287 research outputs found
Large critical current density improvement in Bi-2212 wires through groove-rolling process
Recently the interest about Bi-2212 round wire superconductor for high
magnetic field use has been enhancing despite the fact that an increase of the
critical current is still needed to boost its successful use in such
applications. Recent studies have demonstrated that the main obstacle to
current flow, especially in long wires, is the residual porosity inside these
Powder-In-Tube processed conductors which develops in bubbles-agglomeration
when the Bi-2212 melts. Through this work we tried to overcome this issue
acting on the wire densification by changing the deformation process. Here we
show the effects of groove-rolling versus drawing process on the critical
current density JC and on the microstructure. In particular, groove-rolled
multifilamentary wires show a JC increased by a factor of about 3 with respect
to drawn wires prepared with the same Bi-2212 powder and architecture. We think
that this approach in the deformation process is able to produce the required
improvements both because the superconducting properties are enhanced and
because it makes the fabrication process faster and cheaper
Bilateral 5 Hz transcranial alternating current stimulation on fronto-temporal areas modulates resting-state EEG
Rhythmic non-invasive brain stimulations are promising tools to modulate brain activity by entraining neural oscillations in specific cortical networks. The aim of the study was to assess the possibility to influence the neural circuits of the wake-sleep transition in awake subjects via a bilateral transcranial alternating current stimulation at 5 Hz (theta-tACS) on fronto-temporal areas. 25 healthy volunteers participated in two within-subject sessions (theta-tACS and sham), one week apart and in counterbalanced order. We assessed the stimulation effects on cortical EEG activity (28 derivations) and self-reported sleepiness (Karolinska Sleepiness Scale). theta-tACS induced significant increases of the theta activity in temporo-parieto-occipital areas and centro-frontal increases in the alpha activity compared to sham but failed to induce any online effect on sleepiness. Since the total energy delivered in the sham condition was much less than in the active theta-tACS, the current data are unable to isolate the specific effect of entrained theta oscillatory activity per se on sleepiness scores. On this basis, we concluded that theta-tACS modulated theta and alpha EEG activity with a topography consistent with high sleep pressure conditions. However, no causal relation can be traced on the basis of the current results between these rhythms and changes on sleepines
Airborne Bacteria structure and chemical composition relationships in winter and spring PM10 samples over southeastern Italy
Abstract The Redundancy Discrimination Analysis (RDA) and Spearman correlation coefficients were used to investigate relationships between airborne bacteria at the phylum and genus level and chemical species in winter and spring PM10 samples over Southeastern Italy. The identification of main chemical species/pollution sources that were related to and likely affected the bacterial community structure was the main goal of this work. The 16S rRNA gene metabarcoding approach was used to characterize airborne bacteria. Seventeen phyla and seventy-nine genera contributing each by mean within-sample relative abundance percentage > 0.01% were identified in PM10 samples, which were chemically characterized for 33 species, including ions, metals, OC, and EC (organic and elemental carbon, respectively). Chemical species were associated with six different pollution sources. A shift from winter to spring in both bacterial community structure and chemical species mass concentrations/sources and the relationships between them was observed. RDA triplots pointed out significant correlations for all tested bacterial phyla (genera) with other phyla (genera) and/or with chemical species, in contrast to correlation coefficient results, which showed that few phyla (genera) were significantly correlated with chemical species. More specifically, in winter Bacillus and Chryseobacterium were the only genera significantly correlated with chemical species likely associated with particles from soil-dust and anthropogenic pollution source, respectively. In spring, Enterobacter and Sphingomonas were the only genera significantly correlated with chemical species likely associated with particles from the anthropogenic pollution and the marine and soil-dust sources, respectively. The results of this study also showed that the correlation coefficients were the best tool to obtain unequivocal identifications of the correlations of phyla (genera) with chemical species. The seasonal changes of the PM10 chemical composition, the microbial community structure, and their relationships confidentially suggested that the seasonal changes of atmospheric particles may have likely contributed to seasonal changes of bacterial community in the atmosphere
High temperature heat treatment of B precursor and P.I.T. process optimization to increase Jc performances of MgB2-based conductor
Promising results reported in our previous works led us to think that
production of B powder plays a crucial role in MgB2 synthesis. A new method for
boron preparation has been developed in our laboratory. This particular process
is based on magnesiothermic reaction (Moissan process) with the addition of an
initial step that gives boron powder with nano-metric grain size. In this paper
we report our efforts regarding optimization of PIT method for these nanometric
powders and the resolution of problems previously highlighted such as the
difficulty in powder packaging and the high friction phenomena occurring during
cold working. This increases cracking during the tape and wire manufacturing
leading to its failure. Packaging problems are related to the amorphous nature
of boron synthesized in our laboratory, so a crystallization treatment was
applied to improve crystallinity of B powder. To prevent excessive friction
phenomena we synthesized non-stoichiometric MgB2 and using magnesium as
lubricant. Our goal is the Jc improvement, but a global physical-chemical
characterization was also made to analyze the improvement given by our
treatments: this characterization includes X-ray diffraction, resistivity vs.
temperature measurement, SEM image, besides magnetic and transport Jc
measurements.Comment: 15 pages, 11 figure
Grain size determination of superconducting MgB2 powders from magnetization curve, image analysis and surface area measurement
The present article reports a method for the average grain size evaluation of
superconducting nano-particles through their magnetic properties. The use of
SQUID magnetometry to determine the average MgB2 particle size was investigated
and the results compared with those achieved through other techniques. In
particular the data obtained from zero field cooled magnetization measurement
as function of the temperature were compared with the results obtained by
scanning electron microscopy and Brunauer-Emmett-Teller techniques. The
particle magnetization was measured by a commercial SQUID magnetometer in
magnetic field (1 mT) and temperatures ranging from 5 to 50 K dispersing the
powders in a grease medium. The grain size is obtained by fitting the data
taking into account the Ginzburg-Landau temperature dependence of the London
penetration depth. Variations on typical modeling parameters were explored in
order to gain a better picture of the average grain size and the effectiveness
of various measurement techniques. We find that it is possible to use the
magnetization measurements to determine the average grain size even if the SEM
image analysis allows extracting more information about the grain size
distribution. Furthermore a Matlab routine has been developed in order to get
automatic analysis of SEM images.Comment: 12 pages, 10 figures, 5 table
High-energy ball milling and synthesi temperature study to improve superconducting properties of MgB2 ex-situ tapes and wires
MgB2 monofilamentary nickel-sheated tapes and wires were fabricated by means
of the ex-situ powder-in-tube method using either high-energy ball milled and
low temperature synthesized powders. All sample were sintered at 920 C in Ar
flow. The milling time and the revolution speed were tuned in order to maximize
the critical current density in field (Jc): the maximum Jc value of 6 x 10e4
A/cm2 at 5 K and 4 T was obtained corresponding to the tape prepared with
powders milled for 144h at 180rpm. Vorious synthesis temperature were also
investigated (730-900 C) finding a best Jc value for the wire prepared with
powders synthesized at 745 C. We speculate that this optimal temperature is due
to the fluidifying effect of unreacted magnesium content before the sintering
process which could better connect the grains
Cell Toxicity Study of Antiseptic Solutions Containing Povidone-Iodine and Hydrogen Peroxide
The increasing incidence of periprosthetic joint infections (PJIs) has led to a growing interest in developing strategies to prevent and treat this severe complication. The surgical site's application of antiseptic solutions to eliminate contaminating bacteria and eradicate the bacterial biofilm has been increasing over time. Even though it has been proven that combining antimicrobials could enhance their activities and help overcome acquired microbial resistance related to the topical use of antibiotics, the toxicity of integrated solutions is not well described. This study aimed to evaluate the cytotoxicity of solutions containing povidone-iodine (PI) and hydrogen peroxide (H2O2), alone or in combination, after 1.3 and 5 min of exposure. Chondrocytes, tenocytes, and fibroblast-like synoviocytes were used for cytotoxicity analysis. Trypan blue stain (0.4% in PBS) was applied to evaluate the dead cells. All solutions tested showed a progressive increase in toxicity as exposure time increased except for PI at 0.3%, which exhibited the lowest toxicity. The combined solutions reported a reduced cellular killing at 3 and 5 min than H2O2 at equal concentrations, similar results to PI solutions
Well-being and rurality: a spatial tool for rural development programs evaluation
Improving the quality of life of populations is one of the priorities of rural development policies. Based on the capability approach, the aim is to realise a Quality of Life (QoL) index measuring territorial disparities. The QoL index, aggregated by a non-compensatory method, is compared with rural and inland areas of the study area, Basilicata region. The analysis shows a clear relationship between features of QoL and rurality/peripherality degree and a global QoL below the regional average for 61% of municipalities. In these areas, as expected, the high level of environmental protection is offset by lower socio-economic opportunities but, the possibility to evaluate them through an index over time can help policymakers to address rural policies and evaluate their effects
Detection of high mobility group A2 specific mRNA in the plasma of patients affected by epithelial ovarian cancer
Ovarian cancer is the most lethal gynecological malignancy and the high mortality rate is associated with advanced-stage disease at the time of the diagnosis. In order to find new tools to make diagnosis of Epithelial Ovarian Cancer (EOC) at early stages we have analyzed the presence of specific HMGA2 mRNA in the plasma of patients affected by this neoplasm. HMGA2 overexpression represents a feature of several malignances including ovarian carcinomas. Notably, we detected HMGA2 specific mRNA in the plasma of 40 out 47 patients with EOC, but not in the plasma of healthy donors. All cases found positive for HMGA2 mRNA in the plasma showed HMGA2 protein expression in EOC tissues. Therefore, on the basis of these results, the analysis of circulating HMGA2 specific mRNA might be considered a very promising tool for the early diagnosis of EOC
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