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="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: '9134a91ceb1efd7f',cH: 'uXyHukkuoiFN1mrQwWyVJuwfG8ZC6xd3KBRIm8.k7dI-1739783597-1.2.1.1-B6ZLPHmmpvo5wMXAx11zQyWm4D1ZasRGekVI9Wy9ZMk4wQKRrNHxgzWAQS0g5mIG',cUPMDTk: "\/745\/harvard?__cf_chl_tk=.4ja0h5p18rcfDaVaul0Sw4W5yelaYBSzPz7A1cECeI-1739783597-1.0.1.1-ukJ8VWmaPoI3v.E2myAIY044BCRCpgKoopwOh6HU1O4",cFPWv: 'b',cITimeS: '1739783597',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/745\/harvard?__cf_chl_f_tk=.4ja0h5p18rcfDaVaul0Sw4W5yelaYBSzPz7A1cECeI-1739783597-1.0.1.1-ukJ8VWmaPoI3v.E2myAIY044BCRCpgKoopwOh6HU1O4",md: "_bGocjpNK9gwOKUGZ759Vj3G7bD19sdvRL3ykSDUznA-1739783597-1.2.1.1-v5HQ9BwrChvIAC8PqnEd13pqaPwkpsKZH6FTIVcVJVy5Frh7vndIj1X3B10pFNLdtpw0vP4WxQ_F2hamIO12FPI3AgytRrNHNy5a.s.qtwgtU.qgSGkNAwJ9MUJ_ym2tRa79VEdQ6JL3fG3t20dpFYfN2U0uKa7X94xN7.HoU5bv294vPTPh4yTXlEfsjkw2GP3VbKBorAI1qOA1LTMIrUjq2ap_nrCJ6c2_coShHFwsQj4SDbbhDY89tlaEl4X1Ai6_TJCHLXnjPh7U7ZlxbbwsKonNfmSJc.Zwy5WdWjcRmFuqdoP2qRIr36bvli3ADTQK4odGZJhlYhcVynoY8XO7ouOAaEPtgAjAElxb7eNmJRiZ0uIzPZlR9PzEEuimVZdMQIi9cj4lDc0.scm_x2JFbDNThbW0_WMery2sh3k_cTFmPRqrXO1.VmGV.9QDXhY4s76Q6.mKb3Zmmn6WIQ9Pzqu_56DUtWfENAklfDbltOgw4rMLLZbKDKSBYlLng_lEULbwFBI3BOBn4F3wIj898dswwhfyTj_seLyLnSuipYcQQ.5HHCh3n25ZNMN31zZqsxP1lc2k5Ujf82IfQCPFeQXisbxhGDooRadWI1y9F6YiKs.zpsG0vFNi90E3nCG41AvbSt6EkPpXoosMn.mqFAEkqx9T3i7OT7MgnjZ1fc5HifpskOoPQsxMlM_WyJN5.QcB7h76OucAKcYn8QLmT1nV2UyWm0jsZO0GElSgWhIk.e4kPRa7h.98mpEJ6cDdveLDW.G3YXjFE50U8Bmw3GX4Ip42ry5aS2OsdxQ02De9y_htHpEwMt7bQWC90a5RoognLm12P2TOAuP.CF..yah.njd9ZEHxne51CSQo4rNpYy9Sn4pBHKQR.rca.f0wSpXnmr2AO.gaH8z0UN5yjI2lzcvxeYV_Q.lMUIkjXzfhLHyQuCbGXHahp4xBufyQx7QNmeb2er9DMzGL2Vz8Ba8FKj5K6ST2i6NvPTJojIkNKD6.rrfB5f8tQdybCX4Xe4MkYQRa_dfUvR7IKA1HMd2xmV8888KAZs9p6gWGMSaZKJVmABQzxDxFsiEuIkg9wV1clYpzXEB97Gw6EMczuJCsMSKLHia3s80BV75uECP9gKPzTvA6HbRyMkD2LRcSzv_IY4TvqOWWuS27dnHWos07LroCWDvlKIgvOjTXx481ySnqsGehPKVa8E9ITkBg8g6ADoNbGdXJn5hD2ZwsynqWlIykTUdvV.vNbR4Na1iLAltfhBE7Sdu9vi1GmmtkAqJUlXgwFzb_bSdHA5FUhLusuc9U46hII0NMExU5qIJv_f1E7IdmbxN30wU7GhOv_a_me8T74BC6k.6P1y5EqleAbmRYyuqqHOGQUb551FVJ7B6NCpm3FZaz_sKgmaBHD.PiFOR5gPR5k0qclKbTzeo5oMrKxegkmkJzGDmLL1WmmszUw.8vxmXqqDAdpobL1sohXJhFPBYcPz2chnml.sTJxqL3jCgAS__zL50pisys9FZ8b9WGNXg45cS.TDvY_o_ilB3G5d5fDJFoo6ShpQoisKJVm0bQrWLDsHSLihkD6XdeBCVSXXA7qnDzAntnNQt2MWVOonyIRX4s6_x2hN7nbg9hNDRYGOoilxZGcXC.hnsbbeeNFgUmRgQNCKooisp4CsULHxA4cZvwOSFpuW8Vq3uHnoh6MmeaFSECEyg138g8LqdZrSKYek5mz8dnreR5iwpaVe_nZa2pNFEvgypsziUJ.xAynyQ4iJDszLvrXQ46YsVC8QtLQv.QEK4XElmnbFPWDXKIMqTguTmcDKAeVsHdoSHxBZu8Jv7RqsnxmTLTNHW.dCZvNkZOfBKi_CkL.WN1ipmrBZmLrZhOEJtDyny9c12nL3PbPtA",mdrd: "_OGgTnIpOBqH6Q6Ci0jlxReIWONHT9.I92TpFR82SDE-1739783597-1.2.1.1-C8UUH1EPM59KlJEEayBAGWehR0gKUA3Q1KGqmj7EjY.iwBpCoGABiaukmRBJEu5elYOVQA3Y.sgCqx.CLvym9iblIwVV1SgiQQjqAF8BiylR__3zOFmvUcqYLg2KaAYX._Ly3lDBLOqkj5rV4SV2PUiuRQ054rN9BKyP11gVBKHNE924puiX8ysqvQuIEwxnOafLw3RSU6srdv_PU57lvhhDrRIDKg2kUPtP_Jg8GZ6gbalq2WmV9vNRI69P3MBJwK6GPTLrK3Y.CS_.jTuHTe9VYm2baod5ryAYZF9DLlETjFJP0TWr3oGXxivxKjR.o47eum1g0bvWjBV142NlUaIXgWGsbeJO0NctbEofXay3sxFZA5PPnPigkekeTGXPsvtjDgQLt1oPbmsRGTqN651fuYpg3_lcd1Gh58.f0L2jyTrbYWjo9OUExDU02f5OabHmvCCaCAQvqhVy8m2bKnd_z5pjHkADfptOudNHbPW7MPb_g70ot1Tg9UdbMFqcBVOxGgscZVhf96fbdzG9.YVrqJUIztMt1ntpqJ9O353K4dGcTyfbg9OyC0kLVcyeod6n9d0qYyXBENOgsjknj2dFF6apyrYM_yycA6DJHnWewRNqQD_CjU2DYJVJPyfSyf8ag5WWIBmmhbCT2IVGnZ.kVne0nZiZ344ftdRIZ_gDj20ZRTpMbTnAZRZ9KKbGGhwnWvgbcnMmDz_jndjXQtNqJNa6iEt9pkpJPw5Ve_X8UVG7K.tBOLXetD2lLcxXtfl2vUwoe8az3xf1jWWKAwHnQn4WVtqcfSsyG9IhFJRhH0h_YhdMhLSdeesUASwJgaSuOF73X01kA4bsdzojZWJYiEIBF7nyVh9xtmH7UK4_Kvg8ZVm.M7qaF7TNonKYKzHeyETe8BUOAvrlpeLxjQsOX2PMCQrCzJLH6iw4dVnp_6yhQAURq.KYrKlzcQ3hrTZymkORqkJN92Ko1F7cfB2udwwRgU_0PBnVrTwzJaWgtShNTGUYEbPXjz2etUmHp9uMKfe1o8rk6W7sCPYKU1yNwp3RIOuPJsTRTGSzWAqCcuOv8_iFR3jXlei8dRf8mregjruJ.QHZbCoQBKHyH62P_SeaChR.r1qumGkD8Sn.9GZPqPVg38LRSsM.vKwEWc0.BeXQaIFWmJZ7fD9O6dBRFNCwUcgVEH7Hdt7gxOeBUfqcIO.DpXoyv8dymFVhVXXCd9sBDD.H.GuDqLEG8_cYbooBfouMq1IX0dnV5BHFkCw4CIp3KM2romOzWfqATkBznIj0o4iQJSdZRo8Eud1IdxDB3q1dwRSWZWLnC3P2h_n5MeITRrdkyboxaWa.ruARbtMR6W7LJvxFQ45oMz9NGn6fVJJpgBiTmEmy695qo7mQEjkUl106BeGafDYSm7q.Jm4khYVlUhEQSofdE9u6Sjcxwkhz0HByeLTpAPjabo50f9RkEncIhXUyY24ohpjZArz1TEcLBj7t.rTsbu6F1_.4gI8Fil.6F_kvw5wukrNG.YH6sWQW5N4U8o5.adW0cwYK1KLPi8SYIP58JztiA5FiaVT5fSym2_fcnfkwZSK38923RihMc0TEXU0_r1OQBnKD9YzizGEiyqMI1BFHgVYlY3.OQPLOOOkF7EqnFbYSEqlSFUeeB6c.02bw29i4_N1Ly9uKpgQyhIuaznjOTIJY.jChAs50C0avkq2GfORtynpbCvaLHkutu7MZ3FOy9lsvcKLLNkiV_gfIxYnfBi.F1XDnCW8XYaxQ2eRfoav.h3IUGCkWV44bftKBjy0zPyyTA.DmbWTHiwoe09.gI6KNVWyAQOQhMFa80k_bUUvapsNL6U1UeAlQ9CNaExWClAFL5_0ZGFJ1ZRSjNuPLvVevgW0nIfhIdhvVfKrRc6yYykgYjnXQkSMCOSCNWbn37_wTJxM0.N9pRG82CV8JoQGhgbw68SRinMjBfOZwfhdnBYPa5JkqUmzUbaw4"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=9134a91ceb1efd7f';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, "\/745\/harvard?__cf_chl_rt_tk=.4ja0h5p18rcfDaVaul0Sw4W5yelaYBSzPz7A1cECeI-1739783597-1.0.1.1-ukJ8VWmaPoI3v.E2myAIY044BCRCpgKoopwOh6HU1O4" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>