Superhydrophobic surfaces based on aluminium oxide coatings had been developed on glass substrates via solution based approach for solar panel cover glass applications. The fabricated surface was ...amorphous with an interconnected porous network of nanoflakes. The static contact angle of the prepared coatings was 161° and exhibited superior self–cleaning behaviour at a tilting angle less than 10°. The 300nm thick coating with refractive index value gradually decreased from air (n −1), through the fabricated coating (n −1.35) towards the glass substrate (n – 1.56) enabled it to acquire a high average transmittance of 95% with anti-reflecting property. The photovoltaic performance of commercially available solar cells covered with uncoated glass substrate and aluminium oxide coated glass substrate was measured under various conditions (such as – fabricated, artificially contaminated and self – cleaned conditions) and the results were compared. The uncoated glass substrate and aluminium oxide coated superhydrophobic glass substrate recovered the efficiency of saw dust contaminated solar panel by 67% and 91%, respectively, thereby enabling the fabricated superhydrophobic glass substrate to be effectively useful for self–cleaning cover glass applications.
•Transparent, anti-reflective and superhydrophobic aluminium oxide coatings were fabricated by chemical method.•The coatings were superhydrophobic with static water contact angle of 155°.•The fabricated superhydrophobic substrates were optically transparent.•The coated glass recovered the efficiency of contaminated solar panel by 91% and useful for cover glass applications.
Optical materials with vanishing dielectric permittivity, known as epsilon-near-zero (ENZ) materials, have been shown to possess enhanced nonlinear optical responses in their ENZ region. These strong ...nonlinear optical properties have been firmly established in homogeneous materials; however, it is as of yet unclear whether metamaterials with effective optical parameters can exhibit a similar enhancement. Here, we probe an optical ENZ metamaterial composed of a subwavelength periodic stack of alternating Ag and SiO2 layers and measure a nonlinear refractive index n 2 = (1.2 ± 0.1) × 10–12 m2/W and nonlinear absorption coefficient β = (−1.5 ± 0.2) × 10–5 m/W at its effective zero-permittivity wavelength. The measured n 2 is 107 times larger than n 2 of fused silica and 4 times larger than the n 2 of silver. We observe that the nonlinear enhancement in n 2 scales as 1/(n 0Ren 0), where n 0 is the linear effective refractive index. As opposed to homogeneous ENZ materials, whose optical properties are dictated by their intrinsic material properties and hence are not widely tunable, the zero-permittivity wavelength of the demonstrated metamaterials may be chosen to lie anywhere within the visible spectrum by selecting the right thicknesses of the subwavelength layers. Consequently, our results offer the promise of a means to design metamaterials with large nonlinearities for applications in nanophotonics at any specified optical wavelength.
We present a comprehensive strategy and its practical implementation using the commercial ScanImage software platform to perform hyperspectral point scanning microscopy when a fast time dependent ...signal varies at each pixel level. In the proposed acquisition scheme the scan along the X axis is slowed down while the data acquisition is maintained at high pace to enable the rapid acquisition of the time dependent signal at each pixel level. The ScanImage generated raw 2D images have a very asymmetric aspect ratio between X and Y, the X axis encoding both for space and time acquisition. The results are X axis macro-pixel where the associated time depend signal is sampled therefore providing an hyperspectral information. We exemplified the proposed hyperspectral scheme in the context of time domain coherent Raman imaging where a pump pulse impulsively excites molecular vibrations that are subsequently probed by a time delayed probe pulse. In this case the time dependent signal is a fast acousto-optics delay line that can scan a delay of 4.5ps in 25\(\mu\)s, at each pixel level. We this acquisition scheme we demonstrate ultra-fast hyperspectral vibrational imaging in the low frequency range 10\(cm^{-1}\), 150 \(cm^{-1}\) over a 500 \(\mu m\) field of view in 14ms (7 frames/s). The proposed acquisition scheme can be readily extended to other applications requiring to acquired a fast evolving signal at each pixel level.
Impulsive stimulated Raman scattering (ISRS) using a single short femtosecond pump pulse to excite molecular vibrations offers an elegant pump-probe approach to perform vibrational imaging below ...200cm−1. One shortcoming of ISRS is its inability to offer vibrational selectivity as all the vibrational bonds whose frequencies lie within the short pump-pulse bandwidth are excited. To date, several coherent control techniques have been explored to address this issue and selectively excite a specific molecular vibration by shaping the pump pulse. There has not been any systematic work that reports an analogous shaping of the probe pulse to implement preferential detection. In this work, we focus on vibrational imaging and report vibrational selective detection by shaping the probe pulse in time. We demonstrate numerically and experimentally two pulse-shaping strategies with one functioning as a vibrational notch filter and the other functioning as a vibrational low-pass filter. This enables fast (25μs/pixel) and selective hyperspectral imaging in the low-frequency regime (<200cm−1).
Optical materials with vanishing dielectric permittivity, known as epsilon-near-zero (ENZ) materials, have been shown to possess enhanced nonlinear optical responses in their ENZ region. These strong ...nonlinear optical properties have been firmly established in homogeneous materials; however, it is as of yet unclear whether metamaterials with effective optical parameters can exhibit a similar enhancement. Here, we probe an optical ENZ metamaterial composed of a subwavelength periodic stack of alternating Ag and SiO\(_2\) layers and measure a nonlinear refractive index \(n_2 = (1.2 \pm 0.1) \times 10^{-12}\) m\(^2\)/W and nonlinear absorption coefficient \(\beta = (-1.5 \pm 0.2) \times 10^{-5}\) m/W at its effective zero-permittivity wavelength. The measured \(n_2\) is \(10^7\) times larger than \(n_2\) of fused silica and four times larger than that the \(n_2\) of silver. We observe that the nonlinear enhancement in \(n_2\) scales as \(1/(n_0 \mathrm{Re}n_0)\), where \(n_0\) is the linear effective refractive index. As opposed to homogeneous ENZ materials, whose optical properties are dictated by their intrinsic material properties and hence are not widely tunable, the zero-permittivity wavelength of the demonstrated metamaterials may be chosen to lie anywhere within the visible spectrum by selecting the right thicknesses of the sub-wavelength layers. Consequently, our results offer the promise of a means to design metamaterials with large nonlinearities for applications in nanophotonics at any specified optical wavelength.
Objective: The purpose of the study is to assess parents’ experiences and associate demographic characteristics of parents and children with temper tantrum behavior characteristics of preschool ...children. Methods: A descriptive survey approach was used to conduct this study. A non-probability purposive sampling technique was adopted to recruit 121 parents of children aged between 3-6 years visiting a selected tertiary care hospital in India. All parents completed the parents’ experience of temper tan- trums in the children’s questionnaire. The analysis of results was carried out on IBM SPSS Software version 23.0. Results: A moderate level of temper tantrums showed on the mother’s age, education, occupation, marital status, program attendance, and medical and mental illness in the family, whereas a family’s monthly income above 50,000 indicated a severe level of temper tantrums, and half of the children ex- perienced tantrum behavior to get the attention of their parents, hungry and tired. The most frequently reported tantrum behavior was throwing things and hitting parents and siblings, and most tantrums occurred in public places and in vehicles. The majority of the parents adopted strategies to distract their child’s attention by helping the child talk about the causes of anger. A significant association was found between temper tantrum behavior and demographic characteristics of the marital status of parents (x2 = 15.340, p = 0.002) and the awareness program attended regarding temper tantrums in children (x2 = 4.491, p = 0.034). Conclusion: As temper tantrums peak in the toddler age group, the present study found that parental involvement is a necessity to manage temper tantrums in preschoolers as well. The main parent’s strategies to control the tantrum were distraction of child attention and helped them to talk about the causes of tantrum. Therefore, the study emphasizes the necessity of the involvement of parents and family members.
Objective: The purpose of the study is to assess parents’ experiences and associate demographic characteristics of parents and children with temper tantrum behavior characteristics of preschool ...children. Methods: A descriptive survey approach was used to conduct this study. A non-probability purposive sampling technique was adopted to recruit 121 parents of children aged between 3-6 years visiting a selected tertiary care hospital in India. All parents completed the parents’ experience of temper tan- trums in the children’s questionnaire. The analysis of results was carried out on IBM SPSS Software version 23.0. Results: A moderate level of temper tantrums showed on the mother’s age, education, occupation, marital status, program attendance, and medical and mental illness in the family, whereas a family’s monthly income above 50,000 indicated a severe level of temper tantrums, and half of the children ex- perienced tantrum behavior to get the attention of their parents, hungry and tired. The most frequently reported tantrum behavior was throwing things and hitting parents and siblings, and most tantrums occurred in public places and in vehicles. The majority of the parents adopted strategies to distract their child’s attention by helping the child talk about the causes of anger. A significant association was found between temper tantrum behavior and demographic characteristics of the marital status of parents (x2 = 15.340, p = 0.002) and the awareness program attended regarding temper tantrums in children (x2 = 4.491, p = 0.034). Conclusion: As temper tantrums peak in the toddler age group, the present study found that parental involvement is a necessity to manage temper tantrums in preschoolers as well. The main parent’s strategies to control the tantrum were distraction of child attention and helped them to talk about the causes of tantrum. Therefore, the study emphasizes the necessity of the involvement of parents and family members.
Summary
Tree size shapes forest carbon dynamics and determines how trees interact with their environment, including a changing climate. Here, we conduct the first global analysis of among‐site ...differences in how aboveground biomass stocks and fluxes are distributed with tree size.
We analyzed repeat tree censuses from 25 large‐scale (4–52 ha) forest plots spanning a broad climatic range over five continents to characterize how aboveground biomass, woody productivity, and woody mortality vary with tree diameter. We examined how the median, dispersion, and skewness of these size‐related distributions vary with mean annual temperature and precipitation.
In warmer forests, aboveground biomass, woody productivity, and woody mortality were more broadly distributed with respect to tree size. In warmer and wetter forests, aboveground biomass and woody productivity were more right skewed, with a long tail towards large trees. Small trees (1–10 cm diameter) contributed more to productivity and mortality than to biomass, highlighting the importance of including these trees in analyses of forest dynamics.
Our findings provide an improved characterization of climate‐driven forest differences in the size structure of aboveground biomass and dynamics of that biomass, as well as refined benchmarks for capturing climate influences in vegetation demographic models.
See also the Commentary on this article by Zuidema & van der Sleen, 234: 1544–1546.
When Darwin visited the Galapagos archipelago, he observed that, in spite of the islands' physical similarity, members of species that had dispersed to them recently were beginning to diverge from ...each other. He postulated that these divergences must have resulted primarily from interactions with sets of other species that had also diverged across these otherwise similar islands. By extrapolation, if Darwin is correct, such complex interactions must be driving species divergences across all ecosystems. However, many current general ecological theories that predict observed distributions of species in ecosystems do not take the details of between-species interactions into account. Here we quantify, in sixteen forest diversity plots (FDPs) worldwide, highly significant negative density-dependent (NDD) components of both conspecific and heterospecific between-tree interactions that affect the trees' distributions, growth, recruitment, and mortality. These interactions decline smoothly in significance with increasing physical distance between trees. They also tend to decline in significance with increasing phylogenetic distance between the trees, but each FDP exhibits its own unique pattern of exceptions to this overall decline. Unique patterns of between-species interactions in ecosystems, of the general type that Darwin postulated, are likely to have contributed to the exceptions. We test the power of our null-model method by using a deliberately modified data set, and show that the method easily identifies the modifications. We examine how some of the exceptions, at the Wind River (USA) FDP, reveal new details of a known allelopathic effect of one of the Wind River gymnosperm species. Finally, we explore how similar analyses can be used to investigate details of many types of interactions in these complex ecosystems, and can provide clues to the evolution of these interactions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this research, bioactive compounds found in pomegranate(Punica granatum) and orange(Citrus X sinensis) peels were extracted using ethanol (80 percent). Natural antioxidants have gained ...considerable interest in recent years for their role in preventing the auto-oxidation of fats, oils, and fat-containing products. In the present study, peels of pomegranate and orange were used as a source of natural antioxidants and ethanolic extracts of these peels were prepared. The ethanolic extract of pomegranate exhibited a high percentage of antioxidant activity and phenolic content compared to the ethanolic extract of orange. Ethanolic extracts of orange and pomegranate were added to ghee at 200 ppm concentration. BHA was also added to ghee at a concentration of 200 ppm for comparison. All samples were incubated at 60 - 80˚C for 20 days. The result revealed that ethanolic extracts of pomegranate gave good antioxidant activity and less peroxide value during accelerated oxidative incubation of ghee. Ethanolic extract of pomegranate showed relatively comparable activity to BHA. Therefore, these extracts could be used as preservative ingredients in the food industry.
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