Thin Glass Capillary Research Articles

A novel radioactivity microsensor for high spatial resolution measurements of β radiation

We developed a microsensor for the detection of β‐radiation with submillimeter spatial resolution. The microsensor consists of a scintillating sphere (diameter 100‐300 µm) glued to a tip of an optical fiber (core diameter 140 µm) enclosed in a thin glass capillary. The scintillating sphere was made by embedding YLu scintillation powder and TiO2 light scattering particles in a methacrylate matrix. Photons generated in the scintillator by the β‐particles are guided through the fiber and detected by a photomultiplier connected to the opposite fiber end. The photon counts generated by the photomultiplier are linearly proportional to the volume‐specific radioactivity in the sample. The background signal can be suppressed practically to zero if two fibers connected to two photomultipliers working in coincidence are used. This, however, results in slightly diminished sensor performance (lower sensitivity and signal‐to‐noise ratio). As examples of applications, the diffusion coefficients of 36Cl‐, H14CO3−, and 45Ca2+ in agar‐solidified saline water were measured, and the depth distribution of primary productivity in an intact microbial mat was determined from vertical profiles of 14C after incubation in the light using H14CO3− as tracer.

Analysis of liquid flow into thin capillaries for small weber numbers

Flow of liquids into thin glass capillaries for small Weber and Reynolds numbers is considered. It is found that the flow velocity profile under such conditions of filling of capillaries may noticeably differ from the Poiseuille profile, the difference being determined by adhesion properties of the material.

Focus on spectroscopy

Focus on spectroscopy

Impact of agglomeration on the quantitative assessment of Bacillus stearothermophilus heat inactivation

The impact of agglomeration on the quantitative assessment of thermal spore inactivation was investigated. The agglomeration size distribution in suspensions of Bacillus stearothermophilus spores was determined by using a three-fold dynamic optical back-reflexion measurement (3D ORM). Thermal inactivation data have been modelled using first-order inactivation kinetics, superimposed by the agglomeration size. Since 3D ORM accurately yields the maximum length of an agglomerate, but provides no information on the packing density, two limiting cases have been discriminated in mathematical modelling: three-dimensional, spherical packing for maximum spore count and two dimensional, circular packing for minimum spore count of a particular agglomerate. Thermal inactivation studies have been carried out in thin glass capillaries, where by using numerical simulations the non-isothermal conditions were modelled and taken into account. It is shown that the lag phase often found in thermal spore inactivation (shoulder formation) can sufficiently be described by first-order inactivation kinetics when the agglomeration size is considered.

Transient eutectic solidification in In–Bi–Sn: Two-dimensional experiments and numerical simulation

A technique widely used for the in situ observation of microstructure formation in transparent organic systems was applied to metallic alloys with low melting temperature. In the ternary eutectic alloy system In–Bi–Sn, we observed by light microscopy steady state and transient eutectic microstructure formation during unidirectional solidification in thin (5–10 μm) glass capillaries. Starting from an equilibrated planar single-phase front in a slightly off-eutectic alloy we studied the dynamic processes like nucleation of univariant, and finally invariant ternary eutectic when the liquid transforms into three distinct solid phases. Numerical microstructure simulation was performed by applying a general multiphase and multi-component phase field model which couples directly to the complete thermodynamic dataset of the In–Bi–Sn alloy system. Via comparison of the experimental to the simulated data some thermo-physical values like diffusion coefficients and critical undercooling for nucleation have been evaluated.

Variation of Conductivity of Fullerite Structures Under Different Types of Pressure

It is known that the conductivity of fullerite depends on the applied pressure. In this paper we compare the variation of conductivity of three different fullerite structure with pressure. We examined <TEX>$C_{60}$</TEX> powder, filled into thin glass capillaries and also studied fullerite nanotubules produced within etched swift heavy ion tracks in polymer foils. These investigations are compared with the results of planar Si-<TEX>$C_{60}$</TEX>-Au structures.

Low-Frequency Raman Spectroscopy of Oxyethylene/Oxybutylene/Oxyethylene Triblock Copolymers

C NMR gave accurate values of the chain lengths of the precursor poly(oxybutylene)s and the overall compositions of the copolymer, and thus the average molecular formulas. Comparison of the intensities of the 13 C NMR signals from end and junction groups confirmed triblock architecture. Copolymers with short E-blocks (m < 35) contained a proportion of chains with uncapped B-block ends. The average formulas were not corrected using this information, as noted in subsequent discussion. Raman Spectroscopy. Dried samples were melted and drawn into thin-glass capillaries which were then sealed in air taking precautions to exclude moisture. The samples were again melted and cooled slowly to -20 °C over a period of ca. 1 h at a cooling rate of ca. - 1° C min -1. One sample was melted and cooled rapidly to -20 °C. All spectra were recorded with the samples at -20 °C. Raman scattering at 90° to the incident beam was recorded by means of a Spex Ramalog spectrometer fitted with a 1403 double monochromator and with a third (1442U) monochromator operated in scanning mode. The light source was a Coherent Innova 90 argon ion laser operated at 514.5 nm and 400 mW. Conditions for the low-frequency range were bandwidth BW ) 0.5 cm -1 , scanning increment SI ) 0.1 cm-1, integration time IT ) 10 s. The low-frequency scale was

Surgical transfer of in vivo produced farmed European polecat (Mustela putorius) embryos

Surgical embryo transfer of farmed European polecat ( Mustela putorius) was investigated as part of an ex situ preservation project. The long-term objective of the project is to develop effective technology for ex situ conservation of the European mink ( Mustela lutreola), which is a highly endangered aboriginal European species. Twenty European polecat females, which served as a model species for the European mink, were humanely killed 4–9 days after first mating and embryos were recovered from oviducts and uteri. Donor–recipient pairs ( n=16) were generated by mating the donors ( n=20) once a day for 2 consecutive days with fertile males and by mating the corresponding recipients ( n=16) on the same days with vasectomized males. An embryo recovery rate of 70% (200 recovered embryos/284 corpora lutea) was achieved from 20 donors. Morulae and blastocysts were recovered between Days 5 and 9 after first mating and were regarded as the best developmental stages for uterine embryo transfer. A total of 172 embryos were transferred surgically under general anaesthesia into the ovarian third of the left uterine horn of 16 recipients with a thin glass capillary. Eleven recipients (69%) produced 72 pups equivalent to an average success rate of 42% (72 pups/172 transferred embryos). The average litter size was 4.5 (range 0–9). These results with this model species, farmed European polecat, demonstrate the potential of embryo transfer as an effective method for the preservation of the endangered European mink ( M. lutreola). These species are closely related and have a similar reproductive physiology. However, success of applying embryo transfer in conserving European mink is still dependent on further studies both into its reproductive physiology and developing of improved flushing techniques for anaesthetized donors and the successful transfer of frozen–thawed embryos.

Dextran-modified surface for highly sensitive chemiluminescent ELISA

A highly sensitive chemiluminescent ELISA for 2,4-dichlorophenoxyacetic acid (2,4-D), based on disposable thin-glass capillaries, was developed. The amino-silanised glass capillaries were coated by covalently attaching activated carboxymethyl (CM) dextran of different sizes, to which monoclonal antibodies were coupled. A competitive immunoassay was performed using horseradish peroxidase (HRP)-labelled 2,4-D and a commercially available chemiluminescent substrate. The bound fraction of the 2,4-D-HRP conjugate was quantified by measuring the intensity of the emitted light using a photomultiplier tube detector (PMT). The proposed method resulted in highly improved sensitivity with an IC50 value of 0.002 ng ml−1 for capillaries coated with high molecular weight dextran.

X-ray focusing test and x-ray imaging test by a microcapillary x-ray lens at an undulator beamline

A first focusing test of the undulator radiation at SPring-8 has been done using two types of x-ray refractive lenses in thin glass capillaries. One (lens No. 1) contained bubbles in a glue whereas the other (lens No. 2) contained bubbles in glycerol. The capillaries had inner diameters of 0.2 and 0.8 mm, respectively. Using x rays of 17–18 keV, the undulator source image was investigated at the focal plane. The spherical aberrations and the field distortions were carefully examined by taking the images of a gold mesh. Lens No. 1 had an advantage of high transmissivity in the hard x-ray region (18% at 18 keV) and high tolerance to severe radiation damage, e.g., ∼5×1012 photons/s/0.03 mm2 of the 18 keV x rays for an exposure time of 1 h. On the other hand, lens No. 2 had an advantage of a large aperture, 0.8 mm, and a small field distortion, e.g., less than 10% inside a diameter of 300 μm.

Generation of charged droplets by field ionization of liquid helium

Positively charged helium droplets were produced by ionization of liquid helium in an electrostatic spraying experiment, in which fluid emerging from a thin glass capillary was ionized by applying a high voltage to a needle inside the capillary. At 2.2 K, fine droplets (m in diameter) were produced in pulsed sprays or showers with total currents as high as 0.4 A at relatively low voltages (2-4 kV). Ionization was accompanied by a visible glow at the needle and glass tips. Droplet formation was suppressed at 3.5 K. In contrast, liquid nitrogen formed a well-defined Taylor cone with droplets having diameters comparable to the jet (m) at much lower currents (3 nA) and higher voltages (9 kV), in agreement with previous results. The mechanism for charging in these liquids was proposed to be field ionization, identical to the processes leading to conduction in cryogenic insulating liquids observed by Gomer. The high currents resulting from field ionization in helium, together with the intrinsically low surface tension of helium I, led to charge densities that greatly exceeded the Rayleigh limit, thus preventing formation of a Taylor cone and resulting in Coulomb explosion of the liquid.

Structural characterization of Langmuir–Blodgett films by X-ray diffraction in transmission geometry

In this paper, we present a method which employs X-ray diffraction in transmission geometry for structural determination of Langmuir–Blodgett (LB) films. The LB multilayers are deposited on the outer surface of a thin glass capillary and diffraction pattern was recorded using a pin-hole flat camera. The remarkable advantage of this method is that both the multilayer reflections and in-plane reflections are recorded in one diffraction pattern which provides the following information about the film: layer thickness, electron density profile normal to the layers, in-plane packing of molecules and tilt angle of molecular chains with respect to the plane. As an example, we have determined the lattice parameters and the electron density profile of a lead stearate LB film according to one diffraction pattern where 15 orders of layer reflections and three in-plane reflections were recorded.

DSC And X-Ray Diffraction Coupling

A new technique, that allows simultaneous time-resolved synchrotron X-ray diffraction as a function of temperature (XRDT) and high sensitivity DSC to be carried out in the same apparatus, has been developed. Microcalorimetry and XRDT scans can be performed at any rate between 0.01 and 10°C min−1 with a 0.01°C temperature resolution in the temperature range, 30–130°C and at lower cooling rates but the same heating rates in the −30–+30°C range. The use of a single and very small sample (1 to 20 μl) contained in a thin glass capillary for both measurements and simultaneous data collection prevents any temperature shift between recordings and any possible difference in the thermal histories of the samples.

Enhanced excitation energy transfer in microdroplets — a study by time-resolved fluorescence microscopy

Time-resolved fluorescence microscopy was used to study the fluorescence quenching of rhodamine 6G (R6G) in single microdroplets with diameters equal to or larger than 2 μm. The microdroplets were prepared by dispersing ethylene glycol solutions of R6G in silicone oil. The fluorescence lifetime of R6G was found to be independent of the size of the droplet at low concentrations (1.0 × 10 −4 M or less; a value of 3.60 ± 0.02 ns was observed, which was measured for the bulk solution in a thin glass capillary, indicating that neither the radiative process nor the intramolecular radiationless processes of R6G were influenced by the size of the droplet for droplets greater than 2 μm in diameter. However, a significant size effect on the fluorescence decay was observed at higher concentrations of R6G. At the highest concentration of R6G (5.2 × 10 −3 M) examined in this work, the apparent fluorescence lifetime decreased from 3.60±0.02 ns for droplets larger than 20 μm in diameter to approximately 0.4 ± 0.07 ns for the smallest droplet of 2 μm in diameter. Despite such a significant decrease in the fluorescence lifetime, the decay curves could be analysed satisfactorily by fitting to single exponential functions. When malachite green (MG) was added as an acceptor to a solution of R6G (10 −4 M), a large enhancement of Förster-type energy transfer from R6G to MG, as compared with the bulk solution, was observed for droplets with diameters of less than 10 μm. In this case, all the decay curves obtained were well described by the function derived from the Förster-type energy transfer, but the effective critical distance increased by approximately a factor of two on going from a 10 μm droplet to a 2 μm droplet. On the other hand, the fluorescence quenching of R6G by potassium iodide (KI) showed only a small size effect on the quenching rate constant. The significant size effect observed for droplets of concentrated R6G solution can be interpreted in terms of enhanced Förster-type energy migration, followed by energy trapping by dimers of R6G which act as quenching centres.

Glial reactivity in the retina of adult rats

The present study aimed to characterize the reaction of mammalian (rat) retinal macroglia (Müller cells and astrocytes) to disturbances of their environment in the form of intraorbital section of the optic nerve, intraocular insertion of a thin glass capillary (without damage to the retina) or a combination of both. Glial reactivity was assessed through the use of a battery of antibodies which recognise four different proteins--glial fibrillary protein (GFAP) and three other proteins designated respectively MA1, 4D6 and 4H11. Retinal astrocytes did not exhibit any changes in normally expressed GFAP or MA1. By contrast, the expression of GFAP and MA1 in Müller cells increased 14 days following section of the optic nerve and/or intravitreal insertions of a glass capillary. Three days postoperatively, the expression of GFAP, but not MA1, had already increased significantly in Müller cells. 4D6 and 4H11 proteins were not expressed in astrocytes. In Müller cells, the levels of these proteins increased significantly following combined optic nerve section and intraocular insertion of a glass capillary. Thus, a mechanical disturbance of the intraocular environment constitutes a more effective stimulus in increasing the expression of some Müllerian proteins than damage to the axons of retinal ganglion cells. Such changes have important implications for various ocular treatments that involve intraocular administration of drugs, as well as for the survival/regeneration potential of retinal ganglion cells undergoing Wallerian degeneration.

ν τ — Detection using a new capillary target

New searches for ν μ - ν τ oscillation have recently been motivated by the observed solar neutrino deficit and requirements from cosmology. To achieve further progress in this field a new active target is being developed, based on coherent arrays of thin glass capillaries filled with organic liquid scintillator. The physics motivation is explained, the detector layout and test beam results are presented.

Diffusional edge enhancement observed by NMR in thin glass capillaries

In NMR microscopy the effect of molecular diffusion is usually to degrade resolution and sensitivity due to destructive interference of signals from the moving spins. In samples there may exist regions that differ markedly in the translational diffusion coefficient of the molecules whose spatial distribution is being imaged, and in particular, samples may contain barriers impermeable to the translating spins. We present an experimental demonstration that, in the presence of a magnetic field gradient, a reduction in the translational mean free path of liquid molecules, due to barriers, results in the enhancement of magnetization near barriers. Monte Carlo simulations are compared with experiments. The observed effects are induced by barriers not compartmentalization. This edge enhancement may provide a means through NMR microscopy of visualizing small impermeable structures that might otherwise be invisible.

Finding of Columnar Phases of a Thermotropic-Liquid Crystalline Polypeptide

It is shown that the polymer (NHCH[CH 2 CH 2 CO 2 H]CO) x -(NHCH[CH 2 CH 2 COO(CH 2 ) 6 OPhOCH 3 ]CO) y after making spontaneous orientation in a thin X-ray glass capillary is in columnar mesophase both in crystalline and liquid crystalline states. The molecular packing is rectangular in crystalline state and hexagonal in liquid crystalline state to better pack the polymer helices with alkyl side chains which are stiff, extending perpendicular to the polymer helix in the former state and flexible in the latter state.

Computer modeling for optical waveguide sensors

A two-layer model for the analysis of an optical waveguide chemical vapor sensor is developed using a program written for a low-cost (PC) computer, which takes into account a nonadsorbing glass-fluid interface, the number of optical reflections, and probe beam divergence, for angles of incidence which are skewed about the critical angle for total internal reflection. This model is applied in the analysis of condensed organic vapors employing an uncoated optical thin walled glass capillary device developed at NRL. Reasonable agreement is obtained between the experimental results and model predictions.

Further Studies on Radiocolloids

Summary The continuous measurement of the diffusion of radiocolloids is made possible by use of a photomultiplier tube viewing a ZnS-covered and thin walled glass capillary inside which the α-radiating particles diffuse in aqueous suspension and get adsorbed at the surface. The method was shown to yield satisfactory results for the particle size of alumina powder of known grain size distribution tagged with (Pb+Bi)-212 or Po-210. Po-210 radiocolloids were found to have an average radius of about 10-4 cm and a "specific" radioactivity of about 10-4 whereas the values for radioactive particles generated by decay of Rn-220 in very pure water were 10-6 cm and about 10-4. This means that "pure" (carrierfree) radiocolloids could not be shown to exist.