Cumulative Shifts Research Articles

Collapse as Cultural Revolution: Power and Identity in the Tiwanaku to Pacajes Transition

Inherent foundations of power are often made explicit in state collapse and ethnogenesis, among the most problematic processes tackled by archaeologists. Recent research on collapse globally indicates that conventional models prioritizing external change (e.g., environmental shift, immigration) fail to address the historical intricacies of and human agency involved in state fragmentation. Some recent models treat collapse as a sudden drop in political complexity, and most fail to elaborate how state collapse influenced postcollapse sociopolitical and cultural patterns. Synthesizing substantial recent research on Tiwanaku (A.D. 500–1150) and post-Tiwanaku Pacajes (A.D. 1150–1450) polities in the south-central Andes, I suggest that state collapse involved a fateful conjunction of sociopolitical and environmental transformations. Drought conditions descended upon a centralized yet highly fragile sociopolitical landscape that had become increasingly volatile during Tiwanaku's apogee. Collapse involved rapid transformation as well as slow, cumulative shifts and enduring continuities. It was a cultural revolution that began during Tiwanaku hegemony and drew heavily on existing practices and ideals. Grounded in practice theory, this case study finds human agency squarely in the center of macroprocesses such as collapse and situates Andean foundations of power in the matrix of local ideals, practices, and identities from which hegemonic regimes such as Tiwanaku were forged.

Collapse as Cultural Revolution: Power and Identity in the Tiwanaku to Pacajes Transition

Inherent foundations of power are often made explicit in state collapse and ethnogenesis, among the most problematic processes tackled by archaeologists. Recent research on collapse globally indicates that conventional models prioritizing external change (e.g., environmental shift, immigration) fail to address the historical intricacies of and human agency involved in state fragmentation. Some recent models treat collapse as a sudden drop in political complexity, and most fail to elaborate how state collapse influenced postcollapse sociopolitical and cultural patterns. Synthesizing substantial recent research on Tiwanaku (A.D. 500–1150) and post‐Tiwanaku Pacajes (A.D. 1150–1450) polities in the south‐central Andes, I suggest that state collapse involved a fateful conjunction of sociopolitical and environmental transformations. Drought conditions descended upon a centralized yet highly fragile sociopolitical landscape that had become increasingly volatile during Tiwanaku's apogee. Collapse involved rapid transformation as well as slow, cumulative shifts and enduring continuities. It was a cultural revolution that began during Tiwanaku hegemony and drew heavily on existing practices and ideals. Grounded in practice theory, this case study finds human agency squarely in the center of macroprocesses such as collapse and situates Andean foundations of power in the matrix of local ideals, practices, and identities from which hegemonic regimes such as Tiwanaku were forged.

Effects of Accenting and Regularity on the Detection of Temporal Deviations: Does Regularity Facilitate Performance?

In an experiment on the effect of intensity accents on the perception of time intervals between tones. H. G. Tekman (2001) found that the regular placement of deviant time intervals in short sequences of tones reduced detection, especially if intensity accents marked the deviant time intervals. That was the opposite of what one wòuld have expected on the basis of the dynamic attending theory of M. R. Jones (1976). The effect might have occurred because temporally deviant tones create cumulative onset shifts that affect all the subsequent tones. If the deviations were randomly placed, then they could follow each other in close succession and change the local tempo. In the present study, the changes of local tempo, which might have acted as a cue for the detection of temporal deviations in the random sequences, were eliminated by compensating for deviant time intervals with equal deviations in the opposite direction in the interval that followed. That change in the stimuli eliminated the negative main effect of regularity, and the accenting interacted with regularity in favor of detection in the regular sequences. However, a simple advantage of regular over random sequences was not observed. The author discusses possible reasons for the lack of a facilitatory effect of regularity.

Computer-aided bootstrap generation of characteristic curves for radiographic imaging systems.

Determination of the characteristic curve is essential for quantitative evaluation of digital as well as screen-film radiographic imaging systems. When it is not practical to generate the entire curve through variation of a single exposure parameter, bootstrap methods can be used. For the bootstrap method used here, curve segments are generated by varying one exposure parameter and multiple segments are produced at different exposure levels by varying a second parameter. The segments then are joined to form a single composite characteristic curve. If the second parameter is one for which the sensitivity of the receptor is not constant (such as x-ray tube potential or beam filtration), the shift of each segment along the log relative-exposure axis needed to join the overlapping curve sections is not known and some form of segment matching must be employed. A spline interpolation method and a polynomial fit integral method were developed for automatic segment matching and compared. For both methods, the shifts between successive segment pairs which result in optimal overlap are determined and the cumulative shifts to obtain the complete composite curve are calculated for all segments. The two methods are evaluated for several image receptors and with a known curve generated from an analytic function. Both methods closely agreed in the shifts determined for the image receptors and provided a good visual matching of the curve segments. The spline interpolation method more accurately determined the appropriate shifts for the mathematically generated curve segments. The bootstrap methods can provide complete, accurate characteristic curves, and the segment joining program makes the process fast and precise.

Ultra-high-field MAS NMR assay of a multispin labeled ligand bound to its G-protein receptor target in the natural membrane environment: electronic structure of the retinylidene chromophore in rhodopsin.

11-Z-[8,9,10,11,12,13,14,15,19,20-(13)C10]Retinal prepared by total synthesis is reconstituted with opsin to form rhodopsin in the natural lipid membrane environment. The 13C shifts are assigned with magic angle spinning NMR dipolar correlation spectroscopy in a single experiment and compared with data of singly labeled retinylidene ligands in detergent-solubilized rhodopsin. The use of multispin labeling in combination with 2-D correlation spectroscopy improves the relative accuracy of the shift measurements. We have used the chemical shift data to analyze the electronic structure of the retinylidene ligand at three levels of understanding: (i) by specifying interactions between the 13C-labeled ligand and the G-protein-coupled receptor target, (ii) by making a charge assessment of the protonation of the Schiff base in rhodopsin, and (iii) by evaluating the total charge on the carbons of the retinylidene chromophore. In this way it is shown that a conjugation defect is the predominant ground-state property governing the molecular electronics of the retinylidene chromophore in rhodopsin. The cumulative chemical shifts at the odd-numbered carbons (Delta(sigma)odd) of 11-Z-protonated Schiff base models relative to the unprotonated Schiff base can be used to measure the extent of delocalization of positive charge into the polyene. For a series of 11-Z-protonated Schiff base models and rhodopsin, Delta(sigma)odd appears to correlate linearly with the frequency of maximum visible absorption. Since rhodopsin has the largest value of Delta(sigma)odd, the data contribute to existing and converging spectroscopic evidence for a complex counterion stabilizing the protonated Schiff base in the binding pocket.

Mutations in the S4 domain of a pacemaker channel alter its voltage dependence

In an attempt to study the functional role of the positively charged amino acids present in the S4 segment of hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels, we have introduced single and sequential amino acid replacements throughout this domain in the mouse type 2 HCN channel (mHCN2). Sequential neutralization of the first three positively charged amino acids resulted in cumulative shifts of the midpoint voltage activation constant towards more hyperpolarizing potentials. The contribution of each amino acid substitution was approximately −20 mV. Amino acid replacements to neutralize either the first (K291Q) or fourth (R300Q) positively charged amino acid resulted in the same shift (about −20 mV) towards more hyperpolarized potentials. Replacing the first positively charged amino acid with the negatively charged glutamic acid (K291E) produced a shift of approximately −50 mV in the same direction. None of the above amino acid substitutions had any measurable effect on the time course of channel activation. This suggests that the S4 domain of HCN channels critically controls the voltage dependence of channel opening but is not involved in regulating activation kinetics. No channel activity was detected in mutants with neutralization of the last six positively charged amino acids from the S4 domain, suggesting that these amino acids cannot be altered without impairing channel function.

Diffraction effects in single- and two-laser photothermal lens spectroscopy

A simple method for calculating the effects of optical geometry on photothermal lens signals is shown. This method is based on calculating cumulative electric-field phase shifts produced by a series of Gaussian refractive-index perturbations produced by the photothermal effect. Theoretical results are found for both pulsed-laser and continuous Gaussian laser excitation sources and both single- and two-laser apparatuses commonly employed in photothermal lens spectroscopy. The effects of apparatus geometry on the resulting signal are shown. Analytical time-dependent signal results are found for small signals. Analytical pump-probe focus geometry results allow direct optimization for certain conditions. The calculations indicate that the photothermal lens signal is, in general, optimized for near-field detection-plane geometries.

Effect of cumulative directional attention shifts on the comparison and integration of visual stimuli.

Effect of cumulative directional attention shifts on the comparison and integration of visual stimuli.

Effect of cumulative directional attention shifts on the comparison and integration of visual stimuli.

Effect of cumulative directional attention shifts on the comparison and integration of visual stimuli.