A transport model with coupled ternary exchange and chemisorption retention for hydrazinium cations.

A numerical model was developed to describe the fate and transport of hydrazinium (N2H5+) and competing Ca2+ and H+ cations applied in acidic solutions to columns of Ca2+/H+-saturated sandy soil during steady saturated flow conditions. Instantaneous ternary H+-Ca2+-N2H5+ cation exchange using the Gaines-Thomas approach was combined with second-order, irreversible, kinetic chemisorption of exchange-phase N2H5+ ions as major retention mechanisms for N2H5+. Exchange-mediated chemisorption is assumed to occur as chemical binding of N2H5+ ions located on carboxyl-group exchange sites to nearby carbonyl groups, consequently decreasing the effective soil cation exchange capacity (CEC). Comparison of simulated and observed breakthrough curves (BTCs) for concentrations of N2H5+ and Ca2+ ions in column effluent was used in model evaluation. The cation transport model with cation exchange coupled with exchange-mediated chemisorption provided a valid first approximation for N2H5+ transport.

Increased sedimentation rates and grain sizes 2-4 Myr ago due to the influence of climate change on erosion rates.

Around the globe, and in a variety of settings including active and inactive mountain belts, increases in sedimentation rates as well as in grain sizes of sediments were recorded at approximately 2-4 Myr ago, implying increased erosion rates. A change in climate represents the only process that is globally synchronous and can potentially account for the widespread increase in erosion and sedimentation, but no single process-like a lowering of sea levels or expanded glaciation-can explain increases in sedimentation in all environments, encompassing continental margins and interiors, and tropical as well as higher latitudes. We suggest that climate affected erosion mainly by the transition from a period of climate stability, in which landscapes had attained equilibrium configurations, to a time of frequent and abrupt changes in temperature, precipitation and vegetation, which prevented fluvial and glacial systems from establishing equilibrium states.

Development and psychometric properties of the Student Worry Questionnaire-30.

Described are the development and initial psychometric properties (Ns = 50 and 188) of a self-report measure, the Student Worry Questionnaire-30, for use with college undergraduates. Exploratory principal components analyses (Ns = 388, 350, and 396) with oblimin rotation indicated six domains of worrisome thinking, financial-related concerns, significant others' well-being, social adequacy concerns, academic concerns, and general anxiety symptoms. The total score and scale scores showed internal consistency of .80 to .94. Also, test-retest reliability analyses (.75 to .80) support consistency of responses over 4 wk. Strong evidence for convergent validity) was indicated. Confirmatory factor analysis confirmed the fit of the 6-factor oblique model. Limitations of the present studies, and directions for research are discussed.

Equatorius: a new hominoid genus from the Middle Miocene of Kenya.

A partial hominoid skeleton just older than 15 million years from sediments in the Tugen Hills of north central Kenya mandates a revision of the hominoid genus Kenyapithecus, a possible early member of the great ape-human clade. The Tugen Hills specimen represents a new genus, which also incorporates all material previously referable to Kenyapithecus africanus. The new taxon is derived with respect to earlier Miocene hominoids but is primitive with respect to the younger species Kenyapithecus wickeri and therefore is a late member of the stem hominoid radiation in the East African Miocene.

Concert medicine: spectrum of medical problems encountered at 405 major concerts.

OBJECTIVES: To identify factors predictive of patient load at major commercial concert first-aid stations, and to characterize the spectrum of presenting injuries and illnesses at such events. METHODS: This study was a retrospective case series of patients presenting to on-site first-aid stations at five major concert venues in southern California over a five-year period. The authors compared the number of patients per ten thousand attendees (PPTT) with four potential predictors (music type, overall attendance, temperature, and indoor vs outdoor location) using univariate techniques and negative binomial regression. The spectrum of chief complaints observed is described. RESULTS: There were 1,492 total patients out of 4,638,099 total attendees at 405 separate concerts. The median patient load per concert was 2.1 PPTT, ranging from 0 PPTT at 53 concerts to 71 PPTT at a punk rock festival that turned into a riot. Patient load varied significantly by music category (p = 0.0001) but not with overall attendance, temperature, or indoor vs outdoor location. Median PPTT by music category ranged from 1.3 PPTT for rhythm and blues to 12.6 PPTT for gospel/Christian, with negative binomial regression indicating that rock concerts had 2.5 times (95% CI = 2.0 to 3.0) the overall patient load of non-rock concerts. Music type, however, was able to account for only 4% of the variability observed in the regression model. Trauma-related complaints predominated overall, with similar rates at rock and non-rock concerts. Four cardiac arrests occurred at classical concerts. CONCLUSION: Rock concert first-aid stations evaluated 2.5 times the patient load of non-rock concerts overall, although there was substantial concert-to-concert variability. Trauma-related complaints predominate at both rock and non-rock events. These data may assist individuals and organizations planning support for such events.

The Reasons for Living Inventory for Adolescents (RFL-A): development and psychometric properties.

The role of adaptive beliefs and attitudes against suicide has not been given adequate attention in the clinical or assessment literature. This article reports on the development and initial psychometric properties of a 32-item self-report inventory, the Reasons for Living Inventory for Adolescents (RFL-A). In Phase 1, we used exploratory and confirmatory factor analyses to identify five correlated factors: Future Optimism, Suicide-Related Concerns, Family Alliance, Peer Acceptance and Support, and Self-Acceptance. In Phase 2, we cross-validated the 5-factor oblique model in a different group of adolescents recruited from two high schools. In addition, we examined evidence for convergent, discriminant, and construct validities. The coefficient alpha indices for the RFL-A total and scales were satisfactory. In Phase 3, we evaluated additional evidence of reliability and validity using samples of high school and psychiatric inpatient adolescents. The results suggest that the RFL-A is a short, reliable, and valid measure that is potentially useful in the assessment of adolescent suicidal behavior.

Relationships between experiences of parental violence during childhood and women's self-esteem.

The interrelationships between experience of parental verbal aggression and physical violence during childhood and the development of low self-esteem during adulthood were explored separately for the father-daughter and mother-daughter relationships. Data were collected from 472 women between the ages of 18 and 45 during in-depth interviews drawn from five sources: outpatient alcoholism treatment, DWI (Driving While Intoxicated) education programs, shelter for battered women, outpatient mental health treatment, and randomly from the community. Control variables included respondents' alcohol problems and help-seeking behavior, parental alcohol problems, number of changes in childhood family (e.g., divorce), and respondents' race and social class. Controlling for these variables, experiences of father-to-daughter verbal aggression, moderate violence, and severe violence were found related to lower self-esteem in adulthood for women. Conversely, controlling for these variables, experiences of mother-to-daughter verbal aggression, moderate violence, and severe violence were not found related to lower self-esteem in adulthood for women.

Childhood maltreatment and the risk of substance problems in later life.

This paper examines the risk of developing problems in adolescence and adulthood, particularly those associated with substance use, as a consequence of experiencing physical or sexual abuse during childhood. We review both retrospective and prospective research, conducted with both adolescent and adult respondents. Although there are some marked discrepancies in the findings from retrospective and prospective studies, these are probably due to differences in methodology, particularly between using official records and self-report to identify cases of abuse. Despite the wide range of methodologies and samples used in these studies, most indicate that the experience of childhood abuse is a risk factor for a number of common mental disorders in adolescence and adulthood, including alcohol and drug-related problems. In many cases, the experience of abuse appears to lead in later life to increased feelings of depression and anxiety which, while not sufficient to result in the diagnosis of a mental health disorder, place the victims at greater risk of developing substance problems. Multivariate studies indicate that this positive association remains even when controlling for important variables such as the presence of parental alcohol problems. The paper concludes with a number of recommendations for future research, so that it can be established whether the risk arises specifically from child abuse or neglect, or from the more general impact on child development of adverse family relationships.

Wnt signaling and an APC-related gene specify endoderm in early C. elegans embryos.

In a 4-cell stage C. elegans embryo, signaling by the P2 blastomere induces anterior-posterior polarity in the adjacent EMS blastomere, leading to endoderm formation. We have taken genetic and reverse genetic approaches toward understanding the molecular basis for this induction. These studies have identified a set of genes with sequence similarity to genes that have been shown to be, or are implicated in, Wnt/Wingless signaling pathways in other systems. The C. elegans genes described here are related to wnt/wingless, porcupine, frizzled, beta-catenin/armadillo, and the human adenomatous polyposis coli gene, APC. We present evidence that there may be partially redundant inputs into endoderm specification and that a subset of these genes appear also to function in determining cytoskeletal polarity in certain early blastomeres.

Control theory, labeling theory, and the delivery of services for drug abuse to adolescents.

This article uses panel data and multiple regression of follow-up on baseline variables to test hypotheses that over time: (1) control theory variables are related to decreases in drug use and to each other, (2) labeling theory variables regarding drug use are related to increases in drug use, increases in each other, and negatively to control theory variables, (3) participation in a nonsystem juvenile justice diversion program is related to an increase in drug use, more deviant self-labels, and weaker societal bonds, and (4) the effects of the diversion program differ across gender of respondent. Baseline and follow-up data were collected on a randomly selected comparison group of adolescents (N = 100, 46 females) and a diversion program sample of adolescents (N = 88, 46 females). Slope differences across samples were tested using interaction terms. Where significant interaction terms were found, additional separate sample regression equations were performed. All four hypotheses received some support.

Alcohol, drugs, and violence in children's lives.

This chapter reviews the current state of knowledge concerning the interrelationship between the cycle of alcohol and other drugs (AOD) use and the cycle of violence. This issue is framed in terms of two questions. The first is the extent to which AOD use by the perpetrator is related to the perpetration of violence toward children, defined here as including both physical and sexual abuse. The second question is whether the experience of abuse during childhood is related to the subsequent development of the abuse of alcohol and other drugs. The review indicates that parental AOD abuse is related to physical and sexual abuse. However, because most perpetrators are not parents, the relationship is not yet clear. The data do support the link between experiencing childhood violence and the development of later AOD abuse. Theoretical explanations for each link are reviewed and mediating variables are identified. The review concludes with a presentation of methodological issues and the directions for future research.

Kinetic pathway for folding of the Tetrahymena ribozyme revealed by three UV-inducible crosslinks.

The kinetics of RNA folding were examined in the L-21 ribozyme, an RNA enzyme derived from the self-splicing Tetrahymena intron. Three UV-inducible crosslinks were mapped, characterized, and used as indicators for the folded state of the ribozyme. Together these data suggest that final structures are adopted first by the P4-P6 independently folding domain and only later in a region that positions the P1 helix (including the 5' splice site), a region whose folding is linked to that of a portion of the catalytic core. At intermediate times, a non-native structure forms in the region of the triple helical scaffold, which connects the major folding domains. At 30 degrees C, the unfolded ribozyme passes through these stages with a half-life of 2 min from the time magnesium cations are provided. At higher temperatures, the half-life is shortened but the order of events is unchanged. Thermal melting of the fully folded ribozyme also revealed a multi-stage process in which the steps of folding are reversed: the kinetically slowest structure is the least stable and melts first. These structures of the ribozyme also bind Mg2+ cooperatively and their relative affinity for binding seems to be a major determinant in the order of events during folding. Na+ can also substitute for Mg2+ to give rise to the same crosslinkable structures, but only at much higher concentrations. Specific binding sites for Mg2+ may make this cation particularly efficient at electrostatic stabilization during folding of these ribozyme structures.

Violent victimization among women with alcohol problems.

Empirical evidence regarding the role of childhood victimization in the development of women's alcohol problems is examined in this chapter. In particular, childhood sexual abuse and father-to-daughter violence are found to predict later alcohol problems. Key variables that link experiences of childhood victimization and the development of adult alcohol problems are identified. Strengths and weaknesses of the research provide a better assessment of our confidence in the empirical evidence to date. Possible explanations for how and why the experiences of violent victimization may lead to women's alcohol problems are presented. Finally, important directions for policymakers, clinicians, and researchers are discussed.

A tertiary interaction in the Tetrahymena intron contributes to selection of the 5' splice site.

The utilization of cryptic splice sites has been observed in a number of RNA splicing reactions. In the self-splicing group I intron of Tetrahymena thermophila, point mutations of either A57 or A95 promote cleavage at two sites other than the normal 5' splice site, suggesting that these nucleotides are involved in a common tertiary interaction. These results are unusual since A57 and A95 are neither at nor near the 5' splice site in the sequence or secondary structure. Cleavage at the alternative sites appears to occur by intron cyclization, a reaction with well-established structural and mechanistic similarities to the first step of RNA self-splicing. Alternative docking of P1 (the helix containing the 5' splice site paired to the internal guide sequence of the intron) into the catalytic core accounts for cleavage at the cryptic reaction sites. We propose that the A57/A95 interaction, along with an element implicated previously (J1/2), provide structural connectivity from the reaction site in P1 to the catalytic core of the Tetrahymena intron. It seems likely that RNA splicing in general will require such tertiary interactions to position RNA helices.

Interrelationships between victimization experiences and women's alcohol use.

The interrelationships between experiences of childhood victimization and the development of women's alcohol-related problems are explored. Two different forms of childhood victimization are examined: (1) parent-to-child violence and (2) childhood sexual abuse (familial and nonfamilial). Data were collected from 472 women between the ages of 18 and 45 during in-depth interviews. Women were grouped to allow for the following two sets of comparisons: comparison 1: alcoholics in alcoholism treatment (n = 98), drinking drivers (n = 100) and a household sample (without alcohol problems) (n = 82); comparison 2: women with alcohol problems in treatment (n = 178), women without alcohol problems in treatment (n = 92) and a household sample (n = 82). High rates of childhood victimization for women with alcohol problems suggest that there is a link between victimization and the development, specifically, of women's alcohol problems. The strength of the interrelationships between childhood victimization and the development of women's alcohol problems when holding the treatment condition constant is of particular interest in this study. The rates of childhood victimization were significantly greater for women with alcohol problems in treatment as compared to women without alcohol problems in treatment. Thus, even when holding the treatment condition and family background variables constant, childhood victimization has a specific connection to the development of women's alcohol problems. These findings remained significant even when controlling for demographic and family background differences, including parental alcohol problems.

Medical accelerator safety considerations: report of AAPM Radiation Therapy Committee Task Group No. 35.

Ensuring safe operation for a medical accelerator is a difficult task. Users must assume more responsibility in using contemporary equipment. Additionally, users must work closely with manufacturers in promoting the safe and effective use of such complex equipment. Complex treatment techniques and treatment modality changeover procedures merit detailed, unambiguous written procedural instruction at the control console. A thorough "hands on" training period after receiving instructions, and before assuming treatment responsibilities, is essential for all technologists. Unambiguous written instructions must also be provided to guide technologists in safe response when equipment malfunctions or exhibits unexpected behavior or after any component has been changed or readjusted. Technologists should be given a written list of the appropriate individuals to consult when unexpected machine behavior occurs. They should be assisted in identifying aberrant behavior of equipment. Many centers already provide this instruction, but others may not. Practiced response and discussion with technologists should be a part of an ongoing quality assurance program. An important aspect of a safety program is the need for continuous vigilance. Table III gives a summary of a comprehensive safety program for medical accelerators. Table IV gives a list of summary recommendations as an example of how one might mitigate the consequences of an equipment failure and improve procedures and operator response in the context of the environment described. Most of these recommendations can be implemented almost immediately at any individual treatment center.

Movement of the guide sequence during RNA catalysis by a group I ribozyme.

Ribozymes derived from the self-splicing pre-ribosomal RNA of Tetrahymena act as sequence-specific endonucleases. The reaction involves binding an RNA or DNA substrate by base pairing to the internal guide sequence (IGS) to form helix P1. Site-specific photo-crosslinking localized the 5' end of the IGS in helix P1 to the vicinity of conserved bases between helices P4 and P5, supporting a major feature of the Michel-Westhof three-dimensional structure model. The crosslinked ribozyme retained catalytic activity. When not base-paired, the IGS was still specifically crosslinked, but the major site was 37 A distant from the reactive site in the experimentally supported three-dimensional model. The data indicate that a substantial induced-fit conformational change accompanies P1 formation, and they provide a physical basis for understanding the transport of oligonucleotides to the catalytic core of the ribozyme. The ability of RNA to orchestrate large-scale conformational changes may help explain why the ribosome and the spliceosome are RNA-based machines.

The moderating impact of social support following childhood sexual abuse.

The role of social support in moderating the impact of childhood sexual abuse on adult psychological adjustment was examined. Subjects included 475 women, age 18-45, some of whom were currently receiving treatment, others who were not. Women in the treatment group were receiving therapy for either alcoholism, for being battered, or for mental health problems. The comparison group was drawn from two sources: a random household sample and a sample of women attending drinking driver classes. Among both groups, women who had been sexually abused exhibited more psychological symptoms and lower self-esteem compared to those who were not abused. Latency of disclosure of childhood sexual abuse had no impact on long-term consequences of the abuse for either the treatment or the comparison group. However, among women in the comparison group, those who experienced supportive reactions following disclosure of sexual abuse had fewer psychological symptoms and somewhat higher self-esteem relative to those who did not receive support. Social support had no apparent effect on the long-term adjustment of women in the treatment group. Possible explanations for this pattern and directions for future research are discussed.

The relationship of adolescent peer groups to the incidence of psychosocial problems.

This study combined a treatment sample (n = 127) and a control sample (n = 114) of adolescents (ages 13-17) to investigate the relationship between adolescent peer groups and incidence of psychosocial problems. A content analysis resulted in four separate types of peer groups. The group with the lowest level of involvement in school activities was labeled by other adolescents in negative terms. An analysis of variance indicated that the least involved and most negatively labeled group generally had the most positive attitudes toward alcohol and drug use, the lowest levels of perceived harm due to alcohol and drug use, and the highest levels of alcohol abuse, drug use, delinquency, and depression. This group also had the lowest level of self-esteem, most external locus of control, least perceived access to occupational opportunities, and highest level of societal estrangement. The results are interpreted as providing support for both control and labeling theories. Implications for theory-based intervention are discussed.

An ultraviolet-inducible adenosine-adenosine cross-link reflects the catalytic structure of the Tetrahymena ribozyme.

When a shortened enzymatic version of the Tetrahymena self-splicing intervening sequence (IVS) RNA is placed under catalytic conditions and irradiated at 254 nm, a covalent cross-link forms with high efficiency. The position of the cross-link was mapped by using three independent methods: RNase H digestion, primer extension with reverse transcriptase, and partial hydrolysis of end-labeled RNA. The cross-link is chemically unusual in that it joins two adenosines, A57 and A95. Formation of this cross-link depends upon the identity and concentration of divalent cations present and upon heat-cool renaturation of the IVS in a manner that parallels conditions required for optimal catalytic activity. Furthermore, cross-linking requires the presence of sequences within the core structure, which is conserved among group I intervening sequences and necessary for catalytic activity. Together these correlations suggest that a common folded structure permits cross-linking and catalytic activity. The core can form this structure independent of the presence of P1 and elements at the 3' end of the IVS. The cross-linked RNA loses catalytic activity under destabilizing conditions, presumably due to disruption of the folded structure by the cross-link. One of the nucleotides participating in this cross-link is highly conserved (86%) within the secondary structure of group I intervening sequences. We conclude that A57 and A95 are precisely aligned in a catalytically active conformation of the RNA. A model is presented for the tertiary arrangement in the vicinity of the cross-link.