Optimal observables to determine entanglement of a two qubit state

Experimental determination of entanglement is important not only to characterize the state and use it in quantum information, but also in understanding complicated phenomena such as phase transitions. In this paper we show that in many cases, it is possible to determine entanglement of a two qubit state, as represented by concurrence, with a few observables, most of which are local. In particular, rank 1 and rank 2 states need exclusively measurement of local observables while rank 3 states need measurement of just one correlation observable in addition to local observables. Only the rank 4 states are shown to require a more detailed tomography. The analysis also sheds light on the other measure, non separability since it is a lower bound on concurrence.Comment: 8 pages, 1 figur

BIO-CONTROL OF MULTIPLE DRUG-RESISTANT UROPATHOGENS USING MEDICINAL PLANT EXTRACTS

Objective: The present study was conducted to evaluate the potential of some medicinal plants used in Ayurveda in treating multiple drug-resistant human pathogens causing urinary tract infections (UTIs). Methods: Dried parts of six medicinal plants used in Ayurveda for treating UTI were Soxhlet extracted, and the extract was concentrated in vacuo. Various concentrations of the extract were tested for antimicrobial activity against three clinical isolates of multiple drug-resistant bacteria causing UTI. Results: Preliminary results showed the promising antibacterial effect of plant extracts. Escherichia coli, the most common pathogen associated with UTI, was susceptible to aqueous extracts of all the six medicinal plants. Conclusion: This study concluded that the medicinal plants used in Ayurveda to treat UTIs are effective against multiple drug-resistant uropathogens. Further study in this regard may lead to the identification of novel antimicrobial agent for treating multiple drug-resistant urinary tract pathogens

Anatomy of magnetic anisotropy induced by Rashba spin-orbit interactions

Magnetic anisotropy controls the orientational stability and switching properties of magnetic states, and therefore plays a central role in spintronics. First-principles density-functional-theory calculations are able, in most cases, to provide a satisfactory description of bulk and interface contributions to the magnetic anisotropy of particular film/substrate combinations. In this paper we focus on achieving a simplified understanding of some trends in interfacial magnetic anisotropy based on a simple tight-binding model for quasiparticle states in a heavy-metal/ferromagnetic-metal bilayer film. We explain how to calculate the magnetic anisotropy energy of this model from the quasiparticle spin-susceptibility, compare with more conventional approaches using either a perturbative treatment of spin-orbit interactions or a direct calculation of the dependence of the energy on the orientation of the magnetization, and show that the magnetic anisotropy can be interpreted as a competition between a Fermi-sea term favoring perpendicular anisotropy and a Fermi-surface term favoring in-plane anisotropy. Based on this finding, we conclude that perpendicular magnetic anisotropy should be expected in an itinerant electron thin film when the spin magnetization density is larger than the product of the band exchange splitting and the Fermi level density-of-states of the magnetic state

Mechanics of biopolymer networks, stimuli responsive particle suspensions, and their combinations

The key aim of this thesis is to demonstrate new paradigms in designing stiffness changing soft materials. The systems developed and studied in this work have salient and unprecedented features such as (1) the ability to controllably stiffen up to 100 times (10,000 %) when exposed to an external stimulus of temperature or magnetic field, (2) the ability to uncontrollably assemble into a ultra-soft hydrogel by undergoing 10,000 fold volume expansion within 0.4 s, and (3) transformation from a repulsive colloidal glassy state to a particulate gel thus undergoing change in the dynamics and mechanical properties. With a combination of rigorous experiments and mathematical models, this thesis offers novel ways to achieve functionality in soft materials and may have numerous applications in the fields of soft robotics, defense, and direct-write additive manufacturing. In part one of this thesis, a naturally produced biomaterial, hagfish slime is studied to understand its design principles. Hagfish slime is a unique predator defense material containing a network of long fibrous threads each 10 -15 cm in length. Hagfish releases the threads in a condensed coiled state known as skeins (∼ 100 µm), which must unravel within a fraction of a second and form a soft hydrogel to thwart a predator attack. The mechanisms of how the hagfish controls the unraveling rates, and the properties of the resulting gel are not well understood. The combined experimental and theoretical approach adopted in this thesis address these questions. First, the hypothesis that the viscous hydrodynamics may be responsible for the rapid unravelling rates is considered, and the scenario of a single skein unspooling as the fiber peels away due to viscous drag is discussed. As a result, its is shown that under reasonable physiological conditions viscous-drag-induced unravelling can occur within a few hundred milliseconds, comparable with the physiological time scales. Subsequently, through the rheological study on slime networks it is shown that key rheological and structural features of hagfish slime are insensitive to its concentration, in spite of the uncontrolled gelation process, and this peculiar characteristic may be vital for its physiological use. In part two, the linear and nonlinear rheology of a model system of soft microgel suspensions is investigated. The interaction pair-potential between the microgel is temperature-dependent. By increasing concentration of the suspension, a transition from a viscous liquid to an entropic glass to a soft jammed state at low temperatures where the microgels interact via a repulsive potential. Increasing the temperature of the suspension beyond the Lower Critical Solution Temperature [LCST], introduces additional attractive interactions, and results in the formation of particulate gels. The competition between repulsive and attractive interactions gives a rich temperature-dependent rheological response that is also concentration-dependent. An integrated experimental and quantitative theoretical approach is presented to understand the key linear and nonlinear of the suspensions in various regimes. In part three, two novel soft composite systems capable of unprecedented change in their mechanical properties in response to magnetic and thermal excitation are developed. The composites were formed by integrating stimuli-responsive particles (thermoresponsive microgels and magnetic particles) into the strain stiffening network of biopolymer fibrin. The interactions between the stimuli-responsive particles and biopolymer mesh is hypothesized to induces local stresses in the mesh, which inherently stiffens under the stress owing to its semiflexible nature. This helps achieve a higher sensitivity to the external field in the fabricated composites compared to the traditional flexible-polymer matrix of composite systems. Phenomenological models are developed that quantify this hypothesis, and the derived predictions are qualitatively consistent with the experimental data. This approach of using composites based on semiflexible polymers with strong inherent nonlinearity offers a promising method for developing functional materials with actively tunable mechanical propertie

Labyrinth Seal Leakage Analysis

Seals are basic mechanical devices commonly used in machinery to avoid undesired flow losses of working fluids. To understand the working of these seals specifically those placed between relatively moving parts is still one of the major engineering challenges for the scientific community. Particularly Annular seals are one of the most widely used in rotating machinery comprising turbines, compressors and pumps. They are mounted on the shaft that rotates within a stationary case. These seal designs make an impact on (i) machinery energy conversion efficiency and (ii) rotor dynamic stability due to the interaction between rotor and stator through fluid flow leakage. Among all annular seals straight through rectangular labyrinth seals are the most commonly used ones. Their designs have not changed much a lot since its inception by C.J. Parsons [1] back in 1901. These seals provide resistance to the fluid flow through tortuous path comprising of series of cavities and clearances. The sharp tooth converts the pressure energy to the kinetic which is dissipated through turbulence viscosity interaction in the cavity. To understand the accurate amount of leakage the flow is modeled using the discharge coefficient and for each tooth and the kinetic energy carry over coefficients. This research work is aimed at understanding the fluid flow though labyrinth seals with tooth mounted on the rotor. A matrix of fluid flow simulations has been carried out using commercially available CFD software Fluent® where all parameters effecting the flow field has been studied to understand their effect on the coefficients defining the seal losses. Also the rotor surface speed has been used varied in a step by step manner to understand the fluid flow behavior in high speed turbo-machinery. The carry over coefficient is found to be the function of all the geometric elements defining the labyrinth tooth configuration. A relation between the flow parameters and the carry over coefficient has also been established. The discharge coefficient of the first tooth has been found to be lower and varying in a different manner as compared to a tooth from a multiple cavity seal. Its dependence upon flow parameters and dimensionless geometric constants has been established. The discharge coefficient of the first teeth is found to be increasing with increasing tooth width. Further the compressibility factor has been defined to incorporate the deviation of the performance of seals with compressible fluid to that with the incompressible flow. Its dependence upon pressure ratio and shaft speed has also been established. Using all the above the mentioned relations it would be easy decide upon the tooth configuration for a given rotating machinery or understand the behavior of the seal currently in use

A comparative study of azelastine, cromolyn and olopatadine ophthalmic solution in vernal keratoconjunctivitis in a tertiary care hospital-open label parallel group study design

Background: Vernal keratoconjunctivitis (VKC) is a chronic, bilateral, external ocular inflammatory disease primarily affecting young boys living in warm, dry climates with seasonal variations. The disease causes lot of discomfort to the patient and sometimes can predispose to serious problems like shield ulceration and keratoconus. A number of drugs are used in the management of the condition, with variable results. The aims and objectives of this study was to compare the efficacy and safety of the drugs, cromolyn sodium, azelastine and olopatadine ophthalmic solutions in the treatment of VKC.Methods: Sixty patients of VKC were studied over a period of 6 weeks. They were divided into 3 groups randomly to receive one of the drugs under study. Symptoms and signs were recorded after detailed questioning and examination according to modified criterion of Tabbara and Arafat.Results: There was significant reduction in the mean itching scores with olopatadine as compared to cromolyn sodium and azelastine (p<0.05). Olopatadine significantly decreased mean lacrimation scores as compared to cromolyn sodium and azelastine (p<0.005). Olopatadine, cromolyn and azelastine showed significant reduction of corneal stippling, but no drug was significantly better than the other. Both cromolyn and olopatadine showed reduction of limbal edema equally (p<0.05), olopatadine reduced limbal edema more significantly as compared to azelastine (p<0.05).Conclusions: All the three drugs were found to be safe in the treatment of VKC. Olopatadine may be preferred over the other two drugs since it reduced both itching and discharge most significantly