Early X-ray Research Articles

Radiographic Criteria for the Assessment of the Severity of Respiratory Distress Syndrome of the Newborn

Radiological diagnosis of respiratory distress syndrome of newborns (RDS) is an urgent task. The article presents clinical and radiological parallels of respiratory distress syndrome in newborns. X-ray criteria determining the degree of severity of RDS, allowing to improve early x-ray diagnosis, are identified. Taking into account the tasks in the Perinatal Center of Almazov National Medical Research Center 143 radiographs of newborns for 2017 with established diagnosis of RDS (boys n = 66, 46.2 %, girls n = 77, 53.8 %) were analyzed. The gestational age of newborns was 100 (69.9 %) children at the gestational age up to 32 weeks, and 43 (30.1 %) children at the age of 32 weeks. The body weight of the newborns was 1190 ± 510 g. The severity of neonates with RDS due to the severity of acute respiratory failure that determines the conduct of radiographic studies in the first 1-3 hours of a child’s life to solve the question about the choice of respiratory support and treatment with surfactants.

Exponentially Decaying Extended Emissions Following Short Gamma-Ray Bursts with a Possible Luminosity–E-folding Time Correlation

Abstract The origin of extended emissions following prompt emissions of short gamma-ray bursts (SGRBs) is a mystery. The long-term activity of the extended emission is responsible for promising electromagnetic counterparts to gravitational waves, thus it may be a key to uncovering the progenitor of SGRBs. We investigate the early X-ray light curves of 26 SGRBs with known redshifts observed with the X-Ray Telescope on board the Neil Gehrels Swift Observatory (Swift). We find that the exponential temporal decay model is able to describe the extended emission comprehensively, with a rest-frame e-folding time of 20–200 s. We also estimate the isotropic equivalent energies of the extended emission with the exponential decay model and of the prompt emission, and compare with those of the prompt emission. Then, it is revealed that the extended emission is 0–3 orders of magnitude less powerful than the prompt emission. We find a strong correlation between the expected maximum luminosity and e-folding time, which can be described by a power law with an index of −3.3 and whose chance probability is 8.2 × 10−6 if there is no observation bias of Swift. The exponential temporal decay may be interpreted as coming from the spin-down timescale of the rotation energy of a highly magnetized neutron star, and/or fallback accretion onto a disk surrounding a black hole with an exponentially decaying magnetic flux by magnetic reconnection.

Microblade technology, obsidian sourcing, and the Cody complex in early Holocene Alberta

Despite being an ephemeral presence in Plains archaeological assemblages, the distribution and technical specificity of early Holocene (Denali complex) microblade technology makes it readily identifiable and comparable to similarly-aged Paleoindian projectile point occurrences. In this paper we review the co-occurrence of Denali and Cody complex materials in Alberta, in particular the obsidian and Knife River Flint (KRF) artifacts of these two early Holocene archaeological complexes, employing both lab-based (EDXRF) and portable X-ray fluorescence (pXRF) analyses. A strong pattern is revealed of southern (Wyoming, Idaho, North Dakota) obsidian sources being limited to southern Alberta microblade and Cody artifacts while northern obsidian sources in British Columbia are only attributed to artifact assemblages from northwestern Alberta and northern British Columbia. Northeastern British Columbia and most of Alberta were ice free at 11,000–10,000 cal BP, and Denali-related artifacts across the deglaciated corridor area indicate southward movement of this technology at a time when the region was also being more broadly and intensively utilized by people using Cody complex technology. We offer scenarios to explain Denali and Cody complexes’ archaeological co-occurrence, while recognizing technical issues in pXRF source identification.

A study of the composite supernova remnant MSH 15–56 with Suzaku

The Galactic supernova remnant (SNR) MSH 15–56 is a member of the class of composite SNRs that consists of the remnant shell and a displaced pulsar wind nebula (PWN). The earlier X-ray observations reported the comet-like morphology of the PWN and the ejecta distribution of the SNR. In this work, we present a study of MSH 15–56 using archival Suzaku data. We investigate the nature of the emission and spectral parameters of the remnant. The X-ray spectra are well fitted with a combination of a thermal and non-thermal model with temperature ∼0.6 keV and photon index ∼2.0. The slightly enhanced abundances of Ne, Mg, S and enhanced abundance of Si confirm the presence of ejected material.

“A-OK”: Chest Radiograph during Primary Survey Facilitates Faster, More Accurate Endotracheal Tube Position in Injured Children

The Advanced Trauma Life Support algorithm recommends bedside confirmatory techniques to confirm correct endotracheal tube (ETT) depth, a critical component in the care of pediatric trauma patients. We hypothesized that bedside confirmatory techniques are inaccurate and that early chest X-ray (CXR) would overcome such inaccuracies, allowing for faster intervention of malpositioned ETTs. An "A-OK" algorithm of immediate CXR following intubation in injured children aged <16 years was implemented. Eligible patients the years before and after implementation were identified. The accuracy of bedside confirmatory techniques (use of length-based depths and auscultation of breath sounds) was assessed. Post-"A-OK" patients were compared with pre-"A-OK" controls regarding the speed of malpositioned ETT repositioning. Twenty-eight post-"A-OK" cases and 23 pre-"A-OK" controls were identified. The groups did not differ in baseline characteristics. Bedside confirmatory techniques were accurate in only 61 per cent (length-based depth) and 58 per cent (auscultation of breath sounds) of patients. Time to ETT repositioning was significantly longer in pre-"A-OK" controls than in post-"A-OK" cases (35.2 ± 15.9 minutes vs 21.1 ± 11.8 minutes, P = 0.03). Bedside confirmatory techniques to determine ETT positioning are inaccurate in children. Inclusion of CXR in the primary survey is safe and allows for more rapid repositioning of malpositioned ETTs.

Supermassive Black Hole feedback in early type galaxies

AbstractOptically luminous early type galaxies host X-ray luminous, hot atmospheres. These hot atmospheres, which we refer to as coronae, undergo the same cooling and feedback processes as are commonly found in their more massive cousins, the gas rich atmospheres of galaxy groups and galaxy clusters. In particular, the hot coronae around galaxies radiatively cool and show cavities in X-ray images that are filled with relativistic plasma originating from jets powered by supermassive black holes (SMBH) at the galaxy centers. We discuss the SMBH feedback using an X-ray survey of early type galaxies carried out using Chandra X-ray Observatory observations. Early type galaxies with coronae very commonly have weak X-ray active nuclei and have associated radio sources. Based on the enthalpy of observed cavities in the coronae, there is sufficient energy to “balance” the observed radiative cooling. There are a very few remarkable examples of optically faint galaxies that are 1) unusually X-ray luminous, 2) have large dark matter halo masses, and 3) have large SMBHs (e.g., NGC4342 and NGC4291). These properties suggest that, in some galaxies, star formation may have been truncated at early times, breaking the simple scaling relations.

Structural and Dynamic Properties of the High-Pressure, High-Temperature Phase of Solid Ammonia Borane

The increasing decomposition temperature of solid ammonia borane under high pressure introduces a solid–solid phase transition preceding decomposition. An earlier X-ray diffraction experiment sugge...

Тепловой эффект перехода моноклинной фазы в орторомбическую в сверхвысокомолекулярном полиэтилене

AbstractWe analyze heat effects associated with the solid-state phase transition in ultrahigh molecular weight polyethylene from the unstable monoclinic phase into thermodynamically stable orthorhombic phase. The model proposed here for the structure of supramolecular formations of monoclinic phase does not contradict to earlier X-ray diffraction data for this polymer.

On the Ultra-relativistic Prompt Emission, the Hard and Soft X-Ray Flares, and the Extended Thermal Emission in GRB 151027A

Abstract We analyze GRB 151027A within the binary-driven hypernova approach, with a progenitor of a carbon–oxygen core on the verge of a supernova (SN) explosion and a binary companion neutron star (NS). The hypercritical accretion of the SN ejecta onto the NS leads to its gravitational collapse into a black hole (BH), to the emission of the gamma-ray burst (GRB), and to a copious e + e − plasma. The impact of this e + e − plasma on the SN ejecta explains the early soft X-ray flare observed in long GRBs. Here, we apply this approach to the ultra-relativistic prompt emission (UPE) and to the hard X-ray flares. We use GRB 151027A as a prototype. From the time-integrated and the time-resolved analysis, we identify a double component in the UPE and confirm its ultra-relativistic nature. We confirm the mildly relativistic nature of the soft X-ray flare, of the hard X-ray flare, and of the extended thermal emission (ETE). We show that the ETE identifies the transition from an SN to a hypernova (HN). We then address the theoretical justification of these observations by integrating the hydrodynamical propagation equations of the e + e − into the SN ejecta, with the latter independently obtained from 3D smoothed particle hydrodynamics simulations. We conclude that the UPE, the hard X-ray flare, and the soft X-ray flare do not form a causally connected sequence. Within our model, they are the manifestation of the same physical process of the BH formation as seen through different viewing angles, implied by the morphology and the ∼300 s rotation period of the HN ejecta.

Observational constraints on the structure of gamma-ray burst jets

Motivated by GW170817 we examine constraints that observations put on the angular structure of long gamma-ray burst (GRB) jets. First, the relatively narrow observed distribution of $E_{X}/E_{\gamma}$ (the isotropic equivalent early X-ray afterglow to prompt $\gamma$-ray energy ratio) implies that at any angle that $\gamma$-rays are emitted the Lorentz factor must be high. Specifically, the Lorentz factor of $\gamma$-ray emitting material cannot drop rapidly with angle, and must be $\Gamma(\theta)\gtrsim 50$ even if there are angles for which the gamma-ray received energy is lower by three orders of magnitude compared to the jet core. Second, jets with an angular structure of the $\gamma$-ray emission that over-produce events with a $\gamma$-ray luminosity below the peak of the observed luminosity function are ruled-out. This eliminates models in which the $\gamma$-ray energy angular distribution isn't sufficiently steep and the Lorentz factor distribution isn't sufficiently shallow. Finally, models with a steep structure (e.g. Gaussian) which are detected away from the jet core generate afterglow light-curves that were never observed. We conclude that even if the jet kinetic energy distribution drops continuously with latitude, efficient $\gamma$-ray emission seems to be restricted to material with $\Gamma\gtrsim 50$ and is most likely confined to a narrow region around the core. While our study is confined to long GRBs, where the observed sample is larger and more complete, there are indications that similar conclusions may be applicable also to short GRBs. We discuss the possible implications to the $\gamma$-rays observed in GRB 170817A.

Bedside Ultrasonography for Early Diagnosis of Occult Radial Head Fractures in Emergency Room: A CT-Comparative Diagnostic Study.

Some of the Mason type I fractures cannot be detected on early radiographic images. These occult fractures are considered as a diagnostic challenge for physicians. Our aim was to determine the value of bedside ultrasonography for the detection of Mason I radial head fractures that are non-visible in early X-ray's. A prospective blind single-center diagnostic study was conducted (from June 2012 till May 2013) concerning 23 patients who were clinically suspicious of having a radial head fracture. These patients were evaluated with a bedside high frequency ultrasound in the Emergency Room (E.R.). The two sonographic criteria that were considered to be diagnostic for fracture were: a. effusion besides the radial head-neck and b. cortical discontinuity of the radial head or neck. All patients also underwent a Computed Tomography (CT) as the gold standard imaging modality for diagnosis of occult radial head fractures. Fifteen out of 23 patients were diagnosed with radial head fracture using both ultrasound and CT. On the other hand, there were three patients with negative ultrasound and positive CT, in addition two patients were found positive in the ultrasonographic exam, while this result was not confirmed by the CT scan. In comparison with CT, ultrasound exam appeared to have 83.3% sensitivity, 60% specificity, 88.2% positive prognostic value and 50% negative prognostic value (when at least one diagnostic sonographic criterion was positive). The accuracy of the sonographic study for the diagnosis of the aforementioned fractures was 78.2%. Effusion in contact with the radial neck was the most sensitive sonographic sign (14/15 of the true positive radial head ultrasounds). Bedside ultrasound in the E.R. was proven to be a sensitive tool for early (day-1) diagnosis of the occult radial head fractures. It could be used as an adjacent imaging modality in patients suspicious for radial head fracture, when the initial X-rays are negative. II.

Pull-out of Upper Thoracic Pedicle Screws Can Cause Spinal Canal Encroachment in Growing Rod Treatment.

Proximal foundation failure is a common complication of growing rod (GR) treatment for early-onset scoliosis. Spinal canal encroachment due to pull-out of pedicle screw used as proximal foundation has been anecdotally reported in GR patients. The aim of this study is to report the prevalence of spinal canal encroachment of pedicle screws in GR treatment and determine risk factors using a single-center cohort. Inclusion criteria were: (1) GR for early-onset scoliosis and (2) pull-out of at least 1 proximal anchor pedicle screw. Patients were divided into 2 groups according to the presence of medial screw migration. Medial migration of the screw was confirmed by computed tomography. The extracted data included demographic, clinical, and radiographic information. A total of 21 patients (of 96) met inclusion criteria (21.8%). None of the screws appeared malpositioned on early postoperative x-ray. Average follow-up until screw failure was 50.4 months (64 to 85 mo) and average number of lengthenings 8.1 (4 to 13). Computed tomography revealed canal encroachment in 11 patients (group 1), and no encroachment in 10 (group 2). There was no significant difference between groups for age, follow-up or number of lengthenings. At the time of screw pull-out, coronal plane deformity was increased compared with early postoperative x-ray in all; however, this increase was significantly higher in group 1 (45.7 vs. 35 degrees, P=0.002). Proximal junctional angle (PJA) was increased in both groups at the time of pull-out. While not statistically significant, PJA increased linearly in group 1 but spiked in group 2 at the time of pull-out. There was no neurological event preoperatively, intraoperatively or postoperatively. Failed screws were safely revised in either planned/unplanned surgeries. In patients with proximal anchor failure of GR, especially if there is increase of coronal deformity and/or PJA, possible spinal encroachment should be kept in mind. Level IV-retrospective case series.

Routine early post-operative X-ray following internal fixation of intertrochanteric femoral fractures is unjustified: a quality improvement study

BackgroundThere is no consensus regarding the proper radiographic protocol following closed or open reduction and internal fixation for intertrochanteric femoral fractures. The objective of this study was to assess the role of early postoperative imaging studies when deciding about weight bear limitations and reoperations.MethodsA prospective cohort study of 100 patients (26 men and 74 women, at a mean age of 79.8 years) treated by closed or open reduction and internal fixation for AO31A fractures was conducted. According to the AO classification, there were 25 cases of 31A1, 54 cases of 31A2, and 21 cases of 31A3. For every patient, the intraoperative fluoroscopy studies were recorded and post-operative radiograms were taken during the first week. Excluded were patients for whom the early X-rays were clinically indicated. The intraoperative AP and axial fluoroscopy studies were compared with the radiograms taken during the first post-operative week. The investigators compared the decisions regarding weight-bearing limitations and the need for re-operation before and after conducting the radiograms.ResultsThe early post-operative imaging studies did not change weight-bearing limitations nor did they lead to consecutive surgical treatments.ConclusionsUnless indicated by physical examination, there is no value to routine post-operative radiograms within the first few days after closed reduction and internal fixation of intertrochanteric femoral fractures with regard to weight-bearing limitations and re-operation decisions.Trial registrationIdentifier: NCT02868125.

The Preoperative Microbial Detection is No Prerequisite for the Indication of Septic Revision in Cases of Suspected Periprosthetic Joint Infection.

Aim of This Study Periprosthetic joint infections (PJIs) require a special antimicrobial regimen, fundamentally different from an aseptic treatment, making a correct preoperative diagnosis essential. However, a successful preoperative microbe detection is not always possible. We wanted to find out (1) if a preoperative microbe detection is a prerequisite before starting a septic revision in suspected PJIs or if the preoperative diagnosis can solely be based on (para)clinical signs (persistent CRP >1 mg/dl, early X-ray loosening signs in the first 5 years, leucocytes joint aspiration >1700/µl, conspicuous history, and clinical signs like redness, pain, hyperthermia, swelling, and loss of function); (2) if patients with and without preoperative microbe detection have a different outcome; and (3) if the microbial growth is the most important criterion of a multifactorial PJI definition. Methods We included all first-line two-stage hip (49) and knee (47) revisions, performed in our department from 06/2013 on, with an available 2-year follow-up. A PJI was defined as one of the following four criteria: fistula or purulence, Krenn Morawietz type 2 or 3, joint aspirate > 2000/μl leukocytes or >70% granulocytes, and microbial growth. This multifactorial PJI definition was based on the European Bone and Joint Infection Society (EBJIS). The standardized diagnostic algorithm is described in detail. Results (1) 24 hip and 16 knee cases were treated without preoperative microbe detection solely on the basis of a (para)clinical diagnosis (see above). In the hip 91.6% (22 of 24 cases) showed an intraoperative microbe detection. In the knee, in 68.7% (11 of 16 cases) a microbe was detected intraoperatively and in 93.7% (15 of 16) at least one secure PJI criterion could be confirmed intraoperatively. (2) No statistical significant (p .517) difference between patients with (n = 56, reinfection rate 8.9%) and without (n = 40, 15%) preoperative microbe detection was found in a 2-year follow-up. (3) Microbial growth remains the overall (pre- and intraoperatively) most important criterion (hip 95.9%; knee 89.3%), followed by Krenn Morawietz for the intraoperative diagnosis (hip 67.3%, knee 48.9%), and joint aspiration for the knee and fistula for the hip, respectively, as preoperative criteria. Conclusion High rates of intraoperatively fulfilled EBJIS PJI criteria show that a preoperative microbe detection is not necessary before intervening in suspected PJIs. The indication for a septic revision can solely be based on (para)clinical signs. The new established diagnostic algorithm based on a multifactorial PJI definition showed high precision in finding PJIs.

Alan Archibald Campbell-Swinton (1863–1930) Electrical engineer

Alan Archibald Campbell-Swinton was an electrical engineer, holding memberships of the Institutes of Civil Engine­ering, Electrical Engineering and Mechanical Engineering; as well being a Fellow of the Royal Society. He was also one of the early non-medical X-ray experimenters and is notable for producing the first X-ray image in the United Kingdom, on 8 January 1896. He was active in the Röntgen Society of London and became its President in 1911–1912. One of his major interests was the theory of television production. Campbell-Swinton ended his scientific career as a consulting engineer in London. This brief biography gives special reference to Campbell-Swinton’s work with X-rays.

Traumatic aortic injury presenting to an adult major trauma centre

Introduction Traumatic aortic injury is an uncommon condition. Timely diagnosis may enable early haemostatic resuscitation, essential to prevent worsening of the injury prior to definitive management. The aim of this study was to assess the utility of initial vital signs and presenting clinical characteristics to confirm or rule out aortic injury. Methods A retrospective review of patients from The Alfred Trauma Registry was conducted. Patients presenting between January 2006 and July 2014 and diagnosed with aortic injury were identified. Demographics and presenting clinical characteristics were extracted. Sensitivity of individual clinical variables for the detection of aortic injury was calculated. Results There were 77 patients identified with aortic injury, with an in-hospital mortality rate of 19.5% (95% CI: 10.6–28.3%). Of these, 68 (88.3%) patients presented after high-energy blunt mechanisms. Clinical signs and early chest X-ray findings were poorly sensitive to detect aortic injury. Patients who presented with hypotension had a greater severity of aortic injury, more commonly had associated abnormal investigation findings and were more likely to require blood products and inotropic agents (p &lt; 0.05). However, sensitivity of initial hypotension to rule out aortic injury was 39.0% (95% CI: 28.1–49.9%). Conclusions The diagnosis of aortic injury was uncommon in hospital. Most injuries were secondary to high-velocity road traffic crashes or high falls. Clinical signs were not adequately sensitive to be used for the exclusion of aortic injury. We recommend a high degree of clinical suspicion and liberal imaging among cases where aortic injury is possible.

Surface Oxidation of Pt(111) Studied By Surface X-Ray Diffraction and Grazing-Incidence Small-Angle X-Ray Scattering

Electrochemical growth of Pt oxide is important because of its role in the oxygen-reduction reaction (ORR) and in Pt dissolution, which affect the performance and durability of PEM fuel cell Pt electrocatalysts. It has been known for a long time that potential cycling leads to a restructuring of the surface, in which Pt atoms move away from their lattice sites. The details of this process have not been fully resolved, though early surface X-ray diffraction (SXRD) studies confirmed the key role of a "place exchange" in which Pt and O (or OH) species exchange places [1]. Reported here are in-situ SXRD and Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) studies of Pt(111) electrodes in 0.1 M HClO4 carried out at the European Synchrotron Radiation Facility [2-6]. The atoms are located by a crystal-truncation rod analysis, which shows that the place-exchanged Pt is located directly above its original lattice site. Simultaneous cyclic voltammograms of current and the intensity of the (1,1,1.5) reflection associate the initiation of the place exchange with the "oxide" peak at 1.05 V vs RHE. The voltammogram is unchanged by cycling to 1.15 V, as the place exchange is reversed on the reduction cycle, albeit with significant hysteresis. Cycling to higher potentials leads to irreversible changes to the surface, which were studied in detail with GISAXS. GISAXS probes the evolution of nanoscale features on the surface. Progressive surface roughening occurs with cycling, to an extent that is dependent on the upper reversal potential (E up). The average spacing of the islands ranges from 40-70 Å for E up from 1.4-1.6 V, with smaller spacing for higher potentials. The spacing increases slightly with cycle number but is mainly determined after the first cycle. The islands grow in height and become more prominent and homogeneous in size with the number of cycles. These changes are similar to the evolution of Pt surfaces in UHV undergoing deposition of Pt or surface erosion, showing that the underlying processes such as vacancy coalescence are common for the UHV and electrochemical cases. SXRD experiments in the presence of oxygen show no effect on the place exchange during cycling. The oxygen reduction current decreases at potentials more negative than the initiation of the place exchange, showing that it is limited by the adsorbed intermediate(s) in the ORR (likely OH) and not Pt oxide formation. The authors thank the European Synchrotron Radiation Facility, Deutsche Forschungsgemeinschaft, and the Natural Sciences and Engineering Research Council of Canada for support. [1] H. You, D.J. Zurawski, Z. Nagy, R.M. Yonco, J. Chem. Phys., 100, 4699 (1994). [2] J. Drnec, M. Ruge, F. Reikowski, B. Rahn, F. Carlà, R. Felici, J. Stettner, O.M. Magnussen, D.A. Harrington, Electrochim. Acta, 224, 220 (2017).[3] M. Ruge, J. Drnec, B. Rahn, F. Reikowski, D.A. Harrington, F. Carlà, R. Felici, J. Stettner, O.M. Magnussen, J. Am. Chem. Soc., 139, 4532 (2017).[4] M. Ruge, J. Drnec, B. Rahn, F. Reikowski, D.A. Harrington, F. Carla, R. Felici, J. Stettner, O.M. Magnussen, J. Electrochem. Soc., 164, H608 (2017).[5] J. Drnec, M. Ruge, F. Reikowski, B. Rahn, F. Carlà, R. Felici, J. Stettner, O.M. Magnussen, D.A. Harrington, Pt oxide and oxygen reduction at Pt(111) studied by SXRD, Electrochem. Comm., 84, 50 (2017).[6] J. Drnec, D.A. Harrington, O.M. Magnussen, Current Opinion in Electrochemistry, (2017), doi:10.1016/j.coelec.2017.09.021

Imaging findings of bone infarction in children with systemic lupus erythematosus

To investigate diagnostic value of MRI, X ray and CT for bone infarction in children with systemic lupus erythematosus. Eleven systemic lupus erythematosus children with bone infarction were retrospectively analyzed from January 2015 to January 2017 , and tested by MRI, X-ray and CT. Among them, including 1 male and 10 females aged from 6 to 16 years old with an average of 13 years old. All patients were detected by MRI, 9 patients were detected by X-ray and 3 patients were detected by CT, imaging findings were analyzed. The location of bone infarction involved 60 sits, 30 sites located on metaphyseal-diaphyseal region, 8 located on patella, 21 located on epiphysis, and 1 located on talus. Focus of 11 patients were detected by MRI, the main manifestation showed geographic change, long T1 and T2 signal could seen around focus, and showed double ring sign and three ring sign; 5 of 9 patients by X-ray examination detected focus;2 of 3 patients by CT examination detected focus. No abnormity seen at early stage by X-ray and CT examination, and low density focus around harden edge at chronic stage. MRI could display bone fracture at early stage, X-ray and CT could only display lesion at chronic stage, MRI is the most effective method in diagnosing bone infarction.

Simultaneous Orientational and Conformational Molecular Dynamics in Solid 1,1,2-Trichloroethane

The molecular dynamics in the ambient-pressure solid phase of (1,1,2)-trichloroethane is studied by means of broadband dielectric spectroscopy and molecular dynamics simulations. The dielectric spectra of polycrystalline samples obtained by crystallization from the liquid phase exhibit, besides a space-charge relaxation associated with accumulation of charges at crystalline domain boundaries, two loss features arising from dipolar molecular relaxations. The most prominent and slower of the two loss features is identified as a configurational leap of the molecules which involves a simultaneous change in spatial orientation and structural conformation, namely between two isomeric forms (gauche$^+$ and gauche$^-$) of opposite chirality. In this peculiar dynamic process, the positions of the three chlorine atoms in the crystal lattice remain unchanged, while those of the carbon and hydrogen atoms are modified. This dynamic process is responsible for the disorder observed in an earlier x-ray diffraction study and confirmed by our simulation, which is present only at temperatures relatively close to the melting point, starting 40 K below. The onset of the disorder is visible as an anomaly in the temperature dependence of the dc conductivity of the sample at exactly the same temperature. While the slower relaxation dynamics (combined isomerization/reorientation) becomes increasingly more intense on approaching the melting point, the faster dynamics exhibits significantly lower but constant dielectric strength. Based on our molecular dynamics simulations, we assign the faster relaxation to large fluctuations of the molecular dipole moments, partly due to large-angle librations of the chloroethane species.

Special gamma-ray bursts and special radiation components from gamma-ray bursts

Gamma-ray bursts (GRBs) were first detected in 1960s. Since then, GRBs have been observed extensively in gamma-rays. The afterglows of several hundred GRBs were also detected, providing us with abundant clues for understanding the physics of GRBs. However, X-ray observations of GRBs at the prompt burst phase are still quite lacking. These very early X-ray observations should be very important for probing the activities of GRB central engines. The Einstein Probe, a unique satellite that works mainly in soft X-rays (0.5–4 keV) with a large field of view (1.1 sr), will open up a new window for us to observe the prompt X-ray emission of GRBs. In this article, we review the current status of the studies on some special kinds of GRBs such as those rich in X-rays and those baring special emission components. Especially, we investigate possible contributions of EP to the studies of X-ray flashes (XRFs), low-luminosity GRBs, ultra-long GRBs, and the precursors of GRBs. It is found that: (1) EP is expected to detect about 810 GRB-like events, among which 95% are soft XRFs and only 1% are typical GRBs; (2) EP could detect 0.2–8 low-luminosity GRBs each year (the exact detection rate is strongly dependent on the exact spectral distribution of low luminosity GRBs, which is still largely uncertain currently); (3) EP would detect at least 20–200 ultra-long GRBs each year; (4) EP may be able to detect a lot of GRB precursors (at least 80 events per year), which are still poorly understood. We believe that the EP satellite will lead to encouraging discovers and will deepen our understanding of GRBs in various aspects such as their classifications, their progenitors, the triggering mechanisms and the beaming features, etc. We also note that the EP satellite has great advantages on its wide field of view and good sensitivity, over other similar world-wide instruments. We suggested that the project should be carried out as soon as possible.