Pressure indicators for measurements in wind tunnels

The results of an investigation of new materials sensitive to air pressure in a given pressure range are reported. Examples of their application to wind tunnels are given.Central Aero-Hydrodynamics Institute, Moscow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 2, pp. 183–187, August, 1992.     

Multiple access for UWB impulse radio with pseudochaotic time hopping

Pseudochaotic time hopping (PCTH) is a previously proposed encoding/modulation scheme for ultra-wideband (UWB) impulse radio. PCTH exploits concepts from symbolic dynamics to generate aperiodic spreading sequences, resulting in a noise-like spectrum. We present a multiple-access technique suitable for the PCTH scheme. In particular, we provide an analytical expression of the bit-error rate performance as a function of the number of users and validate it by simulation.     

Cellular UDP-glucose deficiency caused by a single point mutation in the UDP-glucose pyrophosphorylase gene

We previously isolated a mutant cell that is the only mammalian cell reported to have a persistently low level of UDP-glucose. In this work we obtained a spontaneous revertant whose UDP-glucose level lies between those found in the wild type and the mutant cell. The activity of UDP-glucose pyrophosphorylase (UDPG:PP), the enzyme that catalyzes the formation of UDP-glucose, was in the mutant 4% and in the revertant 56% of the activity found in the wild type cell. Sequence analysis of UDPG: PP cDNAs from the mutant cell showed one missense mutation, which changes amino acid residue 115 from glycine to aspartic acid. The substituted glycine is located within the largest stretch of strictly conserved residues among eukaryotic UDPG:PPs. The analysis of the cDNAs from the revertant cell indicated the presence of an equimolar mixture of the wild type and the mutated mRNAs, suggesting that the mutation has reverted in only one of the alleles. In summary, we demonstrate that the G115D substitution in the Chinese hamster UDPG:PP dramatically impairs its enzymatic activity, thereby causing cellular UDP-glucose deficiency.     

Production and properties of micro‐porous glas bubble zinc and aluminium composites

Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated.     

Study of the degree of III conditioning of the phase space of pencil-beam radiotherapy using singular value decomposition

Dose distribution optimization algorithms are necessary in pencil-beam radiotherapy to exploit efficiently the multiple parameters of this powerful irradiation technique. We propose as an optimization technique singular value decomposition (SVD) analysis, which allows the measurement of ill conditioning of the stereotactic radiotherapy inverse problem and yields optimal weights for conformal treatment. Our approach to dose distribution optimization is to recover estimates of the minibeams weights from well-defined previsional dose matrices to study the influence of the different parameters on the stereotactic radiotherapy inverse procedure. The adjustment of the different parameters of the stereotactic irradiation to the “SVD optimizer” procedure is realized taking into account the ratio of the quality reconstruction to the calculation time. It will permit a more efficient use of the SVD optimizer in clinical applications with real three-dimensional lesions. We show the efficiency of the SVD optimizer in analyzing and predicting ill conditioning in stereotactic radiotherapy and in recognizing the topography of the different beams to create an optimal vector containing the beam weights (reconstructed weighting vector).