Self Consistent Field Theory of Twist Grain Boundaries in Block Copolymers

We apply self consistent field theory to twist grain boundaries of block copolymer melts. The distribution of monomers throughout the grain boundary is obtained as well as the grain boundary free energy per unit area as a function of twist angle. We define an intermaterial dividing surface in order to compare it with minimal surfaces which have been proposed. Our calculation shows that the dividing surface is not a minimal one, but the linear stack of dislocations seems to be a better representation of it for most angles than is Scherck's first surface.Comment: 10 pages, 6 figures, submitted for publicatio

Structural characterization of the Fddd phase in a diblock copolymer thin film by electron microtomography

A 3-dimensional Fddd network structure of a polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer (M(n) = 31 500, f(PI) = 0.645) was observed for the first time in real space by transmission electron microtomography (TEMT). In a 650 nm thick film of the PS-b-PI thin film on a silicon wafer, the Fddd phase was developed after annealing at 215 degrees C for 24 h. The single network structure consists of the connected tripodal units of minor PS block domains. The {111}(Fddd) plane, the densest plane of the minor PS phase, was found to orient parallel to the film plane. The transitional structure from the wetting layer at the free surface to the internal {111}(Fddd) plane via a perforated layer structure was also observed.X111313sciescopu

Imbalance of endogenous prostanoids in moderate-to-severe asthma

BACKGROUND: Inhalation studies suggested "protective" roles of exogenous prostaglandin E2, but the clinical relevance of endogenous prostanoids in asthma is poorly known. The objective of this study is to measure sputum levels of prostanoids in asthmatic patients to correlate with clinical indices. METHODS: Mild (n = 41) or moderate-to-severe (19) asthmatics and 27 normal controls were examined for pulmonary function (FEV1 and mid-forced expiratory flow), sputum cell differentials, and sputum levels of prostaglandins D2, E2, F2α, and thromboxane B2 measured by sandwich enzyme immunoassay. RESULTS: Each prostanoid level did not differ among the three groups. Sputum number of bronchial epithelial cells was greater in moderate-to-severe asthmatics than in the other two groups, suggesting epithelial desquamation. Levels of prostaglandin F2α, D2, and thromboxane B2 positively correlated with the severity of airflow obstruction in the 60 asthmatic patients, whereas prostaglandin E2 levels were unrelated to pulmonary function. The ratio of combined "contractile" prostanoids (prostaglandin D2/prostaglandin F2α/thromboxane B2) to prostaglandin E2 was 2.5-fold greater in moderate-to-severe asthmatics than in controls (p = 0.001) or in mild asthmatics (p = 0.0002) but did not differ between the latter two groups. In the two asthmatic groups combined, this ratio positively correlated with the sputum number of epithelial cells. The combined "contractile" prostanoids levels positively correlated with prostaglandin E2 levels in controls and in mild asthmatics but not in moderate-to-severe asthmatics. CONCLUSIONS: An imbalance in production, breakdown, or both between prostaglandin E2 and other prostanoids possibly due to epithelial damage may be involved in the pathogenesis of moderate-to-severe asthma

A Study of the Advances in IoT Security

The Internet-of-things (IoT) holds a lot of benefits to our lives by removing menial tasks and improving efficiency of everyday objects. You are trusting your personal data and device control to the manufactures and you may not be aware of how much risk your putting your privacy at by sending your data over the internet. The internet-of-things may not be as secure as you think when the devices used are constrained by a lot of variables which attackers can exploit to gain access to your data / device and anything they connected to and as the internet-of-things is all about connecting devices together one weak point can be all it takes to gain full access. In this paper we have a look at the current advances in IoT security and the most efficient methods to protect IoT devices

Spinodal Decomposition in a Binary Polymer Mixture: Dynamic Self Consistent Field Theory and Monte Carlo Simulations

We investigate how the dynamics of a single chain influences the kinetics of early stage phase separation in a symmetric binary polymer mixture. We consider quenches from the disordered phase into the region of spinodal instability. On a mean field level we approach this problem with two methods: a dynamical extension of the self consistent field theory for Gaussian chains, with the density variables evolving in time, and the method of the external potential dynamics where the effective external fields are propagated in time. Different wave vector dependencies of the kinetic coefficient are taken into account. These early stages of spinodal decomposition are also studied through Monte Carlo simulations employing the bond fluctuation model that maps the chains -- in our case with 64 effective segments -- on a coarse grained lattice. The results obtained through self consistent field calculations and Monte Carlo simulations can be compared because the time, length, and temperature scales are mapped onto each other through the diffusion constant, the chain extension, and the energy of mixing. The quantitative comparison of the relaxation rate of the global structure factor shows that a kinetic coefficient according to the Rouse model gives a much better agreement than a local, i.e. wave vector independent, kinetic factor. Including fluctuations in the self consistent field calculations leads to a shorter time span of spinodal behaviour and a reduction of the relaxation rate for smaller wave vectors and prevents the relaxation rate from becoming negative for larger values of the wave vector. This is also in agreement with the simulation results.Comment: Phys.Rev.E in prin

Three-Dimensional Visualization and Characterization of Polymeric Self-Assemblies by Transmission Electron Microtomography

Self-assembling structures and their dynamical processes in polymeric systems have been investigated using three-dimensional transmission electron microscopy (3D-TEM). Block copolymers (BCPs) self-assemble into nanoscale periodic structures called microphase-separated structures, a deep understanding of which is important for creating nanomaterials with superior physical properties, such as high-performance membranes with well-defined pore size and high-density data storage media. Because microphase-separated structures have become increasingly complicated with advances in precision polymerization, characterizing these complex morphologies is becoming increasingly difficult. Thus, microscopes capable of obtaining 3D images are required. In this article, we demonstrate that 3D-TEM is an essential tool for studying BCP nanostructures, especially those self-assembled during dynamical processes and under confined conditions.The first example is a dynamical process called order-order transitions (OOTs). Upon changing temperature or pressure or applying an external field, such as a shear flow or electric field, BCP nanostructures transform from one type of structure to another. The OOTs are examined by freezing the specimens in the middle of the OOT and then observing the boundary structures between the preexisting and newly formed nanostructures in three-dimensions. In an OOT between the bicontinuous double gyroid and hexagonally packed cylindrical structures, two different types of epitaxial phase transition paths are found. Interestingly, the paths depend on the direction of the OOT. The second example is BCP self-assemblies under confinement that have been examined by 3D-TEM. A variety of intriguing and very complicated 3D morphologies can be formed even from the BCPs that self-assemble into simple nanostructures, such as lamellar and cylindrical structures in the bulk (in free space).Although 3D-TEM is becoming more frequently used for detailed morphological investigations, it is generally used to study static nanostructures. Although OOTs are dynamical processes, the actual experiment is done in the static state, through a detailed morphological study of a snapshot taken during the OOT. Developing time-dependent nanoscale 3D imaging has become a hot topic. Here, the two main problems preventing the development of in situ electron tomography for polymer materials are addressed. First, the staining protocol often used to enhance contrast for electrons is replaced by a new contrast enhancement based on chemical differences between polymers. In this case, no staining is necessary. Second, a new 3D reconstruction algorithm allows us to obtain a high-contrast, quantitative 3D image from fewer projections than is required for the conventional algorithm to achieve similar contrast, reducing the number of projections and thus the electron beam dose. Combining these two new developments is expected to open new doors to 3D in situ real-time structural observation of polymer materials

Muscleblind-Like 1 Knockout Mice Reveal Novel Splicing Defects in the Myotonic Dystrophy Brain

Myotonic dystrophy type 1 (DM1) is a multi-systemic disorder caused by a CTG trinucleotide repeat expansion (CTGexp) in the DMPK gene. In skeletal muscle, nuclear sequestration of the alternative splicing factor muscleblind-like 1 (MBNL1) explains the majority of the alternative splicing defects observed in the HSALR transgenic mouse model which expresses a pathogenic range CTGexp. In the present study, we addressed the possibility that MBNL1 sequestration by CUGexp RNA also contributes to splicing defects in the mammalian brain. We examined RNA from the brains of homozygous Mbnl1ΔE3/ΔE3 knockout mice using splicing-sensitive microarrays. We used RT-PCR to validate a subset of alternative cassette exons identified by microarray analysis with brain tissues from Mbnl1ΔE3/ΔE3 knockout mice and post-mortem DM1 patients. Surprisingly, splicing-sensitive microarray analysis of Mbnl1ΔE3/ΔE3 brains yielded only 14 candidates for mis-spliced exons. While we confirmed that several of these splicing events are perturbed in both Mbnl1 knockout and DM1 brains, the extent of splicing mis-regulation in the mouse model was significantly less than observed in DM1. Additionally, several alternative exons, including Grin1 exon 4, App exon 7 and Mapt exons 3 and 9, which have previously been reported to be aberrantly spliced in human DM1 brain, were spliced normally in the Mbnl1 knockout brain. The sequestration of MBNL1 by CUGexp RNA results in some of the aberrant splicing events in the DM1 brain. However, we conclude that other factors, possibly other MBNL proteins, likely contribute to splicing mis-regulation in the DM1 brain

How Linear Tension Converts to Curvature: Geometric Control of Bone Tissue Growth

This study investigated how substrate geometry influences in-vitro tissue formation at length scales much larger than a single cell. Two-millimetre thick hydroxyapatite plates containing circular pores and semi-circular channels of 0.5 mm radius, mimicking osteons and hemi-osteons respectively, were incubated with MC3T3-E1 cells for 4 weeks. The amount and shape of the tissue formed in the pores, as measured using phase contrast microscopy, depended on the substrate geometry. It was further demonstrated, using a simple geometric model, that the observed curvature-controlled growth can be derived from the assembly of tensile elements on a curved substrate. These tensile elements are cells anchored on distant points of the curved surface, thus creating an actin “chord” by generating tension between the adhesion sites. Such a chord model was used to link the shape of the substrate to cell organisation and tissue patterning. In a pore with a circular cross-section, tissue growth increases the average curvature of the surface, whereas a semi-circular channel tends to be flattened out. Thereby, a single mechanism could describe new tissue growth in both cortical and trabecular bone after resorption due to remodelling. These similarities between in-vitro and in-vivo patterns suggest geometry as an important signal for bone remodelling

Fatty Acid Binding Protein 1 Is Related with Development of Aspirin-Exacerbated Respiratory Disease

BACKGROUND: Aspirin-exacerbated respiratory disease (AERD) refers to the development of bronchoconstriction in asthmatics following the ingestion of aspirin. Although alterations in eicosanoid metabolites play a role in AERD, other immune or inflammatory mechanisms may be involved. We aimed to identify proteins that were differentially expressed in nasal polyps between patients with AERD and aspirin-tolerant asthma (ATA). METHODOLOGY/PRINCIPAL FINDINGS: Two-dimensional electrophoresis was adopted for differential display proteomics. Proteins were identified by liquid chromatography-tandem mass spectrometry (LC-MS). Western blotting and immunohistochemical staining were performed to compare the amount of fatty acid-binding protein 1 (FABP1) in the nasal polyps of patients with AERD and ATA. Fifteen proteins were significantly up- (seven spots) or down-regulated in the nasal polyps of patients with AERD (n = 5) compared to those with ATA (n = 8). LC-MS revealed an increase in seven proteins expression and a decrease in eight proteins expression in patients with AERD compared to those with ATA (P = 0.003-0.045). FABP1-expression based on immunoblotting and immunohistochemical analysis was significantly higher in the nasal polyps of patients with AERD compared to that in patients with ATA. FABP1 was observed in epithelial, eosinophils, macrophages, and the smooth-muscle cells of blood vessels in the polyps. CONCLUSIONS/SIGNIFICANCE: Our results indicate that alterations in 15 proteins, including FABP1, may be related to the development of AERD