Key Fact Research Articles

Solving Symmetric Algebraic Riccati Equations with High Order Iterative Schemes

We solve symmetric algebraic Riccati equation using efficient high-order iterative schemes which improve the speed of convergence of others widely used in the literature. These high-order iterative schemes involve the Riccati operator and the first Frechet derivative. Applying these iterative schemes is equivalent to solving a fixed number of Lyapunov equations with the same matrix. This key fact makes efficient these methods. Moreover, a local convergence result of one of these high-order iterative schemes is analyzed. Finally, numerical experiments confirm the advantageous performance of these schemes.

Corporate Short-Termism and Intertemporal Choice

This paper presents an intertemporal model of short-termism. Critics have portrayed short-termism in broad brushstrokes as the bane of corporate governance. This paper shows that from a financial perspective short-termism does not have a self-evident, efficiency-based normative value. It applies a well-accepted asset valuation theory to demonstrate that short-termism is not per se inefficient. Intuition suggests that if profitable enough, a short-term strategy would be better than a longterm strategy. The model demonstrates this intuition to be a mathematical and financial truth. Several generalizable observations result therefrom. The model is tested in a case study of Air Products and Chemicals, Inc. v. Airgas, Inc., the most prominent and legally significant Delaware hostile takeover battles in recent years. Short-termism was a key fact in the court’s legal analysis of the target’s poison pill defense. For unique reasons, the case enables a counterfactual analysis of the financial returns based on the target’s intertemporal strategic choices and the time horizons of shareholders. The choice of the short-term is contextual; the outcomes therefrom can result in random errors or rational outcomes. It can also result in a systemic social problem, but only when two levels of market inefficiency coexist: the corporate market is systemically biased in intertemporal decisions, and the capital market is inefficient in incorporating this bias into stock prices. These conditions are special, occurring only infrequently. They are intrinsic qualities of a market bubble. This paper precisely defines the conditions in which short-termism can become a social problem.

Tax Benefit Complexity and Take-Up: Lessons from the Earned Income Tax Credit

Millions of low-income Americans fail to claim tax benefits for which they are eligible, possibly because the rules governing the benefits are extraordinarily complex. I consider efforts to increase tax benefit take-up in light of this complexity. A key fact is that the vast majority of tax filers today prepare their taxes with assisted preparation methods (APMs) like software or professional assistance. APMs eliminate some – but not all – of the barriers to claiming tax benefits for which one is eligible. With respect to claiming the Earned Income Tax Credit (EITC), I argue that most of the relevant complexity is the type that is eliminated by APMs. Consequently, efforts to increase EITC take-up should focus on inducing EITC-eligible individuals to file a tax return using an APM. In contrast, efforts aimed at increasing awareness of the credit (of the type widely employed by governments and nonprofits today) are less likely to be successful, except to the extent they themselves induce an increase in tax filing. Reforms that appear unrelated to a tax benefit may dramatically affect the benefit’s take-up by altering incentives to file a return. I develop these arguments in the context of the EITC, drawing on recent empirical work to support my claims.

A characterization of linearly repetitive cut and project sets**Research supported by EPSRC grants EP/L001462, EP/J00149X, EP/M023540. HK also gratefully acknowledges the support of the Osk. Huttunen foundation.

For the development of a mathematical theory which can be used to rigorously investigate physical properties of quasicrystals, it is necessary to understand regularity of patterns in special classes of aperiodic point sets in Euclidean space. In one dimension, prototypical mathematical models for quasicrystals are provided by Sturmian sequences and by point sets generated by substitution rules. Regularity properties of such sets are well understood, thanks mostly to well known results by Morse and Hedlund, and physicists have used this understanding to study one dimensional random Schrödinger operators and lattice gas models. A key fact which plays an important role in these problems is the existence of a subadditive ergodic theorem, which is guaranteed when the corresponding point set is linearly repetitive.In this paper we extend the one-dimensional model to cut and project sets, which generalize Sturmian sequences in higher dimensions, and which are frequently used in mathematical and physical literature as models for higher dimensional quasicrystals. By using a combination of algebraic, geometric, and dynamical techniques, together with input from higher dimensional Diophantine approximation, we give a complete characterization of all linearly repetitive cut and project sets with cubical windows. We also prove that these are precisely the collection of such sets which satisfy subadditive ergodic theorems. The results are explicit enough to allow us to apply them to known classical models, and to construct linearly repetitive cut and project sets in all pairs of dimensions and codimensions in which they exist.

Unified GPU-Parallelizable Robot Forward Dynamics Computation Using Band Sparsity

This letter proposes a unified GPU-parallelizable approach for robot forward dynamics (FD) computation based on the key fact that parallelism of prevailing FD algorithms benefits from the essential band sparsity of the joint space inertia (JSI) matrix or its inverse. The existing FD algorithms are categorized into three classes: direct JSI algorithms, propagation algorithms, and constraint force algorithms. Their associated systems of linear equations are transformed into a set of block bidiagonal (the first and second classes) and tridiagonal (the third class) linear systems, which can be conveniently and efficiently parallelized over the existing CPU–GPU programming platforms using various state-of-the-art parallel algorithms, such as parallel all-prefix sum (scan) and odd–even elimination. This high-level perspective allows unified and efficient implementation of all three classes of algorithms and also other potentially efficient algorithms, with the bonus that different algorithms can be swiftly compared to recommend problem-specific solutions.

Beneath and Beyond the Forty-Fifth American Presidency

Mesmerized by its antic spectacle and its reinvigoration of hoary pathologies of an American past that will not pass, much resistance-discourse about the forty-fifth U.S. presidency does not foreground the key fact that it is the emanation of a global neoliberalism unique to the twenty-first century. Arguing for an imaginative political vision that extends beyond the horizon of coming election cycles, and past the borders of the nation-state, the essay evokes a venerable African American intellectual tradition as it looks upon the forty-fifth presidency as an opportunity to refuse pessimism and embrace internationalist, pragmatic utopianism.

Why neither demographics nor feature pools can explain the missing Spanish plantation creoles

Theories that plantation creoles were all born as pidgins at West African coast slave castles, including that proposed in McWhorter (2000), have not fared well among creolists, amidst a preference for supposing that creoles are born, or not, according to factors local to a given context. In this paper I spell out why, especially in light of research since, the “Afrogenesis” paradigm is still worth serious consideration. A key fact is the following. Many creolists argue that a creole did not appear when there was extensive black-white contact and many slaves were locally-born, a scenario most often associated with the Spanish Caribbean and Reunion and now proposed for South American colonies by Sessarego (2014) and Díaz-Campos and Clements (2008). However, conditions were of just this kind in early St. Kitts and Barbados, where most scholars now locate the birth of English-based and French-based plantation creoles. The disparity in outcomes between these locations means that after fifty years, there is no coherent theory of how or why creoles come to be. I argue that only Afrogenesis shows the way out of this conundrum. I further discuss why the idea that creoles result from individual blendings of “features” in each location (Mufwene, 2011, 2008) is incommensurate with creole linguistic data.

Geochemistry, petrogenesis and tectonic significance of the volcanic rocks of the Las Tortolas Formation, Coastal Cordillera, northern Chile

The Las Tórtolas Formation extends from 29° to 26° S along the northern chilean coast and has been interpreted as a Carboniferous accretionary prism. This essentially metasedimentary turbiditic formation constituted the late Paleozoic basement of the Upper Triassic-Jurassic magmatism during the inception of the Andean cycle in northern Chile. The geochemical characteristics and field relations studied in the volcanic rocks of the Las Tórtolas Formation, described with detail in this work, mean a key fact to assess the notable paleogeographic changes occurred during the pre-Andean cycle in the western margin of South America.The volcanic domain included in the Las Tórtolas Formation is mainly comprised by basaltic rocks, with minor tuffs and rhyolites, and presents thrust-fault contacts with the mélange facies to the west and the metasedimentary Eastern Series to the east. Together, the Las Tórtolas Formation was conformed by the stacking of the basal highly deformed units of this accretionary complex, represented by the mélange facies, and the volcanic domain that became overlain by the turbiditic sequences at their top.The geochemical characteristics of the Las Tórtolas basaltic rocks involve an enriched mantle source, as a mantle plume. In spite of the N-MORB signature observed in the basal hyaloclastitic basalts, the lava flows, as the metabasites sampled in the mélange facies, yield E-MORB characteristics according to the multi-element and tectonic discrimination diagrams and several immobile element ratios as the Th/Yb, TiO2/Yb and Nb/Yb, among others. Therefore, the origin of the volcanic domain of the Las Tórtolas Formation may be related to a hot mantle plume impinged on the base of the oceanic lithosphere under the tip of the overriding plate, which firstly promoted the partial melting of the depleted surrounding lithosphere (N-MORB hyaloclastites) and continued with the extrusion of lava flows and pyroclastic rocks derived from the enriched source, interlayered with the distal turbiditic succession. The development of the magmatic system along the oceanic crust enabled the formation of magma chambers where small volumes of rhyolitic melts were fractionated. The geochemical evolution of this basaltic magmatism was correlated with the building of volcanic edifices during a first submarine stage (hyaloclastites, pillows and lava flows) and a subsequent sub-aerial explosive phase depicted by sedimentary and rhyolitic breccias.Finally, we explore a tectonic setting defined by a plume overridden by the lithosphere during the relative convergence with the continental margin to explain the formation of the volcanic domain and its accretion to the sedimentary units. Besides, this tectonic configuration may be taken into account as the driving force of the tectonic and magmatic events that characterize the pre-Andean cycle.

Autoduality holds for a degenerating abelian variety

We prove that certain degenerate abelian varieties that include compactified Jacobians, namely stable semiabelic varieties, satisfy autoduality. We establish this result by proving a comparison theorem that relates the associated family of Picard schemes to the Néron model, a result of independent interest. In our proof, a key fact is that the total space of a suitable family of stable semiabelic varieties has rational singularities.

Limits of quotients of polynomial functions in three variables

A method for computing limits of quotients of real analytic functions in two variables was developed in [4]. In this article we generalize the results obtained in that paper to the case of quotients q = f ( x, y, z )/ g ( x, y, z ) of polynomial functions in three variables with rational coefficients. The main idea consists in examining the behavior of the function q along certain real variety X ( q ) (the discriminant variety associated to q ). The original problem is then solved by reducing to the case of functions of two variables. The inductive step is provided by the key fact that any algebraic curve is birationally equivalent to a plane curve. Our main result is summarized in Theorem 2. In Section 4 we describe an effective method for computing such limits. We provide a high level description of an algorithm that generalizes the one developed in [4], now available in Maple as the <code>limit/multi</code> command.

Memory and spaces in dispute in San Carlos de Bariloche: the monument to Gen. Roca in the Civic Center

O artigo aborda a polêmica surgida entre a década de 1990 e a atual em torno de dois grupos de memórias contrapostas sobre um dos acontecimentos históricos-chave da formação do Estado Nacional argentino no século XIX, a denominada "Conquista do Deserto" (1878-1885), e seu principal comandante, o Gen. Julio Argentino Roca (1843-1914). Tal polêmica tem como principal disparador uma série de monumentos em homenagem a Roca presentes nos espaços públicos de diversas cidades da Argentina, dentre as quais, San Carlos de Bariloche, na Patagônia, onde parte da população local alega que a estátua alude não a um passado glorioso, mas ao massacre genocida que teve por alvo principalmente o povo indígena Mapuche que habitava originalmente aquela região. Aqui será exposto como tal monumento tornou-se objeto de uma disputa simbólica que revela, em seu conteúdo e origens, a emergência no espaço urbano de demandas específicas por terra, por autonomia territorial, por condições dignas de vida, reconhecimento identitário e, por fim, pela consolidação de novos espaços de representação social e política para os indígenas argentinos

Promotion of Increasing Tableaux: Frames and Homomesies

A key fact about M.-P. Schützenberger's (1972) promotion operator on rectangular standard Young tableaux is that iterating promotion once per entry recovers the original tableau. For tableaux with strictly increasing rows and columns, H. Thomas and A. Yong (2009) introduced a theory of $K$-jeu de taquin with applications to $K$-theoretic Schubert calculus. The author (2014) studied a $K$-promotion operator $\mathcal{P}$ derived from this theory, but observed that this key fact does not generally extend to $K$-promotion of such increasing tableaux. Here, we show that the key fact holds for labels on the boundary of the rectangle. That is, for $T$ a rectangular increasing tableau with entries bounded by $q$, we have $\mathsf{Frame}(\mathcal{P}^q(T)) = \mathsf{Frame}(T)$, where $\mathsf{Frame}(U)$ denotes the restriction of $U$ to its first and last row and column. Using this fact, we obtain a family of homomesy results on the average value of certain statistics over $K$-promotion orbits, extending a $2$-row theorem of J. Bloom, D. Saracino, and the author (2016) to arbitrary rectangular shapes.

Spontaneous growth of vector fields in gravity

We show that the spontaneous scalarization scenario in scalar-tensor theories is a specific case of a more general phenomenon. The key fact is that the instability causing the spontaneous growth in scalars is due to the nonminimal coupling in the theory, and not related to the nature of the scalar. Another field with the same form of coupling undergoes spontaneous growth as well. We explicitly demonstrate this idea for vectors, naming it "spontaneous vectorization", and study spherically symmetric neutron stars in such a theory. We also comment on other tensor fields the idea can be applied, naming the general mechanism "spontaneous tensorization".

18 What information is provided to patients with tourette syndrome?

<h3>Objective</h3> Information about medical disorders should be provided to patients in a standardised way in order to ensure that key information about their conditions is appropriately conveyed. This is particularly relevant for neuropsychiatric disorders for which misconceptions are widespread, such as Tourette syndrome. We set out to identify and critically appraise the most commonly used Patient Information Leaflets (PILs) about Tourette syndrome worldwide. <h3>Method</h3> A computerised search was carried out using the web search engine Google, which ranks web pages by relevance using the PageRank algorithm. The search terms “Tourette*” AND “leaflet” OR “fact sheet” OR “information sheet” were used to identify PILs developed by a named source in English language with the purpose to provide an overview of Tourette syndrome. The contents of the PILs were subsequently screened for inclusion of the eight key facts identified by Tourettes Action-UK as the gold standard of essential information about Tourette syndrome to be communicated to patients. Each PIL was given a quality score from 0 to 1 for each key fact (total score 0–8): 0 points if the fact was not addressed, 0.5 points if the fact was partially addressed, and 1 point if the fact was fully addressed. <h3>Results</h3> A total of 18 PILs were identified, with quality scores ranging from 4 to 6.5. There were considerable discrepancies in the amount and accuracy of information provided by each PIL. The key facts about the range of severity of Tourette syndrome and the presence of co-morbidities such as ADHD and OCD were adequately covered by all PILs. Key information about the definition of Tourette syndrome and the existence of dedicated charities/support groups was present in 14/18 PILs. (78%) The majority of PILs (13/18; 72%) clearly stated that involuntary swearing as a tic (coprolalia) is present only in a subset of patients with Tourette syndrome. Four PILs (22%) mentioned pharmacological options outside neuroleptics, such as clonidine, and only one PIL (6%) covered behavioural, pharmacological and surgical treatment options. Finally, the recommendation of referring patients with Tourette syndrome to a specialist in neuropsychiatry was not explicitly mentioned in any of the PILs. <h3>Conclusions</h3> There is a wide selection of PILs available on Tourette syndrome, however the information provided in these PILs vary considerably in quality and comprehensiveness. Inclusion of key facts on Tourette syndrome would improve the delivery of care for this clinical population by ensuring that patients have access to more accurate, consistent and useful information.

Curing behaviors and properties of epoxy and self-catalyzed phthalonitrile with improved processability

The curing behaviors for high-performance resin system phthalonitrile-containing benzoxazine and epoxy (BA-Ph/EP), particularly the effect of the binary system composition and processing conditions on their processabilities were investigated and discussed in this article. Results indicated that all BA-Ph/EP prepolymers exhibited low initial processing viscosity (&lt;0.3 Pa s) and have kept stable low viscosity until gel transition. The suitable molding temperature (ranged from 150°C to 180°C) and molding time (ranged from 20 min to 80 min) could be selected for practical applications of BA-Ph/EP systems. The studies of curing behaviors and gelatinization for BA-Ph/EP systems give further understanding of the curing kinetics and guidance for the fabrication of high-performance copolymers/polymers. The introduction of EP could significantly improve the cross-linking density of BA-Ph/EP polymers, and the appropriate content of EP is the key fact for the improvement. In addition, the effects of postcuring conditions on thermal properties and the adhesive property of BA-Ph/EP polymers were monitored. The thermal stabilities and adhesive property of various polymers also showed an obvious influence with the introduction of EP. The systematic study of BA-Ph/EP system could enable a broadened industrial application, especially in the areas that require high-temperature resistance.

Smart frost control in greenhouses by neural networks models

Thermal comfort in greenhouses is a key fact to enhance productivity, due to the excess demand of energy for heating, ventilation and agroclimatic conditioning. Frost, in particular, represents a serious technological challenge if the crop sustainability is to be ensured. A Multi-Layer Perceptron artificial neural network, trained by a Levenberg-Marquardt backpropagation algorithm was designed and implemented for the smart frost control in greenhouses in the central region of Mexico, with the outside air temperature, outside air relative humidity, wind speed, global solar radiation flux, and inside air relative humidity as the input variables. The results showed a 95% confidence temperature prediction, with a coefficient of determination of 0.9549 and 0.9590, for summer and winter, respectively.

Attacking Tobacco: Philip Morris International v. Uruguay

For the last two decades tobacco companies have been using their seemingly infinite resources to maintain markets in poorer countries that have tried to decrease the number of smokers in their nations. In other words it can best be described as “intimidation litigation.” In the interest of public health, Uruguay passed two plain packaging laws that aimed to curb deceptive advertising and make their consumers aware of the significant health consequences of consuming tobacco products. After losing in the two highest Uruguayan courts, Philip Morris challenged the laws in an international tribunal (ICSID) as a breach of the bi-lateral agreement’s fair and equitable treatment clause. Under the guise of public health, Uruguay persuaded the Tribunal to rule in favor of Uruguay’s police powers to regulate public health. This article breaks down how the Tribunal departed from precedent concerning domestic actions that result in an alien’s investment to be expropriated. It deeply explores the risks of allowing a country to pass laws without regard to their foreign investments. This issue was compounded by the fact that the Uruguayan court system has two “supreme courts” that ruled differently on a key fact in the dispute. In response, the international Tribunal nonchalantly equated “justice” as an opportunity to “have their day in court.” This is a shaky and controversial standard at best considering the varying judicial systems throughout the world. Nonetheless, the article concludes by explaining that despite the risks and slipshod logic employed by the Tribunal, the decision in favor of Uruguay makes sense. Tobacco companies have been bullying and suing their way into keeping tobacco products in schools, in stores, and a significant part of peoples lives around the world.

Mohammad Vasef, Aaron Auerbach Diagnostic Pathology: Molecular Oncology Elsevier, Philadelphia, 2016, Hardcover and Expert consult access. ISBN 978-0-323-37678-5. Price £190.79 hardcover, £181.25 for online edition

In a fast developing field of molecular pathology, it is difficult to find up to date molecular diagnostics without considerable searching and literature review. This single-volume edition consisting of nine, well-indexed sections, including molecular pathology of solid and haematological tumours, is a treasure. The expanding knowledge of molecular oncology as a result of next-generation sequencing technology has enabled recent developments in drugable targets and changes in diagnostics. Often questions are asked of pathologists by clinical colleagues into further molecular diagnostics. Having information to hand that is well referenced and helpful both for diagnosis and treatment planning, which is easy to access and interpret, is incredibly important. The sections are colour coordinated, allowing quick browsing of sections. The central nervous system tumours are in the solid tumour sections, coded green; this is easy to find even with the book sitting on the table. This ease of navigation is very useful as I find myself constantly dipping into different sections, so the colour coding is most helpful. Central nervous system tumours are covered in section 8 from pages 8-382 to 8-416, including sections of Glial Tumours, subdivided into High-Grade and Low-Grade Tumours, Pilocytic Astrocytoma and Oligodedroglioma. There are separate sections of Ependymoma, Medulloblastoma, Choroid Plexus Tumours, Meningioma and Retinoblastoma. Also, there are other sections covering lymphoid tumours and of course, the solid tumours that metastasise to the CNS. The chapters include clear histopathological pictures including relevant immunohistochemical stains. The text is written in easy to follow bullet points which are subdivided into sections including clinical, radiological and macroscopic findings as well as histological and, of course, molecular sections. There is a large subsection including the molecular changes with different tumour subtypes, which again are bullet points and split up in molecular subtypes including those with particular clinical relevance. For those looking for an even quicker reference, there are ‘Key Fact’ boxes for all tumour subtypes which provide clinical, histopathological and molecular ‘highlights’ at a glance and are truly excellent summaries, and very useful for exam revision. The expert consult access is as ever, an absolute triumph of modern technology. To be able to carry a searchable edition of the book on your smart phone or tablet means that you are never without the answer. The histological pictures alone are high-definition images that zoom well on electronic devices with high-definition screens and are excellent for showing vital diagnostic features. The text is easy to search and accessible for instant information. One criticism of this is that you do require a high-speed Internet link for the search function, and a downloadable PDF would be useful for those times you cannot access the Internet, such as when in most hospitals in the UK. I would not let that put me off, however. There are very few molecular pathology books, if any, to compare this to, that provide the same amount of detail with such good correlates. The main advantage of the book is it saves sifting through the published literature and brings it together in an easy to follow single volume, which is a distinct advantage as you do not keep picking the wrong volume from the shelf. At a fraction under £200 this is a very well-referenced book, which provides a good bench-side reference for molecular pathology. The major advantage of this book to me is the correlation with the other available findings seen clinically, radiologically and histologically. I highly recommend this book for surgical pathologist as well as those with an interest in molecular pathology and research. For consultants and registrars this provides a good summary in one place to aid our day to day work. It also provides useful high-volume facts which are ideal for exam revision.

Frequency Diffeomorphisms for Efficient Image Registration.

This paper presents an efficient algorithm for large deformation diffeomorphic metric mapping (LDDMM) with geodesic shooting for image registration. We introduce a novel finite dimensional Fourier representation of diffeomorphic deformations based on the key fact that the high frequency components of a diffeomorphism remain stationary throughout the integration process when computing the deformation associated with smooth velocity fields. We show that manipulating high dimensional diffeomorphisms can be carried out entirely in the bandlimited space by integrating the nonstationary low frequency components of the displacement field. This insight substantially reduces the computational cost of the registration problem. Experimental results show that our method is significantly faster than the state-of-the-art diffeomorphic image registration methods while producing equally accurate alignment. We demonstrate our algorithm in two different applications of image registration: neuroimaging and in-utero imaging.

Projective toric polynomial generators in the unitary cobordism ring

According to Milnor and Novikov's classical result, the unitary cobordism ring is isomorphic to a graded polynomial ring with countably many generators: , . In this paper we solve the well-known problem of constructing geometric representatives for the among smooth projective toric varieties, , . Our proof uses a family of equivariant modifications (birational isomorphisms) of an arbitrary complex manifold of complex dimension (, ). The key fact is that the change of the Milnor number under these modifications depends only on the dimension and the number and does not depend on the manifold itself. Bibliography: 22 titles.