Electrons, pseudoparticles, and quasiparticles in the one-dimensional many-electron problem

We generalize the concept of quasiparticle for one-dimensional (1D) interacting electronic systems. The $\uparrow$ and $\downarrow$ quasiparticles recombine the pseudoparticle colors $c$ and $s$ (charge and spin at zero magnetic field) and are constituted by one many-pseudoparticle {\it topological momenton} and one or two pseudoparticles. These excitations cannot be separated. We consider the case of the Hubbard chain. We show that the low-energy electron -- quasiparticle transformation has a singular charater which justifies the perturbative and non-perturbative nature of the quantum problem in the pseudoparticle and electronic basis, respectively. This follows from the absence of zero-energy electron -- quasiparticle overlap in 1D. The existence of Fermi-surface quasiparticles both in 1D and three dimensional (3D) many-electron systems suggests there existence in quantum liquids in dimensions 1$<$D$<$3. However, whether the electron -- quasiparticle overlap can vanish in D$>$1 or whether it becomes finite as soon as we leave 1D remains an unsolved question.Comment: 43 pages, latex, no figures, submitted to Physical Review

European intercomparisation workshops on air quality monitoring. Vol. 3 Measuring of CO, NO, NO_2, and BTX

This report presents the results of two European Intercomparison Workshops on Air Quality Monitoring (CO, NO, NO_2 and BTX) conducted in May 1998 by the WHO Collaborating Centre for Air Quality Management and Air Pollution Control in co-operation with the national reference laboratory of UBA Pilotstation in Offenbach/Main, Germany. The Workshops were to be a contribution to continuing quality assurance and control activities on air quality monitoring in the WHO European Region. Fourteen institutes used the opportunity to compare their measurement methods (12 manual methods and 31 monitors) and standards for ambient air monitoring of carbon monoxide, oxides of nitrogen, benzene, toluene, and xylene. Summing up the laboratory measurements (automatic and manual methods) of NO, NO_2 and CO during both intercomparison Workshops more than 80% of all results agrees with the target value within a tolerance of #+-#10%, and 60 to 80% of all results were within a tolerance of #+-#5%. Best results were obtained for CO measurements (measured by monitors only): 92% agreed with a tolerance of #+-#10% and 76% agreed within #+-#5%. For the comparisons of different analytical methods during the measurements of nitrogen oxides the results showed very good agreement for NO_2. On the other hand, the results for NO were not as good and they indicated some problems with manual methods. Summing up the BTX laboratory measurements (automatic and manual methods) of both intercomparison Workshops, 44 to 60% of all results were within a tolerance of #+-#10%, and between 23 and 35% of all results were within tolerance of #+-#5% from the target value. The comparisons of calibration standards showed very good agreement between the primary calibration standard of UBA Pilotstation and the national transfer standards of the participating laboratories. Some unsystematical differences were identified for manual methods at low NO and NO_2 concentrations in ambient air. Furthermore, some measurement phenomena were identified of automatic and manual methods. Thus, there seems to be a need for further intercomparisons to check and to veryify the causes. Most of the applied methods are reliable and suitable for obtaining air quality data appropriate to evaluate and estimate environmental health risks in the WHO European Region. (orig.)Available from TIB Hannover: RR 838(11) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

European intercomparison workshops on air quality monitoring. Vol. 4 Measuring NO, NO_2, O_3 and SO_2

This report presents the results of two European Intercomparison Workshops on Air Quality Monitoring (NO, NO_2, O_3, and SO_2). The Workshops were a contribution to continuing quality assurance and quality control activities on air quality monitoring for Member States of the WHO European Region. Fourteen institutes mainly from Central and Eastern Europe used the opportunity to compare their measurement methods (15 manual methods and 24 monitors) and standards. (orig.)Available from TIB Hannover: RR 838(13) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Survival of nests of the terecay turtle (Podocnemis unifilis) in the Nichare-Tawadu rivers, Venezuela

Mortality factors and hatching success of 422 terecay turtle (Podocnemis unifilis) nests on seven beaches in the Nichare and Tawadu Rivers, Venezuela, were studied following the oviposition phase. Beaches (3.4-28.4 km(2)), predominantly sandy, and bordered by riparian vegetation, were searched to record nest numbers and their distribution. Elevation and surrounding plant cover were measured for each nest. Most nests were found close to the vegetation's edge (0-11 m), at a significant distance from the water's edge (21-80 m), in more open ground, and along the highest points of the beach (1-3.i m above the water's edge). Nest density was positively correlated with beach elevation but not with beach dimensions. Most nests were concentrated in less than 10% of beach area, along the upper 20% of the beach. Average clutch size was 20.1+/-1.7 eggs, but larger clutches were found significantly further away from vegetation. No significant correlation between hatching success and clutch size was found. A large proportion of nests were subject to animal and human predation but environmental factors (especially flooding) affected some. The major cause of egg loss was human predation. Most clutches collected by humans were found away from vegetation, on the upper 10-20% of beaches, in exposed unvegetated sites. Animals preyed upon those nests along the vegetation's margin (1-2 m) in the upper 0-9% of beaches, in sites of high plant cover (75-100%). Nests reaching the incubation phase were mainly located in the open areas, which are more prone to human predation. About three-quarters of nests showed high hatching rates (91-100%). However, hatchability was highest furthest away from the vegetation. Our results indicate that humans are collecting eggs mostly from sites in which nests have the larger clutches and the higher potential hatching success. Because of this relationship between nest viability and location, sustainable yield programmes must consider where harvesting can take place and must avoid the application of standard harvests per nest