Mechanistic Investigations on the Interaction of Morita-Baylis-Hillman Ketones with 2-Aminothiophenol.

The reaction of Morita-Baylis-Hillman ketones with 2-aminothiophenol mediated by Cs2CO3 results in an oxidative cyclization to 2,2-disubstituted dihydro-1,4-benzothiazines, with the structure of the product indicating the occurrence of an aza-Michael addition along the pathway. In contrast, in the absence of a base, the parent compounds interact to produce a thia-Michael adduct instead. A deeper mechanistic study improved our understanding of the apparent contradiction and provided insight into the base-dependent switch in reactivity.

Estimation of number of unmanned aerial vehicles in a scene utilizing acoustic signatures and machine learning.

With the exponential growth in unmanned aerial vehicle (UAV)-based applications, there is a need to ensure safe and secure operations. From a security perspective, detecting and localizing intruder UAVs is still a challenge. It is even more challenging to accurately estimate the number of intruder UAVs on the scene. In this work, we propose a simple acoustic-based technique to detect and estimate the number of UAVs. Our method utilizes acoustic signals generated from the motion of UAV motors and propellers. Acoustic signals are captured by flying an arbitrary number of ten UAVs in different combinations in an indoor setting. The recorded acoustic signals are trimmed, processed, and arranged to create an UAV audio dataset. The UAV audio dataset is subjected to time-frequency transformations to generate audio spectrogram images. The generated spectrogram images are then fed to a custom lightweight convolutional neural network (CNN) architecture to estimate the number of UAVs in the scene. Following training, the proposed model achieves an average test accuracy of 93.33% as compared to state-of-the-art benchmark models. Furthermore, the deployment feasibility of the proposed model is validated by running inference time calculations on edge computing devices, such as the Raspberry Pi 4, NVIDIA Jetson Nano, and NVIDIA Jetson AGX Xavier.

Generalized multi-cavity laser self-mixing interferometry based on scattering theory.

We present a generalized mathematical model and algorithm for the multi-cavity self-mixing phenomenon based on scattering theory. Scattering theory, which is extensively used for travelling wave is exploited to demonstrate that the self-mixing interference from multiple external cavities can be modelled in terms of individual cavity parameters recursively. The detailed investigation shows that the equivalent reflection coefficient of coupled multiple cavities is a function of both attenuation coefficient and the phase constant, hence propagation constant. The added benefit with recursively model is that it is computationally very efficient to model large number of parameters. Finally, with the aid of simulation and mathematical modelling, we demonstrate how the individual cavity parameters such as cavity length, attenuation coefficient, and refractive index of individual cavities can be tuned to get a self-mixing signal with optimal visibility. The proposed model intends to leverage system description for biomedical applications when probing multiple diffusive media with distinct characteristics, but could be equally extended to any setup in general.

Acyl Transfer-Driven Rauhut-Currier Dimerization of Morita-Baylis-Hillman Ketones.

A serendipitous Rauhut-Currier dimerization of 1,1-disubstituted activated olefins derived from Morita-Baylis-Hillman adducts was observed in the presence of DABCO. The reaction is driven by the migration of an acyl group and produces multifunctionalized enol esters in yields greater than 90% in most cases, without necessitating column chromatographic purification. The acyl transfer is thought to proceed via a transition state typical of a Morita-Baylis-Hillman (MBH) reaction, supported by a brief mechanistic study involving computational calculations.

Synthesis of 2,2-Disubstituted Dihydro-1,4-benzothiazines from Morita-Baylis-Hillman Ketones by an Oxidative Cyclization.

An oxidative cyclization ensued upon interaction of Morita-Baylis-Hillman (MBH) ketones with 2-aminothiophenol in the presence of Cs2CO3, resulting in the formation of new 2,2-disubstituted dihydro-1,4-benzothiazines. The reaction features an aza-Michael addition and an oxidative cyclization involving the formation of a carbon-sulfur bond and works well over a wide range of MBH ketones to deliver the dihydrobenzothiazines in good yields in reasonable reaction times under mild conditions.

Vulnerability of Construction Workers During COVID-19: Tracking Welfare Responses and Challenges.

This paper takes stock of the cash assistance provided by the government to construction workers during the COVID-19 pandemic. As the role of the state construction welfare board has been crucial, some existing issues related to boards and challenges emerged during the crisis have also been discussed. Results show that cash benefit through direct benefit transfer has partially helped workers to overcome their financial distress, but 65% workers did not receive any benefit due to various issues related to registration and seeding of bank accounts with Aadhar. Sluggish process of registration has been a major issue which is being addressed by different mechanisms, but results would be known later. Proper cess collection and its utilisation is still an important issue as 61% of the cess collected in 2019 was not utilised. Even during the crisis, 15% cess was used at most in direct benefit transfer and in-kind (food distribution) support. Majority of the states are running a number of welfare schemes, but the coverage is poor despite proper guidelines set under the Model Welfare Framework of the Ministry of Labour and Employment. The objectives of Mission Mode Projects are appreciable, but the outcomes are not known even after the completion of deadlines. Above all, the emerging issues of maintaining health and hygiene at worksite and living place and getting vaccinated are major challenges for the sustainability of the construction sector. Hence, a collective effort of the government, employers, and workers' organisations is the need of the hour.

Emission characteristics of ultrafine particles from bare and Al2O3 coated graphite for high temperature applications.

Owing to its exceptional properties at high temperature, graphite is used in several applications such as structural material and fuel block in high temperature nuclear reactors. Air ingress is one of the serious safety concerns in these reactors. Oxidation of graphite leading to increased porosity affects its mechanical strength and may lead to core collapse resulting in a severe accident. During such a scenario, generation of graphite particles could be the main hazard. Once generated, these particles often in fine and ultrafine sizes, may carry radioactivity to large distances and/or for long times. These particles owing to their higher surface to volume ratio possess an additional inhalation hazard. Ultrafine particles have the potential to enter into respiratory tract and cause damage to body organs. Coating of graphite components is preferred to reduce the oxidation induced damages at high temperatures. In the present work, effect of alumina (Al2O3) coating on the emission characteristics of particles from graphite under high temperature conditions has been investigated. Bare and Al2O3 coated graphite specimens were heated within a closed chamber at varying temperatures during these experiments. Temporal evolution of concentrations of gases (CO and CO2) and particles were measured. The results reveal that Al2O3 coating on the graphite delayed the oxidation behavior and the structure of graphite remained largely intact at high temperatures. A significant reduction in aerosol formation and CO emission was also noticed for the coated specimens.

Diamine-mediated degradative dimerisation of Morita-Baylis-Hillman ketones.

A degradative dimerisation of Morita-Baylis-Hillman ketones was observed in the presence of a primary diamine. The reaction proceeded swiftly to produce methylene-bridged 1,3-dicarbonyl compounds. A brief mechanistic investigation alluded to a retro-Mannich reaction as the key step of the transformation.

A Hydrazine Insertion Route to N'-Alkyl Benzohydrazides by an Unexpected Carbon-Carbon Bond Cleavage.

A serendipitous carbon-carbon bond cleavage in the reaction of benzoyl acrylates, derived from Morita-Baylis-Hillman adducts, with hydrazines delivered new N',N'-disubstituted benzohydrazides. The reaction features a regioselective formation of two carbon-nitrogen bonds and works well with a range of acrylates and hydrazines. A brief mechanistic investigation alluded to a cyclic hemiaminal as a plausible intermediate.

Microcantilever Displacement Measurement Using a Mechanically Modulated Optical Feedback Interferometer.

Microcantilever motion detection is a useful tool for the characterization of the physical, chemical and biological properties of materials. In the past, different approaches have been proposed and tested to enhance the behavior, size and simplicity of microcantilever motion detectors. In this paper, a new approach to measure microcantilever motion with nanometric resolution is presented. The proposed approach is based on the concept of mechanically-modulated optical feedback interferometry, a technique that has shown displacement measurement capabilities well within the nanometric scale and that, due to its size, compactness and low cost, may be a suitable choice for measuring nanometric motions in cantilever-like sensors. It will be shown that the sensor, in its current state of development, is capable of following a cantilever sinusoidal trajectory at different sets of frequencies ranging up to 200 Hz and peak to peak amplitudes up to λ / 2 with experimental resolutions in the λ / 100 range.

Current Developments on Optical Feedback Interferometry as an All-Optical Sensor for Biomedical Applications.

Optical feedback interferometry (OFI) sensors are experiencing a consistent increase in their applications to biosensing due to their contactless nature, low cost and compactness, features that fit very well with current biophotonics research and market trends. The present paper is a review of the work in progress at UPC-CD6 and LAAS-CNRS related to the application of OFI to different aspects of biosensing, both in vivo and ex vivo. This work is intended to present the variety of opportunities and potential applications related to OFI that are available in the field. The activities presented are divided into two main sensing strategies: The measurement of optical path changes and the monitoring of flows, which correspond to sensing strategies linked to the reconstruction of changes of amplitude from the interferometric signal, and to classical Doppler frequency measurements, respectively. For optical path change measurements, measurements of transient pulses, usual in biosensing, together with the measurement of large displacements applied to designing palliative care instrumentation for Parkinson disease are discussed. Regarding the Doppler-based approach, progress in flow-related signal processing and applications in real-time monitoring of non-steady flows, human blood flow monitoring and OFI pressure myograph sensing will be presented. In all cases, experimental setups are discussed and results presented, showing the versatility of the technique. The described applications show the wide capabilities in biosensing of the OFI sensor, showing it as an enabler of low-cost, all-optical, high accuracy biomedical applications.

Extraction of vibration parameters from optical feedback interferometry signals using wavelets.

This paper proposes the use of the wavelet transform as a technique that is suited for fringe detection and analysis of optical feedback interferometry (OFI) signals, thus allowing the retrieval of extremely small physical motion phenomena. A novel algorithm based on wavelet transform is used to process the OFI signal simultaneously in the time and frequency domains, enabling precise detection of signal fringes and, thus, the extraction of amplitude features of the vibrating target with error in the order of 0.1λ. Furthermore, using a complex Morlet wavelet as an analyzing wavelet enables us to extract important information from the time envelope of the OFI signal. Such an envelope can be useful in detecting fringes even in the presence of speckle reducing the error in a displacement reconstruction. Examples of OFI applications, including nanometric displacement sensing without direction ambiguity as well as the measurement of the frequency and velocity of vibrating targets and the detection in time of no periodic events, are also presented using this wavelet approach.