منابع مشابه
A Prehistoric Solar Observatory in the Middle of Sahara Desert
The prehistoric stone funerary monuments of the Sahara desert, distributed in a huge geographical area, had been created in several different shapes. Some of them have a design that looks like a keyhole, and therefore are known as keyhole tombs. Since they are facing the sunrise, these tombs were also considered as places for the worship of the sun. In this paper, we show that one of them, in A...
متن کاملRainfall regimes of the Green Sahara
During the "Green Sahara" period (11,000 to 5000 years before the present), the Sahara desert received high amounts of rainfall, supporting diverse vegetation, permanent lakes, and human populations. Our knowledge of rainfall rates and the spatiotemporal extent of wet conditions has suffered from a lack of continuous sedimentary records. We present a quantitative reconstruction of western Sahar...
متن کاملextraction and characterization of allium irancum plant extract and its application in the green synthesis of silver nano particles and oxidation of thiocarbony1 compounds
سنتز سبز نانوذرات فلزی (nps) درسالهای اخیر توجه بسیارزیادی را به خود جلب کرده است. زیرا این پروتوکل کم هزینه وسازگار با محیط زیست از روش های استاندارد سنتز. در این پایان نامه ما گزارش میکنیم یک روش ساده و سازگار با محیط زیست برای سنتز نانوذرات نقره با استفاده از محلول آبی عصاره گیاه allium iranicum به عنوان یک عامل کاهش دهنده ی طبیعی. نانو ذرات نقره مشخص شد با استفاده از تکنیک های uv-visible، x...
Dynamics of Green Sahara Periods and Their Role in Hominin Evolution
Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs) with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution ...
متن کاملPoverty amid plenty.
Clinical handoffs are tools aimed at bridging gaps that occur during transitions in care, whether across time (eg, shift changes) or across organisational boundaries (eg, the ward to the intensive care unit). They have long been viewed as potential threats to safety and are attracting increasing attention for several reasons. First, from a control theory point of view, handoffs are inherently h...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Nature
سال: 1981
ISSN: 0028-0836,1476-4687
DOI: 10.1038/292277a0