On analytical expressions for the distribution of the filteredoutput of square envelope receivers with signal and colored Gaussiannoise input

Closed-form expressions for the moment generating function (MGF) of the filtered output of square envelope receivers with signal and colored Gaussian noise input are derived. The informative signal is a binary sequence of rectangular pulses. The considered Gaussian processes are the Wiener process, a Gaussian process with linear covariance (moving average), and the Ornstein-Uhlenbeck process. The derived MGFs are then applied to the problem of finding the quantum limit for optically preamplified, direct detection receivers     

Low temperature perception in plants: effects of cold on protein phosphorylation in cell-free extracts

Activities of prevalent protein phosphatases decreased by nearly 95% and those of individual protein kinases were differentially reduced at low temperature. Inhibition of phosphatase activity at temperatures below 12 degrees C resulted in marked hyperphosphorylation of a 58-kDa protein (PP58). The temperature threshold for hyperphosphorylation of PP58 coincided with the known threshold for cold-induced calcium influx. Since calcium influx is triggered by several environmental stresses, we propose that the observed direct effects of cold on the phosphorylation of specific proteins enable cells to couple a shared calcium signal to a cold-specific transduction pathway.     

Novel Chitinolytic Enzymes with Biological Activity Against Herbivorous Insects

The soil bacteria, Streptomyces albidoflavus, secretes endochitinases and chitobiosidases that are active over a broad range of pH (4–10). Ingestion of this mixture of chitinolytic enzymes significantly reduced the growth and development of Trichoplusia ni and significantly reduced survival of Myzus persicae, Bemisia argentifolii, and Hypothenemus hampei. Perfusion chromatography was used to separate endochitinases from chitobiosidases. The endochitinases had significantly greater biological activity against Bemisia argentifolii than the chitobiosidases. The utility of chitinolytic enzymes as regulators of populations of herbivorous insects is discussed.     

Trypanosoma musculi survival in the kidneys of chronically infected mice: kidney form ultrastructure, surface characteristics, and serological interactions

Sucrose is the major carbon source in molasses, the traditional substrate employed in the industrial acetonebutanol-ethanol (ABE) fermentation by solventogenic clostridia. The utilization of sucrose by Clostridium beijerinckii NCIMB 8052 was investigated. Extracts prepared from cultures grown on sucrose (but not xylose or fructose) as the sole carbon source possessed sucrose phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) activity. Extract fractionation and reconstitution experiments revealed that the entire sucrose Enzyme II complex resides within the membrane in this organism. Sucrose-6-phosphate hydrolase and fructokinase activities were also detected in sucrose grown cultures. The fructokinase activity, which is required specifically during growth on sucrose, was shown to be inducible under these conditions. A pathway for sucrose metabolism in this organism is proposed.     

Optical label switched networks: laboratory trial and network emulator in the IST-STOLAS project

This article reviews the performance of an optical-label-controlled packet routing node as implemented in the European FP5-IST STOLAS project including a set of general engineering rules. Experimental networking scenarios and results from a STOLAS based network emulator supporting optical overspill routing are presented.     

On a recursive formula for the moments of phase noise

We present a recursive formula for the moments of phase noise in communication systems. The phase noise is modeled using continuous Brownian motion. The recursion is simple and valid for an arbitrary initial phase value. The moments obtained bp the recursion are used to calculate approximations to the probability density function of the phase noise, using orthogonal polynomial series expansions and a maximum entropy criterion     

Error probability evaluation of optical systems disturbed by phasenoise and additive noise

A direct and efficient method for evaluation of the error probability of optical heterodyne receivers in the presence of phase noise is presented. A closed form expression for the statistics of the decision variable, including photodetector shot noise and thermal noise from electronic circuitry, is derived. The analysis assumes simple integrating filters in the receiver and is based on a power series expansion of the filtered phase noise. The error probability is calculated using a saddle point approximation which is numerically simple and gives accurate results. The optimal prefilter bandwidth for best phase noise rejection is easily determined     

In-House Networks Using Multimode Polymer Optical Fiber for Broadband Wireless Services

A novel system concept is presented to transport microwave signals over an in-house multimode graded-index polymer optical fiber network, in order to feed the radio access points in high-capacity wireless LANs. By employing optical frequency multiplying, the network's intrinsically limited bandwidth is overcome. The feasibility of this concept to carry data at several hundreds of Mbit/s speed for various microwave signal formats at carrier frequencies in the tens of GHz range is shown. The concept enables cost-effective system implementation, and easy upgrading by offering data signal transparency. It can readily be integrated with other system technologies such as wired Gigabit Ethernet in a single multi-service in-house polymer optical fiber network.     

Cluster validation in clustering‐based one‐class classification

Reconstruction‐based one‐class classification has shown to be very effective in a number of domains. This approach works by attempting to capture the underlying structure of the normal class, typically, by means of clusters of objects. It has the main disadvantage, however, that one has to indicate the number of clusters in advance, for this yields an efficient way of computing a clustering. In this paper, we introduce a new algorithm, OCKRA++, which achieves a better performance, by enhancing a clustering‐based one‐class ensemble classifier (OCKRA) with a cluster validity index that is used to set the best number of clusters during the classifier's training process. We have thoroughly tested OCKRA++ in a particular domain, namely masquerade detection. For this purpose, we have used the Windows‐Users and ‐Intruder simulation Logs data set repository, which contains 70 different masquerade data sets. We have found that OCKRA++ is currently the algorithm that achieves the best area under the curve, with a significant difference, in masquerade detection using the file system navigation approach.