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Are crop circles real?
\"Presents stories of crop circles, designs that appear in crop fields, often overnight. Examines the evidence of various explanations\"-- Provided by publisher.
Book
Blood Flow Distribution in Cerebral Arteries
High-resolution phase—contrast magnetic resonance imaging can now assess flow in proximal and distal cerebral arteries. The aim of this study was to describe how total cerebral blood flow (tCBF) is distributed into the vascular tree with regard to age, sex and anatomic variations. Forty-nine healthy young (mean 25 years) and 45 elderly (mean 71 years) individuals were included. Blood flow rate (BFR) in 21 intra- and extracerebral arteries was measured. Total cerebral blood flow was defined as BFR in the internal carotid plus vertebral arteries and mean cerebral perfusion as tCBF/brain volume. Carotid/vertebral distribution was 72%/28% and was not related to age, sex, or brain volume. Total cerebral blood flow (717±123 mL/min) was distributed to each side as follows: middle cerebral artery (MCA), 21%; distal MCA, 6%; anterior cerebral artery (ACA), 12%, distal ACA, 4%; ophthalmic artery, 2%; posterior cerebral artery (PCA), 8%; and 20% to basilar artery. Deviating distributions were observed in subjects with ‘fetal’ PCA. Blood flow rate in cerebral arteries decreased with increasing age (P<0.05) but not in extracerebral arteries. Mean cerebral perfusion was higher in women (women: 61±8; men: 55±6 mL/min/100 mL, P<0.001). The study describes a new method to outline the flow profile of the cerebral vascular tree, including reference values, and should be used for grading the collateral flow system.
Journal Article
Accurate full-scale patient-specific Circle of Willis models including aneurysms: A novel manufacturing approach
Accurate physical replicas of the Circle of Willis (CoW) are valuable for planning neuroendovascular interventions, validating computational simulations, evaluating medical devices and training physicians. Existing methods often replicate only segments of the CoW or lack geometric precision, which is critical for realistic hemodynamic simulations.
We introduce a novel, cost-effective manufacturing approach to create full-scale, patient-specific CoW models using fused deposition modeling (FDM) 3D printing and lost core silicone casting. We aim to evaluate the accuracy and reproducibility of this manufacturing process.
A patient-specific 3D model of the CoW with four saccular aneurysms was generated from time-of-flight magnetic resonance angiography (TOF-MRA) data. Three identical models were printed using FDM with acrylonitrile styrene acrylate (ASA) for the vascular structure and butenediol vinyl alcohol co-polymer (BVOH) as a water-soluble support material. The printed models were encased in a clear silicone block and the ASA core was then dissolved using acetone. Computed tomography (CT) scans were used to assess geometric accuracy through cloud-to-mesh distance calculations and centerline analysis.
The median absolute surface deviation between the replicas and the initial model was approximately 309 µm for the entire CoW, with interquartile ranges (IQR) between 360 µm and 444 µm. The aneurysm surfaces exhibited lower deviations, averaging 90 µm. Centerline analysis showed median absolute deviations in vessel radius ranging from 48 µm to 114 µm across key vascular pathways. Statistical analysis confirmed minimal discrepancies between replicas and the initial model. Each replica costs approximately €100 in materials and requires five days to produce.
The manufacturing approach produces accurate, reproducible full-scale, patient-specific CoW models, including four aneurysms. This method simplifies the production process, reduces costs and maintains high geometric accuracy, making it suitable for hemodynamic studies, device evaluation, and clinical training.
Journal Article
Rolling Circle Replication for Biosensing, Bioimaging, and Biomedicine
Rolling circle replication (RCR), including rolling circle amplification (RCA) and rolling circle transcription (RCT), is an isothermal enzymatic reaction. Because of its high amplification efficiency, RCR is a powerful biosensing tool for detecting biomolecules. In recent years, RCR has also been extended to the field of bioimaging to better understand biological pathways. Furthermore, RCR provides a simple technique to design and generate DNA/RNA structures with unique advantages in delivering drugs and enhanced targeting ability. In this review, we introduce the fundamentals of RCR and describe the most recent advances in RCR-based detection methods and delivery vehicles for biosensing, bioimaging, and biomedicine. Finally, some challenges and further opportunities of RCR-based biotechnology are discussed.
Rolling circle replication (RCR) is an isothermal nucleic acid amplification approach that holds great potential in biotechnology.RCR can serve as a powerful biosensing platform for the detection of various biomolecules in bioanalysis and diagnosis.In bioimaging, RCR can provide a unique perspective in comprehensive understanding of biological processes and effective diagnosis of diseases.Programmable, biodegradable RCR-based assemblies have been used as versatile advanced drug carriers for targeted theranostics.
Journal Article
Association of middle cerebral artery aneurysms and variation of the A1 segment
The disturbance of blood flow caused by variations in the circle of Willis is an important factor in the occurrence and development of aneurysms. Previous studies have confirmed that a fetal-type posterior cerebral artery(PCA) is closely related to posterior communicating artery (PcoA) aneurysms, while anatomical variations of the anterior cerebral artery (ACA) appear to correlate with the prevalence of aneurysms in the anterior communicating artery (ACoA). However, the relationship between variations in the circle of Willis and middle cerebral artery(MCA) aneurysms remains controversial.
This study retrospectively analyzed the Computed Tomography Angiography (CTA) data of 269 cases of patients with intracranial aneurysms and 269 cases of patients without aneurysms at the Jiangmen Central Hospital from January 2012 to December 2023. The 3D-Slicer software was utilized to measure the artery diameter and investigate the relationship between anatomical variations of the circle of Willis and MCA aneurysm.
In the aneurysm group, there were 39 cases of A1 dysplasia on the affected side, compared to 20 cases in the control group, with a significantly higher prevalence in the aneurysm group (P = 0.0125). The average diameter of middle cerebral arteries was smaller in the aneurysm group (2.304 ± 0.5613 mm) than in the control group (2.611 ± 0.5500 mm), showing a significant difference (P = 0.001).In aneurysm patients, the MCA diameter on the affected side was smaller in the A1 dysplasia group (2.156 ± 0.5256mm) compared to the A1 normal development group (2.405 ± 0.5718mm, P = 0.0114). Additionally, the average maximum aneurysm diameter was larger in the A1 dysplasia group (6.958 ± 5.163mm) than in the A1 normal development group (5.483 ± 3.336mm, P = 0.03).The presence of ipsilateral A1 dysplasia had a statistically significant effect on the occurrence and rupture of MCA aneurysms.
The variation in the circle of Willis may impact the occurrence and rupture of MCA aneurysms by altering blood flow distribution, constricting the diameter of the parent artery, and shifting the location of blood flow impact.
Journal Article
Handbook to UFOs, crop circles, and alien encounters
\"The idea that aliens might visit our planet has gripped Earthlings for a long time. Extraterrestrials are popular in science fiction books, movies, and TV shows. UFO hunters of every kind are searching Earth, sky, and space for answers to the question: Are we along in the galaxy?\"-- Provided by publisher.
Book
Mysterious Circle Numbers. Does πp,q Approach πp When q Is Tending to p?
This paper aims to introduce a mathematical-philosophical type of question from the fascinating world of generalized circle numbers to the widest possible readership. We start with recalling well-known (in part from school) properties of the polygonal approximation of the common circle when approximating the famous circle number π by convergent sequences of upper and lower bounds being based upon the lengths of polygons. Next, we shortly refer to some results from the literature where suitably defined generalized circle numbers of l p - and l p , q -circles, π p and π p , q , respectively, are considered and turn afterwards over to the approximation of an l p -circle by a family of l p , q -circles with q converging to p, q → p . Then we ask whether or not there holds the continuity property π p , q → π p as q → p . The answer to this question leads us to the answer of the question stated in the paper’s title. Presenting here for illustration true paintings instead of strong technical or mathematical drawings intends both to stimulate opening heart and senses of the reader for recognizing generalized circles in his real life and to suggest the philosophical challenge of the consequences coming out from the demonstrated non-continuity property.
Journal Article