Synthesis of N-Alkyl-α-Sulfo-β-Alanines

A number of N-alkyl substituted α-sulfo-β-alanines were synthesized by direct sulfonation of the corresponding N-alkyl-β-alanines.     

IEN-CsF1 accuracy evaluation and two-way frequency comparison

In this paper we report the accuracy evaluation of the Italian primary frequency standard IEN-CsF1. We discuss the shifts the frequency standard is corrected for and the procedure used for the accuracy evaluation. In the last section we report frequency comparisons of our fountain with those of remote laboratories and with International Atomic Time.     

Morphological stability of copper-silver multilayer thin films at elevated temperatures

The kinetics of breakdown of Cu-Ag polycrystalline multilayers during aging at elevated temperatures was investigated. Microlaminates with Cu:Ag layer thicknesses of 2:2, 1:4, 4:1, and 4:0.1 μm were aged for 10 minutes to 192 hours (t), at temperatures ranging from 700 to 900 K. The asdeposited microlaminates had a fine-grained columnar microstructure with well-defined interfaces. Upon annealing, the morphology evolved over three time regimes. In the first regime, the grains in each phase grew quickly to an apparent terminal size, which depended on both the layer thickness and annealing temperature. Next, grooves formed at the intersections of grain boundaries and layer interfaces and grew with a t ^0.25 dependence. The groove growth appeared to be independent of layer thickness and was approximately equal in Cu and Ag. The microlaminates started to break down in the third regime, as grain-boundary grooves on opposite sides of a layer bridged its thickness. Models for grain growth and grooving in thin films were modified for multilayer microlaminates and were shown to fit the experimental data reasonably well. This suggests that the terminal grain size is reached when groove drag overcomes the capillary forces driving grain growth, and that grooving kinetics are dominated by interfacial diffusion.     

Reduction of the cold collisions frequency shift in a multiple velocity fountain: a new proposal

In this paper, we propose a new scheme for operating an atomic fountain frequency standard. A sequence of time-spaced balls of atoms, launched over non-overlapping trajectories, makes possible a reduction of the atomic density and consequently the cold collision frequency shift by one order of magnitude without significant reduction of the useful signal and of the overall stability of the clock. The ultimate accuracy of a Cs fountain could be improved below the 10(-15) level currently achieved in operating clocks.     

Failure of Adhesive Bonds at Constant Strain Rates

Shear strengths of adhesive bonds using AF126 and two thicknesses of aluminum were measured at constant rate of crosshead separation. It was found that the shear strength could be related to temperature and strain rate or failure time over the range of deformation rates used.     

An adaptive multirate algorithm for acquisition of fluorescence microscopy data sets.

We propose an algorithm for adaptive efficient acquisition of fluorescence microscopy data sets using a multirate (MR) approach. We simulate acquisition as part of a larger system for protein classification based on their subcellular location patterns and, thus, strive to maintain the achieved level of classification accuracy as much as possible. This problem is similar to image compression but unique due to additional restrictions, namely causality; we have access only to the information scanned up to that point. While we do want to acquire fewer samples with as low distortion as possible to achieve compression, our goal is to do so while affecting the overall classification accuracy as little as possible. We achieve this by using an adaptive MR scanning scheme which samples the regions of the image area that hold the most pertinent information. Our results show that we can achieve significant compression which we can then use to aquire faster or to increase space resolution of our data set, all while minimally affecting the classification accuracy of the entire system.     

The impact of MAC parameters on the performance of 802.15.4 PAN

The operation of a personal area network, operating under the IEEE Standard 802.15.4 in the beacon enabled mode, is analyzed using the theory of discrete time Markov chains and M/G/1/K queues. The model includes the impact of different parameters such as packet arrival rate, number of stations, station’s buffer size, packet size, and inactive period between the beacons. We have derived several important performance parameters such as probability of access, probability that medium is idle, queue length distribution in the device, and probability distribution of the packet service time. Some important conclusions regarding the implementation of 802.15.4 networks and compatible network devices are outlined.