We present results of theoretical investigation of the stability of small beryllium clusters, Be 2−6 . Due to the fact that the clusters are homonuclear, their stability is sufficiently represented by the binding energy D e calculated per atom. The knowledge of this quantity offers a possibility of calculating more complex energetic effects, such as destruction or fusion of the beryllium clusters and adding or detaching a beryllium atom. The most stable structures among those of the singlet multiplicity were studied using the highly correlated coupled clusters method with iterative single-and double-excitations and the perturbative triple excitations (CCSD(T)). The effect of electron correlation, basis set saturation, basis set superposition error, relativistic effects and the core correlation were carefully investigated and discussed. The optimized virtual orbital space (OVOS) with the controlled accuracy technique is extensively applied to alleviate the computational cost of calculations. In this specific case, the use of the OVOS technique led to speed-ups in computational time by more than an order of magnitude. Finally, we present the basis set extrapolated binding energies with all of the aforementioned corrections properly included, which are the most reliable data for this key property for Be 3−6 clusters to date. Furthermore, these values can serve as a valuable benchmark for testing the accuracy of less time consuming computational methods applicable for larger beryllium clusters.This paper is dedicated to Professor Alexander I Boldyrev on the occasion of his 60th birthday.

h i g h l i g h t sHarmful contributions of ultrafine particles and PM concentration were determined. Vehicular PAH emissions were allocated to the Aitken mode. Traffic-related nucleation particles and soot particles dominate the ultrafines. Heavy metals and PAH in the accumulation mode are related to solid fuel combustion. Major sources of solid fuel combustion are soft wood and domestic coal combustion. a b s t r a c tA comprehensive air quality study has been carried out at two urban background sites in AnnabergBuchholz (Germany) and Ústí nad Labem (Czech Republic) in the GermaneCzech border region between January 2012 and June 2014. Special attention was paid to quantify harmful fractions of particulate matter (PM) and ultrafine particle number concentration (UFP) from solid fuel combustion and vehicular traffic. Source type contributions of UFP were quantified by using the daily concentration courses of UFP and nitrogen oxide. Two different source apportionment techniques were used to quantify relative and absolute mass contributions: positive matrix factorization for total PM 2.5 and elemental carbon in PM 2.5 and chemical mass balance for total PM 1 and organic carbon in PM 1 . Contributions from solid fuel combustion strongly differed between the non-heating period (AprileSeptember) and the heating period (OctobereMarch). Major sources of solid fuel combustion in this study were wood and domestic coal combustion, while the proportion of industrial coal combustion was low (<3%). In Ústí nad Labem combustion of domestic brown coal was the most important source of organic carbon ranging from 34% to 43%. Wood combustion was an important source of organic carbon in Annaberg-Buchholz throughout the year. Heavy metals and less volatile polycyclic aromatic hydrocarbons (PAH) in the accumulation mode were related to solid fuel combustion with enhanced concentrations during the heating period. In contrast, vehicular PAH emissions were allocated to the Aitken mode. Only in Ústí nad Labem a significant contribution of photochemical new particle formation (e.g. from sulfur dioxide) to UFP of almost 50% was observed during noontime. UFPs from traffic emissions (nucleation particles) and primary emitted soot particles dominated at both sites during the rest of the day. The methodology of a combined source apportionment of UFP and PM can be adapted to other regions of the world with similar problems of atmospheric pollution to calculate the relative risk in epidemiological health studies for different sub-fractions of PM and UFP. This will enhance the meaningfulness of published relative risks in health studies based on total PM and UFP number concentrations.

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The paper brings an overview of main challenges and design techniques effectively applicable for ultra-low voltage analog integrated circuits in nanoscale technologies. New design challenges linked with a low value of the supply voltage and the process fluctuation in nanotechnologies, such as device models, robustness to process variation, device mismatch and others are discussed firstly. Then, design techniques and approaches to analog integrated circuits towards (ultra) low-voltage systems and applications are described. Finally, examples of basic building blocks of ultra-low voltage analog ICs designed in standard CMOS technology using such design techniques are presented. Finally, the developed circuits are compared to the state-of-the-art solutions in terms of the main parameters and features.