Bi-unitary perfect polynomials overGF(g)

Summary This paper continues the author's excursions into the arithmetic of polynomials over finite fields. For monic polynomials A, B GF[q, x] where p is a prime, q=p^dand d 1: The divisor B of A is a bi-unitary divisor of A provided 1 is the greatest common unitary divisor of the polynomials B and A/B, and we say that A is bi-unitary perfect (b.u.p.) over GF(q) provided A equals the sum ^**(A) of the distinct bi-unitary divisors of A in GF[q, x]. A diversity of b.u.p. polynomials over GF(q) is found, some of which are neither perfect nor unitary perfect. For p > 2 we can only conjecture a characterisation of the b.u.p. polynomials which split in GF[p, x], so several open questions remain. Examples of non-splitting b.u.p. polynomials over GF(p) are given for p=2, 3, 5 which, in turn, allow the construction of such examples over GF(p^d) for these p.     

Optical fiber photoacoustic-photothermal probe

We describe the operation of an all-optical probe that provides an alternative means of implementing photoacoustic and photothermal investigative techniques, particularly those used in biomedical applications. The probe is based on a transparent, acoustically and thermally sensitive Fabry-Perot polymer film sensor mounted at the end of an optical fiber. We demonstrate the ability of the system to make photoacoustic and photothermal measurements simultaneously and evaluate its photothermal response, using a nonscattering liquid target of known and adjustable absorption coefficient. The acoustic and thermal noise floors were 2 kPa and 6x10(-3) degrees C , respectively, obtained over a 25-MHz measurement bandwidth and 30 signal averages.     

Integrated on-chip derivatization and electrophoresis for the rapid analysis of biogenic amines

We demonstrate the monolithic integration of a chemical reactor with a capillary electrophoresis device for the rapid and sensitive analysis of biogenic amines. Fluorescein isothiocyanate (FITC) is widely employed for the analysis of amino-group containing analytes. However, the slow reaction kinetics hinders the use of this dye for on-chip labeling applications. Other alternatives are available such as o-phthaldehyde (OPA), however, the inferior photophysical properties and the UV lambdamax present difficulties when using common excitation sources leading to a disparity in sensitivity. Consequently, we present for the first time the use of dichlorotriazine fluorescein (DTAF) as a superior in situ derivatizing agent for biogenic amines in microfluidic devices. The developed microdevice employs both hydrodynamic and electroosmotic flow, facilitating the creation of a polymeric microchip to perform both precolumn derivatization and electrophoretic analysis. The favorable photophysical properties of the DTAF and its fast reaction kinetics provide detection limits down to 1 nM and total analysis times (including on-chip mixing and reaction) of <60 s. The detection limits are two orders of magnitude lower than current limits obtained with both FITC and OPA. The optimized microdevice is also employed to probe biogenic amines in real samples.     

Thin-film polymer light emitting diodes as integrated excitation sources for microscale capillary electrophoresis

We report the use of a thin-film polymer light emitting diode as an integrated excitation source for microfabricated capillary electrophoresis. The polyfluorene-based diode has a peak emission wavelength of 488 nm, an active area of 40 microm x 1000 microm and a thickness of similar 2 mm. The simple layer-by-layer deposition procedures used to fabricate the polymer component allow facile integration with planar chip-based systems. To demonstrate the efficacy of the approach, the polyfluorene diode is used as an excitation source for the detection of fluorescent dyes separated on-chip by electrophoresis. Using a conventional confocal detection system the integrated pLED is successfully used to detect fluorescein and 5-carboxyfluorescein at concentrations as low as 10(-6) M with a mass detection limit of 50 femtomoles. The drive voltages required to generate sufficient emission from the polymer diode device are as low as 3.7 V.     

Absorption cross-section and related optical properties of colloidal InAs quantum dots

We report the absorption cross-section of colloidal InAs quantum dots of mean radii from 1.6 to 3.45 nm. We find excellent agreement between the measured results and calculated values based on a model of small-particle light absorption. The absorption cross-section per dot is 6.2 x 10(-16)R(3) cm(2) at 2.76 eV and 3.15 x 10(-16)R(1.28) cm(2) at the first-exciton absorption peak, with the dot radius R in nm. We find that the per-quantum-dot particle oscillator strength of the first-exciton transition is constant for all sizes studied. The radiative lifetime of the first exciton calculated from the oscillator strength increases with dot size and ranges from 4 ns for the smallest dots to 14 ns for the largest ones.     

MINIMUM DOSES OF ULTRAVIOLET RADIATION REQUIRED TO INDUCE MURINE SKIN EDEMA and IMMUNOSUPPRESSION ARE DIFFERENT and DEPEND ON THE ULTRAVIOLET EMISSION SPECTRUM OF THE SOURCE*

Many photoimmunological studies have used UV radiation sources that emit nonsolar UV spectral energy and UV doses based on nonimmunological endpoints, e.g. erythema and skin edema. Interpretation of these data has led to misunderstanding when extrapolated to hypothetical effects in humans exposed to solar UV. The purpose of this study was to: (1) establish UV dose response relationships for murine skin edema and immunosuppression, and (2) determine how different UV spectra affect these relationships. Back skin and ear minimum edema doses (MEdD) for Kodacel-filtered FS20 sunlamp UV (290–400nm) were greater than two-fold higher than those for unfiltered FS20 sunlamp UV (250–400nm). Xenon arc solar simulator UV (295–400nm) MEdD were > 10-fold higher than those for unfiltered sunlamp UV. Back skin and ear MEdD differed two- to five-fold between C3H/ HeN, SWR/J and HRA/Skh-1 mice. The minimum immunosuppression doses (MISD) in C3H mice showed similar UV source spectrum dependence. The solar simulator UV MISD was 5.4- and 1.5-fold higher than for unfiltered and Kodacel-filtered sunlamp UV MISD, respectively. Furthermore, MISD were from 3- to 50-fold higher than the MEdD for the three UV sources. The UV bioeffectiveness spectra indicated that UVC energy (250–290nm) contributed 12% and 18%, respectively, of the total skin edema and immunosuppression UV energy. These data demonstrate the variability in UV sensitivity among mouse strains, the significant differences between murine MEdD and MISD and how these differences are influenced by nonsolar regions (below 295 nm) of the UV spectrum.     

Untersuchungen über die Thermostabilität der aus Hühnerfibroblasten isolierten Ribonucleinsäuren

Zusammenfassung Aus intakten Hühnerfibroblasten können die cytoplasmatischen Ribonucleinsäuren durch Behandlung mit Phenol und Natriumlaurylsulfat bei 2° extrahiert werden. Werden die Nucleinsäuren auf 40° oder darüber hinaus erwärmt und rasch abgekühlt, so ändert sich die Struktur der 28S-Ribosomen-RNS derart, daß sie bereits bei etwa 26S sedmentiert, während die Sedimentationsgeschwindigkeiten der 18S-RNS und der 4S-RNS unverändert bleiben. Darüber hinaus scheint die 28S-RNS gegenüber Spaltung zu kleineren Molekülen besonders empfindlich zu sein; ein wenn auch geringerer Abbau findet selbst in Anwesenheit von Diäthyl-pyrocarbonat statt. Eine kleine Menge einer Ribonucleinsäure, die bei etwa 41S sedimentiert, wurde ebenfalls durch Phenol-Extraktion bei 2° freigesetzt. Diese RNS, die höchstwahrscheinlich mit der im Nucleolus befindlichen Stamm-RNS, aus der die 18S-und 28S-RNS hervorgehen, identisch ist, neigt ebenfalls stark zu Fragmentierung durch Erhitzen auf 40° und darüber hinaus.

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The thermal stability of ribonucleic acids from chick embryo fibroblasts

Cytoplasmic ribonucleic acids can be extracted from chick embryo cells with phenol and sodium dodecyl sulfate at 2°. If these ribonucleic acids are heated to 40° and above and chilled, the structure of the 28S ribosomal RNA is changed so that it sediments at about 26S. The 18S and 4S ribonucleic acids are not altered in sedimentation behaviour by heating and cooling. Moreover the 28S RNA is also more susceptible to breakdown to smaller molecules even in the presence of the ribonuclease inhibitor diethyl pyrocarbonate. A small amount of RNA sedimenting at about 41S, probably ribosomal precursor RNA, can also be extracted at 2°. It is also subject to change in sedimentation rate and to fragmentation when heated above 40°.

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Mit 4 Abbildungen

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Herrn Prof. Dr.Engelbert Broda zum 60. Geburtstag in freundschaftlicher Verehrung gewidmet.     

Rare-earth amidate complexes. Easily accessed initiators for epsilon-caprolactone ring-opening polymerization

The direct synthesis of yttrium amidate complexes using the simple reaction of amide proligands and Y(N(SiMe3)2)3 results in the high-yielding preparation and isolation of crystalline, monomeric materials. The complex, tris(N-2',6'-diisopropylphenyl(naphthyl)amidate)yttrium mono(tetrahydrofuran) (4), was structurally determined to be a 7-coordinate C1 symmetric structure, maintaining one bound tetrahydrofuran molecule. Compound 4 (C12H17[NCO]C10H7)3Y(C4H8O) crystallized in the monoclinic space group P2(1)/c with a = 13.7820(11) A, b = 33.598(3) A, c = 16.0575(12) A, alpha = 90 degrees, beta = 98.762(3) degrees, gamma = 90 degrees, Z = 4. Solution phase NMR spectroscopic characterization of this same complex showed a highly symmetric species, consistent with a fluxional coordination environment for these compounds. Preliminary studies into the initiation of epsilon-caprolactone ring-opening polymerization using these complexes indicate high activity, producing high molecular weight polymer.