Generation of Cationic Two-Coordinate Group-13 Ligand Systems by Spontaneous Halide Ejection: Remarkably Nucleophile-Resistant (Dimethylamino)borylene Complexes

Spontaneous ejection of chloride from a three-coordinate boron Lewis acid can be effected by employing very electron rich metal substituents and leads to the formation of a sterically unprotected terminal (dimethylamino)borylene complex that has a short metal-boron bond and remarkable resistance to attack by nucleophilic and protic reagents.

Thermally Controlled Cyclic Insertion/Ejection of Dopant Ions and Reversible Zinc Blende/Wurtzite Phase Changes in ZnS Nanostructures

We report a reversible phase transformation of platelet-shaped ZnS nanostructures between wurtzite (WZ) and zinc blende (ZB) phases by reversible insertion/ ejection of dopant Mn(II) ions induced by a thermocyclic process. In a reaction flask loaded with WZ ZnS platelets and Mn molecular precursors, during heating Mn ions are incorporated and change the phase of the host nanostructures to ZB; during cooling Mn ions are spontaneously ejected, returning the host nanoplatelets to the original WZ phase. These reversible changes are monitored for several cycles with PL, EPR, XRD, and HRTEM. Interestingly, the (0001) WZ platelets transform to (110) ZB following a nucleation and growth process triggered by a local increase/depletion of the Mn2+ concentration in the nanocrystals.

Thermally Controlled Cyclic Insertion/Ejection of Dopant Ions and Reversible Zinc Blende/Wurtzite Phase Changes in ZnS Nanostructures

We report a reversible phase transformation of platelet-shaped ZnS nanostructures between wurtzite (WZ) and zinc blende (ZB) phases by reversible insertion/ ejection of dopant Mn(II) ions induced by a thermocyclic process. In a reaction flask loaded with WZ ZnS platelets and Mn molecular precursors, during heating Mn ions are incorporated and change the phase of the host nanostructures to ZB; during cooling Mn ions are spontaneously ejected, returning the host nanoplatelets to the original WZ phase. These reversible changes are monitored for several cycles with PL, EPR, XRD, and HRTEM. Interestingly, the (0001) WZ platelets transform to (110) ZB following a nucleation and growth process triggered by a local increase/depletion of the Mn2+ concentration in the nanocrystals.

278. Studies on ass's milk: Composition

The total solids of samples of ass's milk ranged from 7·80 to 9·10, the solids-not-fat from 7·14 to 8·50, and the fat from 0·54 to 0·71%. The nitrogen distribution in ass's milk is: casein 39·5, albumin 35·0, globulin 2·7 and non-protein nitrogen 22·8% of the total nitrogen. Ass's milk contains: casein 0·70, albumin 0·62 and globulin 0·07%. The total protein content is 1·39%. Ass's milk is therefore characterized by a low casein, a low globulin and a high albumin content. The non-protein nitrogen consists of amino nitrogen 8·1, urea nitrogen 24·3 and uric acid 0·7 mg./100 ml. of milk. The urea content is twice that present in cow's milk. The mean chloride and lactose contents of the milk samples are 0·037 and 6·1% respectively. The average calcium and phosphorus content of ass's milk are 0·081 and 0·059% respectively. Half the calcium is ionic, and half is in colloidal form. The phosphorus distribution is: total acid soluble 84·0, acid soluble organic 38·5, easily hydrolysable ester 27·4, inorganic 46·0, and colloidal inorganic 23·0 % of the total phosphorus. The ratio of CaO: P2O5 is 1:1. 46 % of the total phosphorus is in ester form; this is high when compared with only 12 % in cow's milk; most of the phosphoric ester forms soluble barium salts, which is a distinguishing feature of ass's milk. The total sulphur content is 15·8 mg./100 ml. The fat has a penetrating odour and is coloured orange-yellow. It has an iodine value of about 86, which is much higher than that for human milk fat. The Reichert (9·5) and Kirschner values (5·7) are low. In general, the composition of ass's milk resembles that of human rather than of cow's milk.

Direct detection of Salmonella without pre-enrichment in milk, ice-cream and fruit juice by PCR against hilA gene

A novel PCR based assay was devised to specifically detect contamination of any Salmonella serovar in milk, fruit juice and ice-cream without pre-enrichment. This method utilizes primers against hilA gene which is conserved in all Salmonella serovars and absent from the close relatives of Salmonella. An optimized protocol, in terms time and money, is provided for the reduction of PCR contaminants from milk, ice-cream and juice through the use of routine laboratory chemicals. The simplicity, efficiency (time taken 3-4 h) and sensitivity (to about 5-10 CFU/ml) of this technique confers a unique advantage over other previously used time consuming detection techniques. This technique does not involve pre-enrichment of the samples or extensive sample processing, which was a pre-requisite in most of the other reported studies. Hence, this assay can be ideal for adoption, after further fine tuning, by food quality control for timely detection of Salmonella contamination as well as other food-borne pathogens (with species specific primers) in food especially milk, ice-cream and fruit juice. (C) 2011 Elsevier Ltd. All rights reserved.

(Dimethylamino)borylene and Related Complexes of Electron-Rich Metal Fragments: Generation of Nucleophile-Resistant Cations by Spontaneous Halide Ejection

Spontaneous halide ejection from a three-coordinate Lewis acid has been shown to offer a remarkable new route to cationic metal complexes featuring a linear, multiply bonded boron-donor Ligand. The exploitation of electron-rich [CpM(PR3)(2)] fragments within boryl systems of the type LnMB(hal)NR2 leads to the spontaneous formation in polar solvents of chemically robust borylene complexes, [LnM(BNR2)](+), with exceptionally low electrophilicity and short M-B bonds. This is reflected by M-B distances (ca. 1.80 angstrom for FeB systems) which are more akin to alkyl-/aryl-substituted borylene complexes and, perhaps most strikingly, by the very low exothermicity associated with the binding of pyridine to the two-coordinate boron center (Delta H = -7.4 kcal mol(-1), cf. -40.7 kcal mol(-1) for BCl3). Despite the strong pi electron release from the metal fragment implied by this suppressed reactivity and by such short M-B bonds, the barrier to rotation about the Fe=B bond in the unsymmetrical variant [CpFe(dmpe)(BN{C6H4OMe-4}Me)](+) is found to be very small (ca. 2.9 kcal mol(-1)). This apparent contradiction is rationalized by the orthogonal orientations of the HOMO and HOMO-2 orbitals of the [CpML2](+) fragment, which mean that the M-B pi interaction does not fall to zero even in the highest energy conformation.

A modified auxiliary excitation signal for achieving unidirectional ion ejection in quadrupole ion trap mass spectrometers operating in the resonance ejection mode

This paper proposes a technique to cause unidirectional ion ejection in a quadrupole ion trap mass spectrometer operated in the resonance ejection mode. In this technique a modified auxiliary dipolar excitation signal is applied to the endcap electrodes. This modified signal is a linear combination of two signals. The first signal is the nominal dipolar excitation signal which is applied across the endcap electrodes and the second signal is the second harmonic of the first signal, the amplitude of the second harmonic being larger than that of the fundamental. We have investigated the effect of the following parameters on achieving unidirectional ion ejection: primary signal amplitude, ratio of amplitude of second harmonic to that of primary signal amplitude, different operating points, different scan rates, different mass to charge ratios and different damping constants. In all these simulations unidirectional ejection of destabilized ions has been successfully achieved. (C) 2015 Elsevier B.V. All rights reserved.