Lakes are key components of biogeochemical and ecological processes, thus knowledge about their distribution, volume and residence time is crucial in understanding their properties and interactions within the Earth system. However, global information is scarce and inconsistent across spatial scales and regions. Here we develop a geo-statistical model to estimate the volume of global lakes with a surface area of at least 10 ha based on the surrounding terrain information. Our spatially resolved database shows 1.42 million individual polygons of natural lakes with a total surface area of 2.67 × 10(6) km(2) (1.8% of global land area), a total shoreline length of 7.2 × 10(6) km (about four times longer than the world’s ocean coastline) and a total volume of 181.9 × 10(3) km(3) (0.8% of total global non-frozen terrestrial water stocks). We also compute mean and median hydraulic residence times for all lakes to be 1,834 days and 456 days, respectively.
The cerebellum is associated with balance control and coordination, which might be important for gliding on smooth ice at high speeds. A number of case studies have shown that cerebellar damage induces impaired balance and coordination. As a positive model, therefore, we investigated whether plastic changes in the volumes of cerebellar subregions occur in short-track speed skating players who must have extraordinary abilities of balance and coordination, using three-dimensional magnetic resonance imaging volumetry. The manual tracing was performed and the volumes of cerebellar hemisphere and vermian lobules were compared between short-track speed skating players (n = 16) and matched healthy controls (n = 18). We found larger right cerebellar hemisphere volume and vermian lobules VI-VII (declive, folium, and tuber) in short-track speed skating players in comparison with the matched controls. The finding suggests that the specialized abilities of balance and coordination are associated with structural plasticity of the right hemisphere of cerebellum and vermian VI-VII and these regions play an essential role in balance and coordination.
Although developments in liquid dispensers have made the use of 1536-well plates for high-throughput screening (HTS) standard, there is still a gap in dispenser technology for performing matrix experiments with several components. Experiments such as those performed during assay development and enzymological studies are therefore still performed by manual pipetting in lower-density plates. We have evaluated a new dispenser, the Certus liquid dispenser (Gyger Fluidics GmbH, Switzerland), that is capable of flexible dispensing in 1536-well format, with a dead volume of less than 200 µL. Taking advantage of the precision of the dispenser for volumes down to 50 nL, we have created concentration gradients on plates by dispensing different volumes of reagent and then backfilling with buffer. Using this method and the flexibility of the dispenser software, we have performed several multidimensional experiments varying two to three components, including an assay development for an HTS, a mode of inhibition study, and a cofactor optimization, in which we determined 32 K(M) values. Overall, the flexibility of the plate layout for multiple components, the accuracy to dispense volumes ranging 2 log orders, and minimal reagent usage enable this dispenser for complex biochemical experiments.
BODIPY 505/515, a lipophilic bright green fluorescent dye was tested for lipid detection in the microalga Tetraselmis subcordiformis. A concentration of 0.28μgml(-1) and staining for 6min was optimal. Lipid bodies stained with BODIPY505/515 had a characteristic green fluorescence. Their volumes were determined using the sphere volume formula. Lipid accumulation under different nitrogen concentrations was analyzed. With an increase in NaNO(3) concentration from 0 to 240mg L(-1), the maximum algal concentration increased from 8.23±0.62 (×10(5) cells ml(-1)) to 1.61±0.13 (×10(6) cellsml(-1)), while the maximum volume of intracellular neutral lipid decreased from 9.78±1.77 μm(3)cell(-1) to 6.00±0.59μm(3)cell(-1). A comparison of the lipid contents measured by BODIPY 505/515 staining and the gravimetric method showed a positive correlation coefficient of R(2)=0.93. BODIPY 505/515 staining is a promising method in lipid quantitation in T. subcordiformis.
Objective To compare the Welch Allyn SureSight™ wavefront autorefractor with retinoscopy in normal dogs. Animals studied Fifty privately owned dogs (100 eyes) of 20 breeds, free of ocular disease. Mean ± SD age: 5.7 ± 3.25 years (range: 6 months-13 years). Procedures The refractive error was determined in each eye by two experienced retinoscopists using streak retinoscopy as well as by an autorefractor operated by two different examiners. Measurements were performed before and approximately 30-45 min after cycloplegia was induced by cyclopentolate 0.5% and tropicamide 0.5% ophthalmic solutions. Results Mean ± SD noncyclopleged retinoscopy net sphere was -0.55 ± 1.14 (range: -3.75 to 3.5) diopters (D). Mean cyclopleged retinoscopy net sphere was -0.52 ± 1.18 (range: -4.25 to 2) D. Mean ± SD noncyclopleged autorefractor spherical equivalent (SE) was -0.42 ± 1.13 D (range: -3.36 to 2.73) D. Mean cyclopleged autorefractor SE was 0.10 ± 1.47 (range: -5.62 to 3.19) D. Noncyclopleged autorefraction results were not significantly different from streak retinoscopy (whether noncyclopleged or cyclopleged, P = 0.80 and P = 0.26, respectively). Cyclopleged autorefraction results were significantly different from noncyclopleged or cyclopleged streak retinoscopy (P < 0.0001 in both states). There was no significant difference between noncyclopleged and cyclopleged streak retinoscopy (P = 0.97). Conclusions Noncyclopleged autorefraction shows good agreement with streak retinoscopy in dogs and may be a useful clinical technique. Cycloplegia does not significantly affect streak retinoscopy results in dogs.
- Chemphyschem : a European journal of chemical physics and physical chemistry
- Published over 7 years ago
Mechanical properties of glass fiber reinforced composite materials are affected by fiber sizing. A complex film formation, based on a silane film and PVA/PVAc (polyvinyl alcohol/polyvinyl acetate) microspheres on a glass fiber surface is determined at 1) the nanoscale by using atomic force microscopy (AFM), and 2) the macroscale by using the zeta potential. Silane groups strongly bind through the SiOSi bond to the glass surface, which provides the attachment mechanism as a coupling agent. The silane groups form islands, a homogeneous film, as well as empty sites. The average roughness of the silanized surface is 6.5 nm, whereas it is only 0.6 nm for the non-silanized surface. The silane film vertically penetrates in a honeycomb fashion from the glass surface through the deposited PVA/PVAc microspheres to form a hexagonal close pack structure. The silane film not only penetrates, but also deforms the PVA/PVAc microspheres from the spherical shape in a dispersion to a ellipsoidal shape on the surface with average dimensions of 300/600 nm. The surface area value Sa represents an area of PVA/PVAc microspheres that are not affected by the silane penetration. The areas are found to be 0.2, 0.08, and 0.03 μm(2) if the ellipsoid sizes are 320/570, 300/610, and 270/620 nm for silane concentrations of 0, 3.8, and 7.2 μg mL(-1) , respectively. The silane film also moves PVA/PVAc microspheres in the process of complex film formation, from the low silane concentration areas to the complex film area providing enough silane groups to stabilize the structure. The values for the residual silane honeycomb structure heights (Ha ) are 6.5, 7, and 12 nm for silane concentrations of 3.8, 7.2, and 14.3 μg mL(-1) , respectively. The pH-dependent zeta-potential results suggest a specific role of the silane groups with effects on the glass fiber surface and also on the PVA/PVAc microspheres. The non-silanized glass fiber surface and the silane film have similar zeta potentials ranging from -64 to -12 mV at pH’s of 10.5 and 3, respectively. The zeta potentials for the PVA/PVAc microspheres on the glass fiber surface and within the silane film significantly decrease and range from -25 to -5 mV. The shapes of the pH-dependent zeta potentials are different in the cases of silane groups over a pH range from 7 to 4. A triple-layer model is used to fit the non-silanized glass surface and the silane film. The value of the surface-site density for ΓXglass and ΓXsilane , in which X denotes the AlOSi group, differs by a factor of 10(-4) , which suggests an effective coupling of the silane film. A soft-layer model is used to fit the silane-PVA/PVAc complex film, which is approximated as four layers. Such a simplification and compensation of the microsphere shape gives an approximation of the relevant widths of the layers as the follows: 1) the layer of the silane groups makes up 10 % of the total length (27 nm), 2) the layer of the first PVA shell contributes 30 % to the total length (81 nm), 3) the layer of the PVAc core contributes 30 % to the total length (81 nm), and finally 4) the layer of the second PVA shell provides 30 % of the total length (81 nm). The coverage simulation resulted in a value of 0.4, which corresponds with the assumption of low-order coverage, and is supported by the AFM scans. Correlating the results of the AFM scans, and the zeta potentials sheds some light on the formation mechanism of the silane-PVA/PVAc complex film.
This study designs a pH-sensitive nanoparticle carrier of methotrexate (MTX) and combretastatin A4 (CA4) based on pullulan for the combination therapy against hepatocellular carcinoma (HCC). Briefly, N-urocanyl pullulan (URPA) with the degree of substitution (DS) of 5.2% was synthesized and then conjugated with MTX to form MTX-URPA, in which MTX content was 17.8%. MTX-URPA nanoparticles prepared by the dialysis method had spherical shape and the mean size of 187.1 nm, and showed high affinity for HepG2 cells. CA4 was successfully loaded into MTX-URPA nanoparticles and exhibited pH-sensitive in vitro release property. After intravenous injection to PLC/PRF/5-bearing nude mice, CA4 loaded MTX-URPA (CA4/MTX-URPA) nanoparticles achieved the enhanced antitumor and anti-angiogenic effects, the prolonged circulation time in blood, and the increased distributions both in the liver and the tumor. In conclusion, this drug carrier system has significant liver-targeting property and exhibits advantages for the combination therapy against hepatocellular carcinoma.
- Langmuir : the ACS journal of surfaces and colloids
- Published almost 8 years ago
We report a method to synthesize and image Janus spheroid and “kayak” shaped patchy particles that combine both shape and interaction anisotropy. These particles are fabricated by sequentially combining evaporative deposition of chrome and gold with the uniaxial deformation of the colloidal particles into spheroids. We introduce combined reflection and fluorescence confocal microscopy to image each component of the patchy particle. Image analysis algorithms that resolve patch orientation from these image volumes are described and used to characterize self-assembly behavior. Assemblies of the Janus spheroid and kayak particles produced at different salt concentrations demonstrate the functional nature of the patch-to-patch interactions between the particles. Selective gold-to-gold patch bonding is observed at intermediate salt concentrations, while higher salt concentrations yield gel-like structures with non-selective patch-to-patch bonding. At intermediate salt concentrations, differences in the orientational order of the assemblies indicate that both the preferential gold-to-gold patch bonding and the particles' shape anisotropy influence the self-assembled structure.
Cyclodextrin-based nanosponges (NS) are solid nanoparticles, obtained from the cross-linking of cyclodextrins, that have been proposed as delivery systems for many types of drugs. Various NS derivatives are currently under investigation in order that their properties might be tuned for different applications. In this work, new carboxylated cyclodextrin-based nanosponges (Carb-NS) carrying carboxylic groups within their structure were purposely designed as novel Acyclovir carriers. TEM measurements revealed their spherical shape and size of about 400nm. The behaviour of Carb-NS, with respect to the incorporation and delivery of Acyclovir, was compared to that of NS, previously investigated as a drug carrier. DSC, XRPD and FTIR analyses were used to investigate the two NS formulations. The results confirm the incorporation of the drug into the NS structure and NS-Acyclovir interactions. The Acyclovir loading into Carb-NS was higher than that obtained using NS, reaching about 70% w/w. In vitro release studies showed the release kinetics of Acyclovir from Carb-NS to be prolonged in comparison with those observed with NS, with no initial burst effect. The NS uptake into cells was evaluated using fluorescent Carb-NS and revealed the nanoparticle internalisation. Enhanced antiviral activity against a clinical isolate of HSV-1 was obtained using Acyclovir loaded in Carb-NS.
In the present study, densely dispersed silver nanoparticles (Ag NPs) were rapidly green synthesized in the presence of Rumex dentatus aqueous extract, followed by UV-irradiation reduction. The Ag NPs were characterized using UV-vis spectroscopy, FTIR, XRD, and TEM. Then, the Ag NPs were incorporated into interpenetrating polymeric networks based on cationic trimethyl chitosan (TMCS) and anionic poly(acrylamide-co-sodium acrylate) copolymer to develop a new series of composite nanoparticles as potential antibacterial agents. Both TMCS and poly(acrylamide-co-sodium acrylate) were prepared in the study, and characterized using FTIR, DSC, and SEM. The synthesized Ag NPs showed high purity and uniform particle size distribution with particle size ranged between 5 and 30 nm. The composite nanoparticles demonstrated homogeneous spherical shape with size in the range of 378-402 nm. Both Ag NPs and the composite nanoparticles showed promising bactericidal activity as compared with the control. Moreover, the antibacterial activity of the composite nanoparticles increased along with increasing the concentrations of Ag NPs and the TMCS.