887 research outputs found
Regulation of the neuronal proteasome by Zif268 (Egr1)
Most forms of neuronal plasticity are associated with induction of the transcription factor Zif268 (Egr1/Krox24/NGF-IA). In a genomewide
scan, we obtained evidence for potential modulation of proteasome subunit and regulatory genes by Zif268 in neurons, a finding of
significance considering emerging evidence that the proteasome modulates synaptic function. Bioinformatic analysis indicated that the
candidate proteasome Zif268 target genes had a rich concentration of putative Zif268 binding sites immediately upstream of the transcriptional
start sites. Regulation of the mRNAs encoding the psmb9 (Lmp2) and psme2 (PA28�) proteasome subunits, along with the
proteasome-regulatory kinase serum/glucocorticoid-regulated kinase (SGK) and the proteasome-associated antigen peptide transporter
subunit 1 (Tap1), was confirmed after transfection of a neuronal cell line with Zif268. Conversely, these mRNAs were upregulated in
cerebral cortex tissue from Zif268 knock-out mice relative to controls, confirming that Zif268 suppresses their expression in the CNS.
Transfected Zif268 reduced the activity of psmb9, SGK, and Tap1 promoter–reporter constructs. Altered psmb9, SGK, and Tap1 mRNA
levels were also observed in an in vivo model of neuronal plasticity involving Zif268 induction: the effect of haloperidol administration on
striatal gene expression. Consistent with these effects on proteasome gene expression, increased Zif268 expression suppressed proteasome
activity, whereas Zif268 knock-out mice exhibited elevated cortical proteasome activity. Our findings reveal that Zif268 regulates
the expression of proteasome and related genes in neuronal cells and provide new evidence that altered expression of proteasome activity
after Zif268 induction may be a key component of long-lasting CNS plasticity
Characterizing phosphorus forms in Saskatchewan soils using solution 31P NMR spectroscopy
Non-Peer ReviewedIn soils and other environmental samples, phosphorus (P) may be found in a range of inorganic
and organic forms. Inorganic P forms include orthophosphate, which is readily available to
plants, and complex inorganic P forms such as pyrophosphate and polyphosphate. Organic P
forms can be divided into groups such as orthophosphate monoesters (e.g. sugar phosphates,
phytic acid) and orthophosphate diesters (e.g. phospholipids, DNA) and phosphonates.
Identifying P forms is important to enhance crop growth, with and without fertilization, and to
minimize P loss to water, where it can cause harmful algal blooms. This presentation describes
some of our recent research using solution 31P NMR spectroscopy to characterize P forms in a
range of Saskatchewan soils, as well as swine manure
Wavelength dependent collective effects in the multiphoton ionization of atomic deuterium
This paper presents the results of an experimental investigation into collective effects in the transient plasma
formed by multiphoton ionization of atomic deuterium with a pulsed laser. The laser wavelength is varied in a
narrow range around 243 nm, so that the photoionization is resonant with the metastable 2S1/2 state. The ion
yield, the ion time-of-flight spectra, and the yield of Lyman-a photons have been measured as a function of
laser intensity ~from 1 to 340 MW/cm2! and laser detuning around the 1S1/2-2S1/2 two-photon resonance.
During and shortly after the laser pulse, collective effects resulting from the mutual interaction of the photoelectrons
and the ions affect the spatial and temporal distribution of the ions. Because of the near-degeneracy
of the 2S1/2, 2P1/2 , and 2P3/2 states, the resonant multiphoton ionization is affected by the Stark mixing of
these states in the collective field. As a result, the time-dependent yields of ions and of Lyman-a photons are
modulated by the interplay of the multiphoton ionization of the atoms and the collective effects in the plasma.
From the measurements it is deduced that collective effects are important above a critical charge density of
33108 ions/cm3. An asymmetry is observed in the line profile of the total ion yield as a function of laser
detuning. This asymmetry is interpreted to be due to the effect of the collective field upon the intermediate
resonant 2S1/2 state of the photoionization process
Vortex Matter in Mesoscopic Superconducting Disks and Rings
Phase transitions between different (i.e. giant and multi-vortex)
superconducting states and between the superconducting-normal state of
mesoscopic disks and rings are studied in the presence of an external magnetic
field by solving the two non-linear Ginzburg-Landau equations
self-consistently. The flux through a circular disk with a hole in the middle
is not quantized.Comment: 8 pages, 10 figures; to appear in Physica C (proceedings of the
conference on Vortex matter, Crete (september 1999
Wavelength dependent collective effects in the multiphoton ionization of atomic deuterium
This paper presents the results of an experimental investigation into collective effects in the transient plasma
formed by multiphoton ionization of atomic deuterium with a pulsed laser. The laser wavelength is varied in a
narrow range around 243 nm, so that the photoionization is resonant with the metastable 2S1/2 state. The ion
yield, the ion time-of-flight spectra, and the yield of Lyman-a photons have been measured as a function of
laser intensity ~from 1 to 340 MW/cm2! and laser detuning around the 1S1/2-2S1/2 two-photon resonance.
During and shortly after the laser pulse, collective effects resulting from the mutual interaction of the photoelectrons
and the ions affect the spatial and temporal distribution of the ions. Because of the near-degeneracy
of the 2S1/2, 2P1/2 , and 2P3/2 states, the resonant multiphoton ionization is affected by the Stark mixing of
these states in the collective field. As a result, the time-dependent yields of ions and of Lyman-a photons are
modulated by the interplay of the multiphoton ionization of the atoms and the collective effects in the plasma.
From the measurements it is deduced that collective effects are important above a critical charge density of
33108 ions/cm3. An asymmetry is observed in the line profile of the total ion yield as a function of laser
detuning. This asymmetry is interpreted to be due to the effect of the collective field upon the intermediate
resonant 2S1/2 state of the photoionization process
Restricted three body problems at the nanoscale
In this paper, we investigate some of the classical restricted three body
problems at the nanoscale, such as the circular planar restricted problem for
three C60 fullerenes, and a carbon atom and two C60 fullerenes. We model the
van der Waals forces between the fullerenes by the Lennard-Jones potential. In
particular, the pairwise potential energies between the carbon atoms on the
fullerenes are approximated by the continuous approach, so that the total
molecular energy between two fullerenes can be determined analytically. Since
we assume that such interactions between the molecules occur at sufficiently
large distance, the classical three body problems analysis is legitimate to
determine the collective angular velocity of the two and three C60 fullerenes
at the nanoscale. We find that the maximum angular frequency of the two and
three fullerenes systems reach the terahertz range and we determine the
stationary points and the points which have maximum velocity for the carbon
atom for the carbon atom and the two fullerenes system
Flux transitions in a superconducting ring
We perform a numeric study of the flux transitions in a superconducting ring
at fixed temperature, while the applied field is swept at an ideally slow rate.
The current around the ring and its free energy are evaluated. We partially
explain some of the known experimental features, and predict a considerably
large new feature: in the vicinity of a critical field, giant jumps are
expected
Competition between electronic cooling and Andreev dissipation in a superconducting micro-cooler
We discuss very low temperature experiments on superconducting micro-coolers
made of a double Normal metal - Insulator - Superconductor junction. We
investigate with a high resolution the differential conductance of the
micro-cooler as well as of additional probe junctions. There is an explicit
crossover between the single quasi-particle current and the phase-coherent
Andreev current. We establish a thermal model by considering the thermal
contribution due to the Andreev current. The related increase of the electron
temperature is discussed, including the influence of several parameters like
the phase-coherence length or the tunnel junction transparency
- …