The influence of material types on twist angles and torsion stability of a composite shaft

Prednost primjene kompozitnih materijala, u odnosu na konvencionalne materijale, ogleda se u mogućnosti širokog variranja praktično svih svojstava materijala od kojih su sastavljeni, što se postiže putem izbora sastavnih komponenata, njihove količine, rasporeda i orijentacije u okviru materijala, a s ciljem da se iskoriste njihova najbolja svojstva. U nekim slučajevima najbolji rezultati mogu biti postignuti uporabom kombinacije kompozita i tradicionalnih metalnih materijala. U radu su analizirana vratila dobivena kombinacijom aluminija s različitim kompozitnim materijalima – karbonska vlakna/epoksi smola, staklena vlakna/epoksi smola, aramidna vlakna/epoksi smola. Razmatran je njihov utjecaj na vrijednosti kutova uvijanja i kritične vrijednosti momenta uvijanja koje dovode do gubitka stabilnosti vratila. Provedena je i eksperimentalna analiza vratila koje je pokazalo najbolja svojstva (karbonska vlakna/epoksi smola).The advantages of composite materials over the conventional ones include the ability to vary their properties in order to ensure the best combination for each application. This is achieved through selection of their constituent materials, quantities, distribution and fibre orientation angle. In some cases, the best results can be achieved by using a combination of composite and traditional metal materials. This paper analyses shafts made from a combination of aluminium and different composite materials – carbon fibre/epoxy, glass fibre/epoxy, and aramid fibre/epoxy. The influence of these materials on twist angle values and critical torques that impair the shaft stability has also been discussed. Finally, an experimental analysis of the shaft that exhibited the best properties (carbon fibres/epoxy) has been performed

USE OF BISPECTRAL INDEX (BIS) FOR MONITORING OF SEDATION AND TOTAL INTRAVENOUS ANESTHESIA (TIVA) IN PEDIATRIC PATIENTS UNDERGOING COLONOSCOPY

The objectives of this study were to determine whether there was a correlation between bispectral index (BIS) and Ramsey Sedation Scale (RSS) in regard to the type of sedation and total intravenous anesthesia (TIVA) during colonoscopy procedures in children, and to assess the utility of ketamine and propofol combination (ketofol) for this kind of procedures at children’s age. In our prospective study, 40 ASA I-II patients, 3 to 17 years of age, were randomly divided into two groups of 20 patients each.   After premedication with atropine and midazolam, sedation was induced with propofol and fentanyl in Group PF, whereas in Group PK propofol and ketamine were used for induction. Both groups were further divided into two subgroups depending on whether anesthesia was maintained with intermittent doses or continuous infusion of propofol. Ketamine and/or fentanyl were administered as bolus doses. Heart rate (HR), peripheral oxygen saturation (SpO2), RSS and BIS values of all patients were recorded every 5 minutes throughout the colonoscopy procedures.  The strongest degree of correlation between RSS and BIS existed when sedation or TIVA was maintained by the boluses of propofol and fentanyl. The use of ketamine significantly reduced the doses of propofol and fentanyl. BIS can be monitored in all pediatric patients in whom sedation and TIVA are administered during colonoscopy, but the effect of different anesthetics on the EEG signal should be considered in order to adequately assess the depth of sedation and anesthesia.Key words: awareness, monitoring, child, anesthetics, endoscop

DIELECTRIC PROPERTIES OF La/Mn CODOPED BARIUM TITANATE CERAMICS

La/Mn codoped BaTiO3 ceramics with different La2O3 content, ranging from 0.3 to 1.0 at% La, together with undoped BaTiO3,were investigated regarding their microstructure and dielectric properties. The content of MnO2 kept constant at 0.01 at% Mn in all investigated samples. La/Mn codoped and undoped BaTiO3 were obtained by a modified Pechini method and sintered in air at 13000C for two hours.The homogeneous and completely fine-grained microstructure with average grain size from 0.3 to 1mm was observed in samples doped with 0.3 at% La. In high doped samples, apart from the fine grained matrix, the appearance of local area with secondary abnormal grains was observed.The dielectric permittivity and dissipation factor were investigated as a function of frequency and temperature. Dielectric permittivity of doped BaTiO3 was in the range of 3945 to 12846 and decreases with increase of additive content. The highest value of dielectric constant at room temperature (er= 12846) and the greatest change at Curie temperature (er= 17738) were measured in 0.3at% La doped samples. Dissipation factor was range from 0.07 to 0.62 for all investigated samples. The Curie constant (C) and Curie-Weiss temperature (T0) together with critical exponent of nonlinearity (g) were calculated using a Curie-Weiss and modified Curie-Weiss law. The Curie constant increase with increasing dopant content and the highest values were measured in 1.0 La doped samples.  The obtained values of g is in the range from 1.04 to 1.53 and pointed out the sharp phase transformation from ferroelectric to paraelectric phase at Curie temperature

Serum heparan sulfate and chondroitin sulfate concentrations in patients with newly diagnosed exfoliative glaucoma

Background Exfoliative glaucoma (XFG) is typically classified as a high-pressure type of secondary open-angle glaucoma that develops as a consequence of exfoliation syndrome (XFS). Exfoliation syndrome is an age-related, generalized disorder of the extracellular matrix characterized by production and progressive accumulation of a fibrillar exfoliation material (XFM) in intra- and extraocular tissues. Exfoliation material represents complex glycoprotein/proteoglycan structure composed of a protein core surrounded by glycosaminoglycans such as heparan sulfate (HS) and chondroitin sulfate (CS). The purpose of the present study was to investigate HS and CS concentrations in serum samples of patients with newly diagnosed XFG and compare the obtained values with those pertaining to newly diagnosed primary open-angle glaucoma (POAG), normal controls (NC) and subjects with XFS. Methods This case–control study involved 165 subjects, including patients with newly diagnosed XFG, patients with newly diagnosed POAG, subjects with XFS and age- and sex-matched NC. The study was conducted at the Glaucoma Department of Clinic for Eye Diseases, Clinical Centre of Serbia, as the referral center for glaucoma in Serbia. Results The mean age in the XFG, POAG, XFS and NC groups was 73.3 ± 9.0, 66.3 ± 7.8, 75.5 ± 7.0 and 73.5 ± 9.5 years, respectively, XFG vs. POAG, p < 0.001. Mean serum HS concentrations in the XFG, POAG, NC and XFS groups were 3,189.0 ± 1,473.8 ng/mL, 2,091.5 ± 940.9 ng/mL, 2,543.1 ± 1,397.3 ng/mL and 2,658.2 ± 1,426.8 ng/mL respectively, XFG vs. POAG, p = 0.001 and XFG vs. NC, p = 0.032. Mean serum CS concentrations in the XFG, POAG, NC and XFS group were 43.9 ± 20.7 ng/mL, 38.5 ± 22.0 ng/mL, 35.8 ± 16.4 ng/mL and 43.3 ± 21.8 ng/mL, respectively, XFG vs. NC, p = 0.041. Conclusions Our findings revealed greater HS and CS concentrations in XFG patients and XFS subjects compared to those without XFM. Implications of HS and CS in the pathophysiology of XFS and glaucoma should be studied further. Serum is easily accessible and should thus be explored as rich sources of potential biomarkers. Further research should aim to identify XFG biomarkers that could be utilized in routine blood analysis tests, aiding in timely disease diagnosis

Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

Structure and stereochemistry of electrochemically synthesized poly-(1-naphthylamine) from neutral acetonitrile solution

Poly-(1-naphthylamine) films were synthesized potentiodinamically and potentiostatically from 1-naphthylamine in neutral acetonitrile medium using a platinum electrode. These polymer films were investigated by infrared spectroscopy. Contrary to earlier published results neglecting the stereochemistry of the poly-(1-naphthylamine), we predict on the basis of quantum stereochemical analysis of the possible structural subunits of the polymer, that the ordinary NC(4) coupled product is not predominant in the polymer because it is far removed from the expected planarity. Based on the results of IR investigations and semiempirical quantum chemical calculations, it is propose that the polymer products are formed via mixed NC(4), N-C(5) and NC(7) coupling routes. The heats of formation of the oxidized 1-naphthylamine dimers and hexamers were calculated

Numerical and experimental analysis of the cycloid disc stress state

U ovom radu izvršena je analiza stanja naprezanja ciklozupčanika numeričkim i eksperimentalnim metodama za najkritičniji slučaj sprezanja – slučaj jednostrukog zahvata. Ciklozupčanik predstavlja vitalni element cikloreduktora – mehaničkog prijenosnika snage i gibanja novije generacije sa sve većom primjenom u industrijskoj praksi. Izrađen je 3D kompjuterski model jednog konkretnog jednostupanjskog cikloreduktora. Zatim je definiran čitav niz različitih numeričkih modela ciklozupčanika u programskim paketima FEMAP i NASTRAN radi određivanja što realnijeg stanja naprezanja uporabom metode konačnih elemenata (MKE). U cilju verifikacije dobivenih rezultata numeričkim putem, izvršena je eksperimentalna analiza korištenjem metode mjernih traka. Napravljen je fizički model ciklozupčanika kao i ostalih elemenata cikloreduktora koji su s njim u direktnom kontaktu kako bi se dobili što realniji uvjeti u postupku eksperimentalne analize. Dobiveni eksperimentalni rezultati pokazuju dobru sukladnost s numeričkim rezultatima. Čak i za najnepovoljniji teorijski slučaj sprezanja (jednostruki zahvat), koji se kod cikloreduktora u praksi gotovo i ne javlja, vrijednosti naprezanja su u dopuštenim granicama i osiguravaju pouzdan rad prijenosnika tijekom predviđenog radnog vijeka.The paper deals with the stress state analysis of the cycloid disc by using numerical and experimental methods for the most critical case of the meshing - single meshing. Cycloid disc is the vital element of the cycloidal speed reducer - mechanical power transmission of the new generation with growing use in industrial practice. 3D computer model of one specific one-stage cycloidal speed reducer was made. After that, the whole series of different numerical models of the cycloid disc were defined in FEMAP and NASTRAN, in order to determine the most realistic stress state by using FEM. In order to verify the results obtained by numerical methods, experimental analysis was realised using the strain gauges method. Physical model of the cycloid disc was made and also models of other elements of the cycloidal speed reducer which are in direct contact with it, in order to obtain the most realistic conditions for the experimental analysis. Obtained experimental results showed good agreement with numerical results. Even for the most unfavourable case of the theoretical meshing (single meshing), which is almost non-existent in practice, stress values are in allowed limits and provide reliable functioning of the reducer in the foreseen work life period