bluuebunny/crossref_metadata_2025 huggingface dataset:
Real Time Optimization for Robot Control using Receding Horizon Control with Equal Constraint
Authors: Takeuchi Hiroki
Published: December 2002

The equation to define a legged robot's ZMP (zero moment point) suggests a problem that ZMP cannot be obtained uniquely. This is because a redundancy exists in the equation which defines ZMP. Obtaining a true ZMP requires optimization calculation and this took a very long calculation time. We have to execute off‐line optimization beforehand. Then a real‐time control system follows these optimum trajectories which satisfy the ZMP condition. This is inconvenient for real‐time control of a robot. Carrying out a reduction of the equation so that it uniquely defines ZMP may assist in temporarily avoiding this problem. However, a pseudo ZMP is only able to be found. On the other hand, since RHC (receding horizon control), which is the new optimization technique, does not use a gradient method for optimization calculation, then it requires very little calculation time. This short time calculation such as sampling interval makes it possible to perform a real‐time calculation. However, RHC has not yet been applied to robot control. If an equality constraint can be set up in the formulation of RHC, it will be easy to apply to robot control. In this paper, it is proposed that RHC is used adding an equality constraint and then the formulation is performed. We discuss that the ZMP condition is used in the formulation using an equality constraint. Generally, it is difficult to take a ZMP variable as a state variable in a state equation. To ensure an optimal result, careful consideration of the ZMP conditions is required for the formulation. Then, this paper shows that the ZMP is defined as one of the input variables. Since ZMP input is obtained as an optimal solution, the technique proposed can generate a true ZMP trajectory on real time. Simulation results are performed by both the models in a two‐dimensional plane and the three‐dimensional space. This simple modeling enables an easy application to biped, quadruped and the other multiped robots. This simple modeling forms a basis for robot control. © 2003 Wiley Periodicals, Inc.
Obstacle Avoidance for Spatial Hyper‐Redundant Manipulators Using Harmonic Potential Functions and the Mode Shape Technique
Authors: Fahimi F. , Ashrafiuon H. , Nataraj C.
Published: December 2002

This paper deals with the obstacle avoidance problem for spatial hyper‐redundant manipulators in known environments. The manipulator is divided into two sections, a proximal section that has not entered the space among the obstacles and a distal section among the obstacles. Harmonic potential functions are employed to achieve obstacle avoidance for the distal section in three‐dimensional space in order to avoid local minima in cluttered environments. A modified panel method is used to generate the potential of any arbitrary shaped obstacle in three‐dimensional space. An alternative backbone curve concept and an efficient fitting method are introduced to control the trajectory of proximal links. The fitting method is recursive and avoids the complications involved with solving large systems of nonlinear algebraic equations. The combination of a three‐dimensional safe path derived from the harmonic potential field and the backbone curve concept leads to an elegant kinematic control strategy that guarantees obstacle avoidance. © 2003 Wiley Periodicals, Inc.
Bioinspired Engineering of Exploration Systems: A Horizon Sensor/Attitude Reference System Based on the Dragonfly Ocelli for Mars Exploration Applications
Authors: Chahl Javaan , Thakoor Sarita , Le Bouffant Naig , Stange Gert , Srinivasan M. V. , Hine Butler , Zornetzer Steven
Published: December 2002

Bioinspired engineering of exploration systems (BEES) is a fast emerging
new discipline. It focuses on distilling the principles found in successful,
nature‐tested mechanisms of specific crucial functions that are hard to accomplish
by conventional methods, but are accomplished rather deftly in nature by biological
organisms. The intent is not just to mimic operational mechanisms found in
a specific biological organism but to imbibe the salient principles from a
variety of diverse organisms for the desired crucial function. Thereby, we
can build exploration systems that have specific capabilities endowed beyond
nature, as they will possess a mix of the best nature‐tested mechanisms for
each particular function. Insects (for example, honey bees and dragonflies)
cope remarkably well with their world, despite possessing a brain that carries
less than 0.01% as many neurons as ours does. Although most insects have immobile
eyes, fixed focus optics, and lack stereo vision, they use a number of ingenious
strategies for perceiving their world in three dimensions and navigating successfully
in it. We are distilling some of these insect‐inspired strategies for utilizing
optical cues to obtain unique solutions to navigation, hazard avoidance, altitude
hold, stable flight, terrain following, and smooth deployment of payload.
Such functionality can enable access to otherwise unreachable exploration
sites for much sought‐after data. A BEES approach to developing autonomous
flight systems, particularly in small scale, can thus have a tremendous impact
on autonomous airborne navigation of these biomorphic flyers particularly
for planetary exploration missions, for example, to Mars which offer unique
challenges due to its thin atmosphere, low gravity, and lack of magnetic field.
Incorporating these success strategies of bioinspired navigation into biomorphic
sensors such as the horizon sensor described herein fulfills for the first
time the requirements of a variety of potential future Mars exploration applications
described in this paper. Specifically we have obtained lightweight (∼6
g), low power (<40 mW ), and robust autonomous horizon sensing for flight
stabilization based on distilling the principles of the dragonfly ocelli.
Such levels of miniaturization of navigation sensors are essential to enable
biomorphic microflyers (<1 kg) that can be deployed in large numbers for
distributed measurements. In this paper we present the first experimental
test results of a biomorphic flyer platform with an embedded biomorphic ocellus
(the dragonfly‐inspired horizon sensor/attitude reference system). These results
from the novel hardware implementation of a horizon sensor demonstrate the
advantage of our approach in adapting principles proven successful in nature
to accomplish navigation for Mars exploration. © 2003 Wiley Periodicals,
Inc.
Helicase activity is only partially required for Schizosaccharomyces pombe Rqh1p function
Authors: Ahmad Fouzia , Kaplan Craig D. , Stewart Elspeth
Published: December 2002

The RecQ‐related family of DNA helicases is required for the maintenance of genomic stability in organisms ranging from bacteria to humans. In humans, mutation of three RecQ‐related helicases, BLM, WRN and RecQL4, cause the cancer‐prone and premature ageing diseases of Bloom syndrome, Werner's syndrome and Rothmund–Thompson syndrome, respectively. In the fission yeast Schizosaccharomyces pombe, disruption of the rqh1+ gene, which encodes the single Sz. pombe RecQ‐related helicase, causes cells to display reduced viability and elevated levels of chromosome loss. After S‐phase arrest or DNA damage, cells lacking rqh1+ function display elevated levels of homologous recombination and defective chromosome segregation. Here we show that, like other RecQ family members, the Rqh1p protein displays 3′ to 5′ DNA helicase activity. Interestingly, however, unlike other RecQ family members, the helicase activity of Rqh1p is only partially required for its function in recovery from S‐phase arrest or DNA damage. We also report that high cellular levels of Rqh1p result in lethal chromosome segregation defects, while more moderate levels of Rqh1p cause significantly elevated rates of chromosome loss. This suggests that careful regulation of RecQ‐like protein levels in eukaryotic cells is vital for maintaining genome stability. Copyright © 2002 John Wiley & Sons, Ltd.
The identification of the Saccharomyces cerevisiae gene AYT1(ORF‐YLL063c) encoding an acetyltransferase
Authors: Alexander Nancy J. , McCormick Susan P. , Hohn Thomas M.
Published: December 2002

The recent isolation and characterization of Tri101 in Fusarium sporotrichioides has led to the functional identification of the yeast open reading frame (ORF) YLL063c, located on chromosome XII of Saccharomyces cerevisiae. The sequence of YLL063c predicts a protein of 474 residues that has 45% identity and 70% similarity to FsTri101. FsTri101 encodes a trichothecene 3‐O‐acetyltransferase that functions in trichothecene biosynthesis. Feeding studies indicated low levels of C3‐OH acetylation in cultures of the laboratory yeast strain, RW2802. No similar activity was found in RW2802 transformed with an integrative plasmid carrying a disrupted YLL063c gene. Based on these results, which show structural and functional similarities between YLL063c and FsTri101, we propose that YLL063c encodes an acetyltransferase capable of trichothecene 3‐O‐acetylation and have named this gene AYT1. Published in 2002 by John Wiley & Sons, Ltd.
Characterization of a gene encoding tRNA nucleotidyltransferase from Candida glabrata
Authors: Hanic‐Joyce Pamela J. , Joyce Paul B. M.
Published: December 2002

A gene encoding ATP (CTP):tRNA nucleotidyltransferase (EC2.7.7.25) was isolated from Candida (Torulopsis) glabrata by complementation in Saccharomyces cerevisiae. The predicted amino acid sequence of the protein revealed a large region with high sequence similarity to members of the Class II group of the nucleotidyltransferase superfamily and an N‐terminal region characteristic of a mitochondrial targeting sequence. The essential role of the carboxylates within the conserved DXD and RRD motifs was confirmed by mutagenesis. C. glabrata strains bearing truncated CCA1 genes that lacked sequences encoding the putative mitochondrial targeting peptide were unable to grow on non‐fermentable carbon sources but were able to grow on a fermentable carbon source. These results suggest that, as in S. cerevisiae, the C. glabrata CCA‐adding enzyme is a sorting isozyme that functions in multiple cellular compartments. Mapping of the 5′‐ends of primary transcripts of CCA1 revealed multiple transcription start sites located both upstream of and between two in‐frame start codons. When the cells were cultured on a non‐fermentable carbon source the longer transcripts appeared more abundant, suggesting that the choice of transcription start sites was influenced by carbon source. The shorter transcripts, which lacked sequences encoding the mitochondrial targeting information, were more predominant in cells grown on glucose. These observations suggest that expression of CCA‐adding isozymes in C. glabrata may be regulated. The DNA sequence has been assigned GenBank Accession No. AF098803. Copyright © 2002 John Wiley & Sons, Ltd.
Polymorphism of the MPR1 gene required for toxic proline analogue resistance in the Saccharomyces cerevisiae complex species
Authors: Kimura Yasuko , Nakamori Shigeru , Takagi Hiroshi
Published: December 2002

We recently discovered, on the chromosome of Saccharomyces cerevisiae Σ1278b, novel MPR1 and MPR2 genes required for resistance to a toxic analogue of L‐proline, L‐azetidine‐2‐carboxylic acid. The MPR genes, which were absent in the S. cerevisiae genome project strain S288C, encoded a novel acetyltransferase of 229 amino acids that detoxifies the analogue by acetylating it. The MPR1 gene homologue found in Schizosaccharomyces pombe was also shown to encode a similar acetyltransferase. To further analyse the origin and the physiological role of the yeast novel gene, we report here the comparative analysis of the MPR1 gene in the S. cerevisiae complex spp. which belong to the Saccharomyces sensu stricto group. Only the type strain of S. paradoxus exhibited resistance and acetyltransferase activity to L‐azetidine‐2‐carboxylic acid. PCR was then used to isolate the new MPR1 homologue (Spa MPR1) from S. paradoxus with the primers based on the sequence of the MPR1 gene. Gene expression and enzymatic analysis showed that the cloned Spa MPR1 gene encodes an L‐azetidine‐2‐carboxylic acid acetyltransferase of 231 amino acids, which has 87% identity to the MPR1 protein. We also found in the protein databases that S. bayanus contains a DNA fragment that is partly homologous to the MPR1 gene. However, the gene product was considered to lose the enzymatic activity, possibly due to the gene truncation or the base substitution(s) at the important region for catalysis. Further, genomic PCR analysis showed that most of the S. cerevisiae complex spp. have the sequence highly homologous to the MPR1 gene. Copyright © 2002 John Wiley & Sons, Ltd.
Isolation and characterization of the gene URA3 encoding the orotidine‐5′‐phosphate decarboxylase from Torulaspora delbrueckii
Authors: Hernandez‐Lopez Maria Jose , Prieto Jose Antonio , Randez‐Gil Francisca
Published: December 2002

A DNA fragment containing the URA3 gene from Torulaspora delbrueckii was isolated by complementation cloning in Saccharomyces cerevisiae. DNA sequence analysis revealed the presence of an ORF of 795 bp, encoding a 264 amino acid protein, which shares a high similarity to the Saccharomycetaceae Ura3 proteins. Furthermore, the cloned ORF fully complemented the ura3 mutation of S. cerevisiae, confirming that it encodes for the TdUra3 protein. The GeneBank Accession No. for TdURA3 is AF518402. Copyright © 2002 John Wiley & Sons, Ltd.
Kinetic properties and structural characteristics of an unusual two‐domain arginine kinase of the clam Corbicula japonica
Authors: Suzuki Tomohiko , Tomoyuki Taniguchi , Uda Kouji
Published: December 2002

Arginine kinase (AK) from the clam Corbicula japonica is a unique enzyme in that it has an unusual two‐domain structure with molecular mass of 80 kDa. It lacks two functionally important amino acid residues, Asp‐62 and Arg‐193, which are conserved in other 40 kDa AKs and are assumed to be key residues for stabilizing the substrate‐bound structure. K
m
arg and V
max values for the recombinant two‐domain AK were determined. These values were close to those of usual 40 kDa AKs, although Corbicula AK lacks the functionally important Asp‐62 and Arg‐193. Domain 2 of Corbicula AK was separated from the two‐domain enzyme and was expressed in Escherichia coli. Domain 2 still exhibited activity. However, kinetic parameters for domain 2 appeared to be slightly, but significantly, different from those of two‐domain AK. Thus, it is likely that the formation of the contiguous dimer alters the kinetic properties of its constituent domains significantly. Comparison of K
d
arg and K
m
arg for two‐domain AK and its domain 2 showed that the affinity of the enzyme for arginine is greater in the presence of substrate ATP than in its absence. Presumably this difference is correlated with the large structural differences in the enzyme in the presence or absence of substrate, namely open and closed structures. We expressed three mutants of Corbicula AK domain 2 (His‐60 to Gly or Arg, Asp‐197 to Gly), and determined their K
m
arg and V
max values. The affinity for the substrate arginine in mutant enzymes was reduced considerably, accompanied by a decrease in V
max. These results suggest that His‐60 and Asp‐197 affect the substrate binding system, and are consistent with the hypothesis that a hydrogen bond is formed between His‐60 and Asp‐197 in Corbicula AK as a substitute for the Asp‐62 and Arg‐193 bond in normal AKs.
Gene expression monitoring accurately predicts medulloblastoma positive and negative clinical outcomes
Authors: Korenberg Michael J
Published: December 2002

Prediction of medulloblastoma clinical outcome is crucial to personalizing treatment, both to identify high‐risk patients for aggressive or alternative therapy and to spare those at low risk from excessive treatment. The best predictors [Pomeroy et al. (2002) Nature 415, 436–442], based on gene expression monitoring at diagnosis, have shown much less accuracy in recognizing patients with eventual failed outcomes – <50% for the predictor making fewest total errors – than those who would survive, while a single gene predictor exhibited reverse asymmetry. Such inaccuracy in recognizing one of the outcomes is a problem for clinical use. We hypothesized that a non‐linear model could be built to significantly improve prediction of medulloblastoma outcome, thereby promoting use of gene‐expression‐based predictors in a clinical setting. In fact, this approach resulted in fewer errors and much less asymmetry in prediction, and bidirectional accuracy of about 80% could be obtained via its combination with other methods. Indeed, three combinations of methods were identified that yielded significantly better predictions of clinical outcome than previously attained, making feasible predictors of medulloblastoma treatment response with greatly improved bidirectional accuracy essential for clinical use.
Prospective memory functioning in people with and without brain injury
Authors: Groot Yvonne C. T. , Wilson Barbara A. , Evans Jonathan , Watson Peter
Published: December 2002

Prospective remembering has been relatively underinvestigated in neurological patients. This paper describes a group study in which the prospective memory performance of 36 people with brain injury and 28 control participants is compared. We used a new instrument, the Cambridge Behaviour Prospective Memory Test (CBPMT) to assess prospective memory. This comprises 4 time-based and 4 event-based tasks. Participants were allowed to take notes to help them remember the tasks. The relationships between CBPMT scores, scores on formal tests and subjective reports on memory, attention and executive functioning were analyzed. The key findings were that (1) note-taking significantly benefited prospective memory performance, (2) significant relationships were found between scores on the prospective memory test and scores on tests of memory and executive functions, and (3) participants had more difficulty with the time-based than with the event-based prospective memory tasks. The results suggest that compensatory strategies improve prospective memory functioning; memory for content as well as attention and executive functioning processes are involved in prospective memory; and that time-based tasks are more difficult than event-based tasks because they place higher demands on inhibitory control mechanisms. Discussion focuses on the implications of these results for neuropsychological assessment and rehabilitation.
Driving in young adults with attention deficit hyperactivity disorder: Knowledge, performance, adverse outcomes, and the role of executive functioning
Authors: Barkley Russell A. , Murphy Kevin R. , Dupaul George J. , Bush Tracie
Published: December 2002

Past studies find that attention deficit hyperactivity disorder (ADHD) creates a higher risk for adverse driving outcomes. This study comprehensively evaluated driving in adults with ADHD by comparing 105 young adults with the disorder (age 17–28) to 64 community control (CC) adults on five domains of driving ability and a battery of executive function tasks. The ADHD group self-reported significantly more traffic citations, particularly for speeding, vehicular crashes, and license suspensions than the CC group, with most of these differences corroborated in the official DMV records. Cognitively, the ADHD group was less attentive and made more errors during a visual reaction task under rule-reversed conditions than the CC group. The ADHD group also obtained lower scores on a test of driving rules and decision-making but not on a simple driving simulator. Both self- and other-ratings showed the CC group employed safer routine driving habits than the ADHD group. Relationships between the cognitive and driving measures and the adverse outcomes were limited or absent, calling into question their use in screening ADHD adults for driving risks. Several executive functions also were significantly yet modestly related to accident frequency and total traffic violations after controlling for severity of ADHD. These results are consistent with earlier studies showing significant driving problems are associated with ADHD. This study found that these driving difficulties were not a function of comorbid oppositional defiant disorder, depression, anxiety, or frequency of alcohol or illegal drug use. Findings to date argue for the development of interventions to reduce driving risks among adults with ADHD.
Semantic priming in schizophrenia: A review and synthesis
Authors: Minzenberg Michael J. , Ober Beth A. , Vinogradov Sophia
Published: December 2002

In this paper, we present a review of semantic priming experiments in schizophrenia. Semantic priming paradigms show utility in assessing the role of deficits in semantic memory network access in the pathology of schizophrenia. The studies are placed in the context of current models of information processing. In this review we include all English-language reports (from peer-reviewed journals) of single-word semantic priming studies involving participants with schizophrenia. The studies to date show schizophrenic patients to exhibit variable semantic priming effects under automatic processing conditions, and consistent impairments under controlled0attentional conditions. We also describe associations with other neurocognitive dysfunction, neurochemical and electrophysiological disturbances, and clinical manifestations (such as thought disorder).
Semantic monitoring of words with emotional connotation during fMRI: Contribution of anterior left frontal cortex
Authors: Crosson Bruce , Cato M. Allison , Sadek Joseph R. , Gökçay Didem , Bauer Russell M. , Fischler Ira S. , Maron Leeza , Gopinath Kaundinya , Auerbach Edward J. , Browd Samuel R. , Briggs Richard W.
Published: December 2002

Previous studies showed that cortex in the anterior portions of the left frontal and temporal lobes participates in generating words with emotional connotations and processing pictures with emotional content. If these cortices process the semantic attribute of emotional connotation, they should be active whenever processing emotional connotation, without respect to modality of input or mode of output. Thus, we hypothesized that they would activate during monitoring of words with emotional connotations. Sixteen normal subjects performed semantic monitoring of words with emotional connotations, animal names, and implement names during fMRI. Cortex in the anterior left frontal lobe demonstrated significant activity for monitoring words with emotional connotations compared to monitoring tone sequences, animal names, or implement names. Together, the current and previous results implicate cortex in the anterior left frontal lobe in semantic processing of emotional connotation, consistent with connections of this cortex to paralimbic association areas. Current findings also indicate that neural substrates for processing emotional connotation are independent of substrates for processing the categories of living and nonliving things.
Information processing difficulty long after self-reported concussion
Authors: Bernstein Daniel M.
Published: December 2002

Recovery of cognitive function after mild head injury (MHI) is thought to be relatively swift and complete. The present study replicates and extends previous work in which university students with self-reported concussion demonstrated reduced P300 amplitude on a set of easy and difficult attention tasks, in addition to performing more poorly than controls on demanding cognitive tasks many years after injury. In the present study, 13 students with self-reported concussion (MHI group: M time since injury 5 8 years) and 10 controls were matched for age, sex, education, and a variety of cognitive, physical and emotional complaints. Controls outperformed the MHI group on the Digit Symbol substitution task and on a difficult dual task involving tone discrimination and visual working memory. Additionally, controls exhibited larger P300 amplitudes on both an easy and a difficult auditory discrimination task. A combination of electrophysiological, neuropsychological and self-report indices predicted group membership (MHI vs. control) with 88% accuracy. The present results, coupled with previous work, offer preliminary evidence that the combination of event-related potentials and demanding behavioral measures might reveal long-lasting, subtle cognitive problems associated with MHI. These findings may challenge existing notions of complete recovery after MHI.
Effects of alcohol and cigarette use on cognition in middle-aged adults
Authors: Schinka John A. , Vanderploeg Rodney D. , Rogish Miles , Ordorica Patricia Isbell
Published: December 2002

In this retrospective cohort study we examined the independent and interactive effects of drinking and smoking on cognition in a sample of 3361 males, ages 31 to 49, with varying lifetime histories of alcohol and cigarette use. Dependent variables were neuropsychological measures of global and specific cognitive abilities. Comparison of the ability scores of seven groups, defined by their drinking and smoking histories, explained only 5.4% of the multivariate variance in cognitive ability and less than 2% in any individual cognitive measure. Regression analyses for current drinkers and smokers showed only a single significant, but negligible, effect of pack-years of smoking on a measure of global cognitive ability. Differences in cognitive function in groups defined by intensity of alcohol and cigarette use revealed no significant effect for drinking and a significant, but very small, effect for smoking.
Differential sex effects in olfactory functioning: The role of verbal processing
Authors: Öberg Christina , Larsson Maria , Bäckman Lars
Published: December 2002

We investigated sex difference across a number of olfactory tasks. Thirty-six men and 35 women ranging in age from 19 to 36 years were assessed in 6 different tasks: absolute sensitivity for n-butanol, intensity discrimination, quality discrimination, episodic recognition memory for familiar and unfamiliar odors, and odor identification. No sex differences were observed in the tasks tapping primarily sensory acuity (i.e., odor sensitivity, intensity discrimination, and quality discrimination) or in episodic memory for unfamiliar odors. By contrast, women outperformed men in the tasks involving verbal processing (i.e., memory for familiar odors and odor identification). Interestingly, controlling for odor naming ability resulted in that the observed sex difference in episodic odor memory for familiar odors disappeared. This outcome suggests that women's superiority in episodic odor memory is largely mediated by their higher proficiency in odor identification.
Sequence and Structure of the Mouse Connexin45 Gene
Authors: Baldridge Dustin , Lecanda Fernando , Shin Chan-Soo , Stains Joseph , Civitelli Roberto
Published: December 2002

The connexin45 (Cx45) gene was cloned from a mouse genomic Bacterial Artificial Chromosome library. Approximately 8.4 kb of the genomic DNA was sequenced, and the structure of the Cx45 gene was determined. The mouse Cx45 gene is composed of 3 exons, with the entire coding sequence contained within exon III (EMBL Accession Number AJ300716). This structure is unique for the Cx45 gene, since all other members of the connexin family have only two exons. In addition, computer analysis reveals a potential TATA box and two putative AP-1 binding sites in the 5′ region of the gene. Sequence alignment with connexin43 indicates substantial homology in the intronic sequences upstream of the 3′ exons of the two genes, suggesting that the Cx45 gene is inherently similar to the rest of the connexin family, and that it probably evolved from an ancestor common to the other connexins.
Nasomaxillary Hypoplasia and Severe Orofacial Clefting in a Child of a Mother with Phenylketonuria
Authors: Sweeney E. , Fryer A.
Published: December 2002

The offspring of mothers with untreated or poorly controlled phenylketonuria (PKU) (McKusick 261600) are at risk of having congenital anomalies including microcephaly, congenital heart defects and developmental delay (Rouse et al 1997). We report a child born to a mother with poorly controlled PKU and suggests that the facial abnormalities seen in this child could be part of the spectrum of maternal PKU embryopathy.
Glycolipid Analysis of Different Tissues and Cerebrospinal Fluid in Type II Gaucher Disease
Authors: Gornati R. , Berra B. , Montorfano G. , Martini C. , Ciana G. , Ferrari P. , Romano M. , Bembi B.
Published: December 2002

The lipid composition or the liver, spleen, brain, cerebellum and cerebrospinal fluid of a Gaucher disease type II patient who died at the age of 5 months was examined. The glycolipid analysis demonstrated a marked increase of total amounts not only in the peripheral tissues but also in the brain cerebellum and cerebrospinal fluid, with a prevalence of glucosylceramide. A reduction in gangliosides was observed in all the analysed tissues with a relative increase of GD3 in the nervous tissue. The fatty acid composition of glucosylceramide showed a prevalence of stearic acid in the central nervous system, while in the peripheral tissues palmitic acid was prevalent. This result suggests a different origin of the glucosylceramide stored in different tissues. The generalized reduction of gangliosides and their modified distribution together with the central nervous system GD3 increment represent a new observation. These data could be useful in the effort to clarify the pathophysiological mechanism of brain damage in neuronopathic Gaucher disease.
Ca-ATPase Activity and Protein Composition of Sarcoplasmic Reticulum Membranes Isolated from Skeletal Muscles of Typical Hibernator, the Ground Squirrel Spermophilus undulatus
Authors: Malysheva Anna N. , Storey Kenneth B. , Lopina Olga D. , Rubstov Alexander M.
Published: December 2002

Ca-ATPase activity in sarcoplasmic reticulum (SR) membranes isolated from skeletal muscles of the typical hibernator, the ground squirrel Spermophilus undulatus, is about 2-fold lower than that in SR membranes of rats and rabbits and is further decreased 2-fold during hibernation. The use of carbocyanine anionic dye Stains-All has revealed that Ca-binding proteins of SR membranes, histidine-rich Ca-binding protein and sarcalumenin, in ground squirrel, rat, and rabbit SR have different electrophoretic mobility corresponding to apparent molecular masses 165, 155, and 170 kDa and 130, 145, and 160 kDa, respectively; the electrophoretic mobility of calsequestrin (63 kDa) is the same in all preparations. The content of these Ca-binding proteins in SR membranes of the ground squirrels is decreased 3–4 fold and the content of 55, 30, and 22 kDa proteins is significantly increased during hibernation.
A Note on the Ohya-Masuda Quantum Algorithm
Authors: Dugić Miroljub
Published: December 2002

We analyze the Ohya-Masuda quantum algorithm that solves the so-called “satisfiability” problem, which is an NP-complete problem of the complexity theory. We distinguish three steps in the algorithm, and analyze the second step, in which a coherent superposition of states (a “pure” state) transforms into an “incoherent” mixture presented by a density matrix. We show that, if “nonideal” (in analogy with “nonideal” quantum measurement), this transformation can make the algorithm to fail in some cases. On this basis we give some general notions on the physical implementation of the Ohya-Masuda algorithm.
On the structure and motions of cyclones in the northern Gulf of Mexico
Authors: Hamilton Peter , Berger Thomas J. , Johnson Walter
Published: December 2002

The eddy field on the northern slope of the Gulf of Mexico has been investigated using high‐resolution AXBT and AXCP aircraft surveys and ARGOS tracked drifters. A number of vigorous cyclones were mapped. Their vertical structures showed solid body rotation with radii of 50–75 km with a subsurface maximum (∼40 cm s−1) at the outer edge at about 150 m. Flows had little shear in the upper 400 m and only weak currents below depths of 800 to 1000 m. Cyclones were observed to move on and off the slope under the influence of swirl velocities of larger warm‐core eddies, including Loop Current (LC) anticyclones. Rotational periods range from about 7 to 18 days. The mapped eddy fields contained both cyclones and anticyclones with a range of diameters from about 40 to 150 km. The presence of many relatively small‐scale features along the upper slope strongly affects features of the shelf break velocity field that were measured by a moored current meter array. The directions and vertical shears of the moored currents were consistent with flows caused by the northern edges of cyclones and anticyclones. These eddies can cause persistent events and strong cross‐isobath fluctuations of the currents. Counterrotating pairs of eddies on the upper slope seem to be a mechanism for the transport of material on and off the Louisiana and east Texas shelves. Coherences between moorings, 74 km apart, were generally not significant, as might be expected when the currents are dominated by small‐scale eddies. However, an EOF analysis of the shelf break array indicates that about 40% of the along‐slope current variances could be attributed to westward propagating continental shelf waves.
Admittance estimates of mean crustal thickness and density at the Martian hemispheric dichotomy
Authors: Nimmo Francis
Published: December 2002

Admittance estimates from line‐of‐sight (LOS) acceleration profiles of the Mars Global Surveyor spacecraft are used to constrain the mean crustal thickness and surface density centered on the hemispheric dichotomy, from 110°E to 220°E, 40°S to 20°N. Models with uniform crustal properties predict lower than expected bulk crustal densities. Two‐layer models with loading only at the surface and the Moho produce satisfactory fits to the data. The best fit surface density, crustal thickness tc, and elastic thickness Te are 2.5 Mg m−3, 27 km, and 61 km, respectively. Higher elastic thicknesses require lower crustal thicknesses, and vice versa. The best fit ratio of Moho to surface loading F is close to 1. Models with no bottom loading (F = 0) provide a poor fit to the data; underestimates in F result in underestimates of both tc and Te. The surface density is lower than that measured from Martian meteorites and by admittance analyses of young volcanoes but is well constrained by the short‐wavelength admittance values. For misfits up to 1.5 times the minimum value and a fixed surface density of 2.5 Mg m−3, the ranges of tc, Te, and F are 1–75 km, 37–89 km, and 0.4–2.6, respectively. The apparently compensated nature of the large impact basins has been used to infer a lower bound on southern hemisphere crustal thickness of 45 km. If this estimate is correct, the likely mean crustal thickness in the area considered is 55 ± 20 km.
Two dogs, new tricks: A two‐rover mission simulation using K9 and FIDO at Black Rock Summit, Nevada
Authors: Stoker Carol R. , Roush Ted L. , Arvidson Raymond E. , Bresina John L. , Bualat Maria G. , Edwards Laurence J. , Flueckiger Lorenzo J. , Washington Richard M. , Nguyen Laurent A. , Thomas Hans , Wright Anne R.
Published: December 2002

An experiment illustrating two rovers cooperatively exploring a field site was performed at Black Rock Summit, Nevada, in May 2000. The rovers FIDO and K9 are mechanically identical prototype planetary rovers designed at the Jet Propulsion Laboratory. FIDO carried high‐resolution false‐color infrared and low‐resolution monochrome stereo cameras and an infrared point spectrometer on a mast‐mounted pointable platform, a manipulator arm equipped with a color microscopic imager, and a coring drill for sample collection. K9 carried on a mast‐mounted pointable platform high‐resolution color and low‐resolution monochrome stereo cameras, and a Laser Induced Breakdown Spectrometer for standoff elemental analysis. A team located at Jet Propulsion Laboratory commanded the two rovers for 3 days. K9 obtained stereo images of targets, and three‐dimensional models were constructed to determine the best locations for FIDO to obtain core samples. A drilling target was selected 1.5 m from the starting position of FIDO. Six command cycles and 2 m of traversing were required for FIDO to reach, drill into, and place an instrument on the target. K9 required 11 command cycles to traverse 60 m and obtain full‐coverage stereo images of two rock targets along its route. Virtual reality‐based visualization software called Viz provided situational awareness of the environment for both rovers. Commands to K9 were planned using Viz, resulting in improved rover performance. The results show that two rovers can be used synergistically to achieve science goals, but further testing is needed to completely explore the value of two‐rover missions.
ARRAY SEISMOLOGY: METHODS AND APPLICATIONS
Authors: Rost Sebastian , Thomas Christine
Published: December 2002

Since their development in the 1960s, seismic arrays have given a new impulse to seismology. Recordings from many uniform seismometers in a well‐defined, closely spaced configuration produce high‐quality and homogeneous data sets, which can be used to study the Earth's structure in great detail. Apart from an improvement of the signal‐to‐noise ratio due to the simple summation of the individual array recordings, seismological arrays can be used in many different ways to study the fine‐scale structure of the Earth's interior. They have helped to study such different structures as the interior of volcanos, continental crust and lithosphere, global variations of seismic velocities in the mantle, the core‐mantle boundary and the structure of the inner core. For this purpose many different, specialized array techniques have been developed and applied to an increasing number of high‐quality array data sets. Most array methods use the ability of seismic arrays to measure the vector velocity of an incident wave front, i.e., slowness and back azimuth. This information can be used to distinguish between different seismic phases, separate waves from different seismic events and improve the signal‐to‐noise ratio by stacking with respect to the varying slowness of different phases. The vector velocity information of scattered or reflected phases can be used to determine the region of the Earth from whence the seismic energy comes and with what structures it interacted. Therefore seismic arrays are perfectly suited to study the small‐scale structure and variations of the material properties of the Earth. In this review we will give an introduction to various array techniques which have been developed since the 1960s. For each of these array techniques we give the basic mathematical equations and show examples of applications. The advantages and disadvantages and the appropriate applications and restrictions of the techniques will also be discussed. The main methods discussed are the beam‐forming method, which forms the basis for several other methods, different slant stacking techniques, and frequency–wave number analysis. Finally, some methods used in exploration geophysics that have been adopted for global seismology are introduced. This is followed by a description of temporary and permanent arrays installed in the past, as well as existing arrays and seismic networks. We highlight their purposes and discuss briefly the advantages and disadvantages of different array configurations.
Separating natural and bomb‐produced radiocarbon in the ocean: The potential alkalinity method
Authors: Rubin Stephany I. , Key Robert M.
Published: December 2002

The use of radiocarbon (Δ14C) as a tracer for oceanic processes generally requires differentiation of naturally occurring radiocarbon from the bomb component produced by atmospheric nuclear weapons testing. We present a new separation method based on the strong linear correlation between Δ14C and potential alkalinity. Unlike previous techniques the new algorithm is applicable at all latitudes. Additionally, the potential alkalinity method provides an estimate of surface ocean prebomb Δ14C concentrations. Predictions with the technique appear to be unbiased and have uncertainties which are less than previous techniques.
Representing key phytoplankton functional groups in ocean carbon cycle models: Coccolithophorids
Authors: Iglesias‐Rodríguez M. Débora , Brown Christopher W. , Doney Scott C. , Kleypas Joan , Kolber Dorota , Kolber Zbigniew , Hayes Paul K. , Falkowski Paul G.
Published: December 2002

Carbonates are the largest reservoirs of carbon on Earth. From mid‐Mesozoic time, the biologically catalyzed precipitation of calcium carbonates by pelagic phytoplankton has been primarily due to the production of calcite by coccolithophorids. In this paper we address the physical and chemical processes that select for coccolithophorid blooms detected in Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) ocean color imagery. Our primary goal is to develop both diagnostic and prognostic models that represent the spatial and temporal dynamics of coccolithophorid blooms in order to improve our knowledge of the role of these organisms in mediating fluxes of carbon between the ocean, the atmosphere, and the lithosphere. On the basis of monthly composite images of classified coccolithophorid blooms and global climatological maps of physical variables and nutrient fields, we developed a probability density function that accounts for the physical chemical variables that predict the spatiotemporal distribution of coccolithophorids in the world oceans. Our analysis revealed that areas with sea surface temperatures (SST) between 3° and 15°C, a critical irradiance between 25 and 150 μmol quanta m−2 s−1, and decreasing nitrate concentrations (ΔN/Δt < 0) are selective for upper ocean large‐scale coccolithophorid blooms. While these conditions favor both Northern and Southern Hemisphere blooms of the most abundant coccolithophorid in the modern oceans, Emiliania huxleyi, the Northern and Southern Hemisphere populations of this organism are genetically distinct. Applying amplified fragment length polymorphism as a marker of genetic diversity, we identified two major taxonomic clades of E. huxleyi; one is associated with the Northern Hemisphere blooms, while the other is found in the Southern Hemisphere. We suggest a rule of “universal distribution and local selection”: that is, coccolithophorids can be considered cosmopolitan taxa, but their genetic plasticity provides physiological accommodation to local environmental selection pressure. Sea surface temperature, critical irradiance, and ΔN/Δt were predicted for the years 2060–2070 using the NCAR Community Climate System Model to generate future monthly probability distributions of coccolithophorids based upon the relationships observed between the environmental variables and coccolithophorid blooms in modern oceans. Our projected probability distribution analysis suggests that in the North Atlantic, the largest habitat for coccolithophorids on Earth, the areal extent of blooms will decrease by up to 50% by the middle of this century. We discuss how the magnitude of carbon fluxes may be affected by the evolutionary success of coccolithophorids in future climate scenarios.
Seasonal variation in precipitation patterns to the global ocean: An analysis of the GPCP version 2 data set
Authors: Yuan Jinchun , Miller Richard L.
Published: December 2002

Precipitation affects the thermohaline circulation, chemical mass balance, and primary productivity of surface ocean waters. An analysis of temporal and spatial variation of oceanic precipitation was conducted on the Global Precipitation Climatology Project (GPCP) version 2 data set, a monthly 2.5° × 2.5° latitude‐longitude gridded data set for the period 1979 to 1999. While the precipitation patterns observed are generally similar to those reported in previous climatologies, new features and greater detail of global precipitation were revealed from our analysis of the GPCP data set. High precipitation was observed in the intertropical convergence zone (ITCZ), the South Pacific convergence zone (SPCZ), and the storm tracks in the North Pacific and Atlantic Oceans. Low precipitation was observed in the Polar regions and in the subtropics of the East Pacific, East Atlantic, and the Southeast and Northwest Indian Ocean. The spatial coverage of these high and low precipitation regions changed through the year. A strong seasonal cycle of precipitation was observed for the Northern and the Southern Hemispheres. The area‐weighted mean precipitation increased from a minimum of ∼2 mm d−1 in February to a maximum of ∼5 mm d−1 in August in the Northern Hemisphere and from a minimum of ∼2.5 mm d−1 in September to a maximum of ∼3.5 mm d−1 in March in the Southern Hemisphere. Similar seasonal cycles of precipitation were observed for each ocean basin. Global precipitation also varied significantly with both latitude and longitude, with a latitudinal maximum at 56°S, 39°S, 4°S, 6°N, 39°N, and 56°N, and a longitudinal maximum over each ocean. The seasonal varying precipitation patterns are a foundation for evaluating the effect of wet deposition on ocean circulation, flux of chemical species, and its effect on marine ecosystems.
Carbon isotope discrimination in forest and pasture ecosystems of the Amazon Basin, Brazil
Authors: Ometto Jean P. H. B. , Flanagan Lawrence B. , Martinelli Luiz A. , Moreira Marcelo Z. , Higuchi Niro , Ehleringer James R.
Published: December 2002

Our objective was to measure the stable carbon isotope composition of leaf tissue and CO2 released by respiration (δr), and to use this information as an estimate of changes in ecosystem isotopic discrimination that occur in response to seasonal and interannual changes in environmental conditions, and land‐use change (forest‐pasture conversion). We made measurements in primary forest and pastures in the Amazon Basin of Brazil. At the Santarém forest site, δr values showed a seasonal cycle varying from less than −29‰ to approximately −26‰. The observed seasonal change in δr was correlated with variation in the observed monthly precipitation. In contrast, there was no significant seasonal variation in δr at the Manaus forest site (average δr approximately −28‰), consistent with a narrower range of variation in monthly precipitation than occurred in Santarém. Despite substantial (9‰) vertical variation in leaf δ13C, the average δr values observed for all forest sites were similar to the δ13C values of the most exposed sun foliage of the dominant tree species. This suggested that the major portion of recently respired carbon dioxide in these forests was metabolized carbohydrate fixed by the sun leaves at the top of the forest canopy. There was no significant seasonal variation observed in the δ13C values of leaf organic matter for the forest sites. We sampled in pastures dominated by the C4 grass, Brachiaria spp., which is planted after forest vegetation has been cleared. The carbon isotope ratio of respired CO2 in pastures was enriched in 13C by approximately 10‰ compared to forest ecosystems. A significant temporal change occurred in δr after the Manaus pasture was burned. Burning removed much of the encroaching C3 shrub vegetation and so allowed an increased dominance of the C4 pasture grass, which resulted in higher δr values.