Cosmology in a Time-Crystal Background

We investigate the effects of a Time Crystal-like Condensate on cosmological dynamics. It is well known that quadratic gravity reduces to Einstein gravity along with a decoupled higher derivative dynamical scalar \cite{Alvarez-Gaume:2015rwa}. According to \cite{Chakraborty:2020ktp}, the above scalar sector can sustain a Time Crystal-like minimum energy state, with non-trivial time dependence. In the present work we treat the Time Crystal-like state as the background (that replaces the classical Minkowski vacuum) and study cosmic evolution on this ``dynamic'' ground state. In the first part we re-derive \cite{Chakraborty:2020ktp}, in a covariant and more systematic way, the frequencies that characterize the oscillator like Time crystalline condensate and interpret it as a background energy-momentum tensor simulating a matter-like effect. Importantly, no external matter is introduced here and the condensate, consists of a combination of the metric field $g_{\mu\nu}$ and is generated due to the $R^2$-term ($R$ is the Ricci scalar) in quadratic gravity \cite{Alvarez-Gaume:2015rwa}. In a way the spurious degrees of freedom of $R^2$-gravity turns into a useful component. The second part comprises of new effects where the cosmology in Friedmann-Lem\^{i}atre-Robertson-Walker (FLRW) universe is studied in presence of the energy-momentum tensor characterizing the Time Crystal Condensate. Under certain approximations, the scale factor of the FLRW universe is analytically obtained for any spatial geometry. We also find that the Time Crystal Condensate contributes as a new matter candidate having radiation-like behavior in the universe. Additionally, irrespective of the spatial geometry of the universe, the Time Crystal condensate generates a decelerating phase before the early acceleration starts. This is an indication of a contracting phase of the universe before its accelerated expansion.Comment: 11 pages, 4 compound figures. Comments are welcom

Asymmetric rotations and dimerization driven by normal to modulated phase transition in 4-biphenylcarboxy coupled L-phenylalaninate

Amongst the derivatives of 4-biphenylcarboxylic acid and amino acid esters, the crystal structure of 4-biphenylcarboxy-(L)-phenylalaninate is unusual owing to its monoclinic symmetry within a pseudo-orthorhombic lattice. The distortion is described by disparate rotational property around the chiral centers ($\varphi_{\mathrm{chiral}}$ $\simeq$ -129 degrees and 58 degrees) of the two molecules in the asymmetric unit. Each of these molecules comprise of planar biphenyl moieties ($\varphi_{\mathrm{biphenyl}}$ = 0 degrees). Using temperature dependent single crystal X-ray diffraction experiments we show that the compound undergoes a phase transition below $T$ $\sim$ 124 K that is characterized by a commensurate modulation wave vector, $\mathbf{q}$ = $\delta(101)$, $\delta$ = $\frac{1}{2}$. The (3+1) dimensional modulated structure at $T$ = 100 K suggests that the phase transition drives the biphenyl moieties towards non coplanar conformations with significant variation of internal torsion ($\varphi^{\mathrm{max}}_{\mathrm{biphenyl}}$ $\leq$ $20$ degrees). These intramolecular rotations lead to dimerization of the molecular stacks that are described predominantly by intermolecular tilts and small variations in intermolecular distances. Atypical of modulated structures and superstructures of biphenyl and other polyphenyls, the rotations of individual molecules are asymmetric ($\Delta$$\varphi_{\mathrm{biphenyl}}$ $\approx$ 5 degrees) while $\varphi_{\mathrm{biphenyl}}$ of one independent molecule is two to four times larger than the other. Crystal-chemical analysis and phase relations in superspace suggest multiple competing factors involving intramolecular steric factors, intermolecular H--C${\cdot}{\cdot}{\cdot}$C--H contacts and weak C--H${\cdot}{\cdot}{\cdot}$O hydrogen bonds that govern the distinctively unequal torsional property of the molecules

Lead candidates for high-performance organic photovoltaics from high-throughput quantum chemistry – the Harvard Clean Energy Project

The virtual high-throughput screening framework of the Harvard Clean Energy Project allows for the computational assessment of candidate structures for organic electronic materials – in particular photovoltaics – at an unprecedented scale. We report the most promising compounds that have emerged after studying 2.3 million molecular motifs by means of 150 million density functional theory calculations. Our top candidates are analyzed with respect to their structural makeup in order to identify important building blocks and extract design rules for efficient materials. An online database of the results is made available to the community.Engineering and Applied Science

Search for long-lived, massive particles in events with displaced vertices and multiple jets in pp collisions at √s = 13 TeV with the ATLAS detector

A search for long-lived particles decaying into hadrons is presented. The analysis uses 139 fb−1 of pp collision data collected at √s = 13 TeV by the ATLAS detector at the LHC using events that contain multiple energetic jets and a displaced vertex. The search employs dedicated reconstruction techniques that significantly increase the sensitivity to long-lived particles decaying in the ATLAS inner detector. Background estimates for Standard Model processes and instrumental effects are extracted from data. The observed event yields are compatible with those expected from background processes. The results are used to set limits at 95% confidence level on model-independent cross sections for processes beyond the Standard Model, and on scenarios with pair-production of supersymmetric particles with long-lived electroweakinos that decay via a small R-parity-violating coupling. The pair-production of electroweakinos with masses below 1.5 TeV is excluded for mean proper lifetimes in the range from 0.03 ns to 1 ns. When produced in the decay of m(g∼) = 2.4 TeV gluinos, electroweakinos with m(χ∼01) = 1.5 TeV are excluded with lifetimes in the range of 0.02 ns to 4 ns

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

LARVICIDAL EFFECT OF Coffea arabica L., Camellia sinensis (L.) Kuntz, AND Punica granatum L. ON Aedes albopictus (Skuse), THE VECTOR OF DENGUE AND CHIKUNGUNYA

The purpose of the present study is to envisage the larvicidal activities of three common plant extracts in controlling Aedes albopictus (Skuse), a potential vector of Dengue and Chikungunya. Chloroform extract of green coffee beans, Coffea arabica L.; methanol extract of green tea leaves, Camellia sinensis (L.) Kuntz and chloroform extract of pomegranate fruit peel Punica granatum L. were tested against late 3rd instar/ early 4th instar larvae of Ae. albopictus under laboratory condition following WHO methodology, 2005. LC50 values were determined using the probit analysis with 95% confidence limit. The result indicated that after 24 hours and 48 hours of treatment, LC50 values for green coffee bean extract, green tea leaves extract and pomegranate fruit peel extract against Ae. albopictus larvae were 0.08, and 0.06, 0.13 and 0.06, 0.09 and 0.06 respectively. Our findings revealed that chloroform extract of green coffee beans and methanol extract of green tea leaves are the most effective in controlling Aedes albopictus larvae showing 100% mortality after 48 hours of exposure than chloroform extract of pomegranate fruit peel that shows 66% mortality after 48 hours of treatment. The overall larvicidal trend with reference to LC50 after 24 hours and 48 hours was green coffee > green tea > pomegranate. The larvae exposed to green coffee bean crude extract showed deformities related to moulting behavior and larval morphology. As these plants are widely distributed in India, their formulation might manifest effective eco-friendly alternatives for combating this upcoming potential vector of Dengue and Chikungunya