Extreme Rotation Research Articles

Extreme electromagnetic rotation, chemical reaction, Hall and ion slip effects on weakly ionized fluid in a Riga channel

The utilization of external magnetic or electric fields, particularly through a Riga setup, markedly enhances flow dynamics by mitigating frictional forces and turbulent fluctuations, thereby facilitating superior flow management. Such improvements are especially beneficial in optimizing the operational efficiency of machinery and turbines. Our research focuses on the behaviour of a weakly ionized fluid within a porous, infinitely extended Riga channel (or electromagnetic channel) set in a rotational frame work affected by Hall and ion-slip electric fields. This model integrates the cumulative repulsions of an abruptly apply pressure gradients, electro-magnetic force, electromagnetic radiation, as well as chemical reactions. The physical configuration of the model features a stationary RHS wall as well as the LHS wall subjected to transversal vibration, establishing a complex flow environment. This circumstance is analytically modeled utilizing time dependent PDE, with the Laplace transform method applied to achieve a closed-format resolution for the course controlling equations. Through detailed graphical and tabular data, the investigations explored the impacts of assorted pivotal parameters on the model's flow traits and quantities. Our results indicate that an upswing in the modified Hartmann number significantly enhances fluids flow in the conduit, with the most important resultant flow showing marked improvement as Hall and ion-slip parameters amplify, and secondly the resultant flow diminishing chemical reaction parameter. Additionally, species concentration lowers with higher Schmidt numbers and chemical reaction rates, while an expanded modified Hartmann number correlate with enhanced shear stress near the conduit wall. Moreover, an elevation in the radiating parameter reduces the rate of temperature transport at the vibrating wall, whereas this at the stationary wall improves. This study has profound implications across several fields, notably in fusion energy research, spacecraft propulsion systems, satellite operations, aerospace engineering, and advanced manufacturing technologies.

KPF Confirms a Polar Orbit for KELT-18 b

We present the first spectroscopic transit results from the newly commissioned Keck Planet Finder on the Keck-I telescope at W. M. Keck Observatory. We observed a transit of KELT-18 b, an inflated ultrahot Jupiter orbiting a hot star (T eff = 6670 K) with a binary stellar companion. By modeling the perturbation to the measured cross-correlation functions using the Reloaded Rossiter–McLaughlin technique, we derived a sky-projected obliquity of λ = − 94.°8 ± 0.°7 ( ψ=93.8−1.8+1.6° for isotropic i ⋆). The data are consistent with an extreme stellar differential rotation (α = 0.9), though a more likely explanation is moderate center-to-limb variations of the emergent stellar spectrum. We see additional evidence for the latter from line widths increasing toward the limb. Using loose constraints on the stellar rotation period from observed variability in the available TESS photometry, we were able to constrain the stellar inclination and thus the true 3D stellar obliquity to ψ=91.7−1.8+2.2° . KELT-18 b could have obtained its polar orbit through high-eccentricity migration initiated by Kozai–Lidov oscillations induced by the binary stellar companion KELT-18 B, as the two likely have a large mutual inclination as evidenced by Gaia astrometry. KELT-18 b adds another data point to the growing population of close-in polar planets, particularly around hot stars.

ϵ Sagittarii: An Extreme Rapid Rotator with a Decretion Disk

We report high-precision, multiwavelength linear-polarization observations of the bright B9 (or A0) star ϵ Sagittarii. The polarization shows the distinctive wavelength dependence expected for a rapidly rotating star. Analysis of the polarization data reveals an angular rotation rate ω (=Ω/Ωcrit) of 0.995 or greater, the highest yet measured for a star in our Galaxy. An additional wavelength-independent polarization component is attributed to electron scattering in a low-density, edge-on gas disk that also produces the narrow absorption components seen in the spectrum. Several properties of the star (polarization due to a disk, occasional weak Hα emission, and multiple periodicities seen in space photometry) resemble those of Be stars, but the level of activity in all cases is much lower than that of typical Be stars. The stellar properties are inconsistent with single-rotating-star evolutionary tracks, indicating that it is most likely a product of binary interaction. The star is an excellent candidate for observation by interferometry, optical spectropolarimetry to detect the Öhman effect, and ultraviolet polarimetry, any of which would allow its extreme rotation to be tested and its stellar properties to be refined.

Ventilation quality and fiber optic glottic view of AuraGain laryngeal mask in neutral, moderate, and extreme lateral head and neck positions in anesthetized spontaneously breathing children

BackgroundWe investigated the effects of moderate (45°), and extreme (60°) right lateral rotation of the head and neck on the ventilatory performance of Ambu AuraGain Laryngeal mask airway in generally anesthetized spontaneously breathing children. MethodsFifty-two children (aged 2–9 years) were randomized in this open-label observational cohort, to receive Ambu® AuraGain either in moderate (45°) (Group I, n = 26) or extreme (60°) (Group II, n = 26) lateral rotation of the head and neck. The oropharyngeal leak pressure OLP (primary outcome), ventilation score, exhaled tidal volume, and fiberoptic glottic view score, were recorded with the head and neck in a neutral position, then in lateral position after insertion by 1,15,30 and 45 min., and at end of surgery. ResultsThe mean OLP in group I decreased from 23.81 ± 2.87 cmH2O in the neutral position to 23.77±3.78 cmH2O, (P = 0.941) 1 min. after lateral rotation. Whereas, In group II, it increased from 20.38 ± 4.18 cmH2O to 21.88±3.28 cmH2O, (P = 0.002). Afterward, the OLP was maintained decreased in group I and increased in group II (P < 0.05), with no intergroup differences. The ventilation score did not show significant intra or inter-group differences. After lateral rotation, the fiberoptic glottic score showed a trend towards better values in group II than in group I. ConclusionVentilation with AuraGain LMA can efficiently be implemented while the head and neck are in the neutral and laterally rotated positions in anesthetized spontaneously breathing children. Extreme lateral rotation (60°) was better tolerated than the moderate position (45°).

Efficacy of superficial cervical plexus block in the management of neck pain due to surgical positioning in patients undergoing burr-hole craniotomy for unilateral chronic subdural hematoma under scalp block: A prospective randomized control trial

: Alternatives to general anesthesia technique, pain management of surgical sites have been discussed at length in various studies for burr-hole evacuation in geriatric patients. This is the first study addressing the management of pain that occurs due to extreme contra-lateral side neck rotation to access the surgical site. : This trial was conducted (from January 2021 to January 2022) on 60 patients of age ≥ 18 years with ASA grade I/I/III undergoing unilateral burr hole craniotomy for evacuation of chronic subdural hematoma (CSDH) under scalp block. Group D (n=30) received 5 ml of 0.5% bupivacaine by ultrasound-guided superficial cervical plexus block (SCPB), and group P (n=30) received SCPB with placebo (normal saline). The primary outcome was the numerical rating pain score (NRS) pain score during neck movement in the postoperative period. Secondary objectives were muscle spasm assessed by the modified Ashworth scale (MAS), consumption dosage of rescue analgesia, modified Ramsay sedation score (MRSS), and hemodynamic parameters.: NRS scores were significantly lower at 8 hours in the SCPB with drug (D) group compared to the SCPB with placebo group (p-value = 0.019). MAS were higher in group P compared to group D until 12 (&amp;#60;0.001). Consumption of rescue analgesia was higher in group P than group D (&amp;#60;0.001). MRSS was significantly higher in group D compared to group P throughout the intra-operative period (&amp;#60;0.001).: Preoperative superficial cervical plexus block decreases postoperative neck pain and facilitates neck rotation.

Meralgia Paresthetica-An Approach Specific Neurological Complication in Patients Undergoing DAA Total Hip Replacement: Anatomical and Clinical Considerations.

Introduction: Mini-invasive surgical (MIS) approaches to total hip replacement (THR) are becoming more popular and increasingly adapted into practice. THR via the direct anterior approach (MIS DAA) has become a rather controversial topic in hip arthroplasty literature in the last decades. Our retrospective observational study focuses on the prevalence of one approach-specific complication-lateral femoral cutaneous nerve (LFCN) iatrogenic lesion-and tries to clarify the possible pathogenesis of this injury. Methods: This is a retrospective single-cohort observational single-center and single-surgeon study. Our patient records were searched for the period from 2015 to 2017-after a safe period of time after the learning curve for MIS DAA. All intra- and post-operative lesions of the LFCN were recorded. Lesion of the LFCN was confirmed by a neurological examination. Minimum patient follow-up was 2 years. Results: This study involved 417 patients undergoing single-side THR via MIS DAA. Patients were examined on follow-up visits at 6 weeks, 6 months, 1 year, and 2 years after surgery. There were 17 cases of LCFN injury at the 6 weeks early follow-up visit (4.1%). All cases of clinically presenting LFCN injury resolved at the 2-year follow-up ad integrum. Discussion: Possible explanations of such neurological complications are direct iatrogenic injury, vigorous traction, hyperextension, or extreme external rotation of the operated limb. Use of a traction table or concomitant spinal pathology and deformity also play a role. Prevention involves stepwise adaptation of the approach during the learning curve period by attending cadaver lab courses, rational use of traction and hyperextension, and careful surgical technique in the superficial and deep fascial layers. Dynamometers could be used to visualise the limits of manipulation of the operated limb. Conclusions: Neurological complications are not as rare but questionably significant in patients undergoing THR via the DAA. Incidental finding of LFCN injury has no effect on the functional outcome of the artificial joint. It can lead to lower subjective satisfaction of patients with the operation, which can be avoided with careful education and management of expectations of the patients.

On the representation and methodology for wide and short range head pose estimation

Head pose estimation (HPE) is a problem of interest in computer vision to improve the performance of face processing tasks in semi-frontal or profile settings. Recent applications require the analysis of faces in the full 360° rotation range. Traditional approaches to solve the semi-frontal and profile cases are not directly amenable for the full rotation case. In this paper we analyze the methodology for short- and wide-range HPE and discuss which representations and metrics are adequate for each case. We show that the popular Euler angles representation is a good choice for short-range HPE, but not at extreme rotations. However, the Euler angles’ gimbal lock problem prevents them from being used as a valid metric in any setting. We also revisit the current cross-data set evaluation methodology and note that the lack of alignment between the reference systems of the training and test data sets negatively biases the results of all articles in the literature. We introduce a procedure to quantify this misalignment and a new methodology for cross-data set HPE that establishes new, more accurate, SOTA for the 300W-LP/Biwi benchmark. We also propose a generalization of the geodesic angular distance metric that enables the construction of a loss that controls the contribution of each training sample to the optimization of the model. Finally, we introduce a wide range HPE benchmark based on the CMU Panoptic data set. code:https://github.com/pcr-upm/opal23_headpose

Lower Limb Rotational Malalignment: Derotational Osteotomies of the Femur and Tibia in the Setting of Recurrent Patellar Instability

Valgus lower extremity alignment with excessive femoral anteversion and tibial external torsion (Miserable Malalignment Syndrome) results in patellar maltracking. Sagittal plane deformities (rotational alignment) should be quantified along with typical frontal plane alignment. Femoral and tibial rotation can be assessed with both physical examination and radiographic studies. Derotational osteotomies of both the femur and the tibia can then be used for correction. In this chapter, we attempt to provide guidelines for assessing lower extremity rotation and an understanding of normal femoral and tibial rotational values. We then provide examples of corrective femoral osteotomies and tibial rotational osteotomies.

Classifying Mountain Vegetation Types Using Object-Oriented Machine Learning Methods Based on Different Feature Combinations

Mountainous vegetation type classification plays a fundamental role in resource investigation in forested areas, making it necessary to accurately identify mountain vegetation types. However, Mountainous vegetation growth is readily affected by terrain and climate, which often makes interpretation difficult. This study utilizes Sentinel-2A images and object-oriented machine learning methods to map vegetation types in the complex mountainous region of Jiuzhaigou County, China, incorporating multiple auxiliary features. The results showed that the inclusion of different features improved the accuracy of mountain vegetation type classification, with terrain features, vegetation indices, and spectral features providing significant benefits. After feature selection, the accuracy of mountain vegetation type classification was further improved. The random forest recursive feature elimination (RF_RFE) algorithm outperformed the RliefF algorithm in recognizing mountain vegetation types. Extreme learning machine (ELM), random forest (RF), rotation forest (ROF), and ROF_ELM algorithms all achieved good classification performance, with an overall accuracy greater than 84.62%. Comparing the mountain vegetation type distribution maps obtained using different classifiers, we found that classification algorithms with the same base classifier ensemble exhibited similar performance. Overall, the ROF algorithm performed the best, achieving an overall accuracy of 89.68%, an average accuracy of 88.48%, and a Kappa coefficient of 0.879.

Using redundant control to optimize control torque

The object of research is the process of automatic control of the redundant structure of the vessel's executive devices for extreme rotation in the yaw channel. Traditionally, redundant structures have been used to improve the reliability of automated control systems and the maneuverability of vessels. At the same time, control redundancy can also be used to optimize control processes, thereby reducing fuel consumption, increasing control forces and moments, and reducing the time required to perform operations. This allows gaining advantages in movement over vessels not equipped with optimization modules. The paper considers the optimal management of the redundant structure of an offshore vessel, which ensures the rotational movement of the vessel around the center of rotation with the maximum angular velocity. As well as simultaneous maintenance of a given position or movement in the longitudinal and lateral channel, taking into account control restrictions. This problem is reduced to a nonlinear optimization problem with nonlinear and linear control constraints. The method, algorithmic and software of the module of extreme rotation of the vessel with a redundant structure of executive devices have been developed. The workability and efficiency of the developed method, algorithmic and software are verified by mathematical modeling in the closed circuit «Control Object – Control System». The results of the conducted experiment showed that the use of optimal control allows, in comparison with traditional methods of splitting controls, to increase the control moment and angular speed of rotation by 1.5–2 times. The obtained opportunities are explained by the use of a mathematical model of the redundant control structure and the optimization procedure for calculating optimal controls in the on-board computer of the automated system. The developed method can be used on vessels, provided it is integrated into the existing automated system of the on-board computer with an open architecture, to increase the capabilities of automatic traffic control.

Study of Incidence of Ponticulus Posterior In Dry Human Atlas Vertebra and Its Clinical Significance

Background: Atlas is the first cervical vertebra. The vertebral artery lies in the groove on posterior arch of the atlas. The vertebral artery groove may sometimes get converted into a foramen. This is commonly known as ponticulus posterior (ponticulus posticus) or arcuate foramen of the atlas. These foramina may be complete or incomplete. This can lead to compression of the vertebral artery and produce symptoms like headache, syncope, altered consciousness etc. It can also complicate manipulations of the cervical spine by reducing the blood flow during extreme rotations of head and neck. It is also associated with vertebrobasilar artery stroke So, neurosurgeons or orthopaedic surgeons who operate in this area should have a detailed knowledge of variations of groove for the vertebral artery. Materials and Methods: The present study was conducted on 50 dried and fully ossified adult human atlas of unknown age and sex collected from the department of Anatomy, Government Medical college, Nagpur. Each atlas vertebra was carefully observed for the presence or absence of complete or incomplete ponticuli on superior surface of posterior arch of atlas. Results: Out of the 50 vertebra studied 7(14%) showed the presence of Ponticuli. Ponticuli were incomplete in all 7 atlas vertebras. Complete ring was not observed in any of the atlas vertebra .Out of the 7 ponticuli 6(12%) were found to be unilateral and in only 1 (2%) case it was found to be bilateral. Out of the 6 ponticuli 4(8%) were noticed on the Left side and 2(4%) were present on the right side. Conclusion: Presence of incomplete ponticulus posterior might cause cervical pain and even cerebrovascular disorders due to pressure on third part of vertebral artery present in the vertebral artery groove. This anatomical knowledge is important for neurosurgeons, orthopaedic surgeons, radiologists and clinicians while dealing with this region. KEYWORDS: Ponticulus Posterior, Atlas, Cervical Vertebra, Cerebrovascular disorders, Vertebral artery.

Correcting bandwidth depolarization by extreme Faraday rotation

ABSTRACT Measurements of the polarization of radio emission are subject to a number of depolarization effects such as bandwidth depolarization, which is caused by the averaging effect of a finite channel bandwidth combined with the frequency-dependent polarization caused by Faraday rotation. There have been very few mathematical treatments of bandwidth depolarization, especially in the context of the rotation measure (RM) synthesis method for analysing radio polarization data. We have found a simple equation for predicting if bandwidth depolarization is significant for a given observational configuration. We have derived and tested three methods of modifying RM synthesis to correct for bandwidth depolarization. From these tests we have developed a new algorithm that can detect bandwidth-depolarized signals with higher signal-to-noise ratio than conventional RM synthesis and recover the correct source polarization properties (RM and polarized intensity). We have verified that this algorithm works as expected with real data from the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey. To make this algorithm available to the community, we have added it as a new tool in the RM-Tools polarization analysis package.

The initial spin distribution of B-type stars revealed by the split main sequences of young star clusters

Spectroscopic observations of stars in young open clusters have revealed evidence for a dichotomous distribution of stellar rotational velocities, with 10−30% of stars rotating slowly and the remaining 70−90% rotating fairly rapidly. At the same time, high-precision multiband photometry of young star clusters shows a split main sequence band, which is again interpreted as due to a spin dichotomy. Recent papers suggest that extreme rotation is required to retrieve the photometric split. Our new grids of MESA models and the prevalent SYCLIST models show, however, that initial slow (0−35% of the linear Keplerian rotation velocities) and intermediate (50−65% of the Keplerian rotation velocities) rotation are adequate to explain the photometric split. These values are consistent with the recent spectroscopic measurements of cluster and field stars, and are likely to reflect the birth spin distributions of upper main-sequence stars. A fraction of the initially faster-rotating stars may be able to reach near-critical rotation at the end of their main-sequence evolution and produce Be stars in the turn-off region of young star clusters. However, we find that the presence of Be stars up to two magnitudes below the cluster turnoff advocates for a crucial role of binary interaction in creating Be stars. We argue that surface chemical composition measurements may help distinguish these two Be star formation channels. While only the most rapidly rotating, and therefore nitrogen-enriched, single stars can evolve into Be stars, slow pre-mass-transfer rotation and inefficient accretion allows for mild or no enrichment even in critically rotating accretion-induced Be stars. Our results shed new light on the origin of the spin distribution of young and evolved B-type main sequence stars.

Analysis of Real-Time Face-Verification Methods for Surveillance Applications.

In the last decade, face-recognition and -verification methods based on deep learning have increasingly used deeper and more complex architectures to obtain state-of-the-art (SOTA) accuracy. Hence, these architectures are limited to powerful devices that can handle heavy computational resources. Conversely, lightweight and efficient methods have recently been proposed to achieve real-time performance on limited devices and embedded systems. However, real-time face-verification methods struggle with problems usually solved by their heavy counterparts-for example, illumination changes, occlusions, face rotation, and distance to the subject. These challenges are strongly related to surveillance applications that deal with low-resolution face images under unconstrained conditions. Therefore, this paper compares three SOTA real-time face-verification methods for coping with specific problems in surveillance applications. To this end, we created an evaluation subset from two available datasets consisting of 3000 face images presenting face rotation and low-resolution problems. We defined five groups of face rotation with five levels of resolutions that can appear in common surveillance scenarios. With our evaluation subset, we methodically evaluated the face-verification accuracy of MobileFaceNet, EfficientNet-B0, and GhostNet. Furthermore, we also evaluated them with conventional datasets, such as Cross-Pose LFW and QMUL-SurvFace. When examining the experimental results of the three mentioned datasets, we found that EfficientNet-B0 could deal with both surveillance problems, but MobileFaceNet was better at handling extreme face rotation over 80 degrees.

Factors that Increase Elbow Stress in the Throwing Athlete: a Systematic Review of Biomechanical and Motion Analysis Studies of Baseball Pitching and Throwing.

Elbow pain poses a unique challenge in the throwing athlete. Due to the high levels of elbow stress during the throwing motion, elbow injuries are common in throwers of all ages. There are several postulated factors believed to contribute increased stress to the throwing elbow. A detailed review of the published biomechanical studies evaluating the stresses experienced by the throwing elbow is needed. Here, we review these biomechanical studies to extrapolate the contributing factors that increase stress, the modifications that may reduce such stress, and the post-injury rehabilitation that optimizes outcomes and reduces recurrence. The biomechanical forces on the elbow have been further investigated delineated in recent work. Rotational malalignment of the shoulder, including both GIRD and decreased adduction, increases torque experienced by the elbow during pitching motions. Exact interactions between lower extremity, lumbopelvic or trunk rotation, and elbow forces during throwing remain uncertain with mixed results in recent literature. Pitch types may influence elbow stresses although delivery mechanism and distance thrown do not. Several biomechanical factors influence the stresses imparted on the throwing elbow. Throwing volume, proper throwing mechanics, and appropriate rehabilitation are likely to be to be the most influential on mitigating unnecessary stresses imparted to the elbow in the throwing athlete. A proper understanding of these factors may reduce the occurrence of these injuries in this population. Moreover, an understanding of proper rehabilitation following injury may ensure optimized results and reduce recurrence.

Correlation of Tibial Torsion With Lower Limb Alignment and Femoral Anteversion in Patients With Patellar Instability.

Alignment and rotation of the lower extremities have been suggested to be predisposing pathologic factors for patellar instability. To elucidate the relationship between the lower limb alignment and lower extremity rotation in patients with patellar instability. Cross-sectional study; Level of evidence, 3. Included were 83 patients with patellar instability. Computed tomography scans and standing full-leg radiographs were used to measure the tibial tuberosity-trochlear groove (TT-TG) distance, mechanical femorotibial angle (mFTA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), femoral torsion, and tibial torsion of the different segments. The relationships between femoral torsion, tibial torsion of the different segments, and the mFTA, mLDFA, and mMPTA were evaluated. The levels of tibial torsion and femoral torsion in patients with varus, normal, or valgus alignment were compared with 1-way analysis of variance and chi-square test. The total tibial torsion was significantly associated with total femoral anteversion (r = 0.329; P = .002) and mFTA (r = -0.304; P = .005). There were no significant correlations between mFTA and TT-TG distance or femoral anteversion. Compared with patients with valgus malalignment, patients with varus malalignment tended to have higher tibial torsion. Tibial torsion was associated with leg axis alignment and femoral anteversion in patients with patellar instability. Patients with patellar instability, especially those with concurrent leg axis deformities, should undergo further radiological imaging so that tibial torsion can be assessed and a diagnosis of torsion deformity made early in the treatment pathway and the proper surgical plan formulated.

A Case Series of Bosworth Fracture-Dislocations and Review of 129 Reported Cases.

Bosworth fracture dislocations of the ankle are rare injuries of the ankle caused by extreme external rotation of the supinated foot where the proximal fibula fracture fragment is posteriorly dislocated and entrapped behind the posterior-lateral ridge of the tibia. This case series aims to document three such cases treated in our institution over a nine year period. We also provide a review of 129 cases in the existing literature. Medical records and relevant radiographs for each patient were analysed and collected from the time of presentation till the point of latest follow-up. During each clinic visit, all physical exam findings as well as all complications were recorded. The American Foot and Ankle Society (AOFAS) Hindfoot score was also tabulated for each patient at the point of latest review. Closed reduction was unsuccessful in all three patients, and all required open reduction. One patient had an uncomplicated recovery whilst the remaining two suffered significant soft tissue complications. One patient suffered severe soft tissue swelling preventing primary closure at the time of surgery, whilst another suffered post-operative wound dehiscence and infection. Eventually all fractures healed, and all three patients obtained satisfactory AOFAS scores. The diagnosis of Bosworth fracture dislocations of the ankle is often delayed or missed, due to its rare occurrence. Closed reduction is often unsuccessful, and early open reduction is required to avoid poor clinical outcomes due to severe soft tissue damage or even compartment syndrome.

Influence of lower extremity rotation on knee kinematics in single-leg landing

ObjectivesAlthough the rotation of lower extremities has gained increasing recognition as a risk factor for anterior cruciate ligament (ACL) injury. This study clarified the influence of lower extremity rotation on the knee during single-leg landing. Design and Setting: We recruited 30 students to perform single-leg landing from a height of 30 cm with their lower extremities in neutral, and externally and internally rotated. The knee abduction, flexion angles, and abduction angular velocity were measured. Furthermore, the abduction angle was analyzed at knee flexion angles of 15°, 20°, 25°, and 30° and compared among the three conditions using a repeated measures analysis of variance with Bonferroni post hoc tests. ResultsThe maximum abduction angle was significantly greater when internally rotated than in the neutral. The maximum abduction angular velocity was significantly greater in the internally rotated compared to in the neutral. Finally, the abduction angle at a knee flexion angle of 30° was significantly greater when internally rotated compared to in the neutral. ConclusionRotation of the lower extremities affects knee kinematics, and landing on a knee that is internally rotated may increase the risk of ACL injury.

The IACOB project

Context. Stellar rotation is of key importance in the formation process, the evolution, and the final fate of massive stars. Aims. We perform a reassessment of the empirical rotational properties of Galactic massive O-type stars using the results from a detailed analysis of ground-based multi-epoch optical spectra obtained in the framework of the IACOB &amp; OWN surveys. Methods. Using high-quality optical spectroscopy, we established the velocity distribution for a sample of 285 apparently single and single-line spectroscopic binary (SB1) Galactic O-type stars. We also made use of the rest of the parameters from the quantitative spectroscopic analysis presented in prior IACOB papers (mainly Teff, log g, and multiplicity) to study the v sin i behavior and evolution from the comparison of subsamples in different regions of the spectroscopic Hertzsprung–Rusell diagram (sHRD). Our results are compared to the main predictions – regarding current and initial rotational velocities – of two sets of well-established evolutionary models for single stars, as well as from population synthesis simulations of massive stars that include binary interaction. Results. We reassess the known bimodal nature of the v sin i distribution, and find a non-negligible difference between the v sin i distribution of single and SB1 stars. We provide empirical evidence supporting the proposed scenario that the tail of fast rotators is mainly produced by binary interactions. Stars with extreme rotation (&gt;300 km s−1) appear as single stars that are located in the lower zone of the sHRD. We notice little rotational braking during the main sequence, a braking effect independent of mass (and wind strength). The rotation rates of the youngest observed stars lean to an empirical initial velocity distribution with ⪅20% of critical velocity. Lastly, a limit in v sin i detection below 40–50 km s−1 seems to persist, especially in the upper part of the sHRD, possibly associated with the effect of microturbulence in the measurement methodology used.

Pediatric Gastric Volvulus: Is Laparoscopic Hill-Snow-Modified Gastropexy the Effective Long-Term Minimally Invasive Solution?

Introduction: Gastric volvulus (GV) is a rare and life-threatening condition if not promptly diagnosed and treated. Extreme rotation can cause obstruction cutting off blood supply to stomach and distal organs, leading to ischemia and necrosis. It is a clinically significant cause of acute/recurrent abdominal pain and chronic vomiting in children. GV can be classified into the following: primary, secondary, organoaxial, mesenteroaxial, or combined, acute, or chronic. Materials and Methods: Six neonates (5 males-1 female) were admitted to our department for recurrent postprandial vomiting associated with paleness, hyporeactivity, transitory abdominal distension, failure to thrive, and respiratory infections (only-1). Median age: 6 months (range 2-9 months). Patients metabolic and neurological evaluations were normal. A barium-swallow-study (upper gastrointestinal [UGI]) allowed definitive diagnosis. Results: UGI and esophagogastroduodenoscopy (EGDS) showed a gastric abnormal dilatation (gastric fundus), hiatal hernia (HH) in 5 patients, a large/small curvature discrepancy in 3 patients. Four were chronic-organoaxial-GV, 2 chronic-mesenteroaxial-GV. All underwent Laparoscopic-Hill-Snow-gastropexy (LHSG) with HH correction. No intraoperative/postoperative complications were recorded. Refeeding started in first postoperative day. Average hospital stay: 6-days. At long-term follow-up, all patients were symptoms free (able to vomit/burp); 2 referred occasionally epigastric pain sometimes with vomit. At 10-12 years follow-up UGI and EGDS confirmed correct gastric position revealing gastroduedenitis. Discussion: GV is a rare clinical entity in children considering etiology and management with an important morbidity and mortality rate. Its diagnosis could be missed simply. Vomiting or HH on imaging studies should suggest GV regardless patient's stable appearance. Conclusions: Chronic GV can manifest with atypical chest, abdominal, and gastrointestinal symptoms. Early diagnosis and treatment reduce the risk of developing acute form. LHSG is a long-term effective and safe solution with a very low complication rate, and no symptoms correlated to Nissen procedure.