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: '9134ef27b8744dab',cH: 'mfQIaNQHZQvCMj7bepgtEGPdGMI6qqfzSYsg5_iN2qM-1739786466-1.2.1.1-1YiibIrbhDYgukZiG25HHLEQLD7z4_iJv2o8xz2BDaRvWBM4LGV3zHXmFWfPLFQU',cUPMDTk: "\/10008989\/harvard?__cf_chl_tk=a3QKnY.xi8tI2IAoQih.ZsP6nxpxcLcuKZDEZiQs4s0-1739786466-1.0.1.1-QYYod3ftH2RuZ61XAiPzUSyYkLQberolkFcSUttb4O8",cFPWv: 'b',cITimeS: '1739786466',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/10008989\/harvard?__cf_chl_f_tk=a3QKnY.xi8tI2IAoQih.ZsP6nxpxcLcuKZDEZiQs4s0-1739786466-1.0.1.1-QYYod3ftH2RuZ61XAiPzUSyYkLQberolkFcSUttb4O8",md: "JWP3jEwS50bVbbkicMUIS7PbQ9m7iUNtKhw4uwLLQP0-1739786466-1.2.1.1-3DARumXA5OWhDVhMRQBE1x.w2mjg816HVweNE6C4Jp2eXMksJ3r7GOcHiniN3tepxL6SnfBlgsN9mBXMFinwzAHCe71RpbVf5yHRyUzNzmJc2C.nozo9tpAOZHCYYPdRqmWETOJlgGRif9HODjwTFf8ENzlhtedQqn9eR51AtBXNJmAIh_dKD3pj661v8_YVMGKnmH3TcwcrIhxjH9w1kZ8M3m4jbzGMORwKH6jqrw3r_aC_yaE7Figo_G1hKUSoCFlLypXHvdm8rPLTTbPZ5U0lpL5IPAuP10LKRUrQzcfVSA1umpwZKfvKsIAiJXZHCEENrLRN_Ruy0ERNpAbktlee5Pi7ELuaIOdravbGQRkKbMb3OuYe1wFlUG7b6kF9pWTi3tl9TSGlWX3Iy1OVxN6Kijc8RrN5mHkbwabN5i4PlUH8fTRN.nE_GjVzpWm5efO8.nq_ocB6_rQ73Yz63USOfOhPTYSHqWYyblwKNzVDth5wszLCAuRLz5GVq5_XgKxojtLM04J3WQPN8ktLs76Pd5tou6Wq9scuVEST3dsC51mSo5AKLUX7Xg1SoCpwBuHPBzKB8T2E36yzlWaHeHEySyWCvOBeUN6UvO8uhYIYM5ptmHN71TpdJ2xSAkzDOw5brV0cnfestAttUyb7S7U95yaTDrSNZrRXNJEGoWNwxETmyKQwUkVqwspix6pxMJ_IHqO3McJG920eWbCp1lrQxaPT3o3ZtHod9guciuXp4hmz15uxUJpA3gl4Odo8gK4mK7CywDiY6yaRWNbhrsIw0PeFf9w.Y2NPytGBGdjkI0J9eNTZEVk3CBLCkcgiPszIl87o29qTHSHc7aR1qlv4zzQyVL13i_iqxVTETQeYF3iN3TLxcLiHEKgnCobsBpaSSuOzD9GDQVZjGgSEZON3xSuBuLUT4rSPuVpVXROVDdTJokD5dmNzpHKUvEpeqQcreGyum1EvHALGhWX7iQZgonoFN1uFcTbeZ5Sb2HORXJ_XKLDmpmWp3UydQY7YgYxxhI.lKbszeqYSNVoF2db6QfbTxH8QhuoqaQ9_1ee_dnopkEQlFWp9485qqZpaJqIhQqcRBC8gl9ie_WMmaAnPx.I0U8aUYJcVr98ucXjjhR4aMdICIi_jfGffUmgSjm2Q8VWymbEEkcRhgh0jqXDpVIYWHNPEO4JNjSgiIXRyx6uqIPspm28_bqvdD_BiCNc1.ao4wLLjDLNMsgxh1wLDpvs1IhsG_cLiFqG4UGw17aTlGIHnHWl7hWAdxx1T6wv7wt04fD_OwI9OJLljOiBk7CfY1h9zq_mkEGBNjlLl8N6X5TIt.UNFlyyDE0NaT9UbnUL7FgsJyxBPE3Wk5gIhxvI7PjpPbP1uzPxL8EPXLgLbLf4A5U6HIA6jWlmER_Gy3VAMvPCGzMxl4Nn2MTMwuGgxb3dcdC9qt0jP7e_sUcBW8kFnjuBzhjc6ZKmKVkwbTb5eW1fRB4R3T1tVLo8oIi5EMZCLBNZCuFN8NA8u_6Lp6k.sjkHkGJ.dN.tKMyLBZ.cDdh10a36QR79DlSC851XR7DYjgKED8dS05CkUcvH203O2CTM7QqyJBVaC05QIN_vdRoAmEOrUtFYGxrNJcGsQaKdNt60jPRUcHf9avGprMFBu8f66mQASiw3ekcVXwql9untXd4UIBVM90qKesKXxFINVMdn_B.OHWpQgDf3fj.S5MuVRfj8wVoh.1tnBu9no03P.QvBh0VTXZI1vIUDmG6lHqD13xX84sqqBhZM.M6yT5B5QiRMNBrGEnbAfdjPZRCrZ8AEY7w2BRFbBk2f5ps_00F9umvYd7Mx.FlNyvZu4XiAzQt3N1tj8E7lb0nlOolcGNYzSDXo91fVmI.sneD_UlMvSJP7cX1Q",mdrd: "oKVHI0D24erlpilIZL1m9_EVhFazqZP.ihM3Dd1bD2E-1739786466-1.2.1.1-zsoGtsJAFtC0eZrrHXUZbr3HhCGM6diuTHjfYcJx5A_qX5pDxQc5vXCNZGs5HflgaRFBcSEb5rofqXWcJw7UdYCz22kg.rnt_fyFvOY28lZESa6UXC29ZtJs.woYZHUQcLRIKDV4lhvz7UNAZ3dGQtWeB1Zgn_RG6ZqzNTcHdsjTIJcgJA7zc4K0ygZOZIT4bEpw2.zADjQXZo7JYLtXQpsRNzakpkMWg1rCBUsUVmKSMVbDHP6FBwth1._JJh3O2rCR_8Ci_u..x2t.sjkL0_1rE7vGAtKzhU_UNYxM.njgmmb78.iD_NwijKFpW0jwXK12xgMz6xElsvSK3TZav6NWk5cxCaOa6vAGfu55g1inV8Ee_0W37y0uv4U9cpG.U7XBxRLV09Wl0VqQuQUaCZSletQGfYlAcqu9XL1VmGtd1G1uwr6hiNQM4mfjCXGpY948IHnj31C6MarfuwAPNpNGcYB6ayOb3pw.qOKGXL_En8y1HBL4PKoV4M2nzZL6iVJUzGjD5T5jdljqsPq4bG6Tc7RIWdbkGiCiRkoh1zKD3I.PcfHspZpWqWd_gfQIrJRAJ9UL17BrFwQHv17s29qPeHIEZMJ.SQqujRwUwJNasHDEzeAPsDr1pRaELb03HLoubMmd1pEKj8TjumACxwCCtGMzI5S3M7vGWjWg4.uy1pbo5kPDpArOKphCE.BwNzcQiH3wmAL9mQ_Q9mZuqk9cbodquEl55VSLhOoSaQ0TRouFnHtVWwc1Pf4A7EejTlQGoW74jIQX9P8tZcc1_fG5hG9jKV8ruSlY7A_NqDfu8hB55T78SwNFDkwmMPEHc88aRsAeZBqwb1RW5ov0JIiyvUljMbo8ly0JFk8QiwsiYRt0IB0gmCuk2L9eVJpBrZ4WAXdn5nsxJ8mMdR.jlVs8cMz7MWieWCqbQGnjPxUFGvl4m.zFgC5fZySsga9mtj2CMIdtcAMbw.GVHCh6_5xo.kfTS0iqPpeJ9kA268.db4vXARbjwCaXcAMUAKqttyhcon9RQ7Yr018NWNp_f2j5QcmEXExsZr3bMUqPms4nhvRUxkKFXBeT4LeYzULw00sKmHoV92T54z7i2mBrGM.JfvJPS8WekZLxVoEq0D0rK_Zke2az9qXi86gy5qI1knVIIQkCvodEXnqFU66R0tBTeVdK53sbUAPgea5NNET4MZeoIVp.KplLZPwkiHa70FAi0fhWf_CKLQ0VFAqw9KlBezbUmoyJQjT.jD5gD1ihNiUKMKm5EOhYEYNAWREZA_sbaQJYEaKhpJtBNz_8UOmMorbVMYVgrdk38qhWkBuhzUM4lmbPn2fu1Kiy.RkoUyArQaYr2EnDS2x6.SLeC6IYsBfCgq9BaBR3oB5ZSh6ug_3RxMvHtctZTNELW.qw38D1fJ5XUyexxNSX09AnnnxibwxpGZCpFomtRl296Vk5R9ji0BRoUVstBX7SLnTTlWbE240AmSnJXg9Ru4QX9ThyE0pmPi31nuf3FCv7HkXOquLodfc82GV1vak6Jw6OSUb_cNlrjTLDb21IfSqIe05TB89j5O949O9iI90w93dC9U6JtAPMKlpaHyWpTxNx0EP7tUmEsIUobFA5IxaGZFkj7ct9L6gQ9Ifg.y.KwQBKdeFGWGD2k83gSG9HadZxcFe707KKG77ohrI78DJ9yp3zGDPs5pp5RarTIPuOTsZxhXr07Vedhreavs2xPBFVHmJWtk3heUTlKU08sx4gH2MtOpI.Jmx84JE4drSMPm7QY43qu8PbCsBy1bXmAVo8O7yiEUOlzOKdSNERfomgehESSdqi5VvFEFeRQNbhEO7HTt7tOmBFZwlLqUsHAdRTy0FMjq5Hfwho2hHxyxZ0.TYxagZgy6rPotcBez4hMCy4VcGp0eisd9zO_FdvHdE88gO7chrNkPrTxwEw63TOI_VZOXu7V9fx2nJxx872d0okds47C_CcXS0GNSVdXclrGDocEqi2Iu0TRVcBGcYYAg"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=9134ef27b8744dab';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, "\/10008989\/harvard?__cf_chl_rt_tk=a3QKnY.xi8tI2IAoQih.ZsP6nxpxcLcuKZDEZiQs4s0-1739786466-1.0.1.1-QYYod3ftH2RuZ61XAiPzUSyYkLQberolkFcSUttb4O8" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>