Analysis of compressive receivers for the optimal interception offrequency-hopped waveforms

Establishes that the compressive receiver is a practical interceptor of high performance. Given a signal of a particular duration, a compressive receiver can estimate simultaneously all frequency components within a set wide band. This processing is similar to a parallel bank of narrowband filters, which is the optimal detector of frequency-hopped signals. Furthermore, hop frequency is estimated to yield performance equal to the parallel filter configuration. The authors assume interference to be stationary, colored Gaussian noise, and present a model of the compressive receiver that contains all its salient features. Low energy coherence detection is achieved by taking the compressive receiver output as an observation and applying likelihood ratio theory at small signal-to-noise ratios. For small signals, this approach guarantees the largest probability of correct detection for a given probability of false alarm, and thus provides a reference, to which simplified or ad hoc schemes can be compared. Since the low energy coherence detector has an unwieldy structure, a simplified suboptimal detector structure is developed that consists of a simple filter, followed by a sampler and a square-envelope detector. Several candidates for the filter's response are presented. The performance of the low energy coherence detector based on compressive receiver observations is compared to the optimal filter-bank detector based on direct observations, thus showing the exact loss incurred when a compressive receiver is used. The performance of various simplified schemes, based on compressive receiver observations, is analyzed     

Chemistry of mandibular and Dufour's gland secretions of ants in genusMyrmecocystus

Males of several species ofMyrmecocystus produce mandibular gland secretions that contain 2,4-dimethyl-2-hexenoic acid and a variety of monoterpenes that include neral, geranial, citronellol, limonene, and 2,6-dimethyl-5-hepten-1-ol. Other components identified include methyl anthranilate, octanal, octanol, octyl octanoate, and 2-hexyl-2-decenal. Methyl salicylate has been identified as a mandibular gland constituent of workers of several species in addition to mellein and monoterpenes such as cymene, limonene, and the isomers of citral. The Dufour's gland secretions of workers and females of 14 species contain typical formicine alkanes (e.g., undecane), 2-alkanols (e.g., 2-tridecanol), and 2-alkanones (e.g., 2-tridecanone). Two species in the subgenusEremnocystus produce secretions that are distinguished by the presence of significant quantities of tridecyl esters. The functions of these compounds as well as their possible chemosystematic significance in the genusMyrmecocystus are discussed.     

An Open Grid Services Architecture Primer

To expand the use of distributed computer infrastructures as well as facilitate grid interoperability, OGSA has developed standards and specifications that address a range of scenarios, including high-throughput computing, federated data management, and service mobility.     

Estimate of scattering truncation in the cavity attenuated phase shift PMSSA monitor using radiative transfer theory

The recently developed cavity attenuated phase shift particulate matter single scattering albedo (CAPS PM_SSA) monitor has been shown to be fairly accurate and robust for real-time aerosol optical properties measurements. The scattering component of the measurement undergoes a truncation error due to the loss of scattered light from the sample tube in both the forward and backward directions. Previous studies estimated the loss of scattered light typically using the Mie theory for spherical particles, assuming particles are present only on the sampling tube centerline, and without accounting for the effects of sampling tube surface reflection. This study overcomes these limitations by solving the radiative transfer equation in an axisymmetric absorbing and scattering medium using the discrete-ordinates method to estimate the scattering truncation error. The effects of absorption coefficient, scattering coefficient, asymmetry parameter of the scattering phase function, and the reflection coefficient at the sampling tube inner surface were investigated. Under typical conditions of CAPS PM_SSA operation of low extinction coefficients below about 5000 Mm^?1, the scattering loss remains independent of the absorption and scattering coefficients but is dependent on the scattering phase function and the reflection coefficient of the sampling glass tube inner surface. The proposed method was used to investigate the effects of asymmetry parameter and surface reflection coefficient on truncation for absorbing aerosol particles whose scattering phase function can be well represented by the Henyey-Greenstein approximation. The scattering loss increases with increasing the asymmetry parameter and the surface reflection coefficient.

Copyright © 2018 National Research Council Canada     

Range of motion and complications after postburn heterotopic bone excision about the elbow

OBJECTIVE: To review the results of surgical management of heterotopic ossification about the elbow in burned patients. DESIGN: Retrospective analysis with long-term patient follow-up. MATERIALS AND METHODS: Eleven patients with 16 elbows requiring surgery were admitted between January 1, 1982 and December 31, 1993. A posterior approach to the elbow with release of the encased ulnar nerve +/- anterior transposition and transolecranon osteotomy to access extensive bone formation in the olecranon fossa was employed. Eight patients (11 elbows) were available for long-term follow-up conducted at mean 50 +/- 13 months after surgery. Long-term follow-up consisted of measurement of range of elbow motion, as well as clinical assessment of ulnar nerve function. MAIN RESULTS: For the 11 elbows examined postoperatively, the mean range of motion preoperatively in flexion-extension was 11 degrees +/- 5 degrees compared to 89 degrees +/- 12 degrees postoperatively (p < 0.001). Three patients with poor long-term results had ankylosis of the joint preoperatively. Of four patients with ulnar nerve paresis preoperatively, none had ulnar nerve dysfunction at follow-up. Of 16 elbows operated on, four (25%) had postoperative complications. Two suffered soft-tissue breakdown with hardware exposure requiring abdominal flap closure, one early failure of olecranon fixation, and one late infected hardware. CONCLUSIONS: Surgery for both limited range of motion as well as ulnar nerve compression is effective in cases of heterotopic ossification about the elbows of burned patients. Early operative intervention is indicated in progressive disease, particularly ulnar nerve palsy, if soft-tissue quality is adequate. Complications with 25% of elbows suggest that use of olecranon osteotomy for joint access may warrant review.     

Modeling and Managing State in Distributed Systems: The Role of OGSI and WSRF

We often encounter in distributed systems the need to model, access, and manage state. This state may be, for example, data in a purchase order, service level agreements representing resource availability, or the current load on a computer. We introduce two closely related approaches to modeling and manipulating state within a Web services (WS) framework: the Open Grid Services Infrastructure (OGSI) and WS-Resource Framework (WSRF). Both approaches define conventions on the use of the Web service definition language schema that enable the modeling and management of state. OGSI introduces the idea of a stateful Web service and defines approaches for creating, naming, and managing the lifetime of instances of services; for declaring and inspecting service state data; for asynchronous notification of service state change; for representing and managing collections of service instances; and for common handling of service invocation faults. WSRF refactors and evolves OGSI to exploit new Web services standards, specifically WS-addressing, and to respond to early implementation and application experiences. WSRF retains essentially all of the functional capabilities present in OGSI, while changing some syntax (e.g., to exploit WS-addressing) and also adopting a different terminology in its presentation. In addition, WSRF partitions OGSI functionality into five distinct composable specifications. We explain the relationship between OGSI and WSRF and the related WS-notification specifications, explain the common requirements that both address, and compare and contrast the approaches taken to the realization of those requirements.     

Soot concentration and temperature measurements in co-annular, nonpremixed CH4/air laminar flames at pressures up to 4 MPa

Laminar nonpremixed methane-air flames were studied over the pressure range of 0.5 to 4 MPa using a new high-pressure combustion chamber. Flame characterization showed very good flame stability over the range of pressures, with a flame tip rms flicker of less than 1% in flame height. At all pressures, soot was completely oxidized within the visible flame. Spectral soot emission (SSE) and line-of-sight attenuation (LOSA) measurements provided radially resolved measurements of soot volume fraction and soot temperature at pressures from 0.5 to 4.0 MPa. Such measurements provide an improved understanding of the influence of pressure on soot formation and have not been reported previously in laminar nonpremixed flames for pressures above 0.4 MPa. SSE and LOSA soot concentration values typically agree to within 30% and both methods exhibit similar trends in the spatial distribution of soot concentration. Maximum soot concentration depended on pressure according to a power law, where the exponent on pressure is about 2 for the range of pressures between 0.5 and 2.0 MPa, and about 1.2 for 2.0 to 4.0 MPa. Peak carbon conversion to soot also followed a power-law dependence on pressure, where the pressure exponent is unity for pressures between 0.5 and 2.0 MPa and 0.1 for 2.0 to 4.0 MPa. The pressure dependence of sooting propensity diminished at pressures above 2.0 MPa. Soot concentrations measured in this work, when transformed to line-integrated values, are consistent with the measurements of Flower and Bowman for pressures up to 1.0 MPa [Proc. Combust Inst. 21 (1986) 1115-1124] and Lee and Na for pressures up to 0.4 MPa [JSME Int. J. Ser. B 43 (2000) 550-555]. Soot temperature measurements indicate that the overall temperatures decrease with increasing pressure; however, the differences diminish with increasing height in the flame. Low down in the flame, temperatures are about 150 K lower at pressures of 4.0 MPa than those at 0.5 MPa. In the upper half of the flame the differences reduce to 50 K.     

Interaction with the aromatic hydrocarbon receptor, CYP1A induction, and mutagenicity of a series of diaminotoluenes: implications for their carcinogenicity

The present study was undertaken to provide a rationale for the marked difference in carcinogenic potential among isomeric diaminotoluenes, in relation to their ability to induce their own bioactivation through CYP1A induction, their genotoxic potential, and their ability to bind to the cytosolic aromatic hydrocarbon (Ah) receptor. Of the four possible diaminotoluenes only the 2,3- and, to a lesser extent, the 2,4-isomer induced CYP1A activity. Similarly, only these two isomers could displace [3H]T-CDD from the hepatic cytosolic Ah receptor. In the presence of Aroclor 1254- induced microsomes, 2,4- and 2,6-diaminotoluene were potent mutagens in the Ames test. Only 2,4-diaminotoluene could autoinduce its activation. Of the four isomers only 2,4-diaminotoluene is an established carcinogen and this is compatible with the present observations that it is the only isomer that stimulates its own activation through CYP1A induction, is metabolically converted to genotoxic intermediates, and binds to the Ah receptor. 2,6-Diaminotoluene is recognized as a mutagenic noncarcinogen and in the present studies it elicited a positive mutagenic response in the Ames test but failed to induce CYP1A activity and its own activation, and could not bind to the Ah receptor even at concentrations as high as 5 x 10(-4) M. The present findings demonstrate that in vitro studies are very useful tools in predicting the carcinogenic potency of isomeric chemicals.     

A purely chemical HCl laser employing transverse flow

A purely chemical continuous wave HCl laser has been developed. The purely chemical production of nonequilibrium concentrations of Cl atoms is achieved by a branched chain reaction between NO and ClO2. Three modes of accomplishing the prepumping chemistry are discussed and their effects on HCl laser performance are evaluated. A transverse flow laser was operated having a maximum HCl multiline output power of 4 W and a chemical efficiency of 6.6 percent based on the total exothermicity of the pumping reaction.