Thermodynamic approach to the dewetting instability in ultrathin films

The fluid dynamics of the classical dewetting instability in ultrathin films is a non-linear process. However, the physical manifestation of the instability in terms of characteristic length and time scales can be described by a linearized form of the initial conditions of the films's dynamics. Alternately, the thermodynamic approach based on equating the rate of free energy decrease to the viscous dissipation [de Gennes, C. R. Acad. Paris.v298, 1984] can give similar information. Here we have evaluated dewetting in the presence of thermocapillary forces arising from a film-thickness (h) dependent temperature. Such a situation can be found during pulsed laser melting of ultrathin metal films where nanoscale effects lead to a local h-dependent temperature. The thermodynamic approach provides an analytical description of this thermocapillary dewetting. The results of this approach agree with those from linear theory and experimental observations provided the minimum value of viscous dissipation is equated to the rate of free energy decrease. The flow boundary condition that produces this minimum viscous dissipation is when the film-substrate tangential stress is zero. The physical implication of this finding is that the spontaneous dewetting instability follows the path of minimum rate of energy loss.Comment: 8 pages, 3 figures. Under revie

Wearable Systems for Monitoring Mobility-Related Activities in Chronic Disease: A Systematic Review

The use of wearable motion sensing technology offers important advantages over conventional methods for obtaining measures of physical activity and/or physical functioning in individuals with chronic diseases. This review aims to identify the actual state of applying wearable systems for monitoring mobility-related activity in individuals with chronic disease conditions. In this review we focus on technologies and applications, feasibility and adherence aspects, and clinical relevance of wearable motion sensing technology. PubMed (Medline since 1990), PEdro, and reference lists of all relevant articles were searched. Two authors independently reviewed randomised trials systematically. The quality of selected articles was scored and study results were summarised and discussed. 163 abstracts were considered. After application of inclusion criteria and full text reading, 25 articles were taken into account in a full text review. Twelve of these papers evaluated walking with pedometers, seven used uniaxial accelerometers to assess physical activity, six used multiaxial accelerometers, and two papers used a combination approach of a pedometer and a multiaxial accelerometer for obtaining overall activity and energy expenditure measures. Seven studies mentioned feasibility and/or adherence aspects. The number of studies that use movement sensors for monitoring of activity patterns in chronic disease (postural transitions, time spent in certain positions or activities) is nonexistent on the RCT level of study design. Although feasible methods for monitoring human mobility are available, evidence-based clinical applications of these methods in individuals with chronic diseases are in need of further development

Complications Associated with the Percutaneous Insertion of Fiducial Markers in the Thorax

Radiosurgery requires precise lesion localization. Fiducial markers enable lesion tracking, but complications from insertion may occur. The purpose of this study was to describe complications of fiducial marker insertion into pulmonary lesions. Clinical and imaging records of 28 consecutive patients with 32 lung nodules or masses who underwent insertion of a total of 59 fiducial markers before radiosurgery were retrospectively reviewed. Eighteen patients (67%) developed a pneumothorax, and six patients (22%) required a chest tube. The rates of pneumothorax were 82% and 40%, respectively, when 18-gauge and 19-gauge needles were used for marker insertion (P = 0.01). Increased rate of pneumothorax was also associated with targeting smaller lesions (P = 0.03) and tumors not in contact with the pleural surface (P = 0.04). A total of 11 fiducials (19%) migrated after insertion into the pleural space (10 markers) or into the airway (1 marker). Migration was associated with shorter distances from pleura to the marker deposition site (P = 0.04) and with fiducial placement outside of the target lesion (P = 0.03). Fiducial marker placement into lung lesions is associated with a high risk of pneumothorax and a risk of fiducial migration

A review on the clinical implementation of respiratory-gated radiation therapy

Respiratory-gated treatment techniques have been introduced into the radiation oncology practice to manage target or organ motions. This paper will review the implementation of this type of gated treatment technique where the respiratory cycle is determined using an external marker. The external marker device is placed on the abdominal region between the xyphoid process and the umbilicus of the patient. An infrared camera tracks the motion of the marker to generate a surrogate for the respiratory cycle. The relationship, if any, between the respiratory cycle and the movement of the target can be complex. The four-dimensional computed tomography (4DCT) scanner is used to identify this motion for those patients that meet three requirements for the successful implementation of respiratory-gated treatment technique for radiation therapy. These requirements are (a) the respiratory cycle must be periodic and maintained during treatment, (b) the movement of the target must be related to the respiratory cycle, and (c) the gating window can be set sufficiently large to minimise the overall treatment time or increase the duty cycle and yet small enough to be within the gate. If the respiratory-gated treatment technique is employed, the end-expiration image set is typically used for treatment planning purposes because this image set represents the phase of the respiratory cycle where the anatomical movement is often the least for the longest time. Contouring should account for tumour residual motion, setup uncertainty, and also allow for deviation from the expected respiratory cycle during treatment. Respiratory-gated intensity-modulated radiation therapy (IMRT) treatment plans must also be validated prior to treatment. Quality assurance should be performed to check for positional changes and the output in association with the motion-gated technique. To avoid potential treatment errors, radiation therapist (radiographer) should be regularly in-serviced and made aware of the need to invoke the gating feature when prescribed for selected patients

Interactive Simulation of Diaphragm Motion Through Muscle and Rib Kinematics

ISBN-10: 1848825641/ ISBN-13: 978-1848825642 / The original publication is available at www.springerlink.comModelling of diaphragm behaviour is of relevance to a number of clini cal procedures such as lung cancer radiotherapy and liver access interventions. The heterogeneity in tissue composition of the diaphragm, as well as the various physiological phenomena influencing its behaviour, requires a complex model in order to accurately capture its motion. In this paper we present a novel methodology based on a heterogeneous model composed of mass-spring and tensegrity elements. The physiological boundary conditions have been carefully taken into account and applied to our model. Thus, it incorporates the influence of the rib kinematics, the muscle natural contraction/relaxation and the motion of the sternum. Initial validation results show that the behaviour of the model closely follows that of a real diaphragm

Canine respiratory coronavirus employs caveolin-1-mediated pathway for internalization to HRT-18G cells

Canine respiratory coronavirus (CRCoV), identified in 2003, is a member of the Coronaviridae family. The virus is a betacoronavirus and a close relative of human coronavirus OC43 and bovine coronavirus. Here, we examined entry of CRCoV into human rectal tumor cells (HRT-18G cell line) by analyzing co-localization of single virus particles with cellular markers in the presence or absence of chemical inhibitors of pathways potentially involved in virus entry. We also targeted these pathways using siRNA. The results show that the virus hijacks caveolin-dependent endocytosis to enter cells via endocytic internalization

Endovascular coils as lung tumour markers in real-time tumour tracking stereotactic radiotherapy: preliminary results

To evaluate the use of endovascular coils as markers for respiratory motion correction during high-dose stereotactic radiotherapy with the CyberKnife, an image-guided linear accelerator mounted on a robotic arm. Endovascular platinum embolisation coils were used to mark intrapulmonary lesions. The coils were placed in subsegmental pulmonary artery branches in close proximity to the target tumour. This procedure was attempted in 25 patients who were considered unsuitable candidates for standard transthoracic percutaneous insertion. Vascular coils (n = 87) were succesfully inserted in 23 of 25 patients. Only minor complications were observed: haemoptysis during the procedure (one patient), development of pleural pain and fever on the day of procedure (one patient), and development of small infiltrative changes distal to the vascular coil (five patients). Fifty-seven coils (66% of total inserted number) could be used as tumour markers for delivery of biologically highly effective radiation doses with automated tracking during CyberKnife radiotherapy. Endovascular markers are safe and allow high-dose radiotherapy of lung tumours with CyberKnife, also in patients who are unsuitable candidates for standard transthoracic percutaneous marker insertion

The management of imaging dose during imageâ guided radiotherapy: Report of the AAPM Task Group 75

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134823/1/mp5667.pd

Present developments in reaching an international consensus for a model-based approach to particle beam therapy

Particle beam therapy (PBT), including proton and carbon ion therapy, is an emerging innovative treatment for cancer patients. Due to the high cost of and limited access to treatment, meticulous selection of patients who would benefit most from PBT, when compared with standard X-ray therapy (XRT), is necessary. Due to the cost and labor involved in randomized controlled trials, the model-based approach (MBA) is used as an alternative means of establishing scientific evidence in medicine, and it can be improved continuously. Good databases and reasonable models are crucial for the reliability of this approach. The tumor control probability and normal tissue complication probability models are good illustrations of the advantages of PBT, but pre-existing NTCP models have been derived from historical patient treatments from the XRT era. This highlights the necessity of prospectively analyzing specific treatment-related toxicities in order to develop PBT-compatible models. An international consensus has been reached at the Global Institution for Collaborative Research and Education (GI-CoRE) joint symposium, concluding that a systematically developed model is required for model accuracy and performance. Six important steps that need to be observed in these considerations include patient selection, treatment planning, beam delivery, dose verification, response assessment, and data analysis. Advanced technologies in radiotherapy and computer science can be integrated to improve the efficacy of a treatment. Model validation and appropriately defined thresholds in a cost-effectiveness centered manner, together with quality assurance in the treatment planning, have to be achieved prior to clinical implementation