Acoustic properties of turbofan inlets

The acoustic field within a duct containing a nonuniform steady flow was predicted. This analysis used the finite element method to calculate the velocity potential within the duct

The auxiliary use of LANDSAT data in estimating crop acreages: Results of the 1975 Illinois crop-acreage experiment

The author has identified the following significant results. It was found that classifier performance was influenced by a number of temporal, methodological, and geographical factors. Best results were obtained when corn was tasselled and near the dough stage of development. Dates earlier or later in the growing season produced poor results. Atmospheric effects on results cannot be independently measured or completely separated from the effects due to the maturity stage of the crops. Poor classifier performance was observed in areas where considerable spectral confusion was present

Acoustic properties of turbofan inlets

The finite element codes were improved using Hermitian elements and numerical integration of element relations. The question of real variable versus complex variable formulation was resolved and an integrated civil engineering system was implemented on the Georgia Tech Cyber 70/74. Efforts are underway to restructure the program to obtain the most efficient use of array storage

Avoiding catastrophic failure in correlated networks of networks

Networks in nature do not act in isolation but instead exchange information, and depend on each other to function properly. An incipient theory of Networks of Networks have shown that connected random networks may very easily result in abrupt failures. This theoretical finding bares an intrinsic paradox: If natural systems organize in interconnected networks, how can they be so stable? Here we provide a solution to this conundrum, showing that the stability of a system of networks relies on the relation between the internal structure of a network and its pattern of connections to other networks. Specifically, we demonstrate that if network inter-connections are provided by hubs of the network and if there is a moderate degree of convergence of inter-network connection the systems of network are stable and robust to failure. We test this theoretical prediction in two independent experiments of functional brain networks (in task- and resting states) which show that brain networks are connected with a topology that maximizes stability according to the theory.Comment: 40 pages, 7 figure

Enzyme-level interconversion of nitrate and nitrite in the fall mixed layer of the Antarctic Ocean

In the Southern Ocean, the nitrogen (N) isotopes of organic matter and the N and oxygen (O) isotopes of nitrate (NO_3^−) have been used to investigate NO_3^− assimilation and N cycling in the summertime period of phytoplankton growth, both today and in the past. However, recent studies indicate the significance of processes in other seasons for producing the annual cycle of N isotope changes. This study explores the impact of fall conditions on the ^(15)N/^(14)N (δ^(15)N) and ^(18)O/^(16)O (δ^(18)O) of NO_3^− and nitrite (NO_2^−) in the Pacific Antarctic Zone using depth profiles from late summer/fall of 2014. In the mixed layer, the δ^(15)N and δ^(18)O of NO_3^− + NO_2^− increase roughly equally, as expected for NO_3^− assimilation; however, the δ^(15)N of NO_3^−-only (measured after NO_2− removal) increases more than does NO_3^− -only δ^(18)O. Differencing indicates that NO_2^− has an extremely low δ^(15)N, often < −70‰ versus air. These observations are consistent with the expression of an equilibrium N isotope effect between NO_3^− and NO_2^−, likely due to enzymatic NO_3^- - NO_2^− interconversion. Specifically, we propose reversibility of the nitrite oxidoreductase (NXR) enzyme of nitrite oxidizers that, having been entrained from the subsurface during late summer mixed layer deepening, are inhibited by light. Our interpretation suggests a role for NO_3^- - NO_2^− interconversion where nitrifiers are transported into environments that discourage NO_2^− oxidation. This may apply to surface regions with upwelling, such as the summertime Antarctic. It may also apply to oxygen-deficient zones, where NXR-catalyzed interconversion may explain previously reported evidence of NO_2^− oxidation

Topology of the conceptual network of language

We define two words in a language to be connected if they express similar concepts. The network of connections among the many thousands of words that make up a language is important not only for the study of the structure and evolution of languages, but also for cognitive science. We study this issue quantitatively, by mapping out the conceptual network of the English language, with the connections being defined by the entries in a Thesaurus dictionary. We find that this network presents a small-world structure, with an amazingly small average shortest path, and appears to exhibit an asymptotic scale-free feature with algebraic connectivity distribution.Comment: 4 pages, 2 figures, Revte

Foraminiferal isotope evidence of reduced nitrogen fixation in the ice age Atlantic Ocean

Fixed nitrogen (N) is a limiting algal nutrient in the low latitude ocean, and the oceanic N inventory has been suggested to increase during ice ages so as to lower atmospheric CO_2. In organic matter within planktonic foraminifera shells in Caribbean Sea sediments, the ^(15)N/^(14)N from the last ice age is higher than that from the current interglacial, indicating higher nitrate ^(15)N/^(14)N in the Caribbean thermocline. This and species-specific differences are best explained by less N fixation in the Atlantic during the last ice age. The fixation decrease was most likely a response to a known ice age reduction in ocean N loss, and it would have worked to balance the ocean N budget and to curb ice age-to-interglacial change in the N inventory

Nickel-Catalyzed Asymmetric Reductive Cross-Coupling of a-Chloroesters with (Hetero)Aryl Iodides

An asymmetric reductive cross-coupling of alpha-chloroesters and (hetero)aryl iodides is reported. This nickel-catalyzed reaction proceeds with a chiral BiOX ligand under mild conditions, affording alpha-arylesters in good yields and enantioselectivities. The reaction is tolerant of a variety of functional groups, and the resulting products can be converted to pharmaceutically-relevant chiral building blocks. A multivariate linear regression model was developed to quantitatively relate the influence of the alpha-chloroester substrate and ligand on enantioselectivity