Laparoscopic Heller-Dor myotomy in elderly achalasia patients: a single center experience with PSM analysis

INTRODUCTION

Achalasia is a rare esophageal motility disorder of unknown etiology. With the ageing of the general population, treatment in elderly patients has become increasingly common; however, the gold standard treatment in this population remains unclear. The aim of this study was to evaluate the outcomes of laparoscopic Heller-Dor myotomy (LHM) in geriatric patients.

MATERIAL AND METHODS

In this study, consecutive achalasia patients undergoing LHM at the University Hospital 'Federico II' of Naples from November 2018 to November 2022 were prospectively enrolled. Patients were divided into two groups based on their age at intervention: elderly (≥70 years) and younger (<70 years). The two study groups were compared by minimizing the different distribution of covariates through a propensity score matching analysis (PSM).

RESULTS

In both populations, there was a significant improvement in terms of manometric parameters and symptoms after surgery. After applying one-on-one PSM, we obtained a total population of 48 achalasia patients divided into two groups (24 patients each). No significant differences were found in terms of demographic characteristics as well as preoperative and intraoperative variables between two groups. At 12 months from surgery, integrated relaxation pressure (IRP) was significantly lower in patients ≥ 70 years (p = 0.032), while younger patients scored significantly less at the post-operative Eckardt score (p = 0.047).

CONCLUSIONS

Laparoscopic Heller-Dor myotomy is a safe and effective treatment even in elderly patients with rapid post-operative recovery, improvement of symptoms and manometric parameters.

R0 surgical resection of giant dedifferentiated retroperitoneal liposarcomas in the COVID era with and without nephrectomy: A case report

Retroperitoneal sarcomas (RPSs) are rare findings that can grow into large masses without eliciting severe symptoms. At present, surgical resection is the only radical therapy, whenever it can be performed with the aim to achieve a complete removal of the tumor. The present report describes two consecutive cases of RPSs that resulted in dedifferentiated liposarcomas (DDLPSs) and these patients underwent R0 surgical resection with and without a nephron-sparing procedure. The diagnostic workup, the surgical approach, the impact of late surgical management due to the COVID pandemic and the latest literature on the topic are discussed and analyzed. The patients, who refused to undergo any medical examination during the prior 2 years due to the COVID pandemic, were admitted to Federico II University Hospital (Naples, Italy) complaining about weight loss and general abdominal discomfort. In the first case, a primitive giant abdominal right neoplasm of retroperitoneal origin enveloping and medializing the right kidney was observed. The second patient had a similar primitive retroperitoneal giant left neoplasm, which did not affect the kidney. Given the characteristics of the masses and the absence of distant metastases, after a multidisciplinary discussion, radical surgical removal was carried out for both patients. The lesions appeared well-defined from the surrounding tissues, and markedly compressed all the adjacent organs, without signs of infiltration. In the first patient, the right kidney was surrounded and undetachable from the tumor and it was removed en bloc with the mass. The second patient benefited from a nephron-sparing resection, due to the existence of a clear cleavage plane. The postoperative courses were uneventful. Both the histological examinations were oriented towards a DDLPS and both patients benefited from adjuvant chemotherapy. In conclusion, the treatment of giant RPS is still challenging and requires multidisciplinary treatment as well as, when possible, radical surgical removal. The lack of tissue infiltration and the avoidance of excision or reconstruction of major organs (including the kidney) could lead to an easier postoperative course and an improved prognosis. When possible, surgical management of recurrences or incompletely resected masses must be pursued. Since the COVID pandemic caused limited medicalization of a number of population groups and delayed diagnosis of other oncologic diseases, an increased number of DDLPSs could be expected in the near future.

Preoperative planning and intraoperative real-time navigation with indocyanine green fluorescence in robotic liver surgery

PURPOSE

We aimed at exploring indocyanine green (ICG) fluorescence wide spectrum of applications in hepatobiliary surgery as can result particularly useful in robotic liver resections (RLR) in order to overcome some technical limitations, increasing safety, and efficacy.

METHODS

We describe our experience of 76 RLR performed between March 2020 and December 2022 exploring all the possible applications of pre- and intraoperative ICG administration.

RESULTS

Hepatocellular carcinoma and colorectal liver metastases were the most common indications for RLR (34.2% and 26.7% of patients, respectively), and 51.3% of cases were complex resections with high IWATE difficulty scores. ICG was administered preoperatively in 61 patients (80.3%), intraoperatively in 42 patients (55.3%) and in both contexts in 25 patients (32.9%), with no observed adverse events. The most frequent ICG goal was to achieve tumor enhancement (59 patients, 77.6%), with a success rate of 94.9% and the detection of 3 additional malignant lesions. ICG facilitated evaluation of the resection margin for residual tumor and perfusion adequacy in 33.9% and 32.9% of cases, respectively, mandating a resection enlargement in 7.9% of patients. ICG fluorescence allowed the identification of the transection plane through negative staining in the 25% of cases. Vascular and biliary structures were visualized in 21.1% and 9.2% of patients, with a success rate of 81.3% and 85.7%, respectively.

CONCLUSION

RLR can benefit from the routine integration of ICG fluoresce evaluation according to each individual patient and condition-specific goals and issues, allowing liver functional assessment, anatomical and vascular evaluation, tumor detection, and resection margins assessment.

Role of preoperative 3D rendering for minimally invasive parenchyma sparing liver resections

BACKGROUND

3D rendering (3DR) represents a promising approach to plan surgical strategies. The study aimed to compare the results of minimally invasive liver resections (MILS) in patients with 3DR versus conventional 2D CT-scan.

METHODS

We performed 118 3DR for various indications; the patients underwent a preoperative tri-phasic CT-scan and rendered with Synapse3D® Software. Fifty-six patients undergoing MILS with pre-operative 3DR were compared to a similar cohort of 127 patients undergoing conventional pre-operative 2D CT-scan using the propensity score matching (PSM) analysis.

RESULTS

The 3DR mandated pre-operative surgical plan variations in 33.9% cases, contraindicated surgery in 12.7%, providing a new surgical indication in 5.9% previously excluded cases. PSM identified 39 patients in both groups with comparable results in terms of conversion rates, blood loss, blood transfusions, parenchymal R1-margins, grade ≥3 Clavien-Dindo complications, 90-days mortality, and hospital stay respectively in 3DR and conventional 2D. Operative time was significantly increased in the 3DR group (402 vs. 347 min, p = 0.020). Vascular R1 resections were 25.6% vs 7.7% (p = 0.068), while the conversion rate was 0% vs 10.2% (p = 0.058), respectively, for 3DR group vs conventional 2D.

CONCLUSION

3DR may help in surgical planning increasing resectability rate while reducing conversion rates, allowing the precise identification of anatomical landmarks in minimally invasive parenchyma-preserving liver resections.

Iatrogenic biliary leak treated by performing exploratory laparoscopic using indocyanine green (ICG) fluorescence. A case report and review of literature

INTRODUCTION

Cholangiography with indocyanine green fluorescence (ICG) is increasingly used to visualize the bile duct anatomy during laparoscopic cholecystectomy. Biliary leaks are rare complications after laparoscopic cholecystectomy, result could be lethal. Lesion's site is not always visible. We present an interesting case of a patient with biloma due to an iatrogenic lesion of the biliary tract, treated in urgency using ICG fluorescence. To our knowledge, this is the only case in the literature.

CASE PRESENTATION

A 62-years-old patient after 7 days from laparoscopic cholecystectomy presented abdominal pain and fever. Blood tests showed an increase of inflammation indexes. Abdominal US and abdominal CT revealed a conspicuous right sub-hepatic fluid. We performed a laparoscopy using ICG fluorescence to find the biliary leak. Operative time of surgery was 60 min. There were no complications during this procedure.

CONCLUSIONS

ICG is a safe and effective procedure that enables real-time visualization of the biliary system. In some cases, it can also be used in urgent surgery, where the biliary anatomy is much more complex.

KEY WORDS

Biloma, Indocyanine green fluorescence, Iatrogenic biliary leaks, Urgent surgery.

Neoadjuvant chemotherapy for borderline resectable and upfront resectable pancreatic cancer increasing overall survival and disease-free survival?

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic neoplasm. Surgery is the factual curative option, but most patients present with advanced disease. In order to increase resectability, results of neoadjuvant chemotherapy (NAC) on metastatic disease were extrapolated to the neoadjuvant setting by many centers. The aim of our study was to retrospectively evaluate the outcome of patients who underwent upfront surgery (US)-PDAC and borderline (BR)-PDAC, and those resected after NAC to determine prognostic factors that might affect the outcome in these resected patients.

METHODS

One hundred fifty-one patients between January 2012 and March 2021 in our department were reviewed. Epidemiological characteristics and pre-operative induction treatment were assessed. Pathological reports were analyzed to evaluate the quality of oncological resection (R0/R1). Post-operative mortality and morbidity and survival data were reviewed.

RESULTS

One hundred thirteen patients were addressed for US, and 38 were considered BR and referred for surgery after induction chemotherapy. The pancreatic resection R0 was 71.5% and R1 28.5%. pT3 rate was significantly higher in the US than BR (58,4% vs 34,2%, p= 0.005). The mean OS and DFS rates were 29.4 months 15.9 months respectively. There was no difference between OS and DFS of US vs BR patients. N0 patients had significantly longer OS and DFS (p=<0.001). R0 patients had significantly longer OS (p=0.03) and longer DFS (P=0.08). In the multivariate analysis, the presence of postoperative pancreatic fistula, R1 resection, N+ and not access to adjuvant chemotherapy were bad prognostic factors of OS.

CONCLUSIONS

Our study suggests the benefits of NAC for BR patients in downstaging tumors and rendering them amenable to resection, with same oncological result compared to US.

Microwave Ablation for Colorectal Liver Metastases: A Systematic Review and Pooled Oncological Analyses

Simple Summary

Liver resection for colorectal liver metastases (CRLM) represents the best curative option; however, few patients are candidates for surgery. Microwave ablation (MWA) can be a valid alternative in selected patients. This systematic review reports the oncological results of MWA for CRLM. The literature available on the Web was analyzed for reports concerning MWA for resectable CRLM, published before January 2021. Finally, 12 papers concerning MWA complications, recurrence-free (RF) cases, patients free from local recurrence (FFLR), and overall survival rates (OS) were selected. Global RF rates at 1, 3, and 5 years were 65.1%, 44.6%, and 34.3%, respectively. Global FFLR at 3, 6, and 12 months were 96.3%, 89.6%, and 83.7%, respectively. Global OS rates at 1, 3, and 5 years were 86.7%, 59.6%, and 44.8%, respectively. A better FFLR was achieved with an MWA surgical approach at 3, 6, and 12 months, with 97.1%, 92.7%, and 88.6%, respectively. Surgical MWA for CRLM smaller than 3 cm was a safe and valid option. MWA can be entered as part of the flowchart decision of CRLM curative treatment, especially for use in the parenchyma-sparing strategy and as a complement to surgery.

Abstract

(1) Background: colorectal liver metastases (CRLM) are the most common extra-lymphatic metastases in colorectal cancer; however, few patients are fit for curative surgery. Microwave ablation (MWA) showed promising outcomes in this cohort of patients. This systematic review and pooled analysis aimed to analyze the oncological results of MWA for CRLM. (2) Methods: Following PRISMA guidelines, PubMed, Scopus, EMBASE, Google Scholar, Science Direct, and the Wiley Online Library databases were searched for reports published before January 2021. We included papers assessing MWA, treating resectable CRLM with curative intention. We evaluated the reported MWA-related complications and oncological outcomes as being recurrence-free (RF), free from local recurrence (FFLR), and overall survival rates (OS). (3) Results: Twelve out of 4822 papers (395 patients) were finally included. Global RF rates at 1, 3, and 5 years were 65.1%, 44.6%, and 34.3%, respectively. Global FFLR rates at 3, 6, and 12 months were 96.3%, 89.6%, and 83.7%, respectively. Global OS at 1, 3, and 5 years were 86.7%, 59.6%, and 44.8%, respectively. A better FFLR was reached using the MWA surgical approach at 3, 6, and 12 months, with reported rates of 97.1%, 92.7%, and 88.6%, respectively. (4) Conclusions: Surgical MWA treatment for CRLM smaller than 3 cm is a safe and valid option. This approach can be safely included for selected patients in the curative intent approaches to treating CRLM.

Artificial intelligence in the diagnosis and management of colorectal cancer liver metastases

Colorectal cancer (CRC) is the third most common malignancy worldwide, with approximately 50% of patients developing colorectal cancer liver metastasis (CRLM) during the follow-up period. Management of CRLM is best achieved via a multidisciplinary approach and the diagnostic and therapeutic decision-making process is complex. In order to optimize patients' survival and quality of life, there are several unsolved challenges which must be overcome. These primarily include a timely diagnosis and the identification of reliable prognostic factors. Furthermore, to allow optimal treatment options, a precision-medicine, personalized approach is required. The widespread digitalization of healthcare generates a vast amount of data and together with accessible high-performance computing, artificial intelligence (AI) technologies can be applied. By increasing diagnostic accuracy, reducing timings and costs, the application of AI could help mitigate the current shortcomings in CRLM management. In this review we explore the available evidence of the possible role of AI in all phases of the CRLM natural history. Radiomics analysis and convolutional neural networks (CNN) which combine computed tomography (CT) images with clinical data have been developed to predict CRLM development in CRC patients. AI models have also proven themselves to perform similarly or better than expert radiologists in detecting CRLM on CT and magnetic resonance scans or identifying them from the noninvasive analysis of patients' exhaled air. The application of AI and machine learning (ML) in diagnosing CRLM has also been extended to histopathological examination in order to rapidly and accurately identify CRLM tissue and its different histopathological growth patterns. ML and CNN have shown good accuracy in predicting response to chemotherapy, early local tumor progression after ablation treatment, and patient survival after surgical treatment or chemotherapy. Despite the initial enthusiasm and the accumulating evidence, AI technologies' role in healthcare and CRLM management is not yet fully established. Its limitations mainly concern safety and the lack of regulation and ethical considerations. AI is unlikely to fully replace any human role but could be actively integrated to facilitate physicians in their everyday practice. Moving towards a personalized and evidence-based patient approach and management, further larger, prospective and rigorous studies evaluating AI technologies in patients at risk or affected by CRLM are needed.

Portal venous gas after a failed endoscopic retrograde cholangiopancreatography attempt in a patient with a large hepatocellular carcinoma: A case report

The cause of hepatic portal vein gas (HPVG) is variable. Good knowledge of the possible causes, combined with the clinical assessment of the patient and a good quality imaging, is required to correctly identify the underlying cause of HPVG and to best predict the prognosis.

Serrated lesions of the colon and rectum: Emergent epidemiological data and molecular pathways

In 2010, serrated polyps (SP) of the colon have been included in the WHO classification of digestive tumors. Since then a large corpus of evidence focusing on these lesions are available in the literature. This review aims to analyze the present data on the epidemiological and molecular aspects of SP. Hyperplastic polyps (HPs) are the most common subtype of SP (70–90%), with a minimal or null risk of malignant transformation, contrarily to sessile serrated lesions (SSLs) and traditional serrated adenomas (TSAs), which represent 10–20% and 1% of adenomas, respectively. The malignant transformation, when occurs, is supported by a specific genetic pathway, known as the serrated-neoplasia pathway. The time needed for malignant transformation is not known, but it may occur rapidly in some lesions. Current evidence suggests that a detection rate of SP ≥15% should be expected in a population undergoing screening colonoscopy. There are no differences between primary colonoscopies and those carried out after positive occult fecal blood tests, as this screening test fails to identify SP, which rarely bleed. Genetic similarities between SP and interval cancers suggest that these cancers could arise from missed SP. Hence, the detection rate of serrated-lesions should be evaluated as a quality indicator of colonoscopy. There is a lack of high-quality longitudinal studies analyzing the long-term risk of developing colorectal cancer (CRC), as well as the cancer risk factors and molecular tissue biomarkers. Further studies are needed to define an evidence-based surveillance program after the removal of SP, which is currently suggested based on experts’ opinions.

Robotic approach to the liver: Open surgery in a closed abdomen or laparoscopic surgery with technical constraints?

The application of the minimally invasive approach has shown to be safe and effective for liver surgery and is in constant growth. The indications for laparoscopic surgery are steadily increasing across the field. In the early 2000s, robotic surgery led to some additional improvements, such as tremor filtration, instrument stability, 3D view and more comfort for the surgeon. These techniques bring in some advantages compared to the traditional OLR: less blood loss, shorter admissions, fewer adhesions, and a faster postoperative recovery and better outcomes in case of further hepatectomy for tumor recurrence has been shown. Concerning which is the best minimally invasive approach between laparoscopic and robotic surgery, the evidence is still conflicting. The latter shows good potential, since the endo-wristed instruments work similarly to the surgeon's hands, even with an intact abdominal wall. However, the technique is still under development, burdened by important costs, and limited by the lack of some instruments available for the laparoscopic approach. The paucity of universally accepted and proven data, especially concerning long-term outcomes, hampers drawing univocal acceptance at present. Furthermore, the number of variables related both to the patient and the disease further complicates the decision leading to a treatment tailored to each patient with strict selection. This review aims to explore the main differences between laparoscopic and robotic surgery, focusing on indications, operative technique and current debated clinical issues in recent literature.

Polypharmacy but not Potential Inappropriate Prescription Was Associated with Frailty in Older Adults from a Middle-Income Country Outpatient Clinic

OBJECTIVES

the aims of the present study were: (1) investigate the prevalence and association of polypharmacy and pre-frailty or frailty in a middle-income country sample of older adults; and (2) evaluate the prevalence of potential inappropriate prescription (PIP) and its association with pre-frailty or frailty.

DESIGN

Cross-sectional observational study.

SETTING

Outpatient center at a university-based hospital in the state of São Paulo, Brazil.

PARTICIPANTS

629 older adults from both sexes evaluated between June 2014 and July 2016.

MEASUREMENTS

Frailty was identified through the FRAIL scale. All medications received were analyzed by research staff. Presence of PIP was evaluated according to the 2015 updated Beers list. Binary logistic regression tested the association between 4 definitions of polypharmacy (≥ 3, 4, 5, and 6 drugs), and presence of PIP, and the dependent variable pre-frailty and frailty.

RESULTS

15.7% of participants were frail. Polypharmacy was present in 219 (34.8%), and PIP was observed in 184 (29.3%) older adults. All definitions of polypharmacy were significantly associated with frailty (OR between 2.05 to 2.34, p < 0.001). Polypharmacy with 4 or 5 or more drugs were associated with pre-frailty (OR 1.53 and 1.47, respectively). PIP was not associated with frailty (OR 1.47, p = 0.149).

CONCLUSIONS

Several definitions of polypharmacy were associated with frailty, but only two were associated with pre-frailty. The presence of PIP was not associated with pre-frailty or frailty.

Electron Weibel instability in relativistic counterstreaming plasmas with flow-aligned external magnetic fields

The Weibel instability driven by two symmetric counterstreaming relativistic electron plasmas, also referred to as current-filamentation instability, is studied in a constant and uniform external magnetic field aligned with the plasma flows. Both the linear and nonlinear stages of the instability are investigated using analytical modeling and particle-in-cell simulations. While previous studies have already described the stabilizing effect of the magnetic field, we show here that the saturation stage is only weakly affected. The different mechanisms responsible for the saturation are discussed in detail in the relativistic cold fluid framework considering a single unstable mode. The application of an external field leads to a slight increase of the saturation level for large wavelengths, while it does not affect the small wavelengths. Multimode and temperature effects are then investigated. While at high temperature the saturation level is independent of the external magnetic field, at low but finite temperature the competition between different modes in the presence of an external magnetic field leads to a saturation level lower with respect to the unmagnetized case.

Pressure anisotropy and small spatial scales induced by velocity shear

By including the full pressure tensor dynamics in a fluid plasma model, we show that a sheared velocity field can provide an effective mechanism that makes the initial isotropic pressure nongyrotropic. This is distinct from the usual gyrotropic anisotropy related to the fluid compressibility and usually accounted for in double-adiabatic models. We determine the time evolution of the pressure agyrotropy and discuss how the propagation of "magnetoelastic perturbations" can affect the pressure tensor anisotropization and its spatial filamentation, which are due to the action of both the magnetic field and the flow strain tensor. We support this analysis with a numerical integration of the nonlinear equations describing the pressure tensor evolution.

Enhancement of maximum attainable ion energy in the radiation pressure acceleration regime using a guiding structure

Radiation pressure acceleration is a highly efficient mechanism of laser-driven ion acceleration, with the laser energy almost totally transferrable to the ions in the relativistic regime. There is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. In the case of tightly focused laser pulses, which are utilized to get the highest intensity, another factor limiting the maximum ion energy comes into play, the transverse expansion of the target. Transverse expansion makes the target transparent for radiation, thus reducing the effectiveness of acceleration. Utilization of an external guiding structure for the accelerating laser pulse may provide a way of compensating for the group velocity and transverse expansion effects.

Laser-driven Rayleigh-Taylor instability: plasmonic effects and three-dimensional structures

The acceleration of dense targets driven by the radiation pressure of high-intensity lasers leads to a Rayleigh-Taylor instability (RTI) with rippling of the interaction surface. Using a simple model it is shown that the self-consistent modulation of the radiation pressure caused by a sinusoidal rippling affects substantially the wave vector spectrum of the RTI, depending on the laser polarization. The plasmonic enhancement of the local field when the rippling period is close to a laser wavelength sets the dominant RTI scale. The nonlinear evolution is investigated by three-dimensional simulations, which show the formation of stable structures with "wallpaper" symmetry.

Dynamics of self-generated, large amplitude magnetic fields following high-intensity laser matter interaction

The dynamics of magnetic fields with an amplitude of several tens of megagauss, generated at both sides of a solid target irradiated with a high-intensity (~10(19) W/cm(2)) picosecond laser pulse, has been spatially and temporally resolved using a proton imaging technique. The amplitude of the magnetic fields is sufficiently large to have a constraining effect on the radial expansion of the plasma sheath at the target surfaces. These results, supported by numerical simulations and simple analytical modeling, may have implications for ion acceleration driven by the plasma sheath at the rear side of the target as well as for the laboratory study of self-collimated high-energy plasma jets.

Coupling between whistler waves and ion-scale solitary waves: cluster measurements in the magnetotail during a substorm

We present a new model of self-consistent coupling between low frequency, ion-scale coherent structures with high frequency whistler waves in order to interpret Cluster data. The idea relies on the possibility of trapping whistler waves by inhomogeneous external fields where they can be spatially confined and propagate for times much longer than their characteristic electronic time scale. Here we take the example of a slow magnetosonic soliton acting as a wave guide in analogy with the ducting properties of an inhomogeneous plasma. The soliton is characterized by a magnetic dip and density hump that traps and advects high frequency waves over many ion times. The model represents a new possible way of explaining space measurements often detecting the presence of whistler waves in correspondence to magnetic depressions and density humps. This approach, here given by means of slow solitons, but more general than that, is alternative to the standard approach of considering whistler wave packets as associated with nonpropagating magnetic holes resulting from a mirror-type instability.

Radiation-pressure-dominant acceleration: Polarization and radiation reaction effects and energy increase in three-dimensional simulations

Polarization and radiation reaction (RR) effects in the interaction of a superintense laser pulse (I>10(23) W cm-2) with a thin plasma foil are investigated with three dimensional particle-in-cell (PIC) simulations. For a linearly polarized laser pulse, strong anisotropies such as the formation of two high-energy clumps in the plane perpendicular to the propagation direction and significant radiation reactions effects are observed. On the contrary, neither anisotropies nor significant radiation reaction effects are observed using circularly polarized laser pulses, for which the maximum ion energy exceeds the value obtained in simulations of lower dimensionality. The dynamical bending of the initially flat plasma foil leads to the self-formation of a quasiparabolic shell that focuses the impinging laser pulse strongly increasing its energy and momentum densities.

Observation of magnetized soliton remnants in the wake of intense laser pulse propagation through plasmas

Slowly evolving, regularly spaced patterns have been observed in proton projection images of plasma channels drilled by intense (≳10¹⁹ W cm⁻²) short (∼1  ps) laser pulses propagating in an ionized gas jet. The nature and geometry of the electromagnetic fields generating such patterns have been inferred by simulating the laser-plasma interaction and the following plasma evolution with a two-dimensional particle-in-cell code and the probe proton deflections by particle tracing. The analysis suggests the formation of rows of magnetized soliton remnants, with a quasistatic magnetic field associated with vortexlike electron currents resembling those of magnetic vortices.

Dynamic formation of a hot field reversed configuration with improved confinement by supersonic merging of two colliding high-β compact toroids

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-β plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Unlimited ion acceleration by radiation pressure

The energy of ions accelerated by an intense electromagnetic wave in the radiation pressure dominated regime can be greatly enhanced due to a transverse expansion of a thin target. The expansion decreases the number of accelerated ions in the irradiated region resulting in an increase in the ion energy and in the ion longitudinal velocity. In the relativistic limit, the ions become phase locked with respect to the electromagnetic wave resulting in unlimited ion energy gain.

Time window for magnetic reconnection in plasma configurations with velocity shear

It is shown that the rate of magnetic field line reconnection can be clocked by the evolution of the large-scale processes that are responsible for the formation of the current layers where reconnection can take place. In unsteady plasma configurations, such as those produced by the onset of the Kelvin-Helmholtz instability in a plasma with a velocity shear, qualitatively different magnetic structures are produced depending on how fast the reconnection process develops on the external clock set by the evolving large-scale configuration.

Numerical evidence of undriven, fast reconnection in the solar-wind interaction with earth's magnetosphere: formation of electromagnetic coherent structures

We give evidence for the first time of the onset of undriven fast, collisionless magnetic reconnection during the evolution of an initially homogeneous magnetic field advected in a sheared velocity field. We consider the interaction of the solar wind with the magnetospheric plasma at low latitude and show that reconnection takes place in the layer between adjacent vortices generated by the Kelvin-Helmholtz instability. This process generates coherent magnetic structures with a size comparable to the ion inertial scale, much smaller than the system dimensions but much larger than the electron inertial scale. These magnetic structures are further advected in the plasma in a complex pattern but remain stable over a time interval much longer than their formation time. These results can be crucial for the interpretation of satellite data showing coherent magnetic structures in the Earth's magnetosheath or the magnetotail.

Competing mechanisms of plasma transport in inhomogeneous configurations with velocity shear: the solar-wind interaction with earth's magnetosphere

Two-dimensional simulations of the Kelvin-Helmholtz instability in an inhomogeneous compressible plasma with a density gradient show that, in a transverse magnetic field configuration, the vortex pairing process and the Rayleigh-Taylor secondary instability compete during the nonlinear evolution of the vortices. Two different regimes exist depending on the value of the density jump across the velocity shear layer. These regimes have different physical signatures that can be crucial for the interpretation of satellite data of the interaction of the solar wind with the magnetospheric plasma.

Photon bubbles and ion acceleration in a plasma dominated by the radiation pressure of an electromagnetic pulse

The stability of a thin plasma foil accelerated by the radiation pressure of a high intensity electromagnetic (e.m.) pulse is investigated analytically and with particle in cell numerical simulations. It is shown that the onset of a Rayleigh-Taylor-like instability can lead to transverse bunching of the foil and to broadening of the energy spectrum of fast ions. The use of a properly tailored e.m. pulse with a sharp intensity rise can stabilize the foil acceleration.

Three-dimensional magnetic structures generated by the development of the filamentation (Weibel) instability in the relativistic regime

We present three-dimensional, fully relativistic, fluid simulations of the dynamics of inhomogeneous counter streaming beams with the aim of understanding the magnetic structures that can be expected to form as a consequence of the development of the so-called Weibel instability. Ringlike structures in the transverse direction are generated as a consequence of the development of a spatially resonant mode. We describe the structures generated by beams of equal initial density and velocity and by a fast, less dense beam compensated by a slower, denser beam. We consider these two cases as schematic models of a laser produced beam propagating in a plasma with nearly equal density and in a plasma much denser than the injected beam.

Single-cycle high-intensity electromagnetic pulse generation in the interaction of a plasma wakefield with regular nonlinear structures

The interaction of regular nonlinear structures (such as subcycle solitons, electron vortices, and wake Langmuir waves) with a strong wake wave in a collisionless plasma can be exploited in order to produce ultrashort electromagnetic pulses. The electromagnetic field of the nonlinear structure is partially reflected by the electron density modulations of the incident wake wave and a single-cycle high-intensity electromagnetic pulse is formed. Due to the Doppler effect the length of this pulse is much shorter than that of the nonlinear structure. This process is illustrated with two-dimensional particle-in-cell simulations. The considered laser-plasma interaction regimes can be achieved in present day experiments and can be used for plasma diagnostics.

Plasma ion evolution in the wake of a high-intensity ultrashort laser pulse

Experimental investigations of the late-time ion structures formed in the wake of an ultrashort, intense laser pulse propagating in a tenuous plasma have been performed using the proton imaging technique. The pattern found in the wake of the laser pulse shows unexpectedly regular modulations inside a long, finite width channel. On the basis of extensive particle in cell simulations of the plasma evolution in the wake of the pulse, we interpret this pattern as due to ion modulations developed during a two-stream instability excited by the return electric current generated by the wakefield.

Charged state of a spherical plasma in vacuum

The stationary state of a spherically symmetric plasma configuration is investigated in the limit of immobile ions and weak collisions. Configurations with small radii are positively charged as a significant fraction of the electron population evaporates during the equilibration process, leaving behind an electron distribution function with an energy cutoff. Such charged plasma configurations are of interest for the study of Coulomb explosions and ion acceleration from small clusters irradiated by ultraintense laser pulses and for the investigation of ion bunches propagation in a plasma.

Attosecond electromagnetic pulse generation due to the interaction of a relativistic soliton with a breaking-wake plasma wave

During the interaction of a low-frequency relativistic soliton with the electron density modulations of a wake plasma wave, part of the electromagnetic energy of the soliton is reflected in the form of an extremely short and ultraintense electromagnetic pulse. We calculate the spectra of the reflected and of the transmitted electromagnetic pulses analytically. The reflected wave has the form of a single cycle attosecond pulse.

Damping of electromagnetic waves due to electron-positron pair production

The problem of the back reaction during the process of electron-positron pair production by a circularly polarized electromagnetic wave propagating in a plasma is investigated. A model based on the relativistic Boltzmann-Vlasov equation with a source term representing the Schwinger formula for the pair creation rate is used. The damping of the wave, the nonlinear up-shift of its frequency due to the plasma density increase, and the effect of the damping on the wave polarization and on the background plasma acceleration are investigated as a function of the wave amplitude.

Propagation of a short proton beam through a thin plasma slab

A one-dimensional open boundary Vlasov code is used in order to investigate the propagation of a short proton beam through a plasma slab. Collisionless regimes are assumed, where the interaction between the beam and the plasma occurs due to the self-consistent, collective, electric field. Both charge compensated (by an accompanying electron cloud) and noncompensated beams are considered.

Secondary instabilities and vortex formation in collisionless-fluid magnetic reconnection

It is shown that the pattern of current layers formed within a magnetic island in the nonlinear phase of magnetic field line reconnection in a collisionless two-dimensional fluid plasma is subject to the onset of a secondary instability, the effect of which increases with decreasing electron temperature. In the cold electron limit the saturation of the island growth is accompanied by a turbulent redistribution of the current layers and by the development of long lived fluid vortices while, in the opposite limit, the current layer structure remains regular.

Proposed double-layer target for the generation of high-quality laser-accelerated ion beams

In order to achieve a high-quality, i.e., monoenergetic, intense ion beam, we propose the use of a double-layer target. The first layer, at the target front, consists of high-Z atoms, while the second (rear) layer is a thin coating of low-Z atoms. The generation of high-quality proton beams from the double-layer target, irradiated by an ultraintense laser pulse, is demonstrated with three-dimensional particle-in-cell simulations.

Stability of a mass accreting shell expanding in a plasma

A linearized analysis is presented of the stability of a shell which accretes mass as it expands in a plasma under the push of the electromagnetic radiation trapped inside it. The interaction with the radiation is described in terms of a ponderomotive force and the shell dynamics is treated within the snowplow approximation. The mass accretion and the radiation expansion are shown to affect the stability of planar, cylindrical, and spherical shells differently.

Macroscopic evidence of soliton formation in multiterawatt laser-plasma interaction

A novel physical phenomenon has been observed following the interaction of an intense (10(19) W/cm(2)) laser pulse with an underdense plasma. Long-lived, macroscopic bubblelike structures have been detected through the deflection that the associated electric charge separation causes in a proton probe beam. These structures are interpreted as the remnants of a cloud of relativistic solitons generated in the plasma by the ultraintense laser pulse. This interpretation is supported by an analytical study of the soliton cloud evolution, by particle-in-cell simulations, and by a reconstruction of the proton-beam deflection.

Polarization effects and anisotropy in three-dimensional relativistic self-focusing

The relativistic self-focusing of high-intensity laser pulses in underdense plasmas is investigated with three-dimensional particle in cell simulations. The different behavior of a linearly polarized pulse in the two transverse directions is interpreted as a combination of two two-dimensional responses with different polarizations. In the polarization plane a high density sheet is formed, which separates the two regions of oppositely directed quasistatic magnetic field.

Effects of physical exercise on clinic and 24-hour ambulatory blood pressure in young subjects with mild hypertension

BACKGROUND

The aim of the study was to assess the effect of physical activity on 24-hr ambulatory blood pressure (ABPM) and office blood pressure (BP) in 572 male subjects with borderline to mild hypertension from the HARVEST study.

METHODS

Subjects were 18 to 45 years old with diastolic BP of 90-99 mmHg and/or systolic BP of 140-159 mmHg. They never took any anti-hypertensive therapy. All subjects underwent physical examination, office BP measurement and two 24-hr ambulatory BP monitorings performed three months apart. Subjects were classified as non exercisers, group 1 (n=331), mild exercisers, group 2 (n=192) and heavy exercisers, group 3 (n=49). During the three months of follow-up subjects maintained the same physical activity habits. There was no difference in smoking and alcohol consumption between the 3 groups. As the groups differed significantly in age and body mass index data were adjusted for these confounders.

RESULTS

At baseline office and ambulatory systolic BP were similar in the 3 groups, while diastolic BP was proportional to the level of physical activity although the difference was significant only between the group of non-exercisers and mild exercisers. Heart rate (HR) was always inversely related to the intensity of exercise. After three months follow-up office systolic BP was similar among the three groups and diastolic BP slightly decreased in the exercisers (group 1 vs group 3 p=0.02, group 2 vs group 3 p=0.04). At ABPM the group of heavy exercisers showed a significant decrease in daytime systolic BP (135.4plus minus0.6 vs 134plus minus0.8 vs 132.2plus minus1.6 mmHg; group 1 vs group 3 p<0.05) and the difference between systolic ambulatory BP at the 3rd month and at baseline, showed an additional significant decrease according to exercise intensity (24-hr systolic BP group 1 vs group 3 p=0.001, group 2 vs group 3 p=0.004; daytime systolic BP group 1 vs group 3 p=0.0009, group 2 vs group 3 p=0.004; night-time systolic BP group 1 vs group 3 p=0.02, group 2 vs group 3 p=0.02). No changes in ambulatory diastolic BP were observed.

CONCLUSIONS

In conclusion, physical activity has a positive effect in lowering BP attenuating the risk of hypertension in young subjects with borderline hypertension. The anti-hypertensive effect of physical activity persisted after three months and the group of exercisers had an additional reduction in systolic BP detected by ABPM. To obtain accurate information on chronic levels of arterial pressure over time 24-hr ambulatory BP should be preferred to traditional casual readings.

Surface oscillations in overdense plasmas irradiated by ultrashort laser pulses

The generation of electron surface oscillations in overdense plasmas irradiated at normal incidence by an intense laser pulse is investigated. Two-dimensional (2D) particle-in-cell simulations show a transition from a planar, electrostatic oscillation at 2 omega, with omega the laser frequency, to a 2D electromagnetic oscillation at frequency omega and wave vector k > omega/c. A new electron parametric instability, involving the decay of a 1D electrostatic oscillation into two surface waves, is introduced to explain the basic features of the 2D oscillations. This effect leads to the rippling of the plasma surface within a few laser cycles, and is likely to have a strong impact on laser interaction with solid targets.

Three-dimensional singularities of a thin plasma slab

The three-dimensional (3D) nonlinear development of the interchange-like (Rayleigh-Taylor) instability of a thin slab of plasma exhibits interesting features with respect to its two-dimensional (2D) limit investigated by Bulanov, Pegoraro, and Sakai [Phys. Rev. E 59, 2292 (1999)]. We show that, contrary to the 2D case, the 3D evolution equations remain nonlinear when Lagrangian variables are adopted. Explicit solutions are found by the use of a generalized hodograph transformation. Both compression and rarefaction singularities are formed. Local solutions in the neighborhood of the singular points have a generic 2D character.