The Potential of Fast Ignition and Related Experiments with a Petawatt Laser Facility

A model of energy gain induced by fast ignition of thermonuclear burn in compressed deuterium-tritium fuel, is used to show the potential for 300× gain with a driver energy of 1 MJ, if the National Ignition Facility (NIF) were to be adapted for fast ignition. The physics of fast ignition has been studied using a petawatt laser facility at the Lawrence Livermore National Laboratory. Laser plasma interaction in a preformed plasma on a solid target leads to relativistic self-focusing evidenced by x-ray images. Absorption of the laser radiation transfers energy to an intense source of relativistic electrons. Good conversion efficiency into a wide angular distribution is reported. Heating by the electrons in solid density CD₂ produces 0.5 to 1 keV temperature, inferred from the D-D thermo-nuclear neutron yield.     

Margatoxin increases dopamine release in rat striatum via voltage-gated K+ channels

The distribution of iodinated margatoxin ([125I]margatoxin) binding sites in rat was investigated by autoradiography. Rat striatum expresses a high density of margatoxin binding sites and, therefore, the effects of margatoxin, charybdotoxin and iberiotoxin have been studied on [3H]dopamine release from rat striatal slices in vitro. Margatoxin (0.1-100 nM) and charybdotoxin (10-1000 nM), but not iberiotoxin increased the spontaneous and the electrically evoked [3H]dopamine release. [3H]dopamine release by margatoxin was inhibited by tetrodotoxin and omega-conotoxin GVIA, but not by atropine, naloxone, N(omega)-nitro-L-arginine and neurokinin or neurotensin receptor antagonists. In the buffer solution used for release experiments, [125I]margatoxin labels a maximum of 0.12 pmol of sites/mg protein in rat striatal membranes with a Kd of 5 pM. [125I]margatoxin binding was inhibited by margatoxin (Ki of 4 pM), charybdotoxin (Ki of 162 pM) but not by iberiotoxin. We conclude that inhibition of margatoxin-sensitive voltage-gated K+ channels increases [3H]dopamine release demonstrating their role in repolarization of nigrostriatal projections. In contrast, iberiotoxin-sensitive, high-conductance Ca2+-activated K+ channels are not involved in release of [3H]dopamine.     

The diagnosis of patellar luxation in small animals

A standard diagnostic procedure for patellar luxation is described. It is based upon the patellar luxations grade 1 to 4, which have been published before, and contains additional definitions in terms of the animals positioning toward the examiner.     

Role of HIF-1alpha in hypoxia-mediated apoptosis, cell proliferation and tumour angiogenesis

As a result of deprivation of oxygen (hypoxia) and nutrients, the growth and viability of cells is reduced. Hypoxia-inducible factor (HIF)-1alpha helps to restore oxygen homeostasis by inducing glycolysis, erythropoiesis and angiogenesis. Here we show that hypoxia and hypoglycaemia reduce proliferation and increase apoptosis in wild-type (HIF-1alpha+/+) embryonic stem (ES) cells, but not in ES cells with inactivated HIF-1alpha genes (HIF-1alpha-/-); however, a deficiency of HIF-1alpha does not affect apoptosis induced by cytokines. We find that hypoxia/hypoglycaemia-regulated genes involved in controlling the cell cycle are either HIF-1alpha-dependent (those encoding the proteins p53, p21, Bcl-2) or HIF-1alpha-independent (p27, GADD153), suggesting that there are at least two different adaptive responses to being deprived of oxygen and nutrients. Loss of HIF-1alpha reduces hypoxia-induced expression of vascular endothelial growth factor, prevents formation of large vessels in ES-derived tumours, and impairs vascular function, resulting in hypoxic microenvironments within the tumour mass. However, growth of HIF-1alpha tumours was not retarded but was accelerated, owing to decreased hypoxia-induced apoptosis and increased stress-induced proliferation. As hypoxic stress contributes to many (patho)biological disorders, this new role for HIF-1alpha in hypoxic control of cell growth and death may be of general pathophysiological importance.     

Response of V79 cells to low doses of X-rays and negative pi-mesons: clonogenic survival and DNA strand breaks

Mammalian cells are hypersensitive to very low doses of X-rays (< 0.2 Gy), a response which is followed by increased radioresistance up to 1 Gy. Increased radioresistance is postulated to be a response to DNA damage, possibly single-strand breaks, and it appears to be a characteristic of low linear energy transfer (LET) radiation. Here we demonstrate a correspondence between the extent of the increased radioresistance and linear energy transfer of 250 kVp X-rays and plateau and Bragg peak negative pi-mesons. The results support our hypothesis since the size of the increased radioresistant response appears to correspond to the number of radiation induced single-strand breaks. Furthermore, since survival prior to the increased radioresistant response (< 0.2 Gy) was LET-independent, these data support the notion that the increased radioresistant response may dictate the overall survival response to higher doses. However, while these data provide further circumstantial evidence for the involvement of DNA strand breaks in the triggering of increased radioresistance, more direct conclusions cannot be made. The data are not accurate enough to detect structure in the single-strand break profiles, the production of single-strand breaks being apparently linear with dose.     

Minimum norm target estimation algorithm for phased array radar

An algorithm is proposed that uses a broadside phased array to profile any number of arbitrary targets as a function of bearing. The technique places no restriction on either the number or location of the array elements.<>     

A study of the coating-substrate interface layer of an Al2O3-coated cemented carbide cutting tool

The microstructure of the interface bonding zone of the Al₂O₃ coating and the cemented carbide substrate of a coated tool has been analyzed using transmission electron microscopy. It is concluded that a complex aluminium-tantalum oxide of rutile type AlTaO₄ contributes to the strong bonding owing to the similarity of its crystal structure to TiO₂. Synthesis of experimental tools with other oxides very similar to AlTaO₄ as bonding material confirmed this hypothesis.     

Influence of glycoproteins B, C and D on the conversion of virus-to-cell attachment from heparin sensitivity to resistance

In two municipalities in Lower Saxony statistically valid clusters were observed, which attracted great public interest. Committees were set up to initiate a large variety of on-the-spot-investigations. Finally, it was decided to conduct a case control study throughout Lower Saxony to explore potential risk factors which might explain the observed clusters. A limited number of already established and currently discussed hypotheses was chosen for investigation. The study was based on patients registrated at the German Children's Cancer Registry (GCCR). For each child with leukemia diseased between 1988 and 1993 two population-based controls (local and state controls) and one tumour control were selected. Data were collected by means of a questionnaire self-administered by the parents and a telephone interview. In addition, measurements of electromagnetic fields and radon were performed and inspections of the child's birth record were made for the purpose of confirming a potential association between parenteral vitamin K prophylaxis and leukemia or tumours. This paper presents the concept and basic considerations of the study, its design and statistical evaluation. Response rates and a summary of results will be presented, too. The paper will serve as a reference for subsequent publications about more detailed analyses of specific potential risk factors. 425 parents of diseased children and 610 of non-diseased children were asked for participation. The rates of response were 82% for families with diseased and 71% for families with non-diseased children. In total, 781 parents participated in the study. The most important results are as follows: The Greaves' hypothesis (9, 10) was supported by the following results: In children diseased with leukemia, vaccinations were less frequent, virus-related infections occurred more rarely, these children were more frequently first-born children and more frequently breast-feed, and they possibly had fewer contacts with other children in infancy. Our data do not show a significant association between parenteral vitamin K prophylaxis and leukemia or tumours (17). Measurements of electromagnetic fields show a weak association between high-level exposure and an increased risk of developing leukemias. Children who were X-rayed more than four times or were born prematurely and had received intensive care treatment show a positive association with occurrence of leukemia, but the number of these patients was very small and these factors are not independent. The only potential job-related hazard was paternal exposure to plastic and resin fumes. The incidence of miscarriages and abortions was increased in mothers of children with leukemia. Our study did not confirm the hypotheses, that leukemia is associated with gestational age, with consumption of alcohol, nicotine, and medicaments during pregnancy. Nor was any association detected with exposure to wood preservatives and insecticides or with a high socio-economic status. The number of patients living in municipalities with increased incidence of leukemia was too small to show statistically valid results. However, it is noteworthy that some of the above-mentioned risk factors were observed also in these children. One of the purposes of a nation-wide case control study which is currently performed at the GCCR is to validate and complete these results.     

Constraints on cortical and thalamic projections: the no-strong-loops hypothesis

The many distinct cortical areas of the macaque monkey visual system can be arranged hierarchically, but not in a unique way. We suggest that the connections between these cortical areas never form strong, directed loops. For connections between the visual cortex and particular thalamic nuclei, we predict that certain types of connections will not be found. If strong, directed loops were to exist, we suggest that the cortex would go into uncontrolled oscillations.