The stability of Cl-, Br-, and I-passivated Si(100)-(2 × 1) in ambient environments for atomically-precise pattern preservation.

Atomic precision advanced manufacturing (APAM) leverages the highly reactive nature of Si dangling bonds relative to H- or Cl-passivated Si to selectively adsorb precursor molecules into lithographically defined areas with sub-nanometer resolution. Due to the high reactivity of dangling bonds, this process is confined to ultra-high vacuum (UHV) environments, which currently limits its commercialization and broad-based appeal. In this work, we explore the use of halogen adatoms to preserve APAM-derived lithographic patterns outside of UHV to enable facile transfer into real-world commercial processes. Specifically, we examine the stability of H-, Cl-, Br-, and I-passivated Si(100) in inert N2and ambient environments. Characterization with scanning tunneling microscopy and x-ray photoelectron spectroscopy (XPS) confirmed that each of the fully passivated surfaces were resistant to oxidation in 1 atm of N2for up to 44 h. Varying levels of surface degradation and contamination were observed upon exposure to the laboratory ambient environment. Characterization byex situXPS after ambient exposures ranging from 15 min to 8 h indicated the Br- and I-passivated Si surfaces were highly resistant to degradation, while Cl-passivated Si showed signs of oxidation within minutes of ambient exposure. As a proof-of-principle demonstration of pattern preservation, a H-passivated Si sample patterned and passivated with independent Cl, Br, I, and bare Si regions was shown to maintain its integrity in all but the bare Si region post-exposure to an N2environment. The successful demonstration of the preservation of APAM patterns outside of UHV environments opens new possibilities for transporting atomically-precise devices outside of UHV for integrating with non-UHV processes, such as other chemistries and commercial semiconductor device processes.

STM-Induced Desorption and Lithographic Patterning of Cl-Si(100)-(2 × 1).

A scanning tunneling microscope (STM) was used to investigate tip-induced chlorine desorption and lithographic patterning of Cl-terminated Si(100)-(2 × 1) surfaces from 4 to 600 K in ultrahigh vacuum. Until now, STM lithography has exclusively focused on hydrogen-based chemistry for donor device fabrication. As the initial step in developing halogen-based chemistries for STM fabrication of acceptor-based devices, we substituted the hydrogen resist with chlorine. We found that chlorine can be selectively desorbed by the STM tip using both electron and hole injection. Observations show that targeted chlorine was not driven into the surface but desorbed completely as both individual and pairs of atoms. Chlorine depassivation lithography is demonstrated using both field-emission patterning to desorb chlorine from large areas with high efficiency (0.83(1)) and atomic-precision patterning to desorb one to two dimer rows at a time, resulting in 1.5 nm wide lines. Further, varying the experimental parameters for lithography revealed a positive correlation between pattern line widths and both positive sample bias voltage (1.7(2) nm/V) and total electron dose (0.15(2) nm/(mC/cm)), demonstrating that the energy and total number of electrons play a role in desorption from multiple sites.

Temperature dependent 29Si incorporation during deposition of highly enriched 28Si films.

In this study, we examine the mechanisms leading to 29Si incorporation into highly enriched 28Si films deposited by hyperthermal ion beams at elevated temperatures in the dilute presence of natural abundance silane (SiH4) gas. Enriched 28Si is a critical material in the development of quantum information devices because 28Si is free of nuclear spins that cause decoherence in a quantum system. We deposit epitaxial thin films of 28Si enriched in situ beyond 99.99998 % 28Si onto Si(100) using an ion beam deposition system and seek to develop the ability to systematically vary the enrichment and measure the impact on quantum coherence. We use secondary ion mass spectrometry to measure the residual 29Si isotope fraction in enriched samples deposited from ≈ 250 °C up to 800 °C. The 29Si isotope fraction is found to increase from < 1 × 10-6 at the lower temperatures, up to > 4 × 10-6 at around 800 °C. From these data, we estimate the temperature dependence of the incorporation fraction, s, of SiH4, which increases sharply from about 2.9 × 10-4 at 500 °C to 2.3 × 10-2 at 800 °C. We determine an activation energy of 1.00(8) eV associated with the abrupt increase in incorporation and conclude that below 500 °C, a temperature independent mechanism such as activation from ion collisions with adsorbed SiH4 molecules is the primary incorporation mechanism. Direct incorporation from the adsorbed state is found to be minimal.

Cis-element/cytoplasmic protein interaction within the 3'-untranslated region of the GLUT1 glucose transporter mRNA.

The posttranscriptional regulation of glucose transporter GLUT1 gene expression may be mediated by specific interactions of cytosolic proteins and regulatory cis-elements within the untranslated regions (UTRs) of the GLUT1 mRNA. These putative cis/trans interactions were examined in the present studies with RNase T1 protection assays using 32P-labeled GLUT1 3'-UTR prepared from transcription plasmids and cytosolic proteins from C6 rat glioma cells. RNase T1 mapping studies localized a cis-element to nucleotides 2,170-2,207 on the bovine GLUT1 mRNA 3'-UTR. Ultraviolet cross-linking of RNA/protein complexes identified two complexes having molecular masses of 88 and 44 kDa. Competition studies with synthetic RNA and oligodeoxynucleotides showed the 88-kDa complex reacted with nucleotides 2,180-2,197 and that the 44-kDa complex reacted with sequences within nucleotides 1,717-2,132 of the bovine GLUT1 mRNA. The GLUT1 3'-UTR between nucleotides 2,100 and 2,300 was generated by polymerase chain reaction and subcloned at a unique Pfl/MI site within the 3'-UTR of a luciferase gene within the mammalian expression vector pGL2. Transfection of C6 rat glioma cells with the luciferase expression vector containing this portion of the GLUT1 3'-UTR resulted in a sixfold increase in luciferase gene expression in C6 cells. The identification of these cis/trans mechanisms provides support for the hypothesis that the posttranscriptional regulation of GLUT1 gene expression may be mediated by the interaction of specific cytosolic proteins with the GLUT1 mRNA 3'-UTR.

Medial epicondylitis of the elbow.

Ninety-five cases of medial epicondylitis are reported in 83 patients; 90% were related to work and only 10% to sport or leisure activities. Most recovered with conservative treatment. Operation was needed in 12%, which compared with under 4% of patients with lateral epicondylitis over the same period. The results of open release of the common flexor origin were good, with only one exception.

Intramedullary nailing technique and its effect on union rates of tibial shaft fractures.

Seventy tibial shaft fractures treated by intramedullary nailing using two different techniques were compared. The first group (35 cases) was treated with a Herzog intramedullary nail following hand reaming and minimal traction. The second group (35 cases) had a Grosse and Kempf or AO nail inserted following power reaming and skeletal traction. Fracture patterns were similar in both groups. In the hand-reamed group, the mean time to union was 15.2 weeks with two delayed unions and no non-unions. In the power-reamed group, the mean time to union was 19.9 weeks with 10 delayed unions and two non-unions. These differences were statistically significant. Complications in the hand-reamed group included a Sudecks atrophy and one mal-union. In the power-reamed group, there were three transient foot drops, two compartment syndromes and one pulmonary embolus. This difference was not statistically significant. Our findings suggest that surgical technique has an important effect on the healing rates of nailed tibial shaft fractures. When intramedullary nailing is performed, minimal reaming is required and skeletal traction should be avoided if possible.

Differential glycosylation of the GLUT1 glucose transporter in brain capillaries and choroid plexus.

The sodium-independent GLUT1 glucose transporter is expressed in high density in human erythrocytes and in tissues which serve a barrier function. In the polarized endothelial cells of the brain capillaries, which comprise the blood-brain barrier (BBB), GLUT1 is expressed on both apical and basolateral membranes; however, in the epithelium of the choroid plexus, GLUT1 expression is restricted to the basolateral surface. The present study examined whether these differences in subcellular localization of GLUT1 at the BBB and choroid plexus could be correlated with differential N-linked or O-linked glycosylation of the protein. Western blot analysis of solubilized brain capillaries (BC) and choroid plexus (CP) revealed that while the BC GLUT1 had an average molecular mass identical to that of the purified human erythrocyte transporter (54 kDa), the CP GLUT1 was of lower molecular mass (47 kDa). Treatment of brain capillaries and choroid plexus with N-glycanase resulted in a shift in the mobility of the GLUT1 of both samples to a lower molecular mass of 42 kDa; however, in contrast, treatment with O-glycanase produced no change in the mobility patterns of GLUT1, but did result in O-linked deglycosylation of another BBB marker, gamma-glutamyl transpeptidase. In conclusion, BBB and choroid plexus GLUT1 are subject to differential N-linked glycosylation with the protein having an N-linked carbohydrate side chain of higher molecular mass at the BBB in comparison to the choroid plexus.

Scaphoid exostosis causing rupture of the flexor pollicis longus.

A case of attrition rupture of the flexor pollicis longus (FPL) tendon caused by a scaphoid osteophyte in a patient with rheumatoid arthritis is reported. This lesion was found only after a thorough search of the floor of the carpal tunnel was performed.

Tibial shaft fractures with an intact fibula.

The effect of several factors on the healing rates of tibial shaft fractures with an intact fibula were examined. Those found to adversely affect healing rates included: 1. Open fractures; 2. Oblique or comminuted fractures; 3. High-velocity injuries; 4. Angulation in the sagittal plane; 5. Displacement. No other factors examined were associated with delayed union. The predictive values for delayed union are estimated for each of these factors in isolation and in combination.

Developmental modulation of blood-brain barrier and choroid plexus GLUT1 glucose transporter messenger ribonucleic acid and immunoreactive protein in rabbits.

The transport of glucose across the brain capillary endothelium, which makes up the blood-brain barrier (BBB) in vivo, is developmentally up-regulated in the postnatal period, as the brain switches from combustion of circulating ketone bodies to glucose. The principle transporter mediating the uptake of circulating glucose across the BBB is the GLUT1 isoform. To further define molecular mechanisms underlying developmental modulation of the BBB GLUT1 transporter, the amounts of brain microvessel GLUT1 mRNA and immunoreactive protein were quantitated. In addition, an immunocytochemical analysis of GLUT1 expression at the choroid plexus in developing brain was performed, since this transporter isoform is selectively expressed at the choroid plexus epithelium basolateral membrane. Quantitative Western blotting employing purified human erythrocyte glucose transporter as an assay standard showed that the concentration of immunoreactive GLUT1 protein in 70-day-old rabbit brain microvessels (111 +/- 3 pmol/mg protein) was not significantly different from the concentration of D-glucose-displaceable cytochalasin-B-binding sites (102 +/- 25 pmol/mg protein). Thus, GLUT1 is the principle isoform mediating glucose transport across the developing BBB. Quantitative Western blotting was performed on microvessels isolated from brains of rabbits on postnatal days 1, 14, 28, and 70. The concentrations of immunoreactive microvessel GLUT1 at these four stages of development were 13 +/- 2, 4 +/- 1, 49 +/- 2, and 111 +/- 3 pmol/mg protein, respectively. Capillary depletion analysis showed that essentially all of brain GLUT1 mRNA arises from the microvascular fraction, and Northern analysis of 10 micrograms poly(A)+ RNA from brains of rabbits 1, 14, 28, and 70 days postnatally showed a preferential stabilization of the GLUT1 mRNA compared to mRNA for two cytoskeletal proteins, actin and tubulin. Immunocytochemical analysis of immunoreactive GLUT1 in choroid plexus epithelia showed the following developmental modulation of the transporter protein: 1 day < 14 days < 28 days > 70 days. The concentration of immunoreactive GLUT1 at the basolateral membrane of choroid plexus epithelium at 28 days was much greater than the immunostaining of rabbit brain microvessels at the corresponding age. In conclusion, these studies show that immunoreactive GLUT1 protein initially undergoes down-regulation between birth and 14 days and then undergoes marked up-regulation between 14 and 70 days. Conversely, the concentration of GLUT1 mRNA is virtually unchanged in brain of rabbits at 70 vs. 14 days postnatally. These combined data suggest that a principle mechanism underlying the developmental regulation of GLUT1 at the BBB may be posttranscriptional.

Tibial plateau fractures: the arthroscopic option.

Tibial plateau fractures remain one of the most difficult fractures to treat. A multitude of classifications exist and several treatment options have been advocated. In the last few years arthroscopy has been used in the treatment of these fractures. We report our experience of treating over 30 cases by this method and review the literature.

The Exeter bipolar prosthesis in the active elderly patient: the results at 7 years.

Seventy one Exeter bipolar hemiarthroplasties were reviewed after a mean follow up of 3.2 years (range 1-7 years). Patients with displaced subcapital fractures were selected for operation on the basis of good mobility before the fracture. The operation was well tolerated and the mortality at 1 month and 6 months was 3.7% and 6.5% respectively. Using a newly devised hip scoring system 89% had a good or excellent result and 94% had no or only occasional pain. There was no radiological evidence of acetabular erosion.

Arthroscopic management of tibial plateau fractures.

Ten tibial plateau fractures treated arthroscopically are reported. In eight cases, closed internal fixation was performed under arthroscopic control while in another two patients, arthroscopic washout alone was undertaken. Only one case required external splintage (a cast brace), the remainder being mobilized non-weight-bearing without plaster immediately after the operation. The results were good. We suggest that the arthroscope is a useful tool in the treatment of these fractures and provides information not otherwise available. There is a low morbidity, inpatient stay is short and early joint movement can be encouraged.

The intact fibula.

The notes and radiographs of 281 adult tibial shaft fractures were reviewed. In 17 per cent there was an intact fibula. Delayed union rates were lower when the fibula remained intact, thus confirming that this is a good prognostic indicator. This fracture is caused by less severe trauma than fractures where both bones are broken. It is rare over the age of 30 years.

Corrective tibial osteotomy for genu recurvatum by callus distraction using an external fixator.

Genu recurvatum due to an osseous abnormality is a condition that rarely requires surgical intervention. When necessary, the operative solution usually considered is an opening wedge osteotomy using bone graft and plate fixation. The donor site (usually the iliac crest) has a well reported morbidity with a further procedure being required to remove the plate. We report two cases treated by a hemicorticotomy and callus distraction (hemicallotasis) of the tibia using an external fixator. Correction was performed under supervision as an out-patient. Hospital stay was short, the morbidity of the donor site was eliminated, further procedures for removal of the plate were unnecessary and mobility of both the patient and his joints was maintained throughout the period of treatment. Satisfactory correction of the deformity was obtained in both cases.

Proximal tibio-fibular synostosis. A rare congenital anomaly.

A case of proximal tibiofibular synostosis is presented along with a review of the literature. The variety of presenting complaints is discussed and the syndrome is compared with that of radio-ulnar synostosis. Possible modes of treatment are explained.

The plica syndrome.

A retrospective study of 89 patients undergoing 98 arthroscopies of the knee in which a medial synovial plica was noted was undertaken. In 86 cases, the plica was deemed to be pathological and was resected arthroscopically. The symptoms and signs of these patients were noted preoperatively and the results of their operation noted in the outpatient department and subsequently by questionnaire. Our findings agree with other authors in this field and we propose that arthroscopic resection of a pathological plica is a worthwhile procedure.

The association between lowest palpable pulse and wound healing in below knee amputations.

A retrospective study of 191 patients undergoing 203 Burgess type below knee amputations for end-stage peripheral vascular disease showed that the only clinical feature which associated significantly with wound healing was the lowest palpable pulse. The pulse level was noted preoperatively and was compared with the healing rates in the amputation stumps. When the femoral pulse was absent, 79% of below knee amputations failed. When the femoral pulse was palpable, only 29% wound breakdown occurred. When the popliteal or more distal pulses were palpable, only 10% failure was recorded.