The three-dimensional instability of strained vortices in a viscous fluid

The recent theory describing 3-D exact solutions of the Navier–Stokes equations is applied to the problem of stability of 2-D viscous flow with elliptical streamlines. An intrinsically inviscid instability mechanism persists in all such flows provided the length scale of the disturbance is sufficiently large. Evidence is presented that this mechanism may be responsible for 3-D instabilities in high Reynolds number flows whose vortex structures can be locally described by elliptical streamlines

Supported magnetic nanoclusters: Softlanding of Pd clusters on a MgO surface

Low-energy deposition of neutral Pd_N clusters (N=2-7 and 13) on a MgO(001) surface F-center (FC) was studied by spin-density-functional molecular dynamics simulations. The incident clusters are steered by an attractive "funnel" created by the FC, resulting in adsorption of the cluster, with one of its atoms bonded atop of the FC. The deposited Pd_2-Pd_6 clusters retain their gas-phase structures, while for N>6 surface-commensurate isomers are energetically more favorable. Adsorbed clusters with N > 3 are found to remain magnetic at the surface.Comment: 5 pages, 2 figs, Phys.Rev.Lett., accepte

Clinical Outcomes After Ileal Pouch-Anal Anastomosis in Pediatric Patients

Background Ileal pouch-anal anastomosis (IPAA) is the standard surgical reconstruction for patients with familial adenomatous polyposis (FAP) and ulcerative colitis (UC) who undergo total proctocolectomy (TPC). Although patients receive the same reconstruction, their postoperative complications can differ. We hypothesize that indication for TPC and other preoperative clinical factors are associated with differences in postoperative outcomes following IPAA. Methods A retrospective cohort of pediatric patients who underwent proctocolectomy with IPAA from 1996 to 2016 was identified. Preoperative, operative, and postoperative clinical variables were collected. Univariate analyses were performed to evaluate for relevant postoperative clinical differences. Results Seventy-nine patients, 17 with FAP and 62 with UC, were identified. FAP patients spent a mean of 1125 ± 1011 d between initial diagnosis and first surgery compared to 585 ± 706 d by UC patients (P = 0.038). FAP patients took a mean of 57 ± 38 d to complete TPC with IPAA compared to UC patients at 177 ± 121 d (P < 0.001). FAP and UC patients did not differ in mean number of bowel movements at their 6-mo postoperative visit (4.7 ± 2.1 versus 5.6 ± 1.9, respectively [P = 0.134]). FAP patients were less likely to experience pouchitis (P = 0.009), pouch failure (P < 0.001), and psychiatric symptoms (P = 0.019) but more likely to experience bowel obstruction (P = 0.002). Conclusions IPAA is a safe, restorative treatment for FAP and UC patients after TPC. Based on diagnosis and preoperative course, there are differences in morbidity in IPAA patients. Clinical data such as these will allow surgeons to help families anticipate their child's preoperative and postoperative courses and to maximize successful postoperative outcomes

Strongly correlated wave functions for artificial atoms and molecules

A method for constructing semianalytical strongly correlated wave functions for single and molecular quantum dots is presented. It employs a two-step approach of symmetry breaking at the Hartree-Fock level and of subsequent restoration of total spin and angular momentum symmetries via Projection Techniques. Illustrative applications are presented for the case of a two-electron helium-like single quantum dot and a hydrogen-like quantum dot molecule.Comment: 9 pages. Revtex with 2 GIF and 1 EPS figures. Published version with extensive clarifications. A version of the manuscript with high quality figures incorporated in the text is available at http://calcite.physics.gatech.edu/~costas/qdhelproj.html For related papers, see http://www.prism.gatech.edu/~ph274c

Phase-Controlled Force and Magnetization Oscillations in Superconducting Ballistic Nanowires

The emergence of superconductivity-induced phase-controlled forces in the (0.01-0.1) nN range, and of magnetization oscillations, in nanowire junctions, is discussed. A giant magnetic response to applied weak magnetic fields, is predicted in the ballistic Josephson junction formed by a superconducting tip and a surface, bridged by a normal metal nanowire where Andreev states form.Comment: 5 pages, 3 figure

Premelting of Thin Wires

Recent work has raised considerable interest on the nature of thin metallic wires. We have investigated the melting behavior of thin cylindrical Pb wires with the axis along a (110) direction, using molecular dynamics and a well-tested many-body potential. We find that---in analogy with cluster melting---the melting temperature $T_m (R)$ of a wire with radius $R$ is lower than that of a bulk solid, $T_m^b$, by $T_m (R) = T_m^b -c/R$. Surface melting effects, with formation of a thin skin of highly diffusive atoms at the wire surface, is observed. The diffusivity is lower where the wire surface has a flat, local (111) orientation, and higher at (110) and (100) rounded areas. The possible relevance to recent results on non-rupturing thin necks between an STM tip and a warm surface is addressed.Comment: 10 pages, 4 postscript figures are appended, RevTeX, SISSA Ref. 131/94/CM/S

Sclerotherapy for the management of rectal prolapse in children

Purpose Rectal prolapse is a commonly occurring and usually self-limited process in children. Surgical management is indicated for failures of conservative management. However, the optimal approach is unknown. The purpose of this study is to determine the efficacy of sclerotherapy for the management of rectal prolapse. Methods This was a retrospective review of children < 18 years with rectal prolapse who underwent sclerotherapy, predominantly with peanut oil (91%), between 1998 and 2015. Patients with imperforate anus or cloaca abnormalities, Hirschprung disease, or prior pull-through procedures were excluded. Results Fifty-seven patients were included with a median age of 4.9 years (interquartile range (IQR) 3.2–9.2) and median follow-up of 52 months (IQR 8–91). Twenty patients (n = 20/57; 35%) recurred at a median of 1.6 months (IQR 0.8–3.6). Only 3 patients experienced recurrence after 4 months. Nine of the patients who recurred (n = 9/20; 45%) were re-treated with sclerotherapy. This was successful in 5 patients (n = 5/9; 56%). Two patients (n = 2/20; 10%) experienced a mucosal recurrence which resolved with conservative management. Forty-four patients were thus cured with sclerotherapy alone (n = 44/57; 77%). No patients undergoing sclerotherapy had an adverse event. Thirteen patients (n = 13/20; 65%) underwent rectopexy after failing at least one treatment of sclerotherapy. Three of these patients (n = 3/13; 23%) recurred following rectopexy and required an additional operation. Conclusions Injection sclerotherapy for children with rectal prolapse resulted in a durable cure of prolapse in most children. Patients who recur following sclerotherapy tend to recur within 4 months. Another attempt at sclerotherapy following recurrence is reasonable and was successful half of the time. Sclerotherapy should be the preferred initial treatment for rectal prolapse in children and for the initial treatment of recurrence

Dislocation Emission around Nanoindentations on a (001) fcc Metal Surface Studied by STM and Atomistic Simulations

We present a combined study by Scanning Tunneling Microscopy and atomistic simulations of the emission of dissociated dislocation loops by nanoindentation on a (001) fcc surface. The latter consist of two stacking-fault ribbons bounded by Shockley partials and a stair-rod dislocation. These dissociated loops, which intersect the surface, are shown to originate from loops of interstitial character emitted along the directions and are usually located at hundreds of angstroms away from the indentation point. Simulations reproduce the nucleation and glide of these dislocation loops.Comment: 10 pages, 4 figure

Photoelectron spectra of aluminum cluster anions: Temperature effects and ab initio simulations

Photoelectron (PES) spectra from aluminum cluster anions (from 12 to 15 atoms) at various temperature regimes, were studied using ab-initio molecular dynamics simulations and experimentally. The calculated PES spectra, obtained via shifting of the simulated electronic densities of states by the self-consistently determined values of the asymptotic exchange-correlation potential, agree well with the measured ones, allowing reliable structural assignments and theoretical estimation of the clusters' temperatures.Comment: RevTex, 3 gif figures. Scheduled for Oct 15, 1999, issue of Phys. Rev. B as Rapid Communicatio