Tunneling characteristics of Au-alkanedithiol-Au junctions formed via nanotransfer printing (nTP).

Construction of permanent metal-molecule-metal (MMM) junctions, though technically challenging, is desirable for both fundamental investigations and applications of molecule-based electronics. In this study, we employed the nanotransfer printing (nTP) technique using perfluoropolyether (PFPE) stamps to print Au thin films onto self-assembled monolayers (SAMs) of alkanedithiol formed on Au thin films. We show that the resulting MMM junctions form permanent and symmetrical tunnel junctions, without the need for an additional protection layer between the top metal electrode and the molecular layer. This type of junction makes it possible for direct investigations into the electrical properties of the molecules and the metal-molecule interfaces. Dependence of transport properties on the length of the alkane molecules and the area of the printed Au electrodes has been examined systematically. From the analysis of the current-voltage (I-V) curves using the Simmons model, the height of tunneling barrier associated with the molecule (alkane) has been determined to be 3.5 ± 0.2 eV, while the analysis yielded an upper bound of 2.4 eV for the counterpart at the interface (thiol). The former is consistent with the theoretical value of ~3.5-5.0 eV. The measured I-V curves show scaling with respect to the printed Au electrode area with lateral dimensions ranging from 80 nm to 7 µm. These results demonstrate that PFPE-assisted nTP is a promising technique for producing potentially scalable and permanent MMM junctions. They also demonstrate that MMM structures (produced by the unique PFPE-assisted nTP) constitute a reliable test bed for exploring molecule-based electronics.

Influence of wet distillers grains diets on beef cattle fecal bacterial community structure.

BACKGROUND: The high demand for ethanol in the U.S. has generated large stocks of wet distillers grains (DG), a byproduct from the manufacture of ethanol from corn and sorghum grains. Little is known, however, about the potential influence of dietary DG on fecal microbial community structure. A better understanding of the microbial population in beef cattle feces could be an important monitoring tool to facilitate goals of improving nutrient management, increasing animal growth performance and decreasing odors and/or shedding of pathogens. Five diets consisting of a traditional diet fed to finishing beef cattle in the Southern High Plains of Texas-CON (steam-flaked corn control with 0% DG), and four concentrations of DG in the dietary dry matter; 10 C (10% corn-based DG), 5S (5% sorghum-based DG), 10S (10% sorghum DG), and 15S (15% sorghum DG) were fed to steers at the Texas Tech University Burnett Animal Center. Diets were essentially isonitrogenous with a formulated crude protein value of 13.5%. RESULTS: Fecal grab samples were obtained from 20 steers (n = 4 per diet) and the barcoded DNA pyrosequencing method was used to generate 127,530 16S operational taxonomic units (OTUs). A total of 24 phyla were observed, distributed amongst all beef cattle on all diets, revealing considerable animal to animal variation, however only six phyla (core set) were observed in all animals regardless of dietary treatment. The average abundance and range of abundance, respectively of the core phyla were as follows: Firmicutes (61%, 19 to 83%), Bacteroidetes (28%, 11 to 63%), Proteobacteria (3%, 0.34 to 17.5%), Tenericutes (0.15%, 0.0 to 0.35%), Nitrospirae (0.11%, 0.03 to 0.22%), and Fusobacteria (0.086%, 0.017 to 0.38%). Feeding DG-based diets resulted in significant shifts in the fecal microbial community structure compared with the traditional CON. Four low abundance phyla significantly responded to dietary treatments: Synergistetes (p = 0.01), WS3 (p = 0.054), Actinobacteria (p = 0.06), and Spirochaetes (p = 0.06). CONCLUSIONS: This is, to our knowledge, the first study using this method to survey the fecal microbiome of beef cattle fed various concentrations of wet DG. Comparison of our results with other cattle DNA sequencing studies of beef and dairy cattle feces from a variety of geographical locations and different management practices identifies a core set of three phyla shared across all cattle. These three phyla, in order of relative abundance are; Firmicutes, Bacteroidetes, and Proteobacteria. The presence of large animal-to-animal variation in cattle microbiome was noted in our study as well as by others.

Critical analysis of the Chiari malformation Type I found in children with lipomyelomeningocele.

OBJECT: Occasional comments are found in the literature regarding patients with lipomyelomeningocele and concomitant Chiari malformation Type I (CM-I). The object of this study was to explore the association between these two conditions. METHODS: The authors performed a retrospective database analysis of lipomyelomeningocele cases to identify cases of concomitant CM-I. Analysis of posterior fossa volume (based on the Cavalieri principle) was performed in all identified cases in which appropriate neuroimages were available, and the results were compared with those obtained in age-matched controls. Seven (13%) of 54 patients with lipomyelomeningocele were found to also have CM-I. Two of these were symptomatic (cervicothoracic syrinx and occipital headaches) and required posterior fossa decompression. No correlation was found between the amount of hindbrain herniation and the level of the conus medullaris or the type of lipomyelome-ningocele (for example, caudal or transitional). Volumetric studies of the posterior fossa revealed normal age-matched volumes in all but one patient (who had asymptomatic CM-I). CONCLUSIONS: The incidence of CM-I in patients with lipomyelomeningocele appears to be significantly greater than that of the general population and the association rate is too high for the finding to be a chance occurrence. Decreases in the volume of the posterior cranial fossa were not found in the majority of patients in this small cohort; therefore, the cause of the concomitant occurrence of lipomyelomeningocele and CM-I remains undetermined. Clinicians should consider obtaining imaging studies of the entire neuraxis in patients with lipomyelomeningoceles and should investigate other causes for syringes found in association with lipomyelomeningoceles.

The patient with symptoms following resection of a lipomyelomeningocele: do increases in the lumbosacral angle indicate a tethered spinal cord?

OBJECT: The angulation of the sacrum is easily measured. The authors have previously reported on patients who were symptomatic with a diagnosis of myelomeningocele who were found to have changes in their lumbosacral angle (LSA) corresponding to the onset of symptoms indicative of a tethered spinal cord. The aim of this study was to verify this same finding in a group of patients with occult spinal dysraphism (that is, closed neural tube defect). METHODS: A retrospective analysis of 50 consecutive lipomyelomeningocele repair procedures was performed. Data pertaining to 30 age-matched control patients were also analyzed. Measurements were made of the LSA over time in all studied patients harboring lipomyelomeningoceles. Appropriate imaging was available for 25 cases of lipomyelomeningocele (that is, radiographs of the lumbosacral junction were available from the patient's perinatal period and at presentation of symptoms of a tethered spinal cord). Roughly one third of these patients suffered symptoms from a tethered spinal cord at the most recent follow-up examination. Nine patients (36%) were found to have corresponding LSA measurements greater than 70 degrees, and seven (28%) of these patients presented with signs and symptoms of a tethered spinal cord, such as decreased lower-extremity function (two patients), urinary bladder incontinence (three patients), back pain (one patient), and lower-extremity paresthesias (one patient). The LSA measurements were statistically greater (p < 0.05) in the symptomatic patient population than in age-matched control patients and asymptomatic patients. Changes in the LSA in these symptomatic patients ranged from 5 to 24 degrees (mean 13 degrees). Changes in the LSA were noted in only two asymptomatic patients. No single sign or symptom of a tethered spinal cord appeared to correlate to any degree of increase in the LSA. Of the 25 patients excluded from this study because perinatal radiographic images were not available, none was symptomatic at the most recent follow-up examination and none had a grossly exaggerated LSA. CONCLUSIONS: Signs and symptoms indicative of a tethered spinal cord appear to correspond to increases in the LSA. Although the authors do not advocate the use of LSA measurement as the sole indicator of a tethered spinal cord, this imaging finding may prove useful to the clinician as an indication of the tethered spinal cord or as an adjunct in verifying symptomatology in patients harboring a lipomyelomeningocele.

Extracellular ATP signaling and P2X nucleotide receptors in monolayers of primary human vascular endothelial cells.

ATP and its metabolites regulate vascular tone; however, the sources of the ATP released in vascular beds are ill defined. As such, we tested the hypothesis that all limbs of an extracellular purinergic signaling system are present in vascular endothelial cells: ATP release, ATP receptors, and ATP receptor-triggered signal transduction. Primary cultures of human endothelial cells derived from multiple blood vessels were grown as monolayers and studied using a bioluminescence detection assay for ATP released into the medium. ATP is released constitutively and exclusively across the apical membrane under basal conditions. Hypotonic challenge or the calcium agonists ionomycin and thapsigargin stimulate ATP release in a reversible and regulated manner. To assess expression of P2X purinergic receptor channel subtypes (P2XRs), we performed degenerate RT-PCR, sequencing of the degenerate P2XR product, and immunoblotting with P2XR subtype-specific antibodies. Results revealed that P2X(4) and P2X(5) are expressed abundantly by endothelial cell primary cultures derived from multiple blood vessels. Together, these results suggest that components of an autocrine purinergic signaling loop exist in the endothelial cell microvasculature that may allow for "self-regulation" of endothelial cell function and modulation of vascular tone.