8 research outputs found
A Survey on the Krein-von Neumann Extension, the corresponding Abstract Buckling Problem, and Weyl-Type Spectral Asymptotics for Perturbed Krein Laplacians in Nonsmooth Domains
In the first (and abstract) part of this survey we prove the unitary
equivalence of the inverse of the Krein--von Neumann extension (on the
orthogonal complement of its kernel) of a densely defined, closed, strictly
positive operator, for some in a Hilbert space to an abstract buckling problem operator.
This establishes the Krein extension as a natural object in elasticity theory
(in analogy to the Friedrichs extension, which found natural applications in
quantum mechanics, elasticity, etc.).
In the second, and principal part of this survey, we study spectral
properties for , the Krein--von Neumann extension of the
perturbed Laplacian (in short, the perturbed Krein Laplacian)
defined on , where is measurable, bounded and
nonnegative, in a bounded open set belonging to a
class of nonsmooth domains which contains all convex domains, along with all
domains of class , .Comment: 68 pages. arXiv admin note: extreme text overlap with arXiv:0907.144
Creatine supplementation with specific view to exercise/sports performance: An update
Creatine is one of the most popular and widely researched natural supplements. The majority of studies have
focused on the effects of creatine monohydrate on performance and health; however, many other forms of
creatine exist and are commercially available in the sports nutrition/supplement market. Regardless of the form,
supplementation with creatine has regularly shown to increase strength, fat free mass, and muscle morphology
with concurrent heavy resistance training more than resistance training alone. Creatine may be of benefit in other
modes of exercise such as high-intensity sprints or endurance training. However, it appears that the effects of
creatine diminish as the length of time spent exercising increases. Even though not all individuals respond similarly
to creatine supplementation, it is generally accepted that its supplementation increases creatine storage and
promotes a faster regeneration of adenosine triphosphate between high intensity exercises. These improved
outcomes will increase performance and promote greater training adaptations. More recent research suggests that
creatine supplementation in amounts of 0.1 g/kg of body weight combined with resistance training improves
training adaptations at a cellular and sub-cellular level. Finally, although presently ingesting creatine as an oral
supplement is considered safe and ethical, the perception of safety cannot be guaranteed, especially when
administered for long period of time to different populations (athletes, sedentary, patient, active, young or elderly)
International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine
Abstract Creatine is one of the most popular nutritional ergogenic aids for athletes. Studies have consistently shown that creatine supplementation increases intramuscular creatine concentrations which may help explain the observed improvements in high intensity exercise performance leading to greater training adaptations. In addition to athletic and exercise improvement, research has shown that creatine supplementation may enhance post-exercise recovery, injury prevention, thermoregulation, rehabilitation, and concussion and/or spinal cord neuroprotection. Additionally, a number of clinical applications of creatine supplementation have been studied involving neurodegenerative diseases (e.g., muscular dystrophy, Parkinson’s, Huntington’s disease), diabetes, osteoarthritis, fibromyalgia, aging, brain and heart ischemia, adolescent depression, and pregnancy. These studies provide a large body of evidence that creatine can not only improve exercise performance, but can play a role in preventing and/or reducing the severity of injury, enhancing rehabilitation from injuries, and helping athletes tolerate heavy training loads. Additionally, researchers have identified a number of potentially beneficial clinical uses of creatine supplementation. These studies show that short and long-term supplementation (up to 30 g/day for 5 years) is safe and well-tolerated in healthy individuals and in a number of patient populations ranging from infants to the elderly. Moreover, significant health benefits may be provided by ensuring habitual low dietary creatine ingestion (e.g., 3 g/day) throughout the lifespan. The purpose of this review is to provide an update to the current literature regarding the role and safety of creatine supplementation in exercise, sport, and medicine and to update the position stand of International Society of Sports Nutrition (ISSN)