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Regarding the humane use of animals in scientific research, invertebrates are often recommended in toxicological studies. "Freshwater planarians" refers to numerous free-living freshwater members of the Class "Turbellaria" of the phylum Platyhelminthes. This group of invertebrates has received extensive attention from biologists for many years because of their unique biological characteristics, such as the primitive form of the central nervous system and notable capability to regenerate tissues. Using freshwater planarians as test animals in chemical toxicity studies has grown in popularity since the 1960s. Results from various toxicological experiments have collectively suggested that freshwater planarians can serve as not only alternative models for chemical toxicity screenings in laboratories but also as potential bioindicators for the quality of freshwater environments. However, thus far, no standardized battery of tests for conducting toxicological studies that includes freshwater planarians has been proposed. This paper comprehensively reviews the toxicological information obtained from chemically exposed planarians and proposes practical factors for consideration in toxicity experiments with freshwater planarians as test organisms.

Although a freshwater planarian is proposed as a potential model for studying toxicities of environmental pollutants, they are less sensitive to metal exposures, compared to other freshwater invertebrates. We hypothesised that the metal uptake is low in treated planarians, which may lead to their higher tolerance to metals. The acute toxicities of Cu and Zn to Dugesia japonica were determined. The 24- and 48-h median lethal concentrations were 4.50 and 3.46 mg L−1, respectively, for Cu, and 41.97 and 37.79 mg L−1, respectively, for Zn. Accordingly, combining with the data on Cd in our previous study, higher tolerance of planarians to metals was revealed. Also, tissue levels of Cd, Cu, and Zn in treated D. japonica were determined, and their dissolved uptake rate constants (k1) were calculated. Results showed that bioaccumulations of these metals in D. japonica were, indeed, lower than that in other freshwater invertebrates having higher susceptibilities to these metals.

Using specific neurobehaviors as endpoints, previous studies suggested that planarian neurotransmission systems could be targets of Cd neurotoxicity. However, direct evidence for disturbed neurotransmission systems by Cd in treated planarians is still lacking. In planarians, dopamine (DA) and serotonin (5-HT) play critical roles in neuromuscular function, but little is known about their metabolic degradation. Therefore, in this study, we attempted to determine the appearances of DA, 5-HT, and their metabolic products in the freshwater planarian Dugesia japonica, characterize the activity of enzymes involved in their metabolism, and investigate the effects of Cd on planarian 5-HTergic and DAergic neurotransmission systems. Only DA, 5-HT, and 5-hydroxyindole-3-acetic acid (5-HIAA) were found in planarian tissues. Further enzymatic study revealed the activity of planarian monoamine oxidase (MAO) but not catechol-O-methyl transferase (COMT). These findings suggest that planarian MAO catalyzes the metabolism of 5-HT into 5-HIAA. However, DA metabolites from the MAO-involved metabolic pathway were not found, which might be due to a lack of COMT activity. Finally, in Cd-treated planarians, tissue levels of 5-HT and DA were decreased and MAO activity altered, suggesting that planarian neurotransmission systems are disturbed following Cd treatment.

Although toxic responses of freshwater planarians after exposure to environmental toxicants can be observed through external toxicological end points, physiological responses inside the bodies of treated planarians have rarely been investigated. The present study was designed, using cadmium (Cd) as a reference toxicant, to determine its bioaccumulation and toxicodynamics in the freshwater planarian, Dugesia japonica, after acute toxicity was obtained. Accumulated Cd concentrations, metallothionein levels, and the oxidative status in planarians were determined after exposure to Cd. Furthermore, we hypothesized that the acute death of Cd-treated planarians was associated with increased oxidative stress. After Cd-treated planarians were coexposed to antioxidant, N-acetylcysteine (NAC), we found that NAC protected planarians from Cd lethality by maintaining the oxidative status and decreasing the bioaccumulation of Cd. The results of the present study support planarians being used as a practical model for toxicological studies of environmental contaminants in the future.

We report the first experimental breakthrough of a net gain of optical signals in a broadband chromium-doped fiber amplifier (CDFA) for next-generation optical communication systems. Current fiber amplifiers, including commercial erbium-doped fiber amplifier, cover only a relatively small portion of the entire transmission bandwidths (1300-1600 nm) of the low-loss windows of silica fibers. The newly developed CDFAs have opened up the possibility of utilizing the 300-nm entire spectrum of the low-loss fibers to further increase the transmission capacity. In this paper, we present the experimental demonstration of a net gain of 1.2 dB employing gain enhancement technique. With the help of an optical-fiber system examination for the CDFA, a 40-Gb/s error-floor free data transmission was successfully demonstrated by realizing the high-speed transmission of signal with gain through the chromium-doped fibers (CDFs). Further gain improvement in the CDFAs employing few-mode or single-mode CDFs will be presented and discussed.

In this paper, a new type of high-speed electroabsorption modulator (EAM) based on quantum dot (QD) p–i–n heterostructure is demonstrated. The QD layers sandwiched by p-AlGaAs and n-AlGaAs are grown by multilayer InGaAs self-assembled QD with luminance wavelength of 1300 nm, serving as the active region of EAM. The photocurrent spectrum measurement exhibits a red shift of 15 nm in QD transition energy levels on biasing from 0 to 6 V. A quadratic relation of energy shift against the reversed bias is extracted, confirming the quantum-confined Stark effect (QCSE) in QD. On fabricating a 300 μm long EAM, as high as DC 5 dB extinction ratio by 6 V voltage swing at 1310 nm is observed. As compared with well-developed quantum well (QW) EAM (well thickness ∼10 nm) of the same length, the lower density of states still shows the same order of magnitude in extinction ratio, suggesting strong QCSE in such 3-dimensional confined QD. An electrical-to-optical conversion with −3 dB bandwidth of 3.3 GHz is also attained in such QD EAM, where the speed is mainly limited by the parasitic capacitance on substrate. It implies that through optimization of QD and device structures, the advantages of QD properties are quite promising to be used in high-speed optoelectronic fields.

Macrobrachium asperulum is a native freshwater prawn species in Taiwan, and is an ideal model for studying the reproductive biology of freshwater decapods. Also, this species may be a potential aquaculture species. This study was conducted to explore the ovarian development of female M. asperulum, as an important foundation for the knowledge of its reproductive biology. Specimens were collected in four seasons throughout the year to investigate the ovarian cycle and germ cell development, by examining the external morphology and histological structure of the ovaries. The breeding period of M. asperulum is probably from March to September each year. Developing ovaries and germ cells were characterized throughout the entire ovarian cycle. Differentiating germ cells were classified mainly into oogonia, primary oocytes, secondary oocytes, and mature oocytes. Among the four major germ cells, secondary oocytes were further divided into five types. Summarizing the above examinations and based on the rel...

White shrimp, Litopenaeus vannamei, a globally important cultured prawn species, is an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. The main purpose of the present study was to detect the acute toxicity of Cd and Zn to L. vannamei, and to investigate their effects on gill functions, which have not been carried out in this species before, hoping to obtain some important significance. First of all, we examined the acute toxicity of cadmium (Cd) and zinc (Zn) to L. vannamei and obtained 24-, 48-, 72-, and 96-h medium lethal concentration (LC50) values of 2.58, 1.30, 1.14, and 1.07 mgCd l(-1) and 3.98, 2.14, 1.75, and 1.35 mgZn l(-1), respectively. Furthermore, we also found that exposure of shrimp to Cd or Zn caused an inhibition in oxygen consumption of 91.3% and 75.9% lower than that of the control. However, after separate exposure to Cd or Zn, elevations in ammonium excretion were obtained, which were 153.7% and 144.1%, respectively, higher than the control. It is most likely that elevations in ammonium excretion were related to decreased osmotic pressure of shrimp blood. Finally, the distribution of Cd and Zn within gills was also determined.

In this letter, a high-efficiency low-power-driven 40-Gb/s electroabsorption modulator is demonstrated using a new type of waveguide, i.e., self-aligned two-step undercut-etched waveguide (SATSUEW). The low-optical-and-electrical-loss performance can be realized from the smooth side wall, wide ridge, and small core of SATSUEW, enabling high-efficiency high-speed optical modulation. Through a 350-μm-long waveguide, 35-dB extinction ratio and 25-dB/V dc modulation efficiency are observed, while optical insertion loss is kept at -6.5 dB (transmission loss of 1 dB/100 μm). A 40-Gb/s operation using 1-Vpp ac driving power with 13-dB extinction ratio is attained, further verified by 55-GHz electrical-to-optical response. The simulated 40-Gb/s eye diagram using distributive effect exhibits a consistent result with the experiment, suggesting that long SATSUEW can be applied to high-bit-rate and high-efficiency operation and thus relaxing the requirements of material and structure in high-speed optoelectronics.

Velocity-matching effect in cascaded integration (CI) of electroabsorption modulators (EAMs) and semiconductor optical amplifiers (SOAs) utilizing bypass high impedance transmission lines (HITLs) is analyzed and demonstrated in this work. By experimentally and theoretically comparing different types of CI structures, the retarded phase in slower microwave waveguide of EAMs can be compensated from the fast waveguide of HITL to match the optical wave in EAM and SOA waveguides, improving high-speed electrooptical (EO) conversion. It thereby suggests high-frequency EO response of CI structure can be beneficial from not only the impedance-matching, but also further phase-matching condition. A 1.3-mm-long SOA-integrated EAM with phase retardation of less than 0.2 radii at 40 GHz and impedance matching has been demonstrated, leading to a -3-dB EO bandwidth of 46 GHz. It suggests that a controllable phase delay through HITL can be used for releasing the design burden of the long-integrated optoelectronic devices for high-speed high-efficient performance.

Pain relief medications commonly occur in the aquatic environment at measurable levels. While the neurotoxicity of pain relievers to higher vertebrates is currently known, little is known about their effects on aquatic animals. This study investigated the neurotoxicity of pain relievers to aquatic animals. We used three neurological enzymes, cholinesterase (ChE), adenosine triphosphatase (ATPase), and monoamine oxidase (MAO), from a freshwater planarian (Dugesia japonica) and green neon shrimp (Neocaridina denticulata) as biomarkers to examine the effects of pain relievers on in vitro activity. The activity of MAO and ChE, but not ATPase, was significantly inhibited by acetaminophen, but not by other pain relievers examined. It was likely that the inhibitory effects of acetaminophen on shrimp neurological enzymes were more severe than on the planarian. These findings suggest that acetaminophen is potentially neurotoxic to aquatic animals, at least in terms of neurotransmission disturbance.

In recent year, efficiency of multi-crystalline silicon (mc) solar cell had large improvement due to better quality of wafer source. In continental thought, grain boundaries and dislocations are act as recombination center of photo-electrons. Large grain size wafers has lower density of grain boundary and should has higher percentage of converge efficiency. However, in recent year, wafers in small grain size have low dislocation density dominate the mc-solar cell industry and improve the average efficiency of solar cell more than 0.25%.

In this article, mc-Si ingots are grown in industrial scale with directional solidification method. The ingot quality can be controlled by tuning the solidification rates. The defect fraction of which evaluated by photoluminescence and lifetime images are used to estimate ingot quality. The results show that the defect can be suppressed significantly during crystallization, leading to the improvement of solar cell performance. Under identical solar cell fabrication process, the whole-ingot-input cell efficiency is increased from 17.68% to17.79%.

Although freshwater planarians are evolutionarily primitive, they are some of the simplest bilateral animals possessing integrated neural networks similar to those in vertebrates. We attempted to develop planarian Dugesia japonica as a model for investigating the neurotoxicity of environmental pollutants such as cadmium (Cd). This study was therefore designed to study the effects of Cd on the locomotor activity, neurobehavior, and neurological enzymes of D. japonica. After planarians were exposed to Cd at high concentrations, altered neurobehavior was observed that exhibited concentration-dependent patterns. Morphological alterations in Cd-treated planarians included irregular shape, body elongation, screw-like hyperkinesia, and bridge-like position. To study the direct effects of Cd on neurological enzymes, tissue homogenates of planarians were incubated in vitro with Cd before their activity was measured. Results showed that acetylcholinesterase (AChE), adenosine triphosphatase (ATPase), and monoamine oxidase A (MAO-A) activities were inhibited in a concentration-dependent manner. MAO-B activity was significantly induced by Cd at low concentrations and inhibited at high concentrations. Changes in the in vivo activity of AChE and ATPase were also found after planarians were treated with Cd at a sublethal concentration (5.56 μM). These observations indicate that neurotransmission systems in planarians are disturbed after Cd exposure.

A novel scheme of all-optical pattern free 2R regeneration is demonstrated through monolithically integration of EAM and SOA. In comparison to Back-to-back case, a clearer 40 Gb/s eye-diagram with 2 dB improvement is obtained.

In this paper, an InGaAsP/InGaAlAs high-band-offset quantum well for high-speed all-optical wavelength conversion is reviewed. Due to large band offset ratio between electron and heavy hole, InGaAsP/InGaAlAs multiple quantum well can have short carrier sweeping time under electric field from low hole band offset. Large than 33GHz of all-optical frequency response is demonstrated under high bias, confirming such material can be used for high speed all optical network.

Progress of high-speed low-driving-power EAM has been reviewed, where microwave design issues have been addressed. Low power with less than 1Vpp and above 40Gb/s operation has been attained from special design of waveguide structure.

We proposed and demonstrated a novel scheme of photonic ultra-wide-band (UWB) doublet pulse based on monolithic integration of tapered optical-direction coupler (TODC) and multiple-quantum-well (MQW) waveguide. TODC is formed by a top tapered MQW waveguide vertically integrating with an underneath passive waveguide. Through simultaneous field-driven optical index- and absorption- change in MQW, the partial optical coupling in TODC can be used to get a valley-shaped of optical transmission against voltage. Therefore, doublet-enveloped optical pulse can be realized by high-speed and high-efficient conversion of input electrical pulse. By just adjusting bias through MQW, 1530 nm photonic UWB doublet optical pulse with 75-ps pulse width, below -41.3 dBm power, 125% fractional bandwidth, and 7.5 GHz of -10 dB bandwidth has been demonstrated, fitted into FCC requirement (3.1 GHz~10.6 GHz). Doublet-pulse data transmission generated in optical fiber is also performed for further characterization, exhibiting a successful 1.25 Gb/s error-free transmission. It suggests such optoelectronic integration template can be applied for photonic UWB generation in fiber-based communications.

A new type InGaAsP/InGaAlAs quantum well is employed for high-speed, high-efficiency all-optical wavelength conversion. Less than 6.4ps all-optical impulse response with a successful 40Gb/s NRZ data transmission is demonstrated.

A low-pattern-dependent-and-chirp-compensated data transmission is demonstrated from monolithic integration of EAM and SOA. By reversed saturation behaviors between EAM and SOA, clear 10Gbit/s eye diagram with 0.6 GHz chirp-compensation and enhanced signal-to-noise ratio is realized.

Directly modulated distributed feedback (DFB) lasers operating around 1550 nm has been demonstrated. The reversed ridge waveguide (RWG) and high-speed planarized coplanar waveguide (CPW) line are used for electron confinement and reducing resistance and capacitance of device. −3 dB bandwidth of > 20 GHz with 25 Gb/s data transmission was successfully achieved.

A novel low-pattern-dependence pre-chirp technology using EAM-integrated SOA is demonstrated. Reduction of 10Gb/s pattern dependence with chirp-compensation of 0.9GHz is realized by the inherently contrary saturation behaviors of EAM and SOA.

Enhancement of quantum well intermixing (QWI) through sputtered SiO 2 on InGaAs layer is demonstrated. From large thermal expansion coefficient, blue shift of 60nm improvement over InP junction, also verified by laser facbrication.

The purpose of this study is to investigate the factors that cause malformed frogs in upstream Kaoping river (KP site) and Tungkang river (T site) of Southern Taiwan. In this experiment, the activities of monooxygenase (MO), glutathione-S-transferase (GST), acetylcholinesterase (AchE) as well as the concentration of vitellogenin (Vg) in the liver were measured. Results show that activities of MO, GST and AchE, and Vg levels in normal frogs (male/female) were 0.09 +/- 0.02/0.09+/-0.01 deltaA min(-1) mg(-1) protein, 0.12 +/- 0.04/0.13 +/- 0.04 deltaA min(-1) mg(-1) protein, 6.13 +/- 2.69/6.01 +/- 2.09 U mg(-1) protein and 0.87 +/- 0.42/2.18 +/- 0.50 microg mg(-1) protein, respectively. Activities of MO, GST and AchE, and Vg levels in malformed frogs (male/female) were 0.15 +/- 0.04/0.21 +/- 0.07 deltaA min(-1) mg(-1) protein, 0.27 +/- 0.08/0.30 +/- 0.12 deltaA min(-1) mg(-1) protein, 4.59 +/- 2.71/5.19 +/- 3.74 U mg(-1) protein and 1.46 +/- 0.61/3.15 +/- 0.88 microg mg(-1) protein, respectively in KP site, and were 0.16 +/- 0.69/0.1 +/- 80.07 deltaA min(-1) mg(-1) protein, 0.21 +/- 0.07/0.24 +/- 0.08 deltaA min(-1) mg(-1) protein, 5.13 +/- 4.58/3.94 +/- 1.33 U mg(-1) protein and 2.23 +/- 1.47/4.11 +/- 1.63 microg mg(-1) protein, respectively in T site. These results indicate that male and female malformed frogs in both rivers upstream are found with higher activities. No significant difference in AchE activity was found between normal and malformed frogs in this investigation. It is therefore reasonable to speculate that the organic chemicals released from agricultural activities are presumable the main factors that lead to the malformation of frogs.

Photonic UWB pulse generation using monolithic integration of electroabsorption modulator and tapered-optical-directional coupler (TODC) is proposed. Through bias-dependent transfer efficiency, FCC-fitted UWB pulse with system demonstration is realized by valley-type transfer function.

A new type of semiconductor quantum well (QW) for high-speed all optical wavelength converter (AOWC) is proposed and demonstrated in this work. Based on InGaAsP (well)/InGaAlAs (barrier) multiple QW, large electron band offset ratio relative to heavy hole can be attained to shorten sweep rate of photocarrier driven by electric field, realizing high-speed efficient AOWC through cross absorption modulation (XAM). By such QWs, an optical waveguide with high-speed electrode connection is fabricated. A -3dB bandwidth of 38 GHz with 8V bias in time-varying photocurrent and all optical response is observed. The corresponding sweep time is less than 10ps, consistent with calculated tunneling rate of QW and thus confirming high sweep rate through field-driven tunneling processing. All-optical conversion with error-free 40Gb/s data transmission and -11dB of conversion efficiency in system performance is also attained in this device, suggesting that such AOWC has potential for 100Gb/s application.

Cigarette smoke is a risk factor for human health, and many studies were conducted to investigate its adverse effects on humans and other mammals. However, since large amounts of cigarette products are produced and consumed, it is possible that tobacco chemicals can end up in aquatic environments through several routes, thus influencing aquatic organisms. In this study, the presence of tobacco-specific nitrosamine (TSNA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), in aquatic environment was demonstrated. Since toxic effects on and distribution patterns of tobacco chemicals in aquatic organisms were rarely studied, after results of an acute toxicity pretest were obtained, experiment was conducted to investigate the bioaccumulation pattern of NNK and distribution patterns of its metabolites, mainly 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), in NNK-treated freshwater planarians, Dugesia japonica. Results from in vivo and in vitro studies showed that NNK was readily converted to NNAL through the carbonyl reduction in bodies of NNK-treated planarians. Tissue concentrations of both chemicals increased in time- and dose-dependent manners. Furthermore, we examined the end products of NNK/NNAL α-hydroxylation in NNK-treated planarians, but only 1-(3-pyridyl)-1,4-butanediol was detected, suggesting that NNK metabolism in planarians partially differs from that in mammalian systems. This is the first report on NNK metabolism in an aquatic organism and can be used as a foundation for developing freshwater planarians as a new in vivo model for the study of NNK toxicology in the future.

Free-living freshwater planarians are considered to have the potential for development as an experimental model for toxicological studies on xenobiotics, including metals. However, little was known about the distribution patterns of metals in the body of treated planarians. This study was conducted to determine the tissue distribution patterns of cadmium (Cd) in different body portions of the treated planarian, Dugesia japonica. Results showed that Cd accumulated in the head of planarians at a significantly higher concentration than in the tail. After examining the level of metallothionein (MT), we suggested that the tissue distribution pattern of Cd might be related to MT induction patterns. In contrast, in planarians treated with copper (Cu), neither the tissue accumulation of Cu nor the multiples of induction of MTs significantly differed between different portions. Furthermore, a higher Cd accumulation rate in the head of planarians caused more-severe oxidative stress to appear in this portion and also a higher susceptibility to a lethal concentration of Cd. Finally, both in vitro and in vivo acetylcholinesterase activities in both body portions of planarians were inhibited by Cd. The present study provides the first report that different metals are distributed in various body portions with different patterns in the planarian.

Cascaded integration of electroabsorption modulator and high-impedance transmission is used to suppress the standing wave property. A −3dB EO response of 40GHz and clear 40Gb/s eye diagram were demonstrated in this work.

Cadmium (Cd) is a component in quantum dot 705 (QD705). Whether QD705 behaves similar to Cd in vivo is of great concern. We compared the distributional kinetics of cadmium chloride (CdCl(2)) and QD705 in mice after intravenous injection. QD705 showed a longer plasma and body retention than CdCl(2) and could be detected in the brain during early exposure. While both the liver and spleen demonstrated a constant Cd concentration for 28 days after QD705 injection, it is likely that this represents intact QD705 stored in mononuclear phagocytes. The kidneys showed a time-dependent accumulation of Cd in the QD705-exposed animals. By day 28, Cd in the kidneys from QD705 was 3-fold that of CdCl(2). QD705 and CdCl(2) have very different kinetics in distribution and metabolism. The long body retention of QD705 in the kidneys may mean that QD705 has even more renal toxicity than CdCl(2).

A monolithically SOA-integrated EAM using InGaAs self-assembly quantum dot has been demonstrated for the first time. By integrating 300µm long EAM with 375µm long SOA, 3.5dB extinction ratio driven by 6V with 3dB optical gain are obtained, indicating a great potential for high-efficient modulation.

A 40Gb/s data transmission is demonstrated through a new approach, the cascaded integration of EAM and SOA. Low driving power 1Vpp with −3dB bandwidth 47GHz, extinction ratio 20dB, and optical gain of 11.8dB are attained.

A new monolithic integration scheme of fabricating optical spot-size converter (SSC) is realized in this work. High-speed electroabsorption modulator (EAM) is used to integrate such SSC. By laterally tapering the active region of an optical waveguide through undercut active region, a vertically asymmetric waveguide coupler can be defined to form an SSC, where the top is a tapered active waveguide, and the bottom is a large core of passive waveguide mode-matched to single-mode fiber (SMF). Through the top tapered active waveguide, the effective index can be gradually varied in the propagation direction, momentarily matching the bottom low-index passive waveguide. It not only performs the resonant coupling in such asymmetric waveguide coupler, but also locks the transferred power by the tapered structure. InGaAsP/InP multiple quantum wells are used as active region of active waveguide. Based on the highly selective etching properties between InGaAsP and InP, the tapered active waveguide can be fabricated by a method, called selectively undercut-etching-active-region (UEAR), enabling the processing a narrow waveguide structure (up to submicron) by general wet etching from a large waveguide ridge. It also leads to good microwave performance of waveguide. By taking this advantage, a SSC-integrated EAM can perform high-speed electrical-to-optical (EO) response as well as low-insertion loss properties. A mode transfer efficiency of 70% is obtained in such SSC. By narrowing waveguide by UEAR, over 40 GHz of -3dB electrical-to-optical (EO) response is obtained from this device. The high efficient SSC integrated with high-speed EAM suggests that the UEAR technique can have potential for applications in high-speed optoelectronic fields.

Ultra-Wide-Band (UWB) generation in wireless mobile communication system has been attracted with lots of interests due to its advantages of high data rate, better immunity to multi-path propagation, and availability of low-cost carrier-free transceivers. Due to the nature of UWB wave propagation, only a short-range can be applied, bringing a safer scheme of communication, for example, indoor or inside building. UWB-over-fiber technology is thus a potential solution to extend such communication scheme into wider space. Optical UWB signal technology is thus a quite important technique, including generation, direct modulation and distribution of optical UWB. In the optical UWB generations, the monocycle or doublet pulse waveforms have been shown in radio system [1], realizing the system application. Several schemes have been proposed and demonstrated on monocycle or doublet optical pulse shapes, which are based on the fiber dispersion [2], optical gain-switch of laser diode with microwave differentiator [3], the timely frequency-shift-keying modulation [4], or cross-gain of semiconductor with two fiber-Bragg gratings [5]. Among all these techniques, large sizes of fiber elements or complicated structures are employed to realize the optical UWB generation. In this work, a novel and simple scheme of optical UWB generation based on a single electroabsorption modulator (EAM) is proposed and demonstrated. Using the photon detection in multiple-quantum-wells (MQW) waveguide with polarity-inversed electric pulse from short termination, the cross-absorption modulation and also reversely optical modulation can form an optical monocycle pulse. The structure is simple and compact, allowing optical UWB to be adapted into optoelectronic integration field.

Optoelectronic intergraded devices for 40 Gb/s optical modulation are important and have attracted a lots of interests in optical communication. Among the integrated optoelectronic devices of modulation, electroabsorption modulators (EAM) have been widely used in high-speed optical communication due to its high extinction ratio, low driving power, and the capability of integrating with other semiconductor devices [1]. However, based on 40 Gb/s modulation template, the high-speed electrical-to-optical (EO) based on EAMs is still limited on their waveguide properties, such as microwave properties and optical insertion loss [1-3]. Due to the highly loaded capacitance in EAM waveguide, devices suffer from high electrical reflection, high loss. Although such high-speed performance can be enhanced by fabricating small size of waveguide, the trade-off issue in optical insertion loss due to small waveguide still limits the overall performance. In the previous work, a cascaded integration of EAMs and semiconductor optical amplifiers (SOA) is demonstrated with not only the optical gain, but also the improved EO link by comparing the single EAM [4]. By periodically integrating EAMs with high impedance transmission line (HITL), the impedance can be increased to get lower electrical reflection, leading to a broadband EO response. In this work, using such integration technique, the cascaded integration of EAMs and SOAs is demonstrated with successful 40Gb/s digital transmission.

A new monolithic integration of EAM and SOA, chain-integration, is proposed and demonstrated. As compared with conventional EAM/SOA, chain-integration offer higher speed with lower noise. Speed of ≫40GHz, optical link gain of 12dB and 2dB sensitivity improvement of 10Gb/s transmission is found in such device.

The white shrimp, Litopenaeus vannamei, a globally important cultured prawn species, is an ideal animal for studying the impairment caused by the effects of heavy metals that are often detected in coastal areas. In this study, L. vannamei was exposed to different concentrations of cadmium (Cd) and zinc (Zn) for up to 28 d. Histopathological alterations in the hepatopancreas were observed in L. vannamei after long-term exposure to Cd and Zn. Hepatopancreatic injury was further confirmed by the inductions of two biochemical markers, hemolymphatic glutamate-oxalacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT). It was notable that L. vannamei was able to repair its hepatopancreas from the damage caused by Zn, which was evidenced by the results of the histopathological observations, determinations of tissue metal concentrations, and examination of GOT and GPT levels.

Epidemiological studies indicated an enhancement of cigarette smoke-induced carcinogenicity, including hepatocellular carcinoma, by arsenic. We believe that arsenic will enhance the expression of hepatic CYP2A enzyme and NNK metabolism (a cigarette smoke component), thus its metabolites, and carcinogenic DNA adducts. Male ICR mice were exposed to NNK (0.5 mg/mouse) and sodium arsenite (0, 10, or 20 mg/kg) daily via gavaging for 10 days and their urine was collected at day 10 for NNK metabolite analysis. Liver samples were also obtained for CYP2A enzyme and DNA adducts evaluations. Both the cyp2a4/5 mRNA levels and the CYP2A enzyme activity were significantly elevated in arsenic-treated mice liver. Furthermore, urinary NNK metabolites in NNK/arsenic co-treated mice also increased compared to those treated with NNK alone. Concomitantly, DNA adducts (N{sup 7}-methylguanine and O{sup 6}-methylguanine) were significantly elevated in the livers of mice co-treated with NNK and arsenic. Our findings provide clear evidence that arsenic increased NNK metabolism by up-regulation of CYP2A expression and activity leading to an increased NNK metabolism and DNA adducts (N{sup 7}-methylguanine and O{sup 6}-methylguanine). These findings suggest that in the presence of arsenic, NNK could induce greater DNA adducts formation in hepatic tissues resulting in higher carcinogenic potential.

The purpose of this study was to investigate the effects of chlordane and lindane on reproduction obstacles and endocrine disruption in female green neon shrimp (Neocaridina denticulata). Individuals of N. denticulata, a common inhabitant of freshwater systems in Taiwan, was exposed to different levels of chlordane (1 and 10 ng l−1) and lindane (0.1 and 1 μg l−1). The reproductive ability and reproductive hormone levels were observed after exposure. According to our findings, an increase in estrogen, induction of a vitellogenin-like protein, and changes in reproductive performance were observed in both chlordane- and lindane-treated shrimp. Thus, it was concluded that chlordane and lindane may cause some reproduction obstacles and disruption of endocrine functions in N. denticulata.

Metallothioneins (MTs) have been widely considered for their potential use as specific biomarkers to reflect the existence of heavy metal pollution, because their induction has been observed to be obviously elevated after heavy metal exposure in a large number organism studied. However, relatively fewer efforts have been made in MT-related studies of prawn species, such as the white shrimp Litopenaeus vannamei, a globally important aquaculture species. With the results from gel filtration chromatography, we demonstrate the existence of MTs or MT-like proteins in L.vannamei. We further studied the relationship between MT induction and metals accumulation after long-term exposure to the heavy metals Cd and Zn. From our results, it is very clear that the response of L. vannamei to Cd differs from that to Zn, and this should be considered when using MTs in field applications to monitor metals contamination.

Standing wave effect of applied electrical field on optical modulation in multiple-cascaded integration (CI) electroabsorption modulator (EAM) and high-impedance transmission line (HITL) has been investigated in this paper. As modulation frequency is increased to the scale that electrical wavelength is in the order of optical modulator length, multiple electrical reflection and self-interference on impedance-mismatch boundaries becomes significant, leading to strong position-dependent field distribution and degrading modulation bandwidth. Sharp bandwidth roll of electrical-optical (EO) conversion by standing wave has been found experimentally in CI structure, consistent with simulation results. By comparing different segment number and length of CI- structure, larger section number of design can overcome such problem to get more flatten bandwidth response. Such simple CI for 300μm long EAM has been demonstrated with flat EO response of -3dB drop 45GHz and -10dB microwave reflection (up to 65GHz) in 6-segement device, suggesting this scheme design is quite useful for efficient broad band modulation.

We propose and demonstrate, by proof of concept, a novel method of ultra-wide band (UWB) photonic generation using photodetection and cross-absorption modulation (XAM) of multiple quantum wells (MQW) in a single short-terminated electroabsorption modulator (SEAM). As an optical pump pulse excite the MQWs of SEAM waveguide, the probe light pulse with the same polarity can be generated through XAM, simultaneously creating photocurrent pulse propagating along the waveguide. Using the short termination of SEAM accompanied by the delayed microwave line, the photocurrent pulse can be reversed in polarity and re-modulated the waveguide, forming a monocycle UWB optical pulse. An 89 ps cycle of monocycle pulse with 114% fractional bandwidth is obtained, where the electrical power spectrum centered at 4 GHz of frequency ranges from 0.1 GHz to 8 GHz for -10 dB drops. Meanwhile, the generation processing is also confirmed by observing the same cycle of monocycle electrical pulse from the photodetection of SEAM. The whole optical processing is performed inside a compact semiconductor device, suggesting the optoelectronic integration template has a potential for the application of UWB photonic generation.