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PubMed2002

Modularity and hierarchical organization of action programs in human acquisition of graphic skills.

If motor or action programs become modules with practice their defining features (e.g. relative timing) should remain relatively invariant in new tasks. To test this hypothesis 24 adults practiced a graphic skill over 100 trials and were transferred to a more complex task enclosing the practiced figure. The data acquired by a digital tablet resulted in total movement and total pause times to draw the figure indicating skill acquisition and variability measures of relative timing and pause time and sequencing referring to features that identify a module. Being transferred to a more complex task did not lead to significant increases in the time to perform the criterion figure embedded in the new pattern. Modularity was evidenced by the stability of relative timing and sequencing shown in the performance of the criterion figure. Hence, it might be that action programs become modules that are then hierarchically organized to form more complex skills.

Adult↗
PubMed1997

Modular structures in the mushroom body of the cockroach.

The mushroom body (MB) is a higher center of the insect brain and is critical to olfactory and other forms of associative memory. Here, we report that repetitive modular subunits, which we refer to as slabs, are present in the internal matrix of the alpha lobe, a major output neuropil of the MB in the cockroach. The methods employed were osmium-ethyl gallate, Bodian-reduced silver, and Golgi staining procedures. A total of 15 dark and 15 pale slabs, each consisting of specific subsets of intrinsic neurons (Kenyon cells), alternate throughout the length of the alpha lobe. One of the major classes of MB output neurons, which are postsynaptic to Kenyon cells, exhibited segmented dendritic arbors that interact with every other slabs, i.e. only either dark or pale slabs. As each output neuron interacts with each specific set of dark or pale slabs, the slab likely functions as a unit for transmitting MB output signals.

Animals↗
PubMed1998

Construction of a modular yeast two-hybrid cDNA library from human EST clones for the human genome protein linkage map.

Identification of all human protein-protein interactions will lead to a global human protein linkage map that will provide important information for functional genomics studies. The yeast two-hybrid system is a powerful molecular genetic approach for studying protein-protein interactions. To apply this technology to generate a human protein linkage map, the first step is to construct two-hybrid cDNA libraries that cover the entire human genome. With a homologous recombination-mediated approach, we have constructed a modular human EST-derived yeast two-hybrid library in the Gal4 activation domain-based vector, pACT2. Quality analysis of this library indicated that the approach of constructing two-hybrid cDNA libraries from individually arrayed human EST clones is feasible, and such a two-hybrid library is suitable for detecting protein-protein interactions. This is also the first time that a comprehensive two-hybrid system cDNA library has been constructed from a collection of individually arrayed EST clones.

Chromosome Mapping↗
PubMed2003

Modular branched stent graft for endovascular repair of aortic arch aneurysm and dissection.

PURPOSE: We describe a modular stent graft for use in endovascular repair of aneurysms of the aortic arch. METHOD: Carotid-carotid and left carotid-subclavian bypass grafts are created surgically. Two large, fully stented grafts are inserted endoluminally. The proximal component is bifurcated, with a wide proximal trunk and two distal limbs, one long and narrow, the other short and wide. This component is inserted through the carotid artery and deployed with the trunk and short wide limb in the ascending thoracic aorta; the long narrow limb opens into the innominate artery. After delivery system removal and carotid artery repair, a distal component is inserted through a femoral approach to bridge the gap between the short, wide distal limb of the proximal component and the nondilated descending thoracic aorta. The result is a branched stent graft, implanted proximally into the ascending aorta and distally into the innominate artery and descending thoracic aorta. CONCLUSION: The system has been used successfully to treat a large wide-necked pseudoaneurysm of the aortic arch.

Aortic Dissection↗
PubMed2003

Second- and third-generation Omniflex modular femoral stem: results 3 to 8 years after surgery.

Primary cementless total hip arthroplasty (THA) using the Omniflex modular femoral stem was conducted on 73 hips in 70 patients. The arc deposition (AD)-type stem was used in 26 hips, and the hydroxyapatite (HA)-type stem was used in 47 hips. The mean follow-up period of patients in the AD group was 78 (range, 61-96) months and that of patients in the HA group was 52 (range, 36-61) months. Clinically, improvement in the Harris hip score occurred in all cases. Thigh pain was reported in 3 (11.5%) AD hips and in 1 (2.1%) HA hip. Radiologically, bone ingrowth fixation was seen in 88.5% of the AD group and in 97.9% of the HA group. No subtrochanteric stress shielding, stem migration of > 2 mm, or revision THA occurred. The second- and third- generation Omniflex stems are useful cementless devices resulting in favorable initial biologic fixation and little bone atrophy at mid-term follow-up.

Aged↗
PubMed1995

Thermal expansion modular femoral head extractor for revision total hip arthroplasty.

Removal of a prosthetic modular femoral head is sometimes desirable during revision hip arthroplasty. A femoral head extractor was designed to heat and expand the prosthetic femoral head, apply a gentle distraction load, and remove the femoral head without injury to the femoral neck, taper, or bone-prosthesis interface. The device was used clinically in six hip revision cases. In five hips with cobalt-chrome heads and titanium alloy tapers, femoral heads were removed successfully; femoral fixation was maintained and femoral components were not visibly damaged. In the sixth case, the female portion of the taper junction was contained in a long femoral head sleeve. Heating the ball did not adequately expand the sleeve to allow easy ball removal.

Femur Head↗
PubMed1993

The 3-6-year results of a modular noncemented low-bending stiffness hip implant. A preliminary study.

A review of the 3-6-year clinical and radiographic results of a modular noncemented stem has been carried out. This is a three-part stem consisting of a head, stem, and proximal sleeve. The stems are split distally like a clothespin in the coronal plane to reduce bending stiffness. No mechanical failures have occurred, including no bead separation from the single-layer porous-coated taper lock sleeves. Of the 48 cases, 13 had smooth stems distally while the rest were fluted. Five of the fluted stems were solid, that is, nonsplit. Clinical results are 93.7% excellent, 4.2% good, and 2.1% poor with the Harris hip rating. There have been no revisions. Thigh pain incidence with the distal split stem was 4.4%. Radiographic follow-up evaluations revealed nonprogressive radiolucency around one of the ingrowth sleeves. When inserted in varus the smooth stems developed some radiolucency around the distal end. Fluting of the stem appeared to prevent this.

Adult↗
PubMed1992

Late disassembly of a modular acetabular component. A case report.

Disassembly of metal-backed acetabular components used for total hip arthroplasty is becoming more common in both preassembled and modular designs. This complication is usually associated with a dislocation of the femoral component or other radiographic evidence of dissociation. A case of late disassembly of the acetabular component without dislocation or radiographic evidence is presented. The authors believe this complication should be considered, along with infection and aseptic loosening, in all cases of late development of pain following total hip arthroplasty.

Adult↗
PubMed1996

Head-neck modularity for total hip arthroplasty. Is it necessary?

Although modular head-neck combinations for femoral components are convenient and useful, theoretical concerns make them less attractive. In a consecutive series of 100 primary cementless total hip arthroplasties, the neck length chosen for the broach trial reduction was compared with the final neck length chosen after the actual femoral component had been impacted. In 19%, the neck length was changed after insertion of the femoral component. As a result, leg-length inequality or wastage of these femoral components would have resulted. For cementless femoral components, the ability to adjust neck length after component impaction remains important.

Biomechanical Phenomena↗
PubMed1996

Comparative results of a distal modular sleeve, circumferential coating, and stiffness relief using the Anatomic Porous Replacement II.

One hundred forty-eight primary Anatomic Porous Replacement II (APR-II, Intermedics Orthopaedics, Austin, TX) noncemented total hip arthroplasties were studied at follow-up periods of 2 to 5 years. Because the stem geometry has not changed since 1988, it was possible to study three adjunctive criteria for porous-coated hip arthroplasties. The APR-II stem geometry was used in three groups: APR-II stem in 56 hips, APR-IIS stem with distal sleeve in 44 hips, and APR-IIT stem with circumferential coating and hollow stem in 48 hips. The APR-IIT was followed 2 years; the APR-II and APR-IIS were followed an average of 3.4 years (range, 2-5 years). For comparison of the results within these three groups 2-year results were compared. The results of the APR-II and APR-IIS at the last follow-up examination are also reported. There was no statistical difference within the three groups for any clinical comparison: 82% had excellent results, 14% good, 2% fair, and 2% poor. At the 2-year follow-up examination, radiographic fixation of the APR-IIS was worse than that of the APR-II and APR-IIT (P < .0005). The APR-IIS uses a distal sleeve, which results in an adverse stiffness ratio between bone and stem. Fixation of the APR-IIT was better than that of the APR-II (P < .0005), probably because the APR-IIT had an increased volume and circumferential level of porous coating and was hollowed for stiffness relief. At final follow-up examination, fixation of the APR-IIS was still worse than that of the APR-II (P < .0005). There was no progressive loss of fixation for either the APR-II or APR-IIS between 2 and 5 years. Only 1 of 148 patients was revised for osteolysis. No other stem or acetabular component is loose. The adjunctive use of a modular sleeve seems to have little advantage, whereas stiffness relief of the stem seems to be beneficial. Circumferential porous coating seems the most important factor for durable fixation.

Adult↗
PubMed1997

Cementless femoral revision arthroplasty. 2- to 5-year results with a modular titanium alloy stem.

Seventy-five consecutive cementless femoral revision arthroplasties were performed, using a modular titanium alloy stem (S-ROM, Joint Medical Products, Stamford, CT). Sixty-six hips were available for complete follow-up evaluation at 2 to 5 years (average, 3.4 years). Independent clinical analysis compared pre- with postoperative modified Harris hip scores and examined patient satisfaction. Independent radiographic analysis was also undertaken. There were two rerevisions, both for hematogenous sepsis. Of the rest, clinical scores improved from a preoperative value of 44 to a postoperative value of 83. Eighty-nine percent of patients were satisfied or very satisfied with the results of surgery. Fifty-two stems had solid bony ingrowth, seven were stabilized by fibrous tissue, and five were radiographically loose. Five-year survival, with rerevision as endpoint, was 96.4%.

Adult↗
PubMed1998

Effect of locking mechanism on fluid and particle flow through modular acetabular components.

Six modular acetabular components were evaluated to determine whether screw holes in the metal shell offer a route for fluid and debris into the acetabular bone stock. A 56-mm acetabular shell for each trial was mounted to a sealed chamber and loaded at a 25 degrees angle under axial loads of 270-2,700 N and +/- 2.5-N-m torsional load. Polystyrene microspheres (average diameter, 0.5 microm) were placed in double-deionized water at 300 mmH2O pressure in a sealed chamber above the component. The only channel between the fluid above and the collecting chamber below was through the cup-liner interface and 1 screw hole. Fluid and debris in the collecting chamber were harvested after 1,000,000 cycles. The collected sample was filtered through a 0.2-microm-pore filter and analyzed under electron microscopy for evidence of microspheres. Water and polystyrene microspheres were isolated in the collecting chamber for all trials except the Reflection cup (Smith & Nephew Orthopaedics, Memphis, TN) with a screw hole cover and the Micro-Seal cup (Whiteside Biomechanics, St. Louis, MO) with a peripheral seal. A screw placed in the screw hole of the Reflection cup failed to seal the interface. The peripheral seal around the rim of the Micro-Seal polyethylene prevented fluid and particle flow between the metal shell and polyethylene liner.

Acetabulum↗
PubMed1997

Predictive Modular Neural Networks for Time Series Classification.

A predictive modular neural network (PREMONN) architecture for time series classification is presented. The PREMONN has a hierarchical structure. The bottom level consists of a bank of linear or nonlinear predictor modules. The top level is a decision module which employs Bayesian or nonprobabilistic decision rules. For various choices of prediction and decision modules, convergence to correct classification is proven. Also it is shown that PREMONN is robust to noise and the speed/accuracy tradeoff is investigated. The analysis is mainly mathematical; however, we also present classification experiments to corroborate our conclusions. Copyright 1996 Elsevier Science Ltd.

Journal Article↗
PubMed1997

A Cortical-type Modular Neural Network for Hypothetical Reasoning.

We propose a multilayer neural network architecture that can implement the kind of hypothetical reasoning that the cortex seems to perform in making sense of the sensory input. The elementary processing nodes of each homogeneous sheet are not single formal neurons, but complex modules abducted from the functional organization of neocortical columns. As an example, we simulate face recognition in this neocortical architecture. A holistic but coarse initial hypothesis is generated by express forward input description and subsequently refined under the constraints of this hypothesis. Separation of forward input description and feedback generated hypothesis, while using the difference in both descriptions at each of the modular units to control the refinement, enables robust recognition and has the potential for autonomous learning. Copyright 1997 Elsevier Science Ltd.

Journal Article↗
PubMedDate not supplied

Scatter rejection in modular gamma cameras for use in dynamic 3D spect brain imaging system.

All gamma cameras used in nuclear medicine have finite energy resolution, thereby making discrimination of scattered radiation from photopeak events extremely difficult. Different scatter-correction methods have been developed to prevent scattered radiation from degrading the image quality of a gamma-ray image. Rejecting scatter events on an event-by-event basis in data acquisition as much as possible is a preferable option. However, the fact that all scattered events cannot be rejected without sacrificing primary photon sensitivity might require applying scatter correction after acquisition; nevertheless, the scattered photons should not be allowed to enter into the image. Most conventional approaches reject scatter events by using energy windows (EWs). Milster et al. introduced the likelihood window (LW) as an alternative. We also employed this method in a modular gamma scintillation camera that has a 2 x 2 array of photomultipliers (PMTs) coupled to a NaI(TI) crystal. In this work, another scatter rejection scheme, the Bayesian window (BW), is developed. In contrast to the LW and the EW, the BW takes into account the simulated or actual scatter spectrum in making a decision to accept or reject a particular photon. This work compares the effectiveness of scatter rejection by BW, LW, and EW through receiver operating characteristic (ROC) studies. Results indicate that the BW method is the preferable choice.

Bayes Theorem↗