Search

The second axis of the Dual Axis Radiography of Hydrodynamic Testing (DARHT) facility produces up to four radiographs within an interval of 1.6 microseconds. It accomplishes this by slicing four micro-pulses out of a long 1.8-kA, 16.5-MeV electron beam pulse and focusing them onto a bremsstrahlung converter target. The long beam pulse is created by a dispenser cathode diode and accelerated by the unique DARHT Axis-II linear induction accelerator (LIA). Beam motion in the accelerator would be a problem for radiography. High frequency motion, such as from beam breakup instability, would blur the individual spots. Low frequency motion, such as produced by pulsed power variation, would produce spot to spot differences. In this article, we describe these sources of beam motion, and the measures we have taken to minimize it.

Background The reiterated architecture of cranial motor neurons aligns with the segmented structure of the embryonic vertebrate hindbrain. Anterior-posterior identity of cranial motor neurons depends, in part, on retinoic acid signaling levels. The early vertebrate embryo maintains a balance between retinoic acid synthetic and degradative zones on the basis of reciprocal expression domains of the retinoic acid synthesis gene aldhehyde dehydrogenase 1a2 (aldh1a2) posteriorly and the oxidative gene cytochrome p450 type 26a1 (cyp26a1) in the forebrain, midbrain, and anterior hindbrain. Results This manuscript investigates the role of zinc finger of the cerebellum (zic) transcription factors in regulating levels of retinoic acid and differentiation of cranial motor neurons. Depletion of zebrafish Zic2a and Zic2b results in a strong downregulation of aldh1a2 expression and a concomitant reduction in activity of a retinoid-dependent transgene. The vagal motor neuron phenotype caused by loss of Zic2a/2b mimics a depletion of Aldh1a2 and is rescued by exogenously supplied retinoic acid. Conclusion Zic transcription factors function in patterning hindbrain motor neurons through their regulation of embryonic retinoic acid signaling.

Summary form only given. The second axis of the dual-axis radiographic hydrotest (DARHT) facility will provide four radiographic images within ~1.6 microseconds. This will be accomplished by slicing four short pulses out of a ~1.6-microsecond long electron beam produced by the DARHT-II linear induction accelerator and directing them onto a bremsstrahlung converter target. Commissioning of the full 17-MeV configuration the DARHT-II accelerator will begin in spring of 2007 following tests of a new high-perveance (2 kA at 2.5 MV) diode. We will present the results of diode performance measurements as well as initial measurements of the fully accelerated electron beam parameters.

The purpose of this report is to describe the activation of the fourth cathode installed in the DARHT-II Injector. Appendices have been used so that an extensive amount of data could be included without danger of obscuring important information contained in the body of the report. The cathode was a 612 M type cathode purchased from Spectra-Mat. Section II describes the handling and installation of the cathode. Section III is a narrative of the activation based on information located in the Control Room Log Book supplemented with time plots of pertinent operating parameters. Activation of the cathode was performed in accordance with the procedure listed in Appendix A. The following sections provide more details on the total pressure and constituent partial pressures in the vacuum vessel, cathode heater power/filament current, and cathode temperature.

The H/sup -/ injector at Los Alamos National Laboratory (LANL) is being upgraded to provide a 12% duty-factor, 40-mA, 80-kev H/sup -/ beams, which will enable 200-/spl mu/A operation of the Los Alamos Neutron Scattering Center (LANSCE) proton storage ring (PSR). An improved version of the LANSCE operational surface-conversion ion source and a new accelerating column have been developed in collaboration with the Lawrence Berkeley National Laboratory (LBNL) for this application. We report here the results of the initial tests at LANL on a proof-of-principle (POP) ion source built at LBNL and on modeling studies. The POP ion source has been operated at the 40-mA design beam current, and the beam emittance of the 80-keV extracted beam has been measured both at the exit of the accelerating column and in the 80-keV low-energy beam transport (LEBT) line. Significant, current-dependent, emittance growth was observed in the LEBT. Experimental investigations of this growth are described.

The peak intensity of the PSR is limited by a fast transverse instability. In 1996 we started a project to upgrade the PSR to 200 /spl mu/A at 30 Hz, which requires operation above the instability threshold achieved with our present RF system. We have, therefore, resumed our experimental program to understand and control the instability. In this paper we will present our latest data.

The magnet design and fabrication technology for the AHF 50 GeV synchrotron must be of sufficiently high quality to provide a dynamic aperture that does not result in unnecessary beam losses. Tracking studies indicate that the dynamic aperture is smaller than the physical aperture for some sets of systematic and random magnetic field errors in the quadrupoles. Magnet measurements of different quadrupole magnet designs have been analyzed to determine a representative set of systematic and random magnetic field errors that can be manufactured in industry and provide a dynamic aperture larger that the physical aperture. A 2D‐error analysis was performed for different quadrupole magnet designs to ascertain the effect of magnet assembly tolerances and errors on the magnetic field harmonics. The analysis indicated that many systematic harmonics were correlated and that specific assembly tolerances and errors (coil placement tolerances and proximity to pole tip, half‐core and quadrant assembly tolerances) result...

The receptor for leukemia inhibitory factor (LIF) consists of two polypeptides, the LIF receptor and gp130. Agonist stimulation has been shown previously to cause phosphorylation of gp130 on serine, threonine, and tyrosine residues. We found that gp130 fusion proteins were phosphorylated exclusively on Ser-782 by LIF- and growth factor-stimulated 3T3-L1 cell extracts. Ser-780 was required for phosphorylation of Ser-782 but was not itself phosphorylated. Ser-782 is located immediately N-terminal to the di-leucine motif of gp130, which regulates internalization of the receptor. Transient expression of chimeric granulocyte colony-stimulating factor receptor (G-CSFR)-gp130(S782A) receptors resulted in increased cell surface expression in COS-7 cells and increased ability to induce vasoactive intestinal peptide gene expression in IMR-32 neuroblastoma cells when compared with expression of chimeric receptors containing wild-type gp130 cytoplasmic domains. These results identify Ser-782 as the major phosphorylated serine residue in human gp130 and indicate that this site regulates cell surface expression of the receptor polypeptide.

An upgrade program is being carried out at Los Alamos to increase the peak beam current from the present H{sup {minus}} injector to provide 200 {mu}A average current for the proton storage ring at LANSCE. In order to meet this objective, the injector must provide at least 30% more current than presently available. More optimal operation however, requires a factor of two higher peak current in order to reduce circulating losses in the ring. At these higher currents, a lower beam emittance is needed to limit beam losses in the linac. Beam simulations have been carried out to model the operation of the present injector and to determine what changes will be required to operate with these higher beam currents. A collaboration with the Lawrence Berkeley National Laboratory (LBNL) is now in progress to modify the present converter ion source to produce 40-mA peak of H{sup {minus}} beam current with reduced beam emittance. Beam simulations show that a new 80-kV accelerating column will be needed to accelerate and transport these higher current beams with acceptable beam size and divergence. Experimental results for the initial phase of this program are presented together with a comparison to these beam simulations.

Recent experiments on TFTR have extended the operating regime of TFTR in both ohmic- and neutral-beam -heated discharges. The TFTR tokamak has reached its original machine-design specifications ( I p = 2.5 MA and B T = 5.2 T). Initial neutral-beam -heating experiments used up to 6.3 MW of deuterium beams. With the recent installation of two additional beamlines, the power has been increased up to 11 MW. A deuterium pellet injector was used to increase the central density to 2.5 x 10 20 m -3 in high-current discharges. At the opposite extreme, by operating at low plasm a current ( I p ~ 0.8 MA) and low density ( n e~ 1 x 10 19 m -3 ), high ion temperatures (9 + 2 keV) and rotation speeds (7 x 10 5 m s -1 ) have been achieved during injection. In addition, plasma-compression experiments have demonstrated acceleration of beam ions from 82 to 150 keV, in accord with expectations. The wide operating range of TFTR, together with an extensive set of diagnostics and a flexible control system, has facilitated transport and scaling studies of both ohmic- and neutral-beam -heated discharges. The result of these confinement studies are presented.

This paper presents a summary of plasma-material interactions which influence the operation of TFTR with high current (≤ 2.2 MA) ohmically heated, and high-power (∼ 10 MW) neutral-beam heated plasmas. The conditioning procedures which are applied routinely to the first-wall hardware are reviewed. Fueling characteristics during gas, pellet, and neutral-beam fueling are described. Recycling coefficients near unity are observed for most gas fueled discharges. Gas fueled discharges after helium discharge conditioning of the toroidal bumper limiter, and discharges fueled by neutral beams and pellets, show R

The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B /sub T/ increased to 4.0 T, I /sub p/ to 2.0 MA, injection power (P /sub b/ ) to /sup 5/ MW with H/sup 0/ or D/sup 0/ beams, n /sub e/ to 5 x 10/sup 19/ m/sup -3/ and Z /sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (T /sub E/ /sup 0/ n /sub e/ q) has been confirmed at higher I /sub p/ and B /sub T/ , and the maximum T /sub E/ of 0.4 sec has been achieved. With NBI at P /sub b/ substantially (by factor > 2) higher than P /sub OH/ , excellent power and particle accountability have been established. This suggest that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. T /sub E/ is observed to scale approximately as I /sub p/ P /sub b/more » /sup 0.5/ (independent of n /sub e/ ), consistent with previous L-mode scalings. With NBI we have achieved the maximum T /sub E/ of 0.2 s and the maximum T /sub i/ (o) of 4.4 keV in the normal operating regime, and even higher T /sub i/ (o) in the energetic-ion regime with low-n /sub e/ and low I /sub p/ operation.« less

The characteristics of plasma operation on the axisymmetric inner toroidal limiter in TFTR are described. After conditioning, plasmas with low metal content and low zeff are obtained with this limiter. There is no substantial increase in zeff with total input power during neutral beam injection. Compared to operation on the outer blade limiter, additional gas is required to fuel plasmas on the inner limiter. Injection of D pellets increased the plasma density substantially and produced energy confinement times up to 0.5 s in ohmically heated plasmas. The four neutral beam lines have injected up to 13.5 MW total power into the plasma for 0.5 s with up to 90 kV accelerating voltage. The scaling of the plasma stored energy was studied as a function of the input power, plasma current and plasma density. In the range 1.4 to 2.2 MA, the overall and incremental confinement times for both the total and thermal stored energies increase with plasma current at fixed density. There appears to be a weak negative scaling of the total stored energy with density at high injection power.

provides that uthe amount so allotted shall be expended for payment of part of the cost of district, county or other local child-welfare services in areas predominantly rural, and for developing State services for the encouragement and assistance of adequate methods of community child-welfare organization in areas predominantly rural and other areas of special need." Consistent with the intent of the statute, the child welfare worker is concerned with community organization as well as with case-work service. The consultant1 is, to an even greater degree, concerned with community organization within his area, which involves helping individual workers with community organization activities and projects as well as initiating and developing some area-wide projects. This article deals with one such area

Seven of 71 patients with complex partial seizures claimed they were able to abate their seizures, while none of 18 with simple partial seizures were able to do so. Self-abatement exercises included highly stereotyped cognitive and physical components unique to the individual. Those who could abate their seizures had attained higher educational status, better social and vocational adjustment, and better psychological adjustment than did the control group of patients with epilepsy. The self-abatement group was also more likely to have right hemispheric electroencephalographic abnormalities. Characterization of the self-abatement group may be relevant to the selection of candidates for behavioral therapy for epilepsy.

Rad se temelji na analizi potreba u nastavi stranog jezika struke na pravnim fakultetima u Hrvatskoj. Ova analiza orijentirana je na tri temeljna cilja: prvi je utvrđivanje postojeće razine postignuća studenata u okviru njemačkog jezika pravne struke drugi je cilj utvrditi precizna ciljeve i zadatke nastave stranog jezika na studiju prava te odrediti tematske okvire za izbor i izradu nastavnih materijala na temelju kojih bi se u bliskoj budućnosti koncipirao udžbenik njemačkog jezika pravne struke koji bi bio usklađen s potrebama i interesima budućih pravnika.