The effect of photogenerated carriers on the mean time delay for avalanche breakdown in p-n junctions

Avalanche breakdown in p-n junctions is preceded by a delay time between application of an overvoltage and the actual initiation of an avalanche discharge. The mean of this delay time has been studied as a function of photogeneration in p-n junction devices. Results agree well with McIntyre's theory of breakdown probability. The data further indicate that the probability of any given carrier initiating breakdown is independent of carrier concentration over the three orders of magnitude investigated.     

The impact of reading fluency level on interactive information retrieval

Given an information need and the corresponding set of documents retrieved, it is known that user assessments for such documents differ from one user to another. One frequent reason that is put forward is the discordance between text complexity and user reading fluency. We explore this relationship from three different dimensions: quantitative features, subjective-assessed difficulty, and reader/text factors. In order to evaluate quantitative features, we wondered whether it is possible to find differences between documents that are evaluated by the user and those that are ignored according to the complexity of the document. Secondly, a task related to the evaluation of the relevance of short texts is proposed. For this end, users evaluated the relevance of these short texts by answering 20 queries. Documents complexity and relevance assessments were done previously by some human experts. Then, the relationship between participants assessments, experts assessments and document complexity is studied. Finally, a third experimentation was performed under the prism of neuro-Information Retrieval: while the participants were monitored with an electroencephalogram (EEG) headset, we tried to find a correlation among EEG signal, text difficulty and the level of comprehension of texts being read during the EEG recording. In light of the results obtained, we found some weak evidence showing that users responded to queries according to text complexity and user’s reading fluency. For the second and third group of experiments, we administered a sub-test from the Woodcock Reading Mastery Test to ensure that participants had a roughly average reading fluency. Nevertheless, we think that additional variables should be studied in the future in order to achieve a sound explanation of the interaction between text complexity and user profile.

     

Computational modelling of explosions caused by failed Li-ion batteries

The implementation rate of renewable energy sources such as lithium-ion batteries has grown over the last decade. Consequently, the number of explosion occurrences associated with these batteries has also increased. Such events are due to a process called thermal runaway (TR). The flamelet combustion approach has been widely used to model premixed combustion. However, its applicability for modelling accidental explosions from lithium-ion batteries remains limited. Moreover, the effects and contributions from stress, strain, and wrinkling on the flame front in gas mixtures from Li-ion batteries are not fully understood. As far as computational modelling is concerned, the same effects require further investigation. The current research investigates the performance of the flamelet approach for modelling premixed combustion scenarios caused by the gases ejected by a fully charged lithium-ion-phosphate (LFP) battery. A new laminar burning velocity correlation is proposed based on experimental data to calculate overpressure, flame position, and flame velocity in a semi-confined geometry. Promising results are presented resorted by good agreement with experimental data.     

Desorption Electrospray Ionization Mass Spectrometry Assay for Label-Free Characterization of SULT2B1b Enzyme Kinetics

The sulfotransferase (SULT) 2B1b, which catalyzes the sulfonation of 3β-hydroxysteroids, has been identified as a potential target for prostate cancer treatment. However, a major limitation for SULT2B1b-targeted drug discovery is the lack of robust assays compatible with high-throughput screening and inconsistency in reported kinetic data. For this reason, we developed a novel label-free assay based on high-throughput (>1 Hz) desorption electrospray ionization mass spectrometry (DESI-MS) for the direct quantitation of the sulfoconjugated product (CV<10 %; <1 ng analyte). The performance of this DESI-based assay was compared against a new fluorometric coupled-enzyme method that we also developed. Both methodologies provided consistent kinetic data for the reaction of SULT2B1b with its major substrates, indicating the affinity trend pregnenolone>DHEA>cholesterol, for both the phospho-mimetic and wild-type SULT2B1b forms. The novel DESI-MS assay developed here is likely generalizable to other drug discovery efforts and is particularly promising for identification of SULT2B1b inhibitors with potential as prostate cancer therapeutics.