Field Effect and Strongly Localized Carriers in the Metal-Insulator Transition Material VO(2)

The intrinsic field effect, the change in surface conductance with an applied transverse electric field, of prototypal strongly correlated VO(2) has remained elusive. Here we report its measurement enabled by epitaxial VO(2) and atomic layer deposited high-κ dielectrics. Oxygen migration, joule heating, and the linked field-induced phase transition are precluded. The field effect can be understood in terms of field-induced carriers with densities up to ∼5×10(13)  cm(-2) which are trongly localized, as shown by their low, thermally activated mobility (∼1×10(-3)  cm(2)/V s at 300 K). These carriers show behavior consistent with that of Holstein polarons and strongly impact the (opto)electronics of VO(2).

Characterization of Plated Cu Thin Film Microstructures

Electroplated Cu was found to have a fine as-plated microstructure, 0.05 ± 0.03 μm, with multiple grains through the film thickness and evidence of twins and dislocations within grains. Over time at room temperature, the grains grew to greater than 1 μm in size. Studied as a function of annealing temperature, the recrystallized grains were shown to be 1.6 ± 1.0 μm in size, columnar and highly twinned. The grain growth was directly related to the time dependent decrease in sheet resistance. The initial grain structure was characterized using scanning transmission electron microscopy (STEM) from a cross-section sample prepared by a novel focused ion beam (FIB) and lift-out technique. The recrystallized grain structures were imaged using FIB secondary electron imaging. From these micrographs, the grain boundary structures were traced, and an image analysis program was used to measure the grain areas. A Gaussian fit of the log-normal distribution of grain areas was used to calculate the mean area and standard deviation. These values were converted to grain size diameters by assuming a circular grain geometry.

Characterization of Plated Cu Thin Film Microstructures

Electroplated Cu was found to have a fine as-plated microstructure, 0.05 ±0.03 μm, with multiple grains through the film thickness and evidence of twins and dislocations within grains. Over time at room temperature, the grains grew to greater than 1 μm in size. Studied as a function of annealing temperature, the recrystallized grains were shown to be 1.6 ± 1.0 μm in size, columnar and highly twinned. The grain growth was directly related to the time dependent decrease in sheet resistance. The initial grain structure was characterized using scanning transmission electron microscopy (STEM) from a cross-section sample prepared by a novel focused ion beam (FIB) and lift-out technique. The recrystallized grain structures were imaged using FIB secondary electron imaging. From these micrographs, the grain boundary structures were traced, and an image analysis program was used to measure the grain areas. A Gaussian fit of the log-normal distribution of grain areas was used to calculate the mean area and standard deviation. These values were converted to grain size diameters by assuming a circular grain geometry.

Projection of the magnocellular red nucleus to the region of the accessory abducens nucleus in the rabbit

The projection of the magnocellular red nucleus (RNm) to the region of the accessory abducens nucleus (AABD) was traced in rabbit using the bidirectional tracer wheat germ agglutinin-horseradish peroxidase (WGA-HRP). In one set of animals, recordings of antidromic responses from RNm neurons elicited by electrical stimulation of the rubrospinal tract were used to localize injections of WGA-HRP for orthograde labeling of RNm terminals. In a different set of animals, horseradish peroxidase was injected into the retractor bulbi muscle to retrogradely label motoneurons of the AABD. The positions of RNm fibers and terminals were examined and compared to the locations and distribution of AABD cell bodies and labeled dendrites. Analyses revealed that along the entire rostrocaudal extent of the AABD, RNm efferents terminate primarily lateral to, or in the lateral aspects of, labeled motoneurons. For the rostral AABD, RNm efferents terminate only lateral to the nucleus. Although the terminals are not positioned to contact cell bodies of the AABD, they could overlap with dendrites that extend in the lateral direction. RNm efferents terminate more extensively within the posterior AABD, overlapping within both dendritic and cell body regions of the nucleus. Even in this posterior region, however, RNm efferents were distributed primarily over the lateral half of the nucleus. These data show that RNm can monosynaptically influence the AABD, through primarily its lateral and posterior aspects. Our findings also show that a major target of RNm efferents is the reticular cell population located lateral to the AABD, suggesting that the RNm also may affect AABD motoneuronal output indirectly through its projection to reticular cells.

Morphometry of the dorsal raphe nucleus serotonergic neurons in suicide victims

BACKGROUND

The serotonin deficiency hypothesis of suicide has been important heuristically. Few studies have directly examined the brainstem dorsal raphe nucleus (DRN) serotonin neurons. We determined the number and morphometry of DRN serotonergic neurons in suicide victims (n = 7) compared to controls (n = 6).

METHODS

Brainstems were collected at autopsy, fixed and cryoprotected. Tissue was sectioned, stained for Nissl and processed with an antiserum that cross-reacts with tryptophan hydroxylase. All DRN neurons were identified, counted and analyzed every 1000 microns. Neuron morphometry was characterized by soma area (micron 2), sphericity, perimeter, length and density (neurons per mm3).

RESULTS

Neuron number and density was higher in suicide victims (1,780 +/- 127 neurons/mm3) than controls (1,349 +/- 68). The DRN volume did not differ between groups (66 +/- 9 mm3 for controls vs. 67 +/- 5 mm3 for suicides). Mean neuronal area and sphericity did not differ between suicides and controls. The total number and the density of DRN neurons did not correlate with age.

CONCLUSIONS

The finding of an increased number of neurons indicates that impaired serotonergic transmission found in association with serious suicide attempts is not due to fewer neurons.

Corticotropic-releasing hormone and serotonin interact in the human brainstem: behavioral implications

The objective of this human post mortem study was to determine whether neurons which synthesize corticotropic-releasing hormone and serotonin form circuits implicated in the pathophysiology of major depression and suicide. For the first time, a sensitive, dual immunocytochemical procedure was used to identify circuits formed by corticotropic-releasing hormone-synthesizing and serotonergic cell groups. Corticotropic-releasing hormone-immunoreactive varicose fibers and puncta with morphological characteristics of terminals were labeled in the midline raphe, periventricular gray and pontine parabrachial complex, on single-labeled tissues processed immunocytochemically with a rabbit antibody to rat/human corticotropic-releasing hormone. Presumptive synaptic interactions with monoaminergic neurons were demonstrated with dual labeling techniques. Corticotropic-releasing hormone-immunoreactive terminals apposed neuronal somata and primary dendrites of serotonergic neurons in the pontine raphe. Serotonergic neurons were immunolabeled with a mouse antibody to phenylalanine hydroxylase, an enzyme with substantial sequence homology to tryptophan hydroxylase. Interactions in the lateral parabrachial nucleus were suggested by precise overlap of corticotropic-releasing hormone and serotonergic terminal fields. Corticotropic-releasing hormone projections were confirmed to noradrenergic neurons containing neuromelanin in the locus ceruleus. Maps of corticotropic-releasing hormone fiber trajectories suggest that these pathways may derive from the forebrain and, locally, from the human homologue of Barrington's nucleus--a neurochemically specialized division of the laterodorsal tegmental complex. Chemosensory functions were predicted by novel evidence for corticotropic-releasing hormone- and monoaminergic neurovascular and subependymal fiber plexuses. In conclusion, corticotropic-releasing hormone may influence the activity of two major monoaminergic cell systems implicated in the stress-diathesis model of mental illness, through neural and humoral mechanisms.

Evaluation of retroviral vectors based on the gibbon ape leukemia virus

The gibbon ape leukemia viruses (GaLVs) are primate-derived C-type retroviruses with a broad host range. Using an infectious, full-length clone of the GaLV SEATO strain, we have determined that this virus replicates efficiently in 13 of 17 human cell lines tested. In fact, the SB lymphoblast cell line, while resistant to infection by wild-type amphotropic mouse leukemia virus (A-MLV), was infected by GaLV-SEATO. We constructed vectors containing GaLV components and compared the performance of genomes containing an enhancer and promoter derived either from the SEATO or SF strains of GaLV. The GaLV vector genomes were packaged in a Moloney (Mo)MLV core with either an A-MLV or GaLV SEATO envelope. We found that, in some cases, the vector genome appeared to be critical in obtaining optimal infection. For example, vectors with a GaLV SF-based genome infected the human HL60 cell line, whereas vectors with a GaLV SEATO-based genome did not. We also found that most, but not all, of the human cell lines tested were more susceptible to vectors packaged with the GaLV SEATO than A-MLV envelope. The source of the viral core was also important, in that some human cells appeared susceptible to infection only with GaLV genomes packaged in particles composed of a GaLV core and envelope. Our results show that GaLV-based packageable genomes can be expressed in target cells not efficiently infected by vectors containing MoMLV-based genomes. These results suggest that judicious combinations of retroviral genomes and structural components can significantly improve gene transfer into human cells.

Localization of corticotropin-releasing hormone in the human locus coeruleus and pedunculopontine tegmental nucleus: an immunocytochemical and in situ hybridization study

The present study utilized immunocytochemistry and in situ hybridization histochemistry to examine the localization of corticotropin-releasing hormone immunoreactivity and messenger RNA in neurons of the human brainstem. A large population of corticotropin-releasing hormone-immunoreactive neurons appeared in the lateral region of the pontomesencephalic tegmentum. These corticotropin-releasing hormone-containing neurons are predominantly located in the compact subnucleus of the pedunculopontine tegmental nucleus. Proceeding caudally, corticotropin-releasing hormone-immunoreactive neurons in the pedunculopontine tegmental nucleus travel in a dorsomedial direction approaching the ventral border of the locus coeruleus in a dispersed fashion and cluster in a region ventromedial to the locus coeruleus which corresponds to the ventral aspect of the laterodorsal tegmental nucleus. Dense corticotropin-releasing hormone-immunoreactive fibers are present in the dorsal portion of the locus coeruleus and are most prominent in the middle to rostral levels of the nucleus. The cellular and regional localization of corticotropin-releasing hormone messenger RNA in the human brainstem is identical to the perikaryal distribution visualized by immunocytochemistry. Neurons in the laterodorsal tegmental nucleus and pedunculopontine tegmental nucleus express abundant levels of corticotropin-releasing hormone messenger RNA as revealed by dense silver grains overlying these neurons on the emulsion autoradiograms. Within the locus coeruleus, the cellular expression of corticotropin-releasing hormone-immunoreactive and corticotropin-releasing hormone messenger RNA is exclusively localized to non-pigmented neurons. The present study confirms a previous finding describing dense corticotropin-releasing hormone-immunoreactive fibers innervating the human locus coeruleus and extends these findings by identifying corticotropin-releasing hormone immunoreactive and corticotropin-releasing hormone messenger RNA-containing perikarya in the pedunculopontine tegmental nucleus, in the ventral portion of the laterodorsal tegmental nucleus and in the locus coeruleus proper. From morphological observations, the corticotropin-releasing hormone-containing neurons in human pontomesencephalic tegmentum form a continuous population of neurons that are positioned anatomically to exert a putative neuromodulatory influence on locus coeruleus neurons.

Nucleotide sequence of the aliphatic amidase regulator gene (amiR) of Pseudomonas aeruginosa

The nucleotide sequence of a 1001 bp ClaI/XhoI DNA fragment encoding the amidase regulator gene (amiR) from Pseudomonas aeruginosa has been determined. The sequence derives from strain PAC433, a constitutive high expressing amidase mutant, and contains two overlapping open reading frames. Analysis of the sequence has identified one of the reading frames as amiR. The gene encodes a 196 amino acid polypeptide which shows a strong bias towards codons with G or C in the third position. The amiR gene shows no sequence homology with other bacterial regulator proteins.

Basal injury syndrome of Pinus needles

Two types of macroscopic lesions, basal blister and basal necrosis, disrupting the surface tissues of Pinus needles under the fascicular sheath, are described in detail for the first time. In basal blister, hypertrophy and hyperplasia o mesophyll parenchyma cause an oval to elliptical bulge on the needle surface with a longitudinal split of the epidermal and hypodermal layers. In basal necrosis, the epidermal and hypodermal cells become necrotic, while the underlying mesophyll cells undergo structural disorganization. The causal agents are not known but in this study scale insects and deposition of airborne pollutants were associated with basal injury syndrome. The occurrence of basal injury symptoms increased with the age of the needles and the ambient concentration of acid rain precursors. The sulfur and fluoride concentration of the fascicular sheath also increased with the age of the foliage and the ambient pollutant concentrations. Basal injury on sites remote from strong sources of air pollution was significantly correlated with fascicular sheath sulfur concentrations within age-classes of older foliage. These remote site correlations occurred at basal injury rates and fascicular sheath sulfur concentrations lower than those typical of acutely impacted sites near strong sources of air pollution, and thus may represent a chronic impact resulting from acid deposition over wide geographic regions. A soft-bodied scale insect, Matsucoccus secretus Morrison, was often found under the fascicular sheath of Pinus ponderosa Dougl. ex Laws, but did not appear to be a primary cause of basal injury.

Mayan Urbanism: Impact on a Tropical Karst Environment

From the first millennium B.C. through the 9th-century A.D. Classic Maya collapse, nonurban populations grew exponentially, doubling every 408 years, in the twin-lake (Yaxha-Sacnab) basin that contained the Classic urban center of Yaxha. Pollen data show that forests were essentially cleared by Early Classic time. Sharply accelerated slopewash and colluviation, amplified in the Yaxha subbasin by urban construction, transferred nutrients plus calcareous, silty clay to both lakes. Except for the urban silt, colluvium appearing as lake sediments has a mean total phosphorus concentration close to that of basin soils. From this fact, from abundance and distribution of soil phosphorus, and from continuing post-Maya influxes (80 to 86 milligrams of phosphorus per square meter each year), which have no other apparent source, we conclude that riparian soils are anthrosols and that the mechanism of long-term phosphorus loading in lakes is mass transport of soil. Per capita deliveries of phosphorus match physiological outputs, approximately 0.5 kilogram of phosphorus per capita per year. Smaller apparent deliveries reflect the nonphosphatic composition of urban silt; larger societal outputs, expressing excess phosphorus from deforestation and from food waste and mortuary disposal, are probable but cannot be evaluated from our data. Eutrophication is not demonstrable and was probably impeded, even in less-impacted lakes, by suspended Maya silt. Environmental strain, the product of accelerating agroengineering demand and sequestering of nutrients in colluvium, developed too slowly to act as a servomechanism, damping population growth, at least until Late Classic time.

Some difficulties in the Gustafson dental age estimations

The Gustafson technique was a significant contribution to forensic identification. Unfortunately, many statistical errors were present in the published articles. It now seems clear that greater precision can be achieved through modification of the original technique. One of the authors (W. R. M.) will report soon on multiple regression formulae that offer both increased precision and technical simplicity.