Femtosecond time-resolved phase-change microscopy and ablation threshold calculations to understand ultrafast laser ablation

El trabajo recoge experimentos realizados en una configuración sonda-prueba haciendo uso de un láser de femtosegundos, con el objetivo de comprender los fenómenos de ablación de materiales sólidos ras irradiación con láseres de pulso ultracorto.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Secondary traits related to kernel setting in transgenic maize hybrids at low and high plant densities and their potential use in breeding programs

Maize (Zea mays. L) traditional breeding presents limitations when selection is performed by adaptation to suboptimalconditions. One strategy to achieve greater efficiency in these environments is to include measurements ofsecondary traits related to the main grain yield component, i.e. kernel number per plant (KNP), which is associatedto other three secondary traits: plant growth rate during the critical period (PGRcp) for kernel setting, biomasspartitioning index to the ear during this period (PIcp) and the efficiency of the ear to set kernels or reproductiveefficiency (RE). Phenotypic variations in these KNP related traits were evaluated considering: i) plant densities,and ii) simple and staked transgenic maize hybrids. The objective of this study was to identify the contribution ofthese secondary traits to KNP in six modern single-cross transgenic hybrids: the simple and staked transgenic versionsof DK747 and DK190 (Bt: 747MG and 190MG; RR: 747RR and 190RR; and Bt-RR: 747MGRR and 190MGRR)cultivated at low and high plant densities. For this purpose, KNP and secondary traits were recorded at the individualplant level and the data set was analyzed using multivariate analysis techniques. At low plant density, PGRcpwas the critical trait for kernel setting in all hybrids but PIcp or RE also contributed to KNP of the DK747 groupand the D190 group, respectively. At high plant density, a differential contribution of secondary traits to KNP wasrecorded among hybrids. For DK747MG and DK190MG, RE mainly determined KNP, but for the DK747RR andDK747MGRR higher PIcp had a positive impact on KNP. These results highlight the importance of including secondarytraits associated to KNP in breeding programs

Time-resolved laser-induced phase change microscopy: understanding laser-matter effects at the femtosecond scale

LA comunicación describe el desarrollo instrumental y las aplicaciones con un microscopio de cambio de fase con resolución de femtosegundos que se ha puesto a punto en el LAboratorio LAser de la UMAUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

La variación concepcional en Twitter: análisis a partir del modelo de Koch y Oesterreicher

This contribution analyses the conceptional variation in Twitter communication based on the parameters described in Koch and Oesterreicher’s model ([1990] 2007). After outlining the foundations of variational linguistics and the position of conceptional variation within the chain of varieties, and after reviewing the presence of this model in studies of computer-mediated communication, the conceptional characteristics of Twitter communication are presented. The analysis focuses especially on the parameters of public/private communication, emotionality, referentiality and dialogicity, in which it is necessary to specify the distinctive characteristics of communication in social networks as opposed to prototypically immediate communication such as oral conversation.Este artículo analiza la variación concepcional que presenta la comunicación en Twitter a partir de los parámetros descritos en el modelo de Koch/Oesterreicher ([1990] 2007). Tras exponer los fundamentos de la lingüística de las variedades y la posición que tiene la variación concepcional dentro de la cadena de variedades y tras revisar la presencia que ha tenido este modelo en los estudios de comunicación mediada por ordenador, se exponen las características concepcionales de la comunicación en Twitter. El análisis se centra especialmente en los parámetros comunicación pública/privada, familiaridad, referencialización y dialogicidad, en los que es necesario matizar las características distintivas de la comunicación en redes sociales frente a una comunicación prototípicamente inmediata como la conversación oral

Temporal and energetic scale of solid matter interaction phenomena occurring during femtosecond ablation of solids

Ablation using femtosecond lasers exhibits significant differences with that at the nanosecond timescale, where the concurrence of photochemical and photothermal processes taking place during the photon absorption govern the process. In the ultrashort regime, the several phenomena involved in the laser-matter interaction are markedly different. Thus, a prior comprehension of the processes is required in order to extend the range of current applications and improve the analytical results. Our current studies are facing fundamental and applied studies with the aim of better understanding laser-matter interaction processes in condensed phase using femtosecond lasers. To achieve this goal, we have designed experimental strategies expecting to improve the knowledge of the timescale and onset generation of chemical species and surface alterations during femtosecond ablation of solids. Time-resolved optical emission spectroscopy, time-of-flight mass spectrometry and time-resolved phase-change microscopy are currently implemented. The combined use of the cited techniques is allowing the experimental determination of the energy threshold, temporal regime and macroscopic effects occurring in a variety of materials as a consequence of the interaction with an ultra-short laser pulse. The core of the experiment is a 80 Mhz, 100 nJ, 400 fs Ti-Saphire oscillator that is additionally subjected to chirped pulse amplification to produce an output of 3,5 mJ at 35 fs and a maximum repletion rate of 1 KHz. Different wavelengths (800, 400 and 266 nm) are achievable. An intensified CCD and a dual-state reflectron equipped with a cassegrain reflective optics are used for the analysis of the photons and ion generated after laser irradiation. Additionally, a pump-probe microscope with a temporal resolution better than 500 fs has been designed to allow time-resolved studies of phase-change in the ablated samples.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Differential laser-matter interaction in the ablation of solid samples with laser pulses in the interval between 35 fs – 4 ps.

Our communication is focused on the influence of the pulse width in the laser-matter interaction during laser ablation of solid materials. The experiments were performed with an 80 MHz, 100 nJ, 400 fs Ti-Saphire oscillator, amplified to produce an output of 3,5 mJ at 35 fs and a maximum repletion rate of 1 KHz. Modifications in the stretcher-compressor have allowed the continuous selection of amplified pulses in the range between 35 fs to 4 ps. The pulses are subjected to measurements in the autocorrelation, spectral bandwidth and energy per pulse. A 0.5 m focal-length spectrograph fitted with an intensified CCD or fast single-channel detectors is used to determine the time constants, to establish the fluence threshold, and to record multi-channel spectra from the generated plasmas. Additionally, morphological characterization making use of optical and electron microscopy were performed. The effect of the longer laser pulses in the laser-matter interaction - particularly in the extension of the heat-affected zone - and its implication in depth-profiling studies was also checked. For such purpose, a layered sample with a defined structure was analyzed by laser-induced breakdown spectroscopy under different pulse widths conditions. The effect on the averaged ablation rate, depth resolution and layer mixing will be commented.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Thermal Vision for Soil Assessment in a Multipurpose Environmental Chamber under Martian Conditions towards Robot Navigation

Soil assessment is important for mobile robot planning and navigation on natural and planetary environments. Terramechanic characteristics can be inferred from the thermal behaviour of soils under the influence of sunlight using remote sensors such as Long-Wave Infrared cameras. However, this behaviour is greatly affected by the low atmospheric pressures of planets such as Mars, so practical models are needed to relate robot remote sensing data on Earth to target planetary exploration conditions. This article proposes a general framework based on multipurpose environmental chambers to generate representative diurnal cycle dataset pairs that can be useful to relate the thermal behaviour of a soil on Earth to the corresponding behaviour under planetary pressure conditions using remote sensing. Furthermore, we present an application of the proposed framework to generate datasets using the UMA-Laserlab chamber, which can replicate the atmospheric \ch{CO2} composition of Mars. In particular, we analyze the thermal behaviour of four soil samples of different granularity by comparing replicated Martian surface conditions and their Earth's diurnal cycle equivalent. Results indicate a correlation between granularity and thermal inertia that is consistent with available Mars surface measurements recorded by rovers. The resulting dataset pairs, consisting of representative diurnal cycle thermal images with heater, air, and subsurface temperatures, have been made available for the scientific community.Comment: 10 pages, 13 figure

Determination of plasmas formation thresholds using femtosecond laser pulses

Our current research line focuses on studying and understanding processes of laser-material interaction in condensed phase using femtosecond lasers in an attempt to improve the analytical performance of laser-based optical emission spectroscopy. An aspect that attracts great interest is the establishment of the energetic demand for both ion and photons formation process after the beam femtosecond laser arrives. The thermoionic emission requires warming the material until its melting point, whereas that the formation of visible plasma need that energy density put into play forms a liquid heated above its critical temperature, that comes out to the surface explosively. Each element in pure form has a particular threshold, which is modified by the matrix effect and the experimental conditions. We are carrying out a systematic study of wide range of metallic samples as well as binary samples, alloys, complex matrices and others, in order to provide a complete view of the process of interesting analytical samples. The core of the experiment is a 80 Mhz, 100 nJ, 400 fs Ti-Saphire oscillator that is additionally subjected to chirped pulse amplification to produce an output of 3,5 mJ at 35 fs and a maximum repletion rate of 1 KHz. Different wavelengths (800, 400 and 266 nm) are achievable. An intensified CCD and a dual-state reflectron equipped with a cassegrain reflective optics are used for the analysis of the photons and ion generated after laser irradiation

Dichloro Butenediamides as Irreversible Site‐Selective Protein Conjugation Reagent

We describe maleic-acid derivatives as robust cysteine-selective reagents for protein labelling with comparable kinetics and superior stability relative to maleimides. Diamide and amido-ester derivatives proved to be efficient protein-labelling species with a common mechanism in which a spontaneous cyclization occurs upon addition to cysteine. Introduction of chlorine atoms in their structures triggers ring hydrolysis or further conjugation with adjacent residues, which results in conjugates that are completely resistant to retro-Michael reactions in the presence of biological thiols and human plasma. By controlling the microenvironment of the reactive site, we can control selectivity towards the hydrolytic pathway, forming homogeneous conjugates. The method is applicable to several scaffolds and enables conjugation of different payloads. The synthetic accessibility of these reagents and the mild conditions required for fast and complete conjugation together with the superior stability of the conjugates make this strategy an important alternative to maleimides in bioconjugation

LIBS and Acoustic Measurements of Rocks and Regolith Found in the Traverse of the Perseverance Rover Across the Jezero Crater, Mars

The SuperCam instrument of the NASA MARS 2020 Perseverance rover combines a suite of atomic and molecular spectroscopies intended for an extensive description of rocks, soils and minerals in the surroundings of the landing site of the mission – the Jezero crater. The microphone installed on the SuperCam instrument allows the acquisition of acoustic signals resulting from the expansion of laser-induced plasmas towards the atmosphere. Apart from being affected by the propagation characteristics of the Mars atmosphere, the acoustic signal has an additional component related to the properties of the target including surface morphology, hardness, deformation parameters, and elasticity, among others. This information is currently being investigated as a complementary resource for characterization of the ablated material and may well supplement the LIBS data gathered from coincident laser shots. This talk will present SuperCam acoustic data of rocks and minerals found in the traverse of the Perseverance rover and will discuss its correlation with LIBS spectra.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec