Proceedings of the National Academy of Sciences of the United States of America, May 1, 1990
Pulsed-field gel electrophoresis (PFGE) and deletion mapping are being used to construct a physic... more Pulsed-field gel electrophoresis (PFGE) and deletion mapping are being used to construct a physical map of the long arm of human chromosome 13. The present study reports a 2700-kilobase (kb) Not I long-range restriction map encompassing the 13q14-specific loci D13S10, D13S21, and D13S22, which are detected by the cloned DNA markers p7D2, pG24E2.4, and pG14E1.9, respectively. Analysis of a panel of seven cell lines that showed differential methylation at a Not I site between D13S10 and D13S21 proved physical linkage of the two loci to the same 875-kb Not I fragment. D13S22 mapped to a different Not I fragment, precluding the possibility that D13S22 is located between D13S10 and D13S21. PFGE analysis of Not I partial digests placed the 1850-kb Not I fragment containing D13S22 immediately adjacent to the 875-kb fragment containing the other two loci. The proximal rearrangement breakpoint in a cell line carrying a del13(q14.1q21.2) was detected by D13S21 but not by D13S10, demonstrating that D13S21 lies proximal to D13S10. Quantitative analysis of hybridization signals of the three DNA probes to DNA from the same cell line indicated that only D13S10 was deleted, establishing the order of these loci to be cen-D13S22-D13S21-D13S10-tel. Surprisingly, this order was estimated to be 35,000 times less likely than that favored by genetic linkage analysis.
We examine the effect of long-range surface interactions on surface wetting phase transitions in ... more We examine the effect of long-range surface interactions on surface wetting phase transitions in polymer mixtures. Within a perturbation scheme, we have found an analytic solution for the volume-fraction profile near the surface which can be compared with that obtained from a model with short-range surface interactions only. We find that the long-range interactions should not be ignored in the interpretation of recent experimental results.
A theory of inhomogeneous multicomponent systems containing weakly charged polyelectrolytes is de... more A theory of inhomogeneous multicomponent systems containing weakly charged polyelectrolytes is developed. The theory treats the polymer conformation and the electrostatics simutaneously using a functional integral representation of the partition function. A mean-field approximation to the theory leads to two sets of coupled mean-field equations: a generalized Poisson-Boltzmann equation describing the electrostatic potential, and a set of self-consistent field equations describing the equilibrium densities. The theory can be used to study the interfacial properties, microphase structures, and adsorptions of a variety of weakly charged polyelectrolyte systems. As a simple application, the interfaces between the polymer-rich and polymer-poor phases of a polyelectrolyte solution is studied.
We explain the large second-harmonic generation of ultrasound observed in V3Si by Testardi in ter... more We explain the large second-harmonic generation of ultrasound observed in V3Si by Testardi in terms of the interaction of the input shear wave with a dynamical strain induced by the low-temperature structural phase transition. We use the independent-chain model for the d electrons, and expand the free energy in powers of the total strain. The second-harmonic amplitude obtained by assuming a deviation from cubic symmetry arising from a homogeneous static strain is calculated to be too small to explain the experimental result.
A generalized model of multiple trapping from a band of extended or localized states is used to s... more A generalized model of multiple trapping from a band of extended or localized states is used to study timedependent charge transport in amorphous solids. The model differs from a conventional multiple-trapping model by including a distribution of trap release rates for a constant trap energy. An extensive analysis of transient photocurrent experiments on a-Se is carried out to determine the transport parameters for this case. It is found that a small number of parameters can be used to analyze the experimental results over a wide range of temperature and sample thickness. The results of the analysis are interpreted in terms of trapcontrolled hopping, which is a special case of the generalized multiple-trapping model. The asymptotic value of the theoretical photocurrent transient is obtained for the multiple-trapping model, and the results of Scher and Montroll are recovered for the case of extreme or anomalous dispersion, which occurs for a-Se at low temperature (T~=140 K). The density of trapping sites is estimated, and the difficulties associated with considering a continuous distribution of trap release rates are discussed. It is concluded that the generalized multiple-trapping model, defined by simple first-order rate equations, is capable of describing detailed shapes of photocurrent transients, including dispersive and nondispersive charge transport.
A model of multiple trapping from a band of transport states is shown to be equivalent to the con... more A model of multiple trapping from a band of transport states is shown to be equivalent to the continuum limit of the continuous-time-random-walk description of anomalous dispersion developed by Scher and Montroll and the waiting-time distribution function psi(t) is expressed in terms of the parameters of the multiple-trapping model. Calculations of psi(t) as a function of temperature are presented for
We present a high-field biased reptation model of gel electrophoresis. It is predicted that durin... more We present a high-field biased reptation model of gel electrophoresis. It is predicted that during their migration, DNA fragments can get trapped for long periods of time in near-zero-velocity, looplike compact conformations. As a consequence, the electrophoretic mobility of DNA is found to be a nonmonotonic function of the fragment size. We present experimental results showing this unique and unexpected consequence of anomalous dispersion due to DNA self-trapping in compact states.
Proceedings of the National Academy of Sciences of the United States of America, May 1, 1990
Pulsed-field gel electrophoresis (PFGE) and deletion mapping are being used to construct a physic... more Pulsed-field gel electrophoresis (PFGE) and deletion mapping are being used to construct a physical map of the long arm of human chromosome 13. The present study reports a 2700-kilobase (kb) Not I long-range restriction map encompassing the 13q14-specific loci D13S10, D13S21, and D13S22, which are detected by the cloned DNA markers p7D2, pG24E2.4, and pG14E1.9, respectively. Analysis of a panel of seven cell lines that showed differential methylation at a Not I site between D13S10 and D13S21 proved physical linkage of the two loci to the same 875-kb Not I fragment. D13S22 mapped to a different Not I fragment, precluding the possibility that D13S22 is located between D13S10 and D13S21. PFGE analysis of Not I partial digests placed the 1850-kb Not I fragment containing D13S22 immediately adjacent to the 875-kb fragment containing the other two loci. The proximal rearrangement breakpoint in a cell line carrying a del13(q14.1q21.2) was detected by D13S21 but not by D13S10, demonstrating that D13S21 lies proximal to D13S10. Quantitative analysis of hybridization signals of the three DNA probes to DNA from the same cell line indicated that only D13S10 was deleted, establishing the order of these loci to be cen-D13S22-D13S21-D13S10-tel. Surprisingly, this order was estimated to be 35,000 times less likely than that favored by genetic linkage analysis.
We examine the effect of long-range surface interactions on surface wetting phase transitions in ... more We examine the effect of long-range surface interactions on surface wetting phase transitions in polymer mixtures. Within a perturbation scheme, we have found an analytic solution for the volume-fraction profile near the surface which can be compared with that obtained from a model with short-range surface interactions only. We find that the long-range interactions should not be ignored in the interpretation of recent experimental results.
A theory of inhomogeneous multicomponent systems containing weakly charged polyelectrolytes is de... more A theory of inhomogeneous multicomponent systems containing weakly charged polyelectrolytes is developed. The theory treats the polymer conformation and the electrostatics simutaneously using a functional integral representation of the partition function. A mean-field approximation to the theory leads to two sets of coupled mean-field equations: a generalized Poisson-Boltzmann equation describing the electrostatic potential, and a set of self-consistent field equations describing the equilibrium densities. The theory can be used to study the interfacial properties, microphase structures, and adsorptions of a variety of weakly charged polyelectrolyte systems. As a simple application, the interfaces between the polymer-rich and polymer-poor phases of a polyelectrolyte solution is studied.
We explain the large second-harmonic generation of ultrasound observed in V3Si by Testardi in ter... more We explain the large second-harmonic generation of ultrasound observed in V3Si by Testardi in terms of the interaction of the input shear wave with a dynamical strain induced by the low-temperature structural phase transition. We use the independent-chain model for the d electrons, and expand the free energy in powers of the total strain. The second-harmonic amplitude obtained by assuming a deviation from cubic symmetry arising from a homogeneous static strain is calculated to be too small to explain the experimental result.
A generalized model of multiple trapping from a band of extended or localized states is used to s... more A generalized model of multiple trapping from a band of extended or localized states is used to study timedependent charge transport in amorphous solids. The model differs from a conventional multiple-trapping model by including a distribution of trap release rates for a constant trap energy. An extensive analysis of transient photocurrent experiments on a-Se is carried out to determine the transport parameters for this case. It is found that a small number of parameters can be used to analyze the experimental results over a wide range of temperature and sample thickness. The results of the analysis are interpreted in terms of trapcontrolled hopping, which is a special case of the generalized multiple-trapping model. The asymptotic value of the theoretical photocurrent transient is obtained for the multiple-trapping model, and the results of Scher and Montroll are recovered for the case of extreme or anomalous dispersion, which occurs for a-Se at low temperature (T~=140 K). The density of trapping sites is estimated, and the difficulties associated with considering a continuous distribution of trap release rates are discussed. It is concluded that the generalized multiple-trapping model, defined by simple first-order rate equations, is capable of describing detailed shapes of photocurrent transients, including dispersive and nondispersive charge transport.
A model of multiple trapping from a band of transport states is shown to be equivalent to the con... more A model of multiple trapping from a band of transport states is shown to be equivalent to the continuum limit of the continuous-time-random-walk description of anomalous dispersion developed by Scher and Montroll and the waiting-time distribution function psi(t) is expressed in terms of the parameters of the multiple-trapping model. Calculations of psi(t) as a function of temperature are presented for
We present a high-field biased reptation model of gel electrophoresis. It is predicted that durin... more We present a high-field biased reptation model of gel electrophoresis. It is predicted that during their migration, DNA fragments can get trapped for long periods of time in near-zero-velocity, looplike compact conformations. As a consequence, the electrophoretic mobility of DNA is found to be a nonmonotonic function of the fragment size. We present experimental results showing this unique and unexpected consequence of anomalous dispersion due to DNA self-trapping in compact states.
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