124 research outputs found
Chiral Analysis of the Generalized Form Factors of the Nucleon
We apply the methods of Chiral Perturbation Theory to the analysis of the
first moments of the Generalized Parton Distributions in a Nucleon, usually
known as generalized form factors. These quantities are currently also under
investigation in Lattice QCD analyses of baryon structure, providing simulation
results at large quark masses to be extrapolated to the "real world" via Chiral
Effective Field Theory. We have performed a leading-one-loop calculation in the
covariant framework of Baryon Chiral Perturbation Theory (BChPT), predicting
both the momentum and the quark-mass dependence for all the vector and axial
(generalized) form factors. In particular we discuss the results for the limit
of vanishing four-momentum transfer where the GPD-moments reduce to the well
known moments of Parton Distribution Functions (PDFs). We fit our results to
available lattice QCD data, extrapolating down to the physical point. We
conclude by presenting outstanding results from a combined fit to different
GPDs-moments.Comment: 7 pages, 4 figures, Proceedings of Lattice 2007 (July 30 - 4 August
2007, Regensburg, Germany
The First Moments of Nucleon Generalized Parton Distributions
We extrapolate the first moments of the generalized parton distributions
using heavy baryon chiral perturbation theory. The calculation is based on the
one loop level with the finite range regularization. The description of the
lattice data is satisfactory and the extrapolated moments at physical pion mass
are consistent with the results obtained with dimensional regularization,
although the extrapolation in the momentum transfer to does show
sensitivity to form factor effects which lie outside the realm of chiral
perturbation theory. We discuss the significance of the results in the light of
modern experiments as well as QCD inspired models.Comment: 14 pages, 9 figure
The safety of tattoo inks: Possible options for a common regulatory framework
Tattoo prevalence has been increasing in the last 25 years, but specific regulations on tattoo inks are still missing. In the European Union, no supranational regulation is available and only few national provisions cover them. In the United States, tattoo inks are classified as cosmetics but are not approved for injection into the dermis. Health risks for consumers may derive from microbiological contamination and the presence of toxic substances or nanomaterials. However, current regulations and non-binding recommendations, where present, only address the microbiological and chemical risks, completely overlooking nanotoxicity. The aim of this paper is to promote awareness of the risks associated with tattoo inks and the nanomaterials contained therein. In particular, the need for a harmonised regulation or, at least, a set of minimal requirements is highlighted to improve the safety of tattoo inks and market surveillance by regulatory authorities
Microfluidic encapsulation method to produce stable liposomes containing iohexol
Since the discovery of X-rays in the late 1890s, several medical imaging techniques have been developed, such as Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and Ultrasound Imaging, which are used daily to diagnose, monitor, or treat medical conditions. Some of these techniques include the use of contrast agents to enhance the contrast images, therefore, toxic effects must be considered. Among these, Contrast-Induced Nephropathy (CIN) is an acute renal failure resulting from the administration of iodinated contrast media (CM). To date, there is no definitive treatment for CIN and several prevention approaches have been evaluated. Nanoparticles (NPs) represent a promising strategy for treatment and prevention of CIN, due to their ability to deliver CM during diagnosis imaging. In this study, iohexol-containing liposomes were produced using microfluidic technique for first time. Several phosphocholine lipids (e.g. DMPC, DOPC, DPPC and DSPC) with cholesterol (2:1 ratio) were investigated and DLS, FTIR and in vitro release studies at 37 °C were performed, with stability studies conducted on the best formulation. The microfluidic method allowed to obtain a high encapsulation efficiency (over 70%), and release profiles showed an iohexol release around or less than 0.12 mg/ml after 2 h for the majority of the formulations, which is not toxic to the kidney cells
Design of epidermal growth factor immobilization on 3D biocompatible scaffolds to promote tissue repair and regeneration
Exogenous application of human epidermal growth factor (hEGF) stimulates epidermal wound healing. The aim of this study was to develop bioconjugates based on hEGF mimicking the protein in its native state and thus suitable for tissue engineering applications, in particular for treating skin-related disorders as burns. Ribonuclease A (RNase A) was used to investigate a number of different activated-agarose carriers: cyanogen bromide (CNBr)-activated-agarose and glyoxyl-agarose showed to preserve the appropriate orientation of the protein for receptor binding. EGF was immobilized on these carriers and immobilization yield was evaluated (100% and 12%, respectively). A peptide mapping of unbound protein regions was carried out by LC–MS to take evidence of the residues involved in the immobilization and, consequently, the flexibility and surface accessibility of immobilized EGF. To assess cell proliferative activities, 10, 25, 50, and 100 ng/mL of each immobilized EGF sample were seeded on fibroblast cells and incubated for 24, 48 and 72 h. The immobilized growth factor showed significantly high cell proliferative activity at 50 and 100 ng/mL compared to control and soluble EGF. Although both of the immobilized samples show dose-dependency when seeded with high number of fibroblast cells, CNBr-agarose-EGF showed a significantly high activity at 100 ng/mL and 72 h incubation, compared to glyoxyl-agarose-EGF
Nucleon Generalized Parton Distributions from Full Lattice QCD
We present a comprehensive study of the lowest moments of nucleon generalized
parton distributions in N_f=2+1 lattice QCD using domain wall valence quarks
and improved staggered sea quarks. Our investigation includes helicity
dependent and independent generalized parton distributions for pion masses as
low as 350 MeV and volumes as large as (3.5 fm)^3, for a lattice spacing of
0.124 fm. We use perturbative renormalization at one-loop level with an
improvement based on the non-perturbative renormalization factor for the axial
vector current, and only connected diagrams are included in the isosinglet
channel.Comment: 40 pages, 49 figures; Revised chiral extrapolations in sections A-K,
main conclusions unchange
The effect of Process Parameters on Alignment of Tubular Electrospun Nanofibers for Tisue Regeneration Purposes
Electrospinning is known to be an effective and straightforward technique to fabricate polymer non woven matrices made of nano and microfibers. Micro patterned morphology of electrospun matrices results to be outmost advantageous in the biomedical field, since it is able to mimic extracellular matrix (ECM), and favors cell adhesion and proliferation. Controlling electrospun fibers alignment is crucial for the regenerative purposes of certain tissues, such as neuronal and vascular. In this study we investigated the impact of electrospinning process parameters on fiber alignment in tubular nanofibrous matrices made of Poly (L-lactide-co-ε-caprolactone) (PLA-PCL); a Design of Experiments (DoE) approach is here proposed in order to statistically set up the process parameters. The DoE was studied keeping constants the previously set material and environmental
parameters; voltage, flow rate and mandrel rotating speed were the process parameters here investigated as variables. Orientation analysis was based on ImageJ and plugin Orientation J analysis of SEM images. The results show that voltage combined with flow rate has significant impact on electrospun fiber orientation, and the greatest orientation is achieved when all the three input parameters (voltage, flow rate and mandrel rotation speed) are at their maximum value
A screening study of the spatial distribution and cumulative toxicity of agricultural pesticides in the European Union’s waters
Pesticides can be an important stressor to aquatic ecosystems, and their use is strictly regulated in the European Union (EU). However, data on the use of pesticides are rather limited and poorly available, and monitoring is often insufficient to characterize their actual exposure and impact. The aim of the work presented here is to harness the limited data available and assess, for the first time, the distribution of concentrations and toxicity of 148 pesticide active substances (AS) for the whole EU. Starting from available estimates of pesticide use in agriculture and a simple screening-level model of their fate and transport, we quantify pesticide concentrations in soil and water. A comparison with monitoring data shows that predicted water concentrations are in plausible orders of magnitude, hence the model can be regarded as a first-approximation representation of the distribution of pesticides in the environment. The toxicity of individual pesticide active substances (AS) is characterized by their concentrations divided by the respective no observed effect concentrations (NOEC) for aquatic organisms, which represents the “toxic units” (TU) of each AS. The cumulative toxicity of pesticides in soils and streams of the EU is obtained by summing the TU of individual AS. We estimate that the toxicity of individual AS is generally well below 0.1 TU, indicating relatively safe environmental exposure. However, the cumulative toxicity of a mixture of AS can exceed 0.1 toxic units (TU) for more than 27% of the length of the EU’s stream network, and 1 TU for more than 4%. The cumulative toxicity at a given location is driven by only a handful of AS, but these differ from site to site reflecting the variability of pesticide use. Still, we estimate that only about 20 AS out of 148 appear among the top contributors to cumulative toxicity in most cases. While our assessment suggests a relatively widespread risk due to pesticide pollution, it also points to the important limitations concerning knowledge of pesticide use and monitoring of pesticide occurrence in the environment. These limitations need to be addressed in order to evaluate more accurately the effectiveness of EU pesticide policies. The assessment represents a proof-of-concept of a method that can be applied in support of the monitoring of pesticide policies implementation in the EU and elsewhere, once pesticide use can be estimated
Finite volume corrections to the electromagnetic current of the nucleon
We compute corrections to both the isovector anomalous magnetic moment and
the isovector electromagnetic current of the nucleon to in the
framework of covariant two-flavor Baryon Chiral Perturbation Theory. We then
apply these corrections to lattice data for the anomalous magnetic moment from
the LHPC, RBC & UKQCD and QCDSF collaborations
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