Abstract
The physical properties of semiconductors are controlled by chemical doping. In oxide semiconductors, small variations in the density of dopant atoms can completely change the local electric ...and magnetic responses caused by their strongly correlated electrons. In lightly doped systems, however, such variations are difficult to determine as quantitative 3D imaging of individual dopant atoms is a major challenge. We apply atom probe tomography to resolve the atomic sites that donors occupy in the small band gap semiconductor Er(Mn,Ti)O
3
with a nominal Ti concentration of 0.04 at. %, map their 3D lattice positions, and quantify spatial variations. Our work enables atomic-level 3D studies of structure-property relations in lightly doped complex oxides, which is crucial to understand and control emergent dopant-driven quantum phenomena.
Neck masses in children typically fall into one of three categories: developmental, inflammatory/reactive, or neoplastic. Common congenital developmental masses in the neck include thyroglossal duct ...cysts, branchial cleft cysts, dermoid cysts, vascular malformations, and hemangiomas. Inflammatory neck masses can be the result of reactive lymphadenopathy, infectious lymphadenitis (viral, staphylococcal, and mycobacterial infections; cat-scratch disease), or Kawasaki disease. Common benign neoplastic lesions include pilomatrixomas, lipomas, fibromas, neurofibromas, and salivary gland tumors. Although rare in children, malignant lesions occurring in the neck include lymphoma, rhabdomyosarcoma, thyroid carcinoma, and metastatic nasopharyngeal carcinoma. Workup for a neck mass may include a complete blood count; purified protein derivative test for tuberculosis; and measurement of titers for Epstein-Barr virus, cat-scratch disease, cytomegalovirus, human immunodeficiency virus, and toxoplasmosis if the history raises suspicion for any of these conditions. Ultrasonography is the preferred imaging study for a developmental or palpable mass. Computed tomography with intravenous contrast media is recommended for evaluating a malignancy or a suspected retropharyngeal or deep neck abscess. Congenital neck masses are excised to prevent potential growth and secondary infection of the lesion. Antibiotic therapy for suspected bacterial lymphadenitis should target Staphylococcus aureus and group A streptococcus. Lack of response to initial antibiotics should prompt consideration of intravenous antibiotic therapy, referral for possible incision and drainage, or further workup. If malignancy is suspected (accompanying type B symptoms; hard, firm, or rubbery consistency; fixed mass; supraclavicular mass; lymph node larger than 2 cm in diameter; persistent enlargement for more than two weeks; no decrease in size after four to six weeks; absence of inflammation; ulceration; failure to respond to antibiotic therapy; or a thyroid mass), the patient should be referred to a head and neck surgeon for urgent evaluation and possible biopsy.
The inversion of inhomogeneous physical states has great technological importance; for example, active noise reduction relies on the emission of an inverted sound wave that interferes destructively ...with the noise of the emitter
, and inverting the evolution of a spin system by using a magnetic-field pulse enables magnetic resonance tomography
. In contrast to these examples, inversion of a distribution of ferromagnetic or ferroelectric domains within a material is surprisingly difficult: field poling creates a single-domain state, and piece-by-piece inversion using a scanning tip is impractical. Here we report inversion of entire ferromagnetic and ferroelectric domain patterns in the magnetoelectric material Co
TeO
and the multiferroic material Mn
GeO
, respectively. In these materials, an applied magnetic field reverses the magnetization or polarization, respectively, of each domain, but leaves the domain pattern intact. Landau theory indicates that this type of magnetoelectric inversion is universal across materials that exhibit complex ordering, with one order parameter holding the memory of the domain structure and another setting its overall sign. Domain-pattern inversion is only one example of a previously unnoticed effect in systems such as multiferroics, in which several order parameters are available for combination. Exploring these effects could therefore advance multiferroics towards new levels of functionality.
Abstract
The paradigm in which magnetic fields play a crucial role in launching/collimating outflows in many astrophysical objects continues to gain support. However, semi-analytical models including ...the effect of magnetic fields on the dynamics and morphology of jets are still missing due to the intrinsic difficulties in integrating the equations describing a collimated, relativistic flow in the presence of gravity. Only few solutions have been found so far, due to the highly non-linear character of the equations together with the need to blindly search for singularities. These numerical problems prevented a full exploration of the parameter space. We present a new integration scheme to solve r-self-similar, stationary, axisymmetric magnetohydrodynamic (MHD) equations describing collimated, relativistic outflows crossing smoothly all the singular points (Alfvén point and modified slow/fast points). For the first time, we are able to integrate from the disc mid-plane to downstream of the modified fast point. We discuss an ensemble of jet solutions, emphasizing trends and features that can be compared to observables. We present, for the first time with a semi-analytical MHD model, solutions showing counter-rotation of the jet for a substantial fraction of its extent. We find diverse jet configurations with bulk Lorentz factors up to 10 and potential sites for recollimation between 103 and 107 gravitational radii. Such extended coverage of the intervals of quantities, such as magnetic-to-thermal energy ratios at the base or the heights/widths of the recollimation region, makes our solutions suitable for application to many different systems where jets are launched.
We investigate the effect of chemical doping on the electric and magnetic domain pattern in multiferroic hexagonal ErMnO3. Hole- and electron doping are achieved through the growth of Er1−xCaxMnO3 ...and Er1−xZrxMnO3 single crystals, which allows for a controlled introduction of divalent and tetravalent ions, respectively. Using conductance measurements, piezoresponse force microscopy and nonlinear optics we study doping-related variations in the electronic transport and image the corrsponding ferroelectric and antiferromagnetic domains. We find that moderate doping levels allow for adjusting the electronic conduction properties of ErMnO3 without destroying its characteristic domain patterns. Our findings demonstrate the feasibility of chemical doping for non-perturbative property-engineering of intrinsic domain states in this important class of multiferroics.
Context. The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory for exploring the molecular chemistry in the surroundings of an active galactic nucleus (AGN). Aims. Exploring the distribution ...of different molecular species allows us to understand the physical processes affecting the interstellar medium both in the AGN vicinity and in the outer star forming molecular ring. Methods. We carried out 3 mm ALMA observations that include seven different molecular species, namely HCN, HCO+, CCH, CS, HNCO, SiO, HC3N, and SO, as well as the 13C isotopologues of the first two. Spectra were extracted from selected positions and all species were imaged over the central 2 kpc (~30′′) of the galaxy at a resolution of ~2.2′′ × 1.5′′ (150 pc × 100 pc). Results. HCO+ and CS appear to be slightly enhanced in the star forming ring. CCH shows the largest variations across NGC 1097 and is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO, and HC3N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Conclusions. Differences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO+ and HCN/CS differences observed between AGN-dominated and starburst (SB) galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally, we claim that lower HCN/CS is a combination of a small underabundance of CS in AGNs, together with excitation effects, where a high density gas component (~106 cm-3) may be more prominent in SB galaxies. However, the most promising are the differences found among the dense gas tracers that, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well-shielded gas in the disk, surrounding the dense material moderately exposed to the X-ray radiation traced by HC3N. Finally SiO might be the innermost molecule in the disk structure.
Salivary Gland Disorders Wilson, Kevin F., MD; Meier, Jeremy D., MD; Ward, P. Daniel, MD, MS
American family physician,
06/2014, Letnik:
89, Številka:
11
Journal Article
Recenzirano
Salivary gland disorders include inflammatory, bacterial, viral, and neoplastic etiologies. The presentation can be acute, recurrent, or chronic. Acute suppurative sialadenitis presents as ...rapid-onset pain and swelling and is treated with antibiotics, salivary massage, hydration, and sialagogues such as lemon drops or vitamin C lozenges. Viral etiologies include mumps and human immunodeficiency virus, and treatment is directed at the underlying disease. Recurrent or chronic sialadenitis is more likely to be inflammatory than infectious; examples include recurrent parotitis of childhood and sialolithiasis. Inflammation is commonly caused by an obstruction such as a stone or duct stricture. Management is directed at relieving the obstruction. Benign and malignant tumors can occur in the salivary glands and usually present as a painless solitary neck mass. Diagnosis is made by imaging (e.g., ultrasonography, computed tomography, magnetic resonance imaging) and biopsy (initially with fine-needle aspiration). Overall, most salivary gland tumors are benign and can be treated with surgical excision.
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