Discussing the use of complexity theory in engineering management: Implications for sustainability

What is the state-of-the-art literature regarding the adoption of the complexity theory (CT) in engineering management (EM)? What implications can be derived for future research and practices concerning sustainability issues? In this conceptual article, we critically discuss the current status of complexity research in EM. In this regard, we use IEEE Transactions on Engineering Management, because it is currently considered the leading journal in EM, and is as a reliable, heuristic proxy. From this journal, we analyze 38 representative publications on the topic published since 2000, and extrapolated through a rigorous keyword-based article search. In particular, we show that: (1) the adoption of CT has been associated with a wide range of key themes in EM, such as new product development, supply chain, and project management. (2) The adoption of CT has been witnessed in an increasing amount of publications, with a focus on conceptual modeling based on fuzzy logics, stochastic, or agent-based modeling prevailing. (3) Many key features of CT seem to be quite clearly observable in our dataset, with modeling and optimizing decision making, under uncertainty, as the dominant theme. However, only a limited number of studies appear to formally adhere to CT, to explain the dierent EM issues investigated. Thus, we derive various implications for EM research (concerning the research in and practice on sustainability issues)

The Marseille Schmidt survey for active star-forming galaxies. I. Data on 92 emission line objects in two fields

We present data from a moderately deep spectroscopic Schmidt survey (Blim=17.5) of ``active galaxies'' selected by the presence of emission lines in their spectra and/or their UV excess. The redshift, magnitudes, color and diameter reduction methods have been discussed in a previous paper. Here we explain the emission line equivalent width determination method. 92 emission line objects have been found in two adjacent fields (approximately 50deg^2) in the direction of the south extension of the Virgo cluster. We give a catalog containing positions, photographic R and B magnitudes, U-R colors, effective diameters, redshifts, equivalent widths and intensity ratios of the [OIII]4959,5007, Hbeta and [OII] 3727 emission lines. On these fields, we evaluate the completeness limit of the survey at a pseudo B magnitude value of 15.7.Comment: tar gzipped file 7 AA latex2e pages(including 7 figures) + 1 tex table (2 pages) + 5 pages (color ps) charts will appear in A&A, available also at http://hasso.mpia-hd.mpg.de/Surace/surace.html#article

Trimer states with ℤ₃ topological order in Rydberg atom arrays.

Trimers are defined as two adjacent edges on a graph. We study the quantum states obtained as equal-weight superpositions of all trimer coverings of a lattice, with the constraint of having a trimer on each vertex: the so-called trimer resonating-valence-bond (tRVB) states. Exploiting their tensor network representation, we show that these states can host $\mathbb{Z}_3$ topological order or can be gapless liquids with $\mathrm{U}(1) \times \mathrm{U}(1)$ local symmetry. We prove that this continuous symmetry emerges whenever the lattice can be tripartite such that each trimer covers all the three sublattices. In the gapped case, we demonstrate the stability of topological order against dilution of maximal trimer coverings, which is relevant for realistic models where the density of trimers can fluctuate. Furthermore, we clarify the connection between gapped tRVB states and $\mathbb{Z}_3$ lattice gauge theories by smoothly connecting the former to the $\mathbb{Z}_3$ toric code, and discuss the non-local excitations on top of tRVB states. Finally, we analyze via exact diagonalization the zero-temperature phase diagram of a diluted trimer model on the square lattice and demonstrate that the ground state exhibits topological properties in a narrow region in parameter space. We show that a similar model can be implemented in Rydberg atom arrays exploiting the blockade effect. We investigate dynamical preparation schemes in this setup and provide a viable route for probing experimentally $\mathbb{Z}_3$ quantum spin liquids

Spitzer Mid-Infrared Imaging of Nearby Ultraluminous Infrared Galaxies

We have observed 14 nearby (z<0.16) Ultraluminous Infrared Galaxies (ULIRGs) with Spitzer at 3.6-24 microns. The underlying host galaxies are well-detected, in addition to the luminous nuclear cores. While the spatial resolution of Spitzer is poor, the great sensitivity of the data reveals the underlying galaxy merger remnant, and provides the first look at off-nuclear mid-infrared activity.Comment: To appear in the conference proceedings for Spitzer New Views of the Universe, held Nov. 2004 in Pasadena, C

Acetabular revision surgery in the presence of severe bone loss: surgical technique and early results with modular porous tantalum augments and cups

Subject: In the presence of minimal acetabular bone loss most revision procedures can be done with the use of an uncemented hemispheric device with or without morselized allograft. The use of modular porous tantalum augments and cups has been recently introduced to address more severe bone deficiencies. The purpose of this study is to describe the surgical technique and early clinical results obtained with trabecular metal acetabular augments in cases of acetabular revision with severe bone loss. Materials and Methods: Since November 2003 seven acetabular revisions have been done by means of TMT\uae augments and cups: the primary indication for acetabular revision was aseptic loosening in five patients and septic loosening in two patients. According to Paprosky classification the acetabular bone defects were classified as follows: 2B in two hips, 2C in one hip, 3A in two hips and 3B in three hips. In two cases it was the first surgical hip replacement procedure. Five cases were multiple revisions. Results: At an average follow-up of 24 months no implant had evidence of loosening or migration. No dislocations occurred. Discussions and Conclusions: Augments provide mechanical support to hemispheric cups of various dimensions. This surgical technique avoids the use of structural allograft, helps to restore the center of hip rotation and increases contact area between the implant and the host bone for biological fixation. Longer follow-up is required to verify survival of these implants and potential mechanical and biologic complications related to use of this modular TMT\uae system

Femoral revision with the modular ZMR stem. Clinical and x-rays results at medium term follow-up

A retrospective review was conducted to evaluate the medium-term results of the ZMR modular revision taper stem. From March 1999 to December 2002, 65 consecutive hip revision surgeries were performed mostly for aseptic loosening. Femoral bone stock defects were classified according to AAOS\u2019s criteria and consisted mainly in type II and type III. A Wagner osteotomy was performed in 25 cases to remove primary implants that were cemented in 35 cases. Mean post-operative follow-up was 69 months (range, 36 to 91months). Clinical assessment at follow-up showed a significantly improved mean Harris Hip Score from 42 points preoperatively to 81 points postoperatively, while the x-ray examination did show a satisfactory distal integration of the stem in all cases and satisfactory reconstitution of the femoral bone stock in 47% of cases. The average subsidence of the stem at follow-up was under one millimeter. According to the data leg length discrepancy exceeding 15 millimeters caused significantly higher functional impairment and more pain

Lateral parapatellar approach in primary total knee arthroplasty of the valgus knee

Background Anatomic and pathological characteristics of the valgus knee deformity represent a challenging issue for the implant of a total knee arthroplasty. The surgical approach in such cases should allow a direct ad easy exposure of the joint, easy lateral soft tissue balancing and adequate patellar tracking. Materials and Methods Twenty-four total knee arthroplasties were implanted in valgus knees between January 2002 and September 2005. A mean preoperative valgus deformity of 18\ub0 was assessed on standing x-rays. Four posterior stabilized, eighteen posterior stabilized rotating platform prosthesis and two superstabilized prosthesis were implanted in 21 patients. The surgical approach has been in all cases a lateral parapatellectomy. Follow-up assessments were obtained for all patients at a mean 23 months. They consisted of a Knee Society Score and a Patellar Score evaluation, standing AP and lateral radiograms and skyline x-rays obtained at a flection of 45\ub0. Results A mean preoperative Knee Society Clinical Score of 32,7 points (range, -4 to 64 points) significantly improved at follow-up to an average 88,8 points (range, 57 to 99 points; p<0,05). The Knee Society Function Score significantly increased from a preoperative mean score of 32,7 points (range, -20 to 75 points) to an average followup score of 81,2 points (range, 30 to 100 points; p<0.05). The Patella Score revealed absence of anterior pain in all cases but one that reported severe pain. A satisfactory patello-femoral alignement of 4.7\ub0 (range, 1\ub0 to 10\ub0) was obtained at last follow-up x-rays. One intraoperative condilar fracture occured and was treated with a single screw. Discussion The lateral approach of valgus knees led to satisfactory results in primary total knee arthroplasties in a percentage of cases comparable or superior to those presented in literature for different approaches. In addition, lateral release is performed as a part of the approach itself, allows preservation of the blood supplies of the extensor apparatus and an optimal patellar tracking in most cases. Conclusions In conclusion, the lateral approach for a primary total knee arthroplasty could be recommended in valgus knees affected by osteoarthritis because as it proved to be effective in achieving a satisfactory implant positioning and functional outcome while reporting minor complications