Search

Dimethylsulfoxonium propionate (DMSOP) is a recently identified and abundant marine organosulfur compound with purported roles in oxidative stress protection, global carbon and sulfur cycling1. Diverse algae and bacteria synthesise DMSOP from dimethylsulfoniopropionate (DMSP), which potentially limits the production of climate-active gases e.g., dimethylsulfide (DMS) generated from microbial DMSP cleavage1. Here, DMSOP was found at mM levels in saltmarsh sediment, >10-fold higher than DMSP, and orders of magnitude higher than DMSOP levels previously reported in seawater1. Moreover, we showed bacteria could utilise DMSOP as an osmoprotectant. Some bacteria also cleave DMSOP liberating dimethyl sulfoxide (DMSO), an ubiquitous marine metabolite and acrylate1, but the enzymes responsible and their environmental importance were unknown. Here, we elucidated the DMSOP cleavage mechanism/s in diverse heterotrophic bacteria, e.g., SAR11 clade and Roseobacters, and fungi and phototrophic algae, e.g., Emiliania huxleyi, not previously known to have this activity. All these diverse organisms utilised their DMSP lyase ‘Ddd’ or ‘Alma1’ enzymes, that span five protein families, to cleave DMSOP with similar specific activities to DMSP. Bacteria with DMSP lyases that used DMSP as a carbon source likewise used DMSOP. Furthermore, ddd gene transcription in these bacteria was induced by DMSOP, including dddK in SAR11 strain HTCC1062. We determined the structure of DddK bound to DMSOP and concluded that the catalytic mechanisms of DMSOP cleavage by Ddd enzymes were like those for DMSP. Given the predicted teragram DMSOP production budget1, its newly found abundance in marine sediments, and the abundance of microbial DMSP lyase genes and transcripts in marine environments, DMSOP cleavage is likely a globally significant process influencing global carbon and sulfur fluxes and marine ecological interactions.

Arsenic in the marine environment is important because its biogeochemistry is closely linked to the phosphorus cycle . The chemical speciation approaches of dissolved arsenic can identify As(III), As(V), and methylated arsenic species, all of which collectively reveal the involvement of microbial processes in the arsenic cycle. The physical speciation methods, or molecular weight distribution approaches, of dissolved arsenic can disclose the reactivity of arsenic based on the size-reactivity continuum model. We applied a combined physical and chemical characterization method to the dissolved arsenic in seawater from the South China Sea (SCS) to understand arsenic reactivity in the marine biogeochemical cycle . The dissolved inorganic arsenic (DIAs) exhibited typical semi-conservative depth profiles, and the low-molecular-weight (LMW, euphotic zone and mostly remained in the LMW phase. As(V) was therefore the dominant inorganic arsenic species in HMW-DIAs of the SCS. Dissolved organic arsenic (DOAs) exhibited a decreasing trend with depth, with most DOAs restricted to a surface layer of 100 m. Almost half of the DOAs was in the HMW phase, and the HMW-DOAs constituted one-third of the HMW-phase total dissolved arsenic. The occurrence of DOAs in the euphotic zone suggested that arsenic cycling is largely affected by the activities of microbes and plankton organisms. Overall, the biogeochemical cycle of arsenic in the SCS highlights the interactions of physical, chemical and biological factors .

Arsenic (As) has long been recognized as an environmental toxicant. Its biogeochemical cycling in the ocean is often linked to that of phosphorus (P), whose dynamics may affect the efficiency of the marine carbon pump as it relates to CO2 absorption from the atmosphere. The chemical behavior of inorganic arsenate is similar to that of phosphate, and it is also taken up by phytoplankton or bacterioplankton in parallel with phosphate. This absorbed As is then metabolized into arsenite or methylated As and expelled through detoxification processes. However, in surface waters of the oligotrophic ocean where dissolved P is predominantly in organic forms, the regeneration and recycling processes of As remain unclear. Here, we demonstrate the first depth profiles of high-molecular-weight (HMW, 1 kDa-0.4 μm) As and dissolved organic phosphorus (DOP) in oligotrophic waters and their short-term variations in the euphotic zone. HMW-As constituted 21% ± 8% of dissolved As, whereas the high-molecular-weight dissolved organic phosphorus (HMW-DOP) decreased from 74% of the total DOP at the surface to 35% at a 200 m depth. Concurrent variations of HMW-As and HMW-DOP in the upper euphotic zone were identified for the first time. This also provides new evidence from direct observation supporting the size-reactivity continuum model. These temporal changes may result from light-driven enhancement of photoheterotrophy. Overall, our results highlight the contribution of microbes to the production and assimilation of HMW materials and signify their importance in marine As and P cycles.

In vast, warm regions of the oceans, phytoplankton face the problem of arsenic poisoning. Arsenate is toxic because it is chemically similar to phosphate, a scarce nutrient that phytoplankton cells need for growth. Many phytoplankton, including the commonest phytoplankton type in warm oceans, Prochlorococcus, detoxify arsenate by adding methyl groups. Here we show that the most abundant non-photosynthetic plankton in the oceans, SAR11 bacteria, remove the methyl groups, releasing poisonous forms of arsenic back into the water. We postulate that the methylation and demethylation of arsenic compounds creates a cycle in which the phytoplankton can never get ahead and must continually transfer energy to the SAR11 bacteria. We dub this a parasitic process and suggest that it might help explain why SAR11 bacteria are so successful, surpassing all other plankton in their numbers. Field experiments were done in the Sargasso Sea, a subtropical ocean gyre that is sometimes called an ocean desert because, throughout much of the year, there is not enough phosphorous in the water to support large blooms of phytoplankton. Ocean deserts are expanding as the oceans absorb heat and grow warmer., In many regions of the world oceans, phytoplankton face the problem of discriminating between phosphate, an essential nutrient, and arsenate, a toxic analogue. Many phytoplankton, including the most abundant phytoplankton group known, Prochlorococcus, detoxify arsenate (AsV) by reduction to arsenite (AsIII), followed by methylation and excretion of the methylated arsenic products. We synthesized [14C]dimethyl arsenate (DMA) and used it to show that cultured Pelagibacter strain HTCC7211 (SAR11) cells oxidize the methyl group carbons of DMA, producing 14CO2 and ATP. We measured [14C]DMA oxidation rates in the P-depleted surface waters of the Sargasso Sea, a subtropical ocean gyre. [14C]DMA was oxidized to 14CO2 by Sargasso Sea plankton communities at a rate that would cause turnover of the estimated DMA standing stock every 8.1 days. SAR11 strain HTCC7211, which was isolated from the Sargasso Sea, has a pair of arsenate resistance genes and was resistant to arsenate, showing no growth inhibition at As/P ratios of >65:1. Across the global oceans, there was a strong inverse relationship between the frequency of the arsenate reductase (LMWPc_ArsC) in Pelagibacter genomes and phosphate concentrations. We propose that the demethylation of methylated arsenic compounds by Pelagibacter and possibly other bacterioplankton, coupled with arsenate resistance, results in the transfer of energy from phytoplankton to bacteria. We dub this a parasitic cycle because the release of arsenate by Pelagibacter in principle creates a positive-feedback loop that forces phytoplankton to continually regenerate arsenate detoxification products, producing a flow of energy to P-limited ocean regions.

The distributions of many trace elements in the ocean are strongly associated with the growth, death, and re-mineralization of marine plankton and those of suspended/sinking particles. Here, we present an all plastic (Polypropylene and Polycarbonate), multi-layer filtration system for collection of suspended particulate matter (SPM) at sea. This ultra-clean sampling device has been designed and developed specifically for trace element studies. Meticulous selection of all non-metallic materials and utilization of an in-line flow-through procedure minimizes any possible metal contamination during sampling. This system has been successfully tested and tweaked for determining trace metals (e.g., Fe, Al, Mn, Cd, Cu, Ni) on particles of varying size in coastal and open ocean waters. Results from the South China Sea at the South East Asia Time-Series (SEATS) station indicate that diurnal variations and spatial distribution of plankton in the euphotic zone can be easily resolved and recognized. Chemical analysis of size-fractionated particles in surface waters of the Taiwan Strait suggests that the larger particles (>153 µm) were mostly biologically derived, while the smaller particles (10 - 63 µm) were mostly composed of inorganic matter. Apart from Cd, the concentrations of metals (Fe, Al, Mn, Cu, Ni) decreased with increasing size.

Summary Introduction As a rule, diverticulosis of the appendix is identified incidentally during a pathological examination after an appendectomy. The disease is rare and easily ignored. Only one case has been reported in Taiwan. Aim In this study, we retrospectively reviewed the medical records of patients who had undergone appendectomy at the Ton Yen General Hospital, a local hospital in Taiwan. Methods From June 2004 to May 2012, 10 patients with appendiceal diverticulosis were documented. Their clinical presentations, laboratory data, and pathological characteristics were analyzed. Results All patients were diagnosed after their operations. The incidence rate was 0.88% (10/1131). The patients comprised eight men and two women. The age distribution was 22–71 years with an average of 39.2 years. All diverticula were acquired, not congenital. Eight patients presented with acute appendicitis and diverticulitis, one patient presented with a normal appendix and acute diverticulitis, and one patient presented with periappendicitis with a noninflammatory diverticulum. Three patients also presented with mucoceles, one patient with a hyperplastic polyp, and two patients had a severe case of inflammation with epithelial regenerative atypia and mild dysplasia. The number of diverticula for each patient ranged from one to six. Multiple diverticula were present in 80% of the patients. In 90% of the patients, the diverticula were located in the distal portion of the appendix. Perforation was noted in seven (70%) patients. Conclusion The diverticula could have been preoperatively diagnosed with careful differentiation of the clinical presentations. High-resolution ultrasound or CT scans may facilitate diagnosis. The recommended treatment for asymptomatic appendiceal diverticulosis is prophylactic appendectomy because of the high perforation rate and a significant association with neoplasia. Once a surgical specimen is obtained, we advise conducting a thorough pathologic examination and securing additional sections to identify a greater number of diverticula, perforations, and associated neoplasms.

At sub-40 nm CMOS technology nodes, the implementation of shallow trench isolation (STI) becomes more challenging due to shrinking geometries and stricter device leakage requirements. As device geometries are shrinking, STI liner is also becoming thinner and plays an important role for the minimal consumption of device active area while effectively rounding the STI corner and minimizing stress-induced defects. Consequently, STI stress is enhanced by the scaling of STI-pitch, the volume expansion induced by STI liner and film stress of filling materials. This paper discusses the benefits of SiON liner growth by decoupled-plasma-nitridation (DPN) and SiON liner induced stress compared to conventional pure oxide liner growth by in situ steam generation (ISSG). Thin STI SiON liner offers lower sub-threshold leakage current without drive current loss for transistor performance. Moreover, junction leakage current is also reduced with scaling device active area. Thus, better device performance results in better minimum operation voltage (Vcc_min) of low-power 6T-SRAM. This paper demonstrates the influences of thin STI SiON liner growth by DPN in STI manufacture.

Shallow trench isolation (STI) induced mechanical stress affects the device behavior in the advanced complementary metal oxide semiconductor (CMOS) technology. This article presents how to use an optimal STI process to reduce transistor mismatch and leakage current induced standby current in static random access memory (SRAM). The STI induced mechanical stress affects the device behavior in the advanced CMOS technology. The optimized STI process can reduce junction and bulk leakage that occurs on the STI sidewall due to STI compressive stress enhancing boron diffusion and increasing junction electric field of STI sidewall resulting in band-to-band-tunneling (BTBT) degradation. An obvious decrease in BTBT occurs on STI edge sidewall that is observed by using the optimized STI process. Meanwhile, the optimized STI process has better length of diffusion effect. Moreover, the optimized STI process can improve the parasitic device at STI edge because of smaller divot. Since random fluctuation of channel dopant...

Groundwaters in the confined aquifers of the Chianan and Ilan coastal plains of Taiwan are rich in dissolved methane (CH4). Serious endemic “blackfoot disease”, which occurred in the Chianan plain, especially during AD1950-1970, has been demonstrated to have arisen from drinking highly reducing groundwater with abnormal arsenic and humic substance levels. In order to explore the origin of CH4 and its hydrological implications, stable carbon isotope ratios (δ13C) and radiocarbon (14C) ages of exsolved CH4, dissolved inorganic carbon (DIC), and sedimentary biogenic sediments from a total of 34 newly completed water wells at 16 sites were determined. The main results obtained are as follows: (1) The δ 13 C CH 4 (−65‰ to −75‰) values indicate that, except for one thermogenic sample ( δ 13 C CH 4 = 38.2 ‰ ) from the Ilan plain, all CH4 samples analyzed were produced via microbially mediated CO2 reduction. Many δ13CDIC values are considerably greater than −10‰ and even up to ∼10‰ due to Rayleigh enrichment during CO2 reduction. (2) Almost all the 14C ages of CH4 samples from the shallow aquifer (I) (

A short-term cost criterion is introduced to model the productivity of an M/G/1 queuing/production system; the cost is a weighted sum of penalties associated with the work rate control, penalties associated with part waiting time, and penalties on the increase of parts in the queue, assessed during the time required to serve a single part. The distribution of the service time is of general form, parameterized by the work rate (the control variable). The decision epochs for the optimal control policy are restricted to the times when service is initiated for a part. The major advantages of this formulation are generality and mathematical tractability of the optimal solution. A simple nonlinear search routine is needed to determine the optimal work rate. For the special case of an exponential service time distribution and the special case where service is modeled by a diffusion-threshold process, analytical expressions for the optimal control policy in terms of the queue length are obtained. >

A design for the polycrystalline gate is developed for 65 nm low power complementary metal oxide semiconductor (CMOS) technology. Using the poly deposition, a less poly depletion effect and a decrease in the electrical gate dielectric thickness (T ox ) can be obtained. Also, the poly deposition successfully reduces the roughness of the poly surface and produces a smaller poly grain size after subsequent rapid thermal processing steps. Meanwhile, the poly deposition can suppress the short channel effect and can reduce off-state leakage current. The poly deposition results in better voltage ramp dielectric breakdown and uniformity on a specific test vehicle. The I dsat asymmetry characteristics of the device are also improved by the poly deposition. The V cc_min of the 0.525 μm 2 cell size 6T-static random access memory using the poly deposition is also improved due to leakage current reduction and well I dsat asymmetry.

An M/G/1 queue is introduced to model the productivity of a production system. Parts arrive according to to a Poisson process. The distribution of the production time is of general form, parameterized by a control variable - the production rate. The decision epochs for the control policy are restricted to the times when production is initiated for a part. A short-term cost is introduced as a weighted sum of penalties associated with the production rate control, penalties associated with part waiting time and penalties on the increase of parts in the queue, assessed during the time required to produce a single part. The major advantages of this formulation are generality, mathematical tractability of the problem and the properties of the closed-loop production system. A simple nonlinear search routine is required to determine the optimal production rate. For the special case of an exponential production time distribution and the special case where the production is modeled by a diffusion-threshold process, analytical expressions for the optimal control policy in terms of the queue length are obtained. A transportation example is presented to illustrate the design methodology; statistical data from computer simulation is obtained to evaluate the performance of the adaptive control policy.

This paper presents the development of the generalized d'Alembert equations of motion for application to mechanical manipulators with rotary joints. These equations, when applied to a robot arm, result in an efficient and explicit set of closed form second order nonlinear differential equations with vector cross product terms. They give fairly well "structured" equations of motion suitable for control analysis and manipulator design. The interaction and coupling reaction forces/torques between the neighboring joints of a manipulator can be easily identified as coming from the translational and rotational effects of the links. With this information, either a simplified dynamic model can be developed or an appropriate controller can be designed to compensate the nonlinear effects. Applications to manipulator control and design are discussed together with the computational complexities of the dynamic coefficients in the generalized d'Alembert equations of motion.

A parts queueing system is studied where the arrival of parts is according to a Poisson process and a diffusion-threshold process is proposed for modeling the service times. A work rate is the control variable; it is shown to affect the service time probability distribution in an explicit way. The sojourn time for a part is found to be monotone decreasing as a function of this work rate under some reasonable conditions. A class of optimization problems minimizing the weighted sum of the sojourn time and control effort is formulated.

Most of the existing off-line trajectory planning schemes focus on the requirements that the trajectory must be smooth and continuous. This paper, based on discrete time trajectory analysis, extends these concepts and includes the manipulator dynamics in the planning of straight line trajectory in the Cartesian space. The planning of straight line trajectory is performed in the Cartesian space and requires optimization in the jointvariable space. An iterative forward and backward search algorithm coupled with a modified forward search algorithm are developed to determine the joint values at each control set point on the given straight line within the bounds imposed by the smoothness and torque constraints. These sets of joint position, velocity and acceleration will be used as referenced inputs to the manipulator controller for the joint-variable space control [1] or can be used to determine the corresponding Cartesian position, velocity, and acceleration on the straight line for the Cartesian space control. The proposed straight line trajectory planning will be useful for obstacle avoidance and the resolved motion adaptive control [2].