6,098 research outputs found
A residual-based bootstrap test for panel cointegration
We address the issue of panel cointegration testing in dependent panels, showing by simulations that tests based on the stationary bootstrap deliver good size and power performances even with small time and cross-section sample sizes and allowing for a break at a known date. They can thus be an empirically important alternative to asymptotic methods based on the estimation of common factors. Potential extensions include test for cointegration allowing for a break in the cointegrating coefficients at an unknown date
An in vitro investigation of the influence of self-ligating brackets, low friction ligatures, and archwire on frictional resistance
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Effect of tree density on root distribution in Fagus sylvatica stands: a semi-automatic digitising device approach to trench wall method
5Knowledge of root profiles is essential for
measuring and predicting ecosystem dynamics and function.
In the present study, the effects of management
practices on root (0.5 <= ø < 20 mm) spatial distribution
were examined in a 40-year-old coppice stand (CpS 1968)
and other two stands converted from coppice to thinned
high forest in 1994 (CvS 1994) and 2004 (CvS 2004),
respectively. The use of a semi-automatic digitising device
approach was compared with a conventional root mapping
method in order to estimate the time per person required
from fieldwork to the final digital map. In July 2009, six
trench walls per stand were established according to tree
density, i.e. as equidistant as possible from all surrounding
trees. Findings highlighted differences between the stands
with CvS 1994 showing a lower number of small roots
(2 <= ø < 5 mm), a higher mean cross-sectional area
(CSA) of coarse roots (5 <= ø < 20 mm) and different root
depth distribution as compared to CpS 1968 and CvS 2004
whose values were close to each other. The three diameter
classes selected in this study showed significant relationships
in terms of number of roots, scaling down from
coarse- to small- and fine-roots. Forest management
practices significantly affected only the number of small
roots. The number of fine roots (0.5 <= ø < 2 mm) was isometrically related to their root length density (RLD,
cm cm-3). No relationship occurred with RLD of very fine
roots (ø < 0.5 mm). In conclusion, forest management
practices in terms of conversion thinnings significantly
affected belowground biomass distribution of beech forest
in space and time. In particular, frequency of coarse roots
was related to the stand tree density, frequency of small
roots was related to the cutting age. Size of coarse roots
was related to tree density but only several years after
felling. The allometric relationship occurring between fineand
small-roots highlighted how fine root number and RLD
were only indirectly affected by forest management practices.
These findings suggest that future investigations on
the effect of forest thinning practices on fine-root traits like
number, length and biomass several years after felling
cannot ignore those on small roots.openDi Iorio, A.; Montagnoli, A.; Terzaghi, M.; Scippa, G.S.; Chiatante, D.DI IORIO, Antonino; Montagnoli, A.; Terzaghi, M.; Scippa, G. S.; Chiatante, Donat
Fine-root seasonal pattern, production and turnover rate of European beech (Fagus sylvatica L.) stands in Italy Prealps: Possible implications of coppice conversion to high forest
The aim of this study was to investigate the possible effects of coppice conversion to high forest on the beech fine-root
systems. We compared the seasonal pattern of live and dead fine-root mass (d<2 mm), production and turnover in three
beech stands that differed in management practices. Tree density was higher in the 40-year-old coppice stand than in the
stands that were converted from coppice to high forest in 1994 and 2004, respectively. We found that a reduction in tree
density reduced the total fine-root biomass (Coppice stand, 353.8 g m-2; Conversion 1994 stand, 203.6 g m-2;
Conversion 2004 stand, 176.2 g m-2) which continued to be characterised by a bimodal pattern with two major peaks,
one in spring and one in early fall. Conversion to high forest may also affect the fine-root soil depth distribution. Both
fine-root production and turnover rate were sensitive to management practices. They were lower in the Coppice stand
(production 131.5 g m-2 year-1; turnover rate 0.41 year-1) than in the converted stands (1994 Conversion stand:
production 232 g m-2 year-1, turnover rate 1.06 year-1; 2004 Conversion stand: production 164.2 g m-2 year-1,
turnover rate 0.79 year-1)
Cryobank of Mediterranean Brown Trout Semen: Evaluation of the Use of Frozen Semen up to Six Hours Post-Collection
The aim of this study was to evaluate the effects of different cold-storage time intervals between collection and semen-freezing on both fresh and cryopreserved semen motility parameters and the post-thaw fertilizing ability of Mediterranean brown trout semen. The ejaculates were split into six aliquots and stored on ice from 1 to 6 h, until freezing. Fresh and post-thaw sperm motility was evaluated by a Computer-Assisted Sperm Analysis system, whilst the fertilizing ability was assessed by in vivo trials. In fresh semen, at 3 h of storage, a significant decrease of total motility, linear movement (STR, LIN) and beat cross frequency (BCF) was recorded, whilst the amplitude of lateral displacement of the spermatozoon head (ALH) underwent a significant increase. In frozen semen, no significant difference was observed for all the motility parameters evaluated, except for the total motility between 1 and 6 h of storage and the duration of sperm movement between 1 and 5 h. Cold-storage time did not significantly affect the percentage of live embryos following the use of frozen semen. In conclusion, our results showed that, if necessary, the Mediterranean brown trout semen can be frozen even until 6 h post-collection without losing its fertilizing ability
Autosomal-dominant myopia associated to a novel P4HA2 missense variant and defective collagen hydroxylation
We recently described a complex multisystem syndrome in which mild-moderate myopia segregated as an independent trait. A plethora of genes has been related to sporadic and familial myopia. More recently, in Chinese patients severe myopia (MYP25, OMIM:617238) has been linked to mutations in P4HA2 gene. Seven family members complaining of reduced distance vision especially at dusk underwent complete ophthalmological examination. Whole-exome sequencing was performed to identify the gene responsible for myopia in the pedigree. Moderate myopia was diagnosed in the family which was associated to the novel missense variant c.1147A > G p.(Lys383Glu) in the prolyl 4-hydroxylase,alpha-polypeptide 2 (P4HA2) gene, which catalyzes the formation of 4-hydroxyproline residues in the collagen strands. In vitro studies demonstrated P4HA2 mRNA and protein reduced expression level as well as decreased collagen hydroxylation and deposition in mutated fibroblast primary cultures compared to healthy cell lines. This study suggests that P4HA2 mutations may lead to myopic axial elongation of eyeball as a consequence of quantitative and structural alterations of collagen. This is the first confirmatory study which associates a novel dominant missense variant in P4HA2 with myopia in Caucasian patients. Further studies in larger cohorts are advisable to fully clarify genotype-phenotype correlations.We recently described a complex multisystem syndrome in which mild-moderate myopia segregated as an independent trait. A plethora of genes has been related to sporadic and familial myopia. More recently, in Chinese patients severe myopia (MYP25, OMIM:617238) has been linked to mutations in P4HA2 gene. Seven family members complaining of reduced distance vision especially at dusk underwent complete ophthalmological examination. Whole-exome sequencing was performed to identify the gene responsible for myopia in the pedigree. Moderate myopia was diagnosed in the family which was associated to the novel missense variant c.1147A > G p.(Lys383Glu) in the prolyl 4-hydroxylase,alpha-polypeptide 2 (P4HA2) gene, which catalyzes the formation of 4-hydroxyproline residues in the collagen strands. In vitro studies demonstrated P4HA2 mRNA and protein reduced expression level as well as decreased collagen hydroxylation and deposition in mutated fibroblast primary cultures compared to healthy cell lines. This study suggests that P4HA2 mutations may lead to myopic axial elongation of eyeball as a consequence of quantitative and structural alterations of collagen. This is the first confirmatory study which associates a novel dominant missense variant in P4HA2 with myopia in Caucasian patients. Further studies in larger cohorts are advisable to fully clarify genotype-phenotype correlations
Retinitis Pigmentosa: Genes and Disease Mechanisms
Retinitis pigmentosa (RP) is a group of inherited disorders affecting 1 in 3000-7000 people and characterized by abnormalities of the photoreceptors (rods and cones) or the retinal pigment epithelium of the retina which lead to progressive visual loss. RP can be inherited in an autosomal dominant, autosomal recessive or X-linked manner. While usually limited to the eye, RP may also occur as part of a syndrome as in the Usher syndrome and Bardet-Biedl syndrome. Over 40 genes have been associated with RP so far, with the majority of them expressed in either the photoreceptors or the retinal pigment epithelium. The tremendous heterogeneity of the disease makes the genetics of RP complicated, thus rendering genotype-phenotype correlations not fully applicable yet. In addition to the multiplicity of mutations, in fact, different mutations in the same gene may cause different diseases. We will here review which genes are involved in the genesis of RP and how mutations can lead to retinal degeneration. In the future, a more thorough analysis of genetic and clinical data together with a better understanding of the genotype-phenotype correlation might allow to reveal important information with respect to the likelihood of disease development and choices of therapy
ZCT 103/3 - Fizik III (Getaran, Gelombang dan Optik) FEB 04.
Wiki content templating enables reuse of content structures among wiki pages. In this paper we present a thorough study of this widespread feature, showing how its two state of the art models (functional and creational templating) are sub-optimal. We then propose a third, better, model called lightly constrained (LC) templating and show its implementation in the Moin wiki engine. We also show how LC templating implementations are the appropriate technologies to push forward semantically rich web pages on the lines of (lowercase) semantic web and microformats. ation performed by the wiki engine to deliver semantically rich web pages and give to authors simple interfaces (sometimes even invisible interfaces based on syntactic quirks!) to semantically annotate their content or to import semantic metadata
Validation of the Turkey semen cryopreservation by evaluating the effect of two diluents and the inseminating doses
This study was designed to test the fertilizing ability of cryopreserved turkey semen, and here, two experiments were performed: an in vitro analysis to assess the effects of Tselutin and Lake diluents and an in vivo test to determine the fertility and hatching rates by also studying the feat of three insemination doses (250, 400 and 600
7 106 sperm/hen). Pooled semen samples were diluted with Tselutin or Lake extender which contained 20% of dimethylsulfoxide and 1 mM of Ficoll at final sperm concentration of 3
7 109 sperm/mL. Thereafter, semen was packaged into straws and frozen on liquid nitrogen. The post-thaw sperm quality was evaluated considering motility (computer-aided sperm analysis\u2014CASA system) and membrane integrity (flow cytometry). Significantly higher values of progressive motility and some kinetic parameters in semen frozen with Lake were found. When we compared the extenders in vivo, no significant effects were detected, whilst sperm concentration significantly affected both fertility and hatching rates, with the best results obtained with the sperm concentration of 400
7 106 sperm/hen. From the results obtained, it emerged that the extender type only affected sperm motility characteristics, not the fertilizing ability of frozen-thawed semen, while inseminating dose markedly affected fertility and hatching rates
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