Biomedical subjects

Z Hussain

Publications and source records attributed to Z Hussain.

At least 19 recordsLinked to original sources

PubMed2006

Distinct Fermi-momentum-dependent energy gaps in deeply underdoped Bi2212.

We used angle-resolved photoemission spectroscopy applied to deeply underdoped cuprate superconductors Bi2Sr2Ca(1-x)YxCu2O8 (Bi2212) to reveal the presence of two distinct energy gaps exhibiting different doping dependence. One gap, associated with the antinodal region where no coherent peak is observed, increased with underdoping, a behavior known for more than a decade and considered as the general gap behavior in the underdoped regime. The other gap, associated with the near-nodal regime where a coherent peak in the spectrum can be observed, did not increase with less doping, a behavior not previously observed in the single particle spectra. We propose a two-gap scenario in momentum space that is consistent with other experiments and may contain important information on the mechanism of high-transition temperature superconductivity.

Journal Article↗

PubMed2006

Genetic analysis of an ADRV-N-like novel rotavirus strain B219 detected in a sporadic case of adult diarrhea in Bangladesh.

An unusual human rotavirus strain B219 was detected in a stool specimen from a 65-year old patient with diarrhea in Bangladesh during April 2002. Cloning and sequence analysis of five genes of the B219 strain indicated that this virus is genetically closely related to the ADRV-N strain, which caused an adult diarrhea outbreak in China, but distinct from groups A, B, and C rotaviruses known to cause diarrheal diseases in humans. Accordingly, rotavirus strains B219 and ADRV-N were considered to belong to a novel group of human rotavirus, and the ADRV-N-like novel human rotaviruses were suggested to be distributed to a geographically wider area.

Aged↗

PubMed2006

Role of the calcarine cortex (V1) in perception of visual cues for saccades.

OBJECTIVE: To determine the initial level at which the pathways for cue perception, saccades and antisaccades diverge. METHODS: Two procedures: single pulse transcranial magnetic stimulation (sTMS) over posterior occiput and backward masking were used. A visual cue directed saccades to the left or right, either a pro-saccade (to the side of the cue but beyond it) or an antisaccade, i.e., contraversive saccade. No visual target was presented. RESULTS: Latencies of the two types of saccades did not differ. Focal sTMS applied unilaterally over V1 suppressed both perception of a cue flashed 80-90ms earlier contralaterally (but not ipsilaterally) and the appropriate saccade. Masking at a delay of 100ms abolished the appropriate saccade and cue perception. CONCLUSIONS: V1 is essential for the perception of a flashed cue and for executing appropriate pro- and contraversive saccades. Masking may occur beyond V1, where the pathways for perception and for saccades at least to the next visual processing level start separating. SIGNIFICANCE: VI is needed for rapid, accurate perceptual and motor responses to the crudest (left versus right) cues. It is unlikely that the "where" system can have a major direct input bypassing V1.

Attention↗

PubMed2006

Fermi surface and quasiparticle excitations of Sr2RhO4.

The electronic structure of the layered 4d transition metal oxide Sr2RhO4 is investigated by angle resolved photoemission. We find well-defined quasiparticle excitations with a highly anisotropic dispersion, suggesting a quasi-two-dimensional Fermi-liquid-like ground state. Markedly different from the isostructural Sr2RuO4, only two bands with dominant Rh 4dxz,zy character contribute to the Fermi surface. A quantitative analysis of the photoemission quasiparticle band structure is in excellent agreement with bulk data. In contrast, it is found that state-of-the-art density functional calculations in the local density approximation differ significantly from the experimental findings.

Journal Article↗

PubMed2006

Energy dispersion of 4f-derived emissions in photoelectron spectra of the heavy-fermion compound YbIr2Si2.

Angle-resolved photoemission spectra of the heavy-fermion system YbIr(2)Si(2) are reported that reveal strong momentum (k) dependent splittings of the 4f(13) bulk and surface emissions around the expected intersection points of the 4f final states with valence bands in the Brillouin zone. The obtained dispersion is explained in terms of a simplified periodic Anderson model by a k dependence of the electron hopping matrix element disregarding clearly interpretation in terms of a single-impurity model.

Journal Article↗

PubMed2006

Nested fermi surface and electronic instability in Ca3Ru2O7.

High-resolution angular resolved photoemission data reveal well-defined quasiparticle bands of unusually low weight, emerging in line with the metallic phase of Ca(3)Ru(2)O(7) below approximately 30 K . At the bulk structural phase transition temperature of 48 K, we find clear evidence for an electronic instability, gapping large parts of the underlying Fermi surface that appears to be nested. Metallic pockets are found to survive in the small, non-nested sections, constituting a low-temperature Fermi surface with 2 orders of magnitude smaller volume than in all other metallic ruthenates. The Fermi velocities and volumes of these pockets are in agreement with the results of complementary quantum oscillation measurements on the same crystal batches.

Journal Article↗

PubMed2006

Systematic review: Complementary and alternative medicine in the irritable bowel syndrome.

BACKGROUND: Complementary and alternative medical therapies and practices are widely employed in the treatment of the irritable bowel syndrome. AIM: To review the usage of complementary and alternative medicine in the irritable bowel syndrome, and to assess critically the basis and evidence for its use. METHODS: A systematic review of complementary and alternative medical therapies and practices in the irritable bowel syndrome was performed based on literature obtained through a Medline search. RESULTS: A wide variety of complementary and alternative medical practices and therapies are commonly employed by irritable bowel syndrome patients both in conjunction with and in lieu of conventional therapies. As many of these therapies have not been subjected to controlled clinical trials, some, at least, of their efficacy may reflect the high-placebo response rate that is characteristic of irritable bowel syndrome. Of those that have been subjected to clinical trials most have involved small poor quality studies. There is, however, evidence to support efficacy for hypnotherapy, some forms of herbal therapy and certain probiotics in irritable bowel syndrome. CONCLUSIONS: Doctors caring for irritable bowel syndrome patients need to recognize the near ubiquity of complementary and alternative medical use among this population and the basis for its use. All complementary and alternative medicine is not the same and some, such as hypnotherapy, forms of herbal therapy, specific diets and probiotics, may well have efficacy in irritable bowel syndrome. Above all, we need more science and more controlled studies; the absence of truly randomized placebo-controlled trials for many of these therapies has limited meaningful progress in this area.

Acupuncture Therapy↗

PubMed2006

A prospective, randomized trial comparing conventional transurethral prostate resection with PlasmaKinetic vaporization of the prostate: physiological changes, early complications and long-term followup.

PURPOSE: We compared standard transurethral prostate resection with bipolar PlasmaKinetic prostate vaporization for bladder outflow obstruction using a Gyrus PlasmaKinetic Plasma V bar. MATERIALS AND METHODS: A total of 160 men were enrolled in a prospective, randomized trial. Those at higher risk for cancer were excluded by prostate specific antigen and digital rectal examination with or without transrectal ultrasound biopsy. A total of 81 men underwent prostate vaporization and 79 underwent transurethral prostate resection. Preoperative International Prostate Symptom Score and quality of life score, uroflowmetry, post-void residual urine and transrectal ultrasound prostate volume were recorded. Preoperative and postoperative serum hemoglobin, hematocrit and sodium were measured. Perioperative fluid absorption was calculated using weighing on table and blood loss using the Hemocue system. Longer followup of International Prostate Symptom Score and quality of life score, uroflowmetry and post-void residual urine was available in 149 men, including 76 who underwent prostate vaporization and 73 who underwent transurethral prostate resection. Data were analyzed using the 1 or 2-sample t and chi-square tests. RESULTS: The 2 groups were comparable in all preoperative parameters. Perioperative fluid absorption, intraoperative blood loss, preoperative and postoperative serum hematocrit, and sodium changes were not statistically different. Mean resection time was 4 minutes shorter for transurethral prostate resection (28.5 vs 32.6 minutes, p = 0.08). Patients with transurethral prostate resection showed a greater hemoglobin decrease (1.39 vs 0.8 gm/dl, p = 0.002) and required more irrigation postoperatively (28.3 vs 20.4 l, p = 0.001). Four patients with transurethral prostate resection required transfusion compared with none who underwent prostate vaporization. After transurethral prostate resection hospital stay was longer (3.36 vs 3.02 days, p = 0.03). Cancer was detected in 8 patients with transurethral prostate resection (10%), of whom 7 are under prostate specific antigen surveillance and 1 received radical radiotherapy. Mean long-term followup was 258 days (range 82 to 884). Prostate vaporization and transurethral prostate resection were equally effective at followup, as evidenced by changes in maximum urine flow, International Prostate Symptom Score, quality of life score and post-void residual urine. CONCLUSIONS: The 2 operations are highly effective in experienced hands. PlasmaKinetic prostate vaporization resulted in less postoperative bleeding and a slightly shorter hospital stay. The lack of a histological specimen with this version of PlasmaKinetic prostate vaporization may mean that clinically significant cancers are missed.

Adult↗

PubMed2005

Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites.

A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu-O bonds) directions in momentum space, generally assumed to be linked to the 'd-wave' symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction. Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite 'Fermi arcs'. This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity or by invoking orders which are natural competitors of d-wave superconductors. Here we report experimental evidence that a very similar pseudogap state with a nodal-antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La1.2Sr1.8Mn2O7. Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state.

Journal Article↗

PubMed2005

Polaronic behavior of undoped high-T(c) cuprate superconductors from angle-resolved photoemission spectra.

We present angle-resolved photoemission spectroscopy (ARPES) data on undoped La2CuO4, indicating polaronic coupling between bosons and charge carriers. Using a shell model, we calculate the electron-phonon coupling and find that it is strong enough to give self-trapped polarons. We develop an efficient method for calculating ARPES spectra in undoped systems. Using the calculated couplings, we find the width of the phonon sideband in good agreement with experiment. We analyze reasons for the observed dependence of the width on the binding energy.

Journal Article↗

PubMed2005

Multiple bosonic mode coupling in the electron self-energy of (La2-xSrx)CuO4.

High resolution angle-resolved photoemission spectroscopy data along the (0,0)-(pi,pi) nodal direction with significantly improved statistics reveal fine structure in the electron self-energy of the underdoped (La2-xSrx)CuO4 samples in the normal state. Fine structure at energies of (40-46) meV and (58-63) meV, and possible fine structure at energies of (23-29) meV and (75-85) meV, have been identified. These observations indicate that, in (La2-xSrx)CuO4, more than one bosonic modes are involved in the coupling with electrons.

Journal Article↗

PubMed2005

Distal aneurysms of the unpaired ACA: embryologic and therapeutic aspects.

Anatomical variants of the cerebral arteries in general are frequent and due to the complex ontogenesis of these structures. Although encountered in many mammals, a single anterior cerebral artery (ACA) trunk is an infrequent finding in humans with an incidence of 3-5%. This vessel, giving rise to the arteries of both frontal lobes, is subjected to high flow volumes and distal arterial aneurysms have repetitively been encountered, mostly however before the introduction of endovascular treatment strategies. We report on five patients with acute SAH and arterial aneurysms of an unpaired ACA, who underwent coil embolisation. In all cases endovascular treatment using detachable platinum coils resulted in an at least satisfactory degree of aneurysm obliteration without parent artery occlusion or embolic infarcts. All patients had clinical and angiographic follow-up with median follow-up time of 29 months during which no aneurysm regrowth was encountered. In spite of a small patient group our results suggest, that altered flow dynamics due to enlarged single intracranial vessels may predispose to aneurysm formation and that endovascular embolisation is an appropriate treatment option in distal aneurysms of an unpaired ACA.

Embolization, Therapeutic↗

PubMed2004

Orientation-dependent C60 electronic structures revealed by photoemission spectroscopy.

We observe, with angle-resolved photoemission, a dramatic change in the electronic structure of two C60 monolayers, deposited, respectively, on Ag (111) and (100) substrates, and similarly doped with potassium to half filling of the C60 lowest unoccupied molecular orbital. The Fermi surface symmetry, the bandwidth, and the curvature of the dispersion at Gamma point are different. Orientations of the C60 molecules on the two substrates are known to be the main structural difference between the two monolayers, and we present new band-structure calculations for some of these orientations. We conclude that orientations play a key role in the electronic structure of fullerides.

Journal Article↗

PubMed2004

Fermi surface reconstruction in the CDW state of CeTe3 observed by photoemission.

CeTe3 is a layered compound where an incommensurate charge density wave (CDW) opens a large gap ( approximately 400 meV) in optimally nested regions of the Fermi surface (FS), whereas other sections with poorer nesting remain ungapped. Through angle-resolved photoemission, we identify bands backfolded according to the CDW periodicity. They define FS pockets formed by the intersection of the original FS and its CDW replica. Such pockets illustrate very directly the role of nesting in the CDW formation but they could not be detected so far in a CDW system. We address the reasons for the weak intensity of the folded bands, by comparing different foldings coexisting in CeTe3.

Journal Article↗

PubMed2004

Coupling of the B1g phonon to the antinodal electronic states of Bi2Sr2Ca0.92Y0.08Cu2O8+delta.

Angle-resolved photoemission spectroscopy on optimally doped Bi(2)Sr(2)Ca(0.92)Y(0.08)Cu(2)O(8+delta) uncovers a coupling of the electronic bands to a 40 meV mode in an extended k-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the B(1g) oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data.

Journal Article↗

PubMed2004

Fermi surface and quasiparticle dynamics of Na0.7CoO2 investigated by angle-resolved photoemission spectroscopy.

We present the first angle-resolved photoemission study of Na0.7CoO2, the host material of the superconducting NaxCoO2.nH(2)O series. Our results show a hole-type Fermi surface, a strongly renormalized quasiparticle band, a small Fermi velocity, and a large Hubbard U. The quasiparticle band crosses the Fermi level from M toward Gamma suggesting a negative sign of effective single-particle hopping t(eff) (about 10 meV) which is on the order of magnetic exchange coupling J in this system. Quasiparticles are well defined only in the T-linear resistivity (non-Fermi-liquid) regime. Unusually small single-particle hopping and unconventional quasiparticle dynamics may have implications for understanding the phase of matter realized in this new class of a strongly interacting quantum system.

Journal Article↗

PubMed2004

Dichotomy between nodal and antinodal quasiparticles in underdoped (La2-xSrx)CuO4 superconductors.

High resolution angle-resolved photoemission measurements on an underdoped (La(2-x)Srx)CuO4 system show that, at energies below 70 meV, the quasiparticle peak is well defined around the (pi/2,pi/2) nodal region and disappears rather abruptly when the momentum is changed from the nodal point to the (pi,0) antinodal point along the underlying "Fermi surface." It indicates that there is an extra low energy scattering mechanism acting upon the antinodal quasiparticles. We propose that this mechanism is the scattering of quasiparticles across the nearly parallel segments of the Fermi surface near the antinodes.

Journal Article↗

PubMed2004

Direct extraction of the Eliashberg function for electron-phonon coupling: a case study of Be(10(-)10).

We propose a systematic procedure to directly extract the Eliashberg function for electron-phonon coupling from high-resolution angle-resolved photoemission measurement. The procedure is successfully applied to the Be(10(-)10) surface, providing new insights into electron-phonon coupling at this surface. The method is shown to be robust against imperfections in experimental data and suitable for wider applications.

Journal Article↗