bluuebunny/crossref_metadata_2025 huggingface dataset:
Sliding mesh algorithm for CFD analysis of helicopter rotor–fuselage aerodynamics
Authors: Steijl R. , Barakos G.
Published: February 2008

The study of rotor–fuselage interactional aerodynamics is central to the design and performance analysis of helicopters. However, regardless of its significance, rotor–fuselage aerodynamics has so far been addressed by very few authors. This is mainly due to the difficulties associated with both experimental and computational techniques when such complex configurations, rich in flow physics, are considered. In view of the above, the objective of this study is to develop computational tools suitable for rotor–fuselage engineering analysis based on computational fluid dynamics (CFD).

To account for the relative motion between the fuselage and the rotor blades, the concept of sliding meshes is introduced. A sliding surface forms a boundary between a CFD mesh around the fuselage and a rotor‐fixed CFD mesh which rotates to account for the movement of the rotor. The sliding surface allows communication between meshes. Meshes adjacent to the sliding surface do not necessarily have matching nodes or even the same number of cell faces. This poses a problem of interpolation, which should not introduce numerical artefacts in the solution and should have minimal effects on the overall solution quality. As an additional objective, the employed sliding mesh algorithms should have small CPU overhead. The sliding mesh methods developed for this work are demonstrated for both simple and complex cases with emphasis placed on the presentation of the inner workings of the developed algorithms. Copyright © 2008 John Wiley & Sons, Ltd.
Semi‐coupled air/water immersed boundary approach for curvilinear dynamic overset grids with application to ship hydrodynamics
Authors: Huang Juntao , Carrica Pablo M. , Stern Frederick
Published: February 2008

For many problems in ship hydrodynamics, the effects of air flow on the water flow are negligible (the frequently called free surface conditions), but the air flow around the ship is still of interest. A method is presented where the water flow is decoupled from the air solution, but the air flow uses the unsteady water flow as a boundary condition. The authors call this a semi‐coupled air/water flow approach. The method can be divided into two steps. At each time step the free surface water flow is computed first with a single‐phase method assuming constant pressure and zero stress on the interface. The second step is to compute the air flow assuming the free surface as a moving immersed boundary (IB). The IB method developed for Cartesian grids (Annu. Rev. Fluid Mech. 2005; 37:239–261) is extended to curvilinear grids, where no‐slip and continuity conditions are used to enforce velocity and pressure boundary conditions for the air flow. The forcing points close to the IB can be computed and corrected under a sharp interface condition, which makes the computation very stable. The overset implementation is similar to that of the single‐phase solver (Comput. Fluids 2007; 36:1415–1433), with the difference that points in water are set as IB points even if they are fringe points. Pressure–velocity coupling through pressure implicit with splitting of operators or projection methods is used for water computations, and a projection method is used for the air. The method on each fluid is a single‐phase method, thus avoiding ill‐conditioned numerical systems caused by large differences of fluid properties between air and water. The computation is only slightly slower than the single‐phase version, with complete absence of spurious velocity oscillations near the free surface, frequently present in fully coupled approaches. Validations are performed for laminar Couette flow over a wavy boundary by comparing with the analytical solution, and for the surface combatant model David Taylor Model Basin (DTMB) 5512 by comparing with Experimental Fluid Dynamics (EFD) and the results of two‐phase level set computations. Complex flow computations are demonstrated for the ONR Tumblehome DTMB 5613 with superstructure subject to waves and wind, including 6DOF motions and broaching in SS7 irregular waves and wind. Copyright © 2008 John Wiley & Sons, Ltd.
Numerical simulations of viscous flows using a meshless method
Authors: You Changfu , Qiu Yi , Xu Xuchang , Xu Delong
Published: February 2008

This paper uses the element‐free Galerkin (EFG) method to simulate 2D, viscous, incompressible flows. The control equations are discretized with the standard Galerkin method in space and a fractional step finite element scheme in time. Regular background cells are used for the quadrature. Several classical fluid mechanics problems were analyzed including flow in a pipe, flow past a step and flow in a driven cavity. The flow field computed with the EFG method compared well with those calculated using the finite element method (FEM) and finite difference method. The simulations show that although EFG is more expensive computationally than FEM, it is capable of dealing with cases where the nodes are poorly distributed or even overlap with each other; hence, it may be used to resolve remeshing problems in direct numerical simulations. Flows around a cylinder for different Reynolds numbers are also simulated to study the flow patterns for various conditions and the drag and lift forces exerted by the fluid on the cylinder. These forces are calculated by integrating the pressure and shear forces over the cylinder surface. The results show how the drag and lift forces oscillate for high Reynolds numbers. The calculated Strouhal number agrees well with previous results. Copyright © 2008 John Wiley & Sons, Ltd.
Comparative study of potential evapotranspiration and interception evaporation by land cover over Mekong basin
Authors: Zhou M. C. , Ishidaira H. , Takeuchi K.
Published: February 2008

Potential evapotranspiration is a key input to hydrological models. Its estimation has often been via the Penman–Monteith (P‐M) equation, most recently in the form of an estimate of reference evapotranspiration (RET) as recommended by FAO‐56. In this article, the Shuttleworth–Wallace (S‐W) model is implemented to estimate the potential evapotranspiration from soil moisture (PET) and the potential evaporation from interception (PET0) directly in a form that recognizes vegetation diversity and temporal development without reference to experimental measurements and without calibration. The threshold values of vegetation parameters are drawn from the literature based on the International Geosphere–Biosphere Programme (IGBP) land cover classification. The spatial and temporal variation of the leaf area index (LAI) of vegetation is derived from the composite National Oceanic and Atmospheric Administration ‐ Advanced Very High Resolution Radiometer (NOAA‐AVHRR) normalized difference vegetation index (NDVI) using a method based on the SiB2 model, and the Climate Research Unit (CRU) database is used to provide the required meteorological data. All these data inputs are publicly and globally available. Consequently, the implementation of the S‐W model developed in this study is applicable at the global scale, an essential requirement if it is to be applied in data‐poor or ungauged large basins.

A comparison is made between the FAO‐56 method and the S‐W model when applied to the Mekong River basin for the period 1981–2000. The resulting estimates of RET and PET and their association with vegetation types and LAI are examined over the whole basin both annual and monthly and at five specific points. The effect of NDVI on the PET estimate is further evaluated by replacing the monthly NDVI product with the 10‐day product. Multiple regression relationships between monthly PET, RET, LAI, and climatic variables are explored for categories of vegetation types. The estimated RET is a good climatic index that adequately reflects the temporal change and spatial distribution of climate over the basin, but the PET estimated using the S‐W model not only reflects the change in climate but also the vegetation distribution and the development of vegetation in response to climate. Although good statistical relationships can be established between PET, RET, and/or climatic variables, applying these relationships will likely result in large errors because of the strong non‐linearity and scatter between the PET and the LAI of the vegetation. It is concluded that use of the implementation of the S‐W model described in this study results in a physically sound estimate of PET, which accounts for changing land surface conditions. Copyright © 2008 John Wiley & Sons, Ltd.
Impact of paddy irrigation levels on floods and water use in the Mekong River basin
Authors: Masumoto Takao , Hai Pham Thanh , Shimizu Katsuyuki
Published: February 2008

During the Asian monsoon, water use is considered to be well integrated because of the sustainable use of the agricultural water supply. From the viewpoint of watershed management, paddy areas help regulate floods by serving as retarding basins (ponds), but they also ensure a rational supply of water resources by taking advantage of natural hydrologic conditions. Paddies commonly serve both agricultural and flood‐control functions in low‐lying areas in Japan, Cambodia, Vietnam, and other Asian countries. We discuss herein the impact of irrigation levels on floods and water use by analyzing typical examples of paddies harmoniously used for agriculture and flood regulation in and around Tonle Sap Lake and its environs in the Mekong River Basin (drainage area, 790 000 km2; river length, 4400 km). Flood storage by the Tonle Sap involves a unique reverse flow from the river into the lake during the flood season. Rice cultivation starts after the floodwater recedes, so floods and agriculture are closely interrelated. A second example involves reservoirs created by dikes in paddy areas that protect the urban areas of Phnom Penh from floods and supply irrigation water. A third example involves the use of colmatage, in which a levee is created and water is led behind the levee from the Mekong and Bassac Rivers as the water levels in the rivers rise. Part of the water stored in this manner during the flood season can be used for rice production during the dry season. We then estimate the volume of flooded water on paddies in order to evaluate the impact of non‐irrigated paddies on floods and water use. We also evaluate the potential to harmonize the role of paddies in managing floodwaters with their agricultural role and propose policies, for Japan and the rest of the world, that could help resolve flooding problems. Copyright © 2008 John Wiley & Sons, Ltd.
Isotopic investigation of river water mixing around the confluence of the Tonle Sap and Mekong rivers
Authors: Kabeya Naoki , Kubota Tayoko , Shimizu Akira , Nobuhiro Tatsuhiko , Tsuboyama Yoshio , Chann Sophal , Tith Nara
Published: February 2008

The Great Lake (Tonle Sap), located in mid‐western Cambodia, is the largest lake in southeast Asia and joins the Mekong through the Tonle Sap River. During the annual monsoon peak from about the end of May, the flow direction in the Tonle Sap reverses and river water from the Mekong flows to the Great Lake. When the water level of the Mekong decreases sufficiently, usually in October, the Tonle Sap again flows in its normal direction from the Great Lake to the Mekong. This study quantitatively investigated interactions between the Tonle Sap River and the Mekong River using the stable isotope ratios of oxygen (δ18O) in waters from both rivers, and estimated the contribution rate of Tonle Sap River water to Mekong River water during the peak flow period of the Tonle Sap River. During this period, the Tonle Sap River contributed approximately 70–97% along the right bank and 0–5% in the middle and left banks of the Mekong. We also observed δ18O of the Mekong River along a longitudinal section on the right bank side, where the contribution rate of the Tonle Sap River water remained high (80%) even 21 km downstream from the confluence. This study clearly demonstrates that we can determine the mixing rate of these rivers at each point after they converge by using stable oxygen isotopes as tracers, when the Tonle Sap flows in its normal direction. Copyright © 2008 John Wiley & Sons, Ltd.
Technical evaluation and development of low‐head drip irrigation systems in Kenya
Authors: Ngigi Stephen N.
Published: February 2008

Low‐head drip irrigation technology was recently introduced in Kenya. Imported drip systems are delicate to handle and require special maintenance. No guidelines regarding the optimum combination of lateral length, land slope and operating head were provided. To address the constraints, farmers appealed for technical assistance from research institutions. The objective of the present research was to address the farmers' challenges by evaluating existing low‐head drip irrigation systems to ascertain their performance in terms of water distribution/emission uniformity and to develop simple locally assembled drip irrigation kits. The research work focused on evaluation of emission uniformity and flow variation at different water supply heads, lateral lengths and land slopes. A number of the existing high‐head drip systems were evaluated under low‐head conditions with satisfactory results. Low‐head drip irrigation systems can be used effectively at 0.5–1.5 m water heads without compromising emission uniformity. Based on the technical evaluation, locally assembled drip irrigation systems “dream drip kits” were developed. The paper presents the methodology used for technical evaluation of different drip systems, results of the evaluation and a brief description of the design and development of locally assembled drip irrigation systems. Copyright © 2008 John Wiley & Sons, Ltd.
Optimal water productivity of irrigation networks in arid and semi‐arid regions
Authors: Montazar Aliasghar , Rahimikob Ali
Published: February 2008

The aim of this paper is develop a nonlinear optimisation model for the determination of the optimised water allocation and cropping pattern under adequate and limited water supplies. The water productivity index defined as the net profit to the volume of water used was considered as the objective function. The proposed model was executed for the Ghazvin Irrigation Network located in a semi‐arid region in Iran. The results showed that among the crop types grown in the region, onion and alfalfa have the highest and lowest water productivity value, respectively. These values under drought conditions for the optimal cropping pattern of the two crops were estimated at 75 068.86 and 3054.18 Rls m−3. The findings indicated that the overall water productivity of the irrigation network with relevant cropping pattern management might be raised to as high as 12 700 Rls m−3 under drought conditions. In normal and wet years, depending on the water available and the optimal cropping pattern, the values for this index were estimated to be 15 600 and 12 900 Rls m−3, respectively. For the existing cropping pattern, overall irrigation network productivity is estimated at 10 600 Rls m−3. Hence, the results demonstrated that the water productivity of an irrigation network could be improved as result of the optimal cropping pattern and deficit irrigation. For the study area, the maximum variations of this index may be fixed around 18% for different water regimes. The evaluations emphasise the important role of optimisation models in improving irrigation network efficiency and managing water in a sustainable manner. Copyright © 2008 John Wiley & Sons, Ltd.
Retinal nerve fiber layer birefringence evaluated with polarization sensitive spectral domain OCT and scanning laser polarimetry: A comparison
Authors: Götzinger E. , Pircher M. , Baumann B. , Hirn C. , Vass C. , Hitzenberger C. K.
Published: February 2008

A polarization‐sensitive spectral domain optical coherence tomography (PS‐SD‐OCT) system is used to measure phase retardation and birefringence of the human retinal nerve fiber layer (RNFL) in vivo. The instrument records three parameters simultaneously: intensity, phase retardation and optic‐axis orientation. 3D data sets are recorded in the optic nerve‐head area of a healthy and a glaucomatous eye, and the results are presented in various ways: En‐face phase‐retardation maps of the RNFL are generated from the recorded 3D data and results are compared with scanning laser polarimetry (SLP). The depth information provided by OCT is used to segment the RNFL in the intensity image and measure the RNFL thickness. From the retardation and thickness data, 2D birefringence maps of the RNFL are derived. Circumpapillary plots of RNFL retardation and thickness obtained by PS‐SD‐OCT are quantitatively compared with those obtained by SLP. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recombinant heparan sulfate for use in tissue engineering applications
Authors: Whitelock John , Ma J Leo , Davies Neil , Nielsen Natasja , Chuang Christine , Rees Martin , Iozzo Renato V , Knox Sarah , Lord Megan
Published: February 2008

BACKGROUND: Heparan sulfate (HS) is an important component of many extracellular matrices that interacts with mitogens and morphogens to guide and control tissue and organ development. These interactions are controlled by its structure, which varies when produced by different cell types and different species. The major aim of the studies reported here was to isolate and characterize the HS expressed on the N‐terminal domain of human perlecan when it is expressed in human cells.

RESULTS: The recombinant proteoglycan was expressed in greatest quantities when the cells were grown as monolayers in the presence of Medium 199. It was purified as a proteoglycan with a molecular weight between 75 and 150 kDa, which was decorated with HS, chondroitin sulfate (CS) and keratan sulfate (KS) in a similar way to the full‐length perlecan from the same cells. Compositional analysis of the glycosaminoglycan (GAG) chains suggested that it contained the same amount of CS and HS, suggesting that one of the attachment sites may not be glycosylated. The HS chains were responsible for the binding of fibroblast growth factor 2 (FGF2), while the specific roles of the CS and KS remain unclear.

CONCLUSION: Expressing the N‐terminal domain of the proteoglycan perlecan results in a hybrid truncated molecule that binds to growth factors via it's HS and may prove useful to add to scaffolds to encourage cells to respond to growth signals, such as those produced by the FGFs. Copyright © 2008 Society of Chemical Industry
Production of activated carbon from agricultural by‐products
Authors: Paraskeva Panagiota , Kalderis Dimitrios , Diamadopoulos Evan
Published: February 2008

The production of activated carbon from agricultural by‐products is a research field of increasing interest as it deals with the problem of the disposal of agro‐residues, at the same time producing an added‐value product that can be used in a number of environmental applications. The paper presents an overview of the latest developments in processes for the production of activated carbon from agricultural by‐products, with emphasis on the methodology applied, the effect of critical process parameters such as retention time, temperature, chemical to material ratio, as well as the adsorbing capacity of the activated carbons produced in removing select compounds from synthetic and real wastewaters. Agricultural by‐products can be a source for activated carbon production with high surface areas and high adsorption capacity. Copyright © 2008 Society of Chemical Industry
The hematopoietic stem cell niche: what are we trying to replicate?
Authors: Hines Michael , Nielsen Lars , Cooper‐White Justin
Published: February 2008

The pluripotent nature and self‐renewal capability of hematopoietic stem cells (HSCs) has resulted in these cells being seen as the ideal cell source for the on‐demand production of blood and blood products. This potential to save many thousands of lives is as yet unmet, owing to our inability to reliably expand this cell source ex vivo to clinically relevant numbers. This is, to a large extent, due to the absence of a single cell surface antigen to identify them and an optimum set of in vitro conditions sufficient to expand them while maintaining ‘stemness’. This review briefly summarizes the current research efforts aimed at defining the appropriate in vivo conditions to be mimicked in ex vivo culture. In particular, it focuses on the molecules known to participate in the functionality of the bone marrow stem cell niche. These niche molecules include adhesion molecules, extracellular matrix molecules, and soluble and bound growth factors. Finally, this review proposes an approach to find the optimum conditions for this expansion utilizing smart surfaces and a criterion for developing these surfaces. Copyright © 2008 Society of Chemical Industry
CO2 absorption into amine solutions: a novel strategy for intensification based on the addition of ferrofluids
Authors: Komati Srinivas , Suresh Akkihebbal K
Published: February 2008

BACKGROUND: In this paper a novel approach for increasing the mass transfer coefficient in gas/liquid mass transfer is reported and applied to the industrially important system of CO2 absorption. The approach makes use of a ferrofluid additive to the liquid phase. To demonstrate this strategy, a wetted wall column has been built and experiments have been conducted on the CO2/methyl diethanolamine (MDEA) system. This reaction system allows the absorption to be carried out in the transition regime between slow and fast regimes, so that the mass transfer coefficient (kL) and interfacial area (ai) can be measured independently, in the presence and absence of ferrofluids. A surfactant‐coated aqueous magnetic fluid was prepared and shown to be stable in MDEA solutions.

RESULTS: The experimental results, with this fluid, show that there is an enhancement in mass transfer in the presence of ferrofluids, the extent of which depends on the amount of ferrofluid added. The enhancement in mass transfer coefficient was 92.8% for a volume fraction of the fluid of about 50% (solid magnetite volume fraction of about 0.39%). Experiments were also carried out to further enhance the mass transfer rates by employing a periodic oscillating magnetic field. Under the conditions employed, there was no further impact of magnetic field on mass transfer rates.

CONCLUSIONS: Magnetic nanoparticles are able to significantly enhance gas/liquid mass transfer rates when added to the liquid phase. The reasons for this striking effect are under investigation. It is possible for significantly higher enhancements to be produced by the action of an external field, but this requires special fluids to be formulated which are not affected by the chemical solvent used. These results have significance for the absorption of CO2 in industrial absorbers using amine solutions. Copyright © 2008 Society of Chemical Industry
Hydrothermal fractional pretreatment of sea algae and its enhanced enzymatic hydrolysis
Authors: Okuda Kazuhide , Oka Kazuyuki , Onda Ayumu , Kajiyoshi Koji , Hiraoka Masanori , Yanagisawa Kazumichi
Published: February 2008

BACKGROUND: Sea algae cellulose has been little utilized because the cellulose content in sea algae is low. For the effective utilization of sea algae cellulose, cellulose must be converted without drying into valuable material with a high rate and yield. From this viewpoint, effects of hydrothermal pretreatments of sea algae to enhance the glucose production by enzymatic hydrolysis of sea algae cellulose were investigated.

RESULTS: Using hydrothermal pretreatment performed at 423 K for Monostroma nitidum Wittrock (green alga) and at 473 K for Solieria pacifica (red alga) for 30 min, yields of extracted water‐soluble components containing monosaccharides were 0.51 g g−1 for the green alga and 0.62 g g−1 for the red alga. The apparent rate of glucose production from hydrothermally pretreated green alga by enzymatic hydrolysis was > 10 times faster than that of the non‐pretreated sample. Yields of glucose from cellulose by enzymatic hydrolysis were 79.9% for the green alga and 87.8% for the red alga.

CONCLUSION: Cellulose of sea algae was successfully fractionated by hydrothermal pretreatments, which resulted in high susceptibility of sea algae cellulose to enzyme attack. This process leads to the effective utilization of sea algae cellulose. Copyright © 2008 Society of Chemical Industry
Improved activity and stability of pseudomonas capaci lipase in a novel biocompatible ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate
Authors: Shan Haixia , Li Zaijun , Li Ming , Ren Guoxia , Fang Yinjun
Published: February 2008

BACKGROUND: Enzymes may exhibit enhanced activity, stability and selectivity in ionic liquids, depending on the properties of the liquid. The physical–chemical properties of ionic liquids, however, may be modified by altering the anion or cation in the ionic liquid. This feature is a key factor for realizing successful reactions. In this work, a new ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [i‐C4mim][PF6]), was synthesized and investigated as a novel medium for the transesterification reaction of 2‐phenylethanol with vinyl acetate catalyzed by pseudomonas capaci lipase. As contrasts, the reaction was also carried out in two reference solvents; the isomeric ionic liquid [i‐C4mim][PF6], 1‐butyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [C4mim][PF6]), and hexanes.

RESULTS: As reaction medium, [i‐C4mim][PF6] was best among the three solvents. The initial reaction rate, the equilibrium conversion of 2‐phenylethanol and the half‐lifetime of the lipase in [i‐C4mim][PF6] medium were about 1.5, 1.2 and 3‐fold that obtained in [C4mim][PF6] medium, respectively. The lipase in [i‐C4mim][PF6] medium was recycled 10 times without substantial diminution in activity.

CONCLUSION: The ionic liquid [i‐C4mim][PF6] has good biocompatibility, and can be used widely as green media in various biocatalysis reactions to improve the activity and stability of enzymes. Besides hydrophobicity and nucleophilicity, the spatial configuration of ionic liquids is also considered a key factor effecting the behaviour of the enzyme in ionic liquids. Copyright © 2008 Society of Chemical Industry
Expression proteomics of olfactory ensheathing cells
Authors: Marçal Helder , Sarris Maria , Raftery Mark J , Bhasin Vishal , McFarland Clive , Mahler Stephen M
Published: February 2008

BACKGROUND: Transplantation of olfactory ensheathing cells (OEC) to regenerate damaged spinal tracts and induce functional recovery following spinal cord injury (SCI) has been trialed in the clinic. Evidence suggests that the regenerative capacity of OEC is induced by soluble, secreted factors that influence their microenvironment. These factors may regulate OEC self‐renewal and/or induce their capacity to augment spinal cord regeneration. Profiling of secreted factors through a high‐throughput expression proteomics approach was undertaken to identify secreted proteins in the conditioned media of OEC under serum‐free conditions.

RESULTS: Both extracellular matrix and secreted proteins were identified in OEC conditioned media. OEC secrete pro‐regulatory and survival factors that modulate nerve nascence and anti‐angiogenic factors that regulate functional maturation of nervous tissues. Notable proteins identified include retinoic acid binding proteins and suggest that OEC utilise retinoic acid and other vitamins in their molecular pathways to augment their microenvironment and achieve their regenerative capacities.

CONCLUSIONS: Proteins expressed and secreted by OEC indicate that dynamic molecular pathways regulate and influence their cellular self‐renewal and regenerative capacities. OEC provide microenvironmental cues that trigger a dynamic switch between modulating pathways in their cell signaling network. Understanding OEC biology will aid in translation of OEC to the clinic in order to develop improved therapeutic modalities for the treatment of SCI. Copyright © 2008 Society of Chemical Industry
Design of bioreactors for mesenchymal stem cell tissue engineering
Authors: Godara Pankaj , McFarland Clive D , Nordon Robert E
Published: February 2008

There is a growing need for efficient mesenchymal stem cell (MSC) production processes for a wide spectrum of clinical conditions ranging from the treatment of life‐threatening graft‐versus‐host disease to cartilage repair. Development of cell and tissue engineered products derived from MSCs will be enabled by scalable production processes with standards of safety and efficacy similar to those established for the pharmaceutical industry. Many of the bioreactor design principles established for production of biopharmaceuticals can be applied to production of MSC products; however, specific control of the microenvironment is required for MSC expansion and differentiation. We review how porous scaffolds and bioreactor technologies are applied to the study of the MSC microenvironment. Current methods for MSC production are based on growth in tissue culture flasks, which is labour‐intensive and expensive. We suggest that stirred, perfusion or microfluidic bioreactor technologies can more efficiently address the clinical need for large‐scale MSC production. Soft lithography and microfluidic design offer extreme geometric precision to study MSC function as well as defining the microenvironment for tissue engineering at the micron scale. Copyright © 2008 Society of Chemical Industry
Novel AAV serotypes for improved ocular gene transfer
Authors: Lebherz Corinna , Maguire Albert , Tang Waixing , Bennett Jean , Wilson James M.
Published: February 2008

Some of the most successful gene therapy results have been obtained using recombinant viral vectors to treat animal models of inherited and acquired ocular diseases. Clinical trials using adenovirus vector systems have been initiated for two ocular diseases. Adeno‐associated viruses (AAVs) represent an attractive alternative to adenoviral vector systems as they enable stable and long‐term expression and can target a variety of different ocular cell types depending on the capsid serotype; recently clinical trails for congenital blindness was initiated with a vector‐based AAV serotype 2. High levels of retinal gene transfer have been achieved using vectors based on AAV serotypes 1, 2, 4 and 5. This report compares the gene transfer efficacy and stability of expression of vector systems based on three novel AAV serotypes: AAV7, 8, 9, with the established vectors AAV1, 2, 5. We show here that AAV7 and 8 enable superior long‐term transduction of retinal and also anterior chamber structures. Copyright © 2008 John Wiley & Sons, Ltd.
Efficient adenovirus vector‐mediated PPAR gamma gene transfer into mouse embryoid bodies promotes adipocyte differentiation
Authors: Tashiro Katsuhisa , Kawabata Kenji , Sakurai Haruna , Kurachi Shinnosuke , Sakurai Fuminori , Yamanishi Koichi , Mizuguchi Hiroyuki
Published: February 2008

Background

Establishment of a transient gene delivery system, such as adenovirus (Ad) vectors, into embryonic stem (ES) cells and their aggregation form, embryoid bodies (EBs), is essential for its application in regenerative medicine because the transgene should not be integrated in the host genome. In this study, we optimized Ad vector‐mediated transduction into EBs, and examined whether Ad vector‐mediated transduction of adipogenesis‐related gene into EBs could promote the adipocyte differentiation.

Methods

We prepared β‐galactosidase‐expressing Ad vectors under the control of four different promoters (cytomegalovirus (CMV), rouse sarcoma virus, human elongation factor‐1α, and CMV enhancer/β‐actin promoter (CA)) to estimate the transduction efficiency. Adipocyte differentiation efficiency by transduction of the PPAR gamma or C/EBP alpha gene into EBs was examined.

Results

Of the four promoters tested, the CA promoter exhibited the highest transduction efficiency in the EBs. However, Ad vector‐mediated transduction was observed only in the periphery of the EBs. When repeated transduction by Ad vector was performed, gene expression was observed even in the interior of EBs as well. When EB‐derived single cells were transduced by an Ad vector containing the CA promoter, more than 90% of the cells were transduced. Furthermore, Ad vector‐mediated PPAR gamma gene transduction into EBs led to more efficient differentiation into adipocytes than could untransduced EBs, examined in terms of lipogenic enzyme activities and accumulation of the lipid droplets.

Conclusions

Ad vector‐mediated transduction into EBs could be a valuable tool for molecular switching of cell differentiation and could be applied to regenerative medicine. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis of 14C‐ and 14C3‐labelled Org 37462
Authors: Wiegerinck P. H. G. , Hofstede L. W. H. , Sperling F. M. G. M. , Vader J. F.
Published: February 2008

Org 37462 (1) is the active ingredient in Orgalutran®, an innovative product that reduces the time of treatment in in vitro fertilization from four to less than two weeks. Org 37462 is a synthetic decapeptide containing several amino acids that are unnatural in stereochemistry and/or in structure. The synthesis, starting with a ProtectingGroup‐D‐Ala‐resin, is a typical solid state synthesis. For the conduction of several metabolism studies, Org 37462 had to be labelled with carbon 14. It was decided to label D‐3‐(2‐naphthyl)alanine, the last amino acid to be coupled to the resin. We report the synthesis of [14C]‐ and [14C3]‐Org 37462, starting from 2‐bromo‐[14C‐methyl]‐naphthalene and [14C2]‐tert‐butyl glycinate. Copyright © 2008 John Wiley & Sons, Ltd.
Fractionation of Polysaccharide Derivatives and Subsequent Analysis to Differentiate Heterogeneities on Various Hierarchical Levels
Authors: Mischnick Petra , Adden Roland
Published: February 2008

A set of methyl celluloses of DS 1.8 has been fractionated by stepwise solvent extraction. All fractions have been investigated with respect to their monomer composition and methyl distribution in the polymer chains. Deviation from the random model and differences between the four samples could be determined with higher sensitivity and more differentiated than for the unfractionated material. Structure complexity of cellulose ethers on different hierarchical levels is outlined and discussed.
Interactions of Ionic Liquids with Polysaccharides – 2: Cellulose
Authors: Heinze Thomas , Dorn Susann , Schöbitz Michael , Liebert Tim , Köhler Sarah , Meister Frank
Published: February 2008

Some general comments about ionic liquids (ILs) and carbohydrates are given. The main scope of the review is to discuss the present state of the art of chemical modification of cellulose applying IL as reaction media considering own research results. ILs, namely 1‐butyl‐3‐methylimidazolium chloride (BMIMCl), 1‐ethyl‐ 3‐methylimidazolium chloride (EMIMCl), 1‐butyl‐2,3‐dimethylimidazolium chloride (BDMIMCl), 1‐allyl‐2,3‐dimethylimidazolium bromide (ADMIMBr) and 1‐ethyl‐3‐ methylimidazolium acetate (EMIMAc) are solvents for cellulose (even for high molecular bacterial synthesized cellulose) and can easily be applied as reaction media for cellulose modification. We investigated the homogeneous acylation, carbanilation and silylation of the biopolymer cellulose. Under mild conditions and within short reaction time at low temperature (65 °C to 80 °C) and low excess of reagent, various cellulose esters and carbanilates, dendronized cellulose and trimethylsilyl cellulose were obtained. The DS of the cellulose derivatives can be controlled by varying the reaction time, reaction temperature and the IL used as reaction medium.
New Developments in Dissolving and Processing of Cellulose in Ionic Liquids
Authors: Hermanutz Frank , Gähr Frank , Uerdingen Eric , Meister Frank , Kosan Birgit
Published: February 2008

Ionic liquids (IL) are new direct dissolving systems for cellulose characterized by unique dissolving properties and simple technical handling. Selected IL‐systems are non toxic and chemically as well as physically neutral which represents an advantage as compared to the commonly used direct solvent N‐methyl‐ morpholine‐N‐oxide (NMMO). Fibres can easily be prepared by coagulation in water. The BASF company as a leading producer of ionic liquids investigates the technical conversion of the preparation of cellulosic fibres using ionic liquids in cooperation with the Institut für Textilchemie und Chemiefasern (ITCF), Denkendorf and the Thüringisches Institut für Textil‐ und Kunststoff‐Forschung (TITK), Rudolstadt. The major targets of this project are the selection of appropriate IL‐systems, the IL recycling, rheology of spinning dopes and the charcterization of resulting fibre profiles. Essential results of this work and the potential for establishing a technical‐ scale process are summarized.
Innovative Concepts for the Shaping and Modification of Cellulose
Authors: Liebert Tim
Published: February 2008

The conception and first results for a newly established project at the Center of Excellence for Polysaccharide Research in Jena are described. The work is focused on the investigation of new cellulose solvents and activating agents. Besides the use of a variety of Ionic Liquids it is the interaction of carbohydrates with boric acid and boronic acid, which will be exploited for the regeneration and chemical modification of the biomacromolecule. Two new ILs bearing cellulose activating anions were discovered which can dissolve the polysaccharide. Studies on the dissolution and chemical conversion of cellulose in ILs show the potential for homogeneous reactions but also reveal a number of side reactions especially for acetate containing ILs. In case of boronic acids a covalent binding on the secondary OH functions of glucose and glucose based polymers can be evidenced for the first time at intact molecules.
Treatment in Swelling Solutions Modifying Cellulose Fiber Reactivity – Part 1: Accessibility and Sorption
Authors: Jaturapiree Adisak , Ehrhardt Anelise , Groner Sibylle , Öztürk Hale Bahar , Siroka Barbora , Bechtold Thomas
Published: February 2008

Of prime importance in reactions involving insoluble cellulosic fibers is the sorption of reagents, which is governed by their degrees of accessibility in substrates. Swelling treatments of cellulosics in alkali solutions alter substrate accessibility leading to changes in their reactivity. In this paper, the first of a two‐part series, we collate and examine the results from various studies involving different techniques to characterize modifications in cellulosic fibers after swelling treatments in alkali solutions. Results from measurements of structure and accessibility in fibers with techniques such as water retention, inverse size exclusion chromatography (ISEC), iodine sorption, fiber diameters, and fiber‐splitting propensities indicate that the influence of swelling treatments on fiber structure/accessibility is differs with alkali type. The results show that a non‐uniform rather than uniform distribution of reagents within structures is a more accurate representation of reactions involving swollen cellulosic fibers. Hence, the observed changes in cellulose‐fiber reactivity are governed by the degrees of fiber swelling, and reagent sorption and accessibility during swelling treatments.
Treatment in Swelling Solutions Modifying Cellulose Fiber Reactivity – Part 2: Accessibility and Reactivity
Authors: Bui Huong M. , Lenninger Margit , Manian Avinash P. , Abu‐Rous Mohammad , Schimper Christian B. , Schuster K. Christian , Bechtold Thomas
Published: February 2008

The reorganization of cellulose fibers by swelling treatments in alkali solutions results in numerous changes to fiber structure, causing changes of chemical reactivity in the fiber‐solution heterogeneous system. An important part of the change in chemical reactivity is the change of fiber accessibility because it results in exclusion of chemicals such as reagents or catalysts from the fiber. In the second of a two‐part series of papers, we examine the influence of changes in fiber accessibility and/or reactivity due to treatment in swelling solutions on the performance or behavior of substrates during and after chemical finishing treatments. Changes in fiber accessibility due to alkali treatments are visualized with fluorescence microscopy. The effect of alkali treatments on enzymatic hydrolysis and pad‐dry‐cure crosslinking treatments of cellulose substrates are discussed as representative examples to demonstrate the effects of swelling processes on fiber reactivity and accessibility. Model calculations indicate that a considerable redistribution of chemicals in substrates occurs during dry‐cure operations resulting from molecule‐specific exclusion effects. Pilling tests on lyocell knit‐fabrics show the impact of preceding alkali processes on the final physical performance of textile fabric highlighting the importance of correct selection of alkali processes to achieve desired behavior.
Studies on the Stabilization of Modified Lyocell Solutions
Authors: Wendler Frank , Konkin Alexander , Heinze Thomas
Published: February 2008

Additives with functional properties makes the Lyocell process a versatile tool for the creation of new innovative materials beyond the textile sector. Occupying functional groups or active surfaces the additives emphasize the suitability of Lyocell fibers, but simultaneously enhance the complexity of chemical reactions in cellulose/N‐methylmorpholine‐N‐oxide (NMMO) solutions, respectively. Concerning to the concentration acidic ion exchange resins, activated charcoals, carbon black etc. shift the start of decomposition to lower temperatures, decrease the viscosity, enhance the formation of amines as the main degradation products or cause autocatalytic reactions.

New routes in stabilization of modified Lyocell solutions applying a polymeric stabilizer system are described. Using calorimetric, UV/VIS, ESR and HPLC analysis the degradation processes and thermal stability of modified Lyocell solutions compared to the unstabilized were studied. Moreover, as kinetic investigations show a distinguished behavior for modified solutions autocatalytic reactions can be suppressed by the stabilizing system. ESR kinetic study of radicals reveals that formation and recombination rates of radical reactions depend on cellulose concentration in Lyocell solutions and additional ingredients.
Hemicellulose in Dissolving Pulp and its Behaviour during its Processing to Viscose
Authors: Fischer Klaus , Schmidt Ingeborg
Published: February 2008

The amount of “hemicellulose” in pulps varies according to wood species, and the pulping processes including their bleaching agents.

Making viscose cellulosic and non‐cellulosic material is removed during mercerisation which is the first processing step. Low molecular weight material is also formed during the reduction of the degree of polymerisation in order to fit the alkali cellulose for xanthation and dissolving, respectively.

In this work commercially available dissolving pulps with respect to their behaviour during the preparation of viscose fibres shall be discussed. For these investigations a Eucalyptus sulphite and a Eucalyptus pre‐ hydrolysed sulphate pulps were selected.
Properties and Applications of Cellulose Acetate
Authors: Fischer Steffen , Thümmler Katrin , Volkert Bert , Hettrich Kay , Schmidt Ingeborg , Fischer Klaus
Published: February 2008

Cellulose acetate is one of the most important esters of cellulose. Depending on the way it has been processed cellulose acetate can be used for great varies of applications (e.g. for films, membranes or fibers). The properties of the applied cellulose acetates are very important for these applications. A special field for using cellulose acetate is the synthesis of porous, spherical particles, so called cellulose beads. Different types of technical cellulose acetates were used and their ability to form such cellulose beads was characterized. First the different types of cellulose acetates were characterized by means of solubility; turbidity and degree of substitution. In addition the molar mass and the distribution of substituents along the polymeric chain were analyzed. Next, the cellulose beads were synthesized within an emulsion process using these different cellulose acetates. Then the properties (particle size, porosity, morphology) of the cellulose beads were determined. Finally, the relationship between the characteristic of cellulose acetates and properties of cellulose beads was investigated.
Substitution Patterns of Cellulose Ethers ‐ Influence of the Synthetic Pathway
Authors: Bert Volkert , Wagenknecht Wolfgang
Published: February 2008

Commercial cellulose ethers are usually prepared under heterogeneous reaction conditions. In contrast, this contribution also describes the derivatization under homogeneous conditions in N‐methylmorpholine‐N‐oxide monohydrate (NMMNO*H2O) and under heterogeneous conditions after converting native cellulose to amorphous cellulose. Amorphous cellulose is prepared by dissolving cellulose in NMMNO*H2O followed by precipitation in different media. The degree of order and the porosity of the regenerated cellulose is significantly influenced by the content of water in the precipitating agent. The differences are described by measurements using wide angle X‐ray scattering, solid‐state 13C‐NMR, mercury porosimetry, and water/liquid retention values. Three synthetic pathways (heterogeneous, heterogeneous with amorphous cellulose and homogeneous) are compared regarding the structure‐property relationship of the cellulose ethers formed. Carboxymethylation, hydroxyethylation, hydroxypropylation and sulfoethylation are considered in detail. The choice of synthetic pathway has a significant influence on the degree of substitution (DS), the distribution of substituents on the level of the anhydroglucose unit (AGU), solubility behavior, and the viscosity of aqueous solutions. In general an increasing solubility and an increasing viscosity are observed from heterogeneous to heterogeneous with amorphous cellulose to homogeneous reaction conditions. There is a remarkable difference between the heterogeneously produced cellulose ethers with a DS distribution C2 ≥ C6 > C3 and the strictly homogeneous etherification in NMMNO*H2O/organic solvent systems with a DS distribution of C3 > C2 ≫ C6. This high regioselectivity at the secondary OH‐groups of the AGU may be caused by the strong solvation behavior of NMMNO*H2O and thereby a protecting function at the C6‐OH‐group.
Novel Bulky Esters of Biopolymers: Dendritic Cellulose
Authors: Pohl Matthias , Schaller Jens , Meister Frank , Heinze Thomas
Published: February 2008

Dendronized cellulose derivatives are discussed. Regarding our own studies, novel bulky esters of cellulose were synthesized homogeneously in N,N‐ dimethyl acetamide/LiCl or dimethyl sulfoxide in combination with fluoride ions by conversion of the biopolymer with 3,5‐dihydroxybenzoic acid based aryl polyester dendrons. The carboxylic acid moieties were efficiently activated in situ with N,N′‐carbonyldiimidazole or the acid chloride was applied. Cellulose esters with values of the degree of substitution of up to 0.7 were obtained. The functionalization analyzed by NMR spectroscopy occurs not only at position 6 (primary hydroxyl group) but also the secondary one at position 2.