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Climate of the upper atmosphere  [cached]
Jürgen Bremer,Jan Lasˇtovicˇka,Andrei V. Mikhailov,David Altadill
Annals of Geophysics , 2009, DOI: 10.4401/ag-4576
Abstract: In the frame of the European COST 296 project (Mitigation of Ionospheric Effects on Radio Systems, MIERS) investigations of the climate of the upper atmosphere have been carried out during the last four years to obtain new information on the upper atmosphere. Mainly its ionospheric part has been analysed as the ionosphere most essential for the propagation of radio waves. Due to collaboration between different European partners many new results have been derived in the fields of long-term trends of different ionospheric and related atmospheric parameters, the investigations of different types of atmospheric waves and their impact on the ionosphere, the variability of the ionosphere, and the investigation of some space weather effects on the ionosphere.
Abrupt Climate Regime Shifts, Their Potential Forcing and Fisheries Impacts  [PDF]
Jianjun Xu, Alfred M. Powell
Atmospheric and Climate Sciences (ACS) , 2011, DOI: 10.4236/acs.2011.12004
Abstract: The purpose of this paper is to investigate whether a logical chain of events can be established to explain the abrupt climatic regime shift changes in the Pacific that link the atmosphere to the ocean to fisheries impacts. The investigation endeavors to identify synchronous abrupt changes in a series of data sets to establish the feasibility of abrupt of climate change often referred to as regime shifts. The study begins by using biological (fish catch/stock) markers to mathematically identify the dates of abrupt change. The dates are confirmed by a literature search of parameters that also show abrupt changes on the same dates. Using the biological date markers of abrupt change, analyses are performed to demonstrate that the interactions between the atmosphere, ocean, ecosystems and fisheries are a plausible approach to explaining abrupt climate change and its impacts.
Biogeophysical feedbacks trigger shifts in the modelled climate system at multiple scales
S. C. Dekker,H. J. de Boer,V. Brovkin,K. Fraedrich
Biogeosciences Discussions , 2009,
Abstract: Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologic-balance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbacks at local to regional scales could be strong enough to establish multiple states in the climate system. An Earth Model of Intermediate Complexity, PlaSim, is used to investigate the resilience of the climate system to vegetation disturbance at regional to global scales. We hypothesize that by starting with two extreme initialisations of biomass, positive vegetation-climate feedbacks will keep the vegetation-atmosphere system within different attraction domains. Indeed, model integrations starting from different initial biomass distributions diverged to clearly distinct climate-vegetation states in terms of abiotic (precipitation and temperature) and biotic (biomass) variables. Moreover, we found that between these states there are several other steady states which depend on the scale of perturbation. From here global susceptibility maps were made showing regions of low and high resilience. The model results suggest that mainly the boreal and monsoon regions have low resiliences, i.e. instable biomass equilibria, with positive vegetation-climate feedbacks in which the biomass induced by a perturbation is further enforced. The perturbation did not only influence single vegetation-climate cell interactions but also caused changes in spatial patterns of atmospheric circulation due to neighbouring cells constituting in spatial vegetation-climate feedbacks. Large perturbations could trigger an abrupt shift of the system towards another steady state. Although the model setup used in our simulation is rather simple, our results stress that the coupling of feedbacks at multiple scales in vegetation-climate models is essential and urgent to understand the system dynamics for improved projections of ecosystem responses to anthropogenic changes in climate forcing.
Micro- and nano-structured conducting polymeric materials
Gewu Lu,Feng’en Chen,Xufeng Wu,Liangti Qu,Jiaxin Zhang,Gaoquan Shi
Chinese Science Bulletin , 2005, DOI: 10.1360/982005-670
Abstract: Conducting polymeric materials with micro-/ nano-structures have potential applications in fabrication of various optical, electronic, sensing and electrochemical devices. This is mainly because these materials not only possess the characteristics of conducting polymers, but also have special functions based on their micro- or nano-structures. In this review, we summarize the recent work on “soft” and “hard” template-guided syntheses of micro-/nano-structured conducting polymers and open up the prospects of the main trends in this field.
Biogeophysical feedbacks trigger shifts in the modelled vegetation-atmosphere system at multiple scales
S. C. Dekker, H. J. de Boer, V. Brovkin, K. Fraedrich, M. J. Wassen,M. Rietkerk
Biogeosciences (BG) & Discussions (BGD) , 2010,
Abstract: Terrestrial vegetation influences climate by modifying the radiative-, momentum-, and hydrologic-balance. This paper contributes to the ongoing debate on the question whether positive biogeophysical feedbacks between vegetation and climate may lead to multiple equilibria in vegetation and climate and consequent abrupt regime shifts. Several modelling studies argue that vegetation-climate feedbacks at local to regional scales could be strong enough to establish multiple states in the climate system. An Earth Model of Intermediate Complexity, PlaSim, is used to investigate the resilience of the climate system to vegetation disturbance at regional to global scales. We hypothesize that by starting with two extreme initialisations of biomass, positive vegetation-climate feedbacks will keep the vegetation-atmosphere system within different attraction domains. Indeed, model integrations starting from different initial biomass distributions diverged to clearly distinct climate-vegetation states in terms of abiotic (precipitation and temperature) and biotic (biomass) variables. Moreover, we found that between these states there are several other steady states which depend on the scale of perturbation. From here global susceptibility maps were made showing regions of low and high resilience. The model results suggest that mainly the boreal and monsoon regions have low resiliences, i.e. instable biomass equilibria, with positive vegetation-climate feedbacks in which the biomass induced by a perturbation is further enforced. The perturbation did not only influence single vegetation-climate cell interactions but also caused changes in spatial patterns of atmospheric circulation due to neighbouring cells constituting in spatial vegetation-climate feedbacks. Large perturbations could trigger an abrupt shift of the system towards another steady state. Although the model setup used in our simulation is rather simple, our results stress that the coupling of feedbacks at multiple scales in vegetation-climate models is essential and urgent to understand the system dynamics for improved projections of ecosystem responses to anthropogenic changes in climate forcing.
Casimir forces between nano-structured particles  [PDF]
C E Román-Velázquez,Bo E Sernelius
Physics , 2008,
Abstract: We develop a computational study of Casimir forces between three dimensional (3D) finite objects with an internal granular structure. The objects in the model consist of a finite arrangement of nanometer sized spherical particles having a dipolar interaction. In this model system one can both study the basic properties of the Casimir forces, and the effects from changing the parameters of the nano-structured materials that constitute the particles; this last type of study leads to a form of control of the Casimir force and an insight into possible technological applications. We present examples of both kinds of study.
EPR study of nano-structured graphite  [PDF]
Jonas Kausteklis,Pavel Cevc,Denis Arcon,Lucia Nasi,Daniele Pontiroli,Marcello Mazzani,Mauro Ricco
Physics , 2011,
Abstract: We report on a systematic temperature dependent X-band electron paramagnetic resonance (EPR) study of nano-sized graphite particles prepared by ball-milling. In as-prepared samples a very intense and sharp EPR resonance at $g=2.0035$ has been measured. The EPR linewidth shows a Korringa-like linear temperature dependence arising due to the coexistence and strong exchange coupling of itinerant and localized edge states. With a prolonged aging in inert atmosphere changes in the EPR signal suggest gradual structural reconstruction where the localized edge-states dominate the EPR signal. In this case the EPR spin susceptibility shows a maximum at $\approx 23\, {\rm K}$ indicating the development of antiferromagnetic correlations as expected for the graphene lattice with a bipartite symmetry.
Nano-structured alloy and composite coatings for high temperature applications
Gao, Wei;Li, Zhengwei;
Materials Research , 2004, DOI: 10.1590/S1516-14392004000100023
Abstract: nano-structured materials often possess special properties that materials with identical compositions but ordinary grain size do not have. this paper reports our work on the surface nano-crystallisation and nano-structured alloy and composite coatings. a number of processing methods including magnetron sputtering, thermal spray and pulse electro-spark deposition have been used to produce surface nano-crystalline structure. the compositions and microstructures can be well controlled by using different targets or electrodes, nano-structured composites and adjusting processing parameters. surface nano-structured coatings can provide special chemical, mechanical and electronic properties such as high temperature corrosion and corrosive wear resistance. it has potential applications such as turbine blades, engine parts for petrochemical, aerospace and electronic device industries. this paper is focused on the study of the interrelations between processing, microstructure and properties. physical models have been established to explain the effects of nano-crystalline structure on the properties.
Nano-structured alloy and composite coatings for high temperature applications
Gao Wei,Li Zhengwei
Materials Research , 2004,
Abstract: Nano-structured materials often possess special properties that materials with identical compositions but ordinary grain size do not have. This paper reports our work on the surface nano-crystallisation and nano-structured alloy and composite coatings. A number of processing methods including magnetron sputtering, thermal spray and pulse electro-spark deposition have been used to produce surface nano-crystalline structure. The compositions and microstructures can be well controlled by using different targets or electrodes, nano-structured composites and adjusting processing parameters. Surface nano-structured coatings can provide special chemical, mechanical and electronic properties such as high temperature corrosion and corrosive wear resistance. It has potential applications such as turbine blades, engine parts for petrochemical, aerospace and electronic device industries. This paper is focused on the study of the interrelations between processing, microstructure and properties. Physical models have been established to explain the effects of nano-crystalline structure on the properties.
The Shifts Hypothesis - an alternative view of global climate change  [PDF]
P. V Belolipetsky
Physics , 2014,
Abstract: In this study we used HadCRUT4 temperature anomalies for 1950-2013 years in order to investigate properties of recent warming. Our aim was to separate changes produced by short-term ENSO variations and to look on temporal and spatial dynamics of residual temperature anomalies. For this we subtract linear influence of ENSO index from each HadCRUT4 grid box. We found that residual global temperature dynamics looks like staircase function: linear trends for three quasi-stable periods 1950-1987, 1988-1997 and 1998-2013 are near zero and near all warming occurred during two shifts of 1987/1988 and 1997/1998 years. All these allows us to formulate a new hypothesis about recent warming - the Shifts Hypothesis. It explains the structure of recent warming as follows: during shifts of 1987/1988 and 1997/1998 the mean value of global temperature quickly rose, over which natural variability associated with ENSO, PDO and many other local factors occurs. According to IPCC forcing-response paradigm warming process (WP) cleared from all factors should be continuous warming (may be near linear on the considered time interval). This idea is inconsistent to the obtained staircase function. This staircase function may be explained by current IPCC forcing-response paradigm only if it happened so that the combination of compensating factors is near the same as anthropogenic greenhouse gases (GHGs) forcing for each quasi-stable period - 1950-1987, 1988-1997 and 1998-2013. This seems very unlikely. An alternative and more simple explanation is the existence of some regulation mechanism (e.g. global thermostat) not presented in IPCC climate models. This mechanism should maintain global temperature near stable in 1950-1987, 1988-1997 and 1998-2013 periods nevertheless all the time growing forcing due to anthropogenic GHGs.
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