A NICER look at the Aql X-1 hard state

We report on a spectral-timing analysis of the neutron star low-mass X-ray binary (LMXB) Aql X-1 with the Neutron Star Interior Composition Explorer (NICER) on the International Space Station (ISS). Aql X-1 was observed with NICER during a dim outburst in 2017 July, collecting approximately 50 ks of good exposure. The spectral and timing properties of the source correspond to that of a (hard) extreme island state in the atoll classification. We find that the fractional amplitude of the low-frequency (<0.3 Hz) band-limited noise shows a dramatic turnover as a function of energy: it peaks at 0.5 keV with nearly 25% rms, drops to 12% rms at 2 keV, and rises to 15% rms at 10 keV. Through the analysis of covariance spectra, we demonstrate that band-limited noise exists in both the soft thermal emission and the power-law emission. Additionally, we measure hard time lags, indicating the thermal emission at 0.5 keV leads the power-law emission at 10 keV on a timescale of ∼100 ms at 0.3 Hz to ∼10 ms at 3 Hz. Our results demonstrate that the thermal emission in the hard state is intrinsically variable, and is driving the modulation of the higher energy power-law. Interpreting the thermal spectrum as disk emission, we find that our results are consistent with the disk propagation model proposed for accretion onto black holes.United States. National Aeronautics and Space Administration. Neutron Star Interior Composition ExplorerUnited States. National Aeronautics and Space Administration. Astrophysics Research and Analysis Progra

Synthesis and surface modification of iron oxide nanoparticles for drug delivery

Iron oxide nanoparticles are widely researched for a variety of medical applications. Understanding the properties of such compounds is important for further development of nanoparticle-based drugs. Although iron oxide nanoparticles have been used in the healthcare industry already especially as magnetic resonance imaging catalysts, there is still much to be understood about their potential to assist the delivery of the anticancer and anti-bacterial agents. Similarly, Traditional Chinese Medicines have been used for thousands of years for a variety of ailments and conditions. The active constituents of some of these medicines have recently been identified, with extensive research conducted to investigate the mechanisms of these compounds against various diseases. This thesis represents an effort to offer an alternative to current medications in the form of nanoparticles and natural herbal extracts. It employs a systematic approach by synthesizing and surface modifying the compounds before assessing the compounds in vitro against sarcoma cell lines and Clostridia bacterial species. Subsequent studies were conducted to examine in-depth the size-efficacy relationship and drug-release profile. Finally, a large-scale poultry trial was conducted to evaluate the feasibility of a derived compound in controlling outbreak of relevant diseases. <br>     <br>    A study involving three sizes of iron oxide nanoparticles were surface modified and tested against sarcoma cell lines. Surface modification with polyethylene glycol and loading of doxorubicin was performed for further evaluation of performance. A smaller sized nanoparticle with PEG coating was found to be most effective in killing the sarcoma cell lines suggesting increased uptake. The free iron ions potentially cross the nuclear or mitochondrial membrane to produce highly reactive radicals to cause direct damage to DNA, proteins and lipid peroxidation. This study establishes iron oxide nanoparticles loaded with doxorubicin and surface coated with polyethylene glycol to be a potential candidate as an anticancer drug. In vivo experiments to analyze bioavailability and mechanism of action are necessary for future development. <br>     <br>    The active constituent of the herb Goldenseal was identified as Berberine in previous literature. The antimicrobial activity of Berberine was assessed against Clostridia bacterial species representative of current livestock concerns including <i>Clostridium Perfringens</i> and <i>Clostridium Difficile</i>. The compound was found to have inhibitory and bactericidal effects in both. A subsequent study to evaluate feasibility of Berberine as an additive in poultry to control <i>Clostridium Perfringens</i> induced disease was conducted, with results demonstrating significant decrease in mortality and illness. However, the birds were seen to have decreased feed and water intake compared to birds on a standard feed and water diet. The results indicate a good basis for subsequent trials involving microbiota analysis, residues, and toxicology and dose-response efficacy of the compound. This study hopes to be a resource and inspiration for development of alternatives to current medicines. In particular, these findings underline the untapped potential of herbal medicines and the need to undergo an extensive screening of identified herbal active constituents against diseases of concern. This will be crucial as the impact of antibiotic use becomes more pronounced in the future

NICER Observation of Unusual Burst Oscillations in 4U 1728-34

International audienceThe Neutron Star Interior Composition Explorer (NICER) has observed seven thermonuclear X-ray bursts from the Low Mass X-ray Binary (LMXB) neutron star 4U 1728-34 from the start of the mission's operations until February of 2019. Three of these bursts show oscillations in their decaying tail with frequencies that are within 1 Hz of the previously detected burst oscillations from this source. Two of these burst oscillations have unusual properties: They have large fractional rms amplitudes of $48 \pm 9 \%$ and $46 \pm 9 \%$, and they are detected only at photon energies above 6 keV. By contrast, the third detected burst oscillation is compatible with previous observations of this source, with a fractional rms amplitude of $7.7 \pm 1.5\%$ rms in the 0.3 to 6.2 keV energy band. We discuss the implications of these large-amplitude burst oscillations, finding they are difficult to explain with the current theoretical models for X-ray burst tail oscillations