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1. Suppression of indium clustering and quantum confined stark effect of InGaN LED on silicon (111)

   https://doi.org/10.1117/12.2506426  

   Liu, Richard; McCormick, Callan; Bayram, Can (March 2019, Gallium Nitride Materials and Devices XIV)

   Optical properties of InGaN/GaN multi-quantum-well (MQWs) grown on sapphire and on Si(111) are reported. The tensile strain in the MQW on Si is shown to be beneficial for indium incorporation and Quantum-confined Stark Effect reduction in the multi-quantum wells. Raman spectroscopy reveals compressive strains of -0.107% in MQW on sapphire and tensile strain of +0.088% in MQW on Si. Temperature-dependent photoluminescence shows in MQW on sapphire a strong (30 meV peak-to-peak) S-shaped wavelength shift with decreasing temperature (6 K to 300K), whereas MQW on Si luminescence wavelength is stable and red-shifts monotonically. Micro-photoluminescence mapping over 200 by 200 μm2 shows the emission wavelength spatial uniformity of MQW on Si is 2.6 times higher than MQW on sapphire, possibly due to a more uniform indium incorporation in the multi-quantum-wells as a result of the tensile strain in MQW on Si. A positive correlation between emission energy and intensity is observed in MQW on sapphire but not in those on Si. Despite the lower crystal quality of MQW on Si revealed by atomic force microscopy, it exhibits a higher internal quantum efficiency (IQE) than MQW on sapphire from 6 K to 250 K, and equalizes at 300 K. Overall, MQW on Si exhibits a high IQE, higher wavelength spatial uniformity and temperature stability, while providing a much more scalable platform than MQW on sapphire for next generation integrated photonics. 

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2. Charge carrier traps in organic semiconductors: a review on the underlying physics and impact on electronic devices

   https://doi.org/10.1039/C9TC05695E  

   Haneef, Hamna F.; Zeidell, Andrew M.; Jurchescu, Oana D. (January 2020, Journal of Materials Chemistry C)

   The weak intermolecular interactions inherent in organic semiconductors make them susceptible to defect formation, resulting in localized states in the band-gap that can trap charge carriers at different timescales. Charge carrier trapping is thus ubiquitous in organic semiconductors and can have a profound impact on their performance when incorporated into optoelectronic devices. This review provides a comprehensive overview on the phenomenon of charge carrier trapping in organic semiconductors, with emphasis on the underlying physical processes and its impact on device operation. We first define the concept of charge carrier trap, then outline and categorize different origins of traps. Next, we discuss their impact on the mechanism of charge transport and the performance of electronic devices. Progress in the filed in terms of characterization and detection of charge carrier traps is reviewed together with insights on future direction of research. Finally, a discussion on the exploitation of traps in memory and sensing applications is provided. 

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3. How does regulatory uncertainty shape the innovation process? Evidence from the case of nanomedicine

   https://doi.org/10.1007/s10961-022-09980-8  

   Kwon, Seokbeom; Youtie, Jan; Porter, Alan; Newman, Nils (January 2022, The Journal of Technology Transfer)

   This study investigates the effect of regulatory uncertainty on the translation of scientific discovery on emerging research topics to technical applications in science-driven industry. Our empirical analysis using the case of the US Federal Drug and Food Administration’s release of the report on the regulatory approach to nanomedicine in 2007 shows that; (1) the regulatory uncertainty decelerated the translation of nanomedicine research to technical applications, (2) this effect was particular for the nanomedicine research on emerging topics in the field. Our further analysis suggests that the effect of the regulatory uncertainty originated from the suppressed business activities in the field where the regulatory uncertainty presents. Our study elaborates on how regulatory authority actions shape the innovation process by shedding light on the impact of regulatory uncertainty on the development of technical applications of an emerging scientific area. 

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4. Antimatter Gravity: Second Quantization and Lagrangian Formalism

   https://doi.org/10.3390/physics2030022  

   Jentschura, Ulrich D. (September 2020, Physics)

   null (Ed.)

   The application of the CPT (charge-conjugation, parity, and time reversal) theorem to an apple falling on Earth leads to the description of an anti-apple falling on anti–Earth (not on Earth). On the microscopic level, the Dirac equation in curved space-time simultaneously describes spin-1/2 particles and their antiparticles coupled to the same curved space-time metric (e.g., the metric describing the gravitational field of the Earth). On the macroscopic level, the electromagnetically and gravitationally coupled Dirac equation therefore describes apples and anti-apples, falling on Earth, simultaneously. A particle-to-antiparticle transformation of the gravitationally coupled Dirac equation therefore yields information on the behavior of “anti-apples on Earth”. However, the problem is exacerbated by the fact that the operation of charge conjugation is much more complicated in curved, as opposed to flat, space-time. Our treatment is based on second-quantized field operators and uses the Lagrangian formalism. As an additional helpful result, prerequisite to our calculations, we establish the general form of the Dirac adjoint in curved space-time. On the basis of a theorem, we refute the existence of tiny, but potentially important, particle-antiparticle symmetry breaking terms in which possible existence has been investigated in the literature. Consequences for antimatter gravity experiments are discussed. 

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5. Polymorphism of Sex Determination Amongst Wild Populations Suggests its Rapid Turnover Within the Nile Tilapia Species

   https://doi.org/10.3389/fgene.2022.820772  

   Triay, Cécile; Courcelle, Maxime; Caminade, Pierre; Bezault, Etienne; Baroiller, Jean-François; Kocher, Thomas D.; D’Cotta, Helena (May 2022, Frontiers in Genetics)

   Sex-determining regions have been identified in the Nile tilapia on linkage groups (LG) 1, 20 and 23, depending on the domesticated strains used. Sex determining studies on wild populations of this species are scarce. Previous work on two wild populations, from Lake Volta (Ghana) and from Lake Koka (Ethiopia), found the sex-determining region on LG23. These populations have a Y-specific tandem duplication containing two copies of the Anti-Müllerian Hormone amh gene (named amhY and amhΔY ). Here, we performed a whole-genome short-reads analysis using male and female pools on a third wild population from Lake Hora (Ethiopia). We found no association of sex with LG23, and no duplication of the amh gene. Furthermore, we found no evidence of sex linkage on LG1 or on any other LGs. Long read whole genome sequencing of a male from each population confirmed the absence of a duplicated region on LG23 in the Lake Hora male. In contrast, long reads established the structure of the Y haplotype in Koka and Kpandu males and the order of the genes in the duplicated region. Phylogenies constructed on the nuclear and mitochondrial genomes, showed a closer relationship between the two Ethiopian populations compared to the Ghanaian population, implying an absence of the LG23Y sex-determination region in Lake Hora males. Our study supports the hypothesis that the amh region is not the sex-determining region in Hora males. The absence of the Y amh duplication in the Lake Hora population reflects a rapid change in sex determination within Nile tilapia populations. The genetic basis of sex determination in the Lake Hora population remains unknown. 

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