A Monte Carlo multimodal inversion of surface waves

The analysis of surface wave propagation is often used to estimate the S-wave velocity profile at a site. In this paper, we propose a stochastic approach for the inversion of surface waves, which allows apparent dispersion curves to be inverted. The inversion method is based on the integrated use of two-misfit functions. A misfit function based on the determinant of the Haskell–Thomson matrix and a classical Euclidean distance between the dispersion curves. The former allows all the modes of the dispersion curve to be taken into account with a very limited computational cost because it avoids the explicit calculation of the dispersion curve for each tentative model. It is used in a Monte Carlo inversion with a large population of profiles. In a subsequent step, the selection of representative models is obtained by applying a Fisher test based on the Euclidean distance between the experimental and the synthetic dispersion curves to the best models of the Monte Carlo inversion. This procedure allows the set of the selected models to be identified on the basis of the data quality. It also mitigates the influence of local minima that can affect the Monte Carlo results. The effectiveness of the procedure is shown for synthetic and real experimental data sets, where the advantages of the two-stage procedure are highlighted. In particular, the determinant misfit allows the computation of large populations in stochastic algorithms with a limited computational cost

Scale properties of the seismic wavefield - perspectives for full waveform matching

Starting from the nondimensionalization of equations of motion we partition the set of the velocity models in equivalence classes, such that the full waveform of an element in a given class can be calculated from the full waveform of any other element in the same class by scaling model parameters. We give a formal derivation of the seismic wavefield scale properties and we prove their capability through the use of numerical examples. Besides this, we introduce how the scale properties can be used to save computational time in full waveform modeling and inversion. In forward modeling we can use them for the calculation of the full waveform of any model in the same equivalence class of a model whose full waveform has been previously calculated. In full waveform inversion, scale properties can be used for full waveform matching: Given an experimental seismogram and a synthetic one, we can choose, in the same class of the synthetic model, another element whose waveform is closer to the experimental on

SARS-CoV-2 infection among hospitalised pregnant women and impact of different viral strains on COVID-19 severity in Italy: a national prospective population-based cohort study

OBJECTIVE: The primary aim of this article was to describe SARS-CoV-2 infection among pregnant women during the wild-type and Alpha-variant periods in Italy. The secondary aim was to compare the impact of the virus variants on the severity of maternal and perinatal outcomes. DESIGN: National population-based prospective cohort study. SETTING: A total of 315 Italian maternity hospitals. SAMPLE: A cohort of 3306 women with SARS-CoV-2 infection confirmed within 7 days of hospital admission. METHODS: Cases were prospectively reported by trained clinicians for each participating maternity unit. Data were described by univariate and multivariate analyses. MAIN OUTCOME MEASURES: COVID-19 pneumonia, ventilatory support, intensive care unit (ICU) admission, mode of delivery, preterm birth, stillbirth, and maternal and neonatal mortality. RESULTS: We found that 64.3% of the cohort was asymptomatic, 12.8% developed COVID-19 pneumonia and 3.3% required ventilatory support and/or ICU admission. Maternal age of 30-34 years (OR 1.43, 95% CI 1.09-1.87) and ≥35 years (OR 1.62, 95% CI 1.23-2.13), citizenship of countries with high migration pressure (OR 1.75, 95% CI 1.36-2.25), previous comorbidities (OR 1.49, 95% CI 1.13-1.98) and obesity (OR 1.72, 95% CI 1.29-2.27) were all associated with a higher occurrence of pneumonia. The preterm birth rate was 11.1%. In comparison with the pre-pandemic period, stillbirths and maternal and neonatal deaths remained stable. The need for ventilatory support and/or ICU admission among women with pneumonia increased during the Alpha-variant period compared with the wild-type period (OR 3.24, 95% CI 1.99-5.28). CONCLUSIONS: Our results are consistent with a low risk of severe COVID-19 disease among pregnant women and with rare adverse perinatal outcomes. During the Alpha-variant period there was a significant increase of severe COVID-19 illness. Further research is needed to describe the impact of different SARS-CoV-2 viral strains on maternal and perinatal outcomes

Management of major obstetric hemorrhage prior to peripartum hysterectomy and outcomes across nine European countries

Introduction Peripartum hysterectomy is applied as a surgical intervention of last resort for major obstetric hemorrhage. It is performed in an emergency setting except for women with a strong suspicion of placenta accreta spectrum (PAS), where it may be anticipated before cesarean section. The aim of this study was to compare management strategies in the case of obstetric hemorrhage leading to hysterectomy, between nine European countries participating in the International Network of Obstetric Survey Systems (INOSS), and to describe pooled maternal and neonatal outcomes following peripartum hysterectomy. Material and methods We merged data from nine nationwide or multi-regional obstetric surveillance studies performed in Belgium, Denmark, Finland, France, Italy, the Netherlands, Slovakia, Sweden and the UK collected between 2004 and 2016. Hysterectomies performed from 22 gestational weeks up to 48 h postpartum due to obstetric hemorrhage were included. Stratifying women with and without PAS, procedures performed in the management of obstetric hemorrhage prior to hysterectomy between countries were counted and compared. Prevalence of maternal mortality, complications after hysterectomy and neonatal adverse events (stillbirth or neonatal mortality) were calculated. Results A total of 1302 women with peripartum hysterectomy were included. In women without PAS who had major obstetric hemorrhage leading to hysterectomy, uterotonics administration was lowest in Slovakia (48/73, 66%) and highest in Denmark (25/27, 93%), intrauterine balloon use was lowest in Slovakia (1/72, 1%) and highest in Denmark (11/27, 41%), and interventional radiology varied between 0/27 in Denmark and Slovakia to 11/59 (79%) in Belgium. In women with PAS, uterotonics administration was lowest in Finland (5/16, 31%) and highest in the UK (84/103, 82%), intrauterine balloon use varied between 0/14 in Belgium and Slovakia to 29/103 (28%) in the UK. Interventional radiology was lowest in Denmark (0/16) and highest in Finland (9/15, 60%). Maternal mortality occurred in 14/1226 (1%), the most common complications were hematologic (95/1202, 8%) and respiratory (81/1101, 7%). Adverse neonatal events were observed in 79/1259 (6%) births. Conclusions Management of obstetric hemorrhage in women who eventually underwent peripartum hysterectomy varied greatly between these nine European countries. This potentially life-saving procedure is associated with substantial adverse maternal and neonatal outcome.Peer reviewe

The way to move beyond the numbers: the lesson learnt from the Italian Obstetric Surveillance System

Objective.To describe the Italian Obstetric Surveillance System (ItOSS) investigating maternal death through incident case reporting and confidential enquiries.Methods. All maternal deaths occurred in any public and private health facility in 8 Italian regions covering 73% of national births have been notified to the ItOSS. Every incident case is confidentially reviewed to assess quality of care and establish the cause and avoidability of the death.Findings. A total of 106 maternal deaths among 1.455.545 new-borns have been notified to the surveillance system in 2013-17. Haemorrhage, sepsis and hypertensive disorders of pregnancy are the leading causes of direct maternal deaths due to obstetric causes.Conclusions. A maternal mortality surveillance system, including incidence reporting and confidential enquiries along with a retrospective analysis of administrative data sources, emerged as the best option for case ascertainment and for promoting avoidable maternal deaths. 

A new misfit function for multimodal inversion of surface waves

Higher-mode contribution is important in surface-wave inversion because it allows more information to be exploited, increases investigation depth, and improves model resolution. A new misfit function for multimodal inversion of surface waves, based on the Haskell-Thomson matrix method, allows higher modes to be taken into account without the need to associate experimental data points to a specific mode, thus avoiding mode-misidentification errors in the retrieved velocity profiles. Computing cost is reduced by avoiding the need for calculating synthetic apparent or modal dispersion curves. Based on several synthetic and real examples with inversion results from the classical and the proposed methods, we find that correct velocity models can be retrieved through the multimodal inversion when higher modes are superimposed in the apparent dispersion-curve or when it is not trivial to determine a priori to which mode each data point of the experimental dispersion curve belongs. The main drawback of the method is related to the presence of several local minima in the misfit function. This feature makes the choice of a consistent initial model very importan

Comparative evaluation of the new xTAG GPP multiplex assay in the laboratory diagnosis of acute gastroenteritis. Clinical assessment and potential application from a multicentre Italian study.

Objective: Gastroenteritis caused by a single pathogen or multiple pathogens remains a major diagnostic challenge for the laboratory. The treatment of diarrhoea is based on microbiological results. Diagnosis is achieved using different laboratory techniques that have variable sensitivity and specificity. xTAG GPP is a new multiplex PCR assay that simultaneously detects 15 different pathogens responsible for diarrhoea. The results of the first multicentre study in Italy to evaluate the potential clinical application of the GPP assay in the laboratory diagnosis of diarrhoea are reported here. Methods: Faeces specimens (N = 664) from hospitalized patients were tested with the GPP assay using a Luminex 200 instrument. All specimens were run using comparator methods following a routine algorithm: culture for bacteria, enzyme immunoassay and PCR for viruses, and microscopy for parasites. Results: Of the samples tested with the GPP, 53.61% (356/664) gave positive results, as compared to 45.33% by routine testing. Of the positive specimens, 34.55% showed the presence of genomic DNA from multiple pathogens. The Luminex method showed an increase in the percentage of positivity of 8.28%. Conclusions: The GPP assay can be considered a helpful tool for the detection of gastrointestinal pathogens, with a hands-on time of 5 h; it provides accurate data for the clinical management of hospitalized patients and for epidemiological surveillance