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This paper is dedicated to the investigation of selective copper extraction from the black mass of lithium-ion batteries (LIBs) using ammonium sulfate. Thermodynamic analysis performed with the use of Pourbaix diagrams allowed to compare and predict the area of stable copper and cobalt ammine complexes, determine operating pH range (8.7-9.7) for solutions. Concentrations of sodium hydroxide and ammonium sulfate were defined experimentally allowing to achieve high copper extraction (82-87 %) at low cobalt recovery into solutions (0.25-0.52 %). By variation of main leaching parameters optimal process conditions were determined: (NH4)2SO4 45 g/dm3, NaOH 9 g/dm3, 25 С, l : s = 5 : 1, 120 minutes.

The study covers physical and chemical regularities of zinc sulfide concentrate oxygen pressure leaching in sulfuric acid. The effect of lignosulfonate concentration (CLSN = 0.2÷0.8 g/dm3), leaching time (τ = 20÷120 min), temperature (T = 393÷423 K), and oxygen partial pressure (РО2= 0.3÷0.7 MPa) on the degree of zinc and iron extraction into the solution and on the cake grain-size distribution was established. It was shown that lignosulfonate additive intensifies zinc and iron extraction into the solution. Maximum extraction of zinc and iron was 89 and 37 %, respectively, for 120 min of leaching at CLSN = 0.6÷0.8 g/dm3. The differential rate law with respect to lignosulfonate was 0.3 for sphalerite, and 0.9 for iron sulfides. A controversial influence of rising temperature on the process under investigation was found. Temperature elevation from 413 to 423 K leads to a decrease in zinc extraction by 3–4 % due to the formation of sulfur-sulfide aggregates over 150 μm in size. The calculated values of apparent activation energy (Еа) of sphalerite and iron sulfide leaching in the presence of lignosulfonate were 30 and 45 kJ/mole, respectively. It was found out that an increase in oxygen partial pressure from 0.3 to 0.5 MPa has a positive influence on leaching and increases extraction of zinc and iron by 22 and 27 %, respectively. However, an increase in oxygen partial pressure up to 0.7 MPa in the presence of lignosulfonate after 40 min of leaching led to a decrease in leaching rate, possibly as a result of lignosulfonate destruction. It was found that differential rate laws with respect to oxygen are 1.2 for sphalerite and 2.5 for iron sulfides.

This paper looks at the effect produced by surface modification of the super pure zinc sulphide monocrystals with certain surfactants and their combinations (sodium lignosulphonate (SLS), sodium dodecyl sulphate (SDS), sodium dodecylbenzenesulphonate (SDBS) and the following combinations: SLS + SDS, SLS + SDBS on the surface angle of wetting with water and elemental sulphur melt. It was found that as the concentration of individual surfactants in the solution rose, so did the wetting ability of the mineral surface. Thus, at the surfactant concentration of 0.8 g/dm3 the water wetting angle reaches 48.4o for SLS, 22.5o for SDS and 10.3o for SDBS; the elemental sulphur wetting angle is 71.3o for SLS, 76.9o for SDS and 67.9o for SDBS. The work of adhesion in the system ZnS – Surfactant – Н2О increases by 9–11%, and in the system ZnS – Surfactant – S0 — by 5–8%. When using the combinations SLS + SDS (СSLS = 0.2–0.8 g/dm3) and SLS + SDBS (СSLS = 0.2 g/dm3), inverse surface wetting of zinc sulphide with elemental sulphur melt is observed. The maximum wetting angles reached are 93o and 85o, correspondingly. The work of adhesion and the spreading coefficient expectedly decrease. The paper analyzes the effect of individual surfactants and their combinations on the pressure leaching of zinc sulphide concentrate. The use of individual surfactants intensifies the transition of valuable components into the solution. The biggest increase in recovery was seen when using SLS, and namely 27–32% for zinc and 11–16% for copper. The recovery of zinc increased by 31–41% in the presence of SLS + SDS and by 27–34% in the presence of SLS + SDBS. This research was funded by the Russian Science Foundation, Grant No. 18-19-00186.

This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate (SDBS)), and their mixtures on the copper cementation rate by zinc. The results demonstrated a copper cementation rate decreasing at LS and SDBS concentrations increasing. Excessive zinc consumption was also detected on copper-ion cementation due to LS and SDBS anion adsorption onto positively charged zinc cathodic areas and copper particles. This led to a decrease in the growth rate of nuclei of copper particles and energy consumption for the formation of new nucleation centers, as well as the creation of conditions for reducing the overvoltage of hydrogen evolution. At the same time, an increase in temperature led to zinc consumption decreasing in the presence of LS. The reagents under investigation could be ranked according to their degree of negative influence on copper cementation increasing in the following order: SDS < SDBS < LS. Testing LS and SDS mixtures showed their irregular influence on the copper cementation rate at different temperatures. In experiments with LS and SDBS mixtures, a linear decrease in the copper-ion cementation rate upon an increase in SDBS concentration and simultaneous zinc-consumption enhancement was fixed. Due to the negative influence of the investigated reagents, we offered a purification method from organic impurities through the use of multilayered alumosilicates modified by cationic surfactants. The results indicate the high effectiveness of removing organic impurities from solutions, which allowed us to increase the cementation rate in the presence of the LS and SDBS mixture by 50% while, at the same time, decreasing zinc consumption. © 2020, Allerton Press, Inc. This work was supported by the Russian Foundation for Basic Research as part of scientific project no. 18-38-00388.

Gold cementation kinetic features from cyanide solutions using zinc powders of various origins were studied. The first powder was obtained by distillation and is currently used in the vast majority of industries (traditional powder). The second powder was obtained by electrochemical reduction from alkaline solution (electrolytic powder). The main distinguishing feature of these powders is specific surface area. This indicator for the electrolytic powder is 2.6 times higher than for the traditional one (3.02 and 1.16 m2/g, respectively), which is associated with dendritic form of electrolytic powder. For cementation studies, a solution with a gold content of 50.8 μmol/dm3 and 0.04 mol/dm3 sodium cyanide (NaCN) was taken. Studies have shown the presence of a depassivation period associated with oxide film dissolution on the powder surface and overcoming diffusion difficulties. The depassivation period of a traditional powder (10–15 seconds) exceeds the depassivation period of an electrolytic powder (5–8 seconds). Values of cementation reaction experimental rate constants are determined for the process using traditional and electrolytic powders at different ratios of zinc and gold masses in solution. Experimental reaction rate constants for electrolytic powder under the studied conditions are 1.3–1.6 times higher than the experimental rate constants for traditional powder. Zinc oxidation rates are compared under these conditions for various ratios m(Zn)/m(Au). Powder dissolution rates referred to specific surface area (taken in initial period) practically do not differ. The electrolytic powder’s absolute dissolution rate at the initial time is almost two times greater. As powder reacts with an alkaline solution, absolute dissolution rates of electrolytic and traditional powders are equalized.

The study covers kinetic features of gold cementation from cyanide solutions using two zinc powders of various origins. The first one was obtained by distillation and is currently applied in gold cementation from cyanide solutions (traditional powder). The second one was obtained by electrochemical reduction from the alkaline solution (experimental, electrolytic powder). The main distinguishing feature of these cementation powders is their specific surface area. This indicator for the electrolytic powder is 2.6 times higher than for the traditional one (3.02 m2/g and 1.16 m2/g, respectively) due to its dendritic form. The studies used a solution with a gold content of 50.8 μmol/dm3and a sodium cyanide content of 0.04 mol/dm3NaCN was taken. Cementation revealed a powder depassivation period associated with oxide film dissolution and overcoming diffusion difficulties. The traditional powder depassivation period (10–15 sec) exceeds that of the electrolytic powder (5–8 sec). Experimental rate constants of the cementation reaction were determined for the process involving both powders under study at different ratios of zinc and gold masses in the solution. Experimental reaction rate constants for the electrolytic powder under the studied conditions were 1.3– 1.6 times higher than that for the traditional powder. It was found that oxidation rates of zinc powders compared at different ratios of zinc and gold masses are virtually the same. At the same time, absolute rates of electrolytic powder dissolution in the initial period are nearly 2 times greater. As the powder reacts with the alkaline solution, absolute dissolution rates of electrolytic and traditional powders are equalized.

The article focuses on the effect of sodium lignosulfonate (LS), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate (SDBS)), and their mixtures on the rate of copper cementation by zinc. The results obtained demonstrate a decrease in copper cementation rate with the increasing LS and SDBS concentrations. There was also excessive zinc consumption for copper ion cementation noted due to LS and SDBS anion adsorption on positively charged zinc cathodic areas of the cementing agent and the precipitate. This led to a decrease in the rate of copper particle nucleation, energy consumption for forming new copper nucleation centers, and conditions for hydrogen overpotential reduction. In addition, rising temperature led to a decrease in zinc consumption in the presence of LS. Surfactants under investigation may be ranked by the negative impact on copper ion cementation in an ascending order as follows: SDS < SDBS < LS. LS + SDS mixture testing showed its irregular effect on copper cementation rate at test temperatures. Experiments with LS and SDBS mixtures demonstrated a linear decrease in copper ion cementation rate with increasing SDBS concentration and simultaneously rising zinc consumption. Due to the negative impact of investigated reagents discovered, we proposed a method for removing organic impurities from solutions using multilayered aluminosilicates modified by cationic surfactants. The results obtained indicate the high effectiveness of organic impurity removal from solutions providing for a 50 % increase in cementation rate in the presence of LS + SDBS mixture together with a decrease in zinc consumption.

The study covers physicochemical features of dendritic zinc powders and their effect on gold cementation from cyanide solutions. Three zinc powders were obtained in a laboratory environment by electroextraction at different conditions, and these powders featured various particle size and specific surface area. The properties of zinc powders obtained and powder currently used for gold cementation were evaluated using SEM (Jeol JSM-6390LA), BET (Gemini VII 2390) and laser diffraction (Sympatec HELOS & RODOS) methods. It is shown that electrolytic powders have high specific surface area (1.3–2.6 times more) and a low bulk density (3.1–3.8 times less), relative to zinc powder currently used for gold cementation. It was found that due to specific physical properties electrolytic powders have low hydraulic resistance, which eliminates the need for inert additives introduced during cementation, increases unit capacity and reduces the load on equipment. Inert additives elimination will additionally increase the gold content in the resulting product. The dendritic morfology of zinc powders obtained compensates high particle size resulting in the high efficiency of gold precipitation. At the long cementation cycle the effective gold deposition area (with gold extraction of more than 97 %) turned out to be shorter for electrolytic powder compared to fine powder currently used. However, in practice, the cementation cycle is always limited by fine powder throughput and it is not possible to achieve the full zinc potential. The resulting cementation product usually contains 25–35 % of unused zinc. These studies show the effectiveness of using electrolytic zinc powder for gold cementation from cyanide solutions.

This Letter reports the first extraction of individual antineutrino spectra from ^{235}U and ^{239}Pu fission and an improved measurement of the prompt energy spectrum of reactor antineutrinos at Daya Bay. The analysis uses 3.5×10^{6} inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, ^{235}U and ^{239}Pu, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4-6 MeV, a 7% (9%) excess of events is observed for the ^{235}U (^{239}Pu) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is 4.0σ for ^{235}U spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at 5.3σ. In the energy range of 4-6 MeV, a maximal local discrepancy of 6.3σ is observed.

Present article is devoted to study of electrolytic zinc powders usage features in gold mining industry. Electrolytic zinc powders characterized by dendritic shape and a high specific surface area. These features of electrolytic zinc powders provide a number of advantages for gold cementation from alkaline cyanide solutions. Dendritic form of electrolytic zinc powder makes it possible to reduce zinc layer hydraulic resistance on filtering surface, which is important when using cementation technologies based on filtration of gold-bearing solution through zinc powder layer. High specific surface area of electrolytic zinc powders favourably affects the rates of gold recovery from cyanide solutions, which is shown in cementation experiments from model and real (industrial) solutions.

In large cities, soil pollution occurs with heavy metals. Forest stands react to environmental pollution by a decrease in growth and an increase in mortality. A typical object for the city of Moscow is the Timiryazev Academy Forest Experimental District. A comparison of the content of gross forms with the clark content of trace elements in the soil profile revealed a significant excess for the following chemical elements: copper, zinc, lead, arsenic. The content of chromium, nickel, vanadium is lower than the clark content. Comparison of the content of gross forms of trace elements with maximum permissible concentrations showed that the content of nickel, vanadium, cobalt is lower than the maximum permissible concentration. The distribution of the gross forms of the elements along the soil profile is heterogeneous. The maximum content in the profile of sod-podzolic soils falls on the humus horizon, which is associated with the biogenic accumulation of these elements.

The article discusses the personnel problem as an important factor in the development and digitalization of Russian economy in the field of agriculture. The problems of modern labor resources in agricultural production are highlighted. The ways of addressing the problems are explored: changing social working conditions, increasing motivational components both in the state policy in the field of agriculture and in the development of methods and mechanisms for managing labor resources at specific enterprises with special reference to the particular features of their production; creating the necessary modern infrastructure, updating the content of educational programs, training, retraining and professional development, improving the management mechanisms of the industry, etc.

Human life is shaped by two worlds. The first one is the natural world of plants and animals, the earth, the forest, the air and the water-a world that arose long before the appearance of man. Another world is the world of social institutions, arts and crafts that man creates for his livelihood with the help of tools, knowledge, and purposeful transformation of space-the environment of his habitat. Just a little effort is required to destroy fragile and vulnerable life on the Earth; one just needs to tear the soil off, cut forests down, destroy grass cover, and fill reservoirs with sewage. Nature is so unstable, unpredictable and contradictory that in this situation, people need to make efforts to achieve an understanding of how to strengthen and balance the capricious generosity and subtle mechanisms of interaction between nature as a whole and its integral part – the earth.

The open-source scientific software packages OpenGeoSys and IPhreeqc have been coupled to set up and simulate thermo-hydro-mechanical-chemical coupled processes with simultaneous consideration of aqueous geochemical reactions faster and easier on high-performance computers. In combination with the elaborated and extendable chemical database of IPhreeqc, it will be possible to set up a wide range of multiphysics problems with numerous chemical reactions that are known to influence water quality in porous and fractured media. A flexible parallelization scheme using MPI (Message Passing Interface) grouping techniques has been implemented, which allows an optimized allocation of computer resources for the node-wise calculation of chemical reactions on the one hand and the underlying processes such as for groundwater flow or solute transport on the other. This technical paper presents the implementation, verification, and parallelization scheme of the coupling interface, and discusses its performance and precision.

We offer a versatile workflow to convert geological models built with the ParadigmTM GOCAD© (Geological Object Computer Aided Design) software into the open-source VTU (Visualization Toolkit unstructured grid) format for usage in numerical simulation models. Tackling relevant scientific questions or engineering tasks often involves multidisciplinary approaches. Conversion workflows are needed as a way of communication between the diverse tools of the various disciplines. Our approach offers an open-source, platform-independent, robust, and comprehensible method that is potentially useful for a multitude of environmental studies. With two application examples in the Thuringian Syncline, we show how a heterogeneous geological GOCAD model including multiple layers and faults can be used for numerical groundwater flow modeling, in our case employing the OpenGeoSys open-source numerical toolbox for groundwater flow simulations. The presented workflow offers the chance to incorporate increasingly detailed data, utilizing the growing availability of computational power to simulate numerical models.

Objective: to investigate the changes in behavioral response of female rats in the «open field» test in the conditions of radiation with electromagnetic fields of radio frequencies and ionizing radiation at doses of 0.5 and 1.0 Gy. Material and methods. The experiment was conducted on 60 female laboratory rats (6 months) exposed to separate and combined effects of external ionizing radiation (0.5 and 1.0 Gy) and electromagnetic radiation for 15 days. Emotional reactivity, locomotor and exploratory activity of animals were studied with the «open-field» test. Results. The effect of electromagnetic radiation of the range of cellular telecommunication modified the responses of the irradiated (0.5 and 1.0 Gy) female rats which were assessed according to their behavioral patterns in the «open field» test. Thus, the rats exposed to the combined effect of the factors revealed the highest integral level of anxiety.

An ovigerous female of red king crab (Paralithodes camtschaticus) was caught near the White Sea Biological Station of the Zoological Institute of the Russian Academy of Sciences (Kandalaksha Bay, outer part of Chupa Inlet, Krivozerskaya Cove, Cape Kartesh) on August 21, 2013. That was the first record of the red king crab (an alien species having been established in the Barents Sea) in the inner White Sea. Earlier, this species was recorded only in the Voronka, the most distant part of the White Sea, which is substantially closer to the Barents Sea than the White Sea by its oceanographic features. The size of the female crab and its reproductive phase corresponded in general to those observed in the Barents Sea population in summer, but the quantity of developing eggs on pleopods was two order of magnitude lower than in the females of similar size in the Barents Sea. We discuss the ecological characteristics of red king crab, the possibility of its habitation in the inner White Sea, and explanations for finding of the crab specimen near Cape Kartesh. The more likely scenario is introduction by man. In the case of both human-mediated introduction and natural migration from the Voronka of the White Sea, the prospect for naturalization of P. camtschaticus in the inner White Sea is doubtful. This naturalization will be limited by low salinity in the coastal areas where crab reproduction takes place and below zero temperature of the entire water column, not allowing the finding of wintering habitats suitable for adult crab males and females.

Industrial dusts with high zinc content are formed in nonferrous and ferrous metals metallurgy. Hydrometallurgical processing of such dusts can be used. In this case, alkaline solutions with high impurities content are formed. It is possible to produce zinc powder with different technological properties by electroextraction from mentioned alkaline solutions. This work describes investigation of zinc powders usage possibilities to gold cementation from cyanide solutions.

We develop the method for evaluation of the influence of a pulse source of VLF radiation on the flux density of electrons precipitating from the radiation belt of the Earth on the basis of the quasilinear theory of resonant interaction of waves and particles in plasma traps.

The heating of the lower equatorial ionosphere by a radio-frequency (RF) electromagnetic wave is simulated. Estimates of the electron temperature and ionospheric conductivity have been obtained for the cases of quasi-longitudinal and quasi-transverse propagation of an RF heating wave with a low-frequency modulated amplitude.

An exact solution of the ray trajectory equation in the spherically symmetric ionosphere is derived by approximating the height distribution of the electron density by a set of quasi-linear and quasi-parabolic functions.

The principles of nonlinear geometric optics are used to formulate a method for estimating the amplitude of short radio waves during their passage through the lower ionosphere.

The relationships for the amplitude of electron temperature oscillations, as well as for the phase and modulation amplitude of high-power short radio waves propagating through the lower ionosphere, are obtained on the basis of nonlinear geometrical optics.

We studied the state of the reproductive system of male rats after irradiation at a dose of 2.0 Gy, immobilization stress (6 hours/day for 7 days) and their combined effects. On the 30th day after the combined treatment (37 days after irradiation) a decrease in the testicular weight by almost 50% compared with the control and lesions connected with the process of spermatogenesis are observed. In the remote period--on the 60th day (67th after irradiation) the effect of irradiation and irradiation in combination with immobilization stress leads to a sharp drop in the number of epididymal sperm (up to 18% of the control), and a reduction of their viability. The reaction ofthe reproductive system to the immobilization stress is expressed in a certain increase in the mass of the testes and epididymis, moderate imbalances in the composition of spermatogenic cells in the testis tissue, and in the long term--in the increased number of epididymal sperm and the decrease in their viability. Changes of testosterone in the blood serum, especially significant for the combined effect, reflect impairments of the regulation of the reproductive system of males under these conditions. With regard to individual indicators of the reproductive system of male rats in some cases, the- combined effects of radiation and stress had a synergistic, or, on the contrary, antagonistic character.

The effect on bottom organisms of periodic freezing of the upper layer of intertidal sediments during abnormal cold winters has been studied for a long time in seas of a moderate climatic zone. However, the effect of ice cover every year on intertidal communities in polar seas is still poorly investigated. Seasonal and long-term variation in the structure of intertidal soft-bottom communities in two small bights in the White Sea with annual ice cover was studied for over two decades. Sampling was carried out four times a year, in the hydrological spring, summer, autumn, and winter. It was found that bottom macrobenthic communities at upper and lower horizons of the intertidal distinctly differed in the studied sites. Periodic changes caused by the effect of abnormal ice conditions, including the partial removal by ice of sediment with in situ organisms, were discovered. Recovery of communities after disturbance normally took less than half a year. Communities at the lower and upper horizons of the intertidal zone were more stable than intermediate communities, which led to periodic shifts of the biological border between lower and upper intertidal assemblages.

Based on geometrical optics, expressions have been obtained for the estimate of changes in the amplitude and bearing of radio-frequency signals after their passage through an ionosphere region disturbed by a heating facility.

Based on the data from long-term observations on the development of fouling communities of mussel culture farms in the White Sea, an analysis of dynamics of population density of common polychaete species was carried out. The expansion of the polychaete Lepidonotus squamatus for the past 9 years was recorded. Cyclic variations of population density were revealed practically in all studied species. The duration of the period of these cycles varied from 7–8 years (L. squamatus and Amphitrite cirrata), 11–14 years (Nereis pelagica, Harmothoe imbricata, Eulalia viridis, Neoamphitrite figulus) and even about 20 years (Nereimyra punctata and Capitella capitata). Observable periodic variations in the abundance of polychaetes apparently were not related to long-term fluctuations of water temperature.

Based on eigenvector filtering and phase surface methods, the correlation between abundance dynamics and water temperature was studied in seven species of White Sea littoral polychaetes. Cyclic fluctuations in abundance with periods of approximately 5 and 12 years were revealed. Some instances of the 5-year cycles of abundance can be explained by climatic changes in the Arctic.

The paper presents a part of the results obtained within the framework of the research program on numerical analysis of helical features of the developing tropical cyclone, by using the regional ETA model of the atmosphere. A set of integral characteristics and of gridded diagnostics is selected and substantiated, allowing revealing and tracing evolution of large-scale helical-vortex instability associated with specific properties of helical convective turbulence under condition of tropical cyclogenesis. The helicity vertical flux (helicity index) is calculated following the technique by Kurganskii for two tropical cyclones: Man-Yi (2007) and Wilma (2005). It is shown that the helicity index changes during the tropical cyclone evolution reflect adequately the tendencies of pressure and velocity changes and thus the index can be used as an indicative characteristic of intensity of the developing tropical cyclone.

New heterometallic complexes of Co, Ni, and Zn containing [RuNO(NO2)4OH]2− anion as polydentate ligand were synthesized and described by X-ray structural analysis. The distorted octahedral coordination sphere of the nonferrous metal is composed of three oxygen atoms of phosphine oxide ligands and three oxygen atoms of bridging OH and NO2 groups from [RuNO(NO2)4OH]2−. High-level DFT calculations showed that the stability of Ru/M complexes is determined by the charge transfer from remote NO and NO2 groups of the ruthenium anion to M2+ and by the electrostatic interactions of M2+ with coordinating oxygen atoms of OH and two NO2 groups.

We offer a versatile workflow to convert geological models built with the software Paradigm™ GOCAD© into the open-source VTU format for the usage in numerical simulation models. Tackling relevant scientific questions or engineering tasks often involves multidisciplinary approaches. Conversion workflows are needed as a way of communication between the diverse tools of the various disciplines. Our approach offers an open-source, platform independent, robust, and comprehensible method that is potentially useful for a multitude of similar environmental studies. With two application examples in the Thuringian Syncline, we show how a heterogeneous geological GOCAD model including multiple layers and faults can be used for numerical groundwater flow modelling. The presented workflow offers the chance to incorporate increasingly detailed data, utilizing growing availability of computational power to simulate numerical models.

The consequences of prolonged exposure to electromagnetic radiation from cellular phone (897 MHz, daily 8 h/day) in male rats of the 1st generation obtained from irradiated parents and subjected to prolonged exposure to electromagnetic radiation of the range of mobile communications during ontogeny and postnatal development were studied. It has been found that irradiation causes a decrease in the number of births of animals, changing the sex ratio towards the increase in the number of males. It had a significant impact on the reproductive system of males, accelerating their sexual development, revealed at the age of two months. Radiation from cell phones led to significant disproportions in the cell number at different stages of spermatogenesis. It increased the number of mature spermatozoa which decreased viability.

We present a search for t t ¯ events with a tau lepton in the final state. The data sample corresponds to an integrated luminosity of 194 pb −1 collected with the CDF II detector from p p ¯ collisions at a center of mass energy of 1.96 TeV. We observe two events with an expected signal of 1.0 ± 0.2 events and a background of 1.3 ± 0.3 events. We determine a 95% confidence level upper limit on r τ , the ratio of the measured rate of t → τ ν q to the expectation, of 5.2.

The OPERA neutrino experiment in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in direct appearance mode in the vμ→ v τ channel, the v τ signature being the identification of the τ -lepton created in its charged current interaction. The hybrid apparatus consists of a large mass emulsion film/lead target complemented by electronic detectors. Placed in the LNGS, it is exposed to the high-energy long-baseline CERN Neutrino beam to Gran Sasso (CNGS) 730 km away from the neutrino source. The observation of a first v τ candidate event was reported in 2010. In this paper, we discuss the result of the analysis of the data taken during the first two years of operation (2008-2009) underlining the major improvements brought to the analysis chain and to the Monte Carlo simulations. The statistical significance of the one event observed so far is then evaluated to 95%. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.