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Cretaceous eolian deposits provide evidence of variations in the tropical-subtropical atmospheric circulation under greenhouse conditions. However, the misinterpretation of many such deposits as fluvial or deltaic originally hindered precise paleoclimatic reconstructions. Here we report a newly identified Early Cretaceous desert in the Hami Basin, China, which helps understand spatial-temporal variations in aridity and atmospheric circulations within central East Asia during the Early Cretaceous. The Liushuquan Formation is composed of >300-m-thick eolian deposits interpreted as an intermontane erg environment. Paleocurrent indicators within the straight-crested dunes of the Liushuquan Formation yield a mean trend of 101.3° (± 10.1°, 1 standard deviation) throughout the formation, consistent with near-surface westerly winds. Paleo-atmospheric circulation superimposed on topographic effects led to widespread eolianite accumulation during the Early Cretaceous. Combined with the spatiotemporal changes in desert distributions and prevailing surface wind patterns in East Asia, these observations are consistent with the migration of the subtropical high-pressure belt during the Early Cretaceous. We propose the following paleo-atmospheric model: (1) During the late Berriasian−Valanginian, the subtropical high belt drifted southward and northward over shorter time scales within the spatial domain of the paleo-Ordos Basin, then shifted southward at least past the Ordos Basin; (2) until the late Hauterivian−Barremian, the subtropical high-pressure zone was primarily located between the northwestern Tarim Basin and the Ordos Basin; and (3) a significant southward shift of the subtropical high-pressure zone occurred during the Aptian−Albian.

 

This paper is the culmination of four years of an NSF-funded project implementing and assessing an undergraduate additive manufacturing course at three large state universities: Texas Tech University, Kansas State University, and California State University – Northridge. The research questions addressed are: (1) What are the changes in skill and knowledge concerning additive manufacturing experienced by undergraduate students? (2) What is the effect of this course on attitudes towards engineering and self-efficacy in engineering for enrolled undergraduate students? The sample consists of four years of data from the undergraduate students enrolled in the course at all three universities (combined N = 196). Our method for data collection was matched-pair surveys that contained both (i) an assessment for content knowledge and (ii) an attitudinal assessment previously validated in published research for data collection about attitudes towards engineering. Matched-pair surveys means that we collected data from Student X at Time 1 (before being taught) and then again from at Time 2 (after being taught) and are able to directly compare any change in content knowledge or attitude within the same person. We also collected demographic information to be able to see whether changes in, for example, women differed from those in men. All undergraduates experienced statistically significant increases in content knowledge and additive manufacturing skills. In an intriguing finding, female students outperformed male students, which fits with the research that indicates that engineering courses which emphasize pragmatic and real-world applications, as well as those that use group work, will disproportionately help underserved engineering populations like women and people of color succeed. Fitting with the above finding, undergraduates noted that they perceived that they had increased in teamwork, communication, and computer programming skills. These gains were particularly high in female students and students of color. 

Stimulated Raman projection tomography is a label-free volumetric chemical imaging technology allowing three-dimensional (3D) reconstruction of chemical distribution in a biological sample from the angle-dependent stimulated Raman scattering projection images. However, the projection image acquisition process requires rotating the sample contained in a capillary glass held by a complicated sample rotation stage, limiting the volumetric imaging speed, and inhibiting the study of living samples. Here, we report a tilt-angle stimulated Raman projection tomography (TSPRT) system which acquires angle-dependent projection images by utilizing tilt-angle beams to image the sample from different azimuth angles sequentially. The TSRPT system, which is free of sample rotation, enables rapid scanning of different views by a tailor-designed four-galvo-mirror scanning system. We present the design of the optical system, the theory, and calibration procedure for chemical tomographic reconstruction. 3D vibrational images of polystyrene beads and C. elegans are demonstrated in the C-H vibrational region.