Condensation energy in strongly coupled superconductors

We consider the condensation energy in superconductors where the pairing is electronic in origin and is mediated by a collective bosonic mode. We use magnetically-mediated superconductivity as an example, and show that for large spin-fermion couplings, the physics is qualitatively different from the BCS theory as the condensation energy results from the feedback on spin excitations, while the electronic contribution to the condensation energy is positive due to an ``undressing'' feedback on the fermions. The same feedback effect accounts for the gain of the kinetic energy at strong couplings.Comment: 4 pages, revtex 4, 3 eps figure

A promising material for non-linear optics: Observation of second harmonic generation from 4-[N-(4-carboxypentyl)-N-methylamino]-4′-nitrostilbene- coated substrates

Glass coated with a nitro amino stilbene carboxylic acid using the Langmuir-Blodgett technique gave a non-centrosymmetric material exhibiting second harmonic generation, 1.06 to 0.53 μm

The electronic specific heat in the pairing pseudogap regime

When pairing correlations in a quasi two dimensional electron system induce a pseudogap in the single particle density of states, the specific heat must also contain a sizeable pair contribution. The theoretically calculated specific heat for such a system is compared to the experimental results of Loram and his collaborators for underdoped YBa_2Cu_3O_{6+x} and La_{2-x}Sr_{x}CuO_4 samples. The size and doping dependence of the extracted pseudogap energy scale for both materials is comparable to the values obtained from a variety of other experiments.Comment: 4 pages, 5 eps figure

The effect of body stores and of method of supplementation on the efficiency of calcium and phosphorus utilization by sheep

(1) The Ca and P metabolism of two groups of young sheep, depleted of these minerals, was investigated in a series of three balance studies. (2) During the first 10 days on the bone meal supplemented ration, the inorganic P of the blood rose sharply from approximately 2•0 to 5•0 mgm. per 100 c.c. of blood, a level which was more or less maintained to the end of the experiment. (3) Under the conditions obtaining the method of bone meal supplementation had no influence on the efficiency of utilization of Ca and P. The implication of this for the problem of phosphate feeding under practical conditions is briefly discussed. (4) Ca and P utilization dropped considerably in the course of the 80 days on the enriched ration. Retention figures for Ca decreased from 22•5 to 12•7 per cent. and those for P from 53•1 to 32•2 per cent. (5) Due to the fact that no observations are available on the extent of replenishment during the period of bone meal feeding the final interpretations of these results must await the outcome of further investigations.The articles have been scanned in colour with a HP Scanjet 5590; 300dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Photoelectron diffraction: from phenomenological demonstration to practical tool

The potential of photoelectron diffraction—exploiting the coherent interference of directly-emitted and elastically scattered components of the photoelectron wavefield emitted from a core level of a surface atom to obtain structural information—was first appreciated in the 1970s. The first demonstrations of the effect were published towards the end of that decade, but the method has now entered the mainstream armoury of surface structure determination. This short review has two objectives: First, to outline the way that the idea emerged and the way this evolved in my own collaboration with Neville Smith and his colleagues at Bell Labs in the early years: Second, to provide some insight into the current state-of-the art in application of (scanned-energy mode) photoelectron diffraction to address two key issue in quantitative surface structure determination, namely, complexity and precision. In this regard a particularly powerful aspect of photoelectron diffraction is its elemental and chemical-state specificity

Anastomosis groups and pathogenicity of Rhizoctonia solani and binucleate Rhizoctonia from potatoes in South Africa

A survey of anastomosis groups (AGs) of Rhizoctonia species associated with potato diseases was conducted in South Africa. A total of 112 Rhizoctonia solani and 19 binucleate Rhizoctonia (BNR) isolates were recovered from diseased potato plants, characterized for AG and pathogenicity. The AG identity of the isolates was confirmed using phylogenetic analysis of the internal transcribed spacer region of ribosomal DNA. Rhizoctonia solani isolates recovered belonged to AG 3-PT, AG 2- 2IIIB, AG 4HG-I, AG 4HG-III and AG 5, while BNR isolates belonged to AG A and AG R, with frequencies of 74, 6.1, 2.3, 2.3, 0.8, 12.2 and 2.3%, respectively. Rhizoctonia solani AG 3-PT was the most predominant AG and occurred in all the potato growing regions sampled whereas the other AGs occurred in distinct locations. Different AGs grouped into distinct clades with high maximum parsimony and maximum likelihood bootstrap support for both R. solani and BNR. An experiment under greenhouse conditions with representative isolates from different AGs showed differences in aggressiveness between and within AGs. Isolates of AG 2-2IIIB, AG 4HG-III and AG R were the most aggressive in causing stem canker while AG 3-PT, AG 5 and AG R caused black scurf. This is the first comprehensive survey of R. solani and BNR on potatoes in South Africa using a molecularbased approach. This is the first report of R. solani AG 2-2IIIB and AG 4 HG-I causing stem and stolon canker and BNR AG A and AG R causing stem canker and black scurf on potatoes in South Africa.Potatoes South Africa.National Research Foundation of South Africa (UID: 78566 (NRF RISP grant for the ABI3500)).http://apsjournals.apsnet.org/loi/pdishb201

Population genetic structure of Rhizoctonia solani AG 3-PT from potatoes in South Africa

Rhizoctonia solani AG 3-PT is an important potato pathogen causing significant yield and quality losses in potato production globally. However, little is known about the levels of genetic diversity and population structure of this pathogen in South Africa. A total of 114 R. solani AG 3-PT isolates collected from four geographic regions were analyzed for genetic diversity and structure using eight microsatellite loci. Microsatellite analysis found high intrapopulation genetic diversity, population differentiation and evidence of recombination. A total of 78 multilocus genotypes (MLGs) were identified with few MLGs shared among populations. Low levels of clonality (13-39 %) and high levels of population differentiation were observed among populations. Most of the loci were in Hardy-Weinberg equilibrium and all four field populations showed evidence of a mixed reproductive mode of both clonality and recombination. The PCoA clustering method revealed genetically distinct geographic populations of R. solani AG 3-PT in South Africa. This study showed that populations of R. solani AG 3-PT in South Africa are genetically differentiated and disease management strategies should therefore be applied accordingly. This is the first study of the population genetics of R. solani AG 3-PT in potatoes in South Africa and results may help to develop knowledge-based disease management strategies in South Africa and elsewhere.Potatoes South Africa and the Potato Pathology Programme at UP as well as the National Research Foundation.http://www.elsevier.com/locate/funbio2017-05-31hb2016Plant Scienc

Variation in fungicide sensitivity among Rhizoctonia isolates recovered from potatoes in South Africa

Please read abstract in the article.Potatoes South Africahttp://apsjournals.apsnet.org/loi/pdishj2018Plant Production and Soil Scienc

Elephant hide and growth cracking on potato tubers caused by Rhizoctonia solani AG3-PT in South Africa

No Abstracthttp://apsjournals.apsnet.org/loi/pdishb201