Interpretation of Indian orthodox tea using multi-sensing impedometric technique.

Twelve different orthodox Indian tea samples were collected from tea growing and processing sites of Kangra (Valley), India. The percentage of major chemical constituents responsible for the tea quality has been determined by HPLC and UV-vis spectrophotometer. Impedance response using Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC), Polyaniline (PANI) (emraldine salt) and Poly Pyrrole (PPY) working electrodes in tea infusions in the frequency range of 1 Hz to 100 kHz has been measured for 30 days on each tea sample. The impedance response of these working electrodes along with the determined chemical concentrations was subjected to Principal Component Analysis (PCA). It was possible to map the antioxidant levels in these tea samples with few exceptions from the score plot of PCA.

Human opinion dynamics: an inspiration to solve complex optimization problems.

Human interactions give rise to the formation of different kinds of opinions in a society. The study of formations and dynamics of opinions has been one of the most important areas in social physics. The opinion dynamics and associated social structure leads to decision making or so called opinion consensus. Opinion formation is a process of collective intelligence evolving from the integrative tendencies of social influence with the disintegrative effects of individualisation, and therefore could be exploited for developing search strategies. Here, we demonstrate that human opinion dynamics can be utilised to solve complex mathematical optimization problems. The results have been compared with a standard algorithm inspired from bird flocking behaviour and the comparison proves the efficacy of the proposed approach in general. Our investigation may open new avenues towards understanding the collective decision making.

Shock absorption ability of laminate mouth guards in two different malocclusions using fiber Bragg grating (FBG) sensor.

PURPOSE: The majority of orofacial injuries affect the upper jaw, with the maxillary incisors being most prone to injury, often accounting for as many as 80% of all cases. Children with malocclusion in the anterior segment of the maxilla are more prone to traumatic injuries than those exhibiting normal occlusion, because most often the damaging force impacts directly against the maxillary anterior teeth. Hence, because of the difference of dissipation of the impact force because of the presence or absence of malocclusion, the mouthguard's shock absorption capacity would be influenced by certain factors. In the present study, a unique in vitro experiment utilizing fiber Bragg Grating (FBG) as distributed strain sensors was carried out to evaluate the shock absorption ability of laminate customized mouthguards in two different malocclusions compared with normal occlusion. MATERIAL AND METHODS: The impact was produced using a customized pendulum device with three interchangeable impact objects on typhodont models with two different malocclusions and normal occlusion from different heights. Response of gratings was monitored using an optical spectrum analyzer. Strain induced because each impact was determined from the Bragg's wavelength shifts for each grating. For every model, 12 impact strikes were measured using three different impact objects on the two specified sites by releasing the object from two different heights. RESULTS AND CONCLUSIONS: The laminated mouthguards showed significant variation in shock absorption ability when different malocclusions were compared. Hence, modifications in the original design of the laminated mouthguards should be considered for athletic competitors with malocclusion to provide adequate protection against impact. FBG sensor has shown the unique advantage of high sensitivity to strain measurement and can be used in further studies. The height of the impact is an important variable in determining the shock absorption ability of mouthguards.

Optical fiber tip for field-enhanced second harmonic generation.

We propose a simple optical fiber tip for field-enhanced second harmonic generation (SHG). The tip shows nonlinear phenomena of SHG over a wide range of sources, at least from 630 to 830 nm. The optical field corresponding to the second harmonic appears as a nondiffracting bottle beam with voids due to the surface curvature of the tip. The field-enhanced second harmonic can also induce surface plasmons, converting the tip to a plasmonic probe with reduced background signal. The tip can be useful in nanophotonics characterization. As an example, we demonstrate the tip's response as a surface-enhanced Raman spectroscopy probe.

Impedance study of tea with added taste compounds using conducting polymer and metal electrodes.

In this study the sensing capabilities of a combination of metals and conducting polymer sensing/working electrodes for tea liquor prepared by addition of different compounds using an impedance mode in frequency range 1 Hz-100 KHz at 0.1 V potential has been carried out. Classification of six different tea liquor samples made by dissolving various compounds (black tea liquor + raw milk from milkman), (black tea liquor + sweetened clove syrup), (black tea liquor + sweetened ginger syrup), (black tea liquor + sweetened cardamom syrup), (black tea liquor + sweet chocolate syrup) and (black tea liquor + vanilla flavoured milk without sugar) using six different working electrodes in a multi electrode setup has been studied using impedance and further its PCA has been carried out. Working electrodes of Platinum (Pt), Gold (Au), Silver (Ag), Glassy Carbon (GC) and conducting polymer electrodes of Polyaniline (PANI) and Polypyrrole (PPY) grown on an ITO surface potentiostatically have been deployed in a three electrode set up. The impedance response of these tea liquor samples using number of working electrodes shows a decrease in the real and imaginary impedance values presented on nyquist plots depending upon the nature of the electrode and amount of dissolved salts present in compounds added to tea liquor/solution. The different sensing surfaces allowed a high cross-selectivity in response to the same analyte. From Principal Component Analysis (PCA) plots it was possible to classify tea liquor in 3-4 classes using conducting polymer electrodes; however tea liquors were well separated from the PCA plots employing the impedance data of both conducting polymer and metal electrodes.

Immobilization of enzyme on long period grating fibers for sensitive glucose detection.

Glucose oxidase (GOD) immobilized long period grating (LPG) fibers have been proposed for the specific and sensitive detection of glucose. The treatment of LPG fibers with aminopropyl triethoxysilane has induced biding sites for the subsequent GOD immobilization. Field emission scanning electron microscopy, confocal laser scanning microscopy, infrared spectroscopy and Raman spectroscopy have provided detailed evidences about the effectiveness of the adopted biofunctionalization methodology. The enzyme activity is conserved during the immobilization step. Fabricated LPG sensor was tested on different glucose solutions to record the transmission spectra on an optical spectrum analyzer. The wavelength shifts in the transmission spectra are linearly correlated with the glucose concentration in the range of 10-300 mg dL(-1). The fabricated sensor gives fast response and is demonstrated to be of practical utility by determining glucose contents in blood samples. Proposed technique can further be extended to develop LPG fiber based novel, sensitive and label free nanosensors for disease diagnosis and clinical analysis.

Etched multimode microfiber knot-type loop interferometer refractive index sensor.

We propose a novel refractive index sensor based on multimode microfiber knot-type loop (NL) interferometer. The middle portion (~5 cm) of a 15 cm long multimode fiber is etched in 48% hydrofluoric acid to reduce its diameter to ~12 µm. A NL of diameter <1 mm is made from the etched fiber. The ends of etched fiber are spliced with single-mode fibers for launching and detecting light from the NL interferometer. The NL introduces path differences to produce interferometric spectra with free spectral range ~16 nm. The spectrum shifts as the surrounding refractive index of the loop is changed by adding chemicals. We observe the highest sensitivity of the NL interferometer ~172 nm/RIU (refractive index unit) at a refractive index value 1.370 as obtained experimentally using commonly available chemicals. The design could be used as simple, low cost, and highly sensitive biological and chemical sensor.

Tunable wavelength division multiplexing channel isolation filter based on dual chirped long-period fiber gratings.

We propose and demonstrate a wavelength tunable wavelength division multiplexing channel isolation filter based on two concatenated chirped long-period fiber gratings (LPGs). An intergrating space (IGS), deliberately introduced between the two gratings, provides an extra phase difference between the core and cladding modes. Changing this phase by heating the IGS without affecting the gratings tunes the channels. A theoretical account of the filter action is also presented and the results are found to be in excellent agreement with the experiments. Unlike the filters based on normal concatenated chirped LPGs without an IGS, the current filter shows a linear tuning over an increased spectral range.

Fiber Bragg grating sensor for measurement of impact absorption capability of mouthguards.

BACKGROUND: There is no standard technique to monitor impact absorption capability of mouthguards. Earlier investigations have established that strain transferred to the teeth through mouthguard is a good indication of their efficiency. In the present study, a unique experimental scheme utilizing fiber Bragg gratings (FBGs) as distributed strain sensors is proposed and investigated to estimate impact absorption capability of custom-made mouthguard. The proposed methodology is useful due to advantages such as, very small size and flexibility for ease of bonding, self-referencing, and multiplexing capability of using FBG sensors. MATERIAL AND METHODS: Finite-element analysis was performed to simulate the stress distribution due to impact on the mouthguard. The FBGs were fabricated by exposing the core of photosensitive fiber to intense Ultra-Violet light through a 'phase mask'. One FBG sensor was bonded on the jaw model and another on the mouthguard surface at similar positions, so that both gratings are simultaneously affected by impact. Two different sets of the sensors were used, one for the anterior region and another for posterior region. The impact was produced using customized pendulum device with interchangeable impact objects i.e. cricket ball, hockey ball, and steel ball. Response of gratings was monitored using optical spectrum analyzer and strain induced due to each impact was determined from the Bragg wavelength shifts for each grating. RESULTS AND CONCLUSIONS: Strain induced due to impact was calculated from the Bragg wavelength shifts. Difference in the strain values for the two gratings is interpreted as impact energy absorbed by the mouthguard. The Bragg wavelength shifts (induced strain) for FBG bonded on the jaw model was much lower than the shift for FBG bonded on the mouthguard, indicating that most of the impact energy is absorbed by the mouthguard.

Detection of jaggery syrup in honey using near-infrared spectroscopy.

In the present study, a near-infrared (NIR) filter-based technique along with chemometrics as an analytical tool was used for determination of adulteration of Indian honey with jaggery. A total of 56 honey samples adulterated with different concentrations of jaggery syrup were analyzed using the NIR transflectance method at different wavelengths for multivariate analysis to develop a calibration model for jaggery adulteration in honey samples. The data were compressed using principal component analysis method and the model was developed using partial least square regression. The adulteration of all of the samples can be predicted with a standard error of calibration of 4.55 and a coefficient of determination (R(2)) of 0.81. The results demonstrate that the NIR technique along with chemometrics can be successfully used to determine jaggery adulteration in honey non-destructively.

Optical fiber nanoprobe preparation for near-field optical microscopy by chemical etching under surface tension and capillary action.

We propose a technique of chemical etching for fabrication of near perfect optical fiber nanoprobe (NNP). It uses photosensitive single mode optical fiber to etch in hydro fluoric (HF) acid solution. The difference in etching rate for cladding and photosensitive core in HF acid solution creates capillary ring along core-cladding boundary under a given condition. The capillary ring is filled with acid solution due to surface tension and capillary action. Finally it creates near perfect symmetric tip at the apex of the fiber as the height of the acid level in capillary ring decreases while width of the ring increases with continuous etching. Typical tip features are short taper length (approximately 4 microm), large cone angle (approximately 38 degrees ), and small probe tip dimension (<100 nm). A finite difference time domain (FDTD) analysis is also presented to compare near field optics of the NNP with conventional nanoprobe (CNP). The probe may be ideal for near field optical imaging and sensor applications.

Single fiber Bragg grating sensor with two sections of different diameters for longitudinal strain and temperature discrimination with enhanced strain sensitivity.

A single fiber Bragg grating (FBG) sensor with two sections of different diameters is proposed and experimentally demonstrated for discrimination and measurement of strain and temperature. A section of single FBG is etched in hydrofluoric acid solution to reduce diameter of the fiber by factor of <1/2 to increase its strain sensitivity. Different shifts of the Bragg wavelengths of chemically etched and nonetched gratings caused by different strain sensitivities are used to discriminate and measure strain and temperature. Maximum errors of +/-13 microepsilon (microstrain) and +/-1 degrees C are reported over 1700 microepsilon and 60 degrees C measurement ranges, respectively. Depending upon the diameter of the etched fiber grating, the design can also discriminate nanostrain from temperature.