Natural frequency discontinuity of vertical liquid sheet flows at transcritical threshold

The natural and forced dynamic response of a gravitational plane liquid sheet (curtain) of finite length interacting with an unconfined gaseous ambient is numerically and experimentally investigated. The global eigenvalue spectrum obtained by means of a linear inviscid one-dimensional model, accounting for the coupling between the curtain motion and the ambient pressure disturbances, clearly shows an abrupt increase (jump) in the characteristic natural frequency of the flow when the supercritical (We>1) to subcritical (We<1) transition occurs, with the Weber number defined as the ratio between inertia and capillary forces. On the other hand, the numerical simulation of the forced sheet response does not show any discontinuity between supercritical and subcritical conditions, as recently found by Torsey et al. (J. Fluid Mech., vol. 910, 2021, pp. 1-14) in the case of an infinite liquid sheet subjected to imposed ambient pressure disturbances not coupled with the curtain motion. It is argued that the forced liquid sheet behaviour varies continuously in shape and amplitude between the two regimes, not depending on the specific liquid-gas interaction model considered, whilst the natural frequency of the finite flow system does undergo a discontinuity, which can be theoretically predicted by the model of sheet-ambient interaction employed here. As a major result, the experimental evidence of the natural frequency jump is for the first time provided as well

POD and SPOD analysis of vertical liquid sheet

Modal analysis of thin liquid sheet driven by a harmonic forcing in the lateral velocity component at the inlet section is performed. Proper orthogonal decomposition (POD) and spectral POD (SPOD) techniques have been applied on two-dimensional two-phase numerical simulations data, obtained with the VOF approach, to characterize the main spatial and temporal structures. The investigation is carried out varying the Weber number and the Reynolds number. In supercritical regime (Weber number, > 1) both POD and SPOD techniques yield only leading sinuous modes, featuring a traveling perturbation. Spectral analysis confirms the occurrence of a discontinuity in frequency response between the supercritical and subcritical regimes. In subcritical regime ( < 1) the excitation of a combined sinuous-varicose motion is detected when the system is driven at resonance frequency for relatively high Reynolds numbers

Application of a score system to evaluate the risk of malnutrition in a multiple hospital setting

Background: An increased but unpredictable risk of malnutrition is associated with hospitalization, especially in children with chronic diseases. We investigated the applicability of Screening Tool for Risk of Impaired Nutritional Status and Growth (STRONGkids), an instrument proposed to estimate the risk of malnutrition in hospitalized children. We also evaluated the role of age and co-morbidities as risk for malnutrition. Methods. The STRONGkids consists of 4 items providing a score that classifies a patient in low, moderate, high risk for malnutrition. A prospective observational multi-centre study was performed in 12 Italian hospitals. Children 1-18 years consecutively admitted and otherwise unselected were enrolled. Their STRONGkids score was obtained and compared with the actual nutritional status expressed as BMI and Height for Age SD-score. Results: Of 144 children (75 males, mean age 6.5 \ub1 4.5 years), 52 (36%) had an underlying chronic disease. According to STRONGkids, 46 (32%) children were at low risk, 76 (53%) at moderate risk and 22 (15%) at high risk for malnutrition. The latter had significantly lower Height for Age values (mean SD value -1.07 \ub1 2.08; p = 0.008) and BMI values (mean SD-values -0.79 \ub1 2.09; p = 0.0021) in comparison to other groups. However, only 29 children were actually malnourished. Conclusions: The STRONGkids is easy to administer. It is highly sensitive but not specific. It may be used as a very preliminary screening tool to be integrated with other clinical data in order to reliably predict the risk of malnutrition. \ua9 2013 Spagnuolo et al.; licensee BioMed Central Ltd

Sustained low influenza vaccination in health care workers after H1N1 pandemic: A cross sectional study in an Italian health care setting for at-risk patients

Background: Despite consistent recommendations by all Public Health Authorities in support of annual influenza vaccination for at-risk categories, there is still a low uptake of influenza vaccine in these groups including health care workers (HCWs). Aim of this observational two-phase study was to estimate the immunization rates for influenza in four subsequent seasons and for pandemic H1N1 influenza in HCWs of a University Hospital, and to investigate its distribution pattern and the main determinants of immunization. Phase 1 data collection was performed in 2009-2010, during the peak of H1N1 pandemic. Phase 2 data collection, aimed to investigate seasonal influenza vaccination coverage in the three seasons after pandemic, was performed in 2012-2013. Methods: The overall H1N1 vaccination rate was derived by the Hospital immunization registry. In 2010, the personnel of three Departments (Infectious Diseases, Pediatrics and Gynecology/Obstetrics) completed a survey on influenza. A second-phase analysis was performed in 2012 to investigate influenza vaccination coverage in three consecutive seasons. Results: The first-phase survey showed a low coverage for influenza in all categories (17 %), with the lowest rate in nurses (8.1 %). A total of 37 % of health care workers received H1N1 vaccine, with the highest rate among physicians and the lowest in nurses. H1N1 vaccination was closely related to the Department, being higher in the Department of Infectious Diseases (53.7 %) and Pediatrics (42.4 %) than in Gynecology/Obstetrics (8.3 %). The second-phase survey showed the lowest rate of influenza vaccination in 2012/13 season. The main reasons for not being vaccinated were "Unsure of the efficacy of vaccine" and "Feel not at-risk of getting influenza or its complications". Despite recommendations, influenza vaccine uptake remains poor. Conclusion: Immunization is largely perceived as a personal protection rather than a measure needed to prevent disease spreading to at-risk patients. Compulsory vaccination against influenza should be considered as a possible strategy, at least in health institutions where at-risk patients are admitted

Determinants of low measles vaccination coverage in children living in an endemic area

Measles outbreaks were recently reported in Europe due to low immunization rates. In this scenario, identifying the reasons of no vaccination is crucial to set up strategies to improve immunization rate. A cross-sectional study was conducted to investigate the determinants of missed vaccination in children living in Southern Italy, during the 2016 outbreak. A standardized face-to-face questionnaire was used to record demographic data, immunization status, and reasons for missed vaccination. A total of 1141 children (median age 86&nbsp;months, male 47.2%) was enrolled, 77.8% of the children were adequately vaccinated for age, 6.3% were incompletely vaccinated for age, and 15.9% did not receive any vaccine dose. Vaccination rate and reasons for not vaccinating significantly varied according to age, with children ≤ 24&nbsp;months showing the lowest rate (67.8%). Reasons for not vaccinating included fear for side effects (51%), presence of underlying chronic conditions (12.2%), skip scheduled appointment (12.2%), refusal of vaccination (10.3%), acute illnesses (7.2%), and allergy to eggs (4.6%). The presence of underlying condition was a risk factor for inadequate immunization (p &lt; 0.0001). Only 4.7% of conditions were true contraindications to vaccine administration. Conclusion: We reported inadequate measles immunization rate in Southern Italy, with lowest rates in children ≤ 2&nbsp;years or with underlying conditions. Only a minority had true contraindications to vaccine uptake. Implementation strategies addressed to health-care professionals and families should focus on the reported determinants to increase measles vaccination coverage.What is Known:• Measles is a viral, highly communicable disease, preventable by vaccine.• Measles elimination in Europe failed as demonstrated by outbreaks in several countries, due to low immunization rates.What is New:• Inadequate measles immunization rate due to false contraindications in Southern Italy, with lowest rates in children ≤ 2&nbsp;years.• The presence of underlying disease is a risk factor for inadequate immunization

Isolated congenital coronary fistula in adult population: discussion a clinical case and review of current literature

We describe a case of a 56 year-old man with a history of chest pain. No evidence of myocardial ischemia or arrhytmias was observed. Echocardiographic examination in Emergency Department evidenced aortic root dilatation. Angio CT excluded aortic dissection. Trans esophageous Echocardiography (TEE) correctly identified an arterial fistula between the right coronary artery and superior vena cava, confirmed by angio CT 3-D reconstruction and coronarography. The definitive diagnosis was made after integrated approach (using TTE, TEE, CT, coronarography). The anatomic features of the fistula and the aortic root were examinated. Actually the patient is being followed with serial clinical and echocardiography examination for monitoring hemodynamic overload by fistula and size of aortic root for potential surgical correction. Current literature for incidence, diagnosis and the treatment of coronary fistulas is discussed

Prevalence of aneurysm of the interatrial septum in the general population and in patients with a recent episode of cryptogenetic ischemic stroke: a tissue harmonic imaging transthoracic ecocardiography study in 5.631 patients

Cerebral ischemia is among the principal causes of mortality and morbidity in industrialized countries being responsible of 10-12% of all deaths and of an elevated number of permanent disability. The cardioembolic forms may be responsible of the 30-35% of cerebrovascular acute syndrome, nevertheless in a significant percentage of cases, especially among young people, cerebral ischemic episodes are not induced by these cardiembolic forms: these cases are defined as cryptogenetic stroke/TIA. In these patients cardiac abnormalities represented by an aneurysm of the interatrial septum (ASA) and by a patent foramen ovale (PFO) have been frequently observed. The purpose of our prospective study was to evaluate, through transthoracic ecocardiography and tissue harmonic imaging (ETT-THI), the prevalence of ASA in the general population (group A) and the prevalence of ASA-FOP in a subgroup of patients with recent episode of cryptogenetic ischemic stroke/TIA (group B). We studied in a prospective manner from January 1 2003 to October 31t 2004 n. 5.631 patients. The presence of ASA was found in 3,2% of patients of group A, while in patients of group B we identifyed an ASA in 32% and a POF in 42% of the cases. Using a ETT-THI, our study shows in a wide range of a non selected population a prevalence of ASA greater than in previous studies. Such high prevalence in the general population of patients submitted to echocardiography and the higher frequency in subjects with recent cryptogenetic stroke, suggests to search carefully these abnormalities at the level of the interatrial septum using the harmonic imaging method

Search for lepton number and flavour violation in K+ and pi0 decays

The NA62 experiment at CERN collected a large sample of charged kaon decays into final states with multiple charged particles in 2016-2018. This sample provides sensitivities to rare decays with branching ratios as low as 10 −11 . Searches for the lepton number violating K + → π − µ + e+ decay and the lepton flavour violating K + → π + µ − e + and π 0 → µ − e + decays are reported. No evidence for these decays is found and upper limits of the branching ratios are obtained at 90% confidence level. These results improve by one order of magnitude over previous results for these decay modes

New measurement of the radiative decay Ke3g at the NA62 experiment at CERN

The NA62 experiment at CERN reports new results from the study of the radiative kaon decay K+→π0e+νγ (Ke3γ ), using a data sample recorded in 2017 and 2018. Preliminary results with the most precise measurement of the Ke3γ branching ratio, and a T-asymmetry measurement in the Ke3γ decay, are presented

Numerical study on the flow field generated by a double-orifice synthetic jet device

In the last few years Synthetic Jet (SJ) actuators have shown their full potential in controlling and manipulate an incoming crossflow. Indeed, these devices have been able to control separated flows over aerodynamic bodies, delay or anticipate transition to turbulence, suppress or enhance turbulence and control liquid jets and sprays. In many applications arrays of SJ actuators or multiple-orifice (or multi-slot) devices are preferred to single-orifice/single-slot actuators. Multi-orifice strategies have been often employed for the control of separated flows, in order to cover the entire spanwise length of the flow to be controlled or to introduce a spanwise modulation of the control. Moreover, such devices are also employed in cooling applications, since multiple-orifice devices exhibit a larger heat dissipation with respect to a single, centred orifice one. Despite this fact, a great part of the studies concerning the design of a SJ actuator have been based on single-slot or single-orifice configurations. As a consequence, the present work is focused on the interaction between the jets generated by a multiple-orifice actuator. In particular, the external flow field generated by a double-orifice SJ actuator is investigated. The analyzed actuator is sealed at one side by an elastic diaphragm, which is composed of a piezoelectric disk and a flexible shim, and connected to the external environment via two circular orifices. The numerical setup matches the flow parameters of the experiments and the preliminary numerical simulations reported in [1]. A series of numerical simulations are carried out, varying the distance between the orifices. The computational domain includes the entire cavity, the orifices, and the external environment. Differently from [1], the investigation focuses on the development of the external flow field, rather than on the vortex motion near the exit plane and within the cavity. The instantaneous flow field is characterized by the presence of two, in-phase, zero-net-mass-flux jets. These jets become turbulent, converge towards each other and merge. The characteristics of the flow are strongly dependent on the distance between the orifice centers and their momentum [2]. It is important to find a scaling law for the merging point streamwise position as a function of these parameters, since jet merging is responsible for circulation cancellation and could be detrimental for flow control applications. Time-averaged flow fields are obtained, and their features are compared with the (time-averaged) characteristics of three-dimensional, continuous twinjets [3]. Moreover, time and phase-averaged velocity fields and fluctuations are compared with those of single-orifice actuators. Finally, spectral analysis of probes (located along the jets trajectories) and dynamic mode decomposition (DMD) are used to investigate the inner shear-layer interactions and recognize shifts in the dominant frequency along the streamwise direction. The latter analyses are useful to detect the vortical motions which are responsible of the jet convergence, of the entrainment of external fluid and of the far-field behaviour of the jet