Advances in optical tweezers, coupled with the proliferation of two-photon polymerization systems, mean that it is now becoming routine to fabricate and trap non-spherical particles. The shaping of ...both light beams and particles allows fine control over the flow of momentum from the optical to mechanical regimes. However, understanding and predicting the behaviour of such systems is highly complex in comparison with the traditional optically trapped microsphere. In this Article, we present a conceptually new and simple approach based on the nature of the optical force density. We illustrate the method through the design and fabrication of a shaped particle capable of acting as a passive force clamp, and we demonstrate its use as an optically trapped probe for imaging surface topography. Further applications of the design rules highlighted here may lead to new sensors for probing biomolecule mechanics, as well as to the development of optically actuated micromachines.
The optimal treatment for infants with aortic coarctation and hypoplastic aortic arch is controversial. The goal of this study was to report the short-term and mid-term outcomes of aortic arch ...advancement (AAA) in infants with hypoplastic aortic arch.
All infants who underwent AAA at our institution from 1995 to 2012 were included. AAA consisted of coarctectomy and end-to-side anastomosis of the descending aorta to the distal ascending aorta/proximal arch through a median sternotomy. The cohort was divided into four groups: (1) isolated AAA (n=29, 11%), (2) AAA with closure of ventricular septal defect (n=56, 20%), (3) AAA with other biventricular repairs (n=115, 42%), and (4) AAA as part of single-ventricle palliation (n=75, 27%).
The cohort included 275 patients: 125 (45%) were female, and the median age was 14 days (interquartile range, 7-34 days). Genetic abnormalities were present in 48 patients (17%). Neurologic adverse events occurred in 3 patients (1%), all in group 4. Left bronchial compression was seen in 2 patients (0.7%); only one required intervention. Vocal cord dysfunction was noted in 36 of 95 patients (38%) on routine laryngoscopy. Only 1 patient had clinical residual dysfunction at the last follow-up visit. Perioperative mortality was 3% (n=8). At a median follow-up time of 6 years, 8 patients (3%) had reinterventions at a median time of 5 months (3-17 months) after repair.
AAA is a safe, effective, and durable operation with low rates of adverse events and mid-term reintervention. The advantages include native tissue-to-tissue reconstruction and preserved potential for growth. As such, it is the ideal technique for the management of hypoplastic aortic arch in neonates and infants.
Anomalous aortic origin of a coronary artery (AAOCA) is a congenital abnormality of the origin or course of a coronary artery that arises from the aorta. It is the second most common cause of sudden ...cardiac death in young athletes. Its exact prevalence, the pathophysiological mechanisms that cause sudden cardiac death, the actual risk of death for the different types of AAOCA, the optimal way to evaluate these patients, and whether any treatment strategies decrease the risk of sudden cardiac death in patients diagnosed with AAOCA are unknown. This article analyzes what is currently known and unknown about this disease. It also describes the creation of a dedicated multidisciplinary coronary anomalies program and the development of a framework in an initial attempt to standardize the evaluation and management of these patients.
To evaluate safety and efficacy of percutaneous hepatic microwave (MW) ablation performed near the heart.
This study reviewed 118 consecutive peripheral (ablation zone margins within 5 mm of liver ...capsule) percutaneous MW hepatic ablations performed between June 2010 and August 2015. Ablation zones of 27 tumors (22.8%) extended to ≤ 5 mm from myocardium, and these ablations comprised the study group; the remaining ablations formed the control group. The study cohort included 14 men and 10 women (mean age, 59 y) with 16 hepatocellular carcinomas, 9 metastases, and 2 hemangiomas. Periprocedural imaging was used to evaluate tumor size and distance from the heart, ablation zone size, and complications. Mean tumor size and distance to myocardium were 2.6 cm ± 1.7 and 1.1 cm ± 1.1, respectively. The electronic medical record was used to retrospectively assess local tumor progression (LTP) and electrocardiogram and hemodynamic alterations during and after ablation. Statistical analysis was performed with Fisher exact test and t test.
Median follow-up was 13.6 months (range, 1.2-38.7 months). No arrhythmias occurred during or after ablation in the follow-up period (0/27). There was no difference between groups in frequency of alterations in periprocedural blood pressure (25.9% vs 29.6%, p=0.81) or heart rate (18.5% vs 24.2%, P = .61) or rate of LTP (12.0% vs 10.8%, P = 1.0).
Percutaneous MW ablation near the heart may be safe and effective, without increased risk of cardiac complications and with similar rates of LTP, compared with a control group of peripheral liver ablations.
We demonstrate the use of an extended, optically trapped probe that is capable of imaging surface topography with nanometre precision, whilst applying ultra-low, femto-Newton sized forces. This ...degree of precision and sensitivity is acquired through three distinct strategies. First, the probe itself is shaped in such a way as to soften the trap along the sensing axis and stiffen it in transverse directions. Next, these characteristics are enhanced by selectively position clamping independent motions of the probe. Finally, force clamping is used to refine the surface contact response. Detailed analyses are presented for each of these mechanisms. To test our sensor, we scan it laterally over a calibration sample consisting of a series of graduated steps, and demonstrate a height resolution of ∼ 11 nm. Using equipartition theory, we estimate that an average force of only ∼ 140 fN is exerted on the sample during the scan, making this technique ideal for the investigation of delicate biological samples.
The Agricultural Production Systems Simulator (APSIM) is a modular modelling framework that has been developed by the Agricultural Production Systems Research Unit in Australia. APSIM was developed ...to simulate biophysical process in farming systems, in particular where there is interest in the economic and ecological outcomes of management practice in the face of climatic risk. The paper outlines APSIM's structure and provides details of the concepts behind the different plant, soil and management modules. These modules include a diverse range of crops, pastures and trees, soil processes including water balance, N and P transformations, soil pH, erosion and a full range of management controls. Reports of APSIM testing in a diverse range of systems and environments are summarised. An example of model performance in a long-term cropping systems trial is provided. APSIM has been used in a broad range of applications, including support for on-farm decision making, farming systems design for production or resource management objectives, assessment of the value of seasonal climate forecasting, analysis of supply chain issues in agribusiness activities, development of waste management guidelines, risk assessment for government policy making and as a guide to research and education activity. An extensive citation list for these model testing and application studies is provided.
Optical trapping techniques have been used to investigate fundamental biological processes ranging from the identification of the processive mechanisms of kinesin and myosin to understanding the ...mechanics of DNA. To date, these investigations have relied almost exclusively on the use of isotropic probes based on colloidal microspheres. However, there are many potential advantages in utilizing more complex probe morphologies: use of multiple trapping points enables control of the interaction volume; increasing the distance between the optical trap and the sample minimizes photodamage in sensitive biological materials; and geometric anisotropy introduces the potential for asymmetric surface chemistry and multifunctional probes. Here we demonstrate that living cells of the freshwater diatom Nitzschia subacicularis Hustedt can be exploited as advanced probes for holographic optical tweezing applications. We characterize the optical and material properties associated with the high shape anisotropy of the silica frustule, examine the trapping behavior of the living algal cells, and demonstrate how the diatoms can be calibrated for use as force sensors and as force probes in the presence of rat B-cell hybridoma (11B11) cells.
Timely extubation is a well-accepted strategy in the postoperative intensive care unit management of Fontan patients to minimize the deleterious effects of positive-pressure ventilation. In October ...2002, this strategy was extended to extubating selective Fontan patients in the operating room (EOR). This retrospective study examines how EOR has affected outcomes and practice in our Fontan population.
Between October 2002 and June 2006, 112 patients underwent primary Fontan procedures; 38 (34%) were EOR and 74 (66%) were non-EOR. These two cohorts were not different (p < 0.05) in age, weight, surgery time, dominant ventricular morphology, hypoplastic left heart syndrome, prior bidirectional Glenn, concomitant procedures, atrioventricular valve regurgitation, and ventricular function. Analysis of variance was used to compare mean pulmonary artery pressure, mean arterial blood pressure, and mean common atrial pressure as a function of time.
During the first 12 hours postoperatively, mean pulmonary artery pressure and mean common atrial pressure were significantly lower and mean arterial blood pressure was significantly higher in the EOR group than the non-EOR group (p < 0.05). No EOR patient required reintubation. Mean durations of inotropic agents (1.1 versus 2.4 days), chest tubes (5.8 versus 7.2 days), intensive care unit stay (3 versus 4.7 days), and hospital stay (8.6 versus 11.3 days) for EOR patients were shorter than for non-EOR patients (p < 0.05). Intensive care unit and hospital costs for EOR patients were 35% and 31% lower, respectively, than for non-EOR patients (p < 0.05). Kaplan-Meier survival for EOR patients (3 years, 100%) was not different (p = 0.3) than for non-EOR patients (1 and 3 years, 96%).
After the Fontan procedure, selective EOR can be performed safely and improves postoperative hemodynamics, decreases hospital resource utilization, and reduces hospital recovery time.
Objective With improving operative mortality for staged palliation of hypoplastic left heart syndrome, interstage death accounts for an increasing proportion of hypoplastic left heart syndrome ...mortality. We investigated risk factors for death or cardiac transplantation during the interstage period between bidirectional Glenn and Fontan procedures in children with hypoplastic left heart syndrome. Methods Patients with hypoplastic left heart syndrome who underwent bidirectional Glenn between August 1995 and June 2007 were screened. Standard risk patients, defined by having been discharged after both Norwood and bidirectional Glenn, were included for analysis. Patient demographic, echocardiographic, cardiac catheterization, and operative data were reviewed. Interstage attrition was defined as death or cardiac transplantation more than 30 days after bidirectional Glenn and before the Fontan procedure. Statistical analysis was carried out using the Student t test, Pearson chi-square correlation, and Cox proportional hazard modeling for multivariable analysis. Results Ninety-two patients with hypoplastic left heart syndrome were alive at 30 days after bidirectional Glenn. Of these patients, 8 died and 3 underwent cardiac transplantation at a median of 391 days (range, 59–1175 days) after bidirectional Glenn, yielding an interstage attrition rate of 12%. Removing the 7 patients who are still awaiting Fontan (but all of whom are at least 3.5 years after bidirectional Glenn) adjusts the attrition rate to 13%. Interstage attrition did not correlate with hemodynamic data obtained at cardiac catheterization, aortic arch obstruction, or right ventricular dysfunction. Multivariable analysis demonstrated that the presence of moderate or severe tricuspid valve regurgitation (hazard ratio, 6.02; 95% confidence interval, 1.56–23.24; P < .01) and weight z score (hazard ratio, 0.38; 95% confidence interval, 0.16–0.88; P = .02) were independent preoperative risk factors for interstage attrition. Conclusions Interstage attrition between bidirectional Glenn and Fontan procedures occurred in 12% of our study population. Moderate or greater tricuspid valve regurgitation and low weight z score at the time of bidirectional Glenn are important risk factors for interstage attrition between the bidirectional Glenn and Fontan procedures in children with hypoplastic left heart syndrome.
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