Failure of classical elasticity in auxetic foams

A recent derivation [P.H. Mott and C.M. Roland, Phys. Rev. B 80, 132104 (2009).] of the bounds on Poisson's ratio, v, for linearly elastic materials showed that the conventional lower limit, -1, is wrong, and that v cannot be less than 0.2 for classical elasticity to be valid. This is a significant result, since it is precisely for materials having small values of v that direct measurements are not feasible, so that v must be calculated from other elastic constants. Herein we measure directly Poisson's ratio for four materials, two for which the more restrictive bounds on v apply, and two having values below this limit of 0.2. We find that while the measured v for the former are equivalent to values calculated from the shear and tensile moduli, for two auxetic materials (v < 0), the equations of classical elasticity give inaccurate values of v. This is experimental corroboration that the correct lower limit on Poisson's ratio is 0.2 in order for classical elasticity to apply.Comment: 9 pages, 2 figure

Intercomparison of cloud properties in DYAMOND simulations over the Atlantic Ocean

We intercompared the cloud properties of the DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains (DYAMOND) simulation output over the Atlantic Ocean. The domain averaged outgoing longwave radiation (OLR) is relatively similar across the models, but the net shortwave radiation at the top of the atmosphere (NSR) shows large differences among the models. The models capture the triple modes of cloud systems corresponding to shallow, congestus, and high clouds, although their partition in these three categories is strongly model dependent. The simulated height of the shallow and congestus peaks is more robust than the peak of high clouds, whereas cloud water content exhibits larger intermodel differences than does cloud ice content. Furthermore, we investigated the resolution dependency of the vertical profiles of clouds for NICAM (Nonhydrostatic ICosahedral Atmospheric Model), ICON (Icosahedral Nonhydrostatic), and IFS (Integrated Forecasting System). We found that the averaged mixing ratio of ice clouds consistently increased with finer grid spacing. Such a consistent signal is not apparent for the mixing ratio of liquid clouds for shallow and congestus clouds. The impact of the grid spacing on OLR is smaller than on NSR and also much smaller than the intermodel differences

Quasi-Local Energy Flux of Spacetime Perturbation

A general expression for quasi-local energy flux for spacetime perturbation is derived from covariant Hamiltonian formulation using functional differentiability and symplectic structure invariance, which is independent of the choice of the canonical variables and the possible boundary terms one initially puts into the Lagrangian in the diffeomorphism invariant theories. The energy flux expression depends on a displacement vector field and the 2-surface under consideration. We apply and test the expression in Vaidya spacetime. At null infinity the expression leads to the Bondi type energy flux obtained by Lindquist, Schwartz and Misner. On dynamical horizons with a particular choice of the displacement vector, it gives the area balance law obtained by Ashtekar and Krishnan.Comment: 8 pages, added appendix, version to appear in Phys. Rev.

Some Spinor-Curvature Identities

We describe a class of spinor-curvature identities which exist for Riemannian or Riemann-Cartan geometries. Each identity relates an expression quadratic in the covariant derivative of a spinor field with an expression linear in the curvature plus an exact differential. Certain special cases in 3 and 4 dimensions which have been or could be used in applications to General Relativity are noted.Comment: 5 pages Plain TeX, NCU-GR-93-SSC

Interface behavior of a multi-layer fluid configuration subject to acceleration in a microgravity environment, supplement 1

With the increasing opportunities for research in a microgravity environment, there arises a need for understanding fluid mechanics under such conditions. In particular, a number of material processing configurations involve fluid-fluid interfaces which may experience instabilities in the presence of external forcing. In a microgravity environment, these accelerations may be periodic or impulse-type in nature. This research investigates the behavior of a multi-layer idealized fluid configuration which is infinite in extent. The analysis is linear, and each fluid region is considered inviscid, incompressible, and immiscible. An initial parametric study of confiquration stability in the presence of a constant acceleration field is performed. The zero mean gravity limit case serves as the base state for the subsequent time-dependent forcing cases. A stability analysis of the multi-layer fluid system in the presence of periodic forcing is investigated. Floquet theory is utilized. A parameter study is performed, and regions of stability are identified. For the impulse-type forcing case, asymptotic stability is established for the configuration. Using numerical integration, the time response of the interfaces is determined

A Quadratic Spinor Lagrangian for General Relativity

We present a new finite action for Einstein gravity in which the Lagrangian is quadratic in the covariant derivative of a spinor field. Via a new spinor-curvature identity, it is related to the standard Einstein-Hilbert Lagrangian by a total differential term. The corresponding Hamiltonian, like the one associated with the Witten positive energy proof is fully four-covariant. It defines quasi-local energy-momentum and can be reduced to the one in our recent positive energy proof. (Fourth Prize, 1994 Gravity Research Foundation Essay.)Comment: 5 pages (Plain TeX), NCU-GR-94-QSL

Pengaruh Penggunaan Aplikasi Fizzo Novel Terhadap Kemampuan Menulis Teks Drama pada Siswa Kelas XI SMK Negeri 4 Medan Tahun Ajaran 2022/2023

The aim of this research is to determine the effect of using the fizzo novel application on the writing ability of class XI students at SMK Negeri 4 Medan for the 2022/2023 academic year. The population in this study was all students in class The research method used is a quantitative experimental method. The research instrument is a drama text writing test which is assessed based on content aspects and linguistic aspects of the drama text. The results of the research show that there is an influence of using the fizzo novel application on the ability to write drama texts in class XI students at SMK Negeri 4 Medan. This is proven by hypothesis testing which shows that the value of Tcount &gt; Ttable is 11.6 &gt; 1.71 with a significance level of 5%

The Existence of Women in the Pre- and Post-Reformation Period in The Novel Laut Bercerita: A Review of Feminism

Women are faced with various stereotypes of being second-class beings. The female must accept being a being who must be under the position of the male. However, in contrast to such stereotypes, literary works are able to show a deconstruction of the conditions and situations of women as empowered beings. This is illustrated through one of Indonesia's novels entitled Laut Bercerita by Leila S. Chudori. Women are described as figures who have a role to be able to show their existence even though at that time there was political turmoil before 1998. One of the important things that deconstructs stereotypes is the existence of strong women who are able to heal male characters through their efforts. Women who are usually used as second sex in patriarchal confines seek to be undermined in the narrative of the novel. Based on this, the purpose of this study is to dismantle the existence of women in the time of turmoil before and after the reformation in the novel Laut Bercerita. This research is a qualitative descriptive study with the approach of Simon de Beauvoir existentialist feminism. The results of this study show that women managed to get out of the notion of second sex by showing existence in the public domain by getting a proper education and job in the public domain, being able to struggle to find their brother's character and her brother's colleague who were victims of student disappearance in 1998, being able to cure men due to kidnapping and torture in 1998, and the struggle to get information on the development of cases of losing older siblings  and his brother's partner in the period before 1998