Epitaxial Magnetic Oxide Nanocrystals Via Phase Decomposition of Bismuth Perovskite Precursors

The phase instability of bismuth perovskite (BiMO₃), where M is a ferromagnetic cation, is exploited to create self-assembled magnetic oxide nanocrystal arrays on oxide supports. Conditions during pulsed laser deposition are tuned so as to induce complete breakdown of the perovskite precursor into bismuth oxide (Bi₂ O₃ ) and metal oxide (M-O_x ) pockets. Subsequent cooling in vacuum volatizes the Bi₂ O₃ leaving behind an array of monodisperse nanocrystals. In situ reflective high energy electron diffraction beam is exploited to monitor the synthesis in real-time. Analysis of the patterns confi rms the phase separation and volatization process. Successful synthesis of M-O_x, where M = Mn, Fe, Co, and Cr, is shown using this template-free facile approach. Detailed magnetic characterization of nanocrystals is carried out to reveal the functionalities such as magnetic anisotropy as well as larger than bulk moments, as expected in these oxide nanostructures.

The partially reversible formation of Li-metal particles on a solid Li electrolyte:applications toward nanobatteries

The feasibility of large-scale implementation of Li-air batteries (LABs) hinges on understanding the thermodynamic and kinetic factors that control charge-discharge rates, efficiency and life times. Here, the kinetics of bias-induced reactions is explored locally on the surface of Li-ion conductive glass ceramics, a preferred electrolyte for LABs, using direct current-voltage and strain spectroscopies. Above a critical bias, particle growth kinetics were found to be linear in both the bias and time domains. Partial reversibility was observed for Li particles as evidenced by the presence of anodic peaks following the Li(+) reduction, as well an associated reduction in particle height. The degree of reversibility was highest for the smallest particles formed. These observations thus suggest the possibility of producing nanobatteries with an active anode volume of the order of 0.1 al.

Vegetation changes and human settlement of Easter Island during the last millennia: a multiproxy study of the Lake Raraku sediments

Earlier palynological studies of lake sediments from Easter Island suggest that the island underwent a recent and abrupt replacement of palm-dominated forests by grasslands, interpreted as a deforestation by indigenous people. However, the available evidence is inconclusive due to the existence of extended hiatuses and ambiguous chronological frameworks in most of the sedimentary sequences studied. This has given rise to an ongoing debate about the timing and causes of the assumed ecological degradation and cultural breakdown. Our multiproxy study of a core recovered from Lake Raraku highlights the vegetation dynamics and environmental shifts in the catchment and its surroundings during the late Holocene. The sequence contains shorter hiatuses than in previously recovered cores and provides a more continuous history of environmental changes. The results show a long, gradual and stepped landscape shift from palm-dominated forests to grasslands. This change started c. 450 BC and lasted about two thousand years. The presence of Verbena litoralis, a common weed, which is associated with human activities in the pollen record, the significant correlation between shifts in charcoal influx, and the dominant pollen types suggest human disturbance of the vegetation. Therefore, human settlement on the island occurred c. 450 BC, some 1500 years earlier than is assumed. Climate variability also exerted a major influence on environmental changes. Two sedimentary gaps in the record are interpreted as periods of droughts that could have prevented peat growth and favoured its erosion during the Medieval Climate Anomaly and the Little Ice Age, respectively. At c. AD 1200, the water table rose and the former Raraku mire turned into a shallow lake, suggesting higher precipitation/evaporation rates coeval with a cooler and wetter Pan-Pacific AD 1300 event. Pollen and diatom records show large vegetation changes due to human activities c. AD 1200. Other recent vegetation changes also due to human activities entail the introduction of taxa (e.g. Psidium guajava, Eucalyptus sp.) and the disappearance of indigenous plants such as Sophora toromiro during the two last centuries. Although the evidence is not conclusive, the American origin of V. litoralis re-opens the debate about the possible role of Amerindians in the human colonisation of Easter Island.

Research Review: Teenage pregnancy and parenthood: the role of fathers

From the research available in America and Britain it would appear that the men who father children by teenage mothers tend to be a few years older than their teenage partners, although a minority may be significantly older. With regard to the factors associated with fatherhood there are striking similarities to the literature on teenage mothers. Like teenage mothers young fathers tend to be from low socio-economic backgrounds, experience lower educational attainment and fewer employment opportunities than their childless peers. Similarly they tend to experience greater psychological and emotional difficulties and may have a history of delinquent behaviour.

These young fathers are involved in a variety of relationships with teenage mothers, few of which result in marriage and many of which result in the breakdown of cohabitation or the termination of the relationship. This pattern of increasing relationship breakdown over time is related to decreasing paternal contact with children in both America and Britain. Often conflictual relationships with teenage mothers or maternal grandparents and a lack of financial resources are cited by young fathers as barriers to their continued involvement and contact with their children. However, the mothers are much more likely to cite paternal disinterest as the reason for a lack of paternal involvement and there is some indication that mothers and fathers have different views on the level of practical involvement expected from fathers. While most of quantitative data on the subject provides a rather negative picture of paternal involvement, qualitative research highlights how many young fathers genuinely want to be involved with their children and would have more contact and input if they could.

While much less is known about the support provided to young fathers in comparison with their female counterparts, there is some suggestion that the support and role expectations provided by the paternal grandmother may influence how involved young fathers are. There is also some indication that a sizeable minority of young men may receive no such support from their family and may also be treated with hostility or ignored by the maternal grandparents. Young fathers also report limited or no contact with midwives, health visitors and social workers.

Limbal stem cell deficiency:Concept, aetiology, clinical presentation, diagnosis and management

Defects in renewal and repair of ocular surface as a result of limbal stem cell deficiency are now known to cause varying ocular, surface morbidity including persistent photophobia, repeated and persistent surface breakdown and overt conjunctivalisation of the cornea. Ocular conditions with abnormalities of ocular surface repair include pterygium, limbal tumours, aniridia, severe scarring following burns, cicatricial pemphigoid and Stevens-Johnson Syndrome, sequelae of mustard gas exposure and Herpes simplex epithelial disease, radiation keratopathy, contact lens induced keratopathy, neuroparalytic keratitis and drug toxicity. Restoring ocular health in these eyes has traditionally been frustrating. An understanding of these intricate cell renewal and maintenance processes has spurred the evolution in recent years of new treatment methods for several blinding diseases of the anterior segment; many more exciting modalities are in the offing. However, there is inadequate awareness among ophthalmologists about the current principles of management of ocular surface disorders. The purpose of this article is to help elucidate the important principles and current treatment methods relevant to ocular surface disorders.

Autologous scleral patch graft in tube shunt surgery

Purpose . To investigate alternative surgical method to cover subconjunctival portion of the tube in tube shunt surgery in glaucoma Methods. In thirteen eyes of twelve patients who underwent tube shunt surgery at WEH between July 1991 to November 1996 a "rotating" autologous scleral lamellar graft was created to cover the subconjuctival course of the tube. These patients were followed for clinical signs of conjuctival breakdown, graft melt, tube erosion, anterior staphylomas, graft related inflammation, infections or graft related complications. Results. The patients were followed up for a mean of 16 5 months( range 1-60 months). All eyes tolerated the autologous graft well without any clinical evidence of tube erosions, graft melting , graft related or intraocular inflammation Conclusions The use of autologous sciera, to cover the tube in a tube shunt procedure appears to be effective and without inappropriate short term risk. It offers the advantages of availability , lower cost, and eliminates the potential risk of transmission of infectious disease( i.e. slow-virus, HIV etc.).

A preliminary survey of micro-organisms in the gut and pellets of a tropical millipede Doratogonus uncinatus Attems (Diplopoda, Spirostreptida, Spirostreptidae).

Millipede gut microbiology and decomposition of faecal pellets over a period of eight weeks were studied in the laboratory. Bacterial numbers, carbon and nitrogen content, pH and weight loss were monitored. Heterotrophic bacteria were the most abundant and reached a peak in the first two weeks of decomposition. The amount of carbon was constant while ammonium nitrogen decreased from 1.51 % to 0.03 % after eight weeksThe pH of the pellets was slightly acidic and did not change much during the course of decomposition. A succession of micro-organisms was observed on decomposing pellets. Zygomycetes were replaced by Ascomycetes after 20 days of decomposition. Decomposition was significantly affected by temperature. The rate of decomposition was highest at 35[degree]C .

Susceptibility to stress corrosion cracking of NiTi laser weldment in Hanks’ solution

In this study, the susceptibility to stress corrosion cracking (SCC) of laser-welded NiTi wires in Hanks’ solution at 37.5 °C was studied by the slow strain-rate test (SSRT) at open-circuit potential and at different applied anodic potentials. The weldment shows high susceptibility to SCC when the applied potential is near to the pitting potential of the heat-affected zone (HAZ). The pits formed in the HAZ become sites of crack initiation when stress is applied, and cracks propagate in an intergranular mode under the combined effect of corrosion and stress. In contrast, the base-metal is immune to SCC under similar conditions. The increase in susceptibility to SCC in the weldment could be attributed to the poor corrosion resistance in the coarse-grained HAZ.

Role of glycation in modification of lens crystallins in diabetic and nondiabetic senile cataracts

To assess the significance of glycation, nonenzymatic browning, and oxidation of lens crystallins in cataract formation in elderly diabetic patients, we measured three distinct products of glycation, browning, and oxidation reactions in cataractous lens crystallins from 29 diabetic patients (mean +/- SD age 72.8 +/- 8.8 yr) and 24 nondiabetic patients (age 73.5 +/- 8.3 yr). Compounds measured included 1) fructoselysine (FL), the first stable product of glycation; 2) pentosidine, a fluorescent, carbohydrate-derived protein cross-link between lysine and arginine residues formed during nonenzymatic browning; and 3) N epsilon-(carboxymethyl)lysine (CML), a product of autoxidation of sugar adducts to protein. In diabetic compared with nondiabetic patients, there were significant increases (P less than 0.001) in HbA1 (10.2 +/- 3.1 vs. 7.1 +/- 0.7%), FL (7.6 +/- 5.4 vs. 1.7 +/- 1.2 mmol/mol lysine), and pentosidine (6.3 +/- 2.8 vs. 3.8 +/- 1.9 mumol/mol lysine). The disproportionate elevation of FL compared with HbA1 suggests a breakdown in the lens barrier to glucose in diabetes, whereas the increase in pentosidine is indicative of accelerated nonenzymatic browning of diabetic lens crystallins. CML levels were similar in the two groups (7.1 +/- 2.4 vs. 6.8 +/- 3.0 mmol/mol lysine), providing no evidence for increased oxidative stress in the diabetic cataract. Thus, although the modification of lens crystallins by autoxidation reactions was not increased in diabetes, the increase in glycation and nonenzymatic browning suggests that these processes may acclerate the development of cataracts in diabetic patients.

A New Irish? Problems of communication in modern Irish media and new speakers.

While the Gaeltacht (Irish speaking) areas of Ireland are geographically isolated from each other and relatively small in area, it is expected that the number of second language Irish speakers throughout the country should ensure the future of the language. Nevertheless, while the official standard grammar has been established for many decades, there is still a tendency in the spoken language to give precedence to regional dialectal variants in schools and the broadcast media which often raises barriers between native speakers themselves and between learners and native speakers.
All pupils in school in the Republic and many in Northern Ireland learn Irish and there has been a great increase in the number of pupils attending immersion Irish language Gaelscoileanna. But concern has been expressed about the phonetic and structural accuracy achieved in schools, all of which contributes to communication breakdown.
This paper discusses how a greater awareness of the link between phoneme and grapheme in Irish and the proposals for the Lárchanúint (Central Dialect) in the 1980s and current discussions on Caighdeán Leathan agus Caighdeán Cúng (Broad and Narrow Standard) would mitigate these concerns.

The lateritic profile of Balkouin, Burkina Faso: geochemistry, mineralogy and genesis

This study reports on the geochemical and mineralogical characterization of a lateritic profile cropping out in the Balkouin area, Central Burkina Faso, aimed at obtaining a better understanding of the processes responsible for the formation of the laterite itself and the constraints to its development. The lateritic profile rests on a Paleoproterozoic basement mostly composed of granodioritic rocks related to the Eburnean magmatic cycle passing upwards to saprolite and consists of four main composite horizons (bottom to top): kaolinite and clay-rich horizons, mottled laterite and iron-rich duricrust. In order to achieve such a goal, a multi-disciplinary analytical approach was adopted, which includes inductively coupled plasma (ICP) atomic emission and mass spectrometries (ICP-AES and ICP-MS respectively), X-ray powder diffraction (XRPD), scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) and micro-Raman spectroscopy.

The geochemical data, and particularly the immobile elements distribution and REE patterns, show that the Balkouin laterite is the product of an in situ lateritization process that involved a strong depletion of the more soluble elements (K, Mg, Ca, Na, Rb, Sr and Ba) and an enrichment in Fe; Si was also removed, particularly in the uppermost horizons. All along the profile the change in composition is coupled with important changes in mineralogy. In particular, the saprolite is characterized by occurrence of abundant albitic plagioclase, quartz and nontronite; kaolinite is apparently absent. The transition to the overlying lateritic profile marks the breakdown of plagioclase and nontronite, thus allowing kaolinite to become one of the major components upwards, together with goethite and quartz. The upper part of the profile is strongly enriched in hematite (+ kaolinite). Ti oxides (at least in part as anatase) and apatite are typical accessory phases, while free aluminum hydroxides are notably absent. Mass change calculations emphasize the extent of the mass loss, which exceeds 50 wt% (and often 70 wt%) for almost all horizons; only Fe was significantly concentrated in the residual system.

The geochemical and mineralogical features suggest that the lateritic profile is the product of a continuous process that gradually developed from the bedrock upwards, in agreement with the Schellmann classic genetic model. The laterite formation must have occurred at low pH (? 4.5) and high Eh (? 0.4) values, i.e., under acidic and oxidizing environments, which allowed strongly selective leaching conditions. The lack of gibbsite and bohemite is in agreement with the compositional data: the occurrence of quartz (± amorphous silica) all along the profile was an inhibiting factor for the formation of free aluminum hydroxides.

Surface deformations as a necessary requirement for resistance switching at the surface of SrTiO3:N

Atomic force microscopy (AFM), conductive AFM and electrochemical strain microscopy were used to study the topography change at the defect surface of SrTiO3:N, breakdown in the electrical conduction of the tip/sample/electrode system and ionic motion. The IV curves show resistance switching behavior in a voltage range ±6 V < U <± 10 V and a current of maximum ±10 nA. A series of sweeping IV curves resulted in an increase in ionically polarized states (surface charging), electrochemical volume (surface deformations) and sequential formations of stable surface protrusions. The surface deformations are reversible (U <± 5 V) without IVpinched hysteresis and remained stable during the resistance switching (U >± 6 V), revealing the additional necessity (albeit insufficient due to 50% yield of working cells) of surface protrusion formation for resistance switching memory.

Water-mediated electrochemical nano-writing on thin ceria films

Bias dependent mechanisms of irreversible cathodic and anodic processes on a pure CeO2 film are studied using modified atomic force microscopy (AFM). For a moderate positive bias applied to the AFM tip an irreversible electrochemical reduction reaction is found, associated with significant local volume expansion. By changing the experimental conditions we are able to deduce the possible role of water in this process. Simultaneous detection of tip height and current allows the onset of conductivity and the electrochemical charge transfer process to be separated, further elucidating the reaction mechanism. The standard anodic/cathodic behavior is recovered in the high bias regime, where a sizable transport current flows between the tip and the film. These studies give insight into the mechanisms of the tip-induced electrochemical reactions as mediated by electronic currents, and into the role of water in these processes, as well as providing a different approach for electrochemical nano-writing.

Pathophysiology and Pathogenesis of Diabetic Retinopathy

Diabetic retinopathy is traditionally viewed as a disease of the retinal blood vessels, although there is increasing evidence that retinal neurons and glial cells are also affected. This article describes the changes in the diabetic retina that precede the development of clinical diabetic retinopathy, including changes in the rate of retinal blood flow, alterations in the electroretinogram and breakdown of the integrity of the blood-retinal barrier. The long term lesions of diabetic retinopathy are characterised by a complex array of vasodegenerative changes that lead directly to areas of retinal ischaemia. This frequently triggers the onset of macular oedema and/or the proliferative stages of diabetic retinopathy with risk of visual impairment and blindness. Neurodegeneration has also been reported in the retina during both human and experimental diabetic retinopathy, although presently it remains unclear to what extent such changes contribute to visual loss in diabetic retinopathy.

Histopathologists’ approach to keratoacanthoma: a multisite survey of regional variation in Great Britain and Ireland

Introduction: This survey examines regional variation in the diagnosis of keratoacanthoma (KA).

Methods: Twenty-three departments from Great Britain and Ireland were invited. The number of cases coded as KA or cutaneous SCC in the previous 12 months was retrieved. An SCC: KA ratio was calculated. Participants also provided free text responses.

Results: Seventeen departments replied. A total of 11 718 cases were included with a breakdown of 998 KA and 10 720 SCC. The mean SCC:KA ratio was 10.7:1, range (2.5:1 to 139:1). Free text responses are presented.

Discussions: An extreme variation in approach is highlighted by this survey. We believe a multidisciplinary team approach to the diagnosis of KA is essential. There seems to be a need for a carefully considered clinicopathological study, backed up by molecular studies, to better understand the natural biology of this diagnosis.