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Comparing linkage designs based on land facets to linkage designs based on focal species.

ABSTRACT: Least-cost modeling for focal species is the most widely used method for designing conservation corridors and linkages. However, these designs depend on today's land covers, which will be altered by climate change. We recently proposed an alternative approach based on land facets (recurring landscape units of relatively uniform topography and soils). The rationale is that corridors with high continuity of individual land facets will facilitate movement of species associated with each facet today and in the future. Conservation practitioners might like to know whether a linkage design based on land facets is likely to provide continuity of modeled breeding habitat for species needing connectivity today, and whether a linkage for focal species provides continuity and interspersion of land facets. To address these questions, we compared linkages designed for focal species and land facets in three landscapes in Arizona, USA. We used two variables to measure linkage utility, namely distances between patches of modeled breeding habitat for 5-16 focal species in each linkage, and resistance profiles for focal species and land facets between patches connected by the linkage. Compared to focal species designs, linkage designs based on land facets provided as much or more modeled habitat connectivity for 25 of 28 species-landscape combinations, failing only for the three species with the most narrowly distributed habitat. Compared to land facets designs, focal species linkages provided lower connectivity for about half the land facets in two landscapes. In areas where a focal species approach to linkage design is not possible, our results suggest that conservation practitioners may be able to implement a land facets approach with some confidence that the linkage design would serve most potential focal species. In areas where focal species designs are possible, we recommend using the land facet approach to complement, rather than replace, focal species approaches.

SUBMITTER: Brost BM

PROVIDER: S-EPMC3495916 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The aim of this study was to analyze the genomic homology between cattle (Bos taurus) and buffaloes (Bubalus bubalis) and to propose a rearrangement of the buffalo genome through linkage disequilibrium analyses of buffalo SNP markers referenced in the cattle genome assembly and also compare it to the buffalo genome assembly. A panel of bovine SNPs (single nucleotide polymorphisms) was used for hierarchical, non-hierarchical and admixture cluster analyses. Thus, the linkage disequilibrium information between markers of a specific panel of buffalo was used to infer chromosomal rearrangement. Haplotype diversity and imputation accuracy of the submetacentric chromosomes were also analyzed. The genomic homology between the species enabled us to use the bovine genome assembly to recreate a buffalo genomic reference by rearranging the submetacentric chromosomes. The centromere of the submetacentric chromosomes exhibited high linkage disequilibrium and low haplotype diversity. It allowed hypothesizing about chromosome evolution. It indicated that buffalo submetacentric chromosomes are a centric fusion of ancestral acrocentric chromosomes. The chronology of fusions was also suggested. Moreover, a linear regression between buffalo and cattle rearranged assembly and the imputation accuracy indicated that the rearrangement of the chromosomes was adequate. When using the bovine reference genome assembly, the rearrangement of the buffalo submetacentric chromosomes could be done by SNP BTA (chromosome of Bos taurus) calculations: shorter BTA (shorter arm of buffalo chromosome) was given as [(shorter BTA length - SNP position in shorter BTA)] and larger BTA length as [shorter BTA length + (larger BTA length - SNP position in larger BTA)]. Finally, the proposed linkage disequilibrium-based method can be applied to elucidate other chromosomal rearrangement events in other species with the possibility of better understanding the evolutionary relationship between their genomes.

Project description:BackgroundIntervertebral disc nucleus degeneration initiates a degenerative cascade and can induce chronic low back pain. Nucleus replacement aims to replace the nucleus while the annulus is still intact. Over time, several designs have been introduced, but the definitive solution continues to be elusive. Therefore, we aimed to create a new nucleus replacement that replicates intact intervertebral disc biomechanics, and thus has the potential for clinical applications.Materials and methodsTwo implants with an outer ring and one (D2) with an additional midline strut were compared. Static and fatigue tests were performed with an INSTRON 8874 following the American Society for Testing and Materials F2267-04, F2346-05, 2077-03, D2990-01, and WK4863. Implant stiffness was analyzed at 0-300 N, 500-2000 N, and 2000-6000 N and implant compression at 300 N, 1000 N, 2000 N, and 6000 N. Wear tests were performed following ISO 18192-1:2008 and 18192-2:2010. GNU Octave software was used to calculate movement angles and parameters. The statistical analysis package R was used with the Deducer user interface. Statistically significant differences between the two designs were analyzed with ANOVA, followed by a post hoc analysis.ResultsD1 had better behavior in unconfined compression tests, while D2 showed a "jump." D2 deformed 1 mm more than D1. Sterilized implants were more rigid and deformed less. Both designs showed similar behavior under confined compression and when adding shear. A silicone annulus minimized differences between the designs. Wear under compression fatigue was negligible for D1 but permanent for D2. D1 suffered permanent height deformation but kept its width. D2 suffered less height loss than D1 but underwent a permanent width deformation. Both designs showed excellent responses to compression fatigue with no breaks, cracks, or delamination. At 10 million cycles, D2 showed 3-times higher wear than D1. D1 had better and more homogeneous behavior, and its wear was relatively low. It showed good mechanical endurance under dynamic loading conditions, with excellent response to axial compression fatigue loading without functional failure after long-term testing.ConclusionD1 performed better than D2. Further studies in cadaveric specimens, and eventually in a clinical setting, are recommended. Level of evidence 2c.

Project description:Linkage of medical databases, including insurer claims and electronic health records (EHRs), is increasingly common. However, few studies have investigated the behavior and output of linkage software. To determine how linkage quality is affected by different algorithms, blocking variables, methods for string matching and weight determination, and decision rules, we compared the performance of 4 nonproprietary linkage software packages linking patient identifiers from noninteroperable inpatient and outpatient EHRs. We linked datasets using first and last name, gender, and date of birth (DOB). We evaluated DOB and year of birth (YOB) as blocking variables and used exact and inexact matching methods. We compared the weights assigned to record pairs and evaluated how matching weights corresponded to a gold standard, medical record number. Deduplicated datasets contained 69,523 inpatient and 176,154 outpatient records, respectively. Linkage runs blocking on DOB produced weights ranging in number from 8 for exact matching to 64,273 for inexact matching. Linkage runs blocking on YOB produced 8 to 916,806 weights. Exact matching matched record pairs with identical test characteristics (sensitivity 90.48%, specificity 99.78%) for the highest ranked group, but algorithms differentially prioritized certain variables. Inexact matching behaved more variably, leading to dramatic differences in sensitivity (range 0.04-93.36%) and positive predictive value (PPV) (range 86.67-97.35%), even for the most highly ranked record pairs. Blocking on DOB led to higher PPV of highly ranked record pairs. An ensemble approach based on averaging scaled matching weights led to modestly improved accuracy. In summary, we found few differences in the rankings of record pairs with the highest matching weights across 4 linkage packages. Performance was more consistent for exact string matching than for inexact string matching. Most methods and software packages performed similarly when comparing matching accuracy with the gold standard. In some settings, an ensemble matching approach may outperform individual linkage algorithms.

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Comparing linkage designs based on land facets to linkage designs based on focal species.

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