Sample records for zilmer tiiu vihalemm
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Chemical Laws, Idealization and Approximation
ERIC Educational Resources Information Center
Tobin, Emma
2013-01-01
This paper examines the notion of laws in chemistry. Vihalemm ("Found Chem" 5(1):7-22, 2003) argues that the laws of chemistry are fundamentally the same as the laws of physics they are all "ceteris paribus" laws which are true "in ideal conditions". In contrast, Scerri (2000) contends that the laws of chemistry are…
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Chemical Laws, Idealization and Approximation
NASA Astrophysics Data System (ADS)
Tobin, Emma
2013-07-01
This paper examines the notion of laws in chemistry. Vihalemm ( Found Chem 5(1):7-22, 2003) argues that the laws of chemistry are fundamentally the same as the laws of physics they are all ceteris paribus laws which are true "in ideal conditions". In contrast, Scerri (2000) contends that the laws of chemistry are fundamentally different to the laws of physics, because they involve approximations. Christie ( Stud Hist Philos Sci 25:613-629, 1994) and Christie and Christie ( Of minds and molecules. Oxford University Press, New York, pp. 34-50, 2000) agree that the laws of chemistry are operationally different to the laws of physics, but claim that the distinction between exact and approximate laws is too simplistic to taxonomise them. Approximations in chemistry involve diverse kinds of activity and often what counts as a scientific law in chemistry is dictated by the context of its use in scientific practice. This paper addresses the question of what makes chemical laws distinctive independently of the separate question as to how they are related to the laws of physics. From an analysis of some candidate ceteris paribus laws in chemistry, this paper argues that there are two distinct kinds of ceteris paribus laws in chemistry; idealized and approximate chemical laws. Thus, while Christie ( Stud Hist Philos Sci 25:613-629, 1994) and Christie and Christie ( Of minds and molecules. Oxford University Press, New York, pp. 34--50, 2000) are correct to point out that the candidate generalisations in chemistry are diverse and heterogeneous, a distinction between idealizations and approximations can nevertheless be used to successfully taxonomise them.
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Investigation on the Characteristics of Pellet Ablation in a Toroidal Plasma
NASA Astrophysics Data System (ADS)
Sato, K. N.; Sakakita, H.; Fujita, H.
2003-06-01
Characteristics of a cloud ablated from an ice pellet has been investigated in detail in the JIPP T-IIU tokamak plasma by utilizing a new scheme of pellet injection system, "the injection-angle controllable system". A long "helical tail" of ablation light has been observed using CCD cameras and a high speed framing photograph in the case of on-axis and off-axis injection with the injection angle smaller than a certain value. The direction of the helical tail is found to be independent to that of the total magnetic field lines of the torus. From the experiments with the combination of two toroildal filed directions and two plasma current directions, it is considered that the tail seems to rotate, in most cases, to the electron diamagnetic direction poloidally, and to the opposite to the plasma current direction toroidally. Consideration on various cross sections including charge exchange, ionization and elastic collisions leads us to the conclusion that the tail-shaped phenomena may come from the situation of charge exchange equilibrium of hydrogen ions and neutrals at extremely high density regime in the cloud. The relation of ablation behavior with plasma potential and rotation has also been studied. Potential measurements of pellet-injected plasmas using heavy ion beam probe (HIBP) method were carried out for the first time. In the case of an injection angle to be anti-parallel to the electron diamagnetic direction in the poloidal plane, the result shows that the direction of potential change is negative, and consequently the potential after the injection should be negative because it has been measured to be negative in usual ohmic plasmas without pellet injection. Thus, the direction of the "tail" structure seems to be consistent to that of the plasma potential measured, if it is considered that tail structure may be caused by the effect of the plasma potential and the rotation.
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NASA Astrophysics Data System (ADS)
Gaillard, Marie-Jose; Sugita, Shinya; Rundgren, Mats; Smith, Benjamin; Mazier, Florence; Trondman, Anna-Kari; Fyfe, Ralph; Kokfelt, Ulla; Nielsen, Anne-Birgitte; Strandberg, Gustav
2010-05-01
of ca. 1o x 1o. The REVEALS estimates of the past cover of PFTs will be 1) compared with the outputs of the LPJ-GUESS (10 PFTs), a widely-used dynamic vegetation model and 2) used as an alternative to the LPJ-GUESS-simulated vegetation (3 PFTs) to run for the past the regional climate model RCA3 developed at the Rossby Centre, Norrköping, Sweden. The study will evaluate and further refine these models (RCA3 and LPJ-GUESS) using a data-model comparison approach that incorporates new syntheses of palaeoclimatic data as well. It will lead to new assessments of the possible effect of various factors on climate, such as deforestations and afforestations, and changes in vegetation composition and spatial patterns of land cover/land use. Refined climate models and empirical land-cover reconstructions will shed new light on controversial hypotheses of past climate change and human impacts, such as the "Ruddiman hypothesis". First maps of REVEALS estimates of plant functional types (PFTs) are now available for Sweden, Norway, Finland, Denmark, Estonia, Poland, Germany, The Czech Republic, Switzerland and Britain (see Mazier et al. C1.21 and Trondman et al. C1.22). Correlation tests show that the REVEALS estimates are robust in terms of ranking of the PFTs' abundance (see Mazier et al, C1.21). The LANDCLIM project and network are a contribution to the IGBP-PAGES-Focus 4 PHAROS programme on human impact on environmental changes in the past. The following LANDCLIM members are acknowledged for providing pollen records, for help with pollen databases, and for providing results to the project: Mihkel Kangur and Tiiu Koff (Univ. Tallinn, Tallinn); Erik Kjellström (SMHI, Norrköping), Anna Broström, Lena Barnekow and Thomas Persson (GeoBiosphere Science Centre, Lund University); Anneli Poska (Physical Geography and Ecosystems Analysis, Lund University); Thomas Giesecke (Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen), Anne Bjune and John Birks (Dept. of