Suppression of the Coffee Ring Effect in a Single Solvent-Based Silicon Nanoparticle Ink.

Silicon (Si) is made printable by dispersing Si nanoparticles in a single organic solvent. Viscoelastic properties of the prepared inks as well as the uniformity of inkjet-printed thin films are investigated in dependence on the Si volume fraction. It has been demonstrated that no ink additives are needed to completely suppress the occurrence of the coffee ring effect. This is obtained by increasing the ink's volume fraction to induce gelation in order to generate elasticity. The printability of our inks is investigated in terms of Weber, Reynolds, and Ohnesorge numbers and found to be maintained even at high particle loads due to shear-thinning viscosity behavior. When printed onto tungsten (W) substrates, Si inks with ϕ(Si) = 0.4% and ϕ(Si) = 2.1% leave a ring stain after drying, whereas coffee rings are absent for inks with ϕ(Si) = 3.0% and above. The reason for this is a significant ink elasticity achieved by the buildup of a gel network for higher particle loads, which leads to thixotropy-like properties. These are low viscosity for printability and elevated elasticity during ink drying, made possible by a breakup of the gel network during drop formation in conjunction with a rapid network reformation after deposition.

Few-cycle short-wave-infrared light source for strong-field experiments at 200 kHz repetition rate.

We present a compact, few-cycle, short-wave infrared light source delivering 13 µJ, carrier-envelope phase (CEP) stable pulses around 2 µm, operating at 200 kHz repetition rate. Starting from an ytterbium fiber amplifier, the seed is produced via white-light generation followed by difference frequency generation, and later amplified in two BiBO nonlinear crystals. A pulse duration of 15.8 fs is measured with the dispersion scan technique, while the CEP stability is assessed via a monolithic spectral interferometry scheme. We demonstrate the potential of the system to drive strong-field experiments by performing high-order harmonic generation in argon gas.

Overweight and obesity: an emerging problem in patients with congenital heart disease.

Due to technological and medical advances the population of adults with congenital heart disease (ACHD) is constantly growing. Worldwide, congenital heart disease (CHD) affects 1.35-1.5 million children each year and the number of ACHD meanwhile exceeds the number of CHD children. It has been found that a substantial number of ACHD present problematic health behaviors, such as physical inactivity and bad nutritional habits. Recent studies document alarming rates of overweight and obesity among CHD patients which may consequently lead to further health complications in this population. The present article focuses on the distinct psychosocial effects resulting from the diagnosis of CHD and their impact on developing disordered eating patterns and excess weight. It seeks to identify unique risk factors and relevant explanations associated with the increasing prevalence of obesity among CHD patients. This review suggests a vital need to establish clinical guidelines for nutrition and weight management in this patient population as part of a holistic treatment approach.

Publication rate of abstracts presented at the Congress of the European Federation of National Associations of Orthopaedics and Traumatology (EFORT).

BACKGROUND: The publication rate of presented abstracts is an important parameter to assess the scientific quality of medical congresses. It has been investigated for many congresses in orthopaedics and traumatology, but until now, it has not been studied for the congress of the European Federation of National Associations of Orthopaedics and Traumatology (EFORT). The aims of this study were to determine: (1) the publication rate of the EFORT congress, (2) factors that favour publication of abstracts presented at the EFORT congress, (3) the consistency between the congress abstract and publication in relation to authorship. HYPOTHESIS: There are factors that favour publication of abstracts presented at the EFORT congress and there is a high consistency between the congress abstract and publication in relation to authorship. MATERIALS AND METHODS: All 1624 abstracts presented at the EFORT congress in 2011 were included in this study, to allow a 5-year period for publication after the congress. The characteristics of the abstracts presented were studied and the publication rate in peer-reviewed journals was determined using a Medline search. RESULTS: The publication rate for studies presented at the 2011 EFORT congress was 42% (677/1624 abstracts), with a mean of 16 months (-56 to 60 months) between congress and publication. The mean impact factor of the publications was 1.8 (0-7.6). A significantly higher publication rate was found for: oral presentations (52%; 322/617) versus posters (35%; 355/1007) (p<0.01), experimental studies (53%; 110/208) versus clinical studies (40%; 507/1254) (p<0.01), and studies with higher levels of evidence of I or II (59%; 144/244) versus studies with lower levels of evidence of III or IV (36%; 362/1005) (p<0.01). A new author was added in 59% (403/677) of the publications. DISCUSSION: Factors that favour publication of abstracts presented at the EFORT congress are oral presentation, experimental study, and a study with a higher level of evidence of I or II. It is common that a new author is added in the publication. Nevertheless, a high percentage of congress abstracts (58%; 947/1624) remains unpublished. LEVEL OF EVIDENCE: IV, retrospective study.

Relaxation Oscillations and Ultrafast Emission Pulses in a Disordered Expanding Polariton Condensate.

Semiconductor microcavities are often influenced by structural imperfections, which can disturb the flow and dynamics of exciton-polariton condensates. Additionally, in exciton-polariton condensates there is a variety of dynamical scenarios and instabilities, owing to the properties of the incoherent excitonic reservoir. We investigate the dynamics of an exciton-polariton condensate which emerges in semiconductor microcavity subject to disorder, which determines its spatial and temporal behaviour. Our experimental data revealed complex burst-like time evolution under non-resonant optical pulsed excitation. The temporal patterns of the condensate emission result from the intrinsic disorder and are driven by properties of the excitonic reservoir, which decay in time much slower with respect to the polariton condensate lifetime. This feature entails a relaxation oscillation in polariton condensate formation, resulting in ultrafast emission pulses of coherent polariton field. The experimental data can be well reproduced by numerical simulations, where the condensate is coupled to the excitonic reservoir described by a set of rate equations. Theory suggests the existence of slow reservoir temporarily emptied by stimulated scattering to the condensate, generating ultrashort pulses of the condensate emission.

Sensitivity of resonant tunneling diode photodetectors.

We have studied the sensitivity of AlGaAs/GaAs double barrier resonant tunneling diode photodetectors with an integrated GaInNAs absorption layer for light sensing at the telecommunication wavelength of λ = 1.3 µm for illumination powers from pico- to microwatts. The sensitivity decreases nonlinearly with power. An illumination power increase of seven orders of magnitude leads to a reduction of the photocurrent sensitivity from S I  = 5.82 × 10(3) A W(-1) to 3.2 A W(-1). We attribute the nonlinear sensitivity-power dependence to an altered local electrostatic potential due to hole-accumulation that on the one hand tunes the tunneling current, but on the other hand affects the lifetime of photogenerated holes. In particular, the lifetime decreases exponentially with increasing hole population. The lifetime reduction results from an enhanced electrical field, a rise of the quasi-Fermi level, and an increased energy splitting within the triangular potential well. The non-constant sensitivity is a direct result of the non-constant lifetime. Based on these findings, we provide an expression that allows us to calculate the sensitivity as a function of illumination power and bias voltage, show a way to model the time-resolved photocurrent, and determine the critical power up to which the resonant tunneling diode photodetector sensitivity can be assumed constant.

Ghost Branch Photoluminescence From a Polariton Fluid Under Nonresonant Excitation.

An expanding polariton condensate is investigated under pulsed nonresonant excitation with a small laser pump spot. Far above the condensation threshold we observe a pronounced increase in the dispersion curvature, with a subsequent linearization of the spectrum and strong luminescence from a ghost branch orthogonally polarized with respect to the linearly polarized condensate emission. Polarization of both branches is understood in terms of spin-dependent polariton-polariton scattering. The presence of the ghost branch has been confirmed in time-resolved measurements. The effects of disorder and dissipation in the photoluminescence of polariton condensates and their excitations are discussed.

Nanothermometer Based on Resonant Tunneling Diodes: From Cryogenic to Room Temperatures.

Sensor miniaturization together with broadening temperature sensing range are fundamental challenges in nanothermometry. By exploiting a large temperature-dependent screening effect observed in a resonant tunneling diode in sequence with a GaInNAs/GaAs quantum well, we present a low dimensional, wide range, and high sensitive nanothermometer. This sensor shows a large threshold voltage shift of the bistable switching of more than 4.5 V for a temperature raise from 4.5 to 295 K, with a linear voltage-temperature response of 19.2 mV K(-1), and a temperature uncertainty in the millikelvin (mK) range. Also, when we monitor the electroluminescence emission spectrum, an optical read-out control of the thermometer is provided. The combination of electrical and optical read-outs together with the sensor architecture excel the device as a thermometer with the capability of noninvasive temperature sensing, high local resolution, and sensitivity.

Structural and optical properties of position-retrievable low-density GaAs droplet epitaxial quantum dots for application to single photon sources with plasmonic optical coupling.

The position of a single GaAs quantum dot (QD), which is optically active, grown by low-density droplet epitaxy (DE) (approximately 4 QDs/µm(2)), was directly observed on the surface of a 45-nm-thick Al0.3Ga0.7As capping layer. The thin thickness of AlGaAs capping layer is useful for single photon sources with plasmonic optical coupling. A micro-photoluminescence for GaAs DE QDs has shown exciton/biexciton behavior in the range of 1.654 to 1.657 eV. The direct observation of positions of low-density GaAs DE QDs would be advantageous for mass fabrication of devices that use a single QD, such as single photon sources.