Nanostructuring of Continuous Gold Film by Laser Radiation Under Surface Plasmon Polariton Resonance Conditions

The physical mechanisms of metallic nanoparticles formation by laser technology were studied. The system air/Au film/glass was irradiated by laser at the conditions of surface plasmon resonance. A surface electromagnetic wave was excited in Kretchmann configuration by the fundamental and second harmonics of the Q-switched YAG/Nd⁺³ laser with pulse power density close to the threshold of melting. Nanostructuring of Au film was observed only for the second harmonic (λ = 0.532 μm) irradiation at the surface plasmon polariton resonance (SPR) conditions. Estimations were done using the interference model of the differently directed plasmon polariton waves excited by a surface electromagnetic wave on the metal surface. It was shown that a regular pattern of locally heated spots can be formed in a metallic film by pulsed laser irradiation. The spatial distribution of this pattern is close to the period of interference. The observed effect of laser nanofragmentation is explained by the self-organization of plasmon polariton subsystem in the process of Au nanoparticles formation at high laser intensity levels. These methods open new possibilities for nanostructured surfaces formation utilizing simple self-organization processes.     

Muscle Potassium and Potassium Losses During Hypokinesia in Healthy Subjects

Hypokinesia (HK) induces electrolyte losses in electrolyte-deficient tissue, yet the mechanisms of electrolyte losses in electrolyte-deficient tissue remain unknown. Mechanisms of electrolyte deposition could be involved. To determine the effect of prolonged HK on potassium (K⁺) deposition were measured muscle K⁺ content and K⁺ losses. Studies were conducted on 20 physically healthy male volunteers during 30 days pre-experimental period and 364 days experimental period. Subjects were equally divided into two groups: control subjects (CS) and experimental subjects (ES). The CS group was run average distances of 9.8 ± 1.7 km day⁻¹ and the ES group was walked average distances of 2.7 ± 0.6 km day⁻¹. Muscle K⁺ content decreased (p < 0.05) and plasma K⁺ concentration, and K⁺ losses in urine and feces increased (p < 0.05) in the ES group compared to their pre-experimental level and the values in their respective CS group. Muscle K⁺ content, plasma K⁺ level, and urine and fecal K⁺ losses did not show any changes in the CS group compared to their pre-experimental values. The conclusion was that K⁺ losses in K⁺-deficient muscle of healthy subjects could have been attributable to the less efficient K⁺ deposition inherently to prolonged HK.     

Large Nonlinearity Enhancement of Ag/MEH-PPV Nanocomposite by Surface Plasmon Resonance at 1,550 nm

We experimentally demonstrate a large third-order nonlinear susceptibility for a nanocomposite made of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] doped with silver nanoprisms at 1,550 nm, achieved based on nonlinearity enhancement associated with strong surface plasmon resonance. The nonlinear refractive index reaches −1.37 × 10⁻¹² m²/W, which is three orders of magnitude larger than that of pure poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]. An ultrafast response time of 18.7 ps is reached using fast energy transfer from excited states of organic molecules to silver nanoprisms. A low-power and ultrafast nanocomposite photonic crystal all-optical switching is also realized.     

Plasmonic Coupling in Er3+:Au Tellurite Glass

In this paper, we report on luminescence and absorbance effects of Er⁺³:Au-doped tellurite glasses synthesized by a melting-quenching and heat treatment technique. After annealing times of 2.5, 5.0, 7.5, and 10.0 h, at 300 °C, the gold nanoparticles (GNP) effects on the Er⁺³ are verified from luminescence spectra and the corresponding levels lifetime. The localized surface plasmon resonance around 800 nm produced a maximum fluorescence enhancement for the band ranging from 800 to 840 nm, corresponding to the transitions ⁴H_11/2 → ⁴I_13/2 (805 nm) and ⁴S_3/2 → ⁴I_13/2 (840 nm), with annealing time till 7.5 h. The measured lifetime of the levels ⁴H_11/2 and ⁴S_3/2 confirmed the lifetime reduction due to the energy transfer from the GNP to Er⁺³, causing an enhanced photon emission rate in these levels.     

Investigating Fluorescence Quenching of ZnS Quantum Dots by Silver Nanoparticles

Water dispersible zinc sulfide quantum dots (ZnS QDs) with an average diameter of 2.9 nm were synthesized in an environment friendly method using chitosan as stabilizing agent. These nanocrystals displayed characteristic absorption and emission spectra having an absorbance edge at 300 nm and emission maxima (λ _emission) at 427 nm. Citrate-capped silver nanoparticles (Ag NPs) of ca. 37-nm diameter were prepared by modified Turkevich process. The fluorescence of ZnS QDs was significantly quenched in presence of Ag NPs in a concentration-dependent manner with K _sv value of 9 × 10⁹ M⁻¹. The quenching mechanism was analyzed using Stern–Volmer plot which indicated mixed nature of quenching. Static mechanism was evident from the formation of electrostatic complex between positively charged ZnS QDs and negatively charged Ag NPs as confirmed by absorbance study. Due to excellent overlap between ZnS QDs emission and surface plasmon resonance band of Ag NPs, the role of energy transfer process as an additional quenching mechanism was investigated by time-resolved fluorescence measurements. Time-correlated single-photon counting study demonstrated decrease in average lifetime of ZnS QDs fluorescence in presence of Ag NPs. The corresponding F?rster distance for the present QD–NP pair was calculated to be 18.4 nm.     

Biological nitrification–denitrification with alternating oxic and anoxic operations using aerobic granules

Efficient nitrification and denitrification of wastewater containing 1,700 mgl⁻¹ of ammonium-nitrogen was achieved using aerobic granular sludge cultivated at medium-to-high organic loading rates. The cultivated granules were tested in a sequencing batch reactor (SBR) fed with 6.4 or 10.2 kg NH₄⁺-N m⁻³ day⁻¹, a loading significantly higher than that reported in literature. With alternating 2 h oxic and 2 h anoxic operation (OA) modes, removal rate was 45.5 mg NH₄⁺-N g⁻¹ volatile suspended solids⁻¹ h⁻¹ at 6.4 kg NH₄⁺-N m⁻³ day⁻¹ loading and 41.3 ± 2.0 at 10.2 kg NH₄⁺-N m⁻³ day⁻¹ loading. Following the 60 days SBR test, granules were intact. The fluorescence in situ hybridization and confocal laser scanning microscopy results indicate that the SBR-OA granules have a distribution with nitrifers outside and heterotrophs outside that can effectively expose functional strains to surrounding substrates at high concentrations with minimal mass transfer limit. This microbial alignment combined with the smooth granule surface achieved nitrification–denitrification of wastewaters containing high-strength ammonium using aerobic granules. Conversely, the SBR continuous aeration mode yielded a distribution with nitrifers outside and heterotrophs inside with an unsatisfactory denitrification rate and floating granules as gas likely accumulated deep in the granules.     

Effective expression of soluble aglycosylated recombinant human Fcγ receptor I by low translational efficiency in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Human FcγRI (CD64) is an integral membrane glycoprotein functioning as a high-affinity receptor binding to monomeric IgG. In this study, the extracellular region of FcγRI, which is the actual part that interacts with IgG, was expressed as aglycosylated recombinant human FcγRI (rhFcγRI) in Escherichia coli. The soluble form of aglycosylated rhFcγRI was expressed in the periplasm of E. coli. The production of soluble aglycosylated rhFcγRI was increased by low induction levels. Furthermore, this production was increased by low translational efficiency, controlled by modification of the putative region between the ribosome binding site and initiation codon of rhFcγRI fusing signal peptide (MalE, PelB, or TorT) of the expression vector. By the optimization of induction and translational efficiency, the production of soluble aglycosylated rhFcγRI was up to approximately 0.8 mg/l of culture medium. Surface plasmon resonance analysis revealed that the binding affinities of aglycosylated rhFcγRI for human IgG1 (equilibrium dissociation constant K _D = [1.7 ± 0.2] × 10⁻¹⁰ M) and IgG3 (K _D = [1.1 ± 0.2] × 10⁻¹⁰ M) were similar to those of glycosylated rhFcγRI.     

Quantum Yields of Decomposition and Homo-Dimerization of Solid <Emphasis Type="SmallCaps">L</Emphasis>-Alanine Induced by 7.2 eV Vacuum Ultraviolet Light Irradiation: An Estimate of the Half-Life of <Emphasis Type="SmallCaps">L</Emphasis>-Alanine on the Surface of Space Objects

One of the leading hypotheses regarding the origin of prebiotic molecules on primitive Earth is that they formed from inorganic molecules in extraterrestrial environments and were delivered by meteorites, space dust and comets. To evaluate the availability of extraterrestrial amino acids, it is necessary to examine their decomposition and oligomerization rates as induced by extraterrestrial energy sources, such as vacuum ultraviolet (VUV) and X-ray photons and high energy particles. This paper reports the quantum yields of decomposition ((8.2 ± 0.7) × 10⁻² photon⁻¹) and homo-dimerization ((1.2 ± 0.3) × 10⁻³ photon⁻¹) and decomposition of the dimer (0.24 ± 0.06 photon⁻¹) of solid l-alanine (Ala) induced by VUV light with an energy of 7.2 eV. Using these quantum yields, the half-life of l-Ala on the surface of a space object in the present earth orbit was estimated to be about 52 days, even when only photons with an energy of 7.2 eV emitted from the present Sun were considered. The actual half-life of solid l-Ala on the surface of a space object orbit around the present day Earth would certainly be much shorter than our estimate, because of the added effect of photons and particles of other energies. Thus, we propose that l-Ala needs to be shielded from solar VUV in protected environments, such as the interior of a meteorite, within a time scale of days after synthesis to ensure its arrival on the primitive Earth.     

Biomass Production with Willow and Poplar Short Rotation Coppices on Sensitive Areas—the Impact on Nitrate Leaching and Groundwater Recharge in a Drinking Water Catchment near Hanover,Germany

In a lowland drinking water catchment area, nitrate leaching as well as groundwater recharge (GWR) was investigated in willow and poplar short rotation coppice (SRC) plantations of different ages, soil preparation measures prior to planting and harvesting intervals. Significantly increased nitrate concentrations of 16.6 ± 1.6 mg NO₃-N L⁻¹ were measured in winter/spring 2010 on a poplar site, established in 2009 after deep plowing (90 cm) but then, subsequently decreased strongly to below 2 mg NO₃-N L⁻¹ in spring 2011. The fallow ground reference plot showed nitrate concentrations consistently below 1 mg L⁻¹ and estimated annual seepage output loss was only 1.36 ± 1.1 kg ha⁻¹ a⁻¹. Leaching loss from a neighboring willow plot from 2005 was 14.3 ± 6.6 kg NO₃-N ha⁻¹ during spring 2010 but decreased to 2.0 ± 1.5 kg NO₃-N ha⁻¹ during the subsequent drainage period. A second willow plot, not harvested since its establishment in 1994, showed continuously higher nitrate concentrations (10.2 ± 1.7 NO₃-N L⁻¹), while a neighboring poplar plot, twice harvested since 1994 showed significantly reduced nitrate concentrations. Water balance simulations, referenced by soil water tension and throughfall measurements, showed that at 655 mm annual rainfall, GWR from the reference plot (300 mm a⁻¹) was reduced by 40 % (to 180 mm a⁻¹) on the 2005 willow stand, mainly due to doubled rainfall interception losses. However, transpiration was limited by low soil water storage capacities, which in turn led to a moderate impact on GWR. We conclude that well-managed SRC on sensitive areas can prevent nitrate leaching, while impacts on GWR may be mitigated by management options.     

Effects of arbuscular mycorrhizal fungi on seedling growth and development of two wetland plants, Bidens frondosa L., and Eclipta prostrata (L.) L., grown under three levels of water availability

To identify the importance of arbuscular mycorrhizal fungi (AMF) colonizing wetland seedlings following flooding, we assessed the effects of AMF on seedling establishment of two pioneer species, Bidens frondosa and Eclipta prostrata grown under three levels of water availability and ask: (1) Do inoculated seedlings differ in growth and development from non-inoculated plants? (2) Are the effects of inoculation and degree of colonization dependent on water availability? (3) Do plant responses to inoculation differ between two closely related species? Inoculation had no detectable effects on shoot height, or plant biomass but did affect biomass partitioning and root morphology in a species-specific manner. Shoot/root ratios were significantly lower in non-inoculated E. prostrata plants compared with inoculated plants (0.381 ± 0.066 vs. 0.683 ± 0.132). Root length and surface area were greater in non-inoculated E. prostrata (259.55 ± 33.78 cm vs. 194.64 ± 27.45 cm and 54.91 ± 7.628 cm² vs. 46.26 ± 6.8 cm², respectively). Inoculation had no detectable effect on B. frondosa root length, volume, or surface area. AMF associations formed at all levels of water availability. Hyphal, arbuscular, and vesicular colonization levels were greater in dry compared with intermediate and flooded treatments. Measures of mycorrhizal responsiveness were significantly depressed in E. prostrata compared with B. frondosa for total fresh weight (−0.3 ± 0.18 g vs. 0.06 ± 0.06 g), root length (−0.78 ± 0.28 cm vs.−0.11 ± 0.07 cm), root volume (−0.49 ± 0.22 cm³ vs. 0.06 ± 0.07 cm³), and surface area (−0.59 ± 0.23 cm² vs.−0.03 ± 0.08 cm²). Given the disparity in species response to AMF inoculation, events that alter AMF prevalence in wetlands could significantly alter plant community structure by directly affecting seedling growth and development.     

Optical method for monitoring of photodynamic inactivation of bacteria

Photodynamic inactivation is a new promising approach to treat bacterial infections. Usually, the evaluation of the efficacy of this method is done through time-consuming and labor-intensive microbiological test methods. This paper describes the development and implementation of an optical method to evaluate the photodynamic inactivation of bacteria based on non-invasive diffuse reflectance measurements. Five Staphylococcus aureus cultures and 15 mice have been used in this study. A skin lesion was created on the back of all animals, and it was contaminated with S. aureus (5.16 ± 0.013 log CFU/ml). Toluidine Blue O (c = 8.67 × 10 ^− 3 M) has been used as a photosensitiser agent. The bacterial cultures and animals were exposed to laser radiation (λ = 635 nm, P = 15 mW, DE = 8.654 J/cm²) for 20 min. The photodynamic inactivation of bacteria was monitored by acquiring the wounds’ reflection spectra at different time points and by microbiological exams on the bioptical material. The good correlation between the diffuse reflectance and colony-forming units demonstrates the value of this optical method based on diffuse reflectance measurements as a rapid technique to monitor photodynamic bacterial inactivation.     

The viability to a wall shear stress and propagation of <Emphasis Type="Italic">Bifidobacterium longum</Emphasis> in the intensive membrane bioreactor

Bifidobacterium longum grew at 65 L pilot scale of the membrane bioreactor (MBR), externally fitted with ceramic membrane (0.7 m²). Cell mass at the MBR reached 22.18 g L⁻¹ as dry cell weight in 12 h, which is 8.44 times higher than cell mass attained at the vial culture. The growth rate in the vial culture was μ = 0.385 h⁻ and at the batch culture was μ = 1.13 h⁻ in the exponential period and μ = 0.31 h⁻¹ in the stationary period. In the fed-batch mode was μ = 1.102 h⁻¹ for 6 h with inoculation and declined to μ = 0.456 h⁻¹ with feeding of feed medium. The growth rate at the MBR was μ = 0.134 h⁻¹. The number of viable cells was 6.01 × 10¹² cfu L⁻¹ at the batch culture, but increased to 1.15 × 10¹⁴ cfu L⁻¹ at the MBR culture. The specific growth rate of viable cell number (colony-forming units per liter, per hour) improved by 6.01 times from the batch to the MBR culture. The wall shear stress mainly generated by the pump, and the membrane incorporated into the MBR was controlled during the cultivation at the MBR. The viability of B. longum declined to under 10% in the first 2 weeks of the 4-week stability test (40°C) as B. longum was exposed to over wall shear stress 713 Pa, but the viability improved to 30–40% in wall shear stress of 260 Pa or STR culture. The loss in the cell viability can be saved by managing with wall shear stress during the cultivation at the MBR.     

Heterologous expression of polyhydroxyalkanoate depolymerase from <Emphasis Type="Italic">Thermobifida</Emphasis> sp. in <Emphasis Type="Italic">Pichia pastoris</Emphasis> and catalytic analysis by surface plasmon resonance

A polyhydroxyalkanote depolymerase gene from Thermobifida sp. isolate BCC23166 was cloned and expressed as a C-terminal His₆-tagged fusion in Pichia pastoris. Primary structure analysis revealed that the enzyme PhaZ-Th is a member of a proposed new subgroup of SCL-PHA depolymerase containing a proline–serine repeat linker. PhaZ-Th was expressed as two glycosylated forms with apparent molecular weights of 61 and 70 kDa, respectively. The enzyme showed esterase activity toward p-nitrophenyl alkanotes with V _max and K _m of 3.63 ± 0.16 μmol min⁻¹ mg⁻¹ and 0.79 ± 0.12 mM, respectively, on p-nitrophenyl butyrate with optimal activity at 50–55°C and pH 7–8. Surface plasmon resonance (SPR) analysis demonstrated that PhaZ-Th catalyzed the degradation of poly-[(R)-3-hydroxybutyrate] (PHB) films, which was accelerated in (R)-3-hydroxyvalerate copolymers with a maximum degradation rate of 882 ng cm⁻² h⁻¹ for poly[(R)-3-hydroxybutyrate-co-3-hydroxyvalerate] (12 mol% V). Surface deterioration, especially on the amorphous regions of PHB films was observed after exposure to PhaZ-Th by atomic force microscopy. The use of P. pastoris as an alternative recombinant system for bioplastic degrading enzymes in secreted form and a sensitive SPR analytical technique will be of utility for further study of bioplastic degradation.     

Theoretical Study of a Planar Structure Plasmonic Nanolaser in Visible Regime

The potential of a plasmonic nanolaser using semiconductor gain to compensate the metal loss was investigated theoretically in multilayer planar structure geometry. The propagation constant of surface plasmon (SP) mode, Purcell factor, and modal gain were calculated via transfer matrix method. Near SP resonance, the Purcell factor shows sensitive frequency dependence and exponential decay with distance. The huge Purcell factor leads to an impractical current density about several hundreds kiloampere/square centimeter (kA/cm²). When the spectra peak of optical gain in a semiconductor is shifted about 0.7 eV below SP resonance, the moderate Purcell factor shows a rather broadband enhancement. Net modal gain was achieved at an injected current density of 12.1 kA/cm², comparable to that of conventional photonic laser diodes. The structure is further optimized by inserting a (low permittivity) dielectric spacer between the semiconductor active region and metal.

     

Cavamax W7 composite ethosomal gel of clotrimazole for improved topical delivery: development and comparison with ethosomal gel

The present research work was aimed to formulate clotrimazole encapsulated Cavamax W7 composite ethosomes by injection method for improved delivery across epidermis. 3² factorial design was used to design nine formulations (F1-F9) and compared with ethosomal formulations (F10-F12). F9 with vesicle size of 202.8 ± 4.8 nm, highest zeta potential (−83.6 ± 0.96 mV) and %EE of 98.42 ± 0.15 was selected as optimized composite ethosome and F12 as reference ethosomal formulation. As revealed by transmission electron microscopy F9 vesicles were more condensed, uniformly spherical in shape than F12 vesicles. Vesicular stability studies indicated F9 to be more stable as compared to F12. Both F9 and F12 were incorporated in carbopol 934 gel base to get G1–G8 gel formulations and evaluated for in vitro skin permeability. Cavamax W7 composite ethosomal optimized gel (G5) showed higher in vitro percent cumulative drug permeation (88.53 ± 2.10%) in 8 h and steady state flux (J _ss) of 3.39 ± 1.45 μg/cm²/min against the J _ss of 1.57 ± 0.23 μg/cm²/min for ethosomal gel (G1) and 1.13 ± 0.06 μg/cm²/min for marketed formulation. The J _ss flux of G5 was independent of amount of drug applied/unit area of skin. In vivo confocal laser scanning microscopic study of G5 depicted uniform and deeper penetration of rhodamine B (marker) in epidermis from Cavamax W7 composite ethosomal gel in comparison to G1. Finally, G5 demonstrated better (p < 0.05) antifungal activity against Candida albicans and Aspergillus niger than G1 thus, signifying that Cavamax W7 composite ethosomes present a superior stable and efficacious vesicular system than ethosomal formulation for topical delivery of clotrimazole.     

Gold Nanoparticles from Induced Au3+→Au0 Reaction in Polyvinyl Alcohol Molecules in Presence of Sucrose in Hot Water

In hot water (50–60°C), polyvinyl alcohol (PVA) molecules have coordination reaction with Au³⁺ cations, forming an Au³⁺-PVA polymer complex. In the proposed model reaction in small templates, the complex converts to Au⁰ capping in PVA molecules. Adding sucrose (5–10 times the PVA in mass) in a typical batch promotes Au³⁺→Au⁰ reaction, showing absorption coefficient α in Au⁰ surface plasmon band to be enhanced as much as 28 times the value in reaction with PVA. The band shifts at 547 nm from 566 nm (α  =  21.4 cm⁻¹ mol⁻¹) in the PVA sample. Drying Au⁰-PVA/sucrose (2–5 wt% Au⁰) colloid at 60–70°C and then heating at 450°C in air burns off the organic part, leaving behind a light ash colored powder with Au⁰ nanoprisms or nanofibrils (∼30 nm average width). X-ray diffractogram has six reflections, (111), (200), (220), (311), (222), and (400), of Fm3m fcc Au⁰ of lattice parameter a  =  0.4080 nm. The powder has photoluminescence in transversal and longitudinal Au⁰ plasmon bands of 535 and 585 nm, respectively.     

Ab initio studies on the decomposition kinetics of CF<Subscript>3</Subscript>OCF<Subscript>2</Subscript>O radical

The present study deals with the decomposition of CF₃OCF₂O radical formed from a hydrofluoroether, CF₃OCHF₂ (HFE-125), in the atmosphere. The study is performed using ab initio quantum mechanical methods. Two plausible pathways of decomposition of the titled species have been considered, one involving C-O bond scission and the other occurring via F atom elimination. The geometries of the reactant, products and transition states involved in the decomposition pathways are optimized and characterized at DFT (B3LYP) level of theory using 6-311G(d,p) basis set. Single point energy calculations have been performed at G2M(CC,MP2) level of theory. Out of the two prominent decomposition channels considered, the C-O bond scission is found to be dominant involving a barrier height of 15.3 kcal mol⁻¹ whereas the F-elimination path proceeds with a barrier of 26.1 kcal mol⁻¹. The thermal rate constants for the above two decomposition pathways are evaluated using canonical transition state theory (CTST) and these are found to be 1.78 × 10⁶ s⁻¹ and 2.83 × 10⁻⁷ s⁻¹ for C-O bond scission and F-elimination respectively at 298 K and 1 atm pressure. Transition states are searched on the potential energy surfaces involved during the decomposition channels and each of the transition states is characterized. The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation.     

Assaying Total Carotenoids in Flours of Corn and Sweetpotato by Laser Photoacoustic Spectroscopy

This study describes the application of the laser photoacoustic spectroscopy (PAS) for quantification of total carotenoids (TC) in corn flours and sweetpotato flours. Overall, thirty-three different corn flours and nine sweetpotato flours were investigated. All PAS measurements were performed at room temperature using 488-nm argon laser radiation for excitation and mechanical modulation of 9 and 30 Hz. The measurements were repeated within a run and within several days or months. The UV–Vis spectrophotometry was used as the reference method. The concentration range that allows for the reliable analysis of TC spans a region from 1 to 40 mg kg⁻¹ for corn flours and from 9 to 40 mg kg⁻¹ for sweetpotato flours. In the case of sweetpotato flours, the quantification may extend even to 240 mg kg⁻¹ TC. The estimated detection limit values for TC in corn and sweetpotato flours were 0.1 and 0.3 mg kg⁻¹, respectively. The computed repeatability (n = 3–12) and intermediate precision (n = 6–28) RSD values at 9 and 30 Hz are comparable: 0.1–17.1% and 5.3–14.7% for corn flours as compared with 1.4–9.1% and 4.2–23.0% for sweetpotato flours. Our results show that PAS can be successfully used as a new analytical tool to simply and rapidly screen the flours for their nutritional potential based on the total carotenoid concentration.