969 research outputs found
La Separazione mediante HPLC dei due fenoli isomeri Timolo (p-isopropil-m-cresolo) e Carvacrolo (p-isopropil-o-cresolo)
A method is described for the separation by HPLC of two isomer phenols
thymol and carvacrol. Satisfactory resu1ts have been obtained by using
a chromatographic column ÎĽ Bondapak ,C18 and a solvent system constitued
by acetonitrile (40%) and water (60%). The flow rate was 1,5 ml/min. The
use of this technique permits determination and dosage of these two phenols
in essential oils
Urban Scale Monitoring Approach for the Assessment of Rising Damp Effects in Venice
In coastal areas, the rising damp of salty water is a well-known degradation factor of historical masonries, leading to visible features such as crusts, masonry erosion, and plaster loss. Venetian masonries are strongly affected by decay caused by rising damp exacerbated by direct contact with salty water. Recurrent flooding due to high tides and an increase in the frequency of flooding events, also related to climate change, raises concern about the impacts. Although several studies have been carried out on probable future scenarios, a valuation of the decay risk due to rising damp at the urban level still needs to be implemented. This paper proposes a non-invasive and economically sustainable approach for evaluating rising damp effects at an urban scale. The approach includes a collection of archive images of masonries affected by rising damp dating back to the 1990s; a visual survey of the actual conservation state of masonries; a classification based on significant descriptors; and a discussion on exposure conditions and conservation states. The descriptors chosen are rising damp levels, biological growth, plaster loss, efflorescence, and brick erosion. The evaluation was implemented in a georeferenced system suitable for future comparisons, thus providing a management tool for the city's preservation
Tiles from Aosta: A Peculiar Glaze Roof Covering
The 18th century roof tiles from the “Casa delle vigne”, located in the Aosta region (north-east Italy), were investigated as an example of a peculiar historical roof covering: ceramic tiles with a lead-based glaze finishing to waterproof them are used to create colourful patterns. A conservation project proposed the integration of the original tiles with new ones, produced according to traditional methods. Ancient and new tiles were analysed with Fiber Optics Reflectance Spectroscopy, micro-Raman, Fourier Transform Infrared Spectroscopy and X-ray Fluorescence Spectrometry, Thermogravimetry and Differential Scanning Calorimetry for understanding the composition and the production technology of this manufacture. Their resistance to freezing and thawing cycles was then tested, considering their exposure in the severe alpine climate of Aosta. The use of pure clays with low calcium contents, high firing temperature and lead-rich glazes was found in ancient tiles, able to outstand several freezing-thawing cycles without damages. Iron and copper pigments were used in old yellow and green glazes. Zinc-based pigment, low lead and calcium-rich glazes are used in the new ones, which remained mainly coherent to the ceramic body during the freeze-thaw test
Proteostasis Regulators in Cystic Fibrosis: Current Development and Future Perspectives
In cystic fibrosis (CF), the deletion of phenylalanine 508 (F508del) in the CF transmembrane conductance regulator (CFTR) leads to misfolding and premature degradation of the mutant protein. These defects can be targeted with pharmacological agents named potentiators and correctors. During the past years, several efforts have been devoted to develop and approve new effective molecules. However, their clinical use remains limited, as they fail to fully restore F508del-CFTR biological function. Indeed, the search for CFTR correctors with different and additive mechanisms has recently increased. Among them, drugs that modulate the CFTR proteostasis environment are particularly attractive to enhance therapy effectiveness further. This Perspective focuses on reviewing the recent progress in discovering CFTR proteostasis regulators, mainly describing the design, chemical structure, and structure-activity relationships. The opportunities, challenges, and future directions in this emerging and promising field of research are discussed, as well
Sun-as-a-star Observation of White-Light Flares
Solar flares radiates energy at all wavelengths, but the spectral
distribution of this energy is still poorly known. White-light continuum
emission is sometimes observed and the flares are then termed "white-light
flares" (WLF). In this paper, we investigate if all flares are white-light
flares and how is the radiated energy spectrally distributed. We perform a
superposed epoch analysis of spectral and total irradiance measurements
obtained since 1996 by the SOHO and GOES spacecrafts at various wavelength,
from Soft X-ray to the visible domain. The long-term record of solar irradiance
and excellent duty cycle of the measurements allow us to detect a signal in
visible irradiance even for moderate (C-class) flares, mainly during the
impulsive phase. We identify this signal as continuum emission emitted by
white-light flares, and find that it is consistent with a blackbody emission at
~9000K. We estimate for several sets of flares the contribution of the WL
continuum and find it to be of ~70% of the total radiated energy. We re-analyse
the X17 flare that occurred on 28 October 2003 and find similar results. This
paper brings evidence that all flares are white-light flares and that the
white-light continuum is the main contributor to the total radiated energy;
this continuum is consistent with blackbody spectrum at ~9000K. These
observational results are important in order to understand the physical
mechanisms during flares and open the way to a possible contribution of flares
to TSI variations
Decreased STARD10 expression is associated with defective insulin secretion in humans and mice
Genetic variants near ARAP1 (CENTD2) and STARD10 influence type 2 diabetes (T2D) risk. The risk alleles impair glucose-induced insulin secretion and, paradoxically but characteristically, are associated with decreased proinsulin:insulin ratios, indicating improved proinsulin conversion. Neither the identity of the causal variants nor the gene(s) through which risk is conferred have been firmly established. Whereas ARAP1 encodes a GTPase activating protein, STARD10 is a member of the steroidogenic acute regulatory protein (StAR)-related lipid transfer protein family. By integrating genetic fine-mapping and epigenomic annotation data and performing promoter-reporter and chromatin conformational capture (3C) studies in β cell lines, we localize the causal variant(s) at this locus to a 5 kb region that overlaps a stretch-enhancer active in islets. This region contains several highly correlated T2D-risk variants, including the rs140130268 indel. Expression QTL analysis of islet transcriptomes from three independent subject groups demonstrated that T2D-risk allele carriers displayed reduced levels of STARD10 mRNA, with no concomitant change in ARAP1 mRNA levels. Correspondingly, β-cell-selective deletion of StarD10 in mice led to impaired glucose-stimulated Ca2+ dynamics and insulin secretion and recapitulated the pattern of improved proinsulin processing observed at the human GWAS signal. Conversely, overexpression of StarD10 in the adult β cell improved glucose tolerance in high fat-fed animals. In contrast, manipulation of Arap1 in β cells had no impact on insulin secretion or proinsulin conversion in mice. This convergence of human and murine data provides compelling evidence that the T2D risk associated with variation at this locus is mediated through reduction in STARD10 expression in the β cell
Chromospheric Velocities of a C-class Flare
We use high spatial and temporal resolution observations from the Swedish
Solar Telescope to study the chromospheric velocities of a C-class flare
originating from active region NOAA 10969. A time-distance analysis is employed
to estimate directional velocity components in H-alpha and Ca II K image
sequences. Also, imaging spectroscopy has allowed us to determine flare-induced
line-of-sight velocities. A wavelet analysis is used to analyse the periodic
nature of associated flare bursts. Time-distance analysis reveals velocities as
high as 64 km/s along the flare ribbon and 15 km/s perpendicular to it. The
velocities are very similar in both the H-alpha and Ca II K time series.
Line-of-sight H-alpha velocities are red-shifted with values up to 17 km/s. The
high spatial and temporal resolution of the observations have allowed us to
detect velocities significantly higher than those found in earlier studies.
Flare bursts with a periodicity of approximately 60 s are also detected. These
bursts are similar to the quasi-periodic oscillations observed at hard X-ray
and radio wavelength data. Some of the highest velocities detected in the solar
atmosphere are presented. Line-of-sight velocity maps show considerable mixing
of both the magnitude and direction of velocities along the flare path. A
change in direction of the velocities at the flare kernel has also been
detected which may be a signature of chromospheric evaporation.Comment: Accepted for publication in Astronomy and Astrophysics, 5 figure
Population variability in some genes involving the haemostatic system: data on the general population of Corsica (France), Sardinia and Sicily (Italy)
Three different population samples from Corsica (France), Sardinia and Sicily (Italy) were studied using nine genetic markers. For the first time, allele distributions of FGA TaqI, FGB Bcl I, FGB Hind III, PAI-1 Hind III, PLAT TPA-25, GPIIIa Taq I, GPIIb I/D 9bp, FVII HVR4 and FVII -323 10 bp markers, which are thought to be associated with cardiovascular disease risk, were studied in the general population of the three islands. The frequencies of the markers analysed in the present work show some peculiarities: the locus FVII HVR4 is characterized by the presence of a rare allele (H5), found in Corsicans and in Sardinians; the locus FBG BcII shows a low frequency of the B1 allele and the absence of the B1B1 genotype. The frequencies of some alleles have a distribution that is in agreement with the low risk for cardiovascular diseases in south European countries. The results highlight a genetic differentiation between the three Mediterranean islands and the other European populations
PHOENIX model chromospheres of mid- to late-type M dwarfs
We present semi-empirical model chromospheres computed with the atmosphere
code PHOENIX. The models are designed to fit the observed spectra of five mid-
to late-type M dwarfs. Next to hydrogen lines from the Balmer series we used
various metal lines, e. g. from Fe {\sc i}, for the comparison between data and
models. Our computations show that an NLTE treatment of C, N, O impacts on the
hydrogen line formation, while NLTE treatment of less abundant metals such as
nickel influences the lines of the considered species itself. For our coolest
models we investigated also the influence of dust on the chromospheres and
found that dust increases the emission line flux.
Moreover we present an (electronically published) emission line list for the
spectral range of 3100 to 3900 and 4700 to 6800 \AA for a set of 21 M dwarfs
and brown dwarfs. The line list includes the detection of the Na {\sc i} D
lines in emission for a L3 dwarf.Comment: 14 pages, 18 figure
- …