Contraction Sequence Research Articles

Preparation of Novel 4′-Spirocyclopropyl Nucleoside Analogues

AbstractThe stereoselective preparation of a novel 4′-spirocyclopropyl nucleoside analogue has been developed by using a semibenzilic Favorskii rearrangement of a 4′-(2-chloro-3-oxocyclobutyl)spirofuranose as a key step. These chiral spirocyclic intermediates, readily obtained on a multigram scale from chiral-pool starting materials, were shown to be highly suitable precursors for achieving full stereoselectivity in the reduction–ring contraction sequence. The downstream introduction of a nucleobase through Vorbrüggen glycosylation successfully resulted in the formation of the corresponding novel 4′-spirocyclic nucleoside analogue in a stereospecific manner.

Optimal sequential contract with a risk‐averse supplier

AbstractWe study optimal contracts in environments where a risk‐averse supplier discovers cost information privately and gradually over time: the supplier is privately informed about its cost uncertainty at the time of contracting and discovers the realization of cost condition privately after contracting and before production. We show that both the buyer and the supplier prefer more cost uncertainty when the supplier is not very risk‐averse but less cost uncertainty when the supplier is sufficiently risk‐averse. However, the buyer always prefers to contract before the cost uncertainty resolves regardless of the supplier's degree of risk aversion. The nature of the optimal contract also depends on the supplier's risk preference. A separating contract is optimal when the supplier is not very risk‐averse; however, a pooling contract, which offers the same contract terms regardless of the cost uncertainty, can be optimal when the supplier becomes sufficiently risk‐averse. Moreover, the optimal production schedule is often characterized by “inflexible rules.”

Fast Search of the Optimal Contraction Sequence in Tensor Networks

Tensor network and tensor computation are widely applied in scientific and engineering domains like quantum physics, electronic design automation, and machine learning. As one of the most fundamental operations for tensor networks, a tensor contraction eliminates the sharing orders among tensors and produces a compact sub-network. Different contraction sequence usually yields distinct storage and compute costs, and searching the optimal sequence is known as a hard problem. Prior work have designed heuristic and fast algorithms to solve this problem, however, several issues still remain unsolved. For example, the data format and data structure are not efficient, the constraints during modeling are impractical, the search of the optimal solution might fail, and the search cost is very high. In this paper, we first introduce a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$log_k$</tex-math></inline-formula> order representation and design an adjacency matrix-based data structure to efficiently accelerate the search of the optimal contraction sequence. Then, we propose an outer product pruning method with acceptable overhead to reduce the search space. Finally, we use a multithread optimization in our implementation to further improve the execution performance. We also present in-depth analysis of factors that influence the search time. This work provides a full-stack solution for optimal contraction sequence search from both high-level data structure and search algorithm to low-level execution parallelism, and it will benefit a broad range of tensor-related applications.

Position sense at the human forearm over a range of elbow angles.

Ten adult participants carried out two experiments on position sense at the forearm, one a two-arm matching task, the other a one-arm pointing task. For matching, both forearms were strapped to paddles which moved in the vertical plane between 0° and 90°. At the start of each trial, the arms were conditioned with a contraction sequence to control for the thixotropic property of muscle and muscle spindles. In the matching task, the blindfolded participant moved their indicator arm from 45° into flexion or extension to match the position of the reference arm placed at one of five test angles, between 5° and 85°. In the pointing task, only the reference arm was strapped to a paddle and conditioned. Participants indicated the position of the arm, hidden by a screen, by moving a pointer paddle or choosing one of a series of trajectory lines drawn on the screen. In matching, where test angles were in the direction of flexion of 45°, errors were small; in the direction of extension larger errors were made, up to 8° into flexion. In pointing trials, except at the most extended position, all errors lay in the direction of extension. It is argued that position sense by matching is concerned with the relative positions of the body and its parts, position sense by pointing gives information about position of the body and limbs in external space.

An Inertial Generalized Viscosity Approximation Method for Solving Multiple-Sets Split Feasibility Problems and Common Fixed Point of Strictly Pseudo-Nonspreading Mappings

In this paper, we propose a generalized viscosity iterative algorithm which includes a sequence of contractions and a self adaptive step size for approximating a common solution of a multiple-set split feasibility problem and fixed point problem for countable families of k-strictly pseudononspeading mappings in the framework of real Hilbert spaces. The advantage of the step size introduced in our algorithm is that it does not require the computation of the Lipschitz constant of the gradient operator which is very difficult in practice. We also introduce an inertial process version of the generalize viscosity approximation method with self adaptive step size. We prove strong convergence results for the sequences generated by the algorithms for solving the aforementioned problems and present some numerical examples to show the efficiency and accuracy of our algorithm. The results presented in this paper extends and complements many recent results in the literature.

Multigenerational Crumpling of 2D Materials for Anticounterfeiting Patterns with Deep Learning Authentication

Summary Physical unclonable function (PUF) is a cornerstone of anticounterfeiting. However, conventional PUF key-based secure tags encounter several bottlenecks, such as complicated manufacturing, specialized and tedious readout, long authentication time, and insufficient stability. Here, we utilize various two-dimensional materials (2DMs), including Ti3C2Tx MXene and graphene oxide, to construct multigenerational microstructures as PUF patterns. Two intermediate treatments, cation intercalation and moisture-induced lubrication, are introduced in between sequential contractions to engineer the multiscale patterns in a transfer-free and scalable fashion. A deep learning (DL)-facilitated software is developed to pre-categorize the hierarchical topographies with classifiable features. Thereafter, the search-and-compare is conducted within a smaller database to shorten the overall authentication time. The synergy between 2DM tags and DL-facilitated software enables a reliable and environmentally stable anticounterfeiting technology, DeepKey, showing superior encoding capacity (>10144,494) and short authentication time (∼3.5 min). Our 2DM anticounterfeiting tag is finally integrated with QR codes to provide two-layer information security.

Mechanisms of Modulation of Automatic Scapulothoracic Muscle Contraction Timings

Erected posture provides humans a large shoulder mobility that requires complex automatic muscle synergies to accomplish joint stability needs. This is evident in shoulder abduction, wherein the voluntary activation of glenohumeral muscles is coupled with an automatic recruitment of scapulothoracic muscles. Here, we investigated whether volitional modification of the scapular position, and dynamic scapular elevation, modulate the contraction timing of five shoulder muscles (middle deltoid, upper, middle and lower fiber of the trapezius, serratus anterior) during shoulder abduction. The results show matched contraction timings of the deltoid and upper trapezius across the scapular positions, whereas the contraction timings of the middle and lower fibers of the trapezius change secondary to the scapular position. These results might reflect different central strategies to coordinate the automatic sequences of contraction of the scapulothoracic muscles. This suggest a flexible and adaptable predisposition of the motor control system in exploring alternative solutions to accomplish the functional movement needs, such as the fulfillment of unconstrained movements. Intriguingly, the shoulder abduction may represent a powerful, non-invasive, and straightforward tool to deepen the understanding of the neural basis underlying the voluntary motor command modulation of the out-of-volition automatic muscle contractions.

Atomic decompositions and asymmetric Doob inequalities in noncommutative symmetric spaces

We provide asymmetric forms of Doob maximal inequality in the contexts of moments associated with convex functions and symmetric spaces of measurable operators. More precisely, let (M,τ) be a noncommutative measurable space equipped with a filtration (Mn)n≥1. Let (En)n≥1 be the conditional expectations corresponding to (Mn)n≥1. A sample result for the case of convex functions states that if Φ is an Orlicz function that is p-convex and q-concave for 1≤p≤q<2 and 1−p/2<θ<1, then for every x in the column Hardy space HΦc(M), there exist positive operators a,b, and a sequence of contractions (un)n≥1 in M such that for every n≥1,En(x)=aunb andτ(Φ(a1/(1−θ)))+τ(Φ(b1/θ))≲τ(Φ(Sc(x))). For the case of symmetric space, as an illustration, we obtain that if E is a separable symmetric Banach function space which is an interpolation of (Lp,Lq) for 1<p≤q<2, then for every z∈E(M), there exist positive operators α,β, two sequences of contractions (υn)n≥1 and (ηn)n≥1 in M such that for every n≥1,En(z)=αυn+ηnβ and‖α‖E(M)+‖β‖E(M)≲‖z‖E(M).Our approach is based on new algebraic atomic decompositions and improved Davis type decompositions which we develop for both the case of Hardy spaces associated with separable noncommutative symmetric spaces that are interpolation of the couple (Lp,Lq) for 1<p≤q<2 as well as the case of Hardy spaces associated with convex functions that are p-convex and q-concave for 1≤p≤q<2. Some other inequalities are also provided which are of independent interest.

Extraction and complexation of trivalent rare earth elements with tetraalkyl diglycolamides

The extraction and complexation behaviors of four tetraalkyl diglycolamide (TRDGA, where R represents n-butyl, n-hexyl, n-octyl and 2-ethylhexyl) ligands with linear chain or branched chain structure were described with respect to La3+, Pr3+, Nd3+; Eu3+, Gd3+; Y3+, Er3+ and Yb3+ as the representatives of light, middle and heavy rare-earth group ions in HNO3 solution. Effects of acidity, ligand concentration and temperature on the distribution ratio of these ions were examined. High acidity was good for the extraction. For same metal ion, the extractability of DGA ligands followed the order of T2EHDGA < THDGA < TODGA < TBDGA at the same acidity, which was also supported by nuclear magnetic resonance (NMR) analyses. Meanwhile, for different metal ions, their extracted efficiencies by the same DGA ligand increased in the sequence of lanthanide contraction. The average separation factors of adjacent lanthanides within light, middle and heavy rare-earth groups could attain about 2.4, 1.7 and 2.1, respectively. Slope analysis indicated that the formation of predominant 1:3 and 1:2 metal/ligand extracted species for linear chain and branched DGA, respectively. In methanol solution, 1:1, 1:2 and 1:3 Eu3+/DGA species were also observed using fluorescence spectroscopy titration. Fourier transform infrared spectroscopy (FT-IR) analyses suggested that the carbonyl oxygens compared with ether oxygen play a dominant role in coordination. Moreover, the stability constants (log β) and the thermodynamic parameters (ΔH, ΔS and ΔG) for the complexation of Eu3+ with DGAs were also presented.

Algorithms for tensor network contraction ordering

Contracting tensor networks is often computationally demanding. Well-designed contraction sequences can dramatically reduce the contraction cost. We explore the performance of simulated annealing and genetic algorithms, two common discrete optimization techniques, to this ordering problem. We benchmark their performance as well as that of the commonly-used greedy search on physically relevant tensor networks. Where computationally feasible, we also compare them with the optimal contraction sequence obtained by an exhaustive search. Furthermore, we present a systematic comparison with state-of-the-art tree decomposition and graph partitioning algorithms in the context of random regular graph tensor networks. We find that the algorithms we consider consistently outperform a greedy search given equal computational resources, with an advantage that scales with tensor network size. We compare the obtained contraction sequences and identify signs of highly non-local optimization, with the more sophisticated algorithms sacrificing run-time early in the contraction for better overall performance.

La relevancia de las arritmias de origen no cardíaco en pacientes pediátricos

Introducción: como es sabido, las arritmias son una causa importante de las palpitaciones, siendo este un problema común en los individuos que se encuentran dentro del rango de la edad pediátrica. El objetivo de esta investigación es informar al público en general sobre la importancia de la correcta investigación del origen de las palpitaciones, mediante una correcta anamnesis, examen físico y un EKG de 12 derivaciones, ya que esto puede provocar una gran preocupación entre los padres y/o tutores de los escolares.&#x0D; Los pacientes pediátricos suelen buscar atención médica para los síntomas asociados con las arritmias. Las arritmias cardíacas son consideradas como las alteraciones de la secuencia de contracciones y relajación del corazón. Sin embargo, no todas las alteraciones del ritmo son sintomáticas, pero sí requieren una cuidadosa evaluación para su correcto diagnóstico. Los pacientes pueden presentar síntomas como palpitaciones, síncope, sudor o cefalea, mientras que otros pueden no presentar síntomas y ser detectado ante un examen físico de rutina, o una evaluación por alguna otra causa.1,2,3,4&#x0D; La evaluación inicial de un paciente que presenta arritmia consiste en realizar una historia clínica completa, abordando los síntomas, el momento de la arritmia, y las posibles enfermedades subyacentes; un examen físico y un electrocardiograma de 12 derivaciones, si es posible durante la arritmia o sin ella.3&#x0D; Por otro lado, la etiología de las palpitaciones puede ser de tipo cardíacas, o no cardíacas, por tal razón, es primordial definir si existe trastorno metabólico y electrolítico, o antecedentes tiroideos y psicosomáticos, ya que estos pueden desencadenar alteraciones del ritmo cardíaco.5&#x0D; Material y Métodos: para el desarrollo de la siguiente investigación se ha realizado una revisión sistemática de artículos científicos consultando en bases de datos bibliográficas Pub Med/MED LINE, Up to date, Scielo y El Sevier, con restricción de fechas desde el 2015 hasta la actualidad, en los idiomas español e inglés. Con los datos obtenidos de los artículos científicos se pudo analizar el concepto y origen de las arritmias, y así afirmar las causas más frecuentes de estas, y la importancia de la cuidadosa evaluación del paciente junto con su correcto diagnóstico.&#x0D; Resultados: en la presente investigación encontramos que las causas más frecuentes de arritmias de origen no cardíaco en pacientes pediátricos fueron, en primer lugar, los trastornos metabólicos, incluyendo los trastornos electrolíticos como hiper/hipopotasemia e hipercalcemia, hipoglucemia, inestabilidad hemodinámica e hipotermia. Del mismo modo, pacientes con trastornos tiroideos, psicosomáticos y por exposición a medicamentos, especialmente los simpaticomiméticos contenidos en bebidas de altos niveles de cafeína. Y medicamentos para la tos/resfriado pueden desencadenar una alteración del ritmo cardíaco.&#x0D; Conclusiones: no siempre la presencia de palpitaciones es causada por enfermedades cardíacas, sino que existen palpitaciones de origen no cardíacos, provenientes de otros sistemas, las cuales no representa ningún peligro para el individuo. No obstante, todas las palpitaciones deben ser estudiadas para su correcto diagnóstico y tratamiento.

The competitive and welfare effects of long-term contracts with network externalities and bounded rationality

This paper compares the long-term and short-term contracts in terms of their competitive and welfare effects in a dynamic nonlinear pricing model with network externalities and bounded rationality. Contrary to the existing literature and traditional treatments adopted by competition authorities, we find that a long-term contract is at least as competition-friendly and socially efficient as a sequence of short-term contracts. If the consumers have constant types and pessimistic expectation regarding the network size, then for a certain range of parameters, a long-term contract facilitates entry of more efficient competitors and is socially more efficient than the short-term contracts. If the consumers’ types are independent across time, a long-term contract leads to the same competitive outcome as, but gives a higher social surplus than, its short-term counterpart.

The scope of sequential screening with ex post participation constraints

We study the classic sequential screening problem in the presence of ex post participation constraints. We establish necessary and sufficient conditions that determine when the optimal selling mechanism is either static or sequential. In the static contract, the buyers are not screened with respect to their interim type and the object is sold at a posted price. In the sequential contract, the buyers are screened with respect to their interim type and a menu of quantities is offered.We completely characterize the optimal sequential contract with binary interim types and a continuum of ex post values. Importantly, the optimal sequential contract randomizes the allocation of the low-type buyer and awards a deterministic allocation to the high type buyer. Finally, we provide additional results for the case of multiple interim types.

Heterogeneous suppliers’ contract design in assembly systems with asymmetric information

We investigate a supply contract design problem in an assembly supply chain in which two heterogeneous suppliers produce complementary products and deliver them to the assembler. One supplier is more reliable and exhibits no supply risk, and the other is less reliable and exhibits supply risk. The assembler is better informed about demand and assembles these two types of components into final products. To elicit the assembler’s truthful report of private information, the more reliable supplier offers a contract to the assembler to determine the components’ quantities and the transfer payment. The less reliable supplier enduring a disruption designs a contract that includes the components’ quantities, the transfer payment and the unit penalty for any delivery shortfall. We study the cases where either supplier moves first and where they move simultaneously under symmetric and asymmetric demand information. We explore the values of the assembler’s information and find that the first mover is more reliant upon the existence of less asymmetric information and the second mover benefits more from the assembler’ information. Further, we find that a low reliability of the less reliable supplier enlarges the first mover’s value of information. We also examine the values of the contracting sequence and find that under symmetric information, the first mover benefits more from sequential contracting. However, interestingly, under asymmetric information, the first mover may benefit or be harmed by the first-mover right. We also find that a low reliability of the less reliable supplier discourages the supplier from using the first-mover right.

Access to Fused Pyrroles from Cyclic 1,3-Dienyl Boronic Esters and Arylnitroso Compounds.

Complimentary to classical hydroboration and boron-Wittig reactions, a new, efficient access to cyclic 1,3-dienyl boronic esters has been developed via diene or triene metathesis. Subsequently, fused pyrroles were synthesized with a broad substrate scope from the reaction of cyclic 1,3-dienyl boronic esters with arylnitroso compounds using a one-pot hetero-Diels-Alder/ring contraction sequence.

Total Synthesis of Natural Products with Bridged Bicyclo[m.n.1] Ring Systems via Type II [5 + 2] Cycloaddition.

Natural products containing bridged ring systems are widely identified and show significant biological activity. The development of efficient synthesis reactions and strategies to construct bridged ring systems is a long-standing but very significant challenge in organic chemistry. In 2014, our group developed a unique type II [5 + 2] cycloaddition reaction that provides a facile and direct methodology for constructing highly functionalized bridged bicyclo[4.3.1], bicyclo[4.4.1], bicyclo[5.4.1], bicyclo[6.4.1], and other bicyclo[m.n.1] systems containing a strained bridgehead double bond. In this Account, we summarize the methodology development and report the results of application of our unique strategy for the total synthesis of several natural products with bridged ring systems (i.e., cyclocitrinol, cerorubenic acid-III, and vinigrol) during the past 5 years in our laboratory. In the first part, we introduce the logic behind the design and discovery of type II [5 + 2] cycloadditions. The substrates can be easily synthesized by a modular approach, followed by base-promoted group elimination under heat to form an oxidopyrylium ylide, which can undergo cycloaddition under relatively mild conditions with a variety of double bonds to generate bridged bicyclo[m.n.1] frameworks in high yield. The diastereocontrol and unique endo selectivity of this methodology are favorable for further application to the synthesis of complex natural products. In the second part, we highlight our endeavors in the total synthesis of several different types of molecules bearing bridged ring systems using our methodology. The bridged bicyclo[4.4.1] system is the core structure of two different types of natural products, cyclocitrinol and cerorubenic acid-III, that can be efficiently constructed by type II [5 + 2] cycloadditions. The development of suitable strategies and methods for site-selective cleavage of the C-O bond of the oxa-[3.2.1] ring system in the products of type II [5 + 2] cycloadditions is also discussed and highlighted during the syntheses. Moreover, the bridged bicyclo[5.3.1] system is the core structure of vinigrol, which can be constructed through a novel ring contraction sequence of the bicyclo[5.4.1] system formed by a type II [5 + 2] cycloaddition. By combining with a ring contraction cascade, we believe that type II [5 + 2] cycloadditions have the potential to be used as a unified approach to constructing natural products containing bridged bicyclo[m.n.1] frameworks.

Study Biophysics of Esophageal Transport by Combining Simulation, Modeling and Bio-Mechanical Analysis Based on In-Vivo Data

The human esophagus is a tubular organ that transfers food bolus to stomach, through complicated interactions among neural-controlled muscle activation (including upper striated muscle and lower smooth muscle), passive elasticity of esophageal wall and liquid-like bolus. The muscle physiology, including sequential contraction of esophageal body and tonic contraction of lower esophageal sphincter (LES), underpins various aspects of esophageal physiology and pathophysiology. With a team effort across physicians and engineers, several fully-coupled simulation models were developed to study muscle synchrony/asynchrony, myo-architecture, tissue stiffening at organ level, and will be briefly reviewed. More recently, with in-vivo clinical data such as High-resolution impedance manometry (HRIM), a hybrid diagnostic framework was developed. This framework first constructed quantitative geometry from measured impedance based on biophysical analysis, and then fed this geometric information into a simulation model of bolus transit. The predicted velocity elucidates the flow rate in normal and abnormal cases to differentiate motility functionality, whereas the predicted pressure informs stress and stiffness of the tissue. With another in-vivo test, Functional lumen imaging probe (FLIP), the muscle stiffness of esophageal body is analyzed and compared with in-vitro data. The LES property during volumetric dilation, including its phasic contraction-relaxation period and pattern is illustrated and compared among different groups.

Contracting for Innovation Under Ambiguity

In the research intensive sectors, eg. Biotechnology and Software sectors, it is a prominent and growing trend for the big commercial firms to outsource the research activities to smaller but research-oriented firms or research labs. In this paper, I provide an explanation based on the specialization to deal with research specific uncertainties or ambiguities. I model innovation as an ambiguous process, and assume that the commercial firms and research labs differ in their attitude towards ambiguity. I characterize the sequence of short term contracts between the ambiguity averse commercial firm and ambiguity neutral research lab, and examine how the special features of the optimal contract facilitates ambiguity sharing. I find that the commercial firm's ambiguity aversion mitigates the dynamic moral hazard problem. Experimentation stops earlier than is socially optimal. There is a range of posterior beliefs for which the contracting parties choose to liquidate the project even after being granted a Patent, which resembles the Troll phenomenon often observed in real life. Finally, I discuss the policy implications, examining how the Patent Law affects innovation conducted in these research alliances.

Gas-Phase Formation of Fulvenallene (C7H6) via the Jahn-Teller Distorted Tropyl (C7H7) Radical Intermediate under Single-Collision Conditions.

The fulvenallene molecule (C7H6) has been synthesized via the elementary gas-phase reaction of the methylidyne radical (CH) with the benzene molecule (C6H6) on the doublet C7H7 surface under single collision conditions. The barrier-less route to the cyclic fulvenallene molecule involves the addition of the methylidyne radical to the π-electron density of benzene leading eventually to a Jahn-Teller distorted tropyl (C7H7) radical intermediate and exotic ring opening-ring contraction sequences terminated by atomic hydrogen elimination. The methylidyne-benzene system represents a benchmark to probe the outcome of the elementary reaction of the simplest hydrocarbon radical-methylidyne-with the prototype of a closed-shell aromatic molecule-benzene-yielding nonbenzenoid fulvenallene. Combined with electronic structure and statistical calculations, this bimolecular reaction sheds light on the unusual reaction dynamics of Hückel aromatic systems and remarkable (polycyclic) reaction intermediates, which cannot be studied via classical organic, synthetic methods, thus opening up a versatile path to access this previously largely obscure class of fulvenallenes.

Calcium sensitivity during staircase with sequential incompletely fused contractions.

Activity dependent potentiation is thought to result from phosphorylation of the regulatory light chains of myosin, increasing Ca2+ sensitivity. Yet, Ca2+ sensitivity decreases early in a period of intermittent contractions. The purpose of this study was to investigate the early change in Ca2+ sensitivity during intermittent submaximal tetanic contractions. Flexor digitorum brevis muscle fibres were dissected from mice after cervical disarticulation. Fibres were superfused with Tyrode solution at 32 °C. Length was set to yield maximal tetanic force. Indo-1 was microinjected into fibres and allowed to dissipate for 30 min. Fluorescence was measured at 405 and 495 nm wavelength and the ratio was used to estimate [Ca2+]. A control force-Ca2+ relationship was determined with stimulation over a range of frequencies, yielding constants for slope, max force, and half-maximal [Ca2+] (pCa2 +50). Data were collected for sequential contractions at 40 Hz at 2 s intervals. Active force decreased over the first 1-4 contractions then increased. A force-pCa2+ curve was fit to each contraction, using the control values for the Hill slope and max force by adjusting pCa2+50 until the curve passed through the target contraction. Data are presented for three contractions for each fibre: first, maximum shift to the right, and last contraction. There was a significant shift to the right for pCa2+50 (decreased Ca2+ sensitivity), usually early in the series of intermittent contractions, then pCa2 +50 shifted to the left, but remained significantly different from the control value. Although potentiation is associated with increased Ca2+ sensitivity, this increase begins only after Ca2+ sensitivity has decreased and, in most cases, Ca2+ sensitivity does not increase above the control level.