Interferometry of the intensity fluctuations in light III. Applications to astronomy

1958 ◽  
Vol 248 (1253) ◽  
pp. 199-221 ◽  
Keyword(s):  
Spectral Type ◽  
Resolving Power ◽  
Apparent Brightness ◽  
Naked Eye ◽  
Double Stars ◽  
Cool Stars ◽  
Main Mirror ◽  
The Individual ◽  
Low Sensitivity ◽  
Intensity Interferometer

A theoretical analysis is given of the application of an intensity interferometer to the measurement of the angular diameters of stars and the performance of such an instrument is calculated for representative parameters of the apparatus. It is shown that observations with an intensity interferometer are probably limited by the inherently low sensitivity of the technique to the stars visible to the naked eye, but that the resolving power, which is determined by the limitations of radio rather than of optical technique, should be great enough to measure any star, however hot, of sufficient apparent brightness; furthermore, the operation should be substantially unaffected by atmospheric scintillation. Very cool stars of adequate apparent brightness would be completely resolved by the individual mirrors of an intensity interferometer and this fact limits the technique to stars of spectral type earlier than about K 5. However, a modified form of interferometer using a single main mirror should enable this limit to be extended to bright stars of spectral type as late as M 5. Some applications of an intensity interferometer to measurements of both single and double stars are discussed briefly and it is concluded that such an instrument might be of value in astronomy.

scholarly journals Lithium in the Hyades L5 brown dwarf 2MASS J04183483+2131275

2018 ◽  
Vol 615 ◽  
pp. L12 ◽  
Author(s):  
N. Lodieu ◽  
R. Rebolo ◽  
A. Pérez-Garrido
Keyword(s):  
Spectral Type ◽  
Effective Temperature ◽  
Resonance Line ◽  
Resolving Power ◽  
Evolutionary Models ◽  
Maximum Mass ◽  
Brown Dwarf ◽  
Lithium Abundance ◽  
The Individual ◽  
Low Dispersion

Aims. From the luminosity, effective temperature and age of the Hyades brown dwarf 2MASS J04183483+2131275 (2M0418), substellar evolutionary models predict a mass in the range 39−55 Jupiter masses (MJup) which is insufficient to produce any substantial lithium burning except for the very upper range >53 MJup. Our goal is to measure the abundance of lithium in this object, test the consistency between models and observations and refine constraints on the mass and age of the object. Methods. We used the 10.4-m Gran Telescopio Canarias (GTC) with its low-dispersion optical spectrograph to obtain ten spectra of 2277 s each covering the range 6300–10 300 Å with a resolving power of R ~ 500. Results. In the individual spectra, which span several months, we detect persistent unresolved Hα in emission with pseudo equivalent widths (pEW) in the range 45–150 Å and absorption lines of various alkalis with the typical strengths found in objects of L5 spectral type. The lithium resonance line at 6707.8 Å is detected with pEW of 18 ± 4 Å in 2M0418 (L5). Conclusions. We determine a lithium abundance of log N(Li) = 3.0 ± 0.4 dex consistent with a minimum preservation of 90% of this element which confirms 2M0418 as a brown dwarf with a maximum mass of 52 MJup. We infer a maximum age for the Hyades of 775 Myr from a comparison with the BHAC15 models. Combining recent results from the literature with our study, we constrain the mass of 2M0418 to 45–52 MJup and the age of the cluster to 580–775 Myr (1σ) based on the lithium depletion boundary method.

scholarly journals Comparing the Diagnostic Value of Serum D-Dimer to CRP and IL-6 in the Diagnosis of Chronic Prosthetic Joint Infection

2020 ◽  
Vol 9 (9) ◽  
pp. 2917
Author(s):  
Thomas Ackmann ◽  
Burkhard Möllenbeck ◽  
Georg Gosheger ◽  
Jan Schwarze ◽  
Tom Schmidt-Braekling ◽  
...  
Keyword(s):  
Sensitivity And Specificity ◽  
Joint Infection ◽  
Revision Arthroplasty ◽  
Preoperative Assessment ◽  
Diagnostic Value ◽  
Musculoskeletal Infection ◽  
Prosthetic Joint ◽  
The Individual ◽  
Low Sensitivity ◽  
D Dimer

Introduction: D-dimer is a diagnostic criterion for periprosthetic joint infection (PJI) of the Musculoskeletal Infection Society (MSIS) in 2018. The aim of this study was to evaluate the serum D-dimer values in comparison to C-reactive protein (CRP) and interleukin-6 (IL-6) for the diagnosis of PJI. Materials and Methods: We included 119 patients (50 women, 69 men; 71 knees, 48 hips) undergoing revision arthroplasty with preoperative assessment of CRP, IL-6, and serum D-dimer. Cases were classified as infected or aseptic based on the MSIS criteria of 2018. Receiver operating curves and Youden’s index were used to define an ideal cut-off value and sensitivity and specificity for the individual parameters, and respective combinations were calculated using cross-tables. Results: The median D-dimer level (2320 vs. 1105 ng/mL; p < 0.001), the median CRP level (4.0 vs. 0.5 mg/dL; p < 0.001), and the median IL-6 level (21.0 vs. 5.0 pg/mL; p < 0.001) were significantly higher in the group of PJI compared to the group with aseptic failure. The calculated optimal cut-off values were 2750 ng/mL (AUC 0.767) for D-dimer, 1.2 mg/dL (AUC 0.914) for CRP, and 10.0 pg/mL (AUC 0.849) for IL-6. D-dimer showed a sensitivity of 38% and specificity of 94%, whereas the CRP and IL-6 had sensitivities of 88% and 76%, and specificities of 87% and 92%, respectively. Conclusion: In comparison with CRP and IL-6, serum D-dimer showed low sensitivity and specificity in our cohort. While CRP and IL-6 combination had the highest sensitivity, a combination of Il-6 and D-dimer or CRP and IL-6 had the highest specificity.

scholarly journals Dark dust and single-cloud sightlines in the ISM

2020 ◽  
Vol 641 ◽  
pp. A35
Author(s):  
R. Siebenmorgen ◽  
J. Krełowski ◽  
J. Smoker ◽  
G. Galazutdinov ◽  
S. Bagnulo
Keyword(s):  
Interstellar Medium ◽  
Spectral Type ◽  
Column Density ◽  
Resolving Power ◽  
High Resolution Spectroscopy ◽  
Luminosity Distance ◽  
Ob Stars ◽  
Dust Extinction ◽  
Heating Source ◽  
Dust Component

The precise characteristics of clouds and the nature of dust in the diffuse interstellar medium can only be extracted by inspecting the rare cases of single-cloud sightlines. In our nomenclature such objects are identified by interstellar lines, such as K I, that show at a resolving power of λ∕Δλ ~ 75 000 one dominating Doppler component that accounts for more than half of the observed column density. We searched for such sightlines using high-resolution spectroscopy towards reddened OB stars for which far-UV extinction curves are known. We compiled a sample of 186 spectra, 100 of which were obtained specifically for this project with UVES. In our sample we identified 65 single-cloud sightlines, about half of which were previously unknown. We used the CH/CH+ line ratio of our targets to establish whether the sightlines are dominated by warm or cold clouds. We found that CN is detected in all cold (CH/CH+ > 1) clouds, but is frequently absent in warm clouds. We inspected the WISE (3−22 μm) observed emission morphology around our sightlines and excluded a circumstellar nature for the observed dust extinction. We found that most sightlines are dominated by cold clouds that are located far away from the heating source. For 132 stars, we derived the spectral type and the associated spectral type-luminosity distance. We also applied the interstellar Ca II distance scale, and compared these two distance estimates with Gaia parallaxes. These distance estimates scatter by ~40%. By comparing spectral type-luminosity distances with those of Gaia, we detected a hidden dust component that amounts to a few mag of extinction for eight sightlines. This dark dust is populated by ≳ 1 μm large grains and predominately appears in the field of the cold interstellar medium.

scholarly journals The Chemical Composition of Cool Stars: II - The Hydrogen Deficient Stars

1985 ◽  
Vol 87 ◽  
pp. 126-150
Author(s):  
David L. Lambert
Keyword(s):  
Chemical Composition ◽  
Spectral Type ◽  
Heavy Elements ◽  
Carbon Stars ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Cool Stars ◽  
Similarities And Differences ◽  
Lyrae Stars

AbstractThe chemical composition of the R Coronae Borealis and cool hydrogen deficient carbon stars is reviewed. Similarities and differences between these stars and the hot He stars are noted. Proposed origins for the hydrogen deficient stars are sketched. Recent claims that normal (spectral type N) cool carbon stars are hydrogen deficient are shown to be unfounded. Attention is drawn to the curious case of pop. II variables (RV Tauri, W Virginis, and RR Lyrae stars) whose atmospheres show striking deficiencies of heavy elements and may be hydrogen deficient.

Beyond Beer's Law: Spectral Mixing Rules

2020 ◽  
Vol 74 (10) ◽  
pp. 1287-1294 ◽  
Author(s):  
Thomas G. Mayerhöfer ◽  
Jürgen Popp
Keyword(s):  
Index Of Refraction ◽  
Resolving Power ◽  
Mixing Rules ◽  
Mixing Rule ◽  
Heterogeneous Samples ◽  
Beer's Law ◽  
Mass Fractions ◽  
Beer’S Law ◽  
The Individual ◽  
Spectral Mixing

Based on Beer's law, it is assumed that the absorbance of a mixture is that of the neat materials weighted by their relative amounts (linear mixing rule). In this contribution, we show that this is an assumption that holds only under various approximations for which no change of the chemical interactions is just one among several. To understand these approximations, which lead incrementally to different well known mixing rules, we finally derive the linear mixing rule from the Lorentz–Lorenz relation, with the first approximation that the local electric field is correctly described in this relation. Further levels of approximation are that the local field equals the applied field (Newton–Laplace mixing rule) and that the change of the index of refraction and, equivalently, absorption is weak (Gladstone–Dale/Arago–Biot mixing rule). Even then the linear mixing rule is only strictly valid if the indices of refraction in the transparency region at higher frequency than the absorption have the same value and the mixing is homogeneous relative to the resolving power of the light (“micro-homogeneous”). Under these preconditions, linear mixing of the individual absorbances is established. We illustrate the spectral differences between the different mixing rules, all of which are based on volume and not on mass fractions, with examples. For micro-heterogeneous samples, a different linear mixing rule governs the optical properties, which refers to the experimental quantities, reflectance, and transmittance. As a result, for such samples, mixtures of already comparably high content give only weak signals due to band flattening, which are hard to distinguish from baseline effects.

Lithium in Cool Stars Detected in EUV Surveys

2000 ◽  
Vol 198 ◽  
pp. 366-367 ◽  
Author(s):  
G. Tagliaferri ◽  
L. Pastori ◽  
G. Cutispoto ◽  
R. Pallavicini
Keyword(s):  
Spectral Line ◽  
Spectral Type ◽  
Rotational Velocity ◽  
Luminosity Class ◽  
Photometric Observations ◽  
Cool Stars ◽  
Active Cool

We selected a sample of active cool stars detected in the EUV band by the ROSAT WFC and performed spectroscopic and photometric observations. We inferred spectral type, luminosity class, distance, binary status, rotational velocity. Here we show the results of the Li abundances determination from the Li I 6707.8 Å spectral line.

Feasibility studies for simultaneous immunochemical multianalyte drug assay by capillary electrophoresis with laser-induced fluorescence

1994 ◽  
Vol 40 (9) ◽  
pp. 1819-1822 ◽  
Author(s):  
F T Chen ◽  
R A Evangelista
Keyword(s):  
Capillary Electrophoresis ◽  
High Efficiency ◽  
Internal Standard ◽  
Feasibility Studies ◽  
Laser Induced Fluorescence ◽  
Resolving Power ◽  
Multiple Drug ◽  
Peak Areas ◽  
The Individual ◽  
Antigen Antibody

Abstract We present a method for the simultaneous quantification of multiple drug analytes in urine, based on combining immunochemical binding with capillary electrophoretic separation. Two fluorescent drug-cyanine (Cy) dye conjugates were prepared as competing species for the immunoassay. Morphine was derivatized with Cy5 (lambda max = 652 nm, epsilon = 215,000 mol-1cm-1 L), phencyclidine (PCP) with Cy5.5 (lambda max = 675 nm, epsilon = 200,000 mol-1cm-1L). The high-efficiency resolving power of the capillary electrophoresis system (20 microns x 27 cm column) separated the individual labeled drugs, and the antigen-antibody complexes were detected by laser-induced fluorescence (laser: 10 mW He-Ne at 632.8 nm) with Cy5 diacid as internal standard. Simultaneous competitive immunoassay of morphine and PCP in urine showed that the free labeled-drug peak areas were proportional to the concentrations of the drug species present in the urine sample. This immunoassay can be performed routinely and reproducibly in &lt; 5 min with analytical detection limits of 4 nmol/L for PCP and 40 nmol/L for morphine.

scholarly journals Cool star empirical temperature scales

1997 ◽  
Vol 189 ◽  
pp. 127-136
Author(s):  
Michael S. Bessell
Keyword(s):  
The Sun ◽  
Temperature Calibration ◽  
Flux Method ◽  
Cool Star ◽  
Temperature Scales ◽  
Historical Paper ◽  
Cool Stars ◽  
Infra Red ◽  
Michelson Interferometry ◽  
Intensity Interferometer

The empirical temperatures scale for cool stars is generally well established. Temperatures are now known with reasonable precision for stars covering the range of spectral types from A to M. In the historical paper by Code, Davis, Bless and Hanbury Brown (Code et al. 1976), six stars between 10000K and 6500K had radii measured by the intensity interferometer and these six, together with the sun formed the basis of the empirical temperature calibration at the time. Since then, many temperatures have been derived for A-K stars (Blackwell & Lynas-Gray 1994; Alonso et al. 1996a) using the Infra-Red Flux Method (see Megessier 1994,5 and this volume), while lunar occultations (Ridgway et al. 1980) and more recently Michelson interferometry (Di Benedetto & Rabbia 1987; Dyck et al. 1996), have been used to measure the radii of K and M giants. It is a tribute to Hanbury Brown's Intensity Interferometer that temperature scales based on its measurements are essentially unchanged by the new data.

II. The functional relations of the motor roots of the brachial and lumbo-sacral plexuses

1881 ◽  
Vol 32 (212-215) ◽  
pp. 12-20 ◽  
Keyword(s):  
Brachial Plexus ◽  
Experimental Research ◽  
Anatomical Dissection ◽  
Naked Eye ◽  
Functional Relations ◽  
Eye Examination ◽  
The Subject ◽  
The Individual

The functions subserved by the plexiform arrangement of the nerves of the limbs, and the mode of distribution of the several roots of the brachial and lumbo-sacral plexuses, have been the subject of frequent speculation and of occasional experimental research; and the question is one of considerable physiological and pathological interest. A mere naked-eye examination of the mode in which the roots unite to form the larger trunks allows of an approximate deter­mination of the possible roots of each trunk; and by more minute dissection and maceration in dissociating liquids, as has been done by W. Krause in the case of the brachial plexus (“Beiträge zur Neurologie der Oberen Extremität,” 1865), the constituent fibres of the nerve-trunks may be determined with greater precision. But it is obvious that anatomical dissection, however minute, is unable to discriminate between the sensory and motor constituents of the nerve-trunks, or to indicate their functional relations and dis­tribution. The only possible methods by which this can be arrived at are by determ ining the effects of excitation or destruction of the individual roots of the plexus.

scholarly journals Differences in the directions of ejection of x-ray photo-electrons from various atomic levels

1929 ◽  
Vol 126 (800) ◽  
pp. 138-143 ◽  
Keyword(s):  
Resolving Power ◽  
X Rays ◽  
Expansion Chamber ◽  
X Ray ◽  
Chamber Method ◽  
Heavy Atoms ◽  
Intensity Measurements ◽  
The Individual ◽  
Radio Corporation Of America ◽  
Slow Electrons

Very valuable studies of the directions in which photo-electrons are ejected by X-rays have been made recently by Williams, Auger, and Anderson. All of these observers, however, used the C. T. R. Wilson expansion-chamber method which, in spite of its power in working with the individual electron, suffers from the disadvantage that the particular energy level in the atom from which the electron is ejected in general cannot be determined. It is true that in the case of heavy atoms such as xenon and bromine, Auger and Anderson succeeded, through the use of X-rays of particular energies, in distinguishing the electrons thrown out of the K level from those thrown out of the L levels, but to go much further in this direction by the expansion-chamber method (and, for example, to distinguish the L I from the L II or L III electrons) seems hopeless. Consequently, the magnetic spectrograph developed by one of us for studying the velocity of the X-ray electrons as a function of the angle of emission was applied to the problem with the results which it is the purpose of this paper to describe. We, as yet, have not succeeded in determining the actual directions of ejection with the precision which has been attained in the expansion-chamber method, but the resolving power of the apparatus for velocities is so large that the particular level in which each electron group originates is in general quite unambiguous. A description of the apparatus used and the procedure followed has been given in the paper referred to above and need not be repeated here. Ballast lamps of the sort developed at the General Electric Company and sold by the Radio Corporation of America (radiotron UV-886) have proved very useful in holding the current through the solenoid which produces the magnetic field constant during the long exposures (100-200 hours) which are necessary. Eastman X-ray plates were used throughout, as they have been found to be the most sensitive of any so far tried (except Schumann plates which are much too irregular for intensity measurements). The work has been seriously handicapped by the lack of sensibility of the photographic plates for slow electrons and by their rapid falling off in sensibility for electrons of velocities below about 12,000 volts. X-ray tubes with silver, molybdenum and copper anticathodes were used. The characteristic radiation from copper is, however, in spite of its intrinsic intensity, too soft to eject electrons with sufficient velocity to give photographic results in a reasonable length of time with the apparatus used. All the results shown below consequently were obtained with the characteristic rays of either silver or molybdenum.

Sign in / Sign up

Export Citation Format

Share Document