Parton distribution function for quarks in an s-channel approach

We use an s-channel picture of hard hadronic collisions to investigate the parton distribution function for quarks at small momentum fraction x, which corresponds to very high energy scattering. We study the renormalized quark distribution at one loop in this approach. In the high-energy picture, the quark distribution function is expressed in terms of a Wilson-line correlator that represents the cross section for a color dipole to scatter from the proton. We model this Wilson-line correlator in a saturation model. We relate this representation of the quark distribution function to the corresponding representation of the structure function F_T(x,Q^2) for deeply inelastic scattering

Post-Impact Thermal Evolution of Porous Planetesimals

Impacts between planetesimals have largely been ruled out as a heat source in the early Solar System, by calculations that show them to be an inefficient heat source and unlikely to cause global heating. However, the long-term, localized thermal effects of impacts on planetesimals have never been fully quantified. Here, we simulate a range of impact scenarios between planetesimals to determine the post-impact thermal histories of the parent bodies, and hence the importance of impact heating in the thermal evolution of planetesimals. We find on a local scale that heating material to petrologic type 6 is achievable for a range of impact velocities and initial porosities, and impact melting is possible in porous material at a velocity of > 4 km/s. Burial of heated impactor material beneath the impact crater is common, insulating that material and allowing the parent body to retain the heat for extended periods (~ millions of years). Cooling rates at 773 K are typically 1 - 1000 K/Ma, matching a wide range of measurements of metallographic cooling rates from chondritic materials. While the heating presented here is localized to the impact site, multiple impacts over the lifetime of a parent body are likely to have occurred. Moreover, as most meteorite samples are on the centimeter to meter scale, the localized effects of impact heating cannot be ignored.Comment: 38 pages, 9 figures, Revised for Geochimica et Cosmochimica Acta (Sorry, they do not accept LaTeX

An investigation into the factors involved in acclimatization to temperature and death at high temperature in calliphora erythrocephala (meig)

The heat resistance of Calliphora erythrocephala varies during the life history. The egg is most sensitive to high temperature and the puparium most resistant. Puparial resistance develops in the larval stage and declines in the young adult. This adult decline is temperature dependent and seems to be related to changes taking place during maturation. Evidence for the existence of development acclimatization was found to be contradictory, however, physiological acclimatization did occur in the adult. This latter form of acclimatization differs from the typical pattern observed with other species, for the increase in heat resistance with increasing temperature of acclimatization is not proportionate and it declines with adult age. The interaction of these factors makes resistance adaptation in Calliphora erythrocephala a complex phenomena. It is concluded that the primary lesion of heat death in adults is the uncoupling of the sarcosomal enzymes associated with oxidative phosphorylation of ɤ glycerophosphate. The heat sensitivity of this enzyme pathway is correlated with the heat death point of the whole animal and death is probably the result of a breakdown in ATF synthesis, which leads to the interruption of other energy dependent processes. The biochemical lesions during heat death are correlated with dramatic changes in the ultrastructure of sarcosomal cristae, which house the respiratory assemblies. This suggests that the structural and functional integrity of membrane-enzyme complexes are important factors in cellular metabolism. Studies on isolated sarcosomes have shown that the coupling of oxidative phosphorylation is influenced by both age and acclimatized state of the fly. The coupling enzymes are implicated in both the age dependent changes in heat resistance and also capacity adaptation. They are likely to be key factors in the temperature physiology of adult Calliphora

A new set of endogenous control genes for use in quantitative real-time PCR experiments show that formin Ldia2dex transcripts are enriched in the early embryo of the pond snail Lymnaea stagnalis (Panpulmonata)

© 2019 The Author(s). Published by Oxford University Press on behalf of The Malacological Society of London, all rights reserved. Although the pond snail Lymnaea stagnalis is an emerging model organism for molecular studies in a wide variety of fields, there are a limited number of verified endogenous control genes for use in quantitative real-Time PCR. As part of a larger study on snail chirality, or left-right asymmetry, we assayed gene expression in pond snail embryos. We evaluated six candidate control genes, by comparing their expression in three tissues (ovotestis, foot and embryo) and used three software programmes (geNorm, Normfinder and Bestkeeper) to do so. The specific utility of these control genes was then tested by investigating the relative expression of six experimental transcripts, including formin Ldia2, a gene that has been associated with chiral variation in L. stagnalis. All six control genes were found to be suitable for use in the three tissues tested. Of the six experimental genes, it was found that all were relatively depleted in the early embryo compared with other tissues, except the formin Ldia2 gene. Instead, transcripts of the wild-Type Ldia2dex were enriched in the embryo, whereas a nonfunctional frameshifted version, Ldia2sin, was severely depleted. These differences in Ldia2sin expression were less evident in the ovotestis and were not evident in the foot tissue, possibly because nonsense-mediated decay is obscured in actively transcribing tissues. Our work provides a set of control genes that may be useful to the wider community and illustrates how these genes may be used to assay differences in expression in a variety of tissues

Mechalele (Self-Playing Ukulele)

This project involves the design and implementation of a self-playing ukulele. The ukulele plays chords and plucks open strings based on a song or chord progression selected by the user. Each string on the ukulele has a designated hobby servo motor that plucks the string with pre-programmed timing as is shown in Figure 1 (3). The plucking is achieved by attaching a flexible piece of cardboard to the shaft of the servo to act as the guitar pick. By moving the motors together at once, the action of strumming can be approximated. The design uses the last three frets on the ukulele for pressing different strings and allows the ukulele to play different notes and chords. The strings are pressed by small push/pull solenoids (2) that are spring loaded to push the string when active and not touch the string when passive. The output of the system is controlled with user selection buttons that selects song or tuning mode for the ukulele from an LCD display (6). The user can either select tuning or song playing mode using three pushbuttons. In tuning mode, a speaker plays the desired note for a string and the LCD display prompts the user to pluck that string. The frequency of the note is detected from a microphone and the display tells the user if the string is tuned, too high, or too low

Interpreting intraplate tectonics for seismic hazard : a UK historical perspective

It is notoriously difficult to construct seismic source models for probabilistic seismic hazard assessment in intraplate areas on the basis of geological information, and many practitioners have given up the task in favour of purely seismicity-based models. This risks losing potentially valuable information in regions where the earthquake catalogue is short compared to the seismic cycle. It is interesting to survey how attitudes to this issue have evolved over the past 30 years. This paper takes the UK as an example, and traces the evolution of seismic source models through generations of hazard studies. It is found that in the UK, while the earliest studies did not consider regional tectonics in any way, there has been a gradual evolution towards more tectonically based models. Experience in other countries, of course, may differ