5,515 research outputs found
Equivalence of particle-particle random phase approximation correlation energy and ladder-coupled-cluster doubles
We present an analytical proof and numerical demonstrations of the
equivalence of the correlation energy from particle-particle random phase
approximation (pp-RPA) and ladder-couple-cluster-doubles (ladder-CCD). These
two theories reduce to the identical algebraic matrix equation and correlation
energy expressions, under the assumption that the pp-RPA equation is stable.
The numerical examples illustrate that the correlation energy missed by pp-RPA
in comparison with couple-cluster single and double is largely canceled out
when considering reaction energies. This theoretical connection will be
beneficial to future pp-RPA studies based on the well established couple
cluster theory
Compartment syndrome and popliteal vascular injury complicating unicompartmental knee arthroplasty
Popliteal vascular injury and the compartment syndrome of the leg are rare but important complications of knee arthroplasties. Early diagnosis and treatment are of paramount importance in preventing the devastating complications of these conditions. To our knowledge, these complications have not been reported previously after unicompartmental knee arthroplasty in the literature. Low level of suspicion may delay the diagnosis, as popliteal vascular injury and compartment syndrome are not well recognized as possible complications of unicompartmental knee arthroplasty
Treating natural disaster victims is dealing with shortages:An orthopaedics perspective
During natural disasters such as earthquakes or tsunamis, most of the casualties are known to suffer from musculoskeletal injuries. This leads to an enormous need of orthopaedic (surgical) implants such as osteosynthesis plates, which are difficult to provide in developing countries that rely on imported ones. One of the alternatives is utilization of local resources, but only after they have been proven safe to use, and meet the international standards set. Through this paper we would like to urge the international community to include locally produced biomedical products, like osteosynthesis plates in their scientific evaluations and communications. When the quality of local products is proven, the reluctance to use local products also by surgeons from developing countries will disappear and larger scale production can be initiated. This in its turn solves many problems that come after natural disasters and stimulates the national economy in an efficient and effective way
Selecting a single orientation for millimeter sized graphene sheets
We have used Low Energy Electron Microscopy (LEEM) and Photo Emission
Electron Microscopy (PEEM) to study and improve the quality of graphene films
grown on Ir(111) using chemical vapor deposition (CVD). CVD at elevated
temperature already yields graphene sheets that are uniform and of monatomic
thickness. Besides domains that are aligned with respect to the substrate,
other rotational variants grow. Cyclic growth exploiting the faster growth and
etch rates of the rotational variants, yields films that are 99 % composed of
aligned domains. Precovering the substrate with a high density of graphene
nuclei prior to CVD yields pure films of aligned domains extending over
millimeters. Such films can be used to prepare cluster-graphene hybrid
materials for catalysis or nanomagnetism and can potentially be combined with
lift-off techniques to yield high-quality, graphene based electronic devices
Two pressure-induced structural phase transitions in TiOCl
We studied the crystal structure of TiOCl up to pressures of =25~GPa at
room temperature by x-ray powder diffraction measurements. Two pressure-induced
structural phase transitions are observed: At 15~GPa emerges
an 22 superstructure with -axis unique monoclinic
symmetry (space group P2/). At 22~GPa all lattice
parameters of the monoclinic phase show a pronounced anomaly. A fraction of the
sample persists in the ambient orthorhombic phase (space group ) over the
whole pressure range.Comment: 5 pages, 5 figures; accepted for publication in Phys. Rev.
H_2 Emission From Disks Around Herbig Ae and T Tauri Stars
We present the initial results of a deep ISO-SWS survey
for the low J pure rotational emission lines of H2
toward a number of Herbig Ae and T Tauri stars.
The objects are selected to be as isolated as possible
from molecular clouds, with a spectral energy distribution
characteristic of a circumstellar disk. For most
of them the presence of a disk has been established
directly by millimeter interferometry. The S (1) line is
detected in most sources with a peak flux of 0.3-1 Jy.
The S(0) line is definitely seen in 2 objects: GG Tau
and HD 163296. The observations suggest the presence
of "warm" gas at T_(kin) ≈ 100 K with a mass of a
few % of the total gas+ dust mass, derived assuming
a gas-to-dust ratio of 100:1. The S(1) peak flux does
not show a strong correlation with spectral type of
the central star or continuum flux at 1.3 millimeter.
Possible origins for the warm gas seen in H_2 are discussed,
and comparisons with model calculations are
made
A Miniaturized Enzymatic Biosensor for Detection of Sensory-Evoked D-serine Release in the Brain
D-serine has been implicated as a brain messenger with central roles in neural signaling and plasticity. Disrupted levels of D-serine in the brain have been associated with neurological disorders, including schizophrenia, depression and Alzheimer's disease. Electrochemical biosensors are attractive tools for measuring real-time in vivo D-serine concentration changes. Current biosensors suffer from relatively large sizes (≥25 μm) making localized cellular measurements challenging, especially for single cell studies. In this work, a robust methodology for the fabrication of a reproducible miniaturized 10 μm D-serine detecting amperometric biosensor was developed. The miniature biosensor incorporated yeast D-amino acid oxidase immobilized on a poly-meta-phenylenediamine modified 10 μm Pt disk microelectrode. The biosensor offered a limit of detection of 0.361 μM (RSD < 10%) with high sensitivity (283 μA cm-2 mM-1, R2 = 0.983). The biosensor was stable for over four hours of continuous use, demonstrated a storage stability of four days and high analyte selectivity. Biosensor selectivity was validated with LC-MS and interferences with yeast D-amino acid oxidase were evaluated using drugs believed to stimulate D-serine release. Ex vivo D-serine measurements were made from Xenopus laevis tadpole brains, demonstrating the utility of the biosensors for measurements on living tissue. We observed that D-serine levels in the brain fluctuate with sensory experience. The biosensors were also used in vivo successfully. Taken together, this study addresses factors for successful and reproducible miniature biosensor fabrication for measuring D-serine in biological samples, for pharmacological evaluation, and for designing point of care devices
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