Temperature-dependent change of the electronic structure in the Kondo lattice system YbRh2Si2

The heavy-fermion behavior in intermetallic compounds manifests itself in a quenching of local magnetic moments by developing Kondo spin-singlet many-body states combined with a drastic increase of the effective mass of conduction electrons, which occurs below the lattice Kondo temperatureT_K. This behavior is caused by interactions between the strongly localized 4felectrons and itinerant electrons. A controversially discussed question in this context is how the localized electronic states contribute to the Fermi surface upon changing the temperature. One expects that hybridization between the local moments and the itinerant electrons leads to a transition from a small Fermi surface in a non-coherent regime at high temperatures to a large Fermi surface once the coherent Kondo lattice regime is realized belowT_K. We demonstrate, using hard x-ray angle-resolved photoemission spectroscopy that the electronic structure of the prototypical heavy fermion compound YbRh₂Si₂changes with temperature between 100 and 200 K, i.e. far above the Kondo temperature,T_K= 25 K, of this system. Our results suggest a transition from a small to a large Fermi surface with decreasing temperature. This result is inconsistent with the prediction of the dynamical mean-field periodic Anderson model and supports the idea of an independent energy scale governing the change of band dispersion.

Néel Vector Induced Manipulation of Valence States in the Collinear Antiferromagnet Mn2Au

The coupling of real and momentum space is utilized to tailor electronic properties of the collinear metallic antiferromagnet Mn₂Au by aligning the real space Néel vector indicating the direction of the staggered magnetization. Pulsed magnetic fields of 60 T were used to orient the sublattice magnetizations of capped epitaxial Mn₂Au(001) thin films perpendicular to the applied field direction by a spin-flop transition. The electronic structure and its corresponding changes were investigated by angular-resolved photoemission spectroscopy with photon energies in the vacuum-ultraviolet, soft, and hard X-ray range. The results reveal an energetic rearrangement of conduction electrons propagating perpendicular to the Néel vector. They confirm previous predictions on the origin of the Néel spin-orbit torque and anisotropic magnetoresistance in Mn₂Au and reflect the combined antiferromagnetic and spin-orbit interaction in this compound leading to inversion symmetry breaking.

Masseter-to-Facial Cranial Nerve Anastomosis: A Report of 30 Cases

BACKGROUND

Facial nerve paralysis (FP) is a possible complication of cerebellopontine angle tumor surgery. Several donor nerves have been used in the past for facial reanimation. We report the results of 30 cases of masseter-to-facial anastomosis.

OBJECTIVE

To prospectively evaluate the efficacy of V to VII anastomosis after FP.

METHODS

In a prospective study, we included 30 consecutive patients with FP (20 women and 10 men) whose mean age was 48.8 yr (32-76 yr). In almost all cases, FP developed after cerebellopontine angle tumor surgery (29 patients), whereas in one case, FP occurred after skull base trauma. Pre- and postoperative evaluation of facial nerve function was performed using the House-Brackmann (HB) scale and the Sokolovsky scale, as well as by electromyography. Follow-up ranged from 11 to 51 mo and averaged 22 mo.

RESULTS

All patients achieved functional recovery of the facial nerve from VI to either III or IV HB degree. Patients with short time FP showed significantly better postoperative recovery.

CONCLUSION

The results of the V to VII anastomosis demonstrate a significant improvement of facial nerve function and virtually no complications.

Matching emission centers of electrons and photons in current-carrying silver nanoparticle films

Current flow through a nanoparticle film (two-dimensional ensemble of small tunnel-coupled metal particles on a dielectric substrate) is accompanied by electron and photon emission. It has a localized character (originates from emission centers). With an increase in applied voltage, the number of emission centers increases, and with further increase, some of them may burn out. In dark conditions, photon emission centers are visible with a bare eye. To visualize electron emission centers, emission electron microscopy is used. The conducted measurements allow comparison of the number and relative positions of electron and photon emission centers. It is shown that electrons and photons are emitted from the same centers.

What Tactics Should a Surgeon Choose to Treat a Black Extracerebral Tumor? A Case Report of Psammomatous Melanotic Schwannoma of the Meckel Cave and Literature Review

BACKGROUND

Neoplasms located in the Meckel cave account for 0.2%-0.5% of all intracranial tumors. This area is the site of many types of pathologic lesions, most often trigeminal nerve schwannomas and meningiomas. Melanin-containing tumors are rare in this area. These tumor types can be suspected if the magnetic resonance characteristics of a tumor has some differences in comparison with other types of central nervous system neoplasms. In fact, differential diagnosis of melanotic tumors is based mainly on the histopathologic criteria and immunohistochemical profile. This article presents a case report of melanotic schwannoma of the Meckel cave and a literature review of the problem.

CASE DESCRIPTION

A 23-year-old man underwent a 2-stage surgery for a dumbbell pigmented mass lesion located in the Meckel cave. No signs of recurrence were seen on follow-up magnetic resonance imaging (MRI) 3.5 years after the operation.

CONCLUSIONS

Melanin-containing tumor can be suspected in the presence of radiologic characteristics, such as a hyperintense MRI signal on T1-weighted images and a hypointense signal on T2-weighted images. If a black extracerebral tumor is detected, the main course of surgical treatment is maximal excision despite it possibly being a malignant melanoma and the temptation to perform partial resection because of an unfavorable prognosis. Chemotherapy can be justified in the presence of an aggressive melanotic schwannoma.

Hosting of surface states in spin-orbit induced projected bulk band gaps of W(1 1 0) and Ir(1 1 1)

Spin-momentum locking of surface states has attracted great interest in recent years due to envisioned technological applications in the field of spintronics. Normal metal surfaces like W(1 1 0) and Ir(1 1 1) show surface states with energy dispersions and spin-polarization textures, which are reminiscent of topologically non-trivial surface states. In order to understand this phenomenon the connection of bulk and surface states has to be explored. Using time-of-flight momentum microscopy with soft x-ray excitation, we present a comprehensive analysis of the bulk bands of W and Ir. Surface states are determined by the same method with photon excitation in the vacuum ultraviolet region. The superposition of both spectral densities reveals the hosting of surface states within the gap structure of bulk bands projected on the surface Brillouin zone. Quantitative differences in the extension of experimental and theoretical local band gaps indicate an underestimation of electron correlation effects in theory.

[Early postoperative results of surgical treatment of patients with anterior clinoidal meningiomas]

Resection of anterior clinoidal meningiomas is a challenging task due to their localization, frequent involvement of the major cerebral arteries and cranial nerves, a high risk of postoperative neurological deficits, and low radicalness of surgery.

AIM

To evaluate the radicalness of microsurgical removal and a neurological deficit in the early postoperative period in patients with anterior clinoidal meningiomas.

MATERIAL AND METHODS

A total of 35 patients with anterior clinoidal meningiomas underwent surgery at the Department of Neurooncology of the Novosibirsk Federal Neurosurgical Center in the period from 2013 to July 2016. There were 29 (82.9%) females and 6 (17.1%) males. The mean patient age was 50.1 years (31-72 years). According to the Al-Mefty classification (1990), type 1 tumors occurred in 10 (28.6%) patients, type 2 tumors were in 22 (62.8%) patients, and type 3 tumors were in 3 (8.6%) patients. Twenty four (68.6%) patients had large (greater than 4.0 cm) tumors, 7 (20.0%) patients had medium (2.0-4.0 cm) tumors, and 4 (11.4%) patients had small (less than 2.0 cm) meningiomas. The tumor involved the major arteries in 21 (60.0%) patients.

RESULTS

The lateral supraorbital approach was used in 26 (74.3%) patients, and the pterional approach was used in 9 (25.7%) cases. The tumor was resected totally (Simpson II) in 25 (71.4%) cases and subtotally (Simpson IV, subtype A and B) in 10 (28.6%) patients. In the early postoperative period, cerebral symptoms regressed in 20 (57.1%) patients; visual acuity improved in 2 of 13 (15.4%) patients. Four (11.4%) patients developed IIIrd nerve palsy; 2 (5.7%) patients developed severe hemiparesis. The mortality rate was 2.9%.

CONCLUSION

The completeness of resection directly depends on the tumor consistency: soft meningiomas can be totally resected (Simpson II) with a good functional outcome. In the case of solid tumors, total resection may lead to serious ischemic disorders with a high risk of death.

Evaluation of short-term surgical outcomes in facial paralysis patients treated by trigeminal neurotization

The management of patients with facial nerve palsy is a challenge of modern neurosurgery. The study purpose was to evaluate the degree of facial nerve function recovery, following trigeminal neurotization. Trigeminal neurotization was performed in 23 patients within 1 to 10 months after the development of facial paralysis. In most cases, the cause of facial paralysis was surgery for space-occupying lesions of the cerebellopontine angle (95.6%). Outcomes of trigeminal neurotization were evaluated in 17 (73.9%) patients who were followed-up for more than 6 months. In 16 (94.1%) patients, the facial nerve function was recovered to a House-Brackmann grade III-IV. Given the surgery

RESULTS

we can say that trigeminal neurotization is one of the effective treatments for facial paralysis. In most cases, this technique has provided good outcomes without additional complications, which is important for this group of patients.

Anomalous d-like surface resonances on Mo(110) analyzed by time-of-flight momentum microscopy

The electronic surface states on Mo(110) have been investigated using time-of-flight momentum microscopy with synchrotron radiation (hν=35 eV). This novel angle-resolved photoemission approach yields a simultaneous acquisition of the E-vs-k spectral function in the full surface Brillouin zone and several eV energy interval. (kx,ky,EB)-maps with 3.4 Å(-1) diameter reveal a rich structure of d-like surface resonances in the spin-orbit induced partial band gap. Calculations using the one-step model in its density matrix formulation predict an anomalous state with Dirac-like signature and Rashba spin texture crossing the bandgap at Γ¯ and EB=1.2 eV. The experiment shows that the linear dispersion persists away from the Γ¯-point in an extended energy- and k∥-range. Analogously to a similar state previously found on W(110) the dispersion is linear along H¯-Γ¯-H¯ and almost zero along N¯-Γ¯-N¯. The similarity is surprising since the spin-orbit interaction is 5 times smaller in Mo. A second point with unusual topology is found midway between Γ¯ and N¯. Band symmetries are probed by linear dichroism.

[Orbital phlegmon: clinical picture, diagnosis]

The purpose of the study was to enhance the efficiency of early diagnosis of orbital phlegmon, by examining its clinical picture and using instrumental studies. Sixty-three patients with orbital phlegmon were treated at hospital in 1985 to 2007. Its diagnosis employed ultrasound and X-ray studies. Orbital phlegmon was diagnosed in 30 patients with orbital injury and 33 patients with inflammatory diseases of the eyelids, face, nasal sinuses, and infection metastasis from septic foci. The disease was characterized by intoxication syndrome, eyelid inflammatory changes, chemosis, exophthalmos, and ophthalmoplegia. The following complications: neuritis, optic nerve ischemia, meningoencephalitis, brain abscess, cavernous sinus thrombosis, and sepsis were observed. Ultrasound and X-ray (computed tomography, magnetic resonance imaging) studies provide the diagnosis of the disease in early periods and timely medical and surgical treatments.

Gram-scale synthesis of pinusolide and evaluation of its antileukemic potential

Pinusolide (1), a known platelet-activating factor (PAF) receptor binding antagonist, was synthesized from lambertianic acid (2), a labdane-type diterpene readily accessible in multigram quantities from the Siberian pine tree. It was shown that 1 not only decreases the proliferation activity of tumor cells at relatively low concentrations but specifically induces apoptosis at 100 microM via the mitochondrial pathway in the Burkitt lymphoma cell line BJAB. Also, using primary lymphoblasts and leukemic cells from children with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML), a significant DNA fragmentation in pinusolide-treated cells could be detected in an ex vivo apoptosis assay.

[Endoscopic video cameras of the series EVK-103 and EVK-1031Ts]

Russian analogue EVK-103 and digital EVK-1031S video cameras, designed to function jointly with endoscopic television systems, are described.