Curriculum for neurogastroenterology and motility training: A report from the joint ANMS-ESNM task force

Although neurogastroenterology and motility (NGM) disorders are some of the most frequent disorders encountered by practicing gastroenterologists, a structured competency-based training curriculum developed by NGM experts is lacking. The American Neurogastroenterology and Motility Society (ANMS) and the European Society of Neurogastroenterology and Motility (ESNM) jointly evaluated the components of NGM training in North America and Europe. Eleven training domains were identified within NGM, consisting of functional gastrointestinal disorders, visceral hypersensitivity and pain pathways, motor disorders within anatomic areas (esophagus, stomach, small bowel and colon, anorectum), mucosal disorders (gastro-esophageal reflux disease, other mucosal disorders), consequences of systemic disease, consequences of therapy (surgery, endoscopic intervention, medications, other therapy), and transition of pediatric patients into adult practice. A 3-tiered training curriculum covering these domains is proposed here and endorsed by all NGM societies. Tier 1 NGM knowledge and training is expected of all gastroenterology trainees and practicing gastroenterologists. Tier 2 knowledge and training is appropriate for trainees who anticipate NGM disorder management and NGM function test interpretation being an important part of their careers, which may require competency assessment and credentialing of test interpretation skills. Tier 3 knowledge and training is undertaken by trainees interested in a dedicated NGM career and may be restricted to specific domains within the broad NGM field. The joint ANMS and ESNM task force anticipates that the NGM curriculum will streamline NGM training in North America and Europe and will lead to better identification of centers of excellence where Tier 2 and Tier 3 training can be accomplished.

Origin of Chemically Ordered Atomic Laminates ( i-MAX): Expanding the Elemental Space by a Theoretical/Experimental Approach

With increased chemical diversity and structural complexity comes the opportunities for innovative materials possessing advantageous properties. Herein, we combine predictive first-principles calculations with experimental synthesis, to explore the origin of formation of the atomically laminated i-MAX phases. By probing (Mo_2/3 M_1/3²)₂ AC (where M² = Sc, Y and A = Al, Ga, In, Si, Ge, In), we predict seven stable i-MAX phases, five of which should have a retained stability at high temperatures. (Mo_2/3Sc_1/3)₂GaC and (Mo_2/3Y_1/3)₂GaC were experimentally verified, displaying the characteristic in-plane chemical order of Mo and Sc/Y and Kagomé-like ordering of the A-element. We suggest that the formation of i-MAX phases requires a significantly different size of the two metals, and a preferable smaller size of the A-element. Furthermore, the population of antibonding orbitals should be minimized, which for the metals herein (Mo and Sc/Y) means that A-elements from Group 13 (Al, Ga, In) are favored over Group 14 (Si, Ge, Sn). Using these guidelines, we foresee a widening of elemental space for the family of i-MAX phases and expect more phases to be synthesized, which will realize useful properties. Furthermore, based on i-MAX phases as parent materials for 2D MXenes, we also expect that the range of MXene compositions will be expanded.

Electronic structure, bonding characteristics, and mechanical properties in (W2/3Sc1/3)2AlC and (W2/3Y1/3)2AlC i-MAX phases from first-principles calculations

With the recent discovery of in-plane chemically ordered MAX phases (i-MAX) of the general formula ([Formula: see text])₂ AC comes addition of non-traditional MAX phase elements. In the present study, we use density functional theory calculations to investigate the electronic structure, bonding nature, and mechanical properties of the novel (W_2/3Sc_1/3)₂AlC and (W_2/3Y_1/3)₂AlC i-MAX phases. From analysis of the electronic structure and projected crystal orbital Hamilton populations, we show that the metallic i-MAX phases have significant hybridization between W and C, as well as Sc(Y) and C states, indicative of strong covalent bonding. Substitution of Sc for Y (M ²) leads to reduced bonding strength for W-C and Al-Al interactions while M ²-C and M ²-Al interactions are strengthened. We also compare the Voigt-Reuss-Hill bulk, shear, and Young's moduli along the series of M ¹  =  Cr, Mo, and W, and relate these trends to the bonding interactions. Furthermore, we find overall larger moduli for Sc-based i-MAX phases.

On the Structural Stability of MXene and the Role of Transition Metal Adatoms

In the present communication, the atomic structure and coordination of surface adsorbed species on Nb2C MXene is investigated over time. In particular, the influence of the Nb adatoms on the structural stability and oxidation behavior of the MXene is addressed. This investigation is based on the plane-view geometry observations of single Nb2C MXene sheets by a combination of atomic-resolution scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS) and STEM image simulations.

W-Based Atomic Laminates and Their 2D Derivative W1.33 C MXene with Vacancy Ordering

Structural design on the atomic level can provide novel chemistries of hybrid MAX phases and their MXenes. Herein, density functional theory is used to predict phase stability of quaternary i-MAX phases with in-plane chemical order and a general chemistry (W_2/3 M²_1/3 )₂ AC, where M² = Sc, Y (W), and A = Al, Si, Ga, Ge, In, and Sn. Of over 18 compositions probed, only two-with a monoclinic C2/c structure-are predicted to be stable: (W_2/3 Sc_1/3 )₂ AlC and (W_2/3 Y_1/3 )₂ AlC and indeed found to exist. Selectively etching the Al and Sc/Y atoms from these 3D laminates results in W_1.33 C-based MXene sheets with ordered metal divacancies. Using electrochemical experiments, this MXene is shown to be a new, promising catalyst for the hydrogen evolution reaction. The addition of yet one more element, W, to the stable of M elements known to form MAX phases, and the synthesis of a pure W-based MXene establishes that the etching of i-MAX phases is a fruitful path for creating new MXene chemistries that has hitherto been not possible, a fact that perforce increases the potential of tuning MXene properties for myriad applications.

Tailoring Structure, Composition, and Energy Storage Properties of MXenes from Selective Etching of In-Plane, Chemically Ordered MAX Phases

The exploration of 2D solids is one of our time's generators of materials discoveries. A recent addition to the 2D world is MXenes that possses a rich chemistry due to the large parent family of MAX phases. Recently, a new type of atomic laminated phases (coined i-MAX) is reported, in which two different transition metal atoms are ordered in the basal planes. Herein, these i-MAX phases are used in a new route for tailoriong the MXene structure and composition. By employing different etching protocols to the parent i-MAX phase (Mo_2/3 Y_1/3 )₂ AlC, the resulting MXene can be either: i) (Mo_2/3 Y_1/3 )₂ C with in-plane elemental order through selective removal of Al atoms or ii) Mo_1.33 C with ordered vacancies through selective removal of both Al and Y atoms. When (Mo_2/3 Y_1/3 )₂ C (ideal stoichiometry) is used as an electrode in a supercapacitor-with KOH electrolyte-a volumetric capacitance exceeding 1500 F cm^-3 is obtained, which is 40% higher than that of its Mo_1.33 C counterpart. With H₂ SO₄ , the trend is reversed, with the latter exhibiting the higher capacitance (≈1200 F cm^-3 ). This additional ability for structural tailoring will indubitably prove to be a powerful tool in property-tailoring of 2D materials, as exemplified here for supercapacitors.

Large uniaxial magnetostriction with sign inversion at the first order phase transition in the nanolaminated Mn2GaC MAX phase

In 2013, a new class of inherently nanolaminated magnetic materials, the so called magnetic MAX phases, was discovered. Following predictive material stability calculations, the hexagonal Mn₂GaC compound was synthesized as hetero-epitaxial films containing Mn as the exclusive M-element. Recent theoretical and experimental studies suggested a high magnetic ordering temperature and non-collinear antiferromagnetic (AFM) spin states as a result of competitive ferromagnetic and antiferromagnetic exchange interactions. In order to assess the potential for practical applications of Mn₂GaC, we have studied the temperature-dependent magnetization, and the magnetoresistive, magnetostrictive as well as magnetocaloric properties of the compound. The material exhibits two magnetic phase transitions. The Néel temperature is T_N  ~ 507 K, at which the system changes from a collinear AFM state to the paramagnetic state. At T_t = 214 K the material undergoes a first order magnetic phase transition from AFM at higher temperature to a non-collinear AFM spin structure. Both states show large uniaxial c-axis magnetostriction of 450 ppm. Remarkably, the magnetostriction changes sign, being compressive (negative) above T_t and tensile (positive) below the T_t. The sign change of the magnetostriction is accompanied by a sign change in the magnetoresistance indicating a coupling among the spin, lattice and electrical transport properties.

Sodium hydroxide and vacuum annealing modifications of the surface terminations of a Ti3C2(MXene) epitaxial thin film

We investigate, and quantify, changes in structure and surface terminations of epitaxial thin films of titanium carbide (Ti₃C₂) MXene, when treated by sodium hydroxide solution followed by vacuum annealing at 550 °C. Using X-ray photoelectron spectroscopy and scanning transmission electron microscopy, we show that NaOH treatment produce an increase in the c-lattice parameter together with an increase in the O terminations and a decrease in the F terminations. There is also an increase in the percentage of the binding energy of Ti-species in Ti 2p XPS region, which suggests an increase in the overall oxidation state of Ti. After subsequent annealing, the c-lattice parameter is slightly reduced, the overall oxidation state of Ti is decreased, and the F surface terminations are further diminished, leaving a surface with predominantly O as the surface terminating species. It is important to note that NaOH treatment facilitates removal of F at lower annealing temperatures than previously reported, which in turn is important for the range of attainable properties.

Ti₃C₂T_x (MXene) thin film shows elimination of –F and domination of –O surface terminations after NaOH treatment followed by annealing while preserving the electrical conductivity of the film.

Phase formation of nanolaminated Mo2AuC and Mo2(Au1-xGax)2C by a substitutional reaction within Au-capped Mo2GaC and Mo2Ga2C thin films

Au-containing nanolaminated carbides Mo₂AuC and Mo₂(Au_1-xGa_x)₂C were synthesized by a thermally induced substitutional reaction in Mo₂GaC and Mo₂Ga₂C, respectively. The Au substitution of the Ga layers in the structures was observed using cross-sectional high-resolution scanning transmission electron microscopy. Expansion of c lattice parameters was also observed in the Au-containing phases compared to the original phases. Energy dispersive spectroscopy detected residual Ga in Au-substituted layers of both phases with a peculiar Ga in-plane ordering for Au : Ga = 9 : 1 ratio along the Au-Ga layers in Mo₂(Au_1-xGa_x)₂C. These results indicate a generalization of the Au substitution reaction for the A elements in MAX phases.

Synthesis of Ti3AuC2, Ti3Au2C2 and Ti3IrC2 by noble metal substitution reaction in Ti3SiC2 for high-temperature-stable Ohmic contacts to SiC

The large class of layered ceramics encompasses both van der Waals (vdW) and non-vdW solids. While intercalation of noble metals in vdW solids is known, formation of compounds by incorporation of noble-metal layers in non-vdW layered solids is largely unexplored. Here, we show formation of Ti₃AuC₂ and Ti₃Au₂C₂ phases with up to 31% lattice swelling by a substitutional solid-state reaction of Au into Ti₃SiC₂ single-crystal thin films with simultaneous out-diffusion of Si. Ti₃IrC₂ is subsequently produced by a substitution reaction of Ir for Au in Ti₃Au₂C₂. These phases form Ohmic electrical contacts to SiC and remain stable after 1,000 h of ageing at 600 °C in air. The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.

Prediction and synthesis of a family of atomic laminate phases with Kagomé-like and in-plane chemical ordering

The enigma of MAX phases and their hybrids prevails. We probe transition metal (M) alloying in MAX phases for metal size, electronegativity, and electron configuration, and discover ordering in these MAX hybrids, namely, (V_2/3Zr_1/3)₂AlC and (Mo_2/3Y_1/3)₂AlC. Predictive theory and verifying materials synthesis, including a judicious choice of alloying M from groups III to VI and periods 4 and 5, indicate a potentially large family of thermodynamically stable phases, with Kagomé-like and in-plane chemical ordering, and with incorporation of elements previously not known for MAX phases, including the common Y. We propose the structure to be monoclinic C2/c. As an extension of the work, we suggest a matching set of novel MXenes, from selective etching of the A-element. The demonstrated structural design on simultaneous two-dimensional (2D) and 3D atomic levels expands the property tuning potential of functional materials.

Synthesis and properties of CS x F y thin films deposited by reactive magnetron sputtering in an Ar/SF6 discharge

A theoretical and experimental study on the growth and properties of a ternary carbon-based material, CS _x F _y , synthesized from SF₆ and C as primary precursors is reported. The synthetic growth concept was applied to model the possible species resulting from the fragmentation of SF₆ molecules and the recombination of S-F fragments with atomic C. The possible species were further evaluated for their contribution to the film growth. Corresponding solid CS _x F _y thin films were deposited by reactive direct current magnetron sputtering from a C target in a mixed Ar/SF₆ discharge with different SF₆ partial pressures ([Formula: see text]). Properties of the films were determined by x-ray photoelectron spectroscopy, x-ray reflectivity, and nanoindentation. A reduced mass density in the CS _x F _y films is predicted due to incorporation of precursor species with a more pronounced steric effect, which also agrees with the low density values observed for the films. Increased [Formula: see text] leads to decreasing deposition rate and increasing density, as explained by enhanced fluorination and etching on the deposited surface by a larger concentration of F/F₂ species during the growth, as supported by an increment of the F relative content in the films. Mechanical properties indicating superelasticity were obtained from the film with lowest F content, implying a fullerene-like structure in CS _x F _y compounds.

The emergence of psychosis in a patient with severe hypothyroidism: A case report and literature review

Hypothyroidism is associated with changes in mental state that can range from mild cognitive impairment to depression to florid myxedema coma. A few cases have linked the occurence of psychotic symptoms in the context of severe hypothyroidism, an event referred in the literature as “myxedema madness”. We describe the case of a 48-year-old male with no past psychiatric history and a past medical history of hypertension and hypothyroidism who presented to the psychiatric unit for management of new-onset psychosis, particularly paranoid delusions. On basic medical screening, the patient was found to have severe hypothyroidism manifested by a TSH level of 51.85 and a free T4 level less than 0.4. The patient was treated with both an antipsychotic and thyroid hormone replacement, after which his hypothyroid symptoms and his psychosis improved. Liothyronine was also prescribed to speed up the recovery course, as his delusions were thought to be due to his hypothyroidism. The aim of this poster is to shed light on the possibility of development of psychosis concomitantly with severe hypothyroidism, given the rarity of such events, as well as to illustrate the importance of treating the underlying medical cause rather than only focusing on the treatment of the psychiatric symptoms. The use of Liothyronine proved to be beneficial in this case, as the patient's symptoms drastically improved after its administration. This could potentially illustrate the importance of using Liothyronine particularly in the treatment of delusional disorder in severe hypothyroidism.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Guidelines To Validate Control of Cross-Contamination during Washing of Fresh-Cut Leafy Vegetables

The U.S. Food and Drug Administration requires food processors to implement and validate processes that will result in significantly minimizing or preventing the occurrence of hazards that are reasonably foreseeable in food production. During production of fresh-cut leafy vegetables, microbial contamination that may be present on the product can spread throughout the production batch when the product is washed, thus increasing the risk of illnesses. The use of antimicrobials in the wash water is a critical step in preventing such water-mediated cross-contamination; however, many factors can affect antimicrobial efficacy in the production of fresh-cut leafy vegetables, and the procedures for validating this key preventive control have not been articulated. Producers may consider three options for validating antimicrobial washing as a preventive control for cross-contamination. Option 1 involves the use of a surrogate for the microbial hazard and the demonstration that cross-contamination is prevented by the antimicrobial wash. Option 2 involves the use of antimicrobial sensors and the demonstration that a critical antimicrobial level is maintained during worst-case operating conditions. Option 3 validates the placement of the sensors in the processing equipment with the demonstration that a critical antimicrobial level is maintained at all locations, regardless of operating conditions. These validation options developed for fresh-cut leafy vegetables may serve as examples for validating processes that prevent cross-contamination during washing of other fresh produce commodities.

Ti2Au2C and Ti3Au2C2 formed by solid state reaction of gold with Ti2AlC and Ti3AlC2

Ti₂Au₂C and Ti₃Au₂C₂ formation by Au/Ti₂AlC and Au/Ti₃AlC₂ exchange-reactions imply thermodynamic guidelines for identifying materials where these reactions may occur.

An investigation of the in-plane chemically ordered atomic laminates (Mo2/3Sc1/3)2AlC and (Mo2/3Y1/3)2AlC from first principles

We have calculated electronic, vibrational, and elastic properties of (Mo_2/3Sc_1/3)₂AlC and (Mo_2/3Y_1/3)₂AlC, two recently discovered nanolaminated materials in the family of so-called i-MAX phases.

Magnetic MAX phases from theory and experiments; a review

This review presents MAX phases (M is a transition metal, A an A-group element, X is C or N), known for their unique combination of ceramic/metallic properties, as a recently uncovered family of novel magnetic nanolaminates. The first created magnetic MAX phases were predicted through evaluation of phase stability using density functional theory, and subsequently synthesized as heteroepitaxial thin films. All magnetic MAX phases reported to date, in bulk or thin film form, are based on Cr and/or Mn, and they include (Cr,Mn)2AlC, (Cr,Mn)2GeC, (Cr,Mn)2GaC, (Mo,Mn)2GaC, (V,Mn)3GaC2, Cr2AlC, Cr2GeC and Mn2GaC. A variety of magnetic properties have been found, such as ferromagnetic response well above room temperature and structural changes linked to magnetic anisotropy. In this paper, theoretical as well as experimental work performed on these materials to date is critically reviewed, in terms of methods used, results acquired, and conclusions drawn. Open questions concerning magnetic characteristics are discussed, and an outlook focused on new materials, superstructures, property tailoring and further synthesis and characterization is presented.