Explaining urban economic growth through cluster complementarity

Economic development strategies centered on the presence of industry clusters have become quite popular with local policy makers. With this in mind, we test whether or not the degree of cluster complementarity in a given urban area does in fact lead to it having a persistent economic advantage over its peers. Using a spatial factor model built on growth accounting principles, we show that this is indeed the case by identifying key agglomeration factors influencing urban growth. However, our results suggest substantial heterogeneity exists in the types of policies that are likely to best support local economies based on their cluster complementarity.     

Interdependence of cell growth and gene expression: origins and consequences

In bacteria, the rate of cell proliferation and the level of gene expression are intimately intertwined. Elucidating these relations is important both for understanding the physiological functions of endogenous genetic circuits and for designing robust synthetic systems. We describe a phenomenological study that reveals intrinsic constraints governing the allocation of resources toward protein synthesis and other aspects of cell growth. A theory incorporating these constraints can accurately predict how cell proliferation and gene expression affect one another, quantitatively accounting for the effect of translation-inhibiting antibiotics on gene expression and the effect of gratuitous protein expression on cell growth. The use of such empirical relations, analogous to phenomenological laws, may facilitate our understanding and manipulation of complex biological systems before underlying regulatory circuits are elucidated.     

Pros and cons of eliminating veld burning

Fire has been a factor of the environment in Africa since time immemorial and it is often caused by natural agencies such as lightning. It is maintained that there is much prejudice against veld burning, often ill‐founded. Fire has caused and maintained most of the world's grassland. When fire has been prevented plant succession has resulted in bush encroachment in the savanna and surrounding areas or in fynbos encroachment in others. Fire results in much old grass being wasted but, if this is not removed in some manner, the grazing deteriorates. Old grass can be removed by fire, mowing or grazing, using high protein supplements. The consequences of the different methods of removal, other than mowing, may be equally deleterious.     

Scientifiques Sans Frontières Australia Providing Environmental Science Support to Local Communities in Rehabilitation of Waterways

Water, Air, & Soil Pollution -     

Structures of the bacterial ribosome in classical and hybrid states of tRNA binding

During protein synthesis, the ribosome controls the movement of tRNA and mRNA by means of large-scale structural rearrangements. We describe structures of the intact bacterial ribosome from Escherichia coli that reveal how the ribosome binds tRNA in two functionally distinct states, determined to a resolution of ~3.2 angstroms by means of x-ray crystallography. One state positions tRNA in the peptidyl-tRNA binding site. The second, a fully rotated state, is stabilized by ribosome recycling factor and binds tRNA in a highly bent conformation in a hybrid peptidyl/exit site. The structures help to explain how the ratchet-like motion of the two ribosomal subunits contributes to the mechanisms of translocation, termination, and ribosome recycling.     

Validation of a structured questionnaire as an instrument to measure chronic pain in dogs on the basis of effects on health-related quality of life

OBJECTIVE: To validate the use of a novel questionnaire as an instrument for measurement of chronic pain in dogs through its impact on health-related quality of life (HRQL). ANIMALS: 108 dogs with chronic degenerative joint disease and 26 healthy dogs. PROCEDURES: Questionnaire responses were subjected to factor analysis (FA) and questionnaire scores to discriminant analysis to evaluate construct validity. Questionnaire scores were used to explore the potential of this instrument for minimizing respondent bias and for evaluative purposes. RESULTS: FA results revealed a sensible factor structure accounting for 65% of the variance in data, with factors identifiable as domains of HRQL in dogs affected by chronic pain. Further evidence for construct validity was provided when questionnaire scores were used to discriminate, on the basis of 218 questionnaires, between dogs with clinician-awarded pain scores of 0 and dogs with pain scores >or= 1 (88% discrimination, with 95% of no-pain group dogs and 87% of some-pain group dogs correctly categorized). Use of the questionnaire provided minimized respondent bias. CONCLUSIONS AND CLINICAL RELEVANCE: Validation of the questionnaire as an instrument for discriminative and evaluative measurements of orthopedic chronic pain through its impact on HRQL in dogs was provided. Use of the questionnaire, with further testing and refinement, may support improved clinical decision making, facilitate development of evidence-based therapeutic options for chronic diseases, and help veterinarians and owners define humane end points in dogs. IMPACT FOR HUMAN MEDICINE: Information gained here may provide improved measurements of clinical change in animal studies that use dogs with naturally occurring chronic pain to evaluate novel human treatment protocols.     

Evaluation of clinical characteristics, diagnostic test results, and outcome in horses with internal infection caused by Corynebacterium pseudotuberculosis: 30 cases (1995-2003)

OBJECTIVE: To determine clinical signs, results of diagnostic testing, and outcome in horses with internal Corynebacterium pseudotuberculosis infection. DESIGN: Retrospective study. ANIMALS: 30 horses. PROCEDURE: Information pertaining to clinical data, results of diagnostic tests, and costs of hospitalization and treatment was extracted from medical records of affected horses. RESULTS: Internal C. pseudotuberculosis infection was diagnosed on the basis of clinical signs, diagnostic imaging, and clinicopathologic data, including results of serologic tests and bacterial culture. The most common clinical signs were concurrent external abscesses, anorexia, fever, lethargy, weight loss, and signs of respiratory tract disease or abdominal pain. Clinicopathologic abnormalities included a geometric mean reciprocal serum synergistic hemolysin inhibition titer > or = 512, leukocytosis with neutrophilia, hyperglobulinemia, hyperfibrinogenemia, and anemia. Specific organ involvement was diagnosed in 27 of 30 horses. Affected organs included the liver (18 horses), lungs (12), kidneys (7), and spleen (3); multiple organs were affected in 10 horses. Treatment with antimicrobials for a median of 36 days (range, 7 to 97 days) was usually successful, yielding an overall survival rate of 71%. CONCLUSIONS AND CLINICAL RELEVANCE: Early diagnosis and long-term antimicrobial treatment were important for a successful outcome in horses with internal C. pseudotuberculosis infection. Ultrasonographic imaging was an important technique for identifying specific organs affected, aiding in obtaining samples for a definitive diagnosis, and monitoring response to treatment. Pregnant mares with internal infections are at risk for fetal loss. Preexisting chronic organ disease may be associated with a poor prognosis.     

Evaluation of the success of medical management for presumptive thoracolumbar intervertebral disk herniation in dogs

Objective— To determine the success of medical management of presumptive thoracolumbar disk herniation in dogs and the variables associated with treatment outcome.
Study Design— Retrospective case series.
Animals— Dogs (n=223) with presumptive thoracolumbar disk herniation.
Methods— Medical records from 2 clinics were used to identify affected dogs, and owners were mailed a questionnaire about success of therapy, recurrence of clinical signs, and quality of life (QOL) as interpreted by the owner. Signalment, duration and degree of neurologic dysfunction, and medication administration were determined from medical records.
Results— Eighty-three percent of dogs (185/223) were ambulatory at initial evaluation. Successful treatment was reported for 54.7% of dogs, with 30.9% having recurrence of clinical signs and 14.4% classified as therapeutic failures. From bivariable logistic regression, glucocorticoid administration was negatively associated with success ( P =.008; odds ratio [OR]=.48) and QOL scores ( P =.004; OR=.48). The duration of cage rest was not significantly associated with success or QOL. Nonambulatory dogs were more likely to have lower QOL scores ( P =.01; OR=2.34).
Conclusions— Medical management can lead to an acceptable outcome in many dogs with presumptive thoracolumbar disk herniation. Cage rest duration does not seem to affect outcome and glucocorticoids may negatively impact success and QOL. The conclusions in this report should be interpreted cautiously because of the retrospective data collection and the use of client self-administered questionnaire follow-up.
Clinical Relevance— These results provide an insight into the success of medical management for presumptive thoracolumbar disk herniation in dogs and may allow for refinement of treatment protocols.