Concentration Gradient

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Effect of Non Uniform Basic Concentration Gradient on the Onset of Double Diffusive Convection in Micropolar Fluid

Effect of Non Uniform Basic Concentration Gradient on the Onset of Double Diffusive Convection in Micropolar Fluid

In the paper, we study the effect of basic non-uniform concentration gradient on the convective instability of a micropolar fluid. One uniform, five non-uniform basic concentration gradient are chosen for the study and this have been presented in Table 1. We find that,

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A microfluidic spheroid culture device with a concentration gradient generator for high-throughput screening of drug efficacy

A microfluidic spheroid culture device with a concentration gradient generator for high-throughput screening of drug efficacy

Abstract: Three-dimensional (3D) cell culture is considered more clinically relevant in mimicking the structural and physiological conditions of tumors in vivo compared to two-dimensional cell cultures. In recent years, high-throughput screening (HTS) in 3D cell arrays has been extensively used for drug discovery because of its usability and applicability. Herein, we developed a microfluidic spheroid culture device (μFSCD) with a concentration gradient generator (CGG) that enabled cells to form spheroids and grow in the presence of cancer drug gradients. The device is composed of concave microwells with several serpentine micro-channels which generate a concentration gradient. Once the colon cancer cells (HCT116) formed a single spheroid (approximately 120 μm in diameter) in each microwell, spheroids were perfused in the presence of the cancer drug gradient irinotecan for 3 days. The number of spheroids, roundness, and cell viability, were inversely proportional to the drug concentration. These results suggest that the μFSCD with a CGG has the potential to become an HTS platform for screening the efficacy of cancer drugs.

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Concentration gradient induced morphology evolution of silica nanostructure growth on photoresist derived carbon micropatterns

Concentration gradient induced morphology evolution of silica nanostructure growth on photoresist derived carbon micropatterns

In general, Si vapor source is mainly from the active oxidation of the silicon substrate in the presence of cop- per at high temperature, and O vapor source might come from the leakage of the vacuum system [26]. The copper layer breaks to small droplets at the heating process, then Cu-Si eutectic catalysts can be formed to initiate the nanostructure growth on the 3D carbon posts above the eutectic temperature, which matches with the photoresist carbonization process [26]. By dis- solving Si and O source onto the catalyst droplet con- tinuously, the silica nanostructures grow mainly through VLS and VQS mechanisms. The catalyst droplets with smoothly curved surfaces confirm the VLS process, as shown in Figures 2, 4, and 5 [33]. Combining the results of the SEM and TEM, it is concluded that the Si vapor source concentration gradient would lead to unique morphology changes of nanostructures. The underlying reason could be due to the variations of reactive source concentration gradient inside different catalyst droplets caused by the local source concentration gradient in the environment, which is a key factor to determine the

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Evidence for a concentration gradient favoring outward movement of sodium from the thin loop of Henle

Evidence for a concentration gradient favoring outward movement of sodium from the thin loop of Henle

Recent models of the urinary concentrating mechanism have postulated that urea in the medullary interstitium creates a transtubular concentration gradient for sodium between fluid at the end of the descending limb of Henle's loop and the medullary interstitium, favoring the passive outward movement of sodium from Henle's thin ascending limb. These experiments were designed to determine whether such a gradient normally exists. Young nondiuretic Munich-Wistar rats were prepared for micropuncture of the exposed left renal papilla.

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Lactate concentration gradient from right atrium to pulmonary artery

Lactate concentration gradient from right atrium to pulmonary artery

Blood samples were placed on ice and taken to a central lab- oratory for measurement of [Lac] (Ektachem 950 IRC Chem- istry Analyzer with a Vitros Products lactate slide, Ortho- Clinical Diagnostic, Inc., Rochester, NY, USA), hemoglobin concentration ([Hb]) and O 2 saturation (ABL700 Radiometer America Inc., Westlake, OH, USA). We measured cardiac out- put (CO) by the thermodilution method as the average of three sequential determinations.

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Drug screening of biopsy-derived spheroids using a self-generated microfluidic concentration gradient

Drug screening of biopsy-derived spheroids using a self-generated microfluidic concentration gradient

Prostate tumour biopsy screening. Primary prostate cancer tissue from two different patient biopsies was cultured for two weeks prior to microfluidic experiments. Morphological assessment of the expanded biop- sies was conducted to assess the presence of multiple cell types in each culture. From each biopsy preparation, a cancer-cell enriched single-cell suspension was used to prepare a number of gradient-generating devices. Depending on the tissue proliferation during expansion, between 13 and 22 devices could be seeded per biopsy. Alongside the microfluidic experiments, RT-qPCR was performed for each biopsy to assess the presence of pros- tate cancer cells and several prostate cancer biomarkers: androgen receptors (ARs), prostate-specific androgen (KLK3) and alpha-methyl-acyl-CoA racemase (AMACR). Expression of these markers was quantified using a benign prostate cell line (PNT2) as a reference and a prostate cancer cell line (LNCaP, Fig. 4D) for comparison. Pathology reports confirmed that both patients in the study had prostate cancer. Spheroids were allowed to form in the microfluidic device for 3 days in all experiments, before each condition was tested in triplicates. To demon- strate the capabilities of the microfluidic platform, different proof-of-concept experiments were carried out for each biopsy.

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Interest of Serum Ascites Albumin Concentration Gradient in the Diagnosis of Portal Hypertension in Cirrhotic Patients

Interest of Serum Ascites Albumin Concentration Gradient in the Diagnosis of Portal Hypertension in Cirrhotic Patients

Cirrhosis is the final stage of any chronic liver disease. Gastrointestinal bleeding by rupture of esophageal varices (EV) is one of the most feared complications of cirrhosis because of its high mortality. All patients with cirrhosis should undergo endoscopic screening at the time of diagnosis to identify those at high risk of bleeding who may benefit from primary prophylaxis [1]. Upper gastrointestinal fibroscopy (UGF) is a relatively expensive, invasive and restrictive practice [2]. In Africa, and in Togo in particular, the follow-up of cirrhotic patients by UGF remains a challenge for clinicians because of the absence or insufficiency of digestive endoscopy units [3]. The appearance of ascite is the most common complication during cirrhosis [4]. The serum-ascites albumin gradient (SAAG) is a minimally invasive method that is very precise, already described as allowing to classifying the ascites fluid according to the absence or the presence of a portal hypertension (PHT) [5] [6] [7]. According to Starling, SAAG is the best indicator of PHT [2] [8] and several studies have shown that there is a direct relationship between SAAG and the different measures of PHT [6] [9]. Studies on non-invasive methods of EV including platelet ratio and spleen diameter have been conducted in african cirrhotic subjects [10] [11]. In Ivory Coast, a study evaluating SAAG and the endoscopic parameters in 2015 showed a link between a high threshold of SAAG and the presenceof EV [12]. The use of SAAG can be considered as an indirect parameter for the detection of EV and be useful in regions where there is a shortage of human and material resources for the realization of the UGF. This study was conducted to find a more accessible and less restrictive mean such as SAAG to predict EV in cirrhotics with ascit.

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Mass Concentration Gradient Of Aerosol Across Selected States In Northwestern Nigeria

Mass Concentration Gradient Of Aerosol Across Selected States In Northwestern Nigeria

ity in the months of harmattan season (November to March) corresponds to the periods when the entire Sahel region is under the influence of dry dust-laden north easterly winds [23]; [9]. The visibility is low because, the concentration of the harmattan dust particles in the atmosphere absorbs and scat- ters the light rays coming from the sun [24]; [10]. Therefore, higher concentrations of harmattan dust lower the intensity of solar radiation which in turn lowers the visibility. Recent stud- ies by the Nigerian meteorological agency [NIMET] in 2011 shows that visibility reduced to 100-900m in the north and 600-800m in the south [14]. During this period the north and central parts experienced visibility between 100-800m, Kano for instance recorded a visibility of zero meter on the 19 th of February for almost 6hrs while the southern part reported vis- ibility of between 200-900m [14].

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Optimization of Lactoperoxidase and Lactoferrin Separation on an Ion-Exchange Chromatography Step

Optimization of Lactoperoxidase and Lactoferrin Separation on an Ion-Exchange Chromatography Step

A mechanistic model is used to describe the physical phenomena based on a set of mathematical equations. Two types of physical phenomena dominate chromatography; movement of solutes through the packed bed of porous particles via mass transfer mechanisms, and adsorption based on the fundamental thermodynamic interactions between migrating solutes and the stationary phase. The general system of equations used to describe the mass transfer phenomena consist of two sets of partial differential mass conservation equations. The general rate model for a chromatographic process includes convective and diffusive flows through porous particles on the column level and imitates mass transfer resistances and surface interactions on particle level. In IEC, an external film surrounding adsorbent particles is commonly presumed to model the movement of components from column to particle level; the sorption of protein on the particle surface can be described by the steric mass-action (SMA) model, developed by Iyer et al. [15] and generally used for the modeling of salt gradient elution in IEC, for example in [16].

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Subrepellent doses of Slit1 promote Netrin-1 chemotactic responses in subsets of axons

Subrepellent doses of Slit1 promote Netrin-1 chemotactic responses in subsets of axons

analyzed the response of hippocampal neurons depend- ing on the levels of the Netrin-1 receptor UNC5A [17]. Growth cones that are attracted or repelled by Netrin-1 are respectively UNC5A-negative and UNC5A-positive, each subpopulation representing half of the growth cones. These findings are in agreement with our results, showing no significant chemotactic activity of a Netrin-1 gradient on a heterogenous hippocampal population. We have also shown that changing the nature of the extracellular matrix changes the polarity of the turning response of hippocampal neurons to the combination of Netrin-1 and Slit1. These findings are reminiscent of data obtained in Xenopus neurons in which laminin-1 converts netrin-mediated attraction into repulsion [3]. While the switching effect is inverted compared to our observations, probably due to the different neuronal types used, it confirms the key role of the extracellular matrix in regulating axon guidance. Although future ex- periments are needed to precisely understand the mech- anisms, our study demonstrates that Slit1 promotes the chemotactic activity of Netrin-1, either attractive or re- pulsive. Slit1 acts at subthreshold repulsive levels, thereby revealing complex integrated responses to a combined source of Slit1 and Netrin-1. These experi- ments set the foundation for large-scale assessments of combinatorial activities of extracellular cues and provide a quantitative framework to unravel the complex wiring of neuronal networks.

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Computer Simulation of Blood Flow and Particle Transport with Applications to Vessel Embolization and Direct Nanodrug Delivery to Tumors.

Computer Simulation of Blood Flow and Particle Transport with Applications to Vessel Embolization and Direct Nanodrug Delivery to Tumors.

7 Considering heterogeneous blood flow, two main contributing factors are of particular interest in microvessels, i.e., the migration of RBCs due to RBC-wall interactions that results in formation of a wall-depletion layer of RBCs (Goldsmith et al., 1989), and the dispersion of RBCs due to multi-body interactions which leads to shear-induced diffusion (SID) of RBCs. Wall-induced migrations (WIM) is due to the break of fore-aft symmetry of the cell caused by erythrocyte deformability. The lift force experienced by a RBC near the vessel wall has been the interests of several theoretical, numerical and experimental studies (Olla, 1999; Seifert, 1999; Sukumaran & Seifert, 2001; Abkarian et al., 2002; Callens et al., 2008). SID of particles in non-colloidal (non-Brownian) suspensions have been observed for rigid and deformable particles with different shapes (Grandchamp et al., 2013). It is due only to the hydrodynamic interactions between the particles comprising the suspension (Breedveld et al., 2001). However, these interactions can be viewed in part as a diffusion process. Specifically, the resulting particle migration has been shown to exhibit diffusional behavior characterized by a diffusivity D    a 2 2 , where  is the particle concentration.

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Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

Areal-averaged trace gas emission rates from long-range open-path measurements in stable boundary layer conditions

While 3-D sonic anemometer measurements were aligned to the natural wind coordinates for the Fuhrberg experiment conducted over a flat open field, they were not aligned in the Indiana experiment because the measurements were made in close proximity to a lagoon with a 1–3 m drop in elevation to the lagoon liquid surface. Turbulence statistics (variances and co-variances) were calculated for all heights except 0.5 m where it was expected that significant fractions of the turbu- lence would not be measureable by the sonic anemometer. The momentum flux and sensible heat flux were determined by the eddy-covariance method (Foken, 2008). The Monin- Obukov length L was determined with θ v 0 (perturbation in the virtual potential temperature), approximated by θ s 0 (pertur- bation in sonic anemometer temperature), and w 0 (perturba- tion of the vertical wind speed). Since there is often a strong self-correlation between the turbulence quantities used in the calculation of L and the gradient Richardson number is vul- nerable to significant errors when the vertical wind profile is complex, the bulk Richardson number Ri B was used as an

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Near-surface profiles of aerosol number concentration and temperature over the Arctic Ocean

Near-surface profiles of aerosol number concentration and temperature over the Arctic Ocean

In Fig. 4, particle number concentration data collected with the gradient pole over the Arctic pack ice on 28 August are presented. We choose this example because it illustrates a weak gradient that was resolved despite the large variability in the particle counts. For consistency, we take the same data approach as for the temperature case. Fig. 4a displays the height profiles, which appear less uniform than in the tem- perature case discussed above. The irregularity in the profiles was present in the beginning stages of the experimental runs due to lack of practice with raising and lowering the gradi- ent pole and struggling with initial adjustments of the setup in the cold conditions. As can be seen in the latter part of the measurement period, we also tried faster scanning of the profiles, but the results provided poor averaging statistics.

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A nuclear magnetic resonance investigation of brine inclusions in Antarctic and artificial sea ice : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Physics at Massey University

A nuclear magnetic resonance investigation of brine inclusions in Antarctic and artificial sea ice : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Physics at Massey University

The chief characteristic of the crystal structure of sea ice, as compared to fresh-water ice, is the small size of the crystals. This is explained by the fact that the ions of all the salts in sea water reduce the range of action of the crystallisation nuclei so that the nuclei concentration is higher [3]. The presence of liquid and solid layers between the grains hinders and retards the growth of crystals once formed, which also leads to a decrease in size. The micro-crystalline structure of sea ice substantially influences the deformation and strength of the ice cover.

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Laser treatment of bladder cancer

Laser treatment of bladder cancer

patient tolerance of PDT with these sensitisers and despite warnings, most series report a small number of patients who develop significant sunburn. Other ways of administering photosensitisers have been tried with the aim of avoiding skin sensitivity. Direct intra-tumour injection is only suitable for solitary bladder tumours (Amano etal., 1988) and would clearly not be feasible for Cis. Intravesical administration of HpD has not been successful (Benson, 1988), and our studies on the intravesical uptake of phthalocyanine (chapter 6) also show that although significant amounts are absorbed by normal bladder, the uptake can be patchy and unpredictable. The most likely solution to this particular complication lies in newer photosensitisers which, although still given intravenously, are either cleared more rapidly from the skin or, like the phthalocyanines, have a localised absorption peak (fig. 3.1), at a longer wavelength than HpD, away from the main concentration of solar emission, which produces much less of a skin reaction (Tralau et aL, 1989). When using such a sensitiser at low dose levels, the problem of cutaneous sensitivity to sunlight is likely to be virtually eliminated. An alternative approach may be to use singlet oxygen quenchers which can be given after PDT to reduce skin sensitivity in animals, though their clinical efficacy is not yet proven (Dillon et aL, 1988). 3 .4 .2 .5 D osim etry

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Search | Preprints

Search | Preprints

Operation is in continuous state with temperature gradient and uniform particle mixing. FBB are same as bubble column reactor with expanded cross section area at the top of the vessel so as to recirculate the liquid that is constantly pumped from the bottom of the receptacle at a velocity that is satisfactory to preserve them in suspension (Chistietal.2010). Agitation of the medium is supported with the action of the pump in this bioreactor. FBB is one of the method for sustaining high biomass concentration and excellent mass transfer in continuous process. The concentration of the biocatalyst is significantly greater and washout limitations of free cell systems is affected (Gibilaro et al.2001). FBBs provides lesser attrition of solid particle than the conventional mechanical stirrer reactor and also volumetric productivity is higher than the packed bed reactor. FBBs is widely use in bioprocess improvement. The efficiency of fluidized bed reactor depends on the attachment of particles that are maintained in suspension by an upward flow rate of the fluid to be treated. These particles are also called as biofilm carrier either they are inert core on which the biomass is produced by cell attachment; or porous particles in which the biocatalyst is trapped (self-immobilization).

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Original Article Effect of dialysate sodium concentration and sodium gradient on patients with maintenance hemodialysis

Original Article Effect of dialysate sodium concentration and sodium gradient on patients with maintenance hemodialysis

Abstract: Backgrounds: Patients with maintenance hemodialysis (MHD) have a high risk of cardiovascular disease, which is the leading cause of morbidity and mortality. The aim of the present study was to explore the relationship between the sodium gradient and the water load of MHD patients. Methods: Eighty one MHD patients were selected in the study. The serum sodium concentration, sodium gradient, interdialysis weight gain (IDWG), IDWG% of the patients and the incidence of hypotension were analyzed. Correlation analysis was carried out. Results: The serum sodium concentrations were 138.81 ± 3.27 mmol/L and 137.81 ± 2.88 mmol/L before and after dialysis, respec- tively. The sodium concentration of dialysis solution was 135 mmol/L. The absolute sodium gradient was 3.92 ± 2.69 mmol/L. The absolute sodium concentration difference after dialysis was 2.79 ± 2.14 mmol/L. IDWG was 2.06 ± 0.82 kg and the value of IDWG% was 3.71 ± 1.42%. The absolute sodium gradient was positively correlated with IDWG (r=0.349, P=0.001) and IDWG% (r=0.269, P=0.013). Dialysis with the lowest IDWG had the least effect on sodium load and water load in patients. Age was negatively correlated with the sodium concentration before dialysis (r=-0.349, P=0.014), the absolute sodium gradient (r=-0.321, P=0.031), IDWG (r=-0.483, P=0.001) and IDWG% (r=-0.452, P=0.002). Conclusion: The absolute sodium gradient was significantly correlated with IDWG, which con- tributes to improving water load in MHD patients.

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What drives the latitudinal gradient in open ocean surface dissolved inorganic carbon concentration?

What drives the latitudinal gradient in open ocean surface dissolved inorganic carbon concentration?

The reason for the discrepancy is that the Southern Ocean and the North Pacific experience elevations in values due to inputs of deep water whereas the North Atlantic does not. Upwelling occurs in the Southern Ocean and entrainment due to deep winter mixing occurs in the subarctic North Pacific (Mecking et al., 2008; Ohno et al., 2009) where it entrains waters high in both TA (Fry et al., 2016) and DIC. While deep winter mixing also occurs in the high-latitude North At- lantic (de Boyer Montégut et al., 2004), the entrained waters left the surface relatively recently and hence there is little accumulated remineralized DIC and TA in the deep water that is reintroduced to the surface. For this reason, winter entrainment produces little increase in surface nDIC in the North Atlantic. This makes the North Atlantic useful in dis- criminating between the two effects because, uniquely out of the three regions, only the SST effect operates there. As expected, the SST effect is able to completely account for the observed nDIC gradient in the North Atlantic, whereas it cannot in the other two regions (second and third columns in Table 4). The North Atlantic confirms the important contribu- tion of upwelling to latitudinal gradients, while also showing that latitudinal gradients occur in the absence of upwelling.

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Hydric Properties Evolution of Spirulina platensis during Drying: Experimental  Analysis and Modeling

Hydric Properties Evolution of Spirulina platensis during Drying: Experimental Analysis and Modeling

In Figure 5 and Figure 6 are carried the variations water content at various ab- scissa as a function of time for both types of samples. The results are classic: the surfaces dry faster than the heart of the product. But, the differences between the curves are quite considerable. In fact, the water discharged from the zones close to the surface is not compensated by the water flowing from the heart towards the surface under the effect of the large gradients of the liquid phase, the motor terms of the flow. The study is carried out for abscissa between 5 mm and 16 mm. Because, out of this interval, the variations of water content and concentra- tion gradient are too small and the experiments could not be exploited.

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Modelling of the processes of impact of a projectile with elements of individual defence

Modelling of the processes of impact of a projectile with elements of individual defence

Abstract. A two-dimensional and three-dimensional non-stationary problem of the interaction of a homogeneous impactor and a heterogeneous structure made of steel and ceramics and placed in a Kevlar pocket is considered. The model of the human body is a plate of gelatine with cylindrical inserts-imitators of human bones. The results of numerical simulation using different approaches for describing heterogeneous media are compared. On the basis of direct numerical simulation, it is shown that the gradient armor plate (steel + B4C) has the best weight and size parameters.

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