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即使是物理学家,也“惧怕”数学

发表日期 / 2016-11-11 评论 / 7 数学,物理学

早先只知道生物领域对数学“敬而远之”,万万没想到连物理学家面对数学也要皱皱眉头,他们与数学之间又有着怎样的“爱恨情仇”呢?

几杯咖啡才够你清醒一整天?还得看基因

发表日期 / 2016-08-25 评论 / 8 咖啡,基因

(Scientific Reports,2016-08-25)新的研究发现了一种限制咖啡消耗量的基因 PDSS2。研究认为,该基因能够减弱细胞分解咖啡因的能力,使人不需要饮用那么多咖啡就可以得到较明显的提神效果。同时,PDSS2 基因发生变异的人可能饮用更少咖啡。越来越多研究发现,饮用咖啡对健康具有正面影响,了解我们饮用咖啡背后的动因尤为重要。

Observational signatures and non-Gaussianities of general single-field inflation

发表日期 / 2007-01-02 评论 / 3 物理学,理论物理

We perform a general study of primordial scalar non-Gaussianities in single-field inflationary models in Einstein gravity. We consider models where the inflaton Lagrangian is an arbitrary function of the scalar field and its first derivative, and the sound speed is arbitrary. We find that under reasonable assumptions, the non-Gaussianity is completely determined by five parameters. In special limits of the parameter space, one finds distinctive 'shapes' of the non-Gaussianity. In models with a small sound speed, several of these shapes would become potentially observable in the near future. Different limits of our formulae recover various previously known results.

用碳纳米管和石墨烯喂蚕,制造超级蚕丝?

发表日期 / 2016-09-13 评论 / 4 超级蚕丝

Nano Lett. 2016-09-13 清华大学的研究人员日前报道了一种能够让丝线更加强韧的新方法:给蚕喂食石墨烯和单壁碳纳米管。他们说,这种升级版蚕丝可以用于制造耐用防护性面料、可生物降解的医用植入物和环保型可穿戴电子设备。

Tachyon condensation on the brane anti-brane system

发表日期 / 1998-09-01 评论 / 1 物理学,理论物理

A coincident D-brane - anti-D-brane pair has a tachyonic mode. We present an argument showing that at the classical minimum of the tachyonic potential the negative energy density associated with the potential exactly cancels the sum of the tension of the brane and the anti-brane, thereby giving a configuration of zero energy density and restoring space-time supersymmetry.

这么多人热捧LED治疗阿兹海默病,但它真的会有效么?

发表日期 / 2016-12-08 评论 / 5 医学,阿兹海默,LED

很多在小鼠身上的成功的医疗技术都难以在人体试验中取得成功,LED治疗阿兹海默病能成为例外吗?

为何鸟类高速扎入水中却安然无恙?

发表日期 / 2016-10-04 评论 / 5 鸟类高速入水,生物流体力学

PNAS 2016-10-04 某些海鸟能以超高速扎入水中,且脖颈不受到伤害。该现象引起了科学家极大的兴趣。于是,他们利用 3D 打印的“塘鹅头骨”和一段橡皮管建立了一个简化模型,用来探究鸟类高速入水却安然无恙的秘密。

全息宇宙学模型的观测检验

发表日期 / 2017-01-27 评论 / 5 物理学,宇宙学

We test a class of holographic models for the very early universe against cosmological observations and find that they are competitive to the standard ΛCDM model of cosmology. These models are based on three dimensional perturbative super-renormalizable Quantum Field Theory (QFT), and while they predict a different power spectrum from the standard power-law used in ΛCDM, they still provide an excellent fit to data (within their regime of validity). By comparing the Bayesian evidence for the models, we find that ΛCDM does a better job globally, while the holographic models provide a (marginally) better fit to data without very low multipoles (i.e. l≲30), where the dual QFT becomes non-perturbative. Observations can be used to exclude some QFT models, while we also find models satisfying all phenomenological constraints: the data rules out the dual theory being Yang-Mills theory coupled to fermions only, but allows for Yang-Mills theory coupled to non-minimal scalars with quartic interactions. Lattice simulations of 3d QFT's can provide non-perturbative predictions for large-angle statistics of the cosmic microwave background, and potentially explain its apparent anomalies.

北大发现快速制备疫苗新方法

发表日期 / 2016-12-02 评论 / 2 生物学,医学,微生物学

北京大学的研究者找到了一种快速制备病毒疫苗的方法,适用于几乎所有病毒。

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