Synthesis, phase stability, structural and physical properties of 11-type iron chalcogenides

This article reviews recent experimental investigations on two binary Fe-chalcogenides: FeSe and Fe$_{1+y}$Te. The main focus is on synthesis, single crystal growth, chemical composition, as well as on the effect of excess iron on structural, magnetic, and transport properties of these materials. The structurally simplest Fe-based superconductor Fe$_{1+x}$Se with a critical temperature $T_c \approx$ 8.5 K undergoes a tetragonal to orthorhombic phase transition at a temperature $T_s \approx$ 87 K. No long-range magnetic order is observed down to the lowest measured temperature in Fe$_{1+x}$Se. On the other hand, isostructural Fe$_{1+y}$Te displays a complex interplay of magnetic and structural phase transitions in dependence on the tuning parameter such as excess amount of Fe or pressure, but it becomes a superconductor only when Te is substituted by a sufficient amount of Se. We summarize experimental evidence for different competing interactions and discuss related open questions.Comment: 14 pages, 12 figures, Feature Article, Part of Special Issue on Iron-Based High Temperature Superconductor

Decoupled Payments to EU Farmers, Production, and Trade: An Economic Analysis for Germany

After an extended process of reform the European Union has introduced direct payments to farmers which are decoupled from production decisions as a central element of its Common Agricultural Policy. They are also referred to as Single Farm Payments. In this paper we analyze the production and trade effects of this policy and its compatibility with WTO international trade rules. A survey of the literature suggests that the system of direct payments in its present form has effects which are analogous to a subsidization of agricultural land. Thus, they act to increase production and trade. Furthermore we quantify the total economic cost of production of selected commodities in the European Union and compare them to the price at which EU production is sold in foreign markets. Our analysis suggests that the costs of production in the European Union for key agricultural commodities are below international prices. It can be established that commodities for which the European Union is a net exporter are sold below cost, for extended periods of time and in substantial quantities. The EU system of decoupled payments to farmers, thus, acts to inflict economic injury to third countries. Under WTO rules, dumping can only occur when a country is an exporter. In this paper we demonstrate that on the markets included in the analysis dumping occurs on the market for wheat. The extent of injury is exemplified for Australia.European Union, Common Agricultural Policy, WTO rules, decoupled payments, Agribusiness, Agricultural and Food Policy, Food Security and Poverty, International Development, International Relations/Trade, Risk and Uncertainty,

Global agricultural market trends and their impacts on European Union agriculture

The economic, political and climatic conditions in which farmers around the world have to make their production and investment decisions are changing dramatically. This study analyses the driving forces of changes in agricultural world markets and their implications for European Union agriculture for the time period 2003/05 - 2013/15. The impacts on European Union agriculture are quantified using of a multi-market-model. The mega-trend of declining world market prices has ended. Since the turn of the millennium world market prices for agricultural goods have been increasing. This trend can be expected to continue. Not only will prices have a tendency to increase, but also fluctuations of agricultural world market prices are likely to be higher in the future than they have been in the past. The reason for the positive trend in agricultural world market prices is that global demand growth outstrips the growth in global supply, and this trend will continue in the foreseeable future. The global demand for food will continue to grow mainly for two reasons. One is the continued growth in world population; the other is the sustained growth in per capita incomes in developing and newly industrialised countries, with corresponding increase of per capita food consumption. Global food supply will have difficulty keeping pace with the growth in demand. A key factor is that the globally available agricultural land is limited in scale. Consequently, to meet the needs of the rapidly growing world population the necessary production growth will have to a large extent be met by a rise in productivity on the land already being farmed today. However, this will be difficult to accomplish as global agricultural productivity growth has been in decline since the Green Revolution of the 1960s and 1970s. Moreover, the rapid expansion of bio-energy production diverts agricultural land and other inputs away from food production. In addition, increasing water scarcity is starting to act as a constraint to production growth, and climate change is also beginning to affect production. The quantitative results of the analysis for key crops demonstrates that, both in the European Union and globally, agricultural demand will grow faster than supply during the time period 2003/05 - 2013/15. European Union demand for grains can be expected to increase by 10-20 percent and by more than 50 percent in oilseeds. However, European Union supply of wheat and other grains can only be expected to increase by less than 10 percent, corn by 15-20 percent, and oilseeds by more than 30 percent. As a consequence, the price of wheat can be expected to increase by more than 10 percent and the price of corn and oilseeds by more than 30 percent. With regard to the trade balance, the net trade position of European Union agriculture can be expected to deteriorate. While there would be a reduction in net imports of corn, net imports of oilseeds are expected to increase by more than 70 percent. Moreover, it is foreseeable that for wheat the European Union will switch from being a net exporter to a net importer. The same is true for other grains. Two additional aspects warrant further considerations. These are achieving world food security and combating global warming. For the world’s poor, increasing food prices may become a matter of survival. The results of the analysis confirm that the developing countries will not even come close to securing food supply for their rapidly growing population through domestic production, even under the best of all realistic scenarios. Consequently, the increasing food import needs of developing countries can only be met if the industrialised countries produce more and export more food. However, growth in bio-energy production in the European Union will let the region revert back to a net importing position in wheat, and it will have to increase imports of oilseeds. This will reduce the European Union’s ability to help in the fight against starvation in the world, unless there would be an increase in agricultural productivity beyond what is anticipated in this analysis. Climate change is now widely accepted as a fact, and human activity is a contributing factor. While probably not being of major importance during the time period considered in this study, world agriculture will be affected by global warming in the long run. On balance, world food production will be negatively affected as a consequence of climate change. Climate change and the associated additional increase in world food prices will amplify hunger and malnutrition in developing countries. Food production will decline predominantly in the countries which are already characterised by increasing food import needs. These countries are also those that are unable to make the necessary investment in agricultural research to adapt food production to the changing climate and to cope with increase in demand. Higher food prices will also increase the incentives for deforestation in order to claim additional farm land. Deforestation however, is one of the most important causes of global warming. In the global picture, the European Union will be less affected by climate change. It may even benefit. Europe will become a more secure production location in comparison to other world regions. Consequently, it has to take responsibility to significantly contribute to world food security and also to combat global warming by utilising its production potential. To avoid negative repercussions and to fully capitalise on its production potential, it is imperative that the European Union employs strategies which increase overall agricultural productivity on the available agricultural land. Zusammenfassung In diesem Beitrag werden die Bestimmungsfaktoren der Entwicklungen auf den Weltagrarmärkten untersucht und deren Auswirkungen auf die EU Landwirtschaft für den Zeitraum 2003/05 - 2013/15 quantifiziert. Dabei zeigt sich, dass die weltweite Nachfrage nach Agrargütern stärker steigt als das Angebot, so dass der Trend der Weltagrarpreise positiv ist. Die gegenwärtig (Mai 2008) sehr hohen Preise werden indes nicht von Dauer sein. Vielmehr ist mittelfristig mit einem eher moderaten Preisanstieg von etwa 15-30 % im Untersuchungszeitraum zu rechnen. Bei Weizen und anderem Getreide (außer Mais) wird die Europäische Union wieder zu einem Nettoimporteur. Die zu erwartenden Entwicklungen auf den Weltagrarmärkten und die dadurch steigenden Preise für Nahrungsgüter werden zu einer ernsthaften Verschärfung der Welternährungslage führen. Da die Flächen, die weltweit für die Nahrungsgüterproduktion verfügbar sind, begrenzt sind, muss die Steigerung des Angebots, die notwendig ist, um die rasch wachsende Weltbevölkerung in hinreichendem Umfang mit Nahrungsgütern zu versorgen, weitgehend über eine Steigerung der Produktivität derjenigen Flächen erreicht werden, die bereits heute landwirtschaftlich genutzt werden. Eine Steigerung der Produktivität in der Weltlandwirtschaft führt zu geringeren Nahrungsgüterpreisen. Sie verringert daher auch die Anreize auf dem Weg der Brandrodung zusätzliche landwirtschaftliche Nutzflächen zu erschließen. Gegenwärtig tragen diese Brandrodungen 18 % zum anthropogenen Klimawandel bei. Dies ist mehr als der Klimaeffekt der weltweiten Industrieproduktion. Damit ist das landwirtschaftliche Produktivitätswachstum nicht nur zentral im Kampf gegen den Hunger auf der Welt, sondern es leistet auch einen wichtigen Beitrag zur Verringerung des Klimawandels.World agriculture, food security, climate change, agriculture productivity growth, Weltlandwirtschaft, Sicherung der Welternährung, landwirtschaftliches Produktivitätswachstum, International Relations/Trade,

Global agricultural market trends revisited: The roles of energy prices and biofuel production

Global agricultural market, trends energy prices, biofuel production, Agribusiness, Agricultural and Food Policy, Agricultural Finance, Crop Production/Industries,

Low-temperature phase diagram of Fe1+yTe

We used low-temperature synchrotron x-ray diffraction to investigate the structural phase transitions of Fe1+yTe in the vicinity of a tricitical point in the phase diagram. Detailed analysis of the powder diffraction patterns and temperature dependence of the peak-widths in Fe1+yTe showed that two-step structural and magnetic phase transitions occur within the compositional range 0.11 $\leq y \leq$ 0.13. The phase transitions are sluggish indicating a strong competition between the orthorhombic and the monoclinic phases. We combine high-resolution diffraction experiments with specific heat, resistivity, and magnetization measurements and present a revised temperature-composition phase diagram for Fe1+yTe.Comment: 10 pages, 14 figure

Impurity-induced bound states inside the superconducting gap of FeSe

We investigate the local density of states in the vicinity of a native dumbbell defect arising from an Fe vacancy in FeSe single crystals. The tunneling spectra close to the impurity display two bound states inside the superconducting gap, equally spaced with respect to zero energy but asymmetric in amplitude. Using spin-polarized density functional theory (DFT) calculations on realistic slab models with Fe vacancy, we show that such a defect does not induce a local magnetic moment. Therefore, the dumbbell defect is considered as non-magnetic. Thus, the in-gap bound states emerging from a non-magnetic defect-induced pair-breaking suggest a sign changing pairing state in this material.Comment: 8 pages, 6 figure

Emergence of an incipient ordering mode in FeSe

The structurally simplest Fe-based superconductor FeSe with a critical temperature $T_{c}\approx$ 8.5 K displays a breaking of the four-fold rotational symmetry at a temperature $T_{s}\approx 87$ K. We investigated the electronic properties of FeSe using scanning tunneling microscopy/spectroscopy (STM/S), magnetization, and electrical transport measurements. The results indicated two new energy scales (i) $T^{*} \approx$ 75 K denoted by an onset of electron-hole asymmetry in STS, enhanced spin fluctuations, and increased positive magnetoresistance; (ii) $T^{**} \approx$ 22 - 30 K, marked by opening up of a partial gap of about 8 meV in STS and a recovery of Kohler's rule. Our results reveal onset of an incipient ordering mode at $T^{*}$ and its nucleation below $T^{**}$. The ordering mode observed here, both in spin as well as charge channels, suggests a coupling between the spins with charge, orbital or pocket degrees of freedom.Comment: 5 pages, 4 figure

Superconducting gap structure of FeSe

The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall "U"-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe.Comment: 8 pages, 5 figure

Potentials of using milk performance data and FAMACHA score as indicators for Targeted Selective Treatment in Lacaune dairy sheep in Switzerland

Targeted Selective Treatment (TST) is one approach to slow down the development of anthelmintic resistance. Its success is closely linked to the correct identification of animals in need of treatment. In dairy goats it has been proposed to use milk yield as TST indicator and to focus treatments on high yielding dairy goats. In dairy sheep the relationship between milk performance and infection with gastrointestinal nematodes (GIN) is not well known. The aim of this study was to investigate the relationship between milk yield and GIN infection in dairy sheep and based on this, to evaluate milk performance data as a potential TST indicator. Overall 1159 Lacaune ewes of 15 dairy sheep farms in Switzerland were included in the study. The ewes were phenotyped once between August and December 2019, when they were at least 70 days in milk (DIM). Individual faecal samples were taken from every ewe to determine the nematode egg concentration per gram faeces (EPG). In addition, the clinical parameters FAMACHA score and packed cell volume (PCV) were measured. Linear mixed models were used to analyse the effects of the collected parameters on EPG. EPG increased significantly with increasing test day milk yields (P = 0.002), indicating high yielding ewes to be less resistant to GIN infections than low yielding ewes. The effect was most pronounced in earlier lactation but remained within a moderate range. Overall, our results indicated the potential of using milk yield data of rather early lactation as TST indicator in dairy sheep. On farms with predominantly H. contortus the combination with FAMACHA might improve the correct identification of highly infected ewes, as FAMACHA was correlated with EPG (r = 0.37, P < 0.001)

Comparison of the Low-Cost Sun Sensors of the SOURCE and EIVE CubeSats

Sun sensors are commonly used attitude determination equipment which measure a spacecraft’s attitude relative to the sun. Multiple types of low-cost sun sensors were developed for the SOURCE and EIVE CubeSats. The SOURCE sun sensors consist of single photodiodes which are placed in a one-sensor-per-face as well as a pyramid arrangement. EIVE employs digital vector sun sensors based on quad-pin photodiodes. The SOURCE sun sensors in the one-sensor-per-face arrangement archive an accuracy of \u3c10° while the pyramid arrangement accomplishes an accuracy of \u3c7.5° without and \u3c5° with calibration. EIVE’s vector sun sensors offer an raw accuracy of 3°±5°. Multiple calibration approaches are presented with the best results leading to an accuracy of 0.7±3°. A direct comparison between the SOURCE and EIVE sensor types and configurations can be drawn since the same test bench was used to measure all sensors. The objective of this paper is to present and compare the different sun sensor concepts and their results