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,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIzMiIgaGVpZ2h0PSIzMiIgZmlsbD0ibm9uZSI+PHBhdGggZmlsbD0iI0IyMEYwMyIgZD0iTTE2IDNhMTMgMTMgMCAxIDAgMTMgMTNBMTMuMDE1IDEzLjAxNSAwIDAgMCAxNiAzbTAgMjRhMTEgMTEgMCAxIDEgMTEtMTEgMTEuMDEgMTEuMDEgMCAwIDEtMTEgMTEiLz48cGF0aCBmaWxsPSIjQjIwRjAzIiBkPSJNMTcuMDM4IDE4LjYxNUgxNC44N0wxNC41NjMgOS41aDIuNzgzem0tMS4wODQgMS40MjdxLjY2IDAgMS4wNTcuMzg4LjQwNy4zODkuNDA3Ljk5NCAwIC41OTYtLjQwNy45ODQtLjM5Ny4zOS0xLjA1Ny4zODktLjY1IDAtMS4wNTYtLjM4OS0uMzk4LS4zODktLjM5OC0uOTg0IDAtLjU5Ny4zOTgtLjk4NS40MDYtLjM5NyAxLjA1Ni0uMzk3Ii8+PC9zdmc+);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: "publications.waset.org",cType: 'managed',cRay: '92887b123ae84727',cH: '.cIeLZjc95fFUT9UumDoMFJ.a_IYVc4UxMD2k1R8FV8-1743346870-1.2.1.1-ilN1ChWJXolyJTo86oHCsW0O7wdBe46UJXCvuFWutrVdzrc4C_FvrDVIDUlYYfbo',cUPMDTk: "\/10012440\/harvard?__cf_chl_tk=FyI3FgbL.PnJg3hu8q5dGdo1PI1hc79CTupswr33obE-1743346870-1.0.1.1-JPrsZoojLf8eBd5iREt0eqs93eyH16RZKEleYoDeMHU",cFPWv: 'b',cITimeS: '1743346870',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/10012440\/harvard?__cf_chl_f_tk=FyI3FgbL.PnJg3hu8q5dGdo1PI1hc79CTupswr33obE-1743346870-1.0.1.1-JPrsZoojLf8eBd5iREt0eqs93eyH16RZKEleYoDeMHU",md: "w72qduzNqg6lZQRDaG0RyQ70dvk_JF_t_hapPmVb0jg-1743346870-1.2.1.1-7nthBYtI5Mc_r3.Z0KojcaN2i47sCFko3lz7LaEVrKrAj5Dt0yulul5PSpFzrnWHbhU2IjqnlBOZUohlxXeMvqKy3Z2zB66CjF2J4Yxg85OYl1cZiiqnCbiQ_ebC5ElhpGYU8CjN2uf8GVANb3kG5QgjRLJSazzToMedOHGmwDDnswk1wFKeZPDdYNOwAj8Sa5oHzN_XSZ4LW3ua4Z001CpQCvqqeJEP2N2o3Fotdkew2Kjty4VV4icIvtamcxFiit0PF1AtD.bGeA3kDBCzqFuri8thQmPjGxbr4uoyxnEWrd4pOyvz8.vznMcZ1oP8J9_sXlv86RFrO2.IGju262SoMrsQnlofPTBq3KRf75q9NNAMwsEuag3D0gv1hi_hNfA6NGk1eQ4uZA4lg89feh3riWdt9bInjIwdzSPCXyPlWCxW8_jEO328N44Nvy4jqP2lEoQmpGS5OCfcEc2wxFWN.enP8_q9EpLE0TeU4Kcl0O0_YafZ0_s6qL3SXGry_hCylSFVD9IXW2CB56Haif7QxYoUwxint486LpUlDFeoM9YQzX1QwX.xMAu41wo.zLIyEvBydNtY.THklsz.DtYJT2lmN.FbZulR9TqL0rJKIQcJuSTdsYLBBS4fr9nzoB1q0aI1eC5Uzat.YjeUJc4aWu5vl0D_QeFRF0BZ0s0N5yqXt7a0yGRCqF_c.9M_FfE_gNtRwIcVttdc3q33H5m2eWVjCLqNEGzSVl6.JSTY50Z0JQXPL.Nunps2mbnUda3NC1q9p0VHE9Vvk0J67GLRn3VYEcn1y8gk9Daxo6.mVE.Zlf.1.wOoRSZ7N59rDqvlegWWUJA4iO9GcGlFzubQM.jqUT0qnYgZI1G74kQKdpSJcE4oagg1UGw8dXQDOSaHNc8d4byxjXV7cjPF0Zy8lfkHO5SrnH726LTnA4lmMkz5yK5OCxwEIRORGj.je43QHwLiF_1ycxCpTueRoy1vyolc9oet0vkfWD6j7WbX4XnuIzIgo3bUhdrNb1IRIdRuBg325DLl2VebQmZo4mHsdNb5omNQjPAfIbXPmJZGOm6QrAIIqqur9ehYx3Co5UWq3oWne600.pzZuoPrxmgk.OEhOJ_ZaYcBtB7qwKJeUX2vH7zNG0fqFLV1Si9S_wb17ReqHLlao_JGl3khSEyekaI8nFmsLPbBS8ICYZlGlUjrGPIhmR5r.pWISnuLxDeod_5_udPkQnKM29PBqj7ILWcBxhxBkbNRbSGXIKw",mdrd: "Dl8jlTVWhOsPo21VvQW0SWi9pU3BKWy_vKizIamS72I-1743346870-1.2.1.1-Lh5sG2mDP0rzxPj.F29JfD.swQAmIuc0jR1WIgwTvVoiWDdb0zdgH340uQx7bfQDNmxdT2eDEIdsNRvf9HIooYIdr2gp94SA.5e9wrHxO4A7zAaqp_eXCYqjZa47BpyELzVQLxprZQALXqloCtVjaFqWRvm1WHaRBFF0g56I3DBBq4PE4pJxtWDUkD9FFLEE78ZnXj99fLYtSwyjWi0KgMp4y.TcYVsnKvmfcrCnPlUE2a1W6ACSTpP3oKfrX3RG5l0BDz8xRVR7U5io2_jouDv1hEzHQV4Cc3k6L0QsnNx80rxwYbVKogMiUK9gsCjnW76dyeoZXt.T9s0KICnWf0p8Ne6xJUg09b32GeQ06A94Q0TfJPRRH1571QDrL4QJsUKsxoypaei30vSWbSHyeUez4AozpSaXZkK_0_G6vCLESsx362G8fCIx23.jynXSGnax4DRjx6ZdT4f1Z4Fd.RtfGumKUBPmxtLh6fNGLx.ieGYAFcq_EOKaqxDGFjUS5V4KXCaHsXP_7Wvefx5maEVhrLZ5k0vJHsR1kWujTahvp5DELe9nNXCSeZ8.ZDrbKIohAo_OCp2MwTWMDfVbyjeaw4TwO8oepA.4DyFZyM2m2CMTUUcHJkFRZEhknR5WKTFMSmB52Q5RHEw13KrF3._p51r399icfo1QS7i.ffLu3OVCG.bS5OjnV_MZG1zbq2snnqJ0GCHzvp_qpvv64ThJvzDc94q6_jy..5Xxx3.WId2Cvq_S2FjU8z396f5NGj.ZREuJPIjifENQ2Flad92nR06QIzznHKxL3OdezXu_Xn_a.wpR3TKYnIcA0qa1ShxCi.DyqzprAc2sTqD0Q1XTJlaSktQv.gUPRTnJBcec0s5hM4eSqUzM7E2fvnGNK23etaNF8GMy7_ER_86tzibsPj4.mv_TxP.UfkbhfRHkv1mot5QP66pnSZw02YYrE0rnas1E6VFEalqbsROb2gMTIh4NltQ_h_EYvdm7_Jed3cq4uIQ9y1qC9CNXgzOkg8dwqMhymamjMhrO251Ci18_y2ubczHDZnP7j9AU6Ox0toxGohn2NTNd_Koe5k8nA.uJ6r1eoIW5ZFZcsuLjehYWLfVkIlQWEGfrsi2_74UL1OieM.yHpx5KcnD0RyYhDZDqRnr2fA.MGYlU8wHwEnhhEavTdDD9hCDoWVZ7fUI4X61r2GAcVK9.VXXIOl8ozFfcj5_hZUaxSsT0k25cQ25VSOyMFDkYo4ZRK457zEXDlT8HNg9CbASD5uAqTlq.Te9V2Yg8xvGo0AvDrwBL8Lb15wWJICI5djRticia1uQh8DfSyJ2pUFPQ0QzMmg0d4qutJUkHj9ubvaSgE9q2IjubA6z8yo.N7HPOAd6_WaNwAY1LhdU8piU66PGkD09B4N7byAsvRLrVKQlcs_Wu3Ps2Blg9IFjYKalEuurB1DnkxR9HyAJRp2tcbE1XQD0CHo3166j3umGvicUm9ltlchZKdUerGwUarZeyWMOfFW4dvBcbbNvcfax43yZDYYC0D_n9y7VU470N4xgriZrc2mXh.ZR79R33LKkWrVxXPbU2EOIsOwmVGdmMYJiJJ9e7Zt1X2n_PcqDZTonHUYgcZecr9OdR1T4bOZUYhtOYGgj8m1p.nzQXFC6igb_NWoFe4NRChruAo5oj2wHIb.TpEKgD2GFxWO0VnrgSP_zJdAthXNwB2LXrffRBA6OioinGtKf1jk8D8JPaQkjwGgv3wZDxcish2NUOoEwlQOEzSk8.zyTXUMN8.lQ4qhXYZdVmRzT8lZRauDVzhTE6obUaTZIN5rzgZOK2Wny1ZOo_SpBXMmRE2Xhz5WPrx0_CJoeFUAqJIvXA6V8Ms7bB8rBeLsD2VqktamKjLKp6q42C.Mv2Eb_CSJkjrC_YlMduduqMryzjyjgLVMIPICSlp5XNlspTjApfrUj38FxeriN_3MsHfZgWsghiqELCoH8W8OyNxhHy2mljvzzHOQcFGYLCUzCZ0nFzC9G.1TuIv7F4C1NnE2N7_nUfLupgb2FYBDJQV6RvURHzPNoXCWd5JbnV79dp8OVdgi9vr1Rgqww4Sco"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=92887b123ae84727';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, "\/10012440\/harvard?__cf_chl_rt_tk=FyI3FgbL.PnJg3hu8q5dGdo1PI1hc79CTupswr33obE-1743346870-1.0.1.1-JPrsZoojLf8eBd5iREt0eqs93eyH16RZKEleYoDeMHU" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>