1,779 research outputs found
Symmetry breaking effects upon bipartite and multipartite entanglement in the XY model
We analyze the bipartite and multipartite entanglement for the ground state
of the one-dimensional XY model in a transverse magnetic field in the
thermodynamical limit. We explicitly take into account the spontaneous symmetry
breaking in order to explore the relation between entanglement and quantum
phase transitions. As a result we show that while both bipartite and
multipartite entanglement can be enhanced by spontaneous symmetry breaking deep
into the ferromagnetic phase, only the latter is affected by it in the vicinity
of the critical point. This result adds to the evidence that multipartite, and
not bipartite, entanglement is the fundamental indicator of long range
correlations in quantum phase transitions.Comment: 13 pages, 19 figures, comments welcome. V2: small changes, published
versio
The Brans-Dicke-Rastall theory
We formulate a theory combining the principles of a scalar-tensor gravity and
Rastall's proposal of a violation of the usual conservation laws. We obtain a
scalar-tensor theory with two parameters and , the latter
quantifying the violation of the usual conservation laws. The only exact
spherically symmetric solution is that of Robinson-Bertotti besides
Schwarzschild solution. A PPN analysis reveals that General Relativity results
are reproduced when . The cosmological case displays a possibility
of deceleration/acceleration or acceleration/deceleration transitions during
the matter dominated phase depending on the values of the free parameters.Comment: 17 pages, 3 figure
Thermodynamic and dynamic anomalies for a three dimensional isotropic core-softened potential
Using molecular dynamics simulations and integral equations (Rogers-Young,
Percus-Yevick and hypernetted chain closures) we investigate the thermodynamic
of particles interacting with continuous core-softened intermolecular
potential. Dynamic properties are also analyzed by the simulations. We show
that, for a chosen shape of the potential, the density, at constant pressure,
has a maximum for a certain temperature. The line of temperatures of maximum
density (TMD) was determined in the pressure-temperature phase diagram.
Similarly the diffusion constant at a constant temperature, , has a maximum
at a density and a minimum at a density .
In the pressure-temperature phase-diagram the line of extrema in diffusivity is
outside of TMD line. Although in this interparticle potential lacks
directionality, this is the same behavior observed in SPC/E water.Comment: 16 page
Intake Rate and Nutritive Value of Elephant Grass cv. Napier Subjected to Strategies of Rotational Stocking Management
Several research papers on forage tropical grass species have demonstrated that grazing management interferes with sward structure that, in turn, alters patterns of ingestive and foraging behaviour of the grazing animals. For that reason it has been used as explicative variable for adjustments in intake characteristics like bite mass, bite rate, intake rate and nutritive value of the consumed herbage (Fonseca et al. 2012). Tall tufted growing plants like elephant grass (Pennisetum purpureum Schum.) cv. Napier show a continuous pattern of growth characterised by stem elongation during their vegetative state (Da Silva and Carvalho 2005), causing swards to become too tall and out of reach for grazing animals, generating serious difficulties in executing efficient grazing management, particularly when long regrowth periods are used. In that context, the increase in defoliation frequency has positive effects on herbage intake and nutritive value (Palhano et al. 2007), since it favours leaf elongation relative to stem elongation and senescent material accumulation throughout successive grazing cycles. Against that background, the objective of this experiment was to evaluate the components of the short term herbage intake (intake rate, bite mass and bite rate) and the nutritive value of the consumed herbage from elephant grass cv. Napier subjected to strategies of rotational stocking management defined in terms of pre- and post-grazing management targets
Sensitive bi-enzymatic biosensor based on polyphenoloxidasesâgold nanoparticlesâchitosan hybrid filmâgraphene doped carbon paste electrode for carbamates detection
A bi-enzymatic biosensor (LACCâTYRâAuNPsâCS/GPE) for carbamates was prepared in a single step by electrodeposition of a hybrid film onto a graphene doped carbon paste electrode (GPE). Graphene and the gold nanoparticles (AuNPs) were morphologically characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, dynamic light scattering and laser Doppler velocimetry. The electrodeposited hybrid film was composed of laccase (LACC), tyrosinase (TYR) and AuNPs entrapped in a chitosan (CS) polymeric matrix. Experimental parameters, namely graphene redox state, AuNPs:CS ratio, enzymes concentration, pH and inhibition time were evaluated. LACCâTYRâAuNPsâCS/GPE exhibited an improved MichaelisâMenten kinetic constant (26.9 ± 0.5 M) when compared with LACCâAuNPsâCS/GPE (37.8 ± 0.2 M) and TYRâAuNPsâCS/GPE (52.3 ± 0.4 M). Using 4-aminophenol as substrate at pH 5.5, the device presented wide linear ranges, low detection limits (1.68Ă10â 9 ± 1.18Ă10â 10 â 2.15Ă10â 7 ± 3.41Ă10â 9 M), high accuracy, sensitivity (1.13Ă106 ± 8.11Ă104 â 2.19Ă108 ± 2.51Ă107 %inhibition Mâ 1), repeatability (1.2â5.8% RSD), reproducibility (3.2â6.5% RSD) and stability (ca. twenty days) to determine carbaryl, formetanate hydrochloride, propoxur and ziram in citrus fruits based on their inhibitory capacity on the polyphenoloxidases activity. Recoveries at two fortified levels ranged from 93.8 ± 0.3% (lemon) to 97.8 ± 0.3% (orange). Glucose, citric acid and ascorbic acid do not interfere significantly in the electroanalysis. The proposed electroanalytical procedure can be a promising tool for food safety control
(Bio)Sensing Strategies Based on Ionic Liquid-Functionalized Carbon Nanocomposites for Pharmaceuticals: Towards Greener Electrochemical Tools
The interaction of carbon-based nanomaterials and ionic liquids (ILs) has been thoroughly exploited for diverse electroanalytical solutions since the first report in 2003. This combination, either through covalent or non-covalent functionalization, takes advantage of the unique characteristics inherent to each material, resulting in synergistic effects that are conferred to the electrochemical (bio)sensing system. From one side, carbon nanomaterials offer miniaturization capacity with enhanced electron transfer rates at a reduced cost, whereas from the other side, ILs contribute as ecological dispersing media for the nanostructures, improving conductivity and biocompatibility. The present review focuses on the use of this interesting type of nanocomposites for the development of (bio)sensors specifically for pharmaceutical detection, with emphasis on the analytical (bio)sensing features. The literature search displayed the conjugation of more than 20 different ILs and several carbon nanomaterials (MWCNT, SWCNT, graphene, carbon nanofibers, fullerene, and carbon quantum dots, among others) that were applied for a large set (about 60) of pharmaceutical compounds. This great variability causes a straightforward comparison between sensors to be a challenging task. Undoubtedly, electrochemical sensors based on the conjugation of carbon nanomaterials with ILs can potentially be established as sustainable analytical tools and viable alternatives to more traditional methods, especially concerning in situ environmental analysisThis work was financed by FEDERâFundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020âOperacional Programme for Competitiveness and Internationalization (POCI), and by Portuguese funds through FCTâFundação para a CiĂȘncia e a Tecnologia in the framework of the project POCI-01-0145-FEDER-029547âPTDC/ASP-PES/29547/2017.
This work received support by UIDB/50006/2020, UIDP/50006/ 2020 and LA/P/0008/2020 by the Fundação para a CiĂȘncia e a Tecnologia (FCT), MinistĂ©rio da CiĂȘncia, Tecnologia e Ensino Superior (MCTES) through national funds. T.M.B.F. Oliveira thanks the Brazilian agencies CNPq (Proc. 420261/2018-4 and 308108/2020-5) and FUNCAP (Proc. BP4-0172-00111.01.00/20) for their financial support, and he is grateful to UFCA and CAPES (Finance code 001) for supporting his investigations. F.W.P. Ribeiro thanks all support provided by the UFCAâs Pro-Rectory of Research and Innovation and the funding provided by FUNCAP-BPI (Proc. BP4-0172-00150.01.00/20) and CNPq (Proc. 406135/2018-5). P. de Lima-Neto thanks the financial support received from CNPq projects 408626/2018-6 and 304152/2018-8 and FUNCAP project FCT-00141-00011.01.00/18. A. N. Correia thanks the financial support received from CNPq projects: 305136/2018-6 and 405596/2018-9info:eu-repo/semantics/publishedVersio
Scaling of entanglement support for Matrix Product States
The power of matrix product states to describe infinite-size
translational-invariant critical spin chains is investigated. At criticality,
the accuracy with which they describe ground state properties of a system is
limited by the size of the matrices that form the approximation. This
limitation is quantified in terms of the scaling of the half-chain entanglement
entropy. In the case of the quantum Ising model, we find with high precision. This result can be understood as the emergence of an
effective finite correlation length ruling of all the scaling
properties in the system. We produce five extra pieces of evidence for this
finite- scaling, namely, the scaling of the correlation length, the
scaling of magnetization, the shift of the critical point, and the scaling of
the entanglement entropy for a finite block of spins. All our computations are
consistent with a scaling relation of the form ,
with for the Ising model. In the case of the Heisenberg model, we
find similar results with the value . We also show how
finite- scaling allow to extract critical exponents. These results are
obtained using the infinite time evolved block decimation algorithm which works
in the thermodynamical limit and are verified to agree with density matrix
renormalization group results.Comment: A new section comparing with previous results. Published version
(small differences due to proof corrections
Communication: Transient Anion States Of PhenolâŠ(hâo)n (n = 1, 2) Complexes: Search For Microsolvation Signatures.
We report on the shape resonance spectra of phenol-water clusters, as obtained from elastic electron scattering calculations. Our results, along with virtual orbital analysis, indicate that the well-known indirect mechanism for hydrogen elimination in the gas phase is significantly impacted on by microsolvation, due to the competition between vibronic couplings on the solute and solvent molecules. This fact suggests how relevant the solvation effects could be for the electron-driven damage of biomolecules and the biomass delignification [E. M. de Oliveira et al., Phys. Rev. A 86, 020701(R) (2012)]. We also discuss microsolvation signatures in the differential cross sections that could help to identify the solvated complexes and access the composition of gaseous admixtures of these species.14105110
3âAminopropyl-triethoxysilane-Functionalized Tannin-Rich Grape Biomass for the Adsorption of Methyl Orange Dye: Synthesis, Characterization, and the Adsorption Mechanism
A biomass amino silica-functionalized material was successfully prepared by a simple solâgel method. 3-Aminopropyltriethoxysilane (APTES) was added to a tannin-rich grape residue to improve its physicochemical properties and enhance the adsorption performance. The APTES functionalization led to significant changes in the materialâs characteristics. The functionalized material was efficiently applied in the removal of methyl orange (MO) due to its unique characteristics, such as an abundance of functional groups on its surface. The adsorption process suggests that the electrostatic interactions were the main acting mechanism of the MO dye removal, although other interactions can also take place. The functionalized biomass achieved a very high MO dye maximum adsorption capacity (Qmax) of 361.8 mg gâ1. The temperature positively affected the MO removal, and the thermodynamic studies indicated that the adsorption of MO onto APTES-functionalized biomass was spontaneous and endothermic, and enthalpy is driven in the physisorption mode. The regeneration performance revealed that the APTES-functionalized biomass material could be easily recycled and reused by maintaining very good performance even after five cycles. The adsorbent material was also employed to treat two simulated dye house effluents, which showed 48% removal. At last, the APTES biomass-based material may find significant applications as a multifunctional adsorbent and can be used further to separate pollutants from wastewater
Electroanalysis of Imidacloprid Insecticide in River Waters Using Functionalized Multi-Walled Carbon Nanotubes Modified Glassy Carbon Electrode
In this work, a functionalized multi-walled carbon nanotubes modified glassy carbon electrode (GCE/MWCNT-f) was optimized for the direct determination of imidacloprid (IMC) insecticide in river water. The functionalized material was characterized by infrared spectroscopy with Fourier transform (FTIR) and the modified electrode by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Results revealed that the GCE/MWCNT-f effectively increased the response toward IMC reduction by enhancing the reduction peak current and decreasing the peak potential in comparison with the bare electrode. After optimizing the electroanalytical conditions, the GCE/MWCNT-f showed a linear voltammetric response at concentration ranging from 2.40 Ă 10â7 to 3.50 Ă 10â6 mol Lâ1, with detection and quantification limits of 4.15 Ă 10â7 mol Lâ1 and 1.38 Ă 10â6 mol Lâ1, respectively. The recovery rate of IMC in spiked river water samples varied from 90â95%. Thus, this sensor can be a promising tool for the analysis and monitoring of IMC in complex environmental matrices.info:eu-repo/semantics/publishedVersio
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