Spontaneous breakdown of Lorentz symmetry in scalar QED with higher order derivatives

Scalar QED is studied with higher order derivatives for the scalar field kinetic energy. A local potential is generated for the gauge field due to the covariant derivatives and the vacuum with non-vanishing expectation value for the scalar field and the vector potential is constructed in the leading order saddle point expansion. This vacuum breaks the global gauge and Lorentz symmetry spontaneously. The unitarity of time evolution is assured in the physical, positive norm subspace and the linearized equations of motion are calculated. Goldstone theorem always keeps the radiation field massless. A particular model is constructed where the the full set of standard Maxwell equations is recovered on the tree level thereby relegating the effects of broken Lorentz symmetry to the level of radiative corrections.Comment: 14 pages, to appear in Phys. Rev.

Inhomogeneity effect in Wainwright-Marshman space-times

Green and Wald have presented a mathematically rigorous framework to study, within general relativity, the effect of small scale inhomogeneities on the global structure of space-time. The framework relies on the existence of a one-parameter family of metrics that approaches the effective background metric in a certain way. Although it is not necessary to know this family in an exact form to predict properties of the backreaction effect, it would be instructive to find explicit examples. In this paper, we provide the first example of such a family of exact non-vacuum solutions to the Einstein's equations. It belongs to the Wainwright-Marshman class and satisfies all of the assumptions of the Green-Wald framework.Comment: 10 pages; revised version, as published in PR

Divalent Metal Binding Properties of the Methionyl Aminopeptidase from \u3cem\u3eEscherichia coli\u3c/em\u3e

The metal-binding properties of the methionyl aminopeptidase from Escherichia coli (MetAP) were investigated. Measurements of catalytic activity as a function of added Co(II) and Fe(II) revealed that maximal enzymatic activity is observed after the addition of only 1 equiv of divalent metal ion. Based on these studies, metal binding constants for the first metal binding event were found to be 0.3 ± 0.2 μM and 0.2 ± 0.2 μM for Co(II)- and Fe(II)-substituted MetAP, respectively. Binding of excess metal ions (\u3e50 equiv) resulted in the loss of ∼50% of the catalytic activity. Electronic absorption spectral titration of a 1 mM sample of MetAP with Co(II) provided a binding constant of 2.5 ± 0.5 mM for the second metal binding site. Furthermore, the electronic absorption spectra of Co(II)-loaded MetAP indicated that both metal ions reside in a pentacoordinate geometry. Consistent with the absorption data, electron paramagnetic resonance (EPR) spectra of [CoCo(MetAP)] also indicated that the Co(II) geometries are not highly constrained, suggesting that each Co(II) ion in MetAP resides in a pentacoordinate geometry. EPR studies on [CoCo(MetAP)] also revealed that at pH 7.5 there is no significant spin-coupling between the two Co(II) ions, though a small proportion (∼5%) of the sample exhibited detectable spin−spin interactions at pH values \u3e 9.6. EPR studies on [Fe(III)_(MetAP)] and [Fe(III)Fe(III)(MetAP)] also suggested no spin-coupling between the two metal ions. 1H nuclear magnetic resonance (NMR) spectra of [Co(II)_(MetAP)] in both H2O and D2O buffer indicated that the first metal binding site contains the only active-site histidine residue, His171. Mechanistic implications of the observed binding properties of divalent metal ions to the MetAP from E. coli are discussed

The role of the Amyloid Precursor Protein mutations and PERK-dependent signaling pathways in the pathogenesis of Alzheimer’s disease

Alzheimer’s disease (AD) is a highly complex, progressive, age-related neurodegenerative human disease entity. The genetic basis of AD is strictly connected with occurrence of mutations in Amyloid Precursor (APP) gene on chromosome 21. Molecular mechanism that leads to AD development still remains unclear. Recent data reported that it is closely correlated with Endoplasmic Reticulum (ER) stress conditions, which subsequently activate Unfolded Protein Response (UPR) signaling pathways, via the induction of protein kinase RNA-like endoplasmic reticulum kinase (PERK), as a self-protective, adaptive response to adverse stress conditions. That results in the attenuation of global protein synthesis and, on the contrary, selective translation of Activating Transcriptor Factor 4 (ATF4) and secretase β. Interestingly, under prolonged, severe ER stress UPR may switch its signal into apoptotic cell death. That ensues by ATF4-CHOP-mediated activation of a range of pro-apoptotic genes and, on the other hand, downregulation of the expression of the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2) genes. Current investigations suggest that inhibitions of PERK activity may contribute to the attenuation of the deposition of toxic senile plaques in the brain tissue and, as a result, prevent degeneration of neurons and decline in cognitive abilities

On Size Mappings

A real-valued mapping r from the hyperspace of all compact subsets of a givenmetric space X is called a size mapping if r({x}) = 0 for x ∈ X and r(A) ≤ r(B) if a ⊂ B. We investigate what continua admit an open or a monotone size mapping. Special attention is paid to the diameter mappings

Learning Language and Vocabulary in Dialogue with the Real Audience: Exploring Young Writers’ Authentic Writing and Language Learning Experiences

Purpose: To explore the potential of conversations with an authentic audience through blogging for enriching in the young writers the understanding of the communicative function of writing, specifically language and vocabulary use. Design: We situate our work in a language acquisition model of language learning where learners develop linguistic competence in the process of speaking and using the language (Krashen, 1988; Tomasello, 2005). We also believe that language learning benefits from formal instruction (Krashen, 1988). As such, in our work, we likened engaging in blogging to learning a language (here, more broadly conceived as learning to write) through both natural communication (acquisition) and prescription (instruction), and we looked at these forms of learning in our study. We were interested in the communicative function of language learning (Halliday, 1973; 1975; Penrod, 2005) among young blog writers as we see language learning as socially constructed through interaction with other speakers of a language (Tomasello, 2005; Vygotsky, 1978). Findings: The readers and commenters in this study supported young writers in their language study by modeling good writing and effective language use in their communication with these writers. Young writers also benefited from direct instruction through interactions with adults beyond classroom teachers, in our case some of the readers and commenters. Practical Implications: Blogging can extend conversations to audiences far beyond the classroom and make writing an authentic endeavor for young writers. Teachers should take advantage of such a powerful tool in their writing classrooms to support their students’ language study and vocabulary development

A Teacher Goes Gothic: Walter White, Heisenberg, and the Dark Revenge of Science

Much has been written on the natures and personalities of teachers in educational research and publications (Carter, 2009; Beck, 2012; Bulman, 2015; Dalton, 2013; Gillard, 2012; Kelly & Caughlan, 2011). However, mass media can have a powerful influence on how people see teachers. The television series Breaking Bad (Gilligan, 2007-2013) and its representation of teachers, has contributed a unique – if warped -perspective on the subject of teachers and teaching in America. In this article, we argue that three important Gothic and mythic fables from literature are harbingers of Walter White and his transformation – the Faust legend, as told by Christopher Marlowe (1604), the tale of Victor Frankenstein and his monster, by Mary Wollstonecraft Shelley (1818) and Robert Louis Stevenson’s famous character, Mr. Edward Hyde (1886). We note that the comparisons, while apt, are imperfect, and we discuss the philosophical, social and literary implications of them

Kinetic and Spectroscopic Characterization of the H178A Methionyl Aminopeptidase from \u3cem\u3eEscherichia coli\u3c/em\u3e

To gain insight into the role of the strictly conserved histidine residue, H178, in the reaction mechanism of the methionyl aminopeptidase from Escherichia coli (EcMetAP-I), the H178A mutant enzyme was prepared. Metal-reconstituted H178A binds only one equivalent of Co(II) or Fe(II) tightly with affinities that are identical to the WT enzyme based on kinetic and isothermal titration calorimetry (ITC) data. Electronic absorption spectra of Co(II)-loaded H178A EcMetAP-I indicate that the active site divalent metal ion is pentacoordinate, identical to the WT enzyme. These data indicate that the metal binding site has not been affected by altering H178. The effect of altering H178 on activity is, in general, due to a decrease in kcat. The kcat value for Co(II)-loaded H178A decreased 70-fold toward MGMM and 290-fold toward MP-p-NA compared to the WT enzyme, while kcat decreased 50-fold toward MGMM for the Fe(II)-loaded H178A enzyme and 140-fold toward MP-p-NA. The Km values for MGMM remained unaffected, while those for MP-p-NA increased approximately 2-fold for Co(II)- and Fe(II)-loaded H178A. The kcat/Km values for both Co(II)- and Fe(II)-loaded H178A toward both substrates ranged from ∼50- to 580-fold reduction. The pH dependence of log Km, log kcat, and log(kcat/Km) of both WT and H178A EcMetAP-I were also obtained and are identical, within error, for H178A and WT EcMetAP-I. Therefore, H178A is catalytically important but is not required for catalysis. Assignment of one of the observed pKa values at 8.1 for WT EcMetAP-I was obtained from plots of molar absorptivity at λmax(640) vs pH for both WT and H178A EcMetAP-I. Apparent pKa values of 8.1 and 7.6 were obtained for WT and H178A EcMetAP-I, respectively, and were assigned to the deprotonation of a metal-bound water molecule. The data reported herein provide support for the key elements of the previously proposed mechanism and suggest that a similar mechanism can apply to the enzyme with a single metal in the active site

Reversible inhibition of reproduction during regeneration of cerebral ganglia and celomocytes in the earthworm Dendrobaena veneta

Earthworms may be subjected to mechanical/chemical stimuli and/or sub-lethal predator attacks leading to the extrusion of celomocytes and/or loss of body parts; thus, regeneration of cells, tissues and organs has adaptive value. The aim of present study on the lumbricid earthworm Dendrobaena veneta was to determine the interactive effects of celomocytes and the brain on the regeneration of either system after experimental depletion or extirpation, and to assess the effects of such treatments on reproductive performance. Decerebration was achieved either by amputating the first six anterior segments, or by surgery; celomocyte depletion was achieved by a standard electro-stimulation procedure. Celomocytes (amebocyte and eleocytes, respectively) were counted by hemocytometry, and riboflavin content in celomocyte lysates measured by spectrofluorimetry. The main findings were: (i) D. veneta regenerated anatomically intact brain, including neurosecretory cells, within 10 - 18 weeks after its removal plus celomocyte depletion (i.e. dual treatment); (ii) amoebocyte counts recovered to control levels by 10 weeks after extrusion treatment alone, but were still lower (60 %) than in controls at 18 weeks after dual treatment; eleocyte recovery after electro-stimulation alone was slow, reaching control levels only after 18 weeks, and was further retarded (31 % of controls at 18 weeks) by brain extirpation; (iii) riboflavin content was lower than controls only in the dual-treatment worms at 5 weeks; riboflavin content relative to eleocyte numbers was initially higher than controls in both treatment groups; this index was restored to control levels by 18 weeks in the electro-stimulation only treatment whilst recovery was somewhat retarded in the brain-extirpated group; (iv) celomocyte depletion treatment alone slightly impaired reproductive output, whilst brain removal had pronounced and protracted inhibitory effects. The observations engender the hypothesis that brain-derived neurosecretions and immune-competent celomocytes act in tandem to modulate neural regeneration and reproduction