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• A method to train a regional PV model from the total power production is proposed. • A regularization of the parameter estimation increases the model accuracy. • A validation of the approach against TSO data shows promising results. Estimating and forecasting photovoltaic (PV) power generation in regions—e.g. the area controlled by the transmission system operator (TSO)—is a requirement for the operation of the electricity supply system. An accurate calculation of this quantity requires detailed information of the installed PV systems within the considered region; however, this information is not publicly available making forecasting difficult. Therefore, approximating the undefined PV systems information for use in a PV power model (parameterization) is of critical interest. In this paper, we propose a methodological approach for parameterization using time series of aggregated PV power generation. A Bayesian approach is used to overcome the significant number of unknown parameters in the problem. It regularizes the linear system by imposing constraints on deviations from an initial-guess and covariance matrices; the initial guess uses available statistical distributions of PV system metadata. The performance of the proposed forecasting approach is evaluated using estimates of the regional PV power generation from three TSOs and meteorological data from the IFS forecast model (ECMWF). The proposed forecasting approach without the Bayesian parameterization has RMSE of 3.90%, 4.25% and 4.64%, respectively; including the Bayesian approach gives RMSE of 3.82%, 4.23% and 4.51%. For comparison, we also deployed a multiple linear regression which gave RMSE of 3.89%, 4.12% and 4.54%; however, there are considerable downsides to such an approach. Our approach is competitive with TSO forecasting systems despite using far fewer input data and simpler implementation of NWP prediction. This is particularly promising as there are many avenues for future development. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate whether different suture materials in meniscal repair may harm cartilage.Methods: A preloaded linear friction testing setup including porcine knees with porcine cartilage, porcine meniscus, and different suture materials (braided nonabsorbable, absorbable monofilament) was used. Five groups with different tribological pairs were tested: cartilage on meniscus (control), cartilage on cartilage (control No. 2), and cartilage on different meniscus sutures (3 groups). Cartilage integrity was analyzed macroscopically by the India ink method and histologically using Giemsa-eosin-stained undecalcified methyl methacrylate sections. Cartilage lesions were classified by using a quantitative scoring system.Results: The control groups did not show cartilage damage, either macroscopically or histologically. Loading cartilage with sutured menisci led to significant damage of the superficial radial and transitional zones with braided nonabsorbable (P = .03) and absorbable monofilament (P = .02) sutures at final examination. Menisci sutured with braided nonabsorbable material resulted in deeper damage to the cartilage. However, there were no significant differences between the suture materials. Sutures oriented perpendicular to surface motion led to a larger defect than parallel-oriented sutures.Conclusions: Braided nonabsorbable and absorbable monofilament suture materials cause significant damage to cartilage during long-term cyclic loading in vitro. The extent of damage depends on suture orientation.Clinical Relevance: This study provides data on the extent to which different suture materials in meniscus repair may harm cartilage. [ABSTRACT FROM AUTHOR]

Stable protein-DNA nanostructures have been assembled by reconstitution of the multi-ligand binding flavoprotein dodecin on top of flavin-terminated dsDNA monolayers on gold electrodes. These structures could be disassembled by electrochemical flavin reduction via mediated electron transfer. For this purpose a negative potential was applied at the Au working electrode in the presence of the redox mediator bis-(ammoniumethyl)-4,4′-bipyridinium tetrabromide. The stepwise formation of the flavin-terminated dsDNA monolayers as well as the binding and electrochemically triggered release of apododecin were monitored by surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) measurements. The assembly and disassembly of the protein-DNA nanostructures were fully reversible processes, which could be carried out multiple times at the same flavin-dsDNA modified surface. When a negative potential was applied in the absence of a redox mediator apododecin could not be released, i.e. direct electron transfer was not possible. As alternative redox mediators also methylene blue and phenosafranine were studied, but in the presence of these molecules apododecin was released without applying a potential, probably because the tricyclic aromatic compounds are able to replace the flavins at the binding sites. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study was to evaluate the outcome, return to sporting activity, and postoperative articular cartilage and bony morphology of shoulders that underwent arthroscopic suture anchor repair of bony Bankart lesions. Methods The inclusion criteria for this retrospective study were anterior glenoid rim fractures after traumatic shoulder instability that were treated with arthroscopic suture anchor repair. Patients were surveyed by a questionnaire including sport-specific outcome, Rowe score, Western Ontario Shoulder Instability Index, and Oxford Instability Score. Three-tesla magnetic resonance imaging could be performed in 30 patients to assess osseous integration, glenoid reconstruction, and signs of osteoarthritis. Results From November 1999 to April 2010, 81 patients underwent an anterior bony Bankart repair in our department (50 arthroscopic suture anchor repairs, 5 arthroscopic screw fixations, and 26 open repairs). The 55 arthroscopic repairs comprised a consecutive cohort of patients treated by a single surgeon. Of the 50 patients in the suture anchor group, 45 (90%) were available for evaluation. At 82 ± 31 months postoperatively, the mean Rowe score was 85.9 ± 20.5 points, the mean Western Ontario Shoulder Instability Index score was 89.4% ± 14.7%, and the mean Oxford Instability Score was 13.6 ± 5.4 points. Compared with the contralateral shoulder, all scores showed a significantly reduced outcome ( P < .001, P < .001, and P < .001, respectively). A redislocation occurred in 3 patients (6.6%). Regarding satisfaction, 35 patients (78%) were very satisfied, 9 (20%) were satisfied, and 1 was partly satisfied. Overall, 95% of patients returned to any sporting activity after surgery. The number of sports disciplines ( P < .001), duration ( P = .005), level ( P = .02), and risk category ( P = .013) showed a significant reduction compared with the pretrauma condition. However, only 19% of patients reported that shoulder complaints were the reason for the reduction in activity. Nonunion occurred in 16.6%, with a higher frequency in patients with chronic lesions ( P = .031). Anatomic reduction was achieved in 72%, the medial step-off in patients with nonanatomic reduction averaged 1.8 ± 0.9 mm, and the remaining glenoid defect size averaged 6.8% ± 7.3%. Full-thickness cartilage defects of the anterior glenoid were detected in 70% of patients. Conclusions Arthroscopic suture anchor repair may enable an anatomic reduction of bony Bankart lesions with no or only minimal articular steps and provides successful midterm outcomes concerning clinical scores, recurrence, and patient satisfaction. The return to activity is limited for various, mostly non–shoulder-related causes. Chronic lesions may have an inferior healing potential; therefore early surgical stabilization of acute Bankart fragments is suggested to avoid possible nonunion. Level of Evidence Level IV, therapeutic case series. [ABSTRACT FROM AUTHOR]

Background: The purpose of the study was to report early functional and radiographic results of a small series of patients who underwent autologous chondrocyte transplantation–collagen membrane seeding (ACT-Cs) for focal chondral defects of the shoulder. Methods: The outcome of 4 consecutive male patients (mean age, 29.3 ± 6.2 years; range, 21-36 years) who underwent ACT-Cs for treatment of large symptomatic glenohumeral cartilage defects was retrospectively evaluated with clinical and radiographic measures at a mean of 41.3 ± 24.9 months (range, 11-71 months) after surgery. The evaluation included a visual analog scale for pain, the Constant score, the American Shoulder and Elbow Surgeons shoulder index, the Rowe score, and a satisfaction scale. Magnetic resonance imaging evaluation was performed according to the Magnetic Resonance Observation of Cartilage Repair Tissue scoring system. Results: There were 3 humeral full-thickness cartilage defects (each 6.0 cm2) and 1 glenoid full-thickness cartilage defect (2.0 cm2). The mean postoperative visual analog scale score (0.3 of 10), the mean unweighted Constant score (83.3 ± 9.9), and the mean American Shoulder and Elbow Surgeons index (95.3 ± 8.1) were representative of satisfactory shoulder function. The Magnetic Resonance Observation of Cartilage Repair Tissue score was indicative of satisfactory defect coverage with signs of fibrocartilaginous repair tissue. Conclusions: Autologous chondrocyte transplantation at the glenohumeral joint is a remote option for young adults with symptomatic, isolated, large-diameter cartilage lesions. Potential complications as a result of the open approach and 2-step procedure have to be considered carefully. Long-term data, larger patient populations, and randomized studies are required to determine the potential for chondrocyte transplantation techniques to be standard procedure for treatment of symptomatic, large-diameter, full-thickness cartilage defects in the glenohumeral joint. [Copyright &y& Elsevier]

Abstract: Shoulder instability is a common diagnosis that often requires surgical treatment. A detailed knowledge of the shoulder anatomy and its stabilizing structures is of utmost importance for successful treatment of shoulder instabilities. Identifying anatomic variants (e.g., sublabral hole, meniscoid labrum, cordlike middle glenohumeral ligament, and Buford complex) and distinguishing them from pathologic findings may be especially difficult, as shown by the high interobserver variability. Over the last decade, basic research and arthroscopic surgery have improved our understanding of the shoulder anatomy and pathology. In the context of shoulder instability, injuries of the glenoid (bony Bankart), injuries of the glenoid labrum superiorly (SLAP) or anteroinferiorly (e.g., Bankart, anterior labroligamentous periosteal sleeve avulsion, and Perthes), capsular lesions (humeral avulsion of the glenohumeral ligament), accompanying cartilage lesions (Hill-Sachs, glenolabral articular disruption), and rotator interval and pulley lesions, as well as signs of dynamic instability impingement (posterior-superior impingement, anterior-superior impingement) can be exactly diagnosed (magnetic resonance imaging with intra-articular gadolinium, arthroscopy) and treated (arthroscopy). Therefore the purpose of this article is to review the current literature concerning shoulder anatomy/pathology related to shoulder stability/instability to improve clinical diagnosis and surgical treatment of our patients. [Copyright &y& Elsevier]

Abstract: Growth factors like BMP2 have been tested for osteochondral repair, but transfer methods used until now were insufficient. Therefore, the aim of this study was to analyse if stable BMP2 expression after retroviral vector (Bullet) transduction is able to regenerate osteochondral defects in rabbits. Fibrin clots colonized by control or BMP2-transduced chondrocytes were generated for in vitro experiments and implantation into standardized corresponding osteochondral defects (n =32) in the rabbit trochlea. After 4 and 12 weeks repair tissue was analysed by histology (HE, alcian-blue, toluidine-blue), immunohistochemistry (Col1, Col2, aggrecan, aggrecan-link protein), ELISA (BMP2), and quantitative RT-PCR (BMP2, Col1, Col2, Col10, Cbfa1, Sox9). In vitro clots were also analysed by BMP2-ELISA, histology (alcian-blue), quantitative RT-PCR and in addition by electron microscopy. BMP2 increased Col2 expression, proteoglycan production and cell size in vitro. BMP2 transduction by Bullet was efficient and gene expression was stable in vivo over at least 12 weeks. Proteoglycan content and ICRS-score of repair tissue were improved by BMP2 after 4 and 12 weeks and Col2 expression after 4 weeks compared to controls. However, in spite of stable BMP2 expression, a complete repair of osteochondral defects could not be demonstrated. Therefore, BMP2 is not suitable to regenerate osteochondral lesions completely. [Copyright &y& Elsevier]

Abstract: Since efficient transfer of foreign genes into primary articular chondrocytes (CC) is difficult, a VSV.G pseudotyped retroviral vector (Bullet) was developed for marker and growth factor gene transfer. Transduction efficiency was analysed by FACS. BMP2 production was determined by specific hBMP2-ELISA. BMP2 effect on cells regarding proteoglycan production was measured by alcian blue staining and dye quantification. Alkaline phosphatase activity was determined by enzymatic reaction with p-nitrophenyl phosphate at OD 405nm and proliferation rate was analysed by MTT-assay. ATDC5 cells (98.3±0.6%SD) were transduced to express the reporter gene eGFP. After 52 weeks 94.7±0.6%SD of cells were positive. Retroviral transduction efficiency for nlslacZ exceeded 92.3±6.1%SD in rabbit CC and expression remained high after 15 weeks (75.7±14.2%SD). ATDC5 cells and CC expressed the growth factor gene hBMP2 after retroviral transduction at different time-points. BMP2 led to an increase in proteoglycan and alkaline phosphatase production. Initially, the proliferation rate detected by MTT-assay increased in both the cell types; afterwards the proliferation rate was similar to controls. The described retroviral vector system achieved high initial transduction rates in ATDC5 cells and CC. Gene transfer was very stable over the time period analysed, rendering it a useful tool for future in vitro and in vivo studies on cartilage remodelling. [Copyright &y& Elsevier]

Abstract: Bone formation and remodeling in vivo can be assessed by polychrome labeling using calcium-binding fluorescent dyes. The number of fluorochromes, however, limits this technique due to the fact that with increasing number, fluorescent spectra inevitably overlap, which makes discrimination more difficult. In order to enhance discrimination, we performed spectral image analysis. Non-critical size defects of the femur of male Wistar rats served as a model for bone formation. Eight different fluorochromes (calcein blue, xylenol orange, calcein, alizarine complexone, doxycycline, rolitetracycline, hematoporphyrin, and BAPTA) were administered sequentially subcutaneously every third day starting at day 4 after surgery. Following, bone specimen were embedded in methylmethacrylate and analyzed by spectral image acquisition using a Sagnac type interferometer (ASI, Israel). Seven of the eight applied fluorochromes could be resolved using spectral image examination. With BAPTA, we present a new fluorochrome suitable for bone labeling. Due to the superior sensitivity of the spectral image acquisition, the thickness of the bone sections could be reduced so that 5 μm thick sections could be analyzed. Spectral decomposition and subsequent linear unmixing allows depiction of each individual fluorochrome without interference of any other, enabling a reliable and superior morphometric analysis of labeled regions. [Copyright &y& Elsevier]

The small GTPase RhoA is involved in the regulation of various cellular functions like the remodeling of the actin cytoskeleton and the induction of transcriptional activity. G-protein-coupled receptors (GPCRs), which are able to activate Gq/G[sub 11] and G[sub 12]/G[sub 13] are major upstream regulators of RhoA activity, and G[sub 12]/G[sub 13] have been shown to couple GPCRs to the activation of Rho by regulating the activity of a subfamily of RhoGEF proteins. However, the possible contribution of G[sub q]/ G[sub 11] to the regulation of RhoA activity via GPCRs is controversial. We have used a genetic approach to study the role of heterotrimeric G-proteins in the activation of RhoA via endogenous GPCRs. In pertussis toxin-treated Gα[sub 12]/Gα[sub 13]-deficient as well as in Gα[sub q]/Gα[sub 11]-deficient mouse embryonic fibroblasts (MEFs), in which coupling of receptors is restricted to G[sub q]/G[sub 11] and G[sub 12]/G[sub 13], respectively, receptor activation results in Rho activation. Rho activation induced by receptor agonists via G[sub q]/G[sub 11] occurs with lower potency than Rho activation via G[sub 12]/G[sub 13]. Activation of RhoA via G[sub q]/G[sub 11] is not affected by the phospholipase-C blocker U73122 or the Ca[sup 2+]-chelator BAPTA, but can be blocked by a dominant-negative mutant of the RhoGEF protein LARG. Our data clearly show that G[sub 12]/G[sub 13] as well as G[sub q]/G[sub 11] alone can couple GPCRs to the rapid activation of RhoA. G[sub q]/ G[sub 11]-mediated RhoA activation occurs independently of phospholipase C-β and appears to involve LARG. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate subjective and objective clinical and magnetic resonance imaging-based radiologic outcomes after short-term follow-up in patients with focal full-size cartilage lesions of the knee joint treated with all-arthroscopic hydrogel-based autologous chondrocyte transplantation.Methods: A retrospective study on patients with isolated focal cartilage defects of the knee joint who were treated with arthroscopically conducted matrix-induced autologous chondrocyte transplantation was performed. Clinical scores were assessed at baseline and final follow-up using the Tegner Score, visual analog scale, the International Knee Documentation Committee, and the 5 subscales of the Knee Injury and Osteoarthritis Outcome Score. Magnetic resonance imaging scans of the treated knee joints were evaluated with the updated MOCART (Magnetic Resonance Observation of Cartilage Repair Tissue) 2.0 scoring system at follow-up.Results: Twenty-nine consecutive patients were included in the study. Mean time to follow-up was 24.9 ± 1.1 months. Average visual analog scale decreased significantly from 6.5 ± 3.1 preoperatively to 2.3 ± 1.6 at follow-up (P < .0001). Tegner score increased from 3.1 ± 1.3 to 4.3 ± 1.2 (P < .0001) and the International Knee Documentation Committee from 43.8 ± 21.9 to 64.9 ± 18.9 (P < .0001). Also, all Knee Injury and Osteoarthritis Outcome Score subscales displayed significant improvements. Patients showed similar improvements of nearly all clinical scores independent of the defect size. Average MOCART2.0 score was 70.0 ± 13.6 and 20 patients scored ≥70 points. All 8 patients with large defects (>5 cm2) scored ≥75 points.Conclusions: In this small study, injectable matrix-induced autologous chondrocyte transplantation therapy in the knee joint led to favourable clinical and radiologic short-term results with significant improvements in all clinical scores and MOCART2.0 scores, confirming morphologic integrity of the transplanted chondrocytes. Therefore, this minimally invasive procedure represents a promising operative technique for cartilage regeneration, even for large-diameter lesions.Level Of Evidence: IV, therapeutic case series. [ABSTRACT FROM AUTHOR]

• In some cases, the feed-in from renewable energy sources is allocated to the nearest substation for grid calculations. • A procedure is presented for allocating the feed-in from renewable energy sources, e.g. from forecasts, in particular from wind energy, to substations. • This is achieved by maximizing the correlation between the vertical power flows and the generation time series. • For this purpose, a quadratically constrained program under the consideration of energy conservation is solved. The expansion of photovoltaics and wind energy shifts the feed-in from the transmission grids down to the lower voltage levels of the distribution grids. It is a challenging task to determine at which transformer station of the extra-high voltage grid photovoltaic and wind energy is fed via the cascade of the different grid levels. In principle, this allocation problem of generation to transformer stations can be solved with a power flow calculation if the topology and parameters of all grids are known. In reality, however, this knowledge is spread over several grid operators and alternative solutions could be promising. We propose a method for inversely correcting an initially estimated allocation of wind power generators to transformer stations between the transmission and the distribution grid based on correlating the wind power feed-in with the vertical power flows measured at the considered transformer stations. Our experimental setup involves the allocation optimization of about 29 GW of installed wind power to 136 transformer stations within the two largest German control zones. By shifting a total amount of 12.6 GW of allocated wind power between these transformer stations, our scheme is able to detect and correct erroneous allocations and to improve the reliability of the estimated wind power feed-in per transformer station. [ABSTRACT FROM AUTHOR]

Abstract The performance evaluation of forecasting algorithms is an essential requirement for quality assessment and model comparison. In recent years, algorithms that issue predictive distributions rather than point forecasts have evolved, as they better represent the stochastic nature of the underlying numerical weather prediction and power conversion processes. Standard error measures used for the evaluation of point forecasts are not sufficient for the evaluation of probabilistic forecasts. In comparison to deterministic error measures, many probabilistic scoring rules lack intuition as they have to satisfy a number of requirements such as reliability and sharpness, whereas deterministic forecasts only need to be close to the actual observations. This article aims to empower practitioners and users of probabilistic forecasts to be able to choose appropriate uncertainty representations and scoring rules depending on the desired application and available data. A holistic view of the most popular forms of uncertainty representation from single forecasts and ensembles is given, followed by a presentation of the most popular scoring rules. We want to broaden the understanding for the working principles and relationship of different scoring rules and their decomposition for probabilistic forecasts of continuous variables by showing their differences. Therefore, we analyze the behavior of scoring rules, a process frequently referred to as metaverification, in detail on real-world multi-model ensemble forecasts in a number of case studies. Highlights • An extensive overview of different forms of construction and representation of probabilistic forecasts for renewable energies. • A holistic view of forms of uncertainty representation that enable a better comparability of probabilistic forecasting algorithms. • A detailed comparison of characteristics of algorithms that create distribution forecasts. • A performance analysis and a detailed investigation of characteristics of the presented scoring rules. • Detailed investigation of the role of scoring rule decomposition and presentation of differences in the expressiveness of decomposition components. [ABSTRACT FROM AUTHOR]

Abstract: To examine a retroviral gene transfer to chondrocytes in vitro and in vivo in tissue-engineered cell–collagen constructs articular chondrocytes from rabbits and humans were isolated and transduced with VSV.G pseudotyped murine leukemia virus-derived retroviral vectors. Viral supernatants were generated by transient transfection of 293T cells using the pBullet retroviral vector carrying the nlslacZ gene, a Moloney murine leukemia virus gag/pol plasmid and a VSV.G coding plasmid. Transduction efficiency was analyzed by fluorescence-activated-cell-sorter analysis and transduced autologous chondrocytes from rabbits were seeded on collagen-scaffolds and implanted into osteochondral defects in the patellar groove of the rabbit''s femur (n=10). LacZ-expression was analyzed by X-gal staining on total knee explants and histological sections. Retroviral transduction efficiency exceeded 92.3% (SEM±3.5%) in rabbit articular chondrocytes, 74.7% (SEM±1.8%) in human articular chondrocytes and 52.7% (SEM±5.8%) in osteoarthritic human chondrocytes. Reporter gene expression remained high after 15 weeks in 75.7% (SEM±8.2%) of transduced rabbit articular chondrocytes. In vivo, intraarticular β-galactosidase activity could be determined in the majority of implanted chondrocytes in the osteochondral defects after 4 weeks. [Copyright &y& Elsevier]

Abstract: Bioactive implants are promising tools in regenerative medicine. Here we describe a versatile procedure for preparing a gene-activated matrix on titanium. Lyophilized copolymer-protected gene vectors (COPROGs) suspended in poly(d,l-lactide) (PDLLA) solutions in ethyl acetate were used to varnish solid surfaces. The gene-activated PDLLA surfaces were first established on polypropylene 96-well plates. Vector release from these surfaces in aqueous buffer, cell viability and gene transfer efficiency to NIH 3T3 fibroblasts was strongly dependent on the vector dose and its ratio to PDLLA film thickness. A detailed analysis of these relationships allowed establishing correlations which can be used to calculate suitable combinations of COPROGs and PDLLA yielding optimal gene transfer efficiency. This was verified with COPROG-activated PDLLA coatings on titanium foils. HEK 293 and mesenchymal stem cells expressed the BMP-2 gene comprised in the gene-activated surface in a manner that was consistent with the predicted dose–response and toxicity profiles found in NIH 3T3 cells. The systematic procedure presented here for identifying optimal coating compositions can be applied to any combination of vector type and coating material. [Copyright &y& Elsevier]

Abstract: Matrix-assisted chondrocyte transplantation (m-ACI) still lacks any standardization in its execution in terms of cell passage (P), cell yield (C) and in vitro membrane-holding time (T). It was the goal of this study to analyze the effect of shifting cell culture parameters (P, C, T) on the in vitro as well as in vivo effort of a regulated animal m-ACI. Autologous rabbit knee articular chondrocytes were seeded within bilayer collagen I/III 3-D matrices in variation of P, C and T. Each time, 2 PCT-identical by 2 PCT-identical cell-matrix-constructs (CMC)/animal were created. Simultaneously 2 (PCT-distinct) were re-implanted (CMC-e) autologous into artificial trochlear pristine chondral defects in vivo to remain for 12 weeks while the remaining 2 were harvested (CMC-i) for immediate in vitro analysis at the time of transplantation of their identical twins. mRNA of both, CMC-e regenerates and CMC-i membranes, was analyzed for Collagen-1,-2,-10, COMP, Aggrecan, Sox9 expression by use of a mixed linear model, multiple regression analysis. Generally, CMC-i values were higher than CMC-e values for differentiation targets; the opposite was true for dedifferentiation targets. Regarding individual gene expression, in vivo regenerate cell-matrix properties were significantly dependent on initial cell-matrix in vitro values as a sign of linearity. The parameter membrane-holding time (T) had strongest effects on the resulting mRNA expression with slightly less impact of the parameter passage (P), whereas cell yield (C) had clearly less effects. Noting differences between in vitro and in vivo data, in general, optimal expression patterns concerning chondrogenic differentiation were achieved by few passages, medium cellular yield, short membrane-holding time. Clinical m-ACI may benefit from optimal orchestration of the cell culture parameters passage, yield and time. [Copyright &y& Elsevier]

Abstract: For more than 20 years, countries and their agencies which monitor radionuclide discharge sites and storage facilities have relied on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 4355 Peruvian Soil. Its low fallout contamination makes it an ideal soil blank for measurements associated with terrestrial-pathway-to-man studies. Presently, SRM 4355 is out of stock, and a new batch of the Peruvian soil is currently under development as future NIST SRM 4355A. Both environmental radioanalytical laboratories and mass spectrometry communities will benefit from the use of this SRM. The former must assess their laboratory procedural contamination and measurement detection limits by measurement of blank sample material. The Peruvian Soil is so low in anthropogenic radionuclide content that it is a suitable virtual blank. On the other hand, mass spectrometric laboratories have high sensitivity instruments that are capable of quantitative isotopic measurements at low plutonium levels in the SRM 4355 (first Peruvian Soil SRM) that provided the mass spectrometric community with the calibration, quality control, and testing material needed for methods development and legal defensibility. The quantification of the ultra-low plutonium content in the SRM 4355A was a considerable challenge for the mass spectrometric laboratories. Careful blank control and correction, isobaric interferences, instrument stability, peak assessment, and detection assessment were necessary. Furthermore, a systematic statistical evaluation of the measurement results and considerable discussions with the mass spectroscopy metrologists were needed to derive the certified values and uncertainties. The one sided upper limit of the 95% tolerance with 95% confidence for the massic 239Pu content in SRM 4355A is estimated to be 54,000atoms/g. [Copyright &y& Elsevier]