Time interval distributions of atoms in atomic beams

We report an experimental investigation of two-particle correlations between neutral atoms in a Hanbury Brown and Twiss experiment. Both an atom laser beam and a pseudo-thermal atomic beam are extracted from a Bose–Einstein condensate and the atom flux is measured with a single atom counter. We determine the conditional and the unconditional detection probabilities for the atoms in the beam and find good agreement with the theoretical predictions. PACS 03.75.Pp; 05.30.Jp; 07.77.Gx; 42.50.Pq     

Recyclable,non-leaching antimicrobial magnetic nanoparticles

Recyclable antimicrobial magnetic nanoparticles, Fe₃O₄@P(St-co-AcQAC), were prepared through surfactantfree seeded emulsion polymerization involving a polymerizable, hydrophobic quaternary ammonium compound (QAC). These antimicrobial magnetic nanoparticles demonstrated excellent antimicrobial activities against both Grampositive and Gram-negative bacteria, and can be reused for multiple times.     

Freezing temperatures and densities of solutions of some hydrocarbons and sodium oleate inN-methylacetamide. Evidence for a solvophobic interaction

The freezing temperatures and densities (at 31°C) of solutions of octane, nonane, decane, 3,3-diethylpentane, and sodium oleate inN-methylacetamide (NMA) have been measured. The molality of the freezing solution was calculated from the density. The solubilities of octane, nonane, and decane inN-methylacetamide are also reported. Apparent molal volumes calculated from the densities are close to the values in the pure hydrocarbons and are not strong functions of the concentration. This indicates the absence of any unusual packing effect. The calculated free energies of transfer of the hydrocarbons from pure hydrocarbon to NMA solution are much less negative than the corresponding values for water, showing that the bulk solvophobic interaction inN-methylacetamide is smaller than in water. This is consistent with the freezing temperatures of sodium oleate which show that micelles do not form below 0.1 mole-kg^–1. The osmotic coefficients of the hydrocarbons calculated from the freezing temperatures showed negative deviations from ideality that were larger for the hydrocarbons with the higher molecular weights. Two estimates of the pairwise solvophobic interaction inN-methylacetamide indicate that it is also smaller than in water. The solvophobic effect in this solvent does not include the large entropy and enthalpy effects found in aqueous solutions.     

Hydrogencarbonat-Bestimmung im Wasser in Anwesenheit von Anionen anderer schwacher S?uren

Zusammenfassung Die maßanalytische HCO₃ ^–-Bestimmung im Wasser kann bei gleichzeitig vorhandenen Anionen anderer schwacher Säuren, insbesondere in Wässern mit erheblicher Belastung an polaren organischen Stoffen, zu stark erhöhten HCO₃ ^–-Werten und damit zu einer Fehlbeurteilung des untersuchten Wassers führen. Es wurde daher ein Verfahren ausgearbeitet, das den wahren HCO₃ ^–-Gehalt mit einem Fehler von höchstens –5% ermittelt. Hierbei wird das Gesamtkohlendioxid gravimetrisch, das freie Kohlendioxid volumetrisch bestimmt und HCO₃ ^– aus der Differenz berechnet.

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Determination of bicarbonate in water in presence of anions of other weak acids

The contemporary presence of anions of other weak acids is able to simulate a much elevated content by the volumetric determination of bicarbonate, especially in waters with a considerable loading of organic matters. A process was elaborated, which finds out the real content of bicarbonate with an error of —5% at most, consisting in the gravimetric determination of total carbon dioxide and the volumetric determination of free carbon dioxide. HCO₃ ^– is calculated from the difference.

     

Preparation of 3-azetidinols with non-bulky 1-alkyl substituents

Cyclization of either the tetrahydropyranyl or trimethylsilyl ether of 1-(alkylamino)-3-chloro-2-propanols 1 followed by cleavage of the azetidinyl ether provides a general method for the preparation of 1-alkyl-3-azetidinols. Unhindered amines provide a more facile preparation of derivatives of 1 , or its ethers, than do hindered amines, while hindered derivatives of 1 undergo more facile ring closure.     

Freezing points,osmotic coefficients,and activity coefficients of some salts in ethylene carbonate: A high dielectric constant solvent without hydrogen bonding

The freezing points, conductivities, and densities of NaI, KI, CsI, Bu₄NCl, Bu₄NBr, Bu₄NI, Et₄NBr, and Pr₄NBr (where Et = ethyl, Pr = propyl, and Bu =n-butyl) in ethylene carbonate have been measured. Osmotic and activity coefficients were calculated from the results. All of the salts studied are strong electrolytes. The trends in the osmotic coefficients of the alkali metal iodides are NaI>KI>CsI, showing that Na⁺ is more solvated by ethylene carbonate than Cs⁺. For the tetraalkylammonium halides, the order of osmotic coefficients are Et₄NBrPr₄NBrBu₄NCl>Bu₄NBr>Bu₄NI. This is the same order as observed in two other high-dielectric-constant solvents, water andN-methylacetamide. The results indicate that the smaller anions are more solvated than the larger anions in ethylene carbonate in contrast to the usual behavior of dipolar aprotic (basic) solvents, such as dimethyl sulfoxide.     

Isotope effects in aqueous systems. V. Partial molal enthalpies of solution of NaCl−H2O−D2O and related systems (5 to 75°C)1

Solvent isotope effects on differential heats of solution of NaCl in HOH and DOD have been measured between 0.01 and 4m and from 5 to 40°C. These data are supplemented by integral heats of solution measured at 0.465m and from 5 to 75°C, and with heats of dilution over the same temperature range. The integral heat measurements include studies on otheralkali halides (KCl, NaI, NaBr), and the dilution measurements include some data for KCl. In the NaCl studies, particular attention was paid to the low-concentration region. Values of the partial molal enthalpiesL ₁ adL ₂ are derived for solution in both isotopic waters, and new values for the isotope effect on the standard enthalpy of solution ΔL ₂ ^s = (ΔH ₂ ⁰ ) _d←w as a function of temperature are reported. Comparisons are made with previous work where possible. In contrast to statements made by earlier authors, examination of the low-concentration data reveals a \(\surd \overline m\) dependence within experimental error.