NIST Technicalendar September 8 to September 12, 2008 The NIST Technicalendar is issued each Friday. All items MUST be submitted electronically from this web page by 12:00 NOON each Wednesday unless otherwise stated in the NIST Technicalendar. The address for online weekly editions of the NIST Technicalendar and NIST Administrative Calendar is: http://www.nist.gov/tcal/.

In this Issue: Meetings at NIST Meetings Elsewhere Announcements Talks by NIST Personnel NIST Web Site Announcements NIST Administrative Calendar (current)   NIST Vacancy Announcements (current)

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1:00 PM - Electrochemical Impedance Spectroscopy of Tethered-bilayers

No Scheduled Events

No Scheduled Events

10:30 AM - CANCELLED****Nanoparticles with key-lock interactions: from self-assembly to drug delivery****CANCELLED
10:30 AM - The Collapse of the World Trade Center Twin Towers - A Metallurgist's View

No Scheduled Events

9/8 -- MONDAY

1:00 PM - NIST CENTER FOR NEUTRON RESEARCH SEMINAR: Electrochemical Impedance Spectroscopy of Tethered-bilayers
Electrochemical impedance (EI) spectroscopy is one of the most advanced techniques to study the electrical properties of bilayer lipid membrane systems. The applicability of this method, however, is heavily dependent on modelling. Even for structurally simple biomimetic systems such as black lipid membranes, the EI spectral features may exhibit quite sophisticated properties that require adequate mathematical treatment to retrieve physically relevant information about the system. The situation is even more complicated for the tethered to the surface bilayers because of the structural complexity of such systems. In this work, thye analyze the frequency spectra of tethered bilayers using a concept of distributed-parameter networks. They demonstrate that the presence of defects in tethered bilayer systems result in specific low frequency features in the EI spectra. The analysis of these features allows assessing the physical parameters of the tethered bilayer system such as the specific resistance and thickness of the electrolyte reservoir separating the bilayer and metal surface, as well as the capacitance of the metal/reservoir interface. In addition, they demonstrate that, in certain cases, the presence of these defects leads to the constant-phase element (CPE) type of impedance. The values of the exponent of CPE may be used to estimate the defect density as well as to asses the electrical heterogeneity of the submembrane reservoir located between the electrode and the bilayer. They analyze EI spectral data in the context of the Alzheimer's disease-related water-soluble prefibrillar amyloid â (Aâ) peptide and pore-forming á-hemolysin ( á-HL) protein interactions with tethered bilayers. Although the literature suggests that the membrane damage triggered by Aâ and á-HL occurs by qualitatively distinct mechanisms, both proteins trigger similar EI spectral changes and dramatically increase membrane conductance. They now demonstrate how EI spectral analysis allows one to distinguish between these two different mechanisms.
Gintaras Valincius , Institut of Biochemistry, Vilnius, Lithuania. ,.
235 Bldg, Rm. E100. (NIST Contact: Susan Krueger, 301-975-2734, susan.krueger@nist.gov)


9/9 -- TUESDAY

No Scheduled Events

9/10 -- WEDNESDAY

No Scheduled Events

9/11 -- THURSDAY

10:30 AM - CNST NANOFABRICATION RESEARCH GROUP SEMINAR: CANCELLED****Nanoparticles with key-lock interactions: from self-assembly to drug delivery****CANCELLED
By decorating colloidal particles and other nano-objects with various biomolecules, one can introduce highly selective key-lock interactions between them. This leads to a new class of systems and problems in soft condensed matter physics. In my talk, I will review a number of theoretical possibilities and recent experimental achievements in this new field. First, I will discuss DNA-mediated self-assembly of nanostructures and nanoclusters. The specificity and tunability of the interactions result in a remarkable morphological diversity of in such systems. In some of the proposed schemes, DNA can be used to essentially "program" the self-assembly of a desired structure. The colloids with type-dependent interactions can also be used for experimental realization of one of the simplest self-replicating system. Its study may shed some light onto such important problems as prebiotic evolution and origin of life. Finally, I will discuss how cooperative key-lock binding can be also utilized to dramatically enhance cell specificity of drug delivery, e.g. in cancer treatment.
Alexei Tkachenko , Physics Department, University of Michigan.
Bldg. 217, Rm. H107. (NIST Contact: James Liddle, 301-975-6050, james.liddle@nist.gov)

10:30 AM - NIST SIGMA XI COLLOQUIUM: The Collapse of the World Trade Center Twin Towers - A Metallurgist's View
NIST has completed a 4 year investigation of the collapse of the World Trade Center Towers.. The investigation addressed many aspects of the catastrophe, from occupant egress to factors affecting how long the Twin Towers stood after being hit by the airplanes, with the goal of gaining valuable information for the future. A major part of the investigation was the metallurgical analysis of structural steel from the towers. The analysis included characterization of mechanical properties, failure modes, and temperature excursions seen by the steel. This talk on the metallurgical investigation will describe the structure of the towers, recovered steel, and special issues faced in the analysis of the steel. In addition, major results and conclusions of the NIST Investigation will be presented.
Frank Gayle , Metallurgy Division.
Administration Bldg, Red Auditorium. (NIST Contact: Dave Holbrook, 301-975-5202, dave.holbrook@nist.gov)
Special Assistance Available


9/12 -- FRIDAY

No Scheduled Events

ADVANCE NOTICE

9/15/08 1:30 PM - CNST NANOFABRICATION RESEARCH GROUP SEMINAR: Andreev current induced dissipation in a Superconductor – Normal metal – Superconductor tunnel junction
In the recent years, nano-refrigeration using electron tunneling in hybrid Normal metal - Insulator - Superconductor (N-I-S) junctions has gained increasing attention [1]. Its basic principle is the energy selective tunneling due to the presence of an energy gap in the superconductor density of states. With a sub-gap voltage bias, only the most energetic electrons can tunnel out of the normal metal, leaving behind the electrons with less energy. We have measured with a high resolution the differential conductance of S-I-N-I-S junctions, whose analysis gives us an access to the normal metal electronic temperature as a function of the voltage. A quantitative model is proposed, that includes the electron-phonon coupling and the Kapitza resistance at the interface with the substrate. With this model, we have achieved a thorough description of the charge and heat currents [2]. We have also shown that the normal metal phonon temperature drops significantly below the substrate temperature. At very low temperature (T 200mK) and low bias, the phase coherent Andreev current dominates the quasi-particle current. By analyzing quantitatively the heat balance in the S-I-N-I-S junction, we demonstrate that the Andreev current does carry heat. This thermal contribution heats the normal metal electrons, overriding over a large voltage range the tunneling-based cooling [3].
Sukumar Rajauria , Néel Institute, CNRS and Université Joseph Fourier.
Bldg. 217, Rm. H107. (NIST Contact: James Liddle, 301-975-6050, james.liddle@nist.gov)

9/16/08 10:30 AM - CNST ELECTRON PHYSICS GROUP SEMINAR: Towards quantum information processing using single neutral atoms
To realize quantum information processing with neutral atoms, controlled coherent interaction between them is a fundamental requirement. One approach relies on deterministic coupling of two or more atoms to the mode of a high-finesse optical resonator in the strong coupling regime. We investigate such a coupling between neutral atoms and a resonator under controlled conditions: we load a chosen number of Doppler-cooled caesium atoms from a magneto-optical trap into a standing wave optical dipole trap. The positions of the individual atoms are then determined with sub-micrometer precision, enabling us to prepare, to manipulate and to read out the quantum state of each atom. Using the dipole trap as an optical conveyor belt, the atoms are transported into the mode of a high-finesse optical cavity with a finesse of F=106, leading to a maximum single-atom cooperativity parameter of the order of 50. By observing the transmission of a weak resonant probe laser we can detect the interaction dynamics of a single atom coupled strongly to the cavity field. Cooling by the probe laser extends the observation time to several ten seconds, allowing us to investigate the strength and the stability of coupling, which are crucial parameters for the controlled coherent interaction. Moreover, we analyze the atom-field interaction using a method, essential for the creation and measurement of entanglement.
Mkrtych Khudaverdyan , Ph.D. Student/Institute of Applied Physics, Bonn, Germany.
Bldg. 217, Rm. H107. (NIST Contact: Jabez McClelland, 301-975-3721, Jabez.McClelland@nist.gov)

9/16/08 10:30 AM - ATOMIC PHYSICS DIVISION SEMINAR: Carbon-nanotube field-effect transistors as chemical sensors
Single-walled carbon nanotubes are seamless molecular cylinders that are either metallic or semiconducting nanowires. The conductance of a semiconducting nanotube can be tuned by applying a voltage to a nearby gate electrode, providing a one-dimensional field-effect transistor at the nanometer scale. These transistors are very sensitive detectors: Their electrical properties vary strongly when they are exposed to chemicals. After the first experiments seven years ago, where high sensitivity to NH3 (monitored in farms and industries) and NO2 (an air pollutant from motor vehicle exhaust and other combustion sources) was discovered [1], a strong sensitivity to many other molecules, including oxygen, methane, alcohol vapor and proteins, has also been reported. The cause of the change in electrical properties is still unclear. One possibility is that molecules bind to the surface of the nanotubes and charge transfer occurs between the nanotube and the molecules. A second possibility is a change of the barriers for electrical transport at the interface between the nanotube and the electrical contacts. Understanding the mechanism that causes the response to each chemical is an essential step for the design of efficient sensors. I will discuss an experimental method we recently developed to determine the sensing mechanism. We find that, in the case of NO2, sensing occurs through the contacts [2]. [1] J. Kong, N. R. Franklin, C. Zhou, M. G. Chapline, S. Peng, K. Cho, and H. Dai, Science 287, 622 (2000). [2] J. Zhang, A. Boyd, A. Tselev, M. Paranjape, and P. Barbara, Appl. Phys. Lett. 88, 123112 (2006).
Paola Barbara , Physics Department, Georgetown University.
Physics Building, Room B145. (NIST Contact: Neil Zimmerman, 301-975-5887, neil.zimmerman@nist.gov)

9/18/08 11:00 AM - MATERIALS SCIENCE AND ENGINEERING LABORATORY LECTURE SERIES: Electrical Methods for Measuring Mechanical Response of Thin Films
The nanoscale thin films of copper, aluminum, and other materials used as interconnects in semiconductor devices to conduct electrical power, signals, and heat are difficult to manufacture and are potential failure points in operation of the chips, particularly as these features shrink in size and must carry greater electrical and thermal loads. To better measure the mechanical and thermal-mechanical response of interconnects under these demanding conditions, we are developing electrical tests to assess strengths and thermal fatigue lifetimes. This approach allows us to test structures with very fine dimensions as well as those that are buried beneath other layers, without special specimen preparation, i.e. we test in the as-manufactured state. We use four-point probe methods and apply low frequency, high density alternating currents to effect controlled joule heating. Mechanical strains are then induced in the films due to the differences in coefficients of thermal expansion between the film and surrounding materials. Details of the methods as applied to copper and aluminum interconnects will be described, including observations of the evolution of microstructure with progressing damage, as determined by electron microscopy. This work was conducted by Nicholas Barbosa, Roy Geiss, David Read, and Robert Keller of the Materials Reliability Division, Nanoscale Reliability Group. VTC to Boulder in Building 2, Room 0113 at 9am MT
Robert Keller , Materials Research Engineer; Boulder, CO, keller@boulder.nist.gov.
Administration Bldg, Green Auditorium. (NIST Contact: Bill Boettinger, 301-975-6160, william.boettinger)

9/19/08 10:30 AM - NIST COLLOQUIUM SERIES: Magnetic Storms: Building Planetary Cores in the Laboratory
The Earth's magnetic field is dynamic and evolving in a way that suggests we are headed for a magnetic reversal. As there is no predictive science of geomagnetism, we currently lack even simple forecasts. Our scientific understanding is hampered by the complex state of flows within planetary cores that are responsible for generating the magnetic field. We probe aspects of the dynamics of flows in planetary cores and stars using experiments in liquid sodium, liquid helium, liquid nitrogen, or water (not, of course, mixed together!). Using these, we explore how turbulence is affected by rotation and magnetic fields. These experiments are opening up new insights into the dynamics of the Earth's outer core, other planetary interiors, and a host of astrophysical objects.
Daniel Lathrop , Director, Institute for Electronics and Applied Physics, University of Maryland.
Administration Building, Green Auditorium. (NIST Contact: Kum Ham, 301-975-4203, kham@nist.gov)
Special Assistance Available

9/24/08 1:30 PM - CNST ELECTRON PHYSICS GROUP SEMINAR: ULTRACOLD PLASMA DYNAMICS IN A MAGNETIC FIELD
Ultracold plasmas created by photoionizing a sample of laser cooled and trapped cold atoms, has extended the neutral plasma parameters by about two orders of magnitude, as the electron temperatures as low as 1 Kelvin. Previous studies focused on the study of free expansion and electron temperature measurement of the plasma without a magnetic field. In this talk, I will talk about a new technique, time-of-flight projection imaging technique, to study ultracold plasma dynamics with or without a magnetic field, such as plasma expansion and instabilities.
Xianli Zhang , Ph.D. Candidate, University of Maryland.
Bldg. 217, Rm. H107. (NIST Contact: Jabez McClelland, 301-975-3721, jabez.mcclelland@nist.gov)

10/20/08 8:00 AM - CHEMICAL SCIENCE AND TECHNOLOGY LABORATORY OFFICE SEMINAR: "Accelerating Innovation in 21st Century Biosciences: Identifying the Measurement Standards and Technological Challenges"
The National Institute of Standards and Technology (NIST) and the University of Maryland Biotechnology Institute (UMBI) are planning to co-host an October 20-24, 2008 Conference (Symposium and Workshop) focused on identifying and prioritizing measurement, standards, and technology needs that represent barriers to innovation, and impediments to achieving maximal societal and economic benefits of new discoveries in the biosciences.
Invited Speakers , Various Organizations.
Administration Bldg, Red Auditorium. (NIST Contact: Willie May, 301-975-8300, wem@nist.gov) http://www.cstl.nist.gov/Biosciences.html
Special Assistance Available

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MEETINGS ELSEWHERE


9/8 -- MONDAY

No Scheduled Events

9/9 -- TUESDAY

No Scheduled Events

9/10 -- WEDNESDAY

No Scheduled Events

9/11 -- THURSDAY

No Scheduled Events

9/12 -- FRIDAY

No Scheduled Events

ADVANCE NOTICE

No Scheduled Events

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TALKS BY NIST PERSONNEL

YAGER, K. : DIRECTED SELF-ASSEMBLY OF BLOCK-COPOLYMERS: MEASUREMENT OF 3D ORDER.
Center for Self-Assembled Chemical Structure Student Symposium, McGill University, Montreal, Canada, 9/8.

SIMON, JR., C. : REFERENCE SCAFFOLDS FOR TISSUE ENGINEERING.
Society For Biomaterials, Hyatt Regency Buckhead, Atlanta, Georgia, USA, 9/12.

MARBUKH, V. : A FRAMEWORK FOR JOINT CROSS-LAYER AND NODE LOCATION OPTIZATION IN MOBILE SENSOR NETWORKS.
7th International Conference on AD-HOC Networks and Wireless, Nice, France, 9/12.

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ANNOUNCEMENTS

No announcements this week.

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NIST WEB SITE ANNOUNCEMENTS

No Web Site announcements this week.

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For more information, contact Ms. Sharon Hallman, Editor, Stop 2500, National Institute of Standards and Technology, Gaithersburg MD 20899-2500; Telephone: 301-975-TCAL (3570); Fax: 301-926-4431; or Email: tcal@nist.gov.

All lectures and meetings are open unless otherwise stated.

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