Stability of real parametric polynomial discrete dynamical systems

We extend and improve the existing characterization of the dynamics of general quadratic real polynomial maps with coefficients that depend on a single parameter $\lambda$, and generalize this characterization to cubic real polynomial maps, in a consistent theory that is further generalized to real $m$-th degree real polynomial maps. In essence, we give conditions for the stability of the fixed points of any real polynomial map with real fixed points. In order to do this, we have introduced the concept of Canonical Polynomial Maps which are topologically conjugate to any polynomial map of the same degree with real fixed points. The stability of the fixed points of canonical polynomial maps has been found to depend solely on a special function termed Product Position Function for a given fixed point. The values of this product position determine the stability of the fixed point in question, when it bifurcates, and even when chaos arises, as it passes through what we have termed stability bands. The exact boundary values of these stability bands are yet to be calculated for regions of type greater than one for polynomials of degree higher than three.Comment: 23 pages, 4 figures, now published in Discrete Dynamics in Nature and Societ

Evoluția și etica eugeniei

În acest articol încerc să argumentez opinia că, așa cum este definită eugenia, este foarte dificil de făcut o diferențiere clară între știință (medicină, ingineria genetică) și eugenie. Și de stabilit o linie peste care ingineria genetică nu ar trebui să treacă, conform unor norme morale, juridice și religioase. Atâta timp cât acceptăm ajutorul geneticii în găsirea unor modalități de combatere a cancerului, diabetului sau HIV, acceptăm în mod implicit și eugenia pozitivă, conform definiției actuale. Și atâta timp cât acceptăm screening-ul genetic, și intervenții asupra fătului nenăscut, sau avortul, acceptăm în mod implicit și eugenia negativă. În plus, la nivel de guverne, deși oficial eugenia este repudiată, ea a fost legalizată în foarte multe țări până de curând, și încă mai este acceptată și legalizată, chiar dacă în forme mai subtile, și în prezent. În Introducere definesc termenul și modurile de clasificare. Urmează Istoria eugeniei pornind din perioada antică, introducerea eugeniei de Francis Galton, practica eugeniei ca politică de stat în diverse țări, și eugenia actuală (eugenia liberală). Analizez apoi diverse probleme ridicate de Etica eugeniei liberale, și am dezvoltat o secțiune aparte pentru Viitorul eugeniei, cu accent pe proiectul genomului uman. În final, în secțiunea Concluzii expun opiniile personale cu privire la practica actuală a eugeniei. Am folosit ca surse principale de investigație articolele lui Kenneth M. Ludmerer, ”American Geneticists and the Eugenics Movement: 1905-1935”, Kathy J. Cooke, ”Duty or Dream? Edwin G. Conklin's Critique of Eugenics and Support for American Individualism”, Jonathan Anomaly, ”Defending Eugenics”, John R. Harding Jr. ”Beyond Abortion: Human Genetics and the New Eugenics”, Michael Boulter, ”Bloomsbury Scientists”, Chapter Title: The rise of eugenics, 1901–14, Michael Ruse and Edward O. Wilson, ”Moral Philosophy as Applied Science” și Goering, Sara, "Eugenics"

One-parameter Darboux-transformed quantum actions in Thermodynamics

We use nonrelativistic supersymmetry, mainly Darboux transformations of the general (one-parameter) type, for the quantum oscillator thermodynamic actions. Interesting Darboux generalizations of the fundamental Planck and pure vacuum cases are discussed in some detail with relevant plots. It is shown that the one-parameter Darboux-transformed Thermodynamics refers to superpositions of boson and fermion excitations of positive and negative absolute temperature, respectively. Recent results of Arnaud, Chusseau, and Philippe physics/0105048 regarding a single mode oscillator Carnot cycle are extended in the same Darboux perspective. We also conjecture a Darboux generalization of the fluctuation-dissipation theoremComment: 14 pages, 13 figures, correction of the formula in the text after Eq. 7, accepted at Physica Script

Nanostructured LaFeO3 Photocathodes with Onset Potentials for the Hydrogen Evolution Reaction Over 1.4 V vs RHE

The photoelectrochemical properties of phase-pure LaFeO3 (LFO) nanostructured films are investigated upon modification with a thin TiO2 film and Pt nanoparticles as a catalyst. LaFeO3 with crystallite domains in the range of 60 nm are prepared by thermolysis of an ionic-liquid precursor and subsequently deposited onto FTO electrode by spin-coating. Deposition of a TiO2 layer by solution-based methods leads to the formation of a heterojunction, attenuating dark current associated with hole-transfer (water oxidation) at potential above 1.4 V. The LFO/TiO2 heterojunction features photocurrent onset potential for the hydrogen evolution reaction of 1.47 V vs the reversible hydrogen electrode (RHE), which is one of the most positive values reported for a single absorber. Deposition of Pt nanoparticles at the LFO/TiO2 heterostructure generates a significant increase in the HER photocurrent, although bulk recombination remains an important challenge in these constructs

In situ diffraction studies of phase-structural transformations in hydrogen and energy storage materials: An overview

publishedVersio

High Interfacial Hole-Transfer Efficiency at GaFeO3 Thin Film Photoanodes

The photoelectrochemical properties of polycrystalline GaFeO3 (GFO) thin films are investigated for the first time. Thin films prepared by sol–gel methods exhibit phase‐pure orthorhombic GFO with the Pc21n space group, as confirmed by X‐ray diffraction and Raman spectroscopy. Optical responses are characterized by a 2.72 eV interband transition and sub‐bandgap d–d transitions associated with octahedral and tetrahedral coordination of Fe3+ sites. DFT‐HSE06 electronic structure calculations show GFO is highly ionic with very low dispersion in the valence band maximum (VBM) and conduction band minimum (CBM). Electrochemical impedance spectroscopy reveals n‐type conductivity with a flat band potential (Ufb) of 0.52 V versus reversible hydrogen electrode, indicating that GFO has the most positive CBM reported of any ferrite. The photoelectrochemical oxidation of SO32− shows an ideal semiconductor–electrolyte interfacial behavior with no evidence of surface recombination down to the Ufb. Surprisingly, the onset potential for the oxygen evolution reaction also coincides with the Ufb, showing interfacial hole‐transfer efficiency above 50%. The photoelectrochemical properties are limited by bulk recombination due to the short‐diffusion length of minority carriers as well as slow transport of majority carriers. Strategies towards developing high‐efficiency GFO photoanodes are briefly discussed

Impact of Sb and Na Doping on the Surface Electronic Landscape of Cu2ZnSnS4 Thin Films

Open-circuit voltage deficiency is the key limiting factor in Cu2ZnSnS4 (CZTS) thin-film solar cells, which is commonly associated with band tails and deep gap states arising from elemental disorder. The introduction of dopants such as Na and Sb has led to improvement in device performance, yet their effects on the optoelectronic properties of CZTS are yet to be fully elucidated. In this Letter, we unraveled the effect of Sb and Na:Sb co-doping on the surface energy landscape of solution-processed CZTS films employing energy-filtered photoelectron emission microscopy. In the absence of the additives, 150 nm resolution photoemission maps reveal oscillations in the local effective work function as well as areas of low photoemission energy threshold. The introduction of dopants substantially reshapes the photoemission maps, which we rationalize in terms of Cu:Zn and Sn disorder. Finally, we establish unprecedented correlations between the photoemission landscape of thin films and the performance of over 200 devices

Crystal and Electronic Structure of Bismuth Thiophosphate, BiPS4:An Earth Abundant Solar Absorber

The optoelectronic properties of crystalline BiPS4 have been described for the first time for solar energy conversion. Detailed structural analysis is extracted from XRD refinement of powders synthesized by the solid-state method. BiPS4 exhibits a rather unusual 3-dimensional orthorhombic structure with two distinctive Bi sites with octahedral coordination distorted by 6s2 lone pairs. High-resolution TEM imaging clearly shows the two Bi–Bi interatomic distances in close agreement with the XRD analysis. BiPS4 displays a complex Raman spectrum under near-resonant conditions which is rationalized by density functional perturbation theory. Hybrid-functional-DFT calculations show significant spin–orbit coupling effects in Bi 6p bands, not only affecting the band dispersion but also lowering the conduction band minimum by approximately 0.5 eV. The optical properties of BiPS4 powders are dominated by a direct transition at 1.72 eV, closely matching the calculated band gap. Electrochemical experiments revealed n-type conductivity with a flat band potential located at 0.16 V vs RHE. We also show a remarkable agreement between the position of the band edges estimated from first-principles calculations and electrochemical measurements. The time-resolved photoluminescence transient revealed a carrier lifetime of approximately 1 ns, manifesting as strong potential- and wavelength-dependent photocurrent responses. Finally, the nature of the structural defects responsible for the relatively short lifetime is briefly discussed