57 research outputs found
Biochemical assessment of nanostructures in human trabecular bone: Proposal of a Raman microspectroscopy based measurements protocol
Background: Improvements to the understating of the compositional contributions of
bone mineral and organic components to the competence of trabecular bone are crucial.
The purpose of this study was to propose a protocol to study biochemical composition of
trabecular bone, based on two combined Raman analysis methodologies.
Material and Methods: Both cluster and single point Raman mappings were obtained, in
order to assess bone degeneration associated with aging, disease, or injury, and to help in
the evaluation and development of successful therapies. In this study, human trabecular
bone has been analysed throughout a) Raman cluster analysis: bone mineral content,
carbonate-to-phosphate ratio (both from the mineral components), the crosslinking and
nature/secondary structure of collagen (both from the organic components); and b) Single
point Raman spectra, where Raman points related to the minerals and organic components
were also obtained, both techniques were employed in spectra attained at 400 to 1700 cm-
1.
Results: Multivariate analysis confirmed: 1) the different spectral composition, 2) the
existence of centroids grouped by chemical affinity of the various components of the
trabecular bone, and 3) the several traces of centroids and distribution of chemical
compositional clusters.
Conclusions: This study is important, because it delivers a study protocol that provides
molecular variations information in both mineral and collagen structure of trabecular
bone tissue. This will enable clinicians to benefit knowing the microstructural differences
in the bone subjected to degeneration of their patients.Project MAT2017-85999-P supported by the Ministry of Economy and Competitiveness
(MINECO) of Spanish Government and European Regional Development Fund (ERDF)
Periodic pulse train conformation based on the temporal Radon-Wigner transform
By using the Radon–Wigner transform (RWT), we analyze the temporal selfimaging or Talbot effect for producing well-conformed pulse trains with variable repetition rates and duty-cycles. The relationships linking the selfimaging conditions with the fractional orders of the RWT are first obtained for unchirped pulse trains. Then, we extend the analysis to chirped pulse sequences by deriving the conditions to be fulfilled by an equivalent unchirped pulse train producing the same selfimage irradiances. This result becomes relevant for observing well-defined high order fractional selfimaging, which are of interest due to their repetition rate multiplication. Besides, the effect of the finite extension of the pulse train on the selfimage quality is analyzed and a condition is found for relating the required minimum pulse number with the chirp parameter of the pulses
Assessing bone quality through mechanical properties in postmenopausal trabecular bone.
Background: The inner structure of trabecular bone is a result of structural optimisation
provided by remodeling processes. Changes in hormonal status related to menopause
cause bone tissue loss and micro-architectural deterioration with a consequent
susceptibility to fracture. Accumulation of micro-damage in bone, as a function of the
rate of production and rate of repair, underlies the development of stress fractures,
increasing fragility associated to age and osteoporosis, especially in transmenopausal
women. Patients and Methods: Quasi-static and nano-dynamic mechanical
characterisation were undertaken in trabecular bone from femoral neck biopsies of
postmenopausal women. AFM complementary studies were performed to determine
nano-roughness (SRa) and the fibrils width of collagen. Nanoindentations were used to
quantify transmenopausal changes in intrinsic mechanical properties of trabecular bone:
hardness (Hi), modulus of Young (Ei), complex modulus (E*), tan delta (δ), storage
modulus (E') and loss modulus (E"). Results: As result of the quasi-static measurements,
0.149 (0.036) GPa and 2.95 (0.73) GPa of Hi and Ei were obtained, respectively. As result
of the nano-dynamic measurements, 17.94 (3.15), 0.62 (0.10), 13.79 (3.21 and 6.39 (1.28)
GPa of E*, tan (δ), E' and E" were achieved, respectively. 101.07 SRa and 831.28 nm of
fibrils width were additionally obtained. Conclusion: This study poses a first approach to
the measurement of bone quality in postmenopausal trabecular bone by combining quasistatic,
nano-DMA analysis and tribology of dentin surface through AFM characterizationProject MAT2017-85999-P supported by the Ministry of Economy and Competitiveness
(MINECO) and European Regional Development Fund (FEDER)
Periodic pulse train conformation based on the temporal Radon-Wigner transform
By using the Radon–Wigner transform (RWT), we analyze the temporal selfimaging or Talbot effect for producing well-conformed pulse trains with variable repetition rates and duty-cycles. The relationships linking the selfimaging conditions with the fractional orders of the RWT are first obtained for unchirped pulse trains. Then, we extend the analysis to chirped pulse sequences by deriving the conditions to be fulfilled by an equivalent unchirped pulse train producing the same selfimage irradiances. This result becomes relevant for observing well-defined high order fractional selfimaging, which are of interest due to their repetition rate multiplication. Besides, the effect of the finite extension of the pulse train on the selfimage quality is analyzed and a condition is found for relating the required minimum pulse number with the chirp parameter of the pulses.Centro de Investigaciones Óptica
Periodic pulse train conformation based on the temporal Radon-Wigner transform
By using the Radon–Wigner transform (RWT), we analyze the temporal selfimaging or Talbot effect for producing well-conformed pulse trains with variable repetition rates and duty-cycles. The relationships linking the selfimaging conditions with the fractional orders of the RWT are first obtained for unchirped pulse trains. Then, we extend the analysis to chirped pulse sequences by deriving the conditions to be fulfilled by an equivalent unchirped pulse train producing the same selfimage irradiances. This result becomes relevant for observing well-defined high order fractional selfimaging, which are of interest due to their repetition rate multiplication. Besides, the effect of the finite extension of the pulse train on the selfimage quality is analyzed and a condition is found for relating the required minimum pulse number with the chirp parameter of the pulses.Centro de Investigaciones Óptica
Periodic pulse train conformation based on the temporal Radon-Wigner transform
By using the Radon–Wigner transform (RWT), we analyze the temporal selfimaging or Talbot effect for producing well-conformed pulse trains with variable repetition rates and duty-cycles. The relationships linking the selfimaging conditions with the fractional orders of the RWT are first obtained for unchirped pulse trains. Then, we extend the analysis to chirped pulse sequences by deriving the conditions to be fulfilled by an equivalent unchirped pulse train producing the same selfimage irradiances. This result becomes relevant for observing well-defined high order fractional selfimaging, which are of interest due to their repetition rate multiplication. Besides, the effect of the finite extension of the pulse train on the selfimage quality is analyzed and a condition is found for relating the required minimum pulse number with the chirp parameter of the pulses.Centro de Investigaciones Óptica
Pulse processing in optical fibers using the temporal Radon-Wigner transform
It is presented the use of the temporal Radon-Wigner transform (RWT), which is the squared modulus of the fractional Fourier transform (FRT) for a varying fractional order p, as a processing tool for pulses with FWHM of ps-tens of ps. For analysis purposes, the complete numerical generation of the RWT with 0 < p < 1 is proposed to select a particular pulse shape related to a determined value of p. To this end, the amplitude and phase of the signal to be processed are obtained using a pulse characterization technique. To synthesize the processed pulse, the selected FRT irradiance is optically produced employing a photonic device that combines phase modulation and dispersive transmission. The practical implementation of this device involves a scaling factor that depends on the modulation and dispersive parameters. It is explored the variation of this factor in order to obtain an enhancement of the particular characteristic sought in the pulse to be synthesized. To illustrate the implementation of the proposed method, numerical simulations of its application to compress signals commonly found in fiber optic transmission systems, are performed. The examples presented consider chirped Gaussian pulses and pulses distorted by group velocity dispersion and self-phase modulation.Facultad de IngenierÃ
Pulse processing in optical fibers using the temporal Radon-Wigner transform
It is presented the use of the temporal Radon-Wigner transform (RWT), which is the squared modulus of the fractional Fourier transform (FRT) for a varying fractional order p, as a processing tool for pulses with FWHM of ps-tens of ps. For analysis purposes, the complete numerical generation of the RWT with 0 < p < 1 is proposed to select a particular pulse shape related to a determined value of p. To this end, the amplitude and phase of the signal to be processed are obtained using a pulse characterization technique. To synthesize the processed pulse, the selected FRT irradiance is optically produced employing a photonic device that combines phase modulation and dispersive transmission. The practical implementation of this device involves a scaling factor that depends on the modulation and dispersive parameters. It is explored the variation of this factor in order to obtain an enhancement of the particular characteristic sought in the pulse to be synthesized. To illustrate the implementation of the proposed method, numerical simulations of its application to compress signals commonly found in fiber optic transmission systems, are performed. The examples presented consider chirped Gaussian pulses and pulses distorted by group velocity dispersion and self-phase modulation.Facultad de IngenierÃ
Análisis y diseño de un correlador en FPGA, para la recepción de señales moduladas en BPSK
Se realizó un análisis de la implementación digital del receptor digital de modulación de fase. En el mismo se pudo observar que utilizando conversores A/D ideales (básicamente con infinitos bits), la relación señal a ruido a la salida experimenta una mejora, respecto de la relación señal a ruido a la entrada, igual al número de muestras por bit. Esto es cierto mientras la frecuencia de muestreo no supere 2Bn, a partir de este valor, las muestras dejan de ser independientes y la anterior relación deja de cumplirse.Facultad de IngenierÃ
Superbandwidth laser pulses in a dispersive medium: oscillating beyond the Fourier spectrum with unexpected propagation features
The concept of superbandwidth refers to the fact that a band-limited signal
can exhibit, locally, an increase of its bandwidth, i.e., an effective
bandwidth greater than that predicted by its Fourier transform. In this work,
we study the propagation of superbandwidth laser pulses in a dispersive medium,
characterized by the group velocity dispersion. In particular, two important
results arise from the analysis of the instantaneous frequency of the pulse
obtained through the Wigner function distribution: First, it can be observed
local oscillations of the electric field which are beyond the Fourier spectrum
of the incoming pulse. Second, for a range of values of the pulse synthesis
parameters, surprisingly, the dynamics of the instantaneous frequency within
certain temporal regions, corresponds to that of a pulse propagating in a
medium with a group velocity dispersion of opposite sign. This phenomenon is
intrinsic to the special characteristics of the pulse and not to the dispersive
properties of the medium.Comment: 7 pages, 6 figure
- …