aimed at preventing spread of the virus and reducing progression to severe disease, detailed knowledge of the cell types and regulating factors driving cellular entry is urgently needed. Here we assess the expression patterns in genes required for COVID-19 entry into cells and replication, and their regulation by genetic, epigenetic and environmental factors, throughout the respiratory tract using samples collected from the upper (nasal) and lower airways (bronchi). Matched samples from the upper and lower airways show a clear increased expression of these genes in the nose compared to the bronchi and parenchyma. Cellular deconvolution indicates a clear association of these genes with the proportion of secretory epithelial cells. Smoking status was found to increase the majority of COVID-19 related genes including ACE2 and TMPRSS2 but only in the lower airways, which was associated with a significant increase in the predicted proportion of goblet cells in bronchial samples of current smokers. Both acute and second hand smoke were found to increase ACE2 expression in the bronchus. Inhaled corticosteroids decrease ACE2 expression in the lower airways. No significant effect of genetics on ACE2 expression was observed, but a strong association of DNA- methylation with ACE2 and TMPRSS2- mRNA expression was identified in the bronchus.</p