17315 research outputs found
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Blending strategies for green packaging: enhancing polyhydroxybutyrate performance for sustainable solutions
No full textThe rising demand for sustainable alternatives to conventional plastics highlights polyhydroxyalkanoates (PHAs), particularly polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), as promising biodegradable thermoplastics. While PHAs offer advantages like non-toxicity and a reduced carbon footprint, their brittleness, narrow processing window, and high production costs limit their broader use, particularly in packaging, the largest source of municipal solid waste. This review provides an overview of PHAs, emphasizing the properties that make them suitable for packaging and the key factors influencing their market longevity. Blending PHAs with natural polymers, such as polylactic acid, cellulose derivatives, and chitin/chitosan improves mechanical, thermal, and barrier properties while enhancing biodegradability by reducing crystallinity or increasing hydrophilicity, thereby facilitating microbial degradation. Additives such as plasticizers, nucleating agents, and compatibilizers, alongside optimized processing conditions and advanced techniques, like reactive blending and the use of block and graft copolymers, improve interfacial adhesion and blend homogeneity, mitigating brittleness and enhancing flexibility and strength. The thermal instability of PHB, which poses challenges during melt processing, can be addressed by incorporating bioplasticizers to lower its glass transition temperature and melt viscosity, allowing processing at lower temperatures and minimizing thermal degradation. Furthermore, in-situ polymerization and bio-based coupling agents further enhance blend uniformity and overall performance. Special attention is given to the potential of PHB/chitosan blends for developing antibacterial, eco-friendly packaging solutions. By reviewing market trends and advances in PHA processing, this review underscores the potential of PHA-based blends to reduce plastic waste and facilitate their commercialization as sustainable, green packaging materials
Learning from the enemies of freedom: freedom of expression and collective power
No full textThis paper develops an account of freedom of expression by drawing lessons from the strategic logic of China's censorship regime. It argues that freedom of expression helps build the common knowledge needed for overcoming coordination problems and is, thus, a source of collective power. However, realizing the full empowering potential of freedom of expression requires supplementing it with (a) public sources of information that are reliable, trusted, and democratically accountable and (b) measures that will provide citizens with equal opportunity to speak and be heard in ways that will enable them to contribute to their society's stock of common knowledge
Distributed landmark labeling for social networks
No full textDistance queries are a fundamental part of many network analysis applications. They can be used to infer the closeness of two users in social networks, the relation between two sites in a web graph, or the importance of the interaction between two proteins or molecules. Being able to answer these queries rapidly has many benefits in the area of network analysis. Pruned Landmark Labeling (PLL) is a technique used to generate an index for a given graph that allows the shortest path queries to be completed in a fraction of the time when compared to a standard breadth-first or a depth-first search-based algorithm. Parallel Shortest-distance Labeling (PSL) reorganizes the steps of PLL for the multithreaded setting and is designed particularly for social networks for which the index sizes can be much larger than what a single server can store. Even for a medium-size, 5 million vertex graph, the index size can be more than 40 GB. This paper proposes a hybrid, shared- and distributed-memory algorithm, DPSL, by partitioning the input graph via a vertex separator. The proposed method improves both the parallel execution time and the maximum memory consumption by distributing both the data and the work across multiple nodes of a cluster. For instance, on a graph with 5M vertices and 150M edges, using 4 nodes, DPSL reduces the execution time and maximum memory consumption by 2.13× and 1.87×, respectively, compared to our improved implementation of PSL
Entropy driven inductive response of topological insulators
No full text3D topological insulators are characterized by an insulating bulk and extended surface states exhibiting a helical spin texture. In this work, we investigate the hyperfine interaction between the spin-charge coupled transport of electrons and the nuclear spins in these surface states. Previous work has predicted that in the quantum spin Hall insulator phase, work can be extracted from a bath of polarized nuclear spins as a resource [1]. We employ nonequilibrium Green’s function analysis to show that a similar effect exists on the surface of a 3D topological insulator, albeit rescaled by the ratio between electronic mean free path and device length. The induced current due to thermal relaxation of polarized nuclear spins has an inductive nature. We emphasize the inductive response by rewriting the current-voltage relation in harmonic response as a lumped element model containing two parallel resistors and an inductor. In a low-frequency analysis, a universal inductance value emerges that is only dependent on the device’s aspect ratio. This scaling offers a means of miniaturizing inductive circuit elements. An efficiency estimate follows from comparing the spin-flip induced current to the Ohmic contribution. The inductive effect is most prominent in topological insulators which have a large number of spinful nuclei per coherent segment, of which the volume is given by the mean free path length, Fermi wavelength and penetration depth of the surface state
The interactive role of odor associations in friendship preferences
No full textWho we choose to befriend is highly personal, driven by idiosyncratic preferences about other individuals, including sensory cues. How does a person’s unique sensory evaluation of others’ body odor affect friendship formation? Female participants took part in a speed-friending event where they made judgments of friendship potential (FP) following a 4-minute live interaction. Prior to and following the speed-friending event, participants judged the FP of these women based solely on diplomatic odor (including daily perfume/hygiene products) presented on worn t-shirts. Participants also judged FP based on facial appearance (a 100-ms presentation of portrait photographs). Judgments based solely on diplomatic odor predicted FP judgments following in-person interactions, beyond the predictive ability of photograph-based judgments. Moreover, judgments based on the live interaction predicted changes in the second round of diplomatic odor judgments, suggesting that the quality of the live interaction modified olfactory perception. Results were driven more strongly by idiosyncratic preferences than by global perceiver or target effects. Findings highlight the dynamic role of ecologically relevant social olfactory cues in informing friendship judgments, as well as the involvement of odor-based associative learning during the early stages of friendship formation
The versatile role of YidC in membrane protein biosynthesis and quality control
No full textMembrane proteins are essential for bacterial survival, facilitating vital processes such as energy production, nutrient transport, and cell wall synthesis. YidC is a key player in membrane protein biogenesis, acting as both an insertase and a chaperone to ensure proper protein folding and integration into the lipid bilayer. Its conserved structure and adaptability enable it to mediate co-translational and post-translational protein insertion into the membrane through both Sec-dependent and Sec-independent pathways. In addition to facilitating protein insertion, YidC collaborates with FtsH in protein quality control, preventing the accumulation of misfolded proteins that could impair cellular function. This important relationship between YidC and FtsH is poorly understood, and there is a need for further investigation into their collaboration. Understanding how YidC and FtsH coordinate their roles could provide valuable insights into the links between bacterial membrane protein biogenesis and quality control pathways. Moreover, given its central functions, YidC represents a potential target for antimicrobial development. Small molecules disrupting its function in protein folding and insertion, hold promise. However, achieving bacterial specificity without impacting eukaryotic homologs remains a challenge. Here, we review our current understanding of YidC's structure, molecular function in membrane protein biogenesis and quality control, known interactions and its therapeutic potential
Integrated design optimization of a motorized active magnetic bearing spindle for micro-milling applications
No full textContact or air bearings are commonly used in micro-milling spindles. However, active magnetic bearing (AMB) enables high-speed and contact-free rotation with active control of spindle dynamics. Many studies focus on either AMB or motor only and therefore lack a thorough consideration of mutual influence of both elements on spindle performance. In contrast, our approach integrated these elements in a design optimization framework. This framework was built upon a comprehensive set of numerically-corrected multiphysical analytical models considering the electromagnetic, rotordynamic, and mechanical performance of spindle. Using a multi-objective optimization algorithm, a Pareto front was developed allowing designers to choose from alternative optimal spindle dimensions depending on the specific application requirements. We further suggested design modifications accounting for the often-neglected coupling between the fields of motor and AMB by constructing a 3D finite element model. The presented design framework should allow for novel miniaturized AMB spindle designs based on multiphysical modeling capabilities
Impact of nickel substitution on supercapacitor and photocatalytic performances of cobalt-ferrites nanoparticles
No full textNixCo1-xFe2O4 nanoparticles were synthesized by precipitation method and developed as bifunctional nanoparticles for photocatalytic and supercapacitor applications. The crystalline structure and gradual changing of the cell parameters by substituting Ni2+ ions into the Co-ferrite lattice were confirmed by XRD. Raman analysis shows that the Co2+ ions partially substitute Fe3+ ions in tetrahedral sites, and the substitution with Ni2+ ions lead to a rearrangement of cations on octahedral sites. The samples have a mixture of spherical and rectangular shapes with an average size between 4 and 14 nm for Ni-ferrite and Co-ferrite, respectively. All the samples are ferromagnetic at room temperature; both magnetic phases were evidenced by EPR spectroscopy. In substituted Co ferrite, 80 % Ni was identified as the optimum amount, ensuring the best photocatalytic activity against RhB solution under visible irradiation. The photocatalytic mechanism was explained, considering that the samples generate only superoxide radicals under visible light. The sample with the best photocatalytic performance was combined with PVDF membrane to enhance its hydrophilicity and self-cleaning properties. Additionally, Ni-Co ferrite nanoparticles were studied as electrode materials in symmetrical supercapacitor devices. Electrochemical characteristics indicate good performance and cycling stability and confirmed an appreciable increase in specific capacitance by substituting Co2+ with Ni2+ ions
Bound on the minimum distance of double circulant cubic residue codes
No full textWe study a class of pure double circulant binary codes attached to the cyclotomy of order 3 with respect to a prime p≡1(mod3). The minimum distance is bounded below by an argument involving cyclotomic numbers and Weil inequality for multiplicative character sums
Disjointness violations in Wikidata
No full textDisjointness checks are among the most important constraint checks in a knowledge base and can be used to help detect and correct incorrect statements and internal contradictions. Wikidata is a very large, community-managed knowledge base. Because of both its size and construction, Wikidata contains many incorrect statements and internal contradictions. We analyze the current modeling of disjointness on Wikidata, identify patterns that cause these disjointness violations and categorize them. We use SPARQL queries to identify each “culprit” causing a disjointness violation and lay out formulas to identify and fix conflicting information. We finally discuss how disjointness information could be better modeled and expanded in Wikidata in the future