1,819 research outputs found
Sliderule-like property of Wigner's little groups and cyclic S-matrices for multilayer optics
It is noted that two-by-two S-matrices in multilayer optics can be
represented by the Sp(2) group whose algebraic property is the same as the
group of Lorentz transformations applicable to two space-like and one time-like
dimensions. It is noted also that Wigner's little groups have a sliderule-like
property which allows us to perform multiplications by additions. It is shown
that these two mathematical properties lead to a cyclic representation of the
S-matrix for multilayer optics, as in the case of ABCD matrices for laser
cavities. It is therefore possible to write the N-layer S-matrix as a
multiplication of the N single-layer S-matrices resulting in the same
mathematical expression with one of the parameters multiplied by N. In
addition, it is noted, as in the case of lens optics, multilayer optics can
serve as an analogue computer for the contraction of Wigner's little groups for
internal space-time symmetries of relativistic particles.Comment: RevTex 13 pages, Secs. IV and V revised and expande
MTBVAC vaccine is safe, immunogenic and confers protective efficacy against Mycobacterium tuberculosis in newborn mice
Development of novel more efficient preventive vaccines against tuberculosis (TB) is crucial to achieve TB eradication by 2050, one of the Millennium Development Goals (MDG) for the current century. MTBVAC is the first and only live attenuated vaccine based on a human isolate of Mycobacterium tuberculosis developed as BCG-replacement strategy in newborns that has entered first-in-human adult clinical trials. In this work, we characterize the safety, immunogenicity and protective efficacy of MTBVAC in a model of newborn C57/BL6 mice. Our data clearly indicate that MTBVAC is safe for newborn mice, and does not affect animal growth or organ development. In addition, MTBVAC-vaccinated mice at birth showed enhanced immunogenicity and better protection against M. tuberculosis challenge in comparison with BCG
Quantum Dot as Spin Filter and Spin Memory
We consider a quantum dot in the Coulomb blockade regime weakly coupled to
current leads and show that in the presence of a magnetic field the dot acts as
an efficient spin-filter (at the single-spin level) which produces a
spin-polarized current. Conversely, if the leads are fully spin-polarized the
up or down state of the spin on the dot results in a large sequential or small
cotunneling current, and thus, together with ESR techniques, the setup can be
operated as a single-spin memory.Comment: 4 pages, 3 figures, REVTe
Guidance of sentinel lymph node biopsy decisions in patients with T1-T2 melanoma using gene expression profiling.
AIM: Can gene expression profiling be used to identify patients with T1-T2 melanoma at low risk for sentinel lymph node (SLN) positivity?
PATIENTS & METHODS: Bioinformatics modeling determined a population in which a 31-gene expression profile test predicted \u3c5% SLN positivity. Multicenter, prospectively-tested (n = 1421) and retrospective (n = 690) cohorts were used for validation and outcomes, respectively.
RESULTS: Patients 55-64 years and ≥65 years with a class 1A (low-risk) profile had SLN positivity rates of 4.9% and 1.6%. Class 2B (high-risk) patients had SLN positivity rates of 30.8% and 11.9%. Melanoma-specific survival was 99.3% for patients ≥55 years with class 1A, T1-T2 tumors and 55.0% for class 2B, SLN-positive, T1-T2 tumors.
CONCLUSION: The 31-gene expression profile test identifies patients who could potentially avoid SLN biopsy
Comunidad Chorcán y Varas – Hacia la construcción de una estrategia de desarrollo local con base en el turismo social comunitario
Las comunidades originarias de Varas y Chorcán, al igual que la mayoría en la Quebrada de Humahuaca, no han sido ajenas a la problemática general de todas las comunidades originarias de América: desde su casi aniquilación, sojuzgamiento, despojo y opresión de los primeros siglos de conquista europea, hasta el ocultamiento, marginación, relegación, discriminación, que aún perdura en nuestros días. Estas comunidades dedicadas tradicionalmente a tareas agrícolas y ganaderas de pequeña escala, no escapan a la problemática de las poblaciones rurales, aisladas de los centros urbanos, los mercados, los avances tecnológicos y sus beneficios, especialmente en cuestiones de salud, educación, comunicación, etc. En 2003 la UNESCO declara a la Quebrada de Humahuaca como patrimonio cultural de la humanidad a partir de lo cual se produce un rápido y poco planificado desarrollo turístico. Este proyecto apunta a la disminución de la migración que se produce de las zonas rurales a la ciudad por los atractivos que las mismas ofrecen, trayendo como consecuencia la concentración de población diezmada sobre determinados sectores, arrastrando consigo un despoblamiento y desaparición de numerosas comunidades y culturas locales. Pensamos que el Turismo Social, cultural y comunitario tal como se presenta conceptualmente a través de los nuevos paradigmas, es una alternativa real de desarrollo no sólo para aumentar los alcances de los beneficios de la actividad, sino también para atenuar y solucionar problemas intrínsecos a las regiones. A partir de la firme convicción de las comunidades de Chorcán y Varas de avanzar en esta línea, este proyecto busca sentar las bases para el desarrollo de un programa de turismo social comunitario reconstruyendo el rico y complejo entramado cultural comunitario, desarrollando capacidades para su fortalecimiento y sostén principalmente en los referentes más jóvenes. El proceso de preparación y capacitación brindará asimismo herramientas de gestión participativa, manejo de TICs, integración a redes que abrirán caminos a otras posibilidades de desarrollo. La creación y puesta en marcha de una red local, la articulación concreta con organizaciones locales (el BD, la Fundación Mallku Andina, entre otras), permitirán, luego de instaladas las herramientas, un desarrollo autónomo. La propia actividad de turismo cultural comunitario, será un estímulo permanente, ya que generará vivencias exitosas que fortalecerán “dialógicamente” el emprendimiento. Es intención del presente proyecto formar, estimular y fortalecer el liderazgo comunitario, lo que permitirá el crecimiento autónomo
CAID prediction portal: A comprehensive service for predicting intrinsic disorder and binding regions in proteins
Intrinsic disorder (ID) in proteins is well-established in structural biology, with increasing evidence for its involvement in essential biological processes. As measuring dynamic ID behavior experimentally on a large scale remains difficult, scores of published ID predictors have tried to fill this gap. Unfortunately, their heterogeneity makes it difficult to compare performance, confounding biologists wanting to make an informed choice. To address this issue, the Critical Assessment of protein Intrinsic Disorder (CAID) benchmarks predictors for ID and binding regions as a community blind-test in a standardized computing environment. Here we present the CAID Prediction Portal, a web server executing all CAID methods on user-defined sequences. The server generates standardized output and facilitates comparison between methods, producing a consensus prediction highlighting high-confidence ID regions. The website contains extensive documentation explaining the meaning of different CAID statistics and providing a brief description of all methods. Predictor output is visualized in an interactive feature viewer and made available for download in a single table, with the option to recover previous sessions via a private dashboard. The CAID Prediction Portal is a valuable resource for researchers interested in studying ID in proteins. The server is available at the URL: https://caid.idpcentral.org
The repetitive structure of DNA clamps: An overlooked protein tandem repeat
Structured tandem repeats proteins (STRPs) are a specific kind of tandem repeat proteins characterized by a modular and repetitive three-dimensional structure arrangement. The majority of STRPs adopt solenoid structures, but with the increasing availability of experimental structures and high-quality predicted structural models, more STRP folds can be characterized. Here, we describe “Box repeats”, an overlooked STRP fold present in the DNA sliding clamp processivity factors, which has eluded classification although structural data has been available since the late 1990s. Each Box repeat is a β⍺βββ module of about 60 residues, which forms a class V “beads-on-a-string” type STRP. The number of repeats present in processivity factors is organism dependent. Monomers of PCNA proteins in both Archaea and Eukarya have 4 repeats, while the monomers of bacterial beta-sliding clamps have 6 repeats. This new repeat fold has been added to the RepeatsDB database, which now provides structural annotation for 66 Box repeat proteins belonging to different organisms, including viruses
Spin Injection in a Ballistic Two-Dimensional Electron Gas
We explore electrically injected, spin polarized transport in a ballistic
two-dimensional electron gas. We augment the Buettiker-Landauer picture with a
simple, but realistic model for spin-selective contacts to describe multimode
reservoir-to-reservoir transport of ballistic spin 1/2 particles. Clear and
unambiguous signatures of spin transport are established in this regime, for
the simplest measurement configuration that demonstrates them directly. These
new effects originate from spin precession of ballistic carriers; they exhibit
strong dependence upon device geometry and vanish in the diffusive limit. Our
results have important implications for prospective ``spin transistor''
devices.Comment: Submitted to Phys. Rev. Let
Critical assessment of protein intrinsic disorder prediction (CAID) - Results of round 2
Protein intrinsic disorder (ID) is a complex and context-dependent phenomenon that covers a continuum between fully disordered states and folded states with long dynamic regions. The lack of a ground truth that fits all ID flavors and the potential for order-to-disorder transitions depending on specific conditions makes ID prediction challenging. The CAID2 challenge aimed to evaluate the performance of different prediction methods across different benchmarks, leveraging the annotation provided by the DisProt database, which stores the coordinates of ID regions when there is experimental evidence in the literature. The CAID2 challenge demonstrated varying performance of different prediction methods across different benchmarks, highlighting the need for continued development of more versatile and efficient prediction software. Depending on the application, researchers may need to balance performance with execution time when selecting a predictor. Methods based on AlphaFold2 seem to be good ID predictors but they are better at detecting absence of order rather than ID regions as defined in DisProt. The CAID2 predictors can be freely used through the CAID Prediction Portal, and CAID has been integrated into OpenEBench, which will become the official platform for running future CAID challenges
Mesoscopic Stern-Gerlach device to polarize spin currents
Spin preparation and spin detection are fundamental problems in spintronics
and in several solid state proposals for quantum information processing. Here
we propose the mesoscopic equivalent of an optical polarizing beam splitter
(PBS). This interferometric device uses non-dispersive phases (Aharonov-Bohm
and Rashba) in order to separate spin up and spin down carriers into distinct
outputs and thus it is analogous to a Stern-Gerlach apparatus. It can be used
both as a spin preparation device and as a spin measuring device by converting
spin into charge (orbital) degrees of freedom. An important feature of the
proposed spin polarizer is that no ferromagnetic contacts are used.Comment: Updated to the published versio
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