Inversion of dry and saturated P- and S-wave velocities for the pore-aspect-ratio spectrum using a cracked porous medium elastic wave theory

Subsurface rocks contain pores and cracks of various sizes. The cracked porous medium elastic wave theory that describes wave propagation characteristics due to the pore-crack interaction is extended to include cracks of different aspect ratios. The extended theory is applied to model P- and S-wave velocity data of dry and fluid-saturated rock under pressure loading conditions, so as to determine the pore-aspect-ratio spectrum through an inversion procedure. The inversion result is consistent with that from the scanning electron microscope analysis, showing significant improvement versus previous inversion. The inverted pore-aspect-ratio spectrum is input into the wave theory to predict the velocity dispersion of the rock in the full frequency range. The predicted dispersion and its variation trend with pressure agree with the data measured in the (2–200, 106) Hz range at various differential pressures, whereas the modeling using a single-aspect-ratio theory has difficulty matching the data. This research work provides not only a method for analyzing the pore structure characteristics of rocks from the laboratory ultrasonic velocity data, but also a way to predict the seismic wave dispersion from the data.

Improving the Quantification of Deuterium in Zirconium Alloy Atom Probe Tomography Data Using Existing Analysis Methods

Zirconium alloys are common fuel claddings in nuclear fission reactors and are susceptible to the effects of hydrogen embrittlement. There is a need to be able to detect and image hydrogen at the atomic scale to gain the experimental evidence necessary to fully understand hydrogen embrittlement. Through the use of deuterium tracers, atom probe tomography (APT) is able to detect and spatially locate hydrogen at the atomic scale. Previous works have highlighted issues with quantifying deuterium concentrations using APT due to complex peak overlaps in the mass-to-charge-state ratio spectrum between molecular hydrogen and deuterium (H2 and D). In this work, we use new methods to analyze historic and simulated atom probe data, by applying currently available data analysis tools, to optimize solving peak overlaps to improve the quantification of deuterium. This method has been applied to literature data to quantify the deuterium concentrations in a concentration line profile across an α-Zr/deuteride interface.

Eco-friendly analytical methods for the determination of compounds with disparate spectral overlapping: application to antiviral formulation of sofosbuvir and velpatasvir

Green analytical chemistry is one of the newest trends in analytical chemistry nowadays targeting the concept of green laboratory practices on chemists and environment. In this text, green practices are proposed in this work for the determination of sofosbuvir (SF) and velpatasvir (VP) in their pharmaceutical formulation. The analysis of SF in a binary mixture with VP represents an analytical challenge due to the complete overlapping of the UV spectrum of SF by that of VP. Therefore, the direct absorbance and derivative measurements cannot resolve such interference and failed to determine SF. In this paper, three direct and simple methods were developed for the analysis of SF without any interference from VP without sample pre-treatment. The proposed methods include measuring the second derivative amplitude of the ratio spectrum of the mixture using VP as a divisor, measuring the absorbance difference of the mixture in NaOH solution against its HCl solution, and using the derivative compensation technique. On the other hand, VP was determined specifically in presence of SF by two methods. Firstly, by its reaction with 4-chloro-7-nitrobenzofurazan (NBD-Cl) where the reaction product was measured spectrophotometrically and spectrofluorometrically and secondly through the reaction of VP with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH). The calibration curves showed good correlation coefficient (r2 > 0.999). The developed methods were highly precise with RSD% values less than 2%. The method greenness profile was compared with other published methods by applying the eco-scale protocol. Assessment results proved that our analytical procedure is greener than other reported methods. Moreover, upon comparison with other methods, the proposed methods showed better or comparable sensitivity in addition to being inexpensive and ecofriendly. Accordingly, these methods could be readily applied for quality control purposes as an eco-friendly, simple and efficient analytical tool.

The development of non-coherent passive radar techniques for space situational awareness with the Murchison Widefield Array

The number of active and non active satellites in Earth orbit has dramatically increased in recent decades, requiring the development of novel surveillance techniques to monitor and track them. In this paper, we build upon previous non-coherent passive radar space surveillance demonstrations undertaken using the Murchison Widefield Array (MWA). We develop the concept of the Dynamic Signal to Noise Ratio Spectrum (DSNRS) in order to isolate signals of interest (reflections of FM transmissions of objects in orbit) and efficiently differentiate them from direct path reception events. We detect and track Alouette-2, ALOS, UKube-1, the International Space Station, and Duchifat-1 in this manner. We also identified out-of-band transmissions from Duchifat-1 and UKube-1 using these techniques, demonstrating the MWA’s capability to look for spurious transmissions from satellites. We identify an offset from the locations predicted by the cataloged orbital parameters for some of the satellites, demonstrating the potential of using MWA for satellite catalog maintenance. These results demonstrate the capability of the MWA for Space Situational Awareness and we describe future work in this area.

Ratio spectrum derivative quantitative analysis of propranolol and diazipam in combind pharmaceutical mixtures

Two new spectrophotometric methods were developed for the simultaneously estimation of DZP and PRO using the first ratio derivative method (DD1) and the second ratio derivative (DD2). The two methods were succeeded to the estimation of both drugs with a range of concentrations from (5-50 µg.ml-1), depending on Peak to baseline, peak area, peak to peak at specific wavelengths for each compound. The analytical results and of the estimate of The DZP and PRO showed that Rec% values ranged from 95.04-104.97% and 96.30-104.69, and RSD% were between 0.00948-4.87736 % and 0.1163-3.37655%, for the first and second ratio derivative respectively. The method has been successfully applied to the estimation of both PRO and DZP in its pharmaceuticals forms.

Determination of antihypertensive drugs by using ratio difference spectrophotometric method

An accurate, sensitive and time saving spectrophotometric method has been developed and validated for the determination of two antihypertensive drug mixtures. Mixture 1 contains spironolactone (SPIR), furosemide (FUR) and anthranilic acid (ANTH) (impurity of furosemide) and mixture 2 contains triamterene (TRI), hydrochlorothiazide (HCZ) and chlorothiazide (CZ) (impurity of hydrochlorothiazide). In mixture 1, the determination of drugs depends on dividing the spectrum of ternary mixture by the spectrum of 10 µg/mL of standard furosemide and then spironolactone and anthranilic acid were determined using the difference in amplitude between 242.3 and 254.6 nm, and between 250.8 and 242.4 nm in the ratio spectrum, respectively. On the other hand, furosemide could be determined by dividing the spectrum of ternary mixture by the spectrum of 10 µg/mL of standard spironolactone and then it was determined using the difference in amplitude between 244.8 and 229.7 nm in the ratio spectrum. In mixture 2, the determination of drugs depends on dividing the spectrum of ternary mixture by spectrum of 10 µg/mL of standard triamterene and then hydrochlorothiazide and chlorothiazide were determined using the difference in amplitude between 268.9 and 232.8 nm, and between 292.9 and 250.7 nm in the ratio spectrum, respectively. On the other hand, triamterene could be determined by dividing spectrum of ternary mixture by spectrum of 10 µg/mL of standard hydrochlorothiazide and then triamterene was determined using the difference in amplitude between 230.1 and 244 nm in the ratio spectrum. The developed analytical methods were validated regarding good accuracy and precision according to The International Conference on Harmonisation guidelines, and they were applied to pharmaceutical preparations in addition to laboratory prepared mixtures successfully. Statistically the results were compared with those obtained by reported method and no significant difference was found.