Development and multiplexed control of latching pneumatic valves using microfluidic logical structures

Novel latching microfluidic valve structures are developed, characterized, and controlled independently using an on-chip pneumatic demultiplexer. These structures are based on pneumatic monolithic membrane valves and depend upon their normally-closed nature. Latching valves consisting of both three- and four-valve circuits are demonstrated. Vacuum or pressure pulses as short as 120 ms are adequate to hold these latching valves open or closed for several minutes. In addition, an on-chip demultiplexer is demonstrated that requires only n pneumatic inputs to control 2(n-1) independent latching valves. These structures can reduce the size, power consumption, and cost of microfluidic analysis devices by decreasing the number of off-chip controllers. Since these valve assemblies can form the standard logic gates familiar in electronic circuit design, they should be useful in developing complex pneumatic circuits.     

Hydrogen bonds: relation between lengths and electron densities at bond critical points

The electron densities for a number of molecules with either inter- or intra-molecular hydrogen bonds are analyzed using the theory of atoms in molecules. The levels of theory used include second order M?ller Plesset and density functional methods. The molecules investigated ranges from small molecules/ions to an alanine octa-peptide. The hydrogen bond length, BL, varies from 1.15 to 3.01 ? and ρ_b, the electron density at the bond critical point, spans the interval 0.0033 to 0.168 (au). We find that the data may be represented by the relation ), where A and B are empirical constants. The relation is compared to a similar relation derived from solid state experiments. Since the ρ_b values are related to the bond strengths, this general relationship may useful for hydrogen bond studies.     

Structure and stability of networked metallofullerenes of the transition metals

A DFT investigation of substitutionally doped fullerenes MC59 of second- and third-row transition metals shows that their stability increases toward the right-hand side of the d-block. Whereas the structural deviation from that of C60 depends on the size of the metal atom, stability is governed by electronic properties of the transition metal atom. A range of MC59 compounds of group 6-8 metals are predicted to have sufficient stability for experimental observation.     

Intramolecular glycosylation under neutral conditions for synthesis of 1,4-linked disaccharides

[structure: see text]. A new method for intramolecular glycosylation, in which the donor and acceptor were linked via a 3,5-dinitrosalicylic acid derivative, was developed. Simply dissolving the tethered glycoside in CH3NO2 and warming to 40-60 degrees C led to formation of 1,4-linked disaccharides under neutral, hence, exceptionally mild, conditions.     

Saddlepoint expansions for sums of Markov dependent variables on a continuous state space

Summary Based on the conjugate kernel studied in Iscoe et al. (1985) we derive saddlepoint expansions for either the density or distribution function of a sumf(X ₁)+...+f(X _n ), where theX _i 's constitute a Markov chain. The chain is assumed to satisfy a strong recurrence condition which makes the results here very similar to the classical results for i.i.d. variables. In particular we establish also conditions under which the expansions hold uniformly over the range of the saddlepoint. Expansions are also derived for sums of the formf(X ₁,X ₀)+f(X ₂,X ₁)+...+f(X _n ,X _n–1) although the uniformity result just mentioned does not generalize.