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="120"></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: 'non-interactive',cRay: '91799baf2f568992',cH: 'ZMtThqAvjUtwrxoMIv8Kh_13DkeH_ALH28mtdf2_4.k-1740506564-1.2.1.1-1vuHa08rf2N.fMMwVj39NHTU6tFI3X025egirQWeqTmBBgwiAkDFmAlwIJ_Mo9Vq',cUPMDTk: "\/6639\/harvard?__cf_chl_tk=rleYYx.njmGXcDik5zb05oRH5lvT9QWWedbOKhp5sg0-1740506564-1.0.1.1-T7s40NVMF1U3mexEPkJGC2hwE.7kYxkgPlAhEngnqOg",cFPWv: 'b',cITimeS: '1740506564',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/6639\/harvard?__cf_chl_f_tk=rleYYx.njmGXcDik5zb05oRH5lvT9QWWedbOKhp5sg0-1740506564-1.0.1.1-T7s40NVMF1U3mexEPkJGC2hwE.7kYxkgPlAhEngnqOg",md: "S5B..MlSQFOst7MYQm8qLOxceo9ufHWjVaFP6JHlrxQ-1740506564-1.2.1.1-JsAGZf5SRKDm3WndI7nw2xM5hT3F9Ls8sFjwtG5sdbbE34r4dwcB4TCEEbEMelfaJ0CcvlwOUngYeBxz0bdM0j_jN_9qYyLS0dr8PElvVQc1RqhVwGgbV_r0c3wEPKqGa5m9BlErkbKMkxhRRjPCSqWk2hcIVQ.9L_tZe2OH7j5tNG.WJoRyNDYXt1WwIzReGRo_jhYel7mnk1ebGfGSX0tcFTzOW0PHxL0bYTJ1CzqWIudSx85EjncxzuXsoqDBpXHXqi_k_S5HIZANTFeuvursGOpuQb_XvRjEigojS3Y1185IjUh7dm04ymYP2XcSl7lEaQJODKKorpcrv2xt5EQT_6U2gCLjSLwRYqbyKE6UJub0oW0BwRwBdCVLpy2_blQNO0VMcdiryEUqnrio6p8N75_PSdHIrYhBxUXAbOCbZi81CzTS2eU1PrO8VkZJDIb8GGEuOG4KJNRYp9.xoikE4NGYc1afLOBjcp0ZKLYKRMp9MsFUD0DRfNo9skRbKxjqhLKZ573KYHxi1KWZ0XIOB4B.EvnisbkbZReThZM.anCtsHPONs9aWXroyNn73mZ9ugzE5O1mmTabRron5cm.d0IzGtjwEPXEtsTEDxJWGnE7RQgTz3jcIQZ6khttSlNBLr2m30cdINuSfBLSEvTaPbEY667s8KeEipIVQc8sLfkM27j9sC5q_00oYQmH7OI687Vn5o.M9iVpqpdO_j5VFx292ylO_c.8qEMoRLjuqwXurEDZyRNklkchwhjzLlbSB6UTaBKW_xcwz4SUkB.URg2GSWGIUEt43CSLlgyq3xSHNZt1jYXqkZVf_4JqipUDKwtszkcRGvF1LQ8R8U1u1Arbe3WCwUQeiCtVfi6_PcppZLoltCwikGSkHf.6DeRzj5VyOKVdnr98x79hVdqqKu2u.KfsQndliMZxLRdlVdZPZbkq0K6qwC3pOp9Xc9kodO8Mh7FmUJR7cgzS7OJbtRvTtTfHVGasYSpy4KjBhMBA2eIEoAaRQqrl_zbCLz5ng5hKZ_NxayHOKSR4Fzgte2uOq4sxXk_8srQFJWf9_DbYoB4DaBiixuqMW1KP8gbF8AhGkLJgNLGtKLjHS7yHl_tNa.EW2DvpQsE_4PP9BYIEIGnDxhhlvIad6LuLRz5G8VJEtLrzN6Oc2bsS0LZkso0a7wlmBl_n3hlVAZmrw1MTnqLknLlf31tWEnsQAUqqh7dA3E.GNB1ua2f75gmAu94us2AL2ELdvkkEXnBsgMNMfqnvkyXYq4MVeQ2asiR3F737dcM4eZiEwq07.YkJydvvEfTtpxmR.FSmK75mD4MlpjAGn_uePG0dtQFM_4gAnuyFVy8fnI_47kCSDJ5w8tpY8J24D0KU8BzV17ApjQMv_Y4MSjfzYISOI2PX4q6bWnLeJ17XEWJTiQeFKIWq_1nVcgAwHUOm63ASNGgerM6Kxm4iEXh4hCNBKNPL6lmNcC1dcFiJLeYQxnaGtHAT2WoiJ9jnDWYPRpbg5Nad2CD7TKgi7TW7_wI02I4zglXrADgnbwlOI_kbqP8rG5iXUAfqsJiewCszgyuvO3jGTMWgOlUVV.ubgPUCxkSciDQhF8Fr67lpuvirYF8AmQpP4zYROFT3u.6GucewDYJDgno6X6ME5o1TaZZvloC.iEUTrxmt0fsrIowFqsXbSVw3d6k7S7uU68pAKdPxgYEIwVYFFSqmQRD6si1MBn7.OtUvIzECLp88mbqDjcS_Ur2Nn8oJMQZnNQc..bVfvHfbCbg2QO0Krc4P4AYOKHsToeDq.qF5jMuJSR3TCg_9mLlND8XJeij.AXlC1Bi3NqfyCi2oWXPzJI4ZsRllkBgfVbhTtpBD4AJg36IaOLMKRJlDKEAzvB1JeGdzlnMiMi0",mdrd: "YkD0B6GUQXxUqMLf4p1PDmHSf.AppFeZG56mgoe.GpY-1740506564-1.2.1.1-6CmfHz7g69D2Hy9onVFvIzRGg1v0yWKQo6pWqV3Dhb6S.lfn0P7moIrGgoEs_iC80Ix2aukJ8OZAHmYoqGQxsZQmSwnXj4d39iaLv1EthJXjbvmNsMjpxNE.NbyI2ebuLx0zSQ9a6HJMU_SNiT44q8p3TLTBPSvR_yCUQ6RHM8AErP5jFevaBhioXCXrqFIIhkmYfJulIiyviVo1BAbkWcALi9NFdgwxN9AljNrM59i8EXjrV03Avcw41U3fLwquTsNV8vvViHB0xvKnzYuQs1SIefHzyo.CWXhwEmu6VZzxh.npSRVvOsIsKGb1v.D.W_3RsPGlUk9MAIANGzDTA5zKzYfXsCwV3_d_vWaW3OgMYj0q1.a8kJJiB3Q8dXYSoGnXoDKLabnd.z9BOccCNv0CxRsf_JgoH8ji6k8ZpegC5Rtg3svV73jGl7t6RthkTIRzE7Pqekd6SKqxYJ3fceBFH2m3RU0y7ligbkykXhtQLPnDWPxDixWVt9T2CjWQQbKKdDrzvoAE88kWeUi0TRqDX93v2o5cHJGNc4utyg1cgxP9bLAgNknS30Ie4MaKcsNi3GOLR6Jc63qHtEJ8fRfJVUHXvqcclQh4cWrfexNnnxATdJj50xoG4.w7GqS2kWAzE5PTddmZ7zaWLAp8SX_6Dp_cjCorcCnOQvkiBd98rKLZ2nPEnud1ngCQQEWQ7RjVFbukdpbTDbcfwi8OZ2hQDhrQTNHPGFQCaJUGRrR8M1E9gocLzlr.Ttl85sP71La2aHumM92eDjuoxGNCIUw5unZNzAmCXhBWqgLsuUNHov3QVtm8WN4JY4KI.YEDg3sukkpqIeDYW6lss43rqbWoP6B.NBYFyiTmvDZfzEL.ocmCIz7xeQ5xrN77EWyCkpomyKCvbF3qirU6eUPzRziNLPgjisQO6o_kGtK0IPb3KtN6SKnAUmxDegLzB_XVBb49f_KIhYy99lpc1hMnlwF3.XAZHPWT3ajMatC.CG18BWYGScBsVU1FQuy.7G3asIhJ8_Oh23PLH6F3j_3gq6QsUCQCphJ6FKuejXbNRTc61NrI1oT933RX4ucVoHYDS4vTa09Yk7_accedrBQjjjoxy2mq.CJQMkF8KbjJDnD5e89qHobPgf1.UYoZwzpYJtGN5ASh2sDMnsdE57POmeZA9QwvTz03p1msa1vhR49M.kx.IXL..14SgNB63oOgQSU020vrsQAn5ko7EXc6mldfX.iyEv3wft3CtQJUs2hokmMJ.5K06pfedREkfgyKOFLhzYCDpQ2aismgIM1Ore7J5opk8e_8ef92bPahuZkJRX7ZJuJWRX9.O0OrywSyBzyovX8n8fs.y_E4drUwfZp1jNCUHlJDVFVX6cPJooCG.0Cd2aUjOkkW5SrKopqk_Yvv0W5S3mkAJJUKN2jh9cwtn9EdX9wcJyK4TBsDzTY5uQCrs7hrIOzwa73YqfnObGUVceDcE2uaMSj8PACCSiBqLbVSqXMGrSnFQjOHrp8DS8EhonlzOXghGpRvm3t5XZFBYsgE3yGMUmHCllKm53m3uiWV9ZcWysfdGVpEMWlgTqNmdnhtlFJFPI2LPFypL94SH_QPi9Y4TpD10VUG_.bbaaqawLZFTqHQBI0_lK.LVYDLkyiGQOlQIeczTDVMcQZFKi3ZaTcqJt3f4a9zaQIJ1xwtnR.SvvWbqgfhgYP4Q5ZKAu2uWYLyDqSjHMJJcKrTDYGHUEVr3ZXtPhl.W5Kbdu5LXLco6A97ULw.BnyXrIoxDVoDz5k4XX3y14q2joKRduhoB3uMUqWlkqLJeaV.shzgsjdCohQdg26fpyb8o_F_lJmaFbuOTr8vImK.ln7JKYrLnkfAhfpnFeFBQrl0xo0iZ4qEZ.Av2mEJ_pPnbv7ZEiooDQcnGHZEVEcgbVz7InRRhXoNrtF8D.87jPuES4MpY_KrjWu.WsOQpn4m4R1qFTGJqrlh2fgZQsb5"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=91799baf2f568992';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, "\/6639\/harvard?__cf_chl_rt_tk=rleYYx.njmGXcDik5zb05oRH5lvT9QWWedbOKhp5sg0-1740506564-1.0.1.1-T7s40NVMF1U3mexEPkJGC2hwE.7kYxkgPlAhEngnqOg" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>