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.

The diagnosis of delirium and DSM-IV.

This paper reviews the history of the development of the American Psychiatric Association's Diagnostic and Statistical Manual (DSM) using the diagnostic category of delirium as an example. It also attempts to show how clinical practice and experience has molded the current conceptualization of delirium in DSM-IV. The paper presents the process and options the DSM-IV Work Group on Organic Disorders pursued in developing the DSM-IV criteria for the diagnosis of delirium, particularly in relation to ICD-10.

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.

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.

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.

DSM-IV: proposals for revision of diagnostic criteria for delirium. APA Work Group on Organic Disorders of the DSM-IV Task Force and Major Contributors.

This paper reviews the historical development of the American Psychiatric Association's Diagnostic and Statistical Manual. It presents some of the issues that the clinician has found difficult in applying DSM-III and DSM-III-R criteria for delirium. In addition it introduces some options for DSM-IV criteria for delirium based on several empirical studies. These options should be studied and debated carefully over the next year because in part, they represent radical departures from existing diagnostic criteria for delirium.

The language of altered states.

To compare the subjective experience of different forms of altered states of consciousness, computerized content analysis was applied to 66 autobiographical accounts of schizophrenia, hallucinogenic drug states, or mystical ecstasy and to 28 autobiographical control accounts of important personal experiences. The patterns of lexical choice used by the four groups were significantly different in word frequencies from 49 of 83 lexical categories measured. When data from the 13 most statistically significant categories were used in discriminant and classification analyses, 84% of the samples were correctly identified by their word frequencies. These findings suggest that the subjective experiences of schizophrenia, hallucinogenic drug-induced states, and mystical ecstasy are more different from one another than alike.

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.

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.