MALDI-TOF MS and Morphology Studies of Thiacalixarene-Silsesquioxane Products of Oligo- and Polycondensation

For the first time condensed silsesquioxane derivatives of tetratrialkoxysilyl compounds have been characterized by MALDI-TOF mass spectrometry. Tetrasubstituted p-tert-butyl thiacalix[4]arene derivatives containing organosilicon fragments with variable stereochemistry were chosen as organosilicon compounds for polycondensation. Information obtained from mass spectra was used to deduce both the structures of oligomeric derivatives, as well as the structure of silsesquioxane framework. The morphology of formed polysilsesquioxanes was investigated by scanning and transmission electron microscopy.     

Correction to: Security analysis of an audio data encryption scheme based on key chaining and DNA encoding

Multimedia Tools and Applications - A Correction to this paper has been published: https://doi.org/10.1007/s11042-021-10592-x     

3-D Data Denoising and Inpainting with the Low-Redundancy Fast Curvelet Transform

In this paper, we first present a new implementation of the 3-D fast curvelet transform, which is nearly 2.5 less redundant than the Curvelab (wrapping-based) implementation as originally proposed in Ying et al. (Proceedings of wavelets XI conference, San Diego, 2005) and Candès et al. (SIAM Multiscale Model. Simul. 5(3):861–899, 2006), which makes it more suitable to applications including massive data sets. We report an extensive comparison in denoising with the Curvelab implementation as well as other 3-D multi-scale transforms with and without directional selectivity. The proposed implementation proves to be a very good compromise between redundancy, rapidity and performance. Secondly, we exemplify its usefulness on a variety of applications including denoising, inpainting, video de-interlacing and sparse component separation. The obtained results are good with very simple algorithms and virtually no parameter to tune.     

Region-Based Active Contours with Exponential Family Observations

In this paper, we focus on statistical region-based active contour models where image features (e.g. intensity) are random variables whose distribution belongs to some parametric family (e.g. exponential) rather than confining ourselves to the special Gaussian case. In the framework developed in this paper, we consider the general case of region-based terms involving functions of parametric probability densities, for which the anti-log-likelihood function is a special case. Using shape derivative tools, our effort focuses on constructing a general expression for the derivative of the energy (with respect to a domain), and on deriving the corresponding evolution speed. More precisely, we first show by an example that the estimator of the distribution parameters is crucial for the derived speed expression. On the one hand, when using the maximum likelihood (ML) estimator for these parameters, the evolution speed has a closed-form expression that depends simply on the probability density function. On the other hand, complicating additive terms appear when using other estimators, e.g. method of moments. We then proceed by stating a general result within the framework of multi-parameter exponential family. This result is specialized to the case of the anti-log-likelihood function with the ML estimator and to the case of the relative entropy. Experimental results on simulated data confirm our expectations that using the appropriate noise model leads to the best segmentation performance. We also report preliminary experiments on real life Synthetic Aperture Radar (SAR) images to demonstrate the potential applicability of our approach.     

Simultaneous utilization of ammonia,free amino acids and peptides during fermentative growth of Saccharomyces cerevisiae

The efficiency of nitrogen use by yeast is one of the key determinants of the successful completion of alcoholic fermentations. In this work the growth of Saccharomyces cerevisiae S288c in a synthetic medium containing ammonia and free amino acids, supplemented with yeast hydrolysate, was studied. Experiments with ¹⁵NH₄Cl and ¹⁵N‐labelled yeast hydrolysate were carried out to gain insight into which of these three classes of assimilable nitrogen sources yeast cells prefer. Co‐consumption of all three sources was observed; approximately 40% of the total nitrogen in the yeast protein fraction originated from yeast hydrolysate, while free amino acids and ammonia contributed 40 and 20%, respectively. The results indicate that several amino acids are more readily obtained from peptides, most likely when the uptake of their free forms is competitively inhibited and/or repressed. During the second half of each fermentation, a decrease in the incorporation of yeast hydrolysate‐derived nitrogen was observed. These results highlight the nutritional role of peptides in various yeast fermentations. Copyright © 2016 The Institute of Brewing & Distilling     

Design and analysis of a social botnet

Online Social Networks (OSNs) have attracted millions of active users and have become an integral part of today’s web ecosystem. Unfortunately, in the wrong hands, OSNs can be used to harvest private user data, distribute malware, control botnets, perform surveillance, spread misinformation, and even influence algorithmic trading. Usually, an adversary starts off by running an infiltration campaign using hijacked or adversary-owned OSN accounts, with an objective to connect with a large number of users in the targeted OSN. In this article, we evaluate how vulnerable OSNs are to a large-scale infiltration campaign run by socialbots: bots that control OSN accounts and mimic the actions of real users. We adopted the design of a traditional web-based botnet and built a prototype of a Socialbot Network (SbN): a group of coordinated programmable socialbots. We operated our prototype on Facebook for 8 weeks, and collected data about user behavior in response to a large-scale infiltration campaign. Our results show that (1) by exploiting known social behaviors of users, OSNs such as Facebook can be infiltrated with a success rate of up to 80%, (2) subject to user profile privacy settings, a successful infiltration can result in privacy breaches where even more private user data are exposed, (3) given the economics of today’s underground markets, running a large-scale infiltration campaign might be profitable but is still not particularly attractive as a sustainable and independent business, (4) the security of socially-aware systems that use or integrate OSN platforms can be at risk, given the infiltration capability of an adversary in OSNs, and (5) defending against malicious socialbots raises a set of challenges that relate to web automation, online-offline identity binding, and usable security.     

Concept of a miniature optical spectrometer using integrated optical and micro-optical components

We describe the concept of a super compact diffractive imaging spectrometer, with optical components a few millimeters across in all dimensions, capable of detecting optical fluorescence spectra within the entire visible spectral range from 400 nm to 700 nm with resolution of the order of 2 nm. In addition, the proposed spectrometer is capable of working simultaneously with multiple, up to 35, independent input optical channels. A specially designed diffractive optical element integrated with a planar optical waveguide is the key component of the proposed device. In the preliminary experimental tests, a uniform waveguide grating with a microlens was used to mimic operation of the diffractive optical element. A microspectrometer with optical components measured below 1 cm in all dimensions covers the spectral range from 450 nm to 650 nm and shows a spectral resolution of 0.5 nm at wavelengths close to 514 nm and 633 nm.     

Cryptanalysis of an embedded systems’ image encryption

Multimedia Tools and Applications - Recently, a new image encryption-scheme for embedded systems based on continuous third-order hyperbolic sine chaotic system, has been proposed. The...     

Breaking an image encryption scheme based on Arnold map and Lucas series

Multimedia Tools and Applications - Recently, a novel image encryption based on Arnold scrambling and Lucas series has been proposed in the literature. The scheme design is based on...