Numerical investigation of the influence of process parameters and tool path on the temperature in the laser glass deposition (LGD) process

Additive manufacturing has gained interest in the industry due to its flexibility in design and the possibility to integrate functionalities. Thereby, glass has a high potential to be developed also in this field due to its thermal stability, chemical resistance, and optical transmission. Laser glass deposition is a method for fabricating glass components on a glass substrate. The energy input and the resulting temperature are crucial factors in this process, which can influence the material properties and the resulting geometry. Also, depending on the temperature in the substrate, difficulties such as high residual stresses or thermal shock can occur. The temperature on the glass substrate and in the melt zone can be changed either directly by the laser power or laser spot size, or indirectly by other process variables such as travel speed or path planning strategy. In this study, the energy input and the resulting temperature in the melt zone are numerically investigated under selected process parameters. Based on this, a regression function was created so that the generated temperature can be calculated by corresponding laser power, laser spot diameter, and axis velocity. Moreover, different tool path strategies for the production of horizontally multilayered surfaces were thermally investigated. The results showed a more uniform temperature profile with zigzag movement than the spiral tool path. The influence of the turning point angle in path planning on the temperature change was also investigated. It was observed that the 90° corner in contrast to the smaller angle has no significant influence on the temperature change

Synthesis by High-Efficiency Liquid-Phase (HELP) Method of Oligonucleotides Conjugated with High-Molecular Weight Polyethylene Glycols (PEGs)

The chemical modification of synthetic oligonucleotides has recently been investigated to improve their pharmacological utilization. In addition to chemical alterations of the backbone and of the heterocyclic bases, their conjugation with amphiphylic moieties, such as the polyethylene glycol has been proposed. The large scale production of these molecules as demanded for commercial purposes is hampered by the heterogeneity of the solid-phase processes and by the low reactivity of high-molecular weight PEGs in solution. A new synthetic procedure based on the recently developed liquid-phase method (HELP), has been set up to overcome these limitations

Unsupervised machine learning on encrypted data

In the context of Fully Homomorphic Encryption, which allows computations on encrypted data, Machine Learning has been one of the most popular applications in the recent past. All of these works, however, have focused on supervised learning, where there is a labeled training set that is used to configure the model. In this work, we take the first step into the realm of unsupervised learning, which is an important area in Machine Learning and has many real-world applications, by addressing the clustering problem. To this end, we show how to implement the K-Means-Algorithm. This algorithm poses several challenges in the FHE context, including a division, which we tackle by using a natural encoding that allows division and may be of independent interest. While this theoretically solves the problem, performance in practice is not optimal, so we then propose some changes to the clustering algorithm to make it executable under more conventional encodings. We show that our new algorithm achieves a clustering accuracy comparable to the original K-Means-Algorithm, but has less than $5\%$ of its runtime

Radioactive Phosphorylation of Alcohols to Monitor Biocatalytic Diels-Alder Reactions

Nature has efficiently adopted phosphorylation for numerous biological key processes, spanning from cell signaling to energy storage and transmission. For the bioorganic chemist the number of possible ways to attach a single phosphate for radioactive labeling is surprisingly small. Here we describe a very simple and fast one-pot synthesis to phosphorylate an alcohol with phosphoric acid using trichloroacetonitrile as activating agent. Using this procedure, we efficiently attached the radioactive phosphorus isotope 32P to an anthracene diene, which is a substrate for the Diels-Alderase ribozyme—an RNA sequence that catalyzes the eponymous reaction. We used the 32P-substrate for the measurement of RNA-catalyzed reaction kinetics of several dye-labeled ribozyme variants for which precise optical activity determination (UV/vis, fluorescence) failed due to interference of the attached dyes. The reaction kinetics were analyzed by thin-layer chromatographic separation of the 32P-labeled reaction components and densitometric analysis of the substrate and product radioactivities, thereby allowing iterative optimization of the dye positions for future single-molecule studies. The phosphorylation strategy with trichloroacetonitrile may be applicable for labeling numerous other compounds that contain alcoholic hydroxyl groups

What Do Computer Scientists Tweet? Analyzing the Link-Sharing Practice on Twitter

Twitter communication has permeated every sphere of society. To highlight and share small pieces of information with possibly vast audiences or small circles of the interested has some value in almost any aspect of social life. But what is the value exactly for a scientific field? We perform a comprehensive study of computer scientists using Twitter and their tweeting behavior concerning the sharing of web links. Discerning the domains, hosts and individual web pages being tweeted and the differences between computer scientists and a Twitter sample enables us to look in depth at the Twitter-based information sharing practices of a scientific community. Additionally, we aim at providing a deeper understanding of the role and impact of altmetrics in computer science and give a glance at the publications mentioned on Twitter that are most relevant for the computer science community. Our results show a link sharing culture that concentrates more heavily on public and professional quality information than the Twitter sample does. The results also show a broad variety in linked sources and especially in linked publications with some publications clearly related to community-specific interests of computer scientists, while others with a strong relation to attention mechanisms in social media. This refers to the observation that Twitter is a hybrid form of social media between an information service and a social network service. Overall the computer scientists’ style of usage seems to be more on the information-oriented side and to some degree also on professional usage. Therefore, altmetrics are of considerable use in analyzing computer science

Social navigation

In this chapter we present one of the pioneer approaches in supporting users in navigating the complex information spaces, social navigation support. Social navigation support is inspired by natural tendencies of individuals to follow traces of each other in exploring the world, especially when dealing with uncertainties. In this chapter, we cover details on various approaches in implementing social navigation support in the information space as we also connect the concept to supporting theories. The first part of this chapter reviews related theories and introduces the design space of social navigation support through a series of example applications. The second part of the chapter discusses the common challenges in design and implementation of social navigation support, demonstrates how these challenges have been addressed, and reviews more recent direction of social navigation support. Furthermore, as social navigation support has been an inspirational approach to various other social information access approaches we discuss how social navigation support can be integrated with those approaches. We conclude with a review of evaluation methods for social navigation support and remarks about its current state

Crystal structure of [(trimethylsilyl)-bis(dimethylaminoboryl)amino]-(trimethylsilylamino)-(dimethylamino)-borane, [(Me3Si)NH(BNMe2)]N[B(NMe2)2](SiMe3)

C12H37B2N5Si2, monoclinic, P12(1)/c1 (No. 14), a = 15.785(4)Angstrom, b = 11.966(2) Angstrom, c = 11.804(6) Angstrom, beta = 102.19(3)degrees, V = 2179.3 Angstrom(3), Z = 4, R-gt(F) = 0.041, wR(obs)(F-2) = 0 110, T = 293 K

A new borazine-type single source precursor for Si/B/N/C ceramics

The new borazine derivative [ B{CH(CH3)(SiCl3)} NH](3) (TSEB) was prepared by reacting Cl3Si - CH(CH3) - BCl2 (TSDE) with hexamethyldisilazane (hmds) at ambient conditions. TSEB was characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and by mass spectrometry (MS). The specially designed molecule serves as a single source precursor for the synthesis of a highly durable Si/B/N/ C ceramic material via the well known 'polymer route'. Pursuing this philosophy, polymerization of TSEB with methylamine as the cross-linking reagent has lead to a highly homogeneous pre-ceramic polymer, which was further characterized by spectroscopic methods. Subsequent thermal degradation of the as-obtained polyborocarbosilazane was monitored by means of DTA/TG/MS up to 1400 degrees C. The resulting amorphous silicon boron carbonitride of the approximate elemental composition Si3B3N5C4 exhibits an outstanding thermal durability at 2000 degrees C under inert conditions and is also stable in pure oxygen up to at least 1300 degrees C. The ceramic material still contains borazine rings from the TSEB precursor molecule embedded in the covalent Si/B/N/ C network, acting as rigid structural units which reinforce the ceramic material on an atomic scale

Synthesis and characterization of new amorphous Si/B/N/C ceramics with increased carbon content through single-source precursors

New molecular single-source precursors for the preparation of carbon-rich random inorganic networks in the quaternary system Si/B/N/C have been synthesized and fully characterized by spectroscopic methods (infrared, nuclear magnetic resonance and mass spectrometry). As a new structural feature, the precursors contain a methylene bridge between silicon and boron leading to an efficient incorporation of carbon into the random network. Cross linking of the single-source precursors Cl3Si-CH2-BCl2 (trichlorosilyl dichloroboryl methane) and (CH3)Cl2Si-CH2-BCl2 (dichlorosityl dichloroboryl methane) with methylamine and subsequent pyrolysis of the resultant preceramic polymers at 1500 degreesC in an inert gas atmosphere yield the amorphous ceramics Si3B3N7C5 and Si3B3N5Cl7 respectively. Both compositions exhibit high-temperature stability with only low mass losses at heating them to 2000 degreesC and, at the same time, they show a remarkable resistance against oxidation in pure oxygen at least up to 1300 degreesC. (C) 2004 Academie des sciences. Published by Elsevier SAS. All rights reserved