Creation and diagnosis of a solid-density plasma with an X-ray free-electron laser

Matter with a high energy density (>10(5)?joules per cm(3)) is prevalent throughout the Universe, being present in all types of stars and towards the centre of the giant planets; it is also relevant for inertial confinement fusion. Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities. With the advent of the Linac Coherent Light Source (LCLS) X-ray laser, high-intensity radiation (>10(17)?watts per cm(2), previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated. An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 10(6) kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray-matter interactions, and illustrate the importance of electron-ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.     

Species diversity and habitat of grassland passerines during grazing of a prescribe-burned, mixed-grass prairie

No published data exist on responses of grassland passerines and their habitat to combined grazing and burning treatments in northern mixed-grass prairie. At Lostwood National Wildlife Refuge (LNWR) in northwestern North Dakota, we monitored breeding bird occurrence, abundance, and habitat during successive annual grazing treatments (1998-2000) on 5 prescribe-burned, mixed-grass prairie management units (range = 50-534 ha, each burned 3-6 times in the previous 10-20 years). All breeding passerine species characteristic of upland, northern mixed-grass prairie were common (> 10% occurrence) during at least 1 of 3 years on burned and grazed units, except Chestnut-collared Longspur ( Calcarius ornatus ), which was uncommon. Vegetation was generally shorter and sparser than that found on 4 nearby units treated by fire only (1999; density, visual obstruction, and height, all P Molothrus ater ) occurred 2.4 times more frequently on burned and grazed units studied. Our data suggest that species diversity of breeding grassland passerines changes little during initial years of rotation grazing at moderate stocking rates in fire-managed, northern mixed-grass prairie at LNWR.     

Nest site selection in raptor communities of the eastern Great Basin desert

Measures of niche breadth and overlap were used to compare nest site selection in a community of 10 raptor species and the Raven nesting in the eastern Great Basin Desert. Three variables were examined: nest site type, elevation, and exposure. Results suggest a division of component raptor species into relatively abundant core species that show wide niche breadths and uncommon fringe species with narrow niche breadths. Differences in use of each resource are most pronounced along elevation gradient in which three guilds are evident that correspond to raptor species groupings that nest at higher, middle, and lower elevations. Each guild is comprised of a mix of core and fringe species. Raptor species with highest overlap along one or more nest site variables examined are separated by differences in activity patterns.     

Raptors of the Uinta National Forest, Utah

The past and present use of the Uinta National Forest by birds of prey was determined from historical records and surveys conducted during 1973, 1974, and 1975. Data describing the history, present status, and physical characteristics of each nest site were collected, along with the type and intensivity of human activity within a half - mile radius of the nest. In addition, limited data on fall migration of raptors along the Wasatch Front and the food habits of Golden Eagles are presented. Management guidelines, based on the results of this study, are proposed.     

非离子表面活性剂Tween-80存在下5-Br-PADAP分光光度法同时测定微量Cu(Ⅲ)和Fe(Ⅲ)

:在 p H3 .50酸性介质中 ,Cu( )和 Fe( )在非离子表面活性剂 Tween-80存在下与 5-Br-PADAP生成有色配合物 .有色配合物最大吸收波长都位于 570 nm处 ;表观摩尔吸光系数分别为 7.96× 1 0 4 L· mol-1· cm-1和 6.3 0× 1 0 4 L· mol-1· cm-1;Cu( )在 0～ 1 3μg/2 5ml,Fe( )在 0～ 1 8μg/2 5ml范围内符合比耳定律 .用拟定的方法测定了铝片和水样中的 Cu( )和 Fe( ) ,结果令人满意     

Pentaploidy in hybrid salamanders demonstrates enhanced tolerance of multiple chromosome sets

Summary Breeding populations of unisexual hybrid salamanders (genusAmbystoma) are dominated by allotriploid (3n) and allotetraploid (4n) forms, however, sexually mature allopentaploids (5n) may also occur. These are the first known naturally-occurring pentaploid vertebrates, and their genesis differs from that of previously studied autopentaploid urodeles induced or observed in the laboratory. The latter always suffered severely deleterious effects in development, and could not attain sexual maturity.     

Deregulated MYC expression induces dependence upon AMPK-related kinase 5

Deregulated expression of the MYC oncoprotein contributes to the genesis of many human tumours, yet strategies to exploit this for a rational tumour therapy are scarce. MYC promotes cell growth and proliferation, and alters cellular metabolism to enhance the provision of precursors for phospholipids and cellular macromolecules. Here we show in human and murine cell lines that oncogenic levels of MYC establish a dependence on AMPK-related kinase 5 (ARK5; also known as NUAK1) for maintaining metabolic homeostasis and for cell survival. ARK5 is an upstream regulator of AMPK and limits protein synthesis via inhibition of the mammalian target of rapamycin 1 (mTORC1) signalling pathway. ARK5 also maintains expression of mitochondrial respiratory chain complexes and respiratory capacity, which is required for efficient glutamine metabolism. Inhibition of ARK5 leads to a collapse of cellular ATP levels in cells expressing deregulated MYC, inducing multiple pro-apoptotic responses as a secondary consequence. Depletion of ARK5 prolongs survival in MYC-driven mouse models of hepatocellular carcinoma, demonstrating that targeting cellular energy homeostasis is a valid therapeutic strategy to eliminate tumour cells that express deregulated MYC.