Electron-hole pair condensation at the semimetal-semiconductor transition: a BCS-BEC crossover scenario

We act on the suggestion that an excitonic insulator state might separate---at very low temperatures---a semimetal from a semiconductor and ask for the nature of these transitions. Based on the analysis of electron-hole pairing in the extended Falicov-Kimball model, we show that tuning the Coulomb attraction between both species, a continuous crossover between a BCS-like transition of Cooper-type pairs and a Bose-Einstein condensation of preformed tightly-bound excitons might be achieved in a solid-state system. The precursor of this crossover in the normal state might cause the transport anomalies observed in several strongly correlated mixed-valence compounds.Comment: 5 pages, 5 figures, substantially revised versio

Seasonal changes of sources and volatility of carbonaceous aerosol at urban, coastal and forest sites in Eastern Europe (Lithuania)

We measured stable carbon isotope ratios of total carbon (TC) and organic carbon (OC) in fine carbonaceous aerosol fraction sampled in August and September 2013 at urban, coastal and forest sites in Lithuania. δ13C values of TC for all three sites over the whole measurement period varied from −29.3 to −26.6‰, which is in the range of particles emitted by fossil fuel combustion in Eastern Europe. The isotopic composition at the forest and coastal site showed a similar variation during two contrasting pollution periods. δ13C values in the clean period were more variable, whereas the polluted period was characterized by a gradual enrichment in δ13C compared to the clean period. In the polluted period air masses originated from southern, southeastern or southwestern direction, indicating long-range transport of pollutants from Eastern Europe and Southern Europe to Lithuania. Oxidative processing during long-range transport or the different source signatures (e.g., enriched 13C signature of gasoline used in Western Europe vs. Eastern Europe) could cause the less negative δ13COC values during the polluted episode. δ13C for OC desorbed from the filter samples was separately measured during three different temperature steps (200 °C, 350 °C and 650 °C). OC desorbed at 200 °C had the most depleted 13C signature of around −29‰ at all three sites. A comparison with previously published data measured during the winter at the same sites showed that both TC and OC had less negative δ13C values in winter than in summer, which can be explained by the contribution of biomass/coal burning sources in winter. At the urban site δ13C of OC did not change much with increasing desorption temperature in winter, which is typical for primary sources, but in the summer δ13C of OC was depleted for lower desorption temperatures, possibly due to the influence of SOA formation. A higher fraction of more refractory OC in summer compared to winter-time suggests active photochemical processing of the primary organic aerosol as an important process at all three sites

A probabilistic analysis of argument cogency

This paper offers a probabilistic treatment of the conditions for argument cogency as endorsed in informal logic: acceptability, relevance, and sufficiency. Treating a natural language argument as a reason-claim-complex, our analysis identifies content features of defeasible argument on which the RSA conditions depend, namely: change in the commitment to the reason, the reason’s sensitivity and selectivity to the claim, one’s prior commitment to the claim, and the contextually determined thresholds of acceptability for reasons and for claims. Results contrast with, and may indeed serve to correct, the informal understanding and applications of the RSA criteria concerning their conceptual dependence, their function as update-thresholds, and their status as obligatory rather than permissive norms, but also show how these formal and informal normative approachs can in fact align

Oral HRAS Mutation in Orofacial Nevus Sebaceous Syndrome (Schimmelpenning-Feuerstein-Mims-Syndrome): A Case Report With a Literature Survey

Background/Aim: The aim of this study was to present the long-term course of a patient with nevus sebaceous syndrome (NSS). Recent genetic studies place the syndrome in the emerging group of so-called RASopathies. The focus of the report is on surgical treatment and morphological and genetic findings of the face and oral cavity. Case Report: A female patient was treated for congenital alterations of facial skin and oral mucosa. The oral lesions were removed repeatedly. Eruption of teeth on the lesion sites was made easier by the measures taken. However, after repeated ablation of the affected gingiva, the periodontal papillomatous epithelium re-differentiated into the same reddish, conspicuous, hyperplastic epithelium. The teeth in the affected region showed noticeable changes in position, surface, and shape. A HRAS mutation was detected only in the regions of altered oral epithelia and not in adjacent soft tissues. Conclusion: Reports on NSS rarely address oral manifestations. The recorded alterations of oral soft and hard tissues in NSS indicate a topographical relationship between the development of oral mucosa and teeth as well as the long-lasting impact of a sporadic mutation on organ development at this site

Post-holiday memory work: Everyday encounters with fridge magnets

While souvenirs have generated considerable interest within tourism research, less attention has been paid to their post-holiday ‘afterlife’. Utilising perspectives from memory research and more-than-representational theory, this paper focuses on interactions with a ubiquitous souvenir: the fridge magnet. Drawing on semi-structured interviews we illustrate how, because of their embeddedness within everyday domestic rhythms, magnets are active agents in the stimulation of post-holiday memory work. We show how magnets work to generate and protect memories, triggering a diversity of (usually positive) emotional and affective responses. They can also be associated with ambivalent memories; with their role sometimes being more about forgetting. Although being seemingly banal objects, fridge magnets have a complex capacity to affect everyday life long after a holiday ends

Use numbers not words! Communicating hotels’ cleaning programs for COVID-19 from the brand perspective

After hotels in many countries were forced to close in government-imposed lockdowns during the COVID-19 pandemic, there is an inherent need to communicate how they deal with the coronavirus to motivate guests to visit. However, lack of knowledge about how to persuasively communicate about hotels’ cleaning programs for COVID-19 can challenge the industry's survival. We investigated how hotels that position their brand as a particular personality (sincere vs. exciting) could benefit from different communication styles (inclusion of numerical vs. verbal quantifiers) when presenting their COVID-19 cleaning procedures. Study 1 explored tourists’ central attitudinal responses toward hotels’ cleaning programs. Study 2 demonstrated that sincere hotel brands would benefit from using numerical and verbal quantifiers to communicate their cleaning policies, whereas exciting hotel brands would benefit only from numerical quantifiers. Our results invite hotel managers to use their brand personality positioning to influence tourists’ attitudes and intentions in a pandemic context

delta C-13 signatures of organic aerosols:Measurement method evaluation and application in a source study

Analysis of the stable carbon isotope 13C in organic carbon (OC) can give insight into sources and atmospheric processing of carbonaceous aerosols, provided the 13C source signatures are known. However, only few data on 13C signatures of OC emitted by common sources of carbonaceous aerosol are available in Europe. We present and evaluate an improved version of a measurement method to obtain δ13C signatures on organic aerosols desorbed from filter samples at three different desorption temperatures (200 °C, 350 °C and 650 °C) and apply it in a source study. With our calibration approach, the reproducibility of a L-Valine reference material desorbed at a single temperature step of 650 °C shows a standard deviation of 0.19‰ over a period of more than one year. The average δ13C value for this reference material over 248 measurements is −24.10‰, which shows only a slight bias to the nominal value of −24.03‰. Repeated analysis of ambient filter samples desorbed at three temperature steps show typical standard deviations of about 0.3‰ for all temperature steps (200 °C, 350 °C and 650 °C). Isotopic fractionation due to partial thermal desorption during the individual temperature steps was tested on single compound reference materials. It showed significant isotopic fractionation only at temperature steps, in which a very minor fraction of the compound was desorbed. Possible isotope effects caused by charring of organic material were investigated and found to be not significant. The thermal desorption method was applied to various source filter samples from the region of Naples, Italy. We analyzed two different biomass burning sources, exhaust from a city bus and traffic emissions collected in a tunnel and compared these to ambient filter samples from the same region. δ13C signatures of the total OC show values in a narrow range of about −28‰ to −26‰ for all sources, which does not allow a source apportionment only based on 13C. Nevertheless, the results add information to a source inventory of δ13C, where information of 13C in organic aerosol from specific emission sources are rare. City bus emissions show little variation of δ13C over the temperature steps, whereas biomass burning aerosol is enriched in 13C for OC desorbed at 650 °C. For PM10 samples in the urban tunnel an enrichment in δ13C at the 650 °C temperature steps was observed, which is likely caused by the contribution of carbonate carbon to the carbonaceous material desorbed at this temperature step

Linear response within the projection-based renormalization method: Many-body corrections beyond the random phase approximation

The explicit evaluation of linear response coefficients for interacting many-particle systems still poses a considerable challenge to theoreticians. In this work we use a novel many-particle renormalization technique, the so-called projector-based renormalization method, to show how such coefficients can systematically be evaluated. To demonstrate the prospects and power of our approach we consider the dynamical wave-vector dependent spin susceptibility of the two-dimensional Hubbard model and also determine the subsequent magnetic phase diagram close to half-filling. We show that the superior treatment of (Coulomb) correlation and fluctuation effects within the projector-based renormalization method significantly improves the standard random phase approximation results.Comment: 17 pages, 7 figures, revised versio