How to play a disc brake

We consider a gyroscopic system under the action of small dissipative and non-conservative positional forces, which has its origin in the models of rotating bodies of revolution being in frictional contact. The spectrum of the unperturbed gyroscopic system forms a "spectral mesh" in the plane "frequency -gyroscopic parameter" with double semi-simple purely imaginary eigenvalues at zero value of the gyroscopic parameter. It is shown that dissipative forces lead to the splitting of the semi-simple eigenvalue with the creation of the so-called "bubble of instability" - a ring in the three-dimensional space of the gyroscopic parameter and real and imaginary parts of eigenvalues, which corresponds to complex eigenvalues. In case of full dissipation with a positive-definite damping matrix the eigenvalues of the ring have negative real parts making the bubble a latent source of instability because it can "emerge" to the region of eigenvalues with positive real parts due to action of both indefinite damping and non-conservative positional forces. In the paper, the instability mechanism is analytically described with the use of the perturbation theory of multiple eigenvalues. As an example stability of a rotating circular string constrained by a stationary load system is studied in detail. The theory developed seems to give a first clear explanation of the mechanism of self-excited vibrations in the rotating structures in frictional contact, that is responsible for such well-known phenomena of acoustics of friction as the squealing disc brake and the singing wine glass.Comment: 25 pages, 9 figures, Presented at BIRS 07w5068 Workshop "Geometric Mechanics: Continuous and discrete, finite and infinite dimensional", August 12-17, 2007, Banff, Canad

Genetic disorders in the Indian community of South Africa

Objectives. To determine the range of genetic disorders in the Indian population of South Africa, assess relevant historical and demographic factors, and discuss the implications for medical and genetic care. Methods. WSW reviewed the archived data pertaining to patients seen in his paediatric practice in Durban during the past 45 years. Likewise, PB reviewed case details of persons encountered since 1972 in Cape Town, at outreach clinics, and in special institutions for the handicapped throughout South Africa. Additional information was accessed through the Cape Genetic Heritage archive. Results. In addition to the common ubiquitous worldwide genetic disorders, several rare heritable conditions are present in the Indian community of South Africa. These disorders are the consequence of the founder effect and reflect the biological heritage of the early immigrants. Demographic factors (notably endogamy) are also relevant in this respect. As a result of these processes, thalassaemia is by far the most common and important genetic disorder in the Indian population in the country. Conclusion. Awareness of the presence of specific genetic conditions in the Indian community of South Africa is important in the diagnostic process. In turn, diagnostic precision facilitates accurate prognostication and optimal medical and genetic management

The stransverse mass, MT2, in special cases

This document describes some special cases in which the stransverse mass, MT2, may be calculated by non-iterative algorithms. The most notable special case is that in which the visible particles and the hypothesised invisible particles are massless -- a situation relevant to its current usage in the Large Hadron Collider as a discovery variable, and a situation for which no analytic answer was previously known. We also derive an expression for MT2 in another set of new (though arguably less interesting) special cases in which the missing transverse momentum must point parallel or anti parallel to the visible momentum sum. In addition, we find new derivations for already known MT2 solutions in a manner that maintains manifest contralinear boost invariance throughout, providing new insights into old results. Along the way, we stumble across some unexpected results and make conjectures relating to geometric forms of M_eff and H_T and their relationship to MT2.Comment: 11 pages, no figures. v2 corrects minor typos. v3 corrects an incorrect statement in footnote 8 and inserts a missing term in eq (3.9). v4 and v5 correct minor typos spotted by reader

Alih Aksara Dan Alih Bahasa Teks Cerita Nabi Isa as Dalam Naskah Cerita Nabi-nabi Versi Azhari Alkhalidi Rahmatullah

The purpose of this article to present change of the script and translation of story text of Isa in the Cerita Nabi-nabi manuscript Azhari Alkhalidi Rahmatullah version. Goal of this study in order textcan be readand understood bythe public andthe content ofthe text that containsthe values ​​andteachings ofreligionscan be knownby the public.The manuscriptwas written usingArabic-Malay script andMalay language. This study is a philology study and used descriptive method. The method that used was adjusted to the stage of study. On the stage of data collectoin used field research method. On the stage of data description used descriptive method. On the stage of change of the script used change of the script method. On the stage of translation used translation method. The result of this study is presented story text of Isa in theCerita Nabi-nabi manuscript Azhari Alkhalidi Rahmatullah version in Latin script and Indonesian language. The result of this study describe Isa life storystartsfrom the wombuntil hewas appointedby Godto heaven. In the textarearchaicwordsareretained.It aimstomaintain thepurity of thetext

Multidrug resistant Salmonella species isolated from fufu grinding machines in Ghana

Multidrug resistant Salmonella infection has become one of the most dangerous health concerns in Sub-Saharan Africa. Most previous research shows that food and water are the sources of the human Salmonella infection in Ghana. This article examines Salmonella contamination of fufu, a thick paste prepared from pounded boiled tubers, traditionally prepared using pestle and mortar, a common food in West and Central Africa. The fufu grinding machine, a new technology for grinding fufu, is gaining root in many parts of Sub-Saharan Africa, particularly in the urban areas where most people are inclined to use machines to minimize drudgery, leaving behind the traditional way which involves the use of a wooden mortar and pestle. To investigate the sources of these contaminations, 100 samples were collected from 50 randomly sampled fufu grinding machines in the Tamale Metropolis to examine the prevalence and antibiotic susceptibility of Salmonella species. Fufu samples (SA) and fufu wash-out samples (SB) were collected from each grinding machine as described in ISO 6579:2002 protocol for the detection of Salmonella in food. Of the total 100 samples, 27% were confirmed Salmonella positive, of which 16 were fufu samples while 11 were fufu wash-out samples. Forty-eight percent (48%) of the 50 machines were contaminated with Salmonella. Contamination of wooden machines (85.7%) was higher as compared with the metallic machines (41.9%). The resistance levels of the isolates to the various antibiotics used were as follows: gentamicin (7.1%), nitrofurantoin (18.5%), ciprofloxacin (22.2%), erythromycin (81.5%), ceftazidime (85.2%) and  eftriaxone 88.9%). More of the isolates were resistant to three or more antibiotics (81.5% multidrug resistance). From this research, it can be concluded that there is high prevalence of Salmonella isolated from fufu grinding machines in the Tamale metropolis. Measures must be taken by the regulatory authorities to ensure that fufu prepared in grinding machines is safer. Also, awareness creation on antibiotic resistance and strict enforcement of laws on self-prescriptions of drugs would help avert multidrug resistance

Who is spreading rumours about vaccines? Influential user impact modelling in social networks

Vaccine hesitancy, traditionally linked to issues of trust, misinformation and prior beliefs, has been increasingly fuelled by influential groups on social media (SM) and the Internet. Analysis of news media and social networks (SN) accessible in real-time provides a new opportunity for detecting changes in public confidence in vaccines. However, different concerns are important in different regions, and reasons for hesitancy and the role of opinion leaders vary between sub-controversies in the broader vaccination debates. It is therefore important for public health professionals to gain an overview of the emerging debates in cyberspace, identify influential users and rumours, and assess their impact in order to know how to respond. The VAC Medi+Board project aims to visualise the diffusion of rumours through SN and assess the impact of key individuals. We include, as a case study, discussions during winter 2015-16 pertaining to the alleged side-effects of the HPV vaccine

The development of QUADAS : a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews

BACKGROUND: In the era of evidence based medicine, with systematic reviews as its cornerstone, adequate quality assessment tools should be available. There is currently a lack of a systematically developed and evaluated tool for the assessment of diagnostic accuracy studies. The aim of this project was to combine empirical evidence and expert opinion in a formal consensus method to develop a tool to be used in systematic reviews to assess the quality of primary studies of diagnostic accuracy. METHODS: We conducted a Delphi procedure to develop the quality assessment tool by refining an initial list of items. Members of the Delphi panel were experts in the area of diagnostic research. The results of three previously conducted reviews of the diagnostic literature were used to generate a list of potential items for inclusion in the tool and to provide an evidence base upon which to develop the tool. RESULTS: A total of nine experts in the field of diagnostics took part in the Delphi procedure. The Delphi procedure consisted of four rounds, after which agreement was reached on the items to be included in the tool which we have called QUADAS. The initial list of 28 items was reduced to fourteen items in the final tool. Items included covered patient spectrum, reference standard, disease progression bias, verification bias, review bias, clinical review bias, incorporation bias, test execution, study withdrawals, and indeterminate results. The QUADAS tool is presented together with guidelines for scoring each of the items included in the tool. CONCLUSIONS: This project has produced an evidence based quality assessment tool to be used in systematic reviews of diagnostic accuracy studies. Further work to determine the usability and validity of the tool continue

A general framework for searching in distributed data repositories

This paper proposes a general framework for searching large distributed repositories. Examples of such repositories include sites with music/video content, distributed digital libraries, distributed caching systems, etc. The framework is based on the concept of neighborhood; each client keeps a list of the most beneficial sites according to past experience, which are visited first when the client searches for some particular content. Exploration methods continuously update the neighborhoods in order to follow changes in access patterns. Depending on the application, several variations of search and exploration processes are proposed. Experimental evaluation demonstrates the benefits of the framework in different scenarios.published_or_final_versio