A realistic model of human retinal tissues to simulate thermal performance of optical laser photocoagulation therapy is presented. The key criteria to validate the treatment effectiveness is to ensure the photocoagulation temperature between 60 and 70 °C is reached in the treatment region of interest. The model presented consists of truncated volumes of the retinal pigment epithelium (RPE) and adjacent retinal tissues. Two cases of choroid pigmentation are modelled to signify extreme cases of human eye difference: albino and dark colour choroid pigmentation. Conditions for consistent heating over the irradiated treatment spot is modelled for laser beams with different intensity profiles: 'top-hat', Gaussian and 'donut' modes. The simulation considers both uniform heating within retinal tissue layers and spatial intensity decay due to absorption along the direction of laser propagation. For a 500μm spot, pulse length 100 ms and incident power to the cornea of 200 mW, realistic spatial variation in heating results in peak temperatures increasing within the RPE and shifting towards the choroid in the case of choroidal pigmentation. Finite element analysis methodology, where heat transfer theory governs the temperature evolution throughout tissues peripheral to the irradiated RPE is used to determine the zone of therapeutic benefit. While a TEM01donut mode beam produces lower peak temperatures in the RPE for a given incident laser power, it reduces the volume of retinal tissue reaching excessive temperatures and maximises the zone of therapeutic benefit. Described are simulation limitations, boundary conditions, grid size and mesh growth factor required for realistic simulation.

Atmospheric scintillation studies have been traditionally undertaken utilizing nonimaging detection. When imaging devices are used, they typically detect the resultant signal at the receiver plane. Here, a high-speed camera has been utilized in atmospheric scintillation field trials, imaging a laser source (i.e., imaging the object plane) over a near ground path length of 1.5 km. The statistical nature of the acquired atmospheric scintillation data is characterized using a range of probability density functions. The exponentiated Weibull function was found to best describe the nature of scintillation over the broadest range of a scintillation index typical of atmospheric scintillation. A preliminary investigation into the relationship between the fit variables of three of the better-performing probability density functions and the scintillation index is presented, along with suggestions for future use of digital cameras in atmospheric scintillation studies.

Ultimately, this research is to develop a versatile 3D non-axial finite element model of the whole human eye that is not limited to any specific ophthalmic treatment. The goal is to include the asymmetric cooling by an equivalent uniform layer representing the vascular system of the choroid. In this paper, we trialled the feasibility of simulating conductive heat transfer through the retina as the base step towards a 3D model. This was done by developing a 2D axial model of the retina in which most heat is absorbed in the retinal pigment epithelium.

Accuracy of sentinel lymph node identification using radioactive tracers in non-superficial cancers can be limited by radiation shine through and low spatial resolution of detection systems such as intraoperative gamma probes. By utilising a dual radioactive/magnetic tracer, sensitive lymphoscintigraphy can be paired with high spatial resolution intraoperative magnetometer probes to improve the accuracy of sentinel node detection in cancers with complex multidirectional lymphatic drainage. Dextran-coated magnetite nanoparticles (33 nm mean hydrodynamic diameter) were labelled with 99mTc and applied as a lymphotropic tracer in small and large animal models. The dual tracer could be radiolabelled with 98 ± 2% efficiency after 10 min of incubation at room temperature. Biodistribution studies of the tracer were conducted in normal rats (subdermal and intravenous tail delivery, n = 3) and swine (subdermal hind limb delivery, n = 5). In rats the dual tracer migrated through four tiers of lymph node, 20 min after subdermal injection. Results from intravenous biodistribution test for radiocolloids demonstrated no aggregation in vivo, however indicated the presence of some lower-molecular weight radioactive impurities (99mTc-dextran). In swine, the dual tracer could be effectively used to map lymphatic drainage from hind hoof to popliteal and inguinal basins using intraoperative gamma and magnetometer probes. Of the eight primary nodes excised, eight were positively identified by gamma probe and seven by magnetometer probe. The high-purity dual tracer shows early promise for sentinel node identification in complex lymphatic environments by combining sensitive preoperative lymphoscintigraphy with a high-resolution intraoperative magnetometer probe.

Particle size is a fundamental variable in the dust aerosol cycle. A dust layer effective particle size is strongly related to its’ radiative forcing and the extent of its impact on an area of interest. However, in-situ measurements of dust particle size are costly, spatially sparse and time-consuming. This paper presents a simple empirically derived model to estimate effective dust diameter using infrared band brightness temperature difference of the 8.7 and 12.0 µm wavelength bands retrieved from the SEVIRI (Spinning Enhanced Visible and InfaRed Imager) radiometer onboard Meteosat satellites. Three case studies were used to test the model. The results showed consistency between the model and in-situ aircraft fly through sampling of dust particle size. The use of the model is demonstrated by presenting an analysis of a severe dust storm over Western Asia. This model is expected to contribute to addressing the discrepancies between the current particle size retrieval techniques and aircraft measurements. There are many potential applications for this model including providing an independent reference data for atmospheric dust models, forecasting the impact of dust storms on horizontal visibility as well as the solar energy system performance over regions prone to dust storms.

A simplified approach for the fabrication of localised surface plasmon resonance (LSPR) sensors based on gold nanorods (GNRs) is described and validated in a model immunoassay for the activated leukocyte cell adhesion molecule (ALCAM) cancer biomarker. Towards improving on standard bottom-up LSPR sensor fabrication methodologies, we demonstrate that GNRs bioconjugated with monoclonal antibodies can be readily covalently immobilized onto silanized glass substrates to yield highly sensitive LSPR sensors. To maximise the performance of the proposed sensors, mixed polyethylene glycol adlayers were optimized in regards to the bioconjugation of monoclonal antibodies using the standard carbodiimide chemistry. In the optimal condition, the ALCAM GNR LSPR sensors yielded a sensitivity of 330 nm per refractive index and allowed the detection of the ALCAM antigen concentration down to 15 pM. This simple fabrication method could foster the implementation of LSPR sensors in the immunoassay field.

Froth flotation is a key pre-concentration process in many minerals processing operations and also in wastewater treatment. At its heart is the interaction between micrometer-sized particles and air bubbles. An understanding of the factors affecting such interactions can be used to enhance process optimization. Al- though instruments such as the atomic force microscope and surface force apparatus have been used to explore these interactions, they are limited by the mechanical constraint placed on the particle and the sensitivity to stronger short-range ( In this paper we give the first-ever report of force -vs- distance measurements using optical tweezers of the interactions between air bubbles and micrometer-sized silica spheres across a range of electrolyte solutions. In addition to force profiles, adhesive forces of the bubble-particle systems were also measured and found to increase significantly with increasing salt concentration. To benchmark the experimental procedure we also measured forces between a silica sphere and a glass fibre. The results were compared with calculations based on DLVO theory and found to be in qualitative agreement.

Using magnetic tunnelling junction sensors, a novel magnetometer probe for the identification of the sentinel lymph node using magnetic tracers was developed. Probe performance was characterised in vitro and validated in a preclinical swine model. Compared to conventional gamma probes, the magnetometer probe showed excellent spatial resolution of 4.0 mm, and the potential to detect as few as 5 μg of magnetic tracer. Due to the high sensitivity of the magnetometer, all first-tier nodes were identified in the preclinical experiments, and there were no instances of false positive or false negative detection. Furthermore, these preliminary data encourage the application of the magnetometer probe for use in more complex lymphatic environments, such as in gastrointestinal cancers, where the sentinel node is often in close proximity to other non-sentinel nodes, and high spatial resolution detection is required.

A new evolution of OCT is termed molecular OCPM, which is capable of imaging the expression of molecular markers at the cellular level by using functionalized gold nanorods as imaging agents.

Interest in microfluidics is rapidly expanding and the use of microchips as miniature chemical reactors is increasingly common. Microfluidic channels are now complex and combine several functions on a single chip. Fluid flow details are important but relatively few experimental methods are available to probe the flow in confined geometry. We use optical trapping of a small dielectric particle to probe the fluid flow. A highly focused laser beam attracts particles suspended in a liquid to its focal point. A particle can be trapped and then repositioned. From the displacement of the trapped particle away from its equilibrium position one estimates the external force acting on the particle. The stiffness (spring constant) of the optical trap is low thus making it a sensitive force measuring device. Rather than using the optical trap to position and release a particle for independent velocimetry measurement, we map the fluid flow by measuring the hydrodynamic force acting on a trapped particle. The flow rate of a dilute aqueous electrolyte flowing through a plastic microchannel (W x H x L = 5 mm x 0.4 mm x 50 mm) was mapped using a small silica particle (1 mu m diameter). The fluid velocity profile obtained experimentally is in very good agreement with the theoretical prediction. Our flow mapping approach is time efficient, reliable and can be used in low-opacity suspensions flowing in microchannels of various geometries. (c) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

The turbulent nature of the atmosphere causes refractive index fluctuations, which in turn give rise to intensity fluctuations (scintillation) of a propagating optical signal [1]. Scintillation of optical signals affects fields such as free space optical communications (FSOC), light distance and ranging (LIDAR) and conventional radar, and imaging through the atmosphere. Most light sources, natural and man-made are broadband and incoherent. While acknowledging the research conducted with ultra-violet (UV) [2], the majority of scintillation research has used either visible or infra-red (IR) lasers, with very little research being conducted with UV or broadband sources. Particularly important in the defence industry is the use of optical based missile warning systems on aircraft which can detect the UV light signatures of a surface to air missile [3].

The sentinel lymph node (SLN) concept has become a standard of care for patients with breast cancer and melanoma, yet its clinical application to other cancer types has been somewhat limited. This is mainly due to the reduced accuracy of conventional SLN mapping techniques (using blue dye and/or radiocolloids as lymphatic tracers) in cancer types where lymphatic drainage is more complex, and SLNs are within close proximity to other nodes or the tumour site. In recent years, many novel techniques for SLN mapping have been developed including fluorescence, x-ray, and magnetic resonant detection. Whilst each technique has its own advantages/disadvantages, the role of targeted contrast agents (for enhanced retention in the SLN, or for immunostaging) is increasing, and may represent the new standard for mapping the SLN in many solid organ tumours. This review article discusses current limitations of conventional techniques, limiting factors of nanoparticulate based contrast agents, and efforts to circumvent these limitations with modern tracer architecture.

Laser microdrilling is the process of material removal by ablation using focused laser pulses. With brief preamble on laser system, how a micro-orifice is created successfully on 50 µm thick copper foil using modified Nd:YAG ophthalmic laser is elucidated. The micro-orifice is required to control the flow of lubricant from the centrifugal lubricator used in spacecraft moving mechanisms. The orifices are characterized using scanning electron microscope (SEM), and the process parameters are optimized. Orifices from 1.5 µm to 2.7 µm diameter are produced. The work is further extended to drill microholes in 60 µm copper wire. It is observed that the bead formed at melt zone near the hole can be conveniently used for microjoining.

Poor ultraviolet (UV) quantum conversion efficiency contributes to a reduction in the efficiency of silicon based photovoltaic cells. In the UV, the main loss mechanism is through surface recombination of photo-generated carriers due to the shallow absorption depth of high energy photons. One method for greater utilisation of the UV region is by down-shifting UV photons to lower energies where the quantum efficiency of silicon is higher. This work determines the potential enhancement in efficiency that can be obtained by a luminescent down-shifting layer applied to silicon based solar cells. The efficiency is determined through detailed balance arguments. The maximum calculated efficiency enhancement due to an ideal down shifting process is 0.6% absolute using the AM1.5G standard spectra. Applying a similar analysis to a multicrystalline silicon solar cell results in an efficiency enhancement due to the down-shifting process of 0.17% absolute.

In recent years, downscaled coordinate measuring machines (CMMs) are in demand and bring challenges to the development of micro/nanoscale probes for a variety of microscale structure measurement applications. A working prototype apparatus is developed in which a microspherical optical fiber probe tip is created from a strand of standard single mode silica optical fiber using an electric discharge technique. The Taguchi method has been used to investigate the general effects of probe fabrication conditions that result in controllable fabrication of a quality probe tip. With proper control of the process parameters, spherical optical fiber probe tips with the desired diameters in the range of 133–360 μm with a diameter variance within 3% and minimum spherical tip center offset of about 2.2 μm have been achieved. An economical and flexible technique for the fabrication of a quality microspherical probe for micro/nano-CMM application is developed in this work.

A deformable grating light modulator (GLM) also known as a grating light valve™ (GLV) offers fast switching time, low loss, and potential simplicity in fabrication, which are desirable for free-space optical switching systems. The purpose of this paper is to report on the fabrication of a GLM using standard CMOS technology and its simulation results, for use as both a de-multiplexer and switching device simultaneously in this wavelength-selective switching system. In a simplified standard CMOS process, the GLM devices were compatibly fabricated utilizing only four masks in one maskset, and using the stepper lithography system. The investigation showed the potential for using the GLM as an optical switch with low power consumption, and the experimental observations are supported by simulation results.

This paper presents a novel optical fibre based micro contact probe system with high sensitivity and repeatability. In this optical fibre probe with a fused spherical tip, a fibre Bragg grating has been utilized as a strain sensor in the probe stem. When the probe tip contacts the surface of the part, a strain will be induced along the probe stem and will produce a Bragg wavelength shift. The contact signal can be issued once the wavelength shift signal is produced and demodulated. With the fibre grating sensor element integrated into the probe directly, the probe system shows a high sensitivity. In this work, the strain distributions along the probe stem with the probe under axial and lateral load are analysed. A simulation of the strain distribution was performed using the finite element package ANSYS 11. Performance tests using a piezoelectric transducer stage with a displacement resolution of 1.5 nm yielded a measurement resolution of 60 nm under axial loading.

The requirement to make low profile ohmic contacts to a piezo-resistive MEMS pressure sensor has highlighted limitations of ultrasonic wire bonding technology. Wire bonding typically uses 25-50 mu m diameter gold or aluminium wire and ultrasonic welding to the contact pads of micro-electronic devices results in a contact wire proud of the pad surface. If the application involves the MEMS pressure sensor and contacts being encapsulated, then repetitive changes in pressure flexing the contact wires can lead to fracture.A possible solution is to scale down laser welding technology to fuse materials at the micron scale. For this purpose a precision ophthalmic surgical laser system has been modified to investigate optimum conditions for laser welding, both at the micron scale and for the typical geometries involved. Typical-requirements involve a cylindrical contact wire to be bonded to a thin contact pad on the MEMS device. Since the pad size is of similar dimension to the wire, and the requirement for a low profile stable configuration, a keyhole welding strategy is required.The Nd:YAG based ophthalmic laser has been modified, the Q-switch removed and the output pulse width and energy controlled principally via control of the flashlamp.