Fast algorithms for bit-serial routing on a hypercube

In this paper we describe anO(logN)-bit-step randomized algorithm for bit-serial message routing on a hypercube. The result is asymptotically optimal, and improves upon the best previously known algorithms by a logarithmic factor. The result also solves the problem of on-line circuit switching in anO(1)-dilated hypercube (i.e., the problem of establishing edge-disjoint paths between the nodes of the dilated hypercube for any one-to-one mapping).Our algorithm is adaptive and we show that this is necessary to achieve the logarithmic speedup. We generalize the Borodin-Hopcroft lower bound on oblivious routing by proving that any randomized oblivious algorithm on a polylogarithmic degree network requires at least (log² N/log logN) bit steps with high probability for almost all permutations.This research was supported by the Defense Advanced Research Projects Agency under Contracts N00014-87-K-825 and N00014-89-J-1988, the Air Force under Contract AFOSR-89-0271, and the Army under Contract DAAL-03-86-K-0171. This work was completed while the third and fourth authors were at the Laboratory for Computer Science, Massachusetts Institute of Technology.     

A MYSTERY SOLVED

A note about a cipherer related to a one who could cipher.     

THE STATESMAN WHO COULD NOT READ HIS OWN MAIL

An enciphered enclosure missing from a 1678 letter is rediscovered and cryptanalyzed after more than 300 years. It contains information intended for the leading statesman of England at the time which, despite his efforts, he was never able to read.     

Effect of channel geometry on solute dispersion in pressure-driven microfluidic systems

Pressure-driven transport of fluid and solute samples is often desirable in microfluidic devices, particularly where sufficient electroosmotic flow rates cannot be realized or the use of an electric field is restricted. Unfortunately, this mode of actuation also leads to hydrodynamic dispersion due to the inherent fluid shear in the system. While such dispersivity is known to scale with the square of the Peclet number based on the narrower dimension of the conduit (often the channel depth), the proportionality constant can vary significantly depending on its actual cross section. In this article, we review previous studies to understand the effect of commonly microfabricated channel cross sections on the Taylor–Aris dispersion of solute slugs in simple pressure-driven flow systems. We also analyze some recently proposed optimum designs which can reduce the contribution to this band broadening arising from the presence of the channel sidewalls. Finally, new simulation results have been presented in the last section of this paper which describe solutal spreading due to bowing of microchannels that can occur from stresses developed during their fabrication or operation under high-pressure conditions.     

The Rorschach and Holtzman as measures of pathognomic verbalization.

This study was planned to obtain information about the reliability of Rorschach and Holtzman pathognomic verbalization scores (V). The Rorschach and Holtzman protocols of 45 psychiatric patients were scored by scorer A and 19 of the Holtzman protocols were scored "blind" by scorer B. Holtzman interscorer reliability was .81 (p     

Heart rate variability and newborn heart rate responses to illumination changes.

Investigated heart rate (HR) response patterns to the onset and offset of a 30-sec increase in illumination in 16 human newborns. Ss were divided into 2 groups based on a measure of pretrial HR variability. Only Ss with the high pretrial HR variability responded significantly to the change in stimulation. The response to onset was characterized by a significant quartic trend containing both decelerative and accelerative components. The response to offset only approached significance and had a pattern similar to the onset response. Although the occurrence of systematic response patterns was related to the level of pretrial HR variability, this measure of autonomic lability may have been related to influences associated with delivery and not to stable individual differences. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dispersion reduction in open-channel liquid electrochromatographic columns via pressure-driven back flow

Application of electrokinetic forces to drive the mobile phase diminishes analyte dispersion in open-channel liquid chromatographic columns due to minimization of shear in the flow field. However, the retentive layer coating the inner walls of such devices slows down the average convective velocity of solute molecules in its vicinity, inherently causing dispersion of analyte bands. In this article, we explore the possibility of reducing such dispersion in electrochromatographic columns by imposing a pressure-driven back flow in the system. Analysis shows that although such a strategy introduces shear in the flow field, the overall dispersion in the mobile phase is reduced. This occurs as the streamline velocity in such a system is greater near the channel walls than that in the center of the conduit, thereby allowing fluid dispersion to counteract wall retention effects. For an optimally chosen magnitude of the back flow, hydrodynamic dispersion of any target species in the mobile phase may be shown to diminish by a factor of 3 and 10/3 in a circular tube and a parallel-plate geometry, respectively. A similar reduction in slug dispersion is also realized in rectangular conduits for all aspect ratios. In trapezoidal geometries with large wedge angles or isotropically etched profiles, this reduction factor may attain values of 10 or greater.     

Broadband solar radiances from visible band measurements: A method based on ScaRaB observations and model simulations

Using simultaneous and co-located broadband and narrowband observations of solar radiation from the Scanner for Radiation Budget (ScaRaB) instrument on Meteor-3 during 1994-1995, empirical relationships between ScaRaB visible band and broadband solar radiances are derived for different surface types, cloud amounts, solar zenith angles and satellite viewing angles. Relationships between ScaRaB visible channel and National Ocean and Atmosphere Administration (NOAA) Advance Very High Resolution Radiometer (AVHRR) visible channel radiances are derived from radiation transfer model simulations for different surface types and cloud cover. Combining the narrow-to-broadband (NTB) and narrowband-to-narrowband (NTN) relationships, broadband solar radiance can be derived from narrowband radiances measured by the AVHRR on operational meteorological satellites. The derived NTB conversion coefficients are evaluated against independent data. Radiances are converted to fluxes by the application of angular distribution models. Typical differences between fluxes derived from ScaRaB narrowband and broadband channels are of the order of 1 W m-2 with standard deviations of the order 15 W m-2.     

On Probabilistic Networks for Selection, Merging, and Sorting

We study comparator networks for selection, merging, and sorting that output the correct result with high probability, given a random input permutation. We prove tight bounds, up to constant factors, on the size and depth of probabilistic (n,k)-selection networks. In the case of (n, n/2)-selection, our result gives a somewhat surprising bound of on the size of networks of success probability in , where δ is an arbitrarily small positive constant, thus comparing favorably with the best previously known solutions, which have size . We also prove tight bounds, up to lower-order terms, on the size and depth of probabilistic merging networks of success probability in , where δ is an arbitrarily small positive constant. Finally, we describe two fairly simple probabilistic sorting networks of success probability at least and nearly logarithmic depth. Received January 22, 1996, and in final form February 14, 1997.