Wetland Mapping with Quad-Pol Data Acquired during Tandem-X Science Phase

NASA Astrophysics Data System (ADS)

Mleczko, M.; Mroz, M.; Fitrzyk, M.

2016-06-01

The aim of this study was to exploit fully polarimetric SAR data acquired during TanDEM-X - Science Phase (2014/2015) over herbaceous wetlands of the Biebrza National Park (BbNP) in North-Eastern Poland for mapping seasonally flooded grasslands and permanent natural vegetation associations. The main goal of this work was to estimate the advantage of fully polarimetric radar images (QuadPol) versus alternative polarization (AltPol) modes. The methodology consisted in processing of several data subsets through polarimetric decompositions of complex quad-pol datasets, classification of multitemporal backscattering images, complementing backscattering images with Shannon Entropy, exploitation of interferometric coherence from tandem operations. In each case the multidimensional stack of images has been classified using ISODATA unsupervised clustering algorithm. With 6 QUAD-POL TSX/TDX acquisitions it was possible to distinguish correctly 5 thematic classes related to their water regime: permanent water bodies, temporarily flooded areas, wet grasslands, dry grasslands and common reed. This last category was possible to distinguish from deciduous forest only with Yamaguchi 4 component decomposition. The interferometric coherence calculated for tandem pairs turned out not so efficient as expected for this wetland mapping.

Assessment of Reference Height Models on Quality of Tandem-X dem

NASA Astrophysics Data System (ADS)

Mirzaee, S.; Motagh, M.; Arefi, H.

2015-12-01

The aim of this study is to investigate the effect of various Global Digital Elevation Models (GDEMs) in producing high-resolution topography model using TanDEM-X (TDX) Coregistered Single Look Slant Range Complex (CoSSC) images. We selected an image acquired on Jun 12th, 2012 over Doroud region in Lorestan, west of Iran and used 4 external digital elevation models in our processing including DLR/ASI X-SAR DEM (SRTM-X, 30m resolution), ASTER GDEM Version 2 (ASTER-GDEMV2, 30m resolution), NASA SRTM Version 4 (SRTM-V4, 90m resolution), and a local photogrammetry-based DEM prepared by National Cartographic Center (NCC DEM, 10m resolution) of Iran. InSAR procedure for DEM generation was repeated four times with each of the four external height references. The quality of each external DEM was initially assessed using ICESat filtered points. Then, the quality of, each TDX-based DEM was assessed using the more precise external DEM selected in the previous step. Results showed that both local (NCC) DEM and SRTM X-band performed the best (RMSE< 9m) for TDX-DEM generation. In contrast, ASTER GDEM v2 and SRTM C-band v4 showed poorer quality.

Stabilized wide bandgap MAPbBr xI 3-x perovskite by enhanced grain size and improved crystallinity

DOE PAGES

Hu, Miao; Bi, Cheng; Yuan, Yongbo; ...

2015-12-07

In this study, the light instability of CH 3NH 3PbI xBr 3–x has been raised one of the biggest challenges for its application in tandem solar cells. Here we show that an improved crystallinity and grain size of CH 3NH 3PbI xBr 3–x films could stabilize these materials under one sun illumination, improving both the efficiency and stability of the wide-bandgap perovskite solar cells.

Surface display of monkey metallothionein α tandem repeats and EGFP fusion protein on Pseudomonas putida X4 for biosorption and detection of cadmium.

PubMed

He, Xiaochuan; Chen, Wenli; Huang, Qiaoyun

2012-09-01

Monkey metallothionein α domain tandem repeats (4mMTα), which exhibit high cadmium affinity, have been displayed for the first time on the surface of a bacterium using ice nucleation protein N-domain (inaXN) protein from the Xanthomonas campestris pv (ACCC-10049) as an anchoring motif. The shuttle vector pIME, which codes for INAXN-4mMTα-EGFP fusion, was constructed and used to target 4mMTα and EGFP on the surface of Pseudomonas putida X4 (CCTCC-209319). The surface location of the INAXN-4mMTα-EGFP fusion was further verified by western blot analysis and immunofluorescence microscopy. The growth of X4 showed resistance to cadmium presence. The presence of surface-exposed 4mMTα on the engineered strains was four times higher than that of the wild-type X4. The Cd²⁺ accumulation by X4/pIME was not only four times greater than that of the original host bacterial cells but was also remarkably unaffected by the presence of Cu²⁺ and Zn²⁺. Moreover, the surface-engineered strains could effectively bind Cd²⁺ under a wide range of pH levels, from 4 to 7. P. putida X4/pIME with surface-expressed 4mMTα-EGFP had twice the cadmium binding capacity as well as 1.4 times the fluorescence as the cytoplasmic 4mMTa-EGFP. These results suggest that P. putida X4 expressing 4mMTα-EGFP with the INAXN anchor motif on the surface would be a useful tool for the remediation and biodetection of environmental cadmium contaminants.

Time-averaged discharge rate of subaerial lava at Kīlauea Volcano, Hawai‘i, measured from TanDEM-X interferometry: Implications for magma supply and storage during 2011-2013

USGS Publications Warehouse

Poland, Michael P.

2014-01-01

Differencing digital elevation models (DEMs) derived from TerraSAR add-on for Digital Elevation Measurements (TanDEM-X) synthetic aperture radar imagery provides a measurement of elevation change over time. On the East Rift Zone (EZR) of Kīlauea Volcano, Hawai‘i, the effusion of lava causes changes in topography. When these elevation changes are summed over the area of an active lava flow, it is possible to quantify the volume of lava emplaced at the surface during the time spanned by the TanDEM-X data—a parameter that can be difficult to measure across the entirety of an ~100 km2 lava flow field using ground-based techniques or optical remote sensing data. Based on the differences between multiple TanDEM-X-derived DEMs collected days to weeks apart, the mean dense-rock equivalent time-averaged discharge rate of lava at Kīlauea between mid-2011 and mid-2013 was approximately 2 m3/s, which is about half the long-term average rate over the course of Kīlauea's 1983–present ERZ eruption. This result implies that there was an increase in the proportion of lava stored versus erupted, a decrease in the rate of magma supply to the volcano, or some combination of both during this time period. In addition to constraining the time-averaged discharge rate of lava and the rates of magma supply and storage, topographic change maps derived from space-based TanDEM-X data provide insights into the four-dimensional evolution of Kīlauea's ERZ lava flow field. TanDEM-X data are a valuable complement to other space-, air-, and ground-based observations of eruptive activity at Kīlauea and offer great promise at locations around the world for aiding with monitoring not just volcanic eruptions but any hazardous activity that results in surface change, including landslides, floods, earthquakes, and other natural and anthropogenic processes.

High Resolution Deformation Time Series Estimation for Distributed Scatterers Using Terrasar-X Data

NASA Astrophysics Data System (ADS)

Goel, K.; Adam, N.

2012-07-01

In recent years, several SAR satellites such as TerraSAR-X, COSMO-SkyMed and Radarsat-2 have been launched. These satellites provide high resolution data suitable for sophisticated interferometric applications. With shorter repeat cycles, smaller orbital tubes and higher bandwidth of the satellites; deformation time series analysis of distributed scatterers (DSs) is now supported by a practical data basis. Techniques for exploiting DSs in non-urban (rural) areas include the Small Baseline Subset Algorithm (SBAS). However, it involves spatial phase unwrapping, and phase unwrapping errors are typically encountered in rural areas and are difficult to detect. In addition, the SBAS technique involves a rectangular multilooking of the differential interferograms to reduce phase noise, resulting in a loss of resolution and superposition of different objects on ground. In this paper, we introduce a new approach for deformation monitoring with a focus on DSs, wherein, there is no need to unwrap the differential interferograms and the deformation is mapped at object resolution. It is based on a robust object adaptive parameter estimation using single look differential interferograms, where, the local tilts of deformation velocity and local slopes of residual DEM in range and azimuth directions are estimated. We present here the technical details and a processing example of this newly developed algorithm.

Multiplex tandem mass spectrometry assay for newborn screening of X-linked adrenoleukodystrophy, biotinidase deficiency, and galactosemia with flexibility to assay other enzyme assays and biomarkers.

PubMed

Hong, Xinying; Kumar, Arun Babu; Ronald Scott, C; Gelb, Michael H

2018-03-29

All States screen for biotinidase deficiency and galactosemia, and X-linked adrenoleukodystrophy (X-ALD) has recently been added to the Recommended Uniform Screening Panel (RUSP).We sought to consolidate these tests by combining them into a single multiplex tandem mass spectrometry assay as well as to improve the current protocol for newborn screening of galactosemia.A 3 mm punch of a dried blood spot (DBS) was extracted with organic solvent for analysis of the C26:0-lysophosphatidylcholine biomarker for X-ALD.An additional punch was used to assay galactose-1-phosphate uridyltransferase (GALT) and biotinidase.All assays were combined for a single injection for analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) (2.3 min per sample).The GALT LC-MS/MS assay does not give a false positive for galactosemia if glucose-6-phosphate dehydrogenase is deficient.The multiplex assay shows acceptable reproducibility and provides for rapid analysis of X-ALD, biotinidase deficiency, and galactosemia.The throughput and ease of sample preparation are acceptable for newborn screening laboratories.We also show that the LC-MS/MS assay is expandable to include several other diseases including Pompe and Hurler diseases (enzymatic activities and biomarkers).Because of consolidation of assays, less manpower is needed compared to running individual assays on separate platforms.The flexibility of the LC-MS/MS platform allows each newborn screening laboratory to analyze the set of diseases offered in their panel. Copyright © 2018 Elsevier Inc. All rights reserved.

Heterobimetallic Catalysis: Platinum-Gold-Catalyzed Tandem Cyclization/C-X Coupling Reaction of (Hetero)Arylallenes with Nucleophiles.

PubMed

Alonso, José Miguel; Muñoz, María Paz

2018-04-16

Heterobimetallic catalysis offers new opportunities for reactivity and selectivity but still presents challenges, and only a few metal combinations have been explored so far. Reported here is a Pt-Au heterobimetallic catalyst system for the synthesis of a family of multi-heteroaromatic structures through tandem cyclization/C-X coupling reaction. Au-catalyzed 6-endo-cyclization takes place as the first fast step. Pt-Au clusters are proposed to be responsible for the increased reactivity in the second step, that is, the intermolecular nucleophilic addition which occurs through an outer-sphere mechanism by hybrid homogeneous-heterogeneous catalysis. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strength design of Zr(x)Ti(x)Hf(x)Nb(x)Mo(x) alloys based on empirical electron theory of solids and molecules

NASA Astrophysics Data System (ADS)

Li, Y. K.; Chen, Y. W.; Cheng, X. W.; Wu, C.; Cheng, B.

2018-05-01

In this paper, the valence electron structure parameters of Zr(x)Ti(x)Hf(x)Nb(x)Mo(x) alloys were calculated based on the empirical electron theory of solids and molecules (EET), and their performance through these parameters were predicted. Subsequently, the alloys with special valence electron structure parameters were prepared byarc melting. The hardness and high-temperature mechanical properties were analyzed to verify the prediction. Research shows that the influence of shared electron number nA on the strongest bond determines the strength of these alloys and the experiments are consistent with the theoretical prediction.

MiniX-STR multiplex system population study in Japan and application to degraded DNA analysis.

PubMed

Asamura, H; Sakai, H; Kobayashi, K; Ota, M; Fukushima, H

2006-05-01

We sought to evaluate a more effective system for analyzing X-chromosomal short tandem repeats (X-STRs) in highly degraded DNA. To generate smaller amplicon lengths, we designed new polymerase chain reaction (PCR) primers for DXS7423, DXS6789, DXS101, GATA31E08, DXS8378, DXS7133, DXS7424, and GATA165B12 at X-linked short tandem repeat (STR) loci, devising two miniX-multiplex PCR systems. Among 333 Japanese individuals, these X-linked loci were detected in amplification products ranging in length from 76 to 169 bp, and statistical analyses of the eight loci indicated a high usefulness for the Japanese forensic practice. Results of tests on highly degraded DNA indicated the miniX-STR multiplex strategies to be an effective system for analyzing degraded DNA. We conclude that analysis by the current miniX-STR multiplex systems offers high effectiveness for personal identification from degraded DNA samples.

Tandem pseudopericyclic reactions: [1,5]-X sigmatropic shift/6pi-electrocyclic ring closure converting N-(2-X-carbonyl)phenyl ketenimines into 2-X-quinolin-4(3H)-ones.

PubMed

Alajarín, Mateo; Ortín, María-Mar; Sanchez-Andrada, Pilar; Vidal, Angel

2006-10-13

N-(2-X-Carbonyl)phenyl ketenimines undergo, under mild thermal conditions, [1,5]-migration of the X group from the carbonyl carbon to the electron-deficient central carbon atom of the ketenimine fragment, followed by a 6pi-electrocyclic ring closure of the resulting ketene to provide 2-X-substituted quinolin-4(3H)-ones in a sequential one-pot manner. The X groups tested are electron-donor groups, such as alkylthio, arylthio, arylseleno, aryloxy, and amino. When involving alkylthio, arylthio, and arylseleno groups, the complete transformation takes place in refluxing toluene, whereas for aryloxy and amino groups the starting ketenimines must be heated at 230 degrees C in a sealed tube in the absence of solvent. The mechanism for the conversion of these ketenimines into quinolin-4(3H)-ones has been studied by ab initio and DFT calculations, using as model compounds N-(2-X-carbonyl)vinyl ketenimines bearing different X groups (X = F, Cl, OH, SH, NH(2), and PH(2)) converting into 4(3H)-pyridones. This computational study afforded two general reaction pathways for the first step of the sequence, the [1,5]-X shift, depending on the nature of X. When X is F, Cl, OH, or SH, the migration occurs in a concerted mode, whereas when X is NH(2) or PH(2), it involves a two-step sequence. The order of migratory aptitudes of the X substituents at the acyl group is predicted to be PH(2) > Cl > SH > NH(2) > F> OH. The second step of the full transformation, the 6pi-electrocyclic ring closure, is calculated to be concerted and with low energy barriers in all the cases. We have included in the calculations an alternative mode of cyclization of the N-(2-X-carbonyl)vinyl ketenimines, the 6pi-electrocyclic ring closure leading to 1,3-oxazines that involves its 1-oxo-5-aza-1,3,5-hexatrienic system. Additionally, the pseudopericyclic topology of the transition states for some of the [1,5]-X migrations (X = F, Cl, OH, SH), for the 6pi-electrocyclization of the ketene intermediates to the 4

Fragile X Mental Retardation Syndrome: Structure of the KH1-KH2 Domains of Fragile X Mental Retardation Protein

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valverde,R.; Poznyakova, I.; Kajander, T.

Fragile X syndrome is the most common form of inherited mental retardation in humans, with an estimated prevalence of about 1 in 4000 males. Although several observations indicate that the absence of functional Fragile X Mental Retardation Protein (FMRP) is the underlying basis of Fragile X syndrome, the structure and function of FMRP are currently unknown. Here, we present an X-ray crystal structure of the tandem KH domains of human FMRP, which reveals the relative orientation of the KH1 and KH2 domains and the location of residue Ile304, whose mutation to Asn is associated with a particularly severe incidence ofmore » Fragile X syndrome. We show that the Ile304Asn mutation both perturbs the structure and destabilizes the protein.« less

Precise Determination of the Baseline Between the TerraSAR-X and TanDEM-X Satellites

NASA Astrophysics Data System (ADS)

Koenig, Rolf; Rothacher, Markus; Michalak, Grzegorz; Moon, Yongjin

TerraSAR-X, launched on June 15, 2007, and TanDEM-X, to be launched in September 2009, both carry the Tracking, Occultation and Ranging (TOR) category A payload instrument package. The TOR consists of a high-precision dual-frequency GPS receiver, called Integrated GPS Occultation Receiver (IGOR), for precise orbit determination and atmospheric sounding and a Laser retro-reflector (LRR) serving as target for the global Satellite Laser Ranging (SLR) ground station network. The TOR is supplied by the GeoForschungsZentrum Potsdam (GFZ) Germany, and the Center for Space Research (CSR), Austin, Texas. The objective of the German/US collaboration is twofold: provision of atmospheric profiles for use in numerical weather predictions and climate studies from the occultation data and precision SAR data processing based on precise orbits and atmospheric products. For the scientific objectives of the TanDEM- X mission, i.e., bi-static SAR together with TerraSAR-X, the dual-frequency GPS receiver is of vital importance for the millimeter level determination of the baseline or distance between the two spacecrafts. The paper discusses the feasibility of generating millimeter baselines by the example of GRACE, where for validation the distance between the two GRACE satellites is directly available from the micrometer-level intersatellite link measurements. The distance of the GRACE satellites is some 200 km, the distance of the TerraSAR-X/TanDEM-X formation will be some 200 meters. Therefore the proposed approach is then subject to a simulation of the foreseen TerraSAR-X/TanDEM-X formation. The effect of varying space environmental conditions, of possible phase center variations, multi path, and of varying center of mass of the spacecrafts are evaluated and discussed.

X-chromosomal inactivation directly influences the phenotypic manifestation of X-linked protoporphyria

PubMed Central

Brancaleoni, V.; Balwani, M.; Granata, F.; Graziadei, G.; Missineo, P.; Fiorentino, V.; Fustinoni, S.; Cappellini, M.D.; Naik, H.; Desnick, R.J.; Di Pierro, E.

2015-01-01

X-linked protoporphyria (XLP), a rare erythropoietic porphyria, results from terminal exon gain-of-function mutations in the ALAS2 gene causing increased ALAS2 activity and markedly increased erythrocyte protoporphyrin levels. Patients present with severe cutaneous photosensitivity and may develop liver dysfunction. XLP was originally reported as X-linked dominant with 100% penetrance in males and females. We characterized 11 heterozygous females from six unrelated XLP families and show markedly varying phenotypic and biochemical heterogeneity, reflecting the degree of X-chromsomal inactivation of the mutant gene. ALAS2 sequencing identified the specific mutation and confirmed heterozygosity among the females. Clinical history, plasma and erythrocyte protoporphyrin levels were determined. Methylation assays of the androgen receptor and zinc-finger MYM type 3 short tandem repeat polymorphisms estimated each heterozygotes X-chromosomal inactivation pattern. Heterozygotes with equal or increased skewing, favoring expression of the wild-type allele had no clinical symptoms and only slightly increased erythrocyte protoporphyrin concentrations and/or frequency of protoporphyrin-containing peripheral blood fluorocytes. When the wild-type allele was preferentially inactivated, heterozygous females manifested the disease phenotype and had both higher erythrocyte protoporphyrin levels and circulating fluorocytes. These findings confirm that the previous dominant classification of XLP is inappropriate and genetically misleading, as the disorder is more appropriately designated XLP. PMID:25615817

First report on an X-linked hypohidrotic ectodermal dysplasia family with X chromosome inversion: Breakpoint mapping reveals the pathogenic mechanism and preimplantation genetics diagnosis achieves an unaffected birth.

PubMed

Wu, Tonghua; Yin, Biao; Zhu, Yuanchang; Li, Guangui; Ye, Lijun; Liang, Desheng; Zeng, Yong

2017-12-01

To investigate the etiology of X-linked hypohidrotic ectodermal dysplasia (XLHED) in a family with an inversion of the X chromosome [inv(X)(p21q13)] and to achieve a healthy birth following preimplantation genetic diagnosis (PGD). Next generation sequencing (NGS) and Sanger sequencing analysis were carried out to define the inversion breakpoint. Multiple displacement amplification, amplification of breakpoint junction fragments, Sanger sequencing of exon 1 of ED1, haplotyping of informative short tandem repeat markers and gender determination were performed for PGD. NGS data of the proband sample revealed that the size of the possible inverted fragment was over 42Mb, spanning from position 26, 814, 206 to position 69, 231, 915 on the X chromosome. The breakpoints were confirmed by Sanger sequencing. A total of 5 blastocyst embryos underwent trophectoderm biopsy. Two embryos were diagnosed as carriers and three were unaffected. Two unaffected blastocysts were transferred and a singleton pregnancy was achieved. Following confirmation by prenatal diagnosis, a healthy baby was delivered. This is the first report of an XLHED family with inv(X). ED1 is disrupted by the X chromosome inversion in this XLHED family and embryos with the X chromosomal abnormality can be accurately identified by means of PGD. Copyright © 2017. Published by Elsevier B.V.

Elliptic Curve Integral Points on y2 = x3 + 3x ‑ 14

NASA Astrophysics Data System (ADS)

Zhao, Jianhong

2018-03-01

The positive integer points and integral points of elliptic curves are very important in the theory of number and arithmetic algebra, it has a wide range of applications in cryptography and other fields. There are some results of positive integer points of elliptic curve y 2 = x 3 + ax + b, a, b ∈ Z In 1987, D. Zagier submit the question of the integer points on y 2 = x 3 ‑ 27x + 62, it count a great deal to the study of the arithmetic properties of elliptic curves. In 2009, Zhu H L and Chen J H solved the problem of the integer points on y 2 = x 3 ‑ 27x + 62 by using algebraic number theory and P-adic analysis method. In 2010, By using the elementary method, Wu H M obtain all the integral points of elliptic curves y 2 = x 3 ‑ 27x ‑ 62. In 2015, Li Y Z and Cui B J solved the problem of the integer points on y 2 = x 3 ‑ 21x ‑ 90 By using the elementary method. In 2016, Guo J solved the problem of the integer points on y 2 = x 3 + 27x + 62 by using the elementary method. In 2017, Guo J proved that y 2 = x 3 ‑ 21x + 90 has no integer points by using the elementary method. Up to now, there is no relevant conclusions on the integral points of elliptic curves y 2 = x 3 + 3x ‑ 14, which is the subject of this paper. By using congruence and Legendre Symbol, it can be proved that elliptic curve y 2 = x 3 + 3x ‑ 14 has only one integer point: (x, y) = (2, 0).

The X-15/HL-20 operations support comparison

NASA Technical Reports Server (NTRS)

Morris, W. Douglas

1993-01-01

During the 1960's, the United States X-15 rocket-plane research program successfully demonstrated the ability to support a reusable vehicle operating in a near-space environment. The similarity of the proposed HL-20 lifting body concept in general size, weight, and subsystem composition to that of the X-15 provided an opportunity for a comparison of the predicted support manpower and turnaround times with those experienced in the X-15 program. Information was drawn from both reports and discussions with X-15 program personnel to develop comparative operations and support data. Based on the assumption of comparability between the two systems, the predicted staffing levels, skill mix, and refurbishment times of an operational HL-20 appear to be similar to those experienced by the X-15 for ground support. However, safety, environmental, and support requirements have changed such that the HL-20 will face a different operating environment than existed at Edwards during the 1950's and 1960's. Today's operational standards may impose additional requirements on the HL-20 that will add to the maintenance and support burden estimate based on the X-15 analogy.

Band structure engineering for solar energy applications: Zinc oxide(1-x) selenium(x) films and devices

NASA Astrophysics Data System (ADS)

Mayer, Marie Annette

New technologies motivate the development of new semiconducting materials, for which structural, electrical and chemical properties are not well understood. In addition to new materials systems, there are huge opportunities for new applications, especially in solar energy conversion. In this dissertation I explore the role of band structure engineering of semiconducting oxides for solar energy. Due to the abundance and electrochemical stability of oxides, the appropriate modification could make them appealing for applications in both photovoltaics and photoelectrochemical hydrogen production. This dissertation describes the design, synthesis and evaluation of the alloy ZnO1-xSe x for these purposes. I review several methods of band structure engineering including strain, quantum confinement and alloying. A detailed description of the band anticrossing (BAC) model for highly mismatched alloys is provided, including the derivation of the BAC model as well as recent work and potential applications. Thin film ZnOxSe1-x samples are grown by pulsed laser deposition (PLD). I describe in detail the effect of growth conditions (temperature, pressure and laser fluence) on the chemistry, structure and optoelectronic properties of ZnOxSe1-x. The films are grown using different combinations of PLD conditions and characterized with a variety of techniques. Phase pure films with low roughness and high crystallinity were obtained at temperatures below 450¢ªC, pressures less than 10-4 Torr and laser fluences on the order of 1.5 J/cm 2. Electrical conduction was still observed despite heavy concentrations of grain boundaries. The band structure of ZnO1-xSex is then examined in detail. The bulk electron affinity of a ZnO thin film was measured to be 4.5 eV by pinning the Fermi level with native defects. This is explained in the framework of the amphoteric defect model. A shift in the ZnO1-xSe x valence band edge with x is observed using synchrotron x-ray absorption and emission

Overall water splitting on (Ga(1-x)Zn(x))(N(1-x)O(x)) solid solution photocatalyst: relationship between physical properties and photocatalytic activity.

PubMed

Maeda, Kazuhiko; Teramura, Kentaro; Takata, Tsuyoshi; Hara, Michikazu; Saito, Nobuo; Toda, Kenji; Inoue, Yasunobu; Kobayashi, Hisayoshi; Domen, Kazunari

2005-11-03

The physical and photocatalytic properties of a novel solid solution between GaN and ZnO, (Ga(1-x)Zn(x))(N(1-x)O(x)), are investigated. Nitridation of a mixture of Ga(2)O(3) and ZnO at 1123 K for 5-30 h under NH(3) flow results in the formation of a (Ga(1-x)Zn(x))(N(1-x)O(x)) solid solution with x = 0.05-0.22. With increasing nitridation time, the zinc and oxygen concentrations decrease due to reduction of ZnO and volatilization of zinc, and the crystallinity and band gap energy of the product increase. The highest activity for overall water splitting is obtained for (Ga(1-x)Zn(x))(N(1-x)O(x)) with x = 0.12 after nitridation for 15 h. The crystallinity of the catalyst is also found to increase with increasing the ratio of ZnO to Ga(2)O(3) in the starting material, resulting in an increase in activity.

NMR study of nematic spin fluctuations in a detwinned single crystal of underdoped Ba ( Fe 1 ₋ x Co x ) 2 As 2

DOE PAGES

Kissikov, T.; Dioguardi, A. P.; Timmons, E. I.; ...

2016-10-11

Here, we report the experimental details of how mechanical detwinning can be implemented in tandem with high-sensitivity nuclear magnetic resonance measurements and use this setup to measure the in-plane anisotropy of the spin-lattice relaxation rate in underdoped Ba(Fe 1–xCo x) 2As 2 with x = 0.048. The anisotropy reaches a maximum of 30% at TN, and the recovery data reveal that the glassy behavior of the spin fluctuations present in the twinned state persist in the fully detwinned crystal. A theoretical model is presented to describe the spin-lattice relaxation rate in terms of anisotropic nematic spin fluctuations.

Supplementation of H1N1pdm09 split vaccine with heterologous tandem repeat M2e5x virus-like particles confers improved cross-protection in ferrets.

PubMed

Music, Nedzad; Reber, Adrian J; Kim, Min-Chul; York, Ian A; Kang, Sang-Moo

2016-01-20

Current influenza vaccines induce strain-specific immunity to the highly variable hemagglutinin (HA) protein. It is therefore a high priority to develop vaccines that induce broadly cross-protective immunity to different strains of influenza. Since influenza A M2 proteins are highly conserved among different strains, five tandem repeats of the extracellular peptide of M2 in a membrane-anchored form on virus-like particles (VLPs) have been suggested to be a promising candidate for universal influenza vaccine. In this study, ferrets were intramuscularly immunized with 2009 H1N1 split HA vaccine ("Split") alone, influenza split vaccine supplemented with M2e5x VLP ("Split+M2e5x"), M2e5x VLP alone ("M2e5x"), or mock immunized. Vaccine efficacy was measured serologically and by protection against a serologically distinct viral challenge. Ferrets immunized with Split+M2e5x induced HA strain specific and conserved M2e immunity. Supplementation of M2e5x VLP to split vaccination significantly increased the immunogenicity of split vaccine compared to split alone. The Split+M2e5x ferret group showed evidence of cross-reactive protection, including faster recovery from weight loss, and reduced inflammation, as inferred from changes in peripheral leukocyte subsets, compared to mock-immunized animals. In addition, ferrets immunized with Split+M2e5x shed lower viral nasal-wash titers than the other groups. Ferrets immunized with M2e5x alone also show some protective effects, while those immunized with split vaccine alone induced no protective effects compared to mock-immunized ferrets. These studies suggest that supplementation of split vaccine with M2e5x-VLP may provide broader and improved cross-protection than split vaccine alone. Published by Elsevier Ltd.

SphinX x-ray spectrophotometer

NASA Astrophysics Data System (ADS)

Kowaliński, Mirosław

2012-05-01

This paper presents assumptions to a PhD thesis. The thesis will be based on the construction of Solar Photometer in X-rays (SphinX). SphinX was an instrument developed to detect the soft X-rays from the Sun. It was flown on board the Russian CORONAS-Photon satellite from January 30, 2009 to the end of November, 2009. During 9 months in orbit SphinX provided an excellent and unique set of observations. It revealed about 750 flares and brightenings. The instrument observed in energy range 1.0 - 15.0 keV with resolution below ~0.5 keV. Here, the SphinX instrument objectives, design, performance and operation principle are described. Below results of mechanical and thermal - vacuum tests necessary to qualify the instrument to use in space environment are presented. Also the calibration results of the instrument are discussed. In particular detail it is described the Electrical Ground Support Equipment (EGSE) for SphinX. The EGSE was used for all tests of the instrument. At the end of the paper results obtained from the instrument during operation in orbit are discussed. These results are compared with the other similar measurements performed from the separate spacecraft instruments. It is suggested design changes in future versions of SphinX.

First principles studies on the redox ability of (Ga(1-x)Zn(x))N(1-x)O(x) solid solutions and thermal reactions for H2 and O2 production on their surfaces.

PubMed

Du, Yaojun A; Chen, Yun-Wen; Kuo, Jer-Lai

2013-12-07

The (Ga1-xZnx)N1-xOx solid solution has been emerging as an effective photocatalyst for water splitting utilizing the visible solar spectrum, regarded as a host GaN bulk doped with ZnO impurities. H2 and O2 production occur simultaneously and stoichiometrically on the surface of (Ga1-xZnx)N1-xOx particles. In this work, we characterize the redox ability of (Ga1-xZnx)N1-xOx and find that a solid solution with a ZnO concentration of 0.125 < x < 0.250 is optimal for water splitting. This is consistent with the experimental finding that the maximum photocatalytic activity of (Ga1-xZnx)N1-xOx is achieved at x = 0.13. The thermal reactions of water splitting are modeled on both the GaN and an idealized (Ga1-xZnx)N1-xOx (101[combining macron]0) surface. The computed activation barriers allow us to gain some clues on the efficiency of water splitting on a specific photocatalyst surface. Our results suggest that the non-polar (101[combining macron]0) and polar (0001) surfaces may play different roles in water splitting, i.e., the (101[combining macron]0) surface is responsible for O2 production, while hydroxyl groups could dissociate on the (0001) surface.

Refined genetic mapping of X-linked Charcot-Marie-Tooth neuropathy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fain, P.R.; Barker, D.F.; Chance, P.F.

1994-02-01

Genetic linkage studies were conducted in four multigenerational families with X-linked Charcot-Marie-Tooth disease (CMTX), using 12 highly polymorphic short-tandem-repeat markers for the pericentromeric region of the X Chromosome. Pairwise linkage analysis with individual markers confirmed tight linkage of CMTX to the pericentromeric region in each family. Multipoint analyses strongly support the order DXS337-CMTX-DXS441-(DXS56, PGK1). 38 refs., 2 figs., 1 tab.

Analysis of the charmonium-like states X*(3860), X(3872), X(3915), X(3930) and X(3940) according to their strong decay behaviors

NASA Astrophysics Data System (ADS)

Yu, Guo-Liang; Wang, Zhi-Gang; Li, Zhen-Yu

2018-04-01

Inspired by the newly observed state X*(3860), we analyze the strong decay behaviors of some charmonium-like states, X*(3860), X(3872), X(3915), X(3930) and X(3940), with the 3 P 0 model. We carry out our work based on the hypothesis that all of these states are charmonium systems. Our analysis indicates that, as a 0++ charmonium state, X*(3860) can reproduce the experimental data. As for X(3872), it can tentatively be interpreted as the mixture of a {{c}}\\bar{{{c}}} system and a {\\overline{{{D}}}}{{* 0}}{{{D}}}{{0}} molecular state. If we consider X(3940) as a 31 S 0 state, its total width in the present work is much lower than the experimental result. Thus, the 31 S 0 charmonium state seems not to be a good candidate for X(3940). Furthermore, our analysis implies that it is reasonable to assign X(3915) and X(3930) to be the same state, 2++. However, combining our analysis with that in Refs.[14, 71], we speculate that X(3915)/X(3930) might also be the mixture of a {{c}}\\bar{{{c}}} system and a molecular state. Supported by the Fundamental Research Funds for the Central Universities (2016MS133)

On the physical parameters for Centaurus X-3 and Hercules X-1.

NASA Technical Reports Server (NTRS)

Mccluskey, G. E., Jr.; Kondo, Y.

1972-01-01

It is shown how upper and lower limits on the physical parameters of X-ray sources in Centaurus X-3 and Hercules X-1 may be determined from a reasonably simple and straightforward consideration. The basic assumption is that component A (the non-X-ray emitting component) is not a star collapsing toward its Schwartzschild radius (i.e., a black hole). This assumption appears reasonable since component A (the radius of the central occulting star) appears to physically occult component X. If component A is a 'normal' star, both observation and theory indicate that its mass is not greater than about 60 solar masses. The possibility in which component X is either a neutron star or a white dwarf is considered.

Impact of aircraft NO x emission on NO x and ozone over China

NASA Astrophysics Data System (ADS)

Liu, Yu; Isaksen, I. S. A.; Sundet, J. K.; Zhou, Xiuji; Ma, Jianzhong

2003-07-01

A three-dimensional global chemistry transport model (OSLO CTM2) is used to investigate the impact of subsonic aircraft NO x emission on NO x and ozone over China in terms of a year 2000 scenario of subsonic aircraft NO x emission. The results show that subsonic aircraft NO x emission significantly affects northern China, which makes NO x at 250 hPa increase by about 50 pptv with the highest percentage of 60% in January, and leading to an ozone increase of 8 ppbv with 5% relative change in April. The NO x increase is mainly attributed to the transport process, but ozone increase is produced by the chemical process. The NO x increases by less than 10 pptv by virtue of subsonic aircraft NO x emission over China, and ozone changes less than 0.4 ppbv. When subsonic aircraft NO x emission over China is doubled, its influence is still relatively small.

Polarimetry of X-rays and messengers of High Energy phenomena

NASA Astrophysics Data System (ADS)

Costa, E.

2017-05-01

Astrophysics of High Energies has been historically based on radio, X-ray and γ -ray data. Understanding the mechanism and the site of acceleration of Cosmic Rays, has been probably the most important goal of this discipline. Recently high energy neutrinos and gravitational waves have shown up as new messengers and we expect a major role from X-ray observations, to understand the nature and location of the emitters. In fact X-rays have been for more than half a century the driver to study the Violent Universe. Yet one feature of this messengers, the Polarimetry, is still totally unexploited. Within a few years, a mission will add two important parameters to understand the physical context of high energy phenomena, namely the amount and angle of X-ray polarimetry.

NASA's Future X-ray Missions: From Constellation-X to Generation-X

NASA Technical Reports Server (NTRS)

Hornschemeier, A.

2006-01-01

Among the most important topics in modern astrophysics are the formation and evolution of supermassive black holes in concert with galaxy bulges, the nature of the dark energy equation of state, and the self-regulating symmetry imposed by both stellar and AGN feedback. All of these topics are readily addressed with observations at X-ray wavelengths. NASA's next major X-ray observatory is Constellation-X, which is being developed to perform spatially resolved high-resolution X-ray spectroscopy. Con-X will directly measure the physical properties of material near black holes' last stable orbits and the absolute element abundances and velocities of hot gas in clusters of galaxies. The Con-X mission will be described, as well as its successor, Generation-X (anticipated to fly approx.1 decade after Con-X). After describing these missions and their driving science areas, the talk will focus on areas in which Chandra observing programs may enable science with future X-ray observatories. These areas include a possible ultra-deep Chandra imaging survey as an early Universe pathfinder, a large program to spatially resolve the hot intracluster medium of massive clusters to aid dark energy measurements, and possible deep spectroscopic observations to aid in preparatory theoretical atomic physics work needed for interpreting Con-X spectra.

Measurement of the x- and Q-dependence of the asymmetry A on the nucleon

NASA Astrophysics Data System (ADS)

Clas Collaboration; Dharmawardane, K. V.; Kuhn, S. E.; Bosted, P.; Prok, Y.; Adams, G.; Ambrozewicz, P.; Anghinolfi, M.; Asryan, G.; Avakian, H.; Bagdasaryan, H.; Baillie, N.; Ball, J. P.; Baltzell, N. A.; Barrow, S.; Batourine, V.; Battaglieri, M.; Beard, K.; Bedlinskiy, I.; Bektasoglu, M.; Bellis, M.; Benmouna, N.; Biselli, A. S.; Bonner, B. E.; Bouchigny, S.; Boiarinov, S.; Bradford, R.; Branford, D.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Butuceanu, C.; Calarco, J. R.; Careccia, S. L.; Carman, D. S.; Carnahan, B.; Cazes, A.; Chen, S.; Cole, P. L.; Collins, P.; Coltharp, P.; Cords, D.; Corvisiero, P.; Crabb, D.; Crannell, H.; Crede, V.; Cummings, J. P.; de Masi, R.; Devita, R.; de Sanctis, E.; Degtyarenko, P. V.; Denizli, H.; Dennis, L.; Deur, A.; Djalali, C.; Dodge, G. E.; Donnelly, J.; Doughty, D.; Dragovitsch, P.; Dugger, M.; Dytman, S.; Dzyubak, O. P.; Egiyan, H.; Egiyan, K. S.; Elouadrhiri, L.; Eugenio, P.; Fatemi, R.; Fedotov, G.; Feuerbach, R. J.; Forest, T. A.; Funsten, H.; Garçon, M.; Gavalian, G.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Golovatch, E.; Gonenc, A.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guillo, M.; Guler, N.; Guo, L.; Gyurjyan, V.; Hadjidakis, C.; Hafidi, K.; Hakobyan, R. S.; Hardie, J.; Heddle, D.; Hersman, F. W.; Hicks, K.; Hleiqawi, I.; Holtrop, M.; Huertas, M.; Hyde-Wright, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Ito, M. M.; Jenkins, D.; Jo, H. S.; Joo, K.; Juengst, H. G.; Keith, C.; Kellie, J. D.; Khandaker, M.; Kim, K. Y.; Kim, K.; Kim, W.; Klein, A.; Klein, F. J.; Klusman, M.; Kossov, M.; Kramer, L. H.; Kubarovsky, V.; Kuhn, J.; Kuleshov, S. V.; Lachniet, J.; Laget, J. M.; Langheinrich, J.; Lawrence, D.; Li, Ji; Lima, A. C. S.; Livingston, K.; Lu, H.; Lukashin, K.; MacCormick, M.; Manak, J. J.; Markov, N.; McAleer, S.; McKinnon, B.; McNabb, J. W. C.; Mecking, B. A.; Mestayer, M. D.; Meyer, C. A.; Mibe, T.; Mikhailov, K.; Minehart, R.; Mirazita, M.; Miskimen, R.; Mokeev, V.; Morand, L.; Morrow, S. A.; Moteabbed, M.; Mueller, J.; Mutchler, G. S.; Nadel-Turonski, P.; Napolitano, J.; Nasseripour, R.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Niczyporuk, B. B.; Niroula, M. R.; Niyazov, R. A.; Nozar, M.; O'Rielly, G. V.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Paterson, C.; Philips, S. A.; Pierce, J.; Pivnyuk, N.; Pocanic, D.; Pogorelko, O.; Polli, E.; Pozdniakov, S.; Preedom, B. M.; Price, J. W.; Protopopescu, D.; Qin, L. M.; Raue, B. A.; Riccardi, G.; Ricco, G.; Ripani, M.; Ritchie, B. G.; Ronchetti, F.; Rosner, G.; Rossi, P.; Rowntree, D.; Rubin, P. D.; Sabatié, F.; Salgado, C.; Santoro, J. P.; Sapunenko, V.; Schumacher, R. A.; Serov, V. S.; Sharabian, Y. G.; Shaw, J.; Shvedunov, N. V.; Skabelin, A. V.; Smith, E. S.; Smith, L. C.; Sober, D. I.; Stavinsky, A.; Stepanyan, S. S.; Stepanyan, S.; Stokes, B. E.; Stoler, P.; Strakovsky, I. I.; Strauch, S.; Suleiman, R.; Taiuti, M.; Taylor, S.; Tedeschi, D. J.; Thoma, U.; Thompson, R.; Tkabladze, A.; Tkachenko, S.; Todor, L.; Tur, C.; Ungaro, M.; Vineyard, M. F.; Vlassov, A. V.; Weinstein, L. B.; Weygand, D. P.; Williams, M.; Wolin, E.; Wood, M. H.; Yegneswaran, A.; Yun, J.; Zana, L.; Zhang, J.; Zhao, B.; Zhao, Z.

2006-09-01

We report results for the virtual photon asymmetry A on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton (NH315) and deuteron (ND315) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present Letter, we concentrate on our results for A(x,Q) and the related ratio g/F(x,Q) in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer Q from 0.05 to 5.0GeV and in final-state invariant mass W up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong Q-dependence of A(x,Q) for W below 2 GeV. At higher W, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but A(x,Q) is not strictly Q-independent. We add significantly to the world data set at high x, up to x=0.6. Our data exceed the SU(6)-symmetric quark model expectation for both the proton and the deuteron while being consistent with a negative d-quark polarization up to our highest x. This data set should improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.

Covalently Linked Tandem Lesions in DNA

PubMed Central

Patrzyc, Helen B.; Dawidzik, Jean B.; Budzinski, Edwin E.; Freund, Harold G.; Wilton, John H.; Box, Harold C.

2013-01-01

Reactive oxygen species (ROS) generate a type of DNA damage called tandem lesions, two adjacent nucleotides both modified. A subcategory of tandem lesions consists of adjacent nucleotides linked by a covalent bond. Covalently linked tandem lesions generate highly characteristic liquid chromotography-tandem mass spectrometry (LC-MS/MS) elution profiles. We have used this property to comprehensively survey X-irradiated DNA for covalently linked tandem lesions. A total of 15 tandem lesions were detected in DNA irradiated in deoxygenated aqueous solution, five tandem lesions were detected in DNA that was irradiated in oxygenated solution. PMID:23106212

Accuracy assessment of TanDEM-X IDEM using airborne LiDAR on the area of Poland

NASA Astrophysics Data System (ADS)

Woroszkiewicz, Małgorzata; Ewiak, Ireneusz; Lulkowska, Paulina

2017-06-01

The TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) mission launched in 2010 is another programme - after the Shuttle Radar Topography Mission (SRTM) in 2000 - that uses space-borne radar interferometry to build a global digital surface model. This article presents the accuracy assessment of the TanDEM-X intermediate Digital Elevation Model (IDEM) provided by the German Aerospace Center (DLR) under the project "Accuracy assessment of a Digital Elevation Model based on TanDEM-X data" for the southwestern territory of Poland. The study area included: open terrain, urban terrain and forested terrain. Based on a set of 17,498 reference points acquired by airborne laser scanning, the mean errors of average heights and standard deviations were calculated for areas with a terrain slope below 2 degrees, between 2 and 6 degrees and above 6 degrees. The absolute accuracy of the IDEM data for the analysed area, expressed as a root mean square error (Total RMSE), was 0.77 m.

SphinX: The Solar Photometer in X-Rays

NASA Astrophysics Data System (ADS)

Gburek, Szymon; Sylwester, Janusz; Kowalinski, Miroslaw; Bakala, Jaroslaw; Kordylewski, Zbigniew; Podgorski, Piotr; Plocieniak, Stefan; Siarkowski, Marek; Sylwester, Barbara; Trzebinski, Witold; Kuzin, Sergey V.; Pertsov, Andrey A.; Kotov, Yurij D.; Farnik, Frantisek; Reale, Fabio; Phillips, Kenneth J. H.

2013-04-01

Solar Photometer in X-rays (SphinX) was a spectrophotometer developed to observe the Sun in soft X-rays. The instrument observed in the energy range ≈ 1 - 15 keV with resolution ≈ 0.4 keV. SphinX was flown on the Russian CORONAS-PHOTON satellite placed inside the TESIS EUV and X telescope assembly. The spacecraft launch took place on 30 January 2009 at 13:30 UT at the Plesetsk Cosmodrome in Russia. The SphinX experiment mission began a couple of weeks later on 20 February 2009 when the first telemetry dumps were received. The mission ended nine months later on 29 November 2009 when data transmission was terminated. SphinX provided an excellent set of observations during very low solar activity. This was indeed the period in which solar activity dropped to the lowest level observed in X-rays ever. The SphinX instrument design, construction, and operation principle are described. Information on SphinX data repositories, dissemination methods, format, and calibration is given together with general recommendations for data users. Scientific research areas in which SphinX data find application are reviewed.

NACA Aircraft on Lakebed - D-558-2, X-1B, and X-1E

NASA Technical Reports Server (NTRS)

1955-01-01

Early NACA research aircraft on the lakebed at the High Speed Research Station in 1955: Left to right: X-1E, D-558-2, X-1B There were four versions of the original Bell X-1 rocket-powered research aircraft that flew at the NACA High-Speed Flight Research Station, Edwards, California. The bullet-shaped X-1 aircraft were built by Bell Aircraft Corporation, Buffalo, N.Y. for the U.S. Army Air Forces (after 1947, U.S. Air Force) and the National Advisory Committee for Aeronautics (NACA). The X-1 Program was originally designated the XS-1 for EXperimental Supersonic. The X-1's mission was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the 'sound barrier.' Three different X-1s were built and designated: X-1-1, X-1-2 (later modified to become the X-1E), and X-1-3. The basic X-1 aircraft were flown by a large number of different pilots from 1946 to 1951. The X-1 Program not only proved that humans could go beyond the speed of sound, it reinforced the understanding that technological barriers could be overcome. The X-1s pioneered many structural and aerodynamic advances including extremely thin, yet extremely strong wing sections; supersonic fuselage configurations; control system requirements; powerplant compatibility; and cockpit environments. The X-1 aircraft were the first transonic-capable aircraft to use an all-moving stabilizer. The flights of the X-1s opened up a new era in aviation. The first X-1 was air-launched unpowered from a Boeing B-29 Superfortress on January 25, 1946. Powered flights began in December 1946. On October 14, 1947, the X-1-1, piloted by Air Force Captain Charles 'Chuck' Yeager, became the first aircraft to exceed the speed of sound, reaching about 700 miles per hour (Mach 1.06) and an altitude of 43,000 feet. The number 2 X-1 was modified and redesignated the X-1E. The modifications included adding a conventional canopy, an ejection seat, a low-pressure fuel system

The Binary Asteroid in-situ Explorer (BASiX) Mission

NASA Astrophysics Data System (ADS)

Dissly, Richard; Scheeres, D. J.; Nilsen, E.; Roark, S.; Frazier, W.; Bank, T.; Rosing, D.; Jordan, E.; BASiX Science Team

2010-10-01

The Binary Asteroid in-situ Explorer (BASiX) Mission represents the next phase of asteroid exploration, carrying out geophysical experiments by active engagement with an asteroid in a controlled and repeatable manner. BASiX will address new and timely scientific goals that address unresolved issues at the heart of our understanding of these bodies and which serve as barriers to their future exploration. A primary objective of the BASiX Mission is to determine the fundamental mechanical and strength properties of an asteroid through the creation of craters on the asteroid surface using calibrated charges. BASiX also takes advantage of these experiments to further understand the weathering and seismic properties of an asteroid. By carrying out these experiments at a binary Near Earth Asteroid (NEA), BASiX also advances our understanding of these ubiquitous bodies in the small asteroid population. BASiX is an efficient and simple mission concept that can deliver revolutionary science with its threshold mission and adds substantial enhancements with its baseline mission. BASiX assembles an international team of top small body scientists and astronomers and is led by PI Dan Scheeres (University of Colorado). BASiX is managed by JPL, which is also where mission and science operations will be based. The BASiX Spacecraft is built by Ball Aerospace & Technologies Corp. Instruments are built by JPL and Ball with additional contributed instruments from CNES.

X-15 landing on lakebed

NASA Technical Reports Server (NTRS)

1961-01-01

The North American X-15 settles to the lakebed after a research flight from what is now the NASA Dryden Flight Research Center, Edwards, California. The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of rated thrust (actual thrust reportedly climbed to 60,000 lb). North American Aviation built three X-15 aircraft for the program. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow-on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and canted horizontal surfaces on the tail to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control. Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of about 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing. Generally, one of two types of X-15 flight profiles

(Ba1- x Bi0.33 x Sr0.67 x )(Ti1- x Bi0.67 x V0.33 x )O3 and (Ba1- x Bi0.5 x Sr0.5 x )(Ti1- x Bi0.5 x Ti0.5 x )O3 solid solutions: phase evolution, microstructure, dielectric properties and impedance analysis

NASA Astrophysics Data System (ADS)

Chen, Xiuli; Li, Xiaoxia; Yan, Xiao; Liu, Gaofeng; Zhou, Huanfu

2018-06-01

Perovskite solid solution ceramics of (Ba1- x Bi0.33 x Sr0.67 x )(Ti1- x Bi0.67 x V0.33 x )O3 and (Ba1- x Bi0.5 x Sr0.5 x )(Ti1- x Bi0.5 x Ti0.5 x )O3 (BBSTBV, BBSTBT, 0.02 ≤ x ≤ 0.2) were prepared by the traditional solid state reaction technique. The phase evolution, microstructure and dielectric properties of BBSTBV and BBSTBT ceramics were researched. X-Ray diffraction results illustrated that both BBSTBV and BBSTBT could form a homogenous solid solution which has a similar structure with BaTiO3. The optimized properties of (Ba0.8Bi0.1Sr0.1)(Ti0.8Bi0.1Ti0.1)O3 ceramics with stable ɛ r ( 1769-2293), small Δ ɛ/ ɛ 25 °C values (± 15%) over a broad temperature range from - 58 to 151 °C and low tan δ ≤ 0.03 from - 11 to 131 °C were obtained. In the high-temperature region, the relaxation and conduction process are attributed to the thermal activation and the oxygen vacancies may be the ionic charge carriers in perovskite ferroelectrics.

X-rays from superbubbles in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Chu, You-Hua; Mac Low, Mordecai-Marc

1990-01-01

Diffuse X-ray emission not associated with known supernova remnants (SNRs) are found in seven Large Magellanic Cloud H II complexes encompassing 10 OB associations: N44, N51D, N57A, N70, N154, N157 (30 Dor), and N158. Their X-ray luminosities range from 7 x 10 to the 34th ergs/s in N57A to 7 x 10 to the 36th ergs/s in 30 Dor. All, except 30 Dor, have simple ring morphologies, indicating shell structures. Modeling these as superbubbles, it is found that the X-ray luminosities expected from their hot interiors fall an order of magnitude below the observed values. SNRs close to the center of a superbubble add very little emission, but it is calculated that off-center SNRs hitting the ionized shell could explain the observed emission.

Investigation of ZrO x /ZrC-ZrN/Zr thin-film structural evolution and their degradation using X-ray diffraction and Raman spectrometry

NASA Astrophysics Data System (ADS)

Usmani, B.; Vijay, V.; Chhibber, R.; Dixit, A.

2016-11-01

The thin-film structures of DC/FR magnetron-sputtered ZrO x /ZrC-ZrN/Zr tandem solar-selective coatings are investigated using X-ray diffraction and room-temperature Raman spectroscopic measurements. These studies suggest that the major contribution is coming from h-ZrN0.28, c-ZrC, h-Zr3C2 crystallographic phases in ZrN-ZrC absorber layer, in conjunction with mixed ZrO x crystallographic phases. The change in structure for thermally annealed samples has been examined and observed that cubic and hexagonal ZrO x phase converted partially into tetragonal and monoclinic ZrO x phases, whereas hexagonal and cubic ZrN phases, from absorber layer, have not been observed for these thermally treated samples in air. These studies suggest that thermal treatment may lead to the loss of ZrN phase in absorber, degrading the thermal response for the desired wavelength range in open ambient conditions in contrast to vacuum conditions.

Supplementation of H1N1pdm09 split vaccine with heterologous tandem repeat M2e5x virus-like particles confers improved cross-protection in ferrets

PubMed Central

Music, Nedzad; Reber, Adrian J.; Kim, Min-Chul; York, Ian A.; Kang, Sang-Moo

2015-01-01

Current influenza vaccines induce strain-specific immunity to the highly variable hemagglutinin (HA) protein. It is therefore a high priority to develop vaccines that induce broadly cross-protective immunity to different strains of influenza. Since influenza A M2 proteins are highly conserved among different strains, five tandem repeats of the extracellular peptide of M2 in a membrane-anchored form on virus-like particles (VLPs) have been suggested to be a promising candidate for universal influenza vaccine. In this study, ferrets were intramuscularly immunized with 2009 H1N1 split HA vaccine (“Split”) alone, influenza split vaccine supplemented with M2e5x VLP (“Split+M2e5x”), M2e5x VLP alone (“M2e5x”), or mock immunized. Vaccine efficacy was measured serologically and by protection against a serologically distinct viral challenge. Ferrets immunized with Split+M2e5x induced HA strain specific and conserved M2e immunity. Supplementation of M2e5x VLP to split vaccination significantly increased the immunogenicity of split vaccine compared to split alone. The Split+M2e5x ferret group showed evidence of cross-reactive protection, including faster recovery from weight loss, and reduced inflammation, as inferred from changes in peripheral leukocyte subsets, compared to mock-immunized animals. In addition, ferrets immunized with Split+M2e5x shed lower viral nasal-wash titers than the other groups. Ferrets immunized with M2e5x alone also show some protective effects, while those immunized with split vaccine alone induced no protective effects compared to mock-immunized ferrets. These studies suggest that supplementation of split vaccine with M2e5x-VLP may provide broader and improved cross-protection than split vaccine alone. PMID:26709639

Monitoring X-Ray Emission from X-Ray Bursters

NASA Technical Reports Server (NTRS)

Halpern, Jules P.; Kaaret, Philip

1999-01-01

The scientific goal of this project was to monitor a selected sample of x-ray bursters using data from the All-Sky Monitor (ASM) on the Rossi X-Ray Timing Explorer together with data from the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory to study the long-term temporal evolution of these sources in the x-ray and hard x-ray bands. The project was closely related to "Long-Term Hard X-Ray Monitoring of X-Ray Bursters", NASA project NAG5-3891, and and "Hard x-ray emission of x-ray bursters", NASA project NAG5-4633, and shares publications in common with both of these. The project involved preparation of software for use in monitoring and then the actual monitoring itself. These efforts have lead to results directly from the ASM data and also from Target of Opportunity Observations (TOO) made with the Rossi X-Ray Timing Explorer based on detection of transient hard x-ray outbursts with the ASM and BATSE.

Equal-Curvature X-Ray Telescopes

NASA Technical Reports Server (NTRS)

Saha, Timo T.; Zhang, William

2002-01-01

We introduce a new type of x-ray telescope design; an Equal-Curvature telescope. We simply add a second order axial sag to the base grazing incidence cone-cone telescope. The radius of curvature of the sag terms is the same on the primary surface and on the secondary surface. The design is optimized so that the on-axis image spot at the focal plane is minimized. The on-axis RMS (root mean square) spot diameter of two studied telescopes is less than 0.2 arc-seconds. The off-axis performance is comparable to equivalent Wolter type 1 telescopes.

X-2 on Transportation Dolly

NASA Technical Reports Server (NTRS)

1952-01-01

This 1952 photograph shows the X-2 #2 aircraft mounted on a special transportation dolly at Edwards Air Force Base, California. The dolly was steerable and was used for transporting the X-2 around and for towing it off the lakebed at Edwards Air Force Base after a landing. This was the number 2 airplane (46-675), which was lost on May 12, 1953, on a captive flight over Lake Ontario when the airplane exploded during a liquid-oxygen topoff test, killing the pilot, Jean Ziegler, and EB-50A crewman Frank Wolko. Almost no debris was recovered from Lake Ontario, so no cause for the explosion could be determined. Later, however, investigations of similar explosions in the X-1 #3, X-1A, and X-1D traced the problem to Ulmer leather gaskets, which exuded tricresyl phosphate. This substance caused detonations in the supercold atmosphere of the airplanes' liquid oxygen tanks. As the X-2 #2 also had these gaskets, they were probably the cause of the explosion in that aircraft as well. The X-2 was a swept-wing, rocket-powered aircraft designed to fly faster than Mach 3 (three times the speed of sound). It was built for the U.S. Air Force by the Bell Aircraft Company, Buffalo, New York. The X-2 was flown to investigate the problems of aerodynamic heating as well as stability and control effectiveness at high altitudes and high speeds (in excess of Mach 3). Bell aircraft built two X-2 aircraft. These were constructed of K-monel (a copper and nickel alloy) for the fuselage and stainless steel for the swept wings and control surfaces. The aircraft had ejectable nose capsules instead of ejection seats because the development of ejection seats had not reached maturity at the time the X-2 was conceived. The X-2 ejection canopy was successfully tested using a German V-2 rocket. The X-2 used a skid-type landing gear to make room for more fuel. The airplane was air launched from a modified Boeing B-50 Superfortress Bomber. X-2 Number 1 made its first unpowered glide flight on Aug. 5, 1954

Active x-ray optics for Generation-X, the next high resolution x-ray observatory

NASA Astrophysics Data System (ADS)

Elvis, Martin; Brissenden, R. J.; Fabbiano, G.; Schwartz, D. A.; Reid, P.; Podgorski, W.; Eisenhower, M.; Juda, M.; Phillips, J.; Cohen, L.; Wolk, S.

2006-06-01

X-rays provide one of the few bands through which we can study the epoch of reionization, when the first galaxies, black holes and stars were born. To reach the sensitivity required to image these first discrete objects in the universe needs a major advance in X-ray optics. Generation-X (Gen-X) is currently the only X-ray astronomy mission concept that addresses this goal. Gen-X aims to improve substantially on the Chandra angular resolution and to do so with substantially larger effective area. These two goals can only be met if a mirror technology can be developed that yields high angular resolution at much lower mass/unit area than the Chandra optics, matching that of Constellation-X (Con-X). We describe an approach to this goal based on active X-ray optics that correct the mid-frequency departures from an ideal Wolter optic on-orbit. We concentrate on the problems of sensing figure errors, calculating the corrections required, and applying those corrections. The time needed to make this in-flight calibration is reasonable. A laboratory version of these optics has already been developed by others and is successfully operating at synchrotron light sources. With only a moderate investment in these optics the goals of Gen-X resolution can be realized.

Potential of Multitemporal Tandem-X Derived Crop Surface Models for Maize Growth Monitoring

NASA Astrophysics Data System (ADS)

Hütt, C.; Tilly, N.; Schiedung, H.; Bareth, G.

2016-06-01

In this study, first results of retrieving plant heights of maize fields from multitemporal TanDEM-X images are shown. Three TanDEM-X dual polarization spotlight acquisitions were taken over a rural area in Germany in the growing season 2014. By interferometric processing, digital terrain models (DTM) were derived for each date with 5m resolution. From the data of the first acquisition (June 1st) taken before planting, a DTM of the bare ground is generated. The data of the following acquisition dates (July 15th, July 26th) are used to establish crop surface models (CSM). A CSM represents the crop surface of a whole field in a high resolution. By subtracting the DTM of the ground from each CSM, the actual plant height is calculated. Within these data sets 30 maize fields in the area of interest could be detected and verified by external land use data. Besides the spaceborne measurements, one of the maize fields was intensively investigated using terrestrial laser scanning (TLS), which was carried out at the same dates as the predicted TanDEM-X acquisitions. Visual inspection of the derived plant heights, and accordance of the individually processed polarisations over the maize fields, demonstrate the feasibility of the proposed method. Unfortunately, the infield variability of the intensively monitored field could not be successfully captured in the TanDEM-X derived plant heights and merely the general trend is visible. Nevertheless, the study shows the potential of the TanDEM-X constellation for maize height monitoring on field level.

X43 Hyper-X

NASA Image and Video Library

2004-02-11

NASA's Hyper-x Program Manager, Vince Rausch talks about the upcoming launch of the X43A vehicle over the Pacific Ocean later this month from his office at NASA Langley Research Center in Hampton, VA. Hyper X is a high risk, high payoff program. The flight of the X43 A will demonstrated in flight for the first time, air breathing hypersonic propulsion technology. (Photo by Jeff Caplan)

X-Pinch And Its Applications In X-ray Radiograph

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou Xiaobing; Wang Xinxin; Liu Rui

2009-07-07

An X-pinch device and the related diagnostics of x-ray emission from X-pinch were briefly described. The time-resolved x-ray measurements with photoconducting diodes show that the x-ray pulse usually consists of two subnanosecond peaks with a time interval of about 0.5 ns. Being consistent with these two peaks of the x-ray pulse, two point x-ray sources of size ranging from 100 mum to 5 mum and depending on cut-off x-ray photon energy were usually observed on the pinhole pictures. The x-pinch was used as x-ray source for backlighting of the electrical explosion of single wire and the evolution of X-pinch, andmore » for phase-contrast imaging of soft biological objects such as a small shrimp and a mosquito.« less

A special ionisation chamber for quality control of diagnostic and mammography X ray equipment.

PubMed

Costa, A M; Caldas, L V E

2003-01-01

A quality control program for X ray equipment used for conventional radiography and mammography requires the constancy check of the beam qualities in terms of the half-value layers. In this work, a special double-faced parallel-plate ionisation chamber was developed with inner electrodes of different materials, in a tandem system. Its application will be in quality control programs of diagnostic and mammography X ray equipment for confirmation of half-value layers previously determined by the conventional method. Moreover, the chamber also may be utilised for measurements of air kerma values (and air kerma rates) in X radiation fields used for conventional radiography and mammography. The chamber was studied in relation to the characteristics of saturation, ion collection efficiency, polarity effects, leakage current, and short-term stability. The energy dependence in response of each of the two faces of the chamber was determined over the conventional radiography and mammography X ray ranges (unattenuated beams). The different energy response of the two faces of the chamber allowed the formation of a tandem system useful for the constancy check of beam qualities.

X-15 landing on lakebed

NASA Technical Reports Server (NTRS)

1960-01-01

In this 17-second video clip, the X-15 is shown in flight and then landing on Rogers Dry Lakebed adjacent to Edwards Air Force Base. It is followed by an F-104A chase aircraft, whose pilot provided a second set of eyes to the X-15 pilot on landing in case of any problems. The video shows the skids on the back of the X-15 contacting the lakebed, with the aircraft's nose then rotating downward until the nose landing gear was on the lakebed.

American X-Vehicles: An Inventory, X-1 to X-45

NASA Technical Reports Server (NTRS)

Miller, Jay; Jenkins, Dennis R.

2000-01-01

For a while, it seemed the series of experimental aircraft sponsored by the Air Force and the National Aeronautics and Space Administration had run its course. Between the late 1940s and the late 1970s, almost thirty designations had been allocated to aircraft meant to explore new flight regimes or untried technologies. Then, largely, it ended. But there was a resurgence in the mid- to late-1990s, and as we enter the year 2000 the designations are up to X-45. Many have a misconception that X-Planes have always explored the high-speed and high-altitude flight regimes, something popularized by Chuck Yeager in the original X-1 and the exploits of the twelve men that flew the X-15. Although these flight regimes have always been in the spotlight, many others have been explored by X-Planes. The little Bensen X-25 never exceeded 85 mph, and others were limited to speeds of several hundred mph. There has been some criticism that the use of X designations has been corrupted somewhat by including what are essentially prototypes of future operational aircraft, especially the two JSF demonstrators. But this is not new-the X-11 and X-12 from the 1950s were going to be prototypes of the Atlas intercontinental ballistic missile, and the still-born Lockheed X-27 was always intended as a prototype of a production aircraft. So although this practice does not represent the best use of X designations it is not without precedent. This document is an inventory of the experimental aircraft starting with the X-1 aircraft and ending with the X-45 aircraft.

A combined multi-interferogram algorithm for high resolution DEM reconstruction over deformed regions with TerraSAR-X data

NASA Astrophysics Data System (ADS)

Zhao, Chaoying; Qu, Feifei; Zhang, Qin; Zhu, Wu

2012-10-01

The accuracy of DEM generated with interferometric synthetic aperture radar (InSAR) technique mostly depends on phase unwrapping errors, atmospheric effects, baseline errors and phase noise. The first term is more serious if the high-resolution TerraSAR-X data over urban regions and mountainous regions are applied. In addition, the deformation effect cannot be neglected if the study regions are suffering from surface deformation within the SAR acquisition dates. In this paper, several measures have been taken to generate high resolution DEM over urban regions and mountainous regions with TerraSAR data. The SAR interferometric pairs are divided into two subsets: (a) DEM subsets and (b) deformation subsets. These two interferometric sets serve to generate DEM and deformation, respectively. The external DEM is applied to assist the phase unwrapping with "remove-restore" procedure. The deformation phase is re-scaled and subtracted from each DEM observations. Lastly, the stochastic errors including atmospheric effects and phase noise are suppressed by averaging heights from several interferograms with weights. Six TerraSAR-X data are applied to generate a 6-m-resolution DEM over Xi'an, China using these procedures. Both discrete GPS heights and local high resolution and high precision DEM data are applied to calibrate the DEM generated with our algorithm, and around 4.1 m precision is achieved.

Photoluminescence studies on Cd(1-x)Zn(x)S:Mn2+ nanocrystals.

PubMed

Sethi, Ruchi; Kumar, Lokendra; Pandey, A C

2009-09-01

Highly monodispersed, undoped and doped with Mn2+, binary and ternary (CdS, ZnS, Cd(1-x)Zn(x)S) compound semiconductor nanocrystals have been synthesized by co-precipitation method using citric acid as a stabilizer. As prepared sample are characterized by X-ray diffraction, Small angle X-ray scattering, Transmission electron microscope, Optical absorption and Photoluminescence spectroscopy, for their optical and structural properties. X-ray diffraction, Small angle X-ray scattering and Transmission electron microscope results confirm the preparation of monodispersed nanocrystals. Photoluminescence studies show a significant blue shift in the wavelength with an increasing concentration of Zn in alloy nanocrystals.

Seebeck Coefficient of Cation-Substituted Disulfides CuCr1-x Fe x S2 and Cu1-x Fe x CrS2

NASA Astrophysics Data System (ADS)

Korotaev, Evgeniy V.; Syrokvashin, Mikhail M.; Filatova, Irina Yu.; Pelmenev, Konstantin G.; Zvereva, Valentina V.; Peregudova, Natalya N.

2018-03-01

The effect of cation substitution on the Seebeck coefficient of CuCr1-x Fe x S2 (x = 0 to 0.30) and Cu1-x Fe x CrS2 (x = 0 to 0.03) in the temperature range of 100 K to 450 K has been investigated. Increasing iron concentration led to a metal-insulator transition which suppressed the thermoelectric power. However, for low iron concentration (x < 0.03), the Seebeck coefficient of CuCr1-x Fe x S2 and Cu1-x Fe x CrS2 exceeded the values for the undoped copper-chromium disulfide matrix CuCrS2 at temperature below 300 K.

Ga/1-x/Al/x/As LED structures grown on GaP substrates.

NASA Technical Reports Server (NTRS)

Woodall, J. M.; Potemski, R. M.; Blum, S. E.; Lynch, R.

1972-01-01

Ga(1-x)Al(x)As light-emitting diode structures have been grown on GaP substrates by the liquid-phase-epitaxial method. In spite of the large differences in lattice constants and thermal-expansion coefficients, room-temperature efficiencies up to 5.5% in air have been observed for a peak emission of 8500 A. Using undoped GaP substrates, which are transparent to the infrared and red portions of the spectrum, thin structures of Ga(1-x)Al(x)As with large external efficiencies can now be made.

X-Ray Emission from the Soft X-Ray Transient Aquila X-1

NASA Technical Reports Server (NTRS)

Tavani, Marco

1998-01-01

Aquila X-1 is the most prolific of soft X-ray transients. It is believed to contain a rapidly spinning neutron star sporadically accreting near the Eddington limit from a low-mass companion star. The interest in studying the repeated X-ray outbursts from Aquila X-1 is twofold: (1) studying the relation between optical, soft and hard X-ray emission during the outburst onset, development and decay; (2) relating the spectral component to thermal and non-thermal processes occurring near the magnetosphere and in the boundary layer of a time-variable accretion disk. Our investigation is based on the BATSE monitoring of Aquila X-1 performed by our group. We observed Aquila X-1 in 1997 and re-analyzed archival information obtained in April 1994 during a period of extraordinary outbursting activity of the source in the hard X-ray range. Our results allow, for the first time for this important source, to obtain simultaneous spectral information from 2 keV to 200 keV. A black body (T = 0.8 keV) plus a broken power-law spectrum describe accurately the 1994 spectrum. Substantial hard X-ray emission is evident in the data, confirming that the accretion phase during sub-Eddington limit episodes is capable of producing energetic hard emission near 5 x 10(exp 35) ergs(exp -1). A preliminary paper summarizes our results, and a more comprehensive account is being written. We performed a theoretical analysis of possible emission mechanisms, and confirmed that a non-thermal emission mechanism triggered in a highly sheared magnetosphere at the accretion disk inner boundary can explain the hard X-ray emission. An anticorrelation between soft and hard X-ray emission is indeed prominently observed as predicted by this model.

Diagnosing and Mapping Pulmonary Emphysema on X-Ray Projection Images: Incremental Value of Grating-Based X-Ray Dark-Field Imaging

PubMed Central

Meinel, Felix G.; Schwab, Felix; Schleede, Simone; Bech, Martin; Herzen, Julia; Achterhold, Klaus; Auweter, Sigrid; Bamberg, Fabian; Yildirim, Ali Ö.; Bohla, Alexander; Eickelberg, Oliver; Loewen, Rod; Gifford, Martin; Ruth, Ronald; Reiser, Maximilian F.; Pfeiffer, Franz; Nikolaou, Konstantin

2013-01-01

Purpose To assess whether grating-based X-ray dark-field imaging can increase the sensitivity of X-ray projection images in the diagnosis of pulmonary emphysema and allow for a more accurate assessment of emphysema distribution. Materials and Methods Lungs from three mice with pulmonary emphysema and three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Median signal intensities of transmission (T), dark-field (V) and a combined parameter (normalized scatter) were compared between emphysema and control group. To determine the diagnostic value of each parameter in differentiating between healthy and emphysematous lung tissue, a receiver-operating-characteristic (ROC) curve analysis was performed both on a per-pixel and a per-individual basis. Parametric maps of emphysema distribution were generated using transmission, dark-field and normalized scatter signal and correlated with histopathology. Results Transmission values relative to water were higher for emphysematous lungs than for control lungs (1.11 vs. 1.06, p<0.001). There was no difference in median dark-field signal intensities between both groups (0.66 vs. 0.66). Median normalized scatter was significantly lower in the emphysematous lungs compared to controls (4.9 vs. 10.8, p<0.001), and was the best parameter for differentiation of healthy vs. emphysematous lung tissue. In a per-pixel analysis, the area under the ROC curve (AUC) for the normalized scatter value was significantly higher than for transmission (0.86 vs. 0.78, p<0.001) and dark-field value (0.86 vs. 0.52, p<0.001) alone. Normalized scatter showed very high sensitivity for a wide range of specificity values (94% sensitivity at 75% specificity). Using the normalized scatter signal to display the regional distribution of emphysema provides color-coded parametric maps, which show the best correlation with histopathology. Conclusion In a murine model, the complementary information provided by X

Diagnosing and mapping pulmonary emphysema on X-ray projection images: incremental value of grating-based X-ray dark-field imaging.

PubMed

Meinel, Felix G; Schwab, Felix; Schleede, Simone; Bech, Martin; Herzen, Julia; Achterhold, Klaus; Auweter, Sigrid; Bamberg, Fabian; Yildirim, Ali Ö; Bohla, Alexander; Eickelberg, Oliver; Loewen, Rod; Gifford, Martin; Ruth, Ronald; Reiser, Maximilian F; Pfeiffer, Franz; Nikolaou, Konstantin

2013-01-01

To assess whether grating-based X-ray dark-field imaging can increase the sensitivity of X-ray projection images in the diagnosis of pulmonary emphysema and allow for a more accurate assessment of emphysema distribution. Lungs from three mice with pulmonary emphysema and three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Median signal intensities of transmission (T), dark-field (V) and a combined parameter (normalized scatter) were compared between emphysema and control group. To determine the diagnostic value of each parameter in differentiating between healthy and emphysematous lung tissue, a receiver-operating-characteristic (ROC) curve analysis was performed both on a per-pixel and a per-individual basis. Parametric maps of emphysema distribution were generated using transmission, dark-field and normalized scatter signal and correlated with histopathology. Transmission values relative to water were higher for emphysematous lungs than for control lungs (1.11 vs. 1.06, p<0.001). There was no difference in median dark-field signal intensities between both groups (0.66 vs. 0.66). Median normalized scatter was significantly lower in the emphysematous lungs compared to controls (4.9 vs. 10.8, p<0.001), and was the best parameter for differentiation of healthy vs. emphysematous lung tissue. In a per-pixel analysis, the area under the ROC curve (AUC) for the normalized scatter value was significantly higher than for transmission (0.86 vs. 0.78, p<0.001) and dark-field value (0.86 vs. 0.52, p<0.001) alone. Normalized scatter showed very high sensitivity for a wide range of specificity values (94% sensitivity at 75% specificity). Using the normalized scatter signal to display the regional distribution of emphysema provides color-coded parametric maps, which show the best correlation with histopathology. In a murine model, the complementary information provided by X-ray transmission and dark-field images adds incremental

X ray spectra of X Per. [oso-8 observations

NASA Technical Reports Server (NTRS)

Becker, R. H.; Boldt, E. A.; Holt, S. S.; Pravdo, S. H.; Robinson-Saba, J.; Serlemitsos, P. J.; Swank, J. H.

1978-01-01

The cosmic X-ray spectroscopy experiment on OSO-8 observed X Per for twenty days during two observations in Feb. 1976 and Feb. 1977. The spectrum of X Per varies in phase with its 13.9 min period, hardening significantly at X-ray minimum. Unlike other X-ray binary pulsar spectra, X Per's spectra do not exhibit iron line emission or strong absorption features. The data show no evidence for a 22 hour periodicity in the X-ray intensity of X Per. These results indicate that the X-ray emission from X Per may be originating from a neutron star in a low density region far from the optically identified Be star.

X-rays from Magnetic B-type Stars

NASA Astrophysics Data System (ADS)

Fletcher, Corinne; Petit, Véronique; Caballero-Nieves, Saida Maria; Nazé, Yaël; Owocki, Stan; Wade, Gregg; Cohen, David; Townsend, Richard; David-Uraz, Alexandre; Shultz, Matt

2018-01-01

Recent surveys have found that ~10% of OB-type stars host strong (~1kG), mostly dipolar magnetic fields. The prominent idea describing the interaction between the stellar winds and the magnetic field is the magnetically confined wind shock model. In this model, the ionized wind material is forced to move along the closed magnetic field loops and collides at the magnetic equator creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the wind material confined by the magnetic fields of these stars. Some of these magnetic B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force is predicted to cause faster wind outflows along the field lines, which could lead to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this question from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere model, developed for slow rotators and implement the physics of rapid rotation. Using X-ray spectroscopy from ESA’s XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role an added centrifugal acceleration plays in the magnetospheres of these stars.

Influence of Composition on the Thermoelectric Properties of Bi1- x Sb x Thin Films

NASA Astrophysics Data System (ADS)

Rogacheva, E. I.; Nashchekina, O. N.; Orlova, D. S.; Doroshenko, A. N.; Dresselhaus, M. S.

2017-07-01

Bi1- x Sb x solid solutions have attracted much attention as promising thermoelectric (TE) materials for cooling devices at temperatures below ˜200 K and as unique model materials for solid-state science because of a high sensitivity of their band structure to changes in composition, temperature, pressure, etc. Earlier, we revealed a non-monotonic behavior of the concentration dependences of TE properties for polycrystalline Bi1- x Sb x solid solutions and attributed these anomalies to percolation effects in the solid solution, transition to a gapless state, and to a semimetal-semiconductor transition. The goal of the present work is to find out whether the non-monotonic behavior of the concentration dependences of TE properties is observed in the thin film state as well. The objects of the study are Bi1- x Sb x thin films with thicknesses in the range d = 250-300 nm prepared by thermal evaporation of Bi1- x Sb x crystals ( x = 0-0.09) onto mica substrates. It was shown that the anomalies in the dependence of the TE properties on Bi1- x Sb x crystal composition are reproduced in thin films.

Valence band offsets of Sc x Ga1-x N/AlN and Sc x Ga1-x N/GaN heterojunctions

NASA Astrophysics Data System (ADS)

Tsui, H. C. L.; Goff, L. E.; Palgrave, R. G.; Beere, H. E.; Farrer, I.; Ritchie, D. A.; Moram, M. A.

2016-07-01

The valence band offsets of Sc x Ga1-x N/AlN heterojunctions were measured by x-ray photoelectron spectroscopy (XPS) and were found to increase from 0.42 eV to 0.95 eV as the Sc content x increased from 0 to 0.15. The increase in valence band offset with increasing x is attributed to the corresponding increase in spontaneous polarization of the wurtzite structure. The Sc x Ga1-x N/AlN heterojunction is type I, similar to other III-nitride-based heterojunctions. The data also indicate that a type II staggered heterojunction, which can enhance spatial charge separation, could be formed if Sc x Ga1-x N is grown on GaN.

Comparative Analysis of InSAR Digital Surface Models for Test Area Bucharest

NASA Astrophysics Data System (ADS)

Dana, Iulia; Poncos, Valentin; Teleaga, Delia

2010-03-01

This paper presents the results of the interferometric processing of ERS Tandem, ENVISAT and TerraSAR- X for digital surface model (DSM) generation. The selected test site is Bucharest (Romania), a built-up area characterized by the usual urban complex pattern: mixture of buildings with different height levels, paved roads, vegetation, and water bodies. First, the DSMs were generated following the standard interferometric processing chain. Then, the accuracy of the DSMs was analyzed against the SPOT HRS model (30 m resolution at the equator). A DSM derived by optical stereoscopic processing of SPOT 5 HRG data and also the SRTM (3 arc seconds resolution at the equator) DSM have been included in the comparative analysis.

X-15 ship #1 on lakebed

NASA Technical Reports Server (NTRS)

1960-01-01

The X-15 aircraft, ship #1 (56-6670), sits on the lakebed early in its illustrious career of high speed flight research. The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of thrust. North American Aviation made three X-15 aircraft for the program. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and canted horizontal surfaces on the tail to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control. Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of about 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing. Generally, one of two types of X-15 flight profiles was used; a high-altitude flight plan that called for the pilot to maintain a

Magnetic phase diagram of ErGe 1-xSi x (0<x<1)

NASA Astrophysics Data System (ADS)

Thuéry, P.; El Maziani, F.; Clin, M.; Schobinger-Papamantellos, P.; Buschow, K. H. J.

1993-10-01

The composition-temperature magnetic phase diagram of ErGe 1- xSi x (0 < x < 1) has been deduced from the powder neutron diffraction investigation of the magnetic structure of several samples in the 1.5-15 K range. These compounds present an antiferromagnetic behaviour with 7.2 < TN < 11.5 K. Four magnetic phases are present: two that are commensurate with the crystal lattice (wavevectors (1/2,0,1/2) and (0,0,1/2) and two incommensurate (wavevectors (0,0, kz and ( k' x,0, k' z) with a slight deviation of kx, k' x and k' z from 1/2). Whatever x, an incommensurate phase appears below TN, the wavevector being (0,0, kz) for x < 0.40 and ( k' x,0, k' z) for x > 0.40. For 0.17 ≥ x ≤ 0.55, a first-order transition occurs as function of the temperature between these two phases. For x ≥ 0.65, a lock-in transition takes place at TIC, leading from the wavevector ( k' x,0, k' z) to (1/2,0,1/2), as was already observed in ErSi. Finally, for x < 0.17 or 0.55 < x < 0.65, the wavevectors of the incommensurate phases characterized by (0,0, kz) or ( k' x,0, k' z) respectively remain unchanged in the whole temperature range below TN. For x≥0.65, a small amount of a magnetic phase characterized by the wavevector (0,0, 1/2) coexists with the main phases, below a Néel temperature T' N slightly lower than TN. In all cases, the erbium magnetic moments are colinear along the orthorhombic α-axis; the arrangement of the moments in the commensurate phases is the same as in ErSi and the incommensurate orderings correspond to sine-wave amplitude modulations. A brief account on the theoretical interpretation of this phase diagram is finally given.

The Mapping X-ray Fluorescence Spectrometer (MapX)

NASA Astrophysics Data System (ADS)

Sarrazin, P.; Blake, D. F.; Marchis, F.; Bristow, T.; Thompson, K.

2017-12-01

Many planetary surface processes leave traces of their actions as features in the size range 10s to 100s of microns. The Mapping X-ray Fluorescence Spectrometer (MapX) will provide elemental imaging at 100 micron spatial resolution, yielding elemental chemistry at a scale where many relict physical, chemical, or biological features can be imaged and interpreted in ancient rocks on planetary bodies and planetesimals. MapX is an arm-based instrument positioned on a rock or regolith with touch sensors. During an analysis, an X-ray source (tube or radioisotope) bombards the sample with X-rays or alpha-particles / gamma-rays, resulting in sample X-ray Fluorescence (XRF). X-rays emitted in the direction of an X-ray sensitive CCD imager pass through a 1:1 focusing lens (X-ray micro-pore Optic (MPO)) that projects a spatially resolved image of the X-rays onto the CCD. The CCD is operated in single photon counting mode so that the energies and positions of individual X-ray photons are recorded. In a single analysis, several thousand frames are both stored and processed in real-time. Higher level data products include single-element maps with a lateral spatial resolution of 100 microns and quantitative XRF spectra from ground- or instrument- selected Regions of Interest (ROI). XRF spectra from ROI are compared with known rock and mineral compositions to extrapolate the data to rock types and putative mineralogies. When applied to airless bodies and implemented with an appropriate radioisotope source for alpha-particle excitation, MapX will be able to analyze biogenic elements C, N, O, P, S, in addition to the cations of the rock-forming elements >Na, accessible with either X-ray or gamma-ray excitation. The MapX concept has been demonstrated with a series of lab-based prototypes and is currently under refinement and TRL maturation.

Effects of X-Ray Dose On Rhizosphere Studies Using X-Ray Computed Tomography

PubMed Central

Zappala, Susan; Helliwell, Jonathan R.; Tracy, Saoirse R.; Mairhofer, Stefan; Sturrock, Craig J.; Pridmore, Tony; Bennett, Malcolm; Mooney, Sacha J.

2013-01-01

X-ray Computed Tomography (CT) is a non-destructive imaging technique originally designed for diagnostic medicine, which was adopted for rhizosphere and soil science applications in the early 1980s. X-ray CT enables researchers to simultaneously visualise and quantify the heterogeneous soil matrix of mineral grains, organic matter, air-filled pores and water-filled pores. Additionally, X-ray CT allows visualisation of plant roots in situ without the need for traditional invasive methods such as root washing. However, one routinely unreported aspect of X-ray CT is the potential effect of X-ray dose on the soil-borne microorganisms and plants in rhizosphere investigations. Here we aimed to i) highlight the need for more consistent reporting of X-ray CT parameters for dose to sample, ii) to provide an overview of previously reported impacts of X-rays on soil microorganisms and plant roots and iii) present new data investigating the response of plant roots and microbial communities to X-ray exposure. Fewer than 5% of the 126 publications included in the literature review contained sufficient information to calculate dose and only 2.4% of the publications explicitly state an estimate of dose received by each sample. We conducted a study involving rice roots growing in soil, observing no significant difference between the numbers of root tips, root volume and total root length in scanned versus unscanned samples. In parallel, a soil microbe experiment scanning samples over a total of 24 weeks observed no significant difference between the scanned and unscanned microbial biomass values. We conclude from the literature review and our own experiments that X-ray CT does not impact plant growth or soil microbial populations when employing a low level of dose (<30 Gy). However, the call for higher throughput X-ray CT means that doses that biological samples receive are likely to increase and thus should be closely monitored. PMID:23840640

Real-time X-ray Diffraction: Applications to Materials Characterization

NASA Technical Reports Server (NTRS)

Rosemeier, R. G.

1984-01-01

With the high speed growth of materials it becomes necessary to develop measuring systems which also have the capabilities of characterizing these materials at high speeds. One of the conventional techniques of characterizing materials was X-ray diffraction. Film, which is the oldest method of recording the X-ray diffraction phenomenon, is not quite adequate in most circumstances to record fast changing events. Even though conventional proportional counters and scintillation counters can provide the speed necessary to record these changing events, they lack the ability to provide image information which may be important in some types of experiment or production arrangements. A selected number of novel applications of using X-ray diffraction to characterize materials in real-time are discussed. Also, device characteristics of some X-ray intensifiers useful in instantaneous X-ray diffraction applications briefly presented. Real-time X-ray diffraction experiments with the incorporation of image X-ray intensification add a new dimension in the characterization of materials. The uses of real-time image intensification in laboratory and production arrangements are quite unlimited and their application depends more upon the ingenuity of the scientist or engineer.

Cone-beam x-ray luminescence computed tomography based on x-ray absorption dosage

NASA Astrophysics Data System (ADS)

Liu, Tianshuai; Rong, Junyan; Gao, Peng; Zhang, Wenli; Liu, Wenlei; Zhang, Yuanke; Lu, Hongbing

2018-02-01

With the advances of x-ray excitable nanophosphors, x-ray luminescence computed tomography (XLCT) has become a promising hybrid imaging modality. In particular, a cone-beam XLCT (CB-XLCT) system has demonstrated its potential in in vivo imaging with the advantage of fast imaging speed over other XLCT systems. Currently, the imaging models of most XLCT systems assume that nanophosphors emit light based on the intensity distribution of x-ray within the object, not completely reflecting the nature of the x-ray excitation process. To improve the imaging quality of CB-XLCT, an imaging model that adopts an excitation model of nanophosphors based on x-ray absorption dosage is proposed in this study. To solve the ill-posed inverse problem, a reconstruction algorithm that combines the adaptive Tikhonov regularization method with the imaging model is implemented for CB-XLCT reconstruction. Numerical simulations and phantom experiments indicate that compared with the traditional forward model based on x-ray intensity, the proposed dose-based model could improve the image quality of CB-XLCT significantly in terms of target shape, localization accuracy, and image contrast. In addition, the proposed model behaves better in distinguishing closer targets, demonstrating its advantage in improving spatial resolution.

Cone-beam x-ray luminescence computed tomography based on x-ray absorption dosage.

PubMed

Liu, Tianshuai; Rong, Junyan; Gao, Peng; Zhang, Wenli; Liu, Wenlei; Zhang, Yuanke; Lu, Hongbing

2018-02-01

With the advances of x-ray excitable nanophosphors, x-ray luminescence computed tomography (XLCT) has become a promising hybrid imaging modality. In particular, a cone-beam XLCT (CB-XLCT) system has demonstrated its potential in in vivo imaging with the advantage of fast imaging speed over other XLCT systems. Currently, the imaging models of most XLCT systems assume that nanophosphors emit light based on the intensity distribution of x-ray within the object, not completely reflecting the nature of the x-ray excitation process. To improve the imaging quality of CB-XLCT, an imaging model that adopts an excitation model of nanophosphors based on x-ray absorption dosage is proposed in this study. To solve the ill-posed inverse problem, a reconstruction algorithm that combines the adaptive Tikhonov regularization method with the imaging model is implemented for CB-XLCT reconstruction. Numerical simulations and phantom experiments indicate that compared with the traditional forward model based on x-ray intensity, the proposed dose-based model could improve the image quality of CB-XLCT significantly in terms of target shape, localization accuracy, and image contrast. In addition, the proposed model behaves better in distinguishing closer targets, demonstrating its advantage in improving spatial resolution. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Deep-Ultraviolet Luminescence of Rocksalt-Structured Mg x Zn1-x O (x > 0.5) Films on MgO Substrates

NASA Astrophysics Data System (ADS)

Kaneko, Kentaro; Tsumura, Keiichi; Ishii, Kyohei; Onuma, Takayoshi; Honda, Tohru; Fujita, Shizuo

2018-04-01

Rocksalt-structured Mg x Zn1-x O films with Mg composition x of 0.47, 0.57, and 0.64 were grown on (100)-oriented MgO substrates using mist chemical vapor deposition. Cathodoluminescence measurements showed deep ultraviolet (DUV) emission peaking at 4.88 eV (254 nm), 5.15 eV (241 nm), and 5.21 eV (238 nm), respectively, at 12 K. The peak energies were lower than the band gap energies by ca. 1 eV, suggesting that the deep ultraviolet (DUV) emission may be recognized as near band edge luminescence but is associated with impurities, defects, or band fluctuations. The use of carbon-free precursors in the growth is suggested to eliminate carbon impurities and to improve the optical properties of Mg x Zn1-x O.

Average and local crystal structures of (Ga 1–xZn x)(N 1–xO x) solid solution nanoparticles

DOE PAGES

Feygenson, Mikhail; Neuefeind, Joerg C.; Tyson, Trevor A.; ...

2015-11-06

We report the comprehensive study of the crystal structure of (Ga 1–xZn x)(N 1–xO x) solid solution nanoparticles by means of neutron and synchrotron x-ray scattering. In our study we used four different types of (Ga 1–xZn x)(N 1–xO x) nanoparticles, with diameters of 10–27 nm and x = 0.075–0.51, which show the narrow energy-band gaps from 2.21 to 2.61 eV. The Rietveld analysis of the neutron diffraction data revealed that the average crystal structure is the hexagonal wurtzite (space group P6 3mc), in agreement with previous reports on similar bulk materials. The pair-distribution function (PDF) analysis of the samemore » data found that the local structure is more disordered than the average one. It is best described by the model with a lower symmetry space group P1, where atoms are quasirandomly distorted from their nominal positions in the hexagonal wurtzite lattice.« less

Critical thickness of MBE-grown Ga 1-xIn xSb ( x<0.2) on GaSb

NASA Astrophysics Data System (ADS)

Nilsen, T. A.; Breivik, M.; Selvig, E.; Fimland, B. O.

2009-03-01

Several Ga 1-xIn xSb layers, capped with 1 μm of GaSb, were grown on GaSb(0 0 1) substrates by molecular beam epitaxy in a Varian Gen II Modular system using either the conventional sample growth position with substrate rotation, or a tilted sample position with no substrate rotation. The GaInSb layers were examined by X-ray diffraction (XRD) using both symmetrical and asymmetrical reflections. The "tilted sample method" gave a variation of ±25% in thickness of the Ga 1-xIn xSb layers, while the indium (In) content varied by ±10% around the nominal value. The disappearance of thickness fringes in 004 XRD scans was used to determine the onset of relaxation, as determining the in-plane lattice constant for tilted samples was found to be difficult. Determining residual strain in samples grown by the tilted method was likewise found to be very difficult. The critical thickness for several In mole fractions between 5% and 19% was determined and was found to be from 2.2 to 2.7 times higher than predicted by Matthews and Blakeslee (1974) [J. Crystal Growth 27 (1974) 118] but lower than that predicted by People and Bean (1985) [Appl. Phys. Lett. 47 (1985) 322].

Influence of compositional variation on structural, electrical and magnetic characteristics of (Ba1-x Gd) (Ti1-x Fe x ) O3 (0.2 ≤ x ≤ 0.5)

NASA Astrophysics Data System (ADS)

Sahoo, Sushrisangita; Mahapatra, P. K.; Choudhary, R. N. P.; Alagarsamy, Perumal

2018-01-01

The effect of composition variation of (Ba1-x Gd x )(Ti1-x Fe x )O3 (0.2 ≤ x ≤ 0.5) on structural, optical, electrical and multiferroic properties was investigated. The polycrystalline samples were fabricated by a chemico-thermal route. While the compound with composition x ≤ 0.3 has a tetragonal structure akin to BaTiO3, the higher compositions (x > 0.3) crystallize in a mixed phase of the tetragonal and orthorhombic structure. The different polarization mechanisms in the compound were analyzed on the basis of ferroelectric-paraelectric phase transition at 120 °C, magnetic reorientation mediated by Gd3+ ↔ Fe3+ exchange interaction at 200 °C and that induced by antiferromagnetic ordering mediated through the Fe3+ ↔ Fe3+ exchange interactions at 380 °C. Analysis of ac conductivity on the basis of Jonscher’s power law indicates the presence of correlated barrier hopping conduction mechanism in the samples. Among the studied samples, the composition with x = 0.3 exhibiting improved material properties like lower optical band gap and higher optical absorption, high dielectric constant (830 at room temperature and peak value of 3944 at 160 °C and 6478 at 377.5 °C), and the room temperature ME coefficient of 1.53 mV cm-1 Oe-1 have promising technological applications.

Synthesis of layered perovskite oxides, ACa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10] (A = K, Rb, Cs), and characterization of new solid acids, HCa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10] (O < x [le] 2), exhibiting variable Bronsted acidity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gopalakrishnan, J.; Uma, S.; Bhat, V.

1993-01-01

Layered perovskite oxides of the formula ACa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10] (A = K, Rb, Cs and 0 , x [le] 2) have been prepared. The members adopt the structures of the parent ACa[sub 2]Nb[sub 3]O[sub 10]. Interlayer alkali cations in the niobium-titanium oxide series can be ion-exchanged with Li[sup +], Na[sup +], NG[sub 4][sup +], of H[sup +] to give new derivatives. Intercalation of the protonated derivatives with organic bases reveals that the Bronsted acidity of the solid solution series, HCa[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10], depends on the titanium content. While the x = 1 member (HCaLaNb[submore » 2]TiO[sub 10]) is nearly as acidic as the parent HCa[sub 2]Nb[sub 3]O[sub 10], the x = 2 member (HLA[sub 2]NbTi[sub 2]O[sub 10]) is a weak acid hardly intercalating organic bases with pK[sub a] [approximately] 11.3. The variation of acidity is probably due to an ordering of Nb/Ti atoms in the triple octahedral perovskite slabs, [Ca[sub 2-x]La[sub x]Nb[sub 3-x]Ti[sub x]O[sub 10

X-ray filter for x-ray powder diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinsheimer, John Jay; Conley, Raymond P.; Bouet, Nathalie C. D.

Technologies are described for apparatus, methods and systems effective for filtering. The filters may comprise a first plate. The first plate may include an x-ray absorbing material and walls defining first slits. The first slits may include arc shaped openings through the first plate. The walls of the first plate may be configured to absorb at least some of first x-rays when the first x-rays are incident on the x-ray absorbing material, and to output second x-rays. The filters may comprise a second plate spaced from the first plate. The second plate may include the x-ray absorbing material and wallsmore » defining second slits. The second slits may include arc shaped openings through the second plate. The walls of the second plate may be configured to absorb at least some of second x-rays and to output third x-rays.« less

X-15 ship #3 on lakebed

NASA Technical Reports Server (NTRS)

1961-01-01

The X-15-3 (56-6672), seen here on the lakebed at Edwards Air Force Base, Edwards, California, was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of thrust. North American Aviation built three X-15 aircraft for the program. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow-on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and movable horizontal stabilizers to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control. Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of about 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to 11 min. flight was powerless and ended with a 200-mph glide landing. Generally, one of two types of X-15 flight profiles was used; a high-altitude flight plan that called for the pilot to maintain a steep rate of climb, or a speed profile that

Provision of an X-environment using the HEPiX-X11 scripts

NASA Astrophysics Data System (ADS)

Jones, R. W. L.; Cons, L.; Taddei, A.

1997-02-01

At CERN, we have created a user X11 environment within the HEPiX framework. Customisation is possible at the HEPiX, site, cluster, machine, group and user level, in order of increasing priority. The management of the X11 session is divorced from the window management. FVWM is the default window manager, being light on system resources while providing most of the desired functionality. The assembly of a correctly ordered. fvwmrc is done automatically by the scripts, with customisation allowed at all of the above levels. Two tools are provided to query aspects of that environment. These may be used both at the start of the X-session or when commencing any application. The first is guesskbd, a tool to identify the user's keyboard. A second, provides useful information about a given display.

Report on the 18th International Conference on X-ray and Inner-Shell Processes (X99).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gemmell, D. S.; Physics

2000-01-01

The 18th conference of the series served as a forum for discussing fundamental issues in the field of x-ray and inner-shell processes and their application in various disciplines of science and technology. Special emphasis was given to the opportunities offered by modern synchrotron x-ray sources. The program included plenary talks, progress reports and poster presentations relating to new developments in the field of x-ray and inner-shell processes. The range of topics included: X-ray interactions with atoms, molecules, clusters, surfaces and solids; Decay processes for inner-shell vacancies; X-ray absorption and emission spectroscopy - Photoionization processes; Phenomena associated with highly charged ionsmore » and collisions with energetic particles; Electron-spin and -momentum spectroscopy; X-ray scattering and spectroscopy in the study of magnetic systems; Applications in materials science, biology, geosciences, and other disciplines; Elastic and inelastic x-ray scattering processes in atoms and molecules; Threshold phenomena (post-collision interaction, resonant Raman processes, etc.); Nuclear absorption and scattering of x-rays; 'Fourth-generation' x-ray sources; Processes exploiting the polarization and coherence properties of x-ray beams; Developments in experimental techniques (x-ray optics, temporal techniques, detectors); Microscopy, spectromicroscopy, and various imaging techniques; Non-linear processes and x-ray lasers; Ionization and excitation induced by charged particles and by x-rays; and Exotic atoms (including 'hollow' atoms and atoms that contain 'exotic' particles).« less

Effects of Sb Content (x) on (Bi(1-x)Sb(x))2Te3 Thermoelectric Thin Film Deposited by Effusion Cell Evaporator.

PubMed

Yong, Ho; Na, Sekwon; Gang, Jun-Gu; Jeon, Seong-Jae; Hyun, Seungmin; Lee, Hoo-Jeong

2015-10-01

This paper investigates the effects of the Sb content (x) on (Bi(1-x)Sb(x))2Te3 thermoelectric films with x changing widely from 0 (Sb2Te3) to 1 (Bi2Te3). First, the XRD analysis discloses that with the Sb content (x) increasing, the phase changed gradually from Bi2Te3 to Sb2Te3 as Sb atoms replaced substitutionally Bi atoms. Further microstructure analysis reveals that an extensive grain growth occurred during post-annealing for the samples with high Sb contents. According to the measurement of electrical and thermoelectric properties, the polarity of the charge carrier and Seebeck coefficient switched n-type to p-type in the range of x = 0.45~0.63. For the n-type samples, the power factor is highest when x = 0.18 around 46.01 μW/K(2) whereas Sb2Te3, for the p-type samples, shows the highest value, 62.48 μW/K(2)cm.

Theoretical investigation on thermodynamic properties of ZnO1-x Te x alloys

NASA Astrophysics Data System (ADS)

Long, Debing; Li, Mingkai; Luo, Minghai; Zhu, Jiakun; Yang, Hui; Huang, Zhongbing; Ahuja, Rajeev; He, Yunbin

2017-05-01

In this study, the formation energy, phase diagram (with/without phonon contribution) and the relationship between bond stiffness and bond length for wurtzite (WZ) and zincblende (ZB) structures of ZnO1-x Te x (0  ⩽  x  ⩽  1) alloys have been investigated by combining first-principles calculations and cluster expansion method. The formation energy of ZnO1-x Te x alloys is very high in both structures, which means that it is difficult for ZnO and ZnTe to form stable ternary alloys ZnO1-x Te x . In the phase diagrams, both structures do not have stable phase of ternary alloys and ZnO1-x Te x ternary alloys can only exist in the form of metastable phase. These results indicate that ZnO and ZnTe easily form solid solubility gap when they form alloys. After considering vibrational free energy, we found the solubility of Te in ZnO and O in ZnTe was increased and the vibrational entropy improved the solubility furthermore. The phonon contribution is not ignorable to improve solid solubility. The phonon density of states was analyzed for ZnO1-x Te x alloys and the contribution from vibrational entropy was discussed.

Cooperation between a hierarchical set of recruitment sites targets the X chromosome for dosage compensation

PubMed Central

Albritton, Sarah Elizabeth; Kranz, Anna-Lena; Winterkorn, Lara Heermans; Street, Lena Annika; Ercan, Sevinc

2017-01-01

In many organisms, it remains unclear how X chromosomes are specified for dosage compensation, since DNA sequence motifs shown to be important for dosage compensation complex (DCC) recruitment are themselves not X-specific. Here, we addressed this problem in C. elegans. We found that the DCC recruiter, SDC-2, is required to maintain open chromatin at a small number of primary DCC recruitment sites, whose sequence and genomic context are X-specific. Along the X, primary recruitment sites are interspersed with secondary sites, whose function is X-dependent. A secondary site can ectopically recruit the DCC when additional recruitment sites are inserted either in tandem or at a distance (>30 kb). Deletion of a recruitment site on the X results in reduced DCC binding across several megabases surrounded by topologically associating domain (TAD) boundaries. Our work elucidates that hierarchy and long-distance cooperativity between gene-regulatory elements target a single chromosome for regulation. DOI: http://dx.doi.org/10.7554/eLife.23645.001 PMID:28562241

X-15A-2 with full scale ablative coating (pink X-15) on NASA ramp

NASA Technical Reports Server (NTRS)

1967-01-01

In June 1967, the X-15A-2 rocket powered research aircraft received a full-scale ablative coating to protect the craft from the high temperatures associated with supersonic flight. This pink eraser-like substance, applied to the #2 aircraft (56-6671), was then covered with a white sealant coat before flight. This coating would help the #2 aircraft reach the record speed of 4,520 mph (Mach 6.7). The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. However, the X-15A-2 had been elongated to 52 ft 5 in. Like the other two X-15s, it was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of thrust. North American Aviation built three X-15 aircraft for the program. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and movable horizontal stabilizers to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wings provided roll control. Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of

Screening for X-linked creatine transporter (SLC6A8) deficiency via simultaneous determination of urinary creatine to creatinine ratio by tandem mass-spectrometry.

PubMed

Mercimek-Mahmutoglu, Saadet; Muehl, Adolf; Salomons, Gajja S; Neophytou, Birgit; Moeslinger, Dorothea; Struys, Eduard; Bodamer, Olaf A; Jakobs, Cornelis; Stockler-Ipsiroglu, Sylvia

2009-04-01

High urinary creatine to creatinine ratio (U-CrCrtR) is a potential diagnostic marker of X-linked creatine transporter (SLC6A8) deficiency. We developed a tandem mass-spectrometry method to simultaneously determine urinary creatine and creatinine in 975 individuals (0-18 years). U-CrCrtR increased up to 8 years and decreased thereafter. U-CrCrtR was 2.29 and 2.12 (99th percentile: 1.87) in two males with subsequently confirmed SLC6A8 mutations. The frequency of SLC6A8 deficiency was 2.3% in 157 males at risk.

Characterization of X80 and X100 Microalloyed Pipeline Steel Using Quantitative X-ray Diffraction

NASA Astrophysics Data System (ADS)

Wiskel, J. B.; Li, X.; Ivey, D. G.; Henein, H.

2018-06-01

Quantitative X-ray diffraction characterization of four (4) X80 and three (3) X100 microalloyed steels was undertaken. The effect of through-thickness position, processing parameters, and composition on the measured crystallite size, microstrain, and J index (relative magnitude of crystallographic texture) was determined. Microstructure analysis using optical microscopy, scanning electron microscopy, transmission electron microscopy, and electron-backscattered diffraction was also undertaken. The measured value of microstrain increased with increasing alloy content and decreasing cooling interrupt temperature. Microstructural features corresponding to crystallite size in the X80 steels were both above and below the detection limit for quantitative X-ray diffraction. The X100 steels consistently exhibited microstructure features below the crystallite size detection limit. The yield stress of each steel increased with increasing microstrain. The increase in microstrain from X80 to X100 is also associated with a change in microstructure from predominantly polygonal ferrite to bainitic ferrite.

Current and lattice matched tandem solar cell

DOEpatents

Olson, Jerry M.

1987-01-01

A multijunction (cascade) tandem photovoltaic solar cell device is fabricated of a Ga.sub.x In.sub.1-x P (0.505.ltoreq.X.ltoreq.0.515) top cell semiconductor lattice matched to a GaAs bottom cell semiconductor at a low-resistance heterojunction, preferably a p+/n+ heterojunction between the cells. The top and bottom cells are both lattice matched and current matched for high efficiency solar radiation conversion to electrical energy.

A Hybrid Tandem Solar Cell Combining a Dye-Sensitized and a Polymer Solar Cell.

PubMed

Shao, Zhipeng; Chen, Shuanghong; Zhang, Xuhui; Zhu, Liangzheng; Ye, Jiajiu; Dai, Songyuan

2016-06-01

A hybrid tandem solar cell was assambled by connecting a dye sensitized solar cell and a polymer solar cell in series. A N719 sensitized TiO2 was used as photocathode in dye-sensitized subcell, and a MEH-PPV/PCBM composite was used as active layer in the polymer subcell. The polymer subcell fabricated on the counter electrode of the dye sensitized solar cell. A solution processed TiO(x) layer was used as electron collection layer of the polymer sub cell and the charge recombination layer. The effects of the TiO(x) interlayer and the spectral overlap between the two sub cells have been studied and optimized. The results shows that a proper thickness of the TiO(x) layer is needed for tandem solar cells. Thick TiO(x) will enhance the series resistance, but too thin TiO(x), layer will damage the hole blocking effect and its hydrophilic. The resulting optimized tandem solar cells exhibited a power conversion efficiency of 1.28% with a V(oc) of 0.95 V under simulated 100 mW cm(-2) AM 1.5 illumination.

X-15 ship #3 on lakebed

NASA Technical Reports Server (NTRS)

1962-01-01

The X-15 ship #3 (56-6672) is seen here on the lakebed at the Edwards Air Force Base, Edwards, California. Ship #3 made 65 flights during the program, attaining a top speed of Mach 5.65 and a maximum altitude of 354,200 feet. Only 10 of the 12 X-15 pilots flew Ship #3, and only eight of them earned their astronaut wings during the program. Robert White, Joseph Walker, Robert Rushworth, John 'Jack' McKay, Joseph Engle, William 'Pete' Knight, William Dana, and Michael Adams all earned their astronaut wings in Ship #3. Neil Armstrong and Milton Thompson also flew Ship #3. In fact, Armstrong piloted Ship #3 on its first flight, on 20 December 1961. On 15 November 1967, Ship #3 was launched over Delamar Lake, Nevada with Maj. Michael J. Adams at the controls. The vehicle soon reached a speed of Mach 5.2, and a peak altitude of 266,000 feet. During the climb, an electrical disturbance degraded the aircraft's controllability. Ship #3 began a slow drift in heading, which soon became a spin. Adams radioed that the X-15 'seems squirrelly,' and then said 'I'm in a spin.' Through some combination of pilot technique and basic aerodynamic stability, Adams recovered from the spin, and entered an inverted Mach 4.7 dive. As the X-15 plummeted into the increasingly thicker atmosphere, the Honeywell adaptive flight control system caused the vehicle to begin oscillating. As the pitching motion increased, aerodynamic forces finally broke the aircraft into several major pieces. Adams was killed when the forward fuselage impacted the desert. This was the only fatal accident during the entire X-15 program. The X-15 was a rocket powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was

Remote X-Ray Diffraction and X-Ray Fluorescence Analysis on Planetary Surfaces

NASA Technical Reports Server (NTRS)

Blake, David F.; DeVincenzi, D. (Technical Monitor)

1999-01-01

The legacy of planetary X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) began in 1960 when W. Parish proposed an XRD instrument for deployment on the moon. The instrument was built and flight qualified, but the Lunar XRD program was cancelled shortly before the first human landing in 1969. XRF chemical data have been collected in situ by surface landers on Mars (Viking 1 & 2, Pathfinder) and Venus (Venera 13 & 14). These highly successful experiments provide critical constraints on our current understanding of surface processes and planetary evolution. However, the mineralogy, which is more critical to planetary surface science than simple chemical analysis, will remain unknown or will at best be imprecisely constrained until X-ray diffraction (XRD) data are collected. Recent progress in X-ray detector technology allows the consideration of simultaneous XRD (mineralogic analysis) and high-precision XRF (elemental analysis) in systems miniaturized to the point where they can be mounted on fixed landers or small robotic rovers. There is a variety of potential targets for XRD/XRF equipped landers within the solar system, the most compelling of which are the poles of the moon, the southern highlands of Mars and Europa.

The 1979 X-ray outburst of Centaurus X-4

NASA Technical Reports Server (NTRS)

Kaluzienski, L. J.; Holt, S. S.; Swank, J. H.

1980-01-01

X-ray observations of the first major outburst of the classical transient X-ray source Centaurus X-4 since its discovery in 1969 are presented. The observations were obtained in May, 1979, with the all-sky monitor on board Ariel 5. The flare light curve is shown to exhibit many of the characteristics of other transients, including a double-peaked maximum, as well as significant, apparently random, variations and a lower peak flux and shorter duration than the 1969 event. Application of a standard epoch-folding technique to data corrected for linear decay trends indicates a possible source modulation at 0.3415 days (8.2 hours). Comparison of the results with previous other data on Cen X-4 and the characteristics of the soft X-ray transients allows a total X-ray output of approximately 3 x 10 to the 43rd ergs to be estimated, and reveals the duration and decay time of the 1979 Cen X-4 outburst to be the shortest yet observed from soft X-ray transients. The observations are explained in terms of episodic mass exchange from a late-type dwarf onto a neutron star companion in a relatively close binary system.

Modelling the thermal conductivity of (U xTh 1-x)O 2 and (U xPu 1-x)O 2

DOE PAGES

Cooper, M. W. D.; Middleburgh, S. C.; Grimes, R. W.

2015-07-15

The degradation of thermal conductivity due to the non-uniform cation lattice of (U xTh 1-x)O 2 and (U xPu 1-x)O 2 solid solutions has been investigated by molecular dynamics, using the non-equilibrium method, from 300 to 2000 K. Degradation of thermal conductivity is predicted in (U xTh 1-x)O 2 and (U xPu 1-x)O 2 as compositions deviate from the pure end members: UO 2, PuO 2 and ThO 2. The reduction in thermal conductivity is most apparent at low temperatures where phonon-defect scattering dominates over phonon-phonon interactions. The effect is greater for (U xTh 1-x)O 2 than U xPu 1-x)Omore » 2 due to the greater mismatch in cation size. Parameters for an analytical expressions have been developed that describe the predicted thermal conductivities over the full temperature and compositional ranges. Finally, these expressions may be used in higher level fuel performance codes.« less

Accretion and Outflows in X-ray Binaries: What's Really Going on During X-ray Quiescence

NASA Astrophysics Data System (ADS)

MacDonald, Rachel K. D.; Bailyn, Charles D.; Buxton, Michelle

2015-01-01

X-ray binaries, consisting of a star and a stellar-mass black hole, are wonderful laboratories for studying accretion and outflows. They evolve on timescales quite accessible to us, unlike their supermassive cousins, and allow the possibility of gaining a deeper understanding of these two common astrophysical processes. Different wavelength regimes reveal different aspects of the systems: radio emission is largely generated by outflows and jets, X-ray emission by inner accretion flows, and optical/infrared (OIR) emission by the outer disk and companion star. The search for relationships between these different wavelengths is thus an area of active research, aiming to reveal deeper connections between accretion and outflows.Initial evidence for a strong, tight correlation between radio and X-ray emission has weakened as further observations and newly-discovered sources have been obtained. This has led to discussions of multiple tracks or clusters, or the possibility that no overall relation exists for the currently-known population of X-ray binaries. Our ability to distinguish among these options is hampered by a relative lack of observations at lower luminosities, and especially of truly X-ray quiescent (non-outbursting) systems. Although X-ray binaries spend the bulk of their existence in quiescence, few quiescent sources have been observed and multiple observations of individual sources are largely nonexistent. Here we discuss new observations of the lowest-luminosity quiescent X-ray binary, A0620-00, and the place this object occupies in investigations of the radio/X-ray plane. For the first time, we also incorporate simultaneous OIR data with the radio and X-ray data.In December 2013 we took simultaneous observations of A0620-00 in the X-ray (Chandra), the radio (EVLA), and the OIR (SMARTS 1.3m). These X-ray and radio data allowed us to investigate similarities among quiescent X-ray binaries, and changes over time for this individual object, in the radio/X

The STAR-X X-Ray Telescope Assembly (XTA)

NASA Technical Reports Server (NTRS)

McClelland, Ryan S.; Bautz, Mark W.; Bonafede, Joseph A.; Miller, Eric D.; Saha, Timo T.; Solly, Peter M.; Zhang, William W.

2017-01-01

The Survey and Time-domain Astrophysical Research eXplorer (STAR-X) science goals are to discover what powers the most violent explosions in the Universe, understand how black holes grow across cosmic time and mass scale, and measure how structure formation heats the majority of baryons in the Universe. To achieve these goals, STAR-X requires a powerful X-ray telescope with a large field of view, large collecting area, and excellent point spread function. The STAR-X instrument, the X-Ray Telescope Assembly (XTA), meets these requirements using a powerful X-ray mirror technology based on precision-polished single crystal silicon and a mature CCD detector technology. The XTA is composed of three major subsystems: an X-ray Mirror Assembly (MA) of high resolution, lightweight mirror segments fabricated out of single crystal silicon; a Focal Plane Assembly (FPA) made of back-illuminated CCD's capable of detecting X-rays with excellent quantum efficiency; and a composite Telescope Tube that structurally links the MA and FPA. The MA consists of 5,972 silicon mirror segments mounted into five subassemblies called meta-shells. A meta-shell is constructed from an annular central structural shell covered with interlocking layers of mirror segments. This paper describes the requirements, design, and analysis of the XTA subsystems with particular focus on the MA.

The STAR-X X-Ray Telescope Assembly (XTA)

NASA Astrophysics Data System (ADS)

McClelland, Ryan S.

2017-08-01

The Survey and Time-domain Astrophysical Research eXplorer (STAR-X) science goals are to discover what powers the most violent explosions in the Universe, understand how black holes grow across cosmic time and mass scale, and measure how structure formation heats the majority of baryons in the Universe. To achieve these goals, STAR-X requires a powerful X-ray telescope with a large field of view, large collecting area, and excellent point spread function. The STAR-X instrument, the X-Ray Telescope Assembly (XTA), meets these requirements using a powerful X-ray mirror technology based on precision-polished single crystal silicon and a mature CCD detector technology. The XTA is composed of three major subsystems: an X-ray Mirror Assembly (MA) of high resolution, lightweight mirror segments fabricated out of single crystal silicon; a Focal Plane Assembly (FPA) made of back-illuminated CCDs capable of detecting X-rays with excellent quantum efficiency; and a composite Telescope Tube that structurally links the MA and FPA. The MA consists of 5,972 silicon mirror segments mounted into five subassemblies called metashells. A meta-shell is constructed from an annular central structural shell covered with interlocking layers of mirror segments. This paper describes the requirements, design, and analysis of the XTA subsystems with particular focus on the MA.

Search for Hard X-Ray Emission from the Soft X-Ray Transient Aquila X-1

NASA Astrophysics Data System (ADS)

Harmon, B. A.; Zhang, S. N.; Paciesas, W. S.; Tavani, M.; Kaaret, P.; Ford, E.

1994-12-01

We are investigating the possibility of hard x-ray emission from the recurrent soft x-ray transient and x-ray burst source Aquila X-1 (Aql X-1). Outbursts of this source are relatively frequent with a spacing of ~ 4-10 months (Kitamoto, S. et al. 1993, ApJ, 403, 315). The recent detections of hard tails (\\(>\\)20 keV) in low luminosity x-ray bursters (Barret, D. & Vedrenne, G. 1994, ApJ Supp. S. 92, 505) suggest that neutron star transient systems such as Aql X-1 can produce hard x-ray emission which is detectable by BATSE. We are correlating reported optical and soft x-ray observations since 1991 of Aql X-1 with BATSE observations in order to search for hard x-ray emission episodes, and to study their temporal and spectral evolution. We will present preliminary results of this search in the 20-1000 keV band using the Earth occultation technique applied to the large area detectors. If this work is successful, we hope to alert the astronomical community for the next Aql X-1 outburst expected in 1995. Simultaneous x-ray/hard x-ray and optical observations of Aql X-1 during outburst would be of great importance for the modeling of soft x-ray transients and related systems.

Effect of X-ray exposure on the pharmaceutical quality of drug tablets using X-ray inspection equipment.

PubMed

Uehara, Kazuaki; Tagami, Tatsuaki; Miyazaki, Itaru; Murata, Norikazu; Takahashi, Yoshifumi; Ohkubo, Hiroshi; Ozeki, Tetsuya

2015-06-01

X-ray inspection equipment is widely used to detect missing materials and defective goods in opaque containers. Its application has been expanded to the pharmaceutical industry to detect the presence of drug tablets in aluminum foil press-through packaging. However, the effect of X-rays on the pharmaceutical quality of drug tablets is not well known. In this study, the effect of X-rays on the pharmaceutical quality of drug tablets was investigated. Exposure of acetaminophen, loxoprofen and mefenamic acid tablets to X-ray doses of 0.34 mGy (thrice the dose by X-ray scanning) to 300 Gy (maximum dose from our X-ray equipment) was demonstrated, and the samples were evaluated by formulation tests. Exposure to X-rays did not affect the pharmaceutical quality of the drug content. The samples exposed to X-rays exhibited almost the same profile in formulation tests (dissolution test, disintegrating test and hardness test) as control samples (0 Gy). The combination of X-ray exposure with accelerated temperature and humidity tests (six months) also did not affect the pharmaceutical quality. The color change of light-sensitive drugs (nifedipine and furosemide tablets) after X-ray exposure was negligible (< 1.0). In contrast, tablet color was remarkably changed by light from a D65 lamp. The X-ray scanning and X-ray exposure under our experimental conditions did not affect the pharmaceutical quality of drug tablets.

SSM on AstroSat detects neutron star X-ray transient, Aql_X-1 in its outburst

NASA Astrophysics Data System (ADS)

Ramadevi, M. C.; Ravishankar, B. T.; Sarwade, Abhilash R.; Vaishali, S.; Hasan, Mohammed; Agarwal, Vivek Kumar; Baby, Blessy Elizabeth; Bhattacharya, Dipankar; Seetha, S.; Agarwal, Anil

2017-06-01

We report on the X-ray outburst of the neutron star X-ray source Aql X-1 as observed by SSM onboard AstroSat. Flux reported by SSM on its first observation of the source during this outburst on 01 June 2017 at 08:55 UT is about 820 milliCrab (2.24 +/- 0.02 photons/s-cm^2).

X-1E on Display Stand at Dryden

NASA Technical Reports Server (NTRS)

1996-01-01

The Bell Aircraft Corporation X-1E is shown in this artistic night photo taken in February 1996. This aircraft is displayed on a pedestal in front of the main building (4800) at NASA Dryden Flight Research Center, Edwards, California. There were four versions of the Bell X-1 rocket-powered research aircraft that flew at the NACA High-Speed Flight Research Station, Edwards, California. The bullet-shaped X-1 aircraft were built by Bell Aircraft Corporation, Buffalo, N.Y. for the U.S. Army Air Forces (after 1947, U.S. Air Force) and the National Advisory Committee for Aeronautics (NACA). The X-1 Program was originally designated the XS-1 for EXperimental Supersonic. The X-1's mission was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the 'sound barrier.' Three different X-1s were built and designated: X-1-1, X-1-2 (later modified to become the X-1E), and X-1-3. The basic X-1 aircraft were flown by a large number of different pilots from 1946 to 1951. The X-1 Program not only proved that humans could go beyond the speed of sound, it reinforced the understanding that technological barriers could be overcome. The X-1s pioneered many structural and aerodynamic advances including extremely thin, yet extremely strong wing sections; supersonic fuselage configurations; control system requirements; powerplant compatibility; and cockpit environments. The X-1 aircraft were the first transonic-capable aircraft to use an all-moving stabilizer. The flights of the X-1s opened up a new era in aviation. The first X-1 was air-launched unpowered from a Boeing B-29 Superfortress on January 25, 1946. Powered flights began in December 1946. On October 14, 1947, the X-1-1, piloted by Air Force Captain Charles 'Chuck' Yeager, became the first aircraft to exceed the speed of sound, reaching about 700 miles per hour (Mach 1.06) and an altitude of 43,000 feet. The number 2 X-1 was modified and redesignated the X-1E

X-1A on lakebed

NASA Technical Reports Server (NTRS)

1955-01-01

The Bell Aircraft Corporation X-1A (48-1384) is photographed in 1955 sitting on the Rogers Dry Lakebed at Edwards, California. This view of the right side of the aircraft shows a middle section that contrasts quite distinctively with the over-all white paint scheme of the X-1A during its NACA High-Speed Flight Research Station tenure. The extreme cold of the liquid oxygen used as a propellant (along with alcohol) and its deleterious affect on paint dictated that the fuselage area next to the tank be left unpainted. The X-1A arrived at Edwards Air Force Base, California, on January 7, 1953. Bell test pilot Jean 'Skip' Ziegler made six test flights between 14 February and 25 April 1953. Air Force test pilots Maj. Charles 'Chuck' Yeager and Maj. Arthur 'Kit' Murray made 18 flights between 21 November 1953 and 26 August 1954. NACA test pilot Joe Walker made one successful flight on 20 July 1955. During a second flight attempt on 8 August 1955, an explosion damaged the aircraft shortly before launch. Walker climbed back up into the JTB-29A mothership, and the X-1A was jettisoned over the Edwards AFB bombing range.

Crystal structure study of dielectric oxynitride perovskites La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x} (x=0, 0.2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habu, Daiki; Masubuchi, Yuji; Torii, Shuki

As is the case with SrTaO{sub 2}N, both cis-ordering of nitride anions and octahedral titling are also preferable in La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x} (x=0, 0.2) oxynitride perovskites. A larger dielectric constant of ε{sub r}≈5.0×10{sup 3} was estimated for the pure oxynitride with x=0.2, compared with ε{sub r}≈750 for the product with x=0, by extrapolating the ε{sub r} values obtained from powders mixed with paraffin at various mixing ratios. The crystal structure of x=0.2 with larger tolerance factor than x=0 increased the octahedral tilting, which contributes to the increased dielectric constant. The increased dielectric constant supports the exchange mechanism formore » the dielectric property between two kinds of –Ti–N– helical coils (clockwise and anticlockwise) derived from the above cis-ordering of nitride anions. - Graphical abstract: Very large dielectric constant values were estimated for La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x}; ε{sub r}≈5.0×10{sup 3} in x=0.2 and ε{sub r}≈750 in x=0. - Highlights: • Cis-configuration of nitride anions was confirmed in La{sub 1−x}Sr{sub x}TiO{sub 2+x}N{sub 1−x} (x=0, 0.2). • Dielectric constant values were estimated to be 750 for x=0 and 5.0×10{sup 3} for x=0.2, respectively. • The large dielectric property is to the exchange mechanism between clockwise and anticlockwise –Ti–N– coil motifs.« less

Overcoming Etch Challenges on a 6″ Hg1- x Cd x Te MBE on Si Wafer

NASA Astrophysics Data System (ADS)

Apte, Palash; Norton, Elyse; Robinson, Solomon

2017-10-01

The effect of increasing photoresist (PR) thickness on the inductively coupled plasma (ICP) dry etched characteristics of a 6″ (c.15 cm) molecular beam epitaxy Hg1- x Cd x Te/Si wafer is investigated. It is determined that the Hg1- x Cd x Te etch rate (ER) does not vary significantly with a change in the PR thickness. Also, the vertical ER of the PR is seen to be independent of the PR thickness, but the lateral ER is seen to reduce significantly with increased PR thickness. Indeed, very little reduction in the pixel mesa area post-dry etch is seen for the thicker PR. Consequently, the trench sidewall angle is also seen to vary as a function of the PR thickness. Since ICP is the more attractive choice for dry etching Hg1- x Cd x Te, this simple, cost-effective way to extend the capabilities of dry etching (larger mesa top area post-dry etch, ability to create tailor-made trench sidewall angles for optimal conformal passivation deposition, and potential for reduced dry etch damage) described here would allow for the fabrication of next generation infrared detectors with increased yield and reduced cost. Although similar results have been presented using the electron cyclotron resonance system to dry etch Hg1- x Cd x Te, to the best of our knowledge, this is the first time that such results have been presented using an ICP system.

XAssist: A System for the Automation of X-ray Astrophysics Analysis

NASA Astrophysics Data System (ADS)

Ptak, A.

2004-08-01

XAssist is a NASA AISR-funded project for the automation of X-ray astrophysics. It is capable of data reprocessing, source detection, and preliminary spatial, temporal and spectral analysis for each source with sufficient counts. The bulk of the system is written in Python, which in turn drives underlying software (CIAO for Chandra data, etc.). Future work will include a GUI (mainly for beginners and status monitoring) and the exposure of at least some functionality as web services. The latter will help XAssist to eventually become part of the VO, making advanced queries possible, such as determining the X-ray fluxes of counterparts to HST or SDSS sources (including the use of unpublished X-ray data), and add the ability of ``on-the-fly'' X-ray processing. Pipelines are running on Chandra and XMM-Newton observations of galaxies to demonstrate XAssist's capabilities, and the results are available online (in real time) at http://www.xassist.org. XAssist itself as well as various associated projects are available for download.

Evolution of Cygnus X-3 through its Radio and X-ray States

NASA Astrophysics Data System (ADS)

Szostek, A.; Zdziarski, A. A.; McCollough, M. L.

2009-05-01

Based on X-ray spectra and studies of the long-term correlated behavior between radio and soft X-ray, we present a detailed evolution of Cyg X-3 through its radio and X-ray states. We comment on the nature of the hard X-ray tail and possible Simbol X contribution in constraining the models.

Current- and lattice-matched tandem solar cell

DOEpatents

Olson, J.M.

1985-10-21

A multijunction (cascade) tandem photovoltaic solar cell device is fabricated of a Ga/sub x/In/sub 1-x/P (0.505 equal to or less than x equal to or less than 0.515) top cell semiconductor lattice-matched to a GaAs bottom cell semiconductor at a low resistance heterojunction, preferably a p/sup +//n/sup +/ heterojunction between the cells. The top and bottom cells are both lattice-matched and current-matched for high efficiency solar radiation conversion to electrical energy.

Determination of iodinated X-ray contrast media in sewage by solid-phase extraction and liquid chromatography tandem mass spectrometry.

PubMed

Echeverría, S; Borrull, F; Fontanals, N; Pocurull, E

2013-11-15

A method for the quantitative determination of five iodinated X-ray contrast media (ICMs) in sewage was developed by solid-phase extraction and high-performance liquid chromatography-tandem mass spectrometry. A fused-core analytical column was successfully applied for the first time for the separation of ICMs. Oasis HLB was selected from the sorbents tested because of its higher recoveries. The optimized method allowed the determination of the ICMs at low ng/L levels in both influent and effluent sewage, with detection limits of 40 ng/L and 10 ng/L for most compounds in influent and effluent sewage, respectively. The five ICMs studied were determined in all samples analysed, with iopromide being the analyte found at the highest concentration (8.9 µg/L), while iopamidol was the analyte found at lowest concentration (1.3 µg/L) in influent sewage. Effluent sewage did not show a significant decrease in ICM concentrations. © 2013 Elsevier B.V. All rights reserved.

Electronic structure of charge- and spin-controlled Sr(1-(x+y))La(x+y)Ti(1-x)Cr(x)O3.

PubMed

Iwasawa, H; Yamakawa, K; Saitoh, T; Inaba, J; Katsufuji, T; Higashiguchi, M; Shimada, K; Namatame, H; Taniguchi, M

2006-02-17

We present the electronic structure of Sr(1-(x+y))La(x+y)Ti(1-x)Cr(x)O3 investigated by high-resolution photoemission spectroscopy. In the vicinity of the Fermi level, it was found that the electronic structure was composed of a Cr 3d local state with the t(2g)3 configuration and a Ti 3d itinerant state. The energy levels of these Cr and Ti 3d states are well interpreted by the difference of the charge-transfer energy of both ions. The spectral weight of the Cr 3d state is completely proportional to the spin concentration x irrespective of the carrier concentration y, indicating that the spin density can be controlled by x as desired. In contrast, the spectral weight of the Ti 3d state is not proportional to y, depending on the amount of Cr doping.

An ab initio study on BeX 3- superhalogen anions (X = F, Cl, Br)

NASA Astrophysics Data System (ADS)

Anusiewicz, Iwona; Skurski, Piotr

2002-06-01

The vertical electron detachment energies (VDE) of 10 BeX 3- (X = F, Cl, Br) anions were calculated at the outer valence Green function (OVGF) level with the 6-311++G(3df) basis sets. The largest vertical electron binding energy was found for BeF 3- system (7.63 eV). All negatively charged species possess the vertical electron detachment energies that are larger than 5.5 eV and thus may be termed superhalogen anions. The strong dependence of the VDE of the BeX 3- species on the ligand-central atom (Be-X) distance and on the partial atomic charge localized on Be was observed and discussed, as well as the other factors that may influence the electronic stability of such anions. In addition, the usefulness of the various theoretical treatments for estimating the VDEs of superhalogen anions was tested and analyzed.

X-ray Reciprocal Space Mapping of Graded Al x Ga1 - x N Films and Nanowires.

PubMed

Stanchu, Hryhorii V; Kuchuk, Andrian V; Kladko, Vasyl P; Ware, Morgan E; Mazur, Yuriy I; Zytkiewicz, Zbigniew R; Belyaev, Alexander E; Salamo, Gregory J

2016-12-01

The depth distribution of strain and composition in graded Al x Ga1 - x N films and nanowires (NWs) are studied theoretically using the kinematical theory of X-ray diffraction. By calculating [Formula: see text] reciprocal space maps (RSMs), we demonstrate significant differences in the intensity distributions from graded Al x Ga1 - x N films and NWs. We attribute these differences to relaxation of the substrate-induced strain on the NWs free side walls. Finally, we demonstrate that the developed X-ray reciprocal space map model allows for reliable depth profiles of strain and Al composition determination in both Al x Ga1 - x N films and NWs.

An XXX male resulting from paternal X-Y interchange and maternal X-X nondisjunction.

PubMed Central

Annerén, G; Andersson, M; Page, D C; Brown, L G; Berg, M; Läckgren, G; Gustavson, K H; de la Chapelle, A

1987-01-01

A 2-year-old boy was found to have a 47,XXX karyotype. Restriction-fragment-length-polymorphism analysis showed that, of his three X chromosomes, one is of paternal and two are of maternal origin. The results of Y-DNA hybridization were reminiscent of those in XX males in two respects. First, hybridization to Southern transfers revealed the presence in this XXX male of sequences derived from the Y-chromosomal short arm. Second, in situ hybridization showed that this Y DNA was located on the tip of the X-chromosomal short arm. We conclude that this XXX male resulted from the coincidence of X-X nondisjunction during maternal meiosis and aberrant X-Y interchange either during or prior to paternal meiosis. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:2889356

First principles calculations of electronic structure and magnetic properties of Cr-based magnetic semiconductors Al{sub 1-x}Cr{sub x}X (X=N, P, As, Sb)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saeed, Y., E-mail: yasir_saeed54321@yahoo.co; Shaukat, A., E-mail: schaukat@gmail.co; Nazir, S., E-mail: nazirsafdar@gmail.co

2010-01-15

First principles calculations based on the density functional theory (DFT) within the local spin density approximation are performed to investigate the electronic structure and magnetic properties of Cr-based zinc blende diluted magnetic semiconductors Al{sub 1-x}Cr{sub x}X (X=N, P, As, Sb) for 0<=x<=0.50.The behaviour of magnetic moment of Al{sub 1-x}Cr{sub x}X at each Cr site as well as the change in the band gap value due to spin down electrons has been studied by increasing the concentration of Cr atom and through changing X from N to Sb. Furthermore, the role of p-d hybridization is analyzed in the electronic band structuremore » and exchange splitting of d-dominated bands. The interaction strength is stronger in Al{sub 1-x}Cr{sub x}N and becomes weaker in Al{sub 1-x}Cr{sub x}Sb. The band gap due to the spin down electrons decreases with the increased concentration of Cr in Al{sub 1-x}Cr{sub x}X, and as one moves down along the isoelectronic series in the group V from N to Sb. Our calculations also verify the half-metallic ferromagnetic character in Cr doped AlX. - Graphical abstract: The prototype structures of Cr doped AlX (X=N, P, As, Sb) compounds: (A) zinc blende AlP for x=0, (B) Cr{sub 1}Al{sub 7}P{sub 8} for x=0.125, (C) Cr{sub 1}Al{sub 3}P{sub 4} for x=0.25, (D) Cr{sub 1}Al{sub 1}P{sub 2} for x=0.5.« less

Evaluation and comparision of dc resistivity of NiZr x Co x Fe2-2x O4, Ni0.5Sn0.5Co x Mn x Fe2-2x O4, Mg1-x Ca x Ni y Fe2-y O4 and Mg1-x Ni x Co y Fe2-y O4 nanocrytalline materials

NASA Astrophysics Data System (ADS)

Ali, Rajjab; Gilani, Zaheer Abbas; Shahzad Shifa, Muhammad; Asghar, H. M. Noor Ul Huda Khan; Azhar Khan, Muhammad; Naeem Anjum, Muhammad; Nauman Usmani, Muhammad; Farooq Warsi, Muhammad; Khawaja, Imtiaz U.

2017-11-01

Four series nanocrystalline ferrites with nominal composition, NiZr x Co x Fe2-2x O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8) Ni0.5Sn0.5Co x Mn x Fe2-2x O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8), Mg1-x Ca x Ni y Fe2-y O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8; y  =  0, 04, 0.8, 1.2, 1.6) and Mg1-x Ni x Co y Fe2-y O4 (x,y  =  0.0, 0.2, 0.4, 0.6, 0.8) have been fabricated using the microemulsion synthesis route. The synthesized materials are investigated for dc electrical resistivity measurements. The variation of dc electrical resistivity of these materials has been explainedon the basis of hopping mechanism of both holes and electrons.

High Performance Non-Dispersive X-Ray Spectrometers for Charge Exchange Measurements

NASA Technical Reports Server (NTRS)

Porter Frederick; Adams, J.; Beiersdorfer, P.; Brown, G. V.; Karkatoua, D.; Kelley, R. L.; Kilbourne, C. A.; Lautenagger, M.

2010-01-01

Currently, the only measurements of cosmological charge exchange have been made using low resolution, non-dispersive spectrometers like the PSPC on ROSAT and the CCD instruments on Chandra and XMM/Newton. However, upcoming cryogenic spectrometers on Astro-H and IXO will add vast new capabilities to investigate charge exchange in local objects such as comets and planetary atmospheres. They may also allow us to observe charge exchange in extra-solar objects such as galactic supernova remnants. With low spectral resolution instruments such as CCDs, x-ray emission due to charge exchange recombination really only provides information on the acceptor species, such as the solar wind. With the new breed of x-ray calorimeter instruments, emission from charge exchange becomes highly diagnostic allowing one to uniquely determine the acceptor species, ionization state, donor species and ionization state, and the relative velocity of the interaction. We will describe x-ray calorimeter instrumentation and its potential for charge exchange measurements in the near term. We will also touch on the instrumentation behind a decade of high resolution measurements of charge exchange using an x-ray calorimeter at the Lawrence Livermore National Laboratory.

Disk Disruptions and X-ray Intensity Excursions in Cyg X-2, LMC X-3 and Cyg X-3

NASA Astrophysics Data System (ADS)

Boyd, P. T.; Smale, A. P.

2001-05-01

The RXTE All Sky Monitor soft X-ray light curves of many X-ray binaries show long-term intensity variations (a.k.a "superorbital periodicities") that have been ascribed to precession of a warped, tilted accretion disk around the X-ray source. We have found that the excursion times between X-ray minima in Cyg X-2 can be characterized as a series of integer multiples of the 9.8 binary orbital period, (as opposed to the previously reported stable 77.7 day single periodicity, or a single modulation whose period changes slowly with time). While the data set is too short for a proper statistical analysis, it is clear that the length of any given intensity excursion cannot be used to predict the next (integer) excursion length in the series. In the black hole candidate system LMC X-3, the excursion times are shown to be related to each other by rational fractions. We find that the long term light curve of the unusual galactic X-ray jet source Cyg X-3 can also be described as a series of intensity excursions related to each other by integer multiples of a fundamental underlying clock. In the latter cases, the clock is apparently not related to the known binary periods. A unified physical model, involving both an inclined accretion disk and a fixed-probability disk disruption mechanism is presented, and compared with three-body scattering results. Each time the disk passes through the orbital plane it experiences a fixed probability P that it will disrupt. This model has testable predictions---the distribution of integers should resemble that of an atomic process with a characteristic half life. Further analysis can support or refute the model, and shed light on what system parameters effectively set the value of P.

Influence of processing in mercury and selenium vapor on the electrical properties of Cd /SUB x/ Hg /SUB 1-x/ Se, Zn /SUB x/ Hg /SUB 1-x/ Se solid solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gavaleshko, N.P.; Khomyak, V.V.; Makogonenko, V.N.

1985-12-01

In order to determine the predominant intrinsic point defects in Cd /SUB x/ Hg /SUB 1-x/ Se and Zn /SUB x/ Hg /SUB 1-x/ Se solid solutions, the authors study the influence of annealing in mercury and selenium vapor on the carrier concentration and mobility. When the specimens are annealed in selenium vapor the electron concentration at first increases and then becomes constant. A theoretical analysis of the results obtained indicate that selenium vacancies are the predominant point defects in the solutions, and that the process of defect formation itself is quasiepitaxial.

Optical Metrology for the Segmented Optics on the Constellation-X Spectroscopy X-Ray Telescope

NASA Technical Reports Server (NTRS)

Content, David; Colella, David; Fleetwood, Charles; Hadjimichael, Theo; Lehan, John; McMann, Joseph; Reid, Paul; Saha, Timo; Wright, Geraldine; Zhang, William

2004-01-01

We present the metrology requirements and metrology implementation necessary to prove out the reflector technology for the Constellation X(C-X) spectroscopy X-ray telescope (SXT). This segmented, 1.6m diameter highly nested Wolter-1 telescope presents many metrology and alignment challenges. In particular, these mirrors have a stringent imaging error budget as compared to their intrinsic stiffness; This is required for Constellation-X to have sufficient effective area with the weight requirement. This has implications for the metrology that can be used. A variety of contract and noncontact optical profiling and interferometric methods are combined to test the formed glass substrates before replication and the replicated reflector segments.The reflectors are tested both stand-alone and in-situ in an alignment tower.Some of these methods have not been used on prior X-ray telescopes and some are feasible only because of the segmented approach used on the SXT. Methods discussed include high precision coordinate measurement machines using very low force or optical probe axial interferometric profiling azimuthal circularity profiling and use of advanced null optics such as conical computer generated hologram (CGHs).

Onion-like nanoscale structures and fullerene-type cages formed by electron irradiation on turbostratic B{sub x}C{sub 1{minus}x} (x<0.2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golberg, D.; Bando, Y.; Kurashima, K.

Flakes of CVD grown B{sub x}C{sub 1{minus}x} (x<0.2) films were exposed to intense electron irradiation (flux density up to {approximately}100 A/cm{sup 2}) in a 300 kV high resolution electron microscope equipped with a field emission gun. The starting flakes revealed a turbostratic B{sub x}C{sub 1{minus}x} structure. The composition of the starting materials and irradiated products was determined by using electron energy loss spectroscopy (EELS). Depending on the electron dose applied, irradiation of the turbostratic material led to formation of soap-bubble-like irregularly-shaped objects (linear dimensions of {approximately}2--5 nm), onion- and semi-onion-like structures (d{approximately}10nm), nested fullerenes (3--14 shells) and elementary fullerene-type cagesmore » (d{approximately}0.7 nm). It is thought that these curled and closed nanostructures arise from a continuous bending of the hexagonal B{sub x}C{sub 1{minus}x} sheets under electron irradiation. Finally, some possible structural models of B{sub x}C{sub 1{minus}x} fullerenes are considered.« less

Long-Term X-Ray Variability of Circinus X-1

NASA Technical Reports Server (NTRS)

Saz Parkinson, P. M.; Tournear, D. M.; Bloom, E. D.; Focke, W. B.; Reilly, K. T.

2003-01-01

We present an analysis of long term X-ray monitoring observations of Circinus X-1 (Cir X-1) made with four different instruments: Vela 5B, Ariel V ASM, Ginga ASM, and RXTE ASM, over the course of more than 30 years. We use Lomb-Scargle periodograms to search for the approx. 16.5 day orbital period of Cir X-1 in each of these data sets and from this derive a new orbital ephemeris based solely on X-ray measurements, which we compare to the previous ephemerides obtained from radio observations. We also use the Phase Dispersion Minimization (PDM) technique, as well as FFT analysis, to verify the periods obtained from periodograms. We obtain dynamic periodograms (both Lomb-Scargle and PDM) of Cir X-1 during the RXTE era, showing the period evolution of Cir X-1, and also displaying some unexplained discrete jumps in the location of the peak power.

In(x)Ga(₁-x)As nanowires on silicon: one-dimensional heterogeneous epitaxy, bandgap engineering, and photovoltaics.

PubMed

Shin, Jae Cheol; Kim, Kyou Hyun; Yu, Ki Jun; Hu, Hefei; Yin, Leijun; Ning, Cun-Zheng; Rogers, John A; Zuo, Jian-Min; Li, Xiuling

2011-11-09

We report on the one-dimensional (1D) heteroepitaxial growth of In(x)Ga(1-x)As (x = 0.2-1) nanowires (NWs) on silicon (Si) substrates over almost the entire composition range using metalorganic chemical vapor deposition (MOCVD) without catalysts or masks. The epitaxial growth takes place spontaneously producing uniform, nontapered, high aspect ratio NW arrays with a density exceeding 1 × 10(8)/cm(2). NW diameter (∼30-250 nm) is inversely proportional to the lattice mismatch between In(x)Ga(1-x)As and Si (∼4-11%), and can be further tuned by MOCVD growth condition. Remarkably, no dislocations have been found in all composition In(x)Ga(1-x)As NWs, even though massive stacking faults and twin planes are present. Indium rich NWs show more zinc-blende and Ga-rich NWs exhibit dominantly wurtzite polytype, as confirmed by scanning transmission electron microscopy (STEM) and photoluminescence spectra. Solar cells fabricated using an n-type In(0.3)Ga(0.7)As NW array on a p-type Si(111) substrate with a ∼ 2.2% area coverage, operates at an open circuit voltage, V(oc), and a short circuit current density, J(sc), of 0.37 V and 12.9 mA/cm(2), respectively. This work represents the first systematic report on direct 1D heteroepitaxy of ternary In(x)Ga(1-x)As NWs on silicon substrate in a wide composition/bandgap range that can be used for wafer-scale monolithic heterogeneous integration for high performance photovoltaics.

An X-ray excited wind in Centaurus X-3

NASA Technical Reports Server (NTRS)

Day, C. S. R.; Stevens, Ian R.

1993-01-01

We propose a new interpretation of the behavior of the notable X-ray binary source Centaurus X-3. Based on both theoretical and observational arguments (using EXOSAT data), we suggest that an X-ray excited wind emanating from the O star is present in this system. Further, we suggest that this wind is responsible for the mass transfer in the system rather than Roche-lobe overflow or a normal radiatively driven stellar wind. We show that the ionization conditions in Cen X-3 are too extreme to permit a normal radiatively driven wind to emanate from portions of the stellar surface facing toward the neutron star. In addition, the flux of X-rays from the neutron star is strong enough to drive a thermal wind from the O star with sufficient mass-flux to power the X-ray source. We find that this model can reasonably account for the long duration of the eclipse transitions and other observed features of Cen X-3. If confirmed, this will be the first example of an X-ray excited wind in a massive binary. We also discuss the relationship between the excited wind in Cen X-3 to the situation in eclipsing millisecond pulsars, where an excited wind is also believed to be present.

Choosing the Active X: The Human Version of X Inactivation.

PubMed

Migeon, Barbara R

2017-12-01

Humans and rodents differ in how they carry out X inactivation (XI), the mammalian method to compensate for the different number of X chromosomes in males and females. Evolutionary changes in staging embryogenesis and in mutations within the XI center alter the process among mammals. The mouse model of XI is predicated on X counting and subsequently choosing the X to 'inactivate'. However, new evidence suggests that humans initiate XI by protecting one X in both sexes from inactivation by XIST, the noncoding RNA that silences the inactive X. This opinion article explores the question of how the active X is protected from silencing by its own Xist locus, and the possibility of different solutions for mouse and human. Copyright © 2017 Elsevier Ltd. All rights reserved.

Lack of X inactivation associated with maternal X isodisomy: evidence for a counting mechanism prior to X inactivation during human embryogenesis.

PubMed

Migeon, B R; Jeppesen, P; Torchia, B S; Fu, S; Dunn, M A; Axelman, J; Schmeckpeper, B J; Fantes, J; Zori, R T; Driscoll, D J

1996-01-01

We have previously reported functional disomy for X-linked genes in females with tiny ring X chromosomes and a phenotype significantly more abnormal than Turner syndrome. In such cases the disomy results from failure of these X chromosomes to inactivate because they lack DNA sequences essential for cis X inactivation. Here we describe a novel molecular mechanism for functional X disomy that is associated with maternal isodisomy. In this case, the severe mental retardation and multiple congenital abnormalities in a female with a mosaic 45,X/ 46,X,del(X)(q21.3-qter)/ 46X,r(X) karyotype are associated with overexpression of the genes within Xpter to Xq21.31 in many of her cells. Her normal X, ring X, and deleted linear X chromosomes originate from the same maternal X chromosome, and all are transcriptionally active. None expresses X inactive specific transcript (XIST), although the locus and region of the putative X inactivation center (XIC) are present on both normal and linear deleted X chromosomes. To our knowledge, this is the first report of a functional maternal X isodisomy, and the largest X chromosome to escape inactivation. In addition, these results (1) show that cis inactivation does not invariably occur in human females with two X chromosomes, even when the XIC region is present on both of them; (2) provide evidence for a critical time prior to the visible onset of X inactivation in the embryo when decisions about X inactivation are made; and (3) support the hypothesis that the X chromosome counting mechanism involves chromosomal imprinting, occurs prior to the onset of random inactivation, and is required for subsequent inactivation of the chromosome.

Global SO(3) x SO(3) x U(1) symmetry of the Hubbard model on bipartite lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmelo, J.M.P., E-mail: carmelo@fisica.uminho.p; Ostlund, Stellan; Sampaio, M.J.

2010-08-15

In this paper the global symmetry of the Hubbard model on a bipartite lattice is found to be larger than SO(4). The model is one of the most studied many-particle quantum problems, yet except in one dimension it has no exact solution, so that there remain many open questions about its properties. Symmetry plays an important role in physics and often can be used to extract useful information on unsolved non-perturbative quantum problems. Specifically, here it is found that for on-site interaction U {ne} 0 the local SU(2) x SU(2) x U(1) gauge symmetry of the Hubbard model on amore » bipartite lattice with N{sub a}{sup D} sites and vanishing transfer integral t = 0 can be lifted to a global [SU(2) x SU(2) x U(1)]/Z{sub 2}{sup 2} = SO(3) x SO(3) x U(1) symmetry in the presence of the kinetic-energy hopping term of the Hamiltonian with t > 0. (Examples of a bipartite lattice are the D-dimensional cubic lattices of lattice constant a and edge length L = N{sub a}a for which D = 1, 2, 3,... in the number N{sub a}{sup D} of sites.) The generator of the new found hidden independent charge global U(1) symmetry, which is not related to the ordinary U(1) gauge subgroup of electromagnetism, is one half the rotated-electron number of singly occupied sites operator. Although addition of chemical-potential and magnetic-field operator terms to the model Hamiltonian lowers its symmetry, such terms commute with it. Therefore, its 4{sup N}{sub a}{sup D} energy eigenstates refer to representations of the new found global [SU(2) x SU(2) x U(1)]/Z{sub 2}{sup 2} = SO(3) x SO(3) x U(1) symmetry. Consistently, we find that for the Hubbard model on a bipartite lattice the number of independent representations of the group SO(3) x SO(3) x U(1) equals the Hilbert-space dimension 4{sup N}{sub a}{sup D}. It is confirmed elsewhere that the new found symmetry has important physical consequences.« less

Crystal growth and properties of Ag 7_ xTaSe 6_ xI x (0 x 1)

NASA Astrophysics Data System (ADS)

Wada, H.; Sato, A.

1993-03-01

National Institute for Research in Inorganic Materials, Namiki 1-1, Tsukuba, Ibaraki 305, Japan A series of argyrodite compounds with the formula Ag7 xTaSe6 xIx (0 x 1) have been prepared for the first time by a sealed silica tube method. Single crystals have been obtained by heating at 800°C for 2 weeks. Their morphology and crystal structure have been studied by reflected-light microscopy, SEM, EDAX and X-ray diffraction. The silver ionic conductivities of the samples have been also measured.

Low-Energy Microfocus X-Ray Source for Enhanced Testing Capability in the Stray Light Facility

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; O'Dell, Stephen; Kolodziejczak, Jeff

2015-01-01

Research toward high-resolution, soft x-ray optics (mirrors and gratings) necessary for the next generation large x-ray observatories requires x-ray testing using a low-energy x-ray source with fine angular size (<1 arcsecond). To accommodate this somewhat demanding requirement, NASA Marshall Space Flight Center (MSFC) has procured a custom, windowless low-energy microfocus (approximately 0.1 mm spot) x-ray source from TruFocus Corporation that mates directly to the Stray Light Facility (SLF). MSFC X-ray Astronomy team members are internationally recognized for their expertise in the development, fabrication, and testing of grazing-incidence optics for x-ray telescopes. One of the key MSFC facilities for testing novel x-ray instrumentation is the SLF. This facility is an approximately 100-m-long beam line equipped with multiple x-ray sources and detectors. This new source adds to the already robust compliment of instrumentation, allowing MSFC to support additional internal and community x-ray testing needs.

"X-Ray Transients in Star-Forming Regions" and "Hard X-Ray Emission from X-Ray Bursters"

NASA Technical Reports Server (NTRS)

Halpern, Jules P.; Kaaret, Philip

1999-01-01

This grant funded work on the analysis of data obtained with the Burst and Transient Experiment (BATSE) on the Compton Gamma-Ray Observatory. The goal of the work was to search for hard x-ray transients in star forming regions using the all-sky hard x-ray monitoring capability of BATSE. Our initial work lead to the discovery of a hard x-ray transient, GRO J1849-03. Follow-up observations of this source made with the Wide Field Camera on BeppoSAX showed that the source should be identified with the previously known x-ray pulsar GS 1843-02 which itself is identified with the x-ray source X1845-024 originally discovered with the SAS-3 satellite. Our identification of the source and measurement of the outburst recurrence time, lead to the identification of the source as a Be/X-ray binary with a spin period of 94.8 s and an orbital period of 241 days. The funding was used primarily for partial salary and travel support for John Tomsick, then a graduate student at Columbia University. John Tomsick, now Dr. Tomsick, received his Ph.D. from Columbia University in July 1999, based partially on results obtained under this investigation. He is now a postdoctoral research scientist at the University of California, San Diego.

X-33

NASA Image and Video Library

2004-04-15

Pictured here is an artist's concept of the experimental X-33 in-flight. The X-33 program was designed to pave the way to a full-scale commercially developed, reusable launch vehicle (RLV). The program that will put the U.S. on a path toward safe, affordable, reliable access to space by providing the latest technology was ready for space flight. The X-33 is the flagship technology demonstrator for technologies that will dramatically lower the cost of access to space. The X-33 program was cancelled in 2001.

Preparation of Single-Layer MoS 2xSe 2(1-x) and Mo xW 1-xS 2 Nanosheets with High-Concentration Metallic 1T Phase

DOE PAGES

Tan, Chaoliang; Zhao, Wei; Chaturvedi, Apoorva; ...

2016-02-24

The high-yield and scalable production of single-layer ternary transition metal dichalcogenide nanosheets with ≈66% of metallic 1T phase, including MoS 2xSe 2(1-x) and Mo xW 1-xS 2 is here achieved via electrochemical Li-intercalation and the exfoliation method. Thin film MoS 2xSe 2(1-x) nanosheets drop-cast on a fluorine-doped tin oxide substrate are used as an efficient electrocatalyst on the counter electrode for the tri-iodide reduction in a dye-sensitized solar cell.

X-Ray Polarization from High Mass X-Ray Binaries

NASA Technical Reports Server (NTRS)

Kallman, T.; Dorodnitsyn, A.; Blondin, J.

2015-01-01

X-ray astronomy allows study of objects which may be associated with compact objects, i.e. neutron stars or black holes, and also may contain strong magnetic fields. Such objects are categorically non-spherical, and likely non-circular when projected on the sky. Polarization allows study of such geometric effects, and X-ray polarimetry is likely to become feasible for a significant number of sources in the future. A class of potential targets for future X-ray polarization observations is the high mass X-ray binaries (HMXBs), which consist of a compact object in orbit with an early type star. In this paper we show that X-ray polarization from HMXBs has a distinct signature which depends on the source inclination and orbital phase. The presence of the X-ray source displaced from the star creates linear polarization even if the primary wind is spherically symmetric whenever the system is viewed away from conjunction. Direct X-rays dilute this polarization whenever the X-ray source is not eclipsed; at mid-eclipse the net polarization is expected to be small or zero if the wind is circularly symmetric around the line of centers. Resonance line scattering increases the scattering fraction, often by large factors, over the energy band spanned by resonance lines. Real winds are not expected to be spherically symmetric, or circularly symmetric around the line of centers, owing to the combined effects of the compact object gravity and ionization on the wind hydrodynamics. A sample calculation shows that this creates polarization fractions ranging up to tens of percent at mid-eclipse.

X-1 research aircraft landing on lakebed

NASA Technical Reports Server (NTRS)

1947-01-01

The first of the rocket-powered research aircraft, the X-1 (originally designated the XS-1), was a bullet-shaped airplane that was built by the Bell Aircraft Company for the US Air Force and the National Advisory Committee on Aeronautics (NACA). The mission of the X-1 was to investigate the transonic speed range (speeds from just below to just above the speed of sound) and, if possible, to break the 'sound barrier'. The first of the three X-1s was glide-tested at Pinecastle Air Force Base, FL, in early 1946. The first powered flight of the X-1 was made on Dec. 9, 1946, at Edwards Air Force Base with Chalmers Goodlin, a Bell test pilot, at the controls. On Oct. 14, 1947, with USAF Captain Charles 'Chuck' Yeager as pilot, the aircraft flew faster than the speed of sound for the first time. Captain Yeager ignited the four-chambered XLR-11 rocket engines after being air-launched from under the bomb bay of a B-29 at 21,000 ft. The 6,000-lbthrust ethyl alcohol/liquid oxygen burning rockets, built by Reaction Motors, Inc., pushed him up to a speed of 700 mph in level flight. Captain Yeager was also the pilot when the X-1 reached its maximum speed of 957 mph. Another USAF pilot. Lt. Col. Frank Everest, Jr., was credited with taking the X-1 to its maximum altitude of 71,902 ft. Eighteen pilots in all flew the X-1s. The number three plane was destroyed in a fire before ever making any powered flights. A single-place monoplane, the X-1 was 31 ft long, 10 ft high, and had a wingspan of 29 ft. It weighed 4,900 lb and carried 8,200 lb of fuel. It had a flush cockpit with a side entrance and no ejection seat. This roughly 30-second video clip shows the X-1 landing on Rogers Dry Lakebed followed by the safety chase aircraft.

The Athena X-ray Integral Field Unit (X-IFU)

NASA Technical Reports Server (NTRS)

Barret, Didier; Trong, Thein Lam; Den Herder, Jan-Willem; Piro, Luigi; Barcons, Xavier; Huovelin, Juhani; Kelley, Richard; Mas-Hesse, J. Miquel; Mitsuda, Kazuhisa; Paltani, Stephane;

(Ba1-x Bi x )(Ti1-x Ni0.5x Sn0.5x )O3 Solid Solution: Phase Evolution, Microstructure, Dielectric Properties, and Impedance Analysis

NASA Astrophysics Data System (ADS)

Chen, Xiuli; Li, Xiaoxia; Yan, Xiao; Liu, Gaofeng; Zhou, Huanfu

2018-02-01

(Ba1-x Bi x )(Ti1-x Ni0.5x Sn0.5x )O3 (BBTNS, 0.02 ≤ x ≤ 0.1) samples have been synthesized by traditional solid-state reaction technique and their structural transformation and dielectric properties investigated. X-ray diffraction (XRD) analysis revealed that BBTNS could form a homogeneous solid solution, and the transformation from tetragonal to pseudocubic phase occurred at 0.04 ≤ &!nbsp;x ≤ 0.06. Optimized properties with stable ɛ r (˜ 1829 to 1838), small Δɛ/ɛ 25°C values (± 15%) over a broad temperature range from -60°C to 140°C, and low tan Δ (≤ 0.02) from 4°C to 194°C were obtained at x = 0.1. The relaxation and conduction process in the high-temperature region are attributed to thermal activation, and oxygen vacancies may be the ionic charge carriers in perovskite ferroelectrics.

ATRX ADD domain links an atypical histone methylation recognition mechanism to human mental-retardation syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iwase, Shigeki; Xiang, Bin; Ghosh, Sharmistha

ATR-X (alpha-thalassemia/mental retardation, X-linked) syndrome is a human congenital disorder that causes severe intellectual disabilities. Mutations in the ATRX gene, which encodes an ATP-dependent chromatin-remodeler, are responsible for the syndrome. Approximately 50% of the missense mutations in affected persons are clustered in a cysteine-rich domain termed ADD (ATRX-DNMT3-DNMT3L, ADD{sub ATRX}), whose function has remained elusive. Here we identify ADD{sub ATRX} as a previously unknown histone H3-binding module, whose binding is promoted by lysine 9 trimethylation (H3K9me3) but inhibited by lysine 4 trimethylation (H3K4me3). The cocrystal structure of ADD{sub ATRX} bound to H3{sub 1-15}K9me3 peptide reveals an atypical composite H3K9me3-binding pocket,more » which is distinct from the conventional trimethyllysine-binding aromatic cage. Notably, H3K9me3-pocket mutants and ATR-X syndrome mutants are defective in both H3K9me3 binding and localization at pericentromeric heterochromatin; thus, we have discovered a unique histone-recognition mechanism underlying the ATR-X etiology.« less

ATRX ADD Domain Links an Atypical Histone Methylation Recognition Mechanism to Human Mental-Retardation Syndrome

DOE Office of Scientific and Technical Information (OSTI.GOV)

S Iwase; B Xiang; S Ghosh

ATR-X (alpha-thalassemia/mental retardation, X-linked) syndrome is a human congenital disorder that causes severe intellectual disabilities. Mutations in the ATRX gene, which encodes an ATP-dependent chromatin-remodeler, are responsible for the syndrome. Approximately 50% of the missense mutations in affected persons are clustered in a cysteine-rich domain termed ADD (ATRX-DNMT3-DNMT3L, ADD{sub ATRX}), whose function has remained elusive. Here we identify ADD{sub ATRX} as a previously unknown histone H3-binding module, whose binding is promoted by lysine 9 trimethylation (H3K9me3) but inhibited by lysine 4 trimethylation (H3K4me3). The cocrystal structure of ADD{sub ATRX} bound to H3{sub 1-15}K9me3 peptide reveals an atypical composite H3K9me3-binding pocket,more » which is distinct from the conventional trimethyllysine-binding aromatic cage. Notably, H3K9me3-pocket mutants and ATR-X syndrome mutants are defective in both H3K9me3 binding and localization at pericentromeric heterochromatin; thus, we have discovered a unique histone-recognition mechanism underlying the ATR-X etiology.« less

Structural and relaxor-like dielectric properties of unfilled tungsten bronzes Ba5-5xSm5xTi5xNb10-5xO30

NASA Astrophysics Data System (ADS)

Wei, T.; Dong, Z.; Zhao, C. Z.; Guo, Y. Y.; Zhou, Q. J.; Li, Z. P.

2016-03-01

New unfilled tetragonal tungsten bronze (TTB) oxides, Ba5-5xSm5xTi5xNb10-5xO30 (BSTN-x), where 0.10 ≤ x ≤ 0.35, have been synthesized in this work. Their crystal structure was determined and analyzed based on Rietveld structural refinement. It is found that single TTB phase can be formed in a particular x range (i.e., 0.15 ≤ x ≤ 0.3) due to the competition interaction between tolerance factor and electronegativity difference. Furthermore, dielectric and ferroelectric results indicate that phase transitions and ferroelectric states are sensitive to x. Referring to the local chemistry, we suggest that the raise of vacancies at the A2-site compared with that of A1-site will intensely depress the normal ferroelectric phase and is in favor of relaxor ferroelectric state. Macroscopically, previous A-site size difference standpoint on fill TTB compounds cannot give a reasonable explanation about the variation of dielectric maximum temperature (Tm) for present BSTN-x compounds. Alternatively, tetragonality (c/a) is adopted which can well describe the variation of Tm in whole x range. In addition, one by one correspondence between tetragonality and electrical features can be found, and the compositions involving high c/a are usually stabilized in normal ferroelectric phase. It is believed that c/a is a more appropriate parameter to illustrate the variation of ferroelectric properties for unfilled TTB system.

On the Samarium Substitution Effects in Y3-x Sm x Al5O12 (x = 0.1-3.0)

NASA Astrophysics Data System (ADS)

Skaudzius, Ramunas; Sakirzanovas, Simas; Kareiva, Aivaras

2018-04-01

Yttrium aluminium garnet substituted by samarium Y3-x Sm x Al5O12, (YSmAG, x = 0.1, 0.15, 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5 and 3.0) was prepared by an aqueous sol-gel processing using etane-1,2-diol as complexing agent. The end products obtained at 1000°C in air were characterized by x-ray diffraction analysis, infrared spectroscopy (FT-IR) and scanning electron microscopy. It was demonstrated, however, that the total substitution of yttrium by samarium does not proceed in the YSmAG. The single cubic garnet phase was formed only at a low concentration of samarium (x = 0.1, 0.15, 0.25, 0.5, 0.75, 1.0). With further substitutional levels, if the amount of samarium was x = 1.5, 2.0, 2.5 and 3, respectively, the formation a of minor amount of side perovskite samarium aluminate SmAlO3 (SmAP) phase was observed. Surprisingly, when yttrium was totally replaced by the samarium (x = 3.0) the main synthesis product was SmAP. The possible formation of Sm3Al5O12 (SmAG) garnet was also investigated for the first time by variation of the temperature in the range of 780-835°C.

American X-Vehicles: An Inventory X-1 to X-50 Centennial of Flight Edition

NASA Technical Reports Server (NTRS)

Jenkins, Dennis R.; Landis, Tony; Miller, Jay

2003-01-01

For a while, it seemed the series of experimental aircraft sponsored by the U. S. government had run its course. Between the late 1940s and the late 1970s, almost thirty designations had been allocated to aircraft meant to explore new flight regimes or untried technologies. Then, largely, it ended. But there was a resurgence in the mid- to late- 1990s, and as we enter the fourth year of the new millennia, the designations are up to x-50. Many have a misconception that X-vehicles have always explored the high-speed and high-altitude flight regimes - something popularized by Chuck Yeager in the original X-1 and the exploits of the twelve men that flew the X-15. Although these flight regimes have always been in the spotlight, many others have been explored by X-vehicles. The little Bensen X-25 never exceeded 85 mph, and others were limited to speeds of several hundred mph. There has been some criticism that the use of X designations has been corrupted somewhat by including what are essentially prototypes of future operational aircraft, especially the two JSF demonstrators. But this is not new-the X-11 and X-12 from the 1950s were going to be prototypes of the Atlas intercontinental ballistic missile, and the still-born Lockheed X-27 was always intended as a prototype of a production aircraft. So although this practice does not represent the best use of 'X' designations, it is not without precedent.

Room-temperature ferromagnetic Zn1- x Ni x S nanoparticles

NASA Astrophysics Data System (ADS)

Kunapalli, Chaitanya Kumar; Shaik, Kaleemulla

2018-05-01

Nickel-doped zinc sulfide nanoparticles (Zn1- x Ni x S) at x = 0.00, 0.02, 0.05, 0.08 and 0.10 were synthesized by solid-state reaction. The (nickel sulfide) NiS and (zinc sulfide) ZnS nanoparticles in desired ratios were taken, mixed and ground for 6 h at a speed rate of 300 rpm using a planetary ball mill. The milled nanoparticles were sintered at 600 °C for 8 h using a high-temperature vacuum furnace. The structural, optical, luminescence and magnetic properties of the Zn1- x Ni x S nanoparticles were characterized by powder X-ray diffraction (XRD), UV-Vis-NIR diffuse reflectance spectroscopy, photoluminescence (PL) spectroscopy and vibrating sample magnetometer (VSM). No change in crystal structure was observed from XRD by substitution of Ni into ZnS lattice. The mean crystallite size was found to be 37 nm. The band gap of Zn1- x Ni x S nanoparticles decreased from 3.57 to 3.37 eV on increasing the dopant concentration. The room-temperature photoluminescence (PL) spectra of Zn1- x Ni x S nanoparticles showed two broad and intense emission peaks at 420 and 438 nm with excitation wavelength of 330 nm. The Zn1- x Ni x S nanoparticles showed ferromagnetism at 100 K and at room temperature (300 K) and also the strength of magnetization increased with Ni concentration. The maximum magnetization value of 0.18 emu/g was observed for x = 0.10 at 100 K. The strength of the magnetization observed at 100 K was higher than that of magnetization observed at 300 K.

Oxygen-induced Al surface segregation in Al(x)Ga(1-x)As and the effect of Y overlayers on the oxidation of the Y/Al(x)Ga(1-x)As interface

NASA Technical Reports Server (NTRS)

Mesarwi, A.; Ignatiev, A.

1992-01-01

The oxidation of Al(x)Ga(1-x)As (x = 0.15, AlGaAs) was studied by AES and XPS at 350 C and different oxygen exposures (up to 5 x 10 exp 4 L). Also studied were the effects of yttrium overlayers (theta = 3 ML) on the oxidation of the AlGaAs surface. Substantial oxygen-induced Al surface segregation has been observed for both yttriated and nonyttriated AlGaAs surfaces which increased with increasing oxygen exposure. Also observed is a significant Y-enhanced oxidation of the AlGaAs surface. Oxidation of the yttriated AlGaAs surface was found to be a factor of 4 greater than that of the nonyttriated surface. Also, while oxidation of the nonyttriated AlGaAs yielded mainly Al2O(x) (x less than 3) and only little Ga2O3, the yttriated AlGaAs surface oxide layer was principally Ga2O3 and stoichiometric Al2O3. However, both the yttriated and nonyttriated surfaces were found to contain metallic As within the oxide layer.

Structure cristalline du composé Hg3-xSbx(S+Se)2+xI2-x (x ≃ 0.1)

PubMed Central

Kars, Mohammed; Herrero, Adrian Gómez; Roisnel, Thierry; Rebbah, Allaoua; Otero-Diáz, L. Carlos

2016-01-01

Single crystals of the mercury chalcohalide Hg3-xSbx(S+Se)2+xI2-x (x ≃ 0.1) (mercury anti­mony sulfide selenide iodide), were grown by a chemical transport reaction. The structure contains three independent A (Hg/Sb) atoms; each atom is strongly covalently bonded with two X (Se/S) atoms to form approximately linear X–A–X units. The X–A–X units link to form A 4 X 4 rings, which are combined into infinite crankshaft-type bands running along the [100] direction. Four equatorial E (I/X = Se,S) atoms at relatively long distances complete the distorted octa­hedral coordination of A (Hg/Sb). The crystal under investigation was twinned by non-merohedry with a refined twin domain fraction of 0.814 (6):0.186 (6). The structure is isotypic with Hg3Se2I2 [Beck & Hedderich (2000 ▸). J. Solid State Chem. 151, 73–76], but the current determination reveals a coupled substitution, with partial replacement of Hg+2 by Sb+3, balanced by the equivalent substitution of I−1 by S−2 and Se−2. Bond-valence calculations are consistent with this relative substitution model. PMID:27006793

Ternary lanthanum sulfide selenides {alpha}-LaS{sub 2-x}Se{sub x} (0<x<2) with mixed dichalcogenide anions X{sub 2}{sup 2-} (X=S, Se)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartsch, Christian; Doert, Thomas, E-mail: thomas.doert@chemie.tu-dresden.de

2012-01-15

Mixed lanthanum sulfide selenides LaS{sub 2-x}Se{sub x} (0<x<2) were obtained by metathesis reactions starting from anhydrous lanthanum chloride and alkali metal polychalcogenides. The LaS{sub 2-x}Se{sub x} compounds crystallize in space group P2{sub 1}/a, no. 14, and adopt the {alpha}-LnS{sub 2} (Ln=Y, La-Lu) structure type with a pronounced site preference for the chalcogen atoms. The mixed chalcogenides form a complete miscible series with lattice parameters a=820-849 pm, b=413-425 pm and c=822-857 pm ({beta} Almost-Equal-To 90 Degree-Sign) following Vegard's rule. Raman signals indicate the presence of mixed X{sub 2}{sup 2-} dianions, a species rarely evidenced in literature, besides the well known anionsmore » S{sub 2}{sup 2-} and Se{sub 2}{sup 2-}. The band gaps of the LaS{sub 2-x}Se{sub x} compounds, determined by optical spectroscopy, decrease nearly linearly with increasing amount of selenium. - Graphical abstract: Raman spectra and site occupancies in the structures of selected lanthanum sulfide selenides. Highlights: Black-Right-Pointing-Pointer Vegard series of mixed lanthanum sulfide selenides LaS{sub 2-x}Se{sub x} (0<x<2). Black-Right-Pointing-Pointer Pronounced site ordering of chalcogen positions. Black-Right-Pointing-Pointer Optical band gaps decrease with Se content. Black-Right-Pointing-Pointer Raman measurements evidence mixed X{sub 2}{sup 2-} dimeric anions.« less

Optical and X-ray rebrightening in NS X-ray Nova Aql X-1

NASA Astrophysics Data System (ADS)

Meshcheryakov, A.; Bikmaev, I.; Irtuganov, E.; Sakhibullin, N.; Vlasyuk, V. V.; Spiridonova, O. I.; Khamitov, I.; Medvedev, P.; Pavlinsky, M. N.; Tsygankov, S. S.

2017-06-01

The current outburst in NS X-ray Nova Aql X-1 has started 28 May 2017, as it was reported earlier (see ATel#10441, #10450, #10452). During optical monitoring campaign of Aql X-1, performed at 1.5-m Russian-Turkish telescope (TUBITAK National Observatory) and 1-m SAO RAS optical telescope (Special Astrophysical Observatory) we report a substantial increase of optical brightness of Aql X-1 in the last few days.

X-ray studies of quasars with the Einstein Observatory. IV - X-ray dependence on radio emission

NASA Technical Reports Server (NTRS)

Worrall, D. M.; Tananbaum, H.; Giommi, P.; Zamorani, G.

1987-01-01

The X-ray properties of a sample of 114 radio-loud quasars observed with the Einstein Observatory are examined, and the results are compared with those obtained from a large sample of radio-quiet quasars. The results of statistical analysis of the dependence of X-ray luminosity on combined functions of optical and radio luminosity show that the dependence on both luminosities is important. However, statistically significant differences are found between subsamples of flat radio spectra quasars and steep radio spectra quasars with regard to dependence of X-ray luminosity on only radio luminosity. The data are consistent with radio-loud quasars having a physical component, not directly related to the optical luminosity, which produces the core radio luminosity plus 'extra' X-ray emission.

Structure and dielectric properties of (Ba0.7Sr0.3)1- x Na x (Ti0.9Sn0.1)1- x Nb x O3 ceramics

NASA Astrophysics Data System (ADS)

Ghoudi, Hanen; Chkoundali, Souad; Aydi, Abdelhedi; Khirouni, Kamel

2017-11-01

(Ba0.7Sr0.3)1- x Na x (Ti0.9Sn0.1)1- x Nb x O3 ceramics with compositions x = 0.6, 0.7, 0.8 and 0.9 were synthesized using the solid-state reaction method. These ceramics were examined by X-ray diffraction and dielectric measurements over a broad temperature and frequency ranges. X-ray diffraction patterns revealed a single-perovskite phase crystallized in a cubic structure, for x < 0.8, and in tetragonal, for x ≥ 0.8, with Pm3m and P4mm spaces groups, respectively. Two types of behaviors, classical ferroelectric or relaxor, were observed depending on the x composition. It is noted that temperatures T C (the Curie temperature) or T m (the temperature of maximum permittivity) rise when x increases and the relaxor character grows more significantly when x composition decreases. To analyze the dielectric relaxation degree of relaxor, various models were considered. It was proven that an exponential function could well describe the temperature dependence of the static dielectric constant and relaxation time.

Exploring the palladium- and platinum-bis(pyridine) complex motif by NMR spectroscopy, X-ray crystallography, (tandem) mass spectrometry, and isothermal titration calorimetry: do substituent effects follow chemical intuition?

PubMed

Weilandt, Torsten; Löw, Nora L; Schnakenburg, Gregor; Daniels, Jörg; Nieger, Martin; Schalley, Christoph A; Lützen, Arne

2012-12-21

A series of ten palladium-bis(pyridine) complexes, as well as their corresponding platinum complexes, have been synthesized. The pyridine ligands in each series carried different σ-donor and/or π-acceptor/donor substituents at the para-position of their pyridine rings. These complexes were analysed by NMR spectroscopy, X-ray crystallography, (tandem) MS, and isothermal titration calorimetry (ITC) to validate whether these methods allowed us to obtain a concise and systematic picture of the relative and absolute thermodynamic stabilities of the complexes, as determined by the electronic effects of the substituents. Interestingly, the NMR spectroscopic data hardly correlated with the expected substituent effects but the heteronuclear platinum-phosphorus coupling constants did. Crystallographic data were found to be blurred by packing effects. Instead, tandem MS and ITC data were in line with each other and followed the expected trends. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

THE DEVELOPMENT OF A 1990 GLOBAL INVENTORY FOR SO(X) AND NO(X) ON A 1(DEGREE) X 1(DEGREE) LATITUDE-LONGITUDE GRID.

DOE Office of Scientific and Technical Information (OSTI.GOV)

VAN HEYST,B.J.

1999-10-01

Sulfur and nitrogen oxides emitted to the atmosphere have been linked to the acidification of water bodies and soils and perturbations in the earth's radiation balance. In order to model the global transport and transformation of SO{sub x} and NO{sub x}, detailed spatial and temporal emission inventories are required. Benkovitz et al. (1996) published the development of an inventory of 1985 global emissions of SO{sub x} and NO{sub x} from anthropogenic sources. The inventory was gridded to a 1{degree} x 1{degree} latitude-longitude grid and has served as input to several global modeling studies. There is now a need to providemore » modelers with an update of this inventory to a more recent year, with a split of the emissions into elevated and low level sources. This paper describes the development of a 1990 update of the SO{sub x} and NO{sub x} global inventories that also includes a breakdown of sources into 17 sector groups. The inventory development starts with a gridded global default EDGAR inventory (Olivier et al, 1996). In countries where more detailed national inventories are available, these are used to replace the emissions for those countries in the global default. The gridded emissions are distributed into two height levels (0-100m and >100m) based on the final plume heights that are estimated to be typical for the various sectors considered. The sources of data as well as some of the methodologies employed to compile and develop the 1990 global inventory for SO{sub x} and NO{sub x} are discussed. The results reported should be considered to be interim since the work is still in progress and additional data sets are expected to become available.« less

Structural, magneto-optical properties and cation distribution of SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Auwal, I.A.; Güngüneş, H.; Güner, S.

Highlights: • SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites have been prepared by sol-gel autocombustion. • XRD patterns show that SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites exhibit hexagonal structure. • The intrinsic coercivity (H{sub ci}) above 15000 Oe reveals that all samples are magnetically hard materials. - Abstract: SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} (0.0 ≤ x ≤ 0.33) hexaferrites were produced via sol-gel auto combustion. XRD patterns show that all the samples are single-phase M-type strontium hexaferrite (SrM). The magnetic hysteresis (σ-H) loops revealed the ferromagnetic nature ofmore » nanoparticles (NPs). The coercive field decreases from 4740 Oe to 2720 Oe with increasing ion content. In particular, SrBi{sub x}La{sub x}Y{sub x}Fe{sub 12−3x}O{sub 19} NPs with x = 0.0, 0.1, 0.2 have suitable magnetic characteristics (σ{sub s} = 62.03–64.72 emu/g and H{sub c} = 3105–4740 Oe) for magnetic recording. The intrinsic coercivity (H{sub ci}) above 15000 Oe reveals that all samples are magnetically hard materials. Tauc plots were used to specify the direct optical energy band gap (E{sub g}) of NPs. The E{sub g} values are between 1.76 eV and 1.85 eV. {sup 57}Fe Mössbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting, relative area and hyperfine magnetic field values on Bi{sup 3+} La{sup 3+} and Y{sup 3+} substitutions have been determined.« less

Growth and characterization of low composition Ge, x in epi-Si1‑x Gex (x  ⩽  10%) active layer for fabrication of hydrogenated bottom solar cell

NASA Astrophysics Data System (ADS)

Ajmal Khan, M.; Sato, R.; Sawano, K.; Sichanugrist, P.; Lukianov, A.; Ishikawa, Y.

2018-05-01

Semiconducting epi-Si1‑x Ge x alloys have promising features as solar cell materials and may be equally important for some other semiconductor device applications. Variation of the germanium compositional, x in epi-Si1‑x Ge x , makes it possible to control the bandgap between 1.12 eV and 0.68 eV for application in bottom solar cells. A low proportion of Ge in SiGe alloy can be used for photovoltaic application in a bottom cell to complete the four-terminal tandem structure with wide bandgap materials. In this research, we aimed to use a low proportion of Ge—about 10%—in strained or relaxed c-Si1‑x Ge x /c-Si heterojunctions (HETs), with or without insertion of a Si buffer layer grown by molecular beam epitaxy, to investigate the influence of the relaxed or strained SiGe active layer on the performance of HET solar cells grown using the plasma enhanced chemical vapor deposition system. Thanks to the c-Si buffer layer at the hetero-interface, the efficiency of these SiGe based HET solar cells was improved from 2.3% to 3.5% (fully strained and with buffer layer). The Jsc was improved, from 8 mA cm‑2 to 15.46 mA cm‑2, which might be supported by strained c-Si buffer layer at the hetero-interface, by improving the crystalline quality.

RXTE Observations of LMC X-1 and LMC X-3

NASA Technical Reports Server (NTRS)

Wilms, J.; Nowak, M. A.; Dove, J. B.; Pottschmidt, K.; Heindl, W. A.; Begelman, M. C.; Staubert, R.

1999-01-01

Of all known persistent stellar-mass black hole candidates, only LMC X-1 and LMC X-3 consistently show spectra that are dominated by a soft, thermal component. We present results from long (170 ksec) Rossi X-ray Timing Explorer (RXTE) observations of LMC X-1 and LMC X-3 made in 1996 December. The spectra can be described by a multicolor disk blackbody plus an additional high-energy power-law. Even though the spectra are very soft (Gamma approximately 2.5), RXTE detected a significant signal from LMC X-3 up to energies of 50 keV, the hardest energy at which the object was ever detected. Focusing on LMC X-3 , we present results from the first year of an ongoing monitoring campaign with RXTE which started in 1997 January. We show that the appearance of the object changes considerably over its approximately 200 d long cycle. This variability can either be explained by periodic changes in the mass transfer rate or by a precessing accretion disk analogous to Her X-1.

RXTE Observations of LMC X-1 and LMC X-3

NASA Technical Reports Server (NTRS)

Wilms, J.; Nowak, M. A.; Dove, J. B.; Pottschmidt, K.; Heindl, W. A.; Begelman, M. C.; Staubert, R.

1998-01-01

Of all known persistent stellar-mass black hole candidates, only LMC X-1 and LMC X-3 consistently show spectra that are dominated by a soft, thermal component. We present results from long (170 ksec) Rossi X-ray Timing Explorer (RXTE) observations of LMC X-1 and LMC X-3 made in 1996 December. The spectra can be described by a multicolor disk blackbody plus an additional high-energy power-law. Even though the spectra are very soft (Gamma approximately 2.5), RXTE detected a significant signal from LMC X-3 up to energies of 50 keV, the hardest energy at which the object was ever detected. Focusing on LMC X-3, we present results from the first year of an ongoing monitoring campaign with RXTE which started in 1997 January. We show that the appearance of the object changes considerably over its approximately 200d long cycle. This variability can either be explained by periodic changes in the mass transfer rate or by a precessing accretion disk analogous to Her X-1.

Role of the chemical substitution on the luminescence properties of solid solutions Ca{sub (1−x)}Cd{sub (x)}WO{sub 4} (0 ≤ x ≤1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taoufyq, A.; Laboratoire Matériaux et Environnement LME, Faculté des Sciences, Université Ibn Zohr, BP 8106, Cité Dakhla, Agadir; CEA, DEN, Département d'Etudes des Réacteurs, Service de Physique Expérimentale, Laboratoire Dosimétrie Capteurs Instrumentation, 13108 Saint-Paul-lez-Durance

2015-10-15

Highlights: • Luminescence can be modified by chemical substitution in solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4}. • The various emission spectra (charge transfer) were obtained under X-ray excitation. • Scheelite or wolframite solid solutions presented two types of emission spectra. • A luminescence component depended on cadmium substitution in each solid solution. • A component was only characteristic of oxyanion symmetry in each solid solution. - Abstract: We have investigated the chemical substitution effects on the luminescence properties under X-ray excitation of the solid solutions Ca{sub (1−x)}Cd{sub (x)}WO{sub 4} with 0 ≤ x ≤ 1. Two types of wide spectralmore » bands, associated with scheelite-type or wolframite-type solid solutions, have been observed at room temperature. We decomposed each spectral band into several spectral components characterized by energies and intensities varying with composition x. One Gaussian component was characterized by an energy decreasing regularly with the composition x, while the other Gaussian component was only related to the tetrahedral or octahedral configurations of tungstate groups WO{sub 4}{sup 2−} or WO{sub 6}{sup 6−}. The luminescence intensities exhibited minimum values in the composition range x < 0.5 corresponding to scheelite-type structures, then, they regularly increased for cadmium compositions x > 0.5 corresponding to wolframite-type structures.« less

Differential Thermal Analysis of Hg(1-x)Mn(x)Te Alloys in the X=0 to 0.3 Range

NASA Technical Reports Server (NTRS)

Price, M. W.; Scripa, R. N.; Szofran, F. R.; Lehoczky, S. L.; Su, C-H

1998-01-01

Understanding the experimental conditions necessary for the development of radial and axial compositional homogeneity in directionally solidified Hg(0.89)Mn(0.11)Te(MMT) crystals has been difficult due to the lack of segregation coefficient data on the Hg(1-x)Mn(x)Te alloy system in the X = 0 to 0.3 composition range. Determining segregation coefficient data from the available Hg(1-x)Mn(x)Te alloy phase equilibria data is not practical due to discrepancies in the shape of the reported solidus and liquidus curves in the X = 0 to 0.3 range. To resolve these discrepancies and to obtain segregation coefficient data which can be used to understand homogeneity in directionally solidified MMT crystals, the solidus and liquidus temperatures of seven Hg(1-x)Mn(x)Te alloys in the X = 0 to 0.3 range were determined using differential thermal analysis (DTA). The Hg(1-x)Mn(x)Te phase diagram constructed for the X = 0 to 0.3 range of this alloy system from the DTA measurements clarifies the shape of the solidus and liquidus curves in this range. The segregation coefficient for the Hg(1-x)Mn(x)Te system was found to vary from 5 to 4.4 as the solidus composition increased from 0-30 atomic percent MnTe. This information will be useful in the analysis of axial and radial homogeneity of directionally solidified MMT crystals.

Infrared photocurrent management in monolithic perovskite/silicon heterojunction tandem solar cells by using a nanocrystalline silicon oxide interlayer.

PubMed

Mazzarella, Luana; Werth, Matteo; Jäger, Klaus; Jošt, Marko; Korte, Lars; Albrecht, Steve; Schlatmann, Rutger; Stannowski, Bernd

2018-05-14

We performed optical simulations using hydrogenated nanocrystalline silicon oxide (nc-SiO x :H) as n-doped interlayer in monolithic perovskite/c-Si heterojunction tandem solar cells. Depending on the adjustable value of its refractive index (2.0 - 2.7) and thickness, nc-SiO x :H allows to optically manage the infrared light absorption in the c-Si bottom cell minimizing reflection losses. We give guidelines for nc-SiO x :H optimization in tandem devices in combination with a systematic investigation of the effect of the surface morphology (flat or textured) on the photocurrent density. For full-flat and rear textured devices, we found matched photocurrents higher than 19 and 20 mA/cm 2 , respectively, using a 90 nm nc-SiO x :H interlayer with a refractive index of 2.7.

Development of x-ray laminography under an x-ray microscopic condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoshino, Masato; Uesugi, Kentaro; Takeuchi, Akihisa

2011-07-15

An x-ray laminography system under an x-ray microscopic condition was developed to obtain a three-dimensional structure of laterally-extended planar objects which were difficult to observe by x-ray tomography. An x-ray laminography technique was introduced to an x-ray transmission microscope with zone plate optics. Three prototype sample holders were evaluated for x-ray imaging laminography. Layered copper grid sheets were imaged as a laminated sample. Diatomite powder on a silicon nitride membrane was measured to confirm the applicability of this method to non-planar micro-specimens placed on the membrane. The three-dimensional information of diatom shells on the membrane was obtained at a spatialmore » resolution of sub-micron. Images of biological cells on the membrane were also obtained by using a Zernike phase contrast technique.« less

Lumbosacral spine x-ray

MedlinePlus

X-ray - lumbosacral spine; X-ray - lower spine ... The test is done in a hospital x-ray department or your health care provider's office by an x-ray technician. You will be asked to lie on the x-ray ...

X-ray beamsplitter

DOEpatents

Ceglio, Natale M.; Stearns, Daniel S.; Hawryluk, Andrew M.; Barbee, Jr., Troy W.

1989-01-01

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5-50 pairs of alternate Mo/Si layers with a period of 20-250 A. The support membrane is 10-200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window.

A search for X-ray polarization in cosmic X-ray sources. [binary X-ray sources and supernovae remnants

NASA Technical Reports Server (NTRS)

Hughes, J. P.; Long, K. S.; Novick, R.

1983-01-01

Fifteen strong X-ray sources were observed by the X-ray polarimeters on board the OSO-8 satellite from 1975 to 1978. The final results of this search for X-ray polarization in cosmic sources are presented in the form of upper limits for the ten sources which are discussed elsewhere. These limits in all cases are consistent with a thermal origin for the X-ray emission.

Spectral and temporal properties of the X-ray pulsar SMC X-1 at hard X-rays

NASA Technical Reports Server (NTRS)

Kunz, M.; Gruber, D. E.; Kendziorra, E .; Kretschmar, P.; Maisack, M.; Mony, B.; Staubert, R.; Doebereiner, S.; Englhauser, J.; Pietsch, W.

1993-01-01

The binary X-ray pulsar SMC X- 1 has been observed at hard X-rays with the High Energy X-Ray Experiment (HEXE) on nine occasions between Nov. 1987 and March 1989. A thin thermal bremsstrahlung fit to the phase averaged spectrum yields a plasma temperature (14.4 +/- 1.3) keV and a luminosity above (1.1 +/- 0.1) x 10 exp 38 erg/s in the 20-80 keV band. Pulse period values have been established for three observations, confirming the remarkably stable spin-up trend of SMC X-1. In one of the three observations the pulse profile was seen to deviate from a dominant double pulsation, while at the same time the pulsed fraction was unusually large. For one observation we determined for the first time the pulsed fraction in narrow energy bands. It increases with photon energy from about 20 percent up to over 60 percent in the energy range from 20 to 80 keV.

IXPE - The Imaging X-Ray Polarimetry Explorer

NASA Technical Reports Server (NTRS)

Ramsey, Brian

2014-01-01

The Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer Mission that will be proposed in response to NASA's upcoming Announcement of Opportunity. IXPE will transform our understanding of the most energetic and exotic astrophysical objects, especially neutron stars and black holes, by measuring the linear polarization of astronomical objects as a function of energy, time and, where relevant, position. As the first dedicated polarimetry observatory IXPE will add a new dimension to the study of cosmic sources, enlarging the observational phase space and providing answers to fundamental questions. IXPE will feature x-ray optics fabricated at NASA/MSFC and gas pixel focal plane detectors provided by team members in Italy (INAF and INFN). This presentation will give an overview of the proposed IXPE mission, detailing the payload configuration, the expected sensitivity, and a typical observing program.

Crystal growth of argyrodite-type phases Cu 8-xGeS 6-xI x and Cu 8-xGeSe 6-xI x (0⩽ x⩽0.8)

NASA Astrophysics Data System (ADS)

Tomm, Yvonne; Schorr, Susan; Fiechter, Sebastian

2008-04-01

The growth of single crystalline argyrodites of type Cu 8-xGeX 6-xY x ( X=S, Se; Y=I) is reported. These materials undergo solid-solid phase transitions at temperatures ranging from 30 to 90 °C. In the high temperature phase, Cu 8GeS 6 crystallizes in the cubic space group F4¯3m. In the low temperature phase, the compound is present in the orthorhombic space group Pmn2 1. Cu 8GeSe 6 appears exclusively in the hexagonal space groups P6 3mc or P6 3cm, respectively. Single crystals of these argyrodites were obtained by chemical vapor transport in a temperature gradient Δ T=980-950 and Δ T=700-620 °C for sulfides and selenides, respectively. As a result of the growth process, the high temperature phase remains stable even at ambient temperature by incorporation of the transport agent iodine during the growth process. As determined by energy dispersive X-ray analysis (EDAX), the composition of the sulfide crystals grown ranges from Cu 8GeS 6 to Cu 7.16GeS 5.16I 0.84. The selenide crystallizes as Cu 7.69GeSe 5.69I 0.31. In contrast, the solid state reaction of the elements Cu, Ge and X produces a material in the low temperature modification with an ideal composition of Cu 8GeX 6.

Investigating the local structure of B-site cations in (1-x)BaTiO3-xBiScO3 and (1-x)PbTiO3-xBiScO3 using X-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Blanchard, Peter E. R.; Grosvenor, Andrew P.

2018-05-01

The structural properties of (1-x)BaTiO3-xBiScO3 and (1-x)PbTiO3-xBiScO3 were investigated using powder X-ray diffraction and X-ray absorption spectroscopy. Diffraction measurements confirmed that substituting small amounts of BiScO3 into BaTiO3 initially stabilizes a cubic phase at x = 0.2 before impurity phases begin to form at x = 0.5. BiScO3 substitution also resulted in noticeable changes in the local coordination environment of Ti4+. X-ray absorption near-edge spectroscopy (XANES) analysis showed that replacing Ti4+ with Sc3+ results in an increase in the off-centre displacement of Ti4+ cations. Surprisingly, BiScO3 substitution has no effect on the displacement of the Ti4+ cation in the (1-x)PbTiO3-xBiScO3 solid solution.

First-principles study of alloying effects on fluorine incorporation in Al x Ga1-x N alloys

NASA Astrophysics Data System (ADS)

Wang, Rong; Tan, Wei; Zhang, Jian; Chen, Feng-Xiang; Wei, Su-Huai

2018-02-01

Incorporation of fluorine (F) into the AlGaN layer is crucial to the fabrication of enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistors (HEMTs). However, the understanding of properties of F doping in AlGaN alloys is rather limited. Using first-principles calculations and the special quasirandom structure (SQS) approach, we investigate the alloying effects on the doping properties of F-incorporated Al x Ga1-x N alloys. We find that substitutional F on N sites (FN) and interstitial F (Fi) are dominant defects for F in Al x Ga1-x N alloys. For these two types of defects, both the global composition x and the local motif surrounding the dopant play important roles. On contrary, the incorporation of substitutional F on Ga sites (FGa) or Al sites (FAl) are affected only by the composition x. We also find that there exists a large asymmetric bowing for the effective formation energies of FN and Fi. These results are explained in terms of local structural distortion and electronic effects. The mechanism discussed in this paper can also be used in understanding doping in other semiconductor alloys.

Low-temperature glasslike properties in (NaCl)1-x(NaCN)x

NASA Astrophysics Data System (ADS)

Watson, Susan K.; Pohl, R. O.

1995-04-01

Thermal conductivity, internal friction, transverse sound velocity (60 mK to 300 K), and specific-heat data (100 mK to 40 K) for (NaCl)1-x(NaCN)x (x=0, 0.025, 0.05, 0.1, 0.76, 1) show a progression from crystalline to glasslike behavior as the CN- concentration is increased from 0 to 76 %. The evolution of glasslike properties is compared to that in other crystals in which glasslike properties evolve with increasing disorder, e.g., (KBr)1-x(KCN)x and Ba1-xLaxF2-x. For (KBr)1-x(KCN)x, Sethna and Chow have shown that as the concentration of the almost freely rotating CN- ions is increased the average potential barrier for CN- reorientation also increases through elastic quadrupolar interactions. For x~0.5, only a small density of low-energy states is left, which equals that observed in structural glasses. In Ba1-xLaxF2-x, on the other hand, the crystal field for small doping x is so large that no atomic motion occurs at low temperatures. (NaCl)1-x(NaCN)x is shown to represent an intermediate case, in that the crystal field is non-negligible at small x, yet glasslike low-energy excitations indicative of very small potential barrier heights evolve with increasing x. It is argued that random internal strains cause a decrease of the barrier heights in these crystals, which lead to the low-energy excitations. It is proposed that random strains have a similar effect in other disordered crystals as in Ba1-xLaxF2-x, which for small x show no low-energy mobile states, yet which for large x become glasslike.

X-ray lithography masking

NASA Technical Reports Server (NTRS)

Smith, Henry I. (Inventor); Lim, Michael (Inventor); Carter, James (Inventor); Schattenburg, Mark (Inventor)

1998-01-01

X-ray masking apparatus includes a frame having a supporting rim surrounding an x-ray transparent region, a thin membrane of hard inorganic x-ray transparent material attached at its periphery to the supporting rim covering the x-ray transparent region and a layer of x-ray opaque material on the thin membrane inside the x-ray transparent region arranged in a pattern to selectively transmit x-ray energy entering the x-ray transparent region through the membrane to a predetermined image plane separated from the layer by the thin membrane. A method of making the masking apparatus includes depositing back and front layers of hard inorganic x-ray transparent material on front and back surfaces of a substrate, depositing back and front layers of reinforcing material on the back and front layers, respectively, of the hard inorganic x-ray transparent material, removing the material including at least a portion of the substrate and the back layers of an inside region adjacent to the front layer of hard inorganic x-ray transparent material, removing a portion of the front layer of reinforcing material opposite the inside region to expose the surface of the front layer of hard inorganic x-ray transparent material separated from the inside region by the latter front layer, and depositing a layer of x-ray opaque material on the surface of the latter front layer adjacent to the inside region.

The X-ray Integral Field Unit (X-IFU) for Athena

NASA Technical Reports Server (NTRS)

Ravera, Laurent; Barret, Didier; Willem den Herder, Jan; Piro, Luigi; Cledassou, Rodolphe; Pointecouteau, Etienne; Peille, Philippe; Pajot, Francois; Arnaud, Monique; Pigot, Claude;

X-ray beamsplitter

DOEpatents

Ceglio, N.M.; Stearns, D.G.; Hawryluk, A.M.; Barbee, T.W. Jr.

1987-08-07

An x-ray beamsplitter which splits an x-ray beam into two coherent parts by reflecting and transmitting some fraction of an incident beam has applications for x-ray interferometry, x-ray holography, x-ray beam manipulation, and x-ray laser cavity output couplers. The beamsplitter is formed of a wavelength selective multilayer thin film supported by a very thin x-ray transparent membrane. The beamsplitter resonantly transmits and reflects x-rays through thin film interference effects. A thin film is formed of 5--50 pairs of alternate Mo/Si layers with a period of 20--250 A. The support membrane is 10--200 nm of silicon nitride or boron nitride. The multilayer/support membrane structure is formed across a window in a substrate by first forming the structure on a solid substrate and then forming a window in the substrate to leave a free-standing structure over the window. 6 figs.

Pressure effects on magnetic ground states in cobalt doped multiferroic Mn 1-xCo xWO 4

DOE PAGES

Wang, Jinchen; Ye, Feng; Chi, Songxue; ...

2016-04-28

Using x-ray and high pressure neutron diffraction, we studied the pressure effect on structural and magnetic properties of multiferroic Mn 1-xCo xWO 4 single crystals (x = 0, 0.05, 0.135 and 0.17), and compared it with the effects of doping. Both Co doping and pressure stretch the Mn-Mn chain along the c direction. At high doping level (x = 0.135 and 0.17), pressure and Co doping drive the system in a very similar way and induce a spin-flop transition for the x = 0.135 compound. In contrast, magnetic ground states at lower doping level (x = 0 and 0.05) aremore » robust against pressure but experience a pronounced change upon Co substitution. As Co introduces both chemical pressure and magnetic anisotropy into the frustrated magnetic system, our results suggest the magnetic anisotropy is the main driving force for the Co induced phase transitions at low doping level, and chemical pressure plays a more significant role at higher Co concentrations.« less

Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} (0{<=}x{<=}1): synthesis, structure and dielectric properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thirumal, M.; Jawahar, I.N.; Surendiran, K.P.

2002-11-20

Oxides belonging to the families Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} and Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} were synthesized by the solid state reaction route. Sintering temperatures of 1300 deg. C led to oxides with disordered (cubic) perovskite structure. However, on sintering at 1425 deg. C hexagonally ordered structures were obtained for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} over the entire range (0{<=}x{<=}1) of composition, while for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} the ordered structure exists in a limited range (0{<=}x{<=}0.5). The dielectric constant is close to 30 for the Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9} family of oxides while the Mg analoguesmore » have lower dielectric constant of {approx}18 in the range 50 Hz to 500 kHz. At microwave frequencies (5-7 GHz) dielectric constant increases with increase in niobium concentration (22-26) for Ba{sub 3}ZnTa{sub 2-x}Nb{sub x}O{sub 9}; for Ba{sub 3}MgTa{sub 2-x}Nb{sub x}O{sub 9} it varies between 12 and 14. The 'Zn' compounds have much higher quality factors and lower temperature coefficient of resonant frequency compared to the 'Mg' analogues.« less

Report of a new case with pentasomy X and novel clinical findings

PubMed Central

Demirhan, O; Tanriverdi, N; Yilmaz, MB; Kocaturk-Sel, S; Inandiklioglu, N; Luleyap, U; Akbal, E; Comertpay, G; Tufan, T; Dur, O

2015-01-01

Pentasomy X is an extremely rare sex chromosome abnormality, a condition that only affects females, in which three more X chromosomes are added to the normally present two chromosomes in females. We investigated the novel clinical findings in a 1-year-old female baby with pentasomy X, and determined the parental origins of the X chromosomes. Our case had thenar atrophy, postnatal growth deficiency, developmental delay, mongoloid slant, microcephaly, ear anomalies, micrognathia and congenital heart disease. A conventional cytogenetic technique was applied for the diagnosis of the polysomy X, and quantitative fluorescent polymerase chain reaction (QF-PCR) using 11 inherited short tandem repeat (STR) alleles specific to the chromosome X for the determination of parental origin of X chromosomes. A cytogenetic evaluation revealed that the karyotype of the infant was 49,XXXXX. Comparison of the infant’s features with previously reported cases indicated a clinically recognizable specific pattern of malformations referred to as the pentasomy X syndrome. However, to the best of our know-ledge, this is the first report of thenar atrophy in a patient with 49,XXXXX. The molecular analysis suggested that four X chromosomes of the infant originated from the mother as a result of the non disjunction events in meiosis I and meiosis II. We here state that the clinical manifestations seen in our case were consistent with those described previously in patients with pentasomy X. The degree of early hypotonia constitutes an important early prognostic feature in this syndrome. The pathogenesis of pentasomy X is not clear at present, but it is thought to be caused by successive maternal non disjunctions. PMID:26929910

Thoracic spine x-ray

MedlinePlus

Vertebral radiography; X-ray - spine; Thoracic x-ray; Spine x-ray; Thoracic spine films; Back films ... The test is done in a hospital radiology department or in the health care provider's office. You will lie on the x-ray table in different positions. If the x-ray ...

SMART-X: Square Meter, Arcsecond Resolution Telescope for X-rays

NASA Astrophysics Data System (ADS)

Vikhlinin, Alexey; SMART-X Collaboration

2013-04-01

SMART-X is a concept for a next-generation X-ray observatory with large-area, 0.5" angular resolution grazing incidence adjustable X-ray mirrors, high-throughput critical angle transmission gratings, and X-ray microcalorimeter and CMOS-based imager in the focal plane. High angular resolution is enabled by new technology based on controlling the shape of mirror segments using thin film piezo actuators deposited on the back surface. Science applications include observations of growth of supermassive black holes since redshifts of ~10, ultra-deep surveys over 10's of square degrees, galaxy assembly at z=2-3, as well as new opportunities in the high-resolution X-ray spectroscopy and time domains. We also review the progress in technology development, tests, and mission design over the past year.

SphinX Measurements of the 2009 Solar Minimum X-Ray Emission

NASA Astrophysics Data System (ADS)

Sylwester, J.; Kowalinski, M.; Gburek, S.; Siarkowski, M.; Kuzin, S.; Farnik, F.; Reale, F.; Phillips, K. J. H.; Bakała, J.; Gryciuk, M.; Podgorski, P.; Sylwester, B.

2012-06-01

The SphinX X-ray spectrophotometer on the CORONAS-PHOTON spacecraft measured soft X-ray emission in the 1-15 keV energy range during the deep solar minimum of 2009 with a sensitivity much greater than GOES. Several intervals are identified when the X-ray flux was exceptionally low, and the flux and solar X-ray luminosity are estimated. Spectral fits to the emission at these times give temperatures of 1.7-1.9 MK and emission measures between 4 × 1047 cm-3 and 1.1 × 1048 cm-3. Comparing SphinX emission with that from the Hinode X-ray Telescope, we deduce that most of the emission is from general coronal structures rather than confined features like bright points. For one of 27 intervals of exceptionally low activity identified in the SphinX data, the Sun's X-ray luminosity in an energy range roughly extrapolated to that of ROSAT (0.1-2.4 keV) was less than most nearby K and M dwarfs.

The effects of starting materials in the synthesis of (Ga(1-x)Znx)(N(1-x)O(x)) solid solution on its photocatalytic activity for overall water splitting under visible light.

PubMed

Hisatomi, Takashi; Maeda, Kazuhiko; Lu, Daling; Domen, Kazunari

2009-01-01

The influence of starting materials on the physicochemical and photocatalytic properties of (Ga(1-x)Zn(x))(N(1-x)O(x)) were investigated in an attempt to optimize the preparation conditions. The catalyst was successfully prepared by nitriding a starting mixture of ZnO and Ga2O3. A mixture of metallic zinc and GaN, however, did not afford the desired compound. The crystallinity, surface area, composition, and absorption characteristics of the resultant (Ga(1-x)Zn(x))(N(1-x)O(x)) solid solution are found to be dependent on the morphology of ZnO but largely insensitive to the choice of Ga2O3 polymorph. The use of coarser-grained ZnO results in a coarser-grained catalyst with elevated zinc and oxygen content and reduced uniformity in composition and crystallinity. The results demonstrate the importance of selecting appropriate ZnO and Ga2O3 starting materials for maximizing the photocatalytic activity of (Ga(1-x)Zn(x))(N(1-x)O(x)) for overall water splitting under visible light.

On X-Ray Variability in Seyfert Galaxies

NASA Technical Reports Server (NTRS)

Turner, T. J.; George, I. M.; Nandra, K.; Turcan, D.

1999-01-01

This paper presents a quantification of the X-ray variability amplitude for 79 ASCA observations of 36 Seyfert 1 galaxies. We find that consideration of sources with the narrowest permitted lines in the optical band introduces scatter into the established correlation between X-ray variability and nuclear luminosity. Consideration of the X-ray spectral index and variability properties together shows distinct groupings in parameter space for broad and narrow-line Seyfert 1 galaxies, confirming previous studies. A strong correlation is found between hard X-ray variability and FWHM Hbeta. A range of nuclear mass and accretion rate across the Seyfert population can explain the differences observed in X-ray and optical properties. An attractive alternative model, which does not depend on any systematic difference in central mass, is that the circumnuclear gas of NLSy1s is different to BLSy1s in temperature, optical depth, density or geometry.

Centaurus X-3. [early x-ray binary star spectroscopy

NASA Technical Reports Server (NTRS)

Hutchings, J. B.; Cowley, A. P.; Crampton, D.; Van Paradus, J.; White, N. E.

1979-01-01

Spectroscopic observations of Krzeminski's star at dispersions 25-60 A/mm are described. The primary is an evolved star of type O6-O8(f) with peculiarities, some of which are attributable to X-ray heating. Broad emission lines at 4640A (N III), 4686 A(He II) and H-alpha show self-absorption and do not originate entirely from the region near the X-ray star. The primary is not highly luminous (bolometric magnitude about -9) and does not show signs of an abnormally strong stellar wind. The X-ray source was 'on' at the time of optical observations. Orbital parameters are presented for the primary, which yield masses of 17 + or - 2 and 1.0 + or - 3 solar masses for the stars. The optical star is undermassive for its luminosity, as are other OB-star X-ray primaries. The rotation is probably synchronized with the orbital motion. The distance to Cen X-3 is estimated to be 10 + or - 1 kpc. Basic data for 12 early-type X-ray primaries are discussed briefly

Magnesium effects on CdSe self-assembled quantum dot formation on Zn xCd yMg 1-x-ySe layers

NASA Astrophysics Data System (ADS)

Noemi Perez-Paz, M.; Lu, Hong; Shen, Aidong; Jean Mary, F.; Akins, Daniel; Tamargo, Maria C.

2006-09-01

Optical and morphological studies are used to investigate the effects of chemical composition and, in particular, the magnesium content of the Zn xCd yMg 1-x-ySe barrier layers on the size, density and uniformity of CdSe self-assembled quantum dots (QDs). A reduction of the uncapped QD size, as well as a blue shift of the capped QD photoluminescence peak position by increasing Mg concentration in the Zn xCd yMg 1-x-ySe barrier has been demonstrated by changing the Mg cell temperature during growth. In addition, a more uniform and more densely packed QD layer has been observed with an increase of the MgSe fraction in the Zn xCd yMg 1-x-ySe barrier layer using three-dimensional topographic atomic force microscopy images of the surface of uncapped QDs. Results point to Mg as a chemical factor that induces QD formation, either by increasing the density of atomic steps or/and by changing the energy of the Zn xCd yMg 1-x-ySe surface.

Magnetic properties of Ce xY 1-xPt compared to Ce xLa 1-xPt ones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ocko, M.; Zadro, K.; Drobac, D.

In this paper, we have investigated the magnetic properties of the Ce xY 1-xPt Kondo ferromagnetic alloy system in the temperature range from 1.8 K to 320 K. The results of these investigations can be summarized as follows: dc-susceptibility can be described by the Curie-Weiss law at higher temperatures down to about 100 K, but also at low temperatures above the ferromagnetic phase transition. At higher temperatures, the extracted Curie-Weiss parameter, θ p, is negative and at low temperature θ C is positive. The extracted effective magnetic moment above 100 K increases with the Ce content up to almost themore » theoretical value of the isolated Ce 3+ ion, μ = 2.54 μ B, for CePt. This suggests an increase of the hybridization with decreasing Ce content, or said equivalently, it means that the increase of the Kondo interaction diminishes effective magnetic moment. These observations confirm the main conclusions inferred from an earlier transport properties investigation of this alloy system. The corresponding θ C differs within 1 K from the Curie temperature, T C, which is determined by the resistivity measurements. The most intriguing result of the investigation of Ce xY 1-xPt is the linear concentration dependence of T C vs. x and, moreover, it is the same as in Ce xLa 1-xPt although in the former system the hybridization diminishes considerably the effective magnetic moment per Ce ion, while in the latter system, hybridization is minor and independent of x. Finally, we offer the explanations of these intriguing experimental results.« less

Magnetic properties of Ce xY 1-xPt compared to Ce xLa 1-xPt ones

DOE PAGES

Ocko, M.; Zadro, K.; Drobac, D.; ...

2017-12-05

In this paper, we have investigated the magnetic properties of the Ce xY 1-xPt Kondo ferromagnetic alloy system in the temperature range from 1.8 K to 320 K. The results of these investigations can be summarized as follows: dc-susceptibility can be described by the Curie-Weiss law at higher temperatures down to about 100 K, but also at low temperatures above the ferromagnetic phase transition. At higher temperatures, the extracted Curie-Weiss parameter, θ p, is negative and at low temperature θ C is positive. The extracted effective magnetic moment above 100 K increases with the Ce content up to almost themore » theoretical value of the isolated Ce 3+ ion, μ = 2.54 μ B, for CePt. This suggests an increase of the hybridization with decreasing Ce content, or said equivalently, it means that the increase of the Kondo interaction diminishes effective magnetic moment. These observations confirm the main conclusions inferred from an earlier transport properties investigation of this alloy system. The corresponding θ C differs within 1 K from the Curie temperature, T C, which is determined by the resistivity measurements. The most intriguing result of the investigation of Ce xY 1-xPt is the linear concentration dependence of T C vs. x and, moreover, it is the same as in Ce xLa 1-xPt although in the former system the hybridization diminishes considerably the effective magnetic moment per Ce ion, while in the latter system, hybridization is minor and independent of x. Finally, we offer the explanations of these intriguing experimental results.« less

X-Ray Psoralen Activated Cancer Therapy (X-PACT)

PubMed Central

Oldham, Mark; Yoon, Paul; Fathi, Zak; Beyer, Wayne F.; Adamson, Justus; Liu, Leihua; Alcorta, David; Xia, Wenle; Osada, Takuya; Liu, Congxiao; Yang, Xiao Y.; Dodd, Rebecca D.; Herndon, James E.; Meng, Boyu; Kirsch, David G.; Lyerly, H. Kim; Dewhirst, Mark W.; Fecci, Peter; Walder, Harold; Spector, Neil L.

2016-01-01

This work investigates X-PACT (X-ray Psoralen Activated Cancer Therapy): a new approach for the treatment of solid cancer. X-PACT utilizes psoralen, a potent anti-cancer therapeutic with current application to proliferative disease and extracorporeal photopheresis (ECP) of cutaneous T Cell Lymphoma. An immunogenic role for light-activated psoralen has been reported, contributing to long-term clinical responses. Psoralen therapies have to-date been limited to superficial or extracorporeal scenarios due to the requirement for psoralen activation by UVA light, which has limited penetration in tissue. X-PACT solves this challenge by activating psoralen with UV light emitted from novel non-tethered phosphors (co-incubated with psoralen) that absorb x-rays and re-radiate (phosphoresce) at UV wavelengths. The efficacy of X-PACT was evaluated in both in-vitro and in-vivo settings. In-vitro studies utilized breast (4T1), glioma (CT2A) and sarcoma (KP-B) cell lines. Cells were exposed to X-PACT treatments where the concentrations of drug (psoralen and phosphor) and radiation parameters (energy, dose, and dose rate) were varied. Efficacy was evaluated primarily using flow cell cytometry in combination with complimentary assays, and the in-vivo mouse study. In an in-vitro study, we show that X-PACT induces significant tumor cell apoptosis and cytotoxicity, unlike psoralen or phosphor alone (p<0.0001). We also show that apoptosis increases as doses of phosphor, psoralen, or radiation increase. Finally, in an in-vivo pilot study of BALBc mice with syngeneic 4T1 tumors, we show that the rate of tumor growth is slower with X-PACT than with saline or AMT + X-ray (p<0.0001). Overall these studies demonstrate a potential therapeutic effect for X-PACT, and provide a foundation and rationale for future studies. In summary, X-PACT represents a novel treatment approach in which well-tolerated low doses of x-ray radiation are delivered to a specific tumor site to generate UVA light which

Thermal and electrochemical behavior of Cu{sub 4−x}Li{sub x}S{sub 2} (x=1, 2, 3) phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Erica M.; Poudeu, Pierre F.P., E-mail: ppoudeup@umich.edu

Several compositions of the Cu{sub 4−x}Li{sub x}S{sub 2} (x=1, 2, 3) series were synthesized via solid-state reaction of the elements. The structural stability at various temperatures and the effect of Li:Cu ratio on the thermal conductivity and the electrochemical performance of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells during charge–discharge process were investigated. Differential scanning calorimetry (DSC) measurements showed a sharp endothermic peak at 140 °C for Cu{sub 4−x}Li{sub x}S{sub 2} samples with x=1 and 2, which is ascribed to a structural phase transition. X-ray diffraction (XRD) measurements on various Cu{sub 4−x}Li{sub x}S{sub 2} samples at temperatures below and above 140 °Cmore » indicated a structural phase transition from the room temperature low-symmetry structure to the high temperature cubic structure of Cu{sub 2}S. The thermal conductivity of Cu{sub 4−x}Li{sub x}S{sub 2} samples decreases with decreasing Cu:Li ratio and with increasing temperature. The thermal conductivity of Cu{sub 4−x}Li{sub x}S{sub 2} samples at room temperature decreases from 1.2 W/m K for Cu:Li=3:1 to 0.7 W/m K for Cu:Li=1:3. Cyclic voltammetry of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells showed that high discharge capacity (165 mA h g{sup −1}) and stable reversible charge–discharge process is observed for Cu:Li=2:2, whereas other Cu:Li ratios lead to low discharge capacity and poor reversibility. The electrochemical behavior of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells is rationalized by taking into account the competing reactions of Li{sup +} ions with CuS and Cu{sub 2}S during discharge. - Graphical abstract: Tuning Li content in Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells to maintain a Cu/Li ratio equal to unity affords maximum capacity and high stability of the charge–discharge process. - Highlights: • Cu:Li ratio strongly influenced crystal structure and properties of Cu{sub 4-x}Li{sub x}S{sub 2}. • Compositions with x = 1 and

XAssist: A System for the Automation of X-ray Astrophysics Analysis

NASA Astrophysics Data System (ADS)

Ptak, A.; Griffiths, R.

XAssist is a NASA AISR-funded project for the automation of X-ray astrophysics, with emphasis on galaxies. It is nearing completion of its initially funded effort, and is working well for Chandra and ROSAT data. Initial support for XMM-Newton data is present as well. It is capable of data reprocessing, source detection, and preliminary spatial, temporal and spectral analysis for each source with sufficient counts. The bulk of the system is written in Python, which in turn drives underlying software (CIAO for Chandra data, etc.). Future work will include a GUI (mainly for beginners and status monitoring) and the exposure of at least some functionality as web services. The latter will help XAssist to eventually become part of the VO, making advanced queries possible, such as determining the X-ray fluxes of counterparts to HST or SDSS sources (including the use of unpublished X-ray data), and add the ability of ``on-the-fly'' X-ray processing. Pipelines are running on ROSAT, Chandra and now XMM-Newton observations of galaxies to demonstrate XAssist's capabilities, and the results are available online (in real time) at http://www.xassist.org. XAssist itself as well as various associated projects are available for download.

CubeX: The CubeSAT X-ray Telescope for Elemental Abundance Mapping of Airless Bodies and X-ray Pulsar Navigation

NASA Astrophysics Data System (ADS)

Nittler, L. R.; Hong, J.; Kenter, A.; Romaine, S.; Allen, B.; Kraft, R.; Masterson, R.; Elvis, M.; Gendreau, K.; Crawford, I.; Binzel, R.; Boynton, W. V.; Grindlay, J.; Ramsey, B.

2017-12-01

The surface elemental composition of a planetary body provides crucial information about its origin, geological evolution, and surface processing, all of which can in turn provide information about solar system evolution as a whole. Remote sensing X-ray fluorescence (XRF) spectroscopy has been used successfully to probe the major-element compositions of airless bodies in the inner solar system, including the Moon, near-Earth asteroids, and Mercury. The CubeSAT X-ray Telescope (CubeX) is a concept for a 6U planetary X-ray telescope (36U with S/C), which utilizes Miniature Wolter-I X-ray optics (MiXO), monolithic CMOS and SDD X-ray sensors for the focal plane, and a Solar X-ray Monitor (heritage from the REXIS XRF instrument on NASA's OSIRIS-REx mission). CubeX will map the surface elemental composition of diverse airless bodies by spectral measurement of XRF excited by solar X-rays. The lightweight ( 1 kg) MiXO optics provide sub-arcminute resolution with low background, while the inherently rad-hard CMOS detectors provide improved spectral resolution ( 150 eV) at 0 °C. CubeX will also demonstrate X-ray pulsar timing based deep space navigation (XNAV). Successful XNAV will enable autonomous deep navigation with little to no support from the Deep Space Network, hence lowering the operation cost for many more planetary missions. Recently selected by NASA Planetary Science Deep Space SmallSat Studies, the first CubeX concept, designed to rideshare to the Moon as a secondary spacecraft on a primary mission, is under study in collaboration with the Mission Design Center at NASA Ames Research Center. From high altitude ( 6,000 km) frozen polar circular orbits, CubeX will study > 8 regions ( 110 km) of geological interest on the Moon over one year to produce a high resolution ( 2-3 km) elemental abundance map of each region. The novel focal plane design of CubeX also allows us to evaluate the performance of absolute navigation by sequential observations of several

(3+1)D superspace structural determination of two new modulated composite phases: Sr 1+ x(Cu xMn 1- x)O 3; x=3/11 and x=0.3244

NASA Astrophysics Data System (ADS)

El Abed, Ahmed; Gaudin, Etienne; zur Loye, Hans-Conrad; Darriet, Jacques

2003-01-01

We report the structure determination of two new phases belonging to the A 1+ x(A' xB 1- x)O 3 family of oxides with A=Sr, A'=Cu, and B=Mn, where x=3/11 and x=0.3244, corresponding to a commensurate and incommensurate composite structure, respectively. These two compounds are the first examples of oxides belonging to the Sr 1+ x(Cu xMn 1- x)O 3 family. Their structures were solved in the (3+1) dimensional superspace formalism as modulated composite structures with two subsystems [(Cu,Mn)O 3] and [Sr]. The superspace group used to solve the structures is R 3¯m(00γ)0s . The first phase ( x=3/11), corresponding to the chemical formula Sr 14Cu 3Mn 8O 33, was obtained as a single crystal with unit cell parameters of a=9.6025(3) Å and c1=2.5660(8) Å ( q=7/11 c1∗, Z=3), where c1 is the lattice parameter corresponding to the c-axis of the trigonal subsystem [(Cu,Mn)O 3]. The second phase ( x=0.3244(1)), is a polycrystalline sample with unit cell parameters of a=9.5933(7) and c1=2.5933(3) ( q=0.6622 c1∗, Z=3). In both structures, one dimensional chains run along the c-axis which contain octahedra and trigonal prisms occupied by manganese and copper atoms, respectively. The refinement results show that in both cases copper occupies the rectangular faces of the trigonal prism while manganese occupies the octahedral sites. The magnetic measurements of the polycrystalline phase (Sr 1+ x(Cu xMn 1- x)O 3, x=0.3244(2)) and the Curie constant obtained from the high temperature susceptibility are in agreement with a spin state configuration of S=3/2 for Mn 4+ and S=1/2 for Cu 2+.

Unusual Black Hole Binary LMC X-3: A Transient High-Mass X-Ray Binary That Is Almost Always On?

NASA Technical Reports Server (NTRS)

Torpin, Trevor J.; Boyd, Patricia T.; Smale, Alan P.; Valencic, Lynne A.

2017-01-01

We have analyzed a rich, multimission, multiwavelength data set from the black hole X-ray binary (BHXB) LMC X-3, covering a new anomalous low state (ALS), during which the source flux falls to an unprecedentedly low and barely detectable level, and a more normal low state. Simultaneous X-ray and UV/optical monitoring data from Swift are combined with pointed observations from the Rossi X-ray Timing Explorer (RXTE) and X-ray Multi- Mirror Mission (XMM-Newton) and light curves from the Monitor of All-Sky X-ray Image (MAXI) instrument to compare the source characteristics during the ALS with those seen during the normal low state. An XMM-Newton spectrum obtained during the ALS can be modeled using an absorbed power law with Gamma = 1.41‚+/- 0.65 and a luminosity of 7.97 x 10(exp 33) erg/s (0.6-5 keV). The Swift X-ray and UV light curves indicate an X-ray lag of approx. 8 days as LMC X-3 abruptly exits the ALS, suggesting that changes in the mass accretion rate from the donor drive the X-ray lag. The normal low state displays an asymmetric profile in which the exit occurs more quickly than the entry, with minimum X-ray flux a factor of approx. 4300 brighter than during the ALS. The UV brightness of LMC X-3 in the ALS is also fainter and less variable than during normal low states. The existence of repeated ALSs in LMC X-3, as well as a comparison with other BHXBs, implies that it is very close to the transient/persistent X-ray source dividing line. We conclude that LMC X-3 is a transient source that is almost always "on."

X-ray Spectral Formation In High-mass X-ray Binaries: The Case Of Vela X-1

NASA Astrophysics Data System (ADS)

Akiyama, Shizuka; Mauche, C. W.; Liedahl, D. A.; Plewa, T.

2007-05-01

We are working to develop improved models of radiatively-driven mass flows in the presence of an X-ray source -- such as in X-ray binaries, cataclysmic variables, and active galactic nuclei -- in order to infer the physical properties that determine the X-ray spectra of such systems. The models integrate a three-dimensional time-dependent hydrodynamics capability (FLASH); a comprehensive and uniform set of atomic data, improved calculations of the line force multiplier that account for X-ray photoionization and non-LTE population kinetics, and X-ray emission-line models appropriate to X-ray photoionized plasmas (HULLAC); and a Monte Carlo radiation transport code that simulates Compton scattering and recombination cascades following photoionization. As a test bed, we have simulated a high-mass X-ray binary with parameters appropriate to Vela X-1. While the orbital and stellar parameters of this system are well constrained, the physics of X-ray spectral formation is less well understood because the canonical analytical wind velocity profile of OB stars does not account for the dynamical and radiative feedback effects due to the rotation of the system and to the irradiation of the stellar wind by X-rays from the neutron star. We discuss the dynamical wind structure of Vela X-1 as determined by the FLASH simulation, where in the binary the X-ray emission features originate, and how the spatial and spectral properties of the X-ray emission features are modified by Compton scattering, photoabsorption, and fluorescent emission. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Full-field transmission x-ray imaging with confocal polycapillary x-ray optics

PubMed Central

Sun, Tianxi; MacDonald, C. A.

2013-01-01

A transmission x-ray imaging setup based on a confocal combination of a polycapillary focusing x-ray optic followed by a polycapillary collimating x-ray optic was designed and demonstrated to have good resolution, better than the unmagnified pixel size and unlimited by the x-ray tube spot size. This imaging setup has potential application in x-ray imaging for small samples, for example, for histology specimens. PMID:23460760

Synthesis and crystal structures of new oxyapatites BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhuravlev, V.D., E-mail: zhvd@ihim.uran.ru; Tyutyunnik, A.P.; Zubkov, V.G.

2012-10-15

New germanate-vanadates with the general formula BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, x=1-3, have been synthesized by the nitrate-citrate method and characterized. Structural refinement based on X-ray powder diffraction data showed that these compounds are isostructural with BiCa{sub 4}(VO{sub 4}){sub 3}O (space group P6{sub 3}/m (N 176), Z=2, a=9.8327-9.8755(3), and c=7.1203-7.2133(2) ). They may be viewed as continuous series of solid solutions where Ca{sup 2+} and V{sup 5+} cations in the crystal lattice of vanadate BiCa{sub 4}(VO{sub 4}){sub 3}O are replaced by La{sup 3+} and Ge{sup 4+} cations. In the process of substitution, the La{sup 3+} cations occupy mainlymore » the 4f lattice sites of the germanate-vanadate oxyapatites, but the filling of the 4f and 6h lattice sites in the germanate BiCaLa{sub 3}(GeO{sub 4}){sub 3} is equivalent. IR and Raman spectra were studied. The Raman spectra clearly show a two-mode behavior: the lines of GeO{sub 4} and VO{sub 4} are separated from each other, and the (V/Ge)O{sub 4} tetrahedra exhibit a quasi-independent behavior. - Graphical abstract: Schematic drawing of the BiCa{sub 3}La(VO{sub 4}){sub 2}(GeO{sub 4})O structure in projection on the ac plane. Green-V and Ge, red-Ca(1) and La(1), yellow-Ca(2), La(2) and Bi, dark-blue-O(1)-O(4), blue-O(5). Highlights: Black-Right-Pointing-Pointer The citrate synthesis of germanate-vanadate oxyapatites. Black-Right-Pointing-Pointer The synthesized compounds crystallize in the hexagonal symmetry. Black-Right-Pointing-Pointer A single series of solid solutions BiCa{sub 4-x}La{sub x}(VO{sub 4}){sub 3-x}(GeO{sub 4}){sub x}O, (x=0-3). Black-Right-Pointing-Pointer IR an Raman spectra of mixed crystals.« less

X-15 cockpit

NASA Technical Reports Server (NTRS)

1963-01-01

This photo shows the X-15 cockpit. The X-15 was unique for many reasons, including the fact that it had two types of controls for the pilot. For flight in the dense air of the usable atmosphere, the X-15 used conventional aerodynamic controls such as rudder surfaces on the vertical stabilizers to control yaw and movable horizontal stabilizers to control pitch when moving in synchronization or roll when moved differentially. For flight in the thin air outside of the appreciable Earth's atmosphere, the X-15 used a reaction control system. Hydrogen peroxide thrust rockets located on the nose of the aircraft provided pitch and yaw control. Those on the wing provided roll control. The conventional aerodynamic controls used a stick, located in the middle of the floor, and pedals. The reaction control system used a side arm controller, seen in this photo on the left. The X-15 was a rocket-powered aircraft 50 ft long with a wingspan of 22 ft. It was a missile-shaped vehicle with an unusual wedge-shaped vertical tail, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was capable of developing 57,000 lb of thrust. North American Aviation built three X-15 aircraft for the program. The X-15 research aircraft was developed to provide in-flight information and data on aerodynamics, structures, flight controls, and the physiological aspects of high-speed, high-altitude flight. A follow-on program used the aircraft as a testbed to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. Because of the large fuel consumption, the X-15 was air launched from a B-52 aircraft at 45,000 ft and a speed of about 500 mph. Depending on the mission, the rocket engine provided thrust for the first 80 to 120 sec of flight. The remainder of the normal 10 to

Maternal and reproductive performance of Brahman x Angus, Senepol x Angus, and Tuli x Angus cows in the subtropics.

PubMed

Chase, C C; Riley, D G; Olson, T A; Coleman, S W; Hammond, A C

2004-09-01

To determine the maternal and reproductive performance of F1 cows in the subtropics, 42 Brahman x Angus, 34 Senepol x Angus, and 50 Tuli x Angus cows were bred to Angus bulls to calve first and subsequently bred to Charolais bulls to calve as 3- to 8-yr-olds. Age at first calving did not differ among crossbred cows. Angus-sired calf birth weights were heavier (P < 0.01) from Senepol x Angus than either Brahman x Angus or Tuli x Angus cows. Weaning weights of Angus-sired calves were heavier (P < 0.01) from Brahman x Angus (213.5 kg) than either Senepol x Angus (194.9 kg) or Tuli x Angus (191.5 kg) cows. As 3- to 8-yr-old cows, calf birth weights were heavier (P < 0.05) from Senepol x Angus compared with Brahman x Angus but not Tuli x Angus cows. Weaning weights of Charolais-sired calves were heaviest (P < 0.05) from Brahman x Angus cows (268.9 kg), lightest from Tuli x Angus cows (233.4 kg), and intermediate from Senepol x Angus cows (245.0 kg). Calf crop born and calf crop weaned were lowest (P < 0.05) for Senepol x Angus cows (76.9 and 70.2%) and did not differ between Brahman x Angus (89.0 and 86.1%) and Tuli x Angus (94.7 and 86.5%) cows. Tuli x Angus cows tended (P < 0.10) to have a lower percentage of unassisted births and lower (P < 0.10) calf survival to weaning than Brahman x Angus cows but not Senepol x Angus cows. As 3- to 8-yr-olds, weaning weight per cow exposed was greatest (P < 0.05) for Brahman x Angus (234.2 kg), least (P < 0.05) for Senepol x Angus (173.0 kg), and intermediate (P < 0.05) for Tuli x Angus (209.1 kg) cows. Also as 3- to 8-yr-olds, efficiency (205-d calf weight per 100 kg of cow exposed) was similar for Brahman x Angus (42.2) and Tuli x Angus cows (40.7), and both were greater (P < 0.01) than for Senepol x Angus cows (33.8). These data indicate that, in the subtropics, maternal and reproductive performance of Tuli x Angus cows, but not Senepol x Angus cows, was comparable to Brahman x Angus cows, except for lower calf survivability

An ab initio study on MgX 3- and CaX 3- superhalogen anions (X=F, Cl, Br)

NASA Astrophysics Data System (ADS)

Anusiewicz, Iwona; Sobczyk, Monika; Dąbkowska, Iwona; Skurski, Piotr

2003-06-01

The vertical electron detachment energies (VDEs) of twenty MX 3- (M=Mg, Ca; X=F, Cl, Br) anions were calculated at the OVGF level with the 6-311++G(3df) basis sets. The largest vertical electron binding energy was found for MgF 3- system (8.793 eV). All negatively charged species possess the VDEs that are larger than 5.9 eV and thus may be termed superhalogen anions. The strong dependence of the VDE of the MX 3- species on the ligand-central atom (M-X) distance and on the partial atomic charge localized on Mg or Ca was observed and discussed, as well as the other factors that may influence the electronic stability of such anions.

X-Ray Standing Waves on Surfaces

DTIC Science & Technology

1993-01-01

dependent distributional changes of iodine on Pt 6.3 X-ray standing wave study of a Langmuir - Blodgett multilayer film 7. Conclusions 8. Acknowledgments...4B. 6.3 X-ray standing wave study of a Langmuir - Blodgett multilayer film As mentioned previously the total external reflection condition occurs...for a Zn atom layer embedded in the top arachidate bilayer of a Langmuir - Blodgett (LB) multilayer film which was deposited on the surface of a gold

Simulation and Laboratory results of the Hard X-ray Polarimeter: X-Calibur

NASA Astrophysics Data System (ADS)

Guo, Qingzhen; Beilicke, M.; Kislat, F.; Krawczynski, H.

2014-01-01

X-ray polarimetry promises to give qualitatively new information about high-energy sources, such as binary black hole (BH) systems, Microquasars, active galactic nuclei (AGN), GRBs, etc. We designed, built and tested a hard X-ray polarimeter 'X-Calibur' to be flown in the focal plane of the InFOCuS grazing incidence hard X-ray telescope in 2014. X-Calibur combines a low-Z Compton scatterer with a CZT detector assembly to measure the polarization of 20- 80 keV X-rays making use of the fact that polarized photons Compton scatter preferentially perpendicular to the E field orientation. X-Calibur achieves a high detection efficiency of order unity. We optimized of the design of the instrument based on Monte Carlo simulations of polarized and unpolarized X-ray beams and of the most important background components. We have calibrated and tested X-Calibur extensively in the laboratory at Washington University and at the Cornell High-Energy Synchrotron Source (CHESS). Measurements using the highly polarized synchrotron beam at CHESS confirm the polarization sensitivity of the instrument. In this talk we report on the optimization of the design of the instrument based on Monte Carlo simulations, as well as results of laboratory calibration measurements characterizing the performance of the instrument.

X-ray observations of LMC X-3 with the monitor proportional counter aboard the HEAO 2 Einstein observatory - A comparison with Cygnus X-1

NASA Technical Reports Server (NTRS)

Weisskopf, M. C.; Darbro, W. A.; Elsner, R. F.; Williams, A. C.; Kahn, S. M.; Grindlay, J. E.; Naranan, S.; Sutherland, P. G.

1983-01-01

A comparison is presented of the black hole candidates LMC X-3 and Cygnus X-1 based on Einstein observations of LMC X-3 with the monitor proportional counter. A spectral analysis shows LMC X-3 to be more like the typical bright galactic X-ray source than Cygnus X-1. A search for periodic pulsations over a period range from 0.2 ms to over 1000 s set upper limits at the 90 percent confidence level of the order of 10 percent. An analysis of the aperiodic variability of LMC X-3 shows none of the shot noise behavior characteristic of Cygnus X-1. The absence of distinctive X-ray properties common to both sources suggests that the identification of black hole candidates on the basis of X-ray properties similar to Cygnus X-1 (or LMC X-3) is not reliable.

Comment on "Parametric Instability Induced by X-Mode Wave Heating at EISCAT" by Wang et al. (2016)

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Borisova, T. D.; Yeoman, T. K.

2017-12-01

In their recent article Wang et al. (2016) analyzed observations from EISCAT (European Incoherent Scatter) Scientific Association Russian X-mode heating experiments and claimed to explain the potential mechanisms for the parametric decay instability (PDI) and oscillating two-stream instability (OTSI). Wang et al. (2016) claim that they cannot separate the HF-enhanced plasma and ion lines excited by O or X mode in the EISCAT UHF radar spectra. Because of this they distinguished the parametric instability excited by O-/X-mode heating waves according to their different excitation heights. Their reflection heights were determined from ionosonde records, which provide a rough measure of excitation altitudes and cannot be used for the separation of the O- and X-mode effects. The serious limitation in their analysis is the use of a 30 s integration time of the UHF radar data. There are also serious disagreements between their analysis and the real observational facts. The fact is that it is the radical difference in the behavior of the X- and O-mode plasma and ion line spectra derived with a 5 s resolution, which provides the correct separation of the X- and O-mode effects. It is not discussed and explained how the parallel component of the electric field under X-mode heating is generated. Apart from the leakage to the O mode, results by Wang et al. (2016) do not explain the potential mechanisms for PDI and OTSI and add nothing to understanding the physical factors accounting for the parametric instability generated by an X-mode HF pump wave.

X-Ray and UV Orbital Phase Dependence in LMC X-3

NASA Technical Reports Server (NTRS)

Dolan, Joseph F.; Boyd, P. T.; Smale, A. P.

2001-01-01

The black-hole binary LMC X-3 is known to be variable on time scales of days to years. We investigated X-ray and ultraviolet variability in the system as a function of the 1.7 d binary orbit using a 6.4 day observation with the Rossi X-ray Timing Explorer (RXTE) in 1998 December. An abrupt 14 % flux decrease lasting nearly an entire orbit was followed by a return to previous flux levels. This behavior occurred twice at nearly the same binary phase, but is not present in consecutive orbits. When the X-ray flux is at lower intensity, a periodic amplitude modulation of 7 % is evident in data folded modulo the orbital period. The higher intensity data show weaker correlation with phase. This is the first report of X-ray variability at the orbital period of LMC X-3. Archival RXTE observations of LMC X-3 during a high flux state in 1996 December show similar phase dependence. An ultraviolet light curve obtained with the High Speed Photometer (HSP) on the Hubble Space Telescope (HST) shows a phase dependent variability consistent with that observed in the visible, ascribed to the ellipsoidal variation of the visible star. The X-ray spectrum of LMC X-3 is acceptably represented by a phenomenological disk black-body plus a power law. Changes in the spectrum of LMX X-3 during our observations are compatible with earlier observations during which variations in the 2-10 keV flux are closely correlated with the disk geometry spectral model parameter.

Influence of oxygen vacancies on the magnetic and electrical properties of La1-xSrxMnO3-x/2 manganites

NASA Astrophysics Data System (ADS)

Trukhanov, S. V.; Lobanovski, L. S.; Bushinsky, M. V.; Khomchenko, V. A.; Pushkarev, N. V.; Troyanchuk, I. O.; Maignan, A.; Flahaut, D.; Szymczak, H.; Szymczak, R.

2004-11-01

The crystal structure, magnetization and electrical transport depending on the temperature and magnetic field for the doped stoichiometric La_{1-x}^{3 + } Sr_x^{2 + } Mn_{1-x}^{3 + } Mn_x^{4 + } O_3^{2-} as well as anion-deficient La_{1-x}^{3 + } Sr_x^{2 + } Mn^{3 + }O_{3-x/2}^{2-} (0le x le 0.30) ortomanganite systems have been experimentally studied. It is established that the stochiometric samples in the region of the 0 le x le 0.125 are an O'-orthorhombic perovskites whereas in the 0.175 le x le 0.30 - a rhombohedric. For the anion-deficient system the symmetry type of the unit cell is similar to the stoichiometric one. As a doping level increases the samples in the ground state undergo a number of the magnetic transitions. It is assumed that the samples with the large amount of oxygen vacancies are a cluster spin glasses (0.175 < x le 0.30) and temperature of the magnetic moment freezing is 40 K. All the anion-deficient samples are semiconductors and show considerable magnetoresistance over a wide temperature range with a peak for the x = 0.175 only. Concentration dependences of the spontaneous magnetization and magnetic ordering temperature for the anion-deficient La_{1-x}^{3 + } Sr_x^{2 + } Mn^{3 + }O_{3-x/2}^{2-} system have been established by the magnetic measurements and compared with those for the stoichiometric La_{1-x}^{3 + } Sr_x^{2 + } Mn_{1-x}^{3 + } Mn_x^{4 + } O_3^{2-} one. The magnetic propeprties of the anion-deficient samples may be interpreted on the base of the superexchange interaction and phase separation (chemical disorder) models.

Properties of unrelaxed InAs{sub 1-X}Sb{sub X} alloys grown on compositionally graded buffers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belenky, G.; Donetsky, D.; Kipshidze, G.

Unrelaxed InAs{sub 1-x}Sb{sub x} layers with lattice constants up to 2.1% larger than that of GaSb substrates were grown by molecular beam epitaxy on GaInSb and AlGaInSb compositionally graded buffer layers. The topmost section of the buffers was unrelaxed but strained. The in-plane lattice constant of the top buffer layer was grown to be equal to the lattice constant of unrelaxed and unstrained InAs{sub 1-x}Sb{sub x} with given X. The InAs{sub 0.56}Sb{sub 0.44} layers demonstrate photoluminescence peak at 9.4 {mu}m at 150 K. The minority carrier lifetime measured at 77 K for InAs{sub 0.8}Sb{sub 0.2} was {tau} = 250 ns.

Systematic and Performance Tests of the Hard X-ray Polarimeter X-Calibur

NASA Astrophysics Data System (ADS)

Endsley, Ryan; Beilicke, Matthias; Kislat, Fabian; Krawczynski, Henric; X-Calibur/InFOCuS

2015-01-01

X-ray polarimetry has great potential to reveal new astrophysical information about the emission processes of high energy sources such as black hole environments, X-ray binary systems, and active galactic nuclei. Here we present the results and conclusions of systematic and performance measurements of the hard X-ray polarimeter, X-Calibur. Designed to be flown on a balloon-borne X-ray telescope, X-Calibur will achieve unprecedented sensitivity and makes use of the fact that polarized X-rays preferentially Compton-scatter perpendicular to their E-field vector. Extensive laboratory measurements taken at Washington University and the Cornell High-Energy Synchrotron Source (CHESS) indicate that X-Calibur combines a detection efficiency on the order of unity with a high modulation factor of µ ≈ 0.5 averaged over the whole detector assembly, and with values up to µ ≈ 0.7 for select subsections of the polarimeter. Additionally, we are able to suppress background flux by more than two orders of magnitude by utilizing an active shield and scintillator coincidence. Comparing laboratory data with Monte Carlo simulations of both polarized and unpolarized hard X-ray beams illustrate that we have an exceptional understanding of the detector response.

Unusual Black Hole Binary LMC X-3: A Transient High-mass X-Ray Binary That Is Almost Always On?

NASA Astrophysics Data System (ADS)

Torpin, Trevor J.; Boyd, Patricia T.; Smale, Alan P.; Valencic, Lynne A.

2017-11-01

We have analyzed a rich, multimission, multiwavelength data set from the black hole X-ray binary (BHXB) LMC X-3, covering a new anomalous low state (ALS), during which the source flux falls to an unprecedentedly low and barely detectable level, and a more normal low state. Simultaneous X-ray and UV/optical monitoring data from Swift are combined with pointed observations from the Rossi X-ray Timing Explorer (RXTE) and X-ray Multi-Mirror Mission (XMM-Newton) and light curves from the Monitor of All-Sky X-ray Image (MAXI) instrument to compare the source characteristics during the ALS with those seen during the normal low state. An XMM-Newton spectrum obtained during the ALS can be modeled using an absorbed power law with {{Γ }}=1.41+/- 0.65 and a luminosity of 7.97× {10}33 erg s-1 (0.6-5 keV). The Swift X-ray and UV light curves indicate an X-ray lag of ˜8 days as LMC X-3 abruptly exits the ALS, suggesting that changes in the mass accretion rate from the donor drive the X-ray lag. The normal low state displays an asymmetric profile in which the exit occurs more quickly than the entry, with minimum X-ray flux a factor of ˜4300 brighter than during the ALS. The UV brightness of LMC X-3 in the ALS is also fainter and less variable than during normal low states. The existence of repeated ALSs in LMC X-3, as well as a comparison with other BHXBs, implies that it is very close to the transient/persistent X-ray source dividing line. We conclude that LMC X-3 is a transient source that is almost always “on.”

Optics Requirements For The Generation-X X-Ray Telescope

NASA Technical Reports Server (NTRS)

O'Dell, S. .; Elsner, R. F.; Kolodziejczak, J. J.; Ramsey, B. D.; Weisskopf, M. C.; Zhang, W. W.; Content, D. A.; Petre, R.; Saha, T. T.; Reid, P. B.;

Anchoring the Distance Scale via X-Ray/Infrared Data for Cepheid Clusters: SU Cas

NASA Astrophysics Data System (ADS)

Majaess, D.; Turner, D. G.; Gallo, L.; Gieren, W.; Bonatto, C.; Lane, D. J.; Balam, D.; Berdnikov, L.

2012-07-01

New X-ray (XMM-Newton) and JHKs (Observatoire du Mont-Mégantic) observations for members of the star cluster Alessi 95, which Turner et al. discovered hosts the classical Cepheid SU Cas, were used in tandem with UCAC3 (proper motion) and Two Micron All Sky Survey observations to determine precise cluster parameters: E(J - H) = 0.08 ± 0.02 and d = 405 ± 15 pc. The ensuing consensus among cluster, pulsation, and trigonometric distances (d=414+/- 5(\\sigma _{\\bar{x}}) +/- 10 (\\sigma) pc) places SU Cas in a select group of nearby fundamental Cepheid calibrators (δ Cep, ζ Gem). High-resolution X-ray observations may be employed to expand that sample as the data proved pertinent for identifying numerous stars associated with SU Cas. Acquiring X-ray observations of additional fields may foster efforts to refine Cepheid calibrations used to constrain H 0.

The first search for X-ray polarization in the Centaurus X-3 and Hercules X-1 pulsars

NASA Technical Reports Server (NTRS)

Silver, E. H.; Weisskopf, M. C.; Kestenbaum, H. L.; Long, K. S.; Novick, R.; Wolff, R. S.

1979-01-01

The first search for X-ray polarization in the Cen X-3 and Her X-1 pulsars was performed by the OSO 8 polarimeters in 1975 July and 1975 August, respectively. Three-sigma upper limits to the polarization in Cen X-3 of 13.5% and 19% at 2.6 keV and 5.2 keV, respectively, were obtained when the data were averaged over the pulse and binary periods. The upper limit for Her X-1 at 2.6 keV is 60%. A search for pulse-phase dependent X-ray polarization from both objects was also performed. At the 91% confidence level, emission from Cen X-3 exhibits evidence for X-ray polarization at 2.6 keV that varies with pulse phase. Upper limits to polarization are presented for the leading and trailing edges and peak of the Her X-1 pulse at 2.6 keV.

Chandra Observations of SN 1987A: The Soft X-Ray Light Curve Revisited

NASA Technical Reports Server (NTRS)

Helder, E. A.; Broos, P. S.; Dewey, D.; Dwek, E.; McCray, R.; Park, S.; Racusin, J. L.; Zhekov, S. A.; Burrows, D. N.

2013-01-01

We report on the present stage of SN 1987A as observed by the Chandra X-Ray Observatory. We reanalyze published Chandra observations and add three more epochs of Chandra data to get a consistent picture of the evolution of the X-ray fluxes in several energy bands. We discuss the implications of several calibration issues for Chandra data. Using the most recent Chandra calibration files, we find that the 0.5-2.0 keV band fluxes of SN 1987A have increased by approximately 6 x 10(exp-13) erg s(exp-1)cm(exp-2) per year since 2009. This is in contrast with our previous result that the 0.5-2.0 keV light curve showed a sudden flattening in 2009. Based on our new analysis, we conclude that the forward shock is still in full interaction with the equatorial ring.

X-15 simulator

NASA Technical Reports Server (NTRS)

1961-01-01

This photo shows the X-15 flight simulator located at the NASA Flight Research Center, Edwards, California, in the 1960s. One of the major advances in aircraft development, pilot training, mission planning, and research flight activities in the 1950s and 1960s was the use of simulators. For the X-15, a computer was programmed with the flight characteristics of the aircraft. Before actually flying a mission, a research pilot could discover many potential problems with the aircraft or the mission while still on the ground by 'flying' the simulator. The problem could then be analyzed by engineers and a solution found. This did much to improve safety. The X-15 simulator was very limited compared to those available in the 21st century. The video display was simple, while the computer was analog rather than digital (although it became hybrid in 1964 with the addition of a digital computer for the X-15A-2; this generated the nonlinear aerodynamic coefficients for the modified No. 2 aircraft). The nonlinear aerodynamic function generators used in the X-15 simulator had hundreds of fuses, amplifiers, and potentiometers without any surge protection. After the simulator was started on a Monday morning, it would be noon before it had warmed up and stabilized. The electronics for the X-15 simulator took up many large consoles. The X-15 was a rocket-powered aircraft. The original three aircraft were about 50 ft long with a wingspan of 22 ft. The modified #2 aircraft (X-15A-2 was longer.) They were a missile-shaped vehicles with unusual wedge-shaped vertical tails, thin stubby wings, and unique side fairings that extended along the side of the fuselage. The X-15 weighed about 14,000 lb empty and approximately 34,000 lb at launch. The XLR-99 rocket engine, manufactured by Thiokol Chemical Corp., was pilot controlled and was rated at 57,000 lb of thrust, although there are indications that it actually achieved up to 60,000 lb. North American Aviation built three X-15 aircraft for

Water electrolysis on La 1-xSr xCoO 3-δ perovskite electrocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mefford, J. Tyler; Rong, Xi; Abakumov, Artem M.

2016-03-23

Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr 2+ substitution into La 1-xSr xCoO 3-δ. We attempt tomore » rationalize the high activities of La 1-xSr xCoO 3-δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO 2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.« less

Water electrolysis on La 1-xSr xCoO 3-δ perovskite electrocatalysts

DOE PAGES

Mefford, J. Tyler; Rong, Xi; Abakumov, Artem M.; ...

2016-03-23

Here, perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B–O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co–O bond and the concentration of oxygen vacancies are controlled through Sr 2+ substitution into La 1–xSr xCoO 3–δ. We attemptmore » to rationalize the high activities of La 1–xSr xCoO 3–δ through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO 2.7, with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.« less

Confocal total reflection X-ray fluorescence technology based on an elliptical monocapillary and a parallel polycapillary X-ray optics.

PubMed

Zhu, Yu; Wang, Yabing; Sun, Tianxi; Sun, Xuepeng; Zhang, Xiaoyun; Liu, Zhiguo; Li, Yufei; Zhang, Fengshou

2018-07-01

A total reflection X-ray fluorescence (TXRF) spectrometer based on an elliptical monocapillary X-ray lens (MXRL) and a parallel polycapillary X-ray lens (PPXRL) was designed. This TXRF instrument has micro focal spot, low divergence and high intensity of incident X-ray beam. The diameter of the focal spot of MXRL was 16.5 µm, and the divergence of the incident X-ray beam was 3.4 mrad. We applied this TXRF instrument to the micro analysis of a single-layer film containing Ni deposited on a Si substrate by metal vapor vacuum arc ion source. Copyright © 2018 Elsevier Ltd. All rights reserved.

A novel method for sex determination by detecting the number of X chromosomes.

PubMed

Nakanishi, Hiroaki; Shojo, Hideki; Ohmori, Takeshi; Hara, Masaaki; Takada, Aya; Adachi, Noboru; Saito, Kazuyuki

2015-01-01

A novel method for sex determination, based on the detection of the number of X chromosomes, was established. Current methods, based on the detection of the Y chromosome, can directly identify an unknown sample as male, but female gender is determined indirectly, by not detecting the Y chromosome. Thus, a direct determination of female gender is important because the quality (e.g., fragmentation and amelogenin-Y null allele) of the Y chromosome DNA may lead to a false result. Thus, we developed a novel sex determination method by analyzing the number of X chromosomes using a copy number variation (CNV) detection technique (the comparative Ct method). In this study, we designed a primer set using the amelogenin-X gene without the CNV region as the target to determine the X chromosome copy number, to exclude the influence of the CNV region from the comparative Ct value. The number of X chromosomes was determined statistically using the CopyCaller software with real-time PCR. All DNA samples from participants (20 males, 20 females) were evaluated correctly using this method with 1-ng template DNA. A minimum of 0.2-ng template DNA was found to be necessary for accurate sex determination with this method. When using ultraviolet-irradiated template DNA, as mock forensic samples, the sex of the samples could not be determined by short tandem repeat (STR) analysis but was correctly determined using our method. Thus, we successfully developed a method of sex determination based on the number of X chromosomes. Our novel method will be useful in forensic practice for sex determination.

X-ray Monitoring of eta Carinae: Variations on a Theme

NASA Technical Reports Server (NTRS)

Corcoran, M. F.

2004-01-01

We present monitoring observations by the Rossi X-ray Timing Explorer of the 2-10 keV X-ray emission from the supermassive star eta Carinae from 1996 through late 2003. These data cover more than one of the stellar variability cycles in temporal detail and include especially detailed monitoring through two X-ray minima. We compare the current X-ray minimum which began on June 29, 2003 to the previous X-ray minimum which began on December 15, 1997, and refine the X-ray period to 2024 days. We examine the variations in the X-ray spectrum with phase and with time, and also refine our understanding of the X-ray peaks which have a quasi-period of 84 days, with significant variation. Cycle-to-cycle differences are seen in the level of X-ray intensity and in the detailed variations of the X-ray flux on the rise to maximum just prior to the X-ray minimum. Despite these differences the similarities between the decline to minimum, the duration of the minimum, and correlated variations of the X-ray flux and other measures throughout the electromagnetic spectrum leave little doubt that that the X-ray variation is strictly periodic and produced by orbital motion as the wind from eta Carinae collides with the wind of an otherwise unseen companion.

X-SAR: The X-band synthetic aperture radar on board the Space Shuttle

NASA Technical Reports Server (NTRS)

Werner, Marian U.

1993-01-01

The X-band synthetic aperture radar (X-SAR) is the German/Italian contribution to the NASA/JPL Shuttle Radar Lab missions as part of the preparation for the Earth Observation System (EOS) program. The Shuttle Radar Lab is a combination of several radars: an L-band (1.2 GHz) and a C-band (5.3 GHz) multipolarization SAR known as SIR-C (Shuttle Imaging Radar); and an X-band (9.6 GHz) vertically polarized SAR which will be operated synchronously over the same target areas to deliver calibrated multifrequency and multipolarization SAR data at multiple incidence angles from space. A joint German/Italian project office at DARA (German Space Agency) is responsible for the management of the X-SAR project. The space hardware has been developed and manufactured under industrial contract by Dornier and Alenia Spazio. Besides supporting all the technical and scientific tasks, DLR, in cooperation with ASI (Agencia Spaziale Italiano) is responsible for mission operation, calibration, and high precision SAR processing. In addition, DLR developed an airborne X-band SAR to support the experimenters with campaigns to prepare for the missions. The main advantage of adding a shorter wavelength (3 cm) radar to the SIR-C radars is the X-band radar's weaker penetration into vegetation and soil and its high sensitivity to surface roughness and associated phenomena. The performance of each of the three radars is comparable with respect to radiometric and geometric resolution.

X-ray photoemission study of NiS2-xSex (x=0.0 1.2)

NASA Astrophysics Data System (ADS)

Krishnakumar, S. R.; Sarma, D. D.

2003-10-01

Electronic structure of NiS2-xSex system has been investigated for various compositions (x) using x-ray photoemission spectroscopy. An analysis of the core-level as well as the valence-band spectra of NiS2 in conjunction with many-body cluster calculations provides a quantitative description of the electronic structure of this compound. With increasing Se content, the on-site Coulomb correlation strength (U) does not change, while the bandwidth W of the system increases, driving the system from a covalent insulating state to a pd-metallic state.

Chandra X-Ray Observatory (CXO) on Orbit Animation

NASA Technical Reports Server (NTRS)

1999-01-01

This is an on-orbit animation of the Chandra X-Ray Observatory (CXO), formerly Advanced X-Ray Astrophysics Facility (AXAF). In 1999, the AXAF was renamed the CXO in honor of the late Indian-American Novel Laureate Subrahmanyan Chandrasekhar. The CXO is the most sophisticated and the world's most powerful x-ray telescope ever built. It is designed to observe x-rays from high energy regions of the Universe, such as hot gas in the remnants of exploded stars. It produces picture-like images of x-ray emissions analogous to those made in visible light, as well as gathers data on the chemical composition of x-ray radiating objects. The CXO helps astronomers worldwide better understand the structure and evolution of the universe by studying powerful sources of x-rays such as exploding stars, matter falling into black holes, and other exotic celestial objects. TRW, Inc. was the prime contractor for the development of the CXO and NASA's Marshall Space Flight Center was responsible for its project management. The Smithsonian Astrophysical Observatory controls science and flight operations of the CXO for NASA from Cambridge, Massachusetts. The Observatory was launched July 22, 1999 aboard the Space Shuttle Columbia, STS-93 mission.

Quantum phase transition and non-Fermi liquid behavior in Fe1-x Co x Si (x ⩾ 0.7)

NASA Astrophysics Data System (ADS)

Shanmukharao Samatham, S.; Suresh, K. G.; Ganesan, V.

2018-04-01

We report on the nature of electron correlations in Fe1-x Co x Si (0.7 ≤slant x < 1 ) using combined results of magnetization, specific heat and transport properties. Doping driven quantum critical point is observed to occur at x˜ 0.75 . The magnetically unstable regime is identified to be centered around x\\in [0.75, 0.95 ]. The emergence of non-Fermi liquid behaviors in x  =  0.8 (near to ferromagnetic quantum critical point) and x  =  0.9 (disorder-induced) compositions are discussed on the basis of the power-law dependence of susceptibility χ ˜ T-g (g ˜ 1.07 for x  =  0.8 and 0.55 for x  =  0.9), specific heat C/T ˜ T-1+λ (λ ˜ 1.52 for x  =  0.8 and 0.9) and resistivity Δρ ˜ Td (d ˜ 1.56 for x  =  0.8 and 1.38 for x  =  0.9). Further, a comprehensive classification of doping dependent physical properties of Fe1-x Co x Si is presented in the revisited temperature-composition (T-x) phase diagram.

Spectrally resolved localized states in GaAs 1– xBi x

DOE PAGES

Christian, Theresa M.; Alberi, Kirstin; Beaton, Daniel A.; ...

2017-02-01

In this study, the role of localized states and their influence on the broader band structure remains a crucial question in understanding the band structure evolution in GaAs 1-xBi x. Here in this work, we present clear spectroscopic observations of recombination at several localized states in GaAs 1-xBi x. Sharp and recognizable photoluminescence features appear in multiple samples and redshift as a function of GaBi fraction between x = 0.16% and 0.4% at a linearized rate of 34 meV per % Bi, weaker than the redshift associated with band-to-band recombination. Interpreting these results in terms of radiative recombination between localizedmore » holes and free electrons sheds light on the relative movement of the conduction band minimum and the characteristics of localized bismuth-related trap states in GaAs 1-xBi x alloys.« less

The X chromosome of monotremes shares a highly conserved region with the eutherian and marsupial X chromosomes despite the absence of X chromosome inactivation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watson, J.M.; Spencer, J.A.; Graves, J.A.M.

1990-09-01

Eight genes, located on the long arm of the human X chromosome and present on the marsupial X chromosome, were mapped by in situ hybridization to the chromosomes of the platypus Ornithorhynchus anatinus, one of the three species of monotreme mammals. All were located on the X chromosome. The authors conclude that the long arm of the human X chromosome represents a highly conserved region that formed part of the X chromosome in a mammalian ancestor at least 150 million years ago. Since three of these genes are located on the long arm of the platypus X chromosome, which ismore » G-band homologous to the Y chromosome and apparently exempt from X chromosome inactivation, the conservation of this region has evidently not depended on isolation by X-Y chromosome differentiation and X chromosome inactivation.« less

Electrical and structural properties of In-implanted Si 1–xGe x alloys

DOE PAGES

Feng, Ruixing; Kremer, F.; Sprouster, D. J.; ...

2016-01-14

Here, we report on the effects of dopant concentration and substrate stoichiometry on the electrical and structural properties of In-implanted Si 1–xGe x alloys. Correlating the fraction of electrically active In atoms from Hall Effect measurements with the In atomic environment determined by X-ray absorption spectroscopy, we observed the transition from electrically active, substitutional In at low In concentration to electrically inactive metallic In at high In concentration. The In solid-solubility limit has been quantified and was dependent on the Si 1–xGe x alloy stoichiometry; the solid-solubility limit increased as the Ge fraction increased. This result was consistent with densitymore » functional theory calculations of two In atoms in a Si 1–xGe x supercell that demonstrated that In–In pairing was energetically favorable for x ≲ 0.7 and energetically unfavorable for x ≳ 0.7. Transmission electron microscopy imaging further complemented the results described earlier with the In concentration and Si 1–xGe x alloy stoichiometry dependencies readily visible. We have demonstrated that low resistivity values can be achieved with In implantation in Si 1–xGe x alloys, and this combination of dopant and substrate represents an effective doping protocol.« less

The Hard X-Ray Emission from Scorpius X-1 Seen by INTEGRAL

NASA Technical Reports Server (NTRS)

Sturner, Steve; Shrader, C. R.

2008-01-01

We present the results of our hard X-ray and gamma-ray study of the LMXB Sco X-1 utilizing INTEGRAL data as well as contemporaneous RXTE PCA data. We have investigated the hard X-ray spectral properties of Sco X-1 including the nature of the high-energy, nonthermal component and its possible correlations with the location of the source on the soft X-ray color-color diagram. We find that Sco X-1 follows two distinct spectral tracks when the 20-40 keV count rate is greater than 130 counts/second. One state is a hard state which exhibits a significant high-energy, powerlaw tail to the lower energy thermal spectrum. The other state shows a much less significant high-energy component. We found suggestive evidence for a correlation of these hard and soft high-energy states with the position of Sco X-1 on the low-energy X-ray color-color diagram. We have searched for similar behavior in 2 other Z sources: GX 17+2 and GX 5-1 with negative results.

X-38 on Lakebed after Landing on Second Free Flight

NASA Technical Reports Server (NTRS)

1999-01-01

NASA's X-38, a prototype of a Crew Return Vehicle (CRV) resting on the lakebed near the Dryden Flight Research Center after the completion of its second free flight. The X-38 was launched from NASA Dryden's B-52 Mothership on Saturday, February 6, 1999, from an altitude of approximately 23,000 feet. The X-38 Crew Return Vehicle (CRV) research project is designed to develop the technology for a prototype emergency crew return vehicle, or lifeboat, for the International Space Station. The project is also intended to develop a crew return vehicle design that could be modified for other uses, such as a joint U.S. and international human spacecraft that could be launched on the French Ariane-5 Booster. The X-38 project is using available technology and off-the-shelf equipment to significantly decrease development costs. Original estimates to develop a capsule-type crew return vehicle were estimated at more than $2 billion. X-38 project officials have estimated that development costs for the X-38 concept will be approximately one quarter of the original estimate. Off-the-shelf technology is not necessarily 'old' technology. Many of the technologies being used in the X-38 project have never before been applied to a human-flight spacecraft. For example, the X-38 flight computer is commercial equipment currently used in aircraft and the flight software operating system is a commercial system already in use in many aerospace applications. The video equipment for the X-38 is existing equipment, some of which has already flown on the space shuttle for previous NASA experiments. The X-38's primary navigational equipment, the Inertial Navigation System/Global Positioning System, is a unit already in use on Navy fighters. The X-38 electromechanical actuators come from previous joint NASA, U.S. Air Force, and U.S. Navy research and development projects. Finally, an existing special coating developed by NASA will be used on the X-38 thermal tiles to make them more durable than

Intricate Li-Sn Disorder in Rare-Earth Metal-Lithium Stannides. Crystal Chemistry of RE3Li4- xSn4+ x (RE = La-Nd, Sm; x < 0.3) and Eu7Li8- xSn10+ x ( x ≈ 2.0).

PubMed

Suen, Nian-Tzu; Guo, Sheng-Ping; Hoos, James; Bobev, Svilen

2018-05-07

Reported are the syntheses, crystal structures, and electronic structures of six rare-earth metal-lithium stannides with the general formulas RE 3 Li 4- x Sn 4+ x (RE = La-Nd, Sm) and Eu 7 Li 8- x Sn 10+ x . These new ternary compounds have been synthesized by high-temperature reactions of the corresponding elements. Their crystal structures have been established using single-crystal X-ray diffraction methods. The RE 3 Li 4- x Sn 4+ x phases crystallize in the orthorhombic body-centered space group Immm (No. 71) with the Zr 3 Cu 4 Si 4 structure type (Pearson code oI22), and the Eu 7 Li 8- x Sn 10+ x phase crystallizes in the orthorhombic base-centered space group Cmmm (No. 65) with the Ce 7 Li 8 Ge 10 structure type (Pearson code oC50). Both structures can be consdered as part of the [RESn 2 ] n [RELi 2 Sn] m homologous series, wherein the structures are intergrowths of imaginary RESn 2 (AlB 2 -like structure type) and RELi 2 Sn (MgAl 2 Cu-like structure type) fragments. Close examination the structures indicates complex occupational Li-Sn disorder, apparently governed by the drive of the structure to achieve an optimal number of valence electrons. This conclusion based on experimental results is supported by detailed electronic structure calculations, carried out using the tight-binding linear muffin-tin orbital method.

STROBE-X: X-ray Timing & Spectroscopy on Dynamical Timescales from Milliseconds to Years

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Ray, P. S.; Maccarone, T; Chakrabarty, D.; Gendreau, K.; Arzoumanian, Z.; Jenke, P.; Ballantyne, D.; Bozzo, E.; Brandt, S.;

STROBE-X: X-Ray Timing Spectroscopy on Dynamical Timescales from Microseconds to Years

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Ray, P. S.; Gendreau, K.; Arzoumanian, Z.; Chakrabarty, D.; Remillard, R.; Feroci, M.; Maccarone, T.; Wood, K.; Jenke, P.

2017-01-01

We describe a probe-class mission concept that provides an unprecedented view of the X-ray sky, performing timing and 0.2-30 keV spectroscopy over timescales from microseconds to years. The Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) comprises three primary instruments. The first uses an array of lightweight optics (3-m focal length) that concentrate incident photons onto solid state detectors with CCD-level (85-130 eV) energy resolution, 100 ns time resolution, and low background rates to cover the 0.2-12 keV band. This technology is scaled up from NICER, with enhanced optics to take advantage of the longer focal length of STROBE-X. The second uses large-area collimated silicon drift detectors, developed for ESA's LOFT, to cover the 2-30 keV band. These two instruments each provide an order of magnitude improvement in effective area compared with its predecessor (NICER and RXTE, respectively). Finally, a sensitive sky monitor triggers pointed observations, provides high duty cycle, high time resolution, high spectral resolution monitoring of the X-ray sky with approx. 20 times the sensitivity of the RXTE ASM, and enables multi-wavelength and multi-messenger studies on a continuous, rather than scanning basis.For the first time, the broad coverage provides simultaneous study of thermal components, non-thermal components, iron lines, and reflection features from a single platform for accreting black holes at all scales. The enormous collecting area allows detailed studies of the dense matter equation of state using both thermal emission from rotation-powered pulsars and harder emission from X-ray burst oscillations. The combination of the wide-field monitor and the sensitive pointed instruments enables observations of potential electromagnetic counterparts to LIGO and neutrino events. Additional extragalactic science, such as high quality spectroscopy of clusters of galaxies and unprecedented timing investigations of active

STROBE-X: X-ray Timing & Spectroscopy on Dynamical Timescales from Microseconds to Years

NASA Astrophysics Data System (ADS)

Wilson-Hodge, Colleen A.; Ray, Paul S.; Maccarone, Thomas J.; Chakrabarty, Deepto; Gendreau, Keith C.; Arzoumanian, Zaven; Jenke, Peter; Ballantyne, David; Bozzo, Enrico; Brandt, Soren; Brenneman, Laura; Christophersen, Marc; DeRosa, Alessandra; Feroci, Marco; Goldstein, Adam; Hartmann, Dieter; Hernanz, Margarita; McDonald, Michael; Phlips, Bernard; Remillard, Ronald; Stevens, Abigail; Tomsick, John; Watts, Anna; Wood, Kent S.; Zane, Silvia; STROBE-X Collaboration

2018-01-01

We describe a probe-class mission concept that provides an unprecedented view of the X-ray sky, performing timing and 0.2-30 keV spectroscopy over timescales from microseconds to years. The Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) comprises three primary instruments. The first uses an array of lightweight optics (3-m focal length) that concentrate incident photons onto solid state detectors with CCD-level (85-130 eV) energy resolution, 100 ns time resolution, and low background rates to cover the 0.2-12 keV band. This technology is scaled up from NICER, with enhanced optics to take advantage of the longer focal length of STROBE-X. The second uses large-area collimated silicon drift detectors, developed for ESA's LOFT, to cover the 2-30 keV band. These two instruments each provide an order of magnitude improvement in effective area compared with its predecessor (NICER and RXTE, respectively). Finally, a sensitive sky monitor triggers pointed observations, provides high duty cycle, high time resolution, high spectral resolution monitoring of the X-ray sky with ~20 times the sensitivity of the RXTE ASM, and enables multi-wavelength and multi-messenger studies on a continuous, rather than scanning basis. We include updated instrument designs resulting from the GSFC IDL run in November 2017.For the first time, the broad coverage provides simultaneous study of thermal components, non-thermal components, iron lines, and reflection features from a single platform for accreting black holes at all scales. The enormous collecting area allows detailed studies of the dense matter equation of state using both thermal emission from rotation-powered pulsars and harder emission from X-ray burst oscillations. The combination of the wide-field monitor and the sensitive pointed instruments enables observations of potential electromagnetic counterparts to LIGO/Virgo and neutrino events. Extragalactic science, such as constraining bulk metalicity

STROBE-X: X-ray Timing & Spectroscopy on Dynamical Timescales from Microseconds to Years

NASA Astrophysics Data System (ADS)

Wilson-Hodge, Colleen A.; Ray, Paul S.; Gendreau, Keith; Chakrabarty, Deepto; Feroci, Marco; Maccarone, Thomas J.; Arzoumanian, Zaven; Remillard, Ronald A.; Wood, Kent; Griffith, Christopher; Jenke, Peter

2017-08-01

We describe a probe-class mission concept that provides an unprecedented view of the X-ray sky, performing timing and 0.2-30 keV spectroscopy over timescales from microseconds to years. The Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) comprises three primary instruments. The first uses an array of lightweight optics (3-m focal length) that concentrate incident photons onto solid state detectors with CCD-level (85-130 eV) energy resolution, 100 ns time resolution, and low background rates to cover the 0.2-12 keV band. This technology is scaled up from NICER, with enhanced optics to take advantage of the longer focal length of STROBE-X. The second uses large-area collimated silicon drift detectors, developed for ESA's LOFT, to cover the 2-30 keV band. These two instruments each provide an order of magnitude improvement in effective area compared with its predecessor (NICER and RXTE, respectively). Finally, a sensitive sky monitor triggers pointed observations, provides high duty cycle, high time resolution, high spectral resolution monitoring of the X-ray sky with ~20 times the sensitivity of the RXTE ASM, and enables multi-wavelength and multi-messenger studies on a continuous, rather than scanning basis.For the first time, the broad coverage provides simultaneous study of thermal components, non-thermal components, iron lines, and reflection features from a single platform for accreting black holes at all scales. The enormous collecting area allows detailed studies of the dense matter equation of state using both thermal emission from rotation-powered pulsars and harder emission from X-ray burst oscillations. The combination of the wide-field monitor and the sensitive pointed instruments enables observations of potential electromagnetic counterparts to LIGO and neutrino events. Additional extragalactic science, such as high quality spectroscopy of clusters of galaxies and unprecedented timing investigations of active galactic

The Hard X-ray Emission from Scorpius X-1 as Seen by INTEGRAL

NASA Technical Reports Server (NTRS)

Sturner, S. J.; Shrader, C. R.; Weidenspointner, G.

2008-01-01

We present the results of our hard X-ray and gamma-ray study of the LMXB Sco X-1 utilizing INTEGRAL data as well as contemporaneous RXTE PCA data. We have concentrated on investigating the hard X-ray spectral properties of Sco X-1 including the nature of the high-energy, nonthermal component of the spectrum and its possible correlations with the location of the source on the X-ray color-color diagram. We find that Sco X-1 has two distinct spectral when the 20-40 keV count rate is greater than 140 counts/second. One state is a hard state which exhibits a significant high-energy, powerlaw tail to the lower energy thermal spectrum. The other state shows no evidence for a powerlaw tail whatsoever. We found suggestive evidence for a correlation of these hard and soft high-energy states with the position of Sco X-1 on the low-energy X-ray color-color diagram.

Temporal Gain Correction for X-Ray Calorimeter Spectrometers

NASA Technical Reports Server (NTRS)

Porter, F. S.; Chiao, M. P.; Eckart, M. E.; Fujimoto, R.; Ishisaki, Y.; Kelley, R. L.; Kilbourne, C. A.; Leutenegger, M. A.; McCammon, D.; Mitsuda, K.

2016-01-01

Calorimetric X-ray detectors are very sensitive to their environment. The boundary conditions can have a profound effect on the gain including heat sink temperature, the local radiation temperature, bias, and the temperature of the readout electronics. Any variation in the boundary conditions can cause temporal variations in the gain of the detector and compromise both the energy scale and the resolving power of the spectrometer. Most production X-ray calorimeter spectrometers, both on the ground and in space, have some means of tracking the gain as a function of time, often using a calibration spectral line. For small gain changes, a linear stretch correction is often sufficient. However, the detectors are intrinsically non-linear and often the event analysis, i.e., shaping, optimal filters etc., add additional non-linearity. Thus for large gain variations or when the best possible precision is required, a linear stretch correction is not sufficient. Here, we discuss a new correction technique based on non-linear interpolation of the energy-scale functions. Using Astro-HSXS calibration data, we demonstrate that the correction can recover the X-ray energy to better than 1 part in 104 over the entire spectral band to above 12 keV even for large-scale gain variations. This method will be used to correct any temporal drift of the on-orbit per-pixel gain using on-board calibration sources for the SXS instrument on the Astro-H observatory.

IMMEDIATE EFFECTS OF A DYNAMIC ROTATION-SPECIFIC WARM-UP ON X-FACTOR AND X-FACTOR STRETCH IN THE AMATEUR GOLFER.

PubMed

Henry, Elizabeth; Berglund, Kathy; Millar, Lynn; Locke, Frederick

2015-12-01

Recent evidence suggests performing a warm-up prior to golf can improve performance and reduce injuries. While some characteristics of effective golf warm-ups have been determined, no studies have explored the immediate effects of a rotational-specific warm-up with elements of motor control on the biomechanical aspects of the full X-Factor and X-Factor Stretch during the golf swing. Thirty-six amateur golfers (mean ± SD age: 64 ± 8 years old; 75% male) were randomized into a Dynamic Rotation-Specific Warm-up group (n=20), or a Sham Warm-up group (n=16). X-Factor and X-Factor Stretch were measured at baseline and immediately following the warm-up. Mixed model ANCOVAs were used to determine if a Group*Time interaction existed for each variable with group as the between-subjects variable and time as the within-subjects variable. The mixed model ANCOVAs did not reveal a statistically significant group*time interaction for X-Factor or X-Factor Stretch. There was not a significant main effect for time for X-Factor but there was for X-Factor Stretch. These results indicate that neither group had a significant effect on improving X-Factor, however performing either warm-up increased X-Factor Stretch without significant difference between the two. The results of this study suggest that performing the Dynamic Rotation-Specific Warm-up did not increase X-Factor or X-Factor Stretch when controlled for age compared to the Sham Warm-up. Further study is needed to determine the long-term effects of the Dynamic Rotation-Specific Warm-up on performance factors of the golf swing while examining across all ages. 2b.

The Generation-X X-ray Observatory Vision Mission and Technology Study

NASA Technical Reports Server (NTRS)

Figueroa-Feliciano, Enectali

2004-01-01

The new frontier in astrophysics is the study of the birth and evolution of the first stars, galaxies and black holes in the early Universe. X-ray astronomy opens a window into these objects by studying the emission from black holes, supernova explosions and the gamma-ray burst afterglows of massive stars. However, such objects are beyond the grasp of current or near-future observatories. X-ray imaging and spectroscopy of such distant objects will require an X-ray telescope with large collecting area and high angular resolution. Our team has conceived the Generation-X Vision Mission based on an X-ray observatory with 100 sq m collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the Constellation-X resolution goal). Such an observatory would be capable of detecting the earliest black holes and galaxies in the Universe, and will also study extremes of density, gravity, magnetic fields, and kinetic energy which cannot be created in laboratories. NASA has selected the Generation-X mission for study under its Vision Mission Program. We describe the studies being performed to develop the mission concept and define candidate technologies and performance requirements for Generation-X. The baseline Generation-X mission involves four 8m diameter X-ray telescopes operating at Sun-Earth L2. We trade against an alternate concept of a single 26m diameter telescope with focal plane instruments on a separate spacecraft. A telescope of this size will require either robotic or human-assisted in-flight assembly. The required effective area implies that extremely lightweight grazing incidence X-ray optics must be developed. To achieve the required aerial density of at least 100 times lower than in Chandra, we will study 0.1mm thick mirrors which have active on-orbit figure control. We discuss the suite of required detectors, including a large FOV high angular resolution imager, a

The cool component and the dichotomy, lateral expansion, and axial rotation of solar X-ray jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David A.

2013-06-01

We present results from a study of 54 polar X-ray jets that were observed in coronal X-ray movies from the X-ray Telescope on Hinode and had simultaneous coverage in movies of the cooler transition region (T ∼ 10{sup 5} K) taken in the He II 304 Å band of the Atmospheric Imaging Assembly (AIA) on Solar Dynamics Observatory. These dual observations verify the standard-jet/blowout-jet dichotomy of polar X-ray jets previously found primarily from XRT movies alone. In accord with models of blowout jets and standard jets, the AIA 304 Å movies show a cool (T ∼ 10{sup 5} K) componentmore » in nearly all blowout X-ray jets and in a small minority of standard X-ray jets, obvious lateral expansion in blowout X-ray jets but none in standard X-ray jets, and obvious axial rotation in both blowout X-ray jets and standard X-ray jets. In our sample, the number of turns of axial rotation in the cool-component standard X-ray jets is typical of that in the blowout X-ray jets, suggesting that the closed bipolar magnetic field in the jet base has substantial twist not only in all blowout X-ray jets but also in many standard X-ray jets. We point out that our results for the dichotomy, lateral expansion, and axial rotation of X-ray jets add credence to published speculation that type-II spicules are miniature analogs of X-ray jets, are generated by granule-size emerging bipoles, and thereby carry enough energy to power the corona and solar wind.« less

Structure Evolution and Reactivity of the Sc(2- x)V xO3+δ (0 ≤ x ≤ 2.0) System.

PubMed

Lussier, Joey A; Simon, Fabian J; Whitfield, Pamela S; Singh, Kalpana; Thangadurai, Venkataraman; Bieringer, Mario

2018-05-07

Solid oxide fuel cells (SOFCs) are solid-state electrochemical devices that directly convert chemical energy of fuels into electricity with high efficiency. Because of their fuel flexibility, low emissions, high conversion efficiency, no moving parts, and quiet operation, they are considered as a promising energy conversion technology for low carbon future needs. Solid-state oxide and proton conducting electrolytes play a crucial role in improving the performance and market acceptability of SOFCs. Defect fluorite phases are some of the most promising fast oxide ion conductors for use as electrolytes in SOFCs. We report the synthesis, structure, phase diagram, and high-temperature reactivity of the Sc (2- x) V x O 3+δ (0 ≤ x ≤ 2.00) oxide defect model system. For all Sc (2- x) V x O 3.0 phases with x ≤ 1.08 phase-pure bixbyite-type structures are found, whereas for x ≥ 1.68 phase-pure corundum structures are reported, with a miscibility gap found for 1.08 < x < 1.68. Structural details obtained from the simultaneous Rietveld refinements using powder neutron and X-ray diffraction data are reported for the bixbyite phases, demonstrating a slight V 3+ preference toward the 8b site. In situ X-ray diffraction experiments were used to explore the oxidation of the Sc (2- x) V x O 3.0 phases. In all cases ScVO 4 was found as a final product, accompanied by Sc 2 O 3 for x < 1.0 and V 2 O 5 when x > 1.0; however, the oxidative pathway varied greatly throughout the series. Comments are made on different synthesis strategies, including the effect on crystallinity, reaction times, rate-limiting steps, and reaction pathways. This work provides insight into the mechanisms of solid-state reactions and strategic guidelines for targeted materials synthesis.

The Cambridge-Cambridge X-ray Serendipity Survey: I X-ray luminous galaxies

NASA Technical Reports Server (NTRS)

Boyle, B. J.; Mcmahon, R. G.; Wilkes, B. J.; Elvis, M.

1994-01-01

We report on the first results obtained from a new optical identification program of 123 faint X-ray sources with S(0.5-2 keV) greater than 2 x 10(exp -14) erg/s/sq cm serendipitously detected in ROSAT PSPC pointed observations. We have spectroscopically identified the optical counterparts to more than 100 sources in this survey. Although the majority of the sample (68 objects) are QSO's, we have also identified 12 narrow emission line galaxies which have extreme X-ray luminosities (10(exp 42) less than L(sub X) less than 10(exp 43.5) erg/s). Subsequent spectroscopy reveals them to be a mixture of star-burst galaxies and Seyfert 2 galaxies in approximately equal numbers. Combined with potentially similar objects identified in the Einstein Extended Medium Sensitivity Survey, these X-ray luminous galaxies exhibit a rate of cosmological evolution, L(sub X) varies as (1 + z)(exp 2.5 +/- 1.0), consistent with that derived for X-ray QSO's. This evolution, coupled with the steep slope determined for the faint end of the X-ray luminosity function (Phi(L(sub X)) varies as L(sub X)(exp -1.9)), implies that such objects could comprise 15-35% of the soft (1-2 keV) X-ray background.

SCO X-1: Origin of the radio and hard X-ray emissions

NASA Technical Reports Server (NTRS)

Ramaty, R.; Cheng, C. C.; Tsuruta, S.

1973-01-01

The consequences of models for the central radio source and the hard X-ray ( 30 keV) emitting region in Sco X-1 are examined. It was found that the radio emission could result from noncoherent synchrotron radiation and that the X-rays may be produced by bremsstrahlung. It is shown that both mechanisms require a mass outflow from Sco X-1. The radio source is located at r approximately 3x10 to the 12th power cm from the center of the star, and its linear dimensions do not exceed 3x10 to the 13th power cm. The magnetic field in the radio source is on the order of 1 gauss. If the hard X-rays are produced by thermal bremsstrahlung, their source is located at 10 to the 9th power approximately r approximately 5x10 to the 9th power cm, the temperature is 2x10 to the 9th power K, and the emission measure is 2x10 to the 56th power/cu cm. This hot plasma loses energy inward by conduction and outward by supersonic expansion. The rates of energy loss for both processes are about 10 to the 36th power erg/s, comparable to the total luminosity of Sco X-1.

Studies on Se75Te25-x In x chalcogenide glasses; a material for phase change memory

NASA Astrophysics Data System (ADS)

Srivastava, Archana; Tiwari, S. N.; Alvi, M. A.; Khan, Shamshad A.

2018-01-01

This research paper describes the non-isothermal crystallization during phase transformation in Se75Te25-x In x glasses synthesized by melt quenching method. For crystallization studies in these glasses, non-isothermal differential scanning calorimetry (DSC) measurements was done at constant heating rates of 5, 10, 15, 20 and 25 K min-1 in air atmosphere. The glass transition temperature (T g), on-set crystallization temperature (T c), peak crystallization temperature (T p) and melting temperatures (T m) were derived by DSC thermograms. Using various thermal parameters the activation energy of glass transition and crystallization were determined by using Kissinger, Moynihan and Ozawa approaches and found to be in good agreement. The value of the activation energy of glass transition (ΔE t) was found to be minimum for Se75Te19In6 alloys confirming its maximum probability of transition in a metastable state. Thermal stability parameters of Se75Te25-x In x were determined and found to be increased with indium content. High resolution x-ray diffraction and field emission scanning electron microscopy studies were employed for the study of phase transformation in Se75Te25-x In x glasses. The outcome of these studies shows that the investigated materials may be suitable for phase change memory devices.

Long-term studies with the Ariel 5 ASM. I - Hercules X-1, Vela X-1, and Centaurus X-3

NASA Technical Reports Server (NTRS)

Holt, S. S.; Kaluzienski, L. J.; Boldt, E. A.; Serlemitsos, P. A.

1979-01-01

Twelve hundred days of 3-6 keV X-ray data from Her X-1, Vela X-1, and Cen X-3 accumulated with the Ariel 5 All-Sky Monitor are interrogated. The binary periodicities of all three can be clearly observed, as can the 35 day variation of Her X-1, for which we can refine the period to 34.875 plus or minus 0.030 days. No such longer-term periodicity less than 200 days is observed from Vela X-1. The 26.6 days low-state recurrence period for Cen X-3 is not observed, but a 43.0 day candidate periodicity is found which may be consistent with the precession of an accretion disk in that system. The present results are illustrative of the long-term studies which can be performed on approximately 50 sources over a temporal base which will ultimately extend to at least 1800 days.

3rd International Conference on X-ray Technique

NASA Astrophysics Data System (ADS)

Potrakhov, N. N.; Gryaznov, A. Yu; Lisenkov, A. A.; Kostrin, D. K.

2017-02-01

In this preface a brief history, modern aspects and future tendencies in development of the X-ray technique as seen from the 3rd International Conference on X-ray Technique that was held on 24-25 November 2016 in Saint Petersburg, Russia are described On 24-25 November 2016 in Saint Petersburg on the basis of Saint Petersburg State Electrotechnical University “LETI” n. a. V. I. Ulyanov (Lenin) was held the 3rd International Conference on X-ray Technique. The tradition to hold a similar conference in our country was laid in Soviet times. The last of them, the All-Union Conference on the Prospects of X-ray Tubes and Equipment was organized and held more than a quarter century ago - on 21-23 November 1999, at the initiative and under the leadership of the chief engineer of the Leningrad association of electronic industry “Svetlana” Borovsky Alexander Ivanovich and the chief of special design bureau of X-ray devices of “Svetlana” Shchukin Gennady Anatolievich. The most active part in the organization and work of the conference played members of the department of X-ray and electron beam instruments of Leningrad Electrotechnical Institute “LETI” (the former name of Saint Petersburg State Electrotechnical University “LETI”), represented by head of the department professor Ivanov Stanislav Alekseevich.

X-ray binaries

NASA Technical Reports Server (NTRS)

1976-01-01

Satellite X-ray experiments and ground-based programs aimed at observation of X-ray binaries are discussed. Experiments aboard OAO-3, OSO-8, Ariel 5, Uhuru, and Skylab are included along with rocket and ground-based observations. Major topics covered are: Her X-1, Cyg X-3, Cen X-3, Cyg X-1, the transient source A0620-00, other possible X-ray binaries, and plans and prospects for future observational programs.

AXSIS: Exploring the frontiers in attosecond X-ray science, imaging and spectroscopy.

PubMed

Kärtner, F X; Ahr, F; Calendron, A-L; Çankaya, H; Carbajo, S; Chang, G; Cirmi, G; Dörner, K; Dorda, U; Fallahi, A; Hartin, A; Hemmer, M; Hobbs, R; Hua, Y; Huang, W R; Letrun, R; Matlis, N; Mazalova, V; Mücke, O D; Nanni, E; Putnam, W; Ravi, K; Reichert, F; Sarrou, I; Wu, X; Yahaghi, A; Ye, H; Zapata, L; Zhang, D; Zhou, C; Miller, R J D; Berggren, K K; Graafsma, H; Meents, A; Assmann, R W; Chapman, H N; Fromme, P

2016-09-01

X-ray crystallography is one of the main methods to determine atomic-resolution 3D images of the whole spectrum of molecules ranging from small inorganic clusters to large protein complexes consisting of hundred-thousands of atoms that constitute the macromolecular machinery of life. Life is not static, and unravelling the structure and dynamics of the most important reactions in chemistry and biology is essential to uncover their mechanism. Many of these reactions, including photosynthesis which drives our biosphere, are light induced and occur on ultrafast timescales. These have been studied with high time resolution primarily by optical spectroscopy, enabled by ultrafast laser technology, but they reduce the vast complexity of the process to a few reaction coordinates. In the AXSIS project at CFEL in Hamburg, funded by the European Research Council, we develop the new method of attosecond serial X-ray crystallography and spectroscopy, to give a full description of ultrafast processes atomically resolved in real space and on the electronic energy landscape, from co-measurement of X-ray and optical spectra, and X-ray diffraction. This technique will revolutionize our understanding of structure and function at the atomic and molecular level and thereby unravel fundamental processes in chemistry and biology like energy conversion processes. For that purpose, we develop a compact, fully coherent, THz-driven atto-second X-ray source based on coherent inverse Compton scattering off a free-electron crystal, to outrun radiation damage effects due to the necessary high X-ray irradiance required to acquire diffraction signals. This highly synergistic project starts from a completely clean slate rather than conforming to the specifications of a large free-electron laser (FEL) user facility, to optimize the entire instrumentation towards fundamental measurements of the mechanism of light absorption and excitation energy transfer. A multidisciplinary team formed by laser

X-Ray

MedlinePlus

... of gray. For some types of X-ray tests, a contrast medium — such as iodine or barium — is introduced into your body to provide greater detail on the images. Why it's done X-ray technology is used to examine many parts of the ...

Genomic relationships based on X chromosome markers and accuracy of genomic predictions with and without X chromosome markers

PubMed Central

2014-01-01

Background Although the X chromosome is the second largest bovine chromosome, markers on the X chromosome are not used for genomic prediction in some countries and populations. In this study, we presented a method for computing genomic relationships using X chromosome markers, investigated the accuracy of imputation from a low density (7K) to the 54K SNP (single nucleotide polymorphism) panel, and compared the accuracy of genomic prediction with and without using X chromosome markers. Methods The impact of considering X chromosome markers on prediction accuracy was assessed using data from Nordic Holstein bulls and different sets of SNPs: (a) the 54K SNPs for reference and test animals, (b) SNPs imputed from the 7K to the 54K SNP panel for test animals, (c) SNPs imputed from the 7K to the 54K panel for half of the reference animals, and (d) the 7K SNP panel for all animals. Beagle and Findhap were used for imputation. GBLUP (genomic best linear unbiased prediction) models with or without X chromosome markers and with or without a residual polygenic effect were used to predict genomic breeding values for 15 traits. Results Averaged over the two imputation datasets, correlation coefficients between imputed and true genotypes for autosomal markers, pseudo-autosomal markers, and X-specific markers were 0.971, 0.831 and 0.935 when using Findhap, and 0.983, 0.856 and 0.937 when using Beagle. Estimated reliabilities of genomic predictions based on the imputed datasets using Findhap or Beagle were very close to those using the real 54K data. Genomic prediction using all markers gave slightly higher reliabilities than predictions without X chromosome markers. Based on our data which included only bulls, using a G matrix that accounted for sex-linked relationships did not improve prediction, compared with a G matrix that did not account for sex-linked relationships. A model that included a polygenic effect did not recover the loss of prediction accuracy from exclusion of X

Imaging proportional counters for the stellar X-ray polarimeter. [on Soviet Spectrum X-Gamma mission

NASA Technical Reports Server (NTRS)

Watkins, R. B., Jr.; Kaaret, P.

1990-01-01

The xenon-filled IPCs being developed for the Stellar X-ray Polarimeter are described. The requirements placed on the IPCs by the design of the polarimeter are discussed and results on the performance of prototype counters are presented. The design of a prototype of the IPCs is described. Finally, the performance of the prototype is reported. Due to the extremely low count rates encountered in X-ray polarimetry, efficient background rejection is the most critical parameter of the IPCs. Using a background rejection scheme employing anticoincidence and pulse shape discrimination, a rejection efficiency of 99 percent has been achieved for Co-60-induced events over an energy range of 2 to 15 keV while retaining more than 80 percent of the X-ray efficiency.

Hard X-ray Observation of Cygnus X-1 By the Marshall Imaging X-ray Experiment (MIXE2)

NASA Technical Reports Server (NTRS)

Minamitani, Takahisa; Apple, J. A.; Austin, R. A.; Dietz, K. L.; Koloziejczak, J. J.; Ramsey, B. D.; Weisskopf, M. C.

1998-01-01

The second generation of the Marshall Imaging X-ray Experiment (MIXE2) was flown from Fort Sumner, New Mexico on May 7-8, 1997. The experiment consists of coded-aperture telescope with a field of view of 1.8 degrees (FWHM) and an angular resolution of 6.9 arcminutes. The detector is a large (7.84x10(exp 4) sq cm) effective area microstrip proportional counter filled with 2.0x10(exp5) Pascals of xenon with 2% isobutylene. We present MIXE2 observation of the 20-80keV spectrum and timing variability of Cygnus X-1 made during balloon flight.

Polarized light microscopy study on the reentrant phase transition in a (Ba 1–xK x)Fe 2As 2 single crystal with x = 0.24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yong; Tanatar, Makariy A.; Timmons, Erik

In this study, a sequence of structural/magnetic transitions on cooling is reported in the literature for hole-doped iron-based superconductor (Ba 1–xK x)Fe 2As 2 with x = 0.24. By using polarized light microscopy, we directly observe the formation of orthorhombic domains in (Ba 1–xK x)Fe 2As 2 (x = 0.24) single crystal below a temperature of simultaneous structural/magnetic transition T N ~ 80 K. The structural domains vanish below ~30 K, but reappear below T = 15 K. Our results are consistent with reentrance transformation sequence from high-temperature tetragonal (HTT) to low temperature orthorhombic (LTO1) structure at T N ~more » 80 K, LTO1 to low temperature tetragonal (LTT) structure at T c ~ 25 K, and LTT to low temperature orthorhombic (LTO2) structure at T ~ 15 K.« less

Polarized light microscopy study on the reentrant phase transition in a (Ba 1–xK x)Fe 2As 2 single crystal with x = 0.24

DOE PAGES

Liu, Yong; Tanatar, Makariy A.; Timmons, Erik; ...

2016-11-09

In this study, a sequence of structural/magnetic transitions on cooling is reported in the literature for hole-doped iron-based superconductor (Ba 1–xK x)Fe 2As 2 with x = 0.24. By using polarized light microscopy, we directly observe the formation of orthorhombic domains in (Ba 1–xK x)Fe 2As 2 (x = 0.24) single crystal below a temperature of simultaneous structural/magnetic transition T N ~ 80 K. The structural domains vanish below ~30 K, but reappear below T = 15 K. Our results are consistent with reentrance transformation sequence from high-temperature tetragonal (HTT) to low temperature orthorhombic (LTO1) structure at T N ~more » 80 K, LTO1 to low temperature tetragonal (LTT) structure at T c ~ 25 K, and LTT to low temperature orthorhombic (LTO2) structure at T ~ 15 K.« less

CANYVAL-X: Enabling a new class of scientific instruments

NASA Astrophysics Data System (ADS)

Shah, Neerav; Calhoun, Philip C.; Park, Sang-young; Keidar, Michael

2016-05-01

Significant new discoveries in space science can be realized by replacing the traditional large monolithic space telescopes with precision formation flying spacecraft to form a “virtual telescope.” Such virtual telescopes will revolutionize occulting imaging systems, provide images of the Sun, accretion disks, and other astronomical objects with unprecedented milli-arcsecond resolution (several orders of magnitude beyond current capability).Since the days of Apollo, NASA and other organizations have been conducting formation flying in space, but not with the precision required for virtual telescopes. These efforts have focused on rendezvous and docking (e.g., crew docking, satellite servicing, etc.) and/or ground-controlled coordinated flight (e.g., EO-1, GRAIL, MMS, etc.). While the TRL of the component level technology for formation flying is high, the capability for the system-level guidance, navigation, and control (GN&C) technology required to align a virtual telescope to an inertial astronomical target with sub-arcsecond precision is not fully developed.The CANYVAL-X (CubeSat Astronomy by NASA and Yonsei using Virtual Telescope Alignment eXperiment) mission is an engineering proof of concept featuring a pair of CubeSats flying as a tandem telescope with a goal of demonstrating the system-level GN&C needed to form a virtual telescope. NASA partnered with the George Washington University and the Yonsei University to design and develop CANYVAL-X. CANYVAL-X will demonstrate key technologies for using virtual telescopes in space, including micro-propulsion using millinewton thrusters, relative position sensing, and communications control between the two spacecraft. CANYVAL-X is scheduled to launch on a Flacon-9 in summer of 2016.

Recent X-ray Variability of Eta Car Approaching The X-ray Eclipse

NASA Technical Reports Server (NTRS)

Corcoran, M.; Swank, J. H.; Ishibashi, K.; Gull, T.; Humphreys, R.; Damineli, A.; Walborn, N.; Hillier, D. J.; Davidson, K.; White, S. M.

2002-01-01

We discuss recent X-ray spectral variability of the supermassive star Eta Car in the interval since the last X-ray eclipse in 1998. We concentrate on the interval just prior to the next X-ray eclipse which is expected to occur in June 2003. We compare the X-ray behavior during the 2001-2003 cycle with the previous cycle (1996-1998) and note similarities and differences in the temporal X-ray behavior. We also compare a recent X-ray observation of Eta Car obtained with the Chandra high energy transmission grating in October 2002 with an earlier observation from Nov 2002, and interpret these results in terms of the proposed colliding wind binary model for the star. In addition we discuss planned observations for the upcoming X-ray eclipse.

Einstein X-ray survey of the Pleiades - The dependence of X-ray emission on stellar age

NASA Technical Reports Server (NTRS)

Micela, G.; Sciortino, S.; Serio, S.; Vaiana, G. S.; Bookbinder, J.; Golub, L.; Harnden, F. R., Jr.; Rosner, R.

1985-01-01

The data obtained with two pointed observations of 1 deg by 1 deg fields of the Pleiades region have been analyzed, and the results are presented. The maximum-likelihood X-ray luminosity functions for the Pleiades G and K stars in the cluster are derived, and it is shown that, for the G stars, the Pleiades X-ray luminosity function is significantly brighter than the corresponding function for Hyades G dwarf stars. This finding indicates a dependence of X-ray luminosity on stellar age, which is confirmed by comparison of the same data with median X-ray luminosities of pre-main sequence and local disk population dwarf G stars. It is suggested that the significantly larger number of bright X-ray sources associated with G stars than with K stars, the lack of detection of M stars, and the relatively rapid rotation of the Pleiades K stars can be explained in terms of the onset of internal differential rotation near the convective envelope-radidative core interface after the spin-up phase during evolution to the main sequence.

Auger electron diffraction study of Fe 1- xNi x alloys epitaxially grown on Cu(100)

NASA Astrophysics Data System (ADS)

Martin, M. G.; Foy, E.; Chevrier, F.; Krill, G.; Asensio, M. C.

1999-08-01

We have combined Auger electron diffraction (AED), low-energy electron diffraction (LEED) and high-energy electron diffraction (RHEED) to examine the structure of Fe xNi 1- x alloys when the Fe content approaches 65%. At this concentration, the 'invar effect' takes place, so the magnetization falls to zero, and the thermal expansion coefficient is very small. The Fe xNi 1- x alloys, grown as metastable thin films by molecular-beam epitaxy on Cu(100) substrates, were studied as a function of the x stoichiometry. In contrast to the related bulk alloy compounds, we observe the collapse of the fcc-to-bcc structural transition in the Fe-rich films. Furthermore, the local atomic structure around Fe and Ni in the alloy has been simultaneously determined by the angular intensity distributions of Fe L 3VV (703 eV) and Ni L 3VV (848 eV) Auger electrons measured as a function of polar and azimuthal angles. For the films deposited at room temperature, we have confirmed the pseudomorphic growth morphology and the uniformity of the alloys.

MOXE: An X-ray all-sky monitor for Soviet Spectrum-X-Gamma Mission

NASA Technical Reports Server (NTRS)

Priedhorsky, W.; Fenimore, E. E.; Moss, C. E.; Kelley, R. L.; Holt, S. S.

1989-01-01

A Monitoring Monitoring X-Ray Equipment (MOXE) is being developed for the Soviet Spectrum-X-Gamma Mission. MOXE is an X-ray all-sky monitor based on array of pinhole cameras, to be provided via a collaboration between Goddard Space Flight Center and Los Alamos National Laboratory. The objectives are to alert other observers on Spectrum-X-Gamma and other platforms of interesting transient activity, and to synoptically monitor the X-ray sky and study long-term changes in X-ray binaries. MOXE will be sensitive to sources as faint as 2 milliCrab (5 sigma) in 1 day, and cover the 2 to 20 KeV band.

X-ray imaging crystal spectrometer for extended X-ray sources

DOEpatents

Bitter, Manfred L.; Fraenkel, Ben; Gorman, James L.; Hill, Kenneth W.; Roquemore, A. Lane; Stodiek, Wolfgang; von Goeler, Schweickhard E.

2001-01-01

Spherically or toroidally curved, double focusing crystals are used in a spectrometer for X-ray diagnostics of an extended X-ray source such as a hot plasma produced in a tokomak fusion experiment to provide spatially and temporally resolved data on plasma parameters using the imaging properties for Bragg angles near 45. For a Bragg angle of 45.degree., the spherical crystal focuses a bundle of near parallel X-rays (the cross section of which is determined by the cross section of the crystal) from the plasma to a point on a detector, with parallel rays inclined to the main plain of diffraction focused to different points on the detector. Thus, it is possible to radially image the plasma X-ray emission in different wavelengths simultaneously with a single crystal.

Suzaku Detection of Diffuse Hard X-Ray Emission Outside Vela X

NASA Technical Reports Server (NTRS)

Katsuda, Satoru; Mori, Koji; Petre, Robert; Yamaguchi, Hiroya; Tsunemi, Hiroshi; Bocchino, Fabrizio; Bamba, Aya; Miceli, Marco; Hewitt, John W.; Temim, Tea;

Lifting the veil on the X-ray universe

NASA Astrophysics Data System (ADS)

1999-11-01

ESA's X-ray Multi Mirror mission - XMM - is the second Cornerstone in ESA's Long Term Scientific Programme (*). This new X-ray space telescope promises even more discoveries. With the large collecting area of its mirrors and the high sensitivity of its cameras, XMM is expected to increase radically our understanding of high-energy sources - clues to a mysterious past, and keys to understanding the future of the Universe. 174 wafer-thin X-ray mirrors X-rays coming from celestial objects are highly energetic and elusive. They can best be measured and studied after focusing a sufficient number upon sensitive detectors. To achieve this, XMM's Mirror Modules have been given a gargantuan appetite for X-rays. The space observatory combines three barrel-shaped telescope modules. In each are nested 58 wafer-thin concentric mirror shells highly polished and subtly shaped. Passing through at an extremely shallow angle, the so-called "grazing incidence", the X-rays will be beamed to the science instruments situated on the focal plane at the other extremity of the satellite. The three mirror modules have a total mirror surface of over 120m2 - practically the size of a tennis court.. The collecting power of XMM's three telescopes is the greatest ever seen on an X-ray space mission, many times more than the most recently launched X-ray satellite. The design and assembly of the mirror modules, their testing for operation in space and their precise calibration constitute one of the greatest achievements of the XMM programme. The flimsy mirror shells, with their gold reflective surface on a nickel backing, were made by replication like carbon copies from master moulds. They were shaped to an accuracy of a thousandth of a millimetre, and then polished to a smoothness a thousand times better than that. Packaged one within another like Russian dolls, each mirror was focused and centred with respect to its neighbour to an accuracy of 25 microns - a quarter of the width of a human hair

A Rutile Chevron Modulation in Delafossite-Like Ga 3–x In 3 Ti x O 9+x/2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rickert, Karl; Boullay, Philippe; Malo, Sylvie

2016-05-02

The structure solution of the modulated, delafossite-related, orthorhombic Ga 3–xIn 3Ti xO 9+x/2 for x = 1.5 is reported here in conjunction with a model describing the modulation as a function of x for the entire system. Previously reported structures in the related A 3–xIn 3Ti xO 9+x/2 (A = Al, Cr, or Fe) systems use X-ray diffraction to determine that the anion lattice is the source of modulation. Neutron diffraction, with its enhanced sensitivity to light atoms, offers a route to solving the modulation and is used here, in combination with precession electron diffraction tomography (PEDT), to solve themore » structure of Ga 1.5In 3Ti 1.5O 9.75. We construct a model that describes the anion modulation through the formation of rutile chevrons as a function of x. This model accommodates the orthorhombic phase (1.5 ≤ x ≤ 2.1) in the Ga 3-xIn 3Ti xO 9+x/2 system, which transitions to a biphasic mixture (2.2 ≤ x ≤ 2.3) with a monoclinic, delafossite-related phase (2.4 ≤ x ≤ 2.5). The optical band gaps of this system are determined, and are stable at ~3.4 eV before a ~0.4 eV decrease between x = 1.9 and 2.0. After this decrease, stability resumes at ~3.0 eV. Resistance to oxidation and reduction is also presented.« less

On the Nature of the mHz X-ray Quasi-Periodic Oscillations from Ultraluminous X-ray source M82 X-1: Search for Timing-Spectral Correlations

NASA Technical Reports Server (NTRS)

Pasham, Dheeraj R.; Strohmayer, Tod E.

2013-01-01

Using all the archival XMM-Newton X-ray (3-10 keV) observations of the ultraluminous X-ray source (ULX) M82 X-1, we searched for a correlation between its variable mHz quasi-periodic oscillation (QPO) frequency and its hardness ratio (5-10 keV/3-5 keV), an indicator of the energy spectral power-law index. When stellar-mass black holes (StMBHs) exhibit type-C low-frequency QPOs (0.2-15 Hz), the centroid frequency of the QPO is known to correlate with the energy spectral index. The detection of such a correlation would strengthen the identification of M82 X-1's mHz QPOs as type-C and enable a more reliable mass estimate by scaling its QPO frequencies to those of type-C QPOs in StMBHs of known mass.We resolved the count rates and the hardness ratios of M82 X-1 and a nearby bright ULX (source 5/X42.3+59) through surface brightness modeling.We detected QPOs in the frequency range of 36-210 mHz during which M82 X-1's hardness ratio varied from 0.42 to 0.47. Our primary results are (1) that we do not detect any correlation between the mHz QPO frequency and the hardness ratio (a substitute for the energy spectral power-law index) and (2) similar to some accreting X-ray binaries, we find that M82 X-1's mHz QPO frequency increases with its X-ray count rate (Pearson's correlation coefficient = +0.97). The apparent lack of a correlation between the QPO centroid frequency and the hardness ratio poses a challenge to the earlier claims that the mHz QPOs of M82 X-1 are the analogs of the type-C low-frequency QPOs of StMBHs. On the other hand, it is possible that the observed relation between the hardness ratio and the QPO frequency represents the saturated portion of the correlation seen in type-C QPOs of StMBHs-in which case M82 X-1's mHz QPOs can still be analogous to type-C QPOs.

X-Rays

MedlinePlus

X-rays are a type of radiation called electromagnetic waves. X-ray imaging creates pictures of the inside of ... different amounts of radiation. Calcium in bones absorbs x-rays the most, so bones look white. Fat ...

Experimental Approaches for Solution X-Ray Scattering and Fiber Diffraction

PubMed Central

Irving, T. C.

2008-01-01

X-ray scattering and diffraction from non-crystalline systems have gained renewed interest in recent years, as focus shifts from the structural chemistry information gained by high-resolution studies to the context of structural physiology at larger length scales. Such techniques permit the study of isolated macromolecules as well as highly organized macromolecular assemblies as a whole under near-physiological conditions. Time-resolved approaches, made possible by advanced synchrotron instrumentation, add a critical dimension to many of these investigations. This article reviews experimental approaches in non-crystalline x-ray scattering and diffraction that may be used to illuminate important scientific questions such as protein/nucleic acid folding and structure-function relationships in large macromolecular assemblies. PMID:18801437

Laboratory evaluation of compressor blades considered for use in CIP/CUP compressors. [GAT2, 214X, X224, and D-15Al alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ritchie, K.L.

1976-04-30

Four die-casting alloys, the external-pressure-pin and conventional casting methods, an accelerated aging heat treatment, and an airfoil fillet modification were evaluated for 33F-S1 compressor blades considered for use in axial flow compressors installed during the Cascade Improvement and Uprating Programs at the three gaseous diffusion plants. Based on castability, resonant frequency, resistance to fatigue cracking, and shank breaking load, the ranking of the four alloys from highest to lowest is GAT2, 214X, X224, and D-15. The GAT2 alloy ranked highest in all categories except impact value; the impact values of both X224 and 214X alloys exceeded that of the GAT2more » alloy, thus indicating the latter is relatively more brittle. However, in view of its other excellent properties, including fatigue cracking resistance, GAT2 alloy is worthy of consideration for use in blades for CIP/CUP or Add-on Plant compressors, particularly if castability becomes a problem with the presently used 214X alloy. Use of the external-pressure-pin casting method is not recommended because the resulting casting difficulties cannot be justified by the small increases in shank breaking loads. The airfoil fillet modification, which is a change from the conventional circular fillet to an elliptical fillet, resulted in increases (1.5 to 4.0 percent) in the average resonant frequency and in resistance to fatigue cracking (15 to 100 percent). The results of giving the blades an accelerated aging heat treatment, designed to simulate in excess of 10,000 hours of cascade exposure, showed that overaging had no significant effect on average resonant frequency but that overaging improved blade quality by reducing residual casting stress. (auth)« less

Hard X-ray spectrum of Cygnus X-1

NASA Technical Reports Server (NTRS)

Nolan, P. L.; Gruber, D. E.; Knight, F. K.; Matteson, J. L.; Rothschild, R. E.; Marshall, F. E.; Levine, A. M.; Primini, F. A.

1981-01-01

Long-term measurements of the hard X-ray spectrum from 3 keV to 8 MeV of the black-hole candidate Cygnus X-1 in its low state are reported. Observations were made from October 26 to November 18, 1977 with the A2 (Cosmic X-ray) and A4 (Hard X-ray and Low-Energy Gamma-Ray) experiments on board HEAO 1 in the spacecraft's scanning mode. The measured spectrum below 200 keV is found to agree well with previous spectra which have been fit by a model of the Compton scattering of optical or UV photons in a very hot plasma of electron temperature 32.4 keV and optical depth 3.9 or 1.6 for spherical or disk geometry, respectively. At energies above 300 keV, however, flux excess is observed which may be accounted for by a distribution of electron temperatures from 15 to about 100 keV.

Ultraviolet photodetector based on Mg{sub x}Zn{sub 1-x}O films using plasma-enhanced atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Yu-Chang; Lee, Hsin-Ying, E-mail: hylee@ee.ncku.edu.tw; Lee, Ching-Ting

2016-01-15

A plasma-enhanced atomic layer deposition (PE-ALD) system was used to deposit magnesium zinc oxide (Mg{sub x}Zn{sub 1−x}O) films with various Mg content (x). The Mg{sub x}Zn{sub 1-x}O films were applied to metal–semiconductor–metal ultraviolet (UV) photodetectors (MSM-UPDs) as an active layer. The Mg content in the Mg{sub x}Zn{sub 1-x}O films was modulated by adjusting the ZnO–MgO cycle ratios to 15:1, 12:1, and 9:1. Correspondingly, the Mg content in the Mg{sub x}Zn{sub 1-x}O films characterized using an energy dispersive spectrometer was 0.10, 0.13, and 0.16, respectively. The optical bandgap of the Mg{sub x}Zn{sub 1-x}O films increased from 3.56 to 3.66 eV withmore » an increase in Mg content from 0.10 to 0.16. The peak position of photoresponsivity for the Mg{sub x}Zn{sub 1-x}O MSM-UPDs was also shifted from 350 to 340 nm. The UV-visible rejection ratios of the Mg{sub x}Zn{sub 1-x}O MSM-UPDs were higher than 3 orders of magnitude. In addition, excellent detectivity and noise equivalent power for the Mg{sub x}Zn{sub 1-x}O MSM-UPDs were observed at a bias voltage of 5 V. The high performance of the Mg{sub x}Zn{sub 1-x}O MSM-UPDs was achieved by PE-ALD at a low temperature.« less

Contribution of parsec-scale material on to the polarized X-ray spectrum of type 1 Seyfert galaxies

NASA Astrophysics Data System (ADS)

Marin, F.; Dovčiak, M.; Kammoun, E. S.

2018-07-01

Type 1 radio-quiet active galactic nuclei (AGN) are seen from the polar direction and offer a direct view of their central X-ray engine. If most of X-ray photons have travelled from the primary source to the observer with minimum light-matter interaction, a fraction of radiation is emitted at different directions and is reprocessed by the parsec-scale equatorial circumnuclear region or the polar outflows. It is still unclear how much the polarization expected from type 1 AGN is affected by radiation that have scattered on the distant AGN components. In this paper, we examine the contribution of remote material on to the polarized X-ray spectrum of type 1 Seyfert galaxies (Seyfert-1s) using radiative transfer Monte Carlo codes. We find that the observed X-ray polarization strongly depends on the initial polarization emerging from the disc-corona system. For unpolarized and parallelly polarized photons (parallel to the disc), the contribution is negligible below 3 keV and tends to increase the polarization degree by up to one percentage points at higher energies, smoothing out the energy-dependent variations of the polarization angle. For perpendicularly polarized corona photons, the addition of the circumnuclear scattered (parallel) component adds to the polarization above 10 keV, decreases polarization below 10 keV and shifts the expected 90° rotation of the polarization angle to lower energies. In conclusion, we found that simulations of Seyfert-1s that do not account for reprocessing on the parsec-scale equatorial and polar material are under- or overestimating the X-ray polarization by 0.1-1 percentage points.

Effect of the Sm content on the structure and electrochemical properties of La 1.3 - xSm xCaMg 0.7Ni 9 ( x = 0-0.3) hydrogen storage alloys

NASA Astrophysics Data System (ADS)

Tang, Rui; Wei, Xuedong; Liu, Yongning; Zhu, Changchun; Zhu, Jiewu; Yu, Guang

La 1.3 - xSm xCaMg 0.7Ni 9 (x = 0-0.3) hydrogen storage alloys were prepared by inductive melting and the effect of the Sm content on the structure and electrochemical properties was investigated in the paper. The Sm substitution for La in La 1.3 - xSm xCaMg 0.7Ni 9 (x = 0-0.3) alloys does not change the main phase structure (the rhombohedral PuNi 3-type structure), but leads to a shrinkage of unit cell and a decrease of hydrogen storage capacity. With the increase of the Sm content in the alloys, the maximum discharge capacity of electrode decreases from 400.2 (x = 0) to 346.6 mAh g -1 (x = 0.3), but the high-rate dischargeability and cycling stability is improved. After 100 cycles, the capacity retention rate increases from 75 (x = 0) to 85% (x = 0.3).

Selective growth of Ge1- x Sn x epitaxial layer on patterned SiO2/Si substrate by metal-organic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Takeuchi, Wakana; Washizu, Tomoya; Ike, Shinichi; Nakatsuka, Osamu; Zaima, Shigeaki

2018-01-01

We have investigated the selective growth of a Ge1- x Sn x epitaxial layer on a line/space-patterned SiO2/Si substrate by metal-organic chemical vapor deposition. We examined the behavior of a Sn precursor of tributyl(vinyl)tin (TBVSn) during the growth on Si and SiO2 substrates and investigated the effect of the Sn precursor on the selective growth. The selective growth of the Ge1- x Sn x epitaxial layer was performed under various total pressures and growth temperatures of 300 and 350 °C. The selective growth of the Ge1- x Sn x epitaxial layer on the patterned Si region is achieved at a low total pressure without Ge1- x Sn x growth on the SiO2 region. In addition, we found that the Sn content in the Ge1- x Sn x epitaxial layer increases with width of the SiO2 region for a fixed Si width even with low total pressure. To control the Sn content in the selective growth of the Ge1- x Sn x epitaxial layer, it is important to suppress the decomposition and migration of Sn and Ge precursors.

High-density arrays of x-ray microcalorimeters for Constellation-X

NASA Astrophysics Data System (ADS)

Kilbourne, C. A.; Bandler, S. R.; Chervenak, J. A.; Figueroa-Feliciano, E.; Finkbeiner, F. M.; Iyomoto, N.; Kelley, R. L.; Porter, F. S.; Saab, T.; Sadleir, J.

2005-12-01

We have been developing x-ray microcalorimeters for the Constellation-X mission. Devices based on superconducting transition edge sensors (TES) have demonstrated the potential to meet the Constellation-X requirements for spectral resolution, speed, and array scale (> 1000 pixels) in a close-packed geometry. In our part of the GSFC/NIST collaboration on this technology development, we have been concentrating on the fabrication of arrays of pixels suitable for the Constellation-X reference configuration. We have fabricated 8x8 arrays with 0.25-mm pixels arranged with 92% fill factor. The pixels are based on Mo/Au TES and Bi/Cu absorbers. We have achieved a resolution of 4.9 eV FWHM at 6 keV in such devices. Studies of the thermal transport in our Bi/Cu absorbers have shown that, while there is room for improvement, for 0.25 mm pixels our existing absorber design is adequate to avoid line-broadening from position dependence caused by thermal diffusion. In order to push closer to the 4-eV requirement and 2-eV goal at 6 keV, we are refining the design of the TES and the interface to the absorber. For the 32x32 arrays ultimately needed for Constellation-X, signal lead routing and heatsinking will drive the design. We have had early successes with experiments in electroplating electrical vias and thermal busses into micro-machined features in silicon substrates. The next steps will be fabricating arrays that have all of the essential features of the required flight design, testing, and then engineering a prototype array for optimum performance.

Low-temperature sequential pulsed chemical vapor deposition of ternary B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N thin film alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haider, Ali, E-mail: ali.haider@bilkent.edu.tr, E-mail: biyikli@unam.bilkent.edu.tr; Kizir, Seda; Ozgit-Akgun, Cagla

In this work, the authors have performed sequential pulsed chemical vapor deposition of ternary B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N alloys at a growth temperature of 450 °C. Triethylboron, triethylgallium, trimethylindium, and N{sub 2} or N{sub 2}/H{sub 2} plasma have been utilized as boron, gallium, indium, and nitrogen precursors, respectively. The authors have studied the compositional dependence of structural, optical, and morphological properties of B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N ternary thin film alloys. Grazing incidence X-ray diffraction measurements showed that boron incorporation in wurtzite lattice of GaN and InN diminishes the crystallinity of B{sub x}Ga{sub 1-x}N and B{submore » x}In{sub 1-x}N sample. Refractive index decreased from 2.24 to 1.65 as the B concentration of B{sub x}Ga{sub 1-x}N increased from 35% to 88%. Similarly, refractive index of B{sub x}In{sub 1-x}N changed from 1.98 to 1.74 for increase in B concentration value from 32% to 87%, respectively. Optical transmission band edge values of the B{sub x}Ga{sub 1-x}N and B{sub x}In{sub 1-x}N films shifted to lower wavelengths with increasing boron content, indicating the tunability of energy band gap with alloy composition. Atomic force microscopy measurements revealed an increase in surface roughness with boron concentration of B{sub x}Ga{sub 1-x}N, while an opposite trend was observed for B{sub x}In{sub 1-x}N thin films.« less

Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

NASA Technical Reports Server (NTRS)

Stern, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

2008-01-01

Superconducting-nanowire single-photon detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize Nb(x)Ti(1-x)N in the high-superconducting-transition temperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

Aircraft NO(x) had no Unique Fingerprint on Sonex; Lightning Dominated Fresh NO(x) Sources

NASA Technical Reports Server (NTRS)

Thompson, A.; Sparling, L.; Kondo, Y.; Anderson, B.; Gregory, G.; Sachse, G.

1999-01-01

Key questions to which SONEX was directed were the following: Can aircraft corridors be detected? Is there a unique tracer for aircraft NO(x)? Can a "background" NO(x) (or NO(y) be defined? What fraction of NO(x) measured during SONEX was from aircraft? How representative was SONEX of the North Atlantic in 1997 and how typical of other years? We attempt to answer these questions through species-species correlations, probability distribution functions (PDFs), and meteorological history. There is not a unique aircraft tracer, largely due to the high variability of air mass origins and tracer ratios, which render "average" quantities meaningless. The greatest NO and NO(y) signals were associated with lightning and convective NO sources. Well-defined background CO, NO(y) and NO(y)/ozone ratio appear in subsets of two cross-track flights with subtropical origins and five flights with predominantly mid-latitude air. Forty percent of the observations on these 7 flights showed NO(y)/ozone to be above background, evidently due to unreacted NO(x). This NO(x) is a combination of aircraft, lightning and surface pollution injected by convection. The strongly subtropical signatures in SONEX observations, confirmed by pv (potential vorticity) values along flight tracks, argues for most of the unreacted NO(x) originating from lightning. Potential vorticity statistics along SONEX flight tracks in 1992-1998, and for the North Atlantic as a whole, show the SONEX meteorological environment to be representative of the North Atlantic flight corridor in the October-November period.

Manifestation of hopping conductivity and granularity within phase diagrams of LaO1-x F x BiS2, Sr1-x La x FBiS2 and related BiS2-based compounds

NASA Astrophysics Data System (ADS)

Arouca, R.; Silva Neto, M. B.; Chaves, C. M.; Nagao, M.; Watauchi, S.; Tanaka, I.; ElMassalami, M.

2017-09-01

Layered BiS 2 -based series, such as LaO 1-x F x BiS 2 and Sr 1-x La x FBiS 2 , offer ideal examples for studying normal and superconducting phase diagram of a solid solution that evolves from a nonmagnetic band-insulator parent. We constructed typical x-T phase diagrams of these systems based on events occurring in thermal evolution of their electrical resistivity, ρ(x, T) . Overall evolution of these diagrams can be rationalized in terms of (i) Mott-Efros-Shklovskii scenario which, within the semiconducting x regime (x_MIT = Mott metal-insulator transition), describes the doping influence on the thermally activated hopping conductivity. (ii) A granular metal (superconductor) scenario which, within x_MIT< x < x_solubility , describes the evolution of normal and superconducting properties in terms of conductance g, Coulomb charging energy E c and Josephson coupling J; their joint influence is usually captured within a g-\\frac{gE_c}{J}-T phase diagram. Based on analysis of the granular character of ρ(x, T) , we converted the x-T diagrams into projected g - T diagrams which, being fundamental, allow a better understanding of evolution of various granular-related properties (in particular the hallmarks of normal-state \\partialρ/\\partial T<0 feature and superconductor-insulator transition) and how such properties are influenced by x, pressure or heat treatment.

Observation of X-ray eclipses from LMC X-4

NASA Technical Reports Server (NTRS)

Li, F.; Rappaport, S.; Epstein, A.

1978-01-01

Observations made with the Rotation Modulation Collimator system (RMC) have revealed that X-ray source X-4 in the Large Magellanic Cloud (LMC X-4) is most likely part of a binary system. An analysis of the star's coordinates is presented, with attention given to orbital period and flux intensity variations. Stellar mass and orbital inclination angle are estimated for both X-4 and its companion star.

Electrical switching studies on Si15Te85-xCux bulk (1 ≤ x ≤ 5) glasses

NASA Astrophysics Data System (ADS)

Roy, Diptoshi; Nadig, Chinmayi H. S.; Krishnan, Aravindh; Karanam, Akshath; Abhilash, R.; Jagannatha K., B.; Das, Chandasree

2018-05-01

Bulk ingots of Si15Te85-xCux (1 ≤ x ≤ 5) glasses are concocted by typical melt quenching technique. XRD validate the non-crystalline feature of the prepared quenched sample. The samples are found to display threshold type of electrical switching behavior. The switching behavior on all the samples is noticed without any disturbances. Compositional dependence of threshold voltage of Si15Te85-xCux (1 ≤ x ≤ 5) glasses has been studied and it has been found that VT increases as the atomic percentage of dopant (copper) increases in the host matrix. The distinguished behavior has been envisaged and correlated to the improvement in network connectivity and rigidity with the addition of Cu.

Comets C/2003 X5-X11 and Y2-Y10 (SOHO)

NASA Astrophysics Data System (ADS)

Battams, K.; Boschat, M.; Zhou, X.-M.; Hoffman, T.; Leprette, X.; Matson, R.; Kracht, R.; Sachs, J.; Marsden, B. G.; Kisala, R.

2004-06-01

Further to IAUC 8356, K. Battams reports measurements for additional Kreutz sungrazing comets found on SOHO website C2 images by M. Boschat (C/2003 X5, X7, Y5, Y8), X.-m. Zhou (C/2003 X6, X9, X11), T. Hoffman (C/2003 X8), X. Leprette (C/2003 X10, Y2), R. Matson (2003 Y3, Y9, Y10), R. Kracht (C/2003 Y4, Y7), and J. Sachs (C/2003 Y6). C/2003 Y6 and Y7 were also visible on C3 images. The reductions by B. G. Marsden (and by R. Kisala for C/2003 Y8, Y9, Y10) and orbital elements by Marsden appear on the MPECs cited below. Comet 2003 UT R.A. (2000) Decl. MPEC C/2003 X5 Dec. 4.896 16 46.9 -24 12 2004-L24 C/2003 X6 6.396 16 52.2 -24 20 2004-L24 C/2003 X7 7.829 16 58.6 -24 27 2004-L24 C/2003 X8 8.246 17 00.9 -24 31 2004-L24 C/2003 X9 8.621 17 02.2 -24 34 2004-L24 C/2003 X10 11.188 17 14.5 -24 41 2004-L25 C/2003 X11 13.588 17 25.7 -24 57 2004-L25 C/2003 Y2 19.621 17 53.6 -25 08 2004-L25 C/2003 Y3 19.979 17 55.0 -25 02 2004-L25 C/2003 Y4 20.729 17 58.8 -25 14 2004-L25 C/2003 Y5 22.771 18 08.5 -25 08 2004-L25 C/2003 Y6 23.571 18 14.3 -27 22 2004-L26 C/2003 Y7 24.638 18 20.0 -27 44 2004-L26 C/2003 Y8 25.288 18 19.6 -25 00 2004-L67 C/2003 Y9 25.479 18 20.7 -24 46 2004-L67 C/2003 Y10 26.064 18 23.5 -24 50 2004-L67

Optically stimulated luminescence in x-ray irradiated xSnO-(25-x)SrO-75B2O3 glass

NASA Astrophysics Data System (ADS)

Nanto, H.; Nakagawa, R.; Takei, Y.; Hirasawa, K.; Miyamoto, Y.; Masai, H.; Kurobori, T.; Yanagida, T.; Fujimoto, Y.

2015-06-01

An intense optically stimulated luminescence (OSL) was observed, for the first time, in x-ray irradiated xSnO-(25-x)SrO-75B2O3 glass. It was found that the peak wavelength of OSL emission spectrum and its stimulation spectrum is about 400 nm and 600 nm, respectively. The OSL intensity is depended on the SnO contents (x=0.05-1.5) and the most intense OSL was observed in 1.0 mol% SnO doped glass. It was found that the OSL intensity is increased with increasing x-ray absorbed dose. Fairly good fading characteristics were observed in the x-ray irradiated glass, showing that this glass is useful as a candidate for OSL sensor materials for ionizing radiation monitoring.

Differences in chemical doping matter: Superconductivity in Ti 1-xTa xSe 2 but not in Ti 1-xNb xSe 2

DOE PAGES

Luo, Huixia; Zhu, Yimei; Xie, Weiwei; ...

2016-02-21

We report that 1T-TiSe 2, an archetypical layered transition metal dichalcogenide, becomes superconducting when Ta is substituted for Ti but not when Nb is substituted for Ti. This is unexpected because Nb and Ta should be chemically equivalent electron donors. Superconductivity emerges near x = 0.02 for Ti 1–xTa xSe 2, while, for Ti 1–xNb xSe 2, no superconducting transitions are observed above 0.4 K. The equivalent chemical nature of the dopants is confirmed by X-ray photoelectron spectroscopy. ARPES and Raman scattering studies show similarities and differences between the two systems, but the fundamental reasons why the Nb and Tamore » dopants yield such different behavior are unknown. We present a comparison of the electronic phase diagrams of many electron-doped 1T-TiSe 2 systems, showing that they behave quite differently, which may have broad implications in the search for new superconductors. Here, we propose that superconducting Ti 0.8Ta 0.2Se 2 will be suitable for devices and other studies based on exfoliated crystal flakes.« less

X-MIME: An Imaging X-ray Spectrometer for Detailed Study of Jupiter's Icy Moons and the Planet's X-ray Aurora

NASA Technical Reports Server (NTRS)

Elsner, R. F.; Ramsey, B. D.; Waite, J. H.; Rehak, P.; Johnson, R. E.; Cooper, J. F.; Swartz, D. A.

2004-01-01

Remote observations with the Chandra X-ray Observatory and the XMM-Newton Observatory have shown that the Jovian system is a source of x-rays with a rich and complicated structure. The planet's polar auroral zones and its disk are powerful sources of x-ray emission. Chandra observations revealed x-ray emission from the Io Plasma Torus and from the Galilean moons Io, Europa, and possibly Ganymede. The emission from these moons is certainly due to bombardment of their surfaces of highly energetic protons, oxygen and sulfur ions from the region near the Torus exciting atoms in their surfaces and leading to fluorescent x-ray emission lines. Although the x-ray emission from the Galilean moons is faint when observed from Earth orbit, an imaging x-ray spectrometer in orbit around these moons, operating at 200 eV and above with 150 eV energy resolution, would provide a detailed mapping (down to 40 m spatial resolution) of the elemental composition in their surfaces. Such maps would provide important constraints on formation and evolution scenarios for the surfaces of these moons. Here we describe the characteristics of X-MIME, an imaging x-ray spectrometer under going a feasibility study for the JIMO mission, with the ultimate goal of providing unprecedented x-ray studies of the elemental composition of the surfaces of Jupiter's icy moons and Io, as well as of Jupiter's auroral x-ray emission.

Genetic analysis of eight population groups living in Taiwan using a 13 X-chromosomal STR loci multiplex system.

PubMed

Hwa, Hsiao-Lin; Lee, James Chun-I; Chang, Yih-Yuan; Yin, Hsiang-Yi; Chen, Ya-Hui; Tseng, Li-Hui; Su, Yi-Ning; Ko, Tsang-Ming

2011-01-01

A 13 X-chromosomal short tandem repeat (STR) multiplex system (DXS6807, DXS8378, DSX9902, DXS7132, DXS9898, DXS6809, DXS6789, DXS7424, DXS101, GATA172D05, HPRTB, DXS8377, and DXS7423) was tested on 1,037 DNA samples from eight population groups currently living in Taiwan. Different distributions of the allelic frequencies in different populations were presented. DXS8377 and DXS101 were the two most polymorphic loci in these eight populations, whereas DXS7423 was the least informative marker in most of the populations studied. The genetic distances between the populations and the constructed phylogenetic tree revealed a long genetic distance between Asian and Caucasian populations as well as isolation of the Tao population. The phylogenetic tree grouped populations into clusters compatible with their ethnogeographic relationships. This 13 X-chromosomal short tandem repeat multiplex system offers a considerable number of polymorphic patterns in different populations. This system can be useful in forensic identification casework and ethnogeographic research.

On the morphology of outbursts of accreting millisecond X-ray pulsar Aquila X-1

NASA Astrophysics Data System (ADS)

Güngör, C.; Ekşi, K. Y.; Göğüş, E.

2017-10-01

We present the X-ray light curves of the last two outbursts - 2014 & 2016 - of the well known accreting millisecond X-ray pulsar (AMXP) Aquila X-1 using the monitor of all sky X-ray image (MAXI) observations in the 2-20 keV band. After calibrating the MAXI count rates to the all-sky monitor (ASM) level, we report that the 2016 outburst is the most energetic event of Aql X-1, ever observed from this source. We show that 2016 outburst is a member of the long-high class according to the classification presented by Güngör et al. with ˜ 68 cnt/s maximum flux and ˜ 60 days duration time and the previous outburst, 2014, belongs to the short-low class with ˜ 25 cnt/s maximum flux and ˜ 30 days duration time. In order to understand differences between outbursts, we investigate the possible dependence of the peak intensity to the quiescent duration leading to the outburst and find that the outbursts following longer quiescent episodes tend to reach higher peak energetic.

Effects of variability of X-ray binaries on the X-ray luminosity functions of Milky Way

NASA Astrophysics Data System (ADS)

Islam, Nazma; Paul, Biswajit

2016-08-01

The X-ray luminosity functions of galaxies have become a useful tool for population studies of X-ray binaries in them. The availability of long term light-curves of X-ray binaries with the All Sky X-ray Monitors opens up the possibility of constructing X-ray luminosity functions, by also including the intensity variation effects of the galactic X-ray binaries. We have constructed multiple realizations of the X-ray luminosity functions (XLFs) of Milky Way, using the long term light-curves of sources obtained in the 2-10 keV energy band with the RXTE-ASM. The observed spread seen in the value of slope of both HMXB and LMXB XLFs are due to inclusion of variable luminosities of X-ray binaries in construction of these XLFs as well as finite sample effects. XLFs constructed for galactic HMXBs in the luminosity range 1036-1039 erg/sec is described by a power-law model with a mean power-law index of -0.48 and a spread due to variability of HMXBs as 0.19. XLFs constructed for galactic LMXBs in the luminosity range 1036-1039 erg/sec has a shape of cut-off power-law with mean power-law index of -0.31 and a spread due to variability of LMXBs as 0.07.

The Athena X-ray Integral Field Unit (X-IFU)

NASA Astrophysics Data System (ADS)

Pajot, F.; Barret, D.; Lam-Trong, T.; den Herder, J.-W.; Piro, L.; Cappi, M.; Huovelin, J.; Kelley, R.; Mas-Hesse, J. M.; Mitsuda, K.; Paltani, S.; Rauw, G.; Rozanska, A.; Wilms, J.; Barbera, M.; Douchin, F.; Geoffray, H.; den Hartog, R.; Kilbourne, C.; Le Du, M.; Macculi, C.; Mesnager, J.-M.; Peille, P.

2018-04-01

The X-ray Integral Field Unit (X-IFU) of the Advanced Telescope for High-ENergy Astrophysics (Athena) large-scale mission of ESA will provide spatially resolved high-resolution X-ray spectroscopy from 0.2 to 12 keV, with 5^' ' } pixels over a field of view of 5 arc minute equivalent diameter and a spectral resolution of 2.5 eV (FWHM) up to 7 keV. The core scientific objectives of Athena drive the main performance parameters of the X-IFU. We present the current reference configuration of the X-IFU, and the key issues driving the design of the instrument.

Random On-Board Pixel Sampling (ROPS) X-Ray Camera

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhehui; Iaroshenko, O.; Li, S.

Recent advances in compressed sensing theory and algorithms offer new possibilities for high-speed X-ray camera design. In many CMOS cameras, each pixel has an independent on-board circuit that includes an amplifier, noise rejection, signal shaper, an analog-to-digital converter (ADC), and optional in-pixel storage. When X-ray images are sparse, i.e., when one of the following cases is true: (a.) The number of pixels with true X-ray hits is much smaller than the total number of pixels; (b.) The X-ray information is redundant; or (c.) Some prior knowledge about the X-ray images exists, sparse sampling may be allowed. Here we first illustratemore » the feasibility of random on-board pixel sampling (ROPS) using an existing set of X-ray images, followed by a discussion about signal to noise as a function of pixel size. Next, we describe a possible circuit architecture to achieve random pixel access and in-pixel storage. The combination of a multilayer architecture, sparse on-chip sampling, and computational image techniques, is expected to facilitate the development and applications of high-speed X-ray camera technology.« less

Tuning Thermoelectric Properties of Type I Clathrate K 8–x Ba x Al 8+x Si 38–x through Barium Substitution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sui, Fan; Kauzlarich, Susan M.

2016-05-10

The thermal stability and thermoelectric properties of type I clathrate K8Al8Si38 up to 873 K are reported. K8Al8Si38 possesses a high absolute Seebeck coefficient value and high electrical resistivity in the temperature range of 323 to 873 K, which is consistent with previously reported low temperature thermoelectric properties. Samples with Ba partial substitution at the K guest atom sites were synthesized from metal hydride precursors. The samples with the nominal chemical formula of K8–xBaxAl8+xSi38–x (x = 1, 1.5, 2) possess type I clathrate structure (cubic, Pm3n), confirmed by X-ray diffraction. The guest atom site occupancies and thermal motions were investigatedmore » with Rietveld refinement of synchrotron powder X-ray diffraction. Transport properties of Ba-containing samples were characterized from 2 to 300 K. The K–Ba alloy phases showed low thermal conductivity and improved electrical conductivity compared to K8Al8Si38. Electrical resistivity and Seebeck coefficients were measured over the temperature range of 323 to 873 K. Thermal conductivity from 323 to 873 K was estimated from the Wiedemann–Franz relation and lattice thermal conductivity extrapolation from 300 to 873 K. K8–xBaxAl8+xSi38–x (x = 1, 1.5) synthesized with Al deficiency showed enhanced electrical conductivity, and the absolute Seebeck coefficients decrease with the increased carrier concentration. When x = 2, the Al content increases toward the electron balanced composition, and the electrical resistivity increases with the decreasing charge carrier concentration. Overall, K6.5Ba1.5Al9Si37 achieves an enhanced zT of 0.4 at 873 K.« less

Bimodal Imaging at ICON Using Neutrons and X-rays

NASA Astrophysics Data System (ADS)

Kaestner, A. P.; Hovind, J.; Boillat, P.; Muehlebach, C.; Carminati, C.; Zarebanadkouki, M.; Lehmann, E. H.

For experiments with low contrast between the relevant features it can be beneficial to add a second modality to reduce ambiguity. At Paul Scherrer Institut the two neutron imaging facilities NEUTRA (thermal neutrons) and ICON (cold neutrons) we have installed X-ray beamlines for on-site bimodal imaging with neutrons and X-rays. This allows us to leave the sample untouched in the sample environment throughout an experiment and to reduce the waiting times between acquisitions using each modality. The applications and energy ranges of the X-ray installations are different at the two facilities. At NEUTRA larger samples are intended (60-320 kV) and at ICON small samples and simultaneous acquisition are intended (40-150 kV). Here, we report the more recent installation at ICON. The X-ray beamline uses a cone beam source and is arranged across the neutron beamline. The beamline is designed to allow up to ten times magnification. This matches the voxel-size that can be achieved with the micro-setup for neutrons. The oblique arrangement of the X-ray beamline further makes real-time acquisition possible since both modalities have a free view of the sample at any time. Reconstruction of cone beam data requires more knowledge about the beam geometry and sample position. Therefore, the beamline is equipped with laser based distance sensors and a calibration procedure has been developed to increase the accuracy of the reconstruction. The purpose of using multimodal acquisition is to fuse the data in a way that enhances the output of the experiment. We demonstrate the current system performance and provide a basic analysis with experiment data.

Analysis of 12 X-STR loci in the population of south Croatia.

PubMed

Mršić, Gordan; Ozretić, Petar; Crnjac, Josip; Merkaš, Siniša; Račić, Ivana; Rožić, Sara; Sukser, Viktorija; Popović, Maja; Korolija, Marina

2017-02-01

The aim of the study was to assess forensic pertinence of 12 short tandem repeats (STRs) on X-chromosome in south Croatia population. Investigator ® Argus X-12 kit was used to co-amplify 12 STR loci belonging to four linkage groups (LGs) on X-chromosome in 99 male and 98 female DNA samples of unrelated donors. PCR products were analyzed by capillary electrophoresis. Population genetic and forensic parameters were calculated by the Arlequin and POPTREE2 software, and an on-line tool available at ChrX-STR.org. Hardy-Weinberg equilibrium was confirmed for all X-STR markers in female samples. Biallelic patterns at DXS10079 locus were detected in four male samples. Polymorphism information content for the most (DXS10135) and the least (DXS8378) informative markers was 0.9212 and 0.6347, respectively. In both male and female samples, combined power of discrimination exceeded 0.999999999. As confirmed by linkage disequilibrium test, significant association of marker pair DXS10074-DXS10079 (P = 0.0004) within LG2 and marker pair DXS10101-DXS10103 (P = 0.0003) within LG3 was found only in male samples. Number of observed haplotypes in our sample pool amounted 3.01, 7.53, 5 and 3.25% of the number of possible haplotypes for LG1, LG2, LG3 and LG4, respectively. According to haplotype diversity value of 0.9981, LG1 was the most informative. In comparison of south Croatia with 26 world populations, pair-wise [Formula: see text] values increase in parallel with geographical distance. Overall statistical assessment confirmed suitability of Investigator ® Argus X-12 kit for forensic casework in both identification and familial testing in the population of south Croatia.

High temperature transport properties of co-substituted Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} (Ln = Yb, Lu; 0.02 ≤ x ≤ 0.08)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nag, Abanti, E-mail: abanti@nal.res.in; Bose, Rapaka S.C.

Highlights: • The thermoelectric Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} (Ln = Yb, Lu) perovskite are prepared by solid state reaction. • The high temperature transport properties are explored. • The co-substituted Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} shows non-metal-like temperature dependence of resistivity. • The Seebeck coefficient of Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} exhibits metallic nature. • The puzzling transport phenomenon is originated from oxygen vacancy related defect centres. - Abstract: The co-substituted Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} (Ln = Yb, Lu; 0.02 ≤ x ≤ 0.08) are synthesized by solid-state reaction and the electronic transport propertiesmore » are investigated. Rietveld refinement confirms the formation of single phase orthorhombic structure with gradual increase of cell parameters with doping level. The electronic transport properties such as Seebeck coefficient and electrical resistivity decrease with increasing the dopant concentration for both the co-substituted compositions. All the compositions of Ca{sub 1−x}Ln{sub x}Mn{sub 1−x}Nb{sub x}O{sub 3} show nonmetal-like temperature dependence of resistivity; whereas metal-like temperature dependence of thermopower. This inconsistency is explained by the formation of oxygen vacancy associated defect centres that originates from partial reduction of Mn{sup 4+} to Mn{sup 3+} due to co-substitution. The defect centres act as extrinsic carriers and cause additional contribution to the entropy of the system, leading to increase of Seebeck coefficient as a function of temperature. The transport mechanism of charge carriers is explained in the framework of Mott’s small polaron hopping mechanism.« less

UbiX is a flavin prenyltransferase required for bacterial ubiquinone biosynthesis

PubMed Central

White, Mark D.; Payne, Karl A.P.; Fisher, Karl; Marshall, Stephen A.; Parker, David; Rattray, Nicholas J.W.; Trivedi, Drupad K.; Goodacre, Royston; Rigby, Stephen E.J.; Scrutton, Nigel S.; Hay, Sam; Leys, David

2016-01-01

Ubiquinone, or coenzyme Q, is a ubiquitous lipid-soluble redox cofactor that is an essential component of electron transfer chains1. Eleven genes have been implicated in bacterial ubiquinone biosynthesis, including ubiX and ubiD, which are responsible for decarboxylation of the 3-octaprenyl-4-hydroxybenzoate precursor2. Despite structural and biochemical characterization of UbiX as an FMN-binding protein, no decarboxylase activity has been detected3–4. We report here that UbiX produces a novel flavin-derived cofactor required for the decarboxylase activity of UbiD5. UbiX acts as a flavin prenyltransferase, linking a dimethylallyl moiety to the flavin N5 and C6 atoms. This adds a fourth non-aromatic ring to the flavin isoalloxazine group. In contrast to other prenyltransferases6–7, UbiX is metal-independent and requires dimethylallyl-monophosphate as substrate. Kinetic crystallography reveals that the prenyl transferase mechanism of UbiX resembles that of the terpene synthases8. The active site environment is dominated by π-systems, which assist phosphate-C1’ bond breakage following FMN reduction, leading to formation of the N5-C1’ bond. UbiX then acts as a chaperone for adduct reorientation, via transient carbocation species, leading ultimately to formation of the dimethylallyl C3’-C6 bond. The study establishes the mechanism for formation of a new flavin-derived cofactor, extending both flavin and terpenoid biochemical repertoire. PMID:26083743

Measuring the X-shaped structures in edge-on galaxies

NASA Astrophysics Data System (ADS)

Savchenko, S. S.; Sotnikova, N. Ya.; Mosenkov, A. V.; Reshetnikov, V. P.; Bizyaev, D. V.

2017-11-01

We present a detailed photometric study of a sample of 22 edge-on galaxies with clearly visible X-shaped structures. We propose a novel method to derive geometrical parameters of these features, along with the parameters of their host galaxies based on the multi-component photometric decomposition of galactic images. To include the X-shaped structure into our photometric model, we use the imfit package, in which we implement a new component describing the X-shaped structure. This method is applied for a sample of galaxies with available Sloan Digital Sky Survey and Spitzer IRAC 3.6 μm observations. In order to explain our results, we perform realistic N-body simulations of a Milky Way-type galaxy and compare the observed and the model X-shaped structures. Our main conclusions are as follows: (1) galaxies with strong X-shaped structures reside in approximately the same local environments as field galaxies; (2) the characteristic size of the X-shaped structures is about 2/3 of the bar size; (3) there is a correlation between the X-shaped structure size and its observed flatness: the larger structures are more flattened; (4) our N-body simulations qualitatively confirm the observational results and support the bar-driven scenario for the X-shaped structure formation.

Standard Observing Bands: Is Now the Time to Replace S/X with X/Ka?

NASA Technical Reports Server (NTRS)

Jacobs, C. S.; Lanyi, G. E.; Naudet, C. J.

2004-01-01

In this paper we will argue that the VLBI community should be developing a road map to transition from S/X to simultaneous X and Ka-band (32 GHz) observations. There are both negative and positive reasons for planning such a transition. On the negative side, we will outline concerns that S-band observations may be headed toward obsolescence. On the positive side, we will refer to evidence that X/Ka has potential for providing a more stable reference frame than S/X. We will propose timetables for a transition to X/Ka observing starting from the current status of X/Ka and plans that are now taking shape. First X/Ka fringes were obtained in 2001 with the Deep Space Network. Future plans will be discussed including a proposed X/Ka-band upgrade to the VLBA. Lastly, we will consider the need for a period of overlap between S/X and X/Ka so that the long and rich history of astrometric and geodetic VLBI is not compromised.

Doping effect on the structural properties of Cu1-x(Ni, Zn, Al and Fe)xO samples (0<x<0.10): An experimental and computational study

NASA Astrophysics Data System (ADS)

Amaral, J. B.; Araujo, R. M.; Pedra, P. P.; Meneses, C. T.; Duque, J. G. S.; dos S. Rezende, M. V.

2016-09-01

In this work, the effect of insertion of transition metal, TM (=Ni, Zn, Al and Fe), ions in Cu1-xTMxO samples (0<x<0.10) prepared via co-precipitation method is studied through experimental and computational methods. The analyses of X-ray diffraction (XRD) patterns using Rietveld refinement show that i) at x=0, all samples present a monoclinic crystal system with space group C2/c and ii) for increasing the TM-doping, Ni and Zn-doped samples show a small amount of spurious phases for concentrations above x=0.05. Based on these results, a defect disorder study for using atomistic computational simulations which is based on the lattice energy minimization technique is employed to predict the location of the dopant ions in the structure. In agreement with XRD data, our computational results indicate that the trivalent (Al and Fe ions) are more favorable to be incorporated into CuO matrix than the divalent (Ni and Zn ions).

Results from the X-ray polychromator on SMM

NASA Astrophysics Data System (ADS)

Culhane, J. L.; Acton, L. W.; Gabriel, A. H.

Observations of the soft X-ray emitting plasma by means of the X-Ray Polychromator (XRP) on the Solar Maximum Mission satellite are described. The scientific advances achieved by use of the XRP are in the areas of: (1) flare morphology, (2) spectroscopy and plasma diagnostics, (3) chromospheric evaporation and the physics of flare loops, (4) studies of the microwave emission mechanisms of active regions, (5) the fluorescent excitation of Fe II K-alpha radiation, (6) measurement of variations of calcium abundance for X-ray plasmas, and (7) soft X-ray observations of spray transients. The findings in each of these areas are discussed.

Results from the X-ray polychromator on SMM

NASA Technical Reports Server (NTRS)

Culhane, J. L.; Acton, L. W.; Gabriel, A. H.

1984-01-01

Observations of the soft X-ray emitting plasma by means of the X-Ray Polychromator (XRP) on the Solar Maximum Mission satellite are described. The scientific advances achieved by use of the XRP are in the areas of: (1) flare morphology, (2) spectroscopy and plasma diagnostics, (3) chromospheric evaporation and the physics of flare loops, (4) studies of the microwave emission mechanisms of active regions, (5) the fluorescent excitation of Fe II K-alpha radiation, (6) measurement of variations of calcium abundance for X-ray plasmas, and (7) soft X-ray observations of spray transients. The findings in each of these areas are discussed.

STROBE-X: X-ray Timing & Spectroscopy on Dynamical Timescales from Microseconds to Years

NASA Astrophysics Data System (ADS)

Wilson-Hodge, Colleen A.; Ray, Paul S.; Gendreau, Keith; Chakrabarty, Deepto; Feroci, Marco; Maccarone, Tom; Arzoumanian, Zaven; Remillard, Ronald A.; Wood, Kent; Griffith, Christopher; STROBE-X Collaboration

2017-01-01

We describe a proposed probe-class mission concept that will provide an unprecedented view of the X-ray sky, performing timing and spectroscopy over a broad band (0.2-30 keV) probing timescales from microseconds to years. The Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X) comprises two primary instruments. The soft band (0.2-12 keV) will be covered by an array of lightweight optics (3-m focal length) that concentrate incident photons onto small solid state detectors with CCD-level (85-130 eV) energy resolution, 100 ns time resolution, and low background rates. This technology, fully developed for NICER, would be scaled up with enhanced optics to take advantage of the longer focal length of STROBE-X. The harder band (2 to at least 30 keV) would be covered by large-area collimated silicon drift detectors,developed for the European LOFT mission concept. Each instrument would provide an order of magnitude improvement in effective area compared with its predecessor (NICER in the soft band and RXTE in the hard band). A sensitive sky monitor would act as a trigger for pointed observations, provide high duty cycle, high time resolution, high spectral resolution monitoring of the X-ray sky with ~20 times the sensitivity of the RXTE ASM, and enable multi-wavelength and multi-messenger studies on a continuous, rather than scanning basis.The broad coverage will enable thermal components, non-thermal components, iron lines, and reflection features to be studied simultaneously from a single platform for the first time in accreting black holes at all scales. The enormous collecting area will enable studies of the dense matter equation of state using both soft thermal emission from rotation-powered pulsars and harder emission from X-ray burst oscillations. Revolutionary science, such as high quality spectroscopy of clusters of galaxies and unprecedented timing investigations of active galactic nuclei, would also be obtained.We describe the mission

Forensic characteristics and phylogenetic analyses of the Chinese Yi population via 19 X-chromosomal STR loci.

PubMed

He, GuangLin; Li, Ye; Zou, Xing; Li, Ping; Chen, PengYu; Song, Feng; Gao, Tianzhen; Liao, Miao; Yan, Jing; Wu, Jin

2017-09-01

The demographic characteristics and genetic polymorphism data of 56 Chinese nationalities or 31 administrative divisions in Chinese mainland have repeatedly been the genetic research hotspots. While most genetic studies focused on some particular Chinese populations based on autosomal or Y-chromosomal genetic markers, the forensic characteristics and phylogenetic analyses of the seventh largest Chinese population (Yi ethnicity) on the X-chromosomal genetic markers are scarce. Here, allele frequencies and forensic statistical parameters for 19 X-chromosomal short tandem repeat loci (DXS7424-DXS101, DXS6789-DXS6809, DXS7423-DXS10134, DXS10103-HPRTB-DXS10101, DXS10159-DXS10162-DXS10164, DXS10148-DXS10135-DXS8378, and DXS7132-DXS10079-DXS10074-DXS10075) of 331 Chinese Yi individuals were obtained. All 19 X-chromosomal short tandem repeat (STR) loci in females were consistent with the Hardy-Weinberg equilibrium test. A total of 214 alleles were identified with the corresponding allele frequencies spanned from 0.0019 to 0.6106. The combined PE, PDF, and PDM were 0.9999999214, 0.9999999999999999999993, and 0.9999999999998, respectively. The high combined MEC Krüger , MEC Kishida , MEC Desmarais , and MEC Desmarais Duo were achieved as 0.9999999617638, 0.9999999999971, 0.9999999999971, and 0.9999999931538, respectively. The findings suggested that the panel of 19 X-STR loci is highly polymorphic and informative in the Yi ethnic population and can be considered to be a powerful tool in forensic complex kinship identification. Population differentiation analyses among 12 populations indicated that significant differences in genetic structure were observed in between the Yi ethnicity and the Chinese Uyghur as well as Kazakh, and genetic homogeneity existed in similar ethno-origin or geographic origin populations.

X-24B on Lakebed Showing Upper Body Shape

NASA Technical Reports Server (NTRS)

1972-01-01

The sleek, futuristic shape of the X-24B lifting body research vehicle can be clearly seen in this look-down view of the aircraft on Rogers Dry Lake, adjacent to the NASA Flight Research Center, Edwards, California. The X-24 was one of a group of lifting bodies flown by the NASA Flight Research Center (now Dryden Flight Research Center), Edwards, California, in a joint program with the U.S. Air Force at Edwards Air Force Base from 1963 to 1975. The lifting bodies were used to demonstrate the ability of pilots to maneuver and safely land wingless vehicles designed to fly back to Earth from space and be landed like an airplane at a predetermined site. Lifting bodies' aerodynamic lift, essential to flight in the atmosphere, was obtained from their shape. The addition of fins and control surfaces allowed the pilots to stabilize and control the vehicles and regulate their flight paths. Built by Martin Aircraft Company, Maryland, for the U.S. Air Force, the X-24A was a bulbous vehicle shaped like a teardrop with three vertical fins at the rear for directional control. It weighed 6,270 pounds, was 24.5 feet long and 11.5 feet wide (measuring just the fuselage, not the distance between the tips of the outboard fins). Its first unpowered glide flight was on April 17, 1969, with Air Force Maj. Jerauld Gentry at the controls. Gentry also piloted its first powered flight on March 19, 1970. The X-24A was flown 28 times in the program that, like the HL-10, validated the concept that a Space Shuttle vehicle could be landed unpowered. The fastest speed achieved by the X-24A was 1,036 miles per hour (mph-Mach 1.6). Its maximum altitude was 71,400 feet. It was powered by an XLR-11 rocket engine with a maximum theoretical vacuum thrust of 8,480 pounds. The X-24A was later modified into the X-24B. The bulbous shape of the X-24A was converted into a 'flying flatiron' shape with a rounded top, flat bottom, and double delta platform that ended in a pointed nose. The X-24B demonstrated

(Quasi)-convexification of Barta's (multi-extrema) bounding theorem: Inf_x\\big(\\ssty\\frac{H\\Phi(x)}{\\Phi(x)} \\big) \\le E_gr \\le Sup_x \\big(\\ssty\\frac{H\\Phi(x)}{\\Phi(x)} \\big)

NASA Astrophysics Data System (ADS)

Handy, C. R.

2006-03-01

There has been renewed interest in the exploitation of Barta's configuration space theorem (BCST) (Barta 1937 C. R. Acad. Sci. Paris 204 472) which bounds the ground-state energy, Inf_x\\big({{H\\Phi(x)}\\over {\\Phi(x)}} \\big ) \\leq E_gr \\leq Sup_x \\big({{H\\Phi(x)}\\over {\\Phi(x)}}\\big) , by using any Φ lying within the space of positive, bounded, and sufficiently smooth functions, {\\cal C} . Mouchet's (Mouchet 2005 J. Phys. A: Math. Gen. 38 1039) BCST analysis is based on gradient optimization (GO). However, it overlooks significant difficulties: (i) appearance of multi-extrema; (ii) inefficiency of GO for stiff (singular perturbation/strong coupling) problems; (iii) the nonexistence of a systematic procedure for arbitrarily improving the bounds within {\\cal C} . These deficiencies can be corrected by transforming BCST into a moments' representation equivalent, and exploiting a generalization of the eigenvalue moment method (EMM), within the context of the well-known generalized eigenvalue problem (GEP), as developed here. EMM is an alternative eigenenergy bounding, variational procedure, overlooked by Mouchet, which also exploits the positivity of the desired physical solution. Furthermore, it is applicable to Hermitian and non-Hermitian systems with complex-number quantization parameters (Handy and Bessis 1985 Phys. Rev. Lett. 55 931, Handy et al 1988 Phys. Rev. Lett. 60 253, Handy 2001 J. Phys. A: Math. Gen. 34 5065, Handy et al 2002 J. Phys. A: Math. Gen. 35 6359). Our analysis exploits various quasi-convexity/concavity theorems common to the GEP representation. We outline the general theory, and present some illustrative examples.

Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

NASA Technical Reports Server (NTRS)

Stem, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

2008-01-01

Superconducting-nanowire singlephoton detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize NbxTi1 xN in the high-superconducting-transitiontemperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

The X11L/X11{beta}/MINT2 and X11L2/X11{gamma}/MINT3 scaffold proteins shuttle between the nucleus and cytoplasm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sumioka, Akio; Saito, Yuhki; Sakuma, Megumi

2008-03-10

The X11/MINT family proteins are adaptor scaffolding proteins involved in formation of multiprotein complexes, and trafficking and metabolism of membrane proteins such as the beta-amyloid precursor protein. We found that a significant portion of X11L and X11L2 are recovered in nuclear fraction of mouse brain homogenates. EGFP-X11s were not detected in the nucleus of N2a neuroblastoma cells; however, administration of leptomycin B (LMB) induced substantial nuclear accumulation of EGFP-X11L and EGFP-X11L2, while EGFP-X11 showed little accumulation. Fluorescence loss in photobleaching (FLIP) analysis indicated that EGFP-X11L2 and EGFP-X11L are shuttled between the cytoplasm and nucleus, the former more effectively than themore » latter. We identified a nuclear export signal (NES) in the N-terminus of X11L2, mutation of which induces nuclear accumulation of EGFP-X11L2 in the absence of LMB. X11L2 fused to the Gal4 DNA binding domain (DBD) showed transcriptional activity, suggesting that X11L2 could function as a transcriptional activator if tethered near a promoter. Interestingly, attenuation of the nucleo-cytoplasmic shuttling of GAL4-DBD-X11L2 by mutating the NES or attaching the SV40 nuclear localization signal significantly decreased the apparent transcriptional activity. Our observations suggest that X11L2 functions in the nucleus by a mechanism distinct from conventional transactivators.« less

Generation-X: An X-ray observatory designed to observe first light objects

NASA Astrophysics Data System (ADS)

Windhorst, Rogier A.; Cameron, R. A.; Brissenden, R. J.; Elvis, M. S.; Fabbiano, G.; Gorenstein, P.; Reid, P. B.; Schwartz, D. A.; Bautz, M. W.; Figueroa-Feliciano, E.; Petre, R.; White, N. E.; Zhang, W. W.

2006-03-01

The new cosmological frontier will be the study of the very first stars, galaxies and black holes in the early Universe. These objects are invisible to the current generation of X-ray telescopes, such as Chandra. In response, the Generation-X ("Gen-X") Vision Mission has been proposed as a future X-ray observatory which will be capable of detecting the earliest objects. X-ray imaging and spectroscopy of such faint objects demands a large collecting area and high angular resolution. The Gen-X mission plans 100 m 2 collecting area at 1 keV (1000× that of Chandra), and with an angular resolution of 0.1″. The Gen-X mission will operate at Sun-Earth L2, and might involve four 8 m diameter telescopes or even a single 20 m diameter telescope. To achieve the required effective area with reasonable mass, very lightweight grazing incidence X-ray optics must be developed, having an areal density 100× lower than in Chandra, with mirrors as thin as 0.1 mm requiring active on-orbit figure control. The suite of available detectors for Gen-X should include a large-area high resolution imager, a cryogenic imaging spectrometer, and a grating spectrometer. We discuss use of Gen-X to observe the birth of the first black holes, stars and galaxies, and trace their cosmic evolution.

HEAO 1 high-energy X-ray observations of Centaurus X-3

NASA Technical Reports Server (NTRS)

Howe, S. K.; Primini, F. A.; Bautz, M. W.; Lang, F. L.; Levine, A. M.; Lewin, W. H. G.

1983-01-01

Pulsations of 4.8 sec were detected up to energies above 38 keV by the present High Energy X-ray and Low Energy Gamma-Ray HEAO 1 satellite experiment observations of Cen X-3, and an analysis of the X-ray spectrum as a function of pulse phase indicates that the spectrum hardens during an interval of about 1.2 sec which lags the pulse peak by about 0.6 sec. The results of correlated observations of pulse period and X-ray intensity include (1) the detection of a high intensity state during which the pulse period is on the average increasing, (2) the measurement of comparable high intensities during episodes of both period increase and decrease, (3) the detection of X-ray pulsations at a much reduced level during a period of low intensity, and (4) the detection of a transition between spin-down, and spin-up episodes that coincides with a rapid decrease in X-ray intensity.

Two tandemly repeated telomere-associated sequences in Nicotiana plumbaginifolia.

PubMed

Chen, C M; Wang, C T; Wang, C J; Ho, C H; Kao, Y Y; Chen, C C

1997-12-01

Two tandemly repeated telomere-associated sequences, NP3R and NP4R, have been isolated from Nicotiana plumbaginifolia. The length of a repeating unit for NP3R and NP4R is 165 and 180 nucleotides respectively. The abundance of NP3R, NP4R and telomeric repeats is, respectively, 8.4 x 10(4), 6 x 10(3) and 1.5 x 10(6) copies per haploid genome of N. plumbaginifolia. Fluorescence in situ hybridization revealed that NP3R is located at the ends and/or in interstitial regions of all 10 chromosomes and NP4R on the terminal regions of three chromosomes in the haploid genome of N. plumbaginifolia. Sequence homology search revealed that not only are NP3R and NP4R homologous to HRS60 and GRS, respectively, two tandem repeats isolated from N. tabacum, but that NP3R and NP4R are also related to each other, suggesting that they originated from a common ancestral sequence. The role of these repeated sequences in chromosome healing is discussed based on the observation that two to three copies of a telomere-similar sequence were present in each repeating unit of NP3R and NP4R.

Cosmic x ray physics

NASA Technical Reports Server (NTRS)

Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

1990-01-01

The annual progress report on Cosmic X Ray Physics is presented. Topics studied include: the soft x ray background, proportional counter and filter calibrations, the new sounding rocket payload: X Ray Calorimeter, and theoretical studies.

Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

DOE PAGES

Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; ...

2015-03-02

We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ~10 6 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >10 7 laser pulses, wemore » also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.« less

Structural, Dielectric, and Electrical Properties of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3

NASA Astrophysics Data System (ADS)

Panda, Niranjan; Pattanayak, Samita; Choudhary, R. N. P.

2015-12-01

Polycrystalline samples of Bi1- x Pb x Fe1- x (Zr0.5Ti0.5) x O3 (BPFZTO) with x = 0.0, 0.2, 0.3, and 0.4 were prepared by high-temperature solid-state reaction. Preliminary structural analysis of calcined powders of the materials by use of x-ray powder diffraction confirmed formation of single-phase systems with the tetragonal structure. Room-temperature scanning electron micrographs of the samples revealed uniform distribution of grains of low porosity and different dimensions on the surface of the samples. The frequency-temperature dependence of dielectric and electric properties was studied by use of dielectric and complex impedance spectroscopy over a wide range of frequency (1 kHz to 1 MHz) at different temperatures (25-500°C). The dielectric constant of BiFeO3 (BFO) was enhanced by substitution with Pb(Zr0.5Ti0.5)O3 (PZT) whereas the dielectric loss of the BPFZTO compounds decreased with increasing PZT content. A significant contribution of both grains and grain boundaries to the electrical response of the materials was observed. The frequency-dependence of the ac conductivity of BPFZTO followed Jonscher's power law. Negative temperature coefficient of resistance behavior was observed for all the BPFZTO samples. Conductivity by thermally excited charge carriers and oxygen vacancies in the materials was believed to be of the Arrhenius-type.

X-43A/Hyper-X Vehicle Arrives at NASA Dryden

NASA Technical Reports Server (NTRS)

1999-01-01

A head-on view of the X-43A Hypersonic Experimental Vehicle, or 'Hyper-X,' in its protective shipping framework as it arrives at the Dryden Flight Research Center in October 1999. The X-43A was developed to research a dual-mode ramjet/scramjet propulsion system at speeds from Mach 7 up to Mach 10 (7 to 10 times the speed of sound, which varies with temperature and altitude). Hyper-X, the flight vehicle for which is designated as X-43A, is an experimental flight-research program seeking to demonstrate airframe-integrated, 'air-breathing' engine technologies that promise to increase payload capacity for future vehicles, including hypersonic aircraft (faster than Mach 5) and reusable space launchers. This multiyear program is currently underway at NASA Dryden Flight Research Center, Edwards, California. The Hyper-X schedule calls for its first flight later this year (2000). Hyper-X is a joint program, with Dryden sharing responsibility with NASA's Langley Research Center, Hampton, Virginia. Dryden's primary role is to fly three unpiloted X-43A research vehicles to validate engine technologies and hypersonic design tools as well as the hypersonic test facility at Langley. Langley manages the program and leads the technology development effort. The Hyper-X Program seeks to significantly expand the speed boundaries of air-breathing propulsion by being the first aircraft to demonstrate an airframe-integrated, scramjet-powered free flight. Scramjets (supersonic-combustion ramjets) are ramjet engines in which the airflow through the whole engine remains supersonic. Scramjet technology is challenging because only limited testing can be performed in ground facilities. Long duration, full-scale testing requires flight research. Scramjet engines are air-breathing, capturing their oxygen from the atmosphere. Current spacecraft, such as the Space Shuttle, are rocket powered, so they must carry both fuel and oxygen for propulsion. Scramjet technology-based vehicles need to carry

Unraveling unusual X-chromosome patterns during fragile-X syndrome genetic testing.

PubMed

Esposito, Gabriella; Tremolaterra, Maria Roberta; Savarese, Maria; Spiniello, Michele; Patrizio, Maria Pia; Lombardo, Barbara; Pastore, Lucio; Salvatore, Francesco; Carsana, Antonella

2018-01-01

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability (ID). Together with fragile X-associated tremor and ataxia (FXTAS) and fragile X-associated premature ovarian failure (POF)/primary ovarian insufficiency (POI), FXS depends on dysfunctional expression of the FMR1 gene on Xq27.3. In most cases, FXS is caused by a >200 CGG repeats in FMR1 5'-untranslated region (UTR) and by promoter hypermethylation that results in gene silencing. Males and females with unmethylated premutated alleles (repeats between 55 and 200) are at risk for FXTAS and POF/POI. FXS molecular testing relied on PCR and methylation-specific Southern blot analysis of the FMR1 5'UTR. Atypical Southern blot patterns were studied by X-chromosome microsatellite analysis, copy number dosage at DMD locus, amelogenin gender-marker analysis and array-comparative genomic hybridization (array-CGH). Six men affected by ID and three women affected by ID and POF/POI underwent FXS molecular testing. They had normal FMR1 CGG repeats, but atypical X chromosome patterns. Further investigations revealed that the six males had Klinefelter syndrome (XXY), one female was a Turner mosaic (X0/XX) and two women had novel rearrangements involving X chromosome. Diagnostic investigation of atypical patterns at FMR1 locus can address patients and/or their relatives to further verify the condition by performing karyotyping and/or array-CGH. Copyright © 2017. Published by Elsevier B.V.

X-ray luminescence computed tomography imaging based on X-ray distribution model and adaptively split Bregman method

PubMed Central

Chen, Dongmei; Zhu, Shouping; Cao, Xu; Zhao, Fengjun; Liang, Jimin

2015-01-01

X-ray luminescence computed tomography (XLCT) has become a promising imaging technology for biological application based on phosphor nanoparticles. There are mainly three kinds of XLCT imaging systems: pencil beam XLCT, narrow beam XLCT and cone beam XLCT. Narrow beam XLCT can be regarded as a balance between the pencil beam mode and the cone-beam mode in terms of imaging efficiency and image quality. The collimated X-ray beams are assumed to be parallel ones in the traditional narrow beam XLCT. However, we observe that the cone beam X-rays are collimated into X-ray beams with fan-shaped broadening instead of parallel ones in our prototype narrow beam XLCT. Hence we incorporate the distribution of the X-ray beams in the physical model and collected the optical data from only two perpendicular directions to further speed up the scanning time. Meanwhile we propose a depth related adaptive regularized split Bregman (DARSB) method in reconstruction. The simulation experiments show that the proposed physical model and method can achieve better results in the location error, dice coefficient, mean square error and the intensity error than the traditional split Bregman method and validate the feasibility of method. The phantom experiment can obtain the location error less than 1.1 mm and validate that the incorporation of fan-shaped X-ray beams in our model can achieve better results than the parallel X-rays. PMID:26203388

Effects of K-Doping on Thermoelectric Properties of Bi1- x K x CuOTe

NASA Astrophysics Data System (ADS)

An, Tae-Ho; Lim, Young Soo; Seo, Won-Seon; Park, Cheol-Hee; Yoo, Mi Duk; Park, Chan; Lee, Chang Hoon; Shim, Ji Hoon

2017-05-01

The effects of K-doping on the thermoelectric properties of Bi1- x K x CuOTe ( x = 0 to 0.08) have been investigated. The compounds were synthesized by a one-step solid-state reaction method and consolidated by a spark plasma sintering process. As the amount of K-doping was increased, the electrical and thermal conductivities increased while the Seebeck coefficient decreased due to increasing hole concentration. A ZT value of 0.69 was obtained for the compound K0.01Bi0.99CuOTe at 700 K, to the best of our knowledge the highest value reported for this material system. The origin of this enhanced ZT is discussed in terms of the density of states effective mass estimated by a single parabolic band model and electronic structures calculated based on density functional theory.

Study on the solid solution of YMn{sub 1-x}Fe{sub x}O{sub 3}: Structural, magnetic and dielectric properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samal, S.L.; Green, W.; Lofland, S.E.

The solid solution of YMn{sub 1-x}Fe{sub x}O{sub 3} (x=0.0, 0.1, 0.2, 0.3, 0.5, 1.0) was synthesized from the citrate precursor route. The hexagonal crystal structure related to YMnO{sub 3} was stable for x{<=}0.3. Rietveld refinement was carried out on the composition for x=0.3 and was refined to a major hexagonal phase ({approx}97%) with 3% of orthorhombic Y(Fe/Mn)O{sub 3} phase. The a-axis lattice constant increases and the c-axis lattice constant decreases with x for x{<=}0.2. The increase in the c-axis lattice constant at x=0.3 could be due to the doping of significant amount of d{sup 5} ion (high spin Fe{sup 3+}more » ion) in a trigonal bipyramidal crystal field. The detailed structural, magnetic and dielectric properties are discussed. - Graphical abstract: Temperature dependence of {epsilon} of YMn{sub 1-x}Fe{sub x}O{sub 3} (0.0{<=}x{<=}0.3) at 100 kHz. Inset shows the temperature variation of inverse magnetic susceptibility.« less

Dy-V magnetic interaction and local structure bias on the complex spin and orbital ordering in Dy₁₋ xTb xVO₃ (x=0 and 0.2)

DOE PAGES

Yan, J.-Q.; Cao, H. B.; McGuire, M. A.; ...

2013-06-10

The spin and orbital ordering in Dy₁₋ xTb xVO₃ (x=0 and 0.2) was studied by measuring x-ray powder diffraction, magnetization, specific heat, and neutron single-crystal diffraction. The results show that G-OO/C-AF and C-OO/G-AF phases coexist in Dy 0.8Tb 0.20VO 3 in the temperature range 2–60 K, and the volume fraction of each phase is temperature and field dependent. The ordering of Dy moments at T* = 12 K induces a transition from G-OO/C-AF to a C-OO/G-AF phase. Magnetic fields suppress the long-range order of Dy moments and thus the C-OO/G-AF phase below T*. The polarized moments induced at the Dymore » sublattice by external magnetic fields couple to the V 3d moments, and this coupling favors the G-OO/C-AF state. Also discussed is the effect of the Dy-V magnetic interaction and local structure distortion on the spin and orbital ordering in Dy₁₋ xTb xVO₃.« less

Structure and radiation effect of Er-stuffed pyrochlore Er2(Ti2-xErx)O7-x/2 (x = 0-0.667)

NASA Astrophysics Data System (ADS)

Yang, D. Y.; Xu, C. P.; Fu, E. G.; Wen, J.; Liu, C. G.; Zhang, K. Q.; Wang, Y. Q.; Li, Y. H.

2015-08-01

Er-stuffed pyrochlore series Er2(Ti2-xErx)O7-x/2 (x = 0, 0.162, 0.286, 0.424 and 0.667) were synthesized using conventional ceramic processing procedures. The structure of Er2(Ti2-xErx)O7-x/2 is effectively tailored by the Er stuffing level (x). In order to study the radiation effect of Er-stuffed pyrochlores, irradiation experiments were performed with 400 keV Ne2+ ions to fluences ranging from 5 × 1014 to 3.0 × 1015 ions/cm2 at cryogenic condition. Irradiation induced microstructural evolution was examined using a grazing incidence X-ray diffraction technique. It is found that the irradiated layer of Er2(Ti2-xErx)O7-x/2 undergoes significant lattice disordering and swelling at fluences of ⩽1.5 × 1015 ions/cm2 and amorphization at fluences of ⩾1.5 × 1015 ions/cm2. The radiation effect depends strongly on the chemical compositions of the samples. Both the lattice swelling percentage and the amorphous fraction decrease with increasing x. The experimental results are discussed in the context of cation antisite defect. The defect formation energy which varies as a function of x is responsible for the difference in the structural behaviors of Er2(Ti2-xErx)O7-x/2 under 400 keV Ne2+ ion irradiation.

Hybrid density functional study of band alignment in ZnO-GaN and ZnO-(Ga(1-x)Zn(x))(N(1-x)O(x))-GaN heterostructures.

PubMed

Wang, Zhenhai; Zhao, Mingwen; Wang, Xiaopeng; Xi, Yan; He, Xiujie; Liu, Xiangdong; Yan, Shishen

2012-12-05

The band alignment in ZnO-GaN and related heterostructures is crucial for uses in solar harvesting technology. Here, we report our density functional calculations of the band alignment and optical properties of ZnO-GaN and ZnO-(Ga(1-x)Zn(x))(N(1-x)O(x))-GaN heterostructures using a Heyd-Scuseria-Ernzerhof (HSE) hybrid functional. We found that the conventional GGA functionals underestimate not only the band gap but also the band offset of these heterostructures. Using the hybrid functional calculations, we show that the (Ga(1-x)Zn(x))(N(1-x)O(x)) solid solution has a direct band gap of about 2.608 eV, in good agreement with the experimental data. More importantly, this solid solution forms type-II band alignment with the host materials. A GaN-(Ga(1-x)Zn(x))(N(1-x)O(x))-ZnO core-shell solar cell model is presented to improve the visible light absorption ability and carrier collection efficiency.

Effect of polarizable lone pair cations on the second-harmonic generation (SHG) properties of noncentrosymmetric (NCS) Bi(2-x)Y(x)TeO₅ (x = 0-0.2).

PubMed

Jo, Hongil; Kim, Yeong Hun; Lee, Dong Woo; Ok, Kang Min

2014-08-14

Y(3+)-doped noncentrosymmetric (NCS) bismuth tellurite materials, Bi(2-x)Y(x)TeO5 (x = 0, 0.1, and 0.2), have been synthesized through standard solid-state reactions and structurally characterized by powder neutron diffraction. The reported NCS materials crystallize in the orthorhombic space group Abm2 (no. 39), and exhibit pseudo-three-dimensional frameworks that are composed of BiO3, BiO5, and TeO3 polyhedra. Detailed diffraction studies show that the cell volume of Bi(2-x)Y(x)TeO5 decreases with an increasing amount of Y(3+)on the Bi(3+) sites. However, no ordering between Bi(3+) and Y(3+) was observed in the Bi(2-x)Y(x)TeO5. Powder second-harmonic generation (SHG) measurements, using 1064 nm radiation, reveal that Bi2TeO5, Bi(1.9)Y(0.1)TeO5, and Bi(1.8)Y(0.2)TeO5 exhibit SHG efficiencies of approximately 300, 200, and 60 times that of α-SiO2, respectively. The reduction in SHG for Y(3+)-doped materials is consistent with the lack of net moment originating from polyhedra with a polarizable Bi(3+) cation.

Extragalactic Hard X-ray Surveys: From INTEGRAL to Simbol-X

NASA Astrophysics Data System (ADS)

Paltani, S.; Dwelly, T.; Walter, R.; McHardy, I. M.; Courvoisier, T. J.-L.

2009-05-01

We present some results of the deepest extragalactic survey performed by the INTEGRAL satellite. The fraction of very absorbed AGN is quite large. The sharp decrease in the absorption fraction with X-ray luminosity observed at lower-energy X-rays is not observed. The current lack of truly Compton-thick objects, with an upper limit of 14% to the size of this population, is just compatible with recent modeling of the cosmic X-ray background. We also study the prospects for a future hard X-ray serendipitous survey with Simbol-X. We show that Simbol-X will easily detect a large number of serendipitous AGN, allowing us to study the evolution of AGN up to redshifts about 2, opening the door to the cosmological study of hard X-ray selected AGN, which is barely possible with existing satellites like Swift and INTEGRAL.

Observation of femtosecond X-ray interactions with matter using an X-ray–X-ray pump–probe scheme

PubMed Central

Inoue, Ichiro; Inubushi, Yuichi; Sato, Takahiro; Tono, Kensuke; Katayama, Tetsuo; Kameshima, Takashi; Ogawa, Kanade; Togashi, Tadashi; Owada, Shigeki; Amemiya, Yoshiyuki; Tanaka, Takashi; Hara, Toru

2016-01-01

Resolution in the X-ray structure determination of noncrystalline samples has been limited to several tens of nanometers, because deep X-ray irradiation required for enhanced resolution causes radiation damage to samples. However, theoretical studies predict that the femtosecond (fs) durations of X-ray free-electron laser (XFEL) pulses make it possible to record scattering signals before the initiation of X-ray damage processes; thus, an ultraintense X-ray beam can be used beyond the conventional limit of radiation dose. Here, we verify this scenario by directly observing femtosecond X-ray damage processes in diamond irradiated with extraordinarily intense (∼1019 W/cm2) XFEL pulses. An X-ray pump–probe diffraction scheme was developed in this study; tightly focused double–5-fs XFEL pulses with time separations ranging from sub-fs to 80 fs were used to excite (i.e., pump) the diamond and characterize (i.e., probe) the temporal changes of the crystalline structures through Bragg reflection. It was found that the pump and probe diffraction intensities remain almost constant for shorter time separations of the double pulse, whereas the probe diffraction intensities decreased after 20 fs following pump pulse irradiation due to the X-ray–induced atomic displacement. This result indicates that sub-10-fs XFEL pulses enable conductions of damageless structural determinations and supports the validity of the theoretical predictions of ultraintense X-ray–matter interactions. The X-ray pump–probe scheme demonstrated here would be effective for understanding ultraintense X-ray–matter interactions, which will greatly stimulate advanced XFEL applications, such as atomic structure determination of a single molecule and generation of exotic matters with high energy densities. PMID:26811449

AlGaAs top solar cell for mechanical attachment in a multi-junction tandem concentrator solar cell stack

NASA Technical Reports Server (NTRS)

Dinetta, L. C.; Hannon, M. H.; Mcneely, J. B.; Barnett, A. M.

1991-01-01

The AstroPower self-supporting, transparent AlGaAs top solar cell can be stacked upon any well-developed bottom solar cell for improved system performance. This is an approach to improve the performance and scale of space photovoltaic power systems. Mechanically stacked tandem solar cell concentrator systems based on the AlGaAs top concentrator solar cell can provide near term efficiencies of 36 percent (AMO, 100x). Possible tandem stack efficiencies greater than 38 percent (100x, AMO) are feasible with a careful selection of materials. In a three solar cell stack, system efficiencies exceed 41 percent (100x, AMO). These device results demonstrate a practical solution for a state-of-the-art top solar cell for attachment to an existing, well-developed solar cell.

Human X-Linked genes regionally mapped utilizing X-autosome translocations and somatic cell hybrids.

PubMed Central

Shows, T B; Brown, J A

1975-01-01

Human genes coding for hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferase), glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49; D-glucose-6-phosphate:NADP+ 1-oxidoreductase), and phosphoglycerate kinase (PGK, EC 2.7.2.3; ATP:3-phospho-D-glycerate 1-phosphotransferase) have been assigned to specific regions on the long arm of the X chromosome by somatic cell gentic techniques. Gene assignment and linear order were determined by employing human somatic cells possessing an X/9 translocation or an X/22 translocation in man-mouse cell hybridization studies. The X/9 translocation involved the majority of the X long arm translocated to chromosome 9 and the X/22 translocation involved the distal half of the X long arm translocated to 22. In each case these rearrangements appeared to be reciprocal. Concordant segregation of X-linked enzymes and segments of the X chromosome generated by the translocations indicated assignment of the PGK gene to a proximal long arm region (q12-q22) and the HPRT and G6PD genes to the distal half (q22-qter) of the X long arm. Further evidence suggests a gene order on the X long arm of centromere-PGK-HPRT-G6PD. Images PMID:1056018

Cosmic x ray physics

NASA Technical Reports Server (NTRS)

Mccammon, Dan; Cox, D. P.; Kraushaar, W. L.; Sanders, W. T.

1991-01-01

The annual progress report on Cosmic X Ray Physics for the period 1 Jan. to 31 Dec. 1990 is presented. Topics studied include: soft x ray background, new sounding rocket payload: x ray calorimeter, and theoretical studies.

Deep ancestry of mammalian X chromosome revealed by comparison with the basal tetrapod Xenopus tropicalis.

PubMed

Mácha, Jaroslav; Teichmanová, Radka; Sater, Amy K; Wells, Dan E; Tlapáková, Tereza; Zimmerman, Lyle B; Krylov, Vladimír

2012-07-16

The X and Y sex chromosomes are conspicuous features of placental mammal genomes. Mammalian sex chromosomes arose from an ordinary pair of autosomes after the proto-Y acquired a male-determining gene and degenerated due to suppression of X-Y recombination. Analysis of earlier steps in X chromosome evolution has been hampered by the long interval between the origins of teleost and amniote lineages as well as scarcity of X chromosome orthologs in incomplete avian genome assemblies. This study clarifies the genesis and remodelling of the Eutherian X chromosome by using a combination of sequence analysis, meiotic map information, and cytogenetic localization to compare amniote genome organization with that of the amphibian Xenopus tropicalis. Nearly all orthologs of human X genes localize to X. tropicalis chromosomes 2 and 8, consistent with an ancestral X-conserved region and a single X-added region precursor. This finding contradicts a previous hypothesis of three evolutionary strata in this region. Homologies between human, opossum, chicken and frog chromosomes suggest a single X-added region predecessor in therian mammals, corresponding to opossum chromosomes 4 and 7. A more ancient X-added ancestral region, currently extant as a major part of chicken chromosome 1, is likely to have been present in the progenitor of synapsids and sauropsids. Analysis of X chromosome gene content emphasizes conservation of single protein coding genes and the role of tandem arrays in formation of novel genes. Chromosomal regions orthologous to Therian X chromosomes have been located in the genome of the frog X. tropicalis. These X chromosome ancestral components experienced a series of fusion and breakage events to give rise to avian autosomes and mammalian sex chromosomes. The early branching tetrapod X. tropicalis' simple diploid genome and robust synteny to amniotes greatly enhances studies of vertebrate chromosome evolution.

Deep ancestry of mammalian X chromosome revealed by comparison with the basal tetrapod Xenopus tropicalis

PubMed Central

2012-01-01

Background The X and Y sex chromosomes are conspicuous features of placental mammal genomes. Mammalian sex chromosomes arose from an ordinary pair of autosomes after the proto-Y acquired a male-determining gene and degenerated due to suppression of X-Y recombination. Analysis of earlier steps in X chromosome evolution has been hampered by the long interval between the origins of teleost and amniote lineages as well as scarcity of X chromosome orthologs in incomplete avian genome assemblies. Results This study clarifies the genesis and remodelling of the Eutherian X chromosome by using a combination of sequence analysis, meiotic map information, and cytogenetic localization to compare amniote genome organization with that of the amphibian Xenopus tropicalis. Nearly all orthologs of human X genes localize to X. tropicalis chromosomes 2 and 8, consistent with an ancestral X-conserved region and a single X-added region precursor. This finding contradicts a previous hypothesis of three evolutionary strata in this region. Homologies between human, opossum, chicken and frog chromosomes suggest a single X-added region predecessor in therian mammals, corresponding to opossum chromosomes 4 and 7. A more ancient X-added ancestral region, currently extant as a major part of chicken chromosome 1, is likely to have been present in the progenitor of synapsids and sauropsids. Analysis of X chromosome gene content emphasizes conservation of single protein coding genes and the role of tandem arrays in formation of novel genes. Conclusions Chromosomal regions orthologous to Therian X chromosomes have been located in the genome of the frog X. tropicalis. These X chromosome ancestral components experienced a series of fusion and breakage events to give rise to avian autosomes and mammalian sex chromosomes. The early branching tetrapod X. tropicalis’ simple diploid genome and robust synteny to amniotes greatly enhances studies of vertebrate chromosome evolution. PMID:22800176

Ternary lithium stannides Li xT 3Sn 7-x ( T=Rh, Ir)

NASA Astrophysics Data System (ADS)

Sreeraj, Puravankara; Kurowski, Daniel; Hoffmann, Rolf-Dieter; Wu, Zhiyun; Pöttgen, Rainer

2005-11-01

The ternary stannides Li xRh 3Sn 7-x ( x=0.45, 0.64, 0.80) and Li xIr 3Sn 7-x ( x=0.62 and 0.66) were synthesized from the elements in sealed tantalum tubes in a water-cooled sample chamber of an induction furnace. The samples were characterized by X-ray diffraction on powders and single crystals. The stannides adopt the cubic Ir 3Ge 7-type structure (space group Im3¯m, Z=4). In this structure type the tin atoms occupy the Wyckoff positions 12 d and 16 f and form two interpenetrating frameworks consisting of cubes and square antiprisms. The rhodium and iridium atoms center the square antiprisms and are arranged in pairs. With increasing lithium substitution the lattice parameter of Ir 3Sn 7 (936.7) decreases via 932.2 pm ( x=0.62) to 931.2 pm ( x=0.66), while the Ir-Ir distance remains almost the same (290 pm). A similar trend is observed for the rhodium compounds. The lithium atoms substitute Sn on both framework sites. However, the 16 f site shows a substantially larger preference for Li occupation. This is in contrast to the isotypic magnesium based compounds.

Characterization of thin films of the solid electrolyte Li(x)Mg(1-2x)Al(2+x)O4 (x = 0, 0.05, 0.15, 0.25).

PubMed

Put, Brecht; Vereecken, Philippe M; Mees, Maarten J; Rosciano, Fabio; Radu, Iuliana P; Stesmans, Andre

2015-11-21

RF-sputtered thin films of spinel Li(x)Mg(1-2x)Al(2+x)O4 were investigated for use as solid electrolyte. The usage of this material can enable the fabrication of a lattice matched battery stack, which is predicted to lead to superior battery performance. Spinel Li(x)Mg(1-2x)Al(2+x)O4 thin films, with stoichiometry (x) ranging between 0 and 0.25, were formed after a crystallization anneal as shown by X-ray diffraction and transmission electron microscopy. The stoichiometry of the films was evaluated by elastic recoil detection and Rutherford backscattering and found to be slightly aluminum rich. The excellent electronic insulation properties were confirmed by both current-voltage measurements as well as by copper plating tests. The electrochemical stability window of the material was probed using cyclic voltammetry. Lithium plating and stripping was observed together with the formation of a Li-Pt alloy, indicating that Li-ions passed through the film. This observation contradicted with impedance measurements at open circuit potential, which showed no apparent Li-ion conductivity of the film. Impedance spectroscopy as a function of potential showed the occurrence of Li-ion intercalation into the Li(x)Mg(1-2x)Al(2+x)O4 layers. When incorporating Li-ions in the material the ionic conductivity can be increased by 3 orders of magnitude. Therefore it is anticipated that the response of Li(x)Mg(1-2x)Al(2+x)O4 is more adequate for a buffer layer than as the solid electrolyte.

High Resolution X-ray Scattering Studies of Structural Phase Transitions in BaFe2-x Cr x As 2

NASA Astrophysics Data System (ADS)

Gaulin, B. D.; Clancy, J. P.; Wagman, J. J.; Sefat, A. S.

2011-03-01

While the effects of electron-doping on the parent compounds of the 122 family of Fe-based superconductors have been extremely well-studied in recent years, far less is known about the influence of hole-doping in compounds such as BaFe 2-x Cr x As 2 . In contrast to the electron-doped 122 systems, the hole-doped compounds do not become superconducting. Furthermore, while the hole-doped compounds exhibit similar structural and magnetic phase transitions, they appear to be much less sensitive to dopant concentration. We have performed high resolution x-ray scattering and magnetic susceptibility measurements on single crystal samples of BaFe 2-x Cr x As 2 for Cr concentrations ranging from 0 <= x <= 0.67 . These measurements allow us to determine the magnetic and structural phase transitions for this series and map out the low temperature phase diagram as a function of doping. In particular, we have carried out detailed measurements of the tetragonal (I4/mmm) to orthorhombic (Fmmm) structural phase transition which reveal how the orthorhombicity of the system evolves with increasing Cr concentration and how this correlates with the values of Ts and Tm .

Compositional dependence of magnetic anisotropy in chemically synthesized Co3- x Fe x O4 (0 ≤ x ≤ 2)

NASA Astrophysics Data System (ADS)

Hayashi, Kensuke; Yamada, Keisuke; Shima, Mutsuhiro

2018-01-01

Magnetic anisotropy of Co3- x Fe x O4 (CFO, 0 ≤ x ≤ 2) thin-film and powder samples prepared by a sol-gel method has been investigated as a function of Fe composition x. Structural analyses by X-ray diffraction show that CFO powder samples exhibit diffraction peaks associated with the spinel structure when x < 2, while CFO thin-film samples with thickness of 130-510 nm yield the peaks when 0 ≤ x ≤ 2. CFO thin-film samples are highly (111)-oriented with the Lotgering factor greater than 0.9 when 0.6 ≤ x ≤ 1.3. The magnetic anisotropy constant K 1 of CFO powder samples estimated from their room-temperature hysteresis loops yields a minimum when x = 0.9. Relatively large in-plane magnetic anisotropy (K eff = 5.7 × 105 erg/cm3) is observed for the CFO thin-film sample when x = 1.3. With increasing x, the magnetic easy axis of the spinel CFO changes from 〈111〉 to 〈100〉 when x = 0.9.

Focusing X-Ray Telescopes

NASA Technical Reports Server (NTRS)

O'Dell, Stephen; Brissenden, Roger; Davis, William; Elsner, Ronald; Elvis, Martin; Freeman, Mark; Gaetz, Terrance; Gorenstein, Paul; Gubarev, Mikhall; Jerlus, Diab;

Studies on RF sputtered (WO3)1-x (V2O5)x thin films for smart window applications

NASA Astrophysics Data System (ADS)

Meenakshi, M.; Sivakumar, R.; Perumal, P.; Sanjeeviraja, C.

2016-05-01

V2O5 doped WO3 targets for RF sputtering thin film deposition were prepared for various compositions. Thin films of (WO3)1-x (V2O5)x were deposited on to glass substrates using these targets. Structural characteristics of the prepared targets and thin films were studied using X-ray diffraction. Laser Raman studies were carried out on the thin films to confirm the compound formation.

Pulse periods and the long-term variations of the X-ray pulsars VELA X-1 and Centaurus X-3

NASA Astrophysics Data System (ADS)

Tsunemi, Hiroshi

The paper reports recent determinations of the pulse period for two X-ray pulsars, Vela X-1 and Cen X-3, made in 1987 with the All Sky Monitor (ASM) on board the Ginga satellite. The heliocentric pulse periods are 283.09 + or - 0.01 s and 4.8229 + or - 0.0001 s, respectively. These are the longest and shortest values in their respective observational histories. The random walk model for the Vela X-1 pulsar can explain this result as well as those obtained previously. It is also noted that the pulse-period change for the Cen X-3 system shows a 9-yr periodicity. This is probably due to the activity of the companion star rather than to Doppler-shift variations due to a third body or the precession of the neutron star.

Magnetism of Ho 1-xTb xAl₂ alloys: Critical dependence of a first-order transition on Tb concentration

DOE PAGES

Khan, Mahmud; Mudryk, Ya.; Gschneidner, K. A.; ...

2011-12-27

HoAl₂ exhibits a first-order spin reorientation transition at 20 K, which is manifested as a sharp peak in the heat capacity. When Ho is partially replaced by only 5% of Tb, the sharp heat-capacity peak in Ho 1-xTb xAl₂ (x = 0.05) disappears, and then reappears again for x ≥ 0.07. For x = 0.05, the anomaly corresponding to the spin reorientation transition is barely seen in the heat capacity, but as x exceeds 0.07 the weak anomaly transforms to a sharp peak. The spin reorientation transition temperature increases to 29 K for x = 0.05, and as x increasesmore » further the transition shifts to lower temperature and returns to ~20 K for x = 0.25. The transition is no longer observed when x exceeds 0.60. Temperature-dependent x-ray powder-diffraction data confirm the first-order nature of the spin reorientation transition for the alloy with x = 0.40, and indicate that the compound retains the room-temperature cubic structure within the sensitivity of the technique. Experimental observations are discussed considering the easy magnetization directions of HoAl₂ and TbAl₂.« less

Design and Tests of the Hard X-Ray Polarimeter X-Calibur

NASA Technical Reports Server (NTRS)

Beilicke, M.; Binns, W. R.; Buckley, J.; Cowsik, R.; Dowkontt, P.; Garson, A.; Guo, Q.; Israel, M. H.; Lee, K.; Krawczynski, H.;