Effects of El Niño–Southern Oscillation events on catches of Bigeye Tuna (Thunnus obesus) in the eastern Indian Ocean off Java

The effects of El Niño–Southern Oscillation events on catches of Bigeye Tuna (Thunnus obesus) in the eastern Indian Ocean (EIO) off Java were evaluated through the use of remotely sensed environmental data (sea-surface-height anomaly [SSHA], sea-surface temperature [SST], and chlorophyll a concentration), and Bigeye Tuna catch data. Analyses were conducted for the period of 1997–2000, which included the 1997–98 El Niño and 1999–2000 La Niña events. The empirical orthogonal function (EOF) was applied to examine oceanographic parameters quantitatively. The relationship of those parameters to variations in catch distribution of Bigeye Tuna was explored with a generalized additive model (GAM). The mean hook rate was 0.67 during El Niño and 0.44 during La Niña, and catches were high where SSHA ranged from –21 to 5 cm, SST ranged from 24°C to 27.5°C, and chlorophyll-a concentrations ranged from 0.04 to 0.16 mg m–3. The EOF analysis confirmed that the 1997–98 El Niño affected oceanographic conditions in the EIO off Java. The GAM results indicated that SST was better than the other environmental factors (SSHA and chlorophyll-a concentration) as an oceanographic predictor of Bigeye Tuna catches in the region. According to the GAM predictions, the highest probabilities (70–80%) for Bigeye Tuna catch in 1997–2000 occurred during oceanographic conditions during the 1997–98 El Niño event.

Development of low entropy coding in a recurrent network.

In this paper we present an unsupervised neural network which exhibits competition between units via inhibitory feedback. The operation is such as to minimize reconstruction error, both for individual patterns, and over the entire training set. A key difference from networks which perform principal components analysis, or one of its variants, is the ability to converge to non-orthogonal weight values. We discuss the network's operation in relation to the twin goals of maximizing information transfer and minimizing code entropy, and show how the assignment of prior probabilities to network outputs can help to reduce entropy. We present results from two binary coding problems, and from experiments with image coding.

Composition and decomposition in bimanual dynamic learning.

Our ability to skillfully manipulate an object often involves the motor system learning to compensate for the dynamics of the object. When the two arms learn to manipulate a single object they can act cooperatively, whereas when they manipulate separate objects they control each object independently. We examined how learning transfers between these two bimanual contexts by applying force fields to the arms. In a coupled context, a single dynamic is shared between the arms, and in an uncoupled context separate dynamics are experienced independently by each arm. In a composition experiment, we found that when subjects had learned uncoupled force fields they were able to transfer to a coupled field that was the sum of the two fields. However, the contribution of each arm repartitioned over time so that, when they returned to the uncoupled fields, the error initially increased but rapidly reverted to the previous level. In a decomposition experiment, after subjects learned a coupled field, their error increased when exposed to uncoupled fields that were orthogonal components of the coupled field. However, when the coupled field was reintroduced, subjects rapidly readapted. These results suggest that the representations of dynamics for uncoupled and coupled contexts are partially independent. We found additional support for this hypothesis by showing significant learning of opposing curl fields when the context, coupled versus uncoupled, was alternated with the curl field direction. These results suggest that the motor system is able to use partially separate representations for dynamics of the two arms acting on a single object and two arms acting on separate objects.

中药青蒿萜类代谢物谱分析及青蒿素生物合成的研究

青蒿素是从中药青蒿，学名黄花蒿（Artemisia annua L.）植物地上部分分离出的抗疟疾有效单体，为一种倍半萜内酯类化合物，其生物合成途径属于植物类异戊二烯代谢途径。青蒿素生物合成途径及其调控机制仍不完全清楚，本论文采用GC-MS 和GC×GC-TOFMS 方法对青蒿萜类代谢物谱进行检测，用多维统计学方法对检测结果进行整理和比较分析，研究青蒿素生物合成及其与青蒿中其他萜类代谢的关系，取得了以下结果： 一、通过GC×GC-TOFMS 方法对青蒿挥发油成分进行分析，共鉴定出303 种组分。其中挥发油中相对百分含量大于1%的10 种组分中有9 种为萜类化合物，含量接近总挥发油的50%。在相对百分含量大于0.1%的49 种成分中，有30 种萜类化合物。有27 种相对百分含量大于0.1%的成分首次在青蒿挥发油中报道，其中包括10 种萜类化合物。 二、利用GC-MS 方法分析了青蒿001 和SP18 两个青蒿素高产株系不同生长时期萜类代谢物谱，结果表明：青蒿中萜类化合物在不同时期合成和积累是动态变化的，萜类化合物的种类和数量在营养生长期随生长时间的延长而提高，在营养生长后期和现蕾前期达到最高水平，进入生殖生长后随生长时间的延长而迅速降低。通过多维统计PLS-DA（Partial Leasted Square Discriminant Analysis） 分析，确定001 中有17 个化合物的含量在不同生长时期有明显变化，其中15 个为萜类化合物。SP18 中有18 个化合物的含量在不同生长时期有明显变化，其中16 个为萜类化合物。青蒿素，青蒿酸，二氢青蒿酸，青蒿素B 都是含量变化明显的标记物。其中青蒿酸和二氢青蒿酸含量在营养生长后期达到最高水平，进入生殖生长后迅速下降，而青蒿素和青蒿素B 在整个检测时期含量变化相对较小，在营养生长时期含量已经较高，在现蕾前期含量稍有上升，进入现蕾期后有所下降，本研究确定现蕾前期为代谢物谱分析最佳取样时期，并为药材采收提供指导。 三、不同基因型青蒿代谢物谱研究表明，青蒿素高产株系SP18 和001 代谢物表现出一定的差异，通过多维统计PLS-DA 分析，共找出了22 种在两种基因型中差异明显的化合物，其中包括倍半萜化合物12 种，单萜化合物3 种，三萜化合物4 种。SP18 特征化合物为樟脑和两个未鉴定倍半萜化合物，而001 特征化合物是龙脑和β-法呢烯。另外两种基因型中青蒿素及相关前体化合物的积累模式差异明显，SP18 中二氢青蒿酸和青蒿素含量高，而青蒿酸和青蒿素B 含量极低；001 中二氢青蒿酸和青蒿素含量相对SP18 要低，但青蒿素B 和青蒿酸含量比SP18 要高。该结果表明在青蒿素高产株系中，青蒿素含量与二氢青蒿酸的含量呈正相关，结合Brown 等的活体标记研究结果分析，从二氢青蒿酸到青蒿素的转化可能是青蒿素合成的限速步骤。 四、利用GC×GC-TOFMS 方法对转基因青蒿萜类代谢物谱进行了分析，共对200 个左右化合物峰进行PLS-DA 和OSC-PLS (Orthogonal Signal Correction–Partial leasted Square)多维统计分析，结果表明：青蒿萜类代谢物谱在外源基因转入后发生显著变化，与对照株系相比均呈现显著差异。其中过量表达Amorpha-4,11-diene 合酶基因（ads）株系中青蒿素及相关化合物变化最明显，而过量表达FPP 合酶基因（fps）株系中青蒿素及相关化合物变化相对较小，在受到调控而成为差异标记物的化合物中，70%是倍半萜类化合物。 五、考察了外源茉莉酸甲酯对青蒿素生物合成的影响，结果表明：300 μM 外源茉莉酸甲酯能提高青蒿素含量，在处理后第8 天青蒿素含量提高38%。青蒿萜类代谢物谱研究表明，茉莉酸甲酯不仅可以诱导青蒿中青蒿素的合成，还能诱导很多化合物，特别是倍半萜和三萜类的合成。OSC-PLS 分析结果找出了9 个处理后含量明显提高的标记物，其中6 个倍半萜化合物，3 个三萜化合物。标记物鲨烯含量提高了67%，另一个未鉴定出结构的倍半萜提高了60%，这些化合物可能与青蒿素有着类似的调控机制，而外源喷洒茉莉酸甲酯可以作为提高青蒿素产量的有效途径之一。

Climate signals in the lower stratosphere and upper troposphere

Empirical orthogonal function (EOF) analysis and regression analysis are used to investigate zonally averaged seasonal temperature anomaly patterns and trends in the lower stratosphere and upper troposphere. The first four EOFs explain 64 percent of the temperature variance and can be related, respectively, to the solar flux (SF) and El Niño/Southern Oscillation (ENSO), to the quasi-biennial oscillation (QBO), to atmospheric carbon dioxide (CO2) and turbidity (TB), and to ENSO. The signal of the fourth EOF is modulated in January to March by the solar flux, with the sense of the modulation determined by the phase of the quasi-biennial oscillation.

ENSO influences on atmospheric circulation and precipitation in the western United States

EXTRACT (SEE PDF FOR FULL ABSTRACT): The influence of ENSO on atmospheric circulation and precipitation over the western United States is presented from two perspectives. First, ENSO-associated circulation patterns over the North Pacific/North America sector were identified using an REOF (rotated empirical orthogonal function) analysis of the 700-mb height field and compositing these for extreme phases of the Southern Oscillation Index. ... Second, we examine the variability of precipitation during the warm and cool phases of ENSO for different locations in the western United States.

The near-AD 1600 multi-proxy puzzle

EXTRACT (SEE PDF FOR FULL ABSTRACT): A varve chronology with annual resolution (AD 1117-1992) has been developed recently for Santa Barbara Basin. Varve thickness and water content show an exponential trend consistent with expected patterns in the presence of sediment compaction over time. Annual varve thickness was decomposed into orthogonal components using singular spectrum analysis (SSA) to identify and retrieve inter-decadal oscillations. ... This suggests a connection with global-scale decadal cycles identified in the subtropical Pacific gyre circulation and, possibly, with solar-driven phenomena. The near-1600 AD event coincides with (a) a similarly sudden change of state in nearby Santa Monica Basin that triggered the onset of anoxic conditions and the preservation of laminated sediments, (b) an extreme drought over the American Southwest, (c) a transformation of the age structure in a number of forest populations throughout Arizona and New Mexico. Total organic carbon burial flux in Santa Barbara Basin varves also shows a marked change after AD 1600. A possible climatic link is proposed that involves pathways for moisture transport in the Southwest at decadal and longer time scales.

Analysis of the piston ring/liner oil film development during warm-up for an SI-engine

A one-dimensional ring-pack lubrication model developed at MIT is applied to simulate the oil film behavior during the warm-up period of a Kohler spark ignition engine [1]. This is done by making assumptions for the evolution of the oil temperatures during warm-up and that the oil control ring during downstrokes is fully flooded. The ring-pack lubrication model includes features such as three different lubrication regimes, i.e. pure hydrodynamic lubrication, boundary lubrication and pure asperity contact, non-steady wetting of both inlet and outlet of the piston ring, capability to use all ring face profiles that can be approximated by piece-wise polynomials and, finally, the ability to model the rheology of multi-grade oils. Not surprisingly, the simulations show that by far the most important parameter is the temperature dependence of the oil viscosity. This dependence is subsequently examined further by choosing different oils. The baseline oil is SAE 10W30 and results are compared to those using the SAE 30 and the SAE 10W50 oils.

Behavior of bulk melt-textured YBCO single domains subjected to crossed magnetic fields

We have experimentally investigated the crossed magnetic field effects on bulk melt-processed YBCO single domains. The samples were first permanently magnetized along their c-axis and then subjected to several cycles of a transverse magnetic field parallel to the ab planes. The magnetic properties along the c and ab directions were simultaneously measured using a couple of orthogonal pick-up coils as well as a Hall probe placed against the sample surface. The effects of both sweep amplitude and polarity were investigated. Field sweeps of alternate polarities are shown to affect the decay of the c-axis magnetization much more strongly than field sweeps of unique polarity do. However, the c-axis magnetization does not show any saturation even after a large number of field sweeps. Next, a micro-Hall probe scanning system was used to measure the distribution of magnetic induction over the top surface of the single domain subjected to the same combination of magnetic fields. The results are shown to be consistent with those determined with the sensing coils and bring out the role played by geometric effects.

Experimental demonstration of a record high 11.25Gb/s real-time optical OFDM transceiver supporting 25km SMF end-to-end transmission in simple IMDD systems.

The fastest ever 11.25Gb/s real-time FPGA-based optical orthogonal frequency division multiplexing (OOFDM) transceivers utilizing 64-QAM encoding/decoding and significantly improved variable power loading are experimentally demonstrated, for the first time, incorporating advanced functionalities of on-line performance monitoring, live system parameter optimization and channel estimation. Real-time end-to-end transmission of an 11.25Gb/s 64-QAM-encoded OOFDM signal with a high electrical spectral efficiency of 5.625bit/s/Hz over 25km of standard and MetroCor single-mode fibres is successfully achieved with respective power penalties of 0.3dB and -0.2dB at a BER of 1.0 x 10(-3) in a directly modulated DFB laser-based intensity modulation and direct detection system without in-line optical amplification and chromatic dispersion compensation. The impacts of variable power loading as well as electrical and optical components on the transmission performance of the demonstrated transceivers are experimentally explored in detail. In addition, numerical simulations also show that variable power loading is an extremely effective means of escalating system performance to its maximum potential.

Adaptively modulated optical OFDM modems utilizing RSOAs as intensity modulators in IMDD SMF transmission systems.

Detailed investigations of the transmission performance of adaptively modulated optical orthogonal frequency division multiplexed (AMOOFDM) signals converted using reflective semiconductor optical amplifiers (RSOAs) are undertaken over intensity-modulation and direct-detection (IMDD) single-mode fiber (SMF) transmission systems for WDM-PONs. The theoretical RSOA model adopted for modulating the AMOOFDM signals is experimentally verified rigorously in the aforementioned transmission systems incorporating recently developed real-time end-to-end OOFDM transceivers. Extensive performance comparisons are also made between RSOA and SOA intensity modulators. Optimum RSOA operating conditions are identified, which are independent of RSOA rear-facet reflectivity and very similar to those corresponding to SOAs. Under the identified optimum operating conditions, the RSOA and SOA intensity modulators support the identical AMOOFDM transmission performance of 30Gb/s over 60km SMFs. Under low-cost optical component-enabled practical operating conditions, RSOA intensity modulators with rear-facet reflectivity values of >0.3 outperform considerably SOA intensity modulators in transmission performance, which decreases significantly with reducing RSOA rear-facet reflectivity and optical input power. In addition, results also show that use can be made of the RSOA/SOA intensity modulation-induced negative frequency chirp to improve the AMOOFDM transmission performance in IMDD SMF systems.

Significant improvements in optical power budgets of real-time optical OFDM PON systems.

Based on a comprehensive theoretical optical orthogonal frequency division multiplexing (OOFDM) system model rigorously verified by comparing numerical results with end-to-end real-time experimental measurements at 11.25Gb/s, detailed explorations are undertaken, for the first time, of the impacts of various physical factors on the OOFDM system performance over directly modulated DFB laser (DML)-based, intensity modulation and direct detection (IMDD), single-mode fibre (SMF) systems without in-line optical amplification and chromatic dispersion compensation. It is shown that the low extinction ratio (ER) of the DML modulated OOFDM signal is the predominant factor limiting the maximum achievable optical power budget, and the subcarrier intermixing effect associated with square-law photon detection in the receiver reduces the optical power budget by at least 1dB. Results also indicate that, immediately after the DML in the transmitter, the insertion of a 0.02nm bandwidth optical Gaussian bandpass filter with a 0.01nm wavelength offset with respect to the optical carrier wavelength can enhance the OOFDM signal ER by approximately 1.24dB, thus resulting in a 7dB optical power budget improvement at a total channel BER of 1 × 10(-3).

Performance optimization of adaptive loading algorithms for SMF-based optical OFDM transceivers

Detailed investigations of the effectiveness of three widely adopted optical orthogonal frequency division multiplexing (OOFDM) adaptive loading algorithms, including power loading (PL), bit loading (BL), and bit-and-power loading (BPL), are undertaken, over < 100km single-mode fibre (SMF) system without incorporating inline optical amplification and chromatic dispersion (CD) compensation. It is shown that the BPL (PL) algorithm always offers the best (worst) transmission performance. The absolute transmission capacity differences between these algorithms are independent of transmission distance and launched optical power. Moreover, it is shown that in comparison with the most sophisticated BPL algorithm, the simplest PL algorithm is effective in escalating the OOFDM SMF links performance to its maximum potential. On the other hand, when employing a large number of subcarriers and a high digital-to-analogue DAC)/analogue-to-digital (ADC) sampling rate, the sophisticated BPL algorithm has to be adopted. © 2011 IEEE.

Simple adaptively modulated optical OFDM modems using subcarrier modulation with input/output reconfigurability

Three novel designs of adaptively modulated optical orthogonal frequency division multiplexing modems using subcarrier modulation (AMOOFDM-SCM) are proposed, for the first time, each of which requires a single IFFT/FFT operation. These designs has a number of salient advantages including a significantly simplified modem configuration due to the involvement of a single IFFT/FFT operation, input/output reconfigurability, dynamic bandwidth allocation capability, cost reduction and system flexibility and performance robustness to variations in transmission link conditions. Investigations show that these three modems are capable of supporting >60Gb/s AMOOFDM-SCM signal transmission over 20km, 40km and 60km single-mode fibre-based intensity modulation and direct detection transmission links without optical amplification and chromatic dispersion compensation. Copyright © 2010 The authors.

Experimental demonstration of real-time optical OFDM Transmission at 7.5 Gb/s over 25-km SSMF using a 1-GHz RSOA

The 7.5-Gb/s real-time end-to-end optical orthogonal frequency-division- multiplexing (OOFDM) transceivers incorporating variable power loading on each individual subcarrier are demonstrated experimentally using a live-optimized reflective semiconductor optical amplifier intensity modulator having a modulation bandwidth as narrow as 1 GHz. Real-time OOFDM signal transmission at 7.5 Gb/s over 25-km standard single-mode fiber is achieved across the $C$-band in simple intensity modulation and direct detection systems without in-line optical amplification and dispersion compensation. © 2006 IEEE.