Bimodal Occurrence Research Articles

Assembly rules vary seasonally in stable phytoplankton associations of the Gulf of Naples (Mediterranean Sea)

AbstractCoastal phytoplankton present remarkable variability because of complex patterns and relationships of hydrological parameters at the land–sea interface. We analysed a time series of 917 phytoplankton samples collected in the period 1984–2010 at the coastal station LTER‐MC (Gulf of Naples, Mediterranean Sea) with the aims of determining: (i) whether recurrent species associations are recognizable in this variable coastal environment; (ii) what are their composition and seasonal patterns; (iii) what are the environmental variables driving their distributions, and (iv) to what extent those associations are functionally homogeneous. Using a cluster analysis of a dataset of the 87 more frequent and abundant species in the samples, we identified seven main groups of species. Five of them were recurrent over the years in the same seasons, while two other groups showed a bimodal occurrence or no clear seasonality, respectively. Differences in the occurrence of those assemblages were primarily associated with the season (i.e., temperature), and the coastal nature of the site (mainly salinity). Except for the winter cluster, which included mostly coccolithophores and silicoflagellates, diatoms were present in all associations, along with species belonging to diverse phylogenetic groups. The diversity of morphological features defining ecological traits varied across the different associations, with a maximum divergence in the spring association and a minimum in winter. We conclude that the stability of the associations is related to the marked phenological recurrence of their individual species and their overlap in specific periods of the year, while convergent or divergent trait compositions in the different associations indicate a variable strength of the environmental filtering across the seasonal succession.

Analysis of low-level somatic mosaicism reveals stage and tissue-specific mutational features in human development.

Most somatic mutations that arise during normal development are present at low levels in single or multiple tissues depending on the developmental stage and affected organs. However, the effect of human developmental stages or mutations of different organs on the features of somatic mutations is still unclear. Here, we performed a systemic and comprehensive analysis of low-level somatic mutations using deep whole-exome sequencing (average read depth ~500×) of 498 multiple organ tissues with matched controls from 190 individuals. Our results showed that early clone-forming mutations shared between multiple organs were lower in number but showed higher allele frequencies than late clone-forming mutations [0.54 vs. 5.83 variants per individual; 6.17% vs. 1.5% variant allele frequency (VAF)] along with less nonsynonymous mutations and lower functional impacts. Additionally, early and late clone-forming mutations had unique mutational signatures that were distinct from mutations that originated from tumors. Compared with early clone-forming mutations that showed a clock-like signature across all organs or tissues studied, late clone-forming mutations showed organ, tissue, and cell-type specificity in the mutation counts, VAFs, and mutational signatures. In particular, analysis of brain somatic mutations showed a bimodal occurrence and temporal-lobe-specific signature. These findings provide new insights into the features of somatic mosaicism that are dependent on developmental stage and brain regions.

Prevalence and Risk Factors of Glaucoma Following Pediatric Cataract Surgery with Primary Implantation in Tertiary Eye Hospital, Bangladesh

Background: Glaucoma is a typical side effect of juvenile cataract surgery. According to various research, it seems to have a bimodal occurrence. In Bangladesh, these difficulties constitute a hardship. Objective: In this study our main aim is to evaluate the prevalence and Risk Factors of Glaucoma Following Pediatric Cataract Surgery with Primary Implantation in Tertiary Eye Hospital. Method: This cross-sectional study was carried out at tertiary eye hospital, Bangladesh from August 2021 to June 2022. Where a total of 200 children who underwent unilateral or bilateral cataract surgery with primary IOL implantation in the first year of their life. All eyes presenting with an isolated cataract or an anterior form of persistence of fetal vasculature not requiring posterior vitrectomy or a moderate microphthalmia allowing primary IOL implantation and with a follow-up of >1year were included in the study. Results: During the study, 70% were female and majority were belong to 7-12 years age group, 55%. According to Intraoperative, and Postoperative Characteristics of study group where bilateral cataract was seen in 45% cases followed by 49% cases were capsular bag, 37% cases were sulcus, 46% used trypan bag. Comparing the SG group to the group that did not develop glaucoma, follow-up time was longer (mean 7,5 vs 5.6 years, P<.001), age at surgery was lower (mean 4 vs 5.0 years; P¼.045), reintervention was more frequent (P<.001), and trypan blue was used more frequently (P¼.008). In univariate analysis, the following factors were significantly associated with an increased risk of SG: axial length<16.5 mm, bilateral cataract, perioperative use of trypan blue, additional surgical procedures, and younger age at surgery. Conclusion: We may infer that the risk of SG increases with time, and that SG appears to have a bimodal occurrence, with an estimated linear incidence rate each year. Follow-up should begin quickly after surgery and last for a long time, and clinicians ......

Neoproterozoic copper-gold mineralization in the Amani area, southwestern Tanzania

The Amani area in southwestern Tanzania contains several prospects where primary Cu-Au mineralization occurs at surface, the most noteworthy of these being the Amani Hills and Mpanga Hill prospects. At the Amani Hills prospect, structurally-controlled gold mineralization is hosted in quartz-muscovite schists of the Amani Group and minor high-grade gneisses belonging to the Kabelege Group. Here, quartz-carbonate veins contain pyrite-pyrrhotite-chalcopyrite, with free-milling gold occurring predominantly in quartz and along sulphide grain boundaries. These veins are associated with sericite-epidote-albite alteration of the wallrocks. At the Mpanga Hill prospect, Cu ± Au mineralization is hosted within impure micaceous marbles of the Rafiki Group. At this prospect, both the sulphidised carbonate host rocks and quartz-carbonate veins contain chalcopyrite, bornite and pyrite assemblages, with accessory phases of Au ± Pb ± Zn ± Ag ± Bi ± Se. Fluid inclusion microthermometry indicate that auriferous veins at both prospects record a bimodal occurrence of early low-temperature and low-salinity (≤23.2 wt% NaCl eq.) fluids that are overprinted by later, high temperature and hypersaline fluids (32.8 – 54 wt% NaCl eq.). These ore-forming fluids contain H2O-NaCl ± CO2 ± CH4 compositions and were trapped at near-lithostatic to supralithostatic conditions of 330 – 400 °C and 1.7 – 6.9 kbar. These hydrothermal fluids were likely variably sourced and were focussed along kilometre-scale brittle-ductile reverse shear zones in the Amani area, where fluid-rock interactions led to Cu-Au mineralization. 40Ar/39Ar dating of muscovite constrained the timing of copper – gold mineralization in the Amani area to between c. 550 – 600 Ma. Mineralization is therefore related to the Pan-African aged Kuunga orogeny, which resulted from the collision between the Tanzania Craton and Bangweulu Block during the assembly of supercontinent Gondwana. The new findings presented in this study highlight the exploration potential of copper – gold mineralization along large-scale Proterozoic shear zones in the underexplored and overlooked Upangwa terrane of southwestern Tanzania.

Petrogenesis of the ca. 820–810 Ma felsic volcanic rocks in the Bikou Group: Implications for the tectonic setting of the western margin of the Yangtze Block

The petrogenesis of Neoproterozoic igneous rocks at the northwestern margin of the Yangtze Block and their tectonic setting are controversial. Here we present whole–rock major and trace elements and Nd–Hf isotopic data for felsic volcanic rocks from the Bikou Group. These ca. 820–810 Ma volcanic rocks consist of dacite and rhyolite with SiO2 ranging from 64.4 to 77.0 wt%. Most rocks show decreasing P2O5 with increasing SiO2 and Th and have I–type granite affinities (metaluminous volcanic rocks). However, four rhyolites from the lower part of the Bikou Group show A–type granite affinities (alkaline rhyolites), characterized by high 10,000*Ga/Al and FeOt/(FeOt + MgO) ratios and high (Zr + Nb + Ce + Y) contents. The felsic volcanic rocks commonly have relatively high Zr saturation temperature (up to 960 °C) and most of the felsic volcanic rocks have εNd(t) and εHf(t) values lower than the contemporaneous basalts in the Bikou Group, but higher than the basement rocks in the study area. Among them, four alkaline rhyolites have εNd(t) and εHf(t) values higher than the metaluminous volcanic rocks in the lower Bikou Group. We propose that the metaluminous volcanic rocks were likely produced by partial melting of newly underplated basaltic crust, with involvement of different proportions of basement rocks, whereas a two–stage model is proposed for the formation of the alkaline rhyolites, i.e. partial melting of newly underplated basaltic crust forming early granitoids, followed by low pressure partial melting of these granitoids to generate the alkaline rhyolitic magma. Combined with previous studies, the bimodal occurrence of volcanic rocks within the Bikou Group, and the A–type granite affinity of some rhyolites, as well as the presence of ocean island (OIB)–type basalts in the upper part of Bikou Group, suggest an extensional setting. This is consistent with opening of the Kangdian rift basin to the southwest at this time. We thus propose that the ca. 820–810 Ma Bikou bimodal volcanic rocks formed in response to the breakup of the Rodinia supercontinent.

Study of Mechanical Degradation and Microstructural Characterization in a Ni-Based Superalloy Component of a Gas Turbine

The microstructural characterization of a blade made of Ni-based superalloy was carried out and discussed. The blade was removed from service, of a gas turbine, due to preventive maintenance. This component was studied on different cross sections according to the surface temperature obtained by ANSYS software. The cross sections were characterized by Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and High Resolution Scanning Electron Microscopy (HR-SEM). It was determined that the maximum value of total deformation is 0.001717 mm, located in the surface upper section of the blade, which not correspond to the section with the highest value of temperature calculated with ANSYS software. These results were consistent with the rafted microstructure observed at the upper region of the blade. Microcavities close to the MC carbides with a size of about 40x10-6 m were also observed. The mechanical behavior of the Ni-based superalloy was studied by Rockwell Hardness testing (RHT). So, morphological changes were identified in the occurrence of the strengthening precipitated, γ', according to the operating conditions: stress and temperature. The average radius of the γ' precipitated was obtained by computer image analysis using ImageJ software. No clear relationship was found between the hardness values obtained and the coarsened γ' precipitated. A bimodal occurrence of coarsened γ' particles was identified distributed through γ matrix by HR-SEM. Thus, this study was carried out with the purpose to identify the critical parameters that promote microstructural changes in the Ni-based superalloy and therefore affect the mechanical behavior in this turbine blade.

Ainda Existe Espaço para o Tratamento Conservador nas Fraturas Complexas da Diáfise do Úmero?

As fraturas da diáfise do úmero representam cerca de 1 a 3% de todas as fraturas, e cerca de 20% das fraturas umerais. A maioria das fraturas da diáfise do úmero, nomeadamente as oblíquas longas e as cominutivas, pode ser tratada conservadoramente, porém a tendência atual vai no sentido do tratamento cirúrgico, mesmo nas fraturas que se obtinham bons resultados com o tratamento não cirúrgico. O presente trabalho descreve o bom resultado diante de um tratamento conservador numa fratura diafisária complexa do úmero, demonstrando ainda existir espaço para o tratamento não cirúrgico, e discute a importância da relação médico-doente diante diversas opções terapêuticas.

Clinical profile of adults with Guillain Barre Syndrome in North-West Rajasthan, India

Background: Guillain Barre Syndrome is a heterogenous symptom complex and an important cause of acute flaccid paralysis in children as well as adults. This study was conducted to see the clinical profile of adults admitted with Guillain Barre Syndrome. Methods: This prospective study was conducted in the department of medicine and neurology of S. P. Medical College and A.G. Hospitals, Bikaner, Rajasthan, India. Clinical diagnosis of Guillain Barre Syndrome was based on proposed criteria. Clinical data of 30 such patients were analysed. Results: In this part of India, Guillain Barre Syndrome is common in early decades and second peak is seen in 4 th decade. Male to female ratio was 3.28:1. 70% patients were from rural area. Maximum number of cases came in month of May followed by April, March, July, 23.33%, 16.66%, 13.33%, 13.33% respectively. No patient came in January and October. Preceeding illness was present in 73.3% of cases. Neurological examination showed that 63.33% cases presented with quadriparesis, 50% had cranial nerve involvement, 36.6% cases had paraparesis only, 36.6% had autonomic instability. Conclusions: In this part of Rajasthan, Guillain Barre Syndrome has bimodal occurrence with male preponderance. Commoner in rural population. March to July found common months of occurrence of disease. Most patients have antecedent illness and quadriparesis is commonest presentation.

Locking plate fixation of distal femoral fractures is a challenging technique: a retrospective review.

Distal femoral fractures have typically a bimodal occurrence: in young people due to a high-energy trauma and in older people related to a low-energy trauma. These fractures are associated to a very high morbidity and mortality in elderly. Distal femoral fractures might be treated with plates, intramedullary nails, external fixations, and prosthesis. However, difficulties in fracture healing and the rate of complications are important clinical issues. The purpose of this retrospective review was to present our experience in treatment of distal femoral fracture in a sample of older people in order to evaluate the technical pitfalls and strategies used to face up the fractures unsuccessfully treated with locking plates. We included people aged more than 65 years, with a diagnosis of distal femoral fracture, treated with locking plates. We considered 'unsuccessfully treated' the cases with healing problems or hardware failures. Of the 12 patients (9 females and 3 males; mean aged 68.75 ± 3.31 years) included, we observed 3 'unsuccessfully cases', 2 due to nonunions and 1 due to an early hardware failure, all treated using a condylar blade plate with a bone graft. One patient obtained a complete fracture healing after 1 year and in the other cases there was a nonunion. We observed as most common technical pitfalls: inadequate plate lengthening, fracture bridging, and number of locking screws. The use of locking plates is an emerging technique to treat these fractures but it seems more challenging than expected. In literature there is a lack of evidences about the surgical management of distal femoral fractures that is still an important challenge for the orthopaedic surgeon that has to be able to use all the fixation devices available.

Parameterization of a bucket model for soil-vegetation-atmosphere modeling under seasonal climatic regimes

Abstract. We investigate the potential impact of accounting for seasonal variations in the climatic forcing and using different methods to parameterize the soil water content at field capacity on the water balance components computed by a bucket model (BM). The single-layer BM of Guswa et al. (2002) is employed, whereas the Richards equation (RE) based Soil Water Atmosphere Plant (SWAP) model is used as a benchmark model. The results are analyzed for two differently-textured soils and for some synthetic runs under real-like seasonal weather conditions, using stochastically-generated daily rainfall data for a period of 100 years. Since transient soil-moisture dynamics and climatic seasonality play a key role in certain zones of the World, such as in Mediterranean land areas, a specific feature of this study is to test the prediction capability of the bucket model under a condition where seasonal variations in rainfall are not in phase with the variations in plant transpiration. Reference is made to a hydrologic year in which we have a rainy period (starting 1 November and lasting 151 days) where vegetation is basically assumed in a dormant stage, followed by a drier and rainless period with a vegetation regrowth phase. Better agreement between BM and RE-SWAP intercomparison results are obtained when BM is parameterized by a field capacity value determined through the drainage method proposed by Romano and Santini (2002). Depending on the vegetation regrowth or dormant seasons, rainfall variability within a season results in transpiration regimes and soil moisture fluctuations with distinctive features. During the vegetation regrowth season, transpiration exerts a key control on soil water budget with respect to rainfall. During the dormant season of vegetation, the precipitation regime becomes an important climate forcing. Simulations also highlight the occurrence of bimodality in the probability distribution of soil moisture during the season when plants are dormant, reflecting that soil, it being of coarser or finer texture, can be preferentially in either wetter or drier states over this period.

Detecting bimodality in plant size distributions and its significance for stand development and competition

Bimodal distributions in plant size, with a major mode of small and minor mode of large-size plants, have been reported for a range of single species stands in different growing conditions. The occurrence of bimodality has implications for the dynamics of competition within a stand and potentially for stand productivity. However, deduction of the existence of bimodality has been by visual assessment of histograms of a single measure of plant size which can lead to differences of opinion about its existence. We show that the bivariate distribution of plant height and weight is more informative about stand structure than univariate distributions. We demonstrate how sub-populations of small- and large-size plants can be identified using a bivariate mixture distribution fitted using evolutionary computation. For the multiple datasets we analyse, a bimodal distribution fits in preference to unimodal or trimodal distributions. Small- and large-plant sub-populations, respectively, form a lower and upper canopy. The numbers of plants in these canopies change during stand development and vary with initial spacing, contrary to reports for other species. Early in stand development, large plants show spatial separation between themselves but spatial association with small plants, and as stands develop the number of large plants declines markedly but they remain spatially separated between each other. Bivariate analysis of height and weight, and spatial analysis of individuals of different sizes, provides a more comprehensive description of stand structure than that obtained in previous studies.

Apatite Microstructure and Composition in Manganese Formation of Eastern Ghats, Orissa, India

Apatite grains in a stratabound manganese ore body from Eastern Ghats in Leliguma, Koraput district south Orissa, India were studied under optical and electron microscope. Apatite shows bimodal occurrence: one associated with granite/pegmatitic phase and other with manganese phase, and exhibits different microstructure and composition. Apatite in pegmatitic association (occurring as inclusion in quartz and feldspar) is small in size and occurs as subhedral grains having irregular boundaries and poor in manganese content (MnO: 0.16%). Apatite associated with manganese mineral phases (cryptomelane / romanechite) is mostly euhedral, relatively larger in size, contains higher manganese value, and exhibits some peculiar features like twinning, zoning, overgrowth, and occasionally contains inclusion of quartz and feldspar grains. Apatite grains occurring as inclusions within quartz and feldspar are of hydrothermal origin and formed along with pegmatitic minerals. Such apatite is almost devoid of manganese but relatively enriched in Sr, F and LREE content. The apatite in manganese mineral association formed during supergene process. The apatite of latter generation appears as idiomorphic crystals; contains up to 6.85% of MnO in solid solution and shows relatively higher HREE values. The higher HREE values may be due to its derivation from stratiform Mn-ore bodies and associated granitised rock during remobilization, solution and precipitation of Mn –rich fluid along structurally weak planes resulting in development of a stratabound ore body.

Bentonite chemical features as proxy of late Cretaceous provenance changes: A case study from the Western Interior Basin of Canada

Bentonite beds are fairly common in both marine and terrestrial Upper Cretaceous (Campanian–Maastrichtian) deposits of the Western Interior Basin of western Canada and northwestern United States. A detailed stratigraphic, sedimentologic, geochemical (X-ray fluorescence), and mineralogical (X-ray diffraction) study of twenty-one bentonites from the Puskwaskau and Wapiti formations in the Grande Prairie area (west-central Alberta, Canada) is here presented. Major and trace-element concentrations from altered volcanic ashes document the presence in the study area of predominantly trachyandesitic and rhyolitic volcanogenic products, resulted from intense volcanic arc to within-plate pyroclastic activity. Concentration values of high field strength elements (HFSE) and selected large ion lithophile elements (LILE) (e.g. Nb, Zr, Th, and Y) obtained by X-ray fluorescence spectroscopy strongly support the presence of multiple volcanic sources. Integrated paleoenvironmental and geochemical criteria for provenance determination indicate a bimodal occurrence of basic and acid volcanic products interpreted as reflection of source areas characterized by different tectonic setting and magmatic composition. A comparative analysis of geochemical compositions between Grande Prairie bentonites and 30 known volcanic beds from central and southern Alberta, Manitoba and Montana 1. documents a trend toward more acidic and alkali-depleted volcanic products during the late Campanian–early Maastrichtian interval, and 2. suggests a well constrained stratigraphic and geographic subdivision of the non-marine successions of the foreland basin on the basis of geochemical characteristic of volcanic ash beds. Furthermore, geochemical “fingerprints” of several decimeter to meter thick bentonite beds have been coupled with volcanic ash subsurface signature in order to investigate their role as marker beds. This multiple-approach provides a reliable tool for basin-scale identification and correlation of non-marine sedimentary successions.

A rare cause of secondary hypertension.

A 20-year-old obese man was referred to our hospital with 1-year hypertension and mild hypokalaemia (potassium, 3.3 mmol/l). The ratio of postcaptopril plasma aldosterone concentration (PAC) to plasma renin activity (PRA) was high [25.8 (ng/dl)/0.33 (ng/ml/h) = 77.4]. The PAC postsaline loading test remained high (28.1 ng/dl). The 24-h urinary catecholamines and VMA (vanillyl mandelic acid) were within normal limits. Primary aldosteronism was diagnosed, and a computed tomography disclosed an isodense mass with a maximal diameter of 4 cm over the right adrenal gland (Figure ​(Figure1).1). The patient then underwent right laparoscopic adrenalectomy. Grossly, a well-encapsulated 4.5 × 4.0 × 3.5 cm yellowish tumour with central necrosis was noted. Histologically, the tumour was composed of pleomorphic cells with high-grade nuclei, prominent nucleoli, and >1/3 of the tumour presenting patternless sheets of cells. Furthermore, the mitotic count was >5 in 50 high power fields with atypical mitotic figures (Figure ​(Figure2a2a and b). Adrenocortical carcinoma (ACC) was diagnosed according to the modified Weiss classification system [1]. Subsequent immunohistochemical studies confirmed that the tumour was aldosterone producing (Figure ​(Figure2c2c and d). Two months after the operation, PAC and PRA were 32.7 ng/dl and 25.45 ng/ml/h, respectively, and the patient became normotensive. Fig. 1 Adrenal tumour. Non-contrast CT scan shows an oval tumour, 4 cm in diameter, in the right adrenal region. Fig. 2 Histopathology of adrenocortical carcinoma. (a) Pleomorphic tumour cells form patternless sheets of cells. (b) Tumour cells with eosinophilic cytoplasm, high nuclear grade and atypical mitotic figures (arrows) (haematoxylin and eosin stain, 100×; ... ACCs are rare and account for an estimated 0.05–0.2% of all malignancies [2]. Hormonally functioning tumours occur in ∼50% of ACC patients. Nevertheless, the aldosterone-producing ACC are even rarer. There is a bimodal occurrence by age, with a peak incidence at 4 cm should raise clinical suspicion of adrenocortical malignancy, even at a young age.

Bimodality and hysteresis in systems driven by confined Lévy flights

We demonstrate the occurrence of bimodality and dynamical hysteresis in a system describing an overdamped quartic oscillator perturbed by additive white and asymmetric Lévy noise. Investigated estimators of the stationary probability density profiles display not only a turnover from unimodal to bimodal character but also a change in a relative stability of stationary states that depends on the asymmetry parameter of the underlying noise term. When varying the asymmetry parameter cyclically, the system exhibits a hysteresis in the occupation of a chosen stationary state.

Seasonal Development and Population Fluctuations of Arrowhead Scale, Unaspis yanonensis (Homoptera: Diaspididae), in Citrus orchards in Jeju, Korea

Arrowhead scale, Unaspis yanonensis (Kuwana), feeds on the foliage, stems, and fruits of citrus trees, and causes tree dieback when heavy infestations occur. The objective of this study was to collect basic data to establish seasonal management strategies for U. yanonensis. The abundances of male nymphs and female adults were monitored in unsprayed citrus orchards. The overwintered females started to produce their progenies (1st gen.) from mid-May. The populations of the 1st nymphs in the 1st generation showed a bimodal occurrence pattern, with a 1st larger peak between late May and early June, and a 2nd smaller peak in June. The nymphs in the 2nd generation, which were laid from newly developed females, were observed from late July, and the 1st peak occurred in mid-August, followed by an obscure later peak (the 2nd peak) around late September. The numbers of live females for the overwintered populations began to decrease gradually from early June by the impact of the predacious Chilocorus kuwanae, as well as by natural mortality factors, and dropped to a low level in mid-July. When there were abundant predator attacks, the U. yanonensis female populations sharply decreased from early June and were almost nonexistent in July. New female adults (1st generation adults) appeared from late June and peaked in mid-July. The 2nd generation female adults, consequently, the overwintering generation, occurred from mid- September, and gradually increased to late October. Overall, these results will be useful in terms of management strategies for U. yanonensis in citrus orchards.

Bimodal occurrence of aspartoacylase in myelin and cytosol of brain

The growing use of N-acetylaspartate as an indicator of neuronal viability has fostered interest in the biological function(s) of this unusual amino acid derivative. In considering the various physiological roles that have been proposed for this relatively abundant molecule one is obliged to take into account its unusual metabolic compartmentalization, according to which synthesis and storage occur in the neuron and hydrolytic cleavage in the oligodendrocyte. The latter reaction, catalyzed by aspartoacylase (ASPA), produces acetyl groups plus aspartate and has been proposed to occur in both soluble and membranous subfractions of white matter. Our study supports such bimodal occurrence and we now present immunoblot, proteomic, and biochemical evidence that the membrane-bound form of ASPA is intrinsic to purified myelin membranes. This was supported by a novel TLC-based method for the assay of ASPA. That observation, together with previous demonstrations of numerous lipid-synthesizing enzymes in myelin, suggests utilization of acetyl groups liberated by myelin-localized ASPA for lipid synthesis within the myelin sheath. Such synthesis might be selective and could explain the deficit of myelin lipids in animals lacking ASPA.

Fluid inclusion record of the hypozonal orogenic Renco gold deposit (Zimbabwe) during the retrograde P–T evolution

The hypozonal Renco gold deposit in Zimbabwe is hosted by a shear zone system cutting granulite-facies enderbites. The geologic history of the region testifies to a polyphase tectonometamorphic evolution. Along the exhumation path, three major events are notable during which fluid inclusions could have been formed. Detailed petrographic work and comparison of calculated isochores with the P–T evolution, allows correlation of inclusion formation with the tectonometamorphic evolution. Fluid inclusions in the mineralized lithologies of the Renco gold mine are dominated by carbonic inclusions of highly variable densities. The high density carbonic inclusions are related to the peak of metamorphism. Their lower density counterparts show a bimodal occurrence. Some are re-equilibrated equivalents of the inclusions trapped at peak metamorphic conditions whereas others clearly post-date this event and are related to gold mineralization. The latter type of carbonic inclusions occurs in distinct microstructural domains of quartz crystals (i.e. subgrain-, grain boundaries). Therefore, these inclusions are interpreted to have formed because of selective trapping of CO2 from a mixed H2O–CO2 low salinity ore fluid. All the aqueous inclusions observed at Renco can be attributed to a late, retrograde greenschist-facies overprint.

Comparison of Aerosol Single Scattering Albedos Derived by Diverse Techniques in Two North Atlantic Experiments

Aerosol single scattering albedo v (the ratio of scattering to extinction) is important in determining aerosol climatic effects, in explaining relationships between calculated and measured radiative fluxes, and in retrieving aerosol optical depths from satellite radiances. Recently, two experiments in the North Atlantic region, the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2), determined aerosol v by a variety of techniques. The techniques included fitting of calculated to measured radiative fluxes; retrievals of v from skylight radiances; best fits of complex refractive index to profiles of backscatter, extinction, and size distribution; and in situ measurements of scattering and absorption at the surface and aloft. Both TARFOX and ACE-2 found a fairly wide range of values for v at midvisible wavelengths (;550 nm), with 0.85 # vmidvis # 0.99 for the marine aerosol impacted by continental pollution. Frequency distributions of v could usually be approximated by lognormals in vmax 2 v, with some occurrence of bimodality, suggesting the influence of different aerosol sources or processing. In both TARFOX and ACE-2, closure tests between measured and calculated radiative fluxes yielded best-fit values of vmidvis of 0.90 6 0.04 for the polluted boundary layer. Although these results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., thermal offsets, unknown gas absorption). The other techniques gave larger values for vmidvis for the polluted boundary layer, with a typical result of vmidvis 5 0.95 6 0.04. Current uncertainties in v are large in terms of climate effects. More tests are needed of the consistency among different methods and of humidification effects on v.

Metabasites and Charnockites as Bimodal Occurrence Around Narsipatnam Area in the Eastern Ghats Granulite Belt, India

Amphibolites included in the Ossa-Morena/Central Iberian suture of SW Iberia offer the opportunity of investigating the subduction and collision events, followed by exhumation, which affected this major boundary during the Variscan orogeny. This suture contact is marked by a band of highly deformed and metamorphosed rocks, namely, the Central Unit. The main deformation affecting this unit is a ductile shearing that produced an intense planar–linear fabric. This shearing has two components: a dominant left lateral one and a subordinate dip-slip normal one, which can be taken to be responsible for the exhumation of this unit in Devonian–Carboniferous times.The rocks studied in the present paper are garnet-free amphibolites and garnet-bearing amphibolites intercalated between gneisses. They appear as lens-, dike- or elongated-shaped bodies, their thickness ranging between a metre and several hectometres. The investigation of their metamorphic evolution has been carried out by computing phase diagram sections (pseudosections) for specified bulk rock compositions. This method enables us to achieve a twofold goal: (i) to model the P–T path undergone by the rocks during the metamorphism in question, and (ii) to assess the influence of the fluid phase abundance on the formation and the preservation of the mineral assemblages as well as on the density decrease of the rocks during exhumation.The metabasites of the Central Unit underwent a metamorphic evolution, characterized by an initial eclogite facies event with peak pressures around 1.9 GPa and temperatures about 550 °C, during which grossular-rich garnet and jadeite-rich clinopyroxene coexisted with chlorite, glaucophane, and paragonite. The former two hydrous minerals disappeared during the subsequent stage, characterised by a slight decompression with strong heating. At the peak temperature (≈725 °C and 1.6 GPa), important amounts of water were released owing to paragonite breakdown. This water produced (i) the formation of large amounts of amphibole coexisting with jadeite-rich clinopyroxene and sodium-rich plagioclase, and (ii) a sharp density decrease of the rocks, which must have contributed to their exhumation. Fast uplift is consistent with the deduced sharp isothermal decompression (1.18 GPa). This was, in turn, followed by simultaneous strong cooling and decompression (≈455 °C and 0.3 GPa), which produced the calcium enrichment observed in plagioclase and the jadeite decrease and diopside enrichment in clinopyroxene. This final retrograde evolution occurred at fluid absent conditions, thus allowing the preservation of previously formed high-pressure assemblages.