Revealing single emitter spectral dynamics from intensity correlations in an ensemble fluorescence spectrum

We show that the single emitter linewidth underlying a broadened ensemble emission spectrum can be extracted from correlations among the stochastic intensity fluctuations in the ensemble spectrum. Spectral correlations can be observed at high temporal and spectral resolutions with a cross-correlated pair of avalanche photodiodes placed at the outputs of a scanning Michelson interferometer. As illustrated with simulations in conjunction with Fluorescence Correlation Spectroscopy, our approach overcomes ensemble and temporal inhomogeneous broadening to provide single emitter linewidths, even for emitters under weak, continuous, broadband excitation.Comment: 9 pages, 5 figure

Aborto e (não) desejo de maternidade(s) : questões para a psicologia

A interrupção voluntária da gravidez ou abortamento induzido é um problema de saúde pública no Brasil. Mais do que suscitar opiniões pessoais, necessitamos debatê- lo à luz dos estudos que descrevem e/ou registram a prevalência do abortamento na população utilizando métodos de pesquisa reconhecidos para lidar com a especificidade do fenômeno. Dessa forma, destacamos o estudo apresentado na Pesquisa Nacional de Aborto, o qual aponta que uma dentre cada cinco brasileiras já fez pelo menos um aborto na vida. No entanto é importante destacar que, das mulheres que abortam, são as pobres (e negras) as mais atingidas pela desigualdade de acesso a formas seguras de interrupção de gravidez. Quanto aos abortamentos que são previstos em lei nos casos de gravidez decorrente de estupro, grave risco de vida à mulher/mãe e, mais recentemente, casos de anencefalia, o Estado brasileiro disponibiliza o acesso pelo Sistema de Único de Saúde (SUS). Contudo, mesmo nesses casos os estudos apontam que a mulher depara-se com grandes barreiras de acesso, além do estigma e de vários fatores que acabam por dificultar a obtenção do direito. A interrupção da gravidez toca em pelo menos dois pontos tabus em nossa cultura: de um lado, a discussão sobre quando se deve reconhecer aquela potência de vida dentro da mulher como sujeito e, por outro lado, a maternidade e os valores e ideais que a cercam, um tema importante a todos nós psicólogas e psicólogos. Tem a Psicologia refletido criticamente sobre o conceito de “maternidade”? Como tem sido pensada a mulher que não deseja ser mãe? A que não ama seus filhos? A que decide interromper uma gravidez? A presente coletânea, mais do que responder a estas questões, tem como intuito fomentar o debate e levar, às psicólogas e aos psicólogos, reflexões de profissionais que têm se debruçado sobre o tema. As organizadoras

From Digital Divide to Technostress during the COVID-19 Pandemic: A Scoping Review

publishedVersio

FPGA implementation of a 32x32 autocorrelator array for analysis of fast image series

With the evolving technology in CMOS integration, new classes of 2D-imaging detectors have recently become available. In particular, single photon avalanche diode (SPAD) arrays allow detection of single photons at high acquisition rates (\geq 100 kfps), which is about two orders of magnitude higher than with currently available cameras. Here we demonstrate the use of a SPAD array for imaging fluorescence correlation spectroscopy (imFCS), a tool to create 2D maps of the dynamics of fluorescent molecules inside living cells. Time-dependent fluorescence fluctuations, due to fluorophores entering and leaving the observed pixels, are evaluated by means of autocorrelation analysis. The multi-{\tau} correlation algorithm is an appropriate choice, as it does not rely on the full data set to be held in memory. Thus, this algorithm can be efficiently implemented in custom logic. We describe a new implementation for massively parallel multi-{\tau} correlation hardware. Our current implementation can calculate 1024 correlation functions at a resolution of 10{\mu}s in real-time and therefore correlate real-time image streams from high speed single photon cameras with thousands of pixels.Comment: 10 pages, 7 figure

Mantle upwelling, melt generation, and magma transport beneath mid-ocean ridges

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997.Vita.Includes bibliographical references.by Laura Suzan Magde.Ph.D

Informal Caregivers and Psychosocial Support: Analysis of European Dementia Policy Documents

publishedVersio

Intramolecular fluorescence correlation spectroscopy in a feedback tracking microscope

We derive the statistics of the signals generated by shape fluctuations of large molecules studied by feedback tracking microscopy. We account for the influence of intramolecular dynamics on the response of the tracking system, and derive a general expression for the fluorescence autocorrelation function that applies when those dynamics are linear. We show that tracking provides enhanced sensitivity to translational diffusion, molecular size, heterogeneity and long time-scale decays in comparison to traditional fluorescence correlation spectroscopy. We demonstrate our approach by using a three-dimensional tracking microscope to study genomic $\lambda$-phage DNA molecules with various fluorescence label configurations.Comment: 11 pages, 5 figures, supplemental info: http://minty.stanford.edu/papers/Publications/McHale10aSI.pd

How confined lubricants diffuse during shear

The translational diffusion of a fluorescent dye embedded at a dilute concentration in a confined fluid was compared at rest and during shear. The fluid, octamethylcyclotetrasiloxane (OMCTS), was confined between step-free muscovite mica to thickness 3-4 layers. Fluorescence correlation spectroscopy showed that the time scales of intensity-intensity autocorrelation functions were essentially the same during shear and at rest, except they were faster during shear by a factor of 2 to 5. This dynamical probe of how liquids order in molecularly thin films fails to support the hypothesis that shear produced a melting transition.open242

Monitoring peripheral protein oligomerization on biological membranes

Peripheral proteins transiently interact with cellular membranes where they regulate important cellular events such as signal transduction. A number of peripheral proteins harbor lipid-binding modules that not only bind selectively with nanomolar affinity to biological membranes but also oligomerize on the membrane surface. In some cases specific lipid binding or specific lipid compositions can induce peripheral protein oligomerization on cellular membranes. These oligomers serve different roles in biological signaling such as regulating protein-protein interactions, induction of membrane bending, or facilitating membrane scission. A number of technologies have been employed to study protein oligomerization with fluctuation analysis of fluorescently labeled molecules recently developed for use with commercial laser scanning microscopes. In this chapter the approach of Raster Image Correlation Spectroscopy coupled with Number and Brightness (N&B) analysis to investigate protein oligomerization on cellular membranes in live cells is presented. Important considerations are discussed for designing experiments, collecting data, and performing analysis. N&B analysis provides a robust method for assessing membrane binding and assembly properties of peripheral proteins and lipid-binding modules

Synthesis and potential use of 1,8-naphthalimide type O-1(2) sensor molecules

New double (fluorescent and spin) sensor molecules containing 4-amino substituted 1,8-naphthalimide as a fluorophore and a sterically hindered amine (pre-nitroxide) or pyrroline nitroxide as a quencher and radical capturing moiety were synthesized. All sensors were substituted with a diethylaminoethyl side-chain to increase the water solubility. Steady state fluorescence properties of these compounds and their responses to ROS in vitro are reported with perspectives of plant physiology use in vivo