Computing the multifractal spectrum from time series: An algorithmic approach

We show that the existing methods for computing the f(\alpha) spectrum from a time series can be improved by using a new algorithmic scheme. The scheme relies on the basic idea that the smooth convex profile of a typical f(\alpha) spectrum can be fitted with an analytic function involving a set of four independent parameters. While the standard existing schemes [16, 18] generally compute only an incomplete f(\alpha) spectrum (usually the top portion), we show that this can be overcome by an algorithmic approach which is automated to compute the Dq and f(\alpha) spectrum from a time series for any embedding dimension. The scheme is first tested with the logistic attractor with known f(\alpha) curve and subsequently applied to higher dimensional cases. We also show that the scheme can be effectively adapted for analysing practcal time series involving noise, with examples from two widely different real world systems. Moreover, some preliminary results indicating that the set of four independant parameters may be used as diagnostic measures is also included.Comment: 10 pages, 16 figures, submitted to CHAO

Structural domain and spin ordering induced glassy magnetic phase in single layered manganite Pr0.22_{0.22}Sr1.78_{1.78}MnO4_4

The single layered manganite Pr$_{0.22}$Sr$_{1.78}$MnO$_4$ undergoes structural transition from high temperature tetragonal phase to low temperature orthorhombic phase below room temperature. The orthorhombic phase was reported to have two structural variants with slightly different lattice parameters and Mn-3$d$ levels show orbital ordering within both the variants, albeit having mutually perpendicular ordering axis. In addition to orbital ordering, the orthorhombic variants also order antiferromagnetically with different N\'eel temperatures. Our magnetic investigation on the polycrystalline sample of Pr$_{0.22}$Sr$_{1.78}$MnO$_4$ shows large thermal hysteresis indicating the first order nature of the tetragonal to orthorhombic transition. We observe magnetic memory, large relaxation, frequency dependent ac susceptbility and aging effects at low temperature, which indicate spin glass like magnetic ground state in the sample. The glassy magnetic state presumably arises from the interfacial frustration of orthorhombic domains with orbital and spin orderings playing crucial role toward the competing magnetic interactions.Comment: 6 pages, 4 figures, Accepted in Europhysics Letter

Localizing genuine multiparty entanglement in noisy stabilizer states

Characterizing large noisy multiparty quantum states using genuine multiparty entanglement is a challenging task. In this paper, we calculate lower bounds of genuine multiparty entanglement localized over a chosen multiparty subsystem of multi-qubit stabilizer states in the noiseless and noisy scenario. In the absence of noise, adopting a graph-based technique, we perform the calculation for arbitrary graph states as representatives of the stabilizer states, and show that the graph operations required for the calculation has a polynomial scaling with the system size. As demonstrations, we compute the localized genuine multiparty entanglement over subsystems of large graphs having linear, ladder, and square structures. We also extend the calculation for graph states subjected to single-qubit Markovian or non-Markovian Pauli noise on all qubits, and demonstrate, for a specific lower bound of the localizable genuine multiparty entanglement corresponding to a specific Pauli measurement setup, the existence of a critical noise strength beyond which all of the post measured states are biseparable. The calculation is also useful for arbitrary large stabilizer states under noise due to the local unitary connection between stabilizer states and graph states. We demonstrate this by considering a toric code defined on a square lattice, and computing a lower bound of localizable genuine multiparty entanglement over a non-trivial loop of the code. Similar to the graph states, we show the existence of the critical noise strength in this case also, and discuss its interesting features.Comment: 36 pages, 21 figures, 2 table

Association of Serum Uric Acid Levels in Acute Ischemic Stroke

BACKGROUND: For decades the role of Uric acid as a independent risk factor for noncommunicable disease is a subject of discussion. Serum Uric acid is a powerful antioxidant that scavenge many harmful free radicals like hydroxyl ions, peroxinitrite along with other anti-oxidants like ascorbic acid .But elevated serum uric acid can act as pro-oxidant that cause various inflammatory reactions. Serum uric acid can cause endothelial dysfunction, nitric oxide reduction in cells, platelet dysfunction, vascular smooth muscle cells proliferation and activates RAAS. AIM OF THE STUDY: 1. To study the association between serum uric acid level and acute ischemic stroke. 2. To study the association between serum uric acid level and other risk factors like SHT, DM, CAD, Obesity. METHODS: This is an analytical cross sectional study done at Govt. Royapettah Hospital. Serum uric acid levels were measured within 24hrs of onset of scute ischemic stroke. 50 patients were studied. Serum uric acid level was taken as 6.5mg/dl. This value was compared with various other variables. RESULTS: Of the study population 66% were male and 34% were female. 38% of the population were 60 yrs of age. 76% were hemiparetic and 24% were hemiplegic. 76% had serum uric acid 6.5mg/dl. The study revealed the strong association between the serum uric acid and DM, SHT, CAD, Dyslipidemia with a p value 0.05. All patients admitted with hemiplegia have serum uric level >7mg/dl which is highly significant. CONCLUSION: The study shows that uric acid levels may be considered as an independent predictor for ischemic stroke. SUA has a strong association with DM, SHT and CAD

Crystal structural studies of ethyl-5-(4-chlorophenylsulfonyl)-4-hydroxy-2, 6-dip-tolyl-1, 2, 5, 6-tetrahydropyridine-3-carboxylate and diethyl 4-hydroxy-2-(4-nitrophenyl)-5-(phenylsulfonyl)-6-(phenylsulfonylmethyl)cyclohexa-3,6-diene-1,3-dicarboxylate

The crystal structures of trans,trans-Ethyl-5-(4-chlorophenylsulfonyl)-4-hydroxy-2,6-dip-tolyl-1,2,5,6-tetrahydropyridine-3-carboxylate (Ia) and cis-Diethyl 4-hydroxy-2-(4-nitrophenyl)-5-(phenylsulfonyl)-6-(phenylsulfonylmethyl)cyclohexa-3,6-diene-1,3-dicarboxylate (Ib) were elucidated by single crystal X ray diffraction. Compound (Ia) C28H28Cl NO5S, crystallizes in the monoclinic system, space group P 21/c, with a = 9.4530(7) Å, b = 25.366(2) Å, c = 11.4353(8) Å, β = 103.092(7)°, V = 2670 (3) Å3 and   Z = 4. The compound (Ib), C31H29N1O11S2, crystallizes in the monoclinic system, space group P 21/c, with a = 21.179(4) Å, b = 8.4998(16) Å, c = 17.347(3) Å, β = 102.563(3)°, V = 3048.0(10) Å3 and Z = 4. The central piperidine ring of compound (Ia) adopts the sofa conformation and the central cyclohexadiene ring of compound (Ib) adopts the boat conformation.  Details of the compounds preparation, crystal structures and hydrogen bonding interactions of the compounds are discussed

Approaching the Ground State of Frustrated A-site Spinels: A Combined Magnetization and Polarized Neutron Scattering Study

We re-investigate the magnetically frustrated, {\it diamond-lattice-antiferromagnet} spinels FeAl$_2$O$_4$ and MnAl$_2$O$_4$ using magnetization measurements and diffuse scattering of polarized neutrons. In FeAl$_2$O$_4$, macroscopic measurements evidence a "cusp" in zero field-cooled susceptibility around 13~K. Dynamic magnetic susceptibility and {\it memory effect} experiments provide results that do not conform with a canonical spin-glass scenario in this material. Through polarized neutron scattering studies, absence of long-range magnetic order down to 4~K is confirmed in FeAl$_2$O$_4$. By modeling the powder averaged differential magnetic neutron scattering cross-section, we estimate that the spin-spin correlations in this compound extend up to the third nearest-neighbour shell. The estimated value of the Land\'{e} $g$ factor points towards orbital contributions from Fe$^{2+}$. This is also supported by a Curie-Weiss analysis of the magnetic susceptibility. MnAl$_2$O$_4$, on the contrary, undergoes a magnetic phase transition into a long-range ordered state below $\approx$ 40~K, which is confirmed by macroscopic measurements and polarized neutron diffraction. However, the polarized neutron studies reveal the existence of prominent spin-fluctuations co-existing with long-range antiferromagnetic order. The magnetic diffuse intensity suggests a similar short range order as in FeAl$_2$O$_4$. Results of the present work supports the importance of spin-spin correlations in understanding magnetic response of frustrated magnets like $A$-site spinels which have predominant short-range spin correlations reminiscent of the "spin liquid" state.Comment: 10 pages, 10 figures, double-column, accepted in Phys. Rev. B, 201

Disorder-driven electronic localization and phase separation in superconducting Fe1+yTe0.5Se0.5 single crystals

We have investigated the influence of Fe-excess on the electrical transport and magnetism of Fe1+yTe0.5Se0.5 (y=0.04 and 0.09) single crystals. Both compositions exhibit resistively determined superconducting transitions (Tc) with an onset temperature of about 15 K. From the width of the superconducting transition and the magnitude of the lower critical field Hc1, it is inferred that excess of Fe suppresses superconductivity. The linear and non-linear responses of the ac-susceptibility show that the superconducting state for these compositions is inhomogeneous. A possible origin of this phase separation is a magnetic coupling between Fe-excess occupying interstitial sites in the chalcogen planes and those in the Fe-square lattice. The temperature derivative of the resistivity drho/dT in the temperature range Tc < T < Ta with Ta being the temperature of a magnetic anomaly, changes from positive to negative with increasing Fe. A log 1/T divergence of the resistivity above Tc in the sample with higher amount of Fe suggests a disorder driven electronic localization.Comment: 7 page

The chaotic behavior of the black hole system GRS 1915+105

A modified non-linear time series analysis technique, which computes the correlation dimension $D_2$, is used to analyze the X-ray light curves of the black hole system GRS 1915+105 in all twelve temporal classes. For four of these temporal classes $D_2$ saturates to $\approx 4-5$ which indicates that the underlying dynamical mechanism is a low dimensional chaotic system. Of the other eight classes, three show stochastic behavior while five show deviation from randomness. The light curves for four classes which depict chaotic behavior have the smallest ratio of the expected Poisson noise to the variability ($< 0.05$) while those for the three classes which depict stochastic behavior is the highest ($> 0.2$). This suggests that the temporal behavior of the black hole system is governed by a low dimensional chaotic system, whose nature is detectable only when the Poisson fluctuations are much smaller than the variability.Comment: Accepted for publication in Astrophysical Journa