Absence Of Inversion Research Articles

C-Type Antiferromagnetic Structure of Topological Semimetal CaMnSb2

Determination of the magnetic structure and confirmation of the presence or absence of inversion ( P ) and time reversal ( T ) symmetry is imperative for correctly understanding the topological magnetic materials. Here high-quality single crystals of the layered manganese pnictide CaMnSb2 are synthesized using the self-flux method. De Haas–van Alphen oscillations indicate a nontrivial Berry phase of ∼ π and a notably small cyclotron effective mass, supporting the Dirac semimetal nature of CaMnSb2. Neutron diffraction measurements identify a C-type antiferromagnetic structure below T N = 303(1) K with the Mn moments aligned along the a axis, which is well supported by the density functional theory (DFT) calculations. The corresponding magnetic space group is Pn′m′a′, preserving a P×T symmetry. Adopting the experimentally determined magnetic structure, band crossings near the Y point in momentum space and linear dispersions of the Sb 5p y, z bands are revealed by the DFT calculations. Furthermore, our study predicts the possible existence of an intrinsic second-order nonlinear Hall effect in CaMnSb2, offering a promising platform to study the impact of topological properties on nonlinear electrical transports in antiferromagnets.

ПЕРЕКЛАД СТИЛІСТИЧНИХ ОСОБЛИВОСТЕЙ МОВЛЕННЯ ВЕДУЧОГО ТЕЛЕВІЗІЙНОГО ІНТЕРВ’Ю

The work is devoted to the study of translation peculiarities of stylistic features of a TV interviewer’s English speech into Ukrainian. The correct translation of the content of a speech segment requires good knowledge of vocabulary, and the capability to recognize the stylistic features of a foreign language in communication, and the techniques used to translate them into the native language. Translation of metaphors, metonymy, comparisons is of particular difficulty for the translator, however, it is the ability to use various techniques in translation that helps the translator to convey the meaning of the statement to the listener adequately. The television interview is characterized as an independent journalistic genre, is a kind of television communication, a purposeful individual-social speech phenomenon, which consists of the organized interaction detween the speakers and finds its expression in a specific dialogically constructed form. The results of this study show that each translated stylistic unit is characterized by a set of transformations typical for it. In most cases, these transformations involve lexical and syntactic stylistic devices. At the level of vocabulary, the speech of a TV interviewer is characterized by a significant number of colloquialisms, colloquial cliches, phraseological units. At the level of syntax, the typical indicators of the conversational style of the TV nterviewer are parallel constructions, repeated requests, elliptical sentences, repetitions, unfinished phrases, and the absence of inversion in interrogative sentences. The information obtained as the result of convergence of stylistic devices as a set of components participating together with other linguistic units in the formation of expressiveness, emotiveness and evaluation is one of the important sources of the language pragmatic function.

Magnetic field induced Weyl semimetal from Wannier-function-based tight-binding model

Weyl semimetals (WSMs) have Weyl nodes where conduction and valence bands meet in the absence of inversion or time-reversal symmetry (TRS), or both. Interesting phenomena are expected in WSMs such as the chiral magnetic effect, anomalous Hall conductivity or Nernst effect, and unique quantum oscillations. The TRS-broken WSM phase can be driven from a topological Dirac semimetal (DSM) by magnetic field or magnetic dopants, considering that DSMs have degenerate Weyl nodes stabilized by rotational symmetry, i.e. Dirac nodes. Here we develop a Wannier-function-based tight-binding (WF-TB) model to investigate the formation of Weyl nodes and nodal rings induced by B field in the topological DSM Na$_3$Bi. The field is applied along the rotational axis. Remarkably, our study based on the WF-TB model shows that upon B field each Dirac node is split into four separate Weyl nodes along the rotational axis near the Fermi level; two nodes with single chiral charge (single Weyl nodes) and two with double chiral charge (double Weyl nodes). This result is in contrast to the common belief that each Dirac node splits into two Weyl nodes. In the effective models, the existence of double Weyl nodes ensures nonzero cubic terms in momentum. We further examine the evolution of Fermi arcs at a side surface as a function of chemical potential. The number of Fermi arcs is consistent with the corresponding Fermi surface Chern numbers, corroborating our finding of the double Weyl nodes. Furthermore, our study reveals the existence of nodal rings in the mirror plane below the Fermi level upon B field. These nodal rings persist with spin-orbit coupling, in contrast to typical nodal ring semimetals. Our WF-TB model can be used to compute interesting features arising from Berry curvature such as anomalous Hall and thermal conductivities, and our findings can be applied to other topological DSMs like Cd$_3$As$_2$.

Methyl methacrylate particles with amino groups on the surface: Colloid stability and sorption of biologically active substances

ABSTRACTThe present article investigates the influence of dispersion medium on the aggregate stability of cross-linked poly-(methyl methacrylate) particles on the surface layer of which aliphatic amino groups are localized. It is shown that particle size depends on the ionic strength of dispersion medium. The research determines the optimal content of cross-linked agent, ethylene glycol dimetharylate that results in the formation of cationic particles being stable in saline. Particle modification is performed by bovine serum albumin and luminophore fluorescein 5(6)-isothiocyanate. Protein sorption is observed not to influence luminescent properties of the particles. It is also determined that due to the aggregate stability of particles obtained from 5 wt% of ethylene glycol dimethacrylate in saline, the monodispersity and the absence of inversion of zeta potential in wide pH range is retained, such particles may be considered as perspective carriers of biologically active substances.

Intrinsic circular polarization in centrosymmetric stacks of transition-metal dichalcogenide compounds.

The circular polarization (CP) that the photoluminescence inherits from the excitation source in n monolayers of transition-metal dichalcogenides (MX_{2})_{n} has been previously explained as a special feature of odd values of n, where the inversion symmetry is absent. This "valley polarization" effect results from the fact that, in the absence of inversion symmetry, charge carriers in different band valleys could be selectively excited by different circular polarized light. Although several experiments observed CP in centrosymmetric MX_{2} systems, e.g., for bilayer MX_{2}, they were dismissed as being due to some extrinsic sample irregularities. Here we show that also for n=even, where inversion symmetry is present and valley polarization physics is strictly absent, such intrinsic selectivity in CP is to be expected on the basis of fundamental spin-orbit physics. First-principles calculations of CP predict significant polarization for n=2 bilayers: from 69% in MoS_{2} to 93% in WS_{2}. This realization could broaden the range of materials to be considered as CP sources.

Composition and secondary formation of fine particulate matter in the Salt Lake Valley: Winter 2009

Under the National Ambient Air Quality Standards (NAAQS), put in place as a result of the Clean Air Amendments of 1990, three regions in the state of Utah are in violation of the NAAQS for PM10 and PM2.5 (Salt Lake County, Ogden City, and Utah County). These regions are susceptible to strong inversions that can persist for days to weeks. This meteorology, coupled with the metropolitan nature of these regions, contributes to its violation of the NAAQS for PM during the winter. During January–February 2009, 1-hr averaged concentrations of PM10-2.5, PM2.5, NOx, NO2, NO, O3, CO, and NH3 were measured. Particulate-phase nitrate, nitrite, and sulfate and gas-phase HONO, HNO3, and SO2 were also measured on a 1-hr average basis. The results indicate that ammonium nitrate averages 40% of the total PM2.5 mass in the absence of inversions and up to 69% during strong inversions. Also, the formation of ammonium nitrate is nitric acid limited. Overall, the lower boundary layer in the Salt Lake Valley appears to be oxidant and volatile organic carbon (VOC) limited with respect to ozone formation. The most effective way to reduce ammonium nitrate secondary particle formation during the inversions period is to reduce NOx emissions. However, a decrease in NOx will increase ozone concentrations. A better definition of the complete ozone isopleths would better inform this decision.Implications: Monitoring of air pollution constituents in Salt Lake City, UT, during periods in which PM2.5 concentrations exceeded the NAAQS, reveals that secondary aerosol formation for this region is NOx limited. Therefore, NOx emissions should be targeted in order to reduce secondary particle formation and PM2.5. Data also indicate that the highest concentrations of sulfur dioxide are associated with winds from the north-northwest, the location of several small refineries.

Acute myeloid leukaemia with abnormal eosinophil precursors without inversion 16

A 46-year-old previously healthy man presented with a 2week history of fever and diarrhoea. A full blood count showed: white blood cells 49·5 9 10/l (blast cells 42 9 10/l, eosinophils 1·5 9 10/l), haemoglobin concentration 166 g/l and platelets 52 9 10/l. There was no basophilia and Auer rods were not seen. A coagulation screen was normal. The bone marrow was markedly hypercellular with over 80% cellularity, including 80% myeloblasts, which were positive for CD13, CD33, CD43, CD64 (dim), CD117 and myeloperoxidase, and negative for CD14, CD15, CD34, CD45, CD64, terminal deoxynucleotidyl transferase, human leucocyte antigen (HLA)-DR and lysozyme. Notably, there were 12% eosinophil precursors, many of which displayed large basophilic granules admixed with eosinophilic granules (image), morphologically strongly reminiscent of acute myelocytic leukaemia with inv (16)(p13·1q22) or t(16;16)(p13·1;q22). Fluorescence in situ hybridization was negative for an inversion 16, as well as for PDGFRA and PDGFRB rearrangement. Karyotypic analysis demonstrated a normal male karyotype. Molecular analysis showed a FLT3 internal tandem duplication and an NPM1 exon 12 mutation. This analysis was negative for the FLT3D835 variant. The patient underwent induction chemotherapy (cytarabine and idarubicin; 7 + 3) with a diagnosis of acute myeloid leukaemia. He achieved complete remission, and was referred for evaluation for bone marrow transplantation. The absence of inversion 16 and other recurrent abnormalities associated with eosinophilia was a surprise in this case given the striking morphological features.

Holistic processing impairment can be restricted to faces in acquired prosopagnosia: Evidence from the global/local Navon effect

Previous studies have shown that acquired prosopagnosia is characterized by impairment at holistic/configural processing. However, this view is essentially supported by studies performed with patients whose face recognition difficulties are part of a more general visual (integrative) agnosia. Here, we tested the patient PS, a case of acquired prosopagnosia whose face-specific recognition difficulties have been related to the inability to process individual faces holistically (absence of inversion, composite, and whole-part effects with faces). Here, we show that in contrast to this impairment, the patient presents with an entirely normal response profile in a Navon hierarchical letter task: she was as fast as normal controls, faster to identify global than local letters, and her sensitivity to global interference during identification of local letters was at least as large as normal observers. These observations indicate that holistic processing as measured with global/local interference in the Navon paradigm is functionally distinct from the ability to perceive an individual face holistically.

Outcome evaluation of total hip arthroplasty by means of statistical gait analysis

valgus patients than in the control. The shank–calcaneus rotation on coronal plane revealed the absence of inversion during terminal stance with respect to the control. Discussion The gait analysis protocol used allowed identification of specific measures for functional evaluation of hallux valgus in dynamic conditions. Four angles revealed clinically relevant observations and in agreement with the traditional radiographic assessment. Inconsistency was found for the hallux–metatarso–phalangeal angle, likely associated to the artefactual calculation of projections angles when these are large, which is now under analysis to be compensate. References

Regional Saharan dust modelling during the SAMUM 2006 campaign

The regional dust model system LM-MUSCAT-DES was developed in the framework of the SAMUM project. Using the unique comprehensive data set of near-source dust properties during the 2006SAMUMfield campaign, the performance of the model system is evaluated for two time periods in May and June 2006. Dust optical thicknesses, number size distributions and the position of the maximum dust extinction in the vertical profiles agree well with the observations. However, the spatio-temporal evolution of the dust plumes is not always reproduced due to inaccuracies in the dust source placement by the model. While simulated winds and dust distributions are well matched for dust events caused by dry synoptic-scale dynamics, they are often misrepresented when dust emissions are caused by moist convection or influenced by small-scale topography that is not resolved by the model. In contrast to long-range dust transport, in the vicinity of source regions the model performance strongly depends on the correct prediction of the exact location of sources. Insufficiently resolved vertical grid spacing causes the absence of inversions in the model vertical profiles and likely explains the absence of the observed sharply defined dust layers.

Cyclotron mechanism of free-electron lasing without inversion

We consider one of the “paradoxical” effects of the theory of radiation and matter interaction: stimulated emission in the absence of inversion. The theory of simultaneous inversionless emission of two high-frequency waves due to their parametric interaction with ensemble of free electrons in magnetic field is developed. The analytical investigation and numerical simulation of the most interesting scheme of this two-photon interaction are presented. New effects are revealed; namely they are self-induced parametric instability of sufficiently strong waves and enhanced parametric instability in sufficiently dense electron medium.

Intersubband gain in a Bloch oscillator and quantum cascade laser

The link between the gain of quantum cascade structures and the gain in periodic superlattices is presented. The proposed theoretical model based on the density matrix formalism is able to treat the gain mechanism of the Bloch oscillator and quantum cascade laser on the same footing by taking into account in-plane momentum relaxation. The model predicts a dispersive contribution in addition to the (usual) population-inversion-dependent intersubband gain in quantum cascade structures and---in the absence of inversion---provides the quantum-mechanical description for the dispersive gain in superlattices. It corroborates the predictions of the semiclassical miniband picture, according to which gain is predicted for photon energies lower than the Bloch oscillation frequency, whereas net absorption is expected at higher photon energies, as a description which is valid in the high-temperature limit. A redshift of the amplified emission with respect to the resonant transition energy results from the dispersive gain contribution in any intersubband transition, for which the population inversion is small.

Laser amplification without population inversion on the D_1 line of the Cs atom with semiconductor diode lasers

The importance of lasing without inversion (LWI) in comparison with the use of nonlinear optical techniques and techniques based on high-intensity femtosecond light pulses to generate high-frequency coherent radiation is outlined. The original development and utilization of an experimental facility based on semiconductor diode lasers to study the fundamental aspects of LWI on the D1 line of the Cs atom, which is rarely attempted, is described. This experimental facility is used to observe inversionless amplification on the D1 line of the Cs atom by use of a Λ atomic scheme. A combination of EIT and broadband pumping of atoms from the lower to the upper level of the probe transition allowed the observation of the inversionless gain. Justification for the absence of inversion in the probe transition is provided. We report a single-pass inversionless gain of ≈11% with relatively weak incoherent pumping. The results show improvement over the previously reported inversionless gain observed in Na, Rb, and Cs, illustrating the potential advantage of using the D1 line of Cs.

Occurrence of double strand DNA breaks and pairing of homologous chromosomes are preconditions of crossing over in Drosophila melanogaster, and its timing.

Brood pattern analysis of the effect of a heat shock (35 degrees C 24h) given to the parental females in presence and absence of In (2L + 2R) Cy in heterozygous condition in the second chromosome on recombination and interference in the cv-v-f region of the X chromosome showed the following: (i) In the absence of the inversion recombination frequencies in both gene intervals increased in the daily broods, which represent oocytes in which premeiotic DNA synthesis was occurring during the heat shock treatment. (ii) In the presence of the inversion recombination frequencies did not increase in any of the daily broods. (iii) The frequencies of double crossovers did not increase in any broods either in the presence or in the absence of inversion. (iv) The coefficient of coincidence changed in virtually all broods both in the presence and absence of the inversion, indicating that the heat shock affects the distribution of single crossovers. (v) The results showed that the effect of the heat shock on the coefficient of coincidence was similar during premeiotic DNA synthesis both in the absence and presence of the inversion, but different in the broods representing oocytes which were undergoing the first meiotic division, suggesting that crossing over occurs during this division, probably during pachytene.

Inversion-free amplification of a probe field in a medium consisting of two-level degenerate atoms in the presence of a magnetic field

The propagation of a probe field in a medium consisting of two-level atoms, degenerate in relation to the Jg = 1/2 → Je = 1/2 transition, is examined. The atoms are pumped by a circularly polarised resonant field in the presence of a static magnetic field. It is shown that under these conditions one of the normal waves may be amplified in the absence of inversion in the medium. In strong optical and magnetic fields, inversion-free amplification is possible for a pump with a finite spectral width, which may be much greater than the natural width of the excited level.

“Inversionless” stimulated emission of radiation by nonequilibrium ensembles of classical oscillators

We find classical analogs of quantum systems capable of stimulated emission of radiation in the absence of inversion. We show that cyclotron parametric instability in low-frequency modulation of the distribution function of resonant particles can amplify a bichromatic high-frequency field when amplification of each spectral component separately is impossible. We point to similar modes for a Cherenkov resonance and a model system with lumped parameters. Finally, we suggest using this effect for converting microwave radiation to a higher frequency.

Emission of gamma rays by electron-nuclear doubletransitions

In this paper we discuss the relevance of electron-nuclear double transitions for the problem of the amplification of gamma rays. We consider the electron-nuclear coupled system of 151Eu in a CaF2 lattice, in the presence of a strong static magnetic field. We analyze the possibility of pumping this electron-nuclear coupled system from the ground atomic electron Zeeman level to a higher electron level with the aid of a microwave magnetic field, while the nucleus is simultaneously undergoing a gamma-ray transition to the nuclear ground state. It is shown that an overall inversion condition can be satisfied even in the absence of inversion of the nuclear populations, provided that the ratio of the electron populations in the excited and ground electron Zeeman states has a sufficiently small value.

Bay of Bengal Monsoon

Synoptic charts for 00 and 12 GMT for 1 and 2 June 1963 have been examined and it is observed that there was no cyclone at. 110N, Long, 95°E at 00 GMT on 2 June as indicated by Ramage (1963, 1964) in his 500-mb stream lines chart, There could only be a short-lived vortex of small extent near the boundary of the fresh monsoon air; such a vortex was present both at 700 and 500 mb as shown by aircraft reports. It is shown that to use data of dropsoundings for the lst when there was no cyclone, to determine structure of the so-called cyclone in existence on the 2nd at a distance of 500 to 900 km from its centre, is not justified. The causes responsible for absence of inversion generally at 850 mb over the Bay have been discussed. The conditions over the Arabian Sea 200-300 miles west of Western Ghats and over the Bay during the monsoon season are such that models for one cannot be made applicable for the other, just as the subtropical cyclone model for the Pacific cannot be valid for the Bay when there is no inversion at 850-mb level.

On the time reversal in crystals of low point symmetry

The problems of additional time reversal degeneracy and the transformation properties of the “time-reversed” wave functions are studied in detail in cases where the low point symmetry (especially the absence of inversion) does not allow, for instance, the use of the formula derived by Elliott (1954). Some special examples are given and misleading statements in the literature are pointed out. The conclusions are summarized so as to be handy in actual applications. Spin is taken into account throughout the whole discussion. Multiplication tables for all double crystallographic point groups can be obtained from the Appendix.

TWO MULTICELLULAR MOTILE GREEN ALGAE,VOLVULINAPLAYFAIR ANDASTREPHOMENE, A NEW GENUS

This paper∗ deals with a new type of green alga originally found on the Cape Flats and since obtained in the United States of America and Australia. Initially identified as a second species of Volvulina Playfair, the considerations which led to the establishment of a distinct genus, Astrephomene, including the appearance from the Flats of Volvulina itself, are summarized, Playfair's description analysed and the resultant conclusion that he was dealing with two different algae mentioned; the steps that resulted in the verification of this conclusion are indicated. The two methods of culture used in the investigation are described. An amended description of Volvulina steinii Playfair is given and the results of observations made during a study of the alga in culture are recorded. The genus Astrephomene with the single species A. gubernaculifera is defined, a full account of its structure and life history given and its similarity to and difference from Volvulina pointed out, particularly the absence of inversion and the possession of a unique directive organ, the ‘rudder’. The results of cultures selected to illustrate certain points are summarized and the value of soil cultures in the study of algae emphasized. The validity of Playfair's genus is discussed, references by Stein and Carter are analysed and the possibility of its occurrence in India suggested. The relation between nutrition and certain features common to both algae is discussed, the characters of the two compared and the taxonomic position of each considered. A new family of the Volvocales, astrephomenaceae, is proposed for the reception of the monotypic genus, Astrephomene.