A low-voltage RF-CMOS receiver front-end for a wireless fall detection microsystem

Dissertação para obtenção do Grau de Mestre em Engenharia Eletrotécnica e de Computadores, pela Universidade Nova de Ciências e Tecnologia

Green synthesis of 2-Oxazoline-based polymers with antimicrobial activity using scCO2

Using a green methodology, 17 different poly(2-oxazolines) were synthesized starting from four different oxazoline monomers. The polymerization reactions were conducted in supercritical carbon dioxide under a cationic ring-opening polymerization (CROP) mechanism using boron trifluoride diethyl etherate as the catalyst. The obtained living polymers were then end-capped with different types of amines, in order to confer them antimicrobial activity. For comparison, four polyoxazolines were end-capped with water, and by their hydrolysis the linear poly(ethyleneimine) (LPEI) was also produced. After functionalization the obtained polymers were isolated, purified and characterized by standard techniques (FT-IR, NMR, MALDI-TOF and GPC). The synthesized poly(2-oxazolines) revealed an unusual intrinsic blue photoluminescence. High concentration of carbonyl groups in the polymer backbone is appointed as a key structural factor for the presence of fluorescence and enlarges polyoxazolines’ potential applications. Microbiological assays were also performed in order to evaluate their antimicrobial profile against gram-positive Staphylococcus aureus NCTC8325-4 and gram-negative Escherichia coli AB1157 strains, two well known and difficult to control pathogens. The minimum inhibitory concentrations (MIC)s and killing rates of three synthesized polymers against both strains were determined. The end-capping with N,N-dimethyldodecylamine of living poly(2- methyl-2-oxazoline) and poly(bisoxazoline) led to materials with higher MIC values but fast killing rates (less than 5 minutes to achieve 100% killing for both bacterial species) than LPEI, a polymer which had a lower MIC value, but took a longer time to kill both E.coli and S.aureus cells. LPEI achieved 100% killing after 45 minutes in contact with E. coli and after 4 hours in contact with S.aureus. Such huge differences in the biocidal behavior of the different polymers can possibly underlie different mechanisms of action. In the future, studies to elucidate the obtained data will be performed to better understand the killing mechanisms of the polymers through the use of microbial cell biology techniques.

Fiber functionalization for biomedical applications

Deep-eutectic solvents (DES) are considered novel renewable and biodegradable solvents, with a cheap and easy synthesis, without waste production. Later it was discovered a new subclass of DES that even can be biocompatible, since their synthesis uses primary metabolites such as amino acids, organic acids and sugars, from organisms. This subclass was named natural deep-eutectic solvents (NADES). Due to their properties it was tried to study the interaction between these solvents and biopolymers, in order to produce functionalized fibers for biomedical applications. In this way, fibers were produced by using the electrospinning technique. However, it was first necessary to study some physical properties of NADES, as well as the influence of water in their properties. It has been concluded that the water has a high influence on NADES properties, which can be seen on the results obtained from the rheology and viscosity studies. The fluid dynamics had changed, as well as the viscosity. Afterwards, it was tested the viability of using a starch blend. First it was tested the dissolution of these biopolymers into NADES, in order to study the viability of their application in electrospinning. However the results obtained were not satisfactory, since the starch polymers studied did not presented any dissolution in any NADES, or even in organic solvents. In this way it was changed the approach, and it was used other biocompatible polymers. Poly(ethylene oxide), poly(vinyl alcohol) and gelatin were the others biopolymers tested for the electrospinning, with NADES. All polymers show good results, since it was possible to obtain fibers. However for gelatin it was used only eutectic mixtures, containing active pharmaceutical ingredients (API’s), instead of NADES. For this case it was used mandelic acid (antimicrobial properties), choline chloride, ibuprofen (anti-inflammatory properties) and menthol (analgesic properties). The polymers and the produced fibers were characterized by scanning electron microscope (SEM), Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). With the help of these techniques it was possible to conclude that it was possible to encapsulate NADES within the fibers. Rheology it was also study for poly(ethylene oxide) and poly(vinyl alcohol), in a way to understand the influence of polymer concentration, on the electrospinning technique. For the gelatin, among the characterization techniques, it was also performed cytotoxicity and drug release studies. The gelatin membranes did not show any toxicity for the cells, since their viability was maintained. Regarding the controlled release profile experiment no conclusion could be drawn from the experiments, due to the rapid and complete dissolution of the gelatin in the buffer solution. However it was possible to quantify the mixture of choline chloride with mandelic acid, allowing thus to complete, and confirm, the information already obtained for the others characterization technique.

Students' choice of a master in management in Portugal: A means-end chain approach

In the increasingly competitive market of higher education introduced by the Bologna Declaration, understanding the decision-making of master in management students is at the center of institutional management and marketing efforts on its mission to attract prospective students in a less costly, more efficient manner. The means-end chain approach, applied to the choice of a Portuguese institution in which to pursue a master in management, points to the position in rankings and to the non-specificity of the program as the most important attributes. Additionally, results show that students with distinct demographic, household, or background characteristics choose in significantly different manners.

Bloodstream infection in patients with end-stage renal disease in a teaching hospital in central-western Brazil

Introduction Vascular access in patients undergoing hemodialysis is considered a critical determinant of bloodstream infection (BSI) and is associated with high morbidity and mortality. The purpose of this study was to investigate the occurrence of BSI in patients with end-stage renal disease using central venous catheters for hemodialysis. Methods A cohort study was conducted in a public teaching hospital in central-western Brazil from April 2010 to December 2011. For every patient, we noted the presence of hyperemia/exudation upon catheter insertion, as well as fever, shivering, and chills during hemodialysis. Results Fifty-nine patients were evaluated. Thirty-five (59.3%) patients started dialysis due to urgency, 37 (62.7%) had BSI, and 12 (20%) died. Hyperemia at the catheter insertion site (64.9%) was a significant clinical manifestation in patients with BSI. Statistical analysis revealed 1.7 times more cases of BSI in patients with hypoalbuminemia compared with patients with normal albumin levels. The principal infective agents identified in blood cultures and catheter-tip cultures were Staphylococcus species (24 cases), non-fermentative Gram-negative bacilli (7 cases of Stenotrophomonas maltophilia and 5 cases of Chryseobacterium indologenes), and Candida species (6). Among the Staphylococci identified, 77.7% were methicillin-resistant, coagulase-negative Staphylococci. Of the bacteria isolated, the most resistant were Chryseobacterium indologenes and Acinetobacter baumannii. Conclusions Blood culture was demonstrated to be an important diagnostic test and identified over 50% of positive BSI cases. The high frequency of BSI and the isolation of multiresistant bacteria were disturbing findings. Staphylococcus aureus was the most frequently isolated microorganism, although Gram-negative bacteria predominated overall. These results highlight the importance of infection prevention and control measures in dialysis units.

Measuring end-to-end delay in real-time auralisation systems

One of the major challenges in the development of an immersive system is handling the delay between the tracking of the user’s head position and the updated projection of a 3D image or auralised sound, also called end-to-end delay. Excessive end-to-end delay can result in the general decrement of the “feeling of presence”, the occurrence of motion sickness and poor performance in perception-action tasks. These latencies must be known in order to provide insights on the technological (hardware/software optimization) or psychophysical (recalibration sessions) strategies to deal with them. Our goal was to develop a new measurement method of end-to-end delay that is both precise and easily replicated. We used a Head and Torso simulator (HATS) as an auditory signal sensor, a fast response photo-sensor to detect a visual stimulus response from a Motion Capture System, and a voltage input trigger as real-time event. The HATS was mounted in a turntable which allowed us to precisely change the 3D sound relative to the head position. When the virtual sound source was at 90º azimuth, the correspondent HRTF would set all the intensity values to zero, at the same time a trigger would register the real-time event of turning the HATS 90º azimuth. Furthermore, with the HATS turned 90º to the left, the motion capture marker visualization would fell exactly in the photo-sensor receptor. This method allowed us to precisely measure the delay from tracking to displaying. Moreover, our results show that the method of tracking, its tracking frequency, and the rendering of the sound reflections are the main predictors of end-to-end delay.

Students’ perceptions of competencies by the end of a masters’ degree

Os modelos atuais de empregabilidade, abrangentes e complexos, incluem não apenas o conjunto de competências técnicas e transversais necessárias à integração no mercado de trabalho, mas consideram também uma componente subjetiva que integra as crenças e atitudes individuais. Apresentam-se os resultados preliminares de um estudo centrado nas perceções de competências e preparação para o mercado de trabalho, realizado com 214 alunos, finalistas de mestrado. Os resultados obtidos apontam para uma elevada correlação entre competências práticas, competências de empregabilidade, preparação e expectativas de sucesso na transição para o trabalho. Realça-se ainda a importância da integração de uma componente prática nos currículos educativos.

End-of-day dryness, corneal sensitivity and blink rate in contact lens wearers

Purpose: To study the relationship among the variables intensity ofthe end-of-day (EOD) dryness, corneal sensitivity and blink rate in soft contact lens (CL) wearers. Methods: Thirty-eight soft CL wearers (25 women and 13 men; mean age 27.1 ± 7.2 years) were enrolled. EOD dryness was assessed using a scale of 0–5 (0, none to 5, very intense). Mechanical and thermal (heat and cold) sensitivity were measured using a Belmonte’s gas esthesiometer. The blink rate was recorded using a video camera while subjects were wearing a hydrogel CL and watching a film for 90 min in a controlled environmental chamber. Results: A significant inverse correlation was found between EOD dryness and mechanical sensitivity (r: −0.39; p = 0.02); however, there were no significant correlations between EOD dryness and thermal sensitivity. A significant (r: 0.56; p < 0.001) correlation also was observed between EOD dryness and blink rate, but no correlations were found between blink rate and mechanical or thermal sensitivity. Conclusions: CL wearers with higher corneal sensitivity to mechanical stimulation reported more EOD dryness with habitual CL wear. Moreover, subjects reporting more EOD dryness had an increased blink rates during wear of a standard CL type. The increased blink rate could act to improve the ocular surface environment and relieve symptoms

Poly lactic acid based biodegradable stents and functionalization techniques: brief review

Commercial stents, especially metallic ones, present several disadvantages, and this gives rise to the necessity of producing or coating stents with different materials, like natural polymers, in order to improve their biocompatibility and minimize the disadvantages of metallic ones. This review paper discusses some applications of natural-based polymers in stents, namely polylactic acid (PLA) for stent development and chitosan for biocompatible coatings of stents . Furthermore, some effective stent functionalization techniques will be discussed, namely Layer by Layer (LBL) technique.

The role of the mammalian DNA end-processing enzyme polynucleotide kinase 3'-phosphatase in spinocerebellar ataxia Type 3 pathogenesis

DNA strand-breaks (SBs) with non-ligatable ends are generated by ionizing radiation, oxidative stress, various chemotherapeutic agents, and also as base excision repair (BER) intermediates. Several neurological diseases have already been identified as being due to a deficiency in DNA end-processing activities. Two common dirty ends, 3'-P and 5'-OH, are processed by mammalian polynucleotide kinase 3'-phosphatase (PNKP), a bifunctional enzyme with 3'-phosphatase and 5'-kinase activities. We have made the unexpected observation that PNKP stably associates with Ataxin-3 (ATXN3), a polyglutamine repeat-containing protein mutated in spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph Disease (MJD). This disease is one of the most common dominantly inherited ataxias worldwide; the defect in SCA3 is due to CAG repeat expansion (from the normal 14-41 to 55-82 repeats) in the ATXN3 coding region. However, how the expanded form gains its toxic function is still not clearly understood. Here we report that purified wild-type (WT) ATXN3 stimulates, and by contrast the mutant form specifically inhibits, PNKP's 3' phosphatase activity in vitro. ATXN3-deficient cells also show decreased PNKP activity. Furthermore, transgenic mice conditionally expressing the pathological form of human ATXN3 also showed decreased 3'-phosphatase activity of PNKP, mostly in the deep cerebellar nuclei, one of the most affected regions in MJD patients' brain. Finally, long amplicon quantitative PCR analysis of human MJD patients' brain samples showed a significant accumulation of DNA strand breaks. Our results thus indicate that the accumulation of DNA strand breaks due to functional deficiency of PNKP is etiologically linked to the pathogenesis of SCA3/MJD.

End-systolic pressure-diameter relation of the left ventricle during transient and sustained elevations of blood pressure

OBJECTIVE: To assess the effect of transient and sustained variations in cardiac load on the values of the end-systolic pressure-diameter relation (ESPDR) of the left ventricle. METHODS: We studied 13 dogs under general anesthesia and autonomic blockade. Variations of cardiac loads were done by elevation of blood pressure by mechanical constriction of the aorta. Two protocols were used in each animal: gradual peaking and decreasing pressure variation, the "transient arterial hypertension protocol" (TAH), and a quick and 10 min sustained elevation, the "sustained arterial hypertension protocol"(SAH). Then, we compared the ESDR in these two situations. RESULTS: Acute elevation of arterial pressure, being it "transitory" or "sustained", did not alter the heart frequency and increased similarly the preload and after load. However, they acted differently in end systolic pressure-diameter relation. It was greater in the SAH than TAH protocol, 21.0±7.3mmHg/mm vs. 9.2±1.2mmHg/mm (p<0.05). CONCLUSION: The left ventricular ESPDR values determined during sustained pressure elevations were higher than those found during transient pressure elevations. The time-dependent activation of myocardial contractility associated with the Frank-Starling mechanism is the major factor in inotropic stimulation during sustained elevations of blood pressure, determining an increase in the ESPDR values.

Chemical functionalization in bionanoparticles

Dissertação de mestrado em Biofísica e Bionanossistemas

Evaluation of Electrocardiographic T-peak to T-end Interval in Subjects with Increased Epicardial Fat Tissue Thickness

Abstract Background: The association between periatrial adiposity and atrial arrhythmias has been shown in previous studies. However, there are not enough available data on the association between epicardial fat tissue (EFT) thickness and parameters of ventricular repolarization. Thus, we aimed to evaluate the association of EFT thickness with indices of ventricular repolarization by using T-peak to T-end (Tp-e) interval and Tp-e/QT ratio. Methods: The present study included 50 patients whose EFT thickness ≥ 9 mm (group 1) and 40 control subjects with EFT thickness < 9 mm (group 2). Transthoracic echocardiographic examination was performed in all participants. QT parameters, Tp-e intervals and Tp-e/QT ratio were measured from the 12-lead electrocardiogram. Results: QTd (41.1 ± 2.5 vs 38.6 ± 3.2, p < 0.001) and corrected QTd (46.7 ± 4.7 vs 43.7 ± 4, p = 0.002) were significantly higher in group 1 when compared to group 2. The Tp-e interval (76.5 ± 6.3, 70.3 ± 6.8, p < 0.001), cTp-e interval (83.1 ± 4.3 vs. 76±4.9, p < 0.001), Tp-e/QT (0.20 ± 0.02 vs. 0.2 ± 0.02, p < 0.001) and Tp-e/QTc ratios (0.2 ± 0.01 vs. 0.18 ± 0.01, p < 0.001) were increased in group 1 in comparison to group 2. Significant positive correlations were found between EFT thickness and Tp-e interval (r = 0.548, p < 0.001), cTp-e interval (r = 0.259, p = 0.01), and Tp-e/QT (r = 0.662, p < 0.001) and Tp-e/QTc ratios (r = 0.560, p < 0.001). Conclusion: The present study shows that Tp-e and cTp-e interval, Tp-e/QT and Tp-e/QTc ratios were increased in subjects with increased EFT, which may suggest an increased risk of ventricular arrhythmia.