Langmuir-Blodgett Films of Amphiphiles with Cyano Headgroups

Surface pressure-area isotherms for a number of structurally related aromatic cyano derivatives were recorded. T15 (4-cyano-4″-n-pentyl-p-terphenyl) gave the most cohesive monolayer owing to a greater degree of intermolecular π orbital overlap. This compound gave Z-type multilayer deposition and an explanation for this transfer behaviour is proposed based on dipole-dipole interactions between adjacent layers. An X-ray diffraction study showed the layer thickness to be 20.5 ± 0.5Å and a molecular packing model consistent with this value is presented. Preliminary comparisons are made with the monolayer and multilayer behaviour of long-chain alkyl cyanides.     

重氢原子进入钛晶格中引起“过热”现象的量热实验

氘原子进入钛晶格后产生电解“过热”现象。对“过热”热量的准确测量是判定电解过程中是否有“过热”的重要依据。采用我们研究的大功率开放量热设备［２］，用重水进行电解实验。出现了“过热”，“过热”功率为１６－６９瓦，±０３瓦，分别为输入电功率的３０％－３２％。     

On calorimetry by optical beam deflection method

In this work, we analyze different factors that may affect heat measurements, in a device, based on the optical beam deflection method (OBD). We demonstrate that it is possible to improve the heat limit of detection (HLOD) of the device by increasing its sensitivity using a proper cell or a proper monitoring phase. On the other hand, we prove experimentally that the gradient of the refraction index is almost vertical, so it is possible to apply a theoretical model based on one-dimensional heat propagation to predict the temporal behavior and the magnitude of the deflection beam.     

The ATLAS and CMS detectors at the LHC

The construction of the LHC detectors presented formidable challenges and, together with physics exploitation, has required the resources and talents of many thousands of scientists and engineers.     

用量热法测量离子源引出束参数

一、引言 离子源不仅在核物理实验,而且在半导体掺杂,金属表面改性,防腐辐照方面均有广泛用途。 从离子源中引出的离子束带有电荷,用法拉第筒等探测器,直接测量离子电流是很方便的。但是,电测法存在一个共同的问题,当离子束轰击到探测器的表面或内壁时,产生二次电子发射,其发射系数受多种因素的影响,很难校正,影响测量数据的精度。     

Energy loss correction for a crystal calorimeter

Material effect of inner-detectors on the performances of the BESⅢ Electromagnetic Calorimeter (EMC)is investigated.The BESⅢ Time-Of-Flight counters(TOF)have been utilized to improve the energy resolution and detection efficiency for photons after a careful energy calibration.A matching algorithm between TOF and EMC energy deposits is developed,and the effects of beam-related background are discussed.The energy resolution is improved and the photon detection efficiency can be increased by the combined measurement of EMC and TOF detectors.     

Systematic studies of small scintillators for new sampling calorimeter

A new sampling calorimeter using very thin scintillators and the multi-pixel photon counter (MPPC) has been proposed to produce better position resolution for the international linear collider (ILC) experiment. As part of this R&D study, small plastic scintillators of different sizes, thickness and wrapping reflectors are systematically studied. The scintillation light due to beta rays from a collimated ⁹⁰Sr source are collected from the scintillator by wavelength-shifting (WLS) fiber and converted into electrical signals at the PMT. The wrapped scintillator that gives the best light yield is determined by comparing the measured pulse height of each 10 × 40 × 2 mm strip scintillator covered with 3M reflective mirror film, teflon, white paint, black tape, gold, aluminum and white paint+teflon. The pulse height dependence on position, length and thickness of the 3M reflective mirror film and teflon wrapped scintillators are measured. Results show that the 3M radiant mirror film-wrapped scintillator has the greatest light yield with an average of 9.2 photoelectrons. It is observed that light yield slightly increases with scintillator length, but increases to about 100% when WLS fiber diameter is increased from 1.0 mm to 1.6 mm. The position dependence measurement along the strip scintillator showed the uniformity of light transmission from the sensor to the PMT. A dip across the strip is observed which is 40% of the maximum pulse height. The block type scintillator pulse height, on the other hand, is found to be almost proportional to scintillator thickness.      

Excess molar enthalpies of binary mixtures containing ethylene glycols or poly(ethylene glycols) + ethyl alcohol at 308.15 K and atmospheric pressure

Excess molar enthalpies, , of binary mixtures containing ethylene glycols and poly(glycols) + ethyl alcohol were measured by a flow microcalorimeter at 308.15 K and at atmospheric pressure over the whole composition range. Binary mixtures contain ethyl alcohol + ethylene glycol, + di(ethylene glycol), + tri(ethylene glycol), + tetra(ethylene glycol), + poly(ethylene glycol)-200, + poly(ethylene glycol)-300, + poly(ethylene glycol)-400, + poly(ethylene glycol)-600. Effects of the molecular weight distribution (MWD), of the polymer were investigated too, by preparing three additional samples of poly(ethylene glycol) with the same number average molecular weight (M_n ≈ 300), but different MWD. For all mixtures, results were fitted to the Redlich–Kister polynomial. curves are asymmetrical, showing positive values which vary from 280 J mol⁻¹ (diethylene glycol + ethyl alcohol) to 1034 J mol⁻¹ (mixture containing PEGs (200 + 400) + ethyl alcohol). Effects of changes in the glycols chain length and in MWD on the molecular interactions among the mixture components are discussed.     

Excess molar enthalpies of binary mixtures containing poly(ethylene glycol) 200+four cyclic ethers at (288.15, 298.15 and 313.15) K and at atmospheric pressure

Excess molar enthalpies, H_m^E, of binary mixtures containing poly(ethylene glycol) (PEG) 200+1,3-dioxolane, PEG 200+1,4-dioxane, PEG 200+oxolane and PEG 200+oxane were determined using a flow microcalorimeter at (288.15, 298.15 and 313.15) K and at atmospheric pressure. The H_m^E curves are always positive, with maxima varying from 393 J mol⁻¹ (1,3-dioxolane) to 658 J mol⁻¹ (oxolane), showing asymmetrical trends. The effect of the temperature is well marked on the calorimetric data that increase as the temperature is increased. The Redlich-Kister polynomial was used to estimate the binary fitting parameters. Root-mean-square deviations from the regression lines are reported.     

Progress on standardization of electron beam dosimetry for radiation processing

The high dose standards and dissemination system of electron beams are being established at NIM. The graphite and/ or water calorimeters and liquid chemical dosimeter are to be accepted as standards. The transfer dosimeter selected are alanine/ESR dosimeter and radiochromic film (FWT - 60). Several kinds of radiochromic films, undyed cellulose triacetate, polyethylene and blue cellophane will be recommended as working dosimeter. A series of intercomparison studies are conducted between calorimeter and dichromate dosimeter. Agreement is found within 2%. Water calorimeters and dichromate dosimeters are used to make absolute dosimetric measurements of electron beams. These calibrated beams are then used to calibrate several types of dosimeters, such as alanine, radiochromic films, undyed and dyed polyethylene. Preliminary studies show that water calorimeter and dichromate dosimeter are reproducible and sufficiently accurate for electron beam calibration. The estimated overall uncertainty of the measurement is better than 5% at 95% confidence level.