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Size Changes (size + change)
Selected AbstractsLongitudinal quantitative evaluation of lesion size change in femoral head osteonecrosis using three-dimensional magnetic resonance imaging and image registrationJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2006Masaki Takao Abstract It remains controversial whether some lesions of femoral head osteonecrosis regress during the natural course of the disease. With image registration, accurately matched image sets of the same subject can be acquired at different times. We applied image registration to evaluate lesion size change and assessed accuracy and usefulness compared to volume measurements and a conventional method. We also investigated whether lesions regress with this technique and with volume measurements. Baseline and 1 year minimum follow-up scans were conducted on 25 patients (31 hips) without radiological evidence of collapse. A three-dimensional (3D) spoiled gradient recalled echo sequence was used in the coronal direction (slice thickness,=,2 mm; slice pitch,=,1 mm). Size change was evaluated on all contiguous pairs of matched images after image registration. As a conventional method, coronal images (slice thickness,=,5 mm) were reconstructed, and size change was evaluated on the five representative coronal slices. Evaluation with the conventional method identified eight lesions with apparent reduction; assessments using image registration and volume measurements identified three lesions, all within a year of initial steroid treatment and remaining at ARCO stage I at follow up. Evaluation of lesion size change using image registration was comparable to volume measurements. Inaccurate estimation of lesion size change due to mismatching of slice planes can be excluded. We demonstrated that some early lesions detected less than a year after initial steroid treatment can show size reduction with image registration as well as with volume measurements. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1231,1239, 2006 [source] Global change and carnivore body size: data are stasisGLOBAL ECOLOGY, Issue 2 2009Shai Meiri ABSTRACT Aim, Global warming and other anthropogenic changes to the environment affect many aspects of biology and have often been invoked as causing body size changes in vertebrates. Here we examine a diverse set of carnivore populations in search of patterns in body size change that could reflect global warming (in accord with Bergmann's rule). Location, Global. Methods, We used > 4400 specimens representing 22 carnivore species in 52 populations collected over the last few decades to examine whether size changed with collection date when geography and sex are accounted for. We then examined several factors related to global warming, body mass, diet, and the attributes of the different datasets, to see whether they affect the standardized slope (,) of the size versus time regression. Results, Six of 52 populations we examined show a significant effect of year of collection on body size at the 0.05 probability level. The response of size to global warming does not reflect spatial patterns of size variation, nor do diet or body mass affect tendency of populations to change in body size. Size changes are no more pronounced in populations that have been sampled more recently. However, change, where it occurs, is rapid. Main conclusions, There may be a tendency in the literature to report only cases where recent changes are prevalent. Although in our data only a minority of populations show body size changes, we may see changes accelerating in the future in response to more drastic climatic changes and other anthropogenic changes. [source] Restoration removal with and without the aid of magnificationJOURNAL OF ORAL REHABILITATION, Issue 4 2001A. H. Forgie This study aims to quantify any cavity size change following removal of tooth-coloured restorations in vitro using unaided vision and 2·6× magnification. Occlusal composite restorations were removed under simulated clinical conditions and changes in cavity size were measured, blind to method, using standardized photographs. The outline of the cavity was digitized and its area was used as a surrogate for cavity size. The change in cavity size was determined for unaided vision and 2·6× magnification, with any differences between the techniques investigated. There were significant increases in cavity size using both techniques and although the increase in size was less when magnification was used, the difference was not statistically significant. Cavity size changes significantly during re-restoration and the use of magnification may be of benefit for some clinicians in reducing the size of the change. [source] Longitudinal quantitative evaluation of lesion size change in femoral head osteonecrosis using three-dimensional magnetic resonance imaging and image registrationJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2006Masaki Takao Abstract It remains controversial whether some lesions of femoral head osteonecrosis regress during the natural course of the disease. With image registration, accurately matched image sets of the same subject can be acquired at different times. We applied image registration to evaluate lesion size change and assessed accuracy and usefulness compared to volume measurements and a conventional method. We also investigated whether lesions regress with this technique and with volume measurements. Baseline and 1 year minimum follow-up scans were conducted on 25 patients (31 hips) without radiological evidence of collapse. A three-dimensional (3D) spoiled gradient recalled echo sequence was used in the coronal direction (slice thickness,=,2 mm; slice pitch,=,1 mm). Size change was evaluated on all contiguous pairs of matched images after image registration. As a conventional method, coronal images (slice thickness,=,5 mm) were reconstructed, and size change was evaluated on the five representative coronal slices. Evaluation with the conventional method identified eight lesions with apparent reduction; assessments using image registration and volume measurements identified three lesions, all within a year of initial steroid treatment and remaining at ARCO stage I at follow up. Evaluation of lesion size change using image registration was comparable to volume measurements. Inaccurate estimation of lesion size change due to mismatching of slice planes can be excluded. We demonstrated that some early lesions detected less than a year after initial steroid treatment can show size reduction with image registration as well as with volume measurements. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1231,1239, 2006 [source] Phase Transition Behavior of Novel pH-Sensitive Polyaspartamide Derivatives Grafted with 1-(3-Aminopropyl)imidazoleMACROMOLECULAR BIOSCIENCE, Issue 9 2006Kwangwon Seo Abstract Summary: New pH-sensitive polyaspartamide derivatives were synthesized by grafting 1-(3-aminopropyl)imidazole and/or O -(2-aminoethyl)- O,-methylpoly(ethylene glycol) 5000 on polysuccinimide for application in intracellular drug delivery systems. The DS of 1-(3-aminopropyl)imidazole was adjusted by the feed molar ratio, and the structure of the prepared polymer was confirmed using FT-IR and 1H NMR spectroscopy. Their pH-sensitive properties were characterized by light transmittance measurements, and the particle size and its distribution were investigated by dynamic light scattering measurements at varying pH values. The pH-sensitive phase transition was clearly observed in polymer solutions with a high substitution of 1-(3-aminopropyl)imidazole. The prepared polymers showed a high buffering capacity between pH 5 and 7, and this increased with the DS of 1-(3-aminopropyl)imidazole. The pH dependence of the aggregation and de-aggregation behavior was examined using a fluorescence spectrometer. For MPEG/imidazole- g -polyaspartamides with a DS of 1-(3-aminopropyl)imidazole over 82%, self aggregates associated with the hydrophobic interactions of the unprotonated imidazole groups were observed at pH values above 7, and their mean size was over 200 nm, while the aggregates of polymers were dissociated at pH values below 7 by the protonation of imidazole groups. These pH-sensitive polyaspartamide derivatives are potential basic candidates for intracellular drug delivery carriers triggered by small pH changes. Mean particle size change of MPEG/imidazole- g -polyaspartamide as pH is varied. [source] Stem cell implantation in ischemic mouse heart: a high-resolution magnetic resonance imaging investigation,NMR IN BIOMEDICINE, Issue 6 2005Ekkehard Küstermann Abstract Advances in the biology of stem cells have evoked great interest in cell replacement therapies for the regeneration of heart tissue after myocardial infarction. However, results from human trials are controversial, since the destination of the injected cells, their engraftment and their long-term fate have remained unclear. Here we investigate whether transplanted cells can be identified in the intact and lesioned murine myocardium employing high-resolution MRI. Cardiac progenitor cells, expressing the enhanced green fluorescent protein (EGFP), were labeled with ultra-small paramagnetic iron-oxide (USPIO) nanoparticles and transplanted into the intact or injured myocardium of mice. Their precise location was determined with high-resolution MRI and compared with histological tissue sections, stained with Prussian blue for iron content. These experiments showed that iron nanoparticle-loaded cells could be identified at high resolution in the mouse heart. However, ischemic myocardium (after cryoinjury or left coronary artery ligation) was characterized by a signal attenuation similar to that induced by USPIO-labeled cells in T -weighted MR images, making detection of labeled stem cells in this area by T -sensitive contrast rather difficult. In animals with myocardial injury only, the signal attenuated areas were of the same size in proton density- and T -weighted MR images. In injured animals also receiving labeled cells the lesioned area appeared larger in T - than in proton density-weighted MR images. This sequence-dependent lesion size change is due to the increased signal loss caused by the iron oxide nanoparticles, most sensitively detectable in the T -sensitive images. Thus, using the novel combination of these two parameter weightings, USPIO-labeled cells can be detected at high resolution in ischemic myocardium. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ontogeny of robusticity of craniofacial traits in modern humans: A study of South American populationsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2010Paula N. Gonzalez Abstract To date, differences in craniofacial robusticity among modern and fossil humans have been primarily addressed by analyzing adult individuals; thus, the developmental basis of such differentiation remains poorly understood. This article aims to analyze the ontogenetic development of craniofacial robusticity in human populations from South America. Geometric morphometric methods were used to describe cranial traits in lateral view by using landmarks and semilandmarks. We compare the patterns of variation among populations obtained with subadults and adults to determine whether population-specific differences are evident at early postnatal ontogeny, compare ontogenetic allometric trajectories to ascertain whether changes in the ontogeny of shape contribute to the differentiation of adult morphologies, and estimate the amount of size change that occurs during growth along each population-specific trajectory. The results obtained indicate that the pattern of interpopulation variation in shape and size is already established at the age of 5 years, meaning that processes acting early during ontogeny contribute to the adult variation. The ontogenetic allometric trajectories are not parallel among all samples, suggesting the divergence in the size-related shape changes. Finally, the extension of ontogenetic trajectories also seems to contribute to shape variation observed among adults. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Ecogeographic size variation in small-bodied subfossil primates from Ankilitelo, Southwestern MadagascarAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2007Kathleen M. Muldoon Abstract Variation in body size is well documented for both extant and extinct Malagasy primates, and appears to be correlated with geographic patterns of resource seasonality. Less attention has been paid to extant lemurs in subfossil collections, although it has been suggested that subfossil forms of extant species are characterized by greater size than their modern counterpart. This trend of phyletic size change has been related to climate change, habitat fragmentation, or human hunting. However, space- and time-averaging in the subfossil samples of previous studies may have obscured more general ecogeographic patterns underlying these size differences. Our objective is to examine size variation in subfossil still-extant primates within a regional comparative context to determine if subfossil and living forms conform to similar ecogeographic patterns. We report on the subfossil still-extant primate assemblage from Ankilitelo, southwestern Madagascar (,500 yr BP) to test this hypothesis. The Ankilitelo primates were compared with museum specimens of known locality. Extant taxa were assigned to one of five distinct ecogeographic regions, including spiny thicket, dry deciduous forest, succulent woodland, lowland and subhumid rainforest. Comparisons of tooth size in extant lemurs reveal significant geographical patterns of variation within genera. In general, the primates from Ankilitelo are indeed larger than their modern counterpart. However, these differences fit an ecoregional model of size variation, whereby Ankilitelo species are comparable in size to living forms inhabiting ecoregions present near the cave today. This suggests that Malagasy primates have been subjected to similar patterns of resource seasonality for at least 500 years. Am J Phys Anthropol, 2007. © 2007 Wiley-Liss, Inc. [source] Ontogeny and phyletic size change in living and fossil lemursAMERICAN JOURNAL OF PRIMATOLOGY, Issue 2 2010Matthew J. Ravosa Abstract Lemurs are notable for encompassing the range of body-size variation for all primates past and present,close to four orders of magnitude. Benefiting from the phylogenetic proximity of subfossil lemurs to smaller-bodied living forms, we employ allometric data from the skull to probe the ontogenetic bases of size differentiation and morphological diversity across these clades. Building upon prior pairwise comparisons between sister taxa, we performed the first clade-wide analyses of craniomandibular growth allometries in 359 specimens from 10 lemuroids and 176 specimens from 8 indrioids. Ontogenetic trajectories for extant forms were used as a criterion of subtraction to evaluate morphological variation, and putative adaptations among sister taxa. In other words, do species-level differences in skull form result from the differential extension of common patterns of relative growth? In lemuroids, a pervasive pattern of ontogenetic scaling is observed for facial dimensions in all genera, with three genera also sharing relative growth trajectories for jaw proportions (Lemur, Eulemur, Varecia). Differences in masticatory growth and form characterizing Hapalemur and fossil Pachylemur likely reflect dietary factors. Pervasive ontogenetic scaling characterizes the facial skull in extant Indri, Avahi, and Propithecus, as well as their larger, extinct sister taxa Mesopropithecus and Babakotia. Significant interspecific differences are observed in the allometry of indrioid masticatory proportions, with variation in the mechanical advantage of the jaw adductors and stress-resisting elements correlated with diet. As the growth series and adult data are largely coincidental in each clade, interspecific variation in facial form may result from selection for body-size differentiation among sister taxa. Those cases where trajectories are discordant identify potential dietary adaptations linked to variation in masticatory forces during chewing and biting. Although such dissociations highlight selection to uncouple shared ancestral growth patterns, they occur largely via transpositions and retention of primitive size-shape covariation patterns or relative growth coefficients. Am. J. Primatol. 72:161,172, 2010. © 2009 Wiley-Liss, Inc. [source] Assessing the long-term impact of Ranavirus infection in wild common frog populationsANIMAL CONSERVATION, Issue 5 2010A. G. F. Teacher Abstract Amphibians are declining worldwide, and one cause of this is infectious disease emergence. Mass mortalities caused by a virus or a group of viruses belonging to the genus Ranavirus have occurred in wild common frogs Rana temporaria in England since the 1980s, and ranaviral disease is widespread in amphibians in North America and Canada, where it can also cause mass die-offs. Although there have been numerous reports of Ranavirus -associated mass mortality events, no study has yet evaluated the long-term impacts of this disease. This study follows up archived records of English common frog mortalities likely caused by Ranavirus. There is a preliminary indication that common frog populations can respond differently to the emergence of disease: emergence may be transient, catastrophic, or persistent with recurrent mortality events. We subsequently focused on populations that had recurring mortality events (n=18), and we report median declines of 81% in the number of adult frogs in these populations from 1996 to 2008. Comparable uninfected populations (n=16) showed no change in population size over the same time period. Regressions show that larger frog populations may be more likely to experience larger declines than smaller populations, and linear models show that percentage population size change is significantly correlated with disease status, but that habitat age (a possible proxy for environmental quality) has no significant effect on population size change. Our results provide the first evidence of long-term localized population declines of an amphibian species which appear to be best explained by the presence of Ranavirus infection. [source] Effects of locomotor stimulation and protein synthesis inhibition on circadian rhythms in size changes of L1 and L2 interneurons in the fly's visual systemDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2007Elzbieta Kula Abstract Axons of monopolar cell interneurons L1 and L2 in the first optic lobe (lamina) of the fly Musca domestica undergo cyclical changes in diameter. These axons swell during the day and shrink during the night. In addition, the axons' size depends on light conditions since they are largest in continuous light (LL), somewhat smaller under day/night (LD) conditions, and smallest under constant darkness (DD). In this study we found that sizes of both cells can further increase in free flying flies under LD conditions, while the visual stimulation alone does not have significant effect on the cross-sectional area of L1 and L2 axons. The stimulation of free flying had no effect on L1 and L2 sizes if it was performed at the beginning of subjective day in LL or DD. Our results indicate that a maximal increase in size of L1 and L2 is observed when stimulation of free flying is synchronized with a fly' daily peak of activity. We also found that protein synthesis is needed to increase size of monopolar cell axons during the day when they normally swell. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Body size changes in ground beetle assemblages , a reanalysis of Braun et al. (2004)'s dataECOLOGICAL ENTOMOLOGY, Issue 5 2006GÁBOR L. LÖVEI Abstract 1.,Data in Braun et al.'s (2004) recent paper on size trends in ground beetles (Carabidae) are re-analysed, after re-classifying the species according to feeding categories. 2.,When ground beetles are classified as predatory species, mixed feeders or herbivores, and evaluated separately, the size trends indicate group-specific differences. Most of these do not support the efficiency-specialisation hypothesis. 3.,Taxonomic groups rarely fit into one ecological category and ecological analyses should explicitly consider this hurdle. [source] Evolution in ecological field experiments: implications for effect sizeECOLOGY LETTERS, Issue 3 2008Sharon Y. Strauss Abstract Rapid evolution in response to strong selection, much of which is human-induced, has been indisputably documented. In this perspective, we suggest that adaptation may influence the effect size of treatments in ecological field experiments and alter our predictions of future dynamics in ecological systems. Field experiments often impose very strong and consistent selection over multiple generations. Focal populations may adapt to these treatments and, in the process, increase or decrease the magnitude of the treatment effect through time. We argue that how effect size changes through time will depend on the evolutionary history of the experimental population, the type of experimental manipulation, and the traits involved in adaptive responses. While no field study has conclusively demonstrated evolution in response to treatments with concomitant changes in ecological effect size, we present several examples that provide strong circumstantial evidence that such effects occur. We conclude with a consideration of the differences between plastic and genetic responses to treatments and discuss future research directions linking adaptation to ecological effect size. [source] Spreads, Depths, and Quote Clustering on the NYSE and Nasdaq: Evidence after the 1997 Securities and Exchange Commission Rule ChangesFINANCIAL REVIEW, Issue 4 2002Kee H. Chung This paper examines liquidity and quote clustering on the NYSE and Nasdaq using data after the two market reforms,the 1997 order,handling rule and minimum tick size changes. We find that Nasdaq,listed stocks exhibit wider spreads and smaller depths than NYSE,listed stocks and stocks with higher proportions of even,eighth and even,sixteenth quotes have wider quoted, effective, and realized spreads on both the NYSE and Nasdaq. This result differs from the findings by Bessembinder (1999, p. 404) that "trade execution costs on Nasdaq in late 1997 are no longer significantly explained by a tendency for liquidity providers to avoid odd,eighth quotations," and "odd,sixteenth avoidance has little relevance for explaining post,reform Nasdaq trading costs." [source] Global change and carnivore body size: data are stasisGLOBAL ECOLOGY, Issue 2 2009Shai Meiri ABSTRACT Aim, Global warming and other anthropogenic changes to the environment affect many aspects of biology and have often been invoked as causing body size changes in vertebrates. Here we examine a diverse set of carnivore populations in search of patterns in body size change that could reflect global warming (in accord with Bergmann's rule). Location, Global. Methods, We used > 4400 specimens representing 22 carnivore species in 52 populations collected over the last few decades to examine whether size changed with collection date when geography and sex are accounted for. We then examined several factors related to global warming, body mass, diet, and the attributes of the different datasets, to see whether they affect the standardized slope (,) of the size versus time regression. Results, Six of 52 populations we examined show a significant effect of year of collection on body size at the 0.05 probability level. The response of size to global warming does not reflect spatial patterns of size variation, nor do diet or body mass affect tendency of populations to change in body size. Size changes are no more pronounced in populations that have been sampled more recently. However, change, where it occurs, is rapid. Main conclusions, There may be a tendency in the literature to report only cases where recent changes are prevalent. Although in our data only a minority of populations show body size changes, we may see changes accelerating in the future in response to more drastic climatic changes and other anthropogenic changes. [source] SEM evaluation of root canal debridement with Sonicare CanalBrush irrigationINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2010M. I. Salman Salman MI, Baumann MA, Hellmich M, Roggendorf MJ, Termaat S. SEM evaluation of root canal debridement with Sonicare CanalBrush irrigation. International Endodontic Journal, 43, 363,369, 2010. Abstract Aim, To determine the efficacy of Sonicare CanalBrush irrigation for root canal cleaning. Methodology, Fifty human molar root canals were shaped with sequential NiTi rotary instruments up to size F3 (size 30, 0.09 taper; ProTaper system) and then enlarged apically with a Profile size 40, 0.04 taper. Five different irrigation protocols were tested (n = 10 canals per group) with 2 mL of distilled water (control, group I) or 2.5% NaOCl (control group II and test groups III, IV and V) between instrument size changes. Group III,IV received a final rinse with 17% EDTA for one min. This was extended by 30 s in group IV, whereas group V received this additional 30 s of 17% EDTA sonically dispersed with a Sonicare CanalBrush. For cleanliness evaluations, roots were split longitudinally, examined with scanning electron microscopy and scored according to Hülsmann et al. (1997) for debris and smear layer on the surface of the root canal wall. Walls were assessed at the coronal, middle and apical thirds. Data were analysed with the Kruskal,Wallis and Mann,Whitney tests. Results, Irrigation with 17% EDTA significantly reduced debris and smear layer scores (P < 0.05) compared to controls. The coronal and middle thirds had lower debris and smear layer scores than the apical third (P < 0.05). In all thirds, sonic agitation of the irrigant with a CanalBrush (group V) resulted in significantly cleaner canal walls compared to all other groups (P < 0.05). Conclusions, Irrigation by agitation with the Sonicare CanalBrush improved root canal debridement in the coronal, middle and particularly the apical thirds of the root canal. [source] Model-based uncertainty in species range predictionJOURNAL OF BIOGEOGRAPHY, Issue 10 2006Richard G. Pearson Abstract Aim, Many attempts to predict the potential range of species rely on environmental niche (or ,bioclimate envelope') modelling, yet the effects of using different niche-based methodologies require further investigation. Here we investigate the impact that the choice of model can have on predictions, identify key reasons why model output may differ and discuss the implications that model uncertainty has for policy-guiding applications. Location, The Western Cape of South Africa. Methods, We applied nine of the most widely used modelling techniques to model potential distributions under current and predicted future climate for four species (including two subspecies) of Proteaceae. Each model was built using an identical set of five input variables and distribution data for 3996 sampled sites. We compare model predictions by testing agreement between observed and simulated distributions for the present day (using the area under the receiver operating characteristic curve (AUC) and kappa statistics) and by assessing consistency in predictions of range size changes under future climate (using cluster analysis). Results, Our analyses show significant differences between predictions from different models, with predicted changes in range size by 2030 differing in both magnitude and direction (e.g. from 92% loss to 322% gain). We explain differences with reference to two characteristics of the modelling techniques: data input requirements (presence/absence vs. presence-only approaches) and assumptions made by each algorithm when extrapolating beyond the range of data used to build the model. The effects of these factors should be carefully considered when using this modelling approach to predict species ranges. Main conclusions, We highlight an important source of uncertainty in assessments of the impacts of climate change on biodiversity and emphasize that model predictions should be interpreted in policy-guiding applications along with a full appreciation of uncertainty. [source] AM,FM techniques in the analysis of optical coherence tomography signalsJOURNAL OF BIOPHOTONICS, Issue 6-7 2009Costas Pitris Abstract The subtle tissue changes associated with the early stages of malignancies, such as cancer, are not clearly discernible even at the current, improved, resolution of optical coherence tomography (OCT) systems. However, these changes directly affect the spectral content of the OCT image that contains information regarding these unresolvable features. Spectral analysis of OCT signals has recently been shown to provide additional information, resulting in improved contrast, directly related to scatterer size changes. Amplitude modulation,frequency modulation (AM,FM) analysis, a fast and accurate technique for the estimation of the instantaneous frequency, phase, and amplitude of a signal, can also be applied to OCT images to extract scatterer-size information. The proposed technique could make available an extremely valuable tool for the investigation of disease characteristics that now remain below the resolution of OCT and could significantly improve the technology's diagnostic capabilities. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] NADPH-diaphorase activity in the superficial layers of the superior colliculus of rats during agingMICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2006Florentina Díaz Abstract Neurons in the superficial layers of the superior colliculus are key elements in the visual system of rodents since they receive extensive afferent projections from retinal ganglion cells. The NADPH-diaphorase histochemical technique was used to detect differences in neuronal nitric oxide synthase (nNOS) in the superficial layers of the superior colliculus (sSC) of young adult (3 months) and aged (24 and 26 months) rats. The orientation of the dendritic processes of NADPH-diaphorase-positive neurons, cross-sectional area, and number of neurons per mm2 were analyzed. NADPH-d histochemistry revealed a high number of NADPH-d-positive cells in the stratum zonale and stratum griseum superficiale in adult and aged animals. NADPH-d-positive neurons were classified into the following morphological types: marginal, horizontal, pyriform, narrow-field vertical, wide-field vertical, and stellate. During aging, narrow field vertical and wide field vertical neurons present somatic atrophy and an increase in dendritic processes with dorsoventral orientation, whereas wide field vertical neurons show a decrease in those with lateromedial orientation. Marginal neurons undergo somatic hypertrophy at 26 months when compared with those at 3 months. The remaining types of neurons do not undergo size changes. Finally, the number of NADPH-d-positive neurons per mm2 in the various types of morphology does not significantly change with age. It is suggested to be likely that the aging process in the nitrergic neurons of the sSC does not lead to significant changes in the synthesis of NO from the constitutive NOS isoforms. Microsc. Res. Tech. 69:21,28, 2006. © 2006 Wiley-Liss, Inc. [source] THE EFFECTS OF ITQ IMPLEMENTATION: A DYNAMIC APPROACHNATURAL RESOURCE MODELING, Issue 4 2000LEE G. ANDERSON ABSTRACT. This paper investigates the intertemporal effects of introducing Individual Transferable Quota, ITQ, fishery management programs on stock size, fleet size and composition, and returns to quota holders and to vessel operators. Theoretical analysis is conducted using a specific version of a general dynamic model of a regulated fishery. It is demonstrated that the effects will differ depending upon the prevailing regulation program, current stock size, and existing fleet size, composition and mobility and upon how the stock and fleet change over time after the switch to ITQs. The paper expands upon previous works by modeling the dynamics of change in fleet and stock size and by allowing for changes in the TAC as stock size changes, by comparing ITQs to different regulations, and by allowing the status quo before ITQ implementation to be something other than a bioeconomic equilibrium. Specific cases are analyzed using a simulation model. The analysis shows that the annual return per unit harvest to quota owners can increase or decrease over the transition period due to counteracting effects of changes in stock and fleet size. With ITQs denominated as a percentage of the TAC, the current annual value of a quota share depends upon the annual return per unit of harvest and the annual amount of harvest rights. Because the per unit value can increase or decrease over time, it is also possible that the total value can do the same. Distribution effects are also studied and it is shown that while the gains from quota share received are the present value of a potentially infinite stream of returns, potential losses are the present value of a finite stream, the length of which depends upon the remaining life of the vessel and the expected time it will continue to operate. [source] Microsatellite evolution in modern humans: a comparison of two data sets from the same populationsANNALS OF HUMAN GENETICS, Issue 2 2000L. JIN We genotyped 64 dinucleotide microsatellite repeats in individuals from populations that represent all inhabited continents. Microsatellite summary statistics are reported for these data, as well as for a data set that includes 28 out of 30 loci studied by Bowcock et al. (1994) in the same individuals. For both data sets, diversity statistics such as heterozygosity, number of alleles per locus, and number of private alleles per locus produced the highest values in Africans, intermediate values in Europeans and Asians, and low values in Americans. Evolutionary trees of populations based on genetic distances separated groups from different continents. Corresponding trees were topologically similar for the two data sets, with the exception that the (,,)2 genetic distance reliably distinguished groups from different continents for the larger data set, but not for the smaller one. Consistent with our results from diversity statistics and from evolutionary trees, population growth statistics Sk and ,, which seem particularly useful for indicating recent and ancient population size changes, confirm a model of human evolution in which human populations expand in size and through space following the departure of a small group from Africa. [source] Impact of the Change in Tick Size on Transaction Costs and Liquidity: An Empirical Investigation of the Taiwan Stock Exchange,ASIA-PACIFIC JOURNAL OF FINANCIAL STUDIES, Issue 4 2010Su-Wen Kuo C12; G15 Abstract The minimum price variation on the Taiwan Stock Exchange reduced for most price categories on March 1, 2005. The present paper simultaneously examines the institutional and endogenous impacts of tick size changes on transaction costs, market liquidity, and trading activity. The empirical evidence suggests that following a reduction in tick size, uniform declines are discernible in transaction costs and market liquidity. In particular, those stocks with a larger relative tick size reduction, higher trading volume, and higher order handling cost components have greater reductions in spread and market depth. Moreover, endogenous tick size reductions have an adverse effect on the trading activity for low-price stocks, due to the relative disadvantage in explicit transaction costs. Finally, the present study observes a general diminution in trade size resulting from a reduction in tick size in the Taiwan Stock Exchange. This study attributes plausible rationales to the fact that after tick size reductions, informed traders employ a smaller trade size to hide private information, or front-runners place a smaller trade size to avoid market turbulence. [source] How to test different density-dependent fecundity hypotheses in an increasing or stable populationJOURNAL OF ANIMAL ECOLOGY, Issue 1 2006MIGUEL FERRER Summary 1We report on a simulation study of increasing and stable populations working under two different hypotheses of density dependence of fecundity: the habitat heterogeneity hypothesis (HHH) and the individual adjustment hypothesis (IAH). Our aim is to find critical differences between the two regulatory hypotheses in natural populations. 2Populations under HHH show a strong negative relationship between fecundity and the coefficient of variation of fecundity. We also found a strong negative relationship between fecundity and skewness, demonstrating that, as fecundity decreases, the form of the distribution of brood sizes changes, being more left-skewed due to more territories failing to produce any offspring. 3This strong relationship was found only in the simulations of populations under HHH; whether increasing or stable, and under different ratios of good : poor territories and different population sizes. In contrast, no relationship between mean fecundity and skewness was found among simulations under IAH. 4Populations under IAH also showed a significant relationship between mean fecundity and the coefficient of variation of fecundity, but with a lower slope than in populations under HHH. 5In conclusion, skewness was found to be an adequate critical test that showed significant and strong relationships with mean fecundity only in populations under HHH, whether increasing or stable. This test is useful for species with a discrete distribution of offspring with a small number of integer categories, including most of the bird and mammal species. [source] | |||||||||||||||||||