We report on the efficiency of electrical power generation in individual rectangular nanochannels by means of streaming currents, the pressure-driven transport of counterions in the electrical double layer. Our experimental study as a function of channel height and salt concentration reveals that the highest efficiency occurs when double layers overlap, which corresponds to nanoscale fluidic channels filled with aqueous solutions of low ionic strength. The highest efficiency of approximately 3% was found for a 75 nm high channel, the smallest channel measured. The data are well described by Poisson-Boltzmann theory with an additional electrical conductance of the Stern layer.

We theoretically evaluate the prospect of using electrokinetic phenomena to convert hydrostatic energy to electrical power. An expression is derived for the energy conversion efficiency of a two-terminal fluidic device in terms of its linear electrokinetic response properties. For a slitlike nanochannel of constant surface charge density, we predict that the maximum energy conversion efficiency occurs at low salt concentrations. An analytic expression for the regime of strong double-layer overlap reveals that the efficiency depends only on the ratio of the channel height to the Gouy-Chapman length, and the product of the viscosity and the counterion mobility. We estimate that an electrokinetic energy conversion device could achieve a maximum efficiency of 12% for simple monovalent ions in aqueous solution.

Using laser fluorescence microscopy, we study the shape and dynamics of individual DNA molecules in slitlike nanochannels confined to a fraction of their bulk radius of gyration. With a confinement size spanning 2 orders of magnitude, we observe a transition from the de Gennes regime to the Odijk regime in the scaling of both the radius of gyration and the relaxation time. The radius of gyration and the relaxation time follow the predicted scaling in the de Gennes regime, while, unexpectedly, the relaxation time shows a sharp decrease in the Odijk regime. The radius of gyration remains constant in the Odijk regime. Additionally, we report the first measurements of the effect of confinement on the shape anisotropy. DOI: 10.1103/PhysRevLett.101.108303 PACS numbers: 82.35.Àx, 87.80.Fe A detailed understanding of the static and dynamic properties of DNA in confined environments is essential for the design of devices for single-molecule analysis and manipulation [1,2]. In addition, it provides better insight in natural processes like DNA packaging in viruses [3] and DNA segregation in bacteria [4]. In bulk, DNA molecules form random coils that are sphere shaped on average, with radius of gyration R bulk . Upon confining DNA to a nanochannel, different regimes of confinement can be distinguished. The important length scales are the bulk radius R bulk , the height of the confining channel h, and the persistence length of the molecule a. In the de Gennes regime, where 2a < h < 2R bulk , the molecule still has threedimensional orientational freedom at a short length scale, forming three-dimensional blobs, while at larger scales the molecule is flattened; see Fig. 1(c). The effect of confinement on the diffusion constant in this regime has been investigated optically in slitlike nanochannels [5]. Using the same technique, the extension, diffusion constant, and relaxation time were measured in tubelike confinement [6,7]. When the height of the nanochannel reaches the persistence length (h % 2a), the orientation of the molecule becomes restricted even at the shortest length scales, drastically affecting the response of the molecule to confinement. The onset of this Odijk regime has been reported for tubelike nanochannels [6], while truly two-dimensional polymers were investigated much earlier, by adsorbing them on a lipid membrane [8]. However, an assessment of the radius of gyration of DNA in slitlike confinement, which is crucial for size separation schemes [5,9], has been lacking so far.In this Letter, we present measurements of the radius of gyration and shape anisotropy of DNA confined to slitlike nanochannels varying in height from 33 nm to 1:3 m. Our measurements show three regimes of DNA conformations: compression, elongation, and saturation. At h % 100 nm, we see a strong discontinuity in the scaling of the radius of gyration and the relaxation time, which we interpret as the transition from the de Gennes to the Odijk regime.We studied -phage DNA (48 kb, double-strand), stained with YOYO-1 (Molecular Probes), a...

Background:We analysed the outcomes of 726 cases of primary head and neck cancer patients managed between 1996 and 2008, including those managed in the multidisciplinary clinic or team setting (MDT) and those managed outside of an MDT by individual disciplines (non-MDT) in the same institution.Methods:Data were collected from the Hospital Based Cancer Registry and a database within the Head and Neck Cancer Clinic. Univariable comparisons and multivariable analyses were performed using a logistic regression model. Survival by staging was analysed. Comparisons of management and outcomes were made between MDT and non-MDT patients.Results:395 patients (54%) had been managed in the MDT vs 331 patients (46%) non-MDT. MDT patients were more likely to have advanced disease (likelihood ratio χ2=44.7, P<0.001). Stage IV MDT patients had significantly improved 5-year survival compared with non-MDT patients (hazard ratio=0.69, 95% CI=0.51–0.88, P=0.004) and more synchronous chemotherapy and radiotherapy (P=0.004), and the non-MDT group had more radiotherapy as a single modality (P=0.002).Conclusions:The improved survival of MDT-managed stage IV patients probably represents both the selection of multimodality treatment and chemotherapeutic advances that these patients received in a multidisciplinary team setting by head and neck cancer specialists as opposed to cancer generalists in a non-MDT setting.