2,627 research outputs found
Frobenius pairs in abelian categories: correspondences with cotorsion pairs, exact model categories, and Auslander-Buchweitz contexts
In this work, we revisit Auslander-Buchweitz Approximation Theory and find
some relations with cotorsion pairs and model category structures. From the
notions of relatives generators and cogenerators in Approximation Theory, we
introduce the concept of left Frobenius pairs in an
abelian category . We show how to construct from
a projective exact model structure on
, as a result of Hovey-Gillespie Correspondence applied to
two compatible and complete cotorsion pairs in . These
pairs can be regarded as examples of what we call cotorsion pairs relative to a
thick subcategory of . We establish some correspondences between
Frobenius pairs, relative cotorsion pairs, exact model structures and
Auslander-Buchweitz contexts. Finally, some applications of these results are
given in the context of Gorenstein homological algebra by generalizing some
existing model structures on the categories of modules over Gorenstein and
Ding-Chen rings, and by encoding the stable module category of a ring as a
certain homotopy category. We also present some connections with perfect
cotorsion pairs, covering classes, and cotilting modules.Comment: 54 pages, 10 figures. The statement and proof of 2.6.21 was
corrected. Typos corrected. Section 4 was improved, and new results in
Section 5 were adde
Quantum tunneling of the interfaces between normal-metal and superconducting regions of a type-I Pb superconductor
Evidence of a non-thermal magnetic relaxation in the intermediate state of a type-I superconducor is presented. It is attributed to quantum tunneling of interfaces separating normal and superconducting regions. Tunneling barriers are estimated and temperature of the crossover from thermal to quantum regime is obtained from Caldeira-Leggett theory. Comparison between theory and experiment points to tunneling of interface segments of size comparable to the coherence length, by steps of order one nanometer
Field induced magnetic transition and metastability in Co substituted
A detailed investigation of first order ferrimagnetic (FRI) to
antiferromagnetic (AFM) transition in Co (15%) doped is carried out.
These measurements demonstrate anomalous thermomagnetic irreversibility and
glass-like frozen FRI phase at low temperatures. The irreversibility arising
between the supercooling and superheating spinodals is distinguised in an
ingenious way from the irreversibility arising due to kinetic arrest. Field
annealing measurements shows reentrant FRI-AFM-FRI transition with increasing
temperature. These measurements also show that kinetic arrest band and
supercooling band are anitcorrelated i.e regions which are kinetically arrested
at higher temperature have lower supercooling temperature and vice versa.Comment: 10 pages, 8 figure
Situación y perspectivas de la truficultura en España
En este trabajo se presenta un panorama de la situación de la truficultura en España, desde sus comienzos en los años 50 a la actualidad, y sus perspectivas de futuro. Se destacan la actividad cientÃfica y
técnica, desarrolladas en Centros de Investigación y Universidades españolas, en aspectos diversos:
micorrización en vivero, certificación de planta micorrizada, ecologÃa de la trufa, recuperación de truferas
naturales, cultivo y seguimiento de plantaciones truferas, taxonomÃa quÃmica, control de las especies de trufa,
reforestación y selvicultura trufera.
Se aprecia un aumento en el apoyo que se le da al sector desde las Administraciones Públicas, tanto
desde la perspectiva forestal, la agraria o la, ya indicada, de la investigación.
Se aportan datos de produccion, precios, áreas de recogida, mercados, investigación, plantaciones
truferas. Se da un breve resumen de las perspectivas del sector trufero en España. SUMMARY
The objective of this work is to provide a overview of truffle cultivation in Spain from its beginnings in
the 1950s to the present, and its prospects for the future. At the moment, truffle cultivation in Spain is a reality.
There is a great deal of activity on the part of farmers as well as on the part of scientific researchers in
universities and specialised centres who are investigating a wide range of aspects on the subject:
mycorrhization in nurseries, mycorrhized plant certification, ecology, recuperation of wild truffle stands,
monitoring of truffle plantations, chemical taxonomy, control of truffle species, and reforestation and truffle
cultivation.
A growing support for the truffle sector from the Public Administration can be observed, as much from
the agrarian and forestry perspective as from the mentioned research perspective.
Data on production, prices, collection areas, markets, publications, truffle plantations and research are
given. Finally, we give a brief summary of future prospects for the truffle sector in Spain
Quantum Magnetic Deflagration in Mn12 Acetate
We report controlled ignition of magnetization reversal avalanches by surface
acoustic waves in a single crystal of Mn12 acetate. Our data show that the
speed of the avalanche exhibits maxima on the magnetic field at the tunneling
resonances of Mn12. Combined with the evidence of magnetic deflagration in Mn12
acetate (Suzuki et al., cond-mat/0506569) this suggests a novel physical
phenomenon: deflagration assisted by quantum tunneling.Comment: 4 figure
Low temperature microwave emission from molecular clusters
We investigate the experimental detection of the electromagnetic radiation
generated in the fast magnetization reversal in Mn12-acetate at low
temperatures. In our experiments we used large single crystals and assemblies
of several small single crystals of Mn12-acetate placed inside a cylindrical
stainless steel waveguide in which an InSb hot electron device was also placed
to detect the radiation. All this was set inside a SQUID magnetometer that
allowed to change the magnetic field and measure the magnetic moment and the
temperature of the sample as the InSb detected simultaneously the radiation
emitted from the molecular magnets. Our data show a sequential process in which
the fast inversion of the magnetic moment first occurs, then the radiation is
detected by the InSb device, and finally the temperature of the sample
increases during 15 ms to subsequently recover its original value in several
hundreds of milliseconds.Comment: changed conten
E. coli bacteraemia and antimicrobial resistance following antimicrobial prescribing for urinary tract infection in the community
Background: Urinary tract infections are one of the most common infections in primary and secondary care, with the majority of antimicrobial therapy initiated empirically before culture results are available. In some cases, however, over 40% of the bacteria that cause UTIs are resistant to some of the antimicrobials used, yet we do not know how the patient outcome is affected in terms of relapse, treatment failure, progression to more serious illness (bacteraemia) requiring hospitalization, and ultimately death. This study analyzed the current patterns of antimicrobial use for UTI in the community in Scotland, and factors for poor outcomes. Objectives: To explore antimicrobial use for UTI in the community in Scotland, and the relationship with patient characteristics and antimicrobial resistance in E. coli bloodstream infections and subsequent mortality. Methods: We included all adult patients in Scotland with a positive blood culture with E. coli growth, receiving at least one UTI-related antimicrobial (amoxicillin, amoxicillin/clavulanic acid, ciprofloxacin, trimethoprim, and nitrofurantoin) between 1st January 2009 and 31st December 2012. Univariate and multivariate logistic regression analysis was performed to understand the impact of age, gender, socioeconomic status, previous community antimicrobial exposure (including long-term use), prior treatment failure, and multi-morbidity, on the occurrence of E. coli bacteraemia, trimethoprim and nitrofurantoin resistance, and mortality. Results: There were 1,093,227 patients aged 16 to 100 years old identified as receiving at least one prescription for the 5 UTI-related antimicrobials during the study period. Antimicrobial use was particularly prevalent in the female elderly population, and 10% study population was on long-term antimicrobials. The greatest predictor for trimethoprim resistance in E. coli bacteraemia was increasing age (OR 7.18, 95% CI 5.70 to 9.04 for the 65 years old and over group), followed by multi-morbidity (OR 5.42, 95% CI 4.82 to 6.09 for Charlson Index 3+). Prior antimicrobial use, along with prior treatment failure, male gender, and higher deprivation were also associated with a greater likelihood of a resistant E. coli bacteraemia. Mortality was significantly associated with both having an E. coli bloodstream infection, and those with resistant growth. Conclusion: Increasing age, increasing co-morbidity, lower socioeconomic status, and prior community antibiotic exposure were significantly associated with a resistant E. coli bacteraemia, which leads to increased mortality
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