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: '91351977cecf8977',cH: 'wvbXp0n5iayk5g5BtkMfuv8Kg4LVGP4QArwsGDHR.sk-1739788199-1.2.1.1-fkCqx6JwMw.FWC3PU7fQ0BtHZ4PcFNjOSV9JImiDk2h_JM01d83NQiANBy_y6q8r',cUPMDTk: "\/10013631\/harvard?__cf_chl_tk=cOD9t_aZ8WwtSprY8gKU.x.IohIQD3BTJIx95_VO89Y-1739788199-1.0.1.1-zgHj467i2GjtETIx0EycURu9_95Mbj3fdWjE1QnA4BE",cFPWv: 'b',cITimeS: '1739788199',cTTimeMs: '1000',cMTimeMs: '120000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/10013631\/harvard?__cf_chl_f_tk=cOD9t_aZ8WwtSprY8gKU.x.IohIQD3BTJIx95_VO89Y-1739788199-1.0.1.1-zgHj467i2GjtETIx0EycURu9_95Mbj3fdWjE1QnA4BE",md: "vCUgUGUm0604JQouDlug0Ha.JxD2E3edz6bWcraHZtk-1739788199-1.2.1.1-w.MRv.VrLndJ46IZhlO3X7yxRIzqBDfF2ulHeXY7AV4vxp8l.VMVDMB63BqN4aKqcf04YrpdT6vaskLBpcYlR_RTa3muxgjPGZUxYRRIcgB4UgqAcQBhv3VfpI0RPuwI3Pyst9IdLAM3vu7kwd3rE2fH2ozNCCl3dmRh8eUcqMuQM2jbpbnkm2xN.aTMl4Sl16PVoO4gEGkHc40YJWXr.S_p3W4T.1VMn8JnH_H5ewKh8D.TGirqTa7Dz8F3HUu5utw5kjNZq_KquWB4x5crWf7v2oGsfFh7Qp6iz4EzaquuycbmE9tKM6C4ul1GLrnfYZn_FDdLBNg38VaPl02EqHmT5S.C0wEEFeXcd96Hf2qX3kNCmQRqWLcCC0d_omPNrWM7h81Oc5w3LyLfki2cehiNNiTw1XckoliQ28Y6r0_bQSRaNhTGLWaGSTV4i3AhEnMihQe9e4TdT_p3wDfkYBfICQvgqWEjroYtpS17gvjO__SaE1LEE2PS0Vy8RoGB3ox5PQfS9LIRMEzkDDtaKB435GNz3.D7e7oRMp.V1u5VceKKnbNfiRelV3lsQaZZcBJ4vUwfcvJveZfDbx_5ieiGctrIdK3EXZLLOqz2jCW8XFmxfSguQ8Fn4b1Y4KsmGMx_9XApYLD8v5g4E_Ynko.QuO3aWHO3lMktI_YoVy2FrHOoI_IY6exOW..sUxVAj0uk7a67l9f6YWN1UKs7NcbouXbsxmGNGtnnp.1Y3d5Y_3AA2zAN2pFxBzXHuT1qmMwE9miv3md9hL6aNRQ7UAeWU2rLet0gKHwP78oW0Yz877yQIu7XKJA4PV0_P4D6mzgpRWHjVCgF_qT6udEtTdc0kUrqurm1jsIS4f_B6w2QHYZKwKTnSR2U2z3L9b7yCqeWN4aZSgxoZ0vgAMCl49_JDZnWmSBt1nbxuPFTNDzQOki5_CugobkUtj3L4SzV6jSGX4rvdwjqQCte1lPJLS0T6UV2LpkdTRPNmmi6wF0AuzH4jsMsaz7dkf5D6J1xYZeNsKf7v.2mdLK41RogvNoCNJbqKsal_S.QxzqkLpwJAxBsQ6XGsAVYjaWtU0_Zv.sxLqJN03lTssNHmS6MMCacBKR2kxJApaaCnjze5u9Vd_hHVOsH1XZQOnxNRRkWc562JH1m3AleC0BaOHWhNs040_62WfU0PgZD46oQyO9wMHjIP9zu6DxBbJF65mP34fbgw9.EGI0ZjsrsTjsVjKCAALeN0ef8d1RSFgwVELk8riDGaiykNAe9z6L8RkCHO6Xa.VeVq8dKQnEUAVhr_8hulg7yC2af3vqsfAVuRtZZPnCLV1alBkzRpkFggB8j2azgC6nUUqJ8EDarGvngIKik_y6nIecNt9W5M3mrH_paKNX1VVx7x7Khd616rBu.p1enx6dKr33c2JDOoABccgFn64a_ZfyH1D4_C96l_8st1KD95AAuZb2WnvrHz_IS4vOC.YJCc9IzQN0par_jO.9SkrJoey19p.YzMbLVfOD8Z02QE9k4K541hDJUiDj4tXRKCd9JDPmrEIdUztbRs92J_poX4qdgad5dWaZDioHqvp9ekam3I3YvJC8aev7.9cVA0z.dsr3XBz_0ZBzGiZ14QONWGijROf3IreMMSexcxF2fEDLrurhQ5zFGQdW4M0hIMx5rjOrUW2_M5KlhE.iZLtLFR0puaMFNvFWZkIpO6mejIOsKmWvWadxfaDV7gEvwWDwZRgXav7D4b3.XTPFE.lSIEVL.0Jnz5OlV.V7pkDSE27FJEdrQecYeZm6_K3xdcR65x3ub7FwQ2hA9Gy9NdXh4teILBqw03nqty0NikgwImhsfxl_DR.AbNWrelwYA6ceF1QYk.CRBR8A6xKW0NjoAHWoAsZHkuZ.wqFg",mdrd: "ZWykalH74bs7ISHNyq9QwgD_HgjSEDe_4LPMjKN6V.s-1739788199-1.2.1.1-JgGHNyNIAusL.was3ZRF07z2aYa8OYsw4lY0fSJCsI0pvsTivHZyVmNnd_EkfquNtmH4knoTnEv6mxyVxyVXjt7H3wP3gD_JX8ZHMHC2u_1_VGgff_qt2m5CAbCSlsNIHHsTViqIhIFIwGcmu.GYTQGaDammsq9i64Rdi0YIG5PihuI7RJVKQR4s9vy4VXjOcs_oHIjIEDNQRSx7BAEykD1ZIzm19b90L2ArWlqoSEMdGev75SdOjP83ieW2Nt250B7JJFm23XtfUB4ku4Crj2m4pvibeF8hv0TlOtlafjqFbEhNYhf.NXhmdecCAO9M4KHLp292.fcx7HqXhAurQ7NiDULAxW70vPBdUrefK24LVmVg28NEEVRH.kzTiTkBzOtHOqf5pWJ7O.6.8wOjldjR_pmJPCflQ0Sei.nzfBFb5j6PHjCHpwLwPNA5K4gqDKStm6aU_aqaD.jTHpEaNsbV.nBvi62lyz7d3UAhN7wZFJHYI0JC52RJzD1nnbnXgb0scHnQmMydWsHqLVtwOn5mVtzESO2PGaquc0iUiQjJput6MyFnYKTsBWT2S75Qt.i1Lx.ZkpaZng8PVSc7Gx3XbZvURZ59AR4EO3YaJ_lAkFu8gSGP5nIK8z1.A1IFO2Z3n_vFW7vhRhmbF.WlxH1svCKCZOM9gXrAuOnj.76qxM166cIj4LcsgJkpfYiHAUDYBQ51lG__QexKS5_nvoO91c7h2mnLyT9..VGtyUqjer62wum454yK_l2GDBz.zL4nzzJBCNICqj7lBvT1y_7Gpnq5.srLwO5OPDwfPwZgftyEn3udAt7BvAoM1SEBJgcE5pq7bZm6Wk6C5UOIeo5PQ0tCrF8Ss1c7OcihGIt3PIzfdGcL.Tw0A2ZV_8vwxyvoA_e8XxXtb4d.TDUPtc49.zrQHUXhISGqAwwxF6tkTotnP2FD5yaxUBQAeAh8_I1ykovM2mlKOXW6N7eYGUG886WOjYd4lYusIzTmgleTZMkqvsWz2W0ZpMA_r0x0wNHlkq.d41S2Bh5NFEwKeo9xt1lddnOj_mb7e1kdJKKgPuqJ4_mfoMyw2yyjJyrqGBF3EKw8Tu6aICNSv2vATpnqVHIP96iTeiCszaf_M_JyKpDqRhUCLKl14CtHYDUJVnUs41cRyJJHXIdp.3fTF_UtfZ50yHgohZtZJhXN5FerLpgJ_lrLUgOpfqBzRxcmD9aUyNxWgV2xXORuzXQaW4FBzGduHtyQBocCvIraB7OZEydIj1ltw36FytlEg8mpzPi6Oxfz8TcHfYvPkvirpNqBKP56MQJYiienupYQfrLOepANxTPptPk7H9Rn3SATxio.jexeyxl9Qicx8bjNTPNj8Vtg30FSHm0.OSTPrKXUdrBCjrgS0XdTYnMbUa3YVfNU.i3faFdl5KYcD.DKXc6RAbUcgC5SEHU64Rj4CmmDzCkyKY7hQxwcdKnD62oNhBLpofhMk_U.3lcZVEyxaEyGQnGBzIBUgrBQzJC5sOgfB3JiU.c_B1nWVuG9zbzmN6M9PjfFzMBgIfrPuBFe3814soWV_VG7wohWylz8BMsP0VHrvXA3MXWBN.wE8zgxmKqOjpmQxwYg67bXAmf.v__YIB5pB38k24Bu2QqpU_ozfpqUc354kmTSmjhO0SEov9UJWyuqmbcImNltb7olUyUR9twzmzCe4bI8drqOyzh2CHGT2kTdG0vcihUQ6u011RpYWIkdKeLcuRatXz.uWUjhq9Onn6ZrR9GS3p7yJ.86A7UP56ZnL9mHXeX.gLHxeN5gC0ABR2gdXCyg2T4Rgo9qKXU_fi0pFd8zZI7YxBJNS4NQjQYE34CgH_iqXkDdXu0hVBOTEqwV0fiKB10XeCt3RBJdTEiLnAqDlUGJ2Nc_mmF_NKnzQcO4nTDZZSfBToK0oGtLLGw4jCqKufA8.vWmkuSiWWf96BSVrnhjebhQqyr1oiriZ6PX3dymE8Uf_0RV1eHM0pdZ4j0lF8CHHA"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=91351977cecf8977';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, "\/10013631\/harvard?__cf_chl_rt_tk=cOD9t_aZ8WwtSprY8gKU.x.IohIQD3BTJIx95_VO89Y-1739788199-1.0.1.1-zgHj467i2GjtETIx0EycURu9_95Mbj3fdWjE1QnA4BE" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>