Quantum Holography in a Graphene Flake with an Irregular Boundary.

Electrons in clean macroscopic samples of graphene exhibit an astonishing variety of quantum phases when strong perpendicular magnetic field is applied. These include integer and fractional quantum Hall states as well as symmetry broken phases and quantum Hall ferromagnetism. Here we show that mesoscopic graphene flakes in the regime of strong disorder and magnetic field can exhibit another remarkable quantum phase described by holographic duality to an extremal black hole in two-dimensional anti-de Sitter space. This phase of matter can be characterized as a maximally chaotic non-Fermi liquid since it is described by a complex fermion version of the Sachdev-Ye-Kitaev model known to possess these remarkable properties.

Interplay of Chiral and Helical States in a Quantum Spin Hall Insulator Lateral Junction.

We study the electronic transport across an electrostatically gated lateral junction in a HgTe quantum well, a canonical 2D topological insulator, with and without an applied magnetic field. We control the carrier density inside and outside a junction region independently and hence tune the number and nature of 1D edge modes propagating in each of those regions. Outside the bulk gap, the magnetic field drives the system to the quantum Hall regime, and chiral states propagate at the edge. In this regime, we observe fractional plateaus that reflect the equilibration between 1D chiral modes across the junction. As the carrier density approaches zero in the central region and at moderate fields, we observe oscillations in the resistance that we attribute to Fabry-Perot interference in the helical states, enabled by the broken time reversal symmetry. At higher fields, those oscillations disappear, in agreement with the expected absence of helical states when band inversion is lifted.

Giant topological longitudinal circular photo-galvanic effect in the chiral multifold semimetal CoSi.

The absence of mirror symmetry, or chirality, is behind striking natural phenomena found in systems as diverse as DNA and crystalline solids. A remarkable example occurs when chiral semimetals with topologically protected band degeneracies are illuminated with circularly polarized light. Under the right conditions, the part of the generated photocurrent that switches sign upon reversal of the light's polarization, known as the circular photo-galvanic effect, is predicted to depend only on fundamental constants. The conditions to observe quantization are non-universal, and depend on material parameters and the incident frequency. In this work, we perform terahertz emission spectroscopy with tunable photon energy from 0.2 -1.1 eV in the chiral topological semimetal CoSi. We identify a large longitudinal photocurrent peaked at 0.4 eV reaching  ~550 µ A/V2, which is much larger than the photocurrent in any chiral crystal reported in the literature. Using first-principles calculations we establish that the peak originates only from topological band crossings, reaching 3.3 ± 0.3 in units of the quantization constant. Our calculations indicate that the quantized circular photo-galvanic effect is within reach in CoSi upon doping and increase of the hot-carrier lifetime. The large photo-conductivity suggests that topological semimetals could potentially be used as novel mid-infrared detectors.

Occurrence and bioaccumulation study of PCDD and PCDF from mineral feed additives.

Extraction of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was evaluated in sepiolite matrices. Soxhlet extraction using different extracting strategies and acid treatment were tested. Acid treatment or Soxhlet extraction using a mixture of toluene:ethanol as solvent allowed to reach the minimum requirements for recovery rates. However, Soxhlet extraction using a mixture cyclohexane:toluene as extracting solvent did not allow to comply with these minimum requirements. Significant differences were obtained in TEQ units when acid treatment was applied in comparison to Soxhlet extraction. This fact can be explained because the use of drastic acid conditions allows removing strongly adsorbed analytes which can be uniquely extracted after a total destruction of the crystalline. On the contrary, Soxhlet extraction was not able to destroy the structure of sepiolite and as a consequence the PCDDs/Fs remain adsorbed in the internal structure of the mineral. A bioaccumulation study was also conducted to evaluate the transference of PCDDs/Fs from the sepiolite into the animal when fed with feed containing sepiolite. Four groups of chickens were exposed through diet to a control feed, feed with 3% w/w sepiolite, spiked feed contaminated with PCDDs/Fs and feed containing contaminated kaolinitic clay. Livers of animals were analyzed throughout the exposure period. Results of this trial showed that the performance of broilers was not affected by the presence of dioxins at levels tested, and chickens did not show any abnormal behaviour. Dioxins intentionally added to the diet were significantly absorbed and accumulated in liver, whereas the PCDDs/Fs from sepiolite were not available for chickens since livers from broilers fed 3% sepiolite presented similar WHO-TEQ values than those from broilers fed control diet.

[Phytobezoar dissolution with Coca-Cola]. / Disolución de fitobezoar con Coca-Cola.

The treatment of phytobezoar is empiric. The various therapeutic choices include dietary modifications, prokinetic drugs, gastric lavage, enzymatic dissolution, endoscopic treatment, and surgery. We present two cases of phytobezoar with successful outcome after Coca-Cola administration.

Large incisional hernia repair using intraperitoneal placement of expanded polytetrafluoroethylene.

BACKGROUND: Several methods for using a prosthetic material to repair incisional hernias have been described, but only one previous report discussed pure intraperitoneal placement of expanded polytetrafluoroethylene (ePTFE). METHODS: Retrospective review of medical records of 84 patients in whom pure intraperitoneal placement of ePTFE was used between March 1995 and October 1997. RESULTS: No intraoperative complications occurred. Postoperatively, 2 patients required mechanical ventilation, 5 had seromas, 3 had hematomas, 1 had an abscess, and 1 had wound necrosis. There was 1 death due to necrotizing fascitis. The prosthesis infection rate was 1.7%. During follow-up ranging from 1 to 3 years, there were 2 hernia recurrences. CONCLUSIONS: Pure intraperitoneal placement of ePTFE has several advantages over other techniques, including minimal dissection and, possibly, a decreased risk of infection.

[Clinico-epidemiologic study of bacterial meningitis in Aragon]. / Estudio clinicoepidemiológico de las meningitis bacterianas en Aragón.

BACKGROUND: The aim of the present study was to know the incidence, etiology, prognostic factors and rate of mortality of bacterial meningitis in Aragón (Spain). METHODS: The clinical records of all the patients with bacterial meningitis seen in the hospitals in Aragón (Spain), from 1985 to 1988 inclusive were reviewed. RESULTS: The mean of the annual rates of incidence for Aragón (Spain) was 7.52/100,000 inhabitants. In patients under the age of 15 years the most frequent etiologies were Neisseria meningitidis (59.0%), Haemophilus influenzae (13.7%) and Streptococcus pneumoniae (9.4%); the global rate of mortality was 3.5% similar to that of sequelae. In those over the age of 14 years, the most frequent etiologies were N. meningitidis (33%), S. pneumoniae (18.4%) and Staphylococcus spp. (13.6%); the rate of global mortality was 19.5% and that of sequelae 10.8% with resistance of S. pneumoniae to penicillin and/or ampicillin in 45.5% of the cases in children and in 26.3% in adults. No significant evolutive differences related with the existence of resistances or the administration of antibiotics prior to lumbar punction were observed in any of the age groups. CONCLUSIONS: N. meningitidis is the main etiologic agent in Aragón in both children and adults. The greatest rates of mortality and sequelae were observed in the youngest and oldest age groups with a similar relation being seen in infection by gramnegative bacilli and S. pneumoniae, thus making these patients to be considered as being at high risk.

Mycobacterium malmoense lymphadenitis in Spain: first two cases in immunocompetent patients.

Reported here are two cases of Mycobacterium malmoense lymphadenitis that occurred in two immunocompetent children in Spain. To the best of our knowledge, these are the first documented cases of extrapulmonary infection by M. malmoense in Spain. This report serves to draw attention to this emerging nontuberculous mycobacterium that is gaining increasing recognition as a pulmonary and extrapulmonary pathogen in different countries.

[Partial splenic embolization in hypersplenism]. / Embolización parcial esplénica en el hiperesplenismo.

Partial splenic embolization is a new procedure in the treatment of hypersplenism in infancy. We have used embolization of the spleen as an alternative to splenectomy in a patient with critical hypersplenism. The patient was a 6 year old girl with portal hypertension. The white blood cell and platelet count returned to normal 24 hours after embolization and tre frequency of bleeding episodes was reduced. There were no splenic abscesses and no other significant complications of the treatment.

Efficacy, safety and predictive factors of therapeutic success with sildenafil for erectile dysfunction in patients with different spinal cord injuries.

STUDY DESIGN: Multicenter, open, prospective, before-after study. OBJECTIVE: To assess the efficacy and safety of sildenafil therapy for erectile dysfunction in patients with spinal cord injury, and the association between the response to sildenafil and factors such as causes and levels of spinal cord injury, grade of ASIA deficit, time since injury, orgasmic perception, and degree of baseline erection. SETTING: Homes of outpatients of 16 spinal cord injury units in Spain. METHOD: One hundred and seventy patients with erectile dysfunction secondary to spinal cord injury, from whom baseline data were collected on their sexual function, and who started treatment with sildenafil 50 mg. An efficacy assessment was made by the patient and his partner, and the score of the International Index of Erectile Function (IIEF) was recorded. RESULTS: It was reported by 88.2% of the patients and 85.3% of their partners that treatment with sildenafil had improved their erections, regardless of the baseline characteristics of the spinal cord injury and erectile function. In responders, this improvement was confirmed by an increase from 12.5 to 24.8 points (P<0.001) of the Erectile Function Domain of IIEF. A significant improvement was also seen in patients' satisfaction with sexual activity and general satisfaction derived from sexual life. Preservation of orgasmic perception and a baseline degree of erection of 3 or 4 (P=0.006) were predictors of therapeutic success. No serious adverse events occurred. CONCLUSION: Sildenafil is an effective, well-tolerated treatment for erectile dysfunction caused by spinal cord injury, regardless of the cause, neurological level, ASIA grade, and time since injury. SPONSORSHIP: Spanish Society of Paraplegia.