| 1. |
- Vedantham, H. K., et al.
(author)
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Lunar occultation of the diffuse radio sky : LOFAR measurements between 35 and 80 MHz
- 2015
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 450, s. 2291-2305
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Journal article (peer-reviewed)abstract
- We present radio observations of the Moon between 35 and 80 MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies 35 < ν < 80 MHz since it is ‘colder’ than the diffuse Galactic background it occults, (ii) using the (negative) flux of the lunar disc, we can reconstruct the spectrum of the diffuse Galactic emission with the lunar thermal emission as a reference, and (iii) that reflected RFI (radio-frequency interference) is concentrated at the centre of the lunar disc due to specular nature of reflection, and can be independently measured. Our RFI measurements show that (i) Moon-based Cosmic Dawn experiments must design for an Earth-isolation of better than 80 dB to achieve an RFI temperature <1 mK, (ii) Moon-reflected RFI contributes to a dipole temperature less than 20 mK for Earth-based Cosmic Dawn experiments, (iii) man-made satellite-reflected RFI temperature exceeds 20 mK if the aggregate scattering cross-section of visible satellites exceeds 175 m2 at 800 km height, or 15 m2 at 400 km height. Currently, our diffuse background spectrum is limited by sidelobe confusion on short baselines (10–15 per cent level). Further refinement of our technique may yield constraints on the redshifted global 21 cm signal from Cosmic Dawn (40 > z > 12) and the Epoch of Reionization (12 > z > 5).
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| 2. |
- Jelic, V., et al.
(author)
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Initial LOFAR observations of epoch of reionization windows II. Diffuse polarized emission in the ELAIS-N1 field
- 2014
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 568, s. A101-
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Journal article (peer-reviewed)abstract
- Aims. This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications or extracting of the cosmological 21 cm signal from the LOw-Frequency ARray - Epoch of Reionization (LOFAR-EoR) data Methods. We used the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes. Results. The brightness temperature of the detected Galactic emission is on average similar to 4 K in polarized intensity and covers the range from -10 to +13 rad m(-2) in Faraday depth, The total polarized intensity and polarization angle show a wide range of morphological features. We have also used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. The LOFAR and WSRT images show a similar complex morphology at comparable brightness levels, but their spatial correlation is very low. The fractional polarization at 150 MHz, expressed as a percentage of the total intensity, amounts to approximate to 1.5%. There is no indication of diffuse emission in total intensity in the interferometric data. in line with results at higher frequencies Conclusions. The wide frequency range. high angular resolution, and high sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of similar to 1-2 rad m(-2) in Faraday depth. The different polarized patterns observed at 150 MHz and 350 MHz are consistent with different source distributions along the line of sight wring in a variety of Faraday thin regions of emission. The presence of polarized foregrounds is a serious complication for epoch of reionization experiments. To avoid the leakage of polarized emission into total intensity, which can depend on frequency, we need to calibrate the instrumental polarization across the field of view to a small fraction of 1%.
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| 3. |
- Asad, K. M. B., et al.
(author)
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Polarization leakage in epoch of reionization windows - I. Low Frequency Array observations of the 3C196 field
- 2015
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 451:4, s. 3709-3727
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Journal article (peer-reviewed)abstract
- Detection of the 21-cm signal coming from the epoch of reionization (EoR) is challenging especially because, even after removing the foregrounds, the residual Stokes I maps contain leakage from polarized emission that can mimic the signal. Here, we discuss the instrumental polarization of Low Frequency Array (LOFAR) and present realistic simulations of the leakages between Stokes parameters. From the LOFAR observations of polarized emission in the 3C196 field, we have quantified the level of polarization leakage caused by the nominal model beam of LOFAR, and compared it with the EoR signal using power spectrum analysis. We found that at 134-166 MHz, within the central 4A degrees of the field the (Q, U) -> I leakage power is lower than the EoR signal at k < 0.3 Mpc(-1). The leakage was found to be localized around a Faraday depth of 0, and the rms of the leakage as a fraction of the rms of the polarized emission was shown to vary between 0.2 and 0.3 per cent, both of which could be utilized in the removal of leakage. Moreover, we could define an 'EoR window' in terms of the polarization leakage in the cylindrical power spectrum above the point spread function (PSF)-induced wedge and below k(ayen) similar to 0.5 Mpc(-1), and the window extended up to k(ayen) similar to 1 Mpc(-1) at all k(aSyen) when 70 per cent of the leakage had been removed. These LOFAR results show that even a modest polarimetric calibration over a field of view of a parts per thousand(2) 4A degrees in the future arrays like Square Kilometre Array will ensure that the polarization leakage remains well below the expected EoR signal at the scales of 0.02-1 Mpc(-1).
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| 4. |
- Jelić, V., et al.
(author)
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Linear polarization structures in LOFAR observations of the interstellar medium in the 3C 196 field
- 2015
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 583
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Journal article (peer-reviewed)abstract
- Aims: This study aims to characterize linear polarization structures in LOFAR observations of the interstellar medium (ISM) in the 3C 196 field, one of the primary fields of the LOFAR-Epoch of Reionization key science project.Methods: We have used the high band antennas (HBA) of LOFAR to image this region and rotation measure (RM) synthesis to unravel the distribution of polarized structures in Faraday depth.Results: The brightness temperature of the detected Galactic emission is 5-15 K in polarized intensity and covers the range from -3 to +8 rad m(-2) in Faraday depth. The most interesting morphological feature is a strikingly straight filament at a Faraday depth of +0.5 rad m(-2) running from north to south, right through the centre of the field and parallel to the Galactic plane. There is also an interesting system of linear depolarization canals conspicuous in an image showing the peaks of Faraday spectra. We used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. For the first time, we see some common morphology in the RM cubes made at 150 and 350 MHz. There is no indication of diffuse emission in total intensity in the interferometric data, in line with results at higher frequencies and previous LOFAR observations. Based on our results, we determined physical parameters of the ISM and proposed a simple model that may explain the observed distribution of the intervening magneto-ionic medium.Conclusions: The mean line-of-sight magnetic field component, B-parallel to, is determined to be 0.3 +/- 0.1 mu G and its spatial variation across the 3C 196 field is 0.1 mu G. The filamentary structure is probably an ionized filament in the ISM, located somewhere within the Local Bubble. This filamentary structure shows an excess in thermal electron density (n(e)B(parallel to) > 6.2 cm(-3) mu G) compared to its surroundings.
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| 5. |
- Binzel, R.P., et al.
(author)
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Compositional distributions and evolutionary processes for the near-Earth object population: Results from the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS)
- 2019
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In: Icarus. - : Elsevier. - 0019-1035 .- 1090-2643. ; 324, s. 41-76
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Journal article (peer-reviewed)abstract
- Advancing technology in near-infrared instrumentation and dedicated planetary telescope facilities have enabled nearly two decades of reconnoitering the spectral properties for near-Earth objects (NEOs). We report measured spectral properties for more than 1000 NEOs, representing >5 percent of the currently discovered population. Thermal flux detected below 2.5 microns allows us to make albedo estimates for nearly 50 objects, including two comets. Additional spectral data are reported for more than 350 Mars-crossing asteroids. Most of these measurements were achieved through a collaboration between researchers at the Massachusetts Institute of Technology and the University of Hawaii, with full cooperation of the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. We call this project the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS; myth-neos). While MITHNEOS has continuously released all spectral data for immediate use by the scientific community, our objectives for this paper are to: (1) detail the methods and limits of the survey data, (2) formally present a compilation of results including their taxonomic classification within a single internally consistent framework, (3) perform a preliminary analysis on the overall population characteristics with a concentration toward deducing key physical processes and identifying their source region for escaping the main belt. Augmenting our newly published measurements are the previously published results from the broad NEO community, including many results graciously shared by colleagues prior to formal publication. With this collective data set, we find the near-Earth population matches the diversity of the main-belt, with all main-belt taxonomic classes represented in our sample. Potentially hazardous asteroids (PHAs) as well as the subset of mission accessible asteroids (ΔV≤ 7 km/s) both appear to be a representative mix of the overall NEO population, consistent with strong dynamical mixing for the population that interacts most closely with Earth. Mars crossers, however, are less diverse and appear to more closely match the inner belt population from where they have more recently diffused. The fractional distributions of major taxonomic classes (60% S, 20% C, 20% other) appear remarkably constant over two orders of magnitude in size (10 km to 100 m), which is eight orders of magnitude in mass, though we note unaccounted bias effects enter into our statistics below about 500m. Given the range of surface ages, including possible refreshment by planetary encounters, we are able to identify a very specific space weathering vector tracing the transition from Q- to Sq- to S-types that follows the natural dispersion for asteroid spectra mapped into principal component space. We also are able to interpret a shock darkening vector that may account for some objects having featureless spectra. Space weathering effects for C-types are complex; these results are described separately by Lantz, Binzel, DeMeo. (2018, Icarus 302, 10-17). Independent correlation of dynamical models with taxonomic classes map the escape zones for NEOs to main-belt regions consistent with well established heliocentric compositional gradients. We push beyond taxonomy to interpret our visible plus near-infrared spectra in terms of the olivine and pyroxene mineralogy consistent with the H, L, and LL classes of ordinary chondrites meteorites. Correlating meteorite interpretations with dynamical escape region models shows a preference for LL chondrites to arrive from the ν6 resonance and H chondrites to have a preferential signature from the mid-belt region (3:1 resonance). L chondrites show some preference toward the outer belt, but not at a significant level. We define a Space Weathering Parameter as a continuous variable and find evidence for step-wise changes in space weathering properties across different planet crossing zones in the inner solar system. Overall we hypothesize the relative roles of planetary encounters, YORP spin-up, and thermal cycling across the inner solar system.
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| 6. |
- Ghavami, S., et al.
(author)
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Apoptosis and cancer : mutations within caspase genes
- 2009
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In: Journal of Medical Genetics. - : B M J Group. - 0022-2593 .- 1468-6244. ; 46:8, s. 497-510
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Research review (peer-reviewed)abstract
- The inactivation of programmed cell death has profound effects not only on the development but also on the overall integrity of multicellular organisms. Beside developmental abnormalities, it may lead to tumorigenesis, autoimmunity, and other serious health problems. Deregulated apoptosis may also be the leading cause of cancer therapy chemoresistance. Caspase family of cysteinyl-proteases plays the key role in the initiation and execution of programmed cell death. This review gives an overview of the role of caspases, their natural modulators like IAPs, FLIPs, and Smac/Diablo in apoptosis and upon inactivation, and also in cancer development. Besides describing the basic mechanisms governing programmed cell death, a large part of this review is dedicated to previous studies that were focused on screening tumours for mutations within caspase genes as well as their regulators. The last part of this review discusses several emerging treatments that involve modulation of caspases and their regulators. Thus, we also highlight caspase cascade modulating experimental anticancer drugs like cFLIP-antagonist CDDO-Me; cIAP1 antagonists OSU-03012 and ME-BS; and XIAP small molecule antagonists 1396-11, 1396-12, 1396-28, triptolide, AEG35156, survivin/Hsp90 antagonist shephedrin, and some of the direct activators of procaspase-3.
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| 7. |
- Owings, T. M., et al.
(author)
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Plantar pressures in diabetic patients with foot ulcers which have remained healed
- 2009
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In: Diabetic Medicine. - : Wiley. - 1464-5491 .- 0742-3071. ; 26:11, s. 1141-1146
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Journal article (peer-reviewed)abstract
- Aims The recurrence of foot ulcers is a significant problem in people with diabetic neuropathy. The purpose of this study was to measure in-shoe plantar pressures and other characteristics in a group of neuropathic patients with diabetes who had prior foot ulcers which had remained healed. Methods This was an epidemiological cohort study of patients from diabetes clinics of two Swedish hospitals. From a database of 2625 eligible patients, 190 surviving patients with prior plantar ulcers of the forefoot (hallux or metatarsal heads) caused by repetitive stress were identified and 49 patients agreed to participate. Barefoot and in-shoe plantar pressures were measured during walking. Data on foot deformity, activity profiles and self-reported behaviour were also collected. Results Mean barefoot plantar peak pressure at the prior ulcer site (556 kPa) was lower than in other published series, although the range was large (107-1192 kPa). Mean in-shoe peak pressure at this location averaged 207 kPa when measured with an insole sensor. Barefoot peak pressure only predicted similar to 35% of the variance of in-shoe peak pressure, indicating variation in the efficacy of the individual footwear prescriptions (primarily extra-depth shoes with custom insoles). Conclusions We propose that the mean value for in-shoe pressures reported in these patients be used as a target in footwear prescription for patients with prior ulcers. Although plantar pressure is only one factor in a multifaceted strategy to prevent ulcer recurrence, the quantitative focus on pressure reduction in footwear is likely to have beneficial effects.
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| 8. |
- DeMeo, Francesca E., et al.
(author)
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Isolating the mechanisms for asteroid surface refreshing
- 2023
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In: Icarus. - : Elsevier. - 0019-1035 .- 1090-2643. ; 389
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Journal article (peer-reviewed)abstract
- Evidence is seen for young, fresh surfaces among Near-Earth and Main-Belt asteroids even though space-weathering timescales are shorter than the age of the surfaces. A number of mechanisms have been proposed to refresh asteroid surfaces on short timescales, such as planetary encounters, YORP spinup, thermal degradation, and collisions. Additionally, other factors such as grain size effects have been proposed to explain the existence of these “fresh-looking” spectra. To investigate the role each of these mechanisms may play, we collected a sample of visible and near-infrared spectra of 477 near-Earth and Mars Crosser asteroids with similar sizes and compositions — all with absolute magnitude H > 16 and within the S-complex and having olivine to pyroxene (ol/(ol+opx)) ratios >0.65. We taxonomically classify these objects in the Q (fresh) and S (weathered) classes. We find four trends in the Q/S ratio: (1) previous work demonstrated the Q/S ratio increases at smaller sizes down to H ≲16, but we find a sharp increase near H∼19 after which the ratio decreases monotonically. (2) in agreement with many previous studies, the Q/S ratio increases with decreasing perihelion distance, and we find it is non-zero for larger perihelia >1.2AU, (3) as a new finding our work reveals the Q/S ratio has a sharp, significant peak near ∼5° orbital inclination, and (4) we confirm previous findings that the Q/S ratio is higher for objects that have the possibility of encounter with Earth and Venus versus those that do not, however this finding cannot be distinguished from the perihelion trend. No single resurfacing mechanism can explain all of these trends, so multiple mechanisms are required. YORP spin-up scales with size, thermal degradation is dependent on perihelion, planetary encounters trend with inclination, perihelion and MOID, noting that asteroid–asteroid collisions are also dependent on inclination. It is likely that a combination of all four resurfacing mechanisms are needed to account for all observational trends.
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| 9. |
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| 10. |
- Lazzarini, P A, et al.
(author)
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Effectiveness of offloading interventions for people with diabetes-related foot ulcers : A systematic review and meta-analysis
- 2023
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In: Diabetes/Metabolism Research Reviews. - : John Wiley & Sons. - 1520-7552 .- 1520-7560. ; 40:3
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Research review (peer-reviewed)abstract
- BACKGROUND: Offloading treatment is crucial to heal diabetes-related foot ulcers (DFU). This systematic review aimed to assess the effectiveness of offloading interventions for people with DFU.METHODS: We searched PubMed, EMBASE, Cochrane databases, and trials registries for all studies relating to offloading interventions in people with DFU to address 14 clinical question comparisons. Outcomes included ulcers healed, plantar pressure, weight-bearing activity, adherence, new lesions, falls, infections, amputations, quality of life, costs, cost-effectiveness, balance, and sustained healing. Included controlled studies were independently assessed for risk of bias and had key data extracted. Meta-analyses were performed when outcome data from studies could be pooled. Evidence statements were developed using the GRADE approach when outcome data existed.RESULTS: From 19,923 studies screened, 194 eligible studies were identified (47 controlled, 147 non-controlled), 35 meta-analyses performed, and 128 evidence statements developed. We found non-removable offloading devices likely increase ulcers healed compared to removable offloading devices (risk ratio [RR] 1.24, 95% CI 1.09-1.41; N = 14, n = 1083), and may increase adherence, cost-effectiveness and decrease infections, but may increase new lesions. Removable knee-high offloading devices may make little difference to ulcers healed compared to removable ankle-high offloading devices (RR 1.00, 0.86-1.16; N = 6, n = 439), but may decrease plantar pressure and adherence. Any offloading device may increase ulcers healed (RR 1.39, 0.89-2.18; N = 5, n = 235) and cost-effectiveness compared to therapeutic footwear and may decrease plantar pressure and infections. Digital flexor tenotomies with offloading devices likely increase ulcers healed (RR 2.43, 1.05-5.59; N = 1, n = 16) and sustained healing compared to devices alone, and may decrease plantar pressure and infections, but may increase new transfer lesions. Achilles tendon lengthening with offloading devices likely increase ulcers healed (RR 1.10, 0.97-1.27; N = 1, n = 64) and sustained healing compared to devices alone, but likely increase new heel ulcers.CONCLUSIONS: Non-removable offloading devices are likely superior to all other offloading interventions to heal most plantar DFU. Digital flexor tenotomies and Achilles tendon lengthening in combination with offloading devices are likely superior for some specific plantar DFU locations. Otherwise, any offloading device is probably superior to therapeutic footwear and other non-surgical offloading interventions to heal most plantar DFU. However, all these interventions have low-to-moderate certainty of evidence supporting their outcomes and more high-quality trials are needed to improve our certainty for the effectiveness of most offloading interventions.
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| 11. |
- Marsset, Michaël, et al.
(author)
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The Debiased Compositional Distribution of MITHNEOS: Global Match between the Near-Earth and Main-belt Asteroid Populations, and Excess of D-type Near-Earth Objects
- 2022
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In: Astronomical Journal. - : Institute of Physics (IOP). - 0004-6256 .- 1538-3881. ; 163:4
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Journal article (peer-reviewed)abstract
- We report 491 new near-infrared spectroscopic measurements of 420 near-Earth objects (NEOs) collected on the NASA InfraRed Telescope Facility as part of the MIT-Hawaii NEO Spectroscopic Survey. These measurements were combined with previously published data from Binzel et al. and bias-corrected to derive the intrinsic compositional distribution of the overall NEO population, as well as of subpopulations coming from various escape routes (ERs) in the asteroid belt and beyond. The resulting distributions reflect well the overall compositional gradient of the asteroid belt, with decreasing fractions of silicate-rich (S- and Q-type) bodies and increasing fractions of carbonaceous (B-, C-, D- and P-type) bodies as a function of increasing ER distance from the Sun. The close compositional match between NEOs and their predicted source populations validates dynamical models used to identify ERs and argues against any strong composition change with size in the asteroid belt between ∼5 km and ∼100 m. A notable exception comes from the overabundance of D-type NEOs from the 5:2J and, to a lesser extend, the 3:1J and ν6 ERs, hinting at the presence of a large population of small D-type asteroids in the main belt. Alternatively, this excess may indicate preferential spectral evolution from D-type surfaces to C and P types as a consequence of space weathering, or point to the fact that D-type objects fragment more often than other spectral types in the NEO space. No further evidence for the existence of collisional families in the main belt, below the detection limit of current main-belt surveys, was found in this work.
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