Highly potent germination inhibitors in aqueous eluate of fruits of Bishop's weed (Ammi majus L.) and avoidance of autoinhibition

The aqueous eluate from fruits ofAmmi majus (Bishop's weed, Umbelliferae) remarkably inhibited germination of adjacent seeds ofAnastatica hierochuntica, lettuce, or tomato but had no effect on intact fruits ofAmmi. Similar inhibition was found in dark or in light, except that seeds ofA. hierochuntica were significantly more inhibited in the dark than in the light. Xanthotoxin was isolated, identified, and found to account for about a sixth of the inhibitory activity of the eluate. After fruits ofAmmi were submerged in a large volume of water for 4 days, the fruits still exuded enough inhibitors to prevent germination ofA. hierochuntica, lettuce, or tomato. Data support also the proposal that the phytotoxins are compartmentalized between the inner and the outer fruit envelopes. The inner layer excludes inhibitors from the embryo and autotoxicity is thus avoided, whereas the outer one ensures a gradual liberation of the phytotoxic compounds. This, as well as the high reactivity of the eluate, the high densities ofAmmi fruits in nature, and their relatively limited annual germination, suggest chemical inhibition of neighboring plant species other thanAmmi. Hence, in addition to their chemical protection against predators of either lower or higher organisms, furanocoumarins in fruits ofAmmi majus may contribute to its success as a weed.     

Use of the Nasicon/Na2SO4 couple in a solid state sensor for SO x (x=2,3)

The e.m.f. of a concentration cell for SO _x (x=2,3)-O₂ incorporating Nasicon as the main solid electrolyte has been measured in the temperature range 720 to 1080 K. The cell arrangement can be represented as, $$Pt, O'_2 + SO'_2 + SO'_3 \left| {Na_2 SO_4 \left\| {\left. {Nasicon} \right\|} \right.} \right.\left. {Na_2 SO_4 } \right|SO''_3 + SO''_2 + O''_2 , Pt$$ The Na₂SO₄ acts both as an auxiliary electrode, converting chemical potentials of SO _x and O₂ to equivalent sodium potentials, and as an electrolyte. The presence of Na₂SO₄ provides partial protection of Nasicon from chemical reaction with gas mixtures containing SO _x . The open circuit e.m.f. of the cell is in close agreement with values given by the Nernst equation. For certain fixed inlet gas compositions of SO₂+O₂, the e.m.f. varies non-linearly with temperature. The intrinsic response time of the cell to step changes in gas composition is estimated to vary from ～2.0 ksec at 723K to ～ 0.2 ksec at 1077K. The cell functions well for large differences in partial pressures of SO₃(p″_{SO 3}/p′_{SO 3}≈10⁴) at the electrodes.     

Thermal analysis of styrene–alkyl methacrylate polymers. I. Glass transition temperatures

The glass transition temperatures (T_g's) of several polystyrenes and styrene–alkyl methacrylate copolymers and terpolymers were measured using thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). The polymers studied had number-average molecular weights from 3000 to 250,000 g/mole. The results indicate that the composition dependence of the T_g's for the copolymers and terpolymers can be satisfactorily described by a general Fox equation. In general, the measured T_g's of the copolymer and terpolymer samples depend more on the steric effects of the constituent pendent groups than on their molecular weights. The chain flexibility rather than the size of the pendent group is the determining factor in the glass transition properties of the styrene polymers.     

Recycling of ethylene propylene diene monomer (EPDM) waste. III. Processability of EPDM rubber compound containing ground EPDM vulcanizates

The rheological behavior of ethylene propylene diene monomer (EPDM) compounds containing ground EPDM waste (W‐EPDM) of known composition was studied by using a Monsanto processability tester in a temperature range of 90–110°C and a shear rate range of 306.7–1533.24 s^?1. It is found that the shear viscosity decreases slightly with increasing W‐EPDM loading because of wall slip that results from the migration of lubricants from the W‐EPDM. The addition of W‐EPDM to raw EPDM results in a decreased die swell at all temperatures and shear rates. SEM photomicrographs of the EPDM extrudate surface show improved surface smoothness and reduced extrudate distortion when EPDM is blended with W‐EPDM. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2204–2215, 2003     

Ablation of ice-solids and wax-solids mixtures in turbulent axisymmetric water jets

The ablation rate of frozen mixtures of water or wax with finely divided solids subjected to a turbulent axisymmetric water jet was investigated both experimentally and theoretically. The range of the water jet Reynolds number was 8700–29300 and the jet temperature varied between 22 and 60°C. The solids used were very fine kaolinite clay, titanium oxide and aluminium powder. The type of solids and their concentration were found to affect the ablation rate of ice-solids and wax-solids mixtures. This is mainly due to changes in the physical properties of the melt layer of the water-solids or wax-solids mixtures which forms between the impinging jet and the frozen mixtures.     

Allelochemical resistance of bald cypress,Taxodium distichum,heartwood to the subterranean termite,Coptotermes formosanus

The heartwood of bald cypress,Taxodium distichum (L.) Rich., resisted feeding attack by the Formosan subterranean termite,Coptotermes formosanus Shiraki. Hexane-extracted heartwood, however, was consumed at > 12 times the amount of sound heartwood eaten. A bioassay usingT. distichum sapwood as a feeding substrate was employed to assess the antitermitic activity of successive hexane, acetone, and methanol extracts of heartwood shavings and isolates derived from the active hexane extract. Two fractions, eluted from the crude hexane extract by liquid chromatography, significantly reduced termite feeding compared to the parent extract, while a third fraction was less active than the original hexane extract. Each fraction contained one major component. All three components were structurally related diterpenes. The two most active heartwood constituents were identified by GC-MS and NMR as ferruginol and manool, while the third and least active, but most prevalent, compound in heartwood was identified as nezukol. Results of bioassays suggest that these allelochemicals act principally as feeding deterrents with accompanying termite mortality due to starvation.     

The lipids of the oriental hornet,Vespa orientalis F.

Analysis of the hornet’s hemolymph revealed the presence of C₁₆ and C₁₈ fatty acids (70%), which were accompanied by minor quantities (ranging from 0.1% to 0.6%) of the following acids: C_10∶0, C_11∶0, C_12∶0, C_13∶0, C_14∶0, C_15∶0, C_16∶0, and C_17∶0. The hemolymph of the queen larvae contained more C_18∶1 than the hemolymph of the worker larvae, and the percentage of C_16∶1 was higher in the fat body and the midgut than in the hemolymph. The significance of these results is discussed.     

Kinetic analysis of cellular internalization and expulsion of unstructured D-chirality cell penetrating peptides

Most cell penetrating peptides (CPPs) are unstructured and susceptible to proteolytic degradation. One alternative is to incorporate D-chirality amino acids into unstructured CPPs to allow for enhanced uptake and intracellular stability. This work investigates CPP internalization using a series of time, concentration, temperature, and energy dependent studies, resulting in a three-fold increase in uptake and 50-fold increase in stability of D-chirality peptides over L-chirality counterparts. CPP internalization occurred via a combination of direct penetration and endocytosis, with a percentage of internalized CPP expelling from cells in a time-dependent manner. Mechanistic studies identified that cells exported the intact internalized D-chirality CPPs via an exocytosis independent pathway, analogous to a direct penetration method out of the cells. These findings highlight the potential of a D-chirality CPP as bio-vector in therapeutic and biosensing applications, but also identify a new expulsion method suggesting a relationship between uptake kinetics, intracellular stability, and export kinetics.     

Effect of processing techniques and residual solvent on the thermal/mechanical properties of epoxy-cellulose nanocrystal nanocomposites

Epoxy nanocomposites reinforced with 0–5 wt% cellulose nanocrystal (CNC) were fabricated by solution casting method. The CNCs were first dispersed in the hardener together with a co-solvent and subsequently mixed with epoxy monomer using two different protocols: bulk mixing and dropwise mixing. The dropwise mixing resulted in more homogeneously-dispersed CNCs and provided better mechanical properties, particularly higher tensile strength, tensile modulus, and work of fracture with increasing CNC content. Investigation of various CNC/hardener mixtures with different solvent content showed that the residual solvent in the composite mixture had an impact on the curing behavior of the nanocomposite epoxy and may have lowered its crosslinking density, leading to T_g depression. However, the presence of the solvent was shown to be essential for the preparation of a well-dispersed CNC phase in the hardener solution, and to form homogenous composite mixtures. Our results show that the reinforcement effect due to higher CNC concentration is more significant than the solvent effect in the hardener system and shows greater improvement in mechanical properties. The CNC component reversed the solvent plasticizing effect through its superior mechanical reinforcing effects, and the dropwise mixing process led to better dispersion compared with the bulk mixing process.