310 research outputs found
Indoor exposure to environmental tobacco smoke and dampness: respiratory symptoms in Sardinian children- DRIAS study
Indoorexposuresathome,environmentaltobaccosmoke(ETS)andmould/dampnessadverselyaffect respiratoryhealthofchildren.DisturbiRespiratorinell’InfanziaeAmbienteinSardegna(DRIAS) (RespiratorySymptomsinchildrenandtheEnvironmentinSardegna,Italy)aimsatrelatingthe prevalenceofrespiratoryandallergicsymptomstoindoorexposuresinSardinianchildren. DRIAS,across-sectionalinvestigationofrespiratorysymptoms/diseases,usedamodifiedversionof ISAACquestionnaire,included4122childrenattending29primaryschoolsintheschoolyear 2004–2005. If bothparentssmoketheprevalenceforcurrentwheezeandcurrentasthmaisalmostdoubledin comparisonwithneversmokers,forpersistentcoughandphlegmaroleissuggestedwhenonlymother smokes.Amongmotherssmokinginpregnancy,theprevalenceofcurrentwheezeandcurrentasthmais increased. ExposuretoETSandfamilyatopyhaveajointeffectresultinginanalmosttriplingof prevalenceforcurrentwheezeandmorethanfourtimesforcurrentasthma.Exposureto‘‘dampness’’ (mouldordampness)bothduringthefirstyearoflifeandcurrentlyisassociatedwithincreased prevalenceofcurrentwheeze,persistentcoughorphlegmandcurrentrhino-conjunctivitis;ifexposure is onlyduringthefirstyearoflifeadoublingormoreofprevalenceisobservedforcurrentwheeze, current asthma,andpersistentcoughorphlegm. DRIASresultsaddevidencetothecausalroleofchildhoodexposuretoETSinthedevelopmentof respiratorysymptoms(cough,phlegm,andwheezing)andasthma.ThejointeffectofETSandfamily atopyiscorroborated.Theresultsstrengthentheevidenceforacausalassociationbetween‘‘dampness’’ and respiratoryhealth,pointingtoitspossibleindependentroleincausingasthma,along-lasting exposureentailsadoubledprevalenceforbothasthmaticandbronchitissymptoms
Galactic periodicity and the oscillating G model
We consider the model involving the oscillation of the effective
gravitational constant that has been put forward in an attempt to reconcile the
observed periodicity in the galaxy number distribution with the standard
cosmological models. This model involves a highly nonlinear dynamics which we
analyze numerically. We carry out a detailed study of the bound that
nucleosynthesis imposes on this model. The analysis shows that for any assumed
value for (the total energy density) one can fix the value of
(the baryonic energy density) in such a way as to
accommodate the observational constraints coming from the
primordial abundance. In particular, if we impose the inflationary value
the resulting baryonic energy density turns out to be . This result lies in the very narrow range allowed by the observed values of the primordial
abundances of the other light elements. The remaining fraction of
corresponds to dark matter represented by a scalar field.Comment: Latex file 29 pages with no figures. Please contact M.Salgado for
figures. A more careful study of the model appears in gr-qc/960603
Modeling and performance assessment of the split-pi used as a storage converter in all the possible dc microgrid scenarios. Part II: Simulation and experimental results
Bidirectional DC/DC converters such as the Split-pi can be used to integrate an energy storage system (ESS) into a DC microgrid providing manifold benefits. However, this integration deserves careful design because the ESS converter must behave like a stiff voltage generator, a non-stiff voltage generator, or a current generator depending on the microgrid configuration. Part I of this work presented a comprehensive theoretical analysis of the Split-pi used as an ESS converter in all the possible DC microgrid scenarios. Five typical microgrid scenarios were identified. Each of them required a specific state-space model of the Split-pi and a suitable control scheme. The present paper completes the study validating the theoretical analysis based on simulations and experimental tests. The chosen case study encompassed a 48 V, 750 W storage system interfaced with a 180 V DC microgrid using a Split-pi converter. It can represent a reduced-power prototype of terrestrial and marine microgrids. A prototypal Split-pi converter was realized in the lab, and several experimental tests were performed to assess the performance in each scenario. The results obtained from the experimental tests were coherent with the simulations and validated the study
Monteggia fracture associated with ipsilateral intercondylar distal humeral fracture with posterior interosseous nerve palsy: case report, medico-legal implications, and methodological assessment analysis
BACKGROUND: The Monteggia fracture, defined as a fracture of the proximal third of the ulnar shaft associated with an anterior or posterior dislocation of the proximal radial epiphysis, is a serious injury accounting for 0.7% of all elbow fractures and dislocations in adults. For adult patients, good results can only be obtained through early diagnosis and adequate surgical treatment. Monteggia fracture-dislocations associated with distal humeral fracture are extremely rare injuries in adults and there are few cases described in the literature. Medico-legal implications arising from such conditions have a host of complexities that cannot be discounted.CASE REPORT: This case report revolves around a patient affected by a type I Monteggia fracture-dislocation, according to the Bado classification, associated with an ipsilateral intercondylar distal humeral fracture. To our knowledge, this combination of lesions has never been reported before in adult patients. A positive result was obtained due to early diagnosis, achievement of anatomical reduction, and optimal stabilization with internal fixation which made it possible to achieve early functional recovery.CONCLUSIONS: Monteggia fracture -dislocations associated with ipsilateral intercondylar distal humeral fracture are extremely rare in adults. In the case herein reported, a favorable outcome was obtained due to early diagnosis, achievement of anatomical reduction and management with internal fixation with plate and screws, as well as early functional training. Misdiagnosis makes such lesions risky in terms of potentially delayed treatment, increasing the need for surgical interventions and the possibility of high-risk complications and disabling sequelae, with possible medico -legal implications. In the case of unrecognized injuries under urgent circumstances, the injuries may become chronic, making the treatment more complex. The ultimate outcomes of a misdiagnosed Monteggia lesion can lead to very serious functional and aesthetic damage
Symmetric vacuum scalar--tensor cosmology
The existence of point symmetries in the cosmological field equations of
generalized vacuum scalar--tensor theories is considered within the context of
the spatially homogeneous cosmologies. It is found that such symmetries only
occur in the Brans--Dicke theory when the dilaton field self--interacts.
Moreover, the interaction potential of the dilaton must take the form of a
cosmological constant. For the spatially flat, isotropic model, it is shown how
this point symmetry may be employed to generate a discrete scale factor duality
in the Brans--Dicke action.Comment: 10 pages, latex, To appear in Class. Quantum Gra
Modeling and performance assessment of the split-pi used as a storage converter in all the possible dc microgrid scenarios. Part i: Theoretical analysis
The integration of an electrical storage system (ESS) into a DC microgrid using a bidirectional DC/DC converter provides substantial benefits but requires careful design. Among such converter topologies, the Split-pi converter presents several merits at the cost of non-isolated operation. However, the few works in the literature on the Split-pi presented only closed-loop control with a single control loop; furthermore, they neglected the reactive components’ parasitic resistances and did not perform any experimental validation. This work aimed at investigating the use of the Split-pi converter as a power interface between an ESS and a DC microgrid. Five typical microgrid scenarios are presented, where each of which requires a specific state-space model and a suitable control scheme for the converter to obtain high performance. In this study, two different state-space models of the converter that consider the parasitic elements are presented, the control schemes are discussed, and criteria for designing the controllers are also given. Several simulations, as well as experimental tests on a prototype realized in the lab, were performed to validate the study. Both the simulation and experimental results will be presented in part II of this work. The proposed approach has general validity and can also be followed when other bidirectional DC/DC converter topologies are employed to interface an ESS with a DC microgrid
Modeling and Experimental Validation of a Voltage-Controlled Split-Pi Converter Interfacing a High-Voltage ESS with a DC Microgrid
The Split-pi converter can suitably interface an energy storage system (ESS) with a DC microgrid when galvanic isolation is not needed. Usually, the ESS voltage is lower than the grid-side voltage. However, limitations in terms of the ESS current make the use of a high-voltage ESS unavoidable when high power levels are required. In such cases, the ESS voltage can be higher than the microgrid voltage, especially with low microgrid voltages such as 48 V. Despite its bidirectionality and symmetry, the Split-pi exhibits a completely different dynamic behavior if its input and output ports are exchanged. Thus, the present work aims to model the Split-pi converter operating with an ESS voltage higher than the grid-side voltage in three typical microgrid scenarios where the controlled variable is the converter's output voltage. The devised state-space model considers the parasitic elements and the correct load model for each scenario. Furthermore, it is shown that the presence of the input LC filter can make the design of the loop controllers more complicated than in the case of a lower ESS voltage than the grid-side voltage. Finally, the study is validated through simulations and experimental tests on a lab prototype, and a robustness analysis is performed
Open Inflationary Universes in the Induced Gravity Theory
The induced gravity theory is a variant of Jordan--Brans--Dicke theory where
the `dilaton' field possesses a potential. It has the unusual feature that in
the presence of a false vacuum there is a {\em stable} static solution with the
dilaton field displaced from the minimum of its potential, giving perfect de
Sitter expansion. We demonstrate how this solution can be used to implement the
open inflationary universe scenario. The necessary second phase of inflation
after false vacuum decay by bubble nucleation is driven by the dilaton rolling
from the static point to the minimum of its potential. Because the static
solution is stable whilst the false vacuum persists, the required evolution
occurs for a wide range of initial conditions. As the exterior of the bubble is
perfect de Sitter space, there is no problem with fields rolling outside the
bubble, as in one of the related models considered by Linde and Mezhlumian, and
the expansion rates before and after tunnelling may be similar which prevents
problematic high-amplitude super-curvature modes from being generated. Once
normalized to the microwave background anisotropies seen by the COBE satellite,
the viable models form a one-parameter family for each possible .Comment: 7 pages RevTeX file with three figures incorporated (uses RevTeX and
epsf). Also available by e-mailing ARL, or by WWW at
http://star-www.maps.susx.ac.uk/papers/early_papers.htm
Dynamic vacuum variable and equilibrium approach in cosmology
A modified-gravity theory is considered with a four-form field strength F, a
variable gravitational coupling parameter G(F), and a standard matter action.
This theory provides a concrete realization of the general vacuum variable q as
the four-form amplitude F and allows for a study of its dynamics. The theory
gives a flat Friedmann-Robertson-Walker universe with rapid oscillations of the
effective vacuum energy density (cosmological "constant"), whose amplitude
drops to zero asymptotically. Extrapolating to the present age of the Universe,
the order of magnitude of the average vacuum energy density agrees with the
observed near-critical vacuum energy density of the present universe. It may
even be that this type of oscillating vacuum energy density constitutes a
significant part of the so-called cold dark matter in the standard
Friedmann-Robertson-Walker framework.Comment: 24 (not 25) pages, v7(=v6 with latex problem corrected): published
version in preprint styl
Open Inflation With Scalar-tensor Gravity
The open inflation model recently proposed by Hawking and Turok is
investigated in scalar-tensor gravity context. If the dilaton-like field has no
potential, the instanton of our model is singular but has a finite action. The
Gibbons-Hawking surface term vanishes and hence, can not be used to make
nonzero. To obtain a successful open inflation one should introduce
other matter fields or a potential for the dilaton-like fields.Comment: 10 pages.1 figure. Some comments and references are improved. to be
published in PR
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