To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Monochorionic twins, resulting from a single fertilized egg giving rise to two separate embryos, are monozygotic and considered genetically identical. However, discordant phenotypes have been reported in monozygotic twins. We analyzed a retrospective cohort of 155 monochorionic pregnancies (312 twins) with major discordant structural anomalies coded by the ICD-10 system in order to describe the spectrum of anomalies, the management of the pregnancies, and the perinatal outcome. Treatment options included conservative management, selective feticide with bipolar cord coagulation, or complete termination. All survivors underwent at least 24 months of postnatal follow-up. Discordancy was complicated by twin-to-twin transfusion syndrome in eight pregnancies (5%) and by selective intrauterine growth restriction in 41 (26%). Major structural anomalies affected one system in 139 cases (90%) and multiple systems in 16 (10%). Median gestational age at diagnosis was 19.1 weeks (IQR 16.4–21.3). The most frequent single-system anomalies involved the nervous and circulatory systems. In total, 72 anomalous twins (46%) and 116 normal co-twins (74%) were delivered at a median gestational age of 34.6 weeks (IQR 31.0–36.3). Neonatal/infant death of the anomalous twin occurred in 22 cases (14%), with an overall survival rate of 32% (50/155). Surviving anomalous twins underwent major surgery in 22/50 cases (44%), four of whom (8%) now suffer from severe neurologic morbidity. This study shows that a wide spectrum of major discordant structural anomalies can be found in monochorionic pregnancies. The outcome for the anomalous twin is poor, while the survival rate for the normal co-twin was 71%, with a favorable overall prognosis.
In the framework of the Astronomical Validation and Early Science activities of the Sardinia Radio Telescope (SRT, www.srt.inaf.it), we performed 22 GHz imaging observations of SNR W44 and IC443. Thanks to the single-dish imaging performances of SRT and innovative ad hoc imaging techniques, we obtained maps that provide a detailed view of the structure of the remnants. We are planning to exploit the high-frequency radio data of SNRs to better characterize the spatially-resolved spectra and search for possible spectral steepening or breaks in selected SNR regions, assessing the high-energy tail of the region-dependent electron distribution.
We present single-dish imaging of the well-known Supernova Remnants (SNRs) IC443 and W44 at 1.5 GHz and 7 GHz with the recently commissioned 64-m diameter Sardinia Radio Telescope (SRT). Our images were obtained through on-the-fly mapping techniques, providing antenna beam oversampling, automatic baseline subtraction and radio-frequency interference removal. It results in high-quality maps of the SNRs at 7 GHz, which are usually lacking and not easily achievable through interferometry at this frequency due to the very large SNR structures. SRT continuum maps of our targets are consistent with VLA maps carried out at lower frequencies (at 324 MHz and 1.4 GHz), providing a view of the complex filamentary morphology. New estimates of the total flux density are given within 3% and 5% error at 1.5 GHz and 7 GHz respectively, in addition to flux measurements in different regions of the SNRs.
In the framework of the Sardinia Radio Telescope (SRT) Early Science Program, we obtained single-dish high-resolution imaging of the Supernova Remnants IC443 and W44 at 7 GHz. By coupling them with SRT 1.5 GHz maps, we provided spatially-resolved spectral measurements that are highlighting a spread in spectral slope distribution. The observed features range from flat or slightly inverted spectra corresponding to bright radio limbs and filaments, to relatively steep spectra in fainter radio regions. Different theoretical possibilities explaining the above challenging findings are discussed. In particular, we exclude that the observed region-dependent wide spread in spectral slope distribution could be related to absorption processes. Our high-frequency results can be directly related to distinct electron populations in the SNRs including secondary hadronic electrons and resulting from different shocks conditions and/or undergoing different cooling processes. Integrated fluxes associated with the whole SNRs obtained by SRT in comparison with previous results in the literature support the evidence for a slight spectral steepening above 1 GHz for both sources, which could be related to primary electrons or more likely secondary hadronic electrons cut-offs.
At the first meeting of the newly formed Commission on Spectrophotometry, at Paris in 1935, a thorough discussion, aided by several reports, took place on the principles of this branch of astrophysics. So it will be sufficient now to treat only such special points of theory and practice as have won interest by researches of the last few years.
Photovisual and spectroscopic observations of HBV 475 in the range λλ 3800–11 000 Å by means of S-20 and S-1 Carnegie Intensifies and prismatic cameras (dispersion 60 A/mm at Hγ), made in 1969 through 1971, have revealed the simultaneous presence of hot and cold sources of radiation, both variable.
In 1969 when the magnitudes were B = 12.45, V = 12.05, U = 11.40 the hot source gave origin to a quite strong ultraviolet continuum and to emission lines among which the most intense are due to: HI (H16 to Hα and P14 to P7); OI 8446; Fell (mult. 27, 37, 38, 42, 48, 49); [NII] 5755; Hel (4471, 5876, 6678, 7065, 10 830 very strong); [OIII] (5007, 4959, 4363); [NeIII] (3869, 3968); Hell 4686 weak.
The decline of the mongoose lemur Eulemur mongoz has resulted in a change of its conservation status from Vulnerable to Critically Endangered. Assessing the current threats to the species and the attitudes of the people coexisting with it is fundamental to understanding whether and how human impacts may affect populations. A questionnaire-based analysis was used to study the impact of agriculture and other subsistence activities, and local educational initiatives, on lemur abundance, group size and composition in the Comoros. On the islands of Mohéli and Anjouan we recorded 214 lemurs in 63 groups, the size and composition of which depended both on environmental parameters and the magnitude and type of anthropogenic pressure. There was no evidence of an impact of anthropogenic disturbance on abundance. In contrast, group size and composition were sensitive to human impacts. The most important threats were conflicts related to crop raiding, as well as illegal capture and hunting. The promotion of educational activities reduced the negative impact of hunting and illegal activities. These results highlight a need for urgent conservation measures to protect the species.
Using an improved isodensitometric technique it has been possible to study in great detail the photometric structure and the evolution of eight flares. A comparison has been made between the evolutive curves and the ones obtained from measurements of solar X-rays and radio fluxes at λλ 3·2 and 21 cm.
A reduction of the flare areas (and of the emitted energies) before the flash phase and a continuous pulsation of the flare have been observed. Further it seems that the flares associated with radio bursts or X-ray events are those which show regions of a sufficiently high intensity, the emitting areas not being a very important parameter.
The correlation in time between the various examined aspects of the AR seems to indicate that the sequence for the beginning of the different phenomena is, in general: optical flare, X-ray events, radio events.
In this study, the investigation of crystallization behaviour of Hf-rich aluminate is presented. Different alloys were deposited by ALCVD™ with composition ranging between 16 and 47 Al2O3 mol%. Post-deposition annealings were carried out in single or sequential mode using purified N2 at atmospheric pressure. Process temperature and time were varied from 700°C to 900°C and from 1' to 30' respectively. Upon these conditions, film thermal evolution was observed without any relevant increasing of in interface layer and any change in material composition. Measurements on 20 Al2O3 mol% films evidenced that thermal treatments up to 800°C promoted initial shrinking in thickness and material densification. Above 900°C, all considered aluminates were found to crystallize in orthorhombic phase maintaining original alloy composition. The higher the alumina content, the lower the grain size, the higher the crystallites density. Stability of orthorhombic crystalline structure was demonstrated upon single prolonged annealing up to 30' and upon sequential processes. In correspondence with film crystallization, enhancement of dielectric constant was detected with an increasing trend upon hafnia content. For 20 Al2O3 mol% aluminate, change in k form 19 to 40-45 was observed together with limited degradation in conduction and breakdown characteristics.
Tetrathiafulvalene and bis(ethylenedithio)tetrathiaful-valene radical-cation salts of the a-Keggin anion [PMo12O40] have been synthesized and characterized. They both are mixed-valence compounds and contain the paramagnetic anion [PMO12O40] 4-. The former contains irregular TTF ϱ+ chains isolated by the inorganic anions. From the IR spectrum a ϱ=+0.5 is suggested. The latter is two-dimensional, where BEDT-TTF molecules are ionised, ϱ=+0.5, and arranged in irregular chains. They show electrical conductivity typical of organic semiconductors.
In the first part of this paper we briefly discuss some historical constraints useful for understanding when Galileo for the first time aimed his telescope to the Moon which most probably was the first astronomical object observed by the Scientist. In the second part we discuss the dates of the observations on which the etchings, published in the Sidereus Nuncius, are based. It results that the five etchings refer to observations performed in December 1609 and January 1610. The measurement of the position, of some peculiar structures of the lunar surface clearly represented by Galileo in the etchings, shows that he was very careful in trying to produce a faithful graphical rendering of what he was observing.
Fifty-eight patients underwent vestibular neurotomy via the posterior fossa approach between September 1992 and December 1998 at the ENT department of Legnano. All patients presented a history of disabling unilateral Menière’s disease and underwent complete neuro-otologic evaluation following the 1985 American Academy of Otolaryngology - Head and Neck Surgery (AAO-HNS) guidelines. All patients underwent MRI imaging, ABR and electronystagmographic testing before surgery. Objective analysis of results is reported using the criteria published by the Committee on Hearing and Equilibrium of the AAO-HNS in 1985. According to the AAO formula, 52 patients obtained a score of 0, indicating complete control of major vertigo spells, while four were classified within the ’substantial control’ group. Immediate hearing results indicated that 93 per cent of the patients maintained a level within 10 dB from the preoperative level. Only one patient experienced a subtotal hearing loss yet retained measurable hearing. No major complications were reported. We conclude that a retrosigmoid approach to vestibular neurotomy can be considered a safe and effective procedure in relieving medically refractory vertigo in Menière’s disease while preserving the hearing. Tinnitus and long-term hearing deterioration are not influenced by the procedure.