Synthesis and characterization of pH- and thermoresponsive Poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-co-itaconic acid) hydrogels crosslinked with <Emphasis Type="Italic">N</Emphasis>-maleyl chitosan

Biodegradable cross-linker N-maleyl chitosan (N-MACH) was synthesized with chitosan (CS) and maleic anhydride (MA) by acylation. With N-MACH cross-linker, a series of cross-linked poly(N-isopropylacrylamide-co-itaconic acid) [P(NIPAAm-co-IA)] hydrogels were prepared, and their pH-and temperature-responsive behaviors, water contents, swelling/deswelling kinetics were investigated. By alternating the NIPAAm/IA weight ratios, hydrogels had the volume phase transition temperature (VPTT) changed from 33 to 38 °C, whereas cross-linking density did not affect the VPTT apparently. The water content of hydrogels was controlled by the monomer weight ratios of NIPAAm/IA, swelling media, and the cross-linking density. The results of the influence of pH value on the swelling behaviors showed that the minimum swelling ratios of the hydrogels appeared in neutral buffer solution, which was attributed to chemical composition of the hydrogels and the swelling media. In the swelling/deswelling kinetics, all the dried hydrogels exhibited fast swelling within 480 min and fast deswelling within 20 min, which was independent of the content of IA and cross-linker.     

pH-responsive swelling behavior,elasticity and molecular characteristics of poly(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylaminoethyl methacrylate) gels at various initial monomer concentrations

The equilibrium swelling degree and the modulus of elasticity of pH-responsive poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) gels prepared at various initial monomer concentrations were investigated both in buffer solutions and in aqueous salt solutions. As pH of the solution is increased, PDMAEMA gels first remain in the swollen state up to pH 7.7, then exhibit pH-sensitive phase transitions at 8.0 in which PDMAEMA gels attain a collapsed state. The swelling kinetic measurements of PDMAEMA gels showed that pH sensitivity of PDMAEMA is quite stable and the swelling process is reproducible in accordance with pH changing. The swelling behavior of PDMAEMA gels was analyzed by Flory-Rehner theory and the results were combined by the results of compression measurements to calculate the molecular characteristics of gels. The resulting pH-responsive PDMAEMA gels were elastic and displayed good swelling behavior both in buffer solutions and in aqueous salt solutions, therefore, they can be used as a kind of carrying material in drug delivery systems.     

Preparation and properties of a novel thermosensitive <Emphasis Type="Italic">N</Emphasis>-trimethyl chitosan hydrogel

A novel injectable thermosensitive hydrogel system composed of N-trimethyl chitosan chloride (TMC) and β-glycerophosphate (β-GP), coded as TMC/β-GP, was designed. The morphology and rheological behavior of hydrogels were characterized by scanning electron microscopy and rheometer, respectively. Their swelling properties were carefully studied. The results revealed that the TMC/β-GP system was liquid with low viscosity at low temperature, which allowed it to be an ideal injectable material for biomedical applications. It was interesting that the system kept in liquid status for a long time near 4 °C and transformed rapidly to gel status within 1 min upon heating to 37 °C. The hydrogel could be dissolved at acid pH, while it absorbed water at neutral and basic conditions. The release of BSA from TMC/β-GP gels was slow at neutral pH. The TMC/β-GP hydrogel is a promising vehicle for the drug release, tissue repairing and regeneration.     

Aqueous radical polymerization of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylacrylamide redox-initiated by aerobically catalytic oxidation of water-soluble tertiary amines

Catalytic oxidation of water-soluble tertiary amines by complexes of Cu^II, Fe^III and Co^II was utilized to initiate radical polymerization of N,N-dimethylacrylamide (DMAAm) in aqueous solution at 70–80 °C. The oxidation of tertiary amines by Cu^II was studied by proton nuclear magnetic resonance spectroscopy and online ultraviolet–visible spectrophotometry. The polymerization kinetics was monitored by gas chromatography, and molecular weight of the PDMAAm was measured by gel-permeation chromatography coupled with multi-angle laser light scattering. Oxidation of tertiary amines occurs predominantly via formation of C_alpha·radicals to initiate polymerization of electron-deficient monomers and N-dealkylation, and redox equilibrium between Cu^I/L and Cu^II/L is established at a faster rate in aqueous media. Fe^III and Cu^II complexes are efficient catalysts as each catalyst molecule could generate above 10 propagating radicals in 5 h, while Co^II complex might involve in oxidation of tertiary amines in non-radical pathway, leading to a low catalytic efficiency. Water-soluble tertiary amines such as N,N-dialkylethanolamine (alkyl = methyl, ethyl etc.) are reducing agents of a higher activity in aqueous media than those primary or secondary analogues. Our strategy renders it possible to prepare polymer of alpha-amino functionality via one-pot process from commercially available commodity reagents under practical conditions with negligible catalyst residue.     

Synthesis,characterization and antibacterial activity of quaternized <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">O</Emphasis>-(2-carboxyethyl) chitosan

N,O-(2-carboxyethyl)chitosan (N,O-2-CEC) was prepared from chitosan with 3-chloropropionic acid as modifying agent and NaOH as catalyst. Different quaternary ammonium groups were introduced into N,O-2-CEC by the reaction between N,O-2-CEC and different 2,3-epoxypropyl trialkyl ammonium chlorides in the presence of 25% NaOH aqueous solution, and obtained different quaternized N,O-2-carboxyethyl chitosans (QCECs). Structures of QCECs were characterized by FT-IR, ¹HNMR and gel permeation chromatography (GPC). Antimicrobial activity of QCECs was evaluated against a gram-negative bacterium Escherichia coli and a gram-positive bacterium Staphylococcus aureus. Compared with N,O-2-CEC and quaternized chitosans, the QCECs had much stronger antimicrobial activity, which increased with increasing chain length of the alkyl in the quaternary ammonium groups. The presence of benzyl in quaternary ammonium groups could endow QCECs with much better antimicrobial activity.     

Graphene oxide/poly(<Emphasis Type="Italic">N</Emphasis>-isopropyl acrylamide)/sodium alginate-based dual responsive composite beads for controlled release characteristics of chemotherapeutic agent

In this work, graphene oxide (GO)-incorporated composite beads were developed from poly(N-isopropyl acrylamide)/sodium alginate (PNIPAM/NaAlg) using ionotropic gelation technique. The interaction between GO and PNIPAM/NaAlg with Ca²⁺ ions as a cross-linker was investigated by Fourier transform spectroscopy. X-Ray diffraction pattern showed that the GO was distributed uniformly in the PNIPAM/NaAlg with Ca²⁺ ions while scanning electron micrograph technique revealed that composite beads were formed in spherical shape. The controlled release characteristics of composite beads were studied using 5-fluorouracil (5-FU) as anti-cancer model drug. The encapsulation efficiencies were found to be between 90 and 92% in all formulations. Furthermore, the equilibrium swelling ratio (%) and in vitro release studies of the beads were carried out in two different pH values of 1.2 and 7.4 and at different temperature conditions of 25 and 37 °C. The obtained results showed that the swelling ratio decreased with an increase in GO concentration. In vitro release studies performed in response to both pH and temperature and they proved that the 5-FU drug was released from composite beads over 32 h without burst release. Cytotoxicity results showed pristine composite beads are good cytocompatible. In addition, the cytotoxicity of 5-FU was found to be improved when incorporated with composite beads than pure 5-FU. It is therefore concluded that the developed composite beads have dual response and can be used as controlling released carriers in cancer drug delivery applications.     

<Emphasis Type="Italic">N</Emphasis>-Acylated Bacteriohopanehexol-Mannosamides from the Thermophilic Bacterium <Emphasis Type="Italic">Alicyclobacillus acidoterrestris</Emphasis>

Identification of molecular species of various N-acylated bacteriohopanehexol-mannosamides from the thermophilic bacterium Alicyclobacillus acidoterrestris by semipreparative HPLC and by RP-HPLC with ESI is described. We used triple-quadrupole type mass spectrometer, ¹H and ¹³C NMR for analyzing this complex lipid. CD spectra of two compounds (model compound—7-deoxy-d-glycero-d-allo-heptitol obtained by stereospecific synthesis, and an isolated derivative of hopane) were also measured and the absolute configuration of both compounds was determined. On the basis of all the above methods, we identified the full structure of a new class of bacteriohopanes, represented by various N-acylated bacteriohopanehexol-mannosamides.     

Microspheres of copolymeric <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone and 2-ethoxyethyl methacrylate for the controlled release of nifedipine

Free radical copolymerization of N-vinyl-2-pyrrolidone (NVP) with 2-ethoxyethyl methacrylate (EOEMA) was carried out with 2,2′-azobisisobutyronitrile (AIBN) initiator in 1,4-dioxane solvent at 60 °C. The resulting copolymers were characterized by FTIR, ¹H-NMR and ¹³C-NMR methods. Microspheres were prepared by varying the amount of NVP with respect to EOEMA. Nifedipine (NFD), a water-insoluble antihypertensive drug, was loaded into these microspheres by the oil in water emulsion technique followed by solvent evaporation. The effect of the proportion of NVP in the NVP/EOEMA copolymer on the controlled release of NFD from the microsphere matrix was investigated. Scanning electron micrographs (SEM) of the microspheres indicated spherical shapes in the size range 17–47 μm, even after loading with NFD. In vitro studies of the release of NFD from the NVP/EOEMA microspheres in pH 7.4 medium showed that the rate of NFD release was enhanced when the NVP content of the copolymer was high; the size of the microspheres also increased with increasing NVP content of the copolymer. Release data were analyzed using an empirical relation in order to elucidate the kinetics of the NFD release. This analysis indicated that a Fickian transport mode operates in this system.     

Removal of cationic dyes from aqueous solutions with poly (<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-<Emphasis Type="Italic">co</Emphasis>-itaconic acid) hydrogels

In this study, N-isopropylacrylamide-based temperature and pH-sensitive hydrogels were synthesized by free radical polymerization for removal of cationic dyes from aqueous solutions. For this purpose, N-isopropylacrylamide was copolymerized with various amounts of sodium salt of itaconic acid in the presence of crosslinking agent (N,N-methylene bisacrylamide). The chemical structures of hydrogels were characterized by FT-IR analysis. In order to investigate swelling properties of the hydrogels, water absorption (swelling) and shrinking (deswelling) kinetics, the equilibrium swelling ratios in water and different pH buffer solutions, and the temperature dependent swelling ratios were determined. Then, their adsorption properties such as adsorption capacities, kinetics, isotherms were investigated in case of their usage in removal of Safranine T (ST), Brilliant Green (BG), and Brilliant Cresyl Blue (BCB) aqueous solutions. According to adsorbed dye amount, the adsorption capacities are followed the order BG > ST ≅ BCB. In addition, the results indicated that the pseudo-second-order kinetic model fitted better than the data obtained from pseudo-first-order model for the adsorption of all dyes onto hydrogels. Furthermore, according to effect of the initial dye concentration findings, it is concluded that, Freundlich isotherm explains the adsorption better than Langmuir isotherm.     

Synthesis,characterization and thermal dehydration and degradation kinetics of chitosan Schiff bases of <Emphasis Type="Italic">o</Emphasis>-, <Emphasis Type="Italic">m</Emphasis>- and <Emphasis Type="Italic">p</Emphasis>-nitrobenzaldehyde

The chitosan Schiff bases were synthesised through the condensation reaction of chitosan with o-, m- and p-nitrobenzaldehyde (abbreviated as CSB-o, CSB-m and CSB-p) in the ratio 1:1 and were characterised by means of FTIR, UV, XRD and SEM. The thermal dehydration and degradation kinetics of all these Schiff bases were studied using different isoconversional and maximum rate (peak) methods, viz. Kissinger–Akahira–Sunose (KAS), Tang, Starink, Flynn–Wall–Ozawa (FWO) and Bosewell from DSC data and the thermal stability from TG. The activation energy values of thermal dehydration and degradation reactions obtained from isoconversional methods of FWO and Bosewell are slightly higher than that obtained from other methods. All the isoconversional and maximum rate (peak) methods yielded consistent values of E _α for both the dehydration and degradation reactions and is in the order CSB-o < CSB-m < CSB-p. The Schiff bases observed (from TG) the same order of thermal stability.     

Ferrocenyl Monomers and Polymers of <Emphasis Type="Italic">N</Emphasis>-Allyl and <Emphasis Type="Italic">N</Emphasis>-Acrylatenaphthalimides

A series of N-allyl, N-ethylmethacrylate and N-phenylmethacrylatenaphthalimide monomers have been prepared with –C=CFc, –C≡CFc and –C≡CSiMe₃ substituents at the 4-position of the naphthalimide ring. All have been characterised by elemental analysis and spectroscopy; the X-ray structure of N-allyl-4-ethenylferrocenylnapththalimide is also reported. Free-radical polymerisation of these monomers gave homopolymers, random co- and terpolymers with polydispersities ranging from 1.7 to 3.2. Incorporation into a polymer matrix has no effect on the spectroscopic and electrochemical properties of the naphthalimide or ferrocenyl components. The ferrocenyl polymers are electrochromic and when oxidised give naphthalimide charge-transfer bands in the NIR; this electrochromism was examined by OTTLE techniques.     

Synthesis,Characterization and Properties of <Emphasis Type="Italic">N</Emphasis>-Alkyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-di(2-hydroxyethyl) Amine Oxides

N‐Dodecyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₂DHEAO) and N‐stearyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₈DHEAO) were synthesized with N‐alkyl‐diethanolamine and hydrogen peroxide. Their chemical structures were confirmed using ¹H‐NMR spectra, mass spectral fragmentation and FTIR spectroscopic analysis. It was found that C₁₂DHEAO and C₁₈DHEAO reduced the surface tension of water to a minimum value of approximately 28.75 mN m^?1 at concentration of 2.48 × 10^?3 mol L^?1 and 32.45 mN m^?1 at concentration of 5.21 × 10^?5 mol L^?1, respectively. The minimum interfacial tension (IFT_min) and the dynamic interfacial tension (DIT) of oil–water system were measured. When C₁₈DHEAO concentration was in the range of 0.1–0.5%, the IFT_min between liquid paraffin and C₁₈DHEAO solutions all reached the ultra‐low interfacial tension. Furthermore, their foam properties were investigated by Ross‐Miles method, and the height of foam of C₁₂DHEAO was 183 mm. It was also found that they showed strong emulsifying power.     

Swelling behaviour and paracetamol release from poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-itaconic acid) hydrogels

Copolymer hydrogels of N-isopropylacrylamide and itaconic acid (IA), crosslinked with N,N′-methylenebisacrylamide, were prepared by radical copolymerization. These hydrogels were investigated with regard to their composition to find materials with satisfactory swelling and drug release properties. A paracetamol is used as a model drug to investigate drug release profile of the hydrogels. It was found that the investigated hydrogels exhibited pH- and temperature-dependent swelling behaviour with restricted swelling and lower equilibrium degree of swelling at lower pH values and temperatures above the LCST value of PNIPAM (around 34 °C). The diffusion exponent for paracetamol release indicate that the mechanism of paracetamol release are governed by Fickian diffusion, while in all release media initial diffusion coefficient was lower than late time diffusion coefficient. Furthermore, the paracetamol release rate depends on the hydrogel degree of swelling and it increased in the first stage of diffusion process, whereas was no significant difference thereafter. The presence of the IA moieties incorporated into the network weakened the shear resistance of the hydrogels. In order to calculate the pore size the characteristic ratio for PNIPAM, C _n  = 11.7, was calculated. Based on the pore size, the investigated hydrogels can be regarded as microporous. According to the obtained results swelling behaviour, mechanical properties, drug-loading capacity and the drug release rate could be controlled by hydrogel composition and crosslinking density, which is important for application of the investigated hydrogels as drug delivery systems.     

UV-induced synthesis of chitosan-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide semi-IPN superabsorbent hydrogels

Superabsorbent hydrogels of chitosan-g-polyacrylamide with N,N′-methylene-bis-acrylamide as a crosslinker were prepared via UV irradiation in the absence of photoinitiator under homogeneous conditions. The product was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy to confirm the formation of hydrogels. The transparent hydrogels have been observed to exhibit as much as 2987% swelling in acidic solution. In addition, the hydrogel which hydrolyzed for 6 h (0.24 × 10³ min) can have a water uptake of 106 times its weight (5300% swelling for 0.5 g hydrogel). The effect of several variables such as time, temperature, pH, acrylamide/chitosan ratio, crosslinker amount, and different media was explored. Finally, the prepared hydrogel have been used in adsorption of Zn(II) ions from water with high removal efficiency (0.636 meq g⁻¹ or 20.8 mg g⁻¹) at pH = 7. The experimental data of the adsorption equilibrium from Zn(II) solution fit well with the pseudo-second-order model.     

Porous Carrageenan-<Emphasis Type="Italic">g</Emphasis>-polyacrylamide/bentonite superabsorbent composites: swelling and dye adsorption behavior

A novel superabsorbent composite based on kappa-Carrageenan (κC) was prepared by graft copolymerization of acrylamide (AAm) onto κC in the presence of bentonite powder using methylenebisacrylamide (MBA) as a crosslinking agent, ammonium persulfate (APS) as an initiator, and sodium carbonate as a pore-forming agent. The swelling behavior in distilled water and in solutions with different pH values was investigated. The results indicated that with increasing carrageenan/bentonite weight ratio, the swelling capacity is increased but the gel content is decreased. The swelling rate of the hydrogels was improved by introducing sodium carbonate as pore-forming agent. The prepared superadsorbent composites were used as adsorbent for a cationic dye, methylene blue. Isotherm of adsorption and the effect of pH, adsorption dosage, contact time and initial dye concentration on dye adsorption were also studied. The results showed that maximum adsorption capacity of methylene blue on the prepared adsorbents is 156.25 mg g^?1 and adsorption is well-described by Langmuir isotherm model.     

Synthesis and Properties of 1,1-bis{[3-(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylamino)propyl]amido}alkane-di-<Emphasis Type="Italic">N</Emphasis>-oxides

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)propyl]amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylamino-1,3-propanediamine followed by oxidation with aqueous hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ_CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), efficiency of surface adsorption (pC₂₀), standard free energies of adsorption (ΔG°_ads), and micellization (ΔG°_CMC). All investigated di-amidoamines and di-N-oxides were practically non-toxic to selected bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle Test inoculated with activated sludge. Surface and biological properties showed that this group of N-oxide-type compounds has high surface activity and fulfills requirements for environmental acceptance.

Synthesis of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-<Emphasis Type="Italic">b</Emphasis>-<Emphasis Type="Italic">N</Emphasis>-vinylcarbazole) copolymers via RAFT polymerization and its stimuli responsive morphology in aqueous media

Here, we report the successful synthesis of series of stimuli responsive amphiphilic diblock copolymers (SRABCs) poly(N-isopropylacrylamide-b-N-vinylcarbazole) [poly(NIPAAm-b-NVK)] through reversible addition fragmentation chain transfer (RAFT) polymerization. Copolymers with fixed hydrophilic [poly(NIPAAm)] block length and variable (with three different) hydrophobic [poly(NVK)] block lengths were synthesized and the block length ratio was confirmed from their molecular weight data. The self-assembly nature of synthesized block copolymers was confirmed by determining critical micelle concentration (CMC). Self-assembled block copolymers showed rice-grain like morphology for copolymers having equivalent hydrophobic/hydrophilic chain length but in case of block copolymers having smaller and bigger hydrophobic chain length with respect to hydrophilic chain length displayed vesicular morphology. The thermo and pH responsiveness of the block copolymers was found to be influenced by variation in length and chemical composition of the blocks. Due to their thermo and pH responsiveness resulted self-assembled structures underwent morphology transitions from vesicular and rice grain like to micellar structure in aqueous medium. The probable applications of the studied stimuli responsive amphiphilic diblock copolymers can be found in the nanotechnology and biotechnology are indicated.

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Graphical abstract Synthesis, self-assembly and stimuli responsiveness of poly(NIPAAm-b-NVK) copolymers.

     

Morphology and drug release behavior of <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide/acrylic acid copolymer as stimuli-responsive nanogels

Thermo- and pH-responsive N-isopropylacrylamide (NIPAM) nanogels can be obtained by copolymerization of acrylic acid (AA) comonomer through differential microemulsion polymerization. The effects of comonomer, cross-linker, surfactant contents, and water/oil ratio were preliminarily investigated by a 2⁴ full factorial design in order to eliminate the insignificant parameters from the polymerization analysis. The smallest poly(NIPAM-co-AA) nanogel particles were 40 ± 1 nm in diameter with 6 wt% of solid content and 98% conversion without coagulation. The comonomer amounts controlled the morphologies and LCST of the poly(NIPAM-co-AA) nanogels. The hairy microgels of poly(NIPAM-co-AA) with a 10:90 mol ratio of AA/ NIPAM had a lower critical solution temperature (LCST) of 6 °C. With an increase in the AA amount to a 17 mol ratio, the LCST increased to 27 °C, resulting in core-shell morphology. The morphology of resultant nanogels was characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, and differential scanning calorimetry. Nuclear magnetic resonance spectroscopy was used to calculate the mole ratio of NIPAM and AA in resultant nanogels after dialysis. Both nanogel mole ratio and morphology effectively retained the cationic anti-cancer drug of methylene blue for several hours, an important basic requirement for a drug delivery system. Compared to core-shell microgels, a higher methylene blue release was obtained from the hairy microgels in simulated intestinal fluid.     

Inhibitory Effects of Semiochemicals on the Attraction of an Ambrosia Beetle <Emphasis Type="Italic">Euwallacea</Emphasis> nr. <Emphasis Type="Italic">fornicatus</Emphasis> to Quercivorol

The Euwallacea fornicatus (Eichhoff) species complex includes the polyphagous shot hole borer (PSHB), an ambrosia beetle infesting avocado limbs, Persea americana Mill. Synthetic quercivorol, a monoterpene alcohol, is known to attract females (males are flightless) over a range of release rates spanning three orders of magnitude. The upper release dose was extended 10-fold using sticky traps baited with quercivorol released at 1× (0.126 mg/day), 10×, and 108× relative rates to obtain a dose?response curve fitting a kinetic formation function. Naturally infested limbs of living avocado trees were wrapped with netting to exclude the possibility of catching emerging beetles on the encircling sticky traps. The results indicate PSHB are significantly attracted to infested limbs. Ethanol released over a 64-fold range (lowest rate of 7.5 mg/day) was moderately inhibitory of PSHB attraction to 1× quercivorol. β-caryophyllene and eucalyptol did not appear to affect attraction at the rates tested. A field test of potential inhibitors of 1× quercivorol was done using ~1 mg/day releases of monoterpene ketones: (?)-(S)-verbenone, (+)-(R)-verbenone, 3-methyl-2-cyclo-hexen-1-one (MCH or seudenone), piperitone, (+)-(S)-carvone, and racemic cryptone. Only piperitone and the two enantiomers of verbenone were strongly inhibitory. A blend of piperitone and verbenone tested together at different distances (0, 0.5, 1, 2, and 4 m) from a 1× quercivorol baited sticky trap became increasingly ineffective in inhibiting the attractant as separation distance increased. Due to the relatively short-range repellency (<1 m), the inhibitors would need to be released from several places on each tree to effectively repel PSHB from avocado trees. Effective attraction radii, EAR, and circular EARc are estimated for the quercivorol baits released at 1×, 10× and 108× rates. Push-pull simulations of moving beetles were performed in 1 ha plots with 2, 4, or 16 traps of 10× EARc and 400 trees (0, 1, or 3 inhibitors per tree) of which ten had an infested limb (EARc?=?0.5 m). The simulations indicate that push-pull methods would be more effective in reducing PSHB mating than simply using mass-trapping alone.     

Atmospheric nitrogen loss factor (<Emphasis Type="Italic">f</Emphasis>) used in determining nitrogen-based municipal wastewater effluent irrigation rates: design and nitrogen-balance estimated <Emphasis Type="Italic">f</Emphasis> values

Design irrigation rates for treated municipal wastewater effluent (MWE) are usually determined from nitrogen (N) mass-balances, in which the fraction (f) of the total N in the MWE that is lost to the atmosphere is commonly obtained from US Environmental Protection Agency (USEPA) tabulated (design) values: 0.15–0.25 for secondary-treated effluents and 0.1 for tertiary-treated effluents. In 2011 and 2012, f values from an N balance in a tall fescue (Festuca arundinacea Schreb.) hay field in Central Pennsylvania were quantified and compared to the USEPA design f values. The grass field was spray-irrigated with MWE (C:N ratio = 0.04–0.2; near neutral pH, and 70–87% of the MWE-TN was NO₃–N) at a rate of ≤5-cm wk^?1. Monthly N balances were calculated from April to September in the surface horizon of a Hagerstown soil. The f values of 0.05, 0.1, and 0.2 seemed appropriate for the months of May and June, August and September, and July, respectively. Positive fnb estimates and the logarithm of measured monthly N removal in the aboveground biomass (kg ha^?1) were negatively correlated (R² = 0.99 for monthly mean air temperatures ≥20 °C and R² = 0.2 for monthly mean air temperatures <20 °C). The study’s results suggest that existing design f values are likely less applicable especially due to the biological N-removal processes currently present in many wastewater treatment plants needing to meet effluent N limits. Thus, more studies to determine empirical f values in effluent irrigation are needed to refine design f values.