diffi culty in the generation of core-shell NPs with a lipid shell containing various amounts of water, which governs the rigidity of the NPs; larger amounts of interfacial water would result in more fl exible NPs. [13][14][15] Microfl uidic platforms can generate lipid-polymer hybrid NPs via rapid reaction and precise manipulation of fl uids inside microchannels; [16][17][18][19][20] however, the fabrication of hybrid NPs with varying water content has not been achieved by microfl uidics. Here, we develop a two-stage microfl uidic platform that can assemble core-shell poly(lactic-co -glycolic acid) (PLGA)-lipid NPs in a single-step. [ 16,21 ] Lipid-covered PLGA NPs or liposomes that have the same size and surface properties, but varying rigidity as a result of tuning the interfacial water layer, can be realized using the same microchip. It enables us to explore how the rigidity of NPs differentially regulates the cellular uptake and to elucidate the intrinsic mechanism. It also allows the treatment of various diseases through the use of specifi c particles.Particle rigidity is tuned by varying the amounts of interfacial water between the PLGA core and lipid shell of the hybrid NPs; this is achieved by altering the injection order of the PLGA and lipid-poly(ethylene glycol) (PEG) organic solutions in the microfl uidic chip. The microfl uidic device shown in Scheme 1 consists of two stages: 1) The fi rst stage comprises three inlets and a straight synthesis microchannel; 2) The second stage is composed of one centered inlet and a spiral mixing channel (see Supporting Information (SI), Figure S1 for more details). We synthesized particles of varying water content and rigidity using the same chip but different order of the introducing reagents. In mode 1, the fi rst stage is used for generating PLGA NPs through interfacial precipitation, while the second stage forms lipid-coated NPs as a result of hydrophobic attraction between the lipid tail and PLGA (P-L NPs; Scheme 1 A, Figure S2 (SI)). In mode 2, we change the injection order by introducing the lipid solution at the fi rst stage and the PLGA solution at the second stage. In this way, lipids form into a liposome in aqueous solution at the fi rst stage, followed by re-assembly onto the surface of PLGA NPs at the second stage through effective mixing (P-W-L NPs; Scheme 1 B, Figure S2 (SI)). The throughput of NPs by a single chip is 41 mL h −1 (≈8 mg h −1 for P-W-L NPs, and ≈6.5 mg h −1 for P-L NPs). For both mode 1 and mode 2, transmission electron microscopy (TEM) images ( Figure 1 A; Figure S2, SI) show complete lipid coverage on the surface of PLGA NPs. The different injection order of the solutions may result in the presence of interfacial water between the PLGA core and lipid shell of the P-W-L NPs (mode 2) but not in P-L NPs (mode 1), which is confi rmed by cryogenic TEM (cryo-TEM Figure 1 B; see also SI). For the P-L NPs, the lipid shell is tightly attached to the PLGA core, while for the P-W-L Even though much research has shown that nanoparticles (NPs) ca...

Abstract-Network operators control the flow of traffic through their networks by adapting the configuration of the underlying routing protocols. For example, they tune the integer link weights that interior gateway protocols like OSPF and IS-IS use to compute shortest paths. The resulting optimization problem-to find the best link weights for a given topology and traffic matrix-is computationally intractable even for the simplest objective functions, forcing the use of local-search techniques. The optimization problem is difficult because these protocols split traffic evenly along shortest paths, with no ability to adjust the splitting percentages or direct traffic on other paths. In this paper, we propose an extension to these protocols, called Distributed Exponentially-weighted Flow SpliTting (DEFT), where the routers can direct traffic on non-shortest paths, with an exponential penalty on longer paths. DEFT leads not only to a simpler optimization problem, but also to weight settings that provably perform always better than OSPF and IS-IS. In the optimization problem we present, both link weights and flows of traffic are integrated as optimization variables into the formulation and jointly solved by a two-stage iterative method. Our novel formulation leads to a much more efficient way to identify good link weights than the local-search heuristics used for OSPF and IS-IS today. DEFT retains the simplicity of having routers compute paths based on configurable link weights, while approaching the performance of more complex routing protocols that can split traffic arbitrarily over any paths.

The ion distribution and electroosmotic flow of sodium chlorine solutions confined in cylindrical nanotubes with high surface charge densities are studied with molecular dynamics (MD). To obtain a more practical physical model for electroosmotic driven flow in a nanoscale tube, the MD simulation process consists of two steps. The first step is used to equilibrate the system and to obtain a more realistic ion distribution in the solution under different surface charge densities. Then, an external electric field is acted to drive the liquids. The simulation results indicate that with the increase of the surface charge density, both the thickness of the electric double layer and the peak height of the counterion density increase. However, the phenomenon of charge inversion does not occur even as the surface charge density increases to -0.34 C/m2, which is rather difficult to reach for real materials in practical situations. This simulation result confirms the recent experimental observation that monovalent ions of sufficiently high concentrations can reduce or even cancel the charge inversion occurred in the case of multivalent ions [F. H. J. van der Heyden et al. Phys. Rev. Lett. 2006, 96, 224502].

Abstract-This paper settles an open question with a positive answer: optimal traffic engineering (or optimal multi-commodity flow) can be realized using just link-state routing protocols with hop-by-hop forwarding. Today's typical versions of these protocols, OSPF and IS-IS, split traffic evenly over shortest paths based on link weights. However, optimizing the link weights for OSPF/IS-IS to the offered traffic is a well-known NP-hard problem, and even the best setting of the weights can deviate significantly from an optimal distribution of the traffic. In this paper, we propose a new link-state routing protocol, PEFT, that splits traffic over multiple paths with an exponential penalty on longer paths. Unlike its predecessor, DEFT [1], our new protocol provably achieves optimal traffic engineering while retaining the simplicity of hop-by-hop forwarding. The new protocol also leads to a significant reduction in the time needed to compute the best link weights. Both the protocol and the computational methods are developed in a conceptual framework, called Network Entropy Maximization, which is used to identify the traffic distributions that are not only optimal but also realizable by link-state routing.

We report on experimental studies of the average phonon mean free path in the c-axis direction of graphite. Through systematically measuring the cross-plane thermal conductivity of thin graphite flakes with thickness ranging from 24 nm to 714 nm via a differential three omega method, we demonstrate that the average phonon mean free path in the c-axis direction of graphite is around 200 nm at room temperature, much larger than the commonly believed value of just a few nanometers. This study provides direct experimental evidence for the recently projected very long phonon mean free path along the c-axis of graphite.

Abstract-This paper settles an open question with a positive answer: optimal traffic engineering (or optimal multi-commodity flow) can be realized using just link-state routing protocols with hop-by-hop forwarding. Today's typical versions of these protocols, OSPF and IS-IS, split traffic evenly over shortest paths based on link weights. However, optimizing the link weights for OSPF/IS-IS to the offered traffic is a well-known NP-hard problem, and even the best setting of the weights can deviate significantly from an optimal distribution of the traffic. In this paper, we propose a new link-state routing protocol, PEFT, that splits traffic over multiple paths with an exponential penalty on longer paths. Unlike its predecessor, DEFT [1], our new protocol provably achieves optimal traffic engineering while retaining the simplicity of hop-by-hop forwarding. The new protocol also leads to a significant reduction in the time needed to compute the best link weights. Both the protocol and the computational methods are developed in a conceptual framework, called Network Entropy Maximization, which is used to identify the traffic distributions that are not only optimal but also realizable by link-state routing.

A novel technique is reported for counting the number and the percentage of CD4+ T lymphocytes in a polydimethylsiloxane (PDMS) microchannel. This system integrates optical fluorescence detection with resistive pulse sensing enhanced by a metal oxide semiconductor field effect transistor (MOSFET). The MOSFET signal indicates the total number of the cells passing through the detection channel, while the concurrent fluorescence signal records only the number of cells tagged with a specific fluorescent dye. The absolute count of the CD4+ T cells and its percentage to the total lymphocytes can be analyzed by combining the two counting results, which shows comparable accuracy to those from the commercial flow cytometer. The fastest observed counting rate for a single-channel microchip is 8.5 cells per second. This technique is highly promising as it could greatly reduce the cost for HIV diagnosis and treatment and make it accessible to resource-poor developing countries.

The thermal transport properties of metal–organic frameworks (MOFs) developed for molecular storage and catalytic separations play an important role in adsorption or catalysis processes but are rarely reported. We calculate the anisotropic thermal conductivities (κ) of water-stable Zn-MOF-74 with the Boltzmann transport equation and the density-functional-based tight-binding (DFTB) method, which allows for a sufficiently large number of atoms in the simulations without much compromise on accuracy. We find an anisotropic κ of 0.44 and 0.68 W/m·K at 300 K, across and along the pore directions, with acoustic contributions of 8% and 30%, respectively. These unusually low acoustic contributions are explained by the rattling-like behavior of phonons with large vibrational amplitude, low group velocity, and large scattering rate, which are caused by the unique 1-D tubing bundle structure. On the other hand, the cylindrical pores enable larger phonon speed and higher directional structural rigidity along the pore direction, leading to a higher κ. The frequency-accumulated, directional κ is explained using the spectral analysis and correlated to the structure characteristics.