Tripling the capacity of wireless communications using electromagnetic polarization

Wireless communications are a fundamental part of modern information infrastructure. But wireless bandwidth is costly, prompting a close examination of the data channels available using electromagnetic waves. Classically, radio communications have relied on one channel per frequency, although it is well understood that the two polarization states of planar waves allow two distinct information channels; techniques such as 'polarization diversity' already take advantage of this. Recent work has shown that environments with scattering, such as urban areas or indoors, also possess independent spatial channels that can be used to enhance capacity greatly. In either case, the relevant signal processing techniques come under the heading of 'multiple-input/multiple-output' communications, because multiple antennae are required to access the polarization or spatial channels. Here we show that, in a scattering environment, an extra factor of three in channel capacity can be obtained, relative to the conventional limit using dual-polarized radio signals. The extra capacity arises because there are six distinguishable electric and magnetic states of polarization at a given point, rather than two as is usually assumed.     

Effect ofPlasmodium berghei infection on benzoic acid metabolism in mice

Summary The metabolism of benzoic acid was studied inPlasmodium berghei infected mice both in vitro and in vivo. Results of in vitro studies showed a considerable decrease in the ability of the infected liver to detoxify benzoic acid by hippuric acid formation. The in vivo study showed that hippuric acid formation decreases with increasing parasitemia and the emergence of benzoyl-glucoronide. This new pathway stops operating with further increase in parasitemia.     

Precursors to regulatory peptides: their proteolytic processing

Summary Precursors to regulatory peptides undergo maturation processes which include protelytic processing. The enzymes involved in this process remove the hydrophobic peptide located at the amino-terminus of the precursor. Endoprotease cleavage also occurs at single and two adjacent basic residues, this is followed by a removal of basic residues located at the C-terminus of the peptides by a carboxypeptidase-like enzyme.     

Homozygous HOXA1 mutations disrupt human brainstem, inner ear, cardiovascular and cognitive development

We identified homozygous truncating mutations in HOXA1 in three genetically isolated human populations. The resulting phenotype includes horizontal gaze abnormalities, deafness, facial weakness, hypoventilation, vascular malformations of the internal carotid arteries and cardiac outflow tract, mental retardation and autism spectrum disorder. This is the first report to our knowledge of viable homozygous truncating mutations in any human HOX gene and of a mendelian disorder resulting from mutations in a human HOX gene critical for development of the central nervous system.     

Sustainability of three apple production systems

Escalating production costs, heavy reliance on non-renewable resources, reduced biodiversity, water contamination, chemical residues in food, soil degradation and health risks to farm workers handling pesticides all bring into question the sustainability of conventional farming systems. It has been claimed, however, that organic farming systems are less efficient, pose greater health risks and produce half the yields of conventional farming systems. Nevertheless, organic farming became one of the fastest growing segments of US and European agriculture during the 1990s. Integrated farming, using a combination of organic and conventional techniques, has been successfully adopted on a wide scale in Europe. Here we report the sustainability of organic, conventional and integrated apple production systems in Washington State from 1994 to 1999. All three systems gave similar apple yields. The organic and integrated systems had higher soil quality and potentially lower negative environmental impact than the conventional system. When compared with the conventional and integrated systems, the organic system produced sweeter and less tart apples, higher profitability and greater energy efficiency. Our data indicate that the organic system ranked first in environmental and economic sustainability, the integrated system second and the conventional system last.     

Transferrin receptor is necessary for development of erythrocytes and the nervous system

Plasma iron circulates bound to transferrin (Trf), which solubilizes the ferric ion and attenuates its reactivity. Diferric Trf interacts with cell-surface Trf receptor (Trfr) to undergo receptor-mediated endocytosis into specialized endosomes. Endosomal acidification leads to iron release, and iron is transported out of the endosome through the activity of divalent metal transporter 1 (DMT1, formerly Nramp2), a transmembrane iron transporter that functions only at low pH. Trf and Trfr then return to the cell surface for reuse, completing a highly efficient cycle. Although the Trf cycle is assumed to be the general mechanism for cellular iron uptake, this has not been validated experimentally. Mice with hypotransferrinaemia (hpx) have little or no plasma Trf. They have severe anaemia, indicating that the Trf cycle is essential for iron uptake by erythroid cells. Other hpx tissues, however, are generally normal, and there is a paradoxical increase in intestinal iron absorption and iron storage. To test the hypothesis that the Trf cycle has unique importance for erythropoiesis, we disrupted the Trfr gene in mice. This results in elimination of the Trf cycle, but leaves other Trf functions intact. Mice lacking Trfr have a more severe phenotype than hpx mice, affecting both erythropoiesis and neurologic development. Furthermore, haploinsufficiency for Trfr results in impaired erythroid development and abnormal iron homeostasis.