Senior Recital:Rebecca Harms, Violin

Kemp Recital Hall Saturday Evening November 21, 1998 6:00p.m

Variation in small sapling density, understory cover, and resource availability in four neotropical forests

Even though many forest plants spend all or a significant portion of their lives in the forest understoty, few studies have compared understory composition, structure, and resource availability among forests. We used standardized transect-based methods to compare small sapling densities (10-50 cm tall), understory vegetation cover, canopy openness, and nutrient availability in non-gap portions of four lowland Neotropical forests: La Selva, Costa Rica (LS), Barro Colorado Island, Panama (BCI), Cocha Cashu, Peru (CC), and north of Manaus, Brazil (KM41). Sites differed significantly in all variables except canopy openness. LS had high palm and non-fern herb cover and low density of small saplings (0.7-1.6/m2) compared to other sites. CC had high fern cover, whereas BCI had low cover in all categories of understory vegetation (palms, ferns, and non-fern herbaceous plants). BCI, CC, and KM41 had similar small sapling densities, ranging from 4.8-7.5/m 2. Within each forest, cation (Ca, Mg, K, and Na) availability was usually higher on more fertile soil orders (Inceptisols, Alfisols, and Entisols) than on more weathered soil types (Ultisols and Oxisols). Extractable P was highest at LS and CC and lowest on BCI (no data for KM41). Spatial autocorrelation was present for some variables in some transects to distances beyond our detection ability (\u3e25 m). Understory palm cover was negatively correlated with small sapling density at fine (1 m2 quadrat) and coarse spatial scales (among forests), although across forests the effect of palms was due entirely to the difference between LS and the other three forests. These results provide cross-site support for the hypothesis that understory cover by palms decreases the density of small saplings that comprise the advance regeneration of the forest

Dietary Cocoa Flavanols Do Not Alter Brain Excitability in Young Healthy Adults

The ingestion of dietary cocoa flavanols acutely alters functions of the cerebral endothelium, but whether the effects of flavanols permeate beyond this to alter other brain functions remains unclear. Based on converging evidence, this work tested the hypothesis that cocoa flavanols would alter brain excitability in young healthy adults. In a randomised, cross-over, double-blinded, placebo-controlled design, transcranial magnetic stimulation was used to assess corticospinal and intracortical excitability before as well as 1 and 2 h post-ingestion of a beverage containing either high (695 mg flavanols, 150 mg (−)-epicatechin) or low levels (5 mg flavanols, 0 mg (−)-epicatechin) of cocoa flavanols. In addition to this acute intervention, the effects of a short-term chronic intervention where the same cocoa flavanol doses were ingested once a day for 5 consecutive days were also investigated. For both the acute and chronic interventions, the results revealed no robust alteration in corticospinal or intracortical excitability. One possibility is that cocoa flavanols yield no net effect on brain excitability, but predominantly alter functions of the cerebral endothelium in young healthy adults. Future studies should increase intervention durations to maximize the acute and chronic accumulation of flavanols in the brain, and further investigate if cocoa flavanols would be more effective at altering brain excitability in older adults and clinical populations than in younger adults

Sektorspezifische Regulierung: Transitorisch oder ad infinitum?

Unter diesem Titel hat das ifo Institut in diesem Frühjahr eine Studie veröffentlicht, die zehn Jahre nach der Einführung der sektorspezifischen Regulierung und beträchtlichen Markterfolgen in der Telekommunikation prüfte, ob das ursprüngliche Ziel einer vorübergehenden Regulierung aus den Augen verloren wurde. In der Studie wird festgestellt, dass trotz erheblicher Entwicklung des Wettbewerbs die Mitarbeiterzahl in den meisten europäischen Regulierungsbehörden weiter gestiegen ist, Regulierungsverfahren komplizierter geworden und neue Regulierungsaufgaben und -gebiete hinzugekommen sind. Mit einem Wort: Alle Zeichen deuten auf eine Verfestigung der Regulierung hin. Das Thema stieß auf reges Interesse. Deswegen wurden mehrere Autoren zur Stellungnahme eingeladen. Eine Einführung in die Thematik gibt Hans Schedl, wissenschaftlicher Mitarbeiter des ifo Instituts und Mitautor der Studie

Sektorspezifische Regulierung: Transitorisch oder ad infinitum?

Unter diesem Titel hat das ifo Institut in diesem Frühjahr eine Studie veröffentlicht, die zehn Jahre nach der Einführung der sektorspezifischen Regulierung und beträchtlichen Markterfolgen in der Telekommunikation prüfte, ob das ursprüngliche Ziel einer vorübergehenden Regulierung aus den Augen verloren wurde. In der Studie wird festgestellt, dass trotz erheblicher Entwicklung des Wettbewerbs die Mitarbeiterzahl in den meisten europäischen Regulierungsbehörden weiter gestiegen ist, Regulierungsverfahren komplizierter geworden und neue Regulierungsaufgaben und -gebiete hinzugekommen sind. Mit einem Wort: Alle Zeichen deuten auf eine Verfestigung der Regulierung hin. Das Thema stieß auf reges Interesse. Deswegen wurden mehrere Autoren zur Stellungnahme eingeladen. Eine Einführung in die Thematik gibt Hans Schedl, wissenschaftlicher Mitarbeiter des ifo Instituts und Mitautor der Studie.Regulierung, Aufsichtsbehörde, Telekommunikation, Telekommunikationsgesellschaft, Wettbewerb, Vergleich, Welt

The Effects of Acute Rauwolscine (α-Yohimbine) Ingestion on Repeated Wingate Sprint Performance in Healthy Males

Topics in Exercise Science and Kinesiology Volume 4: Issue 1, Article 1, 2023. Background: Rauwolscine (RW), also known as α-Yohimbine, is an α-2-adrenergic receptor antagonist which possesses sympathomimetic properties. RW is commercially sold in pre-workout and energy supplements. However, the ergogenic potential of RW has not been determined. The purpose of this study was to investigate the effects of acute RW supplementation on repeated sprint performance. Methods: Healthy male participants (n=12) completed 3 × 15-second Wingate anaerobic tests (WAnT) separated by 2 minutes of active recovery. Blood lactate (La) was collected before exercise (Pre) and immediately following exercise (Post). Mean power, peak power, fatigue index, heart rate (HR), and rate of perceived exertion (RPE) were taken immediately after each WAnT. Point of application #1: Acute RW supplementation does not result in the enhancement of repeated anaerobic sprint performance. Point of application #2: HR and RPE are not altered during repeated sprints with RW ingestion. Point of application #3: RW ingestion results in higher La levels post-exercise despite no changes in fatigue index

Vegetation response to invasive Tamarix control in southwestern U.S. rivers: a collaborative study including 416 sites

Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial-temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix less than active removal by mechanically using hand and chain-saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow-up treatments for Tamarix resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix-infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species

Flow of bottom water in the northwestern Weddell Sea

The Weddell Sea is known to feed recently formed deep and bottom water into the Antarctic circumpolar water belt, from whence it spreads into the basins of the world ocean. The rates are still a matter of debate. To quantify the flow of bottom water in the northwestern Weddell Sea data obtained during five cruises with R/V Polarstern between October 1989 and May 1998 were used. During the cruises in the Weddell Sea, five hydrographic surveys were carried out to measure water mass properties, and moored instruments were deployed over a time period of 8.5 years to obtain quasi-continuous time series. The average flow in the bottom water plume in the northwestern Weddell Sea deduced from the combined conductivity-temperature-depth and moored observations is 1.3±0.4 Sv. Intensive fluctuations of a wide range of timescales including annual and interannual variations are superimposed. The variations are partly induced by fluctuations in the formation rates and partly by current velocity fluctuations related to the large-scale circulation. Taking into account entrainment of modified Warm Deep Water and Weddell Sea Deep Water during the descent of the plume along the slope, between 0.5 Sv and 1.3 Sv of surface-ventilated water is supplied to the deep sea. This is significantly less than the widely accepted ventilation rates of the deep sea. If there are no other significant sources of newly ventilated water in the Weddell Sea, either the dominant role of Weddell Sea Bottom Water in the Southern Ocean or the global ventilation rates have to be reconsidered