Time and Its Object: A Perspective from Amerindian and Melanesian Societies on the Temporality of Images

This volume examines the way objects and images relate to and shape notions of temporality and history. Bringing together ethnographic studies from the Lowlands of Central and South America and Melanesia, it explores the temporality inhering in images and artefacts from a comparative perspective. The chapters focus on how peoples in both regions ‘live in’ and ‘navigate’ time each through their distinctive systems of images and the processes and actions by which these come to be manifest in objects. With original theoretical and ethnographic contributions, the book is valuable reading for scholars interested in visual and material culture and in anthropological approaches to time

Towards Digital Social Infrastructure? Digital Neighborly Connectedness as a Social Resource

Social infrastructure is made up of various material as well as non-material goods, ranging from venues for leisure such as movie theaters to indispensable everyday commodities, like sidewalks and streets. This is true both for urban and rural areas. However, the increasing emergence of digital aspects of social infrastructure has seemed to go unnoticed to some extent, with research specifically focusing on these digital aspects of social infrastructure being scarce at best—even though digitalization is currently a major emerging meta-development worldwide. The goal of our contribution is therefore to investigate the digital sphere and integrate it into the concept of social infrastructure. Drawing on descriptive findings from a multi-sited, community-based survey of residents in four rural areas in Germany (N = 413) as well as from 40 qualitative interviews, we present an integrative and expanded conceptualization of what we term a tangible digital social infrastructure. To do so, we examine digital neighborly connectedness as a social resource during the Covid-19 pandemic as a case study. We argue that digital neighborly connectedness served as both an integral part of on-site social infrastructure and as a social resource, especially during pandemic times. We discuss our results in light of current research on social infrastructure, with a specific focus on the scope of what counts as social infrastructure, as well as current discourse on social infrastructure in rural areas

Quantum Criticality in doped CePd_1-xRh_x Ferromagnet

CePd_1-xRh_x alloys exhibit a continuous evolution from ferromagnetism (T_C= 6.5 K) at x = 0 to a mixed valence (MV) state at x = 1. We have performed a detailed investigation on the suppression of the ferromagnetic (F) phase in this alloy using dc-(\chi_dc) and ac-susceptibility (\chi_ac), specific heat (C_m), resistivity (\rho) and thermal expansion (\beta) techniques. Our results show a continuous decrease of T_C (x) with negative curvature down to T_C = 3K at x*= 0.65, where a positive curvature takes over. Beyond x*, a cusp in cac is traced down to T_C* = 25 mK at x = 0.87, locating the critical concentration between x = 0.87 and 0.90. The quantum criticality of this region is recognized by the -log(T/T_0) dependence of C_m/T, which transforms into a T^-q (~0.5) one at x = 0.87. At high temperature, this system shows the onset of valence instability revealed by a deviation from Vegard's law (at x_V~0.75) and increasing hybridization effects on high temperature \chi_dc and \rho. Coincidentally, a Fermi liquid contribution to the specific heat arises from the MV component, which becomes dominant at the CeRh limit. In contrast to antiferromagnetic systems, no C_m/T flattening is observed for x > x_cr rather the mentioned power law divergence, which coincides with a change of sign of \beta. The coexistence of F and MV components and the sudden changes in the T dependencies are discussed in the context of randomly distributed magnetic and Kondo couplings.Comment: 11 pages, 11 figure

Universally diverging Grueneisen parameter and the magnetocaloric effect close to quantum critical points

At a generic quantum critical point, the thermal expansion $\alpha$ is more singular than the specific heat $c_p$. Consequently, the "Gr\"uneisen ratio'', \GE=\alpha/c_p, diverges. When scaling applies, \GE \sim T^{-1/(\nu z)} at the critical pressure $p=p_c$, providing a means to measure the scaling dimension of the most relevant operator that pressure couples to; in the alternative limit $T\to0$ and $p \ne p_c$, \GE \sim \frac{1}{p-p_c} with a prefactor that is, up to the molar volume, a simple {\it universal} combination of critical exponents. For a magnetic-field driven transition, similar relations hold for the magnetocaloric effect $(1/T)\partial T/\partial H|_S$. Finally, we determine the corrections to scaling in a class of metallic quantum critical points.Comment: 4 pages, 1 figure; general discussion on how the Grueneisen exponent measures the scaling dimension of the most relevant operator at any QCP is expande

Kondo-Cluster-Glass State near a Ferromagnetic Quantum Phase Transition

We report on a comprehensive study of CePd$_{1-x}$Rh$_x$ $(0.6 \leq x \leq 0.95)$ poly- and single crystals close to the ferromagnetic instability by means of low-temperature ac susceptibility, magnetization and volume thermal expansion. The signature of ferromagnetism in this heavy-fermion system can be traced from 6.6 K in CePd down to 25 mK for $x=0.87$. Despite pronounced non-Fermi-liquid (NFL) effects in both, specific heat and thermal expansion, the Gr\"uneisen ratio {\it does not} diverge as $T\to 0$, providing evidence for the absence of a quantum critical point. Instead, a peculiar "Kondo-cluster-glass" state is found for $x\geq 0.65$, and the NFL effects in the specific heat, ac susceptibility and magnetization are compatible with the quantum Griffiths phase scenario.Comment: 4 pages, 4 figure

Dry electrodes for surface electromyography based on architectured titanium thin films

Electrodes of silver/silver chloride (Ag/AgCl) are dominant in clinical settings for surface electromyography (sEMG) recordings. These electrodes need a conductive electrolyte gel to ensure proper performance, which dries during long-term measurements inhibiting the immediate electrode’s reuse and is often linked to skin irritation episodes. To overcome these drawbacks, a new type of dry electrodes based on architectured titanium (Ti) thin films were proposed in this work. The architectured microstructures were zigzags, obtained with different sputtering incidence angles (α), which have been shown to directly influence the films’ porosity and electrical conductivity. The electrodes were prepared using thermoplastic polyurethane (TPU) and stainless-steel (SS) substrates, and their performance was tested in male volunteers (athletes) by recording electromyography (EMG) signals, preceded by electrode-skin impedance measurements. In general, the results showed that both SS and TPU dry electrodes can be used for sEMG recordings. While SS electrodes almost match the signal quality parameters of reference electrodes of Ag/AgCl, the performance of electrodes based on TPU functionalized with a Ti thin film still requires further improvements. Noteworthy was the clear increase of the signal to noise ratios when the thin films’ microstructure evolved from normal growth towards zigzag microstructures, meaning that further tailoring of the thin film microstructure is a possible route to achieve optimized performances. Finally, the developed dry electrodes are reusable and allow for multiple EMG recordings without being replaced.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and Bilateral Project FCT/DAAD 2016/2017 “Sunshine” (No. 3340). Joel Borges acknowledges FCT for his Researcher Contract from project NANO4BIO POCI-01-0145-FEDER-032299, with FCT reference PTDC/FIS-MAC/32299/2017. Marco S. Rodrigues acknowledges FCT for his PhD Scholarship, SFRH/BD/118684/2016