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PubMed2004

Decay of spatially periodic patterns in a nematic liquid crystal.

A detailed theoretical and experimental analysis of the decay of electroconvection patterns is presented in a planarly aligned nematic liquid crystal. The relaxation time is measured as a function of the wave number of the pattern using a light diffraction technique. A theoretical analysis exhibits a rich structure of the dispersion curves for the decay rates. An interesting relation between the realistic case of no-slip boundary conditions and the simpler free-slip case is found. The experimentally determined relaxation rates for both "conductive" and "dielectric" initial patterns follow the theoretical solution with subsequent jumps between branches when the wave number is increased.

Journal Article↗
PubMed2006

Role of initial conditions in the decay of spatially periodic patterns in a nematic liquid crystal.

The decay of stripe patterns in planarly aligned nematic liquid crystals has been studied experimentally and theoretically. The initial patterns have been generated by the electrohydrodynamic instability and a light diffraction technique has been used to monitor their decay. In our experiments different decay rates have been observed as a function of the pattern wave number. According to our theoretical analysis they belong to a spectrum of decay modes and are individually selected in dependence on the initial conditions. Additional insight has emerged from a refined physical optical description of the diffraction intensity. The results compare well with experiments, which include also controlled modifications of the initial conditions to assess different decay modes.

Journal Article↗
PubMed1991

Nucleotide sequence and spatial expression pattern of a drought- and abscisic Acid-induced gene of tomato.

The nucleotide sequence of le16, a tomato (Lycopersicon esculentum Mill.) gene induced by drought stress and regulated by abscisic acid specifically in aerial vegetative tissue, is presented. The single open reading frame contained within the gene has the capacity to encode a polypeptide of 12.7 kilodaltons and is interrupted by a small intron. The predicted polypeptide is rich in leucine, glycine, and alanine and has an isoelectric point of 8.7. The amino terminus is hydrophobic and characteristic of signal sequences that target polypeptides for export from the cytoplasm. There is homology (47.2% identity) between the amino terminus of the LE 16 polypeptide and the corresponding amino terminal domain of the maize phospholipid transfer protein. le16 was expressed in drought-stressed leaf, petiole, and stem tissue and to a much lower extent in the pericarp of mature green tomato fruit and developing seeds. No expression was detected in the pericarp of red fruit or in drought-stressed roots. Expression of le16 was also induced in leaf tissue by a variety of other abiotic stresses including polyethylene glycol-mediated water deficit, salinity, cold stress, and heat stress. None of these stresses or direct applications of abscisic acid induced the expression of le16 in the roots of the same plants. The unique expression characteristics of this gene indicates that novel regulatory mechanisms, in addition to endogenous abscisic acid, are involved in controlling gene expression.

Journal Article↗
PubMed1987

Developmental patterns of spatial ability: an early sex difference.

Over 1,800 public school students (grades K-12, ages 6-18) took a battery of 7 spatial tests tailored to their respective developmental levels. Analyses of resulting data indicate that it is feasible to measure spatial ability throughout this developmental range with modified versions of adult paper-and-pencil tests, that a male advantage in spatial performance appears reliably by age 10, and that the magnitude of the advantage remains constant through age 18. Analysis of covariance suggests that an early female precocity in language skills may mask a male advantage in spatial ability during the primary school years. There is no indication of a sex difference in kindergarten children.

Adolescent↗
PubMed1996

Nonuniform heating patterns of commercial electrodes for radiofrequency catheter ablation.

INTRODUCTION: Previous investigations of the biophysics of myocardial ablation using radiofrequency energy have focused mainly on the electrode-myocardial interface. Relatively little has been written about the overall function of commercial electrodes used for ablation. The purpose of this study was to evaluate the heating patterns of several commercial electrodes used for myocardial ablation. METHODS AND RESULTS: The specific absorption rate, a unit of measure proportional to the initial rate of rise of the temperature at the electrode-tissue interface and reflecting the energy deposition from the electrode, was measured during radiofrequency energy application at multiple points around each electrode. These measurements were combined to form a specific absorption rate pattern, which reflected the spatial pattern of energy deposition from the electrode. There was significant nonuniformity of the specific absorption rate pattern of each electrode evaluated. The proximal edge of the electrode and the curvature of the distal portion of the electrode were two sites of accentuated heating relative to the remaining portions of the electrode. The magnitude of this nonuniformity was similar between the 4-mm length electrodes of different manufacturers, but increased progressively in larger (5- and 8-mm length) electrodes. CONCLUSIONS: The heating patterns of commercial electrodes used for myocardial ablation are nonuniform. These data have implications for electrode design and utilization.

Catheter Ablation↗
PubMed1973

Neuronal locus specificity: altered pattern of spatial deployment in fused fragments of embryonic xenopus eyes.

Before optic nerve outgrowth in Xenopus laevis embryos, a change of state occurs in the differentiating retinal cell population which renders the cells refractory to information about subsequent changes in their positions, and commits individual ganglion cells to develop specific position-dependent properties (locus specificities) which subserve the formation of orderly retinotopic connections in the optic tectum. When different parts of eye primordia from stages before optic nerve outgrowth are fused, each piece in such a reconstructed eye does not generate ganglion cells with the partial-set of locus specificities normally arising from that region of the intact eye. It is inferred that separate parts of the early embryonic retina do not contain stable programs for spatial deployment of locus specificity, and that development of definitive locus specificities in retinal ganglion cells requires additional cellular interactions among the retinal cells later in development.

Action Potentials↗
PubMed1997

Temporal and spatial expression pattern of the angiotensinogen gene in mice and rats.

In situ hybridization for mouse angiotensinogen (Ao) mRNA was performed using a Stu I-Pst I 0.43-kb fragment of exon 2 as a template to synthesize RNA probes. The mouse Ao mRNA expression patterns were different from those reported for rats. Ao mRNA was expressed in the fetal liver as early as 12.5 days postcoitus, and the liver remained the predominant organ of its expression in utero. Within the developing kidney, Ao mRNA was demonstrated at 17.5 days postcoitus in the proximal straight tubules undergoing loop formation in the medulla. In the matured mouse kidney, the expression site is within the outer stripe of outer medulla, hence identified as the pars recta, not proximal convoluted tubules. Additional studies revealed that, in rats also, Ao mRNA was localized in the pars recta. This was in contrast to previously published results that showed that Ao mRNA was localized primarily in the proximal convoluted tubules in rats. Thus the pars recta appears to be an important intrarenal source of Ao for both rats and mice throughout pre- and postnatal periods, whereas the liver can be the major extrarenal source in utero in mice, but not in rats.

Aging↗
PubMed1993

Patterns of spatial dispersion, locomotion and foraging behaviour in three groups of the Yunnan snub-nosed langur (Rhinopithecus bieti).

Aspects of the behaviour of three groups of Yunnan snub-nosed langurs, Rhinopithecus bieti, were observed over the course of three field seasons from 1986 to 1988. The major findings of the study were: (1) The habitats of R. bieti were mainly at heights of 3,600-4,150 m above sea level. (2) Groups were very large, with group sizes ranging from more than 100 to 269 individuals. (3) Spatial dispersion densities ranged from about 27 to 106 m2/individual during sleeping and resting, to feeding dispersions as large as 5,000-15,000 m2. (4) The locomotor repertoire of R. bieti consisted largely of walking, jumping and climbing. On very rare occasions, semibrachiation was observed, but true brachiation was never observed. The locomotor repertoires of juveniles were more diverse than those of subadults or adults. (5) Communication consisted mainly of eye-to-eye contact accompanied by murmurs; while loud calls were heard only rarely. (6) Groups moved between sleeping and feeding sites in single file. It is concluded that R. bieti is a mainly terrestrial species.

Aging↗
PubMed2003

Distal antenna and distal antenna related encode nuclear proteins containing pipsqueak motifs involved in antenna development in Drosophila.

Legs and antennae are considered to be homologous appendages. The fundamental patterning mechanisms that organize spatial pattern are conserved, yet appendages with very different morphology develop. A genetic hierarchy for specification of antennal identity has been partly elucidated. We report identification of a novel family of genes with roles in antennal development. The distal antenna (dan) and distal antenna-related (danr) genes encode novel nuclear proteins that are expressed in the presumptive distal antenna, but not in the leg imaginal disc. Ectopic expression of dan or danr causes partial transformation of distal leg structure toward antennal identity. Mutants that remove dan and danr activity cause partial transformation of antenna toward leg identity. Therefore we suggest that dan and danr contribute to differentiation of antenna-specific characteristics. Antenna-specific expression of dan and danr depends on a regulatory hierarchy involving homothorax and Distal-less, as well as cut and spineless. We propose that dan and danr are effector genes that act downstream of these genes to control differentiation of distal antennal structures.

Amino Acid Motifs↗
PubMed1988

Spatially restricted patterns of expression of the homeobox-containing gene Hox 2.1. during mouse embryogenesis.

The mouse Hox 2.1 gene contains a homeobox sequence and is therefore a candidate for a vertebrate gene involved in the control of embryonic patterning or positional specification. To investigate this possibility, we have used in situ hybridization to determine the pattern of Hox 2.1 expression during mouse embryogenesis. At 8.5 days post coitum, Hox 2.1 is expressed at a low level in the posterior neuroectoderm and mesoderm, and in the neuroectoderm of the presumptive hindbrain. At 12.5 days p.c., Hox 2.1 is expressed in an anteroposterior restricted domain extending from the hindbrain throughout the length of the spinal cord, predominantly in the dorsal region. Between 12.5 and 13.5 days p.c. the domain becomes localized to the occipital and cervical regions. We also detect Hox 2.1 RNA in the embryonic lung, stomach, mesonephros and metanephros, as well as in myenteric plexus, dorsal root ganglia and the nodose ganglion, and in mature granulocytes. The embryonic expression of Hox 2.1 in neural tissue is compared with that of Hox 3.1, which also shows anteroposterior restricted domains of gene expression. These patterns of expression are not clearly consistent with Hox 2.1 or Hox 3.1 having roles in segmental patterning. However, the data are consistent with these genes having regulatory roles in anteroposterior positional specification in the neuroectoderm and mesoderm, and suggest that Hox 2.1 may also have functions during organogenesis.

Animals↗
PubMed1997

The effect of shape and location on temporal masking of spatial vibrotactile patterns.

Target patterns presented to uncued locations on a single fingerpad were followed by either same-shape (SS) maskers or different-shape (DS) maskers presented to either the same location (SLoc) or a different location (DLoc). DS maskers interfered with identification more when they were at SLoc than when they were at DLoc, but the reverse was true for SS maskers; they interfered more at DLoc than at SLoc. When targets were presented to cued locations, performance in the absence of maskers improved, but the pattern of interference from maskers resembled that for uncued presentation. The proportion of masker responses on incorrect trials revealed that both temporal masking and response competition may be involved in the effects of location on pattern identification.

Adult↗
PubMedDate not supplied

[The effect of electric field on the spatial-time patterns in the reaction-diffusion system].

A model of electrodiffusion processes in the vicinity of cell membrane was developed. The model takes into account chemical reactions, Coulomb interactions between charged particles and the effect of external electric field. It was concluded that the applied electric field can change the characteristics of space-time patterns in the system. Dissipative structures slowly move and this is accompanied by a change in the number of structure elements. The characteristic equation includes odd powers of the wavenumber, which can lead to the appearance of soliton-like structures. The dissipative structures can appear not only due to the Turing diffusion instability but due to the disperse instability under electric field the applied.

Animals↗
PubMed2003

[Soil organic carbon pool and its spatial distribution pattern in the Circum Bohai Region].

The research and management of soil carbon pool and the effect of land-use on it are the key project of study on global change. In this paper, the data of 1,374 soil profiles in the Circum Bohai Region were used to estimate the soil organic carbon (SOC) pool of this region. The results showed that in this region, the total soil organic carbon pool in 1 m depth was 2.1 Pg C, and the biggest SOC pool was brown soil, occupying 55.6% of the total SOC. The second one was moisture soil, accounted for 26.9%. The SOC pools of aeolian sandy soil and dark brown soil were very small, only about 0.1% of the total. However, the soil organic carbon density (OCD) of boggy soil was the biggest (22.90 kg C.m-2), the second was dark brown soil (16.04 kg C.m2), and the lowest were aeolian sandy soil (2.88 kg C.m-2) and solonchak (6.0 kg C.m-2), implying that desertification and salinalization could reduce soil organic carbon. Moreover, the results also suggested that the topsoil held 673.30 Tg C. It meant that there was about one-third of the total SOC could be easy to be disturbed. According to the OCD at its level distribution gradient, it could be divided into four regions, i.e., coastal region, plain region, northwestern region, and hilly region. The order of OCD from high to low was hilly region, northwestern region, plain region, and coastal region. This regulation reflected not only the role of climate and landform, but also the effect of human activity intensification on SOC. Therefore, it was very important to protect and manage the land in this region well for the SOC maintenance and the sustainable land use.

Carbon↗