5,355 research outputs found
The Black Hole Mass - Galaxy Bulge Relationship for QSOs in the SDSS DR3
We investigate the relationship between black hole mass and host galaxy
velocity dispersion for QSOs in Data Release 3 of the Sloan Digital Sky Survey.
We derive black hole mass from the broad Hbeta line width and continuum
luminosity, and the bulge stellar velocity dispersion from the [OIII] narrow
line width. At higher redshifts, we use MgII and [OII] in place of Hbeta and
[OIII]. For redshifts z < 0.5, our results agree with the black hole mass -
bulge velocity dispersion relationship for nearby galaxies. For 0.5 < z < 1.2,
this relationship appears to show evolution with redshift in the sense that the
bulges are too small for their black holes. However, we find that part of this
apparent trend can be attributed to observational biases, including a Malmquist
bias involving the QSO luminosity. Accounting for these biases, we find ~0.2
dex evolution in the black hole mass-bulge velocity dispersion relationship
between now and redshift z ~ 1.Comment: Accepted by ApJ, 15 pages, 9 figure
A Tissue Displacement-based Contusive Spinal Cord Injury Model in Mice
Producing a consistent and reproducible contusive spinal cord injury (SCI) is critical to minimizing behavioral and histological variabilities between experimental animals. Several contusive SCI models have been developed to produce injuries using different mechanisms. The severity of the SCI is based on the height that a given weight is dropped, the injury force, or the spinal cord displacement. In the current study, we introduce a novel mouse contusive SCI device, the Louisville Injury System Apparatus (LISA) impactor, which can create a displacement-based SCI with high injury velocity and accuracy. This system utilizes laser distance sensors combined with advanced software to produce graded and highly-reproducible injuries. We performed a contusive SCI at the 10th thoracic vertebral (T10) level in mice to demonstrate the step-by-step procedure. The model can also be applied to the cervical and lumbar spinal levels
High speed single photon detection in the near-infrared
InGaAs avalanche photodiodes (APDs) are convenient for single photon
detection in the near-infrared (NIR) including the fibre communication bands
(1.31/1.55 m). However, to suppress afterpulse noise due to trapped
avalanche charge, they must be gated with MHz repetition frequencies, thereby
severely limiting the count rate in NIR applications. Here we show gating
frequencies for InGaAs-APDs well beyond 1 GHz. Using a self-differencing
technique to sense much weaker avalanches, we reduce drastically afterpulse
noise. At 1.25 GHz, we obtain a detection efficiency of 10.8% with an
afterpulse probability of 6.16%. In addition, the detector features low jitter
(55 ps) and a count rate of 100 MHz
A Novel Vertebral Stabilization Method for Producing Contusive Spinal Cord Injury
Clinically-relevant animal cervical spinal cord injury (SCI) models are essential for developing and testing potential therapies; however, producing reliable cervical SCI is difficult due to lack of satisfactory methods of vertebral stabilization. The conventional method to stabilize the spine is to suspend the rostral and caudal cervical spine via clamps attached to cervical spinous processes. However, this method of stabilization fails to prevent tissue yielding during the contusion as the cervical spinal processes are too short to be effectively secured by the clamps (Figure 1). Here we introduce a new method to completely stabilize the cervical vertebra at the same level of the impact injury. This method effectively minimizes movement of the spinal column at the site of impact, which greatly improves the production of consistent SCIs. We provide visual description of the equipment (Figure 2-4), methods, and a step-by-step protocol for the stabilization of the cervical 5 vertebra (C5) of adult rats, to perform laminectomy (Figure 5) and produce a contusive SCI thereafter. Although we only demonstrate a cervical hemi-contusion using the NYU/MASCIS impactor device, this vertebral stabilization technique can be applied to other regions of the spinal cord, or be adapted to other SCI devices. Improving spinal cord exposure and fixation through vertebral stabilization may be valuable for producing consistent and reliable injuries to the spinal cord. This vertebral stabilization method can also be used for stereotactic injections of cells and tracers, and for imaging using two-photon microscopy in various neurobiological studies
Happiness and the Human Development Index : the paradox of Australia
According to the well-being measure known as the U.N. Human
Development Index, Australia now ranks 3rd in the world and higher than all other English-speaking nations. This paper questions that assessment. It reviews work on the economics of happiness, considers implications for policymakers, and explores where Australia lies in international subjective
well-being rankings. Using new data on approximately 50,000 randomly sampled individuals from 35 nations, the paper shows that Australians have some of the lowest levels of job satisfaction in the world. Moreover, among the sub-sample of English-speaking nations, where a common language
should help subjective measures to be reliable, Australia performs poorly on a range of happiness indicators. The paper discusses this paradox. Our purpose is not to reject HDI methods, but rather to argue that much remains
to be understood in this area
The SPICE carbon isotope excursion in Siberia: a combined study of the upper Middle Cambrian-lowermost Ordovician Kulyumbe River section, northwestern Siberian Platform
An integrated, high-resolution chemostratigraphic (C, O and Sr isotopes) and
magnetostratigraphic study through the upper Middle Cambrianâlowermost Ordovician shallowmarine
carbonates of the northwestern margin of the Siberian Platform is reported. The interval was
analysed at the Kulyumbe section, which is exposed along the Kulyumbe River, an eastern tributary
of the Enisej River. It comprises the upper Ustâ-Brus, Labaz, Orakta, Kulyumbe, Ujgur and lower
Iltyk formations and includes the Steptoean positive carbon isotopic excursion (SPICE) studied here
in detail from upper Cambrian carbonates of the Siberian Platform for the first time. The peak of the
excursion, showing ÎŽ13C positive values as high as+4.6â°and least-altered 87Sr/86Sr ratios of 0.70909,
is reported herein from the Yurakhian Horizon of the Kulyumbe Formation. The stratigraphic position
of the SPICE excursion does not support traditional correlation of the boundary between theOrakta and
Labaz formations at the Kulyumbe River with its supposedly equivalent level in Australia, Laurentia,
South China and Kazakhstan, where the Glyptagnostus stolidotus and G. reticulatus biozones are
known to immediately precede the SPICE excursion and span the MiddleâUpper Cambrian boundary.
The CambrianâOrdovician boundary is probably situated in the middle Nyajan Horizon of the Iltyk
Formation, in which carbon isotope values show a local maximum below a decrease in the upper
part of the Nyajan Horizon, attributed herein to the Tremadocian Stage. A refined magnetic polarity
sequence confirms that the geomagnetic reversal frequency was very high during Middle Cambrian
times at 7â10 reversals per Ma, assuming a total duration of about 10 Ma and up to 100 magnetic
intervals in the Middle Cambrian. By contrast, the sequence attributed herein to the Upper Cambrian
on chemostratigraphic grounds contains only 10â11 magnetic intervals
Magnetic field dependence of the energy of negatively charged excitons in semiconductor quantum wells
A variational calculation of the spin-singlet and spin-triplet state of a
negatively charged exciton (trion) confined to a single quantum well and in the
presence of a perpendicular magnetic field is presented. We calculated the
probability density and the pair correlation function of the singlet and
triplet trion states. The dependence of the energy levels and of the binding
energy on the well width and on the magnetic field strength was investigated.
We compared our results with the available experimental data on GaAs/AlGaAs
quantum wells and find that in the low magnetic field region (B<18 T) the
observed transition are those of the singlet and the dark triplet trion (with
angular momentum ), while for high magnetic fields (B>25 T) the dark
trion becomes optically inactive and possibly a transition to a bright triplet
trion (angular momentum ) state is observed.Comment: 9 pages, 10 figures submitted to Phys. Rev.
Surface acoustic wave-induced electroluminescence intensity oscillation in planar light-emitting devices
Electroluminescence emission from surface acoustic wave-driven light-emitting
diodes (SAWLEDs) is studied by means of time-resolved techniques. We show that
the intensity of the SAW-induced electroluminescence is modulated at the SAW
frequency (~1 GHz), demonstrating electron injection into the p-type region
synchronous with the SAW wavefronts.Comment: 4 pages, 3 figure
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