3,622 research outputs found
Ovarian metabolism of xenobiotics
At birth, the mammalian ovary contains a finite number of primordial follicles, which once depleted, cannot be replaced. Xenobiotic exposures can destroy primordial follicles resulting in premature ovarian failure and, consequently, early entry into menopause. A number of chemical classes can induce premature ovarian failure, including environmental, chemotherapeutic and industrial exposures. While our knowledge on the mechanistic events that occur in the ovary with chemical exposures is increasing, our understanding of the ovary\u27s capacity to metabolize such compounds is less established. This review will focus on three chemicals for which information on ovarian metabolism is known: trichloroethylene, 7,12-dimethylbenz[a]anthracene and 4- vinylcyclohexene. The current state of understanding of ovarian bioactivation and detoxification processes for each will be described
Testing Lorentz and CPT symmetry with hydrogen masers
We present details from a recent test of Lorentz and CPT symmetry using
hydrogen masers. We have placed a new limit on Lorentz and CPT violation of the
proton in terms of a recent standard model extension by placing a bound on
sidereal variation of the F = 1 Zeeman frequency in hydrogen. Here, the
theoretical standard model extension is reviewed. The operating principles of
the maser and the double resonance technique used to measure the Zeeman
frequency are discussed. The characterization of systematic effects is
described, and the method of data analysis is presented. We compare our result
to other recent experiments, and discuss potential steps to improve our
measurement.Comment: 26 pages, 16 figure
Plasma Physics
Contains reports on five research projects.United States Atomic Energy Commission (Contract AT(30-1)-1842)Project MACAdvanced Research Agency, Department of Defense, under Office of Naval Research Contract Nonr-4102(01
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Status of the SLC damping ring kicker systems
The damping ring kickers for the SLAC Linear Collider must meet extreme requirements on rise and fall time, flatness, time and amplitude jitter and drift, voltage, repetition rate, and reliability. After several generations of improvements to the pulsers, magnets, and controls, and evolution in the understanding of the requirements, the kicker systems are no longer a serious constraint on SLC performance. Implications for future linear colliders are discussed. 14 refs
The new biology of ageing
Human life expectancy in developed countries has increased steadily for over 150 years, through improvements in public health and lifestyle. More people are hence living long enough to suffer age-related loss of function and disease, and there is a need to improve the health of older people. Ageing is a complex process of damage accumulation, and has been viewed as experimentally and medically intractable. This view has been reinforced by the realization that ageing is a disadvantageous trait that evolves as a side effect of mutation accumulation or a benefit to the young, because of the decline in the force of natural selection at later ages. However, important recent discoveries are that mutations in single genes can extend lifespan of laboratory model organisms and that the mechanisms involved are conserved across large evolutionary distances, including to mammals. These mutations keep the animals functional and pathology-free to later ages, and they can protect against specific ageing-related diseases, including neurodegenerative disease and cancer. Preliminary indications suggest that these new findings from the laboratory may well also apply to humans. Translating these discoveries into medical treatments poses new challenges, including changing clinical thinking towards broad-spectrum, preventative medicine and finding novel routes to drug development
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