RESUMO
This research focuses on the numerical simulation of stridor; a high pitched, abnormal noise, resulting from turbulent airflow and vibrating tissue through a partially obstructed airway. Characteristics of stridor noise are used by medical doctors as indication for location and size of the obstruction. The relation between type of stridor and the various diseases associated with airway obstruction is unclear; therefore, simply listening to stridor is an unreliable diagnostic tool. The overall aim of the study is to better understand the relationship between characteristics of stridor noise and localization and size of the obstruction. Acoustic analysis of stridor may then in future simplify the diagnostic process, and reduce the need for more invasive procedures such as laryngoscopy under general anesthesia. In this paper, the feasibility of a coupled flow, acoustic and structural model is investigated to predict the noise generated by the obstruction as well as the propagation of the noise through the airways, taking into account a one-way coupled fluid, structure, and acoustic interaction components. The flow and acoustic solver are validated on a diaphragm and a simplified airway model. A realistic airway model of a patient suffering from a subglottic stenosis, derived from a real computed tomography scan, is further analyzed. Near the mouth, the broadband noise levels at higher frequencies increased with approximately 15-20 dB comparing the stridorous model with the healthy model, indicating stridorous sound.
Assuntos
Acústica , Obstrução das Vias Respiratórias/patologia , Simulação por Computador , Obstrução das Vias Respiratórias/diagnóstico por imagem , Obstrução das Vias Respiratórias/fisiopatologia , Fenômenos Biomecânicos , Humanos , Cinética , Modelos Biológicos , Pressão , Reologia , Som , Tomografia Computadorizada por Raios X , VibraçãoRESUMO
OBJECTIVE: To assess for lenticulostriate vasculopathy (LSV) on cranial ultrasound (cUS) scans of very preterm infants: incidence and aetiology, evolution during neonatal period, association with clinical parameters, and MRI equivalent. DESIGN: Prospective study. SETTING: Tertiary neonatal referral centre. PATIENTS: Very preterm infants (<32 weeks) underwent sequential cUS throughout the neonatal period and MRI around term age. cUS were evaluated for LSV and other changes, and MRI for changes in signal and myelination in deep grey matter. LSV was divided into early-onset (
Assuntos
Doença Cerebrovascular dos Gânglios da Base , Doenças do Prematuro , Doenças Talâmicas , Idade de Início , Doença Cerebrovascular dos Gânglios da Base/diagnóstico , Doença Cerebrovascular dos Gânglios da Base/epidemiologia , Doença Cerebrovascular dos Gânglios da Base/etiologia , Peso ao Nascer , Feminino , Idade Gestacional , Humanos , Hipotensão/epidemiologia , Recém-Nascido , Recém-Nascido Prematuro , Doenças do Prematuro/diagnóstico , Doenças do Prematuro/epidemiologia , Doenças do Prematuro/etiologia , Imageamento por Ressonância Magnética , Masculino , Gravidez , Gravidez Múltipla , Estudos Prospectivos , Crânio/diagnóstico por imagem , Doenças Talâmicas/diagnóstico , Doenças Talâmicas/epidemiologia , Doenças Talâmicas/etiologia , UltrassonografiaRESUMO
Spore-forming bacteria can be a problem in the food industry, especially in the canning industry. Spores present in ingredients or present in the processing environment severely challenge the preservation process since their thermal resistance may be very high. We therefore asked the question which bacterial spore formers are found in a typical soup manufacturing plant, where they originate from and what the thermal resistance of their spores is. To answer these questions molecular techniques for bacterial species and strain identification were used as well as a protocol for the assessment of spore heat stress resistance based on the Kooiman method. The data indicate the existence and physiological cause of the high thermal resistance of spores of many of the occurring species. In particular it shows that ingredients used in soup manufacturing are a rich source of high thermal resistant spores and that sporulation in the presence of ingredients rich in divalent metal ions exerts a strong influence on spore heat resistance. It was also indicated that Bacillus spores may well be able to germinate and resporulate during manufacturing i.e. through growth and sporulation in line. Both these spores and those originating from the ingredients were able to survive certain thermal processing settings. Species identity was confirmed using fatty acid analysis, 16SrRNA gene sequencing and DNA-DNA hybridisation. Finally, molecular typing experiments using Ribotyping and AFLP analysis show that strains within the various Bacillus species can be clustered according to the thermal resistance properties of their spores. AFLP performed slightly better than Ribotyping. The data proofed to be useful for the generation of strain specific probes. Protocols to validate these probes in routine identification and innovation aimed at tailor made heat processing in soup manufacturing have been formulated.
Assuntos
Bacillus/fisiologia , Contaminação de Alimentos/análise , Conservação de Alimentos/métodos , Temperatura Alta , Filogenia , Esporos Bacterianos/crescimento & desenvolvimento , Bacillus/classificação , Bacillus/genética , Técnicas de Tipagem Bacteriana , Análise por Conglomerados , Contagem de Colônia Microbiana , Qualidade de Produtos para o Consumidor , Ácidos Graxos/análise , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Humanos , RNA Ribossômico 16S/genética , Especificidade da Espécie , Esporos Bacterianos/classificação , Esporos Bacterianos/genéticaRESUMO
The isothermal survival curves of the heat resistant spores of Bacillus sporothermodurans IC4, in the range of 117-125 degrees C, were determined in chicken, mushroom and pea soups by the capillary method. They were all non-linear with a noticeable upper concavity and could be described by the equation log(10) [N(t)/N(0)]=-b(T)t(n) with a fixed power, n, of the order of 0.7-0.8. The temperature dependence of b(T) could be described by the equation b(T)=log(e)[1+exp[k(T-T(c))]], where T(c) is the temperature where intensive inactivation starts and k is the slope of b(T) at temperatures well above T(c). They were 121-123 degrees C and 0.2-0.4 degrees C(-1), respectively, depending on the soup. These parameters were used to estimate the survival curves of the spores in two non-isothermal heat treatments using the procedure originally proposed by Peleg and Penchina [Crit. Rev. Food Sci. Nutr. 40 (2000) 159]. The results were compared with experimental survival curves, determined by the direct injection method, in another laboratory. There was a general agreement, although not perfect, between the predicted and experimentally observed survival ratios. Also, the isothermal survival parameters, estimated directly from the non-isothermal inactivation data using the model, were in general agreement with those calculated from the isothermal data. This suggests that the heat inactivation patterns of B. sporothermodurans IC4 spores in soups can be at least roughly estimated using the same general survival model, which has until now only been experimentally validated for vegetative bacterial cells.