Novel periodic alternating tangential filtration harvest approach provides incresed volumetric productivity

Perfusion cell culture processes provide opportunities to increase product yield through improved cell growth, increased productivity and extended process duration. Most commonly, perfusion cell culture also leads to a continuous harvest operation and collection of harvested cell culture fluid to be processed downstream. As an alternative to continuous harvest, we evaluated instead a periodic harvest approach applied to a non-steady state perfusion cell culture process using alternative tangential flow (ATF). In this ATF perfusion process, product is first accumulated in the bioreactor using ultrafiltration for 15 days with the product then being harvested by microfiltration at end of the process. To further extend the culture time beyond 15 days and maximize productivity, we investigated a sequence of five periodic harvests from a single upstream bioreactor run. The periodic harvests were achieved using an ATF configuration in which ultrafiltration and microfiltration hollow fiber filters were stacked in series (Figure 1). The ultrafiltration hollow fiber retains the product while the microfiltration filter allows product to be collected in the permeate. Permeate was only drawn from the microfiltration filter during the periodic harvest cycles while the permeate was drawn from the ultrafiltration filter during the none harvest cycle periods. This allowed for the accumulation of product in the bioreactor between the periodic harvests. Five harvest cycles were conducted over a 24-day perfusion process. Each harvest cycle was collected for a day with the first harvest cycle starting on day 11. Please click Additional Files below to see the full abstract

Flooding Hazard in Howard County: Causes and Green Infrastructure Solutions

Final project for BSCI215: Global Sustainability (Fall 2015). University of Maryland, College Park.Howard Count

SUMO-Targeted Ubiquitin Ligase, Rad60, and Nse2 SUMO Ligase Suppress Spontaneous Top1–Mediated DNA Damage and Genome Instability

Through as yet undefined proteins and pathways, the SUMO-targeted ubiquitin ligase (STUbL) suppresses genomic instability by ubiquitinating SUMO conjugated proteins and driving their proteasomal destruction. Here, we identify a critical function for fission yeast STUbL in suppressing spontaneous and chemically induced topoisomerase I (Top1)–mediated DNA damage. Strikingly, cells with reduced STUbL activity are dependent on tyrosyl–DNA phosphodiesterase 1 (Tdp1). This is notable, as cells lacking Tdp1 are largely aphenotypic in the vegetative cell cycle due to the existence of alternative pathways for the removal of covalent Top1–DNA adducts (Top1cc). We further identify Rad60, a SUMO mimetic and STUbL-interacting protein, and the SUMO E3 ligase Nse2 as critical Top1cc repair factors in cells lacking Tdp1. Detection of Top1ccs using chromatin immunoprecipitation and quantitative PCR shows that they are elevated in cells lacking Tdp1 and STUbL, Rad60, or Nse2 SUMO ligase activity. These unrepaired Top1ccs are shown to cause DNA damage, hyper-recombination, and checkpoint-mediated cell cycle arrest. We further determine that Tdp1 and the nucleotide excision repair endonuclease Rad16-Swi10 initiate the major Top1cc repair pathways of fission yeast. Tdp1-based repair is the predominant activity outside S phase, likely acting on transcription-coupled Top1cc. Epistasis analyses suggest that STUbL, Rad60, and Nse2 facilitate the Rad16-Swi10 pathway, parallel to Tdp1. Collectively, these results reveal a unified role for STUbL, Rad60, and Nse2 in protecting genome stability against spontaneous Top1-mediated DNA damage

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements