In order to obtain the high accuracy required for a metrological atomic force microscope, the sample approach mechanism meets strict specifications. The design presented in this paper offers a stiff construction, which limits the influences of floor vibrations on the measurement. Next to this, thermal considerations in the design decrease the uncertainties introduced by temperature variations of the environment. Uncertainties can also be caused by misalignment of the sample holder with respect to the measurement system of three interferometers. To limit these uncertainties, the approach mechanism provides sufficient alignment possibilities. The performance of the sample approach mechanism was evaluated by means of a finite element simulation of its dynamic stiffness. A series of experiments provide the unknown parameters to the simulation model. The dynamic stiffness lies around 395Hz, which is sufficiently high to provide accurate measurements.
Tumor growth in NMRI mice infected neonatally with the Moloney strain of murine sarcoma virus (M-MSV) was effectively inhibited by the synthetic double-stranded polyribonucleotide (poly rl:rC). This protective effect was obtained with repeated doses of poly rl:rC injected on alternate days from 1 day to 11 days after virus inoculation, as well as with a single dose of poly rl:rC injected 12 hours before virus inoculation. The antitumor effect of a single injection of poly rl:rC 12 hours before virus challenge could be duplicated by exogenous interferon administered in amounts closely mimicking the interferon blood levels obtained endogenously with poly rl:rC. This indicates that the whole antitumor effect of a single dose of poly rl:rC, injected 12 hours before M-MSV infection, is due to interferon production.
No abstract is provided for this article.
The acyclic adenosine analogue (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine [S]-HPMPA) is a potent and selective inhibitor of adenovirus (Ad) replication in cell culture. We studied the mechanism of inhibition using a reconstituted in vitro DNA replication system. The diphosphoryl derivative (S)-HPMPApp, but not (S)-HPMPA, inhibited the DNA replication of origin containing fragments strongly. The inhibitory effect was exerted at the level of elongation, while initiation was resistant to the drug. Remarkably, the elongation of short strands was only slightly impaired, while inhibition was maximal upon synthesis of long DNA fragments. (S)-HPMPApp appeared to be competitive with dATP, suggesting that the Ad DNA polymerase is the prime target for the drug. We purified the Ad DNA polymerase in complex to the precursor terminal protein to homogeneity from cells infected with overproducing recombinant vaccinia viruses. Employing gapped DNA or poly(dT).oligo(dA) templates, only a weak inhibition was observed. However, inhibition was strongly enhanced in the presence of the adenovirus DNA binding protein (DBP). We interpret this to mean that the increased processivity of the polymerization reaction in the presence of DBP leads to increased drug sensitivity.
No abstract is provided for this article.
Polymeric parts produced by Laser Sintering (LS) present a consistent amount of pores with a wide pore size distribution. The knowledge about the porosity value and its distribution within the part allows to perform a quality control of the LS process, and gives insights in how to improve it. In this work the influence of the sample size on the porosity measurement is discussed, as well as its representativeness of the LS process itself. The reliability of porosity measurement of those parts using X-ray Computed Tomography (CT) is assessed taking into account the influence of the CT scanning parameters, the reconstruction and noise reduction algorithms using a design-of-experiment approach. The quality of the CT datasets obtained is assessed by calculating Contrast-to-Noise Ratio (CNR) and Signal-to-Noise Ratio (SNR) on representative reconstructed images. Repeatability of the measurements is also assessed along the entire workflow: CT acquisition, reconstruction and porosity measurement using commercial software packages.
Abstract 1. Durch Umsetzung des nach bekannter Methode zugänglichen Purins (I) mit entsprechenden Nucleophilen werden die Derivate (II) dargestellt.
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