Quadrant dynamic clipped histogram equalization with gamma correction for color image enhancement

The detailed examination of low contrast image is a challenging issue. Thus, it makes difficult for the viewer to bring out the detailed features of the image. Histogram equalization (HE) is an efficient way to intensify the contrast of images. However, classical HE techniques result in immoderate intensification. Hence, an efficient contrast enhancement algorithm called quadrant dynamic clipped HE with gamma correction is proposed. This transformation addresses both over-enhancement and fine detail preservation, which ensures no false contouring. In the proposed method, histogram of the input image is partitioned into four sections using its mean value. Histogram clipping and gamma correction is used to control the color enhancement rate. Then, clipped subhistogram is equalized independently and then they combined together to form an enhanced image. The performance assessment of the proposed and other existing methods is evaluated in terms of entropy, contrast, colorfulness, and saturation. Test results demonstrates that the proposed method outperforms the other existing HE methods in terms of preserving entropy, colorfulness, saturation, and obtaining uniform degree enhancement.     

Fuzzy dissimilarity contextual intensity transformation with gamma correction for color image enhancement

Multimedia Tools and Applications - The color image enhancement algorithm proposed here yields an improvement of the image data that suppresses undesired distortions or enhances some image features...     

Synthesis and Biological Evaluation of Imidazopyridine–Oxindole Conjugates as Microtubule‐Targeting Agents

A library of imidazopyridine–oxindole conjugates was synthesised and investigated for anticancer activity against various human cancer cell lines. Some of the tested compounds, such as 10 a , 10 e , 10 f , and 10 k , exhibited promising antiproliferative activity with GI₅₀ values ranging from 0.17 to 9.31 μM . Flow cytometric analysis showed that MCF‐7 cells treated by these compounds arrested in the G₂/M phase of the cell cycle in a concentration‐dependent manner. More particularly, compound 10 f displayed a remarkable inhibitory effect on tubulin polymerisation. All the compounds depolarised mitochondrial membrane potential and caused apoptosis. These results are further supported by the decreased phosphorylation of Akt at Ser473. Studies on embryonic development revealed that the lead compounds 10 f and 10 k caused delay in the development of zebra fish embryos. Docking of compound 10 f with tubulin protein suggested that the imidazo[1,2‐a]pyridine moiety occupies the colchicine binding site of tubulin.     

Adaptive uniform finite-/fixed-time convergent second-order sliding-mode control

ABSTRACT

This paper presents an adaptive gain algorithm for second-order sliding-mode control (2-SMC), specifically a super-twisting (STW)-like controller, with uniform finite/fixed convergence time, that is robust to perturbations with unknown bounds. It is shown that a second-order sliding mode is established as exact finite-time convergence to the origin if the adaptive gain does not have the ability to get reduced and converge to a small vicinity of the origin if the adaptation algorithm does not overestimate the control gain. The estimate of fixed convergence time of the studied adaptive STW-like controller is derived based on the Lyapunov analysis. The efficacy of the proposed adaptive algorithm is illustrated in a tutorial example, where the adaptive STW-like controller with uniform finite/fixed convergence time is compared to the adaptive STW controller with non-uniform finite convergence time.     

Symmetric keys image encryption and decryption using 3D chaotic maps with DNA encoding technique

In present digital era, multimedia like images, text, documents and videos plays a vital role, therefore due to increase in usage of digital data; there comes high demand of security. Encryption is a technique used to secure and protect the images from unfair means. In cryptography, chaotic maps play an important role in forming strong and effective encryption algorithm. In this paper 3D chaotic logistic map with DNA encoding is used for confusion and diffusion of image pixels. Additionally, three symmetric keys are used to initialize 3D chaos logistic map, which makes the encryption algorithm strong. The symmetric keys used are 32 bit ASCII key, Chebyshev chaotic key and prime key. The algorithm first applies 3D non-linear logistic chaotic map with three symmetric keys in order to generate initial conditions. These conditions are then used in image row and column permutation to create randomness in pixels. The third chaotic sequence generated by 3D map is used to generate key image. Diffusion of these random pixels are done using DNA encoding; further XOR logical operation is applied between DNA encoded input image and key image. Analysis parameters like NPCR, UACI, entropy, histogram, chi-square test and correlation are calculated for proposed algorithm and also compared with different existing encryption methods.

     

Circularly polarized dual‐band zeroth order epsilon negative antenna using asymmetric unit cells

In this paper, a dual‐band zeroth order resonance (ZOR) circularly polarized epsilon negative antenna is proposed for the case where shunt ZOR (f_sh ) is higher than series ZOR (f_se ). Epsilon negative unit cells resonate f_sh , while a pseudo‐open termination unit cell with a series capacitance resonate f_se , resulting in a dual‐band ZOR. The pseudo‐open termination unit cell can be placed anywhere around the epsilon negative unit cells for proper matching. Circular polarization (CP) is achieved by creating orthogonal components using asymmetric unit cells (AUCs). Zeroth order resonator inherently provides 90° phase shift between two orthogonal polarizations. Left hand circular polarization (LHCP) is achieved by adding stubs to the unit cells with two 90° right bends. Electric field distribution is used to verify the resonances for zeroth order and it is found that both the resonances follow zeroth order characteristics. The measured resonances are 4.11 GHz (f_se ) and 4.60 GHz (f_sh ) with measured average axial ratio of 2.4 dB at f_se and 1.5 dB at f_sh , respectively. The measured LHCP peak gain for f_se is 1.53 dBic and for f_sh is 2.34 dBic. The proposed design covers a frequency range of 3.6 to 4.6 GHz by varying the length of the stubs.     

Brightness preserving optimized weighted bi-histogram equalization algorithm and its application to MR brain image segmentation

Medical image segmentation is crucial for neuroscience research and computer-aided diagnosis. However, intensity inhomogeneity and existence of noise in magnetic resonance images lead to incorrect segmentation. In this article, an effective method called enhanced fuzzy level set algorithm is presented to segment the white matter, gray matter, and cerebrospinal fluid automatically in contrast-enhanced brain images. In this method, first, exposure threshold is computed to divide the input histogram into two sub-histograms of different gray levels. The input histogram is clipped using a mean gray level to control the excessive enhancement rate. Then, these two sub-histograms are modified and equalized independently to get a better contrast enhanced image. Finally, an enhanced fuzzy level set algorithm is employed to facilitate image segmentation. The extensive experimental results proved the outstanding performance of the proposed algorithm compared with other existing methods. The results conform its effectiveness for MR brain image segmentation.     

Improvement of bone microarchitecture in methylprednisolone induced rat model of osteoporosis by using thiolated chitosan-based risedronate mucoadhesive film

Objective: In this study, we investigated the potential of thiolated chitosan-based mucoadhesive film, loaded with risedronate sodium in the treatment of osteoporosis.

Significance: Risedronate sodium is a bisphosphonate derivative having very low bioavailability when administered through the oral route. Moreover, the adverse effects associated with the drug when administered through GIT necessitate an alternative and feasible route which can improve its bioavailability and therapeutic efficacy.

Methods: Thiolation of chitosan was interpreted by different analytical techniques. The mucoadhesive films were prepared by the solvent evaporation method and evaluated for drug content analysis, swelling degree, mucoadhesive parameters, and permeation characterization. For the screening of preclinical efficacy and pharmacodynamic parameters, a methylprednisolone induced osteoporotic rat model was used. The trabecular microarchitecture and biochemical markers were evaluated for determination of bone resorption.

Results: The different analytical characterization of synthesized thiolated chitosan revealed that chitosan was successfully incorporated with thiol groups. The formulation containing 2:1 ratio of thiolated chitosan and HPMC-4KM was found to have the maximum swelling degree, mucoadhesive strength with a good force of adhesion and better in vitro permeability compared to the marketed formulation. With respect to trabecular microarchitecture, the drug-loaded film formulation showed superior and promising results. Furthermore, the film formulation also improved the serum level of biomarkers better than the marketed formulation.

Conclusions: The results significantly suggest that risedronate loaded novel mucoadhesive film formulation could be a logical approach in the therapeutic intervention of osteoporosis.     

Kinetic parameters of a two-phase model forin situ epoxidation of soybean oil

The process ofin situ epoxidation consists of a two-phase system that involves reactions in both phases, mass transfer between phases, and thermodynamic driving forces for the mass transfer. In this paper, we present a model that treats the process as a two-phase system and uses local phase concentrations to calculate reaction and mass transfer rates. The process ofin situ epoxidation has been broken down into a set of systematic steps, and rate constants for each step have been determined. A conventional stirred tank reactor, equipped with cooling coils, eliminated the heat and mass transfer limitations so that the true kinetics ofin situ epoxidation were observed. It is shown that significantly larger rates (larger by factors of 2–10) are obtained when heat and mass transfer limitations are removed. The two-phase model adequately predicts the epoxidation kinetics over a wide range of temperatures (50–90°C). In addition, the model also correctly predicts the effect of adding an inert solvent.