Displacement reactions of 2,3-dichloro-6-nitroquinoxaline: synthesis of s-triazolo[3,4-a]quinoxaline

2,3-Dichloro-6-nitroquinoxaline (1) undergoes displacement reactions with 1-methylpiperazine in the hot to give the bis-derivative (2) and at 30°C selectively at position-2 to afford the mono-derivative (3). Structure-proof for the latter involves transformation of 3 through hydrazine derivative (4). to the traizoloquinoxaline (5) and its 1-phenyl derivative (6) and comparison of the chemical shifts of protons at C-9 in the pair

Percolating through networks of random thresholds: Finite temperature electron tunneling in metal nanocrystal arrays

We investigate how temperature affects transport through large networks of nonlinear conductances with distributed thresholds. In monolayers of weakly-coupled gold nanocrystals, quenched charge disorder produces a range of local thresholds for the onset of electron tunneling. Our measurements delineate two regimes separated by a cross-over temperature $T^*$. Up to $T^*$ the nonlinear zero-temperature shape of the current-voltage curves survives, but with a threshold voltage for conduction that decreases linearly with temperature. Above $T^*$ the threshold vanishes and the low-bias conductance increases rapidly with temperature. We develop a model that accounts for these findings and predicts $T^*$.Comment: 5 pages including 3 figures; replaced 3/30/04: minor changes; final versio

Radiation and String Atmosphere for Relativistic Stars

We extend the Vaidya radiating metric to include both a radiation field and a string fluid. Assuming diffusive transport for the string fluid, we find new analytic solutions of Einstein's field equations. Our new solutions represent an extention of Xanthopoulos superposition.Comment: To appear in Phys. Rev. D, Rapid Communicatio

Non Markovian Quantum Repeated Interactions and Measurements

A non-Markovian model of quantum repeated interactions between a small quantum system and an infinite chain of quantum systems is presented. By adapting and applying usual pro jection operator techniques in this context, discrete versions of the integro-differential and time-convolutioness Master equations for the reduced system are derived. Next, an intuitive and rigorous description of the indirect quantum measurement principle is developed and a discrete non Markovian stochastic Master equation for the open system is obtained. Finally, the question of unravelling in a particular model of non-Markovian quantum interactions is discussed.Comment: 22 page

Quantum Stochastic Processes: A Case Study

We present a detailed study of a simple quantum stochastic process, the quantum phase space Brownian motion, which we obtain as the Markovian limit of a simple model of open quantum system. We show that this physical description of the process allows us to specify and to construct the dilation of the quantum dynamical maps, including conditional quantum expectations. The quantum phase space Brownian motion possesses many properties similar to that of the classical Brownian motion, notably its increments are independent and identically distributed. Possible applications to dissipative phenomena in the quantum Hall effect are suggested.Comment: 35 pages, 1 figure

Radio continuum properties of young planetary nebulae

We have selected a small sample of post-AGB stars in transition towards the planetary nebula and present new Very Large Array multi-frequency high-angular resolution radio observations of them. The multi-frequency data are used to create and model the targets' radio continuum spectra, proving that these stars started their evolution as very young planetary nebulae. In the optically thin range, the slopes are compatible with the expected spectral index (-0.1). Two targets (IRAS 18062+2410 and 17423-1755) seem to be optically thick even at high frequency, as observed in a handful of other post-AGB stars in the literature, while a third one (IRAS 20462+3416) shows a possible contribution from cold dust. In IRAS 18062+2410, where we have three observations spanning a period of four years, we detect an increase in its flux density, similar to that observed in CRL 618. High-angular resolution imaging shows bipolar structures that may be due to circumstellar tori, although a different hypothesis (i.e., jets) could also explain the observations. Further observations and monitoring of these sources will enable us to test the current evolutionary models of planetary nebulae.Comment: 8 pages, 3 figures, accepted for publication in MNRA

Stability, Gain, and Robustness in Quantum Feedback Networks

This paper concerns the problem of stability for quantum feedback networks. We demonstrate in the context of quantum optics how stability of quantum feedback networks can be guaranteed using only simple gain inequalities for network components and algebraic relationships determined by the network. Quantum feedback networks are shown to be stable if the loop gain is less than one-this is an extension of the famous small gain theorem of classical control theory. We illustrate the simplicity and power of the small gain approach with applications to important problems of robust stability and robust stabilization.Comment: 16 page

The Stratonovich formulation of quantum feedback network rules

We express the rules for forming quantum feedback networks using the Stratonovich form of quantum stochastic calculus rather than the Ito, or SLH form. Remarkably the feedback reduction rule implies that we obtain the Schur complement of the matrix of Stratonovich coupling operators where we short out the internal input/output coefficients.Comment: 14 pages, 6 figures (The Stratonovich form of the Series Product added in the revision.

Enabling Markets, Trade and Policies for Enhancing Sorghum Uptake

A number of dynamic changes are taking place in the sorghum economies globally in the last two to three decades both in developed and developing regions where the crop is grown. In Asia, its use as a staple food crop is declining with a shift in consumption towards rice and wheat. Rising per capita incomes, urbanization, change in tastes and preferences are driving this change. However, at the same time, its demand in alternative uses like poultry feed and potable alcohol manufacture is growing. In recent years driven by the greater awareness of the health benefits of sorghum, there is also a growing demand for processed sorghum products particularly in India for ready to use and eat food products mainly in urban areas (from a low base). To sustain the change in the sorghum economies (plate to plough), there is a need to reorient the marketing system by linking farmers to the end users through innovative institutional arrangements. Policies should ensure sorghum competitiveness on farm and directly or indirectly promote its use in food processing and alternative non-food uses. In developed countries and in Latin American countries, sorghum is mainly used as feed but its use is fluctuating and variable depending on its price competitiveness and policies related to trade in feed crops. In the last one to two decades with governments mandating use of renewable fuels for blending with gasoline, sorghum along with maize are being used for ethanol production that has implications for the livestock sector. Policies related to ethanol production will have implication for sorghum production and trade