78 research outputs found

    Comparison of a Solvent-Free Tar Quantification Method to the International Energy Agency’s Tar Measurement Protocol

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    This paper presents a new method for measuring tar concentration in biomass-derived producer gas streams. This solvent-free method is much simpler than the evaporative method of the International Energy Agency (IEA) tar protocol. In tests on producer gas from a fluidized bed biomass gasifier this so-called dry condenser method yielded tar measurements with precision better than 5% and accuracy averaging to within 10% of the IEA tar protocol. Comparisons of water vapor concentrations in producer gas as determined by the two methodologies showed poor agreement, which appears to be due to the low precision of both techniques for this measurement, possibly the result of dissolved hydrocarbons in the recovered aqueous phases

    Noether's first theorem and the energy-momentum tensor ambiguity problem

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    Noether's theorems are widely praised as some of the most beautiful and useful results in physics. However, if one reads the majority of standard texts and literature on the application of Noether's first theorem to field theory, one immediately finds that the ``canonical Noether energy-momentum tensor'' derived from the 4-parameter translation of the Poincaré group does not correspond to what's widely accepted as the ``physical'' energy-momentum tensor for central theories such as electrodynamics. This gives the impression that Noether's first theorem is in some sense not working. In recognition of this issue, common practice is to ``improve" the canonical Noether energy-momentum tensor by adding suitable ad-hoc ``improvement'' terms that will convert the canonical expression into the desired result. On the other hand, a less common but distinct method developed by Bessel-Hagen considers gauge symmetries as well as coordinate symmetries when applying Noether's first theorem; this allows one to uniquely derive the accepted physical energy-momentum tensor without the need for any ad-hoc improvement terms in theories with exactly gauge invariant actions. Given these two distinct methods to obtain an energy-momentum tensor, the question arises as to whether one of these methods corresponds to a preferable application of Noether's first theorem. Using the converse of Noether's first theorem, we show that the Bessel-Hagen type transformations are uniquely selected in the case of electrodynamics, which powerfully dissolves the methodological ambiguity at hand. We then go on to consider how this line of argument applies to a variety of other cases, including in particular the challenge of defining an energy-momentum tensor for the gravitational field in linearized gravity. Finally, we put the search for proper Noether energy-momentum tensors into context with recent claims that Noether's theorem and its converse make statements on equivalence classes of symmetries and conservation laws: We aim to identify clearly the limitations of this latter move, and develop our position by contrast with recent philosophical discussions about how symmetries relate to the representational capacities of our theories

    Iatrogenic Subtotal Stenosis of the Right Subclavian Artery Treated With Percutaneous Transluminal Angioplasty

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    This report describes a rare vascular complication of surgical placement of a marking clip and a possible approach to problem solving. A 55-year-old patient presented with loss of sensation in the fingers and loss of peripheral pulsations in the right arm 4 days after right upper lobectomy for a pT2N1 moderately differentiated adenocarcinoma of the lung. Duplex examination and computed tomography were performed the same day and showed a subtotal stenosis of the right subclavian artery, which was caused by the surgical placement of a metal clip to mark the surgical boundary. Selective angiography was subsequently performed. Percutaneous transluminal angioplasty (PTA) successfully dilated the stenosis and pushed the clip off. Flow in the right subclavian artery (RSA) was completely restored as were neurology and peripheral pulses. In conclusion, arterial stenosis by a surgical (marking) clip may be feasibly treated with PTA

    Incidence, Risk Factors, and Impact of Severe Neutropenia After Hyperthermic Intraperitoneal Mitomycin C

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    Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are considered the standard of care for patients with peritoneal dissemination of appendiceal cancer and are increasingly being evaluated for use in patients with carcinomatosis from colon cancer. Mitomycin C (MMC) is one of the most frequently used HIPEC agents in the management of peritoneal-based gastrointestinal malignancies. This study analyzes the incidence and risk factors for developing neutropenia following MMC-HIPEC combined with CRS. All patients undergoing CRS and MMC-HIPEC for appendiceal cancer between January 1993 and October 2006 were retrospectively reviewed. Logistic regression was used to identify risk factors for the development of neutropenia, defined as an absolute neutrophil count (ANC) <1,000/mm3. One hundred and twenty MMC-HIPEC were performed in 117 patients with appendiceal cancer. The incidence of neutropenia was 39%. Neutropenia occurred in 57.6% of female and 21.3% of male patients (p < 0.0001). Female gender and MMC dose per body surface area (BSA) were independent risk factors for neutropenia on multivariable logistic regression [odds ratio (OR) of neutropenia in females = 3.58 (95% confidence interval, CI: 1.52, 8.43); OR for 5 unit (mg/m2) increase in MMC dose per BSA = 3.37 (95% CI: 1.72, 6.63)]. Neutropenia did not increase the risk of mortality, postoperative infection or length of hospital stay. Neutropenia is a frequent complication associated with MMC-HIPEC. Female sex and MMC dose per BSA are independent risk factors for neutropenia. These differences must be considered in the management of patients undergoing MMC-HIPEC to minimize the toxicity of the procedure

    Characterization of genome-wide p53-binding sites upon stress response

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    The tumor suppressor p53 is a sequence-specific transcription factor, which regulates the expression of target genes involved in different stress responses. To understand p53's essential transcriptional functions, unbiased analysis of its DNA-binding repertoire is pivotal. In a genome-wide tiling ChIP-on-chip approach, we have identified and characterized 1546 binding sites of p53 upon Actinomycin D treatment. Among those binding sites were known as well as novel p53 target sites, which included regulatory regions of potentially novel transcripts. Using this collection of genome-wide binding sites, a new high-confidence algorithm was developed, p53scan, to identify the p53 consensus-binding motif. Strikingly, this motif was present in the majority of all bound sequences with 83% of all binding sites containing the motif. In the surrounding sequences of the binding sites, several motifs for potential regulatory cobinders were identified. Finally, we show that the majority of the genome-wide p53 target sites can also be bound by overexpressed p63 and p73 in vivo, suggesting that they can possibly play an important role at p53 binding sites. This emphasizes the possible interplay of p53 and its family members in the context of target gene binding. Our study greatly expands the known, experimentally validated p53 binding site repertoire and serves as a valuable knowledgebase for future research

    A picture of medically assisted reproduction activities during the COVID-19 pandemic in Europe

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    STUDY QUESTION: How did coronavirus disease 2019 (COVID-19) impact on medically assisted reproduction (MAR) services in Europe during the COVID-19 pandemic (March to May 2020)? SUMMARY ANSWER: MAR services, and hence treatments for infertile couples, were stopped in most European countries for a mean of 7 weeks. WHAT IS KNOWN ALREADY: With the outbreak of COVID-19 in Europe, non-urgent medical care was reduced by local authorities to preserve health resources and maintain social distancing. Furthermore, ESHRE and other societies recommended to postpone ART pregnancies as of 14 March 2020. STUDY DESIGN, SIZE, DURATION: A structured questionnaire was distributed in April among the ESHRE Committee of National Representatives, followed by further information collection through email. PARTICIPANTS/MATERIALS, SETTING, METHODS: The information was collected through the questionnaire and afterwards summarised and aligned with data from the European Centre for Disease Control on the number of COVID-19 cases per country. MAIN RESULTS AND THE ROLE OF CHANCE: By aligning the data for each country with respective epidemiological data, we show a large variation in the time and the phase in the epidemic in the curve when MAR/ART treatments were suspended and restarted. Similarly, the duration of interruption varied. Fertility preservation treatments and patient supportive care for patients remained available during the pandemic. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Data collection was prone to misinterpretation of the questions and replies, and required further follow-up to check the accuracy. Some representatives reported that they, themselves, were not always aware of the situation throughout the country or reported difficulties with providing single generalised replies, for instance when there were regional differences within their country. WIDER IMPLICATIONS OF THE FINDINGS: The current article provides a basis for further research of the different strategies developed in response to the COVID-19 crisis. Such conclusions will be invaluable for health authorities and healthcare professionals with respect to future similar situations.peer-reviewe

    Hypothyroidism in an Area of Endemic Goiter and Cretinism in Central Java, Indonesia

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    In an area of severe endemic goiter in Central Java, Indonesia, clinical overt or mild hypothyroidism appeared to be present in 7 out of 20 cretins and also in 12 out of 94 non-cretinous subjects, all 5–20 years of age, living in the village of Sengi. Hypothyroidism was not found in a control group of 70 subjects of the same age living in Londjong just outside the edemia. In hypothyroid subjects the plasma PBI-concentration was 0.98 ± 0.32 µg/100 ml (mean ± SD) vS 2.72 ± 1.24 µg/100 ml in euthyroid subjects from Sengi and 4.86 ± 0.80 µg/100 ml in controls from Londjong. Values for T3 were 56.3 ± 31.7 ng/100 ml in hypothyroids, 140.5 ± 38.5 ng/100 ml in euthyroids from Sengi and 121.6 ± 27.4 ng/100 ml in controls. The TSH levels (geometric mean and range) in these 3 groups were, respectively, 210.1 (108.0–342), 15.6(3.0– 372) and 4.1 (0.8–7.0) µU/ml. The differences between themean concentration of PBI, T3 and TSH in the hypothyroid and euthyroid groups were highly significant (P < 0.001). These data strengthen the clinical diagnosis of hypothyroidism in cretins as well as in non-cretinous subjects. All hypothyroid subjects had a PBI < 1.8 µg/100 ml and T3 < 120 ng/100 ml and TSH < 100 µU/ml. In 8 hypothyroid subjects, restudied 18 months after iodized oil injection, hypothyroidism was either corrected or markedly improved. It therefore appears that iodine deficiency per se in post natal life may lead to (juvenile) hypothyroidism, which can be corrected by iodine therapy. Our findings have implications for the definition and diagnosis of endemic cretinism. Not all hypothyroid subjects in an area of endemic iodine deficiency should be classified as cretins
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