bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ Lubrication Dispersion of Multi‐Walled Carbon Nanotubes in Poly(propylene) Melts
Authors: Hong Joung Sook , Hong In Gook , Lim Hyung Tag , Ahn Kyung Hyun , Lee Seung Jong
Published: November 2011

An in situ lubrication dispersion method is developed to achieve electrical conductivity in PP containing a small amount of MWCNTs. Good dispersion of the MWCNTs in PP is observed even after a short mixing time because the interactions between the entangled nanotubes are reduced. By in situ lubrication dispersion, the electrical percolation threshold of the PP nanocomposite can be as low as 0.5–0.7 wt% MWCNT. Rheological data also support percolation at 0.5 wt% MWCNT. With 0.5 wt% MWCNT, the slope of G′ at low frequency approaches unity and shows non‐terminal behavior. The proposed dispersion method enhances the wetting of MWCNTs and improves MWCNT dispersion compared to both direct mixing of MWCNT powder with a polymer melt and conventional master batch dilution.

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Synthesis and characterization of new selenophene‐based conjugated polymers for organic photovoltaic cells
Authors: Lee Woo‐Hyung , Lee Sang Kyu , Son Seon Kyoung , Choi Ji‐Eun , Shin Won Suk , Kim Kyoungkon , Lee Soo‐Hyoung , Moon Sang‐Jin , Kang In‐Nam
Published: November 2011

Three new polymers poly(3,4′′′‐didodecyl) hexaselenophene) (P6S), poly(5,5′‐bis(4,4′‐didodecyl‐2,2′‐biselenophene‐5‐yl)‐2,2′‐biselenophene) (HHP6S), and poly(5,5′‐bis(3′,4‐didodecyl‐2,2′‐biselenophene‐5‐yl)‐2,2′‐biselenophene) (TTP6S) that have the same selenophene‐based polymer backbone but different side chain patterns were designed and synthesized. The weight‐averaged molecular weights (Mw) of P6S, HHP6S, and TTP6S were found to be 19,100, 24,100, and 19,700 with polydispersity indices of 2.77, 1.48, and 1.41, respectively. The UV–visible absorption maxima of P6S, HHP6S, and TTP6S are at 524, 489, and 513 nm, respectively, in solution and at 569, 517, and 606 nm, respectively, in the film state. The polymers P6S, HHP6S, and TTP6S exhibit low band gaps of 1.74, 1.95, and 1.58 eV, respectively. The field‐effect mobilities of P6S, HHP6S, and TTP6S were measured to be 1.3 × 10−4, 3.9 × 10−6, and 3.2 × 10−4 cm2 V−1 s−1, respectively. A photovoltaic device with a TTP6S/[6,6]‐phenyl C71‐butyric acid methyl ester (1:3, w/w) blend film active layer was found to exhibit an open circuit voltage (VOC) of 0.71 V, a short circuit current (JSC) of 5.72 mA cm−2, a fill factor of 0.41, and a power conversion efficiency (PCE) of 1.67% under AM 1.5 G (100 mW cm−2) illumination. TTP6S has the most planar backbone of the tested polymers, which results in strong π–π interchain interactions and strong aggregation, leading to broad absorption, high mobility, a low band gap, and the highest PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
A 2D Model for Characterising First‐order Variability in Sublimation of Buried Glacier Ice, Antarctica: Assessing the Influence of Polygon Troughs, Desert Pavements and Shallow Subsurface Salts
Authors: Kowalewski Douglas E. , Marchant David R. , Head James W. , Jackson David W.
Published: November 2011

To assess the role of thermal contraction‐crack polygons (sublimation polygons) in modulating sublimation of buried glacier ice in Antarctica, we applied a 2D numerical model using COMSOL Multiphysics that calculates the rate and spatial variability of vapour diffusion through porous media. Specifically, we examined vapour transport through Granite drift, a dry supraglacial till marked with thermal contraction‐crack polygons that rests on glacier ice reportedly ≥8‐million years in age. The model results show that sublimation varies with drift texture and surface topography. Initially, the rates are highest beneath relatively coarse‐grained sand‐wedge deposits at polygon margins, creating deep, surface troughs. As troughs approach ~1‐m depth, the cooler atmospheric and soil temperatures that arise from solar shielding reduce the rates of ice sublimation to levels below that at polygon centres, preventing runaway ice loss at polygon margins. Including the effects of a salt‐cemented horizon at 10 − 15‐cm depth (porosity 20%) and a rocky surface pavement (75% ground coverage), our modelled ice loss at polygon centres, for example, is 0.022 mm a−1, an order of magnitude lower than previous estimates (0.14 mm a−1). This finding highlights the importance of including field‐based data for drift texture, topography and microclimate variation in modelling ice sublimation. The results also suggest that stable conditions (no ice loss) at polygon centres are possible with either a 1.9°C decrease in mean annual atmospheric temperature or a 12 per cent increase in mean annual relative humidity. These results indicate that the preservation of buried, multi‐million‐year‐old ice is plausible in the coldest and driest regions of Antarctica. Copyright © 2011 John Wiley & Sons, Ltd.
Synthesis and NMR elucidation of novel tetrapeptides
Authors: Makatini Maya , Chetty Thashini , Onajole Oluseye K. , Govender Thavendran , Govender Patrick , Maguire Glenn E. M. , Kruger Hendrik G.
Published: November 2011

The synthesis and NMR elucidation of Ala‐Val‐Pro‐Ile and five novel peptide‐based derivatives are reported. These peptides mimic the natural second mitochondria‐derived activator of caspase (Smac) protein. Purification was achieved using preparative HPLC and the NMR elucidation of all compounds is reported for the first time. A series of overlapping signals were observed in the 1D NMR spectra thus making assignment a difficult task to undertake. The use of 2D NMR techniques with the inclusion of efficient adiabatic symmetrized ROESY proved to be an effective tool in overcoming these difficulties. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.
Preparation, luminescence and structural properties of rare‐earth‐doped RbLuS2 compounds
Authors: Jarý V. , Havlák L. , Bárta J. , Nikl M.
Published: November 2011

Rare‐earth (RE = Ce, Pr, Sm, Tb) doped ternary sulfides of the general formula RbLu0.99RE0.01S2 and undoped RbLuS2 were synthesized in the form of crystalline hexagonal platelets by chemical reaction in the electric resistance furnace under the flow of hydrogen sulfide. Only a single crystalline phase of the rhombohedral lattice system (space group $ {\rm R}\bar 3{\rm m}) $ was detected by X‐ray powder diffraction. Absorption and luminescence characteristics were measured. The band edge of RbLuS2 is found at 310 nm, and characteristic Pr3+, Sm3+ and Tb3+ 4f–4f emission lines in the visible spectral range are observed. A charge transfer transition in the Pr3+ excitation spectrum in the near UV spectral region is revealed and an efficient energy transfer from the host to the emission centers is found. The application potential for white LED or X‐ray phosphors is discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of compatibilizers and processing temperature on microcellular injection‐molded polypropylene/(waste tire powder) composites
Authors: Zhang Zhen‐Xiu , Fan Jun‐ling , Pal Kaushik , Kim Jin Kuk , Xin Zhen‐Xiang
Published: November 2011

Nowadays the economic recycling of waste tires has become a global challenge. The use of waste tire powder as a dispersed elastomeric phase in a polypropylene (PP) matrix offers an interesting opportunity for recycling of waste tire rubber. Compatibilized PP/(waste tire powder) composites are microcellularly processed to create a new class of materials with unique properties. Recent studies have demonstrated the feasibility of developing microcellular structures in PP/waste ground rubber tire (WGRT) composites. Microcellular PP/WGRT composites are prepared by an injection‐molding process using a chemical blowing agent. In this study, cell sizes, cell density, void fraction, and mechanical properties of the composite foams were measured, as well as the shear viscosity of the unfoamed composites. The influence of various compatibilizers and processing temperatures on cell morphology and the mechanical properties of injection‐molded PP/WGRT composites were investigated. It was seen that the addition of maleic anhydride‐grafted styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) increased the shear viscosity of the composites. The void fraction and cell density of the PP/WGRT composites increased with addition of compatibilizers, whereas the average cell sizes decreased. A processing temperature range of 180–195°C gave finer microcellular structure and regular cell distribution. The SEBS‐g‐MA enhanced the elongation properties and acted as an effective compatibilizer in this particular system. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers
Likelihood-Based Clustering of Meta-Analytic SROC Curves
Authors: Holling Heinz , Böhning Walailuck , Böhning Dankmar
Published: November 2011

Meta-analysis of diagnostic studies experience the common problem that different studies might not be comparable since they have been using a different cut-off value for the continuous or ordered categorical diagnostic test value defining different regions for which the diagnostic test is defined to be positive. Hence specificities and sensitivities arising from different studies might vary just because the underlying cut-off value had been different. To cope with the cut-off value problem interest is usually directed towards the receiver operating characteristic (ROC) curve which consists of pairs of sensitivities and false-positive rates (1-specificity). In the context of meta-analysis one pair represents one study and the associated diagram is called an SROC curve where the S stands for “summary”. In meta-analysis of diagnostic studies emphasis has traditionally been placed on modelling this SROC curve with the intention of providing a summary measure of the diagnostic accuracy by means of an estimate of the summary ROC curve. Here, we focus instead on finding sub-groups or components in the data representing different diagnostic accuracies. The paper will consider modelling SROC curves with the Lehmann family which is characterised by one parameter only. Each single study can be represented by a specific value of that parameter. Hence we focus on the distribution of these parameter estimates and suggest modelling a potential heterogeneous or cluster structure by a mixture of specifically parameterised normal densities. We point out that this mixture is completely nonparametric and the associated mixture likelihood is well-defined and globally bounded. We use the theory and algorithms of nonparametric mixture likelihood estimation to identify a potential cluster structure in the diagnostic accuracies of the collection of studies to be analysed. Several meta-analytic applications on diagnostic studies, including AUDIT and AUDIT-C for detection of unhealthy alcohol use, the mini-mental state examination for cognitive disorders, as well as diagnostic accuracy inspection data on metal fatigue of aircraft spare parts, are discussed to illustrate the methodology.
Development and Immigration: Experiences of Non-US Born Black Women
Authors: Seguino Stephanie
Published: November 2011

An exploration of inequality at the intersection of race, gender, and nationality offers a means to explore how complex economic and social forces combine to shape women's outcomes in ways that differ from men's. Women's responsibility for care work and other forms of unpaid labor inhibits labor force participation, and in some cases, redounds heavily on children. Those responsibilities, coupled with labor market discrimination against black women, US or foreign born, increases the difficulties single mothers face in providing for families.
The uneasy relationship between national security and personal freedom: New Zealand and the ‘War on Terror’
Authors: Small David
Published: November 2011

As part of the ‘War on Terror’ declared in response to the 11 September 2001 attacks, countries introduced legislation to bolster national security, often at the expense of personal freedoms and long-established legal principles. Like the Cold War, the ‘War on Terror’ is cast as a global struggle of good against evil. New Zealand defied Cold War logic with its anti-nuclear policy. Examining the difficulties of upholding personal freedoms and the rule of law while bolstering national security, this article analyses New Zealand's anti-terrorism legislation and shows that it has steadily moved away from its initial measured approach. It argues that New Zealand could and should develop an anti-terrorism model appropriate to low-risk societies, and that, like its anti-nuclear stance during the Cold War, such an independent approach would be a valuable contribution to the world community.
Seasonal phototransformation of dissolved organic matter to ammonium, dissolved inorganic carbon, and labile substrates supporting bacterial biomass across the Baltic Sea
Authors: Aarnos Hanna , Ylöstalo Pasi , Vähätalo Anssi V.
Published: November 2011

We studied the photochemical transformation of dissolved organic matter (DOM) to dissolved inorganic carbon (DIC), ammonium (NH4+), and labile organic substrates supporting bacterial carbon biomass along a salinity gradient throughout the Baltic Sea during summer, autumn, and spring. The photoproduced DIC, NH4+, and labile DOM supporting bacterial biomass were related to the number of photons absorbed during the irradiations of biologically recalcitrant DOM to determine apparent quantum yields. The apparent quantum yields for the photoproduction of DIC and NH4+ lacked seasonal variation, but behaved differently along the salinity gradient; the photoproduction of DIC decreased, while photoammonification increased with increasing salinity. The apparent quantum yield for the photoproduction of labile DOM supporting bacterial biomass was highest in summer and unaffected by salinity. The annual photoammonification rate over the entire Baltic Sea ranged from 0.038 to 0.049 Tg N, equivalent to 13%–23% of the annual atmospheric deposition of inorganic N. The annual phototransformation of dissolved organic carbon (DOC), including the direct photomineralization and indirect bacterial mineralization of photoproduced labile DOM (total of 2.71–3.94 Tg C), exceeded the annual river loading of photoreactive DOC, assuming that half of the total river DOC input to the Baltic Sea is photoreactive. As the annual photomineralization of DOC exceeded the annual terrestrial input of photoreactive DOC to the Baltic Sea, the photochemical transformation is a major sink for terrestrial DOC in such coastal systems.
The mechanisms of sea ice melt pond formation and evolution
Authors: Polashenski Chris , Perovich Donald , Courville Zoe
Published: November 2011

A series of observations were made on melting first year, landfast Arctic sea ice near Barrow, Alaska to explore the seasonal evolution of melt pond coverage. Observations of pond coverage, albedo, and ice properties are combined with terrestrial lidar measurements of surface topography and meltwater balance to quantitatively identify the timing and role of mechanisms driving pond coverage. The formation of interposed fresh ice is found to eliminate meltwater percolation through early pond formation and allow widespread ponding well above sea level. Pond drainage to sea level occurs principally by horizontal meltwater transport over the ice surface to macroscopic flaws. Freeboard loss, caused by buoyancy decline as the ice thins, controls pond growth late in the melt season after percolation begins. The majority of the macroscopic flaws that drain melt ponds to sea level are observed to develop from brine drainage channels within the ice. A simple thermodynamic model of meltwater percolation illustrates that fresh meltwater inflow causes pores in the ice to either shrink and freeze shut or enlarge based on initial size and ice temperature. This threshold behavior of pore diameter controls both the blockage of smaller pores with interposed ice and the enlargement of larger brine drainage channels to allow meltwater drainage. The results identify links between the temporal evolution of pond coverage and ice temperature, salinity, and thickness, providing new opportunities to realistically parameterize ponds and summer ice albedo within sea ice models.
A waveguide model of the return stroke channel with a “metamaterial” corona
Authors: Lehtinen Nikolai G.
Published: November 2011

We model the lightning return stroke channel as a three layer cylindrical waveguide, consisting of (1) highly conducting thin core channel; (2) “metamaterial” corona, i.e., corona with an effective bulk anisotropic dielectric permittivity tensor which is due to the fine structure of leaders branching away from the main channel; and (3) the surrounding non‐conducting air. The lowest axially symmetric TM mode in this waveguide represents the return stroke current wave. We find time‐ and space‐domain solutions for the current wave in a channel connected to the ground driven by an axial current of Bruce‐Golde model temporal shape concentrated at the point of the channel connection to the ground. The front of the current wave is found to be dispersed, and the speed of the front is significantly (by a factor of 5–10 for some parameters) slower than the speed of light. The calculated radial electric field is found to be consistent with experimental measurements. When the second layer of the waveguide is filled with an isotropic material, the slowdown of the wavefront is found to be smaller. The time‐ and space‐domain calculations are also supported by the numerical solution of a dispersion equation, which shows that the phase velocity may be significantly less than the speed of light.
Impact of a large tropical reservoir on riverine transport of sediment, carbon, and nutrients to downstream wetlands
Authors: Kunz Manuel J. , Wüest Alfred , Wehrli Bernhard , Landert Jan , Senn David B.
Published: November 2011

Large dams can have major ecological and biogeochemical impacts on downstream ecosystems such as wetlands and riparian habitats. We examined sediment removal and carbon (C), nitrogen (N), and phosphorus (P) cycling in Itezhi‐Tezhi Reservoir (ITT; area = 364 km2, hydraulic residence time = 0.7 yr), which is located directly upstream of a high ecological value floodplain ecosystem (Kafue Flats) in the Zambezi River Basin. Field investigations (sediment cores, sediment traps, water column samples), mass balance estimates, and a numerical biogeochemical reservoir model were combined to estimate N, P, C, and sediment removal, organic C mineralization, primary production, and N fixation. Since dam completion in 1978, 330 × 103 tons (t) of sediment and 16 × 103, 1.5 × 103, 200 t of C, N, and P, respectively, have accumulated annually in ITT sediments. Approximately 50% of N inputs and 60% of P inputs are removed by the reservoir, illustrating its potential in decreasing nutrients to the downstream Kafue Flats floodplain. The biogeochemical model predicted substantial primary production in ITT (∼280 g C m−2 yr−1), and significant N‐fixation (∼30% for the total primary production) was required to support primary production due to marginal inputs of inorganic N. Model simulations indicate that future hydropower development in the reservoir, involving the installation of turbines driven by hypolimnetic water, will likely result in the delivery of low‐oxygen waters to downstream ecosystems and increased outputs of dissolved inorganic N and P by a factor of ∼4 and ∼2 compared to current dam management, respectively.
Preview: the New York meeting
Authors: Rothenberg Marian S.
Published: November 2011

Applications of physics and new directions in teaching—these are the emphases in the joint meeting of The American Physical Society and the American Association of Physics Teachers. The four-day meeting, which takes place from Monday 29 January through Thursday 1 February in New York, will include APS sessions on air quality, transistors (organized with the Society of Physics Students), laser fusion, air–sea interactions, nuclear physics in medicine, technological perspectives for solid-state physics, applications of solid-state physics, and liquid crystals; AAPT has scheduled sessions on computers in physics teaching, multimedia teaching, new programs for two-year colleges, critiques of and improvements on the Keller plan, and outstanding new programs in secondary schools. And the two societies are jointly sponsoring a discussion of those parts of the “Bromley report” the report of the National Academy of sciences Physics Survey Committee) that deal with general education, as well as a session on nonprofessional courses that relate physics and society.
“The Dirty Hand in the Latex Glove”: A Study of Hand Hygiene Compliance When Gloves Are Worn
Authors: Fuller Christopher , Savage Joanne , Besser Sarah , Hayward Andrew , Cookson Barry , Cooper Ben , Stone Sheldon
Published: November 2011

Background and Objective.

Wearing of gloves reduces transmission of organisms by healthcare workers' hands but is not a substitute for hand hygiene. Results of previous studies have varied as to whether hand hygiene is worse when gloves are worn. Most studies have been small and used nonstandardized assessments of glove use and hand hygiene. We sought to observe whether gloves were worn when appropriate and whether hand hygiene compliance differed when gloves were worn.

Design.

Observational study.

Participants and Setting.

Healthcare workers in 56 medical or care of the elderly wards and intensive care units in 15 hospitals across England and Wales.

Methods.

We observed hand hygiene and glove usage (7,578 moments for hand hygiene) during 249 one-hour sessions. Observers also recorded whether gloves were or were not worn for individual contacts.

Results.

Gloves were used in 1,983 (26.2%) of the 7,578 moments for hand hygiene and in 551 (16.7%) of 3,292 low-risk contacts; gloves were not used in 141 (21.1%) of 669 high-risk contacts. The rate of hand hygiene compliance with glove use was 41.4% (415 of 1,002 moments), and the rate without glove use was 50.0% (1,344 of 2,686 moments). After adjusting for ward, healthcare worker type, contact risk level, and whether the hand hygiene opportunity occurred before or after a patient contact, glove use was strongly associated with lower levels of hand hygiene (adjusted odds ratio, 0.65 [95% confidence interval, 0.54-0.79]; P<.0001).

Conclusion.

The rate of glove usage is lower than previously reported. Gloves are often worn when not indicated and vice versa. The rate of compliance with hand hygiene was significantly lower when gloves were worn. Hand hygiene campaigns should consider placing greater emphasis on the World Health Organization indications for gloving and associated hand hygiene.

Trial Registration.

National Research Register N0256159318.
VIII.–‐Studies On Cell Division In Tissue Culture
Authors: Canti R. G. , Spear F. G. , Spear F. G. , Cox S. F.
Published: November 2011

(a) The Effect of Gamma Ray Radiation on Cell Division in Tissue Culture in Vitro.

(b) The Effect of Low Temperature on Cell Division in Vitro.

(c) The Effect of X‐Rays on Mitosis in Tissue Culture in Vitro.
XII.–‐The Mode Of Formation Of The Image In The Microscope
Authors: Rheinberg Julius
Published: November 2011

It is shown that, as regards the formation of the image by the microscope, the Abbe theory and the Airy theory and its variants do not in any way conflict. The Abbe theory, by reason of the way it originated, deals in the first place with objects so illuminated as to lack self‐luminosity to the maximum extent. The Airy theory deals with completely self‐luminous objects. These are the two limiting cases. A gradual but strictly limited approach towards self‐luminosity is presented by the structural elements of objects according to the way they may be illuminated. It is indicated how all cases can be, and are, indeed, most conveniently dealt with by the Abbe theory.
METALLOGRAPHY AT LOW TEMPERATURES
Authors: Rosenhain Walter , Murphy A. J.
Published: November 2011

Methods are described for the microscopic investigation of the structure of mercury and amalgams in the solid state. Specimens of the metals are solidified by means of carbon dioxide snow or other refrigerant, and are polished, etched and examined microscopically at temperatures below −40° C. Typical photomicrographs are included.
GANGLIONEUROMA OF THE ADRENAL MEDULLA IN ALBINO RATS
Authors: Haddow A. , Horning E. S.
Published: November 2011

SYNOPSIS

Ganglioneuromas of the adrenal medulla are occasionally reported in man, but to the best of the authors' knowledge the histology of these tumours has not previously been described in rodents. Ganglioneuromas of the adrenal gland developed in 2 male albino rats during treatment with aminostilbene and aromatic nitrogen mustard carcinogens respectively. As these adrenal lesions showed no evidence of calcification or extensive degeneration it is therefore considered likely that they arose after treatment with the carcinogen had commenced. The histological structure of these nerve tumours in the treated rats coincides quite closely with that previously described in human adrenal ganglioneuromas.

Abnormal accumulations of Nissl substance are seen in the large mature ganglionic cells of the rat adrenal tumours, which the authors think is closely linked with their failure to function as normal neurones. When considering the incapacity of adult nerve cells to undergo mitosis, the histogenesis of these tumours is a subject of special interest. The possible development of ganglioneuromas from undifferentiated proliferating neural crest tissue of the developing sympathetic ganglia or adrenal medulla is also discussed.
MALIGNANT TRANSFORMATION IN A TRANSPLANTABLE FIBROADENOMA OF THE RAT
Authors: Selbie F. R.
Published: November 2011

SYNOPSIS

The changes undergone by a transplantable fibroadenoma of the rat during 24 passages over a period of 15 years are described. Both the stroma and the epithelial elements have shown independent growth resulting in pure sarcomata and pure carcinomata with metastases. It is suggested that the same tumour can be benign or malignant, its behaviour being determined either by the local resistance of the host or by excess of proliferative energy.
EXPERIMENTS WITH A VARIABLE AMPLITUDE AND PHASE MICROSCOPE
Authors: Oettlé A. G.
Published: November 2011

SYNOPSIS.

A special Cooke microscope was used to examine the principles of phase‐contrast applied to a series of simple objects. With transparent objects the image contrast with different methods depends on the phase change introduced by the object. Simple absorption of the direct light without phase change increases contrast of both phase and absorbing objects at first, but eventually produces central dark‐ground illumination. With objects of widely differing phase change optimum phase‐contrast is obtained with a quarter‐Nave phase‐plate. The exact degree of phase change required is not critical. Absorption of the direct light increases the sensitivity and it is suggested that 100 P.c., 20 p.c., and 6 p.c. transmission objectives would suit most requirements. Absorption of diffracted light is useful with objects of high phase change, but as these are already easy to see the scope of this method is limited. Phase‐contrast is maximal at the border of the image of a large object, but it extends further into the image than is generally realized. As a means of immersion refractometry phasecontrast is more sensitive than the microscopical methods commonly employed. Precautions to be observed in the use of the star test and Abbe test plate are mentioned.
RECENT DISCOVERIES CONCERNING MITOCHONDRIA AND GOLGI APPARATUS AND THEIR SIGNIFICANCE IN CELLULAR PHYSIOLOGY
Authors: Bourne Geoffrey H.
Published: November 2011

SYNOPSIS.

Mitochondria

Recent researches have shown that mitochondria contain a high percentage of a number of enzymes which play an important part in the aerobic metabolism of the cell. The mitochondria therefore rise to importance as the major centres of cell respiration. The fact that many of these enzymes are constituents of the Krebs tricarboxylic acid cycle‐a cycle which has been described as the meeting point of protein, fat, and carbohydrate metabolism‐indicates that mitochondria may in addition be concerned both with breakdown of protein and fat as well as carbohydrate and with the synthesis of these three substances.

Golgi apparatus

A mass of evidence now supports the conception of the Golgi apparatus as being composed of lipo‐protein spheres which possess unusual capabilities of segregation for a variety of substances. It is suggested that the primary function of these spheres is to protect the cell by segregating noxious substances. In secretory cells this segregating ability is used to accumulate secretory products which have been synthesized by the mitochondria.
X.—THE USE OP POLYVINYL ALCOHOL AND ITS DERIVATIVES AS MICROSCOPICAL MOUNTING MEDIA.; PAET II.—HYDROCARBON‐MISCIBLE MOUNTING MEDIA
Authors: Gray Peter , Wess Gloria
Published: November 2011

SYNOPSIS

A mounting medium with a refractive index of 1·474 had been developed from a 23 p.c. dispersion of polyvinyl acetate in “cellosolve” plasticized with 13 p.c. of diamyl phthalate. When heated the medium hardened in 2–3 days to a stable transparent film which did not cause stain‐fading in test mounts stained with either Ehrlich's acid alum haematoxylineosin B or with Mallory's acid fuchsin‐orange G‐aniline blue and exposed for 6 weeks to heat, artificial, or natural lighting.
XI.—THE TEACHING OF THE USE OF THE POLARIZING MICROSCOPE
Authors: Hartshorne N. H. , Stuart A.
Published: November 2011

SYNOPSIS

It is emphasized that students must fully understand the optics of the lens system of the polarizing microscope, and also that they must acquire the ability to “see” in three dimensions, so as to appreciate clearly the relationships between the optical and morphological vectors of crystals. To achieve the second of these requirements free use should be made of skeletal models in teaching and some suitable models for this purpose are described. Another teaching aid which the authors regard as indispensable is the projection microscope. Suggestions are made regarding the best ways in which polarization colours, extinction and extinction angles, and interference figures may be explained and demonstrated. Special considerations affecting the teaching of biologists are mentioned. Finally the equipment and lay‐out of the teaching laboratory are discussed, and a new type of lock‐up working table is described.
II.—MICROSCOPY IN THE REGION OF WAVE‐LENGTH Λ= 2,000Å. to 1,000Å
Authors: Johnson B. K.
Published: November 2011

Synopsis

The paper describes the technique for using the microscope in the region 2,000Å. to 1,000Å. and the instrument for doing this. The experimental work shows that if the instrument is mounted in a chamber containing nitrogen instead of in vacuo the technique is greatly facilitated. Reflecting objectives of the Schwarzschild type and a refracting type monochromat (made in fluorite) have been used in this work. Photomicrographs taken with the instrument are included in the paper.
VII.—THE PERFORMANCE OF SPHERICAL‐MIRROR REFLECTING OBJECTIVES WHEN USED FOR ULTRA‐VIOLET PHOTOMICROGRAPHY
Authors: Wilkins M. H. F.
Published: November 2011

Synopsis

Some of the factors influencing design and performance of spherical‐mirror reflecting objectives are briefly discussed. The Beck reflecting objective of 0.60 N.A. was designed primarily for micro‐spectrography, but gives fair all‐round performance when used for photomicrography with visible or ultra‐violet light. Photomicrographs are shown taken with the Beck 0.60 N.A. objective and a solid quartz 0.90 N.A. objective.
FLAGELLA AND CELL WALL OF SPIRILLA
Authors: Pijper Adrianus
Published: November 2011

SYNOPSIS

With sunlight dark‐ground microscopy two new spirilla, one motile and the other not, at first showed typical single polar flagella and later polar flagella dissimilar in number, shape, size, and place of attachment. After that many frankly lateral flagella of various kinds arose, bringing about a peritrichous appearance. Finally the spirilla became covered with a mass of fibrils mixed with odd flagella. Cell walls of spirilla apparently contain a network of submicroscopic fibrils. These may become twisted into typical and atypical flagella and may also come off as masses of fibrils. None of these structures can be regarded as motor organs.
OVULATION, FERTILIZATION, AND EARLY CLEAVAGE IN THE HAMSTER (Mesocricetus auratus)
Authors: Austin C. R.
Published: November 2011

SYNOPSIS

The mean number of eggs ovulated was found to be 10.0 eggs per hamster, range 3 to 17. The fertilization rate was 85.7 p.c. In eggs recovered shortly after ovulation the mean overall diameter was 117.8μ, the thickness of the zona pellucida was 11.6μ, and the diameter of the vitellus was 73.2μ in unpenetrated eggs and 70.9μ in penetrated eggs. The first polar body always persisted until after ovulation. When the second maturation spindle could be identified it was always in metaphase in unpenetrated eggs examined soon after ovulation. The hamster egg has an unusually large perivitelline space.

The zona pellucida dissolved in acid solutions at pH 2.8 and lower; it was readily digested by trypsin solutions, the zona from penetrated eggs being a little less resistant than that from unpenetrated eggs. The zona may undergo expansion during cleavage and was often lacking from eggs in the 4‐cell and later stages.

When hamsters were kept from birth or weaning under controlled illumination (light from 4.0 p.m. to 7.0 a.m., dark from 7.0 a.m. to 4.0 p.m.), ovulation occurred chiefly between 2.0 p.m. and 4.0 p.m. There was a delay of approximately 2 hr. between ovulation and spermatozoon penetration.

With natural lighting (July to September), nearly half the eggs recovered at 7.0 p.m. were in stages immediately preceding the first cleavage. On the next day (day 2) all fertilized eggs were 2‐cell, on day 3 they were 3‐ to 8‐cell, and on day 4 they were morulæ or early blastocysts.

The process of fertilization is briefly described and compared with that seen in rat and mouse eggs. The male and female pronuclei resemble each other in size and form and are often indistinguishable. When one pronucleus is larger than the other it is probably the male. In nuclear and nucleolar dimensions the hamster egg resembles the mouse egg rather than the rat egg.

In 519 penetrated eggs the incidence of polyspermy was 1.08 p.c. Not one of the penetrated eggs, however, had a supplementary spermatozoon. The zona reaction in the hamster egg is therefore very‐rapid and may constitute the only protection against polyspermy.

Six eggs presenting anomalous features are described.

Results are discussed in relation to previous observations on the hamster and other species.
AN ELECTRON MICROSCOPE STUDY*
Authors: Gatenby J. Brontë , Tahmisian T. N.
Published: November 2011

SYNOPSIS

In the fresh water and marine sponges, the Golgi apparatus in the collar cells in each type is differently arranged. In the former there are contractile vacuoles which have no direct connection with the Golgi apparatus; in the latter there are apparently non‐contractile bound vacuoles surrounded by a lamel‐lated osmiophile material; the vacuoles presumably form a water reserve. In the amœbocytes of both types of sponges, the Golgi apparatus is in the form of dictyosomes flattened against the nuclear membrane, and in fresh water sponges these dictyosomes have no direct connection with contractile vacuoles.
I.—PROSPECTS FOR SUBSTANCE DIFFERENTIATION BY ELECTRON AND X‐RAY MICRO‐METHODS*
Authors: Cosslett V. E.
Published: November 2011

SYNOPSIS

Various methods have been considered for identifying specific elements or compounds in the electron microscope or by related techniques. X‐ray emission spectrometry has high detection sensitivity (to 10−14 gm.) combined with an accuracy of location similar to that of the optical microscope (to 0.5 μ). Electron transmission measurements give a much higher spatial resolving power, but the prospects for quantitative analysis on unstained biological material are very limited. Recent theoretical work on electron scattering, in the conditions of electron microscopy, suggests that not only heavy element stains but the normally used organic reagents as well may prove useful in devising analytical procedures similar to the stoichiometric staining methods of optical microscopy, though with distinctly less latitude in sensitivity. The use of a much lower voltage than is usual for electron microscopy, of the order of 10 kV, would give greater image contrast and therefore better accuracy of analysis. Three other physical effects are briefly discussed which may be possible of development for quantitative analysis with electron beams: energy loss, phase shift, and secondary electron emission.
B.—QUANTITATIVE ELECTRON STAINING OF VIRUS PARTICLES
Authors: Valentine R. C.
Published: November 2011

SYNOPSIS

As test objects for measuring the uptake of electron stains, virus particles have the advantage that their thickness is constant and known with fair accuracy. The fraction of the incident beam scattered by them out of the image can easily be deduced from the optical densities of electron micrographs and the degree of staining thus measured quantitatively. Some results are given and discussed in terms of electron scattering theory.
III.—THE USE OF STEREOSCOPIC TECHNIQUE IN ELECTRON MICROSCOPY
Authors: Little K.
Published: November 2011

SYNOPSIS

An account is given of some of the means by which, using three‐dimensional viewing, effective use can be made of the great depth of focus of the electron microscope. Some modifications in methods of preparation of specimens are mentioned. The main drawback to the method which has been encountered —lack of adequate stereoscopic vision in many people—is briefly discussed.
THE GOLGI APPARATUS OF THE CLUB CELLS OF THE CATFISH SYNODONTIS SCHALL BL. SCH.
Authors: Lutfy R. G.
Published: November 2011

SYNOPSIS

The Golgi apparatus of the epidermal club cells of the catfish Synodontis Schall can be revealed by the classical methods and is formed of chromophobe vacuoles surrounded by chromophil walls. At certain phases the vacuoles are either missing, or they may be submicroscopic and thus beyond the limits of resolution of the light microscope.

The Golgi apparatus undergoes marked morphological changes and hypertrophy according to the age and the physiological condition of the club cell.

In the early stages of the growth of the club cell, hypertrophy of its Golgi apparatus takes place by the production of a large number of spherical bodies which are mostly dictyosome‐like. Further additions to the Golgi material are mainly in the form of long filaments which spread out into the cell cytoplasm and enclose at intervals spherical inner chromophobe vacuoles. There is evidence that some of the filaments may develop from the early‐formed dictyosomes by the lateral extension of the osmiophil material.

With the further growth of the club cell, the Golgi vacuoles change from spherical to oval and later to more elongated forms, giving the Golgi material the conventional canalicular picture. Later the Golgi apparatus undergoes fragmentation, the fragments being found close to the cell periphery.

In some of the club cells the Golgi fragments are seen in close contact with vacuoles which are interpreted as of secretory nature. These vacuoles are of common occurrence in the peripheral cytoplasm of most of the larger club cells.

The secretion referred to arises in the cell cytoplasm in the immediate vicinity of the osmiophil material and not inside the Golgi chromophobe vacuoles.
THE SPERMIOGENESIS OF PETROBIUS MARITIMUS
Authors: Mathur R. S.
Published: November 2011

SYNOPSIS

The sperm of Petrobius maritimus is a normal flagellate type and is formed in the normal manner. The acrosome is a clearly marked and easily followed structure. In the final stages the acrosome can be seen to be deposited on the proximal end of the nucleus as a composite structure with a small granule at the tip. It is a secretory product of the Golgi body and not the Golgi body itself. The spent acroblast (dictyosome, Golgi body) drifts down the lengthening spermatid as the acroblast reject, as normally occurs in flagellate spermiogenesis. The centriole region probably consists of the centriole plus the centriole adjunct, but is too small to be resolved by the light microscope. The mitochondrial nebenkern is formed by the aggregation, but apparently not the agglutination, of the mitochondria, and is not typical of the mitochondrial nebenkern of holometabolous insects.
LIGHT AND ELECTRON MICROSCOPY AND ITS USE IN THE STUDY OF FACTORS INFLUENCING SPERMATOGENESIS IN THE RAT
Authors: Lacy Dennis
Published: November 2011

SYNOPSIS

The value of employing both light and electron microscopy in cytological research is discussed. It is pointed out, however, that depending upon the kind of problem being studied it may be necessary to employ a wide variety of experimental techniques. This is particularly true when attempting to relate structure to function. To emphasize this, and to present a synthesis of some recent work, observations made by the writer and collaborators on the testes of normal, irradiated and oestrogen‐treated rats are described. The following main results are reported: 1. The residual bodies, cast off by the newly‐formed spermatozoa, consist of basic cytoplasmic constituents; they are especially rich in R.N.A. 2. The residual bodies are phagocytosed by the Sertoli cells and degenerate. During the latter process their R.N.A. component is absorbed or dispersed. Their lipid, however, remains and probably constitutes the bulk of the lipid seen with the Sertoli cells during later stages of the seminiferous cycle. 3. A lipid cycle is shown both by the germ cells and the Sertoli cells. The germ cells contain most lipid during about stages 1–8. The Sertoli cells contain most lipid during about stages 9–14. The two cycles are essentially out of phase with each other. 4. The lipid of the germ cells, residual bodies and Sertoli cells, gives a negative reaction to Schultz's test for cholesterol. 5. High doses of radiation (10,000 rads; 50,000 rads) cause the germ cells to degenerate; they are then phagocytosed by the Sertoli cells. The degenerating germ cells form large amounts of lipid which comes to lie freely embedded within the Sertoli cytoplasm. This lipid gradually becomes markedly cholesterol‐positive. 6. Preliminary tests suggest that the cholesterol‐positive lipid of irradiated animals possesses progestin‐like activity. 7. During prolonged treatment with oestrogenic hormone, large amounts of lipid slowly accumulate within the Sertoli cells. This lipid gradually gives a strong positive cholesterol‐reaction.

As a working hypothesis it is suggested that in normal animals the lipid within the Sertoli cells represents a steroid hormone or its precursor which it utilized by the germ cells at some particular stage, or stages, of their development. On this basis the residual bodies initiate the production of this hormone. Thus the well‐marked co‐ordination of spermatogenetic stages about a radial axis in seminiferous tubules of the rat may depend upon the phagocytosis of the residual bodies and the secretion of a steroid hormone by the Sertoli cells.
AN ELECTRON MICROSCOPE STUDY OF SOME CYTOPLASMIC INCLUSIONS OF THE NEURONES OF THE PRAWN, LEANDER SERRATUS
Authors: Malhotra S. K. , Meek G. A.
Published: November 2011

SYNOPSIS

Neurones from the thoracic and abdominal ganglia of the prawn, Leander serratus, were studied by optical and electron microscopy. The following cytoplasmic inclusions have been studied:

1. The endoplasmic reticulum, which is more or less uniformly distributed throughout the cytoplasm in a vesicular form. Parallel lamellæ associated with granules have rarely been encountered. Sufficiently large aggregates of organized endoplasmic reticulum, corresponding to the Nissl bodies of vertebrates, have not been seen.

2. The “dictyosomes”, which are composed of stacks of paired non‐granular membranes. The stacks are generally seen as rods, crescents, and horse‐shoes in electron micrographs, and resemble the complex known generally as the “Golgi apparatus”. The evidence indicates that these lamellar structures correspond to the spherical or nearly spherical bodies that are seen in living cells and colour with neutral red.

3. The “trophospongium”, which is shown to consist of branching invaginations of the cell membrane, containing processes from the glial cells. It ramifies in the form of long, thin, branching filaments throughout the cytoplasm. Some workers with the light microscope have mistaken these branching invaginations for mitochondria.

4. The mitochondria, which are mostly short. Long, filamentous mitochondria which might be expected to give the appearance of the “trophospongium” have not been encountered.
IMPROVEMENTS IN DETERMINING TOTAL COUNTS OF BACTERIA
Authors: Norris K. P. , Powell E. O.
Published: November 2011

SYNOPSIS

An interferometric method of measuring the thickness of counting chambers is described. It is simple enough to be used every time a chamber is assembled. Accurate measurement of chamber depth removes a large systematic error from total counts as ordinarily calculated. Experiments on various other details of counting technique lead to recommendations conducive to still further improvement. The standard error of a count under the best conditions need be no more than 50 p.c. greater than the error due to random sampling.
SOME OBSERVATIONS ON MICROSCOPE COVER‐GLASSES
Authors: Norris K. P.
Published: November 2011

SYNOPSIS

Measurements made on over 3400 cover‐glasses of 16 different grades show that only 43 satisfied the Royal Microscopical Society's specification of thickness and only 18 of these were of the specified refractive index. Many cover‐glasses are highly wedge‐shaped and in some samples there is a significant high positive correlation between the mean thickness and the slope of the wedge.
THE FALGIC ACID DYES AND THEIR APPLICATIONS IN HISTOLOGICAL STAINING
Authors: Gurr E. , MacConaill M. A.
Published: November 2011

SYNOPSIS

Sections stained with acid fuchsin and counterstained with light green SF (yellowish) show a striking polychrome effect in shades of red, violet, and blue. This is noteworthy for at least two reasons:

Blue is, of course, a primary colour and cannot, therefore, be produced by the mere admixture of red and green, which are the colours of the two dyes used. Chemical union must therefore take place between these two acid dyes to produce a series of new dyes, one of which is blue.

It has long been known to histologists that a basic dye will unite chemically with an acid dye to form a two‐colour stain, but similar union between two acid dyes was not hitherto thought possible or even considered.
LYMPH NODE STRUCTURE IN THE SUMATRAN RHINOCEROS
Authors: Cave A. J. E. , Aumonier F. J.
Published: November 2011

SYNOPSIS

The histology is described, for the first time, of certain of the lymph nodes of the rare Sumatran Rhinoceros (Didermocerus sumatrensis). These have a marked structural resemblance to the spleen, but reveal no uniform evidence of being hæmolymph organs, though their metaplasia thereinto is indicated.
EMBEDDING COALS AND COKES IN PLASTIC FOR MICROSCOPIC EXAMINATION
Authors: Zeidler W. , Taylor G. H.
Published: November 2011

SYNOPSIS

Coal, coke and some other carbonaceous materials present special difficulties in both thin sectioning and polishing, whether the sample is granular or in lump form. Improved techniques using polyester resin have been worked out, and have been found more reliable and convenient than other methods of thin sectioning and polishing. Large parallel‐sided thin sections, wholly enclosed in plastic, are useful for studying and demonstrating comparatively gross structures, but may also be used at high magnification to study fine detail. Methods of preparing sections and surfaces of very small amounts of material (i.e. down to 0·1 mg or even less) are described, also the use of vacuum embedding and impregnation.