An equation of state for expanded metals

We present a model equation of states for expanded metals, which contains a pressure term due to a screened-Coulomb potential with a screening parameter reflecting the Mott-Anderson metal-to-nonmetal transition. As anticipated almost 80 years ago by Zel'dovich and Landau, this term gives rise to a second coexistence line in the phase diagram, indicating a phase separation between a metallic and a nonmetallic liquid.

Metals and non-metals in the periodic table

The demarcation of the chemical elements into metals and non-metals dates back to the dawn of Dmitri Mendeleev's construction of the periodic table; it still represents the cornerstone of our view of modern chemistry. In this contribution, a particular emphasis will be attached to the question 'Why do the chemical elements of the periodic table exist either as metals or non-metals under ambient conditions?' This is perhaps most apparent in the p-block of the periodic table where one sees an almost-diagonal line separating metals and non-metals. The first searching, quantum-mechanical considerations of this question were put forward by Hund in 1934. Interestingly, the very first discussion of the problem-in fact, a pre-quantum-mechanical approach-was made earlier, by Goldhammer in 1913 and Herzfeld in 1927. Their simple rationalization, in terms of atomic properties which confer metallic or non-metallic status to elements across the periodic table, leads to what is commonly called the Goldhammer-Herzfeld criterion for metallization. For a variety of undoubtedly complex reasons, the Goldhammer-Herzfeld theory lay dormant for close to half a century. However, since that time the criterion has been repeatedly applied, with great success, to many systems and materials exhibiting non-metal to metal transitions in order to predict, and understand, the precise conditions for metallization. Here, we review the application of Goldhammer-Herzfeld theory to the question of the metallic versus non-metallic status of chemical elements within the periodic system. A link between that theory and the work of Sir Nevill Mott on the metal-non-metal transition is also highlighted. The application of the 'simple', but highly effective Goldhammer-Herzfeld and Mott criteria, reveal when a chemical element of the periodic table will behave as a metal, and when it will behave as a non-metal. The success of these different, but converging approaches, lends weight to the idea of a simple, universal criterion for rationalizing the instantly-recognizable structure of the periodic table where …the metals are here, the non-metals are there … The challenge of the metallic and non-metallic states of oxides is also briefly introduced. This article is part of the theme issue 'Mendeleev and the periodic table'.

On the occurrence of metallic character in the periodic table of the chemical elements

The classification of a chemical element as either 'metal' or 'non-metal' continues to form the basis of an instantly recognizable, universal representation of the periodic table (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23; Poliakoff M. & Tang S. 2015 Phil. Trans. R. Soc. A 373: , 20140211). Here, we review major, pre-quantum-mechanical innovations (Goldhammer DA. 1913 Dispersion und Absorption des Lichtes; Herzfeld KF. 1927 Phys. Rev. 29: , 701-705) that allow an understanding of the metallic or non-metallic status of the chemical elements under both ambient and extreme conditions. A special emphasis will be placed on recent experimental advances that investigate how the electronic properties of chemical elements vary with temperature and density, and how this invariably relates to a changing status of the chemical elements. Thus, the prototypical non-metals, hydrogen and helium, becomes metallic at high densities; and the acknowledged metals, mercury, rubidium and caesium, transform into their non-metallic forms at low elemental densities. This reflects the fundamental fact that, at temperatures above the absolute zero of temperature, there is therefore no clear dividing line between metals and non-metals. Our conventional demarcation of chemical elements as metals or non-metals within the periodic table is of course governed by our experience of the nature of the elements under ambient conditions. Examination of these other situations helps us to examine the exact divisions of the chemical elements into metals and non-metals (Mendeleeff D. 1905 The principles of chemistry, vol. II, p. 23).

Polarizabilities of Isolated Silicon Clusters

The static electric polarizabilities a of silicon clusters with up to 60 atoms have been measured employing a mass selective molecular beam deflection method. The polarizability per atom αN = α/N of the SiN-clusters has been investigated for Si11 and the size ranges N = 14-28, 22-34, 28-44, 34-50, 41 -58, and 42-68. The results show that the polarizability per atom decreases from N = 11 until a minimum at N≥28 is reached. The polarizability per atom increases for N > 28, passes through a maximum at N≈36 and finally converges between N≈50-70 against the value αN =1.9Å3. If the model of a homogeneous dielectric sphere is applied to the larger clusters one calculates that the value αN =1.9Å3 corresponds to a dielectric constant of ε = 3.2. This value is significantly smaller than the dielectric constant of bulk silicon εb = 11.8.

The present paper focuses on the maximum in the polarizability at N≈36. This effect is discussed with special emphasis to recent Car-Parinello calculations which have predicted cage-like silicon structures that enclose a core of several highly coordinated atoms. This structure suggests an improved dielectric sphere model where the core is represented by a smaller sphere with its own dielectric constant εc. It is shown within this model that the observed maximum in polarizability is due to a significant enhancement of the core dielectric constant to a value of εc ≈50. This enhancement is related by means of a simple model to the effect that silicon becomes metallic under high pressure

Die elektrische Leitfähigkeit wäßriger Salzlösungen bis zu 130° C und 8000 bar

Die Äquivalentleitfähigkeiten Λ von LiCl, KCl, CsCl, CsJ, K2SO4 und [(C2H5)4N] J in wäßriger Lösung wurden bei 45 °C, 75 °C, 100°C und 130°C in Abhängigkeit vom Druck zwischen 1 und 8000 bar bestimmt. Dazu wurde eine geeignete Hochdruck-Leitfähigkeitsmeßzelle konstruiert.

Sämtliche Λ-Werte, mit Ausnahme derjenigen des LiCl bei 45°C, fallen monoton mit steigendem Druck. Die Druckabhängigkeit ist am stärksten bei den Elektrolyten mit großen Ionen und nimmt mit geringer werdender Ionengröße ab. Bei 8 kbar ist sie für CsJ und [(C2H5)4N] J auf 60 bis 70% des jeweiligen Wertes bei Normaldruck gefallen. Beim LiCl führt der Abfall nur bis auf 80 bis 90% des Normalwertes. Der Vergleich mit der Druckabhängigkeit der Wasserviskosität η zeigt, daß die WALDEN-Regel Λη = const nicht bestätigt ist. Die Aktivierungsenergien der Leitfähigkeit bei konstantem Volumen liegen zwischen 1,6 und 2,2 kcal/mol und sinken mit steigender Kompression. Für das Aktivierungsvolumen ergeben sich Werte um 1,2 cm3/mol.

Electronic and Geometrical Structure of Se5, Se6, Se7, and Se8

The vacuum-UV-photoelectron spectra of Se2, Se5, Se6, Se7, and Se8 have been recorded at a photon energy of h ν= 10.0 eV. The isolated molecules are examined in a supersonic molecular beam employing a new photoelectron-photoion coincidence technique. The structure of the photoelectron spectra of selenium molecules with even and odd numbers of atoms differs in a characteristic manner. While the spectra of Se6 and Se8 show one single broad band, three separated bands with different intensities are observed for Se5 and two for Se7. The spectra are compared to molecular orbital energy calculations based on theoretically supposed geometries. The comparison indicates that Se6 and Se8 have Dnd-symmetrical ring structures, whereas Se5 and Se7 are C1h-symmetrical rings

'... a metal conducts and a non-metal doesn't'

In a letter to one of the authors, Sir Nevill Mott, then in his tenth decade, highlighted the fact that the statement '... a metal conducts, and a non-metal doesn't' can be true only at the absolute zero of temperature, T=0 K. But, of course, experimental studies of metals, non-metals and, indeed, the electronic and thermodynamic transition between these canonical states of matter must always occur above T=0 K, and, in many important cases, for temperatures far above the absolute zero. Here, we review the issues-theoretical and experimental-attendant on studies of the metal to non-metal transition in doped semiconductors at temperatures close to absolute zero (T=0.03 K) and fluid chemical elements at temperatures far above absolute zero (T>1000 K). We attempt to illustrate Mott's insights for delving into such complex phenomena and experimental systems, finding intuitively the dominant features of the science, and developing a coherent picture of the different competing electronic processes. A particular emphasis is placed on the idea of a 'Mott metal to non-metal transition' in the nominally metallic chemical elements rubidium, caesium and mercury, and the converse metallization transition in the nominally non-metal elements hydrogen and oxygen. We also review major innovations by D. A. Goldhammer (Goldhammer 1913 Dispersion und absorption des lichtes) and K. F. Herzfeld (Herzfeld 1927 Phys. Rev. 29, 701-705. (doi:10.1103/PhysRev.29.701)) in a pre-quantum theory description of the metal-non-metal transition, which emphasize the pivotal role of atomic properties in dictating the metallic or non-metallic status of the chemical elements of the periodic table under ambient and extreme conditions; a link with Pauling's 'metallic orbital' is also established here.

Critical region and metal–nonmetal transition in expanded fluid mercury: advanced evaluation of small-angle X-ray scattering data

The small-angle X-ray scattering data of expanded fluid mercury published in the literature were evaluated using a modified form of the Teubner–Strey equation for microemulsions together with the general treatment of two-phase systems according to Porod. The parameters obtained in the critical region and the metal–nonmetal (M–NM) transition are evidence of a nanoemulsion composed of M and NM domains. The structure of this emulsion is characterized by density, volume fraction and size parameters (average chord length, polydispersity) of the domains. On the basis of these parameters, a structural model for fluid mercury in the liquid–vapour critical region and the M–NM transition is developed. Analysis of the relationship between the volume fraction of the M domains and the electrical conductivity reveals that a percolation transition occurs, with a threshold located near the liquid–vapour critical density. This observation is consistent with recent theoretical developments.

A new variant of the heat shock protein GRP78 as target for antibody- treatment of pancreatic cancer

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Background: Pancreatic malignancies belong to the top-five killers among all cancers worldwide. The 5-year survival rate with conventional therapy is below 5%. This shows that there is a big need for new therapeutical approaches. The fully human monoclonal antibody SAM-6 is a germ-line coded IgM, isolated from a cancer patient by TRIOMA technology. SAM-6 antibody binds to a modified O-linked carbohydrate moiety expressed on a membrane-bound variant of GRP78, which is a member of the HSP70 family. Heat-shock proteins (HSPs) are critical components of a cell's defense mechanism against injury associated with adverse stresses. They can protect cells against subsequent, otherwise lethal, outcome. Although HSPs are very beneficial to the normal cell, cancer cells often over-express HSPs on the membrane. They use them in response to stresses associated with various therapies, diminishing the treatment effects. Methods: In vitro and in vivo assays were used to investigate the apoptotic effects of antibody SAM-6 on pancreas cancer cells. Results: Binding of SAM-6 antibody to GRP78 induces an overfeeding of malignant cells with oxidized LDL. The cancer cells over-accumulate depots of cholesterol and triglyceride esters and finally undergo apoptosis. The deadly effect of SAM-6 could be demonstrated in vitro and in vivo in experimental animal models. Conclusions: These data show that cancer-specific modifications of cell surface protection molecules are ideal targets for immuno-therapeutical approaches.

No significant financial relationships to disclose.

Deactivation of regulatory proteins hnRNP A1 and A2 during SC-1 induced apoptosis

Phosphorylation and activation of caspases play an important role in the induction of apoptosis. During tumor specific apoptosis, induced by the human monoclonal antibody SC-1, tyrosine phosphorylation and serine dephosphorylation of several proteins is observed. In this paper we describe the identification of two dephosphorylated proteins as heterogeneous nuclear ribonucleoproteins A1 and A2 (hnRNP A1, hnRNP A2). The dephosphorylation of these proteins is important for apoptosis since the amount of apoptotic cell death can be decreased by the specific serine/threonine phosphatase inhibitor okadaic acid. We also investigated the effect of serine kinase inhibitor H7 on SC-1 induced apoptosis, which leads to a dose dependent increase in apoptosis. We could also show that 24 hours after the induction of apoptosis the hnRNP A1 protein is cleaved into different cleavage products. Further, we found a decreased expression of caspase-2 in early apoptosis signalling and an overexpression 24 hours after induction of apoptosis. Our results show that the phosphorylation status of the hnRNP A1 and A2 plays a significant role in early SC-1 induced apoptosis signalling and further indicate the role of caspase activation during the apoptotic process.

Regulation of the new coexpressed CD55 (decay-accelerating factor) receptor on stomach carcinoma cells involved in antibody SC-1-induced apoptosis

The human monoclonal antibody SC-1 was isolated from a patient with a diffuse-type adenocarcinoma of the stomach using somatic cell hybridization. The immunoglobulin (Ig)M antibody reacts specifically with diffuse- (70%) and intestinal-type (25%) gastric adenocarcinoma and induces apoptosis in vitro and in vivo. When used in clinical trials with stomach carcinoma patients, significant apoptotic and regressive effects in primary tumors have been observed with the antibody SC-1. The SC-1 receptor is a new 82 kd membrane-bound isoform of glycosylphosphatidylinositol (GPI)-linked CD55 (decay-accelerating factor, DAF). CD55 is known to protect cells from lysis through autologous complement and is coexpressed with the ubiquitously distributed 70 kd isoform. The SC-1-specific CD55 isoform is up-regulated shortly after antibody binding, followed by an internalization of the antibody/receptor-complex, whereas the membranous expression of wild-type CD55 remains unchanged. The apoptotic process is marked by cleavage of cytokeratin 18, indicating the involvement of caspase-6 in the apoptotic process. In contrast to other apoptotic pathways, a cleavage of poly(ADP-ribose)polymerase (PARP) is not observed. The expression of the cell-cycle regulator c-myc becomes up-regulated, whereas expression of topoisomerase IIalpha is down-regulated. Induction of apoptosis leads to an increase in the internal Ca(2+) concentration, which is not necessary for the apoptotic process but for the transport of newly synthesized SC-1-specific CD55 isoform to the membrane.