Polarized heat current generated by quantum pumping in two-dimensional topological insulators

We consider transport properties of a two dimensional topological insulator in a double quantum point contact geometry in presence of a time-dependent external field. In the proposed setup an external gate is placed above a single constriction and it couples only with electrons belonging to the top edge. This asymmetric configuration and the presence of an ac signal allow for a quantum pumping mechanism, which, in turn, can generate finite heat and charge currents in an unbiased device configuration. A microscopic model for the coupling with the external time-dependent gate potential is developed and the induced finite heat and charge currents are investigated. We demonstrate that in the non-interacting case, heat flow is associated with a single spin component, due to the helical nature of the edge states, and therefore a finite and polarized heat current is obtained in this configuration. The presence of e-e interchannel interactions strongly affects the current signal, lowering the degree of polarization of the system. Finally, we also show that separate heat and charge flows can be achieved, varying the amplitude of the external gate.Comment: 13 pages, 5 figure

Chaining of welding and finish turning simulations for austenitic stainless steel components

The chaining of manufacturing processes is a major issue for industrials who want to understand and control the quality of their products in order to ensure their in-service integrity (surface integrity, residual stresses, microstructure, metallurgical changes, distortions,…). Historically, welding and machining are among the most studied processes and dedicated approaches of simulation have been developed to provide reliable and relevant results in an industrial context with safety requirements. As the simulation of these two processes seems to be at an operationnal level, the virtual chaining of both must now be applied with a lifetime prediction prospect. This paper will first present a robust method to simulate multipass welding processes that has been validated through an international round robin. Then the dedicated “hybrid method”, specifically set up to simulate finish turning, will be subsequently applied to the welding simulation so as to reproduce the final state of the pipe manufacturing and its interaction with previous operations. Final residual stress fields will be presented and compared to intermediary results obtained after welding. The influence of each step on the final results will be highlighted regarding surface integrity and finally ongoing validation works and numerical modeling enhancements will be discussed

Oxygen vacancies in tungsten oxide and their influence on tungsten oxide silicon heterojunction solar cells

Tungsten oxide WOx can be incorporated into amorphous crystalline silicon heterojunction solar cells as hole contact and for interface modification between p type amorphous silicon and indium tin oxide. This paper aims at understanding the influence of tungsten oxides properties on silicon heterojunction solar cells. Using in system photoelectron spectroscopy on thermally evaporated WOx layers, it was verified that WOx with a stoichiometry close to WO3 features a work function close to 6 eV and is therefore suitable as hole contact on silicon. Additionally the oxygen vacancy concentration in WOx was measured using photoelectron spectroscopy. High oxygen vacancy concentrations in WOx lead to a low band bending in the WOx silicon junction. Furthermore solar cells were fabricated using the same WOx, and the band bending in these cells is correlated with their fill factors FF and open circuit voltages VOC VOC . Combining these results, the following picture arises positively charged oxygen vacancies raise the Fermi level in WOx and reduce the band bending at the WOx silicon junction. This, in turn, leads to reduced VOCVOC and FF. Thus, when incorporating WOx into silicon solar cells it is important to minimize the oxygen vacancy density in WOx. Therefore deposition methods, enabling adjustment of the WOx stoichiometry are preferabl

Two-scale composite finite element method for Dirichlet problems on complicated domains

In this paper, we define a new class of finite elements for the discretization of problems with Dirichlet boundary conditions. In contrast to standard finite elements, the minimal dimension of the approximation space is independent of the domain geometry and this is especially advantageous for problems on domains with complicated micro-structures. For the proposed finite element method we prove the optimal-order approximation (up to logarithmic terms) and convergence estimates valid also in the cases when the exact solution has a reduced regularity due to re-entering corners of the domain boundary. Numerical experiments confirm the theoretical results and show the potential of our proposed metho

Valence band alignment and hole transport in amorphous crystalline silicon heterojunction solar cells

To investigate the hole transport across amorphous crystalline silicon heterojunctions, solar cells with varying band offsets were fabricated using amorphous silicon suboxide films. The suboxides enable good passivation if covered by a doped amorphous silicon layer. Increasing valence band offsets yield rising hole transport barriers and reduced device effciencies. Carrier transport by thermal emission is reduced and tunnel hopping through valence band tail states increases for larger barriers. Nevertheless, stacks of films with different band gaps, forming a band offset staircase at the heterojunction could allow the application of these layers in silicon heterojunction solar cell

From Soup to Nuts: Expanding Liaison and Technical Services for OER Development

This case study highlights an ongoing library collaboration with faculty recipients of a statewide Wikipedia Image Open educational resources (OER) are free and openly licensed educational materials that can be used for teaching, learning, research, and other purposes. OER textbook grant at a rural public research university in the southeast. It emphasizes the evolving needs of teaching faculty open to OER grant writing and development, and the necessity of librarians to be creative in delivering this support. The authors describe how they expanded liaison and technical service roles to educate faculty about the meaning and benefits of OERs, guided selection of appropriately licensed and pedagogically aligned materials, supported development of the grant proposal, and supported development and maintenance of the OER product itself. Central to this study is how liaison and technical services librarians collaborated with faculty to open up the LibGuides CMS platform to host OER materials. This paper provides a comprehensive case study encompassing service development in support of the grant funding process, development of the content management infrastructure for hosting and developing the OER product, next steps, and recommendations of best practices. Throughout, the authors argue for the importance of intra-library collaboration and expanding liaison and technical services roles for effective OER support

NanoUPLC-MSE proteomic data assessment of soybean seeds using the Uniprot database.

Background: Recombinant DNA technology has been extensively employed to generate a variety of products from genetically modified organisms (GMOs) over the last decade, and the development of technologies capable of analyzing these products is crucial to understanding gene expression patterns. Liquid chromatography coupled with mass spectrometry is a powerful tool for analyzing protein contents and possible expression modifications in GMOs. Specifically, the NanoUPLC-MSE technique provides rapid protein analyses of complex mixtures with supported steps for high sample throughput, identification and quantization using low sample quantities with outstanding repeatability. Here, we present an assessment of the peptide and protein identification and quantification of soybean seed EMBRAPA BR16 cultivar contents using NanoUPLC-MSE and provide a comparison to the theoretical tryptic digestion of soybean sequences from Uniprot database. Results: The NanoUPLC-MSE peptide analysis resulted in 3,400 identified peptides, 58% of which were identified to have no miscleavages. The experiment revealed that 13% of the peptides underwent in-source fragmentation, and 82% of the peptides were identified with a mass measurement accuracy of less than 5 ppm. More than 75% of the identified proteins have at least 10 matched peptides, 88% of the identified proteins have greater than 30% of coverage, and 87% of the identified proteins occur in all four replicates. 78% of the identified proteins correspond to all glycinin and betaconglycinin chains. The theoretical Uniprot peptide database has 723,749 entries, and 548,336 peptides have molecular weights of greater than 500 Da. Seed proteins represent 0.86% of the protein database entries. At the peptide level, trypsin-digested seed proteins represent only 0.3% of the theoretical Uniprot peptide database. A total of 22% of all database peptides have a pI value of less than 5, and 25% of them have a pI value between 5 and 8. Based on the detection range of typical NanoUPLC-MSE experiments, i.e., 500 to 5000 Da, 64 proteins will not be identified. Conclusions: NanoUPLC-MSE experiments provide good protein coverage within a peptide error of 5 ppm and a wide MW detection range from 500 to 5000 Da. A second digestion enzyme should be used depending on the tissue or proteins to be analyzed. In the case of seed tissue, trypsin protein digestion results offer good databank coverage. The Uniprot database has many duplicate entries that may result in false protein homolog associations when using NanoUPLC-MSE analysis. The proteomic profile of the EMBRAPA BR-16 seed lacks certain described proteins relative to the profiles of transgenic soybeans reported in other works

Sum Rules and Ward Identities in the Kondo Lattice

We derive a generalized Luttinger-Ward expression for the Free energy of a many body system involving a constrained Hilbert space. In the large $N$ limit, we are able to explicity write the entropy as a functional of the Green's functions. Using this method we obtain a Luttinger sum rule for the Kondo lattice. One of the fascinating aspects of the sum rule, is that it contains two components, one describing the heavy electron Fermi surface, the other, a sea of oppositely charged, spinless fermions. In the heavy electron state, this sea of spinless fermions is completely filled and the electron Fermi surface expands by one electron per unit cell to compensate the positively charged background, forming a ``large'' Fermi surface. Arbitrarily weak magnetism causes the spinless Fermi sea to annihilate with part of the Fermi sea of the conduction electrons, leading to a small Fermi surface. Our results thus enable us to show that the Fermi surface volume contracts from a large, to a small volume at a quantum critical point. However, the sum rules also permit the possible formation of a new phase, sandwiched between the antiferromagnet and the heavy electron phase, where the charged spinless fermions develop a true Fermi surface.Comment: 24 pages, 4 figures. Version two contains a proof of the "Entropy formula" which connects the entropy directly to the Green's functions. Version three contains corrections to typos and a more extensive discussion of the physics at finite

Everyone Loves Gummi Bears! Removing the Intimidation factor from Research Data Management with Yummy Fun.

How do you get students excited about research data management and attract over 70 participants to a voluntary workshop? How do you get Librarians excited about teaching a research data management workshop to undergraduates? With the promise of Gummi Bears and hands-on fun! During this workshop session, presenters will break down their experience overhauling a faculty workshop into an active learning session to expose students of all experience levels to basic research data management concepts and techniques. Presenters will walk participants through their design process from inception to delivery, highlighting how Gummi Bears lessened students’ intimidation with this complex topic (20 minutes). Participants will then engage in the workshop activities and work on the same specific deliverables created by students, highlighting the connection between the activities and the specific learning objectives and supported ACRL frames (35 minutes). Half of the group will work the simulation on provided laptops, and half of the group will work the simulation in physical form. A detailed breakdown of workshop assessment will provide insight into the adaptability of the workshop, and how to adjust the workshop to different experience levels, as well as addressing possible lack of technology availability (10 minutes). Finally, participants will engage in a discussion of marketing tactics possible to facilitate student and faculty buy-in, as well as ask any additional questions (10 minutes). Participants will be provided access to workshop materials and a best practices handout for running the workshop at their own institutions. Presentation Description How do you get students excited about research data management? How do you get Librarians excited about teaching a research data management workshop to undergraduates? With the promise of Gummi Bears and hands-on fun! Presenters will walk participants through their design process from inception to delivery, highlighting how Gummi Bears lessened students’ intimidation with this complex topic. Participants will be provided access to workshop materials and a best practices handout for running the workshop at their own institutions. Session Goals Provide guidance and instruction in offering research data management workshop to students. Provide hands-on opportunity for participants to experience the workshop as a student (both digitally and physically). Provide assessment options that clearly indicate support of ACRL Framework. Provide materials so participants can run a similar workshop at their own institutions. Session Objectives Participants will understand how gummi bears are a neutral data point that can be adapted to a variety of research interests and experience levels. Participants will experience creating the same deliverables that students will be asked to complete. Participants will gain knowledge on assessment options that will support the learning objectives and specific ACRL frames. Participants will brainstorm marketing techniques aimed at developing faculty buy-in for workshop. Participants will understand how a similar workshop can be run at their own institution

Archives and STEM: The Perfect Formula for Immersive Cross-Disciplinary Instruction

Presented at Georgia International Conference on Information Literacy Reaching out to STEM Students beyond the one-shot requested instruction sessions is challenging. Creating faculty buy-in for non-traditional STEM instruction is doubly challenging. This poster will highlight a recent activity designed to draw STEM participation in utilizing a unique set of resources from the institution’s Archival Collections. Normally viewed as primarily relevant to history and humanities students, this collection provides the backbone for a fully immersive Escape Room Activity and exposure to primary sources normally not considered part of the normal STEM course work. The hands-on activity provides an opportunity for critical thinking, reflection, and teamwork. The poster will highlight the archival collection, the challenges of designing instruction for cross-disciplinary work, building faculty buy-in and support, and assessment options addressing the ACRL Framework; specifically Scholarship as Conversation, and Information has Value. A handout with URL links will provide participants the opportunity to evaluate their collections and best practices tips for designing a similar activity