On the analytic continuation of the critical line

We perform a numerical study of the systematic effects involved in the determination of the critical line at real baryon chemical potential by analytic continuation from results obtained at imaginary chemical potentials. We present results obtained in a theory free of the sign problem, three-color QCD with finite isospin chemical potential, and comment on general features which could be relevant also to the continuation of the critical line in real QCD at finite baryon density.Comment: 7 pages, 3 figures, Contribution to The XXVII International Symposium on Lattice Field Theory, Beijing, July 25-31, 200

Analytic continuation of the critical line: suggestions for QCD

We perform a numerical study of the systematic effects involved in the determination of the critical line at real baryonic chemical potential by analytic continuation from results obtained at imaginary chemical potentials. We present results obtained in theories free of the sign problem, such as two-color QCD with finite baryonic density and three-color QCD with finite isospin chemical potential, and comment on general features which could be relevant also to the continuation of the critical line in real QCD at finite baryonic density.Comment: 12 pages, 13 figures, 7 tables (revised version accepted by Phys. Rev. D80, 034501(2009)

Fabrication of elastomeric nanofluidic devices for manipulation of long DNA molecules

We propose a method for the separation of long DNA molecules, based on elastomeric nanochannels with tunable cross section. These nanoconfinement structures can be used to stretch DNA molecules and lower their conformational entropy. The sieving mechanism of entropic recoil, proposed by Cabodi et al. [1], will be implemented using an array of elastomeric nanocheannels. Structures of various dimensions are fabricated taking advantage of replica molding techniques, starting from Focused Ion Beam (FIB) patterned silicon substrates. Poly(dimethylsiloxane) (PDMS) and hard-PDMS [2] are used to replicate the features on the silicon mold. After plasma oxidation the nanochannels are sealed using a glass cover slip. A piezoelectric system will be integrated on the device in order to exploit the elastomeric propertis of PDMS, reversibly deform the nanochannels and tune their cross section. This system will allow a dynamic variation of the confinement conditions affecting molecules mobility inside the nanochannels. \ua9 Institute for Computer Science, Social-Informatics and Telecommunications Engineering 2009

Conformations of DNA in Triangular Nanochannels

Despite the widespread use of triangular nanochannels for the manipulation and analysis of DNA, studies on the confining effects induced by these nanofluidic structures on the molecules are still absent. Here, we perform coarse-grained Monte Carlo simulations to study the conformations of DNA in nanochannels. The influence of the shape of the nanochannel cross section is examined by comparing the elongation of molecules in triangular, rectangular, and square channels. Furthermore, the conformation of \u3bb-DNA under weak confinement is studied both computationally and experimentally. Good agreement between optical measurements and simulations supports the reliability of the numerical model in predicting the molecule conformation, making it a reliable method to obtain information essential in many applications, such as DNA barcoding

Modulating DNA Translocation by a Controlled Deformation of a PDMS Nanochannel Device

Several strategies have been developed for the control of DNA translocation in nanopores and nanochannels. However, the possibility to reduce the molecule speed is still challenging for applications in the field of single molecule analysis, such as ultra-rapid sequencing. This paper demonstrates the possibility to alter the DNA translocation process through an elastomeric nanochannel device by dynamically changing its cross section. More in detail, nanochannel deformation is induced by a macroscopic mechanical compression of the polymeric device. This nanochannel squeezing allows slowing down the DNA molecule passage inside it. This simple and low cost method is based on the exploitation of the elastomeric nature of the device, can be coupled with different sensing techniques, is applicable in many research fields, such as DNA detection and manipulation, and is promising for further development in sequencing technology

Mechanical squeezing of an elastomeric nanochannel device: numerical simulations and ionic current characterization

Peculiar transport phenomena appear at nanoscale, since surface effects strongly affect the behaviour of fluids. Electrostatic and steric interactions, capillary forces and entropic effects play a key role in the behaviour of fluids and biomolecules. Since these effects strongly depend on the size of the nanofluidic system, a careful characterization of the fluidic environment is necessary. Moreover, the possibility to dynamically modulate the size of nanochannels is very appealing in the field of biomolecule manipulation. Recently, we have developed a lab-onchip made of poly(dimethylsiloxane) (PDMS). This polymeric device is based on a tuneable nanochannel able to dynamically change its dimension in order to fit the application of interest. In fact, a mechanical compression applied on the top of the elastomeric device squeezes the nanochannel, reducing the channel cross section and allowing a dynamical optimization of the nanostructures. In this paper, this squeezing process is fully characterized both numerically and experimentally. This analysis provides information on the reduction of the nanochannel dimensions induced by compression as a function of the work of adhesion and of the stiffness of the materials composing the device. Moreover, calculations demonstrate the possibility to predict the change of the nanochannel size and shape induced by the compression. The possibility to dynamically tune the channel size opens up new opportunities in biomolecular sensing or sieving and in the study of new hydrodynamics effects

Stretching of DNA confined in nanochannels with charged walls

There is currently a growing interest in control of stretching of DNA inside nanoconfined regions due to the possibility to analyze and manipulate single biomolecules for applications such as DNA mapping and barcoding, which are based on stretching the DNA in a linear fashion. In the present work, we couple Finite Element Methods and Monte Carlo simulations in order to study the conformation of DNA molecules confined in nanofluidic channels with neutral and charged walls. We find that the electrostatic forces become more and more important when lowering the ionic strength of the solution. The influence of the nanochannel cross section geometry is also studied by evaluating the DNA elongation in square, rectangular, and triangular channels. We demonstrate that coupling electrostatically interacting walls with a triangular geometry is an efficient way to stretch DNA molecules at the scale of hundreds of nanometers. The paper reports experimental observations of \u3bb-DNA molecules in poly(dimethylsiloxane) nanochannels filled with solutions of different ionic strength. The results are in good agreement with the theoretical predictions, confirming the crucial role of the electrostatic repulsion of the constraining walls on the molecule stretching