Teaching an Engineering Systems Doctoral Seminar: Concepts and Structure

This paper describes the current state of the evolving engineering systems doctoral seminar in the Engineering Systems Division (ESD) at MIT. This subject is required for all first year engineering systems doctoral students. It is intended to bring them into the culture of ESD, and to establish a common base on which subsequent subjects can build. It is the first of three required subjects that make up the core of the ESD doctoral program. The seminar is intended to provide students with the foundations and context of engineering systems, largely focused on providing an appreciation for the many facets of socio-technical complexity. We discuss the seminar’s pedagogy, learning objectives, assignments and readings, and provide insights gained from teaching the course

Conformational and aggregation properties of a pegylated alanine-rich polypeptide

The conformational and aggregation behavior of PEG conjugates of an alanine-rich polypeptide (PEG-c17H6) were investigated and compared to that of the polypeptide equipped with a deca-histidine tag (17H6). These polypeptides serve as simple and stimuli-responsive models for the aggregation behavior of helix-rich proteins, as our previous studies have shown that the helical 17H6 self-associates at acidic pH and converts to β-sheet structures at elevated temperature under acidic conditions. In the work here, we show that PEG-c17H6 also adopts a helical structure at ambient/subambient temperatures, at both neutral and acidic pH. The thermal denaturation behavior of 17H6 and PEG-c17H6 is similar at neutral pH, where the alanine-rich domain has no self-association tendency. At acidic pH and elevated temperature, however, PEGylation slows β-sheet formation of c17H6, and reduces the apparent cooperativity of thermally induced unfolding. Transmission electron microscopy of PEG-c17H6 conjugates incubated at elevated temperatures showed fibrils with widths of ∼20-30 nm, wider than those observed for fibrils of 17H6. These results suggest that PEGylation reduces β-sheet aggregation in these polypeptides by interfering, only after unfolding of the native helical structure, with interprotein conformational changes needed to form β-sheet aggregates.National Center for Research Resources (NCRR); Center for Neutron Science (U.S. Dept. of Commerce

29 years of vegetation community change across environmental gradients in a Mojave Desert mountain range

There is a great deal of uncertainty as to how biological communities respond to changes in land use and climate change, a situation particularly relevant in protected areas such as national parks that were designated to conserve specific biological features. Utilizing extant vegetation data sets with repeatable methodology can provide opportunities for insight into previous vegetation change and provide base line data for long-term monitoring projects useful for modeling vegetation community trajectories. We have relocated and resurveyed 106 sites from a vegetation community study initiated in 1979 in the Newberry Mountains, southern Nevada, within Lake Mead National Recreation Area managed by the National Park Service. The original methods were repeated and used to establish permanent long-term monitoring plots. All perennial plant species were measured for density, frequency and cover within each plot. In comparing 1979 and 2008 data sets we wanted to know if changes have occurred in the vegetation community and if the degree of change differs along environmental gradients and among individual species

DNA bending by a phantom protein

Background: Despite its stiffness, duplex DNA is extensively bent and folded during packiging and gene expression in biological systems. Modulation of the electrostatic repulsion between phosphate in the DNA backbone may be important in the bending of DNA by proteins. Here we analyze the shape of DNA molecules that have been modified chemically to mimic the electrostatic consequences of a bund proteinResults: We have simulated salt bridges between DNA phosphates and cationic amino acid sidechains of a phantom protein by tethering ammonium cations to one face of the DNA helix. Thethered ammonium cations, but not neutral acetylated controls, induced DNA to bend toward its neutralized surface.Conclusions: The shape of DNA molecules bearing a laterally-asymmetric distribution of tethered cations agrees qualitatively with theoretical predictions and with results previously obtained using neutral phosphate analogs. These data suggest principles that might be applied to the design of artificial DNA-bending proteins

Breaking the Grenville–Sveconorwegian link in Rodinia reconstructions

The Grenville, Sveconorwegian, and Sunsas orogens are typically inferred to reflect collision between Laurentia, Baltica, and Amazonia at ca. 1.0 Ga, forming a central portion of the Rodinia supercontinent. This triple‐junction configuration is often nearly identical in otherwise diverse Rodinia reconstructions. However, available geological data suggest that although the Grenville and Sveconorwegian provinces shared a similar tectonic evolution from pre‐1.8 to ca. 1.5 Ga, they record distinctly different tectonic histories leading up to, during, and possibly following Grenville–Sveconorwegian orogenesis. Moreover, palaeomagnetic data suggest the two continents were separated at peak orogenesis, further invalidating any direct correlation. A number of possible interpretations are permissible with available geological and palaeomagnetic data, of which a “classic” triple‐junction configuration appears least likely. In contrast to the commonly inferred intertwined Proterozoic evolution of Baltica and Laurentia, the possibility remains that they were unrelated for a billion years between 1.5 and 0.45 Ga

A radiologic analysis: Relationships of the thoracic spine to aid palpation of the thoracic transverse processes

Introduction: In the field of osteopathic manipulative medicine, palpation is an important skill used by physicians to localize structures to diagnose and treat patients with somatic dysfunction throughout the musculoskeletal system. Specifically, in the thoracic spine, physicians can use the more superficial spinous process of each vertebra to assist in locating the deeper, more challenging to palpate, transverse process of the vertebra. Historically, the “rule of threes”, proposed by Mitchell et al in 1979, describing the relationships between spinous processes and transverse processes of the thoracic spine has been taught in osteopathic medical schools. However, another model was more recently proposed by Geelhoed et al in 2006. To our knowledge, these models have never been analyzed radiologically using computed tomography in patients. Objectives: To evaluate the accuracy of several proposed models, including the rule of 3’s and Geelhoed’s rule, which aid in palpation of the transverse processes of the thoracic spine based on their relation to the spinous processes. Furthermore, the study aims to analyze the intervertebral and intravertebral relationships of the transverse processes and spinous processes of the thoracic spine. Methods: This was an observational study with retrospective analysis of high-resolution computed tomography of the chest in the prone position. Four measurements were taken per thoracic vertebra in the coronal plane during inspiration. Based on the measurements, it was determined whether each individual vertebra followed the models or not. The measurements were further analyzed to define additional intervertebral and intravertebral relationships between the transverse and spinous processes of the thoracic spine. Results: We predict that the high-resolution computed tomography will reveal the intervertebral and intravertebral relationships as well as the aid in defining the accuracy of the relationships between the spinous processes proposed in osteopathic manipulative models. Conclusion: We conclude that retrospective radiological studies using state of the art images has the ability to confirm and/or expand our ability to utilize osteopathic principles and models in diagnosing and treating patients

Measurements of Mesospheric Sodium Abundance above the Hawaiian Islands

Laser guide stars have increased the utility of adaptive optics systems by expanding the number of observable objects. The most common type of laser excites sodium in the mesosphere, and mesospheric sodium density is key to the performance of the laser. While a variety of observatories have conducted studies of the mesospheric sodium density, there are no published studies from Hawaii, which is home to some of the largest telescopes in the world. This paper presents mesospheric sodium densities measured by the University of Illinois lidar for 165 hr spanning 25 nights over 3 years. The mean sodium column density is 4.3 x 109 ± 0.2 x 109 cm-2, with a seasonal peak in the winter, as found at many other sites. The variations in a given night can be as high as the seasonal variation. We predict the average photon returns for the 15 W Keck II laser and a proposed 50 W laser at the Advanced Electro-Optical System 3.6 m telescope for the observed sodium abundances

Histotripsy Effects on the Bladder Trigone: Functional and Histologic Consequences in the Canine Model

Background: Histotripsy is an extracorporeal therapeutic ultrasound (US) technology, where high-amplitude acoustic energy is applied to targeted tissue. Previous research has demonstrated the feasibility, safety, and effectiveness of histotripsy tissue homogenization and debulking of the prostate in the canine model. Before translating this technology for human use, it is prudent to examine the susceptibility of critical periprostatic structures to cavitation injury in the event of histotripsy mistargeting. In this study, we sought to characterize the tissue effects and biologic response of directly treating the bladder trigone with histotripsy. Materials and Methods: In eight anesthetized canines, 750,000 histotripsy pulses were applied uniformly across a 2?1.5-cm area encompassing the bladder trigone and ureteral orifices. Prostate and bladder trigone were harvested immediately after treatment (2 subjects) or at 14 days (6 subjects). Flexible cystourethroscopy, US imaging, and creatinine levels were obtained at intervals until harvest, 14 days after treatment. In one control subject, harvested at 2 days, the same treatment algorithm was applied to the prostate. Results: Transrectal US imaging revealed a cavitation bubble cloud on the surface of the bladder trigone and progressive development of tissue edema during treatment. Flexible cystourethroscopy immediately after treatment confirmed edema and erythema of the trigone. In the six subjects survived 2 weeks after treatment, one incidence of transient, self-limited ureteral obstruction was noted based on hydronephrosis and creatinine levels. At harvest, ureteral orifices were confirmed patent by passage of a guide wire. Histologic evaluation revealed hemorrhage acutely with mild localized fibrosis at 14 days. Conclusions: In this study, designed along the lines of a worst-case, destructive testing scenario, direct targeting of the bladder trigone with supratherapeutic histotripsy failed to induce significant tissue damage or clinical complication. These results are reassuring and will guide treatment strategy in upcoming human clinical trials of histotripsy treatment for benign prostatic hyperplasia.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140374/1/end.2013.0234.pd