University of Costa Rica

About: University of Costa Rica is a education organization based out in San José, Costa Rica. It is known for research contribution in the topics: Population & Venom. The organization has 9817 authors who have published 16781 publications receiving 238208 citations. The organization is also known as: UCR & Universidad de Costa Rica.

Biology and geology of eastern Pacific coral reefs

Abstract: The tropical eastern Pacific region has historically been characterized as devoid of coral reefs. The physical conditions of the region are apparently not conducive to reef growth: low temperatures, low salinity, and high nutrient loads. But recent work has demonstrated persistent coral growth in some locations at relatively high accretion rates, dating at least 5600 y before present. Coral reefs of the eastern Pacific are typically small (a few hectares), with discontinuous distribution and low species diversity. On a global scale, the eastern Pacific reefs may be considered minimum examples of coral reefs, as they have developed in possibly one of the most restrictive environments in the history of coral reefs. Disturbances are frequent, bioerosion intense, and recovery seems to be extremely slow. There is a general paucity of fossil corals and reefs on the American Pacific coast, probably due to the low preservation potential. In this review, distinct characteristics of the eastern Pacific and its coral reefs are highlighted. These factors make the region one of the smallest natural marine laboratories to study coral community structure and function on a regional level. The eastern Pacific is not only a testing ground for biological theory, but it is also a laboratory for paleoclimatic and oceanographic reconstruction.

The role of mammals in creating and modifying seedshadows in tropical forests and some possible consequences of their elimination

Abstract: Mammal populations are increasingly hunted, yet the consequences of their disappearance from tropical forests have only recently been explored. Here, we summarize current research on the role of mammals in seed dispersal and postdispersal processes, such as seed predation and secondary dispersal, in different tropical regions. We evaluate how mammal features influence seedshadows and ultimately forest regeneration. Finally, we discuss the potential effect of changes in seedshadows caused by the elimination of many medium- and large-sized mammals. The complex role that mammals play in creating and modifying seedshadows in tropical forests cannot be easily quantified, and in this review we emphasize the variation that exists both within and among mammal taxa and across continents. To bridge this gap in information, we suggest that more studies should evaluate the relative importance of the disappearance of both seed dispersers and seed predators for particular plant species so that we may begin to understand the balance between these two influences. We also suggest that future studies identify ecological redundancy in nonhunted vertebrates within any particular community to evaluate compensatory behavior that may help ameliorate some of the negative effects of hunting of large and medium mammals.

An Indoor Navigation System for the Visually Impaired

Abstract: Navigation in indoor environments is highly challenging for the severely visually impaired, particularly in spaces visited for the first time. Several solutions have been proposed to deal with this challenge. Although some of them have shown to be useful in real scenarios, they involve an important deployment effort or use artifacts that are not natural for blind users. This paper presents an indoor navigation system that was designed taking into consideration usability as the quality requirement to be maximized. This solution enables one to identify the position of a person and calculates the velocity and direction of his movements. Using this information, the system determines the user's trajectory, locates possible obstacles in that route, and offers navigation information to the user. The solution has been evaluated using two experimental scenarios. Although the results are still not enough to provide strong conclusions, they indicate that the system is suitable to guide visually impaired people through an unknown built environment.

Nuclear-bound quarkonium

Abstract: We show that the QCD van der Waals interaction due to multiple gluon exchange provides a new kind of attractive nuclear force capable of binding heavy quarkonia to nuclei. The parameters of the potential are estimated by identifying multigluon exchange with the Pomeron contributions to elastic meson-nucleon scattering. The gluonic potential is then used to study the properties of cc\ifmmode\bar\else\textasciimacron\fi{} nuclear-bound states. In particular, we predict bound states of the ${\ensuremath{\eta}}_{c}$ with $^{3}\mathrm{He}$ and heavier nuclei. Production modes and rates are also discussed.

Acute Effects of Exercise on Blood Pressure: A Meta-Analytic Investigation

Abstract: Hypertension affects 25% of the world's population and is considered a risk factor for cardiovascular disorders and other diseases. The aim of this study was to examine the evidence regarding the acute effect of exercise on blood pressure (BP) using meta-analytic measures. Sixty-five studies were compared using effect sizes (ES), and heterogeneity and Z tests to determine whether the ES were different from zero. The mean corrected global ES for exercise conditions were -0.56 (-4.80 mmHg) for systolic BP (sBP) and -0.44 (-3.19 mmHg) for diastolic BP (dBP; z ≠ 0 for all; p < 0.05). The reduction in BP was significant regardless of the participant's initial BP level, gender, physical activity level, antihypertensive drug intake, type of BP measurement, time of day in which the BP was measured, type of exercise performed, and exercise training program (p < 0.05 for all). ANOVA tests revealed that BP reductions were greater if participants were males, not receiving antihypertensive medication, physically active, and if the exercise performed was jogging. A significant inverse correlation was found between age and BP ES, body mass index (BMI) and sBP ES, duration of the exercise's session and sBP ES, and between the number of sets performed in the resistance exercise program and sBP ES (p < 0.05). Regardless of the characteristics of the participants and exercise, there was a reduction in BP in the hours following an exercise session. However, the hypotensive effect was greater when the exercise was performed as a preventive strategy in those physically active and without antihypertensive medication.