Acoustic interactions between inversion symmetric and asymmetric two-level systems.

Amorphous solids, as well as many disordered lattices, display remarkable universality in their low temperature acoustic properties. This universality is attributed to the attenuation of phonons by tunneling two-level systems (TLSs), facilitated by the interaction of the TLSs with the phonon field. TLS-phonon interaction also mediates effective TLS-TLS interactions, which dictates the existence of a glassy phase and its low energy properties. Here we consider KBr:CN, the archetypal disordered lattice showing universality. We calculate numerically, using conjugate gradients method, the effective TLS-TLS interactions for inversion symmetric (CN flips) and asymmetric (CN rotations) TLSs, in the absence and presence of disorder, in two and three dimensions. The observed dependence of the magnitude and spatial power law of the interaction on TLS symmetry, and its change with disorder, characterizes TLS-TLS interactions in disordered lattices in both extreme and moderate dilutions. Our results are in good agreement with the two-TLS model, recently introduced to explain long-standing questions regarding the quantitative universality of phonon attenuation and the energy scale of ≈ 1-3 K below which universality is observed.

Single-base resolution nucleosome mapping on DNA sequences.

Nucleosome DNA bendability pattern extracted from large nucleosome DNA database of C. elegans is used for construction of full length (116 dinucleotide positions) nucleosome DNA bendability matrix. The matrix can be used for sequence-directed mapping of the nucleosomes on the sequences. Several alternative positions for a given nucleosome are typically predicted, separated by multiples of nucleosome DNA period. The corresponding computer program is successfully tested on best known experimental examples of accurately positioned nucleosomes. The uncertainty of the computational mapping is +/-1 base. The procedure is placed on publicly accessible server and can be applied to any DNA sequence of interest.

Nucleosome DNA bendability matrix (C. elegans).

An original signal extraction procedure is applied to database of 146 base nucleosome core DNA sequences from C. elegans (S. M. Johnson et al. Genome Research 16, 1505-1516, 2006). The positional preferences of various dinucleotides within the 10.4 base nucleosome DNA repeat are calculated, resulting in derivation of the nucleosome DNA bendability matrix of 16x10 elements. A simplified one-line presentation of the matrix ("consensus" repeat) is ...A(TTTCCGGAAA)T.... All 6 chromosomes of C. elegans conform to the bendability pattern. The strongest affinity to their respective positions is displayed by dinucleotides AT and CG, separated within the repeat by 5 bases. The derived pattern makes a basis for sequence-directed mapping of nucleosome positions in the genome of C. elegans. As the first complete matrix of bendability available the pattern may serve for iterative calculations of the species-specific matrices of bendability applicable to other genomic sequences.

Reconstruction of natural RNA sequences from RNA shape, thermodynamic stability, mutational robustness, and linguistic complexity by evolutionary computation.

The process of designing novel RNA sequences by inverse RNA folding, available in tools such as RNAinverse and InfoRNA, can be thought of as a reconstruction of RNAs from secondary structure. In this reconstruction problem, no physical measures are considered as additional constraints that are independent of structure, aside of the goal to reach the same secondary structure as the input using energy minimization methods. An extension of the reconstruction problem can be formulated since in many cases of natural RNAs, it is desired to analyze the sequence and structure of RNA molecules using various physical quantifiable measures. In prior works that used secondary structure predictions, it has been shown that natural RNAs differ significantly from random RNAs in some of these measures. Thus, we relax the problem of reconstructing RNAs from secondary structure into reconstructing RNAs from shapes, and in turn incorporate physical quantities as constraints. This allows for the design of novel RNA sequences by inverse folding while considering various physical quantities of interest such as thermodynamic stability, mutational robustness, and linguistic complexity. At the expense of altering the number of nucleotides in stems and loops, for example, physical measures can be taken into account. We use evolutionary computation for the new reconstruction problem and illustrate the procedure on various natural RNAs.

Posterior chamber intraocular lens implantation after capsular tear: ultrasound biomicroscopy evaluation.

PURPOSE: To evaluate by ultrasound biomicroscopy (UBM) the exact position of a posterior chamber intraocular lens (PC IOL) implanted above a posterior capsule tear and to correlate the findings with the outcomes and complication rate. SETTING: Department of Ophthalmology, Rabin Medical Center, Petah Tiqva, Israel. METHODS: In a retrospective noncomparative case series, 36 patients (36 eyes) who had extracapsular cataract extraction (ECCE) complicated by capsular tear were evaluated. In all cases, a PC IOL was implanted above the remnant of the capsule without suturing. Ultrasound biomicroscopy was performed to study the exact position of the optic and haptic. The outcomes and complication rate were determined from patient examinations performed during a follow-up of 1 to 6 years. RESULTS: Optic tilt was found in 20 of 36 patients (56%). In 17 patients (47%), both haptics were located in the sulcus. In 15 patients (42%), 1 haptic was observed in the sulcus and 1 in the bag or elsewhere. No correlation was found between the position of the optic and the location of the haptics. Minimal postoperative complications were observed, and only 1 patient required another surgery for a dislocated IOL. CONCLUSION: By UBM, half the patients had optic tilt and more than half the IOLs were not implanted in the sulcus, the intended location.

Use of high-frequency ultrasound imaging to improve delineation of anterior uveal melanoma for proton irradiation.

The aim of this study was to evaluate high-frequency ultrasound imaging (HFUI) as an aid in localizing anterior margins of tumours of the eye for proton therapy. Proton irradiation of ocular melanoma requires an accurate assessment of all tumour margins. The tumour is marked surgically by suturing to the sclera four or five tantalum rings on the borders of the tumour defined by transillumination. In order to evaluate the clinical usefulness of high-frequency ultrasound imaging, four and five rings were surgically placed in a patient with an iris/ciliary body melanoma and in a patient with ciliochoroidal melanoma using transillumination to localize the tumour margins. Subsequently margins were verified by HFUI. In the first patient, the distances between the rings and the limbus were measured using calipers during surgery and were compared with HFUI measurements and measurements from planning software. The distances were comparable within 0.5 mm. In the second patient the treatment was planned in two different ways using EYEPLAN software. In the first scenario the shape of the tumour and its relation to the rings were obtained from the surgeon's mapping, the fundus drawing using a transilluminating point light source, and the HFUI. In the second scenario, the shape of the tumour was deduced from the ring positions only. It was observed that the maximum difference between the tumour edge as seen on high-frequency ultrasound images and the rings was 2.6 mm. The tumour volume was underestimated by 39% when tumour shape was obtained from ring positions only. During the past year we have utilized HFUI in 18 patients having tumours involving the anterior segment of the eye, among which four were treated with proton therapy. In conclusion, we believe that high-frequency ultrasound imaging provides additional information with respect to the location of tumour margins in ciliary body and anterior uveal melanoma. Occult extension of the tumour within the ciliary body or posterior iris may not be appreciated by transillumination alone.

Digital red-free photography for the evaluation of retinal blood vessel displacement in epiretinal membrane.

OBJECTIVE: To evaluate the displacement of retinal blood vessels during the natural course of epiretinal membrane (ERM) formation. DESIGN: Consecutive observational case series. PARTICIPANTS: Thirteen patients (13 eyes) diagnosed with unilateral idiopathic ERM and 10 normal fellow eyes of the same patients served as a control group and constituted the study group. TESTING: All eyes underwent digital red-free filter photography of the fundus using the Topcon Imagenet-1024 System. Photographs were taken on entry to the study and again after 8 to 13 months. Distances were measured between the major and minor blood vessel junctions at the upper and lower temporal arcades and between the disc margin and vessel junctions temporal to the macula on follow-up examinations. To clearly visualize vessel shift, both photographs of each patient were overlaid using the peripheral landmarks of major blood vessel crossings as reference points. MAIN OUTCOME MEASURES: The parameters measured were shifting of blood vessels caused by the ERM formation. The distances were measured in micrometers using the measurement feature of the Topcon Imagenet System. RESULTS: Blood vessel shift (range, 30 microm-434 microm) was noted in all 13 eyes, but in 15 measurements the shift was less than 30 microm and was considered as no shift. In four eyes (31%), the distances decreased in all directions, indicating contraction of the ERM. In four eyes (31%), the distances increased in all directions, indicating release of the ERMs. A mixed pattern of release and contraction of the ERM in the same eye was noted in five eyes (38%). No shift of blood vessels was noted in the control eyes. Findings on image overlay corresponded with the objective measurements. CONCLUSIONS: Noninvasive digital red-free photography is an informative tool for the objective measurement of the vessel displacement during ERM formation. Contraction and release of the ERM were noted.

Ultrasound biomicroscopic detection of anterior ocular segment foreign body after trauma.

PURPOSE: To describe the role of ultrasound biomicroscopy in the detection and localization of foreign bodies in anterior ocular segment foreign body after trauma. METHODS: In a prospective study, ultrasound biomicroscopy was performed in five eyes of five consecutive patients with suspected anterior ocular segment foreign body. RESULTS: In all five eyes, ultrasound biomicroscopy detected and precisely localized small foreign bodies (metallic in two eyes, stone in one eye, plastic in one eye, and ceramic in one eye) in the cornea (one eye), superficial sclera (one eye), and anterior ocular segment (three eyes). Operative procedures to remove the intraocular foreign bodies (three cases) were guided by the ultrasound biomicroscopy information. CONCLUSIONS: Ultrasound biomicroscopy is a noninvasive method for detecting anterior segment intraocular foreign bodies after perforating trauma. It can be used to accurately diagnose foreign bodies and assist in surgical management, particularly when direct visualization is obscured because of the trauma. In eyes with partial-thickness corneoscleral lacerations or sealed full-thickness corneoscleral laceration and suspected anterior ocular segment foreign body, ultrasound biomicroscopy is a safe and effective method for detecting and localizing foreign bodies in the anterior ocular segment.

Ultrasonography of the optic nerves: clinical application in children with pseudotumor cerebri.

OBJECTIVE: Pseudotumor cerebri (PTC) in children has a wide spectrum of clinical presentations, from headache, which may be posterior and associated with nausea, vomiting or diplopia, to nonspecific headache, which may not be posterior and related or unrelated to other symptoms. In children with nonspecific headache, supportive evidence for diagnosis may be required before invasive procedures such as lumbar punctures are performed. Ultrasonography of the optic nerves (USON) is a noninvasive examination that can provide information about optic nerve changes, including those resulting from increased intracranial pressure. The applicability of USON in the diagnosis and follow-up of PTC was examined. STUDY DESIGN: Seventeen children were referred to our service because of a clinical suspicion of PTC, suggested by the presence of swollen optic nerve discs and/or headache, without clinical evidence of another cause. All had normal brain computed tomography and/or magnetic resonance imaging results before referral. Each child was examined with USON while in the supine position and with a 30-degree head tilt and underwent a lumbar puncture. USON was repeated on follow-up evaluation. RESULTS: The diagnosis of PTC was confirmed by lumbar puncture in 10 children and ruled out in 6 children. Overall, the USON results correlated with an increased opening pressure on lumbar puncture in 11 children. CONCLUSION: We noted an excellent correlation between the clinical results and the USON findings in PTC, and in many cases repeated lumbar punctures could be avoided. USON is more easily applied than a lumbar puncture, without the accompanying risks. It may be used as an indicator of increased intracranial pressure, as well as a follow-up tool. However, further studies are required before the accuracy of USON can be fully established.

In search of behavioral individuality.

Living things are not created identical: In sexually reproducing species, individuals-except monozygotic twins-are different. Although widely acknowledged, behavioral individuality has received relatively little empirical or theoretical attention. Yet it seems likely that research focusing on individual differences will yield important insights for evolutionarily minded students of behavioral biology, including those interested in better understanding Homo sapiens.

Ultrasonographic findings of the optic disc in congenital glaucoma.

A 2-month-old female infant with intractable congenital glaucoma and diffuse corneal opacification underwent trabeculectomy with 5-fluorouracil (5-FU) injection in both eyes followed by penetrating keratoplasty (PKP) combined with partial cyclocryotherapy in the right eye. The latter procedure was undertaken despite the B-scan ultrasonographic finding of extensive optic disc cupping in order to provide the infant with some degree of improved visual function. The anatomic and functional results are discussed.

Extensive fibrous downgrowth after traumatic corneoscleral wound dehiscence.

Two months after cataract surgery, subconjuctival would gaping developed in our patients as a result of trauma and was resutured. Subsequently, corneal edema and a retrocorneal membrane were noticed. During penetrating keratoplasty, a thick fibrous membrane was found growing from the posterior corneal surface into the anterior and posterior chambers. Histopathologic studies revealed fibrous down-growth from the corneal stroma through a gap in Descemet's layer, forming a retrocorneal membrane.

Adverse behavioral reactions attributed to triazolam in the Food and Drug Administration's Spontaneous Reporting System.

Reports of adverse behavioral reactions to triazolam, a triazolobenzodiazepine ultra-short-acting hypnotic, were examined in the postmarketing surveillance Spontaneous Reporting System of the Food and Drug Administration. Reports for triazolam of confusion, amnesia, bizarre behavior, agitation, and hallucinations were compared with reports of these reactions for temazepam, another short-acting hypnotic. Analysis of individual case reports from marketing through 1985 for triazolam vs temazepam showed 133 vs two for confusion, 109 vs three for amnesia, 59 vs two for bizarre behavior, 58 vs four for agitation, and 40 vs one for hallucinations. Considering extent of use, reporting rates for triazolam were 22 to 99 times those for temazepam, depending on the reaction. Reactions to triazolam tended to occur at higher doses and in older patients. This and an updated analysis of aggregate reports for the first 7 years of marketing of each drug with reporting rates and adjustment for various factors suggest a higher occurrence of these reactions with triazolam, but selection factors cannot be completely ruled out. When treating insomnia, physicians should emphasize sleep hygiene practices as alternatives to drug therapy; if drug therapy is required, they should prescribe hypnotics at the lowest recommended doses for the shortest clinically necessary durations and discontinue medication use should any adverse reactions occur.