Multiple unknown degradants generated from the insect repellent DEET by photoinduced processes on TiO2

This paper deals with the photocatalytic transformation of N,N-diethyl-m-toluamide (DEET), one of the most widespread and efficient mosquito repellents, under simulated solar irradiation using titanium dioxide as the photocatalytic source of oxidizing species. The investigation involved monitoring of the DEET decomposition, the identification of intermediate compounds and the assessment of mineralization. High-resolution mass spectrometry was employed to assess the evolution of the photocatalyzed process over time. Fifty-one main species were identified after DEET transformation. Several isomeric species were formed and were characterized by analyzing MS and MS(n) spectra in full, and by comparison with parent molecule fragmentation pathways. In the DEET molecule, the initial transformation involved mono- and polyhydroxylation followed by oxidation of the alcohol groups, cleavage of the alkyl chains or ring opening. All these intermediates are easily degraded and DEET is completely mineralized after 4 h of irradiation. Microtox bioassay (Vibrio fischeri) was employed to evaluate the ecotoxicity of solutions treated by photocatalysis.     

2-difluoromethylene-4-methylenepentanoic acid, a paradoxical probe able to mimic the signaling role of 2-oxoglutaric acid in cyanobacteria

2-Difluoromethylene-4-methylenepentanoic acid (DFMPA), a seemingly deviated analog of 2-oxoglutaric acid (2-OG), could surprisingly mimic its signaling function in cyanobacteria. Computer modeling revealed the favorable binding of DFMPA toward the 2-OG receptor, NtcA, via mutual conformational changes, suggesting that structural alteration of 2-OG is tolerated for it to exercise its signaling role. This extremely useful finding could be exploited for the design of affinity probes with which to study new 2-OG receptors in related signaling pathways.     

Manifestation of the bound state \bar NN (1870) in the annihilation process \bar pd \to p_s 5\pi

It is shown that the existence of an N?N bound state with a mass of approximately 1870 MeV and width 10 MeV follows from analysis of the experimental data on the momentum distribution of recoil protons in the annihilation process p?d→p _s5π.     

The LAPEX experiment for observation of the supernova SN 1987A in hard X-rays

Summary The LAPEX payload is described in the configuration that will be launched to observe the supernova SN 1987A. The balloon flight will be performed from Alice Springs (Australia) in April 1989 as a part of a NASA balloon campaign. The experiment will allow simultaneous observations of source and background in order to minimize systematic errors due to background variations. The limiting flux sensitivity of the instrument in the (20÷200) keV energy band is 4·10⁻⁶ ph/(cm²s keV) or ∼2.5 mCrab for a 10⁴ s observation of SN 1987A. The presence of a⁵⁷Co emission line in the SN 1987A photon spectrum could be detected down to an intensity level of ∼8·10⁻⁵ photons/cm²s as at 99.7% confidence level. The high resolution of the event timing (<0.1 ms) will make it possible to detect millisecond pulsations with amplitudes down to ∼4% of the expected average flux from SN 1987A in the (20÷60) keV band. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

Nanostructured silicon as a photonic material

Photonics applications of silicon are presented. In particular it is demonstrated that silicon when rendered low dimensional, e.g. in form of nanocrystals or quantum wires, can be turned into an active photonic materials which shows light amplification characteristics, non-linear optical effects, photon confinement in both one and two dimensions, photon trapping with evidences of light localization, and gas sensing properties.     

Balloon program for hard-X-ray astronomy

Summary An observation program of X-ray sources in the (20÷200) keV energy band by means of a balloon-borne NaI(Tl) seintillator array was undertaken in 1980. Three balloon flights have been performed and 10 X-ray rources observed, some more than once. We present details of this balloon program and results obtained from the analysis of the Crab observation performed in October 1980. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–June 1984.