Acoustic emission as a method of monitoring of fracture phenomena in dried materials

Celem pracy jest przedstawienie emisji akustycznej (EA) jako metody monitorowania mikro- i makropęknięć w materiałach suszonych, na przykładzie suszenia walca ceramicznego. Zaprezentowane dane eksperymentalne dotyczą suszenia konwekcyjnego i mikrofalowego. Rozważania teoretyczne bazują na termomechanicznym modelu suszenia ciał kapilarno-porowatych, opracowanym przez autorów. Rozwiązania numeryczne dotyczące ewolucji i rozkładu naprężeń wzdłuż promienia i obwodu walca przedstawiono dla warunków brzegowych odpowiadających konwekcyjnemu suszeniu. Wyniki badań z użyciem EA wykazują istnienie dwóch obszarów wzmożonej emisji dla suszenia konwekcyjnego i jednego obszaru dla suszenia mikrofalowego. Porównanie danych teoretycznych i eksperymentalnych dla suszenia konwekcyjnego pozwala stwierdzić, że obszary te odpowiadają występowaniu naprężeń maksymalnych w modelu teoretycznym. W pracy tej stwierdzono, że EA może być zastosowana do diagnozowania pęknięć i stanów niebezpiecznych w suszonych materiałach oraz, że suszenie mikrofalowe pozwala uzyskać lepszy produkt końcowy, ponieważ energia sygnałów jako reprezentacja naprężeń jest mniejsza dla tego rodzaju suszenia.Acoustic emission (AE) monitoring is used to detect micro- and macrocracking in dried ceramic cylinder. The experimental results of convective and microwave drying are presented. The theoretical considerations are based on the thermomechanical model of drying of capillary-porous materials worked out by authors. The solution of the mathematical model presenting the evolution and distribution of stresses along radius of the cylinder and its circumference is given for the convective drying only. The AE tests show two ranges of intensive signal existence for convective drying and one range for microwave drying. The comparison of theoretical and experimental for convective drying data allows to state, that these ranges refer to maximal stresses pointed out by the theoretical model. It was stated, that microwave drying can give the better final product than convective drying, because the energy of signals as the representation of stresses is lower than in the case of convective drying

Anisotropy of X-ray critical scattering in EEBAC

X-ray critical scattering from EEBAC (C20H21NO3) near the smectic A-nematic phase transition were investigated. The critical exponents y = 1.23 ± 0.06, ν∥ = 0.71 ± 0.04, ν ⊥ = 0.45 ± 0.05 were extracted from our data. The ratio of the longitudinal to transverse correlation lengths ξ∥/ξ ⊥, increases gradually with decreasing reduced temperature t = (T - Tc)/Tc, changing by a factor of 2.3 over the reduced temperature range 10-4 ≤t≤ 10-2.On a étudié expérimentalement la diffusion des rayons X par EEBAC (C20H21NO3) au voisinage de la transition smectique A-nématique. Les valeurs des exposants critiques estimées à partir des résultats obtenus sont : γ = 1,23 ± 0,06, ν∥ = 0,71 ± 0,04, ν ⊥ = 0,45 ± 0,05. Le rapport de la longueur de corrélation parallele ξ∥ à la longueur de corrélation perpendiculaire ξ ⊥ : ξ ∥ /ξ⊥ augmente graduellement quand la température réduite t=(T - Tc)/T c diminue. Sa valeur change d'un facteur 2,3 dans le domaine de température réduite 10-4 ≤t≤10-2

Beginning of the ozone recovery over Europe? − Analysis of the total ozone data from the ground-based observations, 1964−2004

The total ozone variations over Europe (~50° N) in the period 1964–2004 are analyzed for detection of signals of ozone recovery. The ozone deviations from the long-term monthly means (1964–1980) for selected European stations, where the ozone observations (by the Dobson spectrophotometers) have been carried out continuously for at least 3–4 decades, are averaged and examined by a regression model. A new method is proposed to disclose both the ozone trend variations and date of the trend turnaround. The regression model contains a piecewise linear trend component and the terms describing the ozone response to forcing by "natural" changes in the atmosphere. Standard proxies for the dynamically driven ozone variations are used. The Multivariate Adaptive Regression Splines (MARS) methodology and principal component analysis are used to find an optimal set of the explanatory variables and the trend pattern. The turnaround of the ozone trend in 1994 is suggested from the pattern of the piecewise linear trend component. Thus, the changes in the ozone mean level are calculated over the periods 1970–1994 and 1994–2003, for both the original time series and the time series having "natural" variations removed. Statistical significance of the changes are derived by bootstrapping. A first stage of recovery (according to the definition of the International Ozone Commission), i.e. lessening of a negative trend, is found over Europe. It seems possible that the increase in the ozone mean level since 1994 of about 1–2% is due to superposition of the "natural" processes. Comparison of the total ozone ground-based network (the Dobson and Brewer spectrophotometers) and the satellite (TOMS, version 8) data over Europe shows the small bias in the mean values for the period 1996–2004, but the differences between the daily ozone values from these instruments are not trendless, and this may hamper an identification of the next stage of the ozone recovery over Europe. Keywords. Atmospheric composition and structure (Middle atmosphere-composition and chemistry) – Meteorology and atmospheric dynamics (Climatology, Middle atmosphere dynamics

Possibilities of using plasma techniques of surface engineering for modification of polymer membranes

Oceniano możliwości wykorzystania plazmy niskotemperaturowej do aktywowania warstwy wierzchniej membran polimerowych oraz deponowania na nich ultracienkich warstw metalicznych. Stwierdzono, że za pomocą takich technik inżynierii powierzchni możliwa jest skuteczna modyfikacja właściwości funkcjonalnych membran polimerowych, istotnych w zastosowaniach do wysokoefektywnego oczyszczania wód i ścieków.The paper discusses the possibilities of using low temperature plasma in activating the surface layer of polymer membranes and depositing ultra-thin metallic layers on their surface. It has been found that the above surface engineering techniques enable effective modification of functional properties of polymer membranes, which are important in high-efficiency water and wastewater treatment

The Use of Lactide Polymers in Bone Tissue Regeneration in Dentistry—A Systematic Review

(1) Background: Different compositions of biodegradable materials are being investigated to successfully replace non-resorbable ones in bone tissue regeneration in dental surgery. The systematic review tried to address the question, “Can biodegradable polymers act as a replacement for conventional materials in dental surgery procedures?” (2) Methods: An electronic search of the PubMed and Scopus databases was conducted in October 2022. The following keywords were used: (lactide polymers) and (hydroxyapatite or fluorapatite) and (dentistry) and (regeneration). Initially, 59 studies were found. Forty-one studies met the inclusion criteria and were included in the review. (3) Results: These usually improved the properties and induced osteogenesis, tissue mineralisation and bone regeneration by inducing osteoblast proliferation. Five studies showed higher induction of osteogenesis in the case of biomaterials, UV-HAp/PLLA, ALBO-OS, bioresorbable raw particulate hydroxyapatite/poly-L-lactide and PLGA/Hap, compared to conventional materials such as titanium. Four studies confirmed improvement in tissue mineralisation with the usage of biomaterials: hydroxyapatite/polylactic acid (HA/PLA) loaded with dog’s dental pulp stem cells (DPSCs), Coll/HAp/PLCL, PDLLA/VACNT-O:nHAp, incorporation of hydroxyapatite and simvastatin. Three studies showed an acceleration in proliferation of osteoblasts for the use of biomaterials with additional factors such as collagen and UV light. (4) Conclusions: Lactide polymers present higher osteointegration and cell proliferation rate than the materials compared. They are superior to non-biodegradable materials in terms of the biocompability, bone remodelling and healing time tests. Moreover, because there is no need of reoperation, as the material automatically degrades, the chance of scars and skin sclerosis is lower. However, more studies involving greater numbers of biomaterial types and mixes need to be performed in order to find a perfect biodegradable material

Early and Delayed Onset of Response to Antidepressants in Individual Trajectories of Change During Treatment of Major Depression: A Secondary Analysis of Data From the Genome-Based Therapeutic Drugs for Depression (GENDEP) Study

Objective: The timing and rate of improvement after the initiation of an antidepressant has implications for establishing the mechanism of antidepressant action and for answering the clinically relevant question of how long an appropriate trial of antidepressant medication should be. We explore the individual trajectories of relative change in depression severity to establish what proportion of individuals experience early and late onset of improvement. Method: Longitudinal latent class analysis was applied in a secondary analysis of data obtained from the Genome-Based Therapeutic Drugs for Depression (GENDEP) study. In the GENDEP trial, conducted in 9 European academic psychiatry centers from July 2004 to June 2008, 811 treatment-seeking adult subjects with DSM-IV major depression received escitalopram or nortriptyline for 12 weeks. Montgomery- Asberg Depression Rating Scale measurements were taken weekly. The secondary analysis reported in this article was conducted in 2010. Results: A model with 9 latent classes provided a good description of the individual trajectories of symptom change over time. These classes included 3 nonresponder classes, 3 classes with varying degrees of improvement concentrated in the first 3 weeks (early improvement), and 3 classes with varying degrees of improvement that was more prominent in the second 3 weeks than in the first 3 weeks (delayed improvement). More than half of the subjects who eventually reached remission showed a pattern of delayed improvement, and their eventual outcome could not be predicted from early time points. Early marked response occurred more frequently in subjects treated with nortriptyline than in those treated with escitalopram (12.9% vs 7.5%, X 2 = 6.29, P = .01). Delayed complete remission occurred more frequently in subjects treated with escitalopram than in those treated with nortriptyline (13.6% vs 6.1%, X 2 = 11.52, P = .0007). Conclusions: Both early and delayed improvement are common. Although early changes are maintained, the eventual outcome of 12-week antidepressant treatment can be accurately predicted only after 8 weeks. Trial Registration: http://www.controlled-trials.com Identifier: ISRCTN03693000. © Copyright 2011 Physicians Postgraduate Press, Inc.SCOPUS: ar.jinfo:eu-repo/semantics/publishe