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We study the evolution of the friendship index in complex social networks over time. The elements of the networks are the users, and the connections correspond to the interactions between them. The friendship index of a node is defined as the ratio of the average degree of its neighbors to the degree of the node itself. Obviously, in the process of network growth, the value of the friendship index for any node in the network may change due to the fact that new edges can be attached to this node or its neighbors. In this paper, we study the dynamics of the friendship index of a single node over time for growth networks generated on the basis of the preferential attachment mechanism. We find both the asymptotics of their expected values and the variances over time. In addition, we analyze the behavior of the friendship index for five real networks. [ABSTRACT FROM AUTHOR]

Aims. The aim of this work is to show that the seasonal changes and vertical distribution profiles of hydrogen chloride (HCl) on Mars, as observed by the ExoMars Trace Gas Orbiter, are consistent with the production of gas-phase chlorine atoms from airborne dust and a subsequent rapid uptake of HCl onto water ice particles. Methods. A 1D photochemistry model was equipped with a chlorine reaction network and driven by dust, water ice, and water vapour profiles measured by the ExoMars Trace Gas Orbiter instrumentation in Mars year 34. The release of Cl and O atoms from airborne dust via the hydration and photolysis of perchlorate within dust grains was parameterised using prior laboratory studies, and the heterogeneous uptake of chlorine species onto dust and water ice was included for processes known to occur in Earth's atmosphere. Results. Observed seasonal variations in Martian HCl are reproduced by the model, which yielded low HCl abundances (<1 ppbv) prior to the dust season that rise to 2–6 ppbv in southern latitudes during the dust season. Structured atmospheric layers that coincide with locations where water ice is absent are also produced. As a consequence of the Cl atoms released via our proposed mechanism, the atmospheric lifetime of methane is shortened by two orders of magnitude. This suggests that the production of Cl induced by the breakdown of hydrated perchlorate via UV radiation (or another electromagnetic radiation) in airborne Martian dust, consistent with observed profiles of HCl, could help reconcile reported variations in methane with photochemical models. [ABSTRACT FROM AUTHOR]

The umbilical cord is a material that enhances regeneration and is devoid of age-related changes in the extracellular matrix (ECM). The aim of this work was to develop a biodegradable scaffold from a decellularized human umbilical cord (UC-scaffold) to heal full-thickness wounds. Decellularization was performed with 0.05% sodium dodecyl sulfate solution. The UC-scaffold was studied using morphological analysis methods. The composition of the UC-scaffold was studied using immunoblotting and Fourier transform infrared spectroscopy. The adhesion and proliferation of mesenchymal stromal cells were investigated using the LIVE/DEAD assay. The local reaction was determined by subcutaneous implantation in mice (n = 60). A model of a full-thickness skin wound in mice (n = 64) was used to assess the biological activity of the UC-scaffold. The proposed decellularization method showed its effectiveness in the umbilical cord, as it removed cells and retained a porous structure, type I and type IV collagen, TGF-β3, VEGF, and fibronectin in the ECM. The biodegradation of the UC-scaffold in the presence of collagenase, its stability during incubation in hyaluronidase solution, and its ability to swell by 1617 ± 120% were demonstrated. Subcutaneous scaffold implantation in mice showed gradual resorption of the product in vivo without the formation of a dense connective tissue capsule. Epithelialization of the wound occurred completely in contrast to the controls. All of these data suggest a potential for the use of the UC-scaffold. [ABSTRACT FROM AUTHOR]

Articular cartilage damage still remains a major problem in orthopedical surgery. The development of tissue engineering techniques such as autologous chondrocyte implantation is a promising way to improve clinical outcomes. On the other hand, the clinical application of autologous chondrocytes has considerable limitations. Mesenchymal stromal cells (MSCs) from various tissues have been shown to possess chondrogenic differentiation potential, although to different degrees. In the present study, we assessed the alterations in chondrogenesis-related gene transcription rates and extracellular matrix deposition levels before and after the chondrogenic differentiation of MSCs in a 3D spheroid culture. MSCs were obtained from three different tissues: umbilical cord Wharton's jelly (WJMSC—Wharton's jelly mesenchymal stromal cells), adipose tissue (ATMSC—adipose tissue mesenchymal stromal cells), and the dental pulp of deciduous teeth (SHEDs—stem cells from human exfoliated deciduous teeth). Monolayer MSC cultures served as baseline controls. Newly formed 3D spheroids composed of MSCs previously grown in 2D cultures were precultured for 2 days in growth medium, and then, chondrogenic differentiation was induced by maintaining them in the TGF-β1-containing medium for 21 days. Among the MSC types studied, WJMSCs showed the most similarities with primary chondrocytes in terms of the upregulation of cartilage-specific gene expression. Interestingly, such upregulation occurred to some extent in all 3D spheroids, even prior to the addition of TGF-β1. These results confirm that the potential of Wharton's jelly is on par with adipose tissue as a valuable cell source for cartilage engineering applications as well as for the treatment of osteoarthritis. The 3D spheroid environment on its own acts as a trigger for the chondrogenic differentiation of MSCs. [ABSTRACT FROM AUTHOR]

One of the approaches to restoring the structure of damaged cartilage tissue is an intra‐articular injection of tissue‐engineered medical products (TEMPs) consisting of biocompatible matrices loaded with cells. The most interesting are the absorbable matrices from decellularized tissues, provided that the cellular material is completely removed from them with the maximum possible preservation of the structure and composition of the natural extracellular matrix. The present study investigated the mechanical, biochemical, and biological properties of decellularized porcine cartilage microparticles (DCMps) obtained by techniques, differing only in physical treatments, such as freeze–thaw cycling (Protocol 1), supercritical carbon dioxide fluid (Protocol 2) and ultrasound (Protocol 3). Full tissue decellularization was achieved, as confirmed by the histological analysis and DNA quantification, though all the resultant DCMps had reduced glycosaminoglycans (GAGs) and collagen. The elastic modulus of all DCMp samples was also significantly reduced. Most notably, DCMps prepared with Protocol 3 significantly outperformed other samples in viability and the chondroinduction of the human adipose‐derived stem cells (hADSCs), with a higher GAG production per DNA content. A positive ECM staining for type II collagen was also detected only in cartilage‐like structures based on ultrasound‐treated DCMps. The biocompatibility of a xenogenic DCMps obtained with Protocol 3 has been confirmed for a 6‐month implantation in the thigh muscle tissue of mature rats (n = 18). Overall, the results showed that the porcine cartilage microparticles decellularized by a combination of detergents, ultrasound and DNase could be a promising source of scaffolds for TEMPs for cartilage reconstruction. [ABSTRACT FROM AUTHOR]

We studied the evolution of complex social networks over time. The elements of the networks are users, and the connections correspond to the interactions between them. At a particular moment in time, each node of a complex network has such characteristics as its degree, as well as the total degree of its neighbors. Obviously, in the process of network growth, these characteristics are constantly changing due to the fact that new edges are attached to this node or its neighbors. In this paper, we study the dynamics of these characteristics over time for networks generated on the basis of a nonlinear preferential attachment mechanism, and we find both the asymptotics of their expected values and the characteristics of their spread around the mean. In addition, we analyze the behavior of these local characteristics for three real social networks. The applicability of the findings to actual problems in the study of social media in the digital humanities is discussed. [ABSTRACT FROM AUTHOR]

Carbon monoxide is a non‐condensable gas in the Martian atmosphere produced by the photolysis of CO2. Its abundance responds to the condensation and sublimation of CO2 from the polar caps, resulting in seasonal variations of the CO mixing ratio. ACS onboard the ExoMars Trace Gas Orbiter have measured CO in infrared bands by solar occultation. Here we provide the first long‐term monitoring of the CO vertical distribution at the altitude range from 0 to 80 km for 1.5 Martian years from Ls = 163° of MY34 to the end of MY35. We obtained a mean CO mixing ratio of ∼960 ppmv at latitudes from 45°S to 45°N and altitudes below 40 km, mostly consistent with previous observations. We found a strong enrichment of CO near the surface at Ls = 100–200° in high southern latitudes with a layer of 3,000–4,000 ppmv, corresponding to local depletion of CO2. At equinoxes we found an increase of the CO mixing ratio above 50 km to 3,000–4,000 ppmv at high latitudes of both hemispheres explained by the downwelling flux of the Hadley circulation on Mars, which drags the CO enriched air. General circulation models tend to overestimate the intensity of this process, bringing too much CO. The observed minimum of CO in the high and mid‐latitudes southern summer atmosphere amounts to 700–750 ppmv, agreeing with nadir measurements. During the global dust storm of MY34, when the H2O abundance peaks, we see less CO than during the calm MY35, suggesting an impact of HOx chemistry on the CO abundance. Plain Language Summary: Carbon monoxide (CO) is a product of the photodissociation of the main component of the Martian atmosphere, CO2 (96%). During the polar night on Mars, the temperature drops so low that ∼30% of the global atmospheric carbon dioxide freezes out, condensed into snowflakes. They settle to the ground to form a seasonal polar cap, which sublimates in spring. Unlike CO2, CO is not a condensable species, so its relative abundance increases when CO2 and the atmospheric pressure drops, forming a prominent seasonal cycle. This behavior of CO was well documented by spacecraft measurements of column abundances, while its vertical distribution remained poorly known until recently. Still, it helps to separate the impacts of atmospheric dynamics and chemistry, addressing the problem of the Martian atmosphere's stability. We present the first climatology of the CO vertical distribution lasting more than one Martian year based on solar occultations by the ExoMars Trace Gas Orbiter. We report a previously unobserved CO layer near the surface in high southern latitudes in late winter and spring and document the difference between two Martian years caused by the global dust storm. These observations give new challenges to General Circulation Models for understanding the modern atmosphere of Mars. Key Points: The first climatology of CO vertical profiles is collected for the period Ls = 163° of Martian Year 34 to the end of Martian Year 35The mean CO volume mixing ratio is ∼960 ppmv at 0–35 km and 45°S–45°NStrong enrichment of CO, >3,000 ppmv, is detected at 10–20 km at Ls = 100–200 in high southern latitudes and above 50 km at equinoxes near Poles [ABSTRACT FROM AUTHOR]

We assimilate atmospheric temperature profiles and column dust optical depth observations from the ExoMars Trace Gas Orbiter Atmospheric Chemistry Suite thermal infrared channel (TIRVIM) into the Mars Planetary Climate Model. The assimilation period is Mars Year 34 Ls = 182.3°–211.4°, covering the onset and peak of the 2018 global dust storm. We assimilated observations using the Local Ensemble Transform Kalman Filter with 36 ensemble members and adaptive inflation; our nominal configuration assimilated TIRVIM temperature profiles to update temperature and dust profiles, followed by dust column optical depths to update the total column dust abundance. The observation operator for temperature used the averaging kernels and prior profile from the TIRVIM retrievals. We verified our analyses against in‐sample TIRVIM observations and independent Mars Climate Sounder (MCS) temperature and dust density‐scaled opacity profiles. When dust observations were assimilated, the root‐mean‐square temperature error verified against MCS fell by 50% during the onset period of the storm, compared with assimilating temperature alone. At the peak of the storm the analysis reproduced the location and magnitude of the peak in the nighttime MCS dust distribution, along with the surface pressure diurnal cycle measured by Curiosity with a bias of less than 10 Pa. The analysis winds showed that, at the peak of the storm, the meridional circulation strengthened, a 125 m s−1 asymmetry developed in the midlatitude zonal jets, the diurnal tide weakened near the equator and strengthened to 10–15 K at midlatitudes, and the semi‐diurnal tide strengthened almost everywhere, particularly in the equatorial lower atmosphere. Plain Language Summary: ExoMars Trace Gas Orbiter has been in low orbit around Mars since early 2018. During 2018 a large amount of dust was lifted from Mars' surface into the atmosphere. This eventually obscured most of the planet, forming a global dust storm. These storms have a large effect on the temperature and weather in Mars' atmosphere. We used observations from the spacecraft's thermal infrared instrument. This measures how much light comes from the atmosphere and surface at wavelengths where heat is emitted, and can be used to work out the atmospheric temperature and dust content at different times of day. We combined these observations with a numerical model of Mars' atmosphere, considering uncertainties in the measured atmospheric properties and the modeled atmosphere. We compared our results with temperature and dust observations made by Mars Climate Sounder on board Mars Reconnaissance Orbiter. Including dust observations was better than just using temperature observations. While the dust storm was raging, north‐south wind speeds increased, the strong eastward wind in the northern hemisphere became much stronger than in the southern hemisphere, and differences between day and night became larger. Our results mean we can better understand aspects of Mars' atmosphere throughout the daily cycle. Key Points: We assimilate temperature and dust observations from ExoMars Trace Gas Orbiter‐Atmospheric Chemistry Suite‐TIRVIM during the MY34 global dust storm (GDS)The analysis verifies well against independent Mars Climate Sounder temperature and dust profiles, and Curiosity pressure measurementsAt the peak of the GDS the winds strengthen, the diurnal tide migrates poleward, and the semi‐diurnal tide strengthens [ABSTRACT FROM AUTHOR]

Thermal tides in the Martian atmosphere are analyzed using temperature profiles retrieved from nadir observations obtained by the TIRVIM Fourier‐spectrometer, part of the Atmospheric Chemistry Suite onboard the ExoMars Trace Gas Orbiter. The data is selected near the northern summer solstice at solar longitude (LS) 75°–105° of Martian Year 35. The observations have a full local time coverage, which enables analyses of daily temperature anomalies. The observed zonal mean temperature is lower by 4–6 K at ∼100 Pa, but higher toward the summer pole, compared to the Laboratoire de Météorologie Dynamique (LMD) Mars General Circulation Model (GCM). Wave mode decomposition shows dominant diurnal tide and important semi‐diurnal tide and diurnal Kelvin wave, with maximal amplitudes of 5, 3, and 2.5 K, respectively, from tens to hundreds of Pa. The results generally agree well with the LMD Mars GCM, but with noticeable earlier phases of diurnal (∼1 hr) and semi‐diurnal (∼3 hr) tides. Plain Language Summary: Unlike the Earth, daily temperature variation on Mars is as large as tens of degrees because of its thin atmosphere. The sunlight absorbed by the Martian surface and dust in the atmosphere leads to dramatic temperature increase in the lower atmosphere during daytime. Such large and regular changes can trigger temperature waves, and some modes of them can propagate into higher altitudes, where they become the major factor controlling the daily temperature variation. In this work, temperature profiles obtained using thermal‐infrared spectra are analyzed. Zonal mean temperature is compared with numerical simulations of the Martian atmosphere. Different types of the wave modes are computed through decomposition. Results from the observation agree well with model prediction when the observation mechanisms are taken into consideration. Estimation of the strength of these waves can be improved in the future with improved design of observation strategies. Key Points: Thermal tides in the Martian atmosphere are investigated using temperature profiles retrieved from TIRVIM nadir observationsDiurnal tide dominates daily temperature variations; semi‐diurnal tide and diurnal Kelvin wave are also importantObservations agree well with numerical simulations, but suggest phases of diurnal and semi‐diurnal tides earlier than predicted [ABSTRACT FROM AUTHOR]

Background: Urinary tract infections (UTIs) are common in women, and during pregnancy can cause significant morbidity. Growing and greatly varying antimicrobial resistance (AMR) of Enterobacteriaceae, responsible for most UTIs, necessitates regular local AMR surveillance. In obstetric population, where beta-lactams are the mainstay for treatment of severe UTIs, particular focus should be placed on beta-lactam resistance. This study aimed to evaluate AMR rates and frequency of extended spectrum beta-lactamase (ESBL) and carbapenemase genes in uropathogenic Enterobacteriaceae among reproductive-age women in St. Petersburg, Russia.Materials/methods: Urine samples were collected from consecutive reproductive-age women, who attended the D.O. Ott Research Institute of Obstetrics, Gynecology and Reproductology from October 2017 to November 2019, and cultured according to routine procedures. Susceptibility to antibiotics and ESBL production was determined using the disc diffusion method according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. All urine samples and Enterobacteriaceae isolates were tested for ESBL and carbapenemase genes using real-time PCR.Results: Enterobacteriaceae were detected in 91 (56 pregnant and 35 non-pregnant) of 119 (76%) included women. The vast majority of Enterobacteriaceae strains were susceptible to nitrofurantoin, fosfomycin and meropenem (99-100%). The frequency of strains susceptible to penicillins and cephalosporins ranged from 59% to 82%; 78% of strains were susceptible to ciprofloxacin. ESBL production was phenotypically detected in 15 (16%) Enterobacteriaceae strains, with CTX-M genes revealed in all cases. In all corresponding urine samples, CTX-M genes were also detected. The remaining 104 urine samples were negative for CTX-M genes. In none of the isolates and urine samples, carbapenemase genes were present.Conclusions: The frequency of ESBL producing Enterobacteriaceae was relatively high (16%), with CTX-M genes detected in all cases in both urine and urine cultures. Rapid PCR detection of CTX-M genes directly in urine samples from women with pyelonephritis can be valuable for timely informing treatment choices. [ABSTRACT FROM AUTHOR]

Evaluation of circulating group B streptococcus (GBS) strains is important to assess the potential effects of GBS prevention strategies in a certain region. This study aimed at estimating the distributions of capsular polysaccharide (CPS) types and pilus profiles, and the rates of antimicrobial resistance among GBS strains isolated from colonized pregnant women and newborns in 2010–2011 and 2017–2018 in St. Petersburg, Russia. A total of 261 GBS isolates have been investigated. Antibiotic susceptibility testing was performed using the disc-diffusion method. CPS types and pilus profiles were determined by using PCR. Over the 9-year period, the resistance of GBS to both erythromycin and clindamycin has significantly increased, exceeding 30% in 2017–2018. The most prevalent CPS types were Ia, III, and V. Significant shifts were observed in the frequency of CPS types III (decreased) and V (increased), which resulted in a significant reduction (from 77 to 63%) in the potential coverage by a trivalent vaccine (including serotypes Ia, Ib, and III), whereas that of a pentavalent vaccine (including serotypes Ia, Ib, II, III, and V) remained largely unchanged (approximately 95%). The most common pilus profiles were PI-1/2a, PI-2a, and PI-1a/2b, and pilus genotype distribution has not changed with time. High and steadily growing resistance of perinatal GBS strains to clindamycin requires restricting its use to penicillin-allergic women at high risk for anaphylaxis and testing the GBS strains for their susceptibility to this antibiotic. A pentavalent CPS-based vaccine covers the vast majority of perinatal GBS strains in Russia. [ABSTRACT FROM AUTHOR]

The aim of the paper is to provide an analysis of news and financial data using their network representation. The formation of network structures from data sources is carried out using two different approaches: by building the so-called market graph in which nodes represent financial assets (e.g., stocks) and the edges between nodes stand for the correlation between the corresponding assets, by constructing a company co-mention network in which any two companies are connected by an edge if a news item mentioning both companies has been published in a certain period of time. Topological changes of the networks over the period 2005-2010 are investigated using the sliding window of six-month duration. We study the stability of the market graph and the company co-mention network over time and establish which of the two networks was more stable during the period. In addition, we examine the impact of the crisis of 2008 on the stability of the market graph as well as the company co-mention network. The networks that are considered in this paper and that are the objects of our study (the market graph and the company co-mention network) have a non-changing set of nodes (companies), and can change over time by adding/removing links between these nodes. Different graph similarity measures are used to evaluate these changes. If a network is stable over time, a measure of similarity between two graphs constructed for two different time windows should be close to zero. If there was a sharp change between the graphs constructed for two adjacent periods, then this should lead to a sharp increase in the value of the similarity measure between these two graphs. This paper uses the graph similarity measures which were proposed relatively recently. In addition, to estimate how the networks evolve over time we exploit QAP (Quadratic Assignment Procedure). While there is a sufficient amount of works studying the dynamics of graphs (including the use of graph similarity metrics), in this paper the company co-mention network dynamics is examined both individually and in comparison with the dynamics of market graphs for the first time. [ABSTRACT FROM AUTHOR]

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today1. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations2–5. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere6,7, which—given methane's lifetime of several centuries—predicts an even, well mixed distribution of methane1,6,8. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections2,4. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater4 would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally. Highly sensitive measurements of the atmosphere of Mars with the ExoMars Trace Gas Orbiter do not detect any methane over a range of latitudes in both hemispheres, in contrast to previous local or remote detections. [ABSTRACT FROM AUTHOR]

With the aim to compare methods for counting the number of lines of a raster matrix, intersecting a round mark image, and a number of pixels belonging to this image for measuring its radius, a numerical simulation is carried out in the present article. It is proved that the application of the method for counting the number of pixels belonging to the image of the round mark allows obtaining more than 30 times gain in the accuracy of this image radius measurement using the same equipment. The formulas proposed in the article are used for software implementation of non-contact vibration measurement systems. [ABSTRACT FROM AUTHOR]

In planetary research, Fourier transform infrared spectrometers (FTIR) solve a number of important scientific goals related both to the atmosphere and to the surface sounding. For remote orbital measurements, these goals are the thermal sounding of the atmosphere using, in particular, the 15-µm CO band, sensitive detections of minor gaseous species and aerosol characterization. FTIR can address similar atmospheric science goals when observing from a planetary surface allowing for better-resolved boundary layer and achieving greater accuracy (longer integration) for minor species detection. For studies of planetary surfaces, characterization of mineralogical composition in a wide IR range including sensitive measurements of hydration of the soil on airless bodies can be done. We outline a family of FTIR instruments dedicated to studies of Mars and the Moon. TIRVIM is a channel of ACS on ExoMars TGO (in orbit around Mars since October 2016). It is a 2-inch interferometer for nadir and solar occultation measurements of Mars' atmosphere. It covers a spectral range of 1.7-17 µm with spectral resolution up to 0.13 cm. LUMIS is a similar instrument for Luna-Resource Orbiter (Luna-26) Roscosmos mission dedicated to the search for hydration of the lunar regolith in the 6-µm band. The spectral range of LUMIS is broad (1.7-17 µm), but its sensitivity is optimized for the 4-8 µm region. The spectral resolution is 50 cm. We also describe recent developments focused on technical solutions for miniaturized FTIR instruments with a very high spectral resolution (0.05 cm and higher). The prototype targets measurements of minor atmospheric species from the surface of Mars using the Sun tracking. One important task is to provide a high precision of interferometer's mirror movement. Another task is the development of a precise two-coordinate mechanism to seek for and follow the Sun. [ABSTRACT FROM AUTHOR]

Mesenchymal stromal cells (MSCs) have shown a high potential for cartilage repair. Collagen-based scaffolds are used to deliver and retain cells at the site of cartilage damage. The aim of the work was a comparative analysis of the capacity of the MSCs from human adipose tissue to differentiate into chondrocytes in vitro and to stimulate the regeneration of articular cartilage in an experimental model of rabbit knee osteoarthrosis when cultured on microheterogenic collagen-based hydrogel (MCH) and the microparticles of decellularized porcine articular cartilage (DPC). The morphology of samples was evaluated using scanning electron microscopy and histological staining methods. On the surface of the DPC, the cells were distributed more uniformly than on the MCH surface. On day 28, the cells cultured on the DPC produced glycosaminoglycans more intensely compared to the MCH with the synthesis of collagen type II. However, in the experimental model of osteoarthrosis, the stimulation of the cartilage regeneration was more effective when the MSCs were administered to the MCH carrier. The present study demonstrates the way to regulate the action of the MSCs in the area of cartilage regeneration: the MCH is more conducive to stimulating cartilage repair by the MSCs, while the DPC is an inducer for a formation of a cartilage-like tissue by the MSCs in vitro. [ABSTRACT FROM AUTHOR]

This article takes an approach to creating a machine learning model for the oil and gas industry. This task is dedicated to the most up-to-date issues of machine learning and artificial intelligence. One of the goals of this research was to build a model to predict the possible risks arising in the process of drilling wells. Drilling of wells for oil and gas production is a highly complex and expensive part of reservoir development. Thus, together with injury prevention, there is a goal to save cost expenditures on downtime and repair of drilling equipment. Nowadays, companies have begun to look for ways to improve the efficiency of drilling and minimize non-production time with the help of new technologies. To support decisions in a narrow time frame, it is valuable to have an early warning system. Such a decision support system will help an engineer to intervene in the drilling process and prevent high expenses of unproductive time and equipment repair due to a problem. This work describes a comparison of machine learning algorithms for anomaly detection during well drilling. In particular, machine learning algorithms will make it possible to make decisions when determining the geometry of the grid of wells—the nature of the relative position of production and injection wells at the production facility. Development systems are most often subdivided into the following: placement of wells along a symmetric grid, and placement of wells along a non-symmetric grid (mainly in rows). The tested models classify drilling problems based on historical data from previously drilled wells. To validate anomaly detection algorithms, we used historical logs of drilling problems for 67 wells at a large brownfield in Siberia, Russia. Wells with problems were selected and analyzed. It should be noted that out of the 67 wells, 20 wells were drilled without expenses for unproductive time. The experiential results illustrate that a model based on gradient boosting can classify the complications in the drilling process better than other models. [ABSTRACT FROM AUTHOR]

The surname of author Cathy Quantin-Nataf was misspelled 'Quantin-Nata', authors Ehouarn Millour and Roland Young were missing from the ACS and NOMAD Science Teams list, and minor changes have been made to the author and affiliation lists; see accompanying Amendment. These errors have been corrected online. [ABSTRACT FROM AUTHOR]