Stability and secondary resonances in the spatial restricted three-body problem for small mass ratios

This paper is devoted to the study of secondary resonances and the stability of the Lagrangian point L-4 in the spatial restricted three-body problem for moderate mass ratios mu, meaning that mu <= 0.0045. However, we concentrated our investigations on small mass ratios mu <= 0.001, which represent the mass ratios for stable configurations of tadpole orbits in the Solar system. The stability is investigated by numerical methods, computing stability maps in different parameter planes. We started investigating the mass of the secondary: from Earth-mass bodies up to Jupiter-mass bodies. In addition, we changed the orbital elements (eccentricity and inclination) of the secondary and Trojan body. For this parameter space, we found high-order secondary resonances, which are present for various inclinations. To determine secondary resonances we used Rabe's equation and the frequency analysis. In addition, we investigated the stability in and around these secondary resonances

Low thrust propulsion in a coplanar circular restricted four body problem

This paper formulates a circular restricted four body problem (CRFBP), where the three primaries are set in the stable Lagrangian equilateral triangle configuration and the fourth body is massless. The analysis of this autonomous coplanar CRFBP is undertaken, which identies eight natural equilibria; four of which are close to the smaller body, two stable and two unstable, when considering the primaries to be the Sun and two smaller bodies of the solar system. Following this, the model incorporates `near term' low-thrust propulsion capabilities to generate surfaces of articial equilibrium points close to the smaller primary, both in and out of the plane containing the celestial bodies. A stability analysis of these points is carried out and a stable subset of them is identied. Throughout the analysis the Sun-Jupiter-Asteroid-Spacecraft system is used, for conceivable masses of a hypothetical asteroid set at the libration point L4. It is shown that eight bounded orbits exist, which can be maintained with a constant thrust less than 1:5 10&#x100000;4N for a 1000kg spacecraft. This illustrates that, by exploiting low-thrust technologies, it would be possible to maintain an observation point more than 66% closer to the asteroid than that of a stable natural equilibrium point. The analysis then focusses on a major Jupiter Trojan: the 624-Hektor asteroid. The thrust required to enable close asteroid observation is determined in the simplied CRFBP model. Finally, a numerical simulation of the real Sun-Jupiter-624 Hektor-Spacecraft is undertaken, which tests the validity of the stability analysis of the simplied model

An update on treatment modalities for ulnar nerve entrapment: A literature review

Context: Ulnar nerve entrapment is a relatively common entrapment syndrome second only in prevalence to carpal tunnel syndrome. The potential anatomic locations for entrapment include the brachial plexus, cubital tunnel, and Guyon�s canal. Ulnar nerve entrapment is more so prevalent in pregnancy, diabetes, rheumatoid arthritis, and patients with occupations involving periods of prolonged elbow flexion and/or wrist dorsiflexion. Cyclists are particularly at risk of Guyon�s canal neuropathy. Patients typically present with sensory deficits of the palmar aspect of the fourth and fifth digits, followed by motor symptoms, including decreased pinch strength and difficulty fastening shirt buttons or opening bottles. Evidence Acquisition: Literature searches were performed using the belowMeSHTerms using Mendeley version 1.19.4. Search fields were varied until further searches revealed no new articles. All articles were screened by title and abstract. Decision was made to include an article based on its relevance and the list of final articles was approved three of the authors. This included reading the entirety of the artice. Anyquestion regarding the inclusion of anarticlewasdiscussed by all authors untilanagreementwasreached. Results: X-rayandCTplay a role in diagnosiswhenabonyinjury is thought to be related to the pathogenesis (i.e., fracture of thehook of the hamate.) MRI plays a role where soft tissue is thought to be related to the pathogenesis (i.e., tumor or swelling.) Electromyography and nerve conduction also play a role in diagnosis. Medicalmanagement, in conjunction with physical therapy, shows limited promise. However, minimally invasive techniques, including peripheral percutaneous electrode placement and ultrasound-guided electrode placement, have all been recently studied and show great promise. When these techniques fail, clinicians should resort to decompression, which can be done endoscopically or through an open incision. Endoscopic ulnar decompression shows great promise as a surgical option with minimal incisions. Conclusions: Clinical diagnosis of ulnar nerve entrapment can often be delayed and requires the suspicion as well as a thorough neurological exam. Early recognition and diagnois are important for early institution of treatment. A wide array of diagnostic imaging can be useful in ruling out bony, soft tissue, or vascular etiologies, respectively. However, clinicians should resort to electrodiagnostic testing when a definitive diagnois is needed. Many new minimally invasive techniques are in the literature and show great promise; however, further large scale trials are needed to validate these techniques. Surgical options remains as a gold standard when adequate symptom relief is not achieved through minimally invasive means. © 2020, Author(s)

Virtual student-led neuroscience conferencing: a UK multicentre prospective study investigating delegate outcomes and delivery mode

Background Clinical neuroscience training programmes are becoming increasingly competitive to enter. UK university neuroscience societies act as a local environment for students to develop their career interests and provide portfolio building opportunities through hosting events such as annual conferences. Recently there has been a transition to more of these events being held online yet the impact of this, if any, remains unclear. This prospective study aimed to identify the impact of student-led neuroscience conferences on delegates and examine attitudes towards an online delivery approach. Methods Multi-centre prospective survey study using pre-conference, post-conference, and 6-month post-conference online questionnaires distributed at 6 virtual student-led neuroscience conferences in 2021. The questionnaires had five-domains: demographics, career aspirations, academic skillsets, an educational manipulation check (EMC) and mode of delivery preference. Results Nine hundred twenty-four surveys were completed across 559 conference attendances. 79.9% of delegates were medical students. Interest in a neuroscience career (p < 0.001), preparedness to undertake research (p < 0.001) and presentation (p < 0.001), as well as EMC scores (p < 0.001) increased immediately post conference. Most participants at 6 months post-attendance had completed an academic project (71.9%) or presentation (50.9%), although 88.8% were lost to follow up. Online format was preferred (65%) with reasons including elimination of travel and access to home facilities whilst lack of face-to-face interaction and engagement were recognised limitations. Conclusion UK student-led online neuroscience conferences play a role in developing knowledge and may facilitate career interest, academic skillset and longer term portfolio building. A hybrid virtual and in-person experience would offer an ideal solution to future conferencing, providing options promoting engagement and interactivity whilst advocating sustainability, accessibility and widening participation

Radiation dose reduction at a price: the effectiveness of a male gonadal shield during helical CT scans

BACKGROUND: It is estimated that 60 million computed tomography (CT) scans were performed during 2006, with approximately 11% of those performed on children age 0–15 years. Various types of gonadal shielding have been evaluated for reducing exposure to the gonads. The purpose of this study was to quantify the radiation dose reduction to the gonads and its effect on image quality when a wrap-around male pediatric gonad shield was used during CT scanning. This information is obtained to assist the attending radiologist in the decision to utilize such male gonadal shields in pediatric imaging practice. METHODS: The dose reduction to the gonads was measured for both direct radiation and for indirect scattered radiation from the abdomen. A 6 cm(3 )ion chamber (Model 10X5-6, Radcal Corporation, Monrovia, CA) was placed on a Humanoid real bone pelvic phantom at a position of the male gonads. When exposure measurements with shielding were made, a 1 mm lead wrap-around gonadal shield was placed around the ion chamber sensitive volume. RESULTS: The use of the shields reduced scatter dose to the gonads by a factor of about 2 with no appreciable loss of image quality. The shields reduced the direct beam dose by a factor of about 35 at the expense of extremely poor CT image quality due to severe streak artifacts. CONCLUSION: Images in the direct exposure case are not useful due to these severe artifacts and the difficulties in positioning these shields on patients in the scatter exposure case may not be warranted by the small absolute reduction in scatter dose unless it is expected that the patient will be subjected to numerous future CT scans

Reproducibility of quantitative F-18-3'-deoxy-3'-fluorothymidine measurements using positron emission tomography

Positron emission tomography (PET) using F-18-3'-deoxy-3'-fluorothymidine ([F-18]FLT) allows noninvasive monitoring of tumour proliferation. For serial imaging in individual patients, good reproducibility is essential. The purpose of the present study was to evaluate the reproducibility of quantitative [F-18]FLT measurements. Nine patients with non-small-cell lung cancer (NSCLC) and six with head-and-neck cancer (HNC) underwent [F-18]FLT PET twice within 7 days prior to therapy. The maximum pixel value (SUVmax) and a threshold defined volume (SUV41%) were defined for all delineated lesions. The plasma to tumour transfer constant (K-i) was estimated using both Patlak graphical analysis and nonlinear regression (NLR). NLR was also used to estimate k(3), which, at least in theory, selectively reflects thymidine kinase 1 activity. The level of agreement between test and retest values was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. All primary tumours and > 90% of clinically suspected locoregional metastases could be delineated. In total, 24 lesions were defined. NLR-derived K-i, Patlak-derived K-i, SUV41% and SUVmax showed excellent reproducibility with ICCs of 0.92, 0.95, 0.98 and 0.93, and SDs of 16%, 12%, 7% and 11%, respectively. Reproducibility was poor for k(3) with an ICC of 0.43 and SD of 38%. Quantitative [F-18]FLT measurements are reproducible in both NSCLC and HNC patients. When monitoring response in individual patients, changes of more than 15% in SUV41%, 20-25% in SUVmax and Patlak-derived K-i, and 32% in NLR3k-derived K-i are likely to represent treatment effect