The contact force between lunar-based equipment and lunar soil.

Lunar-based equipment plays a vital role in the exploration of the moon because it undertakes the tasks of moving, transporting, digging, and so on. In order to control the gait of lunar-based equipment more precisely and guarantee mobile stability, the contact mechanism between its foot and lunar soil is worthy of in-depth study. In this paper, a contact model is proposed to predict the stress, strain, and displacement both on the contact surface and in the lunar soil when the foot is under vertical load. The axial stress in the proposed contact model is verified through the experiment and its accuracy in the lunar equipment is verified through simulation. The error is in a reasonable range and the influence depth of load conforms to the experiment results. This paper provides a relatively accurate model to describe the contact force between the lunar-based equipment's foot and the lunar soil and will promote the research of lunar exploration.

[Effects of water and nitrogen source types on soil enzyme activity and nitrogen utilization efficiency of wheat]. / æ°´åˆ†å’Œæ°®æºç±»åž‹å¯¹å°éº¦æ ¹é™ åœŸå£¤é ¶æ´»æ€§å’Œæ°®ç´ åˆ©ç”¨æ•ˆçŽ‡çš„å½±å“.

To provide basis for high-yield and high-efficiency of wheat production, with two wheat cultivars, 'Zhengmai 366' (strong gluten) and 'Bainong 207' (medium gluten), we investigated the effects of four nitrogen source types, ammonium chloride (NT1), calcium nitrate (NT2), urea (NT3) and calcium ammonium nitrate (NT4), applied under two water treatments, no irrigation (W1) and irrigation at jointing and heading stages (W2), on soil N-supplying capacity, grain yield and nitrogen utilization efficiency. The results showed that content of soil ammonium and nitrate at flowering stage decreased with increasing soil depths. Compared with the corresponding value of 'Zhengmai 366' under W1 treatment, W2 treatment decreased the contents of soil ammonium and nitrate in the 0-60 cm layer, and enzymes activities of urease, invertase and catalase by 10.0%, 13.3%, 7.5%, 2.8%, and 3.9%, respectively. For the two wheat cultivars, the content of ammo-nium was significantly higher under NT1 and NT3 treatments than that of others, while the content of nitrate under NT2 and NT3 treatments was significantly higher than that of others. Additionally, NT3 and NT4 treatments increased soil urease and invertase activities at the middle and later stages of grain filling. Compared with NT1 treatment, NT3 and NT4 fertilization increased grain yield and nitrogen use efficiency of cultivar 'Zhengmai 366' by 14.9% and 20.7%, 25.6% and 13.9%, under W2 treatment, respectively. Soil nitrate content in the 0-20 cm layer and the ammonium content in the 20-40 cm layer were positively correlated with wheat grain yield and nitrogen utilization efficiency. Under both water conditions, applying urea and calcium ammonium nitrate improved soil enzyme activity at the middle and later stages of grain filling, which was beneficial for wheat yield and nitrogen use efficiency.

Clinical efficacy of low dose recombinant tissue-type plasminogen activator for the treatment of acute intermediate-risk pulmonary embolism.

OBJECTIVES: To investigate the efficacy and safety of initial thrombolysis by recombinant tissue-type plasminogen activator (rt-PA) in compared with anticoagulant therapy in patients with acute intermediate-risk pulmonary embolism (PE).  Methods: Sixty-six patients with acute intermediate-risk PE were randomly assigned to receive rt-PA or LMWH between June 2014 and June 2017 in our department. We obtained information regarding the difference in the right ventricle/left ventricle (RV/LV) ratio, pulmonary artery systolic pressure (PASP), clinical symptoms improvement, PE-related mortality, hemodynamic decompensation, recurrent PE, and major and minor bleeding.  Results: In the rt-PA group, the mean PASP was reduced from 52.0±12.2 at baseline to 34.8±9.4 (p less than 0.001) and the mean RV/LV ratio was reduced from 1.26±0.22 at baseline to 0.96±0.18 (p less than 0.001) at 24 hours. In the LMWH group, the mean PASP was 53.4±12.8 at baseline and 48.5±11.9 at 24 hours (p=0.11), and the mean RV/LV ratio was 1.22±0.19 at baseline and 1.17±0.21 at 24 hours (p=0.31). In comparison with the LMWH group, there was a significant reduction in PASP and an improvement in the symptom severity in the rt-PA group. At 90 days, there was no difference in mortality, recurrent venous thromboembolism and major bleeding as a safety outcome, but increased minor bleeding and decreased hemodynamic decompensation occurred in the rt-PA group. Conclusions: In patients with acute intermediate-risk PE, low dose thrombolytic therapy is considered safe and effective, it can be recommended as an alternative option in clinical treatment.

Bamboo vs. crops: an integrated emergy and economic evaluation of using bamboo to replace crops in south Sichuan Province, China.

Based on long-term monitoring conducted in Chang-ning county, a pilot site of the 'Grain for Green Program' (GFGP), an integrated emergy and economic method was applied to evaluate the dynamic ecological-economic performance of 3 kinds of bamboo systems planted on sloping farmland. The results confirmed the positive effects of all 3 kinds of bamboo systems on water conservation and soil erosion control. The benefits gained progressively increased during the first 8 years after conversion, going from 4639 to 16127 EMyuan/ha/yr on average. All three bamboo plantations were much more sustainable than common agricultural crops planted on sloping land (CP) on both the short and long-term scales with their Emergy Sustainability Index (ESI) and Emergy Index for Sustainable Development (EISD), respectively, being 14.07-325.71 and 80.35-265.80 times that of CP. However, all 3 bamboo plantations had a Net Economic Benefit (NEB) less than that of CP during the first 8 years after conversion. Even with the government-mandated ecological compensation applied, the annual NEBECs of the Bambusa rigida (BR) and Phyllostachys pubescense (PP) plantations were, respectively, 3922.03 and 7422.77 yuan/ha/yr lower than the NEB of CP. Emergy-based evaluation of ecosystem services provides an objective reference for applying ecological compensation in strategy-making, but it cannot wholly solve the economic viability problem faced by all bamboo plantations. Inter-planting annual herbs or edible fungus, such as Dictyophora echinovolvata, within bamboo forests, especially in young bamboo plantations, might be a direction for optimizing bamboo cultivation that would improve its economic viability.

Engineering a functional three-dimensional human cardiac tissue model for drug toxicity screening.

Cardiotoxicity is one of the major reasons for clinical drug attrition. In vitro tissue models that can provide efficient and accurate drug toxicity screening are highly desired for preclinical drug development and personalized therapy. Here, we report the fabrication and characterization of a human cardiac tissue model for high throughput drug toxicity studies. Cardiac tissues were fabricated via cellular self-assembly of human transgene-free induced pluripotent stem cells-derived cardiomyocytes in pre-fabricated polydimethylsiloxane molds. The formed tissue constructs expressed cardiomyocyte-specific proteins, exhibited robust production of extracellular matrix components such as laminin, collagen and fibronectin, aligned sarcomeric organization, and stable spontaneous contractions for up to 2 months. Functional characterization revealed that the cardiac cells cultured in 3D tissues exhibited higher contraction speed and rate, and displayed a significantly different drug response compared to cells cultured in age-matched 2D monolayer. A panel of clinically relevant compounds including antibiotic, antidiabetic and anticancer drugs were tested in this study. Compared to conventional viability assays, our functional contractility-based assays were more sensitive in predicting drug-induced cardiotoxic effects, demonstrating good concordance with clinical observations. Thus, our 3D cardiac tissue model shows great potential to be used for early safety evaluation in drug development and drug efficiency testing for personalized therapy.

Integrated emergy and economic evaluation of lotus-root production systems on reclaimed wetlands surrounding the Pearl River Estuary, China.

Lotus (Newnbo nucifera, Gaertn) is the most important aquatic vegetable in China, with a cultivation history of over 3000 years. The emergy, energy, material, and money flows of three lotus root cultivation modes in Wanqingsha, Nansha District, Guangzhou, China were examined using Energy Systems Language models and emergy evaluation to better understand their ecological and economic characteristics on multiple spatial and temporal scales. The natural resource foundations, economic characteristics and sustainability of these modes were evaluated and compared. The results showed that although all three modes were highly dependent on purchased emergy inputs, their potential impacts as measured by the local (ELRL) and global (ELRW) environmental loading ratios were less than 1.2 and 0.7, respectively. The lotus-fish mode was the most sustainable with its emergy index of sustainable development (EISD) 2.09 and 2.13 times that of the pure lotus and lotus-shrimp modes, respectively. All three lotus-root production modes had superior economic viability, since their Output/Input ratio ranged from 2.56 to 4.95. The results indicated that agricultural systems may have different environmental impacts and sustainability characteristics at different spatial and temporal scales, and that these impacts and characteristics can be simultaneously explored using integrated emergy and economic evaluations.

Electrospun polystyrene scaffolds as a synthetic substrate for xeno-free expansion and differentiation of human induced pluripotent stem cells.

The use of human induced pluripotent stem cells (hiPSCs) for clinical tissue engineering applications requires expansion and differentiation of the cells using defined, xeno-free substrates. The screening and selection of suitable synthetic substrates however, is tedious, as their performance relies on the inherent material properties. In the present work, we demonstrate an alternative concept for xeno-free expansion and differentiation of hiPSCs using synthetic substrates, which hinges on the structure-function relationship between electrospun polystyrene scaffolds (ESPS) and pluripotent stem cell growth. ESPS of differential porosity was obtained by fusing the fibers at different temperatures. The more porous, loosely fused scaffolds were found to efficiently trap the cells, leading to a large number of three-dimensional (3D) aggregates which were shown to be pluripotent colonies. Immunostaining, PCR analyses, in vitro differentiation and in vivo teratoma formation studies demonstrated that these hiPSC aggregates could be cultured for up to 10 consecutive passages (P10) with maintenance of pluripotency. Flow cytometry showed that more than 80% of the cell population stained positive for the pluripotent marker OCT4 at P1, P5 and P10. P10 cells could be differentiated to neuronal-like cells and cultured within the ESPS for up to 18months. Our results suggest the usefulness of a generic class of synthetic substrates, exemplified by ESPS, for 'trapped aggregate culture' of hiPSCs. STATEMENT OF SIGNIFICANCE: To realize the potential of human induced pluripotent stem cells (hiPSCs) in clinical medicine, robust, xeno-free substrates for expansion and differentiation of iPSCs are required. In the existing literature, synthetic materials have been reported that meet the requirement for non-xenogeneic substrates. However, the self-renewal and differentiation characteristics of hiPSCs are affected differently by the biocompatibility and physico-chemical properties of individual substrates. Although some rules based on chemical structure and substrate rigidity have been developed, most of these efforts are still empirical, and most synthetic substrates must still be rigorously screened for suitability. In this paper, we demonstrate an alternative concept for xeno-free expansion and differentiation of hiPSCs using synthetic substrates, which hinges on the structure-function relationship between electrospun polystyrene scaffolds (ESPS) and pluripotent stem cell growth. ESPS of differential porosity was obtained by fusing the fibers at different temperatures. The more porous, loosely fused scaffold was found to efficiently trap the cells, leading to a large number of three-dimensional (3D) aggregates. In the form of these trapped aggregates, we showed that hiPSCs could be cultured for up to 10 consecutive passages (P10) with maintenance of pluripotency, following which they could be differentiated to a chosen lineage. We believe that this novel, generic class of synthetic substrates that employs 'trapped aggregate culture' for expansion and differentiation of hiPSCs is an important conceptual advance, and would be of high interest to the readership of Acta Biomaterialia.

Alginate Microfiber System for Expansion and Direct Differentiation of Human Embryonic Stem Cells.

Pluripotent human embryonic stem cells (hESCs) are a potential renewable cell source for regenerative medicine and drug testing. To obtain adequate cell numbers for these applications, there is a need to develop scalable cell culture platforms to propagate hESCs. In this study, we encapsulated hESCs in calcium alginate microfibers as single cells, for expansion and differentiation under chemically defined conditions. hESCs were suspended in 1% (w/v) alginate solution at high cell density (>10(7) cells/mL) and extruded at 5 m/min into a low calcium concentration bath (10 mM) for gelation. Mild citrate buffer (2.5 mM), which did not affect hESCs viability, was used to release the cells from the calcium alginate hydrogel. Encapsulation as single cells was critical, as this allowed the hESCs to grow in the form of relatively small and uniform aggregates. This alginate microfiber system allowed for expansion of an hESC line, HUES7, for up to five passages while maintaining pluripotency. Immunohistochemistry, polymerase chain reaction, and other analyses showed that passage 5 (P5) HUES7 cells expressed proteins and genes characteristic of pluripotent stem cells, possessed normal karyotype, and were able to form representative tissues of the three embryonic germ layers in vitro and in vivo. Encapsulated HUES7 cells at P5 could also be induced to directly differentiate into liver-like cells. Collectively, our experiments show that the alginate microfiber system can be used as a three-dimensional cell culture platform for long-term expansion and differentiation of hESCs under defined conditions.

A defined xeno-free and feeder-free culture system for the derivation, expansion and direct differentiation of transgene-free patient-specific induced pluripotent stem cells.

A defined xeno-free system for patient-specific iPSC derivation and differentiation is required for translation to clinical applications. However, standard somatic cell reprogramming protocols rely on using MEFs and xenogeneic medium, imposing a significant obstacle to clinical translation. Here, we describe a well-defined culture system based on xeno-free media and LN521 substrate which supported i) efficient reprogramming of normal or diseased skin fibroblasts from human of different ages into hiPSCs with a 15-30 fold increase in efficiency over conventional viral vector-based method; ii) long-term self-renewal of hiPSCs; and iii) direct hiPSC lineage-specific differentiation. Using an excisable polycistronic vector and optimized culture conditions, we achieved up to 0.15%-0.3% reprogramming efficiencies. Subsequently, transgene-free hiPSCs were obtained by Cre-mediated excision of the reprogramming factors. The derived iPSCs maintained long-term self-renewal, normal karyotype and pluripotency, as demonstrated by the expression of stem cell markers and ability to form derivatives of three germ layers both in vitro and in vivo. Importantly, we demonstrated that Parkinson's patient transgene-free iPSCs derived using the same system could be directed towards differentiation into dopaminergic neurons under xeno-free culture conditions. Our approach provides a safe and robust platform for the generation of patient-specific iPSCs and derivatives for clinical and translational applications.

Patterned prevascularised tissue constructs by assembly of polyelectrolyte hydrogel fibres.

The in vivo efficacy of engineered tissue constructs depends largely on their integration with the host vasculature. Prevascularisation has been noted to facilitate integration of the constructs via anastomosis of preformed microvascular networks. Here we report a technique to fabricate aligned, spatially defined prevascularised tissue constructs with endothelial vessels by assembling individually tailored cell-laden polyelectrolyte hydrogel fibres. Stable, aligned endothelial vessels form in vitro within these constructs in 24 h, and these vessels anastomose with the host circulation in a mouse subcutaneous model. We create vascularised adipose and hepatic tissues by co-patterning the respective cell types with the preformed endothelial vessels. Our study indicates that the formation of aligned endothelial vessels in a hydrogel is an efficient prevascularisation approach in the engineering of tissue constructs.

Efficient neuronal differentiation and maturation of human pluripotent stem cells encapsulated in 3D microfibrous scaffolds.

Developing an efficient culture system for controlled human pluripotent stem cell (hPSC) differentiation into selected lineages is a major challenge in realizing stem cell-based clinical applications. Here, we report the use of chitin-alginate 3D microfibrous scaffolds, previously developed for hPSC propagation, to support efficient neuronal differentiation and maturation under chemically defined culture conditions. When treated with neural induction medium containing Noggin/retinoic acid, the encapsulated cells expressed much higher levels of neural progenitor markers SOX1 and PAX6 than those in other treatment conditions. Immunocytochemisty analysis confirmed that the majority of the differentiated cells were nestin-positive cells. Subsequently transferring the scaffolds to neuronal differentiation medium efficiently directed these encapsulated neural progenitors into mature neurons, as detected by RT-PCR and positive immunostaining for neuron markers ßIII tubulin and MAP2. Furthermore, flow cytometry confirmed that >90% ßIII tubulin-positive neurons was achieved for three independent iPSC and hESC lines, a differentiation efficiency much higher than previously reported. Implantation of these terminally differentiated neurons into SCID mice yielded successful neural grafts comprising MAP2 positive neurons, without tumorigenesis, suggesting a potential safe cell source for regenerative medicine. These results bring us one step closer toward realizing large-scale production of stem cell derivatives for clinical and translational applications.

A 3D microfibrous scaffold for long-term human pluripotent stem cell self-renewal under chemically defined conditions.

Realizing the potential of human pluripotent stem cell (hPSC)-based therapy requires the development of defined scalable culture systems with efficient expansion, differentiation and isolation protocols. We report an engineered 3D microfiber system that efficiently supports long-term hPSCs self-renewal under chemically defined conditions. The unique feature of this system lies in the application of a 3D ECM-like environment in which cells are embedded, that affords: (i) uniform high cell loading density in individual cell-laden constructs (∼10(7) cells/ml); (ii) quick recovery of encapsulated cells (<10min at 37°C) with excellent preservation of cell viability and 3D multicellular structure; (iii) direct cryopreservation of the encapsulated cells in situ in the microfibers with >17-fold higher cell viability compared to those cultured on Matrigel surface; (iv) long-term hPSC propagation under chemically defined conditions. Four hPSC lines propagated in the microfibrous scaffold for 10 consecutive passages were capable of maintaining an undifferentiated phenotype as demonstrated by the expression of stem cell markers and stable karyotype in vitro and the ability to form derivatives of the three germ layers both in vitro and in vivo. Our 3D microfibrous system has the potential for large-scale cultivation of transplantable hESCs and derivatives for clinical applications.

Thermally induced gelable polymer networks for living cell encapsulation.

We report the encapsulation of MIN6 cells, a pancreatic beta-cell line, using thermally induced gelable materials. This strategy uses aqueous solvent and mild temperatures during encapsulation, thereby minimizing adverse effects on cell function and viability. Using a 2:1 mixture of PNIPAAm-PEG-PNIPAAm tri-block copolymer and PNIPAAm homopolymer that exhibit reversible sol-to-gel transition at approximately 30 degrees C, gels were formed that exhibit mechanical integrity, and are stable in H(2)O, PBS and complete DMEM with negligible mass loss at 37 degrees C for 60 days. MTT assays showed undetectable cytotoxicity of the polymers towards MIN6 cells. A simple microencapsulation process was developed using vertical co-extrusion and a 37 degrees C capsule collection bath containing a paraffin layer above DMEM. Spherical capsules with diameters ranging from 500 to 900 microm were formed. SEM images of freeze-dried capsules with PBS as the core solution showed homogenous gel capsule membranes. Confocal microscopy revealed that the encapsulated cells tended to form small aggregates over 5 days, and staining for live and dead cells showed high viability post-encapsulation. A static glucose challenge with day-5 cultured microencapsulated cells exhibited glucose-dependent insulin secretion comparable to controls of free MIN6 cells grown in monolayers. These results demonstrate the potential use of these thermo-responsive polymers as cell encapsulation membranes.

Three-dimensional co-culture of rat hepatocyte spheroids and NIH/3T3 fibroblasts enhances hepatocyte functional maintenance.

Functional maintenance of primary hepatocytes in culture can be improved by several distinct approaches involving optimization of the extracellular matrix microenvironment, media composition and cell-cell interactions, both homotypic and heterotypic. Using a galactose-decorated surface, we have developed a method to combine these two approaches by co-culturing rat primary hepatocyte spheroids with NIH/3T3 mouse fibroblast cells. Spheroids were performed by culturing hepatocytes for 3 days on galactosylated poly(vinylidene difluoride) membrane; NIH/3T3 cells were subsequently seeded and co-cultured with the spheroids. Results showed that although NIH/3T3 cells alone responded poorly to the galactosylated PVDF surface and displayed limited attachment, NIH/3T3 fibroblasts attached to the periphery of the hepatocyte spheroids and proliferated around them. Co-cultured hepatocyte spheroids exhibited significantly higher liver-specific functions as compared to spheroids cultured alone. Albumin secretion level in this co-culture system peaked on day 11, which was 1.8- and 2.9-times higher than the peak expression level in spheroid homo-culture control in serum-free (day 3) and serum-containing media (day 4), respectively. The albumin secretion function was maintained for at least two weeks; it was 5.1 (in serum-free medium) and 17.8 (in serum-containing medium) times higher than spheroid homo-culture on day 13. Similarly, the co-culture system also expressed approximately 5.5- and 3.1-times higher 3-methylcholanthrene-induced cytochrome P450 enzymatic activity on day 14 as compared to the homo-culture control in serum-free and serum-containing medium, respectively. In conclusion, this unique co-culture system demonstrated the synergistic roles of homotypic cell-cell interaction, heterotypic cell-cell interaction, cell-substrate interaction and soluble stimuli in hepatocyte functional maintenance.

Galactosylated poly(vinylidene difluoride) hollow fiber bioreactor for hepatocyte culture.

To overcome the limitations of long-term expression of highly differentiated hepatocyte functions, we have developed a novel bioreactor in which hepatocytes are seeded in a ligand-immobilized hollow fiber cartridge. Galactosylated Pluronic polymer is immobilized on poly(vinylidene difluoride) (PVDF) hollow fiber surface through an adsorption scheme yielding a substrate with hepatocyte-specific ligand and a hydrophilic surface layer, which can resist nonspecific protein adsorption and facilitate cell binding to the galactose ligand. Interestingly, the galactosylated PVDF hollow fiber shows enhanced serum albumin diffusion across the membrane. Freshly isolated rat hepatocytes were seeded and cultured in the extralumenal space of the hollow fiber cartridge for 18 days in a continuously circulated system. Albumin secretion function of the seeded hepatocytes was monitored by analyzing circulating medium by enzyme-linked immunosorbent assay. Urea synthesis and P-450 function (7-ethoxycoumarin dealkylase activity) were measured periodically by doping the circulating medium with NH4Cl and 7-ethoxycoumarin, respectively. Hepatocytes cultured on galactosylated PVDF hollow fibers maintained better albumin secretion and P-450 functions than on unmodified and serum-coated PVDF hollow fibers when cultured in serum-containing medium. Morphological examination by scanning electron microscopy showed that hepatocytes cultured on galactosylated PVDF hollow fibers developed significant aggregation, in contrast to those cultured on unmodified PVDF fibers or on serum-coated PVDF fibers. Transmission electron microscopy images revealed that tight junctions and canaliculus-like structures formed in these aggregates. These results suggest the potential application of this galactosylated PVDF hollow fiber cartridge for the design of a bioartificial liver assist device.

Galactosylated PVDF membrane promotes hepatocyte attachment and functional maintenance.

One of the major challenges in BLAD design is to develop functional substrates suitable for hepatocyte attachment and functional maintenance. In the present study, we designed a poly(vinylidene difluoride) (PVDF) surface coated with galactose-tethered Pluronic polymer. The galactose-derived Pluronic F68 (F68-Gal) was adsorbed on PVDF membrane through hydrophobic-hydrophobic interaction between PVDF and the polypropylene oxide segment in Pluronic. The galactose density on the modified PVDF surface increased with the concentration of the F68-Gal solution, reaching 15.4 nmol galactosyl groups per cm2 when a 1 mg/ml of F68-Gal solution was used. The adsorbed F68-Gal remained relatively stable in culture medium. Rat hepatocytes attachment efficiency on F68-Gal modified PVDF membrane was similar to that on collagen-coated surface. The attached hepatocytes on PVDF/F68-Gal membrane self-assembled into multi-cellular spheroids after 1 day of culture. These attached hepatocytes in spheroids exhibited higher cell functions such as albumin synthesis and P450 1A1 detoxification function compared to unmodified PVDF membrane and collagen-coated surface. These results suggest the potential of this galactose-immobilized PVDF membrane as a suitable substrate for hepatocyte culture.

Environmental effect of vegetation restoration on degraded ecosystem in low subtropical China.

The environmental effect of degraded ecosystem's vegetation restoration in low subtropical China was studied. Results indicated that the vegetation recovery on degraded lands significantly ameliorates surrounding environment, increases species diversity, improves soil structure, raises soil fertility, enhances productivity, and promotes regional agricultural production and social economic development dramatically. Through the combining engineering and biological measures, the restoration of degraded ecosystem in low subtropical area is possible and economical. The restoration experience in Xiaoliang, Wuhua and other sites are valuable for other degraded subtropical area was introduced.

New emergy indices for sustainable development.

The emergy indices for the evaluation of system's sustainable development ability were studied. Results indicated that the emergy indices are simplified and merged, and a new emergy index for sustainable development (EISD) is deduced. Employing EISD, two cases are conducted. The first one is to compare three different dike-pond agro-ecological engineering modes, which are: melon-melon-cabbage-four domestic fishes (mode I), melon-melon-cabbage-pig-four domestic fishes (mode II) and melon-melon-cabbage-pig-four domestic fishes combined with Siniperca chuatsi B. (mode III). The result is that the EISD of mode I is 0.53. Mode II's EISD is 5.26 times of mode I, and mode III's EISD is 6.83 times of mode I. The second one is to evaluate the development of Zhongshan City, Pearl Delta, during 1996 to 2000. The result indicated that the EISD of Zhongshan had appreciably declined from 1996 to 1998, and quickly improved from 1998 to 2000, partly because of its environment protection and product construction. Both of the two cases studies showed that EISD can assessment the sustainable development ability more roundly, with the consideration of environmental impact and social-economic effect at the same time.

Effects of litter removal on plant species diversity: a case study in tropical Eucalyptus forest ecosystems in South China.

The removal of litterfall in the Eucalyptus plantations in South China affected the plant biodiversity in these ecosystems was found based on the field observation and lab analysis. The protection times of species diversity of three Eucalyptus communities were different (Community I with no protection, Community II with 7-year-protection, Community III with 35-year-protection). The total numbers of species in these communities (from Community I to II to III) are 1, 6, and 17 respectively. The results showed that the protection of litterfall from being taken out of the ecosystem is important and can increase plant species diversity. This study combined biomass data, the chemical and physical properties of the soil, and the diversity of microbes in the communities. It is concluded that the mechanism of the effects of litter removal on biodiversity includes three factors: removing the suitable habitat of microbe and animal, decreasing the soil nutrient, and changing the special habitat for the germination and growth of invading plants. These results should have important implications for managing these Eucalyptus forest ecosystems in South China.

New polyphosphoramidate with a spermidine side chain as a gene carrier.

A new cationic polymer (PPA-SP), polyphosphoramidate bearing spermidine side chain, was prepared as a non-viral vector for gene delivery. PPA-SP was synthesized from poly(1,2-propylene H-phosphonate) by the Atherton-Todd reaction. The weight average molecular weight of PPA-SP was 3.44x10(4) with a number average degree of polymerization of 90, as determined by GPC/LS/RI method. The average net positive charge per polymer chain was 102. PPA-SP was able to condense plasmid DNA efficiently and formed complexes at an N/P ratio (free amino groups in polymer to phosphate groups in DNA) of 2 and above, as determined by agarose gel electrophoresis. This new gene carrier offered significant protection to DNA against nuclease degradation at N/P ratios above 2, and showed lower cytotoxicity than PLL and PEI in cell culture. The LD(50) of PPA-SP was 85 microg/ml in COS-7 cells, in contrast to 20 and 42 microg/ml for PLL and PEI, respectively. The complexes prepared in saline at N/P ratios of 5 approximately 10 had an average size of 250 nm and zeta-potential of 26 mV. PPA-SP mediated efficient gene transfection in a number of cell lines, and the transfection protocol was optimized in HEK293 cells using a luciferase plasmid as a marker gene. Gene expression mediated by PPA-SP was greatly enhanced when chloroquine was used in conjunction at a concentration of 100 microM. Under the optimized condition, PPA-SP/DNA complexes yield a luciferase expression level closed to PEI/DNA complexes or Transfast mediated transfection. In a non-invasive CNS gene delivery model, PPA-SP/DNA complexes yielded comparable bcl-2 expression as PEI/DNA complexes in mouse brain stem following injection of the complexes in the tongue.