The Out-of-India hypothesis: What do molecules suggest?

The remarkable geological and evolutionary history of peninsular India has generated much interest in the patterns and processes that might have shaped the current distributions of its endemic biota. In this regard the Out of India hypothesis, which proposes that rafting peninsular India carried Gondwanan forms to Asia after the break-up of Gondwana super continent, has gained prominence. Here we have reviewed molecular studies undertaken on a range of taxa of supposedly Gondwanan origin to better understand the Out-of-India scenario. This re-evaluation of published molecular studies indicates that there is mounting evidence supporting Out-of-India scenario for various Asian taxa. Nevertheless, in many studies the evidence is inconclusive due to lack of information on the age of relevant nodes. Studies also indicate that not all Gondwanan forms of peninsular India dispersed out of India. Many of these ancient lineages are confined to peninsular India and therefore are relict Gondwanan lineages. Additionally for some taxa an Into India rather than Out-of-India scenario better explains their current distribution. To identify the Out-of-India component of Asian biota it is imperative that we understand the complex biogeographical history of India. To this end, we propose three oversimplified yet explicit phylogenetic predictions. These predictions can be tested through the use of molecular phylogenetic tools in conjunction with palaeontological and geological data.

Microwave absorption studies of iron encapsulating carbon-polymer nanocomposite films

Iron encapsulated carbon nanoparticle polyvinyl chloride composite films have been prepared by solvent mixing and drying method. The films were characterized by scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM). A 5 nm thin graphitic carbon coating is observed on cubic Fe nanoparticles. The microwave absorption studies by wave guide technique in the Ka band range showed highest electromagnetic interference shielding efficiency of 18dB on a 300 micron thick film. The shielding efficiency depends on weight % of the filler in the composite. The data obtained for different films indicate that these lightweight materials are good candidates for potential electromagnetic interference shielding applications.

Effect of increased manganese addition and mould type on the slurry erosion characteristics of Cr-Mn iron systems

The wear resistance of high chromium iron is well recorded. However, the same is not the case as regards the use of manganese at higher percentages in high chromium irons and its influence on wear behaviour. Hence, this work highlights the slurry wear characteristics of chromium 16–19%) iron following the introduction of manganese at two levels i.e. 5 and 10%. It is known that the wear properties are dictated by the microstructural features. To alter the structure, the cooling rate of casting has been varied by adopting two different types of moulds (i.e. sand and metal) and subsequently subjecting to thermal treatment. The as-cast and heat treated samples are examined for microstructure and then evaluated for hardness and slurry erosion properties. As the manganese content is increased from 5 to 10%, the hardness showed a decrease in value both in the as-cast and heat treated conditions. The slurry erosion loss, expectedly, showed an increase irrespective of the sample condition (i.e. mould type/heat treatment adopted). The findings are corroborated with the microstructural features obtained through optical and scanning electron microscopy.

Iron(III) Schiff base complexes of arginine and lysine as netropsin mimics showing AT-selective DNA binding and photonuclease activity

Iron(III) complexes [Fe(L)(2)]Cl (1-3), where L is monoanionic N-salicylidene-arginine (sal-argH for 1), hydroxynaphthylidene-arginine (nap-argH for 2) and N-salicylidene-lysine (sal-lysH for 3), were prepared and their DNA binding and photo-induced DNA cleavage activity studied. Complex 3 as its hexafluorophosphate salt [Fe(sal-lysH)(2)](PF6)center dot 6H(2)O (3a) was structurally characterized by single crystal Xray crystallography. The crystals belonged to the triclinic space group P-1. The complex has two tridentate ligands in FeN2O4 coordination geometry with two pendant cationic amine moieties. Complexes 1 and 2 with two pendant cationic guanidinium moieties are the structural models for the antitumor antibiotics netropsin. The complexes are stable and soluble in water. They showed quasi-reversible Fe(III)/Fe(II) redox couple near 0.6 V in H2O-0.1 M KCl. The high-spin 3d(5)-iron(III) complexes with mu(eff) value of similar to 5.9 mu(B) displayed ligand-to-metal charge transfer electronic band near 500 mm in Tris-HCl buffer. The complexes show binding to Calf Thymus (CT) DNA. Complex 2 showed better binding propensity to the synthetic oligomer poly(dA)center dot poly(dT) than to CT-DNA or poly(dG)center dot poly(dC). All the complexes displayed chemical nuclease activity in the presence of 3-mercaptopropionic acid as a reducing agent and cleaved supercoiled pUC19 DNA to its nicked circular form. They exhibited photo-induced DNA cleavage activity in UV-A light and visible light via a mechanistic pathway that involves the formation of reactive hydroxyl radical species. (C) 2010 Elsevier Inc. All rights reserved.

The effects of manganese content and mould size on abrasion and slurry erosion behaviour of chromium-manganese iron systems investigated by positron lifetime spectroscopy

Abrasion and slurry erosion behaviour of chromium-manganese iron samples with chromium (Cr) in the range similar to 16-19% and manganese (Mn) at 5 and 10% levels have been characterized for hardness followed by microstructural examination using optical and scanning electron microscopy. Positron lifetime studies have been conducted to understand the defects/microporosity influence on the microstructure. The samples were heat treated and characterized to understand the structural transformations in the matrix. The data reveals that hardness decreased with increase in Mn content from 5 to 10% in the first instance and then increase in the section size in the other case, irrespective of the sample conditions. The abrasion and slurry erosion losses show increase with increase in the section size as well as with increase in Mn content. The positron results show that as hardness increases from as-cast to heat treated sample, the positron trapping rate and hence defect concentration showed opposite trend as expected. So a good correlation between defects concentration and the hardness has been observed. These findings also corroborate well with the microstructural features obtained from optical and scanning electron microscopy. (C) 2009 Elsevier B. V. All rights reserved.

Field performance of in-service cast iron gas reticulation pipe buried in reactive clay

Field instrumentation of an in-service cast iron gas pipe buried in a residential area is detailed in this paper. The aim of the study was to monitor the long-term pipe behavior to understand the mechanisms of pipe bending in relation to ground movement as a result of seasonal fluctuation of soil moisture content. Field data showed that variation of soil temperature, suction, and moisture content are closely related to the prevailing climate. Change of soil temperature is generally related to the ambient air temperature, with a variation of approximately −3°C −3°C per meter depth from the ground surface in summer (decrease with depth) and winter (increase with depth). Seasonal cyclic variation in moisture content was observed with maxima in February and March, and a minimum around September. The pipe top was under tensile strain during summer and subsequently subjected to compressive strain as soil swelling occurred as a result of increase in moisture content. The study suggests that downward pipe bending occurs in summer because of soil shrinkage, while upward pipe bending occurs in winter when the soil swells.

Clinical reasoning: The relative contribution of identification, interpretation and hypothesis errors to misdiagnosis

The aim of this study was to identify and describe the types of errors in clinical reasoning that contribute to poor diagnostic performance at different levels of medical training and experience. Three cohorts of subjects, second- and fourth- (final) year medical students and a group of general practitioners, completed a set of clinical reasoning problems. The responses of those whose scores fell below the 25th centile were analysed to establish the stage of the clinical reasoning process - identification of relevant information, interpretation or hypothesis generation - at which most errors occurred and whether this was dependent on problem difficulty and level of medical experience. Results indicate that hypothesis errors decrease as expertise increases but that identification and interpretation errors increase. This may be due to inappropriate use of pattern recognition or to failure of the knowledge base. Furthermore, although hypothesis errors increased in line with problem difficulty, identification and interpretation errors decreased. A possible explanation is that as problem difficulty increases, subjects at all levels of expertise are less able to differentiate between relevant and irrelevant clinical features and so give equal consideration to all information contained within a case. It is concluded that the development of clinical reasoning in medical students throughout the course of their pre-clinical and clinical education may be enhanced by both an analysis of the clinical reasoning process and a specific focus on each of the stages at which errors commonly occur.

Ternary Iron(III) complex showing photocleavage of DNA in the photodynamic therapy window

A new ternary iron(III) complex [FeL(dpq)] containing dipyridoquinoxaline (dpq) and 2,2-bis(3,5-di-tert-butyl-2-hydroxybenzyl)aminoacetic acid (H3L) is prepared and structurally characterized by X-ray crystallography. The high-spin complex with a FeN3O3 core shows a quasi-reversible iron(III)/iron(II) redox couple at -0.62 V (vs SCE) in DMF/0.1 M TBAP and a broad visible band at 470 nm in DMF/Tris buffer. Laser photoexcitation of this phenolate (L)-to-iron(III) charge-transfer band at visible wavelengths including red light of >= 630 nm leads to cleavage of supercoiled pUC19 DNA to its nicked circular form via a photoredox pathway forming hydroxyl radicals.

Size-dependent magnetic properties of iron carbide nanoparticles embedded in a carbon matrix

Here we report on the magnetic properties of iron carbide nanoparticles embedded in a carbon matrix. Granular distributions of nanoparticles in an inert matrix, of potential use in various applications, were prepared by pyrolysis of organic precursors using the thermally assisted chemical vapour deposition method. By varying the precursor concentration and preparation temperature, compositions with varying iron concentration and nanoparticle sizes were made. Powder x-ray diffraction, transmission electron microscopy and Mossbauer spectroscopy studies revealed the nanocrystalline iron carbide (Fe3C) presence in the partially graphitized matrix. The dependence of the magnetic properties on the particle size and temperature (10 K < T < 300 K) were studied using superconducting quantum interference device magnetometry. Based on the affect of surrounding carbon spins, the observed magnetic behaviour of the nanoparticle compositions, such as the temperature dependence of magnetization and coercivity, can be explained.

NMR study of internal motions in certain iron group fluosilicates

NMR study of ferrous fluosilicate hexahydrate indicated the presence of motion of both proton and fluorine nuclei. Only a single narrow line was observed for protons for any arbitrary orientation of a single crystal with respect to the applied magnetic field. This can be interpreted in terms of a phase-correlated flip motion of the interproton vectors between two disordered orientations or in terms of a hindered rotation of the Fe(H2O) 6 octahedron about the fourfold axes, together with the flip motion. The fluorine second moment indicated that the SiF6 octahedron also is undergoing reorientation. The temperature variation of the powder linewidth showed a transition around 195°K and led to rather low values for the potential barriers hindering the motions. No significant temperature variation of the linewidth was observed for hexahydrated cobalt fluosilicate in the temperature range between 90°K and room temperature. Similar observations in a powder sample of tetrahydrated copper fluosilicate also showed the presence of internal motions. The linewidth transition in this case took place at about 220°K and was found to be rather abrupt. The potential barrier for the motion was found to be relatively high.

Composition of aqueous solutions in equilibrium with sulfides and oxides of iron at 3500°C

Solutions of potassium chloride (pH-buffered and 1-molat) equilibrated at 350°C with pyrrhotite, pyrite, and magnetite contained approximately 1 millimole of reduced sulfur and less than 0.1 millimole of oxidized sulfur per kilogram. Similar solutions equilibrated with pyrite, magnetite, and hematite contained approximately 1 millimole of reduced sulfur, but 3 to 6 millimoles of oxidized sulfur per kilogram. Both types of solutions contained less than 0.1 millimole of iron per kilogram at pH ≥ 6 and approximately 100 millimoles per kilogram at pH 2.

Control of nitrate reductase by iron in Neurospora crassa

Iron deficiency has been found to occur in Neurospora crassa grown in sole nitrate medium, even when levels of iron, normal with respect to the usual ammonium nitrate medium, were provided. Under this condition, mycelial nitrate reductase and catalase levels were high, there was inhibition of growth, and there was accumulation of an iron-binding compound and nitrite in the culture filtrate. These were counteracted by increasing the iron level of the sole nitrate medium, except that the catalase level increased still further. Evidence is presented for the control of nitrate reductase by iron.

Studies on iron metabolism in Neurospora crassa

Neurospora crassa Em 5297a secretes an ironbinding compound (X) when grown under conditions of iron deficiency. Decreasing the concentration of iron in the medium results in an increase of X and a corresponding fall in catalase activity. Under iron-deficient conditions the production of X precedes the fall in catalase activity. The iron complex of the iron-binding compound (XFe) can act as a good iron source to the organism to maintain normal growth and catalase activity, even though the iron is held very firmly in the chemical sense. While ferrichrome is as potent as XFe, as an iron source to N. crassa, ferrichrome A and ferric acethydroxamate are only partially beneficial. XFe, when provided as the sole iron source, also influences nonheme iron enzyme activities like succinic dehydrogenase and aconitase. XFe is permeable to N. crassa mycelia and is incorporated at a much faster rate compared with that from a simple chelate such as ferric citrate.