Long-Term Bonding Efficacy of CAD/CAM Hybrid Restorative Materials and Universal Adhesives

OBJECTIVES

In-office and lab milled prostheses are the staple for indirect restorations. It is therefore critical to determine their long-term bonding durability.

METHODS

CAD/ CAM blocks of two classes of restorative materials: 1) a nano-ceramic reinforced polymer matrix (NCPM) and, 2) a polymer-infiltrated ceramic network (PICN) were bonded using four different universal adhesives (UA) and silane systems. A lithium disilicate glassceramic (LDS) was used as a reference. The blocks were bisected and bonded with different UA/resin-cement pairs. Bonded blocks were then cut into 1.0x1.0x12.0 mm bar specimens for microtensile bond testing. Half the bars were subjected to bond strength testing immediately and the other half after aging by 50,000 thermal cycles between 5°C and 55°C. ANOVA and post-hoc tests were used to compare mean bond strength among groups.

RESULTS

NCPM presented consistently high bond strength regardless of bonding techniques, while the bond strength of PICN and LDS were lower when bonded with UA relative to traditional silanes. The more hydrophilic UA produced higher bond strengths.

DISCUSSION

Glass-ceramics exhibited lower bond strength with UA than the conventional etch-rinse-silane techniques. However, UAs preserved bonding interface in the long-term.

SIGNIFICANCE

NCPM displayed superior bond strength relative to PICN and LDS regardless of the type of adhesives and bonding techniques.

Surgical Training Simulators for Rhinoplasty: A Systematic Review

Rhinoplasty training currently follows an apprenticeship model that is largely observational. Trainees have limited experience in performing maneuvers of this complex surgery. Rhinoplasty simulators can address this issue by providing trainees with the opportunity to gain surgical simulator experience that could improve technical competences in the operating room. This review amalgamates the collective understanding of rhinoplasty simulators described to date. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, PubMed, OVID Embase, OVID Medline, and Web of Science databases were all searched for original research on surgical simulators for rhinoplasty education and reviewed by independent reviewers. Articles underwent title and abstract screening, and then relevant articles underwent full-text review to extract simulator data. Seventeen studies, published between 1984 and 2021, were included for final analysis. Study participant numbers ranged from 4 to 24, and included staff surgeons, fellows, residents (postgraduate year 1-6), and medical students. Cadaveric surgical simulators comprised eight studies, of which three were with human cadavers, one study was a live animal simulator, two were virtual simulators, and six were three-dimensional (3D) models. Both animal and human-based simulators increased the confidence of trainees significantly. Significant improvement in various aspects of rhinoplasty knowledge occurred with implementation of a 3D-printed model in rhinoplasty education. Rhinoplasty simulators are limited by a lack of an automated method of evaluation and a large reliance on feedback from experienced rhinoplasty surgeons. Rhinoplasty simulators have the potential to provide trainees with the opportunity for hands-on training to improve skill and develop competencies without putting patients in harm's way. Current literature on rhinoplasty simulators largely focuses on simulator development, with few simulators being validated and assessed for utility. For wider implementation and acceptance, further refinement of simulators, validation, and assessment of outcomes is required.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

The patient perspective, experience and satisfaction of day case unicompartmental knee arthroplasty: A short-term mixed-methods study

BACKGROUND

Day case unicompartmental knee arthroplasty (UKA) is increasingly being performed worldwide. When performed in the appropriate patient, day case UKA has been demonstrated to be safe, cost effective and improve resource allocation. Limited evidence highlights increased patient satisfaction of day case UKA when compared with inpatient UKA. A detailed study of the patient perspective, experience and satisfaction following day case UKA has not been described before.

METHODS

A retrospective case series review of 21 consecutive patients (19 unilateral, 2 bilateral) undergoing day case UKA in an elective orthopaedic centre was undertaken. A qualitative and quantitative patient assessment of the day case UKA experience was administered. A five-point Likert scale satisfaction questionnaire, Oxford Knee Score (OKS) and open-ended interview was undertaken. The qualitative responses underwent thematic analysis.

RESULTS

One hundred percent of patients expressed satisfaction (76.2% completely satisfied, 33.8% moderately satisfied) with day case UKA. The majority of patients (90.5%) reported that if they had to undergo UKA again they would prefer a day case over an inpatient procedure. Patients consider surgical outcome, physiotherapy provision, discharge planning, postoperative medications and follow up as key aspects of day case UKA care. One patient was re-admitted following discharge.

CONCLUSIONS

The present study demonstrates a high level of patient satisfaction with day case UKA. The results reported herein are subject to the study limitations of sample size, recall bias and inclusion criteria. We recommend that the themes identified by patients are addressed through a multidisciplinary approach with well-defined clinical pathways for a high-quality patient-centred experience.

Smartphone-based technology for nanomolecular detection of aflatoxin B1 by aptamer-conjugated magnetic nanoparticles

The need for a healthy market in the rapid and accurate screening of a variety of pathogenic agents and toxins in the environment and food has led to an increase in the development of new biosensors, which have ideal characteristics, such as high sensitivity and specificity with rapid detection and simple preparation of the sample. Among the food contaminants, mycotoxins have been identified as a major challenge for the food industry, and rapid and accurate detection has attracted the attention of food inspection and monitoring organisations. In this study, a nanomolecular detection method is described using aflatoxin B1 (AFB1)-specific aptamers attached to streptavidin-coated magnetic nanoparticles. A prominent feature of the AFB1-specific aptamers is a guanine-rich (G-rich) sequence with a G-quadruplex structure after capturing AFB1 molecules and mimicking peroxidase activity. The enzymatic reaction evaluated in the presence of chromogenic substrate and measurement is done by a smartphone-specific application for colorimetric measurement. The results indicated that the assay could measure AFB1 in rice, flour, seed, maize, and pistachio. In addition, the application of hybrid nanomaterial technology resulting from the binding of biotin-labelled aptamers to the surface of streptavidin-coated magnetic nanoparticles minimises preparation and treatment of samples, improves results, and consequently reduces false negative and positive responses in the detection field. This study may eventually lead to the design and development of a fast, sensitive, specific, and on-site AFB1-based nanomolecular colorimetric detection system via a smartphone-based application that can be readily accessible to all applicants, from professionals to manufacturers of foodstuffs.

Understanding the holistic experiences of living with a kidney transplant: an interpretative phenomenological study (protocol)

Background

Currently very little is known about the perceptions and experiences of kidney transplant recipients from a qualitative perspective. As highlighted by the European Kidney Health Alliance recommendations, providing holistic care to kidney patients is important however this is currently an unmet care need in renal disease. It is imperative to understand patient experiences to ensure that they are included in key strategies and future renal service planning. Ignoring these important patient views means that there is a significant risk of inappropriate renal service provision and lack of adequate support impacting on overall health.

Method

A purposive sampling strategy will recruit individuals currently living with a kidney transplant, 6 months to 5 years post-transplant. A maximum of 30 patients will be recruited between two Regional Nephrology units within the United Kingdom via clinical gatekeepers. In-depth interviews will be undertaken with participants living with a kidney transplant across the two sites. Interviews will be digitally-recorded, transcribed verbatim and subjected to interpretative phenomenological analysis.

Discussion

Renal healthcare professionals need to understand more than the biological impact of receiving a kidney transplant. Understanding the holistic and multi-domain experiences that these patients experience will help healthcare professionals to recognize the needs of this group and ensure more responsive care.

Blastomere cleavage plane orientation and the tetrahedral formation are associated with increased probability of a good-quality blastocyst for cryopreservation or transfer: a time-lapse study

OBJECTIVE

To determine whether blastomere spatial arrangement in early human embryos is reflective of embryonic potential.

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

Single academic center.

PATIENT(S)

Patients undergoing a single blastocyst transfer.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Developmental kinetics, blastocyst quality, embryo dysmorphisms, and live birth rate.

RESULT(S)

A total of 716 embryos were examined in detail for cleavage plane orientation, blastomere arrangement, and morphokinetic behavior. Tetrahedral (TET) and nontetrahedral embryos (nTET) differed significantly in developmental kinetics. The frequency of dysmorphisms, multinucleation, and irregular chaotic division was higher in nTET embryos. Only 44% of nTET versus 62.9% of TET embryos were scored as top-quality blastocysts. After adjusting for age, our data indicated that having TET embryos significantly increased the odds of having a blastocyst for cryopreservation/transfer (odds ratio, 3.58; confidence interval, 2.42-5.28) when compared with nTET. A total of 164 fresh single ETs were performed with blastocyst-stage embryos. The implantation rate for TET- and nTET-derived blastocysts were similar (64.7% and 62%, respectively). The live birth rate was 55% in both groups. A meridonal first division was noted in 85% of the fresh SET blastocysts.

CONCLUSION(S)

Cleavage plane orientation during the first three divisions appeared to dictate final blastomere spatial arrangement. The TET formation at the four-cell stage was predictive for embryos most likely to develop into good-quality blastocysts for cryopreservation/transfer. Morphokinetic markers of embryo potential were significantly different between TET and nTET embryos.

Chaos in a ring circuit

A ring-shaped logic circuit is proposed here as a robust design for a True Random Number Generator (TRNG). Most existing TRNGs rely on physical noise as a source of randomness, where the underlying idealized deterministic system is simply oscillatory. The design proposed here is based on chaotic dynamics and therefore intrinsically displays random behavior, even in the ideal noise-free situation. The paper presents several mathematical models for the circuit having different levels of detail. They take the form of differential equations using steep sigmoid terms for the transfer functions of logic gates. A large part of the analysis is concerned with the hard step-function limit, leading to a model known in mathematical biology as a Glass network. In this framework, an underlying discrete structure (a state space diagram) is used to describe the likely structure of the global attractor for this system. The latter takes the form of intertwined periodic paths, along which trajectories alternate unpredictably. It is also invariant under the action of the cyclic group. A combination of analytical results and numerical investigations confirms the occurrence of symmetric chaos in this system, which when implemented in (noisy) hardware, should therefore serve as a robust TRNG.

Compact laser system for a laser-cooled ytterbium ion microwave frequency standard

The development of a transportable microwave frequency standard based on the ground-state transition of ¹⁷¹Yb⁺ at ∼12.6 GHz requires a compact laser system for cooling the ions, clearing out of long-lived states and also for photoionisation. In this paper, we describe the development of a suitable compact laser system based on a 6U height rack-mounted arrangement with overall dimensions 260 × 194 × 335 mm. Laser outputs at 369 nm (for cooling), 399 nm (photoionisation), 935 nm (repumping), and 760 nm (state clearout) are combined in a fiber arrangement for delivery to our linear ion trap and we demonstrate this system by cooling of ¹⁷¹Yb⁺ ions. Additionally, we demonstrate that the lasers at 935 nm and 760 nm are close in frequency to water vapor and oxygen absorption lines, respectively; specifically, at 760 nm, we show that one ¹⁷¹Yb⁺ transition is within the pressure broadened profile of an oxygen line. These molecular transitions form convenient wavelength references for the stabilization of lasers for a ¹⁷¹Yb⁺ frequency standard.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Interviews and focus groups in qualitative research: an update for the digital age

Qualitative research is used increasingly in dentistry, due to its potential to provide meaningful, in-depth insights into participants' experiences, perspectives, beliefs and behaviours. These insights can subsequently help to inform developments in dental practice and further related research. The most common methods of data collection used in qualitative research are interviews and focus groups. While these are primarily conducted face-to-face, the ongoing evolution of digital technologies, such as video chat and online forums, has further transformed these methods of data collection. This paper therefore discusses interviews and focus groups in detail, outlines how they can be used in practice, how digital technologies can further inform the data collection process, and what these methods can offer dentistry.

Azoospermia and embryo morphokinetics: testicular sperm-derived embryos exhibit delays in early cell cycle events and increased arrest prior to compaction

Purpose

Sperm play an essential role in embryonic genome activation and embryonic progression to blastocyst. In the present work, we focus on development of embryos created as a result of ICSI with testicular or epididymal sperm from azoospermic males and compare this to outcomes from normospermic males. The objective of this study was to determine if sperm origin influences clinical outcomes, the kinetics of embryo development, or the incidence of cleavage anomalies and multinucleation.

Methods

A total of 93 consecutive intracytoplasmic sperm injection cycles (ICSI) performed for 83 couples were included in this study. Observations were made on 594 fertilized oocytes cultured in the EmbryoScope using time-lapse microscopy (TLM). Epididymal sperm (n = 29) cycles or surgically retrieved sperm from the testis (TESE; n = 37 cycles) of men with either obstructive (OA) or non-obstructive azoospermia (NOA) were used to inject oocytes. A further 27 ICSI cycles were performed using ejaculated sperm from normospermic males, designated as our control sperm (CS) group. Kinetic data and cycle outcomes were retrospectively analyzed.

Results

The clinical pregnancy rate was not different between the three groups (TESE 51.4%, PESA 57.7%, and CS 59.3%). A non-significant decrease was observed in both implantation (30.9%) and live birth rate (43%) with TESE as compared to PESA (35.3%, 58%, respectively) and CS groups (45.1%, 56%, respectively). Failure to compact was significantly higher amongst TESE-NOA embryos (35.2%; P < 0.001) as compared to TESE-OA (4%), PESA (9%), and CS (3.8%) embryos. The two points at which TESE-derived embryos (both NOA and OA) behaved most differently from PESA and CS embryos was at cc2 (t3-t2; time to initiation of the second cell cycle) and tSB (time to start of blastulation). A significantly lower percentage of TESE embryos exhibited kinetics typically ascribed to high quality embryos with the greatest developmental potential. Finally, the incidence of direct uneven cleavage (DUC) was observed to be significantly higher after ICSI with sperm retrieved from azoospermic males.

Conclusions

TLM allowed a more in depth comparison of paternal influence on embryo morphokinetics and helped to identify specific differences in cell cycle kinetics. TESE-NOA embryos exhibited a higher incidence of compaction failure.

The association between idiopathic thrombocytopenic purpura and cardiovascular disease: a retrospective cohort study

Essentials We estimated the cardiovascular risk of patients with idiopathic thrombocytopenic purpura (ITP). The risk of cardiovascular disease was 38% higher in ITP patients compared with controls. Among the ITP patients, splenectomy was associated with higher cardiovascular disease. Clinicians should consider cardiovascular risk when managing ITP patients.

SUMMARY

Background Idiopathic thrombocytopenic purpura (ITP) is classically characterized by a transient or persistent decrease of platelet count. Mortality is higher in the ITP population than the general population, with a possible association with increased cardiovascular disease (CVD). Objectives The objective was to assess the strength of the association between ITP and CVD, with a secondary aim to assess the impact of splenectomy on CVD. Methods A population-based retrospective, open cohort study using clinical codes was performed using data from 6591 patients with ITP and 24 275 randomly matched controls (up to 1:4 ratio matched by age, sex, body mass index and smoking status). The main outcome was the risk of CVD, which included ischemic heart disease, stroke, trans-ischemic attack and heart failure. Adjusted incidence rate ratios were calculated using Poisson regression. Results During a median 6-year observation period there was a CVD diagnosis recorded in 392 (5.9%) ITP patients and 1114 (4.5%) control patients. There was an increased risk of developing CVD in the ITP cohort (incidence rate ratio [IRR], 1.38; 95% confidence interval [CI], 1.23-1.55), which remained robust even after a sensitivity analysis only including incident cases of ITP. Findings suggested that patients who had undergone splenectomy were at even further increased risk of developing CVD when compared with the ITP population who had not undergone splenectomy (adjusted IRR, 1.69; 95% CI, 1.22-2.34). Conclusion There is an increased risk of developing CVD in patients with ITP and even further increased risk for those patients with ITP who underwent splenectomy.

Sensitive colorimetric assay using insulin G-quadruplex aptamer arrays on DNA nanotubes coupled with magnetic nanoparticles

Described here is a methodology for fabrication of a sensitive colorimetric nanoassay for measurement of insulin using G-quadruplex aptamer arrays on DNA nanotubes (DNTs) coupled with magnetic nanoparticles. The spectroscopic findings (e.g. visible spectra, velocity assay and limit of detection determination) indicated a highly sensitive performance of this new nanoassay in comparison to those results obtained from the insulin assay with non-arrayed aptamers. The clinical performance statistics (i.e. paired sample t-test, Bland-Altman plot and scatter diagram) from the newly developed assay and the enzyme-linked immunosorbent assay suggested its reliable precision and its acceptable repeatability for measurement of insulin in human sera. This is, to our knowledge, the first study for the application of magnetic nanoparticle-coupled DNTs for carrying G-quadruplex aptamers for detection of biomolecules (such as insulin) in human serum.

Fluorescent detection of point mutation via ligase reaction assisted by quantum dots and magnetic nanoparticle-based probes

A nanodiagnostic genotyping method was presented for point mutation detection directly in human genomic DNA based on ligase reaction coupled with quantum dots and magnetic nanoparticle-based probes.

Note: A high-performance, low-cost laser shutter using a piezoelectric cantilever actuator

We report the design and characterization of an optical shutter based on a piezoelectric cantilever. Compared to conventional electro-magnetic shutters, the device has intrinsically low power and is acoustically quiet. The cantilever position is controlled by a high-voltage op-amp circuit for easy tuning of the range of travel, and mechanical slew rate, which enables a factor of 30 reduction in mechanical noise compared to a rapidly switched device. We achieve shuttering rise and fall times of 11 μs, corresponding to mechanical slew rates of 1.3 ms^-1, with a timing jitter of less than 1 μs. When used to create optical pulses, we achieve minimum pulse durations of 250 μs. The reliability of the shutter was investigated by operating continuously for one week at 10 Hz switching rate. After this period, neither the shutter delay or actuation speed had changed by a measurable amount.

Frequency Comparison of [Formula: see text] Ion Optical Clocks at PTB and NPL via GPS PPP

We used precise point positioning, a well-established GPS carrier-phase frequency transfer method to perform a direct remote comparison of two optical frequency standards based on single laser-cooled [Formula: see text] ions operated at the National Physical Laboratory (NPL), U.K. and the Physikalisch-Technische Bundesanstalt (PTB), Germany. At both institutes, an active hydrogen maser serves as a flywheel oscillator which is connected to a GPS receiver as an external frequency reference and compared simultaneously to a realization of the unperturbed frequency of the (2)S1/2(F=0)-(2)D3/2(F=2) electric quadrupole transition in [Formula: see text] via an optical femtosecond frequency comb. To profit from long coherent GPS-link measurements, we extrapolate the fractional frequency difference over the various data gaps in the optical clock to maser comparisons which introduces maser noise to the frequency comparison but improves the uncertainty from the GPS-link instability. We determined the total statistical uncertainty consisting of the GPS-link uncertainty and the extrapolation uncertainties for several extrapolation schemes. Using the extrapolation scheme with the smallest combined uncertainty, we find a fractional frequency difference [Formula: see text] of -1.3×10(-15) with a combined uncertainty of 1.2×10(-15) for a total measurement time of 67 h. This result is consistent with an agreement of the frequencies realized by both optical clocks and with recent absolute frequency measurements against caesium fountain clocks within the corresponding uncertainties.

The Ueno method for substaging pT1 colorectal adenocarcinoma by depth and width measurement: an interobserver study

AIM

Early pT1 polyp colorectal cancers (CRCs) present challenges for accurate pathology substaging. Haggitt and Kikuchi stages depend on polyp morphology and are often difficult to apply due to suboptimal orientation or fragmentation, or absence of the muscularis propria in polypectomy or submucosal resection specimens. European guidelines for quality assurance suggest using Ueno's more objective approach, using depth and width measurements beyond muscularis mucosae. We have investigated interobserver variation using Ueno's approach.

METHOD

Ten consecutive pT1 polyp CRCs were identified and the slides assessed by six gastrointestinal pathologists for depth and width of invasion. A further 60 polyps were studied by a group of specialist and general pathologists. Agreement was assessed by analysis of variance. A polyp CRC is classified as high risk if it has a depth ≥ 2000 μm or a width ≥ 4000 μm and low risk with a depth < 2000 μm or a width < 4000 μm. Concordance for the dichotomized values was assessed using the kappa statistic.

RESULTS

The intraclass correlation coefficient (ICC) for depth was 0.83 and for width 0.56 in the 10-polyp group. The ICC for the 60-polyp CRCs was 0.67 for depth and 0.37 for width. In both groups, when polyp CRCs are divided into high- and low-risk categories based on depth, there was substantial and moderate agreement (κ = 0.80 and 0.47) but only fair agreement when based on width (κ = 0.34 and 0.35).

CONCLUSION

Ueno's method has the advantage of being independent of polyp morphology. Our study shows better concordance for depth measurement and reproducibility in nonfragmented specimens, with poorer agreement when based on width.

Transportable cavity-stabilized laser system for optical carrier frequency transmission experiments

We report the design and performance of a transportable laser system at 1543 nm, together with its application as the source for a demonstration of optical carrier frequency transmission over 118 km of an installed dark fiber network. The laser system is based around an optical reference cavity featuring an elastic mounting that bonds the cavity to its support, enabling the cavity to be transported without additional clamping. The cavity exhibits passive fractional frequency insensitivity to vibration along the optical axis of 2.0×10(-11)  m(-1) s(2). With active fiber noise cancellation, the optical carrier frequency transmission achieves a fractional frequency instability, measured at the user end, of 2.6×10(-16) at 1 s, averaging down to below 3×10(-18) after 20,000 s. The fractional frequency accuracy of the transfer is better than 3×10(-18). This level of performance is sufficient for comparison of state-of-the-art optical frequency standards and is achieved in an urban fiber environment.

Frequency ratio of two optical clock transitions in 171Yb+ and constraints on the time variation of fundamental constants

Singly ionized ytterbium, with ultranarrow optical clock transitions at 467 and 436 nm, is a convenient system for the realization of optical atomic clocks and tests of present-day variation of fundamental constants. We present the first direct measurement of the frequency ratio of these two clock transitions, without reference to a cesium primary standard, and using the same single ion of 171Yb+. The absolute frequencies of both transitions are also presented, each with a relative standard uncertainty of 6×10(-16). Combining our results with those from other experiments, we report a threefold improvement in the constraint on the time variation of the proton-to-electron mass ratio, μ/μ=0.2(1.1)×10(-16)  yr(-1), along with an improved constraint on time variation of the fine structure constant, α/α=-0.7(2.1)×10(-17)  yr(-1).

Birmingham and Lambeth Liver Evaluation Testing Strategies (BALLETS): a prospective cohort study

OBJECTIVE

To evaluate mildly abnormal liver function test (LFT) results in general practice among patients who do not have known liver disease.

DESIGN

Prospective cohort study of people with abnormal LFT results identified in primary care. Participants were intensively investigated using a common protocol and followed up for 2 years. Substudies investigated the psychological sequelae of abnormal test results, clinicians' reasons for testing, decision options when LFT results were abnormal and early detection of liver fibrosis.

SETTING

Eleven primary-care practices: eight in Birmingham and three in Lambeth.

PARTICIPANTS

Adults with abnormal LFT results who did not have pre-existing or obvious liver disease. Eight analytes were included in the panel of LFTs.

MAIN OUTCOME MEASURES

Statistical tests were used to identify the interactions between clinical features, the initial pattern of abnormal LFT results and (1) specific viral, genetic and autoimmune diseases, such as viral hepatitis, haemochromatosis and primary biliary cirrhosis; (2) a range of other serious diseases, such as metastatic cancer and hypothyroidism; (3) 'fatty liver' not associated with the above; and (4) the absence of detectable disease.

RESULTS

Fewer than 5% of people with abnormal LFT results had a specific disease of the liver, and many of these were unlikely to need treatment. The diagnostic potential of the LFT panel is largely subsumed into just two analytes: alanine aminotransferase (ALT) and alkaline phosphatase (ALP). Gamma-glutamyltransferase (GGT) offers a small increase in sensitivity at the margin at the cost of a large loss of specificity. Eighty-four per cent of abnormal LFT results remain abnormal on retesting 1 month later. In many cases, carrying out a definitive or specific test will be more efficient than repeating LFTs, with a view to specific testing only if the test remains abnormal. An ultrasound diagnosis of 'fatty liver' was present in nearly 40% of patients with abnormal LFTs and a small amount of weight loss over 2 years was associated with a reduced incidence of liver fat. There was a J-shaped relationship between alcohol intake and fatty liver in men. An abnormal LFT result causes temporary anxiety, which does not appear to promote sustained behaviour change.

CONCLUSIONS

Liver disease is rare among people with abnormal LFT results in primary care. Only two analytes (ALT and ALP) are helpful in identifying the majority of liver disease. GGT adds little information in return for a high false-positive rate but it is sensitive to alcohol intake. LFT results seldom revert from abnormal to normal over a 1-month period, and modelling shows that repeating an abnormal LFT panel, as recommended in the current guidelines, is inefficient. LFTs are often undertaken to meet perceived patient need for a blood test, but as they are neither specific nor indicative of any particular disease they are among the least suitable tests for this purpose. Obesity and raised ALT provide strong evidence for a presumptive diagnosis of 'fatty' liver. Abnormal LFTs and 'fatty' liver provoke only short-term anxiety and neither is associated with sustained weight loss. Even a small amount of weight loss reduces liver fat.

FUTURE WORK RECOMMENDATIONS

(1) the cases of 'fatty liver' and controls should be followed up in the long term to identify features that predict development of hepatosteatosis and then cirrhosis; (2) the acceptability of replacing the traditional six- to eight-analyte LFT panel with a drop down menu including the ALT/ALP combination should be evaluated.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Robust frequency stabilization of multiple spectroscopy lasers with large and tunable offset frequencies

We have demonstrated a compact, robust device for simultaneous absolute frequency stabilization of three diode lasers whose carrier frequencies can be chosen freely relative to the reference. A rigid ULE multicavity block is employed, and, for each laser, the sideband locking technique is applied. A small lock error, computer control of frequency offset, wide range of frequency offset, simple construction, and robust operation are the useful features of the system. One concrete application is as a stabilization unit for the cooling and trapping lasers of a neutral-atom lattice clock. The device significantly supports and improves the clock's operation. The laser with the most stringent requirements imposed by this application is stabilized to a line width of 70 Hz, and a residual frequency drift less than 0.5 Hz/s. The carrier optical frequency can be tuned over 350 MHz while in lock.

Evidence for non-communicable diseases: analysis of Cochrane reviews and randomised trials by World Bank classification

INTRODUCTION

Prevalence of non-communicable diseases (NCDs) is increasing globally, with the greatest projected increases in low-income and middle-income countries. We sought to quantify the proportion of Cochrane evidence relating to NCDs derived from such countries.

METHODS

We searched the Cochrane database of systematic reviews for reviews relating to NCDs highlighted in the WHO NCD action plan (cardiovascular, cancers, diabetes and chronic respiratory diseases). We excluded reviews at the protocol stage and those that were repeated or had been withdrawn. For each review, two independent researchers extracted data relating to the country of the corresponding author and the number of trials and participants from countries, using the World Bank classification of gross national income per capita.

RESULTS

797 reviews were analysed, with a reported total number of 12 340 trials and 10 937 306 participants. Of the corresponding authors 90% were from high-income countries (41% from the UK). Of the 746 reviews in which at least one trial had met the inclusion criteria, only 55% provided a summary of the country of included trials. Analysis of the 633 reviews in which country of trials could be established revealed that almost 90% of trials and over 80% of participants were from high-income countries. 438 (5%) trials including 1 145 013 (11.7%) participants were undertaken in low-middle income countries. We found that only 13 (0.15%) trials with 982 (0.01%) participants were undertaken in low-income countries. Other than the five Cochrane NCD corresponding authors from South Africa, only one other corresponding author was from Africa (Gambia).

DISCUSSION

The overwhelming body of evidence for NCDs pertains to high-income countries, with only a small number of review authors based in low-income settings. As a consequence, there is an urgent need for research infrastructure and funding for the undertaking of high-quality trials in this area.