109 research outputs found
A powerful computational crystallography method to study ice polymorphism
Classical Molecular Dynamics (MD) simulations are employed as a tool to
investigate structural properties of ice crystals under several temperature and
pressure conditions. All ice crystal phases are analyzed by means of a
computational protocol based on a clustering approach following standard MD
simulations. The MD simulations are performed by using a recently published
classical interaction potential for oxygen and hydrogen in bulk water, derived
from neutron scattering data, able to successfully describe complex phenomena
such as proton hopping and bond formation/breaking. The present study
demonstrates the ability of the interaction potential model to well describe
most ice structures found in the phase diagram of water and to estimate the
relative stability of sixteen known phases through a cluster analysis of
simulated powder diagrams of polymorphs obtained from MD simulations. The
proposed computational protocol is suited for automated crystal structure
identification.Comment: RevTex 4.1, 7 figures - to be published in the Journal of Chemical
Physic
Sinonasal angioleiomyoma with adipocyte differentiation: clinicopathologic study of 2 cases and review of the literature
Angioleiomyoma (ALM) is a benign tumor of the skin and soft tissues composed of well differentiated smooth muscle cells arranged around and among many vascular channels. Few cases have been reported in the sinonasal region, where ALM may show a variable amount of mature adipose tissue that may make hard the distinction from angiomyolipoma.
We report here two cases that presented with a three- and six-month history of left nasal obstruction respectively. In both patients, clinical examination and imaging studies failed to reveal features of tuberous sclerosis complex and demonstrated a mass obliterating the nasal cavity arising from the inferior turbinate. Both masses were endoscopically excised. Pathologic analysis revealed highly vascularized tumors composed of well differentiated smooth muscle cells intermingled with a variable number of mature adipocytes. Immunostaining for melanocytic markers was negative. Based on these findings, both tumors were diagnosed as sinonasal-ALM with adipocytic differentiation.
These two cases indicate that both clinical data (i.e. absence of features of tuberous sclerosis complex) and immunohistochemistry (i.e. absence of melanocytic markers) are mandatory for the recognition of sinonasal-ALM with adipocytic differentiation. The term angiomyolipoma to identify these lesions is confusing and should be abandoned
Gap solitons in a nonlinear quadratic negative index cavity
By integrating the full Maxwell's equations we predict the existence of gap solitons in a quadratic, Fabry-Perot negative index cavity. An intense, fundamental pump pulse shifts the band structure that forms when magnetic and electric plasma frequencies are different so that a weak, second harmonic pulse initially tuned inside the gap is almost entirely transmitted. The process is due cascading, which occurs far from phase matching conditions, and causes pulse compression. A nonlinear polarization spawns a dark soliton, while a nonlinear magnetization produces a bright soliton
Control of superluminal transit through a heterogeneous medium
We consider pulse propagation through a two component composite medium (metal
inclusions in a dielectric host) with or without cavity mirrors. We show that a
very thin slab of such a medium, under conditions of localized plasmon
resonance, can lead to significant superluminality with detectable levels of
transmitted pulse. A cavity containing the heterogeneous medium is shown to
lead to subluminal-to-superluminal transmission depending on the volume
fraction of the metal inclusions. The predictions of phase time calculations
are verified by explicit calculations of the transmitted pulse shapes. We also
demonstrate the independence of the phase time on system width and the volume
fraction under specific conditions.Comment: 21 Pages,5 Figures (Published in Journal of Modern Optics
Sporadic high-grade malignant peripheral nerve sheath tumor of the hypoglossal nerve
Malignant tumors of peripheral nerve sheaths (MPNSTs) are rare malignant soft tissue tumors arising either from a peripheral nerve or from a pre-existing benign nerve sheath tumor. They occur most often in the context of Neurofibromatosis type-1 (NF-1) and are characterized by poor prognosis and aggressive behavior with a high rate of recurrence and distant metastases. We describe a 50-year-old woman who presented with right neck swelling, progressive dysphagia and tongue paresis. Imaging analysis revealed a mass involving the right parapharyngeal space. The tumor was excissed through a transcervical approach. At surgery, the tumor was strictly adherent to the hypoglossal nerve. Pathologic evaluation of the mass revealed a high-grade MPNST. Based on the pathological diagnosis, a clinical work-up for NF-1 was performed but it resulted negative. Occurrence of sporadic high-grade MPNST in the parapharyngeal space is rare and development from the hypoglossal nerve exceptional. As far as we know, only in two cases, both with clinical features consistent with NF1, the tumor was reported to be arised from the hypoglossal nerve
p63 isoforms regulate metabolism of cancer stem cells
p63 is an important regulator of epithelial
development expressed in different variants containing (TA)
or lacking (\u394N) the N-terminal transactivation domain. The
different isoforms regulate stem-cell renewal and differentiation
as well as cell senescence. Several studies indicate
that p63 isoforms also play a role in cancer development;
however, very little is known about the role played by p63 in
regulating the cancer stem phenotype. Here we investigate the
cellular signals regulated by TAp63 and \u394Np63 in a model of
epithelial cancer stem cells. To this end, we used colon cancer
stem cells, overexpressing either TAp63 or \u394Np63 isoforms,
to carry out a proteomic study by chemical-labeling approach
coupled to network analysis. Our results indicate that p63 is
implicated in a wide range of biological processes, including metabolism. This was further investigated by a targeted strategy at
both protein and metabolite levels. The overall data show that TAp63 overexpressing cells are more glycolytic-active than \u394Np63
cells, indicating that the two isoforms may regulate the key steps of glycolysis in an opposite manner. The mass-spectrometry
proteomics data of the study have been deposited to the ProteomeXchange Consortium (http://proteomecentral.
proteomexchange.org) via the PRIDE partner repository with data set identifiers PXD000769 and PXD000768
A graphical environment to express the semantics of control systems
We present the concept of a unified graphical environment for expressing the
semantics of control systems. The graphical control system design environment
in Simulink already allows engineers to insert a variety of assertions aimed
the verification and validation of the control software. We propose extensions
to a Simulink-like environment's annotation capabilities to include formal
control system stability, performance properties and their proofs. We provide a
conceptual description of a tool, that takes in a Simulink-like diagram of the
control system as the input, and generates a graphically annotated control
system diagram as the output. The annotations can either be inserted by the
user or generated automatically by a third party control analysis software such
as IQC or -tool. We finally describe how the graphical
representation of the system and its properties can be translated to annotated
programs in a programming language used in verification and validation such as
Lustre or C
Analysis of the RLMS Adaptive Beamforming Algorithm Implemented with Finite Precision
This paper studies the influence of the use of finite wordlength on the operation of the RLMS adaptive beamformingalgorithm. The convergence behavior of RLMS, based on the minimum mean square error (MSE), is analyzed for operation with finite precision. Computer simulation results verify that a wordlength of nine bits is sufficient for the RLMS algorithm to achieve performance close to that provided by full precision. The performance measures used include residual MSE, rate of convergence, error vector magnitude (EVM), and beam pattern. Based on all these measures, it is shown that the RLMS algorithm outperforms other earlier algorithms, such as least mean square (LMS), recursive least square (RLS), modified robust variable step size (MRVSS) and constrained stability LMS (CSLMS)
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