The Influence of Shelter and Weeds on Early Growth of Sitka Spruce and Lodgepole Pine

An experiment in Helmsdale Forest (Highland Region, Scotland)examined the effects of shelter and weed competition on Sitkaspruce (Picea sitchensis (Bong.) Can.) and lodgepole pine (Pinuscontorta Douglas ex Loudon). Different levels of shelter fromwind were achieved by using netting and were measured usingtatter flags. Three treatments compared weed competition byremoving no vegetation, heather (Calluna vulgaris L.) only orall ground vegetation respectively. Results indicate a definiterelationship between material lost from tatter flags and treedry weight at five years. Even the smallest increase in shelterresulted in increased growth of Sitka spruce and the beneficialeffect of shelter became most apparent 4 to 5 years after planting.Tree dry weight was found to be correlated with root collardiameter and height but not fifth year height increment. Resultsfrom weeding treatments were unclear and differed between species.This was because bird damage interacted with weeding, the completelyweeded plots being most heavily damaged; and because the methodof hand weeding (pulling out the whole plant including roots)damaged fine tree roots. Bird damage was prevented by nettingbut in unnetted plots it was found impossible to separate birddamage from other factors although it was clearly more seriouson lodgepole pine.     

Economic Impact Studies of Regional Public Colleges and Universities

ABSTRACT This article reviews methodological issues confronting authors and users of economic impact studies of public colleges and universities. Questions addressed include the following: How should economic impact of regional public colleges and universities be defined? What considerations should govern the definition or the geographical study area? How should tax support of publicly supported institutions be addressed? The article includes perspectives from recent literature considering these questions from both short-term and long-term perspectives. Resolution of these issues depends upon careful delineation and communication of the alternative states of world between which the hypothetical impact is measured.     

Cyanazine metabolism in corn,fall panicum,and green foxtail*

The metabolism of cyanazine (2-chloro-4-(1-cyano-1-methyl-ethylamino)-6-ethylamino- 1,3,5-triazine) by corn (Zea mays, L.), fall panicum (Panicum dichotomiflorum Michx.), and green foxtail (Setaria viridis L.) was compared. Cyanazine metabolism by plants at the four-leaf stage was examined by thin-layer chromatography following foliar or root treatments with ¹⁴C-cyanazine. Five days following foliar ¹⁴C-cyanazine applicalion, fall panicum and green foxtail contained a larger number of water- and chloroform-soluble metabolites than corn, whereas, following root treatment, the opposite was true. Corn rapidly hydrolysed the nitrile group and hydroxylated the two-position on the triazine ring. Accumulation of the dealkylated cyanazine was evident in green foxtail, the most susceptible of the species studied. Metabolism of cyanazine supplied to the roots appeared to differ from foliar treatments in the weed species as more unchanged cyanazine was recovered. Rapid metabolism of cyanazine by corn roots provided evidence for an active cyanazine detoxication mechanism in the roots.     

Studies on competition between Setaria anceps and Eleusine indica

Experiments were conducted at Kairi. Queensland. Australia on the competitive effects or Eleusine indica (L.) Gaertn. on Setaria anceps Stapf. ev. Nandi. In one experiment S, anceps top dry weights and seed yields were reduced to a similar extent by 20, 40. 80 or 164 (unthinned) E. indica plants/m². Similarly, the dry matter yields from populations of 20–164 plants/m² of E. indica did not differ significantly. Varying the density of S. anceps from 6 to 9.3 plants/m² had little effect on the yield of either species. The mean production of E. indica seed was 1968 kg/ha or approximately 5.3 10⁹ seeds/ha. In two experiments where equal populations of both species were planted at varying times in relation to each other the above ground dry matter yield of S. anceps was not significantly affected when E. indica emerged 2 weeks or later than S. anceps. This was true whether the S. anceps was planted in rows or uniformly throughout the plot. Ina third, similar experiment S. anceps top dry matter was significantly reduced by 21% when the E. indica emerged 2 weeks after the crop. In a time of weeding experiment, removal of E. indica for the first 13 days after planting was sufficient to prevent a significant reduction in S. anceps top dry matter and seed yields. In this experiment the two species were shown to be mutually exclusive.     

Suspected Malignant Hyperthermia after Halothane Anesthesia in a Cat

A 6 month old domestic shorthaired cat died of suspected malignant hyperthermia. Anesthesia was induced and maintained with halothane vaporized in oxygen and nitrous oxide, after acepromazine premedication. Before an incision was made, the cat's heart rate dropped from 140 to 90 beats/min concomitant with a drop in blood pressure. Glycopyrrolate administration resulted in severe ventricular tachycardia (340 beats/min). Halothane and nitrous oxide were discontinued and the surgery was abandoned. Lidocaine administration resulted in a normal sinus rhythm. In recovery, the cat was tachypneic and struggling, with a rectal temperature of 40.1°C that quickly increased to 41.4°C. While the cat was being cooled, cardiac dysrhythmias progressed to ventricular fibrillation that was not responsive to cardiorespiratory resuscitation. Blood specimens obtained while the cat was being cooled showed hyperkalemia (10.0 mEq/L) and increased serum creatine kinase activity (780 IU/L). There was extreme extensor rigidity (rigor mortis) within 5 min of cardiac arrest. Results of microscopic and electron microscopic examination of muscle showed occasional perivascular infiltrates of lymphocytes with infrequent perimysial and epimysial neutrophils and a few sarcomeres with streaming of Z-bands (suggesting a contracted state). Histochemical evaluation of skeletal muscle showed no significant difference between type I and type II fibers.     

Ex Vivo Biomechanics of Kirschner-Ehmer External Skeletal Fixation Applied to Canine Tibiae

The purpose of this study was to determine the respective contribution of each of the following parameters to the compressive, bending, and torsional rigidity of the Kirschner-Ehmer (KE) external fixation splint as applied to canine tibiae with an osteotomy gap: bilateral versus unilateral splints; increasing the number of fixation pins; altering the diameter of fixation pins and side bars; decreasing side bar distances from the bone; increasing pin separation distances in each pin group; decreasing distances between pin groups; altering pin clamp orientation; and altering side bar conformation. Bilateral splints were 100% (mean) stiffer than unilateral splints, with stiffness enhanced to the greatest extent in mediolateral bending and torsion. Increasing pin numbers stiffened both bilateral (mean, 41%; 8 versus 4) and unilateral splints (mean, 14%; 8 versus 4). Medium KE splints were 85% (mean) stiffer than small KE splints. Decreasing side bar distances to the bone from 1.5 cm to 1.0 cm to 0.5 cm increased stiffness of both bilateral and unilateral splints by a mean of 13% to 35%. Widening pin spacing from 1.67 cm to 2.5 cm increased stiffness in craniocaudal bending only (56% increase, bilateral splints; 73% increase, unilateral splints). Decreasing the distance between pin groups from 5.84 cm to 2.5 cm increased stiffness in torsion between 23% (unilateral splints) and 45% (bilateral splints) and decreased stiffness of unilateral splints by 29% in craniocaudal bending. Altering pin clamp configuration so that the bolts of the clamp were inside the side bar rather than outside the side bar increased stiffness in axial compression only (73% increase, bilateral splints; 54% increase, unilateral splints). Conforming the lateral side bar to the tibiae increased only axial compressive stiffness by 77% but was no different than placing the clamps inside the side bars of an unconformed bilateral splint. These results quantify the relative importance of specific parameters affecting KE splint rigidity as applied to unstable fractures in the dog.     

The Effects of Cerclage Wiring on the Immature Canine Diaphysis A Biomechanical Analysis

When cerclage wiring is used in skeletally immature dogs, the wires become imbedded in the cortical bone due to radial appositional bone growth.
Six groups of five dogs each received one or two extraperiosteal cerclage wires at the mid-diaphysis of the left femur at the age of five months. Ten dogs were killed immediately, ten dogs were killed at eight weeks postoperatively, and ten at twelve weeks. Both femora from each animal were collected and subjected to torsional loading to failure within.5 seconds. The maximum torque, shear stress, energy absorption, angular deformation, and torsional stiffness were determined and subjected to í test analysis.
Application of the wires predictably caused an increase in weight and cortical bone thickening at the implant site, which was primarily due to endosteal bone deposition in the 8-and 12-week groups. The 8-and 12-week wired bones were stiffer and failed at a lower angular deformation than did their corresponding control femurs, but the zero-time bones did not show this tendency. Significantly less shear stress accumulation and energy absorption at failure were present In the 8-and 12-week implants, but no difference was seen in the zero-time femora. The 8-week groups showed a greater difference between the wired and control femurs than did the 12-week groups. No significant difference was found between one-and two-wire implants in the study.
The results indicate that confinement of dogs with clinically wired fractures of immature canine femurs should extend past eight weeks.