Perforated Disk Research Articles

Residents' journal review

Residents' journal review

Dynamic microfiltration with a perforated disk for effective harvesting of microalgae

A dynamic microfiltration system has been receiving increasing attention as a means of preventing membrane fouling phenomena that reduce microalgae harvesting efficiency. This study describes the addition of a perforated disk to a dynamic microfiltration system for effective membrane-based microalgae harvesting. Fluid velocity near the membrane surface and shear stress on the membrane surface, as generated by different disks and rotation speeds, were simulated by computational fluid dynamics software, SolidWorks. A high correlation of shear stress on the membrane with microalgae harvesting efficiency was validated by a simulation-based empirical approach. Notably, fluid velocity near the membrane surface and average shear stress on the membrane surface with the perforated disk were approximately 2- and 7-fold, respectively, higher than observed with an unperforated disk. In empirical-experimental microfiltration of Chlorella vulgaris, the perforated disk (800rpm) showed a 2-fold-higher plateau permeate flux of 381L/m2/h compared with the unperforated disk (800rpm), enabling a 2-fold-greater alleviation of microalgal fouling at the same rotation speed. The perforated disk was found to be an effective generator of high shear stress in dynamic microfiltration, resulting in improved filtration during harvesting of microalgae.

Enhanced production of artemisinin by hairy root cultivation of Artemisia annua in a modified stirred tank reactor.

Artemisinin is an important drug commonly used in the treatment of malaria as a combination therapy. It is primarily produced by a plant Artemisia annua, however, its supply from plant is significantly lower than its huge demand and therefore alternative in vitro production routes are sought. Hairy root cultivation could be one such alternative production protocol. Agrobacterium rhizogenes was used to induce hairy roots of A. annua. Statistical optimization of media was thereafter attempted to maximize the biomass/artemisinin production. The growth and product formation kinetics and the significant role of O2 in hairy root propagation were established in optimized media. Mass cultivation of hairy roots was, thereafter, attempted in a modified 3-L Stirred Tank Bioreactor (Applikon Dependable Instruments, The Netherlands) using optimized culture conditions. The reactor was suitably modified to obtain profuse growth of hairy roots by segregating and protecting the growing roots from the agitator rotation in the reactor using a perforated Teflon disk. It was possible to produce 18 g biomass L(-1) (on dry weight basis) and 4.63 mg L(-1) of artemisinin in 28 days, which increased to 10.33 mg L(-1) by the addition of elicitor methyl jasmonate.

Top-seeded solution growth of three-inch-diameter 4H-SiC using convection control technique

The top-seeded solution growth of 4H-SiC at three inches in diameter has been investigated using Si–Ti alloy as a solvent. A perforated graphite disk called “immersion guide” (IG) was positioned in the solution in order to control solution flow. The morphological instability was improved and growth rate was significantly increased using the IG compared with conventional growth without the IG. Numerical fluid flow analysis with coupled heat and mass transportation was performed as well to understand convection and growth behavior. The origins of these improvements in the growth performance are discussed based on the numerical results. By controlling solution flow, we could successfully grow a three-inch-diameter 4H-SiC with 4-mm thickness.

Superconducting State of a Disk with a Pentagonal/Hexagonal Trench/Barrier

We study the influence of a pentagonal (hexagonal) trench or barrier on the superconducting properties of a perforated disk. Effects associated to the pinning (anti-pinning) force of the central hole and the trench (barrier) and the interplay between the boundary conditions and the shape of the inner defects on the vortex configuration are studied for a thin disk. Also, we considered two cases for the value of the order parameter at the surface. The first one is ψ s ≠0; this is the usual supercondutor/vacuum interface, for which the deGennes parameter is b→∞. The second one is ψ s =0, which is the surface of the sample in a complete normal state, simulated by b=0. The vorticity, Gibbs free energy, magnetic induction, supercurrent density, magnetization and Cooper pairs density as a function of the external magnetic field are calculated. We show that in our sample new phenomena are possible due to the competing interactions of the boundary and the geometry of the sample and the added geometry of the nanoengineered trench and barrier.

Relationship between odontogenic bacteremia and orthodontic stripping

The aim of this study was to evaluate the prevalence of bacteremia associated with an orthodontic stripping procedure. The study included 29 orthodontic patients (mean age, 18.2 ± 3.4 years). We used a standardized stripping procedure: a perforated stripping disk with a contra-angle hand piece was used at a low speed (<15,000 rpm; 10 seconds) on the mandibular anterior teeth. Blood samples were collected by inserting a cannula into the left antecubital fossa. A baseline sample was taken before treatment, and a second sample was taken after the stripping procedure. These samples were inoculated into aerobic and anaerobic blood culture bottles and incubated, and the bacterial cultures were identified; the samples collected before and after the stripping procedure were statistically analyzed. Transient bacteremia was not detected in any pretreatment blood sample, but it was found in 1 postoperative blood sample; this sample tested positive for Streptococcussanguis. The bacterial species in the positive postoperative blood sample was S sanguis, which might be associated with infective endocarditis. Clinicians should explain the level of risk to the patient and consult a concerned medical specialist.

Untangling Tumor Vasculature

Tumor vasculature is highly dynamic, dense, and non‐homogeneous. These features make it difficult to identify key determinants of tumor angiogenesis and remodeling at the single vessel level. To overcome this problem, we isolated growing tumors from the host tissue, by placing a perforated PDMS disk between the tumor and the dorsal skin in transparent windows in mice. Using this model we are able to observe and quantify various processes and stages of network formation. Between days 9–14 microvascular sprouts emerged from the perforations/holes and merged to form loops in and out of holes. Later, sprouts led by tip cells separated from the perfused, looping vessels. Surprisingly, many of the sprouts migrated away from the tumor, instead connecting to sprouts from other holes or from the edge of the PDMS disk. At day 19, smooth muscle cells were associated with the larger vessel connecting two holes. Other changes were observed after treatment with a VEGF inhibitor. In the first two days, feeding vessels dilated, but within 1–2 weeks, large vessels constricted and smaller branches are pruned. This was associated with dramatic changes in flow direction, increased perfusion and flow interruption in some vessels. The experimental model offers a novel approach for identifying key steps in tumor vascularization so that more effective and specific targeting strategies can be developed. Supported by NIH R01CA149285.

Processing and chemical composition of rhubarb (Rheum rhabarbarum) juice

A simple and effective processing method for rhubarb stalks including washing, comminution in a perforated disk mill followed by immediate dejuicing of the mash is presented. Rhubarb is an easy to process vegetable which does not necessarily need a special mash treatment like enzymation or heating to get high juice yields. The chemical composition of rhubarb juice is characterised by a low relative density and low Brix (4–4.8 °Brix), due to a low sugar content (about 12 g/l), whereas the total acidity is high (about 17 g/l). The major acid is malic acid, followed by oxalic acid and citric acid. The polyphenol content and the antioxidative capacity (TEAC) is relatively low; the same holds for anthocyanins (11.3–14.8 mg/l) which are consisting of cyanidin-3-rutinoside and small amounts of cyaniding-3-glucoside and delphinidin-3-rutinoside. Rhubarb juice contains a high amount of minerals, esp. potassium (up to 4000 mg/l), and magnesium (average 100 mg/l), whereas calcium is not present due to precipitation with oxalic acid. As is the case for some other vegetables juices, rhubarb juice contains high concentrations of nitrate (about 850 mg/l).

Efficiency of pneumatic and horizontal perforated disk meter mechanism in corn no-tillage seeders in soil with different mobilization reports

This work objectified to evaluate the efficiency of two meter mechanism of corn seeds when submitted to different forward speed and soil management system during the non-tillage seeding. It was used a factorial design in randomized blocks. The factors whose effects were examined were related to the seeders with pneumatic and horizontal disk meter mechanisms for the distribution of the seeds, to the set tractor-seeder forward speeds (4.4; 8.0 and 9.8 km h-1), and to the soil management system considering the corn no-tillage seeding over minimum tillage with chisel plow and the no-tillage system for the seeding of oat culture (Avena strigosa Schreb). It was verified that the forward speed didn't influence the initial and final stands of plants but it interfered in the regularity of longitudinal distribution of plants. The smallest speed provided the largest percentile of normal spacing between plants. The pneumatic meter mechanism presented better performance than the horizontal disk perforated in the longitudinal distribution of plants. About corn productivity aspect it's indifferent the recommendation of use for pneumatic and perforated horizontal disk meter mechanism of seeds.

MRI and clinical findings of posterior disk displacement in the temporomandibular joint

The objective of this study was to evaluate the magnetic resonance imaging and clinical findings of patients with posterior disk displacement in the temporomandibular joint. Magnetic resonance and clinical findings of 62 temporomandibular joints (44 patients) with posterior disk displacement were retrospectively analyzed. According to the criteria proposed by Westesson et al., 52 temporomandibular joints (84%) were the thin flat disk type and the remaining 10 (16%) were the perforated disk type. Fifteen temporomandibular joints (24%) had a history of luxation. Clicking was observed in 26 temporomandibular joints (42%), all of which were the thin flat disk type (chi-square test, P < .01). Pain was observed in 19% of patients with the thin flat disk type and 60% of those with the perforated disk type (P < .05). Magnetic resonance imaging could clearly reveal the details of posterior disk displacement in the temporomandibular joint. The clinical findings were dissimilar between the thin flat and the perforated disk type.

Recovery of methane-rich gas from solid-feed anaerobic digestion of ipomoea ( Ipomoea carnea)

Studies are presented on new types of anaerobic digesters in which chopped or dry crushed Ipomoea carnea was fed without any other pretreatment, in an attempt to develop commercially viable means of utilizing the otherwise very harmful plant. Two types of solid-feed anaerobic digesters (SFADs) were studied. The first type had a single vessel in which the bottom 35% portion was separated from the top portion by a perforated PVC disk. The weed was charged from the top and inoculated with anaerobically digested cowdung–water slurry. The fermentation of the weed in the reactor led to the formation of volatile fatty acids (VFAs) plus some biogas. The leachate, rich in the VFAs, was passed through the perforated PVC sheet and collected in the lower portion of the vessel. The other type of reactors had two vessels, the first one was fully charged with the weed and the second received the VFA leachate. With both types were attached upflow anaerobic filters (UAFs) which converted the leachate into combustible biogas consisting of ∼70% methane. All SFADs developed very consistent performance in terms of biogas yield within 17 weeks of start. The two-compartment reactors yielded significantly more biogas than the single-compartment reactors of corresponding total volume, and the reactors with which anaerobic filters (AF) were attached yielded more biogas than the ones without AF. The best performing units generated 2.41 m 3 of biogas per m 3 of digester volume, as compared to 0.1–0.2 m 3 of biogas, m −3 d −1, obtainable with conventional digesters. This indicates the viability of this technology. The spent weed can be vermicomposted directly to obtain good soil-conditioner cum fertilizer; earthworm Eudrilus eugeniae produced 540 mg vermicast per animal every day, achieving near total conversion of feed to vermicast in 20 days. The proposed systems, thus, makes it possible to accomplish total utilization of ipomoea.

Recovery of energy from Taro ( Colocasia esculenta) with solid-feed anaerobic digesters (SOFADs)

We present studies on solid-feed anaerobic digesters (SOFADs) in which chopped Colocasia esculenta was fed without any other pretreatment, in an attempt to develop an efficient means of utilizing the semi-aquatic weed that is otherwise an environmental nuisance. Two types of SOFADs were studied. The first type had a single vessel with two compartments. The lower portion of the digester, 25% of the total volume, was separated from the upper by a perforated PVC disk. The weed was charged from the top and inoculated with anaerobically digested cow dung–water slurry. The fermentation of the weed in the digester led to the formation of volatile fatty acids (VFAs) plus some biogas. The bioleachate, rich in the VFAs, passed through the perforated PVC disk and was collected in the lower compartment of the digester. The other type of digesters, referred to as anaerobic multi-phase high-solids digesters (AMHDs), had the same type of compartmentalized digester unit as the first type and an additional methaniser unit. Up-flow anaerobic filters (UAFs) were used as methaniser units, which converted the bioleachate into combustible biogas consisting of ∼60% methane. All SOFADs developed a consistent performance in terms of biogas yield within 20 weeks from the start. Among the two types of digesters studied, the AMHDs were found to perform better with a twofold increase in biogas yield compared to the first type of digesters.

Gas sensor measurement system capable of sampling volatile organic compounds (VOCs) in wide concentration range

A gas sensor measurement system has been developed by using a vapor-generating bubbler, analyte-diluted delivery lines and a detection chamber. The bubbler with a perforated disk design permits to pick up analyte vapor with fixed efficiency under a carrier flow rate of 0.5–100 sccm. The pickup efficiency was modulated logarithmically by varying the bubbler temperature. The practically controllable range in acetone flux was nearly three orders of magnitude through the variation of the carrier flow rate, and an order of magnitude by the use of the bubble temperature, independently. The generated vapor was diluted efficiently through a cascading two-step process which leads to homogeneous mixing up to the flow ratio of dilution:carrier = 500:0.25, and then delivered into a small-gapped planar detection chamber operated at room temperature. The newly-designed planar chamber induces fast equilibrium and high local concentration on a sensor surface, thus resulting in a short detection time and a higher response magnitude. From measuring chemoresistive responses of carbon black-polymer composites upon exposure to acetone analyte, the measurement system was confirmed to be reliably applicable to a wide concentration range of from 3.7 ppm to 10.7%.

Nucleation of superconductivity in a mesoscopic loop of varying width

We study the evolution of the superconducting state in a perforated disk by varying the size of the hole. The superconducting properties are investigated by means of transport measurements around the superconducting/normal phase boundary ${T}_{c}(H)$. A transition from a one-dimensional to a two-dimensional regime is seen when increasing the magnetic field for disks with small holes. A good agreement is found between the measured ${T}_{c}(H)$ line and the calculations performed in the framework of the linearized Ginzburg-Landau theory. The effect of breaking the axial symmetry of the structure by moving the hole away from the center of the disk is also studied. An enhanced critical field is found for the asymmetric structures, possibly due to the recovery of the singly connected state.

Limit Load Analysis of Perforated Disks With Square Penetration Pattern

Limit load analysis of perforated disks with a square penetration pattern is presented. The results of limit analysis are used to obtain yield surfaces for solid material equivalent to perforated disk based on homogenization approach. Theoretical and experimental results are compared. Approximations of the yield surfaces are proposed.

A hydrodynamic siren as an underwater sound source

This paper describes the acoustic characteristics of a hydrodynamic siren in which a perforated disk (rotor) rotates in front of a similar disk (stator) fixed with very slight clearance and compressed water passes through holes in the rotor and stator. The stream is interrupted with the frequency given by the product of the rotation rate times the hole number. The rotor and stator have 8 and 20 holes on their inner and outer circles, respectively. The sound due to the greatest common divisor of 8 and 20 (i.e., 4) is also generated by the superposition of two waveforms derived from 8 and 20 holes. The siren thus produces thickly populated line spectrums that extend from 0.1–5 kHz. The motor and pump are controlled by inverters to stably adjust the rotation rate of the rotor and the pressure of the water, respectively. The maximum sound pressure level integrated over the above spectrum range reaches about 190 dB re: 1 Pa at 1 m when the water pressure is 9 kg/cm2.This siren has been used as a jammer or broadband mixed sound projector for sea experiments on adaptive beamformers.

Experimental study of the stress-strain state and load-carrying capacity of models of power-plant flywheels made of composite materials

1. The use of a design In the form of a thin additional ring on the rim of a disk flywheel (type II) lowers the load-carrying capacity of the latter. 2. The use of a perforated disk (type IV) as a flywheel to reduce or equalize the stresses is inexpedient, since the stored kinetic energy is reduced more than the stresses. Theoretical determination of the actual stress-strain state of shaped disks made of anisotropic material requires the use of methods which consider the effect of axial anisotropy. 3. Henceforth in designing energy storage devices, a disk flywheel of type V should be considered to have promise.

A field method for measuring short-circuiting in clay soils

A field method is described for measurement of short-circuiting, which is defined as vertical flow of free water along the walls of continuous macropores in unsaturated soil. A cylinder with a diameter and height of 20 cm is filled with undisturbed surface soil and is placed on a perforated disk in a funnel. The funnel is supported to allow periodic measurement of the volume of outflow from the soil. The assembly is placed along the track of a spray-gun, which is commonly used for sprinkling irrigation. At least four samples can be measured during one run. The method is illustrated by discussing the measured short-circuiting in surface soils of: (1) a heavy clay soil; (2) a light clay soil with two different types of structure in and adjacent to potato ridges; and (3) a heavy clay soil with two types of surface microrelief. Short-circuiting is unfavourable because water moves rapidly beyond the root zone without moistening and leaching the soil between the macropores. The water may carry surface-applied fertilizers.

Solution of the problems of a perforated disk, a conical bar, and a flat wedge of nonlinear viscoelastic material in pure shear, torsion, and bending, respectively

Exact solutions and approximations have been obtained for the problems of a disk with an opening twisted by opposite moments uniformly distributed over the inner and outer surfaces and of a conical bar twisted by a moment applied at the vertex of the cone. An approximate solution has been found for the problem of a flat wedge bent by pressure uniformly distributed along one of its sides. The disk is made of nonlinear viscoelastic material. In [1] it was proposed that problems for such a material be solved by the method of approximations. The rheological law of the nonlinear viscoelastic material of the cone and the wedge in Laplace—Carson transforms is the relation of the theory of small elastoplastic deformations with a power law of strain hardening.

A NEW PRINCIPLE OF PELLET FEEDER DESIGN1

Most current commercial devices dispense dry food pellets by moving the pellets horizontally toward a discharge point. Individual pellets, captured by perforations in a horizontal metal disk, are discharged one by one by stepwise rotation of the disk within the pellet reservoir. In our laboratory, where the average pellet discharge rate is some 20,000 pellets per week, feeders of this type produced occasional problems. Some were electronic; others involved failure always to capture a pellet in each perforation, particularly when the pellet supply was low. But the most common problem was an accumulation of pellet chips and dust under and around the perforated disk, which ultimately jammed the mechanism. Despite weekly cleaning and maintenance, troubles arose at least twice a month, prompting a search for a simpler pellet‐feeder design which would be more reliable and require less maintenance. The present pellet feeder employs a vertical rather than horizontal design principle. It has been used extensively in operant conditioning applications for more than a year. More than 200,000 pellets have been reliably discharged from a single feeder without a breakdown. No maintenance, other than a weekly cleaning of the discharge tube, has been required.