Repositório Institucional da Universidade de Aveiro
Not a member yet
41903 research outputs found
Sort by
Survival Rate of Dental Implants in Patients with History of Periodontal Disease: A Retrospective Cohort Study
No full textPurpose – To evaluate the differences between the survival rates of implants placed in patients with no history of periodontal disease (NP) and in patients with history of chronic periodontal disease (CP).
Materials and Methods – A retrospective cohort study was conducted in which all consenting patients treated with dental implants in a private clinic in Oporto, Portugal, from November 2, 2002 through February 11, 2011 were included. All patients were treated consecutively by the same experimental operator.
This study aimed to analyze how the primary outcomes (presence of disease, time of placement and time of loading) and the secondary outcomes (severity generalized periodontitis, brand, implant length, prosthesis type, prosthesis metal-ceramic (PFM) extension) influence the survival rate of dental implants.
The survival analysis was performed through the Kaplan-Meier method and the equality of survival distributions for all groups was tested with the log-rank test with a significance level of 0.05 for all comparisons.
Results - The sample consisted of 202 patients (47% NP and 53% CP) and 689 implants (31% NP and 69% CP). The survival rate in NP and CP groups showed no statistically significant differences (95.8% versus 93.1%, p>=0.05). Implants were lost before loading in 54.9% of the cases. The majority of the implants were lost in the first year and stabilized after the second year.
Survival rates in NP and CP patients showed no statistically significant differences when comparing the following factors: sub-classification of the disease, implant brands, implant length (short/standard), type of prosthesis, extension of the PFM and time of placement and loading (p>=0.05).
Conclusions –This work disclosed no statistically significant differences in terms of survival rates when compared to the control group. Placing implants in patients with a history of periodontal disease appears to be viable and safe
Formação para a Promoção do Espírito Empresarial
No full textDoutoramento em Gestão IndustrialO presente trabalho pretende contribuir de algum modo para a compreensão
do fenómeno da formação para a promoção do espírito empreendedor,
principalmente entre os alunos finalistas da Universidade de Aveiro.
Após uma revisão de literatura nos domínios do empreendedorismo, da
formação de adultos e do ensino do empreendedorismo e empresariado foi
desenvolvida uma acção de intervenção/formação que decorreu integrada num
Curso de Empresariado que se desenvolveu na Universidade de Aveiro, no 1º
semestre de 1999.
Durante esta acção foram concretizadas algumas medidas tendentes a
procurar resposta às questões de investigação que inicialmente nos
propusemos, nomeadamente se um programa de intervenção (ensino/
aprendizagem) sobre empreendedorismo produz efeitos positivos ao nível da
mudança de atitudes nos formandos, se o programa que tem sido seguido é
susceptível de ser melhorado e como, e se um só programa será conveniente
para uma população tão heterogénea.
Este nosso trabalho de investigação qualitativa do tipo caso único, embora
apenas com valor exploratório permite sugerir que será possível desenvolver
algumas competências conducentes ao incremento do espírito empreendedor
entre os elementos da população alvo destes cursos de formação em
empresariado.This peace of research aims at the comprehension of the phenomenon of
training to promote the entrepreneurial spirit, principally amongst last year
students of the U.A.
After a literature review in the domains of entrepreneurship, adult training and
the education of entrepreneurship and enterprise, a training intervention was
developed, which was integrated in a course of enterprise that took place at the
U.A, in the first semester of 1999.
During this action, same measures were implemented that tended to seek an
answer to the research questions, which were initially suggested. It was of
particular interest to understand if an intervention program (education/learning)
about entrepreneurship produces positive effects in terms of attitude change of
trainees, if the program that was implemented could be improved and if so,
how, and finally, if just one program would be convenient for such a
heterogeneous population.
This work of qualitative research, of the type of a “unique case”, although only
of an exploratory nature, helps to suggest means to develop competences that
might improve the entrepreneurial spirit amongst the target population of these
courses of enterprise
Between Shi and Ish
No full textWe introduce a new family of hyperplane arrangements in dimension n≥3 that includes
both the Shi arrangement and the Ish arrangement. We prove that all the members of a given subfamily have the same number of regions – the connected components of the
complement of the union of the hyperplanes – which can be bijectively labeled with the Pak–Stanley labeling. In addition, we show that, in the cases of the Shi and the Ish
arrangements, the number of labels with
reverse centers of a given length is equal, and conjecture that the same happens with all of the members of the family
Development of an ITS-G5 station, from the physical to the MAC layer
No full textWireless vehicular networks for cooperative Intelligent Transportation Systems (ITS) have raised widespread interest in the last few years, due to their potential applications and services. Cooperative applications with data sensing, processing and communication provide an unprecedented potential to improve vehicle and road safety, passenger’s comfort and ef ciency of traf c management and road monitoring. Safety, ef ciency and comfort applications envisaged for ITS exhibit tight latency and throughput requirements. For example safety critical services require guaranteed maximum latencies lower than 100 ms, while most infotainment applications require QoS support and data rates higher than 1 Mbit/s. In this context, BRISA, a motorway operator, challenged a team from Institute of Telecommunications (IT) to contribute with research in this area, to work speci cally on the then emergent IEEE 802.11p amendment. Back then, standards in this eld were (and still are) evolving and only a very limited number of Commercially Off The Shelf (COTS) components were available. Available COTS chip sets implemented an incomplete stack and, more importantly, have closed implementations (black box) of the standard, with a limited access to the API and programming model. This was an impairment to BRISA track record on open access to technology and independence from manufacturers. On the other hand, from the point of view of a research institution as IT, having the chance of developing from scratch, new technology and draft protocol implementations was considered quite relevant, as it potentiates the inclusion of innovative solutions beyond standards. Examples of such innovative solutions include support for real-time operation and fault-tolerance mechanisms. That was the rationale behind the development of a new ITS-G5 station, which will be described in a tutorial way in this chapter. The chapter presents the architecture of the PHY and MAC layers developed, including the RF front- end, the baseband PHY processing chains, the time sensitive lower MAC implementation and the software upper MAC. The most important design decisions, the validation methodologies and the interoperability tests are also discussed. The chapter ends with the presentation of the real-time extensions and primitives of the platform enabling the implementation of real-time protocols
Introduction to Intelligent Transportation Systems
No full textTransportation systems are very important in modern life; therefore, massive research efforts has been devoted to this field of study in the recent past. Effective vehicular connectivity techniques can significantly enhance efficiency of travel, reduce traffic incidents and improve safety, alleviate the impact of conges- tion; devising the so-called Intelligent Transportation Systems (ITS) experience. This chapter aims to provide basic concepts and background that is useful for the understanding of this book. An overview of intelligent transportation systems and their applications is presented, followed by a brief discussion of vehicular com- munications. The chapter also overviews the concepts related to dependability on distributed real-time systems in the scope if ITS
Estudo dos hábitos alimentares, comportamento e teste da hipótese de competição entre limícolas invernantes na ria de Aveiro : o caso do borrelho-grande-de-coleira (Charadrius hiaticula L.)
No full textMestrado em Ciências das Zonas CosteirasEncontrando-se entre os ecossistemas mais produtivos do globo, as zonas
húmidas são actualmente alvo de profunda intervenção humana, pelo que a
superfície por elas ocupada tem vindo a diminuir.
A Ria de Aveiro não é uma excepção, encontrando-se já profundamente
artificializada. Desde o início da sua formação, por volta do século X, esta
laguna começou a ser usada (e modificada) pelos habitantes da região.
A maioria das espécies de aves limícolas utiliza as zonas costeiras, e em
particular os ecossistemas estuarinos, como áreas de invernada. A Ria de
Aveiro assume importância ornitológica internacional, uma vez que alberga
mais de 1% de algumas populações invernantes da Europa, como o Borrelhogrande-
de-coleira, Charadrius hiaticula, espécie ainda pouco estudada neste
local.
No presente trabalho propõe-se, então, investigar alguns aspectos relativos à
biologia desta espécie, nomeadamente a fenologia da população invernante,
os seus hábitos alimentares e ainda o comportamento nas zonas de
alimentação.
O trabalho de campo foi realizado no Canal de Mira, teve início em Setembro
de 2000 e findou em Março de 2002.
Foram efectuados censos de baixa-mar e determinada a distribuição
geográfica dos indivíduos nos vários sectores da área de estudo, utilizados já
em trabalhos anteriores.
Verificou-se um padrão de variação do número de indivíduos bastante
semelhante nas duas épocas de invernada.
Durante a alimentação, os indivíduos apresentam preferência por quatro dos
sectores considerados, provavelmente pelas suas características ao nível da
disponibilidade de alimento e propriedades do sedimento. A perturbação
humana foi também considerada, tendo sido determinado o número de
mariscadores presentes em cada sector do Canal de Mira.
Para a investigação dos hábitos alimentares foram colhidos e analisados
dejectos produzidos nos locais de alimentação. Foi também feita a colheita de
sedimento nos mesmos locais. Poliquetas e Gasterópodes (Hydrobia ulvae)
constituem as principais presas do Borrelho-grande-de-coleira.
Através de observações individuais e aleatórias, foi possível quantificar o
tempo dispendido pelas aves nas diversas actividades. Assim, durante o
período de baixa-mar, grande percentagem do tempo (cerca de 90%) é
dedicado à alimentação enquanto que, durante a enchente, as aves se
aplicam também nos cuidados com as penas (actividades de conforto). No que
respeita a vasante, a alimentação é também a actividade predominante.
Esta espécie apresenta algum gregarismo e, aparentemente, ocorrem
fenómenos de competição intra-específica. Partilha muitas vezes os locais de
alimentação com Charadrius alexandrinus e Calidris alpina; foram observados
comportamentos agressivos para com os primeiros, não tendo ocorrido
quaisquer situações reveladoras de competição inter-específica com C. alpina.
A necessidade de investigação, visando a obtenção de técnicas e processos
de recuperação e gestão urge nas zonas húmidas. Nesta linha de pensamento
fica sublinhado o interesse que teria, em trabalhos futuros, a investigação do
uso das restantes áreas da Ria de Aveiro por parte do Borrelho-grande-decoleira,
principalmente as salinas, locais onde também ocorre, não só para a
alimentação como para refúgios de preia-mar.Being one of the globe’s most productive ecosystems, the wetlands have
suffered profound human intervention, thus reducing their surface occupation
ratio.
The Ria de Aveiro is no exception, as it has been deeply artificialized. Since
the beginning of its formation, around the 10th century, the inhabitants of this
region have used (and modified) this lagoon.
The majority of the wader species exploit the coastal zones, and in particular,
the estuarine ecosystems as wintering areas. The Ria de Aveiro withholds an
international ornithological importance as it holds more than 1% of some of the
wintering populations of Europe, such as the Ringed Plover, Charadrius
hiaticula, a relatively understudied specie in this region.
The present dissertation investigates some of this species’ biological relative
aspects, namely its wintering population distribution and variation, its feeding
habits and its behaviour in the feeding areas.
The field work, performed in the Mira Channel, commenced in September,
2000, concluded in March, 2002.
Low-tide censuses were carried out and the geographic distribution of the
birds in the various study areas sectors, analysed in previous work, was
determined.
A pattern in the variation of the number of birds was detected, being quite
simillar in the two winter seasons studied.
During feeding, the Ringed Plover individuals present a preference for four of
the proposed sectors, probably because of their characteristics regarding food
availability and sediment properties. The shellfish gatherers’ distribution was
determined and therefore the human disturbance factor was weighed into the
analysis.
Excrement recovered from feeding spots were analysed for feeding habits
investigation. Sediment samples were also gathered from the same sites.
Ringed plover feasts mainly on polychaetes and gastropods (Hydrobia ulvae).
The average time used by birds in different activities was quantified through
individual and random observations. Thus, during low-tide periods a high time
is spent feeding, while during flood the birds apply themselves in feather
tending (comfort activities). Feeding is also predominant as the tides rush out.
The species present some gregarism and, apparently, exhibit intra-specific
competition phenomena. These birds share the feeding sites with Charadrius
alexandrinus and Calidris alpina; aggressive behaviour towards the first was
observed whilst no inter-specific competition was detected toward the latter.
Wetland investigation is urgent for defining techniques, recuperation
processes and management. Moreover the interest, here underlined, in future
work, other areas of the Ria de Aveiro, namely of the salt-pans, which Ringed
plovers also seek, not only for feeding but also for high-tide refuge
Aspectos de dimensionamento de redes MPLS: optimização de nós e ligações
No full textMestrado em Engenharia Electrónica e de TelecomunicaçõesEsta dissertação estuda o problema do dimensionamento de redes de
telecomunicações baseadas na tecnologia MPLS (MultiProtocol Label
Switching). O problema estudado considera a perspectiva de um
operador de telecomunicações que tem como objectivo a determinação
da rede física de menor custo capaz de suportar o tráfego esperado.
Neste trabalho considera-se tanto o dimensionamento das ligações entre
nós como o dimensionamento dos equipamentos a instalar nos nós. Os
dois problemas considerados são resolvidos sequencialmente, sendo
cada um modelado como um problema de Programação Linear Inteira.
O problema do dimensionamento das ligações é, para instâncias
realistas, demasiado complexo para ser resolvido de forma exacta. Por
esta razão, têm vindo a ser desenvolvidas heurísticas que produzam
resultados satisfatórios em intervalos de tempo aceitáveis. No entanto, a
aplicação de heurísticas levanta o problema da avaliação da qualidade
das soluções obtidas: a qualidade da solução é medida através da
diferença percentual entre o custo da solução obtida e um limite inferior
teórico. Tomando como ponto de partida uma heurística conhecida de
dimensionamento das ligações de redes de telecomunicações, este
trabalho propõe e estuda alguns métodos com vista à determinação de
melhores limites inferiores teóricos. Através dos métodos propostos, foi
possível encontrar limites inferiores substancialmente melhores do que
os anteriormente conhecidos para as soluções dadas pela heurística.
O segundo problema abordado é o problema do dimensionamento dos
nós da rede. Este dimensionamento é feito com base na informação
sobre as ligações a instalar entre cada par de nós (i.e., a solução do
problema do dimensionamento das ligações) e nos equipamentos de
rede (routers e cartas de rede) existentes. A solução deste problema
indica quais os equipamentos a adquirir para cada nó da rede, quais os
que devem ser transferidos de um nó para outro e quais os
equipamentos a armazenar para possível uso futuro. Neste trabalho é
apresentado um modelo de Programação Linear Inteira que descreve o
problema e que permite resolver instâncias realistas do mesmo de forma
óptima em intervalos de tempo curtos.
Finalmente, é apresentada uma ferramenta de dimensionamento de
redes MPLS que integra o dimensionamento das ligações e dos nós da
rede.The present work addresses the problem of dimensioning MPLS based
telecommunications networks. The problem considers the operator point
of view that aims to determine the least cost physical network capable of
routing a given traffic matrix.
Both link and node dimensioning are considered. The overall solution is
obtained by sequentially solving the two problems, which are modelled as
Integer Linear Programming problems.
The link dimensioning problem is, for realistic instances, too complex to
be exactly solved. For this reason, heuristic techniques are being
proposed in the literature to solve this problem in realistic computing
times The use of heuristics raises the problem of assessing the quality of
the obtained solutions: the quality of a solution is given by the percentual
difference between the cost of the solution and a theoretical lower bound.
Using a known link dimensioning heuristic, this work proposes and
studies some methods to compute better lower bounds than the ones
previously known to the solutions of the heuristic.
The second addressed problem is the dimensioning of the
telecommunications network’s nodes. This dimensioning is based on
information obtained from the link dimensioning step (how many
interfaces of which type to install on each link), on available network
equipment (routers and network cards), purchasable or already installed.
The solution to this problem indicates which routers and network cards
must be purchased for each node, which must be transferred between
nodes, which must be stored for future use and which – previously kept in
storage – must be reused. It is proposed an Integer Linear Programming
Model that describes this problem and achieves optimal solutions of
realistic instances in short computing times.
Finally, an MPLS network dimensioning tool integrating both link and
node dimensioning is presented
Estudo do ciclo reprodutor e crescimento de Hydrobia ulvae (Pennant, 1777) na Ria de Aveiro e suas implicações no âmbito da biomonitorização da poluição por TBT
No full textMestrado em Ciências das Zonas CosteirasCom o objectivo de contribuir para a validação da utilização de Hydrobia ulvae
em programas de biomonitorização da poluição por tributilestanho (TBT) na
Ria de Aveiro, foi estudado o seu ciclo reprodutor, crescimento e imposexo
num banco de lodo situado na Ermida (Canal de Ílhavo – Ria de Aveiro). O
local de estudo foi amostrado no período de baixa-mar, entre Dezembro de
1999 e Dezembro de 2000, com uma periodicidade aproximadamente mensal.
O estudo histológico das gónadas de Hydrobia ulvae revelou a existência de
uma época de desova muito alargada, que ocorreu, provavelmente, entre
Julho e Fevereiro.
O comprimento médio do pénis dos machos variou ao longo do ciclo
reprodutor, atingindo valores mais elevados entre o fim do Verão e o início do
Outono, época em que a maturação das gónadas foi mais intensa.
A análise de histogramas de frequência da altura das conchas de Hydrobia
ulvae ao longo do período de estudo revelou a ocorrência de quatro episódios
de recrutamento, em Março, Maio, Julho e Setembro, compostos por animais
com uma altura média da concha entre 1,2 e 1,8 mm. Estima-se que, a partir
desse momento, estes indivíduos terão crescido até 6,4 - 6,8 mm ao fim de
17-21 meses. A longevidade foi calculada em cerca de 2 anos. Verificou-se,
também, a ocorrência de uma variação sazonal na taxa de crescimento, com
valores nulos no Inverno e máximos entre a Primavera e o Outono.
Os índices de imposexo – VDS (sequência do vaso deferente), FPL
(comprimento médio do pénis das fêmeas) e %FA (percentagem de fêmeas
afectadas) – não apresentaram um padrão de variação sazonal ao longo do
período de estudo, mas antes oscilações erráticas em torno de um valor médio
de 1,0, 0,4 e 89%, respectivamente. A evolução do índice de imposexo RPL
(comprimento relativo do pénis das fêmeas) foi, em parte, influenciada pela
variação sazonal do comprimento médio do pénis dos machos.
Não se observaram comportamentos migratórios importantes de Hydrobia
ulvae no local de estudo que tenham influenciado a evolução dos níveis de
imposexo da população ao longo do ano.
Considerando que o valor do índice RPL depende da variação sazonal do
comprimento médio do pénis dos machos, a comparação deste índice entre
populações só é válida se as mesmas se encontrarem em idêntico estádio do
ciclo reprodutor.
Visto que os indivíduos adultos seleccionados para os estudos de imposexo
são substituídos anualmente por animais recrutados no ano anterior, as
campanhas de biomonitorização efectuadas com uma periodicidade anual
podem mostrar uma eventual diminuição dos níveis de poluição por TBT no
futuro.The reproductive cycle, growth and imposex of Hydrobia ulvae were studied at
a muddy flat located at Ermida (Canal de Ílhavo – Ria de Aveiro), aiming the
validation of this species for tributyltin (TBT) pollution monitoring in the Ria de
Aveiro. Sampling was performed at approximately monthly intervals, during low
tide, from December 1999 to December 2000.
The histological study of the gonads of Hydrobia ulvae showed that egg
spawning occurred during a long period, probably from July to February.
A variation of the male penis length was observed along the reproductive cycle,
with maximum values registered during the ripening of the testis, which
occurred mainly between late summer and early fall.
The analysis of the frequency histograms of the Hydrobia ulvae shell height
showed the occurrence of four annual recruitments - in March, May, July and
September - composed by animals with 1.2-1.8 mm shell height. These
specimens probably grew up to 6.4 - 6.8 mm after 17-21 months. The longevity
was estimated to be of about 2 years. There was a clear seasonal variation of
the growth rate with null values in the winter and maximum values between the
spring and the fall.
The evolution of the imposex indices along the year – VDS (vas deferens
sequence), FPL (female penis length) and %FA (percentage of affected
females) – didn't show any seasonal pattern but rather an erratic oscillation
around a mean value of 1.0, 0.4 and 89%, respectively. However, the evolution
of the RPL (relative penis length) index was, in part, induced by the seasonal
variation of the male penis length.
Hydrobia ulvae did not show strong migratory movements at the sampling
station that could have influenced the imposex levels of the population.
Considering that RPL is influenced by the variation of the male penis length,
the use of RPL for imposex comparisons between populations ought to be
performed on individuals at approximately the same reproductive stage.
Since the specimens selected for imposex studies are substituted every year in
the population by the animals recruited one year before, the biomonitoring
surveys that are repeated on an annual basis may depict any possible
reduction of TBT pollution levels in the future
On the dynamics of accelerated observers in Special Relativity
No full textThis paper investigates the dynamics of the motion of accelerated observers in Special Relativity (SR) theory. The
presented discussion highlights the memristive character of the
force dynamics, when velocity takes the role of state variable. Under this state-space representation, both spatial and time components of the four-force exhibit distinct memristive dynamics, with pinched
hysteresis loops, similar to the dynamics of an ideal memristor. This
contribution establishes that non-volatile information retention is
for this case equivalent to uniform motion. This observation allows
for an interpretation of memory effects as the consequence of a conservation law, in this case, conservation of linear moment
Health status, living arrangements, and service use at 100: findings from the Oporto centenarian study
No full textThis paper describes the sociodemographic characteristics,
health status, and service use of centenarians living in the
community and centenarians residing in an elder care facility/
nursing home and examines their main differences.
Participants were 140 centenarians from the populationbased
Oporto Centenarian Study (Mage = 101.2; SD = 1.6).
Main findings revealed that the majority of the centenarians
lived at home with their family members (57.9%). Increased
health care needs, living alone, and family caregiving constraints
were the most common reasons for entering a nursing
home. Community-dwelling centenarians were cared for
mostly by their children and were less dependent and in better
cognitive health than those who resided in a nursing home.
Differences were found in the pattern of health service use
according to the centenarians’ residence, ability to pay medical
expenses, and dependency level. Findings highlight the need
for an accurate assessment of caregiving support systems,
particularly family intergenerational duties, and of the factors
constraining the access and use of health and social services.
Policy makers may be guided by the insights gained from this research and work toward improvement of support options and removal of barriers to service access