YAG(Ce) crystal characterization with proton beams

A YAG(Ce) crystal has been characterized with a proton beam up to 100 MeV. Tests were performed to investigate the possibility of using this detector as a proton calorimeter. A crystal size has been chosen that is able to stop up to 200 MeV. Energy resolution and light response have been measured at Laboratori Nazionali del Sud with a proton beam up to 60 MeV and a spatial homogeneity study of the crystal has been performed at Loma Linda University Medical Center with a 100 MeV proton beam. The YAG(Ce) crystal showed a good energy resolution equal to 3.7% at 60 MeV and measurements, performed in the 30-60 MeV proton energy range, were fitted by Birks' equation. Using a silicon tracker to determine the particle entry point in the crystal, a spatial homogeneity value of 1.7% in the light response has been measured.     

Chemical characterization and classification of pollen

We report on the in situ characterization of tree pollen molecular composition based on Raman spectroscopy. Different from purification-based analysis, the nondestructive approach allows (i) to analyze various classes of molecules simultaneously at microscopic resolution and (ii) to acquire fingerprint-like chemical information that was used for the classification of pollen from different species. Hierarchical cluster analysis of spectra from fresh pollen samples of 15 species partly related at the genus level and family level indicates separation of species based on the complete Raman spectral signature and yields classification in accord with biological systematics. The results have implications for the further elucidation of pollen biochemistry and also for the development of chemistry-based online pollen identification methods.     

Further utilisation of 2-naphthol esters: polarographic determination of phosphatase and arylsulphatase activities

Summary The Polarographic method of the determination of alkaline and acid phosphatases and arylsulphatases using esters of 2-naphthol has been elaborated. The enzymatically released 2-naphthol is nitrosated and the nitrosation product (1-nitroso-2-naphthol) is reduced on the mercury drop-electrode with the production of a well-developed four-electron wave. The method was applied for the determination of the enzymatic activity of tissue homogenates and commercial enzyme preparations.

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Weitere Anwendbarkeit von 2-Naphthol-Estern : Polarographische Bestimmung der Aktivität von Phosphatase und Arvlsulphatase

Zusammenfassung Es wurde eine Methode zur polarographischen Bestimmung der Aktivität der alkalischen und sauren Phosphatasen und Arylsulphatasen bei Benützung der 2-Naphthol-Ester ausgearbeitet. Das durch enzymatische Hydrolyse freigesetzte 2-Naphthol wird nitrosiert und das Nitrosierungsprodukt (1-Nitroso-2-Naphthol) auf der Quecksilber-Tropfelektrode bei Entstehung einer gut entwickelten Welle reduziert. Diese Methode wurde bei Bestimmung der enzymatischen Aktivität in Gewebehomogenaten wie auch in enzymatischen Handelspräparaten verwendet.

     

Chemical Signals of Elephant Musth: Temporal Aspects of Microbially-Mediated Modifications

Mature male African (Loxodonta africana) and Asian (Elephas maximus) elephants exhibit periodic episodes of musth, a state in which serum androgens are elevated, food intake typically decreases, aggressiveness often increases, and breeding success is enhanced. Urine is a common source of chemical signals in a variety of mammals. Elephants in musth dribble urine almost continuously for lengthy periods, suggesting that the chemicals in their urine may reveal their physiological condition to conspecifics. We investigated the volatile urinary chemicals in captive male elephants using automated solid phase dynamic extraction (SPDE) and gas chromatography-mass spectrometry (GC-MS). We found higher levels of alkan-2-ones, alkan-2-ols, and some aromatic compounds in urine from males in musth than in urine from non-musth males or from females. Levels of ketones and alcohols increased as the urine aged, likely due to microbial metabolism of fatty acids. Protein-derived aromatic metabolites also increased in abundance after urination, likely due to microbial hydrolysis of hydrophilic conjugates. We suggest that microbes may play an important role in timed release of urinary semiochemicals during elephant musth.     

The chemistry of alkyl dihalides in zeolite NaX at room temperature

Alkyl dihalides adsorbed in NaX zeolite undergo room temperature, substitutional dehalogenation, single dehydrohalogenation, combined dehalogenation–dehydrohalogenation, or two consecutive dehydrohalogenations. The preference for a particular reaction depends on the nature and relative positions of the halogens, and on alkyl chain length. Nuclear magnetic resonance chemical shifts and mass spectrometric assignments to the reagents and products indicate the particular reactions taking place.All of the alkyl dihalides containing the iodo group (diiodoalkanes) studied (αα, αβ, α,γ) undergo only substitutional dehalogenation to form zeolite bound iodoalkoxy. The same chemistry was observed with both short and long chain diiodoalkanes. The dichloroalkane and dibromoalkane chemistry is dependent on the relative halogen positions and the alkyl chain length. The α, α dichloroalkanes and dibromoalkanes examined by us undergo single dehydrohalogenation, with the exception of 2,2-dichloropropane, which forms a mixture of dehydrohalogenation and substitutional dehalogenation products. The chemistry of α, β alkyl dihalides (Cl, Br) in NaX is dependent on the carbon chain length. The dihaloethanes (Cl, Br) undergo both substitutional dehalogenation and dehydrohalogenation. As the chain length increases to three carbon atoms or more, only dehydrohalogenation reactions take place. No alkyne products were observed with α, β dichloroalkanes and dibromoalkanes, an indication that NaX is too weak a base to initiate sequential dehydrohalogenations. The chemistry of α, γ dichloroalkanes and dibromoalkanes were also dependent on the chain length. The α, γ dihalopropanes (Cl, Br) in NaX form a propene-framework bound product, associated with dehydrohalogenation and subsequent substitutional dehalogenation. The α, γ dihalobutanes (Cl, Br) undergo two consecutive dehydrohalogenations to form dienes.