Complications of limb salvage surgery in childhood tumors and recommended solutions

Bone and soft tissue malignancies are associated with serious diagnostic and therapeutic problems in every level of pubertal growth in children. Current treatment modality preferred in bone and soft tissue tumors is wide resection of tumor followed by the reconstruction of consequent defect by various methods. Chemotherapy and radiotherapy are applied for systemic effects to the patient pre- and post-operatively and for local effects that facilitate the surgical procedure. Mostly, it is very difficult to control problems following wide resection and reconstruction. In this study, our aim is to discuss the problems encountered in different resection and reconstruction approaches in childhood bone and soft tissue tumors, and the recommended solutions addressed to these problems. From 1990 to 2003, a total of 68 patients (38 female, 30 male) with a mean age of 13.1 (1.5–18) were included in the study. 85.3% of patients were diagnosed as osteosarcoma and the rest was Ewing’s sarcoma. Seventy-five percent of patients had stage IIB disease. The lesions of 34 patients were detected to be in distal femur, 26 in proximal tibia and fibula, 4 in foot and ankle joint, and the remaining 4 in pelvis. As reconstructive surgery, 40 patients had modular prosthesis, vascularized fibular graft was performed in 13 patients, and 10 patients underwent arthrodesis with vascularized fibular graft. 20.6% of patients had shortened limb, infection was detected in 4 patients, laxity in 5, and restricted motion in 4 as complication of prosthesis. With sacrificed physis, 13 patients had a mean value of 4.6 cm limb shortness. Limb salvage surgery has been considered as the gold standard treatment in orthopedic oncological surgery. More understanding of the biology of sarcoma, introduction of new effective chemotherapeutic agents, development of new techniques concerning the surgical resection, advances in diagnostic methods, and improvements in reconstructive surgery all make a major contribution to limb salvage surgery. Since some problems are still encountered, we offer a therapeutic algorithm for complications in the management of childhood tumors that we have encountered so far

Influence of protein concentration and coagulation temperature on rennet-induced gelation characteristics and curd microstructure

peer-reviewedThis study characterized the coagulation properties and defined the cutting window (CW; time between storage modulus values of 35 and 70 Pa) using rheometry for milk standardized to 4, 5, or 6% protein and set at 28, 32, or 36°C. Milks were standardized to a protein-to-fat ratio of approximately 1 by blending ultrafiltration retentate, skim milk, and whole milk. The internal curd microstructure for selected curd samples was analyzed with transmission electron microscopy and scanning electron microscopy. Lowering the coagulation temperature caused longer rennet coagulation time and time to reach storage modulus of 35 Pa, translating into a wider CW. It also led to a lower maximum curd-firming rate (MCFR) with lower firmness at 40 min at a given protein level. Increasing protein levels resulted in the opposite effect, although without an effect on rennet coagulation time at a given temperature. On coagulation at 28°C, milk with 5% protein resulted in a similar MCFR (∼4 Pa/min) and CW (∼8.25 min) compared with milk with 4% protein at 32°C, which reflects more standard conditions, whereas increasing milk to 6% protein resulted in more than doubling of the curd-firming rate (MCFR = 9.20 Pa/min) and a shorter CW (4.60 min). Gels set at 28°C had lower levels of rearrangement of protein network after 40 min compared with those set at 36°C. Protein levels, on the other hand, had no influence on the levels of protein network rearrangement, as indicated by loss tangent values. The internal structure of curd particles, as investigated by both scanning electron microscopy and transmission electron microscopy, appeared to have less cross-linking and smaller casein aggregates when coagulated at 28°C compared with 36°C, whereas varying protein levels did not show a marked effect on aggregate formation. Overall, this study showed a marked interactive effect between coagulation temperature and protein standardization of milk on coagulation properties, which subsequently requires adjustment of the CW during cheesemaking. Lowering of the coagulation temperature greatly altered the curd microstructure, with a tendency for less syneresis during cutting. Further research is required to quantify the changes in syneresis and in fat and protein losses to whey due to changes in the microstructure of curd particles arising from the different coagulation conditions applied to the protein-fortified milk

Entropy and Temperature of a Static Granular Assembly

Granular matter is comprised of a large number of particles whose collective behavior determines macroscopic properties such as flow and mechanical strength. A comprehensive theory of the properties of granular matter, therefore, requires a statistical framework. In molecular matter, equilibrium statistical mechanics, which is founded on the principle of conservation of energy, provides this framework. Grains, however, are small but macroscopic objects whose interactions are dissipative since energy can be lost through excitations of the internal degrees of freedom. In this work, we construct a statistical framework for static, mechanically stable packings of grains, which parallels that of equilibrium statistical mechanics but with conservation of energy replaced by the conservation of a function related to the mechanical stress tensor. Our analysis demonstrates the existence of a state function that has all the attributes of entropy. In particular, maximizing this state function leads to a well-defined granular temperature for these systems. Predictions of the ensemble are verified against simulated packings of frictionless, deformable disks. Our demonstration that a statistical ensemble can be constructed through the identification of conserved quantities other than energy is a new approach that is expected to open up avenues for statistical descriptions of other non-equilibrium systems.Comment: 5 pages, 4 figure

Monitoring of yeast metabolism with calorimetry

A system for calorimetric measurements is established in a 1500 L pilot bioreactor. Saccharomyces cerevisiae, baker’s yeast has three metabolic pathways: 1) purely oxidative, glucose consuming; 2) purely reductive, glucose consuming and ethanol producing and 3) purely oxidative, ethanol consuming. Designing experiments to lead the yeast to a single pathway, the accuracy of the calorimetric measurements are verified. Using on-line data of microbial heat production and substrate consumption, the combustion enthalpies of glucose and ethanol in purely oxidative (aerobic) fed batch fermentations are determined as 15900 and 29000 kJ/kg respectively, Combustion enthalpy of glucose in purely reductive (anaerobic) environment is determined as 511 kJ/kg. These values are in good corresponding with literature data. It is now possible to determine the fraction of substrate uptake utilized for energy (catabolism, k) and biosynthesis (anabolism, a) metabolisms on-line. In oxidative (aerobic) fermentations we determined kSox=0.45 for glucose, kEox=0.63 for ethanol and in reductive (anaerobic) fermentations kSred=0.96 for glucose; the anabolism factors are aSox=0.55, aEox=0.37 and aSred=0.04 respectively. The single pathways can occur together so that an experiment is designed with changing environmental conditions to prove the overall calorimetric model. The result is that measured and the calculated microbial heat energy rates are in good accordance. Calorimetric measurements can be used to monitor yeast metabolism on-line, for advanced control strategies or, to predict fermentations or for designing heat exchanger or bioreactor systems

A linear programming-based method for job shop scheduling

We present a decomposition heuristic for a large class of job shop scheduling problems. This heuristic utilizes information from the linear programming formulation of the associated optimal timing problem to solve subproblems, can be used for any objective function whose associated optimal timing problem can be expressed as a linear program (LP), and is particularly effective for objectives that include a component that is a function of individual operation completion times. Using the proposed heuristic framework, we address job shop scheduling problems with a variety of objectives where intermediate holding costs need to be explicitly considered. In computational testing, we demonstrate the performance of our proposed solution approach

A statistical mechanics framework for static granular matter

The physical properties of granular materials have been extensively studied in recent years. So far, however, there exists no theoretical framework which can explain the observations in a unified manner beyond the phenomenological jamming diagram [1]. This work focuses on the case of static granular matter, where we have constructed a statistical ensemble [2] which mirrors equilibrium statistical mechanics. This ensemble, which is based on the conservation properties of the stress tensor, is distinct from the original Edwards ensemble and applies to packings of deformable grains. We combine it with a field theoretical analysis of the packings, where the field is the Airy stress function derived from the force and torque balance conditions. In this framework, Point J characterized by a diverging stiffness of the pressure fluctuations. Separately, we present a phenomenological mean-field theory of the jamming transition, which incorporates the mean contact number as a variable. We link both approaches in the context of the marginal rigidity picture proposed by [3, 4].Comment: 21 pages, 15 figure

Segregation of Polymers in Confined Spaces

We investigate the motion of two overlapping polymers with self-avoidance confined in a narrow 2d box. A statistical model is constructed using blob free-energy arguments. We find spontaneous segregation under the condition: $L > R_{//}$, and mixing under $L < R_{//}$, where L is the length of the box, and $R_{//}$ the polymer extension in an infinite slit. Segregation time scales are determined by solving a mean first-passage time problem, and by performing Monte Carlo simulations. Predictions of the two methods show good agreement. Our results may elucidate a driving force for chromosomes segregation in bacteria

Dynamics of Ordering in Alloys with Modulated Phases

This paper presents a theoretical model for studying the dynamics of ordering in alloys which exhibit modulated phases. The model is different from the standard time-dependent Ginzburg-Landau description of the evolution of a non-conserved order parameter and resembles the Swift-Hohenberg model. The early-stage growth kinetics is analyzed and compared to the Cahn-Hilliard theory of continuous ordering. The effects of non-linearities on the growth kinetics are discussed qualitatively and it is shown that the presence of an underlying elastic lattice introduces qualitatively new effects. A lattice Hamiltonian capable of describing these effects and suitable for carrying out simulations of the growth kinetics is also constructed.Comment: 18 pages, 3 figures (postscript files appended), Brandeis-BC9