Modified Gravity with a Non-minimal Gravitational Coupling to Matter

We consider modified theories of gravity with a direct coupling between matter and geometry, denoted by an arbitrary function in terms of the Ricci scalar. Due to such a coupling, the matter stress tensor is no longer conserved and there is an energy transfer between the two components. By solving the conservation equation, we argue that the matter system should gain energy in this interaction, as demanded by the second law of thermodynamics. In a cosmological setting, we show that although this kind of interaction may account for cosmic acceleration, this latter together with direction of the energy transfer constrain the coupling function.Comment: 13 Pages, Two figures, Accepted for publication in Physical Review

Unsupervised Parkinson’s Disease Assessment

Parkinson’s Disease (PD) is a progressive neurological disease that affects 6.2 million people worldwide. The most popular clinical method to measure PD tremor severity is a standardized test called the Unified Parkinson’s Disease Rating Scale (UPDRS), which is performed subjectively by a medical professional. Due to infrequent checkups and human error introduced into the process, treatment is not optimally adjusted for PD patients. According to a recent review there are two devices recommended to objectively quantify PD symptom severity. Both devices record a patient’s tremors using inertial measurement units (IMUs). One is not currently available for over the counter purchases, as they are currently undergoing clinical trials. It has also been used in studies to evaluate to UPDRS scoring in home environments using an Android application to drive the tests. The other is an accessible product used by researchers to design home monitoring systems for PD tremors at home. Unfortunately, this product includes only the sensor and requires technical expertise and resources to set up the system. In this paper, we propose a low-cost and energy-efficient hybrid system that monitors a patient’s daily actions to quantify hand and finger tremors based on relevant UPDRS tests using IMUs and surface Electromyography (sEMG). This device can operate in a home or hospital environment and reduces the cost of evaluating UPDRS scores from both patient and the clinician’s perspectives. The system consists of a wearable device that collects data and wirelessly communicates with a local server that performs data analysis. The system does not require any choreographed actions so that there is no need for the user to follow any unwieldy peripheral. In order to avoid frequent battery replacement, we employ a very low-power wireless technology and optimize the software for energy efficiency. Each collected signal is filtered for motion classification, where the system determines what analysis methods best fit with each period of signals. The corresponding UPDRS algorithms are then used to analyze the signals and give a score to the patient. We explore six different machine learning algorithms to classify a patient’s actions into appropriate UPDRS tests. To verify the platform’s usability, we conducted several tests. We measured the accuracy of our main sensors by comparing them with a medically approved industry device. The our device and the industry device show similarities in measurements with errors acceptable for the large difference in cost. We tested the lifetime of the device to be 15.16 hours minimum assuming the device is constantly on. Our filters work reliably, demonstrating a high level of similarity to the expected data. Finally, the device is run through and end-to-end sequence, where we demonstrate that the platform can collect data and produce a score estimate for the medical professionals

Impact of sulphur contamination on the performance of mixed ionic-electronic conducting membranes for oxygen separation and hydrogen production

PhD ThesisMixed ionic-electronic conducting (MIEC) membranes are a promising technology for oxygen separation but they are not commercialised yet due to sealing issue and sensitivity to impurities in feedstock. In this study, La0.6Sr0.4Co0.2Fe0.8O3- (LSCF6428) was successfully sealed for long-term operation of 963 h using a gold-glass-ceramic sealant. The membrane was then tested for air separation in presence of hydrogen sulphide for 100 h and results showed that the impurity caused a drop in oxygen flux to zero within few hours. The flux could not be fully restored after hydrogen sulphide removal and only 6 to 35% was recovered. It was proposed that hydrogen sulphide was adsorbed on the membrane in the form of sulphur and it occupied oxygen vacancies. With time, strontium segregates toward sulphur to form irreversible layer of strontium sulphate. To restore the damaged surface, the membrane was treated by 1% (mol) of hydrogen for 20 h and the recovery improved from 6 to 12%. It was discovered that the poisoning mechanism is a function of oxygen partial pressure and change of partial pressure from 0.21 to 0.01 bar resulted in 90% recovery and this can be used as a strategy to reduce the damage. The next step was to test the membrane for hydrogen production using 1% (mol) of methane and results showed that methane conversion was steady at 33% for 350 h. Methane oxidation was also carried in presence of hydrogen sulphide but it resulted in drop of conversion to 8%. However, the conversion was slowly regenerating with time and it reached a constant value of 15%. This recovery was interpreted by the reaction of methane with hydrogen sulphide or methane decomposition and the membrane acted as a catalyst for these reactions. After hydrogen sulphide removal from the feed, the conversion kept on decreasing and this was linked to the change of membrane properties and therefore the membrane could not provide the sites for methane-oxygen reaction. For better stability under hydrogen sulphide, the membrane was modified by adding a powder of LSCF6428 material over the dense membrane. This dual layer membrane was stable for air separation under hydrogen for 33 h and the flux was only reduced by 5%

Working memory learning method and astrocytes number in different subfields of rat's Hippocampus

The aim of this study was evaluation of the astrocytes number in different subfields of rat's Hippocampus after spatial learning with usage of Morris Water Maze technique and working memory method. In this study, between 2005-2006 years in Pasteur institute of Iran-Tehran and histological department of Gorgan University with usage of Morris Water Maze and working memory technique, we used 14 male albino wistar rats. Seventh rats were in control group and 7 rats in working memory group. After histological preparation, the slides were stained with PTAH staining for showing the Astrocytes. Present results showed significant difference in astrocytes number in CA1, CA2 and CA3 areas of hippocampus between control and reference memory group. The number of astrocytes is increased in working memory group. Then we divided the hippocampus to three parts: Anterior, middle and posterior and with compare of different area (CA1, CA2 and CA3) of hippocampus, we found that the differences between Anterior-middle and Middle-Posterior of CA1 and CA2 area of hippocampus were significant, whereas the difference between Anterior-Posterior parts was not significant in CA1 and CA2 areas. In CA3 area, the difference between Anterior-Middle and Anterior-Posterior parts was significant, whereas the difference between middle and posterior parts was not significant. We concluded that the number of astrocytes increased due to spatial learning and working memory technique. © 2008 Science Publications

Writing Sample

In Search of the Pan Flutes , Nine Hundred published in Refugees Welcome Anthology, Triumph walk published in Carers UK Anthology, Seven Stones published in , Scotland, To Journey Alone published in Journeys: poetry and prose from the Stratford-upon-Avon Literary Festival contest

Comparing Representations of Contribution Labels in Goal Models

Goal models have been proposed to be an effective method to support decision making in early requirements engineering. Key to using them is the concept of contribution links that represent how the satisfaction of one goal affects that of another. Multiple proposals have been offered for representing contribution; however, the degree to which users can intuitively understand the meaning behind contribution representations and utilize them appropriately has not been thoroughly studied. This work reports the results of an experimental study that compares the intuitiveness of two contribution representation approaches by measuring the performance of untrained users and exploring the role of individual differences (cognitive styles and arithmetic attitude and ability) in establishing the right intuition. Results show significant differences between the two representations as well as effects of various levels of individual factors. The results inspire further research on contribution links and support the operationalizability of intuitiveness as a criterion for evaluating conceptual modelling language designs

Anisotropy of Alfv\'enic Turbulence in the Solar Wind and Numerical Simulations

We investigate the anisotropy of Alfv\'enic turbulence in the inertial range of slow solar wind and in both driven and decaying reduced magnetohydrodynamic simulations. A direct comparison is made by measuring the anisotropic second-order structure functions in both data sets. In the solar wind, the perpendicular spectral index of the magnetic field is close to -5/3. In the forced simulation, it is close to -5/3 for the velocity and -3/2 for the magnetic field. In the decaying simulation, it is -5/3 for both fields. The spectral index becomes steeper at small angles to the local magnetic field direction in all cases. We also show that when using the global rather than local mean field, the anisotropic scaling of the simulations cannot always be properly measured.Comment: 9 pages, 8 figure

Prediction of Compressive Strength of Fibrous Composites Using Two Different Approaches

This paper presents two different approaches to predict the compressive strength of fibrous composites using three-dimensional analysis. These approaches are based on the optimization of compressive stress resulting from the relationship between the compressive stress of the fibrous composite and the shear strength of the matrix material. The first approach is an estimation of compressive strength based on the actual initial misalignment of fibers in the rotated plane. The second approach is an approximation of compressive strength in accordance with the components of the initial fiber misalignment relative to the global axes of the fibrous composite material. The initial fiber misalignment is defined as a curve in the form of a cosine function that has components on the two planes containing the longitudinal axis and defined by initial misalignment angles. Equilibrium equations are then derived for an infinitesimal element along the axis of the fibers using the total potential energy principle. Maximum compressive strength is calculated using the corresponding shear stresses and shear deformations in the matrix, since shear is the dominant mode of failure. The compressive strength corresponding to the shear mode is found to be related to the tangent shear modulus of a fibrous composite material. The two different approaches are used to study the following composites: Carbon/epoxy XAS/914C saturated and dry, Carbon/Peek AS4/PEEK (APC-2), AS4/E7K8, Glass-Vinyl Ester, Glass-Polyester and unidirectional HTS40/977-2. The results obtained in this paper are found to agree well with experimental results and theoretical results available in literature

Structural Basis of Prospero-DNA Interaction Implications for Transcription Regulationin Developing Cells

SummaryThe crystal structure of a complex between the novel homeodomain of the neural transcription factor Prospero and DNA shows that the invariant residues Lys1290, Asn1294, and Asp1297 make specific contacts with the noncanonical DNA binding site. The overall structure includes the homeodomain and the adjacent Prospero domain and confirms that they act as a single structural unit, a Homeo-Prospero domain. The Prospero domain facilitates the proper alignment of the protein on the DNA. Knowledge of the structure reconciles two different DNA sequences that have been proposed as transcriptional targets for Prospero. As in the apo structure, the C terminus of the Prospero domain shields a short helix within the homeodomain that includes a nuclear export signal (NES). The structural results suggest that exposure of the NES is not coupled directly to DNA binding. We propose a DNA recognition mechanism specific to Prospero-type homeodomains in developing cells