3,150 research outputs found
Structural studies of mesoporous ZrO-CeO and ZrO-CeO/SiO mixed oxides for catalytical applications
In this work the synthesis of ZrO-CeO and
ZrO-CeO/SiO were developed, based on the process to form
ordered mesoporous materials such as SBA-15 silica. The triblock copolymer
Pluronic P-123 was used as template, aiming to obtain crystalline single phase
walls and larger specific surface area, for future applications in catalysis.
SAXS and XRD results showed a relationship between ordered pores and the
material crystallization. 90% of CeO leaded to single phase homogeneous
ceria-zirconia solid solution of cubic fluorite structure (Fmm). The
SiO addition improved structural and textural properties as well as the
reduction behavior at lower temperatures, investigated by XANES measurements
under H atmosphere
A Biased Resistor Network Model for Electromigration Failure and Related Phenomena in Metallic Lines
Electromigration phenomena in metallic lines are studied by using a biased
resistor network model. The void formation induced by the electron wind is
simulated by a stochastic process of resistor breaking, while the growth of
mechanical stress inside the line is described by an antagonist process of
recovery of the broken resistors. The model accounts for the existence of
temperature gradients due to current crowding and Joule heating. Alloying
effects are also accounted for. Monte Carlo simulations allow the study within
a unified theoretical framework of a variety of relevant features related to
the electromigration. The predictions of the model are in excellent agreement
with the experiments and in particular with the degradation towards electrical
breakdown of stressed Al-Cu thin metallic lines. Detailed investigations refer
to the damage pattern, the distribution of the times to failure (TTFs), the
generalized Black's law, the time evolution of the resistance, including the
early-stage change due to alloying effects and the electromigration saturation
appearing at low current densities or for short line lengths. The dependence of
the TTFs on the length and width of the metallic line is also well reproduced.
Finally, the model successfully describes the resistance noise properties under
steady state conditions.Comment: 39 pages + 17 figure
30-day in-hospital mortality after acute myocardial infarction in Tuscany (Italy): An observational study using hospital discharge data
Abstract
Background:
Coronary heart disease is the leading cause of mortality in the world. One of the outcome indicators
recently used to measure hospital performance is 30-day mortality after acute myocardial infarction (AMI). This
indicator has proven to be a valid and reproducible indicator of the appropriateness and effectiveness of the
diagnostic and therapeutic process for AMI patients after hospital admission. The aim of this study was to examine
the determinants of inter-hospital variability on 30-day in-hospital mortality after AMI in Tuscany. This indicator is a
proxy of 30-day mortality that includes only deaths occurred during the index or subsequent hospitalizations.
Methods:
The study population was identified from hospital discharge records (HDRs) and included all patients
with primary or secondary ICD-9-CM codes of AMI (ICD-9 codes 410.xx) that were discharged between January 1,
2009 and November 30, 2009 from any hospital in Tuscany. The outcome of interest was 30-day all-cause
in-hospital mortality, defined as a death occurring for any reason in the hospital within 30 days of the admission
date. Because of the hierarchical structure of the data, with patients clustered into hospitals, random-effects
(multilevel) logistic regression models were used. The models included patient risk factors and random intercepts
for each hospital.
Results:
The study included 5,832 patients, 61.90% male, with a mean age of 72.38 years. During the study period,
7.99% of patients died within 30 days of admission. The 30-day in-hospital mortality rate was significantly higher
among patients with ST segment elevation myocardial infarction (STEMI) compared with those with non-ST
segment elevation myocardial infarction (NSTEMI). The multilevel analysis which included only the hospital variance
showed a significant inter-hospital variation in 30-day in-hospital mortality. When patient characteristics were added
to the model, the hospital variance decreased. The multilevel analysis was then carried out separately in the two
strata of patients with STEMI and NSTEMI. In the STEMI group, after adjusting for patient characteristics, some
residual inter-hospital variation was found, and was related to the presence of a cardiac catheterisation laboratory.
Conclusion:
We have shown that it is possible to use routinely collected administrative data to predict mortality
risk and to highlight inter-hospital differences. The distinction between STEMI and NSTEMI proved to be useful to
detect organisational characteristics, which affected only the STEMI subgroup.
Keywords:
Myocardial infarction, Mortality, Cardiovascular risk, Medical record
SARS-CoV-2/COVID-19 vaccines: The promises and the challenges ahead
: The development of a new vaccine usually consists of a linear sequence of several steps and lasts many years [...]
Tumor infiltrating regulatory t cells in sporadic and colitis-associated colorectal cancer: The red little riding hood and the wolf
Regulatory T cells represent a class of specialized T lymphocytes that suppress unwanted immune responses and size the activation of the immune system whereby limiting collateral damages in tissues involved by inflammation. In cancer, the accumulation of Tregs is generally associated with poor prognosis. Many lines of evidence indicate that Tregs accumulation in the tumor microenvironment (TME) suppresses the immune response against tumor-associated antigens (TAA), thus promoting tumor progression in non-small cell lung carcinoma (NSLC), breast carcinoma and melanoma. In colorectal cancer (CRC) the effect of Tregs accumulation is debated. Some reports describe the association of high number of Tregs in CRC stroma with a better prognosis while others failed to find any association. These discordant results stem from the heterogeneity of the immune environment generated in CRC in which anticancer immune response may coexists with tumor promoting inflammation. Moreover, different subsets of Tregs have been identified that may exert different effects on cancer progression depending on tumor stage and their location within the tumor mass. Finally, Tregs phenotypic plasticity may be induced by cytokines released in the TME by dysplastic and other tumor-infiltrating cells thus affecting their functional role in the tumor. Here, we reviewed the recent literature about the role of Tregs in CRC and in colitis-associated colorectal cancer (CAC), where inflammation is the main driver of tumor initiation and progression. We tried to explain when and how Tregs can be considered to be the “good” or the “bad” in the colon carcinogenesis process on the basis of the available data concluding that the final effect of Tregs on sporadic CRC and CAC depends on their localization within the tumor, the subtype of Tregs involved and their phenotypic plasticity
A new electric streamer for the characterization of river embankments
River embankments are linear earth structures, worldwide diffused, commonly used for flood protection. Their integrity and stability are fundamental prerequisites for the protection efficiency they can offer to the increasing frequency and magnitude of extreme flood events associated to changes in climate. Proper characterization and monitoring are essential to verify the construction requirements of newly built structures and to evaluate the durability of aged ones. Considering their linear extent, the characterization requires not only local geotechnical investigations but also the application of efficient and economically affordable methods. This is even more essential when the investigations are performed after, or in foresee of, significant flood events, when these structures get stressed and timing of the surveys is crucial. In these conditions, new survey methodologies, with the use of mobile systems, are a main research topic. In this paper the application of a new electric streamer, specifically designed for these aims, is presented. The technical solutions adopted for its construction are described and its application to the characterization of three different river embankments is presented. These case studies were chosen in accordance with the Po River Interregional Agency (AIPO), which is the authority deputed to the safety of flood protection structures in North-West Italy, along the hydrographic network of the Po River. The selected embankments are all earth structures, constructed above the natural alluvial soils, but are characterized by different conditions and challenges. The results obtained with the new system were comparable to standard Electric Resistivity Tomography (ERT) methods. The new system has significant advantages in terms of reducing the survey time, improving the efficiency of the surveys and increasing the data coverage. This resulted in a better definition of potentially dangerous anomalies
Raman excitation spectroscopy of carbon nanotubes: effects of pressure medium and pressure
Raman excitation and emission spectra for the radial breathing mode (RBM) are
reported, together with a preliminary analysis. From the position of the peaks
on the two-dimensional plot of excitation resonance energy against Raman shift,
the chiral indices (m, n) for each peak are identified. Peaks shift from their
positions in air when different pressure media are added - water, hexane,
sulphuric acid - and when the nanotubes are unbundled in water with surfactant
and sonication. The shift is about 2 - 3 cm-1 in RBM frequency, but
unexpectedly large in resonance energy, being spread over up to 100meV for a
given peak. This contrasts with the effect of pressure. The shift of the peaks
of semiconducting nanotubes in water under pressure is orthogonal to the shift
from air to water. This permits the separation of the effects of the pressure
medium and the pressure, and will enable the true pressure coefficients of the
RBM and the other Raman peaks for each (m, n) to be established unambiguously.Comment: 6 pages, 3 Figures, Proceedings of EHPRG 2011 (Paris
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