The Integer Quantum Hall Effect transverse conductivity is derived assuming the electrons form a lattice described by the doubly periodic states of Rodrigues and Doria (2021). We consider the ...simplest scenario of one electron per Landau level in the unit cell to find complex electronic patterns revealing that besides the counter clockwise circulation set by the magnetic field, there is also clockwise circulation contrary to it. These circulations describe vortices and anti-vortices, thus there are novel topological excitations whose spatial distributions and individual vorticities are numerically calculated for the first eleven Landau levels. Although we work in a particular gauge, the Landau gauge, our results are gauge invariant as they hold for gauge invariant quantities, such as the wave function probability and the current density.
•The topological properties of the IQHE are fixed by the integer N associated with the transverse conductivity plateaus, Ne2/h, N is the number of filled Landau levels (n=0,…,N−1). Here we find that N does not describe all the topological properties of the IQHE thanks to the use of the doubly periodic functions obtained by Rodrigues and Doria (2021).•The treatment developed in details in the present paper, is for the case of one electron per Landau level in the unit cell (p=1), where the number of trapped magnetic flux, and also the vorticity in the unit cell, is one.•Novel topological properties of the IQHE are shown here, as besides the counter clockwise circulation set by the magnetic field, there is also clockwise circulation contrary to it in each Landau level above the fundamental one.•We explicitly obtain the spatial distributions of vortices and anti-vortices and their individual vorticities in the unit cell for the first time.•The present approach also provides a straightforward description of the IQHE solely based on bulk properties without any appeal to the use of boundaries, and so, proves that edge states are not fundamental to the description of the IQHE.
We claim that fractionally charged quasi-particles arise in a conducting layer in presence of an external magnetic field perpendicular to it, as a consequence of spin-momentum locking. The presence ...of fractionary quasi-particles is checked by two independent methods, both based on the residual local magnetic field that determines the topological properties of the layer. The methods correspond to the Chern-Simons index and the direct visualization of the local field component perpendicular and very close to the layer. We assume doubly periodic states in the layer, described in terms of orthonormal functions, which were recently developed in Ref. 1. Our results stem from the three-term decomposition of the kinetic energy 2,3, which shows that the Rashba term is already contained in the Schrödinger kinetic energy.
•The Dirac linear spectrum is obtained from the non-relativistic Schroedinger parabolic kinetic energy.•The Schroedinger parabolic kinetic energy contains the Rashba term.•Fractionally charged quasi-particles are found by computing the Chern-Simons index and also by the direct inspection of the local magnetic field.•There is a local magnetic field that defines the topological stability of the quasi-particles and is 10−5 weaker than the applied field.•Our calculations assume double periodicity in the layer.
The aim of this study was to investigate the effect of the dry and rainy season on the antibacterial activity and chemical composition of the Brazilian red propolis. The samples were collected in ...rainy (RP-PER) and dry (RP-PED) seasons and analyzed by HPLC-DAD. The extracts were tested alone and in association with antibiotics against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The HPLC analysis identified luteolin and quercetin as the main compounds. Seasonal variation was observed according to concentrations of the compounds. The MIC values against E. coli ranged from 128 μg/mL to 512 μg/mL (EC 06 and EC ATCC). The red propolis showed MIC values of 512 μg/mL against both strains of P. aeruginosa used in our study (PA03 and PA24) and against strains of Gram-positive bacteria S. aureus the MICs ranged from 64 μg/mL to ≥1024 μg/mL (SA10). A synergistic effect was observed when we combined the RP-PED with gentamicin against all the strains tested. When we combined the RP-PED with Imipenem, we only observed synergistic effect against P. aeruginosa. According to our synergistic activity results, the utilization of red propolis collected in the drier periods can be used as an adjuvant against multiresistant bacterial infections.
The indiscriminate use of antibiotics has made bacterial resistance an important public health problem, since many antibiotics have become ineffective. Phototherapy can be considered an alternative ...to reduce the abusive use of antimicrobials, thus impacting microbial resistance. The objective of this study was to determine the chemical profile and to evaluate the effect of blue LED lights on the antibacterial activity of essential oils from Piper species, as well as their aminoglycoside antibiotic activity modulation using the microdilution method to determine the Minimum Inhibitory Concentration (MIC). The antibiotic activity modulating effect of these oils was also determined using the broth microdilution method with 96-well plates which were exposed to LED light for 20 min. Chemical components were characterized by gas chromatography coupled to mass spectrometry, revealing β-copaen-4-α-ol, germacrene A and germacrene B as major essential oil constituents for Piper arboreum (OEPar), Piper aduncum (OEPad) and Piper gaudichaudianum (OEPg), respectively. OEPar obtained a MIC of 512 μg/mL against Staphylococcus aureus and a MIC ≥ 1024 μg/mL against Escherichia coli. OEPad and OEPg showed MIC values ≥ 1024 μg/mL against the utilized strains. The essential oils modulated the effect of the antibiotics amikacin and gentamicin, with this effect being potentiated when exposed to blue LED. The blue LED light in the absence of the essential oil also showed an ability to modulate aminoglycoside antibiotic activity in this study, presenting mostly synergistic effects. In conclusion, the results obtained in this study demonstrate that photodynamic therapy using blue LED light interferes with the antibacterial action of P. arboreum, P. aduncum and P. gaudichaudianum essential oils and aminoglycoside antibiotic activity.
•The blue LED light interferes with the action of essential oils in a synergistic manner.•The blue LED light interferes with the action of the antibiotics in a synergistic manner.•The photoactivation of EO is a promising methodology against bacterial infections.
•The main phytocompound identified in the EOCV was sabinene.•Was verified the variation of the chemical composition of the essential oil during one year.•Was demonstrated the antibacterial activity ...of the essential oil, sabinene and hydrate sabinene.•Was demonstrated the modulatory activity of bacterial resistance to aminoglycosides.
Cordia verbenacea DC (Boraginaceae), popularly known as “Erva Baleeira,” has been widely studied with respect to its chemical and pharmacological properties, and its anti-inflammatory, analgesic and anti-ulcerogenic activities have been demonstrated. The objective of this study was to determine the essential oil content with regard to time of collection of leaves and to evaluate the antibacterial activity and antibiotic-modifying activity of the oil, sabinene and sabinene hydrate against multidrug-resistant strains. GC/MS analysis showed that in samples of the essential oil obtained at different times over one year, there was qualitative and quantitative variation in chemical composition, with statistical significance (p<0.001 and p<0.05). The MIC of essential oil, sabinene and sabinene hydrate was ≥1024μg/mL, demonstrating no clinically relevant antibacterial activity. In tests for modulation of bacterial resistance to aminoglycosides, essential oil, sabinene and sabinene hydrate showed significant changes (p<0.001) in MIC values, enhancing the effect of the antibiotics tested, thereby demonstrating synergistic potential. These results serve as a reference for choosing the best time to obtain the oil according to the constituent of interest, as well as for using the oil and its constituents as modifying agents of bacterial resistance to aminoglycoside.
Bacterial resistance has risen as an important health problem with impact on the pharmaceutical industry because many antibiotics have become ineffective, which has affected their commercialization. ...The Brazilian biodiversity is marked by a vast variety of natural products with significant therapeutic potential, which could bring new perspectives in the treatment of infections caused by resistant microorganisms. The present study aimed to evaluate the antibacterial effect of the essential oil obtained from Eugenia jambolana (EjEO) using the method of microdilution method to determine the Minimum Inhibitory Concentration (MIC). The modulatory effect of this oil on antibiotic activity was determined using both the broth microdilution and gaseous contact methods. The antibacterial effect of the association of the gaseous contact and the use of a LED unit with red and blue lights was also determined. The chemical components of the EjEO were characterized by HPLC, which revealed the presence of α-pinene as a major constituent. The EjEO presented a MIC≥128μg/mL against S. aureus and ≥1024μg/mL against E. coli. The combination of the EjEO with antibiotics presented synergism against E. coli and antagonism against S. aureus. An antagonistic effect was obtained from the association of EjEO with amikacin and erythromycin by the method of gaseous contact. On the other hand, the association of EjEO with ciprofloxacin presented a synergistic effect against S. aureus and E. coli exposed to LED lights. A similar effect was observed in the association of the EjEO with norfloxacin presented synergism against S. aureus in the same conditions. In conclusion, our results demonstrated that the essential oil obtained from Eugenia jambolana interfere with the action of antibiotics against bacteria exposed to LED lights. Thus, further researches are required to elucidate the mechanisms underlying these effects, which could open new perspectives in the development of new antibacterial therapies.
•The Eugenia jambolana essential oil affect the antibiotic activity.•The LED lights interfere with the action of antibiotic activity.•These effects are not observed when the antibiotics were associated with the oil and the LED lights in the same time.
Zero Helicity States in the LaAlO3-SrTiO3 Interface B. Rodrigues, Edinardo I.; Vargas-Paredes, Alfredo A.; Doria, Mauro M. ...
Journal of superconductivity and novel magnetism,
05/2017, Letnik:
30, Številka:
5
Journal Article
Recenzirano
The transverse magnetic moment and torque observed by Li et al. (Nat. Phys.
7
, 762 (
6
)) in the LaAlO
3
/SrTiO
3
interface is claimed to have a purely kinetic origin. To explain the data, we ...describe the electronic state by a two-component order parameter with zero helicity. The zero helicity state breaks the spatial reflection symmetry of the kinetic energy according to the mechanism described here. The resulting state is a lattice of vortex-skyrmions that result in a transverse magnetization due to the asymmetry in the mass and thickness anisotropy between the two sides of the interface.
Properties of the spin-momentum locked state Doria, Mauro M.; Rodrigues, Edinardo I. B.
Journal of physics. Conference series,
03/2022, Letnik:
2164, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
Spin-momentum locking is becoming a cornerstone for the understanding and applications of novel condensed matter systems. Here we assume that it holds locally in position space and from it ...predict the existence of a local magnetic field. Although residual, this local magnetic field is important because it brings the topological stability that transforms particles into quasi-particles. The present approach shows that the Rashba term is already contained in the Schrödinger kinetic energy and a Dirac linear spectrum can be obtained without invoking a Dirac equation for the particles.
We report an infinite number of orthonormal eigenfunction bases for the quantum problem of a free electron in presence of an applied external magnetic field, suitable to describe doubly periodic ...electronic densities. The completeness of these bases is shown here and so, a single basis, labeled by the number of magnetic fluxons trapped in the unit cell (integer p), expands any function in the unit cell. The present framework unveils for the electronic density an egg-box pattern that displays fractional charge and magnetic flux. In case of electrons confined to the lowest Landau level we obtain an analytic expression for the local magnetic field created by their own motion and find that it yields an attractive magnetic interaction. The well-known de Haas–van Alphen oscillations are retrieved, thus showing the correctness of the present theoretical framework.
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