沙漠深处未来城

正为什么一个盛产石油的国家要在阿拉伯沙漠的腹地建立一座太阳能环保城市?答案是:为了改变世界。马斯达尔城给人的第一印象是仿佛海市蜃楼般不真实。从远处看,它就像是一栋多彩的建筑物孤独地矗立在天际线上。导致这种奇怪感觉的部分原因是马斯达尔城奇特的地理位置:毗邻阿布扎比机场,通往阿拉伯湾的高速公路从城中穿过,位于环境恶劣的沙漠深处。在这座城市和阿     

The Role of Conscious Attention in Perception

Impressions, energy radiated by phenomena in the momentary environmental scene, enter sensory neurons, creating in afferent nerves a data stream. Following Kant, by our inner sense the mind perceives its own thoughts as it ties together sense data into an internalized scene. The mind, residing in the brain, logically a Language Machine, processes and stores items as coded grammatical entities. Kantian synthetic unity in the linguistic brain is able to deliver our experience of the scene as we appear to see it. Uniquely, the brain records its own history, synthesizing a Movie-in-the-Brain, called the Noumenal Cosmos. Attempting thereby to represent the actual Universe, this makes for a sovereign brain that governs itself. The brain is domicile of an Ego, with its selfhood at stake at all times. Yet, it can know itself only by its actions, in which it appears as an actor in its own movie. Phenomena enter garbled, as confused apparitions, and must be put in good form using top–down feedback control by Ego, so that each movie frame makes rational sense within the overall context of the Noumenal Cosmos. A stack of frames is processed typically in 40 Hz rhythm with 300 ms process time each, for about 12 in the stack at any time. Successive neural centers are processing the stack in the brain assembly line, based on data from increasingly global receptive fields. Ego stitches together the movie frames, but only the top frame is in consciousness for 25 ms. The top frame contains the whole scene where the Ego makes an appearance as the actor that imposes Kantian synthetic unity on the scene, merely an assembly of grammatical texts, in a system-internal coded process language, fitting the scene into the Noumenal Cosmos. But Ego observes Ego only to the extent permitted by the objectivity rule, only what it does and thinks, not its true face. From the Noumenal Cosmos, the Ego receives grammatical messages in the internal sense code. They are integrated into a whole in the reaction of the Ego to the momentary scene. The voluntary nature of Ego’s decisions is explained, based on its ability to code in advance its own actions sequentially in time, as it sees fit with a view to an orderly Noumenal Cosmos, records of code being arranged spatially in neural structures.     

让人难忘的卡布里

正卡布里的旅行美好得让人难忘。地中海的阳光适时地打在卡布里半山彩色的屋顶上,也同时在心里留下了一块幸福的光斑。正午时分,从波西塔诺小镇的码头出海,和卡布里来接我们的托尼先生一起搭乘游轮驶往迷人的卡布里岛。托尼是一位高大英俊的典型意大利男人,一身经典的绅士穿着。他有着一双蔚蓝的眼睛,提着一只路易威登的咖啡色旅行软包,大多数的时候他表情     

Inhibition of cholesterol recycling impairs cellular PrPSc propagation

The infectious agent in prion diseases consists of an aberrantly folded isoform of the cellular prion protein (PrP^c), termed PrP^Sc, which accumulates in brains of affected individuals. Studies on prion-infected cultured cells indicate that cellular cholesterol homeostasis influences PrP^Sc propagation. Here, we demonstrate that the cellular PrP^Sc content decreases upon accumulation of cholesterol in late endosomes, as induced by NPC-1 knock-down or treatment with U18666A. PrP^c trafficking, lipid raft association, and membrane turnover are not significantly altered by such treatments. Cellular PrP^Sc formation is not impaired, suggesting that PrP^Sc degradation is increased by intracellular cholesterol accumulation. Interestingly, PrP^Sc propagation in U18666A-treated cells was partially restored by overexpression of rab 9, which causes redistribution of cholesterol and possibly of PrP^Sc to the trans-Golgi network. Surprisingly, rab 9 overexpression itself reduced cellular PrP^Sc content, indicating that PrP^Sc production is highly sensitive to alterations in dynamics of vesicle trafficking.     

沙枣(Elaeagnus angustifolia L.)体内、外胚胎发育的比较研究

本文应用经典制片法和离体培养法。对沙枣体内、外胚胎发育的各阶段做比较研究。主要区别于原胚期:1)、形态发生:体内只有一种方式,即两极分化方式。而离体的有二种方式,即器官发生和胚状体发生途径。2)、胚性细胞起源:体内只一种起源(即起源于受精卵),离体的胚性细胞的起源有三种方式:a由紧邻表皮细胞的单个薄壁细胞产生;b由表皮细胞横分裂产生和c由表皮及其下的薄璧细胞共同参与产生。3)胚性细胞的细胞学特征:体内发生的合子具明显的极性分化,细胞质、淀粉粒和细胞核集中在合点端。它第一次分裂后,顶、基细胞在细胞学特征上具明显区别。而离体条件下的胚性细胞第一次分裂后无典型的顶、基细胞之分。故也缺乏典型的胚柄细胞。胚分化和成熟期、二者在形态学特征上基本相同     

HIV-1 evades antibody-mediated neutralization through conformational masking of receptor-binding sites

The ability of human immunodeficiency virus (HIV-1) to persist and cause AIDS is dependent on its avoidance of antibody-mediated neutralization. The virus elicits abundant, envelope-directed antibodies that have little neutralization capacity. This lack of neutralization is paradoxical, given the functional conservation and exposure of receptor-binding sites on the gp120 envelope glycoprotein, which are larger than the typical antibody footprint and should therefore be accessible for antibody binding. Because gp120-receptor interactions involve conformational reorganization, we measured the entropies of binding for 20 gp120-reactive antibodies. Here we show that recognition by receptor-binding-site antibodies induces conformational change. Correlation with neutralization potency and analysis of receptor-antibody thermodynamic cycles suggested a receptor-binding-site 'conformational masking' mechanism of neutralization escape. To understand how such an escape mechanism would be compatible with virus-receptor interactions, we tested a soluble dodecameric receptor molecule and found that it neutralized primary HIV-1 isolates with great potency, showing that simultaneous binding of viral envelope glycoproteins by multiple receptors creates sufficient avidity to compensate for such masking. Because this solution is available for cell-surface receptors but not for most antibodies, conformational masking enables HIV-1 to maintain receptor binding and simultaneously to resist neutralization.     

Pathways to neuronal injury and apoptosis in HIV-associated dementia

Human immunodeficiency virus-1 (HIV-1) can induce dementia with alarming occurrence worldwide. The mechanism remains poorly understood, but discovery in brain of HIV-1-binding sites (chemokine receptors) provides new insights. HIV-1 infects macrophages and microglia, but not neurons, although neurons are injured and die by apoptosis. The predominant pathway to neuronal injury is indirect through release of macrophage, microglial and astrocyte toxins, although direct injury by viral proteins might also contribute. These toxins overstimulate neurons, resulting in the formation of free radicals and excitotoxicity, similar to other neurodegenerative diseases. Recent advances in understanding the signalling pathways mediating these events offer hope for therapeutic intervention.