2001 ABSTRACTS

CONDUCTANCE QUANTIZATION IN Au NANOCONTACTS
Staples High School, Westport, Connecticut

The quest for the miniaturization of electronic devices increases the need of understanding electron transport in nanostructures. Over the past decade, three techniques have been used to study conductance quantization, but none allow for fast and inexpensive data acquisition. In this research, a novel technique for measuring conductance quantization in metallic nanowires was developed. A piezoelectric speaker element is used to gently bring gold wires of macroscopic dimensions in and out of contact to form a nanowire. The voltage drop across the nanowire is measured by an oscilloscope interfaced with a computer. Several computer programs were written to facilitate data analysis. This technique allows for data acquisition at an unprecedented rate of 86 million data points per day, 3-1000 times faster than other techniques. The device built costs $35, approximately 3000 times less expensive than other devices.
The accuracy of the setup is demonstrated by the clear conductance plateaus observed for gold. The conductance plateaus in individual traces last between 2-5 ms, indicating the highly stable nature of the nanowire as the gold tips are pulled apart. Quantization at higher conductance values (up to 50 times the conductance quantum) is reported for the first time. An analysis of the recorded traces illustrates that the transitions between plateaus at these higher multiples are not abrupt jumps but rather sloped lines due to additional resistance caused by electron scattering. These results provide an explanation for the less prominent histogram peaks generally observed at higher values of the conductance quantum.
 

ALEXANDER C. MITTAL

THE IN VITRO ANTICANCER EFFECTS OF Mangifera indica EXTRACTS ON DHL LYMPHOMA
Greenwich High School, Greenwich, CT

Diffuse histiocytic lymphoma (DHL) is a highly malignant lymphoma. The in vitro anticancer effects of aqueous extracts of Mangifera indica on DHL cells were investigated in this study. Extracts were prepared and cultured lymphoma cells were exposed to concentrations of 10 mg/ml to 100 mg/ml of extracts of peel, pulp, and seed of M. indica. The number of viable and nonviable cells was assayed at 24 and 48 hours.
At 24 hours, peel extract had no significant effect on growth of cells. Cells exposed to pulp and seed extracts expressed increased cell death over the controls for all concentrations. At 100 mg/ml, pulp extract treatment resulted in 21% cell death (P<0.001) and seed extract treatment resulted in 27% cell death (P<0.001).
At 48 hours, peel extract exhibited strong anticancer effects, with 37% cell death (P<0.001) at a 100 mg/ml concentration. At the same concentration, pulp and seed extract resulted in 14% (P<0.001) and 19% (P<0.001) cell death, respectively.
A dose response correlation of greater than 0.96 was identified for all extract trials with the exception of the 24-hour peel extract trials.
Normal lymphocytes exposed to 10 mg/ml to 100 mg/ml of aqueous peel extracts did not show increased cell death.
Aqueous peel, pulp, and seed extracts of M. indica were effective in inhibiting the growth of DHL cells. Peel extract had the greatest anticancer effect, while it did not cause increased cell death to normal lymphocytes. This novel finding could lead to new treatment for DHL and possibly other cancers.
 

ROWENA MITTAL

Use of Microwave Irradiation for Rapid Intraoperative Frozen Section Tumor Diagnosis
Greenwich High School, Greenwich, CT USA

Routine eosin and hematoxylin staining of frozen sections takes about ten minutes and allows for a diagnosis and appropriate treatment of the cancer during tumor surgery. However, in more difficult cases (approximately 5%) an accurate diagnosis can only be determined after additional immunostaining, which stains for the presence of specific antigens. The immunostaining procedure is a three-hour process and cannot be performed intraoperatively. Microwave irradiation (MWI) is known to increase diffusion rates of substances and affect protein conformation, which may accelerate the immunostaining process by increasing the rate of reaction between antibodies and antigens. In this research, the utility of MWI to shorten the length of the immunostaining method was evaluated to achieve an intraoperative diagnostic procedure. Frozen sections, fresh or fixed in acetone, alcohol, or formalin, were immunostained by indirect method with application of MWI during incubation periods. The findings of the research have shown that: 1) shortest procedure time was achieved with unfixed tissue, 2) among the fixatives, acetone best preserved cell and antigen structure, 3) moderate MWI time at moderate power was more effective than shorter incubation time or higher power, 4) combination of staining steps did not give positive results, and 5) MWI of sections before immunostaining aided in antigen retrieval. With the reduction of the immunostaining processing time for frozen sections to approximately 10-15 minutes, this MWI method has a potential for intraoperative tumor diagnosis.

MICHAEL NYBERG

MOSQUITO CONTROL VIA ACOUSTIC LARVICIDE- A PESTICIDE FREE SOLUTION
Lyme-Old Lyme High School, Old Lyme, Connecticut

Mosquito infestation has become a more prevalent problem because an increasing number of diseases fatal to mankind are now being transmitted by mosquito bites. Current methods of mosquito control have proven detrimental to humans and the environment. In addition, mosquitoes and larvae are growing resistant to many chemical pesticides.
Searching for an acoustic frequency that would be resonant with an internal organ of a mosquito larva, I have discovered that the air bladder within the thorax is resonant within the acoustic octave of 16kHz to 32kHz. When resonance is achieved, the energy absorbed by the air ruptures the air bladder tissue and forms an embolism. This embolism migrates through the thorax and abdomen further destroying other internal organs. Power levels as low as .25-watts/ cm2 are sufficient for larvicide effects. Introducing 100-watts/ cm2 will treat a wetlands diameter of 180 yards. These experimental results were quantitatively proven by applying Urick's equation for bubble resonance [fr=(1/(2pa))*Ö(3gPo/r)]: g=ratio of specific heat of gas (1.4 at zero depth), Po=hydrostatic pressure, r=density of water, a=bubble radius in cm. fr=326/a. The effective radius of the air bladder is 0.0132cm, which results in a calculated resonance of 24.7kHz. This is the midpoint of the octave obtained by the experimental results. This octave had no effect on the pupa therefore this may not affect other non-target specimens.
A patent is pending.

JOHN J. SHEDLETSKY

DISCRETE SIMULATION OF REACTION-DIFFUSION SYSTEMS APPLIED TO MORPHOLOGICAL DEVELOPMENT
Brewster High School, Brewster, New York

A key process in the primordial transition from colonies of independent unicellular organisms to the first instances of multicellular life is the development of an intercellular dependency amongst the constituents. A cellular automaton that demonstrates the spontaneous formation of a symbiotic relationship between cells, as well as macroscopic self-organizational properties, was empirically refined through the creation of and experimentation with a computer simulation. The model introduces a large variety of different stimuli as input to each cell, including: the absorption of diffusive material from an outside environment, the state of neighboring cells, and limitless potential variability in the number of possible cell types and their properties.
The reaction-diffusion system described in this research creates remarkably differentiated organisms. Furthermore, properties of the organisms produced by the model, such as intercellular symbiosis, characteristic form, self-regulation, well-defined internal and external structure, and environmental sensitivity correspond to phenomenon observed in actual biological organisms. It was found that if a number of cell types are defined with complementary properties, a situation involving intercellular symbiosis has the possibility of developing. Cooperation between cells of different types can result in a synergy, expanding the organism's ability to gather and utilize materials from the environment. Such a symbiosis, or specialization of components, would have been an important step in the progression of unicellular colonies to the first instances of multicellular life. Observations and analysis of the mechanisms studied in the organisms produced by the modeling software may provide insights into the operation and development of complex life.