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Abstract  

The reactivity of MgO obtained from calcination of magnesium carbonate at different temperatures has been investigated by means of hydration in a constant relative humidity environment at 40°C for periods up to 24 days. Natural magnesite and AR grade basic MgCO3 calcined in the range of 500–1000°C was characterised in terms of surface area, crystallite size, morphology, and hydration rate. It was found that the hydration rate is dependent on the surface area and crystallite size where temperature was the main variable affecting them. The most reactive MgO was produced at the lowest calcination temperature with the highest surface area and the smallest crystallite size. The basic MgO specimens showed higher degree of hydration compared to the natural MgO specimens due to the smaller surface area and larger crystallite size. The low MgO content of the starting natural magnesite is also attributable to the lower reactivity. This preliminary study serves as a mean to investigate potential utilisation of reactive MgO as a supplementary cementitious material in eco-friendly cements.

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Journal of Thermal Analysis and Calorimetry
Authors: Ticiano do Nascimento, Irinaldo Basílio Júnior, Rui Macêdo, Elisana Moura, Camila Dornelas, Vanderson Bernardo, Vânia Rocha, and Csaba Nóvak

Abstract  

This article characterizes the stability of indinavir sulfate using different analytical techniques of quality control to evaluate important steps in the manufacturing process of indinavir, specifically involving storage and compression. Indinavir A, B, and C were obtained from different suppliers and submitted to DSC, Karl Fisher, NIR, XRPD analyses and dissolution assay. DSC curves of indinavir presented endothermic peaks of fusion at 149–150 °C for indinavir A and B (form I) and 139–143 °C for indinavir C (form II). When indinavir A and B were submitted to high Relative Humidity (RH) pseudo-polymorphic form II was formed. Indinavir C converted into an amorphous substance when submitted to compression. Near infrared and Karl Fisher assays detected high values of water for indinavir C in relation to indinavir A and B. X-ray powder diffraction of indinavir B and C showed displacement of 0.05–0.10 θ in the peaks and higher angle of diffraction in relation to indinavir A. Amorphous indinavir C demonstrated a higher intrinsic dissolution rate than indinavir A and B. Indinavir form I should be monitored during the pharmaceutical process to avoid its conversion to indinavir form II or an amorphous substance which can alter the dissolution rate.

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Abstract  

7Be activity concentrations were measured in the lower atmosphere at Thessaloniki, Northern Greece (40°38′N, 22°58′E) over the year 2009, a year of a particular minimum of solar activity. The mean annual activity concentration of 7Be at that year was 6.01 mBq m−3. The variability of 7Be surface concentrations related to the solar cycle appeared to be deviated about 40% between the maximum and the minimum values. A positive correlation (R = 0.97) was revealed between the activity concentrations of 7Be and the temperature, confirming that the increased rates of vertical transport within the troposphere, especially during the warmer months, resulted in carrying down to the surface layer air masses enriched in 7Be. Relatively high values of 7Be activity concentrations were observed by increasing of the tropopause height. A negative correlation (R = −0.65) between the 7Be activity concentrations and the relative humidity was due to the condensation process in the lower atmosphere which resulted in increased aerosol particle sizes with higher scavenging rates of aerosols and low activity concentrations of 7Be in the atmosphere. Influence of precipitation on the changes of 7Be activity concentrations was also observed.

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Abstract  

The seasonal variation of the 7Be activities in air and the size distribution of the 7Be aerosols were studied by using a continuous air sampler and a five stage cascade impactor. The mean monthly activity level of 7Be at the Korea Atomic Energy Research Institute (KAERI) site varied from 0.5 to 4.8 Bq·m−3 and revealed a seasonal variation, in which the 7Be activity levels were high in winter and low in summer. The mass size distribution showed a bi-modal distribution with a higher peak around 0.49 μm and a smaller peak between 3 μm and 7.2 μm. The activity median aerodynamic diameter (AMAD) decreased with increasing ambient 7Be concentrations. The mean residence times by using a mean growth rate of 0.004 μm·h−1 were estimated to be 2.5–6.4 days. The AMAD has an increasing tendency with higher relative humidity. It seemed that the high humidity condition facilitated the growth of the aerosol, resulting in increased deposition rates of the aerosols and the low 7Be content in the surface air. The AMAD of the 7Be aerosols increased with an increasing temperature, but the temperature dependency of AMAD should be explained with geological and meteorological conditions.

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Abstract  

MDF cements using the blends of sulfoaluminate ferrite belite (SAFB) clinkers and ordinary Portland cement (OPC) in mass ratio 85:15 with Al2O3, and starch, polyphosphate (poly-P) or butylacrylate/acrylonitrile were subjected to moist atmospheres (ambient, 52 and 100% relative humidity (RH)) to investigate their moisture resistance. Their chemical, thermal, electron microscopic and magnetic properties were also studied before and after moisture attack. Butylacrylate/acrylonitrile (BA/AN) copolymer was found to be the most suitable for MDF cement synthesis since the sample containing BA/AN showed the best moisture resistant. There are significant differences in scanning electron microscopy (SEM) of MDF cements before and after moisture attack and with different polymers. New data on the paramagnetic nonhysteresis magnetization curves for all the samples are observed. The MDF cements synthesized from SAFB clinker with dissolved poly-P give the best signal/noise (S/N) ratio. Three main temperature regions on TG curves of both series of MDF cements are observed. In the inter-phase section of MDF cements, the content of classical cement hydrates decomposing by 250C is increased. Combustion of organic material took place by 550C. In the temperature range 550-800C, the decomposition of CaCO3 occurs.

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Journal of Thermal Analysis and Calorimetry
Authors: E.T. Stepkowska, J. Perez-Rodriguez, M. Aviles, M. Jimenez de Haro, and M. Sayagues

Abstract  

Specific surface, S, of CSH-gel particles of disordered layered structure, was studied by water sorption/retention in two cement pastes differing in strength, i.e. C-33 (weaker) and C-43 (stronger), w/c=0.4. Hydration time in liquid phase was t h=1 and 6 months, followed by hydration in water vapour either on increasing stepwise the relative humidity, RH=0.5→0.95→1.0 (WS) or on its lowering in an inverse order (WR). Specific surface was estimated from evaporable (sorbed) water content, EV (110C), assuming a bi- and three-molecular sorbed water layer at RH=0.5 or 0.95, respectively (WS). On WR it was three- and three- to four-molecular (50 to 75%), respectively, causing a hysteresis of sorption isotherm. At RH=0.5 the S increased with cement strength from 146 m2 g-1 (C-33, 1 m) to 166 m2 g-1 (C-43, 1 m) and with hydration time to 163 (C-33, 6 m) and to 204 m2 g-1 (C-43, 6 m). At RH=1.0 (and 0.95), higher S-value were measured but these differences were smaller: S amounted to 190-200 m2 g-1 in C-33 (1 and 6 m) and 198-210 m2 g-1 in C-43 (1 and 6 m). Thus no collapse occurred on air drying of paste C-43 (6 m).

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Abstract  

South-Eastern part of Romania has a highest potential seismic risk in Europe due to the earthquake-prone Vrancea zone placed at conjunction of four tectonic blocks in the South-Eastern part of Carpathian Arc. This paper is an attempt to analyze the development of radon pre-earthquake anomaly in relation with moderate seismic events in Vrancea area through permanent monitoring with solid state nuclear track detectors CR-39 detectors. Radon in air above the ground was measured during 1 year period (November 2010–October 2011) in four selected test sites: Vrancioaia (VRI) and Plostina (PLOR) located in Vrancea zone, and Muntele Rosu-Cheia and Bucharest. During sampling period recorded earthquakes that occurred mostly in Vrancea epicentral region were minor-moderate of moment magnitudes in range of
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. The average radon concentration in air above the ground measured with CR-39 detectors and 10 days period recorded simultaneously at all test sites, registered the following values: (1) in Vrancea area (similar in VRI and PLOR) was 1094.58 
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 150.3 Bq/m3; (2) at Muntele Rosu-Cheia seismic station measured in a mountain tunnel laboratory was 3695.91 ± 440 Bq/m3; (3) at Bucharest station was 380.53 
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 69.17 Bq/m3, and 10 days CRn fluctuations in the range of (88 
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 40 to 912
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 130 Bq/m3). Clear radon anomalies, mostly at VRI and PLOR in Vrancea epicentral area as well as at Muntele Rosu-Cheia have been measured before seven minor earthquakes which were recorded in the range of moment magnitude
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in Vrancea area. Temporal variation of radon in air near the ground have been examined in relation with meteorological parameters like as air temperature, relative humidity, air pressure and wind velocity. Permanent monitoring of radon concentration anomalies in seismic area Vrancea is an important issue as surveillance tool in the field of earthquake hazard for Romania.
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Acta Chromatographica
Authors: M. Pacenti, S. Dugheri, R. Gagliano-Candela, G. Strisciullo, E. Franchi, F. Degli Esposti, N. Perchiazzi, P. Boccalon, G. Arcangeli, and V. Cupelli

Summary

2-Chloroacetophenone (CA) is widely used as tear gas by law-enforcement agents, and by civilians for personal protection. Crimes involving robbery and rape using tear gas sprays have recently increased. Experimental and in-field evaluations have been performed to validate use of solid-phase microextraction (SPME) with a porous fiber for sampling and analysis of CA in air before analysis by fast gas chromatography-mass spectrometry equipped with a new device called a multi-fiber system. CA vapor was generated by use of a syringe pump in a dynamic system in which temperature, relative humidity, and air velocity were monitored. The theoretical sampling rate for time-weighted average and rapid-SPME were, furthermore, estimated by use of the Fuller-Schettler-Giddings diffusion coefficient and the theory of heat transfer, respectively, and were in accordance with experimental values. Concentrations of CA were analyzed in a military store containing tear gas canisters, to evaluate the risk. The results obtained in this field study showed values ranging from 0.206 to 2.46 mg m−3.

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factors such as light, relative humidity, and pollutants on objects both in outdoor and indoor environments are studied in preventive conservation. To achieve this, monitoring is performed of the microclimate surrounding the object using both diffusive

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.03 Paste cubes were manufactured with a water/cement ratio equal to 0.5 and with dimensions of 3.5 cm 3 . They were cured for 24 h in a humidity chamber at 20 °C with a relative humidity greater than 95%. After the initial curing, the test specimens were

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