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The first experiments on the National Ignition Facility (NIF) have employed the first four beams to measure propagation and laser backscattering losses in large ignition-size plasmas. Gas-filled targets between 2 and 7 mm length have been heated from one side by overlapping the focal spots of the four beams from one quad operated at 351 nm (3ω) with a total intensity of 2 × 1015 W cm−2. The targets were filled with 1 atm of CO2 producing up to 7 mm long homogeneously heated plasmas with densities of ne = 6 × 1020 cm−3 and temperatures of Te = 2 keV. The high energy in an NIF quad of beams of 16 kJ, illuminating the target from one direction, creates unique conditions for the study of laser–plasma interactions at scale lengths not previously accessible. The propagation through the large-scale plasma was measured with a gated x-ray imager that was filtered for 3.5 keV x-rays. These data indicate that the beams interact with the full length of this ignition-scale plasma during the last ~1 ns of the experiment. During that time, the full aperture measurements of the stimulated Brillouin scattering and stimulated Raman scattering show scattering into the four focusing lenses of 3% for the smallest length (~2 mm), increasing to 10–12% for ~7 mm. These results demonstrate the NIF experimental capabilities and further provide a benchmark for three-dimensional modelling of the laser–plasma interactions at ignition-size scale lengths.

The National Ignition Facility is under construction at the Lawrence Livermore National Laboratory for the U.S. Department of Energy Stockpile Stewardship Program. Optical streak cameras are an integral part of the experimental diagnostics instrumentation. To accurately reduce data from the streak cameras a temporal calibration is required. This article describes a technique for generating trains of precisely timed short-duration optical pulses that are suitable for temporal calibrations.

The National Ignition Facility is operational at Lawrence Livermore National Laboratory (LLNL). The inertial confinement fusion and HED programs at LLNL have formed diagnostic research and development groups to institute improvements outside the charter of core diagnostics. We will present data from instrumentation being developed. A major portion of our work is improvements to detectors and readout systems. We have efforts related to charge-coupled device (CCD) development. Work has been done in collaboration with the University of Arizona to back thin a large format CCD device. We have developed in collaboration with a commercial vendor a large format, compact CCD system. We have coupled large format CCD systems to our optical and x-ray streak cameras leading to improvements in resolution and dynamic range. We will discuss gate width and uniformity improvements to microchannel plate-based framing cameras. We will present data from single shot data link work and discuss technology aimed at improvements of dynamic range for high-speed transient measurements from remote locations.

We characterize the response of chemical vapor deposition (CVD) diamond detectors to inertial confinement fusion (ICF) neutrons generated at the OMEGA laser fusion facility in Rochester, NY. Four detectors are tested: three utilizing “optical grade” CVD diamond, and one utilizing “electronic grade” CVD diamond. Using a 50 Ω measurement system, we find that the optical grade wafers, biased to 1000 V/mm, have an average sensitivity of 0.24 μV ns/n for 2.5 MeV (DD fusion) neutrons and 0.62 μV ns/n for 14.0 MeV (DT fusion) neutrons. At the same E field, the electronic grade wafer has a sensitivity of 0.56 and 1.43 μV ns/n for 2.5 and 14 MeV neutrons, respectively. Linear dynamic range for the optical grade material is shown to be at least 105. Average full width at half maximum response times, as measured with pulsed laser and 3 GHz scope, are 376 and 880 ps for optical and electronic grades, respectively. These characteristics make CVD diamond suitable for ICF applications such as neutron time-of-flight spec...

Measurements of the neutron emission from inertial confinement fusion implosions provide important information about target performance that can be compared directly with numerical models. For room-temperature target experiments on OMEGA at the Laboratory for Laser Energetics (LLE) the neutron temporal diagnostic (NTD), originally developed at Lawrence Livermore National Laboratory, is used to measure the neutron burn history with high resolution and good timing accuracy. The NTD is mechanically incompatible with cryogenic target experiments because of the standoff required to remain clear of the cryogenic target handling system, A cryogenic-compatible neutron temporal diagnostic (cryoNTD) has been designed for LLE’s standard ten-inch manipulator diagnostic inserters. This instrument provides high-resolution neutron emission measurements for cryogenic implosions. Experimental results of the performance of cryoNTD compared to NTD on room-temperature direct-drive implosions and on cryogenic implosions are presented.

We report on a NuSTAR and XMM-Newton program that has observed a sample of three extremely luminous, heavily obscured WISE-selected AGN at z~2 in a broad X-ray band (0.1 - 79 keV). The parent sample, selected to be faint or undetected in the WISE 3.4um (W1) and 4.6um (W2) bands but bright at 12um (W3) and 22um (W4), are extremely rare, with only ~1000 so-called W1W2-dropouts across the extragalactic sky. Optical spectroscopy reveals typical redshifts of z~2 for this population, implying rest-frame mid-IR luminosities of L(6um)~6e46 erg/s and bolometric luminosities that can exceed L(bol)~1e14 L(sun). The corresponding intrinsic, unobscured hard X-ray luminosities are L(2-10)~4e45 erg/s for typical quasar templates. These are amongst the most luminous AGN known, though the optical spectra rarely show evidence of a broad-line region and the selection criteria imply heavy obscuration even at rest-frame 1.5um. We designed our X-ray observations to obtain robust detections for gas column densities N(H)1e24 /cm2, implying the sources are extremely obscured, consistent with Compton-thick, luminous quasars. The discovery of a significant population of heavily obscured, extremely luminous AGN does not conform to the standard paradigm of a receding torus, in which more luminous quasars are less likely to be obscured. If a larger sample conforms with this finding, then this suggests an additional source of obscuration for these extreme sources., 7 pages; submitted to ApJ

The University of Rochester’s Laboratory for Laser Energetics (Rochester, New York) is leading an effort to develop a modern, fully automated streak camera. Characterization of a prototype camera shows spatial resolution better than 20 lp/mm, temporal resolution of 12 ps, line-spread function of 40 μm (full width at half maximum) contrast transfer ratio of 60% at 10 lp/mm, system gain of 101 charge-coupled device electrons per photoelectron, and a dynamic range of 500 for a 2 ns window.

A first set of shock timing, laser-plasma interaction, hohlraum energetics and hydrodynamic experiments have been performed using the first 4 beams of the National Ignition Facility (NIF), in support of indirect drive Inertial Confinement Fusion (ICF) and High Energy Density Physics (HEDP). In parallel, a robust set of optical and X-ray spectrometers, interferometer, calorimeters and imagers have been activated. The experiments have been undertaken with laser powers and energies of up to 8 TW and 17 kJ in flattop and shaped 1–9 ns pulses focused with various beam smoothing options. The experiments have demonstrated excellent agreement between measured and predicted laser-target coupling in foils and hohlraums, even when extended to a longer pulse regime unattainable at previous laser facilities, validated the predicted effects of beam smoothing on intense laser beam propagation in long scale-length plasmas and begun to test 3D codes by extending the study of laser driven hydrodynamic jets to 3D geometries.

A high-energy, ultraviolet Thomson scattering probe beam has been implemented on the Omega laser facility at the University of Rochester. The new probe operates at a wavelength of 264 nm, with a maximum energy of 260 J in a pulse length of 1 ns. The probe is focused with an F/6.7 lens to a minimum focal spot of 40 mum within a pointing tolerance of

The ICF program at Livermore has a large inventory of optical streak cameras that were built in the 1970s and 1980s. The cameras include microchannel plate image-intensifier tubes (IIT) that provide signal amplification and early lenscoupled CCD readouts. Today, these cameras are still very functional, but some replacement parts such as the original streak tube, CCD, and IIT are scarce and obsolete. This article describes recent efforts to improve the performance of these cameras using today’s advanced CCD readout technologies. Very sensitive, large-format CCD arrays with efficient fiber-optic input faceplates are now available for direct coupling with the streak tube. Measurements of camera performance characteristics including linearity, spatial and temporal resolution, line-spread function, contrast transfer ratio (CTR), and dynamic range have been made for several different camera configurations: CCD coupled directly to the streak tube, CCD directly coupled to the IIT, and the original configuration with a smaller CCD lens coupled to the IIT output. Spatial resolution (limiting visual) with and without the IIT is 8 and 20 lp/mm, respectively, for photocathode current density up to 25% of the Child-Langmuir (C-L) space-charge limit. Temporal resolution (fwhm) deteriorates by about 20% when the cathode current density reaches 10% of the C-L space charge limit. Streak tube operation with large average tube current was observed by lluminating the entire slit region through a Ronchi ruling and measuring the CTR. Sensitivity (CCD electrons per streak tube photoelectron) for the various configurations ranged from 7.5 to 2,700 with read noise of 7.5 to 10.5 electrons. Optimum spatial resolution is achieved when the IIT is removed. Maximum dynamic range requires a configuration where a single photoelectron from the photocathode produces a signal that is 3 to 5 times the read noise.

Due to the planar construction of present x-ray streak tubes significant off-center defocusing is observed in both static and dynamic images taken with one-dimensional resolution slits. Based on the streak tube geometry curved photocathodes with radii of curvature ranging from 3.5 to 18 inches have been fabricated. We report initial off-center focusing performance data on the evaluation of these "improved" photocathodes in an X-ray streak camera and an update on the theoretical simulations to predict the optimum cathode curvature.

This article discusses the duties of hospital governing boards, medical staffs, medical staff officers, and individual medical staff members regarding the credentialing of physicians, including the potential liability of these groups for negligent medical care and wrongful denial of staff privileges. This article also proposes possible measures these groups may take to avoid or limit their exposure to such liability.

We have previously shown that incubation of human macrophages with antigen-antibody complexes prepared with native human low density lipoprotein (LDL) and rabbit anti-LDL antibodies (LDL-ICs) results in an increased intracellular accumulation of cholesteryl esters (CEs) and induces a marked increase in the number of LDL receptors. To determine whether the increased CE accumulation in these cells occurred during incubation of the cells with LDL-ICs or whether it was secondary to the uptake of LDL by overexpressed LDL receptors, we incubated human macrophages with LDL-ICs for 22 hours, followed by incubation with native LDL for another 20 hours. We found that about 90% of the accumulated CEs could be accounted for by the first incubation with LDL-ICs. We then proceeded to show that the CEs accumulated during incubation of cells with LDL-ICs was secondary to enhanced uptake and impaired degradation of the LDL complexed with immunoglobulin G (IgG) (LDL-IC), which led to a marked intracellular accumulation of undergraded LDL (levels 199-fold higher than those obtained when the cells were incubated with the same concentration of native LDL not complexed with IgG). We have also shown that not all CEs accumulated in these cells were derived from accumulation of undegraded LDL and that some of them were derived from the reesterification of free cholesterol released during hydrolysis of LDL. LDL-ICs promoted increased CE accumulation and foam cell formation at concentrations as low as 25 micrograms/ml. To determine which receptors were involved in the uptake of LDL-ICs, we performed experiments in which the uptake of LDL-ICs was competitively inhibited with heat-aggregated gamma globulin, native LDL, beta-very low density lipoprotein, or acetylated LDL. Our results demonstrated that LDL-IC uptake was most effectively inhibited by heat-aggregated gamma globulin, partially inhibited by native LDL or by a monoclonal antibody to the LDL receptor, and not inhibited by acetylated LDL or beta-very low density lipoprotein. Thus, we conclude that the majority of LDL-ICs are taken up through Fc gamma receptors. Finally, we investigated whether the increase in LDL receptor expression was dependent on the receptor pathway used by the LDL-ICs, and we were able to demonstrate that when macrophages were incubated with LDL-ICs prepared with F(ab')2 fragments of the anti-LDL antibody, LDL receptor expression was not enhanced. Therefore, we postulate that the uptake of LDL-ICs through Fc gamma receptors results in an uncoupling of the normal regulation of the LDL receptor expression.

A diagnostic is being designed for the National Ignition Facility, using fusion gamma rays to measure highly time-resolved bang times and deuterium-tritium (d-t) interaction rates for imploding inertial fusion capsules. As a complement to neutron-based methods, gas Cherenkov detectors were chosen for this purpose because of proven ultrahigh bandwidth, thresholding versatility, and minimal time-of-flight dispersion. Gas Cherenkov detector prototypes, involving streak cameras and fast photomultiplier, microchannel plate detectors, are being tested using d-t implosions at the Omega Laser Facility. The possibility of simultaneous streak camera and photomultiplier, microchannel plate recordings of a source in one gas Cherenkov detector instrument is advantageous for reasons of independent measurement and extended reaction-history coverage. A multiplexed gas Cherenkov detector system was demonstrated successfully using electron pulses produced by the Idaho State University linear electron accelerator. A reaction-history diagnostic scheme composed of several types of detectors is proposed. The detectors considered reflect current and improving technology that allows coverage over a significant range of a reaction history generated from National Ignition Facility implosions.

A 3{omega} transmitted beam diagnostic has been commissioned on the Omega Laser at the Laboratory for Laser Energetics, University of Rochester [Soures et.al., Laser Part. Beams 11 (1993)]. Transmitted light from one beam is collected by a large focusing mirror and directed onto a diagnostic platform. The near field of the transmitted light is imaged; the system collects information from twice the original f-cone of the beam. Two gated optical cameras capture the near field image of the transmitted light. Thirteen spatial positions around the measurement region are temporally resolved using fast photodiodes to allow a measure of the beam spray evolution. The Forward stimulated Raman scattering and forward simulated Brillion scattering are spectrally and temporally resolved at 5 independent locations within twice the original f-cone. The total transmitted energy is measured in two spectral bands ({delta}{lambda} 400 nm).

The National Ignition Facility (NIF) will provide up to 1.8MJ of laser energy for imploding inertial confinement fusion (ICF) targets. Ignited NIF targets are expected to produce up to 1019 DT neutrons. This will provide unprecedented opportunities and challenges for the use of nuclear diagnostics in ICF experiments. In 2005, the suite of nuclear-ignition diagnostics for the NIF was defined and they are under development through collaborative efforts at several institutions. This suite includes PROTEX and copper activation for primary yield measurements, a magnetic recoil spectrometer and carbon activation for fuel areal density, neutron time-of-flight detectors for yield and ion temperature, a gamma bang time detector, and neutron imaging systems for primary and downscattered neutrons. An overview of the conceptual design, the developmental status, and recent results of prototype tests on the OMEGA laser will be presented.

Two experiments are reported which compared the effects of a period of low temperature (3 C). before placing to sprout at ambient temperature, with continuous storage at ambient temperature, on sprout growth in thirteen potato varieties. In four varieties. Desiree, Majestic, Pentland Meteor and Vanessa, the period of low temperature induced an earlier onset of sprout growth and increased total and individual sprout length per tuber. In the varieties Civa, Craig’s Alliance, Dunluce. Home Guard. Arran Comet and Ulster Sceptre, the period of cold did not hasten the onset of sprout growth but markedly increased the numbers of growing sprouts and total sprout length, although individual sprout length was reduced. In the remaining varieties the period of low temperature had no effects on onset of sprout growth or sprout lengths at the end of storage.

SUMMARY Seed tubers of the varieties King Edward, Majestic and Pentland Crown selected as ‘clean’ (lesion-free), moderately, or severely affected by gangrene lesions were planted in field experiments. Infection delayed plant emergence, increased the number of stems/plant, sometimes caused gaps in crops and was associated with increased blackleg. On average severely affected seed yielded 20% less than ‘clean’ seed. Seed infection also increased the proportion of tubers in smaller size grades so that crops from severely infected King Edward seed averaged 1·4 ton/acre (3·5 t/ha) less small ware and 2·5 ton/acre (6·3 t/ha) less large ware than ‘clean’ seed. With Majestic, small ware was increased (0·7 ton/acre (1·8 t/ha)) and large ware decreased (4·4 ton/acre(11·0 t/ha)); Pentland Crown was similarly affected (small ware increased 0·8 ton/acre (2·0 t/ha); large ware decreased 3·9 ton/acre (9·8 t/ha)). In eight of twelve experiments unselected diseased stocks yielded significantly less than ‘clean’ tubers. Other experiments compared seed stocks with different proportions of gangrene-infected seed tubers. Yields decreased as the proportion of diseased seed tubers increased, but differences were significant only when more than 60% were affected. Surprisingly, yields from ‘clean’ tubers also decreased as the proportion of diseased tubers increased in the stocks from which they were selected. Gangrene on progeny tubers after storage was not always related to the amount of gangrene visible on the seed. It was increased by riddling or wounding and decreased by dipping tubers in organo-mercury fungicide before or soon after wounding.

SummaryThree experiments carried out in 3 years (1973–5) which examined the effects of length of sprouting period and temperature of sprouting on growth and yield of three early potato varieties are described. In Home Guard in 1973 at the earliest harvests, tuber yields increased with increase in length and temperature of sprouting period. At later harvests tuber yields decreased with increase in sprouting period especially at the higher temperature (13 rather than 8 °C) and increasing the temperature of sprouting reduced tuber yield. In 1974 length of sprouting period had few effects on yield at any harvest and increasing the temperature increased yields only at the first harvest. In Vanessa cold storage at 3 °C prior to entry to sprouting temperatures induced an earlier onset of sprout growth than continuous exposure to temperatures conducive to sprout growth. Long sprouting periods produced less sprout growth and at the earliest harvest lower tuber yields than all except the shortest period. Judged from the onset of sprout growth increases in length and temperature of sprouting generally increased tuber yields especially at early harvests. In Pentland Javelin sprout growth was very slow and tuber yields at early harvests decreased at both sprouting temperatures if sprouting began after mid-November. At later harvests effects of both factors were small.The implications of differences in the effects of sprouting periods according to variety and, in Home Guard, season, are discussed in relation to the provision of the most desirable sprouting environment and to variety testing. The similarity in the effects of lengthening the sprouting period and of increasing the temperature of sprouting suggest that temperature is the major causal factor in sprout growth and its effect on field growth. Sprouting periods may therefore be measured most accurately by accumulated day degrees > 0 °C and a close relationship between such a scale and tuber yields is demonstrated. The relevance of such scales for advice to growers is discussed.Tuber growth rates for Vanessa and to a lesser extent Home Guard in 1974 were extremely high, in excess of 10 t/ha/week for Vanessa. These high rates were associated with high levels of radiation received by coastal sites in May and June and are discussed in relation to the canopy structure of the varieties.

The effect of T cell growth factor (TCGF) on the cell cycle of four T cell lines that differed in their response to TCGF was studied. Activated normal marmoset T cells (OH-1) were totally dependent on the addition of TCGF for long-term proliferation. In the absence of TCGF, the cells were incapable of traversing the cell cycle and became arrested in G1. The addition of TCGF to arrested OH-1 cells stimulated them to enter the S phase after a lag phase of 24 to 33 hr. The TCGF-stimulated cells reached a maximum of cells in the S phase by 12 hr after the initiation of DNA synthesis. TCGF was required for a minimum of 18 hr before cells would enter the S phase. In the absence of TCGF, activated owl monkey (8I) and human (RG) lymphocytes displayed a TCGF-sensitive block; addition of TCGF stimulated these cells to enter the S phase after 12 and 16 hr, respectively. In contrast, an owl monkey tumor-derived T cell line (OMT-1), not dependent on exogenous TCGF for proliferation, was able to progress slowly through the cell cycle without a TCGF-sensitive block. These cells responded to TCGF by showing an initial increase in cells that entered the S phase after a lag of 6 hr and a continuing movement of additional cells into S over the course of the next several hours.

Potato tubers of five cultivais were incubated at five temperatures between 2 and 20°C for 1 month and then inoculated with Phoma exigua var. foveata and stored at 5°C. Larger rots usually developed on tubers previously incubated at the higher temperatures but cultivar differences were greatest where tubers had been incubated at 2°C. In another experiment, rot size was related to the duration of incubation at 20°C before inoculation. In a series of experiments, tubers were stored at different temperatures after inoculation; other factors (e.g. wound type or r.h.) were also investigated in some of these. Combining the results of all experiments a linear decrease of % wounds infected (logit transformation) with storage temperature was demonstrated. The size of rots was not simply related to temperature, but tended to increase over the range 2–10°C and then stabilized or declined at higher temperatures. Relative humidity treatments of 75% v. 95% did not consistently affect either the incidence of rotting or rot size. The other factors investigated did not usually interact significantly with temperature. The relevance of the results for resistance testing is discussed and a simple equation relating disease incidence to inoculum levels, type of damage and temperature is proposed.

SUMMARYSix experiments which compared a range of contrasting varieties are reported. Two experiments were at a very early, coastal site in N. Pembrokeshire (Trefin), two at a site in South Pembrokeshire (Trefloyne) and two at a coastal site in N. Norfolk (Brancaster). No variety was in every experiment but several were in the majority of experiments. In some experiments sprout growth was manipulated by control of storage temperatures. A variety classified as early or second early produced the highest yields in all experiments but the yields of the best maincrop varieties were high and substantially better than many early varieties. The highest-yielding variety at the first harvest maintained this advantage throughout June and July. At two sites (Trefin and Brancaster) the highest-yielding variety was consistent from year to year but overall the ranking order of varieties for yields was inconsistent, e.g. Arran Comet was the highest-yielding variety at Trefin in both years and one of the lowest yielding at Brancaster.The results suggest that it is unwise to attempt to rank varieties for early yields by an overall score. The maturity classification of varieties is not necessarily an accurate guide to the utility of a variety. A consideration of the physiological age of the seed and growing conditions provided some explanation of these effects and their implication for breeding are discussed.

SUMMARY In experiments extending over 3 yr, King Edward tubers harvested on various dates from early September until early November were uniformly wounded and kept at 15 oC and c. 95% r.h. for periods of up to 21 days for wounds to cure. When tubers were subsequently inoculated with Phoma exigua var.foveata and incubated at 5 oC for 12 wk, curing for 3 and 7 days decreased gangrene incidence to respectively c. 13 and 4% of the non-cured controls. When tubers were inoculated before curing and immediately after wounding, curing for 7 days decreased gangrene incidence to only c. 68% of the non-cured controls. Curing was also progressively less effective the later the date of harvesting, suggesting that there would be advantages in harvesting potato crops early in the autumn.

SUMMARY Potato tubers were uniformly wounded at harvest, or after storage for different periods at 5°C, and scored for gaagreae after 12 weeks at 5°C. The incidence of gangrene usually increased with the time of storage before wounding. Benomyl (1.0 per cent dip or 10 per cent dust) or thiabendazole (0.1 per cent dip or 10 per cent dust) greatly decreased the number of infected tubers if applied before or at the time of wounding, but were ineffective when application was delayed for two weeks or more. Only thiabendazole dust was effective when wounds made after fungicide treatment were inoculated with soil infested with Phoma exigua var. foveata.

Human macrophages play a key role in atherogenesis and are believed to be the progenitors of the cholesteryl ester (CE)-laden foam cells present in early atherosclerotic lesions. Several mechanisms by which macrophages accumulate CE have been recently described. One involves a perturbation in LDL metabolism subsequent to macrophage activation. Thus, we decided to study the effect of macrophage activation by immune complexes on N-LDL metabolism. Initially, LDL-containing immune complexes (LDL-IC) were chosen, since increased plasma levels of these IC have been reported in patients with coronary heart disease. Human macrophages stimulated for 22 h with LDL-IC (250 micrograms/ml) and incubated afterwards for 20 h with 10 micrograms/ml 125I-N-LDL showed a six- and fourfold increase in the accumulation and degradation, respectively, of 125I-N-LDL over the values observed in nonstimulated cells. Scatchard analysis of 125I-N-LDL-specific binding suggests an increase (20-fold) in the number of LDL receptors in macrophages stimulated with LDL-IC. We studied other immune complexes varying in size and antigen composition. Some of the IC were able to stimulate, although to a lesser degree, the uptake of N-LDL by macrophages. Lipoprotein IC are more efficient and have the greatest capacity to increase N-LDL uptake and CE accumulation. We conclude that human macrophage activation by LDL-IC leads to an increase in LDL receptor activity and promotes in vitro foam cell formation.

SUMMARY The persistence in soil of captan and thiram was investigated by means of a technique in which the fungicidal content of soil was assayed by incubating plugs of soil containing fungicide on agar plates seeded with spores of Myrothecium verrucaria and measuring the diameter of the zone of fungal inhibition that was produced. When the fungicides were well distributed in soil they showed extremely low persistence, both fungicides having a half-life of between 1 and 2 days. In contrast, when the fungicides were added to soil in the form of dressings on the surface of glass beads they persisted well in soil, little change from their initial concentration occurring even after 21 days. These results suggest that captan and thiram persist far longer in soil when localized in high concentrations than when uniformly distributed through soil. If a glass bead is regarded as a reasonable simulation of a seed these results help to explain the effectiveness of these fungicides as seed dressings despite their apparently low persistence in soil.

A single crystal of silver oxalate was studied by x‐ray diffraction during the process of thermal decomposition. The diffraction patterns indicated that some fragmentation of the single crystal occurred early in the reaction. Except for distortion, the monoclinic structure was maintained until all trace of silver oxalate disappeared. The gradual appearance of polycrystalline silver was apparent. The diffraction patterns showed that a portion of the silver assumed preferred orientations, the ratio of oriented to unoriented silver remaining constant throughout the reaction. Four different preferred orientations were found and were defined relative to the silver oxalate lattice.

A data-recovery feature has been developed for recovering electron-beam recorded information which is microscopic in dimension and has been partially obliterated by flaws in a photographic-film recording medium. This feature provides (1) backup procedures that exploit redundancies in the recording format for the synchronization and identification of data, (2) coding for error detection and correction of 5 independent characters in5 0 data character lines, (3) variation of machine parameters that affect reading performance, and (4) statistically optimized schedules for applying a variety of recovery techniques. Error rate is reduced from one error line in about 100 lines to less than one error line in 2.7 × 106 lines.

An x‐ray diffraction study reveals that silver oxalate is monoclinic, having the symmetry of the space group P21/c—C2h5. The unit cell has the following dimensions: a=3.46±0.02A, b=6.16±0.02A, c=9.47±0.04A, β=76°±1°. There are two molecules of Ag2C2O4 per unit cell. All atoms are located in sets of fourfold general positions. The parameters of the silver and oxygen atoms are determined from two‐dimensional Fourier syntheses, using the experimental crystal structure factors for the h0l and 0kl planes. The positions of the carbon atoms are approximately determined by requiring that the carbon‐carbon and carbon‐oxygen bond distances be reasonable. The silver oxalate structure may be considered to be made up of chain molecules of composition (Ag2C2O4)x extending through the lattice parallel to the b axis. These chains appear to be held together by longer silver‐oxygen bonds to form the three‐dimensional structure.

SUMMARY Methods are described for assessing inoculum of Phoma exigua by directly wounding potato test tubers and by inoculating soil into Arran Banner test tubers or slices. Large samples of tubers were wounded by dropping onto perforated metal sheet or grading on farm riddles, but standardization was achieved by inflicting four uniform wounds with shaped brass teeth. Tubers were then incubated for 12 wk at 5 oC. Soil samples to be tested were inoculated into crush wounds on surface-sterilized test tubers or tuber slices which were incubated for 8 wk at 5 oC. Assessments were speeded by immersing wounded slices in a mixture of Agrimycin and isopropylphenyl carbamate (IPC) solutions before inoculating, and then incubating for 2–3 wk at 10 oC. Although the sensitivity of test tubers is limited by their latent infection, comparisons of the tests in 3–5 years showed that the test tuber methods were frequently more sensitive than direct wounding, especially when amounts of inoculum were small.

kVe have improved the performance of the avalanche-transistor deflector-driver (sweep) circuitry used in the high-speed, electrooptic streak camera at Lawrence Livermore National Laboratory (LLNL). In the previous design for the sweep circuit, trigger-to-output delay time drifted on some cameras. This delay drift is a function of a somewhat randomly unstable breakdown voltage of some avalanche transistors. I.oth temperature and differences in manufacturing ethods for transistors affect this instability. However, a sig-nificant improvement in system performance is achieved by long-term burn in and by selection of only the most stable transistors for the sweep circuit. The peak-to-peak sweep voltage has been increased about 8O by increasing the number of avalanche transistors in the string and raising the Q of the resonant circuit. The result is an improvement in sweep uniformity by a factor of appoximately 2. Design equations for selecting components are given. Fast-recovery diodes are used to prevent undershoot and to keep the beam out of the intensifier field of view until after the intensifier is gated off. The sweep time range has been extended to over 100 ns.

The RCA C73435 image tube is biased at voltages far from its original design in the LLNL ultrafast (10 ps) streak camera. Its output resolution at streak camera operating potentials has been measured as a function of input slit width, incident-light wavelength, and focus-grid voltage. The temporal resolution is insensitive to focus-grid voltage for a narrow (100 ym) input slit but is very sensitive to focus-grid voltage for a wide (2 mm) input slit. At the optimum wide-slit focus voltage, temporal resolution is insensitive to slit width. Spatial resolution is nearly independent of focus-grid voltage for values that give good temporal resolution. Both temporal and spatial resolution depend on the incident-light wavelength. Data for 1.06-ym light show significantly better focusing than for 0.53-ym light. Streak camera operation is simulated with a computer program that calculates photoelectron trajectories. Electron ray tracing describes all of the observed effects of slit width, incident-light wavelength, and focus-grid voltage on output resolution.

We studied the focusing properties of an ITT F4157 image tube that was biased at voltages far from the original design and is used for operation in an ultrafast (10 ps) streak camera. Its output resolution at streak camera operating potentials was measured as a function of input slit width, incident-light wavelength, and focus-grid voltage, with results similar to those reported for the RCA C73435 streak tube. The temporal resolution is insensitive to focus-grid voltage for a narrow (50 μm) input slit, but is very sensitive to focus-grid voltage for a wide (500 μm) input slit. Spatial resolution is nearly independent of focus-grid voltage for values that give good temporal resolution. Both temporal and spatial resolution depend on the incident-light wavelength. Streak camera operation is simulated with a computer program that calculates photoelectron trajectories. Electron ray tracing describes the observed effects of slit width, incident-light wavelength, and focus-grid voltage on the output resolution.

The RCA streak tube can be operated satisfactorily at voltages other than those we have been using for nearly ten years. Our soft x-ray streak camera uses the RCA C73435 streak tube body fitted with a removable x-ray cathode. The front of the streak tube is exposed to the vacuum of an experimental chamber, which is not entirely under the control of a streak camera operator. Occasionally, the vacuum becomes poor enough to cause corona and arcing from the cathode to the chamber wall. The corona problem is more difficult because the dimensions of the x-ray camera body are smaller than for the optical camera body. Therefore, we investigated the effects on camera performance of decreasing the accelerating voltage at the cathode from the customary 17 kV. Several operating points were evaluated and 12 kV cathode-to-anode with 5 kV cathode-to-grid were selected for more detailed investigation. Transverse spatial resolution and dynamic range were found to be essentially the same as at our normal operating point of 17 kV for the cathode and 2500 V on the grid. Magnification, sweep linearity and absolute sensitivity changed as expected. In the course of the investigation, we measured the dynamic range with our CCD readout system. The effect of coulomb repulsion at the crossover point was also measured and found not to affect dynamic range.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

SUMMARY Pathogens damage potatoes in so many ways and at so many stages of cropping, transport and storage that it is difficult to estimate their total effect. This paper describes methods used to measure how fungal pathogens affected crop health and yield, and experiments that measured how much the yield lost through gaps was compensated by extra growth of neighbouring plants. Some tubers in stocks were diseased, so healthy controls were not available and contrasts could be made only by selecting grades differing in symptom severity. The differences measured represented only part of the damage because many infections are symptomless, and vigorous plants compensate for the small yields of weak or absent neighbours. Plots gapped randomly to varying degrees at emergence or flowering showed that yields were decreased by 0–332 (± 0–129) %and“833 (± 0–094) % respectively, for every 1 % of plants removed. When up to 24 % of plants were removed the regression of percentage gaps on yield did not become significantly non-linear.