Blast wave pressure measurement and analysis in air and granular media inside a shock tube using a fiber Bragg grating sensor.

In this work, we have demonstrated the use of a fiber Bragg grating (FBG) sensor to measure the pressure profile of blast waves generated inside a vertical shock tube (VST). An FBG pressure sensor probe has been designed and developed that can be incorporated into the wall of the VST. The VST facility is used to generate blast waves with decay times of the order of a few milliseconds to simulate explosive events. Pressure measurement experiments have been carried out at different incident blast wave peak pressures inside the VST. The FBG pressure sensor measurements are validated against a standard piezoelectric pressure transducer at an acquisition rate of 1 MHz. The pressure signals of both sensors are found to match well with similar rise times and decay profiles. The validated FBG pressure sensor is then incorporated into a sand column mounted in the test section of the VST to measure the pressure profile of blast wave-induced stress waves in granular media. The FBG and piezoelectric pressure sensor data are compared using fast Fourier transform analysis and continuous wavelet transform. The feasibility of FBG sensors for blast pressure measurement under harsh conditions imposed inside shock tube environments is established.

Detection of polarization-spatial classical optical entanglement in partially coherent light fields using intensity measurements.

Detection of polarization-spatial classical optical entanglement through implementation of partial transpose on measured intensities is explored. A sufficient criterion for polarization-spatial entanglement in partially coherent light fields based on intensities measured at various orientations of the polarizer, as implied through partial transpose, is outlined. Detection of polarization-spatial entanglement using the outlined method is demonstrated experimentally through a Mach-Zehnder interferometer setup.

Estimation of dislocated phases and tunable orbital angular momentum using two cylindrical lenses.

A first-order optical system consisting of two cylindrical lenses separated by a distance is considered. It is found to be non-conserving of orbital angular momentum of the incoming paraxial light field. The first-order optical system is effectively demonstrated to estimate phases with dislocations using a Gerchberg-Saxton-type phase retrieval algorithm by making use of measured intensities. Tunable orbital angular momentum in the outgoing light field is experimentally demonstrated using the considered first-order optical system by varying the distance of separation between the two cylindrical lenses.

Polarization-spatial Gaussian entanglement in partially coherent light fields.

The problem of bipartite entanglement in partially coherent paraxial vector light fields is addressed. A generalized uncertainty principle suited for the polarization-spatial degrees of freedom is introduced. Partial transpose is implemented through the obtained generalized uncertainty principle. Partial transpose is shown to be necessary and sufficient in detecting entanglement for a class of partially coherent vector light fields which have a spatial part to be Gaussian. An experimental realization of the studied entangled states using classical optical interferometry is outlined.

Estimation of dislocated phases in wavefronts through intensity measurements using a Gerchberg-Saxton type algorithm.

Estimation of the phase of a singular paraxial light field from experimentally measured intensities using a Gerchberg-Saxton type algorithm is demonstrated. A combination of cylindrical lenses which does not conserve the orbital angular momentum of the light field is used in obtaining the measured intensities. Consistent extraction of the phases in regard of the orbital angular momentum is demonstrated both at the input and output transverse planes, using the measured intensities.

Gaussian spatial-polarization entanglement in a folded Mach-Zehnder interferometer.

Gaussian spatial-polarization entanglement in a coherent vectorial paraxial light field is studied. Detection of spatial-polarization entanglement through fringe movement on rotation of a linear polarizer, with the light field passing through the polarizer, is outlined. The fringe movement is shown to be a sufficient condition for the detection of spatial-polarization entanglement in coherent paraxial vector light fields. Two Gaussian light fields with a small relative tilt but with significant spatial overlap and with orthogonal polarizations are shown to possess close to 1 ebit of spatial-polarization entanglement. Tunable Gaussian spatial-polarization entanglement is experimentally demonstrated in a folded Mach-Zehnder interferometer.

Parenting Styles and their Influence on Child's Dental Behavior and Caries Status: An Analytical Cross-Sectional Study.

Aim: The present study aimed to evaluate the association between parenting styles, child's behavior in dental setting and dental caries status. Study design: Children aged 3-7 years on their first dental visit were included in the study. Their parents were asked to complete Parenting Style Dimension Questionnaire (PSDQ) to assess their parenting style. Oral prophylaxis was performed for the children and their behavior was assessed using Frankl behavior rating scale. Their caries status was recorded using DMFT/deft index. Results: Out of 315 parents, 240 parents exhibited authoritative parenting style, 45 exhibited permissive and 30 exhibited authoritarian parenting style. Permissive parenting was associated with four-fold increase in the child's negative dental behavior and authoritarian parenting showed two-fold increase in the negative behavior of children compared to authoritative parenting. Children of both authoritative and authoritarian parents showed less caries status and the permissive parenting depicted threefold increase in the caries status compared to authoritative parenting. Conclusion: Children of both the permissive and authoritarian parents showed more negative dental behavior than children of authoritative parents. Children of permissive parents showed increased caries status compared to the children of authoritative parents.

Impact of different modes of school dental health education on oral health-related knowledge, attitude and practice behaviour: an interventional study.

PURPOSE: The study was planned to evaluate the effectiveness of three modes of school dental health education (SDHE) on the oral health-related knowledge, attitude and practice (KAP) behaviour of school children. METHODS: An interventional study was carried out among 8-9 year old school children from January 2016 to January 2018. Three hundred and sixty children from three schools in Tiruchengode, Tamil Nadu, India participated in this study. Each school was randomly allotted with a mode (drama, modified snake and ladder game, flashcard) of SDHE, which was delivered for 20 min, every 6 months for 2 years. A validated questionnaire with 18 questions was used to record oral health-related KAP behaviour at baseline and after 2 years. RESULTS: At the end of 2 years, there was an increase in the percentage of correct response for all the nine knowledge questions, in all the three modes. The mean difference in the cumulative knowledge score between baseline and 2 years was 1.39 ± 2.05 for drama mode, 1.8 ± 1.51 for game mode and 1.7 ± 1.5 for flashcard mode of SDHE. There was a significant difference in three knowledge questions and one attitude practice behaviour question between the three groups at the end of 2 years. CONCLUSIONS: All the three modes were effective in improving the oral health-related KAP behaviour of school children. Game mode made a better impact on the knowledge scores of these children, and it was observed to be more child-friendly and entertaining.

Evaluation of remineralisation potential of experimental nano hydroxyapatite pastes using scanning electron microscope with energy dispersive X-ray analysis: an in-vitro trial.

AIM: To analyse the remineralisation potential of experimental nano hydroxyapatite (nHAP) paste on artificial caries lesions using scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX). METHODS: Sixty-five enamel specimens were randomly divided into 4 test groups (n = 15): 1% commercially available nHAP paste (CnHAP) group, 1% experimental nHAP paste (EnHAP) group, 10% EnHAP group, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) group and control group (n = 5). Artificial carious lesions were induced in all the specimens and treated with respective paste twice daily for 14 days. The specimens were subjected to EDX analysis at baseline, after demineralisation and after remineralisation. The surface characteristics of the remineralised enamel specimens were evaluated by SEM. RESULTS: All the test groups showed significant change in calcium and phosphorus weight percentage (wt%) after remineralisation. The 10 % EnHAP showed higher mean value of calcium and phosphorus wt% followed by 1% CnHAP, 1% EnHAP and CPP-ACP. After remineralisation, both 10% EnHAP and CPP-ACP showed favourable enamel surface changes in SEM analysis. CONCLUSION: Commercially available and experimental nHAP have the potential to remineralise artificially induced carious lesions.

Temperature sensor based on multi-layer MoS2 coated etched fiber Bragg grating.

The development of an etched fiber Bragg grating (eFBG)-based temperature sensor with a uniform multi-layer molybdenum-di-sulphide (MoS2) coating is presented in this paper. Multi-layer MoS2 has been coated on clad etched FBG sensors by DC magnetron sputtering of molybdenum (Mo) and subsequent sulfurization. The dependence of temperature sensitivity on the coating thickness of MoS2 on eFBGs has been tested from room temperature to 100°C. It has been found that MoS2 coated clad etched FBG sensors with a coating thickness of around 10 nm exhibit a maximum temperature sensitivity of ∼95 pm/°C (almost one order higher than that of bare fiber Bragg gratings), with a resolution of ∼0.01°C obtained using an FBG interrogator with 1 pm resolution.

Highly sensitive fiber Bragg grating-based pressure sensor using side-hole packaging.

In this work, an analysis of pressure response of a fiber Bragg grating (FBG) sensor in a side-hole package is presented using the finite element method. Various parameters of the side-hole packaging such as hole radius, the distance of separation between them, the radius and length of the package, and the choice of the package material are considered and optimized in order to promote maximum pressure sensitivity of the FBG sensor. This investigation on optimization of the side-hole package parameters gives rise to pressure sensitivity of nearly 105 times as compared with the bare FBG sensor, with the numerical values of 3 pm/MPa for a bare FBG sensor to ∼280,000 pm/MPa for an optimized side-hole package FBG sensor. Such high-pressure sensitivity of an FBG sensor is being reported for the very first time in this work, to the best of our knowledge, and can be considered as the initial step toward the realization of a highly sensitive hydrophone based on FBG for sensing underwater acoustic signals.

Radial-angular entanglement in Laguerre-Gaussian mode superpositions.

Classical optic entanglement between the radial and angular degrees of freedom in Laguerre-Gaussian mode superpositions is explored within the framework of symmetric first-order optical systems. The Gouy phase picked by a Laguerre-Gaussian mode on free propagation is seen to be of consequence to the radial-angular entanglement in the mode superpositions. We illustrate examples of mode superpositions for which radial-angular entanglement is preserved on passage through symmetric first-order optical systems. An indicator of radial-angular entanglement in two-mode Laguerre-Gaussian superpositions is demonstrated to be a robust free space signaler in the presence of atmospheric turbulence, through examples.

Ag nanowire-assisted low threshold WGM lasing from polymer optical fiber.

Whispering Gallery Mode (WGM) emission has been observed from Ag nanowire doped polymer optical fiber laser. Low threshold lasing and high photostability of the active medium has been noticed with a given concentration of Ag nanowires in the microcavity of the fiber. Quantum yield and lifetime measurements of the dye (active medium) with and without nanowires confirm that presence of nanowires enhance the rate of radiative decay of the fluorophore, thereby providing low pump pulse energy for the excitation of lasing modes in the cavity, as compared with a bare dye-doped polymer fiber laser.

Fiber bragg grating sensor based device for simultaneous measurement of respiratory and cardiac activities.

This paper reports a novel optical ballistocardiography technique, which is non-invasive, for the simultaneous measurement of cardiac and respiratory activities using a Fiber Bragg Grating Heart Beat Device (FBGHBD). The unique design of FBGHBD offers additional capabilities such as monitoring nascent morphology of cardiac and breathing activity, heart rate variability, heart beat rhythm, etc., which can assist in early clinical diagnosis of many conditions associated with heart and lung malfunctioning. The results obtained from the FBGHBD positioned around the pulmonic area on the chest have been evaluated against an electronic stethoscope which detects and records sound pulses originated from the cardiac activity. In order to evaluate the performance of the FBGHBD, quantitative and qualitative studies have been carried out and the results are found to be reliable and accurate, validating its potential as a standalone medical diagnostic device. The developed FBGHBD is simple in design, robust, portable, EMI proof, shock proof and non-electric in its operation which are desired features for any clinical diagnostic tool used in hospital environment.

Enhanced strain and temperature sensing by reduced graphene oxide coated etched fiber Bragg gratings.

This Letter reports on an etched fiber Bragg grating (eFBG) sensor coated with reduced graphene oxide (RGO) having enhanced sensitivity for physical parameters such as strain and temperature. The synergetic effect of the changes in grating pitch and refractive index of RGO with change in temperature or strain enhances the shift in Bragg wavelength (λB). The RGO-coated eFBG sensors exhibit a strain sensitivity of 5.5 pm/µÏµ (∼5 times that of bare fiber Bragg gratings) and temperature sensitivity of 33 pm/°C (∼3 times that of bare fiber Bragg gratings). The resolutions of ∼1 µÏµ and ∼0.3°C have been obtained for strain and temperature respectively, using RGO-coated eFBG sensors.

Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide.

An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules.

Sensitive detection of C-reactive protein using optical fiber Bragg gratings.

An accurate and highly sensitive sensor platform has been demonstrated for the detection of C-reactive protein (CRP) using optical fiber Bragg gratings (FBGs). The CRP detection has been carried out by monitoring the shift in Bragg wavelength (ΔλB) of an etched FBG (eFBG) coated with an anti-CRP antibody (aCRP)-graphene oxide (GO) complex. The complex is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. A limit of detection of 0.01mg/L has been achieved with a linear range of detection from 0.01mg/L to 100mg/L which includes clinical range of CRP. The eFBG sensor coated with only aCRP (without GO) show much less sensitivity than that of aCRP-GO complex coated eFBG. The eFBG sensors show high specificity to CRP even in the presence of other interfering factors such as urea, creatinine and glucose. The affinity constant of ∼1.1×10(10)M(-1) has been extracted from the data of normalized shift (ΔλB/λB) as a function of CRP concentration.

Radial arterial compliance measurement by fiber Bragg grating pulse recorder.

In the present work, we report a novel, in vivo, noninvasive technique to determine radial arterial compliance using the radial arterial pressure pulse waveform (RAPPW) acquired by fiber Bragg grating pulse recorder (FBGPR). The radial arterial compliance of the subject can be measured during sphygmomanometric examination by the unique signatures of arterial diametrical variations and the beat-to-beat pulse pressure acquired simultaneously from the RAPPW recorded using FBGPR. This proposed technique has been validated against the radial arterial diametrical measurements obtained from the color Doppler ultrasound. Two distinct trials have been illustrated in this work and the results from both techniques have been found to be in good agreement with each other.

Evaluation of different health education interventions among preschoolers: a randomized controlled pilot trial.

OBJECTIVE: The aim of this study is to assess the impact of three different health education methods among preschoolers. STUDY DESIGN: The study group included 100 preschoolers of the same socio-economic status randomly selected and divided into four groups. Debris index (DI-S) was recorded for all children followed by the dental health education. Group A received dental health education from the Dentist; Group B from the class teacher trained by the Dentist and Group C from the dental residents dressed mimicking cartoon characters. Group D acted as the control group. Post-intervention evaluation program was carried out after 3 months. Data were analyzed by Chi-square test, paired t-test and analysis of variance (ANOVA) appropriately using the SPSS Version 17.1. RESULTS: Comparison of pre- and post-intervention data showed that there was a statistically significant improvement in the (DI-S) scores in all groups except the control group. Group C showed a significant improvement compared to the other Groups A, B, and D (P<0.04). CONCLUSION: Drama as a method of health education can have a bigger impact on the oral health attitude and practices of the preschoolers. These modes can serve to reinforce as well as improve the oral health practices among pre-school children.

CO2 sensing at room temperature using carbon nanotubes coated core fiber Bragg grating.

The sensing of carbon dioxide (CO2) at room temperature, which has potential applications in environmental monitoring, healthcare, mining, biotechnology, food industry, etc., is a challenge for the scientific community due to the relative inertness of CO2. Here, we propose a novel gas sensor based on clad-etched Fiber Bragg Grating (FBG) with polyallylamine-amino-carbon nanotube coated on the surface of the core for detecting the concentrations of CO2 gas at room temperature, in ppm levels over a wide range (1000 ppm-4000 ppm). The limit of detection observed in polyallylamine-amino-carbon nanotube coated core-FBG has been found to be about 75 ppm. In this approach, when CO2 gas molecules interact with the polyallylamine-amino-carbon nanotube coated FBG, the effective refractive index of the fiber core changes, resulting in a shift in Bragg wavelength. The experimental data show a linear response of Bragg wavelength shift for increase in concentration of CO2 gas. Besides being reproducible and repeatable, the technique is fast, compact, and highly sensitive.