4,211 research outputs found
Focusing and imaging with increased numerical apertures through multimode fibers with micro-fabricated optics
The use of individual multimode optical fibers in endoscopy applications has
the potential to provide highly miniaturized and noninvasive probes for
microscopy and optical micromanipulation. A few different strategies have been
proposed recently, but they all suffer from intrinsically low resolution
related to the low numerical aperture of multimode fibers. Here, we show that
two-photon polymerization allows for direct fabrication of micro-optics
components on the fiber end, resulting in an increase of the numerical aperture
to a value that is close to 1. Coupling light into the fiber through a spatial
light modulator, we were able to optically scan a submicrometer spot (300 nm
FWHM) over an extended region, facing the opposite fiber end. Fluorescence
imaging with improved resolution is also demonstrated.Comment: 5 pages, 3 figure
The old anticentre open cluster Berkeley 32: membership and fundamental parameters
We have obtained medium-low resolution spectroscopy and BVI CCD imaging of
Berkeley 32, an old open cluster which lies in the anticentre direction. From
the radial velocities of 48 stars in the cluster direction we found that 31 of
them, in crucial evolutionary phases, are probable cluster members, with an
average radial velocity of +106.7 (sigma = 8.5) km/s. From isochrone fitting to
the colour magnitude diagrams of Berkeley 32 we have obtained an age of 6.3
Gyr, (m-M)0 = 12.48 and E(B-V) = 0.10. The best fit is obtained with Z=0.008. A
consistent distance, (m-M)0 ~= 12.6 +/- 0.1, has been derived from the mean
magnitude of red clump stars with confirmed membership; we may assume (m-M)0 ~=
12.55 +/- 0.1. The colour magnitude diagram of the nearby field observed to
check for field stars contamination looks intriguingly similar to that of the
Canis Major overdensity.Comment: MNRAS, in press. Degraded resolution for Fig.
Optical pulsations from a transitional millisecond pulsar
Weakly magnetic, millisecond spinning neutron stars attain their very fast
rotation through a 1E8-1E9 yr long phase during which they undergo
disk-accretion of matter from a low mass companion star. They can be detected
as accretion-powered millisecond X-ray pulsars if towards the end of this phase
their magnetic field is still strong enough to channel the accreting matter
towards the magnetic poles. When mass transfer is much reduced or ceases
altogether, pulsed emission generated by particle acceleration in the
magnetosphere and powered by the rotation of the neutron star is observed,
preferentially in the radio and gamma-ray bands. A few transitional millisecond
pulsars that swing between an accretion-powered X-ray pulsar regime and a
rotationally-powered radio pulsar regime in response to variations of the mass
in-flow rate have been recently identified. Here we report the detection of
optical pulsations from a transitional pulsar, the first ever from a
millisecond spinning neutron star. The pulsations were observed when the pulsar
was surrounded by an accretion disk and originated inside the magnetosphere or
within a few hundreds of kilometres from it. Energy arguments rule out
reprocessing of accretion-powered X-ray emission and argue against a process
related to accretion onto the pulsar polar caps; synchrotron emission of
electrons in a rotation-powered pulsar magnetosphere seems more likely.Comment: 32 pages, 7 figures. The first two authors contributed equally to
this wor
The influence of a new clinical motion for endodontic instruments on the incidence of postoperative pain
Previous studies showed that motor motions play an important role in determining apical extrusion of debris. Therefore a new clinical motion (MIMERACI) has been proposed. The basic idea is to progress slowly (1mm advancement), and after each 1mm, to remove the instrument from the canal, clean flutes and irrigate. The aim of the study was to prove whether the clinical use of MIMERACI technique would influence or not postoperative pain.MATERIALS AND METHODS:
100 teeth requesting endodontic treatment were selected for the study and divided into two similar groups based on anatomy, pre-operative symptoms and vitality, presence or absence of periapical lesion. All teeth were shaped, cleaned and obturated by the same operator, using the same NiTi instruments. The only difference between the two groups was the instrumentation technique: tradional (group A) vs MIMERACI (group B). Assessment of postoperative pain was performed 3 days after treatment. Presence, absence and degree of pain were recorded with a visual analogue scale (VAS), validated in previous studies. Collected data statistically analyzed using one-way ANOVA post hoc Tukey test.
RESULTS:
For VAS pain scores MIMERACI technique showed significantly better results than group A (p=0,031). Overall, both incidence and intensity of symptoms were significantly lower. Flare ups occurred in 3 patients, but none treated with the MIMERACI Technique.
CONCLUSIONS:
Since extruded debris can elicit more postoperative pain, results obtained by using MIMERACI technique are probably due to many factors: better mechanical removal and less production of debris and more efficient irrigation during instrumentation
Near Infrared Spectroscopy of High Redshift Active Galactic Nuclei. II. Disappearing Narrow Line Regions and the Role of Accretion
We present new near infrared spectroscopic measurements for 29 luminous
high-z quasars and use the data to discuss the size and other properties of the
NLRs in those sources. The high resolution spectra have been used to carefully
model the Fe II blends and to provide reliable [O III], Fe II and Hb
measurements. We find that about 2/3 of all high luminosity sources show strong
[O III] lines while the remaining objects show no or very weak such line. While
weak [O III] emitters are also found among lower luminosity AGN, we argue that
the implications for very high luminosity objects are different. In particular,
we suggest that the averaging of these two populations in other works gave rise
to claims of a Baldwin relationship in [O III] which is not confirmed by our
data. We also argue that earlier proposed relations of the type R_NLR \propto
L_[O III]^{1/2}, where R_NLR is the NLR radius, are theoretically sound yet
they must break down for R_NLR exceeding a few kpc. This suggests that the NLR
properties in luminous sources are different from those observed in nearby AGN.
In particular, we suggest that some sources lost their very large, dynamically
unbound NLR while others are in a phase of violent star-forming events that
produce a large quantity of high density gas in the central kpc. This gas is
ionized and excited by the central radiation source and its spectroscopic
properties may be different from those observed in nearby, lower luminosity
NLRs. We also discuss the dependence of EW(Hb) and Fe II/Hb on L, M_BH, and
accretion rate for a large sample of AGNs. The strongest dependence of the two
quantities is on the accretion rate and the Fe II/Hb correlation is probably
due to the EW(Hb) dependence on accretion rate. We show the most extreme values
measured so far of Fe II/Hb and address its correlation with EW([O III]).Comment: 10 pages (emulateapj), 9 figures. Accepted by Ap
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