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As part of a multi-epoch and multi-wavelength study of the physics of core dominated radio sources we have investigated the occurrence of apparent superluminal motion and other indications for bulk relativistic motion (b.r.m) in a statistically complete, flux density limited (S5GHz ≥ 1Jy) sample of 13 objects with flat radio spectra These sources come from the S5-survey (Kühr et al., 1981) and are optically identified as 7 quasars and 6 BL-Lac objects. They have been observed over a wide range of frequencies, from radio through X-rays (s. Eckart et al., 1986 and references therein). Radiomaps have been obtained at frequencies from 327 MHz to 22.2 GHz with resolutions from arcseconds to 0.2 mas, using the VLA, MERLIN and telescopes of the US- and European-VLBI networks. A recent status report on the VLBI-observations is given by Witzel (1987). In this paper we summarize the results on the direct evidence for b.r.m. in this sample as derived from repeated VLBI-observations at 5 GHz, as well as supporting evidence from SSC-calculations and flux density variability of the 5GHz VLBI core components (Table 1).
Interferometry offers an improvement in the accuracy with which astrometric measurements can be made. Using this technique, radio astronomers together with geodeticists have established a global inertial reference frame that is accurate to 0.1 milliarcseconds. At optical wavelengths, interferometry was first developed by Michelson at the turn of the twentieth century, but due to the complexities of precise beam combination at high speeds, it has lagged in its development. Now, with the availability of lasers, detectors and computers that allow path length compensation on millisecond time scales and distance determination between light collectors with a precision of 0.01 μm, interferometry at optical wavelengths will achieve the results in astrometry comparable to those at radio wavelengths.
We used the Mark III Optical Interferometer on Mt. Wilson in 1991 and 1992 to measure the diameters of 42 stars with 10 nm wide filters centered at 712 nm and at 754 nm. These filters probe the stellar atmosphere in a strong TiO band (712 nm) and in a “continuum” band relatively free of TiO absorption (754 nm). The data were taken on a North-South baseline that could be configured to lengths between 3.0 m and 31.5 m. Observations of the target stars were interleaved with frequent measurements of calibrator stars. The square of the calibrated visibility amplitude V2 was determined as a function of baseline length, and a uniform disk model fitted to these data (for details see Mozurkewich et al. 1991). The average formal error of the diameter measurements - derived from the χ2 of the model fits - is 2.5%. Data for a subset of 12 stars have already been published (Quirrenbach et al. 1993).
Gravitational interaction is a straightforward interpretation of some of the peculiar optical morphologies shown by galaxies. There have also been attempts to study the effects of a gravitational interaction on the radio continuum emission. Statistically, the central radio sources (inner 1 kpc) in interacting spiral galaxies are about three times stronger than in isolated spirals; on the other hand, the intensity of the extended emission does not seem to be affected (Stocke, 1978; Hummel, 1981). Peculiar radio morphologies are not a general property of interacting galaxies, since in the complete sample studied by Hummel (1981) of spirals with a probability ≥0.8 of being physically related to their companion, less than 5% have a peculiar radio morphology.
In the wake of the recent terrorist attacks, such as the 2008 Mumbai hotel explosion or the December 25th 2009 “underwear bomber”, our group has developed a technique (US patent #7368292) to apply differential reflective spectroscopy to the problem of detecting explosives in order to detect terrorist threats. Briefly, light (200-500 nm) is shone on a surface such as a piece of luggage at an airport or a parcel at a courier distribution center. Upon reflection, the light is collected with a spectrometer combined with a camera. A computer processes the data and produces in turn a differential reflection spectrum taken between two adjacent areas of the surface. This differential technique is highly sensitive and provides spectroscopic data of explosives. As an example, 2,4,6, trinitrotoluene (TNT) displays strong and distinct features in differential reflectograms near 420 nm. Similar, but distinctly different features are observed for other explosives such as RDX, PETN or ANFO. Our detection system uses a two dimension detector (CCD camera) which provide spatial and spectroscopic information in each of the two dimensions. By scanning (involving fixed optical equipment and scanning moving bags or parcels on a conveyor belt), the surface to be surveyed the system provide the spatial location of the potential threat. We present in this paper how our detector works and how it is applied to the problem of explosive screening for explosives at airports and mail sorting centers. Additionally, we will present the effect of the explosives morphology on the detection response. In particular we will evaluate the implication on the limit of detection of the instrument as well as discuss the sample morphology with respect to a realistic threat scenario.
Host-matrix gels were prepared by hydrolysis of TEOS with the addition of
cadmium nitrate, formamide as DCCA (drying control chemical additive) and
submitted to a preselected dose of high power ultrasound. The impregnation
of the dry “sonogel” with KSeCN solution under vacuum conditions promoted
the formation of the CdSe nanocrystals and enhanced the mechanical
properties of the matrix. A transparent red xerogel was obtained and
characterized by optical spectroscopy, TEM and SAXS measurements. The
results support a structural model of a porous matrix containing CdSe
nanocrystals exhibiting a bimodal size distribution that depends on the Se
content of the impregnating solutions. The blue shift of the optical
absorption bands reveal the quantum-size confinement effects of CdSe
The electromigration resistance, the sub-micron contact area filling capability, the crystal structure, the preferred orientation, and the CMOS device characteristics of self-ion-enhanced physical vapor deposited aluminum metallizations have been studied. It has been found that optimal conditions can be achieved by increasing the deposition rate and by applying some ionization and acceleration of the aluminum particles.
The quest to improve the high performance in ULSI circuits, is driving the search for new materials with low dielectric constants (k=2.5–3.0) for the back end of the line (BEOL) interconnect structures. Novel SiCOH films comprising Si, C, O and H, have been deposited by a PECVD deposition technique. The films have been characterized as-deposited and after anneals of up to 8 hours at 400°C. The atomic composition of the films has been determined by RBS and FRES analysis and their optical properties have been determined by FTIR and index of refraction measurements. The mechanical properties have been determined by measurements of stress and of crack development velocity in water. Metal insulator silicon structures have been used to test the electrical properties of the SiCOH films. After an initial stabilization anneal, the SiCOH films are thermally stable up to 400°C have low tensile stresses (<50 MPa), an extremely low crack propagation velocity, and a hydrophobic behavior. According to the deposition conditions the films have dielectric constants in the range of 2.8 to 3.5. These film properties, combined with an easy-to-integrate deposition process indicate that the material has a strong potential as an interconnect dielectric.
A porous polymer material, which is made of a two-phase composite and contains 35% porosity with a pore size less than 50Å, is found to have a dielectric constant of 1.8. It absorbs almost no water. The electrical properties, such as capacitance and leakage current, do not change with time and temperature.
The adhesion of thin film polymers will be critical in the integration of low-κ materials into microelectronic processing. This study describes the adhesion of two promising low-κ polymers (polyimide and benzocyclobutene) to a silicon dioxide surface. Critical adhesion values were measured using interface fracture mechanics samples in a double cantilever beam geometry. The effect of subcritical (time-dependent) delamination was also evaluated for these systems. Subcritical debonding data are important in understanding the effect of environment and temperature on interface reliability. To that end, experiments were conducted over a range of humidities to elucidate the effect of moisture on interface delamination. The important effect of the acceleration of debond growth rates due to cyclic loading is also described. In addition, XPS studies are presented to characterize the debond path in these layered systems.
A new TFT-LCD panel with an air-bridge type gate to data line inter-crossing has been proposed and its characteristics have been measured. The proposed structure has air-gap between gate and data line intercrossing. This air-bridge TFT-LCD panel has very small amount of capacitance between gate and data line. The new panel structure achieves 9 times faster signal delay compared with conventional panel, which enables to have enough design margin of over 20-inch diagonal size UXGA panel. We have examined thermal and mechanical durability of new panel to verify capability for commercial AMLCD application.