2,520 research outputs found
Array comparative genomic hybridization screening in IVF significantly reduces number of embryos available for cryopreservation
Objective
During IVF, non-transferred embryos are usually selected for cryopreservation on the basis of morphological criteria. This investigation evaluated an application for array comparative genomic hybridization (aCGH) in assessment of surplus embryos prior to cryopreservation.
Methods
First-time IVF patients undergoing elective single embryo transfer and having at least one extra non-transferred embryo suitable for cryopreservation were offered enrollment in the study. Patients were randomized into two groups: Patients in group A (n=55) had embryos assessed first by morphology and then by aCGH, performed on cells obtained from trophectoderm biopsy on post-fertilization day 5. Only euploid embryos were designated for cryopreservation. Patients in group B (n=48) had embryos assessed by morphology alone, with only good morphology embryos considered suitable for cryopreservation.
Results
Among biopsied embryos in group A (n=425), euploidy was confirmed in 226 (53.1%). After fresh single embryo transfer, 64 (28.3%) surplus euploid embryos were cryopreserved for 51 patients (92.7%). In group B, 389 good morphology blastocysts were identified and a single top quality blastocyst was selected for fresh transfer. All group B patients (48/48) had at least one blastocyst remaining for cryopreservation. A total of 157 (40.4%) blastocysts were frozen in this group, a significantly larger proportion than was cryopreserved in group A (p=0.017, by chi-squared analysis).
Conclusion
While aCGH and subsequent frozen embryo transfer are currently used to screen embryos, this is the first investigation to quantify the impact of aCGH specifically on embryo cryopreservation. Incorporation of aCGH screening significantly reduced the total number of cryopreserved blastocysts compared to when suitability for freezing was determined by morphology only. IVF patients should be counseled that the benefits of aCGH screening will likely come at the cost of sharply limiting the number of surplus embryos available for cryopreservation
Rigorous results on superconducting ground states for attractive extended Hubbard models
We show that the exact ground state for a class of extended Hubbard models
including bond-charge, exchange, and pair-hopping terms, is the Yang
"eta-paired" state for any non-vanishing value of the pair-hopping amplitude,
at least when the on-site Coulomb interaction is attractive enough and the
remaining physical parameters satisfy a single constraint. The ground state is
thus rigorously superconducting. Our result holds on a bipartite lattice in any
dimension, at any band filling, and for arbitrary electron hopping.Comment: 12 page
Selection of single blastocysts for fresh transfer via standard morphology assessment alone and with array CGH for good prognosis IVF patients: results from a randomized pilot study
Background
Single embryo transfer (SET) remains underutilized as a strategy to reduce multiple gestation risk in IVF, and its overall lower pregnancy rate underscores the need for improved techniques to select one embryo for fresh transfer. This study explored use of comprehensive chromosomal screening by array CGH (aCGH) to provide this advantage and improve pregnancy rate from SET.
Methods
First-time IVF patients with a good prognosis (age <35, no prior miscarriage) and normal karyotype seeking elective SET were prospectively randomized into two groups: In Group A, embryos were selected on the basis of morphology and comprehensive chromosomal screening via aCGH (from d5 trophectoderm biopsy) while Group B embryos were assessed by morphology only. All patients had a single fresh blastocyst transferred on d6. Laboratory parameters and clinical pregnancy rates were compared between the two groups.
Results
For patients in Group A (n=55), 425 blastocysts were biopsied and analyzed via aCGH (7.7 blastocysts/patient). Aneuploidy was detected in 191/425 (44.9%) of blastocysts in this group. For patients in Group B (n=48), 389 blastocysts were microscopically examined (8.1 blastocysts/patient). Clinical pregnancy rate was significantly higher in the morphology+aCGH group compared to the morphology-only group (70.9 and 45.8%, respectively; p=0.017); ongoing pregnancy rate for Groups A and B were 69.1 vs. 41.7%, respectively (p=0.009). There were no twin pregnancies.
Conclusion
Although aCGH followed by frozen embryo transfer has been used to screen at risk embryos (e.g., known parental chromosomal translocation or history of recurrent pregnancy loss), this is the first description of aCGH fully integrated with a clinical IVF program to select single blastocysts for fresh SET in good prognosis patients. The observed aneuploidy rate (44.9%) among biopsied blastocysts highlights the inherent imprecision of SET when conventional morphology is used alone. Embryos randomized to the aCGH group implanted with greater efficiency, resulted in clinical pregnancy more often, and yielded a lower miscarriage rate than those selected without aCGH. Additional studies are needed to verify our pilot data and confirm a role for on-site, rapid aCGH for IVF patients contemplating fresh SET
Growth of detector-grade CZT by Traveling Heater Method (THM): An advancement
In this present work we report the growth of Cd{sub 0.9}Zn{sub 0.1}Te doped with In by a modified THM technique. It has been demonstrated that by controlling the microscopically flat growth interface, the size distribution and concentration can be drastically reduced in the as-grown ingots. This results in as-grown detector-grade CZT by the THM technique. The three-dimensional size distribution and concentrations of Te inclusions/precipitations were studied. The size distributions of the Te precipitations/inclusions were observed to be below the 10-{micro}m range with the total concentration less than 10{sup 5} cm{sup -3}. The relatively low value of Te inclusions/precipitations results in excellent charge transport properties of our as-grown samples. The ({mu}{tau}){sub e} values for different as-grown samples varied between 6-20 x 10{sup -3} cm{sup 2}/V. The as-grown samples also showed fairly good detector response with resolution of {approx}1.5%, 2.7% and about 3.8% at 662 keV for quasi-hemispherical geometry for detector volumes of 0.18 cm{sup 3}, 1 cm{sup 3} and 4.2 cm{sup 3}, respectively
In vitro antifungal susceptibility of Cladophialophora carrionii, agent of human chromoblastomycosis
From Gapped Excitons to Gapless Triplons in One Dimension
Often, exotic phases appear in the phase diagrams between conventional
phases. Their elementary excitations are of particular interest. Here, we
consider the example of the ionic Hubbard model in one dimension. This model is
a band insulator (BI) for weak interaction and a Mott insulator (MI) for strong
interaction. Inbetween, a spontaneously dimerized insulator (SDI) occurs which
is governed by energetically low-lying charge and spin degrees of freedom.
Applying a systematically controlled version of the continuous unitary
transformations (CUTs) we are able to determine the dispersions of the
elementary charge and spin excitations and of their most relevant bound states
on equal footing. The key idea is to start from an externally dimerized system
using the relative weak interdimer coupling as small expansion parameter which
finally is set to unity to recover the original model.Comment: 18 pages, 10 figure
Optical transmission losses in materials due to repeated impacts of liquid droplets
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76812/1/AIAA-7018-720.pd
Size-dependent Correlation Effects in Ultrafast Optical Dynamics of Metal Nanoparticles
We study the role of collective surface excitations in the electron
relaxation in small metal particles. We show that the dynamically screened
electron-electron interaction in a nanoparticle contains a size-dependent
correction induced by the surface. This leads to new channels of quasiparticle
scattering accompanied by the emission of surface collective excitations. We
calculate the energy and temperature dependence of the corresponding rates,
which depend strongly on the nanoparticle size. We show that the
surface-plasmon-mediated scattering rate of a conduction electron increases
with energy, in contrast to that mediated by a bulk plasmon. In noble-metal
particles, we find that the dipole collective excitations (surface plasmons)
mediate a resonant scattering of d-holes to the conduction band. We study the
role of the latter effect in the ultrafast optical dynamics of small
nanoparticles and show that, with decreasing nanoparticle size, it leads to a
drastic change in the differential absorption lineshape and a strong frequency
dependence of the relaxation near the surface plasmon resonance. The
experimental implications of our results in ultrafast pump-probe spectroscopy
are also discussed.Comment: 29 pages including 6 figure
Skyrmion Excitations in Quantum Hall Systems
Using finite size calculations on the surface of a sphere we study the
topological (skyrmion) excitation in quantum Hall system with spin degree of
freedom at filling factors around . In the absence of Zeeman energy, we
find, in systems with one quasi-particle or one quasi-hole, the lowest energy
band consists of states with , where and are the total orbital and
spin angular momentum. These different spin states are almost degenerate in the
thermodynamic limit and their symmetry-breaking ground state is the state with
one skyrmion of infinite size. In the presence of Zeeman energy, the skyrmion
size is determined by the interplay of the Zeeman energy and electron-electron
interaction and the skyrmion shrinks to a spin texture of finite size. We have
calculated the energy gap of the system at infinite wave vector limit as a
function of the Zeeman energy and find there are kinks in the energy gap
associated with the shrinking of the size of the skyrmion. breaking ground
state is the state with one skyrmion of infinite size. In the presence of
Zeeman energy, the skyrmion size is determined by the interplay of the Zeeman
energy and electron-electronComment: 4 pages, 5 postscript figures available upon reques
Chaotic memristor
We suggest and experimentally demonstrate a chaotic memory resistor
(memristor). The core of our approach is to use a resistive system whose
equations of motion for its internal state variables are similar to those
describing a particle in a multi-well potential. Using a memristor emulator,
the chaotic memristor is realized and its chaotic properties are measured. A
Poincar\'{e} plot showing chaos is presented for a simple nonautonomous circuit
involving only a voltage source directly connected in series to a memristor and
a standard resistor. We also explore theoretically some details of this system,
plotting the attractor and calculating Lyapunov exponents. The multi-well
potential used resembles that of many nanoscale memristive devices, suggesting
the possibility of chaotic dynamics in other existing memristive systems.Comment: Applied Physics A (in press
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