Lowermost End Research Articles

Segmental Flexibility in Adolescent Idiopathic Scoliosis Assessed Using the Fulcrum-bending Radiography Method.

Assessment of segmental flexibility at each disk level of the scoliotic curve in patients with adolescent idiopathic scoliosis (AIS) has rarely been performed, despite its importance for surgical planning of fusion levels. The fulcrum-bending radiography method could be used to assess flexibility at specific spinal segments of the scoliotic curve for preoperative planning. Therefore, our aim was to use the fulcrum-bending method to evaluate the pattern of segmental flexibility in patients with AIS. Our retrospective analysis was based on preoperative fulcrum-bending radiographs in 21 patients presenting with main thoracic curve scoliosis. The apex vertebra was defined as the "0" level, with the sequential cranial disk levels defined as "+1 to +5" and the sequential caudal levels as "-1 to -5." The segmental Cobb angle was measured on both, standing and fulcrum-bending radiographs. The segmental flexibility index (FI) was calculated as: [(the segmental Cobb angle in standing position-the segmental Cobb angle in the fulcrum-bending position)/the segmental Cobb angle in standing position]×100. The FI was measured from the upper-most to the lower-most end vertebrae of the main curve. There was a significant difference in the FI among segments, with the greatest flexibility detected at the level of the -5 disk (median FI, 50%) and least flexibility at the periapical segments (+1 and -1; FI, 50%-66.7%). The curve around the apex and upper thoracic segments in thoracic AIS is relatively rigid. Understanding differences in FI between each disk level is important for optimal corrective surgery.

Effects of precipitation and different distributions of grass strips on runoff and sediment in the loess convex hillslope

The characteristics of runoff and sediment under different grass strip patterns are important in the study of the mechanisms regulating vegetation in convex hillslope. In this work, using a physical model of a convex hillslope as a carrier, it is analyzed the characteristics of runoff and sediment under five grass strip patterns, as well as regulation mechanism of grass strips on soil erosion through intermittent simulated rainfall experiments. The results show that some grass strip patterns significantly (p<0.05) influenced both runoff and sediment yield in convex hillslope. Under different grass strip patterns, the runoff amount increased slightly, the runoff time gradually stabilized, and the sediment yield decreased sharply with the increase in rainfall episodes. The water storage and sediment reduction functions with the grass strip on the lower part of the upslope were generally clearer than those with grass on the upper part; however, positioning the grass strip closer to the lowermost end of upslope the grass strip did not clearly improve the water storage and sediment reduction functions. Appropriate positioning of the grass strips can effectively adjust the sediment concentration, and thus further reduce the runoff detachment rate, decrease average runoff velocity by 46%, and weaken the input of energy into the downslope as limiting the acceleration area of runoff rely on the appropriate position. The optimal position for grass strips in the convex hillslope was identified as 60% of the upslope length. In this location, the soil and water conservation functions of the grass strip were optimal, with the runoff and sediment reduced by 7.35% and 62.93%, respectively. The water storage function of the grass strip was weak; however, its direct sediment interception function was relatively better. The effect of vegetation patterns on soil erosion was largely through their effects on rill formation and development and density on the convex slope, especially on the downslope. Moreover, the role of vegetation not only changed the rill erosion position, more importantly, transformed the erosion pattern. This study furthers understanding of the regulation mechanism of grass strip patterns on soil erosion.

The ecology of subindividual variability in plants: patterns, processes, and prospects

Abstract. Diversification of ecology into subdisciplines that run from macroecology to landscape, community, and population ecology largely reflects its specialization on different segments of the spatial gradient over which recognizable ecological patterns and processes occur. In all these cases, the elemental units involved in the patterns and processes of interest to ecologists are individuals from the same or different species. No distinct flavor of ecology has yet emerged that focuses on patterns and processes revolving around the lowermost end of the spatial gradient, which in the case of plants corresponds to the within-individual domain. Intraindividual heterogeneity in organ traits, however, is quantitatively important and has multiple consequences for plant individuals, populations, and communities, and for animal consumers as well. This paper first provides an overview of current knowledge on plant traits that vary subindividually, the magnitude of subindividual variation, and its spatial patterning. Examples will then be presented on the consequences of subindividual variation for plants and animal consumers at individual, population, or community levels. Finally, the recently emerging links between genetics, epigenetics, subindividual variation, and population ecology will be illustrated using results on variation in seed size, a functional plant trait playing an important role in plant population dynamics. Further observational and experimental studies are needed which link ecological and phenotypic measurements of plants to their epigenetic and genetic characteristics, in order to understand the three-way relationships between subindividual variability, genetic features, and epigenetic mosaicism. Another proposed line of inquiry should focus on evaluating whether subindividual epigenetic mosaics eventually translate into epigenetically heterogeneous progeny, thus contributing to the maintenance of population and community functional diversity.

Analytical model of impact disruption of satellites and asteroids

A model of impact disruption of the bodies with sizes from the laboratory scale to that of an order of 100km is developed. On the lowermost end of the target size the model is based on the numerous laboratory data related to the mass–velocity distribution of the impact produced fragments. On the minor-planets scale the model is supported by the data related to the largest observed craters on small icy satellites and on some asteroids (Leliwa-Kopystynski, J., Burchell, M.J., Lowen, D. [2008]. Icarus 195, 817–826). The model takes into account the target disruption and the dispersion of the impact produced fragments against the intermolecular forces acting on the surfaces of the contacts of the fragments and against self-gravitation of the target. The head-on collisions of non-rotating and non-porous targets and impactors are considered. The impactor delivers kinetic energy but its mass is neglected in comparison to mass of the target. For this simple case the analytical formulae for specific disruption energy as well as for specific energy of formation of the largest craters are found. They depend on a set of parameters. Of these the most important (i.e. with the greatest influence on the final result) are three rather weakly known parameters. They are: (i) The exponent γ in the distribution function of the fragments. (ii) The characteristic velocity v0 that appears in the velocity distribution of the ejected fragments. (iii) The exponent β in the mass–velocity distribution. The influence of the choice of the numerical values of these parameters on the final results has been studied. Another group of parameters contains the relevant material data. They are: (a) The energy σ of breaking of the intermolecular bonds of the target material per unit of the fragment surface and (b) the density ρ of the target. According to our calculations the transition between the strength regime and the gravitational regime is in the range of the target radius from ∼0.4km to ∼4km. This estimate holds within a large range of parameters.An application of the results for impact cratering and/or for disruption of satellites and asteroids requires data concerning the impactor energy. We have considered rocky–rocky impacts (an asteroid on an asteroid) and icy–icy impacts (a satellite impacted by a comet). Hypothetical impacts onto some particular asteroids and satellites are discussed as examples.

Simple 3D images from fossil and Recent micromaterial using light microscopy

Abstract We present a technique for extracting 3D information from small-scale fossil and Recent material and give a summary of other contemporary techniques for 3D methods of investigation. The only hardware needed for the here-presented technique is a microscope that can perform dark field and/or differential interference contrast with a mounted digital camera and a computer. Serial images are taken while the focus is successively shifted from the uppermost end of the specimen to the lowermost end, resulting in about 200 photographs. The data are then processed almost completely automatically by successive use of three freely available programs. Firstly, the stack of images is aligned by the use of CombineZM, which is used to produce a combined image with a high depth of field. Secondly, the aligned images are cropped and sharp edges extracted with the aid of ImageJ. Thirdly, although ImageJ is also capable of producing 3D representations, we preferred to process the image stack further using osirix as it has the facility to export various formats. One of the interesting export formats is a virtual Quicktime movie file (QTVR), which can be used for documentation, and stereo images can also be produced from this Quicktime VR. This method is easy to apply and can be used for documenting specimens in 3D (at least some aspects) without having to prepare them. Therefore, it is particularly useful as a safe method for documenting limited material, before using methods that may destroy the specimen of interest, or to investigate type material that cannot be treated with any preparatory technique. As light microscopes are available in most labs and free computer programs are easily accessible, this method can be readily applied.

Comparative ultrastructure of the epidermal ciliary rootlets and associated structures in species of the Nemertodermatida and Acoela (Plathelminthes)

The fine morphology of epidermal ciliary structures in four species of the Nemertodermatida and four species of the Acoela was studied, with emphasis on Meara stichopi (Nemertodermatida). The cilium of M. stichopi has a distal shelf and is proximally separated from the basal body by a cup-shaped structure. The bottom of the cup consists of a bilayered dense plate, or basal plate. The basal body consists of peripheral microtubule doublets continuous with those of the cilium. In the upper part of the basal body, the doublets are set at an angle and are anchored to the enclosing cell membrane by Y-shaped structures. The lower part of the basal body tapers eventually. The striated main rootlet arises on the anterior face of the basal body, initially like a flattened strap, and continues along the basal body shaped as a tube which further down becomes solid. The hour-glass-shaped posterior rootlet arises on the posterior face of the basal body. Contrary to the main rootlet, the striations in the proximal part of the posterior rootlet run parallel to the microtubule doublets of the basal body. A pair of microtubule bundles lead from the posterior rootlet to the two main rootlets in the hind ciliary row, and follow these to their lower tip. In the other species of the Nemertodermatida studied, the structure of the ciliary basal body and the ciliary rootlets is similar to that of M. stichopi. Structural differences in the species of the Acoela are that the lowermost end of the basal body is narrow and bent forwards, the proximal part of the main rootlet is trough-shaped, the main rootlet is accompanied by a pair of lateral rootlets and the posterior rootlet with associated microtubule bundles is thin. The epidermal ciliary structures in species of the Nemertodermatida and Acoela have a number of shared characters which are unique within the Plathelminthes. However, almost all of these characters are found in Xenoturbella bocki (Xenoturbellida), and some even in species of other ”phyla” of the ”lower” Metazoa. Hence, these characters cannot be considered apomorphic for the Acoelomorpha. A character seemingly present only in species of the Nemertodermatida and Acoela is the bilayered dense plate. This feature might represent an autapomorphic character state for the Acoelomorpha.

Nature’s Metropolis: Chicago and the Great West by William Cronon

Book Reviews Nature’s Metropolis: Chicago and the Great West. By William Cronon. New York: W. W. Norton, 1991. Pp. xxiii + 530; illustrations, maps, notes, appendix, bibliography, index. $27.50. Chicago was incorporated as a city under the laws of Illinois in 1837, when the population was little more than 3,000. It was located at the lowermost end of Lake Michigan at the point of the deepest penetration of the Great Lakes into the continental United States, but there was no means of transportation other than horse-drawn wagons on crude dirt roads to connect it with the vast area of land to the west. The two short branches of the narrow, shallow, sluggish Chicago River were all the flowing water that nature provided, but the South Branch lay so close to the Des Plaines River and the Mississippi drainage basin that in periods of high water the intervening land was flooded. If it was not much to start with, there was the promise of great potential wealth, and a few far-sighted citizens, filled with almost mystical dreams of economic destiny, were aware of it. They proved to be right: during the thirty-four years between incorporation and the Great Fire of 1871, the population of the city expanded from a paltry village to a flourishing commercial and industrial city of 300,000. The story of this unparalleled expansion in size, wealth, and power has been told with varying emphases many times, most recently by William Cronon, a professor of history at Yale University. His version is told in terms of the economic interaction of the city with the physiography, geology, and soil fertility of its hinterland, which extended from the Great Lakes westward a thousand miles to the Rocky Mountains. A series of economic and technological processes developed sideby -side in the years after the establishment of the human community. First and above all was the transformation of the tail-grass prairie, with its immense herds of bison, into an ordered agricultural domain, given mainly to the growing of wheat and corn and the raising of hogs and cattle. The natural resources were a seemingly limitless area of fertile ground and a precipitation exactly suited to an agriculture equally suited to human needs. The Native Americans who previously occupied the land were forcefully driven into scattered enclaves and the bison soon exterminated. To the north of the prairie lands in the Great Lakes region stood the forests, where every kind of useful wood grew in what again seemed unlimited abundance. White pine was the Permission to reprint a review from this section may be obtained only from the reviewer. 591 592 Book Reviews TECHNOLOGY AND CULTURE most valuable structural timber, and by the turn of the century it was so thoroughly cut that it was largely gone. Over the prairies, the high plains to the west of them, and the former forestlands, the raising of livestock took the place of bison and other native fauna. By the end of the century the physiography and ecology of the immense region had been so completely transformed that the only vestiges of its original character survived in a few state parks and national forests. At the same time Chicago, beneficiary of the conquering spirit, had grown into the major financial, mercantile, and manufacturing city of the midnation. The account of this transformation and an analysis of how it came about form the substance of Cronon’s narrative, the essential theme being that the city of Chicago and the open lands that spread around it grew together in a natural-cultural symbiosis of prairie agriculture, forest lumbering, city enterprises, canals, and railroads. The human and civic world could not have grown without the natural, and the latter could not have been transformed to useful ends without human intervention. The book is thus a long, intricately detailed illustration of the main theme of Paul Bairoch’s Cities and Economic Development, which establishes the thesis that the growth of cities over millennia could not have occurred without the simultaneous growth of agricul­ ture. Chicago is in no way unique in this respect; what sets it apart from other cities is the immensity of...

Lower Atoka Group (Lower Middle Pennsylvanian), Northern Fort Worth Basin, Texas--Depositional Systems, Facies, and Hydrocarbon Distribution: ABSTRACT

Lower Atoka is an informal name applied to the lowermost End_Page 247------------------------------ depositional sequence of the Atoka Group, which is partly equivalent to the Big Saline Formation. Depositionally it reflects a transition from carbonate to terrigenous-dominated environments. Chert litharenites derived from the Ouachita structural belt and locally from the Muenster arch first prograded across the northern part of the Fort Worth basin during lower Atoka deposition. Lower Atoka strata are interpreted to be a fluvially dominated fan-delta system which exhibits characteristics of both a fan delta and a high-constructive elongate delta. Fan-delta characteristics include tectonically active source, poorly developed alluvial plain, and interfingering and/or coexisting terrigenous and carbonate facies. High-constructive elongate delta characteristics include elongate, digitate sand-body geometry and a facies tract reflecting rapid progradation and aggradation. Contemporaneous faulting within the basin was a major factor in distribution of lower Atoka facies. Sediment was confined to the downthrown sides of contemporaneous faults resulting in superposed fan-delta deposits. Stacking and coalescing of early fans constructed an alluvial plain. When sediment supplies exceeded fault movement, the fan deltas continued to prograde across the basin. Cumulative oil and gas (equivalent) production from the lower Atoka is over 130 million bbl. Production is facies controlled and the distribution of fields coincides with the distribution of fan-delta lobes. Fields are aligned predominantly on the basinward side of major faults and they produce from fan-delta channel-fill and coarse-grained fan-delta plain facies. End_of_Article - Last_Page 248------------

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Basic Studies on the Resistance Received by a Wheel Rolling on a Soft Ground

In this report, description is first made from the results of experiments made by the electrical, automatic M-T (Mashima-Takahashi) wheel rolling resistance measuring device. The Takahashi's theoretical equation, based on the experimental results, are then derived which show the relations among the resultant rolling resistance R received by the wheel from soft ground (S. G.), its horizontal component H and vertical component V, the direction θ, the coordinates (X, Y) of the point Q where the force is applied, the driving torque of wheel M, etc., on one hand and the breadth of wheel b, the wheel diameter 2r, the sinking depth at the lowermost end of wheel y0, the characteristic constants of S. G. sample k and n, coefficient of friction μ, etc., on the other hand. It is explained that these formulas represented in vector are convenient for practical purposes. From the formulas, it is also found that the values of R, H, V, θ, Q (X, Y), etc. differ between the two cases, i.e. when the wheel is pulled and the wheel rotates under axial driving. Finally, the theoretical formulas on the rolling resistance of a vehicle running on S. G. are obtained from the formulas for a single wheel. Applications of the studies for practical purposes are also described.

Mount Etna and the 1971 eruption - Structural implications of the 1971 Mount Etna eruption

The author believes the 1971 eruption has been triggered by an uprise of the magma column which had for several decades fed the persistent activity located in both the NE crater and in the central crater’s chasm. This uprise split open a set of en-echelon fissures first on the southern, then on the eastern upper slopes of Mt Etna. Degassing occurred at the uppermost part of the successive fissure systems, while the degassed lava flows poured out at the lowermost end. When the ENE tectonic fault-system came into operation and controlled the second half of the eruption, it led to the engulfment of the degassing vent and subsequently acted as an undergound channel through which the degassed lavas could flow freely until they poured out at the lower end of the fault zone. This fault zone follows one of the main tectonic trends which intersect below Mt Etna, the main other ones being oriented SW-NE and WSW—ENE.

High oesophageal stricture with hiatal hernia and a lower oesophagus lined by columnar epithelium.

A 23-year-old man with a six months9 history of dysphagia was found to have hiatus hernia with reflux and a stricture of the mid-oesophagus. Death from unrelated causes permitted detailed histological examination. This showed a high squamo-columnar junction with ulceration confined to the squamous epithelium immediately above the junction. The columnar epithelium of the lower oesophagus was largely of cardiac type, but a few gastric body type glands were present at the lowermost end. This mixed pattern and the complete lack of inflammation or fibrosis beneath the columnar epithelium favours a congenital rather than metaplastic origin. A high squamo-columnar junction is of clinical significance only in the presence of reflux when oesophagitis and stricture develop at an unusually high level.