1,570 research outputs found
Orientation effects on spectral emission features of quasars
We present an analysis of the orientation effects in Sloan Digital Sky Survey (SDSS) quasar composite spectra. In a previous work, we have shown that the equivalent width (EW) of the [O III] λ5007 Å (vacuum rest wavelength 5008.24 Å) line is a reliable indicator of the inclination of the accretion disc. Here, we have selected a sample of ∼12 000 quasars from the SDSS 7th Data Release and divided it in subsamples with different values of EW_{[{O {III}]}}. We find inclination effects both on broad and narrow quasars emission lines, among which an increasing broadening from low to high EW for the broad lines and a decreasing importance of the blue component for the narrow lines. These effects are naturally explained with a variation of source inclination from nearly face-on to edge-on, confirming the goodness of EW_{[{O {III}]}} as an orientation indicator. Moreover, we suggest that orientation effects could explain, at least partially, the origin of the anticorrelation between [O III] and Fe II intensities, I.e. the well-known eigenvector 1
EW [OIII] as an orientation indicator
We present an analysis of the average spectral properties of 12,000 SDSS quasars as a function of accretion disk inclination, as measured from the equivalent width of the [O III] 5007Å line. The use of this indicator on a large sample of quasars from the SDSS DR7 has proven the presence of orientation effects on the features of UV/optical spectra, confirming the presence of outflows in the NLR gas and that the geometry of the BLR is disk-like. Relying on the goodness of this indicator, we are now using it to investigate other bands/components of AGN. Specifically, the study of the UV/optical/IR SED of the same sample provides information on the obscuring “torus”. The SED shows an increase of the IR fraction moving from face-on to to edge-on positions, in agreement with models where the torus is coaxial with the accretion disk, and characterised by a clumpy structure
Liver enlargement predicts obstructive sleep apnea–hypopnea syndrome in morbidly obese women
Obstructive sleep apnea–hypopnea syndrome (OSAHS) is frequently present in patients with severe obesity, but its prevalence especially in women is not well defined. OSAHS and non-alcoholic fatty liver disease are common conditions, frequently associated in patients with central obesity and metabolic syndrome and are both the result of the accumulation of ectopic fat mass. Identifying predictors of risk of OSAHS may be useful to select the subjects requiring instrumental sleep evaluation. In this cross-sectional study, we have investigated the potential role of hepatic left lobe volume (HLLV) in predicting the presence of OSAHS. OSAHS was quantified by the apnea/hypopnea index (AHI) and oxygen desaturation index in a cardiorespiratory inpatient sleep study of 97 obese women [age: 47 ± 11 years body mass index (BMI): 50 ± 8 kg/m2]. OSAHS was diagnosed when AHI was ≥5. HLLV, subcutaneous and intra-abdominal fat were measured by ultrasound. After adjustment for age and BMI, both HLLV and neck circumference (NC) were independent predictors of AHI. OSAHS was found in 72% of patients; HLLV ≥ 370 cm3 was a predictor of OSAHS with a sensitivity of 66%, a specificity of 70%, a positive and negative predictive values of 85 and 44%, respectively (AUC = 0.67, p < 0.005). A multivariate logistic model was used including age, BMI, NC, and HLLV (the only independent predictors of AHI in a multiple linear regression analyses), and a cut off value for the predicted probability of OSAHS equal to 0.7 provided the best diagnostic results (AUC = 0.79, p < 0.005) in terms of sensitivity (76%), specificity (89%), negative and positive predictive values (59 and 95%, respectively). All patients with severe OSAHS were identified by this prediction model. In conclusion, HLLV, an established index of visceral adiposity, represents an anthropometric parameter closely associated with OSAHS in severely obese women
E-ELT HIRES the high resolution spectrograph for the E-ELT: integrated data flow system
The current E-ELT instrumentation plan foresees a High Resolution Spectrograph conventionally indicated as HIRES whose Phase A study has started in 2016. An international consortium (stemmed from the existing "HIRES initiative") is conducting a preliminary study of a modular E-ELT instrument able to provide highresolution spectroscopy (R 100; 000) in a wide wavelength range (0.37-2.5 μm). For the aims of data treatment (which encompasses both the reduction and the analysis procedures) an end-to-end approach has been adopted, to directly extract scientific information from the observations with a coherent set of interactive, properly validated software modules. This approach is favoured by the specific science objectives of the instrument, which pose unprecedented requirements in terms of measurement precision and accuracy. In this paper we present the architecture envisioned for the HIRES science software, building on the lessons learned in the development of the data analysis software for the ESPRESSO ultra-stable spectrograph for the VLT
The most luminous blue quasars at 3.0<z<3.3. II. CIV/X-ray emission and accretion disc physics
We analyse the properties of the CIV broad emission line in connection with
the X-ray emission of 30 bright SDSS quasars at z~3.0-3.3 with pointed
XMM-Newton observations, which were selected to test the suitability of AGN as
cosmological tools. In our previous work, we found that a large fraction (~25%)
of the quasars in this sample are X-ray underluminous by factors of >3-10. As
absorbing columns of >10 cm can be safely ruled out, their
weakness is most likely intrinsic. Here we explore possible correlations
between the UV and X-ray features of these sources to investigate the origin of
X-ray weakness. We fit their UV SDSS spectra and analyse their CIV properties
(e.g., equivalent width, EW; line peak velocity, ) as a
function of the X-ray photon index and 2-10 keV flux. We confirm the trends of
CIV and EW with UV luminosity at 2500 angstrom for both
X-ray weak and X-ray normal quasars, as well as the correlation between X-ray
weakness and CIV EW. In contrast to some recent work, we do not observe any
clear relation between the 2-10 keV luminosity and . We
find a correlation between the hard X-ray flux and the integrated CIV flux for
X-ray normal quasars, whilst X-ray weak quasars deviate from the main trend by
more than 0.5 dex. We argue that X-ray weakness might be interpreted in a
starved X-ray corona picture associated with an ongoing disc-wind phase. If the
wind is ejected in the vicinity of the black hole, the extreme-UV radiation
that reaches the corona will be depleted, depriving the corona of seeds photons
and generating an X-ray weak quasar. Yet, at the largest UV luminosities
(>10 erg s), there will still be an ample reservoir of ionising
photons that can explain the excess CIV emission observed in the X-ray weak
quasars with respect to normal sources of similar X-ray luminosities.Comment: 22 pages, 15 figures (with 3 more figures in the Appendix), abstract
abridged. Accepted for publication in A&
EELT-HIRES the high resolution spectrograph for the E-ELT: software and hardware solutions for its control
The current E-ELT instrumentation plan foresees a High Resolution Spectrograph conventionally indicated as EELTHIRES whose Phase A study has started in March 2016. Since 2013 however, a preliminary study of a modular E-ELT instrument able to provide high-resolution spectroscopy (R 100,000) in a wide wavelength range (0.37-2.5 μm) has been already conducted by an international consortium (termed "HIRES initiative"). Taking into account the requirements inferred from this preliminary work in terms of both high-level operations as well as low-level control, we will present in this paper possible solutions for HIRES hardware and software architecture. The validity of the proposed architectural and hardware choices will be eventually discussed based also on the experience gained on a real-working instrument, ESPRESSO, the next generation high-stability spectrograph for the VLT and to certain extent the precursor of HIRES. <P /
PD-L1 expression heterogeneity in non-small cell lung cancer: Evaluation of small biopsies reliability
Immunotherapy with checkpoint inhibitors, allowing recovery of effector cells function, has demonstrated to be highly effective in many tumor types and represents a true revolution in oncology. Recently, the anti-PD1 agent pembrolizumab was granted FDA approval for the first line treatment of patients with advanced non-small cell lung cancer (NSCLC) whose tumors show PD-L1 expression in \ue2\u89\ua5 50% of neoplastic cells and as a second line treatment for patients with NSCLC expressing PD-L1 in \ue2\u89\ua51% of neoplastic cells, evaluated with a validated assay. For the large majority of patients such evaluation is made on small biopsies. However, small tissue samples such as core biopsies might not be representative of tumors and may show divergent results given the possible heterogeneous immunoexpression of the biomarker. We therefore sought to evaluate PD-L1 expression concordance in a cohort of 239 patients using tissue microarrays (TMA) as surrogates of biopsies stained with a validated PD-L1 immunohistochemical assay (SP263) and report the degree of discordance among tissue cores in order to understand how such heterogeneity could affect decisions regarding therapy. We observed a discordance rate of 20% and 7.9% and a Cohen's \uce\uba value of 0.53 (moderate) and 0,48 (moderate) for \ue2\u89\ua5 1% and \ue2\u89\ua5 50% cutoffs, respectively. Our results suggest that caution must be taken when evaluating single biopsies from patients with advanced NSCLC eligible for immunotherapy; moreover, at least 4 biopsies are necessary in order to minimize the risk of tumor misclassification
UNet and MobileNet CNN-based model observers for CT protocol optimization: comparative performance evaluation by means of phantom CT images
Purpose: The aim of this work is the development and characterization of a model observer (MO) based on convolutional neural networks (CNNs), trained to mimic human observers in image evaluation in terms of detection and localization of low-contrast objects in CT scans acquired on a reference phantom. The final goal is automatic image quality evaluation and CT protocol optimization to fulfill the ALARA principle. Approach: Preliminary work was carried out to collect localization confidence ratings of human observers for signal presence/absence from a dataset of 30,000 CT images acquired on a PolyMethyl MethAcrylate phantom containing inserts filled with iodinated contrast media at different concentrations. The collected data were used to generate the labels for the training of the artificial neural networks. We developed and compared two CNN architectures based respectively on Unet and MobileNetV2, specifically adapted to achieve the double tasks of classification and localization. The CNN evaluation was performed by computing the area under localization-ROC curve (LAUC) and accuracy metrics on the test dataset. Results: The mean of absolute percentage error between the LAUC of the human observer and MO was found to be below 5% for the most significative test data subsets. An elevated inter-rater agreement was achieved in terms of S-statistics and other common statistical indices. Conclusions: Very good agreement was measured between the human observer and MO, as well as between the performance of the two algorithms. Therefore, this work is highly supportive of the feasibility of employing CNN-MO combined with a specifically designed phantom for CT protocol optimization programs
Results from CHIPIX-FE0, a Small Scale Prototype of a New Generation Pixel Readout ASIC in 65nm CMOS for HL-LHC
CHIPIX65-FE0 is a readout ASIC in CMOS 65nm designed by the CHIPIX65 project for a pixel detector at the HL-LHC, consisting of a matrix of 64x64 pixels of dimension 50x50 μm2. It is fully functional, can work at low thresholds down to 250e− and satisfies all the specifications. Results confirm low-noise, fast performance of both the synchronous and asynchronous front-end in a complex digital chip. CHIPIX65-FE0 has been irradiated up to 600 Mrad and is only marginally affected on analog performance. Further irradiation to 1 Grad will be performed. Bump bonding to silicon sensors is now on going and detailed measurements will be presented.
The HL-LHC accelerator will constitute a new frontier for particle physics after year 2024. One major experimental challenge resides in the inner tracking detectors, measuring particle position: here the dimension of the sensitive area (pixel) has to be scaled down with respect to LHC detectors.
This paper describes the results obtained by CHIPIX65-FE0, a readout ASIC in CMOS 65nm designed by the CHIPIX65 project as small-scale demonstrator for a pixel detector at the HL-LHC. It consists of a matrix of 64x64 pixels of dimension 50x50 um2 pixels and contains several pieces that are included in RD53A, a large scale ASIC designed by the RD53 Collaboration: two out of three front-ends (a synchronous and an asynchronous architecture); several building blocks; a (4x4) pixel region digital architecture with central local buffer storage, complying with a 3 GHz/cm2 hit rate and a 1 MHz trigger rate maintaining a very high efficiency (above 99%). The chip is 100% functional, either running in triggered or trigger-less mode. All building-blocks (DAC, ADC, Band Gap, SER, sLVS-TX/RX) and very front ends are working as expected.
Analog performance shows a remarkably low ENC of 90e-, a fast-rise time below 25ns and low-power consumption (about 4μA/pixel) in both synchronous and asynchronous front-ends; a very linear behavior of CSA and discriminator. No significant cross talk from digital electronics has been measured, achieving a low threshold of 250e-. Signal digitization is obtained with a 5b-Time over Threshold technique and is shown to be fairly linear, working well either at 80 MHz or with higher frequencies of 300 MHz obtained with a tunable local oscillator.
Irradiation results up to 600 Mrad at low temperature (-20°C) show that the chip is still fully functional and analog performance is only marginally degraded. Further irradiation will be performed up to 1 Grad either at low or room temperature, to further understand the level of radiation hardness of CHIPIX65-FE0.
We are now in the process of bump bonding CHIPIX65-FE0 to 3D and possibly planar silicon sensors during spring. Detailed results will be presented in the conference paper
- …