A covariant constituent-quark formalism for mesons

Using the framework of the Covariant Spectator Theory (CST) [1] we are developing a covariant model formulated in Minkowski space to study mesonic structure and spectra. Treating mesons as effective $q\bar{q}$ states, we focused in [2] on the nonrelativistic bound-state problem in momentum space with a linear confining potential. Although integrable, this kernel has singularities which are difficult to handle numerically. In [2] we reformulate it into a form in which all singularities are explicitely removed. The resulting equations are then easier to solve and yield accurate and stable solutions. In the present work, the same method is applied to the relativistic case, improving upon the results of the one-channel spectator equation (1CSE) given in [3].Comment: 6 pages, 5 figures, Presented at EEF70, Workshop on Unquenched Hadron Spectroscopy: Non-Perturbative Models and Methods of QCD vs. Experimen

A systematic procedure to enhance reproducibility of SWASV cycles in the determination of toxic metals in real samples

This work presents for the first time a systematic study on the optimization of the electrochemical cleaning time of a mercury film when it is used as a working electrode material in the analysis of toxic metals, such as Pb2+, used as model metal, in real samples by SWASV. The optimization study for the film’s cleaning time aimed at attaining a Pb2+ minimum value in the film after the re-oxidation step of the pre-concentrated metal, given the impossibility of complete removal of traces of the electroactive species from the film. This value was kept constant in each concentration range studied ensuring thus that all assays were performed in initial identical conditions. An assay performed on a synthetic sample was taken as reference. In it, given the absence of matrix effects, and after the electrochemical cleaning step, a direct proportionality was observed between the residual amounts of Pb2+ in the film (which for the cleaning time used was never completely removed) and Pb2+ concentration in the solution. This fact determined a high correlation between Pb2+ peak current and Pb2+ concentration which was not observed when real samples (tree leaves) were analyzed. This behavior may result from the presence of the interfering surfactants always present in real samples of complex matrix. Cleaning time optimization was performed for the following Pb2+ concentration ranges in the real samples of complex matrix: 0.006-0.020, 0.020-0.080, 0.060-0.200 and 0.100-0.600 ppb. As expected, in order to obtain identical levels of film’s cleaning efficiency, the need for longer cleaning times has been observed for higher concentrations. The optimized cleaning times for the concentration ranges under study were 120, 150, 180 e 300 s, respectively

Innovation and environmental policy: Clean vs. dirty technical change

We study a two sector endogenous growth model with environmental quality with two goods and two factors of production, one clean and one dirty. Technological change creates clean or dirty innovations. We compare the laissez-faire equilibrium and the social optimum and study first- and second-best policies. Optimal policy encourages research toward clean technologies. In a second-best world, we claim that a portfolio that includes a tax on the polluting good combined with optimal innovation subsidy policies is less costly than increasing the price of the polluting good alone. Moreover, a discriminating innovation subsidy policy is preferable to a non-discriminating one

Alteration of the conserved residue tyrosine-158 to histidine renders human O6-alkylguanine-DNA alkyltransferase insensitive to the inhibitor O6- benzylguanine

The DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) protects cells from alkylation damage. O6-Benzylguanine (BG) is a potent inactivator of human AGT (ED50 of 0.1 μM) that is currently undergoing clinical trials to enhance chemotherapy by alkylating agents. In a screen of AGT mutants randomly mutated at position glycine-160, we found that the double mutant Y158H/G160A protected Escherichia coli from killing by N- methyl-N'-nitro-N-nitrosoguanidine (MNNG) even in the presence of BG and that the AGT activity of this mutant was strongly resistant to BG (ED50 of 180 μM). Because the single mutant G160A was not resistant to BG, this suggested that the presence of the charged histidine residue at position 158 was responsible. This hypothesis was confirmed by the construction of the single mutation Y158H. The Y158H-mutant AGT was slightly less active than wild-type AGT for the repair of mcthylated DNA in vitro, but it protected E. coli from killing by MNNG even in the presence of BG and had an ED50 for the inactivation by BG of 620 μM. In contrast, mutant Y158F had an ED50 of 0.2 μM. Previous studies (M. Xu-Welliver et al., Cancer Res., 58: 1936-1945, 1998) have shown that mutant P140K is highly resistant to BG (ED50 of > 1200 μM). Models of human AGT suggest that the side chain of the lysine inserted into this mutant is close to tyrosine-158 and that the positively charged lysine side-chain may interfere with BG binding. The double mutants P140K/Y158H and P140K/Y158F resembled P140K and Y158H in being highly resistant to BG, but the use of a sensitive assay for reaction of BG with AGT indicated that their abilities to react were in the order P140K/Y158H < P140K < P140K/Y158F. These results confirm that the presence of a positively charged residue close to the active site of human AGT renders it highly resistant to BG without substantially affecting activity toward methylated DNA substrates. Such mutants may limit the value of BG therapy if they arise in malignant cells during chemotherapy, but the mutant sequences may be useful for gene therapy approaches in which BG-resistant human AGTs are used to prevent hematopoietic toxicity. At least 28 AGT sequences (from 25 species) have now been described. In 25 of these, the position equivalent to 158 in the human AGT is also a tyrosine, and in the other 3, it is a phenylalanine. The importance of an aromatic ring side chain at this position is emphasized by previous studies (S. Edara et al., Carcinogenesis, 16: 1637- 1642, 1995), which show that the replacement by alanine renders human AGT inactive. Our results show that histidine can also substitute for tyrosine at this position

Acute myelogenous leukemia presenting as diabetes insipidus

Central diabetes insipidus, is a syndrome characterized by the excretion of abnormally elevated volumes of diluted urine, due to the diminution of reabsorption of water in the collecting ducts, induced by the diminution of production of antidiuretic hormone. The involvement of the central nervous system in the leukaemia is frequent, but the association leukaemia/diabetes insipidus is rare. We describe a clinical case of a 40 years old female, whose first manifestation of leukaemia was diabetes insipidus; we discuss the difficulties of diagnosis, the particularities of the case and its evolution

Síndrome hipertensiva hiponatrémica em destaque – um caso clínico

Descrita pela primeira vez em 1952, a síndrome hipertensiva hiponatrémica (SHH) é a combinação de hipertensão severa, hiponatremia e isquémia renal. Mais do que rara, a síndrome é principalmente subdiagnosticada. Isto limita o conhecimento real e completo da sua fisiopatologia e jus_fica a inexistência de estudos aleatorizados prospe_vos com avaliação real de opções terapêu_cas. A necessidade de aumentar a consciencialização para a síndrome por parte da comunidade médica é premente, especialmente se _vermos em consideração que é uma síndrome potencialmente curável e com taxas de mortalidade que chegam aos 25% nos adultos. Assim, apresenta-se um caso de SHH, com necessidade de nefrectomia para controlo e tratamento definitivo da síndrome.info:eu-repo/semantics/publishedVersio

Fetal growth and glycemic control in type 1 diabetes pregnancy

INTRODUCTION: Conflicting results have been reported with respect to the relationship between direct or indirect measures of glycemic control in mothers with type 1 diabetes and macrosomia. OBJECTIVE: To evaluate the frequency of LGA babies in type 1 diabetic pregnancies and analyse the influence of some maternal characteristics and glucose control in oversized babies. MATERIAL AND METHODS: A retrospective study of 18 pregnant women with type 1 diabetes mellitus was performed. It was divided in two groups: group 1 (G1- n=9)--pregnant women with LGA babies and group 2 (G2- n=9)--pregnant women with AGA (Appropriate weight for gestational age) babies. We evaluate the follow parameters: HbA1c in the third trimester of pregnancy, fasting and 1 h postprandial capillary glucose levels, pregestational BMI, maternal age, duration of Diabetes mellitus, weight gain during pregnancy, microvascular diabetes complications (retinopathy and nefropathy), and type of delivery. We defined LGA birth weight over the 90 centile. RESULTS: LGA babies occurred in 50% of gestations. We did not find any statistical differences in maternal age, diabetes mellitus duration, pregestational BMI, weight gain during pregnancy, microvascular diabetes complications, HbA1c levels (medium value in the two groups 6,5%). The glucose fasting values were higher in G1: 95,7 +/- 31.7 mg/ dl, vs G2: 83.3 +/- 17.1 mg/dl without, however, reaching statistically significant differences. There was statically differences in postprandial glucose values G1: 160.3 +/- 60.2 mg/dl vs G2: 111.9 +/- 27.1 mg/dl -- p= 0.043. CONCLUSIONS: The frequency of LGA babies was elevated 50% in type 1 diabetic pregnancies, although normal HbA1c values. Thus we conclude that the 1 h postprandial glucose levels should be considered a strong predictor of fetal growth

Artificial reefs: from ecological processes to fishing enhancement tools

info:eu-repo/semantics/publishedVersio