6,936 research outputs found
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
Journal of Applied Hydrography
Fokusthema: International Issue: Joint publication by AFHy and DHyG for HYDRO 2
Developing active biomaterials for implantable devices: platforms to investigate capacitive charge based control of biofouling
Implantable devices, in particular biosensors, have clear utility within medicine, but face a hurdle
to long-term function due to adsorption of biomolecules (biofouling) and subsequent immune re-
sponse to implants, the foreign body response (FBR). Strategies to control this immune reaction
have included material selection, drug release and, more recently, engineered surface properties.
The increasing use of embedded electronics within many classes of implanted devices presents an
opportunity to exploit electromagnetic phenomena at the device surface to mitigate biofouling and
FBR. Such active biomaterials would allow dynamic modification of the apparent material properties
of an implanted device.
A hypothesis was developed that biological interaction with a biomaterial surface can be altered
by capacitive charging. A platform was constructed to test this and related hypotheses around cell
and protein surface interactions in vitro and adapted into a second platform for initial characterisa-
tion work on an early in vivo model using chick eggs. These platforms were designed to be easy
to fabricate and to provide multiple electrical connections into a substrate in contact with biological
solutions or tissue.
Electrodes were fabricated from fluoropolymer coated tantalum pentoxide, a high-κ dielectric,
and compared against adjacent, identically coated, silicon dioxide regions. Cells from the MDA-
MB-231 cancer cell line were cultured on these regions under electrical stimulation. A voltage de-
pendent reduction of cell attachment and spreading was detected on capacitively charged surfaces
compared to uncharged controls. The tentative results, suggest capacitively charged surfaces hold
promise as active biomaterials. A second cell type MCF-7 did not reproduce the effect, implying
a more coherent understanding is required of the mechanisms behind cell surface interactions on
these surfaces.
Multiple independent bioelectrochemical cell-surface interactions were observed using the plat-
form and several quantification techniques were successfully employed. It is therefore argued that
the platform may have wide applicability as a future research tool
Examples of works to practice staccato technique in clarinet instrument
Klarnetin staccato tekniğini güçlendirme aşamaları eser çalışmalarıyla uygulanmıştır. Staccato
geçişlerini hızlandıracak ritim ve nüans çalışmalarına yer verilmiştir. Çalışmanın en önemli amacı
sadece staccato çalışması değil parmak-dilin eş zamanlı uyumunun hassasiyeti üzerinde de
durulmasıdır. Staccato çalışmalarını daha verimli hale getirmek için eser çalışmasının içinde etüt
çalışmasına da yer verilmiştir. Çalışmaların üzerinde titizlikle durulması staccato çalışmasının ilham
verici etkisi ile müzikal kimliğe yeni bir boyut kazandırmıştır. Sekiz özgün eser çalışmasının her
aşaması anlatılmıştır. Her aşamanın bir sonraki performans ve tekniği güçlendirmesi esas alınmıştır.
Bu çalışmada staccato tekniğinin hangi alanlarda kullanıldığı, nasıl sonuçlar elde edildiği bilgisine
yer verilmiştir. Notaların parmak ve dil uyumu ile nasıl şekilleneceği ve nasıl bir çalışma disiplini
içinde gerçekleşeceği planlanmıştır. Kamış-nota-diyafram-parmak-dil-nüans ve disiplin
kavramlarının staccato tekniğinde ayrılmaz bir bütün olduğu saptanmıştır. Araştırmada literatür
taraması yapılarak staccato ile ilgili çalışmalar taranmıştır. Tarama sonucunda klarnet tekniğin de
kullanılan staccato eser çalışmasının az olduğu tespit edilmiştir. Metot taramasında da etüt
çalışmasının daha çok olduğu saptanmıştır. Böylelikle klarnetin staccato tekniğini hızlandırma ve
güçlendirme çalışmaları sunulmuştur. Staccato etüt çalışmaları yapılırken, araya eser çalışmasının
girmesi beyni rahatlattığı ve istekliliği daha arttırdığı gözlemlenmiştir. Staccato çalışmasını yaparken
doğru bir kamış seçimi üzerinde de durulmuştur. Staccato tekniğini doğru çalışmak için doğru bir
kamışın dil hızını arttırdığı saptanmıştır. Doğru bir kamış seçimi kamıştan rahat ses çıkmasına
bağlıdır. Kamış, dil atma gücünü vermiyorsa daha doğru bir kamış seçiminin yapılması gerekliliği
vurgulanmıştır. Staccato çalışmalarında baştan sona bir eseri yorumlamak zor olabilir. Bu açıdan
çalışma, verilen müzikal nüanslara uymanın, dil atış performansını rahatlattığını ortaya koymuştur.
Gelecek nesillere edinilen bilgi ve birikimlerin aktarılması ve geliştirici olması teşvik edilmiştir.
Çıkacak eserlerin nasıl çözüleceği, staccato tekniğinin nasıl üstesinden gelinebileceği anlatılmıştır.
Staccato tekniğinin daha kısa sürede çözüme kavuşturulması amaç edinilmiştir. Parmakların
yerlerini öğrettiğimiz kadar belleğimize de çalışmaların kaydedilmesi önemlidir. Gösterilen azmin ve
sabrın sonucu olarak ortaya çıkan yapıt başarıyı daha da yukarı seviyelere çıkaracaktır
Exploring the role of Wnt signalling in heart failure with preserved ejection fraction.
According to the European Society of Cardiology long-term out-patient registry, heart failure with preserved ejection fraction (HFpEF) accounts for approximately 16% of heart failure cases, with survival rates failing to improve due to the lack of effective treatments and the increasing prevalence of co-morbidities. It has been widely documented throughout the literature that Wingless/int1 (Wnt) signalling plays a role in the development of both cardiomyocyte hypertrophy and cardiac fibrosis, which are key features of HFpEF. Useful in vivo models of HFpEF are lacking; however, a recently-published 'two-hit' (metabolic and mechanical stress) in vivo model of HFpEF shows promise. Targeting Wnt signalling as a potential therapeutic intervention in this HFpEF model has not yet been investigated, so the present study was therefore carried out in order to investigate whether pharmacological inhibition of Wnt signalling could improve detrimental structural and/or functional changes associated with HFpEF. The present study aimed to: 1) examine the role of Wnt signalling in cardiomyocyte hypertrophy; 2) investigate whether Wnt signalling contributes to the development of HFpEF using an in vivo model of the condition; and 3) determine whether the administration of a Wnt inhibitor (Wnt-c59) alters the maladaptive structural and/or functional changes associated with HFpEF. Initial in vitro experiments using H9c2 cells determined the optimum experimental conditions for AngII (1μM)-induced cardiomyocyte hypertrophy. Furthermore, subsequent experiments determined that AngII-induced cardiomyocyte hypertrophy is mediated, at least in part, via activation of canonical Wnt signalling; this thesis is the first to demonstrate this pro-hypertrophic pathway in human cardiomyocytes. A role for Wnt signalling in the pathogenesis of HFpEF (a condition characterised by cardiac hypertrophy) was then examined in an in vivo model of the condition, induced by the chronic administration of a high fat diet and Nω-nitro-L-arginine methyl ester (L-NAME; 0.5g/L) to mice for 7 weeks. Findings from this study demonstrated that this mouse model of HFpEF was characterised by hypertension, cardiac hypertrophy and fibrosis, diastolic dysfunction (measured via pressure volume loop analysis), but there was no evidence demonstrating activation of canonical Wnt signalling in the hearts of these animals. Thus, on the basis of this study, a role for canonical Wnt signalling in the development of HFpEF is not supported. Notwithstanding this, treatment of HFpEF mice with Wnt-c59 (5mg/kg/day) did ameliorate diastolic dysfunction via mechanisms that may contribute to increased ventricular compliance, such as BNP-induced phosphorylation of titin and/or favourable regulation of the ratio of collagen subtype expression. However, this requires further investigation. In conclusion, this study has identified a hypertrophic role for Wnt signalling in vitro, indicating a link between renin angiotensin-aldosterone system (RAAS) activation and the initiation of Wnt signalling. Furthermore, in the 'two-hit' model of HFpEF there was no evidence of activation of canonical Wnt signalling; however, treatment of HFpEF mice with Wnt-c59 did ameliorate diastolic dysfunction via mechanisms that may contribute to increased ventricular compliance
Instrumentation and validation of a robotic cane for transportation and fall prevention in patients with affected mobility
Dissertação de mestrado integrado em Engenharia Física, (especialização em Dispositivos, Microssistemas e Nanotecnologias)O ato de andar é conhecido por ser a forma primitiva de locomoção do ser humano, sendo que este
traz muitos benefícios que motivam um estilo de vida saudável e ativo. No entanto, há condições de saúde
que dificultam a realização da marcha, o que por consequência pode resultar num agravamento da saúde,
e adicionalmente, levar a um maior risco de quedas. Nesse sentido, o desenvolvimento de um sistema de
deteção e prevenção de quedas, integrado num dispositivo auxiliar de marcha, seria essencial para reduzir
estes eventos de quedas e melhorar a qualidade de vida das pessoas. Para ultrapassar estas necessidades
e limitações, esta dissertação tem como objetivo validar e instrumentar uma bengala robótica, denominada
Anti-fall Robotic Cane (ARCane), concebida para incorporar um sistema de deteção de quedas e um
mecanismo de atuação que possibilite a prevenção de quedas, ao mesmo tempo que assiste a marcha.
Para esse fim, foi realizada uma revisão do estado da arte em bengalas robóticas para adquirir um
conhecimento amplo e aprofundado dos componentes, mecanismos e estratégias utilizadas, bem como os
protocolos experimentais, principais resultados, limitações e desafios em dispositivos existentes.
Numa primeira fase, foi estipulado o objetivo de: (i) adaptar a missão do produto; (ii) estudar as
necessidades do consumidor; e (iii) atualizar as especificações alvo da ARCane, continuação do trabalho de
equipa, para obter um produto com design e engenharia compatível com o mercado. Foi depois estabelecida
a arquitetura de hardware e discutidos os componentes a ser instrumentados na ARCane. Em seguida foram
realizados testes de interoperabilidade a fim de validar o funcionamento singular e coletivo dos componentes.
Relativamente ao controlo de movimento, foi desenvolvido um sistema inovador, de baixo custo e
intuitivo, capaz de detetar a intenção do movimento e de reconhecer as fases da marcha do utilizador. Esta
implementação foi validada com seis voluntários saudáveis que realizaram testes de marcha com a ARCane
para testar sua operabilidade num ambiente de contexto real. Obteve-se uma precisão de 97% e de 90% em
relação à deteção da intenção de movimento e ao reconhecimento da fase da marcha do utilizador.
Por fim, foi projetado um método de deteção de quedas e mecanismo de prevenção de quedas para
futura implementação na ARCane. Foi ainda proposta uma melhoria do método de deteção de quedas, de
modo a superar as limitações associadas, bem como a proposta de dispositivos de deteção a serem
implementados na ARCane para obter um sistema completo de deteção de quedas.The act of walking is known to be the primitive form of the human being, and it brings many benefits
that motivate a healthy and active lifestyle. However, there are health conditions that make walking difficult,
which, consequently, can result in worse health and, in addition, lead to a greater risk of falls. Thus, the
development of a fall detection and prevention system integrated with a walking aid would be essential to
reduce these fall events and improve people quality of life. To overcome these needs and limitations, this
dissertation aims to validate and instrument a cane-type robot, called Anti-fall Robotic Cane (ARCane),
designed to incorporate a fall detection system and an actuation mechanism that allow the prevention of
falls, while assisting the gait. Therefore, a State-of-the-Art review concerning robotic canes was carried out to
acquire a broad and in-depth knowledge of the used components, mechanisms and strategies, as well as
the experimental protocols, main results, limitations and challenges on existing devices.
On a first stage, it was set an objective to (i) enhance the product's mission statement; (ii) study the
consumer needs; and (iii) update the target specifications of the ARCane, extending teamwork, to obtain a
product with a market-compatible design and engineering that meets the needs and desires of the ARCane
users. It was then established the hardware architecture of the ARCane and discussed the electronic
components that will instrument the control, sensory, actuator and power units, being afterwards subjected
to interoperability tests to validate the singular and collective functioning of cane components altogether.
Regarding the motion control of robotic canes, an innovative, cost-effective and intuitive motion
control system was developed, providing user movement intention recognition, and identification of the user's
gait phases. This implementation was validated with six healthy volunteers who carried out gait trials with
the ARCane, in order to test its operability in a real context environment. An accuracy of 97% was achieved
for user motion intention recognition and 90% for user gait phase recognition, using the proposed motion
control system.
Finally, it was idealized a fall detection method and fall prevention mechanism for a future
implementation in the ARCane, based on methods applied to robotic canes in the literature. It was also
proposed an improvement of the fall detection method in order to overcome its associated limitations, as
well as detection devices to be implemented into the ARCane to achieve a complete fall detection system
The Role of Transient Vibration of the Skull on Concussion
Concussion is a traumatic brain injury usually caused by a direct or indirect blow to the head that affects brain function. The maximum mechanical impedance of the brain tissue occurs at 450±50 Hz and may be affected by the skull resonant frequencies. After an impact to the head, vibration resonance of the skull damages the underlying cortex. The skull deforms and vibrates, like a bell for 3 to 5 milliseconds, bruising the cortex. Furthermore, the deceleration forces the frontal and temporal cortex against the skull, eliminating a layer of cerebrospinal fluid. When the skull vibrates, the force spreads directly to the cortex, with no layer of cerebrospinal fluid to reflect the wave or cushion its force. To date, there is few researches investigating the effect of transient vibration of the skull. Therefore, the overall goal of the proposed research is to gain better understanding of the role of transient vibration of the skull on concussion. This goal will be achieved by addressing three research objectives. First, a MRI skull and brain segmentation automatic technique is developed. Due to bones’ weak magnetic resonance signal, MRI scans struggle with differentiating bone tissue from other structures. One of the most important components for a successful segmentation is high-quality ground truth labels. Therefore, we introduce a deep learning framework for skull segmentation purpose where the ground truth labels are created from CT imaging using the standard tessellation language (STL). Furthermore, the brain region will be important for a future work, thus, we explore a new initialization concept of the convolutional neural network (CNN) by orthogonal moments to improve brain segmentation in MRI. Second, the creation of a novel 2D and 3D Automatic Method to Align the Facial Skeleton is introduced. An important aspect for further impact analysis is the ability to precisely simulate the same point of impact on multiple bone models. To perform this task, the skull must be precisely aligned in all anatomical planes. Therefore, we introduce a 2D/3D technique to align the facial skeleton that was initially developed for automatically calculating the craniofacial symmetry midline. In the 2D version, the entire concept of using cephalometric landmarks and manual image grid alignment to construct the training dataset was introduced. Then, this concept was extended to a 3D version where coronal and transverse planes are aligned using CNN approach. As the alignment in the sagittal plane is still undefined, a new alignment based on these techniques will be created to align the sagittal plane using Frankfort plane as a framework. Finally, the resonant frequencies of multiple skulls are assessed to determine how the skull resonant frequency vibrations propagate into the brain tissue. After applying material properties and mesh to the skull, modal analysis is performed to assess the skull natural frequencies. Finally, theories will be raised regarding the relation between the skull geometry, such as shape and thickness, and vibration with brain tissue injury, which may result in concussive injury
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