808 research outputs found
Aportación de la densitometría ósea en las artroplastias de rodilla
El presente trabajo consiste en una revisión clínica y radiológica de 84 artroplastias
modulares de rodilla de las cuales, en 19 se ha estudiado la masa ósea periprotésica
(7 cementadas y 12 sin cementar) antes, al mes y a los seis meses de la intervención mediante
un densitómetro de doble fotón. Aparte, se ha probado la correlación directa entre la indicación
peroperatoria de no cementar y una mayor masa ósea en todas las zonas periprotésicas;
por otro lado, se ha observado una diferente distribución de la densidad mineral ósea en la
tibia tras la intervención, según se haya utilizado o no cemento. Estos hallazgos confirman el
estudio densitométrico previo a la intervención como un método complementario útil en la
indicación de la cementación de la artroplastia total de rodilla.A clinical and radiological revision of 84 modular knee arthroplasties is
presented. Periprosthesis bone mineral content was studied in 19 prostheses (7 cemented
and 12 uncemented) before, surgery one and 6 months after the intervention using a densitometer
of double energy. A direct correlation between the implantation of a non-cemented
prosthesis and the growth of the bone mass in all the periprosthesis areas was found, existing
a different distribution of the mineral bone density of the tibia after the intervention
depending on the use of cement. These findings show that the densitometric study previous
to an intervention as a useful complementary method in the indication of cemented total
knee arthroplasty
Chaotic scattering with direct processes: A generalization of Poisson's kernel for non-unitary scattering matrices
The problem of chaotic scattering in presence of direct processes or prompt
responses is mapped via a transformation to the case of scattering in absence
of such processes for non-unitary scattering matrices, \tilde S. In the absence
of prompt responses, \tilde S is uniformly distributed according to its
invariant measure in the space of \tilde S matrices with zero average, < \tilde
S > =0. In the presence of direct processes, the distribution of \tilde S is
non-uniform and it is characterized by the average (\neq 0). In
contrast to the case of unitary matrices S, where the invariant measures of S
for chaotic scattering with and without direct processes are related through
the well known Poisson kernel, here we show that for non-unitary scattering
matrices the invariant measures are related by the Poisson kernel squared. Our
results are relevant to situations where flux conservation is not satisfied.
For example, transport experiments in chaotic systems, where gains or losses
are present, like microwave chaotic cavities or graphs, and acoustic or elastic
resonators.Comment: Added two appendices and references. Corrected typo
Dripping Faucet Dynamics Clarified by an Improved Mass-Spring Model
An improved mass-spring model for a dripping faucet is presented. The model
is constructed based on the numerical results which we recently obtained from
fluid dynamical calculations. Both the fluid dynamical calculations and the
present mass-spring model exhibit a variety of complex behavior including
transition to chaos in good agreement with experiments. Further, the
mass-spring model reveals fundamental dynamics inherent in the dripping faucet
system.Comment: 17 pages, 17 figure
Estudio comparativo de la fijación con o sin cemento en Prótesis Total de Rodilla
Revisamos retrospectivamente una serie de 86 pacientes portadores de 110
prótesis totales modulares de rodilla colocadas como tratamiento de la gonartrosis. Se analizan
los resultados obtenidos en los pacientes a los que se le realizó una fijación híbrida cementada
(componente femoral no cementado y componente tibial y patelar cementado) respecto a los
que se le realizó una prótesis de anclaje biológico sin ningún tipo de cementación. El análisis
de la función clínica, movilidad de la rodilla, estudio radiológico y complicaciones de ambas series
no demuestran diferencias significativas entre ambos grupos con un periodo de seguimiento
de 45 meses (r=12-60).We have retrospectively review 86 patients with 110 total knee arthroplasty for
the treatment of osteoarthrosis. We have analyzed the results obtained in a group of patients
with partial fixation with cement and another group fixated without any cement. Clinical and
radiological results and complications in both groups were similar without significant differences
with an average follow-up of 45 months (12-60)
Experiencia a medio plazo con prótesis total de rodilla semiconstreñida
Revisamos 25 prótesis totales de rodilla semiconstreñidas tipo Endo-Model Waldemar-
Link implantadas en 23 pacientes con una edad media de 69,5 años y un seguimiento medio
de 32 meses. Para la evaluación de los resultados clínicos hemos utilizado el protocolo de la Academia
Americana en el que se incluyen los parámetros de: dolor, capacidad para la marcha, facilidad
para subir y bajar escaleras, necesidad o no de bastones y flexoextensión de la articulación,
tanto antes como después de la intervención. Asimismo hemos realizado un estudio radiológico de
las prótesis en el que se ha valorado el centraje de los componentes protésicos en dos planos AP y
L y las imágenes líticas periprotésicas. Los resultados obtenidos han sido satisfactorios observando
en la totalidad de los pacientes una disminución del dolor y un aumento de su capacidad funcional.
En ningún caso se han observado infecciones profundas de la prótesis. Se ha comprobado un
aumento en el arco de flexión en las prótesis en que la punta del vástago femoral estaba desviada
hacia la cortical anterior, sin que esto se acompañase de un déficit en la extensión.We have reviewed 25 total knee prosthesis (Endo-Model type, Waldemar-Link) performed
in 23 patients with an age average of 69,5 years-old and a average follow-up of 32 months.
The clinical assessment applied was the AAOS protocol including the parameters of: pain, ability to go
up and down the stairs, to need of sticks, flexion and extension of the joint, before and after the operation.
In the radiological study we have evaluated the correct alignment of the components in two
planes A-P and L, and the periprosthetic lucencies. The results obtained have been satisfying in all the
patients with a diminution of the pain and better function of the joint. No deep infection was observed
and the flexion was better in prosthesis with anterior deviation of the femoral rod in the lateral plane
Self-sufficient asymmetric reduction of β-ketoesters catalysed by a novel and robust thermophilic alcohol dehydrogenase co-immobilised with NADH
β-Hydroxyesters are essential building blocks utilised by the pharmaceutical and food industries in the synthesis of functional products. Beyond the conventional production methods based on chemical catalysis or whole-cell synthesis, the asymmetric reduction of β-ketoesters with cell-free enzymes is gaining relevance. To this end, a novel thermophilic (S)-3-hydroxybutyryl-CoA dehydrogenase from Thermus thermophilus HB27 (Tt27-HBDH) has been expressed, purified and biochemically characterised, determining its substrate specificity towards β-ketoesters and its dependence on NADH as a cofactor. The immobilization of Tt27-HBDH on agarose macroporous beads and its subsequent coating with polyethyleneimine has been found the best strategy to increase the stability and workability of the heterogeneous biocatalyst. Furthermore, we have embedded NADH in the cationic layer attached to the porous surface of the carrier. Since Tt27-HBDH catalyses cofactor recycling through 2-propanol oxidation, we achieve a self-sufficient heterogeneous biocatalyst where NADH is available for the immobilised enzymes but its lixiviation to the reaction bulk is avoided. Taking advantage of the autofluorescence of NADH, we demonstrate the activity of the enzyme towards the immobilised cofactor through single-particle analysis. Finally, we tested the operational stability in the asymmetric reduction of β-ketoesters in batch, succeeding in the reuse of both the enzyme and the co-immobilised cofactor up to 10 reaction cycles
On the Derivational Entropy of Left-to-Right Probabilistic Finite-State Automata and Hidden Markov Models
[EN] Probabilistic finite-state automata are a formalism that is widely used in many problems of automatic speech recognition and natural language processing. Probabilistic finite-state automata are closely related to other finite-state models as weighted finite-state automata, word lattices, and hidden Markov models. Therefore, they share many similar properties and problems. Entropy measures of finite-state models have been investigated in the past in order to study the information capacity of these models. The derivational entropy quantifies the uncertainty that the model has about the probability distribution it represents. The derivational entropy in a finite-state automaton is computed from the probability that is accumulated in all of its individual state sequences. The computation of the entropy from a weighted finite-state automaton requires a normalized model. This article studies an efficient computation of the derivational entropy of left-to-right probabilistic finite-state automata, and it introduces an efficient algorithm for normalizing weighted finite-state automata. The efficient computation of the derivational entropy is also extended to continuous hidden Markov models.This work has been partially supported through the European Union's H2020 grant READ (Recognition and Enrichment of Archival Documents) (Ref: 674943) and the MINECO/FEDER-UE project TIN2015-70924-C2-1-R. The second author was supported by the "Division de Estudios de Posgrado e Investigacion" of Instituto Tecnologico de Leon.Sánchez Peiró, JA.; Rocha, MA.; Romero, V.; Villegas, M. (2018). On the Derivational Entropy of Left-to-Right Probabilistic Finite-State Automata and Hidden Markov Models. Computational Linguistics. 44(1):17-37. https://doi.org/10.1162/COLI_a_00306S1737441Abney, S., McAllester, D., & Pereira, F. (1999). Relating probabilistic grammars and automata. Proceedings of the 37th annual meeting of the Association for Computational Linguistics on Computational Linguistics -. doi:10.3115/1034678.1034759Bakis, R. (1976). Continuous speech recognition via centisecond acoustic states. The Journal of the Acoustical Society of America, 59(S1), S97-S97. doi:10.1121/1.2003011Can, D., & Saraclar, M. (2011). Lattice Indexing for Spoken Term Detection. IEEE Transactions on Audio, Speech, and Language Processing, 19(8), 2338-2347. doi:10.1109/tasl.2011.2134087Chi, Z. 1999. Statistical properties of probabilistic context-free grammar. Computational Linguistics, 25(1):131–160.Corazza, A., & Satta, G. (2007). Probabilistic Context-Free Grammars Estimated from Infinite Distributions. IEEE Transactions on Pattern Analysis and Machine Intelligence, 29(8), 1379-1393. doi:10.1109/tpami.2007.1065Dupont, P., Denis, F., & Esposito, Y. (2005). Links between probabilistic automata and hidden Markov models: probability distributions, learning models and induction algorithms. Pattern Recognition, 38(9), 1349-1371. doi:10.1016/j.patcog.2004.03.020Hernando, D., Crespi, V., & Cybenko, G. (2005). Efficient Computation of the Hidden Markov Model Entropy for a Given Observation Sequence. IEEE Transactions on Information Theory, 51(7), 2681-2685. doi:10.1109/tit.2005.850223Huber, M. F., T. Bailey, H. Durrant-Whyte, and U. D. Hanebeck. 2008. On entropy approximation for Gaussian mixture random vectors. In IEEE International Conference on Multisensor Fusion and Integration for Intelligent Systems (MFI), pages 181–188, Seoul.Ilic, V. M. 2011. Entropy semiring forward-backward algorithm for HMM entropy computation. CoRR., abs/1108.0347.Kemp, T. and T. Schaaf. 1997. Estimating confidence using word lattices. Eurospeech, pages 827–830, Rhodes.Mann, G. S. and A. McCallum. 2007. Efficient computation of entropy gradient for semi-supervised conditional random fields. In Proceedings of HLT-NAACL, Companion Volume, Short Papers, pages 109–112.Mohri, M., Pereira, F., & Riley, M. (2002). Weighted finite-state transducers in speech recognition. Computer Speech & Language, 16(1), 69-88. doi:10.1006/csla.2001.0184Nederhof, M.-J., & Satta, G. (2008). Computation of distances for regular and context-free probabilistic languages. Theoretical Computer Science, 395(2-3), 235-254. doi:10.1016/j.tcs.2008.01.010Puigcerver, J., A. H. Toselli, and E. Vidal. 2014. Word-graph and character-lattice combination for KWS in handwritten documents. In International Conference on Frontiers in Handwriting Recognition (ICFHR), pages 181–186, Crete.Sanchis, A., A. Juan, and E. Vidal. 2012. A word-based naïve Bayes classifier for confidence estimation in speech recognition. IEEE Transactions on Audio, Speech, and Language Processing, 20(2):565–574.Soule, S. (1974). Entropies of probabilistic grammars. Information and Control, 25(1), 57-74. doi:10.1016/s0019-9958(74)90799-2Thompson, R. A. (1974). Determination of Probabilistic Grammars for Functionally Specified Probability-Measure Languages. IEEE Transactions on Computers, C-23(6), 603-614. doi:10.1109/t-c.1974.224001Tomita, M. 1986. An efficient word lattice parsing algorithm for continuous speech recognition. In Proceedings of ICASSP, pages 1569–1572, Tokyo.Ueffing, N., F. J. Och, and H. Ney. 2002. Generation of word graphs in statistical machine translation. In Proceedings on Empirical Method for Natural Language Processing, pages 156–163, Philadelphia, PA.Vidal, E., Thollard, F., de la Higuera, C., Casacuberta, F., & Carrasco, R. C. (2005). Probabilistic finite-state machines - part I. IEEE Transactions on Pattern Analysis and Machine Intelligence, 27(7), 1013-1025. doi:10.1109/tpami.2005.147Wessel, F., Schluter, R., Macherey, K., & Ney, H. (2001). Confidence measures for large vocabulary continuous speech recognition. IEEE Transactions on Speech and Audio Processing, 9(3), 288-298. doi:10.1109/89.906002Wetherell, C. S. (1980). Probabilistic Languages: A Review and Some Open Questions. ACM Computing Surveys, 12(4), 361-379. doi:10.1145/356827.35682
Estudio de la marcha en pacientes tratados ortopédicamente de fractura unilateral del calcáneo
Veinticinco pacientes afectos de fractura unilateral desplazada articular de calcá-
neo fueron tratados mediante inmovilización con yeso, siendo los resultados a los 6 años (rango:
3-10), excelentes en 5 pacientes, buenos en 4, regulares en 7 y malos en 9. De este grupo se excluyeron
los afectos de patología local o general asociada, siendo útiles para el estudio de la marcha
12 pacientes a los que se les hizo deambular sobre plataformas dinamométricas para registrar
la fuerza de reacción al suelo, demostrando una disminución de la fuerza vertical de apoyo y
despegue (F1 y F3) y un aumento estadísticamente significativo del tiempo de apoyo total durante
la marcha. Abogamos por la restitución anatómica del calcáneo como medio para mejorar la
capacidad funcional del paciente.Twenty-five patients with unilateral displaced joint calcaneus fracture were treated
by cast being the results after 6 years (range: 3-10), excellent in 5 patients, good in 4 patients,
poor in 7 and bad in 9. We excluded for the study the patients with associated local or general
pathology being useful for our study 12 patients. These patients walked on a dynamometric platform
in order to analyse floor reaction forces, proving a diminuí ion of vertical support and takeoff
forces (Fl and F2), and statistically significant a increase of total support phase during gait
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