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: '91510c567f28fd63',cH: 'pZ8NR7zAeFcMCgjREAF4.X2aVTl47nI75505P7PgnbU-1740081263-1.2.1.1-Dq1upGv8BYs_YXgQ8vJKjvDVqxs7wt5gTrXXZeJRLXAWOmJVCxlnh8A9vIR09oME',cUPMDTk: "\/10013524\/harvard?__cf_chl_tk=r4MBPjCGnLu1y.lkGqm8M4ShPrwmJ_lPgSPE49b_Qd0-1740081263-1.0.1.1-mjoac81ggLPBpW6ASPxtWMdAUTLPqrHivO4lSfzT98c",cFPWv: 'b',cITimeS: '1740081263',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "unsupported-browser",fa: "\/10013524\/harvard?__cf_chl_f_tk=r4MBPjCGnLu1y.lkGqm8M4ShPrwmJ_lPgSPE49b_Qd0-1740081263-1.0.1.1-mjoac81ggLPBpW6ASPxtWMdAUTLPqrHivO4lSfzT98c",md: "BOfc9MbufeUPrHota7W0K2yNyHj2zlCZjo2E0s2odsw-1740081263-1.2.1.1-YJ20ZDBmwhbLreATkLZn6O1Att.Ps2CkGf6wYBEiFv2vlhUpBGaHn8wzQVK0r.IZH4oqMt_MTQhdsFChXTFdJip4UywIYEXpkJ7aEtAzUY6p.qxYl_WU7zcioGYEBGoW9yA_zRbG9DIGaQGClrpyObN6sWMohgnVZ3LWyqzS1okVOVFMGJoDLYPsfKNGuiuceeIF8YT04Lf99xfyjwbpUvDlMSIQahg1M5cR7wBTtWgz4rle1MmMy5wv1_nB6oOnbyGWJfmtDhaX1ZZHK5d1qc3iCQ0JKV4cK.IX6L1XKrO_wF_UbPotn.6QYdZX7Odh6QfVaas3Ggi7RxCJvygQ.FDKhFr17sHGS8DZDltAtSZkDADXZChul0X4gAcOBdiB_SXXPzWWLoV21.cKWsK72DoKGbm317NFXAywrtOzgnJ6tTw_g6d0Hll3r.n0ygDUrn4wwSaL3srkPIyL9yWsoNHM2j9qEfFMSgzWWqhSLvkqT.tY9eVimAWhQDYSFmiJmqrhcQ3wTjOWEr1g_Zn5WLPL57cRggLE7NXAiL6zWRhhf_y4CMMproxXn8xTefEzxRw.nosUivtQZvDx9.QcX9GTwpeAROpobPE03QgFG4XokhAMfEb2JfoCK4ao84Lv4HG63RZLYcP66kvrpmorZo5oZ7aub5pEiyD8yoZIx7CkUwXp6dxDDaORICWxWB7N3YDvzSQ6xtOl0NqpThsUATtGTwYWSWUwsE5ykWGf7Mvy6IQ8iFFCYb.0HO.jVgBvk3LPld56fZDElEhK0m6HKyc2mkRSsBbwDY.fMRWGpg.HDutgl9sTiJ4vIKYMALcV9LsLgGU0WLyVHpaxcYOXWOMRQh2wSAtuqlGkLVHONyjmR3daTZcg2vUi73J.qJK6vUf1twBs1VsRJM5ShFn6CxxehR6aBNZ875bZOJGoZQmBjHqZbFu2u8d2f9vD206bXTxiELrLdpxLWWl.WBWZnF.9zKQGXcbJsxWz7fDV_wsgjjzRcPgklX6gKJBGNdY3Ru9JzP11JH3syiYwbSWJXW6E7GODjNe78Uq1XQ7e.LDz9cyrWmThpjyNNqhlzr28pGzBtcX53ttNngE5YwanNakMwgRj_Sl.YUfCJT9qKDYPVc8.FKBYmMPZh3YtrJdL8fLgRyDRfezQc9CofHt5NMpll5kSRsUmNH5mYltl_64_bspfTSehax5v4Ki3dMM2jQBdOMyRi_su2LyhS0GvpB_CK.fQ80kurNSXAphlihqXZYM2C9sHsd.7.L0aLjEc5VyoVT51pKogcKjO4n4LfLaD0121kQPuoRfiLgVxRoi3Hx1Gx9Hbc_tMaaQsr3kihVpe7Jq.1H8MAbhRcd6WR1MDxj4.FW3M3q3uc6QfNfzLQgJG65Ie1dtl9BNPHej2eBMsn4JmSNP5nm.mqJ4hnFAa3qPdoIITflc7dkePX.6Yb51mCrVM.gvcxcP8UkHWGSejVrjr1WVw.YnF05puvio_i_2Nat2pHp3hlObO60QjZ4Q8ce7g9.OD57xjQapzsj4AnkgiUSulA0KhgpsUSROoEFM_T5N.XE0sVITgh8iA.zsyePe6O1ngTJ.Ly_2JNbPH.FqyEqYccvKSoiGTIX9gZ6xmbQHCY3XGysp0LiO_l6ishuHrT5.B4hokUMWVURRb9tldHU0pjoxjZjbaPM2WcyG5zt7EiYEru87mP2E_JEcivZm0pAoHL8.8DgQf7zsH3XUHPZy05DaVTQlXX45hqoMglAPlATBvX1Iayd1.cCedcm14jjx9M8XXB70MB.5QmEjiTC73MCA2Qwz5mWRPxB3XnQKmQk7.4LJAF.WYv.KTZU0GllQ2fC0mxpBxJMktrP4ZX2Y6PcQT0mZ6HermNihS9zDerr1iQaTo6j4",mdrd: "1PfLaIRVnvbdFWHaLTUnbtpZ7M5Hi1isT7JqPJuUhKA-1740081263-1.2.1.1-XBEoB2M60A6cNH3P6tgCjHentPUKj_jLGBLucvuqyMSE3RPKVVE_RNEPKIVX9wXKNBNyrwrvIMMWdxgHm9iMxC9I5_Iard3Rllpt_dAsDjfd5tv46e5ztuT.5Ssebqt_fQD6nx3x9_GDTBAYJDIcFMB9jpo_9BWA3l0y8Gwq5J4OVRzUFIym0h8QKYl4yhqsLLiiPbh1VUcILs9erhM9kz1jd8QRL0kTmiAtMLpAw04K90M6QsuqHD8AfMM6qT_g6dssc2zhrKyVbRsmtrDeV4m5Oe5hN2e0w4sMJoXg92xBu46b9BTf4aTJMT1MAmDTFLyxk83Il.V_Xmt5jJK0Epm1CwKAqFmqZ87P1ypZFGfp10.F0Sy0qLWRHIBr.7H9I.dxvKCdMEAVBxF9.0JQflq3XiUKg.E4uRyxseA8ZmbK9nzgJWpglHuPKce29QGEn_UE3tp0HRYacVrd15qYWa315AR7cl.oioIGnBNqoHySq3p1jEvWVOIswpxvCSC4XyTGa2zAAmUHp9ZcW5QT7gLvCI73FzGtdQFcamnt.k0k7veZAnfsVXMm1wrIJvmwUFzOn5vJwJQ_WHDhockgsOFqFE26Xtltnid_cvDmyw5lC3Ic1ZHYQ_iZ3UnsfWw_prdkBXTwuHrLI_ZSUsxYK4gT_4fFcieWx8PZKMDLQlpzcqxGBZxAwkS_wJfMnLxd7OwLNxO0EidGNE9bFHMqSSqyPyM6akGbperT1CI0y7iRo_d2.mNP0LRA3ODyE1si3Hg0f0vsEtSxhXpwS6EGoJ4iLItgHHA7GghtMduVDkGFAAKmYz8_uJ1TheUQv_ccB5IzGzfD01x_bcH6BCep6gb5MWboNK0EsoVBFUrzx3Y4RD1_5qE2OlJzyRiI12lydVTVDSIf2RwFY49aI.13Ugj7E7EWGZHfgwqbAihPwCp1qIZG9LAPzOyqIUXN79eR0ISvA0yuO9Iexq9AoW8TPZ3GtEM_CaHm1uwYWUxW7ISWsNOkGebhDMKvM4FM8TFNG0Cgnbj33R6VzlhYIIquPOWGgLdGnWAAc4oknSobdkw0kQ2qdGvI_tXFxd4ubBk3J9UD_5x3Oz3jb1EamcYpxAWw3yEjyP02iCH8vKNxKBbY0XUL8Xj5EVgnypgGzOoZbG8CteUs7q_zF48TkSgNvBmnUADJjqjUSImj4Na_ja0wHsBDuL0SKANLTBB42FpjXpNskNjx7qiig1xfWppmN_yBoaw9.P0ITBFDsfCh9AQIfjfoLV2_nCsVAyY6JQnh4vnttBjN47gzIc5qxSp8Hs.c13EHFwpQkPtiNtR29rK.6xSX5Lsuq7xRzHRq0PKxrrGxkkUOLkA3nc1Wupbsvzn00DAod5ofqrk7W59i_52Clc7k9hsQqDKY01t4FCUkMFkv2gJy6GFUbsNJ8xmdRW1YjfwOuiAm1.DS0HkubojiXhFKn.Fqq.ngzaIJqnO8YfIjVtlNvDOnouXlUzYBxq.obsitGgqqE_n6lwweF.ZNEwZimO75U1k2K1tAM8hC_KrRvbbyzVNGmdmcAvTgiMhbJjTRUa6D01sswZ463MMGlGyI23XJgteIuXOVkmkAR.XJtu.9S7bnTPiMAC_6y0vgWbojeJbuR0QqjGbWXH8y2I9ADltrTng7nKDKWwwvCn2ZMDiwa5TA0zNJWdiBpI.wulWKEa6i4DEbcKsUddZORGIqGTlq.qrP8YJTKHkjrib1TOJVnohtclS6qxFOacrjB5X.5lOgAZCDk1zj.LUlzdz2p1jpnkiFEh73wcP0jCqtMIxtoyRwRPzyvAgGQx2lBp5.Tac5LnHWS55ZPE6.1AdocMladYTfwEcMhIoWXk97Vi3z3PVk6DfNA2ORHWHNfrsTG3cPU4R0KL_3CCtt7jaoa9C.jeWG12iIE3m4oeHYTnZd2dNCRFqXnJ3Zdr.cbDurZbdV2kBsgjYx5FgcKe3O0wDw1GbG5taQZ1Iu"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=91510c567f28fd63';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, "\/10013524\/harvard?__cf_chl_rt_tk=r4MBPjCGnLu1y.lkGqm8M4ShPrwmJ_lPgSPE49b_Qd0-1740081263-1.0.1.1-mjoac81ggLPBpW6ASPxtWMdAUTLPqrHivO4lSfzT98c" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>