Q-enhancement with on-chip inductor optimization for reconfigurable Δ-Σ radio-frequency ADC

The paper details on-chip inductor optimization for a reconfigurable continuous-time delta-sigma (Δ-Σ) modulator based radio-frequency analog-to-digital converter. Inductor optimisation enables the Δ-Σ modulator with Q enhanced LC tank circuits employing a single high Q-factor on-chip inductor and lesser quantizer levels thereby reducing the circuit complexity for excess loop delay, power dissipation and dynamic element matching. System level simulations indicate at a Q-factor of 75 Δ- Σ modulator with a 3-level quantizer achieves dynamic ranges of 106, 82 dB and 84 dB for RFID, TETRA, and Galileo over bandwidths of 200 kHz, 10 MHz and 40 MHz respectively.

Evolution of the extracellular matrix in deuterostomes and the influence of calcitropic hormones

Tese de dout., Biologia (Biologia Molecular), Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2010

Recent developments in the Portuguese nut sector

This work aims to present the main results of an overview study of the nut sector in Portugal. Within the group of horticultural products, different kinds of nuts have been receiving financial supports for several years. The objective was the achievement of a technical recovery and the improvement of commercial organisations. In spite of this help, the sector does not show a clear signal of dynamism. In this study, information has been taken from data series on production, exports and imports and also about empirical approaches on market mechanismsT. hese instruments have helpedt o better identify problems that seemto be responsible for the lack of performance of the Portuguese nut sector in international markets.

How hydrogen peroxide and CXCL8 modulate neutrophil recruitment "in vivo"

Tese de doutoramento, Ciências Biomédicas (Biologia Celular e Molecular), Universidade de Lisboa, Faculdade de Medicina, 2014

The role of alpha-synuclein phosphorylation in synucleinopathies

Tese de doutoramento, Ciências Biomédicas (Neurociências), Universidade de Lisboa, Faculdade de Medicina, 2014

Adaptive digital receivers for analog front-end mismatch correction

Phase and gain mismatches between the I and Q analog signal processing paths of a quadrature receiver are responsible for the generation of image signals which limit the dynamic range of a practical receiver. In this paper we analyse the effects these mismatches and propose a low-complexity blind adaptive algorithm to minimize this problem. The proposed solution is based on two, 2-tap adaptive filters, arranged in Adaptive Noise Canceller (ANC) set-up. The algorithm lends itself to efficient real-time implementation with minimal increase in modulator complexity.

Characterization of adenosinergic system in Rett syndrome

Tese de mestrado, Neurociências, Faculdade de Medicina, Universidade de Lisboa, 2015

The effect of clock jitter on the performance of continuous-time delta-sigma ADC for GNSS signals

Next generation Global Navigation Satellite System (GNSS) receivers will operate in multiple navigation bands. An efficient way to achieve this with lower power and cost is to employ BandPass Sampling (BPS); nevertheless, the sampling operation injects large amounts of jitter noise, which degrades the performance of the receiver. Continuous–Time (CT) Delta–Sigma (ΔΣ) modulators are capable of suppressing this noise but the impact of clock jitter at the output of the Digital– to–Analog Converter (DAC) in the feedback path of the modulator should be taken into account. This paper presents an analytical approach for describing clock jitter in GNSS receivers when a CT–ΔΣ modulator is utilized for Analog–to–Digital Conversion (ADC). The validity of the presented approach is verified through time–domain simulations using a behavioural model of the fourth–order CT–ΔΣ modulator with 1–bit NRZ DAC feedback pulse.

Evaluation of nonlinear distortion in MIMO transmitters

In this paper, an evaluation of unwanted effects in Multiple Input Multiple Output (MIMO) transmitters is described. Complete 2×2 and 4×4 MIMO Orthogonal Frequency Division Multiplex (OFDM) transmitters are simulated for the purpose of quantifying all potential unwanted effects such as Power Amplifiers' (PAs) nonlinearity, linear and nonlinear crosstalk, and IQ modulator imperfections. An experimental analysis of a 2×2 MIMO transmitter using two-tones and WCDMA signal is presented.

中国四个城市吸引海外回流人才比较研究：一个政策的视角 (Returned highly skilled migrants in four Chinese cities: a policy perspective)

Most studies of returned highly skilled migrants in China were guided by a national approach, emphasizing how the size and direction of the return migration were shaped by national policies and practices. What have been overlooked are the flows of returned skills at the municipal level where talent attraction and employment really take place. To fill this gap, the author conducted a comparative study of the returned highly-skilled migration in Beijing, Shanghai, Guangzhou and Shenzhen, the four most important cities in China. Based on in-depth interviews with returned skills from different countries and with various occupational backgrounds, complemented by the analysis of talent policies that have been issued by each city since the early 1990s and relevant statistical data, this study finds that, first, municipal cities tend to make ‘localized policies’ in order to suit local situation and to increase flexibility and efficiency in their effort of enticing of talents, demonstrating a wide range of variations not yet discussed in previous literature. It is thus crucial to pay timely attention to municipalities in order to obtain a more accurate and balanced picture of returned skilled migration in China. Second, the flow of returned skills shall be perceived in a broader analytical framework, in which the attractiveness to skills comes mostly from the long-term career potentials made possible by the industrial structure of individual city and mediated by social, cultural and geographical factors. It is only within this larger framework and through the interaction with other factors that government policies play their modulator roles.

Aggregation Limits Surface Expression of Homomeric GluA3 Receptors

AMPA receptors are glutamate-gated cation channels assembled from GluA1-4 subunits and have properties that are strongly dependent on the subunit composition. The subunits have different propensities to form homomeric or various heteromeric receptors expressed on cell surface, but the underlying mechanisms are still poorly understood. Here, we examined the biochemical basis for the poor ability of GluA3 subunits to form homomeric receptors, linked previously to two amino acid residues, Y454 and R461, in its ligand-binding domain (LBD). Surface expression of GluA3 was improved by co-assembly with GluA2 but not with stargazin, a trafficking chaperone and modulator of AMPA receptors. The secretion efficiency of GluA2 and GluA3 LBDs paralleled the transport difference between the respective full-length receptors and was similarly dependent on Y454/R461, but not on LBD stability. In comparison to GluA2, GluA3 homomeric receptors showed a strong and Y454/R461-dependent tendency to aggregate both in the macroscopic scale measured as lower solubility in nonionic detergent and in the microscopic scale evident as the preponderance of hydrodynamically large structures in density gradient centrifugation and native gel electrophoresis. We conclude that the impaired surface expression of homomeric GluA3 receptors is caused by nonproductive assembly and aggregation to which LBD residues Y454 and R461 strongly contribute. This aggregation inhibits the entry of newly synthesized GluA3 receptors to the secretory pathway.

Low Complexity All-Pass Based Polyphase Decimation Filters for ECG Monitoring

This paper presents a low complexity high efficiency decimation filter which can be employed in EletroCardioGram (ECG) acquisition systems. The decimation filter with a decimation ratio of 128 works along with a third order sigma delta modulator. It is designed in four stages to reduce cost and power consumption. The work reported here provides an efficient approach for the decimation process for high resolution biomedical data conversion applications by employing low complexity two-path all-pass based decimation filters. The performance of the proposed decimation chain was validated by using the MIT-BIH arrhythmia database and comparative simulations were conducted with the state of the art.

Platelets induce Pai-1 mRNA expression in monocytes through TGF-BETA

Introduction: Plasminogen activator inhibitor type-1 (PAI-1) is a physiological modulator of fibrinolysis. High plasma PAI-1 is associated with the 4G/5G promoter polymorphism and with increased cardiovascular risk. Here we explored the role of platelets in regulating expression of the PAI-1 gene in monocytes. Methods: Blood from PAI-1 4G/5G genotyped volunteers (n=6) was incubated with the platelet GPVI-specific agonist, cross-linked collagen related peptide (CRP-XL), in the presence or absence of Mab 9E1 that blocks the binding of P-selectin to PSGL1. Monocytes were isolated by +ve selection on CD14 beads and monocyte PAI-1 mRNA expression was measured by real-time PCR. Results: Activation of platelets with CRP-XL resulted in platelets binding to >70% of monocytes and was accompanied by >5000-fold induction of PAI-1 mRNA, peaking at 4hrs. PAI-1 expression was independent of the 4G/5G genotype. Blocking the binding of platelets to monocytes enhanced PAI-1 induction (p<0.05 at 4 hrs). Incubation of isolated monocytes with the releasate from CRP-XL stimulated platelets also led to PAI-1 mRNA expression. The platelet secretome contains >100 different proteins. To identify the soluble factor(s) responsible for induction of PAI-1, neutralizing antibodies to likely candidates were added to monocytes incubated with the platelet releasate. Anti- TGF-beta inhibited platelet releasate-mediated PAI-1 mRNA induction by >80%. Monocyte PAI-1 was also induced by stimulation of PSGL-1 with a P-selectin-Fc chimera, in the absence of platelets, which was also blocked by the TGF-beta antibody. Conclusions: These results suggest that platelets induce PAI-1 mRNA in monocytes predominantly via TGF-beta, released from both platelets, and monocytes via activation by PSGL-1 signalling.This stimulation is independent of 4G/5G genotype

NFC RF Analog Challenge and Enhanced High Speed Transmitter Design

This paper investigates the inherent radio frequency analog challenges associated with near field communication systems. Furthermore, the paper presents a digital based sigma-delta modulator for near field communication transmitter implementations. The proposed digital transmitter architecture is designed to best support data intensive applications requiring higher data rates and complex modulation schemes. An NFC transmitter based on a single-bit sigma-delta DAC is introduced, and then the multi-bit extension with necessary simulation results are presented to confirm the suitability of the architecture for near field communication high speed applications.

Estudo comparativo entre sistemas RoF com modulação directa e com modulação externa

O RoF (Radio over Fiber) é uma tecnologia que permite a transmissão de sinais rádio de elevada largura de banda, fornecida pela fibra óptica, e simultaneamente mantêm a característica de mobilidade das redes de comunicação móvel. Esta dissertação de mestrado tem como objectivo estudar, simular e comparar sistemas RoF com modulação directa e com modulação externa, utilizando um sinal WiMAX, por ser uma tecnologia recente e com potencial de utilização futura. Desta forma foram avaliados três tipos de moduladores externos, sendo que o modulador EA (Electro-Absorption) é o que permite obter melhores valores de EVM e de SNR devido ao facto deste ter menores perdas de inserção na fibra. Da comparação entre o esquema com modulação directa e o esquema com modulação externa, é possível concluir que para larguras de banda mais baixas a utilização de modulação directa é mais eficiente que a modulação externa, mas à medida que a largura de banda aumenta a modulação externa apresenta claramente melhor desempenho. Isto deve-se ao facto de a modulação directa produzir mais chirp que a modulação externa, sendo que o chirp limita a largura de banda e o comprimento da fibra. De forma a melhorar o desempenho do sistema com modulação directa foi introduzido uma fibra com compensação de dispersão. Foi possível concluir que a utilização de fibra com compensação de dispersão é uma boa solução quando se pretende transmitir sinais de elevada largura de banda em esquemas com modulação directa.