SOME PROPERTIES OF SUSPENDED SEDIMENT ADSORBED CATIONS IN TURBID FRESHWATERS OF SOUTH AFRICA

SUMMARY

Large quantities of suspended sediments are common in many of South Africa's fresh-waters. Temporal and spatial variations in tile amounts of cations adsorbed were recorded. The adsorption appears to be dependent on valency, because greater quantities of the higher valencies are adsorbed. Ca⁺⁺ dominated the adsorbed cations and Mg the dissolved fraction. Water originating from the Beaufort Series contained high sodium concentrations. Fe⁺⁺ dominated the adsorbed minor cations. Large quantities of sediments transported by rivers enter impoundments. The adsorbed ions transported in this way are influenced by the type of suspended sediment and form a significant part of the total input of ions.     

Enhancement of optical coherence microscopy in turbid media by an optical parametric amplifier

We report the enhancement in imaging performance of a spectral‐domain optical coherence microscope (OCM) in turbid media by incorporating an optical parametric amplifier (OPA). The OPA provides a high level of optical gain to the sample arm, thereby improving the signal‐to‐noise ratio of the OCM by a factor of up to 15 dB. A unique nonlinear confocal gate is automatically formed in the OPA, which enables selective amplification of singly scattered (ballistic) photons against the multiply‐scattered light background. Simultaneous enhancement in both imaging depth and spatial resolution in imaging microstructures in highly light‐scattering media are demonstrated with the combined OPA‐OCM setup.

Typical OCM inteferograms (left) and images (right) without and with OPA.     

Screening for enzyme activity in turbid suspensions with scattered light

New screening techniques for improved enzyme variants in turbid media are urgently required in many industries such as the detergent and food industry. Here, a new method is presented to measure enzyme activity in different types of substrate suspensions. This method allows a semiquantitative determination of protease activity using native protein substrates. Unlike conventional techniques for measurement of enzyme activity, the BioLector technology enables online monitoring of scattered light intensity and fluorescence signals during the continuous shaking of samples in microtiter plates. The BioLector technique is hereby used to monitor the hydrolysis of an insoluble protein substrate by measuring the decrease of scattered light. The kinetic parameters for the enzyme reaction (V(max,app) and K(m,app)) are determined from the scattered light curves. Moreover, the influence of pH on the protease activity is investigated. The optimal pH value for protease activity was determined to be between pH 8 to 11 and the activities of five subtilisin serine proteases with variations in the amino acid sequence were compared. The presented method enables proteases from genetically modified strains to be easily characterized and compared. Moreover, this method can be applied to other enzyme systems that catalyze various reactions such as cellulose decomposition.     

Influence of chemical and visual stimuli in food-search behaviour of Procambarus clarkii under clear conditions

Chemical communication may play a major role in aquatic environments because of visibility limitations, but when turbidity is reduced do chemical and visual stimuli interact to elicit food-search behaviour by Procambarus clarkii? Does P. clarkii use visual cues to detect its prey? We conducted behavioural experiments in a Y maze, under non-turbid conditions. In the experiments P. clarkii was exposed to chemical plus visual (CV) and visual only (V) stimuli transmitted by Chironomus riparius. The results revealed that P. clarkii detected CV and V cues associated with the presence of C. riparius. In controls, with no prey, crayfish displayed only searching behaviour, whereas in treatments they exhibited searching, detection and attack behaviours. Further, there were no significant differences between CV and V stimuli in the mean number of attacks performed by crayfish. Thus, our findings indicate that under low turbidity, visual cues are sufficient to mediate prey detection by P. clarkii.     

A multipurpose, fast scan spectrophotometer for measuring turbid (biological) materials

A new optical spectrophotometer has been developed, based on a recently patented monochromator for spectral measurements of clear and, in particular, of turbid materials in the millisecond time range. The number of optical and mechanical components of the spectrophotometer has been reduced to a minimum, resulting in excellent light throughput, a low stray-light level, low cost, compactness and rigidity. The spectrophotometer has been designed for all kinds of spectral measurements such as absorption, transmission, reflection and luminescence/radiation in a single-beam mode as documented by several examples. In principle, there is no restriction of wavelengths, ranging from UV to NIR and up to the IR range. As many functions as possible are relocated from the hardware to the software part of the design, which allows for extraordinary flexibility and simplicity. An appropriate computer program providing data acquisition, control and calibration functions as well as real-time display of spectra has been developed on the basis of a compiler language; indispensable “fast routines” are written in assembler language.Presented at the joint meeting of the German Botanical Society and the German Zoological Society entitled: Spectroscopy and Optical Techniques in Animal and Plant Biology, Münster, 30th Sept-3rd October 1996     

Two‐photon focal modulation microscopy for high‐resolution imaging in deep tissue

Two‐photon microscopy (2PM) is one of the most widely used tools for in vivo deep tissue imaging. However, the spatial resolution and penetration depth are still limited due to the strong scattering background. Here we demonstrate a two‐photon focal modulation microscopy. By utilizing the modulation and demodulation techniques, background rejection capability is enhanced, thus spatial resolution and imaging penetration depth are improved. Compared with 2PM, the transverse resolution is increased by 70%, while the axial resolution is increased to 2‐fold. Furthermore, when applied in conventional 2PM mode, it can achieve inertial‐free scanning in either transverse or axial direction with in principle unlimited scanning speed. Finally, we applied 2PFMM in thick scattering samples to further examine the imaging performance. The results show that the signal‐to‐background ratio of 2PFMM can be improved up to five times of 2PM at the depth of 500 μm. Fluorescent imaging in the mouse brain tissue. 3D Thy1‐GFP hippocampal neurons imaged by (A) 2PM compared with (B) 2PFMM; (C‐H) xy maximum‐intensity projection imaged by 2PM compared with 2PFMM. Scale bar 50 μm.      

高斯光束通过生物体混浊介质模型的测量

将各向同性的沸浊介质材料作为生物组织的光学模型,用2mw单模He-Ne高斯激光透过该混浊介质材料,测量透射率、偏振度及透射光强的分布,得到了偏振度（ν）与透射率（T）的关系曲线。当透射率T＜30％时,偏振度ν→0,高斯激光束透过混浊介质材料,受散射影响,光强偏离高斯分布,并提出了透射光强分布公式。     

Increase of rotifer diversity after sewage diversion in the hypertrophic lagoon,Albufera of Valencia,Spain

The Albufera of Valencia is a large oligohaline hypertrophic lagoon, regulated by sluice gates according to the needs of the surrounding rice field cultivation. It is in a turbid state with permanent cyanobacterial blooms. A slight improvement was detected after diversion in the 1990s of part of the sewage flowing into it. After sewage diversion, we found that: (1) Chlorophyll concentration and rotifer densities decreased; (2) Rotifer proportions declined, due mainly to a relative increase in cladocerans; (3) Rotifer diversity increased. The two dominants of the 1980s, Polyarthra spp. in the colder period and Brachionus angularis in the warmer one, reverted after sewage diversion to a more diverse assemblage reminiscent of the 1970s, with a higher number of dominant species. In the summer of 1998, both Brachionus calyciflorus and its predator Asplanchna brightwelli, dominant in 1973, became abundant again. In 1998, an increase in the number of dominant species was also observed during water renewal periods, some of these species were new or seldomly found before in the lagoon (Proalides tentaculatus-digitus, Trichocerca pusilla at the end of rice culture, Brachionus variabilis at the end of winter flooding). Another change that indicates an improvement of water conditions is a more distinct and longer clear water phase, which occurs in the water renewal period at the end of winter and involves a Daphnia magna peak. The increased importance of this phase, promoted the flourishment of Brachionus variabilis, a facultative Daphnia epibiont never found before in the lake.     

五子参药汤治疗COPD稳定期肺脾两虚、痰浊内蕴证的临床观察

目的:本文旨在推广高才达主任医师治疗慢性阻塞性肺病稳定期的临床经验,以及观察五子参药汤治疗慢性阻塞性肺疾病稳定期属肺脾两虚、痰浊内蕴症的临床疗效。方法:随机选取我院慢性阻塞性肺疾病(稳定期)患者90例分为对照组(n=45)和治疗组(n=45),对照组吸入沙美特罗替卡松粉气雾剂进行治疗,治疗组在对照组基础上加服五子参药汤,两组疗程均为12 w。对比两组治疗前后临床症状、肺功能、慢阻肺患者自我评估测试(CAT量表)、改良版英国医学研究委员会呼吸问卷(m MRC)量表及治疗后6个月内因COPD急性加重的再次住院次数。结果:治疗组的有效率优于对照组(91.11%vs 82.45%,P<0.05);治疗后,两组第1秒用力呼气容积(FEV1)、FEV1占预计值百分比(FEV1%)和FEV1/FVC较治疗前均有增加,且治疗组高于对照组(P<0.05);两组m MRC量表、CAT量表评分较治疗前均有下降,且治疗组低于对照组(P<0.05)。结论:五子参药汤可有效治疗肺脾两虚、痰浊内蕴型稳定期慢性阻塞性肺疾病,值得临床推广。