Sharp Decrease In Temperature Research Articles

Thermal, structural, and conductivity properties of As14Sb26S(60−x)–(AgI)x chalcogenide glasses

The present work describes the preparation of a new series of chalcogenide glasses in an As14Sb26S(60−x) (AgI)x system intending to explore its thermal, structural, optical, mechanical, and electrical properties. The differential scanning calorimetry results of the studied glasses show the sharp decrease in glass transition temperature (Tg) with the successive incremental inclusion of AgI in the composition, implying the structural changes in the glass network. A thorough Raman analysis corroborates the occurrence of changes in the glass network due to the formation of AsI3 units and Ag–S–As bonds with increasing AgI content. Also, structural changes can be reflected with the change in the optical bandgap (Eg) that was calculated using Tauc equations where it was found that Eg is in harmony with the observed structural variations of glasses. The studied glasses possess a transmittance window (∼0.68–12 μm) with transmittance above 60% in the mid-infrared region. These structural changes are closely related to the significant enhancement of conductivity of the present glasses from 10−8 to 10−6 S/cm at 373 K with a decrease in activation energies. Impedance spectra for the glass with highest AgI revealed the presence of two different relaxation processes. AC conductivity data followed an Arrhenius behavior as well as Jonscher’s power law. The present work provides insights into glass network modifications due to silver iodide inclusion and its role in the enhancement of conductivity.

3D Plotting of Gold Solubility and Gold Fineness: Quantitative Analysis of Ore-Forming Conditions in Hydrothermal Gold Deposits

Abstract The 3D plotting of gold solubility and gold fineness aims to illustrate how to quantify their correlations with ore-forming conditions in hydrothermal gold deposits. The thermodynamic calculation of the Au-Ag solid solutions in Mathematica and the 3D plotting in MATLAB are used to build isopleths of gold solubility and gold fineness at different temperatures (200℃, 400℃), pressures (0.1, 5 kbar), salinities (1, 40 wt% NaCl eq.), and sulfur concentrations (0.01, 0.5 mol/kg). The plot indicates that the ore-forming conditions have different correlations with gold solubility and gold fineness. Average rates of change for the correlations are quantified, showing distinct values in the four pH-logfO2 fields of (I) HSO4−, (II) SO42−, (III) H2S, and (IV) HS−, where dominant gold and silver complexes have different dependencies on the conditions. The quantification of the plots illustrates that a decrease in gold solubility by one order of magnitude is possibly caused by a decrease in temperature of ≥40℃, the salinity of ≥9.6 wt% NaCl eq. or sulfur concentration of ≥0.14 mol/kg, or an increase in pressure of ≥3 kbar, while a decrease in gold fineness by 100 units is possibly caused by a decrease in temperature of ≥14 ℃, pressure of ≥1.4 kbar, or salinity of ≥4 wt% NaCl eq., or an increase in sulfur concentration of ≥0.07 mol/kg. Quantification results suggest that a sharp decrease in temperature may result in large-scale gold mineralization and a great variation in gold fineness. In addition, the quantification reveals that the correlation between gold solubility and gold fineness can be expressed by a function, providing a rapid method for 3D plotting.

Hyperthermia in children: from etiology to pathogenetic therapies. A review

Fever is the most common symptom of most infectious diseases and, to a moderate extent, has a protective-compensatory effect with increased blood bactericidality and activation of immune mechanisms. A pathological variant of fever, in which there is a rapid and inadequate increase in body temperature, accompanied by microcirculation disorder, metabolic disorders, increasing dysfunction of vital organs and systems, in particular, the damage to the central nervous system is hyperthermic syndrome, which requires active antipyretic and symptomatic therapy. Polysystemic dysfunctions associated with hyperthermia and the course of the infectious process can change the metabolic status of antipyretic drugs and sensitivity to their action, which can increase the frequency and severity of side effects, including the development of hypothermia and/or a sharp decrease in body temperature. This will be prevented by a pathegenetic approach to the correction of hyperthermia using antipyretic drugs, the action of which is based on the stimulation of natural, endogenous anti-inflammatory and antipyretic mechanisms.

Adiabatic wall temperature in the supersonic flow of moist air with spontaneous condensation

The expansion of moist air in supersonic nozzles is accompanied by spontaneous condensation of water vapor due to a sharp decrease in flow temperature and pressure. However, in the near-wall boundary layer due to the viscous dissipation, moist air temperature decreases slightly in comparison with initial one. This leads to the fact that the vapor remains overheated in the near-wall region and condensation does not spread to its entire depth. Droplets formed in the core flow as a result of condensation can penetrate into the near-wall region due to turbulent diffusion and evaporate due to higher temperature in the near-wall region. This process causes cooling of the near-wall gas layers and, consequently, a decrease in the adiabatic wall temperature. A decrease in the adiabatic wall temperature relative to the stagnation temperature leads to a decrease in aerodynamic heating and, consequently, in the heat flux from the gas to the body. In this paper, measurements of the adiabatic temperature of the supersonic nozzle wall for moist air flow with condensation are presented. Temperature measurements were made using an infrared thermal imager. Initial moisture content varied in the range of 1.5–20.2 g/(kg. dry air) and initial relative humidity in the range 20–90%. It is shown that in the region behind the zone of spontaneous condensation (“condensation shock”), adiabatic wall temperature depends on the initial moisture content and can be either greater or less than the value of a single-phase (dry air) flow with identical initial flow parameters. Estimates of the flow parameters behind the condensation region are obtained using one-dimensional diabatic flow equations and experimental static pressure distributions along the nozzle length. The correlation between the initial moisture content, the average droplet size and the temperature recovery factor is shown.

Spatial distributions of particle number size distributions generated during cooking processes and the impacts of range hoods

Cooking oil fume (COF) is associated with an increased risk of health effects. The particle number size distribution (PNSD) of COF presenting as lognormal structures is recognized as a key metric in determining its exposure toxicities, but the information of its spatial distributions and impacting factors are still lacking. This study conducted real-time monitoring COF PNSD during the cooking processes in a kitchen laboratory. Results showed that COF PNSD presented as a combination of two lognormal distributions. The peak diameters of PNSD inside the kitchen were: 385 nm (very close to the source), 126 nm (5 cm above the source), 85 nm (10 cm above the source) to 36 nm (breath point, 50 cm above the source), 33 nm (sucking surface of the ventilation hood), 31 nm (1 m horizontally to the source), and 29 nm (3.5 m horizontally to the source). The reasons of this observation was the sharp decrease of temperature from the pot to the indoor environment reduced the surface partial pressure of the COF particles and caused a large amount of semi-volatile organic carbons (SVOCs) with lower saturation ratios condensed on the COF surface. With the temperature difference became insignificant with the distance further to the source, the reduction of the supersaturation helped the gasification of these SVOCs. Dispersion led to a linearly horizontal decreases ((1.85 ± 0.10) × 106#/cm3/m) in particle numbers with further distances, making the peak particle number concentrations decrease from 3.5 × 105#/cm3 at the breath point to 1.1 × 105#/cm3 at the point 3.5 m to the source. Cooking dishes also presented as mode diameters of 22-32 nm at the breath point. The amount of edible oil used in different dishes is positively correlated with the peak concentration of COF. Only increasing the exhaust force of the range hood cannot significantly change the sucked COF particle numbers and sizes, owning to that COF particles are mainly small sizes. New technologies on cleaning small size particles and efficient supplemental air should be given more considerations.

Verification of the Ekman Upwelling Criterion with In Situ Temperature Measurements in the Southeastern Baltic Sea

Upwelling leads to a sharp and strong decrease in water temperature in the coastal zone of the southeastern Baltic Sea. The quality of existing hydrodynamic models cannot fully meet the requirements of accurate upwelling forecasts. This study provides insight into the applicability of the simplified Ekman upwelling criterion method for the southeastern Baltic Sea. The upwelling criterion is the ratio of the vertical velocity and the duration of the upwelling wind to the mixed layer density. The vertical velocity was determined by the divergence of the integral Ekman transport in the transverse direction. Calculation of the criterion was based on wind data from NCEP/CFSR reanalysis. The upwelling criterion was compared with in situ temperatures from direct measurements near the D-6 oil platform taken in 2015–2017. Only 46% of calculated upwelling cases were confirmed by temperature decreases in the sub-surface. It was found that more than half of the cases of strong temperature decreases were caused by a northern wind (Ekman upwelling), when the criterion exceeded the threshold value. Comparison of the hydrodynamic model results and direct measurements shows that the model’s quality is far from perfect, and the simplified methods can be used as alternatives to models. Some recommendations were made for future upwelling research.

Studying the internal structures of the central region of prestellar core L1517B in Taurus molecular cloud using ammonia (NH3) (1,1) and (2,2) lines

Abstract Measurement of internal structures in the prestellar core is essential for understanding the initial conditions prior to star formation. In this work, we study the ammonia lines (NH $_{3}$ ) (J, K = 1,1 and 2,2) in the central region of the prestellar core L1517B with the Karl G. Jansky Very Large Array (VLA) radio telescope (spatial resolution $\sim$ 3.7′′). Our analysis indicates that the central region of the core is close-to-round in shape obtained both from NH $_{3}$ (1,1) and (2,2) emissions. Radially averaged kinetic temperature ( $T_{k}$ ) is almost constant with a mean value of $\sim$ 9 K. A radially sharp decrease in kinetic temperature ( $T_{k}$ ) has not been observed inside the central dense nucleus of this prestellar core. In addition, we also notice that there is an overall velocity gradient from north-east to south-west direction in this region, which may be indicative of the rotational motion of the core. We then calculate the parameter $\beta$ , which is defined as the ratio of rotational energy to gravitational potential energy and find that $\beta$ equals to $\sim$ 5 $\times$ 10 $^{-3}$ ; which indicates that rotation has no effect at least inside the central region of the core. We also perform the viral analysis and observe that the central region may be in a stage of contraction. From this study, we also show that turbulence inside the central region is subsonic in nature (sonic Mach number, $M_{s}$ $<$ 1) and has no prominent length-scale dependence. Furthermore, we notice that the decrement of excitation temperature ( $T_{ex}$ ) and column density of NH $_{3}$ from the centre of the core to the outer side with the peak values of $\sim$ 5.6 K and $\sim$ 10 $^{15}$ cm $^{-2}$ , respectively. In conclusion, this work examines different physical and kinematical properties of the central region of the L1517B prestellar core.

Co-firing characteristics and fuel-N transformation of ammonia/pulverized coal binary fuel

As a feasible way to decarbonize coal combustion under the background of carbon neutrality in recent years, ammonia co-firing with pulverized coal is receiving considerable critical attention from the academic and industrial communities. This paper investigates the effects of coal type, NH3 injection mode, temperature, excess air ratio (α) and NH3 co-firing ratio (ENH3) on combustion characteristics and fuel-N transformation of ammonia/pulverized coal in a 6 kW drop tube furnace. Emission of O2, CO2, CO, NO, NO2 and NH3 at the furnace exit was monitored online. The unburned carbon (UBC) content and elementary composition in fly ash were also tested. Results show that NOx generation behaviors of premixed and staged modes are significantly different. Typically, NOx emission peaks at ENH3 = 20 % under high temperature and staged mode. As for NH3/coal cases at 1000 °C, NOx level is even lower than pure coal combustion, but NH3 residue is higher. The water gas shift reaction (WGSR) under fuel-rich condition generates more CO, and the conversion ratio from fuel-N to NOx decreases when α diminishes. Ammonia co-firing can achieve lower CO emission with anthracitic coal from Gongyi (GY-coal) while lower NOx emission with bituminous coal from Inner Mongolia (IM-coal). Ammonia co-firing can considerably improve the transformation from fuel-N to N2. From the perspective of emission control and decarbonization, ENH3 = 40 % is an optimal ammonia co-firing ratio which not only can reduce half of CO2 but also brings the conversion ratio from fuel-N to NOx and residual NH3 to the minimum level. The micromorphology of ash samples is greatly affected by coal/ammonia co-firing. In premixed mode, the surface of ash sample is porous and adhered to each other; while in staged mode, obvious fractures and cuts exist between the ash particles due to the sharp decrease of local gas temperature.

Experimental results of the study of underburned hydrogen during burning in oxygen medium

The area of research is the experimental study of the composition of steam as a result of the combustion of hydrogen in an oxygen atmosphere in order to assess the underburning of hydrogen. The existing experience of experimental research on the combustion of hydrogen in an oxygen atmosphere is analyzed. Among the known works, the underburning of hydrogen was determined after mixing the dissociated vapor with a cooling component, which contributes to its sharp decrease in temperature. As a result, this leads to a decrease in the number of recombinations of unreacted hydrogen towards the formation of steam, which leads to an increased content of hydrogen in the steam. A large number of works are devoted to the combustion of various types of fuel with hydrogen additives in internal combustion engines in a number of European and Asian countries.The purpose of the article is to supplement and summarize a series of experiments on the study of hydrogen underburning when burning in an oxygen atmosphere without using a cooling component for mixing with combustion products (water vapor). Only external cooling of the flame tube of the experimental setup was used. This experiment was performed for the first time. For the conditions of experiments carried out by the authors of the article, a diagram, components and measuring instruments of the experimental setup are presented. The initial data on the pressure and temperature of hydrogen, oxygen, cooling water are given. The main expressions of the procedure for determining the underburning of hydrogen are given. The main results of experimental measurements are presented. The graphical results of measuring the steam temperature along the length of the flame tube of the experimental setup, the flow rates of hydrogen and oxygen, the temperature and flow rate of cooling water, the pressure inside the flame tube and in the steam extraction pipeline for chemical analysis are shown. On the basis of generalization of a series of experiments, an exponential character of the decrease in the underburning of hydrogen along the length of the flame tube of the experimental setup was obtained, which indicates the intense processes of hydrogen recombination towards the formation of steam. It was found that during the time of 0.069 s with the movement of dissociated steam inside a flame tube 980 mm long, the underburning of hydrogen decreases from 5.85 to 0.016% of the mass during stoichiometric combustion and to 0.0138% of the mass with an excess of the oxidant equal to 1.4.

STUDY OF PHYSICAL AND MECHANICAL PROPERTIES OF POLYMER-IMPREGNATED COMPOSITION IN CLINICAL PURULENT OSTEOLOGY

Bone cement, or PMMA (polymethyl methacrylate) is often used in purulent surgery. Scientific literature contains very contradictory data on the physical and mechanical properties of polymer-impregnated compositions, in particular, on the temperature of the PMMA polymerization process and the ways to reduce it, such as introduction of antimicrobial drugs for prevention and treatment of infectious complications in patients after injuries and musculoskeletal surgery.
 The aim of the study is to conduct an in vitro experiment and to evaluate the temperature of the exothermic polymerization reaction of bone cement (PMMA) and possible ways to reduce it.
 Materials and Methods. The authors conducted 8 series of experiments in vitro. In each series, a disk (45–50 mm in diameter, 5–7 mm thick) was made by hand after mixing the components of the polymer composition. The temperature of the ongoing exothermic reaction was measured on the disk surface using a non-contact infrared thermometer ADA TemPro 300 in a continuous scanning mode.
 Results. The temperature of the exothermic polymerization reaction of PMMA Synicem 1-based bone cement was 92.8±1.6 °C (min 91.2 °C, max 94.9 °C), and Palacos®MV+G-based bone cement 92.7±1.2 °С (min 91.1 °C, max 93.8 °C). Reducing the monomer amount by 50 % (polymer / monomer ratio was equal to 4:1) and simultaneously introducing “Sextaphage” (10 ml) led to a sharp temperature decrease of the exothermic reaction by more than 30 °C.
 Conclusions. One of the ways to reduce the temperature of the exothermic reaction in vitro is to change the ratio of polymer powder and liquid monomer, reducing the amount of monomer introduced into the polymer composition.

Formation of the Cenozoic Ailao Shan mid-crustal tectonic discontinuity: Role of Oligo-Miocene stratified sub-horizontal middle to lower crustal flow in the southeastern Tibetan Plateau

Structural, kinematic and geothermometry analyses are applied to unravel the structural evolution of the Ailao Shan Tectonic belt (ALTB) with a specific goal of understanding how crustal masses in southeastern Tibetan Plateau flowed during the Indian-Eurasian continental collision. A mid-crustal tectonic discontinuity that is characterized by a narrow ultramylonite belt separates the highly sheared high-grade metamorphic unit (HMU) from the low-grade metamorphic unit (LMU) along the ALTB. It is shown that rocks from the HMU and LMU possess deformation associations of identical structural geometries and kinematics, but at contrasting metamorphic conditions. Calculated mean kinematic vorticity numbers indicate that the ultramylonite belt was affected by dominant simple shearing, while the HMU and LMU on both sides of the belt were deformed by general shearing dominated by pure shearing. Geothermometry analyses on sheared two-mica schists from the HMU and quartz veins from the LMU reveal different deformation conditions, i.e., 610–777 °C, 0.4–0.6 GPa and 320–391 °C, respectively. There is also a sharp decrease in deformation temperature inferred from deformation microstructures and quartz c-axis fabrics, from 550–650 °C for the HMU to 350–400 °C for the LMU. These results suggest that there is an apparent temperature break of ca. 220 °C over a total structural distance of approximately 1 km between these two units at the present outcrop level. Our results show that the HMU and LMU are kinematically linked while rheologically decoupled, and were originally deformed by sub-horizontal shearing at different crustal levels in the same strain field. The ultramylonite belt between them potentially inherited a preexisting basement/cover contact along the ALTB and brought the two units into contact. We suggest that progressive stratified flow of middle to lower crustal masses during the extrusion of the Sundaland block at Oligocene to Early Miocene was responsible for the concurring high- and low-temperature fabrics at different crustal levels. Contemporaneous doming during the progressive crustal flow resulted in exhumation of the lower crustal rocks. During the process, the ultramylonite belt occurred as a tectonic discontinuity (TDC) that leads to the loss of a thick pile (ca. ∼6.3–7.8 km) of crustal masses in the middle crust.

Особенности формирования и эволюции полярного циклона в Баренцевом и Карском морях в декабре 2020 года

Based on the GDAS (Global Data Assimilation System) information, the conditions for the formation and evolution of a polar cyclone in the Barents Sea in December 2020 are studied. The cyclone in interesting because after entering the Kara Sea, the cyclone did not weaken as usual but continued to intensify. The formation of the cyclone occurred near the ice edge under conditions of the cold Arctic air outbreak. After entering the Kara Sea, the cyclone continued to deepen, which was facilitated by latent and sensible heat fluxes in the ice-free western part of the sea. According to weather station data, when the cyclone moved further over land, the wind direction changed from mainly southern to northern, and wind speed increased significantly. There also was a sharp decrease in air temperature by 7–10 °С for three hours. Keywords: polar cyclone, global data assimilation system, wind speed, latent and sensible heat fluxes

Analysis of Temperature Anomalies during Thermal Monitoring of Frozen Wall Formation

The paper describes a distributed temperature sensing system that was used to monitor the artificial freezing of soils during the construction of a potash mine shaft. The technique of reconstructing the temperature field by solving the inverse problem in the entire volume of frozen soils using the measured temperatures in four thermal monitoring (TM) wells is described. Two local anomalies in temperature distributions in TM wells are described and analyzed theoretically using thermo-hydraulic modeling. The first anomaly concerns the asymmetric temperature distribution in one of the soil layers and is associated with the influence of natural groundwater flow in the horizontal direction. The second anomaly consists of a sharp decrease in water temperature in the section of the TM well located inside the freezing contour. Calculations showed that it is most likely associated with the entry of cold groundwater from the overlying layers of soils through a well filter at a depth of 160 m and the subsequent movement of the water up the well.

CO and H2 adsorption on Au-Ni bimetallic surfaces: a combined experimental and DFT theoretical study

Au-Ni bimetallic thin films were grown on refractory metal substrates. CO and H2 adsorption on Au-Ni bimetallic surfaces have been studied by a combination of in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. It is found CO desorption peak shifts from 413 K on pure Ni surfaces to 293 K on the isolated Ni atoms formed by alloying with Au atoms. The sharp decrease of CO desorption temperature on Au-Ni surfaces with increasing Au coverage is caused by the change of the favored CO adsorption sites from bridge/hollow sites on pure Ni surfaces to Ni top sites on Au-Ni bimetallic surfaces. In situ PM-IRRAS shows two CO adsorption bands on Au sites at 2119 cm−1 and 2103 cm−1 on Au-Ni surfaces at 80 K, which are due to CO bound on under-coordinated Au atoms and electron negatively charged Au sites modified with nearby Ni atoms, respectively. Even with the Au-Ni surface temperature at as low as 100 K, CO adsorption induced Ni surface segregation has been observed by in situ PM-IRRAS. Furthermore, DFT calculation results discover the adsorption energy of CO on Ni top sites continues to decrease with increasing Au coverage due to the geometric ensemble effect and the lowered d-band center after Ni alloying with Au. H2 desorption temperature decreases from 363 K on pure Ni thin films to 302 K with increasing Au coverage to 0.6 ML. A new H2 peak appears at around 170 K on the Au-Ni surfaces with Au coverages between 0.6 ML and 0.9 ML. This new H2 TPD peak is assigned to H2 desorption from the totally isolated Ni sites. With Au coverage above 1.5 ML, there is no any H2 desorption detected. The combined surface science studies and DFT calculations provide new insights into the surface structure-activity correlation of Ni-base bimetallic surface alloys.

Emergency cooling of superheated surfaces by nanofluids additives in the event of a water boiling crisis

In order to prevent accidental overheating in metallurgy, electrical engineering, power engineering, nuclear power plants (NPP) etc., we have developed a series of nanofluids (NFs) which are stable under high temperature, boiling and radiation conditions. In our work, a new AlSi-7 nanofluid based on natural aluminosilicates with unique thermal behavior was developed for the first time. The boiling curve, covering all modes including transient and film boiling and burnout heat flux up to 3.7 MW/m2 is presented. The possibility of using this NF for emergency cooling of a superheated heat exchange surface was studied. For this purpose, the automatic unit for simultaneous recording of NFs boiling curves and the changes of the main heat transfer parameters (such as heat flux, heat transfer coefficient and temperature of the heating surface) in real time conditions under a constant rise of heat flux are presented. These NFs consisted of metals oxides, natural aluminosilicates and carbon nanomaterials (including nano-diamonds, multi-walled carbon nanotubes (CNTs) and thermo-expanded graphite (TEG)). Results showed the possibility of increasing the heat transfer coefficient (HTC) and critical heat flux (CHF) by 1.5–3.0 times compared with those of distilled water. By adding nanofluids to boiling water in the event of a boiling crisis, emergency cooling of an overheated heat transfer surface resulted in a sharp decrease in temperature of the heating surface from 700 to 125 °C without reducing the heat load has been proven.

ПОКАЗАТЕЛИ КРОВИ БЫЧКОВ КАЛМЫЦКОЙ ПОРОДЫ НА ОТКОРМЕ ПРИ ВКЛЮЧЕНИИ В ИХ РАЦИОН МЕСТНЫХ ПРИРОДНЫХ КОРМОВЫХ ДОБАВОК В УСЛОВИЯХ ЦЕНТРАЛЬНОЙ ЯКУТИИ

Obtaining high results in the production of highquality beef in beef cattle breeding is impossible without well-organized fattening of gobies. In the conditions of Yakutia, fattening of gobies from 15 months of age can be carried out in autumn, after the summer grazing feeding. Under economic conditions of feeding, high growth rates of fattening young animals cannot be obtained. Therefore, intensive fattening with the use of mineral feeding of cattle is used. The paper presents research materials on the morphological and biochemical composition of blood and its serum in calves of the Kalmyk breed, which are on scientific and industrial fattening. In the experimental group of animals, local natural feed additives – zeolite and salt – were added to the diet, which served as adaptogens and sources of mineral elements. During the feeding period before the slaughter, the morphological composition of blood in terms of indicators has insignificant decreases, but within the physiological norm. We see these changes in the gobies of the experimental control group and associate them with a sharp decrease in atmospheric air temperature to –15 °C in the first ten days of November 2019 and a constant transition to roughage. It is also possible that the use of natural feed additives in the form of feeding zeolite and salt increases metabolic processes in the animal's body. A comparative analysis of biochemical parameters in the blood serum of gobies of the experimental group confirmed significant differences in hepatic enzymes (ALT and AST) in animals. The use of non-traditional natural feed additives with the inclusion in the diet of fattening gobies affects the hematological and biochemical parameters of blood and its serum, and, accordingly, meat quality.

The littoral zone of polar lakes: inshore–offshore contrasts in an ice-covered High Arctic lake

In ice-covered polar lakes, a narrow ice-free moat opens up in spring or early summer, and then persists at the edge of the lake until complete ice loss or refreezing. In this study, we analyzed the horizontal gradients in Ward Hunt Lake, located in the Canadian High Arctic, and addressed the hypothesis that the transition from its nearshore open-water moat to offshore ice-covered waters is marked by discontinuous shifts in limnological properties. Consistent with this hypothesis, we observed an abrupt increase in below-ice concentrations of chlorophyll a beyond the ice margin, along with a sharp decrease in temperature and light availability and pronounced changes in benthic algal pigments and fatty acids. There were higher concentrations of rotifers and lower concentrations of viruses at the ice-free sampling sites, and contrasts in zooplankton fatty acid profiles that implied a greater importance of benthic phototrophs in their inshore diet. The observed patterns underscore the structuring role of ice cover in polar lakes. These ecosystems do not conform to the traditional definitions of littoral versus pelagic zones but instead may have distinct moat, ice-margin, and ice-covered zones. This zonation is likely to weaken with ongoing climate change.

Low-Temperature Adapted Nitrifying Microbial Communities of Finnish Wastewater Treatment Systems

In this study, the microbial community of nitrifying activated sludge adapted to Finnish climate conditions was studied to clarify the microbial populations involved in low-temperature nitrification. Microbial community analysis of five full-scale wastewater treatment plants (WWTPs) showed several differences compared to WWTPs from other countries with a similar climate. In particular, very low abundance of ammonium oxidizing bacteria (AOBs) (altogether ˂ 0.25% of total community) as well as typical NOBs (˂0.35%) and a high abundance of orders Cytophagales and Micrococcales was observed in all Finnish WWTPs. To shed light on the importance of autotrophic and heterotrophic nitrifying processes, laboratory studies of activated sludge were carried out with a presence of and a lack of organic carbon in wastewater at 10 ± 1 °C. Two different sludge retention times (SRTs) were compared to determine the effect of this operational parameter on low-temperature nitrogen removal. The important role of previously reported Candidatus Nitrotogaarctica for nitrite oxidizing in cold climate conditions was confirmed in both full-scale and laboratory scale results. Additionally, potential participation of Dokdonella sp. and Flexibacter sp. in nitrogen removal at low-temperatures is proposed. Operation at SRT of 100 days demonstrated more stable and efficient nitrogen removal after a sharp temperature decrease compared to 14 days SRT.

Factors Affecting the Weakening Rate of Tropical Cyclones over the Western North Pacific

Abstract In this study, based on the 6-hourly tropical cyclone (TC) best track data and the ERA-Interim reanalysis data, statistical analyses as well as a machine learning approach, XGBoost, are used to identify and quantify factors that affect the overwater weakening rate (WR) of TCs over the western North Pacific (WNP) during 1980–2017. Statistical analyses show that the TC rapid weakening events usually occur when intense TCs cross regions with a sharp decrease in sea surface temperature (DSST) with relatively faster eastward or northward translational speeds, and move into regions with large environmental vertical wind shear (VWS) and dry conditions in the upshear-left quadrant. Results from XGBoost indicate that the relative intensity of TC (TC intensity normalized by its maximum potential intensity), DSST, and VWS are dominant factors determining TC WR, contributing 26.0%, 18.3%, and 14.9% to TC WR, and 9, 5, and 5 m s−1 day−1 to the variability of TC WR, respectively. Relative humidity in the upshear-left quadrant of VWS, zonal translational speed, divergence at 200 hPa, and meridional translational speed contribute 12.1%, 11.8%, 8.8%, and 8.1% to TC WR, respectively, but only contribute 2–3 m s−1 day−1 to the variability of TC WR individually. These findings suggest that the improved accurate analysis and prediction of the dominant factors may lead to substantial improvements in the prediction of TC WR.

D band filling and magnetic phase separation in transition metal-doped Mn3SnC

The structural and magnetic properties of transition metal-doped Mn3SnC are studied with an aim to understand the effect of transition metal atom on magnetostructural properties of the antiperovskite compound. The doped Mn2.8T0.2SnC (T = Cr, Fe, Co, Ni and Cu) compounds show a distinctly different magnetic behavior which can be related to electronic filling of the d band of the transition metal atom. While Cr and Fe doped Mn3SnC show properties similar to that of Mn3SnC, the Co, Ni and Cu doped compounds exhibit nucleation of secondary phases which are devoid of carbon and having Heusler and DO19 type hexagonal structure. A strong magnetic interaction is observed between the impurity phases and the major antiperovskite phase leading to a sharp decrease in magnetostructural transition temperature of the antiperovskite phase and a cluster glassy ground state.