1,720,991 research outputs found
On the gravity of light
No full textA solution of the old problem raised by Tolman, Ehrenfest, Podolsky and
Wheeler, concerning the lack of attraction of two light pencils ‘moving parallel’,
is proposed, considering that the light can be a source of nonlinear gravitational
waves corresponding (from a quantum point of view) to spin-1 massless
particles
Is the Light too light?
No full textThe gravitational interaction of light is analyzed considering its dual characteristic nature, i.e. as an (electromagnetic) wave or as a particle (photon). Considered as an electromagnetic wave, the light can be source of gravitational waves belonging to the larger class of exact solutions of Einstein field equations which are invariant for a non-Abelian two-dimensional Lie algebra of Killing fields. It is shown that in the would be quantum theory of gravity they correspond to spin-1 massless particles
The phase transition method for SAR measurement in MRI
No full textDuring an MR procedure, the patient absorbs a portion of the transmitted RF energy, which may result in tissue heating and other adverse effects, such as alterations in visual, auditory and neural functions. The Specific Absorption Rate (SAR), in W/kg, is the RF power absorbed per unit mass of tissue and is one of the
most important parameters related with thermal effects and acts as a guideline for MRI safety. Strict limits to the SAR levels are imposed by patient safety international regulations (CEI - EN 60601 - 2 - 33) and SAR measurements are required in order to verify its respect. The recommended methods for mean SAR measurement are quite problematic and often require a maintenance man intervention and long stop machine. For example, in the CEI recommended pulse energy method, the presence of a maintenance man is required in order to correctly
connect the required instrumentation; furthermore, the procedure is complex and requires remarkable processing and calculus. Simpler are the calorimetric methods, also if in this case long acquisition times are required in order to have significant temperature variations and accurate heat capacity knowledge (CEI - EN 60601 - 2 - 33). The phase transition method is a new method to measure SAR in MRI which has the advantages to be very simple and to overcome all the typical calorimetric method problems. It does not require in gantry temperature measurements, any specific heat or heat capacity knowledge, but only mass and time measurement. On the other hand, it is necessary to establish if all deposited power SAR can be considered acquired and measured. In this paper, that will be shown
FLIM-Phasor Analysis (FLIM-φ) of Aβ-Induced Membrane Order Alterations: Towards a Cell-Based Biosensor for Early Alzheimer’s Disease Diagnosis
Full text linkAlzheimer’s disease (AD) is a progressive neurodegenerative disorder, and its early detection can be critical for a prompt intervention that can potentially slow down the disease progression and improve the patient’s quality of life. However, a diagnosis based solely on clinical symptoms can be challenging, especially in the early stages, while the detection of specific biomarkers such as amyloid-β peptide (Aβ) and tau proteins can provide objective evidence for diagnosis. In this work, we explored the effects of Aβ peptide on cell membrane properties thanks to fluorescence lifetime imaging (FLIM) combined with the phasor analysis (FLIM-φ). The results showed that the membrane viscosity is altered by the presence of Aβ peptide and that cells experience this effect even at nanomolar concentrations of peptide. This considerable sensitivity opens up the possibility of envisioning a cell-based biosensor able to detect very low concentrations of Aβ in a biological fluid, thus enabling timely diagnosis and intervention
The effect of trehalose on W7FW14F apomyoglobin and insulin fibrillization: new insight into inhibition activity. Biochemistry, 2008, 12;47(6):1789-96.
No full textAbundance of intrinsic disorder in SV-IV, a multifunctional androgen-dependent protein secreted from rat seminal vesicle
Full text linkThe potent immunomodulatory, anti-inflammatory and procoagulant properties of the
protein no. 4 secreted from the rat seminal vesicle epithelium (SV-IV) have been
previously found to be modulated by a supramolecular monomer-trimer equilibrium.
More structural details that integrate experimental data into a predictive framework
have recently been reported. Unfortunately, homology modelling and fold-recognition
strategies were not successful in creating a theoretical model of the structural
organization of SV-IV. It was inferred that the global structure of SV-IV is not similar
to any protein of known three-dimensional structure. Reversing the classical approach
to the sequence-structure-function paradigm, in this paper we report on novel
information obtained by comparing physicochemical parameters of SV-IV with two
datasets made of intrinsically unfolded and ideally globular proteins. In addition, we
have analysed the SV-IV sequence by several publicly available disorder-oriented
predictors. Overall, disorder predictions and a re-examination of existing experimental
data strongly suggest that SV-IV needs large plasticity to efficiently interact with the
different targets that characterize its multifaceted biological function and should be
therefore better classified as an intrinsically disordered protein
Interaction of 'toxic' and 'immunogenic' A-gliadin peptides with a membrane-mimetic environment
No full textCeliac disease (CD) is characterized by abnormally high concentrations of certain peptides in the small bowel. These peptides can be grouped in ‘toxic’ and ‘immunogenic’ classes, which elicit an innate immune response and an HLA-mediated adaptive response, respectively. It is not clear on which molecular mechanisms responses to these different classes are based, but the 31–43 (P31–43) and the 56–68 (P56–68) A-gliadin fragments are usually adopted as sequence representatives of toxic and immunogenic peptides, respectively. Here we report fluorescence experiments aiming to mimic the interaction of these peptides with the cell membrane surface by using sodium dodecyl sulphate (SDS) as a membrane-mimetic medium. We show that P31–43 is able to bind SDS micelles in a way that resembles mixed micelle formation. On the other hand, no binding at all could be detected for P56–68. This different behaviour could be related to the paracellular or transcellular route through which gluten peptides may cross the intestinal epithelium, and open new insights into the pathogenetic mechanisms of CD
Identifying toxicity pathways of apomyoglobin amyloid prefibrillar oligomers using a combined proteomic and 1H-NMR metabolomic approach
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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