Synthesis of MIL-53 thin films by vapour-assisted conversion

A simple method for the preparation of MIL-53 thin films is reported. By employing a vapour-assisted conversion (VAC) approach we were able to prepare homogeneous MIL-53 films on a variety of glass, silicon or alumina substrates. Our strategy uses a vessel that allows film growth in an environment with a solvent-saturated atmosphere, in this case DMF. The VAC preparative conditions lead to the formation of a homogeneous film of the MOF and avoids the formation of alternative aggregates, such as starting materials. The effect of reaction temperature and time are investigated allowing identification of the optimum conditions to produce good film quality

Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence

Cataloged from PDF version of article.Silicon nanocrystals, average sizes ranging between 3 and 7 nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800 degrees C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. While the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix. (c) 2006 American Institute of Physics

Binning effects on in-situ raindrop size distribution measurements

This paper investigates the binning effects on drop size distribution (DSD) measurements obtained by Joss-Waldvogel disdrometer (JWD), Precipitation Occurrence Sensor System (POSS), Thies disdrometer (Thies), Parsivel OTT disdrometer, two-dimensional video disdrometer (2DVD) and optical spectro-pluviometer (OSP) instruments, therefore the evaluation comprises non-regular bin sizes and the effect of minimum and maximum measured sizes of drops. To achieve this goal, 2DVD measurements and simulated gamma size distributions were considered. The analysis of simulated gamma DSD binned according each instrument was performed to understand the role of discretisation and truncation effects together on the integral rainfall parameters and estimators of the DSD parameters. In addition, the drop-by-drop output of the 2DVD is binned to simulate the raw output of the other disdrometers which allowed us estimate sampling and binning effects on selected events from available dataset. From simulated DSD it has been found that binning effects exist in integral rainfall parameters and in the evaluation of DSD parameters of a gamma distribution. This study indicates that POSS and JWD exhibit underestimation of concentration and mean diameter due to binning. Thies and Parsivel report a positive bias for rainfall and reflectivity (reaching 5% for heavy rainfall intensity events). Regarding to DSD parameters, distributions of estimators for the shape and scale parameters were analyzed by moment, truncated moment and maximum likelihood methods. They reported noticeable differences between instruments for all methodologies of estimation applied. The measurements of 2DVD allow sampling error estimation of instruments with smaller capture areas than 2DVD. The results show that the instrument differences due to sampling were a~relevant uncertainty but that concentration, reflectivity and mass-weighted diameter were sensitive to binning

Thin film synthesis of hybrid ultramicroporous materials (HUMs)- a comparative approach

© 2020 The thin-film synthesis of the hybrid ultramicroporous material (HUM) TIFSIX-3-Ni on glass substrates are reported for the first time. Several methods of film formation are employed including dip-coating, seeding and secondary growth, vapour-assisted conversion, rapid thermal deposition and in-situ coating. Using the in-situ approach with dimethylformamide as solvent, we were able to grow homogeneous TIFSIX-3-Ni films at relatively low temperatures (85 °C) and short times (5 h) without substrate modification. During this study, we also significantly reduced the TIFSIX powder synthesis time to 15 h

Altered NR2A/NR2B ratio in hippocampus of spatial learning-impaired aged rats

The activation of the N-methyl-D-aspartate receptor (NMDAR) is critical for the induction of synaptic plasticity in the hippocampus. Aging can alter glutamatergic synaptic transmission in the hippocampus, and cognitive impairments in aged animals are accompanied by reduced NMDARmediated plasticity at Schaffer collateral—CA1 synapses. However, the specific contribution of NMDAR subunits to NMDAR-mediated synaptic responses in aged tissue has not yet been fully understood. The main purpose of present study was to examine whether there is an impact of aging on NMDAR subunit expression and whether synaptic plasticity may depend on NMDAR subunit composition in the aged hippocampus

Altered NR2A/NR2B ratio in hippocampus of spatial learning-impaired aged rats

The activation of the N-methyl-D-aspartate receptor (NMDAR) is critical for the induction of synaptic plasticity in the hippocampus. Aging can alter glutamatergic synaptic transmission in the hippocampus, and cognitive impairments in aged animals are accompanied by reduced NMDARmediated plasticity at Schaffer collateral—CA1 synapses. However, the specific contribution of NMDAR subunits to NMDAR-mediated synaptic responses in aged tissue has not yet been fully understood. The main purpose of present study was to examine whether there is an impact of aging on NMDAR subunit expression and whether synaptic plasticity may depend on NMDAR subunit composition in the aged hippocampus

Evaluation of GPM IMERG Performance Using Gauge Data over Indonesian Maritime Continent at Different Time Scales

Accurate precipitation observations are crucial for water resources management and as inputs for a gamut of hydrometeorological applications. Precipitation data from Integrated Multi-Satellite Retrievals for Global Precipitation Measurement (GPM) (IMERG) have recently been widely used to complement traditional rain gauge systems. However, the satellite precipitation data needs to be validated before being widely used in the applications and this is still missing over the Indonesian maritime continent (IMC). We conducted a validation of the IMERG product version 6 for this region. The evaluation was carried out using gauge data in the period from 2016 to 2020 for three types of IMERG: Early (E), Late (L), and Final (F) from annual, monthly, daily and hourly data. In general, the annual and monthly data from IMERG showed a good correlation with the rain gauge, with the mean correlation coefficient (CC) approximately 0.54–0.78 and 0.62–0.79, respec-tively. About 80% of stations in the IMC area showed a very good correlation between gauge data and IMERG-F estimates (CC = 0.7–0.9). For the daily assessment, the CC value was in the range of 0.39 to 0.44 and about 40% of stations had a correlation of 0.5–0.7. IMERG had a fairly good ability to detect daily rain in which the average probability of detection (POD) for all stations was above 0.8. However, the false alarm ratio (FAR) value is quite high (<0.5). For hourly data, IMERG’s performance was still poor with CC around 0.03–0.28. For all assessments, IMERG generally overesti-mated rainfall in comparison with rain gauge. The accuracy of the three types of IMERG in IMC was also influenced by season and topography. The highest and lowest CC values were observed for June–July–August and December–January–February, respectively. However, categorical statistics (POD, FAR and critical success index) did not show any clear seasonal variation. The CC value decreased with higher altitude, but with slight difference for each IMERG type. For all assessments conducted, IMERG-F generally showed the best rainfall observations in IMC, but with slightly difference from IMERG-E and IMERG-L. Thus, IMERG-E and IMERG-L data that had a faster latency than IMERG-F show potential to be used in rainfall observations in IMC

On the optimal measuring area for pointwise rainfall estimation: a dedicated experiment with 14 laser disdrometers

Laser disdrometers measure the particle size distribution (PSD) of hydrometeors through a small cross-sectional (tens of square centimeters) surface. Such a limited area induces a sampling effect in the estimates of the PSD, which translates to error in the reflectivity–rain-rate (Z–R) relationship used for ground radar estimates of rainfall, estimates of kinetic energy of precipitation, and any other hydrometeorological application relying on particle size information. Here, the results of a dedicated experiment to estimate the extent of the effect of limited area sampling of rainfall are presented. Using 14 Parsivel, version 1 (Parsivel-1), disdrometers placed within 6 m2, it was found that the combined area of at least seven disdrometers is required for the estimates to start converging to a stable value. The results can be used to quantify the degree of over-/underestimation of precipitation parameters for a single instrument due to the limited collecting area effect. It has been found that a single disdrometer may underestimate instantaneous rain rate by 70%.Funding from projects CGL2013- 48367-P, CGL2016-80609-R (Ministerio de Economía y Competitividad), UNCM08-1E-086 (Ministerio de Ciencia e Innovacion), and CYTEMA (UCLM) is gratefully acknowledged

WRF Simulations of the 20-22 January 2007 Snow Events over Eastern Canada: Comparison with In-Situ and Satellite Observations

One of the grand challenges of the Global Precipitation Measurement (GPM) mission is to improve cold season precipitation measurements in middle and high latitudes through the use of high-frequency passive microwave radiometry. For this, the Weather Research and Forecasting (WRF) model with the Goddard microphysics scheme is coupled with a satellite data simulation unit (WRF-SDSU) that has been developed to facilitate over-land snowfall retrieval algorithms by providing a virtual cloud library and microwave brightness temperature (Tb) measurements consistent with the GPM Microwave Imager (GMI). This study tested the Goddard cloud microphysics scheme in WRF for two snowstorm events, a lake effect and a synoptic event, that occurred between 20 and 22 January 2007 over the Canadian CloudSAT/CALIPSO Validation Project (C3VP) site in Ontario, Canada. The 24h-accumulated snowfall predicted by the WRF model with the Goddard microphysics was comparable to the observed accumulated snowfall by the ground-based radar for both events. The model correctly predicted the onset and ending of both snow events at the CARE site. WRF simulations capture the basic cloud properties as seen by the ground-based radar and satellite (i.e., CloudSAT, AMSU-B) observations as well as the observed cloud streak organization in the lake event. This latter result reveals that WRF was able to capture the cloud macro-structure reasonably well

Gas Transport Properties of the Metal-Organic Framework (MOF)-Assisted Polymer of Intrinsic Microporosity (PIM-1) Thin-Film Composite Membranes

The current study summarizes the findings of single-gas transport performances of mixed matrix thin-film composite membranes consisting of metal-organic frameworks (MOFs) incorporated into a polymer of intrinsic microporosity (PIM-1). Mg-MOF-74, MIL-53, TIFSIX-3, and Zn2(bim)4 were investigated as stand-alone materials and as incorporated into the PIM-1 polymer matrix serving as a selective layer of thin-film composite membranes by various methods: Fourier-transform infrared spectroscopy, solid-state NMR, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The effect of MOF loading and nature on the mixed-matrix membrane morphology and operation were analyzed by varying the MOF content in the polymer matrix from 2 to 10 wt % with respect to the dry polymer weight. The results show that the incorporation of MOFs into the PIM-1 polymer matrix boosts the permeance and selectivity of H2 and O2 over N2, and the prepared PIM-1/TIFSIX_4 mixed matrix membrane shows better separation performance for CO2/CH4 than pure PIM-1. Such membranes can be good candidates for ammonia purge gas, oxygen enrichment, and acid gas treatment applications