Quantum limited particle sensing in optical tweezers

Particle sensing in optical tweezers systems provides information on the position, velocity and force of the specimen particles. The conventional quadrant detection scheme is applied ubiquitously in optical tweezers experiments to quantify these parameters. In this paper we show that quadrant detection is non-optimal for particle sensing in optical tweezers and propose an alternative optimal particle sensing scheme based on spatial homodyne detection. A formalism for particle sensing in terms of transverse spatial modes is developed and numerical simulations of the efficacy of both quadrant and spatial homodyne detection are shown. We demonstrate that an order of magnitude improvement in particle sensing sensitivity can be achieved using spatial homodyne over quadrant detection.Comment: Submitted to Biophys

The geometrical origin of the strain-twist coupling in double helices

The geometrical coupling between strain and twist in double helices is investigated. Overwinding, where strain leads to further winding, is shown to be a universal property for helices, which are stretched along their longitudinal axis when the initial pitch angle is below the zero-twist angle (39.4 deg). Unwinding occurs at larger pitch angles. The zero-twist angle is the unique pitch angle at the point between overwinding and unwinding, and it is independent of the mechanical properties of the double helix. This suggests the existence of zero-twist structures, i.e. structures that display neither overwinding, nor unwinding under strain. Estimates of the overwinding of DNA, chromatin, and RNA are given.Comment: 8 pages, 4 figures; typos fixed; added ref. and acknowledgemen

Phonological processing deficit - a culprit behind developmental dyslexia?

Udostępnienie publikacji Wydawnictwa Uniwersytetu Łódzkiego finansowane w ramach projektu „Doskonałość naukowa kluczem do doskonałości kształcenia”. Projekt realizowany jest ze środków Europejskiego Funduszu Społecznego w ramach Programu Operacyjnego Wiedza Edukacja Rozwój; nr umowy: POWER.03.05.00-00-Z092/17-00

Pre-service teachers use e-learning technologies to enhance their learning

The purpose of this study was twofold. The primary purpose was to improve pre-service teacher education by using technology to help pre-service teachers bridge the gap between academic preparation and practice. The secondary, but still important, objective was to familiarize pre-service teachers in the use of technology to support their future pedagogical activities. Therefore, this research sought to develop a method for training undergraduate students in designing, implementing, and evaluating lesson plans to solidify the relationship between research, pedagogy, and teaching practice. Specifically, this study investigated the implementation of e-learning as a method of instruction to help pre-service teachers evaluate and improve upon the implementation of their lesson plans during their real world practicum experiences. The study was guided by the following research questions: 1) What successes, challenges, and benefits do university instructors and pre-service teachers experience in using and analyzing video in teacher education methods coursework? 2) In what ways did the use of e-learning help the pre-service teachers improve their teaching during the practicum experience? Results showed that participants reported improved lesson planning, improved lesson implementation, visual interpretations of best practices, modeling, and peer and university instructor feedback as successes of the e-learning project. Challenges included participants’ frustrations of being overworked and overwhelmed with the technical problems associated with e-learning. Overall participants judged the e-learning project as a very positive aspect of their teacher training

The Cowl - v.51 - Winter Sports Preview - Oct 29, 1986

The Cowl - student newspaper of Providence College. Vol 51 - Winter Sports Preview - October 29, 1986. 24 pages