Unusual Two-Step Assembly of a Minimalistic Dipeptide-Based Functional Hypergelator

Self-assembled peptide hydrogels represent the realization of peptide nanotechnology into biomedical products. There is a continuous quest to identify the simplest building blocks and optimize their critical gelation concentration (CGC). Herein, a minimalistic, de novo dipeptide, Fmoc-Lys(Fmoc)-Asp, as an hydrogelator with the lowest CGC ever reported, almost fourfold lower as compared to that of a large hexadecapeptide previously described, is reported. The dipeptide self-assembles through an unusual and unprecedented two-step process as elucidated by solid-state NMR and molecular dynamics simulation. The hydrogel is cytocompatible and supports 2D/3D cell growth. Conductive composite gels composed of Fmoc-Lys(Fmoc)-Asp and a conductive polymer exhibit excellent DNA binding. Fmoc-Lys(Fmoc)-Asp exhibits the lowest CGC and highest mechanical properties when compared to a library of dipeptide analogues, thus validating the uniqueness of the molecular design which confers useful properties for various potential applications.     

Automatic tuning of decentralized PID controllers for MIMO processes

An automatic tuning algorithm for decentralized PID control in multiple-input multiple-output (MIMO) plants is presented. This algorithm generalizes the authors' recent auto-tuner for two-input two-output systems to any number of inputs and outputs. The algorithm consists of two stages. In the first, the desired critical point, which consists of the critical gains of all the loops and a critical frequency, is identified. The auto-tuner identifies the desired critical point with almost no a priori information about the process. During the identification phase all controllers are replaced by relays, thus generating limit cycles with the same period in all loops. It is shown that each limit cycle corresponds to a single critical point of the process. By varying the relays parameters different points can be determined. The auto-tuner contains a procedure which converges rapidly to the desired critical point while maintaining the amplitudes of the process variables as well as of the manipulated variables within prespecified ranges. In the second stage, the data of the desired critical point is used to tune the PID controllers by the Ziegler-Nichols rules or their modifications. This paper focuses on the first stage. The steady-state process gains, which are required for the appropriate choice of the desired critical point, are determined by the auto-tuner in closed-loop fashion simultaneously with the identification of the critical point. The identification of the process gains is achieved at no extra plant time. Based upon a large number of simulated cases, the proposed auto-tuner seems to be efficient and robust. The paper discusses the underlying principles of the auto-tuner and its properties and capabilities are demonstrated via examples.     

Photo Sequencing

A group of people taking pictures of a dynamic event with their mobile phones is a popular sight. The set of still images obtained this way is rich in dynamic content but lacks accurate temporal information. We propose a method for photo-sequencing—temporally ordering a set of still images taken asynchronously by a set of uncalibrated cameras. Photo-sequencing is an essential tool in analyzing (or visualizing) a dynamic scene captured by still images. The first step of the method detects sets of corresponding static and dynamic feature points across images. The static features are used to determine the epipolar geometry between pairs of images, and each dynamic feature votes for the temporal order of the images in which it appears. The partial orders provided by the dynamic features are not necessarily consistent, and we use rank aggregation to combine them into a globally consistent temporal order of images. We demonstrate successful photo-sequencing on several challenging collections of images taken using a number of mobile phones.     

铸铁坩锅抗铝融蚀等离子喷涂技术

针对提高化铝用铸铁坩埚抗融蚀寿命的实际问题,选用价格较低、耐高温、抗融蚀性好的Ａｌ２Ｏ３陶瓷材料作为坩埚内壁的工作层,采用等离子喷涂技术来提高其抗融蚀性。但由于Ａｌ２Ｏ３陶瓷涂层的致密性差、结合强度及抗热震寿命低等缺点,不适宜化铝坩埚在７２０℃长时间加温,且液铝呈搅拌行为的工作条件下使用。本文在Ａｌ２Ｏ３喷涂粉末中加入１３％ＴｉＯ２,促使涂层的组织结构发生变化,提高了涂层的结合强度,改善了涂层的致     

A probabilistic alternative to regression suites

Automated regression suites are essential in developing large applications, while maintaining reasonable quality and timetables. The main argument against the automation of regression suites, in addition to the cost of creation and maintenance, is the observation that if you run the same test many times, it becomes increasingly less likely to find bugs. To alleviate such problems, a new regression suite practice, using random test generators to create regression suites on-the-fly, is becoming more common. In this practice, instead of maintaining tests, we generate test suites on-the-fly by choosing several specifications and generating a number of tests from each specification.     

Automatic boosting of cross-product coverage using Bayesian networks

Closing the feedback loop from coverage data to the stimuli generator is one of the main challenges in the verification process. Typically, verification engineers with deep domain knowledge manually prepare a set of stimuli generation directives for that purpose. Bayesian networks based CDG (coverage directed generation) systems have been successfully used to assist the process by automatically closing this feedback loop. However, constructing these CDG systems requires manual effort and a certain amount of domain knowledge from a machine learning specialist. We propose a new method that boosts coverage in the early stages of the verification process with minimal effort, namely a fully automatic construction of a CDG system that requires no domain knowledge. Experimental results on a real-life cross-product coverage model demonstrate the efficiency of the proposed method.     

Continuous input nonlocal games

We present a family of nonlocal games in which the inputs the players receive are continuous. We study three representative members of the family. For the first two a team sharing quantum correlations (entanglement) has an advantage over any team restricted to classical correlations. We conjecture that this is true for the third member of the family as well.     

The effect of polyethylene crystallinity and polarity on thermal stability and controlled release of essential oils in antimicrobial films

Antimicrobial packaging can preserve and increase shelf life of free preservatives food products. Active materials present in the packaging material can migrate, in a controlled manner, to the food surface, avoiding bacterial and fungal proliferation and keeping the food product edible for longer periods of time. Essential oils (EO) are natural antimicrobial agents that can be released to the headspace with no direct contact between the package and the food. To minimize loses of EO during high heat melt processing, a three stages process was implemented and tested. Antimicrobial films were prepared by melt mixing a variety of polyethylene copolymers in the presence of organo‐modified montmorillonite nano clay (NC) and thymol, an EO present in oregano and thyme. A controlled EO desorption from films can be achieved by changing the polymer crystallinity and polarity. As the crystallinity increased, the thermal stability of the EO during the extrusion process improved. The addition of NC affects the structure and homogeneity of the crystals. The combination of high polymer crystallinity and chemical affinity between EO and NC increased the thermal stability of the EO during film processing, enabling to control the desorption rate. The effect of multilayer structure based on varied densities and polarities was also studied. Increasing the polarity of the outer layers in multilayered film reduced the EO desorption rate as a result of chemical interactions between the polymer and the EO. The final antimicrobial activity of the films was also found to be dependent on the EO partitioning. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40309.     

Crosslinked,biodegradable polyurethanes for precision-porous biomaterials: Synthesis and properties

Crosslinked poly(ester urethane)s and their acrylate derivatives based on trifunctional polycaprolactone and trifunctional aliphatic isocyanates were synthesized. Biodegradable scaffolds with uniform, controlled micron-scale porosity were fabricated with these materials. Mechanical and swelling properties of monolithic and microporous materials were studied. Cytotoxicity, hydrolytic, and enzymatic degradation and their effects on mechanical properties of the biodegradable scaffolds were investigated. The polymer degradation products were found not to be cytotoxic at moderate concentrations and to permit cell attachment and spreading. Degradation rates and mechanical properties could be tuned to desired performance criteria for a given application by adjusting crosslink density and the ratio of hard segment to soft segment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48943.     

Detection of Campylobacter jejuni in naturally contaminated chicken skin by melting peak analysis of amplicons in real-time PCR

Contamination of poultry by Campylobacter spp. is a significant source of human diarrheal diseases. Traditional methods currently used to detect Campylobacter in foods are time-consuming and labor-intensive. In this study, primers designed for the Campylobacter jejuni cadF gene sequence were used in a SYBR Green I real-time PCR assay as an alternative to a conventional bacteriological method for the rapid detection of C. jejuni from poultry. Twelve portions of chicken purchased from two local grocery stores and 39 portions obtained from a commercial processing plant were examined. Samples of the skin were enriched in Bolton broth at 37 degrees C for 3 h and then at 42 degrees C for 9, 21, or 45 h under microaerobic conditions. DNA was extracted from 1-ml aliquots of the enrichment cultures using 1% Triton X-100. The DNA was used as the template in a real-time polymerase chain reaction (PCR) assay. After 24 h of enrichment, C. jejuni was isolated from 13 samples and all of the positive cultures were also detected by the real-time PCR procedure. C. jejuni was detected by both methods from samples artificially contaminated with 1 or 10 CFU of C. jejuni per 10 g, after 24 h of enrichment. The real-time PCR method was found to be sensitive and specific. It significantly reduced the time required for the detection of C. jejuni in poultry following enrichment of samples.