Unexpected Frequency Research Articles

Macular Complications Associated With Posterior Staphyloma

To report macular abnormalities associated with posterior staphyloma in eyes with myopia. In a retrospective study, we surveyed 116 eyes of 58 patients with myopic refractions. Myopic fundus abnormalities are related to clinically quantified posterior staphyloma formation. A posterior staphyloma was present in 88 (75.9%) of 116 eyes with myopic refractions of -3 diopters or more. Best-corrected visual acuity was decreased among eyes in all staphyloma grades. Eyes with the shallowest staphyloma depth (grade 1) displayed the largest drop in visual acuity as well as the greatest frequency of choroidal neovascular membranes and hemorrhages. A linear relationship was observed between staphyloma grade and conus formation (P = .001), retinal pigment epithelial defects (P = .0001), lacquer cracks (P = .0001), and chorioretinal atrophy (P = .001). All these variables were increased in staphylomatous eyes. A significant difference in means by staphyloma grade was observed for myopic refractive error (P = .001), axial length (P = .001), and best-corrected visual acuity (logMAR, P = .0001). There was an unexpected high frequency of choroidal neovascular membranes, hemorrhage, and poor best-corrected visual acuity in the lower staphyloma categories. This suggests that the development of a choroidal neovascular membrane requires relative preservation of the choriocapillaris as present in eyes with less advanced stages of posterior staphyloma formation.

Unexpected de Haas-van Alphen Oscillation in 2D Multiband Systems due to Chemical Potential Oscillation and Its Relevance to Magnetic Breakdown Systems

In two-dimensional (2D) multiband metals, the interference through chemical potential oscillation (CPO), which is described in the text, is shown to cause conventionally unexpected frequency components in the de Haas-van Alphen (dHvA) oscillation; as an example, the numerical result for a two-band case is shown. Then, we discuss the relevance of the CPO to the appearance of the prohibited dHvA oscillation in 2D magnetic breakdown (MB) systems, where “the prohibited dHvA oscillation” means the one not permitted in the standard semiclassical theory which incorporates MB. From these, we propose that the CPO is the main cause of what is called the prohibited difference-frequency oscillation in the dHvA effect of κ-(ET) 2 Cu(NCS) 2 .

Method to characterize the vibrational response of a beetle type scanning tunneling microscope

We describe a method for analyzing the external vibrations and intrinsic mechanical resonances affecting scanning probe microscopes by using the microscope as an accelerometer. We show that clear correlations can be established between the frequencies of mechanical vibrational modes and the frequencies of peaks in the tunnel current noise power spectrum. When this method is applied to our “beetle” type scanning tunneling microscope (STM), we find unexpected low frequency “rattling resonances” in the 500–1700 Hz range that depend on the exact lateral position of the STM, in addition to the expected mechanical resonances of the STM above 4 kHz which are in good agreement with theoretical estimates. We believe that these rattling resonances may be a general problem for scanning probe microscopes that use some type of kinetic motion for coarse positioning.

Identification of a new plasma alpha(1,3)fucosyltransferase (FUT6) allele requires an extended genotyping strategy.

Screening the FUT6 gene of 40 Swedish individuals, originally selected for genotyping of FUT3, revealed an unexpected high frequency of mutations. Four were originally typed as homozygous for the enzyme lethal mutation G739A by Taq alpha I restriction pattern, but only one lacked plasma alpha(1,3)fucosyltransferase activity. Cloning and sequencing of FUT6 from 2 of them revealed a new allele, without the G739A mutation, but with two new point mutations C738T and G977A. Segregation of this allele was confirmed in Swedish and Indonesian families. Since G739A and C738T mutations are only one nucleotide apart and induce the same modification of Taq alpha I cleavage, a new screening strategy for FUT6 was adopted. The homozygous inactivating G739A mutation was for the first time identified in Caucasian and Polynesian individuals, both lacking plasma enzyme activity. The mutation C370T was present in 25 of the 40 Swedish individuals and the inactivating mutation C945A was not found at all. These findings stress the dangers of transferring restriction enzyme genotype strategies from one population to another and of inferring phenotypes from genotypes without phenotyping and/or performing confirmatory cloning and sequencing.

Establishment and characterization of αs1-casein–specific T-cell lines from patients allergic to cow’s milk: Unexpected higher frequency of CD8+ T-cell lines

To study cow’s milk allergy at the cellular level, we assessed the reactivity of peripheral blood mononuclear cells from patients allergic to cow’s milk to αs1-casein, which is one of the major allergens in cow’s milk. Proliferation of the cells to αs1-casein activation showed a rather weak response. Therefore to understand T-cell reactivity to αs1-casein in more detail, we prepared αs1-casein–specific T-cell lines from patients allergic to cow’s milk and established 26 T-cell lines. These T-cell lines could be classified into three groups by analyzing their surface marker expression: those containing predominantly CD4+CD8- T cells, those containing both CD4+CD8- and CD4-CD8+ T cells, and those containing predominantly CD4-CD8+ T cells. The CD8+ T cells were obtained at an unexpectedly higher frequency from the patients. These T-cell lines produced interferon-γ and IL-4. These results suggest that CD8+ T cells specific for αs1-casein and CD4+ T cells were primed by the stimulation with αs1-casein in patients allergic to milk and that both T cells may play a key role in the onset, progression of, or recovery from cow’s milk allergy. (J ALLERGY CLIN IMMUNOL 1996;97:1342-9.)

Femtosecond continuum interferometer for transient phase and transmission spectroscopy

We measure difference phase spectra (DPS) over the whole visible spectrum by frequency-domain interferometry (FDI), using chirped femtosecond continuum pulses. The effects of the probe-pulse chirp on time-resolved dispersion relations are studied. Because of the correspondence between time and frequency in the chirp, temporal evolution of the optical Kerr response in CS2 is projected into DPS. In addition, it is found that the chirped continuum shows unexpected frequency shifts owing to induced phase modulation even when the continuum has a flat spectrum. The chirp character can be readily obtained from the projected traces, and the potential application to the single-shot pulse-shape measurement by FDI is discussed. It is shown that the delay-time-corrected spectra satisfy the Kramers–Kronig relations if the continuum has a flat spectrum and does not have higher chirp than the linear chirp but that the distortion caused by the induced modulation of the continuum remains unremoved in the corrected spectra.

Identification of a New Plasma «(1,3) Fucosyltransferase (FUT6) Allele Requires an Extended Genotyping Strategy

Screening the FUT6 gene of 40 Swedish individuals, originally selected for genotyping of FUT3, revealed an unexpected high frequency of mutations. Four were originally typed as homozygous for the enzyme lethal mutation G739A by Taqal restriction pattern, but only one lacked plasma a(l,3)fucosyltransferase activity. Cloning and sequencing of FUT6 from 2 of them revealed a new allele, without the G739A mutation, but with two new point mutations C738T and G977A. Segregation of this allele was confirmed in Swedish and Indonesian families. Since G739A and C738T mutations are only one nucleotide apart and induce the same modification of Taqal cleavage, a new screening strategy for FUT6 was adopted. The homozygous inactivating G739A mutation was for the first time identified in Caucasian and Polynesian individuals, both lacking plasma enzyme activity. The mutation C370T was present in 25 of the 40 Swedish individuals and the inactivating mutation C945A was not found at all. These findings stress the dangers of transferring restriction enzyme genotype strategies from one population to another and of inferring phenotypes from genotypes without phenotyping and/or performing confirmatory cloning and sequencing.

Human neoplasms elicit multiple specific immune responses in the autologous host.

Expression of cDNA libraries from human melanoma, renal cancer, astrocytoma, and Hodgkin disease in Escherichia coli and screening for clones reactive with high-titer IgG antibodies in autologous patient serum lead to the discovery of at least four antigens with a restricted expression pattern in each tumor. Besides antigens known to elicit T-cell responses, such as MAGE-1 and tyrosinase, numerous additional antigens that were overexpressed or specifically expressed in tumors of the same type were identified. Sequence analyses suggest that many of these molecules, besides being the target of a specific immune response, might be of relevance for tumor growth. Antibodies to a given antigen were usually confined to patients with the same tumor type. The unexpected frequency of human tumor antigens, which can be readily defined at the molecular level by the serological analysis of autologous tumor cDNA expression cloning, indicates that human neoplasms elicit multiple specific immune responses in the autologous host and provides diagnostic and therapeutic approaches to human cancer.

Auditory attentional bandwidth: Effect of level and frequency range

This study investigated the relations between theoretical auditory filters and "attentional filters" observed when measuring the detectability in noise of tones of expected or unexpected (probe) frequency. The effect of the level of the noise and the frequency range (narrow or wide) of the probes was assessed. For each 2IFC trial, a tone of the expected target frequency was presented as a cue preceding the two observation intervals--the signal was more often the expected than an unexpected frequency. For the narrow frequency range of probe frequencies, increasing the masker level resulted in a broadening of the probe-signal contour (percent correct as a function of probe frequency); however, detection was significantly better only for probe frequencies farthest from the target frequency. For the wide range of probe frequencies, the percentage of correct detections depended less systematically on masker level; however, detection was better and the attentional band wider than in the narrow frequency range. The results suggest that attentional focusing does not simply reflect auditory filtering: A more central and adaptive process may operate from the outputs of adjacent or more distant auditory filters.

Traumatic intracranial aneurysms in childhood and adolescence. Case reports and review of the literature.

We report four pediatric traumatic intracranial aneurysms occurring before the age of 10 years. Two of these aneurysms were the result of closed head injury. The remaining two were iatrogenic aneurysms which occurred in unusual circumstances. These four children represent 33% of the pediatric intracranial aneurysms seen at the Children's Hospital of Eastern Ontario from 1974 to 1992. Diagnosis of traumatic intracranial aneurysms requires a high index of suspicion: any head-injured or postoperative child who experiences delayed neurologic deterioration, or who fails to improve as expected following treatment, should promptly undergo diagnostic intracranial imaging. Documented subarachnoid hemorrhage, intracerebral or intraventricular hemorrhage, or subdural haematoma in this clinical setting should be further investigated by cerebral angiography to exclude a traumatic aneurysm or other vascular lesion. Traumatic aneurysms typically arise at the skull base or from distal anterior or middle cerebral arteries or branches consequent to direct mural injury or to acceleration-induced shear. Reported traumatic aneurysms account for 14%-39% of all pediatric aneurysms. Iatrogenic aneurysms also occur with unexpected frequency during childhood and adolescence. Pediatric traumatic cerebral aneurysms may present early or late. Most present early with intracranial hemorrhage. Late presentation occurs infrequently, typically as an aneurysmal mass. Once diagnosed, these aneurysms should be promptly treated by craniotomy employing routine microsurgical techniques, or in some cases, by endovascular detachable balloon techniques. Delay in operative treatment entails significant risks of repeated hemorrhage and death. Outcome in these children is primarily determined by the extent of traumatic cerebral injury and the preoperative clinical status. The latter directly depends upon diagnosis of the aneurysm prior to either initial or repeated hemorrhage.

Heterogeneity of acute lymphoblastic leukemia in HIV-seropositive patients

As opposed to large-cell or Burkitt's-type non-Hodgkin's lymphoma, acute lymphoblastic leukemia (ALL) is rarely observed in HIV-seropositive patients and is not a criteria of AIDS in the 1986 classification established by the C.D.C. Furthermore, the few cases of ALL reported so far were B-cell ALL, Burkitt's-type. We recently observed, with unexpected frequency, ALL cases in this setting: over a 5-year period, 5 of 25 HIV-positive patients referred to our center for hematological malignancies, had ALL. Three patients, who had previously been asymptomatic with regard to HIV infection, had typical Burkitt's-type ALL. Complete remission was achieved in all cases with high-dose lymphoma-type chemotherapy regimens, but 2 patients relapsed 3 and 27 months after diagnosis. Their clinical characteristics and outcome are discussed with reference to the cases reported thus far in the literature. One patient had common early pre-B ALL with the Philadelphia chromosome, and one had a T-cell ALL with an unusual CD7+, CD4-, CD8- phenotype. Prognosis was very poor in both cases. The exact incidence and the therapeutic management of B-cell ALL in HIV-positive patients warrants further evaluation. In addition, we show that there may be a heterogeneity among ALL cases in this setting, with the first description of 2 non-Burkitt's ALL with atypical features in HIV-positive patients.

Anomalous frequency behavior in low-frequency sea-surface backscatter

Surface backscattering strengths have been measured between 70 and 1500 Hz using broadband SUS charges as sources in the Critical Sea Test 7 at-sea test. While the results of the measurements for frequencies of 1 kHz and below have been presented previously, the extension of the results up to 1.5 kHz have shown some unexpected frequency behavior in the scattering strengths as a function of wind speed. For wind speeds of 15 m/s and higher, scattering strengths at a fixed grazing angle are found to peak in the 600- to 1000-Hz region and then decline with increasing frequency, while for lower wind speeds the scattering strengths increase roughly monotonically with increasing frequency. Possible explanations for this behavior will be discussed. [Work supported by ONR.]

Characteristics of the acquired immunodeficiency syndrome in Brazil.

The clinical and epidemiologic characteristics of the acquired immunodeficiency syndrome (AIDS) were studied in a tropical area of Brazil. During an 18-month period (July 1989-January 1991), 111 consecutive AIDS patients (102 men and nine women) were evaluated. Patients reported homosexual/bisexual activities (60%), intravenous drug use (19%), or both (6%), heterosexual activities (11%), blood transfusions (2%), and 2% belonged to an undetermined category. Weight loss, fever, oral thrush, and diarrhea were present in > or = 70% of the patients at presentation. An unexpected high frequency of hepatomegaly (49%) was detected, and found to be significantly associated with tuberculosis (P < 0.0001). Although the epidemiologic features of human immunodeficiency virus transmission were comparable to the United States/European pattern, the clinical spectrum of opportunistic infections more closely resembled that reported in Africa and Haiti, with a greater frequency of fungal and mycobacterial infections than Pneumocystis carinii pneumonia and viral infections.

The 31P NMR spectra of Cd 3P 2 and Zn 3P 2

The magic-angle spinning 31P NMR spectrum of Cd 3P 2 is reported. Three lines with intensities nearly 1:1:2 are observed, as expected from the X-ray determined crystal structure. In light of this agreement and the reported identical crystal structures, the 31P NMR of Zn 3P 2 is re-examined. At room temperature, a doublet of equal intensities is observed and has been explained previously as an accidental overlap. This interpretation is confirmed by the observation that the overlap is removed at low temperatures. In addition, an unexpected overall frequency shift with temperature is observed and attributed to a Knight-shift-type mechanism.

Unexpected frequency effects on the rate of oxidative processes induced by ultrasound

Sonication of water generates radicals which oxidize compounds in solution. In this work we give evidence that in the presence of argon or oxygen these oxidative processes occur in enhanced yields when a high frequency (514 kHz) is used in comparison with the more commonly used low frequency (20 kHz)

Lateralization of rectangularly modulated noise: Explanations for counterintuitive reversals

A number of years ago Hafter and Shelton [J. Acoust. Soc. Am. Suppl. 1 68, S16 (1980), Hafter and Shelton, J. Acoust. Soc. Am. 90, 1901-1907 (1991)] demonstrated that diotic bandpass noise that is multiplied by a dichotic pair of periodic rectangular gating functions could be strongly perceived toward the ear receiving the signal with the gating function that is lagging in time. These results were surprising because sounds presented with interaural time delays (ITDs) are normally perceived toward the ear receiving the signal that is leading in time. In order to better understand these counterintuitive phenomena an analytical expression for the cross-correlation function of these gated-noise stimuli is derived, and it is shown that many of the general properties of the data can be accounted for by considering only the properties of this function. The lateralization of the gated-noise stimuli is compared to predictions of three types of models of binaural signal processing: models based on the cross-correlation function of the entire signal, models based on the interaural group delay or phase delay at low frequencies, and the position-variable model, which is based on the response of the peripheral auditory system to the stimuli. It is shown that the observed lateralization results, including the unexpected reversals and various frequency effects, can be explained without further assumption by an extended implementation of the position-variable model [Stern and Colburn, J. Acoust. Soc. Am. 64, 127-140 (1978)]. The cross-correlation functions of the original stimuli can also be related to the lateralization data, but in a much less natural fashion. It is argued that models based on the interaural group delay of the original stimuli will not describe the observed results, although low-frequency phase delay is qualitatively consistent with the observed lateralization phenomena.

Novel measurements of nuclear spin cross-relaxation in metal hydrides

Recent NMR measurements of proton relaxation have shown an unexpected frequency dependence in several metal-hydrogen systems at low temperatures. An explanation proposed by the Ames group involves cross-relaxation of protons to quadrupolar metal nuclei. We test this hypothesis with relaxation experiments involving large amplitude field modulation. The field modulation sweeps the proton resonance through the distribution of metal frequencies. Thus the protons come into contact with more metal nuclei, increasing the proton relaxation rate. Relaxation measurements have been performed on several samples and the proton resonance frequency, the modulation frequency and the modulation amplitude have been varied. Also, proton relaxation rates T 1 −1 have been measured on slowly spinning samples where the rotation produces periodic variations of the metal quadrupolar frequencies.

Strongly dispersive low frequency Raman modes in germanium

We report the observation of unexpected low frequency (10cm −1 - 70cm −1) features in the Raman spectra of germanium. The frequencies of these modes depend upon the excitation wavelength of the laser. We propose that these features are due to scattering by two acoustic phonons of large wave vectors resonant at the E 1 and E 1 + Δ 1 gaps. This provides a method of determining the reduced masses of the E 1 and E 1 + Δ 1 critical points.

Autologous bone marrow transplantation in solid tumors

The design and results of recent studies of high-dose therapy in metastatic breast cancer, early-stage breast cancer, stage IV neuroblastoma, recurrent or bulky disease and testicular cancer, particularly the proportion of long-term disease-free survivors, are described. The outcome in these subgroups with conventional therapy is described for comparison. The results of these studies suggest that high-dose therapy with autologous marrow support increases the proportion of patients with long-term survival without evidence of disease. Newer supportive care approaches with recombinant growth factors and mobilized peripheral blood cells and recurrent high-dose therapy cycles of non-cross resistant regimens may improve outcome further in these diseases and increase the application to more resistant tumors. The controversy about the importance of and the unexpected high frequency of marrow contamination is outlined.

Novel measurements of nuclear spin cross-relaxation in metal hydrides

Recent NMR measurements of proton relaxation have shown an unexpected frequency dependence in several metal-hydrogen systems at low temperatures. An explanation proposed by the Ames group involves cross-relaxation of protons to quadrupolar metal nuclei. We test this hypothesis with relaxation experiments involving large amplitude field modulation. The field modulation sweeps the proton resonance through the distribution of metal frequencies. Thus the protons come into contact with more metal nuclei, increasing the proton relaxation rate. Relaxation measurements have been performed on several samples and the proton resonance frequency, the modulation frequency and the modulation amplitude have been varied. Also, proton relaxation rates T 1 −1 have been measured on slowly spinning samples where the rotation produces periodic variations of the metal quadrupolar frequencies.