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Fermi surface origin of the low-temperature magnetoresistance anomaly
No full textMagnetoresistance (MR) at a fixed field can demonstrate a non-monotonic temperature dependence—an anomaly—in many systems, including low-dimensional chalcogenides, spin- and charge-density-wave metals, and topological semimetals. These systems are often low-carrier-density compensated metals, and the physics are expected to be quasi-classical. Nevertheless, the MR anomaly also exists in the highly conductive metals Cr, Mo, and W for both linear and quadratic field dependence, with their non-saturation attributed to either open orbit or electron-hole compensation. We argue that quantum transport across sharp Fermi surface arcs, but not necessarily the full cyclotron orbit, governs this MR anomaly, thereby accounting for the profound effects of disorder. In Cr, an overlay exists between three temperature dependences: MR at a constant high field, linear MR at a low field, and Shubnikov-de Haas (SdH) oscillations of the smallest orbit. In Mo, the MR anomaly extends beyond the temperature of its SdH oscillations but disappears before Kohler’s scaling reemerges
Gaussian fluctuations of nonreciprocal systems
No full textNonreciprocal systems can be thought of as disobeying Newton's third law—an action does not cause an equal and opposite reaction. In recent years there has been a dramatic rise in interest toward such systems. On a fundamental level, they can be a basis of describing nonequilibrium and active states of matter, with applications ranging from physics to social sciences. However, often the first step to understanding complex nonlinear models is to linearize about the steady states. It is thus useful to develop a careful understanding of linear nonreciprocal systems, similar to our understanding of Gaussian systems in equilibrium statistical mechanics. In this work we explore simplest linear nonreciprocal models with noise and spatial extent. We describe their regions of stability and show how nonreciprocity can enhance the stability of a system. We demonstrate the appearance of exceptional and critical exceptional points with the respective enhancement of fluctuations for the latter. We show how strong nonreciprocity can lead to a finite-momentum instability. Finally, we comment how nonreciprocity can be a source of colored, 1/f type noise
The singlet excited states of fulvene and of its 6,6-dimethyl derivative:a combined study of their energy levels by absorption spectroscopy, configuration interaction, and density functional calculations
No full textThe ultraviolet and vacuum ultraviolet (VUV) photo absorption spectra of fulvene were reconsidered by a combination of configuration interaction and density functional methods and extended to the newly acquired VUV photo absorption spectrum of the 6,6-dimethylfulvene derivative, where several Rydberg states have been identified. Singlet states of fulvene were studied using multi-root multi-reference configuration interaction with the H2C unit either coplanar with, or perpendicular to the ring. In contrast to ethylene, the lowest states are coplanar. The vibrational structure of the lowest (1B2) excited states of fulvene is well reproduced by calculated values. The second singlet state of fulvene, previously assigned as 1A1 on the basis of intensity, is incompatible with the calculated planar 1A1 state, which itself is a saddle point. This state shows significant quartic character on bending, and the best interpretation of the observed UV band of fulvene is of a bent form. The UV spectral state with low onset intensity is probably a 1B1 state of CS symmetry. Theoretical Rydberg states were determined for fulvene; the closest fit to the two known Rydberg states is to the 3p and 4p states (1B1). Comparison of the separation of the 2A2 and 2B1 states in the photoelectron spectra of the two compounds, with the threshold photoelectron spectrum of fulvene, shows that the 2B1 state vibrational structure is largely lost for both molecules. A reconsideration of the interaction between the X2A2 and A2B1 ionic states has led to the identification of the 4A2 quartic state of fulvene
Are philosophers functionally integrated enough to socially know?
No full textAccording to accounts like Alexander Bird’s Minimal Functional Account of social knowledge, various groups like those within the sciences can socially know that <p>, even if no particular individual within that group knows that <p>. Bird’s primary example of a group that has such knowledge is the community of semiconductor physicists – which, as he contends, is sufficiently functionally integrated to satisfy accounts like his own. But, what about specialist communities within philosophy? Do they satisfy accounts like Bird’s own? Should they? As I will suggest in this article, some of them should, but do not appear to do so – at least, as of yet
Explanations of the difference between prohibitive balancing and permissive balancing
No full textBalanced epistemic reasons for beliefs that p and ¬p combine towards a prohibition on either belief while balanced reasons for two incompatible actions combine to permit either action. This “combinatorial contrast” needs explaining. After showing that a straightforward explanation is inadequate, I consider various accounts for this contrast. Stephanie Leary’s explanation is insufficient for prohibitive balancing of epistemic reasons due to its lack of reasons for suspension. John Brunero’s explanation incorporates reasons for suspension but cannot accommodate reasons against suspension. A general point, which applies to any explanatory attempt that focuses on prohibitive balancing, is that a successful explanation for prohibitive balancing needs reasons for suspension that are both strong enough and weak enough to give correct verdicts. Tucker’s explanation is also prone to doubts from this general requirement, as well as other problems, including those similar to those found in the previous two explanations
Personality states
No full textPersonality states refer to an individuals’ feelings, thoughts, behaviours, and goals at a particular time. We review recent research with a focus on broad factor models of personality (Big Five, HEXACO), identifying several themes. First, studies show both convergence and significant differences between average states and traits and provide initial evidence that state fluctuations play a role in long-term trait change. Second, recent studies have identified theoretically plausible contingencies between situation characteristics and personality states as well as sizeable individual differences in these contingencies. Third, in applied contexts, personality states are associated with variables such as job performance, sleep quality, and stress. Finally, we highlight recent advances in the measurement of personality states
N-Salicyl-amino acid derivatives with antiparasitic activity from Pseudomonas sp. UIAU-6B
No full textPseudomonads strains represent a promising source of bioactive compounds with potential pharmaceutical applications. The necessity to find new drugs is underscored by the increased concern over antimicrobial resistance in the human system. In this study, we isolated two previously undescribed N-salicyl-amino acids as natural products (1 and 2) and other two new derivatives (3 and 4) from the organic extract of a culture broth in a modified starch–glucose–glycerol (SGG) medium of Pseudomonas sp. UIAU-6B. The structure of the new natural products, pseudomonins D–G (1–4) isolated alongside other three known compounds, pseudomonine (5), pseudomonin B (6) and salicylic acid (7), were elucidated based on high-resolution mass spectrometry, 1D and 2D NMR analyses. The absolute configurations of the threonine residue in compounds 1 and 2 were determined by Marfey’s analysis. Compound 4 displayed a very weak pan-trypanocidal activity against Trypanosoma brucei, Trypanosoma cruzi and Leishmania major with EC50 values of 101–137 μM, while compounds 2 and 5 showed modest activity against Leishmania major, but none of the remaining compounds showed activity at the highest concentrations tested. The plausible biosynthetic hypotheses toward the compounds were also proposed
Hope at the End of the Psalms
No full textAnalyses of the book of Psalms in recent years have detected not only editorial shaping to the book, but an eschatological trajectory as the collection unfolds. This essay critically assesses those accounts, and seeks to test them through an examination of “hope” in the Psalms. Judging by key lexemes, there is a clustering towards Book V, with key nodal points in Pss 119, 130, and 146-147. Exegetical examination of these key texts contributes not only to an appreciation of the “canonical shape” of the Psalter, but brings into the foreground the nature of hope for these psalmists
Sustainable management of non-timber forest products in Peruvian Amazonia:lessons learnt from participatory use of smartphone technology
No full textOver a billion people rely on tropical forest resources for their livelihoods, so sustainable resource use is essential for long-term human and ecosystem health. Smartphone technologies are increasingly proposed as a cost-effective and accessible way of widening community participation in environmental monitoring, but existing studies typically focus on the technological capabilities of smartphones for data collection, rather than how they represent local community interests or affect conservation outcomes. To address this gap, we report on the participatory and technical potential and limitations of smartphone-assisted collaboration for sustainable management of aguaje palms (Mauritia flexuosa), a commercially valuable species in the Peruvian Amazon. We assessed the potential of smartphone-based data collection, using OpenDataKit (ODK), for monitoring forest resources, working with a community management group and the Peruvian National Service of Natural Protected Areas to quantify and map the distribution, abundance and productivity of aguaje palms. Our study highlights tensions between technical and participatory elements of the process. We demonstrate the accessibility of ODK to users with varied levels of digital literacy, its ability to represent multiple interests and the potential to innovatively combine small ODK datasets with vegetation data and Google Earth Engine mapping. However, our work highlights the risk that dependence on digital technologies can exclude stakeholders with poor connectivity, since the process mainly engaged digitally connected partners. Based on this experience, we provide four lessons to support good practice and avoid misalignment of technological and participatory interests in the design and implementation of participatory environmental management using smartphone and open-source technology