Underwater Sound Characteristics of a Ship with Controllable Pitch Propeller

The time-dependent spectral characteristics of underwater sound radiated by an oceanic vessel have complex dependencies on ship machinery, propeller dynamics, and the hydrodynamics of the ship exhaust and motion, as well as onboard activities. Here, the underwater sound radiated by a ship equipped with a controllable pitch propeller (CPP) is analyzed and quantified via its (i) power spectral density for signal energetics, (ii) temporal coherence for machinery tonal sound, and (iii) spectral coherence for propeller amplitude-modulated cavitation noise. Frequency-modulated (FM) tonal signals are also characterized in terms of their frequency variations. These characteristics are compared for different propeller pitch ratios, ranging from 20% to 82% at a fixed number of propeller revolutions per minute (RPM). The efficacy and robustness of ship parameter estimation at different pitches are discussed. Finally, an analysis of one special measurement is provided: propeller pitch and RPM over the duration of the measurement when the ship changes speed. The 50% pitch was found to be a crucial point for this ship, around which the tonal characteristics of its underwater radiated sound attain their peak values while broadband sound and associated spectral coherences are at a minimum. The findings here elucidate the effects of pitch variation on underwater sound radiated by ships with controllable pitch propellers and has applications in ship design and underwater noise mitigation

Milling of aerospace alloys using supercritical CO2 assisted machining

Novel “sub-zero” cooling methods are an emerging technology employed in machining of aerospace alloys that has been the focus of substantial ongoing research. A series of different cooling media have been used in an effort to decrease the friction and the amount of heat generated in the cutting zone. This study focused on the use of supercritical carbon dioxide (scCO2) as a coolant in the face milling of titanium alloy Ti-6Al-4V. Traditional flood emulsion coolant was compared with through tool scCO2 as well as scCO2 with minimum quantity lubrication (MQL)

Total invasion of the pancreatic gland by a rare aggressive IPMN: Report of a case

AbstractINTRODUCTIONThe intraductal papillary mucinous neoplasms (IPMNs) are increasingly diagnosed entities with high potential of malignancy and significant recurrence rates.PRESENTATION OF CASEIn this case report a rare mixed IPMN with full invasion of the pancreatic ducts was identified.DISCUSSIONDifficulties in determining the grade of pancreatic duct involvement make the surgical management tough.CONCLUSIONIn multifocal IPMNs the management of the patients is even more challenging. In this case the patient was treated successfully with total pancreatectomy

COPD exacerbation: Lost in translation

The introduction and acceptance of a standard definition for exacerbations of COPD can be helpful in prompt diagnosis and management of these events. The latest GOLD executive committee recognised this necessity and it has now included a definition of exacerbation in the guidelines for COPD which is an important step forward in the management of the disease. This definition is pragmatic and compromises the different approaches for exacerbation. However, the inclusion of the "healthcare utilisation" approach (".. may warrant a change in regular medication") in the definition may introduce in the diagnosis of exacerbation factors related to the access to health care services which may not be related to the underlying pathophysiologal process which characterizes exacerbations. It should be also noted that the aetiology of COPD exacerbations has not yet been included in the current definition. In this respect, the definition does not acknowledge the fact that many patients with COPD may suffer from additional conditions (i.e. congestive cardiac failure or pulmonary embolism) that can masquerade as exacerbations but they should not be considered as causes of them. The authors therefore suggest that an inclusion of the etiologic factors of COPD exacerbations in the definition. Moreover, COPD exacerbations are characterized by increased airway and systemic inflammation and significant deterioration in lung fuction. These fundamental aspects should be accounted in diagnosis/definition of exacerbations. This could be done by the introduction of a "laboratory" marker in the diagnosis of these acute events. The authors acknowledge that the use of a test or a biomarker in the diagnosis of exacerbations meets certain difficulties related to performing lung function tests or to sampling during exacerbations. However, the introduction of a test that reflects airway or systemic inflammation in the diagnosis of exacerbations might be another step forward in the management of COPD

Validation and psychometric properties of the Maltese version of the Duke Anticoagulation Satisfaction Scale (DASS)

Purpose: Assessing treatment satisfaction can guide specific interventions to improve anticoagulation adherence and reduce adverse outcomes. We aimed to assess the psychometric properties (reliability and validity) of the Maltese translation of the Duke Anticoagulation Satisfaction Scale (DASS). Patients and methods: The DASS explores three dimensions (limitations, hassles/burdens, psychological impact). The translation process included forward and backward translations. Reliability was evaluated through internal consistency and reproducibility. Validity was evaluated through floor/ceiling effect, convergent/discriminant validity, construct validity, and known-group validity. Results: The Maltese version of the DASS, administered to 174 patients on warfarin for different clinical indications, showed good reliability (Cronbach’s alpha 0.87; intraclass correlation coefficient for test–retest 0.73). Floor effect was identified mainly in the limitations and hassles/burdens subscales. Significant positive correlations were found between the DASS total score and its subscales (limitations 0.80, hassles/burdens 0.85, psychological impact 0.68). Female sex, shorter warfarin treatment duration (≤5 years), previous hospitalization and history of bleeding were associated with lower satisfaction. Conclusion: Psychometric properties of the Maltese DASS were comparable to the original English version. The Maltese version of the DASS is a valid and reliable instrument that can be used by health care professionals to assess the level of satisfaction of Maltese-speaking anticoagulated patients

Reliability and validity of the Maltese version of the perception of anticoagulant treatment questionnaire (PACT-Q)

Purpose: Anticoagulant therapy has an impact on the health-related quality of life, as it is a chronic treatment for most clinical indications and also requires some lifestyle changes. Since there was no validated questionnaire available in the Maltese language, the aim of our study was to translate and validate the Perception of Anticoagulant Treatment Questionnaire (PACT-Q2). Patients and methods: The PACT-Q2 explores two dimensions (convenience and anticoagulant treatment satisfaction). Forward and backward translations were performed. The Maltese version of the PACT-Q2 was administered to 174 patients on warfarin treatment enrolled from different anticoagulation clinics in Malta. Reliability was assessed through internal consistency (Cronbach’s alpha) and test-retest (intraclass correlation coefficient [ICC]). Validity was assessed through floor/ceiling effect, factor analysis (root mean square error of approximation [RMSEA], standardized root mean squared residual [SRMR], goodness-of-fit index [GFI], adjusted goodness-of-fit index [AGFI], comparative fit index [CFI]), subscales correlation and known-group validity. Results: Reliability was very good for the convenience subscale (Cronbach’s alpha 0.86, ICC 0.87), but less good for the satisfaction subscale (Cronbach’s alpha 0.62, ICC 0.40). Floor effect was 0%; ceiling effect was low (6.3% convenience, 1.2% satisfaction). Fit parameters were close to acceptable cut-offs (RMSEA =0.09, SRMR =0.10, GFI =0.82, AGFI =0.78, CFI =0.79). There was no correlation between the two subscales (r=0.01, p=0.83). Patients with history of bleeding showed lower convenience (r=−0.16, p=0.08) and lower satisfaction (r=−0.21, p=0.01). Conclusions: Our results support the finding that the Maltese translation of the PACT-Q2 is a valid and reliable instrument

Secondary infertility caused by the retention of fetal bones after an abortion: a case report

<p>Abstract</p> <p>Introduction</p> <p>Unwanted contraception through prolonged retention of fetal bone is a rare cause of secondary infertility. It is usually associated with a history of abortion, either spontaneous or induced.</p> <p>Case presentation</p> <p>We describe a case of intrauterine retention of fetal bone diagnosed 8 years after the termination of a pregnancy. The patient had no complaints of pain, irregular vaginal bleeding or discharge. A hysteroscopy was performed and irregular structures were removed. These fragments were fetal bones, which probably functioned as an intrauterine contraceptive device. After removal of the fetal bone fragments the patient conceived spontaneously within 6 months.</p> <p>Conclusion</p> <p>This case report stresses the importance of taking a thorough history and evaluation of the endometrium by transvaginal ultrasound or hysteroscopy in women with secondary infertility.</p

On the rocking behavior of rigid objects

A novel formulation for the rocking motion of a rigid block on a rigid foundation is presented in this work. The traditional piecewise equations are replaced by a single ordinary differential equation. In addition, damping effects are no longer introduced by means of a coefficient of restitution but understood as the presence of impulsive forces. The agreement with the classical formalism is very good for both free rocking regime and harmonic forcing excitation

Spawning rings of exceptional points out of Dirac cones

The Dirac cone underlies many unique electronic properties of graphene and topological insulators, and its band structure--two conical bands touching at a single point--has also been realized for photons in waveguide arrays, atoms in optical lattices, and through accidental degeneracy. Deformations of the Dirac cone often reveal intriguing properties; an example is the quantum Hall effect, where a constant magnetic field breaks the Dirac cone into isolated Landau levels. A seemingly unrelated phenomenon is the exceptional point, also known as the parity-time symmetry breaking point, where two resonances coincide in both their positions and widths. Exceptional points lead to counter-intuitive phenomena such as loss-induced transparency, unidirectional transmission or reflection, and lasers with reversed pump dependence or single-mode operation. These two fields of research are in fact connected: here we discover the ability of a Dirac cone to evolve into a ring of exceptional points, which we call an "exceptional ring." We experimentally demonstrate this concept in a photonic crystal slab. Angle-resolved reflection measurements of the photonic crystal slab reveal that the peaks of reflectivity follow the conical band structure of a Dirac cone from accidental degeneracy, whereas the complex eigenvalues of the system are deformed into a two-dimensional flat band enclosed by an exceptional ring. This deformation arises from the dissimilar radiation rates of dipole and quadrupole resonances, which play a role analogous to the loss and gain in parity-time symmetric systems. Our results indicate that the radiation that exists in any open system can fundamentally alter its physical properties in ways previously expected only in the presence of material loss and gain