Catalytic hydrogenation of o-nitroanisole in a microreactor: Reactor performance and kinetic studies

Hydrogenation of o-nitroanisole to o-anisidine was conducted in a packed-bed microreactor as a model hydrogenation reaction of importance to the pharmaceutical and fine chemicals industries with the aim of investigating the reactor performance and kinetics of the reaction. The effects of different processing conditions viz. hydrogen pressure, o-nitroanisole concentration, temperature, and residence time on the conversion of o-nitroanisole, space-time yield (STY), and selectivity of o-anisidine were studied using 2% Pd/zeolite catalyst. The kinetic study was undertaken in a differential reactor mode keeping the conversion of o-nitroanisole at less than 10%. During the kinetic study, it was observed that the intermediate 2-methoxynitrosobenzene was present in the reactor at low catalyst loading and low conversions because of short residence time in the reactor. Therefore, for the kinetics study, the overall reaction was treated as comprising two separate reactions: first the reduction of o-nitroanisole to 2-methoxynitrosobenzene and then, the reduction of 2-methoxynitrosobenzene to o-anisidine. Internal and external mass and heat transfer limitations in the microreactor were examined. Different rate laws using different mechanisms from the literature were considered to fit the experimental data. Two rate equations for the two consecutive reactions assuming Langmuir-Hinshelwood mechanism provided the best fit to the experimental data. These two rate equations predicted the experimental rates within 10% error. Experiments were also carried out in an integral reactor, and the reactor performance data were found to be in agreement with the predictions of the theoretical models.     

System-Level Specification Testing Of Wireless Transceivers

This paper presents an efficient system-level manufacturing test methodology for wireless transceiver systems. Conventional system-level testing procedures incur large test times and require the use of multiple test hardware configurations for measuring frequency and modulation-domain performance specifications, e.g., system-gain, nonlinearity, noise-figure, channel power, adjacent-channel power-ratio, error vector magnitude, modulation signal-to-noise ratio and bit error rate. The proposed test methodology addresses these problems by simplifying the test stimulus application and test response capture/analysis procedures. In addition, the number of test hardware configurations needed to measure all the performance specifications is minimized and fewer as well as shorter tests are used to determine all the test specification values of interest. Test accuracy is achieved by optimizing the test stimulus so that the observed response has strong statistical correlation with the target test specification values. Experimental results show significant testing time reduction and was validated on 1.575 GHz and 900 MHz wireless transceiver prototypes.     

Affinity Studies of Hemicyanine Derived Water Soluble Colorimetric Probes with Reactive Oxygen/Nitrogen/Sulfur Species

Peroxynitrite (ONOO^-) is an essential endogenous reactive oxygen species (ROS) generated in mitochondria under various pathological and physiological conditions. An increase in its level in mitochondria is related to numerous diseases. Herein, we report a series of hemicyanine-derived water-soluble colorimetric probes ( 1 – 4 ) and the reactivity of which was studied with various reactive oxygen, nitrogen, and sulfur species. Probes 1 – 4 are formed by conjugating 1,2,3,3-tetramethyl-3H-indolium iodide and 4-hydroxybenzaldehyde or its derivatives through an alkene linkage formed by the Knoevenagel reaction. Oxidative cleavage of the electron-rich double bond of the conjugated hemicyanine dye revealed a discerning affinity of probe 3 towards peroxynitrite among all reactive oxygen species. The rapid change in color of 3 provides a sensitive and selective method for detecting peroxynitrite with a low detection limit of 180 nM. Notably, the water solubility of the probe displays excellent performance for the selective detection of peroxynitrite among ROS and reactive nitrogen (RNS)/sulfur species (RSS). UV-vis, ¹H NMR, and ¹³C NMR spectroscopic data and results from theoretical calculations provide further information on the interaction of peroxynitrite with probe 3 .     

Water transport in cellular tissues during thermal processing

Accurate modeling of water transport in food materials requires knowledge of how transport properties depend on the material structure. Water transport in a cellular tissue depends on its pathway (intracellular versus extracellular), which in turn depends on temperature. Using a combination of permeability measurement, pore‐size distribution analysis and bioimpedance analysis, it is shown that water in a cellular tissue (e.g., potatoes) is mostly intracellular at lower temperatures at which cell membranes are intact. During drying at high‐temperatures, cell membranes in potatoes are damaged, and the moisture transport pathway is primarily extracellular (through intercellular spaces and the lacunae created by the killed cells), with a much lower resistance to water transport. The difference in moisture diffusivity in potatoes for the two pathways has been estimated to be three orders of magnitude. Therefore, transport properties measured or predicted at low temperatures cannot be used for high temperatures because they correspond to different moisture migration pathways. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Multiphase and multicomponent transport with phase change during meat cooking

A multiphase model based on unsaturated flow in a hygroscopic porous medium, which accounts for the important physical phenomena that take place during thermal treatment of meat, is developed. Frozen meat is considered as a porous solid comprising of water, fat and protein with gas trapped in its pores. As it is heated, water and fat melt, and, are gradually released from the solid protein matrix to the pore space. With further rise in temperature, liquid water evaporates. Since four fluid components (liquid water phase, liquid fat phase, water vapor and air) are present in the pore space, a mass balance equation is written for each component. Local thermal equilibrium assumption leads to one energy balance equation for the whole system. The model is validated for double-sided contact heating of hamburger patties by comparing temperature and moisture profiles with experimental studies. Dominant modes of transport are identified.     

Diagnosis of Wireless Sensor Networks in Presence of Permanent and Intermittent Faults

In this paper we consider the problem of distributed fault diagnosis in Wireless Sensor Networks (WSNs). The proposed Fault Diagnosis Algorithm (FDA) aims to handle both permanent and intermittent faults. The sensor nodes with permanent communication faults can be diagnosed by using the conventional time-out mechanism. In contrast, it is difficult to detect intermittent faults due to their inherent unpredictable behavior. The FDA is based on the comparison of sensor measurements and residual energy values of neighboring sensor nodes, exploiting their spatial correlations. To handle intermittent faults, the comparisons are made for \(r\) rounds. Two special cases of intermittent faults are considered: one, when an intermittently faulty node sends similar sensor measurement and similar residual energy value to some of its neighbors in all \(r\) rounds; another, when it sends these values, either or both of which deviates significantly from that of some neighbors in all \(r\) rounds. Through extensive simulation and analysis, the proposed scheme is proved to be correct, complete, and efficient to handle intermittent faults and hence, well suited for WSNs.     

Effect of alloying on the electronic structure and magnetic properties of Fe,Co and Ni with Au and Ag

We use the self-consistent, augmented space recursion technique to study the electronic structure and magnetic properties of alloys of the transition metals, Fe, Co and Ni with the noble metals, Ag and Au. We analyse the effect of local environment and the hybridization between the constituent bands on the electronic and magnetic properties.     

Computationally efficient angle estimation for signals with knownwaveforms

This paper presents a large sample decoupled maximum likelihood (DEML) angle estimator for uncorrelated narrowband plane waves with known waveforms and unknown amplitudes arriving at a sensor array in the presence of unknown and arbitrary spatially colored noise. The DEML estimator decouples the multidimensional problem of the exact ML estimator to a set of 1-D problems and, hence, is computationally efficient. We shall derive the asymptotic statistical performance of the DEML estimator and compare the performance with its Cramer-Rao bound (CRB), i.e., the best possible performance for the class of asymptotically unbiased estimators. We will show that the DEML estimator is asymptotically statistically efficient for uncorrelated signals with known waveforms. We will also show that for moderately correlated signals with known waveforms, the DEML estimator is no longer a large sample maximum likelihood (ML) estimator, but the DEML estimator may still be used for angle estimation, and the performance degradation relative to the CRB is small. We shall show that the DEML estimator can also be used to estimate the arrival angles of desired signals with known waveforms in the presence of interfering or jamming signals by modeling the interfering or jamming signals as random processes with an unknown spatial covariance matrix. Finally, several numerical examples showing the performance of the DEML estimator are presented in this paper     

Does autopsy of antenatally diagnosed malformed foetuses aid genetic counselling?

BACKGROUND: Many pregnancies are terminated because of ultrasonographic diagnosis of malformation in the foetus. A detailed foetal autopsy is needed to arrive at a definite diagnosis on the basis of which genetic counselling can be provided. METHODS: Sixty-one foetuses, terminated because of antenatal diagnosis of congenital malformations by ultrasound, were autopsied. The ultrasound diagnosis was compared with the diagnosis reached after autopsy. RESULTS: In 31 cases (51%) the autopsy provided additional findings. In 21 cases (34.4%), the autopsy changed the primary diagnosis. The revised diagnosis led to a change in the risk of recurrence in 18 cases (29.5%). CONCLUSION: Genetic counselling depending solely on ultrasonographic foetal diagnosis may be erroneous. For appropriate genetic counselling, a detailed foetal examination should be carried out after termination in cases with ultrasonographically detected congenital malformations.     

Low-cost test of embedded RF/analog/mixed-signal circuits in SOPs

Increasing levels of integration and high speeds of operation have made the problem of testing complex systems-on-packages (SOPs) very difficult. Testing packages with multigigahertz RF and optical components is even more difficult as external tester costs tend to escalate rapidly beyond 3 GHz. The extent of the problem can be gauged by the fact that test cost is approaching almost 40% of the total manufacturing cost of these packages. To alleviate test costs, various solutions relying on built-off test (BOT) and built-in test (BIT) of embedded high-speed components of SOPs have been developed. These migrate some of the external tester functions to the tester load board (BOT) and to the package and the die encapsulated in the package (BIT) in an "intelligent" manner. This paper provides a discussion of the emerging BOT and BIT schemes for embedded high-speed RF/analog/mixed-signal circuits in SOPs. The pros and cons of each scheme are discussed and preliminary available data on case studies are presented.