Shallow energy levels induced by γ rays in standard and oxygenated floating zone silicon

Shallow defect levels in floating zone (FZ) and diffusion oxygenated FZ (DOFZ) silicon, before and after irradiation with a ⁶⁰Co γ-source up to 300 Mrad, have been studied by thermally stimulated currents (TSC) and deep level transient spectroscopy (DLTS) in the temperature range 4.2–110 K. Besides vacancy oxygen (VO) and interstitial-substitutional carbon (C_iC_s) emissions, several TSC peaks have been observed. A trap with an activation energy of 11 meV has been observed at 6 K only in irradiated DOFZ. Two hole traps at 80 meV and 95 meV have been observed both in irradiated FZ and DOFZ, while a trap at 100 meV, related to an interstitial-oxygen (IO₂) complex, has been revealed only in irradiated DOFZ. A TSC peak close to 24 K has been resolved into two components, whose concentrations are independent of irradiation fluence: a trap at 55 meV and a level which remains charged after emission at 80 meV. Our measurements confirm the formation, only in DOFZ, of a radiation induced donor at 230 meV. It appears to be responsible for the improved radiation hardness of oxygenated Si together with the suppression of deep acceptors, since no shallower radiation-induced donors have been detected in DOFZ samples. PACS 71.55.Cn; 29.40.Wk; 61.80.Hg; 61.82.Fk     

Isotachophoresis as a useful tool for monitoring neurological complications of acute leukaemia in children

Cerebrospinal fluid proteins from 42 children with acute lymphoblastic leukaemia were analysed by isotachophoresis. The isotachopherograms of cerebrospinal fluid taken from patients undergoing central nervous system prophylaxis with neurological complications showed an increase of several peaks (albumin, prealbumin, and an unidentified peak), and changes in the globulin zone, compared with those from patients who had completed central nervous system prophylaxis for at least six months. The most striking finding was that these alterations were not associated with any other biochemical changes in the cerebrospinal fluid, as assayed by routine analysis. Isotachophoresis may be useful in the monitoring of therapy in children affected with acute lymphoblastic leukaemia.     

The measurement of atmospheric pollutants by passive sampling at the Uffizi Gallery,Florence

Diffusive sampling can be adopted to analyse in detail the temporal and spatial trends of pollutants concentration in specific historic buildings or in museums. An application of this method is discussed in this paper and the results of a still ongoing monitoring campaign at the Uffizi Gallery in Florence, in the framework of an EU-founded Project (MIMIC), are presented. Distinct trends in the concentration of NO2, NOx, HONO, HNO3, O3 and SO2 have been observed in eight successive sampling periods from March 2001 to February 2002. Considerations are given on possible implications for the conservation of indoor artworks.     

γ‐Azaproline Confers pH Responsiveness and Functionalizability on Collagen Triple Helices

Proline derivatives bearing substituents at Cγ are valuable tools for biological and materials investigations. However, the stereochemistry at Cγ can produce undesired steric or stereoelectronic interactions. Here, we introduce γ‐azaproline (γ‐azPro), which lacks a stereogenic center at Cγ, as a pH‐responsive and functionalizable proline analogue that can adapt to its environment. Conformational analyses by NMR spectroscopy and DFT calculations revealed that the imidazolidine ring of γ‐azPro is flexible. Incorporation of γ‐azPro into collagen model peptides (CMPs) produced pH‐responsive triples helices and triple helices that can be easily functionalized.     

Monitoring the air quality around an oil refinery through the use of diffusive sampling

Diffusive sampling has been used to study the spatial distribution of SO₂, NO₂, NO_x, NH₃ and BTX (benzene, toluene and xylenes) near an oil refinery located in Falconara, Italy, over the period from March to October 2001. Three different categories of sampling sites (roadside, residential and background) were studied. In total, 56 sites were monitored. The results were evaluated on the basis of the limit values found in the European Directives. The results of the defined study indicate that the measured concentrations were substantially lower than the ambient air quality standard with the maximum concentrations being generally found much closer to emission sources. The monitoring method described here can be used to assess integrated concentration levels over long periods of time and to identify pollution hotspots where concentrations are likely to be consistently high. Identification of these hotspots may help to assess air quality and to implement proper action plans, especially in locations where industrial and urban pollution coexist.     

A calorimeter coupled with a magnetic spectrometer for the detection of primary cosmic antiprotons

Summary A tracking calorimeter made of 3200 brass streamer tubes together with 3200 pick-up strips has been built to complement a magnetic spectrometer in order to detect cosmic antiprotons in space. The characteristics of such a calorimeter, the results of a preliminary test of a prototype as well as the properties of the whole apparatus are presented. The apparatus, designed to operate on a balloon at an altitude of about 40 km, can be considered as a second generation detector, capable in principle to solve the problem of the presence of low energy (≤1 Ge V/c) antiprotons in the cosmic rays which is still open because of the disagreement between the existent experimental data.

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Riassunto Un calorimetro tracciante costituito da cinquanta piani realizzati con 3200 tubi a streamer in ottone accoppiati ad un egual numero di strip per la raccolta del segnale indotto, è uno strumento ideale per operare in connessione con uno spettrometro magnetico, allo scopo di rilevare antiprotoni cosmici. Si presentano le caratteristiche di tale calorimetro, i risultati del test preliminare di un prototipo e le proprietà dell'intero apparato. L'apparato stesso, progettato per essere trasportato da un pallone ad una quota di circa 40 km, può essere considerato come un rivelatore di seconda generazione, capace in linea di principio di risolvere la questione ancora aperta, a causa del disaccordo tra i dati sperimentali esistenti, della presenza nei raggi cosmici di antiprotoni di bassa energia (≤1 Ge V/c).

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Резюме Трековый калориметр, состоящий из 3200 латунных стримерных трубок, связанных с 3200 чувствительных лент, дополняется магнитным спектрометром для детектирования первичных космических протонов. Представляются характеристики такого калориметра, результаты предварительных испытаний прототипа калориметра, а также свойства всей аппаратуры в целом. Предложенная аппаратура, которая будет действовать на воздушном шаре на высоте порядка 40 Km, может рассматриваться как второе поколение детекторов, способных, в принципе, решить проблему обнаружения антипротонов низких энергий (≤1 Гэ В/с) в космических лучах, которая до сих пор остается открытой из-за несоответствия существующих экспериментальных данных.

     

Laboratory development and field evaluation of a new diffusive sampler to collect nitrogen oxides in the ambient air

Diffusive samplers for the determination of NO(x) and NO2 based on collection on a coated carbon paper filter have been developed. NO is first oxidized to NO2 and then collected on the reactive surface. When NO2 and NOx samplers are exposed simultaneously, NO can be calculated by difference. The sampler has been derived from a Palmes design as recently modified by Bertoni et al. for the determination of BTX (benzene, toluene, xylenes). Laboratory tests were conducted in controlled atmosphere to evaluate linearity, uptake rate, face velocity effects, sample stability, influence of relative humidity, precision and accuracy. The samplers are capable of reliable measurements of the two species at common levels of a polluted atmosphere in urban settings yielding average concentration levels over 1 month and beyond.The uptake rate of NO2 was found to be 11.7 mL/min in a very good agreement (within 5%) with the value calculated from theory. The measured uptake rate for NO(x) was determined in experiments involving sampling at different concentration levels in comparison to chemiluminescence (CL) measurements. The precision of the measurements for co-located passive samplers was better than 5%. The accuracy of the data collected is within +/-20% of the actual value measured by CL. The laboratory and field results show that the NO(x) and NO2 samplers meet the data quality goal requested by the first EU Directive 1999/30/EU for these pollutants.