bluuebunny/crossref_metadata_2025 huggingface dataset:
Introns and Splicing Elements of Five Diverse Fungi
Authors: Kupfer Doris M. , Drabenstot Scott D. , Buchanan Kent L. , Lai Hongshing , Zhu Hua , Dyer David W. , Roe Bruce A. , Murphy Juneann W.
Published: October 2004

Genomic sequences and expressed sequence tag data for a diverse group of fungi (
Saccharomyces cerevisiae
,
Schizosaccharomyces pombe
,
Aspergillus nidulans
,
Neurospora crassa
, and
Cryptococcus neoformans
) provided the opportunity to accurately characterize conserved intronic elements. An examination of large intron data sets revealed that fungal introns in general are short, that 98% or more of them belong to the canonical splice site (ss) class (5′GU…AG3′), and that they have polypyrimidine tracts predominantly in the region between the 5′ ss and the branch point. Information content is high in the 5′ ss, branch site, and 3′ ss regions of the introns but low in the exon regions adjacent to the introns in the fungi examined. The two yeasts have broader intron length ranges and correspondingly higher intron information content than the other fungi. Generally, as intron length increases in the fungi, so does intron information content. Homologs of U2AF spliceosomal proteins were found in all species except for
S. cerevisiae
, suggesting a nonconventional role for U2AF in the absence of canonical polypyrimidine tracts in the majority of introns. Our observations imply that splicing in fungi may be different from that in vertebrates and may require additional proteins that interact with polypyrimidine tracts upstream of the branch point. Theoretical protein homologs for Nam8p and TIA-1, two proteins that require U-rich regions upstream of the branch point to function, were found. There appear to be sufficient differences between
S. cerevisiae
and
S. pombe
introns and the introns of two filamentous members of the Ascomycota and one member of the Basidiomycota to warrant the development of new model organisms for studying the splicing mechanisms of fungi.
Transcriptional Transitions during
Dictyostelium
Spore Germination
Authors: Xu Qikai , Ibarra Miroslava , Mahadeo Dana , Shaw Chad , Huang Eryong , Kuspa Adam , Cotter David , Shaulsky Gad
Published: October 2004

Many protozoa form spores in response to adversity; therefore, spore germination is a key process in their life cycle.
Dictyostelium discoideum
sporulates in response to starvation following a developmental program. Germination is characterized by two visible changes, spore swelling and the emergence of amoeba from the spore capsule. Several studies have indicated that an additional process termed spore activation is also required, but the physiological changes that characterize the three phases are largely uncharacterized. We used microarrays to monitor global transcriptional transitions as a surrogate measure of the physiological changes that occur during germination. Using two independent methods to induce germination, we identified changes in mRNA levels that characterized the germination process rather than changes that resulted from the induction method. We found that germination is characterized by three transitions. The first transition occurs during activation, while the spores appear dormant, the largest transition occurs when swelling begins, and the third transition occurs when emergence begins. These findings indicate that activation and swelling are not passive occurrences, such as dilution of inhibitors or spore rehydration, but are active processes that are accompanied by dramatic events in mRNA degradation and de novo transcription. These findings confirm and extend earlier reports that genes such as
celA
are regulated during spore germination. We also found by mutation analysis that the unconventional myosin gene
myoI
, which is induced during early germination, plays roles in the maintenance of dormancy and in spore swelling. This finding suggests that some of the observed transcriptional changes are required for spore germination.
Msn2- and Msn4-Like Transcription Factors Play No Obvious Roles in the Stress Responses of the Fungal Pathogen
Candida albicans
Authors: Nicholls Susan , Straffon Melissa , Enjalbert Brice , Nantel André , Macaskill Susan , Whiteway Malcolm , Brown Alistair J. P.
Published: October 2004

In
Saccharomyces cerevisiae
, the (C
2
H
2
)
2
zinc finger transcription factors Msn2 and Msn4 play central roles in responses to a range of stresses by activating gene transcription via the stress response element (STRE; CCCCT). The pathogen
Candida albicans
displays stress responses that are thought to help it survive adverse environmental conditions encountered within its human host. However, these responses differ from those in
S. cerevisiae
, and hence we predicted that the roles of Msn2- and Msn4-like proteins might have been functionally reassigned in
C. albicans. C. albicans
has two such proteins: CaMsn4 and Mnl1 (for Msn2- and Msn4-like).
CaMSN4
, but not
MNL1
, weakly complemented the inability of an
S. cerevisiae msn2 msn4
mutant to activate a STRE
-lacZ
reporter. Also, the disruption of CaMsn4 and Mnl1 had no discernible effect upon the resistance of
C. albicans
to heat, osmotic, ethanol, nutrient, oxidative, or heavy-metal stress or upon the stress-activated transcriptome in
C. albicans
. Furthermore, although Cap1-dependent activation of a Yap response element-luciferase reporter was observed, a STRE reporter was not activated in response to stresses in
C. albicans
. Ectopic expression of CaMsn4 or Mnl1 did not affect the cellular or molecular responses of
C. albicans
to stress. Under the conditions tested, the putative activation and DNA binding domains of
CaMsn4
did not appear to be functional. These data suggest that CaMsn4 and Mnl1 do not contribute significantly to stress responses in
C. albicans
. The data are consistent with the idea that stress signaling in this fungus has diverged significantly from that in budding yeast.
Integration of Stress Responses: Modulation of Calcineurin Signaling in
Saccharomyces cerevisiae
by Protein Kinase A
Authors: Kafadar Kimberly A. , Cyert Martha S.
Published: October 2004

Calcineurin is a Ca
2+
/calmodulin-dependent protein phosphatase required for
Saccharomyces cerevisiae
to adapt to a variety of environmental stresses. Once activated, calcineurin dephosphorylates the Zn-finger transcription factor Crz1p/Tcn1p, causing it to accumulate in the nucleus where it activates gene expression. Here we show that cyclic AMP-dependent protein kinase A (PKA) phosphorylates and negatively regulates Crz1p activity by inhibiting its nuclear import. Activation of PKA in vivo decreases Crz1p-dependent transcription. PKA phosphorylates Crz1p in vitro, and we identify specific residues required for this phosphorylation, all of which reside in or adjacent to the nuclear localization signal. Mutation of these residues to alanine results in increased nuclear import of Crz1p and results in higher levels of both basal and Ca
2+
-induced Crz1p transcriptional activity. PKA regulates the general stress response in yeast and coordinates this response with nutrient availability. In contrast, calcineurin regulates the cellular response to a restricted set of environmental insults. Thus, these studies identify a specific biochemical mechanism through which the activities of multiple stress-activated signaling pathways are integrated in vivo.
Inner Kinetochore of the Pathogenic YeastCandida glabrata
Authors: Stoyan Tanja , Carbon John
Published: October 2004

The human pathogenic yeastCandida glabratais the second most commonCandidapathogen afterCandida albicans, causing both bloodstream and mucosal infections. The centromere (CEN) DNA ofC. glabrata(CgCEN), although structurally very similar to that ofSaccharomyces cerevisiae, is not functional inS. cerevisiae. To further examine the structure of theC. glabratainner kinetochore, we isolated severalC. glabratahomologs ofS. cerevisiaeinner kinetochore protein genes, namely, genes for components of the CBF3 complex (Ndc10p, Cep3p, and Ctf13p) and genes for the proteins Mif2p and Cse4p. The amino acid sequence identities of these proteins were 32 to 49% relative toS. cerevisiae. CgNDC10,CgCEP3, andCgCTF13are required for growth inC. glabrataand are specifically found atCgCEN, as demonstrated by chromatin immunoprecipitation experiments. Cross-complementation experiments revealed that the isolated genes, with the exception ofCgCSE4, are species specific and cannot functionally substitute for the corresponding genes inS. cerevisiaedeletion strains. Likewise, theS. cerevisiaeCBF3 genesNDC10,CEP3, andCTF13cannot functionally replace their homologs inC. glabrataCBF3 deletion strains. Two-hybrid analysis revealed several interactions between these proteins, all of which were previously reported for the inner kinetochore proteins ofS. cerevisiae. Our findings indicate that although many of the inner kinetochore components have evolved considerably between the two closely related species, the organization of theC. glabratainner kinetochore is similar to that inS. cerevisiae.
Gene Replacement of Fructose-1,6-Bisphosphate Aldolase Supports the Hypothesis of a Single Photosynthetic Ancestor of Chromalveolates
Authors: Patron Nicola J. , Rogers Matthew B. , Keeling Patrick J.
Published: October 2004

Plastids (photosynthetic organelles of plants and algae) are known to have spread between eukaryotic lineages by secondary endosymbiosis, that is, by the uptake of a eukaryotic alga by another eukaryote. But the number of times this has taken place is controversial. This is particularly so in the case of eukaryotes with plastids derived from red algae, which are numerous and diverse. Despite their diversity, it has been suggested that all these eukaryotes share a recent common ancestor and that their plastids originated in a single endosymbiosis, the so-called “chromalveolate hypothesis.” Here we describe a novel molecular character that supports the chromalveolate hypothesis. Fructose-1,6-bisphosphate aldolase (FBA) is a glycolytic and Calvin cycle enzyme that exists as two nonhomologous types, class I and class II. Red algal plastid-targeted FBA is a class I enzyme related to homologues from plants and green algae, and it would be predicted that the plastid-targeted FBA from algae with red algal secondary endosymbionts should be related to this class I enzyme. However, we show that plastid-targeted FBA of heterokonts, cryptomonads, haptophytes, and dinoflagellates (all photosynthetic chromalveolates) are class II plastid-targeted enzymes, completely unlike those of red algal plastids. The chromalveolate enzymes form a strongly supported group in FBA phylogeny, and their common possession of this unexpected plastid characteristic provides new evidence for their close relationship and a common origin for their plastids.
A Cell Number Counting Factor Regulates Akt/Protein Kinase B To Regulate
Dictyostelium discoideum
Group Size
Authors: Gao Tong , Knecht David , Tang Lei , Hatton R. Diane , Gomer Richard H.
Published: October 2004

Little is known about how individual cells can organize themselves to form structures of a given size. During development,
Dictyostelium discoideum
aggregates in dendritic streams and forms groups of ∼20,000 cells.
D. discoideum
regulates group size by secreting and simultaneously sensing a multiprotein complex called counting factor (CF). If there are too many cells in a stream, the associated high concentration of CF will decrease cell-cell adhesion and increase cell motility, causing aggregation streams to break up. The pulses of cyclic AMP (cAMP) that mediate aggregation cause a transient translocation of Akt/protein kinase B (Akt/PKB) to the leading edge of the plasma membrane and a concomitant activation of the kinase activity, which in turn stimulates motility. We found that

countin
−

cells (which lack bioactive CF) and wild-type cells starved in the presence of anticountin antibodies (which block CF activity) showed a decreased level of cAMP-stimulated Akt/PKB membrane translocation and kinase activity compared to parental wild-type cells. Recombinant countin has the bioactivity of CF, and a 1-min treatment of cells with recombinant countin potentiated Akt/PKB translocation to membranes and Akt/PKB activity. Western blotting of total cell lysates indicated that countin does not affect the total level of Akt/PKB. Fluorescence microscopy of cells expressing an Akt/PKB pleckstrin homology domain-green fluorescent protein (PH-GFP) fusion protein indicated that recombinant countin and anti-countin antibodies do not obviously alter the distribution of Akt/PKB PH-GFP when it translocates to the membrane. Our data indicate that CF increases motility by potentiating the cAMP-stimulated activation and translocation of Akt/PKB.
Nucleus-Encoded Genes for Plastid-Targeted Proteins in
Helicosporidium
: Functional Diversity of a Cryptic Plastid in a Parasitic Alga
Authors: de Koning Audrey P. , Keeling Patrick J.
Published: October 2004

Plastids are the organelles of plants and algae that house photosynthesis and many other biochemical pathways. Plastids contain a small genome, but most of their proteins are encoded in the nucleus and posttranslationally targeted to the organelle. When plants and algae lose photosynthesis, they virtually always retain a highly reduced “cryptic” plastid. Cryptic plastids are known to exist in many organisms, although their metabolic functions are seldom understood. The best-studied example of a cryptic plastid is from the intracellular malaria parasite,
Plasmodium
, which has retained a plastid for the biosynthesis of fatty acids, isoprenoids, and heme by the use of plastid-targeted enzymes. To study a completely independent transformation of a photosynthetic plastid to a cryptic plastid in another alga-turned-parasite, we conducted an expressed sequence tag (EST) survey of
Helicosporidium
. This parasite has recently been recognized as a highly derived green alga. Based on phylogenetic relationships to other plastid homologues and the presence of N-terminal transit peptides, we have identified 20 putatively plastid-targeted enzymes that are involved in a wide variety of metabolic pathways. Overall, the metabolic diversity of the
Helicosporidium
cryptic plastid exceeds that of the
Plasmodium
plastid, as it includes representatives of most of the pathways known to operate in the
Plasmodium
plastid as well as many others. In particular, several amino acid biosynthetic pathways have been retained, including the leucine biosynthesis pathway, which was only recently recognized in plant plastids. These two parasites represent different evolutionary trajectories in plastid metabolic adaptation.
TbDSS-1, an Essential
Trypanosoma brucei
Exoribonuclease Homolog That Has Pleiotropic Effects on Mitochondrial RNA Metabolism
Authors: Penschow Jonelle L. , Sleve Daniel A. , Ryan Christopher M. , Read Laurie K.
Published: October 2004

Mitochondrial gene expression in trypanosomes is controlled primarily at the levels of RNA processing and RNA stability. This regulation undoubtedly involves numerous ribonucleases. Here we characterize the
Trypanosoma brucei
homolog of the yeast DSS-1 mitochondrial exoribonuclease, which we term TbDSS-1. Biochemical fractionation indicates that TbDSS-1 is mitochondrially localized, as predicted by its N-terminal sequence. In contrast to its yeast homolog, TbDSS-1 does not appear to be associated with mitochondrial ribosomes. Targeted downregulation of TbDSS-1 by RNA interference in procyclic-form
T. brucei
results in a severe growth defect. In addition, TbDSS-1 depletion leads to a decrease in the levels of never edited cytochrome oxidase subunit I (COI) mRNA and both unedited and edited COIII mRNAs, indicating this enzyme functions in the control of mitochondrial RNA abundance. We also observe a considerable reduction in the level of edited apocytochrome b (CYb) mRNA and a corresponding increase in unedited CYb mRNA, suggesting that TbDSS-1 functions, either directly or indirectly, in the control of RNA editing. The abundance of both gCYb[560] and gA6[149] guide RNAs is reduced upon TbDSS-1 depletion, although the reduction in gCYb[560] is much more dramatic. The significant reduction in gCYb levels could potentially account for the observed decrease in CYb RNA editing. Western blot analyses of mitochondrial RNA editing and stability factors indicate that the perturbations of RNA levels observed in TbDSS-1 knock-downs do not result from secondary effects on other mitochondrial proteins. In all, these data demonstrate that TbDSS-1 is an essential protein that plays a role in mitochondrial RNA stability and RNA editing.
Functional Characterization of Myosin I Tail Regions in
Candida albicans
Authors: Oberholzer Ursula , Iouk Tatiana L. , Thomas David Y. , Whiteway Malcolm
Published: October 2004

The molecular motor myosin I is required for hyphal growth in the pathogenic yeast
Candida albicans
. Specific myosin I functions were investigated by a deletion analysis of five neck and tail regions. Hyphal formation requires both the TH1 region and the IQ motifs. The TH2 region is important for optimal hyphal growth. All of the regions, except for the SH3 and acidic (A) regions that were examined individually, were required for the localization of myosin I at the hyphal tip. Similarly, all of the domains were required for the association of myosin I with pelletable actin-bound complexes. Moreover, the hyphal tip localization of cortical actin patches, identified by both rhodamine-phalloidin staining and Arp3-green fluorescent protein signals, was dependent on myosin I. Double deletion of the A and SH3 domains depolarized the distribution of the cortical actin patches without affecting the ability of the mutant to form hyphae, suggesting that myosin I has distinct functions in these processes. Among the six myosin I tail domain mutants, the ability to form hyphae was strictly correlated with endocytosis. We propose that the uptake of cell wall remodeling enzymes and excess plasma membrane is critical for hyphal formation.
FKBP12 Controls Aspartate Pathway Flux in
Saccharomyces cerevisiae
To Prevent Toxic Intermediate Accumulation
Authors: Arévalo-Rodríguez Miguel , Pan Xuewen , Boeke Jef D. , Heitman Joseph
Published: October 2004

FKBP12 is a conserved member of the prolyl-isomerase enzyme family and serves as the intracellular receptor for FK506 that mediates immunosuppression in mammals and antimicrobial actions in fungi. To investigate the cellular functions of FKBP12 in
Saccharomyces cerevisiae
, we employed a high-throughput assay to identify mutations that are synthetically lethal with a mutation in the
FPR1
gene, which encodes FKBP12. This screen identified a mutation in the
HOM6
gene, which encodes homoserine dehydrogenase, the enzyme catalyzing the last step in conversion of aspartic acid into homoserine, the common precursor in threonine and methionine synthesis. Lethality of
fpr1 hom6
double mutants was suppressed by null mutations in
HOM3
or
HOM2
, encoding aspartokinase and aspartate β-semialdehyde dehydrogenase, respectively, supporting the hypothesis that
fpr1 hom6
double mutants are inviable because of toxic accumulation of aspartate β-semialdehyde, the substrate of homoserine dehydrogenase. Our findings also indicate that mutation or inhibition of FKBP12 dysregulates the homoserine synthetic pathway by perturbing aspartokinase feedback inhibition by threonine. Because this pathway is conserved in fungi but not in mammals, our findings suggest a facile route to synergistic antifungal drug development via concomitant inhibition of FKBP12 and Hom6.
Insights into the Survival of
Chlamydomonas reinhardtii
during Sulfur Starvation Based on Microarray Analysis of Gene Expression
Authors: Zhang Zhaoduo , Shrager Jeff , Jain Monica , Chang Chiung-Wen , Vallon Olivier , Grossman Arthur R.
Published: October 2004

Responses of photosynthetic organisms to sulfur starvation include (i) increasing the capacity of the cell for transporting and/or assimilating exogenous sulfate, (ii) restructuring cellular features to conserve sulfur resources, and (iii) modulating metabolic processes and rates of cell growth and division. We used microarray analyses to obtain a genome-level view of changes in mRNA abundances in the green alga
Chlamydomonas reinhardtii
during sulfur starvation. The work confirms and extends upon previous findings showing that sulfur deprivation elicits changes in levels of transcripts for proteins that help scavenge sulfate and economize on the use of sulfur resources. Changes in levels of transcripts encoding members of the light-harvesting polypeptide family, such as LhcSR2, suggest restructuring of the photosynthetic apparatus during sulfur deprivation. There are also significant changes in levels of transcripts encoding enzymes involved in metabolic processes (e.g., carbon metabolism), intracellular proteolysis, and the amelioration of oxidative damage; a marked and sustained increase in mRNAs for a putative vanadium chloroperoxidase and a peroxiredoxin may help prolong survival of
C. reinhardtii
during sulfur deprivation. Furthermore, many of the sulfur stress-regulated transcripts (encoding polypeptides associated with sulfate uptake and assimilation, oxidative stress, and photosynthetic function) are not properly regulated in the
sac1
mutant of
C. reinhardtii
, a strain that dies much more rapidly than parental cells during sulfur deprivation. Interestingly, sulfur stress elicits dramatic changes in levels of transcripts encoding putative chloroplast-localized chaperones in the
sac1
mutant but not in the parental strain. These results suggest various strategies used by photosynthetic organisms during acclimation to nutrient-limited growth.
All-terrain vehicle injury in children: strategies for prevention: Table 1
Authors: Aitken M E , Graham C J , Killingsworth J B , Mullins S H , Parnell D N , Dick R M
Published: October 2004

Objective:A variety of educational efforts, policies, and regulations have been adopted to reduce all-terrain vehicle (ATV) injury in children. Despite this, ATV use by children continues and serious injuries are common. The purpose of this study was to investigate the knowledge, practices, and beliefs of ATV users to help develop effective educational strategies to promote safer ATV use.

Design:Focus groups were conducted to characterize participant ATV use and safety awareness as well as to explore avenues for prevention. Feedback on draft ATV safety public service announcements was elicited. Themes of transcribed focus group data were summarized.

Setting:Rural state with high ATV use and injury rates.

Subjects:Adult and adolescent ATV users.

Interventions:None.

Main outcome measures:Summaries of focus group discussions.

Results:ATV riders frankly discussed current use and safety behaviors and were aware of some ATV risks. Youths felt that age specific regulation was unlikely to be a helpful strategy. Participants endorsed messages demonstrating graphic consequences as likely to get the attention of young riders regarding risks. Educational settings were suggested, including hunter and driver safety classes.

Conclusions:Efforts to improve ATV safety awareness should clearly show pediatric ATV injury risk and safety practices. Campaigns must also show realistic understanding of current use practices to be credible for users. Messages emphasizing the consequences of ATV use were endorsed as most likely to have impact. Approaches based on age based restrictions were considered unrealistic and alternative strategies were suggested.
Risk factors for serious fall related injury in elderly women living at home
Authors: Bergland A , Wyller T B
Published: October 2004

Objectives:To study whether balance, function, and other health status indicators can predict serious fall related injury in elderly women living at home.

Methods:In this prospective study, the authors took a random sample of 307 women aged 75 years and over (mean 80.8 years, response rate 74.5%), living in the community. Serious fall injuries which occurred over a period of during one year were recorded, together with baseline registrations of health, function, and tests of walking and balance.

Results:In all, 155 women (50.5%) fell one or more times. One hundred and fifty six (51%) of the 308 falls resulted in a fall related injury, 74 (24%) in a serious fall related injury, and 40 falls (13%) resulted in fractures. The presence of rheumatic disorders, inability to rise from the floor, arthrosis of the hip, having had more than one fall during the one year follow up period, and an increased tendency to sway in the frontal plane when doing a calculation task were independent and significant predictors for serious fall related injury (fractures included). The independent predictors of fall induced fractures were experiencing more than one fall in the follow up period, cognitive impairment, and receiving care from professional or other.

Conclusion:The study suggests that rheumatic disorders and the inability to get up from lying on the floor were the strongest independent risk factors for serious fall related injury. Experiencing more than one fall in the follow up period and cognitive impairment are the strongest independent predictors for fall induced fractures. Age was not a significant predictor of serious fall related injury. Assessment of these markers is feasible in a clinical setting and is a useful way of identifying those who are at risk of serious fall related injuries.
Risk factors for work related violence in a health care organization
Authors: Findorff M J , McGovern P M , Wall M , Gerberich S G , Alexander B
Published: October 2004

Objective:Identify the exposure effects of job family, patient contact, and supervisor support on physical and non-physical work related violence.

Design:Cross sectional study of employees in a Midwest health care organization, utilizing a specially designed mailed questionnaire and employer secondary data.

Subjects:Respondents included 1751 current and former employees (42% response rate).

Results:Physical and non-physical violence was experienced by 127 (7.2%) and 536 (30.6%) of the respondents, respectively. Multivariate analyses of physical violence identified increased odds for patient care assistants (odds ratio (OR) 2.5, 95% confidence interval (CI) 1. 1 to 6.1) and decreased odds for clerical workers (OR 0.1, 95% CI 0.03 to 0.5). Adjusted for job family, increased odds of physical violence were identified for moderate (OR 5.9, 95% CI 2.1 to 16.0) and high (OR 7.8, 95% CI 2.9 to 20.8) patient contact. Similar trends were identified for non-physical violence (OR 1.4, 95% CI 1.1 to 2.0 and OR 1.7, 95% CI 1.3 to 2.3). Increased supervisor support decreased the odds of both physical (OR 0.7, 95% CI 0.6 to 0.95) and non-physical violence (OR 0.5, 95% CI 0.4 to 0.6), adjusting for job family and demographic characteristics.

Conclusions:Increased odds of physical violence were identified for the job family of nurses, even when adjusted for patient contact. Increased patient contact resulted in increased physical and non-physical violence, independent of job family, while supervisor support resulted in decreased odds of physical and non-physical violence.
Quality of information on risk factors reported by ski patrols
Authors: Hagel B E , Pless I B , Goulet C , Platt R W , Robitaille Y
Published: October 2004

Objective:To determine the reliability of reporting of information on risk factors from a standard accident report form used by ski patrols and a follow up mail questionnaire or telephone interview among injured skiers and snowboarders.

Setting:19 ski areas in the Canadian province of Quebec between November 2001 and April 2002.

Participants:4377 injured skiers and snowboarders seen by the ski patrol, who completed a follow up mail questionnaire or telephone interview.

Main outcome measures:κ and weighted κ statistics were used to measure the chance corrected agreement for self reported ability, age, skiing time on day of injury, lessons, type of practice, use of helmet at time of injury, and hill difficulty.

Results:The κ value for helmet use at the time of injury was 0.88 (95% confidence interval 0.87 to 0.90) and for other risk factors ranged from 0.45 (skiing time on day of injury) to 0.98 (age). Few differences were seen in reporting by body region of injury. Reporting consistency was lower for respondents who completed telephone interviews compared with those who completed mail questionnaires and those who responded more than four months after the injury.

Conclusions:Moderate to almost perfect agreement, depending on the risk factor, exists between ski patrols’ accident report forms and follow up information. Ski patrol reports can be a reliable and readily available source of information on risk factors for skiing and snowboarding.
Urban youths’ perspectives on violence and the necessity of fighting: Table 1
Authors: Johnson S B , Frattaroli S , Wright J L , Pearson-Fields C B , Cheng T L
Published: October 2004

Objectives:To assess youth perceptions of the causes and consequences of violence generally, the causes and consequences of fighting specifically, and to determine how best to approach fighting in the context of violence prevention activities.

Methods:Thirteen structured focus group interviews with youths from three high violence urban settings: a large, urban high school, a training center for disadvantaged youths, and a school for adjudicated youths. Participants were 120 urban, predominately African-American youths and young adults ages 14–22 years (mean: 17.2 years). Seven focus groups were conducted with females, and six with males.

Results:Adolescents identified the causes of violence on multiple levels including: individual, family, interpersonal, and community level factors. Most youths (89%) had been in a physical fight. Participants felt that fighting was not “right”, but identified situations in which it was necessary. Specifically, fighting was used as a problem solving tool, and could prevent escalation of violence. Youths felt that the adults in their lives, including physicians, were generally ill equipped to give advice about violence, as adults’ experiences were so removed from their own. Participants looked to experienced role models to offer problem solving and harm reduction strategies. Youths were open to receiving anticipatory guidance about violence and fighting from primary care physicians they felt comfortable with, and who showed respect for their experiences.

Conclusions:Interventions that include blanket admonitions against fighting should be reassessed in light of youth perceptions that fighting plays a complex role in both inciting and preventing more serious violence.
Lost working days, productivity, and restraint use among occupants of motor vehicles that crashed in the United States
Authors: Ebel B E , Mack C , Diehr P , Rivara F P
Published: October 2004

Background:In 2001, 6.3 million passengers were involved in motor vehicle crashes. This study aimed to determine the number of work days lost as a result of motor vehicle crashes and factors that influenced people’s return to work.

Methods:This was a retrospective, population based cohort study of occupants in motor vehicles involved in crashes from the 1993–2001 Crashworthiness Data System produced by the National Highway Traffic Safety Administration. The sample population of people aged 18–65 years included two groups: occupants who survived and were working before the crash and occupants who were injured fatally and were estimated to have been working before the crash. Multivariate linear regression was used to analyze the impact of restraint use and injury type on return to work.

Results:Overall, 30.1% of occupants of vehicles that crashed missed one or more days of work. A crash resulted in a mean 28.0 (95% confidence interval 15.8 to 40.1) days lost from work, including losses associated with fatalities. The 2.1 million working occupants of vehicles that crashed in 2001 lost a total of 60 million days of work, resulting in annual productivity losses of over $7.5 billion (2964 to 12 075). Unrestrained vehicle occupants accounted for $5.6 billion in lost productivity.

Conclusions:Motor vehicle crashes result in large and potentially preventable productive losses that are mostly attributable to fatal injuries.
International Collaborative Effort on Injury Statistics: 10 year review
Authors: Fingerhut L A
Published: October 2004

International comparisons of injury data may be useful for examining differences in risk and for suggesting potential interventions or hypotheses for future studies. However important issues to be considered in conducting comparisons are related to both the underlying quality of the data and how the data are collected. The International Collaborative Effort (ICE) on Injury Statistics grew out of concerns over the comparability of international injury data. This article outlines the history behind the development of the Injury ICE, brief descriptions of current and past projects, collaborations, and reflections on the value of collaboration.
A ONE-PARAMETER FAMILY OF MINIMAL SURFACES WITH FOUR PLANAR ENDS
Authors: ABI-KHUZAM FARUK F.
Published: October 2004

Using Jacobian elliptic functions we construct a one-parameter family of regular complete minimal surfaces of genus one with total curvature – 16π and having four embedded planar ends. The explicit formulas obtained reveal that two ends are asymptotic to one and the same plane.
HERMITIAN STRUCTURES AND HARMONIC MORPHISMS IN HIGHER DIMENSIONAL EUCLIDEAN SPACES
Authors: BAIRD P. , WOOD J. C.
Published: October 2004

We construct new complex-valued harmonic morphisms from Euclidean spaces from functions which are holomorphic with respect to Hermitian structures. In particular, we give the first global examples of complex-valued harmonic morphisms from ℝn for each n>4 which do not arise from a Kähler structure; it is known that such examples do not exist for n≤4.
ON OCNEANU'S THEORY OF ASYMPTOTIC INCLUSIONS FOR SUBFACTORS, TOPOLOGICAL QUANTUM FIELD THEORIES AND QUANTUM DOUBLES
Authors: EVANS DAVID E. , KAWAHIGASHI YASUYUKI
Published: October 2004

A fully detailed account of Ocneanu's theorem is given that the Hilbert space associated to the two-dimensional torus in a Turaev-Viro type (2+1)-dimensional topological quantum field theory arising from a finite depth subfactor N⊂M has a natural basis labeled by certain M∞- M∞ bimodules of the asymptotic inclusion M∨(M'∩M∞)⊂M∞, and moreover that all these bimodules are given by the basic construction from M∨(M'∩M∞)⊂M∞ if the fusion graph is connected. This Hilbert space is an analogue of the space of conformal blocks in conformal field theory. It is also shown that after passing to the asymptotic inclusions we have S- and T-matrices, analogues of the Verlinde identity and Vafa's result on roots of unity. It is explained that the asymptotic inclusions can be regarded as a subfactor analogue of the quantum double construction of Drinfel'd. These claims were announced by Λ. Ocneanu in several talks, but he has not published his proofs, so details are given here along the lines outlined in his talks.
DEVELOPABLE COMPLEX ANALYTIC SUBMANIFOLDS
Authors: FISCHER GERD , WU H.
Published: October 2004

Examples of developable submanifolds are difficult to come by. For this reason, we collect in Sec. 1 some examples. There is one due to Cayley [2] that may not be so well-known, and there is also a new one which is algebraic. A knowledge of these examples is not essential for the subsequent sections, however. The organisation of the remainder of this paper is self-explanatory from the table of contents, except to mention that Sec. 7 contains the precise statements and proofs of Theorems 4–6.

This paper and Sec. 2 of the paper [8] of Griffiths and Harris treat the same topic, although the latter is mainly interested in developable submanifolds in projective space. The discerning reader would note that our outlook and emphasis are orthogonal to those of [8] and that there are more differences than similarities between these two works.
ALEXANDROV SPACES WITH SYSTOLS ALMOST TWICE THE DIAMETERS
Authors: KOH LIANG-KHOON
Published: October 2004

Let X be an Alexandrov space with Systol(X)=2 and diameter at a point almost 1, we prove that the fundamental group of X must be Z2.
CLARIFYING CHAOS: EXAMPLES AND COUNTEREXAMPLES
Authors: BROWN RAY , CHUA LEON O.
Published: October 2004

Over the past fifteen years there have been various attempts to define chaos. In an effort to find a universally acceptable definition we began constructing new examples of chaotic systems in the hope that the salient features of chaos could be captured. Our efforts to date have failed and the examples we have constructed seem to suggest that no such definition exists. However, these examples have proved to be valuable in spite of our inability to hone a universal definition of chaos from them. Consequently, we present this list of examples and their significance. Some interesting conclusions that we can draw from them are: It is possible to construct simple closed form solutions of chaotic one-dimensional maps; sensitive dependence on initial conditions, the most widely used definition of chaos, has many counterexamples; there are invertible chaotic dynamical systems defined by simple differential equations that do not have horseshoes; three important properties that are thought to characterize chaos, continuous power spectral density, exponentially sensitive dependence on initial conditions, and exponential loss of information (Chaitin’s concept of algorithmic complexity), are independent.

Chaos seems to be tied to our notion of rates of divergence of orbits or degradation of information such as is found in systems with positive Lyapunov exponents. The reliance on rates seems to open the door to a pandora’s box of rates, both higher and lower than exponential. The intuitive notion of pseudo-randomness, a practical feature of chaos, is present in examples that do not have positive Lyapunov exponents. And in general, nonlinear polynomial rates of degradation of information are also quite “unpredictable”.

We conclude that it appears that for any given definition of chaos, there may always be some “clearly” chaotic systems which do not fall under that definition, thus making chaos a cousin to Gödel’s undecidability.
WADA BASIN BOUNDARIES IN CHAOTIC SCATTERING
Authors: POON LEON , CAMPOS JOSÉ , OTT EDWARD , GREBOGI CELSO
Published: October 2004

Chaotic scattering systems with multiple exit modes typically have fractal phase space boundaries separating the sets of initial conditions (basins) going to the various exits. If the exits number more than two, we show that the system may possess the stronger property that any initial condition which is on the boundary of one exit basin is also simultaneously on the boundary of all the other exit basins. This interesting property is known as the Wada property and basin boundaries having this property are called Wada basin boundaries.
ARNOLD FLAMES AND RESONANCE SURFACE FOLDS
Authors: McGEHEE RICHARD P. , PECKHAM BRUCE B.
Published: October 2004

Periodically forced planar oscillators are often studied by varying the two parameters of forcing amplitude and forcing frequency. For low forcing amplitudes, the study of the essential oscillator dynamics can be reduced to the study of families of circle maps. The primary features of the resulting parameter plane bifurcation diagrams are “(Arnold) resonance horns” emanating from zero forcing amplitude. Each horn is characterized by the existence of a periodic orbit with a certain period and rotation number. In this paper, we investigate divisions of these horns into subregions — different subregions corresponding to maps having different numbers of periodic orbits. The existence of subregions having more than the “usual” one pair of attracting and repelling periodic orbits implies the existence of “extra folds” in the corresponding surface of periodic points in the Cartesian product of the phase and parameter spaces. The existence of more than one attracting and one repelling periodic orbit is shown to be generic. For some of the families we create, the resulting parameter plane bifurcation pictures appear in shapes we call “Arnold flames”. Results apply both to circle maps and forced oscillator maps.
CONTROLLING CHAOS IN A TWO-WELL OSCILLATOR
Authors: MOON F. C. , JOHNSON M. A. , HOLMES W. T.
Published: October 2004

The chaotic dynamics of a nonlinear buckled elastic beam are shown to be controllable in a periodic orbit using a digital occasional proportional feedback control circuit. The method is similar to that developed by Hunt [1991] and does not require a detailed knowledge of the underlying two-dimensional map. The control is effected by perturbing the potential wells synchronously with the forcing function. Experiments show that the system possesses both periodic orbits and strange attractors different than those of the uncontrolled system.
INDUCED HYSTERESIS-FREE TRANSITIONS IN A BISTABLE SYSTEM
Authors: RAAB VOLKER
Published: October 2004

A new concept is developed to facilitate transitions between the two stable states of a bistable dynamical system. The transitions take place without loss of stability or hysteresis. The underlying theoretical concept is to couple an additional dynamical variable to the original system in a strictly linear fashion. Explicit formulae are given which determine the couplings. The method is applied to the double well oscillator. In its bifurcation diagrams possible paths from one stationary point to the other are indicated.
CHAOTIC ATTRACTORS FROM HOMOTOPIC MIXING OF VECTOR FIELDS
Authors: METTIN ROBERT , MAYER-KRESS GOTTFRIED
Published: October 2004

We introduce homotopy transformations of vector fields as an efficient way to design families of chaotic attractors or transients with specific geometrical and dynamical properties. Those properties are inherited from different progenitor attractors, which allows a morphing between the progenitors. The method can provide a simple tool for a systematic design of attractors of desired dynamical characteristics. It is based on the robustness of invariant manifolds of the homotopic vector fields with respect to parametric perturbations. We analytically construct a convex subfamily of Chua attractors which illustrates this approach. Connections to control and synchronisation schemes of chaotic systems are shown. We also discuss applications in the area of sound synthesis.
SPIRAL WAVES AND THE HEART
Authors: GRAY RICHARD A. , JALIFE JOSÉ
Published: October 2004

The human heart normally beats at a fairly regular rate of once per second. Under abnormal conditions, however, the heart may beat irregularly, at fast rates, leading quickly to death. The most dangerous of these irregular heart rhythms are due to recirculating electrical waves of activity. However, the detailed mechanisms of these “reentrant arrhythmias” are unclear. It has been suggested that these recirculating waves are spiral waves. This review article presents recent studies of the heart providing evidence that reentrant arrhythmias result from spiral waves of electrical activity. Spiral waves are generic to many excitable media, therefore the theory of spiral waves is well developed and also reviewed herein. Many of the predictions of spiral wave theory are being realized in the heart and leading investigators in new directions.
TRAVELLING WAVES IN A CIRCULAR ARRAY OF CHUA’S CIRCUITS
Authors: NEKORKIN VLADIMIR I. , KAZANTSEV VICTOR B. , VELARDE MANUEL G.
Published: October 2004

The possibility of travelling waves in a one-dimensional circular array of Chua's circuits is investigated. It is shown that the problem can be reduced to the analysis of the periodic orbits of a three-dimensional system of ordinary differential equations (ODEs) describing the individual dynamics of Chua's circuit. The results of analytical and numerical studies of the bifurcation associated with the appearance of the periodic orbits are presented. A criterion for stability of the travelling waves is also provided.
FORECASTING b-VALUES FOR SEISMIC EVENTS
Authors: CAO LIANGYUE , FANG HAIPING , LI QUANLIN , CHEN JINBIAO
Published: October 2004

A technique of nonlinear deterministic prediction is applied to test the short-term predictability of b-values for seismic events recorded in Tangshan region in China. The prediction results are satisfactory and significantly better than that of conventional AR models. This implies that the underlying mechanism, as expressed by the b-value data sequence, is deterministic. And it could be helpful for earthquake predictions.
MULTICHANNEL COMMUNICATION USING AUTOSYNCHRONIZATION
Authors: PARLITZ U. , KOCAREV L.
Published: October 2004

A method is presented for encoding and transmitting several information signals using a single (chaotic) carrier. The messages are encoded by modulation of parameters of the dynamical system of the transmitter. These modulations are reproduced at the receiver by an autosynchronization loop that controls the corresponding parameters of the receiver such that receiver and transmitter keep synchronized.
DIFFERENT AND COEXISTING ROUTES TO CHAOS ALONG A COMMON BIFURCATION PATH IN THE MAXWELL-BLOCH EQUATIONS
Authors: PASTOR I. , PÉREZ-GARCÍA VÍCTOR M. , ENCINAS-SANZ F. , GUERRA J. M.
Published: October 2004

Field amplitude and intensity solutions of the Maxwell-Bloch equations for a laser have been theoretically analyzed. The frequencies appearing in the intensity and field spectrum for parameter values corresponding to a period-doubling road to chaos have been analyzed, both numerically and analytically. These frequencies can be expressed as rational linear combinations of two base frequencies. Differences between the roads affecting intensity and field variables have been evidenced.
CELLULAR AUTOMATA AND OPTIMAL PATH PLANNING
Authors: STÄMPFLE M.
Published: October 2004

Cellular automata are deterministic dynamical systems in which time, space, and state values are discrete. Although they consist of uniform elements, which interact only locally, cellular automata are capable of showing complex behavior. This property is exploited for solving path planning problems in workspaces with obstacles. A new automaton rule is presented which calculates simultaneously all shortest paths between a starting position and a target cell. Based on wave propagation, the algorithm ensures that the dynamics settles down in an equilibrium state which represents an optimal solution. Rule extensions include calculations with multiple starts and targets. The method allows applications on lattices and regular, weighted graphs of any finite dimension. In comparison with algorithms from graph theory or neural network theory, the cellular automaton approach has several advantages: Convergence towards optimal configurations is guaranteed, and the computing costs depend only linearly on the lattice size. Moreover, no floating-point calculations are involved.
1-D MAPS, CHAOS AND NEURAL NETWORKS FOR INFORMATION PROCESSING
Authors: ANDREYEV YU.V. , DMITRIEV A.S. , KUMINOV D.A. , CHUA L.O. , WU C.W.
Published: October 2004

An application of complex dynamics and chaos in neural networks to information processing is studied. Mathematical models based on piecewise-linear maps implementing basic functions of information processing via complex dynamics and chaos are discussed. Realizations of these models by neural networks are presented. In contrast to other methods of using neural networks and associative memory to store information, the information is stored in dynamical attractors such as limit cycles, rather than equilibrium points. Retrieval of information corresponds to getting the state into the basin of attraction of the attractor. We show that noise-corrupted information or partial information are sufficient to drive the state into the basin of attraction of the attractor, thus these systems exhibit the property of associative memory.