Fiber-connectorized ultrafast-laser-inscribed K-band integrated optics beam combiner for the CHARA telescope array.

A fiber-connectorized K-band integrated-optics two-telescope beam combiner was developed for long-baseline interferometry at the CHARA telescope array utilizing the ultrafast laser inscription (ULI) technique. Single-mode waveguide insertion losses were measured to be ∼1.1d B over the 2-2.3 µm window. The development of asymmetric directional couplers enabled the construction of a beam combiner that includes a 50:50 coupler for interferometric combination and two ∼75:25 couplers for photometric calibration. The visibility of the bare beam combiner was measured at 87% and then at 82% after fiber-connectorization by optimizing the input polarization. These results indicate that ULI technique can fabricate efficient fiber-connectorized K-band beam combiners for astronomical purposes.

Axi-Stack: a method for manufacturing freeform air-silica optical fibre.

We present a method with potential for fabricating freeform air-silica optical fibre preforms which is free from the stacking constraints associated with conventional stack-and-draw. The method, termed Axi-Stack, is enabled by the precision machining of short cross-sectional preform discs by ultrafast laser assisted etching; a laser-based microfabrication technique which facilitates near arbitrary shaping of the preform structure. Several preform discs are stacked axially and fused together via ultrafast laser welding to construct the preform, which can be drawn to fibre using conventional methods. To illustrate the Axi-Stack process, we detail the fabrication of a 30 cm long solid-core photonic crystal fibre preform with a square lattice of cladding holes and characterise fibre drawn from it.

Miniaturised gap sensor using fibre optic Fabry-Pérot interferometry for structural health monitoring.

A miniaturised structural health monitoring device has been developed capable of measuring the absolute distance between close parallel surfaces using Fabry-Pérot interferometry with nm-scale sensitivity. This is achieved by fabricating turning mirrors on two opposite cores of a multi-core fibre to produce a probe with dimensions limited only be the fibre diameter. Two fabrication processes have been investigated: Focused ion beam milling, which has resulted in a sensor measurement accuracy, sensitivity and range of ±0.056 µm, ±0.006 µm and ∼16000  µm respectively; and ultrafast laser assisted etching of the cleaved fibre end, where a sensor measurement accuracy, sensitivity and range of ±0.065 µm, ±0.006 µm and ∼7500 µm have been demonstrated.

Investigating focus elongation using a spatial light modulator for high-throughput ultrafast-laser-induced selective etching in fused silica.

Ultrafast-laser-induced selective chemical etching is an enabling microfabrication technology compatible with optical materials such as fused silica. The technique offers unparalleled three-dimensional manufacturing freedom and feature resolution but can be limited by long laser inscription times and widely varying etching selectivity depending on the laser irradiation parameters used. In this paper, we aim to overcome these limitations by employing beam shaping via a spatial light modulator to generate a vortex laser focus with controllable depth-of-focus (DOF), from diffraction limited to several hundreds of microns. We present the results of a thorough parameter-space investigation of laser irradiation parameters, documenting the observed influence on etching selectivity and focus elongation in the polarization-insensitive writing regime, and show that etching selectivity greater than 800 is maintained irrespective of the DOF. To demonstrate high-throughput laser writing with an elongated DOF, geometric shapes are fabricated with a 12-fold reduction in writing time compared to writing with a phase-unmodulated Gaussian focus.

An improved process for the fabrication and surface treatment of custom-made titanium cranioplasty implants informed by surface analysis.

Cranioplasty implants are routinely fabricated from commercially pure titanium plates by maxillofacial prosthetists. The differing fabrication protocols adopted by prosthetists working at different hospital sites gives rise to considerable variations in surface topography and composition of cranioplasty implants, with residues from the fabrication processes having been found to become incorporated into the surface of the implant. There is a growing recognition among maxillofacial prosthetists of the need to standardise these protocols to ensure quality and consistency of practice within the profession. In an effort to identify and eliminate the source of the inclusions associated with one such fabrication protocol, the present study examined the surfaces of samples subjected to each of the manufacturing steps involved. Surface and elemental analysis techniques identified the main constituent of the surface inclusions to be silicon from the glass beads used to texture the surface of the implant during fabrication. Subsequent analysis of samples prepared according to a revised protocol resulted in a more homogeneous titanium dioxide surface as evidenced by the reduction in area occupied by surface inclusions (from 8.51% ± 2.60% to 0.93% ± 0.62%). These findings may inform the development of improved protocols for the fabrication of titanium cranioplasty plates.

A Miniature Fibre-Optic Raman Probe Fabricated by Ultrafast Laser-Assisted Etching.

Optical biopsy describes a range of medical procedures in which light is used to investigate disease in the body, often in hard-to-reach regions via optical fibres. Optical biopsies can reveal a multitude of diagnostic information to aid therapeutic diagnosis and treatment with higher specificity and shorter delay than traditional surgical techniques. One specific type of optical biopsy relies on Raman spectroscopy to differentiate tissue types at the molecular level and has been used successfully to stage cancer. However, complex micro-optical systems are usually needed at the distal end to optimise the signal-to-noise properties of the Raman signal collected. Manufacturing these devices, particularly in a way suitable for large scale adoption, remains a critical challenge. In this paper, we describe a novel fibre-fed micro-optic system designed for efficient signal delivery and collection during a Raman spectroscopy-based optical biopsy. Crucially, we fabricate the device using a direct-laser-writing technique known as ultrafast laser-assisted etching which is scalable and allows components to be aligned passively. The Raman probe has a sub-millimetre diameter and offers confocal signal collection with 71.3% ± 1.5% collection efficiency over a 0.8 numerical aperture. Proof of concept spectral measurements were performed on mouse intestinal tissue and compared with results obtained using a commercial Raman microscope.

Optimisation of ultrafast laser assisted etching in fused silica.

Ultrafast laser assisted etching (ULAE) in fused silica is an attractive technology for fabricating three-dimensional micro-components. ULAE is a two-step process whereby ultrafast laser inscription (ULI) is first used to modify the substrate material and chemical etching is then used to remove the laser modified material. In this paper, we present a detailed investigation into how the ULI parameters affect the etching rate of laser modified channels and planar surfaces written in fused silica. Recently, potassium hydroxide (KOH) has shown potential to outperform the more commonly used hydrofluoric acid (HF) as a highly selective etchant for ULAE. Here we perform a detailed comparison of HF and KOH etching after laser inscription with a wide range of ultrafast laser irradiation parameters. Etching with KOH is found to be significantly more selective, removing the laser modified material up to 955 times faster than pristine material, compared with up to 66 when using HF. Maximum etching rates for the two etchants were comparable at 320 µm/hour and 363 µm/hour for HF and KOH respectively. We further demonstrate that highly selective, isotropic etching of non-planar surfaces can be achieved by controlling the polarization state of the laser dynamically during laser inscription.

Magnetic zero-modes, vortices and Cartan geometry.

We exhibit a close relation between vortex configurations on the 2-sphere and magnetic zero-modes of the Dirac operator on [Formula: see text] which obey an additional nonlinear equation. We show that both are best understood in terms of the geometry induced on the 3-sphere via pull-back of the round geometry with bundle maps of the Hopf fibration. We use this viewpoint to deduce a manifestly smooth formula for square-integrable magnetic zero-modes in terms of two homogeneous polynomials in two complex variables.

Liquorice: a root cause of secondary hypertension.

We describe a patient presenting with hypertension and hypokalaemia who was ultimately diagnosed with liquorice- induced pseudohyperaldosteronism. This rare cause of secondary hypertension illustrates the importance of a methodical approach to the assessment of hypertension.

Touch not the cat bot a glove*: ANCA-positive pauci-immune necrotizing glomerulonephritis secondary to Bartonella henselae.

A 36-year-old male presented with a secondary, but anti-neutrophil cytoplasmic antibody (ANCA) (proteinase-3) positive, vasculitis with renal insufficiency due to a pauci-immune necrotizing glomerulonephritis. An infective process was initially excluded by blood cultures and an echocardiogram prior to immunosuppression. The patient's condition failed to improve and re-evaluation confirmed infective endocarditis requiring valve replacement. Subsequent tissue cultures identified Bartonella henselae. Antibiotic treatment led to full resolution of physical, biochemical and immunological markers. This is the first case of B. henselae endocarditis-associated ANCA positivity with a pauci-immune glomerulonephritis. It demonstrates the importance of revisiting standard investigations in patients not improving expectantly on conventional therapy.

Endocapillary glomerulonephritis secondary to human parvovirus B19 presenting with nephrotic syndrome: a report of two cases and a review of the literature.

Human parvovirus B19 infection causes several clinical syndromes. Systemic complications due to this illness are rare. Parvovirus B19 associated renal disease is being increasingly recognized. We report two cases with characteristic presentation with a nephrotic syndrome due to parvovirus B19. We discuss the importance of identifying this infection as a cause of endocapillary glomerulonephritis.

A randomized, crossover design study of sevelamer carbonate powder and sevelamer hydrochloride tablets in chronic kidney disease patients on haemodialysis.

BACKGROUND: Sevelamer carbonate is an improved, buffered form of sevelamer hydrochloride developed for the treatment of hyperphosphataemia in CKD patients. Sevelamer carbonate formulated as a powder for oral suspension presents a novel, patient-friendly alternative to tablet phosphate binders. This study compared the safety and efficacy of sevelamer carbonate powder with sevelamer hydrochloride tablets in CKD patients on haemodialysis. METHODS: This was a multi-centre, open-label, randomized, crossover design study. Thirty-one haemodialysis patients were randomly assigned to either sevelamer carbonate powder or sevelamer hydrochloride tablets for 4 weeks followed by a crossover to the other regimen for an additional 4 weeks. RESULTS: The mean serum phosphorus was 1.6 +/- 0.5 mmol/L (5.0 +/- 1.5 mg/dL) during sevelamer carbonate powder treatment and 1.7 +/- 0.4 mmol/L (5.2 +/- 1.1 mg/dL) during sevelamer hydrochloride tablet treatment. Sevelamer carbonate powder and sevelamer hydrochloride tablets are equivalent in controlling serum phosphorus; the geometric least square mean ratio was 0.95 (90% CI 0.87-1.03). No statistically significant or clinically meaningful differences were observed in calcium x phosphorus product and lipid levels between sevelamer carbonate powder and sevelamer hydrochloride tablets. Serum bicarbonate levels increased 2.7 +/- 3.7 mmol/L (2.7 +/- 3.7 mEq/L) during sevelamer carbonate treatment. No statistically significant change in bicarbonate was observed during sevelamer hydrochloride treatment. Sevelamer carbonate powder and sevelamer hydrochloride were well tolerated during this study. CONCLUSIONS: Sevelamer carbonate powder and sevelamer hydrochloride tablets are equivalent in controlling serum phosphorus and well tolerated in CKD patients on haemodialysis. Bicarbonate levels improved only during sevelamer carbonate treatment. Sevelamer carbonate powder should provide a welcomed new option for the treatment of hyperphosphataemia for CKD patients on dialysis.

Limitations of caspofungin in the treatment of obstructive pyonephrosis due to Candida glabrata infection.

BACKGROUND: Caspofungin is a new antifungal agent with high-level activity against a number of Candida species including those that are resistant to azoles. Its good safety profile and low nephrotoxicity makes it an attractive drug to treat fungal infections in patients with compromised renal function. However, little is known about the clinical efficacy in the treatment of complicated urinary tract infections due to Candida species such as pyonephrosis. CASE PRESENTATION: We report a case of obstructive pyonephrosis due to an azole (fluconazole and itraconazole) resistant Candida glabrata strain that failed to respond to intravenous treatment with caspofungin. A sustained clinical and microbiological response was only achieved after percutaneous drainage and instillation of amphotericin B deoxycholate into the renal pelvis in combination with intravenous liposomal amphotericin B. CONCLUSION: This case demonstrates the limitation of intravenous antifungal agents such as caspofungin as the sole treatment of an obstructive upper urinary tract infection due to Candida species. In order to achieve long term sustained cure from an obstructive pyonephrosis, pus and fungal balls should be drained and an anti-fungal agent such as amphotericin B deoxycholate instilled locally. The pharmacokinetics and role of caspofungin in the treatment of complicated Candida urinary tract infection is reviewed.

Drug-induced tubulo-interstitial nephritis secondary to proton pump inhibitors: experience from a single UK renal unit.

BACKGROUND: Acute tubulo-interstitial nephritis (TIN) is an important cause of acute renal failure, and is often caused by hypersensitivity to drugs. The aim of this study was to determine the aetiology of interstitial nephritis among an unselected cohort of patients, and to identify those drugs commonly implicated. METHODS: A single-centre retrospective analysis was carried out of renal biopsy results from 296 consecutive patients between 1995 and 1999. RESULTS: Acute TIN was identified in 24 (8.1%) biopsies. Eight out of 14 cases with presumed drug-related TIN could be attributed to the proton pump inhibitors omeprazole and lansoprazole. The two cases of lansoprazole-associated TIN are the first to be reported with this drug. The presentation and favourable response to treatment of these patients are described. CONCLUSION: Drugs are the most common cause of interstitial nephritis in the population studied. Those drugs most commonly associated with interstitial nephritis were the proton pump inhibitors omeprazole and lansoprazole.