鳄鱼皮肤图案源自精确机械折叠
瑞士科学家研究显示，鳄鱼面部与下颌独特的鳞片图案是由一种精确的皮肤机械折叠过程形成的。研究结果验证了之前的观点，即这些鳞片来自某种机械过程而非遗传机制，同时为了解这一过程背后的细节提供了新的见解。相关研究12月12日发表于《自然》。
动物的附属器官——如羽毛、毛发和鳞片——通常作为受遗传调控的单元在胚胎发育期间发育。但这一规则也有例外，如鳄鱼头部的鳞片被发现完全由机械过程产生。不过，形成头部鳞片图案的精确机制一直很难确定，一定程度上是因为用鳄鱼胚胎做实验存在技术难度。
日内瓦大学的Michel Milinkovitch和同事通过将尼罗鳄胚胎实验与计算机模拟相结合，生成了一个三维机械发育模型，重现了鳄鱼头部鳞片的图案结构。他们发现，这些鳞片会通过简单的机械过程自我组织，比如因皮肤比皮下骨骼发育更快以及这些不同组织的硬度差异而导致的挤压褶皱。研究者总结道，这个过程会使鳄鱼头部的鳞片形成不规则的几何图案，这与鳄鱼身体鳞片作为受遗传调控单元的发育方式截然不同。（来源：中国科学报 冯维维）
幼年（2 岁）的尼罗鳄。图片来自：瑞士日内瓦大学A. Debry & M. C. Milinkovitch
相关论文信息：https://doi.org/10.1038/s41586-024-08268-1
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element block and removes
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else // I didn't find a way for script blocks to fire some onload event. So in this case directly call the Anthem_LoadPageScript for the next script.
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function Anthem_EvalClientSideScript(result) {
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//Fix for bug #1429412, "Reponse callback returns previous response after file push".
//see http://sourceforge.net/tracker/index.php?func=detail&aid=1429412&group_id=151897&atid=782464
function Anthem_Clear__EVENTTARGET() {
var form = Anthem_GetForm();
Anthem_SetHiddenInputValue(form, "__EVENTTARGET", "");
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function Anthem_InvokePageMethod(methodName, args, clientCallBack, clientCallBackArg) {
Anthem_Clear__EVENTTARGET(); // fix for bug #1429412
return Anthem_CallBack(null, "Page", null, methodName, args, clientCallBack, clientCallBackArg, true, true);
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function Anthem_InvokeMasterPageMethod(methodName, args, clientCallBack, clientCallBackArg) {
Anthem_Clear__EVENTTARGET(); // fix for bug #1429412
return Anthem_CallBack(null, "MasterPage", null, methodName, args, clientCallBack, clientCallBackArg, true, true);
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function Anthem_InvokeControlMethod(id, methodName, args, clientCallBack, clientCallBackArg) {
Anthem_Clear__EVENTTARGET(); // fix for bug #1429412
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if (typeof(WebForm_OnSubmit) == "function") {
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control.src = imageUrlDuringCallBack;
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control.value = textDuringCallBack;
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SetLabelText(control.id, textDuringCallBack);
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control.innerHTML = textDuringCallBack;
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function Anthem_PreProcessCallBackOut() {
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this.ParentElement = null;
this.OriginalText = '';
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function Anthem_PostProcessCallBack(
result,
control,
e,
eventTarget,
clientCallBack,
clientCallBackArg,
imageUrlDuringCallBack,
textDuringCallBack,
postCallBackFunction,
preProcessOut
) {
if (typeof(postCallBackFunction) == "function") {
postCallBackFunction(control, e);
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// Re-enable the control if it was disabled during callback
control.disabled = false;
var inputType = control.getAttribute("type");
inputType = (inputType == null) ? '' : inputType.toUpperCase();
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Anthem_RemoveHiddenInput(form, eventTarget + ".y");
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control.innerHTML = preProcessOut.OriginalText;
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if (typeof(clientCallBack) == "function") {
clientCallBack(result, clientCallBackArg);
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function Anthem_FireCallBackEvent(
control,
e,
eventTarget,
eventArgument,
causesValidation,
validationGroup,
imageUrlDuringCallBack,
textDuringCallBack,
enabledDuringCallBack,
preCallBackFunction,
postCallBackFunction,
callBackCancelledFunction,
includeControlValuesWithCallBack,
updatePageAfterCallBack
) {
// Cancel the callback if the control is disabled. Although most controls will
// not raise their callback event if they are disabled, the LinkButton will.
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if (control.disabled) return;
var preProcessOut = new Anthem_PreProcessCallBackOut();
var preProcessResult = Anthem_PreProcessCallBack(
control,
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eventTarget,
causesValidation,
validationGroup,
imageUrlDuringCallBack,
textDuringCallBack,
enabledDuringCallBack,
preCallBackFunction,
callBackCancelledFunction,
preProcessOut
);
if (preProcessResult) {
var eventType = e.type;
Anthem_FireEvent(
eventTarget,
eventArgument,
function(result) {
Anthem_PostProcessCallBack(
result,
control,
eventType,
eventTarget,
null,
null,
imageUrlDuringCallBack,
textDuringCallBack,
postCallBackFunction,
preProcessOut
);
},
null,
includeControlValuesWithCallBack,
updatePageAfterCallBack
);
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}
function AnthemListControl_OnClick(
e,
causesValidation,
validationGroup,
textDuringCallBack,
enabledDuringCallBack,
preCallBackFunction,
postCallBackFunction,
callBackCancelledFunction,
includeControlValuesWithCallBack,
updatePageAfterCallBack
) {
var target = e.target || e.srcElement;
if (target.nodeName.toUpperCase() == "LABEL" && target.htmlFor != '')
return;
var eventTarget = target.id.split("_").join("$");
Anthem_FireCallBackEvent(
target,
e,
eventTarget,
'',
causesValidation,
validationGroup,
'',
textDuringCallBack,
enabledDuringCallBack,
preCallBackFunction,
postCallBackFunction,
callBackCancelledFunction,
true,
true
);
}
// Returns the top, left control location in FireFox
function GetControlLocation(control) {
var offsetX = 0;
var offsetY = 0;
var parent;
for (parent = control; parent; parent = parent.offsetParent) {
if (parent.offsetLeft) {
offsetX += parent.offsetLeft;
}
if (parent.offsetTop) {
offsetY += parent.offsetTop;
}
}
return { x: offsetX, y: offsetY };
}
function GetLabelText(id) {
var labels = document.getElementsByTagName('label');
for (var i = 0; i < labels.length; i++) {
if (labels[i].htmlFor == id) {
return labels[i].innerHTML;
}
}
return null;
}
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