THE LONG RUN OUTLOOK FOR WORLD FOOD PRODUCTION

Food Security and Poverty,

4.6 billion year old aragonite and its implications for understanding the geological record of Ca-carbonate

Owing to its diagenetic instability, aragonite is rare in the geological record and almost entirely absent from pre-carboniferous sedimentary rocks. The former presence of this mineral in older deposits has to be inferred from petrographic, chemical or isotopic proxies. Crystals of aragonite that formed around 4563 million years ago occur in carbonaceous chondrite meteorites, showing that under certain conditions, the orthorhombic polymorph of Ca-carbonate can survive essentially indefinitely. Together with other carbonate minerals, phyllosilicates and sulphides, this aragonite formed by low-temperature water-mediated alteration of anhydrous minerals and glass in the interior of the meteorite’s parent asteroid(s). The survival of aragonite for such a long time can be attributed to the loss of free water by its incorporation into phyllosilicates, and to the very low permeability of the fine-grained and organic-rich rock matrix that prevented the ingress of fresh solutions via intergranular flow. By analogy with these meteorites, terrestrial aragonite is likely to survive where it has been similarly isolated from liquid water, particularly in organic-rich mudrocks, and such deposits may provide important new evidence for deducing the original mineralogy of skeletal and non-skeletal carbonates in deep-time

Diffusion-controlled and replacement microtextures in alkali feldspars from two pegmatites: Perth, Ontario and Keystone, South Dakota

Macro- and micro-perthitic microclines from pegmatites from Perth, Ontario (Wards catalogue 46 E 0510) and Keystone, South Dakota (Wards 46 E 5125) have been studied using light and electron microscopy. A sample of the type perthite from Perth, Ontario (Hunterian Museum, Glasgow, M2361) was compared using light microscopy. It differs in bulk composition and microtexture from the Wards sample. The Perth sample from Wards is a mesoperthite, with sub-periodic ~mm-thick albite veins near (100), with irregular surfaces. The microcline has regular tartan twins and formed from orthoclase by a continuous process. The Keystone sample is a microperthite, with non-periodic albite veins mainly in {110}. Irregular tartan twins, volumes of irregular microcline and subgrains suggest that the microcline formed by dissolution–reprecipitation. Microcline in both samples contains semicoherent cryptoperthitic albite films that formed after the development of tartan twins. The bulk compositions of these intergrowths imply exsolution below ~400°C. Diffusion parameters imply sustained heating for between 0.11 My at 400°C, 1.5 GPa and 8.4 My at 300°C, 1 GPa. Unrealistic times are required at 200°C. Subsequently, the crystals reacted with a fluid leading to replacive growth of the vein perthites. Unusually, Albite twin composition planes in replacive subgrains have sub-periodic dislocations, formed by coalescence of advancing growth twins. Processes that might lead to periodic, replacive intergrowths are discussed. The Perth and Keystone feldspars have been used for experimental work on dissolution during weathering and on anomalous thermoluminescence fading. Their microtextures make them unsuitable for obtaining properties that can be extrapolated to feldspars in general

Microstructure and growth of the lenses of schizochroal trilobite eyes

Lenses within the schizochroal eyes of phacopine trilobites are made principally of calcite and characterisation of them using light microscopy and high-resolution electron imaging and diffraction has revealed an array of microstructural arrangements that suggest a common original pattern across the suborder. The low convexity lenses of Odontochile hausmanni and Dalmanites sp. contain calcite fibres termed trabeculae. The c axis of trabecular calcite lies parallel to the lens axis, and adjacent trabeculae are distinguished by small differences in their a axis orientations. Despite the common alignment, the boundaries between trabeculae cross-cut the c axis as they fan out towards the lens base. Trabeculae are absent from the lens immediately beneath the visual surface and instead a radial fringe is present and is composed of micrometre-thick sheets of calcite whose c axes are oriented at a low angle to the visual surface. High convexity lenses are more common than those of lower convexity among the species studied, and they have a much thicker radial fringe. Beneath this fringe all of the lens calcite is oriented with its c axis parallel to the lens axis and it lacks trabeculae. We propose that both the high and low convexity lenses formed by rapid growth of calcite from a surface that migrated inwards from the cornea, and they may have had an amorphous calcium carbonate precursor. The trabeculae and radial fringes are unlikely to have had any beneficial effect on the transmission or focusing of light but rather are the outcomes of an elegant solution to the problem of how to construct a biconvex lens from a crystalline solid

Water Resources Problems in Developing Countries

Resource /Energy Economics and Policy,

Routine characterization and interpretation of complex alkali feldspar intergrowths

Almost all alkali feldspar crystals contain a rich inventory of exsolution, twin, and domain microtextures that form subsequent to crystal growth and provide a record of the thermal history of the crystal and often of its involvement in replacement reactions, sometimes multiple. Microtextures strongly influence the subsequent behavior of feldspars at low temperatures during diagenesis and weathering. They are central to the retention or exchange of trace elements and of radiogenic and stable isotopes. This review is aimed at petrologists and geochemists who wish to use alkali feldspar microtextures to solve geological problems or who need to understand how microtextures influence a particular process. We suggest a systematic approach that employs methods available in most well founded laboratories. The crystallographic relationships of complex feldspar intergrowths were established by the 1970s, mainly using single-crystal X-ray diffraction, but such methods give limited information on the spatial relationships of the different elements of the microtexture, or of the mode and chronology of their formation, which require the use of microscopy. We suggest a combination of techniques with a range of spatial resolution and strongly recommend the use of orientated sections. Sections cut parallel to the perfect (001) and (010) cleavages are the easiest to locate and most informative. Techniques described are light microscopy; scanning electron microscopy using both backscattered and secondary electrons, including the use of surfaces etched in the laboratory; electron-probe microanalysis and analysis by energy-dispersive spectrometry in a scanning electron microscope; transmission electron microscopy. We discuss the use of cathodoluminescence as an auxiliary technique, but do not recommend electron-backscattered diffraction for feldspar work. We review recent publications that provide examples of the need for great care and attention to pre-existing work in microtextural studies, and suggest several topics for future work

A nonparametric empirical Bayes framework for large-scale multiple testing

We propose a flexible and identifiable version of the two-groups model, motivated by hierarchical Bayes considerations, that features an empirical null and a semiparametric mixture model for the non-null cases. We use a computationally efficient predictive recursion marginal likelihood procedure to estimate the model parameters, even the nonparametric mixing distribution. This leads to a nonparametric empirical Bayes testing procedure, which we call PRtest, based on thresholding the estimated local false discovery rates. Simulations and real-data examples demonstrate that, compared to existing approaches, PRtest's careful handling of the non-null density can give a much better fit in the tails of the mixture distribution which, in turn, can lead to more realistic conclusions.Comment: 18 pages, 4 figures, 3 table

Functions of Menace: A Comparison of The Room and The Birthday Party

An atmosphere of menace surrounds the action of Harold Pinter\u27s plays, The Room and The Birthday Party. Several critics seem to agree that the menace originates in the outer world and threatens to intrude upon the security of a room, where people attempt to hide. But the menace may also originate within the room--from the inner world and not the outer. The Room illustrates how a character deals with a menace that is within, while The Birthday Party deals with agents of menace from the outer world. Rose Hudd, in The Room, is dissociated from the outer world against her will, but refuses to acknowledge her situation. In order to avoid admitting that the menace is contained within her room, she displaces her fears onto that which is outside the room. The repetition of her references to the outer world and to the basement emphasizes their menacing nature. Rose\u27s words concerning the outside paint a picture of an insensitive, desolate and cruel world, and she constantly compares the warmth and light of her room to the cold, damp basement. Rose\u27s preoccupation with the outer world and the basement suggests that she is struggling to maintain the denial that the true menace is contained within her room. In that room--the importance of which is underscored by the title--Rose is subservient to Bert\u27s physical and mental needs. Her servility is her only function in life, which breeds a sense of emptiness--a meaninglessness that is subtly presented through contrasts provided by members of the outside world who visit Rose. During the scenes with Mr. Kidd and the Sands, there are subtle hints that Rose desires to return to the outer world, and it is Riley who affords her the opportunity to do so. At first, Rose perceives Riley to be the menace she has feared, projecting Bert\u27s autocratic dependence and violence onto Riley. But Riley gently prods Rose into confessing that her isolation is stifling her, as she forsakes her denial mechanisms. At the end of the play, it is Bert who surfaces as the destructive force, for his behavior clearly marks him as the menace. With a violent beating, he destroys Riley and Rose\u27s chance for escape. Bert undermines Rose\u27s existence through passive control. He controls his van in the same manner, and when he speaks of his van in the final scene, Bert seems to be warning Rose that she will not escape his dominance. The Room ends with Rose being pushed even further into a meaningless existence. On the other hand, the agents of menace in The Birthday Party are acknowledged by Stanley, but they also succeed in undermining his existence. In this play, the agents of menace do not threaten to keep Stanley trapped in isolation. Instead, Goldberg and McCann remove him from a stagnant condition which he is reluctant to leave. Stanley\u27s isolation, like Rose\u27s, offers him little purpose in his life. He has little contact with the outside world, and consequently dwindles to a state of inactivity. Stanley is satisfied to remain within the house, and as a mark of his passive existence, becomes dependent on Meg to satisfy his needs. Meg\u27s maternalizing reinforces Stanley\u27s reluctance to leave the house. Goldberg and McCann gain control of Stanley and his fate seems to rest in their hands. Their purpose is to remove Stanley from isolation, which they succeed in doing. There seems to be three alternatives for Stanley once he leaves the house. There is a strong suggestion that Goldberg and McCann will kill him, but there is also the slight possibility that they will return him to society. A return to society could mean the acceptance of the trite social conformity Goldberg represents, which would be a spiritual death for Stanley. But possibly Stanley could re-adjust and become a functioning member of society. Oddly enough, though, either of these possibilities will be an improvement over Stanley\u27s present existence. A life in the outside world, even though shallow like Goldberg\u27s, will be less empty than the stagnation Stanley is being removed from. The Room and The Birthday Party seem to suggest that the threat of menace is omnipresent, originating from both within and outside a room. In both plays, the agents of menace succeed in their goals. Bert pushes Rose deeper into a meaningless existence, and Goldberg and McCann remove Stanley from stagnation. The basic difference between these agents of menace is that while Bert forces Rose into a more hopeless situation, Goldberg and McCann force Stanley into an improved existence. The menace in The Room is destructive. But the menace in The Birthday Party, although terrifying, may well be constructive

Functions of Menace: A Comparison of The Room and The Birthday Party

An atmosphere of menace surrounds the action of Harold Pinter\u27s plays, The Room and The Birthday Party. Several critics seem to agree that the menace originates in the outer world and threatens to intrude upon the security of a room, where people attempt to hide. But the menace may also originate within the room--from the inner world and not the outer. The Room illustrates how a character deals with a menace that is within, while The Birthday Party deals with agents of menace from the outer world. Rose Hudd, in The Room, is dissociated from the outer world against her will, but refuses to acknowledge her situation. In order to avoid admitting that the menace is contained within her room, she displaces her fears onto that which is outside the room. The repetition of her references to the outer world and to the basement emphasizes their menacing nature. Rose\u27s words concerning the outside paint a picture of an insensitive, desolate and cruel world, and she constantly compares the warmth and light of her room to the cold, damp basement. Rose\u27s preoccupation with the outer world and the basement suggests that she is struggling to maintain the denial that the true menace is contained within her room. In that room--the importance of which is underscored by the title--Rose is subservient to Bert\u27s physical and mental needs. Her servility is her only function in life, which breeds a sense of emptiness--a meaninglessness that is subtly presented through contrasts provided by members of the outside world who visit Rose. During the scenes with Mr. Kidd and the Sands, there are subtle hints that Rose desires to return to the outer world, and it is Riley who affords her the opportunity to do so. At first, Rose perceives Riley to be the menace she has feared, projecting Bert\u27s autocratic dependence and violence onto Riley. But Riley gently prods Rose into confessing that her isolation is stifling her, as she forsakes her denial mechanisms. At the end of the play, it is Bert who surfaces as the destructive force, for his behavior clearly marks him as the menace. With a violent beating, he destroys Riley and Rose\u27s chance for escape. Bert undermines Rose\u27s existence through passive control. He controls his van in the same manner, and when he speaks of his van in the final scene, Bert seems to be warning Rose that she will not escape his dominance. The Room ends with Rose being pushed even further into a meaningless existence. On the other hand, the agents of menace in The Birthday Party are acknowledged by Stanley, but they also succeed in undermining his existence. In this play, the agents of menace do not threaten to keep Stanley trapped in isolation. Instead, Goldberg and McCann remove him from a stagnant condition which he is reluctant to leave. Stanley\u27s isolation, like Rose\u27s, offers him little purpose in his life. He has little contact with the outside world, and consequently dwindles to a state of inactivity. Stanley is satisfied to remain within the house, and as a mark of his passive existence, becomes dependent on Meg to satisfy his needs. Meg\u27s maternalizing reinforces Stanley\u27s reluctance to leave the house. Goldberg and McCann gain control of Stanley and his fate seems to rest in their hands. Their purpose is to remove Stanley from isolation, which they succeed in doing. There seems to be three alternatives for Stanley once he leaves the house. There is a strong suggestion that Goldberg and McCann will kill him, but there is also the slight possibility that they will return him to society. A return to society could mean the acceptance of the trite social conformity Goldberg represents, which would be a spiritual death for Stanley. But possibly Stanley could re-adjust and become a functioning member of society. Oddly enough, though, either of these possibilities will be an improvement over Stanley\u27s present existence. A life in the outside world, even though shallow like Goldberg\u27s, will be less empty than the stagnation Stanley is being removed from. The Room and The Birthday Party seem to suggest that the threat of menace is omnipresent, originating from both within and outside a room. In both plays, the agents of menace succeed in their goals. Bert pushes Rose deeper into a meaningless existence, and Goldberg and McCann remove Stanley from stagnation. The basic difference between these agents of menace is that while Bert forces Rose into a more hopeless situation, Goldberg and McCann force Stanley into an improved existence. The menace in The Room is destructive. But the menace in The Birthday Party, although terrifying, may well be constructive

TESTS OF BIRD DAMAGE CONTROL MEASURES IN SUDAN, 1975

The Red-billed Quelea (Quelga quelaa), because of its widespread destruction of grain crops throughout its range in Africa, is one of the most studied and written about granivorous bird species. Less publicized are more local bird pests in Africa which may be equally Important. The Village Weaver, (Ploceus cucullatus), for example, is a pest in many countries, while some other Ploecids with limited destructive habits create local problems. Significant crop losses also occur where there are large populations of Golden Sparrows (Passer luteus), House Sparrows (Passer domesticus), Red Bishops (Euplectes oryx), Doves (Streptopelia spp.), Glossy Starlings (Lamprotornis chalybaeus), Parakeets (Psittacula spp.), and some waterfowl (Mackworth-Praed and Grant, 1952; Pans Manual No. 3, 1974; Park, 1974). Crop losses from local bird pests were reported in early February 1975 to the Sudan Plant Protection Bird Control Unit of the Ministry of Agriculture. A mechanized farm scheme in Khartoum North had large concentrations of Red Bishops roosting in maize and feeding on an early-maturing wheat variety (Mexicana). Small flocks of Golden Sparrows and House Sparrows also were present. Bird damage was clearly visible, especially at the corners and along the edges of the ripening wheatfields. Ground spraying with Queletox (60% a.1. Fenthion) on roosts of the Golden and House Sparrows was conducted along hedge rows of acacia (Acacia mellifera) located at the north end of the farm. Although the spray killed large numbers of roosting birds, damage con- tinued as the wheat matured. Pilot field trials were thus organized to test the effectiveness of other crop protection techniques. Because birds fed throughout many blocks of wheat which matured at different periods, it was felt that several different experiments could be conducted without Interfering with each other. The control techniques Included an acoustical repellent, a chemical repellent, a chemical frightening agent, and a trap. The experiments, conducted from February 7 through February 23, 1975, were not designed as an integrated control operation