Laboratory Shaker Research Articles

Concurrent validity of the PAM accelerometer relative to the MTI Actigraph using oxygen consumption as a reference

The purpose of this study was to examine the concurrent validity of the Personal Activity Monitor (PAM) accelerometer relative to the Actigraph accelerometer using oxygen consumption as a reference, and to assess the test-retest reliability of the PAM. Thirty-two fit, normal weight adults (aged 21-54) performed two activities, treadmill walking and stair walking, while wearing the PAM, the Actigraph and the Cosmed K4b(2). Correlation coefficients and agreement in absolute energy expenditure (EE) levels between PAM, Actigraph and Cosmed were calculated. The test-retest reliability was examined among 296 PAM's using a laboratory shaker. Intraclass correlation coefficients (ICC) and coefficient of variation (CV) were determined. Correlations for treadmill walking and stair walking, respectively, were r(2)=0.95 and r(2)=0.65 for PAM with Actigraph, r(2)=0.82 and r(2)=0.93 for PAM with VO(2) and r(2)=0.64 and 0.74 for Actigraph with VO(2). Both the PAM and Actigraph underestimated EE during treadmill and stair walking by a substantial amount. The test-retest reliability of the PAM was high [ICC=0.80; 95% confidence interval (CI) (0.28;0.92) and intra-CV=1.5%]. The PAM and Actigraph accelerometer are comparable in assessing bodily movement during treadmill and stair walking. The PAM is a valid device to rank subjects in EE and can be useful in collecting objective data to monitor habitual physical activity.

THE EFFECT OF FRUIT MATURITY AND STORAGE DURATION ON FRICTION DISCOLOURATION OF ‘PACKHAM’S TRIUMPH’ AND ‘DOYENNE DU COMICE’ PEARS

Friction discolouration (FD) is causing the South African pear industry multi-million rand losses due to blemished fruit being rejected for the export market and being sold locally. The occurrence of FD was studied over two seasons using ‘Packham’s Triumph’ and ‘Doyenne du Comice’ (Pyrus communis) fruit. The influence of fruit maturity and storage duration were investigated by harvesting over three maturities and storing fruit for up to three months. FD was induced using a modified laboratory shaker that was shown to closely mimic pack line damage. Polyphenol oxidase (PPO) activity and total phenolics (TP) content were also evaluated. ‘Doyenne du Comice’ was more prone to FD than ‘Packham’s Triumph’. Harvest maturity significantly influenced FD susceptibility, with the middle picking maturity generally giving higher FD ratings. Increasing storage duration generally increased FD ratings, although not consistently. PPO activity was not influenced by harvest maturity, but was influenced by storage duration. In ‘Packham’s Triumph’, the TP content was not affected by harvest maturity or storage duration, whereas both these factors significantly influenced TP content in ‘Doyenne du Comice’. Susceptibility to development of FD symptoms is not easily linked to either PPO activity or TP content, and seasonal differences in susceptibility make prediction of possible levels of FD very difficult. INTRODUCTION Friction discolouration (FD) is a well known and serious postharvest problem in the pear industry (Wang and Mellenthin, 1973; Mellenthin and Wang, 1974). The reduction of visual quality is one of the foremost causes for consumer discontent (Raese, 1989). FD is also referred to as skin browning, abrasion marks, belt burns and friction bruises (Smith, 1946). This disorder is characterised by diffuse brown skin discolourations, especially at high points on irregular fruit surfaces (Meheriuk et al., 1994). Such discolourations are induced by a number of mechanical injuries that fruit are subjected to during harvest, packing, transportation and marketing (Mitcham et al., 2001; Feng et al., 2004), followed by biochemical reactions that lead to browning (JimenezAtienzar et al., 2004). The effect of fruit maturity on susceptibility to skin discolouration has been studied in ‘Bartlett’ (Mitcham et al., 2001), ‘Doyenne du Comice’ (Amarante et al., 2001a) and an array of cultivars by both Kvale (1979, 1988) and Amiot et al. (1995). It has been reported that the timely harvesting of the fruit might influence the degree to which this disorder is experienced. It is commonly accepted that both bruising and frictional forces give rise to the skin browning, at epidermal level (Mitcham et al., 2001). Storage duration as a controllable component in the post harvest chain has been studied by a number of researchers (Mellenthin and Wang, 1974; Kvale, 1988; Spanos and Wrolstad, 1990; Amiot et al., 1995; Mitcham et al., 2001). Polyphenol oxidase (PPO) enzyme activity is known to influences the extent and degree of browning of pear peel (Gauillard and Richard-Forget, 1997). Sufficient and

Intrauterine Cerebral Processing of External Vibroacoustic Stimuli

The human and the sheep fetus, the animal model of human pregnancy, respond to external stimuli such as vibrations or noises with behavior state changes from 0.8 gestation onwards. It is not clear yet 1) if the behavior state changes that represent a „subcortical“ arousal are accompanied by a „cortical“ arousal as a condition of conscious perception of the stimuli; 2) to what extent the perception of the stimuli depends on the behavior state and the quality of the stimulus; and 3) if the proprioceptive system is important for perception of the vibratory component of the signal. Via Cesarean section, sheep fetuses were chronically instrumented at 0.8 gestation with ECoG (electrocorticogram) electrodes as well as EOG, EMG and EKG electrodes to define fetal behavior states. After a recovery period of five days, stimuli were presented from the abdominal wall of the ewe during periods of NREM and REM sleep. We tested pure vibratory (30min) and acoustic (5h) stimuli as well as dynamic amplitude and frequency modulated and two static vibroacoustic stimuli (VAS) produced by an electronic artificial larynx (EAL) and a laboratory shaker. ECoG changes were analyzed using linear (power spectral analysis) and non-linear methods. For non-linear analysis we used an algorithm based on the Wolf algorithm (calculation of the leading Lyapunov exponent) which calculates a point prediction error (PE) regarding the course of the time series in the phase space. The vibratory and acoustic stimuli did not induce a cortical arousal. The VAS produced an arousal with similar effectiveness during NREM and REM sleep. The dynamic stimulus induced 100%, the EAL 70% and the laboratory shaker 40–50% responses. The PE showed a high predictability in NREM and a low predictability of the ECoG in REM sleep. Although the power spectrum differed between VAS in NREM (decrease of delta activity) and REM sleep (beta activation), the PE showed that the cortical activation pattern did not depend on the sleep state and the stimulus. Processes of cortical activation and deactivation during spontaneous sleep state changes and VAS were similar in their time courses. Cochlear ablation prevented from arousal, suggesting that stimuli were detected through the auditory rather than the proprioceptive system. The results show that external VAS induce a cortical arousal during the last trimester depending on the stimulus. The time course of cortical activation within 32s suggests an arousal via the ascending activating reticular system rather than via specific fiber systems.

Correlation of surface morphology of polyethylene films to ink adhesion and removal

The basic phenomenon of ink adhesion and removal has been studied by looking at the surface of polyethylene films that have been subjected to a ceramic bead impact ink-removal process where printed polyethylene films, zirconium silicate beads, and water were agitated in a laboratory shaker. AFM images show that the polyethylene packaging film surfaces studied have a typical morphology of polyethylene films crystallized under mechanical stress which consists of rows, approximately 1 μm in width, of lamellar-like structures. Upon impact of the ceramic beads on the polyethylene films, the surface is roughened and the surface rows appear to be deformed. FTIR data show that the surface crystallinity of the PE film decreases with the impact ink removal process. A deinking mechanism is proposed where the beads tear the ink film, abrade the surface and deform the polyethylene substrate.

Dynamic structural–acoustic–piezoelectric finite-element analysis of a sonar array for a supercavitating high-speed underwater vehicle

Three-dimensional nonlinear dynamic finite-element analysis (FEA) is utilized herein in order to examine the coupled structural, acoustic, and piezoelectric noise propagation physics within a high-frequency sonar array for a supercavitating underwater research vehicle. Specifically, steady-state dynamic simulations of the sonar array’s coupled performance are carried out that model both (a) the acoustic radiation field resulting from electrically actuated ceramic array elements, and (b) the ceramic array element electrical response due to incident structure-borne excitation; fluid-borne excitation is being examined presently and may also be presented if completed in time. This paper focuses primarily on the interesting issues related to accurately modeling such a complex coupled system. For example, the frequency-dependent properties of a nonlinear elastomer absorption material within the array must be carefully characterized at very high frequencies in order to gain accurate results. Additionally, determining electrical properties of the piezoelectric ceramic material can pose a significant problem. Finally, performing a three-dimensional simulation at high frequencies with coupled physics analyses is not a trivial undertaking.. Laboratory shaker experiments performed in order to validate the modeling will also be presented.

Ferric chloride leaching of mechanically activated chalcopyrite

Mechanical activation is a means of accelerating the leaching process. Contributing to the success of this technique are (1) increased surface area; (2) increased surface reactivity; and (3) the microstructural modifications stemming from the deformation. Previous studies have focused on gaining a fundamental understanding of these factors. This study represents a divergence from this approach, as we set out to determine the effectiveness of the technique when applied on a scale more reflective of how the process might actually be practised. To this end, chalcopyrite was autogenously milled in a horizontal mill, and leaching was conducted using a 5 M chloride leach solution. Leaching of as-received concentrate resulted in copper extractions of 75% in 5 h of leaching, whereas leaching mechanically activated concentrates resulted in copper extractions over 95% after 3 h of leaching. This study investigated the critical parameters affecting the efficiency of mechanical activation as a means of accelerating the oxidative leaching of sulfide minerals. The processes of attrition and fragmentation enhance reaction rates by increasing both the surface area and the density of defects. A small laboratory shaker mill and a small tumbling mill were used to mechanically process chalcopyrite; the former using steel grinding media, the latter using sized ore. The increase in surface area was determined using BET; and X-ray diffraction analysis was utilized to determine the full width at half maximum (FWHM) for chalcopyrite, which is subsequently used as a marker of the relative deformation. Leaching experiments were conducted with as-received concentrate and with processed concentrate. The contributions of the increased surface area and the deformed structure were correlated with the leaching kinetics.

Technical Note: A two-degree-of-freedom ambulance stretcher suspension: Part 3: Laboratory and road test performance

Parts 1 and 2 of this paper gave a design overview and described the dynamics of a prototype two-degree-of-freedom pneumatic suspension for an ambulance stretcher. This concluding part briefly reviews laboratory shaker table and ambulance road test performance of the suspension with passive pneumatic damping. The suspension system is found to offer compact low-cost isolation with lower natural frequencies than achieved in earlier mechanical systems.

Limitation of Small-Solute Exchange across the Visceral Peritoneum: Effects of Vibration

To evaluate the importance of the peritoneal membrane diffusion resistances to small solutes prevailing outside the capillaries in the visceral versus the parietal peritoneum during acute peritoneal dialysis (PD). Experimental study in anesthetized Wistar rats undergoing PD in a single exchange (120 min) using 1.36% Dianeal as dialysis fluid. Vibration, using a standard laboratory shaker at 10 Hz, was used to induce dialysate mixing and reduce the impact of "unstirred layers" in intact and eviscerated rats. Nonvibrated rats served as controls. The mass transfer area coefficient (PS) for chromium 51-ethylenediamine tetraacetic acid (51 Cr-EDTA), continuously infused intravenously, the plasma-to-peritoneal clearance (Cl-->D) of radioiodinated (125I) serum albumin (human)(RISA), as well as the total clearance out of the peritoneal cavity (Cl) of Evans blue labeled albumin, given as an intraperitoneal volume marker, and the portion of this Cl reaching the plasma per unit time (Cl-->P) were assessed. In intact rats there was a marked increase in PS for 51 Cr-EDTA, from 0.297 +/- 0.036 mL/min to 0.642 +/- 0.122 mL/min (n = 7, p < 0.01), and a moderate increase in Cl and Cl-->D, from 37.6 +/- 1.3 microL/min to 63.3 +/- 9.0 microL/min and from 6.04 +/- 0.51 microL/min to 9.54 +/- 0.93 microL/min (n = 7, p < 0.05), respectively, upon vibration. However, the plasma absorption clearance of albumin (Cl-->P) was unchanged after vibration. Furthermore, in eviscerated rats, vibration caused no significant changes in either of the exchange parameters measured. In conclusion, the visceral peritoneal transport of small solutes is normally limited by the presence of diffusion resistance outside the capillaries, which may be markedly reduced by "stirring" of the dialysate by vibration. Normally, the parietal, rather than the visceral, peritoneum is the major site for small-solute mass transfer in stationary animals. However, the visceral peritoneum apparently becomes increasingly important after stirring. The moderate increases in transperitoneal clearances of macromolecules occurring upon vibration, which were quite unexpected, indicate that vibration may also increase the dialysate/peritoneal membrane contact and/or cause some recruitment of capillaries.

Effect of titanium dioxide concentration on the survival of Pseudomonas stutzeri during irradiation with near ultraviolet light

Cells of Psudomonas stutzeri in suspensions of TiO 2 ranging in concentration from 0.5 to 4.0 g l −1 were irradiated with a blacklight blue u.v. source displaying peak emissivity at approximately 370 mm. Irradiation under these conditions is known to result in the generation of lethal free radicals. During irradiation the suspensions were agitated, using a specially modified laboratory shaker, to ensure efficient exposure of the TiO 2 . A u.v. radiation dose of 175 kJ m −2 resulted in cell fractional survival ranging from 5.5 × 10 −5 , at the lowest TiO 2 concentration, to 1.0 × 10 −6 , at the highest TiO 2 concentration. The advantages of contactors employing TiO 2 suspensions are briefly compared to immobilized TiO 2 systems

Effect of textile supports on the properties of immobilized trypsin

Biologically active substances which have been immobilized on various textile carriers have been produced over a number of years in the "Tekstil'galantereya" NPO. The greatest circulation has been received by Dartseks-tripsin (VFS 42-1862-88) and paks-tripsin (BFS 42-1863-88), which are trypsin (Tr) which has been immobilized on dialdehyde cellulose (DAHC) or on polycaproamide which has been activated with glutaraldehyde (PCA-GA). Tr preparations have also been prepared which have been immobilized on PCA with inherent aldehyde groups which were obtained as a result of "mild" oxidation under oxidation of a polycaproamide matrix under special conditions (specimens PCA-A-Tr). The DAHC has been prepared as a result of periodate oxidation of medicinal gauze (All-Union State Standard 19412-27). Partial hydrolysis of the PCA was carried out with alkali; activation of the PCA matrix, with excess glutaraldehyde in alkaline medium. The amount of carbonyl groups on the carrier was determined by condensation with hydroxylamine in alcoholic medium (pH = 3.2) [1] or by oxidation with iodine under weakly alkaline conditions (0.1 n borax solution) [2]. The unmodified carrier was used as a control. The quantity of immobilized protein was determined by the Lowry-Hart ley method [3, 4], using as a control a carrier of the same degree of oxidation which had been treated concurrently with the immobilized specimen with the same solutions and under the same conditions [5]. The proteolytic activity of the specimen (A) was determined by the Kunitz method [6], using as a substrate a 2% casein solution according to Hammersten in a 1/15-molar phosphate buffer (pH = 7.8), with constant agitation on a laboratory shaker at 37°C. If necessary, the immobilized specimens were washed with water and a phosphate buffer until there was no protein in the wash water. After drying, the moisture content of the specimens immobilized on DAHC was 4-6%; and on the modified PCA, about 2%. As service characteristics, we examined the decrease in proteolytic activity upon the action of y-radiation in a dose of 25 kGr on the specimens of immobilized trypsin, the decrease in proteolytic activity during the process of immobilization, during storage, and also the thermal inactivation in a 1/15-molar phosphate buffer solution (pH = 7.8). As was established for Tr specimens immobilized on DAHC, the following exert a considerable effect on the retention of proteolytic activity: the number of aldehyde groups in the matrix [7], the amount of immobilized protein [8], and the pH and composition of the washing solution before drying the specimens [9]. Here, while increasing the content of aldehyde groups in the matrix (at an equal protein content) aids in retaining proteolytic activity after ~,-irradiation [10], in the process of storage or thermal inactivation in a model solution, the converse is true (see Table 1). Increasing the amount of immobilized Tr (at an identical degree of DAHC oxidation) leads to retention of the proteolytic activity of DAHC-Tr specimens during the storage process (at 15°C in the dark), but to the reverse effect in ~,-irradiation [8]. Therefore, we tried to examine specimens of immobilized Tr which had been prepared under identical conditions. In thermal inactivation of immobilized Tr in solution (pH = 7.8), a significant hydrolytic degradation of the carrier is observed; breakage of the azomethine bond may take place, plus desorption of the protein from the carrier. For DAHC with an elevated degree of oxidation, the rate of hydrolytic degradation is increased, as a result of which autolysis of the Tr is superimposed on the process of thermal inactivation, both of the Tr present in the free state (after desorption or breakage of the azomethine bond), and also of Tr which is partially modified by fragments of the carrier.

Formation of large particles in a 99Tcm-tin colloid preparation.

The effect of prolonged continuous movement on particle size within a 99Tcm-tin colloid preparation was investigated, making use of photon correlation spectroscopy for size estimation. No increase in particle size was found when the preparation was left undisturbed for up to 7 h, the mean (+/- S.D.) size being found to be 239 +/- 24 nm. When the preparation was placed in a laboratory rotator for the same period of time, there was a gradual increase in mean particle size to 404 +/- 127 nm. The increase in size was much greater, however, after 7 h of continuous agitation in a laboratory shaker, a mean value of 2260 +/- 746 nm being observed. An antimony sulphide colloid was subjected to continuous agitation for the same period of time but there was no evidence of aggregation. It is supposed that continuous movement of reconstituted 99Tcm-tin colloid, leading to a marked increase in particle size, may explain occasional instances of significant lung intake.

Experimental Studies on Epizoochorous Dispersal in Californian Plants

Experiments studying degrees of adherence ability to various surfaces were undertaken with presumably epizoochorous diaspores of 14 native and eight introduced species from southern California. A commonly available laboratory shaker was modified so as to provide a standard means for dislodging diaspores from surfaces. Diaspores were dropped onto a cloth-covered board and percentages of dislodged diaspores recorded after inversion and then after intervals of shaking. Three fabrics were used: a velvet with short pile, an artificial wood with short curly strands, and a furlike fabric with straight strands. Attachment to the velvet was nil for most species, showing that a lower threshold for strand length necessary to promote attachment exists. On the artificial wool, some species tended toward brief attachment, some toward prolonged attachment, and some were intermediate. Results with the furlike fabric were similar, but a difference could be seen in that diaspores with hooklike devices adhered better to the artificial wool; a few species (notably grasses with bristly awns) showed better adherence on the furlike fabric. Diaspores were also tested on natural animal surfaces (one feather and four fur samples). Natural substrates proved comparable to artificial counterparts. Distinctive categories of diaspores are evident, based upon diaspore morphology and adherence capability. Nature of surface proves more important than weight or size of the diaspore in promoting adherence.

The Behaviour of Vibrational Surface Residual Stress Relief in FC25 Cast Iron

The relief of surface residual stress in a FC25 Pearlitic Graphite Cast Iron plate has been experimentally studied using a large laboratory shaker. When the vibratory stress amplitude added to the residual stress is more than 0.02% offset stress in the materials, more residual stress is relieved. When the value is smaller than the added value, residual stress is not relieved. Unequally distributed residual stress throughout the specimen can be relieved through vibration. This is accomplished by changing the point at which the materials are held in the vibration equipment. By determining the number of vibration cycles and the stress amplitude, fatigue damage on the materials can be prevented under certain condition. After exposing the materials to vibratory stress, remarkable change in residual stress was not observed after exposure in open air for one month.

Conifer Cone Harvesting: An Experimental Approach

ABSTRACT THE objective of this study is to quantify various para-meters affecting the vibratory removal of the conifore cones. The three conifer species used in this experiment were (a) Ponderosa Pine, (b) Douglas Fir and (c) Western White Pine. The initial test was to determine pull and torsional forces required for cone detachment. The effects of various factors such as amplitude, direc-tion, duration and repetitions of vibration on cone removal and damage to the tree were studied. In order to isolate these factors, individual limbs from each of the three species were cut and vibrated by a laboratory shaker. The resulting data indicate the constraints pro-vided by the tree and the best approach to use in attemp-ting to harvest the cones by whole tree shaking.

Vibratory Stress Relief: A Fundamental Study of Its Effectiveness

Techniques have been devised for inducing consistent residual stress distributions into cantilever beams and for measuring their variation through the section. Commercial vibratory stress relief procedures have been simulated using a laboratory shaker, and it has been shown that resonant vibration techniques are capable of producing almost complete surface stress relief in specimens of hot rolled mild steel, cold drawn mild steel, and an aluminium alloy. The variables involved in the process are examined and conclusions are reached regarding cyclic strain amplitudes, cycle numbers, and frequency and fatigue effects.

Computer Modeling of Flow Induced In-Reactor Vibrations

An assessment of the reliability of finite element method computer models, as applied to the computation of flow induced vibration response of components used in nuclear reactors, is presented. The prototype under consideration was the East Flux Test Facility reactor being constructed for US-ERDA. Data were available from an extensive test program which used a scale model simulating the hydraulic and structural characteristics of the prototype components, subjected to scaled prototypic flow conditions as well as to laboratory shaker excitations. Corresponding analytical solutions of the component vibration problems were obtained using the NASTRAN computer code. Modal analyses and response analyses were performed. The effect of the surrounding fluid was accounted for. Several possible forcing function definitions were considered. Results indicate that modal computations agree well with experimental data. Response amplitude comparisons are good only under conditions favorable to a clear definition of the structural and hydraulic properties affecting the component motion.

Mechanical stress (shaking) and reticuloendothelial function in the chick embryo

Stage 34 (8 day) and 41 (15 day) chick embryos were exposed (3 min) to two separate amounts of mechanical (shaking) stress. Eggs were shaken in the horizontal plane through their long axes. A laboratory shaker (Eberbach) was used to produce the stress and one complete excursion defined as carriage movement through 7.92 cm (3.96 cm in opposite directions). Reticuloendothelial system (RES) activity, as measured by colloidal carbon clearance (CCC), was evaluated following administration via an allantoic vein. Shaking stage 34 or 41 embryos at 100 excursions per minute (EPM) did not affect CCC; shaking them at 300 EPM resulted in an immediate and significant depression of CCC. Stage 41 embryos exposed to 300 EPM and reincubated for either 1, 2 or 4 hours prior to CCC determination reverted to control CCC values sooner than stage 34 embryos subjected to the same regimen. Functional RES response to mechanically induced stress has now been shown for the first time in an embryonic system (at two distinct developmental stages). The response appears to parallel that reported for various adult organisms. Furthermore, we suggest a temporal relationship regarding functional development of the embryonic RES.

Interaction between growth hormone and cortisol on the regulation of liver tyrosine transaminase activity.

1. Stress (30-min rough agitation upon a noisy laboratory shaker) decreased pituitary growth hormone content (tibia test) of the adult rat. 2. Shaker stress had no effect upon the corticoidsensitive enzyme tyrosine-α-ketoglu tar ate transaminase in the liver of the intact rat. This stress, however, increased the activity of a second corticoid- sensitive enzyme, tryptophan pyrrolase. The adrenalectomized rat similarly stressed exhibited a decreased transaminase activity with no change in tryptophan pyrrolase. This inhibitory effect was abolished by hypophysectomy. 3. Growth hormone, when administered just prior to cortisol, inhibited the enzyme inducing effects of the steroid upon transaminase. The induction of tryptophan pyrrolase, by cortisol, was not affected by growth hormone. 4. The opposing actions of growth hormone and adrenal corticoids on the activity of hepatic tyrosine transaminase may be representative of a category of adaptive responses which include 2 or more neuroendocrine mechanisms that interact at the tissue-cell level to regulate the activity of specific enzyme systems. (Endocrinology83: 475, 1968)

A Laboratory Shaker for Chemical Extraction of Soil and Plant Samples

A Laboratory Shaker for Chemical Extraction of Soil and Plant Samples

Inexpensive, Space-Saving Laboratory Shaker

Inexpensive, Space-Saving Laboratory Shaker