Anisotropic critical currents in FeSe0.5Te0.5 films and the influence of neutron irradiation

We report on measurements of the superconducting properties of FeSe05Te05 thin films grown on lanthanum aluminate. The films have high transition temperatures (above 19 K) and sharp resistive transitions in fields up to 15 T. The temperature dependence of the upper critical field and the irreversibility lines are steep and anisotropic, as recently reported for single crystals. The critical current densities, assessed by magnetization measurements in a vector VSM, were found to be well above 10^9 Am-2 at low temperatures. In all samples, the critical current as a function of field orientation has a maximum, when the field is oriented parallel to the film surface. The maximum indicates the presence of correlated pinning centers. A minimum occurs in three films, when the field is applied perpendicular to the film plane. In the forth film, instead, a local maximum caused by c-axis correlated pinning centers was found at this orientation. The irradiation of two films with fast neutrons did not change the properties drastically, where a maximum enhancement of the critical current by a factor of two was found

Tc=21K in epitaxial FeSe0.5Te0.5 thin films with biaxial compressive strain

High purity epitaxial FeSe0.5Te0.5 thin films with different thickness were grown by Pulsed Laser Ablation on different substrates. By varying the film thickness, Tc up to 21K were observed, significantly larger than the bulk value. Structural analyses indicated that the a axis changes significantly with the film thickness and is linearly related to the Tc. The latter result indicates the important role of the compressive strain in enhancing Tc. Tc is also related to both the Fe-(Se,Te) bond length and angle, suggesting the possibility of further enhancement

Role of the annealing parameters on the resistance of indium tin oxide nanocrystalline films

The optical and electrical properties of films made of nanoparticles of indium tin oxide (ITO) are widely studied because of the significance of this material for transparent electrodes, smart windows, and nonlinear optics components. In this work, a systematic study of the resistance in ITO nanocrystalline films, as a function of post-fabrication parameters, such as the temperature and time of annealing, has been performed. A tunability of the resistance with the annealing parameters, in a range of three orders of magnitude, has been demonstrated. The optical properties of the nanocrystalline films were also evaluated as a function of the same parameters. Results show a different influence of temperature and time on the modification of the absorption properties. Temperature and time can be used synergistically to obtain thin films with desired optical and electrical properties through post-fabrication treatments

Highly effective and isotropic pinning in epitaxial Fe(Se,Te) thin films grown on CaF2 substrates

We report on the isotropic pinning obtained in epitaxial Fe(Se,Te) thin films grown on CaF2 (001) substrate. High critical current density values larger than 1 MA/cm2 in self field in liquid helium are reached together with a very weak dependence on the magnetic field and a complete isotropy. Analysis through Transmission Electron Microscopy evidences the presence of defects looking like lattice disorder at a very small scale, between 5 and 20 nm, which are thought to be responsible for such isotropic behavior in contrast to what observed on SrTiO3, where defects parallel to the c-axis enhance pinning in that directio

Microscopic analysis of the chemical reaction between Fe(Te,Se) thin films and underlying CaF2_2

To understand the chemical reaction at the interface of materials, we performed a transmission electron microscopy (TEM) observation in four types of Fe(Te,Se) superconducting thin films prepared on different types of substrates: CaF2 substrate, CaF2 substrate with a CaF2 buffer layer, CaF2 substrate with a FeSe buffer layer, and a LaAlO3 substrate with a CaF2 buffer layer. Based on the energy-dispersive X-ray spectrometer (EDX) analysis, we found possible interdiffusion between fluorine and selenium that has a strong influence on the superconductivity in Fe(Te,Se) films. The chemical interdiffusion also plays a significant role in the variation of the lattice parameters. The lattice parameters of the Fe(Te,Se) thin films are primarily determined by the chemical substitution of anions, and the lattice mismatch only plays a secondary role.Comment: 30 pages, 9 figur

Impact of upstream landslide on perialpine lake ecosystem: An assessment using multi-temporal satellite data

Monitoring freshwater and wetland systems and their response to stressors of natural or anthropogenic origin is critical for ecosystem conservation. A multi-temporal set of 87 images, acquired by Sentinel-2 satellites over three years (2016–2018), provided quantitative information for assessing the temporal evolution of key ecosystem variables in the perialpine Lake Mezzola (northern Italy), which has suffered from the impacts of a massive landslide that took place upstream of the lake basin in summer 2017. Sentinel-2 derived products revealed an increase in lake turbidity triggered by the landslide that amounted to twice the average values scored in the years preceding and following the event. Hotspots of turbidity within the lake were in particular highlighted. Moreover, both submerged and riparian vegetation showed harmful impacts due to sediment deposition. A partial loss of submerged macrophyte cover was found, with delayed growth and a possible community shift in favor of species adapted to inorganic substrates. Satellite-derived seasonal dynamics showed that exceptional sediment load can overwrite climatic factors in controlling phenology of riparian reed beds, resulting in two consecutive years with shorter than normal growing season and roughly 20% drop in productivity, according to spectral proxies. Compared to 2016, senescence came earlier by around 20 days on average in 2017 season, and green-up was delayed by up to 50 days (20 days, on average) in 2018, following the landslide. The approach presented could be easily implemented for continuous monitoring of similar ecosystems subject to external pressures with periods of high sediment loads

Thermal properties of SmFeAs(O1-xFx) as probe of the interplay between electrons and phonons

A comparative study of thermal properties of SmFeAsO, SmFeAs(O0.93F0.07) and SmFeAs(O0.85F0.15) samples is presented. Specific heat and thermal conductivity show clear evidences of the spin density wave (SDW) ordering below TSDW 135 K in undoped SmFeAsO. At low level of F-doping, SmFeAs(O0.93F0.07), SDW ordering is suppressed and superconducting features are not yet optimally developed in both specific heat and thermal conductivity. At optimal level of F-doping SmFeAs(O0.85F0.15) anomalies related to the superconducting transition are well noticeable. By a compared analysis of doped and undoped samples we conclude that, despite F-doping modifies definitely the electronic ground state, it does not substantially alter phonon and electron parameters, like phonon modes, Sommerfeld coefficient, electro-phonon coupling. The analysis of the thermal conductivity curves provides an evaluation of SDW and superconducting energy gap, showing that phonons can suitably probe features of electronic ground state

Demography of the bottlenose dolphin Tursiops truncatus (Mammalia: Delphinidae) in the Eastern Ligurian Sea (NW Mediterranean): quantification of female reproductive parameters

AbstractThe reproductive histories of 41 adult bottlenose dolphin females were analysed using photo-identification data collected between 2006 and 2014 in four sub-areas of the eastern Ligurian Sea (northwest Mediterranean). The Rapallo sub-area revealed the highest (highly significant) frequency of encounters (per unit effort) of reproductive females in association with young individuals, therefore emerging as a candidate nursery area in the region. The estimated fertility rate of adult females ranged between 290 and 407 births per 1000 individuals per year, higher than that of other known bottlenose dolphin populations, with a calving interval between 2.45 and 3.5 years. These results will be useful for projecting future trends of this (sub)population

Inflammation and oxidative stress transcription profiles due to in vitro supply of methionine with or without choline in unstimulated blood polymorphonuclear leukocytes from lactating Holstein cows.

Neutrophils are the most important polymorphonuclear leukocytes (PMNL), representing the front-line defense involved in pathogen clearance upon invasion. As such, they play a pivotal role in immune and inflammatory responses. Isolated PMNL from 5 mid-lactating Holstein dairy cows were used to evaluate the in vitro effect of methionine (Met) and choline (Chol) supplementation on mRNA expression of genes related to the Met cycle and innate immunity. The target genes are associated with the Met cycle, cell signaling, inflammation, antimicrobial and killing mechanisms, and pathogen recognition. Treatments were allocated in a 3 × 3 factorial arrangement, including 3 Lys-to-Met ratios (L:M, 3.6:1, 2.9:1, or 2.4:1) and 3 levels of supplemental Chol (0, 400, or 800 μg/mL). Three replicates per treatment group were incubated for 2 h at 37°C and 5% atmospheric CO2. Both betaine-homocysteine S-methyltransferase and choline dehydrogenase were undetectable, indicating that PMNL (at least in vitro) cannot generate Met from Chol through the betaine pathway. The PMNL incubated without Chol experienced a specific state of inflammatory mediation [greater interleukin-1β (IL1B), myeloperoxidase (MPO), IL10, and IL6] and oxidative stress [greater cysteine sulfinic acid decarboxylase (CSAD), cystathionine gamma-lyase (CTH), glutathione reductase (GSR), and glutathione synthase (GSS)]. However, data from the interaction L:M × Chol indicated that this negative state could be overcome by supplementing additional Met. This was reflected in the upregulation of methionine synthase (MTR) and toll-like receptor 2 (TLR2); that is, pathogen detection ability. At the lowest level of supplemental Chol, Met downregulated GSS, GSR, IL1B, and IL6, suggesting it could reduce cellular inflammation and enhance antioxidant status. At 400 µg/mL Chol, supplemental Met upregulated PMNL recognition capacity [higher TLR4 and L-selectin (SELL)]. Overall, enhancing the supply of methyl donors to isolated unstimulated PMNL from mid-lactating dairy cows leads to a low level of PMNL activation and upregulates a cytoprotective mechanism against oxidative stress. Enhancing the supply of Met coupled with adequate Chol levels enhances the gene expression of PMNL pathogen-recognition mechanism. These data suggest that Chol supply to PMNL exposed to low levels of Met effectively downregulated the entire repertoire of innate inflammatory-responsive genes. Thus, Met availability in PMNL during an inflammatory challenge may be sufficient for mounting an appropriate biologic response