bluuebunny/crossref_metadata_2025 huggingface dataset:
The Pristine survey. XXVI. Chemical abundances of subgiant stars of the extremelymetal-poor stream C-19
Authors: Bonifacio P. , Caffau E. , Franois P. , Martin N. , Ibata R. , Yuan Z. , Kordopatis G. , Gonzalez Hern'andez J.I. , Aguado D.S. , Thomas G.F. , Viswanathan A. , Dodd E. , Gran F. , Starkenburg E. , Lardo C. , Errani R. , Fouesneau M. , Navarro J.F. , Venn K.A. , Malhan K.
Published: December 2024

The C-19 stellar stream is the most metal-poor stream known to date. While its width and velocity dispersion indicate a dwarf galaxy origin, its metallicity spread and abundance patterns are more similar to those of globular clusters (GCs). If it is indeed of GC origin, its extremely low metallicity ( Fe/H =--3.4, estimated from giant stars)
implies that these stellar systems can form out of gas that is as extremely poor in metals as this. Previously,
only giant stream stars were observed spectroscopically, although the majority
of stream stars are unevolved stars. We pushed the spectroscopic observations to the subgiant branch stars
(G≈ 20) in order to consolidate the chemical and dynamical properties
of C-19. We used the high-efficiency spectrograph X-shooter fed by
the ESO 8.2,m VLT telescope to observe 15 candidate subgiant C-19 members. The spectra were used to measure radial velocities and to determine chemical abundances using the code. We developed a likelihood model that takes metallicity and radial velocities into account. We conclude that
12 stars are likely members of C-19, while 3 stars
(S05, S12, and S13) are likely contaminants.
When these 3 stars are excluded, our model
implies a mean metallicity
rm 〈 Fe/H 〉 = -3.1± 0.1, the mean radial velocity is
〈 v_r〉=-192±3 and the velocity dispersion is vr . This all agrees within errors with previous studies. The A(Mg) of a sample of 15 C-19 members, including 6 giant stars, shows a standard deviation of 0.44,dex, and the mean uncertainty on Mg is 0.25,dex. Our preferred interpretation of the current data is that C-19 is a disrupted GC.
We cannot completely rule out the possibility that the GC could have belonged to a dwarf galaxy that contained more metal-rich stars, however. This scenario would explain
the radial velocity members at higher metallicity, as well as the width and velocity dispersion of the stream. In either case, a GC formed out of gas as poor in metals as these stars seems necessary to explain the existence of C-19.
The possibility that no GC was associated with C-19 cannot be ruled out either.
Illuminated granular water ice shows ‘dust’ emission
Authors: Kreuzig C. , Brecher J. N. , Meier G. , Schuckart C. , Molinski N. S. , Pfeifer J. , Markkanen J. , Knoop C. , Timpe M. , Goldmann M. , Knollenberg J. , Gundlach B. , Blum J.
Published: December 2024

Context. Water ice in micro-granular form is the most common volatile in comets, and its behaviour when approaching the Sun must be understood before cometary activity can be properly modelled.

Aims. To assess the properties of granular water ice, we investigated its evolution under illumination in a cryogenic high-vacuum environment.

Methods. We produced a sample of water ice consisting of micrometre-sized particles, placed it inside a thermal vacuum chamber, and exposed it to high-intensity visible/near-infrared (VIS/NIR) illumination. Due to the energy absorption within the NIR bands of the ice, the sample is locally heated, which causes evaporation close to the surface. The total mass loss of the irradiated sample was measured using a scale and the surface temperatures were recorded with an infrared camera. Furthermore, we used several cameras to observe surface changes and ejected solid particles.

Results. We derived the mass loss due to water-ice sublimation from the spatially resolved surface temperatures. This mass loss amounts to 68%–77% of the total mass loss. The remaining fraction (between 23% and 32%) of the mass is ejected in solid particles, which can be seen by the naked eye.

Conclusions. The self-ejection of water-ice grains can be explained by a geometrical model that describes the sublimation of the icy constituents of the sample, taking into account the size distribution of the water-ice particles and the volume filling factor (VFF) of the sample. According to this model, solid ice particles are emitted when they (or the particle cluster they belong to) lose contact with the sample due to the faster evaporation of a smaller connecting ice grain. We discuss the possible relevance of this process for cometary dust activity.
Molecular chemistry induced by a J-shock toward supernova remnant W51C
Authors: Tu Tian-Yu , Wakelam Valentine , Chen Yang , Zhou Ping , Zhang Qian-Qian
Published: December 2024

Context. Shock waves from supernova remnants (SNRs) strongly affect the physical and chemical properties of molecular clouds (MCs). Shocks propagating into magnetized MCs can be classified into jump or J-shocks and continuous or C-shocks. The molecular chemistry in the re-formed molecular gas behind J-shocks is still only poorly understood. It is expected to provide a comprehensive view of the chemical feedback of SNRs and the chemical effects of J-shocks.

Aims. We conducted a W-band (71.4–89.7 GHz) observation toward a re-formed molecular clump behind a J-shock induced by SNR W51C with the Yebes 40 m radio telescope to study the molecular chemistry in the re-formed molecular gas.

Methods. Assuming local thermodynamic equilibrium (LTE), we estimated the column densities of HCO+, HCN, C2H and o-c-C3H2, and derived their abundance ratio maps with CO. The gas density was constrained by a non-LTE analysis of the HCO+ J = 1–0 line. The abundance ratios were compared with the values in typical quiescent MCs and shocked MCs, and they were also compared with the results of chemical simulations with the Paris-Durham shock code to verify and investigate the chemical effects of J-shocks.

Results. We obtained the following abundance ratios: N(HCO+)/N(CO) ~ (1.0–4.0) × 10−4, N(HCN)/N(CO) ~ (1.8–5.3) × 10−4, N(C2H)/N(CO) ~ (1.6–5.0) × 10−3, and N(o-c-C3H2)/N(CO) ~ (1.2–7.9) × 10−4. The non-LTE analysis suggests that the gas density is nH2 ≳ 104 cm−3. We find that the N(C2H)/N(CO) and N(o-c-C3H2)/N(CO) are higher than typical values in quiescent MCs and shocked MCs by 1–2 orders of magnitude, which can be qualitatively attributed to the abundant C+ and C in the earliest phase of molecular gas re-formation. The Paris-Durham shock code can reproduce, although not perfectly, the observed abundance ratios, especially the enhanced N(C2H)/N(CO) and N(c-C3H2)/N(CO), with J-shocks propagating into both nonirradiated and irradiated molecular gas with a preshock density of nH = 2 × 103 cm−3.
The IACOB project
Authors: Martínez-Sebastián C. , Simón-Díaz S. , Jin H. , Keszthelyi Z. , Holgado G. , Langer N. , Puls J.
Published: December 2024

There is increasing evidence that single-star evolutionary models are unable to reproduce all of the observational properties of massive stars. Binary interaction has emerged as a key factor in the evolution of a significant fraction of massive stars. In this study, we investigate the helium (YHe) and nitrogen (ϵN) surface abundances in a comprehensive sample of 180 Galactic O-type stars with projected rotational velocities of ≤150 km s−1. We found a subsample (∼20% of the total, and ∼80% of the stars with YHe ≥ 0.12) with a YHe and ϵN combined pattern that is unexplainable by single-star evolution. We argue that the stars with anomalous surface abundance patterns are binary interaction products.
Development of a Novel Horner–Wadsworth–Emmons Reagent for the Facile Preparation of Mixed Phosphonoacetates
Authors: Nakao Michiyasu , Okamoto Marie , Isetani Satoshi , Imai Ayato , Kitaike Syuji , Sano Shigeki
Published: December 2024

A novel Horner–Wadsworth–Emmons (HWE) reagent, methyl 2-[bis(3,4,5-trifluorophenoxy)phosphoryl]acetate, was synthesized by the reaction of methyl 2-(dichlorophosphoryl)acetate and 3,4,5-trifluorophenol. Sequential alcoholysis of this HWE reagent with isopropyl alcohol and benzyl alcohol on the phosphorus atom afforded the mixed phosphonoacetate, methyl 2-[(benzyloxy)(isopropoxy)phosphoryl]acetate, in 89% yield for the two steps.
Comparison of Adaptive and Nonadaptive Gap Detection in Noise Test in Typically Developing Children and Adults
Authors: Veeranna Sangamanatha Ankmnal , Christensen Lyerly , Candace-Ann Chapman Jennifer
Published: December 2024

Purpose The purpose of this study is to examine whether the gap detection thresholds (GDT) obtained are similar between an adaptive and nonadaptive procedure in children and adults.

Study Design Standard group comparison.

Study Sample Eighteen typically developing children and 20 young adults with hearing thresholds of 25 dB HL or lower participated in this study.

Methods Forced choice (FC) adaptive GDTs were obtained using psychoacoustic software, and nonadaptive GDTs were obtained using a clinically available gap in noise (GIN) test.

Results Both children and adults showed significantly lower GDTs for the FC adaptive procedure when compared with thresholds obtained using the nonadaptive GIN test. GDTs were less variable for FC adaptive procedure when compared with the nonadaptive procedure.

Conclusion Lower and less variable GDTs can be obtained from children and adults using an FC adaptive procedure.
Prevalence of Burnout and Job Satisfaction Among Interventional Radiologists in Saudi Arabia
Authors: Justaniah Almamoon I. , Aljohani Renad M. , Alzelfawi Lama A.
Published: December 2024

Purpose To evaluate the prevalence of burnout and job satisfaction among interventional radiologists (IRs) in Saudi Arabia.

Methods A cross-sectional survey was conducted in June 2023 among IRs in Saudi Arabia. An online survey was sent to the IR members of the Saudi Interventional Radiology Society via WhatsApp using Google Forms. The survey consisted of a Likert scale satisfaction questionnaire, Maslach Burnout Inventory questionnaire, demographics, and general questions. Statistical analysis was performed; p <0.05 was considered significant when correlating between variables.

Results A total of 80/178 responses were received (44.9%), the majority were men (93.8%). The age group with the highest representation was 30 to 40 years (60%). Those between the ages of 30 and 40 had a higher (mean (standard deviation [SD])) depersonalization (DP) score (9 (3.6)) than those 51 and older (6.8 (4.5)). In addition, those who were practicing IR for 0 to 4 years (9.4 (3.5)) reported more DP than other participants (p = 0.007). Individuals who slept less than 5 hours per day had lower mean personal accomplishment. Most participants (76.3%) expressed satisfaction with their career choice, and 35% were satisfied with hospital staff appreciation, with neutral satisfaction levels for job salary and work/life balance.

Conclusion The study shows that about half of the IRs in Saudi Arabia have high levels of burnout. Most of them were satisfied with IR as a career choice, while less than a third were dissatisfied with both salary and work/life balance.
Rheolytic Pharmacomechanical Thrombectomy in Renal Dialysis Arteriovenous Fistula and Graft Thrombosis: Outcomes from a Tertiary Hospital in Qatar
Authors: Yasin Ahmad L. F. , Zoghoul Sohaib , Al-Ekeer Ahmad N. , M. Alahmad Yaman , Barah Ali , Rehman Saad , Almokdad Omran , Al-Debyani Qayed , Elmagdoub Ayman , Kassamali Rahil Hussein
Published: December 2024

Purpose To investigate the ability to salvage an acutely thrombosed dialysis access using rheolytic pharmacomechanical thrombectomy (PMT), the short- and medium-term patency rates and safety at a tertiary care hospital.

Methods A retrospective review of all patients who underwent rheolytic PMT for a thrombosed arteriovenous fistula (AVF) or arteriovenous graft (AVG) from October 2020 to 2023 was performed. Primary patency was defined as the ability to successfully dialyze through the treated access site without further intervention. Secondary patency included patients who required additional interventions that enabled them to continue dialysis. Data analysis was conducted using SPSS for comprehensive statistical evaluation.

Results A total of 37 thrombectomy procedures, involving 15 AVF and 22 AVG cases, were performed on 31 patients; 20 males and 11 females with a mean age of 62 ± 13 years. The average time from recognizing dialysis access site dysfunction to intervention was 2.6 ± 1.4 days. The mean total rheolytic PMT run time was 295 ± 119 seconds. Immediate technical success was defined as restoration of flow between the arteriovenous anastomosis and the central veins. Technical success was achieved in 91.9% (34/37) of thrombectomies. Clinical success was defined as the ability to achieve successful dialysis within 48 hours of the intervention. In total, 72.9% (27/37) of these cases achieved clinical success. Primary patency rates at 1, 3, and 6 months were 87.5, 78, and 46.9%, respectively. Secondary patency rates at 3, 6, and 12 months were 87.5, 66.7, and 58.3%, respectively. Angioplasty was performed in all procedures, and stent insertion was required in 13.5% (5/37) of thrombectomies.

Conclusion This study adds to the evidence that rheolytic PMT is a safe and effective tool for AVF and AVG salvage. After an initial thrombosis, the chance of re-thrombosis within 12 to 24 months is high and teams looking after these patients should have a strategy for future dialysis access.
Aortic Endograft Sizing
Authors: Ray Andrew T. , Wilkins Luke R. , Sheeran Daniel P. , Clouse W. Darrin , Angle J. Fritz
Published: December 2024

Thoracic endovascular aortic repair (TEVAR) and endovascular abdominal aortic aneurysm repair (EVAR) have become widely accepted techniques for the treatment of aortic aneurysms and dissections. Central to the success of TEVAR and EVAR is accurate endograft sizing. Key aspects to be discussed in this article include the importance of preprocedural centerline imaging with computed tomography angiography to evaluate the proximal and distal seal zones. This article will review TEVAR and EVAR endograft sizing, providing the interventionalist with practical advice to optimize patient selection and to improve procedural success.
Nonlinear interaction of transverse and longitudinal sound waves in metals
Authors: Demikhovskii V. Ya. , Kukushkin V. A.
Published: December 2024

The influence of a strong longitudinally or transversely polarized sound wave on the propagation of weak transverse sound in metals is investigated. It is assumed that the ratio of the wave numbers of the strong and weak waves is equal to an integer or a half-integer. Under nonlinearity conditions, when resonant electrons are trapped by the field of the strong wave, the electromagnetic and deformation coefficients of gain and attenuation of the weak wave are determined. It is shown that the weak sound can be amplified under the conditions w1≲|w1−w|≪1/q1τr,ωr/qc(w/vF)1/2≫1,w1<w, in which case the gain is determined by its deformation part, which is proportional to the parameters ω0τr≫1 (q1, w1 and q, w are the wave numbers and velocities of the weak sound and the strong wave, respectively, ω0 is a typical oscillation frequency of the trapped particles, and τr is the relaxation time). The results of the calculations are compared with experimental data.
Structure factor of two-parameter solitons in an anisotropic one-dimensional spin chain in a magnetic field
Authors: Dzyub I. P. , Zerov Yu. É.
Published: December 2024

The soliton contribution to inelastic scattering of neutrons is calculated in the case of a one-dimensional ferromagnet with a single-ion anisotropy of the “easy plane” type. It is shown that a secondary peak associated with the coherent contribution of soliton-forming spins to the scattering should be observed in the vicinity of the one-magnon peak in the spectrum of scattered neutrons for momentum transfers Q in certain intervals Q0 < Q < Qm.
Surface effects and the specific heat of layered crystals at low temperatures
Authors: Kosevich Yu. A. , Syrkin E. S.
Published: December 2024

We derive the dispersion curve for Rayleigh waves taking account of the surface tension in strongly anisotropic crystals. We calculate the contribution ΔCs which these waves make to the low temperature specific heat of such crystals. The observed tendency for ΔCs to increase as the anisotropy increases agrees with previously reported numerical calculations for the surface contribution to the specific heat, ΔC(T). We discuss the connections among the temperature of the inflection on the bulk specific heat curve, the temperature of the maximum on the ΔC(T) curve, and the anisotropy parameter.
Magnetic susceptibility of alpha oxygen
Authors: Ostrovskii V. S.
Published: December 2024

The behavior of the spin configuration of easy-axis and biaxial antiferromagnets in an arbitrarily directed magnetic field is considered. The earlier observed field dependence of the susceptibility of polycrystalline alpha oxygen can be explained as a result of competition between two spin-flip mechanisms which are effective at different orientations of the crystal in various field strengths. The critical spin-flop field has been found to be in the range 65–70 Oe.
Influence of a magnetic field and simple tension on the resistance of tin whiskers
Authors: Gaidukov Yu. P. , Danilova N. P. , Nikiforenko E. V.
Published: December 2024

The influence of size, magnetic field, and simple tension on the resistance of white tin whiskers has been investigated. Elastic strain measurements were conducted at maximum specific elongations of 2–4% in magnetic fields of up to H = 55 kOe at T = 4.2 °K. The samples, which were 0.8 to 4.3 µm thick, were oriented along the [001] and [100] axes. Size effects were detected in the resistance and magnetoresistance of the whiskers. The main effect is the absence of a strong anisotropy in the magnetoresistance (such anisotropy is typical of bulk specimens) up to Hd ≈ 2 Oe·cm. At elongations of up to 4% specimens with a [001] orientation underwent elastic twinning. The body of experimental data on elastic elongation up to 2% in the case of [100] specimens did not provide evidence of a transition of order 2 1/2.
Law of variation of the specific heat C
v of quantum crystals near the melting point
Authors: Udovidchenko B. G.
Published: December 2024

An approach to the analysis of the lattice dynamics of quantum crystals near the melting line is presented which allows the establishment of the nature of the temperature dependence of the specific heat Cv of such crystals in the indicated temperature range. A comparison of the experimental Cv data available on 3He, 4He, and p-H2 in a density range whose upper limit is roughly 1.5 times higher than the lower limit indicates that the law of variation obtained for the Cv of quantum crystals in the limit T→Tm is obeyed in a temperature range that broadens with increasing crystal density, its width attaining a value of 0.42 Tm in the case of p-H2 at Pm ∼2400 bar.
Transverse focusing of electrons in the presence of nonstationary emitter currents
Authors: Kolesnichenko Yu. A.
Published: December 2024

Transverse focusing of electrons in the presence of nonstationary emitter currents is investigated theoretically under the assumption that the size of the contact b exceeds the effective skin-layer depth δ. It is shown that if the voltage on the emitter changes with frequency ω exceeding the inverse time of flight of the electron through the region at the emitter ω0−1≈b/υF then there is no focusing effect (υF is the Fermi velocity). In the frequency interval Ωω0<ω<ω0 (Ω is the Larmor frequency of the electron), the height of the peak of transverse focusing of electrons depends considerably on the magnitude of ω.
Quantum diffusion in irregular crystals
Authors: Kagan Yu.
Published: December 2024

The quantum subbarrier diffusion of atoms in crystals with defects is considered at low temperatures. A characteristic feature of the problem is that the amplitude of the tunneling transition is small in comparison with all the energy parameters of the problem. This makes it possible to develop a general method on the basis of the use of the kinetic equation for the density matrix. It is shown that even when the defect concentration x is low the band mechanism of motion is disrupted and at some value x = xc ≪ 1 and T = 0 localization of particles occurs. Interaction with phonons at T ≠ 0 removes the localization and at low temperatures leads to the relation D ∼ T9 (two-phonon processes are decisive) for the quantum diffusion coefficient D instead of the familiar law D ∼ T−9 for an ideal crystal. In the limit of the lowest temperatures two-phonon processes become decisive, as a result of which D ∼ T. With increasing temperature, when the dynamic destruction of the bands begins to exceed the static destruction, upon passing through a sharp maximum the diffusion coefficient begins to fall according to the law that is characteristic of a regular crystal. We analyze the effect of localization that occurs in a system of interacting particles diffusing in a strictly regular crystal with an extremely small value of the band width. The latter is responsible for the very weak role of collective processes and one-particle motion proves to be analogous to the motion of particles in an irregular crystal. This leads to localization and to phonon-induced delocalization, similar to that described above. Predicted theoretically earlier, this effect was recently discovered by V. Mikheev et al. during the investigation of the diffusion of 3He in the crystal lattice of 4He. The experiments established a pronounced tendency toward localization when x ≥ 4% and confirmed the D ∼ T9 law. A theory of recombination during a chemical reaction in a crystal at low temperatures has been constructed. The kinetics-limiting factor has been shown to be quantum diffusion which inevitably occurs under the conditions when levels in neighboring potential wells are disrupted, since the particles should draw nearer by an interatomic spacing. It has been established that in the low-temperature limit the recombination rate depends on the temperature only according to a power law and not an exponential relation. This picture of the kinetics was recently detected experimentally during an investigation of the recombination of hydrogen atoms in the crystal lattice of molecular hydrogen. (I. Lukaszewicz, W. Sklarewski, et al.). It is shown how the experimentally discovered anomalous picture of the diffusion of positively charged muons can be explained adequately within the framework of the theory developed for subbarier diffusion in irregular crystals.
The crystal and liquid phases of a pion condensate
Authors: Dyugaev A. M.
Published: December 2024

Critical effects that occur during the π-condensate phase transition are considered. Near the transition point the effective π–π interaction in nuclear matter changes sign. The transition is first-order (almost second-order) with a small jump in the pion field. Depending on the relation between the characteristic pion frequency Δ and the temperature T there exist three phases of matter: a quantum pion gas Δ ≫ T, a classical pion fluid Δ ≪ T, and a pion crystal. The melting point of the pion lattice is very low while the jumps in the entropy and the compressibility on the melting curve are large.
Hydrodynamics of superfluid liquid crystals
Authors: Meierovich A. É.
Published: December 2024

A system of hydrodynamic equations has been obtained for superfluid Fermi systems with singlet pairing and nonzero momentum which are formed, e.g., in the case of small polarization of the spin system. As a result, the energy gap is a periodic function of the coordinates and a spin-density wave is formed. For such systems the complete set of dynamic variables includes both purely hydrodynamic (superfluid and normal) velocities and the displacement vector corresponding to the violations of the translational invariance. All of the tensors of normal and superfluid densities that appear in the system as well as the elastic moduli have been calculated. A dispersion relation has been obtained for thermal vibrations (second sound) and elastic vibrations, and this relation has turned out to be substantially anisotropic. Observation of the predicted effects is most probable in 3He–He II solutions in magnetic fields of the order of several kilooersteds at low temperatures.
Temperature dependence of the surface tension between liquid and solid helium
Authors: Sobyanin A. A.
Published: December 2024

The interaction of the order parameter of the macroscopic wave function Ψ = ηeiϕ, which describes the superfluid state, with the boundary between He װ and solid helium and between He װ and vapor is examined. The contribution of this interaction to the energy of the boundary is calculated. A sharp increase is predicted in the surface tension σ between liquid and solid helium below the superfluid transition point Tλ. The nature of the dependence of σ and t = Tλ— T is different for different relations between the correlation radius of the order parameter and the extrapolation length l, which appears in the boundary condition dΨ/dz|z = 0 = λ−1Ψ(0) (z is the distance from the boundary). For ξ≫l we have σ ∼ t4/3 while for ξ ≪ 1 we have σ ∼ t2/3; in the region where ξ ∼ l the function σ(t) is linear with a fair degree of accuracy. For the free boundary of helium the results obtained provide a good description of the experimental data; for the length l we obtained the value l≈(17±3)Å.
Influence of quantum effects on the phase diagram of a two-dimensional electron crystal
Authors: Abdullaev B. , Lozovik Yu. E.
Published: December 2024

Using the phenomenological melting criterion of Lindemann in the Debye model for a bounded crystal and in the Einstein model for a crystal and also using the modified Lindemann criterion ⟨(xi − xi+1)2⟩/a2 = γ1 (a is the lattice constant), we study the influence of the image forces and the transverse magnetic field on the region of stability of a two-dimensional electron crystal.

Calculation in the microscopic treatment in the self-consistent harmonic approximation (SHA) qualitatively confirms the T–n (temperature–concentration) phase diagram obtained with the Lindemann criterion for a crystal whose particles interact according to the Coulomb law. The influence of the image forces and the magnetic field on the phase diagram is studied within the framework of the SHA at T = 0.
Periodic structures on the charged surface of liquid helium
Authors: Meshkov S. V. , Mel’nikov V. I.
Published: December 2024

It is well known that the uniform distribution of electrons pressed by an electric field to the surface of liquid helium becomes unstable at some critical value. In this case the surface is deformed and a macroscopic structure of the dimple crystal type is formed.

It is shown that at a low charge density the system is described by linear equations and the nonlinearity, stabilizing the structure, is due to the formation of charge-free segments of surface. The parameters of various structures and the transitions between them are investigated.
The Einstein relation in quantum systems
Authors: Kaganov M. I. , Fiks V. B.
Published: December 2024

The Einstein relation between the dispersion coefficient D and the mobility u is considered in various quantum systems. From an analysis of the general thermodynamic relation E≡D/u = n(∂µ/∂n), where µ and n are the chemical potential and density of the moving particles, we have derived expressions for E in ideal Fermi and Bose gases; corrections have been included for the nonideal natures of the gases (in particular, the value of E has been calculated for a Fermi fluid); the transition through the Bose condensation point in a Bose gas has been considered (with allowance for fluctuations). The cases of one- and two-dimensional gases are considered and so is the influence of a quantizing magnetic field. It is shown that in a fluid E = ms2 (m is the particle mass and s is the speed of sound). The Einstein relation in quantum crystals is considered.

Comparison of the kinematic conclusion of the Einstein relation with the thermodynamic conclusion shows that the relation can be used to investigate the energy distribution of particles under nonequilibrium conditions.
Radiation caused by the indeterminacy of the energy of quasiparticles, and relaxation processes in He II
Authors: Adamenko I. N. , Tsyganok V. I.
Published: December 2024

The kinetics of superfluid helium is determined fully by the gas of excitations—phonons and rotons. Conservation laws prohibit rotons to radiate and absorb phonons.

If the finite lifetime of rotons, owing to roton–roton interactions, is taken into account, however, this process proves to be permitted as a result of the indeterminacy of the energy.

On the basis of the temperature Green’s function we have obtained the photon–roton relaxation time for the given process.

It is shown that the kinetic coefficients of superfluid helium at elevated pressures are determined by the time we have found.
The theory of cholesteric liquid crystals in the atom–atom potentials approximation
Authors: Badalyan D. A.
Published: December 2024

A method of statistical-thermodynamic calculation of the properties of cholesteric liquid crystals, in which the pair interaction energy of molecules is presented in the form of the sum of the interaction energies of the atoms that form the molecules (atom–atom potentials approximation). In this case the cholesteric phase is formed as a result of the correlation between the orientations of the chiral molecules.

The method makes it possible to take the distinctive features of the real structure of the molecule into account. The pitch of the spiral as well as the elastic constants have been found as functions of the geometry of the molecule and the constants of the interaction of the atom–atom potentials.
The blue phase of liquid crystals
Authors: Belyakov V. A. , Dmitrenko V. E. , Osadchii S. M.
Published: December 2024

A brief review is made of experimental and theoretical investigations of the blue phase of liquid crystals, which is a thermodynamically stable phase with a complex spatial structure of the order parameter and which exists for some substances in a narrow temperature range of the order of 1 °K between the isotropic and ordinary cholesteric phases. Numerous versions of the structure of blue phases are discussed and a theory is developed for determining the structure by optical methods.

It is shown that optical measurements permit the structure of a blue phase to be determined directly, in much the same way as the x-ray structural determinations of crystal structures. The particular importance of polarization measurements in investigations of a blue phase is emphasized.
Localized and band electrons in transition metals and their disordered alloys. Magnetic, electrical, and superconducting properties
Authors: Kuzemskii A. L.
Published: December 2024

The characteristic features of transition metals, their compounds, and their disordered alloys are shown to be due to the fact that their electronic structure has a very distinct d-band nature. The relation between the band width and Coulomb repulsion parameter determines the wide region from metal to insulator—that of the Mott–Hubbard semiconductor. In the case of a metal, in which subbands with spin up and spin down undergo splitting, a Stoner continuum arises in addition to the branch of spin waves and it substantially changes the picture of inelastic scattering of slow neutrons with large energy and momentum transfers. Taking account of the localized nature of the d electrons is of major importance in describing electron–phonon interaction. The Barisich–Labbe–Friedel electron–phonon interaction Hamiltonian has been considered. The density of states of electrons and phonons as well as the broadening of phonons as a result of the electron–phonon interaction have been calculated. At low temperatures a modified Stoner magnetism criterion has been found. The BLF Hamiltonian has been generalized to the case of disordered alloys. The renormalized electron and phonon densities of states and the electronic specific heat have been calculated. In order to describe the superconductivity we have developed a method which makes it possible to obtain the Eliashberg equations in the lattice-site representation. The Eliashberg functions have been found for a number of pure transition metals (niobium, etc.). On the basis of this treatment we have constructed a theory of disordered superconducting alloys of transition metals with strong coupling.
Phenomenological theory of the isomorphous phase transition in crystalline hydrogen
Authors: Sukharevskii B. Ya. , Leont’eva A. V.
Published: December 2024

We discuss the possible existence of an isolated point of continuous phase transitions, near which — as implied by the phenomenological theory of Landau phase transitions—there exist two isomorphous crystalline phases, differing in the sign of the order parameter.

The results obtained are in qualitative agreement with data available in the literature on crystallization in hydrogen.
Influence of the size factor on the dynamic characteristics of cryocrystals
Authors: Kovalenko S. I. , Krainyukova N. V.
Published: December 2024

We present the results of an electron-diffraction determination of the rms displacements ⟨u2⟩ of atoms in island films of Ar, Kr, and Xe, as well as the degree of orientational ordering of molecules in thin films of the a phases of N2 and CO.

The effective size of the specimens varied from 2–3 to several tens of angstroms while the size L of crystallites varied from 30 to 200 Å. The value of ⟨u2⟩ in the direction perpendicular to the wave vector of the primary electrons was determined from an analysis of the intensity of the diffracted beams as a function of the temperature. The initial data for calculation of the parameter of orientational ordering consisted of the ratio of the intensities of the “superlattice” lines to those of the fundamental lines.

As a result of the observations carried out we found an appreciable increase in ⟨u2⟩ in small particles of solidified inert gases. Comparison of the experimental results with a theoretical calculation enabled us to establish that this effect is due not only to the growth of the contribution of the surface but also to the substantial weakening of the interatomic interaction in small van der Waals crystals. This apparently was also responsible for the substantial lowering of the degree of orientational ordering of N2 and CO molecules in specimens with a small thickness.
“High-temperature” oscillations of the magnetoresistance in bismuth and semimetallic BiSb alloys
Authors: Bogod Yu. A. , Krasovitskii Vit. B. , Lemeshevskaya E. T.
Published: December 2024

The electrical conductivity, magnetoresistance, Shubnikov-de Haas oscillations, and “high-temperature” oscillations (HTO) of the magnetoresistance of semimetallic BiSb alloys are investigated at Sb concentrations C of up to 2.6 at.% The results are compared with those for Bi. It is found that with the aid of the similarity transformation high-temperature oscillations can be expressed in terms of cyclotron masses at extremal cross sections of the Fermi surface. In the region 0 ≤ C ≤ 2.6 at.% the relative change in the periods of the HTO and Shubnikov-de Haas oscillations, due to holes, are observed to be the same. We establish that the amplitude of HTO is described in generalized ln ρ˜ (T) coordinates: for T ≳ 10°K the function ln ρ˜ (T) plotted for specimens with different compositions form a family of parallel straight lines. The shape of the HTO amplitude as a function of the magnetic field is found. We discuss the possibility of applying HTO to the investigation of the energy spectrum over a wide range of temperatures.
Susceptibility of a one-dimensional magnet with an Ising interaction
Authors: Yurishchev M. A.
Published: December 2024

A three-dimensional Ising model with a strong spatial anisotropy in its interaction is approximated by an ensemble of independent clusters of four chains, for which an analytic expression is found to represent the susceptibility. Together with the well-known expression for the transverse susceptibility of a linear Ising chain, the expression found is used to describe the powder susceptibility of CoCl2·2NC5H5. Good agreement is obtained between theory and experiment over the entire temperature interval of the measurements.
An anomaly in the spin–lattice relaxation of the cerium ion in europium ethylsulfate at high pressure
Authors: Neilo G. N. , Prokhorov A. D.
Published: December 2024

The temperature dependences of the spin–lattice relaxation rate of the Ce3+ ion in europium ethylsulfate have been measured at high pressure. It was found that an anomalous reduction in relaxation rate occurs with increasing pressure, which takes place in a jump-like fashion over a temperature interval of 0.2°K.
Quantum localization of conduction electrons under conditions of magnetic breakdown
Authors: Gorelik L. Yu.
Published: December 2024

A model of an incommensurate system, which appears under conditions of coherent magnetic breakdown, is examined. The spectrum and the form of the localized wave functions of the conduction electrons are found. The transition from the periodic system to the incommensurate system is followed.
Surface superconductivity in Nb0.8Ti0.2 alloy
Authors: Vasilev P. G. , Goncharov I. N.
Published: December 2024

Systematic resistive measurements have been carried out on recrystallized Nb0.8Ti0.2 foils 9 µ thick for various orientations of the magnetic field H relative to the plane of the specimen (I⊥H). Analysis of the current-voltage curves with long linear segments indicates the existence of a stable dynamic state of the lattice of tilted vortices. In this case the experimental fact that (du /dI)H||<(du/dI)H⊥, both above and below Hc2, can be explained by the low values of Rfs/Rns (<0.l for H/Hc2 < 1.14). Our investigations have confirmed that a network of regions with Hc2 roughly 10% higher than Hc2grain [which corresponds to the volume of the grains and can be determined from the Rf(H) curve] exists in the specimens.
Low-temperature dynamics of an anisotropic magnetic system
Authors: Zaslavskiĭ O. B.
Published: December 2024

The dynamics of spins in magnetically dilute and magnetically ordered crystals, which exhibit uniaxial anisotropy, examples of which are transition group ions in paramagnetic salts in the first case and a number of cobalt compounds in the second, are examined. The initial state is formed by an arbitrarily oriented strong magnetic field, which is switched off suddenly. The problem is solved exactly for arbitrary values of the spin and temperature. The effect of the temperature and orientation of the magnetic field on the low-temperature dynamics of the system are investigated. The dependences of the average values of the spin components on time and temperature, generally speaking, differ considerably from the corresponding results of the semiclassical analysis.
Low temperature specific heat of thin films
Authors: Gospodarev I. A. , Syrkin E. S.
Published: December 2024

We use the method of Jacobi matrices for a model of a bct crystal to study the low temperature specific heat of thin films bounded by two free (001) surfaces. We analyze the influence of the crystal anisotropy on the film specific heat and on the specific heat associated with the interaction of its two surfaces, for various film thicknesses.
Measurements of the voltage in wide tin films near the phase-slip line
Authors: Dmitrenko I. M. , Sivakov A. G. , Volotskaya V. G.
Published: December 2024

Measurements of the spatial dependence of the electrochemical potential of pairs µs and of quasiparticles µn near the phase slip line in wide (ω ∼ 100 µm) tin films are presented. It is shown that µn varies nearly exponentially over distances ∼lQ, while µs varies over a much shorter distance. The different spatial variation of µn and µs is also retained in a magnetic field and is confirmed by the existence of regions with an unbalance of charge in the vicinity of the phase-slip line. The I–V characteristics in a magnetic field are discussed.
Manifestation of the magnetoelectric interaction in the optical phonon spectrum of a ferroelectric magnetic medium
Authors: Chupis I. E.
Published: December 2024

It is demonstrated that the observed anomalies in the spectrum of the optical phonons of the ferroelectric antiferromagnet BaCoF4 as it orders magnetically are the result of the magnetoelectric exchange interaction. A large effect of a similar nature is predicted in ferroelectric magnetic crystals with a noncentrosymmetric paraelectric phase.
Effect of the optical mode of plasma oscillations on high-frequency energy absorption by an electron crystal on the surface of liquid helium
Authors: Kovdrya Yu. Z. , Buntar’ V. A.
Published: December 2024

The absorption of hf power by electrons on the surface of liquid helium at a frequency of 324 MHz at temperatures ranging from 0.4 to 0.8 °K and with electron densities of (5.5–11)·10−8 cm−2 is investigated. It is shown that in the density range (6.9–8.3)·108 cm−2 in the region of the crystalline state of the electron layer, as the temperature decreases, at some point absorption of hf power increases. The observed effect is due to excitation of the optical mode of plasma oscillations in the electron crystal on liquid helium. The velocity of transverse sound in the electron crystal is estimated.
Spectroscopy of phonons in dirty superconducting contacts
Authors: Yanson I. K. , Bobrov N. L. , Rybaľchenko L. F. , Fisun V. V.
Published: December 2024

The nonlinearities of current-voltage characteristics (IVC) of superconducting niobium point contacts for voltages of the order of the characteristic phonon frequencies are investigated. It is shown that in limiting by dirty contacts (l1≪d), (l1 is the momentum mean-free path of electrons), features are observed on the IVC corresponding to maxima in the first or second derivatives and are situated at energies close to the characteristic phonon energies. These features are due to the energy dependence of the excess current, since the nonlinearity of the IVC in the normal state is several times smaller in absolute magnitude, and its second derivative is monotonic. For a contact diameter d of the order of several tens of ångstroms (the contact resistance is of the order of 100 Ω), the thermal effects can be neglected. It is assumed that in the region of the constriction, the characteristic lengths of the system satisfy the relation ξ ≳ d > Λε (Λε is the diffusion length for energy relaxation of the electrons, ξ is the coherence length) which makes possible inelastic transitions of electrons between pair chemical potentials differing in energy by an account eV (V is the voltage drop across the contact).
Resonant interaction of electromagnetic waves in bismuth
Authors: Leviev G. I. , Trunin M. R.
Published: December 2024

The interaction of a strong electromagnetic wave with frequency Ω and a weak wave with frequency ω in bismuth was observed in a magnetic field parallel to the surface of the metal. The interaction has a resonant character, increasing near fields for which the frequency ω is a multiple of the Larmor frequency.
Anomalies in the heat capacity of the layered crystal CsDy(MoO4)2
Authors: Anders É. E. , Zvyagin A. I. , Startsev S. V. , Shestachenko L. S.
Published: December 2024

Results are given of experimental studies of the heat capacity of CsDy(MoO4)2 in the temperature range 30–250 °K. A second-order phase transition was found at 59.4 °K. The energy parameters of the first-order phase transition at Tc (Cmax) = 42.0 °K have been calculated. It was established that both the phonon subsystem and, because of the presence of dysprosium in the crystal, the electron subsystem have appreciable responsibility for the occurrence of this transition.
Helimagnetic ordering of a Fermi liquid
Authors: Strashnikov O. G. , Povzner A. A. , Geľd P. V.
Published: December 2024

It is established that the helimagnetic ground state of a Fermi liquid can be realized in the presence of a small nonlocality of the exchange and relativistic antisymmetric spin-spin interaction of quasiparticles. An expression is found for the wave vector of the long-period magnetic structure, and the field dependence of the magnetization at T = 0 is determined.
Predicting charge of a nucleosome core particle based on its environment
Authors: Daniel Hannah
Published: December 2024

Magnesium ions have an outsized effect on the NCP’s charge but they aren’t the only factor.
New nucleating agents for shear-induced crystallization of polypropylene
Authors: Zhang Ziyue , Deshmukh Yogesh Sheshrao , Al-Sharif Yasir , Doufas Antonios K. , Hatzikiriakos Savvas G.
Published: December 2024

The effect of shear on the flow-induced crystallization of a polypropylene with and without nucleating agents was studied using shear rheometry. Generally, an increase in strain and strain rate or decrease in temperature is found to decrease the thermodynamic barrier for crystal formation, thus enhancing crystallization kinetics at temperatures between the melting and crystallization points. Second, the use of nucleating agents dramatically increases the crystallization and melting point of polypropylene, thus enhancing the kinetics of crystallization. Herein, we report the quiescent isothermal and shear-induced crystallization (rheology) behavior of a random copolymer polypropylene with ethylene as a co-monomer containing sorbitol nucleating agents (NA) with different degrees of polarity. The presence of sorbitol NA increases the Tm and Tc by 5 °C and 15 °C, respectively. By performing steady-shear experiments at shear rates varying from 0.001 s−1 to 1 s−1, “quiescent crystallization” and “shear-induced crystallization” regions could be identified. From both isothermal and shear-induced crystallization experiments, sorbitol-based NA with the lowest degree of polarity was found to cause the highest crystallization kinetics.
A perspective on ultrafast magnetization switching in ferromagnets using helicity-independent optical pulses
Authors: Polley Debanjan , Bokor Jeffrey
Published: December 2024

We offer a brief overview of the present status of ultrafast helicity-independent all-optical magnetization switching (HI-AOS) phenomena in ferromagnet (FM) films and multilayers. The discovery of HI-AOS in ferrimagnet alloys dates back to 2011. From an application standpoint, utilizing HI-AOS in an FM brings about several benefits. One of these advantages is its enhanced spin polarization, which leads to a higher tunneling magneto-resistance (TMR) across a magnetic tunnel junction device. The enhanced TMR greatly enhances its reading capability. Time-resolved and single-shot magneto-optical Kerr effect measurement has successfully enabled the detection of magnetization switching. The magnetization reversal speed stays within the range of tens of picoseconds. There are two methods to achieve HI-AOS in an FM: (1) ultrafast spin-current-induced magnetization switching, and (2) ultrafast exchange interaction-dominated magnetization switching. We conduct a comprehensive analysis of a selection of recent academic publications that delve into both of these subjects and offer a succinct assessment of the present status of the ultrafast HI-AOS phenomenon in FMs. Finally, we discuss the latest developments in tackling the obstacles the HI-AOS mechanism faces and the exciting prospects for developing a high-speed spintronic memory device.