23,915 research outputs found
The Quantum Algebraic Structure of the Twisted XXZ Chain
We consider the Quantum Inverse Scattering Method with a new R-matrix
depending on two parameters and . We find that the underlying algebraic
structure is the two-parameter deformed algebra enlarged by
introducing an element belonging to the centre. The corresponding Hamiltonian
describes the spin-1/2 XXZ model with twisted periodic boundary conditions.Comment: LateX file, 9 pages, Minor changes (including authors` names in the
hep-th heading
Avaliação de extratores de zinco em solos da Amazônia.
A Fertbio 2002 reuniu a XXV Reunião Brasileira de Fertilidade do Solo e Nutrição de Plantas, a IX Reunião Brasileira sobre Micorrizas, o VII Simpósio Brasileiro de Microbiologia do Solo e a Reunião Brasileira de Biologia do Solo, sob o tema: "Agricultura: bases ecológicas para o desenvolvimento social e econômico sustentado
Influence of nutritional and operational parameters on the production of butanol or 1,3-propanediol from glycerol by a mutant Clostridium pasteurianum
Butanol and 1,3-propanediol (1,3-PDO) are simultaneously produced by Clostridium pasteurianum from glycerol. In this study, random chemical mutagenesis of C. pasteurianum DSM 525 was conducted to improve its tolerance to butanol. Selected nutritional and operational parameters were evaluated to identify strategies that favour the production of each metabolite. From those experiments, it was possible to isolate cells able to produce 22% more butanol than the parent strain in serum bottles. The supplementation of the culture medium with 2 mg l1 of iron increased the production of butanol by 163%, and the optimum inoculum age was found to be 12 h. Overall, the experiments conducted in bioreactor led to lower butanol titers than in serum bottles, which is attributed to the higher pressure present in the bottles. At pH 6.0, N2 sparging notoriously favoured the production of biomass and 1,3-PDO, while a lower pH (5.0) led to a higher butanol yield, although growth was negatively affected. The results herein gathered allowed the identification of specific conditions that favour the production of either butanol or 1,3-PDO. Furthermore, it was found that N2 sparging is a suitable strategy to maximize the titer, yield and productivity of 1,3-PDO using C. pasteurianum.The authors acknowledge the financial support from the Strategic funding of UID/BIO/04469/2013 unit and project ref. RECI/BBB-EBI/0179/2012 (project number FCOMP-01-0124-FEDER-027462) and R. Gallardo's doctoral grant (ref SFRH/BD/42900/2008) funded by Fundação para a Ciência e a Tecnologia. The authors thank the MIT-Portugal Program for the support given to R. Gallardo
Contrast Medium Volume Optimization in Abdominal CT on Basis of Lean Body Weight
This is the final version of the article. Available from Scientific and Academic Publishing via the link in this record.Computed tomography (CT) in abdominal imaging has undergone great advances in recent years. The
administration of iodinated contrast media (CM) has evolved along with the evolution of the CT equipment. The most
common method for calculation of the CM volume in abdominal CT is based on total body weight (TBW), but in this way
some patients get a lower dose and some other patients get a higher dose that the optimal dose they need. In the literature there
are many formulas to calculate the CM volume to be administered in abdominal CT, but practice shows that the variability of
enhancement is wide. The main objective of this study is to verify that the volume of intravenous CM in abdominal CT
calculated on basis of lean body weight (LBW) allows good liver enhancement with small amplitude of variation around the
mean, that is, with less variability in enhancement than CM volume calculated on basis of TBW. In conclusion the calculation
of the volume of CM on basis of LBW translates into a low variability of liver enhancement–25.50 HU. In our results 96.05%
of sample belongs to a good hepatic enhancement. If we stratify sample by groups of BMI, we also verify no significative
differences between slims and fat patients when analysed mean hepatic enhancement
Newly arrived migrant and refugee children in the British educational system
In 2009, Action for Social Integration was commissioned by London Councils to implement a four-year programme to improve the educational attainment for African and Caribbean children and young people in Barnet, Enfield and Haringey. Within this programme, the Social Policy Research Centre (SPRC) at Middlesex University has carried out a small-scale research project aimed at producing a guide for BME and migrant parents of children attending UK schools. The guide provides information to better understand the UK educational system, highlighting what may be different from those of other countries in the world and discussing issues such as language support and parents’ involvement. In order to identify the knowledge gaps and the main issues to include in the guide, the research team conducted a series of interviews, as well as an analysis and mapping of existing demographic data. The research findings presented in this report contribute to a better
understanding of the key challenges and opportunities facing BME parents and their children in London schools
Produção de lipase a partir de leveduras não convencionais isoladas do bagaço de caju
As lipases (E.C. 3.1.1.3) são uma classe de enzimas que catalisam a hidrólise dos triglicerÃdeos de ácidos gordos livres e glicerol. Essas enzimas encontram uma grande aplicação nas indústrias de alimentos, detergentes, cosméticos, sÃntese orgânica e farmacêutica. Neste trabalho, as leveduras Candida tropicalis e Meyerozyma caribbica isoladas do bagaço de caju foram testadas quanto à sua capacidade de produção de lipase. As fermentações foram conduzidas em agitador rotatório a 30 °C e 170 rpm. A medida da atividade foi feita através da hidrólise com o pNFL (p-nitrofenil laurato). Para a produção da enzima foi utilizado um meio de cultura contendo resÃduos agroindustriais, nomeadamente melaço 10 g/L, milhocina 4 g/L, águas russas 1,0 % (v/v). A atividade do sobrenadante da C. tropicalis foi 233 ± 10 U/L e da M. caribbica foi 146 ± 7,30 U/L em 24 h de fermentação. Esses resultados mostram o potencial dessas estirpes para a produção da enzima lipase a partir de resÃduos agroalimentares
Anisotropic Cosmological Constant and the CMB Quadrupole Anomaly
There are evidences that the cosmic microwave background (CMB) large-angle
anomalies imply a departure from statistical isotropy and hence from the
standard cosmological model. We propose a LCDM model extension whose dark
energy component preserves its nondynamical character but wield anisotropic
vacuum pressure. Exact solutions for the cosmological scale factors are
presented, upper bounds for the deformation parameter are evaluated and its
value is estimated considering the elliptical universe proposal to solve the
quadrupole anomaly. This model can be constructed from a Bianchi I cosmology
with cosmological constant from two different ways: i) a straightforward
anisotropic modification of the vacuum pressure consistently with
energy-momentum conservation; ii) a Poisson structure deformation between
canonical momenta such that the dynamics remain invariant under scale factors
rescalings.Comment: 8 pages, 2 columns, 1 figure. v2: figure improved, added comments on
higher eccentricity powers and references. v3: typos corrected, version to
appear in PR
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