Coherence transfer between spy nuclei and nitrogen-14 in solids

Coherence transfer from 'spy nuclei' such as (1)H or (13)C (S=1/2) was used to excite single- or double-quantum coherences of (14)N nuclei (I=1) while the S spins were aligned along the static field, in the manner of heteronuclear single-quantum correlation (HSQC) spectroscopy. For samples spinning at the magic angle, coherence transfer can be achieved through a combination of scalar couplings J(I,S) and second-order quadrupole-dipole cross-terms, also known as residual dipolar splittings (RDS). The second-order quadrupolar powder patterns in the two-dimensional spectra allow one to determine the quadrupolar parameters of (14)N in amino acids.     

A cost effectiveness approach for determining the purchasing and operating policies of a combined meteorological data gathering system

The model we present in this paper was developed to solve a meteorological equipment operations problem involving the purchase and operation of specialized aircraft for the gathering of meteorological data. This aircraft system (termed ‘System B’) will be used to supplement an existing system using weather balloons (termed ‘System A’). The problem involves decision making based upon bi-criterion objectives. These objectives usually occur in the presence of one or both of the following factors: (a) The outputs of the systems have more than one attribute and (b) the outputs may be measured under varying environmental situations. The specific type of problem treated here involves a two objective situation arising from the latter factor. It was found out that due to the nature of this problem it was difficult to implement a utility approach to generate a solution. Therefore, a cost-effectiveness approach is presented to demonstrate a technique for finding the trade-off function between objectives for varying levels of systems and operating characteristics. This approach is similar to that of Subramanian and Ravichandran [8] where a complex two-unit electronic system was studied.     

Deterministic mode alternation,giant pulses and chaos in a bidirectional CO2 ring laser

A CO₂ ring laser with a single longitudinal mode propagating in each direction shows a variety of stable, periodic, and aperiodic phenomena depending on gas pressure, cavity detuning and relative excitation. Three distinct low frequency time scales for dynamical behavior are observed and are explained by numerical solutions of an appropriate model.     

Fusoxysporone - a new type of diterpene from fusarium oxysporum

A novel diterpene, fusoxysporone 1, was isolated from liquid cultures of the fungus Fusarium oxysporum IMB FO 18;2. The skeleton of 1 - related to the viscidane type - is described for the first time and named fusoxysporane. Additionally, fusaric acid and dehydrofusaric acid were identified in extracts of the culture medium.     

Liquid phase kinetic study of the formation and decomposition of methylsulfonyl and cyclohexylsulfonyl radicals in the cyclohexane–MeSO2C1-SO2 System at 150°

The thermally and radiolytically induced chain decomposition of methanesulfonyl chloride (MeSO₂Cl) in liquid cyclohexane (RH) was studied at 150°C. The main products, chlorocyclohexane, sulfur dioxide, and methane, are formed in almost equal yields, and a relatively small amount of methyl chloride is also observed. The formation and addition of SO₂ strongly inhibit the chain decomposition reaction. By kinetic analysis it is shown that the formation of the main products can be explained only in terms of a mechanism that postulates the decomposition of MeSO₂, and that the alternative mechanism of methane and SO₂ formation via the methanesulfinic acid is inconsistent with the kinetic behavior of the system. For the reactions Me + MeSO₂Cl → MeCl + MeSO₂(2b), Me + RH → MeH + R (4), and Me + CCl₄ → MeCCl₄ → MeCl + CCl₃ (15b) the following rate constant ratios are determined; k_2b/k₄=2.17±0.20 and k_2b/k_15b=2.63±0.52. For the reactions R + MeSO₂Cl → RCl + MeSO₂(2a) and R + CCl₄ → RCl + CCl₃ (15a), k_2a/k_15a is equal to 1.55±0.05. In addition the equilibrium constant K₇ for the reaction R + SO₂ ? RSO₂ (7) is estimated as being equal to (9.4±3) × 10³ mole/l.     

Attainable sets for linear stochastic control systems

Let x_t^u(w) be the solution process of the n-dimensional stochastic differential equation dx_t^u = [A(t)x_t^u + B(t) u(t)] dt + C(t) dW_t, where A(t), B(t), C(t) are matrix functions, W_t is a n-dimensional Brownian motion and u is an admissable control function. For fixed ? ? 0 and 1 ? δ ? 0, we say that x?Rⁿ is (?, δ) attainable if there exists an admissable control u such that P{x_t^u?S_?(x)} ? δ, where S_?(x) is the closed ?-ball in Rⁿ centered at x. The set of all (?, δ) attainable points is denoted by $\text{A}$(t). In this paper, we derive various properties of $\text{A}$(t) in terms of K(t), the attainable set of the deterministic control system $\text{x}\text{?}\text{= A(t)x + B(t)u}$. As well a stochastic bang-bang principle is established and three examples presented.     

The molecular structure of N-benzylidene-aniline

The molecular structure of N-benzylidene-aniline has been studied experimentally by the gas electron diffraction method, and also by molecular mechanics calculations. Both approaches gave the same results for the most stable conformer of the free molecule. The phenyl ring bonded to the carbon end of the CN bond was found to be coplanar with this bond, while the other phenyl ring was extensively (ca. 52°) rotated about the NΦ bond.     

The effect of temperature on formaldehyde photooxidation in oxygen-lean atmospheres

The photooxidation of formaldehyde in CH₂O? O₂, oxygen-lean mixtures was studied in the temperature range 298–378 K. H₂ and CO formation and the loss of O₂ proceed by a chain mechanism, which between 328 and 378 K follows the previously suggested kinetics [1] with one modification. The reaction HO₂ + CH₂O ? HO₂CH₂O (5) is now assumed to be reversible and ΔH is estimated to be between 14 and 19 kcal/mol. The relative yields of the chain formed H₂ and CO and of the consumed O₂ remained constant over the entire temperature range indicating that the relative efficiencies of the HO reactions: HO + CH₂O → H₂O HCO? (7), HO + CH₂O → H₂O + HCO (8) and HO + CH₂O → HOCH₂O (9) are temperature independent.