1,458 research outputs found
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 of a wire with radius is lower
than that of a bulk solid, , by . 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
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