h, w = map(int,input().split())
s = [["."]*(w+2)] + \
    [list("." + input() + ".") for _ in range(h)] + \
    [["."]*(w+2)]
flg = 0
for i in range(1,h+1):
    for j in range(1,w+1):
        if s[i][j] == "#":
            if s[i-1][j] == "." and s[i+1][j] == "." and s[i][-1] == "." and s[i][j+1] == "." :
                flg = 1
                break
if flg == 0 : print("Yse")
else : print("No")