RESEARCH in Brief RESEARCH in Brief

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Further information from:

PROF. PETER FRATZL

Max Planck Instituteof Colloids and Interfaces, PotsdamPhone: + 49 331 567-9401Fax: + 49 331 567-9402e-mail:fratzl@mpikg.mpg.de

A detail image of the glass fiber construction ofsponges reveals ingenious structuralengineering.

COLLOIDS AND INTERFACES

Secrets of the Venus’ Flower Basketon it – in some cases the pres-sure reaches 500 atmospheres –the imprisoned shrimps alsomaltreat the structure withtheir pincers. But the prison isescape-proof.

Material researchers in Pots-dam have now investigated thestructures from the nanometerto the centimeter scale. Duringthe course of their work, theydiscovered that the cage isconstructed from at least sevenhierarchically arranged levels.The skeleton itself is comprisedof bioglass fibers. But how can these glass fibers be usedto construct an unbreakablehousing? “We found the answerin the interior of the glassfibers, which are made up ofconcentrically arranged layers afew millimeters thick,” saysMax Planck scientist Peter Fratzl. “These glass layers, inturn, are joined together by avery thin layer of glue madefrom an organic matrix.” Theresearchers believe that theglass itself is formed by theconsolidation of silicate nano-particles that Euplectella syn-thesizes from the water.

The microlayer constructionreduces the brittleness of theglass. Cracks and scratches suchas those caused by the shrimps’pincers do not lead to breaks aseasily as they would with solidglass, since they are diverted inthe organic interlayer and pre-vented from spreading further.Several glass fibers of varyingthicknesses are in turn bundledtogether with glass cement –also composed of silicate

nanoparticles – toform strong con-struction filaments.

The filaments, fortheir part, arearranged vertically,horizontally and di-agonally and woveninto a dense net.“Their structure re-sembles a high-

tech construction,” says Fratzl.“Our investigations with thesponge have shown that thediagonal filaments are suffi-cient to protect the structurefrom torsion.” In addition, thestructure is reinforced by spi-ral-like ribs that prevent thecage-like construction fromcollapsing. “The last layer is thecurved shape of the cage,which continues to grow fromthe bottom,” explains the ma-terial researcher. “Here, thesponge is anchored to theseabed by glass fibers.”

For the Potsdam researchers,Euplectella is a textbook exam-ple of how brittle materials likeglass can produce non-break-able structures. “What wasamazing for us was the factthat the sponge manages tocombine a whole range of me-chanical construction principleson many size scales, from thenanometer to the centimeterrange,” explains Peter Fratzl.Even engineers and designersare still not familiar with thiskind of construction principle.This provides a completely newstimulus for material research.But Euplectella has still not re-vealed all of its secrets: “As yet,it is not clear how a compara-tively primitive organism canproduce such a complex andoptimized structure at all.” ●

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Berlin-based Max Planck Insti-tute for Human Developmentto design an experimentalstudy. At the Jacobs SummerCamp for children from immi-grant and socially disadvan-taged families, two approachesto German language instruc-tion were implemented andtheir effectiveness investigat-ed: implicit support by meansof guided theater activities andexplicit support through sys-tematic instruction in Germanas a second language (GSL).

The researchers addressedthree main questions:® Do immigrant children expe-rience summer learning lossesin terms of their German lan-

camp this time formed thebaseline group. It is only withthe help of such experimentaldesigns incorporating randomassignment to treatment andcontrol conditions that reliableconclusions can be drawn aboutthe efficacy of interventions. Todate, studies of this type are ararity in educational science.The Jacobs Summer Camp pro-ject was also intended to showthat it is possible to implementcontrolled evaluation studies ineducational research.

The researchers were able toanswer the first of their threequestions with a clear “no”: atsix weeks, summer vacations inGermany are much shorter

developed by Heidi Roesch, ex-pert on German instruction atthe Technical University ofBerlin, the GSL teachers height-ened the children’s awarenessof linguistic structures in aplayful approach. Directly fol-lowing the summer camp, itwas clear that the GSL childrenhad made measurable progressin the areas of grammar andreading. In a follow-up testthree months later, they nolonger outperformed the othergroups on grammar. This mayindicate a lack of learning op-portunities in school thatwould allow these abilities tobe consolidated. The GSL chil-dren’s marked learning gains in

Further information from:

DR. JÜRGEN

BAUMGARTEN

Max Planck Institutefor Human Develop-ment, BerlinPhone: + 49 30 82406-284Fax: + 49 30 82499-39e-mail: baumgarten@mpib-berlin.mpg.de

Nature produces the mostunusual building blocks outof the simplest raw materials.The glass sponge Euplectellaprovides a good example ofthis. Peter Fratzl’s team atthe Max Planck Institute ofColloids and Interfaces inPotsdam, together with col-leagues from Bell Laborato-ries and the University ofCalifornia (both in the US),has found out why theseconstructions made of bio-glass fibers are almost un-breakable, helping thesponge survive even in theextremely high pressuresfound deep in the ocean.(SCIENCE, July 8, 2005)

It has inhabited the sea formore than 540 million years,lives at a depth of 40 to 5,000meters and has a cage-likeglassy skeleton: the glasssponge Euplectella. Its shape re-sembles a white cylinder full offine holes. Shrimp larvae canget inside the structure throughthese tiny apertures and usuallylive there in pairs. As the larvaesoon become too large for theholes of their abode, the shrimppair spends their entire life inthe sponge, entering into asymbiosis with it. This may ex-plain why Euplectella is alsocalled the “prison of marriage”in Japan and is a popular wed-ding present.

Just how does the spongemanage to withstand the enor-mous mechanical strain at thebottom of the sea? Aside fromthe great weight bearing down

The Jacobs SummerCamp could provide a model for similarprojects to enhancelanguage skills.

guage proficiency during thesummer break, as might be ex-pected given the findings onsummer setback in the US?® Is it even feasible to imple-ment a vacation program forchildren from immigrant fami-lies and educationally disad-vantaged families in Germany?® Do the two language sup-port measures enhance learn-ing outcomes?

The students who participat-ed in the summer camp wereselected at random from a largegroup of applicants. All of theparticipating students engagedin theater activities during thethree weeks, but only some ofthem received systematic Ger-man instruction. The childrenwho were not selected for the

than in the US, and a notablesummer setback was not dis-cernable during the vacationperiod. The response to the sec-ond question, raised primarilyby skeptical school principalsand staff, was also clear: thesummer camp was very well re-ceived by all participants; near-ly all children attended on adaily basis, and feedback fromboth children and parents wasvery positive. Finally, the studydelivered important insightswith regard to the third ques-tion: the children benefitedmost from the combination oftheater activities and systemat-ic instruction in German as asecond language (GSL).

Using exercises such as “Theverb is the boss of a sentence,”

reading literacy, however, werestill discernible after threemonths. The progress theymade corresponds to about sixmonths of school lessons – andthat as the result of a projectthat lasted just three weeks.

In the future, vacation pro-grams based on the JacobsSummer Camp model mightcontribute to ensuring thatdisadvantaged children are notexcluded from participation insociety. Furthermore, the re-sults of the project indicatethat it would be worthwhile tosupport and strengthen GSLteaching in schools. In Bremen,the Senator for Education andScience has already followedup on the project in school andnon-school settings. ●

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Escape-proofprison: The

skeleton of thedeep-sea sponge

Euplectella, also known as

the “Venus’flower basket”.