1,641 research outputs found
Tunable asymmetric reflectance in silver films near the percolation threshold
We report on the optical characterization of semicontinuous nanostructured
silver films exhibiting tunable optical reflectance asymmetries. The films are
obtained using a multi-step process, where a nanocrystalline silver film is
first chemically deposited on a glass substrate and then subsequently coated
with additional silver via thermal vacuum-deposition. The resulting films
exhibit reflectance asymmetries whose dispersions may be tuned both in sign and
in magnitude, as well as a universal, tunable spectral crossover point. We
obtain a correlation between the optical response and charge transport in these
films, with the spectral crossover point indicating the onset of charge
percolation. Such broadband, dispersion-tunable asymmetric reflectors may find
uses in future light-harvesting systems.Comment: 18 pages, 5 figures, accepted by Journal of Applied Physic
Signatures of superconducting gap inhomogeneities in optical properties
Scanning tunneling spectroscopy applied to the high- cuprates has
revealed significant spatial inhomogeneity on the nanoscale. Regions on the
order of a coherence length in size show variations of the magnitude of the
superconducting gap of order or more. An important unresolved question
is whether or not these variations are also present in the bulk, and how they
influence superconducting properties. As many theories and data analyses for
high- superconductivity assume spatial homogeneity of the gap magnitude,
this is a pressing question. We consider the far-infrared optical conductivity
and evaluate, within an effective medium approximation, what signatures of
spatial variations in gap magnitude are present in various optical quantities.
In addition to the case of d-wave superconductivity, relevant to the high-
cuprates, we have also considered s-wave gap symmetry in order to provide
expected signatures of inhomogeneities for superconductors in general. While
signatures of gap inhomogeneities can be strongly manifested in s-wave
superconductors, we find that the far-infrared optical conductivity in d-wave
is robust against such inhomogeneity.Comment: 8 pages, 7 figure
THE RELATION BETWEEN THE NUMBER OF REPETITIONS AND THE RELATIVE LOAD IN STRENGTH TRAINING
It was the aim of this study to determine the relationship between the number of repetitions that can be lifted at a range of percentages of the 1RM load in leg curl and bench press. Comparisons were made between males and females, and between long distance runners and sprinters. Findings suggest that this relationship is different between the two types of exercise. No differences were found between males and females. When working with highly trained athletes in bench press it is recommended that different regression equations are employed when studying sprint trained or endurance trained athletes
Potential dietary feed additives with antibacterial effects and their impact on performance of weaned piglets : a meta-analysis
This meta-analysis evaluated the use of potential dietary feed additives (pDFA) with antibacterial effects and their impact on the perfomance of weaned piglets. Twenty-three peer-reviewed in vivo studies, comprising 50 trials, were identified between January 2010 and January 2017. The pDFA in these studies could be grouped in 5 classes: antimicrobial peptides, chitosan, lysozyme, medium chain fatty acids/triglycerides and plant extracts. Mixed-effect meta-analyses with type of pDFA as fixed effect were performed for the growth parameters 'average daily gain' (ADG) and 'feed conversion ratio' (FCR), which are the two most important and used economic performance parameters for farmers.
For each class of pDFA, results of the meta-analysis showed significantly higher average daily gain in the group with pDFA compared to the negative control group, while no significant difference with the positive control group was observed. Furthermore, a positive effect on FCR was found, i.e. significantly less feed was needed to gain 1 kg of body weight in the group with pDFA compared to the negative control group. No significant differences with positive control groups were observed for each class of pDFA, except for plant extracts, where the FCR was also significantly reduced in the treatment group. These results suggest that pDFA could reduce the use of antimicrobials without significant negative effects on performance indicators
Potential dietary feed additives with antibacterial effects and their impact on performance of weaned piglets: A meta-analysis
This meta-analysis evaluated the use of potential dietary feed additives (pDFA) with antibacterial effects and their impact on the perfomance of weaned piglets. Twenty-three peer-reviewed in vivo studies, comprising 50 trials, were identified between January 2010 and January 2017. The pDFA in these studies could be grouped in 5 classes: antimicrobial peptides, chitosan, lysozyme, medium chain fatty acids/ triglycerides and plant extracts. Mixed-effect meta-analyses with type of pDFA as fixed effect were performed for the growth parameters ‘average daily gain’ (ADG) and ‘feed conversion ratio’ (FCR), which are the two most important and used economic performance parameters for farmers.
For each class of pDFA, results of the meta-analysis showed significantly higher average daily gain in the group with pDFA compared to the negative control group, while no significant difference with the positive control group was observed. Furthermore, a positive effect on FCR was found, i.e. significantly less feed was needed to gain 1 kg of body weight in the group with pDFA compared to the negative control group. No significant differences with positive control groups were observed for each class of pDFA, except for plant extracts, where the FCR was also significantly reduced in the treatment group. These results suggest that pDFA could reduce the use of antimicrobials without significant negative effects on performance indicators
Continuous gas temperature measurement of cold plasma jets containing microdroplets, using a focussed spot IR sensor
Controlling gas temperature via continuous monitoring is essential in various plasma applications especially for biomedical treatments and nanomaterial synthesis but traditional techniques have limitations due to low accuracy, high cost or experimental complexity. We demonstrate continuous high-accuracy gas temperature measurements of low-temperature atmospheric pressure plasma jets using a small focal spot infrared sensor directed at the outer quartz wall of the plasma. The impact of heat transfer across the capillary tube was determined using calibration measurements of the inner wall temperature. Measured gas temperatures varied from 25 °C–50 °C, increasing with absorbed power and decreased gas flow. The introduction into the plasma of a stream (∼105 s−1) of microdroplets, in the size range 12 μm–15 μm, led to a reduction in gas temperature of up to 10 °C, for the same absorbed power. This is an important parameter in determining droplet evaporation and its impact on plasma chemistry
Mixed state Hall effect in the multiphase superconductors
Hall effect below Tc in multiphase superconductors has been studied on
Bi-based superconductors. Samples with different relative content of 2212 and
2223 phase have been prepared. The phase content has been verified by X-ray
diffraction. Results show that while resistance and ac susceptibility is almost
insensitive to the content of 2212 phase, the qualitative behavior of the Hall
resistance is strongly influenced by the presence of both phases. Theoretical
calculation of Hall resistance has been made based on effective medium
approximation and compared with experimental results.Comment: 7 pages, 7 figure
Community detection in networks with positive and negative links
Detecting communities in complex networks accurately is a prime challenge,
preceding further analyses of network characteristics and dynamics. Until now,
community detection took into account only positively valued links, while many
actual networks also feature negative links. We extend an existing Potts model
to incorporate negative links as well, resulting in a method similar to the
clustering of signed graphs, as dealt with in social balance theory, but more
general. To illustrate our method, we applied it to a network of international
alliances and disputes. Using data from 1993--2001, it turns out that the world
can be divided into six power blocs similar to Huntington's civilizations, with
some notable exceptions.Comment: 7 pages, 2 figures. Revised versio
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