1,428 research outputs found
Word Length Perturbations in Certain Symmetric Presentations of Dihedral Groups
Given a finite group with a generating subset there is a well-established
notion of length for a group element given in terms of its minimal length
expression as a product of elements from the generating set. Recently, certain
quantities called and have been defined that allow
for a precise measure of how stable a group is under certain types of small
perturbations in the generating expressions for the elements of the group.
These quantities provide a means to measure differences among all possible
paths in a Cayley graph for a group, establish a group theoretic analog for the
notion of stability in nonlinear dynamical systems, and play an important role
in the application of groups to computational genomics. In this paper, we
further expose the fundamental properties of and by
establishing their bounds when the underlying group is a dihedral group. An
essential step in our approach is to completely characterize so-called
symmetric presentations of the dihedral groups, providing insight into the
manner in which and interact with finite group
presentations. This is of interest independent of the study of the quantities
. Finally, we discuss several conjectures and open
questions for future consideration
Oral malodor in Special Care Patients: current knowledge
Epidemiological studies report that about 50% of the population may have oral malodor
with a strong social and psychological impact in their daily life. When intra-oral causes are
excluded, referral to an appropriate medical specialist is paramount for management and
treatment of extra-oral causes. The intra-oral causes of halitosis are highly common, and the
dentist is the central clinician to diagnose and treat them. Pseudohalitosis or halitophobia
may occur and an early identification of these conditions by the dentist is important in order
to avoid unnecessary dental treatments for patients who need psychological or psychiatric
therapy. The organoleptic technique is still considered the most reliable examination method
to diagnose genuine halitosis. Special needs patients are more prone than others to have
oral malodor because of concurrent systemic or metabolic diseases, and medications.
The present report reviews halitosis, its implications, and the management in special care
dentistry
Bioinformatics tools for marine biotechnology: A practical tutorial with a metagenomic approach
Background: Bioinformatics has pervaded all fields of biology and has become an indispensable tool for almost all research projects. Although teaching bioinformatics has been incorporated in all traditional life science curricula, practical hands-on experiences in tight combination with wet-lab experiments are needed to motivate students. Results: We present a tutorial that starts from a practical problem: finding novel enzymes from marine environments. First, we introduce the idea of metagenomics, a recent approach that extends biotechnology to non-culturable microbes. We presuppose that a probe for the screening of metagenomic cosmid library is needed. The students start from the chemical structure of the substrate that should be acted on by the novel enzyme and end with the sequence of the probe. To attain their goal, they discover databases such as BRENDA and programs such as BLAST and Clustal Omega. Students' answers to a satisfaction questionnaire show that a multistep tutorial integrated into a research wet-lab project is preferable to conventional lectures illustrating bioinformatics tools. Conclusion: Experimental biologists can better operate basic bioinformatics if a problem-solving approach is chosen
Hydraulic properties of ignimbrites: matrix and fracture permeabilities in two pyroclastic flow deposits from Cimino‑Vico volcanoes (Italy)
Hydrological properties of ignimbrites are known in detail only for some areas, although these rocks cover large areas with
considerable thicknesses in many volcanic regions of the world. This study investigates hydrological properties of two ignimbrites
of Latium (Central Italy), different in age, composition, and origin. The dual porosity of the ignimbrites was examined
through laboratory tests, pumping tests, and outcrop surveys. The degree of welding, composition, and stratigraphy of
the two ignimbrites are the main factors determining their hydrological properties. The two ignimbrites share a low matrix
permeability, showing a different fracturing degree. The more welded ignimbrite is characterized by lower porosity of the
matrix and higher fracturing degree, while the less welded ignimbrite is characterized by higher porosity of the matrix and
lower fracturing degree. Hydraulic conductivity and storage capacity of the highly welded ignimbrite mainly depend on the
denser network of discontinuities. The hydraulic conductivity of the younger ignimbrite, less welded, mainly depend on the
sparser network of discontinuities and on the layer of unconsolidated coarse pyroclastic deposits at its base, while the storage
capacity depends on the more porous matrix. Should the pyroclastic rocks be used as aquifer for water supplies, or, in other
cases, as substratum of waste disposal sites, the dual porosity of the ignimbrites must necessarily include different scales
of analysis in order to evaluate the role of matrix and fractures on the permeability of rock mass. In any case, the results of
laboratory and on-site tests are to be interpreted taking into account the stratigraphy of the ignimbrite
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