A wind-tunnel and analytical study of the conversion from wing lift to rotor lift on a composite-lift V/TOL aircraft

Wind tunnel and analytical study of conversion from wing lift to rotor lift on composite lift VTOL aircraf

From “Spring Break” to “Reading Days”: Contingency, Relations of Power, and Positionalities in Experiences of Overwork During Academic Breaks

In this article, the authors analyze the impacts of their university eliminating Spring Break and replacing it with intermittent Reading Days during the Covid-19 pandemic. With particular attention to contingency, relations of power, and positionalities, they offer narratives of their lived experiences with Reading Days as a graduate student (Author 1) and as a pre-tenure faculty member (Author 2). They also offer analysis of the public conversations surrounding the institutional decision. The article addresses how the particularities of the narratives are symptomatic of a culture of overwork that predates and continues beyond the moment in time and place of the context described. Authors offer takeaways and calls to action that invite readers to continue examining and intervening in larger, persistent structures of inequity—particularly as they come to bear on academic breaks

Vibration effects on heat transfer in cryogenic systems Quarterly progress report, Jul. 1 - Sep. 30, 1967

Water test apparatus used to determine vibration effects on heat transfer in cryogenic system

Practical and effective higher-order optimizations

Inlining is an optimization that replaces a call to a function with that function’s body. This optimization not only reduces the overhead of a function call, but can expose additional optimization oppor-tunities to the compiler, such as removing redundant operations or unused conditional branches. Another optimization, copy propaga-tion, replaces a redundant copy of a still-live variable with the origi-nal. Copy propagation can reduce the total number of live variables, reducing register pressure and memory usage, and possibly elimi-nating redundant memory-to-memory copies. In practice, both of these optimizations are implemented in nearly every modern com-piler. These two optimizations are practical to implement and effec-tive in first-order languages, but in languages with lexically-scoped first-class functions (aka, closures), these optimizations are no

Wind tunnel investigation of static longitudinal and lateral characteristics of a full scale mockup of a light single engine high wing airplane

The model was a full-scale mockup of a light single-engine high-wing monoplane. Tests were made over an angle-of-attack range of -4 deg to 24 deg and over a sideslip range of plus or minus 8 deg at thrust coefficients of 0, 0.14, and 0.30. Control effectiveness and hinge moments were taken on the aileron, elevator, and rudder for a full range of deflections. Downwash measurements at the tail were obtained for the range of thrust coefficient and flap deflection

A model for de novo synthesis and assembly of tight intercellular junctions. Ultrastructural correlates and experimental verification of the model revealed by freeze-fracture

The structure and function of intercellular tight (occluding) junctions, which constitute the anatomical basis for highly regulated interfaces between tissue compartments such as the blood-testis and blood-brain barriers, are well known. Details of the synthesis and assembly of tight junctions, however, have been difficult to determine primarily because no model for study of these processes has been recognized. Primary cultures of brain capillary endothelial cells are proposed as a model in which events of the synthesis and assembly of tight junctions can be examined by monitoring morphological features of each step in freeze-fracture replicas of the endothelial cell plasma membrane. Examination of replicas of non-confluent monolayers of endothelial cells reveals the following intramembrane structures proposed as `markers' for the sequential events of synthesis and assembly of zonulae occludentes: (1) development of surface contours consisting of elongate terraces and furrows (valleys) orientated parallel to the axis of cytoplasmic extensions of spreading endothelial cells, (2) appearance of small circular PF face depressions (or volcano-like protrusions on the EF face) that represent cytoplasmic vesicle-plasma membrane fusion sites, which are positioned in linear arrays along the contour furrows, (3) appearance of 13-15 nm intramembrane particles at the perimeter of the vesicle fusion sites, and (4) alignment of these intramembrane particles into the long, parallel, anastomosed strands characteristic of mature tight junctions. These structural features of brain endothelial cells in monolayer culture constitute the morphological expression of: (1) reshaping the cell surface to align future junction-containing regions with those of adjacent cells, (2) delivery and insertion of newly synthesized junctional intramembrane particles into regions of the plasma membrane where tight junctions will form, and (3) aggregation and alignment of tight junction intramembrane particles into the complex interconnected strands of mature zonulae occludentes. The distribution of filipin-sterol complex-free regions on the PF intramembrane fracture face of junction-forming endothelial plasmalemmae corresponds precisely to the furrows, aligned vesicle fusion sites and anastomosed strands of tight junctional elements.To test the functional significance of these morphological features of junction-forming cells and to validate the interpretation that they are reliable indicators of the stages of tight junction genesis, primary cultures of bovine brain capillary endothelium were treated with 25 [mu]g/ml of Cytochalasin-D or 0.25 mg/ml of n-ethylmaleimide (Sigma Chemical Co.) in order to prevent cytoskeletal mediation of surface contouring (step 1) or to inhibit vesicle fusion with the plasmalemma (step 2) and thereby prevent junction formation as a consequence of failure of the vesicle fusions to insert tight junctional intramembrane particles into the plasma membrane. Examination of platinum replicas of freeze-fractured control and treated endothelial monolayer cultures confirmed the absence of surface contours in Cytochalasin-D-treated cells, which exhibited no zonulae occludentes, and also clearly showed that n-ethylmaleimide-treated cells, which lacked tight junctions, did not have the rich endowment of vesicle fusion sites (and IMPs) which were conspicuous in control cells. Demonstration of the failure of MDCK cells to form tight junctions when cultured in the presence of 5-10 [mu]g/ml of cycloheximide (Griepp et al., 1983) lends further support for the schemata proposed above.Advantages of this model include: (1) all stages of de novo tight junction formation are present in each monolayer culture, and (2) cultures possess vast areas of tight junction-containing membrane which are easily sampled by freeze-fracture. This model will provide the basis for future attempts to identify the signals that regulate tight junction formation, and will facilitate studies to characterize the protein(s) of the endothelial tight junctions, the messages (m-RNA) that code for them, and ultimately, the genes bearing their blueprint.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25900/1/0000463.pd

Isolated rat brain capillarie spossess intact, structurally complex, interendothelial tight junctions; freeze-fracture verification of tight junction integrity

Populations of isolated brai capillaries have been proposed as useful models for in vitro studies of the blood-brain barrier. Preliminary investigations of barrier properties using such preparations of brain microvessels have suggested that the tight interendothelial junctions (zonulae occludentes) are intact and retain the impermeability to the protein tracer horseradish peroxidase, exhibited by them in vivo. The endothelial junctions of isolated capillaries are therefore assumed to be functionally `tight' in vitro. In order to determine the precise structural organization of these occluding junctions, including an estimate of their tightness (complexity), and to demonstrate a method for simple but precise assessment of junctional integrity, pellets of isolated rat brain capillaries were freeze-fractured and then replicated with platinum and carbon. The freeze-fracture images of interendothelial zonulae occludentes revealed complex arrays of intramembrane ridges and grooves characteristics of tight junctions. Longitudinal fractures of the cellular lining of capillaries exposed vast expanses of interendothelial plasma membrane interfaces and the junctional complexes situated between the cells. From such arrays, the elaborate and complex architecture of the zonulae occludentes could bre readily appreciated. Situated on the PF fracture faces are 6-8 parallel ridges which display a high degree of anastomosing between adjacent strands. The EF facture face contains grooves complementary to the PF face ridges. The zonulae occludentes of these capillary endothelial cells are similar in complexity to those reported in the literature for reptilian brain capillaries and therefore can be presumed `very tight'. This study demonstrate that freeze-fracture of pellets of brain capillaries alleviates problems inherent in whole tissue preparations and, in addition, demonstrates the usefulness of freeze-fracture as a tool to monitor junction structure during in vitro investigation of the blood-brain barrier.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24599/1/0000007.pd

Detection of Asynchronous Message Passing Errors Using Static Analysis

Concurrent programming is hard and prone to subtle errors. In this paper we present a static analysis that is able to detect some commonly occurring kinds of message passing errors in languages with dynamic process creation and communication based on asynchronous message passing. Our analysis is completely automatic, fast, and strikes a proper balance between soundness and completeness: it is effective in detecting errors and avoids false alarms by computing a close approximation of the interprocess communication topology of programs. We have integrated our analysis in dialyzer, a widely used tool for detecting software defects in Erlang programs, and demonstrate its effectiveness on libraries and applications of considerable size. Despite the fact that these applications have been developed over a long period of time and are reasonably well-tested, our analysis has managed to detect a significant number of previously unknown message passing errors in their code

Compilation of extended recursion in call-by-value functional languages

This paper formalizes and proves correct a compilation scheme for mutually-recursive definitions in call-by-value functional languages. This scheme supports a wider range of recursive definitions than previous methods. We formalize our technique as a translation scheme to a lambda-calculus featuring in-place update of memory blocks, and prove the translation to be correct.Comment: 62 pages, uses pi

Motor crosslinking augments elasticity in active nematics

In active materials, uncoordinated internal stresses lead to emergent long-range flows. An understanding of how the behavior of active materials depends on mesoscopic (hydrodynamic) parameters is developing, but there remains a gap in knowledge concerning how hydrodynamic parameters depend on the properties of microscopic elements. In this work, we combine experiments and multiscale modeling to relate the structure and dynamics of active nematics composed of biopolymer filaments and molecular motors to their microscopic properties, in particular motor processivity, speed, and valency. We show that crosslinking of filaments by both motors and passive crosslinkers not only augments the contributions to nematic elasticity from excluded volume effects but dominates them. By altering motor kinetics we show that a competition between motor speed and crosslinking results in a nonmonotonic dependence of nematic flow on motor speed. By modulating passive filament crosslinking we show that energy transfer into nematic flow is in large part dictated by crosslinking. Thus motor proteins both generate activity and contribute to nematic elasticity. Our results provide new insights for rationally engineering active materials