Physical Conditioners Research Articles

Sporting activity does not fully prevent bone demineralization at the impaired hip in athletes with amputation.

There is lack of information about bone mineralization at the lumbar spine and bilateral hips of athletes with unilateral lower limb amputation. The present study assessed for the first time the areal bone mineral density at the lumbar spine and at the hip of the able and impaired leg by means of Dual-Energy X-Ray Absorptiometry using a large sample (N = 40) of male athletes. Results showed that bone demineralization in athletes with unilateral lower limb amputation is found at the impaired hip but not at the lumbar spine and may therefore be site-specific. The extent of hip demineralization was influenced by the level of amputation, with about 80% of athletes with above knee amputation and 10% of athletes with below knee amputation showing areal bone mineral density below the expected range for age. Nevertheless, a reduced percentage of fat mass and a lower fat-to-lean mass ratio in the residual impaired leg as well as a greater amount of weekly training was positively associated with bone mineralization at the impaired hip (partial correlation coefficients = 0.377-0.525, p = 0.040-0.003). Results showed that participation in adapted sport has a positive effect on bone health in athletes with unilateral lower limb amputation but is not sufficient to maintain adequate levels of bone mineralization at the impaired hip in athletes with above-knee amputation. Accordingly, physical conditioners should consider implementing sporting programs, according to the severity of the impairment, aimed at improving bone mineralization at the impaired hip and improve body composition in the residual impaired leg.

Assessment of lime‐conditioned dairy manure fine solids captured using dissolved air flotation for fertilization in horticulture

Dissolved air flotation (DAF) has shown potential to substantially improve phosphorus (P) mass balance on dairy farms by capturing P associated with fine solids from liquid manure, enabling new management options. However, at<25% total solids, further dewatering is necessary to facilitate export of recovered fine solids off farm for use in bagged or bulk products. Physical conditioners such as quicklime (QL) and lime kiln dust (LKD) are commonly used to enhance mechanical dewatering of biosolids, but their effect on the properties and fertilization value of DAF-captured manure fine solids has not been documented. We generated plant foods using DAF-captured dairy manure fine solids conditioned with 3, 4.5, and 6% m/m QL or LKD and dewatered using a benchtop press for comparison with thermally dried fine solids. Tomato (Solanum lycopersicum L.) seedlings were grown in a soilless substrate amended with 6% v/v plant food and in an unamended control. Thermally dried and LKD plant foods produced significantly greater seedling biomass than QL plant foods and the unamended control. Quicklime- and LKD-conditioned fine solids contained approximately 30× and 10× less water-extractable P than thermally dried fine solids, respectively, likely due to precipitation of Ca-P minerals. The elevated pH (≥10) of the lime-conditioned fine solids could have also suppressed plant growth. These effects limit horticultural applications but could be beneficial in agricultural field settings where slow-release P is desirable. Research beyond this preliminary assessment is needed to determine the practicality and sustainability of the approach along with longer-term nutrient bioavailability.

Body composition and bone mineral density in athletes with a physical impairment.

BackgroundThe impact of the type and the severity of disability on whole-body and regional body composition (BC), and bone mineral density (BMD) must be considered for dietary advice in athletes with a physical impairment (PI). This study aimed to investigate the impact of the type and the severity of disability on BC, the pattern of distribution of fat mass at the regional level, and BMD in athletes with a PI.MethodsForty-two male athletes with spinal cord injury (SCI, n = 24; age = 40.04 ± 9.95 years, Body Mass Index [BMI] = 23.07 ± 4.01 kg/m2) or unilateral lower limb amputation (AMP, n = 18; age = 34.39 ± 9.19 years, BMI = 22.81 ± 2.63 kg/m2) underwent a Dual-Energy X-Ray Absorptiometry scan. Each athlete with a PI was matched by age with an able-bodied athlete (AB, n = 42; age = 37.81 ± 10.31 years, BMI = 23.94 ± 1.8 kg/m2).ResultsOne-Way Analysis of Variance showed significant differences between the SCI, AMP and AB groups for percentage fat mass (%FM) (P < 0.001, eta squared = 0.440). Post-hoc analysis with Bonferroni’s correction showed that athletes with SCI had significantly higher %FM vs. the AMP and AB groups (25.45 ± 5.99%, 21.45 ± 4.21% and 16.69 ± 2.56%, respectively; P = 0.008 vs. AMP and P < 0.001 vs. AB). The %FM was also significantly higher in the AMP vs. the AB group (P < 0.001). Whole-body BMD was negatively affected in SCI athletes, with about half of them showing osteopenia or osteoporosis. In fact, the mean BMD and T-score values in the SCI group (1.07 ± 0.09 g/cm2 and −1.25 ± 0.85, respectively) were significantly lower in comparison with the AB group (P = 0.001 for both) as well as the AMP group (P = 0.008 for both). The type of disability affected BC and BMD in the trunk, android, gynoid and leg regions in SCI athletes and the impaired leg only in AMP athletes.ConclusionsIn conclusion, the type of disability and, partly, the severity of PI impact on BC and BMD in athletes with a PI. Nutritionists, sports medicine doctors, clinicians, coaches and physical conditioners should consider athletes with SCI or AMP separately. Athletes with a PI would benefit from specific nutrition and training programs taking into account the type of their disability.

Anthropometric Prediction of DXA-Measured Percentage of Fat Mass in Athletes With Unilateral Lower Limb Amputation.

To date there is no anthropometric equation specific to athletes with unilateral lower limb amputation to estimate the percentage of fat mass (%FM). This study investigated the accuracy of a set of anthropometric equations validated on able-bodied populations to predict the %FM assessed by-means of dual-energy x-ray absorptiometry (DXA) in athletes with unilateral lower limb amputation. Furthermore, a predictive anthropometric equation specific to athletes with unilateral lower limb amputation was developed from skinfold thickness measurements using DXA as the reference method for the estimation of the %FM. Twenty-nine white male athletes with unilateral lower limb amputation underwent a DXA scan and an anthropometric assessment on the same day. The %FM, calculated through several existing anthropometric equations validated upon able-bodied populations, was compared with the DXA-measured %FM (%FM_DXA). Accuracy and agreement between the two methods was computed with two-tailed paired-sample t-test, concordance correlation coefficient, reduced major axis regression and Bland-Altman analysis. A stepwise multiple regression analysis with the %FM_DXA as the dependent variable and age and nine skinfold thicknesses as potential predictors was carried out and validated using a repeated 10-fold cross-validation. A linear regression analysis with the sum of nine skinfolds as the independent variable was also carried out and validated using a repeated 10-fold cross-validation. The results showed that the anthropometric equations validated on able-bodied populations are inaccurate in the estimation of %FM_DXA with an average bias ranging from 0.51 to −13.70%. Proportional bias was also found revealing that most of the anthropometric equations considered, tended to underestimate/overestimate the %FM_DXA as body fat increased. Regression analysis produced two statistically significant models (P < 0.001 for both) which were able to predict more than 93% of total variance of %FM_DXA from the values of four skinfold measurements (i.e., thigh, abdominal, subscapular and axillary skinfold measurements) or from the sum of 9 skinfolds. Repeated cross-validation analysis highlighted a good predictive performance of the proposed equations. The predictive equations proposed in this study represent a useful tool for clinicians, nutritionists, and physical conditioners to evaluate the physical and nutritional status of athletes with unilateral lower limb amputation directly in the field.

Comparative study of the effect of rice husk-based powders used as physical conditioners on sludge dewatering

The effects of rice husk flour (RHF), rice husk biochar (RHB), and rice husk-sludge cake biochar (RH-SCB, expresses sludge cake biochar deriving from a sludge that has been previously conditioned with rice husk) used as physical conditioners on sludge dewaterability were compared. The effects of characteristics of physical conditioners on sludge compressibility and zeta potential were analyzed. The optimal rice husk-based powder was RH-SCB, which presented the highest net sludge solid yield (YN, expresses the dry mass flow by filtration) at 20.39 kg/(m2 h) for 70% dry sludge (DS). Characterization analysis indicates that the hardness and surface Fe content of powders which could influence the compressibility coefficient of sludge cake and sludge zeta potential were the major factors influencing sludge dewaterability. The comparison of feasibility and economic analysis showed that adding RH-SCB improves the quality of the sludge filtrate and reduces the pollution potential of conditioned sludge (the ratio of secondary and primary (RSP) of Cu, Zn, Cd reduces from 43.05, 144.00, 7.25 to 7.89, 14.63, 4.27, respectively), and the costs of using RH-SCB were the lowest (at 88.4% lower than that of the raw sludge). Therefore, it is feasible to use RH-SCB to improve sludge dewaterability.

STRUCTURING OF EFFLUENT PARTICLES BY MEANS OF TREATMENT OF BENTONITE BASE MINERAL CONDITIONERS

The turbidimetric and Z-potentiometric methods were used for the assessment of some properties of diatomite – bentonite based conditioners for dewatering of effluents from the digestate of a biogas plant. These physical conditioners were prepared based on natural porous highly dispersible systems such as bentonite and diatomaceous earth. Three types of modified systems in the forms of CaO were used, which differ from each other in the ratio of the content of bentonite and diatomite. The role of the silica-containing component is to ensure the structuring of these systems. Diatomite was used for this purpose.

Effect of physical conditioners (sawdust) on the dewatering of faecal sludge using unplanted filter beds

Abstract The study was conducted at Kwame Nkrumah University of Science and Technology, Kumasi on bench scale, using drying beds to determine the effect of different percentages of sawdust as a bulking agent for the dewatering of faecal sludge. Different percentages of sawdust, 50%, 100%, 150% and 0% (control) by weight of TS of the faecal sludge, with TS of 26.93 g/l which was selected in previous studies, were mixed with the faecal sludge. The sawdust-faecal sludge mixture of 50%, 100%, 150% and 0% TS of faecal sludge dewatered at 5.3, 4.9, 3.9 and 5.6 days respectively with 150% being fastest to dewater. The 150% sawdust-faecal sludge treatment was most efficient with respect to removal of contaminant loads like TVS, SS, COD and NH 3 -N, but was least in TS and EC removal. The 150% sawdust-faecal sludge mixture showed the least organic matter accumulation rate in the top 10cm of the filter media, whereas the 0% was the highest. The percentage TVS of the biosolids produced were 70.1, 77.3, 80.6 and 66.3 for 50%, 100%, 150% and 0% sawdust-faecal sludge mixtures, leading to annual organic matter estimation of 359, 567, 987 and 225 (kg TVS/m 2 /year) respectively

Prediction of 3000-m Running Performance Using Classic Physiological Respiratory Responses

Introduction: Knowing which physiological variables predict running performance could help coaches to optimize training prescription to improve running performance. Objective: The present study investigated which physiological respiratory responses could predict 3000-m running performance. Methods: Seventeen amateur runners (29.82±7.1years; 173.12±9.0cm; 64.59±9.3kg) performed a maximal graded running test on a treadmill. The ventilatory threshold (VT), respiratory compensation point (RCP), and maximal oxygen consumption (VO2max) were assessed, as well as the respective velocities (vVT, vRCP, vVO2max). After 72 to 96 hours the runners performed the 3000-m running field test. The relationships between variables were performed using Pearson product momentum correlations. Thereafter, simple and multiple regression models were applied. The significance level adopted was 5% (p&lt;0.05). Results: The majority of physiological responses were positive and well related to each other (r≥0.70; p&lt;0.05). Despite vVT, vRCP, and vVO2max demonstrating a higher and inverse relationship with 3000-m time (r=-0.92; r =-0.96; r =-0.89; p&lt;0.05), the multiple regression model indicated that vRCP and vVO2max are the best variables to predict 3000-m performance in experienced amateur road runners (R2=0.94). The equation proposed by the model was: 3000-m(s)=1399.21–[31.65*vRCP(km.h-1)]–[12.06*vVO2max (km.h-1)]. Conclusion: The vRCP and vVO2max may be used to predict 3000-m performance using only a maximal running test on a treadmill. In practical terms, coaches and physical conditioners can use performance in the 3000-m to select different exercise running intensities to prescribe exercise training intensities.

Improving the Dewaterability of Sewage Sludge Using Rice Husk and Fe2+-Sodium Persulfate Oxidation

Physical conditioners or skeleton builders are usually used to improve the dewaterability of sewage sludge. In this study, low-cost rice husk (RH) was evaluated as an alternative skeleton builder and combined with Fe2+ and sodium persulfate (SPS) for sewage sludge conditioning. The results show that the sewage sludge conditioned with RH and Fe2+/SPS showed good dewaterability, and the capillary suction time was reduced by 92.8% under optimal conditions. With use of response surface methodology, the optimal composite conditioner concentrations were 151.5 mg/g dry solid (DS) of SPS, 46 mg/g DS of Fe2+, and 333 mg/g DS of RH. After the sludge was conditioned with Fe2+/SPS, some extracellular polymeric substances (EPS) were destroyed, which resulted in the dissolved protein and polysaccharide amounts in the filtrate increasing. The water content analysis indicated the bound water was converted to free water because of the EPS degradation. The particle size analysis showed that the sludge flocs became smaller....

Enhancing faecal sludge dewaterability and end-use by conditioning with sawdust and charcoal dust

ABSTRACTFaecal sludge (FS) treatment in urban slums of low-income countries of sub-Saharan Africa is poor or non-existent. FS contains over 90% water and therefore dewatering it within slums decreases transport costs, facilitates local treatment and end-use. This study was designed to enhance the dewatering efficiency of FS, using two locally available physical conditioners (sawdust and charcoal dust), each applied at dosages of 0%, 25%, 50%, 75%, 100% and 125% TS. The optimum dosage for both conditioners occurred at 50% and 75% for cake moisture content and capillary suction time, respectively. The dewatering rate improved by 14.3% and 15.8%, whereas dewatering extent (% cake solids) improved by 22.9% and 35.7%, for sawdust and charcoal dust, respectively. The dewatering in FS conditioned with sawdust and charcoal dust was mainly governed by absorption and permeation (porosity), respectively. The FS calorific value improved (from 11.4 MJ kg−1) by 42% and 49% with 50% TS dosage of sawdust and charcoal dust, respectively. The FS structure also became porous after dewatering which hastens the subsequent drying and/or composting processes. Due to comparable performance in dewatering, sawdust or charcoal dust, whichever is locally available, is recommended to treat FS in low-income urban slum settlements.

Heart rate and heart rate variability of Yo-Yo IR1 and simulated match in young female basketball athletes: A comparative study

To verify the cardiac autonomic response following the Yo-Yo IR1 and simulated basketball matches (SM) 20 young female Brazilian basketball players (16.92±1.07 years; 179.60±9.27 m; 73.33±15.71 kg; BMI = 22.59±3.56) performed the Yo-Yo intermittent recovery test (Yo-Yo) and the SM. Heart rate (HR) and heart rate variability (HRV) were monitored continually 10-min before, during, and 10-min after both experimental sessions. Global HRV indexes, measured maximal heart rate (HRmax), and several estimated HRmax were assessed. The time duration of Yo-Yo IR1 was lower than SB (6.12 ± 1.81 and 24.21 ± 4.04 min, respectively; ES=5.78). Higher values of measured-HRmax were registered in SM (195.27±8.40 beats.min-1) than during Yo-Yo IR1 (187.47±9.54 beats.min-1; ES=-0.93). No differences were found between the mean HR of the efforts (177±9 and 173±10 beats.min-1 for Yo-Yo and SM, respectively; ES =0.20). The six estimated HRmax ranged from 92.31±4.59 to 102.59±4.41% of the measured HRmax. Higher cardiac autonomic depression was found after SM. The technical-tactical requirement during the SM seemed to be able to reach HRmax but with lower cardiac autonomic response than Yo-Yo. This information may help coaches and physical conditioners to evaluate, prescribe and monitor training sessions regarding HR and HRV responses during common team sports practices.

EVALUATION OF BAGASSE PITH AS A SKELETON BUILDER FOR IMPROVEMENT OF SLUDGE DEWATERING

High contents of colloidal and organic materials in municipal wastewater sludge cause problems in the process of dewatering. The filtering efficiency can be improved by chemical conditioning, but the effectiveness of mechanical dewatering is limited because flocculated sludge is highly compressible. Physical conditioners such as bagasse can be used to facilitate mechanical dewatering. This paper describes the use of bagasse pith (cane sugar waste fiber) to improve the dewatering process of municipal wastewater sludge. The effectiveness of the process was examined using a lab scale filter press. Experiments to evaluate the influence of pith showed that conditioning of sludge with pith entailed better dewatering than that of flocculated sludge alone. Conditioning with pith yields a more porous, rigid and permeable structure that allows the water to pass through it more easily. In addition, bagasse pith has a relatively high cellulose content that effects the C:N ratio; changing it to an average of 35 when dewatered sludge is composted.

Study of the flocculation of anaerobically digested residue and filtration properties of bentonite based mineral conditioners

The turbidimetric and capillary suction time (CST) methods were used for the assessment of some properties (e.g., filtration process, water uptake etc.) of diatomite–bentonite based conditioners for dewatering of effluents from digestate of a biogas plant. These physical conditioners were prepared based on natural porous highly dispersible systems such as bentonite and diatomaceous earth. A characterization of the materials was performed by scanning electron microscopy (SEM) and fluorescence of X-rays spectrometry (XRF). A cationic polyacrylamide polymer (ZETAG® 9014) was added prior to the dewatering process of the anaerobic digestion residue and an optimal dose of the mineral conditioner and the polymer was determined. It was suggested the formula, by means of which the amount of separated water was identified as water retention capacity (WRC). A favorable filterability region was determined with WRC between 1.5 and 4.4 (high level of WRC) and 1.5 and 2.9 (low level of WRC) in terms of the percentage of polymer in the dry cake.

Effect of compressibility of synthetic fibers as conditioning materials on dewatering of activated sludge

Efficient solid–liquid phase separation of excess sludge from the mixed-liquor suspended solids in wastewater treatment is difficult to achieve without prior sludge conditioning. Several physical conditioners have been assessed as skeleton builders or filtering aids to reduce sludge compressibility; however, little is known about how the properties of the physical conditioner affect sludge compressibility and dewaterability. In this study, synthetic poly(ethylene terephthalate) (PET), polypropylene, and viscose rayon (VR) fibers were used as physical conditioners for activated sludge, and the effects of the fiber compressibility on the dewaterability of activated sludge collected from a laboratory-scale reactor were assessed. Based on expression experiments using a laboratory-scale apparatus, it was found that: (1) the rate of consolidation of sludge cakes increased after incorporation of synthetic fibers, particularly at the primary stage. (2) The porosity of the sludge cake was maintained only with fibers that required high pressures for compaction (i.e., PET and VR); thus, high dewaterability of the cakes was achieved with these fibers. It is proposed that the compressibility of the physical conditioner may be one of the more important factors for improving sludge dewaterability.

Durability of autoclaved construction materials of sewage sludge–cement–fly ash–furnace slag

In the present work, we demonstrate an alternative for the final disposal of sewage sludge by using it as an additive in a mixture with cement, fly ash and furnace slag, which can potentially be used to develop newly promising construction materials by autoclave curing. The dewatered sewage sludge is obtained with fly ash and lime. These physical conditioners contribute to both dewatering process and solidifying/stabilizing of sludge.Various mechanical properties such as flexural strength, compressive strength and the toxicity characteristic leaching procedure (TCLP) were evaluated. To evaluate long-term performance, different types of accelerated attacks, i.e. freezing–thawing cycles, accelerated carbonation, wet–dry cycles, and heat–cool cycles were also determined. The obtained test results were indicated that the autoclaved samples exhibit good long-term performance after evaluations of different durability tests. XRD patterns show that the hydration products of autoclaved samples are katoite and C–S–H phases, which mainly contribute to strength of autoclaved products. Morphologies of autoclaved samples also demonstrate the existence of the gel-like and honeycomb-like hydrated products. The results show that this new construction material could be applied as many construction and building materials, i.e. landfill liners and building blocks.

Study on dewaterability of municipal sludge conditioning by physical conditioners with ultrasonic and magnetic field application

An experimental research on dewaterability of municipal sludge with different mixing ratios was conducted with the use of ultrasonic and magnetization as conditioning means, and quicklime powder and straw fiber as conditioners. Research indicates that conditioning by combination of ultrasonic, physical conditioners (quicklime and straw fiber), and magnetization can effectively improve the dewaterability of municipal sludge. U-O-M (represents treating the sludge successively with ultrasonic, physical conditioners and magnetic field) achieved the best dewaterability of municipal sludge through an experiment under the following conditions: 30 s 40 Hz ultrasonic treatment, 4% quicklime powder content, 1% fiber content, and 40 min magnetization with 20 mT strength. The water content after centrifugal dewatering with a 3,000 separation factor was lower than 60%.

Effects of sawdust-CPAM on textile dyeing sludge dewaterability and filter cake properties

Sawdust was used as a filter aid for the textile dyeing sludge dewatering in this study. Results showed that sawdust conditioning in conjunction with cationic polyacrylamide (CPAM) presented much better dewaterability than CPAM alone. The optimal sawdust and CPAM dosage for the best dewaterability was found to be 60 wt.% (mass percent) and 15 kg/t DS (dry solid), the time to filter (TTF) and the yield at 90% degree of the filtration completion (YN90) were 5s and 15.6 kg/m(2)h under the conditions, respectively. TTF and YN90 were more appropriate parameters than specific resistance to filtration (SRF) for assessing the sludge dewaterability as affected by physical conditioners. The moisture content of various filter cake layers gradually became the same with the increase of sawdust dosage. The flocculated sludge cake became relatively incompressible after sawdust conditioning. Sawdust acts to maintain the permeability during the compressed filtration by resisting cake compression.

Conditioning of sewage sludge by Fenton’s reagent combined with skeleton builders

Physical conditioners, often known as skeleton builders, are commonly used to improve the dewaterability of sewage sludge. This study evaluated a novel joint usage of Fenton’s reagent and skeleton builders, referred to as the F–S inorganic composite conditioner, focusing on their efficacies and the optimization of the major operational parameters. The results demonstrate that the F–S composite conditioner for conditioning sewage sludge is a viable alternative to conventional organic polymers, especially when ordinary Portland cement (OPC) and lime are used as the skeleton builders. Experimental investigations confirmed that Fenton reaction required sufficient time (80min in this study) to degrade organics in the sludge. The optimal condition of this process was at pH=5, Fe2+=40mgg−1 (dry solids), H2O2=32mgg−1, OPC=300mgg−1 and lime=400mgg−1, in which the specific resistance to filtration reduction efficiency of 95% was achieved.

Alteration of neuromuscular function in squash

The alteration in neuromuscular function of knee extensor muscles was characterised after a squash match in 10 trained players. Maximal voluntary contraction (MVC) and surface EMG activity of vastus lateralis (VL) and vastus medialis (VM) muscles were measured before and immediately after a 1-h squash match. M-wave and twitch contractile properties were analysed following single stimuli. MVC declined (280.5 ± 46.8 vs. 233.6 ± 35.4 N m, −16%; P < 0.001) after the exercise and this was accompanied by an impairment of central activation, as attested by decline in voluntary activation (76.7 ± 10.4 vs. 71.3 ± 9.6%, −7%; P < 0.05) and raw EMG activity of the two vastii (−17%; P < 0.05), whereas RMS/M decrease was lesser (VL: −5%; NS and VM: −12%; P = 0.10). In the fatigued state, no significant changes in M-wave amplitude (VL: −9%; VM: −5%) or duration were observed. Following exercise, the single twitch was characterised by lower peak torque (−20%; P < 0.001) as well as shorter half-relaxation time (−13%; P < 0.001) and reduced maximal rate of twitch tension development (−23%; P < 0.001) and relaxation (−17%; P < 0.05). A 1-h squash match play caused peripheral fatigue by impairing excitation–contraction coupling, whereas sarcolemmal excitability seems well preserved. Our results also emphasise the role of central activation failure as a possible mechanism contributing to the torque loss observed in knee extensors. Physical conditioners should consider these effects when defining their training programs for squash players.

Interaction of polyelectrolyte with digested sewage sludge and lignite in sludge dewatering

Physical conditioners, often known as skeleton builders, are commonly used for enhancing the rate and the extent of water removal of polyelectrolyte-flocculated sewage sludge. In this study, the interactions of two different cationic polyelectrolytes with lignite (a low rank coal) in conditioning of digested sewage sludge are investigated. Vacuum filtration tests, zeta potential measurements and floc population measurements are performed on flocculated sludge and mixtures of the flocculated sludge and the lignite. The results for the flocculated sludge demonstrate the classical flocculation mechanisms of charge neutralization and particle–particle bridging. However, when lignite is mixed with the flocculated sludge in the conditioning process, the lignite particles agglomerate with the flocculated sludge by polymer bridging, which improves the dewatering properties of the flocculated sludge. The lignite particles strongly agglomerate with the flocculated sludge for the high molecular weight (MW) and low charge density (CD) polyelectrolyte, but the agglomeration is weaker and shear sensitive for the low MW and high CD polyelectrolyte.