Influence of parameterized small-scale gravity waves on the migrating diurnal tide in Earth's thermosphere

Effects of subgrid-scale gravity waves (GWs) on the diurnal migrating tides are investigated from the mesosphere to the upper thermosphere for September equinox conditions, using a general circulation model coupled with the extended spectral nonlinear GW parameterization of Yi\u{g}it et al (2008). Simulations with GW effects cut-off above the turbopause and included in the entire thermosphere have been conducted. GWs appreciably impact the mean circulation and cool the thermosphere down by up to 12-18%. GWs significantly affect the winds modulated by the diurnal migrating tide, in particular in the low-latitude mesosphere and lower thermosphere and in the high-latitude thermosphere. These effects depend on the mutual correlation of the diurnal phases of the GW forcing and tides: GWs can either enhance or reduce the tidal amplitude. In the low-latitude MLT, the correlation between the direction of the deposited GW momentum and the tidal phase is positive due to propagation of a broad spectrum of GW harmonics through the alternating winds. In the Northern Hemisphere high-latitude thermosphere, GWs act against the tide due to an anti-correlation of tidal wind and GW momentum, while in the Southern high-latitudes they weakly enhance the tidal amplitude via a combination of a partial correlation of phases and GW-induced changes of the circulation. The variable nature of GW effects on the thermal tide can be captured in GCMs provided that a GW parameterization (1) considers a broad spectrum of harmonics, (2) properly describes their propagation, and (3) correctly accounts for the physics of wave breaking/saturation.Comment: Accepted for publication in Journal of Geophysical Research - Space Physic

Role of gravity waves in vertical coupling during sudden stratospheric warmings

Gravity waves are primarily generated in the lower atmosphere, and can reach thermospheric heights in the course of their propagation. This paper reviews the recent progress in understanding the role of gravity waves in vertical coupling during sudden stratospheric warmings. Modeling of gravity wave effects is briefly reviewed, and the recent developments in the field are presented. Then, the impact of these waves on the general circulation of the upper atmosphere is outlined. Finally, the role of gravity waves in vertical coupling between the lower and the upper atmosphere is discussed in the context of sudden stratospheric warmings.Comment: Accepted for publication in Geoscience Letter

Storage Capacity of Extremely Diluted Hopfield Model

The storage capacity of the extremely diluted Hopfield Model is studied by using Monte Carlo techniques. In this work, instead of diluting the synapses according to a given distribution, the dilution of the synapses is obtained systematically by retaining only the synapses with dominant contributions. It is observed that by using the prescribed dilution method the critical storage capacity of the system increases with decreasing number of synapses per neuron reaching almost the value obtained from mean-field calculations. It is also shown that the increase of the storage capacity of the diluted system depends on the storage capacity of the fully connected Hopfield Model and the fraction of the diluted synapses.Comment: Latex, 14 pages, 4 eps figure

Gravity waves and high-altitude CO2_2 ice cloud formation in the Martian atmosphere

We present the first general circulation model simulations that quantify and reproduce patches of extremely cold air required for CO$_2$ condensation and cloud formation in the Martian mesosphere. They are created by subgrid-scale gravity waves (GWs) accounted for in the model with the interactively implemented spectral parameterization. Distributions of GW-induced temperature fluctuations and occurrences of supersaturation conditions are in a good agreement with observations of high-altitude CO$_2$ ice clouds. Our study confirms the key role of GWs in facilitating CO$_2$ cloud formation, discusses their tidal modulation, and predicts clouds at altitudes higher than have been observed to date.Comment: Accepted for publication in Geophysical Research Letters (GRL

Structural Econometric Methods in Auctions: A Guide to the Literature

Auction models have proved to be attractive to structural econometricians who, since the late 1980s, have made substantial progress in identifying and estimating these rich game-theoretic models of bidder behavior. We provide a guide to the literature in which we contrast the various informational structures (paradigms) commonly assumed by researchers and uncover the evolution of the eld. We highlight major contributions within each paradigm and benchmark modi cations and extensions to these core models. Lastly, we discuss special topics that have received substantial attention among auction researchers in recent years, including auctions formultiple objects, auctions with risk averse bidders, testing between common and private value paradigms, unobserved auction-speci c heterogeneity, and accounting for an unobserved number of bidders as well as endogenous entry

ÖLÜME FARKLI BAKIŞLAR

Uluslararası Bakalorya Programı, A1 Türk Dili ve Edebiyatı alanında ele alınan bu tezde, İnci Aral’ın Mor adlı yapıtında ölüm temasının figürler üzerindeki etkisi neden ve sonuçlarıyla incelenmiştir. Bu tezin amacı, yapıtta temel değişken olarak ele alınan ölüm temasının, kişinin kendi ölümü, yakınının ölümü, intiharı ve birini öldürme ya da öldürtme hakkındaki düşünce, tutum ve davranışlarının figürlerin yaşadıkları olaylarla ve içinde bulundukları toplum yapısını da göz önünde bulundurarak diğerlerinden nasıl farklılıklar gösterdiğini incelemektir. Üç gelişme bölümünden oluşan tezin giriş bölümünde ölüme karşı olan bakış açısının figürlerin içinde bulundukları toplum ve sınıf farkının da etkisiyle kişiden kişiye farklılık gösterdiği belirtilmiştir. Birinci bölümünde figürlerin genel olarak ölüm hakkındaki görüşleri ve yakınlarının ölümleri hakkındaki düşünceleri üzerinde durulmuştur. Bu görüş İlhan, Armağan, Renginur, Gülcan ve Âdem figürleri üzerinden incelenmiştir. İkinci bölümde figürlerin öldürme, öldürtme ve cinayet hakkındaki görüşleri dikkate alınmıştır. Bu görüş Fikran, Ramazan ve Revan figürleri üzerinden okuyucuya aktarılmıştır. Üçüncü bölümde ise figürlerin kendi ölümleri ve intihar hakkındaki düşünceleri incelenmiştir. Bu düşünceler İlhan, Gülcan, Âdem ve Armağan figürleri üzerinden verilmiştir. Tezin sonucunda figürlerin sahip oldukları ölüm hakkındaki tutum ve düşüncelerinde bireysel ve toplumsal faktörlerin etkili olduğu gözlemlenmiştir