Cellulose Nitrate Plastic (Celluloid) in Archaeological Assemblages: Identification and Care

Invented in the mid-19th century, cellulose nitrate is commonly regarded as the earliest synthetic polymer or plastic. As increasing numbers of historical sites dating from the mid-1800s are excavated, cellulose nitrate objects are more frequently found in archaeological assemblages. The inherent instability of cellulose nitrate makes proper handling, storage, and display conditions vital to the longevity of recovered objects. In this paper, the composition, manufacture, and means of identifying cellulose nitrate are summarized. The processes of degradation and means of slowing those processes are elaborated, as well

The Power of Choice: Reflections of Economic Ability, Status, and Ethnicity in the Foodways of a Free African American Family in Northwestern New Jersey

The choices people make concerning food involve decisions well beyond biological sustenance. Food procurement and consumption, as well as the way in which a dish is served, are choices that are embedded with both overt and less obvious implications of social aspirations and validations (McKee 1999; Reitz, Ruff, and Zierden 2006). Food and the means by which it is prepared and consumed embody and communicate cultural traditions, as well as factors such as social identity, ethnicity, status, class, and consumer choice. In this article, we examine the faunal remains, tablewares, and food-preparation vessels recovered during excavations within a free African American household in an historically white town in northwestern New Jersey, and how these remains reflect and project the social identity of the household occupants, the Mann family. We compare the artifacts recovered from this site with other ante- and postbellum free black house sites in the northern mid-Atlantic region. While we note that some trends are common, like the use of wild species to supplement foods purchased in the marketplace and the presence of mismatched dishes, the amount of variation from site to site suggests each family responded individually to economic, social, and regional factors according to its own taste, beliefs, and ability. In addition to examining the Mann family’s foodways in the context of other free African American sites in the northern mid-Atlantic, we also discuss how foodways played a role in the Mann family’s display of status, as understood by both white and black communities

Can analyses of electronic patient records be independently and externally validated? The effect of statins on the mortality of patients with ischaemic heart disease: a cohort study with nested case-control analysis

Objective To conduct a fully independent and external validation of a research study based on one electronic health record database, using a different electronic database sampling the same population. Design Using the Clinical Practice Research Datalink (CPRD), we replicated a published investigation into the effects of statins in patients with ischaemic heart disease (IHD) by a different research team using QResearch. We replicated the original methods and analysed all-cause mortality using: (1) a cohort analysis and (2) a case-control analysis nested within the full cohort. Setting Electronic health record databases containing longitudinal patient consultation data from large numbers of general practices distributed throughout the UK. Participants CPRD data for 34 925 patients with IHD from 224 general practices, compared to previously published results from QResearch for 13 029 patients from 89 general practices. The study period was from January 1996 to December 2003. Results We successfully replicated the methods of the original study very closely. In a cohort analysis, risk of death was lower by 55% for patients on statins, compared with 53% for QResearch (adjusted HR 0.45, 95% CI 0.40 to 0.50; vs 0.47, 95% CI 0.41 to 0.53). In case-control analyses, patients on statins had a 31% lower odds of death, compared with 39% for QResearch (adjusted OR 0.69, 95% CI 0.63 to 0.75; vs OR 0.61, 95% CI 0.52 to 0.72). Results were also close for individual statins. Conclusions Database differences in population characteristics and in data definitions, recording, quality and completeness had a minimal impact on key statistical outputs. The results uphold the validity of research using CPRD and QResearch by providing independent evidence that both datasets produce very similar estimates of treatment effect, leading to the same clinical and policy decisions. Together with other non-independent replication studies, there is a nascent body of evidence for wider validity

Tracking primary thermalization events in graphene with photoemission at extreme timescales

Direct and inverse Auger scattering are amongst the primary processes that mediate the thermalization of hot carriers in semiconductors. These two processes involve the annihilation or generation of an electron-hole pair by exchanging energy with a third carrier, which is either accelerated or decelerated. Inverse Auger scattering is generally suppressed, as the decelerated carriers must have excess energies higher than the band gap itself. In graphene, which is gapless, inverse Auger scattering is instead predicted to be dominant at the earliest time delays. Here, $<8$ femtosecond extreme-ultraviolet pulses are used to detect this imbalance, tracking both the number of excited electrons and their kinetic energy with time- and angle-resolved photoemission spectroscopy. Over a time window of approximately 25 fs after absorption of the pump pulse, we observe an increase in conduction band carrier density and a simultaneous decrease of the average carrier kinetic energy, revealing that relaxation is in fact dominated by inverse Auger scattering. Measurements of carrier scattering at extreme timescales by photoemission will serve as a guide to ultrafast control of electronic properties in solids for PetaHertz electronics.Comment: 16 pages, 8 figure

Revealing the role of electrons and phonons in the ultrafast recovery of charge density wave correlations in 1TT-TiSe2_2

Using time- and angle-resolved photoemission spectroscopy with selective near- and mid-infrared photon excitations, we investigate the femtosecond dynamics of the charge density wave (CDW) phase in 1$T$-TiSe$_2$, as well as the dynamics of CDW fluctuations at 240 K. In the CDW phase, we observe the coherent oscillation of the CDW amplitude mode. At 240 K, we single out an ultrafast component in the recovery of the CDW correlations, which we explain as the manifestation of electron-hole correlations. Our momentum-resolved study of femtosecond electron dynamics supports a mechanism for the CDW phase resulting from the cooperation between the interband Coulomb interaction, the mechanism of excitonic insulator phase formation, and electron-phonon coupling.Comment: 9 pages, 6 figure