Chemistry of the postpharyngeal gland secretion and its implication for the phylogeny of IberianCataglyphis species (Hymenoptera: Formicidae)

Summary A comparative morphological and chemical study of six endemic species ofCataglyphis from the Iberian Peninsula:C. ibericus, C. rosenhaueri, C. hispanicus, C. humeya, C. velox andC. floricola and the Moroccan speciesC. bombycinus is described. The morphological study relied primarily on genitalia characteristics, whereas the chemical study concentrated on the postpharyngeal gland constituents. Cladograms based on the morphological and chemical data were performed using Ward's method. The dendrogram based on morphological features revealed that the IberianCataglyphis can be classified into three species groupsalbicans, altisquamis andemmae. The same pattern occurred when the dimethylalkanes constituents of the postpharyngeal gland were utilised as character states, with a slight displacement of species within thealtisquamis group. However, when the complete hydrocarbon blend was utilised major discrepancies in the dendrograms occurred.Cataglyphis velox proved to be very similar toC. bombycinus, whereasC. floricola clustered with the other two species of thealtisquamis group. Based on the geographical distribution and paleontological data (Tinaut 1993) it is assumed thatC. floricola recently invaded the Iberian Peninsula. Based on the chemical findings we postulate that chemical character displacement occurred inC. floricola as a result of its sympatry withC. velox after the former colonized the Iberian Peninsula. We further discuss the possible reason for the different dendrograms obtained when only the dimethylalkanes are considered and its implication for the communicative role of the postpharyngeal gland secretion in these ants.     

Sonophotocatalytic Degradation of Chitosan in the Presence of Fe(III)/H2O2 System

The degradation of chitosan by means of ultrasound irradiation and its combination with homogeneous photocatalysis (photo-Fenton) was investigated. Emphasis was given on the effect of additive on degradation rate constants. 24 kHz of ultrasound irradiation was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. To increase the efficiency of degradation process, degradation system was combined with Fe(III) (2.5 × 10⁻⁴mol/L) and H₂O₂ (0.020–0.118 mol/L) in the presence of UV irradiation and the rate of degradation process change from 1.873 × 10⁻⁹−6.083 × 10⁻⁹ mol^1.7 L s⁻¹. Photo-Fenton process led to complete chitosan degradation in 60 min with the rate increasing with increasing catalyst loading. Sonophotocatalysis in the presence of Fe(III)/H₂O₂ was always faster than the respective individual processes. A synergistic effect between ultrasound and ultraviolet irradiation in the presence of Fenton reagent was calculated. The degraded chitosans were characterized by X-ray diffraction (XRD), gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated chitosan was determined by measurements of intrinsic viscosity of samples. The results show that the total degree of deacetylation (DD) of chitosan change, partially after degradation and the decrease of molecular weight led to transformation of crystal structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within the degradation process was suggested. Results of this study indicate that the presence of catalyst in the reaction medium can be utilized to reduce molecular weight of chitosan while maintaining the power of irradiated ultrasound and degree of deacetylation.     

Pheromones and colonization: reassessment of the milkweed bug migration model (Heteroptera: Lygaeidae: Lygaeinae)

Summary. Research on insect migration has justifiably emphasized females – the so-called “oogenesis-flight syndrome”– since it is the females that place the eggs into new habitats. The large and small milkweed bugs, Oncopeltus fasciatus and Lygaeus kalmii, respectively, have featured prominently in studies of insect migration and sequestration of host plant toxins for chemical defense. Here we report that males of these species, and males of another well-studied lygaeine (Neacoryphus bicrucis), produce pheromones in glands usually considered to serve only a defensive role in Heteroptera (the metathoracic scent glands), and that these pheromones are exploited by a tachinid parasitoid as a host-finding kairomone. The pheromones are mixtures of C₆ and C₈ saturated and unsaturated esters reminiscent of lepidopteran pheromones, and the key compound of the O. fasciatus pheromone has now been correctly identified as (E)-2,7-octadienyl acetate. It is proposed that the concept of the oogenesis-flight syndrome for these kinds of insects should accommodate the role of males in the migration process. The hypothesis is presented that male-produced pheromones play a significant role in guiding colonization of new habitats in many heteropteran species. In addition, data are presented suggesting that there is a trade-off between the amount of pheromone produced by colonizing males and the host breadth of the species. Received 21 December 1998; accepted 15 February 1999.     

Magnetic Cr(VI) Ion Imprinted Polymer for the Fast Selective Adsorption of Cr(VI) from Aqueous Solution

In this study, a novel magnetic Cr(VI) ion imprinted polymer (Cr(VI)-MIIP) was successfully synthesized and used as a selective sorbent for the adsorption of Cr(VI) ions from aqueous solution. It can be synthesized through the combination of an imprinting polymer and magnetic nanoparticles. The high selectivity achieved using MIIP is due to the specific recognition cavities for Cr(VI) ions created in Cr(VI)-MIIP. Also, the magnetic properties that could be obtained using magnetic nanoparticles, helps to separate adsorbent with an external magnetic field without either additional centrifugation or filtration procedures. The magnetic Fe₃O₄ nanoparticles (MNPs) were synthesized using an improved co-precipitation method and modified with tetraethylorthosilicate (TEOS) before imprinting. The magnetic Cr(VI) ion imprinted polymer was prepared through precipitation copolymerization of 4-vinylpyridine as the complexing monomer, 2-hydroxyethyl methacrylate as a co-monomer, the Cr⁶⁺ anion as a template, and ethylene glycol dimethacrylate (EGDMA) as a cross-linker in the presence of modified magnetite nanoparticles. This novel synthesized sorbent was characterized using different techniques. Batch adsorption experiments were performed to evaluate the adsorption conditions, selectivity, and reusability. The results showed that the maximum adsorption capacity was 39.3 mg g^?1, which was observed at pH 3 and at 25?°C. The equilibrium time was 20 min, and the amount of adsorbent which gave the maximum adsorption capacity was 1.7 g L^?1. Isotherm studies showed that the adsorption equilibrium data were fitted well with the Langmuir adsorption isotherm model and the theoretical maximum adsorption capacity was 44.86 mg g^?1. The selectivity studies indicated that the synthesized sorbent had a high single selectivity sorption for the Cr(VI) ions in the presence of competing ions. Thermodynamic studies revealed that the adsorption process was exothermic (\(\Delta H\)?<?0) and spontaneous (\(\Delta G\)?<?0). In addition, the spent MIIP can be regenerated up to five cycles without a significant decrease in adsorption capacity.     

Mating expenditures reduced via female sex pheromone modulation in the primitively eusocial halictine bee, Lasioglossum (Evylaeus) malachurum (Hymenoptera: Halictidae)

The present paper reports on behavioral experiments and gas chromatographic analysis of chemical communication in the mating biology of the primitively eusocial sweat bee Lasioglossum (Evylaeus) malachurum. In a dual-choice experiment, a female made odorless was significantly less attractive than an untreated one. Attraction in L. (Evylaeus) malachurum is therefore mediated by a female-produced sex pheromone. Further bioassays showed that unmated gynes are more attractive to males than mated ones. Males are able to differentiate between the two groups of females as little as 3 h after mating. Biotests with different samples obtained from attractive gynes showed surface extracts to be most attractive. Behavioral tests with synthetic copies of the compounds identified as cuticular constituents of virgin gynes were highly attractive to males; the volatile bouquets consisting of n-alkanes, n-alkenes and iso- pentenyl esters of unsaturated fatty acids were the most attractive samples. Isopentenyl esters of unsaturated fatty acids were the key compounds in inducing male inspections as well as stimulating pounces and copulatory attempts. Virgin and nesting gynes differed clearly in the relative and absolute amounts of the volatiles on the cuticle. The total amount of volatiles was significantly higher in virgin gynes and decreased in breeding queens. Hydrocarbons were the dominant group of compounds in both groups of females. The relative amounts of the wax-type ester, hexadecyl oleate, iso- pentenyl esters, and a hitherto unidentified steroid were higher in attractive virgin gynes, while the relative proportions of hydrocarbons and lactones dominated in nesting queens. The site of sex pheromone production in attractive young L. (Evylaeus) malachurum gynes remains unknown. Head glands or Dufour's gland secretions may be involved. Another possible source of the `active principle' found among the cuticular lipids could be glandular cells of the epidermis. The significance of modulation of female sex pheromone composition is discussed in terms of a reduction in mating expenditures. Received: 30 April 1998 / Accepted after revision: 24 July 1998     

Selection and performance estimation of Green Lean Six Sigma Projects: a hybrid approach of technology readiness level,data envelopment analysis,and ANFIS

Environmental Science and Pollution Research - Nowadays budget and schedule constraints have forced organizations to select six sigma projects based on pre-defined success criteria. Also,...