CINXE.COM

Just a moment...

<!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: '9136e6ab3ac9fd3a',cH: 'VGYOHehyvbWmwvB6Sysx56qZpXeiozBJFUm3NzbD9gs-1739807090-1.2.1.1-Ux_cQyYk9VtRpB8at0sx_tP63cTkezQ5COP0IGq6dEbUDg8QITNrSJMGGWO3Y9bb',cUPMDTk: "\/13715\/harvard?__cf_chl_tk=E5TJkKlsl6QFxNVk90ZY_F2zjyGrHH40qZtwTQ74yF8-1739807090-1.0.1.1-vSYOEEaIsOyISTRwvoQm3cZpbjZ1hmbGHkkFI9w2TTo",cFPWv: 'g',cITimeS: '1739807090',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/13715\/harvard?__cf_chl_f_tk=E5TJkKlsl6QFxNVk90ZY_F2zjyGrHH40qZtwTQ74yF8-1739807090-1.0.1.1-vSYOEEaIsOyISTRwvoQm3cZpbjZ1hmbGHkkFI9w2TTo",md: "IZg7HllVJ83ZFLel1s5RJazUD8KcrI09GSjt.5_2YVk-1739807090-1.2.1.1-zHCbXcn7425iagtc.9AB2.eLVZ72U55tW8GTJ7jJEhZswmYAY1cLUd6T7Et6tQYKIK6Vmzn631NDWSRZsAxs_oQOK0VidyxXb06qrv9Gb2LSI0if5vJoC9w5XL7qYv2DfmE1ccDiNBVtTMR5Rv2aOxb2b.NZa4HZ9uKEFD6rZErikiRF4EeeFWO5b74Ph9m1C7YnRNZaJDCrcx7RredESLLQ_awJ0MzBmdLCHloiuWXc97nuSvl1KmumscpO7NB_bn8G.zYoPlNTL.IR4N75ctJyHvMEQSA0yRtAN.tcmiFdIaCzKkPc4vRa8QM.3OFlyiK5F_itwrtDriDuywvz0P6lslBtPmlY9Gz9nRPznYVJX1PzmEpQYDAvRkSnMfMRcIGvmAwNZ.v3YbEUo.8S63js3URJGbiI7NLIMpwYQVwPrRoefX86CROwPPEEHAcvetleS7OkQg4ZruRJ6XLc5AOS9xNvqcA.xV80R0lmy3pA3bksPdx1zenchjwbX01sH26LXjxH8Sz5_7th1O6nQAeW9oQwqXqHRnhhp4jxSOeD8FN_CE1jMDHpIdTBBqK_kgoyN.OnT0hNfuADCHoT_M6X2hfDojBkAOhhbNZpgn9ZNxQADFyPJi4saDw9wl_ymPl2hkqlv.7BoCtdnjq5_LBbwZr5tnJ_1G94SgKlYKhrXNhEHqYKrpHFFNWLGIkhuTr4IYP8QNQ7S83VQaV1AhHeol2FqmZBIHgg5pVqELLK_qtcO5u5C72uHZ.yjMJhq_nKtj2hOaZGQiTIawUeqbWkhC5RUV1ZAh1krcMj4MokBV7XLQfc4YkTQ4u476eYdbC.qVNMkNivnNqzQIES9qRK_RxVrvcQjvNDBXB8aS2IgWkc5C66uCDyF2huwnH2_Pg_nMM2VJgF_23yL2NSOlvXSSAmeqh0fVDOgc2w1bYWqicz7Ab_8d2TOx8rDi7lr7rSXYLWzzwbNHDxhIQWdVRNAkXQJScqj6A7E1gik7Sixw43xvtEiFZlA1HbpDOGLD__F9unFnsMaqYY6p8j1gFgiioAt_knMLv.U7GnXWGGx.XXsC5iIIedISI2FLaPvNL1bATp8KnEnol2XPTRyu7Muy7BcZDl3FznL2b0su4JIGtpmYa0DvvswI1jq1RmEyJkNg9Ad8wU.emhMxd8E6G2dTTqyWulP.DK7Ypl3ZaUk3Uc_QW.ULbTwUU.pnEIj4x7MK2JCASiTFFSHr2l2XbzOlKAd8ExI0hVUTl5Ekt3ZQxnI4UJqKKl5cgeBviOzWk0Y12XIVcDqa6FWCBg5XW52Gm7_gsliMZdgLGTwDSF4_PwOsIib5E7QU.Dqfq1_ecIB0DeE927enOgdhnqRMxsS6zvBiJ1BWCFgeYFQMc4LaaFxhv0qM3tDwPsi8Uxvsph9HOpdRtc3sBt19Rac5V0cliCN0Cv_kEP7ntZrsOQ7e5Z04pvZ8aFL0ecNb9zJGuyFQw5ytHdYFgErUGlBJNVDuqVJsVfU5ESJ5he.b1C6TrfeiwDqQ8xjcfwByLGSxpCoAycr04qgUNQEqY1VE4siRSGbUCRpwOXY_uRCPS0RR4YAY.pyiLWurstwo3iWeAPlVXN_VtqzZmJrJ3bE45PbQ5yfDa8Sn9BFEHVo9CpoY.QQjbsvfCaF857Ljd7KxrU2ojZaENcBdT92AmsCdu0oGd3Djt3YeVZPcoLuP5C6oujykdJ2Zv39m9HUvZd2ZkREIJLIH2e1ZGSyxhpS3pxfh6gz41hVtxm5Uin42n3Hl.MwS3JStj_pHvt8SiVMwGAdPwUZyx90IcAB7PZsdaavhGqegSihWAHuOg_2FRF6kBF8Hl6d1WMvPo36s6jNmAuGLiYgh081vkz2zyEQ1Aio_vyquehopGhbicaR3U",mdrd: "iPFDsSpUCWi2_sDVzxP3WJcZ3QynhdmfL5VvZX7Rzg4-1739807090-1.2.1.1-Ake7ooWY2jDenYVjlotiQG2bTCPqeOP3XljHSB47lqdd2qoN7_Mx_vsyGFry6r5bZzCa.gGBugmlb5uH9UmdxytOAVhrdyyiHRGAezwHeNHcxFfkdpdM_QuoRu.uiqjDbZdAH7FTYfkC9tn7tqKrEg3UCKBz6nlzYOoCCw1Pp0jpm0O0A5o0h.hhwY8.swbffOPsnVg8Ng8czuvesSom3BiNvwR9KlWyiBMVj22RheuRMKudX0dp0CM1PQw87DDZLgNz3mYURkn40aad5ECOBSr9uyqbEp3kT1ZGkgzsN505gs7dhr5FtcfLhT8kfLPCGZG3buFYnqjli3.OLVa8VAG.Z7fTc3Jt0y1pOn9IQelwY8OFJBgDtqDRV8Z.9_uA2pn4.FDUWBE8aqsLvMRbkprcnX8Q8lQEY00LK3hZJ46WSbxMbc55LrnMYswFswHOASajMxTAJxY_xrz4Jz8.pfACZexsf7nKiEWaRa4Lj9dmPYZl8V8so_ZrGs9Eh_UtBszCT3SbMZ8Ucw6FdbpRvTVM9FkNGD8fJJhRxLVMSt1WEqOfuaSiWwLARBpO_R93frYbrS8Iwg93Z.tm4aa5LRT7Ab0usAQ5vF4VE7DAMfPyAd2RG9iMDotMF8vc8Lky4p4vq6g_SJORIn0XwAcDdhFi9o3wbhUZspIvYJe.ceOOP6RMhdVFtVxtujOzOnTghwzR.1648R2_O_ObWDy.U.HXNWeFqCUDQ_Z7NxSKfGDHMyCrR3KBmrZrSJtAlUBC02729IYSYQRJUYJRTP5u0Sm48hu2YXv3wx.B8IrTsExYdmqLcoHoidh5DxliiNYnac1oi.QEM7tFdjPOm2QOX1CHi7nSzX1WD1xwIJVQQhxphFXUMtPxEtnuv0FMif7JjnMfjYDK0g22g78jsv1kV17Vss.23LAPzUseISd4zRCTSK_QWf1YXbv45OqwW.VSTAoZTnEeTbACR0gfw8j1M7sh_xiIOnEXDveJkfU0oPrLZBWZpqQVDWYtDIrXhvT8mzNoNh5vhQMoSKUSJ0jjR3WMml16czS6YwCdprW0i38uQ8VFIbcx3DDmNBQKx8gU707yyXj01Hf38dcFA4s6dVSYF1JWQqdGWBLye1ZoOEU4RwipJNkn7tutK0EOcx_e5dyOmdNkKMXBMKbHSt8aWOQsaXlu3cPYAVju2VuXQasatRGnFvF194RD5nvVtmxQGG7BoOnMhlO4vMFdWYKEL._3j1Ct2Ve2fIqWlWGHao82VQfwlV_IaD5USIJALuDskNN4r.3RX.0UN7D8WQR9Ka_dku3BW1Gtt4zENjpFKEItwQDV6LILjNeEkbLm5LfutNdK8_RtkytGU0qtJ9cuJVTanHzMMe5SFf4bMj6yEQ39oaDmzBSIDdMQOSkdW2bwMNq2HOQSi_znGNY0hLWXLJQldSIlY5qOIho8vX_hsiFMUAey78hsXZnSqFnLx6R6IpjOr4A7Mroey53_vdIs0jVhsbcTkKb00baNdckfrr355haBZGDWMj.yPNwvIyr58KdsRWUquGuEpOJiMsWipZkzKC7IuheL_fWGx7pqvKAfoBVAU8rwEgZGVB9JvdjxMxi5BIWhLKFKBsP9ammFrAACY_hhXlX6x7h6iZJJ5mQ_0huAIW2avEVBB3nhdSEjZtzawOocXyj2WZWisZOIqNrNwM5hbpLA5eZ66gjFFNCbnC7qEhhaOS5BRPwRKnQUFyEpJ7PfXeh7C2yusteVTehGJsVFiXT7jIia4P18dAZZz8vrDWyuGtSSkqFV3R8hGQb4NtOWzB_Wg7fp59LKZgj9Sd3qthqYbdO_mc0jLNoFg8blB0Hk_eUG67RDq5oDIWnT3FHyEQPMdDS6x_x_ut.CaXnVeZRmprl9VV496kHVuW6jKCxacbppVeIGeEvvRc27J1eX9536gniDSbrKdxbX_.SbCf6PUbwPg7uOGEsyLSZm9IocdKCtADfzN92u"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9136e6ab3ac9fd3a';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, "\/13715\/harvard?__cf_chl_rt_tk=E5TJkKlsl6QFxNVk90ZY_F2zjyGrHH40qZtwTQ74yF8-1739807090-1.0.1.1-vSYOEEaIsOyISTRwvoQm3cZpbjZ1hmbGHkkFI9w2TTo" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>