Single molecule magnets on a gold surface: in situ electrospray deposition, x-ray absorption and photoemission

Single molecule magnets based on the dodecamanganese (III, IV) cluster with two different types of ligand (acetate and benzoate) have been studied on the Au(111) surface. Due to the non-volatile and fragile nature of the molecules, we have used ultra-high vacuum electrospray deposition to produce a series of surface coverages from a fraction of a monolayer to multilayer films in both cases. Synchrotron radiation based electron spectroscopy has been used to study the adsorption of the molecules on the Au(111) surface and the effect that this has on the oxidation states of the manganese atoms in the core. In both cases, reduction of the core is observed due to the interaction with the surface, to essentially the same extent despite substantial differences in the size and nature of the ligand shell.     

Development of a real-time power system dynamic performancemonitoring system

Power systems have grown in both size and complexity, and the dynamic characteristics of the systems vary, as well. A computer simulation revealed the possibility of low-frequency oscillation after the connection of a cogeneration plant to the utility grid. Though there are several possible methods to improve the dynamic stability performance of the system, a thorough understanding of the system characteristics and possible operating conditions is required before an appropriate measure can be proposed. In order to collect more operating information without affecting normal system operation, a programmable logic controller (PLC)-based dynamic performance monitoring system (DPMS) was designed and installed at the tie substation. The recorded information will be valuable for system analysis and/or power system stabilizer (PSS) design. The DPMS design, its laboratory testing results, and several field-operation records are discussed in this paper     

Antitumour polycyclic acridines. Part 4. Physico-chemical studies on the interactions between DNA and novel tetracyclic acridine derivatives

The non-covalent interactions between a series of new tetracyclic acridine derivatives (5-11) and DNA have been studied by spectrophotometric analysis, fluorescences quenching, thermal denaturation, and circular and linear dichroism. In order to compare the extent of the DNA binding by compounds 5-11 in their neutral and cationic forms, all experiments were conducted at pH 7.4 (physiological pH) and 5.0. The results indicated that compounds 5-11 are strong DNA-binding ligands with DNA affinities comparable to that of m-AMSA (1) or even higher. They showed a stronger DNA binding activity at pH 5.0 as a result of the N-protonation of the pyridoacridine aromatic chromophore. Ethidium-DNA fluorescence assays showed an A-T base pair preference of the binding distinguishing these novel compounds from simple acridines which show a slight G-C base pair preference. Circular and linear dichroism studies indicated that the drugs bind to DNA by undergoing intercalation inside the duplex macromolecule at high DNA:drug ratios and revealed alternative binding modes at low DNA:drug ratios.     

Recovery of locomotor activity in the adult chronic spinal rat after sublesional transplantation of embryonic nervous cells: specific role of serotonergic neurons

We have reviewed the genetic structure of HIV-1 from the perspective of understanding viral and cellular regulatory factors that affect viral replication. Comparisons are drawn, as appropriate, with other human retroviruses, such as HIV-2, in regard to our understanding of pathogenesis. The synthesis of viral protein and the manner in which viral assembly takes place is also discussed.     

Prognosis in hereditary amyotrophic lateral sclerosis

Two different forms of hereditary amyotrophic lateral sclerosis (ALS) has been separated according to duration of illness. A rapid course with short survival as seen in sporadic ALS is usual, but a comparatively benign type with a mean survival of 12 years has been reported in some families. Four patients from an ALS-afflicted family with five affected members in three generations were examined and then followed up. A conspicuous variability in progression among the patients was observed, with death occurring from 26 months to 12 years after onset; one patient is alive 13 years after onset. Wide differences were also found with respect to initial site of involvement and pyramidal tract signs. Three other families with this mixed pattern of prognosis have been reported previously. Affected individuals within involved families had either short or long duration of the disease, rather than displaying a continuum. However, in view of the existence of a type of hereditary ALS with marked intrafamilial variability, prognosis, even in the presence of previous benign cases, should be cautiously given.     

Cross-reactivity of anti-10kD heat shock protein antibodies in leprosy and tuberculosis patients

The response to recombinant 10-kD heat shock protein (HSP) of Mycobacterium leprae (rML10) was evaluated by indirect ELISA in sera from leprosy patients, household contacts, tuberculosis patients and healthy controls in a leprosy-endemic area in the North East of Argentina. Some technical parameters were analyzed: within-assay and between-assay variability, dose-response curves and detectability indexes (specificity and sensitivity) of ELISA applied to measure anti-10 kDa antibodies. High levels of these antibodies have already been reported in positive bacilloscopy patients; herein we have also demonstrated that tuberculosis patients sera cross-react with this M. leprae antigen. This test seems to have a low sensitivity and specificity for leprosy detection; it confirms that antibodies against highly conserved HSP antigens are important in the polyclonal response against mycobacterial epitopes in leprosy as well as in tuberculosis.