1,354 research outputs found
Second order effects of structural and material damage on ultrasonic waves.
No full textDamage mechanics is a relatively new and powerful approach to the analysis of material degradation and failure. The idea is to build a continuum model of a solid containing a distribution of microcracks. Such a model, relying on the thermodynamics and statistical mechanics of microcracks, very naturally ties into other continuum models of solids, including acoustic and elastic models. In this dissertation, the impact of material and structural damage is investigated, with an emphasis on the relation between this effect and specific second order ultrasonic effects. The investigation has two main streams. The first, more experimental stream involves damage in the bulk. In this case, we chose to look at fatigue damage in the Ni-based alloy, waspaloy, which is used particularly for high strength, high temperature applications in the aerospace industry, as well as exhibiting very intriguing physical and thermodynamic properties. The approach was to monitor the changes in two second order parameters, the so-called nonlinearity, or beta parameter, and the acousto-elastic parameter. Results of these experiments seem to indicate that the latter is a better indicator of fatigue and damage, at least in this material. The second, more theoretical stream concerns damage along an individual weak interface. In this case, a nonlinear "thin layer" model was developed for propagation of ultrasonic waves through a weak bonded interface, as well as a time-domain approach to a general solution to this problem for a multiply layered system. This was combined with a simple damage model, and used to demonstrate how poorly bonded interfaces may be interpreted as locally damaged materials. It was also demonstrated how the nonlinearity of intensive ultrasound passing through or reflecting off an interface bond may be used, along with an appropriate damage model, to estimate the ultimate strength of this bond. Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5188. Adviser: Roman Gr. Maev. Thesis (Ph.D.)--University of Windsor (Canada), 2004
Clinical and anatomical indications for endovenous ablation in treatment of varicose veins
No full textCatedra chirurgie generală, Universitatea de Stat de Medicină și Farmacie „Nicolae Testemiţanu”, Spitalul Clinic Municipal
nr.1, Chişinău, Republica Moldova, Al XIII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” și
al III-lea Congres al Societății de Endoscopie, Chirurgie miniminvazivă și Ultrasonografie ”V.M.Guțu” din Republica MoldovaIntroducere: Ghidurile internaționale recomandă metodele de ablație endovenoasă (MAEV) ca tratament de primă linie pentru pacienții
cu maladia varicoasă (MV). Însă, superioritatea clinică a MAEV rămâne controversată, iar accesibilitatea acestora în Republica
Moldova la moment este încă limitată.
Scopul studiului a fost determinarea indicațiilor clinice și anatomice pentru utilizarea MAEV în baza analizei experienței Clinicii în
tratamentul bolnavilor cu MV.
Material și metode: A fost efectuată analiza retrospectivă a unei baze de date menținute prospectiv, ce a inclus pacienții cu MV
supuși tratamentului chirurgical. Din bază au fost extrase: caracteristicile clinico-demografice ale bolnavilor, rezultatele ultrasonografiei
duplex, metoda de intervenție și tipul anesteziei.
Rezultate: În perioada 2010-2018 au fost efectuate 184 intervenții chirurgicale cu utilizarea MAEV. Ablația termică cu laser a fost
practicată în 126 (68,4%) cazuri, ablația chimică – în 58 cazuri. Anestezia locală infiltrativă a fost utilizată în 88 (47,8%) cazuri; în 20
(10,8%) de cazuri a fost efectuată ablația chimică izolată fără anestezie. Au fost stabilite următoarele indicații clinice și anatomice
pentru utilizarea MAEV: (1) MV recurentă cauzată de reflux în trunchiul safenian rezidual; (2) reflux în vena safena parva cu situarea
înaltă a joncțiunii safeno-poplitee; (3) modificări trofice extinse la nivelul gambei; (4) pacienți cu obezitate gr.II-III; (5) pacienți aflați sub
tratament anticoagulant cronic. Complicații semnificative asociate cu utilizarea MAEV nu au fost înregistrate.
Concluzii: Unele variante clinico-anatomice ale MV prezintă indicații pentru utilizarea preferențială a metodelor miniminvazive de
tratament, care contribuie la reducerea riscurilor asociate cu anestezia, complicațiile de plagă și erorile tehnice.Introduction: The international guidelines recommend methods of endovenous ablation (MEVA) as a first-line treatment for patients
with varicose veins (VV). However, clinical superiority of MEVA remains controversial and its accessibility in Republic of Moldova is
still limited.
Aim of study was determination of clinical and anatomical indications for use of MEVA based on the Department experience in the
treatment of patients with VV.
Material and methods: We performed the retrospective analysis of prospectively maintained database which includes patients with
VV supposed to surgery. Clinical and demographic characteristics of the patients, duplex ultrasound results, type of intervention and
anesthesia were retrieved from the database.
Results: The 184 interventions using MEVA were performed during 2010-2018. Thermal laser ablation was performed in 126 (68.4%)
cases, chemical ablation – in 58 cases. Local tumescent anesthesia was used in 88 (47.8%) cases; in 20 (10.8%) cases isolated
chemical ablation required no anesthesia. There were the following clinical and anatomical indications for MEVA: (1) Recurrent
VV caused by refluxing residual saphenous trunk; (2) reflux in small saphenous vein with high situated sapheno-popliteal junction;
(3) extensive trophic disturbances of the leg; (4) patients with gr.II-III obesity; (5) patients on chronic anticoagulation. Significant
complications associated with use of MEVA were not registered.
Conclusion: Some clinical and anatomical variants of VV represent indications for preferential use of minimally-invasive treatment,
which contribute to reduction of risks associated with anesthesia, wound complications and technical errors
Ultrasonic Force and Related Microscopies
No full textThis chapter describes an approach that depends on the nonlinear nature of the interaction between tip and sample; this has become known as ultrasonic force microscopy (UFM). The combination of acoustic excitation with scanning probe microscopy makes it possible to image and study the elastic and viscoelastic properties of materials with nanoscale spatial resolution. For the applications described in the chapter, the key components of the UFM and the mechanical diode principle are: the inertial stiffness of the cantilever at the ultrasonic vibration frequency; nonlinear detection of additional forces at low frequency and the compliance of the cantilever at the detection frequency. The shape of the force versus indentation curve depends on surface adhesive and elastic properties. In addition to the elastic properties that UFM is intended to image, anything else that affects the tip‐surface interaction will also affect the UFM contrast
Development of a New Forming Process to Fabricate a Wide Range of Phantoms that Highly Match the Acoustical Properties of Human Bone
No full textIn the various stages of developing diagnostic and therapeutic equipment, the use of phantoms can play a very important role in improving the process, and help with implementation, testing and calibrations. However, devices that use different physical factors, such as MRI, Ultrasound, CT Scan, etc. require the phantom to be made with different physical properties. This thesis deals with ultrasound and it introduces a novel composite material and a new forming process to fabricate a wide range of phantoms that highly match the acoustical properties of human bones. In contrast to ex vivo tissues, the proposed material can maintain its custom designed physical and acoustical properties unchanged for long periods of time. As results, the author introduces examples of already manufactured ultrasound phantoms (i.e. human head phantom) and a novel method of simultaneous measurements of skull thickness and its sound velocity using a set of skull bone phantoms
Older Irish People Living in East London and their Stories of Migration and Dance.
No full textThis thesis looks at retired Irish migrants from the 1950s and1960s cohort of migration to England who are now living in East London using stories they shared about their experiences over the life course. By conducting both interviews about the past and observations in the present, this project utilises several methodological approaches to gather a range of rich data. To add to, and diversify, the body of literature on the ‘Irish in Britain’ for Irish migration studies, it draws on the life course framework, narrative stories and the third age theory. The in-depth empirical data shows that the lives of Irish migrants in England today are more diverse than the literature currently reflects and it is the first study of its kind to focus on modern day Irish-run tea dances. Moreover, it shows how the current Irish-run tea dances for migrants in England, provide a similar cultural experience and fulfil similar cultural expectations to the Irish-run dance halls that were popular upon arrival to England fifty years ago. Thus, this thesis offers a distinctive focus on the cultural significance of dance for Irish migrants over time and place while still also considering the other important transitions and the complexities of identity through life
Measurement of the B0–B0 oscillation frequency Δmd with the decays B0→D−π+ and B0→ J/ψK∗0
No full textThe B
0
–B
0
oscillation frequency Δmd is measured by the LHCb experiment using a dataset corresponding
to an integrated luminosity of 1.0 fb−1
of proton–proton collisions at √
s = 7 TeV, and is found to be
Δmd
=0.5156±0.0051 (stat.)±0.0033 (syst.) ps−1
. The measurement is based on results from analyses
of the decays B
0
→ D
−π
+ (D
−
→ K
+π
−π
−) and B
0
→ J/ψK
∗0
(J/ψ →μ
+μ
−,K
∗0
→ K
+π
−) and
their charge conjugated modes
Novel coronavirus infection COVID-19: extrapulmonary manifestations
No full textThe novel coronavirus infection COVID-19 in most cases manifests with respiratory symptoms and fever, however, some patients may have cardiovascular and gastroenterological manifestations. A feature of the clinical syndrome of COVID-19 is the development of pronounced immunopathological reactions and disorders of hemostasis, leading to the development of a wide range of cardiovascular complications. The course of COVID-19 may be complicated by the development of acute myocardial infarction, venous and arterial thrombosis and thromboembolism in various vascular pools, the development of acute myocardial damage and myocarditis. Among the gastroenterological manifestations, diarrhea, nausea or vomiting, as well as abdominal pain, are most often detected. These symptoms may precede the appearance of respiratory signs of the disease, and in some cases come to the fore in the clinical picture of the disease. In addition, in some patients there are laboratory signs of liver injury (increased serum transaminases). The exact pathogenesis of the above disorders continues to be studied
Genome analysis of E. coli isolated from Crohn's disease patients
No full textBackground: Escherichia coli (E. coli) has been increasingly implicated in the pathogenesis of Crohn's disease (CD). The phylogeny of E. coli isolated from Crohn's disease patients (CDEC) was controversial, and while genotyping results suggested heterogeneity, the sequenced strains of E. coli from CD patients were closely related. Results: We performed the shotgun genome sequencing of 28 E. coli isolates from ten CD patients and compared genomes from these isolates with already published genomes of CD strains and other pathogenic and non-pathogenic strains. CDEC was shown to belong to A, B1, B2 and D phylogenetic groups. The plasmid and several operons from the reference CD-associated E. coli strain LF82 were demonstrated to be more often present in CDEC genomes belonging to different phylogenetic groups than in genomes of commensal strains. The operons include carbon-source induced invasion GimA island, prophage I, iron uptake operons I and II, capsular assembly pathogenetic island IV and propanediol and galactitol utilization operons. Conclusions: Our findings suggest that CDEC are phylogenetically diverse. However, some strains isolated from independent sources possess highly similar chromosome or plasmids. Though no CD-specific genes or functional domains were present in all CD-associated strains, some genes and operons are more often found in the genomes of CDEC than in commensal E. coli. They are principally linked to gut colonization and utilization of propanediol and other sugar alcohols. © 2017 The Author(s)
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