Effects of Acute Low-Intensity Cycling on Perceived Stress, Arousal, and Attention

Generally, acute bouts of aerobic exercise have been shown to enhance psychological measures of emotion, mood, and affect. Previous investigations suggest that perceived stress and arousal levels are especially influenced by exercise. Interestingly, very few studies have examined the influence of exercise on attention and whether changes in stress and arousal may augment adaptations in attentional orientation that are often required during exercise. Furthermore, very little is known about the timing of the effects of exercise on these psychological outcomes. PURPOSE: The primary purpose of this study was to examine the effects of low-intensity aerobic exercise on stress, arousal, and attention. A secondary aim was to evaluate the time-course effects of exercise on stress, arousal, and attention. METHODS: Twenty (Mage = 23.2 ± 3.1 years old) college-aged individuals were counterbalanced into low-intensity exercise (LI) and seated control (SC) conditions. During each condition, participants completed a 10-minute resting baseline period, 20 minutes of either sustained cycling or seated rest, and a 20-minute recovery period. Primary outcomes of stress, arousal, and attention were assessed at 10-minute intervals throughout each condition via a Visual Analog Scale for Stress (VAS-S), Felt Arousal Scale (FAS), and Attentional Focus Scale (AFS), respectively. RESULTS: For the VAS-S, a Time main effect was revealed, F(4,16) = 5.76, p = .005, suggesting general reductions in stress following both LI and SC conditions. A Time main effect was also found for the FAS, which was superseded by a Condition x Time interaction, F(4,16) = 3.08, p = .047, indicating a greater increase in arousal levels during the LI condition compared to the SC condition. Lastly, a Time main effect for the AFS was found, F(4,16) = 3.05, p = .049, indicating general shifts from internal to external focus during each condition. CONCLUSION: Taken together, the current results suggest that exercise at lower doses (i.e., low-intensity for 20 minutes) may have minimal influence on more complex psychological perceptions of stress and attention. These results may help us better understand the complicated interactions between common psychological measures used in exercise science research. Additionally, this study may aid in the development of appropriate exercise prescriptions for populations looking to specifically target stress, arousal, and attention

Nitrogen Use and Carbon Sequestered by Corn Rotations in the Northern Corn Belt, U.S.

Diversified crop rotation may improve production efficiency, reduce fertilizer nitrogen (N) requirements for corn (Zea mays L.), and increase soil carbon (C) storage. Objectives were to determine effect of rotation and fertilizer N on soil C sequestration and N use. An experiment was started in 1990 on a Barnes clay loam (U.S. soil taxonomy: fine-loamy, mixed, superactive, frigid Calcic Hapludoll) near Brookings, SD. Tillage systems for corn–soybean (Glycine max [L.] Merr.) rotations were conventional tillage (CS) and ridge tillage (CSr). Rotations under conventional tillage were continuous corn (CC), and a 4-year rotation of corn–soybean–wheat (Triticum aestivum L.) companion-seeded with alfalfa (Medicago sativa L.)–alfalfa hay (CSWA). Additional treatments included plots of perennial warm season, cool season, and mixtures of warm and cool season grasses. N treatments for corn were corn fertilized for a grain yield of 8.5 Mg ha–1 (highN), of 5.3 Mg ha–1 (midN), and with no N fertilizer (noN). Total (1990–2000) corn grain yield was not different among rotations at 80.8 Mg ha–1 under highN. Corn yield differences among rotations increased with decreased fertilizer N. Total (1990–2000) corn yields with noN fertilizer were 69 Mg ha–1 under CSWA, 53 Mg ha–1 under CS, and 35 Mg ha–1 under CC. Total N attributed to rotations (noN treatments) was 0.68 Mg ha–1 under CSWA, 0.61 Mg ha–1 under CS, and 0.28 Mg ha–1 under CC. Plant carbon return depended on rotation and N. In the past 10 years, total C returned from above- ground biomass was 29.8 Mg ha–1 under CC with highN, and 12.8 Mg ha–1 under CSWA with noN. Soil C in the top 15 cm significantly increased (0.7 g kg–1) with perennial grass cover, remained unchanged under CSr, and decreased (1.7 g kg–1) under CC, CS, and CSWA. C to N ratio significantly narrowed (–0.75) with CSWA and widened (0.72) under grass. Diversified rotations have potential to increase N use efficiency and reduce fertilizer N input for corn. However, within a corn production system using conventional tillage and producing (averaged across rotation and N treatment) about 6.2-Mg ha–1 corn grain per year, we found no gain in soil C after 10 years regardless of rotation

Traffic jams and ordering far from thermal equilibrium

The recently suggested correspondence between domain dynamics of traffic models and the asymmetric chipping model is reviewed. It is observed that in many cases traffic domains perform the two characteristic dynamical processes of the chipping model, namely chipping and diffusion. This correspondence indicates that jamming in traffic models in which all dynamical rates are non-deterministic takes place as a broad crossover phenomenon, rather than a sharp transition. Two traffic models are studied in detail and analyzed within this picture.Comment: Contribution to the Niels Bohr Summer Institute on Complexity and Criticality; to appear in a Per Bak Memorial Issue of PHYSICA

Spitzer observations of Bow Shocks and Outflows in RCW 38

We report Spitzer observations of five newly identified bow shocks in the massive star-forming region RCW 38. Four are visible at IRAC wavelengths, the fifth is visible only at 24 microns. Chandra X-ray emission indicates that winds from the central O5.5 binary, IRS~2, have caused an outflow to the NE and SW of the central subcluster. The southern lobe of hot ionised gas is detected in X-rays; shocked gas and heated dust from the shock-front are detected with Spitzer at 4.5 and 24 microns. The northern outflow may have initiated the present generation of star formation, based on the filamentary distribution of the protostars in the central subcluster. Further, the bow-shock driving star, YSO 129, is photo-evaporating a pillar of gas and dust. No point sources are identified within this pillar at near- to mid-IR wavelengths. We also report on IRAC 3.6 & 5.8 micron observations of the cluster DBS2003-124, NE of RCW 38, where 33 candidate YSOs are identified. One star associated with the cluster drives a parsec-scale jet. Two candidate HH objects associated with the jet are visible at IRAC and MIPS wavelengths. The jet extends over a distance of ~3 pc. Assuming a velocity of 100 km/s for the jet material gives an age of about 30,000 years, indicating that the star (and cluster) are likely to be very young, with a similar or possibly younger age than RCW 38, and that star formation is ongoing in the extended RCW 38 region.Comment: 27 pages, 6 figures, accepted to Ap

Presence of Putative Repeat-in-Toxin Gene tosA in Escherichia coli Predicts Successful Colonization of the Urinary Tract

Uropathogenic Escherichia coli (UPEC) strains, which cause the majority of uncomplicated urinary tract infections (UTIs), carry a unique assortment of virulence or fitness genes. However, no single defining set of virulence or fitness genes has been found in all strains of UPEC, making the differentiation between UPEC and fecal commensal strains of E. coli difficult without the use of animal models of infection or phylogenetic grouping. In the present study, we consider three broad categories of virulence factors simultaneously to better define a combination of virulence factors that predicts success in the urinary tract. A total of 314 strains of E. coli, representing isolates from fecal samples, asymptomatic bacteriuria, complicated UTIs, and uncomplicated bladder and kidney infections, were assessed by multiplex PCR for the presence of 15 virulence or fitness genes encoding adhesins, toxins, and iron acquisition systems. The results confirm previous reports of gene prevalence among isolates from different clinical settings and identify several new patterns of gene associations. One gene, tosA, a putative repeat-in-toxin (RTX) homolog, is present in 11% of fecal strains but 25% of urinary isolates. Whereas tosA-positive strains carry an unusually high number (11.2) of the 15 virulence or fitness genes, tosA-negative strains have an average of only 5.4 virulence or fitness genes. The presence of tosA was predictive of successful colonization of a murine model of infection, even among fecal isolates, and can be used as a marker of pathogenic strains of UPEC within a distinct subset of the B2 lineage

Borderline Aggregation Kinetics in ``Dry'' and ``Wet'' Environments

We investigate the kinetics of constant-kernel aggregation which is augmented by either: (a) evaporation of monomers from finite-mass clusters, or (b) continuous cluster growth -- \ie, condensation. The rate equations for these two processes are analyzed using both exact and asymptotic methods. In aggregation-evaporation, if the evaporation is mass conserving, \ie, the monomers which evaporate remain in the system and continue to be reactive, the competition between evaporation and aggregation leads to several asymptotic outcomes. For weak evaporation, the kinetics is similar to that of aggregation with no evaporation, while equilibrium is quickly reached in the opposite case. At a critical evaporation rate, the cluster mass distribution decays as $k^{-5/2}$, where $k$ is the mass, while the typical cluster mass grows with time as $t^{2/3}$. In aggregation-condensation, we consider the process with a growth rate for clusters of mass $k$, $L_k$, which is: (i) independent of $k$, (ii) proportional to $k$, and (iii) proportional to $k^\mu$, with $0<\mu<1$. In the first case, the mass distribution attains a conventional scaling form, but with the typical cluster mass growing as $t\ln t$. When $L_k\propto k$, the typical mass grows exponentially in time, while the mass distribution again scales. In the intermediate case of $L_k\propto k^\mu$, scaling generally applies, with the typical mass growing as $t^{1/(1-\mu)}$. We also give an exact solution for the linear growth model, $L_k\propto k$, in one dimension.Comment: plain TeX, 17 pages, no figures, macro file prepende

Two inhibitors of yeast plasma membrane ATPase 1 (ScPma1p): toward the development of novel antifungal therapies

Given that many antifungal medications are susceptible to evolved resistance, there is a need for novel drugs with unique mechanisms of action. Inhibiting the essential proton pump Pma1p, a P-type ATPase, is a potentially effective therapeutic approach that is orthogonal to existing treatments. We identify NSC11668 and hitachimycin as structurally distinct antifungals that inhibit yeast ScPma1p. These compounds provide new opportunities for drug discovery aimed at this important target

Nonequilibrium Phase Transitions in Models of Aggregation, Adsorption, and Dissociation

We study nonequilibrium phase transitions in a mass-aggregation model which allows for diffusion, aggregation on contact, dissociation, adsorption and desorption of unit masses. We analyse two limits explicitly. In the first case mass is locally conserved whereas in the second case local conservation is violated. In both cases the system undergoes a dynamical phase transition in all dimensions. In the first case, the steady state mass distribution decays exponentially for large mass in one phase, and develops an infinite aggregate in addition to a power-law mass decay in the other phase. In the second case, the transition is similar except that the infinite aggregate is missing.Comment: Major revision of tex