A simple model for the outcomes of collisions between exhaled aerosol droplets and airborne particulate matter: Towards an understanding of the influence of air pollution on airborne viral transmission

A model that predicts the outcome of collisions between droplets and particles in terms of the distribution of the droplet volume post-collision is lacking, in contrast to the case for droplet-droplet interactions. Taking existing models that successfully predict the outcomes (coalescence, stretching or reflexive separation) and post-separation characteristics (sizes, numbers and velocities of the resulting droplets) of droplet-droplet collisions and adapting them to take into account an inextensible, non-deformable particle with varying wettability characteristics, a new model is presented for droplet-particle collisions. The predictions of the new model agree well with experimental observations of droplet-particle collisions in low-viscosity regimes. The model is then applied to the case of collisions between respiratory aerosols generated by breath, speech, cough and sneeze and ambient airborne particulate material (PM) in order to assess the potential contribution of these interactions to the enhanced transmission of pathogens contained in the aerosol, including COVID-19. The results show that under realistic conditions it is possible for aerosol-PM collisions to enrich the pathogen content of smaller (and so more persistent) aerosol fractions, and to transfer pathogens to the surface of PM particles that can travel deep into the respiratory tract. In the context of better knowledge of the size and velocity distributions of respiratory aerosols, this model may be used to predict the extent to which high ambient PM levels may contribute to airborne infection by pathogens such as COVID-19.Comment: 32 pages, 10 figures, 4 tables, supporting informatio

Mechanistic and kinetic insight into spontaneous cocrystallisation of isoniazid and benzoic acid

Solid-state cocrystallisation is of contemporary interest, because it offers an easy and efficient way to produce cocrystals, which are recognized as prospective pharmaceutical materials. Research explaining solid-state cocrystallisation mechanisms is important, but still too scarce to give a broad understanding of factors governing and limiting these reactions. Here we report an investigation of the mechanism and kinetics of isoniazid cocrystallisation with benzoic acid. This reaction is spontaneous; however its rate is greatly influenced by environmental conditions (humidity and temperature) and pre-treatment (milling) of the sample. The acceleration of cocrystallisation in the presence of moisture is demonstrated by kinetic studies at elevated humidity. The rate dependence on humidity stems from moisture facilitated rearrangements on the surface of isoniazid crystallites, which lead to cocrystallisation in the presence of benzoic acid vapour. Furthermore, pre-milling the mixture of the cocrystal ingredients eliminated the induction time of the reaction and considerably increased its rate

Lamellar Structures of MUC2-Rich Mucin: A Potential Role in Governing the Barrier and Lubricating Functions of Intestinal Mucus

Mucus is a ubiquitous feature of mammalian wet epithelial surfaces, where it lubricates and forms a selective barrier that excludes a range of particulates, including pathogens, while hosting a diverse commensal microflora. The major polymeric component of mucus is mucin, a large glycoprotein formed by several MUC gene products, with MUC2 expression dominating intestinal mucus. A satisfactory answer to the question of how these molecules build a dynamic structure capable of playing such a complex role has yet to be found, as recent reports of distinct layers of chemically identical mucin in the colon and anomalously rapid transport of nanoparticles through mucus have emphasized. Here we use atomic force microscopy (AFM) to image a MUC2-rich mucus fraction isolated from pig jejunum. In the freshly isolated mucin fraction, we find direct evidence for trigonally linked structures, and their assembly into lamellar networks with a distribution of pore sizes from 20 to 200 nm. The networks are two-dimensional, with little interaction between lamellae. The existence of persistent cross-links between individual mucin polypeptides is consistent with a non-self-interacting lamellar model for intestinal mucus structure, rather than a physically entangled polymer network. We only observe collapsed entangled structures in purified mucin that has been stored in nonphysiological conditions

Reflections on an Introduction to Project Based Engineering in an Incarcerated Setting

Education programs in incarcerated settings have a goal of improving the current and future lives of the currently incarcerated individuals. There are many programs that support earning a GED, associate degree, or baccalaureate degree when incarcerated. The benefits of these programs include improved behavior while incarcerated, reduced recidivism, and broadening the workforce. Generally, the courses offered as a part of these programs are general education in nature. This paper discusses an Introduction to Project Based Engineering taught in a women’s prison setting. Specifically, it explores the course as a case study reflected on from several angles. Each reflection illuminates the case from a different perspective. The different perspectives are a prison administrator, the instructor, the author of one of the textbooks used in the course, a student more than a decade from release, and a student a few months from release. By taking these reflections together one is able to see the challenges, rewards, and opportunities associated with teaching an Introduction to Project Based Engineering to incarcerated women. Although each perspective highlights different aspects of the course there are common themes. There are also key differences that illustrate the unique needs and wants of the various stakeholders. The common themes and differences are examined. Together they serve as a foundation for adjusting the course to make it more effective and sustainable. Additionally, the reflections examined here shed light on how an Introduction to Project Based Engineering in a traditional setting might be improved

Sliding Contact Dynamic Force Spectroscopy Method for Interrogating Slowly Forming Polymer Cross-Links

Dynamic Single Molecule Force Spectroscopy (SMFS), conducted most commonly using AFM, has become a widespread and valuable tool for understanding the kinetics and thermodynamics of fundamental molecular processes such as ligand-receptor interactions and protein unfolding. Where slowly forming bonds are responsible for the primary characteristics of a material, as is the case in crosslinks in some polymer gels, care must be taken to ensure that a fully equilibrated bond has first formed before its rupture can be interpreted. Here we introduce a method, sliding contact force spectroscopy (SCFS), which effectively eliminates the kinetics of bond formation from the measurement of bond rupture. In addition it permits bond rupture measurements in systems where one of the binding partners may be introduced into solution prior to binding without tethering to a surface. Taking as an exemplar of a slowly forming bond the ‘eggbox’ junction crosslinks between oligoguluronic acid chains (oligoGs) in the commercially important polysaccharide alginate, we show that SCFS measures accurately the equilibrated bond strength of the crosslink when one chain is introduced into the sample solution without tethering to a surface. The results validate the SCFS technique for performing single molecule force spectroscopy experiments, and show that it has advantages in cases where the bond to be studied forms slowly and where tethering of one of the binding partners is impractical

THE AVIFAUNA OF THE MO SINGTO FOREST DYNAMICS PLOT, KHAO YAI NATIONAL PARK, THAILAND

ABSTRACT The 169 species of birds recorded on the 30 ha Mo Singto Forest Dynamics Plot, Khao Yai National Park, Thailand, are a subset of the 329 species recorded in the headquarters area of the park. Most of the Mo Singto-recorded species are typical of evergreen forest interior but the transient occurrence of a small number of other species, inhabitants of forest edge or more open habitats, is documented. Almost one third of species found on the plot were moderate to long-distance migrant, non-breeding, visitors. The largest foraging guilds were foliage-gleaning insectivores and sallying insectivores, together accounting for over one-third of all species. Though obligate frugivores were poorly represented, most insectivorous birds incorporated fruits in their diet. The nearly 30-year history of avian recording at Mo Singto, with intensive community studies having been conducted in the past decade, and the location of the study plot near the submontane-montane transition, make it an ideal site for continuation of detailed monitoring, particularly that related to the impact of climate change

Supramolecular Amino Acid Based Hydrogels: Probing the Contribution of Additive Molecules using NMR Spectroscopy

Supramolecular hydrogels are composed of self-assembled solid networks that restrict the flow of water. l-Phenylalanine is the smallest molecule reported to date to form gel networks in water, and it is of particular interest due to its crystalline gel state. Single and multi-component hydrogels of l-phenylalanine are used herein as model materials to develop an NMR-based analytical approach to gain insight into the mechanisms of supramolecular gelation. Structure and composition of the gel fibres were probed using PXRD, solid-state NMR experiments and microscopic techniques. Solution-state NMR studies probed the properties of free gelator molecules in an equilibrium with bound molecules. The dynamics of exchange at the gel/solution interfaces was investigated further using high-resolution magic angle spinning (HR-MAS) and saturation transfer difference (STD) NMR experiments. This approach allowed the identification of which additive molecules contributed in modifying the material properties

The Grizzly, November 13, 2014

Art Department Debuts New Class • Delta Pi Becomes First Gender-Neutral Fraternity in UC History • Twin Brothers Host 5 Hour Study Marathon • Midterm Election Results • Chinese Culture Should be Shared, Not Hidden • High Prices Cause Complaints • Walking Through a Day With UC EMS • Berman Museum Timeline Installed • Feminists In Action Club Tackles the Issue of Gender Inequality • Opinion: Denial of Birth Control is Unconstitutional; Jewish Frat Vandalized • Letter to the Editor • Back-to-Back Champs • Sticking Together at Ursinushttps://digitalcommons.ursinus.edu/grizzlynews/1916/thumbnail.jp