Resonant transparency of materials with negative permittivity

It is shown that the transparency of opaque material with negative permittivity exhibits resonant behavior. The resonance occurs as a result of the excitation of the surface waves at slab boundaries. Dramatic field amplification of the incident evanescent fields at the resonance improves the resolution of the the sub-wavelength imaging system (superlens). A finite thickness slab can be totally transparent to a \textit{p}-polarized obliquely incident electromagnetic wave for certain values of the incidence angle and wave frequency corresponding to the excitation of the surface modes. At the resonance, two evanescent waves have a finite phase shift providing non-zero energy flux through the non-transparent region

Precipitirajući čimbenici i simptomi u bolesnika s dijabetičkom ketoacidozom

The aim of the study was to determine the most common precipitating factors and symptoms of diabetic ketoacidosis and the possible difference according to age, gender and severity of diabetic ketoacidosis. Medical records from January 1, 2017 until December 31, 2019 were reviewed and patients diagnosed with diabetic ketoacidosis were selected. The study included 52 patients, median age 34 (interquartile range 21-56) years. There was no statistically significant difference between male and female gender. The severity of diabetic ketoacidosis was moderate in the majority of cases (65.4%; p=0.005). The most common precipitating factor was infection (61.7%). In patients with moderate diabetic ketoacidosis, respiratory infections were more common, while gastrointestinal infections were more common in severe diabetic ketoacidosis (33% and 25%, respectively; p=0.03). Nausea (median age 32 years; p=0.004) and vomiting (median age 31 years; p=0.01) were more common in younger age groups, while altered mental status was more common in the older age group (median age 61 years; p=0.001). Infection was the most common precipitating factor. The most common symptoms in younger age groups were nausea and vomiting, and altered mental status in the older age group.Cilj istraživanja je bio utvrditi najčešće precipitirajuće čimbenike i simptome dijabetičke ketoacidoze te postoji li razlika s obzirom na dob, spol i stupanj dijabetičke ketoacidoze. Pregledana je medicinska dokumentacija od 1. siječnja 2017. do 31. prosinca 2019. godine te su izdvojeni bolesnici s dijagnozom dijabetičke ketoacidoze. U istraživanje je uključeno 52 bolesnika. Medijan dobi bio je 34 godine (interkvartilni raspon 21-56 godina). Nije postojala statistički značajna razlika muškog i ženskog spola. U najvećem broju slučajeva radilo se o umjerenom stupnju dijabetičke ketoacidoze (65,4%; p=0,005). Najčešći precipitirajući čimbenik bila je infekcija (61,7%). Kod umjerenog stupnja najčešće se radilo o respiracijskim infekcijama, a u teškom stupnju o gastrointestinalnim infekcijama (33% i 25%; p=0,03). U mlađim dobnim skupinama češće su se pojavljivale mučnina (medijan dobi 32 godine; p=0,004) i povraćanje (medijan dobi 31 godina; p=0,01), a u starijoj dobnoj skupini poremećaj svijesti (medijan dobi 61 godina; p=0,001). Infekcije su bile najčešći precipitirajući čimbenik dijabetičke ketoacidoze. Najčešći simptomi u mlađim dobnim skupinama bili su mučnina i povraćanje, a u starijoj dobnoj skupini poremećaj svijesti

From atmospheric winds to fracture ventilation: Cause and effect

Vadose zone fractures and soil cracks exposed to the atmosphere have an impact on gas exchange processes at the Earth-atmosphere interface. In this study we explored and quantified the role of ground-surface winds on fracture ventilation. While the governing physical mechanisms that cause ventilation are relatively well understood, this is the first work to quantify these processes in natural fractures and to determine the net effect on gas exchange. In this study field measurements pointed to a correlation between surface wind velocity and the ventilate rate of surface-exposed fractures. To better explore and quantify this phenomenon, laboratory experiments were carried out using a Hele-Shaw chamber to simulate a natural fracture and the ventilation of smoke, used as a gas tracer, was explored as a function of controlled surface-wind and fracture aperture. It was found that ventilation depth is linearly correlated to wind velocity and nonlinearly with fracture aperture. Results were used to formulate an empirical model for Earth-atmosphere air exchange. This model can be used to estimate by how much the presence of fractures enhances that exchange under windy conditions. Incorporating this venting process into Earth-atmosphere gas exchange simulations is another step toward improving our ability to better predict and quantify soil aeration, soil temperature variation, water vapor loss and processes related to climate change, such as the fate and transport of greenhouse gases.Keywords: Carbon-Dioxide, Porous solids, Vadose zone, Vapor movements, Air movement, Unsaturated Zone, Pressure fluctuations, Diffusion, Gas, Soi

Serum glucose, sodium and potassium concentrations in patients with diabetic ketoacidosis

Aim To investigate possible differences in serum glucose and sodium and potassium concentrations with respect to age, gender and severity of diabetic ketoacidosis. Methods Medical records from 1 January 2017 to 31 December 2019 were reviewed and patients with the diagnosis of diabetic ketoacidosis were selected. Results The study included 52 patients. Glucose concentration was significantly higher in the age group of 25-44 and >65 years compared to the group of 18-24 years (p=0.02). Sodium concentration was significantly higher in the age group 18-24 and >65 years compared to groups 25-44 and 45-65 years (p=0.002). Females had significantly higher sodium concentration than males (p=0.002). Potassium concentration was significantly higher in the age group 25-44 years compared to other groups (p=0.01). Males had significantly higher potassium concentration (p =0.01). Conclusion This study showed that significant differences exist in electrolyte concentration between specific age groups, male and female gender as well as DKA severity. Knowing these differences could help clinicians to promptly recognize and treat electrolyte derangements, leading to better outcome of patients with DKA

Water uptake in biochars: The roles of porosity and hydrophobicity

We assessed the effects of porosity and hydrophobicity on water uptake by biochars. Biochars were produced from two feedstocks (hazelnut shells and Douglas fir chips) at three production temperatures (370°C, 500°C, and 620°C). To distinguish the effects of porosity from the effects of hydrophobicity, we compared uptake of water to uptake of ethanol (which is completely wetting and not affected by hydrophobic materials). For both feedstocks, low temperature biochars took up less water than high temperature biochars but the same amount of ethanol, suggesting that differences in water uptake based on production temperature reflect differences in surface hydrophobicity, not porosity. Conversely, Douglas fir biochars took up more water than hazelnut shell biochars due to greater porosity. Thus, designing biochars for water holding applications requires two considerations: (a) creating sufficient porosity through feedstock selection, and (b) determining a production temperature that reduces hydrophobicity to an acceptable level.Keywords: Hydrophobicity, Porosity, Biochar, Water uptake, FTIRKeywords: Hydrophobicity, Porosity, Biochar, Water uptake, FTI

Infrared thermography of evaporative fluxes and dynamics of salt deposition on heterogeneous porous surfaces

Evaporation of saline solutions from porous media, common in arid areas, involves complex interactions between mass transport, energy exchange and phase transitions. We quantified evaporation of saline solutions from heterogeneous sand columns under constant hydraulic boundary conditions to focus on effects of salt precipitation on evaporation dynamics. Mass loss measurements and infrared thermography were used to quantify evaporation rates. The latter method enables quantification of spatial and temporal variability of salt precipitation to identify its dynamic effects on evaporation. Evaporation from columns filled with texturally-contrasting sand using different salt solutions revealed preferential salt precipitation within the fine textured domains. Salt precipitation reduced evaporation rates from the fine textured regions by nearly an order of magnitude. In contrast, low evaporation rates from coarse-textured regions (due to low capillary drive) exhibited less salt precipitation and consequently less evaporation rate suppression. Experiments provided insights into two new phenomena: (1) a distinct increase in evaporation rate at the onset of evaporation; and (2) a vapor pumping mechanism related to the presence of a salt crust over semidry media. Both phenomena are related to local vapor pressure gradients established between pore water and the surface salt crust. Comparison of two salts: NaCl and NaI, which tend to precipitate above the matrix surface and within matrix pores, respectively, shows a much stronger influence of NaCl on evaporation rate suppression. This disparity reflects the limited effect of NaI precipitation on matrix resistivity for solution and vapor flows

Surface Oscillations in Overdense Plasmas Irradiated by Ultrashort Laser Pulses

The generation of electron surface oscillations in overdense plasmas irradiated at normal incidence by an intense laser pulse is investigated. Two-dimensional (2D) particle-in-cell simulations show a transition from a planar, electrostatic oscillation at $2\omega$, with $\omega$ the laser frequency, to a 2D electromagnetic oscillation at frequency $\omega$ and wavevector $k>\omega/c$. A new electron parametric instability, involving the decay of a 1D electrostatic oscillation into two surface waves, is introduced to explain the basic features of the 2D oscillations. This effect leads to the rippling of the plasma surface within a few laser cycles, and is likely to have a strong impact on laser interaction with solid targets.Comment: 9 pages (LaTeX, Revtex4), 4 GIF color figures, accepted for publication in Phys. Rev. Let

Multiple extraordinary optical transmission peaks from evanescent coupling in perforated metal plates surrounded by dielectrics

© 2010 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibitedWe study numerically and theoretically the optical transmission of nanostructured gold films embedded in dielectric claddings. We show how multiple transmission peaks appear as the claddings thickness increases. These transmission peaks come not only from surface plasmon polariton excitations but also from the excitation of Fabry-Perot modes sustained at the claddings, coupled through the metal, as long as a periodic pattern is milled in the metal film. We propose that this structure could be used as an ultracompact all-optical switch by surrounding the metal film with Kerr nonlinear dielectric layers. (C) 2010 Optical Society of AmericaWe thank the FCT (Fundacao para a Ciencia e Tecnologia) for funding of this research through the projects SFRH/BD/8278/2002 and PTDC/FIS/68419/2006.Ortuño Molinero, R.; García Meca, C.; Rodríguez Fortuño, FJ.; Martí Sendra, J.; Martínez Abietar, AJ. (2010). Multiple extraordinary optical transmission peaks from evanescent coupling in perforated metal plates surrounded by dielectrics. Optics Express. 18(8):7893-7898. https://doi.org/10.1364/OE.18.007893S78937898188Dragila, R., Luther-Davies, B., & Vukovic, S. (1985). High Transparency of Classically Opaque Metallic Films. Physical Review Letters, 55(10), 1117-1120. doi:10.1103/physrevlett.55.1117Ebbesen, T. W., Lezec, H. J., Ghaemi, H. F., Thio, T., & Wolff, P. A. (1998). Extraordinary optical transmission through sub-wavelength hole arrays. Nature, 391(6668), 667-669. doi:10.1038/35570Koerkamp, K. J. K., Enoch, S., Segerink, F. B., van Hulst, N. F., & Kuipers, L. (2004). Strong Influence of Hole Shape on Extraordinary Transmission through Periodic Arrays of Subwavelength Holes. Physical Review Letters, 92(18). doi:10.1103/physrevlett.92.183901Takakura, Y. (2001). Optical Resonance in a Narrow Slit in a Thick Metallic Screen. Physical Review Letters, 86(24), 5601-5603. doi:10.1103/physrevlett.86.5601Zhou, L., Wen, W., Chan, C. T., & Sheng, P. (2005). Electromagnetic-Wave Tunneling Through Negative-Permittivity Media with High Magnetic Fields. Physical Review Letters, 94(24). doi:10.1103/physrevlett.94.243905Lomakin, V., & Michielssen, E. (2005). Enhanced transmission through metallic plates perforated by arrays of subwavelength holes and sandwiched between dielectric slabs. Physical Review B, 71(23). doi:10.1103/physrevb.71.235117Rakić, A. D., Djurišić, A. B., Elazar, J. M., & Majewski, M. L. (1998). Optical properties of metallic films for vertical-cavity optoelectronic devices. Applied Optics, 37(22), 5271. doi:10.1364/ao.37.005271Genet, C., & Ebbesen, T. W. (2007). Light in tiny holes. Nature, 445(7123), 39-46. doi:10.1038/nature05350Ghaemi, H. F., Thio, T., Grupp, D. E., Ebbesen, T. W., & Lezec, H. J. (1998). Surface plasmons enhance optical transmission through subwavelength holes. Physical Review B, 58(11), 6779-6782. doi:10.1103/physrevb.58.6779Martínez, A., & Martí, J. (2005). Negative refraction in two-dimensional photonic crystals: Role of lattice orientation and interface termination. Physical Review B, 71(23). doi:10.1103/physrevb.71.235115Ruan, Z., & Qiu, M. (2006). Enhanced Transmission through Periodic Arrays of Subwavelength Holes: The Role of Localized Waveguide Resonances. Physical Review Letters, 96(23). doi:10.1103/physrevlett.96.233901Economou, E. N. (1969). Surface Plasmons in Thin Films. Physical Review, 182(2), 539-554. doi:10.1103/physrev.182.539Esembeson, B., Scimeca, M. L., Michinobu, T., Diederich, F., & Biaggio, I. (2008). A High-Optical Quality Supramolecular Assembly for Third-Order Integrated Nonlinear Optics. Advanced Materials, 20(23), 4584-4587. doi:10.1002/adma.200801552Spano, R., Daldosso, N., Cazzanelli, M., Ferraioli, L., Tartara, L., Yu, J., … Pavesi, L. (2009). Bound electronic and free carrier nonlinearities in Silicon nanocrystals at 1550nm. Optics Express, 17(5), 3941. doi:10.1364/oe.17.003941Dani, K. M., Ku, Z., Upadhya, P. C., Prasankumar, R. P., Brueck, S. R. J., & Taylor, A. J. (2009). Subpicosecond Optical Switching with a Negative Index Metamaterial. Nano Letters, 9(10), 3565-3569. doi:10.1021/nl901764