17 research outputs found
Post-spinel transformations and equation of state in ZnGa2O4: Determination at high-pressure by in situ x-ray diffraction
Room temperature angle-dispersive x-ray diffraction measurements on spinel
ZnGa2O4 up to 56 GPa show evidence of two structural phase transformations. At
31.2 GPa, ZnGa2O4 undergoes a transition from the cubic spinel structure to a
tetragonal spinel structure similar to that of ZnMn2O4. At 55 GPa, a second
transition to the orthorhombic marokite structure (CaMn2O4-type) takes place.
The equation of state of cubic spinel ZnGa2O4 is determined: V0 = 580.1(9) A3,
B0 = 233(8) GPa, B0'= 8.3(4), and B0''= -0.1145 GPa-1 (implied value); showing
that ZnGa2O4 is one of the less compressible spinels studied to date. For the
tetragonal structure an equation of state is also determined: V0 = 257.8(9) A3,
B0 = 257(11) GPa, B0'= 7.5(6), and B0''= -0.0764 GPa-1 (implied value). The
reported structural sequence coincides with that found in NiMn2O4 and MgMn2O4.Comment: 20 pages, 4 figures, 2 Table
Dilute ferrimagnetic semiconductors in Fe-substituted spinel ZnGaO
Solid solutions of nominal composition
[ZnGaO][FeO], of the semiconducting spinel
ZnGaO with the ferrimagnetic spinel FeO have been prepared with
= 0.05, 0.10, and 0.15. All samples show evidence for long-range magnetic
ordering with ferromagnetic hysteresis at low temperatures. Magnetization as a
function of field for the = 0.15 sample is S-shaped at temperatures as high
as 200 K. M\"ossbauer spectroscopy on the = 0.15 sample confirms the
presence of Fe, and spontaneous magnetization at 4.2 K. The magnetic
behavior is obtained without greatly affecting the semiconducting properties of
the host; diffuse reflectance optical spectroscopy indicates that Fe
substitution up to = 0.15 does not affect the position of the band edge
absorption. These promising results motivate the possibility of dilute
ferrimagnetic semiconductors which do not require carrier mediation of the
magnetic moment.Comment: 9 pages and 6 figure
The Carnegie Supernova Project I: photometry data release of low-redshift stripped-envelope supernovae
The first phase of the Carnegie Supernova Project (CSP-I) was a dedicated
supernova follow-up program based at the Las Campanas Observatory that
collected science data of young, low-redshift supernovae between 2004 and 2009.
Presented in this paper is the CSP-I photometric data release of low-redshift
stripped-envelope core-collapse supernovae. The data consist of optical
(uBgVri) photometry of 34 objects, with a subset of 26 having near-infrared
(YJH) photometry. Twenty objects have optical pre-maximum coverage with a
subset of 12 beginning at least five days prior to the epoch of B-band maximum
brightness. In the near-infrared, 17 objects have pre-maximum observations with
a subset of 14 beginning at least five days prior to the epoch of J-band
maximum brightness. Analysis of this photometric data release is presented in
companion papers focusing on techniques to estimate host-galaxy extinction
(Stritzinger et al., submitted) and the light-curve and progenitor star
properties of the sample (Taddia et al., submitted). The analysis of an
accompanying visual-wavelength spectroscopy sample of ~150 spectra will be the
subject of a future paper.Comment: Updated a couple of small error
A long-period massive planet around HD106515A
We have performed RV monitoring of the components of the binary system HD
106515 over about 11 years using the high resolution spectrograph SARG at TNG.
The primary shows long-period radial velocity variations that indicate the
presence of a low mass companion whose projected mass is in the planetary
regime (m sin i = 9.33 Mjup). The 9.8 years orbit results quite eccentric
(e=0.57), as typical for massive giant planets. Our results confirm the
preliminary announcement of the planet included in Mayor et al. (2011). The
secondary instead does not show significant RV variations. The two components
do not differ significantly in chemical composition, as found for other pairs
for which one component hosts giant planets. Adaptive optics images obtained
with AdOpt@TNG do not reveal additional stellar companions. From the analysis
of the relative astrometry of the components of the wide pair we put an upper
limit on the mass of the newly detected companion of about 0.25 Msun. State of
art or near future instrumentation can provide true mass determination, thanks
to the availability of the wide companion HD106515B as reference. Therefore,
HD106515Ab will allow deeper insight in the transition region between planets
and brown dwarfs.Comment: A&A, accepted, 8 pages, 10 figure
Supernova 2008J: early time observations of a heavily reddened SN 2002ic-like transient
We provide additional observational evidence that some Type Ia supernovae
(SNe Ia) show signatures of circumstellar interaction (CSI) with hydrogen-rich
material. Early phase optical and near-infrared (NIR) light curves and
spectroscopy of SN 2008J obtained by the Carnegie Supernova Project are studied
and compared to those of SNe 2002ic and 2005gj. Our NIR spectrum is the first
obtained for a 2002ic-like object extending up to 2.2 m. A published
high-resolution spectrum is used to provide insight on the circumstellar
material (CSM). SN 2008J is found to be affected by 1.9 mag of
extinction and to closely resemble SN 2002ic. Spectral and color comparison to
SNe 2002ic and 2005gj suggests 3.1. Spectral decomposition reveals
the underlying SN emission matches a 1991T-like event and, since SN 2008J is as
luminous as SN 2005gj ( 20.3 mag), we conclude that their
CSI emissions are similarly robust. The high-resolution spectrum reveals narrow
emission lines produced from un-shocked gas characterized by a wind velocity of
50 km s. We conclude that SN 2008J best matches an explosion of a
SN Ia that interacts with its CSM.Comment: 8 pages, 4 figures, minor changes to match the published versio
Mendelian adult-onset leukodystrophy genes in Alzheimer´s disease. Critical influence of CSF1R and NOTCH3
Mendelian adult-onset leukodystrophies are a spectrum of rare inherited progressive neurodegenerative disorders affecting the white matter of the central nervous system. Among these, Cerebral Autosomal Dominant and Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL and CARASIL), Cerebroretinal vasculopathy (CRV), Metachromatic leukodystrophy (MLD), Hereditary diffuse Leukoencephalopathy with spheroids (HDLS), Vanishing white matter disease (VWM) present with rapidly progressive dementia as dominant feature and are caused by mutations in NOTCH3, HTRA1, TREX1, ARSA, CSF1R, EIF2B1, EIF2B2, EIF2B3, EIF2B4, EIF2B5, respectively. Given the rare incidence of these disorders and the lack of unequivocally diagnostic features, leukodystrophies are frequently misdiagnosed with common sporadic dementing diseases such as Alzheimer’s disease (AD), raising the question of whether these overlapping phenotypes may be explained by shared genetic risk factors. To investigate this intriguing hypothesis, we have combined gene expression analysis 1) in 6 different AD mouse strains (APPPS1, HOTASTPM, HETASTPM, TPM, TAS10 and TAU), at 5 different developmental stages (Embryo [E15], 2 months, 4 months, 8 months and 18 months), 2) in APPPS1 primary cortical neurons under stress conditions (oxygen-glucose deprivation) and single-variant and single-gene (c-alpha and SKAT tests) based genetic screening in a cohort composed of 332 Caucasian late-onset AD patients and 676 Caucasian elderly controls. Csf1r was significantly overexpressed (Log2FC>1, adj. p-val<0.05) in the cortex and hippocampus of aged HOTASTPM mice with extensive Aβ core dense plaque pathology. We identified 3 likely pathogenic mutations in CSF1R TK domain (p.L868R, p.Q691H and p.H703Y) in our discovery and validation cohort, composed of 465 AD and MCI Caucasian patients from the UK. Moreover, NOTCH3 was a significant hit in the c-alpha test (adj p-val = 0.01). Adult onset Mendelian leukodystrophy genes are not common factors implicated in AD. Nevertheless, our study suggests a potential pathogenic link between NOTCH3, CSF1R and sporadic LOAD, that warrants further investigation
A measuring procedure for single-crystal diffraction using synchrotron radiation
The use of synchrotron radiation (SR) for single-crystal diffraction measurements requires special features of both the instrumentation and the measuring procedure. This paper describes a new algorithm for data collection developed for synchrotron radiation. It has been used successfully at the five-circle diffractometer at HASYLAB (DESY, Hamburg). The main features are: precise location of the reflection position, determination of the measuring parameters by pre-scanning, subsequent fine scanning, and real-time monitoring of several parameters of the beam conditions for data reduction. This allows fast and precise data collection