bluuebunny/crossref_metadata_2025 huggingface dataset:
Carnivorous Mushrooms
Authors: Thorn R. G. , Barron G. L.
Published: October 2006

Ten species of gilled fungi, including the oyster mushroom (
Pleurotus ostreatus
), have been shown to attack and consume nematodes. It is suggested that these wood-decay fungi utilize the nutrients in their prey to supplement the low levels of nitrogen available in wood. This mode of nutrition is similar in principle to that of carnivorous higher plants.
Chondrites: A Trace Fossil Indicator of Anoxia in Sediments
Authors: Bromley Richard G. , Ekdale A. A.
Published: October 2006

The trace fossilChondrites, a highly branched burrow system of unknown endobenthic deposit feeders, occurs in all types of sediment, including those deposited under anaerobic conditions. In some cases, such as the Jurassic Posidonienschiefer Formation of Germany,Chondritesoccurs in black, laminated, carbonaceous sediment that was deposited in chemically reducing conditions. In other cases, such as numerous oxic clastic and carbonate units throughout the geologic column,Chondritestypically represents the last trace fossil in a bioturbation sequence. This indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters.
NautilusGrowth and Longevity: Evidence from Marked and Recaptured Animals
Authors: Saunders W. Bruce
Published: October 2006

Study ofNautilus belauensisin its natural habitat in Palau, West Caroline Islands, shows that growth is slow (0.1 millimeter of shell per day on the average) and decreases as maturity is approached and that individuals may live at least 4 years beyond maturity. Age estimates for seven animals marked and recaptured between 45 and 355 days after release range from 14.5 to 17.2 years. These data indicate that the life-span of Nautilus may exceed 20 years and that its life strategy is very different from that of other living cephalopods.
Molecular Biology of Osmoregulation
Authors: Le Rudulier D. , Strom A. R. , Dandekar A. M. , Smith L. T. , Valentine R. C.
Published: October 2006

The drought of 1983 resulted in some 10 billion dollars in agricultural losses and has focused attention on the vulnerability of our major crops to this devastating form of environmental stress. This article is concerned with the molecular biology of a new class of genes, called
osm
(osmotic tolerance) genes, that protect bacteria like
Escherichia coli
against osmotic stress and may work in a similar manner in plants and animals.
Osm
genes govern the production of a class of molecules, such as betaine and proline, that protect the cell and its constituents against dehydration. These osmoprotectant molecules have been known for many years to accumulate in plants but have only recently been shown to have potent antistress activity for bacteria.
Copepod Fecal Pellets as a Source of Dihydrophytol in Marine Sediments
Authors: Prahl F. G. , Eglinton G. , Corner E. D. S. , O'Hara S. C. M.
Published: October 2006

Dihydrophytol(3,7,11,15-tetramethylhexadecanol) was identified in the nonsaponified lipid fraction of fecal pellets from the copepod
Calanus helgolandicus
fed in the laboratory on a unialgal diet. Direct deposition in the fecal pellets of certain zooplankton species may explain the presence of dihydrophytol in marine sediments. Microbial reduction of phytol in sediment cores does not account for the origin of this compound in all sedimentary environments.
A Borna Virus cDNA Encoding a Protein Recognized by Antibodies in Humans with Behavioral Diseases
Authors: VandeWoude Susan , Richt Juergen A. , Zink Mary Christine , Rott Rudolf , Narayan Opendra , Clements Janice E.
Published: October 2006

Borna disease virus (BDV) causes a rare neurological disease in horses and sheep. The virus has not been classified because neither an infectious particle nor a specific nucleic acid had been identified. To identify the genome of BDV, a subtractive complementary DNA expression library was constructed with polyadenylate-selected RNA from a BDV-infected MDCK cell line. A clone (B8) was isolated that specifically hybridized to RNA isolated from BDV-infected brain tissue and BDV-infected cell lines. This clone hybridized to four BDV-specific positive strand RNAs (10.5, 3.6, 2.1, and 0.85 kilobases) and one negative strand RNA (10.5 kilobases) in BDV-infected rat brain. Nucleotide sequence analysis of the clone suggested that it represented a full-length messenger RNA which contained several open reading frames. In vitro transcription and translation of the clone resulted in the synthesis of the 14- and 24-kilodalton BDV-specific proteins. The 24-kilodalton protein, when translated in vitro from the clone, was recognized by antibodies in the sera of patients (three of seven) with behavioral disorders. This BDV-specific clone will provide the means to isolate the other BDV-specific nucleic acids and to identify the virus responsible for Borna disease. In addition, the significance of BDV or a BDV-related virus as a human pathogen can now be more directly examined.
Trigeminal Ganglion Infection by Thymidine Kinase-Negative Mutants of Herpes Simplex Virus
Authors: Tenser Richard B. , Miller Richard L. , Rapp Fred
Published: October 2006

The incidence of trigeminal ganglion infection after corneal inoculation of guinea pigs with thymidine kinase-negative mutants of herpes simplex virus was markedly reduced compared to infection after inoculation of thymidine kinase-positive virus. Thymidine kinase-negative herpes simplex virus replicated well in ocular tissues in which dividing or potentially dividing cells were present, but not in trigeminal ganglion infection of nondividing neurons. Thymidine kinase-positive virus, however, replicated well in ocular tissues as well as in trigeminal ganglion. These results suggest that thymidine kinase expression of herpes simplex virus may be important in infections of sensory ganglia.
Space Experiments with Particle Accelerators
Authors: Obayashi Tatsuzo , Kawashima N. , Kuriki K. , Nagatomo M. , Ninomiya K. , Sasaki S. , Yanagisawa M. , Kudo I. , Ejiri M. , Roberts W. T. , Chappell C. R. , Reasoner D. L. , Burch J. L. , Taylor W. L. , Banks P. M. , Williamson P. R. , Garriott O. K.
Published: October 2006

Electron and plasma beams and neutral gas plumes were injected into the space environment by instruments on Spacelab 1, and various diagnostic measurements including television camera observations were performed. The results yield information on vehicle charging and neutralization, beam-plasma interactions, and ionization enhancement by neutral beam injection.
Cadmium-Resistant
Pseudomonas putida
Synthesizes Novel Cadmium Proteins
Authors: Higham Denise P. , Sadler Peter J. , Scawen Michael D.
Published: October 2006

Three cysteine-rich proteins of molecular weight 4000 to 7000, containing 4 to 7 gram atoms of cadmium, zinc, and copper per mole were isolated from
Pseudomonas putida
growing in 3 m
M
cadmium. The three proteins were induced during different phases of growth, and the smallest (molecular weight 3600; 3 gram atoms of cadmium) was released into the medium when the cells lysed. The results of amino acid analyses and of ultraviolet, circular dichroism, electron paramagnetic resonance, and cadmium-113 nuclear magnetic resonance spectroscopy suggest a novel cadmium(II)-zinc(II)-copper(I) cluster structure for the major protein.
Large Yearly Production of Phytoplankton in the Western Bering Strait
Authors: Sambrotto R. N. , Goering J. J. , McRoy C. P.
Published: October 2006

Production in the western Bering Strait is estimated at 324 grams of carbon per square meter per year over 2.12 × 10
4
square kilometers. An ice-reduced growing season makes this large amount of primary production unexpected, but it is consistent with the area's large upper trophic level stocks. The productivity is fueled by a cross-shelf flow of nutrient-rich water from the Bering Sea continental slope. This phytoplankton production system from June through September is analogous to a laboratory continuous culture.
Isotope-Edited NMR of Cyclosporin a Bound to Cyclophilin: Evidence for a
Trans
9,10 Amide Bond
Authors: Fesik S. W. , Gampe R. T. , Holzman T. F. , Egan D. A. , Edalji R. , Luly J. R. , Simmer R. , Helfrich R. , Kishore V. , Rich D. H.
Published: October 2006

The binding of a
13
C-labeled cyclosporin A (CsA) analog to cyclophilin (peptidyl prolyl isomerase) was examined by means of isotope-edited nuclear magnetic resonance (NMR) techniques. A
trans
9,10 peptide bond was adopted when CsA was bound to cyclophilin, in contrast to the
cis
9,10 peptide bond found in the crystalline and solution conformations of CsA. Furthermore, nuclear Overhauser effects (NOEs) were observed between the ζ
3
and ε
3
protons of the methylleucine (MeLeu) residue at position 9 of CsA and tryptophan
121
(Trp
121
) and phenylalanine (Phe) protons of cyclophilin, suggesting that the MeLeu
9
residue of CsA interacts with cyclophilin. These results illustrate the power of isotope-edited NMR techniques for rapidly providing useful information about the conformations and active site environment of inhibitors bound to their target enzymes.
Elemental Anomalies at the Cretaceous-Tertiary Boundary, Woodside Creek, New Zealand
Authors: Brooks Robert R. , Reeves Roger D. , Yang Xing-Hua , Ryan Douglas E. , Holzbecher Jiri , Collen John D. , Neall Vincent E. , Lee Julian
Published: October 2006

Iridium and 26 other elements were determined in shale from the Cretaceous-Tertiary boundary at the
locus classicus
(for iridium anomalies) at Woodside Creek, New Zealand. Iridium, gold, copper, cobalt, chromium, nickel, arsenic, molybdenum, and iron were enriched in the basal 2 millimeters of the 8-millimeter shale parting as compared with the rest of the stratigraphic column. No other shale partings in the column had anomalous concentrations of any element when the data were expressed on a carbonate-free basis. The boundary material showed striking compositional similarities with the Stevns Klint Danish boundary shale. Elemental concentrations were in general much higher in the New Zealand material than in nonboundary shales from elsewhere in the world. The high concentration of iridium (153 nanograms per gram) in the basal layer of the boundary, together with the enrichment of other siderophile elements supports the idea of an extraterrestrial source for much of the material. The iridium/gold ratio of 2.1 is also in accordance with such a source. The iridium content of the basal layer is higher than for any other marine boundary shale obtained on land. The integrated iridium value is 187 nanograms per square centimeter of boundary surface.
Covariance Patterns of Foraminiferal δ
18
O: An Evaluation of Pliocene Ice Volume Changes Near 3.2 Million Years Ago
Authors: Prell Warren L.
Published: October 2006

Oxygen isotope data for a Pliocene interval from 3.6 to 2.8 million years ago show a mean increase (0.5 per mil) of benthic δ
18
O at about 3.2 million years ago, whereas planktic δ
18
O does not increase. This lack of covariance indicates that the event at 3.2 million years did not result in a permanent increase in the ice budget of either the Northern or the Southern Hemisphere.
The Population Factor in Africa's Development Dilemma
Authors: Sai Fred T.
Published: October 2006

Despite several decades of international effort, the development problems of sub-Saharan Africa remain acute. By many of the quality of life indexes, the majority of African countries are standing still or moving backward. A rapidly growing population with an adverse dependency ratio places demands on services that present development strategies cannot satisfy. A reorientation of development is necessary to establish realistic population policies and to implement comprehensive family planning programs.
Exciplexes and Electron Transfer Reactions
Authors: Mattes Susan L. , Farid Samir
Published: October 2006

Electronically excited molecules, being better electron donors and acceptors than their ground states, form charge-transfer complexes (exciplexes) which can lead to radical ions. Exciplex emission is widely used to probe polymers and organized media such as membranes and micelles. Exciplexes are also intermediates in photoreactions that lead to unique products. Photochemical electron-transfer processes, which are the basis of silver halide photography and electrophotography, are involved in many reactions of wide scope. Recent studies have led to the discovery of several electron-transfer photooxygenations with a diversity that will probably rival that of singlet oxygen. Both exciplex emission and photochemical electron transfer play important roles in organic photochemistry.
The Oceanic Carbonate System: A Reassessment of Biogenic Controls
Authors: Betzer P. R. , Byrne R. H. , Acker J. G. , Lewis C. S. , Jolley R. R. , Feely R. A.
Published: October 2006

Fluxes of biogenic carbonates moving out of the euphotic zone and into deeper undersaturated waters of the North Pacific were estimated with free-drifting sediment traps. Short-duration (1 to 1.5 day) sampling between 100 and 2200 meters points to a major involvement in the oceanic carbonate system by a class of organisms which had been relegated to a secondary role—aragonitic pteropods. Pteropod fluxes through the base of the euphotic zone are almost large enough to balance the alkalinity budget for the Pacific Ocean. Dissolution experiments with freshly collected materials shed considerable light on a mystery surrounding these labile organisms: although plankton collections from net tows almost always contain large numbers of pteropods, these organisms are never a major component of biogenic materials in long-duration sediment trap collections. Their low abundance in long-duration collections results from dissolution subsequent to collection. Shortduration sampling showed significant increases in the ratio of calcitic foraminifera to aragonitic pteropods in undersaturated waters, indicating the more stable mineralogic form, calcite, was preserved relative to aragonite. Approximately 90 percent of the aragonite flux is remineralized in the upper 2.2 kilometers of the water column.
Contribution of Small Glaciers to Global Sea Level
Authors: Meier Mark F.
Published: October 2006

Observed long-term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers, excluding those in Greenland and Antarctica, to the oceans. The average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance. These data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975. Although the error band is large, these glaciers appear to account for a third to half of observed rise in sea level, approximately that fraction not explained by thermal expansion of the ocean.
Genetic Consequences of Mate Choice: A Quantitative Genetic Method for Testing Sexual Selection Theory
Authors: Boake Christine R. B.
Published: October 2006

To investigate whether female mate choice could be directed at male genetic quality, male chemical signals and progeny fitness were studied in the red flour beetle (
Tribolium castaneum
). Differences among males in the attractiveness of their pheromone to females were statistically significant. Developmental time of progeny was significantly heritable, indicating that some males have "good genes" for this trait. There was no statistically significant correlation between progeny fitness and male attractiveness. These results do not support the hypothesis that in this species the evolution of female preferences for male pheromone is adaptive.
Tidal Currents and Eddy Statistics From Iceberg Trajectories off Labrador
Authors: Garrett Christopher , Middleton John , Hazen Mark , Majaess Fouad
Published: October 2006

Extensive data on the trajectories of icebergs located off the coast of Labrador has yielded information on tidal currents, the effect of wind on iceberg motion, and the properties of the low-frequency eddies. Statistical properties of the data were shown to be related to theoretical ideas on two-dimensional turbulence and to the connection between Eulerian and Lagrangian velocity statistics. The results have led to an estimate of the cross-shelf mixing rate and a statistical prediction scheme for iceberg trajectories.
Three-Dimensional Flow in the Upper Ocean
Authors: Weller Robert A. , Dean Jerome P. , Price James F. , Francis Erika A. , Marra John , Boardman David C.
Published: October 2006

Measurements made from the Research Platform
FLIP
provide some of the first direct observations of three-dimensional flow within the surface mixed layer of the ocean. Relatively narrow regions of downwelling flow were found within the mixed layer, in coincidence with bands of convergent surface flow. At mid-depth in the mixed layer, the downwelling flow had magnitudes of up to 0.2 meter per second and was accompanied by a downwind, horizontal jet of comparable magnitude. There is some evidence that these motions transport heat and phytoplankton within the mixed layer.
Transport Protein Genes in the Murine MHC: Possible Implications for Antigen Processing
Authors: Monaco John J. , Cho Sungae , Attaya Michelle
Published: October 2006

T lymphocyte activation requires recognition by the T cell of peptide fragments of foreign antigen bound to a self major histocompatibility complex (MHC) molecule. Genetic evidence suggests that part of the class II region of the MHC influences the expression, in trans, of MHC class I antigens on the cell surface, by regulating the availability of peptides that bind to and stabilize the class I molecule. Two closely related genes in this region,
HAM1
and
HAM2
, were cloned and had sequence similarities to a superfamily of genes involved in the ATP-dependent transport of a variety of substrates across cell membranes. Thus, these MHC-linked transport protein genes may be involved in transporting antigen, or peptide fragments thereof, from the cytoplasm into a membrane-bounded compartment containing newly synthesized MHC molecules.
A New Arbovirus from
Aedes albopictus
, an Asian Mosquito Established in the United States
Authors: Francy D. B. , Karabatsos N. , Wesson D. M. , Moore C. G. , Lazuick J. S. , Niebylski M. L. , Tsai T. F. , Craig G. B.
Published: October 2006

Ten strains of a new arbovirus belonging to the Bunyamwera group (Bunyaviridae) were recovered from field-collected
Aedes albopictus
mosquitoes in Potosi, Missouri. This evidence indicates that this species may serve as an arbovirus vector in the United States. The urban-suburban distribution, aggressive biting behavior, and broad viral susceptibility of
Ae. albopictus
may lead to the transmission of viruses of known public health importance and perhaps of viruses hitherto not transmitted to humans because of the feeding pattern of their usual vectors.
Physostigmine and Recent Memory: Effects in Young and Aged Nonhuman Primates
Authors: Bartus Raymond T.
Published: October 2006

The effect of physostigmine on recent memory was evaluated in young and aged rhesus monkeys. All aged monkeys had previously shown impaired memory. The performance of the young monkeys treated with physostigmine was similar to that recently reported for young humans—no effects at low doses, some improvement at a restricted range of doses, and deficits at the highest dose. Although the aged subjects also improved at the same general doses, their overall response as a group was much more variable than that of the younger subjects. The performance of some aged monkeys was impaired by low doses that did not affect young monkeys. Continued improvement was observed in some aged monkeys at the highest dose, which typically impaired young monkeys. These variable effects across aged subjects suggest that physostigmine cannot easily or reliably be used as an agent for treating geriatric cognition. Nevertheless, the differential age-related effects suggest that appropriate manipulation of the cholinergic system may eventually be developed to alleviate some of the cognitive impairments suffered by aged subjects.
Crystal Structure of Bee-Venom Phospholipase A
2
in a Complex with a Transition-State Analogue
Authors: Scott David L. , Otwinowski Zbyszek , Gelb Michael H. , Sigler Paul B.
Published: October 2006

The 2.0 angstroms crystal structure of a complex containing bee-venom phospholipase A
2
(PLA
2
) and a phosphonate transition-state analogue was solved by multiple isomorphous replacement. The electron-density map is sufficiently detailed to visualize the proximal sugars of the enzyme's N-linked carbohydrate and a single molecule of the transition-state analogue bound ot its active center. Although bee-venom PLA
2
does not belong to the large homologous Class I/II family that encompasses most other well-studied PLA
2
s, there is segmental sequence similarity and conservation of many functional substructures. Comparison of the bee-venom enzyme with other phospholipase structures provides compelling evidence for a common catalytic mechanism.
Storage and Remobilization of Suspended Sediment in the Lower Amazon River of Brazil
Authors: Meade Robert H. , Dunne Thomas , Richey Jeffrey E. , Santos Umberto de M. , Salati Eneas
Published: October 2006

In the lower Amazon River, suspended sediment is stored during rising stages of the river and resuspended during falling river stages. The storage and resuspension in the reach are related to the mean slope of the flood wave on the river surface; this slope is smaller during rising river stages than during falling stages. The pattern of storage and resuspension damps out the extreme values of high and low sediment discharge and tends to keep them near the mean value between 3.0 × 10
6
and 3.5 × 10
6
metric tons per day. Mean annual discharge of suspended sediment in the lower Amazon is between 1.1 × 10
9
and 1.3 × 10
9
metric tons per year.
Annual Heat Balance of Martian Polar Caps: Viking Observations
Authors: Paige David A. , Ingersoll Andrew P.
Published: October 2006

The Infrared Thermal Mappers aboard the two Viking orbiters obtained solar reflectance and infrared emission measurements of the Martian north and south polar regions during an entire Mars year. The observations were used to determine annual radiation budgets, infer annual carbon dioxide frost budgets, and constrain spring season surface and atmospheric properties with the aid of a polar radiative model. The results provide further confirmation of the presence of permanent CO
2
frost deposits near the south pole and show that the stability of these deposits can be explained by their high reflectivities. In the north, the observed absence of solid CO
2
during summer was primarily the result of enhanced CO
2
sublimation rates due to lower frost reflectivities during spring. The results suggest that the present asymmetric behavior of CO
2
frost at the Martian poles is caused by preferential contamination of the north seasonal polar cap by atmospheric dust.
Zinc Deposition in Acid Lakes: The Role of Diffusion
Authors: Carignan R. , Tessier A.
Published: October 2006

Steep negative concentration gradients of dissolved zinc are present between the overlying waters and the anoxic pore waters of two acid lakes. In the anoxic pore waters, the low zinc concentrations can be explained as due to the formation of relatively insoluble zinc sulfide minerals. Downward diffusive fluxes of dissolved zinc account for at least 50 to 75 percent of the recent zinc deposition to the sediments of these lakes. This downward diffusion occurs to a depth of 2 to 3 centimeters below the sediment water interface, where pronounced maxima in total zinc are observed. These subsurface peaks in total zinc have been interpreted as an indication of recent lake acidification. The present observations indicate that such subsurface peaks may also result from a diagenetic activity unrelated to recent changes in lake acidity.
Insect Resistance to the Biological Insecticide
Bacillus thuringiensis
Authors: McGaughey William H.
Published: October 2006

Resistance to the spore-crystal protein complex of
Bacillus thuringiensis
, the most widely used and intensively studied microbial insecticide, has been presumed to be unlikely to occur. In this study it was found that
Plodia interpunctella
, a major lepidopteran pest of stored grain products, can develop resistance to the insecticide within a few generations. Resistance increased nearly 30-fold in two generations in a strain reared on diet treated with
Bacillus thuringiensis
and after 15 generations reached a plateau 100 times higher than the control level. Resistance was stable when selection was discontinued. The resistance was inherited as a recessive trait.
Plodia interpunctella
strains collected from treated grain bins were more resistant than strains from untreated bins, indicating that the resistance can develop quickly in the field.
Ecological Effects of Salicin at Three Trophic Levels: New Problems from Old Adaptations
Authors: Smiley John T. , Horn Jonathan M. , Rank Nathan E.
Published: October 2006

Salicin, a toxic phenol glycoside, is used by larvae of the beetle
Chrysomela aenicollis
as a substrate for producing defensive secretions. In the east-central Sierra Nevada mountains of California, salicin concentrations ranged from 0.05 percent to over 5 percent of dry weight in leaves of different plants of
Salix orestera
, the Sierra willow. Beetles produced more secretion and suffered less predation on willows containing more salicin. In addition, leaf damage due to herbivory among 16 willow clones ranged from 0 to 20 percent of leaf area and was linearly related to salicin content. These results illustrate how a plant secondary chemical can become a problem for the plant when herbivores are adapted to use the chemical for their own benefit. The results also show the effect of a plant chemical on three trophic levels—the producer, a herbivore, and the predators of the herbivore.
Multiphoton Ionization of Atoms
Authors: Rhodes Charles K.
Published: October 2006

Studies of multiphoton ionization of atoms have revealed several unexpected characteristics. The confluence of the experimental evidence leads to the hypothesis that the basic character of the atomic response involves highly organized, coherent motions of entire atomic shells. The important regime, for which the radiative field strength is greater than an atomic unit (e/a
2
0
), can be viewed in approximate correspondence with the physics of fast (approximately 10 MeV per atomic mass unit) atom-atom scattering. This physical picture provides a basis for the expectation that stimulated emission in the x-ray range can be produced by direct, highly nonlinear coupling of ultraviolet radiation to atoms.
Changes in Mean Concentration, Phase Shifts, and Dissipation in a Forced Oscillatory Reaction
Authors: Lazar James G. , Ross John
Published: October 2006

Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD
+
is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O
2
influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference ΔG of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and ΔG; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).
Perceptual Deficits and the Activity of the Color-Opponent and Broad-Band Pathways at Isoluminance
Authors: Logothetis N. K. , Schiller P. H. , Charles E. R. , Hurlbert A. C.
Published: October 2006

The deficits in texture, motion, and depth perception incurred in monkeys at isoluminance were compared with the responses of neurons of the color-opponent and broad-band systems in the lateral geniculate nucleus. Texture perception, assumed to be carried by the color-opponent system, and motion and depth perception, ascribed to the broad-band pathway, were all found to be compromised but not abolished at isoluminance. Correspondingly, both the color-opponent and the broad-band systems were affected at isoluminance, but the activity of the neurons in neither system was abolished. These results suggest that impairment of visual capacities at isoluminance cannot be uniquely attributed to either of these systems and that isoluminant stimuli are inappropriate for the psychophysical isolation of these pathways.
Time-Resolved Electron Energy Loss Spectroscopy
Authors: Ellis T. H. , Dubois L. H. , Kevan S. D. , Cardillo M. J.
Published: October 2006

Two recent instrumental improvements in high-resolution electron energy loss spectroscopy make possible the recording of complete surface vibrational spectra on the millisecond time scale. This is the first spectroscopic probe capable of directly measuring fundamental surface rate processes in real time with a resolution less than or equal to 1 millisecond. Such measurements are the key to understanding surface kinetics at the molecular level. This article summarizes experiments on the adsorption and decomposition of formic acid on Cu(100) to investigate the temperature and coverage dependence of the formate intermediate. Other results are cited that provide a detailed description of the decomposition of methanol on Ni(110). Also reported are direct measurements of the residence time of carbon monoxide on Cu(100) and the associated desorption kinetics.
Instrumentation in the Next Decade
Authors: Hirschfeld Tomas
Published: October 2006

The progress of instrumentation and measurement science in the next decade will be marked by three major trends. First, as the average instrument achieves a rather considerable level of intelligence, "dumb" systems will become the exception, and we will eventually begin to become proficient in exploiting the resulting capabilities. Second, more sophisticated understanding of measurement science and of actual measurement needs will drive instrumentation design advances such as miniaturized sensors and yet more "hyphenated" instruments and "mapping" instruments. Third, the combination of sensor-based instrumentation and microminiaturization will make possible distributed measurement by allowing point-of-use measurements by nonexperts.
Electrokinetic Separation of Chiral Compounds
Authors: Gassmann E. , Kuo J. E. , Zare R. N.
Published: October 2006

Femtomole amounts of racemic mixtures of derivatized amino acids were resolved and analyzed rapidly in about 10 minutes by means of high-voltage zone electrophoresis with laser-fluorescence detection. The electrophoresis was performed in capillary columns containing a chiral support electrolyte. A number of dansyl amino acids were resolved by the diastereomeric interaction between the DL-amino acid and the copper(II) complex of L-histidine present in the support electrolyte. A combination of electro-osmotic and electrophoretic action caused all species, positively charged, neutral, and negatively charged, to pass through the 0.5- nanoliter detection volume where they were subjected to laser excitation.
Platinized Chloroplasts: A Novel Photocatalytic Material
Authors: Greenbaum Elias
Published: October 2006

Colloidal platinum was prepared and precipitated directly onto photosynthetic thylakoid membranes from aqueous solution and entrapped on fiberglass filter paper. This composition of matter was capable of sustained simultaneous photoevolution of hydrogen and oxygen when irradiated at any wavelength in the chlorophyll absorption spectrum. Experimental data support the interpretation that part of the platinum metal catalyst is precipitated adjacent to the photosystem I reduction site of photosynthesis and that electron transfer occurs across the interface between photosystem I and the catalyst. Photoactivity of the material was dependent on the nature of the ionic species from which the platinum was precipitated. All photoactive samples were prepared from the hexachloroplatinate(IV) ion, whereas samples prepared by precipitation of the tetraammineplatinum(II) ion showed no hydrogen evolution activity and only transient oxygen activity. This system is among the simplest known for photosynthetically splitting water into molecular hydrogen and oxygen.
Common Features of Protein Unfolding and Dissolution of Hydrophobic Compounds
Authors: Murphy Kenneth P. , Privalov Peter L. , Gill Stanley J.
Published: October 2006

Protein unfolding and the dissolution of hydrophobic compounds (including solids, liquids, and gases) in water are characterized by a linear relation between entropy change and heat capacity change. The same slope is found for various classes of compounds, whereas the intercept depends on the particular class. The feature common to these processes is exposure of hydrophobic groups to water. These observations make possible the assignment of the heat capacity change to hydrophobic solvation and lead to the description of protein stability in terms of a hydrophobic and a nonhydrophobic contribution. A general representation of protein stability is given by the heat capacity change and the temperature.
Tumorigenicity in Human Melanoma Cell Lines Controlled by Introduction of Human Chromosome 6
Authors: Trent Jeffrey M. , Stanbridge Eric J. , McBride Heyoung L. , Meese Eckart U. , Casey Graham , Araujo Diana E. , Witkowski Colette M. , Nagle Raymond B.
Published: October 2006

Chromosome banding analysis of human malignant melanoma has documented the nonrandom alteration of chromosome 6. To determine the relevance of chromosome 6 abnormalities in melanoma, a normal chromosome 6 was directly introduced into melanoma cell lines. The resulting (+6) microcell hybrids were significantly altered in their phenotypic properties in culture and lost their ability to form tumors in nude mice. The loss of the chromosome 6 from melanoma microcell hybrids resulted in the reversion to tumorigenicity of these cells in mice. The introduction of the selectable marker (psv
2
neo) alone into melanoma cell lines had no effect on tumorigenicity. These results support the idea that one or more genes on chromosome 6 may control the malignant expression of human melanoma.
Electroactive Polymers and Macromolecular Electronics
Authors: Chidsey Christopher E. D. , Murray Royce W.
Published: October 2006

Electrodes can be coated with electrochemically reactive polymers in several microstructural formats called sandwich, array, bilayer, micro-, and ion-gate electrodes. These microstructures can be used to study the transport of electrons and ions through the polymers as a function of the polymer oxidation state, which is essential for understanding the conductivity properties of these new chemical materials. The microstructures also exhibit potentially useful electrical and optical responses, including current rectification, charge storage and amplification, electron-hole pair separation, and gates for ion flow.
Background and Mass Extinctions: The Alternation of Macroevolutionary Regimes
Authors: Jablonski David
Published: October 2006

Comparison of evolutionary patterns among Late Cretaceous marine bivalves and gastropods during times of normal, background levels of extinction and during the end-Cretaceous mass extinction indicates that mass extinctions are neither an intensification of background patterns nor an entirely random culling of the biota. During background times, traits such as planktotrophic larval development, broad geographic range of constituent species, and high species richness enhanced survivorship of species and genera. In contrast, during the end-Cretaceous and other mass extinctions these factors were ineffectual, but broad geographic deployment of an entire lineage, regardless of the ranges of its constituent species, enhanced survivorship. Large-scale evolutionary patterns are evidently shaped by the alternation of these two macroevolutionary regimes, with rare but important mass extinctions driving shifts in the composition of the biota that have little relation to success during the background regime. Lineages or adaptations can be lost during mass extinctions for reasons unrelated to their survival values for organisms or species during background times, and long-term success would require the chance occurrence within a single lineage of sets of traits conducive to survivorship under both regimes.
Geomorphic Evidence for the Distribution of Ground Ice on Mars
Authors: Squyres Steven W. , Carr Michael H.
Published: October 2006

High-resolution Viking orbiter images show evidence for quasi-viscous relaxation of topography. The relaxation is believed to be due to creep deformation of ice in near-surface materials. The global distribution of the inferred ground ice shows a pronounced latitudinal dependence. The equatorial regions of Mars appear to be ice-poor, while the heavily cratered terrain poleward of ± 30° latitude appears to be ice-rich. The style of creep poleward of ± 30° varies with latitude, possibly due to variations in ice rheology with temperature. The distribution suggests that ice at low latitudes, which is not in equilibrium with the present atmosphere, has been lost via sublimation and diffusion through the regolith, thereby causing a net poleward transport of ice over martian history.
Herbivores' Direct and Indirect Effects on Algal Populations
Authors: Sterner Robert W.
Published: October 2006

The increase in algal reproductive rates caused by nitrogen regeneration from herbivorous zooplankton approximately equaled the zooplankton-caused mortality. This result demonstrates that nutrient regeneration by herbivores is at least sometimes a strong indirect effect in natural communities.
Knowledge-Based Systems
Authors: Davis Randall
Published: October 2006

First developed two decades ago, knowledge-based systems have seen widespread application in recent years. While performance has been a strong focus of attention, building such systems has also expanded our conception of a computer program from a black box providing an answer to something capable of explaining its answers, acquiring new knowledge, and transferring knowledge to students. These abilities derive from distinguishing clearly what the program knows from how that knowledge will be used, making it possible to use the same knowledge in different ways.
Phosphate-Methylated DNA Aimed at HIV-1 RNA Loops and Integrated DNA Inhibits Viral Infectivity
Authors: Buck Henk M. , Koole Leo H. , van Genderen Marcel H. P. , Smit Lia , Geelen Jan L. M. C. , Jurriaans Suzanne , Goudsmit Jaap
Published: October 2006

Phosphate-methylated DNA hybridizes strongly and specifically to natural DNA and RNA. Hybridization to single-stranded and double-stranded DNA leads to site-selective blocking of replication and transcription. Phosphate-methylated DNA was used to interrupt the life cycle of the human immunodeficiency virus type-1 (HIV-1), the causative agent of acquired immunodeficiency syndrome (AIDS). Both antisense and sense phosphate-methylated DNA 20-nucleotide oligomers, targeted at the transactivator responsive region and the primer binding site, caused complete inhibition of viral infectivity at a low concentration. Hybridization of phosphate-methylated DNA with folded and unfolded RNA was studied by ultraviolet and proton nuclear magnetic resonance spectroscopy. The combined results of hybridization studies and biological experiments suggest that the design of effective antisense phosphate-methylated DNA should focus on hairpin loop structures in the viral RNA. For sense systems, the 5′ end of the integrated viral genome is considered to be the important target site.
Transport and Loss of Nitrous Oxide in Soil Water After Forest Clear-Cutting
Authors: Bowden William B. , Bormann F. H.
Published: October 2006

Whole-tree harvesting increased the concentration of nitrous oxide dissolved in soil water by two orders of magnitude over the concentration expected in equilibrium with the atmosphere. In contrast, the nitrous oxide content of soil water in an intact, second-growth forest was close to the expected theoretical value. Nitrous oxide, produced at active sites in the soil, dissolves in soil water and is transported to seeps and streams where it rapidly degasses from the solution and is released into the atmosphere. This loss of nitrous oxide after clear-cutting is not important to the nitrogen economy of the site; however, it may be important to the global atmospheric budget of nitrous oxide. Sources of nitrous oxide may have been overlooked because nitrous oxide emissions can be separated in time and space from the sites of the most intense production of nitrous oxide.
Placers of Cosmic Dust in the Blue Ice Lakes of Greenland
Authors: Maurette M. , Hammer C. , Reeh N. , Brownlee D. E. , Thomsen H. H.
Published: October 2006

A concentration process occurring in the melt zone of the Greenland ice cap has produced the richest known deposit of cosmic dust on the surface of the earth. Extraterrestrial particles collected from this region are well preserved and are collectable in large quantities. The collected particles are generally identical to cosmic spheres found on the ocean floor, but a pure glass type was discovered that has not been seen in deep-sea samples. Iron-rich spheres are conspicuously rare in the collected material.
Paleoenvironment of the Earliest Hominoids: New Evidence from the Oligocene Avifauna of Egypt
Authors: Olson Storrs L. , Rasmussen D. Tab
Published: October 2006

Analysis of fossil birds from the Oligocene Jebel Qatrani Formation in the Fayum depression of Egypt, site of the oldest known hominoid primates, allows precise paleoenvironmental reconstruction of the climatic and biotic conditions that influenced some of the earliest stages of hominoid evolution. Unlike the fossil mammals of the Fayum, which belong largely to extinct groups, most of the birds are referable to living families, with some being close to modern genera. The avifauna consists mainly of aquatic species, with such forms as jacanas (Jacanidae) and shoebilled storks (Balaenicipitidae) indicating expanses of freshwater with dense floating vegetation. An avifauna closely analogous to that of the Fayum is found today only in a limited area of Uganda, north and west of Lake Victoria, a region of swampland bordered by forest and grasslands that presents marked faunal similarities to the environment inferred for the Egyptian Oligocene.
Tick Anticoagulant Peptide (TAP) Is a Novel Inhibitor of Blood Coagulation Factor Xa
Authors: Waxman Lloyd , Smith Donna E. , Arcuri Karen E. , Vlasuk Geroeg P.
Published: October 2006

A low molecular weight serine protease inhibitor (TAP) was purified from extracts of the soft tick,
Ornithodoros moubata
. The peptide is a slow, tight-binding inhibitor, specific for factor Xa (
K
i
= 0.588 ± 0.054 n
M
). The inhibitor also acts as an anticoagulant in several human plasma clotting assays in vitro. Its amino acid sequence (60 residues) has limited homology to the Kunitz-type inhibitors. However, unlike other inhibitors of this class, TAP inhibits only factor Xa. It had no effect at a 300-fold molar excess on factor VIIa, kallikrein, trypsin, chymotrypsin, thrombin, urokinase, plasmin, tissue plasminogen activator, elastase, or
Staphylococcus aureus
V8 protease. TAP's specificity and size suggest that it may have therapeutic value as an anticoagulant.
Optical Guided-Wave Devices
Authors: Alferness R. C.
Published: October 2006

Optical fiber is rapidly becoming the transmission medium of choice for new telecommunication systems. For a true lightwave network to evolve, however, optical control devices such as optical switches and multiplexer-demultiplexers will be essential. Optical guided-wave devices built with photolithographic fabrication techniques and electro-optic substrates are compact, low drive power devices that provide these functions. Research is particularly advanced on integrated-optic devices based on waveguides formed by titanium diffused into lithium niobate. Switch arrays, tunable filters, and high-speed modulators have been demonstrated and used in research systems experiments.
Energy Sources for Detritivorous Fishes in the Amazon
Authors: Araujo-Lima Carlos A. R. M. , Forsberg Bruce R. , Victoria Reynaldo , Martinelli Luiz
Published: October 2006

Detritivorous fishes form an important part of the ichthyomass in the Amazon basin. Most of these fishes are contained in the orders Characiformes and Siluriformes (catfishes). The Characiformes constitute more than 30% of the total fish yield in the Amazon basin, whereas the catfishes are of minor importance. Stable isotope data indicate that Characiformes species receive most of their carbon through food chains originating with phytoplankton, while the Siluriformes receive a significant part of their energy from other plant sources.
Defensive Spray of the Bombardier Beetle: a Biological Pulse Jet
Authors: Dean Jeffrey , Aneshansley Daniel J. , Edgerton Harold E. , Eisner Thomas
Published: October 2006

The defensive spray of the bombardier beetle
Stenaptinus insignis
is ejected in quick pulses (at about 500 pulses per second) rather than as a continuous stream. The pulsation may be a consequence of intermittency in the explosive chemical process that generates the spray. The ejection system of the beetle shows basic similarity to the pulse jet propulsion mechanism of the German V-1 "buzz" bomb of World War II.
Electrophoresis of Flexible Macromolecules: Evidence for a New Mode of Transport in Gels
Authors: Smisek David L. , Hoagland David A.
Published: October 2006

Movement of macromolecules through low concentration agarose gels was investigated with linear poly(styrenesulfonate), linear DNA, star-shaped poly(styrenesulfonate), and circular DNA. Mobilities of weakly entangled flexible macromolecules were independent of molecular radius; within a homologous chemical sequence, electrophoretic separation at low field strengths depended solely on the degree of polymerization. These observations cannot be explained either by sieving or by reptation mechanisms; transport was apparently controlled by spatial variations of chain configurational entropy. Only when the chain was highly entangled did chain topology affect mobility. Evidence for entropically regulated transport clarifies how gel electrophoresis separates flexible macromolecules.
Crystallographic
R
Factor Refinement by Molecular Dynamics
Authors: Brünger Axel T. , Kuriyan John , Karplus Martin
Published: October 2006

Molecular dynamics was used to refine macromolecular structures by incorporating the difference between the observed crystallographic structure factor amplitude and that calculated from an assumed atomic model into the total energy of the system. The method has a radius of convergence that is larger than that of conventional restrained least-squares refinement. Test cases showed that the need for manual corrections during refinement of macromolecular crystal structures is reduced. In crambin, the dynamics calculation moved residues that were misplaced by more than 3 angstroms into the correct positions without human intervention.