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91.
92.
Margaret C. Kline David L. Duewer John C. Travis Melody V. Smith Janette W. Redman Peter M. Vallone Amy E. Decker John M. Butler 《Analytical and bioanalytical chemistry》2009,394(4):1183-1192
Modern highly multiplexed short tandem repeat (STR) assays used by the forensic human-identity community require tight control
of the initial amount of sample DNA amplified in the polymerase chain reaction (PCR) process. This, in turn, requires the
ability to reproducibly measure the concentration of human DNA, [DNA], in a sample extract. Quantitative PCR (qPCR) techniques
can determine the number of intact stretches of DNA of specified nucleotide sequence in an extremely small sample; however,
these assays must be calibrated with DNA extracts of well-characterized and stable composition. By 2004, studies coordinated
by or reported to the National Institute of Standards and Technology (NIST) indicated that a well-characterized, stable human
DNA quantitation certified reference material (CRM) could help the forensic community reduce within- and among-laboratory
quantitation variability. To ensure that the stability of such a quantitation standard can be monitored and that, if and when
required, equivalent replacement materials can be prepared, a measurement of some stable quantity directly related to [DNA]
is required. Using a long-established conventional relationship linking optical density (properly designated as decadic attenuance)
at 260 nm with [DNA] in aqueous solution, NIST Standard Reference Material (SRM) 2372 Human DNA Quantitation Standard was
issued in October 2007. This SRM consists of three quite different DNA extracts: a single-source male, a multiple-source female,
and a mixture of male and female sources. All three SRM components have very similar optical densities, and thus very similar
conventional [DNA]. The materials perform very similarly in several widely used gender-neutral assays, demonstrating that
the combination of appropriate preparation methods and metrologically sound spectrophotometric measurements enables the preparation
and certification of quantitation [DNA] standards that are both maintainable and of practical utility.
Figure NIST Standard Reference Material (SRM) 2372 Human Quantitation Standard 相似文献
93.
J.M. Kline S.S. Penner 《Journal of Quantitative Spectroscopy & Radiative Transfer》1980,24(3):185-189
We describe the measurement of an off-peak spectral absorption coefficient for an isolated spectral line using a laser light source. This type of experiment may be used to determine the following line parameters: the line strength (S), the collision-broadened half-widths for self-broadening (b0c,F and for inert-gas broadening (b0c, I) per unit pressure, and the displacement of the laser frequency from the line center (Δω). The theoretical relations have been applied to absorption measurements on formaldehyde using an HeXe laser light source at 3.508 μ. 相似文献
94.
Kline JL Montgomery DS Bezzerides B Cobble JA DuBois DF Johnson RP Rose HA Yin L Vu HX 《Physical review letters》2005,94(17):175003
Thomson scattering is used to measure Langmuir waves (LW) driven by stimulated Raman scattering (SRS) in a diffraction limited laser focal spot. For SRS at wave numbers klambda(D) less similar 0.29, where k is the LW number and lambda(D) is the Debye length, multiple waves are detected and are attributed to the Langmuir decay instability (LDI) driven by the primary LW. At klambda(D) greater similar 0.29, a single wave, frequency-broadened spectrum is observed. The transition from the fluid to the kinetic regime is qualitatively consistent with particle-in-cell simulations and crossing of the LDI amplitude threshold above that for LW self-focusing. 相似文献
95.
96.
The Si(0 0 1) surface morphology during ion sputtering at elevated temperatures and solid phase epitaxy (SPE) following ion sputtering at room temperature has been investigated using scanning tunneling microscopy. Two types of antiphase boundaries form on Si(0 0 1) surfaces during ion sputtering and SPE. One type of antiphase boundary, the AP2 antiphase boundary, contributes to the surface roughening. AP2 antiphase boundaries are stable up to 700 °C, and ion sputtering and SPE performed at 700 °C result in atomically flat Si(0 0 1) surfaces. 相似文献
97.
Paxton WF Baker PT Kline TR Wang Y Mallouk TE Sen A 《Journal of the American Chemical Society》2006,128(46):14881-14888
We have explored the role of electrokinetics in the spontaneous motion of platinum-gold nanorods suspended in hydrogen peroxide (H2O2) solutions that may arise from the bimetallic electrochemical decomposition of H2O2. The electrochemical decomposition pathway was confirmed by measuring the steady-state short-circuit current between platinum and gold interdigitated microelectrodes (IMEs) in the presence of H2O2. The resulting ion flux from platinum to gold implies an electric field in the surrounding solution that can be estimated from Ohm's Law. This catalytically generated electric field could in principle bring about electrokinetic effects that scale with the Helmholtz-Smoluchowski equation. Accordingly, we observed a linear relationship between bimetallic rod speed and the resistivity of the bulk solution. Previous observations relating a decrease in speed to an increase in ethanol concentration can be explained in terms of a decrease in current density caused by the presence of ethanol. Furthermore, we found that the catalytically generated electric field in the solution near a Pt/Au IME in the presence of H2O2 is capable of inducing electroosmotic fluid flow that can be switched on and off externally. We demonstrate that the velocity of the fluid flow in the plane of the IME is a function of the electric field, whether catalytically generated or applied from an external current source. Our findings indicate that the motion of PtAu nanorods in H2O2 is primarily due to a catalytically induced electrokinetic phenomenon and that other mechanisms, such as those related to interfacial tension gradients, play at best a minor role. 相似文献
98.
J. Billiter K. Bennewitz N. Bjerrum N. E. Loomis S. F. Acree C. N. Murray G. M. Kline M. R. Meacham Florence Fenwick Fr. L. Hahn M. Frommer I. Lifschitz M. Reggiani D. A. Mc Innes M. Dole C. W. Foulk M. Hollingsworth L. R. Parks H. C. Beard K. W. Franke J. J. Willaman Lava Hemedes H. T. S. Britton R. A. Robinson W. H. Harrison P. N. Vridhachalam J. J. Shukoff G. P. Awsejewitsch L. W. Elder Jr. P. Jolibois G. Fouretier P. Dubois H. A. Bromley L. W. Causer A. de Waele T. Callan S. Horrobin R. J. Fosbinder E. H. Ducloux 《Analytical and bioanalytical chemistry》1932,90(11-12):432-443
99.
A sensitive high-performance liquid chromatographic (HPLC) assay for the determination of the cyclic heptapeptide Ac-Cs-Asn-Dtc-Amf-Gly-Asp-Cys-OH (Dtc = beta,beta-dimethylthioproline, Amf = p-aminomethylphenylalanine) in human plasma has been developed. The key steps in the assay include: solid-phase extraction of the drug from plasma, chemical derivatization of the primary amino group with naphthalene-2,3-dicarboxyaldehyde in the presence of N-acetyl-D-penicillamine as a nucleophile to form a fluorescent benzo[f]isoindole derivative, and HPLC with column switching to provide the necessary chromatographic separation of the derivative from endogenous plasma components. The assay has been validated in the concentration range 1-10 ng/ml of plasma. 相似文献
100.
McElhanon JR Zifer T Kline SR Wheeler DR Loy DA Jamison GM Long TM Rahimian K Simmons BA 《Langmuir : the ACS journal of surfaces and colloids》2005,21(8):3259-3266
Two new surfactant molecules are reported that contain thermally labile Diels-Alder adducts connecting the hydrophilic and hydrophobic sections of each molecule. The two surfactants possess identical hydrophobic dodecyl tail segments but have phenol and carboxylic acid hydrophilic headgroups, respectively. Deprotonation with potassium hydroxide affords the formation of water-soluble surfactants. Room temperature aqueous solutions of both surfactants exhibit classical surface-active agent behavior similar to common analagous alkylaryl surfactant molecules. Critical micelle concentrations have been determined for each surfactant through dynamic surface tension and dye solubilization techniques. Small-angle neutron scattering measurements of the aqueous surfactant solutions indicate the presence of spherical micelles with radii of 16.5 angstroms for the carboxylate and 18.8 angstroms for the phenolate. When these surfactants are exposed to elevated temperatures (>50 degrees C), the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments. Aqueous solutions of each surfactant subsequently exhibit a loss of all surface-active behavior and the micellar aggregates are no longer detectable. 相似文献