RESUMEN

In recent years, numerous image encryption schemes have been developed that demonstrate different levels of effectiveness in terms of robust security and real-time applications. While a few of them outperform in terms of robust security, others perform well for real-time applications where less processing time is required. Balancing these two aspects poses a challenge, aiming to achieve efficient encryption without compromising security. To address this challenge, the proposed research presents a robust data security approach for encrypting grayscale images, comprising five key phases. The first and second phases of the proposed encryption framework are dedicated to the generation of secret keys and the confusion stage, respectively. While the level-1, level-2, and level-2 diffusions are performed in phases 3, 4, and 5, respectively, The proposed approach begins with secret key generation using chaotic maps for the initial pixel scrambling in the plaintext image, followed by employing the Fibonacci Transformation (FT) for an additional layer of pixel shuffling. To enhance security, Tribonacci Transformation (TT) creates level-1 diffusion in the permuted image. Level-2 diffusion is introduced to further strengthen the diffusion within the plaintext image, which is achieved by decomposing the diffused image into eight-bit planes and implementing XOR operations with corresponding bit planes that are extracted from the key image. After that, the discrete wavelet transform (DWT) is employed to develop secondary keys. The DWT frequency sub-band (high-frequency sub-band) is substituted using the substitution box process. This creates further diffusion (level 3 diffusion) to make it difficult for an attacker to recover the plaintext image from an encrypted image. Several statistical tests, including mean square error analysis, histogram variance analysis, entropy assessment, peak signal-to-noise ratio evaluation, correlation analysis, key space evaluation, and key sensitivity analysis, demonstrate the effectiveness of the proposed work. The proposed encryption framework achieves significant statistical values, with entropy, correlation, energy, and histogram variance values standing at 7.999, 0.0001, 0.0156, and 6458, respectively. These results contribute to its robustness against cyberattacks. Moreover, the processing time of the proposed encryption framework is less than one second, which makes it more suitable for real-world applications. A detailed comparative analysis with the existing methods based on chaos, DWT, Tribonacci transformation (TT), and Fibonacci transformation (FT) reveals that the proposed encryption scheme outperforms the existing ones.

RESUMEN

Twenty cyanobacterial strains of eight morphospecies isolated from deep-frozen (-15 °C) mat samples originally collected on Ross Island, in Victoria Land, and on the McMurdo Ice Shelf were screened for the presence of genes encoding for production of anatoxins, cylindrospermopsin, microcystin/nodularin and saxitoxin. One strain of each of Microcoleus autumnalis and Phormidesmis priestleyi and two strains of Wilmottia murrayi were found to produce microcystin. No toxin production was detected in the other 16 strains representing five species. The four toxin-producing strains were characterised using both morphological and molecular approaches. Phylogenetic analyses using partial 16S rRNA sequences were consistent with the morphological identification of all four strains. They were all found to contain a fragment of the mcyE gene, which is involved in microcystin biosynthesis. ELISA analysis of extracts from cultures of these strains confirmed the presence of low concentrations of microcystin: 0.35 µg/L in M. autumnalis, <0.15 µg/L in P. priestleyi, 1.60 µg/L in W. murrayi strain 1 and 0.9 µg/L in W. murrayi strain 2. This study includes the first report of microcystin synthesis by W. murrayi.

Asunto(s)

RESUMEN

OBJECTIVES: To evaluate and compare image quality and radiation dose between the helical and wide-volume scans to determine the protocol that provides a lower radiation dose without loss in image quality. METHODS: The study was prospectively conducted on consented adult patients that presented for routine brain CT. Image quality and radiation dose were compared between the helical and wide-volume scans on the Toshiba 160-slice Aquilion Prime CT scanner. The volume computed tomography dose index (CTDIvol) and dose length product (DLP) for each scan mode were collected and compared. Image quality was quantitatively and qualitatively evaluated using the unenhanced brain CT images. The data were analysed using a statistical package for social sciences (SPSS) software version 20 for both the descriptive and inferential statistics. A significant difference in image quality and radiation dose between the helical and wide-volume scans was determined based on a p-value of <0.05. RESULTS: A total of 54 participants were included, with two groups of 27 participants. The CTDIvol and DLP values were significantly p < 0.05 higher in the helical scan (CTDIvol: 65 mGy; DLP: 1597 mGy.cm) compared to the wide-volume scan (CTDIvol: 54 mGy; DLP: 1133 mGy.cm). The grey and white matters show a better signal-to-noise ratio (SNR) for the helical scan. Meanwhile, the contrast-to-noise ratio (CNR) was significantly p < 0.05 higher in the wide-volume scan. The results from the visual grading methods were compared and showed superior image quality in helical over the wide-volume scan. CONCLUSION: Wide-volume provides a lower dose compared to helical and therefore, could be adopted as the routine protocol for brain CT for in house dose optimisation. Where clinical conditions warrant the need for a helical scan, the protocol should be optimised in line with the as low as reasonable achievable (ALARA) principle.

Asunto(s)

RESUMEN

This study developed a rapid reversed-phase high-performance liquid chromatography (RP-HPLC) method equipped with a UV-Vis detector. The aquaponics system>s tilapia and marine snoek fishes were extracted using an autoclaving process and enzymatic treatment. The technique enabled the separation and quantification of cobalamin present in these fishes extracts. Phenomenex Luna® 5 µm C18 (2) 100 A LC-column (150 × 4.6 mm) was used as a stationary phase, while the mobile phase consisted of methanol and phosphoric acid in a ratio of 35:65 (v/v), respectively. The developed method was revealed to be rapid (a retention time of less than 5.0 min), linear (R2 = 0.9988), sensitive (limits of detection and quantification showed to be 0.0004 and 0.0011 µg/mL, respectively), precise (percentage relative standard deviation of 0.14% to 0.76%), and accurate (percentage mean recovery of 87.44 ± 0.33% to 97.08 ± 0.74%). The quantified concentrations of this vitamin in extracts of tilapia and snoek fishes were found to be 08.95 ± 0.35 and 14.97 ± 0.04 µg/mL, respectively. Therefore, we suggested that the developed RP-HPLC technique could be applicable for quality control evaluation in the food and pharmaceutical industries. Besides, the method could be vital for diagnostic analysis in clinical laboratories.

RESUMEN

Catechol O-methyltransferase, an enzyme involved in the metabolism of catechol containing compounds, catalyzes the transfer of a methyl group between S-adenosylmethionine and the hydroxyl groups of the catechol. Furthermore it is considered a potential drug target for Parkinson's disease as it metabolizes the drug levodopa. Consequently inhibitors of the enzyme would increase levels of levodopa. In this study, absorption, fluorescence and infrared spectroscopy as well as computational simulation studies investigated human soluble catechol O-methyltransferase interaction with silver nanoparticles. The nanoparticles form a corona with the enzyme and quenches the fluorescence of Trp143. This amino acid maintains the correct structural orientation for the catechol ring during catalysis through a static mechanism supported by a non-fluorescent fluorophore-nanoparticle complex. The enzyme has one binding site for AgNPs in a thermodynamically spontaneous binding driven by electrostatic interactions as confirmed by negative ΔG and ΔH and positive ΔS values. Fourier transform infrared spectroscopy within the amide I region of the enzyme indicated that the interaction causes relaxation of its ß-structures, while simulation studies indicated the involvement of six polar amino acids. These findings suggest AgNPs influence the catalytic activity of catechol O-methyltransferase, and therefore have potential in controlling the activity of the enzyme.