Das Substanzproblem bei Schlick und Cassirer

Mit Schlick und Cassirer standen sich ein Empirist und ein Neukantianer gegenüber. Die spätere Geschichte hat erwiesen, daß zumindest von der quantitativen Anteilnahme in der akademischen Philosophie sich der Empirismus zur prominenteren Position entwickelt hat. In der Frühzeit des logischen Empirismus trafen die Ansichten Schlicks auf eine mehrfach weiterentwickelte Kantlehre, sozusagen auf einen Spätkantianismus. Den expliziten Reibungspunkt bildete eine Diskussion um Kants synthetisch-apriorische Urteile über die Struktur von Raum und Zeit, motiviert durch die zu Zeiten Schlicks und Cassirers neuen Errungenschaften der Relativitätstheorie. Bezogen auf die Erkenntniskategorie der Substanz lassen sich sowohl bei Schlick als auch bei Cassirer ähnlich physikalisch inspirierte Überlegungen finden, die gleichwohl nicht direkt zwischen ihnen verhandelt wurden. Es zeigt sich nun, daß ihre Konzeptionen - kontrastiert mit den Überlegungen Hermann Weyls - angewandt auf die später gefolgten Quantenfeldtheorien von unterschiedlicher Zuverlässigkeit sind. Hier hätte Cassirer einen umfassenderen Interpretationsvorschlag unterbreiten können, als es ihm rhetorisch in den 1920er Jahren mit seiner Neufassung der Kantschen Lehre gelungen war

Development and Validation of a Calculation Routine for the Precise Determination of Pulse Overlap and Accumulated Fluence in Pulsed Laser Surface Treatment

In laser material processing, a variety of parameters like pulse fluence, total dose, step size, and pulse-to-pulse overlap are used to define and compare laser processes. Of these parameters, the pulse-to-pulse overlap can be the hardest to access as it is not implemented directly but instead depends on the spot diameter, its shape, and the respective scanning path that is used to cover the surface. This article shows that existing calculation routes overestimate the actual overlap by up to 21%. A novel calculation route is developed that greatly facilitates the determination of the pulse overlap and thereby the average number of laser pulses that interact with a given point on the surface. This approach makes it possible to achieve more reliable and comparable laser processes, which in return leads to better control of the procedure as the effect of individual parameters on a given output can be determined with greater precision

Event Indexing Systems for Efficient Selection and Analysis of HERA Data

The design and implementation of two software systems introduced to improve the efficiency of offline analysis of event data taken with the ZEUS Detector at the HERA electron-proton collider at DESY are presented. Two different approaches were made, one using a set of event directories and the other using a tag database based on a commercial object-oriented database management system. These are described and compared. Both systems provide quick direct access to individual collision events in a sequential data store of several terabytes, and they both considerably improve the event analysis efficiency. In particular the tag database provides a very flexible selection mechanism and can dramatically reduce the computing time needed to extract small subsamples from the total event sample. Gains as large as a factor 20 have been obtained.Comment: Accepted for publication in Computer Physics Communication

Why Quarks Are Unobservable

Cet article pose la question de savoir si les quarks — constituants élémentaires de la matière et dernières particules de la physique des hautes énergies à avoir été confirmées — peuvent être observés de manière directe ou indirecte. D’abord, des définitions antérieures de « l’observation » en physique seront examinées — en l’occurrence, celles proposées par Grover Maxwell, Bas van Fraassen et Dudley Shapere. Puis, leurs résultats seront comparés à une définition du concept d’observation et à une différenciation entre l’observation directe et indirecte. Une possibilité de mettre en évidence les quarks de manière expérimentale est le phénomène des jet-events, qui représentent un type spécifique de désagrégation dans les détecteurs de particules. Ces jet-events contribuent à l’étude de cas ici centrale, puisqu’ils sont la preuve la plus convaincante à ce jour des quarks. L’examen de jet-events et leurs évaluations par des physiciens mènent à la conclusion que les quarks ne peuvent être observés, ni directement ni indirectement. Cette thèse sera comparée aux points de vue de Kristin Shrader-Frechette et Michela Massimi sur l’observabilité des quarks. On en tire la conclusion que les quarks ne sont pas observables, si l’on entend employer le terme « observation » dans un sens non métaphorique et en conservant une relation avec ses usages dans la vie quotidienne.This essay deals with the question whether quarks—the basic components of matter and one of the youngest confirmed particles in high energy physics—can be observed directly or indirectly. First, I shall discuss earlier definitions of “observation” in physics suggested by Grover Maxwell, Bas van Fraassen, and Dudely Shapere. Then, I shall compare their results with a new consideration of the idea of “observation” in physics and the distinction between direct and indirect observation. One of the ways that quarks appear in experimental evidence is in jet-events which are special decay patterns in particle detectors. These jet-events are the central case study for this essay since they are the most convincing evidence of quarks so far. My inquiry into the physics behind jet-events and their treatment by physicists leads me to conclude that quarks are neither directly nor indirectly observed. I compare this thesis to other views on the observability of quarks, suggested by Kristin Shrader-Frechette and Michela Massimi. But in short, it seems to me that if the notion “observation” is to have a reasonable relation to an everyday life’s concept of observation, and if it is meant literally instead of metaphorically, then quarks are not observable in any currently-known experimental context

Functional MRI To Evaluate “Sense of Self” following Perforator Flap Breast Reconstruction

Background: Breast reconstruction is associated with high levels of patient satisfaction. Previous patient satisfaction studies have been subjective. This study utilizes functional magnetic resonance imaging (fMRI) to objectively evaluate “sense of self” following deep inferior epigastric perforator (DIEP) flap breast reconstruction in an attempt to better understand patient perception. Methods: Prospective fMRI analysis was performed on four patients before and after delayed unilateral DIEP flap breast reconstruction, and on four patients after immediate unilateral DIEP flap breast reconstruction. Patients were randomly cued to palpate their natural breast, mastectomy site or breast reconstruction, and external silicone models. Three regions of interest (ROIs) associated with self-recognition were examined using a general linear model, and compared using a fixed effects and random effects ANOVA, respectively. Results: In the delayed reconstruction group, activation of the ROIs was significantly lower at the mastectomy site compared to the natural breast (p<0.01). Ten months following reconstruction, activation of the ROIs in the reconstructed breast was not significantly different from that observed with natural breast palpation. In the immediate reconstruction group, palpation of the reconstructed breast was also similar to the natural breast. This activity was greater than that observed during palpation of external artificial models (p<0.01). Conclusions: Similar activation patterns were observed during palpation of the reconstructed and natural breasts as compared to the non-reconstructed mastectomy site and artificial models. The cognitive process represented by this pattern may be a mechanism by which breast reconstruction improves self-perception, and thus patient satisfaction following mastectomy

Applying Ultrashort Pulsed Direct Laser Interference Patterning for Functional Surfaces

Surface structures in the micro- and nanometre length scale exert a major influence on performance and functionality for many specialized applications in surface engineering. However, they are often limited to certain pattern scales and materials, depending on which processing technique is used. Likewise, the morphology of the topography is in complex relation to the utilized processing methodology. In this study, the generation of hierarchical surface structures in the micro- as well as the sub-micrometre scale was achieved on ceramic, polymer and metallic materials by utilizing Ultrashort Pulsed Direct Laser Interference Patterning (USP-DLIP). The morphologies of the generated patterns where examined in relation to the unique physical interaction of each material with ultrashort pulsed laser irradiation. In this context, the pattern formation on copper, CuZn37 brass and AISI 304 stainless steel was investigated in detail by means of a combination of experiment and simulation to understand the individual thermal interactions involved in USP-DLIP processing. Thereby, the pattern’s hierarchical topography could be tailored besides achieving higher process control in the production of patterns in the sub-µm range by USP-DLIP

Generalized Quasilinear Approximation: Application to Zonal Jets

Quasilinear theory is often utilized to approximate the dynamics of fluids exhibiting significant interactions between mean flows and eddies. We present a generalization of quasilinear theory to include dynamic mode interactions on the large scales. This generalized quasilinear (GQL) approximation is achieved by separating the state variables into large and small zonal scales via a spectral filter rather than by a decomposition into a formal mean and fluctuations. Nonlinear interactions involving only small zonal scales are then removed. The approximation is conservative and allows for scattering of energy between small-scale modes via the large scale (through nonlocal spectral interactions). We evaluate GQL for the paradigmatic problems of the driving of large-scale jets on a spherical surface and on the beta plane and show that it is accurate even for a small number of large-scale modes. As GQL is formally linear in the small zonal scales, it allows for the closure of the system and can be utilized in direct statistical simulation schemes that have proved an attractive alternative to direct numerical simulation for many geophysical and astrophysical problems