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We present the first high spectral resolution X-ray observation of the giant elliptical galaxy NGC 4636, obtained with the Reflection Grating Spectrometer on-board the XMM-Newton Observatory. The resulting spectrum contains a wealth of emission lines from various charge states of oxygen, neon, magnesium, and iron. Examination of the cross-dispersion profiles of several of these lines provides clear, unambiguous evidence of resonance scattering by the highest oscillator strength lines, as well as a weak temperature gradient in the inner regions of the interstellar medium. We invoke a sophisticated new Monte Carlo technique which allows us to properly account for these effects in performing quantitative fits to the spectrum. Our spectral fits are not subject to many of the systematics that have plagued earlier investigations. The derived metal abundances are higher than have been inferred from prior, lower spectral resolution observations of this source (Awaki et al. 1994), but are still incompatible with conventional chemical enrichment models of elliptical galaxies. In addition, our data are incompatible with standard cooling flow models for this system - our derived upper limit to the mass deposition rate is below the predicted value by a factor of 3--5., 8 pages, 2 figures; submitted to ApJ

K{alpha} spectra of heliumlike neon and associated lithiumlike, berylliumlike, and boronlike satellite line emission have been observed with a high-resolution crystal spectrometer on the Lawrence Livermore Electron Beam Ion Trap. The KLL dielectronic recombination satellites were resolved from their He-like parent lines in electron energy space, and their wavelengths and resonance strengths measured. The wavelength measurements achieved a typical accuracy of a few mAa, with two measurements accurate to better than one part in 10000. By normalizing to the He-like resonance line, w, we measure Li-like satellite resonance strengths that are 10% to 46% lower than predicted by theoretical models. The wavelengths and relative strengths of Be-like KLL satellites were also measured, and absolute strengths were obtained by normalizing to the collisionally excited Li-like qr satellite blend.

XMM-Newton RGS spectra of MCG-6-30-15 and Mrk 766 exhibit complex discrete structure, which was interpreted in a paper by Branduardi-Raymont et al. (2001) as evidence for the existence of relativistically broadened Lyman alpha emission from carbon, nitrogen, and oxygen, produced in the inner-most regions of an accretion disk around a Kerr black hole. This suggestion was subsequently criticized in a paper by Lee et al. (2001), who argued that for MCG-6-30-15, the Chandra HETG spectrum, which is partially overlapping the RGS in spectral coverage, is adequately fit by a dusty warm absorber model, with no relativistic line emission. We present a reanalysis of the original RGS data sets in terms of the Lee et al. (2001) model, and demonstrate that spectral models consisting of a smooth continuum with ionized and dust absorption alone cannot reproduce the RGS spectra of both objects. The original relativistic line model with warm absorption proposed by Branduardi-Raymont et al. (2001) provides a superior fit to the RGS data, both in the overall shape of the spectrum and in the discrete absorption lines. Limits on the amount of X-ray absorption by dust particles are discussed. We also discuss a possible theoretical interpretation for the putative relativistic Lyman alpha line emission in terms of the photoionized surface layers of the inner regions of an accretion disk., Comment: Replaced with accepted version. To appear in ApJ; tentatively scheduled for the v596 Oct. 10, 2003 issue

The high XMM-Newton throughput allows a detailed investigation of the spatial, spectral and variability properties of the extended and point source emission of the starburst galaxy NGC 253 simultaneously. We characterize the brightest sources by their hardness ratios, detect a bright X-ray transient, and show the spectrum and light curve of the brightest point source, most likely a black-hole X-ray binary. The unresolved emission of two disk regions can be modeled by two thin thermal plasma components of 0.13 and 0.4 keV plus residual harder emission, with the lower temperature component originating from above the disk, the nuclear spectrum by a three temperature plasma (~0.6, 0.9, and 6 keV) with the higher temperatures increasingly absorbed. The high temperature component most likely originates from the starburst nucleus. No non-thermal component, that would point at a significant contribution from an active nucleus (AGN), is needed. Assuming that type IIa supernova remnants (SNRs) are mostly responsible for the E>4 keV emission, the detection with EPIC of the 6.7 keV line allows us to estimate a supernova rate within the nuclear starburst of 0.2 yr^-1. RGS spectra and EPIC images reveal that the limb-brightening of the plume is mostly seen in higher ionization emission lines, while in the lower ionization lines, and below 0.5 keV, the plume is more homogeneously structured. (abridged), 7 pages, 7 figures, accepted for publication in the special A&A Letters issue for XMM-Newton, a full resolution file is available at http://www.rosat.mpe-garching.mpg.de/~wnp/

The iron L-shell ions (Fe17+ to Fe23+) play an important role in determin- ing the thermal and ionization structures and line emission from photoionized plasmas. Current uncertainties in the theoretical low temperature dielectronic recombination (DR) rate coefficients for these ions significantly affect our ability to model and inter- pret the line emission from observations of photoionized plasmas. To help resolve this issue, we have initiated a program of laboratory measurements to produce reliable low temperature DR rates for the L-shell iron. Here we present some of our recent results and discuss some of the astrophysical implications.

The RS CVn binary system HR 1099 was extensively observed by the XMM-Newton observatory in February 2000 as its first-light target. A total of 570 ks of exposure time was accumulated with the Reflection Grating Spectrometers (RGS). The integrated X-ray spectrum between 5-35 Angstrom is of unprecedented quality and shows numerous features attributed to transitions of the elements C, N, O, Ne, Mg, Si, S, Fe, and Ni. We perform an in-depth study of the elemental composition of the average corona of this system, and find that the elemental abundances strongly depend on the first ionisation potential (FIP) of the elements. But different from the solar coronal case, we find an inverse FIP effect, i.e., the abundances (relative to oxygen) increase with increasing FIP. Possible scenarios, e.g., selective enrichment due to Ne-rich flare-like events, are discussed., Comment: 5 pages, 4 figures. Accepted by A&A Letters, XMM issue

Iron ions provide many valuable plasma diagnostics for cosmic plasmas. The accuracy of these diagnostics, however, often depends on an accurate understanding of the ionization structure of the emitting gas. Dielectronic recombination (DR) is the dominant electron-ion recombination mechanism for most iron ions in cosmic plasmas. Using the heavy-ion storage ring at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany, we have measured the low temperature DR rates for Fe[sup q+] where q=15, 17, 18, and 19. These rates are important for photoionized gases which form in the media surrounding active galactic nuclei, X-ray binaries, and cataclysmic variables. Our results demonstrate that commonly used theoretical approximations for calculating low temperature DR rates can easily under- or over-estimate the DR rate by a factor of [approximately]2 or more. As essentially all DR rates used for modeling photoionized gases are calculated using these approximations, our results indicate that new DR rates are needed for almost all charge states of cosmically abundant elements. Measurements are underway for other charge states of iron. [copyright] [ital 1999 American Institute of Physics.]

In photoionized gases with cosmic abundances, dielectronic recombination (DR) proceeds primarily via nlj --> nl'j' core excitations (Dn=0 DR). We have measured the resonance strengths and energies for Fe XVIII to Fe XVII and Fe XIX to Fe XVIII Dn=0 DR. Using our measurements, we have calculated the Fe XVIII and Fe XIX Dn=0 DR DR rate coefficients. Significant discrepancies exist between our inferred rates and those of published calculations. These calculations overestimate the DR rates by factors of ~2 or underestimate it by factors of ~2 to orders of magnitude, but none are in good agreement with our results. Almost all published DR rates for modeling cosmic plasmas are computed using the same theoretical techniques as the above-mentioned calculations. Hence, our measurements call into question all theoretical Dn=0 DR rates used for ionization balance calculations of cosmic plasmas. At temperatures where the Fe XVIII and Fe XIX fractional abundances are predicted to peak in photoionized gases of cosmic abundances, the theoretical rates underestimate the Fe XVIII DR rate by a factor of ~2 and overestimate the Fe XIX DR rate by a factor of ~1.6. We have carried out new multiconfiguration Dirac-Fock and multiconfiguration Breit-Pauli calculations which agree with our measured resonance strengths and rate coefficients to within typically better than, Comment: To appear in ApJS, 44 pages with 13 figures, AASTeX with postsript figures

We study the effect of galaxy shape measurement errors on predicted cosmological constraints from the statistics of shear peak counts with the Large Synoptic Survey Telescope (LSST). We use the LSST Image Simulator in combination with cosmological N-body simulations to model realistic shear maps for different cosmological models. We include both galaxy shape noise and, for the first time, measurement errors on galaxy shapes. We find that the measurement errors considered have relatively little impact on the constraining power of shear peak counts for LSST.

The Seyfert 1 galaxy Mrk 478, observed during the EUVE all-sky survey, is the brightest EUV source among its class. The SW spectrum of this object shows evidence of discrete emission, although this interpretation is tentative, since the source spectrum must be extracted against a bright background. If the EUV flux is, in fact, composed partly of line emission, we consider the implications if this is the result of emission from a collision-driven plasma at temperatures ≳ 106 K. In this context, we discuss some of the constraints imposed on the emission-line region by this observation.

One of the dominant forms of astronomical line emission in the 6 A to 18 A spectral region is line emission produced by n=n′ to n=2 transitions in Fe16+ to Fe23+ (i.e., Fe L‐shell n‐2 line emission). Using the Lawrence Livermore National Laboratory electron beam ion trap (EBIT) facility, we have carried out a number of measurements designed to address astrophysical issues concerning Fe L‐shell line emission. Desired ions are produced and trapped using the nearly monoenergetic electron beam of EBIT Trapped ions are collisionally excited and the resulting X‐ray line emission detected using Bragg crystal spectrometers. We have recently completed a line survey of Fe L‐shell 3‐2 line emission. The line survey will allow a more reliable accounting of line blending in astronomical spectra. We have now begun a series of broadband, high resolution line ratio measurements. These measurements are designed to benchmark atomic calculations used in astronomical plasma emission codes and also for comparison with X‐ray spectral observations of astronomical objects. Initial measurements have been carried out in Fe23+. Preliminary results agree with distorted wave calculations to within 20 percent and better.

The cyclin D1 gene is amplified and overexpressed in a significant fraction of human esophageal tumors, and several other types of human cancer, but the functional significance of this overexpression has not been established. To further address the roles of cyclin D1 in growth control and tumorigenesis, we have overexpressed an antisense cyclin D1 cDNA construct, either constitutively or inducibly, in the HCE7 human esophageal cancer cell line in which cyclin D1 is amplified and expressed at high levels. The expression of antisense cyclin D1 led to decreased expression of cyclin D1 at both mRNA and protein levels, and this was associated with a marked inhibition of cell proliferation. Antisense cyclin D1 expressing cells displayed a decreased plating efficiency, increased doubling time, decreased saturation density, increased cell size, decreased cyclin D1-associated in vitro kinase activity, decreased anchorage-independent growth, and a loss of tumorigenicity in nude mice. These findings provide direct evidence that the overexpression of cyclin D1 in certain tumor cells contributes to their abnormal growth and tumorigenicity. The ability to revert the transformed phenotype of these cells with antisense cyclin D1 suggests that cyclin D1 may be a useful target in cancer therapy.

BACKGROUND/DESIGN: The clonal theory of cancer predicts that transformed cells within a given tumor are derived from a single initiated precursor. Advancement of this precursor through various stages of tumor development occurs with the further accumulation of selective genetic and epigenetic lesions. Mammalian ras genes are important constituents of mitogenic signaling pathways, and when activated, they contribute to deregulated cellular growth. Activated ras genes play important roles in the development of certain skin tumors. Studies on a number of animal tumor model systems have shown that ras gene activation can be an early and perhaps initial event in the development of skin tumors. Activated ras genes are also found in a significant percentage of somatic human squamous cell carcinomas. To gain retrospective insight into the stages at which activated ras genes contribute to squamous cell carcinoma development, we investigated their incidence in actinic keratoses, premalignant precursors to squamous cell carcinomas. Using a nonradioactive polymerase chain reaction-based method developed in our laboratory, we examined a panel of 19 actinic keratoses and 33 squamous cell carcinomas for activated ras genes.DNA analysis revealed ras gene mutations in three (16%) of 19 actinic keratoses and in four (12%) of 33 squamous cell carcinomas. Activating mutations occurred at codon 12 of the K-ras gene, and codons 12, 13, and 61 of the H-ras gene. All positive actinic keratoses and squamous cell carcinomas occurred in sun-exposed regions.Activated ras genes can play important roles during early stages of squamous cell carcinoma development. Aberrant repair of UV-induced pyrimidine dimers is a likely cause of this activation.

X‐ray line emission in the 0.5–1.5 keV band has been detected in the spectra of a growing number of accretion‐powered x‐ray sources. The emission appears to be dominated by strong lines from the Fe L ions, although there are several peculiarities to the emission structure. In particular, the Fe L lines appear not to be accompanied by K‐shell lines of He‐ and H‐like oxygen, which should be several times stronger for most relevant emission mechanisms. If the lines are produced in a photoionized medium surrounding the central source, then the particular species observed may be strongly affected by the thermal stability of the irradiated gas. The coupling between the thermal balance and the ionization balance introduces a strongly non‐linear relation between abundance and strength of the emission lines for the important elements. The absence of strong oxygen emission may simply be due to the fact that the H‐ and He‐like oxygen line emission regions are located entirely in a thermally unstable phase of the medium, as would be predicted to occur for relatively small departures from standard abundances. We explore the fundamental thermal stability properties of an x‐ray photoionized plasma, and their dependence on elemental abundance, and we discuss the obvious importance of these properties for any prospects of determining the chemical composition of accreting gas in accretion‐powered sources from the x‐ray emission spectrum.

Cyclin D1, a putative G1 cyclin, has been implicated in cell cycle control. The human cyclin D1 gene is located on chromosome 11q13 where DNA rearrangement and amplification have been detected in several types of human cancer. Previous studies demonstrated that the cyclin D1 gene is not only rearranged or amplified but also overexpressed in some of these human tumors and tumor-derived cell lines. To further address the roles of cyclin D1 in cell cycle control and tumorigenesis, we have stably overexpressed the human cyclin D1 cDNA in Rat6 embryo fibroblasts by using retrovirus mediated transduction. The cyclin D1 protein was overproduced about 10-fold and was localized predominately in the nucleus. Cyclin D1 overexpressing cells displayed a decrease in the duration of the G1 phase, decreased cell size, and induced tumors when injected into athymic (nude) mice. In addition, overexpression of cyclin D1 in Rat6 cells perturbed the expression of several cellular growth-related genes including c-myc, c-jun, and cyclin A, but not cyclin D3. Taken together, these results indicate that deregulated expression of the cyclin D1 gene can cause disturbances in cell cycle control and gene expression and also enhance tumorigenesis.

We found that the human colon cancer cell line SW480 consists of two distinct subpopulations which we have designated E-type (epithelial) and R-type (round). Pure cultures of each type were obtained by subcloning, and both have maintained their characteristic phenotypes for at least 1 year (40 passages). E-type cells are the major (98%) type in the parental SW480 cell line. They form flat epithelial-like colonies. In contrast, R-type cells, which constitute a minor fraction (2%) of the parental cell line, have a rounded shape and grow in clusters of piled-up cells. Compared to E-type cells or the parental SW480 cells, isolated R-type cells display decreased doubling time, loss of contact inhibition, less adhesiveness to culture plates, higher anchorage-independent growth in soft agar, and a much more aneuploid karyotype. When injected s.c. into nude mice, R-type cells produce much larger tumors within the same period of time than E-type cells, and the tumors are less differentiated than those produced by the E-type cells. Cell fusion experiments between R-type and E-type cells revealed that the R-type phenotype is dominant, and the results suggest that this is due to one or a few genetic changes. Taken together, these findings suggest that the R-type cells represent a more malignant variant of the E-type cells. They may be useful, therefore, for studying mechanisms involved in tumor progression.

Amplification of the hst-1 and int-2 genes on chromosome 11q13 has previously been found in over 20% of human primary esophageal cancers. However, these two genes do not appear to be transcribed in appreciable amounts. Recently, the human cyclin D gene (also referred to as prad1) has been mapped to the 11q13 locus. Here, we report coamplification of the cyclin D and hst-1 genes in 5 of 20 (25%) human squamous esophageal tumors. We also detected significant levels of cyclin D transcription in two esophageal carcinoma cell lines, even though they did not express detectable amounts of hst-1 transcription. These findings provide the first evidence for the amplification of a cyclin gene in human esophageal cancer and suggest that an increase in cyclin D gene dosage could be an important factor in the pathogenesis of esophageal cancer. Additionally, because the 11q13 locus is found to be amplified in many types of human tumors, cyclin gene amplification could also play an important role in the development of other forms of human cancer.

High-resolution broadband, non-dispersive x-ray calorimeter spectrometers have been under development for spaceflight since 1984. As an offshoot of the significant NASA investment in this technology, we have developed a series of calorimeter instruments for laboratory use and installed them at the Electron Beam Ion Trap (EBIT) facility at the Lawrence Livermore National Laboratory. The calorimeter instruments at EBIT have significantly enhanced the capabilities of our laboratory astrophysics program including broad-band measurements of emission from charge exchange recombination and absolute cross sections for collisional excitation. The first Goddard Space Flight Center (GSFC) calorimeter instrument was installed at the EBIT facility in July of 2000 and has seen two major upgrades. The performance of the instrument has significantly improved from the initial instrument that had a resolving power of ~500 at 6 keV, and essentially no quantum efficiency at energies above 20 keV, to the current instrument that has a resolving power of 1350 and 95% quantum efficiency at 6 keV, and a resolving power of 1800 and 32% quantum efficiency at 60 keV.

The Electron Beam Ion Trap Microcalorimeter Spectrometer (ECS) routinely surveys the K-shell x-ray spectra that fall into the energy range between 200 eV and 14,000 eV. The spectra serve as in situ energy references and include the K-shell emission from ions between boron at the low-energy end and krypton at the high end. Example spectra are presented of the n = 2 → n = 1 emission from heliumlike noble gas ions neon, argon, and krypton, from the heliumlike transition metals iron and nickel, as well as the heliumlike ions of boron, silicon, sulfur, and germanium.

We have developed a rapid and highly sensitive nonradioactive method for the detection of a mutant codon 12 human c-K-ras allele in the presence of as many as 10(4) copies of the wild type codon 12 allele. This sensitivity is achieved by selective polymerase chain reaction (PCR) amplification of mutant K-ras gene sequences employing a two stage procedure. The first stage entails the amplification of both K-ras mutant and wild type codon 12 sequences, followed by a selective restriction enzyme digestion of only wild type sequences. The second stage involves a subsequent amplification of undigested amplified fragments, enriched in mutant codon 12 sequences. These products are subject to restriction length polymorphism analysis for the detection of point mutations at codon 12. This technique is rapid, nonradioactive, and eliminates the need for either oligonucleotide hybridization or DNA sequencing. Variations of this selective amplification procedure may prove promising for the detection of specific point mutations in heterogenous cell populations.

Blazed, grazing incidence x-ray reflection gratings are an important component of modern high resolution spectrometers and related x-ray optics. These have traditionally been fabricated by diamond scribing in a ruling engine, or more recently by interferometric lithography followed by ion etching. These traditional methods result in gratings which suffer from a number of deficiencies, including high surface roughness and poor control of the groove profile. These deficiencies lead to poor diffraction efficiency and high levels of scattered light. We have developed a novel fabrication method for fabricating blazed x-ray reflection gratings which utilizes silicon wafers that are cut 0.7° off of the (111) plane. In solutions such as potassium hydroxide (KOH), silicon is etched in 〈111〉 directions orders of magnitude slower than in other directions, resulting in extremely smooth {111} facets. The gratings are patterned using interferometric lithography with 351.1 nm wavelength and transferred into the substrat...

Background/Design: The clonal theory of cancer predicts that transformed cells within a given tumor are derived from a single initiated precursor. Advancement of this precursor through various stages of tumor development occurs with the further accumulation of selective genetic and epigenetic lesions. Mammalian ras genes are important constituents of mitogenic signaling pathways, and when activated, they contribute to deregulated cellular growth. Activated ras genes play important roles in the development of certain skin tumors. Studies on a number of animal tumor model systems have shown that ras gene activation can be an early and perhaps initial event in the development of skin tumors. Activated ras genes are also found in a significant percentage of somatic human squamous cell carcinomas. To gain retrospective insight into the stages at which activated ras genes contribute to squamous cell carcinoma development, we investigated their incidence in actinic keratoses, premalignant precursors to squamous cell carci

We present the first systematic laboratory measurements of high-resolution K-alpha spectra of intermediate ions of iron, Fe X-XVII. These lines are not produced in collisional equilibrium plasmas because of the relevant charge states cannot exist at the high electron temperatures required for appreciable excitation of the K-alpha transitions. However, they can provide excellent spectral diagnostics for nonequilibrium ionization conditions, such the ionizing plasmas of young supernova remnants. To facilitate the line identifications, we compare our spectra with theoretical atomic calculations performed using multiconfiguration parametric potential and Dirac-Fock atomic codes. Our measurements also allow direct comparison with time-dependent ionization balance calculations for ionizing plasmas, and good agreement is found.

We have studied the first extreme ultraviolet spectroscopic data and a high accuracy light curve for the BL Lac object PKS 2155–304 observed with the Extreme Ultraviolet Explorer (EUVE) on July 21–22, 1992. This target was observed with the Deep Survey Spectrometer telescope for approximateley 30,000 sec during the in-orbit-calibration phase of the mission, allowing to obtain simultaneous image and spectrum.

The results of observations of 22 bright Galactic X-ray point sources are presented, and the most reliable measurements to date of X-ray column densities to these sources are derived. The results are consistent with the idea that some of the objects have a component of column density intrinsic to the source in addition to an interstellar component. The K-edge absorption due to oxygen is clearly detected in 10 of the sources and the Fe L and Ne K edges are detected in a few. The spectra probably reflect emission originating in a collisionally excited region combined with emission from a photoionized region excited directly by the central source.

An analysis of five Exosat observations of Cyg X-2, taken around a full binary orbit is presented. The data were obtained using all instrumentation (1000 lines/mm Transmission Grating Spectrometer, Channel Multiplier Array + filters, Medium-Energy experiment, and Gas Scintillation Proportional Counter) simultaneously, and span the full energy range 0.5-20 keV. No clear evidence was found for a correlation of any of the source characteristics with orbital phase. During two of the observations, significant iron K emission at 6.7 keV was detected, the relative strength of which seems to correlate with total X-ray intensity during two sharp intensity dips. The previous detection of discrete emission features in the 12-19 A band with the Einstein grating is confirmed.

The AM Her type object E2003+225 was observed with EXOSAT, IUE and ground-based telescopes on 1983 Oct. 12. The brightness of the ultrasoft X-ray component allowed the Objective Grating Spectrometer (OGS) to be used, which gave a model-independent determination of the temperature of the blackbody spectrum. The star was observed again on 1984 July 24 by IUE with simultaneous optical spectrophotometry. The high resolution of this observation revealed complex line profiles, and a systematic velocity much smaller than previously reported. The composite energy distribution is presented.

A highly variable point X-ray source, first seen by the Einstein IPC, has been positioned with the EXOSAT CMA and identified with a bright (V=8.5) KO star. Although in the direction of the southern half of the Cygnus Loop, this star is almost certainly a foreground object and typical of other active cool stars that are related to RS CVn systems.

Detection d'une modulation de 67 min avec une fraction de pulsation d'environ 30%, durant une observation RX de 26 heures continues de cette binaire de 98 min

Preliminary results of an EXOSAT observation of the transient X-ray source 4U 154.3-47 are presented. The source was observed in August 1983, during a high state, following a Tenma alert that the source was again active. Results from the GSPC and the LE 1000 1/mm grating are presented. The spectrum is complex, but in the 2-10 keV energy range can be well described by a Comptonised thermal distribution. Extrapolating the same model into the lower energy band of the grating requires an absorption column density equivalent to 2x1021 H cm2. A marked under-abundance of Oxygen and overabundance of Nitrogen, along with a strong, unidentified line feature at 9.8 A, are necessary to model the grating data.

X-ray, UV and optical data are presented of the longest period AM Her object, E2003+225, from October 12, 1983, together with a new linear polarization ephemeris. The optical and X-ray data were obtained simultaneously and the UV observations were carried out on the same day. A 6-hr observation with the Exosat 500 line/mm objective grating restricts soft X-ray blackbody temperatures to the range 18-29 eV. The blackbody luminosity exceeds the hard X-ray luminosity by at least a factor of 4.5, but is of the same order as the optical/UV component. Soft (0.1-0.25 keV) and hard X-ray (1-6 keV) light curves covering almost two orbital periods are presented and discussed.

The aqueous interactions of the sparingly soluble silver tellurite show that in a controlled ionic medium and at a constant temperature, an aqueous complex,[Formula: see text] is formed in presence of free tellurite ions. The solubility product of silver tellurite and the stability constant of the complex species have been evaluated from the experimental data.

We present a high resolution (λ/Δλ = 80) Soft X-ray spectrum (44-95 A) of the magnetic white dwarf binary AM Her obtained with the Objective Grating Spectrometer on board the Einstein observatory. Black body fits to the continuum strongly limits the range of allowable parameters and indicate a "color" temperature in the soft X-ray range between 40 and 55 eV (90% confidence limits). After egress from the eclipse the spectrum hardens and indicates a black body temperature increase from 38 eV to 52 eV. This is interpreted as a limb darkening effect of a layer with negative outward temperature gradient. Assuming the radiative flux to be constant, both the soft X-ray spectrum and the UV spectrum are consistent with a plane parallel layer in radiative equilibrium with an effective temperature of 20 eV. The color temperature in the soft X-ray range is insensitive to the effective temperature in such layers. A variable heating source at large optical depth associated with a variable accretion rate, changes the soft X-ray intensity but does not change the soft X-ray nor the UV spectral shape.

An x-ray calibration facility for use in the 0.2-25 keV region is described. The facility employs several types of specially modified sources and detectors to produce and detect both line and continuum radiation in this energy range. We describe an inexpensive commercial x-ray source which has been modified for efficient high intensity operation as well as production of x-rays up to 25 keV. We also describe a system that utilizes multilayer mirrors alone or in a double Bragg geometry to select an energy bandpass. This system is controlled by a microcomputer which translates and rotates the multilayers to provide an easily selectable monochromatic beam with good resolu-tion over a broad energy range. A long focal length Kirkpatrick-Baez mirror pair has been coupled to a pivoting beam line in order to accurately characterize gratings for use in soft x-ray astronomy. The beam line is scanned through the various grating orders. All aspects of the facility incorporate a high degree of flexibility so that a wide variety of calibrations can be easily performed.

A series of prototype blazed reflection gratings, designed for incorporation in a satellite-borne, high efficiency, moderate resolution, astronomical x-ray spectrometer, have been tested for x-ray reflectivity in the relevant spectral orders. Both mechanically-ruled and ion-etched holographic master and replica grat-ings produced by various manufacturers, have been measured at 8.34 A, 13.34 A, and 44.7 A. We find near theoretical performance from a particular ion-etched sample and from one of the mechanically ruled samples. The other mechanically ruled samples exhibit lower efficiency, which can in part be ascribed to imperfections in the groove profile. A comparision between scalar diffraction theory and the rigorous electromagnetic calculations of grating efficiency for these samples is also presented.

Over the next decade, several astrophysical observatories will obtain high-resolution spectra of cosmic x-ray sources. Of particular interest are accretion-powered objects, such as active galactive nuclei, in which the x-ray emitting material is optically thick and therefore cannot be studied using the well-known models developed to explain the optically thin solar corona. In our laboratory, we are attempting to simulate optical depth conditions from which astrophysical processes can be modeled, including photoabsorption, recombination, and fluorescence. A laser-produced plasma, when time-resolved to separate collisional and radiative effects, can function both as a source of soft x rays and as the ionized plasma. The newly developed spectroscopic technique of varied line-space plane gratings is used to provide high spectral resolution at grazing incidence wavelengths, while maintaining stigmatic imaging and the normal incidence focal plane suitable for use with a streak camera detector. We report preliminary results using metal target plasma sources and x-ray film at the detection plane, verifying the predicted performance of the instrument. We have successfully recorded soft x-ray spectra employing two different collecting mirrors to feed convergent light to the grating: (1) a normal incidence multilayered mirror and (2) a grazing incidence Kirkpatrick-Baez mirror system.

The Reflection Grating Spectrometer experiment (RGS) on the X-ray Multi-Mirror Mission spacecraft (XMM) of the European Space Agency (ESA) consists of two identical instruments behind two of the three high throughput X-ray telescopes. The instruments will achieve high energy resolution and high efficiency in the combined first and second order of diffraction in the wavelength range between 5 and 35 A. The design incorporates an array of reflection gratings placed n the converging beam at the exit from the X-ray telescope. The grating stack picks off roughly half of the X-ray light and diffracts it to the array of charge-coupled device (CCD) detectors offset from the telescope focal plane. The remaining light passes undeflected through the grating stack where it can be utilised by instruments located in the focal plane. Both the gratings and the detector are placed on the Rowland circle. The reflection gratings diffract first, second and third order at high to moderate efficiency. The separation of the spectral orders is accomplished using the energy resolution of the CCD detectors. A set of ten CCD-chips (nine for spectroscopy, one for wavelength calibration) are arranged in a strip oriented tangentially to the Rowland circle. Since the optical design is nearly stigmatic, the spectrum of an on-axis point source will appear as a line image along the detector array. In order to reduce noise and dark current an operational temperature of -80°C is adopted for the CCD's. The cooling is provided through a passive radiator. The chips are read out sequentially with a common electronics chain. Each chip is configured in an "image and store" mode in which the image is first acquired over half the chip and transferred to the other half for storage prior to read out.

The predominant cell types in the dermal infiltrate of lichen nitidus are lymphocytes and epithelioid cells. We report two cases of lichen nitidus in which numerous plasma cells were present in the dermal infiltrate.

The X-ray emission from Algol is thought to originate in a corona associated with the K star in this system. We report the results of a 35 hr continuous EXOSAT observation through secondary optical eclipse that was designed to measure the structure of the corona. No obvious X-ray eclipse was seen. The spectrum measured by the ME gives a temperature of 2.5x107 K, consistent with the hard component previously seen by the Einstein SSS. The soft component previously reported by the SSS would only contribute at most 25% to the count rate seen in the LE (used with Al/P). The lack of a hard X-ray eclipse indicates the dimensions of the higher temperature emission region to be comparable to or greater than the size of the K star. An X-ray flare was detected with a peak luminosity of 1.4x1031 erg s-1 and a total duration of 8 hours. The peak temperature was 5.0 keV with an emission measure of 9.4x1053 cm-3. The thermal nature of the flare is confirmed by the detection of an iron line with an EW of ~ 2 keV. By equating the observed decay time of the flare to a known cooling law gives a dimension for the flaring loop of ~ 0.3 stellar radii. This is much smaller than the dimensions of the hard component inferred from the lack of an eclipse. It seems probable that the flare occurred in one of the loops responsible for the lower temperature component seen by the SSS.

The influence of replication on the X-ray diffraction efficiency of blazed reflection gratings is studied by measurements at 0.834 and 1.334 nm. Full electromagnetic calculations show that the differences in the diffraction efficiency of the first generation replicas can be explained by rounding off of the tops of the grooves as measured by stylus measurements of the groove profiles. The efficiency degradation of the second generation replica can not easily be attributed to a different groove shape. The cause of this degradation is as yet unclear. The apex angle of a blazed X-ray grating is not a critical parameter for its efficiency.

We have developed a rapid, nonradioactive large scale method for the detection of ras oncogenes in human tumors. DNA is amplified by the polymerase chain reaction (PCR), and then digested with specific restriction enzymes to detect either endogenous or primer-mediated Restriction Fragment Length Polymorphisms (RFLPs). We report here that three of 15 colon tumors tested contain K-ras codon 12 aspartic acid mutations and one, along with the HCT 116 colon carcinoma cell line, contains a K-ras codon 13 aspartic acid mutation. On the other hand, we did not detect H- or K-ras codon 12 mutations or the K-ras codon 13 aspartic acid mutation in 25 esophageal and 27 gastric cardia tumors isolated from patients in Lin-xing County, China. By incorporating nucleotide substitutions in PCR primers, this method can be applied towards the rapid, non-radioactive screening of virtually any genetic disease caused by known point mutations.