Intermediate Disk Research Articles

Diffusion-Weighted Magnetic Resonance Imaging of Normal and Degenerative Lumbar Intervertebral Discs: A New Method to Potentially Quantify the Physiologic Effect of Physical Therapy Intervention

Observational, repeated measures design. To determine the reliability of the apparent diffusion coefficient (ADC) calculated from diffusion-weighted magnetic resonance images (MRI) of the nuclear region of lumbar intervertebral discs (IVDs), to investigate the differences in the ADC based upon T2-signal intensity, and to examine the test-retest variation in these measures obtained from subjects undergoing serial, diffusion-weighted MRI scans. Impaired diffusion of water within the lumbar IVD is a central characteristic of degenerative disc disease. Diffusion-weighted MRI scans can provide quantitative estimates of water diffusion and may be useful to evaluate the physiologic effects of healing or the change in hydration related to interventions such as traction, manual therapy, or exercise on normal and degenerative lumbar IVDs. Thirty subjects underwent T2 -weighted and diffusion-weighted lumbar MRI scans. Twenty-one of these subjects underwent a second diffusion-weighted MRI scan 4 to 7 weeks after the initial scan. The ADC was calculated from midsagittal diffusion-weighted images for the IVDs of L1-2 to L5-S1. To assess reliability, repeated measures of the ADC were performed on the first 16 scans. The T2-signal of the nuclear region of each disc was classified as hyperintense, intermediate, or hypointense, and its relationship to the mean ADC of the nuclear region was determined. Test-retest variation in the ADC was described using the coefficient of variation (CV), plus or minus the width of the 95% confidence interval of the standard error of measurement (SEM). Intraclass correlation coefficients for estimates of intrarater and interrater reliability ranged from 0.95 to 0.99 and the SEM ranged from 0.006 to 0.026 X 10-3 mm2/s. The mean ADC was significantly greater for hyperintense IVDs compared to intermediate and hypointense IVDs. The CV plus or minus the 95% CI of the SEM between scans ranged from 9.0% to 13.6% for all discs, 6.1% to 10.1% for hyperintense discs, and 13.1% to 23.7% for intermediate discs. The prevalence of hypointense discs was too low to make meaningful judgments about their normal degree of variation over time. The ADC of the nuclear region of the lumbar IVDs may be reliably measured from diffusion-weighted images. Degenerative discs had lower mean ADC values than normal discs but demonstrated greater variation between scans. Diffusion-weighted imaging may be a useful procedure to assess change in diffusion of water in lumbar discs that occurs over time.

Indocyanine green angiography in Vogt–Koyanagi–Harada disease: angiographic signs and utility in patient follow-up

Firstly, to give a review of characteristic indocyanine green angiographic (ICGA) signs in Vogt-Koyanagi-Harada (VKH) disease and, secondly, to determine the utility of ICG angiography in the assessment and follow-up of choroidal inflammatory activity during initial high-dose inflammation suppressive therapy and during the tapering of therapy. We have first reviewed characteristic ICGA signs in VKH. This is followed by a study of four patients with an acute initial VKH uveitis episode who received regular initial and follow-up angiographic examinations for at least 9 months. Classical ICGA signs were recorded at onset and followed for at least 9 months and were correlated with treatment levels. The treatment consisted of high-dose oral corticosteroids (0.8-1.5 mg/kg) preceded by pulse intravenous methylprednisolone (500-1000 mg) for 3 days in hyperacute cases and followed by very slow tapering with the addition of an immunosuppressive agent in cases of insufficient response. The major ICGA signs that were both consistently present and easy to record in the four VKH patients having an acute initial uveitis episode with a pre-treatment angiography and an angiographic follow-up for a minimum of 9 months include (1) early choroidal stromal vessel hyperfluorescence and leakage, (2) hypofluorescent dark dots, (3) fuzzy vascular pattern of large stromal vessels and (4) disc hyperfluorescence. All patients were treated with high-dose inflammation suppressive therapy: in two patients, within 14 and 21 days after initial symptoms, respectively, and in the other two patients, within 6 weeks. Hypofluorescent dark dots, the most constant and easily recordable sign, was very prominent in all cases at presentation. A 90% to complete resolution of dark dots was noted in all four patients after 4 months of therapy. The other three major angiographic signs, early choroidal stromal vessel hyperfluorescence and leakage, indistinct fuzzy vessels at the intermediate angiographic phase and disc hyperfluorescence resolved in all cases within 8 weeks or less of high-dose inflammation suppressive therapy. In three of the four patients, dark dots reappeared after a mean of 7.8 +/- 2.8 months after onset of therapy when the patients were under a mean corticosteroid dose of 13.2 +/- 6.3 mg per day without any significant clinical or fluorescein angiographic signs, indicating subclinical recurrence. An increase in the inflammation suppressive therapy again brought about angiographic resolution of choroidal subclinical disease in all cases. Choroidal inflammation shown by ICG angiography can be suppressed completely by initial high-dose inflammation suppressive therapy. However, recurrent subclinical choroidal inflammation is detected at the end of the tapering period in a high proportion of cases. This indicates that, in the absence of an ICGA follow-up, undetected smoldering subclinical disease may persist, thereby explaining the frequently reported evolution towards sunset glow fundus despite an apparently controlled disease. This is a clear indication that VKH disease should be followed by ICG angiography and, in the case of choroidal subclinical reactivation, a reversal of therapy tapering and an extension of therapy duration should be considered.

V4140 Sgr: A short period dwarf nova with a peculiar behavior

We report on time series of CCD photometry of V4140 Sgr between 1991 and 2001. The analysis reveals that the object was in the decline from an outburst in 1992 and again in outburst in 2001. The historical light curve collected by amateur astronomers shows low amplitude (1-2 mag) outbursts 5-10 days long, recurrent every 80-90 days, confirming its dwarf nova nature. We derive an outburst decline time scale of 1.2 days mag$^{-1}$. Eclipse mapping techniques were applied to data both in quiescence and in outburst to derive accretion disc surface brightness maps. A distance of $d = 170 \pm 30$ pc is obtained from a method similar to that used to constrain the distance to open clusters. From this distance, disc radial brightness temperature distributions are determined. The temperatures in the quiescent disc vary from $6 000$ K in the inner regions to $3 000$ K near the outer disc and are flatter than the $T \propto r^{-{3/4}}$ law for optically thick steady-state disc. The outburst occurs mainly with a significant increase in brightness of the intermediate and outer disc regions. The disc temperatures remain below the critical effective temperature $T_{\rm crit}$ at all disc radii during outburst. The radial temperature distributions in quiescence and in outburst are significantly different from those of other dwarf novae of similar orbital period. These results cannot be explained within the framework of the disc instability model. We suggest that the small amplitude outbursts of V4140 Sgr are caused by bursts of enhanced mass transfer rate from the secondary star.

The expression of collagen IX in the apical disc of idiopathic scoliosis

To study the distribution of collagen IX gene in the disc and to determine its role in the pathogeny of idiopathic scoliosis (IS). The data included apical disc and intermediate disc from 14 cases of adolescent IS, 26 discs from 13 cases of scoliosis of confirmed pathogeny (CPS), which included 10 cases of congenital scoliosis and neurofibromatosis scoliosis. Six discs were obtained from 3 cases of normal young man served as controls. The distribution of collagen IX was studied in the apical disc of IS by immunohistochemistry and in situ hybridization (ISH) with RNA probe. The figure of collagen IX hybridization in the endplate cartilage was input to the figure analysis system. The mRNA content of collagen IX was compared between each group by SPSS software. Collagen IX was mainly distributed in the inner fibrous annulus, nucleus and endplate cartilage. Collagen IX was secreted by the little round chondrocyte-like cells, which was not expressed in the hypertrophic cells. There was significant difference of collagen IX mRNA content between the concave side of apical disc in the IS and the normal disc(P < 0.05), and also between intermediate vertebrae of CS group and normal. There is no obvious abnormal distribution of collagen IX in the disc of idiopathic scoliosis. Collagen IX may be related to the pathogensis of IS. More investigation such as quantity analysis and protein function determination is needed to confirm its role in the pathogenicity of IS.

HST/FOS time-resolved spectral mapping of IP Pegasi at the end of an outburst

We report an eclipse mapping analysis of time-resolved ultraviolet spectroscopy covering three eclipses of the dwarf nova IP Pegasi on the late decline of the 1993 May outburst. The eclipse maps of the first run show evidence of one spiral arm, suggesting that spiral structures may still be present in the accretion disc 9 days after the onset of the outburst. In the spatially resolved spectra the most prominent lines appear in emission at any radius, being stronger in the inner disc regions. The spectrum of the gas stream is clearly distinct from the disc spectrum in the intermediate and outer disc regions, suggesting the occurrence of gas stream overflow. The full width half maximum of C IV is approximately constant with radius, in contrast to the expected $v\propto{R^{-1/2}}$ law for a gas in Keplerian orbits. This line probably originates in a vertically extended region (chromosphere + disc wind). The uneclipsed component contributes ~4% of the flux in C IV in the first run, and becomes negligible in the remaining runs. We fit stellar atmosphere models to the spatially resolved spectra. The radial run of the disc color temperature for the three runs is flatter than the expected $T\propto{R^{-3/4}}$ law for steady-state optically thick discs models, with $T\simeq{20\,000}$ K in the inner regions and $T\simeq{9000}$ K in the outer disc regions. The solid angles that result from the fits are smaller than expected from the parameters of the system. The radial run of the solid angle suggests that the disc is flared in outburst, and decreases in thickness toward the end of the outburst.

Generalized Oldham Coupling (1st Report, Motion Analysis of Intermediate Element)

This paper deals with a new mechanism, the generalized Oldham coupling., This is a turning block double-slider crank mechanism with circular-arc-sliders and is a cyclical varying speed coupling. Type of a cyclical varying speed motion is decided by form of circular-arc-sliders. The motion of the intermediate element disk is similar to that of the “hula-hoop”, but more complicated. This paper aims at analyzing the motion of the intermediate element of the generalized Oldham coupling. First an instantaneous center of rotation of the intermediate element is found, and the fixed centrode is obtained as the locus of this center in the fixed coordinate system. Secondly the moving centrode is also obtained as the locus of this center in the moving coordinate system attached on the intermediate element. The motion of intermediate element is expressed as the motion that this moving centrode rolls on the fixed centrode.

Flare-induced fountains and buried flares in AGN

We discuss the local physical changes at the surface of an AGN accretion disk after the onset of a magnetic flare. The X-ray irradiation by a flare creates a hot spot at the disk surface where the plasma both heats up and expands in the vertical direction in order to regain the hydrostatic equilibrium. Assuming that the magnetic loop causing the flare is anchored deeply within the disk interior, we derive analytical estimates for the vertical dimension H hot and the optical depth τ es of the heated atmosphere as a function of the position within the spot. We perform computations for various values of the accretion rate m, the fraction f cor of radiation dissipated within the disk corona, and the covering factor f cover of the disk surface with flare-illuminated patches. It turns out that generally we can distinguish three characteristic radial zones within the disk showing a qualitatively different behavior of the heated material. In the innermost regions of the disk (inner zone) the expansion of the disk material is restricted by strong gravitational forces. Further out, the flare source, initially above the disk, soon becomes embedded by the expanding disk atmosphere. At these intermediate disk radii (middle zone) the material is optically thick thus greatly modifying the observed radiation by multiple Compton scattering. We show exemplary spectra models obtained from Monte Carlo simulations illustrating the trends. In the outermost regions of the disk (outer zone) the expanding material is optically thin and its influence on the observed spectra is smaller but pressure gradients in radial directions should cause the development of a fountain-like dynamical structure around the flare source. We discuss the observational consequences of our results.

Primary study on collagen X gene expression in the apical disc of idiopathic scoliosis

To study the distribution of collagen X in the intervertebral disc and determine its role in the pathogeny of idiopathic scoliosis (IS). The data included apical disc and intermediate disc from 14 cases of AIS, 26 discs from 13 cases of scoliosis of confirmed pathogeny which included 10 cases of congenital scoliosis and neurofibromatosis scoliosis (CS group). Six discs were obtained from 3 cases of sudden death of normal young man served as controls. The distribution of collagen X in the apical disc of IS was examined by immunohistochemistry and in situ hybridization (ISH) with RNA probe. The figure of collagen X hybridization in the endplate cartilage was input to the figure analysis system. The mRNA content of collagen X was compared between every 2 groups by SPSS software. Collagen X was mainly distributed around the hypertrophic chondrocyte in the endplate cartilage. Its mRNA was expressed in the hypertrophic chondrocyte. Positive signal was found in the nuclei of several scoliosis patients, which was not related to the pathogeny. The collagen X mRNA contents of the apical disc and intermediated disc of the IS group and of the CS group were significantly higher than those of the normal group (P < 0.05). There was no difference between the IS and CS groups. Collagen X is mainly distributed around the hypertrophic chondrocyte in the endplate cartilage. Its can also be secreted by the chondrocyte-like cells in the nucleus under special condition. Higher expression of collagn X gene in scoliosis patients may be the effects of long term abnormal stress which causes calcification of endplate cartilage. Collagen X expressed in the nucleus may be the result of secretion of chondrocyte-like cells in the disc under abnormal mechanical condition.

Main Memory-Based Algorithms for Efficient Parallel Aggregation for Temporal Databases

The ability to model the temporal dimension is essential to many applications. Furthermore, the rate of increase in database size and stringency of response time requirements has out-paced advancements in processor and mass storage technology, leading to the need for parallel temporal database management systems. In this paper, we introduce a variety of parallel temporal aggregation algorithms for the shared-nothing architectures these algorithms are based on the sequential Aggregation Tree algorithm. We are particularly interested in developing parallel algorithms that can maximally exploit available memory to quickly compute large-scale temporal aggregates without intermediate disk writes and reads. Via an empirical study, we found that the number of processing nodes, the partitioning of the data, the placement of results, and the degree of data reduction effected by the aggregation impacted the performance of the algorithms. For distributed result placement, we discovered that Greedy Time Division Merge was the obvious choice. For centralized results and high data reduction, Pairwise Merge was preferred for a large number of processing nodess for low data reduction, it only performed well up to 32 nodes. This led us to a centralized variant of Greedy Time Division Merge which was best for the remaining cases. We present a cost model that closely predicts the running time of Greedy Time Division Merge.

The disc evolution of V2051 Oph on decline from superoutburst

We present an Eclipse Mapping analysis of ten eclipses taken during decline from superoutburst of the dwarf nova V2051 Oph. On decline from superoutburst the disc cools down considerably from nearly 50 000 K in the intermediate disc (∼0.2 RL1) near maximum to about 25 000 K at the end of our observing run, i.e. within four days. The average mass accretion rate through the disc drops in the same time from 1018 g s−1 to below 1017 g s−1. While in some maps the brightness temperature follows the steady-state model, in others the temperature profile shows flattenings and/or an indication of an inward travelling cooling front with a speed of approximately −0.12 km s−1, possibly a reflected heating front with a speed of +1.8 km s−1 and a newly reflected cooling front with the same speed as the first. Such a scenario has been predicted but has not been observed before. Furthermore, we see a prograde precession of the enlarged disc with a precession period of about 52.5 h in very good agreement with the independently determined superhump period observed by Kiyota and Kato. At the same time, the uneclipsed component — presumably a disc wind — decreases significantly in strength during decline from superoutburst.

Submillimeter lines from circumstellar disks around pre-main sequence stars

Observations of submillimeter lines of CO (up to J=6-5), HCO+, HCN (up to J=4-3) and their isotopes from circumstellar disks around low mass pre-main sequence stars are presented. The different line ratios and optical depths indicate that most of the observed line emission arises from an intermediate disk layer with high densities of 1E6-1E8 cm-3 and moderately warm temperatures in the outer regions. The data are compared with three disk models from the literature using a full 2D Monte Carlo radiative transfer code. The abundances of the molecules are constrained from the more optically thin 13C species and indicate depletions of 1-30 for LkCa 15 and very high depletions of > 100 for TW Hya with respect to dark cloud abundances. Evidence for significant freeze-out (factors 10 or larger) of CO and HCO+ onto grain surfaces at temperatures below 22 K is found, but the abundances of these molecules must also be low in the warmer upper layer, most likely as a result of photodissociation. A warm upper layer near the surface of a flaring disk heated by stellar and interstellar radiation is an appropriate description of the observations of TW Hya. LkCa 15 seems to be cooler at the surface, perhaps due to dust settling.

Spatially resolved spectra of the accretion disc of the nova-like variable UU Aquarii

Time-resolved spectroscopy of the nova-like variable UU Aquarii is analysed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from disc centre in the range 3600–6900 A. The spatially resolved spectra show that the continuum emission becomes progressively fainter and redder for increasing disc radius – reflecting the radial temperature gradient – and reveal that the H i and He i lines appear as deep, narrow absorption features in the inner disc regions, transitioning to emission with P Cyg profiles for intermediate and large disc radii. The spectrum of the uneclipsed component has strong H i and He i emission lines plus a Balmer jump in emission, and is explained as optically thin emission from a vertically extended disc chromosphere+wind. Most of the line emission probably arises from the wind. The spatially resolved spectra also suggest the existence of gas stream ‘disc-skimming’ overflow in UU Aqr, which can be seen down to R≃0.2RL1. The comparison of our eclipse maps with those of Baptista, Steiner & Horne suggests that the asymmetric structure in the outer disc previously identified as the bright-spot may be the signature of an elliptical disc similar to those possibly present in SU UMa stars during superoutbursts.

Resonance Rings and Galaxy Morphology

Rings of star formation are a common phenomenon of early to intermediate Hubble type disk galaxies. Most rings form by gas accumulation at resonances, usually under the continuous action of gravity torques from a bar pattern, but sometimes in response to a mild tidal interaction with a nearby companion. In either case, a resonance is a very special place in any galaxy where star formation can be enhanced and may proceed either as a starburst or continuously over a long time period. This article describes the characteristic morphologies of bar-driven and tidally-driven resonance rings.

Ages and Metallicities of LMC Clusters and Their Surrounding Fields

We report on a survey of 25 candidate old LMC clusters. Washington photometry was obtained on the CTIO 0.9m in &lt; 1h, reaching below the turnoff. Ages based on the magnitude difference δT1 between the giant branch clump and the turnoff revealed that no new old clusters were found. The candidates all turned out to be of intermediate age (1–3 Gyr). We confirm that there was apparently no cluster formation in the LMC from 3–9 Gyr ago, and that there was a pronounced epoch of cluster formation beginning 3 Gyrs ago that peaked at ~1.5 Gyrs ago. We also determine ages for the surrounding fields, as well as metallicities for both the clusters and fields from the color of the giant branch. In most cases the stellar population of each cluster is quite similar to that of its field. The mean metallicity for the intermediate age outer disk clusters is −0.65. A few clusters stand out in the age-metallicity relation in the sense that they are intermediate age clusters at relatively low metallicity. In the northern part of the LMC disk 3 fields all have a secondary clump ~0.45 mag fainter than the dominant clump, suggesting a component located behind the LMC at a distance comparable to that of the SMC.

HST spatially resolved spectra of the accretion disc and gas stream of the nova-like variable UX Ursae Majoris

Time-resolved eclipse spectroscopy of the nova-like variable UX UMa obtained with the Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) on 1994 August and November is analysed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disk and gas stream as a function of distance from the disk centre. The inner accretion disk is characterized by a blue continuum filled with absorption bands and lines, which cross over to emission with increasing disk radius, similar to that reported at optical wavelengths. The comparison of spatially resolved spectra at different azimuths reveals a significant asymmetry in the disk emission at ultraviolet (UV) wavelengths, with the disk side closest to the secondary star showing pronounced absorption by an 'iron curtain' and a Balmer jump in absorption. These results suggest the existence of an absorbing ring of cold gas whose density and/or vertical scale increase with disk radius. The spectrum of the infalling gas stream is noticeably different from the disc spectrum at the same radius suggesting that gas overflows through the impact point at the disk rim and continues along the stream trajectory, producing distinct emission down to 0.1 R(sub LI). The spectrum of the uneclipsed light shows prominent emission lines of Lyalpha, N v lambda1241, SiIV Lambda 1400, C IV Lambda 1550, HeII Lambda 1640, and MgII Lambda 2800, and a UV continuum rising towards longer wavelengths. The Balmer jump appears clearly in emission indicating that the uneclipsed light has an important contribution from optically thin gas. The lines and optically thin continuum emission are most probably emitted in a vertically extended disk chromosphere + wind. The radial temperature profiles of the continuum maps are well described by a steady-state disc model in the inner and intermediate disk regions (R greater than or equal to 0.3R(sub LI) ). There is evidence of an increase in the mass accretion rate from August to November (from V = 10 (exp -8.3 +/-0.1) to 10(exp -8.1 +/- 0.1 solar mass yr(exp -1)), in accordance with the observed increase in brightness. Since the UX UMA disc seems to be in a high mass accretion, high-viscosity regime in both epochs, this result suggests that the mass transfer rate of UX UMA varies substantially (approximately equal to 50 per cent) on time-scales of a few months. It is suggested that the reason for the discrepancies between the prediction of the standard disk model and observations is not an inadequate treatment of radiative transfer in the disc atmosphere, but rather the presence of addition important sources of light in the system besides the accretion disk (e.g., optically thin contiuum emission from the disk wind and possible absorption by circumstellar cool gas).

HST spatially resolved spectra of the accretion disc and gas stream of the nova-like variable UX Ursae Majoris

Time-resolved eclipse spectroscopy of the nova-like variable UX UMa obtained with the HST/FOS on 1994 August and November is analysed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from the disc centre. The inner accretion disc is characterized by a blue continuum filled with absorption bands and lines, which cross over to emission with increasing disc radius, similar to that reported by Rutten et al. at optical wavelengths. The comparison of spatially resolved spectra at different azimuths reveals a significant asymmetry in the disc emission at ultraviolet (UV) wavelengths, with the disc side closest to the secondary star showing pronounced absorption by an ‘iron curtain’ and a Balmer jump in absorption. These results suggest the existence of an absorbing ring of cold gas whose density and/or vertical scale increase with disc radius. The spectrum of the infalling gas stream is noticeably different from the disc spectrum at the same radius suggesting that gas overflows through the impact point at the disc rim and continues along the stream trajectory, producing distinct emission down to 0.1 RL1. The spectrum of the uneclipsed light shows prominent emission lines of Lyα, N vλ 1241, Si ivλ 1400, C ivλ 1550, He iiλ 1640, and Mg iiλ 2800, and a UV continuum rising towards longer wavelengths. The Balmer jump appears clearly in emission indicating that the uneclipsed light has an important contribution from optically thin gas. The lines and optically thin continuum emission are most probably emitted in a vertically extended disc chromosphere + wind. The radial temperature profiles of the continuum maps are well described by a steady-state disc model in the inner and intermediate disc regions (R ≤ 0.3 RL1). There is evidence of an increase in the mass accretion rate from August to November (from M. = 10−8.3 ± 0.1 to 10−8.1 ± 0.1 M⊙ yr−1), in accordance with the observed increase in brightness. Since the UX UMa disc seems to be in a high mass accretion, high-viscosity regime in both epochs, this result suggests that the mass transfer rate of UX UMa varies substantially (≃ 50 per cent) on time-scales of a few months. It is suggested that the reason for the discrepancies between the prediction of the standard disc model and observations is not an inadequate treatment of radiative transfer in the disc atmosphere, but rather the presence of additional important sources of light in the system besides the accretion disc (e.g. optically thin continuum emission from the disc wind and possible absorption by circumstellar cool gas).

Stability Behavior of a Shaft-Disk System Subjected to Longitudinal Force

The stability behavior of a spinning Timoshenko shaft with an intermediate attached disk subjected to a longitudinal force is analytically studied. The expressions of frequency (whirl speed) equations for hinged‐hinged, hinged ‐clamped, clamped ‐hinged, and clamped ‐clamped rotors are given. By using the numerical technique, the critical axial and follower loads are sought. Numerical results reveal that the instability mechanisms are complex. Eight different types of instability mechanisms are presented. The critical load jump is possible when the instability mechanism changes from one to another. Furthermore, in some special cases, the critical longitudinal loads are almost zero; therefore, such a rotor combination is extremely unstable and should be avoided for design purposes. Nomenclature A = area of cross section of the shaft ai, bi = coefe cients given by Eqs. (21) and (22), respectively Ci, ¯ Ci = integration constants E = Young’ s modulus G = shear modulus hi = coefe cients given by Eq. (26) I = moment of inertia of the shaft cross section ID, IP = diameter and polar mass moments of inertia of the disk ¯D = nondimensional diameter mass moment of inertia of the disk Id, Ip = diameter and polar moments of inertia per unit length of the shaft j = 1 L = length of the shaft L1 = distance between the left end and the intermediate disk

A Model of the Broad-Band Continuum of NGC 5548

We discuss a model of the central source in Seyfert 1 galaxy NGC 5548. The model assumes a three phase disk structure consisting of a cold outer disk, a hot central disk constituting a Comptonizing X/γ source, and an intermediate unstable and complex phase emitting a soft excess component. The model qualitatively explains broad-band spectrum and variability behavior assuming that the soft excess contributes significantly to the continuum emission and drives variability by geometrical changes of the intermediate disk zone.

Development of an industrial process for minting a new type of bimetallic coin

This paper introduces a technology for minting a new type of bimetallic coin. The coin is manufactured from two metal disks of different materials, one being very thin, joined together by mechanical means during the impartion of the surface details by the minting dies. The proposed technology is based on a multi-stage process consisting of three cold metal forming operations (preforming, rimming and coining) and one intermediate annealing before the coining operation. The main objective of this work is to present the theoretical and experimental results obtained during the development of the process, which are essential for producing this new type of bimetallic coin. The theoretical analysis was based on the utilization of the finite-element method to characterize metal flow, to establish the process sequence and related intermediate disk geometries, and to design an appropriate geometry for the mechanical joint between the two metal disks. Experiments consisted on the coinage of several bimetallic prototypes in order to confirm the theoretical predictions and to validate the new proposed technology, which latter can be seen as an alternative to the existing bimetallic coin technology based on the utilization of an outer ring and a central disk.

The Extremely Active Single Giant 1E 1751+7046 = ET Draconis: Revised Properties and a Reevaluation of Its Evolutionary Status

New spectroscopic observations have resulted in significant revisions to several of the orginally published properties of the X-ray bright, chromospherically active star 1E 1751+7046: the spectral classification has been revised from K5 IV to K0 III, v sin i from 30-40 km s-1 to 23 km s-1, and the reported nondetection of the Li I 6707 A line to a significant log (Li) = 1.8. Chromospheric and transition region surface fluxes from IUE observations and the coronal surface flux from earlier Einstein data are close to saturation levels, and comparable only to very active binaries, pre-main-sequence stars, and FK Comae itself. IUE observations also recorded a flare. Fifteen new radial velocity measurements show no evidence for a companion and are consistent with intermediate or young disk membership. On the other hand, we show the star to be located about 250 pc above the galactic plane, suggesting an intermediate or old disk object. The new spectral class (Teff) and limits on the luminosity indicate that 1E 1751+7046 is a low-mass star on its first ascent of the giant branch. Photometry from the Four College Consortium Automatic Photometry Telescope is consistent with the recently published photometric period of 13.98 days, and the light curve is well fitted by a model consisting of two large spots at latitudes of ~30° and ~50°. There are currently only two possible evolutionary scenarios for this anomalous star: (a) coalescence from a progenitor W UMa-type contact binary; or (b) the dredge-up of both angular momentum and nuclear processed material in a low-mass (~1-2.5 M☉) giant. A space motion, obtainable once a parallax and proper motion are available from Hipparcos, may resolve the age (old disk-young disk) uncertainty: young disk motions would favor the angular momentum transfer scenario. There is no current theory that can account for the observed lithium abundance.