866 research outputs found
A PLL-based multirate structure for time-varying power systems harmonic/interharmonic estimation
This paper describes a phase-locked-loop (PLL)-based power systems harmonic estimation algorithm, which uses an analysis filter bank and multirate processing. The filter bank is composed of bandpass filters. The initial center frequency of each filter is purposely chosen to be equal to harmonic frequencies. However, an adaptation strategy makes it possible to track time-varying frequencies as well as interharmonic components. A downsampler device follows the filtering stage, reducing the computational burden, especially because undersampling operations are performed. Finally, the last stage is composed of a PLL estimator which provides estimates for amplitude, phase, and frequency of the input signal. The proposed method improves the accuracy, computational effort, and convergence time of the previous harmonic estimator based on cascade PLL configuration
A novel model of tumour formation in NF1
Neurofibromatosis type 1 (NF1) is a common genetic disorder that predisposes to the
development of heterogeneous tumours of Schwann cell origin, termed neurofibromas.
Neurofibromas are thought to arise from a combination of genetic events – loss of the
Ras-GAP neurofibromin in the Schwann cell lineage – and microenvironmental cues.
Schwann cells are specialised cells that ensheath and myelinate the axons in the
peripheral nervous system (PNS). In the adult they are present in a quiescent state,
however following damage to the PNS they have a remarkable ability to regenerate.
Distal to the site of injury, Schwann cells dedifferentiate to a progenitor-like state, in
which they contribute to nerve repair by recruiting a robust inflammatory response
and helping axons return to their targets. Work from our laboratory has shown that
activation of the Ras/Raf/ERK pathway plays a central role in driving the switch in
Schwann cell state from a fully differentiated to a proliferating, “progenitor-like” cell.
Crucially, neurofibromas resemble injured nerves in that they are composed of a
mixture of inflammatory cells and Schwann cells that are found dedifferentiated and
dissociated from axons, suggesting that deregulation of Ras/ERK may trigger
tumourigenic events.
In this thesis I present work on how the Ras/Raf/ERK pathway may be regulated in
Schwann cells. I show that the phosphatase MKP3 may be involved in controlling the
levels of ERK activity in Schwann cells during differentiation and following nerve injury.
I also describe a new model for neurofibroma formation. Using transgenic mice I show
that Nf1 loss in adult, myelinating Schwann cells has no effect on peripheral nerves and
does not induce tumourigenesis. However, when coupled with an injury, the mice
developed tumours at a high frequency. Furthermore, I show that in the absence of
Nf1, ERK signalling is deregulated upon injury, implicating this pathway in the tumour
formation. This may have therapeutic relevance, which is currently being tested in our
animal model. In addition, we observed that tumours only arise at the wound site,
despite Schwann cells dedifferentiating along the length of the nerve. This strongly
implies that the microenvironment is a crucial player in the outcome of Nf1 loss and
reveals this new animal model as a promising system to further dissect molecular
events involved in tumourigenesis
The secret language of destiny: stress imprinting and transgenerational origins of disease
Epigenetic regulation modulates gene expression without altering the DNA sequence to facilitate rapid adjustments to dynamically changing environmental conditions. The formation of an epigenetic memory allows passing on this information to subsequent generations. Here we propose that epigenetic memories formed by adverse environmental conditions and stress represent a critical determinant of health and disease in the F3 generation and beyond. Transgenerational programming of epigenetic regulation may represent a key to understand adult-onset complex disease pathogenesis and cumulative effects of life span and familial disease etiology. Ultimately, the mechanisms of generating an epigenetic memory may become of potentially promising diagnostic and therapeutic relevance due to their reversible nature. Exploring the role of environmental factors, such as stress, in causing variations in epigenetic profiles may lead to new avenues of personalized, preventive medicine based on epigenetic signatures and interventions
Occurrence of chiral bioactive compounds in the aquatic environment: A review
In recent decades, the presence of micropollutants in the environment has been extensively studied due to their high frequency of occurrence, persistence and possible adverse effects to exposed organisms. Concerning chiral micropollutants in the environment, enantiomers are frequently ignored and enantiomeric composition often neglected. However, enantioselective toxicity is well recognized, highlighting the need to include enantioselectivity in environmental risk assessment. Additionally, the information about enantiomeric fraction (EF) is crucial since it gives insights about: (i) environmental fate (i.e., occurrence, distribution, removal processes and (bio)degradation); (ii) illicit discharges; (iii) consumption pattern (e.g., illicit drugs, pharmaceuticals used as recreational drugs, illicit use of pesticides); and (iv) enantioselective toxicological effects. Thus, the purpose of this paper is to provide a comprehensive review about the enantioselective occurrence of chiral bioactive compounds in aquatic environmental matrices. These include pharmaceuticals, illicit drugs, pesticides, polychlorinated biphenyls (PCBs) and polycyclic musks (PCMs). Most frequently analytical methods used for separation of enantiomers were liquid chromatography and gas chromatography methodologies using both indirect (enantiomerically pure derivatizing reagents) and direct methods (chiral stationary phases). The occurrence of these chiral micropollutants in the environment is reviewed and future challenges are outlined. © 2017 by the authors.This work was developed at Laboratory of Environmental Research area/Environmental and Applied Chemistry research line of the IINFACTS-CESPU. The authors acknowledge the financial support from PARMADRUGS-CESPU-2014 and ChiralDrugs_CESPU_2017. This research was partially supported through national funds provided by FCT/MCTES: Foundation for Science and Technology from the Minister of Science,
Technology and Higher Education (PIDDAC) and European Regional Development Fund (ERDF) through the
COMPETE: Programa Operacional Factores de Competitividade (POFC) programme, under the Strategic Funding
UID/Multi/04423/2013, in the framework of the programme PT2020. ARR and MSM acknowledge Fundação para
a Ciência e Tecnologia (FCT) for their grants, SFRH/BD/86939/2012 and SFRH/BPD/101703/2014, respectivel
PCR identification of Mycobacterium tuberculosis complex in a clinical sample from a patient with symptoms of tuberculous spondylodiscitis
A 42-year-old male complaining of thoracic spine pain was admitted to the hospital for evaluation. An X-ray and computer tomography of the thoracic spine showed spondylodiscitis of the L3 lumbar and L2-L3 intervertebral disk. The tuberculin skin test (PPD) was strongly positive. A radioscopy-guided fine needle aspirate of the affected area was cultured but did not reveal the cause of the disease. Two biopsy attempts failed to reveal the cause of the disease by culturing or by acid-fast-resistant staining (Ziehl Neelsen) of the specimens. A third biopsy also failed to detect the infectious agent by using microbiological procedures, but revealed the presence of a 245-bp amplicon characteristic of the Mycobacterium tuberculosis complex after PCR of the sample. The result demonstrates the efficacy of PCR for the identification of M. tuberculosis in situations in which conventional diagnosis by culturing techniques or direct microscopy is unable to detect the microorganism. Following this result the patient was treated with the antituberculous cocktail composed by rifampicin, pirazinamide and isoniazid during a six-month period. At the end of the treatment the dorsalgia symptoms had disappeared
Impacts of the SARS-CoV-2 pandemic on the global demand for exotic pets: An expert elicitation approach
The SARS-CoV-2 pandemic has caused immense social and economic costs worldwide. Most experts
endorse the view that the virus has a zoonotic origin with the final spillover being associated
with wildlife trade. Besides human consumption, wild animals are also extensively traded as pets.
Information on zoonotic diseases has been reported to reduce consumer demand for exotic pets.
We conducted a global survey and collected 162 responses from international experts on exotic
pet trade (traders, academics, NGOs, enforcement entities) to understand how the legal and illegal
trade of exotic pets is expected to be affected by the ongoing coronavirus pandemic. Our results
suggest that legal purchase of exotic pets is perceived as decreasing during the first pandemic
wave due to: lower availability of animals for trade, suppliers’ inability to reach consumers and
social distancing measures. The general perception is that in the future (i.e., next five years), both
demand and supply of legally traded exotic pets are expected to either remain unchanged or
decrease only temporarily. The consumer demand for illegal exotic pets is also expected to remain
unchanged following the outbreak. The top two challenges reported by respondents, when
considering the consequences of the pandemic for the exotic pet trade, are inadequate enforcement
of national regulations and increased illegal trade. Our results suggest that the negative
consequences of a zoonotic outbreak may not dissuade consumers of exotic pets. Worldwide, the
transit/storing conditions and lack of health screenings of traded live animals are conducive to
spreading diseases. Consumer demand is a key driver of trade, and enforcement of trade regulations
will remain challenging, unless factors driving consumer demand are adequately incorporated
in problem-solving frameworks. We emphasize the complexity of trade dynamics and the
need to go beyond bans on wildlife trade. Stronger law enforcement, implemented along with
initiatives dissuading consumption of wild exotic pets, are essential to sustainably satisfy the
market demandinfo:eu-repo/semantics/publishedVersio
Multiplicity in Supersymmetric Spin Chains
We discuss a simple procedure for obtaining new integrable spin chains from
old by replacing each single state of the original model by some collection of
states. This works whenever the Lax matrix of the chain has a certain form. The
simplest example is the su(n) XX model. We apply the techniques of the nested
algebraic Bethe ansatz to solve such systems, in the bosonic and supersymmetric
cases.Comment: 14 pages. v2: Added references and minor corrections; v3:
Acknowledgement adde
Evolution of community structure in the world trade web
In this note we study the bilateral merchandise trade flows between 186
countries over the 1948-2005 period using data from the International Monetary
Fund. We use Pajek to identify network structure and behavior across thresholds
and over time. In particular, we focus on the evolution of trade "islands" in
the a world trade network in which countries are linked with directed edges
weighted according to fraction of total dollars sent from one country to
another. We find mixed evidence for globalization.Comment: To be submitted to APFA 6 Proceedings, 8 pages, 3 Figure
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