A laboratory ice machine as a cold oligotrophic artificial microbial niche for biodiscovery.

Microorganisms are ubiquitously distributed in nature and usually appear as biofilms attached to a variety of surfaces. Here, we report the development of a thick biofilm in the drain pipe of several standard laboratory ice machines, and we describe and characterise, through culture-dependent and -independent techniques, the composition of this oligotrophic microbial community. By using culturomics, 25 different microbial strains were isolated and taxonomically identified. The 16S rRNA high-throughput sequencing analysis revealed that Bacteroidota and Proteobacteria were the most abundant bacterial phyla in the sample, followed by Acidobacteriota and Planctomycetota, while ITS high-throughput sequencing uncovered the fungal community was clearly dominated by the presence of a yet-unidentified genus from the Didymellaceae family. Alpha and beta diversity comparisons of the ice machine microbial community against that of other similar cold oligotrophic and/or artificial environments revealed a low similarity between samples, highlighting the ice machine could be considered a cold and oligotrophic niche with a unique selective pressure for colonisation of particular microorganisms. The recovery and analysis of high-quality metagenome-assembled genomes (MAGs) yielded a strikingly high rate of new species. The functional profiling of the metagenome sequences uncovered the presence of proteins involved in extracellular polymeric substance (EPS) and fimbriae biosynthesis and also allowed us to detect the key proteins involved in the cold adaptation mechanisms and oligotrophic metabolic pathways. The metabolic functions in the recovered MAGs confirmed that all MAGs have the genes involved in psychrophilic protein biosynthesis. In addition, the highest number of genes for EPS biosynthesis was presented in MAGs associated with the genus Sphingomonas, which was also recovered by culture-based method. Further, the MAGs with the highest potential gene number for oligotrophic protein production were closely affiliated with the genera Chryseoglobus and Mycobacterium. Our results reveal the surprising potential of a cold oligotrophic microecosystem within a machine as a source of new microbial taxa and provide the scientific community with clues about which microorganisms are able to colonise this ecological niche and what physiological mechanisms they develop. These results pave the way to understand how and why certain microorganisms can colonise similar anthropogenic environments.

Timing of thoracic endovascular aortic repair for uncomplicated acute type B aortic dissection and the association with complications.

OBJECTIVE: Previous publications have clearly established a correlation between timing of thoracic endovascular aortic repair (TEVAR) and complications after treatment of complicated acute type B aortic dissection (ATBAD). However, the temporal association of TEVAR with morbidity after uncomplicated presentations is poorly understood and has not previously been examined using real-world national data. Therefore, the objective of this analysis was to determine whether TEVAR timing of uncomplicated ATBAD (UATBAD) is associated with postoperative complications. METHODS: The Vascular Quality Initiative TEVAR and complex endovascular aneurysm repair registry was analyzed from 2010 to 2019. Procedures performed for non-dissection-related disease as well as for ATBAD with malperfusion or rupture were excluded. Because of inherent differences between timing cohorts, propensity score matching was performed to ensure like comparisons. Univariate and multivariable analysis after matching was used to determine differences between timing groups (symptom onset to TEVAR: acute, 1-14 days; subacute, 15-90 days) for postoperative mortality, in-hospital complications, and reintervention. RESULTS: A total of 688 cases meeting inclusion criteria were identified. After matching 187 patients in each of the 1- to 14-day and 15- to 90-day treatment groups, there were no statistically significant differences between groups. On univariate analysis, the 1- to 14-day treatment group had a higher proportion of cases requiring reintervention within 30 days (15.3%) compared with UATBAD patients undergoing TEVAR within 15 to 90 days (5.2%; P = .02). There was also a difference (P = .007) at 1 year, with 33.8% of the 1- to 14-day UATBAD patients undergoing reintervention compared with 14.5% for the 15- to 90-day group. There were no statistically significant differences on multivariable analysis for long-term survival, complications, or long-term reintervention. There was a trend toward significance (P = .08) with the 1- to 14-day group having 2.3 times the odds of requiring an in-hospital reintervention compared with the 15- to 90-day group. CONCLUSIONS: Timing of TEVAR for UATBAD does not appear to predict mortality or postoperative complications. However, there is a strong association between repair within 1 to 14 days and higher risk of reintervention. This may in part be related to the 1- to 14-day group's representing an inherently higher anatomic or physiologic risk population that cannot be entirely accounted for with propensity analysis. The role of optimal timing to intervention should be incorporated into future study design of TEVAR trials for UATBAD.

Mechanical Analogue of a Majorana Bound State.

The discovery of topologically nontrivial electronic systems has opened a new age in condensed matter research. From topological insulators to topological superconductors and Weyl semimetals, it is now understood that some of the most remarkable and robust phases in electronic systems (e.g., quantum Hall or anomalous quantum Hall) are the result of topological protection. These powerful ideas have recently begun to be explored also in bosonic systems. Topologically protected acoustic, mechanical, and optical edge states have been demonstrated in a number of systems that recreate the requisite topological conditions. Such states that propagate without backscattering could find important applications in communications and energy technologies. Here, a topologically bound mechanical state, a different class of nonpropagating protected state that cannot be destroyed by local perturbations, is demonstrated. It is in particular a mechanical analogue of the well-known Majorana bound states (MBSs) of electronic topological superconductor systems. The topological binding is implemented by creating a Kekulé distortion vortex on a 2D mechanical honeycomb superlattice that can be mapped to a magnetic flux vortex in a topological superconductor.

Majorana-like Zero Modes in Kekulé Distorted Sonic Lattices.

Topological phases have recently been realized in bosonic systems. The associated boundary modes between regions of distinct topology have been used to demonstrate robust waveguiding, protected from defects by the topology of the surrounding bulk. A related type of topologically protected state that is not propagating but is bound to a defect has not been demonstrated to date in a bosonic setting. Here we demonstrate numerically and experimentally that an acoustic mode can be topologically bound to a vortex fabricated in a two-dimensional, Kekulé-distorted triangular acoustic lattice. Such lattice realizes an acoustic analog of the Jackiw-Rossi mechanism that topologically binds a bound state in a p-wave superconductor vortex. The acoustic bound state is thus a bosonic analog of a Majorana bound state, where the two valleys replace particle and hole components. We numerically show that it is topologically protected against arbitrary symmetry-preserving local perturbations, and remains pinned to the Dirac frequency of the unperturbed lattice regardless of parameter variations. We demonstrate our prediction experimentally by 3D printing the vortex pattern in a plastic matrix and measuring the spectrum of the acoustic response of the device. Despite viscothermal losses, the measured topological resonance remains robust, with its frequency closely matching our simulations.

Ultrathin Acoustic Parity-Time Symmetric Metasurface Cloak.

Invisibility or unhearability cloaks have been made possible by using metamaterials enabling light or sound to flow around obstacle without the trace of reflections or shadows. Metamaterials are known for being flexible building units that can mimic a host of unusual and extreme material responses, which are essential when engineering artificial material properties to realize a coordinate transforming cloak. Bending and stretching the coordinate grid in space require stringent material parameters; therefore, small inaccuracies and inevitable material losses become sources for unwanted scattering that are decremental to the desired effect. These obstacles further limit the possibility of achieving a robust concealment of sizeable objects from either radar or sonar detection. By using an elaborate arrangement of gain and lossy acoustic media respecting parity-time symmetry, we built a one-way unhearability cloak able to hide objects seven times larger than the acoustic wavelength. Generally speaking, our approach has no limits in terms of working frequency, shape, or size, specifically though we demonstrate how, in principle, an object of the size of a human can be hidden from audible sound.

Nonreciprocal Thermal Material by Spatiotemporal Modulation.

The thermal properties of a material with a spatiotemporal modulation, in the form of a traveling wave, in both the thermal conductivity and the specific heat capacity are studied. It is found that these materials behave as materials with an internal convectionlike term that provides them with nonreciprocal properties, in the sense that the heat flux has different properties when it propagates in the same direction or in the opposite one to the modulation of the parameters. An effective medium description is presented which accurately describes the modulated material, and numerical simulations support this description and verify the nonreciprocal properties of the material. It is found that these materials are promising candidates for the design of thermal diodes and other advanced devices for the control of the heat flow at all scales.

Gradient Index Devices for the Full Control of Elastic Waves in Plates.

In this work, we present a method for the design of gradient index devices for elastic waves in plates. The method allows the design of devices to control the three fundamental modes, despite the fact that their dispersion relation is managed by different elastic constants. It is shown that by means of complex graded phononic crystals and thickness variations it is possible to independently design the three refractive indexes of these waves, allowing therefore their simultaneous control. The effective medium theory required for this purpose is presented, and the method is applied to the design of the Luneburg and Maxwell lenses as well as to the design of a flat gradient index lens. Finally, numerical simulations are used to demonstrate the performance of the method in a broadband frequency region.

Milestones: The Road to Faculty Development.

PURPOSE: Milestones for the assessment of residents in graduate medical education mark a change in our evaluation paradigms. The Accreditation Council for Graduate Medical Education has created milestones and defined them as significant points in development of a resident based on the 6 competencies. We propose that a similar approach be taken for resident assessment of teaching faculty. We believe this will establish parity and objectivity for faculty evaluation, provide improved data about attending surgeons' teaching, and standardize faculty evaluations by residents. METHODS: A small group of advanced surgery educators determined appropriate educational characteristics, resulting in creation of 11 milestones (Fig. 2) that were reviewed by faculty and residents. The residents have historically answered 16 questions, developed by our surgical education committee (Fig. 3), on a 5-point Likert score (never to very often). Three weeks after completing this Likert-type evaluation, the residents were asked to again evaluate attending faculty using the Faculty Milestones evaluation. The residents then completed a survey of 7 questions (scale of 1-9-disagree to strongly agree, neutral = 5), assessing the new milestones and compared with the previous Likert evaluation system. RESULTS: Of 32 surgery residents, 13 completed the Likert evaluations (3760 data points) and 13 completed the milestones evaluations (1800 data points). The number completing both or neither is not known, as the responses are anonymous when used for faculty feedback. The Faculty Milestones attending physicians' scores have far fewer top of range scores (21% vs 42%) and have a wider spread of data giving better indication of areas for improvement in teaching skills. The residents completed 17 surveys (116 responses) to evaluate the new milestones system. Surveys indicated that milestones were easier to use (average rating 6.13 ± 0.42 Standard Error (SE)), effective (6.82 ± 0.39) and efficient (6.11 ± 0.53), and more objective (6.69 ± 0.39/6.75 ± 0.38) than the Likert evaluations are. Average response was 6.47 ± 0.46 for overall satisfaction with the Faculty Milestones evaluation. More surveys were completed than evaluations, as all residents had an opportunity to review both evaluation systems. CONCLUSIONS: Faculty Milestones are more objective in evaluating surgical faculty and mirror the new paradigm in resident evaluations. Residents found this was an easier, more effective, efficient, and objective evaluation of our faculty. Although our Faculty Milestones are designed for surgical educators, they are likely to be applicable with appropriate modifications to other medical educators as well.

Age does not predict need for reintervention in patients with critical limb ischemia.

OBJECTIVE: Conventional wisdom holds that patients with a need for intervention for femoropopliteal occlusive disease at a younger age have more aggressive disease, although there is a paucity of support in the literature. The purpose of this study was to evaluate this assumption. METHODS: A retrospective cohort of patients undergoing endovascular or open revascularization for femoropopliteal occlusive disease for critical limb ischemia during a 4-year period was assembled. Demographic information, comorbidities, disease characteristics, and time to last follow-up, repeat intervention, amputation, or death was recorded. The patients were stratified by age into a young (≤55 years) group, middle (56-77 years) group, and elderly (≥78 years) group. Univariate and multivariate statistical methods were used to evaluate the primary outcome. RESULTS: The study included 124 patients with a mean age of 64.4 ± 0.8 years. Progression to reintervention or amputation occurred in 50% of the patients during the follow-up period, with 18% dying before having an outcome. Kaplan-Meier analysis showed a trend toward significance (P = .06) in time to reintervention, amputation, or death among the three groups, with time to event of 253, 1083, and 504 days for the young, middle, and elderly groups, respectively. However, differences based on age were not significant (P = .57) in Cox regression analysis. CONCLUSIONS: There does not appear to be an association between time to reintervention and patient age.

Examining Hemodialysis Reliable Outflow catheter performance and cost in hemodialysis access.

BACKGROUND: The Hemodialysis Reliable Outflow (HeRO) vascular access device is a hybrid polytetrafluoroethylene graft-stent construct designed to address central venous occlusive disease. Although initial experience has demonstrated excellent mid-term patency rates, subsequent studies have led to external validity questions. The purpose of this study was to examine a single center experience with this vascular access device in challenging access cases with associated costs. METHODS: A retrospective study representing the authors' cumulative HeRO vascular access device experience was undertaken. The primary endpoint was graft failure or death, with secondary endpoints including secondary intervention rates and cost. RESULTS: Forty-one patients with 15,579 HeRO days and a mean of 12.7 ± 1.5 mo with the vascular access device were available for analysis. Secondary patency was 81.6% at 6 mo and 53.7% at 12 mo. The reintervention rate was 2.84 procedures per HeRO vascular access device year. Associated HeRO costs related to subsequent procedures were estimated at $34,713.63 per patient/y. CONCLUSIONS: These data on the patency and primary outcome data diverge significantly from initial multicenter studies and represent a real-world application of this technology. It is costly to maintain patency. Use of HeRO vascular access devices should be judicious with outcome expectations reduced.

Impact of psychological factors on objective ambulatory measures in patients with intermittent claudication.

OBJECTIVE: The purpose of this study was to evaluate the difference in objective measures of ambulation and psychosocial factors in patients with intermittent claudication (IC) stratified by type D personality, which incorporates elements of social inhibition and negative affectivity. METHODS: During a 1-year period, routine history and physical examination, ankle-brachial index, and pulse volume recording were performed on IC patients. Questionnaires assessing type D personality and psychosocial factors were also collected. The 6-minute walk test (6MWT) was performed, assessing symptoms and distance walked. Univariate and multivariate methods were used to assess the association between ambulation and type D personality. RESULTS: Seventy-one patients were enrolled (mean age, 62.5 ± 1.1 years; mean ankle-brachial index, 0.55 ± 0.03). Mean distance to symptoms and total distance walked were 83.7 ± 80.1 m and 206.5 ± 126.3 m, respectively. Type D personality was present in 29.6% of the population (n = 21). On 6MWT, 83.1% of all patients developed symptoms, and 57.4% quit because of symptoms. Univariate analysis of objective measures of ambulation demonstrated lower distance to symptoms in the type D group and trends toward lower total distance walked and quitting the 6MWT. Multivariate models showed increased odds of quitting the 6MWT (odds ratio, 7.71; P = .01) and less total distance walked by an average of 33.2 ± 13.3 m (P = .02) for the type D group. CONCLUSIONS: Despite equivalent demographic, medical, and psychosocial factors, the type D group was limited in ambulation, suggesting that type D personality is a strong predictor of disease impact in patients with IC.

The Social Security Death Index (SSDI) most accurately reflects true survival for older oncology patients.

INTRODUCTION: The ability to ascertain survival information is important for retrospective and prospective studies. Two databases that can be used are the Social Security Death Index (SSDI) and the National Death Index (NDI). Although the NDI is more complete, there are advantages to the SSDI such as ease of use and cost. The intent of this study was to determine accuracy of the SSDI. METHODS: Publically available data on all known deceased individuals in the state of Ohio in 2003 were obtained from the State of Ohio Department of Health. A random sample of 63,557 of these were compared to the SSDI to identify risk factor for inclusion/exclusion. RESULTS: Overall, 94.7% of all death records were confirmed by the SSDI. Age at death, gender, race, ethnicity, and cause of death were all found to significantly affect the likelihood of inclusion. Specifically, people aged 18-24 were included only 79.8% of the time compared to 96.2% for those over the age of 65. Also, malignancy as cause of death resulted in a 95.3% inclusion while trauma as a cause of death led to 86.5% inclusion. While Caucasians had an inclusion of 95.6%, African Americans were included only 87.8% of the time. Hispanics and women also had lower inclusion rates. DISCUSSION: The SSDI is a strong tool for following up on participants lost to follow up in certain populations but is weaker in others. The SSDI would be particularly useful in a population that is largely older, Caucasian, or has malignant disease.

Homogenization theory for periodic distributions of elastic cylinders embedded in a viscous fluid.

A multiple-scattering theory is applied to study the homogenization of clusters of elastic cylinders distributed in a isotropic lattice and embedded in a viscous fluid. Asymptotic relations are derived and employed to obtain analytical formulas for the effective parameters of homogenized clusters in which the underlying lattice has a low filling fraction. It is concluded that such clusters behave, in the low frequency limit, as an effective elastic medium. Particularly, it is found that the effective dynamical mass density follows the static estimate; i.e., the homogenization procedure does not recover the non-linear behavior obtained for the inviscid case. Moreover, the longitudinal and transversal sound speeds do not show any dependence on fluid viscosity. Numerical simulations performed for clusters made of brass cylinders embedded in glycerin support the reliability of the effective parameters resulting from the homogenization procedure reported here.

Acoustic analogue of graphene: observation of Dirac cones in acoustic surface waves.

We demonstrate the presence of Dirac cones in the dispersion relation of acoustic waves propagating on the surface of a plate of methyl methacrylate containing a honeycomb lattice of cylindrical boreholes. This structure represents the acoustic analogue of graphene, the cylindrical cavities playing the role of carbon atoms while acoustic surface waves are the equivalent of electronic waves in graphene. Analytical expressions for the Dirac frequency and Dirac velocity in acoustics are given as a function of the radius and depth of boreholes. These parameters have been experimentally determined for a constructed structure and the data are in fairly good agreement with the predicted values.

Noise control by sonic crystal barriers made of recycled materials.

A systematic study of noise barriers based on sonic crystals made of cylinders that use recycled materials like absorbing component is reported here. The barriers consist of only three rows of perforated metal shells filled with rubber crumb. Measurements of reflectance and transmittance by these barriers are reported. Their attenuation properties result from a combination of sound absorption by the rubber crumb and reflection by the periodic distribution of scatterers. It is concluded that the porous cylinders can be used as building blocks whose physical parameters can be optimized in order to design efficient barriers adapted to different noisy environments.

Anisotropic mass density by radially periodic fluid structures.

This Letter reports physical realization of acoustic metamaterials with anisotropic mass density. These metamaterials consist of a superlattice of two fluidlike components radially periodic. Several structures are spectroscopically characterized at large wavelengths (homogenization limit) by studying the acoustic resonances existing in the circular cavity where they are embedded. This characterization method allows us to extract the diagonal components of the sound speed tensor. Analytical expressions describing the anisotropic behavior as a function of the corrugation parameter are also developed and their predictions are in agreement with measurements.

Radial wave crystals: radially periodic structures from anisotropic metamaterials for engineering acoustic or electromagnetic waves.

We demonstrate that metamaterials with anisotropic properties can be used to develop a new class of periodic structures that has been named radial wave crystals. They can be sonic or photonic, and wave propagation along the radial directions is obtained through Bloch states like in usual sonic or photonic crystals. The band structure of the proposed structures can be tailored in a large amount to get exciting novel wave phenomena. For example, it is shown that acoustical cavities based on radial sonic crystals can be employed as passive devices for beam forming or dynamically orientated antennas for sound localization.

Homogenization of two-dimensional clusters of rigid rods in air.

The scattering of sound waves by circular-shaped clusters consisting of two-dimensional distributions of rigid cylinders in air is studied in the low-frequency limit (homogenization) both theoretically and experimentally. Analytical formulas for the effective density and sound speed are obtained in the framework of multiple scattering. Here, an experimental demonstration is reported in which a cluster of wooden rods acoustically behaves as a cylinder of argon gas. Moreover, evidence is presented indicating the validity of the homogenization in this cluster at frequencies lower than 3 kHz, which corresponds to a wavelength that is only 4 times the parameter of the embedded lattice and is a quarter of the cluster's diameter.