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At least 613 records · Page 34Linked to original sources
PubMed2005

Ultrasensitive second-harmonic generation frequency-resolved optical gating by aperiodically poled LiNbO3 waveguides at 1.5 microm.

We retrieve intensity and phase profiles of 280 fs, 50 MHz optical pulses with 124 aJ coupled pulse energy (960 photons) by second-harmonic generation (SHG) frequency-resolved optical gating, using aperiodically poled LiNbO3 waveguides. The strong nonlinear interaction that is due to confinement within the micrometer-sized waveguide structure and the linearly chirped poling period contribute, respectively, to high SHG efficiency and broad phase-matching bandwidth. The achieved sensitivity is 2.7 x 10(-6) mW2, improving on the previous record for self-referenced complete pulse characterization by 5 orders of magnitude.

Journal Article↗
PubMed2005

Multistep cascading in periodically poled directional couplers.

We suggest a novel scheme for multistep cascaded parametric processes based on a periodically poled nonlinear directional coupler and derive the conditions for simultaneous phase matching of the second-harmonic generation and sum-frequency mixing processes. We predict an efficient wavelength conversion by the cascaded third-harmonic generation from the third optical communication window (1.53-1.56 microm) to visible in a LiNbO3 poled waveguide coupler.

Journal Article↗
PubMed2005

Observation of triply coincident nonlinearities in periodically poled KTiOPO4.

We report the simultaneous quasi-phase-matching of all three possible nonlinearities for propagation along the X axis of periodically poled (PP) KTiOPO4 (KTP) for second-harmonic generation of 745 nm pulsed light from 1490 nm subpicosecond pulses in a PPKTP crystal with a 45.65 microm poling period. This confirms the recent Sellmeier fits for KTP by Kato and Takaoka [Appl. Opt. 41, 5040 (2002)]. Such coincident nonlinearities are of importance for realizing compact sources of multipartite continuous-variable entanglement [Pfister et al., Phys. Rev. A 70, 020302 (2004)], and we propose a new simpler method for entangling four fields on the basis of this triple coincidence.

Journal Article↗
PubMed2006

Second-harmonic generation in thermally poled chalcohalide glass.

Second-harmonic generation in 60GeS(2)-20Ga(2)S(3)-20KBr chalcohalide glass was investigated by the thermal poling method. A large second-order nonlinear susceptibility, as high as 7.0 pm/V, was obtained in a poled sample by Maker fringe analysis. We believe this to be the first time that a clear second-harmonic wave was observed in chalcohalide glasses containing large amount of alkali ions (6.25 at. %). Such observation is of great potential use in all optical waveguide devices.

Journal Article↗
PubMed2007

Noncollinear double quasi phase matching in one-dimensional poled crystals.

We demonstrate simultaneous phase matching of two different nonlinear processes, using a noncollinear interaction in periodically poled crystal with single grating. The noncollinear scheme provides phase-matching solutions over continuous regions of the optical spectrum and can be used for multiple-harmonic generation as well as all-optical effects. We have demonstrated experimentally third-harmonic generation of a 3 microm pump wavelength in a noncollinear configuration using a periodically poled LiNbO3 crystal. We observed, in good agreement with theoretical calculation, very broad spectral and thermal acceptance bandwidths, as well as a relatively narrow angular bandwidth.

Journal Article↗
PubMed2005

Orientation distribution functions based upon both (P1), (P3) order parameters and upon the four (P1) up to (P4) values: application to an electrically poled nonlinear optical azopolymer film.

The most probable orientational distribution functions of rod-like polar molecules contained in a noncentrosymmetric uniaxial system are established using the first-rank and third-rank Legendre polynomials, (P1(cos theta)) and (P3(cos theta)) order parameters, and the maximum entropy method. Emphasis is put on the different domains of existence in the ((P1), (P3)) plane for the various shapes of the distributions: it is thus shown that, for any positive (P1(cos theta)) value and for decreasing (P3(cos theta)) values, the distribution function may exhibit either a distorted oblate form with an intense maximum at 0 degrees, or a three-leaved rose curve with maxima at 60 degrees, 180 degrees, and 300 degrees, and finally another markedly oblate shape with a strong maximum at 180 degrees. As an illustrative example, we have considered the azobenzene molecular orientations in an electrically poled p(DR1M) homopolymer thin film after a thermal process and several relaxation periods. We have made use not only of the (P1) and (P3) parameters determined from polarized second-harmonic generation (SHG) measurements, but also of the (P2) values extracted from UV-visible spectra and of the (P4) values adjusted according to the information entropy theory. In such a thin film with very large nonlinear properties (d33 coefficients were varying from 437.0 to 117.0 pm/V at 1064 nm) it is evidenced that a strong polar order is maintained even after a long relaxation period of 42 days. So, the distribution functions demonstrate that the poling treatment was quite efficient and they emphasize the importance in the determination of both couples of odd and even order parameters in such uniaxially oriented optical elements.

Algorithms↗
PubMed2006

The drosophila fragile X protein dFMR1 is required during early embryogenesis for pole cell formation and rapid nuclear division cycles.

The FMR family of KH domain RNA-binding proteins is conserved from invertebrates to humans. In humans, inactivation of the X-linked FMR gene fragile X is the most common cause of mental retardation and leads to defects in neuronal architecture. While there are three FMR family members in humans, there is only a single gene, dfmr1, in flies. As in humans, inactivation of dfmr1 causes defects in neuronal architecture and in behavior. dfmr1 has other functions in the fly in addition to neurogenesis. Here we have analyzed its role during early embryonic development. We found that dfmr1 embryos display defects in the rapid nuclear division cycles that precede gastrulation in nuclear migration and in pole cell formation. While the aberrations in nuclear division are correlated with a defect in the assembly of centromeric/centric heterochromatin, the defects in pole cell formation are associated with alterations in the actin-myosin cytoskeleton.

Animals↗
PubMed1977

Pneumothorax: a complication of percutaneous aspiration of upper pole renal masses.

Pneumothorax is a rare complication of percutaneous needle aspiration of suspected upper pole renal cysts. This complication is of particular concern in elderly patients with compromised cardiopulmonary reserve who undergo this procedure on an outpatient basis. An upright expiratory chest film is recommended following needle aspiration of upper pole lesions for detection of asymptomatic pneumothorax.

Aged↗
PubMed2001

Susceptibility to motion sickness induced by optokinetic rotation and self-rotation by walking around a vertical pole.

31 subjects viewed an optokinetic rotating drum for 12 min. in one session and self-rotated by walking quickly around a vertical pole with eyes closed while alternately flexing and extending the neck in another session. The self-rotation session contained 6 trials (3 clockwise and 3 counterclockwise rotations). Each trial contained 20 cycles of self-rotations. Self-reported ratings of nausea and symptoms of motion sickness were obtained for each session. The subjects developed symptoms of nausea, sweating, dizziness, headache, drowsiness, and changes in salivation in both drum rotation and self-rotation sessions. However, the subjects reported higher ratings of nausea in the session of optokinetic rotation than in the session of self-rotation around a vertical pole. These results indicated that both optokinetic rotation and self-rotation with eyes closed while alternately flexing and extending the neck are effective means of inducing nausea and motion sickness.

Adolescent↗
PubMed2005

Design of a mosquito trap support pole for use with CDC miniature light traps.

A mosquito trap support pole constructed from polyvinyl chloride and aluminum pipes was designed to hang a Centers for Disease Control and Prevention miniature light trap and dry ice container. Miniature light traps normally hang from tree branches. The trap support pole is designed to hang traps and dry ice bait in areas where no suitable trees exist.

Animals↗
PubMed1999

Organization of projections from the anterior pole of the nucleus reticularis thalami (NRT) to subdivisions of the motor thalamus: light and electron microscopic studies in the rhesus monkey.

Projections to the motor-related thalamic nuclei from the anterior pole of the reticular thalamic nucleus (NRT) were studied after injections of biotinylated dextran amine and wheat germ agglutinin conjugated horseradish peroxidase at light and electron microscopic levels, respectively. Each injection resulted in anterograde labeling in the three subdivisions of the ventral anterior nucleus (pars parvicellularis, VApc; pars densicellularis, VAdc; and pars magnocellularis, VAmc) and in the ventral lateral nucleus (VL). NRT fibers had beaded shapes and coursed in a posterior direction giving rise to relatively diffuse terminal plexuses. The average size of the beads (0.7 microm2) and their density per 100 microm of fiber length (23.7-25.7) were similar between the nuclei studied. At the electron microscopic level, anterogradely labeled boutons displayed positive immunoreactivity for gamma-aminobutyric acid (GABA), contained pleomorphic synaptic vesicles, and formed relatively long (approximately 0.4 microm) symmetric synaptic contacts. Usually, a single terminal formed synapses on more than one postsynaptic structure. Synaptic contacts were on projection and local circuit neurons and targeted mainly their distal dendrites. In the VAmc, synapses on local circuit neurons composed 48% of the total sample, in the VAdc/VApc and in the VL the proportion was higher, 65% and 62%, respectively. The results suggest that the input from the anterior pole of the monkey reticular nucleus to the motor-related thalamic nuclei is organized differently from what is known on the organization of connections of NRT with sensory thalamic nuclei in other species in that the terminal fields of individual fibers are diffuse rather than focal and that at least 50% of synapses are established on GABAergic local circuit neurons.

Animals↗
PubMed2000

Geriatric ureteropelvic junction obstruction: the possible role of an arteriosclerotic lower pole branch of renal artery: report of two cases.

An 83-year-old woman presented with left flank pain and high grade fever. After left ureteral catheterization and intensive chemotherapy with hemoperfusion, surgical exploration revealed the lower pole branches of the renal vessels were obstructing the ureteropelvic junction (UPJ), and dissection of the vessels released the obstruction. An 82-year-old man presented with right flank pain. Angiography demonstrated UPJ obstruction caused by the lower pole branch of the renal artery. Arterial dissection with dismembered pyeloplasty resulted in improvement of obstruction. In both cases, the patients had a long history of hypertension with mild to severe arteriosclerosis. Arteriosclerosis associated with fixation of the UPJ, may be one of the important factors leading to progressive hydronephrosis in geriatric patients.

Aged↗
PubMed2000

[Measurement of human retinal thickness at posterior pole with retinal thickness analyzer in normal and glaucomatous eyes].

OBJECTIVE: To determine the diagnostic value of retinal thickness analyzer (RTA) in glaucoma. METHODS: RTA was used to measure the retinal thickness at the posterior pole in 77 normal persons (116 eyes) at various ages and 22 cases (35 eyes) with glaucoma. The obtained images were processed by a computer to yield the retinal thickness value and the thickness map at this location, and the data were analyzed with SAS software package. RESULTS: The mean retina thickness of normal subjects was (171.83 +/- 18.50) microm with no significant difference among the various age groups (F = 2.68, P > 0.05), and very significant between the sexes; the thickest retina was at the location between macula and optic nerve head, and the macular nasal retina is 11.7% thicker than its temporal side. The upper and lower retinas of the fovea were basically symmetrical. The retinal thickness in glaucoma patients showed diffuse or local thinning, and there was a very significant difference between the normal group and the glaucomatous group in retina thickness (F = 11.98, P = 0.0001). The sensitivity rate for detecting glaucoma with RTA was up to 80.8%, and specificity to 78.5%. CONCLUSIONS: The thickness map for the retina at posterior pole across the macula in normal subjects is "horse shoe" shaped, that is well matched with the topography of retinal ganglion cell and the retinal nerve fibers in human retina. Diffuse or local thinning of retinal thickness in glaucomatous patients, which is in agreement with the corresponding visual field defect, and the sensitivity of RTA is higher than that of perimeter. The RTA examination is easy to operate, has high reproducibility, no invasion, therefore it is an ideal method to measure the human retinal thickness in vivo.

Adolescent↗
PubMedDate not supplied

Pole and blanket offer best chance of survival.

A wooden pole and a blanket form the emergency transport women in remoter areas of Manipur, India, have to rely on if complications arise during their pregnancies. The patient lies on the blanket, the two ends are tied to the pole, a supporting strip of cloth is fastened round the middle, two men hoist the sling (or Ngabongkhao) on their shoulders and carry the patient to hospital. Population growth and unemployment have forced many people to subsistence farming in remote locations in the India-Myanmar border area, reports Dr. Angom Russia, medical officer of the community health center at Imphal, Manipur. When obstetric emergencies occur, women may have to walk for up to three hours to the nearest road and then hope that a vehicle comes along, picks them up, and takes them to the nearest health center. The Ngabongkhao may represent their best chance of survival.

Asia↗
PubMed1998

Are they fellow countrymen or not? The migration of ethnic Poles from Kazakhstan to Poland.

"This article presents the process of migration of Kazakhs of Polish ancestry from Kazakhstan to Poland which has been taking place since the early 1990s. Poles deported in the past to Kazakhstan were mostly inhabitants of territories which did not belong to Poland; neither were they citizens of Poland. Therefore, the process of adaptation and integration was rather painful. The article points to factors that may simplify and those that may impede integration. The other problem...concerns the piecemeal policy towards Kazakhstan Poles, adopted by the Polish government, which seems risky if not dangerous. The author explains why it may cause a huge wave of illegal immigration to Poland."

Acculturation↗
PubMed2002

The role of the temporal pole in auditory processing.

Experiments in animals have shown that the temporal pole and the amygdala are involved in auditory processing. Comparable data are scarce in humans. It is only known that after temporal lobectomy, hearing may be impaired and dichotic listening scores reduced on the ear contralateral to the operated temporal lobe. Middle-latency auditory evoked potentials (MLAEPs) and late auditory evoked potentials (LAEPs) have been recorded in 14 patients before and after temporal lobectomy for the treatment of drug-resistant temporal lobe epilepsy. The Na and Pa components of MLAEPs were significantly delayed and the Pa component amplitude reduced before and after surgery as compared to a group of 21 healthy subjects. Data in pre- and postoperative period were not statistically different. N100 and P200 component of LAEPs were similarly altered. It is concluded that in humans the amygdala and probably the temporal pole may be involved in the process of auditory activation-inhibition. The possible role of auditory processing impairment in cognitive deficits in TLE patients can also be questioned.

Adult↗
PubMed2002

[Treatment of ureterocele in ureteral duplication: upper pole nephro-ureterectomy by retroperitoneoscopy in children: 24 cases].

OBJECTIVE: The objective of this study is to present the results of 24 upper pole nephrectomies performed by retroperitoneoscopy in children between 1995 and 2000. MATERIAL AND METHODS: This series of 24 children consisted of 15 girls and 9 boys with a mean age of 22 months. The patient was placed in the lateral supine position and 3 to 4 trocars were inserted. Parenchymal section was performed by ultrasound or unipolar scalpel. RESULT: Three cases (12.5%) required open conversion. Nine intraoperative complications (37%) were observed and repaired intraoperatively. Five postoperative complications (20%) consisted of residual perirenal collections, requiring drainage under anaesthesia in only one case. The mean operating time was 2 hours 40 minutes. The mean hospital stay was 3.4 days. The mean follow-up was 32 months. No cases of secondary atrophy of the lower pole were observed. CONCLUSION: Overall, these preliminary results are comparable to those of conventional open surgery. The advantage of this method is a reduction of skin and musculo-aponeurotic scars.

Child, Preschool↗
PubMed1999

[The development of a RF electrical pole catheter for heart ablation].

This article describes a RF electrical pole catheter for heart ablation. There is a device in the catheter, that can adjust the bending of the catheter tip on which there are a pair of electrical poles that is able to record and map the electrical potential of the heart, and to transfer 50 W electrical energy for focus ablution of heart disease.

Cardiac Surgical Procedures↗