Search results for "Biological system"
showing 10 items of 319 documents
Influence of the parameters molecular structure and granularity on the compactibility of a powder
1995
Drug Dev. Ind. Pharm. ISI Document Delivery No.: RP128 Times Cited: 3 Cited Reference Count: 14 Andres, c ndiaye, a thomas, c tromelin, a chaillot, b pourcelot, y; International audience; The aim of this study was to determine whether it is possible to obtain better characterization of materials in order to find out if these one are suitable in Quality Assurance for direct tableting. We tried to show that a methodological approach combining chemical, physical and technological aspects could control the direct compression process. We chose orthoboric acid as a study model for the direct compression. From a chemical point of view, our findings show only one crystalline molecular structure (RX…
Monte Carlo analysis of polymer translocation with deterministic and noisy electric fields
2012
AbstractPolymer translocation through the nanochannel is studied by means of a Monte Carlo approach, in the presence of a static or oscillating external electric voltage. The polymer is described as a chain molecule according to the two-dimensional “bond fluctuation model”. It moves through a piecewise linear channel, which mimics a nanopore in a biological membrane. The monomers of the chain interact with the walls of the channel, modelled as a reflecting barrier. We analyze the polymer dynamics, concentrating on the translocation time through the channel, when an external electric field is applied. By introducing a source of coloured noise, we analyze the effect of correlated random fluct…
Light Scattering as an Easy Tool to Measure Vesicles Weight Concentration
2020
Over the last few decades, liposomes have emerged as promising drug delivery systems and effective membrane models for studying biophysical and biological processes. For all applications, knowing their concentration after preparation is crucial. Thus, the development of methods for easily controlling vesicles concentration would be of great utility. A new assay is presented here, based on a suitable analysis of light scattering intensity from liposome dispersions. The method, tested for extrusion preparations, is precise, easy, fast, non-destructive and uses a tiny amount of sample. Furthermore, the scattering intensity can be measured indifferently at different angles, or even by using the…
Unmixing of human skin optical reflectance maps by Non-negative Matrix Factorization algorithm
2013
International audience; We present in this paper the decomposition of human skin absorption spectra with a Non-negative Matrix Factorization method. In doing so, we are able to quantify the relative proportion of the main chromophores present in the epidermis and the dermis. We present experimental results showing that we obtain a good estimate of melanin and hemoglobin concentrations. Our approach has been validated by analyzing the human skin absorption spectra in areas of healthy skin and areas affected by melasma on eight patients.
The role of mechanical properties of brittle airy foods on the masticatory performance
2010
This work investigates the mastication of two samples of typical cereal food products previously characterised by different sensory, textural and mechanical properties, by two complementary approaches. Electromyographic records and image analysis of chewed food particles first confirm the importance of the brittle behaviour of the products on human mastication. For both products, the fragmentation is followed by a significant agglomeration after less than 10 chewing cycles, both phenomena being correlated to the force magnitude and its evolution. Then, artificial mastication is undertaken to shed more light on the capability of the chewing simulator to discriminate both products under dry m…
Modelling of Reflectance Spectra of Skin Phototypes III
2011
In dermatology, study of human skin colour is related to skin phototype (SPT) in which the Fitzpatrick's scale is the most used skin photo type classification. Assessment of skin response to UV for various reasons plays an important role in dermatology. This is however not easy to be performed because of two reasons. Firstly, skin areas may have different skin tone resulting in different reflectance spectra and secondly, different modalities may produce different reflectance spectra. We hypothesize that the underlying pattern of reflectance spectra must be similar regardless of the modalities use and the skin areas where it is obtained, for a particular person. An observational clinical stu…
Search of a topological pattern to evaluate toxicity of heterogeneous compounds.
2001
Abstract Molecular connectivity has been applied to the search of mathematical models able to predict the carcinogenic and teratogenic activity of a wide group of structurally heterogeneous compounds. Through the linear discriminant analysis and the diagrams of distribution of pharmacological activity, the classification criteria that minimizes the percentage of error are established. The easiness and speed of the calculation of the descriptors used in this work make the models developed useful in data bases containing a huge number of compounds.
Petri Net Modelling of the Starch Enzymatic Liquefaction
2012
This paper investigates the use of the Petri Net modelling language for the description and analysis of the enzymatic reactions that are used for the starch liquefaction. The Coloured Petri Net formalism supported by the CPN Tools modelling and simulation environment is used. The pools of substrates and products are represented as the places and the possible reactions as the transition of the net. The concurrent reactions are modelled trough transitions that are enabled at the same time. The occurrence probabilities associated with each of these concurrent transitions are chosen as the model parameters. The analysis of the specific properties of the model is used to fit the model to data fr…
α-stable distributions for better performance of ACO in detecting damage on not well spaced frequency systems
2014
Abstract In this paper, the Ant Colony Optimization (ACO) algorithm is modified through α -stable Levy variables and applied to the identification of incipient damage in structural components. The main feature of the proposed optimization is an improved ability, which derives from the heavy tails of the stable random variable, to escape from local minima. This aspect is relevant since the objective function used for damage detection may have many local minima which render very challenging the search of the global minimum corresponding to the damage parameter. As the optimization is performed on the structural response and does not require the extraction of modal components, the method is pa…
Time-Dependent Multiple Depot Vehicle Routing Problem on Megapolis Network under Wardrop's Traffic Flow Assignment
2018
In this work multiple depot vehicle routing problem is considered in case of variable travel times between nodes on a metropolis network. This variant of the classic multiple depot vehicle routing problem is motivated by the fact that in urban contexts variable traffic conditions play an essential role and can not be ignored in order to perform a realistic optimization. Time-travel matrices corresponding to each period of planning horizon were formed by solving the traffic assignment problem in conjunction with shortest path problem. Routing problem instances include from 20 to 100 customers randomly chosen from a road network of Saint-Petersburg. The results demonstrate that taking into ac…