1,030 research outputs found
Molecular twist transition in chiral and racemic phospholipid monolayers detected by Maxwell-displacement-current measurements
The molecular basis for the little (lit) mouse phenotype, characterized by a hypoplastic anterior pituitary gland, is the mutation of a single nucleotide that alters Asp 60 to Gly in the growth hormone releasing factor receptor. Detailed analysis of the lit mouse anterior pituitary reveals spatially distinct proliferative zones of growth hormone-producing stem cells and mature somatotrophs, each regulated by a different trophic factor. This sequential growth factor requirement for a specific cell type may exemplify a common strategy for regulating cellular proliferation in other mammalian organs
Physical accessible transformations on a finite number of quantum states
We consider to treat the usual probabilistic cloning, state separation,
unambiguous state discrimination, \emph{etc} in a uniform framework. All these
transformations can be regarded as special examples of generalized completely
positive trace non-increasing maps on a finite number of input states. From the
system-ancilla model we construct the corresponding unitary implementation of
pure pure, pure mixed, mixed pure, and mixed mixed
states transformations in the whole system and obtain the necessary and
sufficient conditions on the existence of the desired maps. We expect our work
will be helpful to explore what we can do on a finite set of input states.Comment: 7 page
Theory on quench-induced pattern formation: Application to the isotropic to smectic-A phase transitions
During catastrophic processes of environmental variations of a thermodynamic
system, such as rapid temperature decreasing, many novel and complex patterns
often form.
To understand such phenomena, a general mechanism is proposed based on the
competition between heat transfer and conversion of heat to other energy forms.
We apply it to the smectic-A filament growth process during quench-induced
isotropic to smectic-A phase transition. Analytical forms for the buckling
patterns are derived and we find good agreement with experimental observation
[Phys. Rev. {\bf E55} (1997) 1655]. The present work strongly indicates that
rapid cooling will lead to structural transitions in the smectic-A filament at
the molecular level to optimize heat conversion. The force associated with this
pattern formation process is estimated to be in the order of
piconewton.Comment: 9 pages in RevTex form, with 3 postscript figures. Accepted by PR
Aircraft Observations of Dust and Pollutants over NE China: Insight into the Meteorological Mechanisms of Long-Range Transport
Substantial concentrations of trace gases and aerosols are lofted and carried from Asia over the Pacific producing an inter-hemispheric impact on atmospheric chemistry and climate. The meteorological mechanism leading to this large-scale transport of dust and pollutants remains a major uncertainty in quantifying the global effects of emissions from the developing world. Models and downwind measurements have identified isentropic advection associated with wave cyclones (warm conveyor belt circulation) as an important mechanism. We present data from a case study conducted over Shenyang in NE China as part of EAST-AIRE in April 2005 in which upstream convection, rather than WCB lofting appears to dominate. Observations from instrumented aircraft flights, back trajectories, and satellite images of clouds (GOES) and aerosols (MODIS) are analyzed. In this heavily industrialized and populated region, the warm-sector PBL air ahead of a cold front was highly polluted. In the free troposphere, between ~1000 and 4000 m altitude, concentrations of trace gases and aerosols were lower, but well above background; we measured ~70 ppb O3, ~300 ppb CO, ~2 ppb SO2, and ~ 8x10-5 m-1 aerosol scattering. These observations show that dry (non-precipitating) convection can be an important mechanism for converting local air pollution problems into regional or global atmospheric chemistry problems. Climatological data indicate that spring (MAM) precipitation over NE China is low, about 90 mm compared to 290 mm over the NE US. Cloud cover, however, is similar with cumulus clouds reported about 7% of the time over NE China and about 9% of the time over the NE US suggesting that lofting in dry convective events may be common over NE Asia. Evaluation of models’ convective schemes and further observations near the source regions are called for.NS
Single- and multi-walled carbon nanotubes viewed as elastic tubes with Young's moduli dependent on layer number
The complete energy expression of a deformed single-walled carbon nanotube
(SWNT) is derived in the continuum limit from the local density approximation
model proposed by Lenosky {\it et al.} \lbrack Nature (London) {\bf 355}, 333
(1992)\rbrack and shows to be content with the classic shell theory by which
the Young's modulus, the Poisson ratio and the effective wall thickness of
SWNTs are obtained as TPa, , , respectively.
The elasticity of a multi-walled carbon nanotube (MWNT) is investigated as the
combination of the above SWNTs of layer distance and the
Young's modulus of the MWNT is found to be an apparent function of the number
of layers, , varying from 4.70TPa to 1.04TPa for N=1 to .Comment: 4 pages, 1 figur
Severe renal bleeding caused by a ruptured renal sheath: case report of a rare complication of percutaneous nephrolithotomy
BACKGROUND: Percutaneous nephrolithotomy is a minimally invasive intervention for renal stone disease. Complications, which are rare and usually presented as case reports, are diversified as the utilization of the procedure is expanded. The procedure causes less blood loss and less morbidity when compared to open surgical procedures. Yet, there are some reports involving severe bleeding and relevant morbidity during surgery. These are usually related with the surgical technique or experience of the surgeon. Renal sheaths are designed to cause minimal trauma inside the kidney and, to our knowledge, there are no reports presenting the rupture of a sheath causing severe bleeding during the procedure. CASE REPORT: We present an adult patient who had severe bleeding during percutaneous nephrolithotomy due to parenchymal injury caused by a ruptured renal sheath. During retrieval, due probably to rough handling of the equipment, a piece of stone with serrated edges ruptured the tip of the sheath, and this tip caused damage inside the kidney. The operation was terminated and measures were taken to control bleeding. The patient was transfused with a total of 1600 ml of blood, and the stones were cleared in a second look operation. CONCLUSION: Although considered to be a minimally invasive procedure, some unexpected complications may arise during percutaneous nephrolithotomy. After being fragmanted, stone pieces may damage surgical equipment, causing acute and severe harm to the kidney. Surgeons must manipulate the equipment with fine and careful movements in order to prevent this situation
Detection of a superconducting phase in a two-atom layer of hexagonal Ga film grown on semiconducting GaN(0001)
The recent observation of superconducting state at atomic scale has motivated
the pursuit of exotic condensed phases in two-dimensional (2D) systems. Here we
report on a superconducting phase in two-monolayer crystalline Ga films
epitaxially grown on wide band-gap semiconductor GaN(0001). This phase exhibits
a hexagonal structure and only 0.552 nm in thickness, nevertheless, brings
about a superconducting transition temperature Tc as high as 5.4 K, confirmed
by in situ scanning tunneling spectroscopy, and ex situ electrical
magneto-transport and magnetization measurements. The anisotropy of critical
magnetic field and Berezinski-Kosterlitz-Thouless-like transition are observed,
typical for the 2D superconductivity. Our results demonstrate a novel platform
for exploring atomic-scale 2D superconductor, with great potential for
understanding of the interface superconductivity
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