MS Thesis Research Articles

Peter Paul Rickham.

Peter Rickham was one of a small group of pioneering surgeons who helped to establish the specialty of paediatric surgery in the United Kingdom.​Kingdom. Figure 1 He founded the first neonatal surgical unit in the world, at Alder Hey Children's Hospital in Liverpool. This unit was to become the benchmark for similar units around the world and immediately brought about an improvement in the survival of newborn infants undergoing surgery from 22% to 74%. Peter was intensely involved with research, and his MS thesis concerned the metabolic response of the newborn infant to surgery. An innovative surgeon, he devised the Rickham reservoir, an integral part of the Holter ventricular drainage system for the treatment of hydrocephalus. His book Neonatal Surgery, published in 1969, was for many years the standard text used widely throughout the world. After qualifying, Peter Rickham trained in paediatric surgery at Great Ormond Street Hospital, London, and at Alder Hey. He spent a year in Boston and Philadelphia as a Harkness travelling fellow before being appointed consultant paediatric surgeon at Alder Hey in 1952. He became director of paediatric surgical studies there in 1965. In 1971 he was appointed professor of paediatric surgery at the University Children's Hospital in Zurich, where he remained until his retirement in 1983. Peter had a distinguished career in the second world war, taking part in the Normandy invasion and serving in the Far East. He reached the rank of major in the Royal Army Medical Corps. He was forceful and outspoken, but passionately involved with his specialty. In the early years following his appointment in Liverpool, he became so exasperated by the local paediatricians' use of barium to diagnose oesophageal atresia that he sent every paediatrician in his catchment area a Christmas card enclosing a radio-opaque catheter so that they could safely diagnose the condition. Predeceased by his first wife, Elizabeth, he leaves his second wife, Lyn; three children; and five grandchildren. Peter Paul Rickham, professor of paediatric surgery University Children's Hospital, Zurich, 1971-83 (b Berlin 1917; q Cambridge/St Bartholomew's Hospital, London, 1943; MS, FRCS), died on 17 November 2003 following a stroke.

IN MEMORIAM: WILLIAM ALEXANDER CALDER III, 1934–2002

The life of William Alexander Calder III was ended abruptly on 23 April 2002, by acute leukemia. The disease was diagnosed only a short time before his death and progressed rapidly. Bill Calder's entire life was fast-paced; his mind and body never seemed to stop in his efforts to reach mountaintops, to solve physiological questions, or to offer solutions to environmental problems for newspaper readers or rural residents of remote parts of Mexico. Bill was born in Cambridge, Massachusetts, on 2 September 1934. At age 16, participation in field trips sponsored by the Atlanta Audubon Society led to an interest in bird watching. He acquired a distaste for collecting when a professor shot a Great Blue Heron but failed to prepare the specimen. After two years at Emory University and summers spent as a Forest Service smoke-jumper in Montana, he completed his BS degree in zoology from the University of Georgia in 1955. Enlisting in the U.S. Coast Guard, he became a pilot of twin-engined seaplanes, search and rescue operations and fish and wildlife patrols in Florida, Texas, and Washington. Graduate school took him to Washington State University where he studied Zebra Finch metabolism for an MS thesis (1963) under the guidance of James R. King, and then to Duke for a Ph.D. dissertation (1966) on roadrunner metabolism with Knut Schmidt-Nielsen. During that time, two summers were spent as a seasonal naturalist at Grand Teton National Park, where his interest in hummingbirds was initiated by a Calliope Hummingbird nest, and one summer as a rangernaturalist at Glacier National Park. After two years teaching at Virginia Polytechnic Institute, he moved to the University of Arizona at Tucson in 1969, becoming a professor in the Department of Ecology and Evolutionary Biology in 1974. He joined the AOU in 1961, becoming an Elective Member in 1974, and a Fellow in 1988. Bill's earlier research publications concerned mainly water balance, respiration, and energetics of birds, but he published two papers on temperature relationships of the water shrew. In 1971 he spent the first of many summers at the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado. There he investigated physiological problems associated with small size, especially of hummingbirds. For the rest of his life, most of his research focused on hummingbirds; it resulted in many papers on their physiology, ecology, and behavior. A significant departure was a sabbatical in New Zealand in 1976-1977, where he studied kiwi physiology. His interest in tiny mammals, tiny birds, and big eggs (as in the kiwi) led him to question many established ideas about the relationship between size and function; he wrote Size, Function, and Life History (1984, Harvard University Press). He contributed chapters to a number of books, most on hummingbirds, matters of size, and conservation issues. Personal research with subsequent publication was not Bill's only goal; he was a dedicated teacher at both the graduate and undergraduate levels. He wanted students to question what they saw and read and to learn to derive their own answers. He was irreverent of established rule and used provocative questions daily in his classroom. He transmitted the joy of doing science; his own work proved it could be fun. Theories were never lacking in his discussions; he could always offer a theory about anything. Many ideas were not productive, but others led to fruitful research. The University of Arizona College of Science honored him in 2002 with its Career Mentoring Award, in recognition of a lifetime of excellence in teaching. He left a compelling model on how to live and how to do science, described by one of his colleagues as equal parts of humor, keen observation, hard work, and absolute honesty. Bill's love of the outdoors was a compulsion; he liked nothing better than to climb the nearest high mountain. At RMBL, he often invited new students or colleagues to talk with him, but that involved bushwhacking to a nearby 13,000 ft (3,950 m) peak! His physiological ecology course was dubbed Backpacking 101. With his wife Lorene, he started graduate student seminars at which they would serve peppermint tea prepared on a wood burning stove and served in specimen jars. He was a regular participant in the 4th of July footrace, an eight mile (13 km) ordeal between Gothic and

Estimation of effective diffusivities and glass transition temperature of polydextrose as a function of moisture content

The glass transition temperature ( T g) of polydextrose was determined by differential scanning calorimetry as a function of moisture content, and was fitted to the Gordon–Taylor equation. T g decreased with an increase in moisture content, confirming the plasticizing effect of water on polydextrose. The effective diffusivity of water in polydextrose ( D), which increased with an increase in storage water activity ( a w), was estimated at room temperature both above and below the glass transition by applying the method of slopes [Effective water diffusivity in starch materials, MS Thesis, Rutgers University (1987); Effect of gelatinization and sugars on the effective moisture diffusivity in starch materials, MS Thesis, Rutgers University (1988)] to the experimental data. D showed a sharp increase in regions close to the glass transition, where polydextrose changed from the glassy to the rubbery state due to increased mobility. D was also correlated to a model [The effect of water activity on moisture diffusivity in soy flour as determined from a free volume based approach (2002)] based on the free volume theory [J. Appl. Polym. Sci. 22 (1978) 2325; AIChE J. 38 (1992) 405], which captured the change in diffusion mechanism as a function of glass transition.

Evaluation of a plastic shoe

Hoof-related lameness in horses is common; however, very few critical studies have been performed to evaluate the ability of different shoes to reduce lameness. Dr. Chris Kawcak, with Drs. David Frisbie and Wayne McIlwraith, worked with Val Perino, an MS student, to develop a project intended to compare horses that were unshod, shod with steel shoes, and shod with plastic shoes (Dynamix shoes) in both balanced and controlled, unbalanced states. The specific aims of the study were to compare clinical lameness, ground reaction force, and hoof strain in unshod, traditionally shod, and Dynamix shod horses in both balanced and controlled, unbalanced states. This led to the hypothesis that Dynamix shod horses would have less clinical lameness, increased ground reaction force, and less hoof strain than unshod and traditionally shod horses. Six horses, ages 3 to 5 years, were chosen for the study and treated in accordance with ACUC protocol. The first groups of measurements were on hooves that were trimmed for normal balance. The left front hooves of all horses were then trimmed in an unbalanced manner starting on week 18. Lameness was graded in each horse at a jog according to a subjective lameness scoring system. Each horse was also jogged across a Tekscan sensor mat at a controlled speed. The force, pressure, and contact area were determined for each hoof. Rosette strain gauges were also applied to the prepared hoof at the medial and lateral quarters in both parallel and perpendicular fashion. Data were analyzed by using a mixed model analysis of variance and least squares mean when appropriate. A P value less than .05 was considered significant. Horses were significantly more lame when they wore Dynamix shoes without the clips compared with clips. The controlled, unbalanced model induced a level of lameness that was appropriate for seeing the effects of treatment. It was also found that the horses were less lame in Dynamix shoes compared with when they were unshod in both balanced and unbalanced states. Ground reaction force was highest in the Dynamix treatment group compared with the traditionally shod group. However, the force was higher in the unshod and Dynamix treatment groups when the hooves were unbalanced, which does not correlate with the increased lameness seen when the hooves were unbalanced. The controlled, unbalanced treatment significantly reduced lateral coronary band compression as seen by a reduction in lateral transverse hoof strain. In conclusion, the Dynamix shoe appears to reduce lameness in both balanced and unbalanced states; however, the clips appear to be an essential component of the design. This is the first time that the Tekscan technology has been used to assess abnormal hoof conformation and the investigators are currently planning to further evaluate the Tekscan system against a force plate to determine the meaning of these data. (From Colorado State University Orthopaedic Researach Center Laboratory Report. The complete study was published as: Perino, V MS Thesis. Colorado State University. 2002.) Copyright 2002, Elsevier Science (USA). All rights reserved. 0737-0806/02/2208-0008$35.00/0 doi:10.1053/jevs.2002.37110 Fig 1. (A) Natural Balance shoe, (B) Egg Bar shoe, and (C) Dynamix shoe.

Runoff from orchard floors—micro-plot field experiments and modeling

Hydrologic response patterns of three ground treatments (resident vegetation, bare soil and ripped resident vegetation) were investigated. An in situ, micro-scale, plot retention-tank system was employed and used in conjunction with a kinematic wave model [Seasonal changes in infiltration and soil water storage in conventional and alternative agricultural systems, MS Thesis, University of California, Davis (2000)] to calculate surface water runoff hydrographs via the orchard floor-specific infiltration function. The model optimized Green and Ampt's infiltration function on the suction at the wetting front until the endpoint of the cumulative runoff hydrograph matched observed runoff volumes. Our approach aimed to minimize data collection in the field and was found useful in the evaluation of different ground treatments as well as in evaluating their ability to reduce runoff under dry and wetted conditions. Infiltration for ripped resident vegetation was approximately an order of magnitude greater than that for bare soil. Resident vegetation yielded intermediate results. However, under elevated soil water conditions (degree of saturation greater than 0.80), differences between response patterns of resident vegetation and bare soil markedly decreased.

New controller for functional electrical stimulation systems

A novel, self-contained controller for functional electrical stimulation systems has been designed. The development was motivated by the need to have a general purpose, easy to use controller capable of stimulating many muscle groups, thus restoring complex motor functions (e.g. standing, walking, reaching, and grasping). The designed controller can regulate the frequency, pulse duration, and charge balance on up to 16 channels, and execute pre-programmed and sensory-driven control operations. The controller supports up to eight analog and six digital sensors, and comprises a memory block for including history of the sensory data (time series). Five independent timers provide the basis for the multi-modal and multi-level control of movement. The PC compatible interface is realised via an IR serial communication channel. The PC based software is user friendly and fully menu driven. This paper also presents a case study where the controller was implemented to restore walking in a paraplegic subject. The assistive system comprised the novel controller, the power and output stages of an eight-channel FES system (IEEE Trans Rehabil Eng, TRE-2 (1994) 234), ankle-foot orthoses, and a rolling walker. Stimulation was applied with surface electrodes positioned over the motoneurons that innervate muscles responsible for the hip and knee flexion and extension. The sensory system included goniometers at knee and hip joints, force-sensing resistors built in the shoe insoles, and digital accelerometers at the hips. A rule-based control algorithm was generated following a two-step procedure: (1) simulation and (2) machine learning as described in earlier studies (IEEE Trans Rehab Eng, TRE-7 (1999) 69). The paraplegic subject walked faster, and with less physiological effort, when automatic control was applied as compared to hand-control. This case study, as well as a previous one for assisting grasping (The design and testing of a new programmable electronic stimulator. N. Fisekovic, MS thesis. University of Belgrade, Belgrade, 2000) indicate that the novel control unit is effectively applicable to FES systems.

Relation between the slope of the rate-level curve, the maximum driven firing-rate, and the neuronal dynamic range in auditory primary afferents of the cat

The power of the auditory primary afferent to indicate intensity change depends partly upon the rate-of-change-of-firing with sound-pressure-level, i.e., the slope of the rate-level curve. The latter was estimated for each of 778 rate-level-functions in the cat (McGee, MS thesis, Creighton, 1983) by fitting lines to the points on the curve that fall between (1) Rs+[c/100](Rmax−Rs) and (2) Rs+[(100−c)/100](Rmax−Rs), for c=30. Rs is spontaneous firing-rate and Rmax is maximum firing-rate. c specifies a pair of points on the curve, symmetric around the centroid. Each slope was divided by the respective maximum driven firing-rate, Rmax−Rs, to obtain the adjusted slope (in 1/dB). Each adjusted slope was then plotted versus the neuron’s dynamic range (in dB), whose endpoints, the threshold and the saturation level, are given by c=1. The resulting plot is smooth and hyperbolic. Threshold and saturation level have also been defined by expressions (1) and (2) in a logistic rate-level equation (Nizami, 24th ARO, 2001) that yields (3) adjusted slope =[ln[(100−c)/c]]/2(dynamic range)]. For c=1 and c=2, these curves neatly sandwich the empirical data. An afferent’s power of discrimination is intimately related to both the maximum driven firing-rate and the neuronal dynamic range.

Trailing Blackberries: From Clear-cuts to Your Table

Received for publication 22 May 2000. I would like to acknowledge the contributions of Angela Anderson and Rengong Meng, whose MS thesis research at Oregon State Univ. contributed to this paper; Kirsten Wennstrom (USDA–ARS/Oregon State Univ.) for overseeing the maintenance of the plant material and crosses discussed; Hugh Daubeny [Agriculture and Agri-Foods Canada, Agassiz, B.C. (retired)], Rick Harrison (Sweetbriar Inc., Watsonville, Calif.), and Ted Mackey (USDA–ARS) for help in collecting the bulk of the Rubus ursinus; and Jim Luby (University of Minnesota) for his inspiration in the initial conception of the work and help in collection of the plant material. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. E-mail address: finnc@bcc.orst.edu The commercial blackberry (Rubus sp.) industry in the United States and Canada can be roughly divided into eastern North America, Oregon, and California components. In the eastern United States, the plantings tend to be fairly small (mostly <0.25 ha, but up to ≈8 ha), geared towards pick-your-own or local sales, with either semierect (e.g., ‘Chester Thornless’) or erect (e.g., ‘Navaho’) cultivars (Clark, 1992). In Oregon, there are ≈2500 ha in production (National Agricultural Statistics Service–Oregon Agricultural Statistics Service, 1999), the crop is primarily machine-harvested for the processing market, and the cultivars are trailing types (e.g., ‘Marion’ and ‘Thornless Evergreen’). The California blackberry industry, while still relatively small, is expanding, using publicly and privately developed trailing, erect, and semierect cultivars that are hand-harvested for wholesale, fresh-market sales. Breeding programs in Florida and Texas have developed blackberry cultivars from indigenous species, but have not accounted for a significant acreage in North America.

STEP-based feature extraction from STEP geometry for Agile Manufacturing

Feature recognition, from low level geometric entities of product design representations within a CAD model to facilitate process planning and manufacturing activities, has been of significant importance in computer integrated manufacturing (CIM). However, the emerging paradigm of Agile Manufacturing has imposed additional requirements of “neutral format” so that form-feature information can be readily shared among multiple partners of a virtual enterprise. Recently, the STandard for the Exchange of Product model data (STEP) has emerged as the means for neutral form exchange of product related data. The “STEP efforts” have broken down the domain of manufacturing related activities in the form of application protocols (APs) target for specific functions which include drafting, configuration control and feature-based process planning to mention a few. Efforts are still on to increase the acceptance and use of this international standard (IS). This paper focuses on our efforts to support the STEP standard with the development of a standards-oriented form-feature extraction system. The developed feature extraction system takes as a input a STEP file defining the geometry and topology of a part and generates as output a STEP file with form-feature information in AP224 format for form feature-based process planning. The system can also be interfaced with a recent IGES to AP202 translator [M.P. Bhandarkar, B. Downie, M. Hardwick, R. Nagi, Migration from IGES to STEP: one-to-one translation of IGES drawing to STEP drafting data, accepted by Computers in Industry, July, 1999; M.P. Bhandarkar, Satisfying information needs in Agile Manufacturing through translation and feature extraction into STEP product data models, MS Thesis, State University of New York at Buffalo, 1997.] to allow conversion of legacy data. The feature recognition algorithm is boundary-representation (B-Rep) based and follows a sequential approach through an existing classification of features. Properties of each feature class are exploited to enable their extraction. The algorithm is currently developed for prismatic solids produced by milling operations and that contain elementary shapes such as plane and cylindrical surfaces (possibly using non-uniform rational B-splines (NURBS)). Special attention has been paid to implementation issues. We demonstrate the efficacy of the system using representative parts.

Precambrian Geological Evolution of the Teton Range, Western Wyoming

The crystalline rocks that form the core of the Teton Range are part of the Wyoming Province, which is one of the oldest portions of North America. Study of the basement of the Tetons, coupled with the results of ongoing research in similar-aged rocks exposed elsewhere in Wyoming, will provide information on how the crust evolved in the early Earth in general and in the Wyoming province in particular. In 1999 the project involved two weeks of fieldwork in Grand Teton National Park and regions to the east, including the Gros Ventre Range, deep canyons of the Buffalo Fork River near Togwotee Pass, and outcrops of basement near Dubois, Wyoming. The main goals of the fieldwork were to complete the sampling of key units in Grand Teton National Park, and to determine whether or not the next nearest outcrops of basement (Gros Ventre, Togwotee Pass and Dubois regions) share the early geologic history preserved in the rocks of Teton National Park. This field work involved four faculty members from UW and a graduate student, who is doing the study as part of her MS thesis. Several months of laboratory analysis at UW have characterized the rocks through thin section, stained slabs, and whole rock geochemical and Nd, Sr, and Ph isotopic methods and produced preliminary U-Pb dates. The principal results from this year 's efforts are that the Teton basement rocks consist of large proportions of juvenile crust, the majority of the rocks formed over a relatively narrow time span from ~2.74 to 2.68 Ga, they were deformed at about 2.67 Ga, and that rocks exposed in the Buffalo Fork River to the east are shallow level equivalents to the deep rocks exposed in the Tetons. Based on these observations and measurements, we hypothesize that the basement rocks of the Tetons formed in an off­shore, island arc setting between 2.74-2.68 Ga, and they were accreted to the Wyoming province at about 2.67 Ga. Post-tectonic intrusion of distinctive peraluminous granites in both the Teton's (Mt. Owens quartz monzonite) and elsewhere in the Wyoming province at 2.55 Ga strengthens our interpretation of a shared history after 2.67 Ga. If this model for the basement rocks in the Teton's holds up, it will be the first case of crustal growth by lateral accretion for the Archean Wyoming province, and one of the earliest examples of plate tectonics style crustal growth documented from anywhere in the world. Plate tectonic growth has dominated the Earth 's evolution from ~2.5 Ga to the present, but it is unclear whether or not analogous processes operated before 2.5 Ga.

A non-ideal multiphase chemical equilibrium algorithm

Two non-ideal, multiphase chemical reaction equilibrium algorithms are presented. An approach to multiphase equilibrium calculations due to Abdel-Ghani et al. [R.M. Abdel-Ghani, EOS mixing rules for multi-phase behaviour, MS thesis, University of Calgary, Calgary, 1995; R.M. Abdel-Ghani, R.A. Heidemann, A.V. Phoenix, Paper presented at the 1994 AIChE Conference, San Francisco, CA, 1994] was modified to include reaction equilibrium, exploiting two proposals by Michelsen [M.L. Michelsen, Fluid Phase Equilibria 53 (1989) 73–80; M.L. Michelsen, Computers Chem. Eng. 18 (1994) 545–550]. In both algorithms, nested processes are used with an inner loop treating the phases as ideal solutions and an outer loop updating non-ideal parts of the models. Both of the algorithms were initiated with a number of phases which were reduced in the outer loop by combining phases as they approach the same composition and density. Initiation strategies for phase amounts and compositions are presented.

Utilizing a GIS Vegetation Model for a Campus-as-arboretum Development

This paper outlines the history of the SFA Arboretum's effort to establish a campus-as-arboretum at the university. In 1996, the participants created a robust Geographic Information System (GIS) for the campus forest based primarily on a 1993-95 campus mapping and tree inventory project in the 144-acre main core of the campus (Wilson to North St.; College to Starr). The project served as the MS thesis of Susan Perkins. In brief, the campus model reveals a pine-dominated Type 2 forest (one rapidly approaching maturity), difficult campus hydrology issues, and a landscape low on diversity with 68 species represented. In 1996, the Arboretum's AutoCAD® map and Excel® tree data files were integrated into the College of Forestry Unix-based ArcInfo® platform. This now provides full GIS capabilities for landscape planners. The resultant maps based on user queries reveal a robust vegetation analysis and management tool. In 1997, the SFA administration, Physical Plant, Grounds, College of Forestry, and SFA Arboretum initiated a “campus beautification” funding campaign. The SFA Arboretum will play a key role in building unique, documented, and mapped woody ornamental collections for the campus. This provides a unique opportunity in the South for long-term Zone 8 woody plant evaluation in a high-visibility and “perpetual” landscape.

Precambrian Geologic Evolution of the Teton Range, Western Wyoming

The crystalline rocks that form the core of the Teton Range are part of the Wyoming Province, which is one of the oldest portions of North America. Study of the basement of the Tetons, coupled with the results of ongoing research in similar aged rocks exposed elsewhere in Wyoming, will provide information on how the crust evolved in the early Earth in general and in the Wyoming province in particular. In 1998 the project involved one week of fieldwork in Teton National Park to collect samples of key units for geochemical studies. This field work involved four faculty members from UW and a graduate student, who is doing the study as part of her MS thesis. The field work has been followed by several months of laboratory analysis at UW. We have characterized the rocks through thin section, stained slabs, and whole rock geochemical and Nd, Sr, and Pb isotopic methods. Geochronology is in progress: datable minerals have been isolated from samples of four different units and precise ages with uncertainties on the order of ± 5 million years are forthcoming.

Locating Discretionary Service Facilities, II: Maximizing Market Size, Minimizing Inconvenience

Discretionary service facilities are providers of products and/or services that are purchased by customers who are traveling on otherwise preplanned trips such as the daily commute. Optimum location of such facilities requires them to be at or near points in the transportation network having sizable flows of different potential customers. N. Fouska (Fouska, N. 1988. Optimal Location of Discretionary Service Facilities. MS Thesis, Operations Research Center, MIT, Cambridge, Mass.) and O. Berman, R. Larson and N. Fouska (BLF [Berman, O., R. C. Larson, N. Fouska. 1992. Optimal location of discretionary service facilities. Trans. Sci. 26(3) 201–211.]) formulate a first version of this problem, assuming that customers would make no deviations, no matter how small, from the preplanned route to visit a discretionary service facility. Here the model is generalized in a number of directions, all sharing the property that the customer may deviate from the preplanned route to visit a discretionary service facility. Three different generalizations are offered, two of which can be solved approximately by greedy heuristics and the third by any approximate or exact method used to solve the p-median problem. We show for those formulations yielding to a greedy heuristic approximate solution, including the formulation in BLF, that the problems are examples of optimizing submodular functions for which the G. Nemhauser, L. Wolsey and M. Fisher (Nemhauser, G. L., L. A. Wolsey, M. L. Fisher. 1978. An analysis of approximations for maximizing sub-modular set functions, I. Math. Prog. 14 265–294.) bound on the performance of a greedy algorithm holds. In particular, the greedy solution is always within 37% of optimal, and for one of the formulations we prove that the bound is tight.

Sampling requirements for nth-order correlations

As has been derived previously [Pflug, MS thesis, Univ. of New Orleans (1990); Pflug et al., J. Acoust. Soc. Am. 91, 975–988 (1992); Pflug et al., J. Acoust. Soc. Am. 94, 2159–2172 (1993)], the sampling intervals required to prevent nonremovable and removable aliasing in higher-order correlations calculated from discrete-time data are Δt3≤1/(3ft) for the bicorrelation and Δt4≤1/(4ft) for the tricorrelation, where ft is the highest or top frequency present in a signal. It is shown here that a general expression for the sampling required to prevent aliasing for each order n of correlation calculated from discrete-time data is Δtn≤1/(nft). Time-domain computer calculations of correlation central ordinate values for orders two through eight are consistent with this result. Removable aliasing can be eliminated for data which are sampled such that Δt≤1/(2 ft) by (1) the application of n-dimensional transform or time-domain masking filters, (2) one-dimensional filtering of the transform domain diagonal factor, or (3) interpolation of the data before correlating.

TETRAPYRROLE‐DEPENDENT PHOTODYNAMIC HERBICIDES

TETRAPYRROLE‐DEPENDENT PHOTODYNAMIC HERBICIDES

Authors

Authors

Are F0 differences after stops accidental or deliberate?

Differences in F0 after stops are generally thought to be unavoidable perturbations of the rate of vocal fold vibration brought about by changes in the tension of the folds during the stop [Hombert, Ohala, and Ewan, Language 55, 37–58 (1979)]. For example, F0 is depressed after voiced stops because the folds are slackened during the closure, but elevated after voiceless stops because the folds are tensed. Recent work has shown, however, that all the mechanisms proposed to account for differences in F0 after stops are seriously flawed [Kingston, MS thesis (1985)] and, furthermore, that stops of the same phonetic type, e.g., voiceless unaspirated, can elevate F0 in one language but depress it in another [Caisse, MS thesis (1982)]. The F0 differences may therefore be introduced deliberately. to enhance the phonological contrast, rather than arising as accidental byproducts of other articulations. This possibility was tested with data from Tamil, a language which contrasts long and short stops where the long stops are predictably voiceless and the short ones are predictably voiced. Since voicing is allophonic rather than distinctive in this language, F0 differences need not appear after stops if they are deliberate. On the other hand, if the F0 differences are simply an accidental byproduct of having the folds vibrating or not, then they should appear regardless of the phonological role of vocal fold vibration. Measurements of F0 after stops in Tamil show no significant difference at the onset of vowels following the two kinds of stops, supporting the contention that F0 differences are deliberate in other languages.

Elemental Concentrations in Native Range Grasses from the Northern Great Plains of Montana

Aldous, A. E. 1929. The eradication of brush and weeds from pasture lands. J. Amer. Soc. Agron. 21:660-666. Baker, R. C. 1967. The effect of season and intensity of herbage removal on the physical and chemical responses of some range plants. MS Thesis, Utah State Univ., Logan. Cameron, E. 1935. A study of the natural control of ragwort (Seneciojacobaea L.). J. Animal Ecol. 23(2):265-322. Coyne, P. I. 1%9. Seasonal trends in total available carbohydrates with respect to phenological stage of development in eight desert range species. PhD Diss., Utah State Univ., Logan. Jameson, D. A. 1963. Responses of individual plants to harvesting. Bot. Rev. 29:532-594. Kulman, J. M. 1971. Effects of insect defoliation on growth and mortality of trees. Annu. Rev. Entomol. 16:289-324. McKell, C. M. 1956. Some characteristics contributing to the establishment of rabbitbrush (Chrysothamnus spp.). PhD Diss., Oregon State College, Corvallis. Romberger, J. A. 1963. Meristems, growth, and development in woody plants. Tech. Bull. No. 1293. U.S. Dep. Agr., Forest Serv. 214 p. Simmonds, F. J. 1951. Further effects of the defoliation of Cordia macrostachys (Jacq.). R. & S. Canadian Entomol. 83(1):24-27. Smith, D., G. M. Paulsen, and C. A. Raguse. 1964. Extraction of total available carbohydrates from grass and legume tissue. Crop. Sci. 2:75-78. Sterrett, J. R., W. E. Chappell, and G. M. Shear. 1968. Temperature and annual growth cycle effects on root suckering in black locust. Weed Sci. 16:250-251. Stoddart, L. A., and A. D. Smith. 1955. Range Management. 2nd ed. McGraw-Hill, New York. 433 p. Tew, R. K. 1970. Root carbohydrate reserves in vegetative reproduction of aspen. Forest Sci. 16:318-320. Thimann, K. V. 1937. On the nature of inhibitions caused by auxin. Amer. J. Bot. 24: 407-412. Thimann, K. V. 1948. The Hormones. I. Academic Press, New York. 886 p. Weinmann, J. 1946. Some fundamental aspects of modem pasture management. Rhod. Agr. J. 43:418-425. Wenger, K. F. 1953. The sprouting of sweetgum in relation to season of cutting and carbohydrate content. Plant Physiol. 28:35-49. Willard, E. E. 1972. Some factors involved in activation of sprouting in little rabbitbrush and snowberry on summer range. PhD Diss., Utah State Univ., Logan. Willard, E. E., and C. M. McKell. 1973. Simulated grazing management systems in relation to shrub growth responses. J. Range Manage. 26:17 1-174. Yocum, L. E. 1945. Plant growth. The Jaques Cattell Press, Lancaster, Penn. 203 p.

General Comments Now, Specifics Later

Walter Karplus has been involved with simulation since 1950, when he was concerned with petroleum exploration and production problems. His MS thesis (University of California, Berkeley, 1951), his work at International Geophysics, Inc., and his PhD dis sertation (University of California, Los Angeles) all involved simulation. Walter has been a member of the faculty of UCLA since 1955 and has also been a con sultant since then to many companies and government organizations. He is a Fellow of IEEE and a recipi ent of the EAI Senior Scientific Simulation Award. No one has done more to advance the state of simula tion methodology, particularly with respect to the handling of distributed systems and associated par tial differential equations than Walter. And all the while he has given outstanding support to the Simula tion Councils (now SCS) by accepting appointments to official positions, by organizing and chairing ses sions and contributing outstanding papers to techni cal meetings, and by his continuing encouragement of all of us.