Preparation of P-47 scintillators for STEM

Uniform P-47 powder scintillators can be prepared with reproducible mass thicknesses by sedimenting the powder in an 0·01% solution of formvar in chloroform. A reflecting coating can be glued by floating a 60 nm aluminium film on the scintillation layer in an 0·1% solution of gelatine in water. The optimum thickness of P-47 for 20–100 keV electrons increases slower than the electron range due to the absorption and scattering of light with increasing thickness. An aluminium coating increases the light output by a factor 1·85 for 20 keV and 1·4 for 100 keV electrons. The noise of the emitted light quanta and the photomultiplier detection system shows a minimum for the optimum thickness of largest light output and is only a factor 1·3–1·6 larger than the calculated shot noise of the incident electron beam.     

The use of a low-viscosity epoxy resin in the preparation of undecalcified bone sections for light microscopy

A method using the Spurr low-viscosity epoxy resin medium for the preparation of Von Kossa impregnated undecalcified bone sections for light microscopy is described. The method gives high quality thin sections (0·6–1·0 μm) of cancellous bone and overcomes some of the difficulties experienced with other plastics. The procedure is relatively simple and is well suited for use in a routine diagnostic laboratory.     

Histologic investigation of glycol methacrylate embedded chick embryonic tissue.

Specific light microscopic investigations (i.e. histochemical) of early embryonic material have always been beset by difficulties in processing and obtaining tissue sections of good quality. The advent of glycol methacrylate (GMA) as an embedding medium now provides a means to overcome these inherent problems with this tissue. Investigations were carried out to assess the histological results produced by different fixatives and times of fixation of GMA embedded 5-day chick embryonic tissue. Optimum cellular preservation of all tissues occurred following fixation in a mixture of acetic acid, 95% ethanol and neutral buffered formalin (AAF). With the procedures described in this study, a new method is available for more comprehensive examination of all types of early embryonic material.     

An improved method for combined autoradiography and histochemistry: the simultaneous detection of 6-3H thymidine and acid phosphatase activity in cryostat sections of mouse thymus and duodenum

A new method is described that enables the simultaneous detection of 6-³H thymidine incorporation and acid phosphatase activity in the same tissue section. Histochemically, naphthol AS B1 released by tissue based acid phosphatase activity from the substrate naphthyl AS B1 phosphoric acid is coupled with a range of diazonium salts to produce insoluble azo dyes. The azo dye tests result in a particulate localization of lysosomal acid phosphatase and also label diffuse sources associated with cell death. The tests selected permit the application of photographic emulsion without the necessity of an inert barrier layer to separate the emulsion from the histochemically treated cryosections. The localization of 6-³H thymidine incorporation and cell death in mouse thymus and duodenum is demonstrated and comparative counts estimating the distribution of 6-³H thymidine incorporation and hydrolase labelled cell death in the thymus are presented. Young mouse thymus (5 weeks) was found to contain 1·36 ± 0·12% dying cells and 6·78 ± 0·03% thymidine incorporating cells, whilst old mouse thymus (53 weeks) was found to contain 2·34 ± 0·6% dying cells and 5·29 ± 0·37% thymidine incorporating cells.     

The influence of tissue processing on quantitative histopathology in breast cancer

Objective grading of breast cancer by morphometry has been suggested for improving the precision of the prognostic prediction. However, the tissue components evaluated might be influenced by variations in the processing, reducing the clinical value. In the present study, the impact of the period of fixation, of the acidity of the fixative and of the embedding medium was investigated by allocating tissue samples from 27 surgical breast cancer specimens systematically randomly to different modes of processing. The volume-weighted mean volume of cancer cell nuclei, v?_V(nuc), was estimated using the method of point-sampled intercepts on vertical sections. In addition, estimates of the mean nuclear profile area, ā_H(nuc), the nuclear volume fraction, V_V(nuc), the nuclear profile density, ND, and the mitotic profile frequency, MF, were obtained. The quantitative histopathological estimates were stable with respect to the investigated variables of the tissue processing. No significant differences were found when comparing the estimates obtained in samples from five tumours fixed in formalin at pH 5·0, 6·0, 7·0, 7·4 and 8·0, respectively. Similarly, no significant correlations between the estimates and the period of formalin fixation (24 h, 3 days and 3 months) were found in samples from five other tumours. However, the v?_V(nuc) was 13% larger (2p = 0·004) and the mean ND 17% smaller (2p = 0·04) in hydroxyethyl-methacrylate-embedded samples from 17 tumours as compared to paraffin-embedded samples. Thus, the shrinkage observed in paraffin seems to affect nuclei less than tissue.     

An interference technique for measuring the thickness of semi-thin and thick sections

An interference method is described for measuring section thickness in the range 0·3–45 μm. An incident illumination objective incorporating a beam splitter and adjustable reference mirror is used to generate interference fringes by reflection from the upper surfaces of sections on glass slides. Sections do not require a reflective coating. The lateral displacement of the zero-order fringe generated using white light is measured in terms of sodium light fringes and photographic enlargement of the fringes allows measurement to ± 30 nm. The method is simple in operation and allows rapid assessment of any local distortions over the entire section area.     

Staining sections of water-miscible resins

Penetration of hydrophilic acid and basic dyes into sections cut from glycol methacrylate (GMA)-embedded tissues was studied; as were the effects on such staining of superficial coatings of thin layers of GMA. Dye size was a major factor in controlling penetration of resin and staining of tissues. ‘Large’ dyes (>1000 Da) entered GMA very slowly, and only stained those tissue components poorly infiltrated by resin. ‘Small’ dyes (< 550 Da) penetrated GMA readily, and stained tissue components whether or not they were resin-infiltrated. Dyes of intermediate size penetrated the resin, but the staining of resin-infiltrated tissue elements was slow. Background staining of resin also varied with dye size. Large dyes gave no staining of GMA. Small dyes did, but were readily removed by water washing. Dyes of intermediate size penetrated resin slowly, and once inside were lost slowly. This gave background staining which required use of the plasticizing solvent ethanol for its removal. Increases in resin cross-linking also reduced staining rates. As a consequence, it is possible to predict the probable suitability, or otherwise, of various staining reagents proposed for use with GMA sections; and also the probable influences of histoprocessing on stain penetration. In particular it is suggested that penetration of colloidal metals and macromolecular reagents (e.g. labelled antibodies and lectins) will be limited to resin-free structures, and to the surface of resin sections. The use of superficial GMA coatings as convenient semipermeable membranes for enzyme histochemistry is also noted.     

Quantitative studies on the preservation of choline and ethanolamine phosphatides during tissue preparation for electron microscopy. II. Other preparative methods

The loss of ¹⁴C-ethanolamine- and ³H-choline-labelled phospholipids from rat liver during preparation for electron microscopy by some less frequently used processing methods has been examined. Permanganate and formaldehyde-potassium dichromate fixation followed by Araldite embedding were investigated and five procedures involving embedding in water-miscible methacrylates (GMA). These procedures included a conventional method of dehydration and embedding in GMA, a low-temperature GMA embedding method, dehydration with ethylene glycol, freeze drying and freeze substitution. These results are compared with those obtained after conventional tissue preparation (presented previously, Cope & Williams, 1969). Formaldehyde-potassium dichromate compared favourably with the conventional procedures for the preservation of both phosphatides, especially phosphatidyl ethanolamine. Permanganate fixation was much less effective. Severe loss of both phosphatides occured after freeze drying and freeze substitution in glutaraldehyde-alcohol. GMA is shown to be a more potent phospholipid solvent than ethanol under the conditions employed. Low-temperature embedding reduced the loss of phosphatidyl choline during embedding. Results obtained by scintillation counting were confirmed by grain counts on thick-section autoradiographs. No direct relationship between extraction and the electron-microscopic appearance of membranes was discernible. It is believed that membrane prominence is largely dependent upon the electron density of the surrounding cytoplasm rather than on the degree of phospholipid extraction.     

Modeling of transport phenomena and solidification cracking in laser spot bead-on-plate welding of AA6063-T6 alloy. Part I—the mathematical model

In this work, the oscillating arc narrow gap all-position gas metal arc (GMA) welding process was developed to improve efficiency and quality in the welding of thick-walled pipes. The statistical models of narrow gap all-position GMA weld bead geometry were developed using response surface methodology (RSM) based on central composite design (CCD). The developed models were checked for their adequacy and significance by ANOVA, and the effects of wire feed rate, travel speed, dwell time, oscillating amplitude and welding position on weld bead dimension were studied. Finally, the optimal welding parameters at welding positions of 0° to 180° were obtained by numerical optimization using RSM.     

An electron microscopy study of the phase Al3Fe

The phase Al₃Fe (monoclinic C2/m, a = 1·549 nm, b = 0·808 nm, c = 1·248 nm, β = 107·8°) has been studied by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). Crystals were obtained from a direct chill-cast ingot of an Al-0·25 wt% Fe-0·13 wt% Si alloy. Extracted crystals were prepared by dissolving the aluminium phase in butanol and filtering off the particles. The extracted Al₃Fe crystals were mainly (100) platelets. The monclinic lattice was confirmed by tilt experiments and the mirror plane was confirmed by convergent beam electron diffraction. Experimental HREM images from the [100] and [110] projection agreed with images calculated by the multislice method. The interpretation of images in terms of a projected crystal structure is discussed. Common defects in Al₃Fe crystals were: twins on (100) and faults on (001). The (001) faults could be described by a displacement 1/2·[100] on a fault plane at z = 0·5 in the unit cell. A model for (001) faults, based on multiple twinning, is proposed.     

Sectioning and imaging hard mineral fibres in biological tissues

A technique is described which overcomes the problems associated with sectioning biological tissue containing hard mineral fibres. 0·2–0·5 μm thick sections were cut with a diamond knife, placed in a folding grid, conventionally stained with uranyl acetate and lead citrate and viewed at an accelerating voltage of 200 kV in the scanning transmission mode.     

A new method to correlate acoustic spectroscopic microscopy (30 MHz) and light microscopy

A powerful new method is used to investigate the correlation between light microscopic and acoustic properties of biological tissues. Specimens of liver were sectioned into successive slices, 250 μm and 10 μm thick. The thick sections were investigated acoustically, the thin sections by means of light microscopy. Markers that could be detected and located, both optically and acoustically, were used to find and reconstruct corresponding regions in the acoustic and optical sections (2·5 × 2·5 mm). Parameter images were reconstructed from the sections investigated acoustically. The acoustic parameters were attenuation at 30 MHz, the slope of the attenuation spectrum (between 10 and 50 MHz), backscattering at 30 MHz, the slope of the backscattering spectrum (between 10 and 50 MHz) and the local ultrasound velocity. Acoustic images were obtained in the frequency range from 10 to 50 MHz, yielding a lateral resolution of about 50 μm. The sections for light microscopy were stained according to the Goldner trichrome staining technique. The histological composition was determined quantitatively, using digital image segmentation techniques. The percentage of collagen-rich fibrous tissue, luminal structure and interstitial spaces, and the number of nuclei were calculated for regions of 250 × 250 μm. These histological features were correlated with the acoustic parameters obtained from the corresponding regions in adjacent sections. It was thus possible to find the histological components responsible for acoustic parameters.     

Observation of biological materials by X-ray photoelectron-conversion contact microscopy

Dried biological specimens, such as fossil diatoms, collagen, nerve tissue and spicule of Trepang, were observed by X-ray photoelectron-conversion contact microscopy. A spatial resolution of 0·2 μm was attained. The fossil diatom image shows a clear difference below and above the carbon K-absorption edge (4·46nm).     

The effects of glycol methacrylate as a dehydrating agent on the dimensional changes of liver tissue

The dimensional changes of liver sections during the course of processing with glycol methacrylate (GMA) or with ethanol are described. Tissue processing with ethanol served as a control. During prolonged processing steps (24 h each), linear shrinkage of tissue specimens dehydrated with GMA at room temperature was 13.2%. Subsequent infiltration with GMA resulted in trivial swelling, and polymerization in slight shrinkage (2.3%). In comparison, processing with cold GMA resulted in shrinkage during dehydration (about 10.8%), a slight swelling in pure GMA, followed by shrinkage during polymerization (2.2%). Short routine processing schedules resulted in similar shrinkage/swelling patterns, although precise values differed slightly. In all experiments, ethanolic dehydration resulted in smaller dimensional tissue changes than did GMA dehydration. The dimensional changes of tissue sections during stretching on water, mounting and drying compensated for the major part of the shrinkage manifested during processing.     

Measurement and compensation of pitch error based on GMA with elimination of its hysteresis

This paper proposes a pitch error compensation technique with decomposition of mechanical signals based on giant magnetostrictive actuator (GMA) to eliminate tool tracking errors and to reach a high machining precision. In ultra-precision cutting, grinding and nontraditional machining, there is a difficult problem for achieving long travel and high precision. Considering the characteristics of giant magnetostrictive materials (GMM), a micro-displacement GMA with a flexure hinge micro-motion table is designed, and used for error compensation. The inherent hysteresis nonlinearity of the GMA is controlled effectively by a sliding mode robust adaptive controller (SMC). Aiming at reducing the positioning error of a precision working table driven by an AC servo motor, the measurement of the dynamical characteristics of the system is carried out by a laser interferometer. The leadscrew pitch error, which accounts for most of the error detected, is separated out by an improved signal filter algorithm. Experimental results show that the positioning error is reduced to an extent within ±8 μm from ±20 μm after compensation, which demonstrates the feasibility of the control and compensation method.     

Use of differential interference contrast microscopy to determine cell renewal times in mouse intestine

Pieces of mouse mid jejunum have been cleared in glycerin and examined by differential interference contrast microscopy at low powers of magnification. The position and number of crypts and villi can be determined in the same specimen using this technique. The calculated value for crypt/villus ratio 4·53 ± 0·99 (mean ± SD) is less than a previously published value obtained using indirect techniques. A revised estimate of cell renewal time, based on this newly determined value for crypt/villus ratio, is 45 h. This agrees with earlier estimates derived from entirely different methods of analysis. The general usefulness of this form of light microscopy in helping one appreciate some three-dimensional problems in mucosal architecture is emphasized.     

Corrosion and wear behaviour of ZrN thin films

Abstract

ZrN coating is an alternative candidate to replace the conventional TiN coating especially for high temperature oxidation resistance applications. ZrN coatings of varying thickness (1·5, 2·0, 2·5, 3·0 and 4·0 μm) were deposited on 316 stainless steel substrates by cathodic arc evaporation in a reactive nitrogen atmosphere. The influences of lamellae thickness on the microstructure, tribological and corrosive properties of the films were investigated. The coefficient of steady state friction of the films ranged from 0·213 to 0·659. The corrosion resistance of the coatings was tested in 1 N H₂SO₄ solution. The results indicate that the microstructure, wear and corrosion properties of the films were dependent on lamellae thicknesses and film structure.     

废水中苯酚的测定方法研究

研究在pH为8.0的NH3.H2O-K2HPO4-KH2PO4缓冲溶液中4-氨基安替比林与苯酚的显色反应。在pH=8.0的缓冲溶液中,苯酚与4-氨基安替比林和铁氰化钾反应生成黄色染料,用三氯甲烷萃取后,其λmax为460nm,表观摩尔吸光系数为2.1×104L.moL-1.cm-1。苯酚质量浓度在0~6mg/mL范围内服从比尔定律。本方法用于测定废水中的苯酚时,结果令人满意。     

Empirically determined freezing time for quick-freezing with a liquid-nitrogen-cooled copper block

A method is presented to determine freezing time empirically. The method is based on determining the amount of stretch of a skinned muscle fibre while it is being frozen. Freezing time, as determined with this method, lies in between 0·5 and 1·5 ms.     

Nanometre scale mechanical properties of extremely thin diamond-like carbon films

Abstract

Extremely thin diamond-like carbon (DLC) films are deposited by the filtered cathodic vacuum arc (FCVA) and plasma chemical vapour deposition (p-CVD) methods. The target thicknesses of the extremely thin protective DLC films deposited on a Si (100) surface by FCVA and p-CVD are 0·1, 0·4, 0·8, 1·0, 2·0, 5·0 and 100·0 nm. Nanoindentation hardness and nanowear resistance are evaluated by atomic force microscopy (AFM). The nanoindentation hardnesses of 100 nm thick DLC films deposited by FCVA and p-CVD are 57 and 25 GPa respectively. The nanowear test by AFM clarifies the mechanical properties of extremely thin DLC films. The wear depths of 1 and 2 nm thick FCVA-DLC films are extremely shallow. The wear depths of the 1·0 and 2·0 nm thick p-CVD-DLC films exceed the film thicknesses after five sliding cycles. These results reveal differences in the wear resistance of extremely thin DLC films and the superior mechanical properties of FCVA-DLC thin films.