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All the scales in the world—from those at your local deli to the big ones at the junkyard—are ultimately calibrated against a 125-year-old chunk of metal in a vault on the outskirts of Paris. Its mass is the definition of a kilogram. There’s just one problem: That chunk of metal seems to be losing weight. We talk to Derek Muller, creator of the Veritasium science education series, about the race to redefine the kilo in less slippery terms—and what a near-perfect silicon crystal sphere has to do with it. And Jon Pratt, an engineer at the National Institute of Standards and Technology, tells us about his team’s alternative “watt balance” strategy to lock down the kilo in terms of Planck’s constant.
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EVAL ERROR: Entity: line 1: parser error : Space required after the Public Identifier ^ Entity: line 1: parser error : SystemLiteral " or ' expected ^ Entity: line 1: parser error : SYSTEM or PUBLIC, the URI is missing ^ Code: line 1: package tmpevalpackage; line 2: sub doEval { line 3: my($parent); line 4: line 5: if($LayoutManager::url_resolved_values{'SEGMENT.nickname'}) { line 6: $parent = $LayoutManager::url_resolved_values{'SEGMENT.nickname'}; line 7: } line 8: elsif($LayoutManager::url_resolved_values{'VIDEO.nickname'}) { line 9: $parent = $LayoutManager::url_resolved_values{'VIDEO.nickname'}; line 10: } line 11: elsif($LayoutManager::url_resolved_values{'DOCUMENT.nickname'}) { line 12: $parent = $LayoutManager::url_resolved_values{'DOCUMENT.nickname'} line 13: } line 14: line 15: if($parent) { line 16: my(@books) = &Database::SelectClause('BOOK',"parent = $parent"); line 17: if(!@books) { line 18: $parent = ''; line 19: } line 20: } line 21: line 22: if(!$parent) { line 23: my(@sel) = &Database::SelectClause('GLOBAL','record all ""'); line 24: if(@sel) { line 25: $parent = 'GLOBAL.' . $sel[0]; line 26: } line 27: $main::ENV{'reading_header'} = "FEATURED READING"; line 28: } line 29: line 30: = ''; line 31: line 32: if($parent) { line 33: my(@books) = &Database::SelectClause('BOOK',"parent = $parent"); line 34: 0 = 0; line 35: my $dots; line 36: foreach(@books) { line 37: my(%data); line 38: &Database::GetRow($_,'BOOK',\%data); line 39: my($status,$title,$author,$url,$image,$width,$height) = &SciFri::Schema::getAmazonItem($data{'isbn'}); line 40: if($data{'title'}) { line 41: $title = $data{'title'}; line 42: } line 43: if($data{'author'}) { line 44: $author = $data{'author'}; line 45: } line 46: if($status eq 'ok') { line 47: .= "<div class=\"box-2x1-item box-slide\" data-href=\"$url\">"; line 48: .= " <div class=\"box-2x1-item-photo\">"; line 49: .= " <div class=\"image-wrapper\" data-jsclass=\"imageWrapper\" data-align=\"right\">"; line 50: .= " <img src=\"$image\" data-width=\"$width\" data-height=\"$height\">"; line 51: .= " </div>"; line 52: .= " </div>"; line 53: .= " <h4>$title</h4>"; line 54: if($author) { line 55: .= " <p>by $author</p>"; line 56: } line 57: .= " <div class=\"box-2x1-more-button\"><a href=\"$url\"><img src=\"/images/v1/icon_text_more_white.png\" width=47 height=15 border=0></a></div>"; line 58: .= "</div>"; line 59: ++0; line 60: } line 61: } line 62: } line 63: if($parent eq "GLOBAL.1") { $main::ENV{'reading_header'} = "FEATURED READING"; } line 64: else { $main::ENV{'reading_header'} = "RELATED READING"; } line 65: }; line 66: &doEval(); line 67: 1;
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