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Biomedical subjects

G Dyer

Publications and source records attributed to G Dyer.

9 recordsLinked to original sources
PubMed2006

Angular distribution of neutrons from deuterated cluster explosions driven by femtosecond laser pulses.

We have studied experimentally the angular distributions of fusion neutrons from plasmas of multi-keV ion temperature, created by 40 fs, multi-TW laser pulses in dense plumes of D2 and CD4 clusters. A slight anisotropy in the neutron emission is observed. We attribute this anisotropy to the fact that the differential cross section for DD fusion is anisotropic even at low collision energies, and this, coupled with the geometry of the gas jet target, leads to beam-target neutrons that are slightly directed. The qualitative features of this anisotropy are confirmed by Monte Carlo simulations.

Journal Article↗
PubMed2005

Dynamic acceleration effects in explosions of laser-irradiated heteronuclear clusters.

Intense, femtosecond irradiation of atomic and molecular clusters can initiate Coulomb explosions, generating particle energies sufficient to drive nuclear fusion. Last and Jortner have proposed, based on particle dynamics simulations, that heteronuclear clusters with a mixture of heavy and light ions will not explode by the simple, equilibrium Coulomb model but that dynamic effects can lead to a boosting of energy of the lighter ejected ions [Phys. Rev. Lett. 87, 033401 (2001)]. We present experimental confirmation of this theoretically predicted ion energy enhancement in methane clusters.

Journal Article↗
PubMed2005

Temperature determination using Kalpha spectra from M -shell Ti ions.

The compact multipulse terawatt (COMET) laser facility at LLNL was used to irradiate Al-coated 2-50 microm Ti foils with approximately 10(19) W cm(-2) , 500 fs, 3-6 J laser pulses. Laser-plasma interactions on the front side of the target generate hot electrons with sufficient energy to excite inner-shell electrons in Ti, creating Kalpha emission which has been measured using a focusing spectrometer with spatial resolution aimed at the back surface of the targets. The spatial extent of the emission varies with target thickness. The high spectral resolution (lambda/Deltalambda approximately equal to 3800) is sufficient to measure broadening of the Kalpha emission feature due to the emergence of blueshifted satellites from ionized Ti in a heated region of the target. A self-consistent-field model is used to spectroscopically diagnose thermal electron temperatures up to 40 eV in the strongly coupled Ti plasmas.

Journal Article↗
PubMed1996

UNICEF's rich history in emergency response.

When conflict erupts or natural disasters strike, UNICEF's challenge is to provide for the emergency needs of civilians, especially women and children, who are caught in the crossfire or plagued by the drought or swept away by the flood. When emergency situations arise, threatening to derail UNICEF's ongoing work in a country, the challenge is to adapt programmes to better address the changing needs of the affected population. UNICEF's goal in all countries undergoing emergencies is to build on the work already done to lay the foundation for long-term peace and progress. In most emergency cases, certain core interventions are applied to meet basic needs, including health (UNICEF's largest activity in emergencies), water supply and sanitation, education, nutrition, community development, advocacy and initiatives addressing the special needs of women and children. Specific programmes for unaccompanied children, women's reproductive health, child soldiers, land-mine awareness and child prisoners are also employed in many emergency situations. UNICEF works towards the day when children and women no longer face acute threats to their survival and development; but until such time as natural disasters and man-made conflict no longer pose threats to them, UNICEF remains committed to the range of activities required to ensure their protection and well-being.

Child↗
PubMed1986

Effect of nearpoint stress on the horizontal forced vergence fixation disparity curve.

The effect of nearpoint stress on the forced vergence fixation disparity curve was investigated directly. Data gathered from asymptomatic subjects with normal binocular vision showed that fixation disparity was not influenced by 25 min of continuous reading. Further investigation using symptomatic subjects with large fixation disparities or steep forced vergence curves showed that the nearpoint reading task had a significant effect on the curves of these subjects. Clinical implications and a possible physiological substrate are presented.

Adolescent↗
PubMed1981

Oestradiol: the predominant intranuclear oestrogen in the endometrium of oestrogen-treated postmenopausal women.

Intracellular oestrogen metabolism has been investigated in endometrial tissue from postmenopausal women receiving oestrogen therapy either alone or in combination with a progestogen. During oestrogen therapy alone, there was a 3.2 fold predominance of oestradiol over oestrone within the endometrial cell nucleus and the mean nuclear oestrogen receptor content was 1.40 pmol/mg DNA. The addition of norethisterone decreased the nuclear oestradiol/oestrone ratio to 1.4:1 by lowering the oestradiol mass. A concurrent reduction in the mean level of the nuclear oestrogen receptor to 0.58 pmol/mg DNA indicated a decrease in oestrogenic stimulation. The activity of oestradiol-17 beta dehydrogenase was significantly increased. There was a plasma excess of oestrone over oestradiol during oestrogen therapy alone and oestrone/oestradiol ratio was not significantly altered following norethisterone administration. The ability of the endometrium to incorporate oestradiol selectively into the nucleus is discussed in relation to the risk of endometrial hyperplasia with unopposed oestrogen therapy. The profound biochemical changes induced by norethisterone help elucidate mechanisms whereby progestogens lower oestrogenic potency and thereby protect the endometrium against excessive stimulation.

Cell Nucleus↗