Chemistry of pore water and solids, formation factors and salt-corrected porosities of DSDP Site 68-503

Recent discoveries relating to the circulation of fluids within the oceanic crust include the finding of both important fluxes of elements and isotopes into the oceans by ridge-crest hydrothermal convection and important fluxes of heat out of the oceanic crust by convection at ridge crests and at some distance from ridge crests. In the present chapter, I present isotopic, chemical, and physical data from sediments and pore waters of Deep Sea Drilling Project (DSDP) Holes 503A and 503B. These results are modeled in terms of pore-water diffusion, advection, and production to ascertain the relative contribution of these processes at this location, 7.5 m.y. removed from ridge-crest hydrothermal activity. The observations made here contribute to the understanding of chemical and heat transport in oceanic crust of moderate age.

Water chemistry of lakes in Zackenbergdalen between 1997-2003, East Greenland

The ecology of arctic lakes is strongly influenced by climate-generated variations in snow coverage and by the duration of the ice-free period, which, in turn, affect the physical and chemical conditions of the lakes (Wrona et al., 2005, http://www.acia.uaf.edu/PDFs/ACIA_Science_Chapters_Final/ACIA_Ch08_Final.pdf). Most arctic lakes are characterised by a long period (8-10 months) of ice-cover, cold water and low algal biomass. The water temperature and nutrient concentrations, and most probably the nutrient input from the catchments, are closely related to the duration of snow- and ice-cover in the lakes. In years when the ice-out is late, - that is, in late July, - phytoplankton photosynthesis is limited by the lack of light and nutrients. Less food is then available to the next link in the food chain, such as copepods and daphnids, with implication on their growth rates.

Isotopic signatures and mercury content of arctic char and their prey, and water chemistry of 18 arctic Canadian lakes

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to d13C and d15N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The d13C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 ± 1.1 to 64.3 ± 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes.

Applying concept mapping strategies to improve students’ lifelong learning in physical chemistry

Este artículo ofrece una reflexión sobre el papel de los mapas conceptuales en el actual escenario de la educación In the present paper, we carry out the application of concept mapping strategies to learning Physical Chemistry, in particular, of all aspect of Corrosion. This strategy is an alternative method to supplement examinations: it can show the teacher how much the students knew and how much they didn´t know; and the students can evaluate their own learning. Before giving tile matter on Corrosion, the teachers evaluated the previous knowledge of the students in the field and explained to the students how create the conceptual maps with Cmap tools. When the subject is finished, teachers are assessed the conceptual maps developed by students and therefore also the level of the students learning. Teachers verified that the concept mapping is quite suitable for complicated theorics as Corrosion and it is an appropriate tool for the consolidation of educational experiences and for improvement affective lifelong learning. By using this method we demonstrated that the set of concepts accumulated in the cognitive structure of every student in unique and every student has therefore arranged the concepts from top to bottom in the mapping field in different ways with different linking" phrases, although these are involved in the same learning task.

Tailoring the surface chemistry of zeolite templated carbon by electrochemical methods

One option to optimize carbon materials for supercapacitor applications is the generation of surface functional groups that contribute to the pseudocapacitance without losing the designed physical properties. This requires suitable functionalization techniques able to selectively introduce a given amount of electroactive oxygen groups. In this work, the influence of the chemical and electrochemical oxidation methods, on the chemical and physical properties of a zeolite templated carbon (ZTC), as a model carbon material, have been studied and compared. Although both oxidation methods generally produce a loss of the original ZTC physical properties with increasing amount of oxidation, the electrochemical method shows much better controllability and, unlike chemical treatments, enables the generation of a large number of oxygen groups (O = 11000- 3300 μmol/g), with a higher proportion of active functionalities, while retaining a high surface area (ranging between 1900-3500 m2/g), a high microporosity and an ordered 3-D structure.

Recent developments in physical chemistry : 3rd Mexican Meeting on Mathematical and Experimental Physics - México City, México - 10-14 September 2007 /

Mode of access: Internet.

Practical physical chemistry,

Mode of access: Internet.

Physical properties of chemical compounds.

Mode of access: Internet.

Introduction to physical chemistry /

Mode of access: Internet.

Practical physical chemistry,

Mode of access: Internet.

The chemistry of the inorganic complex compounds; an introduction to Werner's coordination theory,

Translation of: Chemie der anorganischen komplex Verbindungen.

Physical chemistry,

Mode of access: Internet.

The chemistry of British bituminous coals : an assessment of phase transfer catalysed reactions in the determination of coal structure

Three British bituminous coals, (Gedling, Cresswell, and Cortonwood Silkstone) were selected for study. Procedures were developed, using phase transfer catalysts (PTC's), to degrade the solvent insoluble fractions of the coals. PTC's are of interest because they have the potential to bring about selective high conversion reactions, under mild conditions, (often in the past, severe reaction conditions have had to be used to degrade the coals, this in turn resulted in the loss of much of the structural information). We have applied a variety of physical and chemical techniques to maximise the amount of structural information, these include, elemental analysis, 1H-NMR, 13C-CPMAS-NMR, GPC, GC-MS, FTIR spectroscopy, DRIFT spectroscopy, and gas adsorption measurements. The main conclusions from the work are listed below:- ( 1 ) PTC O-methylation; This reaction removes hydrogen bonds within the coal matrix by 'capping' the phenolic groups. It was found that the polymer-like matrix could be made more flexible, but not significantly more soluble, by O-methylation. I.E. the trapped or 'mobile' phase of the coals could be removed at a faster rate after this reaction had been carried out. ( 2 ) PTC Reductive and Acidic Ether Cleavage; The three coals were found to contain insignificant amounts of dialkyl and alkyl aryl ethers. The number of diaryl ethers could not be estimated, by reductive ether cleavage, (even though a high proportion of all three coals was solublised). The majority of the ethers present in the coals were inert to both cleavage methods, and are therefore assumed to be heterocyclic ethers. ( 3 ) Trif!uoroperacetic Acid Oxidation; This oxidant was used to study the aliphatic portions of the polymer-like macromolecular matrix of the coals. Normally this reagent will only solublise low rank coals, we however have developed a method whereby trifluoroperacetic acid can be used to degrade high rank bituminous coals. ( 4 ) PTC/Permanganate Oxidation; This reagent has been found to be much more selective than the traditional alkaline permanganate oxidation, with a lot more structural information being retained within the various fractions. This degradative method therefore has the potential of yielding new information about the molecular structure of coals.