Less Is More

It sounds allwrong—drilling holes in a piece of wood to make it more resistant to knocks.Butit works because the energy from the blow gets distributed throughout the

wood rather than fo-

cusing on one weakspot.The discovery should lead to more effective and lighter packagingmate-rials.

Carpenters haveknown______(51)centuries that some woods are tougher than others.Hickory,for example,wasturned into axe handles and cartwheel spokes because it can

absorb shockswithout breaking.White oak,for example,is much more easilydamaued,________(52)it is almost as dense.Julian Vincent at Bathe Universityand his team

were convinced thewood's internal structure could explain the differences.

Many trees havetubular vessels that run_______(53)the trunk and carry water to the leav- es.In oak they are large,and arranged in narrow bands,but in hickory they are

smaller,and moreevenly distributed.The researchers________(54)this layout might distribute ablow's en-ergy throughout the wood, soaking up a bigger hit.To test the

idea,they drilledholes 0.65 millimetres across into a block of spruce,a woodwith_______(55)vessels,and found that_______(56)withstood a harder knock_______（57)when

there were more thanabout 30 holes per square centimeter did the wood's performance drop off.

A uniform substancedoesn't cope well with knocks because only a small proportion of the materialis actually______( 58).All the energy from the blow goes towards

breaking thematerial in one or two places , but often the pieces left _________( 59 ) arepristine（未经破坏的）.

But instead of theenergy being concentrated in one place,the holes provide many weak spots thatall absorb energy as they break,says Vincent.“You are controlling the

places______(60) thewood breaks,and it can then absorb more______(61),more safely.”

The researchersbelieve the principle could be applied to any material—_________(62)example,tomanufacture lighter and more protective packaging.It could_______(63)be

used in carbumpers,crash barriers and armor for military vehicles,says UlrikeWegst,_______(64) the Max Plank Institute for Mental Research in Stuttgart.Butshe

emphasizes thatyou'd ________(65)to design the substance with the direction of force inmind.“The direction of loading is crucial,”she says.58._________

A.effected

B.beaten

C.slapped

D.affected