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The growth of optically good quality bulk size single crystal of pure and additives added 4-N, N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) crystal is reported by adopting the conventional slow evaporation solution technique. The grown single crystals were identified by single crystal and power X-ray Diffraction analysis. The luminescence study revealed the transition mechanism of ions. By estimating the hardness, Mayer index, yield strength, elastic stiffness constant, fracture toughness, and brittle index for the grown DAST single crystal using the Vickers micro-hardness analyzer, it is revealed that the grown crystal is a soft material. Using a continuous wave Nd-YAG laser and the standard Z-scan technique, the third-order nonlinearity of the pure and doped DAST single crystal was carefully examined. The third-order nonlinear optical properties show significantly higher values of the nonlinear absorption coefficient (β) and third-order nonlinear susceptibility (χ3). The calculated χ3 of grown pure, EDTA, and DTPA doped DAST crystals are 9.41 × 10−6, 8.06 × 10−6 and 7.92 × 10−6, respectively. The enhanced third-order nonlinear behavior suggests that the title compound is suitable for nonlinear optical applications. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an electromagnetic-piezoelectric integrated vibration based energy harvester to scavenge energy and generate steady power. By adopting rectangular cut cantilever with rectangular portion comprising the PE section and remaining cut portion acts as proof mass and NdFeB magnet which is surrounded by the coil. Power is harvested simultaneously by means of electromagnetic induction and piezoelectric principle. Though it works on different mechanisms, the design and fabrication of the harvester is as simple as the device with single energy conversion process, which results in reduced size and attains a greater power density. The design of hybrid harvester was modeled and investigated by using COMSOL multi-physics which produces 120 μW at its matching frequency with an optimum load. [ABSTRACT FROM AUTHOR]

RF MEMS switch is a micromechanical device fabricated using semiconductor technology that has numerous outstanding advantages such as low power consumption, small volume, high integration, and so on. One of the key features to be considered on the design of RF MEMS switches is the isolation of the DC bias and the RF signal being transmitted. It is attempted by the introduction of an insulator layer in between the actuation beam and the signal line. Silicon Nitride (Si3N4) is used as the material for insulation. This study involves the employment of a varying section fixed–fixed beam which helps in reduction of the spring constant as well as the pull-in voltage. An analytical model for the proposed device is developed and analyzed using MEMS design tools which are of industrial standard. The analysis shows that pull-in voltage can be decreased by 18% when compared to its similar counterparts. Additionally, this method gives the designer more opportunity to create switches with improved stiction immunity that require lower pull-in voltage. Therefore, the RF switch structure proposed in this work remains free from dielectric charging. Thus in this new switch, the pull-in voltage is considerably reduced still maintaining RF-DC isolation. [ABSTRACT FROM AUTHOR]

RF MEMS switch is an actuator which can be used to make or break a signal path in RF Communications. The proposed switch is an electrostatically actuated dual channel switch whose actuating beam has varying cross-section. This letter focuses on developing a mathematical model for the spring constant of a varying section fixed-fixed beam and validating it with simulation results. Unit load method and Moment area method are used in modeling of the beam. The theoretical and simulated results are matching closely and the difference is not more than 16%. Further, the effects of spring constant on the switch parameters like Pull-in Voltage, Switching time, Switching speed and restoring force are studied. The results and relations obtained are presented. [ABSTRACT FROM AUTHOR]

The growth of optically good quality bulk size (35 × 9 × 8 mm3) single crystal of pure 4-N, N-dimethylamino-4-N-methyl stilbazolium tosylate (DAST) crystal was reported by adopting the conventional slow evaporation solution technique. Moreover, we have found that so far nobody has detailed this enormous size DAST crystal which isn't yet announced in the literatures. The cell dimensions of the grown single crystals were obtained by single crystal and power x-ray diffraction studies reveals that the crystal belongs to monoclinic system. The etching study indicates the occurrences of surface dislocations on the crystal. The Vickers microhardness tester was employed to study the mechanical strength and it's found that the crystal belongs to a soft material category. The third order nonlinear optical properties were determined by Z-scan studies which shows significantly higher values of the nonlinear absorption coefficient (β) and third order nonlinear susceptibility (χ3 = 9.41 × 10–6 esu). The enhanced third order nonlinear behavior suggests that the title compound is suitable for nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Flower-like bismuth sulfide (Bi2S3) nanostructures were synthesized from two sulfur sources, namely thiourea and thioacetamide, by microwave irradiation technique. The synthesized materials were annealed at 300 °C for 3 h. The characteristic properties of the as-prepared and annealed samples S1, AS1 (thiourea source) and S2, AS2 (thioacetamide source) were studied by XRD, SEM with EDS, XPS, UV–Vis spectra and FTIR analysis. The XRD analysis revealed that the annealing process had increased the crystallite size of the Bi2S3 samples. The SEM images showed that the flower-like nanostructure of both the samples (S1and S2) was changed to spherical shape (AS1) and irregular shape (AS2) respectively after annealing. The EDS and XPS results confirm the purity and the presence of the Bi and S. The UV–Vis absorption spectra revealed that the optical band gap values of Bi2S3 were reduced due to the annealing process. The FTIR spectra showed the functional groups present in the as-prepared and annealed Bi2S3 samples. The annealed Bi2S3 nanoparticles (AS1) showed remarkable photocatalytic activity and achieved 98.6% RhB dye degradation in 180 min. The rhodamine B (RhB) photodegradation was determined to follow a pseudo-first-order kinetic model, with a rate constant of 0.02142 min−1 being the highest. After three cycles, the annealed Bi2S3 nano photocatalyst showed excellent reusability and stability. [ABSTRACT FROM AUTHOR]

In our previous paper, we have demonstrated the amorphous-glassy-crystalline-amorphous state phase transition of Li2SO4 crystalline samples at the number of shock pulses of 0, 1, 2, and 3, respectively. In the present work, we extend the study on the abovementioned sequence of phase transition in such a way that it is to be examined by the impedance spectroscopy. Based on the observations, the results of the respective spectra well-agree with each other depending on the number of shock pulses. The positional disorder of Li atoms and rotational disorder of SO4 units behave as observed in the impedance spectroscopy by the impact of shock waves such that the resultant significant changes (several orders of magnitude) are noticed in the ionic- conductivity of the titled sample. The conducting behavior of the titled sample with respect to its state is due to the existence of peddle–wheel and percolation mechanisms. [ABSTRACT FROM AUTHOR]

Highly efficient organic nonlinear optical stilbazolium crystals of 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS) single crystal were grown by slow solvent evaporation technique using methanol as a solvent. The structure and cell parameters of the grown crystals were derived from single crystal and powder x-ray diffraction analyses, and the optical properties of the grown crystal were analyzed by a UV–Vis spectrophotometer. The band gap of the grown crystal was found to be 2.28 eV. The vibrating modes of functional groups in the grown crystal were identified by FTIR spectroscopy. The dielectric measurement was made as a function of frequency (1 Hz–1 MHz) at different temperatures (50–200°C) in steps of 50°C. The dielectric constant and dielectric loss were found to be strongly dependent on temperature and frequency of the applied electric field. The semicircle in the Cole–Cole plot showed the presence of dielectric relaxation in the crystal with its radius representing the resistance of the crystal. The resistivity and AC conductivity were calculated from the measured dielectric data. [ABSTRACT FROM AUTHOR]

Haptic feedback in immersive virtual reality (IVR) systems is critical to enable a more intuitive and natural way of interacting with virtual objects. IVR-based haptic medical simulations such as needle insertion procedures have the potential to enhance clinicians' haptic expertise. This work is a preliminary study on the use and implementation of IVR for needle simulators. Although few studies have quantified haptic skills such as force Just Noticeable Difference (JND) with the single finger, none have measured the force JND as recommended in the standard needle insertion protocol in an IVR environment. The hypothesis of this study is that there will be an improvement of force perception in the IVR, compared to that of the non-immersive virtual reality (NIVR) which facilitates the use of IVR for medical simulations. This paper emphasized on two objectives: firstly, the development of the observer state model for both the IVR and NIVR and the theoretical analysis of the psychophysical measures in both of the environments. Secondly, measures of force JND with the three fingers and comparison of these measures in NIVR to that of the IVR using psychophysical study with the force matching task, constant stimuli method, and isometric force probing stimuli to validate the model. Twenty voluntary subjects performed the experiment in both of the environments. Mean force JND and standard deviation of the JND were found to be 9.12% and 3.75% in the NIVR and 5.91% and 3.65% in the IVR (p value < 0.0001) which are in the same range of JNDs found in the literature (5–10%) for the NIVR using a single finger. Surprisingly, the results showed a better force JND in the IVR compared to that of the NIVR. Also, a simple state observer model was proposed to explain the improvement of force JND in the IVR. This study would quantitatively reinforce the use of IVR for the design of various medical simulators. [ABSTRACT FROM AUTHOR]

Conventional controllers in impedance-based haptic interfaces are sampled data systems that utilize position and velocity information for the necessary force feedback. In a canonical virtual wall simulation, this feedback force is generated based on interaction with the wall simulating certain stiffness and damping. Increasing the sampling rate of the controller increases the stable range of virtual wall stiffness. However, an increased sampling rate exacerbates the velocity information, decreasing the stable range of virtual wall damping. In this work, the authors propose a dual-rate sampling scheme in which the position and velocity loops of a haptics controller are decoupled and sampled at different rates. The scheme enables independent sampling of the position data at higher rates, while simultaneously sampling the velocity data at appropriate rates. In this paper, the authors provide experimental and theoretical implications of the effect of dual-rate sampling on the stability of a haptic interface. Experiments with a single degree-of-freedom (DOF) haptic interface reveals an enhanced region of stable virtual wall stiffness for a particular range of virtual wall damping, compared to the values with conventional uniform-rate scheme. Virtual wall stiffness ranging from 150 - 360 Nm/rad was stably implemented over a range of 0 - 1 Nms/rad of virtual wall damping using the proposed scheme at position loop sampling rate of 20kHz and velocity loop sampling rate of 2kHz. Whereas in the conventional scheme, the stable range of virtual stiffness dropped considerably (∼ 0 Nm/rad) for the virtual wall damping above 0.1 Nms/rad when the uniform rate sampling of 20kHz was used for both the position and velocity sampling loops. Theoretical stability analyzes using classical control tools and simulations justified the effectiveness of the proposed scheme. The scheme is easy to implement and extensible to multi-DOF haptic interfaces as well. [ABSTRACT FROM AUTHOR]

Bulk terahertz emitting and technologically advanced DAST crystal is grown using a simple, cost effective and efficient seed rotation technique from a saturated methanol solution. The grown crystal is identified by a single crystal XRD analysis and powder X-ray diffraction studies. HRXRD experiments substantiate a good crystalline perfection without interior grain boundaries. The ferroelectric nature of the crystal has been described by P-E hysteresis loop analysis, which corroborates with better ferroelectric behavior than other benchmarked inorganic materials. The hardness, elastic stiffness, and yield strength shows decreasing trend for increasing loads and the work hardening coefficient confirm that the DAST is a soft material. Two-dimensional nucleation growth with minimum dislocation is evident from the etch patterns. [ABSTRACT FROM AUTHOR]

As per the AHA 2015 and ERC 2015 guidelines for resuscitation, chest compression depth should be between 5 and 6 cm with a rate of 100-120 compressions per minute. Theoretical validation of these guidelines is still elusive. We developed a computer model of the cardiopulmonary resuscitation (CPR) system to validate these guidelines. A lumped element computer model of the cardiovascular system was developed to simulate cardiac arrest and CPR. Cardiac output was compared for a range of compression pressures and frequencies. It was observed from our investigation that there is an optimum compression pressure and rate. The maximum cardiac output occurred at 100 mmHg, which is approximately 5.7 cm, and in the range of 100 to 120 compressions per minute with an optimum value at 110 compressions per minute, validating the guidelines. Increasing the pressure or the depth of compression beyond the optimum, limits the blood flow by depleting the volume in the cardiac chambers and not allowing for an effective stroke volume. Similarly increasing the compression rate beyond the optimum degrades the ability of the chambers to pump blood. The results also bring out the importance of complete recoil of the chest after each compression with more than 400% increase in cardiac output from 90% recoil to 100% recoil. Our simulation predicts that the recommendation to compress harder and faster is not the best counsel as there is an optimum compression pressure and rate for high-quality CPR. [ABSTRACT FROM AUTHOR]

Background: In laparoscopic surgery, no external feedback on the magnitude of the force exerted is available. Hence, surgeons and residents tend to exert excessive force, which leads to tissue trauma. Ability of surgeons and residents to perceive their own force output without external feedback is a critical factor in laparoscopic force-skills training. Additionally, existing methods of laparoscopic training do not effectively train residents and novices on force-skills. Hence, there is growing need for the development of force-based training curriculum. Objective: As a first step towards force-based laparoscopic skills training, this study analysed force perception difference between laparoscopic instrument and finger in contralateral bimanual passive probing task. Methods: The study compared the isometric force matching performance of novices, residents and surgeons with finger and laparoscopic instrument. Contralateral force matching paradigm was employed to analyse the force perception capability in terms of relative (accuracy), and constant errors in force matching. Results: Force perception of experts was found to be better than novices and residents. Interestingly, laparoscopic instrument was more accurate in discriminating the forces than finger. The dominant hand attempted to match the forces accurately, whereas non-dominant hand (NH) overestimated the forces. Further, the NH of experts was found to be most accurate. Furthermore, excessive forces were applied at lower force levels and at very high force levels. Conclusions: Due to misperception of force, novices and residents applied excessive forces. However, experts had good control over force with both dominant and NHs. These findings suggest that force-based training curricula should not only have proprioception tasks, but should also include bimanual force-skills training exercises in order to improve force perception ability and hand skills of novices and residents. The results can be used as a performance metric in both box and virtual reality based force-skills training. [ABSTRACT FROM AUTHOR]

Takayasu's arteritis disease (TA) remains a rarely studied chronic inflammatory disease. Our objective is to analyze peripheral pulse using photoplethysmography (PPG) as a new assessment method for diagnosing TA. So far no literature reports detailed morphological analysis of TA PPG signals. PPG signals of twenty normal and twenty TA patients at five different regions such as left and right thumbs, left and right toes and neck have been acquired simultaneously. Morphological parameters of peripheral signals such as peak-to-peak time, the crest time (CT), reflection index (RI), maximum systolic slope (MSS), maximum diastolic slope, pulse height, area under pulse and pulse transit time are obtained from PPG and electro cardiogram of normal and TA patients. Surprisingly RI is different in all the five locations of TA patients, whereas it is same for normal in all five locations. Mean MSS are significantly lesser than normal subjects. Mean CT of normal subjects is always lesser than normal subject. Morphological parameters based classification method has sensitivity of 80-100 and specificity of 86-100 in all limbs/all parameters. Bilateral dissimilarity in morphological parameters of multi site peripheral signals in the TA patients can be used to diagnose TA patients and find the pathological site. Less population is studied which reflects the rarity of the TA disease. [ABSTRACT FROM AUTHOR]

In this work, a reduced-order forward dynamics of multiclosed-loop systems is proposed by exploiting the associated inherent kinematic constraints at acceleration level. First, a closed-loop system is divided into an equivalent open architecture consisting of several serial and tree-type subsystems by introducing cuts at appropriate joints. The resulting cut joints are replaced by appropriate constraint forces also referred to as Lagrange multipliers. Next, for each subsystem, the governing equations of motion are derived in terms of the Lagrange multipliers, which are based on the Newton-Euler formulation coupled with the concept of Decoupled Natural Orthogonal Complement (DeNOC) matrices, introduced elsewhere. In the proposed forward dynamics formulation, Lagrange multipliers are calculated sequentially at the subsystem level, and later treated as external forces to the resulting serial or tree-type systems of the original closed-loop system, for the recursive computation of joint accelerations. Note that such subsystem-level treatment allows one to use already existing algorithms for serial and tree-type systems. Hence, one can perform the dynamic analyses relatively quickly without rewriting the complete model of the closed-loop system at hand. The proposed methodology is in contrast to the conventional approaches, where the Lagrange multipliers are calculated together at the system level or simultaneously along with the joint accelerations, both of which incur higher order computational complexities, and thereby a greater number of arithmetic operations. Due to the smaller size of matrices involved in evaluating Lagrange multipliers in the proposed methodology, and the recursive computation of the joint accelerations, the overall numerical performances like computational efficiency, etc., are likely to improve. The proposed reduced-order forward dynamics formulation is illustrated with two multiclosed-loop systems, namely, a 7-bar carpet scrapping mechanism and a 3-RRR parallel manipulator. [ABSTRACT FROM AUTHOR]

The chelating ability of aqueous leaf extract of Aerva lanata was assessed in vitro. The aqueous leaf extract showed a dose dependent decrease in chelating ability using FeCl. The highest chelating ability of aqueous leaf extract was observed at 2 × 10 g/mL (100 ± 0.00). The antioxidant activity of the aqueous leaf extract ranged from 42.13% to 88.66%. At 2 × 10 g/mL concentration, a strong positive significant correlation was observed between chelating ability and total phenolics concentration (R = 0.94; P = 0.001). The chelating ability of aqueous leaf extract (2 × 10 g/mL) showed a high positive significant correlation with antioxidant activity (R = 0.78; P = 0.001). Aqueous leaf extract removed the chromium from tannery effluent by 43 mg/g. Allium cepa toxicity test was performed on tannery effluent treated with aqueous leaf extract that increased the root length of onion. [ABSTRACT FROM AUTHOR]

Extraction of extra-cardiac information from photoplethysmography (PPG) signal is a challenging research problem with significant clinical applications. In this study, radial basis function neural network (RBFNN) is used to reconstruct the gastric myoelectric activity (GMA) slow wave from finger PPG signal. Finger PPG and GMA (measured using Electrogastrogram, EGG) signals were acquired simultaneously at the sampling rate of 100 Hz from ten healthy subjects. Discrete wavelet transform (DWT) was used to extract slow wave (0-0.1953 Hz) component from the finger PPG signal; this slow wave PPG was used to reconstruct EGG. A RBFNN is trained on signals obtained from six subjects in both fasting and postprandial conditions. The trained network is tested on data obtained from the remaining four subjects. In the earlier study, we have shown the presence of GMA information in finger PPG signal using DWT and cross-correlation method. In this study, we explicitly reconstruct gastric slow wave from finger PPG signal by the proposed RBFNN-based method. It was found that the network-reconstructed slow wave provided significantly higher ( P < 0.0001) correlation (≥0.9) with the subject's EGG slow wave than the correlation obtained (≈0.7) between the PPG slow wave from DWT and the EEG slow wave. Our results showed that a simple finger PPG signal can be used to reconstruct gastric slow wave using RBFNN method. [ABSTRACT FROM AUTHOR]

This article investigates the possibility of extracting gastric motility (GM) information from finger photoplethysmographic (PPG) signals non-invasively. Now-a-days measuring GM is a challenging task because of invasive and complicated clinical procedures involved. It is well-known that the PPG signal acquired from finger consists of information related to heart rate and respiratory rate. This thread is taken further and effort has been put here to find whether it is possible to extract GM information from finger PPG in an easier way and without discomfort to the patients. Finger PPG and GM (measured using Electrogastrogram, EGG) signals were acquired simultaneously at the rate of 100 Hz from eight healthy subjects for 30 min duration in fasting and postprandial states. In this study, we process the finger PPG signal and extract a slow wave that is analogous to actual EGG signal. To this end, we chose two advanced signal processing approaches: first, we perform discrete wavelet transform (DWT) to separate the different components, since PPG and EGG signals are non-stationary in nature. Second, in the frequency domain, we perform cross-spectral and coherence analysis using autoregressive (AR) spectral estimation method in order to compare the spectral details of recorded PPG and EGG signals. In DWT, a lower frequency oscillation (≈0.05 Hz) called slow wave was extracted from PPG signal which looks similar to the slow wave of GM in both shape and frequency in the range (0-0.1953) Hz. Comparison of these two slow wave signals was done by normalized cross-correlation technique. Cross-correlation values are found to be high (range 0.68-0.82, SD 0.12, R = 1.0 indicates exact agreement, p < 0.05) for all subjects and there is no significant difference in cross-correlation between fasting and postprandial states. The coherence analysis results demonstrate that a moderate coherence (range 0.5-0.7, SD 0.13, p < 0.05) exists between EGG and PPG signal in the 'slow wave' frequency band, without any significant change in the level of coherence in postprandial state. These results indicate that finger PPG signal contains GM-related information. The findings are sufficiently encouraging to motivate further exploration of finger PPG as a non-invasive source of GM-related information. [ABSTRACT FROM AUTHOR]

comprehensive model, which has the advantages of both lumped parameter and distributed parameter, has been developed with the objective of investigating the respiratory influences in radial artery pressure pulse as in photoplethysmography (PPG). It integrates lumped parameter cardiopulmonary (CP) model and transmission line arterial tree model from aorta to radial artery. The cardio-pulmonary interaction is realized by incorporating respiratory-induced variations in intrapleural pressure (Ppl) in circulatory system. The PPG signal of the model is considered as the radial artery pulse. To investigate the interaction Valsalva Maneuver (VM) condition has been simulated for different Ppl magnitude (10, 20, 30, and 40 mmHg) and for different time duration (5, 10, 15, and 20 s), and validated with PPG signal recorded in 10 normal subjects performing VM. The effects of test duration and VM pressure are studied in both the simulation and the experiments with specific focus on the maximal (%∆) changes in Heart Rate (HR), and Mean Arterial Pressure (MAP) during phases II and IV of VM. The correlation coefficients derived from model result have good agreement with experimental results. As radial artery pulse plays important role in both allopathy and alternate medicine systems, this model can serve to study its clinical importance in detecting cardiac and respiratory pathologies. [ABSTRACT FROM AUTHOR]

Diabetic neuropathy is one of the most important factors for foot ulceration in diabetes mellitus (DM) patients. Among different sensibility measures of neuropathy, two-point discrimination (TPD) has been suggested as a reliable method; however, the correlation of TPD with other well-known measures is not known. We measured the loss of protective sensation using Semmes-Weinstein Monofilaments (SWMF), hardness of the foot sole using shore meter (sh), power ratio (PR) using pedopowergraph and TPD using esthesiometer in foot areas of both left and right legs in 14 DM subjects. We have found no correlation either between TPD and shore values (sh) or between TPD and PR. The SWMF (10 g) is found not to provide any additional value in measuring loss of sensation in comparison to TPD. The TPD appears to be measuring different property of the foot compared to other measures. The mechanism of this independence is not well understood and more investigation is required to understand the mechanism. [ABSTRACT FROM AUTHOR]

We report the influence of EDTA and DTPA on the optical and laser damage thresholds of industrially relevant 4-dimethylamino-N-methyl stilbazolium tosylate (DAST) single crystals. Single crystal X-ray diffraction and powder X-ray diffraction studies substantiate that they crystallize in monoclinic system. The dopants facilitate tuning of the refractive indices and their optical conductivity. The laser damage threshold values of EDTA and DTPA-doped DAST crystals were found to be 1.5 and 1.6 times higher than the pure DAST crystal. The voltage-dependant photoconducting studies performed at ambient conditions shows negative photoconducting nature for pure and EDTA-doped DAST crystals while positive photoconducting nature is noticed for DTPA-doped crystal. The etching studies demonstrate the quality of the doped DAST crystals is better than the pure one. [ABSTRACT FROM AUTHOR]