A comparison of patient-reported outcomes in patients undergoing abdominal wall repair with either synthetic or biosynthetic mesh: a pilot study.

PURPOSE: Repair of midline ventral incisional hernias (VIHR) requires mesh reinforcement. Mesh types can be categorised into synthetic, biosynthetic, or biological. There is a lack of evidence to support one type of mesh over another. The aim of this pilot study was to compare mesh sensation in patients having undergone elective open repair with synthetic or biosynthetic mesh. METHODS: Four years of prospectively collected data were retrospectively reviewed on 40 patients who had undergone VIHR, using either biosynthetic or synthetic mesh placed in the retromuscular plane. The decision on type of mesh used was governed by patient characteristics. Patients were invited to complete the Carolinas Comfort Scale (CCS) questionnaire, the higher the score indicating a poorer quality of life. The maximum length of follow-up was 36 months. RESULTS: Twenty patients received permanent synthetic and 20 biosynthetic mesh. There was no clinical evidence of hernia recurrence in either group in the short to medium term. Overall, 97% (39/40) patients reported an average of either no or mild symptoms (mean CCS score 17.9 of 115). Patients with a biosynthetic repair had a significant lower CCS at ≥ 18 months (p < 0.05). CONCLUSION: After VIHR, patients have low CCS scores, indicating good quality of life outcomes, in the short to medium term irrespective of the mesh used. However, biosynthetic mesh had lower CCS scores in the medium term. This may help surgeons and patients make better informed decisions about which mesh to use in their individual circumstances.

Delphi consensus statement for understanding and managing the subcostal hernia: subcostal hernias collaborative report (scholar study).

INTRODUCTION: Subcostal hernias are categorized as L1 based on the European Hernia Society (EHS) classification and frequently involve M1, M2, and L2 sites. These are common after hepatopancreatic and biliary surgeries. The literature on subcostal hernias mostly comprises of retrospective reviews of small heterogenous cohorts, unsurprisingly leading to no consensus or guidelines. Given the limited literature and lack of consensus or guidelines for dealing with these hernias, we planned for a Delphi consensus to aid in decision making to repair subcostal hernias. METHODS: We adopted a modified Delphi technique to establish consensus regarding the definition, characteristics, and surgical aspects of managing subcostal hernias (SCH). It was a four-phase Delphi study reflecting the widely accepted model, consisting of: 1. Creating a query. 2. Building an expert panel. 3. Executing the Delphi rounds. 4. Analysing, presenting, and reporting the Delphi results. More than 70% of agreement was defined as a consensus statement. RESULTS: The 22 experts who agreed to participate in this Delphi process for Subcostal Hernias (SCH) comprised 7 UK surgeons, 6 mainland European surgeons, 4 Indians, 3 from the USA, and 2 from Southeast Asia. This Delphi study on subcostal hernias achieved consensus on the following areas-use of mesh in elective cases; the retromuscular position with strong discouragement for onlay mesh; use of macroporous medium-weight polypropylene mesh; use of the subcostal incision over midline incision if there is no previous midline incision; TAR over ACST; defect closure where MAS is used; transverse suturing over vertical suturing for closure of circular defects; and use of peritoneal flap when necessary. CONCLUSION: This Delphi consensus defines subcostal hernias and gives insight into the consensus for incision, dissection plane, mesh placement, mesh type, and mesh fixation for these hernias.

Measurement of dispersion and index of refraction of 1-decanol with spectrally resolved white light interferometry.

The high density, high nonlinearity, and stability of liquids make them an attractive medium for spectral broadening and supercontinuum generation in ultrafast experiments. To understand ultrashort pulse propagation in these media, their indices of refraction and dispersions must be characterized. We employ a Mach-Zehnder interferometer to generate a series of interferograms, which we refer to as a spectrogram, to develop a new method of using spectrally resolved white light interferometry to determine the refractive indices of materials. We determine the indices of refraction of BK7, sapphire, ethanol, and 1-decanol at 24°C across the visible and near infrared. To our knowledge, this is the first reported dispersion and index of refraction measurement of 1-decanol.

Amplification of femtosecond pulses based on χ(3) nonlinear susceptibility in MgO.

We experimentally demonstrate large, widely tunable gain using Kerr instability amplification in MgO. By pumping the crystal near optical damage at 1.4×1013W/cm2 by a femtosecond Ti:sapphire laser, we amplify visible and near-infrared pulses by factors >5000 or a gain g≈17/mm. We temporally characterize the pulses to show that they are 42 fs in duration, much shorter than the pump pulse. In the non-collinear setup, the angle between the pump and seed selects the amplified wavelength, where we find certain angles amplify both the visible and near-infrared simultaneously. We find that near the maximum pumping intensities, higher-order nonlinearities may play a role in the amplification process.

High-harmonic generation in solids driven by counter-propagating pulses.

We used two 800 nm laser pulses propagating in the opposite directions, to drive the emission of high-order vacuum ultra-violet harmonics off of the surface of an MgO (100) single crystal. We demonstrated the advantages that our approach provides compared to a single beam geometry, in both forward and backward emission.

Cavity-enhanced high harmonic generation for extreme ultraviolet time- and angle-resolved photoemission spectroscopy.

With its direct correspondence to electronic structure, angle-resolved photoemission spectroscopy (ARPES) is a ubiquitous tool for the study of solids. When extended to the temporal domain, time-resolved (TR)-ARPES offers the potential to move beyond equilibrium properties, exploring both the unoccupied electronic structure as well as its dynamical response under ultrafast perturbation. Historically, ultrafast extreme ultraviolet sources employing high-order harmonic generation (HHG) have required compromises that make it challenging to achieve a high energy resolution-which is highly desirable for many TR-ARPES studies-while producing high photon energies and a high photon flux. We address this challenge by performing HHG inside a femtosecond enhancement cavity, realizing a practical source for TR-ARPES that achieves a flux of over 1011 photons/s delivered to the sample, operates over a range of 8-40 eV with a repetition rate of 60 MHz. This source enables TR-ARPES studies with a temporal and energy resolution of 190 fs and 22 meV, respectively. To characterize the system, we perform ARPES measurements of polycrystalline Au and MoTe2, as well as TR-ARPES studies on graphite.

Vectorizing the spatial structure of high-harmonic radiation from gas.

Strong field laser physics has primarily been concerned with controlling beams in time while keeping their spatial profiles invariant. In the case of high harmonic generation, the harmonic beam is the result of the coherent superposition of atomic dipole emissions. Therefore, fundamental beams can be tailored in space, and their spatial characteristics will be imparted onto the harmonics. Here we produce high harmonics using a space-varying polarized fundamental laser beam, which we refer to as a vector beam. By exploiting the natural evolution of a vector beam as it propagates, we convert the fundamental beam into high harmonic radiation at its focus where the polarization is primarily linear. This evolution results in circularly polarized high harmonics in the far field. Such beams will be important for ultrafast probing of magnetic materials.

Light amplification by seeded Kerr instability.

Amplification of femtosecond laser pulses typically requires a lasing medium or a nonlinear crystal. In either case, the chemical properties of the lasing medium or the momentum conservation in the nonlinear crystal constrain the frequency and the bandwidth of the amplified pulses. We demonstrate high gain amplification (greater than 1000) of widely tunable (0.5 to 2.2 micrometers) and short (less than 60 femtosecond) laser pulses, up to intensities of 1 terawatt per square centimeter, by seeding the modulation instability in an Y3Al5O12 crystal pumped by femtosecond near-infrared pulses. Our method avoids constraints related to doping and phase matching and therefore can occur in a wider pool of glasses and crystals even at far-infrared frequencies and for single-cycle pulses. Such amplified pulses are ideal to study strong-field processes in solids and highly excited states in gases.

Sixteen Years of Meiotic Silencing by Unpaired DNA.

The filamentous fungus Neurospora crassa possesses a process called meiotic silencing by unpaired DNA (MSUD). MSUD has a remarkable ability to scan homologous chromosomes for unpaired DNA during meiosis. After unpaired DNA is identified, MSUD silences all RNA from the unpaired DNA along with any RNA transcribed from homologous sequences at other locations in the genome, regardless of their pairing state. The mechanism by which unpaired DNA is detected is unknown. Unpaired DNA segments can be as short as 1.3kb, if not shorter, and DNA sequences with only a small level of polymorphism (6%) can be considered unpaired by MSUD. MSUD research has identified nine proteins required for full efficiency of the process, three of which are homologs of the canonical RNA interference (RNAi) proteins Dicer, Argonaute, and RNA-dependent RNA polymerase. Most MSUD proteins, including the RNAi homologs, appear to dock outside of the nuclear envelope during early stages of meiosis. Only two have been observed inside the nucleus, a low number given that the identification of unpaired DNA and the triggering of silencing must begin within this location. These two proteins may participate in the unpaired DNA detection process. Recent evidence indicates that the search for unpaired DNA is spatially constrained, possibly because of restrictions on the arrangement of chromatin loops during or after homolog pairing. This review attempts to provide a complete analysis of past, present, and future directions of MSUD research, starting with its discovery during a search for a conserved regulator of fungal development and ending with some benefits the process may provide to MSUD capable organisms.

Controlling the orbital angular momentum of high harmonic vortices.

Optical vortices, which carry orbital angular momentum (OAM), can be flexibly produced and measured with infrared and visible light. Their application is an important research topic for super-resolution imaging, optical communications and quantum optics. However, only a few methods can produce OAM beams in the extreme ultraviolet (XUV) or X-ray, and controlling the OAM on these beams remains challenging. Here we apply wave mixing to a tabletop high-harmonic source, as proposed in our previous work, and control the topological charge (OAM value) of XUV beams. Our technique enables us to produce first-order OAM beams with the smallest possible central intensity null at XUV wavelengths. This work opens a route for carrier-injected laser machining and lithography, which may reach nanometre or even angstrom resolution. Such a light source is also ideal for space communications, both in the classical and quantum regimes.

Harmonic generation in solids with direct fiber laser pumping.

High harmonic generation in solids presents the possibility for bringing attosecond techniques to semiconductors and a simple source for frequency comb spectroscopy in the vacuum ultraviolet. We generate up to the seventh harmonic of a Tm fiber laser by focusing in silicon or zinc oxide. The harmonics are strong and stable, with no indication of material damage. Calculations show the potential for generating nineteenth harmonic photons at 12 eV photons of energy.

All-Optical Reconstruction of Crystal Band Structure.

The band structure of matter determines its properties. In solids, it is typically mapped with angle-resolved photoemission spectroscopy, in which the momentum and the energy of incoherent electrons are independently measured. Sometimes, however, photoelectrons are difficult or impossible to detect. Here we demonstrate an all-optical technique to reconstruct momentum-dependent band gaps by exploiting the coherent motion of electron-hole pairs driven by intense midinfrared femtosecond laser pulses. Applying the method to experimental data for a semiconductor ZnO crystal, we identify the split-off valence band as making the greatest contribution to tunneling to the conduction band. Our new band structure measurement technique is intrinsically bulk sensitive, does not require a vacuum, and has high temporal resolution, making it suitable to study reactions at ambient conditions, matter under extreme pressures, and ultrafast transient modifications to band structures.

Linking high harmonics from gases and solids.

When intense light interacts with an atomic gas, recollision between an ionizing electron and its parent ion creates high-order harmonics of the fundamental laser frequency. This sub-cycle effect generates coherent soft X-rays and attosecond pulses, and provides a means to image molecular orbitals. Recently, high harmonics have been generated from bulk crystals, but what mechanism dominates the emission remains uncertain. To resolve this issue, we adapt measurement methods from gas-phase research to solid zinc oxide driven by mid-infrared laser fields of 0.25 volts per ångström. We find that when we alter the generation process with a second-harmonic beam, the modified harmonic spectrum bears the signature of a generalized recollision between an electron and its associated hole. In addition, we find that solid-state high harmonics are perturbed by fields so weak that they are present in conventional electronic circuits, thus opening a route to integrate electronics with attosecond and high-harmonic technology. Future experiments will permit the band structure of a solid to be tomographically reconstructed.

Controlling attosecond angular streaking with second harmonic radiation.

High harmonic generation, which produces a coherent burst of radiation every half cycle of the driving field, has been combined with ultrafast wavefront rotation to create a series of spatially separated attosecond pulses, called the attosecond lighthouse. By adding a coherent second harmonic beam with polarization parallel to the fundamental, we decrease the generating frequency from twice per optical cycle to once. The increased temporal separation increases the pulse contrast. By scanning the carrier envelope phase, we see that the signal is 2π periodic.

Creating high-harmonic beams with controlled orbital angular momentum.

A beam with an angular-dependant phase Φ = ℓϕ about the beam axis carries an orbital angular momentum of ℓℏ per photon. Such beams are exploited to provide superresolution in microscopy. Creating extreme ultraviolet or soft-x-ray beams with controllable orbital angular momentum is a critical step towards extending superresolution to much higher spatial resolution. We show that orbital angular momentum is conserved during high-harmonic generation. Experimentally, we use a fundamental beam with |ℓ| = 1 and interferometrically determine that the harmonics each have orbital angular momentum equal to their harmonic number. Theoretically, we show how any small value of orbital angular momentum can be coupled to any harmonic in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.

Systematic review: outpatient management of acute uncomplicated diverticulitis.

PURPOSE OF REVIEW: Acute uncomplicated diverticulitis is traditionally managed by inpatient admission for bowel rest, intravenous fluids and intravenous antibiotics. In recent years, an increasing number of publications have sought to determine whether care might instead be conducted in the community, with earlier enteral feeding and oral antibiotics. This systematic review evaluates the safety and efficacy of such an ambulatory approach. METHODS: Medline, Embase and Cochrane Library databases were searched. All peer-reviewed studies that investigated the role of ambulatory treatment protocols for acute uncomplicated diverticulitis, either directly or indirectly, were eligible for inclusion. RESULTS: Nine studies were identified as being suitable for inclusion, including one randomised controlled trial, seven prospective cohort studies and one retrospective cohort study. All, except one, employed imaging as part of their diagnostic criteria. There was inconsistency between studies with regards to whether patients with significant co-morbidities were eligible for ambulatory care and whether bowel rest therapy was employed. Neither of these variables influenced outcome. Across all studies, 403 out of a total of 415 (97 %) participants were successfully treated for an episode of acute uncomplicated diverticulitis using an outpatient-type approach. Cost savings ranged from 35.0 to 83.0 %. CONCLUSION: Current evidence suggests that a more progressive, ambulatory-based approach to the majority of cases of acute uncomplicated diverticulitis is justified. Based on this evidence, the authors present a possible outpatient-based treatment algorithm. An appropriately powered randomised controlled trial is now required to determine its safety and efficacy compared to traditional inpatient management.

Injuries and medical issues on the Zambezi "Great River".

We report the injuries and medical issues incurred during a rowing expedition conducted along the Zambezi River in May 2011. All injuries and illnesses requiring medical intervention were recorded during a 30-day expedition. There were 22 rowers and 8 support staff sustaining 32 injuries, an injury incidence of 36 per 1000 days. We discuss the medical issues regarding conducting an expedition along the Zambezi and the medical preparation and education required to successfully support wilderness expeditions.

Ligation of the intersphincteric fistula tract in the management of anal fistula. A systematic review.

AIM: Over the last 5 years, the ligation of the intersphincteric fistula tract (LIFT) procedure has become increasingly popular as a sphincter-preserving technique for the treatment of anal fistula. The aim of this article was to review the published literature on the LIFT procedure. METHOD: The Cochrane database and EMBASE were searched from January 1980 to November 2012, and PubMed from January 1966 to November 2012. All peer-reviewed studies that investigated the LIFT procedure for the treatment of anal fistula were eligible for inclusion. Technical notes, commentaries, letters and meeting abstracts were excluded. The primary outcome measured was the overall fistula closure rate in relation to the length of follow-up. RESULTS: Twenty-nine articles were originally identified using the search criteria. Thirteen were finally included for analysis. Sample sizes ranged from 18 to 93 patients, with a pooled total of 498. Most fistulae, 494 (99%), were of cryptoglandular aetiology, of which 470 (94%) were transsphincteric. Overall success rates ranged from 40 to 95%, with a pooled success of 71% (352 of 495 patients; 3 of 498 were lost to follow-up). Follow-up ranged from 1 to 55 months, with a reported mean or median of 4 to 19.5 months. One hundred and eighty-three patients were formally assessed for continence, out of whom 11 (6%) had a minor disturbance. CONCLUSION: Overall the systematic review shows that the LIFT procedure appears to be an effective sphincter-conserving approach for the treatment of transsphincteric anal fistula with a pooled healing rate of 71% over a mean or median follow-up period ranging from 4 to 19.5 months.