Modeling the atmospheric refractive index structure parameter using macrometeorological observations.

The dynamic fluctuations in the atmospheric refractive index, commonly referred to as optical turbulence, cause phase distortions of the electromagnetic waves propagating through the atmosphere. The consequent scintillations have large implications for free-space optical communication, laser remote sensing, and directed energy applications. The refractive index structure parameter (C n2), quantifying the strength of these fluctuations, is usually estimated using high-frequency micrometeorological measurements, employing sonic anemometer-thermometers or scintillometers. Despite providing highly accurate information, these systems are immensely complex and costly, especially for frequent field applications and remote locations. In this study, we have developed an empirical multinomial model for estimating C n2 using three-year macrometeorological data and validated it against collocated and concurrent micrometeorological measurements, from a tropical semi-arid location. This simpler model would be handy for applications in remote locations having weather station measurements alone.

Enhanced optical pulse broadening in free-space optical links due to the radiative effects of atmospheric aerosols.

Propagation through turbulent media produces complex amplitude fluctuations and temporal spreading of narrow optical pulses. Light-absorbing aerosols present in the atmospheric transmission path will perturb the refractive index structure parameter (Cn2) through atmospheric heating. The consequent enhancement in broadening and attenuation of ultrashort (femtosecond) optical pulses has been calculated by combining multi-satellite observations, radiosonde profiles and computational radiative transfer. It is shown that narrower optical pulses are more vulnerable to aerosol-induced impairments while broader pulses are more resilient, notwithstanding three to four orders of enhanced optical scintillation.

Radiative effects of atmospheric aerosols on the average channel capacity of free-space optical communication systems.

Free-space optical (FSO) communication systems employ unguided light beams propagating through the atmosphere to carry a large volume of data. The reliability of such data transfer can be hampered by various atmospheric effects. Based on an analytical model of a differential phase-shift keying FSO system through exponentiated Weibull turbulence, we investigate the effectiveness of beam width optimization and improved beam alignment, along with aperture averaging on the average channel capacity. Our results show significant signal deterioration produced due to the aerosol-induced optical turbulence, which substantially shadows the performance gain achieved through beam width optimization. Strong aerosol-induced atmospheric heating and the consequent enhanced optical scintillations result in reduction of the channel capacity by as much as 50% of its value when these effects are not considered or negligible. FSO systems are more resilient to aerosol-induced optical turbulence when the normalized beam width is less, and the average channel capacity can be significantly improved by improved beam alignment. These variations are weakly dependent under poor transmitter-receiver alignment conditions. Furthermore, the receiver aperture has a strong control on the link performance. While FSO systems with higher magnitude of normalized beam width have improved performance under all aperture diameter conditions; for a given beam configuration, large aperture diameter ensures a significant improvement in the link performance due to reduction in effects of scintillations.

Fit-for-Discharge Criteria after Esophagectomy: An International Expert Delphi Consensus.

There are no internationally recognized criteria available to determine preparedness for hospital discharge after esophagectomy. This study aims to achieve international consensus using Delphi methodology. The expert panel consisted of 40 esophageal surgeons spanning 16 countries and 4 continents. During a 3-round, web-based Delphi process, experts voted for discharge criteria using 5-point Likert scales. Data were analyzed using descriptive statistics. Consensus was reached if agreement was ≥75% in round 3. Consensus was achieved for the following basic criteria: nutritional requirements are met by oral intake of at least liquids with optional supplementary nutrition via jejunal feeding tube. The patient should have passed flatus and does not require oxygen during mobilization or at rest. Central venous catheters should be removed. Adequate analgesia at rest and during mobilization is achieved using both oral opioid and non-opioid analgesics. All vital signs should be normal unless abnormal preoperatively. Inflammatory parameters should be trending down and close to normal (leucocyte count ≤12G/l and C-reactive protein ≤80 mg/dl). This multinational Delphi survey represents the first expert-led process for consensus criteria to determine 'fit-for-discharge' status after esophagectomy. Results of this Delphi survey may be applied to clinical outcomes research as an objective measure of short-term recovery. Furthermore, standardized endpoints identified through this process may be used in clinical practice to guide decisions regarding patient discharge and may help to reduce the risk of premature discharge or prolonged admission.

Entanglement of near-surface optical turbulence to atmospheric boundary layer dynamics and particulate concentration: implications for optical wireless communication systems.

Localized reduction in optical turbulence due to enhanced atmospheric heating caused by the solar absorption of aerosol black carbon (BC) is reported. Immediate response of atmospheric turbulence to BC-induced atmospheric warming strongly depends on the available solar radiation (time of the day), BC concentration, and atmospheric boundary layer dynamics. Besides the significant climate implications of a reduction in turbulence kinetic energy, a large reduction in the refractive index structure parameter (Cn2) resulting from BC-induced warming would affect the atmospheric propagation of laser beams. Interestingly, aerosols contribute significantly (up to 25%) to the signal deterioration in optical wireless communication systems during convectively stable atmospheric conditions when higher signal-to-noise ratios are expected otherwise due to the reduced thermal convection. Competing effects of the fractional contributions of aerosol extinction and scintillations on beam attenuation are reported; daytime being largely dominated by scintillation effects while the nighttime being dependent on the ambient aerosol concentration as well. We put forward the entanglement of optical turbulence to aerosol concentration, atmospheric boundary layer dynamics, and surface-reaching solar radiation, and discuss the possible implications for optical propagation.

Long-term oncological outcomes following completely minimally invasive esophagectomy versus open esophagectomy.

Open esophagectomy (OE) for esophageal and gastroesophageal junctional cancers is associated with high morbidity. Completely minimally invasive esophagectomy (CMIE) techniques have evolved over the last two decades and significantly reduce surgical trauma compared to open surgery. Despite this, long-term oncological outcomes following CMIE compared to OE remain unclear. This systematic review and meta-analysis aimed to compare overall 5-year survival (OFS) and disease-free 5-year survival (DFFS) between CMIE and OE. It was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A comprehensive electronic literature search from MEDLINE, EMBASE, Web of Science, Scopus and the Cochrane Central Register of Controlled Trials was conducted. The PROSPERO database was also searched for studies comparing OFS and DFFS between CMIE and OE. The Newcastle Ottawa Scale was used to assess study quality for included studies. Overall, seven studies (containing 949 patients: 527 OE and 422 CMIE) were identified from screening. On pooled meta-analysis, there was no significant difference in OFS or DFFS between CMIE and OE cohorts ([odds ratio 1.12; 95% CI: 0.85 to 1.48; P = 0.41] and [odds ratio 1.34; 95% CI: 0.81-2.22; P = 0.25] respectively). Sensitivity and subgroup analysis with high-quality studies, three highest sample sized studies, and three most recent studies also revealed no difference in long-term oncological outcomes between the two operative groups. This review demonstrates long-term oncological outcomes following CMIE appear equivalent to OE based on amalgamation of existing published literature. Limited high-level evidence comparing OFS and DFFS between CMIE and OE exists. Further research with a randomized controlled trial is required to clinically validate these findings.

Variation in esophageal anastomosis technique-the role of collaborative learning.

Centralization of care has improved outcomes in esophagogastric (EG) cancer surgery. However, specialist surgical centers often work within clinical silos, with little transfer of knowledge and experience. Although variation exists in multiple dimensions of perioperative care, the differences in operative technique are rarely studied. An esophageal anastomosis workshop was held to identify areas of common and differing practice within the operative technique. Surgeons showed videos of their anastomosis technique by open and minimally invasive surgery. Each video was followed by a discussion. Surgeons from 10 different EG cancer centers attended. Eight key technical differences and learning points were identified and discussed: the optimum diameter of the gastric conduit; avoiding ischemia in the gastric conduit; minimizing esophageal trauma; the use of an esophageal mucosal collar; omental wrapping; intraoperative leak testing; ideal diameter of the circular stapler and the growing use of linear stapled anastomoses. The workshop received positive feedback from participants and on 2 years follow-up, 40% stated that they believed that the learning of tips and techniques during the workshop has contributed to lowering their anastomotic leak rate. Many differences exist in surgical technique. The reasons for, and crucially the significance of, these differences must be discussed and examined. Workshops provide a forum for peer-to-peer collaborative learning to reflect on one's own practice and improve surgical technique. These changes can, in turn, generate incremental improvements in patient care and postoperative outcomes.

Diagnostic criteria and symptom grading for delayed gastric conduit emptying after esophagectomy for cancer: international expert consensus based on a modified Delphi process.

Delayed gastric conduit emptying (DGCE) after esophagectomy for cancer is associated with adverse outcomes and troubling symptoms. Widely accepted diagnostic criteria and a symptom grading tool for DGCE are missing. This hampers the interpretation and comparison of studies. A modified Delphi process, using repeated web-based questionnaires, combined with live interim group discussions was conducted by 33 experts within the field, from Europe, North America, and Asia. DGCE was divided into early DGCE if present within 14 days of surgery and late if present later than 14 days after surgery. The final criteria for early DGCE, accepted by 25 of 27 (93%) experts, were as follows: >500 mL diurnal nasogastric tube output measured on the morning of postoperative day 5 or later or >100% increased gastric tube width on frontal chest x-ray projection together with the presence of an air-fluid level. The final criteria for late DGCE accepted by 89% of the experts were as follows: the patient should have 'quite a bit' or 'very much' of at least two of the following symptoms; early satiety/fullness, vomiting, nausea, regurgitation or inability to meet caloric need by oral intake and delayed contrast passage on upper gastrointestinal water-soluble contrast radiogram or on timed barium swallow. A symptom grading tool for late DGCE was constructed grading each symptom as: 'not at all', 'a little', 'quite a bit', or 'very much', generating 0, 1, 2, or 3 points, respectively. For the five symptoms retained in the diagnostic criteria for late DGCE, the minimum score would be 0, and the maximum score would be 15. The final symptom grading tool for late DGCE was accepted by 27 of 31 (87%) experts. For the first time, diagnostic criteria for early and late DGCE and a symptom grading tool for late DGCE are available, based on an international expert consensus process.

Performance of free-space optical communication systems: effect of aerosol-induced lower atmospheric warming.

We report the effect of aerosol-induced local atmospheric heating and the resulting changes in the lower atmospheric optical turbulence on the performance of Free-Space Optical (FSO) communication links. A closed form mathematical expression is derived to estimate the influence of aerosol-induced warming on the Bit Error Rate (BER) of a Binary Phase Shift Keying FSO communication link through Gamma-Gamma modeled turbulence. Our results demonstrate a strong impact, with the aerosol-induced turbulence taking a toll on the signal-to-noise ratio of ~20 dB for a BER of 10-9. Aerosol-induced warming produces significant variations in BER compared to the clear atmospheric conditions and can subdue the benefits of improved beam alignment.

Prospective Risk Factor Analysis for the Development of Post-operative Urinary Retention Following Ambulatory General Surgery.

AIMS: Post-operative urinary retention (POUR) is a common cause of unplanned admission following day-case surgery and has negative effects on both patient and surgical institution. We aimed to prospectively evaluate potential risk factors for the development of POUR following day-case general surgical procedures. METHODS: Over a 24-week period, consecutive adult patients undergoing elective day-case general surgery at a single institution were prospectively recruited. Data regarding urinary symptoms, comorbidities, drug history, surgery and perioperative anaesthetic drug use were collected. The primary outcome was the incidence of POUR, defined as an impairment of bladder voiding requiring either urethral catheterisation, unplanned overnight admission or both. Potential risk factors for the development of POUR were analysed by logistic regression. RESULTS: A total of 458 patients met the inclusion criteria during the study period, and data were collected on 382 (83%) patients (74.3% male). Sixteen patients (4.2%) experienced POUR. Unadjusted analysis demonstrated three significant risk factors for the development of POUR: age ≥ 56 years (OR 7.77 [2.18-27.78], p = 0.002), laparoscopic surgery (OR 3.37 [1.03-12.10], p = 0.044) and glycopyrrolate administration (OR 5.56 [2.00-15.46], p = 0.001). Male sex and lower urinary tract symptoms were not significant factors. Multivariate analysis combining type of surgery, age and glycopyrrolate use revealed that only age ≥ 56 years (OR 8.14 [2.18-30.32], p = 0.0018) and glycopyrrolate administration (OR 3.48 [1.08-11.24], p = 0.0370) were independently associated with POUR. CONCLUSIONS: Patients aged at least 56 years and/or requiring glycopyrrolate-often administered during laparoscopic procedures-are at increased risk of POUR following ambulatory general surgery.

Distinctive roles of elevated absorbing aerosol layers on free-space optical communication systems.

The impact of enhanced local heating due to absorption of solar radiation by elevated layers of aerosol black carbon (BC) in the lower troposphere in the performance of free-space optical (FSO) communication links is investigated. It is seen that a strong elevated BC layer at an altitude around 4.5 km enhances the atmospheric stability locally and leads to a large reduction in the atmospheric refractive index structure parameter (Cn2), leading to improved performance of the FSO communication links. For layers in the tropical atmosphere with sufficiently high BC concentration, the signal attenuation due to BC absorption is alleviated by the large reduction in Cn2 due to BC-induced warming and brings down the link outage probability. Synergy between reduction in Cn2 and long wavelength transmission improves the link budget significantly by reducing the beam wander and number of adaptive optics units required.

A structured training program for minimally invasive esophagectomy for esophageal cancer- a Delphi consensus study in Europe.

Evidence suggests that structured training programs for laparoscopic procedures can ensure a safe standard of skill acquisition prior to independent practice. Although minimally invasive esophagectomy (MIO) is technically demanding, no consensus on requirements for training for the MIO procedure exists. The aim of this study is to determine essential steps required for a structured training program in MIO using the Delphi consensus methodology. Eighteen MIO experts from 13 European hospitals were asked to participate in this study. The consensus process consisted of two structured meetings with the expert panel, and two Delphi questionnaire rounds. A list of items required for training MIO were constructed for three key domains of MIO, including (1) requisite criteria for units wishing to be trained and (2) to proctor MIO, and (3) a framework of a MIO training program. Items were rated by the experts on a scale 1-5, where 1 signified 'not important' and 5 represented 'very important.' Consensus for each domain was defined as achieving Cronbach alpha ≥0.70. Items were considered as fundamental when ≥75% of experts rated it important (4) or very important (5). Both Delphi rounds were completed by 16 (89%) of the 18 invited experts, with a median experience of 18 years with minimally invasive surgery. Consensus was achieved for all three key domains. Following two rounds of a 107-item questionnaire, 50 items were rated as essential for training MIO. A consensus among European MIO experts on essential items required for training MIO is presented. The identified items can serve as directive principles and core standards for creating a comprehensive training program for MIO.

Dependence of atmospheric refractive index structure parameter (Cn2) on the residence time and vertical distribution of aerosols.

Effects of absorbing atmospheric aerosols in modulating the tropospheric refractive index structure parameter (Cn2) are estimated using high resolution radiosonde and multi-satellite data along with a radiative transfer model. We report the influence of variations in residence time and vertical distribution of aerosols in modulating Cn2 and why the aerosol induced atmospheric heating needs to be considered while estimating a free space optical communication link budget. The results show that performance of the link is seriously affected if large concentrations of absorbing aerosols reside for a long time in the atmospheric path.

Component analysis of enhanced recovery pathways for esophagectomy.

The objective of this systematic review is to identify key components of enhanced recovery protocols (ERP) that lead to improved length of hospital stay (LOS) following esophagectomy. Relevant electronic databases were searched for studies comparing clinical outcome from esophagectomy followed by a conventional pathway versus ERP. Relevant outcome measures were compared and metaregression was performed to identify the key ERP components associated with reduced in LOS. Thirteen publications were included, ERP was associated with no changes in in-hospital mortality, total complications, anastomotic leak, or pulmonary complications compared with a conventional pathway, however LOS was reduced in the ERP group. Metaregression identified that immediate extubation was associated with reduced LOS (OR = -0.51, 95%CI -0.77 to -0.25; P < 0.01). Several postoperative factors were associated with a significant reduction in length of hospital stay, and in order of most important were (i) gastrograffin swallow ≤5 days (OR = -4.27, 95%CI -4.50 to -4.03); (ii) mobilization on postoperative day ≤1 (OR = -2.49, 95%CI -2.63 to -2.34); (iii) removal of urinary catheter ≤2 days (OR = -0.99, 95%CI -1.15 to -0.84); (iv) oral intake with at least sips of fluid ≤1 day (OR = -0.96, 95%CI -1.24 to -0.68); (v) enteral diet with feeding jejunostomy or gastrostomy ≤ 1 day (OR = -0.57, 95%CI -0.80 to -0.35) and (vi) epidural removal ≤ 4 days (OR = -0.17, 95%CI -0.27 to -0.07). Several core ERP components and principles appear to be associated with LOS reduction. These elements should form a part of the core ERP for the specialty, while surgical teams incorporate other elements through an iterative process.

Mortality in high-risk emergency general surgical admissions.

BACKGROUND: There is increasing evidence of variable standards of care for patients undergoing emergency general surgery in the National Health Service (NHS). The aim of this study was to quantify and explore variability in mortality amongst high-risk emergency general surgery admissions to English NHS hospital Trusts. METHODS: The Hospital Episode Statistics (HES) database was used to identify high-risk emergency general surgery diagnoses (greater than 5 per cent national 30-day mortality rate). Adults admitted to English NHS Trusts with these diagnoses between 2000 and 2009 were included in the study. Thirty-day in-hospital mortality was adjusted for patient and hospital factors. Trusts were grouped into high- and low-mortality outliers, and resource availability was compared between high- and low-mortality outlier institutions. RESULTS: Some 367 796 patients admitted to 145 hospital Trusts were included in the study; the 30-day mortality rate was 15·6 per cent (institutional range 9·2-18·2 per cent). Fourteen and 24 hospital Trusts were identified as high- and low-mortality outlier institutions respectively. Intensive care and high-dependency bed resources, as well as greater institutional use of computed tomography (CT), were independent predictors of reduced mortality (P < 0·001). Low-mortality outlying Trusts had significantly more intensive care beds per 1000 hospital beds (20·8 versus 14·0; P = 0·017) and made significantly greater use of CT (24·6 versus 17·2 scans per bed per year; P < 0·001) and ultrasonography (42·5 versus 30·2 scans per bed per year; P < 0·001). CONCLUSION: There is significant variability in mortality risk between hospital Trusts treating high-risk emergency general surgery patients. Equitable access to essential hospital resources may reduce variability in outcomes.

Ni-Doped ZnO Thin Films: Deposition, Characterization and Photocatalytic Applications.

Root like structured Ni-doped zinc oxide [Zn(1-x)NixO (x = 0.09)] thin films were deposited on a non-conducting glass substrate by indigenously developed spray pyrolysis system at optimized substrate hotness of 573±5 K. Thus obtained Ni-doped ZnO thin films were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM). XRD result revealed that Ni-doped ZnO has a polycrystalline nature with a hexagonal wurtzite structure. For pure ZnO and Ni-doped ZnO thin films, the particle sizes were 60.9 and 53.3 nm while lattice strain values were 1.56×10-3 and 1.14×10-3, respectively. The film surface showed characteristic root-like structure as observed by the SEM. It was observed that the Ni-doped ZnO thin films were grown in high density along with more extent of branching as compared to pure ZnO thin films but retained the root-like morphologies, however, the branches were more-thinner and of shorter lengths. AFM analysis showed that the surface grains of the Ni-doped samples are homogeneous with less RMS roughness values compared with the undoped ZnO samples. The photocatalytic activity of the prepared thin films was evaluated by the degradation of methyl orange (MO) dye under UV light irradiation. Pure ZnO and Ni-doped ZnO thin films took 150 min and 100 min to degrade about 60% MO dye, respectively.

Temporal and spectral characteristics of aerosol optical depths in a semi-arid region of southern India.

The spectral and temporal variations of aerosol optical depths (AOD) observed over Anantapur (a semi-arid region) located in the Southern part of India are investigated by analyzing the data obtained from a Multiwavelength Solar Radiometer (MWR) during January 2005-December 2006 (a total of 404 clear-sky observations) using the Langley technique. In this paper, we highlighted the studies on monthly, seasonal and spectral variations of aerosol optical depth and their implications. The results showed seasonal variation with higher values during pre-monsoon (March-May) and lower in the monsoon (June-November) season at all wavelengths. The pre-monsoon increase is found to be due to the high wind speed producing larger amounts of wind-driven dust particles. The post-monsoon (December-February) AOD values decrease more at higher wavelengths, indicating a general reduction in the number of bigger particles. Also during the post-monsoon, direction of winds in association with high or low pressure weather systems and the air brings more aerosol content to the region which is surrounded by a number of cement plants, lime kilns, slab polishing and brick making units. The quantity of AOD values in pre-monsoon is higher (low during post-monsoon) for wavelength, such as shortwave infrared (SWIR) or near infrared (NIR), which shows that coarse particles contribute more compare with the sub-micron particles. The composite aerosols near the surface follow suit with the share of the accumulation mode to the total mass concentration decreasing from approximately 70% to 30% from post-monsoon to pre-monsoon. Coarse mode particle loading observed to be high during pre-monsoon and accumulation mode particles observed to be high during post-monsoon. The backward trajectories at three representative altitudes with source point at the observing site indicate a possible transport from the outflow regions into Bay of Bengal, southern peninsular India and Arabian Sea. The temporal variations of AOD, Angstrom wavelength exponent and precipitable water content over Anantapur have also been compared with those reported from selected locations in India.

Peritoneal lavage cytology in patients with oesophagogastric adenocarcinoma.

BACKGROUND: The aim of the study was to determine the value of performing peritoneal lavage cytology during laparoscopy in the management of oesophagogastric adenocarcinoma. METHODS: Laparoscopy combined with peritoneal cytology was performed in patients with potentially resectable oesophagogastric adenocarcinoma. Macroscopic peritoneal findings at laparoscopy and the presence of free peritoneal tumour cells were recorded. All patients were followed to death or the census point. Patients with overt peritoneal disease or positive cytology were offered palliative chemotherapy, subject to performance status. RESULTS: Forty-eight (18.8 per cent) of 255 patients had overt peritoneal metastases at staging laparoscopy. Fifteen (7.2 per cent) of the remaining 207 patients had positive cytology; these patients had a median (95 per cent confidence interval) survival of 13 (3.1 to 22.9) months, versus 9 (7.4 to 10.6) months for those with overt peritoneal metastases (P = 0.517). Of patients receiving chemotherapy, those without overt metastases had a slight survival advantage over patients with metastases (median 15 (10.8 to 19.2) versus 9 (7.4 to 10.7) months; P = 0.045). CONCLUSION: Positive peritoneal cytology in the absence of overt peritoneal metastases is not uncommon in oesophagogastric adenocarcinoma. It is a marker of poor prognosis even in the absence of overt peritoneal metastases.