Lower Temperature Values Research Articles

ANTIBIOTIC SUSCEPTIBILITY OF MICROORGANISMS ISOLATED FROM WASTEWATER AT AL-HIKMAH UNIVERSITY FEMALE HOSTELS, ILORIN, NIGEERIA

Physicochemical properties and antibiotic susceptibility of microorganisms isolated from wastewater samples collected from Al-Hikmah University female hostels were assessed. Samples obtained from different female hostels were examined physiochemically and microbiologically using standard procedures. Phytochemical result revealed the low temperature value of 28°C from Oladimeji and Commaissie hostels, while Deremi and Owaish had a value of 29.5°C. Dissolved oxygen of 0.1 ml/L was recorded from all the samples collected. Electrical conductivity ranged from 658 to 997µs, while chocking odour was recorded in all the four samples collected. In terms of pH, Oladimeji hostel had a pH of 10.5, Deremi had a pH of 10.6, while Owaish and Commaissie had a pH of 10.4. The wastewater samples from the four hostels were highly contaminated. Oladimeji hostel showed a mean bacterial 5count of 25.4×10cfu/ml, Deremi hostel, Owaish hostel and Coomassie hostels, showed a mean 4 4 4bacterial count of 5.7×10cfu/ml,16.8×10cfu/ml and 3.5×10cfu/ml respectively. Percentage occurrence of bacteria isolates were Salmonella sp. (12.5%), Klebsiella pneumoniae (12.5%), Escherichia coli (25%), Staphylococcus aureus (12.5%), Actinomyces (12.5%), Shigella sp. (6.25%), Pseudomonas aeruginosa (12.5%) and Proteus vulgaris (6.25%). Antimicrobial sensitivity tests revealed that all the organisms were susceptible to gentamycin except Actinomyces. High microbial load in wastewater samples could have negative effects on human health. This study, further confirms the need to treat wastewater rather than directly discharging it to the environment.

Dual Stimuli-Responsive Copper Nanoparticles Decorated SBA-15: A Highly Efficient Catalyst for the Oxidation of Alcohols in Water

In the present work, a temperature and pH-responsive hybrid catalytic system using copolymer-capped mesoporous silica particles with metal nanoparticles is proposed. The poly(2-(dimethylamino)ethyl methacrylate)(DMAEMA)-co-N-tert-butyl acrylamide) (TBA)) shell on mesoporous silica SBA-15 was obtained through free radical polymerization. Then, copper nanoparticles (CuNPs) decorated SBA-15/copolymer hybrid materials were synthesized using the NaBH4 reduction method. SBA-15 was functionalized with trimethoxylsilylpropyl methacrylate (TMSPM) and named TSBA. It was found that the CuNPs were uniformly dispersed in the mesoporous channels of SBA-15, and the hybrid catalyst exhibited excellent catalytic performance for the selective oxidation of different substituted benzyl alcohols in water using H2O2 as an oxidant at room temperature. The dual (temperature and pH-) responsive behaviors of the CuNPs/p(DMAEMA-co-TBA)/TSBA catalyst were investigated using the dynamic light scattering technique. The conversion of catalytic products and selectivity were calculated using gas chromatographic techniques, whereas the molecular structure of the products was identified using 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The catalyst showed excellent catalytic activity toward the oxidation of alcohol to aldehyde in an aqueous medium below the lower critical solution temperature (LCST) and pKa values (7–7.5) of the copolymer. The main advantages of the hybrid catalyst, as compared to the existing catalysts, are outstanding alcohol conversion (up to 99%) for a short reaction time (1 h), small amount of the catalyst (5 mg), and good recyclability equal to at least five times.

Synergistic effects of co-gasification of municipal solid waste and biomass in fixed-bed gasifier

The co-gasification of refuse derived fuel (RDF) and biomass is a promising technology for environmentally friendly municipal solid waste (MSW) utilization. Herein, we investigated the co-gasification of RDF and straw mixtures. The development of syngas suggested that higher temperature and equivalence ratio (ER) values promote syngas yield during gasification and co-gasification. Temperature plays a positive key role in gas yield and carbon conversion efficiency once the ER is higher than 0.3 during co-gasification. Except for an ER of 0.3, synergistic enhancements in carbon conversion efficiency, gas yield, and cold gas efficiency were observed for co-gasification. The positive synergistic effects of co-gasification mainly appeared in lower ER (0.1−0.2) and higher temperatures (800−900°C); however, the negative synergistic effects more tend to appear in higher ER (0.3−0.4). From the development of bottom ash in co-gasification, at higher temperature and ER values, potassium in the bottom ash was favored to stay in sulfur-containing compounds; whereas at lower temperature and ER values, potassium preferred to exist in potassium chloride. A higher calcium content more easily enriched in small particles that were integrated into aluminosilicate led to the formation of sticking ash particles, which could promote significant melting agglomeration. However, these melting agglomerations could be suppressed by adding straw into the RDF. These results provide a feasible method for the resource utilization of MSW.

Thermal and electrical conductivity of single crystalline kesterite Cu2ZnSnS4

For single crystalline sulfur-based kesterite Cu2ZnSnS4 the electrical and thermal conductivity are measured from 20 K to 320 K. The electrical conductivity decreases exponentially with decreasing temperature. The temperature dependence can be assigned to Mott-variable-range-hopping, an electrical transport process within an impurity band in the band gap. With the 3ω-method a thermal conductivity room temperature value of 5.1 ± 0.5 Wm−1K−1 and a maximal value of 8.0 ± 0.5 Wm−1K−1 at 100 K are found. Phonon-phonon-umklapp-scattering can explain the high temperature range from 100 K to 320 K. The low temperature values of the thermal conductivity are dominated by the temperature-dependence of the specific heat capacity, due to a reduced phonon-mean-free-path, owing to phonon-impurity-scattering.

Experimental and numerical study of a falling film heat exchanger used in a vapour absorption refrigeration system

Falling film evaporators have found applications in a wide range of industries, varying from chemical industries, petroleum refinery, desalination and food process industries. These heat exchangers are preferred mainly because of high heat exchange rates with low temperature difference between the heat exchange fluids at low film fluid flow rates with low evaporation temperature. This study is focused on numerical and experimental investigation of vapour generator (falling film heat exchanger) of a vapour absorption refrigeration (VAR) system. The influence of key operating parameters like mass flow rate of fluid, inlet temperature and the concentration of the thermic fluid as well as the coolant, are experimentally studied and are compared with the numerical results. The deviation between the experimental and numerical results was found to be 8.72%, with a lesser deviation at lower temperatures. The minimum percentage error is 2.15%, for a thermic fluid temperature at 50 °C. There is a stronger agreement in the results for lower values of the glycol water mixture inlet temperature, than at high temperatures. A maximum of 1000 W/m2 heat is transferred to the aqua-ammonia with ammonia concentration of 0.6 by volume is observed for thermic fluid inlet temperatures of 80 °C. The effect of various operating parameters were numerically studied and interpreted. The results obtained were in correlation with the concepts of heat transfer.

Observing imprints of black hole event horizon on X-ray spectra

ABSTRACT A fundamental difference between a neutron star (NS) and a black hole (BH) is the absence of a physical surface in the latter. For this reason, any remaining kinetic energy of the matter accreting on to a BH is advected inside its event horizon. In the case of an NS, on the contrary, accreting material is decelerated on the NS surface, and its kinetic energy is eventually radiated away. Copious soft photons produced by the NS surface will affect the properties of the Comptonized component dominating spectra of X-ray binaries in the hard state. Thus, parameters of the Comptonized spectra – the electron temperature kTe and the Compton y-parameter, could serve as an important tool for distinguishing BHs from NSs. In this paper, we systematically analyse heretofore the largest sample of spectra from the BH and NS X-ray binaries in the hard state for this purpose, using archival RXTE/PCA and RXTE/HEXTE observations. We find that the BHs and NSs occupy distinctly different regions in the y − kTe plane with NSs being characterized by systematically lower values of y-parameter and electron temperature. Due to the shape of the boundary between BHs and NSs on the y − kTe plane, their 1D y and kTe distributions have some overlap. A cleaner one parameter diagnostic of the nature of the compact object in X-ray binaries is provided by the Compton amplification factor A, with the boundary between BHs and NSs lying at A ≈ 3.5–4. This is by far the most significant detection of the imprint of the event horizon on the X-ray spectra for stable stellar-mass BHs.

DOMOIC acid, Pseudo-nitzschia spp and potential vectors at the base of the pelagic food web over the northern Patagonian coast, Southwestern Atlantic

Plankton composition and density, and domoic acid (DA) content in microplankton and mesozooplankton were assessed over the northern Patagonian coastal shelf in late austral summer 2013. Maximum values of DA in these two plankton fractions as well as maximum densities of both Pseudo-nitzschia spp. (mainly the toxigenic P. australis) and DA potential vectors were only detected on the southern coast of San Matías Gulf and the eastern coast of Valdés Peninsula. In this zone, waters were characterized by low temperature, high nitrate, and intermediate values of silicic acid and phosphate. Based on the high association between the DA values recorded and the values of either micro- and mesozooplankton grazer density or biomass, we inferred that DA transfer from Pseudo-nitzschia spp. occurred largely through the small copepods Euterpina acutifrons and Oithona nana, Calanidae nauplii and Calanidae copepodites, Noctiluca scintillans, and euphausiid developmental stages. Small copepods, Calanidae nauplii and copepodites, and cladocerans were proposed as novel DA vectors although this suggestion requires experimental confirmation. This study provides the first lines of evidence of the co-occurrence of Pseudo-nitzschia spp. blooms with DA production and accumulation in mesozooplanktonic grazers at the base of the food web and of the environmental and oceanographic conditions that seem to favor these processes over the northern Patagonian shelf coasts.

Melting, freezing, and dynamics of two-dimensional dipole systems in screening bulk media.

This paper reports on the molecular dynamics simulations of classical two-dimensional (2D) electric dipole systems. The properties of 2D systems with bare (nonscreened) and screened dipole-dipole interactions have been investigated. Based on the polygon construction method, we present simulation results on the phase transition, and we locate the melting and freezing points of 2D dipole systems in terms of a polygon disorder parameter, with the polygon disorder parameter being the sum of nontriangular polygon order parameters. It was found that the phase transition of the system occurs when the polygon disorder parameter has a value 0.165. This result was cross-checked by using both local and overall orientational order parameters. We also identified that the value of the average local orientational order parameter at the phase transition point is 0.67. These results are valid for the ordinary (bare) dipole-dipole interaction as well as the screened dipole-dipole interaction, and they are expected to be general for other 2D systems with repulsive pair interaction. We observed that both melting and freezing points shift to lower values of temperature due to screening. In the liquid state, the radial distribution function and polygon construction method show the loss of order in a structure as screening becomes more severe. Furthermore, the impact of screening on the system's collective excitation spectra and diffusive characteristics at liquid and solid states has been studied. Results show the decrease in the values of both longitudinal and transverse sound speeds and the emergence of anomalous superdiffusive motion in the liquid state due to screening.

Dielectric and impedance spectroscopy of Nd2CoIrO6 double perovskite

Polycrystalline Nd2CoIrO6 double perovskite crystallizes in monoclinic crystal structure with P21/n space group. The average grain size of powder sample is 400–500 nm. The dielectric, impedance and ac conductivity of the sample were studied in the temperature range 5–300 K and in the frequency range 20 Hz–2 MHz. Dielectric constant reveals a step like increase from low temperature value of ∼5 to colossal value of ∼104 at high temperature. High value of dielectric constant is associated with Maxwell–Wagner polarization due to large grain boundary capacitance. Cations (Co2+ and Ir4+) disorder leads to variable range hopping conduction of electrons in grain and grain boundary regions. Distribution of grain size induces distribution of relaxation time as confirmed from depressed semicircles in Nyquist plots. Frequency dependent conductivity follows universal power law behavior.

The low fresh gas flow anesthesia and hypothermia in neonates undergoing digestive surgeries: a retrospective before-after study

BackgroundBased on the previous investigation in our institution, the incidence of intraoperative hypothermia in neonates was high. Since September 1st, 2019, the recommendation had been launched to utilize ≤1 L/min fresh gas flow during the neonates’ surgical procedure. We therefore intended to evaluate the association between low fresh gas flow anesthesia and the occurrence of hypothermia in neonates undergoing digestive surgeries.MethodsA retrospective chart review, before-after study was conducted for neonates who underwent digestive surgeries. The primary outcomes were the incidence of hypothermia. The secondary outcomes included hospital mortality, the value of lowest temperature, blood loss, mean body temperature during the surgery, the length of hypothermia during the surgery and postoperative hospital length-of- stay (PLOS).Results249 neonates fulfilled the eligibility criteria. The overall incidence of intraoperative hypothermia was 81.9%. The low fresh gas flow anesthesia significantly reduced the odds of hypothermia [routine group: 149 (87.6%) versus low flow group: 55 (69.6%); p < 0.01]. Moreover, the low fresh gas flow anesthesia could reduce the length of hypothermia [routine group: 104 mins (50, 156) versus low flow group: 30 mins (0,100); p < 0.01], as well as elevate the value of lowest temperature for neonates [routine group: 35.1 °C (34.5, 35.7) versus low flow group: 35.7 °C (35.3, 36); p < 0.01]. After adjustment for confounding, low fresh gas flow anesthesia and the length of surgical time were independently associated with intraoperative hypothermia.ConclusionsLow fresh gas flow anesthesia is an effective way to alleviate hypothermia in neonates undergoing open digestive surgery.

The influence of self-doping of stibnite ore with impurities on the preparation, heat capacity, magnetic and transport properties of tetrahedrite Cu12Sb4S13

Abstract Stibnite mineral (mainly Sb2S3) has been employed for the synthesis of tetrahedrite Cu12Sb4S13 bulk material by spark plasma sintering. High purity Cu12Sb4S13 can be quickly obtained by two sintering procedures at temperatures from the range of 420 °C to 440 °C for 1 h. Appropriate reduction of Cu content (Cu12+xSb4S13, x ⩽ –0.05) or CuS content (Cu12−ySb4S13−y, y = 0.1 or 0.3) was beneficial to fabricate Cu12Sb4S13. The secondary resintering improved the purity of Cu12Sb4S13 material. The first-order magnetic phase transformation with magnetic hysteresis effect was confirmed by the behavior of susceptibility, heat capacity and resistivity. The magnetization showed a linear increase with increasing field (up to 7 T) and non-saturation behavior was observed. The impurities in stibnite mineral Sb2S3 had a weak influence on the transformation temperature but affected the low-temperature magnetization value (~0.15, close to natural tetrahedrite). Similar transformation was observed by the analysis of heat capacity. The properties such as electrical resistivity, Seebeck coefficient and thermal conductivity were also measured for Cu11:9Sb4S13 and Cu11:9Sb4S12:9. The maximum figure of merit ZT of Cu11:9Sb4S12:9 was 0.22 at 367 K.

Off-design performance analysis of gas turbines

This work deals with the off-design performance analysis of gas turbines. Two gas turbine power stations in Rivers state, Nigeria were used as case studies. Ambient temperature-induced off-design calculations were carried out. This is because no gas turbine operates at its design point in the field and ambient temperature is one of the parameters that changes more frequently in gas turbine operation. Off-design performance models were developed to estimate the power output, thermal efficiency and the exhaust gas temperature at different ambient temperature values. Input data were obtained from the two gas turbine operations and engine adaptation results from previous researches. The power output and the thermal efficiency drops with increase in ambient temperature while the exhaust gas temperature increases with increase in ambient temperature. On the average, power output drops by 1.13 MW when ambient temperature increases by 10 ◦C for the first gas turbine power plant and the value obtained for the second gas turbine power plant which is smaller is 0.473 showing that the power drop is dependent on the power output of the plant. For the same range of ambient temperature increase, thermal efficiency drops by 0.637 % and 0.583 % respectively for the two power plants. Larger drop in power output as well as thermal efficiency occurs at the lower temperature values. The exhaust gas temperature increases with ambient temperature almost uniformly with average value of 1.29 K and 1.21 K respectively for 1◦C increase in ambient temperature. The simulated results closely matched the results obtained from the field at different ambient temperatures. The results of this work will guide power plant operators in economic analysis by estimating the power output beforehand.

Equilibrium calcite-fluid Sr/Ca partition coefficient from marine sediment and pore fluids

The equilibrium partition coefficient of strontium (KSreq) between aqueous solutions and calcite is still poorly known, even though it is a valuable parameter for studies involving the use of calcite trace element geochemistry for reconstructing paleoenvironments and fluid chemistry. In this paper we use pore fluid data from deep sea carbonate sediments to constrain KSreq at low temperature (5–17 °C) and show that the derived values are consistent with laboratory calcite precipitation experiments at 25 °C when the latter are corrected for kinetic effects. Using these low-temperature values, and experimental data available at higher temperature based on replacement reactions, we show that all of the data can be accounted for by a single formulation based on the thermodynamics of the relevant components of seawater-like fluids and the SrCO3–CaCO3 solid solution. The value of pore fluid data is that the fluids and carbonate sediment have been in contact for millions of years so local equilibrium is approached, the overall system can be treated with one-dimensional models, and the temperature is constrained. These natural systems provide an opportunity to investigate low-temperature equilibrium in the carbonate system that is difficult to probe in the laboratory because of sluggish exchange kinetics. We estimate values of KSreq using measured Sr and Ca concentrations in pore fluid and sediment solid calcite and a numerical model of sediment deposition, reaction and transport. The model is used to fit the Sr, Ca, and sulfate concentrations observed in pore fluids of several calcite-dominated sites that we believe are optimal for understanding Sr partitioning. Combining the pore fluid results with experimental measurements at higher temperature results in the following expression which applies for the temperature range 0–200 °C:KSreqT=0.025expΔGr,0R1298.15-1Twhere ΔGr,0 is the free energy change associated with the exchange reaction and temperature is in Kelvin. The uncertainty is approximately ±20%. Recently summarized thermodynamic data yield ΔGr,0 = 1.2 kcal/mol (5.0 kJ/mol) which fits well the lower limit of the high temperature data. The corresponding activity coefficient for the SrCO3 component in the calcite crystal structure is 5.4 for the lower value of ΔGr,0, and 3.17 for the higher value. The derived low-temperature values of KSreq of 0.020 to 0.025 (for 0 °C to 25 °C) have implications for models of marine carbonate diagenesis, and the interpretation of vein carbonate Sr/Ca in oceanic crust. Published data showing much higher KSr values in Mg-bearing solutions are not representative of equilibrium values for either Mg or Sr.

Removal of Phenolic Compounds from Synthetic Solution and Oil Mill Waste Water by Adsorption onto Nanoparticles Synthesized from Phosphate Rock

In this work, we studied the elimination of phenol compounds from phenolic solutions and Oil Mill Waste Water (OMWW) by adsorption method. The adsorbents used are natural phosphate rock coming from Khouribga phosphate mine (Morocco) and an Apatite synthesized from this phosphate by a dissolution–precipitation reactions. Results obtained showed that the structure of natural phosphate and synthesized apatite are respectively Ca9.55(PO4)4.96F1.96 (CO3)1.283 and (Ca10(OH)2(PO4)6). Synthesized apatite has a higher specific surface than natural phosphate (193.62m2/g). The adsorption study showed that the synthesized apatite can be used as an adsorbent to remove phenol from water with very fast reaction kinetics (about 10 min) and an adsorption capacity equal to 15mg/g. The optimal adsorption capacity was found in low values of temperature and in neutral pH. Adsorption kinetics of phenol solution on the two adsorbents can be described by an equation corresponding to a pseudo second order. Freundlich model fitted well with the adsorption isotherms more than the Langmuir model. Characterization of olive mill wastewater shows that, phenol index equal to 0.39 g/l and chemical oxygen demand COD equal to 158 g/l. The treatment of OMWW by adsorption method on the two adsorbents shows that the use of natural phosphate as adsorbent reduced phenol index by 23% and (COD) by 35% while using synthesized apatite reduced phenol index by 30% and COD by 38%.

Synergistic effects of water temperature, microplastics and ammonium as second and third order stressors on Daphnia magna

Daphnids, including the water flea Daphnia magna, can be exploited for wastewater treatment purposes, given that they are filter feeder organisms that are able to remove suspended particles from water. The presence of pollutants, such as microplastics and chemicals, might be considered stressors and modify the behaviour and survival of D. magna individuals. The impact of the cumulative pollutants that regulate the fate of living organisms has yet to be fully determined. Here we present the effect of double and triple combinations of stressors on the behaviour of D. magna. The impact of water temperature, ammonium and polystyrene microplastics on the filtration capacity and survival of D. magna is studied. Water temperatures of 15 °C, 20 °C and 25 °C, microplastic-to-food ratios of 25% and 75%, and ammonium concentrations of 10 and 30 mg N–NH4+ L−1 are tested after making dual and triple combinations of the parameters. A synergistic effect between water temperature and ammonium is normally observed but not in the case of the lower values of ammonium concentration and temperature. The combination of three stressors (water temperature, microplastics and ammonium) is also found to be synergistic, producing the greatest impact on D. magna filtration capacity and reducing their survival. In comparison with the effect of the two stressor conditions, the combination of the three stressors caused a reduction of between 13.1% and 91.7% in the t50% time (the time required for a 50% reduction in the D. magna filtration capacity) and a reduction of between 4.8% and 54.5% in TD50 (the time for 50% mortality).

Metamagnetoelectric effect in multiferroics A2Cu2Mo3O12 (A=Rb and Cs) quantum spin chain

The magnetoelectric and thermodynamic properties of multiferroic A2Cu2Mo3O12 (A=Rb and Cs) compounds are investigated through the theoretical laboratory of a frustrated one-dimensional spin chain of CuO2 ribbon where inter-chain couplings are ignored. The general framework is built under external magnetic and electric field constraints with additional anisotropies. The field scans of magnetoelectric properties highlight a set of interdependent meta-transition giving birth to the metamagnetoelectric effect. Those meta-transitions are likewise reported by typically measured field dependencies of entropy and further of heat capacity that reveals a breakdown of temperature-energy dependence during meta-transitions. The temperature-energy dependence breakdown vanishing reported for high temperature emphasizes the metamagnetoelectric state death beyond relatively low-temperature values. Furthermore, large temperature-fields dependencies are noticed except for critical values where meta-transitions are occurring in the investigated A2Cu2Mo3O12 compounds.

Comparison of Respiratory and Ischemic Heart Mortalities and their Relationship to the Thermal Environment

Chronic respiratory and ischemic heart diseases are globally important parts of total mortality. This study focuses on the occurrence of mortality due to these disease groups in Germany and possible effects of the thermal environment. A retrospective analysis on the mortality rates of chronic lower respiratory diseases (CLRD) and ischemic heart diseases (IHD) at the regional level in Germany for the period 2001–2015 was done in combination with meteorological observations from the network of the German Meteorological Service. In order to control the mortality data for long-term and seasonal trends, a 365-day Gaussian low-pass filter with a filter response function was applied. The thermal environment was analysed using 2 m air temperature (Ta) and the human biometeorological index Perceived Temperature (PT). The relationship of the Relative Risk (RR) of mortality to the thermal environment is displayed as an exposure–response curve, with threshold values at which RR increases significantly towards higher and lower temperature values. CLRD mortality increases above 17.6 °C, at approximately 4.4%/°C (CI: ± 0.3). The increase of IHD mortality above the threshold of 18.8 °C is less steep, at 3.5%/°C (CI: ± 0.2). During hot periods, CLRD mortality increases by 19.9%, which is twice as much as IHD mortality, with an increase of 9.8%. However, cold days and cold periods affect IHD slightly more than CLRD. The results highlight the concerns of CLRD patients during hot days as well as heat waves. This could lead to better precautions being taken for respiratory patients, which are already established for cardiac patients in Germany.

Skeletal muscular relaxation time from postmortem MR imaging of adult humans

Abstract Purpose To measure T1, and T2 values of the skeletal muscle by postmortem magnetic resonance (PMMR) imaging in adult humans at 1.5 T, and to compare them with those of living human subjects. Materials and methods We performed skeletal muscular PMMR imaging on 45 deceased adults (31 men, 14 women; mean age, 55.6 years). We measured T1 and T2 values of the right and left erector spinae muscles. The PMMR imaging data were compared with those from the corresponding sites in 13 healthy subjects. The association among rectal temperature, age and sex in T1 and T2 values was assessed by multiple regression analysis. Results By skeletal muscular PMMR imaging (clinical MR imaging), the average T1 values were: right:745 ± 107 ms (820 ± 108 ms); left:930 ± 133 ms (1022 ± 116 ms), and the average T2 values were: right:62± 9 ms (43± 5 ms); left:59 ± 7 ms (42 ± 5 ms). The left-right T1 difference was due to B1 inhomogeneity. Compared with clinical skeletal muscular MR imaging, PMMR imaging demonstrated significantly shorter T1 values and longer T2 values. On PMMR imaging, T1 values were significantly influenced by rectal temperature, whereas T2 values were significantly influenced by age and sex, but not by rectal temperature. Conclusion In the skeletal muscle, PMMR imaging shows shorter T1 values and longer T2 values than clinical MR imaging. T1 values decrease with lower rectal temperature and T2 values increase with female and elder age.

Analysis of viscosity function models used in friction stir welding

Friction stir welding (FSW) is a solid-state process, where a tool that consists of a shoulder and a pin rotates between the plates to be welded by plastic deformation. This process involves several physical phenomena. To better understand this complex phenomenon, simulations have been performed for a range of maximum viscosity values. The viscosity model used in friction stir welding simulations depends on two variables, the temperature and strain rate; however, the viscosity goes toward infinity for low values of temperature and strain rates. This study analyzed two different friction stir welding simulation, by observing how the viscosity functions behave for low values of temperature and strain rates. The maximum viscosity value was shown to be restricted to values, where the velocity field tends to zero. Furthermore, when the viscosity value exceeds the maximum value, the temperature and viscosity field is significantly impaired. In the correct results, the change in viscosity is restricted to stir zone.

Thermo- and pH-sensitive glycosaminoglycans derivatives obtained by controlled grafting of poly(N-isopropylacrylamide)

Poly(N-isopropyl acrylamide) grafted heparin and chondroitin sulfate were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The copolymers were characterized by NMR, IR, SEC, DLS, SLS and NTA methods. High grafting densities were reached for both glycosaminoglycans. The temperature, pH and polymer concentration affected the low critical solution temperatures values. The increased pNIPAAm chain length, grafting density and concentration led to the sharp phase transition at 35 °C. Spherical nanogels were formed around this temperature. Terminal dodecyl trithiocarbonate groups of the copolymers were reduced to thiols that allowed formation of sensitive nanogels with sharp phase transitions induced by pNIPAAm chains. The copolymers showed no toxicity to the ocular cells and they provided the prolonged release of dexamethasone phosphate at 37 °C. These copolymers are interesting alternatives for ocular drug delivery.