The algebra of rewriting for presentations of inverse monoids

We describe a formalism, using groupoids, for the study of rewriting for presentations of inverse monoids, that is based on the Squier complex construction for monoid presentations. We introduce the class of pseudoregular groupoids, an example of which now arises as the fundamental groupoid of our version of the Squier complex. A further key ingredient is the factorisation of the presentation map from a free inverse monoid as the composition of an idempotent pure map and an idempotent separating map. The relation module of a presentation is then defined as the abelianised kernel of this idempotent separating map. We then use the properties of idempotent separating maps to derive a free presentation of the relation module. The construction of its kernel - the module of identities - uses further facts about pseudoregular groupoids.Comment: 22 page

Generic Ada code in the NASA space station command, control and communications environment

The results of efforts to apply powerful Ada constructs to the formatted message handling process are described. The goal of these efforts was to extend the state-of-technology in message handling while at the same time producing production-quality, reusable code. The first effort was initiated in September, 1984 and delivered in April, 1985. That product, the Generic Message Handling Facility, met initial goals, was reused, and is available in the Ada Repository on ARPANET. However, it became apparent during its development that the initial approach to building a message handler template was not optimal. As a result of this initial effort, several alternate approaches were identified, and research is now on-going to identify an improved product. The ultimate goal is to be able to instantly build a message handling system for any message format given a specification of that message format. The problem lies in how to specify the message format, and one that is done, how to use that information to build the message handler. Message handling systems and message types are described. The initial efforts, its results and its shortcomings are detailed. The approach now being taken to build a system which will be significantly easier to implement, and once implemented, easier to use, is described. Finally, conclusions are offered

High-temperature environments of human evolution in East Africa based on bond ordering in paleosol carbonates

Many important hominid-bearing fossil localities in East Africa are in regions that are extremely hot and dry. Although humans are well adapted to such conditions, it has been inferred that East African environments were cooler or more wooded during the Pliocene and Pleistocene when this region was a central stage of human evolution. Here we show that the Turkana Basin, Kenya—today one of the hottest places on Earth—has been continually hot during the past 4 million years. The distribution of ^(13)C-^(18)O bonds in paleosol carbonates indicates that soil temperatures during periods of carbonate formation were typically above 30 °C and often in excess of 35 °C. Similar soil temperatures are observed today in the Turkana Basin and reflect high air temperatures combined with solar heating of the soil surface. These results are specific to periods of soil carbonate formation, and we suggest that such periods composed a large fraction of integrated time in the Turkana Basin. If correct, this interpretation has implications for human thermophysiology and implies a long-standing human association with marginal environments

Flight testing Flow Diverting Devices on an OH-58A+ for applications to an MH-6 Helicopter

This study investigates the use of Flow Diverting Devices to reduce passenger fatigue and parasite drag (specifically equivalent flat plate drag) for the 160*\u27* Special Operations Aviation Regiment MH-6 Helicopters. Due to cost, scheduling, and airworthiness release (AWR\u27s) issues this manuscript focuses on the actual flight test data of a similar helicopter, the OH-58A+. The flight-testing investigated the level flight performance, and handling qualities with doors removed, with and without the Flow Diverters installed. Consideration was also given in the design to discover ways of minimizing the airflow on the external passengers (amount of deflection), changes in noise level, and to the reduction in the field of view measured from the Design Eye Position. The baseline aircraft (with doors removed) was tested against 3 different types of Flow Diverting Devices (6 inch Sawtooth, 6 inch Flat Plate with Vortex Generators installed, and 8 inch Flat Plate with Vortex Generators installed). It was determined that the airflow can be deflected away from the passengers a maximum of 16 inches with no adverse impact on handling qualities. This is important for several reasons: 1. Possible increase in performance. 2. Passenger comfort. 3. Mission envelope expansion. This mission envelope expansion would include the ability to fly in colder temperatures, feasible to fly in precipitation, as well as possibly having the ability to maintain faster enroute speeds without causing undue fatigue on the passengers. This deflection was achieved with an average increase of 4.0 square feet of equivalent flat plate drag. This is much less than the effect flat plate drag on the MH-6 due to passengers and equipment installed for the mission. Additionally, during the flight testing it was noted that there were no detectable changes to the handling qualities or the noise level inside the test aircraft. Hence, the author concluded that the 8 inch Flat Plate, with Vortex Generators, Flow Diverting Device will successfully divert the airflow around the upper body of the external passengers thus reducing passenger fatigue and increasing their safety during flight. It is reasonable to assume that the MH-6 helicopter will realize a performance enhancement during flight in high drag configurations (with external passengers). Additionally, it is also possible that the MH-6 in the baseline configuration (doors off, external passenger system installed) could realize a slight performance increase. The author made the following recommendations; 1. Develop a set of flow diverters specifically for the MH-6. a. 8 Flat Plate with Vortex Generators. b. The angle should be between 40° and 50°. c. The Flow Diverter should be capable of 2 positions, full open (maximum deflection) and fully closed (no Deflection). However, if there is a performance increase with the flow diverters installed over the baseline MH-6 there would be little reason to use the fully closed position. 2. Conduct Flight Tests with an MH-6 in its typical mission configuration. a. These tests should include flights with and without external ballast. b. At least two of the flight tests should be with an FTE as an external passenger. For a qualitative comparison evaluation one flight test should be with no deflection and the other with maximum deflection. 3. Recommend that all doors are removed at all times with Flow Diverters installed. 4. Recommend the use of the Smoke Generator System with a greater volume of smoke. This can be done by either a specialized smoke canister or with a portable smoke generator

Ultrafast harmonic mode-locking of monolithic compound-cavity laser diodes incorporating photonic-bandgap reflectors

We present the first demonstration of reproducible harmonic mode-locked operation from a novel design of monolithic semiconductor laser comprising a compound cavity formed by a 1-D photonic-bandgap (PBG) mirror. Mode-locking (ML) is achieved at a harmonic of the fundamental round-trip frequency with pulse repetition rates from 131 GHz up to a record high frequency of 2.1 THz. The devices are fabricated from GaAs-Al-GaAs material emitting at a wavelength of 860 nm and incorporate two gain sections with an etched PBG reflector between them, and a saturable absorber section. Autocorrelation studies are reported which allow the device behavior for different ML frequencies, compound cavity ratios, and type and number of intra-cavity reflectors to be analyzed. The highly reflective PBG microstructures are shown to be essential for subharmonic-free ML operation of the high-frequency devices. We have also demonstrated that the single PBG reflector can be replaced by two separate features with lower optical loss. These lasers may find applications in terahertz; imaging, medicine, ultrafast optical links, and atmospheric sensing

Editorial - David Bowie

The death of David Bowie, paradoxically, brings his ontic status into sharp relief, and, in turn, throws light on the construction of the figure of the artist – a spectre – the ‘creative practitioner’. An ontology of Bowie entails an interrogation of presence, absence and the historiographic portrait of the artist as a dead rock star (or not)

Relation modules and identities for presentations of inverse monoids

We investigate the Squier complexes of presentations of groups and inverse monoids using the theory semiregular, regular, and pseudoregular groupoids. Our main interest is the class of regular groupoids, and the new class of pseudoregular groupoids. Our study of group presentations uses monoidal, regular groupoids. These are equivalent to crossed modules, and we recover the free crossed module usually associated to a group presentation, and a free presentation of the relation module with kernel the fundamental group of the Squier complex, the module of identities among the relations. We carry out a similar study of inverse monoid presentations using pseudoregular groupoids. The relation module is defined via an intermediate construction – the derivation module of a homomorphism, – and a key ingredient is the factorisation of the presentation map from a free inverse monoid as the composition of an idempotent pure map and an idempotent separating map. We can then use the properties of idempotent separating maps, and properties of the derivation module as a left adjoint, to derive a free presentation of the relation module. The construction of its kernel – the module of identities – uses further key facts about pseudoregular groupoids

Impact Of Tactile-Cued Self-Monitoring On Independent Biology Work For Secondary Students With Attention Deficit Hyperactivity Disorder

Results from a multiple baseline with changing conditions design across high school students with Attention Deficit Hyperactivity Disorder (ADHD) indicated that the students increased the percentage of independent work they completed in their general education biology class after learning tactile-cued self-monitoring. Students maintained high percentages for completed work when the rate of tactile cues was faded from 1 per minute to 1 every 5 minutes, as well as when all tactile cues were withdrawn during a short-term maintenance phase.  Moreover, the students increased their correctly completed work from percentages substantially lower than the mean of their classmates to percentages that matched and surpassed the mean of their classmates. Qualitative data indicated that the participants and their co-teachers approved of the tactile-cued self-monitoring procedures. Results confirm and extend prior research findings that students improve performance during independent tasks after learning how to use tactile-cued self-monitoring and that students maintain improvements when the tactile cues are systematically faded. Although this research was conducted in a secondary school setting, the method also could be applied to higher education. Postsecondary disability resource center personnel might consider MotivAider use for students with ADHD and other disabilities that affect the capacity to stay on task

Half-sandwich nickel(II) complexes bearing 1,3-di(cycloalkyl)imidazol-2-ylidene ligands

Two new nickel catalysts have been prepared using a convenient procedure where nickelocene, the NHC.HBF4 salts, and [Et4N]Cl were heated in THF using microwave irradiation. The resulting [NiCl(Cp)(NHC)] complexes are air- and moisture stable in the solid state, and represent two new members of this valuable and practical class of nickel catalyst. The new species were fully characterised using methods including NMR spectroscopy and X-ray crystallography. When tested in model Suzuki-Miyaura cross-coupling reactions, these complexes were found to be active for the cross-coupling of aryl bromides and aryl chlorides

Ordered groupoids and the holomorph of an inverse semigroup

We present a construction for the holomorph of an inverse semigroup, derived from the cartesian closed structure of the category of ordered groupoids. We compare the holomorph with the monoid of mappings that preserve the ternary heap operation on an inverse semigroup: for groups these two constructions coincide. We present detailed calculations for semilattices of groups and for the polycyclic monoids.Comment: 16 page