181 research outputs found
The hamiltonian formulation of QCD in terms of angle variables
For the sake of eliminating gauge variant degrees of freedom we discuss the
way to introduce angular variables in the hamiltonian formulation of QCD. On
the basis of an analysis of Gauss' law constraints a particular choice is made
for the variable transformation from gauge fields to angular field variables.
The resulting formulation is analogous to the one of Bars in terms of corner
variables. Therefore the corner or angle formulation may constitute an useful
starting point for the investigation of the low energy properties of QCD in
terms of gauge invariant degrees of freedom.Comment: email: [email protected]; 7 Pages LaTex Paper to
appear in Physics Letters
One or many middle class (es) in Kenya? Towards an analytical frame for distinguishing subgroups
The current debate considers the emerging African middle class as an economic and
political factor that stabilizes economic growth and that strives for democracy. This debate
implies that the middle class is quite homogeneous. However, we know from industrialized
countries that the middle class is sociocultural differentiated. How is this in Africa? To identify
traits and groups of middle classes in Africa we adapt a multi-layered framework. The focus are
(socio-)cultural differences among milieus of urban middle classes in Kenya. The framework
modifies BourdieuÂŽs sociology by differing the areas of analysis social structure, division of
labor, culture, historic socio-culture and influences of a city and of a region The adaptation of
this framework will be exemplified by an exemplary analysis of the milieu of Young Professionals
in Nairobi
Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation : part 2, alkaline earth elements as tracers of watershed hydrochemistry and provenance
This study demonstrates that alkaline earth elements in enamel of hippopotamids, in particular Ba and Sr, are tracers for water provenance and hydrochemistry in terrestrial settings. The studied specimens are permanent premolar and molar teeth found in modern and fossil lacustrine sediments of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River.
Concentrations in enamel vary by two orders of magnitude for Ba (120â9336 ÎŒg gâ1) as well as for Sr (9â2150 ÎŒg gâ1). The variations are partially induced during post-mortem alteration and during amelogenesis, but the major contribution originates ultimately from the variable water chemistry in the habitats of the hippopotamids which is controlled by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of MgO, Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamelâdentin junction by a factor of 1.3â1.9. These elements are well correlated in single specimens, thus suggesting that their distribution is determined by a common, single process, which can be described by closed system Rayleigh crystallization of bioapatite in vivo.
Enamel from most hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores. However, Ba/Sr ranges from 0.1 to 3 and varies on spatial and temporal scales. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic mantle rocks or Archean crustal rocks as the ultimate sources of Sr and Ba. This provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from 2 to 0.5. This trend can be correlated with changes in climate from humid to arid, in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water. The most plausible explanation is that Ba mobility decreased with increasing aridification due to preferential deposition with clay and Fe-oxide-hydroxide or barite on the watershed of Lake Albert
Zur Analyse soziokultureller Differenzierung von Mittelschichten im Globalen SĂŒden: Eine exemplarische Analyse von Milieus in Nairobi
In den letzten Jahren haben Debatten in internationalen Medien wie in verschiedenen wissenschaftlichen Kontexten den Aufstieg âneuer Mittelschichtenâ in Asien, SĂŒdamerika, aber auch in Afrika diskutiert. Dabei wurden die neuen â oder auch erst neu wahrgenommenen â afrikanischen Mittelschichten ĂŒberwiegend als TrĂ€ger ökonomischer Entwicklung oder in politischen Konflikten als Protagonisten demokratischer VerĂ€nderung betrachtet. Diese Sichtweise geht damit von relativ homogenen âafrikanischen Mittelschichtenâ aus und ĂŒbergeht sozioökonomische, politische und kulturelle Unterschiede der verschiedenen Gruppen. Auf der Grundlage empirischer Forschung untersucht der Beitrag, welche Konzepte fĂŒr die Analyse der besonderen Bedingungen soziokultureller DiversitĂ€t von Mittelschichten in Afrika am besten geeignet sind. Im Blick auf Kenia werden insbesondere die Reichweiten und die Anwendungsprobleme des Konzepts der Kleinen Lebenswelten und des Milieu-Ansatzes (im Sinne sozialstruktureller Makro-Milieus) ausgelotet. Als exemplarische Beispiele fĂŒr die Entwicklung spezifischer Abgrenzungskriterien unterschiedlicher soziokultureller Gruppen dienen dabei zwei empirische bestimmte âMilieukerneâ (christlich religiöses Milieu, neo-traditionales Milieu)
A new adhesive technique for internal fixation in midfacial surgery
© 2008 Endres et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens
Gauge fixing by unitary transformations in QCD
The unitary gauge fixing technique is applied to the QCD hamiltonian
formulated in terms of angular variables. It is demonstrated that in this
formulation projections on the physical Hilbert space are unnecessary to
separate physical and unphysical degrees of freedom. Therefore the application
of the unitary gauge fixing technique can be extended to the operator level.Comment: email: [email protected]; 8 pages LaTex; Paper to be
published in Physics Letters
Proteinarray Technology
Bereits in den achtziger Jahren entwickelte Roger Ekins Konzepte ĂŒber den Einsatz von parallelisierten Microspot-Immunoassays fĂŒr die Immundiagnostik (Ekins et al., 1989; 1999). Seine theoretischen Betrachtungen und experimentellen Arbeiten zeigten, daĂ parallelisierte Microspot-Immunoassays als Alternative zu klassischen ELISA-Tests sensitiv und selektiv durchgefĂŒhrt werden können. Der weltweite Durchbruch der Biochip-Technologie erfolgte jedoch erst in den neunziger Jahren mit der stĂŒrmischen Entwicklung der DNA-Chiptechnologie (Nature Genetics Supplement, 'The Chipping Forcast', 1999). Die dafĂŒr konzipierten GerĂ€te wie Arrayer und Biochip-Reader erlauben heute die Herstellung von Mikroarrays mit Tausenden von MeĂpunkten und den empfindlichen, ortsaufgelösten Nachweis gebundener ZielmolekĂŒle.
In der Autoimmundiagnostik bietet die Mikroarraytechnologie enorme Vorteile, da mit geringen Mengen an Patientenserum und geringem Arbeitsaufwand in einem Experimentalle wesentlichen diagnostischen Parameter erfaĂt werden können. Unser Ziel am NMI war die Etablierung eines Mikroarray ELISAs mit dem unterschiedliche Autoantigene nicht nur qualitativsondern auch quantitativ zu erfassen sein sollten. Durch VerdĂŒnnung, das heiĂt Verringerung der pro FlĂ€cheneinheit immobilisierten Antigene war mit einem einzigen Mikroarray-Experiment ohne aufwĂ€ndige SerumverdĂŒnnung eine Titerbestimmung möglich (Joos et al., 2000). Die entwickelten Mikroarrayassays erlauben den parallelen Nachweis von Autoantikörpern, die bei Autoimmunerkrankungen des rheumatischen Formenkreises, der Thyroiditis und des Insulin abhĂ€ngigen Diabetes Mellitus beteiligt sind
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