Microscopic Imaging of the Stress Tensor in Diamond Using in Situ Quantum Sensors.

The precise measurement of mechanical stress at the nanoscale is of fundamental and technological importance. In principle, all six independent variables of the stress tensor, which describe the direction and magnitude of compression/tension and shear stress in a solid, can be exploited to tune or enhance the properties of materials and devices. However, existing techniques to probe the local stress are generally incapable of measuring the entire stress tensor. Here, we make use of an ensemble of atomic-sized in situ strain sensors in diamond (nitrogen-vacancy defects) to achieve spatial mapping of the full stress tensor, with a submicrometer spatial resolution and a sensitivity of the order of 1 MPa (10 MPa) for the shear (axial) stress components. To illustrate the effectiveness and versatility of the technique, we apply it to a broad range of experimental situations, including mapping the stress induced by localized implantation damage, nanoindents, and scratches. In addition, we observe surprisingly large stress contributions from functional electronic devices fabricated on the diamond and also demonstrate sensitivity to deformations of materials in contact with the diamond. Our technique could enable in situ measurements of the mechanical response of diamond nanostructures under various stimuli, with potential applications in strain engineering for diamond-based quantum technologies and in nanomechanical sensing for on-chip mass spectroscopy.

Dynamic stabilization of the optical resonances of single nitrogen-vacancy centers in diamond.

We report electrical tuning by the Stark effect of the excited-state structure of single nitrogen-vacancy (NV) centers located ≲100 nm from the diamond surface. The zero-phonon line (ZPL) emission frequency is controllably varied over a range of 300 GHz. Using high-resolution emission spectroscopy, we observe electrical tuning of the strengths of both cycling and spin-altering transitions. Under resonant excitation, we apply dynamic feedback to stabilize the ZPL frequency. The transition is locked over several minutes and drifts of the peak position on timescales ≳100 ms are reduced to a fraction of the single-scan linewidth, with standard deviation as low as 16 MHz (obtained for an NV in bulk, ultrapure diamond). These techniques should improve the entanglement success probability in quantum communications protocols.

Non-recurrent SEPT9 duplications cause hereditary neuralgic amyotrophy.

BACKGROUND: Genomic copy number variants have been shown to be responsible for multiple genetic diseases. Recently, a duplication in septin 9 (SEPT9) was shown to be causal for hereditary neuralgic amyotrophy (HNA), an episodic peripheral neuropathy with autosomal dominant inheritance. This duplication was identified in 12 pedigrees that all shared a common founder haplotype. METHODS AND RESULTS: Based on array comparative genomic hybridisation, we identified six additional heterogeneous tandem SEPT9 duplications in patients with HNA that did not possess the founder haplotype. Five of these novel duplications are intragenic and result in larger transcript and protein products, as demonstrated through reverse transcription-PCR and western blotting. One duplication spans the entire SEPT9 gene and does not generate aberrant transcripts and proteins. The breakpoints of all the duplications are unique and contain regions of microhomology ranging from 2 to 9 bp in size. The duplicated regions contain a conserved 645 bp exon within SEPT9 in which HNA-linked missense mutations have been previously identified, suggesting that the region encoded by this exon is important to the pathogenesis of HNA. CONCLUSIONS: Together with the previously identified founder duplication, a total of seven heterogeneous SEPT9 duplications have been identified in this study as a causative factor of HNA. These duplications account for one third of the patients in our cohort, suggesting that duplications of various sizes within the SEPT9 gene are a common cause of HNA.

Nano-manipulation of diamond-based single photon sources.

The ability to manipulate nano-particles at the nano-scale is critical for the development of active quantum systems. This paper presents a technique to manipulate diamond nano-crystals at the nano-scale using a scanning electron microscope, nano-manipulator and custom tapered optical fibre probes. The manipulation of a approximately 300 nm diamond crystal, containing a single nitrogen-vacancy centre, onto the endface of an optical fibre is demonstrated. The emission properties of the single photon source post manipulation are in excellent agreement with those observed on the original substrate.

Visible and near infra-red up-conversion in Tm3+/Yb3+ co-doped silica fibers under 980 nm excitation.

The spectroscopic properties of Tm(3+)/Yb(3+) co-doped silica fibers under excitation at 980 nm are reported. Three distinct up-conversion fluorescence bands were observed in the visible to near infra-red regions. The blue and red fluorescence bands at 475 and 650 nm, respectively, were found to originate from the (1)G(4) level of Tm(3+). A three step up-conversion process was established as the populating mechanism for these fluorescence bands. The fluorescence band at 800 nm was found to originate from two possible transitions in Tm(3+); one being the transition from the (3)H(4) to (3)H(6) manifold which was found to dominate at low pump powers; the other being the transition from the (1)G(4) to (3)H(6) level which dominates at higher pump powers. The fluorescence lifetime of the (3)H(4) and (3)F(4) levels of Tm(3+) and (2)F(5/2) level of Yb(3+) were studied as a function of Yb(3+) concentration, with no significant energy back transfer from Tm(3+) to Yb(3+) observed.

The visual fields: an interdisciplinary history I. The evolution of knowledge.

A subjective study of a hemianopic field defect was reported to the London Royal Society in 1824. The German ophthalmologist Albrecht von Graefe devised a means of mapping field defects, which evolved into quantitative perimetry as an exact method of localizing lesions in the visual pathways. Knowledge of these pathways increased during the nineteenth century; final identification of the visual cortex in the occipital lobe was achieved by Japanese and British ophthalmologists and neurologists on the basis of wartime studies of field defects due to cerebral missile wounds.

The visual fields: an interdisciplinary history II. neurosurgeons and quantitative perimetry.

When operations for brain tumours became possible, exact charting of visual field defects assumed great importance in diagnosis and in monitoring post-operative progress. This process, known as quantitative perimetry, was energetically practised and taught by Harvey Cushing and by many of his pupils. The advent of non-invasive methods of imaging the brain and the rise of neuro-ophthalmology as an independent discipline were associated with a decline in neurosurgical commitment to quantitative perimetry, but it remains an important branch of the clinical neurosciences.

Detection of nanoscale electron spin resonance spectra demonstrated using nitrogen-vacancy centre probes in diamond.

Electron spin resonance (ESR) describes a suite of techniques for characterizing electronic systems with applications in physics, chemistry, and biology. However, the requirement for large electron spin ensembles in conventional ESR techniques limits their spatial resolution. Here we present a method for measuring ESR spectra of nanoscale electronic environments by measuring the longitudinal relaxation time of a single-spin probe as it is systematically tuned into resonance with the target electronic system. As a proof of concept, we extracted the spectral distribution for the P1 electronic spin bath in diamond by using an ensemble of nitrogen-vacancy centres, and demonstrated excellent agreement with theoretical expectations. As the response of each nitrogen-vacancy spin in this experiment is dominated by a single P1 spin at a mean distance of 2.7 nm, the application of this technique to the single nitrogen-vacancy case will enable nanoscale ESR spectroscopy of atomic and molecular spin systems.

Characterisation of the advanced glycation endproduct receptor complex in the retinal pigment epithelium.

AIMS: Advanced glycation endproducts (AGEs) accumulate with ageing and may have a significant impact on age related dysfunction of the retinal pigment epithelium (RPE). Many of the cellular effects of AGEs in other cell types are mediated through AGE binding proteins. The aim of this study was to characterise the AGE receptor complex in RPE cells in vitro and to focus on the role of the R3 component (galectin-3) as the primary effector of the complex. METHODS: Primary cultures of bovine RPE cells and the human D407 RPE cell line were exposed to AGE modified albumin. Receptor expression was determined using mRNA analysis by quantitative real time RT-PCR and protein characterisation by western blotting. Immunocytochemical analysis examined the cellular localisation of the various components of the AGE receptor complex. The role of the galectin-3 receptor component was examined by transfection and overexpression using the D407 cell line and analysis of soluble AGE-R3 by ELISA. RESULTS: All three components of the AGE receptor complex were expressed by bovine and human RPE cells. AGE exposure upregulated two components of the receptor complex and also induced significant RPE expression of VEGF mRNA (p<0.05). RPE D407 cells stably transfected to overexpress galectin-3 showed less VEGF induction. In non-transfected RPE which were exposed to AGEs, there was less soluble galectin-3 protein released into the medium (p<0.05), a response that was not evident in transfected cells. CONCLUSION: A conserved AGE receptor complex is evident in primary cultures of bovine RPE cells and also in a human cell line. These cells show a pathological response to AGE exposure, an effect which appears to be modulated by the galectin-3 component of the receptor complex.

Tonic adrenergic and serotonergic inhibition of a withdrawal reflex in rabbits subjected to different levels of surgical preparation.

The excitability of the heel-gastrocnemius withdrawal reflex pathway has been monitored in rabbits undergoing surgical preparation for electrophysiological experimentation under Saffan anaesthesia. Reflexes were evoked by percutaneous electrodes inserted at the heel and recorded as electromyograph signals from the ipsilateral medial gastrocnemius muscle. Two levels of surgery were carried out. The "full surgical" preparation was performed under deep Saffan anaesthesia. The trachea, carotid artery, jugular vein and intrathecal space (via a small laminectomy at L1) were cannulated, the animals were decerebrated by suction, and the left hindlimb was immobilized by screw clamps applied to the tibia and the femur. The sciatic nerve and its branches were exposed by bisection of the posterior biceps muscle and the anaesthetic was withdrawn. In the "reduced surgery" preparation, procedures were carried out with a lighter level of Saffan anaesthesia and operated tissues were infiltrated with local anaesthetic. Only the cannulations were performed in these animals. The excitability of the heel-gastrocnemius reflex declined throughout the full surgical preparation, with the median threshold increasing from 0.8 to 4.2 mA (n=19) and responses to suprathreshold stimuli reducing in size. Most of this effect was reversed after surgery was complete and anaesthesia withdrawn subsequent to decerebration. There were no significant changes in reflex excitability during the reduced surgery preparation (n = 15). Animals prepared by each of these protocols were given increasing intrathecal doses of either the selective alpha2-adrenoceptor antagonist RX 821002 (0.3 to 300 microg) or the serotonin/5-hydroxytryptamine (5-HT)1A-receptor antagonist WAY-100635 (0.01 to 30 microg). Both drugs caused significant, dose-dependent increases in reflex responses, to four to six times pre-drug control in both groups of animals. There were no differences in the effects on reflexes of either drug between the preparations. Thus, surgical preparation of decerebrated rabbits for electrophysiological recording results in depression of hindlimb withdrawal reflexes, although much of this effect did not persist beyond the completion of surgery. Tonic monoaminergic inhibition of reflexes was present to the same extent in both preparations investigated and is not therefore an epiphenomenon of the way in which the animals were prepared.

Advanced glycation end products in vitreous: Structural and functional implications for diabetic vitreopathy.

PURPOSE: Advanced glycation end products (AGEs) form irreversible cross-links with many macromolecules and have been shown to accumulate in tissues at an accelerated rate in diabetes. In the present study, AGE formation in vitreous was examined in patients of various ages and in patients with diabetes. Ex vivo investigations were performed on bovine vitreous incubated in glucose to determine AGE formation and cross-linking of vitreous collagen. METHODS: By means of an AGE-specific enzyme-linked immunosorbent assay (ELISA), AGE formation was investigated in vitreous samples obtained after pars plana vitrectomy in patients with and without diabetes. In addition, vitreous AGEs were investigated in bovine vitreous collagen after incubation in high glucose, high glucose with aminoguanidine, or normal saline for as long as 8 weeks. AGEs and AGE cross-linking was subsequently determined by quantitative and qualitative assays. RESULTS: There was a significant correlation between AGEs and increasing age in patients without diabetes (r = 0.74). Furthermore, a comparison between age-matched diabetic and nondiabetic vitreous showed a significantly higher level of AGEs in the patients with diabetes (P < 0.005). Collagen purified from bovine vitreous incubated in 0.5 M glucose showed an increase in AGE formation when observed in dot blot analysis, immunogold labeling, and AGE ELISA. Furthermore, there was increased cross-linking of collagen in the glucose-incubated vitreous, when observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and protein separation. This cross-linking was effectively inhibited by coincubation with 10 mM aminoguanidine. CONCLUSIONS: This study suggests that AGEs may form in vitreous with increasing age. This process seems to be accelerated in the presence of diabetes and as a consequence of exposure to high glucose. Advanced glycation and AGE cross-linking of the vitreous collagen network may help to explain the vitreous abnormalities characteristic of diabetes.

Retinal VEGF mRNA measured by SYBR green I fluorescence: A versatile approach to quantitative PCR.

PURPOSE: To determine whether continuous monitoring of SYBR Green I fluorescence provides a reliable and flexible method of quantitative RT-PCR. Our aims were (i) to test whether SYBR Green I analysis could quantify a wide range of known VEGF template concentrations, (ii) to apply this method in an experimental model, and (iii) to determine whether 20 existing primer pairs could be used to quantify their cognate mRNAs. METHODS: Real-time quantitative PCR was performed using a LightCycler rapid thermal cycler (Roche). Retinal VEGF mRNA levels were measured in a murine model of oxygen-induced retinopathy during vaso-obliterative and hypoxic phases. RESULTS: This technique was able to detect as few as 10 control template copies, with quantitative data available routinely for 1000 or more copies. The levels of retinal VEGF mRNA expression followed the hypoxia-induced pattern determined previously by conventional methods. All gene-specific primer pairs which amplify a specific product by conventional PCR were successfully converted to SYBR Green analysis, including those for housekeeping genes glyceraldehyde phosphate dehydrogenase (GAPDH), cyclophilin, and acidic ribosomal phosphoprotein PO (ARP/36B4) and for 28S rRNA. In each case melting curve analysis and agarose gel electrophoresis confirmed the specificity of the amplification product. CONCLUSIONS: The sequence-independent detection of DNA with SYBR Green I means that it can be used to quantify the amplification of any cDNA using gene-specific primers. This rapid and flexible method is ideally suited for researchers in vision science wishing to quantify mRNAs from many different genes because it does not require investment in gene-specific hybridization probes.

Novel and recurrent mutations in lamin A/C in patients with Emery-Dreifuss muscular dystrophy.

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by slowly progressive muscle wasting and weakness; early contractures of the elbows, Achilles tendons, and spine; and cardiomyopathy associated with cardiac conduction defects. Clinically indistinguishable X-linked and autosomal forms of EDMD have been described. Mutations in the STA gene, encoding the nuclear envelope protein emerin, are responsible for X-linked EDMD, while mutations in the LMNA gene encoding lamins A and C by alternative splicing have been found in patients with autosomal dominant, autosomal recessive, and sporadic forms of EDMD. We report mutations in LMNA found in four familial and seven sporadic cases of EDMD, including seven novel mutations. Nine missense mutations and two small in-frame deletions were detected distributed throughout the gene. Most mutations (7/11) were detected within the LMNA exons encoding the central rod domain common to both lamins A/C. All of these missense mutations alter residues in the lamin A/C proteins conserved throughout evolution, implying an essential structural and/or functional role of these residues. One severely affected patient possesed two mutations, one specific to lamin A that may modify the phenotype of this patient. Mutations in LMNA were frequently identified among patients with sporadic and familial forms of EDMD. Further studies are needed to identify the factors modifying disease phenotype among patients harboring mutations within lamin A/C and to determine the effect of various mutations on lamin A/C structure and function.

Topography of axonal injury as defined by amyloid precursor protein and the sector scoring method in mild and severe closed head injury.

Axonal injury (AI), as defined by amyloid precursor protein (APP) positive axonal swellings, was recorded on a series of line diagrams of standard brain sections divided into 116 sectors to provide an Axonal Injury Sector Score (AISS) ranging from 0 to 116. This sector scoring method of recording axonal damage and providing a topographic overview of AI was applied to a series of 6 mild head injury cases [Glasgow Coma Scale (GCS) 13-15] and six severe head injury cases (GCS 3-8). The AISS ranged from 4 to 107 overall and varied from 4 to 88 in the mildly injured group and 76 to 107 in the severe head injury group, supporting the concept that there is a spectrum of AI in traumatic head injury and that the AISS is a measure of the extent of AI. APP immunostaining demonstrated positive axonal swellings 1.75 h after head injury and analysis of the pattern of AI in the mild and severe head injury groups showed that axons were more vulnerable than blood vessels and that the axons in the corpus callosum and fornices were the most vulnerable of all.

Cephaloceles: treatment, outcome, and antenatal diagnosis.

A series of 74 cephaloceles (17 cranial meningoceles and 57 meningoencephaloceles) is reported. Infants born with large meningoencephaloceles containing recognizable cerebral tissue usually did badly despite endeavors to conserve brain function by expanding the cranial capacity (5 cases) or decompressing hydrocephalic ventricles (9 cases). Infants with cranial meningoceles almost all did well, even when there was associated hydrocephalus. The etiological diversity of cephaloceles is emphasized. Frontoethmoidal meningoencephaloceles, which occur with noteworthy frequency in South and Southeast Asia, require separate consideration in both genetic counseling and treatment; the associated facial deformities (hypertelorism and orbital dystopia) can be corrected with a one-stage craniofacial reconstruction. Antenatal diagnosis by ultrasound is now often possible and was achieved in 4 cases; we suggest that neurosurgeons should participate in such antenatal evaluations.

Usefulness of beta 2-transferrin assay in the detection of cerebrospinal fluid leaks following head injury.

The clinical value of analyzing various fluids and exudates for beta 2-transferrin (beta 2-Tfn) to detect cerebrospinal fluid (CSF) leakage following head trauma was reviewed in a series of 11 cases. Qualitative detection of beta 2-Tfn was performed by agarose gel electrophoresis of tears, ear and nose exudates, cerebral cyst fluid, and wound discharge fluid in different cases. In each instance the presence of beta 2-Tfn in the analyzed fluid supported the diagnosis of a CSF leak. Equally, the demonstration of the absence of beta 2-Tfn in the fluid excluded the diagnosis of such a leak. Neither false-positive nor false-negative results were found, as indicated by separate radiological investigations and/or subsequent clinical assessment of patients. The detection of beta 2-Tfn in suspect fluids thus provides a highly sensitive and selective, rapid, and noninvasive test for the detection of CSF leakage in cases of head trauma.

Open and closed meniscectomy. A comparative analysis.

We reviewed 230 patients an average of 34 months after they had undergone partial or total meniscectomy by surgeons of different experience in a busy unit. Open and arthroscopic meniscectomies were compared. Arthroscopic partial meniscectomy resulted in a significant reduction of inpatient stay and earlier return to work and sport. Analysis of the type of meniscal damage showed that arthroscopic removal of "bucket handles" achieved better results than open techniques. Comparatively poor results were found for lateral meniscectomy.

Orthopaedic aspects of spinal tumors in children.

A retrospective survey has been made of forty children with spinal tumours. Difficulties in establishing the correct diagnosis are mentioned and the value of radiological and cerebrospinal fluid investigations discussed. The major orthopaedic disabilities are spinal deformity or instability, and paraplegia. The main factor in the development of the former is the site of laminectomy: the higher the level the greater is the likelihood of deformity or instability developing. Measures to prevent this distressing complication are discussed. The role of the orthopaedic surgeon in the management of these children is emphasised.

Frontoethmoidal meningoencephaloceles.

Frontoethmoidal meningoencephaloceles constitute a well-defined clinical entity with remarkable epidemiologic peculiarities, being very prevalent in Southeast and Southern Asia, but relatively rare in Western Europe, Japan, Australia, and North America. They do not show an increased risk of recurrence in siblings and offspring, unlike other cephaloceles and neural tube defects generally, from which they should be distinguished. Combined craniofacial and neurosurgical operative treatment permits one-stage correction of the whole deformity, the associated hypertelorism being reduced by selective orbital translocation and the nasal deformity by rhinoplasty. In planning these procedures, three-dimensional CT scanning is very helpful. Although our experience is chiefly with cases referred in childhood, we have some experience with operations done in infancy and believe this to be the ideal age.

Embolism of cerebral tissue: a cause of coagulopathy and cerebral infarction? Report of a case.

We report a case of potentially survivable closed head injury, which was complicated by disseminated intravascular coagulation and bilateral cerebral infarction. Autopsy disclosed pulmonary emboli composed of cerebral tissue. We suggest that the entry of brain tissue into the systemic blood circulation caused severe disseminated intravascular coagulation, with consequent thrombosis of cerebral veins and spreading infarction.