Cramer-Rao lower bounds for a damped sinusoidal process

The Cramer-Rao lower bounds (CRLBs) for the parameter estimators of a damped sinusoidal process are derived in this paper. Succinct matrix expressions for CRLB's of frequency, damping factor, amplitude, and initial phase are given for both scalar and vector processes. The relationships between the CRLBs of the characteristic parameters are established in the general multimode case. In particular, explicit, closed-form expressions for the single mode scalar/vector-damped/undamped cases are provided     

Low Complexity Preprocessing Approach for Wireless Physical Layer Secret Key Extraction Based on PCA

Achieving communication security, along with high computational efficiency, is one of the challenging issues in the advancement of modern resource constraint wireless networks. Wireless physical layer secure key extraction in conjunction with suitable preprocessing techniques may be a possible way out. Principal component analysis (PCA) is one of the dimensionality reduction techniques employed commonly in various domains for different applications. However, the physical layer secure key extraction employing PCA as dimensionality reduction is untouched so far. This paper presents a comprehensive study on PCA based wireless secret key extraction with real-time experimentation. In this work, we propose to apply PCA as a preprocessing technique to reduce the total number of numerical computations required in the key generation process, by cutting down the dimension of the input data set. We propose to select the extracted principal components to be processed further for key generation, based on their information content and cross-correlation. We analyzed the performance of the proposed in terms of bit disagreement rate, key randomness and pass ratio. The computational complexity of the proposed approach is derived and the effect of dimensionality reduction factor (\({\mathbf{R}}_{\mathbf{f}}\)) on the required numerical computations is analyzed. It is found that substantial improvement in bit disagreement performance is achieved along with a significant reduction in the required numerical computations. Remarkably, these outcomes are achieved by slightly modifying one of the blocks of the traditional key generation system. Furthermore, the practicability of the proposed technique is verified through real-time experimentation in different physical scenarios.

     

Crystallization of 2D Hybrid Organic–Inorganic Perovskites Templated by Conductive Substrates

2D hybrid organic–inorganic perovskites are valued in optoelectronic applications for their tunable bandgap and excellent moisture and irradiation stability. These properties stem from both the chemical composition and crystallinity of the layer formed. Defects in the lattice, impurities, and crystal grain boundaries generally introduce trap states and surface energy pinning, limiting the ultimate performance of the perovskite; hence, an in-depth understanding of the crystallization process is indispensable. Here, a kinetic and thermodynamic study of 2D perovskite layer crystallization on transparent conductive substrates are provided—fluorine-doped tin oxide and graphene. Due to markedly different surface structure and chemistry, the two substrates interact differently with the perovskite layer. A time-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to monitor the crystallization on the two substrates. Molecular dynamics simulations are employed to explain the experimental data and to rationalize the perovskite layer formation. The findings assist substrate selection based on the required film morphology, revealing the structural dynamics during the crystallization process, thus helping to tackle the technological challenges of structure formation of 2D perovskites for optoelectronic devices.     

Use of Templates to Fabricate Nanoscale Spherical Structures for Defined Architectural Control

Architectural design of biomaterial structures is essential to reach the full potential of the materials' chemical and biological properties. Clinically, these properties depend on the targeted applications of delivery, such as tissue regeneration, imaging, or cancer. To get an efficient material for biological applications, key properties are needed, such as degradability, low toxicity, cell specificity, relative efficiency, and capability of delivering multiple molecules. In recent years, significant progress has been made through either the design of the material itself (synthetic or natural polymers, dendrimers, crosslinking) or the fabrication technique (nozzle reactor, emulsion, and template). The combination of these materials and techniques results in a large variety of biomaterials that have varied shape and physico–chemical and biological properties. Nevertheless, these inherent properties are not sufficient and interest in discovering and developing new techniques that present these biomaterials in different light is now under focus. A useful strategy to prepare biomaterials with unique and novel architectures is through the use of templates that have defined geometrical features. This holds great promise, especially for the development of hollow structures, such as spheres. The nanoscale structural design of biomaterials via the use of templates and their potential clinical applications are discussed. In addition, the conceptual hurdles that must be overcome to produce applications that are clinically relevant are examined.

     

Photo-sensing properties of Cd-doped In2S3 thin films fabricated via low-cost nebulizer spray pyrolysis technique

In this study, we report the fabrication of cadmium-doped indium sulfide thin films (In₂S₃:Cd) using a low-cost nebulizer-aided spray pyrolysis process at 350 °C on glass substrates for photo-sensing applications. The impact of 0, 2, 4, and 8 wt% cadmium concentrations on the structure, morphology, optical properties, and photo-sensing capabilities of In₂S₃ thin films were examined systematically. From X-ray diffraction (XRD) analysis, the major peak is located in the (103) plane for all Cd-doped In₂S₃ thin film samples, and the maximum crystallite size for the 4 wt% sample is 59 nm. The field emission scanning electron microscope (FESEM) image revealed a homogenous large-grained surface of Cd-doped In₂S₃ film that completely covered the substrate. UV–Vis absorption analysis demonstrated good absorption for all thin film samples in the visible and ultraviolet regions of the electromagnetic spectrum, particularly, the 4% Cd-doped concentration showed excellent absorption as is observed from Tauc relation. The highest PL intensity at 680 nm was observed for the sample coated with 4 wt% of Cd. Under UV light, the I–V behavior depicts a light current of 1.06?×?10^–6 A for a 5 V bias voltage. The In₂S₃: Cd (4%) sample had the highest responsivity of 2.12?×?10^?1A/W and a detectivity of 1.84?×?10¹¹ Jones, with a high EQE of 50%. The study manifests that the developed Cd (4%)-doped In₂S₃ thin film sample might be better suited for the application of photodetectors.

     

Kinetic Modelling of Colour Degradation in Tomato Puree (Lycopersicon esculentum L.)

The kinetics of colour (measured as Hunter ‘a’ value) degradation in tomato puree (Lycopersicon esculentum L.) has been studied over a temperature range of 50–120 °C (isothermal condition), and also during normal open pan cooking, pressure cooking and cooking in a newly developed and patented fuel-efficient ‘EcoCooker’ (non-isothermal condition). The degradation of colour as measured by Hunter ‘a’ value was found to follow first order kinetics. The temperature dependence of degradation was adequately modelled by Arrhenius equation. A mathematical model has been developed using the isothermal parameters obtained to predict correctly the losses of red colour from the time–temperature data of non-isothermal heating/processing method. The results obtained indicate a colour degradation of similar magnitude in all the three modes of cooking used in the study.     

Cytochrome P450 inhibitory potential of selected Indian spices — possible food drug interaction

Spices constitute an important group of food which is virtually indispensable in the culinary art. In a view, these spices feared to pose a probability to affect the disposition of conventional pharmaceuticals through inhibition of human cytochrome P450 (CYPs) enzymes. In the present study an approach has been made to evaluate the possible CYP inhibition potential with some Indian spices (Capsicum annuum, Murraya koenigii, Zingiber officinale) and their major bioactive compounds, in combination with pooled microsome; as well as commercially available recombinant human CYP3A4, CYP2D6, CYP2C9 and CYP1A2. Quantification of the bioactive compound was determined through RP-HPLC, in order to standardize the plant material. CYP–carbon monoxide (CYP–CO) complex assay result indicated that all the plants and their bioactive compounds have an interaction potential with CYPs. Fluoregenic assay results indicated that the spice extracts have higher inhibition potential comparing to their single bioactive molecule. The higher enzyme inhibition potential by the extracts may be related to the synergistic effects due to the presence of other constituents in the extract. Capsaicin and C. annuum showed the lowest IC₅₀ value and 6-gingerol and Z. officinale extract showed the highest IC₅₀ value among the entire sample tested. The entire sample showed significantly less (P < 0.001, P < 0.01) interaction potential than known inhibitors. These findings indicate that selected spices are unlikely to cause clinically relevant drug interactions involving the inhibition of major CYP isozymes.     

Mixing Time Studies in Multiple Impeller Agitated Reactors

Mixing time studies have been carried in a 0.3m diameter and 0.9m tall vessel equipped with three impellers. Conductivity measurement technique has been used for the measurements of mixing time. Effect of the various parameters i.e. tracer density, tracer volume, speed of rotation and impeller combination on mixing time has been studied for two impeller combinations used viz. PTD‐PTD‐PTD and PTD‐PTD‐DT. A compartment model (with one fitted parameter, the exchange flow rate Q_E) with single compartment per agitation stage has been used to predict the conductivity response and the exchange coefficients are calculated from the model parameter. An attempt has been made to explain the experimental results on the basis of the liquid phase axial dispersion coefficient and cell residence time, calculated from the model parameter Q_E