Dilepton Signal of a Type-II Seesaw at CERN LHC: Reveals a TeV Scale B-L Symmetry

We explore the discovery potential of doubly charged Higgs bosons (\xi^{\pm\pm}) at the CERN Large Hadron Collider (LHC). For moderate values of the coupling constants in the original Type-II seesaw model, these doubly-charged Higgs bosons are not accessible by any present or near future collider experiments. In a gauged B-L symmetric model we introduce two triplet scalars to execute a variant of type-II seesaw at the TeV scale. This leads to a clear like-sign dilepton signal in the decay mode of \xi^{\pm\pm} for a small vacuum expectation value (\lsim 10^5 \eV) of the triplet scalar \xi= (\xi^{++}, \xi^+, \xi^0) of mass \lsim 1 \TeV. To be specific, for a mass range of 200-1000 GeV of \xi^{\pm\pm}, the like-sign dilepton signal can be detected at CERN LHC at a center of mass energy 14 TeV with an integrated luminosity > 30 {\rm fb}^{-1}. The same analysis is also pursued with center of mass energies 7 TeV and 10 TeV as well. We also comment on the decay mode of singly charged scalars and neutral B-L gauge boson in this model.Comment: Minor change in Introduction, Z' contribution to the production of doubly charged scalars are explicitly shown, new figures added, new references added. To appear in Physical Review

Four genes encoding MYB28, a major transcriptional regulator of the aliphatic glucosinolate pathway, are differentially expressed in the allopolypoloid Brassica juncea

Glucosinolates are Capparales-specific secondary metabolites that have immense potential in human health and agriculture. Unlike Arabidopsis thaliana, our knowledge about glucosinolate regulators in the Brassica crops is sparse. In the current study, four MYB28 homologues were identified (BjuMYB28-1,-2,-3,-4) from the polyploid Brassica juncea, and the effects of allopolyploidization on the divergence of gene sequence, structure, function, and expression were assessed. The deduced protein sequences of the four BjuMYB28 genes showed 76.1–83.1% identity with the Arabidopsis MYB28. Phylogenetic analysis revealed that the four BjuMYB28 proteins have evolved via the hybridization and duplication processes forming the B. juncea genome (AABB) from B. rapa (AA) and B. nigra (BB), while retaining high levels of sequence conservation. Mutant complementation and over-expression studies in A. thaliana showed that all four BjuMYB28 genes encode functional MYB28 proteins and resulted in similar aliphatic glucosinolate composition and content. Detailed expression analysis using qRT-PCR assays and promoter-GUS lines revealed that the BjuMYB28 genes have both tissue- and cell-specific expression partitioning in B. juncea. The two B-genome origin BjuMYB28 genes had more abundant transcripts during the early stages of plant development than the A-genome origin genes. However, with the onset of the reproductive phase, expression levels of all four BjuMYB28 increased significantly, which may be necessary for producing and maintaining high amounts of aliphatic glucosinolates during the later stages of plant development. Taken together, our results suggest that the four MYB28 genes are differentially expressed and regulated in B. juncea to play discrete though overlapping roles in controlling aliphatic glucosinolate biosynthesis

Influence of low energy argon plasma treatment on the moisture barrier performance of hot wire-CVD grown SiNx multilayers

The reliability and stability are key issues for the commercial utilization of organic photovoltaic devices based on flexible polymer substrates. To increase the shelf-lifetime of these devices, transparent moisture barriers of silicon nitride (SiNx) films are deposited at low temperature by hot wire CVD (HW-CVD) process. Instead of the conventional route based on organic/inorganic hybrid structures, this work defines a new route consisting in depositing multilayer stacks of SiNx thin films, each single layer being treated by argon plasma. The plasma treatment allows creating smoother surface and surface atom rearrangement. We define a critical thickness of the single layer film and focus our attention on the effect of increasing the number of SiNx single-layers on the barrier properties. A water vapor transmission rate (WVTR) of 2 x 10-4 g/(m2 day) is reported for SiNx multilayer stack and a physical interpretation of the plasma treatment effect is given.Direction des Relations Extérieures, Ecole PolytechniquePICS (French–Portuguese No. 5336) projec

Effect of argon ion energy on the performance of silicon nitridemultilayer permeation barriers grown by hot-wire CVD on polymers

One of the authors (S.M.) acknowledges Direction des Relations Extérieures of Ecole Polytechnique for financial support.Permeation barriers for organic electronic devices on polymer flexible substrates were realized by combining stacked silicon nitride (SiNx) single layers (50 nm thick) deposited by hot-wire chemical vapor deposition process at low-temperature (~100°C) with a specific argon plasma treatment between two successive layers. Several plasma parameters (RF power density, pressure, treatment duration) as well as the number of single layers have been explored in order to improve the quality of permeation barriers deposited on polyethylene terephthalate. In this work, maximumion energy was highlighted as the crucial parameter making it possible to minimize water vapor transmission rate (WVTR), as determined by the electrical calcium test method, all the other parameters being kept fixed. Thus fixing the plasma treatment duration at 8 min for a stack of two SiNx single layers, a minimum WVTR of 5 × 10−4 g/(m2 day), measured at room temperature, was found for a maximum ion energy of ~30 eV. This minimum WVTR value was reduced to 7 × 10−5 g/(m2 day) for a stack of five SiNx single layers. The reduction in the permeability is interpreted as due to the rearrangement of atoms at the interfaces when average transferred ion energy to target atoms exceeds threshold displacement energy.The authors are grateful to Dr. R. Cortes (PMC, Ecole Polytechnique) for XRR analysis, to Dr. P. Chapon (HORIBA Jobin Yvon) for GD-OES analysis and Dr. J. Leroy (CEA Saclay) for XPS analysis. This work was partly supported by the PICS (FrenchPortuguese) project No. 5336. One of the authors (S.M.) acknowledges Direction des Relations Extérieures of Ecole Polytechnique for financial support

Flexible organic–inorganic hybrid layer encapsulation for organic opto-electronic devices

In this work we produce and study the flexible organic–inorganic hybrid moisture barrier layers for the protection of air sensitive organic opto-electronic devices. The inorganic amorphous silicon nitride layer (SiNx:H) and the organic PMMA [poly (methyl methacrylate)] layer are deposited alternatingly by using hot wire chemical vapor deposition (HW-CVD) and spin-coating techniques, respectively. The effect of organic–inorganic hybrid interfaces is analyzed for increasing number of interfaces. We produce highly transparent (∼80% in the visible region) hybrid structures. The morphological properties are analysed providing a good basis for understanding the variation of the water vapor transmission rate (WVTR) values. A minimum WVTR of 4.5 × 10−5g/m2day is reported at the ambient atmospheric conditions for 7 organic/inorganic interfaces. The hybrid barriers show superb mechanical flexibility which confirms their high potential for flexible applications.The authors would like to thank Dr. J.C. Vanel for help in electrical characterizations used in this study. The first author (S.M) acknowledges the financial support from Direction des Relations Extérieures, Ecole Polytechnique during his thesis

The effect of argon plasma treatment on the permeation barrier properties of silicon nitride layers

In this work we produce and study silicon nitride (SiNx) thin films deposited by Hot Wire Chemical Vapor Depo- sition (HW-CVD) to be used as encapsulation barriers for flexible organic photovoltaic cells fabricated on poly- ethylene terephthalate (PET) substrates in order to increase their shelf lifetime. We report on the results of SiNx double-layers and on the equivalent double-layer stack where an Ar-plasma surface treatment was performed on the first SiNx layer. The Ar-plasma treatment may under certain conditions influences the structure of the interface between the two subsequent layers and thus the barrier properties of the whole system. We focus our attention on the effect of plasma treatment time on the final barrier properties. We assess the encapsulation barrier properties of these layers, using the calcium degradation test where changes in the electrical conductance of encapsulated Ca sensors are monitored with time. The water vapor transmission rate (WVTR) is found to be ~3 × 10−3 g/m2·day for stacked SiNx double-layer with 8 min Ar plasma surface treatment.FCT - CNRS PICS (French–Portuguese no: 5336) projectDirection des Relations Extérieures, Ecole Polytechniqu

Covid-19 and higher education: a qualitative study on academic experiences of African international students in the Midwest

COVID-19 pandemic has harshly impacted university students since the outbreak was declared in March 2020. A population impacted the most was international college students due to limited social networks, restrictive employment opportunities, and travel limitations. Despite the increased vulnerability, there has been limited research on the experiences of African-born international students during the pandemic. Using an exploratory qualitative design, this study interviewed 15 African-born international students to understand their experiences during the pandemic. Thematic analysis revealed that the COVID-19 pandemic influenced participants’ academic life directly via an abrupt shift to online learning and indirectly through disruptions in an academic work routine, opportunities for networking, and career advancement, resulting in lower academic performance and productivity. These experiences were worsened by other social and regulatory barriers associated with their non-immigrant status. The study findings suggest an increased need for institutional and community support for international students as vulnerable populations during a crisis to promote sustained academic success

Synthesis of (Hetero)Macrocycles under Environmentally Friendly Conditions

This work was supported in part by the Russian Science Foundation (References Nos. 18-13-00365 and 18-73-00301)

Low-voltage 2D materials-based printed field-effect transistors for integrated digital and analog electronics on paper

Paper is the ideal substrate for the development of flexible and environmentally sustainable ubiquitous electronic systems, which, combined with two-dimensional materials, could be exploited in many Internet-of-Things applications, ranging from wearable electronics to smart packaging. Here we report high-performance MoS2 field-effect transistors on paper fabricated with a “channel array” approach, combining the advantages of two large-area techniques: chemical vapor deposition and inkjet-printing. The first allows the pre-deposition of a pattern of MoS2; the second, the printing of dielectric layers, contacts, and connections to complete transistors and circuits fabrication. Average ION/IOFF of 8 × 103 (up to 5 × 104) and mobility of 5.5 cm2 V−1 s−1 (up to 26 cm2 V−1 s−1) are obtained. Fully functional integrated circuits of digital and analog building blocks, such as logic gates and current mirrors, are demonstrated, highlighting the potential of this approach for ubiquitous electronics on paper