The age of Clovis-13,050 to 12,750 cal yr B.P.

Thirty-two radiocarbon ages on bone, charcoal, and carbonized plant remains from 10 Clovis sites range from 11,110 ± 40 to 10,820 ± 10 14C years before the present (yr B.P.). These radiocarbon ages provide a maximum calibrated (cal) age range for Clovis of ~13,050 to ~12,750 cal yr B.P. This radiocarbon record suggests that Clovis first appeared at the end of the Allerød and is one of at least three contemporary archaeological complexes in the Western Hemisphere during the terminal Pleistocene. Stemmed projectile points in western North America are coeval and even older than Clovis, and the Fishtail point complex is well established in the southern cone of South America by ~12,900 cal yr B.P. Clovis disappeared ~12,750 cal yr B.P. at the beginning of the Younger Dryas, coincident with the extinction of the remaining North American megafauna (Proboscideans) and the appearance of multiple North American regional archaeological complexes.

Sediment Cores from White Pond, South Carolina, contain a Platinum Anomaly, Pyrogenic Carbon Peak, and Coprophilous Spore Decline at 12.8 ka.

A widespread platinum (Pt) anomaly was recently documented in Greenland ice and 11 North American sedimentary sequences at the onset of the Younger Dryas (YD) event (~12,800 cal yr BP), consistent with the YD Impact Hypothesis. We report high-resolution analyses of a 1-meter section of a lake core from White Pond, South Carolina, USA. After developing a Bayesian age-depth model that brackets the late Pleistocene through early Holocene, we analyzed and quantified the following: (1) Pt and palladium (Pd) abundance, (2) geochemistry of 58 elements, (3) coprophilous spores, (4) sedimentary organic matter (OC and sedaDNA), (5) stable isotopes of C (δ13C) and N (δ15N), (6) soot, (7) aciniform carbon, (8) cryptotephra, (9) mercury (Hg), and (10) magnetic susceptibility. We identified large Pt and Pt/Pd anomalies within a 2-cm section dated to the YD onset (12,785 ± 58 cal yr BP). These anomalies precede a decline in coprophilous spores and correlate with an abrupt peak in soot and C/OC ratios, indicative of large-scale regional biomass burning. We also observed a relatively large excursion in δ15N values, indicating rapid climatic and environmental/hydrological changes at the YD onset. Our results are consistent with the YD Impact Hypothesis and impact-related environmental and ecological changes.

Pre-Clovis projectile points at the Debra L. Friedkin site, Texas-Implications for the Late Pleistocene peopling of the Americas.

Lanceolate projectile points of the Clovis complex and stemmed projectile points of the Western Stemmed Tradition first appeared in North America by ~13 thousand years (ka) ago. The origin, age, and chronological superposition of these stemmed and lanceolate traditions are unclear. At the Debra L. Friedkin site, Texas, below Folsom and Clovis horizons, we find stemmed projectile points dating from ~13.5 to ~15.5 ka ago, with a triangular lanceolate point form appearing ~14 ka ago. The sequential relationship of stemmed projectile points followed by lanceolate forms suggests that lanceolate points are derived from stemmed forms or that they originated from two separate migrations into the Americas.

Psychiatry clerkship students' preparation, reflection, and results on the NBME Psychiatry Subject Exam.

OBJECTIVE: Psychiatry clerkship training involves many learning components, one of which is acquisition of scholarly knowledge. The authors investigate the reading materials and learning methods used by clinical clerks in their preparation for the National Board of Medical Examiners (NBME) Psychiatry Subject Exam (PSE). METHODS: Clerkship students from six U.S. medical schools who had recently completed their psychiatry clerkship and PSE were surveyed regarding reading material use, teaching methods encountered, and other relevant resources which may have influenced their PSE scores. RESULTS: The most frequently used PSE preparation material was a "step-or-prep" book, followed by practice questions, handouts, and assigned texts. No single preparation material type or combination proved significantly different in influencing PSE scores. The didactic methods used in clerkships did differ significantly in their influence on PSE scores. Students in the top quartile used slightly more books and different combinations of books than students in the bottom quartile. CONCLUSION: Students exhibited several trends in their preparation for the PSE. The most striking findings were the heavy student reliance on step-or-prep books over other learning resources and that step-or-prep books did not demonstrate significance as a superior preparation resource for the PSE. These trends in third-year psychiatric rotations have important implications for medical student education.

Hyperspectral Fourier transform spectrometer for reflection spectroscopy and spectral self-interference fluorescence microscopy.

A hyperspectral Fourier transform spectrometer has been developed for studying biological material bound to optically reflecting surfaces. This instrument has two modes of operation: a white-light reflection mode and a spectral self-interference fluorescence mode. With the combined capability, information about the conformation of an ensemble of biomolecules may be determined. To the best of our knowledge, ours is the first report of this hybrid white-light reflection, spectral self-interference fluorescence measurement with any type of hyperspectral imager. The measurement technique is presented along with a full description of the system, including theoretical performance projections. Proof-of-principle measurements of artificial samples are shown, and the results are discussed.

Clinical grading in psychiatric clerkships.

OBJECTIVE: The clinical grade assessment is the most frequently used and heavily weighted component in the overall assessment of U.S. psychiatry clerkship students, yet the topic is understudied. The authors aimed to learn more about the nature, perceived virtues, and deficiencies of the clinical grade evaluation. METHODS: A 26-item questionnaire regarding the psychiatry clerkship clinical grading form was distributed to the clerkship directors of 129 medical schools in the U.S. and U.S. territories. The design of the document, its strengths, its weaknesses, grading outcomes, and utilization were assessed. RESULTS: Trends regarding clinical grading in psychiatry clerkships were detected. The clerkship grade form similarities, differences, desirable features, and utilization were ascertained, as were areas for improvement. CONCLUSIONS: The search for an optimal clinical grading process for the thousands of third-year medical students rotating annually is formidable. However, collaboration among psychiatry clerkship directors on development and improvement of clinical evaluation forms can clarify learning objectives and lead to better clinical evaluation tools.

The "shrinking" clerkship: characteristics and length of clerkships in psychiatry undergraduate education.

OBJECTIVE: The authors explored the time that is currently devoted to psychiatry clerkships to determine whether "shortened" clerkships differ in course director satisfaction and evaluation strategies. METHOD: An 18-item questionnaire was sent to 150 U.S. and Canadian clerkship directors. RESULTS: The return rate was 74% (111 questionnaires). Clerkship length ranged from 4 to 8 weeks, with 6 weeks being most common (49.5% of clerkships). Only 18.9% had clerkships lasting 8 full weeks. Shorter clerkships were more likely to rely on the NBME subject test, and less likely to rely on Objective Standardized Clinical Examinations (OSCEs) or oral examinations. Most clerkship directors (81.9%) felt their evaluation procedures reflected their clerkship objectives. Among those who did not or were not sure, a majority (77.7%) felt having too few weeks was among the causes, except for 8-week clerkship directors, who did not mention clerkship length as an issue. CONCLUSIONS: The number of clerkships having 2 full months devoted to psychiatry has decreased in recent years. Shorter clerkships rely heavily on the National Board of Medical Examiners (NBME) Subject Examination as an evaluation tool, testing for book knowledge rather than clinical skills.

Usage of the National Board of Medical Examiners Subject Test in Psychiatry by U.S. and Canadian clerkships.

OBJECTIVE: The authors explored psychiatry clerkship usage of the National Board of Medical Examiners (NBME) Subject Test. METHODS: U.S. and Canadian psychiatry clerkship directors (N=150) were sent an 18-item questionnaire surveying evaluation and remediation practices. RESULTS: Of 111 questionnaires (74%) returned, 76 (69%) reported using the NBME Subject Test. As part of the overall grade, the test was granted a mean weight of 31% and a median weight of 25%. Of 72 clerkship directors who use the test for grading, 42% convert the percentile score and 38% convert the subject score. Of 60 clerkship directors who use the test for passing, 72% convert the raw score (mean=58.3, median=58), and 28% convert the percentile score (mean=12.2(th), median=11(th) percentile). CONCLUSIONS: Most psychiatry clerkship directors use the NBME Subject Test, but no predominant method exists for weighing the test or converting it into a grade.