Seasonal variation in nitrification and nitrate-reduction pathways in coastal sediments in the Gulf of Finland, Baltic Sea

The Baltic Sea is one of the most eutrophic marine areas in the world. The role of nitrogen as a eutrophicating nutrient in the Baltic Sea has remained controversial, due to lack of understanding of nitrogen cycling in the area. We investigated the seasonal variation in sediment nitrification, denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) at two coastal sites in the Gulf of Finland. In addition to the in situ rates, we assessed the potential for these processes in different seasons. The nitrification and nitrogen removal processes were maximal during the warm summer months, when the sediment organic content was highest. In colder seasons, the in situ rates of the nitrification and nitrate reduction processes decreased, but the potential for nitrification remained equal to or higher than that during the warm months. The denitrification and nitrification rates were usually higher in the accumulation basin, where the organic content of the sediment was higher, but the transportation area, despite lower denitrification rates and potential, typically had higher potential for nitrification than the accumulation basin. Anammox and DNRA were not significant nitrate sinks in any of the seasons sampled. The results also show that the denitrification rates in the coastal Gulf of Finland sediment have decreased, and that benthic denitrification might be a less important sink for fixed nitrogen than previously assumed.

A PEFC With Pt-TiO2/C as Oxygen-Reduction Catalyst

Carbon-supported Pt-TiO2 (Pt-TiO2/C) catalyst with varying atomic ratio of Pt to Ti, namely, 1: 1, 2: 1, and 3: 1, is prepared by sol-gel method and its electrocatalytic activity toward oxygen-reduction reaction (ORR) is evaluated for the application in polymer electrolyte fuel cells (PEFCs). The optimum atomic ratio of Pt to Ti in Pt-TiO2/C and annealing temperature are established by cyclic voltammetry and fuel-cell-polarization studies. Pt-TiO2/C annealed at 750 degrees C with Pt and Ti in atomic ratio of 2: 1, namely, 750 Pt-TiO2/C (2: 1), shows enhanced electrocatalytic activity toward ORR. It is found that the incorporation of TiO2 with Pt ameliorates both electrocatalytic activity and stability of cathode in relation to pristine Pt cathode, currently being used in PEFCs. A power density of 0.75 W/cm(2) is achieved at 0.6 V for the PEFC with 750 Pt-TiO2/C (2: 1) as compared with 0.62 W/cm(2) at 0.6 V achieved with the PEFC comprising Pt/C as cathode catalyst while operating under identical conditions. Interestingly, carbon-supported Pt-TiO2 cathode exhibits only 6% loss in electrochemical surface area after 5000 potential cycles while it is as high as 25% for Pt/C. DOI: 10.1115/1.4002466]

A2MoTiO7−x (Atriple bond; length as m-dashrare earth or Y): a new series of oxide pyrochlores prepared by topochemical reduction of A2MoTiO8 scheelites

A series of anion-deficient pyrochlore oxides of the formula A2MoTiO7−x (xless-than-or-equals, slant0.5), where Atriple bond; length as m-dashSm, Gd, Tb, Dy, Ho, Er, Lu and Y, has been prepared by reduction of A2MoTiO8 scheelites. The scheelite-to-pyrochlore conversion is reversible, indicating that the reaction is likely to be topochemical. The oxidation states of molybdenum and titanium are most probably Mo(III) and Ti(IV) for the limiting composition of the pyrochlores A2MoTiO6.5. The new pyrochlores are non-metallic and paramagnetic as expected.

A Convenient Methodology for the Selective Reduction of Carboxylic Acids With Benzyltriethyl-Ammonium Borohydride—Chlorotrimethylsilane

A combination of benzyltriethylammonium borohydride and chlorotrimethylsilane (1:1) in dichloromethane (0-25°C) has been found to be a convenient reagent system for the selective reduction of carboxylic acids to alcohols.

A new approach to the kinetics of size reduction in ball milling

The rate of breakage of feed in ball milling is usually represented in the form of a first-order rate equation. The equation was developed by treating a simple batch test mill as a well mixed reactor. Several case of deviation from the rule have been reported in the literature. This is attributed to the fact that accumulated fines interfere with the feed material and breaking events are masked by these fines. In the present paper, a new rate equation is proposed which takes into account the retarding effect of fines during milling. For this purpose the analogy of diffusion of ions through permeable membranes is adopted, with suitable modifications. The validity of the model is cross checked with the data obtained in batch grinding of ?850/+600 ?m size quartz. The proposed equation enables calculation of the rate of breakage of the feed at any instant of time.

An optimal parallel algorithm for sparse matrix bandwidth reduction on a linear array

A simple and efficient algorithm for the bandwidth reduction of sparse symmetric matrices is proposed. It involves column-row permutations and is well-suited to map onto the linear array topology of the SIMD architectures. The efficiency of the algorithm is compared with the other existing algorithms. The interconnectivity and the memory requirement of the linear array are discussed and the complexity of its layout area is derived. The parallel version of the algorithm mapped onto the linear array is then introduced and is explained with the help of an example. The optimality of the parallel algorithm is proved by deriving the time complexities of the algorithm on a single processor and the linear array.

The roles of nitrification and nitrate reduction pathways in nitrogen cycling of Baltic Sea

The Baltic Sea is one of the largest brackish water bodies in the world. Primary production in the Baltic Sea is limited by nitrogen (N) availability with the exception of river outlets and the northernmost phosphorus limited basin. The excess human induced N load from the drainage basin has caused severe eutrophication of the sea. The excess N loads can be mitigated by microbe mediated natural N removal processes that are found in the oxic-anoxic interfaces in sediments and water column redoxclines. Such interfaces allow the close coupling between the oxic nitrification process, and anoxic denitrification and anaerobic ammonium oxidation (anammox) processes that lead to the formation of molecular nitrogen gas. These processes are governed by various environmental parameters. The effects of these parameters on N processes were investigated in the northern Baltic Sea sediments. During summer months when the sediment organic content is at its highest, nitrification and denitrification reach their maximum rates. However, nitrification had no excess potential, which was probably because of high competition for molecular oxygen (O2) between heterotrophic and nitrification microbes. Subsequently, the limited nitrate (NO3-) availability inhibited denitrification. In fall, winter and spring, nitrification was limited by ammonium availability and denitrification limited by the availability of organic carbon and occasionally by NO3-. Anaerobic ammonium oxidation (anammox) was not an important N removal process in the northern Baltic Sea. Modeling studies suggest that when hypoxia expands in the Baltic Sea, N removal intensifies. However, the results of this study suggest the opposite because bottom water hypoxia (O2< 2 ml l-1) decreased the denitrification rates in sediments. Moreover, N was recycled by the dissimilatory nitrate reduction to ammonium (DNRA) process instead of being removed from the water ecosystem. High N removal potentials were found in the anoxic water column in the deep basins of the Baltic Proper. However, the N removal in the water column appeared to be limited by low substrate availability, because the water at the depths at which the substrate producing nitrification process occurred, rarely mix with the water at the depths at which N removal processes were found. Overall, the natural N removal capacity of the northern Baltic Sea decreased compared to values measured in mid 1990s and early 2000. The reason for this appears to be increasing hypoxia.

Molecular expression for dielectric friction on a rotating dipole: Reduction to the continuum theory

Recently we presented a microscopic expression for dielectric friction on a rotating dipole. This expression has a rather curious structure, involving the contributions of the transverse polarization modes of the solvent and also of the molecular length scale processes. It is shown here that under proper limiting conditions, this expression reduces exactly to the classical continuum model expression of Nee and Zwanzig [J. Chem. Phys. 52, 6353 (1970)]. The derivation requires the use of the asymptotic form of the orientation‐dependent total pair correlation function, the neglect of the contributions of translational modes of the solvent, and also the use of the limit that the size of the solvent molecules goes to zero. Thus, the derivation can be important in understanding the validity of the continuum model and can also help in explaining the results of a recent computer simulation study of dielectric relaxation in a Brownian dipolar lattice.

Nafion®-bound carbon electrodes containing transitionmetal phthalocyanines for oxygen reduction in solid-polymer-electrolyte fuel cells

Catalytic activities of some transition metal-phthalocyanine complexes towards electroreduction of molecular oxygen are examined on Nafion®-bound and bare porous carbon electrodes in 2.5 M H2SO4 electrolyte. It is found that these metal complexes exhibit better catalytic activities towards oxygen reduction with the Nafion®-bound electrodes.

Reduction behaviour of Fe3+/Al2O3 obtained from the mixed oxalate precursor and the formation of the Fe0-Al2O3 metal-ceramic composite

Reduction behaviour of Fe3+/Al2O3 obtained by the decomposition of the oxalate precursor has been investigated by employing X-ray diffraction (XRD), Mössbauer spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. Calcination of Fe3+/Al2O3 at or below 1070 K yields mainly a poorly ordered, fine particulate form of ?-Al2�xFexO3. Calcination at or above 1220 K yields ?-Al2�xFexO3. Reduction of Fe3+/Al2O3 samples calcined at or below 1070 K gives the FeAl2O4 spinel on reduction at 870 K; samples calcined at or above 1220 K give Al2-xFexO3 with a very small proportion of metallic iron. Fe3+/Al2O3 samples calcined at 1220 K or above yield metallic iron and a very small proportion of the spinel on reduction below 1270 K. In the samples reduced at or above 1270 K, the main product is metallic iron in both ferromagnetic and superparamagnetic forms. The oxalate precursor route yields more metallic iron than the sol�gel route.

'South-South' Remittance - Poverty reduction nexus. The Case of 'Hadiya' immigrants in South Africa, as Agents of 'Constituence development' in Ethiopia, and the policy implications of their 'remittance instrument'

This thesis explores the link between South-South remittance and development. It attempts to establish improved understanding about the role of immigrants as agents of constituency growth and development. By doing so, it illuminates the dark corners of the policy implications that the unconventional development agency of immigrants might have for countries in the Organization ft Economic Cooperation and Development (OECD). The thesis problematises the existence of state-centric international cooperation as providing the recipe for failed Aid in the face of global poverty menace. In the last half a century, the relative shi' of focus to non-state actors brought about the proliferation of NGOs. That, intrun, helped improve international access to crisis situations; however, their long-term remedial impacts on poverty and development have been contested. Major misgivings for non-governmental organizations (NGOs) are, on one hand, low level goal-bound expenditures and lack of independence from influence of the state, on the other. Therefore, the thesis enterprises to empirically verify its fundamental question whether remitting immigrants constitute an alternative development agency to the traditional players: the State and NGOs. Its main arguments are: due to state's failures in bringing sustainable development in many countries of the South, the future of poverty reduction and development also rests in immigrants' remittances. Nonetheless, in the last decade, remittance security-nexus dominated its discourse. Because of that remittance was viewed as something requiring global regime and restrictions. These temptations to tightly regulate remittance flows carry the danger of overlooking its trans-boundary nature and its strong link with livelihood of the poor. Therefore, to avoid unintended consequences of interventions, there need to be clear policy that bases itself on a discursive knowledge on the issues of North-South and South-South remittances The study involved both literature based and empirical research. It employed Discourse Analysis (C as main method for the former and snow-balling as its approach for the latter. For the first part the thesis constructed three conceptual models, these are: metrological model, police model and ecological model on remittance development-nexus. Through this modeling, the thesis achieved better deconstruction on the concepts remittance, immigrants and development agency. The protagonists of each model, the values and interests they represent, and their main arguments along various lines of dichotomies have been discussed. For instance, the main treats of meteorological model include: it sees remittance as transitional economic variable which require constant speculations and global management; it acts as meteorological station for following up or predicting the level, direction, flow and movement of global remittance. It focuses on official lines and considers the state as legitimate recipient of advic and positive consequence of remittance. On the other hand, police model views remittance as beir at best, development neutral or as an illicit activity requiring global regulations and tight control. Both immigrants and remittance viewed as subversive to establishments. It gives primacy to state stable agent of development and a partner for international cooperation. The anti-thesis to the police model is supplied by ecological model, which this thesis is a part. Ecological model on remittance and immigrants argues that, tight global regulations alone cannot be a panacea for possible abuse of informal remittance system. Ecological model, not only links remittance to poverty reduction, the main trust of development, but also considers the development agency of immigrants as critical factor for 21st century north-south development intervention. It sees immigrants as development conscious and their remittance instrument as most stable flow of finance to the developing countries. Besides, it sees remittance as effective poverty solutions than Foreign Direct Investment and international AID. This thesis focuses on the significance of South-South remittance and investigates the South Africa - Ethiopia remittance corridor, as case study; and empirically verifies the role of Ethiopian (Kembata and Hadiya) immigrants in South Africa as agents of local development back home. The study involved techniques of interview, group discussions, observations and investigative study. It also looked into the determinants of their migration to South Africa, and their remittance to Ethiopia. The theoretical models in the first part of the thesis have been operationalised throughout the empirical part to verify if the Kembata and Hadiya immigrants played the crucial role in their household poverty and local development in comparison with the Ethiopian state and the NGOs involved in the system. As evidenced by the research the thesis has made three distinct contributions to the discourse of remittance development-nexus. Fist, it systematized the debate about linkages between remittance, immigrants, development agency and policy of international cooperation by creating three conceptual models (school of thoughts); second, it singled out remitting immigrants as new agents of development in the South; third, it deconstructed concept of remittance and established South¬South remittance as additional sphere of academic investigation. In addition to the above contributions, the thesis finds that Kembata and Hadiya immigrants have engaged in various developmental activities in their locality than usually anticipated. Hence, it concludes that Ethiopian immigrants constitute an alternative development agency to the state and other non-state actors in their country, and the lesson can be applied to poverty reduction strategies in most developing countries.