The ultradian clocks of eukaryotic microbes: timekeeping devices displaying a homeostasis of the period

Ultra-high-sensitivity, biopolymer sequencing is a goal in many fields of molecular biology, and collisionally activated decomposition electrospray mass spectrometry (CAD ES MS/MS) using a triple quadrupole mass spectrometer has become a method of choice for work in the high- to mid-femtomole range. However, when the detection of ions becomes statistical, as it may in that range, the mass assignment of fragment ions is inaccurate and either sequencing becomes impossible or ambiguities result due, for example, to the closeness in amino acid residue masses (I/L, N or K/Q, E). Some ambiguities may be resolved by synthesizing possible sequences, but this is unsatisfactory. In considering the limitations of triple quadrupole MS/MS with respect to scanning ion detection, resolution, transmission, and mass accuracy, we reasoned that a novel geometry quadrupole orthogonal acceleration time-of-flight (Q-TOF) instrument would have special merit for ultra-high-sensitivity MS/MS sequencing, and suggested its construction for this purpose some three years ago. A prototype Q-TOF has now been built by Micromass [Morris et al. (1996), Rapid Commun. Mass Spectrom. 10, 889-896], and in the first research on the instrument, including MHC antigen and filarial nematode glycoprotein studies, we demonstrate low-femtomole- and attomole-range sequencing with mass accuracy of better than 0.1 Da throughout the daughter-ion spectrum, thus removing sequencing ambiguities in some of the most challenging work demanding the highest sensitivity.     

Epilepsy, retarded growth and onchocerciasis, in two areas of different endemicity of onchocerciasis in Burundi

A high prevalence of epilepsy (up to 1.3%) was observed in an area hyperendemic for onchocerciasis in the province of Bururi, Burundi. Following this observation, epileptics and controls were examined in 2 communes (administrative units) with different endemicity for onchocerciasis. Altogether, onchocerciasis was more frequent in epileptics (81.8%) than in controls from the same households (68.3%; P < 0.05). This difference was more marked in the hyperendemic area. Other possible causes of epilepsy, including cysticercosis, were infrequent (18 possible cases among 110 epileptics). During this survey, 9 epileptics with growth retardation were seen. They showed most characteristics of Nakalanga syndrome, which was described from Uganda. All 9 such cases were suffering from onchocerciasis. These findings give more evidence of a possible association between onchocerciasis and epilepsy, and between onchocerciasis and Nakalanga syndrome.     

Certain nonlinear partially observable stochastic optimal controlproblems with explicit control laws equivalent to LEQG/LQG problems

This paper is concerned with partially observed stochastic optimal control problems when nonlinearities enter the dynamics of the unobservable state and the observations as gradients of potential functions. Explicit representations for the information state are derived in terms of a finite number of sufficient statistics. Consequently, the partially observed problem is recast as one of complete information with a new state generated by a modified version of the Kalman filter. When the terminal cost is quadratic in the unobservable state and includes the integral of the nonlinearities, the optimal control laws are explicitly computed, similar to linear-exponential-quadratic-Gaussian (LEQG) and linear-quadratic-Gaussian (LQG) tracking problems. The results are applicable to filtering and control of Hamiltonian systems     

Estimating the viewing parameters of random, noisy projections ofasymmetric objects for tomographic reconstruction

The ability to determine the viewing parameters of objects from their projections has enabled well established tomographic techniques to be employed in the 3D reconstruction of objects from images obtained via modalities where the orientation of the objects cannot be controlled. A method is described for the determination of the viewing parameters of randomly acquired projections of asymmetric objects. It extends upon the common lines algorithm by determining the relative orientation of projections from the location of lines of intersection among the Fourier transforms of the projections in 3D Fourier space. A new technique for finding the lines of intersection in the presence of translational displacement, and for subsequently finding the translational displacement, is presented. The complete algorithm is described and its efficacy is demonstrated using real data. A new technique for dealing with noise is also discussed     

On a large-gain theorem

The aim of this paper is to give a general quantitative requirement which the loop gain must satisfy in order to stabilize a given unstable (possibly nonlinear and time-varying) plant, namely that the gain must exceed one.     

Imprudent linking weaves a tangled Web

Hypertext linking is often embraced uncritically by Web authors eager to explore the power of hypertext without first considering its effects on their readers' comprehension. Hypertext linking is not a substitute for thought-we think with ideas, not with dissociated snippets of raw information. Even the most germane bits of information cannot become ideas, regardless of how cleverly they are stacked, listed or linked. Ideas define relevance, provide context and establish patterns. With patterns, most concepts become intelligible, and we need continuity and stability of theme and context to recognize patterns. So, like most powerful technologies, hypertext links are a mixed blessing. Used improperly, they can be detrimental to Web sites. “Loose links” can drive away an audience, dilute the site's message, confuse the reader with irrelevant digressions and become a continuing maintenance headache for site authors and Webmasters     

Large-scale simulation studies in image pattern recognition

Many obstacles to progress in image pattern recognition result from the fact that per-class distributions are often too irregular to be well-approximated by simple analytical functions. Simulation studies offer one way to circumvent these obstacles. We present three closely related studies of machine-printed character recognition that rely on synthetic data generated pseudo-randomly in accordance with an explicit stochastic model of document image degradations. The unusually large scale of experiments - involving several million samples that makes this methodology possible have allowed us to compute sharp estimates of the intrinsic difficulty (Bayes risk) of concrete image recognition problems, as well as the asymptotic accuracy and domain of competency of classifiers     

Magnet Safety Assessment for ITER

The ITER magnet system consists of structurally linked sets of toroidal (TF) and poloidal (PF) field coils, central solenoid (CS), and various support structures. The coils are superconducting, force flow Helium cooled with a Kapton-Glass-Epoxy multilayer insulation system. The stored magnetic energy is about 100GJ in the TF system and 20GJ in the PF-CS. Coils and structure are maintained at 4 K by enclosing them in a vacuum cryostat. The cryostat, comprising an outer envelope to the magnets, forms most of the second radioactivity confinement barrier. The inner primary barrier is formed by the vacuum vessel, its ports and their extensions. To keep the machine size within acceptable bounds, it is essential that the magnets are in close proximity to both of the nuclear confinement barriers. The objective of the magnet design is that, although local damage to one of the barriers may occur in very exceptional circumstances, large scale magnet structural or thermal failure leading to simultaneous breaching of both barriers is not credible. Magnet accidents fall into three categories: thermal (which includes arcing arising from insulation failure and local overheating due to discharge failure in the event of a superconductor quench), structural (which includes component mechanical failure arising from material inadequacies, design errors and exceptional force patterns arising from coil shorts or control failures), and fluid (Helium release due to cooling line failure). After a preliminary survey to select initial faults conceivable within the present design, these faults are systematically analyzed to provide an assessment of the damage potential. The results of this damage assessment together with an assessment of the reliability of the monitoring and protective systems, shows that the magnets can operate with the required safety condition.