Frequency Upshift of the Transverse Optical Phonon Resonance in GaAs by Femtosecond Electron-Hole Excitation.

The impact of transient electric currents on the transverse optical (TO) phonon resonance is studied after excitation by two femtosecond near-infrared pulses via the fourth-order nonlinear terahertz emission. Nonlinear signals due to interband shift currents and heavy-hole-light-hole polarizations are separated from Raman-induced TO phonon coherences. The latter display a frequency upshift by some 100 GHz upon interband excitation of an electron-hole plasma. The frequency shift is caused by transverse electronic shift currents, which modify the dielectric function. A local-field model based on microscopic current densities reproduces the observed frequency upshift.

Prevalence and multicenter observational study on falls of hospitalized children and Italian, linguistic-cultural validation of the Humpty Dumpty Fall Scale.

INTRODUCTION: Falls in hospitals are a major problem also in pediatric settings. No Pediatric Fall Risk Assessment Scales (PFRAS) are validated in Italian. GOALS: to perform the Italian validation of the Humpty-Dumpty Falls Scale (HDFS); to assess its predictive performance; to estimate the frequency of falls in hospitalized children and to analyze possible associations between children's clinical variables and falls. METHODS: The study's first step was the cultural-linguistic validation of HDFS in Italian. Second, evaluation of the Italian HDFS's performance on 1500 hospitalized children. Third, modifications of the Italian HDFS to improve its performance. Fourth, analysis of falls frequency and associations between falls and patients' clinical variables. RESULTS: The Italian HDFS (HDFS-ita) showed good Validity (SCVI=0.92) and inter-rater Reliability (Cohen's kappa=0.965), but poor Sensitivity (77.8%) and Specificity (36.6%). A new 3-item version of the HDFS-ita (HDFS-ita-M) was set, with a cut-off of 7, only for subjects 1 to 15 year-old. Although better, the HDFS-ita-M's performance remains poor (Sensitivity=77.8%, Specificity=53.3%, ROC curve's AOC=0.670). The frequency of pediatric falls was 6.38 per thousand children (CI95% 3.36-12.08) with a maximum frequency in children aged 3 to 6 years (11.28 per thousand children, CI95% 3.84-32.63). Motor/walking disorders (p=0.005), enuresis (p=0.0002), being in single room (p=0.04), admittance to pediatric neuropsychiatry/neurology wards (p=0.001), and neurological disorders (p=0.02) were associated to falls. DISCUSSION: HDFS-ita-M has a better but still poor performance than HDFS-ita. This study provides useful data about pediatric falls and their possible risk factors which will help pediatric hospitals in determining patient safety policies. Further studies are needed to determine an adequate panel of variables to estimate pediatric falls risk.

Resonant Second-Order Nonlinear Terahertz Response of Gallium Arsenide.

The second-order nonlinear response of bulk GaAs in the terahertz (THz) range is mapped via the THz field emitted after near-infrared interband excitation. Phase-resolved THz detection reveals three nonlinear processes occurring in parallel, the Raman excitation of transverse optical phonons, the creation of coherent polarizations on heavy-hole-light-hole transitions, and the generation of displacive shift currents with a THz spectrum controlled by the near-infrared optical phase. Theoretical calculations reproduce the data and demonstrate the interband character of shift currents.

Fast Detection of a Weak Signal by a Stochastic Resonance Induced by a Coherence Resonance in an Excitable GaAs/Al_{0.45}Ga_{0.55}As Superlattice.

The effect of a coherence resonance is observed experimentally in a GaAs/Al_{0.45}Ga_{0.55}As superlattice under dc bias at room temperature, which is driven by noise. For an applied voltage, for which no current self-oscillations are observed, regular current self-oscillations with a frequency of about 82 MHz are induced by exceeding a certain noise amplitude. In addition, a novel kind of a stochastic resonance is identified, which is triggered by the coherence resonance. This stochastic resonance appears when the device is driven by an external ac signal with a frequency, which is relatively close to that of the regular current self-oscillations at the coherence resonance. The intrinsic oscillation mode in the coherence resonance is found to be phase locked by an extremely weak ac signal. It is demonstrated that an excitable superlattice device can be used for the fast detection of weak signals submerged in noise. These results are very well reproduced by results using numerical simulations based on a sequential resonant tunneling model of nonlinear electron transport in semiconductor superlattices.

Terahertz quantum-cascade lasers as high-power and wideband, gapless sources for spectroscopy.

Terahertz (THz) quantum-cascade lasers (QCLs) are powerful radiation sources for high-resolution and high-sensitivity spectroscopy with a discrete spectrum between 2 and 5 THz as well as a continuous coverage of several GHz. However, for many applications, a radiation source with a continuous coverage of a substantially larger frequency range is required. We employed a multi-mode THz QCL operated with a fast ramped injection current, which leads to a collective tuning of equally-spaced Fabry-Pérot laser modes exceeding their separation. A continuous coverage over 72 GHz at about 4.7 THz was achieved. We demonstrate that the QCL is superior to conventional sources used in Fourier transform infrared spectroscopy in terms of the signal-to-noise ratio as well as the dynamic range by one to two orders of magnitude. Our results pave the way for versatile THz spectroscopic systems with unprecedented resolution and sensitivity across a wide frequency range.

Central-line associated bloodstream infections in a tertiary care children's University hospital: a prospective study.

BACKGROUND: The central-line associated bloodstream infections (CLABSI) are the most common healthcare-associated infections in childhood. Despite the international data available on healthcare-associated infections in selected groups of patients, there is a lack of large and good quality studies. The present survey is the first prospective study monitoring for 6 months the occurrence of central-line associated bloodstream infections in all departments of an Italian tertiary care children's university hospital. METHODS: The study involved all children aged less than 18 years admitted to Meyer Children's University Hospital, Florence, Italy who had a central line access between the October 15th, 2014 and the April 14th, 2015. CLABSI were defined according to the Center for Disease Control and Prevention criteria. CLABSI incidence rates with 95% confidence limits were calculated and stratified for the study variables. For each factor the relative risk and 95% confidence intervals were evaluated. Statistical analysis was performed using the statistical software SPSS for Windows, version 22.0 (SPSS Inc., Chicago, IL), p < 0.05 was considered statistically significant. RESULTS: CLABSI rate was 3.73/1000 (95% CI: 2.54-5.28) central line-days. A higher CLABSI incidence was seen with female gender (p = 0.045) and underlying medical conditions (excepting prematurity, surgical diseases and malignancy) (p = 0.06). In our study 5 infections, were caused by extended-spectrum ß-lactamase producing organisms and in one case by carbapenem-resistant Klebsiella pneumoniae. CONCLUSIONS: Our study confirms the spreading of multi-resistant pathogens as causes of healthcare associated infections in children. An increased incidence rate of CLABSI in our study was related to underlying medical conditions. Pediatric studies focusing on healthcare infections in this type of patients should be done in order to deepen our understanding on associated risk factors and possible intervention areas.

Serratia marcescens outbreak in a neonatal intensive care unit: crucial role of implementing hand hygiene among external consultants.

BACKGROUND: Serratia marcescens represents an important pathogen involved in hospital acquired infections. Outbreaks are frequently reported and are difficult to eradicate. The aim of this study is to describe an outbreak of Serratia marcescens occurred from May to November 2012 in a neonatal intensive care unit, to discuss the control measures adopted, addressing the role of molecular biology in routine investigations during the outbreak. METHODS: After an outbreak of Serratia marcescens involving 14 neonates, all admitted patients were screened for rectal and ocular carriage every two weeks. Extensive environmental sampling procedure and hand sampling of the staff were performed. Antimicrobial susceptibility pattern and molecular analysis of isolates were carried out. Effective hand hygiene measures involving all the external consultants has been implemented. Colonized and infected babies were cohorted. Dedicated staff was established to care for the colonized or infected babies. RESULTS: During the surveillance, 65 newborns were sampled obtaining 297 ocular and rectal swabs in five times. Thirty-four Serratia marcescens isolates were collected: 11 out of 34 strains were isolated from eyes, being the remaining 23 isolated from rectal swabs. Two patients presented symptomatic conjunctivitis. Environmental and hand sampling resulted negative. During the fifth sampling procedure no colonized or infected patients have been identified. Two different clones have been identified. CONCLUSIONS: Ocular and rectal colonization played an important role in spread of infections. Implementation of infection control measures, involving also external specialists, allowed to control a serious Serratia marcescens outbreak in a neonatal intensive care unit.

Multimode nanobeam cavities for nonlinear optics: high quality resonances separated by an octave.

We demonstrate the design, fabrication and characterization of nanobeam cavities with multiple higher order modes. Designs with two high Q modes with frequency separations of an octave are introduced, and we fabricate such cavities exhibiting resonances with wavelength separations of up to 740 nm.

Nonlinear frequency conversion using high-quality modes in GaAs nanobeam cavities.

We demonstrate the design, fabrication, and characterization of nanobeam photonic crystal cavities in (111)-GaAs with multiple high-Q modes, with large frequency separations (up to 740 nm in experiment, i.e., a factor of 1.5 and up to an octave in theory). Such structures are crucial for efficient implementation of nonlinear frequency conversion. Here, we employ them to demonstrate sum-frequency generation from 1300 and 1950 nm to 780 nm. These wavelengths are particularly interesting for quantum frequency conversion between Si vacancy centers in diamond and the fiber-optic network.

[The transition from paediatric to adult care: a new paradigm]. / La transizione bambino-adulto: un nuovo paradigma.

In healthcare, the child-adult transition is the point of intersection between two health care systems organized in a network (pediatric and adult care), each with its own specificities and dysfunctions. Information, education and empowerment of young adults are crucial in preparing them for the transition to adult care while centrality of the patient, patient preferences, sharing with patients and their families, and multi-disciplinary approach, are the key words of the transition process. Barriers to overcome include the reluctance of patients and their families to separate from the pediatric care system, the tendency of pediatric healthcare workers not to favour the emancipation process and the inability of healthcare workers providing adult care to perceive the sense of insecurity and dependence experienced by young adults.

Microcavity phonoritons - a coherent optical-to-microwave interface.

Optomechanical systems provide a pathway for the bidirectional optical-to-microwave interconversion in (quantum) networks. These systems can be implemented using hybrid platforms, which efficiently couple optical photons and microwaves via intermediate agents, e.g. phonons. Semiconductor exciton-polariton microcavities operating in the strong light-matter coupling regime offer enhanced coupling of near-infrared photons to GHz phonons via excitons. Furthermore, a new coherent phonon-exciton-photon quasiparticle termed phonoriton, has been theoretically predicted to emerge in microcavities, but so far has eluded observation. Here, we experimentally demonstrate phonoritons, when two exciton-polariton condensates confined in a µm-sized trap within a phonon-photon microcavity are strongly coupled to a confined phonon which is resonant with the energy separation between the condensates. We realize control of phonoritons by piezoelectrically generated phonons and resonant photons. Our findings are corroborated by quantitative models. Thus, we establish zero-dimensional phonoritons as a coherent microwave-to-optical interface.

Flying electron spin control gates.

The control of "flying" (or moving) spin qubits is an important functionality for the manipulation and exchange of quantum information between remote locations on a chip. Typically, gates based on electric or magnetic fields provide the necessary perturbation for their control either globally or at well-defined locations. Here, we demonstrate the dynamic control of moving electron spins via contactless gates that move together with the spins. The concept is realized using electron spins trapped and transported by moving potential dots defined by a surface acoustic wave (SAW). The SAW strain at the electron trapping site, which is set by the SAW amplitude, acts as a contactless, tunable gate that controls the precession frequency of the flying spins via the spin-orbit interaction. We show that the degree of precession control in moving dots exceeds previously reported results for unconstrained transport by an order of magnitude and is well accounted for by a theoretical model for the strain contribution to the spin-orbit interaction. This flying spin gate permits the realization of an acoustically driven optical polarization modulator based on electron spin transport, a key element for on-chip spin information processing with a photonic interface.

Application of electron tomography for comprehensive determination of III-V interface properties.

We present an electron tomography method for the comprehensive characterization of buried III-V semiconductor interfaces that is based on chemical-sensitive high-angle annular dark-field scanning transmission electron microscopy. For this purpose, an (Al,Ga)As/GaAs multi-layer system grown by molecular beam epitaxy is used as a case study. Isoconcentration surfaces are exploited to obtain topographic height maps of 120 nm × 120 nm area, revealing the interface morphology. By applying the height-height correlation function, we are able to determine important interface properties like root mean square roughness and lateral correlation length of various interfaces of the (Al,Ga)As/GaAs system characterized by different Al concentrations. Height-difference maps based on isosurfaces corresponding to 30% and 70% of the total compositional difference at the interfaces are used to create topographic maps of the interface width and to calculate an average interface width. This methodology proves differences in the properties of direct and inverted interfaces and allows the observation of interfacial anisotropies.

Passively mode-locked Tm,Ho:YAG laser at 2 microm based on saturable absorption of intersubband transitions in quantum wells.

We report the first demonstration of a solid state laser passively mode-locked through the saturable absorption of short-wavelength intersubband transitions in doped quantum wells: a continuous wave Ti:sapphire laser end-pumped Tm,Ho:YAG laser at the center wavelength of 2.091 mum utilizing intersubband transitions in narrow In(0.53)Ga(0.47)As/Al(0.53)As(0.47)Sb quantum wells. Stable passive mode-locking operation with maximum average output power of up to 160 mW for 2.9 W of the absorbed pump power could last for hours without external interruption and a mode-locked pulse with duration of 60 ps at repetition rate of 106.5 MHz was generated.

Nosocomial Rotavirus Gastroenteritis in pediatric patients: a multi-center prospective cohort study.

BACKGROUND: Few data are available on the incidence of nosocomial Rotavirus infections (NRVI) in pediatric hospitals and on their economic impact. The goals of this study were: to evaluate the incidence of NRVI in various Italian pediatric wards during the course of two peak RV seasons; to investigate possible risk factors for NRVI; to estimate the costs caused by NRVI. METHODS: prospective cohort study. POPULATION: All the children under 30 months of age who were admitted without any symptom or diagnosis of gastroenteritis in the pediatric hospitals of Florence, Naples, Brescia and Ancona, Italy, during the winter-spring periods 2006-2007 and 2007-2008. Serial RV rapid tests and clinical monitoring were carried out on the cohort. Telephone interviews were performed from 3 to 5 days after discharge. RESULTS: 520 out of 608 children completed the study (85.6%). The overall incidence of NRVI was 5.3% (CI95% 3.6-7.5), (7.9 per 1,000 days of hospital stay, CI 95% 5.3-11.3). The average duration of hospital stay was significantly longer for children who had NRVI (8.1 days, SD 5.4) than for non-infected children (6.4 days, SD 5.8, difference 1.7 days, p = 0.004). The risk of contracting NRVI increased significantly if the child stayed in hospital more than 5 days, RR = 2.8 (CI95% 1.3-6), p = 0.006. In Italy the costs caused by NRVI can be estimated at 8,019,155.44 Euro per year. 2.7% of the children hospitalized with no gastroenteritis symptoms tested positive for RV. CONCLUSIONS: Our study showed a relevant incidence of NRVI, which can increase the length of the children's stay in hospital. Limiting the number of nosocomial RV infections is important to improve patients' safety as well as to avoid additional health costs.

Use of non-conventional nurses' attire in a paediatric hospital: a quasi-experimental study.

AIMS: To test the impact of a multi-coloured non-conventional attire on a population of children admitted to a paediatric hospital. DESIGN: Quasi-experimental before-after controlled study. BACKGROUND: It has been suggested that non-conventional nurses' uniforms in paediatric settings may contribute to lowering children's distrust towards healthcare providers and reduce fear. Little formal research has investigated on the impact of nursing attire in a paediatric setting. No study has so far analysed the effects in actual use of a non-conventional, other than the traditional type of uniform, on a paediatric hospitalised population. Design: A quasi-experimental study. METHODS: We introduced multi-coloured nurses' attire in two wards of a paediatric hospital. Using open questions and semantic differential scales (SDS), we evaluated the effects of this non-conventional attire on a group of hospitalised children, compared to sex-and-age-matched controls interviewed before the introduction. Parents were also interviewed. RESULTS: One hundred and twelve hospitalised children and their parents (n = 112) were studied. The percentage of positive words used by children to define their nurse was higher in children interviewed after the introduction of non-conventional uniforms (96.2% vs. 81.8%, p = 0.01). Children's perception of nurses was significantly improved by the use of multi-coloured attire ('bad'-'good' SDS: p = 0.01; 'disagreeable'-'nice' SDS: p = 0.001). Children's perceptions regarding hospital environment did not change. Parents' perception of nurses' uniform adequacy to the role and capability to reassure resulted improved (p < 0.0001, p = 0.0003). CONCLUSIONS: Multi-coloured non-conventional attire were preferred by hospitalised children and their parents. Their introduction improved the perception children have of their nurses. Moreover, the coloured uniforms improve the parents perception about the reliability of the nurse. RELEVANCE TO CLINICAL PRACTICE: The use of non-conventional nurses' attire can contribute to improve the child-nurse relation, which has the potential to ease the discomfort experienced by children due to hospitalisation.

Public Health since the beginning: Neonatal incubators safety in a clinical setting.

BACKGROUND: The role of environmental cleaning as an effective measure to contain the diffusion of Healthcare Associated Infections (HAIs) has already been demonstrated. Among medical devices, neonatal incubators have been recognized as a source of pathogens involved in the spread of HAIs. Aim of the study was to assess the efficacy of a disinfection protocol for neonatal incubators. METHODS: The cross sectional study took place in the "Neonatal Pediatric Unit" of the Teaching Hospital of Siena: twenty incubators, used for critical newborns, were swabbed in 13 sampling points before and after the implementation of the disinfection protocol. Sanitation procedures were performed by trained staff, implementing the product Umonium38® Neutralis as disinfectant. Different culture media for the identification of the microbial contamination were adopted: plates were incubated for the proper time and the results were referred to Colony Forming Units (CFUs)/swab per point. Descriptive statistical analysis was performed. It was also evaluated the 95% confidence interval (C.I.) of the mean and the percentage of CFUs reduction by the bootstrap bias corrected and accelerated resampling method. RESULTS: Matched points analyzed were 313. The average CFUs percentage of reduction was 93.5% [C.I. 90.6-95.9%]: it was higher, 97.0% [C.I. 94.1-99.1%], in points placed inside the incubators structure compared to the 88.4% [C.I. 83.6-93.0%] obtained outside. CONCLUSION: The disinfection protocol achieved good results. Routine surveillance and supervision of the various aspects of the disinfection processes (procedures, staff and disinfectants) could guarantee a safe environment during the first days of babies' life, avoiding harmful conditions for the newborns' health.

[Influenza vaccination of nurses in an Italian pediatric hospital: effects on absenteeism and on costs, factors associated with vaccine uptake and analysis of personal motivations. A prospective cohort study]. / Una campagna di vaccinazione antinfluenzale gratuita tra gli infermieri in un ospedale pediatrico: fattori associati all'adesione, analisi delle motivazioni, effetti sulle assenze ed analisi dei costi. Studio di coorte prospettico.

AIMS: To evaluate the effects on absenteeism and on costs for the health care system (HCS) of influenza vaccination offered to nurses in a paediatric hospital; the factors associated with vaccination acceptance and non-acceptance; the motivations of vaccine-recipient and non-recipient nurses. METHODS: Cohort study. During the 2005-2006 influenza season we observed the entire nurse population of a Paediatric Hospital (n = 327) who were offered influenza vaccination at no cost at the working place. An anonymous questionnaire was also administered. RESULTS: Vaccination rate was 30.3%. Mean days of sick leave of vaccinated nurses (3.4 per 100 calendar days) and non vaccinated nurses (4.5 per 100 calendar days) differed but not significantly. The saving for HCS due to vaccination of less than 1/3 of nurses was equal to 0.67 nurse-years. Age > or = 40 years (RR 1.47, p = 0.01), length of service > or = 20 years (RR 1.81, p = 0.0003) and working in oncology ward (RR 2.09, p = 0.002) were predictors of adhesion to the vaccination campaign. Among motivations given for vaccination were: not to transmit influenza to hospitalised children (62.8%), to avoid getting sick (55.6%), to protect own family members (49.4%). Only 34% of vaccinated nurses would have made vaccination even if not offered for free. Among non-recipients' main motivations were: vaccination is unnecessary (62.4%), no trust in its efficacy (8.8%). No differences were found in the incidence of influenza symptoms reported by vaccinated and non vaccinated nurses. DISCUSSION: The utility of influenza vaccination to reduce absenteeism of nurses remains unclear. Strategies for influenza vaccination campaigns should particularly address younger nurses and should take into account the beliefs of each nurse in regards to own health.

Noise-enhanced chaos in a weakly coupled GaAs/(Al,Ga)As superlattice.

Noise-enhanced chaos in a doped, weakly coupled GaAs/Al_{0.45}Ga_{0.55}As superlattice has been observed at room temperature in experiments as well as in the results of the simulation of nonlinear transport based on a discrete tunneling model. When external noise is added, both the measured and simulated current-versus-time traces contain irregularly spaced spikes for particular applied voltages, which separate a regime of periodic current oscillations from a region of no current oscillations at all. In the voltage region without current oscillations, the electric-field profile consist of a low-field domain near the emitter contact separated by a domain wall consisting of a charge accumulation layer from a high-field regime closer to the collector contact. With increasing noise amplitude, spontaneous chaotic current oscillations appear over a wider bias voltage range. For these bias voltages, the domain boundary between the two electric-field domains becomes unstable and very small current or voltage fluctuations can trigger the domain boundary to move toward the collector and induce chaotic current spikes. The experimentally observed features are qualitatively very well reproduced by the simulations. Increased noise can consequently enhance chaotic current oscillations in semiconductor superlattices.

Consensus conference on the appropriateness of palivizumab prophylaxis in respiratory syncytial virus disease.

Respiratory syncytial virus infection represents a clinical burden among young children under 24 months. Palivizumab is the only drug licensed in Italy for the prevention of serious lower respiratory tract disease requiring hospitalization caused by respiratory syncytial virus in children at high risk. However recommendations for palivizumab prophylaxis are heterogeneous. Not all the published documents agree about the clinical indications of palivizumab; this could lead to different clinical practices and concerns about the appropriateness of prophylaxis. These issues and the lack of evidence about palivizumab prophylaxis efficacy in specific medical conditions brought on the idea of a consensus conference on the current recommendations for the management and prevention of bronchiolitis, in order to share useful indications. The goal was to perform a review of the evidence regarding the efficacy and the safety of palivizumab and give recommendations in order to harmonize its use. A structured and validated method to conduct the consensus process was adopted. The consensus conference recommends palivizumab prophylaxis in infants born before 29 weeks and younger than 12 months at the start of the epidemic season. According to evidence from literature and experts' opinion, palivizumab prophylaxis is not recommended in preterm infants of gestational age ≥29 weeks, without co-morbidity (i.e., cardiac, bronchopulmonary diseases). The experts identified some clinical rare conditions for which the decision of prophylaxis should be entrusted to the specialists. The evaluation of the appropriateness of palivizumab prophylaxis in the single patient should be documented by the specialists. Pediatr Pulmonol. 2016;51:1088-1096. © 2016 Wiley Periodicals, Inc.