We investigated dibenzo [a,h]thianthrene molecules adsorbed on ultrathin layers of NaCl using a combined low-temperature scanning tunneling and atomic force microscope. Two stable configurations exist corresponding to different isomers of free nonplanar molecules. By means of excitations from inelastic electron tunneling we can switch between both configurations. Atomic force microscopy with submolecular resolution allows unambiguous determination of the molecular geometry, and the pathway of the interconversion of the isomers. Our investigations also shed new light on contrast mechanisms in scanning tunneling microscopy. DOI: 10.1103/PhysRevLett.108.086101 PACS numbers: 68.43.Fg, 68.37.Ef, 68.37.Ps, 82.37.Gk Recently, the chemical structure of a pentacene molecule has been visualized by means of noncontact atomic force microscopy (AFM) [1]. Shortly after, this method assisted in identifying the structure of an organic molecule [2]. In conjunction with the capability of scanning tunneling microscopy (STM) to perform orbital imaging on ultrathin insulating films [3], it is possible to gain independent and complementary information of the molecular as well as of the adsorption geometry, but also of the electronic structure of individual molecules.Unambiguous identification of configurational changes of adsorbed molecules is a challenging task by means of STM alone [4], probing the local density of states rather than geometry. Usually, additional techniques such as nearedge x-ray adsorption fine structure measurements have to be employed [5,6].In this Letter, we present combined STM and AFM experiments of dibenzo[a,h]thianthrene (DBTH) molecules adsorbed on ultrathin layers of sodium chloride. We demonstrate controlled switching between two different molecular configurations by means of inelastic excitations. AFM images with submolecular resolution directly reveal the configurational changes. Stereochemistry could be utilized to determine their interconversion pathway in detail.All AFM measurements were carried out in a homebuilt combined STM and AFM operating in an ultrahigh vacuum (p < 10 À10 mbar) at T ¼ 5 K. The AFM, based on the qPlus tuning fork design (spring constant k 0 % 1:8 Â 10 3 N m À1 , resonance frequency f 0 ¼ 26 057 Hz, quality factor Q % 10 4 ) [7], was operated in the frequency modulation mode [8]. Sub-Å ngstrom oscillation amplitudes have been used to maximize the lateral resolution [9]. Some of the STM measurements ( Figs. 1 and 2) were performed in a similar modified commercial STM from SPS-CreaTec. The bias voltage V was applied to the sample.Sodium chloride was evaporated onto clean Cu(111) single crystals at sample temperatures of about 280 K [10]. All experiments were carried out on a double layer, and we denote this substrate system as NaClð2MLÞ= Cuð111Þ. The DBTH molecules were synthesized as described previously [11].Low coverages of CO (for tip functionalization) and DBTH molecules were adsorbed at sample temperatures below 10 K. Following a recently developed technique, the tip ha...

In this study the GSTmu phenotype and ADH genotype at the ADH3 locus were investigated in a group of 39 alcoholic men with upper respiratory/digestive tract cancer: 21 with oropharyngeal cancer and 18 with laryngeal cancer. The results are compared with those of a control group of 37 alcoholic men without alcohol-related medical complications. Of the control subjects, 48% were found to be GSTmu deficient [GSTmu(-)] and 19% carried the ADH(3)1/ADH(3)1 genotype. In the laryngeal cancer patients, a significantly elevated frequency of both the GSTmu(-) (78%) and ADH(3)1/ADH(3)1 genotype (56%) was observed, relative to the control group. On the basis of this result, the risk of laryngeal cancer associated with the GSTmu(-) and ADH(3)1/ADH(3)1 genotypic combination within the population of alcoholics was estimated to be 12.9 with a 95% confidence interval of 1.8-92 (P < 0.01) relative to alcoholic individuals who have GSTmu [GSTmu(+)] and are not ADH(3)1/ADH(3)1. Thus, alcoholics who are GSTmu(-) and ADH(3)1/ADH(3)1 have at least an 80% greater risk of developing laryngeal cancer than alcoholics who are GSTmu(+) and who are not ADH(3)1/ADH(3)1. In addition, the oropharyngeal cancer patients had excess frequencies of both GSTmu(-) (62%) and ADH(3)1/ADH(3)1 (43%) relative to the control group, but these excess frequencies were not statistically significant. The GSTmu(-) and ADH(3)1/ADH(3)1 genotypic combination may be a constitutional risk factor for laryngeal cancer among alcoholics.

Octahedral molecular sieves (OMS) are built of transition metal-oxygen octahedra that delimit sub-nanoscale cavities. Compared to other microporous solids, OMS exhibit larger versatility in properties, provided by various redox states and magnetic behaviors of transition metals. Hence, OMS offer opportunities in electrochemical energy harnessing devices, including batteries, electrochemical capacitors and electrochromic systems, provided two conditions are met: fast exchange of ions in the micropores and stability upon exchange. Here we unveil a novel OMS hexagonal polymorph of tungsten oxide called h’-WO3, built of (WO6)6 tunnel cavities. h’-WO3 is prepared by a one-step soft chemistry aqueous route leading to the hydrogen bronze h’-H0.07WO3. Gentle heating results in h’-WO3 with framework retention. The material exhibits an unusual combination of 1-dimensional crystal structure and 2-dimensional nanostructure that enhances and fastens proton (de)insertion for stable electrochromic devices. This discovery paves the way to a new family of mixed valence functional materials with tunable behaviors.

The functionalisation of a Si(100) silicon wafer allows for the oriented grafting of a monolayer of Mn12 nanomagnets using a two-step procedure.

Superparamagnetic nanoparticles are promising objects for data storage or medical applications. In the smallest—and more attractive—systems, the properties are governed by the magnetic anisotropy. Here we report a molecule-based synthetic strategy to enhance this anisotropy in sub-10-nm nanoparticles. It consists of the fabrication of composite materials where anisotropic molecular complexes are coordinated to the surface of the nanoparticles. Reacting 5 nm γ-Fe2O3 nanoparticles with the [CoII(TPMA)Cl2] complex (TPMA: tris(2-pyridylmethyl)amine) leads to the desired composite materials and the characterization of the functionalized nanoparticles evidences the successful coordination—without nanoparticle aggregation and without complex dissociation—of the molecular complexes to the nanoparticles surface. Magnetic measurements indicate the significant enhancement of the anisotropy in the final objects. Indeed, the functionalized nanoparticles show a threefold increase of the blocking temperature and a coercive field increased by one order of magnitude.

Two 2,6-bispyrazolylpyridine ligands (bpp) were functionalized with pyrene moieties through linkers of different lengths. In the ligand 2,6-di(1H-pyrazol-1-yl)-4-(pyren-1-yl)pyridine (L1) the pyrene group is directly connected to the bpp moiety via a C-C single bond, while in the ligand 4-(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)benzyl-4-(pyren-1-yl)butanoate (L2) it is separated by a benzyl ester group involving a flexible butanoic chain. Subsequent complexation of Fe(II) salts revealed dramatic the influence of the nature of the pyrene substitution on the spin-transition behaviour of the resulting complexes. Thus, compound [Fe(L1)(2)](ClO(4))(2) (1) is blocked in its high spin state due to constraints caused by a strong intermolecular π-π stacking in its structure. On the other hand, the flexible chain of ligand L2 in compounds [Fe(L2)(2)](ClO(4))(2) (2) and [Fe(L2)(2)](BF(4))(2)·CH(3)CN·H(2)O (3) prevents structural constraints allowing for reversible spin transitions. Temperature-dependent studies of the photophysical properties of compound 3 do not reveal any obvious correlation between the fluorescence of the pyrene group and the spin state of the spin transition core.

A weak version of a conjecture stated by Kannan, Lovász and Simonovits claims that an isotropic logconcave probability μ on R n should be concentrated in a thin Euclidean shell in the following way:where κ = 1/2 and c and C are positive absolute constants. For κ = 1/10.02, this inequality has been established by Klartag. By combining different approaches introduced by Klartag and by Guédon, Paouris and the author, we improve this result by showing that the inequality (1) holds with κ = 1/8.

Two types of factors can theoretically modulate alcohol metabolism toward increased acetaldehyde production. These factors are the following: (a) individual, genetically determined isoenzymes with distinct catalytic properties, and (b) modifications of enzyme activity induced by alcohol itself or liver damage. To investigate the respective roles of these factors in white individuals, we studied the alcohol dehydrogenase phenotype, together with liver alcohol dehydrogenase and aldehyde dehydrogenase activities, in 161 patients. Patients with alcoholic cirrhosis (n = 31) were compared with three types of controls: patients with nonalcoholic cirrhosis (n = 25) and excessive (n = 62) and moderate drinkers (n = 43) without liver disease. No association between alcohol dehydrogenase-3 phenotype and alcoholic cirrhosis was found. The prevalence of atypical alcohol dehydrogenase in the four groups was less than 1%. Patients with cirrhosis, regardless of its cause, had significantly lower alcohol dehydrogenase activity than the patients without cirrhosis (p less than 0.05 and p less than 0.01 vs. excessive and moderate drinkers, respectively). Among the noncirrhotic patients, alcohol dehydrogenase activity was significantly lower in the excessive drinkers than in the moderate drinkers (p less than 0.001). Aldehyde dehydrogenase activity was not different between cirrhosis-free excessive and moderate drinkers; in contrast, compared with these two groups, it was significantly lower in the two cirrhosis groups (p less than 0.01). These results suggest that no phenotypic pattern of alcohol dehydrogenase-3 associated with alcoholic cirrhosis in white patients exists, that liver alcohol dehydrogenase activity falls as a consequence of both alcohol abuse and cirrhosis and that liver aldehyde dehydrogenase activity is unaffected by alcohol abuse and only falls after the onset of cirrhosis.