Development of a bionematicide with Paecilomyces lilacinus to control Meloidogyne incognita

Root-knot disease caused by Meloidogyne incognita is a matter of grave concern because it affects several economically important crop plants. The use of solid-state fermentation (SSF) may help to elaborate efficient formulations with fungi to be employed in the biologic control of nematodes. Attempts were made to select low-cost substrates for spore production of a strain of Paecilomyces lilacinus with known nematicide capacity. Coffee husks, cassava bagasse, and defatted soybean cake were utilized as substrates, and sugarcane bagasse was used as support. Fermentations were carried out in flasks covered with filter paper at 28°C for 10 d. The products obtained by SSF were evaluated for their nematicide activity in pot experiments containing one seedling of the plant Coleus inoculated with the nematode M. incognita. The plants were evaluated 2 mo after inoculation. Fermented products showed a reduction in the number of nematodes. The best results were obtained with defatted soybean cake, which showed almost 100% reduction in the number of nematodes; the reduction with coffee husk was 80% and with cassava bagasse was about 60%.     

A photo-cured coated-wire calcium ion selective electrode for use in flow injection potentiometry

A multi-sensor cell containing a new photo-cured calcium ion selective electrode sensor is reported. Four membranes containing different components are prepared to determine the one with optimum selectivity and sensitivity. This is shown to consist of the N,N,N',N'-tetracyclohexyl-3-oxapentanediamide ligand (ETH 129) as the ionophore, 2-nitrophenyl octyl ether as the plasticiser and tetradodecyl ammonium tetrakis(4-chlorophenyl) borate as the lipophilic additive. The photo-curing process is applied after coating a thin membrane on a silver wire as substrate transducer to produce the calcium sensor. The curing process is demonstrated to be faster (1 min) than previous methods and does not require a nitrogen atmosphere for reproducible production of membrane response characteristics. Four sensors constructed with the identical optimum membrane are shown to function reproducibly in a multi-sensor flow-through cell using the steady-state mode of flow measurement, and an average calibration slope of 28.5+/-0.4 mV change per activity decade is observed over a log-linear concentration range between 0.01 and 10 mM. The sensor is also shown to respond to changes in pH. Hence, in the flow injection potentiometric mode, a constant carrier buffer composition of pH 8.3 is required for accurate potentiometric calcium determinations. The sensor is used to determine calcium in water samples by flow injection potentiometry. The accuracy of the electrode determination relative to atomic absorption spectroscopy was in the range 5-9% for three different water samples.     

Relationship between coffee husk caffeine degradation and respiration of Aspergillus sp. LPBx in solid-state fermentation

Studies were carried out in a packed-bed column fermentor using coffee husk as substrate in order to verify a relationship between caffeine degradation and the respiration of Aspergillus sp. LPBx. Fermentation conditions were optimized by using factorial design experiments. The kinetic study showed that the caffeine degradation was related to the development of mold and its respiration and also with the consumption of reducing sugars present in coffee husk. From the values obtained experimentally for oxygen uptake rate and CO₂ evolved, we determined a biomass yield of 3.811 g of biomass/g of consumed O₂ and a maintenance coefficient of 0.0031 g of consumed O₂/(g of biomass·h). The maximum caffeine degradation achieved was 90%.     

Longitudinal relaxation of initially straight flexible and stiff polymers

The relaxation mechanism of an initially straight flexible or stiff polymer chain of length N in a viscous solvent is studied through Brownian dynamics simulations covering a broad range of time scales. After the short-time free diffusion, the chain's longitudinal reduction R2(0)-R2 approximately Nt1/2 at early intermediate times is shown to constitute a universal behavior for any chain stiffness caused by a quasisteady T approximately Nt(-1/2) relaxation of tensions associated with the deforming action of the Brownian forces. Stiff chains with a persistence length E > or = N are shown to exhibit a late intermediate-time longitudinal reduction R2(0)-R2 approximately N2E(-3/4)t1/4 associated with a T approximately N2E(-3/4)t(-3/4) relaxation of tensions affected by the deforming Brownian and the restoring bending forces.     

A technique for mycelial development of ectomycorrhizal fungi on agar media

A technique was established to study ectomycorrhizal fungi on agar media. Petri dishes, 60 mm in diameter, containing 10 mL of culture medium covered with a cellophane disk were used for easy collection of the mycelium after growth. For analysis of fungal biomass production, a sterilized cellophane sheet was placed on the medium’s surface. Inoculation was achieved by placing a mycelial block onto the center of the cellophane sheet and then incubating at 25°C in the dark. Colony radial growth was measured and biomass dry wt was determined. Fresh mycelia were homogenized with 10 mL of acetate buffer (pH 5.5) for enzyme analysis. A crude extract was obtained by adding all culture medium to 90 mL of distilled water and homogenizing in a Potter. Reducing sugars, enzyme concentration, and pH were determined. Three fungal strains, Suillus collinitus, Pisosithus arrhizus, and Hebeloma cylindrosporum, were grown in different culture media (potato dextrose agar or Pintro’s medium). Parameters measured over time included glucose concentration, phosphatase activity, biomass, and pH.     

Active constraints,indefinite quadratic test problems,and complexity

The observation that at leasts constraints are active when the Hessian of the Lagrangian hass negative eigenvalues at a local minimizer is used to obtain two results: (i) a class of nearly concave quadratic minimization problem can be solved in polynomial time; (ii) a class of indefinite quadratic test problems can be constructed with a specified number of positive and negative eigenvalues and with a known global minimizer.The authors thank the reviewers for their constructive comments. The first author was supported by the National Science Foundation Grant DMS-85-20926 and by the Air Force Office of Scientific Research Grant AFOSR-ISSA-86-0091.     

A heuristic approach for the stochastic optimization of mine production schedules

Traditionally, mining engineers plan an open pit mine considering pre-established conditions of operation of the plant(s) derived from a previous plant optimization. By contrast, mineral processing engineers optimize the processing plants by considering a regular feed from the mine, with respect to quantity and quality of the materials. The methods implemented to optimize mine and metallurgical plans simultaneously are known in the mining industry as global or simultaneous optimizers. The development of these methods has been of major concern for the mining industry over the last decade. Some algorithms are available in commercial mining software packages however, these algorithms ignore the inherent geological uncertainty associated with the deposit being considered, which leads to shortfalls in production, quality, and expected cashflows. This paper presents a heuristic method to generate life-of-mine production schedules that consider operating alternatives for processing plants and incorporate geological uncertainty. The method uses iterative improvement by swapping periods and destinations of the mining blocks to generate the final solution. The implementation of the method at a copper deposit shows its ability to control mine and processing capacities while increasing the expected net present value by 30% when compared with a solution generated using a standard industry practice.     

Correction to: MDOF extension of the modified bridge system method for vehicle–bridge interaction

Nonlinear Dynamics - The article “MDOF extension.     

An analytical statistical model for the RMS delay spread parameter in millimeter frequencies

A new statistical model for rms delay spread is presented. The model has been developed under the assumption of the existence of two paths (two-path model). It is assumed that the amplitude of each path follows the so-called log-Student distribution with one degree of freedom, while the differential propagation delay of the two paths follows the uniform distribution. The parameters involved with the model are m_z and s_z the mean and standard deviation of the ratio of the two paths’ amplitudes. Theoretical curves for τ_rms as well as for the mean and standard deviation of τ_rms are plotted for different values of m_z and s_z. These curves are extremely useful for the choice of the parameters of the model for different cases. In order to examine the validity of the new model, measurements from the literature have been collected and compared with the theoretical results. In all cases a very good agreement, according to the X-square criterion, between theoretical and experimental curves has been observed. As a result, the new model can be used by system engineers for the development of wireless high bit-rate digital systems that will not suffer from intersymbol interference.     

A new emission of ZnS:Ni2+ arising from the 3T1(P) → 3T1(F) transition

A photoluminescence band with zero-phonon transitions at $\text{?}\text{= 12438 cm}{}^{-1}$ (this one subject to self-absorption) and at 12259 cm^-1 has been detected with ZnS:Ni crystals. Based on the appearance of these two lines, on the similarity of the whole spectrum with the ³T₂(F) → ³T₁(F) Ni²⁺ luminescence, and on preparation evidence, this new emission is interpreted as the ³T₁(P) → ³T₁(F) transition of substitutional Ni²⁺(3d⁸) ions in a tetrahedral crystal field.