Classifying Tractable Instances of the Generalized Cable-Trench Problem

Given a graph $G$ rooted at a vertex $r$ and weight functions, $\gamma , \tau: E(G) \to \mathbb{R}$, the generalized cable-trench problem (CTP) is to find a single spanning tree that simultaneously minimizes the sum of the total edge cost with respect to $\tau$ and the single-source shortest paths cost with respect to $\gamma$. Although this problem is provably $NP$-complete in the general case, we examine certain tractable instances involving various graph constructions of trees and cycles, along with quantities associated to edges and vertices that arise out of these constructions. We show that given a path decomposition oracle, for graphs in which all cycles are edge disjoint, there exists a fast method to determine the cable-trench tree. Further, we examine properties of graphs which contribute to the general intractability of the CTP and present some open questions in this direction

The Lantern, 2017-2018

On Dissociation • Untouchable • After Rocket Man • The Science Fair • Cardinal Rule at Stephen J. Memorial • Quentin & Sylvie • Cabello • The Get Out • Painting Day • Black, White and Grey • Family Pruning • How to Remove a Stain • Becoming Ourselves • Wonderbread U • Overture • Pescadero • Gross • Stage Fright • Lucky Daddy • Sarah • Rumble • Silvermine • The Green Iguana • A Poem for Ghost Children • A Poem for Lost Boys • Mother • Drop of Grease • Don\u27t Wanna be White • I • Amelia Earhart Disappeared Into My Vagina: An Ode to Cunts, Menstrual Cups and All Things Woman • Suburban Summer • Nightmares and Dreams Induced by My Mother • Teacups, Skins, etc. • Three Thoughts About My Bedroom • Dear Siri • 2 Queens (Beyonce in Reference to Sonia Sanchez) • Voyeurs • In Front of the Bathroom Mirror • To a Rose • Howl • Mice • Mirror • Language Accordion Volcano Mouth • Lucky Woman • Butterscotch • To Persephone • Wolf • Notes Never Passed • Topple • Bust • Kyoto • Identity • Sunflower • Tornabuoni Bubbles • Olympia • Decayed Hall • Perspectivehttps://digitalcommons.ursinus.edu/lantern/1186/thumbnail.jp

The Marine Viromes of Four Oceanic Regions

Viruses are the most common biological entities in the marine environment. There has not been a global survey of these viruses, and consequently, it is not known what types of viruses are in Earth's oceans or how they are distributed. Metagenomic analyses of 184 viral assemblages collected over a decade and representing 68 sites in four major oceanic regions showed that most of the viral sequences were not similar to those in the current databases. There was a distinct “marine-ness” quality to the viral assemblages. Global diversity was very high, presumably several hundred thousand of species, and regional richness varied on a North-South latitudinal gradient. The marine regions had different assemblages of viruses. Cyanophages and a newly discovered clade of single-stranded DNA phages dominated the Sargasso Sea sample, whereas prophage-like sequences were most common in the Arctic. However most viral species were found to be widespread. With a majority of shared species between oceanic regions, most of the differences between viral assemblages seemed to be explained by variation in the occurrence of the most common viral species and not by exclusion of different viral genomes. These results support the idea that viruses are widely dispersed and that local environmental conditions enrich for certain viral types through selective pressure

Synthesis, Micelle Formation, and Bulk Properties of Poly(ethylene glycol)-b-Poly(pentafluorostyrene)-g-polyhedral Oligomeric Silsesquioxane Amphiphilic Hybrid Copolymers

The synthesis, micelle formation, and bulk properties of semifluorinated amphiphilic poly(ethylene glycol)-b-poly-(pentafluorostyrene)-g-cubic polyhedral oligomeric silsesquioxane (PEG-b-PPFS-g-POSS) hybrid copolymers is reported. The synthesis of amphiphilic PEG-b-PPFS block copolymers are achieved using atom transfer radical polymerization (ATRP) at 100 degrees C in trifluorotoluene using modified poly(ethylene glycol) as a macroinitiator. Subsequently, a proportion of the reactive para-F functionality on the pentafluorostyrene units was replaced with aminopropylisobutyl POSS through aromatic nucleophilic substitution reactions. The products were fully characterized by H-1-NMR and GPC. The products, PEG-b-PPFS and PEG-b-PPFS-g-POSS, were subsequently self-assembled in aqueous solutions to form micellar structures. The critical micelle concentrations (cmc) were estimated using two different techniques: fluorescence spectroscopy and dynamic light scattering (DLS). The cmc was found to decrease concomitantly with the number of POSS particles grafted per copolymer chain. The hydrodynamic particle sizes (R-h) of the micelles, calculated from DLS data, increase as the number of POSS molecules grafted per copolymer chain increases. For example, Rh increased from similar to 60 nm for PEG-b-PPFS to similar to 80 nm for PEG-b-PPFS-g-POSS25 (25 is the average number of POSS particles grafted copolymer chain). Static light scattering (SLS) data confirm that the formation of larger micelles by higher POSS containing copolymers results from higher aggregation numbers (N-agg), caused by increased hydrophobicity. The R-g/R-h values, where R-g is the radius of gyration calculated from SLS data, are consistent with a spherical particle model having a core-shell structure. Thermal characterization by differential scanning calorimetry (DSC) reveals that the grafted POSS acts as a plasticizer; the glass transition temperature (T-g) of the PPFS block in the copolymer decreases significantly with increasing POSS content. Finally, the rhombohedral crystal structure of POSS in PEG-b-PPFS-g-POSS was verified by wide angle X-ray diffraction measurements. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 152-163, 201

The Influence of Peer and Parental Norms on First-Generation College Students’ Binge Drinking Trajectories

Introduction: First-generation college students are those whose parents have not completed a four-year college degree. The current study addressed the lack of research on first-generation college students’ alcohol use by comparing the binge drinking trajectories of first-generation and continuing-generation students over their first three semesters. The dynamic influence of peer and parental social norms on students’ binge drinking frequencies were also examined. Methods: 1342 college students (n = 225 first-generation) at one private University completed online surveys. Group differences were examined at Time 1, and latent growth-curve models tested the association between first-generation status and social norms (peer descriptive, peer injunctive, parental injunctive) on binge drinking trajectories. Results: Overall, binge drinking frequency tended to decline over the first three semesters of college. After controlling for demographics, substance-free dormitory residence, parental alcohol problems and norms, first-generation status was associated with steeper declines in binge drinking frequency. During the first semester, the association between parental injunctive norms and binge drinking frequency was stronger for first-generation students than for continuing-generation students; this influence declined over time for first-generation students. The influence of peer descriptive norms on binge drinking increased for continuing-generation students; while this influence remained stable over time for first-generation students. Conclusions: First-generation student status appears to be protective against binge drinking. Substance-free dormitory residence, and perceived parental and peer norms likely play a role in first-generation students’ tendency to engage in binge drinking less often over the first year of college

Widespread Occurrence of Phage-encoded Exotoxin Genes in Terrestrial and Aquatic Environments in Southern California

Many human diseases are caused by pathogens that produce exotoxins. The genes that encode these exotoxins are frequently encoded by mobile DNA elements such as plasmids or phage. Mobile DNA elements can move exotoxin genes among microbial hosts, converting avirulent bacteria into pathogens. Phage and bacteria from water, soil, and sediment environments represent a potential reservoir of phage- and plasmid-encoded exotoxin genes. The genes encoding exotoxins that are the causes of cholera, diphtheria, enterohemorrhagic diarrhea, and Staphylococcus aureus food poisoning were found in soil, sediment, and water samples by standard PCR assays from locations where the human diseases are uncommon or nonexistent. On average, at least one of the target exotoxin genes was detected in ∼15% of the more than 300 environmental samples tested. The results of standard PCR assays were confirmed by quantitative PCR (QPCR) and Southern dot blot analyses. Agreement between the results of the standard PCR and QPCR ranged from 63% to 84%; and the agreement between standard PCR and Southern dot blots ranged from 50% to 66%. Both the cholera and shiga exotoxin genes were also found in the free phage DNA fraction. The results indicate that phage-encoded exotoxin genes are widespread and mobile in terrestrial and aquatic environments

The Anoikis Effector Bit1 Displays Tumor Suppressive Function in Lung Cancer Cells

<div><p>The mitochondrial Bit1 (Bcl-2 inhibitor of transcription 1) protein is a part of an apoptotic pathway that is uniquely regulated by integrin-mediated attachment. As an anoikis effector, Bit1 is released into the cytoplasm following loss of cell attachment and induces a caspase-independent form of apoptosis. Considering that anoikis resistance is a critical determinant of transformation, we hypothesized that cancer cells may circumvent the Bit1 apoptotic pathway to attain anchorage-independence and tumorigenic potential. Here, we provide the first evidence of the tumor suppressive effect of Bit1 through a mechanism involving anoikis induction in human lung adenocarcinoma derived A549 cells. Restitution of Bit1 in anoikis resistant A549 cells is sufficient to induce detachment induced-apoptosis despite defect in caspase activation and impairs their anchorage-independent growth. Conversely, stable downregulation of Bit1 in these cells significantly enhances their anoikis resistance and anchorage-independent growth. The Bit1 knockdown cells exhibit significantly enhanced tumorigenecity <i>in vivo</i>. It has been previously shown that the nuclear TLE1 corepressor is a putative oncogene in lung cancer, and we show here that TLE1 blocks Bit1 mediated anoikis in part by sequestering the pro-apoptotic partner of Bit1, the Amino-terminal Enhancer of Split (AES) protein, in the nucleus. Taken together, these findings suggest a tumor suppressive role of the caspase-independent anoikis effector Bit1 in lung cancer. Consistent with its role as a tumor suppressor, we have found that Bit1 is downregulated in human non-small cell lung cancer (NSCLC) tissues.</p></div

Bit1 is downregulated in NSCLC tissues.

<p>A. Lung tumor tissue array slides were stained with the affinity purified rabbit anti-Bit1 antibody. Images are representative of each respective case type: normal lung (i, ii 10×), squamous cell carcinoma (iii, iv, viii 10×), adenocarcinoma (v, vi 10×) and large cell carcinoma (vii). B. The average Bit1 immunostaining intensity in normal bronchial and alveolar epithelial tissues and in various types of NSCLC cancer was determined as described in materials and methods. The normal bronchial and alveolar epithelial tissues was statistically significant from the NSCLC tumors using the ANOVA and subsequent Tukey post-hoc analysis (*, P<0.05).</p

Anoikis insensitivity of A549 cells is associated with lack of caspase activation.

<p>A. Cells were cultured being attached (A) or detached from the ECM for 24 hours (D24) and 48 hours (D48) and were harvested for apoptosis analysis using the Cell Death Elisa ELISA. In parallel, cells were also treated with 1 µM staurosporine (STS) for 24 hours and subjected to Cell Death Elisa ELISA. B. Cytosolic fractions were obtained from cells in A and analysed for the presence of cytochrome c by western blot. C. The presence of caspase-3-like activity in the cell lysates from cells treated in A was determined by the cleavage of a fluorescent substrate z-DEVD-AFC (DEVD). D. and E. Cells in A were subjected to western blotting to detect the processing of pro-caspase 3 (D) and PARP (E). In A and C, three independent experiments were performed in triplicates, * indicates p<0.05 as compared to attached conditions (Student's t test).</p