We present a theoretical technique for quantifying the cellular copy-number of fluorophores that relies on the random nature of the photobleaching process. Our approach does not require single-molecule sensitivity, and therefore can be used with commonly used epifluorescence microscopes. Fluctuations arising from photobleaching can be used to estimate the proportionality between fluorescence intensity and copy-number, which can then be used with subsequent intensity measurements to estimate copy-number. We calculate the statistical errors of our approach and verify them with stochastic simulations. By using fluctuations over the entire photobleaching process, we obtain significantly smaller errors than previous approaches that have used fluctuations arising from cytoplasmic proteins partitioning during cellular division. From the time-dependence of the fluctuations as photobleaching proceeds, we can discriminate between desired photobleach fluctuations and background noise or photon shot noise. Our approach does not require cellular division and the photobleaching rate sets a timescale that is adjustable with respect to cellular processes. We hope that our approach will now be applied experimentally.
We investigate the effect of the phase difference of applied fields on the dynamics of mutually coupled Josephson junction. The system desynchronizes for any value of applied phase difference and the dynamics even changes from chaotic to periodic motion for some values of applied phase difference. We report that by keeping the value of phase difference as π, the system continues to be in periodic motion for a wide range of system parameter values which might be of great practical applications.
Many signaling pathways act through shared components, where different ligand molecules bind the same receptors or activate overlapping sets of response regulators downstream. Nevertheless, different ligands acting through cross-wired pathways often lead to different outcomes in terms of the target cell behavior and function. Although a number of mechanisms have been proposed, it still largely remains unclear how cells can reliably discriminate different molecular ligands under such circumstances. Here we show that signaling via ligand-induced receptor dimerization-a very common motif in cellular signaling-naturally incorporates a mechanism for the discrimination of ligands acting through the same receptor.
This paper presents a plausible solution using brain based learning principles as instructional delivery protocols to address the issue of lack of academic engagement among the upper level engineering students. The study was conducted at Tuskegee University, an HBCU and can be implemented universally in other institutes due to its foundation on brain based learning principles. Although student engagement issues inside engineering classrooms have several components, we focus our attention in this paper mainly on two issues: the dis-engagement arising due to the lack of understanding of pre-requisites and insufficient mathematical skills of students reaching junior and senior engineering classes. A previous pilot study confirmed that a large fraction of students who reach junior and senior level classes require repeated review of pre-requisite concepts and need assistance in reviewing their basic and essential mathematical skills before they can successfully engage in their classes. To address these issues, an instructional delivery framework titled "Tailored Instructions and Engineered Delivery Using PROTOCOLs" (TIED-UP) has been designed and explored, where mandatory brain-based learning procedures were used along with a media rich online delivery strategy. This paper summarizes the efforts currently undertaken to develop this framework based on brain-based learning theories to address some of these issues. In this framework, each course concept is broken down to interconnected sub-concepts. Short conceptual videos that use a number of mandatory instructional protocols were developed for the instruction of each of these concept and sub-concept. The study shows that such an intervention has significantly increased students' academic success as measured by grades and caused a substantial decline in their failure rate, when compared against a control group.
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