SST and ice sheet impacts on the MIS–13 climate

As a first qualitative assessment tool, LOVECLIM has been used to investigate the interactions between insolation, ice sheets and the East Asian Monsoon at the Marine Isotopic Stage 13 (MIS–13) in work by Yin et?al. (Clim Past 4:79–90, 2008, Clim Past 5:229–243, 2009). The results are in need of validation with a more sophisticated model, which is done in this work with the ARPEGE atmospheric general circulation model. As in the Earth system Model of Intermediate Complexity, LOVECLIM, ARPEGE shows that the northern hemispheric high insolation in summer leads to strong MIS–13 monsoon precipitation. Data from the Chinese Loess Plateau indicate that MIS–13 was locally a warm and humid period (Guo et?al. in Clim Past 5:21–31, 2009; Yin and Guo in Chin Sci Bull 51(2):213–220, 2006). This is confirmed by these General Circulation Model (GCM) results, where the MIS–13 climate is found to be hotter and more humid both in the presence and absence of any added ice sheets. LOVECLIM found that the combined effects of the ice sheets and their accompanying SSTs contribute to more precipitation in eastern China, whilst in ARPEGE the impact is significant in northeastern China. Nonetheless the results of ARPEGE confirm the counter-intuitive results of LOVECLIM where ice sheets contribute to enhance monsoon precipitation. This happens through a topography induced wave propagating through Eurasia with an ascending branch over northeastern China. A feature which is also seen in LOVECLIM. The SST forcing in ARPEGE results in a strong zonal temperature gradient between the North Atlantic and east Eurasia, which in turn triggers an atmospheric gravity wave. This wave induces a blocking Okhotskian high, preventing the northwards penetration of the Meiyu monsoon front. The synergism between the ice sheets and SST is found through the factor separation method, yielding an increase in the Meiyu precipitation, though a reduction of the Changma precipitation. The synergism between the ice sheets and SST play a non-negligible role and should be taken into consideration in GCM studies. Preliminary fully coupled AOGCM results presented here further substantiate the finding of stronger MIS–13 monsoons and a reinforcement from ice sheets. This work increases our understanding of the signals found in the paleo-observations and the dynamics of the complex East Asian Summer Monsoon.     

Petrogenesis of the granitoid rocks from Askot crystallines,Kumaun Himalaya

The Askot crystallines form a doubly plunging synformal belt and occurs as a detached crystalline belt or klippen in the vast sedimentary terrain lying between Central crystallines towards north and the Almora crystallines to the south. It is dominated by granite gneiss and augen gneiss, and also comprise of metapelites, migmatites and basic intrusives. In this paper, the geochemical studies of the granite gneiss and augen gneiss from the Askot crystallines, Kumaun Himalaya were carried out in order to understand their origin and evolution. The granite gneiss is generally foliated, with less foliated and porphyritic variety seen in the core part. The K-feldspar shows Carlsbad twinning, while plagioclases show complex twinning. They show euhedral zircon and apatite along with titanite as accessory minerals. The granite gneiss is moderately evolved (Mg# ∼50) and has granodiorite composition with metaluminous, calc-alkaline trends. They show higher concentration of Ti, Ca, Mg and low abundance of ∑REE (∼165 ppm) in comparison to augen gneiss. They show volcanic arc signatures and compare well with Lateorogenic granites of Proterozoic times distributed world wide. These calc-alkaline granites appear derived from a Paleoproterozoic mafic/intermediate lower-crust reservoir probably involving arc magma underplating. Granite gneiss is also peraluminous with molar A/CNK>1.1, and the heterogeneity of granite gneiss can be explained with the precursor melts, experiencing assimilation during up-rise through crust or contamination of source itself involving sediments from the subduction zone.     

Hill slope stability analysis using two and three dimensions analysis: A comparative study

Slope instability is very common phenomenon, especially in tectonically active hills of the lesser Himalaya. The deformed, weathered and fragile rocks of the lesser Himalaya are often vulnerable under natural or anthropogenic influences. There were several cases of slope failure along highway sections in Uttarakhand Himalaya. The study was carried out along a highway section of NH-109. The factor of safety (FoS) is commonly most acceptable parameter that analyses the health of slopes. The two dimensional (2D) numerical analysis techniques are commonly used to obtain the FoS. It is observed that many times FoS obtained from 2D analysis techniques do not qualify the actual conditions and are usually lower in value as compared to ground conditions. This, in turn, increases the cost of remedial measures used for protection of slopes. This paper presents a comparative study of 2D and 3D numerical analysis based on the finite difference method (FDM) using fast Langrangian analysis of continua (FLAC) codes. The study indicates that there is no appreciable difference between FoS values obtained from 2D and 3D analysis based on the selected slope conditions. The difference ranges from 0.02 to 0.07 for analysed cases in uniform rock mass. The study also exhibits some of the important analytical observations and effects of variables on resultant FoS.     

Harmonics of low-amplitude anisotropic wave trains in cosmic rays

The purpose of this work is to investigate the first three harmonics of low-amplitude anisotropic wave trains (LAEs) of cosmic ray intensity and their association with solar and heliospheric parameters. The significant behaviour of these events is that the amplitude remains low for the first harmonic and high for the second/third harmonics, whereas direction of the anisotropy shift is towards earlier hours for the first harmonic and towards later hours for the second/third harmonic compared to annual average anisotropy. The first two harmonics are found to correlate well with the solar activity cycle during these LAEs. The amplitude and the direction of the first two harmonics do not show any significant association with the polarity change of the Bx/By component of the interplanetary magnetic field during LAEs. However, the third harmonic (amplitude and phase) shows some positive correlation with the Bx and negative correlation with the By component. The occurrence of LAEs is dominant for the positive polarity of Bx and the negative polarity of By. The occurrence of LAEs is dominant during the period of average solar wind velocity but their occurrence during high-speed solar wind streams cannot be overlooked. The frequency of occurrence of these LAEs is more during co-rotating streams.The amplitude of first and second harmonic shows deviations for different values of geomagnetic activity index Ap. However, the amplitude of second harmonic and direction of all the three harmonics do not show any significant association with the Ap-index. The Ap-index consistently remains in the range 14?Kp?31 during these events.The amplitude of first and third harmonic and the direction of first harmonic show deviations for different values of proton density. However, the amplitude of the second harmonic and the direction of the second and third harmonics do not show any significant association with proton density. The occurrence of LAEs is dominant when proton density remains ?20. The cosmic ray intensity during LAEs has good anti-correlation with interplanetary magnetic field strength (B) and its Bx component, whereas it shows a good correlation with its By component. However, it shows significant anti-correlation with sunspot number, the product (R×V) and (R×B).     

Performance of a damage‐protected beam–column subassembly utilizing external HF2V energy dissipation devices

Ductile‐jointed connections, which generally require some form of supplementary energy dissipation to alleviate displacement response, typically employ mild steel energy dissipation devices. These devices run the risk of low‐cycle fatigue, are effective only for peak cycles that exceed prior displacements, are prone to buckling, and may require replacement following an earthquake. This study presents an experimental investigation employing an alternative to mild steel: a high force‐to‐volume (HF2V) class of damper‐based energy dissipation devices. Tests are performed on a near full‐scale beam–column joint subassembly utilizing externally mounted compact HF2V devices. Two configurations are considered: an exterior joint with two seismic beams and one gravity beam framing into a central column, and a corner joint with only one seismic beam and one gravity beam framing into a column. Quasi‐static tests are performed to column drifts up to 4%. The experiments validate the efficacy of the HF2V device concept, demonstrating good hysteretic energy dissipation, and minimal residual device force, allowing ready re‐centring of the joint. The devices dissipate energy consistently on every cycle without the deterioration observed in the yielding steel bar type of devices. The effectiveness of the HF2V devices on structural hysteretic behavior is noted to be sensitive to the relative stiffness of the anchoring elements, indicating that better efficiency would be obtained in an embedded design. Copyright © 2008 John Wiley & Sons, Ltd.     

Error estimation of closed‐form solution for annual rate of structural collapse

With the increasing emphasis of performance‐based earthquake engineering in the engineering community, several investigations have been presented outlining simplified approaches suitable for performance‐based seismic design (PBSD). Central to most of these PBSD approaches is the use of closed‐form analytical solutions to the probabilistic integral equations representing the rate of exceedance of key performance measures. Situations where such closed‐form solutions are not appropriate primarily relate to the problem of extrapolation outside of the region in which parameters of the closed‐form solution are fit. This study presents a critical review of the closed‐form solution for the annual rate of structural collapse. The closed‐form solution requires the assumptions of lognormality of the collapse fragility and power model form of the ground motion hazard, of which the latter is more significant regarding the error of the closed‐form solution. Via a parametric study, the key variables contributing to the error between the closed‐form solution and solution via numerical integration are illustrated. As these key variables cannot be easily measured, it casts doubt on the use of such closed‐form solutions in future PBSD, especially considering the simple and efficient nature of using direct numerical integration to obtain the solution. Copyright © 2008 John Wiley & Sons, Ltd.     

Impact of ice sheet induced North Atlantic oscillation on East Asian summer monsoon during an interglacial 500,000?years ago

Marine Isotope Stage (MIS) 13, an interglacial about 500,000?years ago, is unique due to an exceptionally strong East Asia summer monsoon (EASM) occurring in a relatively cool climate with low greenhouse gas concentrations (GHG). This paper attempts to find one of the possible mechanisms for this seeming paradox. Simulations with an Earth System model LOVECLIM show that the presence of ice sheets over North America and Eurasia during MIS-13 induces a positive phase of the winter North Atlantic Oscillation (NAO) like feature. The ocean having a longer memory than the atmosphere, the oceanic anomalies associated with NAO persists until summer. The signals of summer NAO are transmitted to East Asia to reinforce the monsoon there through the stationary waves excited at the Asian Jet entrance. The geopotential height shows clearly a mid-latitude wave train with positive anomalies over the eastern Mediterranean/Caspian Sea and the Okhotsk Sea and a negative anomaly over Lake Baikal. This reinforces the effect of the high-latitude wave train induced independently by the Eurasian ice sheet topography as shown in previous study. These features reinforce the Meiyu front and enhance the precipitation over East Asia. The results obtained from LOVECLIM are further confirmed by an atmospheric general circulation model, ARPEGE.     

Effect of extracellular polymeric substances on sludge reduction potential of Bacillus licheniformis

The disposal of wastewater sludge generated during the treatment of the various municipal and industrial wastewaters is a major environmental problem. In this study the thermophilic bacterium Bacillus licheniformis, which enhances the efficiency of sludge reduction, was isolated from waste activated sludge acclimated to 55 °C. The resulting suspended solids’ degradation was 12 % and chemical oxygen demand solubilization was 18 %. To further enhance the sludge reduction potential, extra polymeric substances, which play a major role in the formation of flocs, were removed. A chemical extractant, ethylenediaminetetraacetate that is also a cation binding agent, was used to remove the extra polymeric substances. After the removal of extra polymeric substances, the suspended solids’ degradation increased from 12 to 23 % and the chemical oxygen demand solubilization increased from 18 to 25 %. These observations confirm that Bacillus licheniformis enhanced sludge reduction in non-flocculated sludge (with the removal of extra polymeric substances) as compared to flocculated sludge (without the removal of extra polymeric substances).     

Petrology, geochemistry and genesis of newly discovered Mesoproterozoic highly magnesian, calcite-rich kimberlites from Siddanpalli, Eastern Dharwar Craton, Southern India: products of subduction-related magmatic sources?

The Siddanpalli kimberlites constitute a newly discovered cluster (SKC) of Mesoproterozoic (1090 Ma) dykes occurring in the granite-greenstone terrain of the Gadwal area in the Eastern Dharwar Craton (EDC), Southern India. They belong to coherent facies and contain serpentinized olivines (two generations), phlogopite, spinel, perovskite, ilmenite, apatite, carbonate and garnet xenocrysts. A peculiar feature of these kimberlites is the abundance of carbonate and limestone xenoliths of the eroded platformal Proterozoic (Purana) sedimentary cover of Kurnool/Bhima age. Chemically, the Siddanpalli dykes are the most magnesium-rich (up to 35 wt.% MgO) and silica-undersaturated (SiO₂?<?35 wt.%) of all kimberlites described so far from the Eastern Dharwar Craton. The La/Yb ratio in the Siddanpalli kimberlites (64–105) is considerably lower than that in the other EDC kimberlites (108–145), primarily owing to their much higher HREE abundances. Since there is no evidence of any crustal contamination by granitic rocks we infer this to be a specific character of the magmatic source. A comparison of the REE geochemistry of the Siddanpalli kimberlites with petrogenetic models for southern African kimberlites suggests that they display involvement of a wide range in the degree of melting in their genesis. The different geochemical signatures of the SKC compared to the other known kimberlites in the EDC can be explained by a combination of factors involving: (i) higher degrees of partial melting; (ii) relatively shallower depths of derivation; (iii) possible involvement of subducted component in their mantle source region; and (iv) previous extraction of boninitic magmas from their geological domain.