Electronic correlation effects and the Coulomb gap at finite temperature

We have investigated the effect of the long-range Coulomb interaction on the one-particle excitation spectrum of n-type Germanium, using tunneling spectroscopy on mechanically controllable break junctions. The tunnel conductance was measured as a function of energy and temperature. At low temperatures, the spectra reveal a minimum at zero bias voltage due to the Coulomb gap. In the temperature range above 1 K the Coulomb gap is filled by thermal excitations. This behavior is reflected in the temperature dependence of the variable-range hopping resitivity measured on the same samples: Up to a few degrees Kelvin the Efros-Shkovskii ln$R \propto T^{-1/2}$ law is obeyed, whereas at higher temperatures deviations from this law are observed, indicating a cross-over to Mott's ln$R \propto T^{-1/4}$ law. The mechanism of this cross-over is different from that considered previously in the literature.Comment: 3 pages, 3 figure

Вплив згодовування хелатних комплексів мікроелементів на середньодобовий баланс Cu, Zn та Мn в організмі корів у період роздою

The questions are considered about the effect of feeding of trace elements of different types and concentrations in premixes on the average daily balance of copper (Cu), zinc (Zn), manganese (Mn) in the organism of cows of Ukrainian black mottled dairy breed of the two months after calving. For the experiment, 40 cows were selected and formed four groups: one control and three experimental. The cows in the control group fed a premix of sulfate salts of copper, zinc and manganese in doses that are 100% covered their lack in a forage. Experimental animals from I, II and III groups were fed premixes with chelate complexes of Cu, Zn and Mn, which offset the deficiency of trace elements in the feed ration for 100, 50 and 25% (calculated on pure element), respectively. The diet was counted on a cow with an average live weight of 550 kg, with a daily milk yield of 20 kg 4% fat and balanced on the basis of the main nutrients in accordance with the norms. Іn the feeds, excrements, urine and milk of cows, the content of trace elements copper, zinc and manganese was determined by the standardized atomic absorption method on the spectrophotometer AAS-30 («SaglZeiss», Germany). Found a higher percentage of trace elements deposition in the body cows of feeding of chelates of copper, zinc, and manganese in the concentrations that cover their deficit in the diet in the 100% and 50% in the experimental I and II groups: Cu – 7.3% (P < 0.05) and 1.4%, Zn by 12.2% and 15.0% (P < 0.001), Mn by 13.2% (P < 0.01) and 9.0% (P < 0.05), respectively, in comparison with their sulfate salts in a 100 % dose. Based on the results of the balance study, the use in the feeding of cows during lactation of chelates of trace elements in concentrations intermediate to different experimental groups was proposed, namely – below normal their input in the form of sulfate salts on 25% for copper, 50% – zinc, and 65% – for manganese (calculated on pure element).Розглянуто питання щодо впливу згодовування мікроелементів різних типів і концентрацій у преміксах на середньодобовий баланс Купруму (Сu), Цинку (Zn), Мангану (Mn) в організмі корів української чорно-рябої молочної породи через два місяці після отелення. Встановлено вищий відсоток відкладання мікроелементів в організмі за згодовування коровам хелатів Cu, Zn і Mn у концентраціях, що покривають їхній дефіцит у раціоні на 100% та 50% в І і ІІ дослідних групах: Cu – на 7,3% (Р < 0,05) та 1,4%, для Zn – на 12,2% і 15,0% (Р < 0,001), Мn – на 13,2% (Р < 0,01) та 9,0% (Р < 0,05) відповідно, порівняно з їх сірчанокислими солями у 100 % дозі. На підставі результатів балансового досліду запропоновано використання в годівлі корів у період лактації хелатів мікроелементів у концентраціях, проміжних відносно різних дослідних груп, а саме – нижчих за норми їх введення у формі сірчанокислих солей на 25% для Cu, 50% – Zn, та 65% – для Мn (у розрахунку на чистий елемент)

Cross-comparison of cloud liquid water path derived from observations by two space-borne and one ground-based instrument in northern Europe

Cloud liquid water path (LWP) is one of the target atmospheric parameters retrieved remotely from ground-based and space-borne platforms using different observation methods and processing algorithms. Validation of LWP retrievals is a complicated task since a cloud cover is characterised by strong temporal and spatial variability while remote sensing methods have different temporal and spatial resolutions. An attempt has been made to compare and analyse the collocated LWP data delivered by two satellite instruments SEVIRI and AVHRR together with the data derived from microwave observations by the ground-based radiometer RPG-HATPRO. The geographical region of interest is the vicinity of St. Petersburg, Russia, where the RPG-HATPRO radiometer is operating. The study is focused on two problems. The first one is the so-called scale difference problem, which originates from dissimilar spatial resolutions of measurements. The second problem refers to the land–sea LWP gradient. The radiometric site is located 2.5 km from the coastline where the effects of the LWP gradient are pronounced. A good agreement of data obtained at the microwave radiometer location by all three instruments (HATPRO, SEVIRI, and AVHRR) during warm and cold seasons is demonstrated (the largest correlation coefficient 0.93 was detected for HATPRO and AVHRR datasets). The analysis showed no bias of the SEVIRI results with respect to HATPRO data and a large positive bias (0.013–0.017 kg m−2) of the AVHRR results for both warm and cold seasons. The analysis of LWP maps plotted on the basis of the SEVIRI and AVHRR measurements over land and water surfaces in the vicinity of St. Petersburg revealed the unexpectedly high LWP values delivered by AVHRR during the cold season over the Neva River bay and over the Saimaa Lake and the abnormal land–sea LWP gradient in these areas. For the detailed evaluation of atmospheric state and ice cover in the considered geographical regions during the periods of ground-based and satellite measurements, reanalysis data were used. It is shown that the most probable reason for the observed artefacts in the AVHRR measurements over water and ice surfaces is the coarse resolution of the land–sea and snow–ice masks used by the AVHRR retrieval algorithm. The influence of a cloud field inhomogeneity on the agreement between the satellite and the ground-based data is studied. For this purpose, the simple estimate of the LWP temporal variability is used as a measure of the spatial inhomogeneity. It has been demonstrated that both instruments are equally sensitive to the inhomogeneity of a cloud field despite the fact that they have different spatial resolutions

About low field memory and negative magnetization in semiconductors and polymers

Ginzburg-Landau bulk magnetization of itinerant electrons can provide a negative effective field in the Weiss model by coupling to localized magnetic moments. The coupling enforces remnant magnetization, which can be negative or positive depending on the sample magnetic history. Stable magnetic susceptibility of coupled nonequilibrium subsystems with magnetization reversal is always positive. Gauss-scale fields could be expected for switching between negative and positive remnant moments in semiconductors with coupling at ambient temperatures. Negative magnetization in ultra-high conducting polymers is also discussed within the developed framework.Comment: 8 pages, no figure

Forms of International Cooperation in Environmental Education: the Experience of Saint Petersburg State University

The authors analyse different forms of environmental education projects and programmes implemented in the Baltic Sea region. The first one is "The Baltic University" programme taught in English. The "Baltic University" is a network of more than 200 universities from 14 counties of the Baltic Sea region. This education programme offers an opportunity for students to enroll on bachelor and master degree programmes related to environmental and social problems of the Baltic Sea region. The Polar and Marine Sciences, POMOR master programme, represents the second form of international environmental education. Russian and German researchers from six universities and four research centres have developed the programme. The target group of the programme are Russian and international students, studying together during the whole duration of the programme. It is the first internationally accredited MA programme taught in English. International accreditation proves the compliance of the programme with international education standards. The same cooperation model is used in a new international master programme - Cold Regions Environmental Landscapes Integrated Science (CORELIS). The programme started in 2016. It is implemented jointly by Hamburg university (the lead partner of the project), and university professors from Helsinki (Finland) and Lisbon (Portugal). Researchers from the Austrian National Institute of Polar Research (Austria, and Lund University (Sweden) will join the programme at a later stage. Such an approach will help achieve the synergy of the European and Russian approaches to environmental education. The Russian-Norwegian master programme "Geoecological monitoring and rational use of natural resources in the Northern oil and gas production regions" is a good example of the third form of international environmental education. The programme similar to POMOR and CORELIS. However, it has one distinctive feature - Russian and foreign students study together from the second term only. The authors describe the ways of achieving the learning objectives of these master programmes depending on the students' language skills and their basic knowledge of ecology and nature management

Анализ наночастиц и наноматериалов методом рентгеновской фотоэлектронной спектроскопии

Objectives. The main aim of this review is to summarize the existing knowledge on the use of X-ray photoelectron spectroscopy (XPS) for the characterization of nanoparticles and nanomaterials.Results. XPS or electron spectroscopy for chemical analysis can provide information on the qualitative and quantitative composition, valence states of the elements of the samples under study, the chemical composition of the surface and interfaces that determine the properties of nanoparticles and nanostructured materials. The review describes the role of several different methods for the characterization of nanomaterials, highlights their advantages and limitations, and the possibilities of an effective combination. The main characteristics of XPS are described. Various examples of its use for the analysis of nanoparticles and nanomaterials are given in conjunction with additional methods to obtain complementary information about the object under study.Conclusions. XPS provides depth information comparable to the size of nanoparticles (up to 10 nm depth from the surface) and does not cause significant damage to the samples. Two disadvantages of XPS analysis are sample preparation requiring a dry solid form without contaminations and data interpretation. XPS provides information not only on the chemical identity, but also on the dielectric properties of nanomaterials, recording their charging/discharging behavior. Chemical information from the surface of nanoparticles analyzed by XPS can be used to estimate the thickness of nanoparticle coatings. XPS has a high selectivity, since the resolution of the method makes it possible to distinguish a characteristic set of lines in the photoelectron spectrum at kinetic energies determined by the photon energy and the corresponding binding energies in elements. The intensity of the lines depends on the concentration of the respective element. Obtaining a sufficiently complete picture of the properties of nanomaterials requires the use of a group of complementary instrumental methods of analysis.Цели. Основная цель данного обзора - обобщить существующие знания об использовании метода рентгеновской фотоэлектронной спектроскопии (РФЭС) для характеризации наночастиц и наноматериалов.Результаты. Метод РФЭС или электронной спектроскопии для химического анализа может предоставить информацию о качественном и количественном составе, валентных состояниях элементов исследуемых образцов, химическом составе поверхности и границ раздела, которые определяют свойства наночастиц и наноструктурных материалов. В обзоре описана роль нескольких различных методов для характеристики наноразмерных материалов, подчеркнуты их преимущества, ограничения и возможности эффективной комбинации. Описаны основные характеристики РФЭС. Приведены различные примеры ее использования для анализа наночастиц и наноматериалов в совокупности с дополнительными методами для получения комплементарной информации об изучаемом объекте.Выводы. РФЭС предоставляет информацию о глубине, сравнимой с размером наночастиц (до 10 нм глубины от поверхности), и не вызывает значительного повреждения образцов. Двумя недостатками анализа РФЭС являются подготовка образцов (требуется сухая твердая форма без загрязнения) и интерпретация данных. РФЭС предоставляет информацию не только о химической идентичности, но и о диэлектрических свойствах наноматериалов, регистрируя их поведение при зарядке/разрядке. Химическая информация с поверхности наночастиц, проанализированная с помощью РФЭС, может использоваться для оценки толщины покрытий наночастиц. РФЭС обладает высокой селективностью, поскольку разрешающая способность метода позволяет различить характерный набор линий в фотоэлектронном спектре при кинетических энергиях, определяемых энергией фотонов и соответствующими энергиями связи в элементах. Интенсивность линий зависит от концентрации соответствующего элемента. Получение достаточно полной картины свойств наноматериалов требует использования группы взаимодополняющих инструментальных методов анализа

Hf–Zr anomalies in clinopyroxene from mantle xenoliths from France and Poland: implications for Lu–Hf dating of spinel peridotite lithospheric mantle

Clinopyroxenes in some fresh anhydrous spinel peridotite mantle xenoliths from the northern Massif Central (France) and Lower Silesia (Poland), analysed for a range of incompatible trace elements by laser ablation inductively coupled plasma mass spectrometry, show unusually strong negative anomalies in Hf and Zr relative to adjacent elements Sm and Nd, on primitive mantle-normalised diagrams. Similar Zr–Hf anomalies have only rarely been reported from clinopyroxene in spinel peridotite mantle xenoliths worldwide, and most are not as strong as the examples reported here. Low Hf contents give rise to a wide range of Lu/Hf ratios, which over geological time would result in highly radiogenic εHf values, decoupling them from εNd ratios. The high 176Lu/177Hf could in theory produce an isochronous relationship with 176Hf/177Hf over time; an errorchron is shown by clinopyroxene from mantle xenoliths from the northern Massif Central. However, in a review of the literature, we show that most mantle spinel peridotites do not show such high Lu/Hf ratios in their constituent clinopyroxenes, because they lack the distinctive Zr–Hf anomaly, and this limits the usefulness of the application of the Lu–Hf system of dating to garnet-free mantle rocks. Nevertheless, some mantle xenoliths from Poland or the Czech Republic may be amenable to Hf-isotope dating in the future