Because MHV induces the secretion of pro-inflammatory molecules, such as interleukin-1β (IL-1β), tumor necrosis factor, IL-6, and macrophage-inflammatory 1β, during the infection of neural cells, HCoV-OC43 may act similarly in the CNS of infected children and lead to severe brain damage. Furthermore, SARS-CoV (which has many genetic similarities to both viruses) seems to cause lung damage by activating the same pro-inflammatory molecules, because a particularly high level of circulating IL-1β has been found in children with SARS (34).
An association of acute neural disease with HCoV infection has been clearly demonstrated by the detection of HCoV-OC43 in the cerebrospinal fluid of a child presumed to have acute disseminated encephalomyelitis, and the frequent association between HCoV-HKU1 infection and the development of febrile seizures seems to lead to the same conclusion. Lau et al. studied 10 children infected by this virus and found that half were affected by febrile seizures, the highest prevalence among all the HCoVs (20). Because the fever in all of these children was not particularly high and lasted for a shorter period than fever associated with other viral respiratory infections, it was considered unlikely that all were simple febrile seizures, but possible that they may represent specific neurologic damage induced by HCoV-HKU1 or that the virus may trigger a negative immune response.
However, different conclusions can be drawn when the global spectrum of the diseases caused by these viruses in animals and humans is considered. It is now well known that an enormous reservoir of CoVs exists among animals, particularly horseshoe bats, and that CoV isolates recovered from animals in China have up to 99.8% nucleotide identity with SARS-CoV (27). Because CoVs can easily mutate, this means that (as in 2003) sustained exposure to the infected animals can lead to a SARS-like CoV strain that is newly adapted to infect humans and capable of causing the reappearance of SARS. Moreover, it has been shown experimentally and in nature that all CoVs undergo a high rate of genetic mutations and can recombine when 2 different strains infect the same cells (1). This finding means that it is theoretically possible that future situations similar to those involving SARS-CoV may involve CoVs that currently infect only some animals, thus leading to novel viruses with unpredictable host ranges and pathogenicity.
Consequently, as is usually the case with influenza, a systematic evaluation of the characteristics of CoVs should be planned. Patients with severe respiratory syndrome seem to be the best target for this kind of evaluation and, in this population, studies of children (in whom the incidence of infection is higher) may also have application to adults because the findings may lead to a reduction in the risk for the spread of particularly virulent HCoV strains.
Compared to malignant tumors, benign brain tumors have different biological behavior and natural history. Zeidman et al. reviewed 21 who had serial MRI brain scans to determine the growth rate of nonoperated meningiomas . The decision not to have surgery included absence of related neurologic symptoms or signs and concern about high operative risk of neurologic impairment. They concluded that mean volumetric growth rate was significantly greater than the planimetric growth rate. While they also recorded special imaging characteristics including calcification, T2 hypointensity, dural tail, mass effect, and MLS, none of them were correlated to the growth rate. As meningiomas are mostly benign slow-growing tumors, the ICP remains normal until the tumor becomes very large. Therefore, MLS plays little role in following meningioma patients.
Meta-analysis is a set of techniques that are intended to combine and synthesize findings from a set of studies that investigate a similar phenomenon. For a variety of reasons, there has been a recent increase in the number of meta-analyses that are conducted in sport and exercise psychology. Often in sport and exercise psychology meta-analyses there is a perfunctory attempt to understand the bias that might exist in the selected set of studies. As a result, one form of bias that is commonly unaccounted for is publication bias. Publication bias occurs when there are concerns over how representative findings are from a set of studies compared to the true underlying effect. This type of bias is likely to occur in disciplines that almost exclusively publish statistically significant findings. When a body of literature omits findings that are not statistically significant, estimated effect sizes for the published studies are likely to be inflated. In order to understand how publication bias has influenced the published results, various analytical techniques must be utilized. In particular, this presentation will focus on outlining the role of selection methods, which are a class of techniques designed to be applied to quantify publication bias within a meta-analysis. The selection methods reviewed in this presentation will include the p-curve, p-uniform, and the maximum likelihood estimation strategies. Each of these aforementioned approaches has been advocated for by researchers looking to better understand bias in a sample of studies. P-curve, p-uniform, and maximum likelihood estimates each have unique model assumptions that impact both the utility and usefulness of the technique. The model assumptions will be reviewed and best practice recommendations for assessing bias within a meta-analysis will be discussed. Additional bias evaluation resources for use in future meta-analyses will also be provided.
Athletes, particularly student-athletes, may be a high risk population with respect to mental health. Student athletic therapists are one of the groups to which these athletes may be comfortable disclosing concerns. The current study investigated the relationship between mental health literacy (MHL) and confidence in acting upon mental health issues within a sample of intercollegiate student therapists. Females had higher Beliefs-oriented MHL than males, people with a personal history of mental illness has higher Knowledge-oriented MHL than those without, and Knowledge- and Resource-oriented MHL significantly predict confidence in assisting someone with mental health issues. These results suggest that the multidimensional construct of MHL may be an important antecedent factor in competencies in acting on mental health issues. There are several implications of this, particularly when working with a high-risk population of student-athletes.
I have tried to avoid making statements about floating-point without also giving reasons why the statements are true, especially since the justifications involve nothing more complicated than elementary calculus. Those explanations that are not central to the main argument have been grouped into a section called "The Details," so that they can be skipped if desired. In particular, the proofs of many of the theorems appear in this section. The end of each proof is marked with the z symbol. When a proof is not included, the z appears immediately following the statement of the theorem.
In particular, the relative error corresponding to .5 ulp can vary by a factor of . This factor is called the wobble. Setting = (/2)-p to the largest of the bounds in (2) above, we can say that when a real number is rounded to the closest floating-point number, the relative error is always bounded by e, which is referred to as machine epsilon.
In statements like Theorem 3 that discuss the relative error of an expression, it is understood that the expression is computed using floating-point arithmetic. In particular, the relative error is actually of the expression
There are two different IEEE standards for floating-point computation. IEEE 754 is a binary standard that requires = 2, p = 24 for single precision and p = 53 for double precision [IEEE 1987]. It also specifies the precise layout of bits in a single and double precision. IEEE 854 allows either = 2 or = 10 and unlike 754, does not specify how floating-point numbers are encoded into bits [Cody et al. 1984]. It does not require a particular value for p, but instead it specifies constraints on the allowable values of p for single and double precision. The term IEEE Standard will be used when discussing properties common to both standards.
Unfortunately, with the introduction of ± by the IEEE standard, the meaning of not mathematically defined is no longer totally clear cut. One definition might be to use the method shown in section Infinity. For example, to determine the value of ab, consider non-constant analytic functions f and g with the property that f(x) a and g(x) b as x 0. If f(x)g(x) always approaches the same limit, then this should be the value of ab. This definition would set 2 = which seems quite reasonable. In the case of 1.0, when f(x) = 1 and g(x) = 1/x the limit approaches 1, but when f(x) = 1 - x and g(x) = 1/x the limit is e-1. So 1.0, should be a NaN. In the case of 00, f(x)g(x) = eg(x)log f(x). Since f and g are analytic and take on the value 0 at 0, f(x) = a1x1 + a2x2 + ... and g(x) = b1x1 + b2x2 + .... Thus limx 0g(x) log f(x) = limx 0x log(x(a1 + a2x + ...)) = limx 0x log(a1x) = 0. So f(x)g(x) e0 = 1 for all f and g, which means that 00 = 1.25 26 Using this definition would unambiguously define the exponential function for all arguments, and in particular would define (-3.0)**3.0 to be -27.
The IEEE standard assumes that operations are conceptually serial and that when an interrupt occurs, it is possible to identify the operation and its operands. On machines which have pipelining or multiple arithmetic units, when an exception occurs, it may not be enough to simply have the trap handler examine the program counter. Hardware support for identifying exactly which operation trapped may be necessary.
The preceding paper has shown that floating-point arithmetic must be implemented carefully, since programmers may depend on its properties for the correctness and accuracy of their programs. In particular, the IEEE standard requires a careful implementation, and it is possible to write useful programs that work correctly and deliver accurate results only on systems that conform to the standard. The reader might be tempted to conclude that such programs should be portable to all IEEE systems. Indeed, portable software would be easier to write if the remark "When a program is moved between two machines and both support IEEE arithmetic, then if any intermediate result differs, it must be because of software bugs, not from differences in arithmetic," were true. 2b1af7f3a8