234 research outputs found
Standardized loads acting in knee implants
No full textThe loads acting in knee joints must be known for improving joint replacement, surgical procedures, physiotherapy, biomechanical computer simulations, and to advise patients with osteoarthritis or fractures about what activities to avoid. Such data would also allow verification of test standards for knee implants. This work analyzes data from 8 subjects with instrumented knee implants, which allowed measuring the contact forces and moments acting in the joint. The implants were powered inductively and the loads transmitted at radio frequency. The time courses of forces and moments during walking, stair climbing, and 6 more activities were averaged for subjects with I) average body weight and average load levels and II) high body weight and high load levels. During all investigated activities except jogging, the high force levels reached 3,372–4,218N. During slow jogging, they were up to 5,165N. The peak torque around the implant stem during walking was 10.5 Nm, which was higher than during all other activities including jogging. The transverse forces and the moments varied greatly between the subjects, especially during non-cyclic activities. The high load levels measured were mostly above those defined in the wear test ISO 14243. The loads defined in the ISO test standard should be adapted to the levels reported here. The new data will allow realistic investigations and improvements of joint replacement, surgical procedures for tendon repair, treatment of fractures, and others. Computer models of the load conditions in the lower extremities will become more realistic if the new data is used as a gold standard. However, due to the extreme individual variations of some load components, even the reported average load profiles can most likely not explain every failure of an implant or a surgical procedure
FIGURE 5. Hyalella longipropodus n in A new species of freshwater amphipod (Crustacea, Peracarida, Hyalellidae) from Southern Brazil
No full textFIGURE 5. Hyalella longipropodus n. sp. Limberger, Graichen & Castiglioni, Palmeira das Missões municipality, state of Rio Grande do Sul, Southern Brazil. Paratype, male. (A) peraeopod 3; (B) peraeopod 4; (C) peraeopod 5; (D) peraeopod 6; (E) peraeopod 7; (F) pleopod. Scales 4A to 4E—0.5 mm; 4F—0.2 mm.Published as part of Limberger, Marcio, Castiglioni, Daniela Da Silva & Graichen, Daniel Ângelo Sganzerla, 2021, A new species of freshwater amphipod (Crustacea, Peracarida, Hyalellidae) from Southern Brazil, pp. 182-200 in Zootaxa 5026 (2) on page 189, DOI: 10.11646/zootaxa.5026.2.2, http://zenodo.org/record/527082
Hip contact forces and gait patterns from routine activities
No full textIn vivo loads acting at the hip joint have so far only been measured in few patients and without detailed documentation of gait data. Such information is required to test and improve wear, strength and fixation stability of hip implants. Measurements of hip contact forces with instrumented implants and synchronous analyses of gait patterns and ground reaction forces were performed in four patients during the most frequent activities of daily living. From the individual data sets an average was calculated. The paper focuses on the loading of the femoral implant component but complete data are additionally stored on an associated compact disc. It contains complete gait and hip contact force data as well as calculated muscle activities during walking and stair climbing and the frequencies of daily activities observed in hip patients. The mechanical loading and function of the hip joint and proximal femur is thereby completely documented. The average patient loaded his hip joint with 238% BW (percent of body weight) when walking at about 4 km/h and with slightly less when standing on one leg. This is below the levels previously reported for two other patients (Bergmann et al., Clinical Biomechanics 26 (1993) 969-990). When climbing upstairs the joint contact force is 251% BW which is less than 260% BW when going downstairs. Inwards torsion of the implant is probably critical for the stem fixation. On average it is 23% larger when going upstairs than during normal level walking. The inter- and intra-individual variations during stair climbing are large and the highest torque values are 83% larger than during normal walking. Because the hip joint loading during all other common activities of most hip patients are comparably small (except during stumbling), implants should mainly be tested with loading conditions that mimic walking and stair climbing
FIGURE 3. Hyalella longipropodus n in A new species of freshwater amphipod (Crustacea, Peracarida, Hyalellidae) from Southern Brazil
No full textFIGURE 3. Hyalella longipropodus n. sp., Palmeira das Missões municipality, state of Rio Grande do Sul, Southern Brazil. Paratype, male. (A) habitus; (B) antenna 1; (C) antenna 2; (D) mandible; (E) upper lip; (F) Lower lip; (G) maxilla 1; (H) maxilla 2; (I) maxilliped. Scales: 0.65 mm for 2A; 0.5 mm for 2B, C; 0.2 mm for 2D–I.Published as part of Limberger, Marcio, Castiglioni, Daniela Da Silva & Graichen, Daniel Ângelo Sganzerla, 2021, A new species of freshwater amphipod (Crustacea, Peracarida, Hyalellidae) from Southern Brazil, pp. 182-200 in Zootaxa 5026 (2) on page 187, DOI: 10.11646/zootaxa.5026.2.2, http://zenodo.org/record/527082
Enantioselective synthesis of alpha-fluorinated beta(2)-amino acids
No full textCopyright © 2008 American Chemical SocietyA methodology for the enantioselective synthesis of α-fluorinated β²-amino acids has been developed from readily available carboxylic acids 3. Conversion to the Evan's oxazolidinone followed by enantioselective fluorination and alkylation gave 7 in high diastereomeric excess (>95%). Subsequent removal of the oxazolidinone and amination at the Bn-protected hydroxyl center gave optically active α-fluorinated β²-amino acids.Michael K. Edmonds, Florian H. M. Graichen, James Gardiner, and Andrew D. Abel
Realistic loads for testing hip implants
No full textThe aim here was to define realistic load conditions for hip implants, based on in vivo contact force measurements, and to see whether current ISO standards indeed simulate real loads. The load scenarios obtained are based on in vivo hip contact forces measured in 4 patients during different activities and on activity records from 31 patients. The load scenarios can be adapted to various test purposes by applying average or high peak loads, high-impact activities or additional low-impact activities, and by simulating normal or very active patients. The most strenuous activities are walking (average peak forces 1800 N, high peak forces 3900 N), going up stairs (average peak forces 1900 N, high peak forces 4200 N) and stumbling (high peak forces 11,000 N). Torsional moments are 50% higher for going up stairs than for walking. Ten million loading cycles simulate an implantation time of 3.9 years in active patients. The in vitro fatigue properties of cementless implant fixations are exceeded during stumbling. At least for heavyweight and very active subjects, the real load conditions are more critical than those defined by the ISO standards for fatigue tests
NMR-solution structures of fluoro-substituted beta-peptides: A 3 14-helix and a hairpin turn. The first case of a 90degree(s) O=C-C-F dihedral angle in an a-fluoro-amide group
No full textTo further study the preference of the antiperiplanar (ap) conformation in -fluoro-amide groups, two -peptides, 1 and 2, containing a (2-F)-3hAla and a (2-F)-2hPhe residue, have been synthesized. Their NMR-solution structures in CD3OH were determined and compared with those of non-F-substituted analogs, 3 and 4a. While we have found in a previous investigation (Helv. Chim. Acta 2005, 88, 266) that a stereospecifically introduced F-substituent in the central position of a -heptapeptide is capable of breaking the 314-helical structure by enforcing the FCCO ap-conformation, we could now demonstrate that the same procedure leads to a structure with the unfavorable ca. 90° FCCO dihedral angle, enforced by the 314-helical folding in a -tridecapeptide (cf. 1; Fig. 4). This is interpreted as a consequence of cooperative folding in the longer -peptide. A F-substituent placed in the turn section of a -peptidic hairpin turn was shown to be in an ap-arrangement with respect to the neighboring CO bond (cf. 2; Fig. 7). Analysis of the non-F-substituted -tetrapeptides (with helix-preventing configurations of the two central 2/3-amino acid residues) provides unusually tight hairpin structural clusters (cf. 3 and 4a; Figs. 8 and 9). The skeleton of the -tetrapeptide H-(R)3hVal-(R)2hVal-(R)3hAla-(S)3hPhe-OH (4a) is proposed as a novel, very simple backbone structure for mimicking -peptidic hairpin turns.Raveendra I. Mathad, Bernhard Jaun, Oliver Flögel, James Gardiner, Markus Löweneck, Jeroen D. C. Codée, Peter H. Seeberger, Dieter Seebach, Michael K. Edmonds, Florian H. M. Graichen, and Andrew D. Abel
Graichen, William F. (Death, 1900-11-09)
No full textAddress: 1108 York St.Age at death: 28-2-24130/Pg.98/1900/M W S/Ohio/Dr. Erwin O. Straehley/Gunther Bros. Co./Vine St. HillOriginal record filed in drawer labeled 'GR-GRAY, J'
Observers as Internal Models for Remote Tracking via Encoded Information
No full textIn this paper, we consider a servomechanism problem in which the command and control functions are distributed in space, and hence the system consists of different components linked by a communication channel of finite capacity. The desired control goal is achieved by designing appropriate encoders, decoders and internal models of the exogenous signals. As an application, we describe a how the output of a system can be forced to track a reference signal generated by a remotely located nonlinear oscillator.
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