Local addition

Critical periods may vary depending on the area of the brain and the activity involved. Despite the evidence that patterns of neural activity influence the organization of neuronal circuitry, the mechanisms involved remain elusive. Neuronal activity drives the selective survival and sprouting of branches, accompanied by the local addition of synapses, within appropriate areas furthermore, the lack of activity promotes the pruning of synaptic connections from inactive areas (Katz and Shatz, 1996). These competitive processes increase the refinement and precision of maps and require the activity of excitatory receptors (Constantine-Paton et ah, 1990 Antonini and Stryker, 1993) and locally released growth factors (Thoenen, 1995 Inoue and Sanes, 1997). 

The mean curvature is the local rate of interface area change with a local addition of volume.4 This is perhaps the most important aspect of curvature, especially when combined with 7, which is the work required to create an interface per unit area, A. Imagine that in a pure material the addition of a small volume makes an interface develop a localized small bump. The statement above implies that k = AA/AV in the limit of small volumes therefore, the work to create the bump is 7 A A = yuAV, where 7 is the interfacial energy per unit area (see Eq. 3.73). Equating this work to the work done by the system P AV, where P is the net pressure on the interface... 

The weighted mean curvature is the local rate of interfacial energy change with a local addition of volume. This establishes the connection to the work, 8W, to pass a small volume of material, 8V, through an interface. 8W/8V = /c7(f), in the limit of small volumes. 

Hagerberg, D. (2003). The growth of external ectomycorrhizal mycelia in the field in relation to host nutrient status and local addition of mineral sources. Unpublished Ph.D. thesis, Lund University, Lund, Sweden. 

The elements of the chondritic meteorites, and hence of the terrestrial planets, were formed in previous generations of stars. Their relative abundances represent the result of the general chemical evolution of the galaxy, possibly enhanced by recent local additions from one or more specific sources just prior to collapse of the solar nebula —4.56 Gyr ago. A volumetrically minor, but nevertheless highly significant part of this chemical inventory, is comprised of radioactive elements, from which this age estimate is derived. The famihar long-lived radionuclides, such as Th, Rb, K, and others,... 

We will discuss results of a numerical model that represent the shape-evolution behavior of the system. Deposit profiles within high aspect-ratio lines and vias are presented. The model predicts a different filling behavior in lines than in vias. The local additive flux along the feature sidewall, as well as the inhibition function, give useful insight into the mechanism of superfilling. 

Chemiluminescence in the 450- to 360-nm range resulting from collisions of P" ions with H2 or D2 molecules (center-of-mass kinetic energies Ec.m. = 2.3 to 12.2 eV) was Identified with the A- X emission of PH+ and PD+ ions. A spectral analysis has been performed at the maximum cross section (Ecm. = 6.4 eV) by comparison with computer-simulated spectra which were based on the spectroscopic constants of [7, 9, 10] besides the already known 0- 1, 0 0, and 1- 0 bands, some new bands, 1- 1 for PH+ and 2 0, 1- 2, 0 2 for PD+, could be localized. Additional experiments were carried out to verify that the observed emission is indeed due to the chemiluminescent exchange reaction P ( P, D)+H2 PH-"(A 2A)+H and not to collisionally excited PH+ impurities in the P+ beam [11]. 

In addition to excess carrier effects, van Roosbroeck and Casey (1972) have noted that for these relaxation semiconductors, the recombination front is established at the anode, which thus is where the voltage drop, and therefore heating, occurs. The kinetics are locally enhanced because of this local, additional, thermal effect. 

As was noted in the study of evolution of compositional variations in Section 9.6.4, the local rate of mass accumulation due to a mass flux vector is the negative of the flux divergence. The local addition of material is represented in continuum modeling as a stress-free volumetric strain. At fixed overall strain, the rate of material addition induces a proportional rate of increase in mean normal compressive stress. In the present onedimensional configuration, this connection is expressed as... 

Figure 25. Local addition of a helical turn to a ribbon of directors (see text).

The (arene)Cr(CO)3 complex is neutral and so is not a very powerful electrophile. In the styrene case, when an ester is placed at the other end of the alkene, Michael addition to the acrylate unit occurs in high yield. Even with a chlorine leaving group on the arene complex (see Section 14.3.5), no local addition was observed [201]. Comparable examples of cationic RuCp complexes with cyanide and thiophenol as the nucleophile give examples where the nucleophile has added to the face of the ligand that carries the metal, and it is proposed that this is the favored kinetic approach [202]. 

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