Research Note: Mobility of Herbicide Microcapsules in Saturated Granular Media

The mobility of the microcapsules in saturated granular media was estimated on the basis of conventional breakthrough experiments in vertical columns packed with sands for various physical and chemical conditions. Four types of microcapsules have been tested, all of them were found to have reasonable mobility in clean quartz sand, but not in sandy soil. The immobility in the sandy soil was attributed to some production deficiencies in terms of shape, size and quality of the coating surface. The size of the microcapsules should be considerably smaller than those produced with an order of magnitude of a few micrometers. They should also be more spherical and with a smoother surface. The addition of a proper dispersant had stabilized the microcapsules suspension, and facilitated their transport in the sand. A major flow factor affecting microcapsules mobility is the water flux. The microcapsules should be applied at a high irrigation rate, which also implies a high water content in the soil profile. Considering solely the mobility aspect, it seems that the prospect for successful application of the new method for weed control is limited to granular soils with a high hydraulic conductivity at/or near saturation. However, for the time being the most limiting problem is the production of quality microcapsules with good physical and chemical properties.     

Randomized k-server algorithms for growth-rate bounded graphs

The k-server problem is a fundamental online problem where k mobile servers should be scheduled to answer a sequence of requests for points in a metric space as to minimize the total movement cost. While the deterministic competitive ratio is at least k, randomized k-server algorithms have the potential of reaching o(k)-competitive ratios. Prior to this work only few specific cases of this problem were solved. For arbitrary metric spaces, this goal may be approached by using probabilistic metric approximation techniques. This paper gives the first results in this direction, obtaining o(k)-competitive ratio for a natural class of metric spaces, including d-dimensional grids, and wide range of k.     

Inverse problems for scattering by periodic structures

Suppose the 3-dimensional space is filled with three materials having dielectric constants ? ₁ above S ₁={x ₂=f ₁(x ₁), x ₃ arbitrary}, ? ₂ below S ₂ = {x ₂ =f ₂(x ₁), x ₃ arbitrary} and ? _o in {f ₂(x ₁) <x ₂ 1(x ₁), x ₃ arbitrary} where f ₁ f ₂ are periodic functions. Suppose for a plane wave incident on S ₁ from above we can measure the reflected and transmitted waves of the corresponding time-harmonic solution of the Maxwell equations, say at x ₂=±b,b large. To what extent can we infer from these measurements the location of the pair (S ₁, S ₂ ? In this paper, we establish a local stability: If ( $\tilde S_1 ,\tilde S_2$ ) is another pair of periodic curves “close” to (S ₁, S₂), then, for any δ>0, if the measurements for the two pairs are δ-close, then $\tilde S_1$ and $\tilde S_2$ are 0(δ)-close to S ₁ and S ₂, respectively.     

Electron attachment to propargyl chloride, 305-540 K

Electron attachment to propargyl chloride (HC≡C-CH(2)Cl) was studied in a flowing-afterglow Langmuir-probe apparatus from 305 to 540 K. The sole ion product in this temperature range is Cl(-). Electron attachment is very inefficient, requiring correction for a competing process of electron recombination with molecular cations produced in reaction between Ar(+) and propargyl chloride and subsequent ion-molecule reactions. The electron attachment rate coefficient was measured to be 1.6×10(-10)cm(3)?s(-1) at 305 K and increased to 1.1×10(-9)cm(3)?s(-1) at 540 K.     

Synchronized cluster formation in coupled laser networks

We experimentally investigate the phase dynamics of laser networks with homogenous time-delayed mutual coupling and establish the fundamental rules that govern their state of synchronization. We identified a specific substructure that imposes its synchronization state on the entire network and show that for any coupling configuration the network forms at most two synchronized clusters. Our results indicate that the synchronization state of the network is a nonlocal phenomenon and cannot be deduced by decomposing the network into smaller substructures, each with its individual synchronization state.     

75th anniversary of Vladimir K. Baev

Anniversary Dates

75th anniversary of Vladimir K. Baev     

Rank-into-rank hypotheses and the failure of GCH

In this paper we are concerned about the ways GCH can fail in relation to rank-into-rank hypotheses, i.e., very large cardinals usually denoted by I3, I2, I1 and I0. The main results are a satisfactory analysis of the way the power function can vary on regular cardinals in the presence of rank-into-rank hypotheses and the consistency under I0 of the existence of ${j : V_{\lambda+1} {\prec} V_{\lambda+1}}$ with the failure of GCH at ${\lambda}$ .