Atomic force microscopy of a hydrated bacterial surface protein

The protein surface layer of the bacterium Deinococcus radiodurans (HPI layer) was examined with an atomic force microscope (AFM). The measurements on the air-dried, but still hydrated layer were performed in the attractive imaging mode in which the forces between tip and sample are much smaller than in AFM in the repulsive mode or in scanning tunnelling microscopy (STM). The results are compared with STM and transmission electron microscopy (TEM) data.     

Mass transfer and influence of the local catalyst activity on the conversion in a riser reactor

Gas–solids contacting in risers has been studied based on measurements of mass transfer controlled CO oxidation over a Pt/γ-alumina catalyst, and on experimental results published by Ouyang et al. (1995) for the kinetically controlled ozone decomposition. In the present experiments, the catalyst activity was varied by mixing the active catalyst particles with similar, but inert γ-alumina particles (in ratios from 150 to 2500 m³_inert/m³_cat), whereas Ouyang and co-workers varied the operating temperature ( de 300 à to 500 K). Mass transfer controlled CO oxidation occurs at temperatures above 750 K. A negative square root dependency has been observed for the relationship between the Sherwood number and the solid hold-up. Increasing the gas velocity always improves the gas–solids contacting. The local catalyst activity appears to be an important parameter. As an important conclusion of the present work, it can be stated that at a high local activity, the conversion rate per unit volume of catalyst decreases significantly due to local depletion of reactant.     

Conservation of fish species diversity in navigable waterways

Nineteen waterways in the German lowlands were surveyed between 1992 and 1997 to evaluate their fishes conservation capacity. From 277 sites a total of 84 821 fish of 31 species was collected. Number of species in various waterways ranged from 6 to 26 with a mean±standarddeviation of 15.4±5.4. Mean species diversity was H′=1.61±0.29 (range 1.02–2.20), and corresponding evenness 0.61±0.09 (0.51–0.76). Fish communities of waterways were dominated by perch and roach, both contributing in mean 68.5±12.5% to the total catch. The mean relative abundance of threatened fish listed in “Red Data Books” of Germany or Europe was 7.83±4.82%.Percentage of artificial shoreline structures like riprap or sheet pile wall was inversely correlated to species number, species diversity and abundance of intolerant species. This study was a first approach to estimate the percentage of habitat restoration required to increase species diversity. Even the restoration of one-fifth of the river banks, the restoration of natural shoreline structures from close 0 to 20% of the bankline should result in substantial improvement of fish diversity, and significantly contribute to species conservation and persistence of viable populations of threatened fishes in waterways. In regard to such relatively low restoration effort, biodiversity conservation in waterways is compatible with long-term resource use, navigation and human needs. Even though heavily modified, waterways are also recommended for conservation issues by their large area covered as well as their substantial number of fish species.     

Three unrelated Rh D gene polymorphisms identified among blood donors with Rhesus CCee (r'r') phenotypes

Human red blood cells are traditionally typed as Rhesus (Rh)-positive or -negative depending on the presence or absence of the Rh D antigen. A recent report demonstrated that the Rh D gene is completely absent in Rh D-negative individuals. In this study, Rh D-negative blood donors with ccee (n = 25) and CCee (n = 3) phenotypes were examined for the presence of absence of the D gene. Polymerase chain reaction (PCR) probes that hybridize to the 5' and 3' regions of the Rh CcEe gene and the closely related D gene were used in a Southern analysis. The D gene was absent in all ccee phenotypes examined. The CCee phenotypes showed three Rh D polymorphisms: one donor lacked the D gene, one donor had a partial deletion on one D gene at the 3' region, and the remaining donor appeared to have one normal D gene within the intron/exon regions examined. We conclude that, while the D gene may be absent in the majority of Rh D-negative phenotypes, rarer polymorphisms also occur that prevent expression of the D antigen resulting in the Rh D-negative phenotype.     

Follow-up evaluation of open intra-articular fractures of the calcaneus

The results of a follow-up evaluation of open intra-articular calcaneal fractures are presented. A modified Merle d'Aubigné functional score and Zwipp radiographic score were used. A retrospective analysis of 35 patients with 36 open intra-articular fractures represents the basis of the study. At the time of follow-up examination (on average 44 months after the injury), 5 amputations of the affected extremity and 4 ankle arthrodeses had been carried out. The 23 patients still able to bear weight on the affected hindfoot and possessing a functional ankle joint were radiographically and functionally evaluated. No excellent results were documented. Only 6 good functional and 2 good radiographic outcomes were noted. In 17 instances, a poor functional or radiographic score was given. Devastating results were seen in the course of treatment of third-degree open joint depression or comminuted intra-articular fractures (n = 15): 9 cases of osteomyelitis, 5 amputations, 1 partial calcanectomy, 1 arthrodesis. An open reduction as part of the primary treatment (n = 6) led to local complications in all instances. The most favorable results were seen after nonoperative fracture management: complication-free course of treatment in 4 of 11 patients. All workmen's injuries led to a permanent disability, and these patients received compensation. The treatment and salvage of the soft-tissue envelope should be paramount in all therapeutic decisions. The fracture treatment must not further jeopardize these tissues. An aggressive operative treatment of local complications, including arthrodesis or amputation, is recommended.     

Epitaxial layer morphology of highly strained GaInAs/InP multiple quantum well structures grown by CBE

We present a study of changes in the layer morphology of tensilely strained GalnAs/InP multiple quantum well (MQW) structures in dependence on strain and substrate off-orientation. Growth was performed by chemical beam epitaxy (CBE). For high tensile strain (x_Ga=0.77) lateral thickness fluctuations evolving into facets of the (411)A type are observed in cross-sectional transmission electron microscopy (TEM). These undulations are parallel to [01 ] and present for samples grown on both exactly oriented and off-oriented (100) InP substrates. For off oriented substrates the strain induced generation of macrosteps parallel to the surface steps is detected for x_Ga = 0.65 and x_Ga=0.77. The distance and height of the macrosteps directly correspond to the substrate off orientation angle. While the macrostep generation is a direct consequence of surface steps in combination with strain, the occurrence of the undulations might be connected with the (2 × 4) surface reconstruction during CBE growth. Both mechanisms are discussed with respect to experimental and theoretical literature data.     

Sequence analysis of a 5·6 kb fragment of chromosome II from Saccharomyces cerevisiae reveals two new open reading frames next to CDC28

The sequence of a 5653 bp DNA fragment of the right arm of chromosome II of Saccharomyces cerevisiae contains two unknown open reading frames (YBR1212 and YBR1213) next to gene CDC28. Gene disruption reveals both putative genes as non-essential. ORF YBR1212 encodes a predicted protein with 71% similarity and 65% identity (total polypeptide of 376 aa) with the 378 aa Sur1 protein of S. cerevisiae, while the putative product of ORF YBR1213, which is strongly expressed, has 28% identity with a Lactococcus lactis-secreted 45 kDa protein and 24% identity with the Saccharomyces cerevisiae AGA1 gene product. The total sequence of the fragment has been submitted to the EMBL databank (accession number X80224).     

Experimental analysis of the efficiency of heterostructure GaAs---AlGaAs solar cells

Some years ago Multiple Quantum Wells (MQW) solar cells were introduced as an alternative to obtain high efficiencies. Based on the simple Shockley diode model, the short-circuit current could be increased without loss in the open-circuit voltage. Applying the Detailed Balance Theory, including radiative recombination in the i-region, leads to less optimistic predictions of the limiting efficiency of MQW cells. We present an experimental study in order to compare the efficiency of MQW solar cells with heterostructure cells with graded Al compositions and single bandgap solar cells. Compared to the homojunction AlGaAs cell, an increase of the short-circuit current is observed by the incorporation of GaAs in the i-region. However, the open-circuit voltage is reduced by the implementation of GaAs, due to an increase of the non-radiative recombination current. To estimate the maximum possible open-circuit voltage, the radiative recombination current is determined by measuring the light emission as a function of the applied voltage. From this experiment we conclude that the maximum possible open-circuit voltage of all the heterostructure cells is considerably lower than the homogeneous AlGaAs cell and close to the value of the GaAs cell, showing the relation between the open-circuit voltage and the smallest bandgap in the cell. The measured curves can be well predicted by calculations based on the Detailed Balance Theory. We find no principal advantage of MQW cells over cells with graded composition or single bandgap cells.