Ricardo F. Oliveira

Biodegradation assessment of PLA and its nanocomposites.

Poly(lactic acid) nanocomposites containing Cloisite 15A, Cloisite 30B, and Dellite 43B were prepared by melt-mixing in a batch mixer and were exposed to UV radiation, temperature, and microorganism in solution and in a compost. Exposed samples, collected along the time, were characterized by several techniques. While the addition of organoclays had a positive effect on thermal stability, the degradation rate of nanocomposites increased when exposed to UV radiation and microorganism. Moreover, the degradation rate depends on the organoclay type. Even though the degradation rate is higher for nanocomposites, Fourier transform infrared spectrometry and gel permeation chromatography results demonstrated that the degradation mechanism is the same.

4D+SNN: A Spatio-Temporal Density-Based Clustering Approach with 4D Similarity

Spatio-temporal clustering is a sub field of data mining that is increasingly gaining more scientific attention due to the advances of location-based or environmental devices that register position, time and, in some cases, other semantic attributes. This process pretends to group objects based in their spatial and temporal similarity helping to discover interesting patterns and correlations in large data sets. One of the main challenges of this area is the ability to integrate several dimensions in a general-purpose approach. In this paper, such general approach is proposed, based on an extension of the SNN (Shared Nearest Neighbor) algorithm. The 4D+SNN algorithm allows the integration of space, time and one or more semantic attributes in the clustering process. This algorithm is able to deal with different data sets and different discovery purposes as the user has the ability to weight the importance of each dimension in the discovery process. The results obtained are very promising as show interesting findings on data and open the possibility of integration of several dimensions of analysis in the clustering process.

Development of new spacer device geometry: a CFD study (Part I)

Asthma is a widespread disease, affecting more than 300 million individuals. The treatment in children is based upon an administration of a pressurised metered-dose inhaler added with a spacer. The efficiency of drug delivery to the patient is strongly affected by the transient airflow pattern inside the spacer device. This paper presents a computational fluid dynamics (CFD) analysis of airflow inside a commercially available spacer device with wide application. This study, carried out in Fluent™, was the basis of an optimisation procedure developed to improve the geometry of the spacer and develop a more efficient product. The results show that an appropriate control of the boundary layer development, by changing the spacer shape, reduces the length of the recirculation zones and improves the flow. It can be concluded that CFD is a powerful technique that can be successfully applied to optimise the geometry of such medical devices.

Thermal comfort assessment of a surgical room through computational fluid dynamics using local PMV index.

BACKGROUND Studies concerning indoor thermal conditions are very important in defining the satisfactory comfort range in health care facilities. OBJECTIVE This study focuses on the evaluation of the thermal comfort sensation felt by surgeons and nurses, in an orthopaedic surgical room of a Portuguese hospital. METHODS Two cases are assessed, with and without the presence of a person. Computational fluid dynamic (CFD) tools were applied for evaluating the predicted mean vote (PMV) index locally. RESULTS Using average ventilation values to calculate the PMV index does not provide a correct and enough descriptive evaluation of the surgical room thermal environment. As studied for both cases, surgeons feel the environment slightly hotter than nurses. The nurses feel a slightly cold sensation under the air supply diffuser and their neutral comfort zone is located in the air stagnation zones close to the walls, while the surgeons feel the opposite. It was observed that the presence of a person in the room leads to an increase of the PMV index for surgeons and nurses. That goes in line with the empirical knowledge that more persons in a room lead to an increased heat sensation. CONCLUSIONS The clothing used by both classes, as well as the ventilation conditions, should be revised accordingly to the amount of persons in the room and the type of activity performed.

A CFD Study of a pMDI Plume Spray

Asthma is an inflammatory chronic disease characterized by airway obstructions disorders. The treatment is usually done by inhalation therapy, in which pressurized metered-dose inhalers (pMDIs) are preferred devices. The objective of this paper is to characterize and simulate a pMDI spray plume by introducing realistic factors through a computational fluid dynamics (CFD) study. Numerical simulations were performed with Fluent® software, by using a three-dimensional “testbox” for room environment representation. A salbutamol/HFA-134a formulation was used for characterization, whose properties taken as input for the CFD simulations. Spray droplets were considered to be composed by ethanol, salbutamol and HFA-134a. Propellant evaporation was taken into consideration, as well as, drag coefficient correction. Results showed an air temperature drop of 3.3 °C near the nozzle. Also, an increase in air velocity of 3.27 m/s was noticed. The CFD results seem to be in good agreement with Dunbar (1997) data on particle average velocity along the axial distance from the nozzle.

An Experimental Setup for API Assessment of a Valved Holding Chamber Device

Typically for young children and elders, the asthma treatment procedure using pMDI devices bring some usage coordination difficulties. Therefore, and accordingly to several asthma treatment guidelines, the prescription of a VHC, as an add-on device for the pMDI, is advisable. These devices consist of an expansion chamber where the air slows down, as well as, the pMDI spray plume. Allowing the patient to breathe whenever he wants, independently from the moment of the pMDI actuation, also reduces the “cold-freon” effect and allows a more effective evaporation of the propellant. The effectiveness evaluation of VHC and pMDI devices is made through the quantification of drug delivered to the patient lungs. A simple collection filter is not enough for an accurate assessment of the device. Since the size of the particles delivered matter the most, the use of an impaction apparatus is essential. Accordingly to the Canadian normative for VHC assessment (CAN/CSA/Z264.1-02:2008), the experimental testing shall be done by using a breath simulator instead of a constant flow pump. The evolution of these tests shall move towards more realistic testing conditions. This work reports the project and construction an experimental setup for a correct assessment of the VHC devices effectiveness. The experimental setup is based in the work of Foss & Keppel (1999) and the contribution of Finlay (1998) and Miller (2002). The project and optimization of the major components, such as, breath cycle simulator by means of a cam-follower mechanism, a mixing cone and the vacuum pump used, are herein described and discussed.Copyright

pMDI sprays: theory, experiment and numerical simulation

The inhalation therapy is a cornerstone in asthma treatment. A disease characterized by episodes of wheezing, breathing difficulties, chest tightness and coughing. Essentially it is a chronic inflammatory disorder associated with airway hyper responsiveness [1]. This disease already affects over 300 million people worldwide, growing at a rate of 50% per decade, and causes the death of 220 thousand per year [1].

Experimental Validation of a CFD Model in a Thermal Environment Characterization

Comfort has a great influence on work performance and productivity. Creating a comfortable environment can be achieved by various routes: a good selection of clothing and a proper design of equipment and technical facilities that can render an appropriate acclimatization of the occupational environment. There are several methods for solving problems of thermal comfort, including computer simulation of the thermal system comprising the Human Body - Clothing - Environment. With the evolution of computer technology and CFD (Computational Fluid Dynamics) techniques one can now develop complete analysis of HVAC systems, with regard to the fields of flow velocity, temperature distribution, particularly in the vicinity of the human body. In this way a complete interaction of the human body with the surrounding air can be descried. The difficulty in modeling the human body arises from the complex geometric shape and its thermo-physiological properties, being important to include all these factors in the numerical simulation of the human body in a closed environment. In the current study a CFD model was developed to describe the fluid flow, heat transfer and mass transfer between the ventilation air and a human manikin inside a room. The computational model solves the heat, mass and momentum conservation equations in the computation domain using a finite volume discretization method and the resulting equations are solved in the ANSYS

Morphological transition of Helicobacter pylori adapted to water

AIM This study aims to investigate the morphological transition of Helicobacter pylori during adaptation to water. MATERIALS & METHODS Different strains were adapted to water. Changes regarding cultivability and cellular morphology were recorded. Expression of 11 genes involved in H. pylori morphological changes was evaluated by real-time PCR. RESULTS H. pylori presented increased cultivability in water after adaptation. The permanent loss of the spiral shape was observed, but no transition into coccoid form has occurred. Expression levels of genes involved in peptidoglycan assembly of H. pylori 26695 have shown significant changes between adapted and nonadapted strains. CONCLUSION Adaption to water favors the culturable phenotype and the morphological transition to the rod shape, into a process that implicates the peptidoglycan turnover.

CFD Modeling the Cooling Stage of Reflow Soldering Process

This research is sponsored by the Portugal Incentive System for Research and Technological Development. Project in co -promotion no 002814/2015 (iFACTORY 2015-2018).This work has also been supported by COMPETE and Portuguese Foundation for Science and Technology (FCT) within: the Strategic Project: UID/CEC/00319/2013; Strategic Project UID/SEM/04077/2013; and the Strategic Project UID/EEA/04436/2013.