Big Data meets Quantum Chemistry Approximations: The Δ\Delta-Machine Learning Approach

Chemically accurate and comprehensive studies of the virtual space of all possible molecules are severely limited by the computational cost of quantum chemistry. We introduce a composite strategy that adds machine learning corrections to computationally inexpensive approximate legacy quantum methods. After training, highly accurate predictions of enthalpies, free energies, entropies, and electron correlation energies are possible, for significantly larger molecular sets than used for training. For thermochemical properties of up to 16k constitutional isomers of C$_7$H$_{10}$O$_2$ we present numerical evidence that chemical accuracy can be reached. We also predict electron correlation energy in post Hartree-Fock methods, at the computational cost of Hartree-Fock, and we establish a qualitative relationship between molecular entropy and electron correlation. The transferability of our approach is demonstrated, using semi-empirical quantum chemistry and machine learning models trained on 1 and 10\% of 134k organic molecules, to reproduce enthalpies of all remaining molecules at density functional theory level of accuracy

Water sensitivity and microporosity in organosilica glasses

In this dissertation the water sensitivityand microporosity of organosilica glasses are studied. The research focuses onfundamental material understanding, but stands in close relation with theindustrial application of organically bridged silicas as molecular sievingmembranes. Chapter1 presents a systematic study on the influence of monomerconnectivity, network flexibility and hydrophobicity on the hydrothermaldissolution of organosilicas. Bond strain appears to significantly increasethe tendency to dissolve under hydrothermal conditions.The stabilizing influences of increased connectivity and hydrophobicity werefound to be weak. Chapter2 zooms in on subtle effects of condensationreactions in ethylene-bridged silica when kept at temperatures up to 300 °C. Anexplanation is presented for the previously not understood problem of slow fluxdecline in industrially employed organosilica membranes over periods of monthsto years. The common assumption that a stabilized structural state is reachedafter treatment at 250-300 °C for a few hours is shown to be incorrect. Chapter3 presents a post-treatment to solve the subtlematerial instability reported in Chapter 2, involving exposure to in-situsynthesized HCl gas alternated with heat treatments at 150-300 °C. Treatmentwith HCl was found to predominantly catalyze hydrolysis of siloxane bonds,enabling network optimization via iterative bond breakage and reformation. Chapter 4 presents anew method based on vapor thermogravimetry and gas pycnometry for characterizationof micropores <1 nm with increased accuracy ascompared to conventional adsorption isotherm analysis. Main advantages of the demonstrated method are that diffusion limitationsdue to cryogenic temperatures are eliminated, adsorption is studied withnon-polar gases, micropore cavity sizes are probed separate from micropore entrancesand data can be interpreted in a straightforwardfashion without requiring theoretical models on molecular behavior. Chapter5 presents a systematic study on the microporeproperties of a series of organosilica materials based on the method reportedin Chapter 4. The known classification of 1) short or rigid organic bridgesthat open up the pore structure, 2) longer and more flexible bridges that causepore filling and 3) terminal organic groups that reduce pore formation isfurther specified. The incorporation of any organic group in the silica networkincreased the dispersity in micropore entrance sizes as compared to inorganicsilica in the probed size range. A criticaldiscussion is given of the commonly accepted ‘spacingconcept’ of organic bridges

Structure–property tuning in hydrothermally stable sol–gel-processed hybrid organosilica molecular sieving membranes

Supported microporous organosilica membranes made from bridged silsesquioxane precursors by an acid-catalyzed sol–gel process have demonstrated a remarkable hydrothermal stability in pervaporation and gas separation processes, making them the first generation of ceramic molecular sieving membranes with sufficient performance under industrially relevant conditions. The commercial availability of various α,ω-bis(trialkoxysilyl)alkane and 1,4-bis(trialkoxysilyl)benzene precursors facilitates the tailoring of membrane properties like pore size and surface chemistry via the choice of precursor(s) and process variables. Here, we describe the engineering of sols for making supported microporous thin films, discuss the thermal and hydrothermal stability of microporous organosilicas and give a short overview of the developments and applications of these membranes in liquid and gas separation processes since their first report in 2008

MLQD: A package for machine learning-based quantum dissipative dynamics

Machine learning has emerged as a promising paradigm to study the quantum dissipative dynamics of open quantum systems. To facilitate the use of our recently published ML-based approaches for quantum dissipative dynamics, here we present an open-source Python package MLQD (https://github.com/Arif-PhyChem/MLQD), which currently supports the three ML-based quantum dynamics approaches: (1) the recursive dynamics with kernel ridge regression (KRR) method, (2) the non-recursive artificial-intelligence-based quantum dynamics (AIQD) approach and (3) the blazingly fast one-shot trajectory learning (OSTL) approach, where both AIQD and OSTL use the convolutional neural networks (CNN). This paper describes the features of the MLQD package, the technical details, optimization of hyperparameters, visualization of results, and the demonstration of the MLQD's applicability for two widely studied systems, namely the spin-boson model and the Fenna--Matthews--Olson (FMO) complex. To make MLQD more user-friendly and accessible, we have made it available on the XACS cloud computing platform (https://XACScloud.com) via the interface to the MLatom package (http://MLatom.com)

Tussen macht en onmacht. Een politieke biografie van Anthonie van der Heim (1693-1746)

Het leven en de carrière van Anthonie van Heim (1693-1746) spelen zich af tegen het decor van het Tweede Stadhouderloos Tijdperk (1702-1747). Als zoon van een raadsheer uit de Hoge Raad en neef van Anthonie Heinsius de raadpensionaris van Holland werd hij na zijn studie rechten in Leiden achtereenvolgens benoemd tot secretaris van de Generaliteitsrekenkamer, vanwege zijn aanleg voor financiële aangelegenheden in 1727 tot thesaurier-generaal van de Unie en in 1737 tot raadpensionaris van Holland. Hij had te maken met de ambitie van de Friese stadhouders, spanningen met Pruisen, met Frankrijk en met de erfopvolging van keizer Karel VI. Deze politieke biografie laat de worsteling zien van een raadpensionaris die beperkt was in zijn handelen door de slechte staat der financiën en gehinderd door binnenlandse tegenstellingen en tegenwerking. Vanwege zijn slechte gezondheid moest hij de regie uit handen geven. Moegestreden overleed hij op weg naar zijn kuuroord, Spa.  Cities, Migration and Global Interdependenc

Zatrudnienie na podstawie umów terminowych w świetle nowelizacji Kodeksu pracy z dnia 25 czerwca 2015 roku

On February 22, 2016 the new law which brought substantial changes in Chapter II, Part I of Labour Code entered into force. The main changes concern the contracts of employment concluded for a specific period of time. The amendment abrogates employment contract for a specified task. Furthermore, it provides with details of socio-economic purposes of probation contracts as well as regulates and clarifies the rules of re-employing the worker after the probation contract. However, the main changes concern contracts for specified period of time and implementation of new legal measures the aim of which is to prevent its excessive use by employers. In here we should mention the basis of employment, exception to legal regulations, admissibility of contracts termination before the statutory period of time and the length of the notice period

Improvement of professional qualifications as means of increasing the level of professional competences of members of the civil service corps

The author of the present article broadly analyzes the principles of improving professional qualifications by members of the civil service corps, including both the obligation to develop professional knowledge as well as other factors affecting the level of professional competence of corps members, such as the requirement to be qualified to hold a specific position and to serve a preparatory service. In particular, the study indicates requirements for establishing obligation to develop professional knowledge as one of the main duties of members of the civil service corps, introduces its legal nature and, separate from the principles provided for under the Labor Code, rules for its implementation through the absolute obligation of a corps member to participate in the civil service training system. The author also emphasizes the non-exhaustive nature of the regulation provided for by the Civil Service Act and points to the possibility of improving professional qualifications by members of the civil service corps, on the basis of the provisions of the Labor Code, at the initiative of the employer or with his consent

Umowa o pracę na czas określony oraz problem przyczynowości jej wypowiedzenia – stan obecny oraz tendencje zmian

An employment contract for a fixed term is now treated by the labour market as a flexible form of employment, which is a substitute for a contract of indefinite duration. In this context, there is a problem of the widespread usage of determinants as a basis for employment, employer and the employee’s position in regard to determining the type of employment contract. The article discusses the impact of determinants on the shape of the fix term contracts content, especially the admissibility of the notice before the date on which was concluded. Employees’ week negotiating position causes that employers often impose on them fixed term contracts. In consequence, contracts are concluded for a long period of time and include clauses allowing employer the causeless notice before the exact date of the end of the contact. As far as the job security is concerned, a fixed term contract is comparable to an employment contract for a probationary period. For example in both cases the employer doesn’t have to consult an employee’s notice with trade unions. What may arouse controversy is the negative position of that Constitutional Tribunal. The Tribunal confirms the compliance of the Constitution with the Polish Labour Law in the range of the principle of causeless termination of employment for a specified period.Umowa o pracę na czas określony jest obecnie traktowana przez rynek pracy jako tzw. elastyczna forma zatrudnienia, stanowiąca substytut umowy o pracę na czas nieokreślony. W tym kontekście pojawia się przede wszystkim problem determinantów jej szerokiego stosowania jako podstawy zatrudnienia oraz pozycji pracodawcy i pracownika w kwestii określenia rodzaju umowy o pracę, a zwłaszcza ich wpływu na ukształtowanie treści umowy na czas określony w zakresie dopuszczalności jej wypowiedzenia przed terminem, na który została zawarta. Słaba pozycja negocjacyjna pracownika powoduje, że pracodawca najczęściej narzuca mu ten rodzaj umowy o pracę, jej wieloletni okres oraz klauzulę umożliwiającą jej bezprzyczynowe wypowiedzenie przed terminem. Uwzględniając jeszcze brak obowiązku konsultacji związkowej zamiaru wypowiedzenia, powoduje to, że trwałość stosunku pracy zawartego na podstawie tego rodzaju umowy praktycznie nie różni się od trwałości stosunku pracy nawiązanego w oparciu o umowę o pracę na okres próbny. Na tle przedstawionej praktyki stosowania umowy na czas określony kontrowersje budzi negatywne stanowisko Trybunału Konstytucyjnego potwierdzające zgodność z Konstytucją RP przepisów Kodeksu pracy, ustanawiających zasadę bezprzyczynowego wypowiedzenia umowy o pracę na czas określony