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A new steganographic method by pixel-value differencing (PVD) using general quantization ranges of pixel pairs' difference values is proposed. The objective of this method is to provide a data embedding technique with a range table with range widths not limited to powers of 2, extending PVD-based methods to enhance their flexibility and data-embedding rates without changing their capabilities to resist security attacks. Specifically, the conventional PVD technique partitions a grayscale image into 1 × 2 non-overlapping blocks. The entire range [0, 255] of all possible absolute values of the pixel pairs' grayscale differences in the blocks is divided into multiple quantization ranges. The width of each quantization range is a power of two to facilitate the direct embedding of the bit information with high embedding rates. Without using power-of-two range widths, the embedding rates can drop using conventional embedding techniques. In contrast, the proposed method uses general quantization range widths, and a multiple-based number conversion mechanism is employed skillfully to implement the use of non-power-of-two range widths, with each pixel pair being employed to embed a digit in the multiple-based number. All the message bits are converted into a big multiple-based number whose digits can be embedded into the pixel pairs with a higher embedding rate. Good experimental results showed the feasibility of the proposed method and its resistance to security attacks. In addition, implementation examples are provided, where the proposed method adopts non-power-of-two range widths and employs multiple-based number conversion to expand the data-hiding and steganalysis-resisting capabilities of other PVD methods. [ABSTRACT FROM AUTHOR]

A modified multiway pixel-value differencing method for image steganography using general quantization ranges of pixel pairs’ difference values is proposed, where the widths of the quantization ranges are not limited to be powers of two. The method can be employed to embed a secret message into a cover image with a higher embedding rate. The cover image is partitioned into non-overlapping complete or incomplete blocks using $1 \times 3$ , $2 \times 2$ , $2 \times 3$ , or $3 \times 3$ block templates. The message bitstream, whose bit positions are randomized in advance by use of a random number generator, can be embedded in the resulting blocks. More specifically, one pixel in each block is set as a shared pixel, and the least-significant-bit substitution method with the optimal pixel adjustment process is employed to embed message bits into the shared pixel. Next, the shared pixel in the block is combined with each remaining pixel to form a pixel pair, which is then utilized to embed message bits by a new pixel-value differencing method. Also, the use of non-power-of-two range widths is accomplished by a multiple-based number conversion mechanism, and the shared pixel in each block, as well as each related pixel pair whose two grayscale values pass a falling-off-boundary check, are used to embed the digits of the resulting multiple-based number. The experimental results show that the embedding rates yielded by the proposed method are higher than those yielded by existing multiway pixel-value differencing methods. The stego-images resulting from embedding secret messages retain good image quality, and the RS steganalysis process cannot detect the presence of the embedded secret messages.

The growing preference for incorporating microbial aspartic proteases in industries is due to their high catalytic function and high degree of substrate selectivity. These properties, however, are attributable to molecular alterations in their structure and a variety of other characteristics. Molecular tools, functional genomics, and genome editing technologies coupled with other biotechnological approaches have aided in improving the potential of industrially important microbial proteases by addressing some of their major limitations, such as: low catalytic efficiency, low conversion rates, low thermostability, and less enzyme yield. However, the native folding within their full domain is dependent on a surrounding structure which challenges their functionality in substrate conversion, mainly due to their mutual interactions in the context of complex systems. Hence, manipulating their structure and controlling their expression systems could potentially produce enzymes with high selectivity and catalytic functions. The proteins produced by microbial aspartic proteases are industrially capable and far-reaching in regulating certain harmful distinctive industrial processes and the benefits of being eco-friendly. This review provides: an update on current trends and gaps in microbial protease biotechnology, exploring the relevant recombinant strategies and molecular technologies widely used in expression platforms for engineering microbial aspartic proteases, as well as their potential industrial and biotechnological applications. [ABSTRACT FROM AUTHOR]

Dihydroquinazolinone (DHQZ) has recently been harnessed as a ketone‐derived pro‐aromatic reagent extensively employed in (metalla)photoredox reactions as versatile group transfer agents. In this work, we outline a column chromatography‐free protocol for the multigram‐scale synthesis of pro‐aromatic DHQZs as well as its use in a gram‐scale nickel/photoredox dual‐catalyzed cross‐coupling in single‐batch, photoflow, and simultaneous multiple smaller batches. While the single‐batch approach leveraged moderate yields, a simple plug‐flow photoreactor also exhibited amenable productivity (up to 45 % yield) despite the use of a heterogeneous base. Meanwhile, performing the metallaphotoredox‐catalyzed reaction in multiple smaller batches in an improvised photoreactor facilitated high yields of up to 59 % and good reproducibility, implying a convenient alternative in the absence of photoflow setups. [ABSTRACT FROM AUTHOR]