Method for superposing reconstructed images from digital holograms of the same object recorded at different distance and wavelength

A method for allowing direct perfect superimposition and comparison of Fresnel-transform reconstructions of digital holograms recorded of the same object at different distances and wavelengths is proposed and demonstrated. The method takes into account the dependence of the reconstruction pixel on the distance and the wavelength by the Fresnel-transform algorithm. The method avoids the need for image scaling at the end of the reconstruction process that usually is performed in multi-wavelength digital holography. Demonstration is given by superposing the numerical reconstructions of holograms recorded at different distances and wavelengths. The method can be potentially very useful for real-time monitoring in biological processes or for recognition and ranging by multiple wavelengths of a target with fast movements or finally for very fast investigation and study of very fast processes.     

Small strain and moderate rotation

Kinematical assumptions leading to the approximate theory of small strain accompanied by moderate rotations are discussed with reference to a three-dimensional continuous body. In particular, the relationship with Korn's inequality is examined. It is found that for bounded bodies the coincidence of small strain and moderate rotation on subsets of non-zero volume measure is not possible. Two explicit examples are presented to illustrate this point.     

A rheological approach to the study of concentrated milk clotting

The aim of the present work is to analyze the complex phenomena involved in the concentrated milk clotting process in order to define general criteria applicable to the design of a continuous coagulator. A full characterization of the rheological properties of completely hydrolyzed milk as a function of two different parameters, i.e., the coagulator temperature and the concentration degree of the milk, is presented. The dynamic evolution of loss, G′′, and storage, G′, moduli has been obtained at different frequency values and for different concentration degrees during the clotting process. Time cure tests have been performed on completely hydrolyzed milk samples showing that the rate of curing is very high and that the time for rheological experiments is much too short for testing Winter's theory of gelation. To overcome this problem, the intersect of loss and storage moduli was used for estimating the coagulation. Coagulation is faster when higher temperatures are used and the consistency of the final curd is greater if a more concentrated milk is used. A tentative physical explanation based on the network theories is presented. If an observation time far enough from the crossover point is chosen it can be seen that the curd strength estimated at 40 °C is about 50 times higher than that one evaluated at 25 °C. Among the considered temperatures, a good processing value was evaluated at 40 °C. Received: 6 February 2000 Accepted: 24 October 2000     

Dark energy versus modified gravity

There is now strong observational evidence that the expansion of the Universe is accelerating. The standard explanation invokes an unknown "dark energy" component. But such scenarios are faced with serious theoretical problems, which has led to increased interest in models where instead general relativity is modified in a way that leads to the observed accelerated expansion. The question then arises whether the two scenarios can be distinguished. Here we show that this may not be so easy, demonstrating explicitly that a generalized dark energy model can match the growth rate of the Dvali-Gabadadze-Porrati model and reproduce the 3+1 dimensional metric perturbations. Cosmological observations are then unable to distinguish the two cases.     

Stick-slip instability analysis

A theoretical investigation of friction-induced self-excited oscillations for systems with one degree of freedom is proposed. The friction force is assumed as an odd function of the relative sliding velocity with a jump discontinuity at a value of zero for the relative sliding velocity. The friction characteristic is approximated with a piecewise linear function, i.e. straight line segments with a suitable slope. For the generic system belonging to the class in question, the stick-slip instability region is located on a suitable dimensionless map.

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Sommario Viene proposta un'indagine teorica sulle oscillazioni autoeccitate indotte dall'attrito per sistemi ad un grado di libertà. La forza d'attrito viene assunta come funzione dispari della velocità relativa tra le superfici accoppiate, con una discontinuità di prima specie in corrispondenza del valore nullo della velocità. La caratteristica d'attrito viene approssimata mediante una funzione lineare a tratti con segmenti di opportuna pendenza. Per il generico sistema appartenente alla classe in esame, si perviene all'individuazione, su opportuna mappa adimensionale, della regione di instabilità da stick-slip.

     

Mixture models for ordinal responses to account for uncertainty of choice

In CUB models the uncertainty of choice is explicitly modelled as a Combination of discrete Uniform and shifted Binomial random variables. The basic concept to model the response as a mixture of a deliberate choice of a response category and an uncertainty component that is represented by a uniform distribution on the response categories is extended to a much wider class of models. The deliberate choice can in particular be determined by classical ordinal response models as the cumulative and adjacent categories model. Then one obtains the traditional and flexible models as special cases when the uncertainty component is irrelevant. It is shown that the effect of explanatory variables is underestimated if the uncertainty component is neglected in a cumulative type mixture model. Visualization tools for the effects of variables are proposed and the modelling strategies are evaluated by use of real data sets. It is demonstrated that the extended class of models frequently yields better fit than classical ordinal response models without an uncertainty component.     

Development of small molecule inhibitors and probes of human SUMO deconjugating proteases

Sentrin specific proteases (SENPs) are responsible for activating and deconjugating SUMO (Small Ubiquitin like MOdifier) from target proteins. It remains difficult to study this posttranslational modification due to the lack of reagents that can be used to block the removal of SUMO from substrates. Here, we describe the identification of small molecule SENP inhibitors and active site probes containing aza-epoxide and acyloxymethyl ketone (AOMK) reactive groups. Both classes of compounds are effective inhibitors of hSENPs 1, 2, 5, and 7 while only the AOMKs efficiently inhibit hSENP6. Unlike previous reported peptide vinyl sulfones, these compounds covalently labeled the active site cysteine of multiple recombinantly expressed SENP proteases and the AOMK probe showed selective labeling of these SENPs when added to complex protein mixtures. The AOMK compound therefore represents promising new reagents to study the process of SUMO deconjugation.     

Assemblies of perylene diimide derivatives with melamine into luminescent hydrogels

We report unique and spontaneous formation of hydrogels of perylene derivatives with melamine. The luminescent gel network is formed by H-type aggregation of the perylene core, supramolecularly cross-linked by melamine units. As a result of controlled aggregation in the extended nanofibers, strong exciton fluorescence emission is observed.     

Antimicrobial Effect and Cytotoxic Evaluation of Mg-Doped Hydroxyapatite Functionalized with Au-Nano Rods

Hydroxyapatite (HA) is the main inorganic mineral that constitutes bone matrix and represents the most used biomaterial for bone regeneration. Over the years, it has been demonstrated that HA exhibits good biocompatibility, osteoconductivity, and osteoinductivity both in vitro and in vivo, and can be prepared by synthetic and natural sources via easy fabrication strategies. However, its low antibacterial property and its fragile nature restricts its usage for bone graft applications. In this study we functionalized a MgHA scaffold with gold nanorods (AuNRs) and evaluated its antibacterial effect against S. aureus and E. coli in both suspension and adhesion and its cytotoxicity over time (1 to 24 days). Results show that the AuNRs nano-functionalization improves the antibacterial activity with 100% bacterial reduction after 24 h. The toxicity study, however, indicates a 4.38-fold cell number decrease at 24 days. Although further optimization on nano-functionalization process are needed for cytotoxicity, these data indicated that Au-NRs nano-functionalization is a very promising method for improving the antibacterial properties of HA.