Source Supplier Research Articles

Quality Control of Brachytherapy Equipment in Kazakhstan: Current Stage and Minimum Requirements.

Brachytherapy is used in 17 radiotherapy facilities In Kazakhstan. Each institution has an individual quality control (QC) program in place to ensure the safe and accurate delivery of the treatment dose to the patient. The main objective of this paper is to explore current approaches to quality control of brachytherapy in Kazakhstan and reduce potential discrepancies in testing frequency and tolerance limits by identifying a set of basic quality control requirements. A detailed brachytherapy quality control questionnaire was provided to 17 radiotherapy institutions for completion. A separate questionnaire was sent to two institutions associated with brachytherapy. Questions addressed safety aspects, radiation parameters, total time spent on quality control, and available imaging systems for dose determination. The results of the survey were compared with the recommendations set found in international brachytherapy quality control documents. The results of the questionnaires revealed significant differences in the frequency and methods of testing. For example, only two of the 17 centers have at least some kind of quality assurance program for brachytherapy treatment. Only five centers have equipment with the help of which dosimetric control can be performed, and only two centers have local medical physicists performing this control. One of the centers is checked quarterly, while the other is checked only once a year. In the remaining 15 centers, dosimetric control is performed by specialists who recharge the source without providing any document or protocol. There were also significant differences in the amount of time spent on quality control, mostly related to the variety of approaches to quality control and differences in the availability of resources. Almost all centers (15 of 17) rely only on inspections from the radionuclide source supplier and do not monitor the dosimetric and mechanical parameters of the facility at all. Based on the results of the survey and comparison with international recommendations, a set of basic requirements for brachytherapy quality control is needed.

Development of an incentive model for renewable energy resources using forecasting accuracy in South Korea

AbstractThis study presents an incentive model for a renewable energy source (RES) supplier, based on forecasting accuracy. The incentive model imposes responsibility of forecasting to RES suppliers by providing an additional revenue or penalty, according to forecasting accuracy. For this, a profit analysis reflecting the current environment was performed. The structure of the incentive model is designed based on the results of profit analysis. Subsequently, the price parameter was determined using an artificially generated forecasting error of the RES. In addition, the utilization of energy storage system (ESS) is analyzed, including the operation algorithm and optimal sizing, to verify the utility of the ESS when the incentive model is applied. In the case study, the actual price data and RES data from South Korea were used. The results show that the incentive model can provide a high level of profit or penalty for the RES supplier, according to the forecasting accuracy. It is also shown that the optimal capacity of the ESS based on econometrics can be reduced by more than 50% compared with the current environment, thereby reducing the burden on the ESS investment of RES suppliers.

Prediction of adequate pH and Mg2+dosage using an empirical MgO solubility model for struvite crystallization

The struvite crystallization process can recover struvite crystals as valuable slow-release fertilizers from raw water, including high phosphate and ammonium ions. MgO can be used as a magnesium source and an alkaline chemical simultaneously; however, it is difficult to control the dissolved Mg 2 + concentration because of its insufficient and unpredictable solubility. The purpose of this study was to estimate MgO solubility and determine the optimal operating conditions of pH and Mg 2 + dosage during struvite crystallization. An empirical MgO solubility prediction model was devised to dose an adequate amount of MgO slurry in accordance with the properties of raw water. MgO solubility was determined by H + ions donated by NH 4 + , HCO 3 − , and H 2 PO 4 - as the pH increased in the solution. It was found that the molar ratio of donated H + to dissolved Mg 2 + converged to 2:1. This model was verified by performing jar-tests using digested sludge filtrate. When adjusting to a pH of 8.0–9.3 using only MgO, the predicted Mg 2 + concentrations using the model were compared to the measured Mg 2 + concentrations, and they coincided well within the maximum error of 5.7%. This model was applied to determining the operating conditions of pH and Mg 2 + dosage. As a result, considering phosphate removal efficiency higher than 90%, it was feasible to simultaneously achieve an Mg/P molar ratio of 1.3–1.5 and a pH of 8.2–8.5 by only using MgO. Therefore, MgO is recommendable as an appropriate magnesium source and alkali supplier in the struvite process based on experimental jar-tests and the empirical MgO solubility model. • An empirical MgO solubility prediction model was devised and applied to struvite crystallization process. • MgO solubility was predicted using pH, and concentrations of acidic ions. • The optimal conditions of pH and Mg 2 + dosage were determined by this model.

Logistic models for distribution of straw in crops of fruit tree plots where mulch is applied

This work presents three models for the linking of fruit tree plots which are receptors of rice straw that is applied as mulch, with other straw suppliers plots, whose straw is a byproduct of cultivating cereal. The mulch is applied to fruit tree plots in order to save irrigation water, to reduce the incidence of weeds and to reduce erosion. In other words, they intend to assign a set of supplier plots to each straw receiving plot. Each model solves the problem in one scenario. The first one considers the direct application of straw to a single plot which must be supplied to apply the mulch from several plots. Therefore, these must be selected from a set that act as suppliers. It is not considered prior storage or collection. The second scenario also involves a direct application but in several receiving target plots from several source supplier plots without storage or intermediate storage. The third scenario develops a model that groups provider plots with different collection points; It offers a system that selects the location of the storage points and associates each storage point with a group of receiving plots.

Evaluation cytotoxicity effects of biosynthesized zinc oxide nanoparticles using aqueous Linum Usitatissimum extract and investigation of their photocatalytic activityackn

In this project, ZnO nanoparticles (ZnO-NPs) have been synthesized through a sol–gel process that involve the usage of aqueous Linum Usitatissimum extract, functioning as the stabilizing agent, as well as Zn(NO3)2·6H2O that had the role of zinc source supplier. The synthesized ZnO-NPs have been calcinated at the temperatures of 400, 500, and 600 °C, while the induced effects which had been been evaluated in regards to particle size have indicated that the size of nanoparticles has increased as the temperature had been heightened. In addition, the produced ZnO-NPs have been identified by the means of FT-IR, XRD pattern, UV–Vis spectrophotometry, TGA/DTG, FESEM, EDX, BET, and TEM techniques. Specific surface area and total pore volume of synthesized ZnO has been investigated through the utilization of BET analysis. In the following, we have examined the photocatalytic activity of ZnO-NPs on the degradation of methylene blue (MB) dye and according to the obtained results, they are able to degrade 83% of MB under UV light after 90 min. Moreover, the in vitro cytotoxicity effect of these nanoparticles has been investigated against CT26 cell lines through the means of MTT assay and also, the value of IC50 has been calculated to be about 30.54 ppm.

Impact of product design parameters on in vitro release from intrauterine systems.

Polydimethylsiloxane (PDMS)-based levonorgestrel intrauterine systems (LNG-IUSs) contain a large amount of potent LNG, and therefore it is important to understand the impact of product design parameters on the in vitro and in vivo performance to ensure safety and efficacy, as well as to avoid serious side effects resulting from dose dumping. LNG-IUS is a complex drug-device combination product, and its formulation design, requires consideration of additional factors such as device configuration and dimensions, in addition to formulation and processing parameters. In this study, ten qualitatively (Q1) and quantitatively (Q2) equivalent LNG-IUSs were manufactured with differences in source (supplier) and dimensions (i.e., thickness) of the outer membrane, drug particle size, dimensions of the drug reservoir (i.e., inner diameter), as well as configuration of the entire IUS. A real-time in vitro release testing method was developed for the LNG-IUSs. In addition, an accelerated release testing method was developed using hydro-alcoholic media in order to reduce the time associated with formulation design. Source variations and thickness of their outer membranes had a great impact on the in vitro drug release from the LNG-IUSs. It was demonstrated that the thicker the outer membrane, the slower the drug release rate. The physicochemical properties of the outer membranes obtained from different sources were characterized to understand their impact on the in vitro drug release of the LNG-IUSs. The composition and mechanical strength may play a role in differences in drug release. The LNG-IUS formulation prepared with the larger drug particle size showed a slightly slower daily release rate. The drug release rates from the compositionally equivalent LNG-IUSs linearly correlated to the surface area of the corresponding drug reservoirs. Another factor that affected the drug release rate was the configuration of the entire IUS. It was shown that the placement of the outer membrane was significant, i.e. whether the ends of the drug reservoir were covered or not. It is important to note that real-time release showed zero-order release kinetics over the test period of approximately 900days. The current study provides a comprehensive understanding of the impact of product design parameters on the in vitro drug release of LNG-IUSs. In addition, the developed real-time and accelerated release testing methods showed good discriminatory ability for compositionally equivalent LNG-IUSs prepared using different product design parameters.

Sustainability Orientation, Green Supplier Involvement, and Green Innovation Performance: Evidence from Diversifying Green Entrants

While green innovation has a positive impact on firms’ performance, some established firms that initiate green innovation activities (referring to diversifying green entrants) could suffer from insufficient new green knowledge and skills. Since adopting a sustainability orientation helps firms commit to the creation of superior sustainable practices, and efficiently invest resources necessary to develop appropriate new green products, leading to superior green innovation performance, sustainability orientation offers an alternative approach for diversifying green entrants to achieve green innovation success. Building on resource-based, knowledge-based, and capabilities theories, this study aims to identify key factors that enable sustainability orientation of diversifying green entrants and enhance its effect on green innovation performance. As sustainability issues frequently occur upstream at the supplier level, and since supplier involvement effectively determines new product success, this study theorizes that diversifying green entrants that adopt sustainability orientation require two types of green supplier involvement (as a knowledge source and a co-creator) to enhance the effect of sustainability orientation on green innovation performance. Green knowledge-processing capability and green R&D capability complement green supplier involvement as a knowledge source and green supplier involvement as a co-creator, respectively, to further enhance the amount of green innovation performance. Based on a longitudinal dataset of 336 diversifying green entrants, the results support all our hypotheses. Interestingly, an additional analysis suggests that when diversifying green entrants implement green supplier involvement as a co-creator, they achieve greater green innovation performance than those who implement green supplier involvement as a knowledge source. These findings provide important theoretical implications and practical guidance for established firms to pursue green innovation.

Optimal Lot Size in a Manufacturing System with Imperfect Raw Materials and Defective Finished Products

In real-world manufacturing systems, encountering with imperfect raw materials and generation of defective finished products are inevitable. In order to cope with these practical problems, this paper studies a manufacturer which orders raw materials from external source (supplier), and then produces a finished product. The raw materials contain imperfect quality items and, in addition, the production process is defective. The imperfect raw materials are sold after screening process, while the defective finished products go under a further rework process. It is also assumed that defective rate of machine is a random variable, resulting three possible cases regarding occurrence of backordering shortage. The aim is to determine economic order/production lot sizes for each case in such a way that the total cost of system is minimized. The optimal closed form solution is derived for each case separately. Moreover the applicability of the proposed manufacturing model is illustrated via a numerical example.

Mineralization of Calcium Carbonate on Multifunctional Peptide Assembly Acting as Mineral Source Supplier and Template

Crystal phase and morphology of biominerals may be precisely regulated by controlled nucleation and selective crystal growth through biomineralization on organic templates such as a protein. We herein propose new control factors of selective crystal growth by the biomineralization process. In this study, a designed β-sheet Ac-VHVEVS-CONH2 peptide was used as a multifunctional template that acted as mineral source supplier and having crystal phase control ability of calcium carbonate (CaCO3) during a self-supplied mineralization. The peptides formed three-dimensional nanofiber networks composed of assembled bilayer β-sheets. The assembly hydrolyzed urea molecules to one carbonate anion and two ammonium cations owing to a charge relay effect between His and Ser residues under mild conditions. CaCO3 was selectively mineralized on the peptide assembly using the generated carbonate anions on the template. Morphology of the obtained CaCO3 was fiber-like structure, similar to that of the peptide template. The mineralized CaCO3 on the peptide template had aragonite phase. This implies that CaCO3 nuclei, generated using the carbonate anions produced by the hydrolysis of urea on the surface of the peptide assembly, preferentially grew into aragonite phase, the growth axis of which aligned parallel to the direction of the β-sheet fiber axis.

Optimal pricing and inventory policies with reliable and random-yield suppliers: characterization and comparison

In this paper, we study the joint pricing and inventory replenishment problem for a periodic-review inventory system with random demand and dual suppliers, one of the suppliers is reliable but more expensive, the other supplier is less expensive but is unreliable with random yield. We characterize the firm’s optimal policies that simultaneously determine the optimal ordering and pricing decisions in each period over a finite planning horizon, and investigate the impacts of supply source diversification and supplier reliability on the firm and on its customers. We show that having source diversification or higher reliability of suppliers not only increases the firm’s expected profit, but also results in a lower optimal selling price, thus they benefit both the firm and its customers.

Preparation of nano-sized Mg 0.6 Al 0.8 Ti 1.6 O 5 powders using the inorganic salts route

Abstract Stable magnesium aluminum titanate ceramics (Mg0.6Al0.8Ti1.6O5) compound has been successfully synthesized with a straightforward non-hydrolytic sol–gel process using an inorganic metal compound as cation source supplier at about 600 °C. The raw materials MgCl2·2H2O, AlCl3, TiCl4, and citric acid were dissolved in ethanol. Prepared gel was dried at 120 °C and calcined at various temperatures in an electric furnace. The results of X-ray diffraction (XRD) and simultaneous thermal analysis (STA) demonstrate that the direct crystallization of mono-phase magnesium aluminum titanate from fluffy precursor at a temperature below aluminum titanate decomposition temperature range is feasible. Field emission scanning electron microscopy (FESEM) and Brunauer–Emmett–Teller (BET) analysis show the nano-metric size of particles. The particle size and specific surface area of the powders varied from 16.5 to 27.6 nm and from 98.2 to 58.7 m2 g−1 according to calcination temperatures (600 and 700 °C), respectively. The nano-particles had a strong tendency to agglomerate and were partially sintered at 1100 °C.

A Photocytes-Associated Fatty Acid-Binding Protein from the Light Organ of Adult Taiwanese Firefly, Luciola cerata

BackgroundIntracellular fatty acid-binding proteins (FABPs) are considered to be an important energy source supplier in lipid metabolism; however, they have never been reported in any bioluminescent tissue before. In this study, we determined the structural and functional characteristics of a novel FABP (lcFABP) from the light organ of adult Taiwanese firefly, Luciola cerata, and showed anatomical association of lcFABP with photocytes.Principal FindingsOur results demonstrated the primary structure of lcFABP deduced from the cDNA clone of light organ shares structural homologies with other insect and human FABPs. In vitro binding assay indicated the recombinant lcFABP binds saturated long chain fatty acids (C14-C18) more strongly than other fatty acids and firefly luciferin. In addition, tissue distribution screening assay using a rabbit antiserum specifically against the N-terminal sequence of lcFABP confirmed the light organ-specific expression of lcFABP. In the light organ, the lcFABP constituted about 15% of total soluble proteins, and was detected in both cytosol and nucleus of photocytes.ConclusionsThe specific localization of abundant lcFABP in the light organ suggests that sustained bioluminescent flashes in the light organ might be a high energy demanding process. In photocytes, lcFABP might play a key role in providing long chain fatty acids to peroxisomes for the luciferase-catalyzed long chain acyl-CoA synthetic reaction.

In-air calibration of an HDR 192Ir brachytherapy source using therapy ion chambers

The Gammamed Plus 192Ir high dose rate brachytherapy sources were calibrated using the therapy level ionization chambers (0.1 and 0.6 cc) and the well-type chamber. The aim of the present study was to assess the accuracy and suitability of use of the therapy level chambers for in-air calibration of brachytherapy sources in routine clinical practice. In a calibration procedure using therapy ion chambers, the air kerma was measured at several distances from the source in a specially designed jig. The room scatter correction factor was determined by superimposition method based on the inverse square law. Various other correction factors were applied on measured air kerma values at multiple distances and mean value was taken to determine the air kerma strength of the source. The results from four sources, the overall mean deviation between measured and quoted source strength by manufacturers was found -2.04% (N = 18) for well-type chamber. The mean deviation for the 0.6 cc chamber with buildup cap was found -1.48 % (N = 19) and without buildup cap was 0.11% (N = 22). The mean deviation for the 0.1 cc chamber was found -0.24% (N = 27). Result shows that probably the excess ionization in case of 0.6 cc therapy ion chamber without buildup cap was estimated about 2.74% and 1.99% at 10 and 20 cm from the source respectively. Scattered radiation measured by the 0.1 cc and 0.6 cc chamber at 10 cm measurement distance was about 1.1% and 0.33% of the primary radiation respectively. The study concludes that the results obtained with therapy level ionization chambers were extremely reproducible and in good agreement with the results of the well-type ionization chamber and source supplier quoted value. The calibration procedure with therapy ionization chambers is equally competent and suitable for routine calibration of the brachytherapy sources.

Dosimetry of 192Ir sources used for endovascularbrachytherapy

An in-phantom calibration technique for 192Ir sources used forendovascular brachytherapy is presented. Three different source lengths wereinvestigated. The calibration was performed in a solid phantom using aFarmer-type ionization chamber at source to detector distances ranging from1 cm to 5 cm. The dosimetry protocol for medium-energy x-rays extended with avolume-averaging correction factor was used to convert the chamber reading todose to water. The air kerma strength of the sources was determined as well.EGS4 Monte Carlo calculations were performed to determine the depth dosedistribution at distances ranging from 0.6 mm to 10 cm from the source centre.In this way we were able to convert the absolute dose rate at 1 cm distance tothe reference point chosen at 2 mm distance. The Monte Carlo results wereconfirmed by radiochromic film measurements, performed with a double-exposuretechnique. The dwell times to deliver a dose of 14 Gy at the reference pointwere determined and compared with results given by the source supplier(CORDIS). They determined the dwell times from a Sievert integration techniquebased on the source activity. The results from both methods agreed to within2% for the 12 sources that were evaluated. A Visual Basic routine thatsuperimposes dose distributions, based on the Monte Carlo calculations and thein-phantom calibration, onto intravascular ultrasound images is presented.This routine can be used as an online treatment planning program.

Fatigue Crack Propagation in Metals and Polymers with a Unified Formulation

Abstract As the traditional ΔK-based fatigue crack propagation (FCP) law has recently been elucidated by Chow and his group [1–7] to be inadequate for a complete description of fatigue cracking, we examine in this investigation the applicability of a unified formulation for characterizing FCP of both metals and nonmetals. We start by defining a new cyclic J-integral, ΔJ, which, under the confines of linear elastic fracture mechanics (LEFM), is equivalent to the range of elastic strain energy release rate, ΔG. ΔJ (or ΔG) is used as a proper criterion for FCP so long as the crack does not extend during the unloading portion of one load reversal. ΔJ (or ΔG) as such is also interpreted as the source supplier for the energy flow rate dissipated on crack-tip cyclic plastic deformations. It is then assumed that, under fixed test conditions, the minimum specific work of fracture required for fatigue crack initiation, ΔJth, is a material property independent of the load ratio R. Fatigue threshold values thus predicted are correlated favorably with experimental measurements. For fatigue crack propagation, a unified formulation is subsequently derived from the thermodynamic theory of irreversible processes with the cracked surface area taken as an internal variable together with the assumption that the rate of energy dissipated on FCP depends on ΔJ only. It is noted that, in addition to ΔJ, the role played by (Jc − Jmax) is also required in the unified FCP law. Applicability of the law for producing a master FCP diagram is finally examined using FCP data of both metals and polymers, including mild steel, aluminium alloys, PMMA, PVC, short fiber composites, and adhesives.

Cyclic J-integral in relation to fatigue crack initiation and propagation

Fatigue crack initiation (threshold) and propagation are associated with an appreciable sensitivity to one basic factor, among others (environment, microstructure, frequency, temperature etc.), namely load ratio R. The crack closure concept has frequently been hypothesized as a possible explanation for this. Nevertheless, existing experimental results with respect to crack closure are somewhat conflicting due to significant variabilities of such factors as specimen geometries and stress intensity factor ranges. This paper intends to describe the R- dependent fatigue threshold as well as fatigue crack growth from a different point of view, i.e. from the global energy equivalence concept. The generalized driving force attached to a fatigue crack tip is in the first instance re-examined with the introduction of a new cyclic J-integral. The original definition of a cyclic J-integral is shown to be inadequate as it fails to account for the total energy flux into the crack tip region from external loading mechanisms. Under small scale yielding conditions, the newly defined cyclic J-integral is equivalent to the range of elastic energy release rate, ΔG, for a linear elastic crack independent of loading processes. It is proposed to use ΔJ as an appropriate criterion for fatigue crack growth so long as the crack does not extend during the unloading portion of one load reversal. ΔJ as such is also interpreted as the source supplier for the energy flow rate dissipated on crack tip cyclic plastic deformations. It is then assumed that, under fixed test conditions, the minimum specific work of fracture required for fatigue crack initiation, ΔJ th , is a material property independent of the load ratio R. The so-predicted values of fatigue threshold, ΔK th , are correlated favorably with experimental measurements. For fatigue crack growth (FCG), a unified formulation is capable of being derived from the thermodynamic theory of irreversible processes, if the cracked surface area is taken as an internal variable and the rate of energy dissipated on FCG depends on ΔJ only. The applicability of the formulation for producing a master FCG diagram is examined for both metals and non-metals, including steel, aluminum alloys, PMMA and PVC, etc.

Single Source Supplier Strategies--An Exploratory Study of the Impact of Values, Attitudes and Practices in Large U.S. Manufacturing Firms.

The results of an exploratory study using mailed questionnaire responses from purchasing directors of 54 large manufacturing firms are presented in this paper. The effect of buyer-supplier power, quality related concerns, internal management practices of the firm, supplier relations, supplier selection criteria and top management support on single sourcing behavior is explored.

An overview of errors in line source dosimetry for gamma-ray brachytherapy.

The generally used approach for routine brachytherapy dosimetry depends on a value of source strength provided by the source supplier, the theoretical concept of exposure rate constants for different nuclides, and the applicability of inverse square law to point sources. Corrections for filtration of the radiation within the capsule of the source and attenuation in tissue medium are effected based on attenuation coefficients and data published in the literature. Therefore there is no unique or ideal way of selecting the required data and there could be a spread in the dose values derived by different users. The errors inherent in the current practice of dosimetry of linear sources in brachytherapy are discussed. If the brachytherapy sources are specified in terms of exposure rate at a distance from the source by the source suppliers, the overall uncertainty in the dosimetry at regions of clinical interest around the source could be limited to about +/- 6%.