Recycling Paper to Save Landfills and Trees

While some groups want to save tropical rain forests or marshy wetlands, other conservation-minded groups are interested in judiciously using sanitary landfills, or at least lengthening their lifetime by recycling paper (Hovelson, 1989). The Rolling Hills Audubon Society (RHAS), centered in Indianola (Warren County), sponsored two newspaper collections during 1989 in hopes of raising funds and reducing waste paper going to the South Central Iowa Sanitary Landfill located east of Winterset and south of Highway 92 in Madison County

The geology of the Newbury Mining District

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mining Engineering and Metallurgy, 1905.Accompanied by maps in a folder.by William Gilbert Ball - Charles Horace Clapp.B.S

A method of evaluating efficiency during space-suited work in a neutral buoyancy environment

The purpose was to investigate efficiency as related to the work transmission and the metabolic cost of various extravehicular activity (EVA) tasks during simulated microgravity (whole body water immersion) using three space suits. Two new prototype space station suits, AX-5 and MKIII, are pressurized at 57.2 kPa and were tested concurrently with the operationally used 29.6 kPa shuttle suit. Four male astronauts were asked to perform a fatigue trial on four upper extremity exercises during which metabolic rate and work output were measured and efficiency was calculated in each suit. The activities were selected to simulate actual EVA tasks. The test article was an underwater dynamometry system to which the astronauts were secured by foot restraints. All metabolic data was acquired, calculated, and stored using a computerized indirect calorimetry system connected to the suit ventilation/gas supply control console. During the efficiency testing, steady state metabolic rate could be evaluated as well as work transmitted to the dynamometer. Mechanical efficiency could then be calculated for each astronaut in each suit performing each movement

Effects of Hypovolemia on Cerebral Blood Velocity and Autoregulation During Upright Tilt: Implications for Post-Spaceflight Orthostasis

Orthostatic stability depends on maintenance of adequate cerebral blood flow. Orthostatic instability experienced by returning astronauts is associated with microgravity-induced hypovolemia, suggesting that hypovolemia may disrupt the ability of the cerebral vasculature to regulate blood flow. PURPOSE: To test the hypothesis that hypovolemia reduces cerebral blood velocity and impairs cerebral autoregulation (CA) during upright tilt. METHODS: Nine males (age 23 ± .5 yrs; height 172 ± 2 cm; weight 87 ± 3 kg; mean ± SE) were tilted head-up to 70° on two occasions separated by at least 5 days under euhydration (EUH) and dehydration (DEH) conditions. Dehydration was induced with 40 mg Furosemide and 8 h water restriction. Plasma volumes (PV) and blood volumes (BV) were estimated from venous hemoglobin and hematocrit. ECG, beat-by-beat finger arterial pressures, and cerebral blood velocity (CBV) were measured during a five min supine baseline, and during the first (T1) and last (T2) five min of upright tilt. Dynamic CA was assessed in the frequency domain with cross-spectral analysis of mean arterial pressure (MAP) and mean CBV within the frequency range of 0.07-0.2 Hz. RESULTS: Furosemide reduced PV by 10 ± 2 % and BV by 6 ± 2 % (P = .005 and P = .07). MAP decreased during tilt (P \u3c .007), but the reduction was similar between hydration conditions. CBV during DEH was lower during the entire 10-min tilt by about 7 cm/s (P \u3c .004) compared with EUH. Low frequency coherence was higher during DEH T1 compared with EUH T1 (.67 ± .04 vs .51 ± .04; P = .02), but coherence decreased as tilt continued, and was similar to EUH during T2 (P = 0.7). CONCLUSIONS: Increased coherence during the first 5 min of tilt suggests that reductions of CBV with hypovolemia might be explained by a reduced autoregulatory capacity. However, maintenance of lower CBV despite reduced coherence during the second 5 min of tilt suggests that disruptions of autoregulatory capacity with hypovolemia are transient. Our results provide evidence that hypovolemic astronauts may be at greatest risk for orthostatic intolerance immediately upon assumption of upright posture

The effects of entry on incumbent innovation and productivity

How does firm entry affect innovation incentives in incumbent firms? Microdata suggest that there is heterogeneity across industries. Specifically, incumbent productivity growth and patenting is positively correlated with lagged greenfield foreign firm entry in technologically advanced industries, but not in laggard industries. In this paper we provide evidence that these correlations arise from a causal effect predicted by Schumpeterian growth theory—the threat of technologically advanced entry spurs innovation incentives in sectors close to the technology frontier, where successful innovation allows incumbents to survive the threat, but discourages innovation in laggard sectors, where the threat reduces incumbents' expected rents from innovating. We find that the empirical patterns hold using rich micro panel data for the United Kingdom. We control for the endogeneity of entry by exploiting major European and U.K. policy reforms, and allow for endogeneity of additional factors. We complement the analysis for foreign entry with evidence for domestic entry and entry through imports

No Influence of Ovarian Hormones on Cerebrovascular Responses to the Valsalva Maneuver

Cerebral blood flow is modulated in part by arterial perfusion pressure and autonomic neural activity. Valsalva straining drives increases in cerebral perfusion pressure that may challenge cerebrovascular regulatory mechanisms. These challenges may be even greater during the normal menstrual cycle due to vasoactive influences of ovarian hormones. PURPOSE: To test the hypothesis that cerebral vascular responses to Valsalva straining are enhanced with increased plasma concentrations of estrogen and progesterone. METHODS: Twelve healthy eumenorrheic females (mean age 25 ± 1 yr; height 165 ± 3 cm; weight 66 ± 2 kg; mean ± SE) were studied during the early and late follicular (EF and LF) and early and late luteal (EL and LL) phases of the menstrual cycle. We recorded the ECG, beat-by-beat arterial pressure (Finometer), end-tidal CO2, and cerebral blood velocity (CBV) from the middle cerebral artery (transcranial Doppler ultrasound). Plasma ovarian hormone concentrations were assessed with high performance liquid chromatography. Supine subjects strained to an expiratory pressure of 40 mmHg for 15 seconds, and we recorded magnitudes of changes in arterial pressure and CBV. RESULTS: Compared with EF, estrogen was significantly higher during LF (111 ± 20 pg/ml) and EL (113 ± 27 pg/ml) (both P\u3c0.05). During EL (12 ± 6 pg/ml) and LL (7 ± 2 pg/ml), progesterone was significantly higher when compared with EF(1 ± .3 pg/ml) and LF(1 ± .2 pg/ml) (both P\u3c0.05). The magnitude of arterial pressure overshoot at the release of strain (an indirect indicator of peripheral sympathetic neural activation during straining) was significantly higher during LF (54 ± 9 mmHg) compared to EL and EF (both phases = 35 ± 4 mmHg; P=0.003). Changes in CBV during Valsalva straining and during release from strain were statistically identical across menstrual phases (P\u3e0.05). CONCLUSIONS: Despite indirect evidence that sympathetic neural activity during the Valsalva maneuver is increased when plasma estrogen concentrations are high, responses of the cerebral vasculature to Valsalva straining are unaffected by cycling ovarian hormones

Ovarian Hormones and Cerebral Hemodynamics During Upright Tilt

The cerebral vasculature is a specific target for ovarian hormones. Estrogens in particular activate endothelial factors that decrease vessel tone and increase blood flow. Changes in cerebral blood flow across the menstrual cycle could underlie the observation that women experience orthostatic instability more often than men, but the influence of ovarian hormone levels on cerebral hemodynamics in the upright posture is unclear. PURPOSE: To test the hypothesis that cerebral blood velocity and cerebral autoregulatory capacity change in parallel with ovarian hormone concentrations. METHODS: Nine healthy eumenorrheic women (mean age 24 ± 1 yr, height 166 ± 3 cm, weight 68 ± 2 kg; mean ± SE) were studied during the early and late follicular (EF and LF) and early and late luteal (EL and LL) phases of the menstrual cycle. We recorded the ECG, beat-by-beat arterial pressure, end-tidal CO2, and cerebral blood velocity from the middle cerebral artery (transcranial Doppler). Plasma ovarian hormone concentrations were assessed with high performance liquid chromatography. Subjects breathed in time to a metronome for 10 min (15 breaths/min) in the supine position, and were then tilted head-up to 70° for an additional 10 min of controlled breathing. Cerebral autoregulation was assessed in the frequency domain with cross-spectral analysis of mean arterial pressure (MAP) and mean CBV within the frequency range of 0.07-0.2 Hz. RESULTS: Upright tilt decreased CBV (supine 74 ± 1.7; tilt 65 ± 1.8 cm ∙ s-1; P=.005 pooled across phases) and end-tidal CO2 (P\u3c.001) but did not affect MAP. Coherence increased from .45 ± .02 to .67 ± .03 with tilt (P\u3c .001 pooled across phases) and was significantly higher during LF (.61 ± .03) compared with LL (.48 ± .03; P = .04). Lower coherence during LL compared with LF was associated with higher concentrations of progesterone (P \u3c .001). CONCLUSIONS: Upright tilt decreases CBV, and the magnitude of reduction is not related to ovarian hormone concentrations. Lower coherence during LL compared with LF suggests improved autoregulatory capacity mediated by higher concentrations of progesterone. These results have implications for orthostatic stability in women

Cerebrovascular Hemodynamics during Concentric and Eccentric Phases of Heavy Resistance Exercise

Rapid and drastic fluctuations in arterial blood pressures, such as those occurring during heavy resistance exercise pose a unique challenge to the maintenance of cerebral perfusion. During high-intensity leg cycling, regulation of cerebral perfusion is reduced by rapid decreases in beat-to-beat fluctuations in blood pressure (diastolic phase) rather than rapid increases (systolic phase). The purpose of this study was to test the hypothesis that rhythmic heavy resistance exercise will similarly impair the regulation of cerebral blood flow during the diastolic phase of beat-to-beat fluctuations in pressure. We studied seven healthy male subjects. Beat-to-beat finger arterial pressures, and middle cerebral artery blood velocity (MCAv) were measured during 10 repetitions (REP) of rhythmic high intensity leg press exercise. Velocities and arterial pressures were evaluated during both the isotonic concentric and eccentric phases of each REP. The Gosling pulsatility index (PI) of MCAv of each REP was calculated as MCAv systolic-MCAv diastolic/MCAv mean. During the concentric phase, systolic arterial pressures progressively increased from REP 1 through REP 10 (P \u3c 0.001), while systolic MCAv was not different across all REPs (P \u3e0.2). Diastolic arterial pressures during the eccentric phase also increased from REP 1 through REP 10 (P = 0.03) however diastolic MCAv decreased during REPs 7-10 compared with REP 2 (P ≤ 0.02). MCAv PI also increased during REP 7-10 compared to REP 2 (P ≤ 0.02). Similar to high-intensity leg cycling, our data suggest that during rhythmic high-intensity leg press exercise, cerebral perfusion is well controlled during periods of rapid increases in blood pressure, but regulation of cerebral perfusion is impaired during the diastolic phase of beat-to-beat fluctuations in pressure