Semiconductor attachment to single-walled carbon nanotubes through biological interaction
Helen Gerardi and Stanislaus Wong, Department of Chemistry, Stony Brook University & Brookhaven National Laboratory

Carbon nanotubes, because of their interesting mechanical, chemical, electronic, and optoelectronic properties, are being studied for implementation in a broad range of applications from DNA transfection to fuel cell electrodes. This research focuses on combining nanotubes with other semi-conducting materials such as titanium oxide (TiO2) as a first step to the creation of unique nano-sized devices. The direct attachment of these materials onto carbon nanotubes can prove to be difficult; however, strong biological interactions can prove to be useful in such a composite. The well known biotin- avidin interaction is promising for this type of attachment because of biotin's very small dissociation constant (10-15 M). It has already been shown in previous research that avidin, a glycoprotein, can be linked to amine-terminated ends of oxidized multi-walled carbon nanotubes. The reaction of biotin with titanium dioxide has also been exhibited through a replacement of the valeric chain of biotin with a molecule containing an enediol, such as dopamine. Here, titanium dioxide is attached to single-walled carbon nanotubes through this biological reaction. The exact configuration is under investigation in this research, but it has been proposed that the bidentate ligand attaches to the un-coordinated titanium atoms on the surface of the TiO2 unit cell. The carbon nanotube ends, which have been functionalized by ozonolysis, are then covalently linked to avidin. The reaction between avidin linked to the carbon nanotubes and biotin attached to the titania gives the final product. The attachment of titanium dioxide to carbon nanotubes through this method has been investigated by spectroscopy methods including infrared, UV-Visible, EPR, and AFM. Continued Research. More study is being performed to determine the nature of the final product to determine if the proposed structural configuration is supported by a larger variety of spectroscopic evidence. The applications of such a material have to be decided based on factors such as sufficient charge-separation, photoemission, and so forth.
In addition, other types of semiconducting materials can potentially be attached using the same sort of interaction.

Cocaine Self-Administration in Dopamine D4 Receptor (D4R) mice
R. Habibi, M. Michaelides, U. Patel, C. Reiszel, N. Londono, Medicine, Brookhaven Natl Lab, Upton, NY; K. Suchland, D. K. Grandy, Physiology and Pharmacology, Oregon Health Sci. University, Portland, OR; M. RubinsteinBiology, Univ. de Buenos Aires, Buenos Aires, ARGENTINA; N. D. Volkow, Health and Human Services, Laboratory of Neuroimaging, NIAAA, NIH, Bethesda, MD, and P. K. Thanos, Medicine, Brookhaven Natl Lab, Upton, NY;Psychology, State University of New York at Stony Brook, Stony Brook, NY; Neuroscience, State University of New York at Stony Brook, Stony Brook, NY;Health and Human Services, Laboratory of Neuroimaging, NIAAA, NIH, Bethesda, MD

The D4R has received considerable attention due to its relationship in certain personality traits and psychological disorders, such as gambling (Perez de Castro I, 1997), substance abuse (Lusher, Chandler, & Ball, 2001), Attention Deficit Hyperactivity Disorder (ADHD) (Arcos-Burgos et al., 2004), schizophrenia (Seeman, Guan, & Van Tol, 1993) and bipolar disorder (Muglia et al., 2002). Previous studies have supported the idea that reinforcing effects of cocaine are likely exerted in the mesolimbic regions in mammals, particularly in the hippocampus, caudate putamen and nucleus accumbens (Kuhar, Ritz, & Boja, 1991). These same regions have a high concentration of D4R (Meador-Woodruff et al., 1994). Mutant mice lacking the D4R have been shown to be supersensitive to the psychomotor stimulant effects of ethanol, methamphetamine, and cocaine as compared to the wild type (Rubinstein et al., 1997). Another study determined that the D4R plays a role in vulnerability to stimulant abuse (Katz et al., 2003).
In the present study we examined the cocaine self-administration behavior of knockout (D4R-/-), heterozygous (D4R+/-) and wildtype (D4R+/+) adult mice. The mice followed daily (60minute) cocaine (1mg/kg/infusion) self-administration sessions. The duration of time needed to reach maintenance was examined for each genotype. The criteria for maintenance were established as: (1) stable daily responding (within 20% across two consecutive sessions), (2) a minimum of 20 responses on the reinforced lever, and (3) at least 70% of responses on the reinforced lever. After maintenance is reached, mice were randomly selected to follow two different extinction protocols where saline was substituted for cocaine HCl. Extinction continued until responses between the reinforced and non-reinforced lever were insignificant. Following extinction, mice were assessed to determine the contributions of the D4 receptor in the reinforcing effects of cocaine. Support Contributed By: NIDA, NIAAA (Intramural Research Program, LNI), by the U.S. Department of Energy under contract DEAC02-98CH10886.

Devora Klein

Zina Sanchez

Scintillator Behavior and Data Acquisition for the MARIACHI Project
Zina Sanchez, Devora Klein, Nathan Emerson; Michael MarxPhysics Department, Stony Brook University and Brookhaven National Lab; and Helio Takai, Physics Department, Brookhaven National Lab

The goal of the MARIACHI (Mixed Apparatus for Radar Investigation of Cosmic Rays of High Ionization) project is to gather data on UHECR's (Ultra High Energy Cosmic Rays). This data is obtained in two ways: 1) radar is bounced off of the ionization trails created by the UHECR's and 2) ground arrays of scintillators detect the EAS (Extensive Air Showers) resulting from the UHECR's by measuring the coincidences of signals from different combinations of scintillators in the array. The first method is innovative, and since this second method of data collection is widely used, the results from the radar experiment will be verified by comparing them to the results from the scintillator arrays. The gain of the scintillators varies from one to another and therefore each one was calibrated by testing their efficiencies, which is ratio of particle detection of three stack scintillators to the outer two scintillators. By doing this, the optimum threshold and driving voltage at which each individual scintillator runs was found. As a way of better understanding the EAS the area dependence for high energy particle detection was tested. This data was plotted in graphs of coincidence rates versus distance and detection area. The difference between the detected rates of a rectangular versus a square array was measured and compared to theory. The language R was used to analyze the data. Programs were written to easily read in the event data and form it into clear graphs. While much progress has been made in understanding the behaviors of and resulting data from the scintillators, a detailed understanding of the precise values we measured is still in its early stages.

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