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Electric field lines and voltage potentials associated with graphene nanoribbonDale, Joel Kelly 01 May 2013 (has links)
Graphene can be used to create circuits that are almost superconducting, potentially speeding electronic components by as much as 1000 times [1]. Such blazing speed might also help produce ever-tinier computing devices with more power than your clunky laptop [2]. Graphite is a polymorph of the element carbon [3]. Graphite is made up of tiny sheets of graphene. Graphene sheets stack to form graphite with an interplanar spacing of 0.335 nm, which means that a stack of 3 million sheets would be only one millimeter thick. [1] This nano scale 2 dimensional sheet is graphene. Novoselov and Geim's discovery is now the stuff of scientific legend, with the two men being awarded the Nobel Prize in 2010 [4]. In 2004, two Russian-born scientists at the University of Manchester stuck Scotch tape to a chunk of graphite, then repeatedly peeled it back until they had the tiniest layer possible [2]. Graphene has exploded on the scene over the past couple of years. "Six years ago, it didn't exist at all, and next year we know that Samsung is planning to release their first mobile-phone screens made of graphene." - Dr Kostya Novoselov [4]. It is a lattice of hexagons, each vertex tipped with a carbon atom. At the molecular level, it looks like chicken wire [4]. There are two common lattice formations of graphene, armchair and zigzag. The most studied edges, zigzag and armchair, have drastically different electronic properties. Zigzag edges can sustain edge surface states and resonances that are not present in the armchair case Rycerz et al., 2007 [5]. This research focused on the armchair graphene nanoribbon formation (acGNR).
Graphene has several notable properties that make it worthy of research. The first of which is its remarkable strength. Graphene has a record breaking strength of 200 times greater than steel, with a tensile strength of 130GPa [1]. Graphene has a Young's modulus of 1000, compared to just that of 150 for silicon [1]. To put it into perspective, if you had a sheet of graphene as thick as a piece of cellophane, it would support the weight of a car. [2] If paper were as stiff as graphene, you could hold a 100-yard-long sheet of it at one end without its breaking or bending. [2]
Another one of graphene's attractive properties is its electronic band gap, or rather, its lack thereof. Graphene is a Zero Gap Semiconductor. So it has high electron mobility at room temperature. It's a Superconductor. Electron transfer is 100 times faster than Silicon [1]. With zero a band gap, in the massless Dirac Fermion structure, the graphene ribbon is virtually lossless, making it a perfect semiconductor. Even in the massive Dirac Fermion structure, the band gap is 64meV [6].
This research began, as discussed in Chapter 2, with an armchair graphene nanoribbon unit cell of N=8. There were 16 electron approximation locations (ψ) provided per unit cell that spanned varying Fermi energy levels. Due to the atomic scales of the nanoribbon, the carbon atoms are separated by 1.42Å. The unit vector is given as, ~a = dbx, where d = 3αcc and αcc = 1.42°A is the carbon bond length [5]. Because of the close proximity of the carbon atoms, the 16 electron approximations could be combined or summed with their opposing lattice neighbors. Using single line approximation allowed us to reduce the 16 points down to 8. These approximations were then converted into charge densities (ρ). Poisson's equation, discussed in Chapter 3, was expanded into the 3 dimensional space, allowing us to convert ρ into voltage potentials (φ). Even though graphene is 2 dimensional; it can be used nicely in 3 dimensional computations without the presence of a substrate, due to the electric field lines and voltage potential characteristics produced being 3 dimensional. Subsequently it was found that small graphene sheets do not need to rest on substrates but can be freely suspended from a scaffolding; furthermore, bilayer and multilayer sheets can be prepared and characterized.
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The Antidepressant Drug Tianeptine Blocks Working Memory Errors: Pharmacological and Endocrine Manipulations of Stress-Induced Amnesia in RatsCampbell, Adam Marc 23 March 2004 (has links)
Stress has been shown to influence learning and memory in humans and rats (Diamond et al, 1996; Diamond et al, 1999; Krugers et al, 1997; Kirschbaum et al, 1996; Lupien et al, 1997). The hippocampus and is an area of the brain involved in memory function in humans and rats (Kirschbaum et al, 1996; Lupien et al, 1997) and is highly susceptible to stress (Diamond et al, 1990). Research has indicated that a number of stressors such as exposure to a predator (Diamond et al, 1999) can lead to stress effects. Recently efforts have been made to counteract the effects of stress on brain function and related behavioral performance. The antidepressant drug tianeptine has been used in this setting. Little is known about tianeptine's role in blocking stress effects on behavior and memory performance with regard to interactions with stress hormones, such as corticosterone. Here a set of experiments delineates the role of corticosterone and its link to stress effects on memory as well as an investigation into the actions of tianeptine and ADX in the blockade of stress effects on memory. First, I examined the effects of tianeptine on multi-day RAWM working memory training and a novel one-day learning and memory training task. Second, the effects of propranolol, an anti-anxiety medication, were tested with regard to the alleviation of stress effects on memory, allowing for a comparison between two anti-anxiety drugs, tianeptine and propranolol. Third, adrenalectomy (ADX) and the resultant depletion of adrenal hormones were examined in connection with learning and memory in the one-day learning task. Fourth, the effects and interactions of tianeptine and ADX were examined to see if tianeptine can exert its effects in the absence of adrenal hormones. Tianeptine blocked stress-induced memory errors in two different tasks and under ADX conditions. All effects were independent of corticosterone levels. In contrast, propranolol was ineffective in blocking stress-induced memory changes. The current data may prove useful in the development of antidepressant drugs and further the study of the mechanisms by which stress affects memory.
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Upper limb Botulinum Toxin-A in children with hemiplegic cerebral palsy : physiological corticomotor pathways and effect on health related quality of lifeRedman, Toni Annette January 2008 (has links)
[Truncared abstract] Introduction: The assessment of any therapy requires not only an understanding of how that therapy works but also how it affects health related quality of life (HRQOL). Botulinum Toxin A(BoNT-A) therapy for upper limb spasticity management in children with hemiplegic cerebral palsy(CP) is currently under trial. Despite its use for over a decade for lower limb spasticity, little is known about the mechanisms involved in improving motor function and the effect on the child and their familys HRQOL. Both central and peripheral mechanisms are hypothesised[1]. Whilst evidence of improved quality of movement and ability to perform tasks is emerging[2-4], this cannot be directly correlated with an improvement in HRQOL. In addition, the traditional method of assessing child HRQOL by parent proxy reports has come under question[5, 6]. The World Health Organisation now recommends the collection of both parent proxy and child self-reports[7]. Aims: 1. Investigate the corticomotor projections to the upper limb in school aged children with hemiplegic CP and the changes that occur with BoNT-A therapy by transcranial magnetic stimulation (TMS). 2. Investigate the effect of upper limb BoNT-A therapy on HRQOL of school aged children with hemiplegic CP by completion of the PedsQL 4.0 Generic Core Scales and 3.0 CP Module. 3. Determine the concordance between Child Self-Report and Parent Proxy Report scores for the PedsQL 4.0 Generic Core Scales and 3.0 CP Module. 4. Determine the concordance between PedsQL scores and function as assessed by the Melbourne Assessment of Unilateral Upper Limb Function (MUUL). Methods: Design: Prospective randomised pilot study. Setting: Department of Paediatric Rehabilitation, Princess Margaret Hospital, and Centre for Neurological and Neuromuscular Disorders, Perth. Participants: 22 school aged children with hemiplegic CP aged 7yr 0mth-13yr 11mth (12 treatment, 10 control). 3 Treatment: One episode BoNT-A injections (dose 1-2U/kg/muscle) into the upper limb for treatment group. The control group received usual care. ... Conclusion: This pilot study provides preliminary evidence of the effects of upper limb BoNT-A therapy at both a central physiological and a broader quality of life level in school aged children with hemiplegic CP. At a central level, corticomotor pathway reorganisation occurs in the setting of BoNT-A. However the reorganisation is not limited to the affected side pathways suggesting a systemic BoNT-A effect or developmental changes. Similarly, in this pilot study, there was no statistically significant effect of upper limb BoNT-A on the childs HRQOL as assessed by the PedsQL although positive trends were observed 4 for a number of physical and psychosocial domains. The collection of both child self-report and parent proxy reports when assessing HRQOL is recommended, and function needs to be assessed independently. Larger studies across the broader CP population, the design of CP specific HRQOL tools appropriate for use in the higher functioning CP cohort, and alternative better tolerated methods of investigating the motor system in children with movement disorders are recommended.
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ORGANO-SPÉCIFICITÉ DE L'ENDOTHÉLIUM : MISE EN ÉVIDENCE ET CARACTÉRISATION D'UNE MOLÉCULE RÉGULATRICE DE L'ADHÉSION, NOMMEE ARM-1LAMERANT-FAYEL, Nathalie 17 December 2004 (has links) (PDF)
Afin d'identifier de nouvelles cibles organo-spécifiques de l'endothélium, nous avons comparé l'expression de gènes entre deux lignées de hautes cellules endothéliales et mis en évidence la protéine ARM-1. Des expériences de RT-PCR ont montré une expression spécifique d'ARM-1 dans certaines lignées de cellules endothéliales et de lymphocytes. La surexpression d'ARM-1 dans des cellules endothéliales de peau, n'exprimant pas cette protéine, augmente de façon préférentielle l'adhésion de certaines lignées lymphocytaires sur ces cellules. Ceci renforce l'hypothèse d'un rôle particulier d'ARM-1 au sein des cellules endothéliales. Une étude de fractionnement cellulaire a montré qu'ARM-1 était une protéine sécrétée, pouvant être associée à la membrane. Des expériences d'immunolocalisation n'ont cependant démontré aucune expression d'ARM-1 à la surface cellulaire. Ces résultats suggèrent une action indirecte d'ARM-1 dans l'adhésion plutôt qu'un rôle direct en tant que molécule d'adhésion.
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Faktorer som kan påverka blodtrycksmätning - viktiga kunskaper för sjuksköterskanAxman Sara, Inga Lisa, Björs, Stina January 2009 (has links)
<p><strong>Bakgrund:</strong> Blodtrycksmätning är en av sjuksköterskans arbetsuppgifter och hon/han ska genom den kunna identifiera patientens hälsostatus. Det finns brister hos sjukvårdspersonal runt om i världen om hur korrekt blodtryckemätning ska genomföras. <strong>Syfte:</strong> Syftet med litteraturstudien var att undersöka hur 3 olika faktorer påverkar blodtrycksresultatet vid manuell blodtrycksmätning med fokus på korsade ben, mätning över/utan tröjärm samt armposition. <strong>Metod:</strong> För att finna vetenskapliga artiklar användes databaserna Pubmed, CINAHL och Cochrane. Efter granskning och kvalitetsbedömning återstod det 15 kvantitativa artiklar som användes i denna studie. <strong>Resultat:</strong> Det visade sig tydligt att hur patientens arm- och benposition var vid blodtrycksmätningen påverkade blodtrycksresultatet signifikant. Däremot påverkade inte mätning över tröjärm blodtrycksvärdena nämnvärt. <strong>Diskussion:</strong> Hjärtläge är inte definerat i svenska rekomendationer. Det behövs tydligare definitioner/rekomendationer i Sverige för att undvika feldiagnostisering. Då mätning över tröjärm inte påverkade mätreslutatet underlättar det för patienter som har svårigheter att ta av sig på överkroppen. <strong>Slutsats:</strong> Det viktigt att alla som kontrollerar blodtrycket har kunskaper om vilka fel som kan påverka mätresultaten.</p>
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Konstruktion av Industriellt Vibrationsmätningssystem med signalbehandling baserad på Digitala Vågfilter av Lattice-struktur / Construction of Industrial Vibration Measurement System with signal-processing based on Lattice Wave Digital filter structuresTegelid, Simon, Åström, Jonas January 2010 (has links)
<p>In this bachelor thesis a complete prototype of an industrial vibration measurement platform has been developed. By measuring a number of variables such as acceleration, temperature and speed conclusions can be drawn on machinery health. The aim is to evaluate hardware and software solutions for a possible future product. Based on a requirement specification a proper hardware design has be developed. The hardware consists of a four-layer PCB with an ARM Cortex-M3 microcontroller and about 250 other components. The PCB was designed, assembled, tested and finally housed in a box. Measures have been taken to protect the prototype against external disturbances such as inappropriate supply voltages and transients on the input stages.Software has been written for the microcontroller to perform the various measurements required by the prototype. These include RMS, integration and filtering. Special attention was paid to the latter by implementing filters based on lattice wave digital structures. This structure results in a very efficient implementation. Consideration is taken to be able to generate arbitrary filters independent of the characteristics and design method. To save time the microcontroller implements all the algorithms without any floating point numbers.Furthermore, both hardware and software are adapted for future industrial use. The finished prototype supports a number of communication interfaces in which Modbus (RS-485) and current loop communication can be mentioned.The final result is a very good performing platform with strong future potential.The work was commissioned by the consulting firm Syncore Technologies AB at their office in Mjärdevi, Linköping. The project has, in total, taken 10 weeks and occurred during spring 2010.In this bachelor thesis a complete prototype of an industrial vibration measurement platform has been developed. By measuring a number of variables such as acceleration, temperature and speed conclusions can be drawn on machinery health. The aim is to evaluate hardware and software solutions for a possible future product. Based on a requirement specification a proper hardware design has be developed. The hardware consists of a four-layer PCB with an ARM Cortex-M3 microcontroller and about 250 other components. The PCB was designed, assembled, tested and finally housed in a box. Measures have been taken to protect the prototype against external disturbances such as inappropriate supply voltages and transients on the input stages.Software has been written for the microcontroller to perform the various measurements required by the prototype. These include RMS, integration and filtering. Special attention was paid to the latter by implementing filters based on lattice wave digital structures. This structure results in a very efficient implementation. Consideration is taken to be able to generate arbitrary filters independent of the characteristics and design method. To save time the microcontroller implements all the algorithms without any floating point numbers.Furthermore, both hardware and software are adapted for future industrial use. The finished prototype supports a number of communication interfaces in which Modbus (RS-485) and current loop communication can be mentioned.The final result is a very good performing platform with strong future potential.The work was commissioned by the consulting firm Syncore Technologies AB at their office in Mjärdevi, Linköping. The project has, in total, taken 10 weeks and occurred during spring 2010.</p>
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Utveckling av ett grafiskt användargränssnitt för en RISC mikrodatorHellström, Stefan January 2007 (has links)
<p>Detta examensarbete var en del i ett större projekt på ProElec AB i Söderhamn. Företaget ville ta fram en ny produkt i form av en displayenhet som ska kunna kommunicera med ett annat system via en operatör och ett CAN-protokoll. Användargränssnittet (GUI) i produkten understödjer växelverkan mellan en operatör och exempelvis ett hydrauliskt system på en grävskopa. Syftet med detta arbete var därför att hitta en bra metod som kan användas för att utveckla ett applikationsinterface (API) som sedan används för att implementera detta GUI på displayenheten. Enheten består av en mikrodator och en LCD-skärm och är ett system som har begränsat med minne och resurser. Därför så fanns det krav på att applikationen som använder detta API får snabba svarstider och bra prestanda, men även att den blir användarvänlig. För att kontrollera om resultatet blev bra så gjordes också en test för att se om alla krav uppfylldes. Här visade testet att resultatet blev väldigt bra och att inga kvarstående problem fanns kvar att rätta till i det API som togs fram för displayenheten.</p>
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Picking Up an Object from a Pile of ObjectsIkeuchi, Katsushi, Horn, Berthold K.P., Nagata, Shigemi, Callahan, Tom, Fein, Oded 01 May 1983 (has links)
This paper describes a hand-eye system we developed to perform the binpicking task. Two basic tools are employed: the photometric stereo method and the extended Gaussian image. The photometric stereo method generates the surface normal distribution of a scene. The extended Gaussian image allows us to determine the attitude of the object based on the normal distribution. Visual analysis of an image consists of two stages. The first stage segments the image into regions and determines the target region. The photometric stereo system provides the surface normal distribution of the scene. The system segments the scene into isolated regions using the surface normal distribution rather than the brightness distribution. The second stage determines object attitude and position by comparing the surface normal distribution with the extended-Gaussian-image. Fingers, with LED sensor, mounted on the PUMA arm can successfully pick an object from a pile based on the information from the vision part.
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Faktorer som kan påverka blodtrycksmätning - viktiga kunskaper för sjuksköterskanAxman Sara, Inga Lisa, Björs, Stina January 2009 (has links)
Bakgrund: Blodtrycksmätning är en av sjuksköterskans arbetsuppgifter och hon/han ska genom den kunna identifiera patientens hälsostatus. Det finns brister hos sjukvårdspersonal runt om i världen om hur korrekt blodtryckemätning ska genomföras. Syfte: Syftet med litteraturstudien var att undersöka hur 3 olika faktorer påverkar blodtrycksresultatet vid manuell blodtrycksmätning med fokus på korsade ben, mätning över/utan tröjärm samt armposition. Metod: För att finna vetenskapliga artiklar användes databaserna Pubmed, CINAHL och Cochrane. Efter granskning och kvalitetsbedömning återstod det 15 kvantitativa artiklar som användes i denna studie. Resultat: Det visade sig tydligt att hur patientens arm- och benposition var vid blodtrycksmätningen påverkade blodtrycksresultatet signifikant. Däremot påverkade inte mätning över tröjärm blodtrycksvärdena nämnvärt. Diskussion: Hjärtläge är inte definerat i svenska rekomendationer. Det behövs tydligare definitioner/rekomendationer i Sverige för att undvika feldiagnostisering. Då mätning över tröjärm inte påverkade mätreslutatet underlättar det för patienter som har svårigheter att ta av sig på överkroppen. Slutsats: Det viktigt att alla som kontrollerar blodtrycket har kunskaper om vilka fel som kan påverka mätresultaten.
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Efficient Pairings on Various PlatformsGrewal, Gurleen 30 April 2012 (has links)
Pairings have found a range of applications in many areas of cryptography. As such, to
utilize the enormous potential of pairing-based protocols one needs to efficiently compute
pairings across various computing platforms. In this thesis, we give an introduction to
pairing-based cryptography and describe the Tate pairing and its variants. We then describe
some recent work to realize efficient computation of pairings. We further extend
these optimizations and implement the O-Ate pairing on BN-curves on ARM and x86-64
platforms. Specifically, we extend the idea of lazy reduction to field inversion, optimize
curve arithmetic, and construct efficient tower extensions to optimize field arithmetic. We
also analyze the use of affine coordinates for pairing computation leading us to the conclusion
that they are a competitive choice for fast pairing computation on ARM processors,
especially at high security level. Our resulting implementation is more than three
times faster than any previously reported implementation on ARM processors.
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