Quantitative comparison of volatile compounds among sevenMedicago spp. accessions

Previous research identified the presence of unique semivolatile compounds in alfalfa weevil (Hypera postica Gyllenhal) (AW) -resistantMedicago accessions. These compounds may impart repellency to AW in alfalfa (Medicago sativa L.). The objective of our study was to analyze within- and between-population variation for four of these unique semivolatile compounds across eglandular and glandular-hairedMedicago accessions. SevenMedicago accessions were evaluated under greenhouse conditions in an experiment arranged as randomized complete blocks with four replicates. Volatile compounds were extracted via supercritical fluid extraction and then quantitatively analyzed for levels of 2,7-dimethyl, 2,6-octadienol;cis-geraniol; 1,(E)-8,(Z)-10-tetradecatriene; and 1-hepten-3-ol. Significant difference (P<0.05) among entries were observed for 2,7-dimethyl,2,6-octadienol;cis-geraniol; 1, and (E)-8,(Z)-10-tetradecatriene. These compounds were found only in glandularhaired accessions. There were no significant differences in levels of 1-hepten-3-ol. Our findings demonstrate that the genetic incorporation of 2,7-dimethyl, 2,6-octadienol;cis-geraniol; 1, and (E)-8,(Z)-10-tetradecatriene into cultivated alfalfa will require interspecific crossing. Alfalfa weevil behavioral tests using these compounds must be conducted prior to such crosses in order to ascertain the efficacy of repellency by these compounds.     

Dissolution enhancement of gliclazide using in situ micronization by solvent change method

Gliclazide (GL) is a second-generation sulphonylurea, widely used for the treatment of non-insulin dependent diabetes mellitus. The low water-solubility of GL leads to a low dissolution rate and variable bioavailability. The aim of this study was to enhance the dissolution rate of GL by the preparation of micron-sized particles using a solvent change method. The in situ micronization process was carried out using solvent change method in the presence of HPMC or Brij 35 (0.05 or 0.1 g) as stabilizing agents. GL (0.5 or 1 g) was dissolved in acetone and the stabilizing agent in water (as non-solvent). The non-solvent was poured rapidly into the drug solution under stirring at 26,000 rpm by an ultra-homogenizer, and the resultant was freeze-dried. The crystalline shape of GL changed from rod-shape to diamond- or cube-shape. The FTIR and DSC results showed no interaction between the drug and the stabilizers. Presence of sharp peaks in the XRD diffractograms of microcrystals with 10 times smaller height than untreated crystals indicates that a crystalline habit modification has occurred in the microcrystals without any polymorphic changes. The particle size was reduced about 50 times and the dissolution efficiency of GL at 15 min (DE₁₅%) was increased about 4 times.     

Discovering complexity and emergent properties in project systems: A new approach to understanding project performance

An integrated performance assessment framework based on consideration of complexity and emergent properties in project systems is proposed in this study. The fundamental premise of the proposed Complexity and Emergent Property Congruence (CEPC) framework is that a greater level of congruence between project emergent properties and complexity can potentially increase the possibility of achieving performance goals in construction projects. Two dimensions of project complexity (i.e., detail and dynamic complexity) and three dimensions of project emergent properties (i.e., absorptive, adaptive, and restorative capacities) in the proposed CEPC framework were verified through information collected from in-depth interviews with nineteen senior project managers. In addition, contributing factors to different dimensions of project complexity and emergent properties were identified from the interviews. The results highlight the significance of the CEPC framework in understanding complexity and emergent properties in project systems and providing a new theoretical lens for project performance assessment.     

Acoustic Emission Methodology to Evaluate the Fracture Toughness in Heat Treated AISI D2 Tool Steel

In this article, fracture toughness behavior of tool steel was investigated using Acoustic Emission (AE) monitoring. Fracture toughness (K _IC) values of a specific tool steel was determined by applying various approaches based on conventional AE parameters, such as Acoustic Emission Cumulative Count (AECC), Acoustic Emission Energy Rate (AEER), and the combination of mechanical characteristics and AE information called sentry function. The critical fracture toughness values during crack propagation were achieved by means of relationship between the integral of the sentry function and cumulative fracture toughness (KICUM). Specimens were selected from AISI D2 cold-work tool steel and were heat treated at four different tempering conditions (300, 450, 525, and 575?°C). The results achieved through AE approaches were then compared with a methodology proposed by compact specimen testing according to ASTM standard E399. It was concluded that AE information was an efficient method to investigate fracture characteristics.     

Three-dimensional crack observation,quantification and simulation in a quasi-brittle material

To investigate the fracture behaviour of polygranular graphite (a quasi-brittle material), crack propagation in a short bar chevron notched specimen was studied by synchrotron X-ray computed tomography combined with digital volume correlation. Displacements were measured within the loaded test specimen, particularly the three-dimensional (3-D) profile of crack opening displacement. Analysis of the 3-D displacement field confirmed the existence of distributed damage in a fracture process zone, which significantly increased the effective crack length. Finite element simulations affirmed that the measured crack opening profiles could be reproduced using a cohesive zone model, but not with a linear elastic analysis. Comparing the simulation to the experimental results, it was deduced that the critical strain energy release rate varied across the crack front, i.e. the fracture toughness is constraint-dependent. This is proposed to be a general characteristic of quasi-brittle materials.     

Variation in aphid alarm pheromone content among glandular and eglandular-hairedMedicago accessions

Pea (Acyrthosiphon pisum Harris) and blue alfalfa aphid (A. kondoi Shinji) deterrency in alfalfa (Medicago saliva L.) may result from incorporating higher levels of the aphid alarm pheromone,(E)--farnesene relative to(E)--caryophyllene. We evaluated five eglandular and two glandular-haired alfalfa accessions for differences in(E)--farnesene and(E)--caryophyllene content under glasshouse conditions using supercritical fluid extraction and gas chromatography. In addition, pea and blue alfalfa aphid olfactory behavioral tests were conducted uponMedicago species containing different ratios of(E)--famesene relative to(E)--caryophyllene. No differences in(E)--caryophyllene content were observed among the seven entries (=0.42 ng/g plant material). Significant differences (P 0.05) among entries were observed for(E)--famesene content, with KS94GH6 exhibiting the highest (1.18 ng/g), and CUF 101 the lowest levels (0.35 ng/g). Elite tetraploid sources possessed significantly lower levels (=0.42 ng/g) of(E)--farnesene than did wild and cultivated diploid accessions (=0.83 ng/g). Olfactory behavioral tests for both the pea and blue alfalfa aphids demonstrated KS94GH6 repelled aphids while cultivated alfalfa types attracted aphids in each case. Previously demonstrated aphid resistance in diploid KS94GH6 may result from superior(E)-- farnesene levels, but(E)--farnesene is probably not a factor in cultivated alfalfa resistance. Finally, accession KS94GH6 could act as an excellent germplasm resource for the incorporation of higher(E)--farnesene levels into cultivated alfalfa.Research supported by the New Mexico State University Agricultural Experiment Station.     

The Biodegradation of Methyl Tert-Butyl Ether (MTBE) by Indigenous Bacillus cereus Strain RJ1 Isolated From Soil

Methyl Tert-Butyl Ether (MTBE) is an oxygenated organic compound extensively substituted for lead in gasoline worldwide. MTBE can affect human and environment. In this research, biodegradation capability of MTBE by identified indigenous Bacillus cereus strain RJ1 was studied. Obtained results showed that biological removal of MTBE with 200 mg/L samples in 28°C is 27.5% while in 37°C within 120 days reaches to 34%. In addition, biodegradation of Bacillus cereus RJ1 in 500 mg/L and 1,000 mg/L is 28% and 23.9% in 28°C, respectively. Therefore, this bacterium could clean up MTBE from the environment.