Electron pulse

Bits are put together as bytes. This example is an 8-bit byte. Faster, more powerful computers have more bits to the byte (16, 32, 64). In reading a byte, the bits flow one after the other out of the byte as electronic pulses (a positive voltage for on and zero for off). 

A series of consecutive time bins covers a length of time of a few milliseconds, with each bin representing a time of only a fraction of a nanosecond. When an ion arrives at the microchannel array detector, one time bin notes the resulting electronic pulse. 

All information into or out of a computer is therefore not continuous (analog) but flows as bits switched on and off (digital), like a series of electronic pulses. 

If the solvent is water, the electron pulse produces several stable and unstable species. They arise from the energy transferred to water molecules by the electron beam and include e, HO", H, H+, H2, and H2O2. It is customary to express the yields of these products by referring to their G-values. They represent the number of a given species formed per 100 eV of energy absorbed by the water. The following equation uses the G-values as the coefficients ... 

Reactions such as these are of interest in themselves. Beyond that, one can use the pulse radiolysis experiment as a preparative technique for other species. Thus, the reactions of numerous aliphatic, carbon-centered radicals have been evaluated.22 If one employs a reasonably high concentration of solute, say 0.1-1 M CH3OH, the formation of CH2OH is complete within the electron pulse. Following that, reactions such as the following can be studied ... 

Baxendale, J. H., Busi, F. (eds.) The study of fast processes and transient species by electron pulse radiolysis, D. Reidel Publishing Co., Dordrecht 1982... 

Distance dependence of the hole transfer process from the G-region (5 -GTGTGTG-3 ) to the Py moiety was studied via pulse radiolysis of 5 -Py-conjugated ODNs with a different number of intervening A-T base pairs between the G-region and Py moiety (PyODNn (n= 1 5)) (Scheme 3). Transient absorption with a maximum peak at 470 nm assigned to Py + was observed after the electron pulse during the pulse radiolysis (Fig. 2). This initial for-... 

Fig.2 Transient absorption spectra of PyODN 1 observed several times after the electron pulse. The inset shows the time profile of the transient absorption peak of Py + at 470 nm, which corresponds to the direct oxidation of Py with S04 (Scheme 3, path a)...

Transient absorption with a peak at 410 nm, assigned to TIOH+, was observed after the electron pulse during the pulse radiolysis (Fig. 5). Together with the decay of TIOH+, transient absorption with a maximum peak at 520 nm assigned to Ptz +was observed. In the case of PtzODNl, the observed formation rate of Ptz + and decay rate of TIOH+ were almost the same (Fig. 6a). Therefore, the hole transfer from G + to Ptz in DNA is faster than the diffusional process for PtzODNl (kht>kobs=l-4xl05 s 1). 

Fig. 9 Transient absorption spectra observed at 5 and 100 ps after the electron pulse during pulse radiolyses of a Py-4 and b Ptz-4 in N20-saturated aqueous solution containing 0.2 mM ODN (strand cone.), 20 mM Na phosphate buffer (pH 7.0), and 2 mM T12S04... 

Fig. 10 Transient absorption spectra observed at 5 and 100 /is after the electron pulse during pulse radiolyses of a PtzPy-1 and b PtzPy-3. Also shown are time profiles of the transient absorption of Py + and Ptz + observed at 470 and 520 nm for c PtzPy-1 and d PtzPy-3, respectively...

On the other hand, when the distance between Py and Ptz was longer (PtzPy-3) with five A-T base pairs, the formation and decay of Py + were observed in the time range of 0-100 /zs after an electron pulse. At 100 /US only Ptz + was observed (Fig. 10b). This result indicates that a hole migrates from Py + to Ptz within 100 fis. >From the time profiles of absorption peaks at 470 nm for Py + and 520 nm for Ptz +, secondary formation of Ptz + was also observed concomitant with the decay of Py + for PtzPy-3, while no secondary formation of Ptz + was observed for PtzPy-1 due to the rapid hole transfer (Fig. 10c,d). The rate constant of the hole transfer from Py + to Ptz was determined to be 2.0X104 s 1 for PtzPy-3 from the decay of Py +. 

These results demonstrate that the hole transfer rate decreases with the increase of the distance between Py and Ptz (Scheme 7, path b). When Ptz and Py were separately conjugated to different ODNs, both Py + and Ptz + were observed at 100 /zs after the electron pulse during pulse radiolysis of the mixture of 0.2 mM each of Py- and Ptz-conjugated ODNs in other words no interstrand hole transfer occurred. Therefore, the observed results are accounted for by intramolecular processes. 

As a heavy metal azide, it is considerably endothermic (A// +279.5 kJ/mol, 1.86 kJ/g). While pine silver azide explodes at 340°C [1], the presence of impurities may cause explosion at 270° C. It is also impact-sensitive and explosions are usually violent [2], Its use as a detonator has been proposed. Application of an electric field to crystals of the azide will detonate them, at down to — 100°C [3], and it may be initiated by irradiation with electron pulses of nanosecond duration [4], See other catalytic impurity incidents, irradiation decomposition... 

Hentz and Kenney-Wallace (1972, 1974) made a detailed study of esin 25 neat alcohols and three alkane solutions in 1-hexadecanol at 30° using a 5-ns electron pulse. Most data were new, but in some cases they confirmed earlier observations (Dorfman, 1965 Baxendale and Wardman, 1971). The authors found the spectrum fully developed at the end of the pulse, with no spectral change thereafter. The spectra are all broad, asymmetric, and structureless,... 

Gas Ionization Counters A common gas ionization counter is the Geiger-Muller counter where the electronic pulses derived from the ionization process are registered as counts. The instrument can be adjusted to detect only radiation with a desired penetrating power. 

Electrical methods involve the detection and analysis of electronic pulses generated by droplets in a measurement volume or on a wire. The electronic signals are then converted into digital data and calibrated to produce information on droplet size distribution. A detailed review of electrical methods for droplet size measurements has been made by Jones.[657]... 

Baxendale, J.H. Busi, F., Eds. The Study of Fast Processes and Transient Species by Electron Pulse Radlolysls D. Reidel Dordrecht, 1982. 

FIGURE 9.10 An illustration of the single-beam flame atomic absorption optical path. The modulated light from the source is created either by a chopper or through electronic pulsing. 

After radiation, a strong upsurge in conductivity then decreased and leveled off after about an hour. This was analyzed in terms of trap filling, which showed a linear dependence on the exposure rate, X, at the radiation induced current Ir. For this polymer, mobility of the holes greatly exceeded that of electrons.(12) Additional studies done by electron pulse... 

In a third method for lifetime measurements, the levels to be investigated are excited by a short pulse and subsequently the number of fluorescence quanta is counted as a function of the delay time (e.g. with a multichannel analyzer and a time-to-pulse height converter). The experimental procedure is described by Bennet 2 and has been perfected by several authors using light pulses 22) or electron pulses 23) for excitation. 

---