Capturing electron-driven chiral dynamics in UV-excited molecules.

Chiral molecules, used in applications such as enantioselective photocatalysis1, circularly polarized light detection2 and emission3 and molecular switches4,5, exist in two geometrical configurations that are non-superimposable mirror images of each other. These so-called (R) and (S) enantiomers exhibit different physical and chemical properties when interacting with other chiral entities. Attosecond technology might enable influence over such interactions, given that it can probe and even direct electron motion within molecules on the intrinsic electronic timescale6 and thereby control reactivity7-9. Electron currents in photoexcited chiral molecules have indeed been predicted to enable enantiosensitive molecular orientation10, but electron-driven chiral dynamics in neutral molecules have not yet been demonstrated owing to the lack of ultrashort, non-ionizing and perturbative light pulses. Here we use time-resolved photoelectron circular dichroism (TR-PECD)11-15 with an unprecedented temporal resolution of 2.9 fs to map the coherent electronic motion initiated by ultraviolet (UV) excitation of neutral chiral molecules. We find that electronic beatings between Rydberg states lead to periodic modulations of the chiroptical response on the few-femtosecond timescale, showing a sign inversion in less than 10 fs. Calculations validate this and also confirm that the combination of the photoinduced chiral current with a circularly polarized probe pulse realizes an enantioselective filter of molecular orientations following photoionization. We anticipate that our approach will enable further investigations of ultrafast electron dynamics in chiral systems and reveal a route towards enantiosensitive charge-directed reactivity.

Trends and challenges in microfluidic methods for protein manipulation-A review.

Proteins are important molecules involved in an immensely large number of biological processes. Being capable of manipulating proteins is critical for developing reliable and affordable techniques to analyze and/or detect them. Such techniques would enable the production of therapeutic agents for the treatment of diseases or other biotechnological applications (e.g., bioreactors or biocatalysis). Microfluidic technology represents a potential solution to protein manipulation challenges because of the diverse phenomena that can be exploited to achieve micro- and nanoparticle manipulation. In this review, we discuss recent contributions made in the field of protein manipulation in microfluidic systems using different physicochemical principles and techniques, some of which are miniaturized versions of already established macro-scale techniques.

Strong chiral response in non-collinear high harmonic generation driven by purely electric-dipole interactions.

High harmonic generation (HHG) records the ultrafast electronic response of matter to light, encoding key properties of the interrogated quantum system, such as chirality. The first implementation of chiral HHG [Cireasa et al, Nat. Phys.11, 654 (2015)10.1038/nphys3369] relied on the weak electronic response of a medium of randomly oriented chiral molecules to the magnetic component of an elliptically polarized wave, yielding relatively weak chiro-optical signals. Here we apply state-of-the-art semi-analytical modelling to show that elliptically polarized light can drive a strong chiral response in chiral molecules via purely electric-dipole interactions - the magnetic component of the wave does not participate at all. This strong chiro-optical response, which remains hidden in standard HHG experiments, can be mapped into the macroscopic far-field signal using a non-collinear configuration, creating new opportunities for imaging chiral matter and chiral dynamics on ultrafast time scales.

Ultrafast Imaging of Molecular Chirality with Photoelectron Vortices.

Ultrafast imaging of molecular chirality is a key step toward the dream of imaging and interpreting electronic dynamics in complex and biologically relevant molecules. Here, we propose a new ultrafast chiral phenomenon exploiting recent advances in electron optics allowing access to the orbital angular momentum of free electrons. We show that strong-field ionization of a chiral target with a few-cycle linearly polarized 800 nm laser pulse yields photoelectron vortices, whose chirality reveals that of the target, and we discuss the mechanism underlying this phenomenon. Our Letter opens new perspectives in recollision-based chiral imaging.

Disentangling enantiosensitivity from dichroism using bichromatic fields.

We discuss how tensorial observables, available in photoelectron angular distributions resulting from interaction between isotropic chiral samples and cross polarized ω-2ω bichromatic fields, allow for chiral discrimination without chiral light and within the electric-dipole approximation. We extend the concept of chiral setup [A. F. Ordonez and O. Smirnova, Phys. Rev. A, 2018, 98, 063428], which explains how chiral discrimination can be achieved in the absence of chiral light, to the case of tensorial observables. We derive selection rules for the enantiosensitivity and dichroism of the bl,m coefficients describing the photoelectron angular distribution valid for both weak and strong fields and for arbitrary ω-2ω relative phase. Explicit expressions for simple perturbative cases are given. We find that, besides the known dichroic non-enantiosensitive [R. E. Goetz, C. P. Koch and L. Greenman, J. Chem. Phys., 2019, 151, 074106], and dichroic-and-enantiosensitive bl,m coefficients found recently [P. V. Demekhin, Phys. Rev. A, 2019, 99, 063406], there are also enantiosensitive non-dichroic bl,m coefficients. These reveal the molecular enantiomer independently of the relative phase between the two colors and are therefore observable even in the absence of stabilization of the ω-2ω relative phase.

A geometric approach to decoding molecular structure and dynamics from photoionization of isotropic samples.

We propose a geometric approach to the description and analysis of photoelectron angular distributions resulting from isotropic samples in the case of few-photon ionization by electric fields of arbitrary polarization. This approach formulates the standard photoionization observables - the bl,m expansion coefficients of the photoelectron angular distribution, in terms of geometrical properties of the vector field D⃑(k⃑) ≡ 〈k⃑|d⃑|0〉 describing the electronic transition from a bound state |0〉 into a scattering state |k⃑〉 - the photoionization transition dipole. Besides revealing selection rules for the enantio-sensitivity of bl,m coefficients in multiphoton ionization, our approach yields very compact expressions for both chiral and achiral molecules revealing how the molecular rotational invariants couple to the rotational invariants of the setup defined by the electric field polarization and the arrangement of photoelectron detectors. We apply this approach to one-photon ionization and find that the forward-backward asymmetry parameter b1,0, emerging exclusively in chiral molecules and encoded in the field B⃑(k⃑) ≡ iD⃑*(k⃑) × D⃑(k⃑), is sensitive only to the components of D⃑(k⃑) perpendicular to k⃑, while the regular asymmetry parameter b2,0 emerging in chiral and achiral molecules is sensitive only to the component of D⃑(k⃑) parallel to k⃑. Next, we analyze resonantly enhanced two-photon ionization and show that b0,0 and b1,0 can be written in terms of an effectively stretched D⃑(k⃑), and how b1,0 and b3,0 can be used to probe B⃑(k⃑).

Propensity rules for photoelectron circular dichroism in strong field ionization of chiral molecules.

Chiral molecules ionized by circularly polarized fields produce a photoelectron current orthogonal to the polarization plane. This current has opposite directions for opposite enantiomers and provides an extremely sensitive probe of molecular handedness. Recently, such photoelectron currents have been measured in the strong-field ionization regime, where they may serve as an ultrafast probe of molecular chirality. Here we provide a mechanism for the emergence of such strong-field photoelectron currents in terms of two propensity rules that link the properties of the initial electronic chiral state to the direction of the photoelectron current.

Ultrafast chirality: the road to efficient chiral measurements.

Today we are witnessing the electric-dipole revolution in chiral measurements. Here we reflect on its lessons and outcomes, such as the perspective on chiral measurements using the complementary principles of "chiral reagent" and "chiral observer", the hierarchy of scalar, vectorial and tensorial enantio-sensitive observables, the new properties of the chiro-optical response in the ultrafast and non-linear domains, and the geometrical magnetism associated with the chiral response in photoionization. The electric-dipole revolution is a landmark event. It has opened routes to extremely efficient enantio-discrimination with a family of new methods. These methods are governed by the same principles but work in vastly different regimes - from microwaves to optical light; they address all molecular degrees of freedom - electronic, vibrational and rotational, and use flexible detection schemes, i.e. detecting photons or electrons, making them applicable to different chiral phases, from gases to liquids to amorphous solids. The electric-dipole revolution has also enabled enantio-sensitive manipulation of chiral molecules with light. This manipulation includes exciting and controlling ultrafast helical currents in vibronic states of chiral molecules, enantio-sensitive control of populations in electronic, vibronic and rotational molecular states, and opens the way to efficient enantio-separation and enantio-sensitive trapping of chiral molecules. The word "perspective" has two meanings: an "outlook" and a "point of view". In this perspective article, we have tried to cover both meanings.

Neighborhood effects on use of African-American Vernacular English.

African-American Vernacular English (AAVE) is systematic, rooted in history, and important as an identity marker and expressive resource for its speakers. In these respects, it resembles other vernacular or nonstandard varieties, like Cockney or Appalachian English. But like them, AAVE can trigger discrimination in the workplace, housing market, and schools. Understanding what shapes the relative use of AAVE vs. Standard American English (SAE) is important for policy and scientific reasons. This work presents, to our knowledge, the first experimental estimates of the effects of moving into lower-poverty neighborhoods on AAVE use. We use data on non-Hispanic African-American youth (n = 629) from a large-scale, randomized residential mobility experiment called Moving to Opportunity (MTO), which enrolled a sample of mostly minority families originally living in distressed public housing. Audio recordings of the youth were transcribed and coded for the use of five grammatical and five phonological AAVE features to construct a measure of the proportion of possible instances, or tokens, in which speakers use AAVE rather than SAE speech features. Random assignment to receive a housing voucher to move into a lower-poverty area (the intention-to-treat effect) led youth to live in neighborhoods (census tracts) with an 11 percentage point lower poverty rate on average over the next 10-15 y and reduced the share of AAVE tokens by ∼3 percentage points compared with the MTO control group youth. The MTO effect on AAVE use equals approximately half of the difference in AAVE frequency observed between youth whose parents have a high school diploma and those whose parents do not.

Complications associated with the use of radial arterial catheters in relation to their length: Does size matter?

BACKGROUND: Radial arterial catheters (RAC) are commonly used in emergency services and intensive care units (ICU) for continuous invasive monitoring of blood pressure and arterial blood gas sampling. Complications associated with RAC are rare. Regarding length of RAC catheters and complications, few studies were found in the literature. The present study seeks to provide health care professionals with scientific evidence to select an optimal length of RAC, based on the difference in the incidence of complications between ultrasound-guided catheters of the same diameter but different lengths. METHODS: Observational, descriptive, retrospective study. Patients older than 17 years admitted to the emergency department or ICU were included. RAC were placed with diameters of 20 gauge, between 5 and 8 cm (Arrow-Teleflex), and 22 gauge diameters between 4 and 8 cm (Vygon). Univariate analysis was made to determine behavior of the numerical variables. Normality of variables was determined through a Shapiro-Wilk-test. Qualitative variables were expressed in percentages, quantitative variables in means and standard deviation, or with median and quartiles in the case of a non-normal distribution. Chi-square or Fisher method was used for qualitative variables and the t-test for symmetric quantitative variables. Asymmetric distributions were processed with the Mann-Whitney U test. A value p < 0.05 was considered statistically significant. The statistical analysis was performed with Stata 14.1 program. RESULTS: About 793 RAC were placed between 2016 and 2019 were included, median age was 60 (37-73) (RIQ) years, 49% male. Complications were reported in all groups on average 17.5%, the most frequent being dysfunction/occlusion of the catheter. Given complications of the same diameter and different catheter lengths, there were no statistical differences between groups. CONCLUSION: Selecting one length or another with a catheter of the same diameter does not have statistically significant differences, in terms of the complications this device may cause-meaning that size does not matter.

Enantio-sensitive unidirectional light bending.

Structured light, which exhibits nontrivial intensity, phase, and polarization patterns in space, has key applications ranging from imaging and 3D micromanipulation to classical and quantum communication. However, to date, its application to molecular chirality has been limited by the weakness of magnetic interactions. Here we structure light's local handedness in space to introduce and realize an enantio-sensitive interferometer for efficient chiral recognition without magnetic interactions, which can be seen as an enantio-sensitive version of Young's double slit experiment. Upon interaction with isotropic chiral media, such chirality-structured light effectively creates chiral emitters of opposite handedness, located at different positions in space. We show that if the distribution of light's handedness breaks left-right symmetry, the interference of these chiral emitters leads to unidirectional bending of the emitted light, in opposite directions in media of opposite handedness, even if the number of the left-handed and right-handed emitters excited in the medium is exactly the same. Our work introduces the concepts of polarization of chirality and chirality-polarized light, exposes the immense potential of sculpting light's local chirality, and offers novel opportunities for efficient chiral discrimination, enantio-sensitive optical molecular fingerprinting and imaging on ultrafast time scales.

Caracterización clínica de la peritonitis secundaria en una institución de tercer nivel y factores relacionados con mortalidad / Clinical characterization of secondary peritonitis in a tertiary level of care institution and factors related to mortality

Introducción. La peritonitis secundaria es una enfermedad con altos índices de mortalidad, por lo que se considera de gran importancia identificar los factores que inciden en ella. Método. Se realizó un estudio analítico entre 2019 y 2020 en el que se incluyeron pacientes con peritonitis secundaria, se caracterizaron las variables más relacionadas con el pronóstico, como aspectos demográficos y clínicos, y se analizó la asociación entre la mortalidad y estas variables. Resultados. La mortalidad hospitalaria fue del 30,7 %, encontrando como condiciones relacionadas con la mortalidad la ubicación de la fuente séptica en abdomen superior, la presencia de dolor en abdomen superior, atención en UCI, control del foco en la primera intervención, pacientes que cursaron con falla renal, edad del paciente y valores de hemoglobina. Conclusiones. En la cohorte estudiada se encontraron índices de mortalidad dos veces superiores a los reportados en Suramérica y 1,5 veces a los del resto del país. El mayor poder predictivo de mortalidad en el análisis bivariado fue dado por la presencia de falla renal y el valor de la hemoglobina.

Introduction. Secondary peritonitis is a disease with high mortality rates, so it is considered of great importance to identify the factors that affect it. Methods. An analytical study was carried out between 2019 and 2020 in which patients with secondary peritonitis were included, the variables most related to prognosis were characterized, such as demographic and clinical aspects, and the association between mortality and these variables was analyzed. Results. Hospital mortality was 30.7%, finding conditions related to mortality to be the location of the septic source in the upper abdomen, the presence of pain in the upper abdomen, care in the ICU, control of the focus in the first intervention, patients who underwent kidney failure, patient age, and hemoglobin values. Conclusion. Mortality rates were found in the studied cohort twice higher than those reported in South America and 1.5 times higher than those of the rest of the country. The greatest predictive power of mortality in the bivariate analysis was given by the presence of kidney failure and hemoglobin.

Guillain-Barré syndrome in a COVID-19 patient / Síndrome de Guillain-Barré en paciente con COVID-19

Abstract Coronavirus type 2 is a P-coronavirus whose infection is characterized by a predominantly respiratory clinical picture. However, neurological symptoms are garnering great interest related to pulmonary infection and direct viral invasion of the central nervous system, with a possible association between Guillain-Barré syndrome and SARS-CoV-2 infection. This report describes this relationship in a 44-year-old female patient with classical Guillain-Barré syndrome signs and symptoms on admission, and respiratory signs and symptoms six days prior to the onset of neurological symptoms. There were positive SARS-CoV IgG and IgM blood tests and an epidemiological link of direct contact with people infected with SARS-CoV-2. She required ICU care due to the risk of respiratory failure, along with immunoglobulin treatment, but did not need mechanical ventilation; she improved and was discharged. One month later she consulted again and was thought to have had a Guillain-Barré relapse. She was hospitalized and treated until she progressed and her symptoms resolved. (Acta Med Colomb 2022; 47. DOI:https://doi.org/10.36104/amc.2022.2204).

Resumen El coronavirus tipo 2 es un P-coronavirus cuya infección se caracteriza por clínica de predominio respiratorio; sin embargo, la sintomatologia neurológica está cobrando gran interés asociada a la infección pulmonar e invasión directa del virus al sistema nervioso central. Siendo posible la aso ciación entre el síndrome de Guillain-Barré y la infección por virus SARS-CoV-2. En este reporte se describe dicha asociación en una paciente femenina de 44 años de edad, con clínica clásica de síndrome de Guillain-Barré al ingreso y clínica respiratoria seis días previos a la instalación de los síntomas neurológicos. Reportándose serologías IgG e IgM para SARS-CoV-positivas y nexo epidemiológico de contacto directo con personas infectadas por SARS-CoV-2. Requirió manejo en UCI por riesgo de falla respiratoria, manejo con inmunoglobulinas, sin requerimiento de ventilación mecánica, presentando mejoría y otorgándose salida. Un mes después reconsulta, se considera recaída de Guillain-Barré, se hospitaliza, se inicia manejo hasta evolución y resolución de síntomas. (Acta Med Colomb 2022; 47. DOI:https://doi.org/10.36104/amc.2022.2204).