Leonard Horner in Bonn 1831–1833, finding loess and being incorporated into Lyell’s Loess Legion

Leonard Horner (1785–1864) was a pioneer in the study of loess. His 1836 paper on the geology of Bonn contained detailed descriptions of loess in the Rhine valley. He identified and presented loess as an interesting material for geological study. He investigated loess in the crater of the Rodderberg with Charles Lyell in 1833. He presented the first significant paper on loess in Britain in 1833, but it was not published until 1836. With the assistance of G.A. Goldfuss and J.J. Noegerath he conducted early studies of the Siebengebirge and published the first geological map of the region, and the first picture of loess, at Rhondorf by the Drachenfels. He became the eleventh person to be included in the list of loess scholars which Charles Lyell published in volume 3 of the Principles of Geology. These were Leonhard, Bronn, Boue, Voltz, Steininger, Merian, Rozet, Hibbert in 1833, Noeggerath, von Meyer in 1835, Horner in 1837. Horner arrived after the publication of his studies on the loess at Bonn in 1836

The formation of loess ground by the process of loessification: a history of the concept

Loessification is a process by which a body of non-loess ground is transformed into a body of loess ground. The history of loessification is one of controversy and confrontation, largely because of mutual misunderstandings between geologists and pedologists. Lev S. Berg is the ‘only begetter’ of the theory, first proposed in 1916, and propagated throughout his life. R.J. Russell proposed the same approach to the loess in the Lower Mississippi valley in his famous 1944 paper, which contributed enormously to the study of loess in North America. As understanding of the various processes involved in the formation of loess deposits has developed, a compromise position on loess formation has become possible. The major intrinsic features of loess deposits are the open structure and the collapsibility. It appears that the open structure is caused by aeolian depositional processes and the collapsibility is caused by loessification processes. The compromise was initiated by Marton Pécsi in 1990, He endeavoured to retain a loessification aspect in the study of loess deposits, as the subject appeared to be overwhelmed by the aeolian idea system promoted by geologists; it has been mostly a Central European endeavour. The history of the concept of loessification largely involves (1) its development in Russia, (2) its dissemination and discussion – and attempts at refutation and modification – in the wider world

Narratives of Scarcity: Framing the Global Land Rush

Global resource scarcity has become a central policy concern, with predictions of rising populations, natural resource depletion and hunger. The narratives of scarcity that arise as a result justify actions to harness resources considered ‘underutilised’, leading to contestations over rights and entitlements and producing new scarcities. Yet scarcity is contingent, contextual, relational and above all political. We present an analysis of three framings – absolute, relative and political scarcity – associated with the intellectual traditions of Malthus, Ricardo and Marx, respectively. A review of 134 global and Africa-specific policy and related sources demonstrates how diverse framings of scarcity – what it is, its causes and what is to be done – are evident in competing narratives that animate debates about the future of food and farming in Africa and globally. We argue that current mainstream narratives emphasise absolute and relative scarcity, while ignoring political scarcity. Opening up this debate, with a more explicit focus on political scarcities is, we argue, important; emphasising how resources are distributed between different needs and uses, and so different people and social classes. For African settings, seen as both a source of abundant resources and a site where global scarcities may be resolved, as well as where local scarcities are being experienced most acutely, a political scarcity framing on the global land rush, and resource questions more broadly, is, we suggest, essential.Economic and Social Research Counci

Loess encounters of three kinds: Charles Lyell talks about, reads about, and looks at loess

Charles Lyell (1797–1875) was an important loess pioneer. His major contribution was to distribute information on the nature and existence of loess via his influential book ‘The Principles of Geology’. He was obviously impressed by loess when he encountered it; the initial encounter can be split into three phases: conversations about loess; confronting the actual material in the field; and reading about loess in the literature. Detail can be added to an important phase in the scientific development of the study of loess. Significant events include conversations with Hibbert in 1831, conversations and explorations with von Leonhard and Bronn in 1832, the opportunity to include a section on loess in vol. 3 of ‘Principles’ for publication in 1833, a substantial Rhineland excursion in 1833, the reporting of the results of this excursion in 1834, discussions at the German Association for the Advancement of Science meeting in Bonn in 1835. Of all the people encountered perhaps H.G. Bronn was the most significant. Lyell eventually listed eleven people as relevant to the loess writings: Bronn, von Leonhard, Boue, Voltz, Steininger, Merian, Rozet, Hibbert, Noeggerath, von Meyer, Horner – of these Bronn, von Leonhard, Hibbert and Horner appear to have been the most significant, viewed from 2015

Desert loess: a selection of relevant topics

In discussions on loess, two types are often demarcated: glacial loess and desert loess. The origin of the idea of desert loess appears to lie with V.A. Obruchev who observed wind-carried silt on the Potanin expedition to Central Asia in 1895. It might be considered that desert loess would be defined as loess associated with deserts but it came to be thought of as loess produced in deserts. This led to some controversy as no mechanism for producing silt particles in deserts was readily available. Bruce Butler in Australia in particular cast doubt on the existence of desert-made loess. Butler indicated loess-like deposits in Australia which he called Parna; these are very like loess but the silt sized parti- cles are actually clay mineral agglomerates of silt size- formed in dry lake regions. At the heart of the desert loess discussion is the problem of producing loess material in deserts. It has been suggested that there are no realistic mechanisms for forming large amounts of loess dust but there is a possibility that sand grain impact may produce particle shattering and lead to the formation of quartz silt. This would appear to be a reasonable mechanism for the African deposits of desert loess, but possibly inadequate for the huge deposits in China and Central Asia. The desert loess in China and Central Asia is loess associated with a desert. The material is formed in cold, high country and carried by rivers to the vicinity of deserts. It progresses then from deserts to loess deposit. Adobe ground may be defined as desert loess. Adobe occurs on the fringe of deserts, notably in the Sahelian region of Africa, and in SW USA. The use of adobe in construction represents the major utilization of desert loess in a social con- text. More understanding of adobe is required, in particular with respect to the adobe reaction, the low order chemical reaction which provides modest cementitious properties, and can be likened to the pozzolanic reactions in hydrating cement systems. The location of loess and loess-like ground on the peripheries of deserts is aided by the observation of the nesting sites of bee-eater birds. These birds have a determined preference for loess ground to dig their nesting tunnels; the presence of nest tunnels suggests the occurrence of desert loess, in desert fringe regions. We seek amalgamation and contrast: ten main topics are considered: words and terms, particles, parna, geotechnical, adobe, people, birds, Africa, Central Asia, Mars. The aim is some large generalizations which will benefit all aspects of desert loess investigation

Micromechanics of quartz sand breakage in a fractal context

From a Quaternary science perspective, sand-sized quartz as well as silt-sized quartz is often acknowledged as final products of glacial abrasion through different evolution mechanisms. This view challenges the existence of any universal comminution process, which may relate the formation of detrital quartz sand and silt. The contribution of grain size, energy input, and crystalline integrity in the scale of quartz crushability has long been the matter of much debate. The present empirical work examines the micromechanics of sand-to-silt size reduction in the quartz material. A series of grinding experiments was performed on Leighton Buzzard Lower Greensand using a high-energy agate disc mill. Analogous conditions to glacial abrasion are provided due to the combined abrasion between grains' asperity tips, and also between grains and rotating smooth tungsten carbide pestle. Simulation of discontinuous grain breakage allowed the examination of grains' crystalline defects. To enable an objective assessment of micromechanics of size reduction, measurements of particle and mode size distribution, fractal indexes and micro-morphological signatures were made. The crushing approach was probed through varied grinding times at a constant energy input, as well as varied energy inputs at constant grinding time. Breakage pathway was inspected via laser diffraction spectroscopy and transmission light microscopy. Results suggested that the grain breakdown is not necessarily an energy-dependent process. Non-crystallographically pure (amorphous) quartz sand and silt are inherently breakable materials through a fractal breakdown process. Results also revealed that the internal defects in quartz are independent from size and energy input

Narratives of scarcity: Framing the global land rush

Global resource scarcity has become a central policy concern, with predictions of rising populations, naturalresource depletion and hunger. The narratives of scarcity that arise as a result justify actions to harness resourcesconsidered‘underutilised’, leading to contestations over rights and entitlements and producing new scarcities.Yet scarcity is contingent, contextual, relational and above all political. We present an analysis of three framings–absolute, relative and political scarcity–associated with the intellectual traditions of Malthus, Ricardo andMarx, respectively. A review of 134 global and Africa-specific policy and related sources demonstrates howdiverse framings of scarcity–what it is, its causes and what is to be done–are evident in competing narrativesthat animate debates about the future of food and farming in Africa and globally. We argue that currentmainstream narratives emphasise absolute and relative scarcity, while ignoring political scarcity. Opening upthis debate, with a more explicit focus on political scarcities is, we argue, important; emphasising how resourcesare distributed between different needs and uses, and so different people and social classes. For African settings,seen as both a source of abundant resources and a site where global scarcities may be resolved, as well as wherelocal scarcities are being experienced most acutely, a political scarcity framing on the global land rush, andresource questions more broadly, is, we suggest, essential

Glucose and lactate as metabolic constraints on presynaptic transmission at an excitatory synapse

The synapse has high energy demands, which increase during intense activity. Presynaptic ATP production depends on substrate availability and usage will increase during activity, which in turn could influence transmitter release and information transmission. We investigated transmitter release at the mouse calyx of Held synapse using glucose or lactate (10, 1 or 0 mm) as the extracellular substrates while inducing metabolic stress. High‐frequency stimulation (HFS) and recovery paradigms evoked trains of EPSCs monitored under voltage‐clamp. Whilst postsynaptic intracellular ATP was stabilised by diffusion from the patch pipette, depletion of glucose increased EPSC depression during HFS and impaired subsequent recovery. Computational modelling of these data demonstrated a reduction in the number of functional release sites and slowed vesicle pool replenishment during metabolic stress, with little change in release probability. Directly depleting presynaptic terminal ATP impaired transmitter release in an analogous manner to glucose depletion. In the absence of glucose, presynaptic terminal metabolism could utilise lactate from the aCSF and this was blocked by inhibition of monocarboxylate transporters (MCTs). MCT inhibitors significantly suppressed transmission in low glucose, implying that lactate is a presynaptic substrate. Additionally, block of glycogenolysis accelerated synaptic transmission failure in the absence of extracellular glucose, consistent with supplemental supply of lactate by local astrocytes. We conclude that both glucose and lactate support presynaptic metabolism and that limited availability, exacerbated by high‐intensity firing, constrains presynaptic ATP, impeding transmission through a reduction in functional presynaptic release sites as vesicle recycling slows when ATP levels are low

Loess towards (geo) tourism – proposed application on loess in Vojvodina region (north Serbia)

Loess-palaeosol sequences preserve the most important continental record of climatic and environmental changes during the Quaternary. As a significant element of global geodiversity and geoheritage, loess-palaeosol sequences could be used as resources for a contemporary trend in sustainable tourism – geotourism. This form of tourism appreciates and promotes non-living nature (geodiversity) through its conservation and interpretation. This further leads to enhancing public awareness of these sites. In this study, we report on a proposal for establishing geotourism at the most important loess sites in the Vojvodina region