Collagen containing microcapsules: smart containers for disease controlled therapy

The protein collagen is the major component of connective tissue and it is involved in many biological functions. Its degradation is at the basis of different pathological processes. The up-regulated expression of matrix metalloproteinases and the down-regulated expression of their inhibitors are the causes for such degradation. The aim of this work was to evaluate the possibility to fabricate collagen based containers for drug encapsulation and release by cellular demand by the action of matrix metalloproteinases. In present work collagen type I based microcapsules were fabricated by means of the layer-by-layer assembly of oppositely charged collagen and poly (stirene sulfonate) onto colloidal particles, followed by removal of the cores to obtain hollow microcapsules. The process of shell growth on planar supports was monitored by quartz crystal microbalance. X-ray reflectivity measurements were carried out at the solid/water interface to study the interaction of matrix metalloproteinase 1 with LbL films of collagen. The morphology of hollow capsules was characterized by scanning electron microscopy, and compared to that of capsules exposed to the matrix metalloproteinase 1. Finally the matrix metalloproteinase 1 mediated permeability of capsules variation was studied by Confocal Laser Scanning Microscopy. The results demonstrated the possibility to fabricate a drug delivery system where the release of the drug is dependent on the biochemistry of the pathological state.     

Weld-bead profile and costs optimisation of the CO2 dissimilar laser welding process of low carbon steel and austenitic steel AISI316

The dissimilar full depth laser-butt welding of low carbon steel and austenitic steel AISI 316 was investigated using CW 1.5 kW CO₂ laser. The effect of laser power (1.1–1.43 kW), welding speed (25–75 cm/min) and focal point position (?0.8 to ?0.2 mm) on the weld-bead geometry (i.e. weld-bead area, A; upper width, W_u; lower width, W_l and middle width, W_m) and on the operating cost C was investigated using response surface methodology (RSM). The experimental plan was based on Box–Behnken design; linear and quadratic polynomial equations for predicting the weld-bead widthness references were developed. The results indicate that the proposed models predict the responses adequately within the limits of welding parameters being used. The regression equations were used to find optimum welding conditions for the desired geometric criteria.     

Exploring the tumour extracellular matrix by in vivo Fast Field Cycling relaxometry after the administration of a Gadolinium-based MRI contrast agent

¹H Fast Field Cycling NMR (FFC-NMR) relaxometry is proposed as a powerful method to investigate tumour stroma in vivo upon the administration of a Gd-based contrast agent. To perform this study, an FFC-NMR equipment endowed with a wide bore magnet was used for the acquisition of Nuclear Magnetic Resonance Dispersion profiles on healthy muscle and tumour tissue in living mice. At magnetic field strengths < of ca. 1 MHz, the differences in the relaxation rates of the intra and extracellular compartment become of the same order of magnitude of the exchange rate across the cellular membranes. Under this condition, the water exchange rate between the two compartments yields to a biexponential magnetization recovery that can be analysed by fitting the experimental data with the two-Site eXchange (2SX) model. Using this model, it was possible to obtain, for the two compartments, both relaxation properties and water kinetic constants for water exchange across cell membranes. The method allowed us to determine the effect of the “matrix” on the water proton relaxation times and, in turn, to get some insights of the composition of this compartment, till now, largely unknown.     

Calibrating cellular automaton models for pedestrians walking through corners

Cellular Automata (CA) based pedestrian simulation models have gained remarkable popularity as they are simpler and easier to implement compared to other microscopic modeling approaches. However, incorporating traditional floor field representations in CA models to simulate pedestrian corner navigation behavior could result in unrealistic behaviors. Even though several previous studies have attempted to enhance CA models to realistically simulate pedestrian maneuvers around bends, such modifications have not been calibrated or validated against empirical data. In this study, two static floor field (SFF) representations, namely ‘discrete representation’ and ‘continuous representation’, are calibrated for CA-models to represent pedestrians' walking behavior around 90° bends. Trajectory data collected through a controlled experiment are used to calibrate these model representations. Calibration results indicate that although both floor field representations can represent pedestrians' corner navigation behavior, the ‘continuous’ representation fits the data better. Output of this study could be beneficial for enhancing the reliability of existing CA-based models by representing pedestrians' corner navigation behaviors more realistically.     

Microscopic quantum theory of exciton polaritons with spatial dispersion

Summary The quantum Hamiltonian of excitons in interaction with the electromagnetic field is derived for the case of Frenkel excitons and for the case of Wannier excitons by taking into account spatial dispersion and the singular behaviour of the electron-hole exchange. The exact eigenvalues and eigenstates are obtained for the upper and lower polaritons. In the case of Wannier excitons a correction to the phenomenological quantum theory is found. In both cases the coincidence of the upper polariton limit fork=0 and the longitudinal exciton value atk=0 is proved. Spin effects are shown to introduce a factor two both in the coupling strength and in the transverse-longgitudinal splitting for singlet excitons.

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Riassunto Si deriva l’hamiltoniana quantistica di eccitoni in interazione con il campo elettromagnetico sia nel modello di Frenkel che nel modello di Wannier, includendo la dispersione spaziale e la singolarità del termine di scambio elettrone-buca. Si ottengono autostati e autovalori esatti per il polaritone superiore e quello inferiore. Nel modello di Wannier si trova una correzione alla teoria quantistica fenomenologica. In entrambi i modelli si dimostra la coincidenza del limite ak=0 del polaritone superione con quello dell’eccitone longitudinale. Questo è connesso con la dipendenza dell’accoppiamento eccitone-radiazione e dello scambio elettrone-buca dalla forza di oscillazione della transizione ottica. Gli effetti di spin introducono un fattore due sia nel termine di accoppiamento che nella separazione longitudinale-trasversale di eccitoni di singotetto.

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Резуме Квантовый Гамильтоньян зкцитонов, взаимодействующих с злектромагнитным полем, получен и в случае зкцитонов Френкеля и в случае зкцитонов Ванниера, причем учитывается пространственная дисперсия и особое поведение злектронно-дырочного обмена. Получены точные собственные значения и точные собственные функции Гамильтоньяна. В случае зкцитонов Ванниера найдена поправка результатов, полученных в феноменологической кватовой теории. В обоих случаях доказывается совпад ение энергии верхнего поларитона приk=0 с знергиейпродольного зкцитона приk=0. Доказывается, что наличие спина вызывает удвоение козффициента силы связи и также удвоение поперечно-продоьного расщепления синглетных состояний.

     

Synchronization Gauges and the Principles of Special Relativity

The axiomatic bases of Special Relativity Theory (SRT) are thoroughly re-examined from an operational point of view, with particular emphasis on the status of Einstein synchronization in the light of the possibility of arbitrary synchronization procedures in inertial reference frames. Once correctly and explicitly phrased, the principles of SRT allow for a wide range of theories that differ from the standard SRT only for the difference in the chosen synchronization procedures, but are wholly equivalent to SRT in predicting empirical facts. This results in the introduction, in the full background of SRT, of a suitable synchronization gauge. A complete hierarchy of synchronization gauges is introduced and elucidated, ranging from the useful Selleri synchronization gauge (which should lead, according to Selleri, to a multiplicity of theories alternative to SRT) to the more general Mansouri–Sexl synchronization gauge and, finally, to the even more general Anderson–Vetharaniam–Stedmans synchronization gauge. It is showed that all these gauges do not challenge the SRT, as claimed by Selleri, but simply lead to a number of formalisms which leave the geometrical structure of Minkowski spacetime unchanged. Several aspects of fundamental and applied interest related to the conventional aspect of the synchronization choice are discussed, encompassing the issue of the one-way velocity of light in inertial and rotating reference frames, the global positioning system (GPS)s working, and the recasting of Maxwell equations in generic synchronizations. Finally, it is showed how the gauge freedom introduced in SRT can be exploited in order to give a clear explanation of the Sagnac effect for counter-propagating matter beams.     

Nonlinear optical properties of iodoform complexes

Measurements of the electrooptic effect and of second harmonic generation (SHG) on three complexes of iodoform are presented. In these organic compounds the electrooptic effect and the sHG are strongly correlated and attributed to a purely electronic origin. The complexes of iodoform with sulphur and quinoline respectively, have a very similar crystal structure but display markedly different optical nonlinearities. Even higher optical nonlinear effects comparable to those in the best inorganic compounds are observed in the iodoform/tetramine complex.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday     

Renormalized Fokker-Planck equation for the problem of the beam-beam interaction in electron storage rings

It is shown that the beam-beam interaction in electron storage rings is equivalent to an additional source of noise for the particle betatron oscillations. A weak white noise acting upon a nonlinear oscillator causes a fast loss of coherence in its phase. This loss of coherence induces a broadening of the resonances, thus avoiding the problem of the divergent perturbative series which arises in the study of nonintegrable Hamiltonian systems. A “renormalized” Fokker-Planck equation is established which contains new diffusive terms corresponding to the presence of resonances. The solution of this equation is exhibited explicitly in a simplified case. This allows an analytical approach to the problem of the beam-beam instability, which sets an upper limit to the maximum attainable luminosity in storage rings.     

On Manifolds Admitting Continuous Foliations by Geodesics

We show that complete, simply connected Riemannian manifolds admitting continuous foliations by geodesics with integrable orthogonal distributions are homeomorphic to products F×R. Moreover, the geodesics in the foliation are global minimizers.