Electron-phonon interaction in the solid form of the smallest fullerene C20_{20}

The electron-phonon coupling of a theoretically devised carbon phase made by assembling the smallest fullerenes C$_{20}$ is calculated from first principles. The structure consists of C$_{20}$ cages in an {\it fcc} lattice interlinked by two bridging carbon atoms in the interstitial tetrahedral sites ({\it fcc}-C$_{22}$). The crystal is insulating but can be made metallic by doping with interstitial alkali atoms. In the compound NaC$_{22}$ the calculated coupling constant $\lambda/N(0)$ is 0.28 eV, a value much larger than in C$_{60}$, as expected from the larger curvature of C$_{20}$. On the basis of the McMillan's formula, the calculated $\lambda$=1.12 and a $\mu^*$ assumed in the range 0.3-0.1 a superconducting T$_c$ in the range 15-55 K is predicted.Comment: 7 page

New insight into cataract formation -- enhanced stability through mutual attraction

Small-angle neutron scattering experiments and molecular dynamics simulations combined with an application of concepts from soft matter physics to complex protein mixtures provide new insight into the stability of eye lens protein mixtures. Exploring this colloid-protein analogy we demonstrate that weak attractions between unlike proteins help to maintain lens transparency in an extremely sensitive and non-monotonic manner. These results not only represent an important step towards a better understanding of protein condensation diseases such as cataract formation, but provide general guidelines for tuning the stability of colloid mixtures, a topic relevant for soft matter physics and industrial applications.Comment: 4 pages, 4 figures. Accepted for publication on Phys. Rev. Let

Effect of Hydrostatic Compression on the Energy of the 14.4-kev Gamma Ray from Fe^(57) in Iron

The energy of the recoil-free fraction of they rays emitted by nuclei bound in solids1 has been found to be affected by temperature and by electronic configuration. The latter effect has been named the "isomeric" shift. Compression of a solid should influence the energy through both of these mechanisms. We have measured the effect of hydrostatic compression at 295°K on the energy hν of the recoil-free 14.4-kev γ rays emitted by 0.1-μsec Fe^(57) bound in metallic iron

Suppression of inelastic bound state resonance effects by the dimensionality of atom-surface scattering event

We develop a multidimensional coupled channel method suitable for studying the interplay of bound state resonance and phonon assisted scattering of inert gas atoms from solid surfaces in one, two and three dimensions. This enables us to get insight into the features that depend on the dimensionality of inelastic resonant processes typically encountered in low energy He atom scattering from surfaces, in general, and to elaborate on the observability of recently conjectured near threshold resonances in scattering from Einstein phonons, in particular.Comment: 2 figure

Despite its role in assembly, methionine 35 is not necessary for amyloid β-protein toxicity

Author Manuscript 2011 June 1.An important component of the pathologic process underlying Alzheimer’s disease is oxidative stress. Met[superscript 35] in amyloid β-protein (Aβ) is prone to participating in redox reactions promoting oxidative stress, and therefore is believed to contribute significantly Aβ-induced toxicity. Thus, substitution of Met[superscript 35] by residues that do not participate in redox chemistry would be expected to decrease Aβ toxicity. Indeed, substitution of Met[superscript 35] by norleucine (Nle) was reported to reduce Aβ toxicity. Surprisingly, however, substitution of Met[superscript 35] by Val was reported to increase toxicity. Aβ toxicity is known to be strongly related to its self-assembly. However, neither substitution is predicted to affect Aβ assembly substantially. Thus, the effect of these substitutions on toxicity is difficult to explain. We revisited this issue and compared Aβ40 and Aβ42 with analogs containing Met[superscript 35]→Nle or Met[superscript 35]→Val substitutions using multiple biophysical and toxicity assays. We found that substitution of Met[superscript 35] by Nle or Val had moderate effects on Aβ assembly. Surprisingly, despite these effects, neither substitution changed Aβ neurotoxicity significantly in three different assays. These results suggest that the presence of Met[superscript 35] in Aβ is not important for Aβ toxicity, challenging to the prevailing paradigm, which suggests that redox reactions involving Met35 contribute substantially to Aβ-induced toxicity.Alzheimer's Association (Grant IIRG- 07-5833)National Institutes of Health (U.S.) (Grant AG027818

A globális éghajlatváltozás várható hatásai a növényvédelemben

A légköri CO2 koncentráció és az egyéb üvegházhatásért felelős gázok koncentrációjának növekedése miatt a Föld éghajlata melegszik és a klíma változik. Összeállításban a legfontosabb üvegházhatást kiváltó tényezők általános hatásait vizsgáljuk a növénypatogén mikroorganizmusokra, kártevő rovarokra és a gyomnövényekre, bemutatják a növény természetes ellenálló képességének útjait az abiotikus stressz-hatásokkal szemben. A megemelkedett CO2 koncentráció és a globális hőmérséklet-növekedés megváltoztatja a károsítók viselkedését, egyrészt, mert a megváltozott légköri CO2 tartalom miatt megváltozik fejlődési sebességük és a kiváltott tünetek ill. károk mértéke. Másrészt a megváltozott körülmények miatt megváltoznak maguk a növények is, amelyek ugyancsak változtatják a kórokozók fertőzési jellemzőit, a rovarok fejlődését is. Az előbb említett két fő tényező károsítókra gyakorolt hatása szerteágazó, egyes esetekben stimuláló, más esetekben gátló hatásokra kell számítanunk. Emiatt a hatások eredőjét nehéz tudományosan is megalapozott módon megjósolni. Mindehhez hozzá kell tenni azt is, hogy az éghajlatváltozás a mezőgazdasági régiók eltolódását is maga után vonhatja, és ez kiváltja a termesztett növények és azok károsítóinak változását is. Ennek következménye lehet az is, hogy az új területen megjelenő növénybetegségek és állati kártevők azokat a természetes növényi társulásokat is megváltoztathatják, amelyek azelőtt nem voltak kitéve a kultúrnövényeket károsító – számos esetben sokkal agresszívebb – fajoknak vagy változatoknak

Sequence analysis of 16S rRNA, gyrB and catA genes and DNA-DNA hybridization reveal that Rhodococcus jialingiae is a later synonym of Rhodococcus qingshengii

The results of 16S rRNA, gyrB and catA gene sequence comparisons and reasserted DNA–DNA hybridization unambiguously proved that Rhodococcus jialingiae Wang et al. 2010 and Rhodococcus qingshengii Xu et al. 2007 represent a single species. On the basis of priority R. jialingiae must be considered a later synonym of R. qingshengii .</jats:p

Comparison of Bond Character in Hydrocarbons and Fullerenes

We present a comparison of the bond polarizabilities for carbon-carbon bonds in hydrocarbons and fullerenes, using two different models for the fullerene Raman spectrum and the results of Raman measurements on ethane and ethylene. We find that the polarizabilities for single bonds in fullerenes and hydrocarbons compare well, while the double bonds in fullerenes have greater polarizability than in ethylene.Comment: 7 pages, no figures, uses RevTeX. (To appear in Phys. Rev. B.

The scaling limit of the critical one-dimensional random Schrodinger operator

We consider two models of one-dimensional discrete random Schrodinger operators (H_n \psi)_l ={\psi}_{l-1}+{\psi}_{l +1}+v_l {\psi}_l, {\psi}_0={\psi}_{n+1}=0 in the cases v_k=\sigma {\omega}_k/\sqrt{n} and v_k=\sigma {\omega}_k/ \sqrt{k}. Here {\omega}_k are independent random variables with mean 0 and variance 1. We show that the eigenvectors are delocalized and the transfer matrix evolution has a scaling limit given by a stochastic differential equation. In both cases, eigenvalues near a fixed bulk energy E have a point process limit. We give bounds on the eigenvalue repulsion, large gap probability, identify the limiting intensity and provide a central limit theorem. In the second model, the limiting processes are the same as the point processes obtained as the bulk scaling limits of the beta-ensembles of random matrix theory. In the first model, the eigenvalue repulsion is much stronger.Comment: 36 pages, 2 figure