Essential or redundant? Disentangling the (GR)ESAG families of Trypanosoma brucei

The protozoan parasite Trypanosoma brucei escapes its mammalian host’s immune response by switching expression of its major surface antigen, variant surface glycoprotein (VSG), which forms a protective coat around the cell. The actively expressed VSG is transcribed from one of 14 bloodstream expression sites (BESs), which also encode variable repertoires of expression site associated genes (ESAGs), most of which localise to the parasite surface. These genes form distinct families, are co-transcribed with VSG, and the repertoire expressed changes upon in situ switch. Specific ESAGs are known to protect the parasite from human serum lytic effects, modulate the host’s innate immune response, mediate uptake of essential nutrients, and may adapt the parasite to the serum of different mammalian hosts. In addition to BES-linked ESAGs, these families also encompass non-BES encoded genes related to ESAGs (GRESAGs), some of which, unlike the ESAGs, are expressed in both mammalian and insect lifecycle stages. To investigate the functional relationship between BES and non-BES (GR)ESAGs, I established a system to specifically ablate only BES-derived transcript or multiple (GR)ESAG family members. The former was carried out by tagging BES-linked ESAGs with GFP, and then targeting the GFP ORF by RNAi. The latter involved pan-family RNAi constructs, designed using regions with high identity across individual (GR)ESAG families. Pan-family, but not BES-specific, knockdown induced growth defects, showing that transcript from the active BES itself is not essential for parasite survival in vitro. To investigate this further, a strategy based on Cre recombinase genome engineering was developed to specifically reduce the ESAG repertoire contained within the active BES. Stable cell lines ready for recombination were obtained, and will be used for analysis of modified BESs. Together, the results achieved show that (GR)ESAG families, as opposed to the actively-expressed ESAG copy, are important for parasite survival in vitro, and there is redundancy between BES-linked and non-BES transcripts. Therefore, the often-overlooked GRESAGs may play more significant roles than originally thought

UAS in the NAS Air Traffic Controller Acceptability Study-1: The Effects of Horizontal Miss Distances on Simulated UAS and Manned Aircraft Encounters

This study examined air traffic controller acceptability ratings based on the effects of differing horizontal miss distances (HMDs) for encounters between UAS and manned aircraft. In a simulation of the Dallas/Fort Worth (DFW) East-side airspace, the CAS-1 experiment at NASA Langley Research Center enlisted fourteen recently retired DFW air traffic controllers to rate well-clear volumes based on differing HMDs that ranged from 0.5 NM to 3.0 NM. The controllers were tasked with rating these HMDs from "too small" to "too excessive" on a defined, 1-5, scale and whether these distances caused any disruptions to the controller and/or to the surrounding traffic flow. Results of the study indicated a clear favoring towards a particular HMD range. Controller workload was also measured. Data from this experiment and subsequent experiments will play a crucial role in the FAA's establishment of rules, regulations, and procedures to safely and efficiently integrate UAS into the NAS

UAS Air Traffic Controller Acceptability Study-2: Effects of Communications Delays and Winds in Simulation

This study evaluated the effects of Communications Delays and Winds on Air Traffic Controller ratings of acceptability of horizontal miss distances (HMDs) for encounters between UAS and manned aircraft in a simulation of the Dallas-Ft. Worth East-side airspace. Fourteen encounters per hour were staged in the presence of moderate background traffic. Seven recently retired controllers with experience at DFW served as subjects. Guidance provided to the UAS pilots for maintaining a given HMD was provided by information from self-separation algorithms displayed on the Multi-Aircraft Simulation System. Winds tested did not affect the acceptability ratings. Communications delays tested included 0, 400, 1200, and 1800 msec. For longer communications delays, there were changes in strategy and communications flow that were observed and reported by the controllers. The aim of this work is to provide useful information for guiding future rules and regulations applicable to flying UAS in the NAS

NASA Controller Acceptability Study 1(CAS-1) Experiment Description and Initial Observations

This paper describes the Controller Acceptability Study 1 (CAS-1) experiment that was conducted by NASA Langley Research Center personnel from January through March 2014 and presents partial CAS-1 results. CAS-1 employed 14 air traffic controller volunteers as research subjects to assess the viability of simulated future unmanned aircraft systems (UAS) operating alongside manned aircraft in moderate-density, moderate-complexity Class E airspace. These simulated UAS were equipped with a prototype pilot-in-the-loop (PITL) Detect and Avoid (DAA) system, specifically the Self-Separation (SS) function of such a system based on Stratway+ software to replace the see-and-avoid capabilities of manned aircraft pilots. A quantitative CAS-1 objective was to determine horizontal miss distance (HMD) values for SS encounters that were most acceptable to air traffic controllers, specifically HMD values that were assessed as neither unsafely small nor disruptively large. HMD values between 0.5 and 3.0 nautical miles (nmi) were assessed for a wide array of encounter geometries between UAS and manned aircraft. The paper includes brief introductory material about DAA systems and their SS functions, followed by descriptions of the CAS-1 simulation environment, prototype PITL SS capability, and experiment design, and concludes with presentation and discussion of partial CAS-1 data and results

UAS Air Traffic Controller Acceptability Study

This study evaluated the effects of communications delays and winds on air traffic controller ratings of acceptability of horizontal miss distances (HMDs) for encounters between Unmanned Aircraft Systems (UAS) and manned aircraft in a simulation of the Dallas-Ft. Worth (DFW) airspace. Fourteen encounters per hour were staged in the presence of moderate background traffic. Seven recently retired controllers with experience at DFW served as subjects. Guidance provided to the UAS pilots for maintaining a given HMD was provided by information from Detect and Avoid (DAA) self-separation algorithms (Stratway+) displayed on the Multi-Aircraft Control System. This guidance consisted of amber "bands" on the heading scale of the UAS navigation display indicating headings that would result in a loss of well clear between the UAS and nearby traffic. Winds tested were successfully handled by the DAA algorithms and did not affect the controller acceptability ratings of the HMDs. Voice communications delays for the UAS were also tested and included one-way delay times of 0, 400, 1200, and 1800 msec. For longer communications delays, there were changes in strategy and communications flow that were observed and reported by the controllers. The aim of this work is to provide useful information for guiding future rules and regulations applicable to flying UAS in the NAS. Information from this study will also be of value to the Radio Technical Commission for Aeronautics (RTCA) Special Committee 228 - Minimum Performance Standards for UAS

Architecture of a host–parasite interface: complex targeting mechanisms revealed through proteomics

Surface membrane organization and composition is key to cellular function, and membrane proteins serve many essential roles in endocytosis, secretion, and cell recognition. The surface of parasitic organisms, however, is a double-edged sword; this is the primary interface between parasites and their hosts, and those crucial cellular processes must be carried out while avoiding elimination by the host immune defenses. For extracellular African trypanosomes, the surface is partitioned such that all endo- and exocytosis is directed through a specific membrane region, the flagellar pocket, in which it is thought the majority of invariant surface proteins reside. However, very few of these proteins have been identified, severely limiting functional studies, and hampering the development of potential treatments. Here we used an integrated biochemical, proteomic and bioinformatic strategy to identify surface components of the human parasite Trypanosoma brucei. This surface proteome contains previously known flagellar pocket proteins as well as multiple novel components, and is significantly enriched in proteins that are essential for parasite survival. Molecules with receptor-like properties are almost exclusively parasite-specific, whereas transporter-like proteins are conserved in model organisms. Validation shows that the majority of surface proteome constituents are bona fide surface-associated proteins and, as expected, most present at the flagellar pocket. Moreover, the largest systematic analysis of trypanosome surface molecules to date provides evidence that the cell surface is compartmentalized into three distinct domains with free diffusion of molecules in each, but selective, asymmetric traffic between. This work provides a paradigm for the compartmentalization of a cell surface and a resource for its analysis

Unmanned Aircraft Systems Human-in-the-Loop Controller and Pilot Acceptability Study: Collision Avoidance, Self-Separation, and Alerting Times (CASSAT)

The Federal Aviation Administration (FAA) has been mandated by the Congressional funding bill of 2012 to open the National Airspace System (NAS) to Unmanned Aircraft Systems (UAS). With the growing use of unmanned systems, NASA has established a multi-center "UAS Integration in the NAS" Project, in collaboration with the FAA and industry, and is guiding its research efforts to look at and examine crucial safety concerns regarding the integration of UAS into the NAS. Key research efforts are addressing requirements for detect-and-avoid (DAA), self-separation (SS), and collision avoidance (CA) technologies. In one of a series of human-in-the-loop experiments, NASA Langley Research Center set up a study known as Collision Avoidance, Self-Separation, and Alerting Times (CASSAT). The first phase assessed active air traffic controller interactions with DAA systems and the second phase examined reactions to the DAA system and displays by UAS Pilots at a simulated ground control station (GCS). Analyses of the test results from Phase I and Phase II are presented in this paper. Results from the CASSAT study and previous human-in-the-loop experiments will play a crucial role in the FAA's establishment of rules, regulations, and procedures to safely, efficiently, and effectively integrate UAS into the NAS

The effects of early removal of indwelling urinary catheter after radical hysterectomy

Radical hysterectomy has long been a primary mode of therapy for selected gynecologic malignancies. The lower urinary tract is an area associated with complications following this procedure. Lack of satisfactory reflex micturition and urinary retention, diminished bladder sensation, infection, and fistula formation are common adverse sequelae. Prolonged indwelling catheterization is a cornerstone of postoperative management after radical hysterectomy. An alternative regimen consisting of early postoperative catheter removal, with a strict voiding schedule, and intermittent self-catheterization (ISC) for postvoid residuals (PVR) was prospectively investigated. Intermittent self-catheterization was initiated only if the PVR 12 hr after catheter removal was greater than 75 ml. Twenty-six patients who underwent radical hysterectomy were studied. Catheters were removed between the fifth and ninth postoperative day. Eighteen patients (69%) had PVRs less than 75 ml at 12 hr and were successfully managed with a strict voiding schedule only. Eight patients (31%) had 12-hr PVRs greater than 75 ml and were managed with a strict voiding schedule and ISC until the PVR was less than 75 ml for two consecutive voids. These patients were evaluated with fluorourodynamics and none had an abnormal study. Compared to 25 historical control patients, study group median indwelling catheter duration was less (6.0 days compared to 30.0 days) with no increase in postoperative complications. On the basis of these data, early removal of indwelling urinary catheters after radical hysterectomy appears to be an acceptable alternative to long-term catheterization.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29044/1/0000077.pd

Direct synthesis of multiplexed metal nanowire based devices using carbon nanotubes as vector templates

We present the synthesis of metal nanowires in a multiplexed device configuration using single‐walled carbon nanotubes (SWNTs) as nanoscale vector templates. The SWNT templates control the dimensionality of the wires, allowing precise control of their size, shape and orientation; moreover a solution processable approach enables their linear deposition between specific electrode pairs in electronic devices. Electrical characterizations demonstrate the successful fabrication of metal nanowire electronic devices, while multiscale characterization of the different fabrication steps reveals details of the structure and charge transfer between the material encapsulated and the carbon nanotube. Overall the strategy presented allows facile, low‐cost and direct synthesis of multiplexed metal nanowire devices for nanoelectronic applications