摘要:

A new plate–plate torsion viscosimeter designed for the investigations of liquid crystals is described. This viscosimeter enables the measurement of torques at very low shear rates and the simultaneous optical observation of the sample. Short accounts of the application of the viscosimeter to viscosity measurements, to backflow investigations, and to the study of dissipative structures are given. In the case of dissipative structures, self‐organization of the torsion pendulum system is observed.

ISSN:0034-6748    

DOI:10.1063/1.1137469

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

This article describes the design features, construction, and operation of a liquid‐nitrogen level controller which can be used continuously over a period of several weeks. Liquid level is sensed by pairs of thermistors mounted on a dip stick. Replenishing of liquid nitrogen is achieved as a result of self‐pressurization of a tank containing the cryogen. The transfer system ensures a ripple‐free liquid surface during the replenishing operation. This level controller has been a part of a cryostat for diffusion measurements in liquefied inert gases.

ISSN:0034-6748    

DOI:10.1063/1.1137470

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The thermal relaxation time constant of several Allen Bradley‐type resistors used in low‐temperature thermometry are reported. The results indicate that thermal diffusion within the carbon composite controls this characteristic time and that it is independent of surface heat transfer. A simple formulation based on published data shows that the proper functional form and magnitude are predictable. It is most probable that these results can be used to estimate the time constant for resistors of other dimensions. The results confirm that the most effective method for decreasing the thermal time constant of carbon composition resistors is by reducing their thickness.

ISSN:0034-6748    

DOI:10.1063/1.1137471

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An exploratory experiment is described in which large neon and argon cluster ions are detected with improved sensitivity. The cluster ion beam impinges on a CuBe converter surface, and the positive fragmented and/or sputtered secondary ions, and not the secondary electron, are used for amplification. A drastic change of the mass spectrum from a supersonic expansion is observed.

ISSN:0034-6748    

DOI:10.1063/1.1137472

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A multichannel switch is described which is triggered by a high‐voltage pulse applied to a switch electrode grounded through a single‐turn saturable inductor. Switch voltages up to 30 kV for trigger voltages of 20 kV were successfully tested. Performance similar to other triggering schemes was obtained, but without some attendant complications.

ISSN:0034-6748    

DOI:10.1063/1.1137473

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The performance of a dual‐anode x‐ray source for XPS using various uncollimated and collimated configurations is described. A novel collimator design is discussed and shown to be effective in increasing the signal‐to‐background ratio and reducing anode cross talk without substantial signal loss.

ISSN:0034-6748    

DOI:10.1063/1.1137474

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A circuit is described which provides fast acquisition of two analog signals by the Digital Equipment Corporation family of LSI 11, 11/2, and 11/23 microcomputers. This circuit digitizes each signal with 12 bits of resolution and stores the results directly in microcomputer memory via direct memory access. Real‐time data‐acquisition speeds up to three microseconds per pair of signals may be obtained.

ISSN:0034-6748    

DOI:10.1063/1.1137448

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We describe an easily tuned toroidal uhf cavity well suited for use as a probe for NMR.

ISSN:0034-6748    

DOI:10.1063/1.1137475

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A simple, low‐cost reciprocating crystallizer for crystal growth from aqueous solution has been described. The main feature of this crystallizer is its simple automatic switching arrangement for reciprocating motion.

ISSN:0034-6748    

DOI:10.1063/1.1137443

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The construction of a compact, two‐axis goniometer that has been designed specifically for use on commonly available low‐speed diamond wafering saws is described. The device can be easily attached to practically any back reflection Laue camera and is, therefore, suitable for the orientation and cutting of single crystals parallel to particular crystallographic planes or directions. It is both simple and inexpensive to construct.

ISSN:0034-6748    

DOI:10.1063/1.1137444

出版商:AIP    

年代:1983

数据来源: AIP