Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces.

We investigate the formation of extended defects during molecular-dynamics (MD) simulations of GaN and InGaN growth on (0001) and ([Formula: see text]) wurtzite-GaN surfaces. The simulated growths are conducted on an atypically large scale by sequentially injecting nearly a million individual vapor-phase atoms towards a fixed GaN surface; we apply time-and-position-dependent boundary constraints that vary the ensemble treatments of the vapor-phase, the near-surface solid-phase, and the bulk-like regions of the growing layer. The simulations employ newly optimized Stillinger-Weber In-Ga-N-system potentials, wherein multiple binary and ternary structures are included in the underlying density-functional-theory training sets, allowing improved treatment of In-Ga-related atomic interactions. To examine the effect of growth conditions, we study a matrix of >30 different MD-growth simulations for a range of In x Ga 1-x N-alloy compositions (0 ≤ x ≤ 0.4) and homologous growth temperatures [0.50 ≤ T/T*m (x) ≤ 0.90], where T*m (x) is the simulated melting point. Growths conducted on polar (0001) GaN substrates exhibit the formation of various extended defects including stacking faults/polymorphism, associated domain boundaries, surface roughness, dislocations, and voids. In contrast, selected growths conducted on semi-polar ([Formula: see text]) GaN, where the wurtzite-phase stacking sequence is revealed at the surface, exhibit the formation of far fewer stacking faults. We discuss variations in the defect formation with the MD growth conditions, and we compare the resulting simulated films to existing experimental observations in InGaN/GaN. While the palette of defects observed by MD closely resembles those observed in the past experiments, further work is needed to achieve truly predictive large-scale simulations of InGaN/GaN crystal growth using MD methodologies.

Verbal behavior and schizophrenia. The semantic dimension.

Through the use of computer analysis, the content of the speech of schizophrenics is shown to be distinct from that of the speech of nonschizophrenic psychiatric patients. The data shed light on qualities that delineate some aspects of "bizarreness" in speech of schizophrenics, provide some insight into the diversity of postulated "defects" in schizophrenic thinking, and provide further understanding of the diagnostic process in schizophrenia.

The dose-response ratio in electroconvulsive therapy a preliminary study.

To investigate pretreatment patient variables that might correlate with dose-response characteristics of electroconvulsive therapy (ECT) and treatment outcomes, 14 patients were assessed on a daily basis, before and during treatment, using self-report affective scales, three simple paper-and-pencil tests of cognitive function,and finger-tapping speed. From these data, dose-response ratios and treatment outcome measures were derived. The dose-response ratio of ECT was found to correlate with age--the younger the patient, the more favorable the ratio. This finding is discussed in terms of the known relationships between brain monoamine oxidase levels and age, and the established relationship between seizure duration and treatment efficacy. The dose-response ratio over the first two electroconvulsive treatments as well as lesser degrees of initial congnitive and greater degrees of initial affective impairment correlated strongly with greater overall affective improvement. Some clinical and research implications of these findings are discussed.

Computer content analysis of schizophrenic speech: a preliminary report.

Computer analysis significantly differtiated the thermatic content of the free speech of 10 schizophrenic patients from that of 10 nonschizophrenic patients and from the content of transcripts of dream material from 10 normal subjects. Schizophrenic patients used the thematic categories in factor 1 (the "schizophrenic factor") 3 times more frequently than the nonschizophrenics and 10 times more frequently than the normal subjects (p smaller than 01). In general, the language content of the schizophrenic patient mirrored an almost agitated attempt to locate oneself in time and space and to defend against internal discomfort and confusion. The authors discuss the implications of this study for future research.

Sensorimotor functions and cognitive disturbance in psychiatric patients.

The authors studied 109 consecutive admissions to an acute psychiatric unit in a general hospital to determine the relationship of specific sensorimotor impairments to cognitive disturbance. The results indicated a strong but not exclusive correlation between neurological impairment and thought disorder as well as between neurological impairment and schizophrenia. The theoretical and etiological implications are discussed, as well as the relationship of these findings to other variables.

The language of paranoia.

In order to assess which of three current models is most useful in understanding paranoia, the authors applied computer speech content analysis to 55 patients--24 of whom were in four groups expressing paranoid delusions and 31 of whom were in four groups not expressing such delusions. The results delineated a semantic or verbal profile of paranoid self-presentation. This self-presentation is more identifiable than the effects of any other patient characteristic, even if the delusion is not discussed by the patient. The strength of the statistical evidence supports the model of paranoid delusions as a separate disease rather than as a subtype of schizophrenia or as a trait that exists on a spectrum from normality to pathology.

Diagnostic classification through content analysis of patients' speech.

Speech samples from 71 patients in four diagnostic groups were analyzed by two quantitative methods of speech content analysis, the results of which were entered into a discriminant analysis to test whether patients could be accurately classified back into their appropriate diagnostic groups. These classifications were compared with classifications made by two psychiatrists, blind to the patients' diagnoses, who read transcripts of the speech samples. The results suggest that data from the systematic quantification of lexical choice can be used to classify patients into their respective diagnostic groups and that this classification compares favorably with that done by psychiatric raters.

Linguistic dimensions of affect and thought in somatization disorder.

DSM-III has established diagnostic criteria that separate somatization disorder from other overlapping symptom configurations. Nevertheless, information regarding the experience of somatization disorder is far from complete. Terms such as "masked depression" or "alexithymia" imply that a disturbance of affect is a central but guarded issue for at least some somatizing patients. Through content analysis of speech, the authors investigated the self-experience of somatization disorder in relation to affective disorder. Rather than defended depression, a distinctive characteristic found in the language of patients with somatization disorder reflects a confused, negative self-identity.

Reliability of the Part II Board Certification Examination in Psychiatry: interexaminer consistency.

OBJECTIVE: The aim of the study was to examine the reliability (interexaminer consistency) of the American Board of Psychiatry and Neurology (ABPN) Part II (oral) examination in psychiatry. METHOD: Grades were assigned independently by two examiners who observed the same examination in a 1-year cycle (1,422 candidates, two examinations each). The consistency between these pairs of grades (pass, condition, fail) was analyzed using a weighted kappa statistic. RESULTS: There was perfect agreement between examiners in 67% of examinations, minor disagreement in 26%, and major disagreement in 7% (weighted kappa = 0.54-0.56). CONCLUSIONS: The Part II ABPN examination demonstrates fair to good reliability as measured by interexaminer consistency. Development of more explicit grading criteria should further improve examiner agreement in future examinations.

Reliability of the Part II board certification examination in psychiatry: examination stability.

OBJECTIVE: The aim of this study was to examine the reliability (examination stability) of the American Board of Psychiatry and Neurology (ABPN) Part II (oral) examination in psychiatry. METHOD: The authors analyzed the consistency (agreement between grades given by two independent examiners) for a 1-year examination cycle using a weighted kappa statistic and compared different parts of the examination (live patient and videotape), different examination sites, different days, and different times of the day. RESULTS: There was no significant difference in agreement between examiners by different parts of the examination, examination site, day of the week, or time of day. CONCLUSIONS: The stability of the Part II ABPN examination in psychiatry is not influenced significantly by the format or site of administration. Candidate performance is the predominant factor in the determination of passing or failing grades.

Fundamentals of carbamazepine use in neuropsychiatry.

Carbamazepine, mainly used as an anticonvulsant but also used for trigeminal neuralgias and other neuralgic pains, is now being used experimentally for affective disorders, nonresponsive psychoses, and dyscontrol. However, carbamazepine dosage must be carefully monitored because low initial doses are equivalent to higher later doses, and the drug's addition to a regimen of other drugs may increase carbamazepine's serum levels. Given alone to a pharmacologically naive inpatient, initial dosage of carbamazepine 200 mg/day can be increased by 100 mg every day or every second day; an outpatient can have the dosage increased by 100 mg every third day. Serum levels and side effects should be monitored. White cell counts usually decrease about 25%, but the decrease is not clinically related to the very rare occurrence of agranulocytosis. A side effect of concern is hepatic toxicity, but few such cases have been reported. The most common side effect is allergic rash, which occurs in about 5% of all patients receiving carbamazepine; antihistamines sometimes bring about a remission of the rash. Generic carbamazepine may cause more problems than Tegretol.

Seizure disorders presenting with psychiatric symptomatology.

Seizure disorders can be mistaken for psychiatric disorders and, the two have a number of poorly understood interrelations. Disruptions of consciousness, motor activity, hallucinations, and abrupt mood and anxiety changes can all be seizure manifestations caused by cortical neuronal discharges. This article presents the classification and proposed psychopathology of seizure disorders. It then reviews the psychiatric conditions that frequently mimic elements of such seizure disorders, giving hints that will allow the clinician to correctly identify seizures that are creating psychiatric presentations. Finally, this article makes clear the situations in which anticonvulsant medications may be of value when nothing else seems to be working.

Psychosocial and cognitive function after commissurotomy for intractable seizures.

Cerebral commissurotomy appears to be an effective treatment for persons with severe epilepsy that has not responded to pharmacological treatment. Psychosocial and neuropsychological evaluation of eight patients who have received this surgical treatment suggests that patients who have an uncomplicated operative and postoperative course do not experience functionally significant intellectual, emotional, or social impairment. Limiting the operation to extraventricular division of the corpus callosum may significantly reduce postoperative morbidity. The authors suggest ethical guidelines which they believe should be carefully followed when epileptic patients are being considered for this type of surgery.

Neurology and psychiatry.

There has been a long historical relationship between neurology and psychiatry. This relationship has been nurtured by the common interest in the central nervous system and disturbed behavior associated with dysfunctions of the nervous system. This paper reviews the formal relationships between neurology and psychiatry and particularly looks at the behavioral aspects of neurological disease. For the past 10 years, both from a clinical and a theoretical viewpoint, the importance of understanding central nervous system functioning and dysfunctioning has become increasingly apparent to psychiatrists.

The manipulative patient: an interactional approach.

The words manipulative or manipulation are used in the contemporary psychiatric literature to describe certain persons and their habitual modes of behavior. The terms represent an attempt to describe some essential quality of the patient's style of relating to others. In the following discussion, we will attempt to shift this perspective to a more interpersonal one, seeing the attribution of this label as part of a sequence of communication, mutual perception, and struggle between caretaker and patient. The accusation that a patient is manipulative signals the disruption of the helping process.

Somatization, paranoia, and language.

Somatization and paranoia are circumscribed distortions of reality that are impervious to the normative process of consensual validation. These distortions are often postulated as a means of bolstering lowered self-esteem. We used computerized content analysis of the free speech of patients with these disorders in order to identify and compare dimensions of self-concept reflected in their lexical choices. Interestingly, patients with these disorders differed in the themes prominent in their speech. The higher frequency categories used by the somatization disorder group conveyed an overwhelming sense of negativism, distress, and a preoccupation with an uncertain self-identity. In contrast, the categories used by the paranoid patients portrayed an artificially positive, grandiose self-image and a defensive abstractness. Our exploratory analysis suggests that circumscribed distortions of reality in somatization and paranoid disorders are not associated with the same common defensive style attempting to bolster self-esteem.