CINXE.COM

<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "pnas.org",cType: 'managed',cRay: '92674e111cb45f7d',cH: 'S_JEfia5F9l4HNGn9DiGawXqfJXlbmIipGb0wBMFdmA-1742998996-1.2.1.1-1XvkjmZiPZBVcN2NRfLZJLJ2zXgcvNc5U2kCTH1u6iX48Gu7kcjHGUSjMuaqDSHv',cUPMDTk: "\/doi\/full\/10.1073\/pnas.1511468112?__cf_chl_tk=Edo2oYav0ZMNCuuzf6Wsj0aKV4owgMUTM4AJ7KHBUz4-1742998996-1.0.1.1-_K8CGGwTugFItrZ8DSYsb09NG_Me3zl4Nd2MXy1PvTw",cFPWv: 'b',cITimeS: '1742998996',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/doi\/full\/10.1073\/pnas.1511468112?__cf_chl_f_tk=Edo2oYav0ZMNCuuzf6Wsj0aKV4owgMUTM4AJ7KHBUz4-1742998996-1.0.1.1-_K8CGGwTugFItrZ8DSYsb09NG_Me3zl4Nd2MXy1PvTw",md: "UDrpQTJLblYUNcYYR1yH_dOQsTwIug.G4zXBrMGjBFM-1742998996-1.2.1.1-IcW9BUNIfk5DXgJHcLdlWOTA7J.ZCQ8qGcEI9LUjJp2zwxxNIshMS_aURfu1siegyeIVSho3x8OEq_Nd32X5yTjOnSGEJ4uLGhFiiVDWkKjLGiPr_d3KCD0px4Z_fW86D_pMAOy4FejAlpYGfbqbtkdu1csgV7262eY.r.RRRT3iDus5FcjNH5Q0Y.qKb3KjQGf5HuWOb352w2IC5I9icRd84eSMC_qey.M_vBNm72QR83Qd8qRjR6IcFpdlNjUa1iUAazwh6JPs1Wk1ycnWzJINVtua2gJUn9JZlMjxQ.XqBEz72GAMxCSQd_gPBO78EA.gke4VL5Pj5e3W2GiTDMFFiddHtFFdg6moye7.oDZc.Xi3KHXsUPtJvDibbdb.Tys_vJ8jVR3_eYn8wNQs5rKi5.e7wHaO6cfNv9We2UGEU5Ioi9_KxcZGExcNkOlmNkeX.KPcQf0mhSSoJwFnEPWsok.rul.QFnoi1ZxAqR3TgWtty_3vOTFZdO38QsE2kDVGAVV_SE6JTIadAYXy2y7pCeNCLX4woufV9_1YqPzSQGiKvEWUOqZSnTIwBdNiMDhoL5tav0.ua3fzoNlyEbQKouwlzbgU7rzAYpO3yyQ1czSkzZ4mnsSXp0BTwm6icNtM5OUCDHap9daol1qYP5aJAOrV5gZi5My2BueIeO2s0iFjq8bZ4l58FHFhZBduqoFz1Hb4q4vKPwPFW4G2jp0kc0a1XJG5x5JUwFJNEOiGYWq3Tq7hDTK8fVvcjDhEls3qk2iVcFPPkPog4d8Lh3UeQ72Fw0nOdFRQWRbcI.jVE9RQTmdeQJ.FWw9WtzFcUSqjse4US1UU3g7vJP7wLFGTLs44HD7eiFzOpZexJcdiRZ.wx8gNn8NpDVcPD73GD.G4RS_QssZ4vxalbJMEp4f15QQlSNKHjB_RvySVY60xTrgs3OR5b8XSuZ7bACl8HhRXubsidMjYQc9P4VM1Nfwqx0zlcIwQ9phqQZ80XynepRn4nBdw_eaQRiqRB09eU77ayVScTXq6aEav1BZ5FeICAy4dGADb7s7CDB_l7UWwdAG06mhZrAj022rJRM86dFbx_V2BpoxuxgXWq7Ol8ZE3QScEumgQdLWGrG2jj3jOEJAn4zdPfflh.JPeqbNXUnyF2XKdufnVy5wPRneh38RUtOXNruZy4J3rdJ0_RIi0JzpayGnUEAesxmKv8DhTCqZFRK1e49lw_4KDzXPE7AbQbpiuTgagp6vpHY3Io7JyUT9v7XuYf_W0fCVRZ.yjoNNVX_YIgBX.fVxBGem4yg",mdrd: "XQOAm.MhRY0a4Wcy7Ul92DGE66McSLLwHFJPB9Hymwk-1742998996-1.2.1.1-gK1QS2coCD2eAYnRXC26YOOyhjCIOQXrZ9jYV0ialpzZG1Hmu8MP_0VDaOeTs98W9IRkKIlypMJOT2CUIQcb8EH95ajarowmuLcquS_KNMpie8w_s5zBhBMhPw7b_XTv6rikQYcFLykNTe99HRyo.cj2wQh4VveISLSewoYc1emG4WK1rWXshdNRt4iaEFIp_uYJlcGh9faT654KC1D6nEHz2j1HGxg1.WPvr6actmHUdIX.wNvYnudc1UGxsJJQOLO_o9ARMNzzeDFC7TX_3jNYZmjv55RrCItrZKCQ9r8I9NT_xxrUtGLSG.fhZmcr_36tpjK1n2_ygaFJYVb_pZKMggpaqVVDfTFI.0UZTfP.O2AGK1XnPQt14qR04OeTYjTY0bbA0PeVkx_YBr26_w6jmg0wLhAWlTakIF_VUnatKBwacOKCqSkOn6RWF2RRfb2ub4WVbcxx.i4R7GvzCZgVpF3DMPzD1Yof3QobqPy2_y2hc39TE1yH42Gisca3eB9da70swF7fiVbulvXtnpbGqD3In1bwhIcsCv5wCvis3EuB3xhZ_1tB4Y9YLpdC2vuzM8hzdHsfSnRFBYsTs3bcbhyyPfdQJ2azyA2KJclT.IZSY0vOprT.ffttKKLvMg2IpQcmsY0AVs2HS_stCi9FOeZ8LRRx0Kvx8NnQ9q.5SO1pEc8Ut6f45.HzdbqGn7oy70Fr_50bd42UVyhXfzcT3tRlMxUXVpmvG11qmdXP09veDZcr7u0ys46TVb5ElUovt9Y253gWjtknwKSVG0nk1YH1o42LFsM62_4Os7qDdP80jnpU2msfz8NTVqQFIcDKUGBwg_pqEqfWIz0fOOc3NFyUMjHgtOrQZrX.95Z6yGj8CnYtRmatuVgX2Y3LI3rnzUEz0shEbU4.2X.1xYCqwqzLUgT.i52ky05zF19jq_v8abZMOp.ac4zzdLNbcf2E7IDJOxIZ95lYLhJRb2MK.EtMDE_q9JoJZpRvxjiDolz53WwqOPAVN1N4f0ZdSZFw97iLlMamRGLElzlu.J9X7Vqb4vuqomfk7NLEsRpsUwvPQYIltnP9O8UDcnKAA.U7QBkf_xNrQG_NhUSU.L9qaoLaP3ypWMNcZHjeQ1yrSgb3M.J9YSEMdQ108KIK4WMQwWl6xiIwVfpHhZVdGI.COWOr35gZB4DxTALIA6dH_k8iUJ.ilL8.UCRInPfThhTJ8_lErXlPqyTgURtgWahtrZdSdekJdOvUEOEcmcESGFREuaEI839aBfSYZvd2DGjEXjXDP4CAPJyKDE6mTroHXUSxlbIFzhpxcteGzKgl9ubqY72im7IYNAk81C4hzv3MU01EF9YtyING4X317rg6pqUb4HQdkLCVFQtYstfBE32_3YhIa0mT0C_QZBclZ0icznuvKkmippI8mK6ZzQcjsPs55qIX_SzlPQCwV1evPWelgoh2CzFIFoIs8Hkrsa9MZenLxODCLkNXugScCP_OaXJ1DtC79Ywc3Eecs45tSZlN9U2favEUhRd7KKQzCxpEtZ.IwsprcFl_5KV10Q.dOOP.AjXWo6Q55h_1kSi2NktE4H1AZw13XzIKDWsY.ox6d.OumWu917PLYE7zCrTYkKH47HmRp0z9nGHL3CFCOkzPSBXF3l1SbLM2Eny4WCBR.JTnW11AwIkSJUPSlWTzReNOBVlxYVfqrrvpkz6pnjqxZIrycXiiXYfjckEgfVjeMH137OOA8wSwmirmGr8wyCV9bzLP9qaioYqwYJrWuy4hbWnKl7ftzlGIrml3aSJi_xopAeXYHiFsVRkZSLBEgwJiRHPxh0if1a3cJZJphuK02QHFK0TYl.9Ci9FwVqHL88lizk3ovIcr4BRBtMW8n7Xa3MAp2dwW.sN2O63XaZmPJULko74ava9AWhlClJa8MW2qjACQPoyl8CJrtnrYCEj0ddsC7HUkYfkkngWr0sF4gtg.yBdp4Z_v.e8dRIaqpANkQIHhN5qqjudSzv0RiHA73EEd94yvru3ct6s"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92674e111cb45f7d';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/doi\/full\/10.1073\/pnas.1511468112?__cf_chl_rt_tk=Edo2oYav0ZMNCuuzf6Wsj0aKV4owgMUTM4AJ7KHBUz4-1742998996-1.0.1.1-_K8CGGwTugFItrZ8DSYsb09NG_Me3zl4Nd2MXy1PvTw" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>