174 research outputs found
Counterion condensation and effective charge of PAMAM dendrimers
PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino groups which is monitored via the proton chemical shifts of the adjacent CH2 groups. The effective charge is determined from a combination of diffusion and electrophoresis NMR. The fraction of the charges, which are effective for the interaction with an external electric field or other charges, decreases with increasing generation (size) of the dendrimers
Tip-surface forces, amplitude, and energy dissipation in amplitude-modulation (tapping mode) force microscopy
Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the quantities that control the amplitude reduction. The agreement obtained between analytical and numerical results supports the analytical method.This work has been supported by the DirecciĂłn General de InvestigaciĂłn CientĂfica y TĂ©cnica (PB98-0471) and the
European Union (BICEPS, BIO4-CT-2112). A. S. P. acknowledges financial support from the Comunidad AutĂłnoma de Madrid.Peer reviewe
Mitschriften der Vorlesungen zu Bauconstructionen von [Conrad] Dollinger und Brückenbau von [Adolf] Hänel durch B. Andelfinger um 1877
MITSCHRIFTEN DER VORLESUNGEN ZU BAUCONSTRUCTIONEN VON [CONRAD] DOLLINGER UND BRĂśCKENBAU VON [ADOLF] HĂ„NEL DURCH B. ANDELFINGER UM 1877
Mitschriften und Skripte von Vorlesungen an der Technischen Hochschule und Universität Stuttgart (-)
Mitschriften der Vorlesungen zu Bauconstructionen von [Conrad] Dollinger und Brückenbau von [Adolf] Hänel durch B. Andelfinger um 1877 (Bd. 20, 1877) (1)
Einband (-)
[unbekannter Titel, lose Abbildung] (-)
Bauconstructionslehre von [Conrad] Dollinger (1)
[Einleitung] (1)
Constructionen in Stein (1)
Holzconstructionen (120)
Construction der eisernen Dächer (263)
Brückenbau von [Adolf] Hänel (275)
Steinconstructionen (275)
[Eiserne BalkenbrĂĽcken] (329)
Eiserne BogenbrĂĽcken (371)
[Hölzerne Brücken] (377)
Tunnelbau (409)
Farbinformation (-)
Einband (-
Detection of a flow induced magnetic field eigenmode in the Riga dynamo facility
In an experiment at the Riga sodium dynamo facility, a slowly growing
magnetic field eigenmode has been detected over a period of about 15 seconds.
For a slightly decreased propeller rotation rate, additional measurements
showed a slow decay of this mode. The measured results correspond satisfactory
with numerical predictions for the growth rates and frequencies
Substantial impact of FDG PET imaging on the therapy decision in patients with early-stage Hodgkin's lymphoma
Genotyping and antibiotic resistance of thermophilic Campylobacter isolated from chicken and pig meat in Vietnam
Background Campylobacter species are recognized as the most common cause of
foodborne bacterial gastroenteritis in humans. In this study nine
Campylobacter strains isolated from chicken meat and pork in Hanoi, Vietnam,
were characterized using molecular methods and tested for antibiotic
resistance. Results The nine isolates (eight C. jejuni and one C. coli) were
identified by multiplex PCR, and tested for the presence or absence of 29 gene
loci associated with virulence, lipooligosaccharide (LOS) biosynthesis and
further functions. flaA typing, multilocus sequence typing and microarray
assay investigation showed a high degree of genetic diversity among these
isolates. In all isolates motility genes (flaA, flaB, flhA, fliM),
colonization associated genes (cadF, docB), toxin production genes (cdtA,
cdtB, secD, secF), and the LOS biosynthesis gene pglB were detected. Eight
gene loci (fliY, virB11, Cje1278, Cj1434c, Cj1138, Cj1438c, Cj1440c, Cj1136)
could not be detected by PCR. A differing presence of the gene loci ciaB (22.2
%), Cje1280 (77.8 %), docC (66.7 %), and cgtB (55.6 %) was found. iamA, cdtC,
and the type 6 secretion system were present in all C. jejuni isolates but not
in C. coli. flaA typing resulted in five different genotypes within C. jejuni,
MLST classified the isolates into seven sequence types (ST-5155, ST-6736,
ST-2837, ST-4395, ST-5799, ST-4099 and ST-860). The microarray assay analysis
showed a high genetic diversity within Vietnamese Campylobacter isolates which
resulted in eight different types for C. jejuni. Antibiotic susceptibility
profiles showed that all isolates were sensitive to gentamicin and most
isolates (88.8 %) were sensitive to chloramphenicol, erythromycin and
streptomycin. Resistance rates to nalidixic acid, tetracycline and
ciprofloxacin were 88.9, 77.8 and 66.7 %, respectively. Conclusions To the
best of our knowledge, this study is the first report that shows high genetic
diversity and remarkable antibiotic resistance of Campylobacter strains
isolated from meat in Vietnam which can be considered of high public health
significance. These preliminary data show that large scale screenings are
justified to assess the relevance of Campylobacter infections on human health
in Vietnam
Evaluation of Euler Fluxes for Hypersonic Heating Computations
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83575/1/AIAA-41605-439.pd
Comparison of aerosol chemistry transport model simulations with lidar and Sun photometer observations at a site near Paris
When Subterranean Termites Challenge the Rules of Fungal Epizootics
Over the past 50 years, repeated attempts have been made to develop biological control technologies for use against economically important species of subterranean termites, focusing primarily on the use of the entomopathogenic fungus Metarhizium anisopliae. However, no successful field implementation of biological control has been reported. Most previous work has been conducted under the assumption that environmental conditions within termite nests would favor the growth and dispersion of entomopathogenic agents, resulting in an epizootic. Epizootics rely on the ability of the pathogenic microorganism to self-replicate and disperse among the host population. However, our study shows that due to multilevel disease resistance mechanisms, the incidence of an epizootic within a group of termites is unlikely. By exposing groups of 50 termites in planar arenas containing sand particles treated with a range of densities of an entomopathogenic fungus, we were able to quantify behavioral patterns as a function of the death ratios resulting from the fungal exposure. The inability of the fungal pathogen M. anisopliae to complete its life cycle within a Coptotermes formosanus (Isoptera: Rhinotermitidae) group was mainly the result of cannibalism and the burial behavior of the nest mates, even when termite mortality reached up to 75%. Because a subterranean termite colony, as a superorganism, can prevent epizootics of M. anisopliae, the traditional concepts of epizootiology may not apply to this social insect when exposed to fungal pathogens, or other pathogen for which termites have evolved behavioral and physiological means of disrupting their life cycle
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