Determination of Ionospheric Current Systems by Measuring the Phase Shift on Amateur Satellite Frequencies

We investigate the possibility of measuring and using the phase delay of radio frequency transmissions in the amateur satellite band as a method to determine the distribution of currents systems in the ionosphere. The amateur satellite transmissions at 7MHz, 14M Hz, and 144M Hz are low enough for Faraday rotation to cause a significant phase delay on the propagating signals in addition to the phase delay produced by the total electron content (TEC) in the ionosphere. The ionosphere in the E and F regions is modeled as an equivalent thin planar shell of collision free cold plasma 100 km in thickness located in an altitude range of 100 � 200 km. The earth\u27s magnetic field is superposed with a weaker magnetic field due to a narrow Gaussian strip of current representing an ionospheric electrojet. The prole of the current system is obtained by numerically optimizing the Appleton-Hartree dispersion relation for rays of simulated radio frequency (RF) signals that propagate through the ionosphere shell. The optimization procedure is performed with a differential evolution algorithm. From the optimization procedure, we obtain the ionosphere total electron content (TEC) and the strength, prole, and orientation of the ionospheric current system

THE NEUROPROTECTIVE EFFECTS OF MEDICINAL PLANTS ON ALZHEIMER`S DISEASE: A REVIEW

In the 21st century, the human population is suffering from a neurodegenerative disorder in which neuronal death occurs due to a long-term chronic condition causing substantial major health concerns. When neurons die, they are not regenerated, causing cognitive impairment, i.e., Alzheimer’s disease, Parkinson’s disease, schizophrenia, and dementia. This review concentrates only on Alzheimer’s disease aetiology and various plants having potent neuroprotective activity related to Alzheimer’s disease. The most common aetiology of Alzheimer’s disease is a deposition of APP protein, hyperphosphorylation of Tau protein, a reduction in acetylcholine and oxidative stress, which are discussed briefly. Moreover, pertinent evidence is also discussed for medicinal plants with potent or promising neuroprotective activity related to Alzheimer’s disease

Optimizing mycobacteria molecular diagnostics: No decontamination! Human DNA depletion? Greener storage at 4 °C!

INTRODUCTION Tuberculosis (TB) is an infectious disease caused by the group of bacterial pathogens Mycobacterium tuberculosis complex (MTBC) and is one of the leading causes of death worldwide. Timely diagnosis and treatment of drug-resistant TB is a key pillar of WHO's strategy to combat global TB. The time required to carry out drug susceptibility testing (DST) for MTBC via the classic culture method is in the range of weeks and such delays have a detrimental effect on treatment outcomes. Given that molecular testing is in the range of hours to 1 or 2 days its value in treating drug resistant TB cannot be overstated. When developing such tests, one wants to optimize each step so that tests are successful even when confronted with samples that have a low MTBC load or contain large amounts of host DNA. This could improve the performance of the popular rapid molecular tests, especially for samples with mycobacterial loads close to the limits of detection. Where optimizations could have a more significant impact is for tests based on targeted next generation sequencing (tNGS) which typically require higher quantities of DNA. This would be significant as tNGS can provide more comprehensive drug resistance profiles than the relatively limited resistance information provided by rapid tests. In this work we endeavor to optimize pre-treatment and extraction steps for molecular testing. METHODS We begin by choosing the best DNA extraction device by comparing the amount of DNA extracted by five commonly used devices from identical samples. Following this, the effect that decontamination and human DNA depletion have on extraction efficiency is explored. RESULTS The best results were achieved (i.e., the lowest Ct values) when neither decontamination nor human DNA depletion were used. As expected, in all tested scenarios the addition of decontamination to our workflow substantially reduced the yield of DNA extracted. This illustrates that the standard TB laboratory practice of applying decontamination, although being vital for culture-based testing, can negatively impact the performance of molecular testing. As a complement to the above experiments, we also considered the best Mycobacterium tuberculosis DNA storage method to optimize molecular testing carried out in the near- to medium-term. Comparing Ct values following three-month storage at 4 °C and at -20 °C and showed little difference between the two. DISCUSSION In summary, for molecular diagnostics aimed at mycobacteria this work highlights the importance of choosing the right DNA extraction device, indicates that decontamination causes significant loss of mycobacterial DNA, and shows that samples preserved for further molecular testing can be stored at 4 °C, just as well at -20 °C. Under our experimental settings, human DNA depletion gave no significant improvement in Ct values for the detection of MTBC

Hydropower Advantages over Batteries in Energy Storage of Off-Grid Systems: A Case Study

Microgrids are decentralized power production systems, where the energy production and consumption are very close to each other. Microgrids generally exploit renewable energy sources, encountering a problem of storage, as the power production from solar and wind is intermittent. This research presents a new integrated methodology and discusses a comparison of batteries and pumped storage hydropower (PSH) as energy storage systems with the integration of wind and solar PV energy sources, which are the major upcoming technologies in the renewable energy sector. We implemented the simulator and optimizer model (HOMER), which develops energy availability usage to obtain optimized renewable energy integration in the microgrid, showing its economic added value. Two scenarios are run with this model—one considers batteries as an energy storage technology and the other considers PSH—in order to obtain the best economic and technical results for the analyzed microgrid. The economic analysis showed a lower net present cost (NPC) and levelized cost of energy (LCOE) for the microgrid with PSH. The results showed that the microgrid with the storage of PSH was economical, with an NPC of 45.8 M€ and an LCOE of 0.379 €/kWh, in comparison with the scenario with batteries, which had an NPC of 95.2 M€ and an LCOE of 0.786 €/kWh. The role of storage was understood by differentiating the data into different seasons, using a Python model. Furthermore, a sensitivity analysis was conducted by varying the capital cost multiplier of solar PV and wind turbines to obtain the best optimal economic solutions

Characterization of Multiphase Polypyrrole/Vanadium Oxide Nano Composites for a.c. Conductivity and Dielectric Properties

Vanadium oxide: Phase-1 and Phase-2 nano powers were synthesized from vanadium pentoxide in the presence of glucose using hydrothermal technique. The polypyrrole/vanadium oxide (PV P-1 and PV P-2) nano composites were synthesized with 15, 30, 45 and 60 weight percents of vanadium oxide: Phase-1 and Phase-2 in pyrrole, by the chemical polymerization (oxidation) method. The SEM micrographs of vanadium oxide: Phase-1 and Phase-2 nano powders have shown  mixture of nano belts & rods and PV P-1 & PV P-2 nano composites indicate that the composites have cluster formation with almost spherical nature particles and form elongated chains at some places. Conductivity versus frequency  plots shown that exponential increase for conductivity. The value of s increases to 1.13x10-3 S/cm for 15 wt. % of VO2 P-1 in polypyrrole & to 2.43x10-3 S/cm for 30 wt. % of VO2 P-2 in polypyrrole at 1 MHz

G10/COSMOS : 38 band (far-UV to far-IR) panchromatic photometry using LAMBDAR

We present a consistent total flux catalogue for a ∼1 deg2 subset of the Cosmic Evolution Survey (COSMOS) region (RA ∈ [149∘.55, 150∘.65], Dec. ∈ [1∘.80, 2∘.73]) with near-complete coverage in 38 bands from the far-ultraviolet to the far-infrared. We produce aperture matched photometry for 128 304 objects with i < 24.5 in a manner that is equivalent to the Wright et al. catalogue from the low-redshift (z < 0.4) Galaxy and Mass Assembly (GAMA) survey. This catalogue is based on publicly available imaging from GALEX, Canada–France–Hawaii Telescope, Subaru, Visible and Infrared Survey Telescope for Astronomy, Spitzer and Herschel, contains a robust total flux measurement or upper limit for every object in every waveband and complements our re-reduction of publicly available spectra in the same region. We perform a number of consistency checks, demonstrating that our catalogue is comparable to existing data sets, including the recent COSMOS2015 catalogue. We also release an updated Davies et al. spectroscopic catalogue that folds in new spectroscopic and photometric redshift data sets. The catalogues are available for download at http://cutout.icrar.org/G10/dataRelease.php. Our analysis is optimised for both panchromatic analysis over the full wavelength range and for direct comparison to GAMA, thus permitting measurements of galaxy evolution for 0 < z < 1 while minimizing the systematic error resulting from disparate data reduction methods.Publisher PDFPeer reviewe

Optical frequency comb expansion using mutually injection-locked gain-switched lasers

We propose a novel scheme for the expansion and comb densification of gain-switched optical frequency combs (GS-OFC). The technique entails mutual injection locking of two gainswitched lasers with a common master to generate a wider bandwidth OFC. Subsequently, the OFC is further expanded and/or densified using a phase modulator with optimum drive conditions. We experimentally demonstrate the generation of an OFC with 45 highly correlated lines separated by 6.25 GHz with an expansion factor ~3. In addition, operating in comb densification mode, the channel spacing of the OFC is tuned from 6.25 GHz to 390.625 MHz. Finally, a detailed characterization of the lines, across the entire expanded comb, is reported highlighting the excellent spectral purity with linewidths of ~40 kHz, a relative intensity noise better than −152 dB/Hz, and a high degree of phase correlation between the comb lines. The proposed method is simple, highly flexible and the architecture is suitable for photonic integration, all of which make such an OFC extremely attractive for the employment in a multitude of applications

Galactic googly : the rotation-metallicity bias in the inner stellar halo of the Milky Way

The first and second moments of stellar velocities encode important information about the formation history of the Galactic halo. However, due to the lack of tangential motion and inaccurate distances of the halo stars, the velocity moments in the Galactic halo have largely remained ‘known unknowns’. Fortunately, our off-centric position within the Galaxy allows us to estimate these moments in the galactocentric frame using the observed radial velocities of the stars alone. We use these velocities coupled with the hierarchical Bayesian scheme, which allows easy marginalization over the missing data (the proper motion, and uncertainty-free distance and line-of-sight velocity), to measure the velocity dispersions, orbital anisotropy (β) and streaming motion (vrot) of the halo main-sequence turn-off (MSTO) and K-giant (KG) stars in the inner stellar halo (r ≲ 15 kpc). We study the metallicity bias in kinematics of the halo stars and observe that the comparatively metal-rich ([Fe/H] > −1.4) and the metal-poor ([Fe/H] ≤ −1.4) MSTO samples show a clear systematic difference in vrot ∼ 20-40 km s−1, depending on how restrictive the spatial cuts to cull the disc contamination are. The bias is also detected in KG samples but with less certainty. Both MSTO and KG populations suggest that the inner stellar halo of the Galaxy is radially biased i.e. σr > σθ or σϕ and β ≃ 0.5. The apparent metallicity contrariety in the rotation velocity among the halo sub-populations supports the co-existence of multiple populations in the galactic halo that may have formed through distinct formation scenarios, i.e. in situ versus accretion.Publisher PDFPeer reviewe

Expansion and phase correlation of a wavelength tunable gain-switched optical frequency comb

A novel scheme for the expansion and phase correlation of a wavelength tunable gain-switched optical frequency comb (OFC) is presented. This method entails firstly combining two gain-switched OFCs and expanding them using a phase modulator. Subsequently, the phase correlation between all the comb lines is induced through four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). In this article, the generation of 42 highly correlated comb lines separated by 6.25 GHz, with an optical carrier to noise ratio (OCNR) of more than 50 dB, is experimentally demonstrated. In addition, the wavelength tunability of the scheme, over 30 nm within the C band, is shown. Finally, the degree of phase correlation between comb lines is verified through RF beat tone linewidth measurements. The results show a five orders of magnitude reduction in the beat tone linewidth, due to FWM in an SOA