bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Cross–section of Risk Premia in the Italian Stock Market
Authors: Beltratti Andrea , Di Tria Massimo 
Published: December 2003

Our analysis compares multi–factor models with Italian stock market data for the period 1990–2000. The first, the simple CAPM, is the relevant benchmark because of its simplicity. The second, the extended Fama–French model (including the momentum portfolio), is the best candidate for substituting the one–factor model. The third is a multi–factor model including sectors; and the fourth is a multi–factor model including the change in short–term interest rates as an extra factor. The results of our research are mildly positive. The Fama–French multi–factor model behaves rather well in time series tests. However, in the cross–section, the average premia are not significantly different from zero, supporting the idea that they are not able to explain the cross–section of returns in the Italian market. Moreover, there is weak evidence that the factor portfolios have predictive power for macroeconomic variables characterizing the state of the economy. What may explain the results? There are two main components: first is the presumably large size of shocks to returns in the Italian case, which makes it difficult to explore the relation among expected returns; second is the presence of extra factors which are not accounted for in our analysis.(J.E.L.: G11, G12).
Monetary Policy, Credit and Aggregate Supply: The Evidence from Italy
Authors: Fiorentini Riccardo , Tamborini Roberto 
Published: December 2003

This paper concerns theory and evidence of the monetary transmission mechanisms. Current research has deeply investigated factors, such as dependence of firms on bank credit, that amplify the impact of monetary policy impulses on aggregate demand exerting strong but temporary effects on output and employment. We present an intertemporal macroeconomic equilibrium model of a competitive economy where current production is financed by bank credit, and then we use it to identify supply–side effects of the credit transmission mechanism in data drawn from the Italian economy. We find evidence that the ‘credit variables’ identified by the model – the overnight rate as a proxy of monetary policy and a measure of credit risk – have permanent effects on employment and output by altering credit supply conditions to firms.To save on space, mathematical proofs, statistical tests and data sources have been gathered in two separate appendices that can be examined on request.(J.E.L.: E2, E5).
A Structural Analysis of Credit Risk With Risky Collateral: A Methodology for Haircut Determination
Authors: Cossin Didier , Hricko Tomas 
Published: December 2003

Although many credit risk pricing models exist in the academic literature, very little attention has been paid to the impact of risky collateral on credit risk. It is nonetheless well known that practitioners often mitigate credit risk with collateral, using so–called haircuts for collateral level determination. The presence of collateral has a complex effect that can not be analysed simply with existing models. We analyse the value of credit risk when there is collateral in a range of different situations, including dual–default in a simple setting, stochastic collateral, stochastic bond collateral with stochastic interest rates, continuous and discrete marking–to–market and margin calls. The models confirm many practical intuitions, such as the impact on the haircut level required of the risks of the collateral asset and of the underlying asset to the forward as well as the impact of their correlation. Moreover, the model supports the intuition that the frequency of marking–to–market and collateral are substitutes. The models also stress the possibly unexpected magnitude of these factors. More importantly, they give actual solutions to determining the value of the credit risk depending on the haircut chosen and the frequency of marking–to–markets, results not presented before in the literature. The models are also a good basis to understand the portfolio effect of collateral management. Finally, they illustrate how differences in prices may arise from pure differences of credit risk management, as illustrated here in the case of futures and forwards.(J.E.L.: G13).
The Behaviour of the Real Exchange Rate: Evidence from an Alternative Price Index
Authors: Sarno Lucio , Chowdhury Ibrahim 
Published: December 2003

Although the long–run purchasing power parity (PPP) hypothesis is expected to hold across tradable goods, all price indices available to researchers for testing the validity of PPP contain some proportion of non–tradable goods prices, which may generate substantial persistence in the real exchange rate. We construct time series for quarterly price indices that minimize the presence of non–tradable goods for six major economies. Applying recently developed nonlinear econometric techniques to the resulting five US dollar real exchange rate series for the recent floating exchange rate regime, we provide evidence that the nonlinear mean reverting properties of these real exchange rate series are stronger than the mean reverting properties of real exchange rate time series constructed using the consumer price index (CPI). In turn, these results have a natural economic interpretation.(J.E.L.: F31).
What does Monetary Policy Reveal about a Central Bank's Preferences?
Authors: Castelnuovo Efrem , Surico Paolo 
Published: December 2003

The design of monetary policy depends on the targeting strategy adopted by the central bank. This strategy describes a set of policy preferences, which are actually the structural parameters to analyse monetary policy making. Accordingly, we develop a calibration method to estimate a central bank's preferences from the estimates of an optimal Taylor–type rule. The empirical analysis on US data shows that output stabilization has not been an independent argument in the Fed's objective function during the Greenspan's era. This suggests that the output gap has entered the policy rule only as leading indicator for future inflation, therefore being only instrumental (to stabilize inflation) rather than important per se.(J.E.L.: C61, E52, E58).
Unemployment, Factor Substitution and Capital Formation
Authors: Kaas Leo , Thadden Leopold von 
Published: December 2003

Abstract
We incorporate a wage-bargaining structure in a dynamic general equilibrium model and show how this feature changes short- and long-run properties of equilibria compared with a perfectly competitive setting.We discuss how employment, capital and income shares respond to wage-setting shocks and show that adjustment dynamics depend decisively on the magnitude of the elasticity of substitution between labour and capital. Values of the elasticity below unity add persistence, tend to preserve stability and lead to empirically plausible adjustment patterns. By contrast, values above unity introduce additional volatility, thereby making steady states potentially unstable.
Buyer Subsidies in an Equilibrium Model of Price Dispersion
Authors: Orzen Henrik , Sefton Martin 
Published: December 2003

Abstract
We present a model of equilibrium price dispersion in which a per-unit subsidy to buyers can reduce average prices. The reason is that subsidies have two effects on average prices that work in opposite directions. First, subsidies raise buyers’ willingness-to-pay, and by itself this causes firms to charge higher prices. However, since a higher willingness-to-pay lowers the relative cost of search, subsidies also induce more search. This creates a second effect that puts pressure on firms to reduce prices.We show that the second effect can dominate, thus causing an overall reduction in average price.
The Growth Advantage in Stationary-Phase PhenotypeConferred by
rpoS
Mutations Is Dependent on the pH andNutrientEnvironment
Authors: Farrell Michael J. , Finkel Steven E. 
Published: December 2003

ABSTRACT

Escherichia
coli
cells that are aged in batch culture display an increased
fitness referred to as the growth advantage in stationary phase, or
GASP, phenotype. A common early adaptation to this culture environment
is a mutant
rpoS
allele, such as
rpoS819
, that
results in attenuated RpoS activity. However, it is important to note
that during long-term batch culture, environmental conditions are in
flux. To date, most studies of the GASP phenotype have focused on
identifying alleles that render an advantage in a specific environment,
Luria-Bertani broth (LB) batch culture. To determine what role
environmental conditions play in rendering relative fitness advantages
to
E. coli
cells carrying either the wild-type or
rpoS819
alleles, we performed competitions under a variety of
culture conditions in which either the available nutrients, the pH, or
both were manipulated. In LB medium, we found that while the
rpoS819
allele confers a strong competitive fitness advantage
at basic pH, it confers a reduced advantage under neutral conditions,
and it is disadvantageous under acidic conditions. Similar results were
found using other media.
rpoS819
conferred its greatest
advantage in basic minimal medium in which either glucose or Casamino
Acids were the sole source of carbon and energy. In acidic medium
supplemented with either Casamino Acids or glucose, the wild-type
allele conferred a slight advantage. In addition, populations were
dynamic under all pH conditions tested, with neither the wild-type nor
mutant
rpoS
alleles sweeping a culture. We also found that the
strength of the fitness advantage gained during a 10-day incubation is
pH
dependent.
Responses of theCentral Metabolism in
Escherichia coli
to PhosphoglucoseIsomerase and Glucose-6-Phosphate DehydrogenaseKnockouts
Authors: Hua Qiang , Yang Chen , Baba Tomoya , Mori Hirotada , Shimizu Kazuyuki 
Published: December 2003

ABSTRACT

The
responses of
Escherichia coli
central carbon metabolism to
knockout mutations in phosphoglucose isomerase and glucose-6-phosphate
(G6P) dehydrogenase genes were investigated by using glucose- and
ammonia-limited chemostats. The metabolic network structures and
intracellular carbon fluxes in the wild type and in the knockout
mutants were characterized by using the complementary methods of flux
ratio analysis and metabolic flux analysis based on
[U-
13
C]glucose labeling and
two-dimensional nuclear magnetic resonance (NMR) spectroscopy of
cellular amino acids, glycerol, and glucose. Disruption of
phosphoglucose isomerase resulted in use of the pentose phosphate
pathway as the primary route of glucose catabolism, while flux
rerouting via the Embden-Meyerhof-Parnas pathway and the nonoxidative
branch of the pentose phosphate pathway compensated for the G6P
dehydrogenase deficiency. Furthermore, additional, unexpected flux
responses to the knockout mutations were observed. Most prominently,
the glyoxylate shunt was found to be active in phosphoglucose
isomerase-deficient
E. coli
. The Entner-Doudoroff pathway also
contributed to a minor fraction of the glucose catabolism in this
mutant strain. Moreover, although knockout of G6P dehydrogenase had no
significant influence on the central metabolism under glucose-limited
conditions, this mutation resulted in extensive overflow metabolism and
extremely low tricarboxylic acid cycle fluxes under ammonia limitation
conditions.
FimX, a Multidomain Protein Connecting EnvironmentalSignals to Twitching Motility in
Pseudomonasaeruginosa
Authors: Huang Bixing , Whitchurch Cynthia B. , Mattick John S. 
Published: December 2003

ABSTRACT

Twitching
motility is a form of surface translocation mediated by the extension,
tethering, and retraction of type IV pili. Three independent
Tn
5
-B21 mutations of
Pseudomonas aeruginosa
with
reduced twitching motility were identified in a new locus which encodes
a predicted protein of unknown function annotated PA4959 in the
P.
aeruginosa
genome sequence. Complementation of these mutants with
the wild-type PA4959 gene, which we designated
fimX
, restored
normal twitching motility.
fimX
mutants were found to express
normal levels of pilin and remained sensitive to pilus-specific
bacteriophages, but they exhibited very low levels of surface pili,
suggesting that normal pilus function was impaired. The
fimX
gene product has a molecular weight of 76,000 and contains four
predicted domains that are commonly found in signal transduction
proteins: a putative response regulator (CheY-like) domain, a PAS-PAC
domain (commonly involved in environmental sensing), and DUF1 (or
GGDEF) and DUF2 (or EAL) domains, which are thought to be involved in
cyclic di-GMP metabolism. Red fluorescent protein fusion experiments
showed that FimX is located at one pole of the cell via sequences
adjacent to its CheY-like domain. Twitching motility in
fimX
mutants was found to respond relatively normally to a range of
environmental factors but could not be stimulated by tryptone and
mucin. These data suggest that
fimX
is involved in the
regulation of twitching motility in response to environmental
cues.
Suppression of Factor-Dependent TranscriptionTermination by AntiterminatorRNA
Authors: King Rodney A. , Weisberg Robert A. 
Published: December 2003

ABSTRACT

Nascent
transcripts of the phage HK022
put
sites modify the
transcription elongation complex so that it terminates less efficiently
at intrinsic transcription terminators and accelerates through pause
sites. We show here that the modification also suppresses termination
in vivo at two factor-dependent terminators, one that depends on the
bacterial Rho protein and a second that depends on the HK022-encoded
Nun protein. Suppression was efficient when the termination factors
were present at physiological levels, but an increase in the
intracellular concentration of Nun increased termination both in the
presence and absence of
put. put
-mediated
antitermination thus shows no apparent terminator specificity,
suggesting that
put
inhibits a step that is common to
termination at the different types of
terminator.
YmoA Negatively Regulates Expression of Invasin fromYersiniaenterocolitica
Authors: Ellison Damon W. , Young Briana , Nelson Kristin , Miller Virginia L. 
Published: December 2003

ABSTRACTinvencodes invasin, which is the primary invasion factor ofYersinia enterocolitica. invexpression in vitro is regulated in response to temperature, pH, and growth phase. In vitro,invis maximally expressed at 26°C and repressed at 37°C at neutral pH but, when the pH of the media is adjusted to 5.5, levels ofinvexpression at 37°C are comparable to those at 26°C. A previous genetic screen for regulators ofinvidentified RovA, which was found to be required for activation ofinvin vitro under all conditions tested as well as in vivo. Here we describe a screen that has identified a negative regulator ofinvexpression,ymoA. TheymoBAlocus was identified by transposon mutagenesis as a repressor ofinvexpression in vitro at 37°C at neutral pH. This mutant shows increasedinvexpression at 37°C. The mutant can be fully complemented forinvexpression by a plasmid expressingymoA. These results indicate that YmoA plays a role in the negative regulation ofinv.
Purification of the Formate-Tetrahydrofolate Ligasefrom
Methylobacterium extorquens
AM1 and Demonstrationof Its Requirement for MethylotrophicGrowth
Authors: Marx Christopher J. , Laukel Markus , Vorholt Julia A. , Lidstrom Mary E. 
Published: December 2003

ABSTRACT

The
serine cycle methylotroph
Methylobacterium extorquens
AM1
contains two pterin-dependent pathways for C
1
transfers, the
tetrahydrofolate (H
4
F) pathway and the
tetrahydromethanopterin (H
4
MPT) pathway, and both are
required for growth on C
1
compounds. With the exception of
formate-tetrahydrofolate ligase (FtfL, alternatively termed
formyl-H
4
F synthetase), all of the genes encoding the
enzymes comprising these two pathways have been identified, and the
corresponding gene products have been purified and characterized. We
present here the purification and characterization of FtfL from
M.
extorquens
AM1 and the confirmation that this enzyme is encoded by
an
ftfL
homolog identified previously through transposon
mutagenesis. Phenotypic analyses of the
ftfL
mutant strain
demonstrated that FtfL activity is required for growth on C
1
compounds. Unlike mutants defective for the H
4
MPT pathway,
the
ftfL
mutant strain does not exhibit phenotypes indicative
of defective formaldehyde oxidation. Furthermore, the
ftfL
mutant strain remained competent for wild-type conversion of
[
14
C]methanol to
[
14
C]CO
2
. Collectively, these data
confirm our previous presumptions that the H
4
F pathway is
not the key formaldehyde oxidation pathway in
M. extorquens
AM1. Rather, our data suggest an alternative model for the role of the
H
4
F pathway in this organism in which it functions to
convert formate to methylene H
4
F for assimilatory
metabolism.
A New Pathway for Salvaging the CoenzymeB12Precursor Cobinamide in Archaea RequiresCobinamide-Phosphate Synthase (CbiB) EnzymeActivity
Authors: Woodson Jesse D. , Zayas Carmen L. , Escalante-Semerena Jorge C. 
Published: December 2003

ABSTRACTThe ability of archaea to salvage cobinamide has been under question because archaeal genomes lack orthologs to the bacterial nucleoside triphosphate:5′-deoxycobinamide kinase enzyme (cobUinSalmonella enterica). The latter activity is required for cobinamide salvaging in bacteria. This paper reports evidence that archaea salvage cobinamide from the environment by using a pathway different from the one used by bacteria. These studies demanded the functional characterization of two genes whose putative function had been annotated based solely on their homology to the bacterial genes encoding adenosylcobyric acid and adenosylcobinamide-phosphate synthases (cbiPandcbiB, respectively) ofS. enterica. AcbiPmutant strain of the archaeonHalobacteriumsp. strain NRC-1 was auxotrophic for adenosylcobyric acid, a known intermediate of the de novo cobamide biosynthesis pathway, but efficiently salvaged cobinamide from the environment, suggesting the existence of a salvaging pathway in this archaeon. AcbiBmutant strain ofHalobacteriumwas auxotrophic for adenosylcobinamide-GDP, a known de novo intermediate, and did not salvage cobinamide. The results of the nutritional analyses of thecbiPandcbiBmutants suggested that the entry point for cobinamide salvaging is adenosylcobyric acid. The data are consistent with a salvaging pathway for cobinamide in which an amidohydrolase enzyme cleaves off the aminopropanol moiety of adenosylcobinamide to yield adenosylcobyric acid, which is converted by the adenosylcobinamide-phosphate synthase enzyme to adenosylcobinamide-phosphate, a known intermediate of the de novo biosynthetic pathway. The existence of an adenosylcobinamide amidohydrolase enzyme would explain the lack of an adenosylcobinamide kinase in archaea.
GacA Regulates Symbiotic Colonization Traits of
Vibrio fischeri
and Facilitates a Beneficial Association withan AnimalHost
Authors: Whistler Cheryl A. , Ruby Edward G. 
Published: December 2003

ABSTRACT

The
GacS/GacA two-component system regulates the expression of bacterial
traits during host association. Although the importance of GacS/GacA as
a regulator of virulence is well established, its role in benign
associations is not clear, as mutations in either the
gacS
or
gacA
gene have little impact on the success of colonization in
nonpathogenic associations studied thus far. Using as a model the
symbiotic association of the bioluminescent marine bacterium
Vibrio
fischeri
with its animal host, the Hawaiian bobtail squid,
Euprymna scolopes
, we investigated the role of GacA in this
beneficial animal-microbe interaction. When grown in culture,
gacA
mutants were defective in several traits important for
symbiosis, including luminescence, growth in defined media, growth
yield, siderophore activity, and motility. However,
gacA
mutants were not deficient in production of acylated homoserine lactone
signals or catalase activity. The ability of the
gacA mutants to initiate squid colonization was
impaired but not abolished, and they reached lower-than-wild-type
population densities within the host light organ. In contrast to their
dark phenotype in culture,
gacA
mutants that reached
population densities above the luminescence detection limit had normal
levels of luminescence per bacterial cell in squid light organs,
indicating that GacA is not required for light production within the
host. The
gacA
mutants were impaired at competitive
colonization and could only successfully cocolonize squid light organs
when present in the seawater at higher inoculum densities than
wild-type bacteria. Although severely impaired during colonization
initiation,
gacA
mutants were not displaced by the wild-type
strain in light organs that were colonized with both strains. This
study establishes the role of GacA as a regulator of a beneficial
animal-microbe association and indicates that GacA regulates
utilization of growth substrates as well as other colonization
traits.
Role of
narK2X
and
narGHJI
inHypoxic Upregulation of Nitrate Reduction by
Mycobacteriumtuberculosis
Authors: Sohaskey Charles D. , Wayne Lawrence G. 
Published: December 2003

ABSTRACT

Mycobacterium
tuberculosis
is one of the strongest reducers of nitrate in the
genus
Mycobacterium
. Under microaerobic
conditions, whole cells exhibit upregulation of activity, producing
approximately eightfold more nitrite than those of aerobic cultures of
the same age. Assays of cell extracts from aerobic cultures and hypoxic
cultures yielded comparable nitrate reductase activities.
Mycobacterium bovis
produced only low levels of nitrite, and
this activity was not induced by hypoxia.
M
.
tuberculosis
has two sets of genes,
narGHJI
and
narX
of the
narK2X
operon, that exhibit some degree
of homology to prokaryotic dissimilatory nitrate reductases. Each of
these were knocked out by insertional inactivation. The
narG
mutant showed no nitrate reductase activity in whole culture or in
cell-free assays, while the
narX
mutant showed wild-type
levels in both assays. A knockout of the putative nitrite transporter
narK2
gene produced a strain that had aerobic levels of
nitrate reductase activity but failed to show hypoxic upregulation.
Insertion of the
M. tuberculosis narGHJI
into a
nitrate reductase
Escherichia coli
mutant allowed anaerobic
growth in the presence of nitrate. Under aerobic and hypoxic
conditions, transcription of
narGHJI
was constitutive, while
the
narK2X
operon was induced under hypoxia, as measured with
a
lacZ
reporter system and by quantitative real-time reverse
PCR. This indicates that nitrate reductase activity in
M
.
tuberculosis
is due to the
narGHJI
locus with no
detectable contribution from
narX
and that the hypoxic
upregulation of activity is associated with the induction of the
nitrate and nitrite transport gene
narK2
.
InvBIs a Type III Secretion-Associated Chaperone for theSalmonella entericaEffector ProteinSopE
Authors: Ho Lee Sang , Galán Jorge E. 
Published: December 2003

ABSTRACTSopE is a bacteriophage-encoded effector protein ofSalmonella entericaserovar Typhimurium that is translocated into the cytosol of eukaryotic cells by a type III secretion system (TTSS) (W.-D. Hardt, H. Urlaub, and J. E. Galán, Proc. Natl. Acad. Sci. USA 95:2574-2579, 1998; M. W. Wood, R. Rosqvist, P. B. Mullan, M. H. Edwards, and E. E. Galyov, Mol. Microbiol. 22:327-338, 1996). In this study, we provide evidence that an unlinked gene carried within theSalmonellapathogenicity island 1 (SPI-1),invB(K. Eichelberg, C. Ginocchio, and J. E. Galán, J. Bacteriol. 176:4501-4510, 1994), is required for the secretion of SopE through the SPI-1 TTSS. Furthermore, far-Western blotting analysis shows that SopE directly interacts with InvB through a domain located at its amino terminus. We conclude that InvB is the TTSS-associated chaperone for SopE.