Optical Fourier Transforms of Birefringent Fibres

Abstract

A cylindrical birefringent fibre orientated diagonally between two crossed polarizers can be regarded as a single-, double- or multiple-slit source of light, depending on the refractive index of the medium which surrounds the fibre. When normally trans-illuminated by monochromatic light and observed through a polarizing microscope fitted with a condenser-slit diaphragm, the fibre produces specific interference patterns in the exit pupil of the microscope objective. These patterns manifest themselves as optical Fourier transforms. Their properties and possible applications are discussed. The experiments were performed using polymeric textile fibres.     

Some aspects of nanocrystalline nickel and zinc ferrites processed using microemulsion technique

Abstract

Nanocrystalline nickel and zinc ferrites synthesised using a microemulsion technique were characterised by high resolution transmission electron microscopy and vibrating sample magnetometry. A narrow and uniform distribution of crystals of size range 5-8 nm, distinguished by a clear lack of saturation magnetisation at 9 kOe, were obtained. Also, no coercivity or remanence was observed.     

Influence of inhomogeneous broadening on group velocity in coherently pumped atomic vapour

Abstract

We studied experimentally the influence of thermal atomic motion on light propagation in a vacuum atomic vapour cell above room temperature. We found that atomic motion introduces sizable changes in the spectral properties of the medium, such as dispersion and absorption, if the conditions for coherent population trapping are fulfilled. In particular, studying the group delay of light in the atomic vapour, we confirm the theoretical predictions of Kocharovskaya et al. (2001, Phys. Rev. Lett., 86, 628) and demonstrate that a coherent atomic medium has light dragging abilities large enough to make feasible the realization of frozen light based on atomic motion. We also demonstrate that dragging can be observed in measurements of the electromagnetically induced transparency resonance width, as well as in group delay measurements.     

Lanthanide sorbent based on magnetite nanoparticles functionalized with organophosphorus extractants

Abstract

In this work, an adsorbent was prepared based on the attachment of organophosphorus acid extractants, namely, D2EHPA, CYANEX 272, and CYANEX 301, to the surface of superparamagnetic magnetite (Fe₃O₄) nanoparticles. The synthesized nanoparticles were coated with oleic acid, first by a chemisorption mechanism and later by the respective extractant via physical adsorption. The obtained core–shell functionalized magnetite nanoparticle composites were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy, thermogravimetry, infrared absorption and vibrating sample magnetometry. All the prepared nanoparticles exhibited a high saturation magnetization capacity that varied between 72 and 46 emu g^?1 and decreased as the magnetite nanoparticle was coated with oleic acid and functionalized. The scope of this study also included adsorption tests for lanthanum, cerium, praseodymium, and neodymium and the corresponding analysis of their results. Sorption tests indicated that the functionalized nanoparticles were able to extract the four studied lanthanide metal ions, although the best extraction performance was observed when the sorbent was functionalized with CYANEX 272, which resulted in a loading capacity of approximately 12–14 mg_La/g_MNP. The magnetization of the synthesized nanoparticles was verified during the separation of the lanthanide-loaded sorbent from the raffinate by using a conventional magnet.     

Simultaneous frequency conversion and beam shaping for optical-tweezers applications

Abstract

We review a method which allows the simultaneous frequency-conversion and shaping of a light beam into a variety of patterns. The method is based on the controllable dynamics of vortices nested in the light beams. We outline the theoretical idea behind the technique and discuss experimental observations conducted in SH generation in lithium triborate which demonstrate its feasibility. The technique might find applications in specialized optical tweezers aimed at the wavelength-optimized assembly, fabrication and manipulation of complex microstructures and nanostructures.     

A novel high-throughput fatigue testing method for metallic thin films

Abstract

Thin films are used in a wide variety of computing and communication applications although their fatigue behavior and its dependence on alloying elements are not very well known. In this paper, we present an experimental implementation of a novel high-throughput fatigue testing method for metallic thin films. The methodology uses the fact that the surface strain amplitude of a vibrating cantilever decreases linearly from the fixed end to the free end. Therefore, a thin film attached to a vibrating cantilever will experience a gradient of strain and corresponding stress amplitudes along the cantilever. Each cantilever can be used to extract a lifetime diagram by measuring the fatigue-induced damage front that progresses along the cantilever during up to 10⁸ load cycles.     

Vibrating superconductors

This review is concerned with effects in the energy dissipation and elastic modulus of superconductors vibrating in a magnetic field. The physics of superconducting vibrating reeds and reeds made of superconducting suspensions is thoroughly described as well as the main features observed in other oscillators applied to flux pinning studies. It is argued that among the diversity of methods to study superconducting and pinning properties as a function of magnetic field and temperature, the vibrating reed technique is one of the most sensitive due to the accurate measurement of frequency and dissipation with feasible magnetometry applications. Results of the elastic coupling between the flux line lattice and the atomic lattice in high- and low-T _c superconductors obtained with the vibrating reed are summarized as well as the behavior of vibrating type II superconductors near their lower critical field. Results from mechanical measurements in high-temperature superconductors are reviewed, which support the model of thermally activated depinning and vortex diffusion.     

Behavior of a vibrating wire near the liquid3He-vacuum interface and in a saturated3He-4He mixture

In this paper we describe the effect of the vicinity of a liquid³He-vacuum interface on the behavior of a vibrating wire viscometer. It was found that in the fluid near the liquid interface the quality factor is lower than in the bulk liquid. We further report on the observation of a doubling of the resonance peak of the wire in a saturated³He-⁴He mixture. The frequencies and amplitudes of the two peaks strongly depend on the distance between the phase boundary and the vibrating wire; the temperature and the velocity of the phase boundary have no significant influence on the peak frequencies. The observed peak doubling is attributed to the coupling of the vibrating wire with a standing second-sound wave in the dilute phase where the volume of the dilute phase can be regarded as a resonating cavity for second sound.     

Epidemiology of moderate-to-severe injury patterns observed in rollover crashes

BackgroundPrevious epidemiological studies have highlighted the high risk of injury to the head, thorax, and cervical spine in rollover crashes. However, such results provide limited information on whole-body injury distribution and multiple region injury patterns necessary for the improvement and prioritization of rollover-focused injury countermeasures.MethodsSampled cases representing approximately 133,000 U.S. adult occupants involved in rollover crashes (between 1995 and 2013) sustaining moderate-to-severe injuries were selected from the National Automotive Sampling System Crashworthiness Data System database. A retrospective cohort study, based on a survey of population-based data, was used to identify relevant whole body injury patterns.ResultsAmong belted occupants injured in rollover crashes, 79.2% sustained injuries to only one body region. The three most frequently injured (AIS2+) body regions were head (42.1%), upper extremity (28.0%), and thorax (27.1%). The most frequent multi-region injury pattern involved the head and upper extremity, but this pattern only accounted for 2.3% of all of occupants with moderate or worse injuries.ConclusionsThe results indicated that for rollover-dominated crashes, the frequently observed injury patterns involved isolated body regions. In contrast, multi-region injury patterns are more frequently observed in rollovers with significant planar impacts. Identification of region-specific injury patterns in pure rollover crashes is essential for clarifying injury mitigation targets and developing whole-body injury metrics specifically applicable to rollovers.     

Vibroelectronic emission

A newly discovered effect in which electrons are emitted from a vibrating silver-oxygen-cesium photocathode is described. Pis’ma Zh. Tekh. Fiz. 24, 65–69 (December 12, 1998)     

Fabrication and characterisation of multiwalled carbon nanotubes decorated by magnetic Ni nanoparticles

Abstract

Magnetic carbon nanotube (CNT) composites have been successfully fabricated by employing a microwave assisted method after sensitisation and activation. The phase structures and morphologies of the composites were characterised in detail by transmission electron microscope and X-ray powder diffraction. The results show that sensitisation and activation are absolutely necessary for a dense layer of magnetic nanoparticles obtained on the surface of CNTs. Magnetic measurements using a vibrating sample magnetometer demonstrate that the prepared composites are ferromagnetic.     

Observation of Lateral Displacement of an Optical Beam Enhanced by Surface Plasmon Excitation

Abstract

The lateral shift of a light beam suffering total reflection can be enhanced by the excitation of a surface plasmon wave. A shift of ?19 μm was obtained in one total reflection at the surface plasmon resonance. A characteristic double-peak structure was observed in the reflected field as predicted by theory.     

A Fluorescent Technique for the Observation of Polyvinylpyrrolidone Binder Distribution in Granules

Abstract

A technique is described involving the binding of fluorescein isothiocyanate (FITC) to polyvinylpyrrolidone (PVP). This complex has been used as a binder during fluidised bed granulation. The resulting granules have been observed under light excitement and the distribution of PVP in the granules assessed.     

Interferometric Measurements of Phase Singularities in the Output of a Visible Laser

Abstract

We report the use of a simple interferometric technique which allows direct identification of phase singularities in laser fields. Phase singularities are observed in families of optical patterns formed via cooperative frequency mode locking in a continuous single longitudinal mode Na₂ ring laser. The interferometric technique complements a previously reported astigmatic imaging method, and is superior in that it can be used to elucidate the structure of the higher order stationary patterns.     

Measurement of Strains in Turbine Blades Vibrating at Resonance Using Electro-optic Holography

Abstract

Phase-stepped stroboscopic electro-optic holography is employed for the measurement of strains on the surface of a turbine blade vibrating at resonance. The three components of the displacement vector are separated by recording interferograms using four independent illumination beams. The phase-stepping technique supplemented by the Fourier transform method is applied for the extraction of phase changes due to vibration. In-plane strains in a region of interest on the blade surface are calculated for one of the natural modes of vibration.     

Light-induced optical activity in optically ordered amorphous side-chain azobenzene containing polymer

Abstract

We report the appearance of circular birefringence (optical activity) in amorphous side-chain azobenzene polymer films on illumination with circularly polarized light. The effect is observed only if an optical axis is previously created in the film with the help of linearly polarized light. The photoinduced optical activity is believed to be due to changes in the polymer structure initiated by a circular momentum transfer from the circularly polarized light to the azobenzene chromophores.     

Anomalous transmission in atom optics

Abstract

Anomalous transmission for X-rays in crystals as discovered by Borrmann can also be observed for atoms interacting with a standing light wave on resonance. It may be interpreted as a manifestation of a grey state. We describe phenomena based on anomalous transmission for various regimes of the atom-light interaction and elucidate these by numerical calculations for argon and calcium. The grey state in anomalous transmission is linked to the dark state in velocity selective coherent population trapping in atomic threelevel A systems.     

Spectrum of Scattered Light by an Ionized Two-level Atom

Abstract

The spectrum of scattered light by an ionized two-level atom is investigated. The ionization is considered as a damping out of the ordinary two-level system and its effect on the spectrum is extracted. Because of the ionization damping, the central peak in the spectrum changes significantly according to the parameters involved. For a large ionization damping, a central dip is observed; for a small ionization damping, an additional sharp peak appears on top of the central peak.     

Scattering measurements on curved rough surfaces

Abstract

A theoretical model is developed to examine light scattered from a curved optical surface with a defined surface form. The contribution of the surface form to scattering patterns is separated from that of the surface roughness. Experiments are carried out on a curved surface. Measurements are analysed and compared with theoretical calculations. The power spectrum density function and the autocorrelation function of the surface roughness are recovered from the measured scattering pattern.     

Focusing Properties of the Gaussian Beam Generated by Optical Resonators with Gaussian Reflectivity Mirrors

Abstract

This paper presents a parametric study concerning the focusing properties of the light beam generated by optical resonators with Gaussian reflectivity mirrors. The diffraction integral has been evaluated and analytical expressions are derived for intensity patterns near the focus in systems of different Fresnel numbers. Universal curves have been plotted against dimensionless parameters to show the variations in the intensity patterns due to the change in focusing geometry and the incident beam intensity profile. Modification to the well known diffraction formula are considered in order to extend the conventional Gaussian formalism to the case of Gaussian mirror resonators.