Investigation into improving PCC mix consistency and production rate by two-stage mixing

A two-stage mixing process for concrete involves mixing a slurry of the binder and water separate from the aggregates, and then adding the slurry to the aggregates and continuing mixing. This process could improve cement hydration, concrete homogeneity, and the interfacial transition zone (ITZ) between aggregate and paste. This study deals the first stage of the two-stage mixing process, slurry mixing. The objectives are to determine the optimum mixing time and intensity based on the paste binder properties tested and to make recommendations for further investigation of the second stage of the process. Two mixers were used for slurry mixing. A high shear and low shear mixer with varying mixing time and speed. Different binder combinations were tested utilizing cement, fly ash, and slag. Heat of hydration, maturity, and rheology tests were performed on fresh paste samples. Compressive strength, degree of hydration, and scanning electron microscope (SEM) imaging tests were completed on cured specimens. The results show that increasing the mixing energy (mixing speed and time) produces a more workable and uniform slurry. This conclusion is supported best by the degree of hydration and rheology tests of paste. After mixing energy reaches a certain level, rheological properties of a given paste may show little or no change with increasing mixing time. For a given mixing time, a high shear mixer generally provides paste with higher early-age strengths than a normal mixer. Based on the tests, an optimal mixer and mixing time are recommended for further research on the two-stage mixing process

The 2023 terahertz science and technology roadmap

Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz–∼30 THz). Within its frequency boundaries exist a broad variety of scientific disciplines that have presented, and continue to present, technical challenges to researchers. During the past 50 years, for instance, the demands of the scientific community have substantially evolved and with a need for advanced instrumentation to support radio astronomy, Earth observation, weather forecasting, security imaging, telecommunications, non-destructive device testing and much more. Furthermore, applications have required an emergence of technology from the laboratory environment to production-scale supply and in-the-field deployments ranging from harsh ground-based locations to deep space. In addressing these requirements, the research and development community has advanced related technology and bridged the transition between electronics and photonics that high frequency operation demands. The multidisciplinary nature of THz work was our stimulus for creating the 2017 THz Science and Technology Roadmap (Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001). As one might envisage, though, there remains much to explore both scientifically and technically and the field has continued to develop and expand rapidly. It is timely, therefore, to revise our previous roadmap and in this 2023 version we both provide an update on key developments in established technical areas that have important scientific and public benefit, and highlight new and emerging areas that show particular promise. The developments that we describe thus span from fundamental scientific research, such as THz astronomy and the emergent area of THz quantum optics, to highly applied and commercially and societally impactful subjects that include 6G THz communications, medical imaging, and climate monitoring and prediction. Our Roadmap vision draws upon the expertise and perspective of multiple international specialists that together provide an overview of past developments and the likely challenges facing the field of THz science and technology in future decades. The document is written in a form that is accessible to policy makers who wish to gain an overview of the current state of the THz art, and for the non-specialist and curious who wish to understand available technology and challenges. A such, our experts deliver a 'snapshot' introduction to the current status of the field and provide suggestions for exciting future technical development directions. Ultimately, we intend the Roadmap to portray the advantages and benefits of the THz domain and to stimulate further exploration of the field in support of scientific research and commercial realisation

Interdigitated Back Contact n-Type Solar Cell with Black Silicon Anti-Reflecting Layer: Simulations and Experiments

In this work, we have processed as a reference n-type IBC cells with random pyramids on high quality float-zone silicon wafer. The front surface is passivated with Al2O3 grown by atomic layer deposition. The same structure is simulated with the software Silvaco ATLAS. The simulated IV-characteristic fits the experimental curve in the dark and under AM1.5G with a relative error below 1%. Previous measurements on minority carrier lifetime experiments on black silicon samples passivated with 20nm Al2O3 layer have resulted in an effective surface recombination velocity below 5 cm/s. This value was used to simulate IBC cells with black silicon by adjusting the above-mentioned ATLAS model in order to see the impact of black silicon on the solar cell efficiency. The results show an increase in short-circuit current (Isc) of 6mA and efficiency of 0.3% at normal incidence. Simulation reveals that a lower front surface recombination velocity would not significantly increase the efficiency of the cell. Furthermore, the simulations reveal that the emitter passivation is a critical parameter to increase further the efficiency of the cell

A hierarchical Markov chain based solver for very-large-scale capacitance extraction

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 79-80).This thesis presents two hierarchical algorithms, FastMarkov and FD-MTM, for computing the capacitance of very-large-scale layout with non-uniform media. Fast- Markov is Boundary Element Method based and FD-MTM is Finite Difference based. In our algorithms, the layout is first partitioned into small blocks and the capacitance matrix of each block is solved using standard deterministic methods, BEM for Fast- Markov and FDM for FD-MTM. We connect the blocks by enforcing the boundary condition on the interfaces, forming a Markov Chain containing the capacitive characteristic of the layout. Capacitance of the full layout is then extracted with the random walk method. By employing the "divide and conquer" strategy, our algorithm does not need to assemble or solve a linear system of equations at the level of the full layout and thus eliminates the memory problem. We also propose a modification to the FastMarkov algorithm (FastMarkov with boundary fix) to address the block interface issue when using the finite difference method. We implemented FastMarkov with boundary fix in C++ and parallelized the solver with Message Passing Interface. Compared with standard FD capacitance solver, our solver is able to achieve a speedup almost linear to the number of blocks the layout is partitioned into. On top of it, FastMarkov is easily parallelizable because the computation of the capacitance matrix of one block is independent of other blocks and one path of random walk is independent of other paths. Results and comparisons are presented for parallel plates example and for a large Intel example.by Yan Zhao.S.M

Conformal symmetries for extremal black holes with general asymptotic scalars in STU supergravity

Abstract We present a construction of the most general BPS black holes of STU supergravity ($$\mathcal{N}$$ N = 2 supersymmetric D = 4 supergravity coupled to three vector super-multiplets) with arbitrary asymptotic values of the scalar fields. These solutions are obtained by acting with a subset of the global symmetry generators on STU BPS black holes with zero values of the asymptotic scalars, both in the U-duality and the heterotic frame. The solutions are parameterized by fourteen parameters: four electric and four magnetic charges, and the asymptotic values of the six scalar fields. We also present BPS black hole solutions of a consistently truncated STU supergravity, which are parameterized by two electric and two magnetic charges and two scalar fields. These latter solutions are significantly simplified, and are very suitable for further explicit studies. We also explore a conformal inversion symmetry of the Couch-Torrence type, which maps any member of the fourteen-parameter family of BPS black holes to another member of the family. Furthermore, these solutions are expected to be valuable in the studies of various swampland conjectures in the moduli space of string compactifications.</jats:p

The 2023 terahertz science and technology roadmap

Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz–∼30 THz). Within its frequency boundaries exist a broad variety of scientific disciplines that have presented, and continue to present, technical challenges to researchers. During the past 50 years, for instance, the demands of the scientific community have substantially evolved and with a need for advanced instrumentation to support radio astronomy, Earth observation, weather forecasting, security imaging, telecommunications, non-destructive device testing and much more. Furthermore, applications have required an emergence of technology from the laboratory environment to production-scale supply and in-the-field deployments ranging from harsh ground-based locations to deep space. In addressing these requirements, the research and development community has advanced related technology and bridged the transition between electronics and photonics that high frequency operation demands. The multidisciplinary nature of THz work was our stimulus for creating the 2017 THz Science and Technology Roadmap (Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001). As one might envisage, though, there remains much to explore both scientifically and technically and the field has continued to develop and expand rapidly. It is timely, therefore, to revise our previous roadmap and in this 2023 version we both provide an update on key developments in established technical areas that have important scientific and public benefit, and highlight new and emerging areas that show particular promise. The developments that we describe thus span from fundamental scientific research, such as THz astronomy and the emergent area of THz quantum optics, to highly applied and commercially and societally impactful subjects that include 6G THz communications, medical imaging, and climate monitoring and prediction. Our Roadmap vision draws upon the expertise and perspective of multiple international specialists that together provide an overview of past developments and the likely challenges facing the field of THz science and technology in future decades. The document is written in a form that is accessible to policy makers who wish to gain an overview of the current state of the THz art, and for the non-specialist and curious who wish to understand available technology and challenges. A such, our experts deliver a 'snapshot' introduction to the current status of the field and provide suggestions for exciting future technical development directions. Ultimately, we intend the Roadmap to portray the advantages and benefits of the THz domain and to stimulate further exploration of the field in support of scientific research and commercial realisation

Epigenetische Voralterung bei Keimzentrums-B-Zell-Lymphomen

Die Keimzentrums-B-Zell-Lymphomentitäten Burkitt-Lymphom, Diffuses großzelliges B-Zell-Lymphom und Follikuläres Lymphom machen insgesamt einen Anteil von 80% an den B-Zell-Non-Hodgkin-Lymphomen aus und leiten sich von Antigen-aktivierten Keimzentrums-B-Zellen ab. Da diese drei Lymphomentitäten jeweils spezifische Verteilungen des Erkrankungsalters aufweisen, schien es interessant, den Zusammenhang zwischen dem Altern und der Lymphomagenese zu untersuchen. Altern ist ein komplexer Prozess, der sich sowohl auf molekulare Funktionen in den einzelnen Zellen als auch auf den gesamten Organismus auswirkt. Auch epigenetische Mechanismen weisen altersabhängige Veränderungen auf. In dieser Arbeit wurde das von Steve Horvath beschriebene DNA-Methylierungsalter als epigenetischer Biomarker des biologischen Alters untersucht. Während das DNA-Methylierungsalter nach Horvath bei gesunden Individuen präzise das chronologische Alter schätzt, wurden bei mehreren Tumorarten stärkere Abweichungen des epigenetischen DNA-Methylierungsalters vom chronologischen Alter festgestellt. Da bisher keine Studien zum epigenetischen Alter von Lymphomen veröffentlicht wurden, sollte in dieser Arbeit das DNA-Methylierungsalter nach Horvath von Keimzentrums-B-Zell-Lymphomen im Vergleich zu gesunden Blutproben sowie gesunden B-Zell-Proben verschiedener Differenzierungsstadien untersucht werden. Hierfür wurde das genomweite DNA-Methylierungsprofil der Proben auf dem Methylierungsarray Infinium HumanMethylation450 BeadChip (Illumina) gemessen. Anhand der Methylierungswerte wurde das epigenetische DNA-Methylierungsalter der Proben berechnet und anschließend mit dem chronologischen Alter verglichen. Wie in der Studie von Steve Horvath wich auch in dieser Arbeit das DNA-Methylierungsalter der gesunden Blutproben im Median um 2,9 Jahre vom chronologischen Alter ab, sodass die von Horvath beschriebenen Angaben zur Präzision des DNA-Methylierungsalters bestätigt werden konnten. Während das DNA-Methylierungsalter der gesunden hämatopoetischen Progenitorzell-, Pro-B-Zell-, Prä-B-Zell-, unreifen B-Zell-, naiven B-Zell- und B-Gedächtniszell-Proben mit dem chronologischen Alter übereinstimmte, wiesen die Keimzentrums-B-Zell- und Plasmazell-Proben sowie die Lymphomproben aller drei Entitäten ein signifikant höheres DNA-Methylierungsalter verglichen mit ihrem chronologischen Alter auf. Die epigenetische Voralterung der Keimzentrums-B-Zellen und Plasmazellen im Vergleich zu den frühen B-Zell-Reifestadien lässt sich wahrscheinlich auf die starke Proliferation und die somatische Hypermutation im Rahmen der Keimzentrumsreaktion zurückführen. Von den Keimzentrums-B-Zellen leiten sich die Keimzentrums-B-Zell-Lymphome ab, welche ebenfalls epigenetisch vorgealtert waren. Hierbei wiesen die Burkitt-Lymphomproben die stärkste epigenetische Voralterung mit einem im Median um 45,6 Jahre älteren DNA-Methylierungsalter im Vergleich zu ihrem chronologischen Alter auf, während die epigenetische Voralterung bei den Diffusen großzelligen B-Zell-Lymphom-Proben mit 18,5 Jahren und bei den Follikulären Lymphomproben mit 14,9 Jahren weniger stark ausgeprägt war. Zudem unterschieden sich die Diffusen großzelligen B-Zell-Lymphom- und Follikulären Lymphomproben nicht signifikant im Ausmaß ihrer epigenetischen Voralterung von den Keimzentrums-B-Zell-Proben, während die Burkitt-Lymphomproben eine signifikant größere epigenetische Voralterung als die Keimzentrums-B-Zell-Proben aufwiesen. Somit scheint sich der Prozess der epigenetischen Voralterung, welcher schon bei den Keimzentrums-B-Zellen beobachtet wurde, während der Lymphomagenese der Burkitt-Lymphome fortzusetzen, wohingegen das epigenetische DNA-Methylierungsalter der Diffusen großzelligen B-Zell-Lymphome und der Follikulären Lymphome nicht signifikant durch die Lymphomagenese beeinflusst wird. Da in den Cytosin-phosphatidyl-Guanin-Loci des DNA-Methylierungsalter-Algorithmus nach Horvath die Zielgene der Polycomb-Gruppen-Proteine angereichert sind, könnte die differentielle Methylierung dieser Zielgene in den späten B-Zell-Reifestadien sowie den Keimzentrums-B-Zell-Lymphomen die beobachtete epigenetische Voralterung in diesen Probengruppen erklären. Die Polycomb-Gruppen-Proteine üben eine wichtige Funktion bei der Steuerung der Genexpression in Stammzellen und während der Differenzierung aus. Sowohl während des Alterungsprozesses als auch während der B-Zell-Reifung werden die Zielgene der Polycomb-Gruppen-Proteine hypermethyliert, welche bei Stammzellen normalerweise reprimiert werden. Diese spezifische Hypermethylierung könnte zu einer Dedifferenzierung der Zellen führen und ein erhöhtes Risiko der malignen Entartung zur Folge haben. Da eine epigenetische Voralterung bereits mit einer erhöhten Mortalität assoziiert wurde, könnte das DNA-Methylierungsalter der Lymphome in Zukunft zur Therapieauswahl und zur Abschätzung der Prognose genutzt werden