We present the detection of the putative progenitor of the Type IIb SN 2011dh in archival pre-explosion Hubble Space Telescope images. Using post-explosion Adaptive Optics imaging with Gemini ...NIRI+ALTAIR, the position of the supernova (SN) in the pre-explosion images was determined to within 23 mas. The progenitor candidate is consistent with an F8 supergiant star (logL/L = 4.92 ? 0.20 and T eff = 6000 ? 280 K). Through comparison with stellar evolution tracks, this corresponds to a single star at the end of core C-burning with an initial mass of M ZAMS = 13 ? 3 M . The possibility of the progenitor source being a cluster is rejected, on the basis of: (1) the source not being spatially extended, (2) the absence of excess H Delta *a emission, and (3) the poor fit to synthetic cluster spectral energy distributions (SEDs). It is unclear if a binary companion is contributing to the observed SED, although given the excellent correspondence of the observed photometry to a single star SED we suggest that the companion does not contribute significantly. Early photometric and spectroscopic observations show fast evolution similar to the transitional Type IIb SN 2008ax and suggest that a large amount of the progenitor's hydrogen envelope was removed before explosion. Late-time observations will reveal if the yellow supergiant or the putative companion star were responsible for this SN explosion.
Purpose
PET using radiolabelled amino acids has become a promising tool in the diagnostics of gliomas and brain metastasis. Current research is focused on the evaluation of amide proton transfer ...(APT) chemical exchange saturation transfer (CEST) MR imaging for brain tumour imaging. In this hybrid MR-PET study, brain tumours were compared using 3D data derived from APT-CEST MRI and amino acid PET using O-(2-
18
F-fluoroethyl)-L-tyrosine (
18
F-FET).
Methods
Eight patients with gliomas were investigated simultaneously with
18
F-FET PET and APT-CEST MRI using a 3-T MR-BrainPET scanner. CEST imaging was based on a steady-state approach using a B
1
average power of 1μT. B
0
field inhomogeneities were corrected a Prametric images of magnetisation transfer ratio asymmetry (MTR
asym
) and differences to the extrapolated semi-solid magnetisation transfer reference method, APT# and nuclear Overhauser effect (NOE#), were calculated. Statistical analysis of the tumour-to-brain ratio of the CEST data was performed against PET data using the non-parametric Wilcoxon test.
Results
A tumour-to-brain ratio derived from APT# and
18
F-FET presented no significant differences, and no correlation was found between APT# and
18
F-FET PET data. The distance between local hot spot APT# and
18
F-FET were different (average 20 ± 13 mm, range 4–45 mm).
Conclusion
For the first time, CEST images were compared with
18
F-FET in a simultaneous MR-PET measurement. Imaging findings derived from
18
F-FET PET and APT CEST MRI seem to provide different biological information. The validation of these imaging findings by histological confirmation is necessary, ideally using stereotactic biopsy.
Important issues in designing radiofrequency (RF) coils for human head imaging at ultra‐high field (UHF; ≥7 T) are the inhomogeneity and longitudinal coverage (along the magnet axis) of the transmit ...(Tx) RF field. Both the homogeneity and coverage produced by Tx volume coils can be improved by means of three‐dimensional (3D) RF shimming, which requires the use of multirow Tx‐arrays. In addition, according to recent findings of the ultimate intrinsic signal‐to‐noise ratio (UISNR) theory, the loop‐only receive (Rx) arrays do not provide optimal SNR near the brain center at UHF. The latter can be obtained by combining complementary conductive structures carrying different current patterns (e.g., loops and dipole antennas). In this work, we developed, constructed, and evaluated a novel 32‐element hybrid array design for human head imaging at 7 T. The array consists of 16 transceiver loops placed in two rows circumscribing the head and 16 folded‐end Rx‐only dipoles positioned in the centers of loops. By placing all elements in a single layer, we increased RF power deposition into the tissue and, thus, preserved the Tx‐efficiency. Using this hybrid design also simplifies the coil structure by minimizing the total number of array elements. The array demonstrated whole brain coverage, 3D RF shimming capability, and high SNR. It provided ~15% higher SNR near the brain center and, depending on the RF shim mode, from 20% to 40% higher Tx‐efficiency than a common commercial head array coil.
A 32‐element hybrid array consisting of two rows of 16 transceiver loops and 16 receive‐only folded‐end dipoles was developed for human head 7‐T MRI. Using a hybrid design, we simplified the coil structure by minimizing the total number of elements. The array demonstrated whole brain coverage, 3D RF shimming capability, and high SNR. It provided ~15% higher SNR near the brain center and, depending on the RF shim mode from 20% to 40% higher Tx‐efficiency than a common commercial array.
Recent searches by unbiased, wide-field surveys have uncovered a group of extremely luminous optical transients. The initial discoveries of SN 2005ap by the Texas Supernova Search and SCP-06F6 in a ...deep Hubble pencil beam survey were followed by the Palomar Transient Factory confirmation of host redshifts for other similar transients. The transients share the common properties of high optical luminosities (peak magnitudes ~--21 to --23), blue colors, and a lack of H or He spectral features. The physical mechanism that produces the luminosity is uncertain, with suggestions ranging from jet-driven explosion to pulsational pair instability. Here, we report the most detailed photometric and spectral coverage of an ultra-bright transient (SN 2010gx) detected in the Pan-STARRS 1 sky survey. In common with other transients in this family, early-time spectra show a blue continuum and prominent broad absorption lines of O II. However, about 25 days after discovery, the spectra developed type Ic supernova features, showing the characteristic broad Fe II and Si II absorption lines. Detailed, post-maximum follow-up may show that all SN 2005ap and SCP-06F6 type transients are linked to supernovae Ic. This poses problems in understanding the physics of the explosions: there is no indication from late-time photometry that the luminosity is powered by 56Ni, the broad light curves suggest very large ejected masses, and the slow spectral evolution is quite different from typical Ic timescales. The nature of the progenitor stars and the origin of the luminosity are intriguing and open questions.
The corticotropin releasing factor (CRF) exerts its effects by acting on its receptors and on the binding protein (CRFBP), and has been implicated in alcohol use disorder (AUD). Therefore, ...identification of the exact contribution of each protein that mediates CRF effects is necessary to design effective therapeutic strategies for AUD. A series of in vitro/in vivo experiments across different species were performed to define the biological discrete role of CRFBP in AUD. First, to establish the CRFBP role in receptor signaling, we developed a novel chimeric cell-based assay and showed that CFRBP full length can stably be expressed on the plasma membrane. We discovered that only CRFBP(10 kD) fragment is able to potentiate CRF-intracellular Ca
release. We provide evidence that CRHBP gene loss increased ethanol consumption in mice. Then, we demonstrate that selective reduction of CRHBP expression in the center nucleus of the amygdala (CeA) decreases ethanol consumption in ethanol-dependent rats. CRFBP amygdalar downregulation, however, does not attenuate yohimbine-induced ethanol self-administration. This effect was associated with decreased hemodynamic brain activity in the CRFBP-downregulated CeA and increased hemodynamic activity in the caudate putamen during yohimbine administration. Finally, in alcohol-dependent patients, genetic variants related to the CRFBP(10 kD) fragment were associated with greater risk for alcoholism and anxiety, while other genetic variants were associated with reduced risk for anxiety. Taken together, our data provide evidence that CRFBP may possess both inhibitory and excitatory roles and may represent a novel pharmacological target for the treatment of AUD.
White Blood Cell Counts and Malaria McKenzie, F. Ellis; Prudhomme, Wendy A.; Magill, Alan J. ...
The Journal of infectious diseases,
07/2005, Letnik:
192, Številka:
2
Journal Article
Recenzirano
Odprti dostop
White blood cells (WBCs) were counted in 4697 individuals who presented to outpatient malaria clinics in Maesod, Tak Province, Thailand, and Iquitos, Peru, between 28 May and 28 August 1998 and ...between 17 May and 9 July 1999. At each site and in each year, WBC counts in the Plasmodium falciparum–infected patients were lower than those in the Plasmodium vivax–infected patients, which, in turn, were lower than those in the uninfected patients. In Thailand, one-sixth of the P. falciparum–infected patients had WBC counts of <4000 cells/μL. Leukopenia may confound population studies that estimate parasite densities on the basis of an assumed WBC count of 8000 cells/μL. For instance, in the present study, use of this conventional approach would have overestimated average asexual parasite densities in the P. falciparum–infected patients in Thailand by nearly one-third
In this work we present a first feasibility study of the ClearPEM technology for simultaneous PET-MR imaging. The mutual electromagnetic interference (EMI) effects between both systems were evaluated ...on a 7T magnet by characterizing the response behavior of the ClearPEM detectors and front-end electronics to pulsed RF power and switched magnetic field gradients; and by analyzing the MR system performance degradation from noise pickup into the RF receiver chain, and from magnetic susceptibility artifacts caused by PET front-end materials.
The Auckland Region, New Zealand is at significant risk from tephra falls originating both from the local Auckland Volcanic Field (AVF) and several distant, large-volume centres. We use geological ...data and observations of historical eruptions to develop a catalogue of simulated tephra dispersal patterns for the Auckland Region, using the ASHFALL model. Simulated patterns relate to individual eruptive phases and can be combined to simulate events that vary in volume and duration.
AVF eruption parameters were chosen to replicate fine tephra fall dispersed from small-volume phreatomagmatic eruptions. Modelling of eruptions from distant volcanoes was carried out in two stages. First, the sensitivity of modelled tephra thickness to various model parameters was tested. By far the largest thickness variations were the result of varying wind conditions, followed by eruption volume. The second stage involved modelling volumes that best replicated thicknesses of preserved events within the Auckland Region, allowing the catalogue to be created. Only about 1% of simulations from distant volcanoes reached the Auckland Region, suggesting that preserved tephra layers are either the result of reasonably long-lived eruptions or a number of eruptive phases.
For eruptions originating within the AVF, mean modelled tephra thickness on land is small—approximately 1.6 mm near the coast and thinning rapidly inland. Mean andesitic thicknesses are dominated by eruptions from Egmont volcano, which typically deposit tephra over a narrow section of the Auckland Region with a maximum thickness of approximately 1.7 mm. Rhyolitic eruptions are more widespread, with mean thickness varying from 30 mm in the south of the Region to 9 mm in the north. When all centres are combined and weighted by their conditional likelihood of occurrence, mean thickness ranges from 7 mm in the south to 1.5 mm in the north. However, maximum thicknesses of 150 mm for the AVF, 12 mm for andesitic centres and 830 mm for rhyolitic centres all have the potential to cause much greater damage within parts of the Auckland Region.
A retrospective surveillance study was conducted to examine the micro-geographic variation of malaria incidence in three malaria-endemic communities in the Northern Peruvian Amazon. The annual ...malaria risk rate (per 100) ranged from 38% to 47% for Plasmodium vivax and from 15% to 18% for P. falciparum. Spatial clusters were found for P. vivax in Padre Cocha, Manacamiri, and Zungaro Cocha, and for P. falciparum only in Padre Cocha. Spatial-temporal clusters showed that the highest monthly number of P. vivax cases varied every year from December to March in 1996-1997 and from February to June in 1998-1999, and for P. falciparum from November to April in 1996-1997 and from January to April in 1998-1999. Our results suggest a constant presence of high-risk areas (hot spots) for malaria infection in periods with high or low malaria incidence. Modest targeted control efforts directed at identified high-risk areas may have significant impact on malaria transmission in this region.
A longitudinal study of malariometric indicators and their association with potential risk factors was conducted during August 1997-July 1998 at Padre Cocha, a village of 1,400 residents in the ...Peruvian Amazon. The incidence of Plasmodium falciparum infections during the study year was 166/1,000 persons; that of P. vivax was 826/1,000 persons. The mean duration of symptoms prior to diagnosis was 2 days; presenting geometric mean parasite densities were 3,976 parasites/microl for P. falciparum infections and 2,282 parasites/microl for P. vivax. There were no malaria-associated deaths. Consistent with the epidemic nature of malaria in the area, the incidence of both parasite species increased with age and there were no age-specific differences in mean parasite densities. No specific occupational risks for malaria were identified. Activities significantly associated with malaria risk reflected local vector behavior and included strolling outdoors after 6:00 PM and arising before 6:00 AM for adults, and attending evening church services for children.
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