New Consequences of Induced Transparency in a Double-Lambda scheme: Destructive Interference In Four-wave Mixing

We investigate a four-state system interacting with long and short laser pulses in a weak probe beam approximation. We show that when all lasers are tuned to the exact unperturbed resonances, part of the four-wave mixing (FWM) field is strongly absorbed. The part which is not absorbed has the exact intensity required to destructively interfere with the excitation pathway involved in producing the FWM state. We show that with this three-photon destructive interference, the conversion efficiency can still be as high as 25%. Contrary to common belief,our calculation shows that this process, where an ideal one-photon electromagnetically induced transparency is established, is not most suitable for high efficiency conversion. With appropriate phase-matching and propagation distance, and when the three-photon destructive interference does not occur, we show that the photon flux conversion efficiency is independent of probe intensity and can be close to 100%. In addition, we show clearly that the conversion efficiency is not determined by the maximum atomic coherence between two lower excited states, as commonly believed. It is the combination of phase-matching and constructive interference involving the two terms arising in producing the mixing wave that is the key element for the optimized FWM generation. Indeed, in this scheme no appreciable excited state is produced, so that the atomic coherence between states |0> and |2> is always very small.Comment: Submitted to Phys. Rev. A, 7 pages, 4 figure

TB85: A New Potato Scab Problem in Maine

The scientific literature is filled with conflicting reports on the development of the common scab disease of potatoes and its causal organism. One unresolved question is soil reaction, once thought to be the answer in controlling this disease. Scientific studies an d practical experience over a long period had shown that acid soils having a pH of approximately 5.3 or below usually did not support common scab development, though sporadic and unexplained reports of disease occurrence in these soils were observed. In the late 1950s, however, such reports became more frequent in Maine and before the mid-1960s, losses relate d to scabb y potatoes growing in acid soils were common. Throughout this period overall crop losses from the disease were minimal even though individual growers sometimes lost a large par t of their crop. During the dry 1970 growing season, however, a disease survey estimated that up to 5% of the Maine crop was scabby. Studies of this new form of scab and observations on its development within the state are reported herein.https://digitalcommons.library.umaine.edu/aes_techbulletin/1114/thumbnail.jp

How do patients, politicians, physiotherapists and other health professionals view physiotherapy research in Switzerland? : a qualitative study

Since 2002, the professional education for Swiss physiotherapists has been upgraded to a tertiary educational level. With this change, the need for research related to professional practice has become more salient. The elaboration of research priorities is seen as a possible way to determine the profession's needs, to help coordinate research collaborations and to address expectations regarding physiotherapy. There is still limited evidence about stakeholders' views with regard to physiotherapy research. The objective of this study was to investigate key stakeholders' opinions about research in physiotherapy in Switzerland

Computer Games Are Serious Business and so is their Quality: Particularities of Software Testing in Game Development from the Perspective of Practitioners

Over the last several decades, computer games started to have a significant impact on society. However, although a computer game is a type of software, the process to conceptualize, produce and deliver a game could involve unusual features. In software testing, for instance, studies demonstrated the hesitance of professionals to use automated testing techniques with games, due to the constant changes in requirements and design, and pointed out the need for creating testing tools that take into account the flexibility required for the game development process. Goal. This study aims to improve the current body of knowledge regarding software testing in game development and point out the existing particularities observed in software testing considering the development of a computer game. Method. A mixed-method approach based on a case study and an opinion survey was applied to collect quantitative and qualitative data from software professionals regarding the particularities of software testing in game development. Results. We analyzed over 70 messages posted on three well-established network of question-and-answer communities related to software engineering, software testing and game development and received answers of 38 professionals discussing differences between testing a computer game and a general software, and identified important aspects to be observed by practitioners in the process of planning, performing and reporting tests in this context. Conclusion. Considering computer games, software testing must focus not only on the common aspects of a general software, but also, track and investigate issues that could be related to game balance, game physics and entertainment related-aspects to guarantee the quality of computer games and a successful testing process

Nonlinear optics via double dark resonances

Double dark resonances originate from a coherent perturbation of a system displaying electromagnetically induced transparency. We experimentally show and theoretically confirm that this leads to the possibility of extremely sharp resonances prevailing even in the presence of considerable Doppler broadening. A gas of 87Rb atoms is subjected to a strong drive laser and a weak probe laser and a radio frequency field, where the magnetic coupling between the Zeeman levels leads to nonlinear generation of a comb of sidebands.Comment: 6 pages, 9 figure

Learning physics in context: a study of student learning about electricity and magnetism

This paper re-centres the discussion of student learning in physics to focus on context. In order to do so, a theoretically-motivated understanding of context is developed. Given a well-defined notion of context, data from a novel university class in electricity and magnetism are analyzed to demonstrate the central and inextricable role of context in student learning. This work sits within a broader effort to create and analyze environments which support student learning in the sciencesComment: 36 pages, 4 Figure

From teaching physics to teaching children : beginning teachers learning from pupils

This paper discusses the development of beginning physics teachers' pedagogical content knowledge (PCK) in the context of teaching basic electricity during a one-year Professional Graduate Diploma in Education course (PGDE) and beyond. This longitudinal study used repeated semi-structured interviews over a period of four-and-a-half years. The interview schedule followed a line of development through the secondary school electrical syllabus in Scotland. Fifteen student teachers were interviewed during the PGDE year. Six of them were followed up at the end of the Induction Year (their first year as a newly qualified teacher), and again two-and-a-half years later. Thematic analysis of the interviews showed that before the beginning teachers had taught any classes, their initial focus was on how to transform their own subject matter knowledge (SMK) about electricity into forms that were accessible to pupils. As the beginning teachers gained experience working with classes, they gave vivid descriptions of interacting with particular pupils when teaching electricity which showed the development of their pedagogical knowledge. This played a significant role in the teachers' change of focus from teaching physics to teaching children as they transformed their SMK into forms that were accessible to pupils and developed their general pedagogical knowledge

Evidence for the predictive remapping of visual attention

When attending an object in visual space, perception of the object remains stable despite frequent eye movements. It is assumed that visual stability is due to the process of remapping, in which retinotopically organized maps are updated to compensate for the retinal shifts caused by eye movements. Remapping is predictive when it starts before the actual eye movement. Until now, most evidence for predictive remapping has been obtained in single cell studies involving monkeys. Here, we report that predictive remapping affects visual attention prior to an eye movement. Immediately following a saccade, we show that attention has partly shifted with the saccade (Experiment 1). Importantly, we show that remapping is predictive and affects the locus of attention prior to saccade execution (Experiments 2 and 3): before the saccade was executed, there was attentional facilitation at the location which, after the saccade, would retinotopically match the attended location