Regular Facets Research Articles

Computed Tomography-Guided Facet Synovial Cyst Aspiration

Abstract Lumbar facet joint cysts are the benign collections of fluid at or around the facet joints, which may lead to pain and radicular symptoms. They may be associated with spinal stenosis, nerve root compression, neurogenic claudication, and many other neurological disturbances, as they can encroach on the adjacent neural foramen. Although the recommended treatment is surgical excision, percutaneous interventions provide an effective, acceptable, and safe alternative that may be considered. Hereby, we present the case of a 78-year-old patient known diabetic, hypertensive, and with deranged renal function, with left-sided L5 radiculopathy due to an L4-5 facet synovial cyst. He was treated through computed tomography (CT)-guided percutaneous aspiration and got long-term relief. The technique we used was different from the regular facet cyst aspiration, and the precision offered by CT guidance helped us provide optimum treatment leading to long-term relief. Thus, tailor-made treatment options rather than standard protocols for all patients allow a better risk–benefit ratio, in the field of pain management.

“There is a fear that you will be attacked just for the act of working in health”: a survey of experiences of violence against healthcare in Colombia

BackgroundColombia has experienced decades of conflict between the government and non-state actors. Attacks on healthcare have been a grave but regular facet of that violence. In response, the Misión Médica (MM) program was developed to support, protect, and defend healthcare. Sporadic violence continues, with many recent attacks perpetrated not by armed actors but by residents. Given the history of conflict and ongoing violence, we sought to capture the perspectives of both healthcare workers (HCWs) and community members (CMs) regarding the characteristics and impacts of attacks on health in Colombia to gain insight into how to better prevent violence and mitigate its impacts.MethodsA cross-sectional survey was conducted from January to March 2021 in seven departments in Colombia in regions that witnessed attacks on healthcare. Questionnaires were administered to HCWs and CMs via purposive sampling, probing their experiences with attacks on health with both closed and open-ended questions. The categorical responses were stratified by health worker vs. non-health worker and descriptively analyzed. Narrative responses were analyzed via a hybrid deductive/inductive thematic approach.ResultsSeventy-three individuals participated in the study (36 HCWs and 37 cm). Approximately 77% of HCWs believed that attacks on healthcare impacted health outcomes while 68% of CMs did not see a direct connection between violence against healthcare and poor health outcomes. Awareness of the MM program was significantly different between HCWs (83.3%) and CMs (37.8%). The survey responses explored the characteristics of attacks on health, compounded impacts of violence on the health system, personal impacts, and perspectives on mitigation efforts.ConclusionsThe study demonstrates that: (1) attacks on healthcare are context-dependent and require a local lens for mitigation and management; (2) both HCWs and CMs have critical perspectives that must be considered, (3) the impacts of violence against healthcare are complex and compounded and (4) that awareness of the legal protections of the Geneva Conventions must be combined with education on the health impacts for robust protection strategies. Critically, Both CMs and HCWs experience fear and psychosocial ramifications of these attacks, suggesting the need for stronger protections and resources to support the health workforce and the local community.

Artificial Intelligence in the Management of Rotator Cuff Tears

Technological innovation is a key component of orthopedic surgery. Artificial intelligence (AI), which describes the ability of computers to process massive data and "learn" from it to produce outputs that mirror human cognition and problem solving, may become an important tool for orthopedic surgeons in the future. AI may be able to improve decision making, both clinically and surgically, via integrating additional data-driven problem solving into practice. The aim of this article will be to review the current applications of AI in the management of rotator cuff tears. The article will discuss various stages of the clinical course: predictive models and prognosis, diagnosis, intraoperative applications, and postoperative care and rehabilitation. Throughout the article, which is a review in terms of study design, we will introduce the concept of AI in rotator cuff tears and provide examples of how these tools can impact clinical practice and patient care. Though many advancements in AI have been made regarding evaluating rotator cuff tears-particularly in the realm of diagnostic imaging-further advancements are required before they become a regular facet of daily clinical practice.

The interlacing number for alternating semiregular polytopes

In the classical setting, a convex polytope is said to be semiregular if its facets are regular and its symmetry group is transitive on vertices. This paper continues our study of ‘alternating’ semiregular abstract polytopes. These structures have abstract regular facets, still with combinatorial automorphism group transitive on vertices and with two kinds of regular facets occurring in an alternating fashion. Here we investigate a parameter called the interlacing number k for a compatible pair of regular n-polytopes P and Q: in what circumstances can we have k copies each of P and Q occuring in alternating fashion as the facets of a semiregular (n+1)-polytope S?

Significant photovoltaic enhancement in La-doped BiFeO3 achieved by engineering crystallographic facet arrays

Engineering regular surface crystallographic facet arrays on a large scale is useful for tuning and optimizing photophysical properties of optoelectronic materials. Herein, we achieve textured Bi0.5La0.5FeO3 (BLFO) film surfaces displaying nanosquare arrays composed of {001} and {110} crystallographic facets, via an effective and controllable thermal etching method. Substantially enhanced photocurrent signals from these faceted samples were confirmed via laser-assisted conductive atomic force microscopy at the nanometer scale, where tens of times increment in photo-generated electric field and short circuit current density were further identified. The electronic structures of the {001} and {110} surfaces were compared by ab-initio calculations, and the conduction band minimum of the latter one shows highly dispersive character thus prompted carrier transport can be anticipated. This thermal etching method provides an efficient strategy for fabricating patterned perovskite films with highly active crystallographic facet arrays and thus will inspire new technological possibilities for high-performance photovoltaic devices.

A single-layer urban canopy model with transmissive radiation exchange between trees and street canyons

Urban trees are one of the most effective strategies to mitigate excessive heat stress in cities. To understand the underlying mechanisms of their cooling effect and to assess their use in urban planning, the accurate simulation of how trees interact with the ambient built environment is critical and imperative. However, the representation of urban trees in existing urban canopy models (in particular the single-layer ones) remains oversimplified. Here we develop a new Monte Carlo ray tracing method to explicitly resolve the canopy transmittance and evaluate its impact on radiative view factors between trees and regular building facets. The new method is highly accurate in reproducing analytical solutions. Sensitivity tests of radiative view factors suggest the importance of canopy transmittance in changing the radiation exchange. We then incorporate the ray tracing algorithm into the new version of the Arizona State University (ASU) Single-Layer Urban Canopy Model (ASLUM v3.1). In addition to radiation transmittance, ASLUM v3.1 explicitly resolves the radiative shading, evapotranspiration, and root water uptake of urban trees in street canyons, with significantly improved performance in predictions (especially latent heat flux) when compared to previous versions. We further apply ASLUM v3.1 to evaluate the impacts of trees with varying characteristics on urban radiation exchange and turbulent heat fluxes. Results show that urban trees reduce the net radiation of ground and wall as well as the daytime temperature via shading and transpiration, but may slightly warm the nighttime street canyons through radiative trapping effect.

Temperature measurement in double-sided laser-heated diamond anvil cell and reaction of carbon

In this work, a double-sided laser-heated diamond anvil cell facility for studies at extreme conditions of pressure and temperature that has been developed is described in detail. Phase transitions occurring at extreme conditions can be mapped by accurate measurements of pressure and temperature. Micrometer-sized diamond crystals having regular facets have been synthesized at a pressure of 18 GPa and temperature 1785 K, which is confirmed by visual inspection, micro-Raman and field emission scanning electron micrograph measurements. A low-temperature gradient is observed across the sample surface during the formation of micrometer-sized diamond crystals. Our observation restricts the use of steel gasket as it can react with carbon (C) transported from the diamond anvil. The reaction of C with one of the potential thermal insulating medium Al $$_2$$ O $$_3$$ is observed in the X-ray diffraction measurements.

Universal Alternating Semiregular Polytopes

AbstractIn the classical setting, a convex polytope is said to be semiregular if its facets are regular and its symmetry group is transitive on vertices. This paper continues our study of alternating semiregular abstract polytopes, which have abstract regular facets, still with combinatorial automorphism group transitive on vertices and with two kinds of regular facets occurring in an alternating fashion.Our main concern here is the universal polytope ${\mathcal{U}}_{{\mathcal{P}},{\mathcal{Q}}}$, an alternating semiregular $(n+1)$-polytope defined for any pair of regular $n$-polytopes ${\mathcal{P}},{\mathcal{Q}}$ with isomorphic facets. After a careful look at the local structure of these objects, we develop the combinatorial machinery needed to explain how ${\mathcal{U}}_{{\mathcal{P}},{\mathcal{Q}}}$ can be constructed by “freely assembling” unlimited copies of ${\mathcal{P}}$, ${\mathcal{Q}}$ along their facets in alternating fashion. We then examine the connection group of ${\mathcal{U}}_{{\mathcal{P}},{\mathcal{Q}}}$, and from that prove that ${\mathcal{U}}_{{\mathcal{P}},{\mathcal{Q}}}$ covers any $(n+1)$-polytope ${\mathcal{B}}$ whose facets alternate in any way between various quotients of ${\mathcal{P}}$ or ${\mathcal{Q}}$.

A turbulent time: government sources post-2016 presidential election

PurposeSince the 2016 presidential election, hyper-partisanship has become a regular facet of the political landscape with Democrats and Republicans in increasing conflict. The purpose of this paper is to determine if perception of government sources related to trust and credibility has changed since the 2016 election and if the experiences and strategies of librarians who teach or consult about government information has changed in response to this environment.Design/methodology/approachA 24-question survey was distributed to garner qualitative and quantitative responses from librarians who teach or consult about government information in an academic environment. A total of 122 responses were used for analysis.FindingsAcademic librarians are seeing more concern from patrons about disappearing online government information and wider distrust of government information. Librarians also noticed that the political leanings of students color their perspective around government sources and that librarians also need to keep their political beliefs in check. Respondents emphasized a need for more government literacy and information literacy topics when discussing evaluation of government sources.Research limitations/implicationsThe data collection only included responses from academic librarians. Further research could include in-depth interviews and look at experiences in various library types.Originality/valueWith the timeliness of this topic, there has not been an in-depth investigation into how the Trump administration has changed user trust and perception of government sources from the librarian’s point of view. This paper continues the conversation about how librarians can address the growing distrust of government information and give us insight into the effects of a turbulent political climate on government sources.

EXTREMAL RAYS IN THE HERMITIAN EIGENVALUE PROBLEM FOR ARBITRARY TYPES

The Hermitian eigenvalue problem asks for the possible eigenvalues of a sum of Hermitian matrices given the eigenvalues of the summands. This is a problem about the Lie algebra of the maximal compact subgroup of G = SL(n). There is a polyhedral cone (the \eigencone) determining the possible answers to the problem. These eigencones can be defined for arbitrary semisimple groups G, and also control the (suitably stabilized) problem of existence of non-zero invariants in tensor products of irreducible representations of G. We give a description of the extremal rays of the eigencones for arbitrary semisimple groups G by first observing that extremal rays lie on regular facets, and then classifying extremal rays on an arbitrary regular face. Explicit formulas are given for some extremal rays, which have an explicit geometric meaning as cycle classes of interesting loci, on an arbitrary regular face. The remaining extremal rays on that face are understood by a geometric process we introduce, and explicate numerically, called induction from Levi subgroups. Several numerical examples are given. The main results, and methods, of this paper generalize [B3] which handled the case of G = SL(n).

The Assembly Problem for Alternating Semiregular Polytopes

In the classical setting, a convex polytope is called semiregular if its facets are regular and its symmetry group is transitive on vertices. This paper continues our study of alternating abstract semiregular polytopes $$\mathcal {S}$$ . These structures have two kinds of abstract regular facets $$\mathcal {P}$$ and $$\mathcal {Q}$$ , still with combinatorial automorphism group transitive on vertices. Furthermore, for some interlacing number $$k\geqslant 1$$ , k copies each of $$\mathcal {P}$$ and $$\mathcal {Q}$$ can be assembled in alternating fashion around each face of co-rank 2 in $$\mathcal {S}$$ . Here we focus on constructions involving interesting pairs of polytopes $$\mathcal {P}$$ and $$\mathcal {Q}$$ . In some cases, $$\mathcal {S}$$ can be constructed for general values of k. In other remarkable instances, interlacing with certain finite interlacing numbers proves impossible.

Record‐Low‐Threshold Lasers Based on Atomically Smooth Triangular Nanoplatelet Perovskite

AbstractSingle‐crystalline perovskites are ideal candidates for lasing and other optoelectronic applications. Although significant efforts have been made to grow both bulk single‐crystalline perovskites in liquid solution, their dimensions are still too large to make nanoscale whispering‐gallery‐mode (WGM) resonator based lasers that possess high quality (Q) factor and small volume. Besides, most reported perovskite resonators do not possess atomically smooth surfaces and facets, which limits the Q and thereby increases the lasing threshold. Here, atomically smooth triangular PbI2 templates are fabricated on a mica substrate by the vapor phase deposition method and are converted to atomically smooth perovskites which have regular and unwrinkled facets with average surface roughness less than 2 nm. By using a CH3NH3PbI3 nanoplatelet with a side length of 27 µm and thickness of 80 nm, room temperature WGM lasing with a Q up to 2600 is demonstrated, the highest reported for hybrid organic–inorganic perovskite nanoplatelets. In addition, the volume of the WGM mode is reduced significantly in comparison with the prior reports. The realized high‐quality triangular CH3NH3PbI3 perovskite nanoplatelets with high Q factor and small volume are expected to perform as ideal cavities for long pulse durations lasers and would find potential applications in integrated optoelectronic devices.

High-performance phototransistor based on individual high electron mobility MnWO4 nanoplate

MnWO4 nano-materials have been attracting intensive attention as a potential candidate for modern electronic and optoelectronic nanodevices. However, the availability of highly crystalline MnWO4 nanostructures with controllable geometry shapes still remains a great challenge and further hinders their technologically important applications in optoelectronic devices. Herein, large yield and crystalline MnWO4 nanoplates with regular crystal facets are synthesized on Ti substrate based on a conventional plasma electrolytic oxidation (PEO) process followed by a thermal annealing method. The phototransistor based on individual high electron mobility MnWO4 nanoplate has been fabricated and it shows a classical n-type semiconductor behavior with superior field emission transistor (FET) properties including a very low threshold voltage of 1 V and a high peak transconductance of 2.7 μS. Furthermore, the MnWO4 phototransistor also exhibits fast photoresponse time and high photoresponsivity under light illumination. All these unique characteristics of incident-light control and gate regulation from the MnWO4 nanoplate are expected to further promote its potential applications in multifunctional optoelectronic devices in the future.

Approximation of General Facets by Regular Facets with Respect to Anisotropic Total Variation Energies and Its Application to Crystalline Mean Curvature Flow

AbstractWe show that every bounded subset of a euclidean space can be approximated by a set that admits a certain vector field, the so‐called Cahn‐Hoffman vector field, that is subordinate to a given anisotropic metric and has a square‐integrable divergence. More generally, we introduce a concept of facets as a kind of directed sets, and show that they can be approximated in a similar manner.We use this approximation to construct test functions necessary to prove the comparison principle for viscosity solutions of the level set formulation of the crystalline mean curvature flow that were recently introduced by the authors. As a consequence, we obtain the well‐posedness of the viscosity solutions in an arbitrary dimension, which extends the validity of the result in the previous paper.© 2018 Wiley Periodicals, Inc.

Non-Flat Regular Polytopes and Restrictions on Chiral Polytopes

An abstract polytope is flat if every facet is incident on every vertex. In this paper, we prove that no chiral polytope has flat finite regular facets and finite regular vertex-figures. We then determine the three smallest non-flat regular polytopes in each rank, and use this to show that for $n \geq 8$, a chiral $n$-polytope has at least $48(n-2)(n-2)!$ flags.

Pre-kites: simplices having a regular facet

The investigation of the relation among the distances of an arbitrary point in the Euclidean space $$\mathbb {R}^n$$ to the vertices of a regular n-simplex in that space has led us to the study of simplices having a regular facet. Calling an n-simplex with a regular facet an n-pre-kite, we investigate, in the spirit of Hajja and Walker (Int J Math Ed Sci Tech 32:501–508, 2001), Edmonds et al. (Beitr Algebra Geom 46:491–512, 2005b), Edmonds et al. (Results Math 47:266–295, 2005a), and Hajja (Results Math 49:237–263, 2006), and using tools from linear algebra, the degree of regularity implied by the coincidence of any two of the classical centers of such simplices. We also prove that if $$n \ge 3$$ , then the intersection of the family of n-pre-kites with any of the four known special families is the family of n-kites, thus extending the result in Hajja et al. (Beitr Algebra Geom 56:269–277, 2015). A basic tool is a closed form of a determinant that arises in the context of a certain Cayley–Menger determinant, and that generalizes several determinants that appear in Edmonds et al. (Results Math 47:266–295, 2005a), Hajja (Results Math 49:237–263, 2006), and Hajja and Hayajneh (J Geom 105:539–560, 2014). Thus the paper is a further testimony to the special role that linear algebra plays in higher dimensional geometry.

Spatial distribution of active sites on a ferroelectric PbTiO3 photocatalyst for photocatalytic hydrogen production.

The separation of photogenerated charge carries is a challenging issue in artificial photocatalyst systems for solar energy conversion. It has been reported that spatial charge separation can take place between different facets of semiconductor-based crystals with regular morphology and facets, which could be used to rationally deposit cocatalysts on the right facets. However, the spatial separation of photogenerated electrons and holes is still a big challenge for a particulate photocatalyst without regular morphology and specific facets. In this work, we demonstrated that photogenerated electrons and holes can be regularly separated on ferroelectric PbTiO3 photocatalyst even without regular morphology and facets. The reduction cocatalyst and oxidation cocatalyst could be selectively formed on different sites via an in situ photochemical deposition method. It is found that the photoactivity and hydrogen production for PbTiO3 with spatially separated dual-cocatalysts is remarkably enhanced to more than 100 times greater compared to native PbTiO3, which is much higher than that the case of dual-cocatalysts with a random distribution. The intrinsic electric fields and spontaneous electric polarization in the bulk of PbTiO3 are proposed to play important roles in the spatial distribution of active sites on irregular PbTiO3 particles. Our work emphasizes the essential roles of two important factors, efficient charge separation strategy and the location of dual-cocatalysts on the right sites, to construct integrated artificial photocatalyst systems for solar energy conversion.

Linear and nonlinear optical characterization of methyl-p-hydroxybenzoate (p-MHB) single crystal grown by TSSG method

The nonlinear optical single crystal methyl-p-hydroxybenzoate (p-MHB) was grown by employing top seeded solution growth method (TSSG) for the first time. A good quality small size crystal grown from methanol solution was inserted into the melt as a seed for growth after seasoning it around the melt temperature. Highly transparent optical quality p-MHB single crystal with regular faceting was harvested after the successful growth run. The unit cell parameter of the grown crystal was determined by powder X-ray diffraction (PXRD) and the crystal structure was confirmed by single crystal X-ray diffraction (SCXRD) methods. The UV–Vis–NIR absorption spectrum has been recorded in the range 200–2700nm and it shows that the lower cutoff wavelength exits at 307nm. The study indicates that the grown crystal has good optical transparency window in the visible and near IR region in the range 307–2136nm. Second harmonic generation (SHG) efficiency of the grown crystal was studied by Kurtz-Perry powder method with 1064nm Nd: YAG laser beam as a fundamental source and it was about twice that the standard KDP.

Curvilinear hole filling for 3D digital dental models

Dental models are important for orthodontics diagnostic and treatment. Advances in imaging modality have led to conventional plaster models being replaced by the more versatile laser scanned ones. Due to various physical factors during the scan however, mesh irregularities such as holes and tangling facets are often been introduced. These have thus far impeded the subsequent computational and otherwise efficient analysis on the digital model. This article proposes a mesh pre-processing technique, which resolves prime defects on a dental mesh. The key contribution is the projection of a curvilinear non-planar two-manifold hole on a low distortion contour, upon which a network of regular facets may be re-triangulated. The experiments showed the potential of our scheme where moderately convoluted holes on typical dental mesh can be successfully patched.

Faceting of Equilibrium and Metastable Nanostructures: A Phase-Field Model of Surface Diffusion Tackling Realistic Shapes

Several crystalline structures are metastable or kinetically frozen out-of-equilibrium states in the phase space. When the corresponding lifetime is sufficiently long, typical equilibrium features such as regular and extended faceting can be observed. However, interpreting the extension of the facets and the overall shape in terms of a standard Wulff analysis is not justified. Here, we introduce a convenient general formulation of the anisotropic surface energy density, combined with a suitable phase-field model of surface diffusion. This allows for the investigation of the evolution toward equilibrium of realistically shaped nanostructures, describing an actual kinetic path and including the proper faceting. Numerical solution by the finite element method allows for efficient simulations even for the so-called strong anisotropy condition. After illustrating applications yielding equilibrium crystal shapes (corresponding to the Wulff construction), we focus our attention on faceting of structures in long-...