223 research outputs found
On the stability of a modified Nyström method for Mellin convolution equations in weighted spaces
This paper deals with the numerical solution of second kind integral equations with fixed singularities of Mellin convolution type. The main difficulty in solving such equations is the proof of the stability of the chosen numerical method, being the noncompactness of the Mellin integral operator the chief theoretical barrier. Here, we propose a Nyström method suitably modified in order to achieve the theoretical stability under proper assumptions on the Mellin kernel. We also provide an error estimate in weighted uniform norm and prove the well-conditioning of the involved linear systems. Some numerical tests which confirm the efficiency of the method are shown
MatLab Toolbox for the numerical solution of linear Volterra integral equations arising in metastatic tumor growth models
This paper introduces VIE Toolbox composed by fourteen MatLab functions used for the numerical resolution of Volterra Integral Equations (VIEs) of the second kind on infinite intervals. An application to metastatic tumor growth models is also considered, assuming five different tumor growth laws, e.g. exponential, power-law, Gompertz, generalized logistic and von Bertalanffy-West laws, for lung and breast tumors data
Atmospheric pressure non-equilibriumplasma for the production of composite materials
In the evolving field of tissue engineering, continuous advances are required
to improve scaffold design and fabrication to obtain biomimetic supports for
cell adhesion, proliferation, penetration and differentiation. Both electrospun
fibrous scaffolds and hydrogels are used in this field since they well
reproduce the structure of the extracellular matrix (ECM) of many biological
tissues. Limitations of these two types of materials can be overcome
through their combination, by developing composite structures combining
enhanced mechanical properties (provided by the fibrous components) and
improved cell penetration (provided by the gel phase) in a superior ability to
mimic natural ECM that is constituted by both a fibrous protein network and
a hydrogel matrix. Here we develop new composite materials made of
electrospun PLLA scaffolds and poly(amidoamine) hydrogels with different
degrees of crosslinking. To promote compatibilization and good adhesion
between the two materials, surface chemical reactions between hydrogels
and PLLA mats are induced by inserting amino functional groups on
electrospun PLLA mats by means of atmospheric pressure non-thermal
plasma. Results will be presented concerning the exposure of PLLA
substrates to the plasma region generated by a Dielectric Barrier Discharge
at atmospheric pressure, driven by a HV Amplifier connected to a function
generator operating with a microsecond rise time and operated in N2.
Surface and solid-state thermo-mechanical characterizations of plasma
treated substrates and of resulting composite materials at different
crosslinking degrees are presented. Results of mechanical tests show a high
adhesion between hydrogel and plasma treated PLLA electrospun mats,
underlining the opportunity to use atmospheric non-thermal plasmas to
fabricate a composite starting from two materials otherwise physically
incompatible. Potential effects of nanofibrous-hydrogel were evaluated by
investigating pluripotent stem cells response
Regional differences in APD restitution can initiate wavebreak and re-entry in cardiac tissue: A computational study
Background
Regional differences in action potential duration (APD) restitution in the heart favour arrhythmias, but the mechanism is not well understood.
Methods
We simulated a 150 Ă— 150 mm 2D sheet of cardiac ventricular tissue using a simplified computational model. We investigated wavebreak and re-entry initiated by an S1S2S3 stimulus protocol in tissue sheets with two regions, each with different APD restitution. The two regions had a different APD at short diastolic interval (DI), but similar APD at long DI. Simulations were performed twice; once with both regions having steep (slope > 1), and once with both regions having flat (slope < 1) APD restitution.
Results
Wavebreak and re-entry were readily initiated using the S1S2S3 protocol in tissue sheets with two regions having different APD restitution properties. Initiation occurred irrespective of whether the APD restitution slopes were steep or flat. With steep APD restitution, the range of S2S3 intervals resulting in wavebreak increased from 1 ms with S1S2 of 250 ms, to 75 ms (S1S2 180 ms). With flat APD restitution, the range of S2S3 intervals resulting in wavebreak increased from 1 ms (S1S2 250 ms), to 21 ms (S1S2 340 ms) and then 11 ms (S1S2 400 ms).
Conclusion
Regional differences in APD restitution are an arrhythmogenic substrate that can be concealed at normal heart rates. A premature stimulus produces regional differences in repolarisation, and a further premature stimulus can then result in wavebreak and initiate re-entry. This mechanism for initiating re-entry is independent of the steepness of the APD restitution curve
Plasma medicine: The great prospects when physics meets medicine
The research has demonstrated the antimicrobial properties of plasma urging the incorporation of cold atmospheric plasma (CAP) decontamination in current clinical therapies with the aim to improve the benefits on the patients and on society.Postprint (published version
Cold atmospheric plasma decontamination of SARS-CoV-2 bioaerosols
Bioaerosols (aerosolized particles with biological origin) are strongly suspected to play a significant role in the transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), especially in closed indoor environments. Thus, control technologies capable of effectively inactivating bioaerosols are urgently needed. In this regard, cold atmospheric pressure plasma (CAP) can represent a suitable option, thanks to its ability to produce reactive species, which can exert antimicrobial action. In this study, results; on the total inactivation of SARS-CoV-2 contained in bioaerosols treated using CAP generated in air are reported, demonstrating the possible use of CAP systems for the control of SARS-CoV-2 diffusion through bioaerosols
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