892 research outputs found
Four-Parameter white blood cell differential counting based on light scattering measurements
Measurement of the depolarized orthogonal light scattering in flow cytometry enables one to discriminate human eosinephilic granulocytes from neutrophilic granulocytes. We use this method to perform a four-parameter differential white blood cell analysis. \ud
A simple flow cytometer was built equipped with a 5-mW helium neon laser that measures simultaneously four light scattering parameters. Lymphocytes, monocytes, and granulocytes were identified by simultaneously measuring the light scattering intensity at angles between 1.0° and 2.6° and angles between 3.0° and 11.0°. Eosinophilic granulocytes were distinguished from neutrophilic granulocytes by simultaneous measurement of the orthogonal and depolarized orthogonal light scattering. \ud
Comparison of a white blood cell differentiation of 45 donors obtained by the Technicon H-6000 and our instrument revealed good correlations. The correlation coefficients (r2) found were: 0.99 for lymphocytes, 0.76 for monocytes, 0.99 for neutrophilic granulocytes, and 0.98 for eosinophilic granulocytes. The results demonstrate that reliable white blood cell differentiation of the four most clinically relevant leukocytes can be obtained by measurement of light scattering properties of unstained leukocytes
Mass loss out of close binaries. II
Liberal evolution of interacting binaries has been proposed previously by
several authors in order to meet various observed binary characteristics better
than conservative evolution does. Since Algols are eclipsing binaries the
distribution of their orbital periods is precisely known. The distribution of
their mass ratios contains however more uncertainties. We try to reproduce
these two distributions theoretically using a liberal scenario in which the
gainer star can lose mass into interstellar space as a consequence of its rapid
rotation and the energy of a hot spot. In a recent paper (Van Rensbergen et al.
2010, A&A) we calculated the liberal evolution of binaries with a B-type
primary at birth where mass transfer starts during core hydrogen burning of the
donor. In this paper we include the cases where mass transfer starts during
hydrogen shell burning and it is our aim to reproduce the observed
distributions of the system parameters of Algol-type semi-detached systems. Our
calculations reveal the amount of time that an Algol binary lives with a well
defined value of mass ratio and orbital period. We use these data to simulate
the distribution of mass ratios and orbital periods of Algols. Binaries with a
late B-type initial primary hardly lose any mass whereas those with an early B
primary evolve in a non-conservative way. Conservative binary evolution
predicts only ~ 12 % of Algols with a mass ratio q above 0.4. This value is
raised up to ~ 17 % using our scenario of liberal evolution, which is still far
below the ~ 45 % that is observed. Observed orbital periods of Algol binaries
larger than one day are faithfully reproduced by our liberal scenario. Mass
ratios are reproduced better than with conservative evolution, but the
resemblance is still poor.Comment: 11 pages, 6 figures, accepted for publication in A&A; accepted
versio
Wigner crystals in two-dimensional transition-metal dichalcogenides: Spin physics and readout
Wigner crystals are prime candidates for the realization of regular electron
lattices under minimal requirements on external control and electronics.
However, several technical challenges have prevented their detailed
experimental investigation and applications to date. We propose an
implementation of two-dimensional electron lattices for quantum simulation of
Ising spin systems based on self-assembled Wigner crystals in transition-metal
dichalcogenides. We show that these semiconductors allow for minimally invasive
all-optical detection schemes of charge ordering and total spin. For incident
light with optimally chosen beam parameters and polarization, we predict a
strong dependence of the transmitted and reflected signals on the underlying
lattice periodicity, thus revealing the charge order inherent in Wigner
crystals. At the same time, the selection rules in transition-metal
dichalcogenides provide direct access to the spin degree of freedom via Faraday
rotation measurements.Comment: 15 pages, 12 figure
Occurrence and a possible mechanism of penetration of natural killer cells into k562 target cells during the cytotoxic interaction
The cytotoxic interaction between cloned human Natural Killer (NK) cells and K562 target cells was studied using confocal laser scanning microscopy (CLSM) and conventional fluorescence microscopy. We observed, using fixed as well as living cells, the occurrence of (pseudo)emperipolesis during the interaction. About 30% of conjugated NK cells penetrated, partly or completely, into the target cells (in-conjugation). Virtually all in-conjugated target cells exhibited polymerized actin. Killer cells of in-conjugates were frequently seen approaching the target cell nucleus or aligning along it. If the cytotoxic process was inhibited by the absence of calcium neither actin polymerization nor in-conjugation were observed. A kinetic study showed that in-conjugation starts somewhat later than actin polymerization but still within a few minutes after addition of calcium to conjugates previously formed in the absence of calcium. The presence of cytochalasin D (an inhibitor of actin polymerization) completely inhibited in-conjugation and partly reduced the cytotoxic activity. Zinc ions (endonuclease inhibition) inhibited in-conjugation and decreased the total number of target cells with polymerized actin in a concentration dependent manner. Cytotoxic activity was also reduced but not as efficiently as in-conjugation. \ud
Our study demonstrates that in-conjugation represents a significant fraction of the cytotoxic interaction. The results indicate that it may be a consequence of an actin polymerization and endonuclease activity dependent part of a cytotoxic mechanism. \u
Soil organic carbon predictions in Subarctic Greenland by visible–near infrared spectroscopy
Release of carbon from high-latitude soils to the atmosphere may have significant effects on Earth’s climate. In this contribution, we evaluate visible–near-infrared spectroscopy (vis-NIRS) as a time- and cost-efficient tool for assessing soil organic carbon (SOC) concentrations in South Greenland. Soil samples were collected at two sites and analyzed with vis-NIRS. We used partial least square regression (PLS-R) modeling to predict SOC from vis-NIRS spectra referenced against in situ dry combustion measurements. The ability of our approach was validated in three setups: (1) calibration and validation data sets from the same location, (2) calibration and validation data sets from different locations, and (3) the same setup as in (2) with the calibration model enlarged with few samples from the opposite target area. Vis-NIRS predictions were successful in setup 1 (R2 = 0.95, root mean square error of prediction [RMSEP] = 1.80 percent and R2 = 0.82, RMSEP = 0.64 percent). Predictions in setup 2 had higher errors (R2 = 0.90, RMSEP = 7.13 percent and R2 = 0.78, RMSEP = 2.82 percent). In setup 3, the results were again improved (R2 = 0.95, RMSEP = 2.03 percent and R2 = 0.77, RMSEP = 2.14 percent). We conclude that vis-NIRS can obtain good results predicting SOC concentrations across two subarctic ecosystems, when the calibration models are augmented with few samples from the target site. Future efforts should be made toward determination of SOC stocks to constrain soil–atmosphere carbon exchange
Mass loss out of close binaries
In a liberal evolutionary scenario, mass can escape from a binary during eras
of fast mass transfer. We calculate the mass lost by binaries with a B-type
primary at birth where mass transfer starts during hydrogen core burning of the
donor. We simulate the distribution of mass-ratios and orbital periods for
those interacting binaries. The amount of time the binary shows Algol
characteristics within different values of mass-ratio and orbital period has
been fixed from conservative and liberal evolutionary calculations. We use
these data to simulate the distribution of mass-ratios and orbital periods of
Algols with the conservative as well as the liberal model. We compare
mass-ratios and orbital periods of Algols obtained by conservative evolution
with those obtained by our liberal model. Since binaries with a late B-type
primary evolve almost conservatively, the overall distribution of mass-ratios
will only yield a few Algols more with high mass-ratios than conservative
calculations do. Whereas the simulated distribution of orbital periods of
Algols fits the observations well, the simulated distribution of mass-ratios
produces always too few systems with large values.Comment: 6 pages, 6 figures, accepted for publication in A&A; accepted versio
Towards Quantum Repeaters with Solid-State Qubits: Spin-Photon Entanglement Generation using Self-Assembled Quantum Dots
In this chapter we review the use of spins in optically-active InAs quantum
dots as the key physical building block for constructing a quantum repeater,
with a particular focus on recent results demonstrating entanglement between a
quantum memory (electron spin qubit) and a flying qubit (polarization- or
frequency-encoded photonic qubit). This is a first step towards demonstrating
entanglement between distant quantum memories (realized with quantum dots),
which in turn is a milestone in the roadmap for building a functional quantum
repeater. We also place this experimental work in context by providing an
overview of quantum repeaters, their potential uses, and the challenges in
implementing them.Comment: 51 pages. Expanded version of a chapter to appear in "Engineering the
Atom-Photon Interaction" (Springer-Verlag, 2015; eds. A. Predojevic and M. W.
Mitchell
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