Scattering of a Baseball by a Bat

A ball can be hit faster if it is projected without spin but it can be hit farther if it is projected with backspin. Measurements are presented in this paper of the tradeoff between speed and spin for a baseball impacting a baseball bat. The results are inconsistent with a collision model in which the ball rolls off the bat and instead imply tangential compliance in the ball, the bat, or both. If the results are extrapolated to the higher speeds that are typical of the game of baseball, they suggest that a curveball can be hit with greater backspin than a fastball, but by an amount that is less than would be the case in the absence of tangential compliance.Comment: Accepted for publication in American Journal of Physic

What is a virulence factor?

Bacterial virulence factors enable a host to replicate and disseminate within a host in part by subverting or eluding host defenses. The use of genomic techniques has led to the identification of new virulence factors that may serve as targets for new therapies. These putative virulence factors must be rigorously evaluated with in vitro and in vivo studies with an awareness of the technical limitations of each approach as well as an assessment of the prevalence of this factor in clinical bacterial isolates retrieved from appropriately controlled epidemiologic studies

Design, simulation and experiment of a cusp electron beam for millimeter wave gyro-devices

The design, simulation and experiment of a thermionic cusp electron gun that is to be used for millimeter wave generation will be presented. A cusp gun uses a non-adiabatic magnetic field reversal to obtain azimuthal motion on an electron beam resulting in an annular shaped, axis-encircling beam. The cusp gun was designed to generate a beam of 1.5A at 40kV with an adjustable velocity ratio of up to 3.0. The beam had a simulated axial velocity spread of 7.4% and alpha spread of 10.1%. The beam had an averaged radius of 0.35mm and beam thickness of 0.05mm which is ideal to drive sub-mm wave gyro-devices under investigation

Multi-mode coupling wave theory for helically corrugated waveguide

Helically corrugated waveguide has been used in various applications such as gyro-backward wave oscillators, gyro-traveling wave amplifier and microwave pulse compressor. A fast prediction of the dispersion characteristic of the operating eigenwave is very important when designing a helically corrugated waveguide. In this paper, multi-mode coupling wave equations were developed based on the perturbation method. This method was then used to analyze a five-fold helically corrugated waveguide used for X-band microwave compression. The calculated result from this analysis was found to be in excellent agreement with the results from numerical simulation using CST Microwave Studio and vector network analyzer measurements

Exploring teacher activity in primary design and technology lessons

This paper illustrates actions and behaviours employed by English primary school teachers in teaching design and technology in the present context of the statutory National Curriculum framework for primary design and technology. It considers perspectives relating to general pedagogy, teacher activity and the possible contribution of learning theory and factors which influence choice of teaching methods. A number of sources of evidence are utilised including school inspection reports, teacher interviews and lesson observation. Two contrasting lessons, which illustrate some of the tensions faced by teachers, are considered and aspects of relevant statutory and non-statutory curriculum and guidance documents are explored. Based on a small nonrepresentative sample this research sought to illustrate and explore teaching activity, a larger sample would be required to confirm the findings. A source of tension is identified in that teachers are charged with delivering specified knowledge and skill based outcomes, whilst at the same time developing pupil creativity. Suggestions of alternative approaches to the categorisation of teaching methods, including a form of taxonomy of primary design and technology methods, are made. primary, design and technology, teaching methods, learning, pupil autonomy, teacher directio

Using a Microsoft Surface Pro 3 tablet for mathematics support

This paper reviews the benefits of using a Microsoft Surface Pro tablet in a mathematics support setting. The context of its use is foregrounded and associated educational issues explored

Isotopic labelling of functionalised arenes catalysed by Ir(I) species of the [(COD)Ir(NHC)(py)]PF6 complex class

Ir(I) complexes of the type [(COD)Ir(NHC)(Py)]PF6 have been exposed as efficient catalysts in the area of hydrogen isotope exchange. More specifically, via an ortho-directed C-H activation process, high levels of deuterium incorporation have been achieved using low levels of catalyst over a range of functionalised aromatic compounds. Additionally, the developed protocol has been extended to include a selected pharmacological target, where chemoselective labelling is observed within such a multifunctional substrate

Immunogenicity of a 24-Valent Klebsiella Capsular Polysaccharide Vaccine and an Eight-Valent Pseudomonas O-Polysaccharide Conjugate Vaccine Administered to Victims of Acute Trauma

We measured the antibody response in 10 victims of acute blunt trauma and penetrating trauma who were immunized against Klebsiella pneumoniae and Pseudomonas species within 72 hours of injury. The two vaccines, which were previously shown to be safe and immunogenic in uninjured humans, were a 24-valent K. pneumoniae capsular polysaccharide vaccine and an eight-valent Pseudomonas a-polysaccharide-toxin A conjugate vaccine. The patients were between 18 and 44 years of age, had Injury Severity Scores that ranged between 9 and 34, and did not have chronic infections or malignancies. On days 14 and 28 after immunization, all patients had a response of greater than fourfold to at least six of the nine Pseudomonas vaccine antigens. Half of the patients responded to eight of the nine antigens. Nine patients responded to at least 18 of 24 Klebsiella antigens, and seven patients responded to 22 of the 24 antigens. No important side effects were attributed to the vaccines. The results of this preliminary study indicate that active immunization against potential pathogens is possible in victims of acute traum

Bacillus anthracis-derived edema toxin (ET) counter-regulates movement of neutrophils and macromolecules through the endothelial paracellular pathway

<p>Abstract</p> <p>Background</p> <p>A common finding amongst patients with inhalational anthrax is a paucity of polymorphonuclear leukocytes (PMNs) in infected tissues in the face of abundant circulating PMNs. A major virulence determinant of anthrax is edema toxin (ET), which is formed by the combination of two proteins produced by the organism, edema factor (EF), which is an adenyl cyclase, and protective antigen (PA). Since cAMP, a product of adenyl cyclase, is known to enhance endothelial barrier integrity, we asked whether ET might decrease extravasation of PMNs into tissues through closure of the paracellular pathway through which PMNs traverse.</p> <p>Results</p> <p>Pretreatment of human microvascular endothelial cell(EC)s of the lung (HMVEC-L) with ET decreased interleukin (IL)-8-driven transendothelial migration (TEM) of PMNs with a maximal reduction of nearly 60%. This effect required the presence of both EF and PA. Conversely, ET did not diminish PMN chemotaxis in an EC-free system. Pretreatment of subconfluent HMVEC-Ls decreased transendothelial ¹⁴C-albumin flux by ~ 50% compared to medium controls. Coadministration of ET with either tumor necrosis factor-α or bacterial lipopolysaccharide, each at 100 ng/mL, attenuated the increase of transendothelial ¹⁴C-albumin flux caused by either agent alone. The inhibitory effect of ET on TEM paralleled increases in protein kinase A (PKA) activity, but could not be blocked by inhibition of PKA with either H-89 or KT-5720. Finally, we were unable to replicate the ET effect with either forskolin or 3-isobutyl-1-methylxanthine, two agents known to increase cAMP.</p> <p>Conclusions</p> <p>We conclude that ET decreases IL-8-driven TEM of PMNs across HMVEC-L monolayers independent of cAMP/PKA activity.</p