9,443 research outputs found
Managing Sprawl in the Land of Unintended Consequences
Americans witnessing the bulldozing of their country’s pastures, farmlands, and sensitive habitats to erect suburban housing tracts and commercial centers have come to realize that the remaining open land may be too precious to waste. Residential and commercial development is no longer quickly embraced to stimulate economic progress and prosperity. Municipalities are learning that development often extracts a price — sometimes the loss of community character and local charm, sometimes tax revenues that fall short of increased expenditures, and sometimes just plain ugliness. Responding to the new reality, many community officials have initiated unilateral ordinances regulating the development of open spaces to protect the residents’ way of life. Too often, however, most land-use policies are easily circumvented, leading to a rash of unintended outcomes that more than neutralize their derived benefits. Long accustomed to vast open spaces and the allure of large suburban lots and dwellings, the citizens do not readily embrace restrictions on where and how they may live. This article investigates sprawl by examining the human desires and economic realities that drive it and its development. More important, it examines the benefits of commonly used land regulations and their unintended consequences
On the (nonmonotonic) relation between economic growth and finance
We analyze the simplest possible model of endogenous growth to account for the role of financial development. In our setting, financial development affects productivity and determines the amount of resources subtracted to capital investment. We show that under very general assumptions, the relation between economic growth and financial depth is nonmonotonic, and eventually bell-shaped. We empirically assess our results in a framework that allows to distinguish between long-run and short-run effects. We establish a cointegrating relation and derive the long-run elasticities of per capita gross domestic product (GDP) with respect to employment, the physical capital stock, and financial depth\u2014relying on linear as well as nonlinear models for the finance-growth nexus. We employ the results of the first step estimation to specify an error\u2013correction model and find that there is strong evidence for a nonlinear relationship between financial depth and per capita GDP, consistently with what was predicted by our theoretical model
On Words with the Zero Palindromic Defect
We study the set of finite words with zero palindromic defect, i.e., words
rich in palindromes. This set is factorial, but not recurrent. We focus on
description of pairs of rich words which cannot occur simultaneously as factors
of a longer rich word
On the Number of Closed Factors in a Word
A closed word (a.k.a. periodic-like word or complete first return) is a word
whose longest border does not have internal occurrences, or, equivalently,
whose longest repeated prefix is not right special. We investigate the
structure of closed factors of words. We show that a word of length
contains at least distinct closed factors, and characterize those words
having exactly closed factors. Furthermore, we show that a word of length
can contain many distinct closed factors.Comment: Accepted to LATA 201
Monte Carlo evaluation of the external gamma, neutron and muon induced background sources in the CUORE experiment
CUORE is a 1 ton scale cryogenic experiment aiming at the measurement of the
Majorana mass of the electron neutrino. The detector is an array of 988 TeO2
bolometers used for a calorimetric detection of the two electrons emitted in
the BB0n of 130Te. The sensitivity of the experiment to the lowest Majorana
mass is determined by the rate of background events that can mimic a BB0n. In
this paper we investigate the contribution of external sources i.e.
environmental gammas, neutrons and cosmic ray muons to the CUORE background and
show that the shielding setup designed for CUORE guarantees a reduction of this
external background down to a level <1.0E-02 c/keV/kg/y at the Q-value, as
required by the physical goal of the experiment.Comment: 14 pages, 7 figure
Welfare and Convergence Speed in the Ramsey Model under two Classes of Gorman Preferences
Using a one-sector, discrete-time Ramsey model, we analyze and compare the implications for welfare, capital accumulation, and speed of convergence to the steady state of two classes of utility functions that represent Gorman preferences, namely homothetic and Stone\u2013Geary preferences. For identical economies, we show that the preference structure does not affect only the capital dynamics and social welfare but also the speed of convergence to the steady-state equilibrium
Complete elimination of 1K Pot vibrations in dilution refrigerators
Cryogenic vibrations generated by continuously filled 1K Pots are a well known source of noise in all cryogenic experiments using dilution refrigerators. Starting from recent developments we realized a non invasive modification to the cryostat that completely eliminated vibrations, thermalizing the helium coming from the main bath at the pot temperature. We describe the new experimental setup and complete study of the phenomena
Effect of orthopedic and functional orthodontic treatment in children with obstructive sleep apnea: A systematic review and meta-analysis
Orthodontic treatment is suggested in growing individuals to correct transverse maxillary deficiency and mandibular retrusion. Since, as a secondary effect, these orthodontic procedures may improve pediatric obstructive sleep apnea (OSA), this systematic review assessed their effects on apnea-hypopnea index (AHI) and oxygen saturation (SaO2). Twenty-five (25) manuscripts were included for qualitative synthesis, 19 were selected for quantitative synthesis. Five interventions were analyzed: rapid maxillary expansion (RME, 15 studies), mandibular advancement (MAA, five studies), myofunctional therapy (MT, four studies), and RME combined with MAA (one study). RME produced a significant AHI reduction and minimum SaO2 increase immediately after active treatment, at six and 12 months from baseline. A significant AHI reduction was also observed six and 12 months after the beginning of MAA treatment. MT showed positive effects, with different protocols. In this systematic review and meta-analysis of data from mainly uncontrolled studies, interceptive orthodontic treatments showed overall favorable effects on respiratory outcomes in pediatric OSA. However, due to the low to very low level of the body evidence, this treatment cannot be suggested as elective for OSA treatment. An orthodontic indication is needed to support this therapy and a careful monitoring is required to ensure positive improvement in OSA parameters
Vertical distribution of aerosol optical properties in the Po Valley during the 2012 summer campaigns
Studying the vertical distribution of aerosol particle physical and chemical properties in the troposphere is essential to understand the relative importance of local emission processes vs. long-range transport for column-integrated aerosol properties (e.g. the aerosol optical depth, AOD, affecting regional climate) as well as for the aerosol burden and its impacts on air quality at the ground. The main objective of this paper is to investigate the transport of desert dust in the middle troposphere and its intrusion into the planetary boundary layer (PBL) over the Po Valley (Italy), a region considered one of the greatest European pollution hotspots for the frequency that particulate matter (PM) limit values are exceeded. Events of mineral aerosol uplift from local (soil) sources and phenomena of hygroscopic growth at the ground are also investigated, possibly affecting the PM concentration in the region as well. During the PEGASOS 2012 field campaign, an integrated observing–modelling system was set up based on near-surface measurements (particle concentration and chemistry), vertical profiling (backscatter coefficient profiles from lidar and radiosoundings) and Lagrangian air mass transport simulations by FLEXPART model. Measurements were taken at the San Pietro Capofiume supersite (44°39′ N, 11°37′ E; 11 m a.s.l.), located in a rural area relatively close to some major urban and industrial emissive areas in the Po Valley. Mt. Cimone (44°12′ N, 10°42′ E; 2165 m a.s.l.) WMO/GAW station observations are also included in the study to characterize regional-scale variability. Results show that, in the Po Valley, aerosol is detected mainly below 2000 m a.s.l. with a prevalent occurrence of non-depolarizing particles ( > 50 % throughout the campaign) and a vertical distribution modulated by the PBL daily evolution. Two intense events of mineral dust transport from northern Africa (19–21 and 29 June to 2 July) are observed, with layers advected mainly above 2000 m, but subsequently sinking and mixing in the PBL. As a consequence, a non-negligible occurrence of mineral dust is observed close to the ground ( ~7 % of occurrence during a 1-month campaign). The observations unambiguously show Saharan dust layers intruding the Po Valley mixing layer and directly affecting the aerosol concentrations near the surface. Finally, lidar observations also indicate strong variability in aerosol on shorter timescales (hourly). Firstly, these highlight events of hygroscopic growth of anthropogenic aerosol, visible as shallow layers of low depolarization near the ground. Such events are identified during early morning hours at high relative humidity (RH) conditions (RH > 80 %). The process is observed concurrently with high PM1 nitrate concentration (up to 15 µg cm−3) and hence mainly explicable by deliquescence of fine anthropogenic particles, and during mineral dust intrusion episodes, when water condensation on dust particles could instead represent the dominant contribution. Secondly, lidar images show frequent events (mean daily occurrence of ~ 22 % during the whole campaign) of rapid uplift of mineral depolarizing particles in afternoon–evening hours up to 2000 m a.s.l. height. The origin of such particles cannot be directly related to long-range transport events, being instead likely linked to processes of soil particle resuspension from agricultural lands
The sperm mitochondria: clues and challenges
Sperm cells rely on different substrates to fulfil thei energy demand for different functions and diverse moments of their life. Species specific mechanism involve both energy substrate transport and their utilization: hexose transporters, a protein family of facilitative passive transporters of glucose and other hexose, have been identified in spermatozoa of different species and, within the species, their localization has been identified and, in some cases, linked to specific glycilitic enzyme presence. The catabolism of hexose sources for energy purposes has been studied in various species, and recent advances has been made in the knowledge of metabolic strategies of sperm cells. In particular, the importance of aerobic metabolism has been defined and described in horse, boar and even mouse spermatozoa; bull sperm cells demonstrate to have a good adaptability and capacity to switch between glycolysis and oxidative phosphorylation; finally, dog sperm cells have been demonstrated to have a great plasticity in energy metabolism management, being also able to activate the anabolic pathway of glycogen syntesis. In conclusion, the study of energy management and mitochondrial function in spermatozoa of different specie furnishes important base knowledge to define new media for preservation as well as newbases for reproductive biotechnologies
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