Is Second Harmonic Generation a reliable tool for studying solid-solid phase transition and structural purity?

International audienceThe second harmonic generation (SHG) is a nonlinear optical effect occurring only in noncentrosymmetric space groups. Two photons (at the fundamental angular frequency ω) can interact in a noncentric crystal structure to give a new photon at twice the fundamental frequency (2ω). In previous studies, we demonstrated that the measurement of the intensity of the signal at 2ω (SHG signal) is a very sensitive probe to detect the noncentrosymmetry of crystal arrangements such as conglomerates [1]. This technique was also used, in rare occasions, to follow centrosymmetric to noncentrosymmetric solid-solid phase transitions [2], [3]. Because of the origin of the SHG signal, only centric to noncentric or noncentric to noncentric phase transitions can be investigated via SHG. However, SHG has proved to be highly sensitive even to a slight deviation from centrosymmetric conditions and could be used to detect noncentric nuclei and as a consequence to follow the nucleation of new phases. This could give great information about the order of the transition (as defined by Ehrenfest classification). Indeed, if the transition is of the first-order kind the signal should be discontinuous at the temperature transition but continuous in the case of a second order transition.In this study, we present the results obtained using a device developed to perform SHG measurements versus temperature for the solid-solid phase transition (from centrosymmetric to noncentrosymmetric structures) of several compounds. The case of 3-Hydroxybenzoic Acid is particularly considered. MHBA is an intermediate in the production of germicides, plasticizer and pharmaceuticals and exhibits two polymorphic forms [4] one of which is noncentrosymmetric. Finally, we evaluate the potential of the SHG signal measurements to follow phase transitions by comparison with other usual techniques such as Differential Scanning Calorimetry (DSC), X-Ray Diffraction or Raman Spectroscopy.REFERENCES[1] A. Galland, V.Dupray, B.Berton, S. Morin-Grognet, M. Sanselme, H. Atmani and G.Coquerel, “Spotting Conglomerates by Second Harmonic Generation,” Crystal Growth & Design, vol. 9, no. 6, pp. 2713–2718, Jun. 2009.[2] J. P. Dougherty and S. K. Kurtz, “A second harmonic analyzer for the detection of non- centrosymmetry,” Journal of Applied Crystallography, vol. 9, no. 2, pp. 145–158, Apr. 1976.[3] L. Smilowitz, B. F. Henson, and J. J. Romero, “Intercomparison of Calorimetry, Raman Spectroscopy, and Second Harmonic Generation Applied to Solid−Solid Phase Transitions,” The Journal of Physical Chemistry A, vol. 113, no. 35, pp. 9650–9657, Sep. 2009. [4] F. L. Nordström and Å. C. Rasmuson, “Polymorphism and thermodynamics of m- hydroxybenzoic acid,” European Journal of Pharmaceutical Sciences, vol. 28, no. 5, pp. 377– 384, Aug. 2006

Second harmonic generation: applications in phase diagram investigations

International audienceThe influence of water (in its gaseous state) on the stability of crystallized organic compounds was investigated. Through two examples of solid/vapour equilibria, several behaviours were highlighted (stoichiometric or non stoichiometric hydrates, hydration/dehydration mechanisms, stability domains of multi-hydrates as a function of relative humidity). Phase diagrams (as a function of partial water pressure) and stability diagrams have been proposed for each example. This study illustrates that solid/vapour equilibrium knowledge is a crucial step during the complete characterization of solid organic compounds

The Gracilis Myocutaneous Free Flap: A Quantitative Analysis of the Fasciocutaneous Blood Supply and Implications for Autologous Breast Reconstruction

BACKGROUND: Mastectomies are one of the most common surgical procedures in women of the developed world. The gracilis myocutaneous flap is favoured by many reconstructive surgeons due to the donor site profile and speed of dissection. The distal component of the longitudinal skin paddle of the gracilis myocutaneous flap is unreliable. This study quantifies the fasciocutaneous vascular territories of the gracilis flap and offers the potential to reconstruct breasts of all sizes. METHODS: Twenty-seven human cadaver dissections were performed and injected using lead oxide into the gracilis vascular pedicles, followed by radiographic studies to identify the muscular and fasciocutaneous perforator patterns. The vascular territories and choke zones were characterized quantitatively using the 'Lymphatic Vessel Analysis Protocol' (LVAP) plug-in for Image J® software. RESULTS: We found a step-wise decrease in the average vessel density from the upper to middle and lower thirds of both the gracilis muscle and the overlying skin paddle with a significantly higher average vessel density in the skin compared to the muscle. The average vessel width was greater in the muscle. Distal to the main pedicle, there were either one (7/27 cases), two (14/27 cases) or three (6/27 cases) minor pedicles. The gracilis angiosome was T-shaped and the maximum cutaneous vascular territory for the main and first minor pedicle was 35 × 19 cm and 34 × 10 cm, respectively. CONCLUSION: Our findings support the concept that small volume breast reconstructions can be performed on suitable patients, based on septocutaneous perforators from the minor pedicle without the need to harvest any muscle, further reducing donor site morbidity. For large reconstructions, if a 'T' or tri-lobed flap with an extended vertical component is needed, it is important to establish if three territories are present. Flap reliability and size may be optimized following computed tomographic angiography and surgical delay

Anti-cancer drug validation: the contribution of tissue engineered models

Abstract Drug toxicity frequently goes concealed until clinical trials stage, which is the most challenging, dangerous and expensive stage of drug development. Both the cultures of cancer cells in traditional 2D assays and animal studies have limitations that cannot ever be unraveled by improvements in drug-testing protocols. A new generation of bioengineered tumors is now emerging in response to these limitations, with potential to transform drug screening by providing predictive models of tumors within their tissue context, for studies of drug safety and efficacy. Considering the NCI60, a panel of 60 cancer cell lines representative of 9 different cancer types: leukemia, lung, colorectal, central nervous system (CNS), melanoma, ovarian, renal, prostate and breast, we propose to review current Bstate of art^ on the 9 cancer types specifically addressing the 3D tissue models that have been developed and used in drug discovery processes as an alternative to complement their studyThis article is a result of the project FROnTHERA (NORTE-01-0145-FEDER-000023), supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This article was also supported by the EU Framework Programme for Research and Innovation HORIZON 2020 (H2020) under grant agreement n° 668983 — FoReCaST. FCT distinction attributed to Joaquim M. Oliveira (IF/00423/2012) and Vitor M. Correlo (IF/01214/2014) under the Investigator FCT program is also greatly acknowledged.info:eu-repo/semantics/publishedVersio

EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial

More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

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Impact of chirality on phase diagrams and conversely relative quantification of chirality by using the binary phase diagram of enantiomers

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La thermodynamique comme moyen de prédiction de propriétés physico-chimiques. Application au polymorphisme de composés moléculaires

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Impact of chirality in phase diagrams

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Polymorphism: is it always that clear?

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