Diagnosis and treatment of hereditary hemorrhagic telangiectasia in a pediatric patient with chronic cyanosis.

Background: Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disorder of vascular dysplasias that is characterized by mucocutaneous telangiectasias, gastrointestinal tract bleeding, and arteriovenous malformations (AVMs) of the pulmonary, hepatic, and cerebral vascular systems. Case Summary: A seven-year-old boy presented to his primary care provider with a five-day history of watery diarrhea and was incidentally found to have oxygen saturations in the low eighties, perioral cyanosis, and clubbing on physical exam. He was referred to the pediatric emergency department (ED) for evaluation. Upon presentation to the pediatric ED, oxygen saturation ranged from 74-85%. He was in no acute distress and was afebrile with normal vital signs. The patient was small for his age with height and weight in the thirteenth and third percentiles, respectively, and had central cyanosis and clubbing of fingers and toes. Auscultation revealed diminished lung sounds in the right lower lobe. No mucocutaneous telangiectasias or cardiac murmurs were appreciated. Family history was positive for hereditary hemorrhagic telangiectasia (HHT) with gastrointestinal bleeding and anemia in his maternal great grandmother and maternal grandmother, minor bleeding and mucocutaneous telangiectasias in his mother, and cyanosis with exercise and recurrent epistaxis in his brother. Complete blood count was significant for a hemoglobin level of 18.1 g/dL. A chest x-ray (Figure 1) showed an airspace opacification within the superior segment of the right lower lobe suspicious for an arteriovenous malformation (AVM).peer-reviewe

Antiferromagnetism in EuCu2As2 and EuCu1.82Sb2 Single Crystals

Single crystals of EuCu2As2 and EuCu2Sb2 were grown from CuAs and CuSb self-flux, respectively. The crystallographic, magnetic, thermal and electronic transport properties of the single crystals were investigated by room-temperature x-ray diffraction (XRD), magnetic susceptibility \chi versus temperature T, isothermal magnetization M versus magnetic field H, specific heat Cp(T) and electrical resistivity \rho(T) measurements. EuCu2As2 crystallizes in the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm), whereas EuCu2Sb2 crystallizes in the related primitive tetragonal CaBe2Ge2-type structure (space group P4/nmm). The energy-dispersive x-ray spectroscopy and XRD data for the EuCu2Sb2 crystals showed the presence of vacancies on the Cu sites, yielding the actual composition EuCu1.82Sb2. The \rho(T) and Cp(T) data reveal metallic character for both EuCu2As2 and EuCu1.82Sb2. Antiferromagnetic (AFM) ordering is indicated from the \chi(T), Cp(T), and \rho(T) data for both EuCu2As2 (T_N = 17.5 K) and EuCu1.82Sb2 (T_N = 5.1 K). In EuCu1.82Sb2, the ordered-state \chi(T) and M(H) data suggest either a collinear A-type AFM ordering of Eu+2 spins S=7/2 or a planar noncollinear AFM structure, with the ordered moments oriented in the tetragonal ab plane in either case. This ordered-moment orientation for the A-type AFM is consistent with calculations with magnetic dipole interactions. The anisotropic \chi(T) and isothermal M(H) data for EuCu2As2, also containing Eu+2 spins S=7/2, strongly deviate from the predictions of molecular field theory for collinear AFM ordering and the AFM structure appears to be both noncollinear and noncoplanar.Comment: 21 pages, 22 figures, 4 Table

Modification to the Automatic Ionization Chamber

The automatic ionization chamber has been described previously [1,2]. It has proven quite reliable in service and has many desirable features, especially for balloon-borne equipment. A disadvantage has been that the time of discharge was dependent upon the potential applied to the quartz fiber. Thus, during the comparison of the instrument to be used with the standards, careful measurement of the potential used on the standards was required. Furthermore, care was required to make sure that the battery used during the flight remained constant in potential. It has now been found that the time between rechargings can be made nearly independent of the potential of the fiber by inserting a metal conductor inside and insulating it from the outer conductor surrounding the quartz fiber, and making the potential of this inner conductor the same as that of the fiber

Physical properties of EuPd2As2 single crystals

The physical properties of self-flux grown EuPd2As2 single crystals have been investigated by magnetization M, magnetic susceptibility chi, specific heat Cp, and electrical resistivity rho measurements versus temperature T and magnetic field H. The crystal structure was determined by powder x-ray diffraction measurements, which confirmed the ThCr2Si2-type body-centered tetragonal structure (space group I4/mmm) reported previously. The rho(T) data indicate that state of EuPd2As2 is metallic. Long-range antiferromagnetic (AFM) ordering is apparent from the chi(T), Cp(T), and rho(T) measurements. For H \parallel c the chi(T) indicates two transitions at TN1 = 11.0 K and TN2 = 5.5 K, whereas for H \perp c only one transition is observed at TN1 = 11.0 K. Between TN1 and TN2 the anisotropic chi(T) data suggest a planar noncollinear AFM structure, whereas at T < TN2 the chi(T) and M(H,T) data suggest a spin reorientation transition in which equal numbers of spins cant in opposite directions out of the ab plane. We estimate the critical field at 2 K at which all Eu moments become aligned with the field to be about 22 T. The magnetic entropy at 25 K estimated from the Cp(T) measurements is about $11\%$ smaller than expected, possibly due to an inaccuracy in the lattice heat capacity contribution. An upturn in rho at T < TN1 suggests superzone energy gap formation below TN1. This behavior of rho(T < TN1) is not sensitive to applied magnetic fields up to H = 12 T.Comment: 11 pages, 10 figures, 2 tables and 52 references; To appear in J. Phys.: Condens. Matte

How Cosmic Background Correlations at Large Angles Relate to Mass Autocorrelations in Space

The Sachs-Wolfe effect is known to produce large angular scale fluctuations in the Cosmic Microwave Background Radiation (CMBR) due to gravitational potential fluctuations. We show how the angular correlation function of the CMBR can be expressed explicitly in terms of the mass autocorrelation function $\xi (r)$ in the Universe. We derive analytic expressions for the angular correlation function and its multipole moments in terms of integrals over $\xi (r)$ or its second moment, $J_3 (r)$, which does not need to satisfy the sort of integral constraint that $\xi (r)$ must. We derive similar expressions for bulk flow velocity in terms of $\xi$ and $J_3$. One interesting result that emerges directly from this analysis is that, for angles $\theta$, there is a substantial contribution to the correlation function from a wide range of distance $r$ and that the radial shape of this contribution does not vary greatly with angle.Comment: 9 pages in Plain TeX and 6 figures appended in 9 pages of uuencoded PostScript. Lick Preprint Number 1

Metallic behavior induced by potassium doping of the trigonal antiferromagnetic insulator EuMn2As2

We report magnetic susceptibility \chi, isothermal magnetization M, heat capacity C_p and electrical resistivity \rho measurements on undoped EuMn2As2 and K-doped Eu0.96K0.04Mn2As2 and Eu0.93K0.07Mn2As2 single crystals with the trigonal CaAl2Si2-type structure as a function of temperature T and magnetic field H. EuMn2As2 has an insulating ground state with an activation energy of 52 meV and exhibits antiferromagnetic (AFM) ordering of the Eu+2 spins S=7/2 at T_N1 = 15 K from C_p(T) and \chi(T) data with a likely spin-reorientation transition at T_N2 = 5.0 K. The Mn+2 3d5 spins-5/2 exhibit AFM ordering at T_N = 142 K from all three types of measurements. The M(H) isotherm and \chi(T) data indicate that the Eu AFM structure is both noncollinear and noncoplanar. The AFM structure of the Mn spins is also unclear. A 4% substitution of K for Eu in Eu0.96K0.04Mn2As2 is sufficient to induce a metallic ground state. Evidence is found for a difference in the AFM structure of the Eu moments in the metallic crystals from that of undoped EuMn2As2 versus both T and H. For metallic Eu0.96K0.04Mn2As2 and Eu0.93K0.07Mn2As2, an anomalous S-shape T dependence of \rho related to the Mn magnetism is found. Upon cooling from 200 K, \rho exhibits a strong negative curvature, reaches maximum positive slope at the Mn T_N ~ 150 K, and then continues to decrease but more slowly below T_N. This suggests that dynamic short-range AFM order of the Mn spins above the Mn T_N strongly suppresses the resistivity, contrary to the conventional decrease of \rho that is only observed upon cooling below T_N of an antiferromagnet.Comment: 21 pages, 22 figures, 4 Table