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تربية طفل متمرد : دليل يحفظ العقل لإيقاف السلوك السيئ
يوفر هذا الكتاب، سواء أظهر طفلك أنماطا متكررة من السلوك المندفع الغيرالملائم، لا أكثر، أم استوفى معايير التشخيص لاضطراب العناد الشارد، أساليب داعمة ومنورة، تم اختبارها، لتوجيهك وطفلك في الاتجاه الصحيح، وستتعلم كيفية منح طفلك الأساس والدعم اللذين يحتاجهما ليدرك إشارات التواصل الاجتماعي بدقة أكبر، ويمتلك السيطرة على اندفاعاته، فضلا عن تعزيز العلاقة بينكما، وتوفير الإمكانية لطفلك لتحقيق كل ما تعلم بقدرته على إنجازه.
BOOK
Observation of Dirac monopoles in a synthetic magnetic field
Dirac magnetic monopoles are created, directly imaged and identified in real space in the synthetic magnetic field produced by a spinor Bose–Einstein condensate.
Dirac action creates elusive monopoles
Ever since Dirac developed a comprehensive theory of magnetic monopoles in 1931, physicists have been eager to isolate these hypothetical particles featuring a north or south pole only. Although magnetic monopole analogues have been found in spin ices and other exotic systems, no Dirac monopoles have been observed directly within a medium described by a quantum field. But now David Hall and colleagues report the experimental observation of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose–Einstein condensate. The authors obtain real-space images of monopoles at the termini of vortex lines within the condensate, providing evidence of the existence of Dirac monopoles. The creation and manipulation of Dirac monopoles in a controlled environment opens up a wide range of experimental and theoretical investigations.
Magnetic monopoles—particles that behave as isolated north or south magnetic poles—have been the subject of speculation since the first detailed observations of magnetism several hundred years ago
1
. Numerous theoretical investigations and hitherto unsuccessful experimental searches
2
have followed Dirac’s 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field
3
. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge
3
,
4
. Although analogues of magnetic monopoles have been found in exotic spin ices
5
,
6
and other systems
7
,
8
,
9
, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3 (refs
10
,
11
,
12
,
13
). Here we demonstrate the controlled creation
14
of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose–Einstein condensate. Monopoles are identified, in both experiments and matching numerical simulations, at the termini of vortex lines within the condensate. By directly imaging such a vortex line, the presence of a monopole may be discerned from the experimental data alone. These real-space images provide conclusive and long-awaited experimental evidence of the existence of Dirac monopoles. Our result provides an unprecedented opportunity to observe and manipulate these quantum mechanical entities in a controlled environment.
Journal Article
Real-Time Dynamics of Single Vortex Lines and Vortex Dipoles in a Bose-Einstein Condensate
Understanding the behavior of quantized vortices is essential to gaining insight into diverse superfluid phenomena, from critical-current densities in superconductors to quantum turbulence in superfluids. We observe the real-time dynamics of quantized vortices in trapped dilute-gas Bose-Einstein condensates by repeatedly imaging the vortex cores. The precession frequency of a single vortex is measured by explicitly observing its time dependence and is found to be in good agreement with theory. We further characterize the dynamics of vortex dipoles in two distinct configurations: (i) an asymmetric configuration, in which the vortex trajectories are dynamic and nontrivial, and (ii) a stable, symmetric configuration, in which the dipole is stationary.
Journal Article
Topological superfluid defects with discrete point group symmetries
Discrete symmetries are spatially ubiquitous but are often hidden in internal states of systems where they can have especially profound consequences. In this work we create and verify exotic magnetic phases of atomic spinor Bose–Einstein condensates that, despite their continuous character and intrinsic spatial isotropy, exhibit complex discrete polytope symmetries in their topological defects. Using carefully tailored spinor rotations and microwave transitions, we engineer singular line defects whose quantization conditions, exchange statistics, and dynamics are fundamentally determined by these underlying symmetries. We show how filling the vortex line singularities with atoms in a variety of different phases leads to core structures that possess magnetic interfaces with rich combinations of discrete and continuous symmetries. Such defects, with their non-commutative properties, could provide unconventional realizations of quantum information and interferometry.
Ordinary vortex line defects are well-studied across different physical systems. Here the authors demonstrate, in atomic spinor Bose–Einstein condensates, previously unobserved vortex line defects with discrete polytope symmetries, which are of interest to quantum information applications.
Journal Article
The role of GABAergic modulation in motor function related neuronal network activity
At rest, the primary motor cortex (M1) exhibits spontaneous neuronal network oscillations in the beta (15–30Hz) frequency range, mediated by inhibitory interneuron drive via GABA-A receptors. However, questions remain regarding the neuropharmacological basis of movement related oscillatory phenomena, such as movement related beta desynchronisation (MRBD), post-movement beta rebound (PMBR) and movement related gamma synchronisation (MRGS). To address this, we used magnetoencephalography (MEG) to study the movement related oscillatory changes in M1 cortex of eight healthy participants, following administration of the GABA-A modulator diazepam. Results demonstrate that, contrary to initial hypotheses, neither MRGS nor PMBR appear to be GABA-A dependent, whilst the MRBD is facilitated by increased GABAergic drive. These data demonstrate that while movement-related beta changes appear to be dependent upon spontaneous beta oscillations, they occur independently of one other. Crucially, MRBD is a GABA-A mediated process, offering a possible mechanism by which motor function may be modulated. However, in contrast, the transient increase in synchronous power observed in PMBR and MRGS appears to be generated by a non-GABA-A receptor mediated process; the elucidation of which may offer important insights into motor processes.
► Pharmaco-MEG can determine pharmacological mechanisms of functional oscillations. ► MRBD and PMBR are both directly dependent upon the spontaneous beta activity. ► MRBD in primary motor cortex is enhanced by increased GABA-A receptor drive. ► PMBR and MRGS in primary motor cortex are non-GABA-A receptor mediated.
Journal Article
Experimental Realization of a Dirac Monopole through the Decay of an Isolated Monopole
We experimentally observe the decay dynamics of deterministically created isolated monopoles in spin-1 Bose-Einstein condensates. As the condensate undergoes a change between magnetic phases, the isolated monopole gradually evolves into a spin configuration hosting a Dirac monopole in its synthetic magnetic field. We characterize in detail the Dirac monopole by measuring the particle densities of the spin states projected along different quantization axes. Importantly, we observe the spontaneous emergence of nodal lines in the condensate density that accompany the Dirac monopole. We also demonstrate that the monopole decay accelerates in weaker magnetic field gradients.
Journal Article
Observation of isolated monopoles in a quantum field
Topological defects play important roles throughout nature, appearing in contexts as diverse as cosmology, particle physics, superfluidity, liquid crystals, and metallurgy. Point defects can arise naturally as magnetic monopoles resulting from symmetry breaking in grand unified theories. We devised an experiment to create and detect quantum mechanical analogs of such monopoles in a spin-1 Bose-Einstein condensate. The defects, which were stable on the time scale of our experiments, were identified from spin-resolved images of the condensate density profile that exhibit a characteristic dependence on the choice of quantization axis. Our observations lay the foundation for experimental studies of the dynamics and stability of topological point defects in quantum systems.
Journal Article
Controlled creation of a singular spinor vortex by circumventing the Dirac belt trick
Persistent topological defects and textures are particularly dramatic consequences of superfluidity. Among the most fascinating examples are the singular vortices arising from the rotational symmetry group SO(3), with surprising topological properties illustrated by Dirac’s famous belt trick. Despite considerable interest, controlled preparation and detailed study of vortex lines with complex internal structure in fully three-dimensional spinor systems remains an outstanding experimental challenge. Here, we propose and implement a reproducible and controllable method for creating and detecting a singular SO(3) line vortex from the decay of a non-singular spin texture in a ferromagnetic spin-1 Bose–Einstein condensate. Our experiment explicitly demonstrates the SO(3) character and the unique spinor properties of the defect. Although the vortex is singular, its core fills with atoms in the topologically distinct polar magnetic phase. The resulting stable, coherent topological interface has analogues in systems ranging from condensed matter to cosmology and string theory.
Topological defects and textures are universal phenomena across physics. The authors demonstrate that an initial non-singular spinor texture can be controllably transformed into a pair of singular vortices with cores filled by atoms that continuously connect distinct magnetic phases of matter.
Journal Article
Sequence diversity in CYP3A promoters and characterization of the genetic basis of polymorphic CYP3A5 expression
Variation in the CYP3A enzymes, which act in drug metabolism, influences circulating steroid levels and responses to half of all oxidatively metabolized drugs. CYP3A activity is the sum activity of the family of CYP3A genes, including
CYP3A5
, which is polymorphically expressed at high levels in a minority of Americans of European descent and Europeans (hereafter collectively referred to as 'Caucasians'). Only people with at least one
CYP3A5
*
1
allele express large amounts of CYP3A5. Our findings show that single-nucleotide polymorphisms (SNPs) in
CYP3A5
*
3
and
CYP3A5
*
6
that cause alternative splicing and protein truncation result in the absence of CYP3A5 from tissues of some people. CYP3A5 was more frequently expressed in livers of African Americans (60%) than in those of Caucasians (33%). Because CYP3A5 represents at least 50% of the total hepatic CYP3A content in people polymorphically expressing CYP3A5,
CYP3A5
may be the most important genetic contributor to interindividual and interracial differences in CYP3A-dependent drug clearance and in responses to many medicines.
Journal Article