:John Kirk Townsend: Collector of Audubon's Western Birds and Mammals

petrology and geochemistry of khar-bash (western shahrood) and its relation ship to iron mineralization

منطقه مورد مطالعه در 23 کیلومتری جنوب غرب شهرستاشاهرود قرار دارد که در نقشه 100000/1 شاهرود قرار گرفته است.ناحیه مورد مطالعه در تقسیمات ساختاری ایران بخشی از زون البرز شرقی است . در طی سنوزوئیک این زون به شدت تحت تأثیر فازهای کوهزایی آلپی قرار گرفته و فعالیت های آتشفشانی انوسن در قسمت های غربی آن دیده می شود . از نظر ترکیب سنگ شناسی منطقه مورد مطالعه متنوع و بیشتر شامل سنگ های رسوبی مانند : آ...

Natal Dispersal in Birds & Mammals

Shivering Thermogenesis in Birds and Mammals

Shivering is the only universal facultative thermogenic mechanism in endothermic vertebrates. Skeletal muscle constitutes a large proportion of body mass and a high scope of metabolic rate, and thus heat production, between resting level and active contraction. Its contractile activity is under rapid and accurate neural control. Together with the inherently low metabolic efficiency of muscle, t...

Cortical computation in mammals and birds.

We humans are particularly proud of our cortices. Our brains are bigger than they should be, given our body size; furthermore, our neocortices constitute a larger fraction of the brain than in all other mammals, and our cortices probably contain more neurons than those of any other species on the planet (1). This cortical expansion is thought to give us our cognitive edge over the rest of the a...

Density-dependent dispersal in birds and mammals

Density-dependent dispersal can be caused by various mechanisms, from competition inducing individuals to emigrate (positive density-dependence) to social crowding effects impeding free movement (negative density-dependence). Various spatial population models have incorporated positively density-dependent dispersal algorithms, and recent theoretical models have explored the conditions for densi...