Explore the vast range of titles available.

The development of ultrafast gas electron diffraction with nonrelativistic electrons has enabled the determination of molecular structures with atomic spatial resolution. It has, however, been challenging to break the picosecond temporal resolution barrier and achieve the goal that has long been envisioned—making space- and-time resolved molecular movies of chemical reaction in the gas-phase. Recently, an ultrafast electron diffraction (UED) apparatus using mega-electron-volt (MeV) electrons was developed at the SLAC National Accelerator Laboratory for imaging ultrafast structural dynamics of molecules in the gas phase. The SLAC gas-phase MeV UED has achieved 65 fs root mean square temporal resolution, 0.63 Å spatial resolution, and 0.22 Å−1 reciprocal-space resolution. Such high spatial-temporal resolution has enabled the capturing of real-time molecular movies of fundamental photochemical mechanisms, such as chemical bond breaking, ring opening, and a nuclear wave packet crossing a conical intersection. In this paper, the design that enables the high spatial-temporal resolution of the SLAC gas phase MeV UED is presented. The compact design of the differential pump section of the SLAC gas phase MeV UED realized five orders-of-magnitude vacuum isolation between the electron source and gas sample chamber. The spatial resolution, temporal resolution, and long-term stability of the apparatus are systematically characterized.

We report on a recent set of measurements of the transverse wakefields from longitudinally tapered collimators. The measurements were performed with a low-emittance 1.19 GeV beam in the SLAC linac by inserting a collimator aperture into the beam path and reconstructing the vertical deflection of the beam as a function of the vertical position of the aperture. Each collimator in the experiment was designed to present a relatively large transverse impedance and to minimize the impedance from other contributions such as resistivity. In addition, the collimator parameters were chosen to provide some insight into the scaling of the transverse geometric wakefield as a function of the collimator’s geometry. A description of the experimental apparatus and the aperture design, the method of data collection and analysis, and a comparison to theoretical and numerical predictions are presented.

The development of ultrafast gas electron diffraction with non-relativistic electrons has enabled determination of molecular structures with atomic spatial resolution. It has, however, been challenging to break the picosecond temporal resolution barrier and achieve the goal that has long been envisioned – making space- and-time resolved molecular movies of chemical reaction in the gas-phase. Recently, an ultrafast electron diffraction (UED) apparatus using mega-electron-volt (MeV) electrons was developed at SLAC National Accelerator Laboratory for imaging ultrafast structural dynamics of molecules in the gas phase. The SLAC gas-phase MeV UED has achieved 70 fs root-mean-square temporal resolution, 0.63 Å spatial resolution, and 0.22 Å–1 reciprocal-space resolution. Such high spatial-temporal resolution has enabled the capturing of real-time molecular movies of fundamental photochemical mechanisms, such as chemical bond breaking, ring opening, and a nuclear wave packet crossing a conical intersection. In this paper, the design that enables the high spatial-temporal resolution of the SLAC gas phase MeV UED is presented. The compact design of the differential pump section of the SLAC gas phase MeV UED realized five orders-of-magnitude vacuum isolation between the electron source and gas sample chamber. The spatial resolution, temporal resolution and long-term stability of the apparatus are systematically characterized.

The SLAC Linac can deliver damped bunches with ILC parameters for bunch charge and bunch length to End Station A. A 10Hz beam at 28.5 GeV energy can be delivered there, parasitic with PEP-II operation. We plan to use this facility to test prototype components of the Beam Delivery System and Interaction Region. We discuss our plans for this ILC Test Facility and preparations for carrying out experiments related to collimator wakefields and energy spectrometers. We also plan an interaction region mockup to investigate effects from backgrounds and beam-induced electromagnetic interference.

As a joint effort in the JLC/NLC research program, we have developed a new type of damped detuned accelerator structure with optimized round-shaped cavities (RDDS). This paper discusses some important R&D aspects of the first structure in this series (RDDS1). The design aspects covered are the cell design with sub-MHz precision, HOM detuning, coupling and damping technique and wakefield simulation. The fabrication issues covered are ultra-precision cell machining with micron accuracy, assembly and diffusion bonding technologies to satisfactorily meet bookshelf, straightness and cell rotational alignment requirements. The measurements described are the RF properties of single cavities and complete accelerator section, as well as wakefields from the ASSET tests at SLAC. Finally, future improvements are also discussed.

In this multicenter, randomized trial, neonates with moderate or severe hypoxic–ischemic encephalopathy randomly assigned to whole-body hypothermia had a significantly reduced risk of death or moderate or severe disability at 18 to 22 months of age. This study suggests that whole-body hypothermia may improve substantially the outcomes for infants with hypoxic–ischemic encephalopathy. Neonates with moderate or severe hypoxic–ischemic encephalopathy randomly assigned to whole-body hypothermia had a significantly reduced risk of death or moderate or severe disability at 18 to 22 months of age. Among term infants, hypoxic–ischemic encephalopathy due to acute perinatal asphyxia remains an important cause of neurodevelopmental deficits in childhood. Infants with moderate encephalopathy have a 10 percent risk of death, and those who survive have a 30 percent risk of disabilities. Sixty percent of infants with severe encephalopathy die, and many, if not all, survivors are handicapped. 1 , 2 Treatment is currently limited to supportive intensive care. Reductions in brain temperature by 2°C to 5°C provide neuroprotection in newborn and adult animal models of brain ischemia. 3 – 10 Brain cooling has a favorable effect on multiple pathways contributing to brain injury, including . . .

Background: Adipose tissue is a primary in vivo site of inflammation in obesity. Excess visceral adipose tissue (VAT), when compared to subcutaneous adipose tissue (SAT), imparts an increased risk of obesity-related comorbidities and mortality, and exhibits differences in inflammation. Defining depot-specific differences in inflammatory function may reveal underlying mechanisms of adipose-tissue-based inflammation. Methods: Stromovascular cell fractions (SVFs) from VAT and SAT from obese humans undergoing bariatric surgery were studied in an in vitro culture system with transcriptional profiling, flow cytometric phenotyping, enzyme-linked immunosorbent assay and intracellular cytokine staining. Results: Transcriptional profiling of SVF revealed differences in inflammatory transcript levels in VAT relative to SAT, including elevated interferon- (IFN-) transcript levels. VAT demonstrated a broad leukocytosis relative to SAT that included macrophages, T cells and natural killer (NK) cells. IFN- induced a proinflammatory cytokine expression pattern in SVF and adipose tissue macrophages (ATM). NK cells, which constitutively expressed IFN-, were present at higher frequency in VAT relative to SAT. Both T and NK cells from SVF expressed IFN- on activation, which was associated with tumor necrosis factor- expression in macrophages. Conclusion: These data suggest involvement of NK cells and IFN- in regulating ATM phenotype and function in human obesity and a potential mechanism for the adverse physiologic effects of VAT.

Conserving or restoring landscape connectivity between patches of breeding habitat is a common strategy to protect threatened species from habitat fragmentation. By managing connectivity for some species, usually charismatic vertebrates, it is often assumed that these species will serve as conservation umbrellas for other species. We tested this assumption by developing a quantitative method to measure overlap in dispersal habitat of 3 threatened species—a bird (the umbrella), a butterfly, and a frog—inhabiting the same fragmented landscape. Dispersal habitat was determined with Circuitscape, which was parameterized with movement data collected for each species. Despite differences in natural history and breeding habitat, we found substantial overlap in the spatial distributions of areas important for dispersal of this suite of taxa. However, the intuitive umbrella species (the bird) did not have the highest overlap with other species in terms of the areas that supported connectivity. Nevertheless, we contend that when there are no irreconcilable differences between the dispersal habitats of species that cohabitate on the landscape, managing for umbrella species can help conserve or restore connectivity simultaneously for multiple threatened species with different habitat requirements. Conservar o restaurar la conectividad de paisajes entre fragmentos de hábitats de reproducción es una estrategia común para proteger a las especies amenazadas de la fragmentación de hábitat. Al manejar la conectividad para algunas especies, generalmente vertebrados carismáticos, se asume comúnmente que estas especies servirán como paraguas de conservación para otras especies. Probamos esta suposición desarrollando un método cuantitativo para medir el traslape en la dispersión de hábitat de tres especies amenazadas que habitan en el mismo paisaje fragmentado: un ave (el paraguas), una mariposa y una rana. La dispersión de hábitat se determinó con Circuitscape, al cual se le establecieron parámetros con movimientos de datos colectados para cada especie. Pese a las diferencias en la historia natural y el hábitat de reproducción, encontramos un traslape sustancial en las distribuciones espaciales de áreas importantes para la dispersión de este conjunto de taxones. Sin embargo, la especie paraguas intuitiva (el ave) no tuvo el traslape mayor con otras especies en términos de áreas que apoyen la conectividad. A pesar de todo, sostenemos que cuando no hay diferencias irreconciliables entre la dispersión de hábitats de las especies que cohabitan en el paisaje, manejar todo para la especie paraguas puede ayudar a conservar o restaurar simultáneamente la conectividad para múltiples especies amenazadas con requerimientos de hábitat diferentes.