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="390"></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: "perec.columbia.edu",cType: 'managed',cRay: '9226bcac0c3546c1',cH: 'ZKBPDFYJkXhNwIRehlb_S9SNcFsp.G.ApMC_OeR4vN0-1742321952-1.2.1.1-4mldocZ8M7U3QGqMiWlLbJDkxIiFod1ozLEogNZLP4cpUhskf8yq8lhcCD1wv4P4',cUPMDTk: "\/membership?__cf_chl_tk=0qWH3PNPJgkRkLCXE1b9tCG9ueYrxmEGwVA6ETGGMXI-1742321952-1.0.1.1-VZ1lMptor_ePZzMbIUA12Zxpf1qNen47X7oXbw.1uG4",cFPWv: 'g',cITimeS: '1742321952',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/membership?__cf_chl_f_tk=0qWH3PNPJgkRkLCXE1b9tCG9ueYrxmEGwVA6ETGGMXI-1742321952-1.0.1.1-VZ1lMptor_ePZzMbIUA12Zxpf1qNen47X7oXbw.1uG4",md: "TBhup58DLqDztBnPfxlNUwCODGcsF.JAonGO.Tgp5xw-1742321952-1.2.1.1-HQ7GrtD.62ze6FBbCXJDlhEztfnEOcmxeGiJ1W7UF8eumil.fWSRk6MQq.5qA66o1mvpgkcQx7XEYJhzOgHqGWpTALvIxv.TxRmZ38kncC61fusa2DBJM5x_qGe9_mubHR4Zpv.MOlaDrt2y2GRgwZKW_h4reqjroOtdlQySZ6glLQpDUCwftJjgn4XufrMH3wlqlcyxFnUJzuCWttwSI1CiwuQB6WRaXkpABOjwLksQOkkVkhTKNFlzScCik22..DBdqgJj73LUcr932TAzbVK0v1usegIlGRq61Ua36YKWWSeH59xjybhqC7YaosKtBCvht1DT.aD4zGM6No1PV5brkDSVLazLJWOtfrb0SNvOvRDxFfSOJ09SCfD1w9iQHMr0VkUKzBnWzVOGoSKdjMMoq70kd2q68qsbY09Nrz7Vk8WL2awOD1gm5FxGuCfCKhuCPQ0iUMm8nZW67hrVO1uRqwXvnTNTBNCvDB6SdH7zs98piLs6_0YRoJkYeT1_ITLQ3Yo_k8J6fnqm0_V1NDMMIe1GZOFw2.vHL.8iIKDcFLHzL2r.LLTQHUZl2Mhm3maOIPbi_F1wRxJnXNB72NjIzdEZvfdc1XVi7ISJtGHY9.yBGnK14SHZEQbT6LUzlZQ66MmKIMz6PyCRBu_3PBjSc5TNE8XVIgZlPNCvTsr8gfxI3mLRH6jNIminHe4ARKf5Vakcxoe_ysNM0TGGl.D5UJ6WbMaFfD_URH9IKa.geS39KEGjQM2yLOdZdG8RSNZVigiFUDTon7NKdz8yY8STV3w7C2JEDWbdhUE0iAgGyPEhBExOU0DIq4JMPT7mbXSOIBLWc1xoyYGUedv6DU9EAOgxOleqw.tz7GDBA9s4_JMTjiosEUno3T_8yC5RWWrJFG7.cNQfrdiASIYXqhDVFoWNOLGtAVFMFMJeRe4usgdg363t6yM6pZLH2_HrX.Ftaf1bW6pnDTzCm179LFhM0WAXEKGeudsHUqmiw2lK4zmnJCL_0vsFFyAEE.pmdNhNq4J9qqmjPEWULfOGKphED9GivLRMeMHrSnu6e3AT2Mf.E9Am_TtFfT8DPIoG5SMRuFRm_eGmsP5VgDTyzNaRAhf79UrveAWCIk4V9g0y_A782wjU5Zx8JpRlnRSnBCTUOGboYPMUZjI7F87Y4n.tM_8IKCcS7M3PzwvHG24vpacrD5gcKep_2g9GJJ0XwDm1pFADE0_Dp5npcig6LO_c2.E0Ap7usu3gZy3KBL8",mdrd: "9KaLka4nKAYjxVs6G4EirimY4rgeBDeLxi_XPWEQlYI-1742321952-1.2.1.1-fd9BNnJQyO2Q31xAG94GCGECwjFuCHZguKe5kkYDSYGs9n_wuKGP5sSTk.Ci3H.mVQksNxepXKKLR.sKNg.iAS9G3uOgjuQWSmBqqBjkjzuje_2XpIHb_2odbR1liTbq5tkr.ehVFxvFwLXeSDa9XqmsOGvzwTRVKIEwtBapel_TbOwG0nzZzTDAxlSL6gVp3Z3ETTwwIwRQnQyD0E91NOB7CFe_SOvIBzQ95IDGWbqcMHqppdr9qSlXXC3GFlA4fVPna1pxWrFh4JmyQzuTLMeLYX3xmW0T6jpTcV3Z92b0OalImu5m2FJZeLl4U04rXhuzUoHrbr.6eznJ9PplBgeJGstpIVnl2bv6Gb0DrNqke4fMffgPt8AoXEQinsiwy3j0xX1Vq.WC07qTbzsrav3fBN9G_jZITuFkys48_vfl1NOkjf0mBOswq4g_RJ.JaIwkiSonAUGVFnJ4c2NiyEAB9yidwTp6SLEX3q7CPnJzJLQtllW9yzRAItZYlu3EAJ.RMqZ7mo_WwqPM1P8ggPOOARlCIjC_IDlvF0ETxPGDMgEwaJtiODH40o1sQ_PI1ai3_uxS2jQP2hARHwLnlWl_.1_XOx2.0YBZ3KHeWQPOkfwBMje5EFS45MaANbeF3_DwTiw17VCoU7Guko.GiHj9_gyP0SbJwco01sYAofMDxRQGKRuDJqy9.y8ihkYelqAI0Jzl2sHorqsEpGct_J4bEMcEAWlQTWZlkmcbptKOGoM8j5i4AMS64kEuVz3Z8oMHfkdM9g695HQVGfyxwXJZCYv1osjuwvYu52T.iLWVTfNzqzfz.6hQ_IXlSe6EXGUjatghMAUI..3SXfFr9Uo7xLS4X9KxeBJ6jwymjkjyHKeDrkSA9Es.f7vf8Th3xN5A2.clYkKsXc7SC.vy.VLMShtGWDCtGZ0pSW5uT7_ZdxHp.hsHKHoS_f8CIyOHPE9LnVCsE..Ccd2j0wdB86m2FsmEzsOfQ.nxQV2ByT4si5tMO6c53X3q5oxx1MTL3OE6dTS8VevimmwwAa7ioWZYRSt3ZNFyk.etaJZBNnVdgsw_kDy5SpS4V4pzTYiRg3oNk5NG0llfZOzmii1GBt9TCRYeT58FVPlaU0mGESgpEYhI4RNrp281qd00SczakWctObCbXMEpuNnpf0aCrLmYfEzSelBCyJuWdZwe5eSIp.HLwFy2PySzmd6xmQT0J7qrJBcpEdqPUCjg6j8cLQtfRj2uZfRHq4KUWcMGg3WxthQHlprNFVbHwvFpkdeM1vs_U1gRKvmZYbaOE4el2IxQRO7Or4mHF22hU3zgiEdAdc8smz_f2bgaq69qcqOEGwq4.Sj8C_4TU9MxTGYOTWB6q1R9L5ZEBF4J2O8l0DnfSiaGEN5C9SUl4jYB152a_PIw3iVSJetxgkCNBJ3gKprskCr7YiJWqafeW5YZ_mhdZvPSikMRog9LMim8zaGheurdWnrR44OjLTEVpPfbCXycV1cB_Hqc8hritDZDYZvhXm37XubK28B4FSvxHBe_BFpWfvXO920dxUUty8MxIMMyyKDSC6TYcGoJR1yMFsKry9fmIskol2O0ixZlgvwOiRsHduUtViRp_ulozL8rSle.c9FgLVQAJAVsjWgcPmC9i1g6JLES2r3RnGKPdm2459cl3QjDF3B1FjRQqUFc36LNJfkCqbS9MGSRfVvSBMNQAYpblOsJRjOIUb8EtZLVD.CCc2xpkgjRnY.RvVnlMyTMbXYhXMXcBBT.Y.69UjYzNNHMI8yf1Ts041QBBiMf2guYadoyVZNkCQk1UabGTRQ.Y0fSXrXo84lT0FjCGrKwlQeAZ8QM8pC0R_sXGZwMEjdz0OV0c0FnWaXvvJp5ADYtbWamGTTgcWZce4RQKKK8wsexYqtIIb2Nurdb5n3dfjYoNGKAA4.bNypArOCGzJjveNZaOHMe9NoTKknBJ01_6dC82uCUu_c7.Xkvb0vYwseWk92T.63kPGC0ZA2CfT8R3TVgi.SYqMDq3T.t.76l.A4K_p54DluwsVpPCZk5wQ.qNOG9BIYMP4O3ADFmdg"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9226bcac0c3546c1';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, "\/membership?__cf_chl_rt_tk=0qWH3PNPJgkRkLCXE1b9tCG9ueYrxmEGwVA6ETGGMXI-1742321952-1.0.1.1-VZ1lMptor_ePZzMbIUA12Zxpf1qNen47X7oXbw.1uG4" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>