971 research outputs found
New eco-friendly hybrid composite materials for civil construction
This paper concerns the development of new hybrid composite materials using granulated cork, a by-product of cork industry, cellulose pulp, from recycling of paper residues, and hemp fibres. The binder used is either cellulose pulp or lime-pozzolan mixture. Such materials may be used as composite
boards and mortars for non structural elements of construction, such as dry walls and ceiling or floor levelling and filling. The possibility of using these composites in conjugation with light structural supports has been studied. The paper will present the properties and the manufacturing methods used to produce the above mentioned promising eco-friendly composites that can unfold ways of using industrial wastes as new construction materials with excellent inherent thermal and acoustic properties
Unified description of the dc conductivity of monolayer and bilayer graphene at finite densities based on resonant scatterers
We show that a coherent picture of the dc conductivity of monolayer and
bilayer graphene at finite electronic densities emerges upon considering that
strong short-range potentials are the main source of scattering in these two
systems. The origin of the strong short-range potentials may lie in adsorbed
hydrocarbons at the surface of graphene. The equivalence among results based on
the partial-wave description of scattering, the Lippmann-Schwinger equation,
and the T-matrix approach is established. Scattering due to resonant impurities
close to the neutrality point is investigated via a numerical computation of
the Kubo formula using a kernel polynomial method. We find that relevant
adsorbate species originate impurity bands in monolayer and bilayer graphene
close to the Dirac point. In the midgap region, a plateau of minimum
conductivity of about (per layer) is induced by the resonant disorder.
In bilayer graphene, a large adsorbate concentration can develop an energy gap
between midgap and high-energy states. As a consequence, the conductivity
plateau is supressed near the edges and a "conductivity gap" takes place.
Finally, a scattering formalism for electrons in biased bilayer graphene,
taking into account the degeneracy of the spectrum, is developed and the dc
conductivity of that system is studied.Comment: 25 pages, 13 figures. published version: appendixes improved,
references added, abstract and title slightly changed, plus other minor
revision
Cutinase purification on poly(ethylene glycol)–hydroxypropyl starch aqueous two-phase systems
The partition behaviour of cutinase on poly(ethylene glycol) (PEG)–hydroxypropyl starch aqueous two-phase systems was
characterized. The effect of molecular mass of PEG, the pH of the system and tie-line length on cutinase partition coefficient
and cutinase yield to the top phase was investigated for systems prepared with a purified hydroxypropyl starch (Reppal PES
100) and a crude one (HPS). The effect of the presence of different salts, such as sodium chloride, sodium sulphate and
ammonium sulphate, on cutinase partition was also studied. The results lead to the conclusion that aqueous two-phase
systems composed of PEG and hydroxypropyl starch are not efficient in the purification of cutinase. In the majority of cases,
the partition coefficients were very close to 1, with pH being the factor which affects most cutinase partition. Partition
coefficients were significantly improved when salts were added to the systems. For PEG 4000–Reppal PES 100 [at pH 4.0;
0.5 M (NH4)2 SO4], the partition coefficient for cutinase was 3.7, while a value of 12 was obtained for PEG 4000–HPS (at pH 4.0; 1 M NaC1). An isoelectric point (pI ) of 7.8 was confirmed for cutinase by constructing a cross partition graphic from
the results obtained in the experiments with different salts. 1998 Elsevier Science B.V. All rights reserved
Results of Surgery Versus Stereotactic Body Radiotherapy for Lung Cancer
info:eu-repo/semantics/publishedVersio
Critical Delocalization of Chiral Zero Energy Modes in Graphene
Graphene subjected to chiral-symmetric disorder is believed to host zero energy modes (ZEMs) resilient to localization, as suggested by the renormalization group analysis of the underlying nonlinear sigma model. We report accurate quantum transport calculations in honeycomb lattices with in excess of sites and fine meV resolutions. The Kubo dc conductivity of ZEMs induced by vacancy defects (chiral BDI class) is found to match within 1% accuracy, over a parametrically wide window of energy level broadenings and vacancy concentrations. Our results disclose an unprecedentedly robust metallic regime in graphene, providing strong evidence that the early field-theoretical picture for the BDI class is valid well beyond its controlled weak-coupling regime
Electrically tunable resonant scattering in fluorinated bilayer graphene
Adatom-decorated graphene offers a promising new path towards spintronics in
the ultrathin limit. We combine experiment and theory to investigate the
electronic properties of dilutely fluorinated bilayer graphene, where the
fluorine adatoms covalently bond to the top graphene layer. We show that
fluorine adatoms give rise to resonant impurity states near the charge
neutrality point of the bilayer, leading to strong scattering of charge
carriers and hopping conduction inside a field-induced band gap. Remarkably,
the application of an electric field across the layers is shown to tune the
resonant scattering amplitude from fluorine adatoms by nearly twofold. The
experimental observations are well explained by a theoretical analysis
combining Boltzmann transport equations and fully quantum-mechanical methods.
This paradigm can be generalized to many bilayer graphene-adatom materials, and
we envision that the realization of electrically tunable resonance may be a key
advantage in graphene-based spintronic devices.We thank X. Hong for helpful discussions.
A.S., J.L., and J.Z. are supported by ONR
under Grant No. N00014-11-1-0730 and by NSF CAREER
Grant No. DMR-0748604. A.F. and N.M.R.P.
acknowledge EC under Graphene Flagship (Contract
No. CNECT-ICT-604391). A.F. gratefully acknowledges
the financial support of the Royal Society (U.K.) through
a Royal Society University Research Fellowship. We acknowledge
use of facilities at the PSU site of NSF NNIN
Diabetic Foot Ulcers Classification using a fine-tuned CNNs Ensemble
Diabetic Foot Ulcers (DFU) are lesions in the foot region caused by diabetes mellitus. It is essential to define the appropriate treatment in the early stages of the disease once late treatment may result in amputation. This article proposes an ensemble approach composed of five modified convolutional neural networks (CNNs) - VGG-16, VGG-19, Resnet50, InceptionV3, and Densenet-201 - to classify DFU images. To define the parameters, we fine-tuned the CNNs, evaluated different configurations of fully connected layers, and used batch normalization and dropout operations. The modified CNNs were well suited to the problem; however, we observed that the union of the five CNNs significantly increased the success rates. We performed tests using 8,250 images with different resolution, contrast, color, and texture characteristics and included data augmentation operations to expand the training dataset. 5-fold cross-validation led to an average accuracy of 95.04%, resulting in a Kappa index greater than 91.85%, considered Excellent
Behaviour of cementitious matrices subjected to the combined action of chloride ions and carbonation
Carbonation and chloride action are the two leading causes of degradation in reinforced concrete structures. Despite the combined action of these two mechanisms being a reality, there is little research on the effect of this combination in cementitious matrices. Furthermore, the incorporation of fly ash in cementitious matrices has been frequently used in order to make the matrix more resistant to the action of chlorides. On the other hand, it is known that Ca(OH)2 existing in the matrix is consumed by the pozzolanic reactions, which makes easier the carbonation front advance. Therefore, this paper presents a study of the behavior of cementitious matrices, with and without fly ash, subjected to the combined action of chlorides and carbonation. Two different kinds of mortars were produced: reference (only cement CEM I 42.5R) and fly ash mortar (40% replacement of cement). After curing, the specimens were subjected to three different wetting-drying cycles, considering NaCl solutions and CO2 atmospheres. Afterwards, chloride profiles and carbonation front were measured. Results show that carbonation has a direct influence on chloride penetration, decreasing it for cement mortars with 0% fly ash and increasing it for mortars with 40% cement replacement by fly ash. Moreover, the evolution of carbonation is also influenced by chloride presence, which decreases under the combined action.The authors thank the Foundation for Science and Technology (FCT) for supporting this research. The authors also thank the SECIL for making available cement used in this research and the CIMENTEIRA DO LOURO for providing the aggregates used. This work is co-financed by FEDER funds through the Competitively Factors Operational Programme - COMPETE and by national funds through FCT within the scope of the project POCI-01-0145-FEDER007136.info:eu-repo/semantics/publishedVersio
Transport properties of graphene with one-dimensional charge defects
We study the effect of extended charge defects in electronic transport
properties of graphene. Extended defects are ubiquitous in chemically and
epitaxially grown graphene samples due to internal strains associated with the
lattice mismatch. We show that at low energies these defects interact quite
strongly with the 2D Dirac fermions and have an important effect in the
DC-conductivity of these materials.Comment: 6 pages, 5 figures. published version: one figure, appendix and
references adde
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