Search

Titanium-based implants possessing adequately low elasticity modulus and custom­designed structures are urgently demanded in recent years for orthopedic applications. Electron beam melting (EBM) provides an opportunity to fabricated porous titanium scaffolds that meet the as-mentioned requirements, and it further allows for improved bone regeneration and increased contact area at implant–tissue interface. As a novel additive manufacturing (AM) technique, EBM could conveniently produce scaffolds with tunable porosity and shapes and complex structures based on the popular “bottom-up” concept. In the present work, EBM-produced Ti6Al4V cylinders designed with either a small pore size (EBMS, 640 μm) or a large one (EBML, 1200 μm) were characterized in respect of microstructure, permeability and specific surface area, and their cytocompatibility and osteogenic ability were evaluated subsequently in vitro. Both samples EBMS and EBML could support the attachment and proliferation of hMSCs with minimal inflammatory cytokines secretion. The EBMS scaffolds were relatively more compatible with hMSCs than the EBML and they better sustained osteogenesis probably for their larger specific surface area.

Tomography phase microscopy (TPM) is a new microscopic method that can quantitatively yield the volumetric 3D distribution of a sample׳s refractive index (RI), which is significant for cell biology research. In this paper, a controllable TPM system is introduced. In this system a circulatory phase-shifting method and piezoelectric ceramic are used which enable the TPM system to record the 3D RI distribution at a more controllable speed, from 1 to 40 fps, than in the other TPM systems reported. The resolution of the RI distribution obtained by this controllable TPM is much better than that in images recorded by phase contrast microscopy and interference tomography microscopy. The realization of controllable TPM not only allows for the application of TPM to the measurement of kinds of RI sample, but also contributes to academic and technological support for the practical use of TPM.

Ocean ecosystem models require accurate calculations of both hydrodynamics and biology; those calculations in turn require accurate calculation of in-water irradiance. Ecosystem models now achieve great accuracy in their hydrodynamical predictions, and the biological modules are becoming correspondingly sophisticated. The optical calculations are however often oversimplified, to the possible detriment of the physical and biological predictions. We used a recently developed, extremely fast radiative transfer code, EcoLight-S, to study differences in ecosystem and thermal development in an idealized upwelling-downwelling system when simple versus accurate irradiance calculations are used. The use of accurate irradiances gave up to 57% differences in chlorophyll concentrations after two weeks of simulated time, compared to predictions based on irradiances obtained using a simple exponential attenuation formula. Accurate irradiance calculations increased sea surface temperatures and decreased temperatures at depth, leading to increased stratification. Use of EcoLight-S couples the physical and biological calculations so that biology feeds back to physics, and vice versa. EcoLight-S outputs ancillary quantities such as remote sensing reflectance and in-water spectral irradiance, which can be used to validate ecosystem predictions using remotely sensed ocean color imagery or optical measurements from buoys or gliders, without the need to convert such measurements to chlorophyll values. After optimization, the ecosystem model total run times with EcoLight-S were less than 20% more than for the analytical irradiance models. We also found that the use of 24 h average irradiances gave factor-of-two differences in chlorophyll concentrations compared to the use of a diel irradiance pattern with the same 24 h average value.

The newly built CoSiNE-31 ecosystem model developed for the Pacific Ocean is employed here to evaluate carbon cycling in the equatorial Pacific upwelling region. This model explicitly includes 31 state variables capable of reproducing key biogeochemical features in this region, such as high-nutrient low-chlorophyll conditions. In the so-called Wyrtki Box (5°S–5°N, 90–180°W), the modeled area-averaged carbon export data show the predominance of the particulate organic carbon flux. This is consistent with observations, and amounts to 7.88 mmol C m–2 day–1 at the bottom of the euphotic zone (120 m water depth). Nearly as important is the dissolved organic carbon export flux, at 6.62 mmol C m–2 day–1. The modeled particulate inorganic carbon (PIC) export flux of 2.07 mmol C m–2 day–1 is much higher than the global average, indicating a key role of PIC sedimentation in the study region. The modeled carbon-to-nitrogen export ratio for particulate organic matter (POM) is 7.8, which is consistent with the Redfield ratio. The export ratio increases to 13.8 for dissolved organic matter (DOM). By implication, carbon export is markedly more efficient via DOM than via POM. This is the case also under simulated iron enrichment conditions, although there are measurable increases in carbon export efficiency for both DOM and POM.

Newly available sea surface salinity (SSS) data from the Aquarius together with in situ hydrographic data are used to explore the spatial and temporal characteristics of SSS in the South China Sea (SCS). Using in situ observations as the reference, an evaluation of daily Aquarius data indicates that there exists a negative bias of 0.45 psu for the version 3.0 data set. The root-mean-square difference for daily Aquarius SSS is about 0.53 psu after correcting the systematic bias, and those for weekly and monthly Aquarius SSSs are 0.45 and 0.29 psu, respectively. Nevertheless, the Aquarius SSS shows a reliable freshening in the SCS in 2012, which is larger than the Aquarius uncertainty. The freshening of up to 0.4 psu in the upper-ocean of the northern SCS was confirmed by in situ observations. This freshening in 2012 was caused by a combined effect of abundant local freshwater flux and limited Kuroshio intrusion. By comparing the Kuroshio intrusion in 2012 with that in 2011, we found the reduction as a relatively important cause for the freshening over the northern SCS. In contrast to the northern SCS, reduced river discharge in 2012 played the leading role to the saltier surface in the region near the Mekong River mouth with respect to 2011.

From the perspective of element biosafety and dietetics, the ideal alloying elements for magnesium should be those which are essential to or naturally presented in human body. Element germanium is a unique metalloid in the carbon group, chemically similar to its group neighbors, Si and Sn. It is a dietary trace element that naturally presents in human body. Physiological role of Ge is still unanswered, but it might be necessary to ensure normal functioning of the body. In present study, novel magnesium alloys with dietary trace element Ge were developed. Feasibility of those alloys to be used as orthopaedic implant applications was systematically evaluated. Mg-Ge alloys consisted of α-Mg matrix and eutectic phases (α-Mg + Mg 2 Ge). Mechanical properties of Mg-Ge alloys were comparable to current Mg-Ca, Mg-Zn and Mg-Sr biodegradable metals. As-rolled Mg-3Ge alloy exhibited outstanding corrosion resistance in vitro (0.02 mm/y, electrochemical) with decent corrosion rate in vivo (0.6 mm/y, in rabbit tibia). New bone could directly lay down onto the implant and grew along its surface. After 3 months, bone and implant were closely integrated, indicating well osseointegration being obtained. Generally, this is a pioneering study on the in vitro and in vivo performances of novel Mg-Ge based biodegradable metals, and will benefit the future development of this alloy system. Statement of Significance The ideal alloying elements for magnesium-based biodegradable metals should be those which are essential to or naturally presented in human body. Element germanium is a unique metalloid in the carbon group. It is a dietary trace element that naturally presents in human body. In present study, feasibility of Mg-Ge alloys to be utilized as orthopedic applications was systematically investigated, mainly focusing on the microstructure, mechanical property, corrosion behavior and biocompatibility. Our findings showed that Mg-3Ge alloy exhibited superior corrosion resistance to current Mg-Ca, Mg-Zn and Mg-Sr alloys with favorable biocompatibility. This is a pioneering study on the in vitro & in vivo performances of Mg-Ge biodegradable metals, and will benefit the future development of this alloy system.

In view of collaborative development environment web services supplier in ability, cost, time, supplier relations and component relevance information under uncertainty problems. The fuzzy multi-objective task assignment model of web services are built in a collaborative development environment. Using  cut sets and extension principle to simplify the fuzzy multi-objective assignment mode, we get the solution of simplified assignment model via the Genetic and simulated-annealing algorithm. Finally, the simulation results verify the feasibility of the proposed method, which can ensure the suppliers' tasking in successive software project in collaborative development environment.

Total internal reflection fluorescence microscopy (TIRFM) has been widely used in biomedical research to visualize cellular processes near the cell surface. In this study, a novel multi-angle ring-illuminated TIRFM system, equipped with two galvo mirrors that are on conjugate plan of a 4f optical system was developed. Multi-angle TIRFM generates images with different penetration depths through the controlled variation of the incident angle of illuminating laser. We presented a method to perform three-dimensional (3-D) reconstruction of microtubules from multi-angle TIRFM images. The performance of our method was validated in simulated microtubules with variable signal-to-noise ratios (SNR) and the axial resolution and accuracy of reconstruction were evaluated in selecting different numbers of illumination angles or in different SNR conditions. In U373 cells, we reconstructed the 3-D localization of microtubules near the cell surface with high resolution using over a hundred different illumination angles. Theoretically, the presented TIRFM setup and 3-D reconstruction method can achieve ∼40 nm axial resolution in experimental conditions where SNR is as low as 2, with ∼35 different illumination angles. Moreover, our system and reconstruction method have the potential to be used in live cells to track membrane dynamics in 3-D.

The export flux of particulate organic carbon (POC) consumes upwelled dissolved inorganic carbon (DIC), which hinders surplus CO2 being released to the atmosphere. The export flux of POC is therefore crucial to the carbon and biogeochemical cycles. This study aims to model the long-term (1958–2009) variation of export flux and structure of the biological pump in the South China Sea (SCS) using a three-dimensional physical-biogeochemical coupled (ROMS-CoSiNE) model. The modeled POC export flux in the northeastern and north central SCS is high in winter and low in summer, whereas the flux in the central, southwestern and southern SCS varies following a “W” shape: two maxima in winter and summer, and two minima in spring and autumn. The pattern follows the variation of the East Asian monsoon and is consistent with observations. On the interannual scale, export flux is anti-phased with the El Nino-Southern Oscillation such that El Nino (La Nina) conditions correspond to low (high) export flux. Modeled annual mean POC export flux reaches up to 1.95 mmol m–2 day–1, which is underestimated comparing with field observations. The f-ratio is estimated to be ~0.4. The b value of the Martin equation for POC is 1.18±0.03. Remineralization rate of POC is greater than the classical Martin equation but is consistent with its subtropical counterparts. The modeled results indicate that the SCS is a weak source of atmospheric CO2 with a flux estimated at 1.0 mmol m–2 day–1. The modeled results provide an insight of the temporal and spatial variability of the carbon cycle in this monsoon-driven, semi-enclosed basin.

Based on STM32F407ZET6 microprocessor with ARM Cortex-M4 core, we designed a controller for servo motors and servo drivers of a 4-axis Selective Compliance Assembly Robot Arm (SCARA) robot. The forward and inverse kinematic equations are established, circular interpolation equations in three-dimensional space are derived by using the digital differential analyzer method. The adopted circular interpolation algorithm avoids to judge quadrant and feeding direction, which simplifies the program.

Variability of upper-ocean carbon cycle in the North Pacific during 1958-2010 period is investigated using a physical-biogeochemical model. Comparisons with in situ data from five different oceanographic environments in the South China Sea, Monterey Bay, North Pacific gyre, northwestern Pacific, and Gulf of Alaska indicate that the model usually captures observed seasonal and interannual variability in both sea surface pCO(2) and sea-air CO2 flux. Seasonal variability of pCO(2) and CO2 flux in the North Pacific follows the change in sea surface temperature (SST) closely with high and low values in summer and winter, respectively. Total CO2 modifies pCO(2) seasonal pattern in an opposite manner with respect to SST, and surface wind speed modifies the magnitude of CO2 flux variations. On interannual and decadal time scales, sea surface pCO(2) is primarily controlled by anthropogenic CO2, followed by modulations by the El Nino-Southern Oscillation and the Pacific Decadal Oscillation (PDO), while sea-air CO2 flux is significantly regulated by the PDO and the North Pacific Gyre Oscillation (NPGO). We show that anthropogenic CO2 tends to amplify the influence on CO2 flux from the PDO but to damp the influence from the NPGO.

A novel method of axial displacement measurement based on the double-helix (DH) beam is proposed in this paper. The DH point spread function (DH-PSF) with two prominent lobes which consist of optical beam modes superposing with each other in the Gauss–Laguerre (GL) modal plane has the characteristic that the two lobes can rotate like a binary star about the center of each other in the propagation of the light beam. We figure out the axial displacement with the variation of the rotated angle of the connection line of the two lobes. In this method, a CCD and a phase-only spatial light modulator (SLM) are used in a relatively reliable and simple experimental configuration, with which we can manage to realize high axial measuring resolution. One superb advantage is that the system is immune to the energy fluctuations of the laser source. As a result, the axial displacement measurement has a remarkable application prospect in modern engineering and scientific researches.

A 3-D physical and biological model is used to study the seasonal dynamics of physical and biological processes in the central California Current System. Comparisons of model results with remote sensing and in situ observations along CalCOFI Line 67 indicate our model can capture the spatial variations of key variables (temperature, nutrients, chlorophyll, and so on) on annual mean and seasonal cycle. In the coastal upwelling system, it is the alongshore wind stress that upwells high nutrients to surface from 60 m and stimulates enhanced plankton biomass and productivity in the upwelling season. As a result, coastal species peak in the late upwelling period (May-July), and oceanic species reach the annual maxima in the oceanic period (August-October). The annual maximum occurs in the late upwelling period for new production and in the oceanic period for regenerated production. From the late upwelling period to the oceanic period, stratification is intensified while coastal upwelling becomes weaker. Correspondingly, the coastal ecosystem retreats from similar to 300 to similar to 100 km offshore with significant decline in chlorophyll and primary production, and the oceanic ecosystem moves onshore. During this transition, the decline in phytoplankton biomass is due to the grazing pressure by mesozooplankton in the 0-150 km domain, but is regulated by low growth rates in the 150-500 km offshore domain. Meanwhile, the growth rates of phytoplankton increase in the coastal waters due to deeper light penetration, while the decrease in offshore growth rates is caused by lower nitrate concentrations.

Study design An imaging anatomical measurement. Objective To investigate the anatomical feasibility of percutaneous kyphoplasty for lumbar osteoporotic vertebral compression fractures via a unilateral transverse process-pedicle approach (TPA). Summary of background data Kyphoplasty via a unilateral approach has been reported and good clinical results have been achieved. However, because of the lack of an anatomical study, these approaches have yet to be popularized. Methods A total of 150 lumbar vertebral bodies of 30 patients were simulated kyphoplasty on the computed tomographic scans through conventional transpedicle approach (CTA) and the TPA, respectively. Anatomical parameters including the distance between the entry point and the midline of the vertebral body, the puncture inclination angle, and the success rate of puncture were measured and compared. Results The distance between the entry point and the midline from L1 to L5 lumbar levels varied from 20.6 ± 2.2 mm to 28.6 ± 2.9 mm in the CTA group and from 23.6 ± 2.2 mm to 33.6 ± 2.9 mm in the TPA group. The entry point from L1 to L5 in the TPA group was 3.0 ± 2.1 mm to 5.1 ± 2.7 mm more lateral than that in the CTA group. The medial inclination angles from L1 to L5 were 30.2° ± 6.4° to 47.7° ± 5.4° in the TPA and 15.3° ± 6.0° to 22.8° ± 8.7° in the CTA group. The inclination angles in the TPA group were greater than that in the CTA group and the safe range of the puncture angles was also wider. The success rate was 51.7% in the CTA group and 87.7% in the TPA group. Conclusion The entry point through a TPA was localized at the midline of the transverse process, 3.0 to 5.1 mm outside the lateral margin of the pedicle projection. Compared with CTA, the puncture inclination angle in the TPA approach was much larger with a wider safe puncture range. The TPA approach allowed an easy puncture to meet or surpass the midline of the lumbar vertebral body. Level of evidence N/A.

An iron fertilization experiment conducted during the summer of 2012 dumped over 100 tons of an ironcontaining substance into surface waters of a Haida eddy in the eastern North Pacific to stimulate a large phytoplankton bloom. Announced as a privately funded ocean fertilization effort to increase salmon returns, it attracted considerable press coverage, caused much public controversy and has been widely denounced by the science community. Here, we use available satellite bio-optical measurements from the MODIS/Aqua instrument and AVISO altimeter dynamic height data to examine the timing, magnitude and extent of this artificial iron fertilization experiment, comparing it with natural fertilization events such as volcanic ash deposition and mesascale eddy transport in the Gulf of Alaska. With respect to other Haida eddies over the past 10 years, this event produced the highest chlorophyll concentrations observed late (>400 days) in eddy life history, produced the strongest bloom ever observed in an eddy in late-summer and induced this late-summer bloom earlier in the season than any other eddy. With respect to the local area of the fertilization, this experiment induced the most intensive phytoplanlcton bloom of the past 10 years, similar to 2x stronger than that caused by Kasatochi volcano in 2008, similar to 5 x that typically observed in the region, including any induced by passing eddies of previous years. Due to its limited spatial and temporal scales, however, estimated total annual carbon drawdown over the Gulf of Alaska by this experiment is one order of magnitude smaller than the Kasatochi volcano and mesoscale Haida eddies. The target eddy followed a path typical of previous Haida eddies, but with relatively weak dynamic height and rotational circulation. Satellite-based calculations also suggest that only a small fraction of the dumped iron might have been taken up by phytoplankton. The extent to which this localized experiment may impact higher trophic levels such as salmon remains uncertain. (c) 2014 Elsevier Inc. All rights reserved.

The purpose of this study was to investigate whether the therapeutic activity of gemcitabine (GCB) in hepatocellular carcinoma (HCC) could be increased by the down-regulation of secretory clusterin (sCLU), a glycoprotein that is considered to play a cytoprotective role in the resistance to chemotherapy. The expression of sCLU was detected in HCC tumor tissues and cell lines. A cell viability and apoptosis assay were performed in parental HCC cells or the same cells transfected with sCLU shRNA and treated with or without GCB. The potential downstream pathways were investigated using the Human Apoptosis RT2 Profiler™ PCR Array. The expression levels of sCLU in HCC tissues were significantly higher than in adjacent non-tumor liver tissues and were associated with the histological grade and transarterial chemoembolization. sCLU overexpression was also found in three HCC cell lines and hepatocytes. The depletion of sCLU synergistically increased GCB sensitivity in Bel7402 and SMMC7721 cells and induced cell apoptosis. Based on the PCR array analysis, sCLU depletion also resulted in the up-regulation of BNIP1, GADD45A, TNFRSF10A, and TRADD and down-regulation of AKT1 in Bel7402 and SMMC7721 cells compared with the parental controls. These results were further supported by a Western blot analysis, which showed increased GADD45a protein expression and the decreased expression of phosphorylated AKT. GADD45a overexpression also increased the sensitivity to GCB in the Bel7402 and SMMC7721 cells. Targeting sCLU may be a useful method to enhance the cytotoxic effect of GCB in hepatocellular carcinoma.

A new biogeochemical model has been developed and coupled to a three-dimensional physical model in the Pacific Ocean. With the explicitly represented dissolved organic pools, this new model is able to link key biogeochemical processes with optical processes. Model validation against satellite and in situ data indicates the model is robust in reproducing general biogeochemical and optical features. Colored dissolved organic matter (CDOM) has been suggested to play an important role in regulating underwater light field. With the coupled model, physical and biological regulations of CDOM in the euphotic zone are analyzed. Model results indicate seasonal variability of CDOM is mostly determined by biological processes, while the importance of physical regulation manifests in the annual mean terms. Without CDOM attenuating light, modeled depth-integrated primary production is about 10% higher than the control run when averaged over the entire basin, while this discrepancy is highly variable in space with magnitudes reaching higher than 100% in some locations. With CDOM dynamics integrated in physical-biological interactions, a new mechanism by which physical processes affect biological processes is suggested, namely, physical transport of CDOM changes water optical properties, which can further modify underwater light field and subsequently affect the distribution of phytoplankton chlorophyll. This mechanism tends to occur in the entire Pacific basin but with strong spatial variability, implying the importance of including optical processes in the coupled physical-biogeochemical model.

Common path noise and disturbance in light source and ambient lighting affect detection accuracy of edge contours greatly in optical microscopy. In order to solve this problem, a lateral differential confocal microscopy is proposed based on principle of lateral difference and confocal microscopy. The approach proposed uses confocal dual-receiving light path arrangement and real-time heterodyne subtraction of two signals with lateral offsets by a differential detector to improve the system′s accuracy and detection sensitivity. Theoretical analyses have been presented. In addition, a simple prototype system has been built based on theoretical analyses. Related experiments have been performed under laboratory conditions. Different from former image processing methods, common path noise and additive disturbance in light source and ambient lighting are eliminated before they are recorded. Theoretical analyses and experimental results indicate a more accurate and sensitive result.

[1] In the study, the responses of chlorophyll to decadal oscillations of Kuroshio Extension (KE) between two dynamical states are investigated using satellite data. Associated with the KE stable and unstable states, the surface chlorophyll south of 35°N also undergoes two different contrast patterns: low (high) chlorophyll (∼12% relative to multiyear mean) corresponding to strengthened (weakened) KE jet, i.e., stable (unstable) KE. Two distinct seesaw patterns exist on the north and south side of 35°N for both chlorophyll and sea level anomaly and on the east and west side of 153°E for both chlorophyll and eddy kinetic energy. Similarly, the magnitude of spring bloom was also modulated by decadal variations of KE. The spring bloom was suppressed (enhanced) relative to the magnitude of climatological spring bloom south of 35°N during the KE stable (unstable) period. This change is significant and can reach 35% in extreme years of 2006 and 2009. The decadal variation of chlorophyll in the KE is likely modulated by vertical nutrient supply induced by divergences (convergences) associated with the westward propagation of wind-induced Rossby waves in the central and eastern North Pacific Ocean, which are dynamically modulated by the North Pacific Gyre Oscillations (NPGO) or PDO (Pacific Decadal Oscillations).

Restoring large-scale bone defects, where osteogenesis is slow while infections lurk, with biomaterials represents a formidable challenge in orthopedic clinics. Here, we propose a scaffold-based multipurpose anti-infection and bone repairing strategy to meet such restorative needs. To do this, personalized multifunctional titanium meshes were produced through an advanced additive manufacturing process and dual “TiO2–poly(dopamine)/Ag (nano)” post modifications, yielding macroporous constructs with micro-/nanoporous walls and nanosilver bullets immobilized/embedded therein. Ultrahigh loading capacity and durable release of Ag+ were accomplished. The scaffolds were active against planktonic/adherent bacteria (Gram-negative and positive) for up to 12 weeks. Additionally, they not only defended themselves from biofilm colonization but also helped destroy existing biofilms, especially in combination with antibiotics. Further, the osteoblasts/bacteria coculture study displayed that the engineered surfaces aided...

Based on the extended Huygens–Fresnel diffraction integral, the expressions for the average intensity and the effective size of Laguerre–Gaussian and Bessel–Gaussian Schell-model beams propagating through a paraxial ABCD optical system are obtained in the turbulent atmosphere. The influences of the source coherence and atmospheric turbulence on the propagation of Laguerre–Gaussian and Bessel–Gaussian Schell-model beams in the turbulent atmosphere are investigated in detail. It is found that the beam profile will eventually evolve into a Gaussian-like distribution through turbulence in contrast to ring-shaped far-field pattern in free space. The effective size of Laguerre–Gaussian and Bessel–Gaussian Schell-model beams with lower source coherence is less affected by turbulence. The parameter β and index n of the sources have some effects on intensity distribution and beam spreading through atmospheric turbulence.

National Basic Research Program of China (973 Program) [2009CB421200]; National Natural Science Foundation of China (NSFC) [41121091, 41130857]

Inferred from the satellite and in situ hydrographic data from the 1990s and 2000s, the Kuroshio intrusion into the South China Sea (SCS) had a weakening trend over the past two decades. Associated with the weakened Kuroshio intrusion, the Kuroshio loop and eddy activity southwest of Taiwan became weaker, whereas the water above the salinity minimum became less saline in the northern SCS. The sea surface height southwest of Taiwan increased at a slower rate compared to other regions of the SCS because of the weakened Kuroshio intrusion. Simulations using the Regional Ocean Modeling System (ROMS) Pacific model show that the strength of the Kuroshio intrusion into the SCS decreased from 1993 to 2010 with a negative trend, −0.24 sverdrups (Sv) yr−1 (1 Sv ≡ 106 m3 s−1), in the total Luzon Strait transport (LST). Although wind-induced Ekman transport through the Luzon Strait became weaker, the magnitude at 0.001 Sv yr−1 was too small to compensate for the negative trend of the LST. On the other hand, the piling up of the water induced by monsoon winds was an important mechanism for changing the pressure gradient across the Luzon Strait and eventually affecting the LST. The sea level gradient between the western Pacific and the SCS had a negative trend, −0.10 cm yr−1, corresponding to a negative trend in the geostrophic transport at −0.20 Sv yr−1. The Kuroshio transport east of Luzon Island also had a negative trend, which might also be linked to the weakening Kuroshio intrusion.

New evidences were provided that Kuroshio intrusion in winter is able to increase phytoplankton growth in the open ocean of the northern South China Sea (SCS) based on multiple data sources. Strong fronts due to Kuroshio intrusion and interactions with the SCS water are associated with intense upwelling, supplying high nutrients from the subsurface SCS water and increasing phytoplankton productivity in the frontal region. High chlorophyll is more dynamically related to these fronts than to the alongshore wind, wind stress curl, and eddy kinetic energy on interannual time scale. Further examinations suggest that fronts associated with Kuroshio intrusion into the SCS are linked with large-scale climate variability. During El Nino years, stronger Kuroshio intrusion results in stronger fronts that generate intensified local upwelling and enhanced Luzon winter blooms.

Primary productivity (PP) and phytoplankton structure play an important role in regulating oceanic carbon cycle. The unique seasonal circulation and upwelling pattern of the South China Sea (SCS) provide an ideal natural laboratory to study the response of nutrients and phytoplankton dynamics to climate variation. In this study, we used a three-dimensional (3D) physical–biogeochemical coupled model to simulate nutrients, phytoplankton biomass, PP, and functional groups in the SCS from 1958 to 2009. The modeled results showed that the annual mean carbon composition of small phytoplankton, diatoms, and coccolithophores was 33.7, 52.7, and 13.6 %, respectively. Diatoms showed a higher seasonal variability than small phytoplankton and coccolithophores. Diatoms were abundant during winter in most areas of the SCS except for the offshore of southeastern Vietnam, where diatom blooms occurred in both summer and winter. Higher values of small phytoplankton and coccolithophores occurred mostly in summer. Our modeled results indicated that the seasonal variability of PP was driven by the East Asian Monsoon. The northeast winter monsoon results in more nutrients in the offshore area of the northwestern Luzon Island and the Sunda Shelf, while the southwest summer monsoon drives coastal upwelling to bring sufficient nutrients to the offshore area of southeastern Vietnam. The modeled PP was correlated with El Nino/Southern Oscillation (ENSO) at the interannual scale. The positive phase of ENSO (El Nino conditions) corresponded to lower PP and the negative phase of ENSO (La Nina conditions) corresponded to higher PP.

Understanding how nanomaterials interact with cell membranes is related to how they cause cytotoxicity and is therefore critical for designing safer biomedical applications. Recently, graphene (a two-dimensional nanomaterial) was shown to have antibacterial activity on Escherichia coli, but its underlying molecular mechanisms remain unknown. Here we show experimentally and theoretically that pristine graphene and graphene oxide nanosheets can induce the degradation of the inner and outer cell membranes of Escherichia coli, and reduce their viability. Transmission electron microscopy shows three rough stages, and molecular dynamics simulations reveal the atomic details of the process. Graphene nanosheets can penetrate into and extract large amounts of phospholipids from the cell membranes because of the strong dispersion interactions between graphene and lipid molecules. This destructive extraction offers a novel mechanism for the molecular basis of graphene's cytotoxicity and antibacterial activity.

With the widespread applications of nanomaterials such as carbon nanotubes, there is a growing concern on the biosafety of these engineered nanoparticles, in particular their interactions with proteins. In molecular simulations of nanoparticle-protein interactions, the choice of empirical parameters (force fields) plays a decisive role, and thus is of great importance and should be examined carefully before wider applications. Here we compare three commonly used force fields, CHARMM, OPLSAA, and AMBER in study of the competitive binding of a single wall carbon nanotube (SWCNT) with a native proline-rich motif (PRM) ligand on its target protein SH3 domain, a ubiquitous protein-protein interaction mediator involved in signaling and regulatory pathways. We find that the SWCNT displays a general preference over the PRM in binding with SH3 domain in all the three force fields examined, although the degree of preference can be somewhat different, with the AMBER force field showing the highest preference. The SWCNT prevents the ligand from reaching its native binding pocket by (i) occupying the binding pocket directly, and (ii) binding with the ligand itself and then being trapped together onto some off-sites. The pi-pi stacking interactions between the SWCNT and aromatic residues are found to play a significant role in its binding to the SH3 domain in all the three force fields. Further analyses show that even the SWCNT-ligand binding can also be relatively more stable than the native ligand-protein binding, indicating a serious potential disruption to the protein SH3 function.

The significance of the molecular chirality of drugs has been widely recognized due to the thalidomide tragedy. Most of the new drugs reaching the market today are single enantiomers, rather than racemic mixtures. However, many optically pure drugs, including thalidomide, undergo enantiomerization in vivo, thus negating the single enantiomers' benefits or inducing unexpected effects. A detailed atomic level understanding of chiral conversion, which is still largely lacking, is thus critical for drug development. Herein, we use first-principle density function theory (DFT) to explore the mechanism of enantiomerization of thalidomide. We have identified the two most plausible interconversion pathways for isolated thalidomide: 1) proton transfer from the chiral carbon center to an adjacent carbonyl oxygen atom, followed by isomerization and rotation of the glutarimide ring (before the proton hops back to the chiral carbon atom); and 2) a pathway that is the same as "1", but with the isomerization of the glutarimide ring occurring ahead of the initial proton transfer reaction. There are two remarkable energy barriers, 73.29 and 23.59 kcal mol(-1), corresponding to the proton transfer and the rotation of the glutarimide ring, respectively. Furthermore, we found that water effectively catalyzes the interconversion by facilitating the proton transfer with the highest energy barrier falling to approximately 30 kcal mol(-1), which, to our knowledge, is the first time that this important role of water in chiral conversion has been demonstrated. Finally, we show that the hydroxide ion can further lower the enantiomerization energy barrier to approximately 24 kcal mol(-1) by facilitating proton abstraction, which agrees well with recent experimental data under basic conditions. Our current findings highlight the importance of water and hydroxide ions in the enantiomerization of thalidomide and also provide new insights into the mechanism of enantiomerization at an atomic level.

The widespread application of nanomaterials has spurred an interest in the study of interactions between nanoparticles and proteins due to the biosafety concerns of these nanomaterials. In this review, a summary is presented of some of the recent studies on this important subject, especially on the interactions of proteins with carbon nanotubes (CNTs) and metallofullerenols. Two potential molecular mechanisms have been proposed for CNTs' inhibition of protein functions. The driving forces of CNTs' adsorption onto proteins are found to be mainly hydrophobic interactions and the so-called π-π stacking between CNTs' carbon rings and proteins' aromatic residues. However, there is also recent evidence showing that endohedral metallofullerenol Gd@C82 (OH)22 can be used to inhibit tumor growth, thus acting as a potential nanomedicine. These recent findings have provided a better understanding of nanotoxicity at the molecular level and also suggested therapeutic potential by using nanoparticles' cytotoxicity against cancer cells.

The high resolution tomographic rotates the reference arm and the sample arm to detect the quantitative phase information and the result 3D image has higher resolution and SNR.

Study Design. A retrospective study. Objective. To evaluate the radiological and clinical results of simultaneous surgery with preservation of the posterior vertebral wall for rigid post-traumatic kyphosis in the thoracolumbar spine. Summary of Background Data. Management of rigid post-traumatic kyphosis has been a challenge for surgeons. Current widely used posterior osteotomy procedures have the disadvantages of significant invasiveness, spinal column shortening, and instrumentation-related complications. Methods. From 2004 to 2009, 21 patients with rigid post-traumatic kyphosis in the thoracolumbar spine (T11–L2) were managed in our hospital. Average kyphotic angle was 45.2° ± 11.2° (range, 31°–67°). The surgical technique used was posterior and anterior circumferential release and anterior corpectomy with posterior vertebral wall preservation and short segmental instrumentation. Preoperative and postoperative kyphotic angle was measured to assess the degree of kyphosis correction and maintenance. Changes in low back pain were assessed by Japanese Orthopaedic Association scores. Results. All patients were successfully managed with this procedure without major complications. Most patients (19 of 21) were instrumented with anterior-only fixation, while posterior interspinal wire was added in 2 patients with osteoporosis. The mean blood loss was 470 mL (range, 300–700 mL). Patients were followed for an average of 32 months (range, 6–70 mo) postoperatively. Back pain was relieved to some degree in all patients and the improvement in Japanese Orthopaedic Association scores was 76.9% ± 7.9. Average kyphotic angle was 6.0° ± 5.7° (range, −2 to 17) immediately after surgery and 7.2° ± 5.8° (range, −3 to 17) at final follow-up. Average of 1° of correction loss was documented and all patients obtained solid fusion uneventfully. Conclusion. This technique is indicated for most patients with rigid post-traumatic kyphosis in the thoracolumbar spine and can yield satisfactory clinical results not only in terms of pain relief, kyphosis correction, vertebral height restoration, and spinal canal integrity preservation, but also in reducing the risk of excessive bleeding and spinal cord injury.

In a previous study, we explored the mechanism of urea-induced denaturation of proteins by performing molecular dynamics (MD) simulations of hen lysozyme in 8 M urea and supported the "direct interaction mechanism" whereby urea denatures protein via dispersion interaction (Hua, L.; Zhou, R. H.; Thirumalai, D.; Berne, B. J. Proc. Natl. Acad. Sci. U.S.A. 2008, 105, 16928). Here we perform large scale MD simulations of five representative protein/peptide systems in aqueous urea to investigate if the above mechanism is common to other proteins. In all cases, accumulations of urea around proteins/peptide are observed, suggesting that urea denatures proteins by directly attacking protein backbones and side chains rather than indirectly disrupting water structure as a "water breaker". Consistent with our previous case study of lysozyme, the current energetic analyses with five protein/peptide systems reveal that urea's preferential binding to proteins mainly comes from urea's stronger dispersion interactions with proteins than with bulk solution, whereas the electrostatic (hydrogen-bonded) interactions only play a relatively minor (even negative) role during this denaturation process. Furthermore, the simulations of the peptide system at different urea concentrations (8 and 4.5 M), and with different force fields (CHARMM and OPLSAA) suggest that the above mechanism is robust, independent of the urea concentration and force field used. Last, we emphasize the importance of periodic boundary conditions in pairwise energetic analyses. This article provides a comprehensive study on the physical mechanism of urea-induced protein denaturation and suggests that the "dispersion-interaction-driven" mechanism should be general.

Mesoscale anticyclonic eddies are a common feature in the Gulf of Alaska (GOA). A three-dimensional circulation model is used to examine the general characteristics of eddies in the GOA during 1993–2009. Using an eddy detection algorithm, we tracked on average 6.5 eddies formed each year from the modeled results and 6.9 eddies from altimeter data. Modeled eddy characteristics agree with the remote sensing derived eddy statistics in terms of eddy magnitude, propagation speed, and eddy-core diameter. From the model results, strong seasonal and interannual variations were found in both the number and areal coverage of GOA eddies. At the seasonal scale, more eddies are observed to form from March to May, while the eddy-covered area usually peaks around October. At the interannual scale, our results suggest the years with large eddy-covered area do not necessarily have more eddies generated. The long-term variation of eddy-covered area in the GOA is modulated by El Nino/Southern Oscillation (ENSO) events through altering the local wind stress. Model results indicate one typical Haida eddy could transport 37×10 18 J of heat and 27 km 3 of freshwater from the shelf to the central gulf. The equivalent fluxes caused by Haida eddies are comparable with the annual mean of net heat flux and freshwater flux from the atmosphere into the ocean in the Haida region, implying that mesoscale eddies are important sources contributing to the heat and freshwater budgets.

We perform molecular dynamics simulations of narrow single-walled carbon nanotubes (SWNTs) in aqueous urea to investigate the structure and dynamical behavior of urea molecules inside the SWNT. Even at low urea concentrations (e.g., 0.5 M), we have observed spontaneous and continuous filling of SWNT with a one-dimensional urea wire (leaving very few water molecules inside the SWNT). The urea wire is structurally ordered, both translationally and orientationally, with a contiguous hydrogen-bonded network and concerted urea's dipole orientations. Interestingly, despite the symmetric nature of the whole system, the potential energy profile of urea along the SWNT is asymmetric, arising from the ordering of asymmetric urea partial charge distribution (or dipole moment) in confined environment. Furthermore, we study the kinetics of confined urea and find that the permeation of urea molecules through the SWNT decreases significantly (by a factor of ∼20) compared to that of water molecules, due to the stronger dispersion interaction of urea with SWNT than water, and a maximum in urea permeation happens around a concentration of 5 M. These findings might shed some light on the better understanding of unique properties of molecular wires (particularly the wires formed by polar organic small molecules) confined within both artificial and biological nanochannels, and are expected to have practical applications such as the electronic devices for signal transduction and multiplication at the nanoscale.