Dry-jet wet spinning of polyhydroxyamide fibers     

Seung Koo Park  Seo Hyun Cho  Richard John Farris 《Fibers and Polymers》2000,1(2):92-96

A high molecular weight polyhydroxyamide (PHA) solution in N, N-dimethyl acetamide (DMAc) was prepared from 3,3′-dihydroxybenzidine and isophthalic chloride (IPC), which was used for spinning PHA fiber. Before spinning, the diffusion property of DMAc into various coagulants was examined. The fiber was well formed in coagulants such as water/ethanol with a composition of 5/5, ethanol, and ethanol/isopropanol with a composition of 7/3 and 5/5. However, the PHA fiber spun in the water/ethanol mixture contained voids. After the fiber spun in ethanol was annealed at over 350°C, the ultimate stress and initial modulus of the fiber increased from 75.5 MPa and 3.22 GPa to 369 MPa and 29.5 GPa, respectively. These properties of the PHA fiber spun by the dry spinning method were also enhanced, attaining 154 MPa and 5.56 Gpa, respectively.  相似文献   

The Economics of Agriculture in the Maricopa-Stanfield Irrigation and Drainage District in Central Arizona     

Paul N. Wilson  Richard D. Gibson 《Irrigation and Drainage Systems》2000,14(1-2):121-138

The economic performance of a Central Arizona Projectirrigation district is determined by the economiccondition of the growers the district serves and theunderlying financial structure of the district. Inthe case of the Maricopa-Stanfield Irrigation andDrainage District, adverse economic conditions in theagricultural sector and a high debt obligationrelative to water sales called into question thefinancial sustainability of the district. Districtmanagement took positive steps, like the ManagementImprovement Program (MIP) and departmentrestructuring, to improve the economic performance ofthe water delivery system. These actions relied onthe shared understanding of the waterinterdependencies between agricultural and urban userswhich was obtained through the Diagnostic Analysis ofthe MIP.  相似文献   

The palaeoecological approach to reconstructing former grazing–vegetation interactions     

Richard Bradshaw  Fraser J. G. Mitchell   《Forest Ecology and Management》1999,120(1-3):3-12

Interactions between grazing animals and vegetation are assessed from three temporal perspectives: millions, thousands and hundreds of years. Data abundance and quality are highest for recent time periods, but geological data provide a background to the understanding of present-day grazing–vegetation interactions. The Quaternary glaciations and recent anthropogenic influences have contributed to the loss of European mega-herbivores. The geological record from the Eemian interglacial in Denmark suggests that presence of elephant and rhinoceros did not create widespread openings in forest cover. Large populations of giant deer in Ireland became extinct 11 000 years ago. We propose a theory that the giant deer were sufficiently abundant to convert juniper scrub communities into open grassland at a regional scale. The balance between grazers and browsers has undergone continuous change during the last 10 000 years with significant consequences for forest composition and structure. Hunting statistics and archival records permit crude reconstructions of population dynamics for certain ungulate species. High resolution pollen analysis and long-term monitoring generate reconstructions of vegetation that can be compared with fluctuating grazing pressure during the last few hundred years. Such data can be used to validate simulation models of grazing–vegetation interactions.  相似文献   

PALLIATIVE RADIOTHERAPY OF APPENDICULAR OSTEOSARCOMA IN 95 DOGS     

Oscar  Ramirez  III  DVM  Richard K.  Dodge  MS  Rodney L.  Page  DVM  MS  G. Sylvester  Price  DVM  PhD  Marlene L.  Hauck  DVM  PhD  Tracy A.  Ladue  DVM Felicia  Nutter  DVM  Donald E.  Thrall  DVM  PhD 《Veterinary radiology & ultrasound》1999,40(5):517-522

Ninety-five dogs with either a presumptive (n = 24) or biopsy confirmed diagnosis (n = 71) of osteosarcoma received palliative radiotherapy using 60Co photons. Parallel opposed beams were used with each dog receiving either 10 Gy on days 0, 7 and 21 (n = 58) or 8 Gy on days 0 and 7 (n = 37). The 8 Gy fractionation scheme was given with the intent of retreating upon relapse from pain relief. Only 9 of 37 (24%) dogs in the 8 Gy group returned for retreatment. Forty-seven of the 95 dogs (49%) received concurrent or sequential chemotherapy. Seventy of the 95 dogs (74%) experienced pain relief following treatment. In dogs experiencing pain relief the median duration of response was 73 days. Numerous clinical variables were evaluated as predictors of response. The only variable significantly related to achieving a response was the use of chemotherapy. The following variables were significantly related to the duration of response: extent of bone lysis, chemotherapy use, length of bone involved and tumor site (humerus). In a multivariate analysis (n = 73 dogs), after adjusting for chemotherapy use, extent of bone involvement (p = 0.01) and tumor site (p = 0.02) retained statistical significance, while degree of bone lysis did not (p = 0.11). No difference in response incidence or duration was found between 3 fractions of 10 Gy vs. 2 fractions of 8 Gy. Administration of a low initial dose with the intent of retreatment was not a successful strategy.  相似文献   

REVERSIBLE MAGNETIC RESONANCE IMAGING ABNORMALITIES IN DOGS FOLLOWING SEIZURES     

Linda M.  Mellema  DVM  Philip D.  Koblik  DVM  MS  Gregg D.  Kortz  DVM  Richard A.  Lecouteur  BVSc  PhD  Melissa A.  Chechowitz  DVM  Peter J.  Dickinson  BVSc 《Veterinary radiology & ultrasound》1999,40(6):588-595

Reversible magnetic resonance (MR) imaging lesions have been described in humans following seizures. This condition has not yet been reported in animals. This paper describes reversible abnormalities identified in 3 dogs using MR imaging that was performed initially within 14 days of the last seizure and follow-up imaging that was performed after 10 to 16 weeks of anticonvulsant therapy. All three dogs had lesions in the piriform/temporal lobes, characterized by varying degrees of hyperintensity on T2-weighted images and hypointensity on T1-weighted images. In one dog, contrast enhancement was evident. On reevaluation, partial resolution occurred in all 3 dogs. In a fourth animal with an olfactory meningioma, similar appearing lesions in the temporal cortex and right and left piriform lobes were identified after seizure activity. A surgical biopsy of the temporal cortex and hippocampus was performed and edema, neovascularization, reactive astrocytosis, and acute neuronal necrosis were evident. These histologic findings are similar to those reported in humans with seizures. Recognizing the potential occurrence of reversible abnormalities in MR images is important in developing a diagnostic and therapeutic plan in canine patients with seizures. Repeat imaging after seizure control may help differentiate between seizure-induced changes and primary multifocal parenchymal abnormalities.  相似文献   

The Efficacy of Mechanical Abrasion and Talc Slurry as Methods of Pleurodesis in Normal Dogs     

Richard M. Jerram  BVSc  MRCVS    Theresa W. Fossum  DVM  MS  PhD  Diplomate ACVS    Brian R. Berridge  DVM  PhD    Dan N. Steinheimer  DVM  MS  Diplomate ACVR    Margaret R. Slater  DVM  PhD 《Veterinary surgery : VS》1999,28(5):322-332

OBJECTIVE: To determine the efficacy of mechanical abrasion and talc slurry as methods for pleurodesis in normal dogs. STUDY DESIGN: Experimental study. ANIMALS OR SAMPLE POPULATION: Ten normal beagle dogs. METHODS: Group I dogs had mechanical abrasion (MA) of the pulmonary and costal pleurae performed in one hemithorax with a dry gauze sponge with a median sternotomy approach. Group II dogs had 100 mL of a 1 g talc slurry (TS) administered into one hemithorax through a tube thoracostomy. Administration of the TS was visualized by using video thoracoscopy. All dogs were evaluated at 2, 10, 20, and 30 days postoperatively by means of thoracic radiography and ultrasonographic thoracic wall measurement. The dogs were euthanatized 30 days postoperatively and a gross necropsy was performed. Hemithoraces were assigned a pleurodesis score (0-4) and an obliteration grade (0-6). Tissues were collected for histopathologic examination of pulmonary pleura, costal pleura, and pleural adhesions. Pulmonary and costal pleurae were graded for the degree of fibrosis (0-4). RESULTS: Obliteration grade and costal pleural fibrosis score were significantly higher for the treated sides in the MA dogs compared with the TS dogs. MA Dogs: Mechanical abrasion dogs had pleurodesis, obliteration, and pleural fibrosis scores that were greater on the treated side than the untreated side, however, the differences were not statistically significant. Only two MA dogs had firm adhesion of the pulmonary pleura to the costal pleura in portions of the cranial and middle lung lobes in the treated hemithorax. Thoracic wall surface area covered with adhesions was 15% and 21% in each of these two dogs. The median pulmonary pleural fibrosis score of all MA dogs for the treated hemithorax was 3 compared to 0 on the untreated side. TS Dogs: There was no statistical difference for pleurodesis scores and obliteration grades between the treated and untreated sides. No dogs showed evidence of pulmonary to costal pleural adhesions. Histopathology showed talc crossover into the untreated side in all five dogs. Median pulmonary fibrosis score of the treated hemithorax was 1 compared with 0 on the untreated side. CONCLUSIONS: Neither method of pleurodesis produced sufficient pleural adhesions to obliterate the pleural space. It is possible that the degree of pulmonary pleural fibrosis present in MA dogs may be sufficient to limit air leakage from pulmonary blebs and bullae resulting in successful treatment of spontaneous pneumothorax.  相似文献   

A Model of Tax Increment Financing Adoption Incentives     

Richard F. Dye  Jeffrey O. Sundberg 《Growth and change》1998,29(1):90-110

With tax increment financing (TIF) a municipality pays for economic development expenditures out of future increases in tax collections. If the development expenditures are the sole cause of the increased tax collections, TIF is a fair and reasonable policy. If not, TIF can distort choices and redistribute resources. This paper develops an economic model of TIF as a choice by the sponsoring municipality with an impact on an overlying government. The analytic framework isolates the impact of key variables, permits analysis of the payoff from TIF to each government, and helps inform discussions about equity. The model clearly shows that while the special nature of TIF causes it to favor projects that generate significant tax revenue, that revenue need not be truly incremental with respect to the project alone, and projects therefore need not be efficient to be financially viable to municipalities. In fact, the projects that best fit the goals of TIF legislation may be impossible to finance through TIF. Alternative government programs may be required to help towns develop areas most in need.  相似文献   

Nitrogen fertilization value of compost and dried dung in soils with contrasting synthetic nitrogen fertilization histories     

Adam D. Langworthy  Ross Corkrey  Richard P. Rawnsley  Pieter J. M. Raedts  James L. Hills 《Grass and Forage Science》2023,78(1):184-193

If the production of forage for dairy cattle is to become less reliant on synthetic nitrogen (N) fertilizers, there is need to better understand and account for the N contributed by on-farm and imported organic amendments. A 254-day aerobic soil incubation study (typical length of a growing season in many temperate dairying regions) quantified the inorganic (mineral) N supply from a commercial compost and dried bovine dung (i.e., on-farm effluent solids). Amendments were incubated in soils with contrasting synthetic N fertilization histories (i.e., 70–100 vs. 350–400 kg N/ha per year) to evaluate if higher synthetic N fertilization histories would reduce the lag time that often exists between organic amendment application and significant release of inorganic N for plant uptake. This proposition was based on previous research, which showed greater soil inorganic N availability accelerating organic amendment decomposition. Our experiment did find that the release of inorganic N from evaluated organic amendments was greater in soils with higher synthetic N fertilization histories, but that this effect was not apparent until after the first 6-months of this 9-month experiment. Despite this finding, soils with contrasting synthetic N fertilization histories were not found to differ in their initial inorganic N content, nor microbial activity or other physiochemical properties known to affect N mineralization. Our study highlighted the long-term vision needed when transitioning from synthetic N fertilizers to organic amendments, with most of the N present in the compost and dried dung remaining unavailable for forage production (i.e., remained bound in organic carbon-based molecules).  相似文献   

Influence of Green Seaweed (Ulva rigida) Supplementation on the Quality and Shelf Life of Atlantic Salmon Fillets     

Natasha C. Moroney  Alex H. L. Wan  Anna Soler-Vila  Michael N. O’Grady  Richard D. FitzGerald  Mark P. Johnson 《Journal Of Aquatic Food Product Technology》2017,26(10):1175-1188

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Monitoring and modelling total phosphorus contributions to a freshwater lake with cage‐aquaculture          下载免费PDF全文

Jacquiline E Milne  Christopher H Marvin  Ram Yerubandi  Kevin McCann  Richard D Moccia 《Aquaculture Research》2017,48(1):283-297

A mass‐balance modelling approach combined with a sensitivity analysis was utilized to gain an improved understanding of the relative contributions of phosphorus (P) loading from various anthropogenic and non‐anthropogenic sources into Lake Wolsey (Manitoulin Island, Ontario, Canada), a Type 2 freshwater lake with a cage‐aquaculture facility. Total P loadings were estimated from eight sources (inlet exchange, non‐point sources, cage‐aquaculture facility, internal loading, groundwater seepage, atmospheric deposition, leaf litter and dwellings) and three sinks (outlet exchange, sedimentation and sportfishing). Results indicated that over the study period (May–November 2007) the non‐point sources were the leading contributor of total P to Lake Wolsey (1120 kg P) followed by the cage‐aquaculture facility loading (915 kg P), inlet exchange (539 kg P), groundwater inputs (305 kg P), dwellings (219 kg P), internal P recycling loads from the hypoxic hypolimnion (186 kg P), atmospheric deposition (79 kg P) and decomposing leaf litter (8.1 kg P). When comparing the loadings in this study, the sensitivity analysis showed that non‐point sources were the only significant input parameter of total P loading to the in‐lake concentrations of P in Lake Wolsey(P = 0.05). Information from this project will provide water quality managers with sound scientific information to make defencible decisions pertaining to policy and regulatory approaches for water quality risk assessment and management of cage‐aquaculture in Type 2 sites.  相似文献