24,886 research outputs found
The interaction between the Moon and the solar wind
We study the interaction between the Moon and the solar wind using a
three-dimensional hybrid plasma solver. The proton fluxes and electromagnetical
fields are presented for typical solar wind conditions with different magnetic
field directions. We find two different wake structures for an interplanetary
magnetic field that is perpendicular to the solar wind flow, and for one that
is parallell to the flow. The wake for intermediate magnetic field directions
will be a mix of these two extreme conditions. Several features are consistent
with a fluid interaction, e.g., the presence of a rarefaction cone, and an
increased magnetic field in the wake. There are however several kinetic
features of the interaction. We find kinks in the magnetic field at the wake
boundary. There are also density and magnetic field variations in the far wake,
maybe from an ion beam instability related to the wake refill. The results are
compared to observations by the WIND spacecraft during a wake crossing. The
model magnetic field and ion velocities are in agreement with the measurements.
The density and the electron temperature in the central wake are not as well
captured by the model, probably from the lack of electron physics in the hybrid
model.Comment: Accepted for publication in Earth, Planets and Spac
Rotating binary Bose-Einstein condensates and vortex clusters in quantum droplets
Quantum droplets may form out of a gaseous Bose-Einstein condensate,
stabilized by quantum fluctuations beyond mean field. We show that multiple
singly-quantized vortices may form in these droplets at moderate angular
momenta in two dimensions. Droplets carrying these precursors of an Abrikosov
lattice remain self-bound for certain timescales after switching off an initial
harmonic confinement. Furthermore, we examine how these vortex-carrying
droplets can be formed in a more pertubation-resistant setting, by starting
from a rotating binary Bose-Einstein condensate and inducing a metastable
persistent current via a non-monotonic trapping potential.Comment: 5 page, 4 figure
Uni-directional polymerization leading to homochirality in the RNA world
The differences between uni-directional and bi-directional polymerization are
considered. The uni-directional case is discussed in the framework of the RNA
world. Similar to earlier models of this type, where polymerization was assumed
to proceed in a bi-directional fashion (presumed to be relevant to peptide
nucleic acids), left-handed and right-handed monomers are produced via an
autocatalysis from an achiral substrate. The details of the bifurcation from a
racemic solution to a homochiral state of either handedness is shown to be
remarkably independent of whether the polymerization in uni-directional or
bi-directional. Slightly larger differences are seen when dissociation is
allowed and the dissociation fragments are being recycled into the achiral
substrate.Comment: 9 pages, 4 figures, submitted to Astrobiolog
Initial experiments concerning quantum information processing in rare-earth-ion doped crystals
In this paper initial experiments towards constructing simple quantum gates
in a solid state material are presented. Instead of using specially tailored
materials, the aim is to select a subset of randomly distributed ions in the
material, which have the interaction necessary to control each other and
therefore can be used to do quantum logic operations. The experimental results
demonstrate that part of an inhomogeneously broadened absorption line can be
selected as a qubit and that a subset of ions in the material can control the
resonance frequency of other ions. This opens the way for the construction of
quantum gates in rare-earth-ion doped crystals.Comment: 24 pages, including 12 figure
Full Carbon Account for Russia.
The Forestry Project (FOR) at IIASA has produced a full carbon account (FCA) for Russia for 1990, together with scenarios for 2010. Currently, there are rather big question marks regarding the existing carbon accounts for Russia, and Russia is critical to the global carbon balance due to its size. IIASA is in a position to perform solid analysis of Russia because of the databases that the Institute has built over the years. FOR based this work on a comprehensive geographic information system comprising georeferenced descriptions of the environment and land of Russia, which in turn are based on a number of thematic, digitized maps and databases. For the Russian energy sector and other industrial sectors (except the forest industry), the project used emissions estimates from the recent IIASA study "Global Energy Perspectives" (1998). The project carried out a separate substudy for the Russian forest industry sector. According to FOR's estimate, the total fluxes (including energy and industry sectors) in Russia were a net source of 527 teragrams of carbon (Tg C) in 1990. To illustrate the possible development of the carbon pools and fluxes over the next 10 years, FOR developed three different scenarios for the period 1990-2010, reflecting different assumptions regarding Russia's GDP growth. According to these scenarios, Russia will continue to be a net source of carbon to the atmosphere with 156-385 Tg C in 2010, including the emissions from energy and other industrial sectors. However, analysis of the FCA also shows considerable uncertainties involved in the carbon accounting. These uncertainties exceed the calculated changes in the full flux balance for the period 1990-2010. At present, this raises grave questions regarding the reliability of any accounting system used to measure terrestrial ecosystems for compliance with the Kyoto Protocol.
Sustainability and the Canadian Forest Sector
This paper was presented as a keynote address at the conference on Forest Sustainability - Beyond 2000 held in May 2000 in Thunder Bay, Canada. The conference brought together forest sector leaders and professionals from across Canada.
This paper is an extension of earlier work on the sustainability North American wood supplies (Nilsson et al., 2000). The present paper examines the efficiency of the current established criteria and indicators for sustainable development of the forest sector. The current system of criteria and indicators concentrates on the management aspects instead of the objectives setting. The current system is too complicated to be implemented and neglects the fact that sustainability cannot be achieved by a top-down approach but only by the people working on the ground at the local level. This paper presents a number of guidelines on the necessary steps to be taken in order to move towards A Forest Sector for Sustainable Development
Press-imistic Futures? - Science Based Concepts and Models to Assess the Long-term Competitiveness of Paper Products in the Information Age
Traditional forest sector models used for demand forecasts only predict some "average future" based on extrapolation of the past. However, innovation driven dynamic systems are likely to lead to technological equilibria that are far from this "average future." Thus, traditional models are incapable of assessing the full range of risks and opportunities in the market. Today, decision-makers need tools to explore and understand the system they operate in to be able to act as a pro-active market mover supported by rehearsed ex-ante strategies. In this paper we develop a simple scenario model to visualize possible future developments of information papers. Scenario forecasts are based on trajectories of population and economic growth, changes in life and work styles, substitution behavior, and technological change for individual population cohorts. Cohorts are split according to educational attainment, age, and gender. We also provide a theoretical background on the positive and negative feedback economies due to innovation and knowledge that are crucially determining the dynamics of the system. In a case study, we apply the model for one scenario of newsprint consumption in the USA. In addition, we present the methodology to plot the consumption pattern in a geographically explicit form using the concept of 'Paperscapes.
Strategic Implications of eCommerce for Papermakers
It is expected that the paper and office products supply chain will move online in the very near future. The hubris of new eBusiness models has ended in a fragmented picture of a multitude of personal views relating to future developments on the eEconomy, eIndustry and eEnterprise levels. This paper endeavors to compile the currently existing knowledge in this field and to identify the basic drivers and inhibitors of the new economy that are of relevance to the forest industry. On the eEconomy level, acceleration in macro-economic growth can be expected due to efficiency and productivity improvements that are triggered by the elimination of information barriers thereby creating more efficient markets. On the eIndustry level, globally operating and more adaptive industry networks will improve economic performance by reaping economies of scale. Less volatile markets will result from improved planning and coordination thereby eliminating redundant capacities. An overly horizontally concentrated market structure might bear the danger of locking the paper industry in an underdevelopment trap of innovation exhaustion and organizational inertia. Business entities on the eEnterprise level will have to adopt the principles of openness, connectivity and strategic integration to fully benefit from networking and integration effects along the entire value chain. However a number of issues, such as sharing critical data in a networked economy, will increase demands for newly adapted business culture and management models
The Austrian Carbon Database (ACDb) Study - Overview [Revised 28 October 2003]
This is the final overview report of the Austrian Carbon Database (ACDb) Study, which pursues three main objectives: (1) to support the Austrian Carbon Balance Model (ACBM) II; (2) to internationalize the Austrian carbon analysis and to place Austrias carbon accounting within an international science and policy context focusing on the UN Framework Convention on Climate Change (FCCC); and (3) to provide good practice guidance in consideration of Full Carbon Accounting (FCA) rather than Partial Carbon Accounting (PCA).
The Study is divided into two phases, a deductive and an inductive research phase. The deductive research phase builds upon the theoretical insights gained during the ACDb Study and addresses Objective 2 (Internationalization). The inductive research phase builds upon the generalized experiences from working with uncertainties in building the ACDb and addresses Objectives 1 (ACBM II Support) and 3 (Good Practice Guidance).
The ACDb is a carbon consistent database for Austria that acknowledges FCA. It focuses on publicly available, including measured, data around 1990 and attributes special importance to the direct and transparent understanding of both first (mean values) and second statistical moments (uncertainties). The ACDb does not replace existing, officially agreed and widely accepted, Austrian databases but provides a thematically less detailed, however, carbon consistent standard that allows to quantify the uncertainties underlying these databases when using them in a wider (Austrian-integrated) context than traditionally done.
The focus of the Study is on conclusions that are generally valid and are not only specific for Austria. Based on our deductive and inductive research, we conclude that the Kyoto Protocol and the way national emissions are inventoried urgently need fundamental as well as methodological improvements, more than ever before
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