Hemispherical Glass Research Articles

Axisymmetric Adhesion Test To Examine the Interfacial Interactions between Biologically-Modified Networks and Models of the Extracellular Matrix

The adhesion between artificial extracellular matrixes (ECMs), or scaffolds, and native tissue is an often overlooked component of the tissue engineering design process. Therefore, we developed an axisymmetric adhesion test method to examine the interfacial interactions between hydrogel scaffolds and a model of the articular cartilage ECM. Semi-interpenetrating polymer networks (semi-IPNs), consisting of poly(N-isopropylacrylamide-co-acrylic acid) [P(NIPAAm-co-AAc)] hydrogels and physically entangled linear P(AAc) chains grafted with peptides that bind to hyaluronic acid (HA), were synthesized, and the adhesion between the P(NIPAAm-co-AAc)-based semi-IPNs and hemispherical glass lenses (plain or HA-grafted) was examined as a function of temperature, contact time, and semi-IPN type. The adhesion between the semi-IPNs and the lenses significantly increased with increasing contact time and significantly decreased with increasing temperature, independent of the P(NIPAAm-co-AAc)-based matrix type. Furthermore,...

Novel optical fiber refractometric transducer employing hemispherical detection element

We present the results of a theoretical numerical analysis of a novel fiber optic refractometric transducer. It consists of a hemispherical glass detection element and a pair of the multimode optical fibers attached symmetrically to the element's flat equatorial plane. The internal reflection of light from the element's spherical surface is sensitive to the refractive index of the surrounding medium. We exploit several internal reflections in series and the focusing of the beam by the element's spherical surface to achieve enhanced sensitivity to the refractive index of the surrounding medium and reduced intrinsic optical loss in the transducer. We present the data on the effect of transducer's parameters on its transmission function. We show that the transducer can operate in a relatively wide range of the refractive index of the surrounding medium (we show this for the interval n = 1.0 to n = 1.45). We also present experimental data confirming our theoretical results.

Microspectroscopy Using a Solid Immersion Lens

Oil immersion lenses have been used in optical microscopy for a long time. The light’s wavelength is decreased by the oil’s index of refraction n and this reduces the minimum spot size. Additionally, the oil medium allows a larger collection angle, thereby increasing the numerical aperture. The SIL is based on the same principle, but offers more flexibility because the higher index material is solid. in particular, SILs can be deployed in cryogenic environments. Using a hemispherical glass the spatial resolution is improved by a factor n with respect to the resolution obtained with the microscope’s objective lens alone. The improvement factor is equal to n2 for truncated spheres.As shown in Fig. 1, the hemisphere SIL is in contact with the sample and does not affect the position of the focal plane. The focused rays from the objective strike the lens at normal incidence, so that no refraction takes place.

Uncertainty analysis for roundness measurements by the example ofmeasurements on a glass hemisphere

This paper presents an uncertainty analysis for roundnessmeasurements on a glass hemisphere. The measurements were carried out withthe spindle measuring instrument Talyrond 73. For the correction of spindleerrors, a multi-step error separation technique with ten steps was used.Various input quantities were investigated such as the form deviations ofthe hemisphere, the characteristic of the probing system and thermal drifteffects. Finally, a detailed uncertainty budget was developed. It is shownthat the standard uncertainty for a single profile point is 1.5 nm. Thisresults in a standard uncertainty of u(RONt) = 3 nm for theroundness deviations of the hemisphere.

Slope distribution of a rough surface measured by transmission scattering and polarization

Transmission scattering from medium to air was used to measure the slope distribution of the rough plane surface of a transparent glass hemisphere. A facet model successfully explained the measured results of refraction, scattering, and polarization: Transmission scattering existed for incident angles greater than the critical angle, all measured curves for the normalized scattered intensity versus the facet slope angle for different detection directions overlapped, and the measured polarization of scattering was approximately constant for >99% of the facets. The slope distribution obtained by transmission scattering agrees with those of the surface profiles in the valid range of the profiler and can represent the slope distribution of the rough surface.

Guided-light two-wave-mixing on a spherical surface

A novel guided structure is proposed which is aimed at developing integrated all-optical signal processors exploiting two wave mixing interactions. The structure is based on the whispering propagation on a hemispherical glass substrate and contains a dye-doped photoresist film as the test nonlinear material. Its functionality was demonstrated successfully with two wave mixing experiments that were performed with CW light at 1321 nm and with a probe beam at 647 nm.

Microlenses as amplification for CCD-based detection devices for screening applications in biology, biochemistry, and chemistry

We describe the use of microlenses as amplification for CCD-based detection devices. The possible amplification of a signal in areaction chamber of a nanoplate is estimated with a first-order approximation. This value was proved with a commercially available microlens and with a specially constructed microlens array made of glass hemispheres. Possible applications of this approach to amplification are given.

Friction and wear performance of diamond-like carbon, boron carbide, and titanium carbide coatings against glass

Protection of glass substrates by direct ion beam deposited diamond-like carbon (DLC) coatings was observed using a commercial pin-on-disk instrument at ambient conditions without lubrication. Ion beam sputter-deposited titanium carbide and boron carbide coatings reduced sliding friction, and provided tribological protection of silicon substrates, but the improvement factor was less than that found for DLC. Observations of unlubricated sliding of hemispherical glass pins at ambient conditions on uncoated glass and silicon substrates, and ion beam deposited coatings showed decreased wear in the order: uncoated glass > uncoated silicon > boron carbide > titanium carbide > DLC > uncoated sapphire. Failure mechanisms varied widely and are discussed. Generally, the amount of wear decreased as the sliding friction decreased, with the exception of uncoated sapphire substrates, for which the wear was low despite very high friction. There is clear evidence that DLC coatings continue to protect the underlying substrate long after the damage first penetrates through the coating. The test results correlate with field use data on commercial products which have shown that the DLC coatings provide substantial extension of the useful lifetime of glass and other substrates.

Measurement of birefringence for optical recording of disk substrates

We experimentally investigate the birefringence of bare and coated substrates for magneto-optical recording, using ellipsometry at wavelengths of 632.8 and 780 nm. The polarization rotation and ellipticity of reflected or transmitted light are measured for different incident angles and for different orientations of the incident linear polarization. The measured data are then fitted by the MULTILAYER computer program, which solves the Maxwell equations for a plane wave propagating in a multilayer structure. This approach makes it possible to determine, with high accuracy, the orientations of the principal axes of the substrate and the corresponding refractive indices. The results show that one of the principal axes is always along the substrate's normal direction, but the orientations of the in-plane principal axes can be much different from the radial and track directions. A special feature of the ellipsometers that were used is that a glass hemisphere is placed in contact with the substrate to eliminate refraction of the incident beam. This enables a maximum propagation angle of 70° (with respect to the normal) in the substrate and hence increases the measurement sensitivity. Certain anomalies have been observed, which we believe are associated with the variation of birefringence properties along the thickness direction.

An intercomparison of roundness measurements between ten European national standards laboratories

An intercomparison of high-accuracy roundness measurements has been carried out with the participation of the national standards laboratories of ten European countries. The circulated artefacts were a hemispherical glass standard and a steel disc. A total of eight roundness profiles were examined, two on the hemisphere and six on the disc. The eccentricity between external and internal surfaces of the disc was determined, and the effect of various measuring conditions evaluated. While the overall results show a satisfying agreement for almost all laboratories, room for further improvements still exists. The uncertainty limit was mainly due to the spindle errors of the roundness instruments used in each laboratory. These instruments were proven to be of a good quality at the 0.1 μm level. Below this limit, best results were reported by those laboratories where error separation techniques were available.

Estimate of the structural strength of S94-2 glass in application to deep-water neutrino telescope cases

The experimental characteristics of the strength of S94-2 glass and data on the structural strength of joints in deep-water neutrino telescope cases consisting of pressed 370 and 432 mm in diameter hemispherical glass elements with wall thickness of 10 and 16 mm are examined. The safety factors and values of admissible stresses under compression and bending as well as under conditions of contact compression of the elements by flat metallic supports were established on the basis of an analysis of the obtained characteristics.

Optical properties of normal, diseased, and laser photocoagulated myocardium at the Nd:YAG wavelength

Laser photocoagulation of the myocardium effectively destroys arrhythmogenic foci. The purpose of this study was 1) to compare the optical properties of canine myocardium before and after photocoagulation, 2) to compare the canine model with clinical cases by measuring the optical properties of human myocardium, and 3) to assess the optical properties of human myocardial scar and epicardial fat tissue. Measured optical properties were the absorption coefficient, mu a; scattering coefficient, mu s; and scattering anisotropy factor, g. Optical measurements were performed at 1064 nm wavelength on thin plane parallel tissue slices using the integrating sphere method with glass hemispheres on either side of the sample. The study showed 1) an increase of the scattering coefficient by 40% and a two- to threefold increase in reduced scattering coefficient as a result of photocoagulation; 2) that the mu a (0.035 +/- 0.024 mm-1) and mu s (17.9 +/- 3.8 mm-1) of human myocardium were not significantly different from mu a (0.043 +/- 0.021 mm-1) and mu s (17.3 +/- 2.2 mm-1) of canine myocardium, whereas the human g (0.964 +/- 0.005) was slightly different from the canine g (0.974 +/- 0.008); and 3) that the mu a (0.021 +/- 0.016 mm-1) of epicardial fat and mu s (13.8 +/- 1.1 mm-1) of myocardial scar were significantly lower than those of normal myocardium. A dynamic model of laser-tissue interaction incorporating these changes and inhomogeneities is necessary to better describe light distribution during laser photocoagulation.

Kinetic friction and dynamic elastic contact behaviour of polymers

Friction and contact between a glass hemisphere and plates of various polymers were studied under elastic contact. The contact at various sliding speeds was observed by means of Newton's rings. Although the frictional force was proportional to the area of contact observed, it was necessary to consider the increase in the shearing strength of the adhesive junctions with increasing load W. The area of dynamic contact of low density polyethylene (LDPE) was proportional to W 0.78 in a wide speed range, while the area of static contact was proportional to W 2 3 as expected from Hertz' equation. The shape of the dynamic contact was affected by the retarded elasticity of the polymer and frictional heating. The area of dynamic contact decreased and the shear strength increased in proportion to log v (where v is the speed) provided that frictional heating was negligible. The time dependence of elastic compliance 1 E of LDPE could be obtained by applying Hertz' equation to the dynamic contact observed at various speeds. However, the value of 1 E decreased with decreasing load in sliding. It was shown that the time dependence of elastic compliance plays an important role in determining the area of dynamic contact of polymers.

A computer controlled low energy electron diffractometer for surface crystallography

A new diffractometer has been developed for LEED crystallography. It uses three grid electron optics in front of a large phosphor coated hemispherical glass screen which forms part of the vacuum wall. The LEED pattern on this screen is viewed and intensity data acquired by a computer controlled TV camera. The same computer controls the whole experiment. A predictor-corrector algorithm is used to track the diffracted beams as the primary energy is changed. System evaluation has used a Cu(111) surface and R factor analysis has shown the systematic experimental errors to lead to uncertainty in the fractional surface layer spacing of the order of ±1%. The instrument is thus about twice as accurate and a hundred times faster than conventional LEED systems.

High-level waste glass field burial test: leaching and migration of fission products

In June 1960, 25 nepheline syenite-based glass hemispheres containing the fission products 137Cs, 90Sr, 144Ce and 106Ru were buried below the water table in a sandy-soil aquifer at the Chalk River Nuclear Laboratories of Atomic Energy of Canada Limited. Measurements of soil and groundwater concentrations of 90Sr and 137Cs have been interpreted using non-equilibrium migration models to deduce the leaching history of the glass for these burial conditions. The leaching history derived from the field data has been compared to laboratory leaching of samples taken from a glass hemisphere retrieved in 1978, and also to pre-burial laboratory leaching of identical hemispheres. The time dependence of the leach rates observed for the buried specimens suggests that leaching is inhibited by the formation of a protective surface layer. The effect of the kinetic limitations of the fission-product/sandy-soil interactions is discussed with respect to the migration of 90Sr and 137Cs over a 20 year time scale. It is concluded that kinetically limited sorption by oxyhydroxides, rather than equilibrium ion exchange, controls the long-term migration of 90Sr. Cesium is initially rapidly bound to the micaceous fraction of the sand, but slow remobilization of 137Cs in particulate form is observed and is believed to be related to bacterial action.

Influence of the stiffness of testing machines on the adherence of elastomers

AbstractIt is shown that the introduction of the fracture mechanics concepts, such as the strain energy release rate G, to solve the problem of the adherence of elastomers, the edge of contact being seen as a crack propagating in mode I in the interface, allows one to predict the dependence of the adherence force with the stiffness of testing machines. Moreover, it is shown the general equation of the kinetics of adherence proposed in 1978 by Maugis and Barquins, G–w = wϕ(atv), where w is Dupré's work of adhesion and ϕ a dissipation function characteristic of the material only depending on temperature and crack speed, is confirmed whatever the stiffness of the testing machine and the instantaneous deformation imposed on the system. Experiments realized with a hemispherical glass lens in contact on a polyurethane surface verify theoretical predictions with an accuracy better than 1%.

Spectral differences in glass and perspex thermopile shields and the effects on solar radiation measurements

Anomalies in shortwave and net solar radiation results recorded with solarimeters and perspex shielded pyrradiometers, were investigated. A spectrophotographic analysis showed that glass transmitted 17% more light than perspex over the wave lengths 280–4600 nm. On days with clear skies in spring, glass shielded solarimeters recorded 16.6% higher solar radiation than modified pyrradiometers with perspex shielded thermopiles. The net shortwave radiation measured during the same periods was 26.8% lower than that calculated from solarimeters. Unless proper double glass hemispheres are available to convert all wave pyrradiometers to shortwave radiometers, it would be advisable to use double glass hemisphered solarimeters to record solar radiation. Perspex, therefore, cannot be regarded as a substitute for the superior quality of glass hemispheres in shortwave thermopile shields and for longwave filter material.

Development of an underwater high sensitivity cherenkov detector: Sea urchin

The need for a high gain, high sensitivity Cherenkov light sensor to be used in a deep underwater muon and neutrino detector (DUMAND) array has led to the design of the Sea Urchin detector. In this design a spherical photocathode PMTis optically coupled through a glass hemisphere to a large number of glass spines, each of which is filled with a wavelength-shifting (WLS) solution of a high quantum efficiency phosphor. The Cherenkov radiation is observed in the spine, isotropically re-radiated at a longer wavelength, and a fraction of the fluorescent light is internally reflected in the spine, and guided to the photomultiplier concentrically located in the glass hemisphere. Experiments measuring the optical characteristics of the spines and computer programs simulating light transformation and detection cross sections are described. Overall optical gains in the range 5–10 are achieved. The WLS solution is inexpensive, and may have other applications.

Experimental study of shape imperfections and the load-carrying capacity of hemispherical glass shells

Experimental study of shape imperfections and the load-carrying capacity of hemispherical glass shells

The influence of dynamic loading on sliding friction

THERE have been many studies of the rheology of thin polymeric films in sliding contacts1–4, and many of the results have been obtained with a particular experimental arrangement which involves studying the motion of a glass hemisphere traversing a thin film deposited on a smooth glass flat3–5 (Fig. 1). The development of this subject has concentrated on an important quantity of practical interest, τ, the interfacial shear strength, which may be considered to be the energy dissipated per unit distance per unit contact area. These dissipative processes occurring in a particular film are not generally known. The interfacial shear strength has been found, for a wide range of organic polymers, to depend on many parameters, such as contact pressure, temperature and strain rate, for which simple empirical relations have been found5. Providing the real area of contact can be estimated, these relationships are of value in predicting the friction of certain lubricated contacts. These relationships are broadly similar to those obtained from the study of the variation of the bulk yield stress of polymers and in certain cases the magnitude of the fitting coefficients (for example, τ0 and α below) are similar for a given polymer, in bulk and interfacial shear tests. Direct comparison is difficult because interfacial shear measurements generally correspond to much higher pressures and effective strains and rates of strain. However, it seems that τ may be considered a measure of the bulk shear yield or rupture stress of the organic layer in relatively intense deformation conditions. Using a modification of the basic experimental method we have now obtained detailed information on the effect of velocity or contact time on τ.