725 research outputs found
An Economic Study of the Effect of Android Platform Fragmentation on Security Updates
Vendors in the Android ecosystem typically customize their devices by
modifying Android Open Source Project (AOSP) code, adding in-house developed
proprietary software, and pre-installing third-party applications. However,
research has documented how various security problems are associated with this
customization process.
We develop a model of the Android ecosystem utilizing the concepts of game
theory and product differentiation to capture the competition involving two
vendors customizing the AOSP platform. We show how the vendors are incentivized
to differentiate their products from AOSP and from each other, and how prices
are shaped through this differentiation process. We also consider two types of
consumers: security-conscious consumers who understand and care about security,
and na\"ive consumers who lack the ability to correctly evaluate security
properties of vendor-supplied Android products or simply ignore security. It is
evident that vendors shirk on security investments in the latter case.
Regulators such as the U.S. Federal Trade Commission have sanctioned Android
vendors for underinvestment in security, but the exact effects of these
sanctions are difficult to disentangle with empirical data. Here, we model the
impact of a regulator-imposed fine that incentivizes vendors to match a minimum
security standard. Interestingly, we show how product prices will decrease for
the same cost of customization in the presence of a fine, or a higher level of
regulator-imposed minimum security.Comment: 22nd International Conference on Financial Cryptography and Data
Security (FC 2018
Bardet-Biedl syndrome proteins control cilia length through regulation of actin polymerisation.
Primary cilia are cellular appendages important for signal transduction and sensing the environment. Bardet-Biedl syndrome proteins form a complex that is important for several cytoskeleton-related processes such as ciliogenesis, cell migration and division. However, the mechanisms by which BBS proteins may regulate the cytoskeleton remain unclear. We discovered that Bbs4 and Bbs6 deficient renal medullary cells display a characteristic behaviour comprising poor migration, adhesion and division with an inability to form lamellipodial and filopodial extensions. Moreover, fewer mutant cells were ciliated (48% ± 6 for wild-type cells vs 23% ± 7 for Bbs4 null cells; P-value < 0.0001) and their cilia were shorter (2.55 μm ± 0.41 for wild-type cells vs 2.16 μm ± 0.23 for Bbs4 null cells; P-value < 0.0001). Whilst the microtubular cytoskeleton and cortical actin were intact, actin stress fibre formation was severely disrupted, forming abnormal apical stress fibre aggregates. Furthermore, we observed over-abundant focal adhesions in Bbs4, Bbs6 and Bbs8-deficient cells. In view of these findings and the role of RhoA in regulation of actin filament polymerisation, we showed that RhoA-GTP levels were highly upregulated in the absence of Bbs proteins. Upon treatment of Bbs4-deficient cells with chemical inhibitors of RhoA, we were able to restore cilia length and number as well as the integrity of the actin cytoskeleton. Together these findings indicate that Bbs proteins play a central role in the regulation of the actin cytoskeleton and control cilia length through alteration of RhoA levels
The effect of social media communication on consumer perceptions of brands
Researchers and brand managers have limited understanding of the effects social media communication has on how consumers perceive brands. We investigated 504 Facebook users in order to observe the impact of firm-created and user-generated social media communication on brand equity, brand attitude and purchase intention by using a standardized online survey throughout Poland. To test the conceptual model, we analyzed 60 brands across three different industries: non-alcoholic beverages, clothing and mobile network operators. When analyzing the data, we applied the structural equation modeling technique to both investigate the interplay of firm-created and user-generated social media communication and examine industry-specific differences. The results of the empirical studies showed that user-generated social media communication had a positive influence on both brand equity and brand attitude, whereas firm-created social media communication affected only brand attitude. Both brand equity and brand attitude were shown to have a positive influence on purchase intention. In addition, we assessed measurement invariance using a multi-group structural modeling equation. The findings revealed that the proposed measurement model was invariant across the researched industries. However, structural path differences were detected across the models
Recombinant expression of tandem-HBc virus-like particles (VLPs)
The hepatitis B virus (HBV) core protein (HBc) has formed the building block for virus-like particle (VLP) production for more than 30 years. The ease of production of the protein, the robust ability of the core monomers to dimerize and assemble into intact core particles, and the strong immune responses they elicit when presenting antigenic epitopes all demonstrate its promise for vaccine development (reviewed in Pumpens and Grens (Intervirology 44: 98–114, 2001)). HBc has been modified in a number of ways in attempts to expand its potential as a novel vaccine platform. The HBc protein is predominantly α-helical in structure and folds to form an L-shaped molecule. The structural subunit of the HBc particle is a dimer of monomeric HBc proteins which together form an inverted T-shaped structure. In the assembled HBc particle the four-helix bundle formed at each dimer interface appears at the surface as a prominent “spike.” The tips of the “spikes” are the preferred sites for the insertion of foreign sequences for vaccine purposes as they are the most highly exposed regions of the assembled particles. In the tandem-core modification two copies of the HBc protein are covalently linked by a flexible amino acid sequence which allows the fused dimer to fold correctly and assemble into HBc particles. The advantage of the modified structure is that the assembly of the dimeric subunits is defined and not formed by random association. This facilitates the introduction of single, larger sequences at the tip of each surface “spike,” thus overcoming the conformational clashes contingent on insertion of large structures into monomeric HBc proteins. Differences in inserted sequences influence the assembly characteristics of the modified proteins, and it is important to optimize the design of each novel construct to maximize efficiency of assembly into regular VLPs. In addition to optimization of the construct, the expression system used can also influence the ability of recombinant structures to assemble into regular isometric particles. Here, we describe the production of recombinant tandem-core particles in bacterial, yeast and plant expression systems
Nanomaterial interactions with biomembranes: Bridging the gap between soft matter models and biological context
Synthetic polymers, nanoparticles, and carbon-based materials have great potential in applications including drug delivery, gene transfection, in vitro and in vivo imaging, and the alteration of biological function. Nature and humans use different design strategies to create nanomaterials: biological objects have emerged from billions of years of evolution and from adaptation to their environment resulting in high levels of structural complexity; in contrast, synthetic nanomaterials result from minimalistic but controlled design options limited by the authors' current understanding of the biological world. This conceptual mismatch makes it challenging to create synthetic nanomaterials that possess desired functions in biological media. In many biologically relevant applications, nanomaterials must enter the cell interior to perform their functions. An essential transport barrier is the cell-protecting plasma membrane and hence the understanding of its interaction with nanomaterials is a fundamental task in biotechnology. The authors present open questions in the field of nanomaterial interactions with biological membranes, including: how physical mechanisms and molecular forces acting at the nanoscale restrict or inspire design options; which levels of complexity to include next in computational and experimental models to describe how nanomaterials cross barriers via passive or active processes; and how the biological media and protein corona interfere with nanomaterial functionality. In this Perspective, the authors address these questions with the aim of offering guidelines for the development of next-generation nanomaterials that function in biological media
Oxygen and Cation Ordered Perovskite, Ba2Y2Mn4O11
A three-step route has been developed for the synthesis of a new
oxygen-ordered double perovskite, BaYMn2O5.5 or Ba2Y2Mn4O11. (i) The A-site
cation ordered perovskite, BaYMn2O5+d, is first synthesized at d ~ 0 by an
oxygen-getter-controlled low-O2-pressure encapsulation technique utilizing FeO
as the getter for excess oxygen. (ii) The as-synthesized, oxygen-deficient
BaYMn2O5.0 phase is then readily oxygenated to the d ~ 1 level by means of
1-atm-O2 annealing at low temperatures. (iii) By annealing this
fully-oxygenated BaYMn2O6.0 in flowing N2 gas at moderate temperatures the new
intermediate-oxygen-content oxide, BaYMn2O5.5 or Ba2Y2Mn4O11, is finally
obtained. From thermogravimetric observation it is seen that the final oxygen
depletion from d ~ 1.0 to 0.5 occurs in a single sharp step about 600 C,
implying that the oxygen stoichiometry of BaYMn2O5+d is not continuously
tunable within 0.5 < d < 1.0. For BaYMn2O5.5 synchrotron x-ray diffraction
analysis reveals an orthorhombic crystal lattice and a long-range ordering of
the excess oxygen atoms in the YO0.5 layer. The magnetic behavior of BaYMn2O5.5
(with a ferromagnetic transition at ~ 133 K) is found different from those
previously reported for the known phases, BaYMn2O5.0 and BaYMn2O6.0.Comment: 21 pages, 6 figures, to appear in J. Solid State Che
Spin, charge and orbital ordering in ferrimagnetic insulator YBaMnO
The oxygen-deficient (double) perovskite YBaMnO, containing
corner-linked MnO square pyramids, is found to exhibit ferrimagnetic
ordering in its ground state. In the present work we report
generalized-gradient-corrected, relativistic first-principles full-potential
density-functional calculations performed on YBaMnO in the nonmagnetic,
ferromagnetic and ferrimagnetic states. The charge, orbital and spin orderings
are explained with site-, angular momentum- and orbital-projected density of
states, charge-density plots, electronic structure and total energy studies.
YBaMnO is found to stabilize in a G-type ferrimagnetic state in
accordance with experimental results. The experimentally observed insulating
behavior appears only when we include ferrimagnetic ordering in our
calculation. We observed significant optical anisotropy in this material
originating from the combined effect of ferrimagnetic ordering and crystal
field splitting. In order to gain knowledge about the presence of different
valence states for Mn in YBaMnO we have calculated -edge x-ray
absorption near-edge spectra for the Mn and O atoms. The presence of the
different valence states for Mn is clearly established from the x-ray
absorption near-edge spectra, hyperfine field parameters and the magnetic
properties study. Among the experimentally proposed structures, the recently
reported description based on 4/ is found to represent the stable
structure
Interleukin-1 polymorphisms associated with increased risk of gastric cancer
Helicobacter pylori infection is associated with a variety of clinical outcomes including gastric cancer and duodenal ulcer disease. The reasons for this variation are not clear, but the gastric physiological response is influenced by the severity and anatomical distribution of gastritis induced by H. pylori. Thus, individuals with gastritis predominantly localized to the antrum retain normal (or even high) acid secretion, whereas individuals with extensive corpus gastritis develop hypochlorhydria and gastric atrophy, which are presumptive precursors of gastric cancer. Here we report that interleukin-1 gene cluster polymorphisms suspected of enhancing production of interleukin-1-beta are associated with an increased risk of both hypochlorhydria induced by H. pylori and gastric cancer. Two of these polymorphism are in near-complete linkage disequilibrium and one is a TATA-box polymorphism that markedly affects DNA-protein interactions in vitro. The association with disease may be explained by the biological properties of interleukin-1-beta, which is an important pro-inflammatory cytokine and a powerful inhibitor of gastric acid secretion. Host genetic factors that affect interleukin-1-beta may determine why some individuals infected with H. pylori develop gastric cancer while others do no
Basal body stability and ciliogenesis requires the conserved component Poc1
Centrioles are the foundation for centrosome and cilia formation. The biogenesis of centrioles is initiated by an assembly mechanism that first synthesizes the ninefold symmetrical cartwheel and subsequently leads to a stable cylindrical microtubule scaffold that is capable of withstanding microtubule-based forces generated by centrosomes and cilia. We report that the conserved WD40 repeat domain–containing cartwheel protein Poc1 is required for the structural maintenance of centrioles in Tetrahymena thermophila. Furthermore, human Poc1B is required for primary ciliogenesis, and in zebrafish, DrPoc1B knockdown causes ciliary defects and morphological phenotypes consistent with human ciliopathies. T. thermophila Poc1 exhibits a protein incorporation profile commonly associated with structural centriole components in which the majority of Poc1 is stably incorporated during new centriole assembly. A second dynamic population assembles throughout the cell cycle. Our experiments identify novel roles for Poc1 in centriole stability and ciliogenesis
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