41 research outputs found
Rapid Prototyping for Evaluating Vehicular Communications
[Abstract] This Thesis details the different elements of a rapid prototyping system able to
implement and evaluate vehicular communications fast, according to the continuously
evolving requirements of the industry. The system is basically composed of a testbed
and a channel emulator, which allow evaluating communication transceivers in realistic
vehicular scenarios.
Two different testbeds are introduced: a generic 2x2 system and a vehicular platform.
The former is used to compare and study space-time block coding (STBC) transmissions
at 2.4 GHz over different indoor channels. The latter makes use of software
transceivers whose performance is evaluated when they work under artificial high-speed
Rayleigh-fading scenarios.
To show the capabilities of both platforms, three software transceivers have been
developed following the specifications for the physical layers of the standards IEEE
802.11p, IEEE 802.11a and IEEE 802.16e (Mobile WiMAX). The present work details
the different elements that make up each transceiver and indicates how to connect them
to the rest of the system to perform evaluation measurements.
Finally, single-antenna and multi-antenna performances are measured thanks to the
design and implementation of three FPGA-based channel emulators that are able to
recreate up to seven different vehicular scenarios that include urban canyons, suburban
areas and highways[Resumo] A presente Tese detalla os elementos necesarios para constituir un sistema basado en
prototipado rápido capaz de levar a cabo e avaliar comunicacións vehiculares. O hardware
do sistema está composto básicamente por unha plataforma de probas (testbed)
e un emulador de canal, os cales permiten avaliar o rendemento de transceptores
inartiamicos recreando diferentes escenarios vehiculares.
Inicialmente, este traballo céntrase na descripción do hardware do sistema, detallando
a construcción e proba dunha plataforma multi-antena e un testebed vehicular.
Estos sistemas permitiron, respectivamente, estudar o comportamento de códigos STBC
(space-time block codes) en interiores e medir o rendemento de tranceptores software
ao traballar a distintas velocidades vehiculares en canais con desvaecemento Rayleigh.
Tres transceptores software foron creados seguindo as especificacións das capas
físicas dos estándares IEEE 802.11p, IEEE 802.11a e IEEE 802.16e (Mobile WiMAX).
Este traballo detalla os diferentes componentes de cada transceptor, indicando cómo
conectalos ao resto do sistema para realizar a avaliacition do seu rendemento. Dita
avaliación realizouse coa axuda de tres emuladores de canal basados en tecnoloxía
FPGA (Field Programmable Gate Array), os cales son capaces de recrear ata sete
escenarios vehiculares distintos, incluindo cañóns urbanos, zonas suburbanas e autopistas.[Resumen] La presente Tesis detalla los elementos necesarios para constituir un sistema basado
en prototipado rtiapido capaz de llevar a cabo y evaluar comunicaciones vehiculares.
El hardware del sistema está compuesto por una plataforma de pruebas (testbed) y
un emulador de canal, los cuales permiten evaluar el rendimiento de transceptores
inaltiambricos recreando diferentes escenarios vehiculares.
Inicialmente, este trabajo se centra en la descripcition del hardware del sistema,
detallando la construccition y prueba de una plataforma multi-antena y un testebed
vehicular. Estos sistemas han permitido, respectivamente, estudiar el comportamiento
de ctiodigos STBC (space-time block codes) en interiores y medir el rendimiento en
canal con desvanecimiento Rayleigh de tranceptores software a distintas velocidades
vehiculares.
Tres transceptores software han sido creados siguiendo las especificaciones de las
capas físicas de los estandares IEEE 802.11p, IEEE 802.11a e IEEE 802.16e (Mobile
WiMAX). Este trabajo detalla los diferentes componentes de cada transceptor,
indicando ctiomo conectarlos al resto del sistema para realizar la evaluacition de su
rendimiento. Dicha evaluacition se realiztio con la ayuda de tres emuladores de canal
basados en FPGAs (Field Programmable Gate Array), los cuales son capaces de recrear
comunicaciones multi-antena en hasta siete escenarios vehiculares distintos, incluyendo
cañones urbanos, zonas suburbanas y autopistas
Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study
: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI
Enzyme-Based Microfluidic Chip Coupled to Graphene Electrodes for the Detection of D‑Amino Acid Enantiomer-Biomarkers
An electrochemical microfluidic strategy
for the separation and
enantiomeric detection of d-methionine (d-Met) and d-leucine (d-Leu) is presented. These D-amino acids
(D-AAs) act as biomarkers involved in relevant diseases caused by <i>Vibrio cholerae</i>. On a single layout microfluidic chip (MC),
highly compatible with extremely low biological sample consumption,
the strategy allowed the controlled microfluidic D-AA separation and
the specific reaction between D-amino acid oxidase (DAAO) and each
D-AA biomarker avoiding the use of additives (i.e., cyclodextrins)
for enantiomeric separation as well as any covalent immobilization
of the enzyme into the wall channels or on the electrode surface such
as in the biosensor-based approaches. Hybrid polymer/graphene-based
electrodes were end-channel coupled to the microfluidic system to
improve the analytical performance. d-Met and d-Leu
were successfully detected becoming this proof-of-the-concept a promising
principle for the development of point-of-care (POC) devices for <i>in situ</i> screening of <i>V. cholerae</i> related
diseases
Clinical and Virological Efficacy of Etravirine Plus Two Active Nucleos(t)ide Analogs in an Heterogeneous HIV-Infected Population
Etravirine (ETV) is recommended in combination with a boosted protease inhibitor plus an optimized background regimen for salvage therapy, but there is limited experience with its use in combination with two nucleos(t)ide reverse-transcriptase inhibitors (NRTIs). This multicenter study aimed to assess the efficacy of this combination in two scenarios: group A) subjects without virologic failure on or no experience with non-nucleoside reverse-transcriptase inhibitors (NNRTIs) switched due to adverse events and group B) subjects switched after a virologic failure on an efavirenz- or nevirapine-based regimen. The primary endpoint was efficacy at 52 weeks analysed by intention-to-treat. Virologic failure was defined as the inability to suppress plasma HIV-RNA to,50 copies/mL after 24 weeks on treatment, or a confirmed viral load.200 copies/mL in patients who had previously achieved a viral suppression or had an undetectable viral load at inclusion. Two hundred eighty seven patients were included. Treatment efficacy rates in group A and B were 88.0 % (CI95, 83.9–92.1%) and 77.4 % (CI95
Identificación de daños en el arbolado de tres parques del Distrito Federal
Los indicadores de salud permiten diagnosticar el estado fitosanitario y la evolución de los daños en los bosques; a nivel del arbolado, miden el tipo, la localización y la severidad que le provocan enfermedades, insectos, tormentas y actividades humanas. Para evaluar su efectividad en el área urbana, se aplicó la metodología utilizada por el Inventario Nacional Forestal y de Suelos de México y por el Forest Inventory Analysis con adaptaciones especiales. Los sitios de muestreo se establecieron dentro de los parques Alameda Norte, Alameda Oriente y Alameda Sur en el Distrito Federal. Se realizaron tres muestreos durante primavera-otoño (mayo a octubre 201) y uno en invierno (noviembre 201 a enero 2012). Se estimaron las distribuciones de frecuencia, el índice de severidad de daño (ISD) en cada parque y su ubicación dentro de cada uno. El principal problema identificado en los tres lugares fue el vandalismo. Tanto en la Alameda Norte como en la Alameda Sur se registró un número elevado de árboles muertos en pie. Las actividades antropogénicas y el escaso mantenimiento se relacionaron con las afectaciones detectadas más importantes, independientemente de la diversidad de especies. Los valores altos de ISD se observaron en árboles invadidos por muérdago, mientras que los más bajos, en árboles con señales de vandalismo
Carbon–Nitrogen Bond Construction and Carbon–Oxygen Double Bond Cleavage on a Molecular Titanium Oxonitride: A Combined Experimental and Computational Study
New
carbon–nitrogen bonds were formed on addition of isocyanide
and ketone reagents to the oxonitride species [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(μ-O)}<sub>3</sub>(μ<sub>3</sub>-N)] (<b>1</b>). Reaction of <b>1</b> with XylNC
(Xyl = 2,6-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>) in a 1:3 molar
ratio at room temperature leads to compound [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(μ-O)}<sub>3</sub>(μ-XylNCCNXyl)(NCNXyl)]
(<b>2</b>), after the addition of the nitrido group to one coordinated
isocyanide and the carbon–carbon coupling of the other two
isocyanide molecules have taken place. Thermolysis of <b>2</b> gives [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(μ-O)}<sub>3</sub>(XylNCNXyl)(CN)] (<b>3</b>) where the heterocumulene
[XylNCCNXyl] moiety and the carbodiimido [NCNXyl] fragment in <b>2</b> have undergone net transformations. Similarly, <i>tert</i>-butyl isocyanide (<i>t</i>BuNC) reacts with the starting
material <b>1</b> under mild conditions to give the paramagnetic
derivative [{Ti<sub>3</sub>(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>3</sub>(μ-O)<sub>3</sub>(NCN<i>t</i>Bu)}<sub>2</sub>(μ-CN)<sub>2</sub>] (<b>4</b>). However, compound <b>1</b> provides the oxo ketimide
derivatives [{Ti<sub>3</sub>(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)<sub>3</sub>(μ-O)<sub>4</sub>}(NCRPh)]
[R = Ph (<b>5</b>), <i>p</i>-Me(C<sub>6</sub>H<sub>4</sub>) (<b>6</b>), <i>o</i>-Me(C<sub>6</sub>H<sub>4</sub>) (<b>7</b>)] upon reaction with benzophenone, <i>p</i>-methylbenzophenone, and <i>o</i>-methylbenzophenone,
respectively. In these reactions, the carbon–oxygen double
bond is completely ruptured, leading to the formation of a carbon–nitrogen
and two metal–oxygen bonds. The molecular structures of complexes <b>2</b>–<b>4</b>, <b>6</b>, and <b>7</b> were determined by single-crystal X-ray diffraction analyses. Density
functional theory calculations were performed on the incorporation
of isocyanides and ketones to the model complex [{Ti(η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)(μ-O)}<sub>3</sub>(μ<sub>3</sub>-N)] (<b>1H</b>). The mechanism involves the coordination
of the substrates to one of the titanium metal centers, followed by
an isomerization to place those substrates cis with respect to the
apical nitrogen of <b>1H</b>, where carbon–nitrogen bond
formation occurs with a low-energy barrier. In the case of aryl isocyanides,
the resulting complex incorporates additional isocyanide molecules
leading to a carbon–carbon coupling. With ketones, the high
oxophilicity of titanium promotes the unusual total cleavage of the
carbon–oxygen double bond
Modulating Nitric Oxide Release by <i>S</i>-Nitrosothiol Photocleavage: Mechanism and Substituent Effects
The photochemistry and photophysics of a series of <i>S</i>-nitrosothiols (RSNOs) have
been studied computationally. The photocleavage mechanism of the model
compound CH<sub>3</sub>SNO to release CH<sub>3</sub>S· and ·NO
was studied at the CASPT2 level resulting in a barrierless process
when irradiating in the visible region (S<sub>1</sub>), in the near
UV region (S<sub>2</sub>) and for photosensitized (T<sub>1</sub>)
reaction. The absorption energy required to initiate photocleavage
was calculated at the CASPT2 and B3P86 levels showing the possibility
of the modulation of NO release by RSNO photoactivation as a function
of the substituent R. Good correlations between the wavelengths of
the lowest energy <sup>1</sup>(<i>n</i>,π*) and <sup>1</sup>(π,π*) transitions of aryl <i>S</i>-nitrosothiols
and the corresponding Hammett constants of the substituents have been
obtained
Intermetallic Cooperation in C–H Activation Involving Transient Titanium-Alkylidene Species: A Synthetic and Mechanistic Study
Remote carbon–hydrogen activation
on titanium dinuclear
complexes [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)R<sub>2</sub>}<sub>2</sub>(μ-O)] [R = CH<sub>2</sub>SiMe<sub>3</sub> <b>2</b>, CH<sub>2</sub>CMe<sub>3</sub> <b>3</b>, and
CH<sub>2</sub>Ph <b>5</b>) have been examined both synthetically
and theoretically. While the thermal treatment of the oxoderivative
[{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub>(μ-O)] (<b>2</b>) led to a series of metallacycle complexes (<b>2a</b>–<b>c</b>) by sequential carbon–hydrogen activation processes,
[{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(CH<sub>2</sub>CMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub>(μ-O)] (<b>3</b>) gave rise to the formation of the metallacycle tuck-over species
[Ti<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(μ-η<sup>5</sup>-C<sub>5</sub>Me<sub>4</sub>CH<sub>2</sub>-κC)(CH<sub>2</sub>CMe<sub>3</sub>)(μ-CH<sub>2</sub>CMe<sub>2</sub>CH<sub>2</sub>)(μ-O)] (<b>4</b>), as result of hydrogen abstraction
from a η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub> ligand. However,
the thermolysis of the tetrabenzyl complex [{Ti(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(CH<sub>2</sub>Ph)<sub>2</sub>}<sub>2</sub>(μ-O)] (<b>5</b>) yielded the derivative [Ti<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub>)(μ-η<sup>5</sup>-C<sub>5</sub>Me<sub>4</sub>CH<sub>2</sub>-κC)(CH<sub>2</sub>Ph)<sub>3</sub>(μ-O)] (<b>6</b>) that only exhibits
tuck-over η<sup>5</sup>-C<sub>5</sub>Me<sub>5</sub> metalation.
DFT calculations show that the mechanism involves a first α-hydrogen
abstraction to generate a transient titanium alkylidene, which enables
it to activate β- and γ-C(sp<sup>3</sup>)-H bonds on the
adjacent titanium center. The calculations also establish a reactivity
order for the different type of γ-H abstractions, trimethylsilyl
> neopentyl ≌ benzyl, allowing us to explain the observed
selectivity
Conformational Preference and Chiroptical Response of Carbohydrates d‑Ribose and 2‑Deoxy‑d‑ribose in Aqueous and Solid Phases
This work targets
the structural preferences of d-ribose
and 2-deoxy-d-ribose in water solution and solid phase. A
theoretical DFT (B3LYP and M06-2X) and MP2 study has been undertaken
considering the five possible configurations (open-chain, α-furanose,
β-furanose, α-pyranose, and β-pyranose) of these
two carbohydrates with a comparison of the solvent treatment using
only a continuum solvation model (PCM) and the PCM plus one explicit
water molecule. In addition, experimental vibrational studies using
both nonchiroptical (IR-Raman) and chiroptical (VCD) techniques have
been carried out. The theoretical and experimental results show that
α- and β-pyranose forms are the dominant configurations
for both compounds. Moreover, it has been found that 2-deoxy-d-ribose presents a non-negligible percentage of open-chain forms
in aqueous solution, while in solid phase this configuration is absent