Re-evaluating the vertical mass-flux profiles of aeolian sediment at the southern fringe of the Taklimakan Desert, China

Reliable estimation of the mass-flux profiles of aeolian sediment is essential for predicting sediment transport rates accurately and designing measures to cope with wind-erosion. Vertical mass-flux profiles from seventeen wind-erosion events were re-evaluated using five typical models based on observed data obtained from a smooth bare field at the southern fringe of the Taklimakan Desert, China. The results showed that the exponential-function model and the logarithmic-function model exhibited the poorest fit between observed and predicted mass-flux profiles. The power-function model and the modified power-function model improved the fit to field data to an equivalent extent, while the five-parameter combined-function model with a scale constant（σ） of 0.00001 m（different from the σ value proposed by Fryear, which represented the height above which 50% of the total mass flux occurred） was verified as the best for describing the vertical aeolian sediment mass-flux profiles using goodness of fit（R2） and the Akaike Information Criterion（AIC） values to evaluate model performance. According to relationships among model parameters, the modified power model played a prominent explanatory role in describing the vertical profiles of the observed data, whereas the exponential model played a coordinating role. In addition, it was found that the vertical profiles could not be extrapolated using the five selected models or easily estimated using an efficient model without field observations by a near-surface sampler at 0 to 0.05 m.

Fetch effect on the developmental process of aeolian sand transport in a wind tunnel

As the sand mass flux increases from zero at the leading edge of a saltating surface to the equilibrium mass flux at the critical fetch length,the wind flow is modified and then the relative contribution of aerodynamic and bombardment entrainment is changed.In the end the velocity,trajectory and mass flux profile will vary simultaneously.But how the transportation of different sand size groups varies with fetch distance is still unclear.Wind tunnel experiments were conducted to investigate the fetch effect on mass flux and its distribution with height of the total sand and each size group in transportation.The mass flux was measured at six fetch length locations(0.5,1.2,1.9,2.6,3.4 and 4.1 m)and at three free-stream wind velocities(8.8,12.2 and 14.5 m/s).The results reveal that the total mass flux and the mass flux of each size group with height can be expressed by q=aexp(–bh),where q is the sand mass flux at height h,and a and b are regression coefficients.The coefficient b represents the relative decay rate.Both the relative decay rates of total mass flux and each size group are independent of fetch length after a quick decay over a short fetch.This is much shorter than that of mass flux.The equilibrium of the relative decay rate cannot be regarded as an equilibrium mass flux profile for aeolian sand transport.The mass fluxes of 176.0,209.3 and 148.0μm size groups increase more quickly than that of other size groups,which indicates strong size-selection of grains exists along the fetch length.The maximal size group in mass flux(176.0μm)is smaller than the maximal size group of the bed grains(209.3μm).The relative contribution of each size group to the total mass flux is not monotonically decreasing with grain size due to the lift-off of some small grains being reduced due to the protection by large grains.The results indicate that there are complex interactions among different size groups in the developmental process of aeolian sand transport and more attention should be focused on the fetch effect because it has different influences on the total mass flux,the mass flux profile and its relative decay rate.

Impact of utility-scale solar photovoltaic array on the aeolian sediment transport in Hobq Desert, China

Deserts are ideal places to develop ground-mounted large-scale solar photovoltaic (PV) powerstation. Unfortunately, solar energy production, operation, and maintenance are affected bygeomorphological changes caused by surface erosion that may occur after the construction of the solar PVpower station. In order to avoid damage to a solar PV power station in sandy areas, it is necessary toinvestigate the characteristics of wind-sand movement under the interference of solar PV array. The studywas undertaken by measuring sediment transport of different wind directions above shifting dunes andthree observation sites around the PV panels in the Hobq Desert, China. The results showed that the twoparameterexponential function provides better fit for the measured flux density profiles to the near-surfaceof solar PV array. However, the saltation height of sand particles changes with the intersection anglebetween the solar PV array and wind direction exceed 45°. The sediment transport rate above shifting duneswas always the greatest, while that around the test PV panels varied accordingly to the wind direction.Moreover, the aeolian sediment transport on the solar PV array was significantly affected by wind direction.The value of sand inhibition rate ranged from 35.46% to 88.51% at different wind directions. When theintersection angle exceeds 45°, the mean value of sediment transport rate above the solar PV array reducesto 82.58% compared with the shifting dunes. The results of our study expand our understanding of theformation and evolution of aeolian geomorphology at the solar PV footprint. This will facilitate the designand control engineering plans for solar PV array in sandy areas that operate according to the wind regime.

Plasticity of Xyloglucan Composition in Bean （Phaseolus vulgaris）-Cultured Cells during Habituation and Dehabituation to Lethal Concentrations of Dichlobenil

Bean cells that have been habituated to grow in a lethal concentration （12 μM） of 2,6-dichlorobenzonitrile （dichlobenil or DCB, a cellulose biosynthesis inhibitor） are known to have decreased cellulose content in their cell walls. Xyloglucan, which is bound to cellulose and together with it forms the main loading network of plant cell walls, has also been described to decrease in habituated cells, but whether the change on cellulose affects the xyloglucan structure besides its abundance has not been analyzed. Fragmentation analysis with xyloglucan-specific endoglucanase （XEG） and endocellulase revealed that habituation to DCB caused a change in the fine structure of xyloglucan, namely a decrease in fucosyl residues attached to the galactosyl-xylosyl residues along the glucan backbone. After the removal of herbicide from the medium （dehabituated cells）, xyloglucan recovered its fucosyl residues. In addition, some cello-oligosaccharides could be detected only in habituated cells＇ xyloglucan digested by XEG and endocellulase, corresponding to a glucan co- valently bound or co-precipitated with the hemicelluloses. These results show that structural flexibility of cell walls relies in part on the plasticity of xyloglucan composition and opens up new perspectives to further research in this field.

Candidate Biomarker Discovery for Angiogenesis by Automatic Integration of Orbitrap MS1 Spectral- and X!Tandem MS2 Sequencing Information

Candidate protein biomarker discovery by full automatic integration of Orbitrap full MS1 spectral peptide profiling and X!Tandem MS2 peptide sequencing is investigated by analyzing mass spectra from brain tumor samples using Peptrix. Potential protein candidate biomarkers found for angiogenesis are compared with those previously reported in the literature and obtained from previous Fourier transform ion cyclotron resonance （FT-ICR） peptide profiling. Lower mass accuracy of peptide masses measured by Orbitrap compared to those measured by FT-ICR is com- pensated by the larger number of detected masses separated by liquid chromatography （LC）, which can be directly linked to protein identifications. The number of peptide sequences divided by the number of unique sequences is 9248/6911 ~ 1.3. Peptide sequences appear 1.3 times redundant per up-regulated protein on average in the peptide profile matrix, and do not seem always up-reg- ulated due to tailing in LC retention time （40%）, modifications （40%） and mass determination errors （20%）. Significantly up-regulated proteins found by integration of X!Tandem are described in the literature as tumor markers and some are linked to angiogenesis. New potential biomarkers are found, but need to be validated independently. Eventually more proteins could be found by actively involving MS2 sequence information in the creation of the MS1 peptide profile matrix.

Biochemical reactions in metabolite-protein interaction

Active endogenous metabolites regulate the viability of cells. This process is controlled by a series ofinteractions between small metabolites and large proteins. Previously, several studies had reported thatmetabolite regulates the protein functions, such as diacylglycerol to protein kinase C, lactose regulationof the lac repressor, and HIF-1α stabilization by 2-hydroxyglutarate. However, decades old traditionalbiochemical methods are insufficient to systematically investigate the bio-molecular reactions for a high-throughput discovery. Here, we have reviewed an update on the recently developed chemical proteomicscalled activity-based protein profiling （ABPP）. ABPP is able to identify proteins interacted eithercovalently or non-covalently with metabolites significantly. Thus, ABPP will facilitate the characteriza-tion of specific metabolite regulating; proteins in human disease progression.