Liquid crystal phases of ultracold dipolar fermions on a lattice

Motivated by the search for quantum liquid crystal phases in a gas of ultracold atoms and molecules, we study the density wave and nematic instabilities of dipolar fermions on the two-dimensional square lattice (in the $x-y$ plane) with dipoles pointing to the $z$ direction. We determine the phase diagram using two complimentary methods, the Hatree-Fock mean field theory and the linear response analysis of compressibility. Both give consistent results. In addition to the staggered ($\pi$, $\pi$) density wave, over a finite range of densities and hopping parameters, the ground state of the system first becomes nematic and then smectic, when the dipolar interaction strength is increased. Both phases are characterized by the same broken four-fold (C$_4$) rotational symmetry. The difference is that the nematic phase has a closed Fermi surface but the smectic does not. The transition from the nematic to the smectic phase is associated with a jump in the nematic order parameter. This jump is closely related to the van Hove singularities. We derive the kinetic equation for collective excitations in the normal isotropic phase and find that the zero sound mode is strongly Landau damped and thus is not a well defined excitation. Experimental implications of our results are discussed.Comment: 8 pages, 4 figures; Erratum added in the appendi

Realising biaxial reinforcement via orientation-induced anisotropic swelling in graphene-based elastomers

The biaxial mechanical properties constitute another remarkable advantage of graphene, but their evaluation has been overlooked in polymer nanocomposites. Herein, we provided an innovative and practical method to characterise biaxial reinforcement from graphene via swelling of elastomers, where graphene nanoplatelets were controlled to be oriented in-plane. The in-plane-aligned graphene imposed a biaxial constraining force to the elastomer during the swelling process that led to the anisotropic swelling behaviour of the bulk nanocomposites

Tumour burden score for hepatocellular carcinoma: Is it an authentic prognostic marker?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/163375/2/bjs11927.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/163375/1/bjs11927_am.pd

Mechanisms of mechanical reinforcement by graphene and carbon nanotubes in polymer nanocomposites

Polymer nanocomposites reinforced with carbon-based nanofillers are gaining increasing interest for a number of applications due to their excellent properties. The understanding of the reinforcing mechanisms is, therefore, very important for the maximization of performance. This present review summarizes the current literature status on the mechanical properties of composites reinforced with graphene-related materials (GRMs) and carbon nanotubes (CNTs) and identifies the parameters that clearly affect the mechanical properties of the final materials. It is also shown how Raman spectroscopy can be utilized for the understanding of the stress transfer efficiency from the matrix to the reinforcement and it can even be used to map stress and strain in graphene. Importantly, it is demonstrated clearly that continuum micromechanics that was initially developed for fibre-reinforced composites is still applicable at the nanoscale for both GRMs and CNTs. Finally, current problems and future perspectives are discussed

Dexmedetomidine mitigates myocardial ischemiareperfusion injury via regulation of HMGB1-TLR4-NF-κB signaling axis

Purpose: To study the effect of dexmedetomidine (Dex) on myocardial ischemia-reperfusion injury (MIRI), and the associated mechanism of action.Methods: Sixty Sprague-Dawley (SD) rats were assigned to sham, ischemia-reperfusion (I/R), Dex, and MD groups (methyllycaconitine prior to injection with Dex), with 15 rats in each group. Pathological changes in myocardial tissues were determined in all groups. Protein expression levels of HMGB1, TLR4, NF-κB and myeloid differentiation protein 88 (MyD88) in serum and myocardial tissues were assayed and compared.Results: Protein levels of HMGB1, TLR4, MyD88 and NF-κB were significantly higher in heart muscle I/R rats than those in sham group, but lower in heart muscle of rats in Dex group than in heart muscle of I/R rats (p < 0.05). However, they were significantly up-regulated in MD group, relative to Dex group (p< 0.05).Conclusion: Dex exerts a protective effect against ischemia/reperfusion-induced myocardial damage via HMGB1-TLR4-NF-κB signal axis via CAP, and thus, is a potential agent for the management of myocardial disease

Hybrid poly(ether ether ketone) composites reinforced with a combination of carbon fibres and graphene nanoplatelets

Poly(ether ether ketone) (PEEK), with its superb mechanical properties, excellent chemical resistance and high thermo-oxidative stability is one of the most important engineering thermoplastics for high-end applications. In this work, we investigate the elastic and viscoelastic properties along with the creep mitigation of two sets of samples: PEEK reinforced with graphene nanoplatelets (GNPs) and PEEK reinforced with a hybrid graphene/short carbon fibre (CF) filler. The melt viscosity of the PEEK nanocomposites was found to increase with increasing GNPs content; however, the viscosity of the hybrid CF-GNP samples with the highest filler content was equal to the one of the samples filled only with GNPs at low shear rates. This processability shows the advantage of GNPs over other nano and conventional fillers in the ability to use meaningful loadings. The introduction of GNPs improved significantly the stiffness and the storage modulus of the materials in both PEEK-GNP and PEEK-CF-GNP composites. Moreover, the presence of GNPs within the composites led to a restriction of the mobility of the macromolecular chains of PEEK, which resulted in enhanced creep properties at both room temperature and elevated temperatures. Overall, the nanocomposites produced displayed properties that make them attractive in applications where high stiffness and structural integrity at elevated temperatures are required

The mechanics of reinforcement of polymers by graphene nanoplatelets

A detailed study has been undertaken of the mechanisms of stress transfer in polymeric matrices with different values of Young's modulus, Em, reinforced by graphene nanoplatelets (GNPs). For each material, the Young's modulus of the graphene filler, Ef, has been determined using the rule of mixtures and it is found to scale with the value of Em. Additionally stress-induced Raman bands shifts for the different polymer matrices show different levels of stress transfer from the polymer matrix to the GNPs, which again scale with Em. A theory has been developed to predict the stiffness of the bulk nanocomposites from the mechanics of stress transfer from the matrix to the GNP reinforcement based upon the shear-lag deformation of individual graphene nanoplatelets. Overall it is found that it is only possible to realise the theoretical Young's modulus of graphene of 1.05 TPa for discontinuous nanoplatelets as Em approaches 1 TPa; the effective modulus of the reinforcement will always be less for lower values of Em. For flexible polymeric matrices the level of reinforcement is independent of the graphene Young's modulus and, in general, the best reinforcement will be obtained in nanocomposites with strong graphene-polymer interfaces and aligned nanoplatelets with high aspect ratios

HetFS: A heterogeneous file system for everyone

Storage devices have been getting more and more diverse during the last decade. The advent of SSDs made it painfully clear that rotating devices, such as HDDs or magnetic tapes, were lacking in regards to response time. However, SSDs currently have a limited number of write cycles and a significantly larger price per capacity, which has prevented rotational technologies from begin abandoned. Additionally, Non-Volatile Memories (NVMs) have been lately gaining traction, offering devices that typically outperform NAND-based SSDs but exhibit a full new set of idiosyncrasies. Therefore, in order to appropriately support this diversity, intelligent mechanisms will be needed in the near-future to balance the benefits and drawbacks of each storage technology available to a system. In this paper, we present a first step towards such a mechanism called HetFS, an extension to the ZFS file system that is capable of choosing the storage device a file should be kept in according to preprogrammed filters. We introduce the prototype and show some preliminary results of the effects obtained when placing specific files into different devices.The research leading to these results has received funding from the European Community under the BIGStorage ETN (Project 642963 of the H2020-MSCA-ITN-2014), by the Spanish Ministry of Economy and Competitiveness under the TIN2015-65316 grant and by the Catalan Government under the 2014-SGR- 1051 grant. To learn more about the BigStorage project, please visit http: //bigstorage-project.eu/.Peer ReviewedPostprint (author's final draft

Preparation of Large Monodisperse Vesicles

Preparation of monodisperse vesicles is important both for research purposes and for practical applications. While the extrusion of vesicles through small pores (∼100 nm in diameter) results in relatively uniform populations of vesicles, extrusion to larger sizes results in very heterogeneous populations of vesicles. Here we report a simple method for preparing large monodisperse multilamellar vesicles through a combination of extrusion and large-pore dialysis. For example, extrusion of polydisperse vesicles through 5-µm-diameter pores eliminates vesicles larger than 5 µm in diameter. Dialysis of extruded vesicles against 3-µm-pore-size polycarbonate membranes eliminates vesicles smaller than 3 µm in diameter, leaving behind a population of monodisperse vesicles with a mean diameter of ∼4 µm. The simplicity of this method makes it an effective tool for laboratory vesicle preparation with potential applications in preparing large monodisperse liposomes for drug delivery

Synergy between magneto-rheological fluids and aluminum foams. Prospective alternative for seismic damping

This is the accepted manuscript. Access to the published article can be gained at: http://jim.sagepub.com/cgi/reprint/1045389X15596624v1.pdf?ijkey=SyFHNQwE4XMQqBF&keytype=finiteThis article presents the experimental study of a preliminary investigation of a seismic damper device aimed at improving the behavior of structures when subjected to earthquakes. The damper is the result of a binomial material formed by aluminum foam with pores 1 mm in diameter, wetted by a magnetorheological fluid (MRF). The objective of the present work is to explore the synergy between the two components in a magnetorheological test, and to evaluate the effect of the Al foam pores in the structure buildup of the fluid. The analysis is completed with a compressive test carried out on the MRF-filled foam in the presence of a magnetic field. This kind of test demonstrates that the deformation of the foam for very small loads is limited by the hardening of the fluid because of its MR response. The results of this research suggest that there is a mutual benefit between the components of the device, presumably leading to an enhanced dissipation of vibration energy.Proyectos PE2012-FQM694 (Junta de Andalucía, Spain), FIS2013-47666-C3-1-R (MINECO, Spain), SENER-CONACYT "151496" (UNAM Mexico), CONACYT National Quality Graduate Progra