Very long wavelength infrared focal plane arrays with 50% cutoff wavelength based on type-Ⅱ In As/GaSb superlattice

A very long wavelength infrared（VLWIR） focal plane array based on In As/Ga Sb type-Ⅱ super-lattices is demonstrated on a Ga Sb substrate. A hetero-structure photodiode was grown with a 50% cut-off wavelength of 15.2 μm, at 77 K.A 320×256 VLWIR focal plane array with this design was fabricated and characterized. The peak quantum efficiency without an antireflective coating was 25.74% at the reverse bias voltage of-20 mV, yielding a peak specific detectivity of 5.89×10^10cm·Hz^1/2·W^-1. The operability and the uniformity of response were 89% and 83.17%. The noise-equivalent temperature difference at 65 K exhibited a minimum at 21.4 mK, corresponding to an average value of 56.3 mK.

Wet etching and passivation of GaSb-based very long wavelength infrared detectors

The etching and passivation processes of very long wavelength infrared(VLWIR)detector based on the InAs/GaSb/AlSb type-II superlattice have been studied.By studying the effect of each component in the citric acid solution(citric acid,phosphoric acid,hydrogen peroxide,deionized water),the best solution ratio is obtained.After comparing different passivation materials such as sulfide+SiO_(2),Al_(2)O_(3),Si_(3)N_(4) and SU8,it is found that SU8 passivation can reduce the dark current of the device to a greater degree.Combining this wet etching and SU8 passivation,the of VLWIR detector with a mesa diameter of 500μm is about 3.6Ω·cm^(2) at 77 K.

Very long wave infrared quantum cascade detector based on modular band structure

The optoelectronic performance of quantum cascade detectors(QCDs)is highly sensitive to the design of the energy level structure,leading to the inability of a single structure to achieve broad wavelength tuning.To address this issue,we propose and demonstrate a modular concept for very long wave infrared(VLWIR)QCDs based on a miniband diagonal transition scheme.The modular design makes the wavelength tuning only need to be adjusted for the absorption quantum well module rather than for the whole active region.Theoretical simulation shows that the wavelength tuning range is 39.6 meV(~14–30μm).To prove the feasibility of the scheme,three samples with different absorption well widths were fabricated and characterized.At 10 K,the response wavelengths of the three QCDs are 14,16,and 18μm,respectively,corresponding to responsivities and detectivities exceeding 2 mA/W and 1×10^(10)Jones.

Clinical features and mutations in seven Chinese patients with very long chain acyl-CoA dehydrogenase deficiency

Background:Very long chain acyl-CoA dehydrogenase deficiency(VLCADD)is an inherited metabolic disease caused by deleterious mutations in the ACADVL gene that encodes very long chain acyl-CoA dehydrogenase(VLCAD),and which can present as cardiomyopathy in neonates,as hypoketotic hypoglycemia in infancy,and as myopathy in late-onset patients.Although many ACADVL mutations have been described,no prevalent mutations in the ACADVL gene have been associated with VLCADD.Herein,we report the clinical course of the disease and explore the genetic mutation spectrum in seven Chinese patients with VLCADD.Methods:Seven Chinese patients,from newborn to 17 years old,were included in this study.Tandem mass spectrometry was performed to screen for VLCAD defi ciency.All exons and fl anking introns of the ACADVL gene were analyzed using polymerase chain reaction and direct sequencing.Online analysis tools were used to predict the impact of novel mutations.Results:All cases had elevated serum levels of tetradecanoylcarnitine(C14:1)which is the characteristic biomarker for VLCADD.The phenotype of VLCADD is heterogeneous.Two patients were hospitalized for hypoactivity and hypoglycemia shortly after birth.Three patients showed hepatomegaly and hypoglycemia in infancy.The other two adolescent patients showed initial manifestations of exercise intolerance or rhabdomyolysis.Three of the patients died at the age of 6-8 months.Eleven different mutations in the ACADVL gene in the 7 patients were identified,including seven reported mutations(p.S22X,p.W427X,p.A213T,p.G222R,p.R450H,c.296-297delCA,c.1605+1G>T)and four novel mutations(p.S72F,p.Q100X,p.M437T,p.D466Y).The p.R450H and p.D466Y(14.28%,2/14 alleles)mutations were identifi ed in two alleles respectively.Conclusions:The clinical manifestations were heterogeneous and ACADVL gene mutations were heterozygous in the seven VLCADD Chinese patients.R450H may be a relatively common mutation in Asian populations.The genotype and phenotype had a certain correlation in our patients.

Attenuation and Distortion of Compression Waves Propagating in Very Long Tube

A lot of phenomena related to propagating various waves are seen when the high-speed train goes through the tunnel,the gas pipeline is broken due to an accident or the air brake of the wagon operates.For instance,a compression wave generated ahead of a high-speed train entering a tunnel propagates to the tunnel exit and spouts as a micro pressure wave,which causes an exploding sound.In order to estimate the magnitude correctly,the mechanism of the attenuation and distortion of a compression wave propagating along a very long tunnel must be understood and the experimental information on these phenomena is required.An experimental investigation is carried out to clarify the attenuation and distortion of the propagating compression wave in a very long tube.Experimental results show that the strength of a compression wave decreases with distance.The attenuation and distortion of compression waves are affected by the initial waveform of the compression wave and by the unsteady boundary layer induced by the propagating wave.The shape of a compression wave becomes different with the propagating distance;that is,a shock wave appears just head of a wavefront and an overshoot on pressure distribution is observed behind a shock wave due to the transition of the unsteady boundary layer.

Optimization of Top Coupling Grating for Very Long Wavelength QWIP Based on Surface Plasmon

The relative coupling efficiency of two-dimensional （2D） grating based on surface plasmon for very long wavelength quantum well infrared detector is analyzed by using the three-dimensional finite-difference time domain （3D-FDTD） method algorithm. The relative coupling efficiency with respect to the grating parameters, such as grating pitch, duty ratio, and grating thickness, is analyzed. The calculated results show that the relative coupling efficiency would reach the largest value for the 14.5μm incident infrared light when taking the grating pitch as 4.4 μm, the duty ratio as 0.325, and the grating thickness as 0.07 μm, respectively.

Imaging supermassive black hole shadows with a global very long baseline interferometry array

The imaging of two supermassive black holes by the Event Horizon Telescope Collaboration proved to a new level the correctness of Einstein's general relativity,regarding its prediction of black hole shadows in the highly curved spacetime regime.

Can It Last Very Long?

Experts are of two minds about the bullish commodities marketThe bull market for commodities will last until around 2014. This optimistic prediction comes courtesy of Jim Rogers, doyen of investors and former partner of George Soros, who successfully foresaw the start of a commodity rally back in 1999.

Estimation of free core nutation parameters and availability of computing options

The Earth’s Free Core Nutation(FCN) causes Earth tides and forced nutation with frequencies close to the FCN that exhibit resonance effects.High-precision superconducting gravimeter(SG) and very long baseline interferometry(VLBI) provide good observation techniques for detecting the FCN parameters.However,some choices in data processing and solution procedures increase the uncertainty of the FCN parameters.In this study,we analyzed the differences and the effectiveness of weight function and ocean tide corrections in the FCN parameter detection using synthetic data,SG data from thirty-one stations,and the 10 celestial pole offset(CPO) series.The results show that significant discrepancies are caused by different computing options for a single SG station.The stacking method,which results in a variation of0.24-5 sidereal days(SDs) in the FCN period(T) and 10^(3)-10^(4) in the quality factor(Q) due to the selection of the weighting function and the ocean tide model(OTM),can effectively suppress this influence.The statistical analysis results of synthetic data shows that although different weight choices,while adjusting the proportion of diurnal tidal waves involved,do not significantly improve the accuracy of fitted FCN parameters from gravity observations.The study evaluated a series of OTMs using the loading correction efficiency.The fitting of FCN parameters can be improved by selecting the mean of appropriate OTMs based on the evaluation results.Through the estimation of the FCN parameters based on the forced nutation,it was found that the weight function P_(1) is more suitable than others,and different CPO series(after 2009) resulted in a difference of 0.4 SDs in the T and of 103 in the Q.We estimated the FCN parameters for SG(T=430.4±1.5 SDs and Q=1.52×10^(4)±2.5×10^(3)) and for VLBI(T=429.8±0.7 SDs,Q=1.88×10^(4)±2.1×10^(3)).

A TSE based design for MMSE and QRD of MIMO systems based on ASIP

A Taylor series expansion(TSE) based design for minimum mean-square error(MMSE) and QR decomposition(QRD) of multi-input and multi-output(MIMO) systems is proposed based on application specific instruction set processor(ASIP), which uses TSE algorithm instead of resource-consuming reciprocal and reciprocal square root(RSR) operations.The aim is to give a high performance implementation for MMSE and QRD in one programmable platform simultaneously.Furthermore, instruction set architecture(ISA) and the allocation of data paths in single instruction multiple data-very long instruction word(SIMD-VLIW) architecture are provided, offering more data parallelism and instruction parallelism for different dimension matrices and operation types.Meanwhile, multiple level numerical precision can be achieved with flexible table size and expansion order in TSE ISA.The ASIP has been implemented to a 28 nm CMOS process and frequency reaches 800 MHz.Experimental results show that the proposed design provides perfect numerical precision within the fixed bit-width of the ASIP, higher matrix processing rate better than the requirements of 5G system and more rate-area efficiency comparable with ASIC implementations.

The theory and experiment of very-long-wavelength 256×1 GaAs/Al_(x)Ga_(1-x)As quantum well infrared detector linear arrays

The 256×1 linear array of multiple quantum wells infrared photodetector (QWIP) is designed and fabricated for the peak response wavelength at λP=14.6 μm. The response spectral width is bigger than 2.2 μm. The two-dimensional (2D) diffractive coupling grating has been formed on the top QWIP photosensitive pixel for coupling the infrared radiation to the infrared detective layers. The performance of the device at VB=3 V and T=45 K has the responsibility 4.28×10-2 (A/W), the blackbody detectivity Db*=5.14×109 (cm·Hz1/2/W), and the peak detectivity Dλ*=4.24× 1010 (cm·Hz1/2/W). The sensor pixels are connected with CMOS read out circuit (ROC) hybridization by indium bumps. When integral time is 100 μs, the linear array has the effective pixel of QWIP FPA Nef of 99.2%, the average responsibility  (V/W) of 3.48×106 (V/W), the average peak detectivity Dλ* of 8.29×109 (cm·Hz1/2/W), and the non-uniformity UR of 5.83%. This device is ready for the thermal image application.

A scalable and low power VLIW DSP core for embedded system design

Aims to provide the block architecture of CoStar3400 DSP that is a high performance, low power and scalable VLIW DSP core, it efficiently deployed a variable-length execution set (VLES) execution model which utilizes the maximum parallelism by allowing multiple address generations and data arithmetic logic units to execute multiple instructions in a single clock cycle. The scalability was provided mainly in using more or less number of functional units according to the intended application. Low power support was added by careful architectural design techniques such as fine-grain clock gating and activation of only the required number of control signals at each stage of the pipeline. The said features of the core make it a suitable candidate for many SoC configurations, especially for compute intensive applications such as wire-line and wireless communications, including infrastructure and subscriber communications. The embedded system designers can efficiently use the scalability and VLIW features of the core by scaling the number of execution units according to specific needs of the application to effectively reduce the power consumption, chip area and time to market the intended final product.

Identification of KCS gene family and functional analysis of FAE-like genes from Malania oleifera

KCS(3-ketoacyl-CoA synthase)is the key enzyme catalyzing the first step of very long chain fatty acid(VLCFA)biosynthesis.Studies showed that different KCSs possessed different substrate preference.Malania oleifera are abundance of VLCFAs in its mature seeds,especially the nervonic acid,which is essential for human health.In this study,we identified and characterized 18 KCS genes in M.oleifera genome.Phylogenetic analysis showed that these KCS genes were classified into four subfamilies,including two FAE-like,six KCS-like,eight FDH-like and two CER6.We concentrated on the functional role of two FAE-like genes,Maole003085.T1 and Maole004215.T1 which encoded predicted amino acid residues of 516 and 518 in protein,respectively.Multiple sequence alignment showed that their two proteins contained the known and conserved active sites among FAE-like subfamily.Upon heterologous expression in wild type yeast(Saccharomyces cerevisiae)INVSc1,we found that Maole004215.T1 could produce four new fatty acids including C22:0/C22:1 and C24:0/C24:1,but Maole003085.T1 only produced C22:1.Besides,upon heterologous expression in mutant yeast BY4741-△elo3,we found the Maole003085.T1 could produce C24:0 and C26:0,while the Maole004215.T1 could catalyze the formation of fatty acids C24:0,C26:0 and C28:0.These results showed Maole003085.T1 and Maole004215.T1 had fatty acid elongation activity in yeast,and possessed different substrate preference in the production of different VLCFAs.Interestingly,we found Maole004215.T1 could produce nervonic acid in yeast,which provides molecular basis on the genetic improvement and genic engineering for producing nervonic acid resources by using biotechnological methods.

Mathematical model for computing precise local tie vectors for CMONOC co-located GNSS/VLBI/SLR stations

The seven co-located sites of the Crustal Movement Observation Network of China（CMONOC） in Shanghai, Wuhan, Kunming, Beijing, Xi＇an, Changchun, and Urumqi are equipped with Global Navigation Satellite System（GNSS）, very long baseline interferometry（VLBI）, and satellite laser ranging（SLR） equipment. Co-location surveying of these sites was performed in 2012 and the accuracies of the solved tie vectors are approximately 5 mm.This paper proposes a mathematical model that handles the least squares adjustment of the 3D control network and calculates the tie vectors in one step, using all the available constraints in the adjustment. Using the new mathematical model, local tie vectors can be more precisely determined and their covariance more reasonably estimated.

Efficient matrix inversion based on VLIW architecture

Matrix inversion is a critical part in communication, signal processing and electromagnetic system. A flexible and scalable very long instruction word （VLIW） processor with clustered architecture is proposed for matrix inversion. A global register file （RF） is used to connect al the clusters. Two nearby clusters share a local register file. The instruction sets are also designed for the VLIW processor. Experimental results show that the proposed VLIW architecture takes only 45 latency to invert a 4 × 4 matrix when running at 150 MHz. The proposed design is roughly five times faster than the DSP solution in processing speed.

The Precision Analysis of the Chinese VLBI Network in Probe Delay Measurement

We propose a Very Long Baseline Interferometry(VLBI)precision evaluation method for probe delay measurement,so as to investigate the error contributions from different components in the Chinese VLBI Network(CVN).This method takes the idea of traditional closure delay analysis for distant radio sources.It focuses on the VLBI closure delay only and therefore excludes the influence of probe orbit determination,which makes it very suitable to evaluate the capability of VLBI probe delay measurement.In this paper,we first introduce the principles of closure delay analysis.Then the statistical results of typical CE5(Chinese Chang’e 5 lunar exploration mission)and HX1(Chinese Mars exploration mission)observations are presented,including the comparison of the closure delay precisions between CE5 and HX1 for four closed baseline triangles in CVN.According to the result,we realize that the precision discrepancy between CE5 and HX1 in the closure delay analysis is less than that of residual delay after orbit determination,which reflects the precision level of the VLBI delay measurement.

Effect of lunar gravity models on Chang'E-2 orbit determination using VLBI tracking data

The precise orbit determination of ChanE-2 is the most important issue for successful mission and scientific applications, while the lunar gravity field model with big un- certainties has large effect on Chang＇E-2 orbit determination. Recently, several new gravity models have been produced using the latest lunar satellites tracking data, such as LP16SP, SGM1SOJ, GL0900D and GRGM900C. In this paper, the four gravity models mentioned above were evaluated through the power spectra analysis, admittance and coherence analysis. Effect of four lunar gravity models on Chang＇E-2 orbit determination performance is investigated and assessed using Very Long Baseline Interferometry （VLBI） tracking data. The overlap orbit analysis, the posteriori data residual, and the orbit prediction are used to evaluate the orbit precision between successive arcs. The LPI65P model has better orbit overlap performance than the SGM150J model for Chang＇E-2100 km x 100 km orbit and the SGM150J model performs better for Chang＇E-2100 km x 15 km orbit, while GL0900D and GRGM900C have the best orbit overlap results for the two types of Chang＇E-2 orbit. For the orbit prediction, GRGM900C has the best orbit prediction performance in the four models.

VGOS超宽带观测的首次UT1测量数据处理及分析

在国际甚长基线干涉测量(very long baseline interferometry,VLBI)大地测量与天体测量服务组织协调下,首次利用隶属于VLBI全球观测系统(VLBI global observing system,VGOS)的美国Kokee和德国Wettzell观测站及并置的传统VLBI观测站开展了世界时(universal time,UT1)联合测量试验,观测数据在上海VLBI中心进行了干涉处理。结果表明,VGOS超宽带观测系统的UT1测量精度约为7μs,并置基线的传统S/X双频系统测量精度约为14μs,VGOS系统的UT1解算结果优于S/X系统。通过试验建立了从相关处理、相关后处理到UT1参数解算的完整数据处理流程,验证了上海VLBI相关处理机的VGOS数据处理能力,为承担国内和国际VGOS观测数据的相关处理任务奠定了基础。

Architecture Design of a Variable Length Instruction Set VLIW DSP

The cost of the central register file and the size of the program code limit the scalability of very long instruction word（VLIW） processors with increasing numbers of functional units.This paper presents the architectural design of a six-way VLIW digital signal processor（DSP） with clustered register files.The architecture uses a variable length instruction set and supports dynamic instruction dispatching.The one-level memory system architecture of the processor includes 16-KB instruction and data caches and 16-KB instruction and data on-chip RAM.A compiler based on the Open64 was developed for the system.Evaluations show that the processor is suitable for high performance applications with a high code density and small program code size.

HOS3, an ELO-Like Gene, Inhibits Effects of ABA and Implicates a S-1-P/Ceramide Control System for Abiotic Stress Responses in Arabidopsis thaliana

A hyper-osmotically sensitive mutant of Arabidopsis thaliana, designated hos3-1 （high expression of osmotically responsive genes）, was identified based on its hyper-luminescence of RD29A：LUC promoter fusion plants upon treatment with NaCI and ABA. These responses implicate the disrupted gene as a direct or indirect negative regulator of the RD29A stress-responsive pathway. By sequencing the flanking regions of the T-DNA borders, it was determined that the disrupted gene is at locus At4g36830, annotated as encoding a putative protein with high homology to CIG30 （ELO2/FEN1）. CIG30 has been implicated in synthesis of very long chain fatty acids （VLCFA）, which are essential precursors for sphingolipids and ceramides. Altered stress responses characteristic of ABA-hypersensitivity, including reduced root growth inhibition and reduced germination with ABA treatment and reduced water loss from leaves, were exhibited by allelic hos3-1 and hos3-2 mutants. The hos3-2 mutant is partially suppressed in its transcript abundance and is inherited as a recessive trait. Further, the HOS30RF under the control of the 35SCaMV promoter restored wild-type NaCI- and ABA-root growth sensitivity as well as RD29A：LUC luminescence in mutant plants. We also show here that the HOS3 wild-type gene functionally complements the sensitivity of elo2 and elo3 yeast mutants to monensin. Furthermore, both hos3-1 and hos3-2 alleles shared increased sensitivity to the herbicide Metolachlor, which inhibits acyl chain elongation in synthesis of VLCFA, and HOS3 functionally complemented both elo2 and elo3 and restored levels of VLCFA. Together, these data establish that HOS3 inhibits ABA-mediated stress responses and implicate the VLCFA pathway and products as control points for several aspects of abiotic stress signaling and responses. The results also provide support for a role of ceramide in the control of stomatal behavior.