28 research outputs found
Analyse komplexer biologischer Proben mittels oberflÀchenverstÀrkter Ramanspektroskopie (SERS)
Diese Studie beschĂ€ftigt sich mit dem Nachweis biologischer Proben mit Hilfe der Raman-Mikroskopie. Um ausreichende SignalintensitĂ€ten auch bei niedrigen Konzentrationen zu erhalten, wurde insbesondere der Effekt der oberflĂ€chenverstĂ€rkten Raman-Streuung (SERS) nĂ€her untersucht. Als Proben dienten DNA aus Hering-Sperma und das Protein Albumin. Zur VerstĂ€rkung des Raman-Spektrums wurden zwei unterschiedliche Methoden verwendet. Zum Einen wurden in einem chemischen Reduktionsprozess Nanosilberpartikel hergestellt und den biologischen Proben zugemischt. Zum Anderen wurden mit Hilfe laserangeregter periodischer OberflĂ€chenstrukturierung (LIPSS) erzeugte nanostrukturierte SilberoberflĂ€chen als Substrate fĂŒr die Proben verwendet. Diese Methode wurde bislang nicht fĂŒr die SERS-Analyse biologischer Proben eingesetzt. Erste hier prĂ€sentierte Messungen zeigen, dass beide Verfahren signifikante SERS-VerstĂ€rkungen liefern und potentiell leistungsstarke Methoden fĂŒr die zerstörungsfreie Analyse biologischer Proben darstellen
HPLC-DAD analysis, antimicrobial and antioxidant properties of aromatic Herb Melissa officinalis L., aerial parts extracts
Treating specific tissues without affecting other regions is a difficult task. It is desirable to target the particular tissue where the chemical has its biological effect. To study this phenomenon computationally, in this work we numerically study a mathematical model which is written as a nonlinear system composed by three parabolic partial differential equations. The variables involved in the model are the concentration of the chemical, the concentration of the binding protein and the concentration of the chemical bound to the protein. Our aim is to propose a fully discrete approximation of this problem, using the Finite Element Method and a semi-implicit Euler scheme, in order to solve it numerically. This discrete problem is analysed, obtaining a discrete stability property and some a priori error estimates that show the algorithm converges linearly if the continuous solution is regular enough. Also, some representative examples are shown, as well as the numerical verification of the convergence.Universidade de Vig
Prévention des infections du site opératoire les stratégies thérapeutique et préventives.
Les infections du site opĂ©ratoire constituent La complication la plus redoutable des interventions chirurgicales, et lâune des infections nosocomiales les plus frĂ©quentes.
Leurs consĂ©quences peuvent ĂȘtre dramatiques pour le patient (complications, sĂ©jour prolongĂ©, mortalitĂ©) et coĂ»teuses pour les structures de santĂ©.
Ceci exige une prise de conscience et un engagement collectif de tout le personnel hospitalier pour espĂ©rer des rĂ©sultats satisfaisants dâune prĂ©vention efficace.
Notre travail permet une approche des différents moyens de prévention des infections postopératoires en milieu chirurgical.
Dans cette optique, une stratégie efficace de prévention est basée sur des éléments essentiels:
âą La meilleure connaissance des facteurs de risque de lâinfection et la dĂ©termination correcte des diffĂ©rents modes de contamination.
⹠Le raccourcissement du séjour hospitalier du malade.
âą La dĂ©termination dâantibioprophylaxie. prĂ©opĂ©ratoire dâun protocole adaptĂ©
âą La prĂ©paration idĂ©ale du patient et de lâĂ©quipe mĂ©dicale Ă lâintervention chirurgicale.
âą Le respect des critĂšres dâasepsie du bloc opĂ©ratoire et de stĂ©rilitĂ© du matĂ©riel mĂ©dico-chirurgical.
⹠La prise en charge correcte du malade dans la période postopératoire
Thermal conditions for laser chemical micro processing of metals
This work deals with the identification of the temperature range for a high-quality laser chemical machining of metals with the aim to increase the process control and reproducibility. Therefore, an analytical model to compute the laser induced temperature distributions is developed and verified. A subsequent correlation with the resulting removal geometries as well as performed high-speed shadowgraphs prove that a disturbance-free removal is initiated after exceeding the electrolyte boiling point and is limited by the occurrence of film boiling. Moreover, the removal velocity is primarily determined by the induced temperature gradients and the interaction time. In view of miniaturization, the comparison of defined geometric and qualitative machining features with those of micro electrochemical machining and micro milling reveals the suitability of laser chemical machining to manufacture metallic parts with dimensions < 1 mmÂł
Dynamic Process Behavior in Laser Chemical Micro Machining of Metals
Laser chemical machining (LCM) is a non-conventional processing method that enables a smooth and precise micro structuring of metallic surfaces. However, a high-quality removal is limited to a laser power window of some 100 mW. This is due to the high sensibility to removal disturbances, such as the deposition of metallic salts and oxides. In this work, the dynamic process behavior around the transition from a disturbance-free to a disturbed removal is investigated for the laser chemical machining of titanium (3.7024) and stainless steel (AISI 304) in different phosphoric acid solutions. Therefore, the removal cavities are recorded using confocal scanning microscopy and characterized regarding width, depth and quality in dependence of the laser power, feed velocity and electrolyte concentration. While the removal characteristics within the disturbance-free regime are found to be material-independent, the disturbed regime is strongly dependent on the tendency of the material to gas bubble adherence. Additional CCD records of the interaction zone reveal that the transition to the disturbed regime is accompanied by significant light reflections and thereby indicate the influence of adhering gas bubbles on disturbing the removal process. Moreover, typical removal disturbances are presented and discussed with regard to the responsible mechanisms for their occurrence
Précipitations et rendements du blé dur et de l'orge en culture «bour» dans le Maroc du Centre-ouest
The cereals production of the Western Centre of Morocco can double during certain years, mainly depending on the interannual variations of the yields that has been analysed here with regard to the impact of the rainfall variability. After regrouping precipitation totals into periods of two and three months, we have calculated the correlations between the annual yield of each province and the rainfall recorded at some meteorological stations for the same period. Among all the Western Centre provinces the variability of the annual rainfall totals turned out to have an influence on more than 50% in all the total yields variation. The January- February period always plays a major role.La part de la production cĂ©rĂ©aliĂšre du Centre-ouest dans la production marocaine oscille du simple au double selon les annĂ©es en fonction essentiellement de la variation interannuelle des rendements qui est analysĂ©e ici en relation avec l'influence de la variabilitĂ© des prĂ©cipitations. AprĂšs regroupements des totaux mensuels de pluies en bimestres et trimestres, nous avons procĂ©dĂ© Ă une sĂ©rie de corrĂ©lations deux Ă deux entre les rendements annuels de chaque Direction Provinciale de l'Agriculture (DPA) et les prĂ©cipitations de chacune des stations mĂ©tĂ©orologiques retenues pour la mĂȘme pĂ©riode. Dans toutes les DPA du Centre-ouest, plus de la moitiĂ© des variations des rendements est influencĂ©e par la variabilitĂ© des totaux annuels des pluies. Le bimestre de janvier-fĂ©vrier joue toujours un rĂŽle prĂ©pondĂ©rant.Douguedroit Annick, Durbiano Claudine, Messaoudi Abdelrhafour, AĂŻt Hamza Mohamed. PrĂ©cipitations et rendements du blĂ© dur et de l'orge en culture «bour» dans le Maroc du Centre-ouest. In: MĂ©diterranĂ©e, tome 88, 1-1998. PrĂ©cipitations et cultures cĂ©rĂ©aliĂšres dans le Centre-ouest du Maroc, sous la direction de Annick Douguedroit et Claudine Durbiano. pp. 39-44
Geometrical design of micro-textured DLC coatings toward lubricant-free metal forming
To achieve a stable and high wear resistive functional surface under dry sliding friction, the present study proposes micro-textured diamond like carbon coatings fabricated by ionized physical vapour deposition (I-PVD) using metallic masks. To clarify the optimized geometrical dimensions under dry sliding friction, geometrical conditions of textured array patterns are varied by using metallic masks with different circular hole array patterns fabricated by picosecond pulsed laser processing. The effect of texturing on friction and wear properties is evaluated by ball-on-disk type friction tests for the condition of a constant DLC-coverage per unit area. Thereby, textured DLC pattern with diameters of 50 ÎŒm, 100 ÎŒm and 150 ÎŒm are applied. Within the first 10,000 laps stable and lower coefficient of friction is obtained with the smallest diameters of 50 ÎŒm. However, at further rotation of more than 40,000 laps, the wear of the smaller diameters becomes more pronounced due to the increase of stress concentration at the edge of the structure. Based on these findings, geometrical design of micro-textured DLC coating is discussed with regard to the suppression of three-body ploughing and the prevention of stress concentration
Geometrical design of micro-textured DLC coatings toward lubricant-free metal forming
To achieve a stable and high wear resistive functional surface under dry sliding friction, the present study proposes micro-textured diamond like carbon coatings fabricated by ionized physical vapour deposition (I-PVD) using metallic masks. To clarify the optimized geometrical dimensions under dry sliding friction, geometrical conditions of textured array patterns are varied by using metallic masks with different circular hole array patterns fabricated by picosecond pulsed laser processing. The effect of texturing on friction and wear properties is evaluated by ball-on-disk type friction tests for the condition of a constant DLC-coverage per unit area. Thereby, textured DLC pattern with diameters of 50 ÎŒm, 100 ÎŒm and 150 ÎŒm are applied. Within the first 10,000 laps stable and lower coefficient of friction is obtained with the smallest diameters of 50 ÎŒm. However, at further rotation of more than 40,000 laps, the wear of the smaller diameters becomes more pronounced due to the increase of stress concentration at the edge of the structure. Based on these findings, geometrical design of micro-textured DLC coating is discussed with regard to the suppression of three-body ploughing and the prevention of stress concentration