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Metal clusters described in the framework of a simple tight binding model have been studied. Application of a dynamical approach (FOM), jointly with efficient storage of the sparse Hamiltonian matrix involved, is shown to allow direct evaluation of the electronic state density of sizable cubic-symmetry aggregates. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 584–593, 2007 [ABSTRACT FROM AUTHOR]

Spectral state densities of sizable metal clusters are evaluated directly by resorting to an efficient algorithm (FOM), set up and formerly utilized in other computational contexts. Investigation of SCC, FCC and BCC cluster geometries, described according to a tight-binding model able to take into account size- and surface-effects, leads to convincing evidence of the excellent prerogatives of the approach. [Copyright &y& Elsevier]

The dependence of linear optical response properties of bimetallic core–shell spherical nanoparticles is investigated as a function of size and relative composition. Two kinds of schematic models have been tested for describing the dielectric behavior of bimetallic particles and the related linear electromagnetic response: (i) Drude model, in conjunction with bulk dielectric data relative to the pure metals, in the assumption of a simple combination law; (ii) DFT-based approach to the dynamic polarizability of a binary particle, with the nature of the metals involved taken into account through their Wigner–Seitz radius. [Copyright &y& Elsevier]

The long-standing confined-electron-gas approach employed for simulating in a simple way the size-dependent “free electron” dielectric behavior of isotropic nanoparticles has been extended to the investigation of some spectroscopic properties of gold nanorods. The model adopted takes also into accounts size-independent interband effects estimated in a semiempirical way from bulk dielectric data. Predictions relative to the optical absorption and photoluminescence behavior, associated with the coherent, collective excitation of the electron gas, are derived on the basis of a fairly simple formalism, whose implementation allows to deal with a number of conduction electrons of the order of ca. 104, at a tolerable computational cost. The predictions of the model agree reasonably well with the few available experimental data. The nature of some approximations introduced suggests also the opportunity of a further analysis of specific points. [Copyright &y& Elsevier]

The light absorption of isolated bimetallic alloy nanoparticles composed of Au and Ag is investigated theoretically according to the traditional Mie theory and use of dielectric data. Particular attention is turned to establish the dependence of the absorption on both particle size and composition. The complex dielectric function of clusters involving 254 and 440 active electrons and different stoichiometry has been evaluated on the basis of various models of different degrees of schematicity (Drude theory, noninteracting quantum gas confined in a box, DFT approach), assuming in any case a simple combining rule for the alloy dielectric behavior. The interband contribution to the dielectric function is approximately estimated so as to assess the role of bound-electron effects. [Copyright &y& Elsevier]

Evaluates the construction of the exact quantum propagator of a particle subjected to a constant force. Merits of a procedure on the disentanglement of the time evolution operator; Power of a general treatment on a time-dependent variational approach.

A simple model mimicking the collision between two atomic partners in the presence of an intense radiation field is investigated according to a two-state, non perturbative approach, to put in quantitative evidence inadequacies in both transition probability and cross section arising from the use of transition amplitudes which are not gauge-invariant. [ABSTRACT FROM AUTHOR]

Presents a medical case of a patient with chronic granulomatous disease. History of the patient; Risk factors of the disease; Efficacy of prophylaxis in treating the disease.

Abstract: Far and near field electromagnetic scattering spectra of core-shell and alloy nanoparticles have been calculated in the context of the theory developed by Kerker. The core-shell particles considered are constituted by a spherical core made by Au or Ag with fixed radius, coated by an Ag or Au, isotropic shell of different radius. The needed dielectric functions of the involved metals have been estimated according to a semiempirical standard treatment. The scattering spectra calculated for core-shell and alloy nanoparticles with the same volume ratio show that the plasmon resonance wavelengths for the two geometries are similar, indicating a modest dependence on the internal structure. Conversely, near field scattering intensities and plasmon resonance widths for alloy or core-shell particles display a different behavior, even qualitatively, as a function of the shell volume. The scattering at the interface between the two metals appears to influence to a larger extent the shape of the scattering band, more than the plasmon resonance wavelength. [Copyright &y& Elsevier]

Surface Enhanced Raman Scattering (SERS) is studied for a simple molecule (CO) physisorbed on a nanoparticle belonging to a nanoparticle aggregate, with well defined composition and architecture, in order to assess the effect of metal nanostructure on the Raman enhancement. The approach involves explicit consideration of the molecule, with due allowance for the characteristics of its radiated field, which are believed to be particularly important elements in determining enhancement from complex-shape aggregates. The electrodynamic problem for a nonresonant polarizable point dipole in the presence of an aggregate of spherical scatterers has been resolved numerically, extending to a multi-particle system the treatment put forward by Kerker. [ABSTRACT FROM AUTHOR]

We have studied theoretically the far- and near-field scattering response of bimetallic Ag/Au core−shell and alloy nanoparticles. Particular emphasis is put on the near-field study, which is known to play a fundamental role in surface enhanced spectroscopies. The comparison between the scattering spectra of core−shell and alloy particles shows that for particles with a Au/Ag volume ratio greater than 2, the structural difference does not imply any significant difference in the optical response. For such particles, while the retardation effects are not negligible, the scattering at the interface between the two metals in the core−shell case does not seem to modify the scattering behavior. The scattering at the interface is conversely not negligible for particles with a lower Au/Ag ratio, where the particle inner structure seems to be important. [ABSTRACT FROM AUTHOR]

A strategy for reducing the risk of non-ergodic simulations in Monte Carlo calculations of the thermodynamic properties of clusters is discussed with the support of some examples. The results obtained attest the significance of the approach for the low-temperature regime, as non-ergodic sampling of potential energy surfaces is a particularly insidious occurrence. Fourier path integral Monte Carlo techniques for taking into account quantum effects are adopted, in conjunction with suitable tricks for improving the procedure reliability. Applications are restricted to Lennard-Jones clusters of rare-gas systems. [ABSTRACT FROM AUTHOR]

Background: Coronavirus Disease-19 (COVID-19) has rapidly become a pandemic emergency, distressing health systems in each affected country. Preparation strategies for managing this pandemic have been keys to face the COVID-19 surge all over the world and all levels of care. Materials and Methods: During the epidemic, the Italian society of pediatric emergency-urgency (SIMEUP) promoted a national survey aiming to evaluate preparedness and response of pediatric emergency departments (PED) critical in ensuring optimal management of COVID-19 cases. Results: Our results suggest that Italian PED have promptly set a proactive approach to the present emergency. 98.9% of the hospitals have defined special pathways and assistive protocols concerning the management of pediatric COVID-19 cases. The highest percentage of application of the measures for preventive and protective for COVID-19 concerned the use of personal protective equipments. Conclusions: Results show that the following measures for pediatric patients, admitted in PED, have been promptly implemented throughout the whole country: eg. use of protective devices, pre-triage of patients accessing the hospital. Despite COVID-19 being a new threat, we have shown that by developing an easy-to-follow decision algorithm and clear plans for the interventional platform teams, we can ensure optimal health care workers and patients' safety. [ABSTRACT FROM AUTHOR]

BACKGROUND: Variability in presentation of children with coronavirus disease 2019 (COVID-19) is a challenge in emergency departments (EDs) in terms of early recognition, which has an effect on disease control and prevention. We describe a cohort of 170 children with COVID-19 and differences with the published cohorts. METHODS: Retrospective chart reviews on children (0-18 years) evaluated in 17 Italian pediatric EDs. RESULTS: In our cohort (median age of 45 months; interquartile range of 4 months-10.7 years), we found a high number of patients,1 year with COVID-19 disease. The exposure happened mainly (59%) outside family clusters; 22% had comorbidities. Children were more frequently asymptomatic (17%) or with mild diseases (63%). Common symptoms were cough (43%) and difficulty feeding (35%). Chest computed tomography, chest radiograph, and point-of-care lung ultrasound were used in 2%, 36%, and 8% of cases, respectively. Forty-three percent of patients were admitted because of their clinical conditions. The minimal use of computed tomography and chest radiograph may have led to a reduced identification of moderate cases, which may have been clinically classified as mild cases. CONCLUSIONS: Italian children evaluated in the ED infrequently have notable disease symptoms. For pediatrics, COVID-19 may have rare but serious and life-threatening presentations but, in the majority of cases, represents an organizational burden for the ED. These data should not lower the attention to and preparedness for COVID-19 disease because children may represent a source of viral transmission. A clinically driven classification, instead of a radiologic, could be more valuable in predicting patient needs and better allocating resources. [ABSTRACT FROM AUTHOR]

Detailed data on clinical presentations and outcomes of children with COVID-19 in Europe are still lacking. In this descriptive study, we report on 130 children with confirmed COVID-19 diagnosed by 28 centers (mostly hospitals), in 10 regions in Italy, during the first months of the pandemic. Among these, 67 (51.5%) had a relative with COVID-19 while 34 (26.2%) had comorbidities, with the most frequent being respiratory, cardiac, or neuromuscular chronic diseases. Overall, 98 (75.4%) had an asymptomatic or mild disease, 11 (8.5%) had moderate disease, 11 (8.5%) had a severe disease, and 9 (6.9%) had a critical presentation with infants below 6 months having significantly increased risk of critical disease severity (OR 5.6, 95% CI 1.3 to 29.1). Seventy-five (57.7%) children were hospitalized, 15 (11.5%) needed some respiratory support, and nine (6.9%) were treated in an intensive care unit. All recovered. Conclusion:This descriptive case series of children with COVID-19, mostly encompassing of cases enrolled at hospital level, suggest that COVID-19 may have a non-negligible rate of severe presentations in selected pediatric populations with a relatively high rates of comorbidities. More studies are needed to further understand the presentation and outcomes of children with COVID-19 in children with special needs. What is Known: • There is limited evidence on the clinical presentation and outcomes of children with COVID-19 in Europe, and almost no evidence on characteristics and risk factors of severe cases. What is New: • Among a case series of 130 children, mostly diagnosed at hospital level, and with a relatively high rate (26.2%) of comorbidities, about three-quarter had an asymptomatic or mild disease. • However, 57.7% were hospitalized, 11.5% needed some respiratory support, and 6.9% were treated in an intensive care unit. [ABSTRACT FROM AUTHOR]

The use of antiemetics for vomiting in acute gastroenteritis in children is still a matter of debate. We conducted a double-blind randomized trial to evaluate whether a single oral dose of ondansetron vs domperidone or placebo improves outcomes in children with gastroenteritis. After failure of initial oral rehydration administration, children aged 1–6 years admitted for gastroenteritis to the pediatric emergency departments of 15 hospitals in Italy were randomized to receive one oral dose of ondansetron (0.15 mg/kg) or domperidone (0.5 mg/kg) or placebo. The primary outcome was the percentage of children receiving nasogastric or intravenous rehydration. A p value of 0.014 was used to indicate statistical significance (and 98.6% CI were calculated) as a result of having carried out two interim analyses. 1,313 children were eligible for the first attempt with oral rehydration solution, which was successful for 832 (63.4%); 356 underwent randomization (the parents of 125 children did not give consent): 118 to placebo, 119 to domperidone, and 119 to ondansetron. Fourteen (11.8%) needed intravenous rehydration in the ondansetron group vs 30 (25.2%) and 34 (28.8%) in the domperidone and placebo groups, respectively. Ondansetron reduced the risk of intravenous rehydration by over 50%, both vs placebo (RR 0.41, 98.6% CI 0.20–0.83) and domperidone (RR 0.47, 98.6% CI 0.23–0.97). No differences for adverse events were seen among groups. In a context of emergency care, 6 out of 10 children aged 1–6 years with vomiting due to gastroenteritis and without severe dehydration can be managed effectively with administration of oral rehydration solution alone. In children who fail oral rehydration, a single oral dose of ondansetron reduces the need for intravenous rehydration and the percentage of children who continue to vomit, thereby facilitating the success of oral rehydration. Domperidone was not effective for the symptomatic treatment of vomiting during acute gastroenteritis. [ABSTRACT FROM AUTHOR]

Acute gastroenteritis (AG) represents both the main cause of acute vomiting in children under 3 years old and a major cause of access to the emergency department. Even if several drugs may be able to reduce the emesis, the pharmacological treatment of vomiting in children remains a controversial issue, and several drugs are prescribed outside their authorized drug label with respect dosage, age, indication, or route of administration and are named as off-label. The aim of present study was to assess the off-label use of antiemetic drugs in patients less than 18 years with vomiting related to AG. This study was carried out in eight pediatric emergency departments in Italy. The following data were obtained crossing the pharmacy distribution records with emergency departments' patient data: sex and age of the patients and detailed information for each drug used (indication, dose, frequency, and route of administration). We recorded that antiemetic drugs were prescribed in every year, particularly in children up to 2 years old, and compared with both literature data and data sheet; 30 % of the administered antiemetics were used off-label. In particular, domperidone was the only antiemetic used labeled for AG treatment in pediatric patients, while metoclopramide and ondansetron have been off-label for both age and indications (i.e., AG treatment). Conclusions: In conclusion, we documented an off-label use of antiemetics in children, and this could represents a problem of safety for the patient and a legal risk for the prescribing physician if patients have an unwanted or bad outcome from treatment. [ABSTRACT FROM AUTHOR]

Progress in near-field optical spectroscopy research on metal nanoparticles demands a better understanding of the role played by particle−particle interactions and a deeper insight of the influence of the incident field wavelength. This is particularly true for scanning near-field optical microscopy (SNOM), where the mechanism by which some components of the evanescent illuminating field are transformed into propagating field components that carry information about the sample is at the core of the image formation and where the role played by the interactions between sample and tip remains a still open problem. In this perspective, we investigate numerically the optical behavior of small aggregates of spherical nanoparticles, taking into account the electromagnetic coupling between all particles and the apertureless tip. The tip is modeled as a sphere made of different materials characterized by appropriate dielectric functions. We find that the tip material affects both qualitatively and quantitatively the SNOM images; more important, from the analysis of the calculated scattering cross section, the resonance plasmon location of the whole (aggregate + tip) system undergoes detectable changes, if the tip is constituted of the same material of the sample, as the tip is situated in different positions. This modification of the plasmon frequencies induces a nontrivial variation of the near-field intensity as a function of the tip position and the resulting SNOM image can be distorted with respect to the actual shape of the sample. No simple arguments can be used to relate the value of the local field on the tip surface to the scattering cross section value; depending on the tip material, the comparison between these two measurements can help to clarify the role of basic interactions in the scattering mechanism. [ABSTRACT FROM AUTHOR]

Progress in near-field optical spectroscopy research on metal nanoparticles demands a better understanding of the role of particle−particle and tip−sample interactions. In this perspective, we investigate theoretically, at a very moderate level of sophistication, the optical behavior of simple silver nanoparticle aggregates, in terms of a formalism involving a multipolar expansion of the fields involved, along with a simplified model for the optical behavior of nanostructures previously developed. In particular, the tip−sample interaction is taken into account roughly, treating the tip as an additional, single particle, characterized by proper dielectric behavior. [ABSTRACT FROM AUTHOR]

Near-field and far-field extinction and scattering efficiencies for UV-vis-irradiated spherical gold nanoparticles of varying size have been estimated as a function of the radiation wavelength. Several different dielectric function models are used to explore the role of quantum-size effects. The results suggest that the utilization of bulk dielectric data does not capture quantitatively important size effects and may correspond to an unjustified oversimplification. [ABSTRACT FROM AUTHOR]

The assessment of the performance of STO basis sets for the ab initio estimation of nonlinear electromagnetic response properties of molecules, using a Time Dependent Hartree-Fock procedure, has been extended from the first to the second dynamic hyperpolarizability of three bench polyatomics (H2O, CH4, NH3). Calculations based on extended basis sets are reported and briefly discussed in order to provide a wider perspective on the existing comparisons. [ABSTRACT FROM AUTHOR]

The performance of STO basis sets for the ab initio estimation of the nonlinear electromagnetic response properties of molecules, in terms of a time-dependent Hartree–Fock procedure, is investigated. Applications to the case of the first dynamic hyperpolarizability of three simple polyatomics (H2O, CH4, NH3) adopting several extended basis sets are reported and discussed. Independent estimates for the observables investigated obtained by the same approach in terms of Gaussian basis sets are confronted with our findings in the search for recipes of possible utility. [ABSTRACT FROM AUTHOR]

Ab initio quantum mechanical calculations in terms of multicenter Slater-type orbitals require accurate evaluation of basic one- and two-electron integrals, a difficult mathematical task that becomes in particular challenging in the two-electron case as four different expansion centers are involved. Here, we propose to illustrate the feasibility of attacking the problem of the multiple integrations needed entirely by numerical quadratures, in conjunction with a strategic program organization that allows evaluating simultaneously sets of thousands of integrals exploiting the mean characteristics of the integrands. This approach, envisaged and implemented many years ago by two of the present authors (C.G., O.S.), perhaps without adequate exposure, is endowed in our experience with good properties. The program package, which allows dealing on the same footing with linear and nonlinear molecular geometries, has been largely revised by introducing suitable adjustments and improvements (in particular extension to orbitals with azimuthal quantum number l = 3). © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [ABSTRACT FROM AUTHOR]

According to our hospital guidelines for patients with SARS-CoV-2 infection, the decision to discharge positive patients is based on the resolution of clinical symptoms. On the other hand, it emerges also that sierology may result more reliable than swabs in terms of identifying SARS-CoV-2 infection in children, a finding that has to be confirmed in more numerous cohorts of infected pediatric patients. The antibody response of IgG class to SARS-CoV-2, performed on a blood sample from 19 patients, collected at a mean time of 17.39 ± 6.34 days from hospital discharge, was detected in all tested patients. However, with the exception of two anecdotical Italian infants with SARS-CoV-2 infection who tested positive on rectal swabs [[7]], no systematic evaluation of fecal and urine transmission has been performed yet in SARS-CoV-2 Italian infected children. [Extracted from the article]

Reports on a study of an infant affected by myelodysplastic syndromes (MDS) in whom compete remission was achieved with cyclosporin. Patient; Results of bone marrow biopsy; Treatment; Conclusion.