Access Time

As an example for an efficient yet quite accurate approximation, in the first part of our contribution we describe a combination of a structure adapted multipole method with a multiple time step scheme (FAMUSAMM — fast multistep structure adapted multipole method) and evaluate its performance. In the second part we present, as a recent application of this method, an MD study of a ligand-receptor unbinding process enforced by single molecule atomic force microscopy. Through comparison of computed unbinding forces with experimental data we evaluate the quality of the simulations. The third part sketches, as a perspective, one way to drastically extend accessible time scales if one restricts oneself to the study of conformational transitions, which arc ubiquitous in proteins and are the elementary steps of many functional conformational motions. 

The isothermal curves of mechanical properties in Chap. 3 are actually master curves constructed on the basis of the principles described here. Note that the manipulations are formally similar to the superpositioning of isotherms for crystallization in Fig. 4.8b, except that the objective here is to connect rather than superimpose the segments. Figure 4.17 shows a set of stress relaxation moduli measured on polystyrene of molecular weight 1.83 X 10 . These moduli were measured over a relatively narrow range of readily accessible times and over the range of temperatures shown in Fig. 4.17. We shall leave as an assignment the construction of a master curve from these data (Problem 10). 

Foams that ate relatively stable on experimentally accessible time scales can be considered a form of matter but defy classification as either soHd, Hquid, or vapor. They are sol id-1 ike in being able to support shear elastically they are Hquid-like in being able to flow and deform into arbitrary shapes and they are vapor-like in being highly compressible. The theology of foams is thus both complex and unique, and makes possible a variety of important appHcations. Many features of foam theology can be understood in terms of its microscopic stmcture and its response to macroscopically imposed forces. 

For data storage two types of memory are distinguished (/) main memory with moderate capacity (currentiy 4 x 10 bit in each element) and extremely short access time (<10 s), and (2) mass memory with very high capacity (>10 bit in each element) and moderate access time (>10 s). 

ISO-Nomi 9660), respectively. This is equivalent to 200,000 pages of text. The access time is between 200 and 600 ms. The data transfer rate of a standard audio CD player is 144 KB/s, but dedicated CD-ROM drives can transfer data at up to 300 KB/s by doubling the rotational speed of the disk. 

MO Media Summary. When compared to magnetic recording on hard disks, the advantage of MO data storage is the removabiUty of the disks and the high storage capacity (especially on multiplatter (juke-box) systems) whereas the access times have not yet been reached. 

The question as to whether and to what extent and in what area optical mass storage would replace magnetic systems (disk, tape) was controversially being discussed in the 1980s. In spite of all predictions of an imminent substitution, as of late 1994 magnetic hard disks stiU are the system of choice for computer-dedicated mass storage due to their speed (access time, transfer rate), physical size, and energy consumption this is especially tme when memory-intensive appHcations are mn which use the hard disk as virtual memory. 

More microprocessor-based process equipment, such as smart instruments and single-loop controllers, with digital communications capability are now becoming available and are used extensively in process plants. A fieldbus, which is a low-cost protocol, is necessary to perform efficient communication between the DCS and these devices. So-called mini-MAP architec ture was developed to satisfy process control and instrumentation requirements while incorporating existing ISA standards. It is intended to improve access time while... 

Today, dynamic random-access memories (DRAMs) are transistor/capacitor-based semiconductor devices, with access times measured in nanoseconds and very low costs. Core memories were made of magnetic rings not less than a millimetre in diameter, so that a megabyte of memory would have occupied square metres, while a corresponding DRAM would occupy a few square millimetres. Another version of a DRAM is the read-only memory (ROM), essential for the operation of any computer, and unalterable from the day it is manufactured. We see that developments in magnetic memories involved dramatic reductions in cost and... 

The MARS program access resource file data by means of general functions which allow the program to load the necessary resource file into memory, search for variables, edit variables, and re-save the file to disk. Any number of resource files can be loaded into memory at once. Even quite large resource files are loaded rapidly into memory since the data is packed and no assignments are made at that time. The search and replace functions are also so fast that data access time is never perceptible. 

Synchrotrons have the advantage of brighter beams, multiple wavelength availabihty, and a more focused beam, all of which can greatly improve the quality of data and may be essential for the experiments that are to be carried out. The synchrotrons I have worked at are staffed by excellent people however, they do assume a certain level of user competence and are probably not the place to go to learn how to diffract crystals. Synchrotrons will grant time to users in a peer-reviewed process and generally have quite rapid access times (usually booked per 24-h slot). 

In order to proceed further, a significant step in instrument development was needed, which was achieved with the IN 15 instrument at the Institut Laue Langevin in Grenoble [22,23]. This instrument routinely accesses time scales in the order of 200 ns and opens opportunities for exploring dynamic phenomena that were previously inaccessible. Figure 3.17 and Fig. 3.18 display experimental results from a M =36 kg/mol PE sample on the dynamic single chain struc-... 

Physical integration is mainly a matter of technical or practical import. It may be necessary to make local copies of some data sources in order to ensure reliability or to reduce access times. For example, in the WWW (World Wide Web), Internet service providers often use local caches of popular web sites to improve access time. Because of the way certain servers operate, it may be necessary to have local copies of all data. 

Even with these limitations, holographic data storage using an all optical procedure is an attractive option since it offers the potential for storing terabytes of information with high transfer rates and short access times. ... 

Note Access time for files stored on a NFS mounted disk will usually be longer than for the PC s dedicated hard disk(s). The actual time will depend on the type of network and the amount of network traffic and consequently may vary during the course of the working day. 

Again, this is a rather unwieldy expression. Since the arguments of the exponential and complementary error functions are generally large at experimentally accessible times, this expression can be simplifed to... 

In order to estimate this term with sufficient accuracy, its magnitude has to be at least 10% of the total value of q(t) at the shortest accessible time, say t> 100 ps. This leads to the condition l < ca. 900 s 1/2, which corresponds to k values between 0.1 and lcms-1. However, the time-independent double-layer contribution, qc, has to be subtracted from q(t) first and this may reduce the accuracy of the kinetic information. Therefore, an upper limit for kt similar to that of the chronoampero-metric technique seems more realistic. The value of qc has to be determined separately from a chronocoulogram recorded in the absence of the electroactive species. 

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