The Blackbody Radiation Spectrum Follows from Zero-Point Radiation and the Structure of Relativistic Spacetime in Classical Physics

The analysis of this article is entirely within classical physics. Any attempt to describe nature within classical physics requires the presence of Lorentz-invariant classical electromagnetic zero-point radiation so as to account for the Casimir forces between parallel conducting plates at low temperatures. Furthermore, conformal symmetry carries solutions of Maxwell's equations into solutions. In an inertial frame, conformal symmetry leaves zero-point radiation invariant and does not connect it to non-zero-temperature; time-dilating conformal transformations carry the Lorentz-invariant zero-point radiation spectrum into zero-point radiation and carry the thermal radiation spectrum at non-zero temperature into thermal radiation at a different non-zero-temperature. However, in a non-inertial frame, a time-dilating conformal transformation carries classical zero-point radiation into thermal radiation at a finite non-zero-temperature. By taking the no-acceleration limit, one can obtain the Planck radiation spectrum for blackbody radiation in an inertial frame from the thermal radiation spectrum in an accelerating frame. Here this connection between zero-point radiation and thermal radiation is illustrated for a scalar radiation field in a Rindler frame undergoing relativistic uniform proper acceleration through flat spacetime in two spacetime dimensions. The analysis indicates that the Planck radiation spectrum for thermal radiation follows from zero-point radiation and the structure of relativistic spacetime in classical physics.Comment: 21 page

Developing a design framework for laboratory videos in molecular biosciences

BACKGROUND Video-based learning has become increasingly integrated into higher education (Fadde & Vu, 2014). In particular, use of laboratory video expanded for students unable to attend in-person instruction during the pandemic (Delgado, Bhark, & Donahue, 2021; Slade et al., 2021). However, there remains a paucity of standardised guidelines for designing laboratory-training videos. AIMS This project aims to analyse student perceptions and engagement with laboratory video to inform future laboratory video design. METHODS Nine videos were produced to teach core microbiology laboratory skills (e.g. aseptic technique) for a microbiology course (876 students). Video analytics were collected from YouTube Creator Studio between 11/08/2020 to 29/11/2021, with student perceptions on helpfulness of various video design features collected through a survey (7% response rate) and follow-up interviews. RESULTS The percentage of students watching (audience retention) declined throughout a video, with sharp declines in initial and final 5% of video. Audience retention was significantly higher in scenes focused on technique demonstration or written explanations versus speaking instructor (“talking-head”) (p<0.001), and in presence of supplementary text (p<0.001) or illustrations (p<0.001). Similarly, students rated ‘demonstration’ and ‘writing’ as more helpful than ‘talking-head’ (p<0.001), however a variety of design features were rated as helpful. CONCLUSIONS We find a variety of design features are helpful, with student perceptions of helpfulness agreeing with differences in audience retention throughout laboratory-skill videos. REFERENCES Delgado, T., Bhark, S. J., & Donahue, J. (2021). Pandemic Teaching: Creating and teaching cell biology labs online during COVID-19. Biochemistry and Molecular Bioogyl Education, 49(1), 32-37. https://doi:10.1002/bmb.21482 Fadde, P. J., and Vu, P. (2014). Blended online learning: Benefits, challenges, and misconceptions. In Lowenthal, P. R., York, C. S., Richardson, J. C. (Eds.), Online Learning: Common    Misconceptions,    Benefits,    and    Challenges,    Nova    Science    Publishing, Hauppauge, 33-48. Slade, C., Lawrie, G., Taptamat, N., Browne, E., Sheppard, K., & Matthews, K. E. (2021). Insights into how academics reframed their assessment during a pandemic: disciplinary variation and assessment as afterthought. Assessment and Evaluation in Higher Education, 47(4), 588-605. https://doi:10.1080/02602938.2021.193337

A validation study of a smartphone application for functional mobility assessment of the elderly

AbstractBackgroundTo minimize the reaction time and position judgment error using stopwatch-timed measures, we developed a smartphone application to measure performance in the five-time sit-to-stand (FTSTS) and timed up-and-go (TUG) tests.ObjectiveThis study aimed to validate this smartphone application by comparing its measurement with a laboratory-based reference condition.MethodsThirty-two healthy elderly people were asked to perform the FTSTS and TUG tests in a randomized sequence. During the tests, their performance was concurrently measured by the smartphone application and a force sensor installed in the backrest of a chair. The intraclass correlation coefficient [ICC(2,1)] and Bland–Altman analysis were used to calculate the measurement consistency and agreement, respectively, between these two methods.ResultsThe smartphone application demonstrated excellent measurement consistency with the lab-based reference condition for the FTSTS test [ICC(2,1) = 0.988] and TUG test [ICC(2,1) = 0.946]. We observed a positive bias of 0.27 seconds (95% limits of agreement, −1.22 to 1.76 seconds) for the FTSTS test and 0.48 seconds (95% limits of agreement, −1.66 to 2.63 seconds) for the TUG test.ConclusionWe cross-validated the newly developed smartphone application with the laboratory-based reference condition during the examination of FTSTS and TUG test performance in healthy elderly

Selection from read-only memory with limited workspace

Given an unordered array of $N$ elements drawn from a totally ordered set and an integer $k$ in the range from $1$ to $N$, in the classic selection problem the task is to find the $k$-th smallest element in the array. We study the complexity of this problem in the space-restricted random-access model: The input array is stored on read-only memory, and the algorithm has access to a limited amount of workspace. We prove that the linear-time prune-and-search algorithm---presented in most textbooks on algorithms---can be modified to use $\Theta(N)$ bits instead of $\Theta(N)$ words of extra space. Prior to our work, the best known algorithm by Frederickson could perform the task with $\Theta(N)$ bits of extra space in $O(N \lg^{*} N)$ time. Our result separates the space-restricted random-access model and the multi-pass streaming model, since we can surpass the $\Omega(N \lg^{*} N)$ lower bound known for the latter model. We also generalize our algorithm for the case when the size of the workspace is $\Theta(S)$ bits, where $\lg^3{N} \leq S \leq N$. The running time of our generalized algorithm is $O(N \lg^{*}(N/S) + N (\lg N) / \lg{} S)$, slightly improving over the $O(N \lg^{*}(N (\lg N)/S) + N (\lg N) / \lg{} S)$ bound of Frederickson's algorithm. To obtain the improvements mentioned above, we developed a new data structure, called the wavelet stack, that we use for repeated pruning. We expect the wavelet stack to be a useful tool in other applications as well.Comment: 16 pages, 1 figure, Preliminary version appeared in COCOON-201

Student Perceptions and Engagement in Video-based Learning for Microbiology Education

Online learning increases the physical distance between instructors and students and depending on the mode of delivery, it can be challenging to close this gap. To ameliorate this potential for student isolation, instructors need to communicate to students in a variety of ways, blending original online resources with synchronous interactive learning activities. During 2020, 34 lecture videos were created for a large undergraduate microbiology and immunology course offered at The University of Queensland. The teaching team applied a subset of Mayer’s multimedia learning design principles – embodiment, mixed perspectives, segmenting, signalling – to create videos featuring instructor presence, multiple presentation styles, and dynamic pacing. When compared to voice-over presentations created by automated lecture capture software, the outcomes of this design process increased student engagement in video-based learning across the 2020 and 2021 course offerings. Analysis of student perception data collected by online questionnaires and interviews revealed broad agreement with the design principles used for video-based learning. However, their value of on-screen instructor visibility, graphics, and text was variable as a result of individual preferences. Together these findings present a case study in which instructional videos were developed iteratively through the selective application of multimedia design principles and strategic adaptation of existing learning resources

Quantum Entanglement of Excitons in Coupled Quantum Dots

Optically-controlled exciton dynamics in coupled quantum dots is studied. We show that the maximally entangled Bell states and Greenberger-Horne-Zeilinger (GHZ) states can be robustly generated by manipulating the system parameters to be at the avoided crossings in the eigenenergy spectrum. The analysis of population transfer is systematically carried out using a dressed-state picture. In addition to the quantum dot configuration that have been discussed by Quiroga and Johnson [Phys. Rev. Lett. \QTR{bf}{83}, 2270 (1999)], we show that the GHZ states also may be produced in a ray of three quantum dots with a shorter generation time.Comment: 16 pages, 7 figures, to appear in Phys. Rev.

Casimir interaction between two concentric cylinders: exact versus semiclassical results

The Casimir interaction between two perfectly conducting, infinite, concentric cylinders is computed using a semiclassical approximation that takes into account families of classical periodic orbits that reflect off both cylinders. It is then compared with the exact result obtained by the mode-by-mode summation technique. We analyze the validity of the semiclassical approximation and show that it improves the results obtained through the proximity theorem.Comment: 28 pages, 5 figures include

Phosphorylation of focal adhesion kinase on tyrosine 194 by Met leads to its activation through relief of autoinhibition

Focal adhesion kinase (FAK) has a crucial role in integration of signals from integrins and growth factor receptors. In this study, we demonstrate that growth factor receptors including hepatocyte growth factor receptor Met, epidermal growth factor receptor, and platelet-derived growth factor receptor directly phosphorylate FAK on Tyr194 in the FERM domain (band 4.1 and ezrin/radixin/moesin homology domain). Upon binding to Met or phosphoinositides, FAK may undergo conformational changes, which renders Tyr194 accessible for phosphorylation. Substitution of Tyr194 with Phe significantly suppresses the activation of FAK by Met. In contrast, substitution of Tyr194 with Glu (Y194E substitution) leads to constitutive activation of FAK. The phosphorylation of FAK on Tyr194 may cause conformational changes in the FERM domain, which disrupts the intramolecular inhibitory interaction between the FERM and kinase domains of FAK. Moreover, substitution of the basic residues in the (216)KAKTLRK(222) patch in the FERM domain with Ala antagonizes the effect of the Y194E substitution on FAK activation, thus suggesting that the interactions between the phosphorylated Tyr194 and the basic resides in the (216)KAKTLRK(222) patch may allow FAK to be activated through relief of its autoinhibition. Collectively, this study provides the first example to explain how FAK is activated by receptor tyrosine kinases. Oncogene (2011) 30, 153-166; doi:10.1038/onc.2010.398; published online 30 August 201