Sequence-Dependent Nanofiber Structures of Phenylalanine and Isoleucine Tripeptides

The molecular design of short peptides to achieve a tailor-made functional architecture has attracted attention during the past decade but remains challenging as a result of insufficient understanding of the relationship between peptide sequence and assembled supramolecular structures. We report a hybrid-resolution model to computationally explore the sequence–structure relationship of self-assembly for tripeptides containing only phenylalanine and isoleucine. We found that all these tripeptides have a tendency to assemble into nanofibers composed of laterally associated filaments. Molecular arrangements within the assemblies are diverse and vary depending on the sequences. This structural diversity originates from (1) distinct conformations of peptide building blocks that lead to different surface geometries of the filaments and (2) unique sidechain arrangements at the filament interfaces for each sequence. Many conformations are available for tripeptides in solution, but only an extended β-strand and another resembling a right-handed turn are observed in assemblies. It was found that the sequence dependence of these conformations and the packing of resulting filaments are determined by multiple competing noncovalent forces, with hydrophobic interactions involving Phe being particularly important. The sequence pattern for each type of assembly conformation and packing has been identified. These results highlight the importance of the interplay between conformation, molecular packing, and sequences for determining detailed nanostructures of peptides and provide a detailed insight to support a more precise design of peptide-based nanomaterials.     

Effects of Synthesis Conditions on the Formation of Si-Substituted Alpha Tricalcium Phosphates

Powders of α-TCP containing various amounts of silicon were synthesized by two different methods: Wet chemical precipitation and solid-state synthesis. The obtained powders were then physico–chemically studied using different methods: Scanning and transmission electron microscopy (TEM and SEM), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffractometry (PXRD), infrared and Raman spectroscopies (FT-IR and R), and solid-state nuclear magnetic resonance (ssNMR). The study showed that the method of synthesis affects the morphology of the obtained particles, the homogeneity of crystalline phase and the efficiency of Si substitution. Solid-state synthesis leads to particles with a low tendency to agglomerate compared to the precipitation method. However, the powders obtained by the solid-state method are less homogeneous and contain a significant amount of other crystalline phase, silicocarnotite (up to 7.33%). Moreover, the microcrystals from this method are more disordered. This might be caused by more efficient substitution of silicate ions: The silicon content of the samples obtained by the solid-state method is almost equal to the nominal values.     

The effect of traffic data source on deterioration rates of heavy-duty flexible pavements

The purpose of this study is to assess the effect of traffic data source (estimated vs. actual) on predicted progression rates of roughness and rutting for heavy-duty flexible pavements of rural freeways. Progression rates are predicted using calibrated HDM-4 models. The assessment is performed in terms of variations in maintenance intervention timing associated with the variations in progression rates. Time series pavement condition data (covering 3–5 years) have been collected for 7 sections of rural freeways for use in calibrating HDM-4 deterioration models. They range in length from 10 to 60.8 km and cover different traffic volumes, climate zones and subgrade soil types. For these sections, estimated annual average daily traffic (AADT), growth factors and assumed loading have been extracted from relevant database. Only six segments of these sections have Weigh-in-Motion (WIM) sites so relevant actual AADT, growth factors and axle load distributions have been extracted from WIM reports. The results of running the calibrated HDM-4 deterioration models using different traffic data show that actual traffic data from WIM sites result in higher rates of deterioration to that of estimated data for four sites, resulting in earlier intervention timing and higher present value agency cost. The other two sites have lower rates with actual data due to lower traffic loading than estimated.     

一种调度遥控操作双路径安全校核机制的探索

为解决调度端远方操作路径单一情况下可能出现操作错误的问题,文章探索提出一种对远方操作进行双路径安全确认的构建方案,在常规遥控发起路径之外建立独立的操作许可路径,在操作业务通信的出口处部署操作许可安全网关、操作许可工作站,通过操作发起路径的操作员、监护人和操作许可路径的许可员相结合的多重校验,强化对遥控操作的合法性认证,可以有效避免操作人、操作员站、操作网络环境的不可靠因素带来的操作安全风险,提高电网操作的安全性。     

Synthesis and thermal decomposition of potassium tetraamidoboranealuminate,K[Al(NH2BH3)4]

A new potassium tetraamidoboranealuminate, K[Al(NH₂BH₃)₄], has been synthesized by a mechanochemical reaction between KAlH₄ and NH₃BH₃. The compound, K[Al(NH₂BH₃)₄], crystallizes in a triclinic unit cell with space group symmetry P?1. The crystal structure consists of [K(NH₂BH₃)₆]^5? octahedra which facilitate the bridging between K⁺ in 1D chains, while also bridging K⁺ to Al³⁺ to connect the 1D chains in a 3D network. Thermal analysis reveals that K[Al(NH₂BH₃)₄] decomposes in two exothermic steps at T ～ 94 and 138 °C and releases primarily hydrogen. The total gas release amounts to ～6.0 wt% H₂. The decomposition products are investigated ex situ by powder X-ray diffraction, infrared spectroscopy, and ¹¹B and ²⁷Al NMR and identified as KBH₄ and amorphous phases, possibly BN₃, N₂BH, and/or NBH₂ whereas aluminum is found in four-, five-, and six-fold coordination. Unfortunately, the decomposed sample shows no hydrogen absorption at T = 260 °C and p(H₂) = 110 bar.     

Effects of three types of modified atmospheric packaging on the physicochemical properties of selected glutinous rice

The effect of modified atmospheric packaging (MAP) on the physicochemical properties of selected glutinous (Thadokkham-8 and Thadokkham-11) rice was studied and compared with a non-glutinous rice (Doongara). The freshly harvested/milled grains were packed in four different MAP conditions viz. control, vacuum, CO₂ and N₂ for 12 months at room temperature (23 ± 1 °C). Gas (N₂ or CO₂) was flushed in aluminum bags at the pressure of 300 kPa for 3 s and subsequently hermetically sealed. Vacuum packaging was done at −100 kPa. Results showed that ageing induced changes in the starch granules were less prominent in vacuum and/or MAP samples using CO₂ or N₂. Surface analysis showed that control storage significantly reduced the percentage of lipids and increased the percentage of proteins on the surface in all selected varieties. N₂ and CO₂ storage of TDK8 and DG slowed down the shift of properties of macromolecules and maintained the surface starch/proteins/lipids ratios during 6 months of storage. Moreover, the grains stored in vacuum maintained the lipids with lower proportion of proteins exposed to the surface after cooking. N₂ and CO₂ induced increase in pasting temperature but significant reduction in final viscosity when compared to control. The findings correlated well with thermal analysis. The in situ Thermal Mechanical Compression Test (TMCT) device cooking and texture analysis revealed that modified storage slightly slowed the ageing induced changes in the cooking quality and stickiness of glutinous rice. Among all storage conditions used vacuum was relatively the best to maintain the quality of the grain.     

A Proposal for Addressing Security Issues Related to Dynamic Code Loading on Android Platform

One of the constant challenges faced by the Android community, when it comes to the safety of the end users, is the ability of applications to load code dynamically. This mechanism may be used for both legitimate and malicious purposes. A particular problem is the fact that remote code is not analyzed during the verification process because it doesn’t have to be present in the application package at the publishing time. Previous research has shown that using this concept in an insecure way can cause serious consequences for the user and his device. Solving this problem has proved to be a big challenge that many have tried to address in different ways. This paper deals with the problem of dynamic code loading on Android platform. For the purpose of this paper, an application that demonstrates the abuse of the dynamic code loading concept has been developed and published in the Google Play Store. Also, a proposal of the modified Android ecosystem that should address this problem and improve the security of the whole platform is given.     

The control of paracetamol particle size and surface morphology through crystallisation in a spray dryer

The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed.