Centrifuge Rotor Research Articles

No evidence for an open vessel effect in centrifuge‐based vulnerability curves of a long‐vesselled liana (Vitis vinifera)

Vulnerability to cavitation curves are used to estimate xylem cavitation resistance and can be constructed using multiple techniques. It was recently suggested that a technique that relies on centrifugal force to generate negative xylem pressures may be susceptible to an open vessel artifact in long-vesselled species. Here, we used custom centrifuge rotors to measure different sample lengths of 1-yr-old stems of grapevine to examine the influence of open vessels on vulnerability curves, thus testing the hypothesized open vessel artifact. These curves were compared with a dehydration-based vulnerability curve. Although samples differed significantly in the number of open vessels, there was no difference in the vulnerability to cavitation measured on 0.14- and 0.271-m-long samples of Vitis vinifera. Dehydration and centrifuge-based curves showed a similar pattern of declining xylem-specific hydraulic conductivity (K(s)) with declining water potential. The percentage loss in hydraulic conductivity (PLC) differed between dehydration and centrifuge curves and it was determined that grapevine is susceptible to errors in estimating maximum K(s) during dehydration because of the development of vessel blockages. Our results from a long-vesselled liana do not support the open vessel artifact hypothesis.

Centrifuges and Their Application for Biological Experiments in Space

The need for an in-orbit 1×g control originated from the fact that Space radiation or other environmental factors of Space flight could not be excluded as cause for the effects on biological systems that were mainly interpreted as effects of the weightlessness environment. Indeed, in many experiments the 1×g reference centrifuge on board revealed the same data as the 1×g controls on ground, proving the lack of gravity was causing the results. In other cases, the reference centrifuge data were intermediate or clearly different to the ground data which was either due to interrupted 1×g conditions on board or to other, sometimes not well understood factors. This triggered also the development of sophisticated hardware allowing the start, i.e. the transition from 1×g to 0×g, or the termination of the experiment without stopping the centrifuge. Recently developed facilities provide also a complete life support system on the centrifuge rotor. Besides the in-flight 1×g control, acceleration experiments required a centrifuge for determination of threshold values in orbit.

Effective Modes of Axial Balancing of Centrifugal Pump Rotor

The basic offers on development of a node of axial balancing of a centrifugal pump rotor are in-process stated. Constructional solutions of equilibrating devices on the basis of hydrostatical seal are observed. Comparison with existing balancing devices is held.

Probabilistic Method for Evaluation of Dynamic Characteristics of Rotor in Annular Seals

The paper deals with forced vibrations of centrifugal pump rotor taking into account the random variation of the annular seals parameters in the process of operation under action of random imbalance. The method of spectral resolutions to obtain probabilistic characteristics of vibration velocity and vibration acceleration of center of the masses of rotor model in annular seals was used. Evaluation of the influence of random variation of the parameters of the “rotor-seal” system in the process of pump operating on rotor stability is made.

Vulnerability curves by centrifugation: is there an open vessel artefact, and are ‘r’ shaped curves necessarily invalid?

Vulnerability curves using the 'Cavitron' centrifuge rotor yield anomalous results when vessels extend from the end of the stem segment to the centre ('open-to-centre' vessels). Curves showing a decline in conductivity at modest xylem pressures ('r' shaped) have been attributed to this artefact. We determined whether the original centrifugal method with its different rotor is influenced by open-to-centre vessels. Increasing the proportion of open-to-centre vessels by shortening stems had no substantial effect in four species. Nor was there more embolism at the segment end versus centre as seen in the Cavitron. The dehydration method yielded an 'r' shaped curve in Quercus gambelii that was similar to centrifuged stems with 86% open-to-centre vessels. Both 'r' and 's' (sigmoidal) curves from Cercocarpus intricatus were consistent with each other, differing only in whether native embolism had been removed. An 'r' shaped centrifuge curve in Olea europaea was indistinguishable from the loss of conductivity caused by forcing air directly across vessel end-walls. We conclude that centrifuge curves on long-vesselled material are not always prone to the open vessel artefact when the original rotor design is used, and 'r' shaped curves are not necessarily artefacts. Nevertheless, confirming curves with native embolism and dehydration data is recommended.

Investigation on centrifugal impeller in an axial-radial combined compressor with inlet distortion

Assembling an axial rotor and a stator at centrifugal compressor upstream to build an axial-radial combined compressor could achieve high pressure ratio and efficiency by appropriate size augment. Then upstream potential flow and wake effect appear at centrifugal impeller inlet. In this paper, the axial-radial compressor is unsteadily simulated by three-dimensional Reynolds averaged Navier-Stokes equations with uniform and circumferential distorted total pressure inlet condition to investigate upstream effect on radial rotor. The results show that span-wise nonuniform total pressure distribution is generated and radial and circumferential combined distortion is formed at centrifugal rotor inlet. The upstream stator wake deflects to rotor rotation direction and decreases with blade span increases. Circumferential distortion causes different separated flow formations at different pitch positions. The tip leakage vortex is suppressed in centrifugal blade passages. Under distorted inlet condition, flow direction of centrifugal impeller leading edge upstream varies evidently near hub and shroud but varies slightly at mid-span. In addition, compressor stage inlet distortion produces remarkable effect on blade loading of centrifugal blade both along chordwise and pitchwise.

Steady Air Injection Flow Control in Centrifugal Compressor

In the present work steady air injection upstream of the leading edge was used in a centrifugal compressor, Whose preliminary design of compressor injection systems can be modeled by a geometrical relationship between user-specified yaw angle and resulting blade incidence angle based on simple velocity triangles, the error between the best yaw angle obtained from this relationship and that obtained from numerical simulation is less than 3%. To reveal the mechanism, steady numerical simulations were performed on high pressure ratio centrifugal compressor rotor operated with a rotor tip speed of 586 m/s. Parametric studies of the injection yaw angle was performed to determine the configuration that provide the best steady results for the compression systems studied in this work. The injectors were placed at short distance (ten percent of the inlet tip radius upstream of the compressor face) the objective of this was to achieve maximum control over the leading edge flow by varying individual injection parameters. The injection angle, α, was fifteen while the yaw angle, β, was parametrically varied. The results show that at design speed (n= 50 000 r/min) with injection flow rate equal to 3% of the main flow rate and 25 degree air injection yaw angle can lower the mass flow rate at stall for approximately 7.5%.

Comparison between Two ANSYS Finite Element Modeling Methods of Multistage Centrifugal Pump Rotor

In the last decades, many methods of ANSYS finite element modeling have been proposed. By comparing the two different methods of beam element modeling and entity unit modeling for multistage centrifugal pump rotor, we find that although both methods are insensitive to torsional vibration model, to some extent they affect other vibration models and result in certain deviation in calculation results. Using beam element modeling not only improves the calculation precision, but also saves computing resources. The Appropriate selection of the element type will reduce the amount of input data and computation time.

Fluid‐Structure Interaction Analysis on Turbulent Annular Seals of Centrifugal Pumps during Transient Process

The current paper studies the influence of annular seal flow on the transient response of centrifugal pump rotors during the start‐up period. A single rotor system and three states of annular seal flow were modeled. These models were solved using numerical integration and finite difference methods. A fluid‐structure interaction method was developed. In each time step one of the three annular seal models was chosen to simulate the annular seal flow according to the state of rotor systems. The objective was to obtain a transient response of rotor systems under the influence of fluid‐induced forces generated by annular seal flow. This method overcomes some shortcomings of the traditional FSI method by improving the data transfer process between two domains. Calculated results were in good agreement with the experimental results. The annular seal was shown to have a supportive effect on rotor systems. Furthermore, decreasing the seal clearance would enhance this supportive effect. In the transient process, vibration amplitude and critical speed largely changed when the acceleration of the rotor system increased.

Development and Application of a Tool To Assess Laboratory Hygiene in Contained-Use Facilities

To gain information on laboratory hygiene in contained-use laboratories, a method was developed to study the presence of microorganisms on laboratory equipment. Focusing detection on genetically modified organisms (GMOs) containing the universal M13 primer binding sites enabled the detection of a broad range of GMOs using a single PCR. Swabbing surfaces in three different contained-use laboratories led to detection of M13-containing PCR products in 26 out of 34 swabs. Most sequences (up to five per sample) were detected in swabs from the centrifuge and sink, followed by swabs taken from the bin and incubator (up to four sequences per sample). The obtained sequences varied in length from 171 nucleotides (nt) to 878 nt. In most cases, sequences were only partially similar to sequences published in GenBank. The lengths of the regions with high similarity varied from 94 nt to 795 nt, and these similarities ranged from 81% to 100%. Similarities with more than one sequence were commonly found, complicating the identification of detected sequences. Nonetheless, 84% of the detected sequences were actually handled in the laboratory at the time of sampling. This demonstrates that the method may be used as a quality control tool to assess the efficacy of decontamination and cleaning of commonly used surfaces, such as laboratory benches, freezer doors, and centrifuge rotors, without prior knowledge of the identity or characteristics of the GMOs.

Design of Frequency Control System for Centrifuge in Multi-Parameter Combined Environmental Testing Device

In the centrifuge of the multi-parameter combined environmental testing device, the three-phase induction motor could not be started directly at the frequency of 50Hz due to the large moment of inertia of the centrifuge rotor. Therefore, large torque output of the three-phase induction motor was required at low frequencies. And the specimen needed stepless rotational speed adjustment (40-130r/min). A set of frequency control system was developed based on vector control with PG, inverter and LabVIEW to solve these problems. The principle of the centrifuge was present. The principles of vector control with PG of three-phase induction motor were analyzed. Based on the mechanical characteristic of three-phase induction motor, vector control with PG was employed in the system. The system control software based on LabVIEW was presented, which realized stepless speed adjustment of the centrifuge on a computer. Experimental results show that the developed system could realize the stepless regulation of the specimen’s centrifugal acceleration.

Design of a Permanent Magnet Synchronous Generator for Vehicle Application

This paper discusses the design, fabrication and testing of a centrifugal rotor permanent magnet synchronous generator. The roller of the engine and the shell of the centrifugal outer rotor of the generator are designed together. The permanent material and the fixing block are fixed on the shell of the outer rotor. the centrifugal force increase with the rotate speed increase, so, the permanent material will not be damaged at high speed, and the reliability of the generator is improved. When the rotor turns, the magnet field turns, the generator generates electricity,with the permanent magnet material of high remnant magnetic induction and the optimized design of the generator, the output voltage is improved when the engine at low speed. We develope a single-phase double half-wave electric regulator is to ensure the stability of the output voltage and can direct output direct current.

The D&T report

The D&T report

Gravity control of growth form in Brassica rapa and Arabidopsis thaliana (Brassicaceae): Consequences for secondary metabolism

How gravity influences the growth form and flavor components of plants is of interest to the space program because plants could be used for food and life support during prolonged missions away from the planet, where that constant feature of Earth's environment does not prevail. We used plant growth hardware from prior experiments on the space shuttle to grow Brassica rapa and Arabidopsis thaliana plants during 16-d or 11-d hypergravity treatments on large-diameter centrifuge rotors. Both species showed radical changes in growth form, becoming more prostrate with increasing g-loads (2-g and 4-g). In Brassica, height decreased and stems thickened in a linear relationship with increasing g-load. Glucosinolates, secondary compounds that contribute flavor to Brassica, decreased by 140% over the range of micro to 4-g, while the structural secondary compound, lignin, remained constant at ∼15% (w/w) cell wall dry mass. Stem thickening at 4-g was associated with substantial increases in cell size (47%, 226%, and 33% for pith, cortex, and vascular tissue), rather than any change in cell number. The results, which demonstrate the profound effect of gravity on plant growth form and secondary metabolism, are discussed in the context of similar thigmostresses such as touch and wind.

Investigations on the Separation Efficiency of Tubular Bowl Centrifuges

AbstractIn the last decade a major progress has been achieved in the synthesis and functionalization of nanoscale particles, but the handling of such material systems like separation or classification has been neglected. With tubular centrifuges, even nanoscale particles can be separated from a suspension at reasonable throughputs due to very high g values. This is a great advantage compared to membrane techniques (low throughput) and filtering, disc stack and decanter centrifuges (lower g values). An analysis of the discharged solids in dependence on time and verification of sediment build‐up with a magnetic resonance spectrometer (MRI) provide a comprehensive understanding of the sedimentation process in a tubular bowl centrifuge. MRI allows a noninvasive, direct view into the filled centrifuge rotor; this data is compared with theoretical results.

Flow Study of a Redesigned High-Pressure-Ratio Centrifugal Compressor

A high specific speed, 6:1 total pressure ratio centrifugal compressor rotor has been improved with the knowledge gained from previous investigations on similar types of compressors and with the help of advanced 3D-design calculations. The new rotor has the same main dimensions as its predecessor and was designed for the same operating point. It was manufactured and was tested at DLR with conventional and optical measurement techniques. Performance and optical measurements were carried out up to tip speeds of 586 m/s. The investigations were supported by 3D stage calculations which delivered detailed insight into the impeller and diffuser flow development.

Blood processing

Blood processing

Simultaneous extraction of chitin and astaxanthin from waste of lobsters Jasus lalandii, and use of astaxanthin as an aquacultural feed additive

This work investigates simple methods for simultaneous extraction of astaxanthin and chitin from industrial waste of the South African West Coast rock lobster Jasus lalandii. Removal of proteins from waste is the critical step to yield intact chitin and astaxanthin. Because common chemical methods destroy astaxanthin and damage chitin, we investigated partial proteolysis by papain followed by removal of adhering tissue/protein by centrifugation. Incubation time of waste with papain, papain concentration, waste:medium ratio, duration of centrifugation and the size of holes in the centrifuge rotor were altered to achieve a complete removal of protein/tissue and at minimum cost. From lobster waste that was deproteinised this way, chitin and astaxanthin could be extracted using existing methods. The most suitable extraction conditions (0.5% papain, 1:10 waste:medium ratio, 24 h incubation, centrifugation for 5 min with 5 mm holes) yielded 2.4 ± 0.6 g chitin (4.2%) and 3.1 ± 0.7 mg astaxanthin from 56.8 ± 5.8 g crushed lobster waste. From deproteinised exoskeleton, astaxanthin was extracted in methanol, transferred into various vegetable oils, and its concentration measured using spectrophotometry. Maximum stable concentration of astaxanthin in oil was approximately 80 mg ml−1, above which astaxanthin precipitated. Astaxanthin oil prepared from J. lalandii material included in feeds for shrimps Palaemon pacificus and tilapia Oreochromis mossambicus caused deposition in whole shrimps but not in tilapia tissues.

Cost assessment of the automated VERSANT™ 440 Molecular System versus the semi-automated System 340 bDNA Analyzer platforms

Labor, supply and waste were evaluated for HIV-1 and HCV bDNA on the semi-automated System 340 bDNA Analyzer and the automated VERSANT™ 440 Molecular System (V440). HIV-1 sample processing was evaluated using a 24- and 48-position centrifuge rotor. Vigilance time (hands-on manipulations plus incubation time except initial target hybridization) and disposables were approximately 37 and 12% lower for HIV-1, and 64 and 31% lower for HCV bDNA, respectively, with V440. Biohazardous solid waste was approximately twofold lower for both assays and other waste types were the same for either assay on both platforms. HIV-1 sample processing vigilance time for the 48-position rotor was reduced by 2 h. V440 provides cost savings and improved workflow.

Countercurrent Chromatography and the Journal of Liquid Chromatography: A Love Story

Countercurrent chromatography (CCC) is a separation technique that works with a support‐free liquid stationary phase. Since the mobile phase is also a liquid, biphasic solvent systems are used. The problem with CCC is due to its nature: it is difficult to maintain a stable liquid stationary phase when a liquid mobile phase is pushed through it. All modern CCC columns use centrifugal fields. The hydrodynamic CCC columns use open tubes coiled on spools that rotate in a planetary manner. The hydrostatic CCC columns use channels interconnected by ducts, mounted in a centrifuge rotor. It is difficult to work with a support‐free liquid stationary phase, but the advantages of this chromatographic configuration are so important that it is worth finding better ways and to invent better CCC columns. The main advantage is that all injected compounds can access the whole volume of the liquid stationary phase, compared to the necessary solid‐liquid interphase contacts with classical solid stationary phases. Saturation of the stationary phase, or column overload, is much more difficult in CCC than in classical preparative LC with silica gel based stationary phases. CCC is definitely a preparative technique. The other advantages of a liquid stationary phase include the wide range of polarities that can be obtained using the numerous available solvents and mixing them. No irreversible adsorption is possible in CCC, since the liquid stationary can always be recovered. These advantages and the modern commercially available CCC columns are presented in this article celebrating the 30th birthday of the Journal of Liquid Chromatography that always, with its editor, strongly supported the technique by publishing, at certain occasions, half of the whole scientific CCC production of the world.