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Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6827
Author(s):  
Štefan Gašpár ◽  
Ján Majerník ◽  
Jan Kolínský

Quality properties of castings produced in a die casting process correlate with porosity that is conditioned by a number of factors, which range from input melt quality to setup of technological factors of the die casting, and through structural design of the gating system. One of the primary parameters conditioning the inner soundness of the casting is the liquid metal dose per single operation of die casting. This paper examines the issue of metal dose. The experiments are performed with casting a gate system of an electromotor flange. The gating system examined was die cast with a variable volume of metal dose per single operation. The metal dose was adjusted to reach the height of a biscuit of 10, 20, and 30 mm. The examination of the inner homogeneity of the castings of the individual variants of gating systems with variable height of the biscuit proved that decreasing biscuit height results in an increase of porosity share in the casting volume. The programme MagmaSoft 5.4 revealed the main causes of changes in porosity share. The simulations detected that the change in biscuit height and volume of liquid metal directly influence thermal conditions of the melt in the filling chamber, and in the mould by means of the period in which the holding pressure action is influenced. Simultaneously, the melt flow mode in the sprues and gas entrapment in the melt volume are affected as well. Correlation of the factors consequently influences the final porosity of castings.


2021 ◽  
Author(s):  
Shingo Kukita ◽  
Haruki Kiya ◽  
Yasushi Kondo

Abstract The precision of quantum operations is affected by unavoidable systematic errors. A composite pulse (CP), which has been well investigated in nuclear magnetic resonance (NMR), is a technique that suppresses the influence of systematic errors by replacing a single operation with a sequence of operations. In NMR, there are two typical systematic errors, Pulse Length Error (PLE) and Off Resonance Error (ORE). Recently, it was found that PLE robust CPs have a clear geometric property. In this study, we show that ORE robust CPs also have a simple geometric property, which is associated with trajectories on the Bloch sphere of the corresponding operations. We discuss the geometric property of ORE robust CPs using two examples.


2021 ◽  
Vol 5 (OOPSLA) ◽  
pp. 1-27
Author(s):  
Xipeng Shen ◽  
Guoqiang Zhang ◽  
Irene Dea ◽  
Samantha Andow ◽  
Emilio Arroyo-Fang ◽  
...  

This paper presents a novel optimization for differentiable programming named coarsening optimization. It offers a systematic way to synergize symbolic differentiation and algorithmic differentiation (AD). Through it, the granularity of the computations differentiated by each step in AD can become much larger than a single operation, and hence lead to much reduced runtime computations and data allocations in AD. To circumvent the difficulties that control flow creates to symbolic differentiation in coarsening, this work introduces phi-calculus, a novel method to allow symbolic reasoning and differentiation of computations that involve branches and loops. It further avoids "expression swell" in symbolic differentiation and balance reuse and coarsening through the design of reuse-centric segment of interest identification. Experiments on a collection of real-world applications show that coarsening optimization is effective in speeding up AD, producing several times to two orders of magnitude speedups.


2021 ◽  
Author(s):  
Sultan Jarrar ◽  
Mohammed M. Al Barbarawi ◽  
Suleiman S. Daoud ◽  
Yaman B. Ahmed ◽  
Leen M Al-Kraimeen ◽  
...  

Abstract Background As the incidence of intracranial infections increase due to diagnostic procedures improvement, more real-life data is needed to reach a more solid informed management approach. This study aims to describe and analyse clinical features of intracranial abscesses patients treated at a tertiary hospital in North Jordan during a 10-year period. Methods We retrospectively identified 37 patients treated at King Abdullah University Hospital (KAUH) from 2011 to 2020 in Irbid, North Jordan. Treatment consisted of either aspiration, open craniotomy excision (OCE) or conservative therapy. Extracted variables included demographic data such (age, gender), clinical presentation, lab findings, radiological findings as well as management plan. Retrieved data was compared between the patients who underwent a single operation and those who underwent reoperation after the initial procedure. Results Thirty-seven patients with 55 intracerebral abscesses were identified, 29 of whom had intraparenchymal brain abscesses, 4 patients had epidural empyema, and 4 had subdural empyema. The mean age was 28.8 (± 20.7) years, with a male predominance (78.4%). Sixteen patients underwent open craniotomy excision (OCE), 14 patients were treated by aspiration and 7 patients were treated conservatively. When comparing the single operation and the reoperation groups, there was no statistically significant difference across variables. Conclusion Our study presents valuable insight from a tertiary hospital in north Jordan on intracranial abscesses and empyemas. Our findings confirm that good recovery can be established after aspiration or OCE in the majority of patients. Similar results were obtained when comparing the SOP and the ROP groups.


2021 ◽  
Author(s):  
Pei Qu ◽  
Scott Snyder

The annotinolides are one of the most recent additions to the <i>Lycopodium</i> family of alkaloids, with its members possessing challenging, caged structures that include a [3.2.1]-bicyclic core bearing six contiguous stereocenters, including oxa-, aza-, and all-carbon quaternary centers. Herein, we document a concise and stereoselective route that achieves the first total syntheses of three of its members: annotinolides C, D, and E. Key operations include a gold(I)-catalyzed Conia-ene reaction that fashions much of the main core in a single operation, as well as a number of other challenging and chemoselective transformations to generate the remaining elements. Moreover, efforts utilizing the natural products themselves, seeking adjustments in their oxidation states and the rearrangement of individual ring systems, sheds light on their potential biogenesis with some outcomes counter to those originally proposed. Finally, formal enantioenriched syntheses of the target molecules are also presented.


2021 ◽  
Author(s):  
Pei Qu ◽  
Scott Snyder

The annotinolides are one of the most recent additions to the <i>Lycopodium</i> family of alkaloids, with its members possessing challenging, caged structures that include a [3.2.1]-bicyclic core bearing six contiguous stereocenters, including oxa-, aza-, and all-carbon quaternary centers. Herein, we document a concise and stereoselective route that achieves the first total syntheses of three of its members: annotinolides C, D, and E. Key operations include a gold(I)-catalyzed Conia-ene reaction that fashions much of the main core in a single operation, as well as a number of other challenging and chemoselective transformations to generate the remaining elements. Moreover, efforts utilizing the natural products themselves, seeking adjustments in their oxidation states and the rearrangement of individual ring systems, sheds light on their potential biogenesis with some outcomes counter to those originally proposed. Finally, formal enantioenriched syntheses of the target molecules are also presented.


Molbank ◽  
10.3390/m1212 ◽  
2021 ◽  
Vol 2021 (2) ◽  
pp. M1212
Author(s):  
Giammarco Tenti ◽  
Ángel Cores ◽  
María Teresa Ramos ◽  
J. Carlos Menéndez

Treatment of a N-2-pyridyl-β-ketoamide precursor with bromine afforded the first example of the 3-aryl(α-hydroxy)methylenelimidazo[1,2-a]pyridin-2(3H)-one framework. This transformation proceeded through a domino process comprising an initial bromination, cyclization via an intramolecular SN reaction, and a final keto-enol tautomerism, and allows generation of the fused heterocyclic system and installation of the acyl substituent in a single operation.


Synthesis ◽  
2021 ◽  
Author(s):  
Victor Martín-Heras ◽  
Constantin G. Daniliuc ◽  
Ryan Gilmour

The heptafluoroisopropyl group is emerging as a privileged chemotype in contemporary agrochemistry and features prominently in the current portfolio of leading insecticides. To reconcile the expansive potential of this module with the synthetic challenges associated with preparing crowded, fluorinated motifs, I(I)/I(III) catalysis has been leveraged. Predicated on in situ generation of p-TolIF2, this route enables the direct difluorination of α-trifluoromethyl-β-difluoro-styrenes in a single operation. This formal addition of fluorine across the alkene π-bond is efficient (up to 91%) and is compatible with a broad range of functional groups. The ArCF(CF3)2 moiety is conformationally pre-organized, with the C(sp3)-F bond co-planar to the framework of the aryl ring, thereby minimizing 1,3-allylic strain. Moreover, orthogonal multipolar C-F•••C=O interactions have been identified in a phathalimide derivative. It is envisaged that this programmed vicinal difluorination enabled by a hypervalent iodine species will find application in functional molecule design in a broader sense.


Lab on a Chip ◽  
2021 ◽  
Author(s):  
Daigo Natsuhara ◽  
Ryogo Saito ◽  
Hiroka Aonuma ◽  
Tatsuya Sakurai ◽  
Shunya Okamoto ◽  
...  

In this study, we introduce polydimethylsiloxane (PDMS)-based microfluidic devices capable of sequential dispensing of samples into multiple reaction microchambers in a single operation to provide a fast and easy sample-to-answer...


Author(s):  
Ivan Alekseevich Selishchev ◽  
Svetlana Aleksandrovna Oleinikova

The object of this research is the modern service and production systems, the specific functioning of which lies in a set of sequential and parallel operations with a random duration. A fundamental peculiarity of such systems is the stochastic nature of the duration of a single operation, which depends not only on the external random factors, but also on the choice of resources, and namely on the operator. This substantiates the parallel solution of the task on making a schedule of mutually dependent operations and the task on assigning the operators. In the conditions of resource and time limits, this task is NP difficult and requires the development of algorithms for developing the solution that is close to optimal in the limited time. For the development of mathematical and algorithmic software to solve this task, the author used the critical path method and PERT method, incident wave method, and methods for solving the assignment tasks. As a result, the author acquired a mathematical model that considers the stochastic nature of the duration of a single operation, which depends not only on random factors, but also on the operators. Based on such model, is formulated the optimization task that allows finding the launch time and the corresponding operators to gain the most profit. Based on the analysis of existing approaches and the specificity of the task at hand, the author proposes the algorithm for solving the task founded on successive refinement of the time characteristics of operations.


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