Authenticating Location Based Skyline Queries in Mobile Environment

Abstract: With the booming of Smartphone's and mobile devices, location-based services have experienced massive escalation in nowadays. The outsourcing data processing services to cloud service provider becomes very trending in recent years, which provides solution to the clients instead of data owner. However, we cannot expect real solutions from the data processing services; it may give dishonest results to the clients. Therefore, to provide the correct results some authentication techniques are requiring. In this paper, we learn the authentication techniques for location-based arbitrary-subspace skyline queries (LASQs), which signify an essential class of LBS applications. We suggest a basic Merkle Skyline R-tree method and a novel Partial S4-tree method to authenticate LASQs. For authentication process using this LASQ, the client can contact server frequently during movement and also verify the results by client itself

Experimental signatures of quantum and topological states in frustrated magnetism

Frustration in magnetic materials arising from competing exchange interactions can prevent the system from adopting long-range magnetic order and can instead lead to a diverse range of novel quantum and topological states with exotic quasiparticle excitations. Here, we review prominent examples of such emergent phenomena, including magnetically-disordered and extensively degenerate spin ices, which feature emergent magnetic monopole excitations, highly-entangled quantum spin liquids with fractional spinon excitations, topological order and emergent gauge fields, as well as complex particle-like topological spin textures known as skyrmions. We provide an overview of recent advances in the search for magnetically-disordered candidate materials on the three-dimensional pyrochlore lattice and two-dimensional triangular, kagome and honeycomb lattices, the latter with bond-dependent Kitaev interactions, and on lattices supporting topological magnetism. We highlight experimental signatures of these often elusive phenomena and single out the most suitable experimental techniques that can be used to detect them. Our review also aims at providing a comprehensive guide for designing and investigating novel frustrated magnetic materials, with the potential of addressing some important open questions in contemporary condensed matter physics

Spin re-orientation induced anisotropic magnetoresistance switching in LaCo0.5_{0.5}Ni0.5_{0.5}O3−δ_{3-\delta} thin films

Realization of novel functionalities by tuning magnetic interactions in rare earth perovskite oxide thin films opens up exciting technological prospects. Strain-induced tuning of magnetic interactions in rare earth cobaltates and nickelates is of central importance due to their versatility in electronic transport properties. Here we reported the spin re-orientation induced switching of anisotropic magnetoresistance (AMR) and its tunability with strain in epitaxial LaCo$_{0.5}$Ni$_{0.5}$O$_{3-\delta}$ thin films across the ferromagnetic transition. Moreover, with strain tuning, we could observe a two-fold to four-fold symmetry crossover in AMR across the magnetic transition temperature. The magnetization measurements revealed an onset of ferromagnetic transition around 50 K, and a further reduction in temperature showed a subtle change in the magnetization dynamics, which reduced the ferromagnetic long-range ordering and introduced glassiness in the system. X-ray absorption and X-ray magnetic circular dichroism spectroscopy measurements over Co and Ni L edges revealed the Co spin state transition below the magnetic transition temperature leading to the AMR switching and also the presence of Ni$^{2+}$ and Co$^{4+}$ ions evidencing the charge transfer from Ni to Co ions. Our work demonstrated the tunability of magnetic interactions mediated electronic transport in cobaltate-nickelate thin films, which is relevant in understanding Ni-Co interactions in oxides for their technological applications such as in AMR sensors

Spin-liquid-like state in a square lattice antiferromagnet

Collective behavior of spins, frustration-induced strong quantum fluctuations and subtle interplay between competing degrees of freedom in quantum materials can lead to correlated quantum states with fractional excitations that are essential ingredients for establishing paradigmatic models and have immense potential for quantum technologies. Quenched randomness is a new paradigm in elucidating the emergence of spin-liquidlike states in geometrically frustrated magnets. Herein, we report magnetization, specific heat, electron spin resonance, and muon spin resonance studies on a 3d-electron-based square lattice antiferromagnet Sr3CuTa2O9. In this material, S = 1/2 Cu2+ nearest-neighbor ions constitute a two-dimensional square lattice. The negative value of Curie-Weiss temperature, obtained from the Curie-Weiss fit of high-temperature magnetic susceptibility data indicates the presence of antiferromagnetic interaction between Cu2+ moments. Specific heat data show the absence of long-range magnetic ordering down to 64 mK despite a reasonably strong exchange interaction between Cu2+ spins as reflected from a Curie-Weiss temperature of -27 K. The power-law behavior and the data collapse of specific heat and magnetization data evince the emergence of a random-singlet state in Sr3CuTa2O9. The power-law-like spin auto-correlation function and the data collapse of muon polarization asymmetry with longitudinal field dependence of t/({\mu}0H){\gamma} further support credence to the presence of a randomness-induced liquid-like state. Our results suggest that randomness induced by disorder is a viable route to realize quantum spin liquid-like state in this square lattice antiferromagnet

Observation of spin glass state in weakly ferromagnetic Sr2_2FeCoO6_6 double perovskite

We report the observation of spin glass state in the double perovskite oxide Sr$_{2}$FeCoO$_{6}$ prepared through sol-gel technique. Initial structural studies using x rays reveal that the compound crystallizes in tetragonal $I 4/m$ structure with lattice parameters, $a$ = 5.4609(2) \AA and $c$ = 7.7113(7) \AA. The temperature dependent powder x ray studies reveal no structural phase transition in the temperature range 10 -- 300 K. However, the unit cell volume shows an anomaly coinciding with the magnetic transition temperature thereby suggesting a close connection between lattice and magnetism. Neutron diffraction studies and subsequent bond valence sums analysis show that in Sr$_{2}$FeCoO$_{6}$, the $B$ site is randomly occupied by Fe and Co in the mixed valence states of Fe$^{3+}$/Fe$^{4+}$ and Co$^{3+}$/Co$^{4+}$. The random occupancy and mixed valence sets the stage for inhomogeneous magnetic exchange interactions and in turn, for the spin glass like state in this double perovskite which is observed as an irreversibility in temperature dependent dc magnetization at $T_f\sim$ 75 K. Thermal hysteresis observed in the magnetization profile of Sr$_{2}$FeCoO$_{6}$ is indicative of the mixed magnetic phases present. The dynamic magnetic susceptibility displays characteristic frequency dependence and confirms the spin glass nature of this material. Dynamical scaling analysis of $\chi'(T)$ yields a critical temperature $T_{ct}$ = 75.14(8) K and an exponent $z\nu$ = 6.2(2) typical for spin glasses. The signature of presence of mixed magnetic interactions is obtained from the thermal hysteresis in magnetization of Sr$_{2}$FeCoO$_{6}$. Combining the neutron and magnetization results of Sr$_2$FeCoO$_6$, we deduce the spin states of Fe to be in low spin while that of Co to be in low spin and intermediate spin.Comment: 23 pages, 6 figures, accepted in J. Appl. Phy

Signature of a randomness-driven spin-liquid state in a frustrated magnet

Collective behaviour of electrons, frustration induced quantum fluctuations and entanglement in quantum materials underlie some of the emergent quantum phenomena with exotic quasi-particle excitations that are highly relevant for technological applications. Herein, we present our thermodynamic and muon spin relaxation measurements, complemented by ab initio density functional theory and exact diagonalization results, on the recently synthesized frustrated antiferromagnet Li4CuTeO6, in which Cu2+ ions (S = 1/2) constitute disordered spin chains and ladders along the crystallographic [101] direction with weak random inter-chain couplings. Our thermodynamic experiments detect neither long-range magnetic ordering nor spin freezing down to 45 mK despite the presence of strong antiferromagnetic interaction between Cu2+ moments leading to a large effective Curie-Weiss temperature of -154 K. Muon spin relaxation results are consistent with thermodynamic results. The temperature and magnetic field scaling of magnetization and specific heat reveal a data collapse pointing towards the presence of random-singlets within a disorder-driven correlated and dynamic ground-state in this frustrated antiferromagnet

Ischemic stroke as a complication of cryptococcal meningitis and immune reconstitution inflammatory syndrome: a case report.

BACKGROUND: Cryptococcal meningitis remains the leading cause of adult meningitis in Sub-Saharan Africa. Immune Reconstitution Inflammatory Syndrome (IRIS) following anti-retroviral therapy (ART) initiation is an important complication. Here we report the first documented case of a IRIS reaction presenting as an ischemic stroke. CASE PRESENTATION: A 38 year old newly diagnosed HIV-infected, ART naive Malawian male presented to a tertiary referral hospital in Blantyre, Malawi with a 2 week history of headache. A diagnosis of cryptococcal meningitis was made and the patient was started on 1200 mg fluconazole once daily and flucytosine 25 mg/kg four times daily as part of the Advancing Cryptococcal Treatment for Africa (ACTA) clinical trial. There was an initial clinical and microbiological response to anti-fungal treatment and anti-retroviral therapy was started at week 4. The patient re-presented 16 days later with recurrence of headache, fever, and a sudden onset of left sided weakness in the context of rapid immune reconstitution; peripheral CD4 count had increased from a baseline of 29 cells/μl to 198 cells/μl. Recurrence of cryptococcal meningitis was excluded through CSF examination and fungal culture. Magnetic Resonance Imaging (MRI) of the brain demonstrated multi-focal DWI (diffusion weighted imaging) positive lesions consistent with an ischemic stroke. Given the temporal relationship to ART initiation, these MRI findings in the context of sterile CSF with raised CSF protein and a rapid immune reconstitution, following an earlier favorable response to treatment is most consistent with a paradoxical Immune Reconstitution Inflammatory Syndrome. CONCLUSIONS: Stroke is an increasing cause of morbidity and mortality amongst HIV infected persons. Ischemic stroke is a recognized complication of cryptococcal meningitis in the acute phase and is thought to be mediated by an infectious vasculitis. This is the first time an ischemic stroke has been described as part of a paradoxical IRIS reaction. This report adds to the spectrum of clinical IRIS presentations recognized and highlights to clinicians the potential complications encountered at ART initiation in severely immunocompromised patients

Lifestyle intervention in obese pregnancy and cardiac remodelling in 3-year olds: children of the UPBEAT RCT

Background/Objectives: Obesity in pregnancy has been associated with increased childhood cardiometabolic risk and reduced life expectancy. The UK UPBEAT multicentre randomised control trial was a lifestyle intervention of diet and physical activity in pregnant women with obesity. We hypothesised that the 3-year-old children of women with obesity would have heightened cardiovascular risk compared to children of normal BMI women, and that the UPBEAT intervention would mitigate this risk. Subjects/Methods: Children were recruited from one UPBEAT trial centre. Cardiovascular measures included blood pressure, echocardiographic assessment of cardiac function and dimensions, carotid intima-media thickness and heart rate variability (HRV) by electrocardiogram. Results: Compared to offspring of normal BMI women (n = 51), children of women with obesity from the trial standard care arm (n = 39) had evidence of cardiac remodelling including increased interventricular septum (IVS; mean difference 0.04 cm; 95% CI: 0.018 to 0.067), posterior wall (PW; 0.03 cm; 0.006 to 0.062) and relative wall thicknesses (RWT; 0.03 cm; 0.01 to 0.05) following adjustment. Randomisation of women with obesity to the intervention arm (n = 31) prevented this cardiac remodelling (intervention effect; mean difference IVS −0.03 cm (−0.05 to −0.008); PW −0.03 cm (−0.05 to −0.01); RWT −0.02 cm (−0.04 to −0.005)). Children of women with obesity (standard care arm) compared to women of normal BMI also had elevated minimum heart rate (7 bpm; 1.41 to 13.34) evidence of early diastolic dysfunction (e prime) and increased sympathetic nerve activity index by HRV analysis. Conclusions: Maternal obesity was associated with left ventricular concentric remodelling in 3-year-old offspring. Absence of remodelling following the maternal intervention infers in utero origins of cardiac remodelling. Clinical trial registry name and registration number: The UPBEAT trial is registered with Current Controlled Trials, ISRCTN89971375

Cellular Basis of Tissue Regeneration by Omentum

The omentum is a sheet-like tissue attached to the greater curvature of the stomach and contains secondary lymphoid organs called milky spots. The omentum has been used for its healing potential for over 100 years by transposing the omental pedicle to injured organs (omental transposition), but the mechanism by which omentum helps the healing process of damaged tissues is not well understood. Omental transposition promotes expansion of pancreatic islets, hepatocytes, embryonic kidney, and neurons. Omental cells (OCs) can be activated by foreign bodies in vivo. Once activated, they become a rich source for growth factors and express pluripotent stem cell markers. Moreover, OCs become engrafted in injured tissues suggesting that they might function as stem cells