Evaluation of environmental features that support breastfeeding: A photovoice study.

The United Kingdom (UK) has some of the lowest breastfeeding rates in the world, and Stoke-on-Trent has some of the lowest breastfeeding rates and highest infant mortality rates in the UK. Vicarious experience of formula feeding, formula feeding culture, and a lack of physical environments to support breastfeeding are known barriers to uptake and maintenance. Improving physical environments and increasing the visibility of breastfeeding in public would help to challenge these barriers. This research employs a participatory approach to understand the facilitators and barriers to breastfeeding in public. Nine breastfeeding peer supporters were recruited as co-researcher for a photovoice study. Co-researchers collated images of features in environments which they felt either supported or acted as a barrier to public breastfeeding. An analysis workshop was held to review the data collected and produce collaboratively agreed findings. Various environmental features were highlighted as facilitators to breastfeeding including family rooms, welcoming signage, supportive staff members, and displays of information about breastfeeding. In addition, poorly designed family rooms, lack of inclusivity within breastfeeding spaces, breastfeeding spaces within toilets and a lack of information were barriers to public breastfeeding. This research illustrates that while some environments are well designed to support breastfeeding many others are not. Environments often lack basic provision and/or make token gestures towards breastfeeding support, such as welcome signage, without providing the infrastructure needed to support breastfeeding. More education about breastfeeding friendly spaces and resources for putting this information into practice are needed for environment owners, managers, and policy makers.

Twin-twin transfusion syndrome recipient with arterial calcification and heterozygous variant in ABCC6: Evidence of a gene-environment interaction?

We report a case of a twin-twin transfusion syndrome (TTTS) recipient who, after successful fetoscopic surgery, developed a large pericardial effusion and calcifications of the aorta and main pulmonary artery. The donor fetus never had cardiac strain and never developed cardiac calcifications. A heterozygous likely pathogenic variant in ABCC6 (c.2018T > C, p.Leu673Pro) was identified in the recipient twin. While TTTS recipient twins are at risk of arterial calcifications and right heart failure secondary to the disease, calcifications of the great vessels are also observed in generalized arterial calcification of infancy, a Mendelian genetic disorder with associated biallelic pathogenic variations in ABCC6 or ENPP1, which can result in significant pediatric morbidity or mortality. The recipient twin in this case had some degree of cardiac strain prior to TTTS surgery; however, the progressive calcification of the aorta and pulmonary trunk occurred weeks after TTTS resolution. This case raises the possibility of a gene-environment interaction and emphasizes the need for genetic evaluation in the setting of TTTS and calcifications.

Searching for Chameleon Dark Energy with Mechanical Systems.

A light scalar field framework of dark energy, sometimes referred to as quintessence, introduces a fifth force between normal matter objects. Screening mechanisms, such as the chameleon model, allow the scalar field to be almost massless on cosmological scales while simultaneously evading laboratory constraints. We explore the ability of existing mechanical systems to directly detect the fifth force associated with chameleons in an astrophysically viable regime where it could be dark energy. We provide analytical expressions for the weakest accessible chameleon model parameters in terms of experimentally tunable variables and apply our analysis to two mechanical systems: levitated microspheres and torsion balances, showing that the current generation of these experiments have the sensitivity to rule out a significant portion of the proposed chameleon parameter space. We also indicate regions of theoretically well-motivated chameleon parameter space to guide future experimental work.

Germline and sporadic cancers driven by the RAS pathway: parallels and contrasts.

Somatic mutations in RAS and related pathway genes such as NF1 have been strongly implicated in the development of cancer while also being implicated in a diverse group of developmental disorders named the 'RASopathies', including neurofibromatosis type 1 (NF1), Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NSML), Costello syndrome (CS), cardiofaciocutaneous syndrome (CFC), and capillary malformation-arteriovenous syndrome (CM-AVM). It remains unclear why (i) there is little overlap in mutational subtype between Ras-driven malignancies associated with sporadic disease and those associated with the RASopathy syndromes, and (ii) RASopathy-associated cancers are usually of different histological origin to those seen with sporadic mutations of the same genes. For instance, germline variants in KRAS and NRAS are rarely found at codons 12, 13 or 61, the most common sites for somatic mutations in sporadic cancers. An exception is CS, where germline variants in codons 12 and 13 of HRAS occur relatively frequently. Given recent renewed drug interest following early clinical success of RAS G12C and farnesyl transferase inhibitors, an improved understanding of this relationship could help guide targeted therapies for both sporadic and germline cancers associated with the Ras pathway.

Managing HIV-associated inflammation and ageing in the era of modern ART.

OBJECTIVES: This paper aims to address the concerns around ongoing immune activation, inflammation, and resistance in those ageing with HIV that represent current challenges for clinicians. METHODS: Presentations at a symposium addressing issues of ageing with HIV infection were reviewed and synthesised. RESULTS: The changing natural history and demographics of human immunodeficiency virus (HIV)-infected individuals means new challenges in contemporary management. In the early years of the epidemic,management was focussed on acute, potentially life-threatening AIDS-related complications. From initial monotherapy with first-generation antiretroviral therapy (ART), the development of combination highly active ART (HAART) allowed HIV control but ART toxicities, treatment adherence and drug resistance emerged as major issues. Today, the availability of potent and tolerable ART has made viral suppression achievable in most people living with HIV (PLHIV), and clinicians are confronted with managing a chronic condition among an ageing population. The combination of diseases of ageing and the co-morbidities associated with HIV-infection, even when well controlled, results in a complex set of challenges for many older PLHIV. There is a growing appreciation that many non-AIDS-related co-morbidities are caused, at least in part, by persistent, low-grade immune activation, inflammation, and hypercoagulability, despite suppressive ART. CONCLUSIONS: In order to further improve HIV management, it is important to understand the enduring effects of chronically suppressed HIV infection, the potential contribution of these factors to the ageing process, the possibility of drug resistance, and the impact of different treatment strategies, including early ART initiation.

Integration of the Duke Activity Status Index into preoperative risk evaluation: a multicentre prospective cohort study.

BACKGROUND: The Duke Activity Status Index (DASI) questionnaire might help incorporate self-reported functional capacity into preoperative risk assessment. Nonetheless, prognostically important thresholds in DASI scores remain unclear. We conducted a nested cohort analysis of the Measurement of Exercise Tolerance before Surgery (METS) study to characterise the association of preoperative DASI scores with postoperative death or complications. METHODS: The analysis included 1546 participants (≥40 yr of age) at an elevated cardiac risk who had inpatient noncardiac surgery. The primary outcome was 30-day death or myocardial injury. The secondary outcomes were 30-day death or myocardial infarction, in-hospital moderate-to-severe complications, and 1 yr death or new disability. Multivariable logistic regression modelling was used to characterise the adjusted association of preoperative DASI scores with outcomes. RESULTS: The DASI score had non-linear associations with outcomes. Self-reported functional capacity better than a DASI score of 34 was associated with reduced odds of 30-day death or myocardial injury (odds ratio: 0.97 per 1 point increase above 34; 95% confidence interval [CI]: 0.96-0.99) and 1 yr death or new disability (odds ratio: 0.96 per 1 point increase above 34; 95% CI: 0.92-0.99). Self-reported functional capacity worse than a DASI score of 34 was associated with increased odds of 30-day death or myocardial infarction (odds ratio: 1.05 per 1 point decrease below 34; 95% CI: 1.00-1.09), and moderate-to-severe complications (odds ratio: 1.03 per 1 point decrease below 34; 95% CI: 1.01-1.05). CONCLUSIONS: A DASI score of 34 represents a threshold for identifying patients at risk for myocardial injury, myocardial infarction, moderate-to-severe complications, and new disability.

Why do graduates choose to work in a less attractive specialty? A cross-sectional study on the role of personal values and expectations.

BACKGROUND: Primary health care (PHC), of which preventive medicine (PM) is a subspecialty, will have to cope with a deficiency of staff in the future, which makes the retention of graduates urgent. This study was conducted in Vietnam, where PM is an undergraduate degree in parallel to medical training. It aims to identify facilitating and hindering factors that impact recruitment and retention of PM graduates in the specialty. METHODS: A cross-sectional study enrolled 167 graduates who qualified as PM doctors from a Vietnamese medical school, between 2012 and 2018. Data were collected via an online questionnaire that asked participants about their motivation and continuation in PM, the major life roles that they were playing, and their satisfaction with their job. Multiple regression analyses were used to identify which life roles and motivational factors were related to the decision to take a PM position and to stay in the specialty, as well as how these factors held for subgroups of graduates (men, women, graduates who studied PM as their first or second study choice). RESULTS: Half of the PM graduates actually worked in PM, and only one fourth of them expressed the intention to stay in the field. Three years after qualification, many graduates had not yet decided whether to pursue a career in PM. Satisfaction with opportunities for continuous education was rated as highly motivating for graduates to choose and to stay in PM. Responsibility for taking care of parents motivated male graduates to choose PM, while good citizenship and serving the community was associated with the retention of graduates for whom PM was their first choice. CONCLUSIONS: The findings demonstrate the importance of social context and personal factors in developing primary care workforce policy. Providing opportunities for continued education and enhancing the attractiveness of PM as an appropriate specialty to doctors who are more attached to family and the community could be solutions to maintaining the workforce in PM. The implications could be useful for other less popular specialties that also struggle with recruiting and retaining staff.

A prospective cohort study characterising patients declined emergency laparotomy: survival in the 'NoLap' population.

Patients eligible for emergency laparotomy who do not proceed to surgery are not as well characterised as patients who do proceed to surgery. We studied patients eligible for laparotomy, as defined by National Emergency Laparotomy Audit criteria, from August 2015 to October 2016. We analysed the association of individual variables with survival and two composite scores: P-POSSUM and a general survival model. Out of 314 patients, 214 (68%) underwent laparotomy and 100 (32%) did not. Median (IQR [range]) follow-up was 1.3 (0.1-1.8 [0.0-2.5]) years for the cohort, 1.5 (1.1-2.0 [0.0-2.6]) years after laparotomy and 0.0 (0.0-1.1 [0.0-2.2]) years without laparotomy. There were 126/314 (40%) deaths in the follow-up period, 52/214 (24%) deaths after laparotomy and 74/100 (74%) deaths without surgery. Ninety out of 126 deaths (71%) were within one month of hospital admission. Patient variables were different for the two groups, which when combined in the general survival model generated background median (IQR [range]) life expectancies of 12 (6-21 [0-49]) and 4 (2-6 [0-36]) years, respectively, p < 0.0001. 'Poor fitness' precluded laparotomy in 74/100 (74%) patients. The decision to not operate involved a consultant less often than the decision to operate: 66/100 (66%) vs. 178/214 (83%), p = 0.001. Our study supports the contention that survival beyond 30 postoperative days could be predicted reasonably accurately. Survival in patients who did not have laparotomy was shorter than expected. Emergency laparotomy might have prolonged survival in some patients.

Memory effects in the long-wave infrared avalanche ionization of gases: a review of recent progress.

There are currently intense efforts being directed towards extending the range and energy of long distance nonlinear pulse propagation in the atmosphere by moving to longer infrared wavelengths, with the purpose of mitigating the effects of turbulence. In addition, picosecond and longer pulse durations are being used to increase the pulse energy. While both of these tacks promise improvements in applications, such as remote sensing and directed energy, they open up fundamental issues regarding the standard model used to calculate the nonlinear optical properties of dilute gases. Amongst these issues is that for longer wavelengths and longer pulse durations, exponential growth of the laser-generated electron density, the so-called avalanche ionization, can limit the propagation range via nonlinear absorption and plasma defocusing. It is therefore important for the continued development of the field to assess the theory and role of avalanche ionization in gases for longer wavelengths. Here, after an overview of the standard model, we present a microscopically motivated approach for the analysis of avalanche ionization in gases that extends beyond the standard model and we contend is key for deepening our understanding of long distance propagation at long infrared wavelengths. Our new approach involves the mean electron kinetic energy, the plasma temperature, and the free electron density as dynamic variables. The rate of avalanche ionization is shown to depend on the full time history of the pulsed excitation, as opposed to the standard model in which the rate is proportional to the instantaneous intensity. Furthermore, the new approach has the added benefit that it is no more computationally intensive than the standard one. The resulting memory effects and some of their measurable physical consequences are demonstrated for the example of long-wavelength infrared avalanche ionization and long distance high-intensity pulse propagation in air. Our hope is that this report in progress will stimulate further discussion that will elucidate the physics and simulation of avalanche ionization at long infrared wavelengths and advance the field.

Universal long-wavelength nonlinear optical response of noble gases.

We demonstrate numerically that the long-wavelength nonlinear dipole moment and ionization rate versus electric field strength F for different noble gases can be scaled onto each other, revealing universal functions that characterize the form of the nonlinear response. We elucidate the physical origin of the universality by using a metastable state analysis of the light-atom interaction in combination with a scaling analysis. Our results also provide a powerful new means of characterizing the nonlinear response in the mid-infrared and long-wave infrared for optical filamentation studies.

Human model of burn injury that quantifies the benefit of cooling as a first aid measure.

BACKGROUND: Burn injuries are a major cause of morbidity and mortality worldwide. Cooling is widely practised as a first aid measure, but the efficacy of cooling burns in human skin has not been demonstrated. A safe, consistent, ethically acceptable model of burning and cooling in live human skin in vivo was developed, and used to quantify the effects of cooling. METHODS: Novel apparatus was manufactured to create and cool burns in women who were anaesthetized for breast reconstruction surgery using a deep inferior epigastric artery perforator flap. Burns were excised between 1 and 3 h after creation, and analysed using histopathological assessment. RESULTS: All 25 women who were approached agreed to take part in the study. There were no adverse events. Increased duration of contact led to increased burn depth, with a contact time of 7·5 s at 70°C leading to a mid-dermal burn. Burn depth progressed over time following injury, but importantly this was modified by cooling the burn at 16°C for 20 min. On average, cooling salvaged 25·2 per cent of the dermal thickness. CONCLUSION: This study demonstrated the favourable effects of cooling on human burns. Public heath messaging should emphasize cooling as first aid for burns. This model will allow analysis of the molecular effects of cooling burns, and provide a platform for testing novel therapies aimed at reducing the impact of burn injury.

ANTECEDENTES: Las lesiones por quemadura son una causa importante de morbilidad y mortalidad en todo el mundo. El enfriamiento de las quemaduras se practica ampliamente como medida de primeros auxilios, pero no se ha demostrado su eficacia en la piel de los seres humanos. Para cuantificar los efectos del enfriamiento, se desarrolló un modelo de quemadura y enfriamiento en piel humana in vivo, seguro, estable y éticamente aceptable. MÉTODOS: Se construyó un dispositivo nuevo para crear y enfriar quemaduras en pacientes que fueron anestesiadas para una reconstrucción mamaria utilizando un colgajo perforante de la arteria epigástrica inferior profunda. Las quemaduras se extirparon entre una y tres horas después de su producción y se analizaron por evaluación histopatológica. Para determinar la significación estadística entre grupos se utilizó las pruebas de ANOVA o de t pareadas, según correspondiera. RESULTADOS: Aceptaron participar en el estudio las 25 pacientes a las que se propuso. No hubo efectos adversos. La mayor duración del contacto conllevó un aumento en la profundidad de la quemadura: con un tiempo de contacto de 7,5 segundos a 70°C se obtuvo una quemadura dérmica de segundo grado. La profundidad de la quemadura aumentó con el tiempo de exposición, pero mejoró de forma sustancial al enfriar la quemadura a 16°C durante 20 minutos. El enfriamiento salvó el 25% del espesor dérmico como promedio. CONCLUSIÓN: Este es el primer estudio que demuestra los efectos favorables del enfriamiento sobre las quemaduras humanas. Los consejos de salud deberían hacer más énfasis en el enfriamiento como forma de primeros auxilios en las quemaduras. Este modelo permitirá identificar los efectos moleculares del enfriamiento en las quemaduras y proporcionará una plataforma para probar nuevos tratamientos encaminados a reducir el impacto de las lesiones por quemadura.

Superradiant Amplification of Acoustic Beams via Medium Rotation.

Superradiant gain is the process in which waves are amplified via their interaction with a rotating body, examples including the evaporation of a spinning black hole and electromagnetic emission from a rotating metal sphere. In this Letter we elucidate how superradiance may be realized experimentally in the field of acoustics, and predict the possibility of nonreciprocally amplifying or absorbing acoustic beams carrying orbital angular momentum by propagating them through an absorbing medium that is rotating. We discuss a possible geometry for realizing acoustic superradiant amplification using existing technology.

Working in preventive medicine or not? Flawed perceptions decrease chance of retaining students for the profession.

BACKGROUND: Recruiting and retaining students in preventive medical (PM) specialties has never been easy; one main challenge is how to select appropriate students with proper motivation. Understanding how students perceive PM practice differently from practicing doctors is necessary to guide students, especially for those for whom PM is only a substitute for medicine as their first study preference, properly during their study and, later, the practice of PM. METHODS: One thousand three hundred eighty-six PM students in four Vietnamese medical schools and 101 PM doctors filled out a questionnaire about the relevance of 44 characteristics of working in PM. ANOVAs were conducted to define the relationship between students' interest, year of study, willingness to work in PM, and the degree to which students had realistic perceptions of PM practice, compared to doctors' perceptions. RESULTS: Overall, compared to doctors' perceptions, students overestimated the importance of most of the investigated PM practice's characteristics. Moreover, students' perception related to their preference and willing to pursue a career in PM after graduation. In particular, students for whom PM was their first choice had more realistic perceptions of community practice than those who chose PM as their second choice. And, second-choice students had more realistic perceptions than first-choice students in their final years of study, but expected higher work stress in PM practice. Students who were willing to pursue a career in PM rated the importance of community practice higher than those who were not. We also found that students' perception changed during training as senior students had more realistic perceptions of clinical aspects and working stress than junior students, even though they overemphasized the importance of the community aspects of PM practice. CONCLUSIONS: To increase the number of students actually entering the PM field after graduation, the flawed perceptions of students about the real working environment of PM doctors should be addressed through vocation-oriented activities in the curriculum targeted on groups of students who are most likely to have unrealistic perceptions. Our findings also have implications for other less attractive primary health care specialties that experience problems with recruiting and retaining students.

Guidelines for the safe provision of anaesthesia in magnetic resonance units 2019: Guidelines from the Association of Anaesthetists and the Neuro Anaesthesia and Critical Care Society of Great Britain and Ireland.

There has been an increase in the number of units providing anaesthesia for magnetic resonance imaging and the strength of magnetic resonance scanners, as well as the number of interventions and operations performed within the magnetic resonance environment. More devices and implants are now magnetic resonance imaging conditional, allowing scans to be undertaken in patients for whom this was previously not possible. There has also been a revision in terminology relating to magnetic resonance safety of devices. These guidelines have been put together by organisations who are involved in the pathways for patients needing magnetic resonance imaging. They reinforce the safety aspects of providing anaesthesia in the magnetic resonance environment, from the multidisciplinary decision making process, the seniority of anaesthetist accompanying the patient, to training in the recognition of hazards of anaesthesia in the magnetic resonance environment. For many anaesthetists this is an unfamiliar site to give anaesthesia, often in a remote site. Hospitals should develop and audit governance procedures to ensure that anaesthetists of all grades are competent to deliver anaesthesia safely in this area.

Do health care providers give sufficient information and good counseling during ante-natal care in Lao PDR?: an observational study.

BACKGROUND: It is increasingly recognized that improving the quality of maternal health care delivery is of utmost importance in many countries. In Laos, the quality of antenatal care (ANC) service remains inadequate, but it has never been assessed thoroughly. This study aims to determine the ANC quality at the urban and rural public health facilities in Laos and provides suggestions to improve health education and counseling in addition to other routine care in public ANC services. METHODS: This health-facility based, cross-sectional observation study included both health providers (n = 77) and pregnant women (n = 421) from purposively selected health facilities (n = 16). Information on the mothers' current pregnancies, previous visits and their last children was collected. The time spent for each ANC session as well as ANC services provided were recorded. Descriptive and inferential statistics were applied to analyze the data. RESULTS: Overall performance of ANC services by health care providers was poor in both urban and rural areas. Insufficient provision of information on danger signs during pregnancy, nutrition, breast feeding and iron supplements was revealed. Generally the communication skills, behavior and attitude of health providers were very poor. Less than a quarter of pregnant women were treated with kindness and respect. Only 4% of the observed ANC session took privacy into consideration. Less than 10% of available information materials were used during each ANC session. None of the health providers in both rural and urban areas performed specific counseling. Overall mean (SD) time-spent for each ANC session was 16.21 (4.28) minutes. A positive correlation was identified between the length of working experience of health providers and their physical performance scores (adjusted R square = 0.017). CONCLUSIONS: The overall performance of ANC services by health care providers was inadequate in both urban and rural areas. Insufficient provision of health education and poor communication skills of health care providers were revealed. Existing IEC materials were scarcely used. Taking action to improve the quality of ANC services by training and providing specific guidelines, creating dedicated rooms, and providing sufficient and effective materials for counseling are all greatly needed in public health facilities in Laos.

Antigenic site changes in the rabies virus glycoprotein dictates functionality and neutralizing capability against divergent lyssaviruses.

Lyssavirus infection has a near 100 % case fatality rate following the onset of clinical disease, and current rabies vaccines confer protection against all reported phylogroup I lyssaviruses. However, there is little or no protection against more divergent lyssaviruses and so investigation into epitopes within the glycoprotein (G) that dictate a neutralizing response against divergent lyssaviruses is warranted. Importantly, the facilities required to work with these pathogens, including wild-type and mutated forms of different lyssaviruses, are scarcely available and, as such, this type of study is inherently difficult to perform. The relevance of proposed immunogenic antigenic sites within the lyssavirus glycoprotein was assessed by swapping sites between phylogroup-I and -II glycoproteins. Demonstrable intra- but limited inter-phylogroup cross-neutralization was observed. Pseudotype viruses (PTVs) presenting a phylogroup-I glycoprotein containing phylogroup-II antigenic sites (I, II III or IV) were neutralized by antibodies raised against phylogroup-II PTV with the site II (IIb, aa 34-42 and IIa, aa 198-200)-swapped PTVs being efficiently neutralized, whilst site IV-swapped PTV was poorly neutralized. Specific antibodies raised against PTV-containing antigenic site swaps between phylogroup-I and -II glycoproteins neutralized phylogroup-I PTVs efficiently, indicating an immunodominance of antigenic site II. Live lyssaviruses containing antigenic site-swapped glycoproteins were generated and indicated that specific residues within the lyssavirus glycoprotein dictate functionality and enable differential neutralizing antibody responses to lyssaviruses.

Rotation-dependent nonlinear absorption of orbital angular momentum beams in ruby.

We investigate the effect of a rotating medium on orbital angular momentum (OAM)-carrying beams by combining a weak probe beam shifted in frequency relative to a strong pump beam. We show how the rotational Doppler effect modifies the light-matter interaction through the external rotation of the medium. This interaction leads to an absorption that increases with the mechanical rotation velocity of the medium and with a rate that depends on the OAM of the light beam.

Factors associated with fractures in HIV-infected persons: which factors matter?

This study aims to determine what factors are associated with increased risk of fracture among patients with HIV, in particular whether an important medication used to treat HIV, tenofovir, is associated with fracture. Our study found that while co-infection with hepatitis C and markers of HIV severity were associated with fracture, tenofovir was not. INTRODUCTION: Growing evidence suggests that tenofovir disoproxil fumarate decreases bone density among patients with HIV, but there are conflicting reports as to whether this decrease in bone density translates to higher fracture risk. We aimed to determine what factors were associated with an increased risk of fracture for patients with HIV, in particular whether tenofovir is associated with elevated fracture risk. METHODS: We conducted a retrospective cohort study at two tertiary care hospitals in Boston, MA, between 2001 and 2012 to determine whether tenofovir use is associated with elevated all-site fracture risk, as compared to other antiretroviral medications. We also examined other potential factors associated with fracture among patients with HIV. RESULTS: We identified 1981 HIV-infected patients who had at some point used tenofovir and 682 patients who had not. The mean age was 43 years, and 72 % were male. The hepatitis C co-infection rate was 28 %, about 40 % had nadir CD4 count <200, and about 40 % had a history of an AIDS-defining illness. We did not find an association between risk of fracture and tenofovir disoproxil fumarate (TDF) (adjusted RR (aRR) 0.8, 95 % CI 0.6-1.1). However, co-infection with hepatitis C did increase risk of fracture (aRR 1.6, 95 % CI 1.1-2.3), as did nadir CD4 count <200 (aRR 3.1, 95 % CI 1.9-5.0) and history of AIDS-defining illness (aRR 1.6, 95 % CI 1.1-2.2). CONCLUSION: There was no association found between fracture and tenofovir use, but there were associations between co-infection with hepatitis C and markers of advanced HIV disease and fracture.

Self-Channeling of High-Power Long-Wave Infrared Pulses in Atomic Gases.

We simulate and elucidate the self-channeling of high-power 10 µm infrared pulses in atomic gases. The major new result is that the peak intensity can remain remarkably stable over many Rayleigh ranges. This arises from the balance between the self-focusing, diffraction, and defocusing caused by the excitation induced dephasing due to many-body Coulomb effects that enhance the low-intensity plasma densities. This new paradigm removes the Rayleigh range limit for sources in the 8-12 µm atmospheric transmission window and enables transport of individual multi-TW pulses over multiple kilometer ranges.

Numerical investigation of enhanced femtosecond supercontinuum via a weak seed in noble gases.

Numerical simulations are employed to elucidate the physics underlying the enhanced femtosecond supercontinuum generation previously observed during optical filamentation in noble gases and in the presence of a weak seed pulse. Simulations based on the metastable electronic state approach are shown not only to capture the qualitative features of the experiment, but also reveal the relation of the observed enhancement to recent developments in the area of sub-cycle engineering of filaments.