Abnormal ground reaction forces lead to a general decline in gait speed in knee osteoarthritis patients

AIM To analyse ground reaction forces at higher speeds using another method to be more sensitive in assessing significant gait abnormalities. METHODS A total of 44 subjects, consisting of 24 knee osteoarthritis(OA) patients and 20 healthy controls were analysed. The knee OA patients were recruited from an orthopaedic clinic that were awaiting knee replacement. All subjects had their gait patterns during stance phase at top walking speed assessed on a validated treadmill instrumented with tandem force plates. Temporal measurements and ground reaction forces(GRFs) along with a novel impulse technique were collected for both limbs and a symmetry ratio was applied to all variables to assess inter-limb asymmetry. All continuous variables for each group were compared using a student t-test and χ2 analysis for categorical variables with significance set at α = 0.05. Receiver operator characteristics curves were utilised to determine best discriminating ability.RESULTS The knee OA patients were older(66 ± 7 years vs 53 ± 9 years, P = 0.01) and heavier(body mass index: 31 ± 6 vs 23 ± 7, P < 0.001) but had a similar gender ratio when compared to the control group. Knee OA patients were predictably slower at top walking speed(1.37 ± 0.23 m/s vs 2.00 ± 0.20 m/s, P < 0.0001) with shorter mean step length(79 ± 12 cm vs 99 ± 8 cm, P < 0.0001) and broader gait width(14 ± 5 cm vs 11 ± 3 cm, P = 0.015) than controls without any known lower-limb joint disease. At a matched mean speed(1.37 ± 0.23 vs 1.34 ± 0.07), ground reaction results revealed that pushoff forces and impulse were significantly(P < 0.0001) worse(18% and 12% respectively) for the knee OA patients when compared to the controls. Receiver operating characteristic curves analysis demonstrated total impulse to be the best discriminator of asymmetry, with an area under the curve of 0.902, with a cut-off of-3% and a specificity of 95% and sensitivity of 88%.CONCLUSION Abnormal GRFs in knee osteoarthritis are clearly evident at higher speeds. Analysing GRFs with another method may explain the general decline in knee OA patient's gait.

Predictors of dominance rank and agonistic interactions in captive Livingstone's fruit bats

Male dominance hierarchies have been studied in many animals but rarely in bats(Chiroptera).The dominance rank of social animals may dictate access to resources and mates;therefore,it has important implications for an individual's fitness and is crucial for successful captive man-agement.Between January and December 2018,at both Bristoi Zoo Gardens(Bristol,UK)and Jersey Zoo(Jersey,British Isles),we observed 19 male Livingstone's fruit bats Pteropus livingstonii using focal follows for 345 h overall,noting the outcome of all agonistic interactions.We recorded instigators of interactions,along with winners and losers,and analyzed these data using the R-package"EloRating"to create Elo-rating temporal plots of dominance ranks.We used generalized linear mixed models and multiple linear regression to analyze interaction data and test hypotheses regarding predictors of dominance rank,frequency of agonistic interaction,and choice of interaction partner.Age was positively correlated with dominance rank up to around year 9,when an asymptote was attained.Highly ranked bats instigated the most agonistic interac-tions,and largely directed these interactions at bats with much lower rankings than themselves.Hierarchies were extremely stable throughout the data collection period at both sites.We conclude that Livingstone's fruit bats have a stable linear dominance hierarchy,with high-ranking,typ-ically older males instigating the most interactions with lowest ranking males to secure dominance rank.This study adds to the limited discourse on Pteropus social behaviors,indicating that some bat species may have social systems similar in complexity to some nonhuman primates.

Query Performance Prediction for Information Retrieval Based on Covering Topic Score

We present a statistical method called Covering Topic Score （CTS） to predict query performance for information retrieval. Estimation is based on how well the topic of a user＇s query is covered by documents retrieved from a certain retrieval system. Our approach is conceptually simple and intuitive, and can be easily extended to incorporate features beyond bag- of-words such as phrases and proximity of terms. Experiments demonstrate that CTS significantly correlates with query performance in a variety of TREC test collections, and in particular CTS gains more prediction power benefiting from features of phrases and proximity of terms. We compare CTS with previous state-of-the-art methods for query performance prediction including clarity score and robustness score. Our experimental results show that CTS consistently performs better than, or at least as well as, these other methods. In addition to its high effectiveness, CTS is also shown to have very low computational complexity, meaning that it can be practical for real applications.

终结者:创世纪

In yet another attempt to stop Judgement Day from happening,John Connor(Jason Clarke)sends lyle Reese(Jai Courtney)back to 1984 to save Sarah Connor(Emilia Clarke).Upon arriving Reese discovers that the past(and therefore the future)has changed.