نتایج جستجو برای: loess

تعداد نتایج: 3659  

Journal: :iranian journal of science and technology (sciences) 2014
b. keshavarzi

loess and loess-like deposits cover large areas of golestan province of iran, a well-known region in the world for its high incidence rate of esophageal cancer (ec). despite numerous published works on the possible contributing factors for the observed high incidence rate, very little attention has been given so far to a possible link between the mineralogy of loess deposits in the region and e...

Journal: :پژوهش های جغرافیای طبیعی 0
وحید فیضی دانشجوی دکتری جغرافیا، اقلیم شناسی، دانشگاه تهران حبیب علیمحمدیان استادیار گروه زمین شناسی (گرایش محیط مغناطیس)، سازمان زمین شناسی و اکتشافات معدنی کشور قاسم عزیزی دانشیار، گروه جغرافیای طبیعی، اقلیم شناسی، دانشگاه تهران حسین محمدی استاد، گروه جغرافیای طبیعی، اقلیم شناسی، دانشگاه تهران علی اکبر شمسی پور استادیار، گروه جغرافیای طبیعی، اقلیم شناسی، دانشگاه تهران

introduction in general, loess sediments are one of the most widespread forms of aeolian sediments. during the past few decades, loess stratigraphy studies played key role in the investigation about global climate changes. these sediments are usually yellowish in color and silt makes 70 to 90 percent of its volume. in iran, loesses outcrop are often in northeast part of south caspian sea. the p...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2017
Olivier Moine Pierre Antoine Christine Hatté Amaëlle Landais Jérôme Mathieu Charlotte Prud'homme Denis-Didier Rousseau

The characterization of Last Glacial millennial-timescale warming phases, known as interstadials or Dansgaard-Oeschger events, requires precise chronologies for the study of paleoclimate records. On the European continent, such chronologies are only available for several Last Glacial pollen and rare speleothem archives principally located in the Mediterranean domain. Farther north, in continent...

2014
B. Keshavarzi

Loess and loess-like deposits cover large areas of Golestan province of Iran, a well-known region in the world for its high incidence rate of esophageal cancer (EC). Despite numerous published works on the possible contributing factors for the observed high incidence rate, very little attention has been given so far to a possible link between the mineralogy of loess deposits in the region and E...

2006
Xiaodong Miao William C. Johnson

Multi-proxy analysis was used to produce a high-resolution paleoclimatic record from an exceptionally thick section of the Holocene Bignell Loess near Wauneta, Southwestern Nebraska, in the central Great Plains. The Wauneta section has excellent age control, based on optically stimulated luminescence (OSL) and radiocarbon dating, and records multiple episodes of rapid loess deposition alternati...

2002
Cai Qiangguo

The Loess Plateau lies in the North of China and is one of the most serious regions of soil erosion in the world. Severe loss of soil and water not only has its devastating effect on farming, forestry, stock-breeding and ecological environment of the area concerned, but also is the root of poverty for local people. The Loess Plateau has a long cultivation history, hence population growth, veget...

2001
B. Guo R. X. Zhu Andrew P. Roberts Fabio Florindo

We have conducted a detailed mineral magnetic study of loess unit 8 (L8) and paleosol unit 8 (S8) from three localities (Jingbian, Yichuan, and Duanjiapo) along a N-S transect in the Chinese loess plateau. As expected, the lowfield magnetic susceptibility (χ) has higher values in S8 and lower values in L8. Similarly, superparamagnetic particle concentrations increase in S8 with increasingly hum...

Journal: :Scientific reports 2016
Xin Wang Haitao Wei Mehdi Taheri Farhad Khormali Guzel Danukalova Fahu Chen

Arid central Asia (ACA) is one of the most arid regions in the mid-latitudes and one of the main potential dust sources for the northern hemisphere. The lack of in situ early Pleistocene loess/dust records from ACA hinders our comprehensive understanding of the spatio-temporal record of aeolian loess accumulation and long term climatic changes in Asia as a whole. Here, we report the results of ...

2017
Yuhang Wang Muyi Kang Mingfei Zhao Kaixiong Xing Guoyi Wang Feng Xue

Analyzing spatiotemporal variation of tree cover could enhance understanding of the environment and promote a sustainable resource use of ecosystems. This study investigated the variation in tree cover in the Loess Plateau after an ecological restoration effort called the ‘Grain for Green Project’ (GGP). The results show that the proportion of tree covered area in the Loess Plateau changed from...

2018
Tetsuya Ito Kazuo Fukawa Mai Kamikawa Satoshi Nikaidou Masaaki Taniguchi Aisaku Arakawa Genki Tanaka Satoshi Mikawa Tsutomu Furukawa Kensuke Hirose

Daily feed intake (DFI) is an important consideration for improving feed efficiency, but measurements using electronic feeder systems contain many missing and incorrect values. Therefore, we evaluated three methods for correcting missing DFI data (quadratic, orthogonal polynomial, and locally weighted (Loess) regression equations) and assessed the effects of these missing values on the genetic ...

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