Gray Layer Research Articles

Gold Embrittlement of Solder Joints in Wafer-Level Chip-Scale Package on Printed Circuit Board With Ni/Au Surface Finish

In this paper, the effect of gold amount on the gold embrittlement of solder balls in wafer-level chip-scale package (WLCSP) CSP 80 is investigated. First, precisely controlled amounts of gold were added artificially to solder balls through a reflow process. It is found that for CSP 80 without Au, after 2000 h of thermal aging at 150 degC, the solder balls still fail in the bulk solder. When Au is incorporated, brittle failure occurs after 1000 and 200 h for CSP 80 with 0.3 wt% and 0.5 wt% of Au, respectively. Detailed inspections on the microstructure reveal that, after the reflow process, fine AuSn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> intermetallic compound (IMC) particles disperse uniformly in the bulk solder. After 200 h at 150 degC, the (Cu,Ni) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> ternary compound transforms to Cu-Au-Ni-Sn quaternary compound and the IMC at the interface of solder and under bump metallization (UBM) becomes a completely continuous layer. After 1000 hours at 150 degC, two IMC layers, light gray and dark gray, forme at the interface. EDX analysis confirms that the light and dark gray IMC layers are the (Cu,Ni,Au) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> compound. However, the light gray (Cu,Ni,Au) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> compound contains a higher amount of Au and a lower amount of Ni, while the dark gray (Cu,Ni,Au) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> IMC contains a lower amount of Au and a higher amount of Ni. After 2000 h at 150 degC, the two IMC layer structures still exist.

The feedback circuit connecting the central mesencephalic reticular formation and the superior colliculus in the macaque monkey: tectal connections

The connectional and physiological characteristics of the central mesencephalic reticular formation (cMRF) indicate that it participates in gaze control. The cMRF receives projections from the ipsilateral superior colliculus (SC) via collaterals of predorsal bundle axons. These collaterals target cMRF neurons, which in turn project back upon the SC. In the present study, we examined the pattern of connections made by the cMRF reticulotectal projection by injecting the bidirectional neuroanatomical tracer, biotinylated dextran amine (BDA), into the cMRF of macaque monkeys. Anterogradely labeled reticulotectal terminals were found bilaterally in the SC, with an ipsilateral predominance, and were concentrated in the intermediate gray layer (SGI). BDA also retrogradely labeled SC neurons projecting to the cMRF. These labeled tectoreticular cells were located mainly in SGI. Injection site specific differences in the SC labeling pattern were evident, suggesting the lateral cMRF is more heavily connected to the upper sublamina of SGI, whereas the medial cMRF is more heavily connected with the lower sublamina. In view of the known downstream connections of the cMRF and these SC sublaminae, this organization intimates that the cMRF may contain subdivisions specialized to modulate the eye and the head components of gaze changes. In addition, reticulotectal terminals were observed to have close associations with retrogradely labeled tectoreticular cells in the ipsilateral SC, indicating possible synaptic contacts. Thus, the cMRF's reciprocal connections with the SC suggest this structure plays a role in defining the gaze-related bursting behavior of collicular output neurons.

Late Pleistocene changes in terrestrial biomarkers in sediments from the central Arctic Ocean

Biomarkers in Late Pleistocene sediments collected from the Integrated Ocean Drilling Program (IODP)-Arctic Coring Expedition (ACEX) Hole M0004C (central Arctic Ocean) were investigated. The major biomarkers are long chain n-alkanes, n-fatty acids and n-alkan-1-ols, indicating fresh organic matter (OM) derived predominantly from higher plants. The dominance of terrestrial biomarkers is attributed to severe OM degradation caused by slow sedimentation in oxygen-rich benthic water and/or low primary production due to permanent sea ice coverage. Hopanes, representing thermally altered OM, tend to be abundant in samples with abundant ice rafted debris (IRD). An OM-rich dark grey layer deposited during marine isotope stage (MIS) 6 contains a significant amount of branched glycerol dialkyl glycerol tetraethers (branched GDGTs), suggesting ice erosion of organic-rich continental soil followed by transportation to the central Arctic by drifting ice. The labile–refractory index (i.e., the abundance ratio of long chain n-alkan-1-ols to the sum of long chain n-alkanes and long chain n-alkan-1-ols) decreases above the dark grey layer, indicating that the OM became more refractory. This change suggests that coverage of the source region by OM-rich soil decreased because of extensive glacial erosion during MIS-6.

The metal of the moon goddess

Arsenical copper was widely used in the Early Bronze Age, but it was not employed after the introduction of copper–tin alloys in the period around the Middle Bronze Age.Nevertheless the present research showed that a few ornamental objects of particular kind were made of a copper alloy with a silvery surface, containing arsenic, antimony and often some cobalt and nickel still in the Final Bronze Age and in the Iron Age. This alloy is very fragile and can only be cast, it is very difficult to cut and file and shows a characteristic silvery surface.The shiny and silvery grey colour of these objects is due to a segregation phenomenon. During the slow cooling of the metal the As rich α and γ compound (eutectic) is pushed to the surface through feeders which look like filaments running into the metal body and forms the typical silvery grey layer. The microstructure of the eutectic shows a solid solution phase α and a compound γ, containing 29˙65 As (Cu3As). The eutectic can develop already with 1–2% of As in the alloy.Ornamental objects made of this distinctive and beautiful material were worn by women who had special powers and exceptional functions in the society of the time and were connected with the cult of the moon and fertility goddess.

Regulation of Burst Activity through Presynaptic and Postsynaptic GABABReceptors in Mouse Superior Colliculus

In slice preparations, electrical stimulation of the superficial gray layer (SGS) of the superior colliculus (SC) induces EPSC bursts in neurons in the intermediate gray layer (SGI) when GABA(A) receptor (GABA(A)R)-mediated inhibition is reduced. This preparation has been used as a model system to study signal processing involved in execution of short-latency orienting responses to visual stimuli such as saccadic eye movements. In the present study, we investigated the role of GABA(B) receptors (GABA(B)Rs) in modulating signal transmission in the above pathway with whole-cell patch-clamp recordings in SC slices obtained from GAD67-GFP knock-in mice. Perfusion of the slice with the GABA(B)R antagonist CGP52432 (CGP) greatly prolonged the duration of the EPSC bursts. Local application of CGP to the SGS but not to the SGI produced similar effects. Because SGS stimulation elicited bursts in GABAergic neurons in the SGS when GABA(A)Rs were blocked, these results suggest that GABA released after bursts activates GABA(B)Rs in the SGS, leading to reduced burst duration. We found both postsynaptic and presynaptic actions of GABA(B)Rs in the SGS; activation of postsynaptic GABA(B)Rs induced outward currents in narrow-field vertical cells, whereas it caused shunting inhibition in distal dendrites in wide-field vertical cells. On the other hand, activation of presynaptic GABA(B)Rs suppressed excitatory synaptic transmissions to non-GABAergic neurons in the SGS. These results indicate that synaptically released GABA can activate both presynaptic and postsynaptic GABA(B)Rs in the SGS and limit the duration of burst responses in the SC local circuit.

Organization of Calbindin D28K-Immunoreactive Neurons in the Dog Superior Colliculus

We localized calbindin D28K-immunoreactive (IR) neurons in the superior colliculus (SC) of the dog and studied the distribution and effect of enucleation on the distribution of this protein. We also compared this labeling to that of GABA. Calbindin D28K was localized with antibody immunocytochemistry. Calbindin D28K-IR neurons formed three laminar tiers in the SC, one within the lower superficial gray layer (SGL), the second within the upper intermediate gray layers (IGL), and the third within the deep gray layer (DGL). The third tier was not very distinctive when compared with the other two tiers. Calbindin D28K-IR neurons in the SC varied dramatically in morphology and size, and included round/oval, vertical fusiform, stellate, pyriform, and horizontal neurons. Neurons with varicose dendrite were also labeled in the IGL. Enucleation appeared to have no effect on the distribution of calbindin D28K-IR neurons in the contralateral SC. Two-color immunofluorescence revealed that a small percentage (11.20%) of calbindin D28K-IR neurons co-localized with GABA. The current results demonstrate that the patterned distribution of calbindin D28K-IR neurons in the intermediate and deep SC is comparable with other animals, but that the distribution of this protein in the superficial SC is strikingly different from that in previously studied animals. The results also suggest that retinal projection may not control the activity of the expression of calbindin D28K in the dog SC. These results will not only provide valuable knowledge of the basic neurochemical architecture of the dog visual system, but also provide clues for the understanding of the similarities and differences among species.

Effects of chronic treatment of olanzapine and haloperidol on peptide YY binding densities in the rat brain

This study examined regional changes of peptide YY (PYY) binding densities in the rat brain after chronic administration of olanzapine (1.2 mg/kg/day) and haloperidol (2.0 mg/kg/day) for 36 days. PYY binding densities and distributions were detected by [125I] binding autoradiography after rats were sacrificed either 2 h or 48 h after the last drug administration to examine both immediate and delayed effects following the drug withdrawal. Following 2 h of drug administration, it showed that olanzapine administration significantly decreased PYY binding densities, predominantly in the posterodorsal part of medial amygdaloid nucleus (52%, p<0.05), dorsal part of medial geniculate nucleus (56%, p<0.05), superficial gray layer of the superior colliculus (53%, p<0.05), parabrachial pigmented nucleus (54%, p<0.05) and periaqueductal gray (50%, p<0.05) compared to controls, while rebound increases of PYY binding densities were observed in most of examined regions 48 h later with only medial geniculate nucleus dorsal showing significant increase compared to controls (118%, p<0.01). In contrast, no change in PYY binding densities was found in the haloperidol-treated groups 2 h after drug administration, while only a significant rebound increase was observed in the dorsal part of medial geniculate nucleus (94%, p<0.01) 48 h after the haloperidol withdrawal. Alterations in PYY binding densities in brain regions such as the dorsal part of medial geniculate nucleus, superficial gray layer of superior colliculus, periaqueductal gray and parabrachial pigmented nucleus may represent the specific regions that mediate the clinical effects of antipsychotics via neuropeptide Y system. Our study also implicates NPY receptors as a novel therapeutic target in the treatment of psychotic disorders.

Identity of a pathway for saccadic suppression

Neurons in the superficial gray layer (SGS) of the superior colliculus receive visual input and excite intermediate layer (SGI) neurons that play a critical role in initiating rapid orienting movements of the eyes, called saccades. In the present study, two types of experiments demonstrate that a population of SGI neurons gives rise to a reciprocal pathway that inhibits neurons in SGS. First, in GAD67-GFP knockin mice, GABAergic SGI neurons that expressed GFP fluorescence were injected with the tracer biocytin to reveal their axonal projections. Axons arising from GFP-positive neurons in SGI terminated densely in SGS. Next, SGI neurons in rats and mice were stimulated by using the photolysis of caged glutamate, and in vitro whole-cell patch-clamp recordings were used to measure the responses evoked in SGS cells. Large, synaptically mediated outward currents were evoked in SGS neurons. These currents were blocked by gabazine, confirming that they were GABA(A) receptor-mediated inhibitory postsynaptic currents. This inhibitory pathway from SGI transiently suppresses visual activity in SGS, which in turn could have multiple effects. These effects could include reduction of perceptual blurring during saccades as well as prevention of eye movements that might be spuriously triggered by the sweep of the visual field across the retina.

On the mechanism of gray scale patterning of Ag-containing As 2S 3 thin films

We demonstrate an application of photo-induced silver diffusion into chalcogenide glass thin film for gray scale lithography. The gray scale chalcogenide glass masking layer generated in the present experiments was dry etched using reactive ion etching. The etching rate increases almost linearly with the total dose of absorbed light, thus forming the basis of gray scale lithography. Chemical composition as well as electronic structure on the surface of chalcogenide glassy film has been determined by high-resolution X-ray photoelectron spectroscopy (XPS) of the film at different stages of the patterning process. Influence of thermal annealing of chalcogenide film before Ag deposition has been investigated using scanning electron microscopy (SEM) and XPS techniques. It is observed that thermal annealing of the chalcogenide film slows the process of silver diffusion during the proposed processing procedure. A mechanism is proposed to explain the stages of gray scale lithography based on chalcogenide glass photoresists.

Canine cognitive dysfunction and the cerebellum: Acetylcholinesterase reduction, neuronal and glial changes

The specific functional and pathological alterations observed in Alzheimer's disease are less severe in the cerebellum than in other brain areas, particularly the entorhinal cortex and hippocampus. Since dense core amyloid-beta plaque formation has been associated with an acetylcholinesterase heterogeneous nucleator action, we examined if an acetylcholinesterase imbalance was involved in cerebellum plaque deposition. By using the canine counterpart of senile dementia of the Alzheimer's type, a promising model of human brain aging and early phases of Alzheimer's disease, we investigated how cerebellar pathology and acetylcholinesterase density could be related with cognitive dysfunction. As in Alzheimer's disease, the late affectation of the cerebellum was evidenced by its lack of amyloid-beta plaque and the presence of diffuse deposition throughout all cortical grey matter layers. The highest acetylcholinesterase optic density corresponded to cerebellar islands of the granular layer and was predominantly associated with synaptic glomeruli and the somata of Golgi cells. Its reduction correlated with aging and loss of granule cells, whereas cognitive deficit only correlated with loss of Purkinje cells. The observed Bergmann glia alterations may correspond to a reactive response to the loss and damage of the Purkinje cells, their specific neuronal partner. Regarding the role of acetylcholinesterase mediation in amyloid-beta deposition, our data argue against an interaction between these two proteins because acetylcholinesterase reduction correlates with aging but not with cognitive deficit. Finally, our data support the use of companion dogs of all breeds to study aging and early phases of Alzheimer's disease.

Influence of Oxidation Media on the Transport Properties of Thin Oxide Layers of Zirconium Alloys

Two batches of tubes of Zr1Nb and of Zry-4W were oxidized for 30 days at 425 °C in steam, and for 360 days at 500 °C in air, respectively. The analysis of the I-V characteristics at constant temperatures up to 220 °C of oxide layers of nearly equal thickness gave an activation energy of 1,3 eV for the grey homogeneous steam samples, and of 0.4 eV for the white surface layer, and of 1.3 eV at temperatures over 140 °C, for the grey bottom layer of the air samples, respectively. The I-V characteristics were sub-linear in the air samples, the current growing less at rising voltages, but staightening to super-linear space-charge limited currents at higher temperatures. The injection currents flowing when voltage was applied did not reach constant equilibrium, but at a bend, continued with a lesser slope. The resistivity was about one order of magnitude greater in air samples and greater in Zry-4W. The relative permittivity was greater in the steam samples and greater in Zr1Nb. The currents of the air samples were greater with Au electrodes than with Ag electrodes.

Biotic versus abiotic calcite formation on prehistoric cave paintings: the Arcy-sur-Cure ‘Grande Grotte’ (Yonne, France) case

Abstract The ‘Grande Grotte’ cave at Arcy-sur-Cure (Yonne, France) with its prehistoric paintings shows important calcite concretions. Two types of calcite have been observed on the wall: translucent yellowish layers and opaque white or grey layers that completely obstruct the paintings. Other calcite types are present in the lakes of the cave (floating calcite rafts at the surface of the lake and soft calcite at the bottom of the lake). The morphology of the different calcites was observed at different scales by optical microscopy with normal and polarized light, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The elemental composition was measured by using particle-induced X-ray emission (micro-PIXE) and the structure by X-ray diffraction (XRD), infrared (FT-IR) and Raman spectroscopy. The bacterial diversity and its role in calcite formation were assessed by culture and 16S-SSCP in order to distinguish and to assess various abiotic and biotic formation mechanisms. The investigation of calcite characteristics enables conclusions on the formation mechanism and on a biotic or abiotic origin of the calcites. The change of calcite types on the walls reveals changes of the environmental cave parameters. In addition, interactions of calcites with the prehistoric paint layer could be evaluated.

Properties of cholinergic responses in neurons in the intermediate grey layer of rat superior colliculus

The intermediate grey layer (SGI) of superior colliculus (SC) receives cholinergic innervation from brainstem parabrachial region. To clarify the action of cholinergic inputs to local circuits in the SGI, we investigated the effect of cholinergic agonists and antagonists on a large number of randomly sampled neurons in Wistar rat SGI (n=246) using whole-cell patch clamp technique in slices of the rat SC. Responses of the recorded cells (n=98) to bath application of carbachol were classified into five patterns: (i) nicotinic inward only (n=14); (ii) nicotinic inward+muscarinic inward (n=26); (iii) nicotinic inward+muscarinic inward+muscarinic outward (n=39); (iv) nicotinic inward+muscarinic outward (n=13) and (v) muscarinic outward only (n=4). Among these, a majority of morphologically identified projection neurons exhibited either response pattern (ii) (9/28) or (iii) (15/28), which suggested that the primary action of cholinergic inputs on the SGI output is excitatory. Nicotinic receptor subtypes involved in the nicotinic current were examined by testing the effects of antagonists on the currents induced by bath application of 1,1-dimethyl-4-phenyl-piperazinium or transient pressure application of acetylcholine (ACh). Muscarinic receptor subtypes involved in the muscarinic inward and outward currents were investigated by examining the effects of antagonists on muscarine-induced currents. The results showed that nicotinic inward currents are mediated mainly by alpha4beta2 and partly by alpha7 nicotinic receptors and that muscarinic inward and outward currents are mediated by M3 (plus M1) and M2 muscarinic receptors, respectively.

Microstructure evolution and reaction mechanism during reactive joining of TiAl intermetallic to TiC cermet using Ti–Al–C–Ni interlayer

This study reports on a new approach for joining of TiAl intermetallic to TiC cermets by self-propagating high-temperature synthesis. The adiabatic combustion temperature in the Ti–Al–C–Ni system was calculated and the composition of the reactants was determined by the calculated result. For a typical microstructure of the joint, two continuous grey reaction layers were found near the TiAl substrate and massive Ni-rich zones were observed adjacent to the TiC cermet. It was noted that the voids were inevitable in the reaction products. The crack was always formed at the interface between the interlayer and TiC cermet due to the residual stress. The interfacial joining between TiC cermet and the interlayer depended on the formation of Ni-rich layer. The joining between the TiAl and the interlayer was simplified as the reaction between liquid Al and solid TiAl. The SHS reaction in Ti–Al–C–Ni system was ignited at the melting point of Al. The first reaction took place between liquid Al and solid Ti to form TiAl 3. With the increase of the temperature, Ti reacted with C to form TiC phase.

햄스터 상구의 deeper layers에서 calretinin이 함유 신경세포

Calcium-binding protein calretinin is thought to play important roles in calcium buffering. Recently, we reported on the distribution, morphology of calretinin-immunoreactive (IR) neurons and the effects of eye enucleation on the immunoreactivity of calretinin in the superficial layers of the hamster superior colliculus (SC). In the present study, we describe the distributions and types of labeled cells and effects of enucleation in the deeper layers by immunocytochemistry. We also compare this labeling to that of GABA, the major inhibitory neurotransmitter in the central nervous system. In contrast to the superficial layers, the deeper layers contained many calretinin-IR neurons which formed two tiers. The first tier, which was very distinctive, was found within the intermediate gray layer. The second tier was found in the deep gray layer. Labeled neurons varied dramatically in morphology and included vertical fusiform, stellate, round/oval, and horizontal neurons. In contrast to the superficial layers, enucleation appeared to have no effect on the distribution of calretinin immunoreactivity in the deeper layers. Two-color immunofluorescence revealed that none of calretinin-IR neurons were labeled with an antibody to GABA. The present results demonstrate that calretinin identifies unique neuronal sublaminar organizations in the hamster SC. The present results also demonstrate that none of the calretinin-IR neurons in the hamster SC is GABAergic interneurons. As many calretinin-IR cells are GABAergic interneurons in most other brain areas, this phenomenon in hamster SC is exceptional.

Immunohistochemical labeling of the mu opioid receptor carboxy terminal splice variant mMOR-1B4 in the mouse central nervous system

The mu opioid receptor gene Oprm is alternatively spliced into many variants, providing for the multiplicity of mu opioid receptor subtypes. One of the mouse variants, mMOR-1B4, is unique in that it displays high affinity towards a wide range of mu opioid receptor antagonists, but poor affinity towards most classical mu opioid agonists. The present study examined the immunohistochemical distribution of the mMOR-1B4 variant in mouse brain and spinal cord. mMOR-1B4-like immunoreactivity (mMOR-1B4-LI) was enriched in many regions of the brain, spinal cord and in the dorsal root ganglia. Some of the structures showing prominent mMOR-1B4-LI include the olfactory bulb, cerebral cortex, bed nucleus of stria terminalis, hippocampus, habenular nucleus, amygdala, thalamus, hypothalamus, medium eminence, substantia nigra, ventral tegmental area, oculomotor nucleus, red nucleus, raphe nuclei, periaqueductal gray, locus coeruleus, trigeminal nucleus, reticular formation, area postrema and Purkinje cell layer and deep nuclei of cerebellum. mMOR-1B4-LI was present in afferent neurons of the dorsal root ganglia and their projecting fibers into the superficial laminae of the spinal dorsal horn. Some motor neurons in the anterior horn of the spinal cord also were immunopositive. The overall distribution of mMOR-1B4-LI in the central nervous system is distinguishable from previously characterized variants such as MOR-1-LI, MOR-1C-LI and exon-11-LI. These studies provide evidence for the region- and neuron-specific processing of the Oprm gene and support the possibility of functional differences among the variants.

The superior colliculus of the camel: a neuronal‐specific nuclear protein (NeuN) and neuropeptide study

In this study we examined the superior colliculus of the midbrain of the one-humped (dromedary) camel, Camelus dromedarius, using Nissl staining and anti-neuronal-specific nuclear protein (NeuN) immunohistochemistry for total neuronal population as well as for the enkephalins, somatostatin (SOM) and substance P (SP). It was found that, unlike in most mammals, the superior colliculus is much larger than the inferior colliculus. The superior colliculus is concerned with visual reflexes and the co-ordination of head, neck and eye movements, which are certainly of importance to this animal with large eyes, head and neck, and apparently good vision. The basic neuronal architecture and lamination of the superior colliculus are similar to that in other mammals. However, we describe for the first time an unusually large content of neurons in the superior colliculus with strong immunoreactivity for met-enkephalin, an endogenous opioid. We classified the majority of these neurons as small (perimeters of 40-50 microm), and localized diffusely throughout the superficial grey and stratum opticum. In addition, large pyramidal-like neurons with perimeters of 100 microm and above were present in the intermediate grey layer. Large unipolar cells were located immediately dorsal to the deep grey layer. By contrast, small neurons (perimeters of 40-50 microm) immunopositive to SOM and SP were located exclusively in the superficial grey layer. We propose that this system may be associated with a pain-inhibiting pathway that has been described from the periaqueductal grey matter, juxtaposing the deep layers of the superior colliculus, to the lower brainstem and spinal cord. Such pain inhibition could be important in relation to the camel's life in the harsh environment of its native deserts, often living in very high temperatures with no shade and a diet consisting largely of thorny branches.

Calcium-binding Protein Calretinin Immunoreactivity in the Dog Superior Colliculus

We studied calretinin-immunoreactive (IR) fibers and cells in the canine superior colliculus (SC) and studied the distribution and effect of enucleation on the distribution of this protein. Localization of calretinin was immunocytochemically observed. A dense plexus of anti-­calretinin-IR fibers was found within the upper part of the superficial gray layer (SGL). Almost all of the labeled fibers were small in diameter with few varicosities. The intermediate and deep layers contained many calretinin-IR neurons. Labeled neurons within the intermediate gray layer (IGL) formed clusters in many sections. By contrast, labeled neurons in the deep gray layer (DGL) did not form clusters. Calretinin-IR neurons in the IGL and DGL varied in morphology and included round/oval, vertical fusiform, stellate, and horizontal neurons. Neurons with varicose dendrites were also labeled in the IGL. Most of the labeled neurons were small to medium in size. Monocular enucleation produced an almost complete reduction of calretinin-IR fibers in the SC contralateral to the enucleation. However, many calretinin-IR cells appeared in the contralateral superficial SC. Enucleation appeared to have no effect on the distribution of calretinin-IR neurons in the contralateral intermediate and deep layers of the SC. The calretinin-IR neurons in the superficial dog SC were heterogeneous small- to medium-sized neurons including round/oval, vertical fusiform, stellate, pyriform, and ­horizontal in shape. Two-color immunofluorescence revealed that no cells in the dog SC ­expressed both calretinin and GABA. Many horseradish peroxidase (HRP)-labeled retinal ganglion cells were seen after injections into the superficial layers. The vast majority of the double-labeled cells (HRP and calretinin) were small cells. The present results indicate that antibody to calretinin labels subpopulations of neurons in the dog SC, which do not express GABA. The results also suggest that the calretinin-IR afferents in the superficial layers of the dog SC originate from small class retinal ganglion cells. The expression of calretinin might be changed by the cellular activity of selective superficial collicular neurons. These results are valuable in delineating the basic neurochemical architecture of the dog visual system.

Friction layers produced in two steels during laboratory friction testing

The friction layers produced on SAE type 1065 and 20Mn2WNbB steels during laboratory friction testing have been characterised using optical microscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. A white layer is formed on the surface of SAE 1065 steel, composed of abnormal quenched martensite with a microhardness of 1020 HV(100 g). A dark grey friction layer with a microhardness of 600 HV(100 g) is formed on the surface of 20Mn2WNbB steel. This layer consists of tempered lath martensite with a low carbon content. Formation of the white layer in SAE 1065 steel occurs through austenitisation of the steel surface due to friction at a high sliding rate, followed by rapid cooling to a martensite structure. The martensite structure in this white layer exhibits a finer grain size and higher dislocation density than that obtained by normal quenching. However, in 20Mn2WNbB steel, the quenched martensite structure is transformed into tempered martensite by self-tempering during cooling. Charpy impact tests show that the impact toughness of SAE 1065 steel is significantly decreased owing to the presence of the white layer. However, there is only a small effect of the friction layer on the impact toughness of 20Mn2WNbB steel.

Geochemical evidence for multiphase emplacement in the southern Platreef

The Platreef is predominantly a pyroxenitic PGE–Cu–Ni-bearing package which lies at the base of the northern limb of the Bushveld Complex. Geochemical data from two cores from the southern sector of the Platreef on the farm Turfspruit suggest that the Platreef here is a complex intrusive body comprising three or four feldspathic pyroxenite sills each with a distinctive chemistry. Each package is characterised by difference in Mg#, SiO2:Al2O3 and CaO:Al2O3 ratios, trace element abundances and Pt:Pd and Ni:Cu ratios. Compositional breaks in major and trace element chemistry between the different pyroxenite packages are supported by changes in mineral chemistry. The more primitive feldspathic pyroxenite with the highest Cr content and Mg# occurs towards the top of the succession, whereas pyroxenites lower in the succession show varying degrees of interaction with floor rocks and hornfels xenoliths resulting in inhomogeneous textures, variability in composition even on a metre scale, increased incompatible elements and migration of sulphur from shale to magma.The earliest intrusive pulse that contributed to the Platreef package appears to have reacted with the country rocks and cooled rapidly to form a grey micronoritic layer, equated with the Marginal Zone of the eastern and western limbs of the Bushveld Complex. Thick fine-to-medium grained peridotites ascribed to the Lower Zone are equated with the pyroxenites, harzburgites and serpentinites of the Grasvally area south of Mokopane. These olivine-bearing layers have subsequently been intensely serpentinised. As further pulses of magma followed, it is envisaged that metasedimentary material became detached from the floor and later intrusive pulses, which gave rise to feldspathic pyroxenites, flowed under or over these layers. The result is a succession of pyroxenite sills that are separated from each other by interlayers of serpentinite, clinopyroxenite, pegmatitic norite or cordierite spinel hornfels. The Main Zone differs mineralogically and geochemically from the Platreef. It hosts both xenoliths of hornfels and Platreef pyroxenite, especially towards the base, indicating that the Main Zone intruded post-Platreef. Thus, it is implied that shales or dolomites were originally the roof rocks to the Platreef that became incorporated into the Main Zone magma during emplacement.Within the Platreef package, the number of pyroxenitic layers may vary but preliminary attempts have been made to correlate three pyroxenites in one core with four pyroxenites in a second core from boreholes 2 km apart. The most striking characteristics are that the highest Pt+Pd concentration and lowest Pt:Pd ratio occur in the basal pyroxenite in association with sulphides, with an upward increase in Pt:Pd ratio and Ni:Cu so that the top pyroxenite has a Pt:Pd ratio of 2 and Ni:Cu of > 3 whilst the bottom pyroxenite has a ratio of Pt:Pd ratio of 1 and a Ni:Cu of < 2. These increased ratios upward are not a simple fractionating sequence from the bottom to the top of the Platreef otherwise the top pyroxenite would be the most evolved, which is not the case as it has the most primitive Mg# and highest Cr content. The Platreef is, therefore, a complex zone of sill inter-fingered lithologies reflecting a multiphase emplacement.