222 research outputs found
Generation of Dicke states using adiabatic passage
Entangled states of two ions are realized by using an adiabatic process.
Based on the proposal by Linington and Vitanov, we have generated Dicke states
in optical qubits of two Ca ions by applying frequency-chirped
optical pulses with time-dependent envelopes to perform rapid adiabatic passage
on sideband transitions. One of the biggest advantages of adiabatic approaches
is their robustness against variations in experimental parameters, which is
verified by performing experiments for different pulse widths or peak Rabi
frequencies. Fidelities exceeding 0.5, which is the threshold for inseparable
states, are obtained over wide ranges of parameter values
High contrast experiment of an AO-free coronagraph with a checkerboard pupil mask
A high contrast coronagraph is expected to provide one of the promising ways
to directly observe extra-solar planets. We present the newest results of our
laboratory experiment investigating "rigid" coronagraph with a binary shaped
checkerboard pupil mask, which should offer a highly stable solution for
telescopes without adaptive optics (AO) for wavefront correction in space
missions. The primary aim of this work was to study the stability of the
coronagraph, and to demonstrate its performance without adaptive wavefront
correction. Estimation of both the raw contrast and the gain of the point
spread function (PSF) subtraction were needed. The limiting factor of the
contrast was also important. A binary shaped pupil mask of a checkerboard type
has been designed. The mask, consisting of an aluminum film on a glass
substrate, was manufactured using nano-fabrication techniques with electron
beam lithography. Careful evaluation of coronagraphic performance, including
PSF subtraction, was carried out in air using the developed mask. A contrast of
was achieved for the raw coronagraphic image by areal
averaging of all of the observed dark regions. Following PSF subtraction, the
contrast reached . Speckles were a major limiting factor
throughout the dark regions of both the raw image and the PSF subtracted image.
A rigid coronagraph with PSF subtraction without AO is a useful method to
achieve high contrast observations. Applications of a rigid coronagraph to a
Space Infrared telescope for Cosmology and Astrophysics (SPICA) and other
platforms are discussed.Comment: 13 pages, 6 figure
Trafficking-Deficient G572R-hERG and E637K-hERG Activate Stress and Clearance Pathways in Endoplasmic Reticulum
Background: Long QT syndrome type 2 (LQT2) is the second most common type of all long QT syndromes. It is well-known that trafficking deficient mutant human ether-a-go-go-related gene (hERG) proteins are often involved in LQT2. Cells respond to misfolded and trafficking-deficient proteins by eliciting the unfolded protein response (UPR) and Activating Transcription Factor (ATF6) has been identified as a key regulator of the mammalian UPR. In this study, we investigated the role of ER chaperone proteins (Calnexin and Calreticulin) in the processing of G572R-hERG and E637K-hERG mutant proteins. Methods: pcDNA3-WT-hERG, pcDNA3-G572R-hERG and pcDNA3-E637K-hERG plasmids were transfected into U2OS and HEK293 cells. Confocal microscopy and western blotting were used to analyze subcellular localization and protein expression. Interaction between WT or mutant hERGs and Calnexin/Calreticulin was tested by coimmunoprecipitation. To assess the role of the ubiquitin proteasome pathway in the degradation of mutant hERG proteins, transfected HEK293 cells were treated with proteasome inhibitors and their effects on the steady state protein levels of WT and mutant hERGs were examined. Conclusion: Our results showed that levels of core-glycosylated immature forms of G572R-hERG and E637K-hERG in association with Calnexin and Calreticulin were higher than that in WT-hERG. Both mutant hERG proteins could activate the UPR by upregulating levels of active ATF6. Furthermore, proteasome inhibition increased the levels of core-glycosylated immature forms of WT and mutant hERGs. In addition, interaction between mutant hERGs and Calnexin/Calreticulin wa
Liver-specific deletion of protein tyrosine phosphatase (PTP) 1B improves obesity- and pharmacologically induced endoplasmic reticulum stress
Peer reviewedPostprin
A Functional Nuclear Localization Sequence in the C. elegans TRPV Channel OCR-2
The ability to modulate gene expression in response to sensory experience is critical to the normal development and function of the nervous system. Calcium is a key activator of the signal transduction cascades that mediate the process of translating a cellular stimulus into transcriptional changes. With the recent discovery that the mammalian Cav1.2 calcium channel can be cleaved, enter the nucleus and act as a transcription factor to control neuronal gene expression, a more direct role for the calcium channels themselves in regulating transcription has begun to be appreciated. Here we report the identification of a nuclear localization sequence (NLS) in the C. elegans transient receptor potential vanilloid (TRPV) cation channel OCR-2. TRPV channels have previously been implicated in transcriptional regulation of neuronal genes in the nematode, although the precise mechanism remains unclear. We show that the NLS in OCR-2 is functional, being able to direct nuclear accumulation of a synthetic cargo protein as well as the carboxy-terminal cytosolic tail of OCR-2 where it is endogenously found. Furthermore, we discovered that a carboxy-terminal portion of the full-length channel can localize to the nucleus of neuronal cells. These results suggest that the OCR-2 TRPV cation channel may have a direct nuclear function in neuronal cells that was not previously appreciated
The Smell of Age: Perception and Discrimination of Body Odors of Different Ages
Our natural body odor goes through several stages of age-dependent changes in chemical composition as we grow older. Similar changes have been reported for several animal species and are thought to facilitate age discrimination of an individual based on body odors, alone. We sought to determine whether humans are able to discriminate between body odor of humans of different ages. Body odors were sampled from three distinct age groups: Young (20–30 years old), Middle-age (45–55), and Old-age (75–95) individuals. Perceptual ratings and age discrimination performance were assessed in 41 young participants. There were significant differences in ratings of both intensity and pleasantness, where body odors from the Old-age group were rated as less intense and less unpleasant than body odors originating from Young and Middle-age donors. Participants were able to discriminate between age categories, with body odor from Old-age donors mediating the effect also after removing variance explained by intensity differences. Similarly, participants were able to correctly assign age labels to body odors originating from Old-age donors but not to body odors originating from other age groups. This experiment suggests that, akin to other animals, humans are able to discriminate age based on body odor alone and that this effect is mediated mainly by body odors emitted by individuals of old age
From endoplasmic-reticulum stress to the inflammatory response
The endoplasmic reticulum is responsible for much of a cell's protein synthesis and folding, but it also has an important role in sensing cellular stress. Recently, it has been shown that the endoplasmic reticulum mediates a specific set of intracellular signalling pathways in response to the accumulation of unfolded or misfolded proteins, and these pathways are collectively known as the unfolded-protein response. New observations suggest that the unfolded-protein response can initiate inflammation, and the coupling of these responses in specialized cells and tissues is now thought to be fundamental in the pathogenesis of inflammatory diseases. The knowledge gained from this emerging field will aid in the development of therapies for modulating cellular stress and inflammation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62741/1/nature07203.pd
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