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Different principles used in systems ensuring thermal balance of pilots and cosmonauts are discussed. Physiological and hygienic characteristics of the passive thermal insulation, ventilation systems and liquid cooling (heating) suits are presented. A classification of the means and methods is proposed.
A fast imaging method is described that yields an approximately six-fold acquisition time reduction relative to conventional techniques. The method involves: 1) acquisition of every sixth k-space line; 2) shifting of acquired k-space lines between odd and even frames; and 3) a single-frame correction image. Reconstruction is achieved by temporal interpolation for k-space lines not acquired combined with subtraction of stationary fold-in artifacts. Seven patients with heart disease and one volunteer were evaluated. SNR was measured in myocardium and the ventricular cavity for both the conventional and new technique. The method is best suited for fast imaging of moving objects confined to a small region within a larger stationary object, such as the heart within the thoracic cavity. It can be implemented in cine and functional imaging sequences and, in principle, in perfusion sequences.
The imaging of dynamic processes in the body is of considerable interest in interventional examinations as well as kinematic studies, and spiral imaging is a fast magnetic resonance imaging technique ideally suited for such fluoroscopic applications. In this manuscript, magnetic resonance fluoroscopy pulse sequences in which interleaved spirals are used to continuously acquire data and reconstruct one movie frame for each repetition time interval are implemented. For many applications, not all of k-space needs to be updated each frame, and nonuniform k-space sampling can be used to exploit this rapid imaging strategy by allowing variable update rates for different spatial frequencies. Using the appropriate reconstruction algorithm, the temporal updating rate for each spatial frequency is effectively proportional to the corresponding k-space sampling density. Results from a motion phantom as well as in in vivo gadolinium diethylenetriaminopentaacetic acid (Gd-DTPA) bolus tracking studies in a rat model demonstrate the high temporal resolution achievable using these techniques as well as the tradeoffs available with nonuniform sampling densities. This paper focuses on the acquisition of real-time dynamic information, and all images presented are reconstructed retrospectively. The issues of real-time data reconstruction and display are not addressed.
Data in the literature on bone histomorphometry in the baboon are scant. This study provides data from analysis of trabecular bone of the iliac crest of 16 adult male chacma baboons (Papio ursinus) in captivity. Five animals were young adults judging by the presence of growth cartilage in the iliac crest biopsy. Bone volume resembled that in humans, but trabeculae were thinner and more closely spaced. Bone turnover appeared somewhat lower than in humans. Coupling of resorption and formation was excellent as judged by cellular and kinetic variables; erosion surface was an unreliable indicator of ongoing coupling. The similarities between human and baboon trabecular bone make the baboon suited for the study of microstructure and bone turnover of trabecular bone with relevance to humans.
After loss of active glenohumeral motion the arm cannot be positioned in space and function is impaired. Fusion of the glenohumeral joint creates a new platform for the movement of elbow, hand and fingers and leads to an improvement of function. The use of the reconstructive plate makes the operation easier. Shoulder fusion is especially suited if the function of elbow and hand is well preserved and if the patient is physically active. But fusion is definite and the options of muscle transfer operations and above elbow amputation have to be considered.
This paper speculates about the interplay between adaptational modifications with mutation and selection. Gravity effects are supposed to be very well suited to prove the role of direct adaptations for phylogenic processes. The speculation is based on strong hints that the cell in general reacts to accelerations (besides other mechanical stimuli) in the order of 1g and near weightlessness. Several-generations experiments in space may contribute to solve this fundamental question of evolution.
In this paper, we show how to increase the capacity of Kosko-type bidirectional associative memories by introducing dilation and translation parameters in the pattern space. The essential point of this approach is that the increase of the capacity of the networks almost doesn't affect their complexity. The general idea of the proposed strategy is to tune the networks in such a way that they are better suited to store patterns which are highly correlated without touching their ability to recover easy-to-store information. A detailed example at the end of the paper shows how our approach works in practice.
BACKGROUND: A structured motif allows variable length gaps between several components, where each component is a simple motif, which allows either no gaps or only fixed length gaps. The motif can either be represented as a pattern or a profile (also called positional weight matrix). We propose an efficient algorithm, called SMOTIF, to solve the structured motif search problem, i.e., given one or more sequences and a structured motif, SMOTIF searches the sequences for all occurrences of the motif. Potential applications include searching for long terminal repeat (LTR) retrotransposons and composite regulatory binding sites in DNA sequences. RESULTS: SMOTIF can search for both pattern and profile motifs, and it is efficient in terms of both time and space; it outperforms SMARTFINDER, a state-of-the-art algorithm for structured motif search. Experimental results show that SMOTIF is about 7 times faster and consumes 100 times less memory than SMARTFINDER. It can effectively search for LTR retrotransposons and is well suited to searching for motifs with long range gaps. It is also successful in finding potential composite transcription factor binding sites. CONCLUSION: SMOTIF is a useful and efficient tool in searching for structured pattern and profile motifs. The algorithm is available as open-source at: http://www.cs.rpi.edu/~zaki/software/sMotif/.
The grave clinical aspects of septic shock have stimulated the search for an experimental animal model which more closely relates to human pathophysiology. This study of the cardiovascular-pulmonary-morphologic responses of the baboon to slow infusions of live Escherichia coli organisms was designed to approximate more closely the human clinical entity. Anesthetized young adult baboons received 3-hour intravenous infusions of organisms at an average dosage of 8 times 10-9 organisms per kg. body weight. Responses of animals were followed during a period of 6 hours in the anesthetized state. There was progressive systemic hypotension and steadily decreasing cardiac output. Total peripheral resistance was uniformly depressed during the infusion, but was variable during the post-infusion survival period. Increases in heart rate, alveolar-arterial oxygen tension gradient, and oxygen uptake were uniformly present. These alterations bear close resemblance to those seen in other subhuman primates administered short term doses of live organisms. There were extensive morphologic changes in pulmonary, cardiac, and renal beds. Glomeruli contained multiple fibrin thrombi and disrupted platelets, and the glomerular capillary endothelium was focally edematous and disrupted. The myocardium exhibited capillary endothelial edema and fluid accumulation in interfiber and intrafiber spaces. There were sequestration, degranulation, and fragmentation of polymorphonuclear leukocytes and platelets, and characteristic endothelial lesions within the pulmonary vascular bed. Findings demonstrate both cardiovascular-pulmonary dysfunction and renal, cardiac, and pulmonary morphologic lesions. The baboon shock model appears to be well suited for studies of experimental septic shock and bears close resemblance to the human clinical entity.
The proper management of a pleural effusion in a patient with malignancy is based on an understanding of the normal anatomy and physiology of the pleural space and the ways in which they are altered by disease. The major challenge in diagnosing and treating a cancer patient who develops a pleural effusion is determining the cause of the effusion accurately and quickly and choosing a treatment that is best suited to the individual patient. Careful selection of the treatment for pleural effusions, however, relieves symptoms in the vast majority of patients with little accompanying morbidity.
Conjugated polymers and oligomers can serve as highly responsive fluorescent reporters for biosensor applications. However, their optical properties in aqueous media are highly dependent upon environmental conditions. The structure of the paracyclophane framework provides a platform for designing optical reporters that show little sensitivity to surfactants, and thus is well-suited for fluorescent assays. The permanent intramolecular delocalization through the paracyclophane core dominates intermolecular perturbations in spontaneously formed aggregates.
The pentapeptide proctolin modulates the activity of the rhythmic pattern generators in the crustacean stomatogastric nervous system. Proctolin strongly excites the lateral pyloric and the inferior cardiac neurons of the stomatogastric ganglion (STG), causing them to fire extended high-frequency bursts of action potentials (Hooper and Marder, 1987; Nusbaum and Marder, 1989a,b). We now report that proctolin depolarizes these cells maximally at membrane potentials close to the threshold for action potential generation. In voltage clamp, proctolin evokes an inward current, carried at least partially by Na+, that shows strong outward rectification. Removal of extracellular Ca2+ markedly increases the amplitude of the proctolin-evoked current and linearizes its current-voltage curve. The properties of the proctolin current make it ideally suited to contribute to the activity-dependent modulation of the pyloric network of the STG.
Radial and spiral trajectories exhibit favorable characteristics for dynamic imaging. Nevertheless, changes in image contents during acquisition lead to inconsistencies in the k-space data, which are manifested as streaks or spiral artifacts, respectively. This work proposes the concept of lattice permutation to reorder the data segments for artifact suppression. This acts to reshuffle the alias pattern along the temporal frequency axis. The proposed approach is well suited to sliding window reconstruction, although more sophisticated methods are also possible. For typical image series where the signal energies are concentrated in the low temporal frequencies, the permutation displaces most of the aliased signals from the low temporal frequencies to the high temporal frequencies, where they are attenuated by sliding window reconstruction, while the signals in the low temporal frequencies are mostly contaminated by aliasing from the much weaker signals in the higher temporal frequencies. This results in considerably reduced artifacts without any increase in scan time. In practice, lattice permutation achieves similar artifact suppression as the bit-reversed order, but with a less stringent restriction on the number of segments. At the same time, it provides a more powerful approach to controlling the alias pattern exactly. Results from real-time cardiac imaging are demonstrated.
Electrical impedance spectroscopy was used to characterize the cell environment of multilayered cell cultures (MCCs), a culture system in which cells are grown on a permeable support membrane to form a thick disc of cells with tumor-like properties. Cultures were grown using SiHa tumor cells as well as V79 wild-type cells and V79/DOX cells cultivated to exhibit multidrug resistance. Electrical impedance measurements were made on MCCs over a frequency range of 0. 1 kHz to 1 MHz. Data analysis using a simple electrical model for the cell environment yielded estimates for parameters related to the intra- and extracellular resistance and net membrane capacitance, which were then related to MCC thickness. The extracellular fraction and tortuosity of the MCCs were determined in separate experiments where the rate of diffusion and the equilibrium level of C14-inulin, which does not penetrate the cell membrane, was measured within MCCs. Impedance measurements predicted the barrier to diffusion posed by the extracellular space of MCCs to be roughly two times greater than that inferred from the C14-inulin experiments. However, the relative ranking of the three cell types used to grow MCCs was similar for the two methods. Results indicate that impedance spectroscopy is well suited for use in characterizing the MCC cell environment, offering a fast, nondestructive method for monitoring cell culture growth and integrity.
A dynamic-programming strategy for sequence alignment first proposed in 1975 by Dan Hirschberg can be adapted to yield a number of extremely space-efficient algorithms. Specifically, these algorithms align two sequences using only "linear space," i.e., an amount of computer memory that is proportional to the sum of the lengths of the two sequences being aligned. This paper begins by reviewing the basic idea, as it applies to the global (i.e., end-to-end) alignment of two DNA or protein sequences. Three of our recent extensions of the technique are then outlined. The first extension computes an optimal alignment subject to the constraint that each position, i, of the first sequence must be aligned somewhere between positions L[i] and U[i] of the second sequence, for given values of L and U. The second finds all aligned position pairs (i.e., potential columns of the alignment) that occur in an alignment whose score exceeds a given threshold. The third treats the case where each of the two sequences is allowed to be an alignment (e.g., a sequence of aligned pairs), using a sensitive scoring scheme. We also describe two linear-space methods for computing k best local (i.e., involving only a part of each sequence) alignments, where k > or = 1. One is a linear-space version of the algorithm of Waterman and Eggert (1987), and the other is based on the strategy proposed by Wilbur and Lipman (1983). Finally, we describe programs that implement various combinations of these techniques to provide a multisequence alignment method that is especially suited to handling a few very long sequences. The utility of these programs is illustrated by analysis of the locus control region of the beta-like globin gene cluster of several mammals.
The selective advantages of using light as a source of information are reflected in the diverse types of extant eyes. The physical properties of light restrict how it can be collected and processed, resulting in only eight known optical systems found in animals. Eyes develop through tissue rearrangement and differentiation. Our understanding of the source of genetic information used in developmental programs is growing rapidly and reveals distributions of gene expression with substantial overlap in both time and space. Specific genes and their products are used repeatedly, making causal relationships more difficult to discern. The phenomenon of groups of genes acting together seems to be the rule. Throughout evolution, particular genes have become associated with distinct aspects of eye development, and these suites of genes have been recruited repeatedly as new eyes evolved.
BACKGROUND: The invariant lineage of the nematode Caenorhabditis elegans has potential as a powerful tool for the description of mutant phenotypes and gene expression patterns. We previously described procedures for the imaging and automatic extraction of the cell lineage from C. elegans embryos. That method uses time-lapse confocal imaging of a strain expressing histone-GFP fusions and a software package, StarryNite, processes the thousands of images and produces output files that describe the location and lineage relationship of each nucleus at each time point. RESULTS: We have developed a companion software package, AceTree, which links the images and the annotations using tree representations of the lineage. This facilitates curation and editing of the lineage. AceTree also contains powerful visualization and interpretive tools, such as space filling models and tree-based expression patterning, that can be used to extract biological significance from the data. CONCLUSION: By pairing a fast lineaging program written in C with a user interface program written in Java we have produced a powerful software suite for exploring embryonic development.
American marten (Martes americana) have a close association with mature temperate forests, a habitat that expanded throughout the Pacific Northwest as glaciers receded at the end of the Pleistocene. Similar to several other forest-associated mammals in North America (e.g. black bear), genetic analysis of the marten shows a deep phylogeographical subdivision that reflects populations with distinctive evolutionary histories. Using a suite of 14 microsatellite markers, we explored the genetic structure of marten populations in two reciprocally monophyletic clades in the Pacific Northwest identified previously as M. caurina and M. americana by mitochondrial haplotypes and morphology. Microsatellite phylogeographical patterns were congruent with mitochondrial analyses. These independent data sets shed light upon hybridization patterns, population structure and evolutionary histories. Hybridization between M. caurina and M. americana individuals was documented in two regions of sympatry (Kuiu Island in southeastern Alaska and southern Montana). Northern insular populations of M. caurina exhibited higher differentiation and lower variability relative to northern populations of M. americana. Greater divergence among M. caurina populations may reflect longer isolation and persistence in coastal forest habitat that was fragmented by rising sea level in the early Holocene. Lower differentiation among northern M. americana populations and close relationship to other continental M. americana populations may reflect more recent expansion into the Pacific Northwest and/or continued gene flow among populations. Differentiation among M. caurina populations was attributed to habitat fragmentation (i.e. rising sea level), as opposed to isolation-by-distance; oceanic straits pose significant barriers to gene flow among M. caurina populations and between populations of M. caurina and M. americana.