2D Ionic Liquid-Like State of Charged Rare-Earth Clusters on a Metal Surface.

Rare-earth complexes are vital for separation chemistry and useful in many advanced applications including emission and energy upconversion. Here, 2D rare-earth clusters having net charges are formed on a metal surface, enabling investigations of their structural and electronic properties on a one-cluster-at-a-time basis using scanning tunneling microscopy. While these ionic complexes are highly mobile on the surface at ≈100 K, their mobility is greatly reduced at 5 K and reveals stable and self-limiting clusters.

X-ray Spectroscopy of a Rare-Earth Molecular System Measured at the Single Atom Limit at Room Temperature.

We investigate the limit of X-ray detection at room temperature on rare-earth molecular films using lanthanum and a pyridine-based dicarboxamide organic linker as a model system. Synchrotron X-ray scanning tunneling microscopy is used to probe the molecules with different coverages on a HOPG substrate. X-ray-induced photocurrent intensities are measured as a function of molecular coverage on the sample, allowing a correlation of the amount of La ions with the photocurrent signal strength.

Light- and Chemical-Doping-Induced Magnetic Behavior of Eu Molecular Systems.

Variable temperature electron paramagnetic resonance (VT-EPR) was used to investigate the role of the environment and oxidation states of several coordinated Eu compounds. We find that while Eu(III) chelating complexes are diamagnetic, simple chemical reduction results in the formation of paramagnetic species. In agreement with the distorted symmetry of Eu molecular complexes investigated in this study, the EPR spectrum of reduced complexes showed axially symmetric signals ( = 2.

Artificial Graphene Nanoribbons: A Test Bed for Topology and Low-Dimensional Dirac Physics.

We synthesize artificial graphene nanoribbons by positioning carbon monoxide molecules on a copper surface to confine its surface state electrons into artificial atoms positioned to emulate the low-energy electronic structure of graphene derivatives. We demonstrate that the dimensionality of artificial graphene can be reduced to one dimension with proper "edge" passivation, with the emergence of an effectively gapped one-dimensional nanoribbon structure. These one-dimensional structures show evidence of topological effects analogous to graphene nanoribbons.

One-Dimensional Lateral Force Anisotropy at the Atomic Scale in Sliding Single Molecules on a Surface.

Using a q+ atomic force microscopy at low temperature, a sexiphenyl molecule is slid across an atomically flat Ag(111) surface along the direction parallel to its molecular axis and sideways to the axis. Despite identical contact area and underlying surface geometry, the lateral force required to move the molecule in the direction parallel to its molecular axis is found to be about half of that required to move it sideways. The origin of the lateral force anisotropy observed here is traced to the one-dimensional shape of the molecule, which is further confirmed by molecular dynamics simulations.

Self-Assembly of Metallo-Supramolecules with Dissymmetrical Ligands and Characterization by Scanning Tunneling Microscopy.

Asymmetrical and dissymmetrical structures are widespread and play a critical role in nature and life systems. In the field of metallo-supramolecular assemblies, it is still in its infancy for constructing artificial architectures using dissymmetrical building blocks. Herein, we report the self-assembly of supramolecular systems based on two dissymmetrical double-layered ligands.

Proximity-Induced Superconductivity in Monolayer MoS.

Proximity effects in superconducting normal (SN) material heterostructures with metals and semiconductors have long been observed and theoretically described in terms of Cooper pair wave functions and Andreev reflections. Whereas the semiconducting -layer materials in the proximity experiments to date have been doped and tens of nanometers thick, we present here a proximity tunneling study involving a pristine single-layer transition-metal dichalcogenide film of MoS placed on top of a Pb thin film. Scanning tunneling microscopy and spectroscopy experiments together with parallel theoretical analysis based on electronic structure calculations and Green's function modeling allow us to unveil a two-step process in which MoS first becomes metallic and then is induced into becoming a conventional s-wave Bardeen-Cooper-Schrieffer-type superconductor.

The Effects of Atomic-Scale Strain Relaxation on the Electronic Properties of Monolayer MoS.

The ability to control nanoscale electronic properties by introducing macroscopic strain is of critical importance for the implementation of two-dimensional (2D) materials into flexible electronics and next-generation strain engineering devices. In this work, we correlate the atomic-scale lattice deformation with a systematic macroscopic bending of monolayer molybdenum disulfide films by using scanning tunneling microscopy and spectroscopy implemented with a custom-built sample holder to control the strain. Using this technique, we are able to induce strains of up to 3% before slipping effects take place and relaxation mechanisms prevail.

Evolution of Metastable Defects and Its Effect on the Electronic Properties of MoS Films.

We report on structural and electronic properties of defects in chemical vapor-deposited monolayer and few-layer MoS films. Scanning tunneling microscopy, Kelvin probe force microscopy, and transmission electron microscopy were used to obtain high resolution images and quantitative measurements of the local density of states, work function and nature of defects in MoS films. We track the evolution of defects that are formed under heating and electron beam irradiation.

Inter-Layer Coupling Induced Valence Band Edge Shift in Mono- to Few-Layer MoS.

Recent progress in the synthesis of monolayer MoS, a two-dimensional direct band-gap semiconductor, is paving new pathways toward atomically thin electronics. Despite the large amount of literature, fundamental gaps remain in understanding electronic properties at the nanoscale. Here, we report a study of highly crystalline islands of MoS grown via a refined chemical vapor deposition synthesis technique.

Development of sample handling procedures for foods under USDA's National Food and Nutrient Analysis Program.

The National Food and Nutrient Analysis Program (NFNAP) was implemented in 1997 to update and improve the quality of food composition data maintained by the United States Department of Agriculture (USDA). NFNAP was designed to sample and analyze frequently consumed foods in the U.S.

Isoflavones in retail and institutional soy foods.

A national sampling plan was developed to select the most widely used isoflavone-containing foods in the United States. Foods were selected based on their retail volume and sampled in five geographical areas representing seven metropolitan areas. Isoflavones were analyzed from composite samples, raw and cooked, and reported by brand.

Prosthetic rehabilitation after craniofacial surgery.

We report our experience during the last 6 years with 20 patients fitted with prosthesis (19 patients with osseointegration of screw, 1 patient with primarily gluing method) for camouflage of congenital or acquired (trauma, tumor resection) defects of the ear, nose, or eye. Out of a total of 53 extra-oral implants fitted, 3 were lost in the orbital area due to loosening 6 months after radiation treatment. Another three implants were removed at the request of an 80-year-old patient who preferred a prosthesis retained by spectacles because of recurring infection around one of the implants.

Immortalization of primary baby rat kidney cells by retroviral mediated gene transfer of adenovirus E1A genes.

We describe a retroviral mediated gene transfer system that facilitates the transfer of heterologous genes into primary epithelial cells. Using a series of retroviral vectors containing the genes coding for the 12S and 13S mRNAs from the E1A region of adenovirus type 5 and the hygromycin resistance gene as a selectable marker, we demonstrate that, when packaged as helper virus-free amphotropic particles, these recombinant retroviruses infect murine fibroblasts and rat and human epithelial cells. Moreover, one of these constructs, containing genes for either the 12S or 13S product, is able to immortalize primary baby rat kidney epithelial cells in vitro and, thus, when used in combination with optimized culture conditions, may facilitate the establishment in culture of primary epithelial cells from a wide variety of tissues and species.

Immunohistochemical analysis of antiserum from rhesus monkeys immunized with human colon carcinoma.

In an attempt to generate antibodies which recognize novel tumor-associated antigens we have immunized Rhesus monkeys (Macaca mulatta) with human colon carcinoma cells prepared from freshly excised tumors. Immunohistochemical characterization of polyclonal antisera from one monkey (DF6) revealed preferential reactivity with primary and metastatic colon carcinoma tissue, and a general lack of recognition of nonneoplastic mucosa. Immunoreactivity was localized to the luminal contents of glandular structures and to the apical surfaces of cells lining these glands.

Clonal analysis of the malignant properties of B16 melanoma cells treated with the DNA hypomethylating agent 5-azacytidine.

The role of DNA methylation in the generation of tumor cell variants with altered growth behavior has been investigated. Cultures of the clonally heterogeneous B16 melanoma cell line and a clonal population (B16-CL) derived from it were treated with the DNA hypomethylating agent, 5-azacytidine (5-Aza-CR). The tumorigenic and metastatic properties of (sub)clones isolated from these cultures before and after drug treatment were assayed by injection via multiple routes into syngeneic C57BL/6 mice using a range of cell doses.

Biological characterization and oncogene expression in human colorectal carcinoma cell lines.

To establish well-characterized cellular reagents for the study of colon carcinoma, we have examined 19 human colorectal carcinoma cell lines with regard to morphology, ultrastructure, expression of tumor-associated antigens, proliferative capacity in vitro, anchorage-independent growth, oncogene expression, tumorigenicity and malignant potential. Cell lines examined were cultured under identical conditions, and in vitro and in vivo analyses were performed in parallel on replicate cultures. Three classes of colorectal cell lines were defined according to their tumorigenicity in nude mice.

Epidemiologic study of canine blastomycosis in Wisconsin.

An epidemiologic study was designed to investigate the increasing number of cases of canine blastomycosis being reported in Wisconsin. From January 1980 through July 1982, 200 cases of canine blastomycosis from 39 Wisconsin counties were examined to assess epidemiologic and environmental aspects of this disease. Based on a survey of 176 dog owners, principal disease characteristics for canine blastomycosis were anorexia, lethargy, shortness of breath, chronic cough, and weight loss.

Shaping future strategies for the pharmacological control of tumor cell metastases.

The eradication of established metastases in patients with malignant tumors is the single most important objective in clinical oncology. The current panel of antineoplastic agents discovered through random and semiempirical screening procedures has proven largely ineffective in treating disseminated disease and there is a clear and urgent need for more efficient antimetastatic drugs. Unfortunately, although progress has been made in examining the biology of metastatic spread, our understanding of the pharmacology, biochemistry and molecular genetics of this process is meager and insufficient to provide a rational foundation for the design of mechanism-based antineoplastic agents.

Effect of 5-azacytidine on DNA methylation and the malignant properties of B16 melanoma cells.

The role of DNA methylation in the expression of the metastatic phenotype in B16 murine melanoma cells in syngeneic C57BL/6 mice has been investigated. B16 cultures were incubated in vitro for either 6 or 18 h with the DNA hypomethylating agents, 5-azacytidine (5-Aza-CR) or 5-fluoro-2'-deoxycytidine (FCdR). At various times (1-13 days) following treatment, tumor cells were tested for their ability to form metastatic deposits when injected at different doses either i.

Tumorigenic and metastatic properties of "normal" and ras-transfected NIH/3T3 cells.

To investigate the role of oncogene activation in the pathogenesis of malignant tumors, we have studied the tumorigenic and metastatic properties of NIH/3T3 secondary transfectants (designated A51) containing an activated c-Ha-ras-1 gene derived from the human T24 bladder carcinoma cell line and compared them with untransfected NIH/3T3 cells. Whereas subcutaneous implantation of NIH/3T3 cells in the supraclavicular region produced palpable tumors that failed to metastasize, NIH/3T3 cells inoculated in the footpad gave rise to malignant tumors that metastasized to the lung. Under identical conditions and irrespective of the site of implantation, A51 cells formed rapidly growing primary tumors that produced pulmonary metastases.

Characterization of L5178Y cell phenotypes isolated during progression of the tumor-dormant state in DBA2 mice.

During the course of the L5178Y tumor-dormant state in DBA/2 mice, there is continual selection of a tumor cell subpopulation ("emergent" phenotype) from the uncloned original L5178Y population used to initiate the tumor-dormant state. In vivo and in vitro experiments show that the emergent-phenotype tumor cells are less capable than "original"-phenotype cells, which constitute the majority of the L5178Y cell inoculum, of restimulating cytolytic T-lymphocyte (CTL) activity in tumor-dormant mice and are less susceptible to lysis by those CTL. Both original- and emergent-phenotype tumor cells are capable of eliciting an immune CTL response in naive mice, but again emergent-phenotype cells are poorly lysed by this response.