不同时相日光下颜色的恒常性

一、前言 在光源光谱成份改变的条件下,我们周围物体的颜色在眼睛看来保持相对不变,称为颜色恒常性。1807年Thomas Young首先描述了颜色恒常性现象,他指出室内不管是由蜡烛的黄光或火焰的红光来照明的,书页纸仍然看来是白色的。Young认为,外界某一表面的颜色外观,并不完全决定于网膜的红、绿、蓝三种感受器的吸收特性,而也依赖于周围其它物体射入眼睛的光通量。此后,E.Hering对颜色恒常性做了实验表演。一般认为颜色恒常性是对环境照明感受性的降低。视觉通道只传递由物体表面所反射的光谱成     

Alpha3-integrins are required for hippocampal long-term potentiation and working memory

Integrins comprise a large family of heterodimeric, transmembrane cell adhesion receptors that mediate diverse neuronal functions in the developing and adult CNS. Recent pharmacological and genetic studies have suggested that beta1-integrins are critical in synaptic plasticity and memory formation. To further define the role of integrins in these processes, we generated a postnatal forebrain and excitatory neuron-specific knockout of alpha3-integrin, one of several binding partners for beta1 subunit. At hippocampal Schaffer collateral-CA1 synapses, deletion of alpha3-integrin resulted in impaired long-term potentiation (LTP). Basal synaptic transmission and paired-pulse facilitation were normal in the absence of alpha3-integrin. Behavioral studies demonstrated that the mutant mice were selectively defective in a hippocampus-dependent, nonmatch-to-place working memory task, but were normal in other hippocampus-dependent spatial tasks. The impairment in LTP and working memory is similar to that observed in beta1-integrin conditional knockout mice, suggesting that alpha3-integrin is the functional binding partner for beta1 for these processes in the forebrain.     

Exploring the Possibility of Shared Familial Diathesis for Personality in OCD Probands

The present study aims to probe into the status of the big five personality factors in the OCD probands and their first degree relatives (FDR) viz a viz community controls and also look into the association of the big five factors with symptom severity and obsessive personality traits. Fifty dyads of probands and FDR and community controls matched on the basis of age, sex and education were assessed on NEO Five Factor Inventory, Yale Brown Obsession Compulsion Scale, Beck Depression Inventory and Leyton Obsessional Inventory to fulfill the aims of the study. The findings reveal higher neuroticism and lower extroversion and conscientiousness in the OCD group as compared to controls, endorsement of greater conscientiousness among the FDR as compared to the case-probands, with Agreeableness and Conscientiousness emerging as predictors associated with obsessive symptoms among OCD probands.     

On the short-range order in Al-Mn quasicrystals during low-temperature ageing

Abstract

We report the evolution of diffuse intensity during the low-temperature ageing of Al-Mn quasicrystals. This is taken as evidence of short-range order in the icosahedral phase prior to its decomposition. The implication of these diffuse intensities is discussed     

Indulgence as self‐reward for prior shopping restraint: A justification‐based mechanism

This research investigates the effects of refraining from a purchase temptation at one point in time on choices made at a subsequent opportunity to purchase or consume a tempting product. Four experiments involving scenarios and real decisions demonstrate that the salience of restraint at a prior impulse buying opportunity causes consumers to reward themselves subsequently by choosing indulgence over non-indulgence. We show that indulgence is likely to increase only when prior restraint is salient and hence can be used as a justification. As expected, an index of reasons for vs. against buying mediates the relationship between prior impulse purchase decision and indulgent choice. In further support of the mechanism, we find that prior indulgence can have the same effect as prior restraint, if the prior indulgence is made justifiable. Finally, we show that prior shopping restraint can increase indulgence without a corresponding increase in self-esteem. These findings extend our understanding of self-regulation and demonstrate that everyday consumer decisions such as responses to impulse buying opportunities can have consequential downstream effects.     

Transformation of the decagonal quasicrystalline phase to a B2 crystalline phase in the Al-Cu-Co system by high-energy ball milling

Samples of a decagonal quasicrystalline phase, located in the Al-Cu-Co system and synthesized by a slow cooling technique, have been mechanically milled in a high-energy planetary ball mill for 10, 20 and 30h. The milled powders, as well as powders that had been annealed (after milling) for times ranging from 30 to 150min at 600C, were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A phase transformation from the decagonal phase to a B2 crystalline phase during highenergy ball milling is reported here for the first time. Powders milled for more than 10h contained predominantly the B2-type crystalline phase with a lattice parameter of 0.29nm. This crystalline phase was found to be quite stable after milling for 30h and also on subsequent annealing at 600C. These experimental results lend support to an earlier suggestion that the decagonal phase in Al-Cu-Co is actually less stable than the B2 phase at low temperatures.     

Formation of Al3Ni2-type nanocrystalline τ 3 phases in the Al–Cu–Ni system by mechanical alloying

An elemental powder mixture of Al (70 at.%), Ni (15 at.%) and Cu (15 at.%) was milled in a high-energy ball mill for various times ranging from 10 to 100?h to form ternary intermetallic alloys. X-ray diffraction and transmission electron microscopy techniques were employed for characterization of the samples. The dissolution of the individual elements into an alloy led to the formation of a τ₃ vacancy-ordered phase after 100?h of milling. This phase was found to be quite stable against milling, and no other crystalline and amorphous phases could be detected. The powder after 100?h of milling was found to contain mostly τ₃ nanophases with partial ordering, and with crystallite sizes in the range 10–20?nm along with a lattice strain of ～0.675%. The milled powder, after annealing at 700°C for 20, 40 and 60?h, revealed the formation of a strain-free and ordered τ₃ phase with a crystallite size of 80?nm, indicating grain coarsening. It is interesting to note that the mechanical energy imparted during milling could not completely destroy the vacancy ordering in the τ₃ phase, unlike other stoichiometric Al–Cu–transition metal (TM) systems, where the disordered B2 (bcc) phase is commonly observed instead of any vacancy-ordered phases.     

Evolution of superlattice order in Al–Mn quasicrystals and its relation to face-centred icosahedral quasicrystals

Abstract

We have established a simple icosahedral to face-centred icosahedral ordering transformation in Al–Mn quasicrystals. This result strongly supports the view that the recently discovered face-centred icosahedral quasicrystal in ternary Al–Cu–Fe and related alloys represents a long-range superstructure of simple icosahedral quasicrystals