Search results for "DURATION"
showing 10 items of 447 documents
The Parasitic Colonization of the Horny Layer in Tinea Versicolor
1972
Observations of vertical sections and of tape strippings of areas infested with tinea versicolor indicate that because of their dimorphic state, these parasites can colonize the horny layer. Mycelial hyphae progress downwards into the intercellular spaces of the horny cells where they feed on nonkeratinous substances and extrude proliferating yeast cells which form clusters in nest-like cavities. The yeast-mycelial conversion gives rise to new mycelial hyphae and the cycle is complete. The parasites are actually lodged in tunnels and nests hollowed out in the horny layer. A dynamic balance between the cycle of the parasites and the renewal rate of the horny layer is responsible for the long…
Technical Feasibility of Electromagnetic US/CT Fusion Imaging and Virtual Navigation in the Guidance of Spine Biopsies.
2020
To test the technical feasibility of electromagnetic computed tomography (CT) + ultrasound fusion (US)-guided bone biopsy of spinal lesions. This retrospective study included 14 patients referred for biopsy of spinal bone lesions without cortical disruption or intervertebral disc infection. Lesions were located in the sacrum (n = 4), lumbar vertebral body (n = 7) or intervertebral disc (n = 3). Fusion technology matched a pre-procedure CT scan with real-time ultrasound. The first six procedures were performed under both standard CT and CT + US fusion guidance (group 1). In the last eight procedures, the needle was positioned under fusion imaging guidance alone, and CT was only used at the …
Statistical Properties of Double Hoyt Fading With Applications to the Performance Analysis of Wireless Communication Systems
2018
In this paper, we investigate the statistical properties of double Hoyt fading channels, where the overall received signal is determined by the product of two statistically independent but not necessarily identically distributed single Hoyt processes. Finite-range integral expressions are first derived for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades of the envelope fading process. A closed-form approximate solution is also deduced for the LCR by making use of the Laplace approximation theorem. Applying the derived PDF of the double Hoyt channel, we then provide analytical expressions for the average…
A new model for estimating diffuse solar radiation in Italy from clearness index and minimum air mass
1990
The aim of this study is: (a) to propose a new simple model for estimating the monthly mean daily diffuse radiation D, MJ m−2 day−1, using as input only the clearness index Kt and minimum air mass and (b) to develop a map of diffuse solar radiation incident on a horizontal surface in Italy. The correlation herein suggested is D = 5.6 Kt−0.55 (sin hn)1.58 where hn is the noon altitude of the sun on the 15th of the month, in degrees, and Kt = G/H0; G and H0 are the monthly mean daily global and extraterrestrial solar radiation respectively. This equation is applied to Adrano, Palermo, Macerata and Genova stations, provided with measured data of global and diffuse radiation, and the relative c…
Using Survival Models with Individual Data
2007
Since there exists in this literature a common interest to unravel the sources of both permanence in the self-employment status and firm survival, the present chapter is devoted to provide guidelines to applied researchers about which methods are suitable for any particular application related to self-employment and firm survival. Further, it should be noted that the econometric analysis of survival (duration) is a very wide field, and that the modest aim of the following sections in this chapter is to introduce the reader to such kind of econometric analysis.
Sexual satisfaction in male infertility.
1999
Infertility is proposed to be a continuing stressor for couples suffering from involuntary childlessness. A long duration of the desire for a child and, correspondingly, a longer period of diagnostic and treatment procedures could have a negative impact on sexual satisfaction, thus leading to an unfavorable psychological circuit. The present evaluation should clarify the state of sexual satisfaction and relationships, with relevant parameters in 68 men with fertility problems, of couples with involuntary childlessness. Subjects reported relatively high average levels of present sexual satisfaction with only nonsignificant lower scores (p = .08) compared to recalled sexual satisfaction prior…
Global factors, uncertainty, weather conditions and energy prices: On the drivers of the duration of commodity price cycle phases
2020
We investigate the role of global factors in explaining the length of commodity price cycle phases, using a continuous-time Weibull duration model and data for a panel of 33 countries over the period 1980Q1-2015Q4. We find evidence of increasing (constant) positive duration dependence for commodity price booms and busts (normal time spells). Global macroeconomic conditions - in particular, inflation, economic policy uncertainty and monetary policy actions - significantly affect the duration of all commodity price cycle phases. Global environmental conditions also impact the duration of commodity price booms, with a rise in average temperature (rainfall) increasing (reducing) their length. A…
The Benevolence of Time, Sound Macroeconomic Environment and Governance Quality on the Duration of Sovereign Ratings Phases
2019
Using long-term sovereign ratings data for a panel of 130 countries over the last three decades, we rely on discrete-time Weibull models to investigate the duration and determinants of sovereign ratings phases. We find that the likelihood of the end of the 'speculative-grade' phase increases as time goes by (i.e. positive duration dependence), but the 'investment-grade' phase is not duration dependent. Thus, for sovereigns rated as speculative, the build-up of reputation as good borrowers is a gradual process, whereas the reputation of investment-grade sovereigns solidifies and remains unchanged as time passes. However, the length of both phases has proven to be significantly dependent on t…
On the duration of sovereign ratings cycle phases
2021
Abstract Using long-term sovereign ratings data for a panel of 130 countries over the last three decades, we investigate the duration and determinants of sovereign rating phases through the lens of discrete-time Weibull models. We find that the likelihood of the end of the ‘speculative-grade’ phase increases as time goes by (i.e. there is positive duration dependence), but the ‘investment-grade’ phase is not duration dependent. Thus, for sovereigns rated as speculative, the build-up of reputation as good borrowers is a gradual process, whereas the reputation of investment-grade sovereigns solidifies and remains unchanged as time passes. However, the length of both phases significantly depen…
Extraction of the mismatch negativity elicited by sound duration decrements: A comparison of three procedures
2009
This study focuses on comparison of procedures for extracting the brain event-related potentials (ERPs) - brain responses to stimuli recorded using electroencephalography (EEG). These responses are used to study how the synchronization of brain electrical responses is associated with cognition such as how the brain detects changes in the auditory world. One such event-related response to auditory change is called mismatch negativity (MMN). It is typically observed by computing a difference wave between ERPs elicited by a frequently repeated sound and ERPs elicited by an infrequently occurring sound which differs from the repeated sounds. Fast and reliable extraction of the ERPs, such as the…