Universal rules for fragmentation of land by humans

The morphology of parcel patterns created by humans both in urban and rural areas is investigated. The parcel size distribution function, f(a), provides a criterion, that enables unambiguous classification of each piece of land as city core, suburbs, or rural area. The morphology of the rural area corresponds to a scale-free structure and follows a power-law distribution f(a) ~ a ⁻ⁿ of the parcel areas with the exponent n ≈ 1. In suburbs, the area distribution follows the log-normal distribution. In the city core, f(a) has an unimodal shape with an algebraically decaying tail, n = 2. Our study is based on data originating mainly from North America, the Hawaiian Islands, and Australia. For the regions analyzed, the characteristics of the parcel size distribution are universal and robust with respect to geographical, historical, and economical conditions accompanying development of a given area. The urbanization process can be described in terms of the changes of the morphology of the patterns of land fragmentation. In this formulation, the rural morphology, which can be thought as natural one because it exhibits a scale-free distribution of parcel sizes, is transformed into the artificial morphology developed in the city centers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effects of pubic symphysiodesis in dysplastic puppies

OBJECTIVE--To determine the long-term effects of juvenile pubic symphysiodesis (JPS) in dysplastic puppies. STUDY DESIGN--Prospective, randomized, clinical trial. ANIMALS--Seven dysplastic Chesapeake Bay retrievers and 2 beagle-crosses (BX1 and 2). METHODS--Five puppies had JPS performed with electrocauterization at 12, 16, 20, 22, and 24 weeks of age, respectively. Two puppies served as controls. BX1 and BX2 were used to obtain biopsies of the symphysis. Hips were evaluated for: pelvic development (transverse computerized tomography for acetabular angle [AA] and dorsal acetabular rim angle [DARA]); laxity [hip extended and stress radiography [distraction index (DI)]); Ortolani maneuver with reduction angles; acetabular coverage (Norberg angles); and function (coxofemoral range of motion, hip pain, and gait analysis by force-plate technique at 44 and 137 weeks of age). RESULTS--The pubis fused prematurely in every puppy that was operated on with the JPS technique. Greater acetabular responses were related to younger ages at surgery. The final mean AA in dogs that had JPS was 25 degrees greater than preoperative values; 40% increased over control. The DARA final mean was 10 degrees, 52% less than preoperative values and 46% less than control. The final mean DI in dogs having JPS was 0.28, 47% improved over preoperative values and 58% better than control. Mean pelvic dimensions in dogs that had JPS were 18% less than control. Gait analyses were normal for all dogs at 137 weeks. No urinary or bowel complications occurred. CONCLUSIONS--Significant ventrolateral acetabular rotation, increased hip coverage, diminished hip laxity, normal pain-free gait, and insignificantly reduced pelvic size occurred after JPS. CLINICAL SIGNIFICANCE--Dysplastic hips in young dogs were significantly improved by JPS.     

Quantification of Staphylococcus aureus adhesion to equine bone surfaces passivated with Plasmalyte and hyperimmune plasma

OBJECTIVE: To quantify the adhesion of Staphylococcus aureus to 4 equine bone surfaces passivated in a balanced polyionic solution (Plasmalyte) or hyperimmune equine plasma (Polymune plasma). STUDY DESIGN: In vitro comparative study. SAMPLE POPULATION: Third metacarpal bone (MC3) surface explants from 9 equine cadavers. METHODS: Approximately 1 cm(2) sections of periosteum were removed from MC3 and stapled to sterile stainless steel screens. Three bone surface explants were cut using a surgical saw to present 1 cm(2) surfaces of subperiosteal bone, cut cortical bone, or endosteum. Duplicate explants of each surface were immersed for 1 hour in Plasmalyte or hyperimmune equine plasma. Each explant was then placed in a well of a 6-well sterile tissue culture plate with the surface of interest exposed. Each surface was inoculated with approximately 100 colony-forming units of S. aureus in 10 microL of Mueller Hinton broth and incubated for 6 hours at 37 degrees C. After gentle rinsing to remove non-adherent bacteria, samples were sonicated for 5 minutes at 60 kHz to loosen adhered bacteria. The number of adherent bacteria was determined by serial dilutions and incubation of the sonicate. Scanning electron microscopy (SEM) was performed on samples identically treated from an additional horse to confirm bacterial removal by sonication from all surfaces and support quantitative culture results. RESULTS: Less S. aureus adhered to periosteum than to cortical bone, cut cortical bone, and endosteal surfaces, which were all similar. Exposure of all surfaces to hyperimmune plasma reduced S. aureus adherence compared with Plasmalyte exposure; SEM supported these conclusions. CONCLUSION: Less bacteria adhere to periosteum than other bone surfaces. Hyperimmune plasma reduces bacterial adhesion to all bone tissue surfaces. CLINICAL RELEVANCE: Understanding the factors that affect bacterial adhesion to bone will facilitate development of improved intraoperative lavage solutions to reduce the morbidity and mortality associated with postoperative infection.     

Electrostatic self-assembly of binary nanoparticle crystals with a diamond-like lattice

Self-assembly of charged, equally sized metal nanoparticles of two types (gold and silver) leads to the formation of large, sphalerite (diamond-like) crystals, in which each nanoparticle has four oppositely charged neighbors. Formation of these non-close-packed structures is a consequence of electrostatic effects specific to the nanoscale, where the thickness of the screening layer is commensurate with the dimensions of the assembling objects. Because of electrostatic stabilization of larger crystallizing particles by smaller ones, better-quality crystals can be obtained from more polydisperse nanoparticle solutions.     

Plastic and moldable metals by self-assembly of sticky nanoparticle aggregates

Deformable, spherical aggregates of metal nanoparticles connected by long-chain dithiol ligands self-assemble into nanostructured materials of macroscopic dimensions. These materials are plastic and moldable against arbitrarily shaped masters and can be thermally hardened into polycrystalline metal structures of controllable porosity. In addition, in both plastic and hardened states, the assemblies are electrically conductive and exhibit Ohmic characteristics down to approximately 20 volts per meter. The self-assembly method leading to such materials is applicable both to pure metals and to bimetallic structures of various elemental compositions.     

Canine pubic symphysiodesis: investigation of electrocautery dose response by histologic examination and temperature measurement

OBJECTIVES--To determine thermal necrosis zone and the maximal temperature achieved with various electrocautery doses applied to the pubic symphysis of immature dogs, and to establish the minimal electrocautery dose needed to affect thermal necrosis of the germinal chondrocytes of the immature canine pubis. STUDY DESIGN--A randomized, controlled, prospective study. ANIMALS--Twelve puppies, 15 to 17 weeks of age. METHODS--Each treated puppy was randomly selected to receive 3 of 33 possible doses of electrical current applied at uniform intervals along the pelvic symphysis. Three treatment sites were sham-operated controls. All treatment zones were biopsied 7 days after application of electrocautery. Confocal laser microscopy with calcein green and ethidium homodimer red stains were used to determine cell type and viability within treatment and control zones. The physeal diameter and thermal necrosis zone were measured. Thermal necrosis zone and dose, and temperature and dose were compared using regression analysis. Prediction equation analysis was used to establish dose recommendations. RESULTS--Doses of 40 W produced a highly significant linear relationship (R(2) =.88, P <.01) with thermal necrosis zone, and a significant linear relationship (R(2) =.76, P <.02) with maximal temperature. CONCLUSIONS--The thermal necrosis zone within the pelvic symphysis and maximal temperature achieved can be reliably predicted using electrocautery doses of 40 W. For application of electrocautery to induce pubic symphysiodesis, doses should be chosen based on measured or estimated physeal size. Using prediction equation analysis, the surgeon can plan mean thermal necrosis zone with acceptable variance. CLINICAL RELEVANCE--Unipolar needle electrocautery can be used to reliably achieve symphyseal necrosis. Prediction equation analysis can be used to determine 40-W doses.     

Pharmacokinetics of ceftazidime in dogs following subcutaneous administration and continuous infusion and the association with in vitro susceptibility of Pseudomonas aeruginosa

OBJECTIVE: To determine the pharmacokinetics of ceftazidime following subcutaneous administration and continuous IV infusion to healthy dogs and to determine the minimum inhibitory concentration (MIC) of ceftazidime for clinical isolates of Pseudomonas aeruginosa. ANIMALS: 10 healthy adult dogs. PROCEDURE: MIC of ceftazidime for 101 clinical isolates of P aeruginosa was determined in vitro. Serum concentrations of ceftazidime were determined following subcutaneous administration of ceftazidime (30 mg/kg of body weight) to 5 dogs and continuous IV infusion of ceftazidime (loading dose, 4.4 mg/kg; infusion rate, 4.1 mg/kg/h) for 36 hours to 5 dogs. RESULTS: The MIC of ceftazidime for P aeruginosa was < or = 8 microg/ml; all isolates were considered susceptible. Following SC administration of ceftazidime, mean beta disappearance half-life was 0.8 hours, and mean serum ceftazidime concentration exceeded the MIC for P aeruginosa for only 4.3 hours. Two dogs had gastrointestinal tract effects. Mean serum ceftazidime concentration exceeded 16 microg/ml during continuous IV infusion. None of the dogs developed adverse effects. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of ceftazidime subcutaneously (30 mg/kg, q 4 h) or as a constant IV infusion (loading dose, 4.4 mg/kg; rate, 4.1 mg/kg/h) would maintain serum ceftazidime concentrations above the MIC determined for 101 clinical isolates of P aeruginosa. Use of these dosages may be appropriate for treatment of dogs with infections caused by P aeruginosa.     

COMPARISON OF TWO PALPATION, FOUR RADIOGRAPHIC AND THREE ULTRASOUND METHODS FOR EARLY DETECTION OF MILD TO MODERATE CANINE HIP DYSPLASIA

Hip joint laxity was evaluated in Golden Retriever (n = 60), Labrador Retriever (n = 23), and Labrador/Golden Retriever mix (n = 24) puppies. Ortolani and Bardens maneuvers, four radiographic measurement indices and three dynamic ultrasonographic measurements were used. Each puppy was evaluated twice; at 6.5 to 9 and 43 to 79 weeks of age. These nine methods were compared for accuracy in predicting the development of canine hip dysplasia with or without degenerative joint disease by a median age of 16 months. The Bardens maneuver was a significant predictor of canine hip dysplasia/+/-degenerative joint disease for Golden Retriever puppies, however, it was not a reliable predictor for the other two breeds. Norberg angle measurements taken with femurs in a neutral position with hips distracted (PennHip position) was a significant predictor of degenerative joint disease in two breeds, but not in Golden Retriever puppies. Ultrasound measurement was a reliable predictor of hip canine hip dysplasia/+/-degenerative joint disease for Labrador/Golden Retriever mix puppies, but was not reliable for the other two breeds. Palpation, radiographic, and ultrasonographic methods of evaluating hip joint laxity in puppies at 6.5 to 9 weeks of age were not consistently reliable for all three breeds in predicting hip dysplasia with or without degenerative joint disease at one year of age. A strong association was found between Norberg angle and degenerative joint disease occurrence, as well as between distraction index (PennHip) and degenerative joint disease occurrence when measured at 52 to 79 weeks of age, but not when measured at 6.5 to 9 weeks of age in these breeds. These results emphasize the difficulty of early detection of mild hip dysplasia in the dog.     

Juvenile pubic symphysiodesis in dysplastic puppies at 15 and 20 weeks of age

OBJECTIVE: To examine the effects of juvenile pubic symphysiodesis (JPS) on hip joint conformation, hip laxity, gait, and the development of degenerative joint disease (DJD) in dysplastic puppies operated at 15 and 20 weeks of age. STUDY DESIGN: Randomized controlled prospective study. ANIMALS-Eighteen female hound puppies with increased hip laxity. METHODS: Puppies were randomized to 1 of 4 treatment groups: JPS at 15 weeks of age (n = 6), sham-operated control at 15 weeks of age (n = 3), JPS at 20 weeks of age (n = 6), and sham-operated control at 20 weeks of age (n = 3). Hip extension with pain scoring, Ortolani palpation, hip reduction angle measurement (HRA), PennHIP radiography (University of Pennsylvania) with measurement of distraction index, Norberg angle measurement, and transverse computed tomographic imaging to measure acetabular angle (AA) and dorsal acetabular rim angle (DARA), were tested preoperatively, and at 1 and 2 years of age. RESULTS: JPS resulted in significant changes in AA, HRA, DARA, and conversion to Ortolani negative status. Larger and more rapid changes in hip conformation were seen when surgery was performed at 15 weeks of age. No significant changes were identified in control dogs. Twenty-five percent of JPS dogs developed DJD whereas 83% of control dogs developed DJD. CONCLUSIONS: JPS resulted in significant improvements in hip joint conformation and hip laxity in dysplastic puppies treated at 15 and 20 weeks of age. Improvements in conformation were significantly greater when surgery was performed at 15 weeks of age. CLINICAL RELEVANCE: JPS appears to be a promising treatment for hip dysplasia and is a safe and technically simple procedure to perform.