Angular Relationships Research Articles

Timing of Cleavage Development in Relation to Folding and its Implications: An Example from the Deformed Mesoproterozoic Sedimentary Cover of Kaladgi Basin, Southwestern India

ABSTRACT Detailed analysis of cleavage-fold relationships in the Mesoproterozoic cover sediments of Kaladgi basin, south western India, revealed three types of timing relationships between cleavage and folds: (1) cleavage developed earlier than folds. (2) Cleavage developed later at some stage of folding and (3) non-development of cleavages in folds. In the first case cleavage developed earlier than the folding. Evidences that support such an interpretation include high cleavage-bedding angle throughout the fold, asymmetric fanning of cleavage in the folds with large fan angles and rotation of cleavage more in the steep and short limbs of asymmetric fold. In the second case, cleavage initiated later at some stage during folding which is evident from low cleavage fan angles, relatively low cleavage–bedding angles in the limbs of folds and the offset of bedding trace against cleavage trace due to pressure solution. Even though pressure solution is ubiquitous throughout the fold the effects of offset are more pronounced in the limbs compared to that in the hinge due to changing angular relationship of bedding and cleavage throughout the fold. In the third case, cleavage is absent in the folds resulting in its sporadic occurrences and reflects its diachronous nature. The final geometry of cleavage in relation to folds at any location is a combined effect of relative timing of cleavage development and mechanism of folding involving layer parallel shortening, flexural slip, tangential longitudinal strain, syn- to postfold flattening and hinge migration.

THERMAL ENERGY GENERATION FROM A SOLAR COLLECTOR PARABOLIC DISH REFLECTOR

A prototype of a small modularity parabolic dish reflector or PDR solar collector with two-axis solar tracking system was designed and built at the National Polytechnic Institute (IPN) in MA©xico. The purpose is to generate high temperature thermal energy for application in services of small and medium industry as well as domestic uses. The solar tracking in two-axis was developed based on angular relationships and a control system with proportional-integral action so that even when there is an obstruction of solar radiation either by cloud cover, buildings, trees or any other object that generates shade, the collector remains oriented towards the Sun. For operating and monitoring the prototype, a flow control module and a human machine interface or HMI were developed and implemented, allowing by means of a computer interface, the monitoring of solar radiation, temperature for thermal evaluation. The experimental data obtained indicated that the prototype can generate 30 kg of steam saturated starting from water at an ambient temperature of 298 K.

Open-Closed-Loop PD Iterative Learning Control Corrected With the Angular Relationship of Output Vectors for a Flexible Manipulator

A new iterative learning control (ILC) approach combined with an open-closed-loop PD scheme is presented for a flexible manipulator with a repeatable motion task in the case that only the endpoint pose of the flexible link is measurable. This approach takes advantage of the fact that the ILC performance is independent of the model used, thereby overcoming the drawback of the heavy reliance of PD controllers on the modeling accuracy. The open-closed-loop PD controller is mainly used to simultaneously reduce the effects of the modeling error and disturbances to enhance the controller's robustness. Meanwhile, an angular correction term is introduced by using the angular relationship of the system outputs to reward or penalize the ILC law. Specifically, when the current output tends toward the expected trajectory, the ILC law is enhanced accordingly; otherwise, it is penalized. The convergence conditions for the proposed approach are obtained through theoretical analysis, and experiments using a real flexible manipulator are presented. The results show that the proposed ILC scheme can overcome the impact of the endpoint error caused by link flexibility and has a good control effect.

Stratigraphy and Facies Analysis of the Govanda Formation from Western Zagros, Kurdistan Region, Northeastern Iraq

Stratigraphy and Facies Analysis of the Govanda Formation from Western Zagros, Kurdistan Region, Northeastern Iraq

Comparative Analysis of a Coaxial Magnetic Gear With a Flux Concentration Rotor and Consequent Pole Rotor Typology

By utilizing magnetic field space modulation magnetic gearboxes (MGs) are able to create speed amplification without any physical contact [1–3]. An example of a flux-focusing coaxial MG is illustrated in Fig. 1. This coaxial MG consists of an inner rotor 1 that contains $p_{1} = 4$ pole-pairs an outer rotor 3 with $p_{3} = 13$ pole-pairs and a central ferromagnetic segment central rotor 2 that consists of $n_{2} = 17$ pieces. The $n_{2}$ ferromagnetic segments serve to modulate the inner and outer rotor magnetic fields. In order to create the highest level of field coupling between the inner and outer rotors the number of ferromagnetic segments must be chosen to satisfy $n_{2} = p_{1}+p_{3}$. With this condition satisfied the rotor angular velocity relationship between each rotor is $\mathrm{w}_{2} \mathrm{p}_{2} = \mathrm{w}_{3} \mathrm{p}_{3}+ \mathrm{w}_{1} \mathrm{p}_{1}$ where the subscript denotes rotor number. If the outer rotor is fixed $( \omega _{3} = 0)$ the torque will be maximized and the gearing ratio will be $\mathrm{w}1 = $ Gw 2 where $\mathrm{G} = n_{2}/ p_{1}$. For the example MG shown in Fig. 1 the gear ratio is $\mathrm{G} = 4.25$. In order to try to increase the torque density of a MG a range of different coaxial type rotor typologies have recently been investigated [4–14]. Along with the flux focusing MG design two other coaxial radial type MG rotor typologies that have been shown to create high torque density are the flux concentration Halbach rotor typology [15] and the consequent pole triple-PM rotor MG typology [16]. In this paper, these two design typologies are compared for the first time. The objective is to provide an idealized comparative analysis of the two competing typologies and then present the experimental design and testing of the best design.

Nonlocal Damage Mechanics for Quantification of Health for Piezoelectric Sensor

In this paper, a novel method to quantify the incubation of damage on piezoelectric crystal is presented. An intrinsic length scale parameter obtained from nonlocal field theory is used as a novel measure for quantification of damage precursor. Features such as amplitude decay, attenuation, frequency shifts and higher harmonics of guided waves are commonly-used damage features. Quantification of the precursors to damage by considering the mentioned features in a single framework is a difficult proposition. Therefore, a nonlocal field theory is formulated and a nonlocal damage index is proposed. The underlying idea of the paper is that inception of the damage at the micro scale manifests the evolution of damage at the macro scale. In this paper, we proposed a nonlocal field theory, which can efficiently quantify the inception of damage on piezoelectric crystals. The strength of the method is demonstrated by employing the surface acoustic waves (SAWs) and longitudinal bulk waves in Lithium Niobate (LiNbO3) single crystal. A control damage was introduced and its manifestation was expressed using the intrinsic dominant length scale. The SAWs were excited and detected using interdigital transducers (IDT) for healthy and damage state. The acoustic imaging of microscale damage in piezoelectric crystal was conducted using scanning acoustic microscopy (SAM). The intrinsic damage state was then quantified by overlaying changes in time of flight (TOF) and frequency shift on the angular dispersion relationship.

Environmentally Sensitive Fluorescent Nucleoside Analogues for Surveying Dynamic Interconversions of Nucleic Acid Structures.

Nucleic acids are characterized by a variety of dynamically interconverting structures that play a major role in transcriptional and translational regulation as well as recombination and repair. To monitor these interconversions, Förster resonance energy transfer (FRET)-based techniques can be used, but require two fluorophores that are typically large and can alter the DNA/RNA structure and protein binding. Additionally, events that do not alter the donor/acceptor distance and/or angular relationship are frequently left undetected. A more benign approach relies on fluorescent nucleobases that can substitute their native counterparts with minimal perturbation, such as the recently developed 2-thienyl-3-hydroxychromone (3HCnt) and thienoguanosine (th G). To demonstrate the potency of 3HCnt and th G in deciphering interconversion mechanisms, we used the conversion of the (-)DNA copy of the HIV-1 primer binding site (-)PBS stem-loop into (+)/(-)PBS duplex, as a model system. When incorporated into the (-)PBS loop, the two probes were found to be highly sensitive to the individual steps both in the absence and the presence of a nucleic acid chaperone, providing the first complete mechanistic description of this critical process in HIV-1 replication. The combination of the two distinct probes appears to be instrumental for characterizing structural transitions of nucleic acids under various stimuli.

Constraining the three-dimensional orbits of galaxies under ram pressure stripping with convolutional neural networks

Ram pressure stripping (RPS) of gas from disk galaxies has long been considered to play vital roles in galaxy evolution within groups and clusters. For a given density of intracluster medium (ICM) and a given velocity of a disk galaxy, RPS can be controlled by two angles (theta and phi) that define the angular relationship between the direction vector of the galaxy's three-dimensional (3D) motion within its host cluster and the galaxy's spin vector. We here propose a new method in which convolutional neutral networks (CNNs) are used to constrain theta and phi of disk galaxies under RPS. We first train a CNN by using ~10^5 synthesized images of gaseous distributions of the galaxies from numerous RPS models with different theta and phi. We then apply the trained CNN to a new test RPS model to predict theta and phi. The similarity between the correct and predicted theta and $\phi$ is measured by cosine similarity (cos-Theta) with cos-Theta =1 being perfectly accurate prediction. We show that the average cos-Theta among test models is ~0.95, which means that theta and phi can be constrained well by applying the CNN to the spatial distributions of their gas. This result suggests that if the ICM is in hydrostatic equilibrium (thus not moving), the 3D orbit of a disk galaxy within its host cluster can be constrained by the spatial distribution of the gas being stripped by RPS. We discuss the applications of the method to HI surveys such as WALLABY and SKA projects.

Analysis by UAV Digital Photogrammetry of Folds and Related Fractures in the Monte Antola Flysch Formation (Ponte Organasco, Italy)

The deformation structures (folds and fractures) affecting Monte Antola flysch formation in the area of Ponte Organasco (Northern Apennines-Italy) were analyzed by Unmanned Aerial Vehicle Digital Photogrammetry (UAVDP). This technique allowed the realization of Digital Outcrop Models (DOMs) interpreted in a stereoscopic environment by collecting a large number of digital structural measures (strata, fractures and successively fold axes and axial planes). In particular, by UAVDP was possible to analyze the relationships between folds and fractures all along the study structures. The structural analysis revealed the presence of a series of NE-vergent folds characterized by a typical Apenninic trend and affected by four main sets of fractures. Fractures are always sub-orthogonal to the bedding, maintains constant angular relationships with the bedding and seems linked to the folding deformation. The study shows that the UAVDP technique can overcome the main limitations of field structural analysis such as the scarce presence and the inaccessibility (total or partial) of rock outcrops and allows for acquiring images of rock outcrops at a detailed scale from user-inaccessible positions and different points of view and analyze inaccessible parts of outcrops.

New Insights on the Impact of Tidal Currents on a Low-gradient, Semi-enclosed, Epicontinental Basin—the Curtis Formation, East-central Utah, USA

Based on a methodic sedimentological analysis, the Late Jurassic (Oxfordian) Curtis Formation unravels the intricate facies variability which occurs in a tide-dominated, fluvially starved, low-gradient, semi-enclosed epicontinental basin. This unit crops out in east-central Utah, between the eolian deposits of the underlying Middle Jurassic (Callovian) Entrada Sandstone, from which it is separated by the J-3 unconformity, and the conformable overlying supratidal Summerville Formation of Oxfordian age. A high-resolution sedimentary analysis of the succession led to the recognition of eight facies associations (FA) with six sub-facies associations. Based on the specific three-dimensional arrangement of these eight facies associations, it is proposed to separate the Curtis Formation into three sub-units: the lower, middle and upper Curtis. The J-3 unconformity defines the base of the lower Curtis, which consists of upper shoreface to beach deposits (FA 2), mud-domi­nated (FA 3a) and sand-dominated heterolithic subtidal flat (FA 3b), sand-rich sub- to supratidal flat (FA 4a) and correlative tidal channel infill (FA 4c). It is capped by the middle Curtis, which coincides with the sub- to intertidal channel-dune-flat complex of FA 5, and its lower boundary corresponds to a transgressive surface of regional extent, identified as the Major Transgressive Surface (MTS). This surface suggests a potential correlation between the middle and the upper Curtis and the neighboring Todilto Member of the Wanakah Forma­tion or Todilto Formation. The upper Curtis consists of the heterolithic upper sub- to intertidal flat (FA 6) and coastal dry eolian dunes belonging to the Moab Member of the Curtis Formation (FA 7), and it conformably overlies the middle Curtis.
 The spatial distribution of these sub-units supports the distinction of three different sectors across the study area: sector 1 in the north, sector 2 in the south-southwest, and sector 3 in the east. In sector 1, the Curtis Formation is represented by its three sub-units, whereas sector 2 is dominated by the middle and upper Curtis, and sector 3 encompasses the extent of the Moab Member of the Curtis Formation.
 This study also highlights the composite nature of the J-3 unconformity, which was impacted by various processes occurring before the Curtis Formation was deposited, as well as during the development of the lower and middle Curtis. Local collapse features within the lower and middle Curtis are linked to sand fluid over­pressure within a remobilized sandy substratum, potentially triggered by seismic activity. Furthermore, the occurrence of a sub-regional angular relationship between the middle Curtis and substratum implies that the area of study was impacted by a regional deformational event during the Late Jurassic, before the deposition of the middle Curtis.
 The spatial distribution of these sub-units supports the distinction of three different sectors across the study area: sector 1 in the north, sector 2 in the south-southwest, and sector 3 in the east. In sector 1, the Curtis For­mation is represented by its three sub-units, whereas sector 2 is dominated by the middle and upper Curtis, and sector 3 encompasses the extent of the Moab Member of the Curtis Formation.
 This study also highlights the composite nature of the J-3 unconformity, which was impacted by various processes occurring before the Curtis Formation was deposited, as well as during the development of the lower and middle Curtis. Local collapse features within the lower and middle Curtis are linked to sand fluid over­pressure within a remobilized sandy substratum, potentially triggered by seismic activity. Furthermore, the occurrence of a sub-regional angular relationship between the middle Curtis and substratum implies that the area of study was impacted by a regional deformational event during the Late Jurassic, before the deposition of the middle Curtis.

Multiple Representations of Space by the Cockroach, Periplaneta americana

When cockroaches are trained to a visual–olfactory cue pairing using the antennal projection response (APR), they can form different memories for the location of a visual cue. A series of experiments, each examining memory for the spatial location of a visual cue, were performed using restrained cockroaches. The first group of experiments involved training cockroaches to associate a visual cue (CS—green LED) with an odor cue (US) in the presence or absence of a second visual reference cue (white LED). These experiments revealed that cockroaches have at least two forms of spatial memory. First, it was found that during learning, the movements of the antennae in response to the odor influenced the cockroaches’ memory. If they use only one antenna, cockroaches form a memory that results in an APR being elicited to the CS irrespective of its location in space. When using both antennae, the cockroaches resulting memory leads to an APR to the CS that is spatially confined to within 15° of the trained position. This memory represents an egocentric spatial representation. Second, the cockroaches simultaneously formed a memory for the angular spatial relationships between two visual cues when trained in the presence of a second visual reference cue. This training provided the cockroaches an allocentric representation or visual snapshot of the environment. If both egocentric and the visual snapshot were available to the cockroach to localize the learned cue, the visual snapshot determined the behavioral response in this assay. Finally, the split-brain assay was used to characterize the cockroach’s ability to establish a memory for the angular relationship between two visual cues with half a brain. Split-brain cockroaches were trained to unilaterally associate a pair of visual cues (CS—green LED and reference—white LED) with an odor cue (US). Split-brain cockroaches learned the general arrangement of the visual cues (i.e., the green LED is right of the white LED), but not the precise angular relationship. These experiments provide new insight into spatial memory processes in the cockroach.

Machine-learning-based atom probe crystallographic analysis

Atom probe tomography is known for its accurate compositional analysis at the nanoscale. However, the patterns created by successive hits on the single particle detector during experiments often contain complementary information about the specimen’s crystallography, including structure and orientation. This information remains in most cases unexploited because it is, up to now, retrieved predominantly manually. Here, we propose an approach combining image analysis techniques for feature selection and deep-learning to automatically interpret the patterns. Application of unsupervised machine learning techniques allows to build and train a deep neural network, based on a library generated from theoretically known crystallographic angular relationships. This approach enables direct interpretation of the detector hit maps, as shown here on the example of numerous pure-Al, and is robust enough to function under various conditions of base temperature, pulsing mode and pulse fraction. We benchmark our approach against recent attempts to automate the pattern identification via Hough-transform and discuss the current limitations of our approach. This new automated approach renders crystallographic atom probe tomography analysis more efficient, feature-sensitive, robust, user-independent and reliable. With that, deep-learning algorithms show a great potential to give access to combined atom probe crystallographic and compositional analysis to a large community of users.

Basilar Invagination: A Craniocervical Kyphosis

For more than a century, odontoid process prolapse, which compresses cranial base structures, has been the hallmark of basilar invagination (BI). The angulation of the whole skull toward the cervical spine may be considered to contribute to BI and odontoid prolapse. The objective of this study was to evaluate the craniocervical angular craniometry of patients with BI compared with patients with Chiari malformation (CM) and normal subjects. Angular craniocervical relationships among midline magnetic resonance imaging scans from patients with BI, patients with CM, and normal subjects were evaluated and compared. Angles were measured by Meazure 2.0 software from digitalized images. Using data from 121 images, 42 patients with BI (14 type I BI, 28 type II BI), 47 patients with CM, and 32 control subjects were evaluated. The BI group had a more acute kyphotic angle than the CM group (P < 0.01) and control group. The kyphosis difference was 17.57 ± 2.3° (P < 0.01) between the BI and CM groups and 21.19 ± 2.3° (P < 0.01) between the BI and control groups. Basal angles were significantly larger in the BI group compared with the other 2 groups. A strong correlation was found with kyphosis and CLV and the clivus-canal angle and cervical lordosis angle (P < 0.01). Craniocervical kyphosis in patients with BI was approximately 20° greater than in normal subjects and patients with CM. Craniocervical kyphosis should be considered a pathophysiologic condition in BI.

Tectonic Implications of Detrital Zircon Ages From Lesser Himalayan Mesozoic‐Cenozoic Strata, Pakistan

AbstractWe carried U‐Pb‐Hf geochronology of the clastic sequence covering upper Mesozoic‐Cenozoic period. The upper Mesozoic sequence is overlain unconformably by the Cenozoic strata, marking regional K‐T boundary, which is mapped as angular unconformity. This angular relationship may strongly indicate a compressional orogenic event that occurred during the Late Cretaceous. Late Cretaceous Kohistan‐Karakoram collision and ophiolite emplacement may account for the development of this compression along the northern Indian margin. The U‐Pb‐Hf isotopic analyses of the upper Mesozoic and lower Cenozoic sequence (Hangu Formation and Lower Patala Formation) are similar to the Tethyan and Lesser Himalayan signatures, which indicate the Indian‐plate provenance. The two younger Cretaceous grains recorded in the Hangu Formation might be derived from the Indian‐plate volcanic rocks and/or Tethyan Himalayan volcanic rocks. The absence of ophiolitic age component in the precollision sequence may indicate that these ophiolites are not exposed until final India‐Eurasia collision. The major shift in provenance is recorded in the upper part of the Patala Formation, where the presence of disconformity and the appearance of &lt;100 Ma detrital zircons indicate the contribution of Eurasian source (i.e., Kohistan‐Ladakh arc; KLA), which is further supported by the ɛHf(t) signatures. Upsection, the contribution from Eurasian source increased in the Early Middle Eocene Kuldana Formation. Therefore, we suggest that the provenance mixing close to Paleocene‐Eocene boundary indicates that the India‐Eurasia collision in the north Pakistan occurred at ∼56–55 Ma and subsequent exhumation increased the contribution of the northern (Eurasian) provenance in the upsection.

Boresight Calibration of GNSS/INS-Assisted Push-Broom Hyperspectral Scanners on UAV Platforms

Low-cost unmanned aerial vehicles (UAVs) utilizing push-broom hyperspectral scanners are poised to become a popular alternative to conventional remote sensing platforms such as manned aircraft and satellites. In order to employ this emerging technology in fields such as high-throughput phenotyping and precision agriculture, direct georeferencing of hyperspectral data using onboard integrated global navigation satellite systems (GNSSs) and inertial navigation systems (INSs) is required. Directly deriving the scanner position and orientation requires the spatial and rotational relationship between the coordinate systems of the GNSS/INS and hyperspectral scanner to be measured. The spatial offset (lever arm) between the scanner and GNSS/INS unit can be measured manually. However, the angular relationship (boresight angles) between the scanner and GNSS/INS coordinate systems, which is more critical for accurate generation of georeferenced products, is difficult to establish. This paper presents three calibration approaches to estimate the boresight angles relating hyperspectral push-broom scanner and GNSS/INS coordinate systems. For reliable/practical estimation of the boresight angles, this paper starts with establishing the optimal/minimal flight and control/tie point configuration through a bias impact analysis starting from the point positioning equation. Then, an approximate calibration procedure utilizing tie points in overlapping scenes is presented after making some assumptions about the flight trajectory and topography of covered terrain. Next, two rigorous approaches are introduced – one using ground control points and other using tie features. The approximate/rigorous approaches are based on enforcing the collinearity and coplanarity of the light rays connecting the perspective centers of the imaging scanner, object point, and the respective image points. To evaluate the accuracy of the proposed approaches, estimated boresight angles are used for orthorectification of six hyperspectral UAV dataset acquired over an agricultural field. Qualitative and quantitative evaluations of the results have shown significant improvement in the derived orthophotos to a level equivalent to the ground sampling distance of the used scanner (namely, 3–5 cm when flying at 60 m).

Spatial orientation of the adult cochlea: rotation, tilt, and angle theta 3.

Quantitative description in adult crania of (1) angular orientation of the basal turn of the cochlea relative to the sagittal (termed "rotation") and Frankfort horizontal (termed "tilt") planes, and angle theta 3 [angular relationship of the line defined by the cochlea's spiral center and cochlear (round) window, to the cochlear window]; (2) orientation of the cochlea relative to the plane defined by the horizontal and vertical portions of the facial nerve; (3) orientation of the basal turn of the cochlea relative to the plane of the posterior semicircular canal; and (4) the association of these orientations with the extent of mastoid pneumatization. Postmortem material analysis. From 41 bequeathed anatomical ear-normal cadaveric cranial, high-resolution CT scans were performed of the five crania with the largest and the five with the smallest mastoids. Eleven points in three-dimensional Cartesian space were appointed and studied with the software program FIJI. The median angle values (and ranges) for right ears were: "rotation" 52° (range 47-61); and, "tilt" 84° (79-89). The planes of the cochlear basal turn and facial nerve approximated superimposition: median 15° (2-19). Angle theta 3 for right ears was median 40° (28-44). Bilateral symmetry was found for the relationships between the planes. However, no association of any planar relationship with mastoid pneumatization was suggested. Considering the range of angles found in clinically normal adult specimens, spatial orientation of the cochlea may explain some of the difficulties in implantation.

Cooperative solving method of chute postures in the bending section of a scraper conveyor

This article proposes a cooperatively analytic solving method that calculates the chute posture in the bending section. The method maintains a good posture of the scraper conveyor during its bending process and solves the feeding trajectory of the shearer accurately and precisely. This method modifies and perfects the existing method to obtain the main parameters of the bending section, including the postures of the chutes and pin rails, and the corresponding extension lengths of the advancing units. A virtual-reality software that can visually simulate this entire operation process under different conditions is developed. Considering the gap between the driving wheel and the pin rails, the relationship between the shearer yaw angle and shearer working trajectory in the feeding stage is investigated for different body lengths. The angular relationship between the left and right driving wheels and the pin rails is also researched. Finally, the proposal is verified in experiments on a test prototype and on physical equipment. This analytic method provides a theoretical basis for the cooperative three-dimension localization of three machines in a fully mechanized coal-mining face, ensuring safe automatic production of the mining face.

Clinical significance of superior articular process as a reference point for free-hand pedicle screw insertion in thoracic spine.

The trajectory of the pedicle screw perpendicular to the SAP (superior articular process) is consistent with the universal trajectory presented in the previous study of the entry point using computed tomography. The ideal entry point and trajectory of pedicle screw insertion have been a matter of considerable debate. We attempted to find the relationship between SAP and entry point and trajectory of the pedicle screw.Thoracic spine CT (computed tomography) scans of 9 volunteers were studied. A safe zone for the trajectory of the screw in the axial (MarginAx) and sagittal (MarginSag) was defined as the zone between lines perpendicular to the SAP along the medial and lateral cortex of the pedicle in the axial section, and the superior and inferior cortex in the sagittal section without violation of the pedicle walls. The midline of MarginAx and MarginSag was defined as the safe entry point of the trajectory in the axial and sagittal planes (TrajectoryAx and TrajectorySag), respectively.MarginAx and MarginSag were 4.14 ± 0.99 and 9.03 ± 2.01 mm, respectively. There was a statistically significant difference in TrajectoryAx between the upper and middle, and between the upper and lower (P = .0076 in both cases), but not between the middle and lower thoracic spine (P = .066). TrajectorySag was within 1 mm at the levels of T4, T8, T11 vertebrae and at 0 mm at the other levels. Thus, the midpoint of MarginSag was within 1 mm from the SAP base.There was a constant angular relationship with the SAP and the pedicle axis; the line perpendicular to the SAP can act as a trajectory. Therefore, we suggest that the SAP might be the only accurate and safe reference for pedicle screw insertion in the thoracic spine perpendicular to the SAP using freehand technique.

Angular and metric analysis of the neural structures in the cerebellopontine angle

Introduction: The cerebellopontine angle (CPA) is a subarachnoid space in the lateral aspect of the posterior fossa. In this study, we propose a complementary analysis of the CPA from the cerebellopontine fissure.Methods: We studied 50 hemi-cerebelli in the laboratory of neuroanatomy and included a description of the CPA anatomy from the cerebellopontine fissure and its relationship with the flocculus and the 5th, 6th, 7th, and 8th cranial nerves (CN) origins.Results: The average distance from the 5th CN to the mid-line (ML) was 19.2 mm, 6th CN to ML was 4.4 mm, 7-8 complex to ML was 15.8 mm, flocculus to ML was 20.5 mm, and flocculus to 5th CN was 11.5 mm, additionally, and the diameter of the flocculus was 9.0 mm. The angle between the vertex in the flocculus and the V CN and the medullary-pontine line was 64.8 degrees.Discussion: The most common access to the CPA is through the retrosigmoid-suboccipital region and this approach can be done with the help of an endoscope. The anatomy of origins of neural structures tends to be preserved in cases of CPA lesions.Conclusion: Knowledge of the average distances between the neural structures in the cerebellar-pontine fissure and the angular relationships between these structures facilitates the use of surgical approaches such as microsurgery and endoscopy.

Humanoid design of mechanical fingers using a motion coupling and shape-adaptive linkage mechanism

This paper proposes a novel underactuated finger mechanism based on a motion coupling and shape-adaptive linkage design that combines anthropomorphic free motion and adaptive grasping. The proposed three-joint finger mechanism with one active Degree of Freedom (DOF) consists of a five-linkage mechanism in the proximal phalanx and a mechanism comprising two parallel planar four-bar linkages in the middle phalanx. The respective mechanism allows the simultaneously rotation of their corresponding phalanges in the plane before making contact with an object, and can fully envelop an object, even if certain phalanges are blocked. The duel parallel four-bar linkage mechanism is adopted to improve the grasping capacity of the distal phalanx. An optimal design of the finger is presented according to anthropomorphic phalanx trajectories and maximized grasping forces obtained with consideration for the angular velocity relationships of the three phalanges and their force transmission performances. The functionality of the proposed finger mechanism is verified through multiple simulations and grasping experiments using a prototype finger.