Urease activity in soils

Summary The availability of Ca from different levels of gypsum and calcium carbonate in a non-saline sodic soil has been investigated. Different levels of tagged gypsum (Ca⁴⁵SO₄.2H₂O) and calcium carbonate (Ca⁴⁵CO₃) (i.e. 0, 25, 50, 75, and 100 per cent of gypsum requirement) were mixed thoroughly in 3.5 Kg of a non-saline alkali soil (ESP, 48.4; ECe, 2.68 millimhos/cm). Dhaincha (Sesbania aculeata) — a legume and barley (Hordeum vulgare L.) — a cereal were taken as test crops. Increasing levels of gypsum caused a gradual increase in the yield of dry matter, content of Ca and K in the plant tops and Ca:Na and (Ca+Mg):(Na+K) ratios in both the crops. Application of calcium carbonate caused a slight increase in the dry matter yield, content of Ca and Mg and Ca:Na and (Ca+Mg):(Na+K) ratios in barley, however, in case of dhaincha there was no such effect. Gypsum application caused a gradual decrease in the content of Na and P in both the crops. Total uptake of Ca, Mg, K, N and P per pot increased in response to gypsum application. The effect of calcium carbonate application on the total uptake of these elements was much smaller on dhaincha, but in barley there was some increasing trend.Increasing application of tagged gypsum and calcium carbonate caused a gradual increase in the concentration and per cent contribution of source Ca in both the crops, although, the rate of increase was considerably more in dhaincha. The availability of Ca from applied gypsum was considerably more than that from applied calcium carbonate. Efficiency of dhaincha to utilize Ca from applied sources was considerably more (i.e. about five times) than that of barley     

Magnesium influx in dialyzed squid axons

Summary The influx of magnesium from seawater into squid giant axons has been measured under conditions where internal solute control in the axon was maintained by dialysis. Mg influx is smallest (1 pmol/cm² sec) when both Na and ATP have been removed from the axoplasm by dialysis. The addition of 3mm ATP to the dialysis fluid gives a Mg influx of 2.5 pmol/cm² sec while the addition of [Na] _i and [ATP] _i gives 3 pmol/cm² sec as a value for Mg influx; this corresponds well with fluxes measured in intact squid giant axons.The Mg content of squid axons is 6 mmol/kg axoplasm; this is unaffected by soaking axons in Li or Na seawater for periods of up to 100 min.     

Evolution of a Rhythmic Lamination in the Organophosphatic Shells of Brachiopods

The secondary layer of organophosphatic-shelled brachiopods consists of stratiform laminae in glycosaminoglycans (GAGs), pervaded by canals with chitinous walls. The laminae are composed of various aggregates of protein-coated granules of apatite, 4–8 nm in size, 10 or so soluble proteins, β-chitinous meshes and sheets, and a possibly proteinaceous actin-like network. The succession is disposed in rhythmic sets grading between predominantly apatitic and wholly membranous laminae. The most conspicuous set consists of apatitic rods (baculi) in trellised arrays associated with laminae of compacted mosaics and spherules of apatite. The baculi are composed of mosaics accreting around axial fibrous proteins; apatitic aggregates are also scattered throughout the GAGs and accrete on proteinaceous networks and chitinous meshes. Baculi, subtended between two compact laminae, first appeared in Early Cambrian times and are a synapomorphy of lingulides. Subsequently, the secretion of one or another of the compact laminae was suppressed in the two surviving clades, with sets of the lingulid Glottidia and the discinids, respectively, grading inwardly from, and to, compact laminae. Suppression of baculate secretion also occurred in the dorsal valve of living Discinisca while, in Lingula, baculi have been replaced by botryoidal aggregates of mosaics at least since Carboniferous times.     

Effect of farm yard manure on the availability of Ca from Ca45CO3 in a sodic soil (ESP 77.7)

Summary Application of FYM caused a gradual increase in the dry weight of dhaincha (Sesbania aculeata Pers.) tops. It also caused a gradual increase in the content of Mg and K and a decrease in the content of Ca, Na, N and P in dhaincha tops. Increase in Ca: Na ratio was more steeper than (Ca+Mg): (Na+K) ratio. Total uptake of Ca, Mg, K, N and P increased and that of Na decreased in response to FYM. Contribution of Ca from Ca⁴⁵CO₃ did not differ much at different levels of FYM and it was less than 6 per cent of total Ca in plant tops in all the treatments. re]19721017     

Composition of the early Oligocene ocean from coral stable isotope and elemental chemistry

A sectioned and polished specimen of the coral Archohelia vicksburgensis from the early Oligocene Byram Formation (～30 Ma) near Vicksburg, Mississippi, reveals 12 prominent annual growth bands. Stable oxygen isotopic compositions of 77 growth‐band‐parallel microsamples of original aragonite exhibit well‐constrained fluctuations that range between ?2.0 and ?4.8. Variation in δ¹⁸O of coral carbonate reflects seasonal variation in temperature ranging from 12 to 24 °C about a mean of 18 °C. These values are consistent with those derived from a bivalve and a fish otolith from the same unit, each using independently derived palaeotemperature equations. Mg/Ca and Sr/Ca ratios were determined for 40 additional samples spanning five of the 12 annual bands. Palaeotemperatures calculated using elemental‐ratio thermometers calibrated on modern corals are consistently lower; mean temperature from Mg/Ca ratios are 12.5 ± 1 °C while those from Sr/Ca are 5.8 ± 2.2 °C. Assuming that δ¹⁸O‐derived temperatures are correct, relationships between temperature and elemental ratio for corals growing in today's ocean can be used to estimate Oligocene palaeoseawater Mg/Ca and Sr/Ca ratios. Calculations indicate that early Oligocene seawater Mg/Ca was ～81% (4.2 mol mol^?1) and Sr/Ca ～109% (9.9 mmol mol^?1) of modern values. Oligocene seawater with this degree of Mg depletion and Sr enrichment is in good agreement with that expected during the Palaeogene transition from ‘calcite’ to ‘aragonite’ seas. Lower Oligocene Mg/Ca probably reflects a decrease toward the present day in sea‐floor hydrothermal activity and concomitant decrease in scavenging of magnesium from seawater. Elevated Sr/Ca ratio may record lesser amounts of Oligocene aragonite precipitation and a correspondingly lower flux of strontium into the sedimentary carbonate reservoir than today.     

Availability of Ca from Ca45SO4 in a highly saline-sodic soil

Summary Application of gypsum (tagged Ca⁴⁵SO₄.2H₂O) caused a considerable increase in dry matter yield and content of Ca, Ca⁴⁵, Mg and K and Ca:Na and (Ca+Mg): (Na+K) ratios and a decrease in the content of Na, N and P in dhaincha tops. There was a considerable increase in the total uptake of Ca, Mg, Na, K, N, P and Ca⁴⁵ by plant tops in response to gypsum. Contribution of Ca from applied Ca⁴⁵SO₄ varied from 78.3 to 84.7 per cent of the total Ca in plant tops, whereas, its uptake from this source varied from 52.18 to 98.73 me per 100 g plant tops. re]19720705     

Cationic responses of organs and haemolymph of Biomphalaria pfeifferi (Krauss), Biomphalaria glabrata (Say) and Helisoma trivolvis (Say) (Gastropoda: Planorbirdae) to cationic alterations of the medium

The cationic responses of haemolymph, mantle collar, headfoot, gut + digestive diverticulum and ovotestis + albumin gland of three planorbids to cationic changes in the media are explored. Body organs exhibited cationic homeostasis, although attained with difficulty under very low Ca : Mg and Ca : Na ratios. Haemolymph imbalances were obtained at very low calcium concentrations and at very low Ca : Mg and Ca : Na ratios in the medium; this may be linked to competition for Ca²⁺ uptake sites in the epithelium by Mg²⁺ and possibly Na⁺ ions.Fecundity and shell growth in relation to calcium concentrations and to Ca : Mg and Ca : Na ratios are examined.Normal internal cationic levels, under optimal conditions, were obtained for each species. Significant interspecific differences for haemolymph sodium were found; magnesium levels were slightly higher in Biomphalaria spp. than in Helisoma trivolvis; potassium levels were all similar. Amounts of tissue calcium decreased as follows: Mantle collar head-foot ovotestis + albumin gland-gut + diverticulum. Tissue magnesium levels in the gut were low. H. trivolvis had highest tissue calcium and sodium; B. glabrata had highest tissue potassium.     

Accession and cycling of elements in a coastal stand ofPinus radiata D. Don in New Zealand

Summary The accession and cycling of elements in a 14-year-old coastal stand ofPinus radiata D. Don was measured for one year. The element contents (mg m^–2 year^–1) of bulk precipitation and throughfall respectively were: NO₃–N 41, 12; NH₄–N 133, 154; organic-N 157, 396; Na 4420, 9700; K 387, 2900; Ca 351, 701; Mg 486, 1320. Of the increase in element content of rainwater beneath the forest canopy 20% (NH₄–N), 70% (organic-N), 3% (Na), 90% (K), 20% (Ca) and 30% (Mg) was attributed to leaching; the remainder to washing of aerosols filtered from the atmosphere by the vegetation. The canopy absorbed approximately 40 mg m^–2 year^–1 of NO₃–N. Litterfall was the major pathway for the above-ground biogeochemical cycle of N (93%), Ca (96%) and Mg (74%), and leaching was the major (73%) pathway for K.     

Effects of Ca and Mg concentrations in seawater on the growth and energy budget of juvenile Paralichthys olivaceus (Temminck & Schlegel, 1846)

Effects of seawater calcium (Ca) and magnesium (Mg) concentrations on the growth and energy budget of juvenile Paralichthys olivaceus (Temminck & Schlegel, 1846) were investigated at 20°C and a salinity of 30 psu. The Ca/Mg ratio (Ca : Mg = 1 : 3) in the experimental water was kept constant. Five treatments were set: C1, C2, C3, C4, and C5, and the Ca and Mg concentrations were 700, 1100, 1600, 2200, and 2800 (mg L^?1), respectively. After a 60‐day feeding trial the P. olivaceus survival rates were not affected significantly by Ca or Mg concentrations in the range of 700–2800 mg L^?1. However, the specific growth rates (SGR) and weight gain (WG) of all treatments decreased with ascending Ca and Mg concentrations. The Ca and Mg concentrations had a strong influence on various energy parameters, namely, energy deposited for growth (G), energy lost for respiration (R), and energy lost in excretion (U), but had little influence on energy lost in feces (F). This indicated that the growth rate differences under different concentrations of Ca and Mg mainly resulted from differences of assimilation efficiency and energy channeled into respiration. The highest net growth efficiency was attained at the lowest concentration of Ca and Mg in seawater, and the higher concentrations of Ca and Mg increased the energy channeled to respiration and excretion, which led to significant reduction in growth. Therefore, the optimal growth of P. olivaceus could be obtained by regulating the concentration of Ca and Mg at 700 mg L^?1, where the average energy budget was: 100C (100% energy consumed in food) = 47.21 (±0.63) G + 32.89 (±0.42) R + 16.71 (±0.56) F + 3.19 (±0.05) U.     

Transformation of vanadinite [Pb5(VO4)3Cl] by fungi

Saprotrophic fungi were investigated for their bioweathering effects on the vanadium‐ and lead‐containing insoluble apatite group mineral, vanadinite [Pb₅(VO₄)₃Cl]. Despite the insolubility of vanadinite, fungi exerted both biochemical and biophysical effects on the mineral including etching, penetration and formation of new biominerals. Lead oxalate was precipitated by Aspergillus niger during bioleaching of natural and synthetic vanadinite. Some calcium oxalate monohydrate (whewellite) was formed with natural vanadinite because of the presence of associated ankerite [Ca(Fe²⁺,Mg)(CO₃)₂]. Aspergillus niger also precipitated lead oxalate during growth in the presence of lead carbonate, vanadium(V) oxide and ammonium metavanadate, while abiotic tests confirmed the efficacy of oxalic acid in solubilizing vanadinite and precipitating lead as oxalate. Geochemical modelling confirmed the complexity of vanadium speciation, and the significant effect of oxalate. Oxalate–vanadium complexes markedly reduced the vanadinite stability field, with cationic lead(II) and lead oxalate also occurring. In all treatments and geochemical simulations, no other lead vanadate, or vanadium minerals were detected. This research highlights the importance of oxalate in vanadinite bioweathering and suggests a general fungal transformation of lead‐containing apatite group minerals (e.g. vanadinite, pyromorphite, mimetite) by this mechanism. The findings are also relevant to remedial treatments for lead/vanadium contamination, and novel approaches for vanadium recovery.     

Effect of sodium on cellular calcium transport in rat kidney

Summary The influence of extracellular Na (Na _o ) on cellular Ca transport and distribution was studied in rat kidney slices. Calcium efflux from prelabeled slices was depressed when Na _o was completely replaced by choline or tetraethylammonium (TEA) ions and it was markedly stimulated when Na was reintroduced in a Na-free medium. However, reducing Na _o (with choline or TEA as substituting ions) did not increase the total slice⁴⁰Ca, their total exchangeable Ca pool, or the⁴⁰Ca or⁴⁵Ca of mitochondria isolated from these slices. Kinetic analyses of steady-state⁴⁵Ca desaturation curves showed that reducing Na _o depressed the exchange of Ca across the plasma membrane, slightly decreased the cytosolic Ca pool, but did not significantly affect the mitochondrial Ca pool and Ca cycling. Ouabain (10^–3 m) which should reduce the Na gradient across the plasma membrane had no effect on calcium distribution and transport. These results suggest that in kidney cells low Na _o depresses Ca influx as well as Ca efflux; there may be an interaction between Na and Ca at a possible carrier located in the plasma membrane, but there is no Na/Ca exchange as described in several excitable tissues.     

丛枝菌根真菌和施加不同形态氮肥对杉木幼苗养分吸收的影响

为了解丛枝菌根真菌(AMF)和不同形态氮对杉木(Cunninghamia lanceolata)生长和养分吸收的影响,以1 a生杉木幼苗接种摩西球囊霉(Glomus mosseae)和添加不同形态氮(NH₄⁺-N和NO₃^–-N),对其养分元素和生长状况的变化进行研究。结果表明,AMF显著提高了杉木的苗高和生物量,促进了杉木对N、P、K、Ca、Mg、Fe和Na的吸收,AMF对微量元素Fe、Na的促进作用总体上要强于大量元素K、Ca。与NO₃^–-N相比,AMF显著提高了NH₄⁺-N处理杉木的生物量、总C和N、Ca、Mg、Mn含量,而且这种显著性在叶中普遍高于根和茎。接种AMF可以促进杉木幼苗的生长和对养分元素的吸收,且添加NH₄⁺-N处理的促进作用要强于NO₃^–-N。     

Stromatolitic knobs in Storr's Lake (San Salvador,Bahamas): a model system for formation and alteration of laminae

The initial lamination in young, metabolically active Scytonema knobs developing in Storr's Lake (Bahamas) results from the iterative succession of two different stages of microbial growth at the top of this microbialite. Stage 1 is dominated by vertically oriented cyanobacterial filaments and is characterized by a high porosity of the fabric. Stage 2 shows a higher microbial density with the filaments oriented horizontally and with higher carbonate content. The more developed, dense microbial community associated with Stage 2 of the Scytonema knobs rapidly degrades extracellular organic matter (EOM) and coupled to this, precipitates carbonate. The initial nucleation forms high‐Mg calcite nanospheroids that progressively replace the EOM. No precipitation is observed within the thick sheath of the Scytonema filaments, possibly because of strong cross‐linking of calcium and EOM (forming EOM‐Ca‐EOM complexes), which renders Ca unavailable for carbonate nucleation (inhibition process). Eventually, organominerals precipitate and form an initial lamina through physicochemical and microbial processes, including high rates of photosynthetic activity that lead to ¹³C‐enriched DIC available for initial nucleation. As this lamina moves downward by the iterative production of new laminae at the top of the microbialite, increased heterotrophic activity further alters the initial mineral product at depth. Although some rare relic preservation of ‘Stage 1–Stage 2’ laminae in subfossil knobs exists, the very fine primary lamination is considerably altered and almost completely lost when the knobs develop into larger and more complex morphologies due to the increased accommodation space and related physicochemical and/or biological alteration. Despite considerable differences in microstructure, the emerging ecological model of community succession leading to laminae formation described here for the Scytonema knobs can be applied to the formation of coarse‐grained, open marine stromatolites. Therefore, both fine‐ and coarse‐grained extant stromatolites can be used as model systems to understand the formation of microbialites in the fossil record.     

Potassium and other minor elements in Porites corals: implications for skeletal geochemistry and paleoenvironmental reconstruction

We investigated how the K/Ca, Na/Ca, Mg/Ca, and Sr/Ca ratios of powders ground from Porites coral skeletons are changed by cumulative chemical treatments to the powders: first with distilled/deionized water (DDW), next with 30?% H₂O₂ and then with 0.004?mol?l^?1 HNO₃. The K/Ca, Na/Ca, and Mg/Ca ratios were decreased with the DDW treatment and then increased with the H₂O₂ and HNO₃ treatments; the Sr/Ca ratio was slightly decreased through the cumulative treatments, suggesting fine-scale (tens of ??m or less) elemental heterogeneities in the skeleton??K, Na, and Mg are significantly enriched at the skeletal surface and also at the center of calcification (COC); in contrast, the heterogeneity of Sr is very small. We suggest that the principal mechanisms of K incorporation into coral skeleton are (1) ion incorporation into lattice defects/distortions and (2) ion adsorption onto crystal discontinuities (including crystal?Corganic matter interfaces) as forms of K⁺ and KSO₄ ^?. Furthermore, we measured the element/Ca ratios of a modern Porites coral skeleton along its growth direction at 2-mm intervals. Results showed that all the element/Ca ratios displayed annual cycles, that the K/Ca and Na/Ca ratios covaried with each other, and that the annual-minimum K/Ca and Na/Ca ratios coincided with the annual high-density band in the skeleton. It is unclear what environmental factors may cause the covarying annual cycles of the K/Ca and Na/Ca ratios; however, as a possible explanation, the cycles may be due not to environmental factors, but to a combined effect of (1) the K and Na enrichment at the COC, (2) annual bands of high- and low-density skeleton, and (3) mm-scale element/Ca measurements along the skeletal growth direction. This kind of effect on geochemical proxies of which the concentrations significantly differ between the COC and surrounding skeleton may generate false or distorted paleoenvironmental signals.     

Thermal and Ionic Factors in the Ultraviolet Photolysis of Plant Cell Membranes

The exposure of red beet root tissue to ultraviolet (254 nm) at 2 × 10⁶ erg × cm^?2× min^?1 (0.2 J × cm^?2× min^?1) causes release of betacyanin after a 20 minute induction period. Ultraviolet-photolysis is temperature-sensitive having a thermal threshold at about 10°C. Reduction in pigment release was effected by chlorides of Mg, Ca and Sr, but not by Li, Na or K. This effect was marked but not complete, even at 40 mM concentration. It is concluded that photolysis is indirect, and involves a lytic factor, possibly an oxidant, derived from an original photochemical product.     

Phosphorus fertilizer recovery from calcareous soils amended with humic and fulvic acids

Precipitation of Ca phosphates negatively affects recovery by plants of P fertilizer applied to calcareous soils, but organic matter slows the precipitation of poorly soluble Ca phosphates. To study the effect of high molecular weight organic compounds on the recovery of applied P, a mixture of humic and fulvic acids was applied to calcareous soils with different levels of salinity and Na saturation which were fertilized with 200 and 2000 mg P kg^–1 as NH₄H₂PO₄. Recovery was measured as the ratio of increment in Olsen P-to-applied P after 30, 60 and 150 days, and associated P forms were studied using sequential chemical fractionation and ³¹P NMR spectroscopy. Application of the humic-fulvic acid mixture (HFA) increased the amount of applied P recovered as Olsen P in all the soils except in one soil with the highest Na saturation. In soils with high Ca saturation and high Olsen P, recovery increased from < 15% in the absence of amendment to > 40% at a 5 g HFA kg^–1 amendment rate (30 days incubation and 200 mg P kg^–1 fertilizer rate). This is ascribed to inhibition of the precipitation of poorly soluble Ca phosphates, consistent with the sequential chemical extraction (reduction of the HCl extractable P) and P concentration in 0.01 M CaCl₂ (1:10 soil:solution ratio) extracts. ³¹P NMR spectra revealed that in non-amended samples, most spectral shifts were due to poorly soluble P compounds (carbonate apatite); on the other hand, at the 5 g HFA kg^–1 rate, significant amounts of amorphous Ca phosphate and dicalcium phosphate dihydrate (DCDP) were identified. The increase in the recovery of applied P due to HFA reveals a positive effect of the application of organic matter as soil amendments on the efficiency of P fertilizers and also explains that manures and other organic sources of P were more efficient increasing available P than inorganic P fertilizers in calcareous soils.     

Changes of aliphatic C–H bonds in cyanobacteria during experimental thermal maturation in the presence or absence of silica as evaluated by FTIR microspectroscopy

Aliphatic C–H bonds are one of the major organic signatures detected in Proterozoic organic microfossils, and their origin is a topic of interest. To investigate the influence of the presence of silica on the thermal alteration of aliphatic C–H bonds in prokaryotic cells during diagenesis, cyanobacteria Synechocystis sp. PCC6803 were heated at temperatures of 250–450°C. Changes in the infrared (IR) signals were monitored by micro‐Fourier transform infrared (FTIR) spectroscopy. Micro‐FTIR shows that absorbances at 2,925 cm^?1 band (aliphatic CH₂) and 2,960 cm^?1 band (aliphatic CH₃) decrease during heating, indicating loss of the C–H bonds, which was delayed by the presence of silica. A theoretical approach using solid‐state kinetics indicates that the most probable process for the aliphatic C–H decrease is three‐dimensional diffusion of alteration products under both non‐embedded and silica‐embedded conditions. The extrapolation of the experimental results obtained at 250–450°C to lower temperatures implies that the rate constant for CH₃ (k_CH3) is similar to or lower than that for CH₂ (k_CH2; i.e., CH₃ decreases at a similar rate or more slowly than CH₂). The peak height ratio of 2,960 cm^?1 band (CH₃)/2,925 cm^?1 band (CH₂; R_3/2 values) either increased or remained constant during the heating. These results reveal that the presence of silica does affect the decreasing rate of the aliphatic C–H bonds in cyanobacteria during thermal maturation, but that it does not significantly decrease the R_3/2 values. Meanwhile, studies of microfossils suggest that the R_3/2 values of Proterozoic prokaryotic fossils from the Bitter Springs Group and Gunflint Formation have decreased during fossilization, which is inconsistent with the prediction from our experimental results that R_3/2 values did not decrease after silicification. Some process other than thermal degradation, possibly preservation of specific classes of biomolecules with low R_3/2 values, might have occurred during fossilization.     

Profiles of trace elements and stable isotopes derived from giant long-lived Tridacna gigas bivalves: Potential applications in paleoclimate studies

This study investigates the environmental and biological controls on trace element partitioning and stable isotope composition of modern giant long-lived bivalves (Tridacna gigas) with the aim to use these archives for paleoclimatic reconstructions. Firstly, the intra-shell variability is studied by measuring time equivalent profiles in the different shell layers characterised by different growth rates. Secondly, the inter-site variability is studied by comparing profiles derived from three modern specimens collected in sites across the Indo-Pacific region characterised by different ranges of temperature and productivity.These results show that δ¹⁸O profiles are highly reproducible across the shell regardless of significantly different growth rates. Shell δ¹⁸O is primarily controlled by water δ¹⁸O and temperature. Comparison of intra shell Mg/Ca profiles shows a clear and systematic partitioning where inner layer Mg/Ca values are a least 2–3 times higher than outer layer and hinge areas. Inner layer Mg/Ca shows seasonal oscillations but superimposed on an ontogenetic trend with increasing values and increasing amplitude Mg/Ca oscillations with age. The Sr/Ca profiles do not show clear reproducible seasonal trends in the different shell zones. It is concluded that Mg/Ca and Sr/Ca profiles appear to reflect a combination of biological and environmental controls that will need to be disentangled before using these proxies in paleoclimatic studies.Finally, intra shell Ba/Ca profiles are reproducible in great detail for all modern specimens studied. Inter-site comparison shows that the amplitude and the timing of the Ba/Ca peaks appear to reflect the timing and the amplitude of the chlorophyll peaks associated with phytoplankton blooms at each locality making this tracer a potential paleoproductivity indicator.     

Characteristic Studies on the Pyrolysis Products from Hydrolyzed Canadian Lignocellulosic Feedstocks

Lignocellulosic feedstocks are utilized for the production of fuel ethanol and butanol through dilute acid/enzymatic hydrolysis and fermentation. Hydrolysis residue, a major by-product of biomass hydrolysis, is rich in recalcitrant carbon as majority of cellulosic and hemicellulosic components are released during pretreatment. With the intention of their effective utilization, hydrolysis residues from forestry (pinewood), energy crop system (timothy grass), and agriculture (wheat straw) were pyrolysed in a fixed-bed reactor at 600 °C with slow heating rate of 5 °C/min for 4 h. In order to understand the product (biochar, bio-oil, and gases) properties and advocate their energy and environmental values, chemical characterizations such as carbon–hydrogen–nitrogen–sulfur analysis, inductively coupled plasma-mass spectrometry, pH, electrical conductivity, scanning electron microscopy, porosity analysis, thermogravimetric analysis, X-ray diffraction, Fourier transform infrared (FTIR) and Raman spectroscopy, nuclear magnetic resonance (NMR) and gas chromatography–mass spectrometry (GC-MS) were employed. The yield of biochar, bio-oil and gases was 38.9–41.7, 18.6–22.3, and 24.9–28.8 wt%, respectively. The high pH and electrical conductivity of biochars with substantial amounts of Na, Mg, K, and Ca indicated their alkaline and saline nature, which would necessitate proper agronomical soil applications. Variable intensities of C–C, C–H, C–O, O–H, and C–N functional groups were detected in the FTIR spectra of residues, biochars, and bio-oils. Raman spectroscopy showed the development of graphite (1,580–1,610 cm^?1) and defect (1,325–1,380 cm^?1) carbon structures in biochars. ¹H NMR of bio-oils indicated aromatics, olefinics, and aliphatics, whereas ¹³C NMR indicated carbonyls, aromatics, carbohydrates, alkyls, methoxy, and hydroxy carbon. GC studies of pyrolysis gases identified chiefly H₂ and CO with traces of CH₄, CO₂, and C₂+ components.     

Direct inhibitory action of EGTA-Ca complex on reverse-mode Na/Ca exchange inMyxicola giant axons

Summary Giant axons from the marine annelidMyxicola infundibulum were internally dialyzed with solutions containing²²Na ions as tracers of Na efflux. In experiments performed in Li-substituted seawater, Na efflux that is dependent on external Ca ion concentration, [Ca²⁺] _o , was measured using dialysis to maintain [Na⁺] _i at 100mm, which enhances the [Ca²⁺] _o -dependent Na efflux component, (i.e., reverse-mode Na/Ca exchange). When dialysis fluid contained EGTA (1mm) to buffer the internal Ca concentration, [Ca²⁺] _i , to desired levels, Na efflux lost its normal sensitivity to external calcium. The inhibition was not simply due to the Ca-chelating action of EGTA to produce insufficient [Ca²⁺] _i to activate Na/Ca exchange. The addition of EGTA inhibited Ca _o -dependent Na efflux even when a large enough excess of [Ca²⁺] _i was present to saturate the EGTA and still produce elevated values of [Ca²⁺] _i . Control experiments showed that these high values of [Ca²⁺] _i resulted in normal Na/Ca exchange in the absence of EGTA. It is concluded that the presence of EGTA itself interferes with the manifestation of reverse-mode Na/Ca exchange inMyxicola giant axons.