Bacteriorhodopsin folds through a poorly organized transition state.

The folding mechanisms of helical membrane proteins remain largely uncharted. Here we characterize the kinetics of bacteriorhodopsin folding and employ φ-value analysis to explore the folding transition state. First, we developed and confirmed a kinetic model that allowed us to assess the rate of folding from SDS-denatured bacteriorhodopsin (bRU) and provides accurate thermodynamic information even under influence of retinal hydrolysis. Next, we obtained reliable φ-values for 16 mutants of bacteriorhodopsin with good coverage across the protein. Every φ-value was less than 0.4, indicating the transition state is not uniquely structured. We suggest that the transition state is a loosely organized ensemble of conformations

Five cent candy bars, the how and the why of their purchase

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Business and Engineering Administration, 1940.MIT copy bound with: Preliminary study on the design of electrolytic plant in Colombia for caustic, chlorine and bleach / Agustín Murillo Fernández. 1940.Includes bibliographical references (leaf 38).by Peter Graham Park, Nicholas Williamson.B.S

Statistical Mechanics of DNA-Mediated Colloidal Aggregation

We present a statistical mechanical model of aggregation in colloidal systems with DNA mediated interactions. We obtain a general result for the two-particle binding energy in terms of the hybridization free energy $\Delta G$ of DNA and two model dependent properties: the average number of available DNA bridges \left and the effective DNA conccentration $c_{eff}$. We calculate these parameters for a particular DNA bridging scheme. The fraction of all the $n$-mers, including the infinite aggregate, are shown to be universal functions of a single parameter directly related to the two-particle binding energy. We explicitly take into account the partial ergodicity of the problem resulting from the slow DNA binding-unbinding dynamics, and introduce the concept of angular localization of DNA linkers. In this way, we obtain a direct link between DNA thermodynamics and the global aggregation and melting properties in DNA-colloidal systems. The results of the theory are shown to be in quantitative agreement with two recent experiments with particles of micron and nanometer size. PACS numbers: 81.16.Dn, 82.20.Db, 68.65.-k, 87.14.GgComment: 12 pages, 6 figures, v2: added reference, expanded conclusion, added journal re

High Energy Electron Confinement in a Magnetic Cusp Configuration

We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when beta (plasma pressure/magnetic field pressure) is order of unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high beta a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. The current experiment validates this theoretical conjecture for the first time and represents critical progress toward the Polywell fusion concept which combines a high beta cusp configuration with an electrostatic fusion for a compact, economical, power-producing nuclear fusion reactor.Comment: 12 pages, figures included. 5 movies in Ancillary file

ICU Equipment Tower

The ICU ventilator equipment trolleys, referred to as ICU towers, are essentially an ICU unit on wheels. They bring together vital life support and patient monitoring equipment together as a package on a mobile trolley. This includes a ventilator and ancillary equipment, IV lines, pumps and syringe drivers, patient monitoring equipment, oxygen gas cylinders, and power and gas line management. A key feature of the ICU Tower is that it enables life support equipment and patient monitoring to remain connected to the patient during transport - the transition from the ward to other specialist units within the hospital. By enabling life support and patient monitoring equipment to remain connected to the patient, it mitigates the risk of errors with connecting patient lines and infection control and offers a more efficient workflow for clinicians

Attitudes Toward Motherhood Among Sexual Minority Women in the United States

In this article, we use data from the National Survey of Fertility Barriers—a national, population-based telephone survey—to examine how sexual minority women construct and value motherhood. We analyze the small (N = 43) random sample of self-identified sexual minority women using “survey-driven narrative construction,” which entails converting the structured answers and open-ended responses for each respondent into narratives and identifying themes. We focused on both sexual minority women’s desires and intentions to parent and on the importance they place on motherhood. We found that there is considerable variation in this population. Many sexual minority women distinguish between having and raising children, suggesting a broad notion of motherhood. We also found that sexual minority women without children are not all voluntarily childfree. Our results suggest that survey research on fertility would improve by explicitly addressing sexuality

Enhancing Building Fire Safety Performance by Reducing Miscommunication and Misconceptions

Building fire safety is driven by regulations and technical building codes, at least as a minimum requirement. As fire protection engineers (FPEs) design fire safety measures based on requirements in the regulations, they are often viewed as the primary agents in ensuring the fire safety of buildings. However, their mission often starts with given building design features, such as interior spatial layout, exterior shape, site plan, and so forth, which are mostly determined by architects. The only exception is where the FPE is invited to assist in the project planning, feasibility and early concept design stages of a project. Regardless, architects also can influence building fire safety performance, whether or not they explicitly acknowledge or understand this. Although architects design buildings within the boundaries of the regulatory requirements, the architect’s focus is often related to the visual and spatial aesthetics of buildings linked to building form and functionality, which are not subject to the regulations. These aesthetics can sometimes compete with fire safety objectives. As such, buildings can be unsafe in certain situations due to unintended effects of building design features on actual fire safety performance. This research describes the relationship between architecturally conceived building design features, design expectations for fire safety systems, and the actual or conceivable fire safety performance of the building. Steps are proposed that FPEs can take to identify and address potentially competing objectives and deliver increased fire safety performance