Perfect vortex modes for nondestructive characterization of mode dependent loss in ring core fibers

Ring core fibers (RCF) enable high-performance modal multiplexing with low crosstalk and can support orbital angular momentum (OAM) modes. RCFs are challenging to characterize due to the lack of commercial multiplexers, especially for high OAM orders. For fibers supporting large numbers of modes, typical cutback techniques for characterization are extremely wasteful of fiber, especially as one cutback is required for each mode. We show the differential modal loss across modes 3 to 10 was significantly underestimated using an OTDR when exciting modes individually or when exciting all modes indiscriminately. We exploit perfect vortex beams to achieve reliable and nondestructive characterization of mode-dependent loss (MDL) for OAM modes. Perfect vortex beams allow us to maximize the coupling efficiency at each mode launch, increasing the accuracy of MDL estimate. We fabricated fiber with a refractive index difference between the ring core and the cladding of a 5.1×10⁻². For this fiber, mode orders 3 to 10 are the most suitable for data transmission and were the focus of our work (the fiber support up to OAM order 13). Such a high index difference can lead to MDL. We demonstrate that the modal loss spans from 2.14 to 4.38 dB/km for orders 3 to 10

Raman Signatures of Strong Kitaev Exchange Correlations in (Na1−x_{1-x}Lix_x)2_2IrO3_3 : Experiments and Theory

Inelastic light scattering studies on single crystals of (Na$_{1-x}$Li$_x$)$_2$IrO$_3$ ($x = 0, 0.05$ and $0.15$) show a polarization independent broad band at $\sim$~2750 cm$^{-1}$ with a large band-width $\sim 1800$~cm$^{-1}$. For Na$_2$IrO$_3$ the broad band is seen for temperatures $\leq 200$~K and persists inside the magnetically ordered state. For Li doped samples, the intensity of this mode increases, shifts to lower wave-numbers and persists to higher temperatures. Such a mode has recently been predicted (Knolle et.al.) as a signature of the Kitaev spin liquid. We assign the observation of the broad band to be a signature of strong Kitaev-exchange correlations. The fact that the broad band persists even inside the magnetically ordered state suggests that dynamically fluctuating moments survive even below $T_{N}$. This is further supported by our mean field calculations. The Raman response calculated in mean field theory shows that the broad band predicted for the spin liquid state survives in the magnetically ordered state near the zigzag-spin liquid phase boundary. A comparison with the theoretical model gives an estimate of the Kitaev exchange interaction parameter to be $J_K\approx 57$~meV.Comment: 14pages 4 figure

Unmasking the elusive: an early gestational age placenta accreta case series to illuminate the path towards avoiding missed diagnosis

Placenta accreta is a condition characterized by the abnormal invasion of the placenta into the uterine wall, leading to torrential hemorrhage. This case series, highlights the importance of accurate diagnosis and early detection of this life-threatening complication. The incidence of this iatrogenic complication is rising due to increased caesarean deliveries. While in advance stages of pregnancy the chances of missing accreta are less but in early pregnancy the diagnosis may be elusive. Timely detection by using imaging modalities like ultrasound both 2D and colour Doppler, provide valuable clues. Misdiagnosis may be fatal, especially in the first trimester. The present case series presents 3 cases where initial diagnosis of missed abortion followed by repeated curettage and gestational trophoblastic disease (GTD) was made respectively. The agony of suffering leads the patient to our tertiary care center where the diagnosis of accreta was made. Accurate diagnosis and early detection of placenta accreta are vital to optimize patient outcome. Detecting the nicheand an anteriorly situated low lying placenta with history of previous birth by caesarian section should raise suspicion, and vigilance on the part of treating obstetrician is must

Exploiting the Advantages of Ag/ITO/Enzyme Trapped Gel Layers to Develop a Highly Sensitive and Selective Fiber Optic Plasmonic Urea Sensor

The fabrication and characterization of a surface plasmon resonance (SPR)-based urea biosensor, with thin silver (Ag), ITO (In2O3: SnO2), and enzyme-trapped gel over an unclad portion of plastic-clad silica fiber as a sensing element, is represented. The working principle is to identify changes in the refractive index of the enzyme (urease) entrapped gel layer following the interaction with the incoming analyte. This interaction causes swelling and shrinkage of the gel layer, which alters the effective refractive index of the sensing layer. The wavelength interrogation method is used, and the optimized sensor probe is characterized by urea samples having different pH values. Scanning electron microscopy confirmed the uniformity of the silver layer over the unclad core of the fiber. The sensor operates from 0 to 160 mM of urea concentrations to cover the physiological concentration range of blood urea normally present in the human body. The sensitivity and limit of detection (LOD) offered by the sensor are marked 0.59387 nm/mM near zero concentration of the urea sample and 0.56 mM, respectively, along with the provisions of high stability, remote sensing, and online monitoring of urea. The proposed sensor has proven to be one of a kind due to its fast response time

Impact of yoga on biochemical profile of asthmatics: A randomized controlled study

Background: Asthma is a chronic inflammatory disorder of the airways. The chronic inflammation causes an associated increase in airway hyperresponsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness, and coughing at night or in the early morning. Most of the studies have reported, as the effects of yoga on bronchial asthma, significant improvements in pulmonary functions, quality of life, and decrease in medication use, but none of the studies has attempted to show the effect of yoga on biochemical changes. Objective: To evaluate the effect of yoga on biochemical profile of asthmatics. Materials and Methods: In the present study, 276 patients of mild to moderate asthma (FEV 1 > 60%) aged between 12 to 60 years were recruited from the Department of Pulmonary Medicine, King George′s Medical University, U.P., Lucknow, India. They were randomly divided into two groups: Yoga group (with standard medical treatment and yogic intervention) and control group as standard medical treatment (without yogic intervention). At completion of 6 months of the study period, 35 subjects were dropped out, so out of 276 subjects, only 241 subjects completed the whole study (121 subjects from yoga group and 120 subjects from control group). Biochemical assessment was carried out at baseline and after 6 months of the study period. Results: In yoga group, there was significant improvement found in the proportion of hemoglobin and antioxidant superoxide dismutase in comparison to control group and significant decrease was found in total leukocyte count (TLC) and differential leukocytes count in comparison to control group. There was no significant change found in TLC, polymorphs, and monocytes in between group comparison. Conclusions: Yoga group got significantly better improvement in biochemical variables than control group. Result shows that yoga can be practiced as adjuvant therapy with standard inhalation therapy for better outcome of asthma

Fabrication and Characterization of a SPR Based Fiber Optic Sensor for the Detection of Chlorine Gas Using Silver and Zinc Oxide

A fiber optic chlorine gas sensor working on surface plasmon resonance (SPR) technique fabricated using coatings of silver and zinc oxide films over unclad core of the optical fiber is reported. The sensor probe is characterized using wavelength interrogation and recording SPR spectra for different concentrations of chlorine gas around the probe. A red shift is observed in the resonance wavelength on increasing the concentration of the chlorine gas. The thickness of the zinc oxide film is optimized to achieve the maximum sensitivity of the sensor. In addition to wavelength interrogation, the sensor can also work on intensity modulation. The selectivity of the sensor towards chlorine gas is verified by carrying out measurements for different gases. The sensor has various advantages such as better sensitivity, good selectivity, reusability, fast response, low cost, capability of online monitoring and remote sensing

Antioxidant activity and electrochemical elucidation of the enigmatic redox behavior of curcumin and its structurally modified analogues

Here, we report studies on the antioxidant activity and redox behavior of curcumin and its structurally modified synthetic analogues. We have synthesized a number of analogues of curcumin which abrogate its keto-enol tautomerism or substitute the methylene group at the centre of its heptadione moiety implicated in the hydride transfer and studied their redox property. From cyclic voltammetric studies, it is demonstrated that H-atom transfer from CH2 group at the center of the heptadione link also plays an important role in the antioxidant properties of curcumin along with that of its phenolic -OH group. In addition, we also show that the conversion of 1, 3-dicarbonyl moiety of curcumin to an isosteric heterocycle as in pyrazole curcumin, which decreases its rotational freedom, leads to an improvement of its redox properties as well as its antioxidant activity. (C) 2014 Elsevier Ltd. All rights reserved

Targeting human telomeric G-quadruplex DNA with curcumin and its synthesized analogues under molecular crowding conditions

The formation of telomeric G-quadruplexes has been shown to inhibit telomerase activity. Indeed, a number of small molecules capable of p-stacking with G-tetrads have shown the ability to inhibit telomerase activity through the stabilization of G-quadruplexes. Curcumin displays a wide spectrum of medicinal properties ranging from anti-bacterial, anti-viral, anti-protozoal, anti-fungal and anti-inflammatory to anti-cancer activity. We have investigated the interactions of curcumin and its structural analogues with the human telomeric sequence AG(3)(T(2)AG(3))(3) under molecular crowding conditions. Experimental studies indicated the existence of a AG(3)(T(2)AG(3))(3)/curcumin complex with binding affinity of 0.72 x 10(6) M-1 under molecular crowding conditions. The results from UV-visible absorption spectroscopy, a fluorescent TO displacement assay, circular dichroism and molecular docking studies, imply that curcumin and their analogues interact with G-quadruplex DNA via groove binding. While other analogs of curcumin studied here bind to G-quadruplexes in a qualitatively similar manner their affinities are relatively lower in comparison to curcumin. The Knoevenagel condensate, a methoxy-benzylidene derivative of curcumin, also exhibited significant binding to G-quadruplex DNA, although with two times decreased affinity. Our study establishes the potential of curcumin as a promising natural product for G-quadruplex specific ligands