352 research outputs found
Comparative analysis of behavioral and transcriptional variation underlying CO2 sensory neuron function and development in Drosophila
Carbon dioxide is an important environmental cue for many insects, regulating many behaviors including some that have direct human impacts. To further improve our understanding of how this system varies among closely related insect species, we examined both the behavioral response to CO2 as well as the transcriptional profile of key developmental regulators of CO2 sensory neurons in the olfactory system across the Drosophila genus. We found that CO2 generally evokes repulsive behavior across most of the Drosophilids we examined, but this behavior has been lost or reduced in several lineages. Comparisons of transcriptional profiles from the developing and adult antennae for subset these species suggest that behavioral differences in some species may be due to differences in the expression of the CO2 co-receptor Gr63a. Furthermore, these differences in Gr63a expression are correlated with changes in the expression of a few genes known to be involved in the development of the CO2 circuit, namely dac, an important regulator of sensilla fate for sensilla that house CO2 ORNs, and mip120, a member of the MMB/dREAM epigenetic regulatory complex that regulates CO2 receptor expression. In contrast, most of the other known structural, molecular, and developmental components of the peripheral Drosophila CO2 olfactory system seem to be well-conserved across all examined lineages. These findings suggest that certain components of CO2 sensory ORN development may be more evolutionarily labile, and may contribute to differences in CO2-evoked behavioral responses across species
Synthesis effects on the magnetic and superconducting properties of RuSr2GdCu2O8
A systematic study on the synthesis of the Ru-1212 compound by preparing a
series of samples that were annealed at increasing temperatures and then
quenched has been performed. It results that the optimal temperature for the
annealing lies around 1060-1065 C; a further temperature increase worsens the
phase formation. Structural order is very important and the subsequent grinding
and annealing improves it. Even if from the structural point of view the
samples appear substantially similar, the physical characterization highlight
great differences both in the electrical and magnetic properties related to
intrinsic properties of the phase as well as to the connection between the
grains as inferred from the resistive and the Curie Weiss behaviour at high
temperature as well as in the visibility of ZFC anf FC magnetic signals.Comment: 17 pages, 12 figures. Proc. Int. Workshop " Ruthenate and
rutheno-cuprate materials: theory and experiments", Vietri, October 2001. To
be published on LNP Series, Springer Verlag, Berlin, C. Noce, A. Vecchione,
M. Cuoco, A. Romano Eds, 200
Review article: MHD wave propagation near coronal null points of magnetic fields
We present a comprehensive review of MHD wave behaviour in the neighbourhood
of coronal null points: locations where the magnetic field, and hence the local
Alfven speed, is zero. The behaviour of all three MHD wave modes, i.e. the
Alfven wave and the fast and slow magnetoacoustic waves, has been investigated
in the neighbourhood of 2D, 2.5D and (to a certain extent) 3D magnetic null
points, for a variety of assumptions, configurations and geometries. In
general, it is found that the fast magnetoacoustic wave behaviour is dictated
by the Alfven-speed profile. In a plasma, the fast wave is focused
towards the null point by a refraction effect and all the wave energy, and thus
current density, accumulates close to the null point. Thus, null points will be
locations for preferential heating by fast waves. Independently, the Alfven
wave is found to propagate along magnetic fieldlines and is confined to the
fieldlines it is generated on. As the wave approaches the null point, it
spreads out due to the diverging fieldlines. Eventually, the Alfven wave
accumulates along the separatrices (in 2D) or along the spine or fan-plane (in
3D). Hence, Alfven wave energy will be preferentially dissipated at these
locations. It is clear that the magnetic field plays a fundamental role in the
propagation and properties of MHD waves in the neighbourhood of coronal null
points. This topic is a fundamental plasma process and results so far have also
lead to critical insights into reconnection, mode-coupling, quasi-periodic
pulsations and phase-mixing.Comment: 34 pages, 5 figures, invited review in Space Science Reviews => Note
this is a 2011 paper, not a 2010 pape
Phonon anomalies and electron-phonon interaction in RuSr_2GdCu_2O_8 ferromagnetic superconductor: Evidence from infrared conductivity
Critical behavior of the infrared reflectivity of RuSr_2GdCu_2O_8 ceramics is
observed near the superconducting T_{SC} = 45 K and magnetic T_M = 133 K
transition temperatures. The optical conductivity reveals the typical features
of the c-axis optical conductivity of strongly underdoped multilayer
superconducting cuprates. The transformation of the Cu-O bending mode at 288
cm^{-1} to a broad absorption peak at the temperatures between T^* = 90 K and
T_{SC} is clearly observed, and is accompanied by the suppression of spectral
weight at low frequencies. The correlated shifts to lower frequencies of the
Ru-related phonon mode at 190 cm^{-1} and the mid-IR band at 4800 cm^{-1} on
decreasing temperature below T_M are observed. It provides experimental
evidence in favor of strong electron-phonon coupling of the charge carriers in
the Ru-O layers which critically depends on the Ru core spin alignment. The
underdoped character of the superconductor is explained by strong hole
depletion of the CuO_2 planes caused by the charge carrier self-trapping at the
Ru moments.Comment: 11 pages incl. 5 figures, submitted to PR
Design of an enquiry-based âPractical Onlyâ course for the teaching of basis skills in first year Biology
First year Biology teaching at the Callaghan Campus of the University of Newcastle has undergone a significant reorganisation in 2006. The rearrangement was conducted with the aims of increasing flexible delivery, improving student learning, reducing overall teaching effort, targeting teaching effort to biology majors and standardising course delivery throughout the university campuses. Key to the reorganisation has been the separation of the practical and lecture components of first year into distinctly separate courses. The practical course runs only in semester 2 and is compulsory for students that intend to graduate with a major in biology. Students that do not intend to continue their biology studies past 1st year are not required nor expected to enrol in the course.
Separation of the courses has allowed a renewed focus on basis skills including laboratory and field techniques, the scientific method and practice, report writing and personal interaction. In this paper we present the design of this practical course and explain the process and logic we have used in its construction. Skill acquisition is situated in authentic learning contexts, employing the University campus as a unifying theme. Through an enquiry- based approach, students learn how to think as scientists, posing and testing questions rather than âdoing the experimentâ. The process of building and reinforcing skills (scaffolded learning) and the use of assessment & peer interaction to facilitate the learning process is discussed
Ruthenocuprates RuSr2(Eu,Ce)2Cu2O10: Intrinsic magnetic multilayers
We report ac susceptibility data on RuSr_2(Eu,Ce)_2Cu_2O_(10-y) (Ru-1222, Ce
content x=0.5 and 1.0), RuSr_2GdCu_2O_8 (Ru-1212) and SrRuO_3. Both Ru-1222
(x=0.5, 1.0) sample types exhibit unexpected magnetic dynamics in low magnetic
fields: logarithmic time relaxation, switching behavior, and `inverted'
hysteresis loops. Neither Ru-1212 nor SrRuO_3 exhibit such magnetic dynamics.
The results are interpreted as evidence of the complex magnetic order in
Ru-1222. We propose a specific multilayer model to explain the data, and note
that superconductivity in the ruthenocuprate is compatible with both the
presence and absence of the magnetic dynamics.Comment: 9 pages, 11 figures, Revtex; submitted to Phys.Rev.
Superconducting properties of RuSr2GdCu2O8 studied by SQUID magnetometry
For polycrystalline RuSr2GdCu2O8 (Ru-1212), distinct peaks have been reported
in d.c. magnetization in the superconducting state of the sample. Sr2GdRuO6
(Sr-2116), the precursor for the preparation of Ru-1212, shows similar peaks in
the same temperature regime. Based on measurements performed on both bulk and
powdered samples of Ru-1212 and Sr-2116, we exclude the possibility, that the
observed behavior of the magnetization of Ru-1212 is due to Sr-2116 impurities.
The effect is related to the superconductivity of Ru-1212, but it is not an
intrinsic property of this compound. We provide evidence that the observation
of magnetization peaks in the superconducting state of Ru-1212 is due to flux
motion generated by the movement of the sample in an inhomogeneous field,
during the measurement in the SQUID magnetometer. We propose several tests,
that help to decide, whether the features observed in a SQUID magnetization
measurement of Ru-1212 represent a property of the compound or not.Comment: 22 pages, 9 figure
X-Ray and Radio Observations of Bright GeV Sources
We present X-ray and radio studies of sources which are brightabove 1 GeV
(F_{>1GeV} > 4e-8 ph/cm^2/s. Only 11 out of ~30 of these gamma-ray sources have
been identified with lower energy counterparts: 5 blazars and 6 pulsars. Three
of these pulsars are surrounded by radio pulsar wind nebulae (PWN), two of
which are also seen as bright, extended X-ray synchrotron nebulae. The ASCA
X-ray telescope has observed 28 of the bright GeV sources, revealing an excess
of F_{2-10keV} > 10e-12 ergs/cm^2/s sources within the {\it EGRET} error
contours of the unidentified sources. Although several supernova remnants are
positionally coincident with these sources, we find no X-ray evidence of high
energy particle production in SNR shell shocks consistent with the GeV
positions. We also present initial results from follow on radio imaging studies
of several fields containing unidentified sources. We have discovered new
X-ray/radio nebulae in three of these fields which are strong candidates for
PWN. These sources, along with a similar nebula in CTA 1 and the PWN around PSR
B1853+01 in W44, are all positionally coincident with variable EGRET sources.
This suggests a class of variable gamma-ray sources associated with synchrotron
emitting regions powered by the winds of young pulsars.Comment: 18 pages, 26 figures, To appear in the proceedings of the workshop:
"The Nature of the Unidentified Galactic Gamma-Ray Sources" held at INAOE,
Mexico, October 2000, (A.Carraminana, O. Reiner and D. Thompson,
The Number Of Magnetic Null Points In The Quiet Sun Corona
The coronal magnetic field above a particular photospheric region will vanish
at a certain number of points, called null points. These points can be found
directly in a potential field extrapolation or their density can be estimated
from Fourier spectrum of the magnetogram. The spectral estimate, which assumes
that the extrapolated field is random, homogeneous and has Gaussian statistics,
is found here to be relatively accurate for quiet Sun magnetograms from SOHO's
MDI. The majority of null points occur at low altitudes, and their distribution
is dictated by high wavenumbers in the Fourier spectrum. This portion of the
spectrum is affected by Poisson noise, and as many as five-sixths of null
points identified from a direct extrapolation can be attributed to noise. The
null distribution above 1500 km is found to depend on wavelengths that are
reliably measured by MDI in either its low-resolution or high-resolution mode.
After correcting the spectrum to remove white noise and compensate for the
modulation transfer function we find that a potential field extrapolation
contains, on average, one magnetic null point, with altitude greater than 1.5
Mm, above every 322 square Mm patch of quiet Sun. Analysis of 562 quiet Sun
magnetograms spanning the two latest solar minimum shows that the null point
density is relatively constant with roughly 10% day-to-day variation. At
heights above 1.5 Mm, the null point density decreases approximately as the
inverse cube of height. The photospheric field in the quiet Sun is well
approximated as that from discrete elements with mean flux 1.0e19 Mx
distributed randomly with density n=0.007 per square Mm
3D-printed micro lens-in-lens for in vivo multimodal microendoscopy
Published online: March 1, 2022Multimodal microendoscopes enable co-located structural and molecular measurements in vivo, thus providing useful insights into the pathological changes associated with disease. However, different optical imaging modalities often have conflicting optical requirements for optimal lens design. For example, a high numerical aperture (NA) lens is needed to realize high-sensitivity fluorescence measurements. In contrast, optical coherence tomography (OCT) demands a low NA to achieve a large depth of focus. These competing requirements present a significant challenge in the design and fabrication of miniaturized imaging probes that are capable of supporting high-quality multiple modalities simultaneously. An optical design is demonstrated which uses two-photon 3D printing to create a miniaturized lens that is simultaneously optimized for these conflicting imaging modalities. The lens-in-lens design contains distinct but connected optical surfaces that separately address the needs of both fluorescence and OCT imaging within a lens of 330 ”m diameter. This design shows an improvement in fluorescence sensitivity of >10x in contrast to more conventional fiber-optic design approaches. This lens-in-lens is then integrated into an intravascular catheter probe with a diameter of 520 ”m. The first simultaneous intravascular OCT and fluorescence imaging of a mouse artery in vivo is reported.Jiawen Li, Simon Thiele, Rodney W. Kirk, Bryden C. Quirk, Ayla Hoogendoorn, Yung Chih Chen, Karlheinz Peter, Stephen J. Nicholls, Johan W. Verjans, Peter J. Psaltis, Christina Bursill, Alois M. Herkommer, Harald Giessen, and Robert A. McLaughli
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