Stegomyia indices and pattern recognition of Aedes aegypti (Diptera: Culicidae) in selected agrogeoclimatic zones of Punjab, Pakistan.

Mosquito-borne diseases especially, dengue is gaining currency nowadays in Pakistan. As there is no approved dengue vaccine available worldwide, prevention and control of vector is the only solution amid prevailing circumstances. The present study is a maiden attempt to screen indoor and outdoor breeding containers for the presence of Aedes (Ae.) aegypti larvae from selected study districts of Punjab, Pakistan i.e., Dera Ghazi Khan (DG Khan), Chakwal, and Faisalabad. A total of 384 houses from each study districts were surveyed for a calendar year. Mosquito larvae were collected, preserved, and identified using standard taxonomic keys. House Index (HI), Container Index (CI), and Breteau Index (BI) were estimated. Chi-square analysis was applied to calculate the association between Ae. aegypti larvae and breeding containers. Chakwal was identified with the highest values of Stegomyia indices (HI = 46.61 %, BI = 91.67 %, and CI = 15.28 %) followed by Faisalabad (HI = 34.11 %, BI = 68.75 % and, CI = 13.04 %) and DG Khan (HI = 28.39 %, BI = 68.23 % and, CI = 11.29 %). Earthen jars, tree holes, and water tanks were found significantly (p < 0.05) associated with the abundance of larvae irrespective of the geographical location. However, flower tubs and plastic buckets were found significantly (p < 0.05) associated in Faisalabad and Chakwal while, tyres and plastic bottles were found associated (p < 0.05) with the abundance of Ae. aegypti larvae in Faisalabad and DG Khan. These findings will help the stakeholders to devise appropriate preventive measures in combating the risk of dengue transmission.

Chemical effects on the dynamics of organic molecules irradiated with high intensity x rays.

The interaction of a high intensity x-ray pulse with matter causes ionization of the constituent atoms through various atomic processes, and the system eventually goes through a complex structural dynamics. Understanding this whole process is important from the perspective of structure determination of molecules using single particle imaging. XMDYN, which is a classical molecular dynamics-Monte Carlo based hybrid approach, has been successful in simulating the dynamical evolution of various systems under intense irradiation over the past years. The present study aims for extending the XMDYN toolkit to treat chemical bonds using the reactive force field. In order to study its impact, a highly intense x-ray pulse was made to interact with the simplest amino acid, glycine. Different model variants were used to highlight the consequences of charge rearrangement and chemical bonds on the time evolution. The charge-rearrangement-enhanced x-ray ionization of molecules effect is also discussed to address the capability of a classical MD based approach, i.e., XMDYN, to capture such a molecular phenomenon.

Erratum: Transient ionization potential depression in nonthermal dense plasmas at high x-ray intensity [Phys. Rev. E 103, 023203 (2021)].

This corrects the article DOI: 10.1103/PhysRevE.103.023203.

Transient ionization potential depression in nonthermal dense plasmas at high x-ray intensity.

The advent of x-ray free-electron lasers (XFELs), which provide intense ultrashort x-ray pulses, has brought a new way of creating and analyzing hot and warm dense plasmas in the laboratory. Because of the ultrashort pulse duration, the XFEL-produced plasma will be out of equilibrium at the beginning, and even the electronic subsystem may not reach thermal equilibrium while interacting with a femtosecond timescale pulse. In the dense plasma, the ionization potential depression (IPD) induced by the plasma environment plays a crucial role for understanding and modeling microscopic dynamical processes. However, all theoretical approaches for IPD have been based on local thermal equilibrium (LTE), and it has been controversial to use LTE IPD models for the nonthermal situation. In this work, we propose a non-LTE (NLTE) approach to calculate the IPD effect by combining a quantum-mechanical electronic-structure calculation and a classical molecular dynamics simulation. This hybrid approach enables us to investigate the time evolution of ionization potentials and IPDs during and after the interaction with XFEL pulses, without the limitation of the LTE assumption. In our NLTE approach, the transient IPD values are presented as distributions evolving with time, which cannot be captured by conventional LTE-based models. The time-integrated ionization potential values are in good agreement with benchmark experimental data on solid-density aluminum plasma and other theoretical predictions based on LTE. The present work is promising to provide critical insights into nonequilibrium dynamics of dense plasma formation and thermalization induced by XFEL pulses.

Erratum: Molecular-dynamics approach for studying the nonequilibrium behavior of x-ray-heated solid-density matter [Phys. Rev. E 96, 023205 (2017)].

This corrects the article DOI: 10.1103/PhysRevE.96.023205.

Towards the theoretical limitations of X-ray nanocrystallography at high intensity: the validity of the effective-form-factor description.

X-ray free-electron lasers (XFELs) broaden horizons in X-ray crystallography. Facilitated by the unprecedented high intensity and ultrashort duration of the XFEL pulses, they enable us to investigate the structure and dynamics of macromolecules with nano-sized crystals. A limitation is the extent of radiation damage in the nanocrystal target. A large degree of ionization initiated by the incident high-intensity XFEL pulse alters the scattering properties of the atoms leading to perturbed measured patterns. In this article, the effective-form-factor approximation applied to capture this phenomenon is discussed. Additionally, the importance of temporal configurational fluctuations at high intensities, shaping these quantities besides the average electron loss, is shown. An analysis regarding the applicability of the approach to targets consisting of several atomic species is made, both theoretically and via realistic radiation-damage simulations. It is concluded that, up to intensities relevant for XFEL-based nanocrystallography, the effective-form-factor description is sufficiently accurate. This work justifies treating measured scattering patterns using conventional structure-reconstruction algorithms.

Molecular-dynamics approach for studying the nonequilibrium behavior of x-ray-heated solid-density matter.

When matter is exposed to a high-intensity x-ray free-electron-laser pulse, the x rays excite inner-shell electrons leading to the ionization of the electrons through various atomic processes and creating high-energy-density plasma, i.e., warm or hot dense matter. The resulting system consists of atoms in various electronic configurations, thermalizing on subpicosecond to picosecond timescales after photoexcitation. We present a simulation study of x-ray-heated solid-density matter. For this we use XMDYN, a Monte Carlo molecular-dynamics-based code with periodic boundary conditions, which allows one to investigate nonequilibrium dynamics. XMDYN is capable of treating systems containing light and heavy atomic species with full electronic configuration space and three-dimensional spatial inhomogeneity. For the validation of our approach we compare for a model system the electron temperatures and the ion charge-state distribution from XMDYN to results for the thermalized system based on the average-atom model implemented in XATOM, an ab initio x-ray atomic physics toolkit extended to include a plasma environment. Further, we also compare the average charge evolution of diamond with the predictions of a Boltzmann continuum approach. We demonstrate that XMDYN results are in good quantitative agreement with the above-mentioned approaches, suggesting that the current implementation of XMDYN is a viable approach to simulate the dynamics of x-ray-driven nonequilibrium dynamics in solids. To illustrate the potential of XMDYN for treating complex systems, we present calculations on the triiodo benzene derivative 5-amino-2,4,6-triiodoisophthalic acid (I3C), a compound of relevance of biomolecular imaging, consisting of heavy and light atomic species.

Calculation of x-ray scattering patterns from nanocrystals at high x-ray intensity.

We present a generalized method to describe the x-ray scattering intensity of the Bragg spots in a diffraction pattern from nanocrystals exposed to intense x-ray pulses. Our method involves the subdivision of a crystal into smaller units. In order to calculate the dynamics within every unit, we employ a Monte-Carlo-molecular dynamics-ab-initio hybrid framework using real space periodic boundary conditions. By combining all the units, we simulate the diffraction pattern of a crystal larger than the transverse x-ray beam profile, a situation commonly encountered in femtosecond nanocrystallography experiments with focused x-ray free-electron laser radiation. Radiation damage is not spatially uniform and depends on the fluence associated with each specific region inside the crystal. To investigate the effects of uniform and non-uniform fluence distribution, we have used two different spatial beam profiles, Gaussian and flattop.