The rigidity spectrum of the harmonics of the 27-day variation of the galactic cosmic ray intensity in different epochs of solar activity: 1965–2002

We study temporal changes of the rigidity (R) spectrum of the harmonics of the 27-day variation of the galactic cosmic ray (GCR) intensity using neutron monitors (NM) data for the period 1965–2002. We show that the rigidity spectrum of the third harmonic (9 days) of the 27-day variation of the GCR intensity changes in a similar way as the spectra of the first and second harmonics, being hard in the maximum epochs and soft in the minimum epochs of solar activity. We ascribe this finding to the alternation of the sizes of the modulation regions of the 27-day variation of the GCR intensity in different epochs of solar activity. The average size of the vicinity of the corotating interaction regions, causing the 27-day variation of the GCR intensity, is less in the minimum epochs than in the maximum epochs of solar activity. A vicinity of the corotating interaction regions of larger size involves in modulation higher rigidity particles of GCR than the vicinity of smaller size; thus, this statement can be considered as one of the reasons leading to the hardening of the rigidity spectrum of the harmonics of the 27-day variation of the GCR intensity in maximum epochs compared with minimum epochs of solar activity.We also show that the temporal changes of the power rigidity spectrum of the third harmonic of the 27-day variation of the GCR intensity are negatively correlated with the rigidity spectrum of the 11-year variation of the galactic cosmic ray intensity.We found a recurrence in the temporal changes of the amplitudes of the first harmonic of the 27-day variation of the GCR intensity and in some parameters of solar activity and solar wind.     

Changes in the characteristics of organic compounds depending on the nitritation efficiency

This study focused on nitritation reactions for the removal of highly concentrated nitrogen from water recycled by a MWTP (Municipal Wastewater Treatment Plant) for the preparation of effluent standards which will be strengthened. To examine the changes that occur during a nitritation reaction with a variety of SRT operations when inducing a stable nitritation reaction, a reactor was operated on a laboratory scale in this study. Digestion tank supernatant flowed into a laboratory-scale reactor and organic matter in the effluent under various operation conditions was classified into four types according to ASM standards using the test known as the OUR (Oxygen Uptake Rate)-test. Most organic matter in the digestion tank supernatant appeared to consist of mainly the S_I component out of non-biodegradable organic matter. During the operation period of the effluent in the laboratory-scale reactor, if a nitritation reaction occurs in a stable manner, most biodegradable organic matter is removed, consisting of mainly the S_I component, like the influent. Particularly, nitrogen was removed after the S_S was removed from the organic matters. Moreover, through a multiple correlation analysis between the operation results from a laboratory-scale reaction bath and the organic composition of the effluent, a method to predict the organic composition of effluents that relies on the operation result of the effluent is proposed.     

Native iron in the sediments of Lake Baikal (borehole BDP-98): results of thermomagnetic analysis

We performed a thermomagnetic analysis of 91 samples and a probe microanalysis of five samples of sedimentary rocks from the lower zone of the borehole BDP-98 drilled at the bottom of Lake Baikal. The results show the scarcity of native iron: It was found only in five samples. Its concentration varies from ～10^–5 to 7 × 10^–4%. The distribution of native iron by content is bimodal, with a distinct “zero” mode. This scarcity of native iron in the Baikal sediments distinguishes them from continental (Eurasia) and oceanic (Atlantic) sediments of different ages. It is due to the high rate of sedimentation in the studied interval of BDP-98.     

Impact de la variabilité climatique et du barrage Nangbéto sur l'hydrologie du système Mono-Couffo (Afrique de l'Ouest)

Résumé

En Afrique tropicale, de nombreuses études sur la variabilité climatique montrent qu'une tendance à la sécheresse s'est manifestée à partir de la fin des années 1960. Cette sécheresse a affecté aussi l'hydrosystème Mono-Couffo, en Afrique de l'Ouest, avec une persistance remarquable qui s'est répercutée sur les écoulements. Depuis 1988, avec la mise en eau du barrage de Nangbéto, qui coïncide avec une légère reprise pluviométrique dans les années 1990, on assiste à une modification du régime hydrologique du Mono à Athiémé. Les méthodes statistiques appliquées aux données mensuelles de pluie et débit de la période 1961–2000 ont permis de constater que les déficits pluviométriques des décennies 1970 et 1980 ont engendré des déficits de l'écoulement. Mais, avec la légère reprise pluviométrique (2%) de 1988 à 2000, on assiste à un excédent d'écoulement de 37% sur le Mono à Athiémé à régime « artificiel » depuis 1988; et, par contre, pas d'excédent (0,1%) sur le Couffo à Lanta à régime « naturel ».

Editeur Z.W. Kundzewicz

Citation Amoussou, E., Camberlin, P. et Mahé, G., 2012. Impact de la variabilité climatique et du barrage Nangbéto sur l'hydrologie du système Mono-Couffo (Ouest Afrique). Hydrological Sciences Journal, 57 (4), 805–817.     

Native iron and other magnetic minerals in the sediments of the northwestern Atlantic: Thermomagnetic and microprobe evidence

The thermomagnetic and microprobe analyses of sedimentary samples from DSDP 386, 387, 391A, and 391C boreholes in the northwestern Atlantic reveal the ubiquitous occurrence of particles of native iron. The concentrations of native iron are bimodal everywhere with the zero mode necessarily present. The nickel admixture in native iron forms two groups, one represented by pure iron and the comprising native iron with 5–6% Ni. The redeposition of iron particles manifests itself in the correlation between the concentrations of these particles and terrestrial minerals (magnetite), as well as in the equalization and reduction of the concentration of the iron particles. Pyrite and pyrrhotite are widespread in the studied sediments, and the distribution of native iron does not depend on the presence of pyrite (i.e., on redox conditions) in them. At the same time, the distributions of pyrite and particles of magnetite + titanomagnetite are inversely correlated, which can probably be accounted for by the partial dissolution of magnetite and titanomagnetite in the reducing conditions. The increased concentration of particles of volcanogenic homogeneous titanomagnetite is revealed in the volcanoclastic turbidites of the Oligocene and early and middle Miocene age at the base of the Bermuda Rise (borehole 386). The titanomagnetite composition is characteristic of the basalts of plume magmatism; it corresponds to the depth of the magmatic source in the interval of 50–25 km.     

Mercury levels in feathers of Magellanic penguins

Feathers are useful to determine mercury (Hg) contamination. We evaluated the mercury concentration in feathers of Magellanic penguins (Spheniscus magellanicus) age 1.5 years to 25 years at Punta Tombo, Argentina before and during their molt. Mercury ranged between <1.4 and 367 ng/g dry weight, with three extreme high values (8996 ng/g, 3011 ng/g and 1340 ng/g) all in young adults. The median concentration was lowest for juveniles and significantly higher for adults but with high variation among older adults. Males and females had similar mercury loads. Compared with other penguin species, concentrations in Magellanic penguins were low. Mercury levels for Magellanic penguins in the Southwest Atlantic for older adults averaged 206±98 ng/g, and serve as a baseline for biomonitoring and/or ecotoxicological studies.     

Numerical Simulation of the Airflow Across Trees in a Windbreak

The flow across a three-dimensional (3-D) windbreak comprising individual cypress trees is studied to establish the significance and extent of the 3-D flow patterns. The cypress tree is modelled as a solid cylindrical stem and a conic porous canopy. Cases with a single row of trees or two rows of trees with different distances between the rows are considered; in the case of a single row, several densities of the canopy are used. The steady Reynolds-averaged Navier–Stokes (RANS) approximation is solved using a commercial computational fluid dynamics (CFD) package and a high-resolution mesh. Three-dimensional flow is found in the vicinity of the windbreak up to a leeward distance of 1–2 tree-heights, depending on the density of the canopy, and is manifest as significant lateral variations and reduced vertical flow. At larger leeward distances, a two-dimensional (2-D) flow is established with characteristics similar to existing 2-D studies; the flow leeward of the last row is insensitive to the distance between the rows. Homogeneous 2-D windbreak models are found to be inaccurate in the vicinity of the windbreak. This is exactly the region that needs to be sheltered in many cases, since the inner vegetation is anyway protected by the outer vegetation.     

Charmed meson pair production in high-energy pp collisions within the QCD color dipole approach

A study of double-charmed meson production in high-energy proton–proton collisions at the Large Hadron Collider is presented. Considering the color dipole formalism developed in the transverse momentum representation along with the double parton scattering mechanism, predictions are made for the transverse momentum differential cross section for different pairs of -mesons. The theoretical results cover the center-of-mass energy and forward rapidities available by the LHCb experiment. The proton–proton results considering different unintegrated gluon distributions are compared to the respective data collected at the LHC.