Search

The American Association for the Advancement of Science (AAAS) was tasked with identifying the key science concepts for science literacy in K-12 students in America (AAAS, 1990, 1993). The AAAS Atlas of Science Literacy (2001) has organized roughly half of these science concepts or benchmarks into fifty flow charts. Each flow chart or strand map contains only those AAAS benchmarks relevant to that specific area of K-12 science education. While all the connections and benchmarks are needed for complete K-12 science literacy in that science topic, it is reasonable to assume that some of the blocks and connections are more critical than others. This study develops a quantitative algorithm identifying the specific linear sequence of K-12 benchmarks containing the highest information potential for a subset of Project 2061 strand maps relating to a single topic. As such it represents the shortest and most efficient topical K-12 science-learning path. Science educators should focus their teaching expertise and assessment skills on this defined set of benchmarks in each strand map. It is also where local administrators should focus their funding and science curriculum publishers focus their authoring. (Contains 3 tables, 8 figures, and 5 notes.)

Our understanding of the deglacial evolution of the Antarctic Ice Sheet (AIS) following the Last Glacial Maximum (26,000-19,000 years ago) (1) is based largely on a few well-dated but temporally and geographically restricted terrestrial and shallow-marine sequences (2-4). This sparseness limits our understanding of the dominant feedbacks between the AIS, Southern Hemisphere climate and global sea level. Marine records of iceberg-rafted debris (IBRD) provide a nearly continuous signal of ice-sheet dynamics and variability. IBRD records from the North Atlantic Ocean have been widely used to reconstruct variability in Northern Hemisphere ice sheets (5), but comparable records from the Southern Ocean of the AIS are lacking because of the low resolution and large dating uncertainties in existing sediment cores. Here we present two well-dated, high-resolution IBRD records that capture a spatially integrated signal of AIS variability during the last deglaciation. We document eight events of increased iceberg flux from various parts of the AIS between 20,000 and 9,000 years ago, in marked contrast to previous scenarios which identified the main AIS retreat as occurring after meltwater pulse 1A (3,6-8) and continuing into the late Holocene epoch. The highest IBRD flux occurred 14,600 years ago, providing the first direct evidence for an Antarctic contribution to meltwater pulse 1A. Climate model simulations with AIS freshwater forcing identify a positive feedback between poleward transport of Circumpolar Deep Water, subsurface warming and AIS melt, suggesting that small perturbations to the ice sheet can be substantially enhanced, providing a possible mechanism for rapid sea-level rise., Today, the estimated total iceberg calving flux from Antarctica is about 1,300-2,000 gigatons per year (Gt [yr.sup.-1]) (9), with giant (longer than 18 km) icebergs representing at least half of [...]

Arrest in long bone growth and the subsequent resumption of growth may be visible as radio-paque transverse lines in radiographs (Harris lines, HL; Harris, HA. 1933. Bone growth in health and disease. London: Oxford University Press). The assessment of individual age at occurrence of such lines, as part of paleopathological skeletal studies, is time-consuming and shows large intra-and interobserver variability. Thus, a standardized, automated detection algorithm would help to increase the validity of such paleopathological research. We present an image analysis application facilitating automatic detection of HL. On the basis of established age calculation methods, the individual age-at-formation can be automatically assessed with the tool presented. Additional user input to confirm the automatic result is possible via an intuitive graphical user interface. Automated detection of HL from digital radiographs of a sample of late Medieval Swiss tibiae was compared to the consensus of manual assessment by two blinded expert observers. The intra-and interobserver variability was high. The quality of the observer result improved when standardized detection criteria were defined and applied. The newly developed algorithm detected two-thirds of the HL that were identified as consensus lines between the observers. It was, however, necessary to validate the last one-third by manual editing. The lack of a large test series must be noted. The application is freely available for further testing by any interested researcher. KEY WORDS algorithm; feature detection; radiograph; paleopathology; bone growth

Cases of pathologically changed bone might constitute a diagnostic pitfall and frequently need histological methods to be etiologically properly evaluated. With micro-computed tomography ([mu]CT), a new epoch of 2D and 3D imaging has been launched. We evaluated the diagnostic investigation of this analytical method versus well established histological investigations of historical human bone. Pathological changes due to various etiologies (infectious, traumatic, endocrinological, neoplasia) observed in autopsy-based macerated human skulls (Galler Collection, Natural History Museum Basel, Switzerland) were investigated by [mu]CT and compared with histological thin ground sections using polarized light. Micro-CT images visualize the architecture of the bone with high spatial resolution without preparation or destruction of the sample in the area to be sectioned. Changes in the bone surfaces as well as alterations of the diploe can be assessed. However, morphological patterns caused by reactive response, such as typical arrangements of collagen fibers, can only be visualized by the microscopic investigation of thin ground sections using polarized light. A great advantage of [mu]CT is the high number of slices obtained so that spatial differences within the areas of the specimen become visible. Micro-CT is a valuable tool for the diagnosis of vestiges of skull bone diseases. Its advantages over histology are the fast, automated image acquisition and the fact that the specimen is not completely destroyed. Only excision of the area to be scanned is necessary, if the specimen is too large to be scanned as a whole. Further, the 3D visualization of the micro-architecture allows an easy orientation within the sample, for example, for the choice of the location of the histological slices. However, the need to differentiate woven from lamellar bone still makes histology an indispensable method. Am J Phys Anthropol 133:1099-1111, 2007. KEY WORDS paleopathology; osteomyelitis; syphilis; hyperostosis frontalis interna; hyperparathyroidism

The evolution of Staphylococcus aureus has been described as predominantly clonal, based on evidence from seven housekeeping genes. We aimed to test if this was also true for more polymorphic genes. In a collection of 60 isolates including major European epidemic methicillin-resistant S. aureus (MRSA) and sporadic MRSA strains, we compared the partial gene sequences of seven housekeeping genes (arcC, aroE, glpF, gmk, pta, tpi, and yqiL), six core adhesion genes (present in all strains) (clfA, clfB, fnbA, map, sdrC, and spa), and four accessory adhesion genes (not present in all strains) (ebpS, fnbB, sdrD, and sdrE). Nucleotide diversity of adhesion genes was 2- to 10-fold higher than genes used for multilocus sequence typing. All genes showed evidence for purifying selection with a weakly reduced level among accessory adhesion genes. Among these highly variable genes, there was no evidence for a difference in molecular evolution between epidemic and sporadic strains. Gene trees constructed from concatenated sequences of housekeeping, core adhesion, and accessory adhesion genes were highly congruent, indicating clonality, despite some evidence for homologous exchange. Further evidence for clonality was found with an overall positive correlation of allelic and nucleotidic divergence for both seven housekeeping genes and six core adhesion genes. However, for small allelic differences that fit the demarcations of clonal complexes (CCs) there was no such correlation, suggesting that recombination occurred. Therefore, despite an overall clonal population structure, recombination between related isolates within CCs might have contributed to S. aureus evolution.

The results of geoscientific surveys undertaken during ANT-VIII/6 and ANT-XI/4 on the Gunerus Ridge and KMS, are presented. This included bathymetric mapping, stratigraphy of sediment cores an echosounding surveys. It gives an overview of types, ages and sedimentation rates for sediments and can be used in future piston core sampling to provide a more continuous record of Paleogene-Quaternary sediments.

Geological research shows that the Eltanin asteroid was between one and four kilometers in size and impacted the earth in the late Pliocene period. Marine-geological, bathymetric and seismic experiments indicate that the impact occurred approximately 2.5 million years ago. The impact, which occurred at a depth of between 2,500 meters and 5,000 meters in the Antarctic Ocean, had an explosive force of between ten(super 5) to ten(super 7) Mt TNT explosive.