The Design of a Photonic Crystal Fiber for Hydrogen Cyanide Gas Detection

Data Availability Statement: Data are contained within the article.Hydrogen cyanide gas is a dangerous and fatal gas that is one of the causes of air pollution in the environment. A small percentage of this gas causes poisoning and eventually death. In this paper, a new PCF is designed that offers high sensitivity and low confinement loss in the absorption wavelength of hydrogen cyanide gas. The proposed structure consists of circular layers that are located around the core, which is also composed of circular microstructures. The finite element method (FEM) is used to simulate the results. According to the results, the PCF gives a high relative sensitivity of 65.13% and a low confinement loss of 1.5 × 10−3 dB/m at a wavelength of 1.533 µm. The impact of increasing the concentration of hydrogen cyanide gas on the relative sensitivity and confinement loss is investigated. The high sensitivity and low confinement losses of the designed PCF show that this optical structure could be a good candidate for the detection of this gas in industrial and medical environments.This research received no external funding

Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures

During dynamic nuclear polarization (DNP) at 1.5 K and 5 T, (129)Xe nuclear magnetic resonance (NMR) spectra of a homogeneous xenon/1-propanol/trityl-radical solid mixture exhibit a single peak, broadened by (1)H neighbors. A second peak appears upon annealing for several hours at 125 K. Its characteristic width and chemical shift indicate the presence of spontaneously formed pure Xe clusters. Microwave irradiation at the appropriate frequencies can bring both peaks to either positive or negative polarization. The peculiar time evolution of (129)Xe polarization in pure Xe clusters during DNP can be modelled as an interplay of spin diffusion and T(1) relaxation. Our simple spherical-cluster model offers a sensitive tool to evaluate major DNP parameters in situ, revealing a severe spin-diffusion bottleneck at the cluster boundaries and a significant sample overheating due to microwave irradiation. Subsequent DNP system modifications designed to reduce the overheating resulted in four-fold increase of (129)Xe polarization, from 5.3% to 21%

Recovery of Nickel from Reformer Catalysts of Direct Reduction, Using the Pressurized Dissolving Method in Nitric Acid

In the process of direct reduction of iron pellet and production of sponge iron, NiO/Al2O3 act as a catalyst for the generation of carbon monoxide and hydrogen by vapor and natural gas. As an expensive material used in MIDREX method for steel units, this type of catalyst has major environmental problems after accumulation. The steel industry in Iran hopes to employ the MIDREX technique for the 80 percent of the 50 million tons of steel. Thus, the problem of spent catalysts will become a serious environmental challenge. Through the hydrometallurgy method, the present study investigates a possible solution to the problem of catalyst depot (due to heavy metals such as nickel) via nickel recovery, which may increase the possibility of selling or re-using the precious and expensive metal. The present research studied the Nickel recovery from spent catalysts of NiO/Al2O¬3 used in reduction gas reliefs of the production of sponge iron unit. In this study, the parameters of temperature, concentration, time and Rpm were studied using pressurized dissolving method. 100% efficiency was achieved at 140 °C for 120 minutes, nitric acid concentration of 1.5 mm, Rpm of 600 and 40 s/l 40 grams per liter

The effect of passive leg-raising maneuver on hemodynamic stability during anesthesia induction for adult cardiac surgery

Solmaz Fakhari, Eissa Bilehjani, Haleh Farzin, Hojjat Pourfathi, Mohsen Chalabianlou Cardiovascular Research Center, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran Introduction: Some cardiac patients do not tolerate the intravenous fluid load commonly administered before anesthesia induction. This study investigated preinduction passive leg-raising maneuver (PLRM) as an alternative method to fluid loading before cardiac anesthesia.Methods and materials: During a 6-month period, 120 adult elective heart surgery patients were enrolled in this study and allocated into 2 groups: PLRM group vs control group (n=60). Anesthesia was induced using midazolam, fentanyl, and cisatracurium. Initially, 250 mL of fluid was administrated intravenously in all of patients before anesthesia induction. Then in the PLRM group, PLRM was performed starting 2 minutes before anesthesia induction and continued for 20 minutes after tracheal intubation. In the control group, anesthesia was induced in a simple supine position. Heart rate, invasive mean arterial blood pressure (MAP), and central venous pressure (CVP) were recorded before PLRM, before anesthetic induction, before laryngoscopy, and at 5, 10, and 20 minutes after tracheal intubation. The hypotension episode rate (MAP <70 mmHg) and CVP changes were compared between the 2 groups. The predictive value of the ≥3 mmHg increase in CVP value in response to PLRM for hypotension prevention was defined.Results: Hypotension rates were lower in the PLRM group (63.3% vs 81.6%; P-value 0.04), and MAP was higher among PLRM patients immediately before anesthetic injection, before laryngoscopy, and 20 minutes after intubation, compared to the control group. PLRM increased CVP by 3.57±4.9 mmHg (from 7.50±2.94 to 11.05±3.55 mmHg), which required several minutes to reach peak value, returning to baseline after 15 minutes. This change did not correlate to subsequent MAP changes; an increase in the CVP value ≥3 mmHg decreased the postinduction hypotension rate by 62.50%.Conclusion: Preinduction PLRM can provide a more stable hemodynamic status in adult cardiac surgery patients and decreases anesthesia-induced hypotension rates by 62.50%. Rate of the changes in the CVP value caused by PLRM is not predictive of subsequent MAP changes. Keywords: passive leg-raising maneuver, cardiac surgery, anesthesia induction, hypotension&nbsp

Lineshape-based polarimetry of dynamically-polarized in solid-state mixtures

Dynamic nuclear polarization (DNP) of 15N2O, known for its long-lived singlet-state order at low magnetic field, is demonstrated in organic solvent/trityl mixtures at ?1.5 K and 5 T. Both 15N polarization and intermolecular dipolar broadening are strongly affected by the sample’s thermal history, indicating spontaneous formation of N2O clusters. In situ 15N NMR reveals four distinct powder-pattern spectra, attributed to the chemical-shift anisotropy (CSA) tensors of the two 15N nuclei, further split by the intramolecular dipolar coupling between their magnetic moments. 15N polarization is estimated by fitting the free-induction decay (FID) signals to the analytical model of four single-quantum transitions. This analysis implies (10.2±2.2)% polarization after 37 h of DNP, and provides a direct, instantaneous probe of the absolute 15N polarization, without a need for time-consuming referencing to a thermal-equilibrium NMR signa