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1.
Food Res Int ; 178: 113984, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38309885

RESUMO

The present study aimed to evaluate the feasibility of using near-infrared hyperspectral imaging (NIR-HSI) and chemometrics for classification of individual wheat kernels according to their deoxynivalenol (DON) level. In total, 600 wheat kernels from samples naturally contaminated over the maximum EU level were collected, and the DON content in each individual wheat kernel was analyzed by UHPLC. Linear discriminant analysis (LDA) was employed for building classification models of DON using the EU maximum level as cut off level, and they were tested on balanced and imbalanced test sets. The results showed that the models presented a balanced accuracy of 0.71, that would allow to obtain safe batches from contaminated batches once the unsafe kernels had been rejected, but often more than 30% of the batch would be rejected. The work confirmed that NIR-HSI could be a feasible method for monitoring DON in individual kernels and removing highly contaminated kernels prior to food chain entry.


Assuntos
Tricotecenos , Triticum , Imageamento Hiperespectral , Contaminação de Alimentos/análise , Tricotecenos/análise
2.
Eur Phys J E Soft Matter ; 35(6): 51, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22718498

RESUMO

The occurrence of shear bands in a complex fluid is generally understood as resulting from a structural evolution of the material under shear, which leads (from a theoretical perspective) to a non-monotonic stationary flow curve related to the coexistence of different states of the material under shear. In this paper we present a scenario for shear-banding in a particular class of complex fluids, namely foams and concentrated emulsions, which differs from other scenarios in two important ways. First, the appearance of shear bands is shown to be possible both without any intrinsic physical evolution of the material (e.g. via a parameter coupled to the flow such as concentration or entanglements) and without any finite critical shear rate below which the flow does not remain stationary and homogeneous. Secondly, the appearance of shear bands depends on the initial conditions, i.e. the preparation of the material. In other words, it is history dependent. This behaviour relies on the tensorial character of the underlying model (2D or 3D) and is triggered by an initially inhomogeneous strain distribution in the material. The shear rate displays a discontinuity at the band boundary whose amplitude is history dependent and thus depends on the sample preparation.

3.
Eur Phys J E Soft Matter ; 34(1): 2, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21253804

RESUMO

Up to a global scaling, the geometry of foams squeezed between two solid plates (2D GG foams) essentially depends on two independent parameters: the liquid volume fraction and the degree of squeezing (bubble thickness to diameter ratio). We describe it in two main asymptotic regimes: fully dry floor tiles, where the Plateau border radius is smaller than the distance between the solid plates, and dry pancakes, where it is larger. We predict a rapid variation of the Plateau border radius in one part of the pancake regime, namely when the Plateau border radius is larger than the inter-plate distance but smaller than the geometric mean of that distance and the bubble perimeter. This rapid variation is not related to any topological change in the foam: in all the regimes we consider, the bubbles remain in mutual lateral contact through films located at mid-height between both plates. We provide asymptotic predictions in different types of experiments on such 2D GG foams: when foam is being progressively dried or wetted, when it is being squeezed further or stretched, when it coarsens through film breakage or through inter-bubble gas diffusion. Our analysis is restricted to configurations close to equilibrium, as we do not include stresses resulting from bulk viscous flow or from non-homogeneous surfactant concentrations. We also assume that the inter-plate distance is sufficiently small for gravity to be negligible. The present work does not provide a method for measuring small Plateau border radii experimentally, but it indicates that large (and easily observable) Plateau borders should appear or disappear rather suddenly in some types of experiments with small inter-plate gaps. It also gives expected orders of magnitude that should be helpful for designing experiments on 2D GG foams.


Assuntos
Gases/química , Modelos Químicos , Tensoativos/química , Água/química , Elasticidade , Vidro/química , Tamanho da Partícula , Soluções/química , Tensão Superficial , Fatores de Tempo , Viscosidade , Molhabilidade
4.
AJNR Am J Neuroradiol ; 42(3): 530-537, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33478943

RESUMO

BACKGROUND AND PURPOSE: Few data are available regarding the influence of the timing of ischemic stroke management, such as daytime and nighttime hours, on the delay of mechanical thrombectomy, the effectiveness of revascularization, and clinical outcomes. We aimed to investigate whether admission during nighttime hours could impact the clinical outcome (mRS at 90 days) of patients with acute ischemic stroke treated by mechanical thrombectomy. MATERIALS AND METHODS: We retrospectively analyzed 169 patients (112 treated during daytime hours and 57 treated during nighttime hours) with acute ischemic stroke in the anterior cerebral circulation. The main outcome was the rate of patients achieving functional independence at 90 days (mRS ≤2), depending on admission time. RESULTS: In patients admitted during nighttime hours, the rate of mRS ≤ 2 at 90 days was significantly higher (51% versus 35%, P = .05) compared with those admitted in daytime hours. Patients in daytime and nighttime hours were comparable regarding admission and treatment characteristics. However, patients in nighttime hours tended to have a higher median NIHSS score at admission (P = .08) and to be younger (P = .08), especially among the mothership group (P = .09). The multivariate logistic regression analysis confirmed that patients in nighttime hours had better functional outcomes at 90 days than those in daytime hours (P = .018; 95% CI, 0.064-0.770; OR = 0.221). CONCLUSIONS: In a highly organized stroke care network, mechanical thrombectomy is quite effective in the nighttime hours among acute ischemic stroke presentations. Unexpectedly, we found that those patients achieved favorable clinical outcomes more frequently than those treated during daytime hours. Larger series are needed to confirm these results.


Assuntos
AVC Isquêmico/cirurgia , Trombectomia/métodos , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Tempo , Resultado do Tratamento
5.
Neuroimage Clin ; 24: 102010, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31734532

RESUMO

The dynamic connectome perspective states that brain functions arise from the functional integration of distributed and/or partly overlapping networks. Diffuse low-grade gliomas (DLGG) have a slow infiltrating character. Here we addressed whether and how anatomical disconnection following DLGG growth and resection might interfere with functional resting-state connectivity, specifically in relation to picture naming. Thirty-nine native French persons with a left DLGG were included. All underwent awake surgical resection of the tumor using direct brain electrostimulation to preserve critical eloquent regions. The anatomical disconnectivity risk following the DLGG volume and the resection, and the functional connectivity of resting-state fMRI images in relation to picture naming were evaluated prior to and three months after surgery. Resting-state connectivity patterns were compared with nineteen healthy controls. It was demonstrated that picture naming was strongly dependent on the semantic network that emerged from the integration and interaction of regions within multiple resting-state brain networks, in which their specific role could be explained in the light of the broader resting-state network they take part in. It emphasized the importance of a whole brain approach with specific clinical data input, during resting-state analysis in case of lesion. Adaptive plasticity was found in secondary regions, functionally connected to regions close to the tumor and/or cavity, marked by an increased connectivity of the right and left inferior parietal lobule with the left inferior temporal gyrus. In addition, an important role was identified for the superior parietal lobe, connected with the frontal operculum, suggesting functional compensation by means of attentional resources in order to name a picture via recruitment of the frontoparietal attention network.


Assuntos
Neoplasias Encefálicas , Córtex Cerebral/fisiopatologia , Conectoma , Glioma , Rede Nervosa/fisiopatologia , Plasticidade Neuronal/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Adulto , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/cirurgia , Córtex Cerebral/diagnóstico por imagem , Feminino , Glioma/diagnóstico por imagem , Glioma/patologia , Glioma/cirurgia , Humanos , Masculino , Pessoa de Meia-Idade , Rede Nervosa/diagnóstico por imagem , Procedimentos Neurocirúrgicos
6.
Ann Biomed Eng ; 45(11): 2574-2591, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28831614

RESUMO

A methodology for non-invasive estimation of the pressure in internal carotid arteries is proposed. It uses data assimilation and Ensemble Kalman filters in order to identify unknown parameters in a mathematical description of the cerebral network. The approach uses patient specific blood flow rates extracted from Magnetic Resonance Angiography and Magnetic Resonance Imaging. This construction is necessary as the simulation of blood flows in complex arterial networks, such as the circle of Willis, is not straightforward because hemodynamic parameters are unknown as well as the boundary conditions necessary to close this complex system with many outlets. For instance, in clinical cases, the values of Windkessel model parameters or the Young's modulus and the thickness of the arteries are not available on per-patient cases. To make the approach computational efficient, a reduced order zero-dimensional compartment model is used for blood flow dynamics. Using this simplified model, the proof-of-concept study demonstrates how to use the EnKF as an optimization tool to find parameters and how to make the inverse hemodynamic problem tractable. The predicted blood flow rates in the internal carotid arteries and the predicted systolic and diastolic brachial blood pressures are found to be in good agreement with the clinical measurements.


Assuntos
Artérias Cerebrais/fisiologia , Modelos Cardiovasculares , Velocidade do Fluxo Sanguíneo , Pressão Sanguínea , Artérias Cerebrais/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Incerteza
7.
AJNR Am J Neuroradiol ; 37(12): 2310-2316, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-27418471

RESUMO

BACKGROUND AND PURPOSE: Patients with vascular parkinsonism have higher cognitive decline and more basal ganglia lesions. We aimed to evaluate the relationship of cognitive impairment with functional connectivity between the basal ganglia and cingulate cortex in vascular parkinsonism. MATERIALS AND METHODS: Thirty patients (8 with vascular parkinsonism and 22 with Parkinson disease) and 23 controls were enrolled. The Mattis Dementia Rating Scale and the Stroop Task were used to assess cognitive decline. MR imaging examinations included T1-MPRAGE, FLAIR, and resting-state fMRI sequences. MPRAGE was segmented to obtain basal ganglia and cingulate cortex volumes. FLAIR was segmented to obtain white matter hyperintensity lesion volume. Resting-state fMRI sequences were used to compare basal ganglia functional connectivity with the cingulate cortex between patients and controls. RESULTS: Patients with vascular parkinsonism exhibited impaired attention, resistance to interference, and inhibitory control and an increased number of errors on the Stroop Task. They also had higher caudate nucleus and white matter hyperintensity lesion volumes, which were positively correlated (ρ = 0.75, P < .0001). Caudate nucleus functional connectivity with the perigenual anterior cingulate cortex was increased in patients with vascular parkinsonism compared with controls and patients with Parkinson disease, and it was positively correlated with the caudate nucleus volume (ρ = 0.44, P = .016). Caudate nucleus functional connectivity with the posterior cingulate cortex was decreased in patients with vascular parkinsonism compared with controls and negatively correlated with the number of errors on the Stroop test (ρ = -0.51, P = .0003). CONCLUSIONS: In patients with vascular parkinsonism, cognitive decline could be related to changes of caudate nucleus functional connectivity with the cingulate cortex at resting-state, which may be induced by ischemia-related remodelling.


Assuntos
Gânglios da Base/fisiopatologia , Encéfalo/fisiopatologia , Disfunção Cognitiva/fisiopatologia , Vias Neurais/fisiopatologia , Doença de Parkinson Secundária/fisiopatologia , Gânglios da Base/patologia , Encéfalo/patologia , Disfunção Cognitiva/etiologia , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Vias Neurais/patologia , Doença de Parkinson Secundária/complicações , Doença de Parkinson Secundária/patologia
8.
J Anim Sci ; 93(6): 3044-54, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26115290

RESUMO

The aim of this study was to investigate the effects of vitamin E (VE) supplementation and alfalfa grazing during fattening on fatty acid composition and mRNA expression of genes related to lipid metabolism in the LM of Rasa Aragonesa light lambs. After weaning, 48 lambs were kept indoors and fed a commercial concentrate and a VE supplemented concentrate (480 mg DL-α-tocopheryl acetate/kg DM) for 0 (control [CON]), 10 (VE10d), 20 (VE20d), and 30 d (VE30d) before slaughtering at 22 to 24 kg. Simultaneously, 8 unweaned lambs grazed in alfalfa (154 mg α-tocopherol/kg DM) paddocks with their dams and supplemented with the commercial concentrate (ALF). Immediately after slaughter, LM was sampled to determine gene expression. After 24 h of cooling at 4°C, LM was extracted to determine intramuscular fat (IMF) content and fatty acid composition. The IMF content did not differ with the dietary treatment ( = 0.212). Unweaned grazing alfalfa lambs had greater concentration of rumenic acid (C18:2 c9,t11; P < 0.001) and lower oleic acid (C18:1 c9; = 0.001) content and PUFA n-6:n-3 ratio (P < 0.001) but similar expression of genes implicated in lipid metabolism compared to the concentrate-fed lambs. Vitamin E supplementation did not modify muscle fatty acid composition; however, it increased the expression of FADS2 and ELOVL6, which are involved in desaturation of long-chain fatty acid and the elongation of SFA and MUFA. The results showed that a short period of VE supplementation, especially 10 (VE10d) and 20 d (VE20d), modified gene expression. Overall, the results showed that VE may be acting as a regulatory factor for transcriptional control of genes related to lipid metabolism in the muscle of Rasa Aragonesa light lambs (22-24 kg live weight and younger than 90 d old).


Assuntos
Suplementos Nutricionais , Herbivoria/fisiologia , Metabolismo dos Lipídeos/genética , Medicago sativa/metabolismo , Ovinos/metabolismo , Vitamina E/farmacologia , Acetiltransferases/genética , Acetiltransferases/metabolismo , Ração Animal/análise , Animais , Dieta/veterinária , Ácidos Graxos Dessaturases/genética , Ácidos Graxos Dessaturases/metabolismo , Ácidos Graxos/análise , Ácidos Graxos/metabolismo , Qualidade dos Alimentos , Regulação da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica/fisiologia , Masculino , Carne/análise , Carne/normas , Músculo Esquelético/química , Músculo Esquelético/metabolismo , PPAR gama/genética , PPAR gama/metabolismo , RNA Mensageiro/metabolismo , Ovinos/genética
9.
Methods Inf Med ; 35(1): 41-51, 1996 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-8992223

RESUMO

The study reported in this paper is aimed at evaluating the effectiveness of a knowledge-based expert system (ICTERUS) in diagnosing jaundiced patients, compared with a statistical system based on probabilistic concepts (TRIAL). The performances of both systems have been evaluated using the same set of data in the same number of patients. Both systems are spin-off products of the European project Euricterus, an EC-COMAC-BME Project designed to document the occurrence and diagnostic value of clinical findings in the clinical presentation of jaundice in Europe, and have been developed as decision-making tools for the identification of the cause of jaundice based only on clinical information and routine investigations. Two groups of jaundiced patients were studied, including 500 (retrospective sample) and 100 (prospective sample) subjects, respectively. All patients were independently submitted to both decision-support tools. The input of both systems was the data set agreed within the Euricterus Project. The performances of both systems were evaluated with respect to the reference diagnoses provided by experts on the basis of the full clinical documentation. Results indicate that both systems are clinically reliable, although the diagnostic prediction provided by the knowledge-based approach is slightly better.


Assuntos
Inteligência Artificial , Diagnóstico por Computador , Sistemas Inteligentes , Icterícia/etiologia , Modelos Estatísticos , Humanos , Itália , Estudos Prospectivos , Reprodutibilidade dos Testes , Estudos Retrospectivos , Software
10.
Methods Inf Med ; 39(4-5): 311-8, 2000 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11191699

RESUMO

The study aimed to describe an example of the assessment and validation of knowledge-based clinical expert systems. The paper focuses on ICTERUS, an expert system for jaundice diagnosis. It describes system design, the methodology applied for upgrading and validating the program, and the most important outcomes of the validation procedure. The clinical validation of the system on a very large European database (Euricterus Project) shows that diagnostic conclusions are reliable in about 70% of eligible cases. This figure appears acceptable for a system which provides decision support only on the basis of clinical data, assuming that the final decision is achieved under user responsibility. Expected biases, limitations and inconsistencies in the practical application of the system are discussed.


Assuntos
Diagnóstico por Computador/métodos , Sistemas Inteligentes , Icterícia/diagnóstico , Análise de Variância , Humanos , Itália , Curva ROC , Reprodutibilidade dos Testes , Validação de Programas de Computador
11.
Minerva Med ; 94(2): 111-22, 2003 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-12858160

RESUMO

The paper provides the description of a data-base developed to include in a quite structured format most clinical data used for patient management in a hospital setting. The system was aimed at achieving a reasonable compromise between the significant but complex solutions the research offers and the real needs of medical practice. First of all, the paper defines the requirements for designing a computerized clinical database according to a patient-centered clinical approach. Then, it describes the structure of a prototype aimed at classifying clinical data as a hierachy and describing them according to a structural approach. Next, problems related to the management and upgrading of the system are identified and possible solutions described, with a particular emphasis or knowledge acquisition, refinement and specialization, and on problems related to the functional aspects required for clinical applications. Finally, some meaningful clinical applications are outlined, which use the computerized clinical database as the standard for knowledge organization and data sharing.


Assuntos
Sistemas de Gerenciamento de Base de Dados/organização & administração , Bases de Dados Factuais , Sistemas de Informação Hospitalar/organização & administração , Interface Usuário-Computador
12.
Minerva Med ; 94(3): 167-79, 2003 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-14605597

RESUMO

The Electronic Medical Diary (EMD) is a tool for supporting the daily registration and storage of clinical events related to a specific patient. The collection of all patient-specific clinical data forms the patient database (PDB) which can be defined as a computer-based record able to replace the traditional paper record. The PDB is organized according to the clinical database (CDB), which is a structured terminology of most important clinical data, and may be connected with the many online tools (OLT) which can improve the flow of information within the hospital information system (HIS). In this paper we present the preliminary results of a project aimed at creating an EMD designed in accordance with the methodological model based on the problem-oriented approach. This EMD is patient-centered and each action it enables is related to at least one of the identified problems and one of the current diagnostic hypotheses. The permanent link of the EMD with the CDB is one of the most important features of the prototype here described. It allows the standardization of patients' data, their sharing among all operators involved, and a better organization of the patient management process.


Assuntos
Sistemas Computadorizados de Registros Médicos , Terapia Assistida por Computador , Humanos , Sistemas Computadorizados de Registros Médicos/organização & administração
13.
Gene ; 552(2): 225-33, 2014 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-25241385

RESUMO

The aim of this study was to investigate how different finishing period lengths with α-tocopherol supplementation or alfalfa grazing affect mRNA expression levels of genes related to vitamin E metabolism in L. thoracis (LT) muscle and subcutaneous fat (SF) from lambs of the Rasa Aragonesa breed. Indoors, concentrate-fed light lambs (n=48) were supplemented with 500 dl-α-tocopheryl acetate/kg concentrate for an average finishing period length of 0 (C), 10.7 (VE10d), 21.2 (VE20d) and, 32.3 (VE30d) days before slaughtering. Simultaneously, 8 lambs with their dams were alfalfa-grazed. The α-tocopherol affected in a short-term the expression of genes in LT muscle (ABCA1, LPL, APOE, and SREBP1) and SF (ABCA1, SCARB1, LPL, and PPARG). On the contrary, PPARA gene expression showed a long-term α-tocopherol effect because the highest levels of PPARA mRNA were found in the VE30d.


Assuntos
Carne , Músculo Esquelético/química , Ovinos , alfa-Tocoferol/administração & dosagem , Ração Animal , Animais , Dieta , Feminino , Expressão Gênica , Masculino , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/metabolismo , Ovinos/fisiologia
14.
Meat Sci ; 93(4): 906-13, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23142257

RESUMO

Indoor-kept concentrate-fed light lambs (n=54) were supplemented with 500 mg of dl-α-tocopheryl acetate/kg concentrate for 0, 10, 20 and 30 d before slaughtering at 22-24 kg BW. Simultaneously, 8 lambs with their dams were alfalfa-grazed and the lambs were slaughtered at the same weight. The age at slaughter and carcass characteristics were more affected by grazing than by supplementation with α-tocopherol. The grazing lambs had similar α-tocopherol levels to the lambs fed concentrate with dl-α-tocopheryl acetate for 10 days before slaughter. The length of the feeding period affected the evolution of the color, delaying the blooming and discoloration of the meat. Feeding lambs α-tocopherol enriched concentrate during the last 10 days of life or grazing them on alfalfa drastically diminished the lipid oxidation of the meat. Alfalfa grazing is a feasible alternative to increase light lamb meat shelf life without using additives.


Assuntos
Antioxidantes/farmacologia , Cor , Dieta , Peroxidação de Lipídeos/efeitos dos fármacos , Carne/análise , Medicago sativa , alfa-Tocoferol/farmacologia , Animais , Suplementos Nutricionais , Humanos , Ovinos
15.
Meat Sci ; 90(3): 775-82, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22127148

RESUMO

The aim of this study was to evaluate the use of forage diets (grazing vs. hay) around the time of ewe parturition, on the fatty acids profile of suckling lamb meat (10-12kg body weight). Forty-eight multiparous single-bearing ewes were used. The experimental treatments were conducted during the last 5weeks of pregnancy and the 5weeks of lactation in a 2×2 factorial design. Ewes were fed ad libitum on pastures or hay in the autumn. Results showed that milk from grazing ewes during the pre-partum period had a higher content of PUFA and CLA (P<0.05) and VA, CLA in their suckling lambs' meat (P<0.05). The effect in post-partum feeding was greater, revealing higher CLA, PUFA/SFA, PUFA n-3 and PUFA n-6/n-3 in milk and meat (P<0.05). The CLA, VA and PUFA n-6/n-3 ratios are those that are most affected by grazing. Pre-partum grazing, regardless of post-partum feeding, improves FA composition, increasing CLA content in both milk and meat.


Assuntos
Ração Animal/análise , Dieta/veterinária , Ácidos Graxos/análise , Carne/análise , Leite/química , Fenômenos Fisiológicos da Nutrição Animal , Animais , Animais Lactentes , Peso Corporal , Feminino , Lactação , Ácidos Linoleicos Conjugados/administração & dosagem , Ácidos Linoleicos Conjugados/análise , Período Pós-Parto , Gravidez , Ovinos
16.
J Neuroendocrinol ; 22(12): 1217-25, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-20673299

RESUMO

Endocrine cells in the mammalian pituitary are arranged into three-dimensional homotypic networks that wire the gland and act to optimise hormone output by allowing the transmission of information between cell ensembles in a temporally precise manner. Despite this, the structure-function relationships that allow cells belonging to these networks to display coordinated activity remain relatively uncharacterised. This review discusses the recent technological advances that have allowed endocrine cell network structure and function to be probed and the mathematical models that can be used to analyse and present the resulting data. In particular, we focus on the mechanisms that allow endocrine cells to dynamically function as a population to drive hormone release as well as the experimental and theoretical methods that are used to track and model information flow through the network.


Assuntos
Modelos Teóricos , Hipófise/fisiologia , Animais , Humanos , Neurônios/fisiologia , Hipófise/citologia
18.
Eur Phys J E Soft Matter ; 25(3): 225-51, 2008 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-18360738

RESUMO

A variety of complex fluids consists in soft, round objects (foams, emulsions, assemblies of copolymer micelles or of multilamellar vesicles--also known as onions). Their dense packing induces a slight deviation from their preferred circular or spherical shape. As a frustrated assembly of interacting bodies, such a material evolves from one conformation to another through a succession of discrete, topological events driven by finite external forces. As a result, the material exhibits a finite yield threshold. The individual objects usually evolve spontaneously (colloidal diffusion, object coalescence, molecular diffusion), and the material properties under low or vanishing stress may alter with time, a phenomenon known as aging. We neglect such effects to address the simpler behaviour of (uncommon) immortal fluids: we construct a minimal, fully tensorial, rheological model, equivalent to the (scalar) Bingham model. Importantly, the model consistently describes the ability of such soft materials to deform substantially in the elastic regime (be it compressible or not) before they undergo (incompressible) plastic creep--or viscous flow under even higher stresses.

19.
Int J Biomed Comput ; 42(1-2): 59-66, 1996 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-8880270

RESUMO

The paper describes a quality control program based on the principles of clinical methodology and indicators defined by physicians and hospital administrators according to general as well as local needs. The program is supported by a knowledge-based system which can be used in two ways: with on-line helps and hints to ensure effective and efficient medical decisions on a simulated patient for training purposes; and without facilities supporting the user to be used on an on-line setting for performance evaluation. The quality control program includes the evaluation of effectiveness and efficiency of patient care with respect to the overall process, single hypotheses and individual decisions: the evaluation regards the number and reliability of activated hypotheses, costs, time spent, number and appropriateness of investigations. The overall process is recursive, in that the results of each cycle are used by physicians to define new goals and indicants for the next cycle; quality control is active because physicians under evaluation are directly involved in the definition of goals and indicants and in the evaluation of results; evaluation is objective because indicants are predefined, and evaluation criteria are transparent.


Assuntos
Sistemas Inteligentes , Sistemas de Informação Hospitalar , Sistemas Computadorizados de Registros Médicos , Garantia da Qualidade dos Cuidados de Saúde , Inteligência Artificial , Diagnóstico por Computador , Hospitalização/economia , Itália , Controle de Qualidade , Software
20.
Artigo em Inglês | MEDLINE | ID: mdl-11088370

RESUMO

We report evidence for two distinct strain-induced orientation transitions in a lyotropic bcc cubic crystal submitted to increasing shear rates. The crystal is built up from copolymer spherical micelles in a selective solvent. The distribution of orientations is characterized by x-ray diffraction: in the two oriented states, the dense <111> rows align along the flow, but they differ from each other in the orientations of the dense layers with respect to the shear plane. These orientation transitions have clear rheological signatures in the form of two stress plateaus each associated with the coexistence of two states of orientation. We compare this behavior with the well documented shear-induced orientation transition in wormlike micelles.

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