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PubMed2003

Driving force dependence of intermolecular electron-transfer reactions of fullerenes.

Pulse-radiolytic studies were performed to determine the rate constants of intermolecular electron transfer (k(et)) from fullerenes (C(60), C(76), and C(78)) to a series of arene radical cations in dichloromethane. The one-electron oxidation potentials of the employed arenes-corresponding to the one-electron reduction potentials of arene pi-radical cations-were determined in dichloromethane to evaluate the driving forces of electron-transfer oxidation of fullerenes with arene pi-radical cations. The driving force dependence of log k(et) shows a pronounced decrease towards the highly exothermic region, representing the first definitive confirmation of the existence of the Marcus inverted region in a truly intermolecular electron transfer. Electron-transfer reduction of fullerenes with anthracene radical anion was also examined by laser flash photolysis in benzonitrile. The anthracene radical anion was produced by photoinduced electron transfer from 10,10'-dimethyl-9,9',10,10'-tetrahydro-9,9'-biacridine [(AcrH)(2)] to the singlet excited state of anthracene in benzonitrile. The rate constants of electron transfer (k(et)) from anthracene radical anion to C(60), C(70), and a C(60) derivative were determined from the decay of anthracene radical anion in the presence of various concentrations of the fullerene. Importantly, a significant decrease in the k(et) value was observed at large driving forces (1.50 eV) as compared to the diffusion-limited value seen at smaller driving forces (0.96 eV). In conclusion, our study presents clear evidence for the Marcus inverted region in both the electron-transfer reduction and oxidation of fullerenes.

Journal Article↗
PubMed1991

Postnatal development of thalamic recipient neurons in the monkey striate cortex: II. Influence of afferent driving on spine acquisition and dendritic growth of layer 4C spiny stellate neurons.

This study uses Golgi-impregnated material to examine the effects of altering the nature of afferent driving on the maturation of spines and dendrites on thalamic recipient spiny stellate neurons in layers 4C alpha and beta of the monkey striate cortex. These two laminae receive input from different sets of thalamic afferents with different functional properties. The development of dendritic spine and dendritic branch populations on these neurons in experimental animals is compared to the same features on similar groups of neurons in a series of normal animals described in the preceding study (Lund and Holbach, '91). Three conditions of rearing were used to alter afferent driving from normal: complete darkness (with in some cases return to normal diurnal light-dark cycle), bilateral eye lid suture, and monocular eye lid suture. Some of the normal and dark-reared infant monkeys were examined behaviorally for visual capacity in an earlier study (Regal et al., '76). All conditions of abnormal afferent driving caused changes from the normal developmental patterns of spine and dendritic arbor growth in these first-order neurons of the cortex and each condition differed in the nature of change produced. Major findings of this study are: 1. Vigorous spine acquisition and dendritic growth occurs under all conditions of visual deprivation on alpha and beta neurons. Eventual spine and dendritic attrition occurs under at least conditions of bilateral or monocular lid suture to produce a rather constant adult morphology. We assume, therefore, that visually driven activity is a modulator or shaper of the developmental process for thalamic recipient neurons of visual cortex, rather than being an initiator, terminator, or driving force for their maturation. 2. An innate "clock," whose nature is unknown but is apparently not driven by visual input, initiates and terminates a period of growth of the thalamic recipient neurons between birth and 30-32 weeks of age. 3. Factors controlling dendritic arbor growth and retraction are different from those controlling spine synapse addition or attrition. 4. Whereas the alpha and beta neurons normally show quite different early growth patterns between birth and 30 weeks of age, when both eyes are simultaneously deprived of vision, an early temporal and numerical convergence occurs in patterns of spine population development on the two groups of neurons. This convergent pattern assumes a different form in dark-reared and lid-sutured animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed2005

A novel microfluidic mixer utilizing electrokinetic driving forces under low switching frequency.

This paper presents a novel technique in which low-frequency periodic electrokinetic driving forces are utilized to mix electrolytic fluid samples rapidly and efficiently in a double-T-form microfluidic mixer. Without using any additional equipment to induce flow perturbations, only a single high-voltage power source is required for simultaneously driving and mixing the sample fluids which results in a simple and low-cost system for the mixing purpose. The effectiveness of the mixer as a function of the applied electric field and the periodic switching frequency is characterized by the intensity distribution calculated downstream from the mixing zone. The present numerical and experimental results confirm that the proposed double-T-form micromixer has excellent mixing capabilities. The mixing efficiency can be as high as 95% within a mixing length of 1000 microm downstream from the secondary T-junction when a 100 V/cm driving electric field strength and a 2 Hz periodic switching frequency are applied. The results reveal that the optimal switching frequency depends upon the magnitude of the main applied electrical field. The rapid double-T-form microfluidic mixer using the periodic driving voltage switching model proposed in this study has considerable potential for use in lab-on-a-chip systems.

Electrophoresis, Microchip↗
PubMed1999

DNA molecules can drive the assembly of other DNA molecules into specific four-stranded structures.

Single-stranded DNA molecules containing clustered G-repeats can be assembled into various four-stranded structures linked by G-quartets. Here, we report that such molecules can also drive the assembly of other DNA molecules containing G-repeats into specific four-stranded structures. In these assays, the oligonucleotides 5'-CAGGCTGAGCAGGTACGGGGGAGCTGGGGTAGATTGGAATGTAG-3' (oligo D) and 5'-CGGGGGAGCTGGGGT-3' (oligo B), consisting of sequences found in immunoglobulin switch regions, were annealed in a buffer containing K+ and the annealing products were analyzed by polyacrylamide gel electrophoresis. This analysis revealed that whereas annealing of each oligo alone produced four-stranded structures designated D2 and B2, annealing of mixtures containing both oligos produced additional complexes designated D2* and B2*. D2* and B2* were found to contain only D molecules and only B molecules, respectively. The yield of D2* increased and the yield of B2* decreased, as the concentration ratio oligo B/oligo D was increased. These results indicated that B can drive the assembly of D into D2* and D can drive the assembly of B into B2*. Further studies revealed that while the assembly of D2 followed a second order kinetics, the B-driven assembly of D2* followed a first order kinetics. Dimethyl sulfate footprinting indicated that both D2 and D2* are four-stranded structures containing two parallel and two antiparallel chains. In addition, annealing of D mixed with various B mutants showed that only mutants containing two G-clusters can drive the assembly of D2*. Based on these data, we propose that in the process of D2* assembly, a four-stranded intermediate containing B and D is formed and then dissociates into D2* and B in a rate-limiting first order reaction. Driver mechanisms of this type may cause formation of specific four-stranded structures at G-rich chromosomal sites, thereby regulating processes such as recombination and telomere synthesis.

Base Sequence↗
PubMed2003

The driving force for life's emergence: kinetic and thermodynamic considerations.

The principles that govern the emergence of life from non-life remain a subject of intense debate. The evolutionary paradigm built up over the last 50 years, that argues that the evolutionary driving force is the Second Law of Thermodynamics, continues to be promoted by some, while severely criticized by others. If the thermodynamic drive toward ever-increasing entropy is not what drives the evolutionary process, then what does? In this paper, we analyse this long-standing question by building on Eigen's "replication first" model for life's emergence, and propose an alternative theoretical framework for understanding life's evolutionary driving force. Its essence is that life is a kinetic phenomenon that derives from the kinetic consequences of autocatalysis operating on specific biopolymeric systems, and this is demonstrably true at all stages of life's evolution--from primal to advanced life forms. Life's unique characteristics--its complexity, energy-gathering metabolic systems, teleonomic character, as well as its abundance and diversity, derive directly from the proposition that from a chemical perspective the replication reaction is an extreme expression of kinetic control, one in which thermodynamic requirements have evolved to play a supporting, rather than a directing, role. The analysis leads us to propose a new sub-division within chemistry--replicative chemistry. A striking consequence of this kinetic approach is that Darwin's principle of natural selection: that living things replicate, and therefore evolve, may be phrased more generally: that certain replicating things can evolve, and may therefore become living. This more general formulation appears to provide a simple conceptual link between animate and inanimate matter.

Animals↗
PubMed1995

Lack of interaction between two antihistamines, mizolastine and cetirizine, and ethanol in psychomotor and driving performance in healthy subjects.

The pharmacodynamic interaction between mizolastine, a new H1 antihistamine, and ethanol was assessed in a randomized, double-blind, three-way crossover, placebo-controlled study. Eighteen healthy young male volunteers received mizolastine 10 mg, or cetirizine 10 mg or placebo once daily for 7 days with a 1-week wash-out interval. An oral dose of ethanol or ethanol placebo, given 2 h after dosing on days 5 or 7 of each treatment period, was administered to achieve a peak blood alcohol concentration (BAC) of 0.7 g/l then maintained for 1 h by two further doses of ethanol. Driving ability and psychomotor performance were evaluated using actual and simulated driving tests, critical flicker fusion threshold (CFF), adaptive tracking and divided attention (DAT) tasks. Ethanol produced a significant decrement in all tasks up to 5.5 h after administration: an increase in steering movements of 4.6, in lateral deviation of 0.45 m, in braking reaction time of 80 ms, in driving test and DAT performance of + 3.2; and a decrease in CFF and in tracking speed of 2.6 m.s-1. Neither mizolastine nor cetirizine significantly impaired driving ability or arousal (CFF) compared with the placebo. However, both drugs significantly impaired DAT performance 6:00 h post-dose (increase of + 2.1 for mizolastine and + 2.4 for cetirizine). The tracking speed was significantly decreased 7:50 h after mizolastine administration (-1.3 m.s-1) and more consistently from 1:30 to 7:50 h after cetirizine administration (-1.4 m.s-1). No significant adverse interaction, i.e. potentiation, occurred between ethanol and either antihistamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The relationship of sexual daydreaming to sexual activity, sexual drive, and sexual attitudes for women across the life-span.

The association among sexual daydreaming and sexual attitudes and activity was examined in a cross-sectional life-span sample of women (N = 117, 26 to 78 years). Sexual daydreaming was measured using the Imaginal Processes Inventory (IPI) while sexual history measures of sexual activity, sexual drive, and sexual attitudes were derived from a comprehensive personal interview. A factor analysis and varimax rotation of the sexual history variables, age, and the Sexual Daydream Scale of the IPI revealed three primary factors representing dimensions of sexual activity and drive, attitudes toward sexual activity, and sexual satisfaction. Age was associated with less sexual daydreaming, less sexual drive, less sexual activity, and more negative sexual attitudes. Sexual daydreaming varied directly with sexual drive and sexual activity and with a positive sexual attitude.

Adult↗
PubMed1999

Complete suppression of voluntary motor drive during the silent period after transcranial magnetic stimulation.

To evaluate changes in the motor system during the silent period (SP) induced by transcranial magnetic stimulation (TMS) of the motor cortex, we investigated motor thresholds as parameters of the excitability of the cortico-muscular pathway after a suprathreshold conditioning stimulus in the abductor digiti minimi muscle (ADM) of normal humans. Since the unconditioned motor threshold was lower during voluntary tonic contraction than at rest (31.9+/-5.4% vs. 45.6+/-7.5%), it is suggested that the difference between active and resting motor threshold indicates the magnitude of the voluntary drive on the cortico-muscular pathway. Therefore, we compared conditioned resting and active motor threshold (cRMT and cAMT) during the SP. cRMT showed an intensity-dependent period of elevation of more than 200 ms in duration and approximately 17% of the maximum stimulator output above the unconditioned threshold, due to decreased excitability of the cortico-muscular pathway after the conditioning stimulus. Some 3040 ms after the conditioning stimulus, cAMT approximated cRMT, indicating complete suppression of the voluntary motor drive. This suppression did not start directly after the conditioning stimulus since cAMT was still significantly lower than the cRMT within the first 30-40 ms. Threshold elevation was significantly longer than the SP (220+/-41 vs. 151+/-28 ms). Recovery of the voluntary motor drive started late in the SP and was nearly complete at the end of the SP, although thresholds were still significantly elevated. We conclude that the SP is largely due to a suppression of voluntary motor drive, while the threshold elevation is a different inhibitory phenomenon that is of less importance for the generation of the SP, at least in its late part. It is argued that the pathway of fast cortico-spinal fibers activated by TMS is partially different from the pathway involved in the maintenance of tonic voluntary muscle activation.

Adult↗
PubMed1996

Effects of mefloquine alone and with alcohol on psychomotor and driving performance.

OBJECTIVE: To determine whether mefloquine, a quinoline antimalarial drug, affects psychomotor and actual driving performance when given in prophylactic regimen, alone or in combination with alcohol. METHODS: Forty male and female volunteers were randomly assigned in equal numbers to two groups, and were treated double-blind for one month with mefloquine and placebo. The medication was taken in a 250 mg dose on the evenings of Days 1, 2, 3, 8, 15, 22 and 29. Testing was done on Days 4, 23 and 30, the latter after repeated doses of alcohol sufficient to sustain a blood concentration of about 0.35 mg.ml-1. Two real driving tests were used to measure prolonged (1 h) road tracking and car following performance. Critical Flicker/Fusion Frequency (CFF), critical instability tracking and body sway were also measured in the laboratory. RESULTS: Mefloquine caused no significant impairment in any test at any time relative to placebo. It significantly improved road tracking performance on Day 4. A significant interaction between prior treatment and alcohol was found in the body sway test, as the alcohol-induced change was less after mefloquine than placebo. The sensitivity of the driving test and the CFF test were shown by the significant overall effect of alcohol which did not discriminate between the two prior treatments. CONCLUSION: Mefloquine did not impair driving performance but rather improved it in the longer test, suggesting that the drug may possess psychostimulating properties.

Adult↗
PubMed1998

Characterization of the driving force as a modulator of gating in cardiac ATP-sensitive K+ channels - evidence for specific elementary properties.

Single cardiac ATP-sensitive K+ channels and, comparatively, two other members of the inwardly rectifying K+ channel family, cardiac K+(ir) and K+(ACh) channels, were studied in the inside-out recording mode in order to analyze influence and significance of the electrochemical K+ gradient for open-state kinetics of these K+ channels. The conductive state of K+(ATP) channels was defined as a function of the electrochemical K+ gradient in that increased driving force correlates with shortened open-channel lifetime. Flux coupling of gating can be largely excluded as the underlying mechanism for two reasons: (i) tauopen proved identical in 23 pS, 56 pS and 80 pS channels; (ii) K+(ATP) channel protonation by an external pH shift from 9.5 to 5.5 reduced conductance without a concomitant detectable change of tauopen. Since gating continued to operate at EK, i.e., in the absence of K+ permeation through the pore, K+ driving force cannot be causally involved in gating. Rather the driving force acts to modulate the gating process similar to Rb+ whose interference with an externally located binding site stabilizes the open state. In K+(ir) and K+(ACh) channels, the open state is essentially independent on driving force meaning that their gating apparatus does not sense the electrochemical K+ gradient. Thus, K+(ATP) channels differ in an important functional aspect which may be tentatively explained by a structural peculiarity of their gating apparatus.

Animals↗
PubMed2006

Characteristics and driving factors of marsh changes in Zhalong wetland of China.

Zhalong National Nature Reserve in the northeast of China is a large wetland and a habitat of hundreds species of fauna and flora. The rare red-crowned crane is one kind of endangered birds in it. Recently, Zhalong wetland is shrinking and it encounters many problems including occasional fires, bad water quality, human activities, etc. In order to find out a proper way to protect and restore the wetland, this study, using a geographic information system, the global positioning system and remote sensing techniques, analyses the spatial characteristics of the changes in marsh landscape pattern and examines the driving factors for these changes. Data sources include 8 Landsat Thematic Mapper satellite images of Zhalong area in the period of 1986-2002 and the investigation information on site. Based on the analysis of changes of marsh area and annual precipitation during the 16 years, it is found that there is a close correlation between annual precipitation and marsh area. It means that climate is one of driving factors of marsh pattern changes. To understand influences of other kinds of land uses on marsh spatial distribution in Zhalong wetland, this paper analyses the relationship between marsh and different kinds of land uses, such as water surface, residential area, farm land, salina land and grass land, respectively. According to the patch analysis theory, a fragmental index and a fractal dimension of the marsh are calculated with perimeter-area method. The results indicate that the marsh pattern is affected by human activities significantly. In addition, the location alteration of marsh centroid point over the 16 years is studied. The movement trace of marsh centroid point is concerned with different hydrological situation in different areas of the wetland. In summary the characteristics of the marsh landscape pattern evolution during the 16 years are affected by multiple driving factors. The main driving factors are climate, human activities, distribution of other kinds of land uses and hydrological situation in different areas.

China↗
PubMed1985

Alcohol policy and the Presidential Commission on Drunk Driving: the paths not taken.

The Report of the Presidential Commission on Drunk Driving represents a major federal response to the extraordinary success of a grassroots movement to combat drunk driving. The Report, despite the wide support and publicity that it generated, is seriously flawed. It relies primarily on strategies that are directed at individual behavior change--e.g. education, deterrence, treatment, and publicity campaigns. Research shows that these strategies, standing alone, have only a minimal long-term impact on the drunk driving problem. The Report fails to consider important new research on environmental factors affecting drunk driving, notably alcohol availability, price and tax policies, server intervention programs, alcohol advertising and transportation policies. These environmental strategies are a critical part of a comprehensive prevention policy and can greatly enhance the individual-based strategies relied on in the Commission Report.

Accidents, Traffic↗
PubMed1987

The Canadian drinking-driving countermeasure experience.

An overview of countermeasures implemented and evaluated in Canada to reduce impaired driving and alcohol-related accidents and fatalities are presented. Intervention strategies to detect and/or deter impaired drivers included legal measures, public information and education campaigns, rehabilitative programmes for convicted impaired drivers and technological aids to the prevention and detection of impairment. In general, the impact on drinking and driving of most countermeasures has been limited and short-term. The full effect of many countermeasure efforts was impeded by methodological shortcomings of the evaluations. Overall, the findings suggest that there is a need to take a comprehensive approach, tackling both drinking habits and driving habits. In order to effect behavioural change, a systems-oriented strategy would focus on motivational factors and alternative actions to drinking and driving.

Accidents, Traffic↗
PubMed1987

Influences on passenger vehicle casualty accident frequency and severity: unemployment, driver gender, driver age, drinking driving and restraint device use.

A correlational examination of 84 consecutive months of data on the frequency and severity of passenger vehicle casualty traffic accidents, unemployment rates, drinking driving, restraint device use and the driver demographics of driver age and driver gender suggested the following: Increases in unemployment levels remove young male drivers from the driving population, which in turn reduces the frequency of drinking driving and increases the proportion of restraint device use in this population. These changes combine to reduce both the frequency of casualty accidents per million driven kilometers and the severity of these accidents. However, the apparent relationship between changes in restraint device use and the frequency and severity of casualty accidents, and the apparent relationship between changes in drinking driving and the frequency of casualty accidents can be, to a great extent, a function of unemployment-driven changes in driver demographics.

Accidents, Traffic↗
PubMed1988

Effects of license revocation on drunk-driving offenders.

Revoking or suspending the licenses of persons convicted of driving while intoxicated has often been claimed to be uniquely effective in reducing subsequent dangerous driving, as indexed by crashes and violations. This finding holds despite the impression that many suspended and revoked drivers continue to drive illegally. The research described here inquires into the operation of license actions. It uses intensive personal interviews with offenders to obtain information concerning the nature and amount of illegal driving and the effects of license deprivation on employment and other aspects of the offenders' lives.

Accidents, Traffic↗
PubMed1995

The relationship of age and state license renewal policies to driving licensure rates.

We employ regression analysis to examine the relationship of state driver's license renewal requirements, population characteristics, and driving conditions to state driving licensure rates. Licensure rates are examined for the years 1985 through 1989. We separately examine all-age and senior licensed drivers. We find that license renewal requirements as well as population characteristics and driving conditions have systematic relationships to licensure rates. In particular, license renewal tests are associated with lower senior driving licensure rates.

Adolescent↗
PubMed1975

Decreased hypoxic ventilatory drive in the obesity-hypoventilation syndrome.

Most patients with extreme obesity do not exhibit alveolar hypoventilation, but an intriguing minority do. The mechanism(s) of this phenomenon remain unknown. A disorder in ventilatory control has been suggested as a major factor in the pathogenesis of the obesity-hypoventilation syndrome. Accordingly, hypoxic and hypercapnic ventilatory drives were measured in 10 patients with the typical symptoms of the syndrome: obesity, hypersomnolence, hypercapnia, hypoxemia, polycythemia and cor pulmonale. Hypoxic ventilatory drive, measured as the shape parameter A, averaged 21.9 +/- 5.35, approximately one-sixth that in normal controls, A = 126 +/- 8.6 (P less than 0.01). The ventilatory response to hypercapnia also was markedly reduced, the slope of the response averaging 0.51 +/- 0.005, or about one-third the normal value of 1.83 +/- 0.13 (P less than 0.01). This decreased responsiveness in hypoxic and hypercapnic ventilatory drive was consistent throughout the group. The depression in ventilatory drive found in the obesity-hypoventilation syndrome may be causally related to the alveolar hypoventilation manifested by these patients.

Adult↗
PubMed1990

Curve negotiation performance in a driving simulator as a function of curve geometry.

A study was conducted to investigate driver performance on curves. The between-trial factors were Blood Alcohol Content (BAC) level (0.00, 0.7, 0.12 %) and type of driving scenario (eventful versus uneventful). The within-session factors were edgeline width, type of curve-warning sign, and curve type. Twelve male drivers drove continuously for two hours on each of three nights. Each subject negotiated 150 curves during each two-hour drive. Curve radii ranged from 57.3 to 94.2 m (188 to 309.2 ft). Advisory speeds presented on curve-warning signs ranged from 32.2 to 72.4 km/h (20 to 45 mile/h). The driving simulator was a completely instrumented cab resting on a fixed base. The results showed that curve-entry speed increased as radius of curvature increased. Lateral position error was greater on the curve with the smallest radius and least on the curve with the shortest length. Heading error first increased then decreased as curve radius increased. Neither the amount of road used nor the mean computed lateral acceleration were related to curve radius, heading change or length. These results are attributed to the absence of lateral-acceleration cues in the driving simulator.

Journal Article↗