Matching cutsets in graphs

Let G = (V,E) be an undirected graph. A subset F of E is a matching cutset of G if no two edges of F are incident with the same point, and G-F has more components than G. Chv?atal [2] proved that it is NP-complete to recognize graphs with a matching cutset even if the input is restricted to graphs with maximum degree 4. We prove the following: (a) Every connected graph with maximum degree ?3 and on more than 7 points has a matching cutset. (In particular, there are precisely two connected cubic graphs without a matching cutset). (b) Line graphs with a matching cutset can be recognized in O(|E|) time. (c) Graphs without a chordless circuit of length 5 or more that have a matching cutset can be recognized in O(|V||E|³) time.     

Cerium(IV) ammonium nitrate (CAN)-mediated sulfonylation of styrenes: some interesting observations

Sulfonyl radicals generated by the oxidation of sodium arylsulfinates with cerium(IV) ammonium nitrate (CAN) undergo addition reaction with styrenes to give the sulfonylated products in good yields.     

The imbedded state space approach to reducing dimensionality in dynamic programs of higher dimensions

By exploiting discontinuity properties of the maximal convolution it is possible to drastically reduce dimensionality in finite dynamic programs. In fact, we show how the search over the usual M-dimensional state space can be reduced to a one-dimensional search over an imbedded state space. The versatility of our approach is illustrated on a number of example problems.     

Magnetic resonance imaging of electroconvection in a polar organic solvent

Molecular motion in the polar organic solvent nitrobenzene induced by an electric field is studied by magnetic resonance imaging. Rf pulse sequences that correlate images obtained at two different times under conditions of both continuous and pulsed electric fields are introduced. The resultant image correlation spectra indicate that the time scale of motion in a 9.6 kV/cm electric field is tens of milliseconds. Comparison of the results to an analytic solution for the Fokker-Planck probability function for one-dimensional bounded diffusion yields an electric field dependent effective diffusion coefficient for perdeuterated nitrobenzene of D = 1.08 x 10(-5) cm(2)/s + (3.33 x 10(-3) cm(4)/kV(2)s) E(2) at room temperature. Characteristics of this electroconvection and its consequences for combining multidimensional nuclear magnetic resonance with electrical orientation are also discussed.     

Critical petermann K factor for intensity noise squeezing

We investigate the impact of the Petermann-excess-noise factor K>/=1 on the possibility of intensity noise squeezing of laser light below the standard quantum limit. Using an N-mode model, we show that squeezing is limited to a floor level of 2(K-1) times the shot noise limit. Thus, even a modest Petermann factor significantly impedes squeezing, which becomes impossible when K>/=1.5. This appears as a serious limitation for obtaining sub-shot-noise light from practical semiconductor lasers. We present experimental evidence for our theory.     

Photo‐ and pH‐Responsive Polycarbonate Block Copolymer Prodrug Nanomicelles for Controlled Release of Doxorubicin

Photo/pH dual‐responsive amphiphilic diblock copolymers with alkyne functionalized pendant o‐nitrobenzyl ester group are synthesized using poly(ethylene glycol) as a macroinitiator. The pendant alkynes are functionalized as aldehyde groups by the azide‐alkyne Huisgen cycloaddition. The anticancer drug doxorubicin (DOX) molecules are then covalently conjugated through acid‐sensitive Schiff‐base linkage. The resultant prodrug copolymers self‐assemble into nanomicelles in aqueous solution. The prodrug nanomicelles have a well‐defined morphology with an average size of 20–40 nm. The dual‐stimuli are applied individually or simultaneously to study the release behavior of DOX. Under UV light irradiation, nanomicelles are disassembled due to the ONB ester photocleavage. The light‐controlled DOX release behavior is demonstrated using fluorescence spectroscopy. Due to the pH‐sensitive imine linkage the DOX molecules are released rapidly from the nanomicelles at the acidic pH of 5.0, whereas only minimal amount of DOX molecules is released at the pH of 7.4. The DOX release rate is tunable by applying the dual‐stimuli simultaneously. In vitro studies against colon cancer cells demonstrate that the nanomicelles show the efficient cellular uptake and the intracellular DOX release, indicating that the newly designed copolymers with dual‐stimuli‐response have significant potential applications as a smart nanomedicine against cancer.     

Using low frequency full bottle diamagnetic screening to study collectible wine

A low frequency ν < 30 MHz spectrometer capable of noninvasively and nondestructively screening the diamagnetic properties of full intact bottles of wine is described, and along with principal component analysis, used to compare and contrast sealed bottles of wine. The sensitivity of this approach to various ionic and molecular wine solutes is established by analyzing standard solutions. The successful application of this full bottle method to a library of collectible wine is discussed and suggests that the method can be used to identify counterfeit wine without violating the bottle.     

Supercycled SW(f)-TPPM sequence for heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance

The performance of a supercycled SW(f)-TPPM sequence for heteronuclear dipolar decoupling in solid-state NMR is analyzed here. The decoupling performance of this sequence with respect to experimental parameters, such as, the phase angle, proton offset and MAS frequency is studied. A comparison is made with two other commonly used decoupling schemes in solid-state NMR namely, SPINAL-64 and SW(f)-TPPM, on a sample of U-13C-labeled tyrosine. Our results show that supercycled SW(f)-TPPM performs better than the former sequences. Also, numerical spin dynamics studies are presented which support the experimentally observed efficiency in the decoupling.     

Density Functional Theory Guided Investigation of Ligand-Induced Neptunyl-Neptunyl Interactions

Actinyl-actinyl interactions are particularly prevalent for the pentavalent neptunyl cation (Np(V)O₂)⁺ where these interactions appear either as a T - or D -shape (diamond-shape). T -shaped interactions have been previously identified in high concentration Np(V) solutions containing simple anions (NO₃⁻, ClO₄⁻, Cl⁻) whereas D -shaped have only been isolated in the solid-state in the presence of carboxylate ligands. In this study, Density Functional Theory (DFT) calculations were paired with Raman spectroscopy to evaluate the formation of D -shaped interactions in the presence of aliphatic (R=H (formate), CH₃ (acetate), CH₂CH₃ (propionate)) and aromatic (R=C₆H₅ (benzoate), C₆H₄OH (4-hydroxybenzoate), C₅H₄N (isonicotinate)) carboxylate ligands. DFT studies indicate that the ΔG to form hydrated T - and D -shaped forms are not spontaneous but become so with the addition of the carboxylate ligands. Raman spectra of the Np(V) carboxylate solutions contained vibrational modes associated with the D -shaped interactions, but spectral changes observed over time indicate a dynamic system. Crystallization experiments from the Np(V) carboxylate systems confirmed the presence of D- shaped dimers for the aromatic carboxylates, suggesting that the choice of the anion in solution favors actinyl-actinyl interactions even at low concentrations (≤20 mM) of Np(V).