Assessing Perceptions of Group Work Using Team-Based Learning

Group work is frequently incorporated into courses; however, student perceptions of their experiences and the benefits of group work might differ based on the structure of course. In this study, we examined student perceptions of group work in a team-based learning (TBL) course. Undergraduate students completed pre- and post-surveys on their team work experiences over a semester. Students had lower agreement with the statement “working in groups usually ends up with one person doing all of the work” and higher agreement with “working in a group makes me feel as though I am part of a learning community” at post-test. On an open-ended question comparing their group work experiences in the TBL setting to previous group work experiences, students had positive reactions, indicating that their teammates were prepared, accountable, and worked well together. While our small sample size leaves room to examine individuals’ different experiences with group work more closely, as a whole, TBL appears to provide a structure for group work that ensures individual accountability prior to team work and to provide a space for students to practice transferable skills valued by employers

Paleo- stress and strain rates in an intra-arc strike-slip fault, Sierra Nevada, California

Structures and microstructures of the Proto-Kern Canyon fault (PKCF), a 130-km-long dextral strike-slip shear zone of the southern Sierra Nevada batholith, provide constraints on displacement, flow stress, and strain rate during arc formation. Shear strain analyses of S-C mylonites indicate ~5 km of ductile dextral slip along the PKCF. But field mapping and measurements of individual plutons and metamorphic pendants show these bodies have much more elongated aspect ratios, of up to 1:17, within the shear zone than outside of it. This suggests significantly higher strain and dextral slip of up to 15 km along the highest-strain zone of the PKCF. Petrographic observations of high-strain igneous rocks near Lake Isabella indicate that deformation started at temperatures of 400-450° C and continued through cooling to ~300° C. Based on ^(40)Ar/^(39)Ar dating of hornblende, mica, and K-feldspar, early cooling (~20° C/m.y.) from 88-70 Ma was followed by very slow cooling (~1° C/m.y.). These data, combined with cross-cutting relationships, suggest that dextral ductile shear was active from 90-86 Ma. Grain sizes of dynamically recrystallized pure quartz mylonites in this part of the shear zone were used to estimate flow stresses of 20-40 MPa. Applying mylonitization temperature estimates of 400-350° C and lithostatic pressures of 350- 400 MPa (from Al-in-hbl barometry) yields paleo-strain rates along the PKCF of 10^(-13)-10^(-15) /s. Additional quartzite piezometry, as well as calcite piezometry on marble mylonites, should provide further constraints on stress and strain rates along the length and depth exposures of this intrabatholithic shear zone

A new metal transfer process for van der Waals contacts to vertical Schottky-junction transition metal dichalcogenide photovoltaics

Two-dimensional transition metal dichalcogenides are promising candidates for ultrathin optoelectronic devices due to their high absorption coefficients and intrinsically passivated surfaces. To maintain these near-perfect surfaces, recent research has focused on fabricating contacts that limit Fermi-level pinning at the metal-semiconductor interface. Here, we develop a new, simple procedure for transferring metal contacts that does not require aligned lithography. Using this technique, we fabricate vertical Schottky-junction WS₂ solar cells, with Ag and Au as asymmetric work function contacts. Under laser illumination, we observe rectifying behavior and open-circuit voltage above 500 mV in devices with transferred contacts, in contrast to resistive behavior and open-circuit voltage below 15 mV in devices with evaporated contacts. One-sun measurements and device simulation results indicate that this metal transfer process could enable high specific power vertical Schottky-junction transition metal dichalcogenide photovoltaics, and we anticipate that this technique will lead to advances for two-dimensional devices more broadly

Cellular and Molecular Networking Within the Ecosystem of Cancer Cell Communication via Tunneling Nanotubes

Intercellular communication is vital to the ecosystem of cancer cell organization and invasion. Identification of key cellular cargo and their varied modes of transport are important considerations in understanding the basic mechanisms of cancer cell growth. Gap junctions, exosomes, and apoptotic bodies play key roles as physical modalities in mediating intercellular transport. Tunneling nanotubes (TNTs)—narrow actin-based cytoplasmic extensions—are unique structures that facilitate direct, long distance cell-to-cell transport of cargo, including microRNAs, mitochondria, and a variety of other sub cellular components. The transport of cargo via TNTs occurs between malignant and stromal cells and can lead to changes in gene regulation that propagate the cancer phenotype. More notably, the transfer of these varied molecules almost invariably plays a critical role in the communication between cancer cells themselves in an effort to resist death by chemotherapy and promote the growth and metastases of the primary oncogenic cell. The more traditional definition of “Systems Biology” is the computational and mathematical modeling of complex biological systems. The concept, however, is now used more widely in biology for a variety of contexts, including interdisciplinary fields of study that focus on complex interactions within biological systems and how these interactions give rise to the function and behavior of such systems. In fact, it is imperative to understand and reconstruct components in their native context rather than examining them separately. The long-term objective of evaluating cancer ecosystems in their proper context is to better diagnose, classify, and more accurately predict the outcome of cancer treatment. Communication is essential for the advancement and evolution of the tumor ecosystem. This interplay results in cancer progression. As key mediators of intercellular communication within the tumor ecosystem, TNTs are the central topic of this article

Toward a terahertz-driven electron gun

Femtosecond electron bunches with keV energies and eV energy spread are needed by condensed matter physicists to resolve state transitions in carbon nanotubes, molecular structures, organic salts, and charge density wave materials. These semirelativistic electron sources are not only of interest for ultrafast electron diffraction, but also for electron energy-loss spectroscopy and as a seed for x-ray FELs. Thus far, the output energy spread (hence pulse duration) of ultrafast electron guns has been limited by the achievable electric field at the surface of the emitter, which is 10 MV/m for DC guns and 200 MV/m for RF guns. A single-cycle THz electron gun provides a unique opportunity to not only achieve GV/m surface electric fields but also with relatively low THz pulse energies, since a single-cycle transform-limited waveform is the most efficient way to achieve intense electric fields. Here, electron bunches of 50 fC from a flat copper photocathode are accelerated from rest to tens of eV by a microjoule THz pulse with peak electric field of 72 MV/m at 1 kHz repetition rate. We show that scaling to the readily-available GV/m THz field regime would translate to monoenergetic electron beams of ~100 keV.Comment: 16 pages, 4 figure

Demographics and Medication Use of Patients with Late-Onset Alzheimer's Disease in Hong Kong

BACKGROUND: Alzheimer's disease (AD) is the most common cause of dementia in the elderly population. However, epidemiological studies on the demographics of AD in Hong Kong population are lacking. OBJECTIVE: We investigated the demographics, comorbidities, mortality rates, and medication use of patients with AD in Hong Kong to understand how the disease has been managed locally. METHODS: This was a collaborative study of The Hong Kong University of Science and Technology and the Hospital Authority Data Collaboration Lab. We analyzed the demographic data, clinical records, diagnoses, and medication records of patients with AD under the care of the Hospital Authority between January 1, 2007 and December 31, 2017. RESULTS: We identified 23,467 patients diagnosed with AD. The median age at diagnosis was 84 years old, and 71% of patients were female. The most common comorbidity was hypertension (52.6%). 39.9% of patients received medications for dementia; of those, 68.4% had taken those medications for >  1 year. Compared to nonusers, long-term AD medication users had a significantly younger age of AD onset and were taking more lipid-regulating medication, diabetes medication, or antidepressants. Surprisingly, the use of antipsychotics in patients with AD was quite common; 50.7% of patients had received any type of antipsychotic during disease progression. CONCLUSION: This study provides detailed information on the demographics and medication use of patients with AD in Hong Kong. The data from this AD cohort will aid our future research aiming to identify potential AD risk factors and associations between AD and other diseases