Media Space

Fig. 29 —Head media space with recording density.

Dourish, P., Bly, S. Culture and control in a media space. In Proceedings of the 3 European Conference on Computer-Supported Cooperative Work (ECSCW 93), Dordrecht, The Netherlands, pp. 125-137 (1993)... 

Influency Ability to be persuasive in multiple social contexts and media spaces understanding that each context and space requires a different persuasive strategy and technique... 

Keywords visual programming. Alternate Reality Kit, ARK, computer-based collaborative learning, distributed software systems, local area network. Media Space, motivation, object-oriented, real-time video links, SharedARK, Smalltalk-80, textual programming, virtual reality... 

SharedARK can be thought of as a multi-user, multi-workstation version of the Alternate Reality Kit [12,13] which has been enhanced with a computer-controlled audio-video netwoik. Like ARK, the computer-based component of SharedARK is an interactive, animated environment, in which everything is presented as a visible physical object with velocity and mass. Users employ a mouse-operated hand to press buttons, to carry and even to throw objects across the enormous two-dimensional surface. SharedARK has teen combined with a distributed, computer-controlled audio-video netwoik called the Media Space [14] at PARC in Palo Alto, or the Interactive Intermedia Facility at EuroPARC in Cambridge. Using compressed video and high bandwidth phone lines, SharedARK has teen used in real-time colls orative activities between workstations 600 miles apait. 

One of the astounding dimensions associated with mechanical disk drives is the extremely thin air bearing that separates the media from the head. The reason for such small head/media spacing is quickly apparent when you consider the frequency components for magnetic fields in free space generated by an arbitrary magnetization distribution in a plane at z = 0. Because the fields in free space (z > 0) must satisfy the Laplace equation, the Fourier components of the magnetic field at spatial frequency k decay as... 

This results in a 55 dB signal loss for every increase in spacing equal to a multiple of the recorded bit pattern wavelength. The exponential decay of the stray fields from the recorded pattern in media mandates very small head/media spacing and very small media thickness. 

Boyle, M., Greenberg, S. The Langnage of Privacy Learning from Video Media Space Analysis and Design. ACM Transactions 12, 2 (2005)... 

The Aroma project [17] let users stay in touch by adding to everyday means of communication (such as telephone and email) with a shared media space. The media space was organized as a pair of windows on different workstations, each displaying abstract visual and auditory effects, all together reflecting the state of affairs at the remote site. The visual effects were represented as an abstract, dynamic painting in... 

Zg the conductor outer-media (space/earth return) impedance... 

Mr = remanent magnetization, 6 = layer thickness, d = head-to-medium spacing, Q = a value related to the field gradient of an inductive head ( -0.75),... 

Medium space High space Moderate space Small space... 

Recently we have found a type of tightly bound ATP which exists even in the presence of saturating concentrations of hexokinase (Aflalo, Shavit, 1982) but is exchangeable with exogenous ATP. This bound ATP appears to arise from a free species of ATP sequestered near the active site during photophosphorylation. The slowed down diffusion of the newly made ATP to the outer medium space allows its binding to proximal non-catalytic sites. Thus, mass transfer of nucleotides between the active site and the bulk medium may limit the steady state rate of ATP synthesis and should be considered in proposals on the mechanism of energy transduction. 

In the reaction field method, the space surrounding a dipolar molecule is divided into two regions (i) a cavity, within which electrostatic interactions are sunnned explicitly, and (ii) a surrounding medium, which is assumed to act like a smooth continuum, and is assigned a dielectric constant e. Ideally, this quantity will be... 

Above we described tire nature of Maxwell s equations in free space in a medium, two more vector fields need to be... 

Analogous considerations apply to spatially distributed reacting media where diffusion is tire only mechanism for mixing chemical species. Under equilibrium conditions any inhomogeneity in tire system will be removed by diffusion and tire system will relax to a state where chemical concentrations are unifonn tliroughout tire medium. However, under non-equilibrium conditions chemical patterns can fonn. These patterns may be regular, stationary variations of high and low chemical concentrations in space or may take tire fonn of time-dependent stmctures where chemical concentrations vary in botli space and time witli complex or chaotic fonns. 

Thus far we have considered systems where stirring ensured homogeneity witliin tire medium. If molecular diffusion is tire only mechanism for mixing tire chemical species tlien one must adopt a local description where time-dependent concentrations, c r,f), are defined at each point r in space and tire evolution of tliese local concentrations is given by a reaction-diffusion equation... 

Molecular dynamics simulations are el ficient for searching the conformational space of medium-sized molecules and peptides. Different protocols can increase the elTicieiicy of the search and reduce the computer time needed to sample adequately the available conformations. 

In the case of a porous medium the characteristic difficulties of the intermediate case can be circumvented by a device originally introduced by Maxwell [16] and later exploited in some detail by workers from Oak. Ridge National Laboratory and the University of Maryland [I ]—[21]. The idea was stated very succinctly by Maxwell as follows. "We may suppose the action of the porous material to be similar to that of a number of particles, fixed in space and obstructing the motion of the particles of the moving systems". ... 

A R 1991, A Survey of Methods for Searching the Conformational Space of Small and Medium-iized Molecules. In Lipkowitz K B and D B Boyd (Editors) Reviews in Computational Chemistry /olume 2. New York, VCH Publishers, pp. 1-55. 

Discriminant emalysis is a supervised learning technique which uses classified dependent data. Here, the dependent data (y values) are not on a continuous scale but are divided into distinct classes. There are often just two classes (e.g. active/inactive soluble/not soluble yes/no), but more than two is also possible (e.g. high/medium/low 1/2/3/4). The simplest situation involves two variables and two classes, and the aim is to find a straight line that best separates the data into its classes (Figure 12.37). With more than two variables, the line becomes a hyperplane in the multidimensional variable space. Discriminant analysis is characterised by a discriminant function, which in the particular case of hnear discriminant analysis (the most popular variant) is written as a linear combination of the independent variables ... 

For fast access to the two-electron integrals, a four-dimensional array might be straightforward. The four indices of the four dimensional array correspond to the four basis function indices, p, v, X, and a, respectively. However, the four dimensional array may take a huge main memory or computer disk space even for a medium-size molecule. Therefore, this may not be practical. 

A common surface cartridge is the pleated paper constmction type, which allows larger filtration areas to be packed iato a small space. Oil filters ia the automobile iadustry are of this type. The paper is impregnated, for strength, with epoxy or polyurethane resia. Any other medium ia sheet form, similar to cellulose paper, such as wool, polypropylene, or glass may be used. 

Excited-State Relaxation. A further photophysical topic of intense interest is pathways for thermal relaxation of excited states in condensed phases. According to the Franck-Condon principle, photoexcitation occurs with no concurrent relaxation of atomic positions in space, either of the photoexcited chromophore or of the solvating medium. Subsequent to excitation, but typically on the picosecond time scale, atomic positions change to a new equihbrium position, sometimes termed the (28)- Relaxation of the solvating medium is often more dramatic than that of the chromophore... 

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