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Biomedical subjects

G R McKee

Publications and source records attributed to G R McKee.

15 recordsLinked to original sources
PubMed2006

Radial structure of Alfvén eigenmodes in the DIII-D tokamak through electron-cyclotron-emission measurements.

The spatial structure of toroidal Alfvén eigenmodes and reversed shear Alfvén eigenmodes in DIII-D is obtained from electron-cyclotron-emission measurements. Peak measured temperature perturbations are of similar magnitude for both toroidal Alfvén eigenmodes and reversed shear Alfvén eigenmodes and found to be deltaT(e)/T(e) approximately equal to 0.5%. Simultaneous measurements of density fluctuations using beam-emission spectroscopy indicate deltan(e)/n(e) approximately equal to 0.25%. Predictions of the measured temperature and density perturbation profiles as well as deltaT(e)/deltan(e) from the ideal magnetohydrodynamic code NOVA are in close agreement with experiment.

Journal Article↗
PubMed2006

Detection of zero-mean-frequency zonal flows in the core of a high-temperature tokamak plasma.

A low-frequency, spectrally broad (Deltaf approximately 10 kHz) poloidal flow structure that peaks near zero frequency is observed in time-resolved measurements of the turbulence velocity field in the core region (r/a approximately 0.6-0.9) of DIII-D tokamak plasmas. These flows exhibit a long poloidal wavelength (low m) and a short radial coherence length comparable to the ambient turbulence decorrelation length. Characteristics of these observed poloidal flows are consistent with the theoretically predicted residual or zero-mean-frequency zonal flows.

Journal Article↗
PubMed2006

Multitude of core-localized shear Alfvén waves in a high-temperature fusion plasma.

Evidence is presented for a multitude of discrete frequency Alfvén waves in the core of magnetically confined high-temperature fusion plasmas. Multiple diagnostic instruments confirm wave excitation over a wide spatial range from the device size at the longest wavelengths down to the thermal ion Larmor radius. At the shortest scales, the poloidal wavelengths are comparable to the scale length of electrostatic drift wave turbulence. Theoretical analysis confirms a dominant interaction of the modes with particles in the thermal ion distribution traveling well below the Alfvén velocity.

Journal Article↗
PubMed2002

Observation of coherent sheared turbulence flows in the DIII-D Tokamak.

Time-resolved measurements of the turbulent density flow field in a tokamak plasma reveal low-frequency ( approximately 15 KHz), coherent oscillations in the poloidal flow, v(theta). These flow oscillations have a long poloidal wavelength (m<3) and narrow radial extent (k(r)rho(i) approximately 0.2). The estimated flow-shearing rate is of the same order of magnitude as the turbulence decorrelation rate and may thus regulate the turbulence amplitude. These features are consistent with theoretically predicted axisymmetric, self-regulating, sheared flows recognized as geodesic acoustic modes.

Journal Article↗
PubMed2002

Slow L-H transitions in DIII-D plasmas.

The transition from the low to the high mode of plasma confinement ( L-H transition) is studied in the DIII-D by an experimental technique which allows an arbitrarily slow transition. During an initial transition, periodic turbulent instability bursts are observed near the separatrix which inhibit the full transition. These bursts are damped by self-generated shear flows, and a predator-prey-type relationship is shown to give a good description of the data. As the neutral-beam power is raised, the oscillations change to type III edge localized modes. Another transition then leads to a quiet H mode.

Journal Article↗
PubMed2001

Quiescent double barrier regime in the DIII-D tokamak.

A new sustained high-performance regime, combining discrete edge and core transport barriers, has been discovered in the DIII-D tokamak. Edge localized modes (ELMs) are replaced by a steady oscillation that increases edge particle transport, thereby allowing particle control with no ELM-induced pulsed divertor heat load. The core barrier resembles those usually seen with a low (L) mode edge, without the degradation often associated with ELMs. The barriers are separated by a narrow region of high transport associated with a zero crossing in the E x B shearing rate.

Journal Article↗
PubMed2001

MMPI-2 profiles of filicidal, mariticidal, and homicidal women.

The present study compared the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) clinical and content scale profiles of a group of adult women (N = 73) charged with either murder of their child (filicide) (n = 30), their partner (mariticide) (n = 19), or an unrelated adult (homicide) (n = 24). No significant differences were seen among the three groups on either the MMPI-2 clinical or content scales. Clinical inspection of the 53 valid MMPI-2 profiles (F < 110T) revealed a 6-8 mean profile for the filicidal women, a 2-6 mean profile for the mariticidal women, and a 4-8 mean profile for the homicidal women. Application of the data for criminal forensic psychological evaluations is discussed.

Adult↗
PubMed2001

Characteristics of homicidal and violent juveniles.

Homicidal youth have received considerable attention in the mass media and social science literature in recent years. Due to several methodological obstacles, relatively little is known about the premorbid and offense characteristics of this population. The current investigation compared 30 juvenile males charged with murder with a group of 62 juvenile males charged with other violent felony offenses. Comparisons were made across 33 demographic, historical, clinical, offense, and forensic characteristics. Both groups were similar in their demographic characterishics and family backgrounds. Juvenile homicide defendants, however, were less likely than the comparison group to have a current Axis I psychiatric diagnosis. Homicide defendants were also more likely to have acted alone and to have committed their alleged crime in a domestic setting. Implications of the results are discussed as are suggestions for future research.

Adolescent↗
PubMed1999

Competency to stand trial in family court: characteristics of competent and incompetent juveniles.

Competency to stand trial (CST) has been among the most thoroughly researched psycholegal issues in the past 20 years. However, little attention has been given to CST in juveniles facing delinquency or criminal proceedings. In a sample of 112 pretrial juvenile defendants undergoing court-ordered CST evaluations, 14 percent of the sample was judged incompetent to stand trial (IST). Sixty-one (55%) were considered to have one or more examiner-cited competency deficits that might lead the court to a finding of IST. Only age, intelligence level, and history of previous juvenile arrest differentiated competent from incompetent juveniles. Implications of the results for raising the CST issue in family or circuit courts are discussed as are suggestions for future research.

Adolescent↗
PubMed1998

Maternal filicide: a cross-national comparison.

The present study is a review of 20 adult women charged with murdering their children who were referred to a forensic psychiatric hospital for pretrial evaluation. This study compares the demographic, historical, clinical, forensic, and offense characteristics of these women and their victims to samples of multinational, British, and Canadian filicidal women. The data depict a subset of women who suffered from a diagnosable mental disorder and were contending with many acute stressors in their lives with apparently insufficient personal resources or systemic support. The consistency of characteristics across countries suggests that women who kill their children are nonaddicted, married, low-income, mentally ill, new or recent mothers under 30 who, acting alone and without weapons, kill only one of their children, likely of preschool age.

Adult↗
PubMed1998

Lethal vs nonlethal suicide attempts in jail.

The rate of suicide in jails has been found to be 11 to 14 times greater than suicide within the general population. The purpose of the present study is to compare the demographic, offense, and situational characteristics of 665 adult male and 89 female jail inmates who attempted suicide by either hanging (lethal) or wrist or arm-cutting (nonlethal). Hanging attempts occurred at twice the rate of cutting attempts. Further, the mortality rate of inmates' attempts by hanging (52 deaths in 602 attempts) was 19 times greater than inmates who cut themselves (1 death in 275 attempts). Of all hanging suicide deaths 63% occurred on the inmate's first day of jail. The inmate's race, condition at arrest, hours after booking, type of charge, and size of jail differentiated lethal from nonlethal suicide attempts. Implications of these data for assessment of jail suicide risk and prevention are discussed.

Adult↗
PubMed1998

Competency to stand trial in preadjudicatory juveniles and adults.

This study compared the competency to stand trial (CST) of 108 juveniles (ages 7 to 16 years) and 145 adults (17 years or older) undergoing pretrial, court-ordered forensic psychiatric evaluations. Adults were superior on both global and specific competency abilities (p < .001). Clustered by age (<13, 13 and 14, 15 and 16 years old), preteens accused of crimes failed to meet a Dusky v. United States standard, while 13- and 14-year-olds displayed an equal mix of abilities and deficits. Mid-adolescents (ages 15 and 16) were equivalent to adults in CST abilities except in their knowledge about plea bargaining elements. The ramifications of CST in felony juvenile transfer to adult court as well as the needs for ecologically valid, empirically based CST research on adolescents is discussed.

Adolescent↗
PubMed1996

MMPI-2 profiles of men charged with murder or other offenses.

This study describes MMPI-2 profiles of men charged with murder or other offenses and examines how well the MMPI-2 differentiates between these groups. Records of 135 men charged with murder and 82 charged with other offenses were examined. Results do not support the use of the MMPI-2 to differentiate between murder and other defendants. Both groups may be described as having 6-8/8-6 profiles. The mean MMPI-2 profile for the murder group was compared to the MMPI profile described by Holcomb, Adams, Ponder, and Anderson in 1984. These mean profiles have generally the same configuration and scale elevations but show important differences. This suggests that further research needs to be conducted examining the psychometric equivalence of the MMPI and the MMPI-2. Also, caution should be used when making predictions based solely on MMPI-2 profiles.

Adult↗
PubMed1995

Insanity and adultery: forensic implications of a divorce case.

Legal responsibility for acts presumes that a person's behavior is rationally intentional and under voluntary control. Automatism, a type of insanity defense, contends that the person's conscious, voluntary control of behavior has been impaired by a mental disorder. In a recent case in South Carolina, automatism was offered as a defense to adultery, an at-fault grounds to divorce. On appeal, the State Supreme Court recognized the novel application of mental impairment defenses in domestic litigation and remanded the case for rehearing. Implications of the ruling for clinical and forensic practice in family court are discussed.

Adult↗