potential GDP is dependent on the price level.

the prices of goods and services change while the prices of productive resources hold steady.

the price level and the money wage rate change by the same percentage.

All of the above are correct.

W18Cr4V 淬火+低温回火

ZGMn13 水韧处理

GCr15 淬火+低温回火

20Cr 渗碳+淬火+低温回火

Actin filaments, polymers of the protein actin, are present in most eukaryotic cells and are essential for many of the cell’s movements, especially those involving the cell surface. Without actin filaments, for example, an animal cell could not crawl along a surface, engulf a large particle by phagocytosis, or divide in two.

Like microtubules, many actin filaments are unstable, but by associating with other proteins they can also form stable structures in cells, such as the contractile apparatus of muscle cells. Actin filaments interact with a large number of actin-binding proteins that enable the filaments to serve a variety of functions in cells.

Depending on which of these proteins they associate with, actin filaments can form stiff and stable structures, such as the microvilli on the epithelial cells lining the intestine or the small contractile bundles that can contract and act like tiny muscles in most animal cells .

They can also form temporary structures, such as the dynamic protrusions formed at the leading edge of a crawling cell or the contractile ring that pinches the cytoplasm in two when an animal cell divides. Actin-dependent movements usually require actin’s association with a motor protein called myosin.

it helps to move food along the oesophagus

it helps to prevent food passing back up the oesophagus

it's important in controlling stomach movements

20Cr渗碳后低温回火

ZGMn13-3经水韧处理

W18Cr4V淬火后低温回火

Cr12经锻造处理

45

ZGMn13

ZG45

CrWMn

T8

ZGMn13

1Cr18Ni9Ti

20