Suburban runaways of the 1960's.
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Sensitization of an organism by recurrent disease episodes is postulated as a key mechanism governing the progressive long-term course of affective disorders. The particular significance is that episode sensitization could underly the transition from externally triggered disease episodes to autonomous episode generation. Functionally, this transition might be explained by positive feedback between a disease episode and the activity state of an organism which includes the introduction of a memory trace for generated disease episodes. Here we consider the functional consequences of episode sensitization for the course of recurrent affective disorders. We use a computational approach and extend our previously introduced model for the course of affective disorders by a feedback mechanism for episode sensitization. Depending on sensitization timescale and amount, triggered episodes leave the model in a sustained sensitized state or induce autonomous disease progression. Runaway activation can end in saturation. Remarkably, however, over a broad parametric range the progression ends in intermediate states with fluctuating disease patterns. This behavior results from the model's nonlinear dynamics and represents a situation where the feedback intermittently changes between positive and negative directions. Our simulations strongly support episode sensitization as an important disease mechanism for affective disorders. From a nonlinear standpoint, this mechanism offers an explanation not only for autonomous disease progression but also for occurence and stability of irregular rapid-cycling disease states.
We develop a semiempirical grey radiative model to quantify Titan's surface temperature as a function of pressure and composition of a nitrogen-methane-hydrogen atmosphere, solar flux and atmospheric haze. We then use this model, together with non-ideal gas-liquid equilibrium theory to investigate the behavior of the coupled surface-atmosphere system on Titan. We find that a volatile-rich Titan is unstable with respect to a runaway greenhouse-small increases in solar luminosity from the present value can lead to massive increases in surface temperature. If methane has been photolyzed throughout Titan's history, then this runaway can only be avoided if the photolytic ethane is removed from the surface-atmosphere system.
We report on the observation of a large production of runaway electrons during a disruptive termination of discharges heated with lower-hybrid waves at the Frascati Tokamak Upgrade. The runaway current plateaus, which can carry up to 80% of the predisruptive current, are observed more often than in normal Ohmic disruptions. The largest runaway currents correspond to the slowest plasma current decay rates. This trend is opposite to what is observed in most tokamaks. We attribute this anomalous behavior to the acceleration of the preexistent wave-resonant suprathermal electrons during the disruption decay phase. These results could be relevant for the operation of the ITER tokamak whenever a sizeable amount of lower-hybrid power is made available.
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INTRODUCTION: Runaway pacemaker is a potentially catastrophic complication of any permanent pacing system. METHODS AND RESULTS: A 70-year-old man was found to have erratic behavior of his implantable cardioverter defibrillator (ICD) during a routine outpatient interrogation. His device was turned off, and he was hospitalized in preparation for a pulse generator replacement. During his hospitalization, his ICD unexpectedly began pacing rapidly. Despite prompt resuscitation attempts, the patient died. Postmortem examination of the device demonstrated a crystal oscillator failure. CONCLUSION: A previously unrecognized component malfunction is a potentially lethal complication of ICDs.
A population formulation of neuronal activity is employed to study an excitatory network of (spiking) neurons receiving external input as well as recurrent feedback. At relatively low levels of feedback, the network exhibits time stationary asynchronous behavior. A stability analysis of this time stationary state leads to an analytical criterion for the critical gain at which time asynchronous behavior becomes unstable. At instability the dynamics can undergo a supercritical Hopf bifurcation and the population passes to a synchronous state. Under different conditions it can pass to synchrony through a subcritical Hopf bifurcation. And at high gain a network can reach a runaway state, in finite time, after which the network no longer supports bounded solutions. The introduction of time delayed feedback leads to a rich range of phenomena. For example, for a given external input, increasing gain produces transition from asynchrony, to synchrony, to asynchrony and finally can lead to divergence. Time delay is also shown to strongly mollify the amplitude of synchronous oscillations. Perhaps, of general importance, is the result that synchronous behavior can exist only for a narrow range of time delays, which range is an order of magnitude smaller than periods of oscillation.
OBJECTIVE: To describe the seroprevalence of human immunodeficiency virus type 1 (HIV-1) and risk factors for HIV-1 infection among teenagers attending selected clinics. DESIGN: Anonymous, cross-sectional serosurveys conducted in 130 clinics in 24 cities. SETTINGS: Adolescent medicine clinics, sexually transmitted disease clinics, clinics in juvenile detention and correctional facilities, and homeless and runaway youth centers. PATIENTS: Teenagers in whom serum samples were drawn as part of routine medical services. MAIN OUTCOME MEASURES: Prevalence of HIV-1 infection and reported HIV risk behaviors. RESULTS: From January 1, 1990 through December 31, 1992, serum specimens were collected from 79,802 teenagers; 591 of these specimens were positive for HIV-1 antibody. Seropositive test results were found in all 24 cities surveyed, and in 95 (73%) of the 130 clinics surveyed. The median clinic-specific prevalence was 0.2% (range, 0% to 1.4%) in 22 adolescent medicine clinics, 0.3% (range, 0% to 6.8%) in 33 correctional facilities, 0.5% (range, 0% to 3.5%) in 70 sexually transmitted disease clinics, and 1.1% (range, 0% to 4.1%) in five homeless youth centers. Rates exceeded 1% in 37 sites (28%). Excluding sites with many men reporting sex with men, rates in women were similar or somewhat higher than rates in men. Rates were highest among young men reporting sex with men, with clinic rates ranging from 16% to 17% in two homeless youth sites and 13% to 17% in two sexually transmitted disease clinics. Most teenagers with risk information reported heterosexual activity as their only potential risk exposure to HIV-1. CONCLUSIONS: Seroprevalence of HIV was generally low but varied by type of clinic and geographic area. The highest rates were observed among young women and gay men in some settings, suggesting that targeted prevention messages are needed.
There is an emerging body of clinical evidence that cocaine use in humans can result in serious fear or panic-related emotional disturbances. The present study evaluated the effects of intravenous cocaine administration upon defensive responses of rats to a threatening conspecific in a test situation, an oval runaway, permitting the display of the full range of the rat defensive repertoire. A battery of tests was employed to evaluate avoidance/escape, flight, freezing, defensive upright and defensive attack behaviors. In the first experiment male Long-Evans rats implanted with a chronic indwelling jugular catheter were placed in the runway and tested immediately after administration of either 0, 1, or 4 mg/kg of cocaine hydrochloride. The 4-mg/kg dose produced a dramatic flight response, the direction of which depended upon the direction of the approaching threat source. The same dose produced increased defensive upright postures during forced contact with the stimulus animal. Experiment 2 examined the time course for cocaine-induced hyperdefensiveness. Rats were administered either saline or 4 mg/kg cocaine intravenously and were tested following a delay of either 0, 5, 15, or 30 min following infusion. Cocaine-treated rats again displayed high levels of flight, which declined with increased time between infusion and testing. However, increased defensiveness persisted even at the 30 min delay for several defensive measures including avoidance, freezing, and defensive upright posture. Thus, following an initial period of rapid flight with intravenous cocaine administration, there was a lasting hyperdefensiveness in cocaine-treated rats. The present results suggest that cocaine may exert its panic-producing effects by acting upon neurobehavioral systems subserving defensive behavior, and that understanding of these systems is critical for understanding the neurobiology of panic disorder.
The psychosocial model of the victim-to-patient process explains how chronic abuse damages the self and sets into motion psychological processes that may evolve into various forms of mental illness. This model emphasizes the fragmented identity that derives from victims' attempts to accommodate to the judgments of others about the abuse, namely, it didn't happen; it happened, but it wasn't important and has no consequences; (s)he provoked it; and it wasn't abusive. Victims thus repress and deny the trauma and associated feelings in order to survive. The behavioral and psychological legacy of this adaptation forms the core of survivors' psychopathology and becomes an obstacle to treatment and recovery. The link between the damaged self and AIDS risk in adolescent runaway, homeless, and mentally ill survivor populations is underscored, along with recommendations for urgently needed clinical interventions.
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There is increasing evidence for the process of sympatric speciation, in which reproductive isolation of species occurs without physical isolation. Theoretical models have focused on disruptive natural selection as the crucial pressure for splitting a species. Here we report the theoretical finding that sympatric speciation may be caused by sexual selection even without disruptive natural selection. Specifically, we show that variation in a male secondary sexual character with two conspicuous extremes and the corresponding variance in female mating preference around no preference may jointly evolve into bimodal distributions with increasing modal divergence of the male and female traits, pulling a population apart into two prezygotically isolated populations. This mode of speciation, driven by two runaway processes in different directions, is promoted by an increase in the efficiency of females in discriminating among males or a decrease in the cost of male conspicuousness, indicating that sympatric speciation may occur more readily if barrier-free or predator-free conditions arise. Although even a slight cost of female preference would cancel the runaway process of sexual selection, it would not cancel the divergent runaway processes of sympatric speciation.
Based on the structural-choice theory of victimization, the current study examines the effects of a high-risk environment on the sexual victimization of 311 homeless and runaway youth. Results from logistic regression revealed that survival sex, gender, and physical appearance were significantly associated with sexual victimization. Results from a series of interactions also revealed that the effects of deviant behaviors on sexual victimization varied by gender and age. Although males and females engaged in similar activities, young women were more likely to be victims of sexual assault. These findings suggest that engaging in high-risk behaviors predispose some people to greater risks but it is the combination of these behaviors with gender and/or age that determines who will become victimized.
Experts in the fields of child development, psychology, and criminology agree that family system variables play a key role in the development of delinquent and other deviant behaviors. Professionals in the field of substance abuse estimate that there may be at least 22 million children who have been or are currently being raised in homes with substance-abusing parents. Many studies have documented the relationships between being raised in such an environment and a variety of emotional and deviant characteristics. These individuals have been found to suffer from low self-esteem, depression, anger, and a variety of acting-out behaviors. This study investigated the differences between incarcerated juveniles from substance-abusing families and those from non-substances-abusing families. Significant differences were found in the areas of family violence, abuse; runaway, and self-reported substance abuse.
Thermal stability evaluation of exothermic chemical reactions is of great importance to the safer design and operation of chemical processes. Dominant reaction stoichiometries and their thermochemistry parameters are key elements in the evaluation process. Identification of significant reaction pathways under possible process conditions will lead to an understanding of the overall thermodynamic and kinetic behavior. The kinetics of 1,3-butadiene (BD) is an excellent example of conjugated dienes that undergo addition reactions. At elevated temperatures, 1,3-butadiene monomers can dimerize exothermally, and as temperature increases, secondary exothermic reactions will take place. The very high temperature and pressure rates that these reactions can attain may lead to a reaction runaway or even a thermal explosion. BD is a vapor at ambient conditions, usually stored as a pressurized liquid, and is a carcinogen, so the experimental evaluation is potentially difficult and hazardous. In this paper, the thermal stability of BD is evaluated. Dimerization and other secondary reactions are investigated by experimental thermal analysis using an automatic pressure adiabatic calorimeter (APTAC), by theoretical computational quantum chemistry methods, and empirical thermodynamic-energy correlations. A theoretical approach is conducted to predict some of the BD reaction behavior. Results are compared to other literature data obtained using different experimental methods.
The Boston HAPPENS Program is a collaborative network of care consisting of multiservice outreach agencies; community health centers; and hospitals for HIV-positive, homeless, and hard-to-reach youth. In four years of data collection, the program served more than 2,000 youth, including 54 HIV-positive youth. The youth were 19.9 +/- 2.9 years old; 64 percent female; 45 percent youth of color; 11 percent gay/lesbian, bisexual, or undecided; and 13 percent homeless or runaway. Homeless youth were much more likely to have been involved with a mental health system (47% vs. 12%, P < 0.001), the criminal justice system (20% vs. 2%, P < 0.001), high-risk sexual behaviors (21% vs. 3%, P < 0.001), and substance abuse (25% vs. 6%, P < 0.001) than were other youth served by the program. Comprehensive networks of care offering a continuum of services and a variety of entry routes and types of care sites are needed to connect under-served youth to health care. Outreach and human immunodeficiency virus (HIV) counseling and testing services can offer important portals of entry into health services for at-risk youth. Support services such as outreach, case management, and mental health services are needed to complement medical services by all youth at-risk for contracting HIV. Support services are necessary for the initiation and retention of youth in care so that early case identification and complex treatment regimens can be initiated and tailored to the individual.
Most homeless teenagers are running away from abusive or violent home situations. Many of the daily survival tactics employed by runaways put them at risk for a variety of medical problems, including sexually transmitted diseases, hepatitis, tuberculosis, trauma, accidents, and HIV infection. Mental health issues of depression, low self-esteem, hostility, and suicidal behavior or ideation are common and may be compounded by drug abuse or addiction. Barriers to obtaining care for the uninsured homeless teenager encompass confidentiality issues, minor status, and general distrust of adult authority figures. To improve the health care of homeless adolescents, practitioners must encourage research and data collection while supporting and providing accessible medical outreach programs and mental health services.