bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disruption of the Reductive 1,3-Propanediol Pathway Triggers Production of 1,2-Propanediol for Sustained Glycerol Fermentation by Clostridium pasteurianum
Authors: Pyne Michael E. , Sokolenko Stanislav , Liu Xuejia , Srirangan Kajan , Bruder Mark R. , Aucoin Marc G. , Moo-Young Murray , Chung Duane A. , Chou C. Perry 
Published: June 2016

ABSTRACT

Crude glycerol, the major by-product of biodiesel production, is an attractive bioprocessing feedstock owing to its abundance, low cost, and high degree of reduction. In line with the advent of the biodiesel industry,
Clostridium pasteurianum
has gained prominence as a result of its unique capacity to convert waste glycerol into
n
-butanol, a high-energy biofuel. However, no efforts have been directed at abolishing the production of 1,3-propanediol (1,3-PDO), the chief competing product of
C. pasteurianum
glycerol fermentation. Here, we report rational metabolic engineering of
C. pasteurianum
for enhanced
n
-butanol production through inactivation of the gene encoding 1,3-PDO dehydrogenase (
dhaT
). In spite of current models of anaerobic glycerol dissimilation, culture growth and glycerol utilization were unaffected in the
dhaT
disruption mutant (
dhaT
::Ll.LtrB). Metabolite characterization of the
dhaT
::Ll.LtrB mutant revealed an 83% decrease in 1,3-PDO production, encompassing the lowest
C. pasteurianum
1,3-PDO titer reported to date (0.58 g liter
−1
). With 1,3-PDO formation nearly abolished, glycerol was converted almost exclusively to
n
-butanol (8.6 g liter
−1
), yielding a high
n
-butanol selectivity of 0.83 g
n
-butanol g
−1
of solvents compared to 0.51 g
n
-butanol g
−1
of solvents for the wild-type strain. Unexpectedly, high-performance liquid chromatography (HPLC) analysis of
dhaT
::Ll.LtrB mutant culture supernatants identified a metabolite peak consistent with 1,2-propanediol (1,2-PDO), which was confirmed by nuclear magnetic resonance (NMR). Based on these findings, we propose a new model for glycerol dissimilation by
C. pasteurianum
, whereby the production of 1,3-PDO by the wild-type strain and low levels of both 1,3-PDO and 1,2-PDO by the engineered mutant balance the reducing equivalents generated during cell mass synthesis from glycerol.

IMPORTANCE
Organisms from the genus
Clostridium
are perhaps the most notable native cellular factories, owing to their vast substrate utilization range and equally diverse variety of metabolites produced. The ability of
C. pasteurianum
to sustain redox balance and glycerol fermentation despite inactivation of the 1,3-PDO pathway is a testament to the exceptional metabolic flexibility exhibited by clostridia. Moreover, identification of a previously unknown 1,2-PDO-formation pathway, as detailed herein, provides a deeper understanding of fermentative glycerol utilization in clostridia and will inform future metabolic engineering endeavors involving
C. pasteurianum
. To our knowledge, the
C. pasteurianum dhaT
disruption mutant derived in this study is the only organism that produces both 1,2- and 1,3-PDOs. Most importantly, the engineered strain provides an excellent platform for highly selective production of
n
-butanol from waste glycerol.
A New Catabolic Plasmid in Xanthobacter and
Starkeya
spp. from a 1,2-Dichloroethane-Contaminated Site
Authors: Munro Jacob E. , Liew Elissa F. , Ly Mai-Anh , Coleman Nicholas V. 
Published: June 2016

ABSTRACT

1,2-Dichloroethane (DCA) is a problematic xenobiotic groundwater pollutant. Bacteria are capable of biodegrading DCA, but the evolution of such bacteria is not well understood. In particular, the mechanisms by which bacteria acquire the key dehalogenase genes
dhlA
and
dhlB
have not been well defined. In this study, the genomic context of
dhlA
and
dhlB
was determined in three aerobic DCA-degrading bacteria (
Starkeya novella
strain EL1,
Xanthobacter autotrophicus
strain EL4, and
Xanthobacter flavus
strain EL8) isolated from a groundwater treatment plant (GTP). A haloalkane dehalogenase gene (
dhlA
) identical to the canonical
dhlA
gene from
Xanthobacter
sp. strain GJ10 was present in all three isolates, and, in each case, the
dhlA
gene was carried on a variant of a 37-kb circular plasmid, which was named pDCA. Sequence analysis of the
repA
replication initiator gene indicated that pDCA was a member of the pTAR plasmid family, related to catabolic plasmids from the
Alphaproteobacteria
, which enable growth on aromatics, dimethylformamide, and tartrate. Genes for plasmid replication, mobilization, and stabilization were identified, along with two insertion sequences (IS
Xa1
and IS
Pme1
) which were likely to have mobilized
dhlA
and
dhlB
and played a role in the evolution of aerobic DCA-degrading bacteria. Two haloacid dehalogenase genes (
dhlB1
and
dhlB2
) were detected in the GTP isolates;
dhlB1
was most likely chromosomal and was similar to the canonical
dhlB
gene from strain GJ10, while
dhlB2
was carried on pDCA and was not closely related to
dhlB1
. Heterologous expression of the DhlB2 protein confirmed that this plasmid-borne dehalogenase was capable of chloroacetate dechlorination.

IMPORTANCE
Earlier studies on the DCA-degrading
Xanthobacter
sp. strain GJ10 indicated that the key dehalogenases
dhlA
and
dhlB
were carried on a 225-kb linear plasmid and on the chromosome, respectively. The present study has found a dramatically different gene organization in more recently isolated DCA-degrading
Xanthobacter
strains from Australia, in which a relatively small circular plasmid (pDCA) carries both
dhlA
and
dhlB
homologs. pDCA represents a true organochlorine-catabolic plasmid, first because its only obvious metabolic phenotype is dehalogenation of organochlorines, and second because acquisition of this plasmid provides both key enzymes required for carbon-chlorine bond cleavage. The discovery of the alternative haloacid dehalogenase
dhlB2
in pDCA increases the known genetic diversity of bacterial chloroacetate-hydrolyzing enzymes.
Microbial Antimony Biogeochemistry: Enzymes, Regulation, and Related Metabolic Pathways
Authors: Li Jingxin , Wang Qian , Oremland Ronald S. , Kulp Thomas R. , Rensing Christopher , Wang Gejiao 
Published: June 2016

ABSTRACT
Antimony (Sb) is a toxic metalloid that occurs widely at trace concentrations in soil, aquatic systems, and the atmosphere. Nowadays, with the development of its new industrial applications and the corresponding expansion of antimony mining activities, the phenomenon of antimony pollution has become an increasingly serious concern. In recent years, research interest in Sb has been growing and reflects a fundamental scientific concern regarding Sb in the environment. In this review, we summarize the recent research on bacterial antimony transformations, especially those regarding antimony uptake, efflux, antimonite oxidation, and antimonate reduction. We conclude that our current understanding of antimony biochemistry and biogeochemistry is roughly equivalent to where that of arsenic was some 20 years ago. This portends the possibility of future discoveries with regard to the ability of microorganisms to conserve energy for their growth from antimony redox reactions and the isolation of new species of “antimonotrophs.”
From a Miracle to a Disaster: the Brazilian Economy in the Last 3 Decades
Authors: Gomes Victor , Teixeira Arilton , Bugarin Mirta Sataka , Ellery Jr Roberto 
Published: June 2016

After showing a persistent and high growth rate since the World War II, in the beginning of the eighties the Brazilian growth rate of per capita GNP fell abruptly. In this paper we ask if this fall can be explained by the behavior of technological progress (measured by Total Factor Productivity or TFP). We study the period between 1970 and 1998. We divide this period in two sub-periods. In the first, the seventies, per capita GNP grew at 5.05% a year. In contrast with per capita GNP, TFP grew only until 1974, declining in the rest of the decade. After 1974, the growth rate of per capita GNP was sustained by an increasing investment as a share of GNP due to the increase in public (government plus state-owned firms) and private investments sustained by government subsidies that went from 1% to 4% of GNP in the second half of the seventies. In the second sub-period, the eighties and nineties, both TFP and per capita GNP decreased until 1993, increasing thereafter. We also find in thesecond half of the eighties that investment share was increasing while TFP was decreasing. In this second case it went up mainly as a result of the higher cost of capital relative to consumption. Our main conclusion is that the behavior of the technological progress can fairly describe the dynamics of the Brazilian economy during the period under study.
Stochastic Convergence Across Brazilian States
Authors: Mello Marcelo 
Published: June 2016

We analyze the dynamic properties of the relative income of Brazilian states for the 1985-2008 period. Unit root tests suggest that shocks to relative income have permanent effects, contradicting the stochastic convergence hypothesis. On the other hand, interval estimates of the largest autoregressive root produce wide confidence intervals that include many alternatives consistent with stationarity. Additionally, the confidence interval estimate of the half-life suggests that relative income shocks die out relatively quick, within an average of 0 to 5 years. These results suggest that relative income shocks have a temporary effect, thus supporting the stochastic convergence hypothesis. Furthermore, we build a relative income series for the Brazilian states for the 1947-2008 period andredo the exercises above. Finally, all of our results remain the same when we extend the sample to the 1947-2008 period.
Self-Selection and the Impact of Migration on Earnings
Authors: Avelino Ricardo R. G. 
Published: June 2016

This paper formulates and estimates a comparative advantage model of migration in which individuals maximize the value of log earnings, net of moving costs, by choosing between a pair of locations. Using a subsample of males from the 2003 wave of the PNAD, a comprehensive Brazilian national household survey, I construct six measures to assess the impact of migration on earnings. The results do not support the common notion that migrants constitute a positive selected subsample of the population, i.e., that they have unobservable traits which make them more productive than non-migrants at the destination, after controlling for observable characteristics.
On the empirical content of the formal-informal labor market segmentation hypothesis
Authors: Ulyssea Gabriel , Paes de Barros Ricardo 
Published: June 2016

To date, the empirical literature on the formal-informal labor market segmentation hypothesis has largely focused on the analysis of wage determination in both sectors. The underlying premise in this literature is that, under segmentation, equally productive workers receive higher wages if located in the formal sector. Thus, identifying the existence of wage differentials between equally productive workers would imply that the labor market is segmented. The objective of this paper is to examine the extent to which the premise behind this literature actually has empirical content, and whether or not one can actually identify the existence of segmentation by analyzing wage data alone. For that, we develop a simple framework to describe the main determinants of the cross-sectional wage distributions in both sectors. We show that the evidence can be supported by completely different models of labor market functioning. It thus seems unlikely that one can actually identify the existence of labor market segmentation by analyzing data on wages alone.
Duration Dependence and Timevarying Variables in Discrete Time Duration Models
Authors: D'Addio Anna Cristina , Honoré Bo E. 
Published: June 2016

This paper considers estimation of a dynamic discrete choice model with second order state dependence in the presence of strictly exogenous time-varying explanatory variables. We propose a new method for estimating such models, and a small Monte Carlo study suggests that the method performs well in practice. The method is used to test for duration dependence in labour market spells for young people in France. The novelty in the application is that we are able to control for time-varying explanatory variables. In a discrete time duration model, duration dependence will result in second order state dependence, and the paper therefore also adds to the literature on estimation of duration models with unobserved heterogeneity.
Monetary Policy and Exchange Rate Shocks in Brazil: Sign Restrictions versus A New Hybrid Identification Approach
Authors: Lima Elcyon Caiado Rocha , Maka Alexis , Alves Paloma 
Published: June 2016

This paper analyzes the impacts of monetary policy, exchange rate, demand, and supply exogenous disturbances on the Brazilian economy using a structural vector autoregression model identified by two alternative methodologies. The first uses sign restrictions on impulse responses based on an open-economy macroeconomic model. The second (hybrid) is a new methodology that combines the first with restrictions on the contemporaneous causal interrelationships among variables, derived by Directed Acyclic Graphs. A comparison of the results shows that while the effects of exchange rate shocks are nearly the same, the effects of monetary policy shocks depend on the methodology adopted. There is a strong response of the exchange rate to demand shocks and to shocks originating in the foreign exchange market. Exchange rate shocks have an important role in explaining short-run fluctuations of prices and output. We conclude that the exchange rate is an independent source of shocks and a shock absorber.
The Relation between Expected Returns and Volatility in the Brazilian Stock Market
Authors: Avelino Ricardo R. G. 
Published: June 2016

This paper applies the Markov switching regression model of stock returns with volatility feedback of Turner, Startz and Nelson (1989), suitably extended to incorporate endogenous regime shifts, as in Kim, Piger and Startz (2008), to examine the intertemporal relationship between the risk premium and volatility in the Brazilian stock market over the period 1995-2011. The results suggest that there is a positive relationship between the risk premium and the expected volatility once the volatility feedback effect is taken into account. Unanticipated increases in volatility, in contrast, have a negative impact on the risk premium. This negative impact increasesby 50% when I account for endogeneity of regime shifts.
Modeling and Forecasting of Realized Volatility: Evidence from Brazil
Authors: Wink Junior Marcos Vinício , Pereira Pedro Luiz Valls 
Published: June 2016

Using intraday data for the most actively traded stocks of BOVESPA, this work has considered two recently developed models in the literature of the estimation and forecasting of realized volatility; The Heterogeneous Autorregressive Model of Realized Volatility (HAR-RV), developed by Corsi (2009) and the Mixed Data Sampling (MIDAS-RV), developed by Ghysels et al. (2004). Through statistical comparison of forecasts in-sample and out-of-sample, it was found that superior results of the MIDAS-RV modeloccurred only for the in-sample forecasting. However, for out-of-sample forecasts no statistically different results were found between the models. Also, there are evidences that the use of realized volatility inducesnormality in standardized returns.
Credit Shocks and Monetary Policy in Brazil: A Structural Favar Approach
Authors: Valls Pereira Pedro L. , Da Silva Fonseca Marcelo Gonçalves 
Published: June 2016

This paper investigates the implications of the credit channel of the monetary policy transmission mechanism in the case of Brazil, using a structural FAVAR (SFAVAR) approach. The term structural comes from the estimation strategy, which generates factors that have a clear economic interpretation. The results show that unexpected shocks in the proxies for the external finance premium and the bank balance sheet channel produce large and persistent fluctuations in inflation and economic activity – accounting for more than 30% of the error forecast variance of the latter in a three-year horizon. The Central Bank seems to incorporate developments in credit markets – especially variations in credit spreads – to its reaction function, as impulse-response exercises show the Selic rate declining in response to wider credit spreads and contraction in the volume of new loans. Counterfactual simulations also demonstrate that the credit channel amplified the economic contraction in Brazil during the acute phase of the global financial crisis in the last quarter of 2008, and gave an important impulse to the recovery period that followed through.
What lf Brazil Hadn't Floated the Real in 1999?
Authors: Carvalho Carlos Viana de , Vilela André D. 
Published: June 2016

We estimate a dynamic, stochastic general equilibrium model for the Brazilian economy taking into account the transition from a currency peg to inflation targeting that took place in 1999. The estimated model exhibits quite different dynamic under the two monetary regimes. We use it to the produce counterfactual histories of the transition from one regime to another, given estimated history of structural shocks. Our results suggest that the maintaining the currency peg would have been too costly, as interest rates would have had to remain at extremely high levels for several quarters, and GDP would have collapsed. Accelerating e the pace of nominal exchange rate devaluations after de Asian Crisis would have lead to higher inflation and interest rates, and slightly lower GDP. Finally, the first half of 1998 arguably provided a window of opportunity for a smooth transition between the two monetary regimes.
SAMBA: Stochastic Analytical Model with a Bayesian Approach
Authors: Castro Marcos R. de , Gouvea Solange N. , Minella Andre , Santos Rafael , Souza-Sobrinho Nelson F. 
Published: June 2016

We develop and estimate a DSGE model for the Brazilian economy as part of the macroe-conomic modeling framework of the Central Bank of Brazil. The model combines the building blocks of standard DSGE models (e.g., price and wage rigidities and adjustment costs) with the following features that better describe the Brazilian economy: (i) a fiscal authority pursuing an explicit target for the primary surplus; (ii) administered or regulated prices as part of the consumer price index; (iii) external nance for imports,which amplies the eects of changes in external nancial conditions on the economy;and (iv) imported goods used in the production of intermediate goods. It also includes the presence of nancially constrained households. We estimate the model with Bayesian techniques, using data since 1999, when in ation targeting was implemented in Brazil.Evaluation based on impulse response functions, moment conditions, variance error decomposition, and initial forecasting exercises suggests that the model can be a useful toolfor policy analysis and forecasting.
Forecasting Brazilian Inflation with High-Dimensional Models
Authors: Medeiros Marcelo C , Vasconcelos Gabriel , Freitas Eduardo 
Published: June 2016

In this paper we use high-dimensional models, estimated by the Least Absolute Shrinkage and Selection Operator (LASSO), to forecast the Brazilian inflation. The models are compared to benchmark specifications such as linear autoregressive (AR) and the factor models based on principal components. Our results showed that the LASSO-based specifications have the smallest errors for short-horizon forecasts. However, for long horizons the AR benchmark is the best model with respect to point forecasts. The factor model also produces some good long horizon forecasts in a few cases. We estimated all the models for the two most important Brazilian inflation measures, the IPCA and the IGP-M indexes. The results also showed that there are differences on the selected variables for both measures. Finally, the most important variables selected by the LASSO based models are, in general, related to government debt and money. On the other hand, variables such as unemployment and production were rarely selected by the LASSO.
Exact Solutions forN-Coupled Nonlinear Schrödinger Equations With Variable Coefficients
Authors: Tang Bo , Fan Yingzhe , Wang Jixiu , Chen Shijun 
Published: June 2016

AbstractIn this paper, based on similarity transformation and auxiliary equation method, we construct many exact solutions ofN-coupled nonlinear Schrödinger equations with variable coefficients, which include soliton solutions, combined soliton solutions, triangular periodic solutions, Jacobi elliptic function solutions and combined Jacobi elliptic function solutions. These solutions may give insight into many considerable physical processes.
Schwäche der Tarifautonomie und Legitimitätsfragen im Arbeitsrecht und im Sozialrecht
Authors: Seiwerth Stephan 
Published: June 2016

Abstract
Social partners have played a privileged role in German social security administration since Bismarckian times. In 2014, a new legislation empowered the social partners to set the level of the statutory minimum wage and to demand the extension of collective agreements. This article examines the interdependence of the trade unions’ and employer organisations’ membership numbers and their involvement in state regulation of labour and social security law. In case the interest in autonomous regulations is not going to increase, the state will have to step in with more heteronomous regulation. This would incrementally lead to a system change.
Más allá del paradigma del consenso y del conflicto: Modelo del encuentro educativo.
Authors: Ferreyra Horacio Ademar , Caelles Ará Susana 
Published: June 2016

En este artículo se da una mirada a la educación para el siglo XXI apartir del análisis del Quehacer Educativo, lo que supone una reflexiónen un tiempo y espacio atravesados por el cambio permanente y veloz,la complejidad, el reduccionismo, la liviandad, la liquidez de los valoresy de la responsabilidad personal-social de cada uno y de toda la sociedad.Por eso, entendido el quehacer educativo como humanización, personalización y socialización, es que se presentan algunas reflexionesreferidas al paradigma del consenso y del conflicto, en torno al cual sepropone un modelo alternativo que promueva una educación desde la perspectiva del “encuentro interpersonal”. Modelo del encuentro que supone una práctica pedagógicaque responde a la visión Humanista-Personalista y Dialógica de lo educativo en contexto.
Motivaciones y deserción estudiantil en estudiantes peruanos de medicina
Authors: Bermúdez García Alejandro , Cassana Alessandra 
Published: June 2016

<p>En el número especial 2015, volumen 76 de su prestigiosa revista, se publicó la comunicación corta: “Deserción estudiantil en las carreras de ciencias de la salud en el Perú” de Heredia y col (1). En esta comunicación, se pone de manifiesto una problemática real que ocurre, no solo en nuestro país, en relación a la formación de recursos humanos en salud: la deserción. Estamos de acuerdo que la problemática es multifactorial y muchas veces el impacto de esta decisión es definitivo, no solo para el alumno sino para el entorno familiar que tenía ciertas expectativas y ve como pierde su inversión en tiempo y recursos; de igual manera que lo hace la sociedad, al brindar la oportunidad de formación, dejando de lado a otra persona que postuló y no obtuvo esa vacante desaprovechada.</p>