Search

Advances in lightweight, flexible, and conformal electronic devices depend on materials that exhibit high electrical conductivity coupled with high mechanical strength. Defect-free graphene is one such material that satisfies both these requirements and which offers a range of attractive and tunable electrical, optoelectronic, and plasmonic characteristics for devices that operate at microwave, terahertz, infrared, or optical frequencies. Essential to the future success of such devices is therefore the ability to control the frequency-dependent conductivity of graphene. Looking to accelerate the development of high-frequency applications of graphene, here we demonstrate how readily accessible and processable organic and organometallic molecules can efficiently dope graphene to carrier densities in excess of 10(13) cm(-2) with conductivities at gigahertz frequencies in excess of 60 mS. In using the molecule 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane (F2-HCNQ), a high charge transfer (CT) of 0.5 electrons per adsorbed molecule is calculated, resulting in p-type doping of graphene. n-Type doping is achieved using cobaltocene and the sulfur-containing molecule tetrathiafulvalene (TTF) with a CT of 0.41 and 0.24 electrons donated per adsorbed molecule, respectively. Efficient CT is associated with the interaction between the π electrons present in the molecule and in graphene. Calculation of the high-frequency conductivity shows dispersion-less behavior of the real component of the conductivity over a wide range of gigahertz frequencies. Potential high-frequency applications in graphene antennas and communications that can exploit these properties and the broader impacts of using molecular doping to modify functional materials that possess a low-energy Dirac cone are also discussed.

The ability to induce an energy band gap in bilayer graphene is an important development in graphene science and opens up potential applications in electronics and photonics. Here we report the emergence of permanent electronic and optical band gaps in bilayer graphene upon adsorption of π electron containing molecules. Adsorption of n- or p-type dopant molecules on one layer results in an asymmetric charge distribution between the top and bottom layers and in the formation of an energy gap. The resultant band gap scales linearly with induced carrier density though a slight asymmetry is found between n-type dopants, where the band gap varies as 47 meV/10(13) cm(-2), and p-type dopants where it varies as 40 meV/10(13) cm(-2). Decamethylcobaltocene (DMC, n-type) and 3,6-difluoro-2,5,7,7,8,8-hexacyano-quinodimethane (F2-HCNQ, p-type) are found to be the best molecules at inducing the largest electronic band gaps up to 0.15 eV. Optical adsorption transitions in the 2.8-4 μm region of the spectrum can result between states that are not Pauli blocked. Comparison is made between the band gaps calculated from adsorbate-induced electric fields and from average displacement fields found in dual gate bilayer graphene devices. A key advantage of using molecular adsorption with π electron containing molecules is that the high binding energy can induce a permanent band gap and open up possible uses of bilayer graphene in mid-infrared photonic or electronic device applications.

Adult onset Still's disease is a disorder characterized by spiking fevers, rash, arthritis, serositis and myalgia. Erosive arthritis is a well recognized feature, however, myositis is not. We describe a patient with adult onset Still's disease, polymyositis (PM) and rhabdomyolysis successfully treated with methotrexate (MTX) and corticosteroids. This occurrence has previously been reported, however without the presence of rhabdomyolysis or treatment with MTX. Suppression of disease activity was followed by marked radiographic improvement of the arthritis. MTX and corticosteroids in combination may be indicated for the treatment of adult onset Still's disease when PM and erosive arthritis occur.

The kinetics of inhibition of 5'-adenylic acid deaminase and creatine-ATP transphosphorylase by their respective antibodies are studied and rate constants of combination are ascertained. It is shown that the single substrate 5'-adenylic acid (AMP) of deaminase "protects" the enzyme against antibody inhibition. However, phosphate, a competitive inhibitor of the highly specific deaminase, enhances combination with antibody. With creatine kinase, however, addition of either of the substrates, alone or in combination with the required magnesium, each of which separately bind to the enzyme, does not prevent inhibition of the enzyme by its antibody. However, the "working" enzyme combined with all substrates is "protected" against antibody inhibition.

A specific and characteristic type of anemia is not a feature of all malignant disease. To the contrary, the nature of the anemia will depend upon the causative mechanism, of which blood loss and accelerated erythrocyte removal appear to be the most frequently seen and the most clearly defined. Recognition of anemia due to loss of blood is relatively simple if the subtlety of blood loss in the stool is borne in mind and persistent testing to demonstrate it is carried out. Indeed, anemia characterized by chronic loss of blood in men can only mean chronic gastrointestinal bleeding if certain rare hemoglobin abnormalities can be ruled out. Anemia due to accelerated erythrocyte removal may also be recognized by simple measures. After transfusions raise hemoglobin values to near normal levels, the disappearance of the transfused blood and the rapid return of the pretransfusion severity of anemia are good evidence of the presence of such a mechanism, if blood loss can be ruled out.Adequate management of the anemia of malignant disease depends upon a clear understanding of the various mechanisms involved. It is highly probable that attention to this feature will, in many instances, significantly prolong the productive life of persons with malignant disease.