Neutrino Opacities in Nuclear Matter

Neutrino-matter cross sections and interaction rates are central to the core-collapse supernova phenomenon and, very likely, to the viability of the explosion mechanism itself. In this paper, we describe the major neutrino scattering, absorption, and production processes that together influence the outcome of core collapse and the cooling of protoneutron stars. One focus is on energy redistribution and many-body physics, but our major goal is to provide a useful resource for those interested in supernova neutrino microphysics.Comment: 47 pages, including figures, to be published in a special issue of Nucl. Phys.

Assessment of an in vitro whole cigarette smoke exposure system: The Borgwaldt RM20S 8-syringe smoking machine

<p>Abstract</p> <p>Background</p> <p>There have been many recent developments of <it>in vitro </it>cigarette smoke systems closely replicating <it>in vivo </it>exposures. The Borgwaldt RM20S smoking machine (RM20S) enables the serial dilution and delivery of cigarette smoke to exposure chambers for <it>in vitro </it>analyses. In this study we have demonstrated reliability and robustness testing of the RM20S in delivering smoke to <it>in vitro </it>cultures using an in-house designed whole smoke exposure chamber.</p> <p>Results</p> <p>The syringe precision and accuracy of smoke dose generated by the RM20S was assessed using a methane gas standard and resulted in a repeatability error of ≤9%. Differential electrical mobility particle spectrometry (DMS) measured smoke particles generated from reference 3R4F cigarettes at points along the RM20S. 53% ± 5.9% of particles by mass reached the chamber, the remainder deposited in the syringe or connecting tubing and ~16% deposited in the chamber. Spectrofluorometric quantification of particle deposition within chambers indicated a positive correlation between smoke concentration and particle deposition. <it>In vitro </it>air-liquid interface (ALI) cultures (H292 lung epithelial cells), exposed to whole smoke (1:60 dilution (smoke:air, equivalent to ~5 μg/cm²)) demonstrated uniform smoke delivery within the chamber.</p> <p>Conclusions</p> <p>These results suggest this smoke exposure system is a reliable and repeatable method of generating and exposing ALI <it>in vitro </it>cultures to cigarette smoke. This system will enable the evaluation of future tobacco products and individual components of cigarette smoke and may be used as an alternative <it>in vitro </it>tool for evaluating other aerosols and gaseous mixtures such as air pollutants, inhaled pharmaceuticals and cosmetics.</p

Mechanical stimulation towards tissue engineering of the knee meniscus

Tissue engineering has been proposed to alleviate injury to the knee meniscus, which leads to loss of function and damage to the surrounding articular cartilage. Relatively few studies have been performed to tissue engineer the meniscus; however, much guidance can be found by studying related tissues such as articular cartilage. One technique that has proved beneficial for producing tissue engineered articular cartilage constructs is mechanical stimulation. This thesis describes the investigation of scaffold choices and the development of culture techniques for producing meniscal constructs. In addition, a direct compression stimulator was developed, validated, and applied to the tissue engineered meniscal constructs. Poly-glycolic acid (PGA) and agarose were examined for use as scaffolds. It was found that agarose did not support fibrochondrocyte growth, and that while PGA supported cell production and proliferation, constructs were not mechanically robust after 7 wks in culture. A direct compression bioreactor was developed and validated using articular cartilage and meniscal explants. An attempt to produce better constructs than previously achieved in vitro in terms of mechanical properties, matrix production and organization, was successful using the self-assembly (SA) method. The SA method developed for the meniscus employs a ring-shaped agarose mold seeded with articular chondrocytes (AC) and meniscal fibrochondrocytes (MFC). It was found that a spectrum of biomechanical and biochemical properties could be achieved based on the seeding ratio of ACs:MFCs. It was determined that a 50:50 ratio of AC:MFC produced a construct that best replicated the cross-section of the native meniscus. A direct comparison of SA constructs to constructs formed with PGA was made via an investigation into the effect of dynamic direct compression stimulation. It was found that, after 4 wks in culture, PGA constructs lacked sufficient mechanical integrity to undergo loading. Wk 8 SA constructs were 3.4 times stronger and stiffer in the circumferential direction than in the radial direction. In addition, SA constructs had 3 times more GAG and 2 times more collagen than PGA constructs. The application of dynamic stimulation did not further increase mechanical properties or matrix production in SA constructs, but merits further study examining different loading regimens

Terahertz imaging modalities of ancient egyptian mummified objects and of a naturally mummified rat

During the last few years, terahertz (THz) imaging has been used to investigate artwork and historic artifacts. The application of THz imaging to mummy investigations is very attractive since it provides spectroscopic information over a broad frequency range and its radiation has proven to be harmless to human cells. However, compared with the current standard imaging methods in mummy imaging-X-ray and computed tomography (CT)-it remains a novel, emerging technique whose potential still needs to be fully evaluated. Here, ancient Egyptian mummified objects as well as a naturally mummified rat have been investigated by two different THz imaging systems: a broadband THz time domain imaging system and an electronic THz scanner. The obtained THz images are compared with conventional CT, X-ray, and magnetic resonance images. While the broadband THz time domain setup permits analyses of smaller samples, the electronic THz scanner allows the recording of data of thicker and larger samples at the expense of a limited spectral bandwidth. Terahertz imaging shows clear potential for mummy investigations, although currently CT imaging offers much higher spatial resolution. Furthermore, as commercial mobile THz scanners become available, THz imaging could be applied directly in museums or at excavation sites

Nanoindentation of human meniscal surfaces

Menisci are crescent shaped fibrocartilaginous structures which support load distribution of the knee. The menisci are specifically designed to fit the contour of the femoral condyles, aiding to disperse the stresses on the tibial plateau and in turn safeguarding the underlying articular cartilage. The importance of the meniscal superficial layer has not been fully revealed and it is suspected that this layer plays a pivotal role for meniscal function. In this study, both femoral (proximal) and tibial (distal) contacting meniscal surfaces were mechanically examined on the nano-level among three distinct regions (anterior, central and posterior) of the lateral and medial menisci. Nanoindentation testing showed no significant differences among regions, surfaces or anatomical locations, possibly elucidating on the homogeneity of the meniscal superficial zone structure (E(Instantaneous): 3.17–4.12 MPa, E(Steady)(–)(State): 1.47–1.69 MPa). Nanomechanical moduli values were approximately an order of magnitude greater than micro-scale testing derived moduli values. These findings validate the structural homogeneity of the meniscal superficial zone, showing that material properties are statistically similar regardless of meniscal surface and region. Understanding the mechanical behavior of meniscal surfaces is imperative to properly design an effective meniscal replacement