Rapid Dynamic Changes Research Articles

UV Laser Cross-linking: A Real-Time Assay to Study Dynamic Protein/DNA Interactions During Chromatin Remodeling

We describe the use of laser ultraviolet (UV) cross-linking to study the interaction of transcription factors with in vitro assembled chromatinized DNA templates in real time. Because the laser source delivers a high density of photons in a single ns pulse, the cross-linking reaction is completed in less than 1 microseconds, allowing the investigator to freeze rapid dynamic changes in protein-DNA interactions. Using this approach, we have sampled the dynamic equilibrium of the glucocorticoid receptor (GR) and the chromatin remodeling complex (SWI/SNF) during adenosine triphosphate (ATP)-dependent chromatin remodeling on a chromatinized mouse mammary tumor virus promoter in vitro. UV laser cross-linking shows that the GR and SWI/SNF complex undergoes a periodic binding and displacement event during the process of chromatin remodeling. The assay provides unique information regarding the equilibrium of protein-DNA interactions in real time and can be easily adapted to study the dynamic events in the assembly and disassembly of other multiprotein complexes on chromatin or DNA templates.

Envelope Tracking Techniques for Flicker Mitigation and Voltage Regulation

Envelope tracking has many important applications in electrical distribution systems for either flicker meters or flicker compensators. This paper presents a novel control technique for flicker mitigation. This technique is based on the instantaneous tracking of the measured voltage envelope. The ADAptive LINEar neuron (ADALINE) algorithm, and the Recursive Least Square (RLS) algorithm are introduced for the flicker envelope tracking. The ADALINE algorithm is characterized by a light computational demand, unlike that of existing techniques; the RLS algorithm outperforms the ADALINE algorithm by its fast convergence and robust tracking performance. Both the ADALINE and the RLS algorithms give accurate results even under rapid dynamic changes. The paper investigates the effects of different parameters on the performance of the ADALINE algorithm and that of the RLS algorithm. Extensive simulations of the proposed flicker tracking algorithms are conducted to evaluate their performance for the tracking and mitigation of voltage flicker. The ADALINE and the RLS algorithms are examined by tracking and mitigating the flicker produced by a resistance welder and an arc furnace in a simple distribution system simulated in the PSCAD/EMTDC package.

Estimation techniques for voltage flicker envelope tracking

Flicker envelope tracking has many important applications in distribution systems for either flicker meters or flicker compensators. This paper introduces a new application of the adaptive linear neuron (ADALINE), and the recursive least square (RLS) algorithm for flicker envelope tracking. The ADALINE is characterized by a light computational demand, unlike that of existing techniques; the RLS algorithm betters the ADALINE by its fast convergence and robust tracking performance. Both the ADALINE and the RLS algorithm give accurate results even under rapid dynamic changes. The paper investigates the effects of different parameters on the ADALINE and the RLS algorithm. Extensive simulations of the proposed flicker tracking algorithms are conducted to evaluate their performance. The ADALINE and the RLS algorithm are examined by tracking the flicker produced by a resistance welder in a simple distribution system simulated in the PSCAD/EMTDC package.

Managerial competency modelling and the development of organizational psychology: A Chinese approach

In recent years, China has undergone rapid economic reform and dynamic organizational changes. Several major developments have given special momentum to those changes: China entering the WTO, opening the western regions of China, building up an information network, transforming new management systems nationwide, and encouraging innovations and entrepreneurship. These developments call for more comprehensive and adaptive competencies and new approaches to organizational psychology in China. This provides a national and cultural context of personnel assessment, selection, and development of organizational psychology. Organizational psychology is one of the most active fields for research and application in psychology in China. Three aspects of recent trends are described under a framework of managerial competency modelling. (1) Leadership competence assessment for personnel selection and development has become one of the key aspects of human resources (HR) management in China. Based upon the results from the structured interview and strategic hierarchical job analysis, a model of leadership competency with four dimensions of leadership characteristics and the managerial performance was proposed. The four dimensions are: psychological traits; leadership predispositions; managerial skills; and professional knowledge. (2) HR competency for person‐job‐organization fit. This includes competencies for compensation and motivational strategies, organizational commitment and career management competence, team competence, and group decision‐making skills. (3) Organizational competency for culture and change. This includes an integrative approach to link values with culture, and cross‐cultural leadership skills. On the basis of the recent practice and research developments, a Chinese approach to organizational psychology with important characteristics is summarized: active theoretical development and conceptualization; continuous methodological improvement; close link with HR and management practices; and systematic cross‐cultural socioeconomic perspective. This becomes a key framework for understanding organizational psychology. New directions for research and application in China are highlighted.

Temporal gradients in shear stimulate osteoblastic proliferation via ERK1/2 and retinoblastoma protein.

Bone cells are subject to interstitial fluid flow (IFF) driven by venous pressure and mechanical loading. Rapid dynamic changes in mechanical loading cause transient gradients in IFF. The effects of pulsatile flow (temporal gradients in fluid shear) on rat UMR106 cells and rat primary osteoblastic cells were studied. Pulsatile flow induced a 95% increase in S-phase UMR106 cells compared with static controls. In contrast, ramped steady flow stimulated only a 3% increase. Similar patterns of S-phase induction were also observed in rat primary osteoblastic cells. Pulsatile flow significantly increased relative UMR106 cell number by 37 and 62% at 1.5 and 24 h, respectively. Pulsatile flow also significantly increased extracellular signal-regulated kinase (ERK1/2) phosphorylation by 418%, whereas ramped steady flow reduced ERK1/2 activation to 17% of control. Correspondingly, retinoblastoma protein was significantly phosphorylated by pulsatile fluid flow. Inhibition of mitogen-activated protein (MAP)/ERK kinase (MEK)1/2 by U0126 (a specific MEK1/2 inhibitor) reduced shear-induced ERK1/2 phosphorylation and cell proliferation. These findings suggest that temporal gradients in fluid shear stress are potent stimuli of bone cell proliferation.

A Survey of large, rapid solar wind dynamic pressure changes observed by Interball-1 and IMP 8

Abstract. The high time-resolution solar wind ion flux measurements from Interball-1 and IMP 8 show about one hundred large, rapid dynamic the pressure changes each year. We cataloged these events by the size and transition time of the pressure changes and present a statistical survey of these events. We find that the majority of the pressure changes of more than 1–2 nPa occur over a very short time period, on the order of a few minutes or less. Most of the large pressure changes not associated with shocks are due solely to density changes with speed remaining constant. We find that pressure balance between the thermal and magnetic pressures is not maintained across most of these events, so these events are still evolving.Key words. Interplanetary physics (solar wind plasma)

Continuous Long-term Measurements of the Middle Ear Pressure in Subjects without a History of Ear Disease

A new method was used for continuous measurement of the middle ear (ME) pressure during a 24-h period. In 10 subjects without a history of ear disease a small perforation was made through the tympanic membrane. A tight rubber stopper containing a small polyethylene tube was fitted into the external ear canal. Conventional tubal function tests were performed. The equipment was then carried by the subjects for 24 h of normal activity to monitor any slow or rapid dynamic pressure change in the ME. Body position was found to be the most important factor affecting ME pressure variation, during the 24-h continuous pressure measurements. A significant pressure rise occurred in the recumbent position in all but one subject. Few rapid pressure equilibrations were seen during the recordings, indicating few tubal openings. This implies that the pressure changes in the ME seen in this study were mainly the result of gas exchange over the mucosa. The investigation might be a base for reference when investigating different kinds of pathologic conditions in the ear.

Networks with lateral connectivity. I. dynamic properties mediated by the balance of intrinsic excitation and inhibition.

1. We studied the rapid dynamic changes of neuron response properties in the somatosensory cortex by the use of computer simulations. The model consists of three feedforward layers of spiking neurons, corresponding to skin, subcortex, and cortex structures. Measurements and analysis of model activity throughout this work are similar to those used in neurophysiological experiments. 2. The effects of various parameters on response properties of model neurons were investigated. The most important parameters were the lateral excitation and inhibition in the simulated cortical network. 3. The balance between excitation and inhibition is a key factor in determining the stability of the network model. There is a large excitation-inhibition (E-I) parameter region within which the model can stably respond to inputs. 4. The input-output relations and receptive field (RF) sizes of simulated neurons are modifiable by the E-I balance. The shapes of RFs are determined by both feedforward projections and the spatial distribution of lateral connections. 5. We simulated changes in temporal and spatial properties of neurons in response to manipulations that mimic bicuculine methiodide or glutamate application to the cortex. Simulation results agreed well with experimental data, suggesting that cortical transmitter levels play an important role in the dynamic responses of the neural net through their effects on E-I balance. 6. With parameters of the model set to an inhibition-dominant scheme, the model was able to reproduce experimentally observed rapid RF expansions that follow cortical lesion or input denervation. Simulation results also suggested that spontaneous inputs to a sensory system can serve as a source of tonic inhibition in the cortex. 7. We conclude that lateral connections could produce and maintain a cortical network having dynamic properties without the need to invoke synaptic plasticity. Individual neuron properties could be modified by changing the balance of cortical layer excitation and inhibition. In a real brain, this could be achieved either by changing levels of cortical transmitter (gamma-aminobutyric acid. for example) or by changing tonic background input to the cortical network.

Continuous 24-hour measurement of middle ear pressure.

A new method was developed for continuous measurement of the middle ear pressure during a 24-h period. The equipment consisted of a piezo-electric pressure device and a digital memory. To allow continuous pressure recordings during normal every-day activities the equipment was made light and portable. The measurement accuracy of the equipment as well as the base-line and temperature stability were tested and found to meet to our requirements satisfactorily. In 4 volunteers with different middle ear conditions, a small perforation was made through the tympanic membrane. A rubber stopper containing a small polyethylene tube was fitted into the external ear canal. Tubal function tests were made to establish the equipment's ability to monitor fast pressure changes. The tests were well in accordance with other methods of direct pressure measurements. The equipment was carried by the volunteers for 24 h to monitor any slow or rapid dynamic pressure changes in the middle ear. Four continuous 24-h measurements are presented. The method was found to be suitable for valid measurements of dynamic pressure changes in the middle ear during normal every-day activities. It may become a useful instrument in the search for a better understanding of the development of chronic middle ear disease.

A distributed frame buffer for rapid dynamic changes to 3D scenes

This paper describes a distributed frame buffer architecture, based on the Tiling Algorithm for dynamic modification, and designed to achieve fast display updates in response to dynamic transformations of graphical objects. We report on the overall architecture and some detailed design issues.

Dynamic changes in hypothalamic angiotensin II levels and release in association with progesterone-induced luteinizing hormone surge.

To test the hypothesis that brain angiotensin II (Ang II) may be involved in the preovulatory release of LH on proestrus, we evaluated the pattern of changes in hypothalamic Ang II levels and release in ovariectomized (ovx) rats treated sequentially with estrogen and progesterone. This is an experimental paradigm that reliably evokes dynamic changes in hypothalamic LHRH levels in association with LH hypersecretion, simulating the LH surge on proestrus. Rats were ovx and after 4 weeks received estradiol benzoate followed by progesterone 2 days later at 1000 h. We observed that in these progesterone-treated rats, serum LH levels were low until 1400 h, but thereafter, the rate of LH secretion increased and remained elevated at 1600 h when the experiment was terminated. In these rats, hypothalamic Ang II levels increased abruptly at 1330 h and returned rapidly to baseline levels before the onset of LH surge. Also, a similar pattern in hypothalamic Ang II levels occurred at 1500 h with the rise and peak serum LH levels in the late afternoon. In the second experiment, Ang II levels in the cerebrospinal fluid (CSF) of rats similarly pretreated with ovarian steroids were evaluated. Again, CSF Ang II levels rose abruptly to a peak at 1330 h and returned to baseline range preceding the expected rise in serum LH. Thereafter, no further change in CSF Ang II levels was detected during the period of LH hypersecretion. In the third experiment, perfusates were collected from a push-pull cannula aimed at the paraventricular nucleus in ovx rats similarly treated with ovarian steroids. A peak of Ang II was observed at 1330 h and a later peak at 1430 h. A comparison with LH profiles indicated that these peaks in Ang II levels were evident before and during the LH surge. Thus, in three separate experiments, the results showed that rapid dynamic changes in hypothalamic Ang II levels and release occur in association with the progesterone-induced LH surge in estrogen-primed ovx rats. These findings support the previous observations that Ang II can stimulate LHRH and LH release. Since similar, temporally correlated changes occur in hypothalamic neuropeptide Y and LHRH, the peptides involved in the induction of LH surge, these results are in agreement with the hypothesis that Ang II-expressing neurons may play an important role in the hypothalamic circuitry responsible for stimulation of LH surge in ovarian steroid-treated ovx rats.

Dynamic changes in hypothalamic angiotensin II levels and release in association with progesterone-induced luteinizing hormone surge

To test the hypothesis that brain angiotensin II (Ang II) may be involved in the preovulatory release of LH on proestrus, we evaluated the pattern of changes in hypothalamic Ang II levels and release in ovariectomized (ovx) rats treated sequentially with estrogen and progesterone. This is an experimental paradigm that reliably evokes dynamic changes in hypothalamic LHRH levels in association with LH hypersecretion, simulating the LH surge on proestrus. Rats were ovx and after 4 weeks received estradiol benzoate followed by progesterone 2 days later at 1000 h. We observed that in these progesterone-treated rats, serum LH levels were low until 1400 h, but thereafter, the rate of LH secretion increased and remained elevated at 1600 h when the experiment was terminated. In these rats, hypothalamic Ang II levels increased abruptly at 1330 h and returned rapidly to baseline levels before the onset of LH surge. Also, a similar pattern in hypothalamic Ang II levels occurred at 1500 h with the rise and peak serum LH levels in the late afternoon. In the second experiment, Ang II levels in the cerebrospinal fluid (CSF) of rats similarly pretreated with ovarian steroids were evaluated. Again, CSF Ang II levels rose abruptly to a peak at 1330 h and returned to baseline range preceding the expected rise in serum LH. Thereafter, no further change in CSF Ang II levels was detected during the period of LH hypersecretion. In the third experiment, perfusates were collected from a push-pull cannula aimed at the paraventricular nucleus in ovx rats similarly treated with ovarian steroids. A peak of Ang II was observed at 1330 h and a later peak at 1430 h. A comparison with LH profiles indicated that these peaks in Ang II levels were evident before and during the LH surge. Thus, in three separate experiments, the results showed that rapid dynamic changes in hypothalamic Ang II levels and release occur in association with the progesterone-induced LH surge in estrogen-primed ovx rats. These findings support the previous observations that Ang II can stimulate LHRH and LH release. Since similar, temporally correlated changes occur in hypothalamic neuropeptide Y and LHRH, the peptides involved in the induction of LH surge, these results are in agreement with the hypothesis that Ang II-expressing neurons may play an important role in the hypothalamic circuitry responsible for stimulation of LH surge in ovarian steroid-treated ovx rats.

Investigations on the dynamic structures of adenine- and thymine-containing DNA

The structures of poly(dA-dT), poly(dA-dBr 5U) and of poly(dA) · poly(dT) have been investigated in solution and in fibers, by Raman spectroscopy. Both the alternating poly(dA-dT), poly(dA-dBr 5U) and non-alternating poly(dA) · poly(dT) exhibit, in the region of sugar phosphate backbone vibrations, two bands of almost equal intensity at about 841 cm −1 and 817 cm −1. The analysis of the characteristic bands of thymine residues that are sensitive to sugar puckers gives indication of a significant displacement from the C (2′)- endo conformer suggesting the adoption of alternative conformers such as O (4′)- endo. In contrast, the diagnostic Raman bands for the sugar pucker of adenine residues suggest, instead, predominant adoption of C (2′)- endo conformations. These Raman results are compatible with rapid dynamic changes of sugar puckers between C (2′)- endo and O (4′)- endo for the thymine (and uridine) residues, whereas in adenine residues the sugar puckers fluctuate around the C (2′)- endo pucker in all synthetic DNA molecules studied. Molecular dynamics simulations, performed on six different starting models using two distance-dependent dielectric functions ε( r) = 4 r and a sigmoidal dependence), all gave similar dynamic behavior in agreement with these Raman data and their interpretation. The mean calculated pseudorotation phases of the adenine residues are systematically higher (around C (2′)- endo) than those of the thymine residues (close to O (4′)- endo-C (1′)- exo). Besides, the mean lifetimes of the thymine residues are 1.5 to 2.0-fold higher in the O (4′)- endo than in the C (2′)- endo domain, while those of the adenine residues are two to threefold higher in the C (2′)- endo than in the O (4′)- endo domain. In the Raman spectra of the alternating poly(dA-dBr 5U), the splitting of a band into two components arising from the two contributions of ApBr 5U and Br 5UpA provides strong evidence for a repeating dinucleotide structure in solution. The calculated twist values averaged over the simulation runs are also systematically higher in the 5′T-A3′ step (39 °) than in the 5′A-T3′ step (33 °). Simultaneously, the calculated roll values are positive in the 5′T-A3′ step (6 °) and negative in the 5′A-T3′ step (−9 °), while the propeller twist values are about the same (−11 ° to −16 °). On the other hand, in the homopolymer, the average twist value is close to 36 ° with the roll angle close to 0 ° and large propeller twist values (−20 °).

On the tracking of rapid dynamic changes in seizure EEG.

Estimation of autospectra and coherence and phase spectra of seizure EEG, using the FFT technique, will cause "smearing" of the rapid dynamic changes which occur during the seizure. This is inherent to FFT spectral estimation, due to the averaging process which is necessary in order to get consistent spectral estimates. A different approach suggested in the present study is to carry out multivariate autoregressive modeling of the multichannel seizure EEG, combined with adaptive segmentation. In order to obtain good estimates in cases of short record length, the vectorial AR modeling was based on residual energy ratios. The method has been tested on multichannel seizure EEG recordings from rats with focal epilepsy, caused by intracerebral administration of Kainic acid, and in depth EEG recordings in patients with temporal lobe epilepsy.

Dynamic incompetent cervix uteri. Sonographic observations.

In 15 of 56 patients with incompetent cervix, rapid changes in the degree of dilatation of the cervical canal were observed during sonographic examination, with the same degree of bladder distension. In ten of those 15 patients, the canal was seen to be completely closed at some point during the examination. Because of these rapid dynamic changes in the dilatation of the cervical canal, it is necessary to observe the cervical portion of the uterus several times during the sonographic examination, especially in patients suspected to have incompetent cervix. It is possible for the cervical canal to remain closed for several minutes during the examination. Incompetent cervix can go undetected if the cervix is not observed frequently throughout the sonographic examination.

Intraprocedural passage of an obstructing ureteral calculus

The passage of a urinary calculus during an enhanced computed tomography examination demonstrates the perplexing incongruity one may encounter when there is rapid dynamic change in an organ or part during the relatively slow acquisition of sectional images.

Prognostic value of CT in head injuries.

Five hundred cases of acute head injury were analyzed on the basis of clinical severity, CT findings and outcome. Parenchymal lesions, which were the most important information in predicting the outcome, were classified into six categories: Isodensity WITHOUT Mass Effect, Isodensity WITH Mass Effect, High Density, High and Low Density Complex, Low Density, and Acute Diffuse Cerebral Swelling. Isodensity WITH Mass Effect was related to the worst outcome (59% mortality and 24% functional recovery). This finding was obtained 2 and a half hours following trauma and High and Low Density Complex eventually appeared in repeated CT. Epidural hematoma was associated with parenchymal lesions in only six (40%) out of 15 cases and acute subdural hematoma was accompanied by parenchymal lesions in 21 (84%) out of 25 cases. The remarkable differences in the outcome of those two extracerebral hematomas were entirely dependent on the associated parenchymal lesions. In the minor head injury group, parenchymal lesions were not rare (8.5%) in patients with a loss of consciousness even for a brief period. To follow the rapid dynamic changes in parenchymal lesions, the importance of repeated CT was emphasized.