A 3-channel InP-HEMT with low output conductance Maher, H.; Decobert, J.; Falcou, A. ...
Conference Proceedings. Eleventh International Conference on Indium Phosphide and Related Materials (IPRM'99) (Cat. No.99CH36362),
1999
Conference Proceeding
A triple channel (InGaAs-AlGaInAs-InP) HEMT structure has been investigated for high breakdown voltage applications. This structure takes advantage simultaneously of both the high electron mobility ...at low field in the InGaAs channel and the low impact ionization coefficient in the InP channel. The transistor actually shows good dynamic performances and high breakdown voltage: for a 0.8 /spl mu/m gate length we obtained: gm=240 mS/mm, Idss=225 mA/mm, Vbrd=6.5 V, f/sub t/=35 GHz, f/sub max/>90 GHz. A specific feature of this HEMT structure is its low output conductance (gm/gd=40 at both low and high frequency) attributed in particular to the fact that the barrier layer is undoped, with the /spl delta/-doping sitting in the middle of the channel. For the 0.8 /spl mu/m gate length devices investigated, the output conductance is much lower than for single or dual channel HEMTs fabricated with similar geometry. This feature is maintained for shorter gate length (at Lg=0.2 /spl mu/m). In this paper an analysis of this output conductance is presented, illustrating the importance of impact ionization and residual traps.
The passivation of InP-based optoelectronic devices is an issue that is receiving much focus as it is of utmost importance that devices maintain their performance throughout their lifespan. In this ...paper, we report on the passivation scheme that we developed recently, based on a pre-deposition in-situ surface cleaning by xenon difluoride (XeF
2) followed by a direct UV-enhanced deposition of silicon nitride (SiN
x). HFET transistors as well as photodiodes have been fabricated and passivated successfully using this technique.
Nursing documentation in the Stroke Unit Carletti, E; Gualtieri, A; Aloisi, A ...
Professioni infermieristiche (Consociazione Nazionale Associazioni Infermiere),
2000 Jul-Sep, Letnik:
53, Številka:
3
Journal Article
Recenzirano
The organization of Stroke Unit improved prognosis of stroke patient. The randomized studies emphasized the importance of nursing in such a structure. In order to improve nursing process in our ...Stroke Unit, we designed a nurse record which includes a neurological scale, to define dependence classes and guidelines based on Virgina Henderson's theoretical model. In this paper, we present this nurse record and we describe the various steps of its design.
The development of methods to automatically determine the chemical nature of microplastics by FTIR-ATR spectra is an important challenge. A machine learning method, named k-nearest neighbors ...classification, has been applied on spectra of microplastics collected during Tara Expedition in the Mediterranean Sea (2014). To realize these tests, a learning database composed of 969 microplastic spectra has been created. Results show that the machine learning process is very efficient to identify spectra of classical polymers such as poly(ethylene), but also that the learning database must be enhanced with less common microplastic spectra. Finally, this method has been applied on more than 4000 spectra of unidentified microplastics. The verification protocol showed less than 10% difference in the results between the proposed automated method and a human expertise, 75% of which can be very easily corrected.
•A machine learning algorithm was developed to determine the chemical nature of microplastics.•This method allows a fast and reliable automated identification even whenthousands of FTIR spectra have to be studied.•This method is the first part of a software dedicated to the study of microplastics: POSEIDON.
The stomach content of 60 krill specimens from the Southern Ocean were analyzed for the presence of microplastic (MP), by testing different sample volumes, extraction approaches, and applying ...hyperspectral imaging Fourier-transform infrared spectroscopy (μFTIR). Strict quality control was applied on the generated results. A high load of residual materials in pooled samples hampered the analysis and avoided a reliable determination of putative MP particles. Individual krill stomachs displayed reliable results, however, only after re-treating the samples with hydrogen peroxide. Before this treatment, lipid rich residues of krill resulted in false assignments of polymer categories and hence, false high MP particle numbers. Finally, MP was identified in 4 stomachs out of 60, with only one MP particle per stomach. Our study highlights the importance of strict quality control to verify results before coming to a final decision on MP contamination in the environment to aid the establishment of suitable internationally standardized protocols for sampling and analysis of MP in organisms including their habitats in Southern Ocean and worldwide.
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•Analysis of pooled and individual krill samples for microplastic in three areas of the Southern Ocean•Microplastics analysis using hyperspectral imaging Fourier-transform infrared spectroscopy (μFTIR)•KOH digestion of krill formed a transparent residue on analytical filters which can be misidentified as microplastics.•On average only 0.4 MP per individual krill specimen detected.•Overestimation of microplastics pollution without strict quality control.
Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment. In Flanders, the bioaccumulation in aquatic organisms is currently being monitored using European perch and European eel. ...Since both are native species, there is an ethical need to search for other suitable biomonitors. This study aims to investigate whether the invasive Chinese mitten crab could be used in biomonitoring programs by assessing PFAS accumulation in hepatopancreas, muscle tissue, and carapace. Furthermore, we correlated accumulated concentrations to those in the local abiotic environment. Concentrations in the crabs (highest average ∑PFAS concentration of 688 ± 505 ng/g ww) were often higher than those in crab species from other regions across the globe, confirming that Flanders is highly polluted with PFAS. Concentrations in the crabs did not reflect those in the abiotic environment. This implies that biomonitoring is necessary to investigate the impact of PFAS pollution on organisms in aquatic ecosystems, as important data is missing when only the abiotic environment is monitored. The accumulation profiles differed between the invasive crab and the native European perch and European eel, potentially due to a different ecology and trophic position. Since all three species provide complementary information on the PFAS pollution, a multi-species approach in biomonitoring is recommended. Overall, our results show that the crabs can be used as biomonitor, but more information is necessary to confirm their suitability as bioindicator.
The guanosine analog AT-527 represents a promising candidate against Severe Acute Respiratory Syndrome coronavirus type 2 (SARS-CoV-2). AT-527 recently entered phase III clinical trials for the ...treatment of COVID-19. Once in cells, AT-527 is converted into its triphosphate form, AT-9010, that presumably targets the viral RNA-dependent RNA polymerase (RdRp, nsp12), for incorporation into viral RNA. Here we report a 2.98 Å cryo-EM structure of the SARS-CoV-2 nsp12-nsp7-nsp8
-RNA complex, showing AT-9010 bound at three sites of nsp12. In the RdRp active-site, one AT-9010 is incorporated at the 3' end of the RNA product strand. Its modified ribose group (2'-fluoro, 2'-methyl) prevents correct alignment of the incoming NTP, in this case a second AT-9010, causing immediate termination of RNA synthesis. The third AT-9010 is bound to the N-terminal domain of nsp12 - known as the NiRAN. In contrast to native NTPs, AT-9010 is in a flipped orientation in the active-site, with its guanine base unexpectedly occupying a previously unnoticed cavity. AT-9010 outcompetes all native nucleotides for NiRAN binding, inhibiting its nucleotidyltransferase activity. The dual mechanism of action of AT-527 at both RdRp and NiRAN active sites represents a promising research avenue against COVID-19.
The study of microplastic pollution involves multidisciplinary analyses on a large number of microplastics. Therefore, providing an overview of plastic pollution is time consuming and, despite high ...throughput analyses, remains a major challenge. The objective of this study is to propose a protocol to determine how many microplastics must be analyzed to give a representative view of the particle size distribution and chemical nature, and calculate the associated margin error. Based on microplastic data from Tara Mediterranean campaign, this approach is explained through different examples. In this particular case, the results show that only 3% of the collected microplastics need to be analyzed to give a precise view on the scale of the North West Mediterranean Basin (error <5%), and 17.7% to give an overview manta per manta (error <10%). This approach could be an important practical contribution to microplastic studies.
The Mediterranean Sea is one of the most studied regions in the world in terms of microplastic (MP) contamination. However, only a few studies have analysed the chemical composition of MPs at the ...Mediterranean Sea surface. In this context, this study aims to describe the chemical composition as a function of particle size, mass and number concentrations of MPs collected in the surface waters of the Mediterranean Sea. The chemical composition showed a certain homogeneity at the Mediterranean Sea scale. The main polymers identified by Fourier Transform Infra-Red (FTIR) spectroscopy were poly(ethylene) (67.3 ± 2.4%), poly(propylene) (20.8 ± 2.1%) and poly(styrene) (3.0 ± 0.9%). Nevertheless, discrepancies, confirmed by the literature, were observed at a mesoscale level. Thus, in the North Tyrrhenian Sea, the proportion of poly(ethylene) was significantly lower than the average value of the Mediterranean Sea (57.9 ± 10.5%). Anthropic sources, rivers, or polymer ageing are assumed to be responsible for the variations observed.
•Microplastic from two basins of the Mediterranean Sea were studied.•Microplastic chemical composition was homogeneous at the Mediterranean scale.•Anomaly areas were evidenced in terms of relative composition in PE and PP.•Carbonyl and fouling indices on PE particles provided new insights.•Circulation patterns were proposed to explain the observed distribution.
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