Local Field Spectroscopy of Metal Dimers by TPL Microscopy

We report on two-photon photoluminescence (TPL) spectroscopy on metal dimers made of two gold nanoparticles separated by subwavelength distances. A direct comparison with far-field scattering measurements shows that TPL provides additional data on the structure modes of major importance for their use in surface-enhanced Raman scattering, enhanced fluorescence, and sensing.     

Segregation and mixing in degenerate diffusion in population dynamics

 We study the qualitative properties of degenerate diffusion equations used to describe dispersal processes in population dynamics. For systems of interacting populations, the forms of the diffusion models used determine if the population will intermix or remain disjoint (segregated). The dynamics and stability of segregation boundaries between competing populations is analyzed. General population models with segregation and mixing interactions are derived and connections to behavior in fluid mechanical systems are addressed. Received 19 January 1996; received in revised form 4 April 1996     

A mathematical model of heterogeneous behavior of single muscle fibres

A mathematical model of contracting muscle fibre is studied. The model is composed of an array of segments placed in series; any segment has an elastic element (PE _i ) and a contractile element (CE _i ) that describes the cross bridge kinetics.The corresponding system of nonlinear partial differential equations of the model is analyzed. Existence, uniqueness and continuous dependence of the solution are proven.This work has been supported by Ministero Pubblica Istruzione (fondi per la ricerca scientifica) and by Istituto di Analisi Numerica del C.N.R., Pavia     

The spread of a parasitic infection in a spatially distributed host population

Starting from a stochastic model for the spread of a parasitic infection in a spatially distributed host population we describe the way to a continuum formulation by a deterministic model in terms of a nonlinear partial differential equation and an integro-differential equation. The hosts are assumed to occupy fixed spatial positions, whereas the parasites are mobile, however can propagate only within the hosts. To perform the continuum limit we suppose that the size N _h of the host population, the size N _p of the parasite population, and the ratio N _p /N _h tend to infinity. Accordingly, the parameters determining the time evolution of the host and parasite populations are rescaled suitably.Parts of this work have been elaborated during a stay at the Institute of Applied Mathematics at the University of Zürich     

Using spectrophotometry and spectral mapping technique for the study of the production of manganese-dependent and manganese-independent peroxidases by Pleurotus ostreatus

The activity of manganese-dependent and manganese-independent peroxidases produced by Pleurotus ostreatus in culture media composed of agro-residues was measured by visible spectrophotometry. The overall enzyme activity and its selectivity were separated by using spectral mapping technique followed by nonlinear mapping. The relationships between the parameters of enzyme production and the composition of culture media and fermentation time was assessed by stepwise regression analysis. Calculations proved that the addition of extract of straw to the culture media significantly decreased the overall production of both enzymes, whereas the selectivity of enzyme production was influenced by amount of potato extract and the concentration of total sugar in the culture media. Enzyme activity depended quadratically on the fermentation time.     

Label‐free stimulated Raman scattering imaging reveals silicone breast implant material in tissue

Millions of women worldwide have silicone breast implants. It has been reported that implant failure occurs in approximately a tenth of patients within 10 years, and the consequences of dissemination of silicone debris are poorly understood. Currently, silicone detection in histopathological slides is based on morphological features as no specific immunohistochemical technique is available. Here, we show the feasibility and sensitivity of stimulated Raman scattering (SRS) imaging to specifically detect silicone material in stained histopathological slides, without additional sample treatment. Histology slides of four periprosthetic capsules from different implant types were obtained after explantation, as well as an enlarged axillary lymph node from a patient with a ruptured implant. SRS images coregistered with bright‐field images revealed the distribution and quantity of silicone material in the tissue. Fast and high‐resolution imaging of histology slides with molecular specificity using SRS provides an opportunity to investigate the role of silicone debris in the pathophysiology of implant‐linked diseases.