Two-Dimensional Spectroscopy Isolates Infrared Rovibrational Patterns.

The rovibrational spectra of freely rotating gas phase molecules are often plagued by spectral congestion due to the high density of rotational peaks. The congestion is especially severe at higher infrared frequencies due to the large numbers of overlapping overtones and combination bands that form polyads. As a result, rovibrational peaks in the near-infrared region of the spectrum are seldom assigned. This work describes how two-dimensional (2D) rovibrational spectroscopy can use the coupling between vibrational modes to isolate rovibrational bands that would otherwise remain overlapped and congested. Multidimensional spectroscopic techniques that make use of the large number of cross-peaks that form rich 2D rovibrational patterns are explored. Propyne is used to demonstrate 2D methods for identifying the frequencies and symmetries of coupled vibrations and for assigning rotational quantum numbers, even in regions that are heavily congested.

Multidimensional Pattern Recognition in High-Resolution 2D and 3D Spectra of Gas-Phase Molecules.

ConspectusWhen molecules transition from the condensed phase to the gas phase, their spectra undergo a dramatic transformation as well; each peak in a condensed-phase spectrum can yield thousands of peaks in the gas phase because the molecules are free to rotate and those rotational motions are quantized. These gas-phase spectra contain a wealth of detailed information about molecular structure and behavior, but peak densities are often so high that congestion obscures the patterns needed to assign peaks and extract molecular constants. This Account describes how coherent multidimensional techniques not only reduce peak densities and congestion in gas-phase spectra but also create multidimensional patterns that are easy to recognize and interpret. First, all peaks with the same vibrational quantum numbers form rotational patterns such as X's, double parabolas, and asterisks. These rotational patterns are composed of basic units and can provide immediate information about the molecule's structure, behavior, and rotational selection rules. Second, groups of these rotational patterns can be arranged into vibrational patterns that form arrays of rectangles or parallelograms. These vibrational patterns can be used to determine wave-mixing processes and measure vibrational constants. Coherent multidimensional spectroscopy therefore automatically separates vibrational and rotational information and then sorts peaks by vibrational and rotational quantum number. Furthermore, if the sample is composed of a mixture, then these patterns can also sort peaks by species, and higher-dimensional techniques can even provide the ability to select a species in the mixture. These techniques have successfully produced highly patterned 2D and 3D spectra for samples that otherwise generate patternless spectra such as isotopologue mixtures and vibronically perturbed molecules such as NO2.High densities of states can lead to congestion and perturbations that make it difficult to accurately assign peaks using the information that is traditionally available from 1D spectra: a peak's intensity and its frequency. Coherent 2D and 3D techniques are well-suited for dealing with and learning from perturbations because the coordinate of each peak in multidimensional space includes multiple frequency values. Accurate assignments are possible when peaks in 2D or 3D spectra that are perturbed along one frequency axis are unperturbed along an orthogonal frequency axis. Furthermore, patterns often repeat in adjacent rows or columns, so regions that are less congested can be used to resolve or identify key peaks or patterns in regions that are severely congested. Perturbations can make the spacings within multidimensional rotational and vibrational patterns slightly irregular, but these automatically generated patterns remain easy to recognize and analyze.This Account describes three high-resolution coherent multidimensional spectroscopy techniques, the types of patterns they can produce, and how information can be extracted from these patterns. This work is being conducted at Spelman College, a historically Black college for women where all of the students are undergraduates. The resulting techniques are not only highly effective for dealing with some of the most congested, perturbed, and challenging spectroscopic systems, but they are relatively easy to use, moderate in price to set up, and quick to run.

High resolution two-dimensional infrared (HR-2DIR) spectroscopy of gas phase molecules.

Two-dimensional infrared (2DIR) spectroscopy has become an established method for generating vibrational spectra in condensed phase samples composed of mixtures that yield heavily congested infrared and Raman spectra. These condensed phase 2DIR spectrometers can provide very high temporal resolution (<1 ps), but the spectral resolution is generally insufficient for resolving rotational peaks in gas phase spectra. Conventional (1D) rovibrational spectra of gas phase molecules are often plagued by severe spectral congestion, even when the sample is not a mixture. Spectral congestion can obscure the patterns in rovibrational spectra that are needed to assign peaks in the spectra. A method for generating high resolution 2DIR spectra of gas phase molecules has now been developed and tested using methane as the sample. The 2D rovibrational patterns that are recorded resemble an asterisk with a center position that provides the frequencies of both of the two coupled vibrational levels. The ability to generate easily recognizable 2D rovibrational patterns, regardless of temperature, should make the technique useful for a wide range of applications that are otherwise difficult or impossible when using conventional 1D rovibrational spectroscopy.

Surgical approach for anomalous aortic origin of a coronary artery: A comparison of two techniques.

BACKGROUND: Un-roofing is the most common technique utilized for repair of anomalous aortic origin of a coronary artery (AAOCA). There are very few publications directly comparing un-roofing to another surgical technique, like reimplantation. METHODS: The prospectively collected Children's Memorial Hermann Heart Institute Society of Thoracic Surgeon's Database was retrospectively reviewed from 2007 to 2021. Surgical patients were included if they underwent un-roofing or reimplantation of the AAOCA. The primary outcomes of this study were operative characteristics and postoperative outcomes. Secondary outcomes included angiographic outcomes, aortic regurgitation incidence, ventricular function, and symptom relief. RESULTS: From 2007 to 2021, there were 12 patients who underwent either a reimplantation (n = 9, 73%) or un-roofing (n = 3, 27%) for an AAOCA. The hospital length of stay was a median of 1.8 days longer for reimplantation compared to un-roofing. The last follow-up echocardiogram was a median of 52.2 days later in the reimplantation group. There was one patient (11%) in the reimplantation group that had more than or equal to mild aortic regurgitation and mild systolic ventricular dysfunction. Outpatient follow-up was incomplete and there was no postoperative computed tomographic angiography in the un-roofing cohort. CONCLUSIONS: Coronary artery reimplantation is a valuable alternative surgical technique to un-roofing for the repair of AAOCA. There are still some concerns with the creation of aortic regurgitation or incomplete symptom relief with any surgical technique. Longer-term follow-up and prospective studies will be needed to show an effective reduction of myocardial ischemia and risk of sudden cardiac death.

Two-dimensional pattern recognition methods for rapidly recording and interpreting high resolution coherent three-dimensional spectra.

High resolution coherent multidimensional spectroscopy has the ability to reduce congestion and automatically sort peaks by species and quantum numbers, even for simple mixtures and molecules that are extensively perturbed. The two-dimensional version is relatively simple to carry out, and the results are easy to interpret, but its ability to deal with severe spectral congestion is limited. Three-dimensional spectroscopy is considerably more complicated and time-consuming than two-dimensional spectroscopy, but it provides the spectral resolution needed for more challenging systems. This paper describes how to design high resolution coherent 3D spectroscopy experiments so that a small number of strategically positioned 2D scans may be used instead of recording all the data required for a 3D plot. This faster and simpler approach uses new pattern recognition methods to interpret the results. Key factors that affect the resulting patterns include the scanning strategy and the four wave mixing process. Optimum four wave mixing (FWM) processes and scanning strategies have been identified, and methods for identifying the FWM process from the observed patterns have been developed. Experiments based on nonparametric FWM processes provide significant pattern recognition and efficiency advantages over those based on parametric processes. Alternative scanning strategies that use synchronous scanning and asynchronous scanning to create new kinds of patterns have also been identified. Rotating the resulting patterns in 3D space leads to an insight into similarities in the patterns produced by different FWM processes.

Left Pulmonary Artery Patch Augmentation for Lung Transplant in a Patient With Situs Inversus.

Kartagener syndrome is characterized by situs inversus and defective cilia motion, the latter of which can lead to chronic infections and respiratory failure. If lung transplant is indicated, dextrocardia can pose surgical challenges. We report a rare case of sequential bilateral lung transplant in a 58-year-old man with Kartagener syndrome whose left pulmonary artery was abnormal in length, location, and direction. After placing the donor lungs in their orthotopic position, we augmented the recipient left pulmonary artery with a bovine pericardial patch. After 17 months of follow-up, the patient was in good condition with excellent graft function.

Homocysteine is associated with severity of microvasculopathy in sickle cell disease patients.

The pathophysiology of sickle cell disease (SCD) includes vasculopathy as well as anaemia. Elevated plasma homocysteine is a risk factor for vascular disease and may be associated with increased risk of vascular complications in SCD patients. In the present study, microvascular characteristics were assessed in the bulbar conjunctiva of 18 paediatric and 18 adult SCD patients, using the non-invasive technique of computer-assisted intravital microscopy. A vasculopathy severity index (SI) was computed to quantify the degree of microvasculopathy in each patient. Plasma homocysteine and several of its determinants [serum folate and vitamin B12, plasma pyridoxal-5'-phosphate (vitamin B6 status) and creatinine (kidney function)] were measured. Age was strongly correlated with microvasculopathy in the SCD patients, with the SI increasing about 0·1 unit per one-year increase in age (P < 0·001). After adjusting for age, gender, B-vitamin status and creatinine, homocysteine concentration was directly correlated with severity index (P < 0·05). Age and homocysteine concentration were independent predictors of microvasculopathy in SCD patients. It remains to be determined whether lowering homocysteine concentrations using appropriate B-vitamin supplements (folate and vitamins B12 and B6) - particularly if started early in life - could ameliorate microvasculopathy and its associated complications in SCD patients.

Resuscitating the Chimney Graft to Innominate Artery for Straightforward Cannulation During Infancy.

Arterial cannulation with a chimney polytetrafluoroethylene graft to the innominate artery is commonly used for antegrade cerebral perfusion during neonatal aortic arch surgery. When properly retained and prepared before sternal closure, resuscitation of the polytetrafluoroethylene graft to innominate artery can be performed months later during sternal reentry. It is a safe and reproducible technique for expeditious arterial cannulation at stage II palliation in single-ventricle patients or complete intracardiac repair of biventricular lesions. We report our experience utilizing this technique successfully during reoperation in 90 of 92 patients, with no adverse thromboembolic events identified.

Diaphragmatic Hernia Associated With Absent Ductus Venosus and Anomalous Connection of an Obliterated Umbilical Vein to the Coronary Sinus.

Umbilical vein anomalies are a rare congenital defect, which have been associated with absent ductus venosus, with few cases also involving a congenital diaphragmatic hernia. We describe a case of postnatal development of an anterior diaphragmatic hernia of Morgagni in a four-year-old patient diagnosed prenatally with mesocardia, absent ductus venosus with a large umbilical vein, a large secundum atrial septal defect, and patent ductus arteriosus.

Use of an Extracorporeal Centrifugal Pump with the Berlin Cannulas.

The Berlin EXCOR ventricular assist device has become a standard treatment in pediatric bridge to transplantation. Despite its increased use in pediatric heart failure, the patient population supported with this technology continues to suffer from hematologic issues such as postoperative hemorrhage and neurologic dysfunction secondary to thrombotic events. Finding a balance between hemorrhagic and thrombotic risks in the acute postoperative period poses a significant challenge. In this report, we describe our approach using a temporary centrifugal pump connected to cannulas designed for the Berlin EXCOR ventricular assist device. We believe that the interim use of an extracorporeal centrifugal pump allows time for hemodynamic stability, limits the hemorrhagic risks, and provides relevant hemodynamic information before conversion to the Berlin EXCOR.

Nonparametric High-Resolution Coherent 3D Spectroscopy as a Simple and Rapid Method for Obtaining Excited-State Rotational Constants.

A new method for generating high-resolution coherent 3D (HRC3D) spectra has been developed that is based on the nonparametric four-wave mixing process MENS (multiply enhanced nonparametric spectroscopy). The resulting spectra have rotational patterns that are different from those produced previously using the parametric four-wave mixing process CARS. A change in the rotational pattern facilitates a new approach to scanning where orthogonal 2D slices in 3D space are combined to make a 3D rotational pattern. This 3D rotational pattern may then be used to calculate rotational constants for levels in the excited electronic state and upper regions of the ground electronic state. Unlike previous forms of HRC3D spectroscopy, this new approach provides a stand-alone rapid and simple tool for the rotational analysis of electronic spectra without the need for obtaining peak positions or molecular constants from other (1D or 2D) forms of spectroscopy.

Appraisal of mentorship in cardiothoracic surgery training.

OBJECTIVES: Although the importance of mentorship in training the next generation of cardiothoracic surgeons is widely recognized, the current state of mentorship remains undefined. METHODS: Trainee responses to questions in the 2017 In-Training Examination regarding aspects of mentorship were analyzed. Response rate was 78% (288/370). Mentor-related and trainee-related characteristics were assessed. RESULTS: The majority (84%) of residents had mentors, with a high impact on specialty choice (80%), and 91% of respondents viewed mentorship as critical to success. Nearly half (42%) had program-assigned mentors; 53% found them as productive, and 13% reported more consistent/frequent meetings than personally selected mentors, with 22% reporting less ideal personality match compared with personally selected mentors. Among residents with mentors, 36% lacked mentorship in work-life balance, 23% lacked mentorship in job assistance, and 22% lacked mentorship in career advice. Junior residents more often valued mentors as role models, whereas mentors chosen by senior residents were more impactful in technical training, job counseling, and societal involvement. Compared with men, women more often valued mentors as role models and assisting in networking. Men reported their mentors were more impactful in teaching technical skills and clinical ability than women. CONCLUSIONS: The majority of current cardiothoracic surgery trainees had mentorship; however, gaps remain: Many residents lacked career path guidance, assistance obtaining a job, and advice regarding life-work balance. The role of mentorship varied with program type, seniority, and gender, emphasizing the need to tailor mentorship to the individual and changing needs of the resident.

A Reconfigurable Pneumatic Bending Actuator with Replaceable Inflation Modules.

A fully reconfigurable, pneumatic bending actuator is fabricated by implementing the concept of modularity to soft robotics. The actuator features independent, removable, fabric inflation modules that are attached to a common flexible but non-inflating plastic spine. The fabric modules are individually fabricated by heat sealing a thermoplastic polyurethane-coated nylon fabric, whereas the spine is manufactured through fused deposition modeling 3D printing; the components can be assembled and dismantled without the aid of any external tools. The replacement of specific modules along the array facilitates the reconfiguration of the actuator's bending trajectory and torque output; likewise, the combination of inflation modules with dissimilar geometries translates to several different trajectories on a single spine and allows the actuator to bend into assorted, unique structures. A detailed description of the actuator's design is thoroughly presented. We explored how reconfiguration of the actuator's modular geometry affected both the steady state and the dynamic characteristics of the actuator. The torque output of the actuator is proportional to the magnitude of the pressure applied. The actuator was excited by sinusoidal and square pressure inputs, and a second-order linear fit was performed. There were no perceived changes in its performance even after 100,000 inflation and deflation cycles.

Successful Use of Sternal-Sparing Minimally Invasive Surgery for Proximal Ascending Aortic Pathology.

BACKGROUND: A sternal-sparing approach to surgery of the proximal aorta could decrease postoperative morbidity. METHODS: To determine the potential benefits of using a minimally invasive right thoracotomy approach for the treatment of ascending aortic pathology, we retrospectively reviewed our experience in patients who required circulatory arrest for the treatment of ascending aortic pathology (with or without aortic valve involvement) between January 2009 and November 2014 (N = 177). We compared baseline characteristics, intraoperative characteristics, and postoperative clinical outcomes between those who underwent a sternotomy (n = 103) and those who underwent a minimally invasive right thoracotomy approach (n = 74). All surgical procedures were performed by a single surgeon. Propensity score matching was performed to account for baseline differences between groups. RESULTS: More patients in the minimally invasive group had bicuspid aortic valve, degenerative aortic valve, or aortic insufficiency than in the sternotomy group, but other baseline characteristics were similar between groups. No strokes occurred. In the unmatched cohort, 30-day mortality was 2.7% for the minimally invasive group compared with 1.9% for the sternotomy group (p = 1.00). In the propensity score-matched cohort, 30-day mortality was 3.2% for both groups; circulatory arrest times were longer in the minimally invasive group than in the sternotomy group (p < 0.0001), but the minimally invasive group had fewer red blood cell transfusions, shorter ventilation times, and shorter intensive care unit and hospital length of stay. CONCLUSIONS: A sternal-sparing approach to surgery of the proximal aorta is safe when performed by an experienced surgeon and conserves hospital resources.

Large right ventricular sinusoids in an infant with aorta-left ventricular tunnel and proximal right coronary artery atresia.

We report a 1-month-old infant diagnosed with an aorta-left ventricular tunnel, ventricular septal defect, and right coronary atresia with right ventricular sinusoids. The patient's anatomy and physiology did not indicate right-ventricular-dependent coronary circulation, and therefore right ventricular decompression could be performed without compromising coronary perfusion during surgical correction. A detailed understanding of the coronary anatomy is critical in managing this defect when coronary anomalies are present.

An Electromagnetic System for Inducing a Localized Force Gradient in an ECM and Its Influence on HMVEC Sprouting.

Mechanical properties of the extracellular matrix (ECM) have been observed to influence the behavior of cells. Investigations on such an influence commonly rely on using soluble cues to alter the global intrinsic ECM properties in order to study the subsequent response of cells. This article presents an electromagnetic system for inducing a localized force gradient in an ECM, and reports the experimentally observed effect of such a force gradient on in vitro angiogenic sprouting of human microvascular endothelial cells (HMVECs). This force gradient is realized through the induction of magnetic forces on the superparamagnetic microparticle-embedded ECM ( sECM). Both analytical and statistically meaningful experimental results demonstrate the effectiveness of this approach in influencing the behavior of a targeted HMVEC sprout without affecting that of other sprouts nearby. These results suggest the possibility of selectively controlling the in vitro behavior of cells by the induction of a localized force gradient in the ECM.

Dynamic Surface Control for a Class of Nonlinear Feedback Linearizable Systems With Actuator Failures.

In this brief, we propose a dynamic surface control with actuator failure compensation for a class of feedback linearizable systems with locally Lipschitz nonlinearities. First, a dynamic surface state feedback control scheme is designed, which incorporates radial basis function networks in a novel approach, to compensate system uncertainties and dynamic changes induced by actuator failures. Then, an output feedback controller is obtained by means of high-gain observers. It is proved that our control schemes guarantee the uniform ultimate boundedness of the system, and that the output tracking error converges to an arbitrarily small residual set. Finally, a simulation is carried out to illustrate the performance of the designed control schemes.

A Magneto-Microfluidic System for Investigating the Influence of an Externally Induced Force Gradient in a Collagen Type I ECM on HMVEC Sprouting.

Advances in mechanobiology have suggested that physiological and pathological angiogenesis may be differentiated based on the ways in which the cells interact with the extracellular matrix (ECM) that exhibits partially different mechanical properties. This warrants investigating the regulation of ECM stiffness on cell behavior using angiogenesis assays. In this article, we report the application of the technique of active manipulation of ECM stiffness to study in vitro angiogenic sprouting of human microvascular endothelial cells (HMVECs) in a microfluidic device. Magnetic beads were embedded in the ECM through bioconjugation (between the streptavidin-coated beads and collagen fibers) in order to create a pretension in the ECM when under the influence of an external magnetic field. The advantage of using this magneto-microfluidic system is that the resulting change in the local deformability of the collagen fibers is only apparent to a cell at the pericellular level near the site of an embedded bead, while the global intrinsic material properties of the ECM remain unchanged. The results demonstrate that this system represents an effective tool for inducing noninvasively an external force on cells through the ECM, and suggest the possibility of creating desired stiffness gradients in the ECM for manipulating cell behavior in vitro.

An Introduction to Coherent Multidimensional Spectroscopy.

Coherent multidimensional spectroscopy is a field that has drawn much attention as an optical analogue to multidimensional nuclear magnetic resonance imaging. Coherent multidimensional spectroscopic techniques produce spectra that show the magnitude of an optical signal as a function of two or more pulsed laser frequencies. Spectra can be collected in either the frequency or the time domain. In addition to improving resolution and overcoming spectral congestion, coherent multidimensional spectroscopy provides the ability to investigate and conduct studies based upon the relationship between different peaks. The purpose of this paper is to provide a general introduction to the area of coherent multidimensional spectroscopy, to provide a brief overview of current experimental approaches, and to discuss some emerging developments in this relatively young field.