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Current in vivo and in vitro models fail to accurately recapitulate the human heart microenvironment for biomedical applications. This study explores the use of cardiac spheroids (CSs) to biofabricate advanced in vitro models of the human heart. CSs were created from human cardiac myocytes, fibroblasts and endothelial cells (ECs), mixed within optimal alginate/gelatin hydrogels and then bioprinted on a microelectrode plate for drug testing. Bioprinted CSs maintained their structure and viability for at least 30 d after printing. Vascular endothelial growth factor (VEGF) promoted EC branching from CSs within hydrogels. Alginate/gelatin-based hydrogels enabled spheroids fusion, which was further facilitated by addition of VEGF. Bioprinted CSs contracted spontaneously and under stimulation, allowing to record contractile and electrical signals on the microelectrode plates for industrial applications. Taken together, our findings indicate that bioprinted CSs can be used to biofabricate human heart tissues for long term in vitro testing. This has the potential to be used to study biochemical, physiological and pharmacological features of human heart tissue.

Security of information has become a major issue during the last decades. New algorithms based on chaotic maps were suggested for protection of different types of multimedia data, especially digital images and videos in this period. However, many of them fundamentally were flawed by a lack of robustness and security. For getting higher security and higher complexity, in the current paper, we introduce a new kind of symmetric key block cipher algorithm that is based on \emph{tripled chaotic maps}. In this algorithm, the utilization of two coupling parameters, as well as the increased complexity of the cryptosystem, make a contribution to the development of cryptosystem with higher security. In order to increase the security of the proposed algorithm, the size of key space and the computational complexity of the coupling parameters should be increased as well. Both the theoretical and experimental results state that the proposed algorithm has many capabilities such as acceptable speed and complexity in the algorithm due to the existence of two coupling parameter and high security. Note that the ciphertext has a flat distribution and has the same size as the plaintext. Therefore, it is suitable for practical use in secure communications.Comment: 21 pages, 10 figure

In recent years, a growing number of cryptosystems based on chaos have been proposed. But most of them encountered many problems such as small key space and weak security. In the present paper, a new kind of chaotic cryptosystem based on Composition of Trigonometric Chaotic Maps is proposed.These maps which are defined as ratios of polynomials of degree N, have interesting properties such as invariant measure, ergodicity, variable chaotic region with respect to the control parameters and ability to construct composition form of maps. We have used a composition of chaotic map to shuffle the position of image pixels. Another composition of chaotic map is used * E-mail: S.behnia@iaurmia.ac.ir 1 Cryptography based on Composed Maps 2 in diffusion process. According to the performed analysis, the introduced algorithm can satisfy the required performances such as high level security, large key space and the acceptable encryption speed.