The Techniques of Thin Layer Chromatography and the Study of Carbohydrates Using Thin Layer Chromatography

Refined Kraft pulp is found to contain D (+), Mannose, D (+) Xylose, and Glucose; and not to contain Galactose. Silia gel plates and Kieselguhr plates were used for the separation. Sodium hydroxide was the carrier solvent and the plates conditioned for thirty minutes. The Kamag Vario-KS-Chamber is found to be a good effective laboratory tool. There are many areas where this technique can be used. A detailed historical background is given for a basic background in thin layer chromatography, along with a complete experimental procedure of the use of the Vario-KS-Chamber

Intersections of Longest Paths and Cycles

It is a well known fact in graph theory that in a connected graph any two longest paths must have a vertex in common. In this paper we will explore what happens when we look at k - connected graphs, leading us to make a conjecture about the intersection of any two longest paths. We then look at cycles and look at what would be needed to improve on a result by Chen, Faudree and Gould about the intersection of two longest cycles

Closed Knight\u27s Tours with Minimal Square Removal for All Rectangular Boards

A closed knight\u27s tour of a chessboard uses legal moves of the knight to visit every square exactly once and return to its starting position. In 1991 Schwenk completely classified the rectangular chessboards that admit a closed knight\u27s tour. For a rectangular chessboard that does not contain a closed knight\u27s tour, this paper determines the minimum number of squares that must be removed in order to admit a closed knight\u27s tour. Furthermore, constructions that generate a closed tour once appropriate squares are removed are provided

"der endgültige Schreibprozess ist alleine": Geschichtswissenschaftliche Seminararbeiten als Herausforderungen in der Studieneingangsphase

Das Schreiben von Hausarbeiten im Fach Geschichte stellt für Studierende gerade am Anfang des Studiums eine besondere Herausforderung dar. Die Ergebnisse empirischer Untersuchungen im Rahmen eines Projekts des Historischen Seminars der Universität Mainz erlauben Aussagen darüber, wie diese Herausforderung von Studierenden und Lehrenden wahrgenommen und beurteilt wird. Die Kenntnis solcher Einstellungen kann das Problembewusstsein von Lehrenden fördern und dabei helfen, die Lehre zielgerichtet zu entwickeln.The writing of seminar papers or Hausarbeiten in the discipline of history poses a special challenge for students, especially for university entrants. Research data of empirical studies as part of a project initiated by the Institute of History at the University of Mainz permits conclusions about how this challenge is perceived and assessed by students and teachers. Knowledge of such attitudes could further teachers' problem awareness and help to develop target-oriented teaching

Combined Description of N‾N\bf{\overline{N}N} Scattering and Annihilation With A Hadronic Model

A model for the nucleon-antinucleon interaction is presented which is based on meson-baryon dynamics. The elastic part is the $G$-parity transform of the Bonn $NN$ potential. Annihilation into two mesons is described in terms of microscopic baryon-exchange processes including all possible combinations of $\pi,\eta,\rho,\omega,a_0,f_0,a_1,f_1,a_2,f_2,K,K^*$. The remaining annihilation part is taken into account by a phenomenological energy- and state independent optical potential of Gaussian form. The model enables a simultaneous description of nucleon-antinucleon scattering and annihilation phenomena with fair quality.Comment: revised version, REVTEX, 9 pages, 10 figures available from this URL ftp://ikp113.ikp.kfa-juelich.de/pub/kph140/nucl-th.9411014.u

Correlated ππ\pi\pi and KKˉK\bar K exchange in the baryon-baryon interaction

A dynamical model for correlated two-pion and two-kaon exchange in the baryon- baryon interaction is presented, both in the scalar-isoscalar ($\sigma$) and the vector-isovector ($\rho$) channel. The correlations between the two pseudoscalar mesons are taken into account by means of $\pi\pi - K\bar K$ amplitudes derived from a meson-exchange model, which is in line with the empirical $\pi\pi$ data. It is found that correlated $K\bar K$ exchange plays an important role in the $\sigma$-channel for baryon-baryon states with non- vanishing strangeness. The strength of correlated $\pi\pi$ plus $K\bar K$ exchange in the $\sigma$-channel decreases with the strangeness of the baryon- baryon system becoming more negative. The results for correlated $\pi\pi$- exchange in the vector-isovector channel deviate from what is expected in the naive SU(3) picture for genuine $\rho$-exchange. Shortcomings of a simplified description in terms of sharp mass $\sigma$- and $\rho$-exchange are pointed out.Comment: 51 pages, Latex file, figures available from [email protected]

Untersuchung des Einflusses ionisierender Strahlung auf die Expression der Histonvariante H2A.J in Keratinozyten der präputialen Epidermis

Abstract Hintergrund: Zelluläre Seneszenz beschreibt den terminalen Proliferationstopp von weiterhin metabolisch aktiven Zellen, der durch eine Vielzahl von Stimuli ausgelöst werden kann. Dabei spielt Seneszenz eine ambivalente Rolle, da sie einerseits an der embryonalen Entwicklung, der Wundheilung sowie der Tumorsuppression beteiligt ist und andererseits relevante Prozesse im Rahmen des physiologischen Alterungsprozesses begleitet. Ein möglicher Auslöser prämaturer Seneszenz stellt ionisierende Strahlung dar, deren DNA-schädigende Wirkung im Rahmen der Radiotherapie zur Tumorkontrolle eingesetzt wird. In vorangegangenen Publikationen wurde bereits untersucht, ob durch die Exposition von muriner und humaner Epidermis mit ionisierender Strahlung eine veränderte Expression der Histonvariante H2A.J nachweisbar ist und ob diese mit altersabhängiger Seneszenz assoziiert werden kann. Darüber hinaus zeigten ex-vivo Untersuchungen eine Korrelation zwischen H2A.J-Expression und strahleninduzierter Seneszenz in der humanen, abdominellen Epidermis von erwachsenen Probanden. In dieser Arbeit wurde basierend auf den bereits publizierten Ergebnissen untersucht, ob ein Zusammenhang zwischen der veränderten Expression der Histonvariante H2A.J und zellulärer Seneszenz nach der Exposition mit ionisierender Strahlung auch in der infantilen präputialen Epidermis nachweisbar ist. Material und Methoden: Im Rahmen elektiver Zirkumzisionen wurden 19 Hautproben männlicher Patienten ohne relevante Grunderkrankungen im Alter von 1 - 10 Jahren akquiriert. Die Epidermis wurde mit einer definierten Dosis bestrahlt, anschließend erfolgte die Markierung der Histonvariante H2A.J und proliferations-assoziiertem Ki67 mittels fluoreszenz-gekoppelten Antikörpern und die Visualisierung der H2A.J- und/oder Ki67-positiver Zellen mit Hilfe eines Fluoreszenzmikroskopes. Ergebnisse: Die quantitative Analyse der H2A.J- und Ki67-positiven Zellen ergab keinen signifikanten Unterschied im Vergleich zur Kontrollgruppe. Es konnte jedoch ein bestrahlungsunabhängiger Anstieg an H2A.J-positiven Zellen, ausgehend vom Stratum germinativum hin zum Stratum granulosum, nachgewiesen werden. Schlussfolgerung: Es konnten kein Zusammenhang zwischen der applizierten Dosis und einer veränderten H2A.J-Expression in seneszenten Zellen der präputialen Epidermis von pädiatrischen Probanden festgestellt werden. Die bestrahlungsunabhängige schichtspezifische Verteilung H2A.J-positiver Zellen könnte ein Hinweis auf einen möglichen Zusammenhang zwischen H2A.J und der Differenzierung von Keratinozyten sein.Summary Background: Cellular senescence describes the terminal proliferation arrest of still metabolically active cells, which can be triggered by a variety of stimuli. Senescence plays an ambivalent role, as it is involved in embryonic development, wound healing and tumor suppression on the one hand and accompanies relevant processes in the physiological aging process on the other hand. A possible trigger of premature senescence is ionizing radiation, whose DNA-damaging effect is used in radiotherapy for tumor control. Previous publications have investigated whether exposure of murine and human epidermis to ionizing radiation results in altered expression of the histone variant H2A.J and whether this can be associated with age-related senescence. Furthermore, ex-vivo studies showed a correlation between H2A.J expression and radiation-induced senescence in the human abdominal epidermis of adult volunteers. In this work, based on the previously published results, we investigated whether a correlation between altered expression of the histone variant H2A.J and cellular senescence after exposure to ionizing radiation is also detectable in infantile preputial epidermis. Material and Methods: Nineteen skin samples from male patients without relevant underlying diseases aged 1 - 10 years were acquired during elective circumcisions. The epidermis was irradiated with a defined dose, followed by labeling of histone variant H2A.J and proliferation-associated Ki67 using fluorescence-coupled antibodies and visualization of H2A.J- and/or Ki67-positive cells using a fluorescence microscope. Results: Quantitative analysis of H2A.J- and Ki67-positive cells revealed no significant difference compared with the control group. However, an irradiation-independent increase of H2A.J-positive cells, starting from the stratum germativum to the stratum granulosum, could be detected. Conclusion: No correlation between the applied dose and altered H2A.J expression in senescent cells of the preputial epidermis of pediatric subjects could be detected. The irradiation-independent layer-specific distribution of H2A.J-positive cells may indicate a possible link between H2A.J and keratinocyte differentiation

Deep Inelastic Scattering from off-Shell Nucleons

We derive the general structure of the hadronic tensor required to describe deep-inelastic scattering from an off-shell nucleon within a covariant formalism. Of the large number of possible off-shell structure functions we find that only three contribute in the Bjorken limit. In our approach the usual ambiguities encountered when discussing problems related to off-shellness in deep-inelastic scattering are not present. The formulation therefore provides a clear framework within which one can discuss the various approximations and assumptions which have been used in earlier work. As examples, we investigate scattering from the deuteron, nuclear matter and dressed nucleons. The results of the full calculation are compared with those where various aspects of the off-shell structure are neglected, as well as with those of the convolution model.Comment: 36 pages RevTeX, 9 figures (available upon request), ADP-93-210/T128, PSI-PR-93-13, accepted for publication in Physical Review

Near-threshold production of a0(980)a_0(980)-mesons in πN\pi N and NN collisions and a0/f0a_0/f_0-mixing

We consider near-threshold $a_0(980)$-meson production in $\pi N$ and $NN$ collisions. An effective Lagrangian approach with one-pion exchange is applied to analyze different contributions to the cross section for different isospin channels. The Reggeon exchange mechanism is also evaluated for comparison. The results from $\pi N$ reactions are used to calculate the contribution of the $a_0$ meson to the cross sections and invariant $K \bar K$ mass distributions of the reactions $pp\to pn K^+\bar K^0$ and $pp\to pp K^+K^-$. It is found that the experimental observation of $a_0^+$ mesons in the reaction $pp\to pn K^+\bar K^0$ is much more promising than the observation of $a_0^0$ mesons in the reaction $pp\to pp K^+K^-$. Effects of isospin violation in the reactions $pN \to d a_0$, $pd \to \mathrm{^3He/^3H} a_0$, and $dd \to \mathrm{^4He} a_0$, which are induced by $a_0(980)$--$f_0(980)$ mixing, are also analyzed.Comment: 43 pages, including 16 eps figures, to be bublished in Phys. Atom. Nucl. (Yad. Fiz.) vol. 65, No. 11 (2002