Optical binding in nanoparticle assembly: Potential energy landscapes

Optical binding is an optomechanical effect exhibited by systems of micro- and nanoparticles, suitably irradiated with off-resonance laser light. Physically distinct from standing-wave and other forms of holographic optical traps, the phenomenon arises as a result of an interparticle coupling with individual radiation modes, leading to optically induced modifications to Casmir-Polder interactions. To better understand how this mechanism leads to the observed assemblies and formation of patterns in nanoparticles, we develop a theory in terms of optically induced energy landscapes exhibiting the three-dimensional form of the potential energy field. It is shown in detail that the positioning and magnitude of local energy maxima and minima depend on the configuration of each particle pair, with regards to the polarization and wave vector of the laser light. The analysis reveals how the positioning of local minima determines the energetically most favorable locations for the addition of a third particle to each equilibrium pair. It is also demonstrated how the result of such an addition subtly modifies the energy landscape that will, in turn, determine the optimum location for further particle additions. As such, this development represents a rigorous and general formulation of the theory, paving the way toward full comprehension of nanoparticle assembly based on optical binding

Cyclic homogeneous Riemannian manifolds

In spin geometry, traceless cyclic homogeneous Riemannian manifolds equipped with a homogeneous spin structure can be viewed as the simplest manifolds after Riemannian symmetric spin spaces. In this paper, we give some characterizations and properties of cyclic and traceless cyclic homogeneous Riemannian manifolds and we obtain the classification of simply-connected cyclic homogeneous Riemannian manifolds of dimension less than or equal to four. We also present a wide list of examples of non-compact irreducible Riemannian $3$-symmetric spaces admitting cyclic metrics and give the expression of these metrics

La represión penal del giro sin provisión de fondos

Fil: Dávila, Alejandro A. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Derecho Penal II. Buenos Aires, ArgentinaTemas de Derecho Penal I

Homogeneous spin Riemannian manifolds with the simplest Dirac operator

We show the existence of nonsymmetric homogeneous spin Riemannian manifolds whose Dirac operator is like that on a Riemannian symmetric spin space. Such manifolds are exactly the homogeneous spin Riemannian manifolds $(M,g)$ which are traceless cyclic with respect to some quotient expression $M=G/K$ and reductive decomposition $\mathfrak{g} = \mathfrak{k} \oplus \mathfrak{m}$. Using transversally symmetric fibrations of noncompact type, we give a list of them

How Many More Brazilian Environmental Defenders Have to Perish Before We Act? President Lula\u27s Challenge to Protect Environmental Quilombola Defenders

The Global South has been historically marginalized and continues to suffer from systemic oppression, impeding the realization of their human rights. Afro-descendants and other minority populations in the Global South live in disproportionately environmentally unsafe conditions and are disproportionately more vulnerable to climate change and environmental harm. One of those populations are Quilombolas. Quilombolas are Brazilian Afro-descendant communities who continue to fight to protect their community rights to ancestral lands, natural resources, and survival as a people. The Brazilian government under former Brazilian President Bolsonaro engaged in a persistent and systematic campaign to target, attack, and kill defenders, including Quilombola defenders, who sought to protect the environment and human rights. His government engaged in the systematic deforestation and extraction of natural resources in the Amazon. It is up to Brazil’s re-elected President Luiz Inácio Lula da Silva and his new administration to ensure that the Amazon is protected, and that human rights defenders, including Quilombola defenders, are protected and are able to have justice and accountability for their human rights violations. We must hold the Brazilian state and private actors responsible for human rights violations through the existing rights-based framework through the newly ratified Regional Agreement on Access to Information, Public Participation and Justice in Environmental Matters in Latin America and the Caribbean (“Escazú Agreement”) and the Esperanza Protocol

Time to Wake Up! Pushing the Boundaries in the Americas to Protect the Most Vulnerable, 39 UCLA J. Envtl. L. & Pol\u27y 123 (2021)

It is time to wake up and push for the protection of the environment and against climate change. Vulnerable communities around the world are living in polluted, highly toxic, and unsustainable environments. It is time to protect them through a human rights-based framework. This article proposes that the Inter-American right to a healthy environment provides the possibility of protecting the human rights of the most vulnerable in the Americas by providing a rights-based framework for them to vindicate their environmental human rights. This article focuses on vulnerable populations who have been historically marginalized and discriminated against and/or who are reliant on the natural resources in their environments. This article posits that the greening of human rights, which is the traditional approach to the protection of environmental human rights, is not sufficient to protect vulnerable non-indigenous populations without protection. It is for this reason that we, as a society, must think creatively about environmental human rights advocacy, and create a system that moves forward the development of the right to a healthy environment. We must hold States responsible for their actions and for their support of corporations who exploit natural resources and populations living in them. If we know that so much human suffering is already happening due to environmental harm and climate change, why are we continuing on this path

Quasi-chemical approximation for polyatomic mixtures

The statistical thermodynamics of binary mixtures of polyatomic species was developed on a generalization in the spirit of the lattice-gas model and the quasi-chemical approximation (QCA). The new theoretical framework is obtained by combining: (i) the exact analytical expression for the partition function of non-interacting mixtures of linear $k$-mers and $l$-mers (species occupying $k$ sites and $l$ sites, respectively) adsorbed in one dimension, and its extension to higher dimensions; and (ii) a generalization of the classical QCA for multicomponent adsorbates and multisite-occupancy adsorption. The process is analyzed through the partial adsorption isotherms corresponding to both species of the mixture. Comparisons with analytical data from Bragg-Williams approximation (BWA) and Monte Carlo simulations are performed in order to test the validity of the theoretical model. Even though a good fitting is obtained from BWA, it is found that QCA provides a more accurate description of the phenomenon of adsorption of interacting polyatomic mixtures.Comment: 27 pages, 8 figure

Germanene: a novel two-dimensional Germanium allotrope akin to Graphene and Silicene

Using a gold (111) surface as a substrate we have grown in situ by molecular beam epitaxy an atom-thin, ordered, two-dimensional multi-phase film. Its growth bears strong similarity with the formation of silicene layers on silver (111) templates. One of the phases, forming large domains, as observed in Scanning Tunneling Microscopy, shows a clear, nearly flat, honeycomb structure. Thanks to thorough synchrotron radiation core-level spectroscopy measurements and advanced Density Functional Theory calculations we can identify it to a $\sqrt{3}$x$\sqrt{3}$R(30{\deg}) germanene layer in coincidence with a $\sqrt{7}$x$\sqrt{7}$R(19.1{\deg}) Au(111) supercell, thence, presenting the first compelling evidence of the birth of a novel synthetic germanium-based cousin of graphene.Comment: 16 pages, 4 figures, 1 tabl