Mean Inclination Research Articles

Reliability of Cup Position in Navigated Tha in the Lateral Decubitus Position Using the ‘Flip Technique’

Malpositioning of the acetabular component in total hip arthroplasty (THA) increases the risk of dislocation, reduces the range of motion and may contribute to bearing surface wear. During computer assisted navigation, the anterior pelvic plane is registered intraoperatively by percutaneous palpation, but this may be unreliable. The aim of our study was to evaluate the reliability of imageless navigation in acetabular positioning employing data acquisition in the supine position and surgery in the lateral position ('flip technique'). We report 24 patients affected by primary osteoarthritis undergoing THA in which implants were placed with a conventional free-hand technique using the acetabular transverse ligament for cup orientation. For imageless navigation we used Orthopilot-Aesculap software. All patients had a postoperative computed tomography (CT) scan at three months, using previously validated dedicated software for cup orientation. Data collected using navigation software were compared with CT measurements. The mean acetabular inclination and anteversion recorded intra-operatively using navigation software were respectively 41°5' (SD: 9.61) and 9°5' (SD: 4.01) respectively. The mean inclination and anteversion calculated post-operatively by the CT based image software were 44°2' (SD 5.83) and 14°4' (SD 6.42) respectively. There was a statistically significant difference between the anteversion values (p=0.04). Therefore, the acquisition of parameters in the supine position with surgery performed in the lateral decubitus position creates unreliable data concerning cup anteversion using an imageless navigation system, and therefore the 'flip technique' cannot be recommended.

Propagating and incorporating the error in anisotropy-based inclination corrections

SUMMARY Sedimentary rock palaeomagnetic inclinations that are too shallow with respect to the ambient field inclination may be restored using anisotropy-based inclination corrections or techniques that rely on models of the past geomagnetic field. One advantage of the anisotropy technique is that it relies on measured parameters (declinations, inclinations, bulk rock magnetic fabrics and particle magnetic anisotropy) that have measurement errors associated with them, rather than relying on a geomagnetic field model and statistical treatment of the data. Sofar,however,theerrorassociatedwiththemeasurementshasnotbeenpropagatedthrough the corrections and the reported uncertainties are simply the α95 95 per cent confidence circles of the corrected directions. In this paper we outline different methodologies of propagating the error using bootstrap statistics and analytic approximations using the case example of the Shepody Formation inclinationcorrection.Bothtechniquesareingoodagreementandindicateamoderate, ∼15per cent, uncertainty in the determination of the flattening factor (f) used in the correction. Such uncertainty corresponds to an ∼0.31 ◦ increase of the confidence cone and a bias that steepens the mean inclination by 0.32 ◦ . For other haematite-bearing formations realistic uncertainties for f ranging from 0 and 30 per cent were used (together with an intermediate value of 15 per cent) yielding a maximum expected increase in the confidence cones and steepening of the inclinationsof ∼1 ◦ .Suchresultsindicatethatformoderateerrorsoff theinclinationcorrection itself does not substantially alter the uncertainty of a typical palaeomagnetic study. We also compare the uncertainties resulting from anisotropy-based corrections to those resulting from the elongation/inclination (E/I) technique. Uncertainties are comparable for studies with a large sample number (>100), otherwise the anisotropy-based technique gives smaller uncertainties. Whenanisotropydataarenotavailable,itispossibletoestimateacorrectionusingflattening factors (f) obtained from the literature. A range of flattening factors has been observed for both magnetite and haematite-bearing rocks (0.4 ≤ f ≤ 1 for haematite and 0.54 ≤ f ≤ 1f or magnetite), but the exact value is specific to the anisotropy of the formation. To evaluate the maximum effects of inclination shallowing, the smallest f (for magnetite or haematite) should be used.

Position of the prosthesis components in total ankle replacement and the effect on motion at the replaced joint

In some cases of total ankle replacement, perfect alignment of the prosthetic components is not achieved. This study analyses the extent to which component positioning is critical for the final range of motion. Fourteen patients undergoing total ankle replacement were assessed preoperatively and postoperatively at seven and 13 months follow-up. X-ray pictures of the ankle were taken in static double leg stance, i.e. at neutral joint position, and in maximum plantarflexion and dorsiflexion. Measurements were obtained by a specially devised computer program based on anatomical reference points digitised on the radiograms. These allowed calculation of the position and orientation of the components in the sagittal and coronal planes, together with the joint range of motion. The mean range of motion was about 34 degrees at the first follow-up and maintained at the second. Tibial and talar components were more anterior than the mid-tibial shaft in 11 and nine patients, respectively. Mean inclination was about four degrees posterior for the tibial component and nearly one degree anterior for the talar component. A significantly larger range of motion was found in ankles both with the talar component located and inclined more anteriorly than the tibial. Correlation, though weak, was found between motion at the replaced ankle and possible residual subluxation and inclination of the components. However, a satisfactory range of motion was also achieved in those patients where recommended locations for the components could not be reached because of the size of the original joint deformity.

Spatial orientation of the subtalar joint axis is different in subjects with and without Achilles tendon disorders

BackgroundThere are many possible predisposing factors for Achilles tendon disorders suggested in the literature but their pathogenetic relevance is not proven in most cases. The asymmetric mechanical load distribution within...

Validation of navigation assisted cup placement in total hip arthroplasty

Computer navigation has the potential to provide precise intraoperative knowledge to the surgeon. Previous studies with navigation have confirmed its function for improved component position but few studies have reported the accuracy and precision of navigation system in clinical use. With this study we propose to evaluate the efficacy of navigation in guiding cup placement. Fifty-six patients undergoing primary total hip arthroplasty were prospectively included in this study. Stryker imageless navigation system which is accurate to 0.5° was used in all cases. Intraoperative data was collected for the acetabular component position using navigation for the freehand cup placement and the final cup placement done using navigation. Postoperative evaluation of component position was done with computed tomography (CT) and the deviation from intraoperative freehand and navigation values were calculated. The mean inclination of the freehand reading was 39.5° (range, 20°-58°), mean version of freehand reading was 10.7° (-6°- 27°), and the mean navigation reading was 43.2° (37°-49°) for inclination and 13.0° (-8° - 24°) for version. On postoperative CT scan analysis the mean inclination was 45.3° (34°-56°) and mean version was 15.1° (4°-25°). The deviation of the freehand inclination from the post operative CT scan reading was 11.4° (1°-30°) and the version deviated by a mean of 10.8° (2°-26°). The deviation of the navigation reading from the CT scan reading had a mean of 5.3° (1°-13°) for inclination and 5.6° (1°-17°) for version. The accuracy of the navigation system over conventional freehand cup placement is validated by this study.

Paleomagnetic and rock-magnetic survey of eocene dike swarms from the Tecalitlan area (Western Mexico): Tectonic implications

For long time the western-central Mexico has been affected by oblique subduction caused by Farallon plate beneath North America. As result, smaller plates (e.g. Cocos Plate), several fault systems outlining crustal blocks (e.g. Michoacan block) and magmatic arcs (e.g. Paleocene-Early Oligocene magmatism and the Trans-Mexican Volcanic Belt) were developed. Still, no paleomagnetic data are available for Oligocene and Miocene. The principal aim of this study is to evaluate whether the tectonic rotations and relative motions of these blocks occurred before the Miocene. Here, we report a detailed rock-magnetic and paleomagnetic results from Tecalitlan area, located in the Michoacan block. Sixteen sites (about 150 oriented samples) were collected including one radiometrically dated diabase dike (35.0 ± 1.8 Ma). Rock-magnetic experiments permitted identification of magnetic carriers and assessment of the paleomagnetic stability. Continuous susceptibility measurements vs temperature in most cases yield reasonably reversible curves with Curie points close to that of magnetite. Reliable paleomagnetic directions were obtained for 12 sites. Inclination I and declination D of the mean paleomagnetic direction obtained in this study are I = 33.1°, D = 345.0°, and Fisherian statistical parameters are k = 25, α95 = 8.9°. The corresponding mean paleomagnetic pole position is Plat = 75.7°, Plong = 166.6°, K = 31, A95 = 8.0°. The mean inclination is in reasonably good agreement with the expected value, as derived from reference poles for the stable North America. Magnetic declination is not significantly different from that expected which is in disagreement with a counterclockwise tectonic rotation of about 20° previously reported for the studied area. Based on paleomagnetic results obtained in this study compiled with those currently available from the Michoacan Block, we propose a simple model suggesting that sometime in Eocene epoch the convergence vector of the Farallon plate relative to North America plate was normal to the trench before reaching an actual oblique convergence.

Relationships Between Muscular Strength and Batting Performances in Collegiate Baseball Athletes

Previous research has suggested that grip strength may be an important contributor to batting related performance in the sport of baseball (Spaniol et al. 2006). PURPOSE: To determine the role of several measures of muscular strength on both laboratory and field-based measures of batting performance. METHODS: Members of an NCAA Div. I baseball team (n = 31, body weight [BW] = 89.9 ± 9.6 kg) volunteered to participate in a series of strength and batting tests. Prior to initiating off-season training, one repetition maximum (1 RM) measures were obtained for grip strength (mean of right & left), parallel barbell back squat and incline bench press. A radar gun was used to determine batted ball velocity (BBV) while hitting from a tee. Data from a subset of athletes (n = 11) who had participated in competition the previous season were used to determine batting average (BA) and slugging percentage (Slug %). Pearson product-moment correlation coefficients were used to determine relationships between muscular strength and batting performances (p<0.05). RESULTS: One RM strength and BBV (X ± SD) were as follows; right grip = 49.0 ± 8.6 kg, left grip = 46.3 ± 9.0 kg, squat = 140.0 ± 18.1 kg, incline bench press = 88.4 ± 15.4 kg and BBV = 37.4 ± 3.0 m·s−1. Relationships (rcrit = 0.35) between muscular strength and BBV were as follows; mean grip (r = 0.37) and incline bench press (r = 0.40). Although squat strength was not sig. related to BBV, it was correlated to upper body strength (r = 0.55). Additionally, BW was related to BBV (r = 0.41). For the subset of previously competing athletes, grip strength was correlated to (rcrit = 0.58) Slug % (r = 0.59) and non-significantly to BA (r = 0.46). Discussion: These data exhibit a relationship between grip strength and BBV, although the correlation coefficient was lower than previous reports (r = 0.83, Spaniol 2006). It has been speculated that this relationship is due in part to the necessary rigid link between the bat and the upper limbs at the point of ball impact. Additionally, the relationships between upper body strength and BBV, as well as upper vs. lower body strength, suggest the important role of total body strength in batting performance. While BW is certainly a contributing factor to BBV, it is unlikely that this accounts for all the relationship between strength and BBV. The results for BA and Slug % from the previous season further support the role of muscular strength in batting performances. It should be noted that grip strength for these athletes was lower than previous reports for NCAA Div. I baseball athletes (Spaniol 2005). This may be due to the prior training status of the athletes in the present study, or to the different hand grip dynamometer used, or both. Finally, the BBV velocity reported in the present study was similar to previous reports for NCAA Div. I baseball athletes (Spaniol 2006; 39.1 m·s−1). Practical Applications: While successfully hitting a baseball certainly requires high levels of motor control and skill development, it is clear that muscular strength (i.e., grip strength, upper and lower body strength) is an important contributing factor. Strength and conditioning programs for baseball must be sure to provide adequate amounts of heavy resistance exercise training to ensure appropriate strength levels are attained.

Archaeomagnetic results on three Early Iron Age salt-kilns from Moyenvic (France)

Variations of the Earthfs magnetic field during the first millennium BC in western Europe remain poorly constrained, especially archaeointensity changes. Three salt-kilns (MOA, MOB and MOC) sampled in Moyenvic (Lorraine, eastern France) have been studied to provide new reference data. Each kiln has been dated by radiocarbon to originate from the Early Iron Age or Hallstatt period (between VIII and Vth Century BC). Rock magnetic experiments and hysteresis results suggest the predominance of pseudo-single domain (PSD) Ti-poor magnetite. Archaeomagnetic directions obtained by thermal and alternating field demagnetizations have high mean inclination (close to 70.) and declination (between 19 and 31.). A first set of classical Thellier.Thellier experiments was conducted on 46 samples with a laboratory field almost parallel to the direction of the characteristic remanent magnetization (ChRM). Only 24 of these specimens present a linear NRM.TRM plot. For other specimens, NRM.TRM plots are concave-up with positive pTRM checks. The very large dispersion observed between the determined palaeointensity values suggests some artefacts have not been fully recognized. A second set of Thellier experiments was conducted on 34 sister specimens with the laboratory field applied quasi-perpendicular to the ChRM. In these cases,mineralogical evolutions during heating and chemical remanent magnetization acquisitions have been clearly recognized, despite positive pTRM checks. The concave-up shapes of NRM.TRM plots appear mainly due to mineralogical alteration rather than to the presence of PSD.MD grains. For the entire set of samples the success rate of the palaeointensity determinations is very low with 80 per cent of the samples rejected. Nevertheless, reliable mean archaeointensities have been obtained for two of the three kilns (MOA, 80.1 } 14.5 ƒET and MOB, 86.6 } 6.9 ƒET at the latitude of Paris). The high field strength and the archaeomagnetic directions determined, combined with previous published data, provide further evidence for important changes of the Earth magnetic field in Europe during the first half of the first millennium BC. These large variations of the geomagnetic field during the Iron Ages indicate that archaeomagnetism is highly suitable for dating of structures from this period.

A Comparison Between Imageless Navigated and Manual Freehand Technique Acetabular Cup Placement in Total Hip Arthroplasty

The purpose of this study was to compare acetabular component positioning using an imageless system to a matched control group using conventional techniques. Thirty procedures were performed using navigation. A multislice computed tomographic scan was used to assess cup position. There was no significant difference between mean inclination ( P = .11) and anteversion ( P = .24) but a statistical significant difference for mean deviation from the desired position for inclination ( P = .003) and anteversion ( P = .007). There was a significant difference in the percentages of correctly placed cups with inclination ( P = .046) and with anteversion ( P = .006). Combining both anteversion and inclination, there was a significant difference ( P = .01). We demonstrated a significant increase in accuracy of placement of acetabular cups within the desired position and safe zone using imageless navigation.

Hallux valgus correction in metatarsus adductus

Background To describe the frequent association of metatarsus adductus and hallux valgus in the adult foot as a cause of insufficient correction after application of common surgical techniques. Method and material A retrospective review was made of 16 cases in 15 patients with clinical and radiological metatarsus adductus operated by Hallux valgus from 2006 to 2008. In all cases, a correction of the deformity lower than 10° was observed. Results The mean postoperative correction was 9°. The mean inclination of first cuneummetatarsal joint was 65°. We did not find any relationship between Metatarsus adductus magnitude and postoperative Hallux valgus correction. The best results were observed with Scarf Osteotomy. Discussion There is controversy on the Metatarsus adductus and Hallux valgus relationship. Although poor application of the surgical techniques is the most important cause of correction failure, the limited literature references and the comparison with similar results, may show this association as a cause of the difficulty in the application of conventional surgical techniques. Poor performance of these techniques is an important cause of correction failure and must be evaluated. Conclusion Metatarsus adductus in the adult foot with Hallux valgus to be operated must be detected and seen as a deformity that is difficult to correct. Preoperative planning and choice of surgical technique must assess these angular deformities to avoid a poor result for the patient.

Corrección del Hallux valgus en metatarso adductus

Background To describe the frequent association of Metatarsus adductus and Hallux valgus in the adult foot as a cause of insufficient correction after application of common surgical techniques. Method and material A retrospective review was made of 16 cases in 15 patients with clinical and radiologic metatarsus adductus operated by Hallux valgus from 2006 to 2008. In all cases, a correction of the deformity lower than 10° was observed. Results The mean postoperative correction was 9°. The mean inclination of first cuneometatarsal joint was 65°. We did not find any relationship between Metatarsus adductus magnitude and postoperative Hallux valgus correction. The best results were observed with Scarf Osteotomy. Discussion There is controversy on the Metatarsus adductus and Hallux valgus relationship. Although poor application of the surgical techniques is the most important cause of correction failure, the limited literature references and the comparison with similar results, may show this association as a cause of the difficulty in the application of conventional surgical techniques. Poor performance of these techniques is an important cause of correction failure and must be evaluated. Conclusion Metatarsus adductus in the adult foot with Hallux valgus to be operated must be detected and seen as a deformity that is difficult to correct. Preoperative planning and choice of surgical technique must assess these angular deformities to avoid a poor result for the patient.

Comparison of biomechanical loading during use of conventional stud welding equipment and an alternate system

We investigated the effect of an alternative welding system designed to reduce exposure to extreme trunk flexion on measures of trunk inclination and muscle activity. Among 10 participants, data were collected while using conventional stud welding equipment and while using the alternate system. Paired t-tests were used to compare results between the two welding systems. Mean trunk inclination angle was reduced with the alternate system (34.4° versus 9.7°, p < 0.01). Percent time with trunk inclination angles greater than 60° was also reduced (40.0% versus 4.7%, p < 0.01). In general, the alternate system resulted in less desirable upper trapezius muscle activity levels. The alternate system appears to be effective in reducing exposure to extreme trunk flexion among stud welders. Continued development of the system should explore features designed to reduce shoulder forces and improve productivity.

Palaeomagnetism and 40Ar/39Ar geochronology of upper Palaeogene volcanic rocks from Central Tibet: implications for the Central Asia inclination anomaly, the palaeolatitude of Tibet and post-50 Ma shortening within Asia

SUMMARY Palaeomagnetic results from upper Palaeogene volcanics from three localities in the Qiangtang terrane of Central Tibet record a maximum likelihood palaeolatitude of 28.7 ± 3.7°N. These are the first volcanic-based palaeomagnetic results from the plateau interior that appear to average secular variation well enough to yield a reliable palaeolatitude estimate. This palaeolatitude estimate is significantly lower than the ∼36 ± 3°N predicted for Central Tibet by late Palaeogene Eurasia reference poles, consistent with the so-called Central Asia inclination anomaly, but it is consistent with values predicted from upper Palaeogene reference poles for Mongolia. The mean inclination of coeval sedimentary rocks from Central Tibet is ∼15 ± 5° shallower than our volcanic results, similar to the magnitude of sedimentary inclination shallowing estimated from Elongation/Inclination analysis of remanent directions in clastic rocks from the same region. We conclude that most of the inclination anomaly observed in volcanic rocks and that which remains after removal of sedimentary flattening in clastic rocks probably is due to the combined effect of reference poles that are not representative of stable Asia and by Cenozoic intracontinental shortening within Central Asia on the order of several hundred (not more than 1000) kilometers. Our compilation of palaeomagnetic data from the Qiangtang terrane further suggest that the southern margin of the Lhasa terrane (the southern margin of pre-India Asia) was located as far south as 20°N throughout Eocene time. These palaeolatitudes, in conjunction with the upper crustal shortening record for Asia, indicate that only approximately one third of the post-50 Ma India–Asia convergence is partitioned in Asian lithosphere. Low latitudes also imply that much of the proto-Tibetan plateau occupied southerly, tropical to subtropical latitudes, which has important implications for the weathering and erosion of the Tibetan plateau, palaeoaltimetry proxies and early Cenozoic climate dynamics.

Optimal acetabular orientation for hip resurfacing

Pseudotumours are a rare complication of hip resurfacing. They are thought to be a response to metal debris which may be caused by edge loading due to poor orientation of the acetabular component. Our aim was to determine the optimal acetabular orientation to minimise the risk of pseudotumour formation. We matched 31 hip resurfacings revised for pseudotumour formation with 58 controls who had a satisfactory outcome from this procedure. The radiographic inclination and anteversion angles of the acetabular component were measured on anteroposterior radiographs of the pelvis using Einzel-Bild-Roentgen-Analyse software. The mean inclination angle (47 degrees, 10 degrees to 81 degrees) and anteversion angle (14 degrees, 4 degrees to 34 degrees) of the pseudotumour cases were the same (p = 0.8, p = 0.2) as the controls, 46 degrees (29 degrees to 60 degrees) and 16 degrees (4 degrees to 30 degrees) respectively, but the variation was greater. Assuming an accuracy of implantation of +/- 10 degrees about a target position, the optimal radiographic position was found to be approximately 45 degrees of inclination and 20 degrees of anteversion. The incidence of pseudotumours inside the zone was four times lower (p = 0.007) than outside the zone. In order to minimise the risk of pseudotumour formation we recommend that surgeons implant the acetabular component at an inclination of 45 degrees (+/- 10) and anteversion of 20 degrees (+/- 10) on post-operative radiographs. Because of differences between the radiographic and the operative angles, this may be best achieved by aiming for an inclination of 40 degrees and an anteversion of 25 degrees.

Maximum likelihood solution for inclination-only data in paleomagnetism

SUMMARY We have developed a new robust maximum likelihood method for estimating the unbiased mean inclination from inclination-only data. In paleomagnetic analysis, the arithmetic mean of inclination-only data is known to introduce a shallowing bias. Several methods have been introduced to estimate the unbiased mean inclination of inclination-only data together with measures of the dispersion. Some inclination-only methods were designed to maximize the likelihood function of the marginal Fisher distribution. However, the exact analytical form of the maximum likelihood function is fairly complicated, and all the methods require various assumptions and approximations that are often inappropriate. For some steep and dispersed data sets, these methods provide estimates that are significantly displaced from the peak of the likelihood function to systematically shallower inclination. The problem locating the maximum of the likelihood function is partly due to difficulties in accurately evaluating the function for all values of interest, because some elements of the likelihood function increase exponentially as precision parameters increase, leading to numerical instabilities. In this study, we succeeded in analytically cancelling exponential elements from the log-likelihood function, and we are now able to calculate its value anywhere in the parameter space and for any inclination-only data set. Furthermore, we can now calculate the partial derivatives of the log-likelihood function with desired accuracy, and locate the maximum likelihood without the assumptions required by previous methods. To assess the reliability and accuracy of our method, we generated large numbers of random Fisher-distributed data sets, for which we calculated mean inclinations and precision parameters. The comparisons show that our new robust Arason–Levi maximum likelihood method is the most reliable, and the mean inclination estimates are the least biased towards shallow values.

Estudio de réplicas del Terremoto de Limón usando datos locales: resultados e implicaciones tectónicas

An aftershock study of the Limon earthquake of April 22, 1991 (Ms= 7.6) was done combining data from a temporal network of seismic stations localed inside the afertershock area, and data obtained from the Red Sismologica Nacional (RSN, ICE-UCR). A definition of the aftershock area of 85 x 45 km2 were the location process of a good sample of aftershocks (Mc from 2.4 to 4.0). Also, we estimated that the rupture surface of the mainshock has a mean inclination of 23° to the SW. We that the fault shallows from the Costa Rica-Panama border zone to the northwest side of the rupture area. Some of the hypocenters located suggests that some secondary thrust and siecstral strike slip faults were reactivaded by the mainshock.

Light scattering by textured transparent electrodes for thin-film silicon solar cells

A model is presented to quantify key surface characteristics and simulate light scattering by textured transparent conducting oxides—an important class of materials for thin-film silicon (Si) solar cells. The characterization routine is solely based on the atomic force microscopy (AFM) height-encoded data and eliminates the need for time-consuming measurements of angle resolved scattering (ARS) and spectrally resolved scattering (SRS) of light. The presented method is intended for fast and precise inline monitoring of textured transparent electrodes for superstrate thin-film single- and tandem-junction Si solar cells in the production environment. Root-mean-square roughness, mean inclination angle and a fit parameter of three-dimensional Fast Fourier Transform (3D FFT) with the information on spatial feature distribution can be routinely measured with a high precision from a single AFM scan and are used to simulate both ARS and SRS dependencies. The model explains the observed difference in peak position and width of the ARS of surfaces with different morphologies. Special focus is on chemically textured aluminum-doped zinc oxide (AZO). Results on traditional monolithic AZO and new multi-layer stack designs are presented. The effect of an ‘insertion’ layer on light scattering properties and 3D FFT ‘fingerprints’ is also discussed.

Ecology of sandstone ravine myxomycetes from Saxonian Switzerland (Germany)

We describe the ecology of a highly specialized community of ravine myxomycetes from sandstone gorges of the Saxonian Switzerland region (near Dresden, Germany). Five taxa, Colloderma robustum, Diderma ochraceum, Lamproderma columbinum, L. puncticulatum agg. and Lepidoderma tigrinum, account for 87% of all records. Colloderma robustum and Diderma lucidum are new records for Germany; Diderma ochraceum was known from a few collections only. A total of 127 small-scale vegetation releves showed that the community occurs only in deep and narrow ravines (mean horizon openness 4.9%) on nearly vertical rocks (mean inclination 79°), and preferentially in northern exposition (42% of all releves). Substrate pH is very acidic (mean 3.35). At the fructification time of the myxomycetes (beginning of October) the microclimate is very constant with temperatures around 10°C and nearly 100% relative humidity around the day. Beside green algae (associated with 100% of all myxomycete records, most common was Coccomyxa confluens (Kutz.) Fott s.l.) the bryophytes Mylia taylorii (64%), Dicranodontium denudatum (59%), Tetraphis pellucida (50%) and Diplophyllum albicans (40%) were of high indicator value for this community. Low values for niche width of the five more common myxomycete species reflect the high degree of specialization for the community as a whole, whereas niche overlap between species is high. Low values for the Cole index of association can be interpreted as competition between species or, more likely, reflect the relative rarity of fruiting colonies.

Quantification of 3-D soil macropore networks in different soil types and land uses using computed tomography

Summary The importance of soil macropores as preferential pathways for water, air, and chemical movement in different soils has long been recognized. However, quantification of complex macropore structures and their relationships to soil types and land uses remains elusive. The objectives of this study were to (1) quantify 3-D macropore networks in intact soil columns using an improved approach and (2) investigate the effects of soil type and land use on soil macropore characteristics. Two soils with contrasting textures and structures (Hagerstown silt loam and Morrison sand) from two land uses (row crop and pasture) were investigated. Intact soil columns, 102 mm in diameter and about 350 mm in length, were taken for each soil type-land use combination. The soil columns were scanned using X-ray computed tomography at a voxel resolution of 0.234 mm × 0.234 mm × 2.000 mm. After reconstruction, characteristics of macropore networks were quantified, including continuous macroporosity change along depth, macropore size distribution, network density, surface area, length density, length distribution, mean hydraulic radius, tortuosity, inclination (angle), and connectivity (path number and node density). The approach we developed provided an improved quantification of complex 3-D macropore networks. The analysis of variance indicated that soil type, land use, and their interaction significantly influenced macroporosity, network density, surface area, length density, node density, and mean angle. The interaction of soil type and land use also influenced mean tortuosity and hydraulic radius. Within the same soil type, the soils under pasture land use had greater macroporosity, length density, and node density than that under row crop, especially in the subsoil. This was due to greater organic matter content and more biota activities in the pasture. Within the same land use, the Morrison sand displayed lower overall macroporosity than the Hagerstown silt loam because of weaker structure and higher amount of rock fragments in the Morrison soil and thus less suited for biota activities. The results from this study provide improved quantitative evaluation of a suite of soil macropore features that have significant implications for non-equilibrium flow prediction and chemical transport modeling in field soils.

New paleomagnetic results from the Lhasa block: Revised estimation of latitudinal shortening across Tibet and implications for dating the India–Asia collision

Knowing how and when the Tibetan Plateau formed is of global concern as high topography modifies climate circulation patterns and alters species migration paths. Previous paleomagnetic work suggested that intracontinental shortening from deformation related to the India–Asia collision played a major role in building the Tibetan Plateau. However, these studies were derived from red bed facies, which are often afflicted by inclination shallowing, leading to overestimates of continental shortening. We report new paleomagnetic data from the Lhasa block, the southern continental margin of Asia before the India–Asia collision. A high temperature, characteristic remanent magnetization (ChRM) was isolated from 43 sites of Late Cretaceous red beds, 32 sites of Late Cretaceous lava flows, and nine sites of Eocene tuffs. All the ChRM directions are significantly different from the present-day geomagnetic field, and the mean directions of red beds, lava flows and tuffs pass the fold test. The distribution patterns of ChRM directions derived from volcanic rocks are consistent with a secular variation model, suggesting that secular variation was likely averaged out. In contrast, the red bed ChRM directions exhibit an east–west elongated distribution pattern, indicative of inclination flattening. The mean ChRM inclination of the red beds, 23.5°±2.5°, is consistent with previous results, but significantly shallower than that of 41.9°±4.4° carried by the coeval lava flows. An elongation―inclination analysis of the red bed ChRM directions yielded an unflattened mean inclination of 39.7°, with 95% confidence limits between 37.7° and 41.9°. The paleolatitudes of the Late Cretaceous volcanic rocks and inclination-corrected sediments suggest about 10° less shortening occurred between Lhasa and Siberia than previous estimates, with total shortening lying between 3.3°±2.6° and 7.3°±5.4° since the Late Cretaceous. The mean ChRM inclination derived from the Eocene tuffs, 51.8°±5.2°, is indistinguishable from the expected reference direction. Our new results imply that India–Asia convergence was accommodated mainly through consumption of the India plate and yield a much younger age (ca. 43Ma) for the initial India–Asia collision than previously estimated by paleomagnetic data.