Weak spin interactions in Mott insulating La2O2Fe2OSe2

Identifying and characterizing the parent phases of iron-based superconductors is an important step towards understanding the mechanism for their high-temperature superconductivity. We present an investigation into the magnetic interactions in the Mott insulator La2O2Fe2OSe2. This iron oxyselenide adopts a 2-k magnetic structure with low levels of magnetic frustration. This magnetic ground state is found to be dominated by next-nearest-neighbor interactions J2 and J2′ and the magnetocrystalline anisotropy of the Fe2+ site, leading to 2D-Ising-like spin S=2 fluctuations. In contrast to calculations, the values are small and confine the spin excitations below ∼25 meV. This is further corroborated by sum rules of neutron scattering. This indicates that superconductivity in related materials may derive from a weakly coupled and unfrustrated magnetic structure

Magnetoresistance and magnetic anisotropy in La0.5_{0.5}Sr0.5_{0.5}CoO3−δ_{3-\delta} film

The magnetic and transport properties of La$_{0.5}$Sr$_{0.5}$CoO$_{3-\delta}$ film grown on a LaAlO$_3$ substrate by pulsed-laser deposition are studied. The properties are found to be influenced by a combined influence of the magnetic anisotropy and inhomogeneity. Magnetoresistance anisotropy is determined by the shape anisotropy and the strain-induced magnetic anisotropy due to the film-substrate lattice interaction. Indications of the temperature-driven spin reorientation transition from an out-of plane orderded state at low temperatures to an in-plane ordered state at high temperatures as a result of competition between the mentioned anisotropy sources are found.Comment: 3 pages, 4 figures, reported at Moscow Int. Symp. on Magnetism (MISM 2002), June 200

Temperature Influence on the Properties of Thin Si3N4 Films

Applying Raman spectroscopy, small-angle x-ray scattering, and atomic force microscopy it were studied phase composition and surface morphology of nanoscale films Si3N4 (obtained by RF magnetron sputtering)

Development of a dairy fouling model to assess the efficacy of cleaning procedures using alkaline and enzymatic products

Dairy fouling is defined as the accumulation of thermally insulating materials or deposits from process fluids which are especially formed on heat transfer surfaces. The selection of suitable cleaning strategies to remove dairy fouling requires the understanding of its composition and the relationships with the surfaces where it is formed. For the industry, the development of novel strategies to test cleaning products, as well reducing water and energy consumption during the dairy processing operations is of enormous interest. The results showed the development of a laboratory-milk fouling model (MFM) with an average content of 52.8 mg/cm2 of fouling in the test coupons. Seven different cleaners were tested with a fouling removal effectiveness of between 55% and 97%. Additionally, for evaluating the cleaning process of the model, the turbidity of the cleaning solutions was assessed. We presented an enzymatic alternative to the use of traditional cleaning products, with a similar efficacy against the dairy fouling. 78% of fouling removal after the use of enzymatic solution, in comparison to the 72% of fouling removal after the use of alkaline cleaning products. A reduction in water (−33.3%) and temperature (−28.5%), as well as shorter cleaning times (−33%) than its chemical alternative, was observed.info:eu-repo/semantics/acceptedVersio

Suitability of wave energy converters in northwestern Spain under the near future winter wave climate

Marine renewable energies can play a key role by reducing the dependency on fossil fuels and, therefore, mitigating climate change. Among them, it is expected that wave energy will experience rapid growth in the upcoming decades. Thus, it is important to know how wave climate will change and how suitable the wave energy converters (WECs) will be to the new wave conditions. This paper aims to evaluate the capability of four different WECs—a WaveRoller type device (WRTD), Atargis, AquaBuoy and RM5—to extract wave energy on the Northwest coast of Spain (NWCS). The analysis was performed using the high-resolution wave data obtained from the Simulating Waves Nearshore (SWAN) model over the near future winters (2026–2045). The energy output (PE), the power load factor (ε), the normalized capture width (NCw) and the operational time (OT) were analyzed. According to these parameters, among the devices that work for intermediate-deep waters, Atargis would be the best option (PE=1400 ± 56 kW, ε =55.4 ± 2.2%, NCw=35.5 ± 4.1% and OT =84.5 ± 3.3%). The WRTD would also be a good option for shallow nearshore areas with PE=427 ± 248 kW, ε =12.8 ± 7.4%, NCw = 48.9 ± 9.6% and OT = 88.7 ± 18.9%. A combination of Atargis and WRTDs is proposed to make up the future wave energy farms on the NWCS.Xunta de Galicia | Ref. ED431C 2021/44Ministerio de Ciencia e Innovación | Ref. PID2020-113245RB-I00Agencia Estatal de Investigación | Ref. TED2021-129479A-100Ministerio de Ciencia e Innovación | Ref. IJC2020-043745-IAgencia Estatal de Investigación | Ref. PRE2021-097580Universidade de Vigo/CISU

Final state effects on superfluid 4^{\bf 4}He in the deep inelastic regime

A study of Final State Effects (FSE) on the dynamic structure function of superfluid $^4$He in the Gersch--Rodriguez formalism is presented. The main ingredients needed in the calculation are the momentum distribution and the semidiagonal two--body density matrix. The influence of these ground state quantities on the FSE is analyzed. A variational form of $\rho_2$ is used, even though simpler forms turn out to give accurate results if properly chosen. Comparison to the experimental response at high momentum transfer is performed. The predicted response is quite sensitive to slight variations on the value of the condensate fraction, the best agreement with experiment being obtained with $n_0=0.082$. Sum rules of the FSE broadening function are also derived and commented. Finally, it is shown that Gersch--Rodriguez theory produces results as accurate as those coming from other more recent FSE theories.Comment: 20 pages, RevTex 3.0, 11 figures available upon request, to be appear in Phys. Rev.

Few-body decay and recombination in nuclear astrophysics

Three-body continuum problems are investigated for light nuclei of astrophysical relevance. We focus on three-body decays of resonances or recombination via resonances or the continuum background. The concepts of widths, decay mechanisms and dynamic evolution are discussed. We also discuss results for the triple $\alpha$ decay in connection with $2^+$ resonances and density and temperature dependence rates of recombination into light nuclei from $\alpha$-particles and neutrons.Comment: 9 pages, 8 figures. Proceedings of the 21st European Few Body Conference held in Salamanca (Spain) in August-September 201

Improved QC-STBC OFDM system using null interfeence elimination

YesThe quasi-orthogonal space time block coding (QO-STBC) over orthogonal frequency division multiplexing (OFDM) is investigated. Traditionally, QO-STBC does not achieve full diversity since the detection matrix of QO-STBC scheme is not a diagonal matrix. In STBC, the decoding matrix is a diagonal matrix which enables linear decoding whereas the decoding matrix in traditional QO-STBC does not enable linear decoding. In this paper it is shown that there are some interfering terms in terms of non-diagonal elements that result from the decoding process which limit the linear decoding. As a result, interference from the application of the QO-STBC decoding matrix depletes the performance of the scheme such that full diversity is not attained. A method of eliminating this interference in QO-STBC is investigated by nulling the interfering terms towards full diversity for an OFDM system. It was found that the interference reduction technique permits circa 2dB BER performance gain in QO-STBC. The theoretical and simulation results are presented, for both traditional QO-STBC and interference-free QO-STBC applying OFD

Recent advances in antenna design for 5G heterogeneous networks

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