From the Mendeleev periodic table to particle physics and back to the periodic table

We briefly describe in this paper the passage from Mendeleev's chemistry (1869) to atomic physics (in the 1900's), nuclear physics (in the 1932's) and particle physics (from 1953 to 2006). We show how the consideration of symmetries, largely used in physics since the end of the 1920's, gave rise to a new format of the periodic table in the 1970's. More specifically, this paper is concerned with the application of the group SO(4,2)xSU(2) to the periodic table of chemical elements. It is shown how the Madelung rule of the atomic shell model can be used for setting up a periodic table that can be further rationalized via the group SO(4,2)xSU(2) and some of its subgroups. Qualitative results are obtained from this nonstandard table.Comment: 15 pages; accepted for publication in Foundations of Chemistry (special issue to commemorate the one hundredth anniversary of the death of Mendeleev who died in 1907); version 2: 16 pages; some sentences added; acknowledgment and references added; misprints correcte

Detection of K-Ras mutations in tumour samples of patients with non-small cell lung cancer using PNA-mediated PCR clamping

Non-small cell lung cancers (NSCLC), in particular adenocarcinoma, are often mixed with normal cells. Therefore, low sensitivity of direct sequencing used for K-Ras mutation analysis could be inadequate in some cases. Our study focused on the possibility to increase the detection of K-Ras mutations in cases of low tumour cellularity. Besides direct sequencing, we used wild-type hybridisation probes and peptide-nucleic-acid (PNA)-mediated PCR clamping to detect mutations at codons 12 and 13, in 114 routine consecutive NSCLC frozen surgical tumours untreated by targeted drugs. The sensitivity of the analysis without or with PNA was 10 and 1% of tumour DNA, respectively. Direct sequencing revealed K-Ras mutations in 11 out of 114 tumours (10%). Using PNA-mediated PCR clamping, 10 additional cases of K-Ras mutations were detected (21 out of 114, 18%, P<0.005), among which five in samples with low tumour cellularity. In adenocarcinoma, K-Ras mutation frequency increased from 7 out of 55 (13%) by direct sequencing to 15 out of 55 (27%) by clamped-PCR (P<0.005). K-Ras mutations detected by these sensitive techniques lost its prognostic value. In conclusion, a rapid and sensitive PCR-clamping test avoiding macro or micro dissection could be proposed in routine analysis especially for NSCLC samples with low percentage of tumour cells such as bronchial biopsies or after neoadjuvant chemotherapy

Valency, ionicity and electronic configuration in rare earths

L'étude de la correspondance entre les solutions des équations de Dirac et de Schrödinger conduit à retenir pour celles de Schrödinger les valeurs positives et négatives du nombre quantique orbital, ce qui donne l'ensemble des états quantiques et leurs divisions en sous-couches, caractérisées pour les éléments des terres rares par leur division en terres cériques et terres yttriques.The study of the correspondence between the solutions of the equations of Dirac and Schrödinger leads to the necessity of retaining in the case of Schrödinger, positive and negative values for the orbital quantum number, which gives all the quantum states and their division in subshells characterised for the rare earth by their division into light and heavy rare earth

Building Process in Spinel Structure

The existence of inverse spinel is explained with a model of neutral atoms. The model supposes the existence of a trajectory for each electron keeping the most important aspect of the ionic approach. This allows to discuss the screening constant according to the coordination. The properties of each site are discussed in view of their Curie constants

MAGNETITE AS NORMAL SPINEL AND THE SEMI-CONDUCTOR METAL TRANSITION

L'interprétation des propriétés électriques de Fe3O4 est basée sur un model d'électron lié, et sur une étude statistique de la répartition de l'énergie thermique reçu par cet électron. L'expression de la résistivité est ρ = ρc A/ln[1 + exp - α (Eg/U - 1)]. A et α sont deux constantes, Eg est l'énergie de la barrière de potentiel que doit franchir l'électron pour contribuer au passage du courant, U est l'énergie thermique moyenne reçu par l'électron, et ρc la résistivité qu'aurait le corps si tous les électrons participaient au passage du courant.The electrical properties of Fe3O4 are explained considering the model of a bound electron and the statistical distribution of the thermal energy received by this electron. The resistivity is expressed by ρ = ρc A/ln[1 + exp - α (Eg/U - 1)]. A and α are two constants, Eg is the energy necessary for the electron to contribute to the current flow, U the average thermal energy received by the electron and ρc the resistivity of the compound in the case when all electrons contribute to the current flow

Un atomo di idrogeno... alternativo

Introduciamo una forma laplaciana (non standard) che determina autovalori del momento angolare quadro pari a l(l+1)+1/4, costruendo così un modello d’atomo d’idrogeno con le seguenti caratteristiche: orbitali di tipo toroidale; comparsa di un numero quantico orbitale “di punto zero” (aggiunge fluttuazioni di altezza zenitale con momento ћ/2); autofunzioni di tipo s che si annullano sul nucleo; termini spettroscopici in lz, l e l^2 “naturalmente identici” a quelli del modello standard (la totalità dei termini resta identica se si assume che l’operatore di punto zero è inefficace agli effetti delle Hamiltoniane di perturbazione); procedura di quantizzazione interpretabile come quantizzazione nel piano ad azimut costante + rotazione intorno all’asse polare. Queste proprietà rendono il modello adatto alla scomposizione in moti ad una dimensione, per i quali disponiamo di metodologia di calcolo e interpretazione secondo statistica ergodica di leggi orarie di tipo classico con massa variabile (http://aflb.ensmp.fr/AFLB-361/aflb361m726.pdf). Paragonando al modello quantico standard e al corrispondente caso quasi-classico, ci attendiamo di identificare varie differenze sulle quali investigare