Impact of Covid-19 on probability of being employed in restaurant industry

Worldwide lockdown and rising infection rate of Covid-19 slowed down the economy in all countries. Restaurants, considered an essential business, took a particulary heavy hit from the lockdown. The goal of my research is to find if the effect of Covid-19 infection rate is stil as significant on restaurant workers employment probability or if restaurants found a solution. Using the IPUMS data, USAFacts data and STATA software I observed the impact of COVID-19 infection rate in the local labor market on the probability of being employed in restaurant industry. The results present that the situation is becoming better with time as the COVID-19 effect was twice as small in February of 2021 compared to April of 202

Ultrafast Pump-Push Photocurrent Spectroscopy of Organic Photoconversion Systems

Novel optical pump-push – photocurrent probe ultrafast spectroscopy experiments on organic photoconversion systems show that excessive excitation energy in such systems is not lost but used to reach delocalised states that act as the gateway for long-range charge separation. We also show that the developed experimental approach can be generalised to inorganic and hybrid photoconversion systems

Receptor Modeling Source Apportionment of PM10 and Benzo(a)pyrene in Krakow, Poland

The main energy source in Krakow, Poland is coal combustion, which is believed to be the reason for frequent winter episodes of extremely high ambient air concentrations of particulate matter (PM10) and associated benzo(a)pyrene B(a)P. Results are presented on the source apportionment of PM10 and B(a)P during two episodes of thermal inversion (14/1 ; 2/3, 2005) at four different air monitoring stations and four apartments (indoor) in the city of Krakow, The results are compared to the Zakopane mountain site selected due to its prominent domestic coal heating and little traffic. The source apportionment was based on receptor modeling of the total of 72 ambient PM samples and 21 individual PM sources, chemically characterised for a high number of organic and inorganic compounds including polyaromatics (15 PAH and 18 azaarenes) heavy metals and trace elements (28 compounds), major ions, soot and organic carbon. An array of multivariate receptor models was used i.e. chemical mass balance (CMB), constrained matrix factorisation (CMF), constrained physical receptor modelling (COPREM) positive matrix factorization (PMF), principle component analysis with multi-linear regression analysis (PCA-MLRA), edge analysis (UNMIX), cluster analysis (CA), and self organizing maps SOM). The variation in the receptor dataset (55 compounds, 60 outdoor and 12 indoor PM samples) allowed the models of the pure factor analysis type (PMF, UNMIX, PCA-MLRA) to identify 3-5 factors of mixed sources. The interpretation of the factors was not straightforward, but pointed to a dominating primary source contribution from coal combustion (>60%) and a minor contribution from traffic (<10%). The secondary PM sources (20-30%) comprised industry and traffic. The results of cluster analysis and self organizing maps supported these indications. PMF was able to disaggregate the coal combustion into three factors i.e. ~10% related to industrial activities, ~20% related to home heating by stoves (coal) and ~30% related to boilers. The chemical fingerprints of the receptor samples and the main PM sources in Krakow and Zakopane allowed the pure chemical mass balance; type model (EPA-CMB8.2) to estimate the major contributions from two primary source types i.e. residential heating by coal combustion in small stoves and low efficiency boilers (~45%) and boilers with rudimentary PM reductions techniques such as cyclones (~15%), one major secondary source deriving from industrial and traffic emissions of SO2 + NOx + possibly HCl (~20%). Five minor primary sources were also identified i.e. traffic 5%, biomass burning ~5%, coke/fuel combustion ~5%, industrial high efficiency coal combustion 3%, and road/salt/rock re-suspension ~2%. The indoor PM10 and B(a)P were found to have the same sources as outdoor PM10 and B(a)P The results obtained by the models CMF and COPREM - which are hybrids of factor analysis and chemical mass balance generally agreed with the CMB results. However, their source contribution estimates are slightly different: residential heating ~30%, boilers with rudimentary PM reductions techniques such as cyclones ~30%, industrial high efficiency coal combustion ~15% traffic 3-7%, secondary 13-21%, road/salt/rock re-suspension 2-8%. All receptor models calculated residential heating to be the principal PM source in Zakopane (70-80%).JRC.H.4-Transport and air qualit

Dissymmetrical U-Shaped π-Stacked Supramolecular Assemblies by Using a Dinuclear CuI Clip with Organophosphorus Ligands and Monotopic Fully π-Conjugated Ligands

International audienceReactions between the U-shape binuclear CuI complex A bearing short metal-metal distances and the cyano-capped monotopic π-conjugated ligands 1-5 carrying gradually bulkier polyaromatic terminal fragments lead to the formation of π-stacked supramolecular assemblies 6-10 respectively in 50-80 % yields. These derivatives have been characterized by multinuclear NMR spectroscopy and X-ray diffraction studies. Their solid state structures show the selective formation of U-shaped supramolecular assemblies in which two monotopic π-conjugated systems present large (6,7,9) or medium (8,10) intramolecular π-overlap revealing π-π interactions. These assemblies self-organize into head-to-tail π-stacked dimers that in turn self-assemble affording infinite columnar π-stacks. The nature, the extentand the complexity of the intermolecular contacts within the head-to-tail π-stacked dimer depends on the nature of the terminal polyaromatic fragment carried by the cyano-capped monotopic ligand but it does not alter the result of the self-assembling process. These results demonstrate that the dinuclear molecular clip A bearing short metal-metal distance allows selective supramolecular assembling processes driven by the formation of intra- and intermolecular short π-π interactions in the resulting self-assembled structures demonstrating that their shape is not only dictated by the symmetry of the building blocks. This approach opens perspectives toward the formation of extented π-stacked columns based on dissymmetrical and functionnal π-conjugated systems

Charge Photogeneration in Organic Photovoltaics: Role of Hot versus Cold Charge-Transfer Excitons

The role of excess excitation energy on long-range charge separation in organic donor/acceptor bulk heterojunctions (BHJs) continues to be unclear. While ultrafast spectroscopy results argue for efficient charge separation through high-energy charge-transfer (CT) states within the first picosecond (ps) of excitation, charge collection measurements suggest excess photon energy does not increase the current density in BHJ devices. Here, the population dynamics of charge-separated polarons upon excitation of high-energy polymer states and low-energy interfacial CT states in two polymer/fullerene blends from ps to nanosecond time scales are studied. It is observed that the charge-separation dynamics do not show significant dependence on excitation energy. These results confirm that excess exciton energy is not necessary for the effective generation of charges

Multitrophic Effects of Migratory Birds on Herbivorous Insects In a Shrub Community

I examined the effects of migrant birds on herbivorous insects and resulting plant damage in shrub communities on the Bard College campus. While studies have shown that insectivorous birds place downward pressure on insect and plant communities, there has been no research conducted into investigating possible changes to this pressure from the influx of birds during migration. I wanted to investigate the downstream effects of bird predation on insects and plants by recording changes in plant damage during the bird migration and resident periods from late spring to early summer. From May to July of 2017, I used a series of exclusion experiments to prevent bird predation, and insect traps to record the number of herbivorous insects present, as well as creating clay caterpillar models to record the presence of birds and insects in the system. In my vegetation damage assessments of the fraction of leaf removed and proportion of shrub damaged, I found that excluding birds from the system did in fact increase herbivory damage from insects. I also found that the fraction of a leaf removed was lower during the migratory period, suggesting that the presence of more birds in late spring has an even stronger predation effect, and is even more beneficial to plants. The multitrophic interactions between birds, insects, and plants need more attention to determine the response of local communities as the future of migrant bird species becomes even more uncertain