5.1--Use of an oscillating laser as a heterodyne receiver preamplifier

In this paper the results of a study of the amplification characteristics of lasers for signals injected near their frequencies of oscillation are reported. An approximate theoretical treatment is given which indicates that substantial amplification will occur under conditions for which the anisotropy of the laser cavity is small, the polarization state of the injected signal is orthogonal to that of the primary oscillation, and the two signals are critically coupled. For like polarization of these signals, postive amplification occurs only for substantially reduced laser excitation or increased cavity loss. The experimental observations are in qualitative agreement with the theoretical predictions with gains as high as 600 having been observed for orthogonal polarizations near critical coupling. The optical bandwidth appears to be at least several MHz.     

Discrete compensation of control systems with integrated circuits

This paper combines the compensation of control systems with transient analysis and switching circuit theory to accomplish the discrete compensation of control systems. Several transfer functions are used as examples, and their realizations are discussed in detail. Lead and lag compensation are used, and several general transfer function realizations are presented for clarity. All of the realizations have been implemented with methods suitable for complete circuit integration, i.e., the logic circuits required for implementation are all commonly available in large quantities on a single integrated circuit chip.     

Application of model‐free LQG subspace predictive control to TCP congestion control

We investigate the application of a model‐free linear quadratic Gaussian (LQG) subspace‐based predictive controller to Internet congestion control. Specifically, we consider a classically designed LQG linear congestion controller with a non‐standard performance index and determine whether a model‐free controller is a viable alternative in this instance. We employ the model‐free subspace predictive controller methodology which we customize for end‐to‐end transmission control protocol (TCP) congestion control. A series of network simulations support the use of the more easily implementable model‐free controller over its classical analogue. We further demonstrate that the model‐free controller provides increased stability under transient network conditions when compared with the first feedback congestion controller, TCP Vegas. Copyright © 2007 John Wiley & Sons, Ltd.     

The Dotted straightening algorithm

If a homogeneous bracket polynomial is antisymmetric in certain subsets of its points, then it can be represented in an abbreviated form called a dotted bracket expression. These dotted bracket expressions lead to a more compact expression in terms of tableaux than the usual representation. Consequently, we can derive a much more efficient straightening algorithm than the ordinary one for bracket polynomials already given in dotted form. This dotted straightening algorithm gives precisely the same result as the ordinary one, and preserves the dotted property at every step.     

Subarachnoid-pleural fistula after resection of a pancoast tumor with hyponatremia

Resection of superior sulcus neoplasms is associated with a number of complications resulting from the extensive nature of the resection and the necessity to sacrifice certain adjacent structures. One of the complications of resection is the development of subarachnoid-pleural fistula, with the subsequent appearance of air in the cerebrospinal fluid circulation. We report a case in which a subarachnoid-pleural fistula led to persistent pneumocephaly in a patient who exhibited postoperative hyponatremia, confusion, and gait disturbance.     

Ecological and temporal placement of early Pliocene hominids at Aramis, Ethiopia

Sedimentary deposits in the Middle Awash research area of Ethiopia's Afar depression have yielded vertebrate fossils including the most ancient hominids known. Radioisotopic dating, geochemical analysis of interbedded volcanic ashes and biochronological considerations place the hominid-bearing deposits at around 4.4 million years of age. Sedimentological, botanical and faunal evidence suggests a wooded habitat for the Aramis hominids.     

Detection of apoptosis in human and rat ovarian follicles

OBJECTIVE: The purpose of this study was to determine whether cells acquired from individual human preovulatory follicles undergo apoptosis (physiologic cell death) and, if so, to correlate the degree of apoptosis with characteristics of the follicles or the oocytes derived from the follicles. METHODS: We devised a sensitive nonradioactive method for detecting apoptotic DNA fragmentation in small numbers of cells derived from rat atretic follicles and follicular aspirates of patients undergoing assisted reproductive technologies. RESULTS: Using this method, apoptotic DNA was detected in rat atretic follicles, with optimal detection at 10-100 ng. Furthermore, apoptotic DNA was detected in some, but not all individual human follicular aspirates from several patients, and was found in follicles that produced oocytes that fertilized and developed into embryos. CONCLUSION: Apoptosis occurs in cells from human ovarian preovulatory follicles and may be a normal physiologic process of the follicle during luteinization.