A Thermal‐Reflow‐Based Low‐Temperature,High‐Pressure Sintering of Lyophilized Silk Fibroin for the Fast Fabrication of Biosubstrates

Solid fibroin is a bulk nonporous material that can be prepared with two methods: a liquid–gel–solid transition from a fibroin solution or a sintering procedure starting from silk powder. Both methods have their own disadvantages: the first requires several weeks and the process is size dependent; the second requires high temperatures. To overcome these limitations, a low‐temperature sintering procedure based on a thermal‐reflow is proposed in this work to produce in fast‐fashion monoliths of solid fibroin. Thermal‐reflow is a well‐known mechanism that takes place when the glass transition temperature of the material is lower than the temperature used to process it. Water plays an important role decreasing the glass transition temperature down to 40 °C. For the first time, a thermal reflow is conducted on lyophilized silk fibroin at 40 °C, associating to the water addition a high‐pressure compression. To optimize the process, a full factorial design of experiment is used. The material is then studied in the crucial phases by digital scanning calorimetry, Fourier‐transform infrared spectroscopy, and scanning electron microscopy. Finally, a mechanical characterization and a preliminary in vitro test are conducted.     

Digital divide in quantitative methods: The effects of computer‐assisted instruction and students' attitudes on knowledge acquisition

Computer‐assisted instruction can change the way introductory statistics and quantitative methods courses are taught. Using a two‐group pretest–posttest design, we conducted an experiment using an undergraduate social science student sample to investigate whether the introduction of statistical software to teaching quantitative methods would improve knowledge acquisition and attitudes toward quantitative methods courses. Our project confirmed that implementing computer‐assisted instructional methods increased knowledge acquisition in quantitative methods courses compared with students' academic performance in other courses, measured by grade point average. We also found that student attitudes have weak and mostly nonsignificant influence on quantitative methods knowledge tests. Additionally, the paper suggests a curriculum‐level approach to teaching quantitative methods to undergraduate students.     

Geometry-based methods for general non-planar perspective projections on curved displays

The Journal of Supercomputing - Curved monitors are getting more and more popular nowadays, due to the immersive sensation they provide to users in front of planar monitors. The display in curved...     

A Crystalline, 2D Polyarylimide Cathode for Ultrastable and Ultrafast Li Storage

Organic electrode materials are of long‐standing interest for next‐generation sustainable lithium‐ion batteries (LIBs). As a promising cathode candidate, imide compounds have attracted extensive attention due to their low cost, high theoretical capacity, high working voltage, and fast redox reaction. However, the redox active site utilization of imide electrodes remains challenging for them to fulfill their potential applications. Herein, the synthesis of a highly stable, crystalline 2D polyarylimide (2D‐PAI) integrated with carbon nanotube (CNT) is demonstrated for the use as cathode material in LIBs. The synthesized polyarylimide hybrid (2D‐PAI@CNT) is featured with abundant π‐conjugated redox‐active naphthalene diimide units, a robust cyclic imide linkage, high surface area, and well‐defined accessible pores, which render the efficient utilization of redox active sites (82.9%), excellent structural stability, and fast ion diffusion. As a consequence, high rate capability and ultrastable cycle stability (100% capacity retention after 8000 cycles) are achieved in the 2D‐PAI@CNT cathode, which far exceeds the state‐of‐the‐art polyimide electrodes. This work may inspire the development of novel organic electrodes for sustainable and durable rechargeable batteries.     

Development and validation of a dynamic metamodel based on stochastic radial basis functions and uncertainty quantification

A dynamic radial basis function (DRBF) metamodel is derived and validated, based on stochastic RBF and uncertainty quantification (UQ). A metric for assessing metamodel efficiency is developed and used. The validation includes comparisons with a dynamic implementation of Kriging (DKG) and static metamodels for both deterministic test functions (with dimensionality ranging from two to six) and industrial UQ problems with analytical and numerical benchmarks, respectively. DRBF extends standard RBF using stochastic kernel functions defined by an uncertain tuning parameter whose distribution is arbitrary and whose effects on the prediction are determined using UQ methods. Auto-tuning based on curvature, adaptive sampling based on prediction uncertainty, parallel infill, and multiple response criteria are used. Industrial problems are two UQ applications in ship hydrodynamics using high-fidelity computational fluid dynamics for the high-speed Delft catamaran with stochastic operating and environmental conditions: (1) calm water resistance, sinkage and trim with variable Froude number; and (2) mean value and root mean square of resistance and heave and pitch motions with variable regular head wave. The number of high-fidelity evaluations required to achieve prescribed error levels is considered as the efficiency metric, focusing on fitting accuracy and UQ variables. DKG is found more efficient for fitting low-dimensional test functions and one-dimensional UQ, whereas DRBF has a greater efficiency for fitting higher-dimensional test functions and two-dimensional UQ.     

Leak Size,Detectability and Test Conditions in Pressurized Pipe Systems

The relationships between leak geometry and detectability are explored with a distinction between steady- and unsteady-state based techniques. Various criteria to evaluate the size and detectability of a leak are first discussed. These criteria can be useful for the benchmarking and the comparison of different techniques. Since the test conditions play a crucial rule in leak detectability, the proposed criteria take this effect into account. Furthermore, they show that while in steady-state conditions increases in system pressure enhance leak detectability, in transient state, by contrast, higher pressures tend to decrease detectability. This effect is also confirmed by experimental tests carried out at the Water Engineering Laboratory of the University of Perugia.     

Information-theoretic selection of high-dimensional spectral features for structural recognition

Pattern recognition methods often deal with samples consisting of thousands of features. Therefore, the reduction of their dimensionality becomes crucial to make the data sets tractable. Feature selection techniques remove the irrelevant and noisy features and select a subset of features which describe better the samples and produce a better classification performance. In this paper, we propose a novel feature selection method for supervised classification within an information-theoretic framework. Mutual information is exploited for measuring the statistical relation between a subset of features and the class labels of the samples. Traditionally it has been measured for ranking single features; however, in most data sets the features are not independent and their combination provides much more information about the class than the sum of their individual prediction power. We analyze the use of different estimation methods which bypass the density estimation and estimate entropy and mutual information directly from the set of samples. These methods allow us to efficiently evaluate multivariate sets of thousands of features.Within this framework we experiment with spectral graph features extracted from 3D shapes. Most of the existing graph classification techniques rely on the graph attributes. We use unattributed graphs to show what is the contribution of each spectral feature to graph classification. Apart from succeeding to classify graphs from shapes relying only on their structure, we test to what extent the set of selected spectral features are robust to perturbations of the dataset.     

Cobalt hexacyanoferrate in PAMAM doped silica matrix. 2. Structural and electronic characterization

A composite of silica sol-gel, generation-4 poly(amidoamine) dendrimer (PAMAM) and cobalt hexacyanoferrate (CoHCF) was synthesized as a potential electrochromic material. The solid-state voltammetry of the material had suggested that the two electroactive sites were present. To elucidate the redox properties, the electronic and the structure in the local atomic environment of Fe and Co was investigated by X-ray absorption spectroscopy (XAS). Although the nominal stoichiometries of the investigated CoHCFs were Co₂^IIFe^II(CN)₆ (or K₂Co^IIFe^II(CN)₆) and KCo^IIFe^III(CN)₆, the spectral data demonstrated that Co^III was present in the composite. Among the supporting evidence for some metal-to-metal electronic transition of Fe^III-CN-Co^II to Fe^II-CN-Co^III was the shortening of the measured Co-N bond length in accord with the formation of Co^III. Further, IR measurements confirm the occurrence of charge transfer between Fe and Co sites in the silica-PAMAM composite.     

Synthesis and "in Vitro" Trypanocidal Activity Evaluation of Some Organo-iron Compounds

Eight organo-iron ferrocene derivatives and arenocenium salts were prepared and evaluated by "in vitro" assay against one strain of Trypanosoma cruzi (Y). Six of the eight organo-iron compounds assayed, piperazinium diferrocenoate 1, eta(6)-(o-xylene)-eta(5)-(cyclopentadienyl) Iron(II) hexafluorophosphate 3, eta(6)-(mesitylene)-eta(5)-(cyclopentadienyl) iron(II) hexafluorphosphate 5, eta(6)-(durene)-eta(5)-(cyclopentadienyl) iron(II) hexafluorphosphate 6, eta(6)-(rho-chlorotoluene)-eta(5)-(cyclopentadienyl) Iron(II) hexafluorphosphate 7 and eta(6)-(chlorobenzene)-eta(5)-(cyclopentadienyl) iron(II) picrate 8 , were poorly active in the "in vitro" assays. Only two compounds 1,1'-(N-pyperidinocarbonyl) ferrocene 2(IC(50)=2.4 mug/mL) and eta(6)-(o-xylene)-eta(5)(cyclopentadienyl) iron(II) picrate 4 (IC(50)=12.08 mug/mL), were more active. Thus, some of the compounds are promising to be used against Chagas' disease as a prophylactic agents.