Interfacing capillary-based separations to mass spectrometry using desorption electrospray ionization

The powerful hybrid analysis method of capillary-based separations followed by mass spectrometric analysis gives substantial chemical identity and structural information. It is usually carried out using electrospray ionization. However, the salts and detergents used in the mobile phase for electrokinetic separations suppress ionization efficiencies and contaminate the inlet of the mass spectrometer. This report describes a new method that uses desorption electrospray ionization (DESI) to overcome these limitations. Effluent from capillary columns is deposited on a rotating Teflon disk that is covered with paper. As the surface rotates, the temporal separation of the eluting analytes (i.e., the electropherogram) is spatially encoded on the surface. Then, using DESI, surface-deposited analytes are preferentially ionized, reducing the effects of ion suppression and inlet contamination on signal. With the use of this novel approach, two capillary-based separations were performed: a mixture of the rhodamine dyes at milligram/milliliter levels in a 10 mM sodium borate solution was separated by capillary electrophoresis, and a mixture of three cardiac drugs at milligram/milliliter levels in a 12.5 mM sodium borate and 12.5 mM sodium dodecyl sulfate solution was separated by micellar electrokinetic chromatography. In both experiments, the negative effects of detergents and salts on the MS analyses were minimized.     

2D Electrets of Ultrathin MoO2 with Apparent Piezoelectricity

Since graphene, a variety of 2D materials have been fabricated in a quest for a tantalizing combination of properties and desired physiochemical behavior. 2D materials that are piezoelectric, i.e., that allow for a facile conversion of electrical energy into mechanical and vice versa, offer applications for sensors, actuators, energy harvesting, stretchable and flexible electronics, and energy storage, among others. Unfortunately, materials must satisfy stringent symmetry requirements to be classified as piezoelectric. Here, 2D ultrathin single-crystal molybdenum oxide (MoO₂) flakes that exhibit unexpected piezoelectric-like response are fabricated, as MoO₂ is centrosymmetric and should not exhibit intrinsic piezoelectricity. However, it is demonstrated that the apparent piezoelectricity in 2D MoO₂ emerges from an electret-like behavior induced by the trapping and stabilization of charges around defects in the material. Arguably, the material represents the first 2D electret material and suggests a route to artificially engineer piezoelectricity in 2D crystals. Specifically, it is found that the maximum out-of-plane piezoresponse is 0.56 pm V⁻¹, which is as strong as that observed in conventional 2D piezoelectric materials. The charges are found to be highly stable at room temperature with a trapping energy barrier of ≈2 eV.     

Craniocervical junction tuberculosis: a rare but dangerous disease

BACKGROUND: Mycobacterium tuberculosis of the cervical spine is a rare but dangerous manifestation of extra-pulmonary tuberculosis. The clinical picture ranges from early, nonspecific, insidious symptoms to severe neurological complications and death, attributed to craniocervical junction instability and cervicomedullary compression. The different lines of management include antituberculous medication with traction and external fixation or adjunctive surgery (debridement and stabilization) in patients with severe or persistent neurological complications and/or vertebral instability. METHODS: We describe two patients with advanced craniocervical junction tuberculosis. The early clinical picture was nonspecific in Case 1 and obscured by psychiatric illness in Case 2. The detailed clinical and radiological findings, and the management, will be described. Involvement of the occipital condyles and foramen magnum, which has not been reported previously, will be demonstrated. RESULTS: Both cases underwent transoral biopsy, aspiration, and debridement of retropharyngeal abscess (granuloma). Histological and tissue culture studies proved the abscesses were tuberculous and anti-tuberculous medications were started. Case 1 showed complete resolution of the clinical and radiological findings. Case 2 developed cardiorespiratory arrest while in a halo jacket. He was resuscitated but remained quadriplegic and semiconscious; he developed nosocomial gram negative pneumonia. He was referred back to his local hospital where he died 1 year later. CONCLUSIONS: Tuberculosis is an infrequent but notable cause of cervicomedullary compression. It should be suspected in patients with infective spondylitis who are immunocompromised or reside in an area highly endemic for tuberculosis. Management strategies include antituberculosis medication, transoral biopsy and drainage of the abscess, traction and external fixation, posterior decompression, and internal fixation, according to the clinical and radiological findings.     

Ambiguity Resolution in Direction of Arrival Estimation with Linear Antenna Arrays Using Differential Geometry

Linear antenna arrays (LAs) can be used to accurately predict the direction of arrival (DOAs) of various targets of interest in a given area. However, under certain conditions, LA suffers from the problem of ambiguities among the angles of targets, which may result in misinterpretation of such targets. In order to cope up with such ambiguities, various techniques have been proposed. Unfortunately, none of them fully resolved such a problem because of rank deficiency and high computational cost. We aimed to resolve such a problem by proposing an algorithm using differential geometry. The proposed algorithm uses a specially designed doublet antenna array, which is made up of two individual linear arrays. Two angle observation models, ambiguous observation model (AOM) and estimated observation model (EOM), are derived for each individual array. The ambiguous set of angles is contained in the AOM, which is obtained from the corresponding array elements using differential geometry. The EOM for each array, on the other hand, contains estimated angles of all sources impinging signals on each array, as calculated by a direction-finding algorithm such as the genetic algorithm. The algorithm then contrasts the EOM of each array with its AOM, selecting the output of that array whose EOM has the minimum correlation with its corresponding AOM. In comparison to existing techniques, the proposed algorithm improves estimation accuracy and has greater precision in antenna aperture selection, resulting in improved resolution capabilities and the potential to be used more widely in practical scenarios. The simulation results using MATLAB authenticates the effectiveness of the proposed algorithm.     

Surface Solidification Behaviour of Micro‐Alloyed Steels under Continuous Casting Conditions

Micro‐alloyed steels are important in steel industry with regard to their unique mechanical properties. Their characterisitcs are mainly caused by the refinement of ferrite grain size by controlled precipitation of nitrides during thermomechanical treatment in hot rolling. Uncontrolled precipitations of titanium nitrides in the surface region during casting and solidification can negatively influence the surface quality of continuously cast steel, particularly when casting, thermal soaking and hot rolling are carried out in a combined process chain. Focus of this work are experimental simulations and mathematical investigations of early solidification in a CC mould, primary precipitation of nitrides, and effects of different influences such as mould contact through casting flux or direct mould contact. A laboratory rig to lead solidification on liquid casting flux was developed. The carbon content of the steel melts was varied.     

Management of the patient with aortic root disease and aortic insufficiency

There is no single standardized method of repair for the anatomic variations in aortic root pathology, which may include dissection, aneurysmal dilation, and valve disease and can occur at the annulus, sinuses of Valsalva, or the sinotubular junction. Composite valve/graft replacement, valve resuspension, and allograft each play a significant role in aortic root therapy, but none is applicable in all cases. Patient age, Marfan's syndrome, endocarditis, and previous valve replacement are examples of some of the wide variations in delineating factors.     

Decision Tool for Selecting the Optimal Techniques for Cost and Schedule Reduction in Capital Projects

Projects must meet budget, schedule, safety, and quality goals to be regarded as a success. Many factors come into play, and many decisions are made that influence a project’s outcome. Today, owners are often faced with deciding between an execution strategy that emphasizes either project cost or project schedule. Such a decision may be made not once, but throughout the life of the project. Project teams, when required by the owner to make a cost-schedule trade-off, generate common sense ideas, best practices, and other means of achieving the desired trade-off through brainstorming sessions. This paper offers a tool for systematically identifying the techniques which are most effective in achieving the trade-off goal. Project teams can then use these techniques in a timely fashion to increase the likelihood of project success.