1,623 research outputs found
Correlation functions quantify super-resolution images and estimate apparent clustering due to over-counting
We present an analytical method to quantify clustering in super-resolution
localization images of static surfaces in two dimensions. The method also
describes how over-counting of labeled molecules contributes to apparent
self-clustering and how the effective lateral resolution of an image can be
determined. This treatment applies to clustering of proteins and lipids in
membranes, where there is significant interest in using super-resolution
localization techniques to probe membrane heterogeneity. When images are
quantified using pair correlation functions, the magnitude of apparent
clustering due to over-counting will vary inversely with the surface density of
labeled molecules and does not depend on the number of times an average
molecule is counted. Over-counting does not yield apparent co-clustering in
double label experiments when pair cross-correlation functions are measured. We
apply our analytical method to quantify the distribution of the IgE receptor
(Fc{\epsilon}RI) on the plasma membranes of chemically fixed RBL-2H3 mast cells
from images acquired using stochastic optical reconstruction microscopy (STORM)
and scanning electron microscopy (SEM). We find that apparent clustering of
labeled IgE bound to Fc{\epsilon}RI detected with both methods arises from
over-counting of individual complexes. Thus our results indicate that these
receptors are randomly distributed within the resolution and sensitivity limits
of these experiments.Comment: 22 pages, 5 figure
ANÁLISIS DE LA VULNERABILIDAD POR FENÓMENOS DE REMOCIÓN EN MASA EN LA CUENCA TANAUCA ESTUDIO DE CASO
El fenómeno de remoción en masa constituye una amenaza importante ya que en combinación con la vulnerabilidad de las poblaciones expuestas, determina el riesgo a desastres próximos, este artículo tiene como objetivo dar a conocer un análisis detallado de la vulnerabilidad por estos fenómenos en la cuenca Tanauca, para ello se realizó un análisis de la información secundaria mediante la recopilación de datos basados en el plan de ordenamiento y manejo de cuencas hidrográficas, en el plan básico de ordenamiento territorial del municipio de pamplona y en los datos hidro meteorológicos de la estación ISER de pamplona, en conjunto con estudios realizados para la caracterización física de los suelos presentes en esta zona; El predominio de suelos areno-arcillosos causan una baja permeabilidad y por lo tanto una elevada retención de agua y de nutrientes, no obstante poseen una baja porosidad siendo suelos que carecen de buenas posibilidades de aireación mostrando una gran resistencia a la penetración de raíces y obstaculizando el nacimiento de plantas, el inadecuado manejo agrícola y pecuario al que está expuesto el suelo, ha hecho que este se deteriore significativamente ocasionando una pérdida de la capa vegetal y con efecto de la precipitación originando una erosión laminar quedando expuesta la zona a derrumbes o deslizamientos
DC-electric-field-induced and low-frequency electromodulation second-harmonic generation spectroscopy of Si(001)-SiO interfaces
The mechanism of DC-Electric-Field-Induced Second-Harmonic (EFISH) generation
at weakly nonlinear buried Si(001)-SiO interfaces is studied experimentally
in planar Si(001)-SiO-Cr MOS structures by optical second-harmonic
generation (SHG) spectroscopy with a tunable Ti:sapphire femtosecond laser. The
spectral dependence of the EFISH contribution near the direct two-photon
transition of silicon is extracted. A systematic phenomenological model of the
EFISH phenomenon, including a detailed description of the space charge region
(SCR) at the semiconductor-dielectric interface in accumulation, depletion, and
inversion regimes, has been developed. The influence of surface quantization
effects, interface states, charge traps in the oxide layer, doping
concentration and oxide thickness on nonlocal screening of the DC-electric
field and on breaking of inversion symmetry in the SCR is considered. The model
describes EFISH generation in the SCR using a Green function formalism which
takes into account all retardation and absorption effects of the fundamental
and second harmonic (SH) waves, optical interference between field-dependent
and field-independent contributions to the SH field and multiple reflection
interference in the SiO layer. Good agreement between the phenomenological
model and our recent and new EFISH spectroscopic results is demonstrated.
Finally, low-frequency electromodulated EFISH is demonstrated as a useful
differential spectroscopic technique for studies of the Si-SiO interface in
silicon-based MOS structures.Comment: 31 pages, 14 figures, 1 table, figures are also available at
http://kali.ilc.msu.su/articles/50/efish.ht
Lithium in the Intermediate-Age Open Cluster, NGC 3680
High-dispersion spectra centered on the Li 6708 A line have been obtained for
70 potential members of the open cluster NGC 3680, with an emphasis on stars in
the turnoff region. A measurable Li abundance has been derived for 53 stars, 39
of which have radial velocities and proper motions consistent with cluster
membership. After being transferred to common temperature and abundance scales,
previous Li estimates have been combined to generate a sample of 49 members, 40
of which bracket the cluster Li-dip. Spectroscopic elemental analysis of 8
giants and 5 turnoff stars produces [Fe/H] = -0.17 +/- 0.07 (sd) and -0.07 +/-
0.02 (sd), respectively. We also report measurements of Ca, Si and Ni which are
consistent with scaled-solar ratios within the errors. Adopting [Fe/H] = -0.08
(Sect. 3.6), Y^2 isochrone comparisons lead to an age of 1.75 +/- 0.10 Gyr and
an apparent modulus of (m-M) = 10.30 +/- 0.15 for the cluster, placing the
center of the Li-dip at 1.35 +/- 0.03 solar masses. Among the giants, 5 of 9
cluster members are now known to have measurable Li with A(Li) near 1.0. A
combined sample of dwarfs in the Hyades and Praesepe is used to delineate the
Li-dip profile at 0.7 Gyr and [Fe/H] = +0.15, establishing its center at 1.42
+/- 0.02 solar masses and noting the possible existence of secondary dip on its
red boundary. When evolved to the typical age of the clusters NGC 752, IC 4651
and NGC 3680, the Hyades/Praesepe Li-dip profile reproduces the observed
morphology of the combined Li-dip within the CMD's of the intermediate-age
clusters while implying a metallicity dependence for the central mass of the
Li-dip given by Mass = (1.38 +/-0.04) + (0.4 +/- 0.2)[Fe/H]. The implications
of the similarity of the Li-dichotomy among giants in NGC 752 and IC 4651 and
the disagreement with the pattern among NGC 3680 giants are discussed.Comment: Latex ms. is 56 pages, including 10 figures and 4 tables. Accepted
for the Astronomical Journa
Computational molecular characterization of the flavonoid rutin
In this work, we make use of a model chemistry within Density Functional Theory (DFT) recently presented, which is called M05-2X, to calculate the molecular structure of the flavonoid Rutin, as well as to predict the infrared (IR) and ultraviolet (UV-Vis) spectra, the dipole moment and polarizability, the free energy of solvation in different solvents as an indication of solubility, the HOMO and LUMO orbitals, and the chemical reactivity parameters that arise from Conceptual DFT. The calculated values are compared with the available experimental data for this molecule as a means of validation of the used model chemistry
Characterization by XRD and FTIR of Zeolite A and Zeolite X Obtained from Fly Ash
Fly ashes from the fluidized bed boiler were used to obtain zeolites by the alkaline fusion process, followed by a hydrothermal procedure. The melting was carried out with 98 % granulated NaOH, mixed with ashes in mass ratios 1.2/1, 1.4/1 and 1.6/1 and using three melting temperatures, 450 °C, 550 °C and 650 °C. For the crystallization of the zeolites, the hydrothermal procedure at 90 °C was used. The crystalline phases of the zeolitic materials were quantified by XRD analysis. The morphology of the crystals was identified by SEM. The FTIR spectra revealed that the transformation of sodalite mineral to zeolite A and zeolite X increased with the NaOH/CVT ratio and the temperature
Psychomotor control in a virtual laparoscopic surgery training environment: gaze control parameters differentiate novices from experts
Background: Surgical simulation is increasingly used to facilitate the adoption of technical skills during surgical training. This study sought to determine if gaze control parameters could differentiate between the visual control of experienced and novice operators performing an eye-hand coordination task on a virtual reality laparoscopic surgical simulator (LAP Mentor™). Typically adopted hand movement metrics reflect only one half of the eye-hand coordination relationship; therefore, little is known about how hand movements are guided and controlled by vision. Methods: A total of 14 right-handed surgeons were categorised as being either experienced (having led more than 70 laparoscopic procedures) or novice (having performed fewer than 10 procedures) operators. The eight experienced and six novice surgeons completed the eye-hand coordination task from the LAP Mentor basic skills package while wearing a gaze registration system. A variety of performance, movement, and gaze parameters were recorded and compared between groups. Results: The experienced surgeons completed the task significantly more quickly than the novices, but only the economy of movement of the left tool differentiated skill level from the LAP Mentor parameters. Gaze analyses revealed that experienced surgeons spent significantly more time fixating the target locations than novices, who split their time between focusing on the targets and tracking the tools. Conclusion: The findings of the study provide support for the utility of assessing strategic gaze behaviour to better understand the way in which surgeons utilise visual information to plan and control tool movements in a virtual reality laparoscopic environment. It is hoped that by better understanding the limitations of the psychomotor system, effective gaze training programs may be developed. © 2010 The Author(s).published_or_final_versionSpringer Open Choice, 01 Dec 201
Results from the Super Cryogenic Dark Matter Search (SuperCDMS) experiment at Soudan
We report the result of a blinded search for Weakly Interacting Massive
Particles (WIMPs) using the majority of the SuperCDMS Soudan dataset. With an
exposure of 1690 kg days, a single candidate event is observed, consistent with
expected backgrounds. This analysis (combined with previous Ge results) sets an
upper limit on the spin-independent WIMP--nucleon cross section of () cm at 46 GeV/. These results set the
strongest limits for WIMP--germanium-nucleus interactions for masses 12
GeV/
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