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Physics

Biological physics

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Displaying 176 - 200 of 201

Shell and ligand-dependent blinking of CdSe-based core/shell nanocrystals

July 7, 2010
Author(s)
Bonghwan Chon, Sung Jun Lim, Wonjung Kim, Hyeong G. Kang, Taiha Joo, Jeeseong C. Hwang, Seung Koo Shin
Blinking of zinc blende CdSe-based core/shell nanocrystals is studied as a function of shell materials and surface ligands. CdSe/ZnS, CdSe/ZnSe/ZnS and CdSe/CdS/ZnS core/shell nanocrystals are prepared by colloidal synthesis and six monolayers of larger

Global analysis of Forster resonance energy transfer in live cells measured by fluorescence lifetime imaging microscopy exploiting the rise time of acceptor fluorescence

June 16, 2010
Author(s)
Katharine M. Mullen, Sergey Laptenok, Jan Willem , Antonie Visser, Ivo van Stokkum
A methodology is described for the detection of F rster Resonance Energy Transfer (FRET) in live cells by monitoring the rise time of the acceptor fluorescence using fluorescence lifetime imaging microscopy (FLIM). An advantage of this method is that only

Shell-dependent Blinking of CdSe-Based Core/Shell Nanocrystals

May 10, 2010
Author(s)
Seung Koo Shin, Bonghwan Chon, Sung Jun Lim, Wonjung Kim, Hyeong G. Kang, Taiha Joo, Jeeseong C. Hwang
Blinking of zinc-blende CdSe-based core/shell nanocrystals are studied as a function of shell materials. CdSe/ZnS, CdSe/ZnSe/ZnS, and CdSe/CdS/ZnS core/shell nanocrystals are prepared by epitaxial growth of two-to-six monolayers (MLs) of shell materials

RECIST vs. Volume Measurement in Medical CT Using Ellipsoids of Known Size

April 12, 2010
Author(s)
Zachary H. Levine, Bruce R. Borchardt, Nolan J. Brandenburg, Charles W. Clark, Balasubramanian Muralikrishnan, Craig M. Shakarji, Joseph J. Chen, Eliot L. Siegel
(a) Purpose: We wanted to test the extent to which two common methods of determining the sizes of tumors would perform when compared to a statistically significant number of well-characterized reference objects. The size of the objects was chosen to

Multimodal, Nanoscale, Hyperspectral Imaging Demonstrated on Heterostructures of Quantum Dots and DNA-Wrapped Single-Wall Carbon Nanotubes

October 21, 2009
Author(s)
Hyeong G. Kang, Matthew L. Clarke, Jianyong Tang, John T. Woodward IV, Shin G. Chou, Zhenping Zhou, Angela R. Hight Walker, Tinh Nguyen, Jeeseong Hwang
A multimodality imaging technique integrating atomic force, polarized Raman, and fluorescence lifetime microscopy and a 2D autocorrelation image analysis is applied to study the properties of a mesoscopic heterostucture of nanoscale materials. This

Structural Basis of Pathway-Dependent Force Profiles in DNA

October 21, 2009
Author(s)
Daniel R. Roe, Anne M. Chaka
Understanding the mechanical properties that guide the flexibility of DNA is important, as DNA must bend and/or stretch in order to function biologically. In addition, there is interest in using DNA as a nanoscopic length and force standard. Over the past

Generation and Mixing of Subfemtoliter Aqueous Droplets on Demand

August 27, 2009
Author(s)
Kristian Helmerson, Jianyong N. Tang, Ana Jofre, Rani Kishore, Joseph E. Reiner, Mark E. Greene, Geoffrey M. Lowman, John Denker, Christina N. Willis, Lori Goldner
We describe a novel method of generating monodisperse sub-femtoliter aqueous droplets on demand by means of piezoelectric injection. Droplets with volumes down to 200 aL are generated by this technique. The droplets are injected into a low refractive index

Radiation-Based Quantitative Bioimaging at NIST

August 1, 2009
Author(s)
Lisa R. Karam
The National Institute of Standards and Technology (NIST) provides the physical measurements and standards in a variety of fields, including for ionizing radiation, for the US. Building on a long history of providing standards for medical x rays and

Quantitative Characterization of Quantum Dot-labeled Lambda Phage for Escherichia coli Detection

July 24, 2009
Author(s)
Peter Yim, Matthew L. Clarke, Michael McKinstry, Silvia H. De Paoli Lacerda, Leonard F. Pease III, Marina A. Dobrovolskaia, Hyeong G. Kang, David T. Read, Shanmuga Sozhamannan, Jeeseong C. Hwang
We rapidly and quantitatively detect biological pathogens by combining the specificity of bacteriophage lambda with the sensitivity of CdSe/ZnS quantum dot (QD)-based fluorescence. Specifically, QD-decorated lambda phages bind to and allow detection of

Direct Measurement of Association and Dissociation Rates of DNA Binding in Live Cells by Fluorescence Correlation Spectroscopy

July 1, 2009
Author(s)
Ariel Michelman-Ribeiro, Davide Mazza, Tilman Rosales, Timothy J. Stasevich, Boukari Hacene, Vikas Rishi, Charles Vinson, Jay R. Knutson, James G. NcNally
Measurement of live-cell binding interactions is vital for understanding the biochemical reactions that drive cellular processes. Here we develop, characterize and apply a new procedure to extract information about binding to an immobile substrate from FCS

Primary Standards for Brachytherapy Sources

June 1, 2009
Author(s)
Michael G. Mitch, Christopher G. Soares
The AAPM dosimetry protocol for LDR brachytherapy seeds that emit x-rays of energies ≤ 50 keV is described in the TG-43U1 report (Rivard et al. 2004). In this protocol, it is specified that the strength of such sources be expressed in terms of air-kerma

Dipolar Chains formed by synthesized cobalt nanocubes

May 11, 2009
Author(s)
Guangjun Cheng, Robert D. Shull, Angela R. Hight Walker
Cobalt nanocubes with an average edge length of 50 nm and the epsilon crystalline structure were synthesized via thermo-decomposition in 1,2-dichlorobenzene at 120 oC in the presence of the surfactants. These nanocubes form dipolar chains upon drying in

Terahertz spectroscopy of aqueous L-Proline in reverse micelles

November 21, 2008
Author(s)
Catherine C. Cooksey, Edwin J. Heilweil, Benjamin Greer
A new method for obtaining room temperature terahertz (THz) absorption spectra of aqueous-phase biomolecules in the frequency range 1 THz to 21 THz (35 cm-1 to 700 cm-1) is reported. The spectrum for L-Proline was acquired by solvating the amino acid

THz Investigations of Condensed Phase Biomolecular Systems

October 8, 2008
Author(s)
Kevin O. Douglass, Hailiang Zhang, Susan K. Gregurick, Karen M. Siegrist, David F. Plusquellic
Terahertz (THz) spectroscopic investigations of crystalline dipeptide nanotubes are discussed in the frequency region from 0.6 THz (2 cm-1) to 3 THz (100 cm-1). The THz region provides access to collective modes of biomolecular systems and is therefore

Cholesterol/Phospholipid Interactions in Hybrid Bilayer Membranes

May 25, 2007
Author(s)
Dustin Levy, Kimberly Briggman
The interactions between cholesterol and saturated phospholipids in hybrid bilayer membranes (HBMs) were investigated using the interface-sensitive technique of vibrational sum frequency spectroscopy (VSFS). The unique sensitivity of VSFS to order/disorder

Characterization and Control of Lipid Layer Fluidity in Hybrid Bilayer Membranes

January 31, 2007
Author(s)
Neil A. Anderson, Lee J. Richter, John C. Stephenson, Kimberly A. Briggman
The main gel-to-liquid-crystal (LC) phase transition temperature, Tm, of the distal lipid layer in hybrid bilayer membranes (HBMs) under water was investigated using vibrational sum frequency spectroscopy (VSFS). VSFS has unique sensitivity to order

Determination of Lipid Phase Transition Temperatures in Hybrid Bilayer Membranes

September 9, 2006
Author(s)
Neil A. Anderson, Lee J. Richter, John C. Stephenson, Kimberly A. Briggman
The main gel to liquid crystal (LC) phase transition temperature, Tm, of the lipid monolayers in hybrid bilayer membranes (HBMs) was investigated using vibrational sum frequency spectroscopy (VSFS). The unique sensitivity of VSFS to probe order/disorder
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