i-process Nucleosynthesis and Mass Retention Efficiency in He-shell Flash Evolution of Rapidly Accreting White Dwarfs

© 2017. The American Astronomical Society. All rights reserved. Based on stellar evolution simulations, we demonstrate that rapidly accreting white dwarfs (WDs) in close binary systems are an astrophysical site for the intermediate neutron-capture process. During recurrent and very strong He-shell flashes in the stable H-burning accretion regime H-rich material enters the He-shell flash convection zone. 12 C(p, γ) 13 N reactions release enough energy to potentially impact convection, and i process is activated through the 13 C(α, n) 16 O reaction. The H-ingestion flash may not cause a split of the convection zone as it was seen in simulations of He-shell flashes in post-AGB and low-Z asymptotic giant branch (AGB) stars. We estimate that for the production of first-peak heavy elements this site can be of similar importance for galactic chemical evolution as the s-process production by low-mass AGB stars. The He-shell flashes result in the expansion and, ultimately, ejection of the accreted and then i-process enriched material, via super-Eddington-luminosity winds or Roche-lobe overflow. The WD models do not retain any significant amount of the accreted mass, with a He retention efficiency of ≲ 10% depending on mass and convective boundary mixing assumptions. This makes the evolutionary path of such systems to supernova Ia explosion highly unlikely

Anti-tussive, muco-suppressant and expectorant properties, and the safety profile of a hydro-ethanolic extract of Scoparia dulcis

Background: Scoparia dulcis is used in Ghanaian folkloric medicine for the management of asthma and its related complications. This study was therefore aimed at evaluating the anti-tussive, muco-suppressant and expectorant properties of hydroethanolic extract of S. dulcis (SDE), and to ascertain its safety for use in asthma and obstructive pulmonary disease management.Methods: The number of coughs induced in guinea pigs using citric acid and the concentration of phenol red secreted in tracheae of mice were measured. Preliminary phytochemical analysis was conducted on the extract using standard procedures. Safety for use of the extract was assessed by conducting an acute and delayed toxicity test.Results: The extract showed a dose-independent inhibition (p ≤ 0.001) of cough elicited by 7.5% citric acid, and a dose-dependent increase (p ≤ 0.05) in the amount of phenol red output in mice tracheae similar to that of ammonium chloride. For the muco-suppressant activity, SDE dose-dependently reduced (p ≤ 0.001) the concentration of ammonium chloride-induced phenol red secretions from mice tracheae. Phytochemical screening showed the presence of tannins, alkaloids, glycosides, saponins, steroids, and phenolic compounds. No acute and/or delayed toxic symptoms were observed after an oral administration of up to 5 g/kg of S. dulcis extract.Conclusion: The results showed that S. dulcis extract has anti-tussive, muco-suppressant and, expectorant and/or mucolytic properties; making it a possible remedy for asthma, and obstructive pulmonary disease

Programmatic advertising: An exegesis of consumer concerns

Programmatic advertising is a nascent and rapidly growing information technology phenomenon that reacts to, and impacts upon, consumers and their behavior. Despite its popularity and widespread use, research in the area remains scant and our current knowledge is based upon a preponderance of practitioner-generated literature. This study contributes to our understanding of this technology by unpacking the means by which it functions and interacts with consumers. The study draws upon paradox theory to deconstruct programmatic advertising's inherent tensions as dilemmas and dialectics. Adopting organisations are faced with the dilemma of pursuing the acquisition of increasingly detailed information in order to provide more personalized offerings, yet doing so increases the likelihood of creating a sense of fear and distrust among consumers. The automation of personalized advertising appears attractive yet presents the dilemma that adverts may be inappropriately placed. Finally, the true cost/benefit of programmatic advertising is unclear, and adopters, platform providers and developers need to engage in dialectic in order to fully understand and communicate its financial implications. Through identifying these fundamental constraints, the study affords pathways for programmatic system actors to ameliorate their, and their customers' concerns

Optimized Photolithographic Fabrication Process for Carbon Nanotube Devices

We have developed a photolithographic process for the fabrication of large arrays of single walled carbon nanotube transistors with high quality electronic properties that rival those of transistors fabricated by electron beam lithography.Abuffer layer is used to prevent direct contact between the nanotube and the novolac-based photoresist, and a cleaning bake at 300C effectively removes residues that bind to the nanotube sidewall during processing. In situ electrical measurement of a nanotube transistor during a temperature ramp reveals sharp decreases in the ON-state resistance that we associate with the vaporization of components of the photoresist. Data from nearly 2000 measured nanotube transistors show an average ON-state resistance of 250 ± 100 kΩ. This new process represents significant progress towards the goal of highyield production of large arrays of nanotube transistors for applications including chemical sensors and transducers, as well as integrated circuit components

Simple fluorinated moiety insertion on Aβ 16-23 peptide for stain-free TEM imaging.

Peptide aggregation and fibre formation are one of the major underlying causes of several neurodegenerative disorders such as Alzheimer's disease. During the past decades the characterisation of these fibres has been widely studied in an attempt to further understand the nature of the related diseases and in an effort to develop treatments. Transmission electron microscopy (TEM) is one of the most commonly used techniques to identify these fibres, but requires the use of a radioactive staining agent. The procedure we report overcomes this drawback through simple addition of a fluorinated moiety to a short Amyloid β sequence via solid phase peptide synthesis (SPPS). This method is synthetically straightforward, widely applicable to different aggregation-prone sequences and, above all, allows for stain-free TEM imaging with improved quality compared to standard imaging procedures. The presence of the fluorinated moiety does not cause major changes in the fibre structure or aggregation, but rather serves to dissipate the microscope's electron beam, thus allowing for high contrast and straightforward imaging by TEM.The authors are grateful for funding from the ERC Starting Investigator grant ASPiRe (no. 240629). The authors are also grateful to Dr Marco Di Antonio for assistance with HPLC purification.This is the final published version of the article. It was originally published in Analyst (Sonzini S, Jones ST, Walsh Z, Scherman OA, Analyst, 2015, 140, 2735, doi:10.1039/c4an02278e) http://dx.doi.org/10.1039/c4an02278

Why Pad\'e Approximants reduce the Renormalization-Scale dependence in QFT?

We prove that in the limit where the beta function is dominated by the 1-loop contribution (``large beta_0 limit'') diagonal Pad\'e Approximants (PA's) of perturbative series become exactly renormalization scale (RS) independent. This symmetry suggest that diagonal PA's are resumming correctly contributions from higher order diagrams that are responsible for the renormalization of the coupling-constant. Non-diagonal PA's are not exactly invariant, but generally reduce the RS dependence as compared to partial-sums. In physical cases, higher-order corrections in the beta function break the symmetry softly, introducing a small scale and scheme dependence. We also compare the Pad\'e resummation with the BLM method. We find that in the large-N_f limit using the BLM scale is identical to resumming the series by a $x[0/n]$ non-diagonal PA.Comment: 25 pages, LateX. Replaced so that the figures would fit into the page siz

Enhancing the Educational Experience for Deaf and Hard of Hearing Students in Software Engineering

Software engineering is largely a communication-driven, team-oriented discipline. There are numerous hurdles for ensuring proper communication and interaction between all project stakeholders, including physical, technological, and cultural barriers. These obstructions not only affect software engineering in industry, but in academia as well. One possible issue that is often overlooked in software engineering education is how to best educate Deaf and hard-of-hearing (Deaf/HoH) students, and how to fully engage them in the classroom. In this paper, we present our experiences in teaching software engineering to Deaf/HoH students. In the classroom, these students work very closely in activities and on project teams with their hearing peers. We also present recommendations for creating a more robust software engineering educational experience for not only Deaf/HoH students, but for hearing students as well. We encourage instructors not only in software engineering programs, but in other computing disciplines to consider our recommendations and observations in order to enhance the educational experience for all students in the classroom, whether Deaf/HoH or hearing

Stress dissipation in cucurbit[8]uril ternary complex small molecule adhesives.

The ability to control supramolecular and macroscopic self-assembly and disassembly holds great potential for responsive, reversible adhesives that can efficiently broker stresses accumulated between two surfaces. Here, cucurbit[8]uril is used to directly adhere two functionalized mica substrates creating surface-surface interactions that are held together through photo-reversible CB[8] heteroternary complexes. Comparison of single molecule, bulk and macroscopic adhesion behavior give insight into cooperativity and stress dissipation in dynamic adhesive systems

Xrn1/Pacman affects apoptosis and regulates expression of hid and reaper

Programmed cell death, or apoptosis, is a highly conserved cellular process that is crucial for tissue homeostasis under normal development as well as environmental stress. Misregulation of apoptosis is linked to many developmental defects and diseases such as tumour formation, autoimmune diseases and neurological disorders. In this paper, we show a novel role for the exoribonuclease Pacman/Xrn1 in regulating apoptosis. Using Drosophila wing imaginal discs as a model system, we demonstrate that a null mutation in pacman results in small imaginal discs as well as lethality during pupation. Mutant wing discs show an increase in the number of cells undergoing apoptosis, especially in the wing pouch area. Compensatory proliferation also occurs in these mutant discs, but this is insufficient to compensate for the concurrent increase in apoptosis. The phenotypic effects of the pacman null mutation are rescued by a deletion that removes one copy of each of the pro-apoptotic genes reaper, hid and grim, demonstrating that pacman acts through this pathway. The null pacman mutation also results in a significant increase in the expression of the pro-apoptotic mRNAs, hid and reaper, with this increase mostly occurring at the post-transcriptional level, suggesting that Pacman normally targets these mRNAs for degradation. Our results uncover a novel function for the conserved exoribonuclease Pacman and suggest that this exoribonuclease is important in the regulation of apoptosis in other organisms

The i-process yields of rapidly accreting white dwarfs from multicycle He-shell flash stellar evolution models with mixing parametrizations from 3D hydrodynamics simulations

© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society We have modelled the multicycle evolution of rapidly accreting CO white dwarfs (RAWDs) with stable H burning intermittent with strong He-shell flashes on their surfaces for 0.7 ≤ MRAWD/Mo ≤ 0.75 and [Fe/H] ranging from 0 to −2.6. We have also computed the i-process nucleosynthesis yields for these models. The i process occurs when convection driven by the He-shell flash ingests protons from the accreted H-rich surface layer, which results in maximum neutron densities Nn, max ≈ 1013–1015 cm−3. The H-ingestion rate and the convective boundary mixing (CBM) parameter ftop adopted in the one-dimensional nucleosynthesis and stellar evolution models are constrained through three-dimensional (3D) hydrodynamic simulations. The mass ingestion rate and, for the first time, the scaling laws for the CBM parameter ftop have been determined from 3D hydrodynamic simulations. We confirm our previous result that the high-metallicity RAWDs have a low mass retention efficiency (