Large Variability In Size Research Articles

Quantifying size-asymmetric growth among individual beech trees

We modelled the growth of individual trees in populations of European beech (Fagus sylvatica L.) grown under different thinning regimes using a modified Richards equation. The effect of competition on growth was modelled by coupling the n individual equations simultaneously with a saturation term. By assuming that the growth of an individual within the population is a function of its size to a power a, a measure of the growth advantage of larger individuals (size-asymmetric growth) is provided. If a > 1, larger trees have a disproportionate advantage in growth and by inference, in competition. The degree of size-asymmetric growth, a, exceeded one in stands with large size variability and increased significantly at increasing density. This suggests that the predominant mode of competition is size asymmetric and that this size asymmetry increases with density. A measure of growth asymmetry is more informative than static measures of size inequality in understanding the growth dynamics of managed forest stands. Since a provides a measure of the relative importance of above- versus below-ground competition, it may be useful in interpreting the growth dynamics of forest stands and may provide an additional level of information for modellers of forest growth.

Diagnostic lumbosacral segmental nerve blocks with local anesthetics: A prospective double-blind study on the variability and interpretation of segmental effects

Background and Objectives: Selective spinal nerve infiltration blocks are used diagnostically in patients with chronic low back pain radiating into the leg. Generally, a segmental nerve block is considered successful if the pain is reduced substantially. Hypesthesia and elicited paresthesias coinciding with the presumed segmental level are used as controls. The interpretation depends on a standard dermatomal map. However, it is not clear if this interpretation is reliable enough, because standard dermatomal maps do not show the overlap of neighboring dermatomes. The goal of the present study is to establish if dissimilarities exist between areas of hypesthesia, spontaneous pain reported by the patient, pain reduction by local anesthetics, and paresthesias elicited by sensory electrostimulation. A secondary goal is to determine to what extent the interpretation is improved when the overlaps of neighboring dermatomes are taken into account. Methods: Patients suffering from chronic low back pain with pain radiating into the leg underwent lumbosacral segmental nerve root blocks at subsequent levels on separate days. Lidocaine (2%, 0.5 mL) mixed with radiopaque fluid (0.25 mL) was injected after verifying the target location using sensory and motor electrostimulation. Sensory changes (pinprick method), paresthesias (reported by the patient), and pain reduction (Numeric Rating Scale) were reported. Hypesthesia and paresthesias were registered in a standard dermatomal map and in an adapted map which included overlap of neighboring dermatomes. The relationships between spinal level of injection, extent of hypesthesia, location of paresthesias, and corresponding dermatome were assessed quantitatively. Comparison of the results between both dermatomal maps was done by paired t-tests. Results: After inclusion, data were processed for 40 segmental nerve blocks (L2-S1) performed in 29 patients. Pain reduction was achieved in 43%. Hypesthetic areas showed a large variability in size and location, and also in comparison to paresthesias. Mean hypesthetic area amounted 2.7 ± 1.4 (± SD: range, 0 to 6; standard map) and 3.6 ± 1.8 (0 to 6; adapted map; P < .001) dermatomes. In these cases, hypesthesia in the corresponding dermatome was found in 80% (standard map) and 88% of the cases (adapted map, not significant). Paresthesias occurring in the corresponding dermatome were found in 80% (standard map) compared with 98% (adapted map, P < .001). In 85% (standard map) and 88% (adapted map), spontaneous pain was present in the dermatome corresponding to the level of local anesthetic injection. In 55% (standard map) versus 75% (adapted map, P < .005), a combination of spontaneous pain, hypesthesia, and paresthesias was found in the corresponding dermatome. Conclusions: Hypesthetic areas determined after lumbosacral segmental nerve blocks show a large variability in size and location compared with elicited paresthesias. Confirmation of an adequately performed segmental nerve block, determined by coexistence of hypesthesia, elicited paresthesias and pain in the presumed dermatome, is more reliable when the overlap of neighboring dermatomes is taken into account. Reg Anesth Pain Med 2001;26:147-155.

Remarks on the morphological variability of Biradiolites angulosusD'Orbigny in a sector of the Trieste Karst (Italy)

This work focuses on the study of a 40 meter thick sequence of Turonian-Lower Coniacian limestonesrich in rudist associations in the North-West area of the Trieste Karst near the small village of Sistiana. The examined sequence was subdivided into five intervals. In the systematic study of the rudist species of this sequence, particular attention was paid to Biradiolites angulosus d'Orbigny which shows a large variability in size and number of ridges of the lower valve.

The paranasal sinuses in CT-imaging: Development from birth to age 25

Available data about the size of the different sinuses to date are derived from anatomical or radiological studies. In order to verify or possibly correct the findings of other authors we evaluated the cranial computed tomography (CT)-images of more than 5600 patients. We measured the sex-linked and age-dependent width and length of the four sinuses for both sides in axial sections. For the first time we have a clear picture of the development of the paranasal sinuses for both sexes from birth until the age of 25 years. Our results confirm general ideas concerning the size of the sinuses. Moreover they provide new details, especially about the first occurrence and the course of development in different stages since we found each sinus already present in 1.5% (frontal sinus) to 94% (ethmoid cells) of the newborn of both sexes. Finally, we can state that the periods of expansion are equal in both sexes (ethmoid cells) or last up to 2 or 3 years longer (frontal sinus) in male patients. In agreement the sinuses of both sexes differ between 5.4% (sphenoid sinus) and 17.1% (frontal sinus) in definitive size with statistically significant differences in later ages. The data about sphenoid sinuses deserve special attention since they show a large variability in size (up to 214% in one direction) as well as in shape.

A fuzzy graph theoretic approach to recognize the totally unconstrained handwritten numerals

An automatic off-line character recognition system for totally unconstrained handwritten numerals is presented. The system was trained and tested on the field data collected by the U.S. Postal Services Department from dead letter envelopes. It was trained on 1763 unnormalized samples. The training process produced a feasible set of 105 Fuzzy Constrained Character Graph Models (FCCGMs). FCCGMs tolerate large variability in size, shape and writing style. Characters were recognized by applying a set of rules to match a character tree representation to a FCCGM. A character tree is obtained by first converting the character skeleton into an approximate polygon and then transforming the polygon into a tree structure suitable for recognition purposes. The system was tested on (not including the training set) 1812 unnormalized samples and it proved to be powerful in recognition rate and tolerance to multi-writer, multi-pen, multi-textured paper, and multi-color ink. Reliability, recognition, substitution error, and rejection rates of the system are 97.1, 90.7, 2.9, and 6.4%, respectively.