Hot electron driven enhancement of spin-lattice coupling in 4f ferromagnets observed by femtosecond x-ray magnetic circular dichroism

Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4 fs electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to orders of magnitude compared to equilibrium.Comment: added reference 24, clarified the meaning of photo-induced, emphasized that XMCD probes the magnetic moment localized at 4f electron

Magnetic and hyperfine interaction in RFe4Al8 (R = Ce,Sc) compounds

Magnetic properties of ScFe4Al8 and CeFe4Al8 compounds have been studied by magnetization and Mössbauer effect measurements. Magnetic transition temperatures estimated from Mössbauer spectra (B = 0) 170 K for CeFe4Al8 and 225 K for ScFe4Al8 are not confirmed by magnetization measurements. Contrary, the pronounced maxima at Tmax = 130 and 125 K in DC magnetization curves (B = 1 kOe) were found for ScFe4Al8 and CeFe4Al8, respectively. Thermomagnetic, the so-called zero field (ZFC) and field cooling (FC) experiments show temperature-dependent irreversibilities below the "freezing" temperature, Tf, which diminishes with application of external magnetic field. The Mössbauer studies show the coexistence of magnetically (sextet) and non-magnetically (quadrupole doublet) split patterns in the wide temperature range far away from Tmax. All these observations indicate that the systems studied are either a spin-glass or are the mixture of AF and spin-glass state. © 2001 Elsevier Science B.V

Magnetic properties and Moessbauer effect studies of Ce1-xScxFe4Al8 system

The investigations of the magnetic and electrical properties as well as the 57Fe Moessbauer effect are presented for Ce1-xScxFe4Al8 solid solution with 0<x<1 in the temperature range 4-300 K. Magnetic susceptibility follows a Curie-Weiss law above 200 K. The effective magnetic moment decreases with the Sc content. At temperatures lower than 130 K all compounds studied are antiferromagnets. The Neel temperature, TN is not affected by substitution of Sc for Ce. TN has no reflection in any anomaly in ρ(T). The Moessbauer spectra at temperatures lower than TN exhibit one Zeeman sextet related to the Fe nucleus at the 8(f) position. The hyperfine parameters Hhf, IS, QS have been estimated as a function of Sc concentration. The increasing of Sc content diminishes Hhf on the Fe nucleus. The calculations of electron-density distribution along the 〈1 1 1〉 direction in elemental crystallographic cell indicate a remarkable increase of electron charge at the Fe sites with the Sc content increasing. The 40-49° cone angles of the Fe sublattices at 12 K have been estimated from Moessbauer spectra analysis

Muon-Spin Rotation Measurements of the Magnetic Field Dependence of the Vortex-Core Radius and Magnetic Penetration Depth in NbSe2

Muon-spin rotation spectroscopy has been used to measure the internal magnetic field distribution in NbSe2 for Hc1 << H < 0.25 Hc2. The deduced profiles of the supercurrent density indicate that the vortex-core radius in the bulk decreases sharply with increasing magnetic field. This effect, which is attributed to increased vortex-vortex interactions, does not agree with the dirty-limit microscopic theory. A simple phenomenological equation in which the core radius depends on the intervortex spacing is used to model this behaviour. In addition, we find for the first time that the in-plane magnetic penetration depth increases linearly with H in the vortex state of a conventional superconductor.Comment: 4 pages, RevTeX, 4 encapsulated postscript figures, (to appear in Phys. Rev. Lett. 25Aug97 issue

Bacteriophage biodistribution and infectivity from honeybee to bee larvae using a T7 phage model

Bacteriophages (phages) or viruses that specifically infect bacteria have widely been studied as biocontrol agents against animal and plant bacterial diseases. They offer many advantages compared to antibiotics. The American Foulbrood (AFB) is a bacterial disease affecting honeybee larvae caused by Paenibacillus larvae. Phages can be very significant in fighting it mostly due to European restrictions to the use of antibiotics in beekeeping. New phages able to control P. larvae in hives have already been reported with satisfactory results. However, the efficacy and feasibility of administering phages indirectly to larvae through their adult workers only by providing phages in bees feeders has never been evaluated. This strategy is considered herein the most feasible as far as hive management is concerned. This in vivo study investigated the ability of a phage to reach larvae in an infective state after oral administration to honeybees. The screening (by direct PFU count) and quantification (by quantitative PCR) of the phage in bee organs and in larvae after ingestion allowed us to conclude that despite 104 phages reaching larvae only an average of 32 were available to control the spread of the disease. The fast inactivation of many phages in royal jelly could compromise this therapeutic approach. The protection of phages from hive-derived conditions should be thus considered in further developments for AFB treatment.This study was supported by the project APILYSE, PTDC/CVT-EPI/4008/2014 - POCI-01-0145-FEDER-016598, - funded by FEDER through COMPETE 2020 - Programa Operacional Competitividade e Internacionalização (POCI) and by national funds trough FCT - Fundação para a Ciência e a Tecnologia, I.P. The work was also supported by the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004), funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. HR was supported by FCT through the grant SFRH/BD/128859/2017. RC was founded by FCT and FEDER (POCI-010145-FEDER-007274).info:eu-repo/semantics/publishedVersio

Bacteriophage-encoded depolymerases: their diversity and biotechnological applications

Bacteriophages (phages), natural enemies of bacteria, can encode enzymes able to degrade polymeric substances. These substances can be found in the bacterial cell surface, such as polysaccharides, or are produced by bacteria when they are living in biofilm communities, the most common bacterial lifestyle. Consequently, phages with depolymerase activity have a facilitated access to the host receptors, by degrading the capsular polysaccharides, and are believed to have a better performance against bacterial biofilms, since the degradation of extracellular polymeric substances by depolymerases might facilitate the access of phages to the cells within different biofilm layers. Since the diversity of phage depolymerases is not yet fully explored, this is the first review gathering information about all the depolymerases encoded by fully sequenced phages. Overall, in this study, 160 putative depolymerases, including sialidases, levanases, xylosidases, dextranases, hyaluronidases, peptidases as well as pectate/pectin lyases, were found in 143 phages (43 Myoviridae, 47 Siphoviridae, 37 Podoviridae, and 16 unclassified) infecting 24 genera of bacteria. We further provide information about the main applications of phage depolymerases, which can comprise areas as diverse as medical, chemical, or food-processing industry.DPP acknowledges the financial support from the Portuguese Foundation for Science and Technology (FCT) through the grant SFRH/BD/76440/2011. SS is an FCT investigator (IF/01413/2013). The authors also thank FCT for the Strategic Project of the UID/BIO/04469/2013 unit, FCT and European Union funds (FEDER/COMPETE) for the project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER027462)

Co@NH 2

We present a synthetic strategy for the efficient encapsulation of a deriv. of a well-​defined cobaloxime proton redn. catalyst within a photoresponsive metal-​org. framework (NH2- MIL-​125(Ti)​)​. The resulting hybrid system Co@MOF is demonstrated to be a robust heterogeneous composite material. Furthermore, Co@MOF is an efficient and fully recyclable noble metal-​free catalyst system for light-​driven hydrogen evolution from water under visible light illumination

Magnetic and hyperfine interaction in YbFe4Al8 compound

57Fe Mössbauer spectra of YbFe4Al8 of the tetragonal ThMn12 structure have been investigated. Mössbauer measurements at the lowest temperatures yield information on the iron population in three crystallographic sites 8f, 8j and 8i available for Fe atoms. The obtained results indicate on the coexistence of magnetically ordered and paramagnetic-like Fe moments within antiferromagnetic phase of YbFe4Al8. The MS measurements show that the onset of short range antiferromagnetic interaction in the Fe sublattice takes place at 220 K