Novel synthetic route to octasubstituted naphthalenes from four alkynes and one olefin unit via zirconacyclopentadienes and 1,2-diiodo-3,4,5,6-tetraalkylbenzene

1,2,3,4-Tetrasubstituted benzene derivatives were prepared by the reaction of zirconacyclopentadienes with vinyl bromide in the presence of NiCl(2)(PPh(3))(2). 1,2-Diiodo-3,4,5,6-tetraalkylbenzenes were formed by treatment of 1,2,3,4-tetraalkylbenzenes with iodine and periodic acid in the presence of a catalytic amount of sulfuric acid. Reaction of the 1,2-diiodo-3,4,5,6-tetraalkylbenzenes with zirconacyclopentadienes in the presence of a stoichiometric amount of CuCl gave sterically crowded octasubstituted naphthalenes in moderate yields.     

Site-selective DNA hydrolysis by combining Ce(IV)/EDTA with monophosphate-bearing oligonucleotides and enzymatic ligation of the scission fragments

By using two oligonucleotide additives that bear a monophosphate group at the termini through various linkers, gap structures were formed at predetermined positions in substrate DNA, and the monophosphate groups were placed at both edges of these gaps. At pH 7.0 and 37 degrees C, the phosphodiester linkages in the gap sites were efficiently and selectively hydrolyzed by Ce(IV)/EDTA complex (EDTA = ethylenediamine-N,N,N',N'-tetraacetate). The linkages in the middle of the gaps were predominantly hydrolyzed. Compared with DNA scission using oligonucleotide additives that bear no terminal monophosphate, the present scission was much faster (22-fold for a 3-base gap and 14-fold for a 5-base gap) and more site selective. Introduction of one monophosphate group to either edge of the gaps was also effective for promotion of both site selectivity and scission rate. The monophosphate group(s) at the gap site recruits the Ce(IV) to the target site and magnifies the difference in intrinsic reactivity between the target site and the others. Even at higher reaction temperatures, the site selectivity remained satisfactorily high. Furthermore, the fragments formed by the site-selective scission were connected with various oligonucleotides by using DNA ligase, producing desired recombinant DNAs.     

Effect of savitzky—golay smoothing on second-derivative spectra

The rounding error arising from analog/digital conversion (12-bit) of a spectrum introduces small shoulders on the zero-order spectrum, which are enhanced in the second-derivative spectrum. To reduce this noise, Savitzky-Golay smoothing of the zero-order spectrum was examined by simulation. This smoothing procedure brings the second-derivative spectrum closer to the true spectrum. The effects of smoothing on the ultraviolet spectrum of salicylic acid in ethanolic solution are reported.     

Photoresponsive melamine barbiturate hydrogen-bonded assembly

UV-irradiation of hydrogen-bonded assembly between trans-azobenzene-incorporated melamine and barbiturate in chloroform drastically suppressed transformation from soluble cyclic rosette into insoluble tape-like polymers.     

Mechanism of characteristic shape of resistive transition in Bi2Sr2CaCu2O8 films made by laser evaporation

We measured the temperature dependence of resistivity, (T, H), of Bi₂Sr₂CaCu₂O₈ thin films in magnetic fields. These films have a preferential orientation of the c-axis perpendicular to a surface of the substrate. We could not observe any meaningful anisotropy of the characteristic shape of the resistive transition between two cases of the current flow parallel and perpendicular to the magnetic field in the basal plane. Therefore, it is very difficult to ascribe the broadness to any origin due to the Lorentz force produced by an external current.     

Precise and accurate determination of halogens in organic compounds using an amalgamated gold electrode

Precise and accurate titration of halogens in organic and inorganic materials has been studied. The halogen was titrated with coulometrically generated silver and determined potentiometrically by using an amalgamated gold indicator electrode. An argentometric titration curve using the amalgamated gold indicator electrode showed a large jump in potential at the endpoint as well as in mercurometric determination. Sodium carboxymethyl cellulose (CMC) and aluminum nitrate were added as they are most effective for clarifying the sample solution and eliminating adsorption of the halide ion on the silver halide generated. The electrolytes used were 0.5 M nitric acid containing 0.1% CMC and 0.2 M aluminum nitrate. Approximately 0.2 mmol of chloride, bromide, and iodide ions were titrated with high precision and accuracy. Their standard deviations were 0.03, 0.02, and 0.02%, respectively, with no apparent systematic error. The precise determination of halogens, employing oxygen flask combustion and dissolution of the halide salts in the electrolyte, was carried out with ±0.1% absolute error using samples weighing between 20 and 30 mg.     

Background light measurements in the deep ocean

Summary Ambient light intensities in the ocean at depths between 1500 m and 4700 m near Hawaii Island were measured around the one photoelectron level with 5″ diameter hemispherical photomultipliers. Measurements of count rates above variable thresholds were carried out in ship-suspended and bottom-tethered configurations. The ship-suspended rates show considerable fluctuation and their mean value decreases with depth approximately as exp [−x(m)/877]. The bottomtethered rates are about an order of magnitude lower than the ship-suspended rates and show little fluctuation. The calibration of our instrument indicates an absolute flux at 4700 m depth based on the bottom-tethered measurement of 218 ₋₆₀ ⁺²⁰ photons/cm²·s, which is consistent with calculated intensities due to β-decay electrons from⁴⁰K. The difference in the two cases is attributed to bioluminescence due to environmental stimulation.

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Riassunto Sono state misurate le intensità di luce ambiente nell'oceano a profondità tra 1500 m e 4700 m vicino alle isole Hawaii intorno al livello ad un fotoelettrone con fotomoltiplicatori emisferici di 5″ di diametro. Sono state effettuate le misure delle frequenze di conteggio oltre alle soglie delle variabili in configurazioni appese alla nave e ancorate al fondo. Le frequenze delle configurazioni appese alla nave mostrano una fluttuazione considerevole e il loro valore medio decresce con la profondità come exp [−x(m)/877]. Le frequenze delle configurazioni ancorate al fondo sono circa di un ordine di grandezza inferiore di quelle delle configurazioni appese alla nave e mostrano una piccola fluttuazione. La calibrazione del nostro strumento indica un flusso assoluto a 4700 m di profondità basato sulla misura delle configurazioni ancorate al fondo di 218 ₋₆₀ ⁺²⁰ fotoni/cm²·s, che è consistente con le intensità calcolate dovute al decadimento β degli elettroni da⁴⁰K. Si attribuisce la differenza nei due casi alla bioluminescenza dovuta alla stimolazione ambientale.

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Резюме Измеряются интенсивности свечения окружающей среды в океане на глубинах от 1500 м до 4700 м вблизи Гавайских островов с помощью 5-дюймовых полусферических фотоумножителей. йзмерения скоростей счета выше изменяющихся порогов были проведены в случае подвешенном на корабле и в случае прикрелления ко дну. Интенсивности счета в подвешенном состояиии обнаруживают значительные флуктуации и их средняя величина уменьшается с глубиной приблизительно как ехп [−x(m)/877]. Интенсивности счета в случае прикрепления ко дну примерно на порядок меньше интенсивностей в подвешенном состоянии и обнаруживаут малые флуктуации. Градуировка нашей аппаратуры даст на основе измерений в случае прикрепления ко дну величину абсолутного потока на глубине 4700 м, равную 218 ₋₆₀ ⁺²⁰ фотонов/см² с, которая согласуется с вычисленными интенсивностями, обусловленными электронами β-распада от⁴⁰К. Различия, обнаруженные в двух случаях, приписываются биолюминесценции, связанной с возбуждением окружающеи среды.