313 research outputs found
Common-reflection-surface imaging of shallow and ultrashallow reflectors
We analyzed the feasibility of the common-reflection-surface
(CRS) stack for near-surface surveys as an alternative to the conventional
common midpoint (CMP) stacking procedure. The
data-driven, less user-interactive CRS method could be more
cost efficient for shallow surveys, where the high sensitivity
to velocity analysis makes data processing a critical step. We
compared the results for two field data sets collected to image
shallow and ultrashallow reflectors: an example of shallow Pwave
reflection for targets in the first few hundred meters,
and an example of SH-wave reflection for targets in the first
10 m. By processing the shallow P-wave records using the
CMP method, we imaged several nearly horizontal reflectors
with onsets from 60 to about 250 ms. The CRS stack produced
a stacked section more suited for a subsurface interpretation,
without any preliminary formal and time-consuming velocity analysis, because the imaged reflectors possessed greater coherency
and lateral continuity. With CMP processing of the SHwave
records, we imaged a dipping bedrock interface below
four horizontal reflectors in unconsolidated, very low velocity
sediments. The vertical and lateral resolution was very high, despite
the very shallow depth: the image showed the pinchout of
two layers at less than 10 m depth. The numerous traces used by
the CRS stack improved the continuity of the shallowest reflector,
but the deepest overburden reflectors appear unresolved,
with not well-imaged pinchouts. Using the kinematic wavefield
attributes determined for each stacking operation, we retrieved
velocity fields fitting the stacking velocities we had estimated in
the CMP processing. The use of CRS stack could be a significant
step ahead to increase the acceptance of the seismic reflection
method as a routine investigation method in shallow and
ultrashallow seismics
Inversion of electrical conductivity data with Tikhonov regularization approach: some considerations
Electromagnetic induction measurements, which are generally used to determine lateral variations of apparent
electrical conductivity, can provide quantitative estimates of the subsurface conductivity at different depths.
Quantitative inference about the Earth's interior from experimental data is, however, an ill-posed problem. Using
the generalised McNeill's theory for the EM38 ground conductivity meter, we generated synthetic apparent
conductivity curves (input data vector) simulating measurements at different heights above the soil surface. The
electrical conductivity profile (the Earth model) was then estimated solving a least squares problem with Tikhonov
regularization optimised with a projected conjugate gradient algorithm. Although the Tikhonov approach improves
the conditioning of the resulting linear system, profile reconstruction can be surprisingly far from the desired true
one. On the contrary, the projected conjugate gradient provided the best solution without any explicit regularization
( a= 0) of the objective function of the least squares problem. Also, if the initial guess belongs to the image of the
system matrix, Im(A), we found that it provides a unique solution in the same subspace Im(A)
Dietary Nitrate: Effects on the health of weaning pigs and Antimicrobial activity on seven probiotic Bifidobacterium spp. strains
The potential role of nitrite as an antimicrobial substance in the stomach may be of some importance in the ecology of the gastrointestinal tract and in host physiology. It has been shown that nitrite, under the acidic conditions of the stomach, may kill gut pathogens like Salmonella enteritidis, Escherichia coli, Salmonella typhimurium, and Yersinia enterocolitica, whereas acid alone has only a bacteriostatic effect. An in vivo study was conducted in order to assess the effects of dietary nitrate on microbiota and on the health of the gut (particularly in the stomach and small intestine). 96 weaning pigs were fed a diet containing high nitrate levels (15 mg and 150 mg) and then challenged with Salmonella enterica serovar typhimurium.
Differences in composition of the gut microbiota were assessed by analysing samples from the pigs: To date analysis of 48 pigs has been completed.. Preliminary results demonstrated no effect on the population densities of microbial groups either from the challenge or from nitrate intake. However, increasing the time from challenge decreased either the counts of LAB in the stomach and jejunum or of clostridia in the stomach.
Bifidobacteria also decreased in the stomach contents as nitrate supplementation increased. Supplementing the feedstuff with high dietary nitrate intake and then challenging with Salmonella did not affect the gastric pH or the degree of ulceration in the pigs.
The synergistic bactericidal effects of pH, nitrite and thiocyanate on seven probiotic Bifidobacterium spp. strains were also investigated in an in vitro study.
The results of the in vitro study demonstrated that an inhibitory effect exists on the seven probiotic bifidobacteria investigated with an exposure longer than 2 hours and pH values < 5.0. Addition of thiocyanate also increased the susceptibility of the tested strains. In this in vitro study, the most resistant strains at all conditions were B. animalis subsp. lactis Ra 18 and P32 and B. choerinum Su 877, Su 837 and Su 891
Utilizzo di metodi geofisici ad alta risoluzione per l’individuazione di strutture archeologiche nel sito fenicio-punico-romano di Neapolis (Sardegna occidentale)
Life Cycle Assessment (LCA): New poplar clones allow an environmentally sustainable cultivation
In Italy 72 poplar clones ( Populus spp.) are registered for commercialization. They were selected for fast growth, stem shape and disease resistance. The new selections (named MSA) includes genotypes with very high resistance to all the main diseases and to one insect, Phloeomizus passerinii (Sign.). Fast growth and disease resistance allow to produce wood with low environmental and economic costs; for this reason in some Italian Regions the introduction of a percentage of these clones in poplar stand is mandatory to obtain funding for their establishment (Rural Development Plan). To better understand the environmental advantages deriving from the use of these clones, in comparison with the old genotypes (particularly ‘I-214’), a ‘Life Cycle Assessment’ approach was applied considering as impact indicator the CO 2 equivalent emissions; from stoolbed to commercial stand, primary data were collected from an Italian experience. Firstly with the Inventory Analysis all the raw material, energy, wastes and emissions related were collected for each cultivation phase. The Analysis showed a reduction of 9% of CO 2 eq. ha -1 emitted, growing MSA instead of ‘I-214’. Considering the emissions per volume of wood, ‘I-214’ requests 47.5 kg CO 2 eq. per m 3 , compared with MSA that request 36.6 kg CO 2 eq. per m 3
EXPRESSION OF VESICLE-ASSOCIATED MEMBRANE-PROTEIN-ASSOCIATED PROTEIN B CLEAVAGE PRODUCTS IN PERIPHERAL BLOOD LEUKOCYTES AND CEREBROSPINAL FLUID OF PATIENTS WITH SPORADIC AMYOTROPHIC LATERAL SCLEROSIS
Recent Progress in STIR 5.0
STIR is an open source software for Emission Tomography data manipulation and image reconstruction, covering both PET and SPECT. In this work recent additions to the STIR code base are highlighted, namely the ability to read General Electric (GE) Raw Data Format 9 (RDF9) files, incorporation of GPU operators for forward and back projection, as well as work towards quantitative imaging for both PET and SPECT
Variation in Array Size, Monomer Composition and Expression of the Macrosatellite DXZ4
Macrosatellites are some of the most polymorphic regions of the human genome, yet many remain uncharacterized despite the association of some arrays with disease susceptibility. This study sought to explore the polymorphic nature of the X-linked macrosatellite DXZ4. Four aspects of DXZ4 were explored in detail, including tandem repeat copy number variation, array instability, monomer sequence polymorphism and array expression. DXZ4 arrays contained between 12 and 100 3.0 kb repeat units with an average array containing 57. Monomers were confirmed to be arranged in uninterrupted tandem arrays by restriction digest analysis and extended fiber FISH, and therefore DXZ4 encompasses 36–288 kb of Xq23. Transmission of DXZ4 through three generations in three families displayed a high degree of meiotic instability (8.3%), consistent with other macrosatellite arrays, further highlighting the unstable nature of these sequences in the human genome. Subcloning and sequencing of complete DXZ4 monomers identified numerous single nucleotide polymorphisms and alleles for the three microsatellite repeats located within each monomer. Pairwise comparisons of DXZ4 monomer sequences revealed that repeat units from an array are more similar to one another than those originating from different arrays. RNA fluorescence in situ hybridization revealed significant variation in DXZ4 expression both within and between cell lines. DXZ4 transcripts could be detected originiating from both the active and inactive X chromosome. Expression levels of DXZ4 varied significantly between males, but did not relate to the size of the array, nor did inheritance of the same array result in similar expression levels. Collectively, these studies provide considerable insight into the polymorphic nature of DXZ4, further highlighting the instability and variation potential of macrosatellites in the human genome
Factors affecting adherence to guidelines for antithrombotic therapy in elderly patients with atrial fibrillation admitted to internal medicine wards
Current guidelines for ischemic stroke prevention in atrial fibrillation or flutter (AFF) recommend Vitamin K antagonists (VKAs) for patients at high-intermediate risk and aspirin for those at intermediate-low risk. The cost-effectiveness of these treatments was demonstrated also in elderly patients. However, there are several reports that emphasize the underuse of pharmacological prophylaxis of cardio-embolism in patients with AFF in different health care settings.
AIMS: To evaluate the adherence to current guidelines on cardio-embolic prophylaxis in elderly (> 65 years old) patients admitted with an established diagnosis of AFF to the Italian internal medicine wards participating in REPOSI registry, a project on polypathologies/polytherapies stemming from the collaboration between the Italian Society of Internal Medicine and the Mario Negri Institute of Pharmacological Research; to investigate whether or not hospitalization had an impact on guidelines adherence; to test the role of possible modifiers of VKAs prescription.
METHODS: We retrospectively analyzed registry data collected from January to December 2008 and assessed the prevalence of patients with AFF at admission and the prevalence of risk factors for cardio-embolism. After stratifying the patients according to their CHADS(2) score the percentage of appropriateness of antithrombotic therapy prescription was evaluated both at admission and at discharge. Univariable and multivariable logistic regression models were employed to verify whether or not socio-demographic (age >80years, living alone) and clinical features (previous or recent bleeding, cranio-facial trauma, cancer, dementia) modified the frequency and modalities of antithrombotic drugs prescription at admission and discharge.
RESULTS: Among the 1332 REPOSI patients, 247 were admitted with AFF. At admission, CHADS(2) score was ≥ 2 in 68.4% of patients, at discharge in 75.9%. Among patients with AFF 26.5% at admission and 32.8% at discharge were not on any antithrombotic therapy, and 43.7% at admission and 40.9% at discharge were not taking an appropriate therapy according to the CHADS(2) score. The higher the level of cardio-embolic risk the higher was the percentage of antiplatelet- but not of VKAs-treated patients. At admission or at discharge, both at univariable and at multivariable logistic regression, only an age >80 years and a diagnosis of cancer, previous or active, had a statistically significant negative effect on VKAs prescription. Moreover, only a positive history of bleeding events (past or present) was independently associated to no VKA prescription at discharge in patients who were on VKA therapy at admission. If heparin was considered as an appropriate therapy for patients with indication for VKAs, the percentage of patients admitted or discharged on appropriate therapy became respectively 43.7% and 53.4%.
CONCLUSION: Among elderly patients admitted with a diagnosis of AFF to internal medicine wards, an appropriate antithrombotic prophylaxis was taken by less than 50%, with an underuse of VKAs prescription independently of the level of cardio-embolic risk. Hospitalization did not improve the adherence to guideline
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