Longitudinal Plane Research Articles

Altitude Control of Powered Parafoil Using Fractional Sliding-Mode Backstepping Control Combined with Extended State Observer

This paper presents a method of altitude control of the powered parafoil with uncertainties and disturbances based on sliding-mode backstepping control combined with a linear extended state observer (LESO). First, the dynamics of a powered parafoil is derived in the longitudinal plane using its inclination angle. The problem of altitude control is converted to the issue of angle control. Next, uncertainties and disturbances are considered as a total disturbance. An LESO is used to estimate the total disturbance and form an inner-loop compensation. Backstepping control is employed to regulate the inclination angle to follow the desired value. A fractional sliding surface is introduced to the backstepping control. This ensures the transient performance of altitude control of the powered parafoil. Then, stability analysis shows that the observation errors of the LESO are bounded and the control system is uniformly ultimately bounded. Simulation results of an 8 degree-of-freedom powered parafoil illustrate that the LESO can effectively estimate the states of the system and demonstrate the validity and the superiority of the presented method.

Pictorial Essay of Cervical Duplex Ultrasonography.

Objectives: Cervical duplex ultrasonography (CDU) is a simple, non-invasive, portable technique, that provides valuable high-quality visual information about the integrity of the carotid and vertebral vessels, plaque morphology and flow hemodynamics. CDU is useful in the assessment and follow up of patients with cerebrovascular disease as well as other conditions like inflammatory vasculitis, carotid artery dissection and carotid body tumours. CDU is inexpensive and invaluable in smaller centres. Methods: CDU was performed in all patients in both longitudinal and transverse planes in the out-patient clinic. Brightness mode (B-mode) and Doppler waveforms were obtained. Relevant findings were presented. Results: CDU provides real time visualisation of plaque characteristics and follow up, hemodynamic characteristics in Takayasu arteritis, visualisation of dissection. Conclusion: With availability of MR/CT angiography, CDU can be an adjuvant in follow up, triage and early bed-side diagnosis of the vascular diseases. We present our experience with CDU in the out-patient clinics in this pictorial essay.

Motion characteristics simulations of supercavitating vehicle based on a three-dimensional cavity topology algorithm

The maneuvering motion of a supercavitating vehicle pitching and yawing inevitably occurs when navigating in three-dimensional space. In order to give some insights into design of underwater vehicles, the maneuvering motion in the longitudinal and horizontal planes is investigated in this paper. Considering the definition of multi-body coordinate frames, a three-dimensional cavity topology model is proposed to predict the development of the shape of cavity and interact with the supercavitating vehicle in the simulations. Based on the cavity model, an improved planning model is established to calculate the necessary critical parameters of the planning force. According to the mathematical model above, a numerical algorithm is developed to simulate the maneuvering motion of the supercavitating vehicle. The higher algorithm efficiency is validated by the relative error of 10% order of magnitude and the more stable performance. The real-time scene figures and time-varying curves of the dynamic characteristics are obtained through the developed algorithm to study the influence of fins deflection on the maneuvering motion. The developed algorithm is validated to some extent to be a better alternative than the empirical one and provides a new method for analyses of simulation results of supercavitating vehicles.

Elastic and thermal effects upon the propagation of waves with assigned wavelength

It is well known that harmonic longitudinal elastic waves propagate without damping in time, while the heat equation leads to standing modes that decrease exponentially over time. In this article, it is shown that the elastic deformation when coupled with thermal deformation leads to the following effects on the propagation of harmonic longitudinal waves and on standing modes: (a) the harmonic longitudinal waves become damped in time; (b) the standing modes suffer a slower decrease in time in relation to the pure thermal modes; and (c) the propagation speed of harmonic longitudinal waves increases in relation to that predicted by the purely elastic theory. The dependence of the dimensionless parameters that characterize the effects described at these previous points in relation to the material and coupling characteristics is explicitly presented and then is numerically simulated and graphically illustrated. As regards the Rayleigh waves class, although a rigorous mathematical proof is not offered, the numerical results presented for a lot of common thermoelastic materials show the same effects of thermoelastic coupling as in the case of longitudinal harmonic plane waves. The present article systematically synthesizes the thermal effects on wave propagation, and it provides a reference work with regard to the thermoelastic coupling.

Evaluation of a High-Resolution Large-Area Two-Dimensional Detector Array for Pre-Treatment Verification of Multiple-Target SRS Plans Using a Single Isocenter

<h3>Purpose/Objective(s)</h3> Pre-treatment verification of multiple-target SRS plans using a single isocenter is challenging because of small target sizes and multiple off-isocenter targets. Targets located further away from the isocenter are more sensitive to rotational setup variations, increasing the risk of geometrical miss. It demands high-resolution detector for small target sizes and large detector area for measuring multiple targets at once. The purpose of this study is to evaluate a high-resolution large-area two-dimensional (2D) detector array for pre-treatment verification of multiple-target SRS plans using a single isocenter. <h3>Materials/Methods</h3> A 2D detector array was evaluated for this purpose. It is based on a silicon complementary metal-oxide-semiconductor platform, which enables a compact design, fast read-out, and high pixel density with each pixel comprising a radiation-sensitive photodiode, a capacitor and three transistors. Its spatial resolution is 0.4 mm, with 105,000 pixels across a large active area of 120 × 140 mm². Ten multiple-target SRS plans were selected such that each plan has at least 2 targets appear on a longitudinal plane cross the isocenter. All plans were created in a treatment planning system using 6 MV flattening filter free photon beam. The typical plan consisted of one or two coplanar arcs, and two to three non-coplanar arcs. All plans were delivered in patient geometry with the detector center aligned to the plan isocenter. The detector plane was rotated to the corresponding desired longitudinal plane to measure the composite dose in a single measurement. The smallest target measured was 0.12 cc. The largest center-to-center target separation measured was 12 cm. Six of the plans in which the target separations were relatively short were able to be cross verified with a patient-specific quality assurance (PSQA) tool, whose detector area is of 77 × 77 mm². The measured 2D dose distributions in true composite were compared with the calculated dose distributions. Gamma index analysis was performed using 3%/1 mm criteria with a 10% dose threshold. <h3>Results</h3> With the 2D detector array, the gamma passing rates are all greater than 95% except one, which is 93%. The average gamma-passing rate is 97.7%. For the 6 plans cross verified, the average gamma-passing rates are 98.2% and 96.1% with the 2D detector array and PSQA tool, respectively. <h3>Conclusion</h3> The 2D detector array was demonstrated to be suitable and offers an efficient way for pre-treatment verification of multiple-target SRS plans using a single isocenter. The advantages of this 2D array include: 1) High-resolution of 0.4 mm avoids dose interpolations for plans calculated with 0.5 -1.0 mm dose grid and potentially avoids "false positive" results due to more measured points; 2) Large active area of 120 × 140 mm² allows simultaneous verification of multiple targets in true composite in patient geometry.

Numerical modeling of rolling contact fatigue cracks in the railhead

Rolling contact fatigue (RCF) crack is one of dominating damages on the rail surface due to repeated wheel and rail contact. RCF defects, including squats and head checks, can potentially cause rail fracture failure if not treated in time. It is critical to accurately predict the pertinent damage for different operational conditions. A two-stage simulation strategy was proposed to investigate the mechanisms of RCF-induced cracks on the rail, consisting of a dynamic FEM for wheel and rail interaction and a coupled static FEM/BEM for crack growth. It was found that there are two critical wheel positions for crack propagation during wheel approaching to and departing from the pre-existed crack. The different cracking mechanisms at these two critical wheel positions are correlated with the local physical phenomena, i.e., the traction at the wheel/rail interface, the relative distance between the contact patch and crack, and the sliding at crack faces. The twisting of the cracks from the transverse plane to the longitudinal plane at the railhead significantly reduces crack growth in mode I, enhances crack propagation in modes II and III, and shifts the dominant crack growth from the crack front center to the crack corners. The increased incline of the crack in the rolling direction promotes the crack to grow downward in opening mode I.

Muscle and Tendon Stiffness of the Lower Limb of Professional Adolescent Soccer Athletes Measured Using Shear Wave Elastography.

Background: While adolescents have specific risk factors for acute and chronic injury, there is a lack of preventive medicine algorithms for this vulnerable group. Shear wave elastography (SWE) is currently mainly used for assessing muscle and tendon stiffness in adult athletes and can diagnose tissue pathologies such as tendinopathy. The aim was to investigate differences in quadriceps tendon and muscle stiffness between adolescent and adult professional soccer players using SWE and identify lateral imbalances in order to improve the knowledge of preventive medicine algorithms for professional adolescent athletes. Methods: Standardized SWE examinations of both lower limb tendons and muscles (the quadriceps tendon (QT) and the vastus medialis (VM) muscle) in the longitudinal plane and relaxed tendon position were performed in 13 healthy adolescent soccer athletes (13–17 years), and a control group of 19 healthy adult professional soccer athletes (18–29 years). Results: Adolescent soccer players had lower stiffness values for both the quadriceps tendon (3.11 m/s vs. 3.25 m/s) and the vastus medialis muscle (1.67 m/s vs. 1.71 m/s) than adult athletes. Moreover, QT stiffness in adolescent soccer players was significantly lower on the right side (QT: adult 3.50 m/s (2.73–4.56) vs. adolescent 2.90 m/s (2.61–3.12); p = 0.031). Analysis of the lateral differences revealed softer QT and VM tissue on the right side in over two-thirds of adolescent soccer athletes. Over two-thirds of adults had stiffer QT and VM tissue on the right side. Conclusion: In adolescent soccer players, the stiffness of the QT and VM muscle measured by SWE is lower in the right leg. SWE of the musculoskeletal system may thus become a relevant diagnostic tool to detect early lateral imbalances as a main risk factor for injury and may thus contribute to the prevention of acute and chronic injury prevention in adolescent athletes.

ABCL-242 Definition of Bulky Disease in Early-Stage Diffuse Large B-Cell Lymphoma on Longitudinal and Axial Planes

In early-stage diffuse large B-cell lymphoma (DLBCL), tumor bulkiness and stage-adjusted International Prognostic Index (sa-IPI) are the main determinants of treatment and prognosis. Bulky disease is variably defined from 5 to 10 cm. The aim of our study is to investigate the prognostic significance of bulky disease measured on longitudinal and axial planes on computed tomography (CT) imaging. Medical records of patients diagnosed with early-stage DLBCL and treated in King Hussein Cancer Center were reviewed. Maximal longitudinal and axial planes on initial CT scans were reviewed by two radiologists; sa-IPI was calculated as previously described. Correlation between tumor dimensions and relapse-free survival (RFS) and overall survival (OS) was done using the Pearson correlation test. Survival analyses were performed using the Kaplan-Meier method. A total of 127 patients were included with a median age of 47 years. Fifty-one (40.2%) patients were having extranodal involvement, and sa-IPI was 0-1 in 73 (57.4%). Eighty-two (64.6%) patients were treated with combined modality treatment (RCHOP followed by radiotherapy), and the remaining were treated with RCHOP only. A cut-off of 5 cm correlated with RFS in both the longitudinal and axial dimensions and was used to define bulky disease. Seventy-eight (61.5%) patients with bulky disease in either dimension had 3-year RFS of 76.4% versus 95.4% for patients with non-bulky disease (P=0.0045) and 3-year OS of 71.8% versus 93.2% (P=0.0043), respectively. On multivariate analysis, bulky disease (P=0.028) and sa-IPI >1 (P=0.044) were significantly associated with RFS, whereas OS significantly correlated with sa-IPI >1 (P=0.014). In patients with bulky disease, the use of combined modality treatment resulted in better RFS (62.9% vs. 83.3%, P=0.0157) and OS (81.6% vs. 52.1%, P=0.0042). Tumor bulk of more than 5 cm in the longitudinal or axial dimensions on CT scan should be considered in treatment decisions of patients with early-stage DLBCL, including the use of consolidative radiotherapy. More studies are needed to define the best treatment approach in such patients.

Path Following for Unmanned Combat Aerial Vehicles Using Three-Dimensional Nonlinear Guidance

An effective path-following guidance algorithm for unmanned combat aerial vehicles by pursuing a look-ahead target-point along the desired path is devised. The concept of look-ahead pursuit for 3-D path-following was extended from the planar <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathcal {L}_1}$</tex-math></inline-formula> guidance, which has been widely adopted in the application of lateral guidance of fixed-wing drone. Decoupled implementation of the planar guidance action on each of the longitudinal (vertical) and lateral (horizontal) planes supplies longitudinal-lateral acceleration commands in two perpendicular planes which is well accepted by aviation engineers. The computation of the look-ahead point utilizes a finite and iterative numerical search method by introducing an auxiliary path-related parameter. Furthermore, additional implementation-specific details such as the modification of adaptive <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathcal {L}_1}$</tex-math></inline-formula> length and the protection strategies ensuring wide applicability of the algorithm indeed guarantee certain necessity to be considered in real implementation of the guidance law. The improved schemes eliminate complicated coordinate transformations and are built on the path-independent assumption, thus making them easier to be adjusted between various types of paths, including discrete optimal trajectories. Monte Carlo simulations and real-world flight tests have confirmed the effectiveness of the nonlinear guidance algorithm.

An Ultrasonographic Assessment to Document the Prevalence of Various Congenital Uterine Anomalies and their Probable Clinical Outcome in the Eastern Uttar Pradesh Region

Background: Uterine anomalies arise from abnormal fusion of paramesonephric ducts or failure of apoptosis of septum between two ducts leading to abnormal division of the uterine cavity. Initial dearth of universal standard diagnosis was the reason for the improper reporting of the data associated with prevalence of uterine developmental anomalies. But now various authors have reported the prevalence of uterine anomalies using standard diagnostic techniques. The objective of the study was to assess the prevalence of various uterine congenital anomalies among women of reproductive age (15–45 years) with no previous uterine pathology. Methodology: An ultrasound was utilized to take a transabdominal sonographs of both longitudinal and transverse planes from the supine position of participants who were made to consume 500–1000 mL of water to promote diuresis for the duration of the scan. Scans were then interpreted. Results: From a study of 200 participants whose mean age group fell around 30 ± 8 years, 140 of the women were parous and 60 were nulliparous. Twelve of the participants displayed anomalies that included bicornuate, arcuate, and septate. Five cases of the bicornuate uterus (2.5%), four arcuate uterus (2.0%), and three septate uterus (1.5%) were noted. Conclusion: From a sample size of 200, the occurrence of uterine anomalies is 6%, with no cases of uterine agenesis or a hypoplastic uterus.

Offset impacting of a liquid aluminum droplet train on a molten pool on a horizontally moving substrate during TIG-assisted droplet deposition manufacturing

Internal metallurgical defects and poor mechanical properties and surface quality of the formed parts are the most important challenges of metal micro-droplets deposition manufacturing technology. Lack of strong coalescence between neighboring droplets and the blocking effects of periodic ripples on the fusion process are major sources of abovementioned problems. To address this issue, a tungsten inert gas (TIG) welding arc was introduced to pre-melt the material below the droplet impacting location, thus, one droplet train will be deposited on a curved molten pool surface to fabricate deposited layers in an additive approach. In the present work, a numerical model based on the computational fluid dynamics (CFD) method was developed to investigate the dynamic behaviors of successive droplets’ impact and coalescence on the molten pool created by a tilted TIG welding arc, and focuses on the effect of the offset distance between the impacting point of droplet and the longitudinal plane of molten pool on the deposition morphology and the impact-induced molten pool behaviors. The simulated tracks exhibit regular scaly shapes at different offset distances, which is validated against the corresponding experiments. The results indicated that as the lateral offset distance increases, the symmetric spreading and recoiling of the subsequent droplets on the pre-existing bead will be broken due to the inclined and curved solidification front morphologies, the inclined front morphologies are caused by the increased growth rate of the solidification front at the impact zone. With an increased lateral offset distance, the volume of the molten pool decreases, the width of the rear molten pool increases slightly. The calculated solidification parameters are found to be dependent of the offset distance, and vary significantly at the onset of solidification at different portions of the molten pool. The scientific findings provide useful insights for further researches of TIG-assisted DDM.

OCT sequence registration before and after percutaneous coronary intervention (stent implantation)

To assess the progression of coronary artery disease, Optical Coherence Tomography (OCT) pullbacks acquired at different timepoints should be compared. However, the assessment of temporal sequences is a difficult task, as motion artifacts in the longitudinal and axial plane can decrease the quality of the manual inspection. To address this challenge, the current study presents a two-stage computational framework for the longitudinal and axial registration of two OCT pullbacks. During the first stage of the process, we focus on the accurate detection of the matching image pairs from the respective series, while during the second stage we focus on the axial registration of the matched pairs so that their common features are aligned. The dataset used includes 19 patients from two clinical centers, with two OCT pullbacks per patient: one before the stent implantation procedure and one after it. We applied our method on a synthetic dataset of OCT pullbacks, which was generated based on the in-vivo OCT pullbacks to reproduce the motion artifacts across the planes. In addition, the proposed method was validated on the 19 pairs of in-vivo OCT pullbacks with annotated pre/post stent deployment data. The method was able to reduce the alignment error from 32.17±26.14 to 5.6±6.6 frames, the rotational error from 11.59°±11.22° to 1.18°±0.81° and the distance error from 3.07mm±1.52mm to 0.46mm±0.44mm. In addition, the mean Mutual Information similarity increased by 13.47% after the longitudinal registration and an additional 123.33% after the axial registration on top of the previous one.

Ultrasonographical Evaluation of the Median Nerve Mobility in Carpal Tunnel Syndrome: A Systematic Review and Meta-Analysis.

Diagnostic ultrasound is widely used for evaluating carpal tunnel syndrome (CTS), an entrapment neuropathy of the median nerve (MN). Decreased mobility of the MN inside the carpal tunnel has been reported in CTS, and various methods have been used to evaluate MN mobility; however, there is still no conclusive understanding of its connection with CTS. The purpose of this study is to conduct a systematic review and meta-analysis of the current published literature on ultrasonographic evaluations of transverse and longitudinal MN displacement and to identify the relationship between MN mobility and CTS. This study was conducted in accordance with the 2020 PRISMA statement and the Cochrane Collaboration Handbook. Comparative studies that investigated differences in MN displacement between CTS patients and healthy controls were retrieved by searching the Cochrane Library, Embase and PubMed. A total of 15 case–control studies were included. Nine of 12 studies evaluating transverse MN displacement and 4 of 5 studies evaluating longitudinal MN gliding showed that the MN was less mobile in CTS patients than in healthy subjects. Despite the large heterogeneity among the 15 included studies, this systematic review and meta-analysis provide evidence that the mobility of the MN is significantly reduced in both transverse and longitudinal planes in CTS patients compared to healthy controls. Five of the 15 included studies reported that a decrease in transverse or longitudinal MN displacement in CTS was correlated with clinical symptoms or with severity as measured by a nerve conduction study (NCS).

An Investigation of the Bifurcation Behavior of an F-18 Aircraft Model

Bifurcations of equilibria and limit cycles of an F-18 aircraft model have been investigated in this paper based on one or two continuation parameters. First, it is shown that the aircraft can be in a stable straight-and-level flight state by coordinating the elevator deflection and the engine thrust and fixing the other parameters. Second, the aircraft may be disturbed by perturbations out of the longitudinal plane and get into the lateral-directional motion mode by a branch point bifurcation. Third, when the straight flight state loses its stability, body axis angular rates will present periodic or quasi-periodic motion pattern by the Hopf or Neimark–Sacker bifurcation. Finally, bifurcation structure of limit cycles has been exhibited, including the generalized Hopf bifurcation, the Neimark–Sacker bifurcation, the Hopf-Hopf bifurcation and the fold-Neimark–Sacker bifurcation. Meanwhile corresponding bifurcation curves in two-parameter plane have been depicted with the help of numerical continuation techniques.

Anisotropic turbulence in relativistic plasmas

Signs of turbulence have been observed at the relativistic heavy ion collision at high collision energies. We study the signatures of turbulence in this system and find that there are significant departures from isotropic turbulence in the initial and the pre-equilibrium stages of the collision. As the anisotropic fluctuations are subleading to the isotropic fluctuations, the Kolmogorov spectrum can usually be obtained even for the initial stages. However, the energy spectrum and the temperature fluctuations indicate deviations from isotropic turbulence. Since a strong momentum anisotropy exists between the transverse and the longitudinal plane, we study the energy density spectrum in these two planes by slicing the sphere into different planes. The geometrical anisotropy is reflected in the anisotropic turbulence generated in the rotating plasma and we find that the scaling exponent is different in the two planes. We also obtain the temperature spectrum in the pre-equilibrium stages. The spectrum deviates from the Gaussian spectra expected for an isotropic turbulence. All these seem to indicate that the large scale momentum anisotropy persists in the smaller length scales for the relativistic heavy ion collisions.

Теоретичне дослідження коливальних рухів гичкозбиральної машини, встановленої спереду агрегатуючого трактора

Goal. To increase the quality of gathering and reliability of the top-gathering machine by minimizing the amplitude of its angular oscillations during movement on the unevenness of the soil surface. Methods. Theoretical studies were carried out using the basic principles of higher mathematics and theoretical mechanics, in particular the dynamics of a mechanical system. Numerical calculations and graphical dependences were obtained using a PC with the help of the developed and standard programs. Experimental studies were carried out according to standard methods of field multivariate experiments. Results. Based on the developed equivalent scheme of the frontally attached to the wheeled tractor top-gathering machine, the differential equation of the angular oscillations of the top-gathering machine to the center of instantaneous rotation of the tractor attachment mechanism was compiled. The analytical solution of this equation was obtained thanks to the law of oscillatory motion of the top-gathering machine in the longitudinal-vertical plane. As a result of numerical calculations, graphical dependences were built of the angle of rotation of the top-gathering machine at different speeds of its translational movement and different values of the coefficient of stiffness and damping of the tires of the copying wheels, as well as at different values of the main design parameters of the machine and the step of the unevenness of the soil surface. Conclusions. To reduce the amplitude of the angular oscillations of the harvester in the longitudinal vertical plane, its supporting wheels should be located as far as possible from the instantaneous center of rotation of the tractor’s front attachment mechanism. The central thrust of this mechanism should also be installed at the greatest possible angle of inclination to the vertical. The greater the step of the unevenness of the soil surface, the more stable will be the movement of the front-mounted top-gathering machine in the longitudinal-vertical plane. According to experimental studies, with amplitudes of oscillations of the lower ends of the knives of the rotary cutting device up to 5 cm, the loss of the sliver is insignificant. However, when the amplitude of these fluctuations increases to 7 cm or more, these losses become more significant and their maximum values can reach more than 12%.

Solid-State Rotary Friction-Welded Tungsten and Mild Steel Joints

This paper is a study of the microstructure and other selected properties of solid-state, high-speed, rotary friction-welded tungsten and mild steel (S355) joints. Due to the high affinity of tungsten for oxygen, the welding process was carried out in a chamber with an argon protective atmosphere. Joints of suitable quality were obtained without any macroscopic defects and discontinuities. Scanning electron microscopy (SEM) was used to investigate the phase transformations taking place during the friction welding process. Chemical compositions in the interfaces of the welded joints were determined by using energy dispersive spectroscopy (EDS). The microstructure of friction welds consisted of a few zones, fine equiaxed grains (formed due to dynamic recrystallization) and ultrafine grains in the region on the steel side. A plastic deformation in the direction of the flash was visible mainly on the steel side. EDS-SEM scan line analyses across the interface did not confirm the diffusion of tungsten to iron. The nature of the friction welding dissimilar joint is non-equilibrium based on deep plastic deformation without visible diffusive processes in the interface zone. The absence of intermetallic phases was found in the weld interface during SEM observations. Mechanical properties of the friction-welded joint were defined using the Vickers hardness test and the instrumented indentation test (IIT). The results are presented in the form of a distribution in the longitudinal plane of the welded joint. The fracture during strength tests occurred mainly through the cleavage planes at the interface of the tungsten grain close to the friction surface.

Hippocampal interlamellar cell-cell connectome that counts.

The hippocampus is regarded as a cognition hub, particularly for learning and memory. Previously, neuronal mechanisms underlying various cognitive functions are delineated with the lamellar hippocampal circuitry, dentate gyrus-CA3 or CA2-CA1, within the transverse plane. More recently, interlamellar (often referred to as longitudinal) projections have received intensive attention to help understand signal convergence and divergence in cognition and behavior. Signal propagation along the longitudinal axis is evidenced by axonal arborization patterns and synaptic responses to electro- and photo-stimulation, further demonstrating that information flow is more enriched in the longitudinal plane than the transverse plane. Here, we review the significance of longitudinal connections for cognition, discuss a putative circuit mechanism of place coding, and suggest the reconceptualization of the hippocampal circuitry.

Dose deviations induced by fractional image guidance system errors in intensity-modulated radiotherapy for brain tumor treatment

Background: Intensity-modulated radiotherapy (IMRT) techniques have a steep dose distribution, leading to large dosimetric errors caused by incorrect daily patient setup. Image-guided radiotherapy (IGRT) is an essential technique to verify accurate patient setup. The accuracy of verifying a patient’s position depends on many factors including the image guidance system and image registration software. Objectives: This study investigated the dosimetric and geometric differences between the original plan and simulated plans with setup errors associated with kilovoltage cone-beam computed tomography (kV-CBCT), kV, kV planar image, and electronic portal imaging detector (EPID) for brain tumor treatment using IMRT. Materials and methods: A PIXY Anthropomorphic Training/Teaching Phantom was used in this study. IMRT treatment plans with five co-planar fields from a 6 MV Elekta Versa HD linear accelerator were generated using the RayStation computer treatment planning system. Three image guidance systems, including kV-CBCT, kV planar imager, and EPID were used to perform image registration. To evaluate the efficiency of each image guidance system, a simulated setup error by couch was shifted 0, ±2, and ±4 mm in the lateral, longitudinal, and vertical planes. Errors in the image registration from the actual couch shift were collected. Measured errors were used to generate the treatment plans of 25 fractions using the IMRT technique by random shifts of the isocenter of each fraction while maintaining other planning parameters of the original plan. The dose deviation in planning target volume (PTV) and geometric deviation compared to original plan were recalculated and analyzed. Results: Accuracy of image registration in all image guidance systems indicated that the registration errors were less than 1.7, 2.0, and 1.0 mm for the kV-CBCT, kV planar, and EPID, respectively. The average PTV dosimetric deviation induced by the setup error ranged from -2 to 2 mm per fraction; this study showed dosimetric deviation at D98% approximately -6%, D95% approximately -4% and D2% below -1%, while the average of isodose distribution shift of -5% inside the PTV of the isocenter region were -1.58±0.67, -1.28±0.52 and -1.30±0.80 mm in the cerebella, parasagittal, and convex areas, respectively. An isodose shift of -10% was &lt;1 mm in all PTV locations. Conclusion: The efficiency of image guidance resulted in small errors within ±2 mm using kV-CBCT, kV planar, and EPID. The setup error influenced daily dose distribution, while the PTV recorded underdose of about 4% in the brain IMRT technique.

Mechanical properties and microstructure of cold-rolled Scalmalloy® (Al-4.5Mg-0.6Sc-0.3Zr alloy) at a low reduction in thickness

A selective laser melted Al-4.5Mg-0.6Sc-0.3Zr alloy, also known as Scalmalloy®, was cold-rolled at two different reductions in thickness to observe the effect on microstructure and mechanical properties. Optical microscopy, scanning electron microscopy, tensile testing with digital image correlation, surface roughness testing and microhardness testing was used to examine samples. Hardness increased significantly in the 30% cold-rolled condition – 20.2% in the horizontal plane, 12.5% in the transverse plane, and 18.2% in the longitudinal plane. Surface roughness was reduced to as low as 1.2μm for cold-rolled conditions compared to >15μm for as-built conditions. Yield strengths were less for cold-rolled conditions compared to as-built and ultimate tensile strengths were similar for as-built and 10% cold rolled conditions. However, 30% cold-rolled condition saw a 10.8% increase compared to as built. Strain distribution among samples was uniform for as-built conditions but concentrated in certain areas for cold-rolled conditions. SEM micrographs of fracture surfaces showed some very ductile fractures evident from dimpling. The microstructure was heavily deformed for all cold-rolled conditions in all build directions showing flattened, elongated grains and grain refinement in both the coarse grain and fine grain regions present in Scalmalloy, especially for the 30% cold-rolled condition.