Clathrate and inclusion compounds: Part V. An infrared and Raman study of the decomposition of the Hofmann aniline clathrates M(NH3)2Ni(CN)4.2C6H5NH2 {M = Cd(II) and Ni(II)}

The time-dependent changes which are observed in the infrared and Raman spectra of samples of the two Hofmann aniline clathrates M(NH₃)₂Ni(CN)₄.an₂ {M = Cd(II), Ni(II), an = C₆H₅NH₂} indicate the occurrence of a solid state ligand replacement reaction in which the aniline guest molecule replaces the coordinated ammonia to give Man₂Ni(CN)₄ as the final product. The rate of replacement is greater for the cadmium than for the nickel clathrate, and for both clathrates evacuation of the sample greatly increases the rate of replacement. The Man₂Ni(CN)₄ complexes can themselves act as host lattices forming clathrates containing guest molecules such as aniline.     

Solid phase organic synthesis (SPOS): A novel route to diketopiperazines and diketomorpholines

Summary The solid phase synthesis of libraries containing a 1,3,4,6-tetrasubstituted-2,5-diketo-1,4-piperazine scaffold (DKP) or a 3,4,6-trisubstituted-2,5-diketo-1,4-morpholme scaffold (DKM) from -bromocarboxylic acids and amines is described. Using a design strategy which we refer to as divergent library design, both templates were prepared from a common intermediate. The general utility of this synthetic route in creating novel, non-peptidyl chemical libraries is discussed.     

Observation of optical spring effect in a microtoroidal optomechanical resonator

We present experimental evidence of the optical spring effect in a silica microtoroid resonator. The variation of the measured mechanical resonant frequency as a function of optical power, optical coupling, and optical detuning is in very good agreement with a model for radiation-pressure-induced rigidity in a silica microtoroid.     

Absolute quantification of genetically modified MON810 maize (Zea mays L.) by digital polymerase chain reaction

Quantitative analysis of genetically modified (GM) foods requires estimation of the amount of the transgenic event relative to an endogenous gene. Regulatory authorities in the European Union (EU) have defined the labelling threshold for GM food on the copy number ratio between the transgenic event and an endogenous gene. Real-time polymerase chain reaction (PCR) is currently being used for quantification of GM organisms (GMOs). Limitations in real-time PCR applications to detect very low number of DNA targets has led to new developments such as the digital PCR (dPCR) which allows accurate measurement of DNA copies without the need for a reference calibrator. In this paper, the amount of maize MON810 and hmg copies present in a DNA extract from seed powders certified for their mass content and for their copy number ratio was measured by dPCR. The ratio of these absolute copy numbers determined by dPCR was found to be identical to the ratios measured by real-time quantitative PCR (qPCR) using a plasmid DNA calibrator. These results indicate that both methods could be applied to determine the copy number ratio in MON810. The reported values were in agreement with estimations from a model elaborated to convert mass fractions into copy number fractions in MON810 varieties. This model was challenged on two MON810 varieties used for the production of MON810 certified reference materials (CRMs) which differ in the parental origin of the introduced GM trait. We conclude that dPCR has a high metrological quality and can be used for certifying GM CRMs in terms of DNA copy number ratio.     

Simultaneous acquisition of multiple orders of intermolecular multiple-quantum coherence images

Recent studies have demonstrated the ability to detect images based on intermolecular multiple-quantum coherences (iMQCs) that correspond to flipping of two or more separated spins simultaneously, as opposed to conventional magnetic resonance where only one spin is flipped at a time. Until now, iMQC imaging has only acquired one coherence signal per pulse sequence. Here we report a new sequence that successfully detects five orders of coherence (2, 1, 0, −1, and −2-quantum coherence images) in one pulse sequence, with each signal having its full intensity. The simultaneous acquisition highlights substantial contrast differences between conventional and iMQC images, and between the different types of iMQC images.     

Heavy water detection using ultra-high-Q microcavities

Ultra-high-Q optical microcavities (Q>10(7)) provide one method for distinguishing chemically similar species. Resonators immersed in H(2)O have lower quality factors than those immersed in D(2)O due to the difference in optical absorption. This difference can be used to create a D(2)O detector. This effect is most noticeable at 1,300 nm, where the Q(H(2)O) is 106 and the Q(D(2)O) is 107. By monitoring Q, concentrations of 0.0001% [1 part in 106 per volume] of D(2)O in H(2)O have been detected. This sensitivity represents an order of magnitude improvement over previous techniques. Reversible detection was also demonstrated by cyclic introduction and flushing of D(2)O.     

Temporal behavior of radiation-pressure-induced vibrations of an optical microcavity phonon mode

We analyze experimentally and theoretically mechanical oscillation within an optical cavity stimulated by the pressure of circulating optical radiation. The resulting radio frequency cavity vibrations (phonon mode) cause modulation of the incident, continuous-wave (cw) input pump beam. Furthermore, with increasing cw pump power, an evolution from sinusoidal modulation to random oscillations is observed in the pump power coupled from the resonator. The temporal evolution with pump power is studied, and agreement was found with theory. In addition to applications in quantum optomechanics, the present work suggests that radiation-pressure-induced effects can establish a practical limit for the miniaturization of optical silica microcavities.     

Forcing Function Effects on Nonlinear Trajectories: Identifying Very Local Brain Dynamics

Effects of imposing a sinusoidal acoustic and visual forcing function at various frequencies onto an EEG process are examined in terms of various indices of the nonlinear dynamics. Conjoint use of four methods of data analysis; Lyapunov exponents, the entropic analogue of the Schwarzian derivative, surrogate distributions, and higher-order kernel analyses in the time domain, is illustrated. Local epochs with unstable dynamics are identifed on very short series.