Search

Summary In-situ combustion (ISC) has been proven as a promising technique for the extraction of heavy oils. It has been used in oil fields since the 1920s; however, it is still not as widely used as steam injection. One of the difficulties limiting its wide application is monitoring and controlling the movement of the combustion front. This work is aimed at studying the change in the properties of rock during the ISC process, which is expected to be used for developing an effective monitoring method of the combustion front movement. Rock samples before and after the ISC process were obtained from the Xinjiang Oil field (China) where an ISC industrial pilot has been implemented. In the temperature range of lower than 500℃, the minerals may only alter slightly. Therefore, it is difficult to determine whether the rock was heated or not during the ISC processes using general mineralogical or geochemical methods, for example, X-ray diffraction. This work takes a comprehensive approach to study the variation of rock properties. Magnetic analysis was chosen as the primary method since a very tiny change in the mineral composition during heating leads to profound changes in the magnetic properties. We analyzed magnetic susceptibility (MS), natural remanent magnetization (NRM), hysteresis parameters and thermomagnetic data. In addition, we performed differential thermomagnetic analysis (DTMA) for tracing magnetic minerals based on their Curie temperatures as well as for monitoring transformations in magnetic minerals during heating. Simultaneously, X-ray diffractometer (XRD), optical microscope for thin-sections, and organic content measurements were used as assistive methods to get a comprehensive evaluation on the variation of rock. We found that there is a big difference in magnetic minerals between the initial samples (not subjected to the ISC process) and burned samples from different wells and depths in the ISC pilot. Several magnetic clusters with different coercive force and domain structure were found in these samples. Based on the difference in magnetic properties, we found that the burned samples were heated to different temperatures during the ISC process. In addition, for some rock samples, the heating temperature during the ISC process was determined, and an analysis was made of the propagation of the combustion front. The thermal magnetic properties variation of rock during the ISC process is obvious, which makes it promising to be used for monitoring the propagation direction of the combustion front. Theoretical calculations of magnetic anomalies that occur due to changes in the magnetic properties of rocks during the ISC process indicate the possibility of the detection of such anomalies from the Earth’s surface through high-precision magnetic surveys. The findings in this work provide a theoretical base and direction for developing combustion front monitoring technologies.

Transjugular intrahepatic portosystemic shunt (TIPS) can effectively reduce the portal venous pressure and relieve the clinical complications related to portal hypertension. However, hepatic encephalopathy (HE) is still the main complication post TIPS. Studies have shown that patients over 65 years old with liver function reserve in Child-Pugh grade C are the high-HE-risk group post TIPS, and early TIPS treatment can benefit the survival of these high-risk patients. In this study, TIPS was used to treat 60 cases aged65 years old and liver function reserve in Child-Pugh grade C (decompensated liver cirrhosis) with esophagogastric variceal bleeding. The clinical results of 1-year was observed and the porto systemic gradient (PSG) was evaluated. The relationship between the incidence of HE and the PSG of patients with and without HE were compared to evaluate the effect of PSG on the incidence of HE.经颈静脉肝内门-体分流术（TIPS）能有效地降低门静脉压力以及缓解门静脉高压相关的临床并发症。但是肝性脑病（HE）仍是TIPS术后主要并发症。有研究表明年龄65岁、肝功能Child-Pugh C级患者是发生TIPS术后HE的高危人群，且早期TIPS治疗能使这部分高危患者生存获益。对60例年龄65岁和肝功能Child-Pugh C级失代偿期肝硬化合并食管胃底静脉曲张破裂出血患者行TIPS治疗，观察1年的临床结果，评价门静脉压力梯度（PSG）与HE发生率的关系，再将无HE患者的PSG与有HE患者的PSG进行对比分析，评价PSG对HE发生率的影响。.

We analyzed the clinical observations of target arterial infusion of verapamil combined with chemotherapy as therapy for advanced gastric cancer.From March 2012 to December 2015, a total of 63 patients with advanced gastric cancer were admitted to our department. The target artery in the control group was perfused with chemotherapy drugs only, and the target artery in the therapy group was injected with verapamil combined with chemotherapy drugs.The therapeutic effect of the therapy group was significantly better than that of the control group in the primary foci of gastric cancer. Liver metastatic lesions: 11 patients in the control group had liver metastases and 25 patients in the therapy group had liver metastases. The effective rate (CR+PR) of the therapy group was significantly better than the control group. Clinical benefit evaluation: in the therapy group of 43 cases, 40 cases presented positive clinical benefit and 38 cases positive clinical weight in KFS scoring system; the clinical benefit of the therapy group was significantly better than control group. Survival analysis: the disease progression-free rate and survival rate of the therapy group were 12 months and 24 months, which were higher than those in the control group. The median PFS and median OS were also significantly longer than those in the control group (p0.01). In the therapy group, adverse effects of chemotherapy in 43 patients were relieved in a short time.Target arterial infusion of verapamil combined with chemotherapy drugs for advanced gastric cancer can significantly improve the efficacy of chemotherapy drugs and prolong the survival of patients.

The dynamics of soil organic carbon (SOC) pools determine potential carbon sequestration and soil nutrient improvement. This study investigated the characteristics of SOC pools in five types of cultivated topsoils (0–15 cm) in subtropical China using laboratory incubation experiments under aerobic conditions. The sizes and turnover rates of the active, slow and resistant C pools were simulated using a first-order kinetic model. The relative influence of soil environmental properties on the dynamics of different SOC pools was evaluated by applying principal component analysis (PCA) and aggregated boosted trees (ABTs) analysis. The results show that there were significantly greater sizes of different SOC pools and lower turnover rates of slow C pool in two types of paddy soils than in upland soils. Land use exerted the most significant influence on the sizes of all SOC pools, followed by clay content and soil pH. The soil C/N ratio and pH were the major determinants for turnover rates of the active and slow C pools, followed by clay content which had more impact on the turnover rates of the active C pool than the slow C pool. It is concluded that soil type exerts a significant impact on the dynamics of SOC.

The application of intravenous immune globulin (IVIG) has been recommended for treating hemolysis in neonates for several years. But in clinical work, more than one study reported that IVIG treatment maybe increased the risk of NEC in hemolytic patients. In light of this situation, we performed this meta-analysis.We searched in PubMed, Embase, Cochrane databases for English references, and in Wanfang, VIP, Cnki databases for Chinese references (all last launched on 2015/12/18). Ultimately, 5 studies (Including 4 Chinese articles) were incorporated into this meta-analysis. Odds ratio (OR) and weighted mean difference (WMD) were calculated using a random-effects or fixed-effects model, depending on the data type and heterogeneity of the included studies.(1) Baseline data including gestational age, gender and TBil between IVIG and control groups were compared in hemolytic infants, and showed no significance. (2) With respect to possible inducement of NEC, SGA and formula feeding were found no significance between IVIG and control groups. In contrast, birth weight was found significantly different between the two groups (WMD = 33.35; 95% CI, 20.70-46.01; p0.00001). (3) Regarding the incidence of NEC and mortality, the result showed that there was a significant difference between the IVIG and the control groups in the risk of NEC (OR: 4.53; 95% CI, 2.34-8.79; p0.00001).Our results indicate that IVIG treatment for hemolysis may increase the risk of NEC in infants. But it does not increase the risk of final mortality.

As computers and the Internet become faster and faster, more and more information is transmitted, received, processed, and stored everyday. The demand for high-speed, large-capacity information systems is pushing scientists and engineers to explore all possible approaches, including electrical and optical means. Photorefractive materials and devices are becoming viable alternatives for information systems. Photorefractive materials, including traditional electrooptic photorefractive crystals as well as photopolymers and photosensitive glasses, have demonstrated their potential in information systems. In this article we describe several applications of various photorefractive materials in information storage, processing, and communication systems. Specifically, we briefly discuss the applications of the traditional electrooptic photorefractive crystals and photopolymers in volume holographic data storage (VHDS) and information processing. Then, we discuss our recent works on the applications of photopolymers, holographic polymer dispersed liquid crystals (H-PDLC), and photosensitive glasses in photonic devices for optical fiber communications.

Photorefractive materials, including traditional electro-optic photorefractive crystals as well as photopolymers and photosensitive glasses, have demonstrated their potential in information systems. In this paper, we describe several applications of various photorefractive materials in information storage, processing, and communication systems. Specifically, we briefly review the applications of the traditional electro-optic photorefractive crystals in optical information processing and volume holographic data storage, then discuss our recent works on the applications of photopolymers, holographic polymer dispersed liquid crystals, and photosensitive glasses in photonic devices for optical fiber communications.

Cotton fibre mutants that were fuzzless and/or lintless were crossed with each other and a normal genotype (fuzzy, linted) to produce F 2 and BC 1 generations. F 2 segregation ratios from the cross of fuzzless-lintless × fuzzy-linted, for fuzzy-linted, fuzzless-linted and fuzzless-lintless were 45: 15: 4, From the cross of fuzzless-lintless x fuzzy-linted, the F 2 segregation ratios were 9: 39: 16 whereas the BC 1 F 1 segregation ratios from the F, backcrossed to fuzzless-lintless were 1: 3: 4. These data suggest that the presence or absence of lint and fuzz are controlled by the interaction of four gene loci on non-homologous chromosomes. We designate these loci as N 1 , N 2 , Li 3 and Li 4 , where N 1 N 1 confers the presence of fuzzy, N 2 N 2 confers inhibition of fuzzy initiation and development, and duplicate gene pairs, Li 3 Li 3 and Li 4 Li 4 , determine the presence of lint. Homozygosity for li 3 li 3 and li 4 li 4 might also inhibit fuzz from development. In other words, they were recessive epistatic to fuzz genes.

We have assembled a sequence database for 80 genera of Basidiomycota from the Hymenomycete lineage (sensu Swann & Taylor 1993) for a small region of the mitochondrial large subunit rRNA gene. Our taxonomic sample is highly biased toward known ectomycorrhizal (EM) taxa, but also includes some related saprobic species. This gene fragment can be amplified directly from mycorrhizae, sequenced, and used to determine the family or subfamily of many unknown mycorrhizal basidiomycetes. The method is robust to minor sequencing errors, minor misalignments, and method of phylogenetic analysis. Evolutionary inferences are limited by the small size and conservative nature of the gene fragment. Nevertheless two interesting patterns emerge: (i) the switch between ectomycorrhizae and saprobic lifestyles appears to have happened convergently several and perhaps many times; and (ii) at least five independent lineages of ectomycorrhizal fungi are characterized by very short branch lengths. We estimate that two of these groups radiated in the mid-Tertiary, and we speculate that these radiations may have been caused by the expanding geographical range of their host trees during this period. The aligned database, which will continue to be updated, can be obtained from the following site on the WorldWide Web: http://mendel.berkeley.edu/boletus.html.

It has been postulated that the fungus Ustilago maydis followed its host maize around the world. In order to understand the biogeography of this fungus relative to its host, we used a bioinformatics approach to develop 86 tandem repeat markers useful for population studies of U. maydis. We characterized repeat motifs between two and 155 nucleotides using 36 isolates from USA, Mexico and South America. Our data suggested that (i) repeat motif length does not predict the number of alleles for that locus, and (ii) that the more polymorphic markers can resolve differences in a small geographical area.

Monte Carlo simulations have been used to study the influence of the magnetic field on ion impact at the cathode surface of a sputtering magnetron discharge. The ion parameters (energy, incident angle at the cathode and transit time) have been investigated under four magnetic field strengths and two pressures (1 and 10 Pa). It has been confirmed that the magnetic field has little influence on ion motion. Also, it was found that the magnetic field's influences on ion parameters are given through its influence on electron motion, namely on the ionization site, which is most important in determining the ion energy and transit time. It is proposed that, taking into consideration both the ion energy and the transit time, the appropriate ionization site is the edge of the cathode fall region.

A classical trajectory mapping method was developed to study chemical reactions in solution and in enzymes. In this method, the trajectories were calculated on a classical potential surface and the free energy profile was obtained by mapping the classical surface to the quantum mechanical surface obtained by the semiempirical AM1 method. There is no need to perform expensive quantum mechanical calculations at each iteration step. This method was applied to proton transfer reactions both in aqueous solution and in papain. The results are encouraging, indicating the applicability of this hybrid method to chemical reactions both in solution and in enzymes.

Hepatitis C is a serious public health problem with more than 170 million chronic carriers worldwide. Although hepatitis C infection can be cured in up to 40% of patients, current treatment is not ideal and is associated with a wide spectrum of side effects and complications. Therefore, emerging evidence suggests that patients can receive tailored therapy based on their viral kinetic changes during treatment. With better knowledge of hepatitis C viral genome and life cycle, compounds so called ''Specifically Targeted Antiviral Therapy for HCV or STAT-C'' are under development. This review will discuss current therapies and recent advances in new therapies for hepatitis C.

We have demonstrated an improved optical signal to noise ratio (OSNR) monitor using liquid-crystal (LC) cell phase shifter. The test results show it is a cost effective and practical way to OSNR monitoring.

Atmospheric parameter observations have been conducted during the passage of typhoons and tropical storms, from the troposphere to the middle atmosphere, and thence to the thermosphere, using the VHF radar and HF Doppler sounder at an observation site in Taiwan. The density perturbations caused by the propagation of gravity waves due to the typhoons and tropical storms were calculated on the basis of these observations. The short-term middle atmospheric and thermospheric density changes are significant factors in spacecraft launches. The successful remote measurement of three-dimensional winds, gravity waves, and density perturbations is demonstrated for this subtropical site.

Novel multiplexers–demultiplexers for dense wavelength-division multiplexing systems that use interleaved sampled gratings are presented. It is shown that, with the appropriate design, configurations ranging from hybrid to add–drop as well as all-grating-based multiplexers can easily be realized.

The photorefractive effect is a phenomenon in which the local index of refraction is changed by the spatial variation of the light intensity. Although the phrase “photorefractive effect” has been traditionally used for such effects in electro-optic materials, new materials, including photopolymers and photosensitive glasses, have been developed in recent years and are playing increasingly important roles in optical fiber communication systems. Photopolymers in combination with liquid crystals are ideal materials for wavelength selective tunable devices. The improved optical quality and large dynamic range of photopolymers make them promising materials for holographic recording. Holographic gratings recorded in photopolymers can be employed as distributed Bragg reflectors (DBR). The large birefringence of liquid crystals can be used to tune the index of refraction to cover a large wavelength range (e.g., 40 nm). In addition, the combination of photopolymer and liquid crystal also leads to a new material known as holographic polymer dispersed liquid crystal (H-PDLC) which provides a medium for switchable holograms. Photonic devices made of these materials can be easily incorporated into an optical fiber system because of the low index of refraction of polymers and liquid crystals. Besides photopolymers, photosensitive glasses are also promising for applications in fiber optic systems. Fiber Bragg gratings (FBG) have been used as bandpass filters and dispersion compensators. In this chapter, we describe the applications of photopolymers, H-PDLCs, and FBGs in fiber optic devices. Specifically, some of the recent works on photonic devices such as filters, switches, and high performance dispersion compensators for wavelength division multiplexing (WDM) systems will be described.

Recently CWDM system has emerged into one important platform for optical networks. Its low cost configuration helps the WDM technology applying into new applications such as access and FTTX networks, which are very sensitive to cost structure and cost efficiency. This brings additional challenges to the optical components for more different operation conditions. We introduce here a novel compact CWDM module for demultiplexer or multiplexer that has extremely low insertion loss and can work for outdoor applications. With unique technologies of thin film coatings and compact no-shift packaging, the premium performances are achieved with the savings on cost as well. The total loss of a 8-channel module is only 0.7 dB within the passband of /spl plusmn/7.5 nm, together with the PDL of 0.1 dB. The compact CWDM module is proven to be a low cost solution for metro, access, FTTX, CATV head end/node, and wireless networks.

A series of samples with composition (Tm1−xCax)Ba2Cu3Oy were prepared by the conventional solid‐state reaction method with 0 ⩽ x ⩽ 0.150. Unit cell a‐ and c‐axis increase and b‐axis decreases with increase of the amount of Ca substitution. As a result, orthorhombicity decreases as x increases. Both Tc and y decrease with x, whereas hole concentration (p/Cu) increases with increasing Ca content up to 0.34/Cu for x = 0.075 and then decreases dramatically with x. The highest Tc (89 K) is found for x = 0 sample.

Photonic devices with low insertion loss are important in dense wavelength division multiplexing (DWDM) systems. Currently most of these devices, such as variable optical attenuators (VOA), switches, filters, and dispersion compensators, etc., involve bulk (or micro-optic) components that require conversions between fibers and free-space optical elements leading to high insertion loss. Recently, we have proposed, analyzed, and demonstrated several fiber based devices for DWDM optical communication systems[1-5]. Here we present an in-line fiber VOA [1], a 2x2 switchable wavelength add/drop filter [2J, and high performance dispersion compensators[3-5]. The VOA is built with a side-polished fiber covered with a liquid crystal overlay. By varying the orientation of the liquid crystal molecules using an applied electric field, the loss of the device can be controlled. The 2x2 wavelength switch is designed by recording electrically switchable holographic gratings in a layer of holographic polymer dispersed liquid crystal (H-PDLC) sandwiched between two side-polished fibers. The dispersion compensators are based on high precision fiber Bragg gratings (FBG). A unique method for writing FBGs with arbitrary phase and amplitude distributions is demonstrated. All of these devices are analyzed theoretically and demonstrated experimentally. Both theoretical and experimental results will be presented and discussed. These devices are suitable for DWDM optical information transmission and network management.

Optical switches with wavelength selectivity are important and useful in dense wavelength division multiplexing (DWDM) systems, especially in network reconfiguration. One example of such devices is a switchable add/drop filter which is capable of switching between all-through state and wavelength adding (or dropping) state. The building block of such switches is a 2x2 wavelength switch. Most of the existing 2x2 switches, such as those involving two prisms operating in total internal reflection mode or total transmission mode, require light being coupled in and out of the fiber resulting in large device size and high insertion loss. In this paper, we design, analyze, and demonstrate a novel wavelength-selective 2x2 switch by recording electrically switchable holographic gratings in a layer of holographic polymer dispersed liquid crystal (H-PDLC) sandwiched between two side-polished fibers. We first demonstrate our novel idea experimentally, then analyze our result theoretically, and finally design optimized switches for both 100GHz and 50GHz DWDM systems. This device provides in-line operation capability and is particularly suitable for DWDM network reconfiguration.

Udgivelsesdato: 7 September Comparisons of phylogenetic patterns between coevolving symbionts can reveal rich details about the evolutionary history of symbioses. The ancient symbiosis between fungus-growing ants, their fungal cultivars, antibiotic-producing bacteria and cultivar-infecting parasites is dominated by a pattern of parallel coevolution, where the symbionts of each functional group are members of monophyletic groups. However, there is one outstanding exception in the fungus-growing ant system, the unidentified cultivar grown only by ants in the Apterostigma pilosum group. We classify this cultivar in the coral-mushroom family Pterulaceae using phylogenetic reconstructions based on broad taxon sampling, including the first mushroom collected from the garden of an ant species in the A. pilosum group. The domestication of the pterulaceous cultivar is independent from the domestication of the gilled mushrooms cultivated by all other fungus-growing ants. Yet it has the same overall assemblage of coevolved ant-cultivar-parasite-bacterium interactions as the other ant-grown fungal cultivars. This indicates a pattern of convergent coevolution in the fungus-growing ant system, where symbionts with both similar and very different evolutionary histories converge to functionally identical interactions.

Fiber Bragg grating (FBG) is an important element in many applications including filters and dispersion compensators in fiber communication systems. With recently developed inverse scattering algorithm, FBGs with desired reflection spectrum and/or dispersion properties can now be designed. However, most of these designs require arbitrary grating amplitude and phase control. Previously, fabrication of such FBGs relies on the accurate control of the temporal variation of the intensity pattern using a piezo electric translation stage. The precision of this fabrication method is limited by the noise in the control voltage, which is usually larger than 1%. The distortion in piezo response also affects the performance. In this paper, we develop and demonstrate a novel writing technique for arbitrary FBG fabrication. Our technique is based on a translate-and-write configuration. The incorporation of a precisely controlled shutter allows the apodization and phase of the FBG to be continuously changed at each grating line. The shutter error mainly results from the control signal's timing jitter, which is normally lower than 0.1%. Using this writing technique, we demonstrate a Hamming apodized grating with 20mm length, -22 dB minimum transmission, and < -25 dB reflection side lobe suppression. Furthermore, phase-shift in a grating can be fabricated by a simple delay in the control signal. We also demonstrate FBGs with π, π/2, 3π/2 phase-shifts, respectively. Our experimental results are in excellent agreement with theoretical predictions. To show the capability to fabricate a FBG with arbitrary structure, we demonstrate a 35 mm long zero dispersion grating.

Dispersion-compensating fiber Bragg gratings with approximately 99.9% reflectivity that are made by continuous apodization and phase control are demonstrated. These strong dispersion-compensating gratings provide precision second-order, third-order, or even more complex dispersion compensation, as well as sufficient transmission isolation to be used at add-drop stages without additional filtering. A 99.84% grating with a constant approximately 700-ps/nm dispersion and a 99.94% grating with dispersion varying linearly from 1000 to -1000 ps/nm are demonstrated.

Twenty cross combinations were made with 4 recessive glandless lines (gl2gl2 gl3gl3) used as females and 5 dominant glandless lines (Gl2eGl2e Gl3Gl3) used as male parents to estimate the genetic variance components of kernel oil and protein content of seeds, oil and protein index, and kernel index using a genetic model for parents, F2 and F3. The results showed that all the analyzed traits were mainly controlled by additive effects. Oil content was controlled mainly by maternal additive effect, and other traits by direct additive effect. The average heterosis of F2 over mid-parent based on population mean was -1.99% to 1.11% for all these traits. It suggests that little inbreeding depression exists for F2 and F3 seeds. There were 75% and 60% of the F2 and the F3 combinations in which open-pollinated seeds contained gossypol levels lower than 0.4 gkg-1. This result indicated that it is possible to screen and select high yielding F2 hybrids with a gossypol content lower than the regulated criterion and without lowering seed quality.

WDM fiber optic networks, both in 1.3 pm and 1.55 µm transmission windows, demand mass producible, low cost, low excess loss, wideband, monolithically fused miniature 1×N and N×N couplers for various system applications. Conventional approaches arrange fibers in equilateral polygon shape in a capillary to make 3×3, 4×4, 7×7 or 19×19 fiber couplers. To attain wide bandwidth, complicated fiber preparation processes such as pre-pulling, pre-etching or pre-deposition are required. To eliminate such shortcomings, a systematic theoretical analysis was performed on 1×N and N×N couplers, and a new monolithical fabrication method had been developed.

For potential applications in dense wavelength division multiplexing networks, great efforts have been made to improve the specifications of narrow bandpass filter coatings. Besides environmental stability requirements, which have been met by utilizing ion- or plasma-assisted deposition techniques and appropriate substrate selection [1,2], the spectrum shape requirements of the narrow bandpass filters are especially critical for WDM applications. Multi-cavity design and layer optimization have been adopted to achieve better theoretical results. On the practical side, layer thickness and index monitoring is key to achieving high quality narrow bandpass filters. For multi-cavity Fabry-Perot filters, previous studies [3,4] showed that transmission turning point monitoring is the best monitoring approach due to its error compensation mechanism. However, total compensation is only achievable when the monitoring light is monochromatic. In a practical coating situation, monitoring light always has a finite bandwidth. The bandwidth of the optical monitoring light comes from three sources as depicted in Figure 1. These are the bandwidth of the monochromator, the effective bandwidth caused by non-uniformity thickness inside the monitoring light spot on the filter, and the effective bandwidth caused by the incident angle span of the monitoring light on the filter. For error compensation, smaller bandwidth is preferable. However, monitoring light intensity decreases proportionally with bandwidth (except for a laser light source, whose long coherent length is problematic). Thus, the turning point error increases. A trade-off must be taken to optimize the coating process. Due to analytical complexity, a numerical method approach was taken here.

This report describes two cases of schizophrenia inpatients with polydipsia, intermittent hyponatremia, and water intoxication. Case 1, a 38 year-old male, developed polydipsia after seven years duration of schizophrenia, with a daily intake of water of more than 10 liters as a result of auditory hallucination suggestion. Nocturnal hyponatremia, agitation and exacerbation of psychosis were noted during admission. After 12 treatments of electroconvulsive therapy, the symptoms of psychosis and polydipsia declined. Case 2, a 42 year-old male, had also been a case of schizophrenia for about twenty years, and developed polydipsia with more than 5 liters of daily water intake in a chronic psychiatric hospital for a period of 5 years schizophrenia. He claimed that he enjoyed the pleasure of drinking water. The symptom of water intoxication had been noted intermittently in the past year, leading to at least two seizures. Finally the patient was transferred to our ward due to agitated mood, self-destructive behavior, consciousness loss, and motor weakness. The clinical features, differential diagnosis and treatment concept of polydipsia and water intoxication were also discussed in context.

We present a practical hybrid quantum mechanical/molecular mechanical approach to study chemical reactions in solution and in enzymes. In this method, referred to as the "Classical Trajectory Mapping" method, trajectories are calculated on the classical potential surfaces and, by using the classical surfaces as a reference state for the actual quantum mechanical ground state potential, the free energy profile of the chemical reaction is obtained by the free energy perturbation technique. This method was applied to proton-transfer reactions both in aqueous solution and in papain. The encouraging results indicate the applicability of our method to chemical reactions in the condensed phase and the biological systems.

Broadband SONET (Synchronous Optical Network), SDH (Synchronous Digital Hierarchy), and ATM (Asynchronous Transfer Mode) are widely deployed in public and private networks. OC-48/SDH-16 equipment of 2.5 Gbit/s and high speed network components beyond 2.5 Gbit/s are gaining popularity in various B-ISDN systems. Wavelength chirping of laser diode (LD) creates a hurdle in Gbit/s directly modulated optical transmitter design. Practically, transmitter consisting of a narrow linewidth LD source and an external electro-optic modulator (EOM) can provide a minimum chirping effect and is suitable for multigigabit transmission.1,2 Currently, the typical drive voltage of 3 GHz LiNbO3 EOM is about 3~4 V at 1310 nm. Therefore, the required high speed electronic drive circuits are costly and thus limits the mass deployment of the external modulated transmitter modules. In this paper, we report the demonstration of a low drive voltage (Vx = 1.7 V) EOM with optical modulation bandwidth of 5 GHz.

In coherent optical communication systems and some optical-fiber sensor systems, there is a requirement that the state of polarization (SOP) of incoming light signals match that of the light from the local oscillator. Quite a few methods have been proposed for polarization control. The fiber-loop and wave-plate methods require bulky mechanical driving.1 The fiber-squeezer approach needs too much pressure on the fiber and is not reliable for long-term operation.2

High efficient nonlinear optical materials (NOMS) are highly required for optical computing and optical signal processing. However, currently no such practical NOMs are available. In this project, new organic NOMs have been researched and developed. New organic NOM design principle and approach have been reviewed and investigated. Four new organic NOMs, namely, CMVI, DVDA, MOHNS and HMONS have been synthesized and purified. Nonlinear optical responses of these four samples have been demonstrated and preliminary been characterized. Device fabrication and application for optical computing and optical signal processing have been investigated.

An all-fiber (6x6) optical shutter switch matrix with the control system for microwave phased array has been demonstrated. The device offers the advantages of integrated configuration, low cost, low power consumption, small size, and light weight. The maximum extinction ratio (among 36 individual pixel) of this switch matrix at 840 nm is 24.2 dB, and the switching time is less than 120 microsec. In addition to phased array application, this low cost switch matrix is extremely attractive for fiber optic switching networks.

Analyses and experimental results of microwave semiconductor laser nonlinearity are presented. Various system applications employing the device nonlinear characteristics are discussed. For example, a high performance Ku-band fiber optic link with a system signal-to-noise ration (SNR) of better than 120 dB/Hz was demonstrated at an IF of 70 MHz. Also, the measured link SNR better than 100 dB/Hz was achieved at 26.5 GHz with frequency up-conversion.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An extended application of the magnetron sputtering discharge is described. The discharge, called a magnetically confined discharge in the experiments, is pumped in a pulse mode to produce and excite copper vapor atoms for laser operation. Copper atom densities adequate for laser action (∼1014 cm−3) are obtained in the discharge at temperatures below 400 K. Laser operation is expected in the experimental apparatus with fast‐rise pulse pumping.

A newly developed fiber Bragg grating (FBG) fabrication method is demonstrated. By combining a stable continuous-wave UV laser, a high precision electro-optical UV modulator, a compact and stable holographic setup, and a subnanometer precision air-bearing translation stage, the setup allows both apodization and phase of the FBGs to be continuously changed at each grating line. During the writing process, a fiber is moved constantly by the high-precision air-bearing stage, while the UV laser beam is switched on and off by a customized pulse train with nanosecond timing precision and forms a stable interference pattern on the fiber. The error of this system mainly results from the control signal's timing jitter, which is normally lower than 0.1%. Theoretical analysis and experimental results for gratings with various structures are demonstrated and discussed. They show good agreement, demonstrating that the fabrication method is capable of fabricating gratings with arbitrary apodization and phase design.

Design and optimization techniques of microwave and millimeter-wave fiber-optic systems are described with emphasis on the system level parameters and the characteristics of related optical devices. Direct modulation vs. external modulation of laser diode trans-mitter and direct detection vs. coherent detection of the optoelectronic receiver are discussed and compared in terms of important design parameters, components and practical performance issues.