云南剑川县发现榛子果化石

在云南省剑川县甸南公社龙门邑西南角的灰华晶洞中,最近发现榛子果化石。经初步鉴定,这一化石生成于第四纪晚期,距今约十万年。这一珍贵的棒子果化石,是1981年10月中旬武汉地质学院地质力学系讲师何科昭首先发现的,当时他正带领该校学生在剑川县境内实习。从取回的标本来看,榛子果已全部石化,已由石灰华胶结而成了集合体。单颗榛子果化石墨白色,外表光滑,有硬壳,壳内包着果芯,内有圈层结构,大的直径1.2厘米,小的只有0.2厘米。大者居中,小者罗列四周,大小分带明显。从现场和采集到得标本测量,其集合体总高为30厘米,上部横切面呈椭圆形,长轴为34厘米,短轴20厘米,下部形状不规则,长约14厘米,宽7厘米,标本总体呈漏斗形,榛子果全     

浅地层剖面探测技术在山地型水库生态研究中的应用

山地型水库盆底地形复杂,沉积物分布空间差异大,对获取水库完整的沉积记录带来挑战。我们首次利用浅地层剖面仪,探测广东省大型供水水库水底地形和沉积记录,结果证实水库库底地形复杂多变,局部可见水下滑坡和泥沙淤积;沉积厚度由几厘米至上百厘米不等,部分区域可见明显层状结构,分辨率可达10 cm,是采取柱样的理想位置,并得到实地所采柱样剖面的证实。这说明浅地层剖面探测技术适用于研究山地型水库沉积物分布,是进行水库长期生态学野外采样的必要手段。     

用FCM双参数测量膜抗原及核DNA的技术关键

利用流式细胞仪同时定量测定细胞核DNA及细胞膜表面抗原．对测量原理、条件、各种误差的消除方法及可行性进行了阐述.建立了一种简便易行的测量与分析方法．此方法已被应用于多项研究工作中.     

准分子激光原位角膜磨镶术前术后客观验光和主观验光的比较

目的比较准分子激光原位角膜磨镶术前后客观验光和主观验光的准确性和相关性。方法对在我中心接受LASIK手术69例123眼,在术前和术后一个月进行客观验光(NIDEKARK-700)和主观验光(RODENSTOCK综合验光头),对获得的数据进行相关分析。结果LASIK术后,客观验光的准确性较术前下降,客观验光和主观验光测量结果的差值明显增加;术前近视度越高,术后客观验光和主观验光测量结果的差别越大。在测量散光中,术后1月,客观验光和主观验光测量散光的差值明显增加,客观验光不能准确测量散光的量和轴向。结论LASIK术前用自动验光仪进行的客观验光可靠性较高,与主观验光法测量屈光不正的结果接近;术后,客观验光的准确性较术前下降,不能有效评判屈光不正的性质和量。     

柳江化石智人的身高

作者将柳江人的右侧股骨残段作了复原。根据华南人由肢骨测量身高的公式,如果柳江人股骨属男性,其身高为156.69±3.74厘米,比现代当地居民的平均身高偏矮。     

便携式头颅固位仪的研制

众所周知,在头面部活体测量中,头的定位是决定测量正确与否的一个关键,为使所获取的图像位置恒定,具有科学性和可比性,我们研制了便携式头颅固位仪,现将设计要点、结构和功能报告如下。1　材料和结构头颅固位仪由头颅固位部分和连接部分组成,现分述如下:11　头颅固位部分头颅固位部分(图1)由硬质铝合金做成,由头架园盘和两侧头夹组成。园盘下有一通过园心的横杆,双侧头夹固定于其上;头夹可在横杆上滑动,以适应不同头型和脸型的需要。双侧头夹上有定位耳塞,耳塞可在头夹上上下移动。在耳塞平面上有定位眶针,通过一水平活动关节与耳塞相连。为…     

光闪烁方法测算区域蒸散研究进展

蒸散是土壤-植物-大气连续体(SPAC)水热运移的一个重要环节,是全球水量平衡的重要组成,一直是气象学、水文学、地理学及生态学等相关学科重要的研究主题。区域尺度地表蒸散的时空变化过程十分复杂。迄今为止,在像元尺度水平上,特别在非均匀下垫面和地形起伏条件下,有代表性的进行地表蒸散的观测仍然十分困难。虽然遥感方法可获得区域尺度水平蒸散,但其主要根据经验或半经验模型对区域蒸散进行估算,模型选用的参数以及结果还需地面实测数据进行改进、优化,如何获得与遥感尺度相应的地面蒸散实测数据成为模型验证的重点和难点,光闪烁方法的出现为上述问题的解决带来了希望。光闪烁方法能够适应复杂下垫面,测量结果准确且具有时空平均等优点,成为测量区域蒸散的有效方法、验证遥感模型结果的最佳手段。从理论原理、计算方法、主要应用情况等方面,概述了光闪烁方法观测区域蒸散研究进展,指出了影响测算精度的不确定性因素,并提出了研究展望,旨在进一步推动该方法在区域蒸散观测研究中的应用,促进相关学科的发展。     

光栅显示装置的试制和人眼对比敏感度的测定

本文报道了一个在普通示波器荧光屏上产生光栅和测量对比的方法。由于屏上的光点有一定大小和特殊的光晕,对比度和输入电压线性关系的丧失较快;我们只能测准每厘米(屏上)产生12对线的光栅。用主诉方法,测量了两名受试者的对比敏感度函数,并指出了用这方法测定该函数所带来的微小的不准确性.     

雷兽类在新疆的首次发现

1993年6月22日,中国科学院古脊椎动物与古人类研究所和美国宾州匹兹堡市卡内基自然历史博物馆的科学工作者在新疆吐鲁番盆地大步火车站以南40余公里处（古脊椎所野外编号：93011）发现一破碎雷兽头骨。首先看到这块化石的是克里斯托弗·毕尔德博士。由于风化严重,仅获一右P3（长／宽：26．6／31．0毫米）（V10772）。就地测量,头骨长57．5厘米,颧弓宽42．00厘米,机键宽门．00厘米。化石产自一小山丘底部之发白色含细砾的砂岩（未见底）中（l）,在砂岩之上尚有厚约5—6本的土黄色淡水灰岩层（2）,再上为网格状红色泥岩层,厚约10米（…     

一种自动化的植物细胞壁伸展性能测定仪及其应用

应用实验室常用仪器和电子部件,包括直流稳压电源、等臂双盘天平、记录仪、恒流泵、程控信仪、线性可变差动变压器（ＬＶＤＴ）、是磁阀等,改装和配置成的植物细胞壁菜性能性能测定仪,具有操作简便、测量准确和灵敏度高等优点;对大豆幼苗下胚轴生长区细胞壁的内源伸展活性和重组伸展活性的实测结果与文献报告相符,表明该仪器是一种较为理想的测定植物细胞伸展性能的自动化仪器。     

RBE of a thermal neutron beam and the 10B(n, alpha)7Li reaction on cultured B-16 melanoma cells

The RBE of a thermal neutron beam and the 10B(n, alpha)7Li reaction were determined in cultured B-16 melanoma cells. The Kyoto University Research Reactor (KUR) was used as a thermal neutron source which had a very low contamination of gamma-rays and fast neutrons. The cells were irradiated with the beam in the presence or absence of 10B-boric acid. The absorbed dose from the neutron capture reaction to the cells was calculated by a method of Kitao (1975). Survival curves in both conditions had no shoulder and Do values were 0.506 or 0.604 Gy in the presence or absence of 5 micrograms 10B/ml-medium, respectively. The Do value of the 10B(n, alpha)7Li reaction was also estimated at 0.466 Gy, assuming each component of radiation was additive. The RBEs of the KUR thermal neutron beam and the 10B(n, alpha)7Li reaction relative to 60Co gamma-rays were estimated as 4.62 and 6.01 at 0.1 surviving fraction, respectively. Using these results, we calculated the absorbed dose from the 10B-compound and estimated the specific accumulation in the cultured cells of 10B-compounds which we have previously reported but not quantified (Nakanishi et al. 1980, Ichihashi et al. 1982).     

Selective radiography of 10B distribution in organs using cold and thermal neutron beams

The investigation of boron biodistribution by neutron induced autoradiography was performed using a CR-39 etched track detector. Calibration samples, made of boronated chicken liver, and freeze-dried mouse tissue samples were irradiated both with thermal and cold neutrons. Digital images were made on the basis of track densities, with the selection of tracks due to 10B(n, alpha)7Li reaction. A comparison of results obtained both with thermal and cold neutrons demonstrated that it is possible to obtain equivalent results with both neutron sources, although the background noise due to recoil protons from the fast neutrons of the thermal neutron source is 15 % higher than that of the cold neutron source. 10B concentrations in the range of 0.5 ppm to 150 ppm were determined, with a standard deviation of 13 % and 8 % for the mouse tissue samples and calibration samples, respectively.     

A Monte Carlo investigation of the dosimetric properties of monoenergetic neutron beams for neutron capture therapy

A Monte Carlo simulation study has been carried out to investigate the suitability of neutron beams of various energies for therapeutic efficacy in boron neutron capture therapy. The dosimetric properties of unidirectional, monoenergetic neutron beams of varying diameters in two different phantoms (a right-circular cylinder and an ellipsoid) made of brain-equivalent material were examined. The source diameter was varied from 0.0 to 20.0 cm; neutron energies ranged from 0.025 eV up to 800 keV, the maximum neutron energy generated by a tandem cascade accelerator using 2.5-MeV protons in a 7Li(p,n)7Be reaction. Such a device is currently under investigation for use as a neutron source for boron neutron capture therapy. The simulation studies indicate that the maximum effective treatment depth (advantage depth) in the brain is 10.0 cm and is obtainable with a 10-keV neutron beam. A useful range of energies, defined as those neutron energies capable of effectively treating to a depth of 7 cm in brain tissue, is found to be 4.0 eV to 40.0 keV. Beam size is shown not to affect advantage depth as long as the entire phantom volume is used in determining this depth. Dose distribution in directions parallel to and perpendicular to the beam direction are shown to illustrate this phenomenon graphically as well as to illustrate the differences in advantage depth and advantage ratio and the contribution of individual dose components to tumor dose caused by the geometric differences in phantom shape.     

Direct Observation of Li‐Ion Transport in Electrodes under Nonequilibrium Conditions Using Neutron Depth Profiling

One of the key challenges of Li‐ion electrodes is enhancement of (dis)charge rates. This is severely hindered by the absence of a technique that allows direct and nondestructive observation of lithium ions in operating batteries. Direct observation of the Li‐ion concentration profiles using operando neutron depth profiling reveals that the rate‐limiting step is depended not only on the electrode morphology but also on the cycling rate itself. In the LiFePO₄ electrodes phase nucleation limits the charge transport at the lowest cycling rates, whereas electronic conductivity is rate limiting at intermediate rates, and only at the highest rates ionic transport through the electrode is rate limiting. These novel insights into electrode kinetics are imperative for the improvement of Li‐ion batteries and show the large value of in situ NDP in Li‐ion battery research and development.     

Amino-acid transport in suspension-cultured plant cells

The carrier system which transports L-leucine (L-leu) into suspension-culturedNicotiana tabacum L. cv. Wisconsin 38 cells appeared to be constitutive since it was always present and was not induced by L-leu even in nitrogen-starved cells. However, L-leu uptake rates for cells grown in medium containing L-leu were transiently reduced as a result of either transinhibition or repression. Growth-phase cells appeared to have more L-leu carriers per unit area of membrane than stationary-phase cells, and for this reason growing-phase cells exhibit higher L-leu uptake rates. These higher rates reflect a physiological or developmental condition since growth-phase cells did not dramatically change their L-leu uptake rates when subcultured, while stationary-phase cells doubled their rates within 6 h after being subcultured. Cells grown in a medium lacking a useable carbon souce had uptake rates higher than control rates for several days. These higher rates peaked after about 1 d and then decreased over the next several days. Cells grown in a medium lacking a nitrogen souce responded similarly except that the increased rates peaked after about 3 d and persisted longer. Kinetic analysis of uptake rates in cells grown without a carbon souce for 1 d or without a nitrogen souce for 3 d indicated that the L-leu carrier had K_ms similar to those of untreated cells. These results indicate that cultured tobacco cells respond to their environment by increasing or decreasing the number or activity of kinetically similar L-leu carriers.Abbreviations L and S medium Linsmaier and Skoog (1965) medium with additions - L-leu L-leucine IV=McDaniel et al. 1981     

Influence of Depth of Interaction upon the Performance of Scintillator Detectors

The uncertainty in time of particle detection within a scintillator detector, characterised by the coinci- dence time resolution (CTR), is explored with respect to the interaction position within the scintillator crystal itself. Electronic collimation between two scintillator detectors is utilised to determine the CTR with depth of interaction (DOI) for different materials, geometries and wrappings. Significantly, no rela- tionship between the CTR and DOI is observed within experimental error. Confinement of the interaction position is seen to degrade the CTR in long scintillator crystals by 10%.     

Calculation of boron neutron capture cell inactivation in vitro based on particle track structure and x-ray sensitivity

The Monte-Carlo technique was used to perform quantitative microdosimetric model calculations of cell survival after boron neutron capture irradiations in vitro. The high energy ⁷Li and alpha-particles resulting from the neutron capture reaction ¹⁰B (n,α)⁷Li are of short range and are highly damaging to cells. The biophysical model of the Monte-Carlo calculations is based on the track structure of these α-particles and ⁷Li-ions and the x-ray sensitivity of the irradiated cells. The biological effect of these particles can be determined if the lethal effect of local doses deposited in very small fractional volumes of the cell nucleus is known. This lethal effect can be deduced from experimental data of cell survival after x-ray irradiation assuming a Poisson distribution for lethal events. The input data used in a PC-based computer program are the radial dose distribution inside the track of the released particles, cell survival after x-ray irradiation, geometry of the tumor cells, subcellular ¹⁰B concentration, and thermal neutron fluence. The basic concept of this Monte-Carlo computer model is demonstrated. Validations of computer calculations are presented by comparing them with experimental data on cell survival.     

Neutron-induced gamma dose from a reactor beam filter for boron neutron capture therapy

For the boron neutron capture therapy (NCT) of deep-seated metastatic melanoma, an epithermal (up to a few keV energy) neutron beam from a reactor horizontal facility could be useful if the inherent contamination from fast neutrons and gamma rays could be minimised. Calculations for ANSTO's 10 MW research reactor HIFAR have shown that, even though a filter material such as AlF3 attenuates the fast neutron dose, the beam quality improvement is counteracted by a relative increase in the gamma dose because of the gammas arising from neutron captures in the filter material, particularly the aluminium. The aluminium gammas, most of which arise from thermal neutron capture, are hard and cannot be attenuated by lead or bismuth without comparable attenuation of the epithermal neutron flux. Addition of an absorber such as 6Li to the AlF3 filter was investigated as a means of reducing the hard gamma dose, but the improvement in beam quality was small and at considerable cost to dose intensity. Dose characteristics calculations confirmed the superiority of a tangential beam over a radial beam with better results from an unfiltered tangential beam than from an AlF3 filter in a radial beam. This study showed conclusively that assessments of filter assemblies based on the effect of individual components on either the neutron or gamma dose in isolation are inadequate. In assessing any epithermal neutron filter, thermal neutron shield, and gamma shield combination, the total effect of each on the neutron, gamma, and boron-10 dose must be considered.     

A Tale of Two Sites: On Defining the Carrier Concentration in Garnet‐Based Ionic Conductors for Advanced Li Batteries

Solid electrolytes based on the garnet crystal structure have recently been identified as a promising material to enable advance Li battery cell chemistries because of the unprecedented combination of high ionic conductivity and electrochemical stability against metallic Li. To better understand the mechanisms that give rise to high conductivity, the goal of this work is to correlate Li site occupancy with Li‐ion transport. Toward this goal, the Li site occupancy is studied in cubic garnet as a function of Li concentration over the compositions range: Li_7?xLa₃Zr_2?xTa_xO₁₂ (x = 0.5, 0.75, and 1.5). The distribution of Li between the two interstitial sites (24d and 96h) is determined using neutron and synchrotron diffraction. The bulk conductivity is measured on >97% relative density polycrystalline specimens to correlate Li‐ion transport as a function of Li site occupancy. It is determined that the conductivity changes nonlinearly with the occupancy of the octahedral (96h) Li site. It is shown that the effective carrier concentration is dependent on the Li site occupancy and suggests that this is a consequence of significant carrier–carrier coulombic interactions. Furthermore, the observation of maximum conductivity near Li = 6.5 mol is explained.     

Reversible Short‐Circuit Behaviors in Garnet‐Based Solid‐State Batteries

Garnet‐based solid‐state electrolytes (SSEs) are attractive for solid‐state lithium metal batteries due to their wide electrochemical window, high conductivity, and excellent stability against lithium metal. However, the risk of short‐circuit encumbers the cycle life and capacity of garnet‐based solid‐state batteries without clear reason or mechanism. Here, reversible short‐circuit behavior in the garnet‐based solid‐state batteries, which differs from the short‐circuit in liquid cells, is reported for the first time. In situ neutron depth profiling is adopted to quantitatively measure Li transport, which helps forecast and confirm the reversible nature of the short‐circuit in garnet‐based batteries. A real‐time Li accumulation monitoring system of NMC//CNT/garnet/Li cell is designed to reveal the Li dendrite formation mechanism. The voltage drops of the CNT monitoring electrode during the charging process indicate the formation of Li dendrites inside the garnet bulk, while the smooth voltage profile during the discharging process demonstrates the disappearance of the short‐circuit. This is the first confirmation of short‐circuit behavior that provides clarification of the Li dendrite formation mechanism in garnet‐based solid‐state batteries, which is shown to be a reversible process caused by the low ionic conductivity and non‐negligible electronic conductivity of garnet SSEs.