The presence of cross-sectionally correlated error terms invalidates much inferential theory of panel data models. Recently, work by
Pesaran (2006) has suggested a method which makes use of ...cross-sectional averages to provide valid inference in the case of stationary panel regressions with a multifactor error structure. This paper extends this work and examines the important case where the unobservable common factors follow unit root processes. The extension to
I
(
1
)
processes is remarkable on two counts. First, it is of great interest to note that while intermediate results needed for deriving the asymptotic distribution of the panel estimators differ between the
I
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1
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and
I
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0
)
cases, the final results are surprisingly similar. This is in direct contrast to the standard distributional results for
I
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1
)
processes that radically differ from those for
I
(
0
)
processes. Second, it is worth noting the significant extra technical demands required to prove the new results. The theoretical findings are further supported for small samples via an extensive Monte Carlo study. In particular, the results of the Monte Carlo study suggest that the cross-sectional-average-based method is robust to a wide variety of data generation processes and has lower biases than the alternative estimation methods considered in the paper.
Remote effects modulating the austral summer precipitation over southern Africa during El Niño/El Niño Modoki events are investigated by analyzing the observed events during December–February of the ...years from 1982/83 to 2010/11. Based on the composite analyses, it is found that southern Africa experiences significantly below normal precipitation during El Niño events compared to El Niño Modoki events. During these latter events, precipitation anomalies are not so significant although southern Africa as a whole receives below normal precipitations. The differences in the spatial distribution of precipitation over southern Africa are seen to be related to the sea surface temperature (SST) anomalies of the equatorial Pacific through atmospheric teleconnections.
The low-level (850 hPa) Matsuno–Gill response to anomalously high precipitation over the Pacific during El Niño events results in an anomalous anticyclone extending from the equatorial to the subtropical South Indian Ocean. These anomalous anticyclonic winds weaken the tropical moisture flow into the southern Africa landmass. Rossby wave activity flux analysis of the upper-level (300 hPa) circulation shows an anomalous tropospheric stationary wave from the Pacific propagating toward southern Africa and maintaining an anomalous anticyclone over southern Africa. The anomalous Matsuno–Gill response and the anomalous tropospheric stationary wave response are intense during El Niño events, causing drought over southern Africa. During El Niño Modoki events, these processes are weaker compared to El Niño events.
Impacts of Indian Ocean Dipole mode (IOD) events on global climate are estimated by correlation/regression analysis. The analysis examined land rain and temperature and 3-dimensional atmospheric ...variables for a 42 yr period from January 1958 to December 1999. The correlation between IOD and the El Niño Southern Oscillation (ENSO) is accounted for using the multiple regression technique. We used partial correlation coefficients to describe the unique contribution of IOD to climate variability, independent of ENSO. In the Indian Ocean rim countries, IOD is associated with significant temperature and rain variability manifesting 2 large-scale patterns. In one, land temperature and rain are anomalously high over countries west of the Indian Ocean and anomalously low to its east. In the second pattern, enhanced rainfall is found over the Asian monsoon trough, extending from Pakistan up to southern China. Also noted are IOD impacts on several regions remote from the Indian Ocean. Strong correlation is found over Europe, northeast Asia, North and South America and South Africa concurrent with IOD events. Over these regions, positive IOD events are associated with warm land surface anomalies and reduced rainfall. The troposphere above the Indian Ocean exhibits strong variability during IOD events characterized by the following structures: (1) a Walker cell anomaly over the equator; (2) a deep modulation of monsoon westerlies; and (3) a Hadley cell anomaly over the Bay of Bengal. In the extratropics, IOD is associated with equivalent barotropic geopotential anomalies. These assume annular structure in the northern hemisphere, but Rossby wave train structure in the southern hemisphere.
Liquid droplet impingement (LDI) erosion on a rough surface was studied experimentally in the initial stage of erosion using spray-jet impingement on various levels of sandpaper roughness and single ...groove roughness. The experimental results using an aluminum specimen indicated that the incubation period decreased and the erosion rate increased with increasing the relative roughness, defined as the ratio of roughness height to droplet diameter, in a range of small relative roughness. The growth of the erosion rate in a large relative roughness is almost constant for the sandpaper roughness with increasing the relative roughness, while the erosion rate for the groove roughness decreased at large relative roughness. Therefore, the erosion rate of the groove roughness indicated a peak at small relative roughness. This might be due to the influence of smooth surface surrounding the single groove roughness. A scanning electron microscope (SEM) observation for the small relative roughness of groove showed that erosion was started on the sidewall of the grooves and was followed by the penetration of erosion perpendicular to the groove. The erosion initiation points shifted from the sidewall to the bottom of the groove with increasing the relative roughness, which might be due to the effective impact angle variation across the groove.
•Liquid droplet impingement erosion was studied on rough surface.•Erosion rate increased with increasing sandpaper roughness.•Peak erosion rate was found at small relative groove roughness.•Erosion mechanism was examined on single groove roughness.•Erosion initiates from bottom of groove at large relative roughness.
This paper presents an experimental study on erosion initiation via liquid droplet impingement on smooth and rough aluminum (A1070) walls. Experiments were conducted using a spray jet apparatus with ...three different orifice diameters at various nozzle pressures, which facilitated the variation of droplet characteristics, such as droplet velocity and diameter, which were measured using particle image velocimetry and a shadowgraph imaging technique, respectively. Experimental results are presented for the incubation period based on the spray flow rate, droplet diameter, impact velocity, and surface roughness. It was determined that the incubation period decreases with increasing impact velocity and surface roughness, while droplet diameter has a relatively minor effect on the incubation period. Furthermore, the incubation period based on the impact velocity and surface roughness is defined by an empirical equation for prediction. Scanning electron microscopy observations of erosion initiation on the rough walls reveal that erosion damage was initiated along crystal grain boundaries on the smooth wall, but much larger pits were generated on the rough surface based on the stress concentration effects of the roughness.
•Initiation of LDI erosion on smooth and rough walls was experimentally studied.•Incubation period on rough walls decreased with increasing surface roughness.•Incubation period of LDI erosion was formulated by droplet velocity and surface roughness.•SEM observation on smooth wall showed mass loss of crystals along grain boundaries.•SEM observation on rough wall showed large size of mass loss by pit formation.
Purpose
Wolfram syndrome (WS) is a rare disorder caused by mutations in WFS1 that is characterized by diabetes mellitus, optic atrophy, sensorineural deafness, diabetes insipidus, and ...neurodegeneration. This disease is usually inherited as an autosomal recessive trait, but an autosomal dominant form has been reported. WFS1 encodes a transmembrane protein, which is a maintenance component of endoplasmic homeostasis. These dominant mutations were thought to increase endoplasmic reticulum (ER) stress. Recent studies suggest that 4-phenylbutyrate (PBA) and valproate (VPA) reduce ER stress. The objective of this study was to analyze the effect of PBA and VPA on dominant WFS1 mutants in vitro
.
Methods
We determined whether dominant WFS1 mutants (p.His313Tyr, p.Trp314Arg, p.Asp325_Ile328del, p.Glu809Lys, and p.Glu864Lys) have the dominant negative effect using a luciferase assay of ER stress response element marker as ER stress. Moreover, the rescue of cell apoptosis induced by dominant WFS1 mutants following treatment with PBA or VPA was determined by quantitative real-time PCR of C/EBP homologous protein (CHOP) mRNA expression.
Results
These mutants showed the dominant negative effect on the wild-type WFS1. In addition, the levels of ER stress and CHOP mRNA were significantly elevated by all dominant WFS1 mutants. After treatment with PBA or VPA, ER stress and cell apoptosis were reduced in each mutant.
Conclusions
PBA and VPA could reduce the ER stress and cell apoptosis caused by dominant WFS1 mutants.
The flow field and mass transfer phenomena on wavy walls are studied both experimentally and numerically for application to the pipe-wall thinning of nuclear power plant. The numerical simulations ...are carried out using four turbulence models and the results are compared with the velocity field on wavy planar wall measured by particle image velocimetry, and the mass transfer coefficient data on a pipe wall in literature. The near-wall velocity field of the wavy wall shows the flow separation and reattachment, and the high intensity turbulence energy generation over the recirculation region along the trough. The predictions by AKN model indicate better agreement with the experimental behavior of mean flow and turbulence characteristics on the wavy wall, while the other models fail to predict the reattachment behavior. Further attention is focused on the mass transfer enhancement behavior over the wavy pipe wall. It increases with an increased relative roughness associated with the growth of recirculation region and the increased turbulence energy. However, the growth of mass transfer coefficient saturates at large relative roughness because of the limitation of the recirculation region and the downstream shift of high turbulence energy region over the trough. The mass transfer behaviors on the wavy pipe wall are better predicted by the
k
-
ω
shear stress transport model.
•Flow in and downstream of short elbow was studied at post-critical Reynolds numbers.•Unsteady flow behavior was measured by PIV combined with POD analysis.•A peak spectrum occurred in high ...frequency, while no clear peak in low frequency domain.•High frequency oscillation came from unsteady flow behavior near inner elbow wall.•Unsteady secondary flow behavior was observed in entire cross section of flow through elbow.
Unsteady turbulence structures in and downstream of a short elbow (radius to pipe diameter ratio 1.0) were studied experimentally for sub-to-post-critical Reynolds numbers (Re = 1 × 105 to 3 × 105). Measurement of the velocity field was carried out using particle image velocimetry (PIV) combined with proper orthogonal decomposition (POD) analysis. The mean velocity, turbulence intensity, power spectrum, spatial variation of POD modes, and time variation of instantaneous velocity and vorticity fields were evaluated. The experimental results indicate that a separation region forms around the elbow exit, which is almost independent of the Reynolds number for the post-critical Reynolds numbers. The power spectrum analysis indicates that the periodic oscillation is observed at Strouhal number 0.5, and that it originates from interaction of the secondary flow in the elbow and the unsteady separating flow behavior near the exit of the inner elbow wall. Furthermore, POD analysis was conducted to clarify the variation of POD modes in the elbow flow. It was found that the periodic velocity fluctuation is generated by the oscillation of the flow in spanwise direction downstream of the elbow, which consists of a secondary flow structure directed to the inner elbow wall, and a streamwise longitudinal structure along the centerline of the elbow. The POD reconstructed velocity and vorticity fields indicate periodic oscillation of the entire secondary flow arising from unsteady oscillation of a pair of vortices in the cross section of the elbow; this condition prevails in and downstream of the elbow.
The overall skill of ENSO prediction in retrospective forecasts made with ten different coupled GCMs is investigated. The coupled GCM datasets of the APCC/CliPAS and DEMETER projects are used for ...four seasons in the common 22 years from 1980 to 2001. As a baseline, a dynamic-statistical SST forecast and persistence are compared. Our study focuses on the tropical Pacific SST, especially by analyzing the NINO34 index. In coupled models, the accuracy of the simulated variability is related to the accuracy of the simulated mean state. Almost all models have problems in simulating the mean and mean annual cycle of SST, in spite of the positive influence of realistic initial conditions. As a result, the simulation of the interannual SST variability is also far from perfect in most coupled models. With increasing lead time, this discrepancy gets worse. As one measure of forecast skill, the tier-1 multi-model ensemble (MME) forecasts of NINO3.4 SST have an anomaly correlation coefficient of 0.86 at the month 6. This is higher than that of any individual model as well as both forecasts based on persistence and those made with the dynamic-statistical model. The forecast skill of individual models and the MME depends strongly on season, ENSO phase, and ENSO intensity. A stronger El Niño is better predicted. The growth phases of both the warm and cold events are better predicted than the corresponding decaying phases. ENSO-neutral periods are far worse predicted than warm or cold events. The skill of forecasts that start in February or May drops faster than that of forecasts that start in August or November. This behavior, often termed the spring predictability barrier, is in part because predictions starting from February or May contain more events in the decaying phase of ENSO.
Time-resolved observations of pit formation and cloud structure in a cavitating jet are carried out to understand the erosion mechanism of a cavitating jet issuing from a converging and diverging ...nozzle in a still water environment. Pit formation is detected by a sensor made of gold film (0.2μm in thickness) glued to a transparent glass plate, and the number and size of the pits are evaluated from digital image analysis. High-speed camera shadowgraph imaging allows observation of the cloud structure in the cavitating jet, which captures the cavitation cloud collapse combined with the time-difference analysis. The radial distribution of pits is in close agreement with the erosion depth distribution evaluated from the weight-loss profiles of an aluminum specimen in a cavitating jet. The pit distribution in the cloud collapse is well reproduced in the time-difference analysis. Furthermore, simultaneous observations of the pit and cloud structures show that pits are formed on the wall at the instant of cloud collapses during the periodic behavior of the cavitating jet.
•Time-resolved observations of pits and cloud are carried out in cavitating jet.•Pits are detected by thin gold-film sensor glued on wall.•Cloud collapse is taken by axial imaging by time-difference shadowgraph.•Local erosion rate is reproduced in pits growth rate and cloud collapse intensity•Pits formation occurs at the instant of cloud collapse.
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