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: "publications.waset.org",cType: 'managed',cRay: '91a350f34b843f9b',cH: 'l8AnaW7PAaW22S8jg9LC7leFFftg8ndSD9G38wk_d.w-1740943905-1.2.1.1-BqlaWCjIjbFIX02H2Tv_4uoQiuNg0QegO8r0Fjhl4bHtt8ozlIh.LVOlONiJk6vf',cUPMDTk: "\/4533\/harvard?__cf_chl_tk=FzA5_8bIMc96YQKCVJnm.LD3XRrFM1sb3bF8dGD25sU-1740943905-1.0.1.1-eHIjeFo8oe9.iTd9CaC3U9ZgP2RRcEkzfOJn_20ovyc",cFPWv: 'b',cITimeS: '1740943905',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/4533\/harvard?__cf_chl_f_tk=FzA5_8bIMc96YQKCVJnm.LD3XRrFM1sb3bF8dGD25sU-1740943905-1.0.1.1-eHIjeFo8oe9.iTd9CaC3U9ZgP2RRcEkzfOJn_20ovyc",md: "t5QNY9JWHydgjx0.aM4aT_bczz22DnEq6DH4TmrStHQ-1740943905-1.2.1.1-GE_qIY3m5OR_FV4RdbLf7U9dNq.4r1KCxp9Z_KYGVuKlC5aTtSWrR.wTKq.vZKOLqLHmNvzLVigGAQDVel0Vn00m.XqXL_JbzT3.WrsZZIOSIduKneVLWtQjEq0wMDDw7oU849XdDD.lARLaALSvBvIn1feVlp0TzzQ8ADdAPP9Aif.s9svBE5QJubNizTCyhgOhvoy3vX3tVIqOzuciqNKQVPWKKkad6_8i.LxnybleO14y_u6_CGji378tUscMmJQT7HOqoGHcEcUHNJCR._eTnKHGH.fN56Y1.ue2jWIwjanA35xT6ouZH8IH3WP8DyyDS2v3SVPaOJIDz.oD0WjLJJVQxZXHEqixYoecj795EhTajuSKcsIvPC4..Q87X0MvLODHDe2mvQVAvQcaQJsrrUE44pkAT2NMiyR6LSmJigkxT1X0mK.L1H7ZhS95dA9sN70Q.t3R20e0CcFSYHaA8BjQ9w6vdpqTe2EtNK_oJzULcK_Y6vtU.ETa5QlDskfGJxjv5nFY06ya4fxBvrEGeAC.dTYdN97u.ZeLQK4M9xslYUJdvIsBc9IdKLy6ZHJSsJevvbH3f29xwggxuD.aGUHAHC.vFxq7fEUHtHh3c0vAr7o8jG0hIW2YoeUSOi6ZqMa9sfTViEfteQ.XRzuJ1WU_VMw0fhNmXtYxnyGDD8RElrlzFRrqsszmrxVOVxPOKp1Ll5WvrFBDlQAp2dWjdu6MvPOhSugE.gUGlJZ38x6tkEWKt.WGkgRmtkWMObjsw0oxoLCGWBq1pNDB9csdx85z9XCkvzYy6gjRNjvhmhyzGCpt5Hy7AlfZWJF4Kiws2sR20H9YP3qpUhd4rfL5YigM1KR8ZQo_Z5suoOjWtz99dxGzgOUCmIDH.ifG1gsf5oKrTE9ZpY93EKUVF8iO5GRtfjUgk9HLa0If7aBHW67vGgnW2C18yr7ldKpLT0uNRSgjgBsaBIvPTFrkyxeTG7LJ5Ne2ZeyjMdhZ9f7sD6gDl5hABn.iClFcMckTQ3A53rvVsqOYL93cCt8HVfWmF9TZCdZhQLfO4JD.OHyU0imzdkPTwuIzQX2nsmBrUYBpIerGn2406KrEQ8CjbQ.oZ.5jLlrMSNtAZ12C56.uzYR.RCXL5AnPtDHlH4zKWEmnmTZp3vcevdwn5ApaC2EVkUSznPm3ooicoGsTcVSw6g89m41iTGiebhDSpKfE183Dv5MgKLCNOZ0qv3AxvQ",mdrd: "4aGsIioOBnCyyTnx59NfNsQLK_w0OEli2DVJKxNKNaM-1740943905-1.2.1.1-QkQNjXd_YuEl0Cfk5rbd5XirkzFtGtoe6IU.SJVB6ygCG2qOg0Mvt_ZHiUMVSGTZu8suzq0hBdluw6wxJtvNZsV.xJ9lUrTzpfxOpTDTJ0ohEuQ3GRZhTyrJ8vUSN9s0EZCHRWh.VPh92XtGw1TLi01VrpGtyfQzb_QhbJn1C02GISQEnu8GYFHfVKr6X6eFeqUm1xs8OLrR1YleGPoPHTdxoHIQQdGLLkgHIaGc.3NBs1LEH4kVQJ.IUn8KfV3OsvpY_yf0hbv_9w8DgpNEVzj4R7C_qHDzu9Ol6KEvNocWQR42YFo3MqEcaP5KLKxUgbQT1uj.3Or24ZPUi2kw2sjy4bZ8lPhDWftk.10_uO6U5vLMMsaVomb225awSXZ_HCAhDbgRnaqt8zSc4MEqLWqAty3K1BDzTcRUaiuGZt.AeYgx8L.xwyvpZE4PrAmM28KxvAJ.2xvKrGUESUpJvmtpAb8CwxEVRB2mZbwc_EBdQ5ek1HDWRO_xDnka9CVIz3ILdEqQOqXSYkLYm3iM1IZYz7Zo8z_NxY1q.p4li_w5MVYmGbJ5mYjI8fkUM3eqUAbW6aowSK6t8Ysyzbaatw2uoGDpWUdxo1lFQzvX5Aqj.ADHekJ9tAbfdfN0GQEasrXQ4WM.CKmWubhoEJz9hcg4JpVvEF_brnNCZ9HiZksKsFn1p8L4DnNFaL4DtJot5yGqjmw2zjg1BWE7s0qtnnlNCP0Ymzz30Je5JEuvhrFNQWXTtpvJmAzlXrZXrzrAS_4JZHD1bzj5le.ZPF2uyomP5NbG7fcvy_ZRvmkhaSK7FoB3q7OE2n2FXZQkgc_OVKb1at7OK8Sx226kA0bJReVO4yhsTIyHBHb62Y6g1Vsnc_qRLvFM60wMEtd.Y6IzcCT64C0DsDs8WR6Mb8ESysGT9Ea7D5.8CYLKe.b45t2gXHKmn7uGpxH7dQAG.O586NDT_5VugWPabinn.W9YPN.H.Ce1mnzGGRf22AbDhlCrbXWbwPt3No_F8jblNPNKIfG6PODo0lu.FQvaYq1JHBVmSu3YEGMZqP.aMd2cmFiAd2_JGQ0RH_qmf54NGRPiDLSX7niqpbhHuiocvHweIMhjHaKKyW61dAspNDACpZyyco8WuphgDruyfGv7bu31nBHChVim60EnXX4UkukNsvSs83pP3LcfmxPFrlgMS2BBrbGRsxm_yrD8GVkxoc0WIaTpC9i.V9y1wewjXPqcjExI1sStfAcL5wlAX2HYkdHTh1HEYbrg9v.rnl21zAg_wBhSEWom3vzjBbIotDFfuxEkSVAbWnxhUwdZqKfD99.oVeDlH3L82TMU3Linwjd2h5Mza0_sJYRGNLRomKGPXniffpPrWXJjeBM7ysoM6wwxffwhgB4y_sdR5yPUCFWXgYvsTWM0x3I9cGI4HmtYacqwq16CO6.DwvInnyaILRbRI8.PeWv1f39lfzWDEJow4YFM0Nwmb3zi8ugiQsQpX7OaDCKwew3iPOyplt7gMF0GUAxCgwYpbzJOKxnSffCfkYdglDRKM8cxMYx9qIOD8BN8bFEqJaB4zqEbEcjfZDG27Q1.J7Ahz3UmMjFuilhTfyV7rGm2miv2AobMDYXu44k9deuvuyB6cFMwzgLBqK_MZlY24FPAGaEfhz6_EpLgT9QievMld8oYUVdfHnAmfUOzDZhPKFK0DxuUZbyDvpYSP6OJxQm5pfs7bhDE6f60qBpwM737zgquAJssB7ctDmEPXPxTl8fWhxdeI6.T5IVUyF436WE9Qlep0ibhDA.09BUIc7VH94zG8PTNhCjeS7_s1vdy9mlkSgbgENeHlUvv84whXtd2aaQLoXg1qeutCjl6q9DuMLojvDkl4qaJd0jXuUK3rRhPOOzcHpxQW.Wit9XnLS7w7ky_OiA3O1zPgOQvMJkr8SJn_QZMw5eRgpM35balwORtydln4UdxLNw"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=91a350f34b843f9b';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, "\/4533\/harvard?__cf_chl_rt_tk=FzA5_8bIMc96YQKCVJnm.LD3XRrFM1sb3bF8dGD25sU-1740943905-1.0.1.1-eHIjeFo8oe9.iTd9CaC3U9ZgP2RRcEkzfOJn_20ovyc" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>