Photolysis of Diborane at 1849 Å

The photolysis of diborane at 1849 Å has been studied in a specially constructed, internal‐type mercury‐vapor lamp. The products have been found to be H_2, B_(4)H_(10), B_(5)H_(11), and, at low pressures, a —BH— polymer. Reaction orders at 4°C have been obtained from linear plots of reaction products vs time for a range of diborane pressures from 0.08 to 80 cm, and at two light intensities. Linear relations between products and time existed only at very low conversions (∼1%), which required the development of a low‐temperature separation method for manipulating and analyzing the traces of B_(4)H_(10) and B_(5)H_(11). Because of the reactivity of these compounds, a detailed conditioning procedure was employed for the glass system. A mechanism consistant with the kinetic data and suggested by the kinetic results of thermal and photosensitized decomposition of diborane is postulated: the B_(5)H_(11) is assumed to be formed from a dissociation of B_(2)H_6 into BH_3's, the latter arising from an excited molecule. The B_(4)H_(10) and polymer are assumed to be formed from a dissociation of B_(2)H_6 into B_(2)H_5 and H, followed by radical recombination. There is a significant difference between the kinetics of thermal and photochemical B_(5)H_(11) formation, a result which may be due to the considerable energy excess of the 1849 quantum over that needed for dissociation (∼125‐kcal excess). These kinetic results raise a number of interesting questions, questions which can only be resolved through further investigations of effects due to light intensity, added inert gases, and temperature. The primary quantum yield of the step forming B_(2)H_5 and H is about 10 times higher than that of the one forming BH_3's. A rather rough estimate suggests that the former is of the order of magnitude of unity

Providing Real-World Experiences: the Virginia Tech Externship for Mathematics Specialists

We describe the structure and implementation of the yearlong Externship experience associated with the Mathematics Specialist program at Virginia Polytechnic Institute & State University (Virginia Tech). We discuss the assignments and experiences included in the Externship, the alignment of those experiences with the job description developed by the Virginia Mathematics and Science Coalition Task Force, and teacher comments on the effectiveness of their Externship experiences [1]

GlycoExpress: A toolbox for the high yield production of glycooptimized fully human biopharmaceuticals in perfusion bioreactors at different scales

Background and Novelty: Glycosylation is one of the major post-translational modifications of biotherapeutics important for bioactivity, bioavailability, immunogenicity and patient coverage. By establishment of the GlycoExpress™ toolbox (GEX™) we have generated a set of glycoengineered human cell lines for the high yield production of fully human glycoproteins to optimize the glycosylation of antibodies and non-antibody biotherapeutics for improvement of the clinical efficacy and side effects. The system is biotechnologically superior in quality, reproducibility and yield compared to other including conventional production systems. All four clinical products derived from GlycoExpress cells are produced using a perfusion bioreactor system in order to assure highest possible product quality and reproducibility combined with high yield production. Methods: GlycoExpress cells producing mAb are cultivated with perfusion bioreactor systems applying different cell retention mechanisms such as centrifugation (centritech) or alternating tangential flow (ATF) filtration at different scales. A 10 mL based down-scale perfusion system with good comparability to larger scale cultivations was also established. Growth, product yield and product quality, especially glycosylation, are evaluated during the cultivation. Conclusion: Perfusion culture helps to keep cells in the optimal growing and production phase over the production process which leads to highly stable product quality allowing a flexible duration of the run in one batch size in combination with stable high productivity of the cells over time. Furthermore the product qualities produced in different scales ranging from 10 mL to 1000 L cultivation vessels are highly comparable

A TEXTUAL ANALYSIS OF ONLINE ASEXUAL REPRESENTATION AND VISIBILITY ON REDDIT

Asexuality remains an under-researched topic in media, gender & sexualities studies. Previous research has explored definitional questions of asexuality, interviews and surveys of asexual people, and consideration of asexuality’s place within queer and feminist communities. However, research has not yet fully explored the issue of asexuality invisibility in the media, which currently amounts to symbolic annihilation. While representation of asexuality is nearly non-existent in mainstream and traditional media, digital spaces have been the location of visibility and self-expression for asexuals. In examining how queer representation of asexuality is seen and made visible online, this textual analysis study examined the content created by ten asexuality-focused subdivisions (“subreddits”) of the social media site Reddit. This study found that asexual subreddits serve as areas of community, pride, and discussion on the concept of asexuality for asexual individuals, while they serve as resources and locations of support for those in the early stages of questioning or understanding their own asexuality. These efforts fight symbolic annihilation of asexuality to these groups of people, though whether these sites combat larger invisibilities is unclear

Up and down scale considerations for the continuous production of glycooptimized biopharmaceuticals

Product quality especially with respect to glycosylation is a critical product attribute which can have an immense influence on the activity of glycoproteins and should be closely monitored during process development and manufacturing. GlycoExpressTM cells have been developed in this context to provide human host cell lines with robust glycosylation machineries. This work will address challenges in two case studies for up and down scaling of production processes with focus on product quality and continuous processing. In a first section, data of a process transfer from a 200 L stainless steel to a 1000 L single-use bioreactor for a continuous cell culture application is discussed. The impact of engineering aspects for the bioreactor and the cell retention device as well as product quality considerations are addressed. As a second part, a 10 mL down-scale system for perfusion cultivations in a microbioreactor is introduced and its application for process development is evaluated. A GlycoExpress-based Phase II GMP perfusion process for mAb production at the 200 L stainless steel scale was successfully transferred to a 1000 L single-use bioreactor. Growth, productivity and stable glycosylation were maintained during scale up. The developed perfusion down-scale system SAM shows very good comparability to larger scale ATF runs not only for USP characteristics but also for product quality. The system predicts the response to media supplementation better than batch or chemostat approaches. Design of Experiment studies can be easily performed with this system resulting in highly significant model