3,734 research outputs found
Circadian regulation of reproduction: From gamete to offspring
P01326625; Grants: GNT0519315Few challenges are more critical to the survival of a species than reproduction. To ensure reproductive success, myriad aspects of physiology and behaviour need to be tightly orchestrated within the animal, as well as timed appropriately with the external environment. This is accomplished through an endogenous circadian timing system generated at the cellular level through a series of interlocked transcription/translation feedback loops, leading to the overt expression of circadian rhythms. These expression patterns are found throughout the body, and are intimately interwoven with both the timing and function of the reproductive process. In this review we highlight the many aspects of reproductive physiology in which circadian rhythms are known to play a role, including regulation of the estrus cycle, the LH surge and ovulation, the production and maturation of sperm and the timing of insemination and fertilisation. We will also describe roles for circadian rhythms in support of the preimplantation embryo in the oviduct, implantation/placentation, as well as the control of parturition and early postnatal life. There are several key differences in physiology between humans and the model systems used for the study of circadian disruption, and these challenges to interpretation will be discussed as part of this review.M.J. Boden, T.J. Varcoe, D.J. Kennawa
Temperature dependence of the charge carrier mobility in gated quasi-one-dimensional systems
The many-body Monte Carlo method is used to evaluate the frequency dependent
conductivity and the average mobility of a system of hopping charges,
electronic or ionic on a one-dimensional chain or channel of finite length. Two
cases are considered: the chain is connected to electrodes and in the other
case the chain is confined giving zero dc conduction. The concentration of
charge is varied using a gate electrode. At low temperatures and with the
presence of an injection barrier, the mobility is an oscillatory function of
density. This is due to the phenomenon of charge density pinning. Mobility
changes occur due to the co-operative pinning and unpinning of the
distribution. At high temperatures, we find that the electron-electron
interaction reduces the mobility monotonically with density, but perhaps not as
much as one might intuitively expect because the path summation favour the
in-phase contributions to the mobility, i.e. the sequential paths in which the
carriers have to wait for the one in front to exit and so on. The carrier
interactions produce a frequency dependent mobility which is of the same order
as the change in the dc mobility with density, i.e. it is a comparably weak
effect. However, when combined with an injection barrier or intrinsic disorder,
the interactions reduce the free volume and amplify disorder by making it
non-local and this can explain the too early onset of frequency dependence in
the conductivity of some high mobility quasi-one-dimensional organic materials.Comment: 9 pages, 8 figures, to be published in Physical Review
FishBase: the on-line answer to ichthyological issues
FishBase was initiated by Daniel Pauly and Rainer Froese as an electronic fact sheets database for the economically most important fish species. From 1987 onwards FishBase was developed at the WorldFish Center (former ICLARM), and subsequently financed by the European Commission between 1989 and 2000. Since 2001, FishBase is supported by a consortium, including the WorldFish Center (Malaysia), FAO (Italy), The Royal Museum for Central Africa (Belgium), the Natural History Museums of Paris (France) and Stockholm (Sweden), the Universities of Kiel (Germany), British Columbia (Canada) and Thessaloniki (Greece), and the Chinese Academy of Fishery Sciences (China). At present FishBase is the largest on-line encyclopaedia on fishes, with about 20 - 25 million hits per month.Information on more than 30,000 fish species is available through the FishBase portal (www.fishbase.org) or one of its 6 mirror-sites, including data on the taxonomic position, distribution, morphology and ecology, as well as numerous aspects of aquaculture and fisheries biology. Information is based on scientific publications or provided by experts. Many deep links are provided to other relevant websites such as those of the IUCN (conservation) and GenBank (genetics). The Royal Museum for Central Africa is responsible for the validation and updating of the information on all African fresh- and brackish water fishes and developed in 2007 a portal for the African inland fishes (www.fishbaseforafrica.org).FishBase contains a lot of applications for fish and fisheries scientists, such as tools for fish identification, biogeographical modelling, construction and analysis of trophic pyramids, analysis of fishery and aquaculture statistics, diagnosis of fish diseases, etc. Some of these have already proved their importance to support concepts like ‘fishing down food webs’ (Pauly et al., 1998)
Learning While Doing: Program Evaluation of the Medical Library Association Systematic Review Project
Objectives: The Medical Library Association (MLA) Systematic Review Project aims to conduct systematic reviews to identify the state of knowledge and research gaps for fifteen top-ranked questions in the profession. In 2013, fifteen volunteer-driven teams were recruited to conduct the systematic reviews. The authors investigated the experiences of participants in this large-scale, volunteer-driven approach to answering priority research questions and fostering professional growth among health sciences librarians. Methods: A program evaluation was conducted by inviting MLA Systematic Review Project team members to complete an eleven-item online survey. Multiple-choice and short-answer questions elicited experiences about outputs, successes and challenges, lessons learned, and future directions. Participants were recruited by email, and responses were collected over a two-week period beginning at the end of January 2016. Results: Eighty (8 team leaders, 72 team members) of 198 potential respondents completed the survey. Eighty-four percent of respondents indicated that the MLA Systematic Review Project should be repeated in the future and were interested in participating in another systematic review. Team outputs included journal articles, conference presentations or posters, and sharing via social media. Thematic analysis of the short-answer questions yielded five broad themes: learning and experience, interpersonal (networking), teamwork, outcomes, and barriers. Discussion: A large-scale, volunteer-driven approach to performing systematic reviews shows promise as a model for answering key questions in the profession and demonstrates the value of experiential learning for acquiring synthesis review skills and knowledge. Our project evaluation provides recommendations to optimize this approach
CONVERT: A program to evaluate hardwood sawmill conversion efficiency
CONVERT is a computer program that allows users to evaluate the conversion efficiency of hardwood sawmills. Users can consider six factors that influence conversion efficiency. Four of the factors reflect characteristics of hardwood sawmill machines: headrig kerf, headrig type, resaw kerf, and rough green size. The other factors reflect characteristics of the mill\u27s raw material inputs: average log length and average log diameter
Stellar Astrophysics with a Dispersed Fourier Transform Spectrograph. II. Orbits of Double-lined Spectroscopic Binaries
We present orbital parameters for six double-lined spectroscopic binaries
(iota Pegasi, omega Draconis, 12 Bootis, V1143 Cygni, beta Aurigae, and Mizar
A) and two double-lined triple star systems (kappa Pegasi and eta Virginis).
The orbital fits are based upon high-precision radial velocity observations
made with a dispersed Fourier Transform Spectrograph, or dFTS, a new instrument
which combines interferometric and dispersive elements. For some of the
double-lined binaries with known inclination angles, the quality of our RV data
permits us to determine the masses M_1 and M_2 of the stellar components with
relative errors as small as 0.2%.Comment: 41 pages, 8 figures, accepted by A
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