Quantum simulation with fully coherent dipole--dipole-interactions mediated by three-dimensional subwavelength atomic arrays

Quantum simulators employing cold atoms are among the most promising approaches to tackle quantum many-body problems. Nanophotonic structures are widely employed to engineer the bandstructure of light and are thus investigated as a means to tune the interactions between atoms placed in their vicinity. A key shortcoming of this approach is that excitations can decay into free photons, limiting the coherence of such quantum simulators. Here, we overcome this challenge by proposing to use a simple cubic three-dimensional array of atoms to produce an omnidirectional bandgap for light and show that it enables coherent, dissipation-free interactions between embedded impurities. We show explicitly that the band gaps persist for moderate lattice sizes and finite filling fraction, which makes this effect readily observable in experiment. Our work paves the way toward analogue spin quantum simulators with long-range interactions using ultracold atomic lattices, and is an instance of the emerging field of atomic quantum metamaterials.Comment: 13 pages, 8 figure

The discovery laboratory – A student-centred experiential learning practical: Part I – Overview

Chemical Engineering’s Discovery Laboratory at Imperial College London is a practical teaching programme designed specifically to support student-centred learning at an advanced level, bridging the gap between instructions driven lab experiments and fully open ended research. In the first part of this article we present an overview of this programme with particular attention given to the design of the pedagogical framework and the execution of teaching. The teaching goal is delivered by in-depth experiential learning, where students are assigned a specific subject area to conduct their own research within a set timeframe and boundary conditions that guarantee a successful learning outcome. Academic supervisors and teaching assistants play an important role in this process, where they provide students with continuing guidance throughout. The use of research or industrial grade equipment ensures the students’ preparation for their final year research project as well as their post-graduation careers. In addition to summative assessments, students also receive formative feedback periodically from academic supervisors and teaching assistants. The Discovery Laboratory has received positive feedback from both teachers and students since its inauguration in 2011 and here we share some useful insights for the execution of such a practical teaching programme

Understanding Information-Limiting Environments in Personalized News Platforms—A Systems Perspective

Personalized news platforms (PNPs) have become increasingly popular due to their ability to provide users with tailored, relevant news content. However, their algorithmic selection of news items bears the risk of limiting the diversity of news that users are exposed to, potentially creating information-limiting environments (ILEs). As the emergence of such ILEs involves interdependent sociotechnical interactions, classical positivist approaches have failed to establish an empirically verified theory on this phenomenon. Therefore, we adopt a systems perspective to conceptualize and quantify a model describing the sociotechnical interactions in PNPs that can create ILEs. We then propose an experimental approach to simulate these interactions with real users and validate its viability through an empirical prestudy. In doing so, we contribute to IS research by providing the conceptual and methodological basis for inductive theorizing on the causes of ILEs, which is an essential prerequisite for designing effective interventions to mitigate ILE-induced risks

OSIRIS Payload for DLR's BiROS Satellite

Direct optical communication links might offer a solution for the increasing demand of transmission capacity in satellite missions. Although direct space-to-ground links suffer from limited availability due to cloud coverage, the achievable data rates can be higher by orders of magnitude compared to traditional RF communication systems. DLR’s Institute for Communication and Navigation is currently developing an experimental communication payload for DLR’s BiROS satellite. The OSIRIS payload consists of a tracking sensor for a precise alignment between satellite and groundstation, an optical uplink channel, the two different and independent laser sources and the optical bench with the transmission optics. This paper will give an overview about the BiROS satellite, the OSIRIS payload and the performance of the system, including space-qualification of the hardware and transmission tests

Moving to timed remote assessments: the impact of COVID-19 on year end exams in Chemical Engineering at Imperial College London

Summative year end assessments area major component of student assessment at the Department of Chemical Engineering, Imperial College London.More than 600 studentsparticipate in over40 different exams during the summer term. At the end of the spring term, the college moved to fully remote operation due to COVID-19, leaving the academic community with the challenge of delivering examinationsremotely. At the time pandemic hit the UK, teaching for allmodules in the department had been completed, the exam timetable had already been published and all exam paperspassed the mandatory external quality review. To implement time-limited remote examsas stipulated by the university, the department decided to proceed with anexisting VLE platformfor submission of answer-sheets.This study highlights stakeholder reflections from the academic and student communityduring the implementation of this approachculminating in a mock examination to gauge readiness of the infrastructure as well as the student population.Our survey found that the majority of students (>80%) managed to follow the written instructionsand readily engaged with scanning technologies and the uploading process.In the main, students did not have to adapt their learning or writing style. All stakeholdersprovided constructive suggestions at the end of the mock exam resulting in a relatively smooth transition to this new mode of examination. This study highlights challenges and reflections on making the summer year end examsremote in a very short timeframein a large and diverse Chemical Engineering department at very short notice

Application of Process Modelling Tools in the Scale-Up of Pharmaceutical Crystallisation Processes

Abstract: Crystallisations are frequent process steps in the manufacture of active pharmaceutical ingredients (APIs). They are the primary means of intermediate or product formation and separation to achieve the desired purity and form. These unit operations are complex processes which are difficult to control due to the interlinked chemical and physical effects. For example, chemical aspects such as salt and polymorph concerns are in the forefront of process research, but physical effects manifesting themselves on scale-up, due to equipment influences, can be equally important for the successful outcome of a campaign. Several operational parameters, such as temperature or impeller speed, need to be understood and controlled to achieve constant desupersaturation, consistent narrow particle size distribution around the desired mean, minimal attrition, and homogeneous growth conditions. This paper focuses on the equipment influence on crystallisations, relating it to first principles with respect to heat and momentum transfer, analysing it with computational fluid dynamics (CFD), and demonstrating its process impact using examples from recent development work. Dynamic process modelling and CFD are state-of-the-art engineering tools to identify process requirements and match them with equipment capabilities. The work reported here demonstrates how a semiquantitative application of these tools can lead to a controllable, robust process in an existing plant despite the time and resource limitations usually encountered in the industry

Heat exchanger/reactors (HEX reactors): Concepts, technologies: State-of-the-art

Process intensification is a chemical engineering field which has truly emerged in the past few years and is currently rapidly growing. It consists in looking for safer operating conditions, lower waste in terms of costs and energy and higher productivity; and away to reach such objectives is to develop multifunctional devices such as heat exchanger/reactors for instance. This review is focused on the latter and makes a point on heat exchanger/reactors. After a brief presentation of requirements due to transposition from batch to continuous apparatuses, heat exchangers/reactors at industrial or pilot scales and their applications are described

Process intensification for post combustion CO₂ capture with chemical absorption: a critical review

The concentration of CO₂ in the atmosphere is increasing rapidly. CO₂ emissions may have an impact on global climate change. Effective CO₂ emission abatement strategies such as carbon capture and storage (CCS) are required to combat this trend. Compared with pre-combustion carbon capture and oxy-fuel carbon capture approaches, post-combustion CO₂ capture (PCC) using solvent process is one of the most mature carbon capture technologies. There are two main barriers for the PCC process using solvent to be commercially deployed: (a) high capital cost; (b) high thermal efficiency penalty due to solvent regeneration. Applying process intensification (PI) technology into PCC with solvent process has the potential to significantly reduce capital costs compared with conventional technology using packed columns. This paper intends to evaluate different PI technologies for their suitability in PCC process. The study shows that rotating packed bed (RPB) absorber/stripper has attracted much interest due to its high mass transfer capability. Currently experimental studies on CO₂ capture using RPB are based on standalone absorber or stripper. Therefore a schematic process flow diagram of intensified PCC process is proposed so as to motivate other researches for possible optimal design, operation and control. To intensify heat transfer in reboiler, spinning disc technology is recommended. To replace cross heat exchanger in conventional PCC (with packed column) process, printed circuit heat exchanger will be preferred. Solvent selection for conventional PCC process has been studied extensively. However, it needs more studies for solvent selection in intensified PCC process. The authors also predicted research challenges in intensified PCC process and potential new breakthrough from different aspects

Gender Differences in Myogenic Regulation along the Vascular Tree of the Gerbil Cochlea

Regulation of cochlear blood flow is critical for hearing due to its exquisite sensitivity to ischemia and oxidative stress. Many forms of hearing loss such as sensorineural hearing loss and presbyacusis may involve or be aggravated by blood flow disorders. Animal experiments and clinical outcomes further suggest that there is a gender preference in hearing loss, with males being more susceptible. Autoregulation of cochlear blood flow has been demonstrated in some animal models in vivo, suggesting that similar to the brain, blood vessels supplying the cochlea have the ability to control flow within normal limits, despite variations in systemic blood pressure. Here, we investigated myogenic regulation in the cochlear blood supply of the Mongolian gerbil, a widely used animal model in hearing research. The cochlear blood supply originates at the basilar artery, followed by the anterior inferior cerebellar artery, and inside the inner ear, by the spiral modiolar artery and the radiating arterioles that supply the capillary beds of the spiral ligament and stria vascularis. Arteries from male and female gerbils were isolated and pressurized using a concentric pipette system. Diameter changes in response to increasing luminal pressures were recorded by laser scanning microscopy. Our results show that cochlear vessels from male and female gerbils exhibit myogenic regulation but with important differences. Whereas in male gerbils, both spiral modiolar arteries and radiating arterioles exhibited pressure-dependent tone, in females, only radiating arterioles had this property. Male spiral modiolar arteries responded more to L-NNA than female spiral modiolar arteries, suggesting that NO-dependent mechanisms play a bigger role in the myogenic regulation of male than female gerbil cochlear vessels