Instability Compensation of Recording Interferometer in Phase-Sensitive OTDR.

In the paper, a new method of phase measurement error suppression in a phase-sensitive optical time domain reflectometer is proposed and experimentally proved. The main causes of phase measurement errors are identified and considered, such as the influence of the recording interferometer instabilities and laser wavelength instability, which can cause inaccuracies in phase unwrapping. The use of a Mach-Zender interferometer made by 3 × 3 fiber couplers is proposed and tested to provide insensitivity to the recording interferometer and laser source instabilities.

Detection and Recognition of Voice Commands by a Distributed Acoustic Sensor Based on Phase-Sensitive OTDR in the Smart Home Concept.

In recent years, attention to the realization of a distributed fiber-optic microphone for the detection and recognition of the human voice has increased, whereby the most popular schemes are based on φ-OTDR. Many issues related to the selection of optimal system parameters and the recognition of registered signals, however, are still unresolved. In this research, we conducted theoretical studies of these issues based on the φ-OTDR mathematical model and verified them with experiments.

Fiber-Optic Telecommunication Network Wells Monitoring by Phase-Sensitive Optical Time-Domain Reflectometer with Disturbance Recognition.

The paper presents the application of a phase-sensitive optical time-domain reflectometer (phi-OTDR) in the field of urban infrastructure monitoring. In particular, the branched structure of the urban network of telecommunication wells. The encountered tasks and difficulties are described.

Non-Invasive Acoustic Monitoring of Gas Turbine Units by Fiber Optic Sensors.

In this article, we study the possibility of gas turbine unit (GTU) monitoring using interferometric fiber optic sensors. We used the Mach-Zehnder interferometer (MZI) scheme, which can be easily implemented and simply installed on the turbine, and also allows us to solve the problem of phase unwrapping conveniently. In this research, the following main steps were carried out: an experimental scheme based on the MZI was assembled, and its sensitive arm was fixed on the GTU under study; data on various operation modes of the GTU was collected; the data were subjected to frequency FFT analysis, based on which the main rotational speeds of the turbine were identified.

Protective Policy Index (PPI) global dataset of origins and stringency of COVID 19 mitigation policies.

We have developed and made accessible for multidisciplinary audience a unique global dataset of the behavior of political actors during the COVID-19 pandemic as measured by their policy-making efforts to protect their publics. The dataset presents consistently coded cross-national data at subnational and national levels on the daily level of stringency of public health policies by level of government overall and within specific policy categories, and reports branches of government that adopted these policies. The data on these public mandates of protective behaviors is collected from media announcements and government publications.

Transparent Polymer Blends of Poly(methyl methacrylate) and Poly(propylene glycol).

Polymer blends, obtained by polymerization of methyl methacrylate in the presence of poly(propylene glycol), are investigated. Poly(propylene glycol) acts as a plasticizer, significantly lowering poly(methyl methacrylate)'s glass transition temperature and decreasing its elasticity modulus and yield stress. The mixture of methyl methacrylate with poly(propylene glycol) is more stable than its mixture with currently used poly(ethylene glycol), which leads to more uniform distribution and higher possible content of the plasticizer.

Distributed Acoustic Sensor Using a Double Sagnac Interferometer Based on Wavelength Division Multiplexing.

We demonstrated a fiber optic distributed acoustic sensor based on a double Sagnac interferometer, using two wavelengths separated by CWDM modules. A mathematical model of signal formation principle, based on a shift in two signals analysis, was described and substantiated mathematically. The dependence of the sensor sensitivity on a disturbance coordinate and frequency was found and simulated, and helped determine a low sensitivity zone length and provided sensor scheme optimization.

Scientific Applications of Distributed Acoustic Sensing: State-of-the-Art Review and Perspective.

This work presents a detailed review of the development of distributed acoustic sensors (DAS) and their newest scientific applications. It covers most areas of human activities, such as the engineering, material, and humanitarian sciences, geophysics, culture, biology, and applied mechanics. It also provides the theoretical basis for most well-known DAS techniques and unveils the features that characterize each particular group of applications.

Study of Intra-Chamber Processes in Solid Rocket Motors by Fiber Optic Sensors.

In this study, an experimental study of the burning rate of solid fuel in a model solid propellant rocket motor (SRM) E-5-0 was conducted using a non-invasive control method with fiber-optic sensors (FOSs). Three sensors based on the Mach-Zehnder interferometer (MZI), fixed on the SRM E-5-0, recorded the vibration signal during the entire cycle of solid fuel burning. The results showed that, when using MZI sensors, the non-invasive control of solid fuel burnout is made possible both by recording the time of arrival of the combustion front to the sensor and by analyzing the peaks on the spectrogram of the recorded FOS signal.

Sensitivity Improvement of Phi-OTDR by Fiber Cable Coils.

We present a theoretical and experimental study in which we increased the sensitivity of a phase-sensitive optical time-domain reflectometer (phi-OTDR). This was achieved by constructing coils in the sensor cable, which increased the total amplitude of the impact on the fiber. We demonstrate this theoretically using the example of a phase-sensitive reflectometer model and practically in testing grounds with a buried nearby conventional sensor and a sensor with coils.

Governor's Party, Policies, and COVID-19 Outcomes: Further Evidence of an Effect.

Introduction: This study connects the aggregate strength of public health policies taken in response to the COVID-19 pandemic in the U.S. states to the governors' party affiliations and to state-level outcomes.

COVID-19 Policy Response and the Rise of the Sub-National Governments.

We examine the roles of sub-national and national governments in Canada and the United States vis-à-vis the protective public health response in the onset phase of the global coronavirus disease 2019 (COVID-19) pandemic. This period was characterized in both countries by incomplete information as well as by uncertainty regarding which level of government should be responsible for which policies. The crisis represents an opportunity to study how national and sub-national governments respond to such policy challenges.

Spores of puffball fungus Lycoperdon pyriforme as a reference standard of stable monodisperse aerosol for calibration of optical instruments.

Advanced air quality control requires real-time monitoring of particulate matter size and concentration, which can only be done using optical instruments. However, such techniques need regular calibration with reference samples. In this study, we suggest that puffball fungus (Lycoperdon pyriforme) spores can be utilized as a reference standard having a monodisperse size distribution.

Molecular Targets of the Hydrophobic Block of Pluronics in Cells: a Photo Affinity Labelling Approach.

Purpose: Pluronics are known as inhibitors of multidrug resistance thus making tumor cells sensitive to therapeutic doses of drugs. The purpose of our study consists in revealing molecular targets of the hydrophobic poly(propylene oxide) block of pluronics in living cells and the dependence of the polymers chemosensitizing efficiency upon targeting.

Methods: A photo sensitive tracer was attached to the hydrophobic poly(propylene oxide) block of H-labeled tert-Bu-EO-PO copolymer.

Note: Gaussian mixture model for event recognition in optical time-domain reflectometry based sensing systems.

We propose a novel approach to the recognition of particular classes of non-conventional events in signals from phase-sensitive optical time-domain-reflectometry-based sensors. Our algorithmic solution has two main features: filtering aimed at the de-nosing of signals and a Gaussian mixture model to cluster them. We test the proposed algorithm using experimentally measured signals.

[Methodical issues of the monitoring for ammonium in indoors air].

Introduction. To perform mass studies of the indoors air environment of the ammonium content the actual issues are the shortening of the sampling time and material costs for their implementation, reduction of adverse effects of ammonium with keeping of the objectivity of results. Aim.

Lipid composition determines interaction of liposome membranes with Pluronic L61.

Triblock copolymers of ethylene oxide (EO) and propylene oxide (PO) of EO(n/2)PO(m)EO(n/2) type (Pluronics) demonstrate a variety of biological effects that are mainly due to their interaction with cell membranes. Previously, we have shown that Pluronics can bind to artificial lipid membranes and enhance accumulation of the anti-tumor drug doxorubicin (DOX) inside the pH-gradient liposomes and transmembrane migration (flip-flop) of NBD-labeled phosphatidylethanolamine in the liposomes composed from one component-lecithin. Here, we describe the effects caused by insertion of other natural lipids in lecithin liposomes and the significance of the lipid composition for interaction of Pluronic L61 with the membrane.

Relationship between the structure of amphiphilic copolymers and their ability to disturb lipid bilayers.

Nonionic amphiphiles and particularly block copolymers of ethylene oxide and propylene oxide (Pluronics) cause pronounced chemosensitization of tumor cells that exhibit multiple resistance to antineoplastic drugs. This effect is due to inhibition of P-glycoprotein (P-gp) responsible for drug efflux. It was suggested that the inhibition of P-gp might be due to changes in its lipid surrounding.

[Characteristics of digestion of blood of different animals by the flea Xenopsylla cheopis].

Under experimental conditions fleas X. cheopis engorged and assimilated blood of 4 species of rodents, man, pigeon and two species of reptiles. Histological investigations have shown that the structure of food clot, destruction rate of blood cells and general duration of digestion are changed considerably depending on the host's blood.