Conversation with and through computers

People design what they say specifically for their conversational partners, and they adapt to their partners over the course of a conversation. A comparison of keyboard conversations involving a simulated computer partner (as in a natural language interface) with those involving a human partner (as in teleconferencing) yielded striking differences and some equally striking similarities. For instance, there were significantly fewer acknowledgments in human/computer dialogue than in human/human. However, regardless of the conversational partner, people expected connectedness across conversational turns. In addition, the style of a partner's response shaped what people subsequently typed. These results suggest some issues that need to be addressed before a natural language computer interface will be able to hold up its end of a conversation.     

A role for aeration and intake depth in managing toxic Cylindrospermopsis: A comparison between off‐stream and riverine environments in the Fitzroy Basin,Australia

Cylindrospermopsis is a cyanobacterial species of global concern, due to its ability to produce potent toxins and its near‐cosmopolitan distribution. To date, both management and research efforts for Cylindrospermopsis have focused on riverine settings. By contrast, off‐stream storages are inadequately studied, particularly in terms of population dynamics and toxin profiles, how these are linked with the riverine systems that seed them, and what management options are best for optimizing water quality. This is a critical gap, given that storages are key off‐take points for many water users, including for livestock watering and industrial supply. This study examined the relationship between a riverine and an off‐stream environment, with respect to the development of toxic Cylindrospermopsis blooms in central Queensland. It discusses the role of an aeration system in preventing or delaying bloom development and explores the implications of intake depth with respect to population (cell density) and toxicity. Along the impounded river, the study sites featured warm, stratified conditions and an anoxic hypolimnion. By contrast, the off‐stream storage dam lacked stratification, due to the constant aeration provided by a hypolimnetic bubbler. Cylindrospermopsis raciborskii blooms appeared in both environments, with peak cellular concentrations detected in the subsurface waters. The dynamics of the toxin profiles differed, however, with the riverine concentrations being mostly epilimnetic, whereas the dam featured toxin distributed throughout the water column. Concentrations of both cylindrospermopsin (CYN) and deoxy‐cylindrospermopsin (deoxy‐CYN) were lower in the dam, compared with the riverine sites. A one‐month lag period was evident before C. raciborskii cells appeared in the dam following their observation in the river samples, and a similar period elapsed before the dam populations reached their peak concentrations. These data are invaluable in considering the best management options for off‐stream sites that experience seeding from riverine populations, particularly for toxin producers such as Cylindrospermopsis.     

Cyclic Hexapeptide Mimics of the LEDGF Integrase Recognition Loop in Complex with HIV‐1 Integrase

The p75 splice variant of lens epithelium‐derived growth factor (LEDGF) is a 75 kDa protein, which is recruited by the human immunodeficiency virus (HIV) to tether the pre‐integration complex to the host chromatin and promote integration of proviral DNA into the host genome. We designed a series of small cyclic peptides that are structural mimics of the LEDGF binding domain, which interact with integrase as potential binding inhibitors. Herein we present the X‐ray crystal structures, NMR studies, SPR analysis, and conformational studies of four cyclic peptides bound to the HIV‐1 integrase core domain. Although the X‐ray studies show that the peptides closely mimic the LEDGF binding loop, the measured affinities of the peptides are in the low millimolar range. Computational analysis using conformational searching and free energy calculations suggest that the low affinity of the peptides is due to mismatch between the low‐energy solution and bound conformations.     

Changes in the structure and properties of aluminum alloys solidified in an ultrasonic field

An ultrasonic field was applied to melted metal alloys during their solidification with the aim of obtaining their microstructure in a solid state characterized by small-sized grains. In this paper, the results of experimental research are presented, obtained under the application of an ultrasonic field of 100–350 W during the solidification of an ATC Si₁₀Cu₄ alloy cast in a mold.     

Tridimensional ultrastructure of perfusion fixed gastrointestinal epithelial cells by high resolution scanning electron microscopy

Improvements in the design of modern scanning electron microscopes (SEM) and new methods of specimen preparation incorporating chemical removal of the cytosol and cytoskeleton, now make it possible to view cells and their organelles in three dimensions (3D) at high magnification. In this experiment, high resolution SEM (HRSEM) utilizing new methods of tissue preparation was used to study the intracellular structures of the mouse ileum. In addition, in vivo intestinal perfusion was used to further enhance cellular preservation. Using these modifications it was possible to visualize, in 3D, the fine structure of intestinal epithelial cells and intracellular organelles such as the nucleus, mitochondria, endoplasmic reticulum, and Golgi complex, as well as microvilli and cell membrane. Whole mitochondria appeared as irregularly shaped organelles which contained tubular cristae. Plate-like cristae were not observed. The brush border was found to be a closely packed array of cylindrical projections. The extensive folding and structural intricacy of lateral cell membranes between absorptive cells could only be appreciated by viewing this tissue with 3D HRSEM. The use of HRSEM to study 3D ultrastructure of cells and their organelles will improve our understanding of the structure-function relationships in both the healthy and diseased gastrointestinal tract.     

When Are Group Scheduling Tools Useful?

A geographically dispersed department at the MITRE Corporation participated in a field test of groupware tools. This paper documents the results of their use of a group scheduling tool, Meeting Maker Version 1.5. Research in the late 1980s showed that early group scheduling tools were not useful, in part because they only benefited some users and hence critical mass could not be attained. This study was undertaken to determine whether and how far the tools have evolved. Participants said that Meeting Maker made it easy to schedule meetings and maintain their calendars, and 90% wished to continue using it after the study was complete. Problems were noted when not everyone used or had access to the tool, and three generic solutions are discussed: capabilities that allow users to communicate with non-users, capabilities that allow users to stay connected, and lightweight methods of participation.     

Refactoring in Maintenance and Development of Z Specifications and Proofs

Once you have proved your refinement correct, that is not the end. Real products, and their accompanying specifications, develop over time, with new improved versions having added functionality. There are new maintenance issues that arise when altering and upgrading pre-existing large specifications and their respective proofs.We show how concepts from refactoring can be used to structure this process, and provide a means for well-defined, disciplined modifications. Additionally, we discuss how the analogy between proof and refactoring, as meaning preserving transforms, can be used to suggest the development of a refactoring toolset, and thence a refinement toolset.     

An analytic solution to the coupled pressure–temperature equations for modeling of photoacoustic trace gas sensors

Trace gas sensors have a wide range of applications including air quality monitoring, industrial process control, and medical diagnosis via breath biomarkers. Quartz-enhanced photoacoustic spectroscopy and resonant optothermoacoustic detection are two techniques with several promising advantages. Both methods use a quartz tuning fork and modulated laser source to detect trace gases. To date, these complementary methods have been modeled independently and have not accounted for the damping of the tuning fork in a principled manner. In this paper, we discuss a coupled system of equations derived by Morse and Ingard for the pressure, temperature, and velocity of a fluid, which accounts for both thermal effects and viscous damping, and which can be used to model both types of trace gas sensors simultaneously. As a first step toward the development of a more realistic model of these trace gas sensors, we derive an analytic solution to a pressure–temperature subsystem of the Morse–Ingard equations in the special case of cylindrical symmetry. We solve for the pressure and temperature in an infinitely long cylindrical fluid domain with a source function given by a constant-width Gaussian beam that is aligned with the axis of the cylinder. In addition, we surround this cylinder with an infinitely long annular solid domain, and we couple the pressure and temperature in the fluid domain to the temperature in the solid. We show that the temperature in the solid near the fluid–solid interface can be at least an order of magnitude larger than that computed using a simpler model in which the temperature in the fluid is governed by the heat equation rather than by the Morse–Ingard equations. In addition, we verify that the temperature solution of the coupled system exhibits a thermal boundary layer. These results strongly suggest that for computational modeling of resonant optothermoacoustic detection sensors, the temperature in the fluid should be computed by solving the Morse–Ingard equations rather than the heat equation.