634 research outputs found
Fermion Quasi-Spherical Harmonics
Spherical Harmonics, , are derived and presented (in a
Table) for half-odd-integer values of and . These functions are
eigenfunctions of and written as differential operators in the
spherical-polar angles, and . The Fermion Spherical Harmonics
are a new, scalar and angular-coordinate-dependent representation of fermion
spin angular momentum. They have symmetry in the angle , and hence
are not single-valued functions on the Euclidean unit sphere; they are
double-valued functions on the sphere, or alternatively are interpreted as
having a double-sphere as their domain.Comment: 16 pages, 2 Tables. Submitted to J.Phys.
AEROBIC AND ANAEROBIC SCALING IN FISH
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75506/1/j.1469-185X.1991.tb01134.x.pd
Cellular Radiosensitivity: How much better do we understand it?
Purpose: Ionizing radiation exposure gives rise to a variety of lesions in DNA that result in genetic instability and potentially tumorigenesis or cell death. Radiation extends its effects on DNA by direct interaction or by radiolysis of H2O that generates free radicals or aqueous electrons capable of interacting with and causing indirect damage to DNA. While the various lesions arising in DNA after radiation exposure can contribute to the mutagenising effects of this agent, the potentially most damaging lesion is the DNA double strand break (DSB) that contributes to genome instability and/or cell death. Thus in many cases failure to recognise and/or repair this lesion determines the radiosensitivity status of the cell. DNA repair mechanisms including homologous recombination (HR) and non-homologous end-joining (NHEJ) have evolved to protect cells against DNA DSB. Mutations in proteins that constitute these repair pathways are characterised by radiosensitivity and genome instability. Defects in a number of these proteins also give rise to genetic disorders that feature not only genetic instability but also immunodeficiency, cancer predisposition, neurodegeneration and other pathologies.
Conclusions: In the past fifty years our understanding of the cellular response to radiation damage has advanced enormously with insight being gained from a wide range of approaches extending from more basic early studies to the sophisticated approaches used today. In this review we discuss our current understanding of the impact of radiation on the cell and the organism gained from the array of past and present studies and attempt to provide an explanation for what it is that determines the response to radiation
Influence of experimental set-up and methodology for measurements of metabolic rates and critical swimming speed in Atlantic salmon Salmo salar
In this study, swim‐tunnel respirometry was performed on Atlantic salmon Salmo salar post‐smolts in a 90 l respirometer on individuals and compared with groups or individuals of similar sizes tested in a 1905 l respirometer, to determine if differences between set‐ups and protocols exist. Standard metabolic rate (SMR) derived from the lowest oxygen uptake rate cycles over a 20 h period was statistically similar to SMR derived from back extrapolating to zero swim speed. However, maximum metabolic rate (MMR) estimates varied significantly between swimming at maximum speed, following an exhaustive chase protocol and during confinement stress. Most notably, the mean (±SE) MMR was 511 ± 15 mg O2 kg−1 h−1 in the swim test which was 52% higher compared with 337 ± 9 mg O2 kg−1 in the chase protocol, showing that the latter approach causes a substantial underestimation. Performing group respirometry in the larger swim tunnel provided statistically similar estimates of SMR and MMR as for individual fish tested in the smaller tunnel. While we hypothesised a larger swim section and swimming in groups would improve swimming performance, Ucrit was statistically similar between both set‐ups and statistically similar between swimming alone v. swimming in groups in the larger set‐up, suggesting that this species does not benefit hydrodynamically from swimming in a school in these conditions. Different methods and set‐ups have their own respective limitations and advantages depending on the questions being addressed, the time available, the number of replicates required and if supplementary samplings such as blood or gill tissues are needed. Hence, method choice should be carefully considered when planning experiments and when comparing previous studies.publishedVersio
Suppression of Superfluidity of He in a Nanoporous Glass by Preplating a Kr Layer
Helium in nanoporous media has attracted much interest as a model Bose system
with disorder and confinement. Here we have examined how a change in porous
structure by preplating a monolayer of krypton affects the superfluid
properties of He adsorbed or confined in a nanoporous Gelsil glass, which
has a three-dimensional interconnected network of nanopores of 5.8 nm in
diameter. Isotherms of adsorption and desorption of nitrogen show that
monolayer preplating of Kr decreases the effective pore diameter to 4.7 nm and
broadens the pore size distribution by about eight times from the sharp
distribution of the bare Gelsil sample. The superfluid properties were studied
by a torsional oscillator for adsorbed film states and pressurized liquid
states, both before and after the monolayer Kr preplating. In the film states,
both the superfluid transition temperature and the superfluid
density decrease about 10 percent by Kr preplating. The suppression of film
superfluidity is attributed to the quantum localization of He atoms by the
randomness in the substrate potential, which is caused by the
preplating--induced broadening of the pore size distribution. In the
pressurized liquid states, the superfluid density is found
to increase by 10 percent by Kr preplating, whereas is
decreased by 2 percent at all pressures. The unexpected enhancement of
might indicate the existence of an unknown disorder effect
for confined He.Comment: 27 pages, 8 figures, submitted to J. Phys. Soc. Jp
- …