Sudden incapacitation: USAF experience, 1970-80

During the period 1970-80, there were reported 146 cases of in-flight sudden incapacitation in the USAF. Of these, 62 involved pilots, 14 were navigators, and 70 were student pilots. The etiologies of sudden incapacitation included illness without loss of consciousness, loss of consciousness, spatial disorientation, and improper M-1 maneuver. Each of these categories is analyzed with emphasis upon prevention, for example, not flying with symptomatic preexisting disease, continued emphasis upon spatial disorientation training, and correct performance of the M-1 maneuver. Based upon the data, conclusions and recommendations are suggested to minimize the risk of episodes of in-flight sudden incapacitation.     

Environment for rapidly creating interactive design tools

The Garnet toolkit was specifically designed to make highly interactive graphical programs easier to design and implement. Visual, interactive, user-interface design tools clearly fall into this category. At this point, we have used the Garnet toolkit to create three different interactive design tools: Gilt, a simple interface builder for laying out widgets; Lapidary, a sophisticated design tool for constructing application-specific graphics and custom widgets; and C32, a spreadsheet interface to constraints. The features of the Garnet toolkit that made these easier to create include use of a prototype-instance object system instead of the usual class-instance model, integration of constraints with the object system, graphics model that supports automatic graphical update and saving to disk of on-screen objects, separation of specifying the graphics of objects from their behavior, automatic layout of graphical objects in a variety of styles, and a widget set that supports such commonly used operations as selection, moving and growing objects, and displaying and setting their properties.     

Approximate regular expression pattern matching with concave gap penalties

Given a sequenceA of lengthM and a regular expressionR of lengthP, an approximate regular expression pattern-matching algorithm computes the score of the optimal alignment betweenA and one of the sequencesB exactly matched byR. An alignment between sequencesA=a₁a₂ ... a_M andB=b₁b₂... b_N is a list of ordered pairs, (i₁,j₁), (i₂j₂), ..., (i_t,j_tt) such that i_k < i_k+1 and j_k < j_k+1. In this case the alignmentaligns symbols a_ik and b_jk, and leaves blocks of unaligned symbols, orgaps, between them. A scoring schemeS associates costs for each aligned symbol pair and each gap. The alignment's score is the sum of the associated costs, and an optimal alignment is one of minimal score. There are a variety of schemes for scoring alignments. In a concave gap penalty scoring schemeS={, w}, a function (a, b) gives the score of each aligned pair of symbolsa andb, and aconcave function w(k) gives the score of a gap of lengthk. A function w is concave if and only if it has the property that, for allk > 1, w(k + 1) –w(k) w(k) –w(k –1). In this paper we present an O(MP(logM + log² P)) algorithm for approximate regular expression matching for an arbitrary and any concavew. This work was supported in part by the National Institute of Health under Grant RO1 LM04960.     

Dialectical hermeneutics: a theoretical framework for the implementation of information systems

Abstract. Despite the proliferation of information technology, the implementation of information systems remains problematic. Many systems fail to live up to expectations and some end up as disasters. Research on implementation has been conducted for the past two decades, but no theoretical framework for IS implementation has been widely accepted. This paper proposes dialectical hermeneutics as a theoretical framework for IS implementation research. Dialectical hermeneutics, as an integrative theoretical framework, combines both interpretive and critical elements, and addresses those social and organizational issues which are critical to the successful implementation of information systems. The case study research method was used to examine the implementation of systems in three organizations.     

Design ethnography in information systems

Until recently, most ethnographic research in information systems has been based on the traditional anthropological model of ethnography. In this traditional model of ethnography, one of the most important data‐gathering techniques is participant observation. The ethnographer observes and participates but does not actively seek to change the situation. In recent years, however, a new type of ethnographic research has emerged – one that can be called design ethnography. Design ethnography is where the researcher goes beyond observation and actively engages with people in the field. Our view is that design ethnography has much potential for research in information systems. It is a new form of engaged scholarship that bridges the gap between ethnographic research and design science research.     

A mathematical model for nanoparticle melting with size-dependent latent heat and melt temperature

In this paper, we study the melting of a spherical nanoparticle. The model differs from previous ones in that a number of features have been incorporated to match experimental observations. These include the size dependence of the latent heat and a cooling condition at the boundary (as opposed to the fixed temperature condition used in previous studies). Melt temperature variation and density change are also included. The density variation drives the flow of the outer fluid layer. The latent heat variation is modelled by a new relation, which matches experimental data better than previous models. A novel form of Stefan condition is used to determine the position of the melt front. This condition takes into account the latent heat variation, the energy required to create new surface and the kinetic energy of the displaced fluid layer. Results show that melting times can be significantly faster than predicted by previous theoretical models; for smaller particles, this can be around a factor 3. This is primarily due to the latent heat variation. The previously used fixed temperature boundary condition had two opposing effects on melt times: the implied infinite heat transfer led to faster melting but also artificially magnified the effect of kinetic energy, which slowed down the process. We conclude that any future models of nanoparticle melting must be based on the new Stefan condition and account for latent heat variation.     

Entering the field in qualitative field research: a rite of passage into a complex practice world

The concept of ‘the field’ is significant in ethnographic research as well as qualitative research methods more generally. However, how a field researcher enters the field is usually taken for granted after gaining access to the field. We suggest that entrance is a distinct phase of fieldwork that differs from negotiating access. Entrance is not a trivial event; rather, it is a rite of passage into a complex practice world and marks a critical field moment. Drawing on our ethnography and insights from hermeneutics and anthropology, we show that a practical understanding of the field represents a fusion of horizons where a fieldworker is thrown. The concept of thrownness highlights the fact that the fieldworkers' own historicity and prejudices affect their entrance into the field; hence, entrance into the field orientates an ethnographer in the field and influences the entire period of fieldwork that follows. Our theorizing is intended as a contribution towards advancing the discussion of qualitative research methods.     

Why are slip lengths so large in carbon nanotubes?

A possible explanation for the enhanced flow in carbon nanotubes is given using a mathematical model that includes a depletion layer with reduced viscosity near the wall. In the limit of large tubes the model predicts no noticeable enhancement. For smaller tubes the model predicts enhancement that increases as the radius decreases. An analogy between the reduced viscosity and slip-length models shows that the term slip-length is misleading and that on surfaces which are smooth at the nanoscale it may be thought of as a length-scale associated with the size of the depletion region and viscosity ratio. The model therefore provides a physical interpretation of the classical Navier slip condition and explains why ‘slip-lengths’ may be greater than the tube radius.     

Effect of backpack fit on lung function

Carrying loads close to the trunk with a backpack causes a restrictive type of change in lung function in which Forced Vital Capacity (FVC) and Forced Expiratory Volume in 1 s (FEV1) are reduced without a corresponding decrement in the FEV1.FVC( - 1) %. It is not known whether this is due to the weight of the load acting on the chest or to the tightness of fit of the shoulder and chest straps and waist belt of the pack harness. This study examined FVC, FEV1, FEV1.FVC( - 1) %, peak expiratory flow (PEF), forced expiratory flow between 0.2 and 1.2 s (FEF0.2 - 1.2) after the start of expiration and between 25 and 75% of each FVC (FEF25 - 75%) in 12 healthy males wearing a 15 kg backpack in which the shoulder and chest straps and hip belt were loosened by 3 cm from a 'comfort fit' to achieve a 'loose pack' fit (LPF) and tightened by 3 cm from CF to achieve a 'tight pack' fit (TPF). In comparison with the control condition of no pack, a loose pack fit significantly reduced FVC (by 3.6%, p < 0.01), FEV1 (by 4.3%, p < 0.01) and FEF25 - 75% (by 8.4%, p < 0.01). A tight pack fit significantly reduced FVC (by 8.1%, p < 0.01) and FEV1 (by 9.1%, p < 0.001). It also significantly reduced FEF0.2 - 1.2 (by 7.3%, p < 0.05) and FEF25 - 75% (by 21%, p < 0.01). In comparison with a loose pack fit, the tight pack fit was associated with a significantly lower FVC (by 4.6%, p < 0.01), FEV1 (by 5.0%, p < 0.01), FEF25 - 75% (by 13.8%, p < 0.01) and a fall in FEF0.2 - 1.2 (by 5.5%). The latter was approaching significance (p = 0.077). There were no significant changes in FEV1.FVC( - 1)% and PEF. It is concluded that tightening the fit of a backpack significantly affects lung function in a manner that is typical of a restrictive change in lung function and is very similar in pattern to that of wearing a loosely fitted loaded backpack. The effect of tightness of fit is additional to that due to the weight of the load alone and may also reduce expiratory flow at low lung volumes.