Synthesis and Biological Activities of Azalamellarins

The synthesis of azalamellarins, a new series of lactam analogues of biologically active lamellarins, was achieved using Cu^I‐mediated and microwave‐assisted C? N_amide bond formation. Seventeen azalamellarins, including N‐allylazalamellarins and N‐propylazalamellarins χ‐D, L ‐N, and J‐dehydro J, were synthesized and evaluated for their cytotoxicity against the cancer cell lines HuCCA‐1, A‐549, HepG2, and MOLT‐3. The results showed that certain azalamellarins exhibited good activities in the micromolar IC₅₀ value range (IC₅₀=the drug concentration that causes 50 % of cell‐growth inhibition after 72 h of continuous exposure to the test molecule), comparable to their parent lamellarin analogue.     

Enhancing aperiodic stochastic resonance through noise modulation

We show that the conventional stochastic resonance (SR) effect for aperiodic signals in a model neuron can be enhanced by modulating the intensity of the input noise (which could be introduced artificially in bioengineering applications) with either the input signal or the unit's output rate signal. We analyze SR enhancement theoretically and numerically. We discuss how this work provides the theoretical foundation for the development of an optimal noise-based technique for enhancing sensory function. (c) 1998 American Institute of Physics.     

Curtius rearrangement in the 5-phenyl-1,4-benzodiazepine series. Unprecedented participation by an imine nitrogen

The previously unknown 3-aminomethyl-1,3-dihydro-5-(2′-fluorophenyl)-2H,4-benzodiazepin-2-one, 3a, was synthesized in two steps as a racemate. In the chiral series, 3(S)-azidocarbonylmethyl-1,3-dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one, 12b, was prepared from Nα-Cbz-β-methylaspartate in five synthetic operations and subjected to Curtius rearrangement. The intermediate isocyanate was trapped intramolecularly by the 5-imine nitrogen of the benzodiazepine ring in 12b. This unanticipated result runs counter to the generally held dictum that the isocyanate group has a strictly linear shape.     

The thermal,spectral and magnetic studies ofp-tolylacetic acid compounds of cobalt,nickel and copper

The preparation and some properties of complexes ofp-tolylacetic acid with cobalt, nickel and copper are described. Magnetic measurements, electronic and far infrared spectra show that the metal complexes have octahedral structures. Infrared spectra indicate that coordination takes place through the carboxyl group to the metal ions and that the water molecule in each of the complexes is present as water of crystallisation. Thermogravimetry studies also show that the water molecules in each of the complexes do not form a coordinate bond with the metal ion. Differential thermal analysis show that the dehydration processes are accompanied by endothermic reactions. In each case the anhydrous metal complex undergoes an exothermic reaction to give the metal oxide.This work was supported by the Carnegie Trust for the Universities of Scotland and the Hungarian OTKA foundation (T-4096).     

Acoustic generation of bubbles in excised canine urinary bladders

A high-intensity, 555-kHz acoustic field was used to generate bubbles within urinary bladders excised from dogs. Following the exposure, bubbles were visualized on a diagnostic ultrasound scanner with a 5-MHz in-line mechanical sector scanhead. Scattering of the high-intensity ultrasound by the bubbles was also observed during the exposure as high-amplitude scan lines. The bladders used had been surgically removed after tying off the ureters and urethra to prevent urine loss and exposure to external contaminants. Each bladder was sealed in a plastic bag filled with a degassed saline solution. The bladder was centered in a sealed degassed water path at the common focus of a 7-cm-diam transducer and a 10-cm-diam brass reflector. The 555-kHz transducer and reflector were both focused at 10 cm and were aligned coaxially. Using various acoustic pressure amplitudes, two, 10-s low-frequency exposures, separated by approximately 30 s, occurred at approximately 2-min intervals. Experiments on a single bladder lasted as long as 45 min. The sizes of the largest bubbles, which were easily imaged, were estimated from rise velocity measurements as 50-70 microns in radius, and pressure amplitudes used to generate those large bubbles were estimated as 10-20 bars. The detection of smaller bubbles was limited by the inability to clearly distinguish bubble echoes from artifacts caused by the reverberant field within the bladder. Visual inspection of the exterior and interior bladder wall showed no significant discoloration within the high intensity beam path.(ABSTRACT TRUNCATED AT 250 WORDS)     

The computable embedding problem

Calvert calculated the complexity of the computable isomorphism problem for a number of familiar classes of structures. Rosendal suggested that it might be interesting to do the same for the computable embedding problem. By the computable isomorphism problem and (computable embedding problem) we mean the difficulty of determining whether there exists an isomorphism (embedding) between two members of a class of computable structures. For some classes, such as the class of \mathbbQ \mathbb{Q} -vector spaces and the class of linear orderings, it turns out that the two problems have the same complexity. Moreover, calculations are essentially the same. For other classes, there are differences. We present examples in which the embedding problem is trivial (within the class) and the computable isomorphism problem is more complicated. We also give an example in which the embedding problem is more complicated than the isomorphism problem.     

Papieruntersuchung

Ohne Zusammenfassung     

Rise of the Robots

High-throughput experimentation (HTE) is a growing, enabling technology that allows the execution of large, parallel sets of experiments. Often, automation is required to dose compounds on milligram to sub-milligram scale, to run many parallel reactions, and to analyse large datasets. Unique approaches to screen design, implementation, and analysis are required, distinct from traditional synthetic organic chemistry. The discipline also presents a profitable opportunity for individual scientists to learn about and explore fields adjacent to chemistry, including data science, robotics and equipment engineering, and computer programming. This perspective presents the author's viewpoints on the field of HTE, its implementation within a chemistry career, and the automated future of organic chemistry technology.