Breaking Bad? Gangs, masculinities and murder in Trinidad

The murder rate in Port of Spain, Trinidad, rose dramatically around the turn of the millennium, driven overwhelmingly by young men in gangs in the city’s poor neighborhoods. The literature frequently suggests a causal relationship between gang violence and rising transnational drug flows through Trinidad during this period. However, this is only part of a complex picture and misses the crucial mediating effect of evolving male identities in contexts of pronounced exclusion. Using original data, this article argues that historically marginalized “social terrains” are particularly vulnerable to violence epidemics when exposed to the influence of transnational drug and gun trafficking. When combined with easily available weapons, contextually constructed male hegemonic orders that resonate with the past act as catalysts for contemporary gang violence within those milieus. The study contributes a new empirical body of work on urban violence in Trinidad and the first masculinities-specific analysis of this phenomenon. We argue that contemporary gang culture is a historically rooted, contextually legitimated, male hegemonic street project in the urban margins of Port of Spain

Confined magnon dispersion in ferromagnetic and antiferromagnetic thin films in a second quantization approach: the case of Fe and NiO

We present a methodology based on the calculation of the inelastic scattering from magnons via the spin scattering function in confined geometries such as thin films using a second quantization formalism, for both ferromagnetic and antiferromagnetic materials. The case studies are chosen with an aim to demonstrate the effects of film thickness and crystal orientation on magnon modes, using bcc Fe(100) and NiO with (100) and (111) crystallographic orientations as prototypical systems. Due to the quantization of the quasi-momentum we observe a granularity in the inelastic spectra in the reciprocal space path reflecting the orientation of the thin film. This approach also allows to capture softer modes that appear due to the partial interaction of magnetic moments close to the surface in a thin film geometry, in addition to bulk modes. The softer modes are also affected by crystallographic orientations as illustrated by the different surface-related peaks of NiO magnon density of states at approximately ~ 65 meV for (100) and ~ 42 meV for (111). Additionally, we explore the role of anisotropy on magnon modes, revealing that introducing anisotropy to both Fe and NiO films increases the overall hardness of the magnon modes. The introduction of a surface anisotropy produces a shift of the surface-related magnon DOS peak to higher energies with increased surface anisotropy, and in some cases leading to surface confined mode

Theory of momentum-resolved magnon electron energy loss spectra: The case of Yttrium Iron Garnet

We explore the inelastic spectra of electrons impinging in a magnetic system. The methodology here presented is intended to highlight the charge-dependent interaction of the electron beam in a STEM-EELS experiment, and the local vector potential generated by the magnetic lattice. This interaction shows an intensity $10^{-2}$ smaller than the purely spin interaction, which is taken to be functionally the same as in the inelastic neutron experiment. On the other hand, it shows a strong scattering vector dependence ($\kappa^{-4}$) and a dependence with the relative orientation between the probe wavevector and the local magnetic moments of the solid. We present YIG as a case study due to its high interest by the community

Significant improvement of the Seebeck coefficient of Fe2VAl with antisite defects

In this work we present first principles study of the effect of stoichiometric pairs of antisite defects, V occupying Al site (VAl) and Al occupying V site (AlV), on the electronic structure and Seebeck coefficient of the Fe2VAlHeusler alloy. We show that introduction of these defects opens the bandgap of Fe2VAl, changing it from semi-metal to semiconductor, which results in an increase of the Seebeck coefficient for a range of doping concentrations and temperatures. We calculated Seebeck coefficients at different doping concentrations and temperatures shows good agreement with experimental data

Formation of a ternary oxide barrier layer and its role in switching characteristic of ZnO-based conductive bridge random access memory devices

The insertion of a metal layer between an active electrode and a switching layer leads to the formation of a ternary oxide at the interface. The properties of this self-formed oxide are found to be dependent on the Gibbs free energy of oxide formation of the metal (ΔGf°). We investigated the role of various ternary oxides in the switching behavior of conductive bridge random access memory (CBRAM) devices. The ternary oxide acts as a barrier layer that can limit the mobility of metal cations in the cell, promoting stable switching. However, too low (higher negative value) ΔGf° leads to severe trade-offs; the devices require high operation current and voltages to exhibit switching behavior and low memory window (on/off) ratio. We propose that choosing a metal layer having appropriate ΔGf° is crucial in achieving reliable CBRAM devices

Hydrogel Cross-Linking via Thiol-Reactive Pyridazinediones

Thiol-reactive Michael acceptors are commonly used for the formation of chemically cross-linked hydrogels. In this paper, we address the drawbacks of many Michael acceptors by introducing pyridazinediones as new cross-linking agents. Through the use of pyridazinediones and their mono- or dibrominated analogues, we show that the mechanical strength, swelling ratio, and rate of gelation can all be controlled in a pH-sensitive manner. Moreover, we demonstrate that the degradation of pyridazinedione-gels can be induced by the addition of thiols, thus providing a route to responsive or dynamic gels, and that monobromo-pyridazinedione gels are able to support the proliferation of human cells. We anticipate that our results will provide a valuable and complementary addition to the existing toolkit of cross-linking agents, allowing researchers to tune and rationally design the properties of biomedical hydrogels

3D self-assembled polar vs. non-polar NiO nanoparticles nanoengineered from turbostratic Ni3(OH)4(NO3)2 and ordered β-Ni(OH)2 intermediates

A surfactant-free ammonia and carbamide precursor-modulated engineering of self-assembled flower-like 3D NiO nanostructures based on ordered β-Ni(OH)2 and turbostratic Ni3(OH)4(NO3)2 nanoplate-structured intermediates is reported. By employing complementary structural and spectroscopic techniques, fundamental insights into structural and chemical transformations from intermediates to NiO nanoparticles (NPs) are provided. FTIR, Raman and DSC analyses show that the transformation of intermediates to NiO NPs involves subsequent loss of NO3− and OH− species through a double-step phase transformation at 306 and 326 °C corresponding to the loss of free interlayer ions and H2O species, respectively, followed by the loss of chemically bonded OH− and NO3− ions. Transformation to NiO NPs via the ammonia route proceeds as single-phase transition, accompanied with a loss of OH− species at 298 °C. The full transformation to NiO NPs of both intermediates is achieved at 350 °C through annealing in the air atmosphere. Ammonia-derived NPs maintain nanoflower morphology by self-assembling into nanoplates, which is enabled by H2O-mediated adhesion on the NiO NPs’ {100} neutral surfaces. Structural transformations of turbostratic Ni3(OH)4(NO3)2 nanoplates result in the formation of NiO NPs dominantly shaped by inert polar OH-terminated (111) atomic planes, leading to the loss of the initial self-assembled 3D structure. DFT calculations support these observations, confirming that H2O adsorbs dissociatively on polar {111} surfaces, while only physisorption is energetically feasible on {100} surfaces. NiO NPs obtained via two different routes have overall different properties: carbamide-derived NPs are 3 times larger (15.5 vs. 5.4 nm), possess a larger band gap (3.6 vs. 3.2 eV) and are more Ni deficient. The intensity ratio of surface optical (SO) modes to transversal and longitudinal optical modes is ∼40 times higher in the NiO NPs obtained from β-Ni(OH)2 compared to Ni3(OH)4(NO3)2-derived NPs. The SO phonon lifetime is an order of magnitude shorter in NiO obtained from β-Ni(OH)2, reflecting a much smaller NP size. The choice of a precursor defines the size, morphology, crystallographic surface orientations and band gap of the NiO NPs, with Ni deficiency providing pathways for utilizing them as p-type materials, allowing for the precise nanoengineering of polar and neutral surface-dominated NiO NPs, which is of exceptional importance for use in catalysis