Structured photocathodes for improved high-energy x-ray efficiency in streak cameras

We have designed and fabricated a structured streak camera photocathode to provide enhanced efficiency for high energy X-rays (1-12 keV). This gold coated photocathode was tested in a streak camera and compared side by side against a conventional flat thin film photocathode. Results show that the measured electron yield enhancement at energies ranging from 1 to 10 keV scales well with predictions, and that the total enhancement can be more than 3×. The spatial resolution of the streak camera does not show degradation in the structured region. We predict that the temporal resolution of the detector will also not be affected as it is currently dominated by the slit width. This demonstration with Au motivates exploration of comparable enhancements with CsI and may revolutionize X-ray streak camera photocathode design.

A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams

A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ∼10.3% accuracy with ∼30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX-6 (C20H30) aerogel are discussed in this manuscript.

High quantum efficiency photocathode simulation for the investigation of novel structured designs

A computer model in CST Studio Suite has been developed to evaluate several novel geometrically enhanced photocathode designs. This work was aimed at identifying a structure that would increase the total electron yield by a factor of two or greater in the 1-30 keV range. The modeling software was used to simulate the electric field and generate particle tracking for several potential structures. The final photocathode structure has been tailored to meet a set of detector performance requirements, namely, a spatial resolution of <40 μm and a temporal spread of 1-10 ps. We present the details of the geometrically enhanced photocathode model and resulting static field and electron emission characteristics.

A geophysical shock and air blast simulator at the National Ignition Facility

The energy partitioning energy coupling experiments at the National Ignition Facility (NIF) have been designed to measure simultaneously the coupling of energy from a laser-driven target into both ground shock and air blast overpressure to nearby media. The source target for the experiment is positioned at a known height above the ground-surface simulant and is heated by four beams from the NIF. The resulting target energy density and specific energy are equal to those of a low-yield nuclear device. The ground-shock stress waves and atmospheric overpressure waveforms that result in our test system are hydrodynamically scaled analogs of full-scale seismic and air blast phenomena. This report summarizes the development of the platform, the simulations, and calculations that underpin the physics measurements that are being made, and finally the data that were measured. Agreement between the data and simulation of the order of a factor of two to three is seen for air blast quantities such as peak overpressure. Historical underground test data for seismic phenomena measured sensor displacements; we measure the stresses generated in our ground-surrogate medium. We find factors-of-a-few agreement between our measured peak stresses and predictions with modern geophysical computer codes.

Direct Inoculation of Mycobacteriumavium Subspecies Paratuberculosis Into Ileocecal Peyer’s Patches Results in Colonization of the Intestine in a Calf Model

The objective of this study was to develop an intestinal model of Mycobacterium avium subspecies paratuberculosis ( Map) infection in the calf for evaluation of mucosal pathology and local and systemic immunologic responses. Map was inoculated into Peyer’s patches of young calves using a right flank surgical approach in standing calves to exteriorize the ileocecal junction. Inoculum doses ranging from 103 to 109 colony-forming units of strain K10 Map were injected through the serosal surface into Peyer’s patches of the distal ileum near the ileocecal valve. Fecal samples were collected for culture from each calf weekly until termination of the study. Calves were necropsied at 7, 30, 60, and 90 days after infection, when inoculation sites, lymph nodes, spleen, and peripheral blood were collected for evaluation. Ileocecal lymph nodes were consistently colonized by Map in the 105 to 109 groups. The ileocecal valve was also colonized in 107 and 109 groups. This correlated with fecal culture results as infected calves intermittently shed Map in their feces throughout the study. Granulomatous lesions with giant cells and acid-fast bacilli at the ileocecal junction, ileocecal lymph nodes, and lamina propria of high-dose animals (107 and 109) were identified from each time point. Flow cytometry was used to detect antigen-specific production of interferon-γ and interleukin-4 locally (ileocecal lymph node) and systemically (peripheral blood mononuclear cells), which defined distinct immunologic profiles in low-dose and high-dose calves. This study demonstrates intestinal Map infection via Peyer’s patch inoculation, a novel model with many shared features of natural Map infection.

Inducible nitric oxide synthase immunoreactivity in the granulomatous intestinal lesions of naturally occurring bovine Johne's disease

Inducible nitric oxide synthase (iNOS) is important in the control of a number of intracellular pathogens, including mycobacteria, and is a marker of classic macrophage activation. In human granulomatous diseases such as leprosy, a spectrum of granulomatous lesions is described, ranging from the tuberculoid to lepromatous types. Tuberculoid granulomas are associated with enhanced iNOS production and improved clinical outcomes over the lepromatous types. The aim of this study is to determine whether an association exists between morphology of bovine Johne's disease granulomas and lesion macrophage effector functions. To accomplish this, we retrospectively evaluated 24 cases of bovine Johne's disease. In each case, we recorded the predominant granuloma morphology and evaluated iNOS immunoreactivity and bacterial burden by acid-fast stains and mycobacterial immunolabeling. The results of this study demonstrate that all cases had granulomas with features most similar to the lepromatous type. This morphology correlated with heavy bacterial burdens demonstrated by acid-fast staining and mycobacterial immunoreactivity. None of the cases had high expression of iNOS in mycobacterial-positive granulomas. When iNOS immunoreactivity was identified, it was usually located near the crypts and was distinct from the granulomatous foci.

Cellular distribution of anionic antimicrobial peptide in normal lung and during acute pulmonary inflammation

Anionic peptides (APs) are small antimicrobial peptides present in human and ovine lung. In this study APs were also detected in bovine lung, and production of APs in lungs with acute inflammation induced by various stimuli was determined. The distribution and intensity of APs were determined by immunohistochemistry in lungs of 1) neonatal calves (1-3 days of age) inoculated with Mannheimia (Pasteurella) haemolytica, a known inducer of the bovine beta-defensin lingual antimicrobial peptide (LAP) or pyrogen-free saline (PFS), and 2) growing calves (3 months of age) similarly inoculated with M. haemolytica, a lipopolysaccharide (LPS) from M. haemolytica, an LPS-associated protein from M. haemolytica, or PFS. APs were also detected by western blots with the same antibody in lungs of the calves above, as well as in calves inoculated with Pseudomonas aeruginosa, and an adult cow. Anionic peptide (AP) immunoreactivity was detected in bands (approximate weights) in the western blots of lung at 28-30 (strongest signal), 31, 45, and 52-60 kd regardless of inoculum. The adult cow lacked bands at 45 kd, but it had additional bands at 64 (inconsistently) and 35-38 kd. All these band sizes are consistent with those of the western blots of human and ovine lung. The cellular distribution of APs in lung of neonatal and growing cattle was similar to that in lung of human and sheep. In lungs with acute inflammation induced by live bacteria, LPS, or protein, AP distribution and intensity were similar to those in control (PFS-inoculated) lungs and slightly decreased in bronchioles. This work demonstrates that AP is present in lung of cattle and is thereby conserved among two ruminant species and man. Distribution and intensity of AP production are not enhanced by infection or acute inflammation and are decreased in bronchioles, which suggests that AP is not induced like beta-defensins such as LAP, but, instead, is produced constitutively.

Workgroup issue paper: Indicators and assessment of agricultural sustainability : Methods of Assessing Agricultural Sustainability

Sustainability is emerging as one of the most fundamental concepts for assessing the overall state of an agricultural production system. Essentially, this concept assumes that if a production system is sustainable indefinitely, then it is acceptable. But almost any system is sustainable if sufficient resources are committed to it! So it's obvious that an uncritical adoption of the idea is not acceptable.