432 research outputs found
Nanofabricated tips for device-based scanning tunneling microscopy
We report on the fabrication and performance of a new kind of tip for
scanning tunneling microscopy. By fully incorporating a metallic tip on a
silicon chip using modern micromachining and nanofabrication techniques, we
realize so-called smart tips and show the possibility of device-based STM tips.
Contrary to conventional etched metal wire tips, these can be integrated into
lithographically defined electrical circuits. We describe a new fabrication
method to create a defined apex on a silicon chip and experimentally
demonstrate the high performance of the smart tips, both in stability and
resolution. In situ tip preparation methods are possible and we verify that
they can resolve the herringbone reconstruction and Friedel oscillations on
Au(111) surfaces. We further present an overview of possible applications
Efficient microwave frequency conversion mediated by a photonics compatible silicon nitride nanobeam oscillator
Microelectromechanical systems and integrated photonics provide the basis for many reliable and compact circuit elements in modern communication systems. Electro-opto-mechanical devices are currently one of the leading approaches to realize ultra-sensitive, low-loss transducers for an emerging quantum information technology. Here we present an on-chip microwave frequency converter based on a planar aluminum on silicon nitride platform that is compatible with slot-mode coupled photonic crystal cavities. We show efficient frequency conversion between two propagating microwave modes mediated by the radiation pressure interaction with a metalized dielectric nanobeam oscillator. We achieve bidirectional coherent conversion with a total device efficiency of up to ~60%, a dynamic range of 2 × 10⁹ photons/s and an instantaneous bandwidth of up to 1.7 kHz. A high fidelity quantum state transfer would be possible if the drive dependent output noise of currently ~14 photons s⁻¹ Hz⁻¹ is further reduced. Such a silicon nitride based transducer is in situ reconfigurable and could be used for on-chip classical and quantum signal routing and filtering, both for microwave and hybrid microwave-optical applications
Gravitational wave signatures of the absence of an event horizon. I. Nonradial oscillations of a thin-shell gravastar
Gravitational waves from compact objects provide information about their
structure, probing deep into strong-gravity regions. Here we illustrate how the
presence or absence of an event horizon can produce qualitative differences in
the gravitational waves emitted by ultra-compact objects. In order to set up a
straw-man ultra-compact object with no event horizon, but which is otherwise
almost identical to a black hole, we consider a nonrotating thin-shell model
inspired by Mazur and Mottola's gravastar, which has a Schwarzschild exterior,
a de Sitter interior and an infinitely thin shell with finite tension
separating the two regions. As viewed from the external space-time, the shell
can be located arbitrarily close to the Schwarzschild radius, so a gravastar
might seem indistinguishable from a black hole when tests are only performed on
its external metric. We study the linearized dynamics of the system, and in
particular the junction conditions connecting internal and external
gravitational perturbations. As a first application of the formalism we compute
polar and axial oscillation modes of a thin-shell gravastar. We show that the
quasinormal mode spectrum is completely different from that of a black hole,
even in the limit when the surface redshift becomes infinite. Polar QNMs depend
on the equation of state of matter on the shell and can be used to distinguish
between different gravastar models. Our calculations suggest that
low-compactness gravastars could be unstable when the sound speed on the shell
vs/c>0.92.Comment: 19 pages, 8 figures. In press in Physical Review D. We found a new
family of modes and improved the discussion of nonradial instabilit
Osteoarticular infections in paediatric sickle cell disease: in the era of multidrugresistant bacteria
info:eu-repo/semantics/publishedVersio
Osteoarticular Infections in Infants Under 3 Months of Age
Background: Acute osteoarticular infections (OAI) in infants under 3 months of age (≤3M) are rare and remain a diagnostic challenge. Orthopedic complications and functional sequelae have been less well described in this age group. Our aims were to evaluate trends in aetiology, management, and outcomes of OAI ≤ 3M, and to compare these younger children who have OAI with older children.
Methods: A longitudinal observational study was conducted of OAI cases admitted to tertiary care pediatric hospital from 2008 to 2018. OAI ≤ 3M was compared with children above 3 months. Clinical, microbiological, imaging, and outcome data were analyzed.
Results: We identified 24 (9.1%) of the 263 OAI in children under 3 months. Analyzing OAI ≤ 3M there was a twofold increase since 2014; 54% were males with a median age of 28 days (IQR: 13.5-60.0), 10 (41.7%) were premature and nine (37.5%) had healthcare-associated infections. Microbiological causes were identified in 87.5%, mostly Staphylococcus aureus (57.1%) and Group B Streptococcus (23.8%), and 25% were multidrug-resistant (5 methicillin-resistant S. aureus and 1 Enterobacter cloacae). Bacteremia (100% vs 36.8%, P = 0.037), multidrug resistant bacteria (75% vs 16, P = 0.04), and healthcare-associated infections (100% vs 26.3%, P = 0.014) were associated with sequelae. Comparing OAI ≤ 3M with older children, OAI ≤ 3M were treated with longer antibiotic courses, had more complications and sequelae (17.4% vs 3.2%, P = 0.002).
Conclusions: S. aureus is still the most common cause of OAI ≤ 3M, and 25% of causative bacteria were multidrug-resistant bacteria. Complications and sequelae were more frequent in OAI ≤ 3M when compared with older children.info:eu-repo/semantics/publishedVersio
Do the Spanish university students follow Mediterranean dietary patterns?
Objetivo: Determinar el patrón de consumo de alimentos del alumnado de la Universidad de Alicante (UA) mediante el grado de adecuación a la dieta mediterránea. Método: Estudio transversal descriptivo para estimar la ingesta individual a través de un cuestionario de frecuencia de consumo de alimentos (CFCA) en una muestra representativa de 380 universitarios. Variables a estudio: edad, sexo, área geográfica de procedencia, peso y talla autoreferidos. Así como los alimentos y frecuencias de consumo que componen el CFCA. Se determinó el porcentaje de adecuación teniendo en cuenta, consumo real sobre consumo recomendado por la guía dieta mediterránea tradicional: (100 x raciones consumidas/raciones recomendadas). Se establecieron 5 rangos de porcentaje adecuación: consumo óptimo (80%-119%), consumo aceptable (60%-79%), consumo deficiente (40%-59%), consumo muy deficiente ( 120%). Se realizó contraste de diferencia de proporciones y la prueba t-Student con EPIDAT 3.1, y SPSS 15.0. Resultados: Prevalencia de sobrepeso-obesidad, es mayor en hombres (34,6%) que en mujeres (9,8%), p 120%). We analyzed the differences in proportions distribution and the Student’s t test with EPIDAT 3.1 and SPSS 15.0. Results: The prevalence of overweight/obesity is higher in men (34.6%) than in women (9.8%), p < 0.001, whereas women had higher prevalence of low weight (7.0%) than men (0.7%), p < 0.05. The consumption of grains and derivatives was very deficient (women = 90.6; men = 94.9) whereas the intake of red meats (women = 90.6; men = 92.7) and cold meats (women = 95.9%, men = 96.3%) was excessive. No student had an “optimal intake” or an “acceptable intake” of all the dietary groups (n = 12). Discussion: The educational level and access to the information do not protect the university population from socio-environmental factors that have an influence on their dietary habits. The public health strategies focused on this population group should be strengthen
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