Invariance of quantum correlations under local channel for a bipartite quantum state

We show that the quantum discord and the measurement induced non-locality (MiN) in a bipartite quantum state is invariant under the action of a local quantum channel if and only if the channel is invertible. In particular, these quantities are invariant under a local unitary channel.Comment: 4 pages, no figures, proof of theorm 2 modifie

The influence of wettability and carbon dioxide injection on hydrocarbon recovery

This study can be divided into two sections. First, a detailed study of petrophysical properties and the impact of wettability is performed on cores from a producing heterogeneous carbonate reservoir from the Middle East. Second, a comparison between different injection schemes (waterflooding, gas injection, WAG and CO2 injection) for enhanced oil recovery is made for another giant carbonate reservoir in the Middle East. Knowledge of the wettability of a reservoir rock and its influence on petrophysical properties is a key factor for determining oil recovery mechanisms and making estimates of recovery efficiency. A full suite of experiments on well-characterised systems, including sandpacks, sandstones and carbonate cores, was performed to measure capillary pressure, relative permeability, NMR response and resistivity index. Cores aged in crude oil, with different wettability were studied. As a preliminary step to investigate the effect of wettability on heterogeneous carbonates from the Middle East, sandpack and sandstone samples were first tested because: 1) these samples are known to be quite homogeneous and of a wettability that can be controlled; 2) To test our experimental methods; and 3) to serve as a dataset for modelling studies. First, the static (porosity and permeability) and dynamic (initial water saturation and residual oil saturation) properties of Leavenseat (LV60) and Ottawa (F-42) sandpacks were measured. The formation factor and NMR response for these sandpacks were also determined. These experimental measurements have served as a benchmark for pore-modelling studies that have reproduced the experimental data. Fontainebleau sandstones have also been used as a benchmark in the industry because of its relatively simple pore structure. Mercury injection capillary pressure (MICP) measurements were performed on this sandstone. The MICP experimental measurements showed very low pore volume values, indicating very tight (consolidated) samples. These samples had a diameter of less than 0.02 m which made the experiments quite difficult. Once we had confidence in the experimental methodology, five carbonate samples from a typical Middle East reservoir were imaged and cleaned in order to render them more water wet. Conventional and special core analyses were performed on all the samples. The pore throat distribution from capillary pressure was successfully compared with the pore size distribution inferred from the NMR T2 relaxation curve. Formation resistivity factor and the formation resistivity index were also measured. Capillary pressure and relative permeability curves were measured using refined oil and synthetic formation brine. Then the samples were aged in crude oil from the same field at elevated temperature (120oC) and underwent the same experiments to evaluate the influence of wettability changes on these properties. The experimental data show that there is a significant difference in the relative permeability and capillary pressure of the cleaned and aged samples; the results are explained in terms of the pore-scale configurations of fluids. In contrast, electrical resistivity did not encounter significant changes for different wettability, suggesting that electrical properties in these carbonates are mainly affected by the porosity that remains water-wet, or is only neutrally-wet. This conclusion is supported by the significant displacement that is observed in the aged sample at capillary pressures close to zero. We show that wettability, imbibition capillary pressure and relative permeability have major impact on the waterflood sweep efficiency and hence on the distribution of remaining oil saturation. An incorrect understanding of the distribution of remaining oil saturation may lead to ineffective reservoir management and IOR/EOR decisions. The second part of this thesis is to assess the efficacy of CO2 injection into carbonate oil fields. The reservoir under study is a layered system. The reservoir consists of two main units, i.e. a lower zone of generally low permeability layers and an upper zone of high permeability layers inter-bedded with low permeability layers; the average permeability of the upper zone is some 10-100 times higher than that of the Lower zone. Under waterflooding, the injected water tends to flow through the upper zone along the high permeability layers and no or very slow cross flow of water into the lower zone occurs, resulting in very poor sweep of the lower zone. There is significant scope for improving oil recovery from such type of heterogeneous mixedwet carbonate reservoirs. The apparent impediment to water invading the bottom strata prompts suggests that a miscible fluid could be Injected into the lower zone. We conducted a series of core-flood experiments to compare the performance of different displacement process: waterflooding, hydrocarbon gas flooding and wateralternate gas (WAG) and compared them with CO2 injection. We show that the local displacement efficiency for CO2 flooding is approximately 97% - much higher than that obtained from waterflooding or hydrocarbon gas injection, due to the development of miscibility between CO2 and the oil. We use the results to discuss the potential of CO2 injection for storage and enhanced oil recovery in the Middle East carbonate reservoir discussed above, and proposes further research to develop a fuller understanding of the subsurface behavior of CO2

Tight lower bound to the geometric measure of quantum discord

Dakic, Vedral and Brukner [Physical Review Letters \tf{105},190502 (2010)] gave a geometric measure of quantum discord in a bipartite quantum state as the distance of the state from the closest classical quantum (or zero discord) state and derived an explicit formula for a two qubit state. Further, S.Luo and S.Fu [Physical Review A \tf{82}, 034302 (2010)] obtained a generic form of this geometric measure for a general bipartite state and established a lower bound. In this brief report we obtain a rigorous lower bound to the geometric measure of quantum discord in a general bipartite state which dominates that obtained by S.Luo and S.Fu.Comment: 10 pages,2 figures. In the previous versions, a constraint was ignored while optimizing the second term in Eq.(5), in which case, only a lower bound on the geometric discord can be obtained. The title is also consequently changed. Accepted in Phys.Rev.

A Single Currency For The GCC: Launching A New Culture

The member states of the Gulf Cooperation Council (GCC) are moving towards launching a single currency by January 2010, an advanced step towards monetary union. These countries are characterized with a great degree of similarities whether political, economic, or social. This provides an advantage many regional economic groups lack. A single currency setting, as advocated in the literature, requires fulfillment of many conditions and requirements to assert its feasibility, desirability and durability. The SWOT methodology utilized in this paper presents a list of activities that must be thought of carefully before and after the year 2010, when the single currency is planned to circulate. Time is approaching fast, thus, GCC states should take serious steps in the remaining few years. The paper identifies very important issues that must be investigated and settled ahead of launching the common currency; among them the urgent need to establish super-national institutions and pooling legislations and economic environment

Entanglement Capacity of Nonlocal Hamiltonians : A Geometric Approach

We develop a geometric approach to quantify the capability of creating entanglement for a general physical interaction acting on two qubits. We use the entanglement measure proposed by us for $N$-qubit pure states (PRA \textbf{77}, 062334 (2008)). Our procedure reproduces the earlier results (PRL \textbf{87}, 137901 (2001)). The geometric method has the distinct advantage that it gives an experimental way to monitor the process of optimizing entanglement production.Comment: 8 pages, 1 figure

Quantum Revivals in Periodically Driven Systems close to nonlinear resonance

We calculate the quantum revival time for a wave-packet initially well localized in a one-dimensional potential in the presence of an external periodic modulating field. The dependence of the revival time on various parameters of the driven system is shown analytically. As an example of application of our approach, we compare the analytically obtained values of the revival time for various modulation strengths with the numerically computed ones in the case of a driven gravitational cavity. We show that they are in very good agreement.Comment: 14 pages, 1 figur

The role of endoplasmic reticulum in human adipose tissue

Adipose tissue plays a central role in the regulation of metabolic homeostasis. In obesity adipocytes are challenged by many insults: surplus energy, inflammation, insulin resistance and considerable endoplasmic reticulum (ER) stress. ER stress has been casually linked to increased inflammation and insulin resistance. Also, obesity linked type 2 diabetes is associated with hyperglycaemia, lipotoxicity and endotoxemia. Therefore, the aims of this thesis briefly were to 1) characterise human pre-adipocytes during differentiation, as a suitable primary cellular model to examine intracellular pathways, 2) investigate the role of glucose and fatty acids on ER stress pathway; as these primary insults are considered to have clear impact on inflammation, insulin resistance (IR) status and diabetes pathogenesis 3) to examine the role of lipopolysaccharide (LPS), a gut derived bacterial fragment, on ER stress; as LPS is now considered a systemic circulating factor raised in conditions of IR, 4) the role of salicylate, known to have anti-inflammatory properties which may negate or at least attenuate the effects of ER stress. Components of the ER stress pathways were studied in human abdominal subcutaneous (AbSc) adipose tissue (AT) from obese and lean subjects. Following characterisation, culture and differentiation of primary human pre-adipocytes, these adipocytes were treated with lipopolysaccharide (LPS), high glucose (HG), tunicamycin (Tun) and saturated fatty acids (SFA) either alone or in combination with sodium salicylate (Sal). Quantitative RT-PCR, western blotting, adipokine analysis were used to assess expression levels. Markers of ER stress were significantly increased in AbSc AT from subjects with obesity (P<0.001). Differentiated primary human adipocytes treated with LPS, Tun, HG and SFA showed significant activation of p-eIF2α and ATF6 and their downstream targets (P<0.05). This effect was alleviated in the presence of Sal. There was also significant activation of AktSer473 during ER stress (P<0.05). This thesis presents important evidence that firstly, there is increased ER stress in human adipose tissue of obese individuals, secondly, LPS, hyperglycaemia and saturated fatty acids induce significant ER stress in primary human adipocytes and finally that induction is alleviated by salicylate. Taken together these studies highlights that ER stress occurs in human differentiated pre-adipocytes is exacerbated in conditions of high glucose, high saturated fatty acids and LPS, as well as determining that such primary insults can be reduced by salicylates providing initial evidence that therapeutic agents have the potential capacity to alleviate ER stress in human adipose tissue