Transport properties of fluids in nanochannels: bridging nano to macro

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A method of calculating transport properties in nanochannels is presented in this work. The Molecular Dynamics simulation of a system of liquid argon flowing in a nanochannel formed by krypton walls was the basis for our analysis concerning transport properties and specifically diffusion coefficient, shear viscosity and thermal conductivity. It is shown that for confined systems, such as nanochannels, if one of the transport properties is known, then the others can be estimated. The simulation results reveal that all properties approach bulk values at relatively small channel widths, at about 6-7nm. Below this critical point, the wall effect on fluid atoms is strong and the transport properties change dramatically. In order to extend the calculations over rough-wall nanochannels, we apply the relation extracted for flat wall channels to channels with walls consisted of successive rectangular protrusions and cavities

Chemical and biological approaches to enhance the bacteriophage as a probe in molecular recognition

The aim of the work presented in this thesis was to explore the structural and molecular features of a filamentous bacteriophage for incorporation in biosensing platforms. To tune the bacteriophage surface as a scaffold for molecular recognition, chemical and biological protocols aimed at controlling and enhancing its intrinsic properties were developed. A key part of the work was aimed at anchoring bacteriophage particles by one-end to surfaces, and on labelling its viral capsid with dyes, antibodies and DNA molecules. The tolerance of the bacteriophage for modifications, as well its simplicity and robustness, makes it an attractive probe for biosensors. Furthermore, the filamentous structure of the bacteriophage was demonstrated to be a valuable feature in both microscopy- and spectroscopy-based biosensors. The ability of the bacteriophage to align under flow was considered as a simple, yet efficient approach for the detection of wall shear stress and pathogenic bacteria. A novel method to detect wall shear stress (WSS) was developed by using a fluorescently decorated bacteriophage particle anchored by one-end to a surface. The response of this filamentous nanosensor to flow variations was tracked under a microscope, and gave valuable information on the shear flow of a fluid passing over a surface. Using a custom-made analysis tool and an algorithm, we were able to derive the wall shear stress on the point of attachment of the nanosensor, using endothelial cells as a model system. The proof-of-concept to this work highlighted how a simple bacteriophage construct can be use as a nanosensor for imaging and mapping flow. Linear dichroism (LD) spectroscopy also explores the high aspect ratio of the filamentous bacteriophage. Linear Diagnostics Ltd., a startup company in Birmingham, exploits the natural LD properties of the bacteriophage and integrated it with a biosensing platform targeting pathogenic bacteria. The work reported in this thesis mainly focused on developing alternative approaches that could improve the biosensor sensitivity and simplicity, by modifying the bacteriophage scaffold, further demonstrating its versatility

Transport properties and structure of fluids in hydrophobic/hydrophilic nanochannels

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.When downsizing towards the nanoscale, system dimensions have been found to affect channel flows mainly because of the presence of the walls that interact strongly with fluid particles. Parameters which are not taken into account at the classical theory continuum theory at the macroscale, should be taken into account at the nano or even micro-scale where the surface to volume ratio increases significantly. Such property is the wall/fluid interaction which determines the wetting (hydrophilic behavior) or not (hydrophobic behavior) of a surface. We first investigate the effect of wall/fluid interaction on fluid atom distribution near the wall through the radial distribution function and, next, we calculate the three most important fluid transport properties, i.e., the diffusion coefficient, shear viscosity and thermal conductivity. Transport properties seem to be affected significantly in the channel region adjacent to the wall

A New Lower Bound for Deterministic Truthful Scheduling

We study the problem of truthfully scheduling $m$ tasks to $n$ selfish unrelated machines, under the objective of makespan minimization, as was introduced in the seminal work of Nisan and Ronen [STOC'99]. Closing the current gap of $[2.618,n]$ on the approximation ratio of deterministic truthful mechanisms is a notorious open problem in the field of algorithmic mechanism design. We provide the first such improvement in more than a decade, since the lower bounds of $2.414$ (for $n=3$) and $2.618$ (for $n\to\infty$) by Christodoulou et al. [SODA'07] and Koutsoupias and Vidali [MFCS'07], respectively. More specifically, we show that the currently best lower bound of $2.618$ can be achieved even for just $n=4$ machines; for $n=5$ we already get the first improvement, namely $2.711$; and allowing the number of machines to grow arbitrarily large we can get a lower bound of $2.755$.Comment: 15 page

Finite element analysis of Volterra dislocations in anisotropic crystals: A thermal analogue

The present work gives a systematic and rigorous implementation of Volterra dislocations in ordinary two-dimensional finite elements using the thermal analogue and the integral representation of dislocations through the stresses. The full fields are given for edge dislocations in anisotropic crystals, and the Peach-Koehler forces are found for some important examples

Brain Aging in the Oldest-Old

Nonagenarians and centenarians represent a quickly growing age group worldwide. In parallel, the prevalence of dementia increases substantially, but how to define dementia in this oldest-old age segment remains unclear. Although the idea that the risk of Alzheimer's disease (AD) decreases after age 90 has now been questioned, the oldest-old still represent a population relatively resistant to degenerative brain processes. Brain aging is characterised by the formation of neurofibrillary tangles (NFTs) and senile plaques (SPs) as well as neuronal and synaptic loss in both cognitively intact individuals and patients with AD. In nondemented cases NFTs are usually restricted to the hippocampal formation, whereas the progressive involvement of the association areas in the temporal neocortex parallels the development of overt clinical signs of dementia. In contrast, there is little correlation between the quantitative distribution of SP and AD severity. The pattern of lesion distribution and neuronal loss changes in extreme aging relative to the younger-old. In contrast to younger cases where dementia is mainly related to severe NFT formation within adjacent components of the medial and inferior aspects of the temporal cortex, oldest-old individuals display a preferential involvement of the anterior part of the CA1 field of the hippocampus whereas the inferior temporal and frontal association areas are relatively spared. This pattern suggests that both the extent of NFT development in the hippocampus as well as a displacement of subregional NFT distribution within the Cornu ammonis (CA) fields may be key determinants of dementia in the very old. Cortical association areas are relatively preserved. The progression of NFT formation across increasing cognitive impairment was significantly slower in nonagenarians and centenarians compared to younger cases in the CA1 field and entorhinal cortex. The total amount of amyloid and the neuronal loss in these regions were also significantly lower than those reported in younger AD cases. Overall, there is evidence that pathological substrates of cognitive deterioration in the oldest-old are different from those observed in the younger-old. Microvascular parameters such as mean capillary diameters may be key factors to consider for the prediction of cognitive decline in the oldest-old. Neuropathological particularities of the oldest-old may be related to “longevity-enabling” genes although little or nothing is known in this promising field of future research

PALAEOCLIMATIC EVOLUTION IN LOUTRA ARIDEAS CAVE (ALMOPIA SPELEOPARK, MACEDONIA, N. GREECE) BY STABLE ISOTOPIC ANALYSIS OF FOSSIL BEAR BONES AND TEETH

Carbon and oxygen stable isotope values (δ13C, δ18O) were obtained from structural carbonate in the bioapatite of bear bones (Ursus ingressus) from Loutra Arideas cave, Almopia Speleopark, Macedonia, N. Greece. Samples of Late Pleistocene bear bones were studied for palaeoclimatic reconstruction of the area. The age range of the fossil layers is from 32ka BP to a maximum of 38ka BP. Generally, the palaeoclimatic proxy is correlated with literature data for climatic variations in the area during Late Pleistocene, whereas dietary behavior was investigated taking into account possible diagenetic processes that may have affected the carbonate matrix of the bones