A new OMA method to perform structural dynamic identification: numerical and experimental investigation

Operational modal analysis (OMA) methods are nowadays common in civil, mechanical and aerospace engineering to identify and monitor structural systems without any knowledge on the structural excitation provided that the latter is due to ambient vibrations. For this reason, OMA methods are embedded with stochastic concepts and then it is difficult for users that have no-knowledge in signal analysis and stochastic dynamics. In this paper an innovative method useful for structural health monitoring (SHM) is proposed. It is based on the signal filtering and on the Hilbert transform of the correlation function matrix. Specifically, the modal shapes are estimated from the correlation functions matrix of the filtered output process and then the frequencies and the damping ratios are estimated from the analytical signals of the mono-component correlation functions: a complex signals in which the real part represents the correlation function and the imaginary part is its Hilbert transform. This method is very simple to use since requires only few interactions with the users and thus it can be used also from users that are not experts in the aforementioned areas. In order to prove the reliability of the proposed method, numerical simulations and experimental tests are reported also considering comparisons with the most popular OMA methods

Morphological variation of the newly confirmed population of the javelin sand boa, Eryx jaculus (Linnaeus, 1758) (Serpentes, erycidae) in Sicily, Italy

The presence of the Javelin sand boa in Sicily has recently been confirmed. Here the morphological characters and sexual dimorphism of the Sicilian population of Eryx jaculus are presented. Seven meristic and six metric characters in 96 specimens from Sicily were examined. The results show that tail length, snout-vent length, the distance between nostrils and the number of ventral and subcaudal scales are different between sexes. The characters found in the Sicilian population of the Javelin sand boa resemble those of the African population (ssp. jaculus) rather than the Eurasian population (ssp. turcicus), but biomolecular studies are necessary to understand its taxonomic identity

Digital simulation of multi-variate stochastic processes

Stochastic dynamic analysis of linear or nonlinear multi-degree-of-freedom systems excited by multi-variated processes is usually conducted by using digital Monte Carlo (MC) simulation. Since in structural systems few modal shapes contribute to the response in the nodal space, the computational burden of MC simulation is mainly related to the digital simulation of the input process. Usually, the generation of multi-variated samples of Gaussian input process is performed with the aid of the Shinozuka formula. However, since in this procedure the stochastic process is given as a summation of waves with random amplitude amplified by the square root of the power spectral density, the randomness is due to a random phase angle of each wave, therefore a very large number of waves is required to reach the Gaussianity, i.e. the process is only asymptotically stable. Moreover, the computational burden increases in case of multi-variated processes. The paper aims to drastically reduce the generation time of the input process through the use of a two-step procedure. In the first step, by using the Priestley formula, each wave is normally distributed. This first aspect allows to drastically reduce the computational effort for the mono-variate process since few waves are sufficient to reach the Gaussianity. In the second step, the multi-variate process is reduced as a summation of independent fully coherent vectors if the quadrature spectrum (q-spectrum) can be neglected. An application of digital simulation of the wind velocity field is discussed to prove the efficiency of the proposed approach

Is it time to combine untargeted antifungal strategies to reach the goal of 'early' effective treatment?

LETTER TO EDITO

On the occurrence of the invasive Atlantic blue crab Callinectes sapidus Rathbun 1896 (Decapoda: Brachyura: Portunidae) in Sicilian inland waters

- The Atlantic blue crab Callinectes sapidus Rathbun 1896 is included among the worst invasive alien species in the Mediterranean Sea. Here we report the finding of the species in two Sicilian rivers, the Irminio and the Imera Meridionale, where it was collected up to 6 km distant from the river mouths. Although several records of the species are already available from Italy, this is the first evidence of the occurrence of this invasive crab this far from the coastline throughout the Country. In the light of the well-known impact of the Atlantic blue crab on the invaded water bodies, the monitoring of the species and appropriate mitigation strategies should be implemented in order to protect the threatened native biota of the Sicilian inland waters

Should we continue to use prediction tools to identify patients at risk of Candida spp. infection? If yes, why?

We read with interest the article from Shanin et al. about the Fungal Infection Risk Evaluation (FIRE) study [1] aiming to 'describe the incidence of IFD in UK critical care units and to develop and validate a clinical risk prediction tool to identify non-neutropenic, critically ill adult patients at risk of IFD'. The investigators should be congratulated for the way they collected a huge amount of data from 96 adult intensive care units (ICUs), managed the FIRE database, and developed and validated the risk model. However, they stated that the prediction model would help to identify patients who may benefit from antifungal prophylaxis and that a number of randomized controlled trials (RCTs) demonstrated a beneficial effect of antifungal prophylaxis and/or empiric treatment in terms of incidence of invasive fungal disease (IFD) and mortality. This statement is not supported by available evidence from RCTs. A recent Cochrane Systematic Review including 22 RCTs evaluating prophylaxis, pre-emptive, and empiric antifungal treatment with any antifungal drugs in 2761 non-neutropenic critically ill patients showed no significant effect on mortality (risk ratio (RR) 0.93, 95 % confidence interval (CI) 0.79 to 1.09) and a significant reduction in the risk of invasive fungal infection (IFI) (RR 0.57, 95 % CI 0.39 to 0.83) [2, 3]. In the subgroup analysis for type of intervention, antifungal prophylaxis was not associated with a significant mortality reduction but with a significant reduction of IFI [4]. This systematic review was the update of the one cited in the manuscript and published in 2006 including 12 RCT and 1606 patients

A novel identification procedure from ambient vibration data

Ambient vibration modal identification, also known as Operational Modal Analysis, aims to identify the modal properties of a structure based on vibration data collected when the structure is under its operating conditions, i.e., no initial excitation or known artificial excitation. This procedure for testing and/or monitoring historic buildings, is particularly attractive for civil engineers concerned with the safety of complex historic structures.However, since the external force is not recorded, the identification methods have to be more sophisticated and based on stochastic mechanics. In this context, this contribution will introduce an innovative ambient identification method based on applying the Hilbert Transform, to obtain the analytical representation of the system response in terms of the correlation function. In particular, it is worth stressing that the analytical signal is a complex representation of a time domain signal: the real part is the time domain signal itself, while the imaginary part is its Hilbert transform. A 3DOF numerical example will be presented to show the accuracy of the proposed procedure, and comparisons with data from other methods assess the reliability of the approach. Finally, the identification method will be extended to the real case study of the Chiaramonte Palace, a historic building located in Palermo and known as “Steri”

The early detection of osteoporosis in a cohort of healthcare workers: Is there room for a screening program?

Workforce aging is becoming a significant public health problem due to the resulting emergence of age-related diseases, such as osteoporosis. The prevention and early detection of osteoporosis is important to avoid bone fractures and their socio-economic burden. The aim of this study is to evaluate the sustainability of a screening workplace program able to detect workers with osteoporosis. The screening process included a questionnaire-based risk assessment of 1050 healthcare workers followed by measurement of the bone mass density (BMD) with a pulse-echo ultrasound (PEUS) at the proximal tibia in the at-risk subjects. Workers with a BMD value 64 0.783 g/cm\ub2 were referred to a specialist visit ensuring a diagnosis and the consequent prescriptions. Any possible association between the outcome variable BMD 64 0.783 g/cm\ub2 and the risk factors was eval-uated. The costs were calculated with a full costing method. We identified 60 pathological subjects. We observed increased risks for women, older ages, and menopause (p < 0.01). The yearly cost of our screening program estimated for this study was 8242 euros, and, considering the fragility bone fracture costs, we hypothesize a considerable economic savings, with a possible positive bene-fits/cost ratio of 2.07. We can say that the margin between the investment and results leads to a preference for this type of screening program. Osteoporosis is an occupational health problem, and a workplace screening program could be a cost-effective intervention

In Vitro Biocompatibility Evaluation of Nine Dermal Fillers on L929 Cell Line

Objective. Biomaterial research for soft tissue augmentation is an increasing topic in aesthetic medicine. Hyaluronic acid (HA) fillers are widely used for their low invasiveness and easy application to correct aesthetic defects or traumatic injuries. Some complications as acute or chronic inflammation can occur in patients following the injection. Biocompatibility assays are required for medical devices intended for human use, in order to prevent damages or injuries in the host. In this study, nine HA fillers were tested in order to evaluate their cytotoxicity and their effects on L929 cell line, according to the UNI EN ISO 10993 regulation. Methods. Extracts were prepared from nine HA fillers, and MTS viability assay was performed after 24 h, 48 h, and 72 h of exposure of cells to extracts. Cells cultured with HA filler extracts were monitored for up to 72 h, counted, and stained with haematoxylin/eosin in order to evaluate the cell proliferation rate and morphology. Results. None of the filler tested showed a cytotoxic effect. Two samples showed a higher vitality percentage and higher cell number while two samples showed a lower vitality percentage and lower cell number at 72 h. Conclusion. Data obtained suggest that although examined fillers are not cytotoxic, they show different effects on the in vitro cell proliferation rate. In vitro studies of medical devices could lead to important implications since these could aid to predict effects about their in vivo application. These easy and rapid assays could be useful to test new materials intended for human use avoiding animal tests