Cooperative Lamb shift in a mesoscopic atomic array

According to quantum electrodynamics, the exchange of virtual photons in a system of identical quantum emitters causes a shift of its energy levels. Such shifts, known as cooperative Lamb shifts, have been studied mostly in the near-field regime. However, the resonant electromagnetic interaction persists also at large distances, providing coherent coupling between distant atoms. Here, we report a direct spectroscopic observation of the cooperative Lamb shift of an optical electric-dipole transition in an array of Sr(+) ions suspended in a Paul trap at inter-ion separations much larger than the resonance wavelength. By controlling the precise positions of the ions, we studied the far-field resonant coupling in chains of up to eight ions, extending to a length of 40  μm. This method provides a novel tool for experimental exploration of cooperative emission phenomena in extended mesoscopic atomic arrays.

When can temporally focused excitation be axially shifted by dispersion?

Temporal focusing (TF) allows for axially confined wide-field multi-photon excitation at the temporal focal plane. For temporally focused Gaussian beams, it was shown both theoretically and experimentally that the temporal focus plane can be shifted by applying a quadratic spectral phase to the incident beam. However, the case for more complex wave-fronts is quite different. Here we study the temporal focus plane shift (TFS) for a broader class of excitation profiles, with particular emphasis on the case of temporally focused computer generated holography (CGH) which allows for generation of arbitrary, yet speckled, 2D patterns. We present an analytical, numerical and experimental study of this phenomenon. The TFS is found to depend mainly on the autocorrelation of the CGH pattern in the direction of the beam dispersion after the grating in the TF setup. This provides a pathway for 3D control of multi-photon excitation patterns.

Vectorial phase retrieval for linear characterization of attosecond pulses

The waveforms of attosecond pulses produced by high-harmonic generation carry information on the electronic structure and dynamics in atomic and molecular systems. Current methods for the temporal characterization of such pulses have limited sensitivity and impose significant experimental complexity. We propose a new linear and all-optical method inspired by widely used multidimensional phase retrieval algorithms. Our new scheme is based on the spectral measurement of two attosecond sources and their interference. As an example, we focus on the case of spectral polarization measurements of attosecond pulses, relying on their most fundamental property-being well confined in time. We demonstrate this method numerically by reconstructing the temporal profiles of attosecond pulses generated from aligned CO(2) molecules.

The effect of self-assembled monolayers on polarization-dependent two-photon photoemission and on the angular distribution of the photoelectrons

The effect of a self-assembled organized organic monolayer on the two-photon photoemission from semiconductor substrates was investigated. It has been found that the monolayer affects the relative yield of photoelectrons emitted by p-polarized versus s-polarized light. In addition, the monolayer affects the angular distribution of the ejected electrons. The effect on the photoelectron yield is attributed to the monolayer "smoothing" the electronic potential on the surface by eliminating surface states and dangling bonds. The effect on the angular distribution is attributed to a post-ejection interaction between the photoelectrons and the adsorbed molecules.

Dentin micro-architecture using harmonic generation microscopy

OBJECTIVES

We present a novel way to create high-resolution three-dimensional images of tooth dentin by harmonic generation scanning laser microscopy.

METHODS

The images were taken using a pulsed infrared laser. Three-dimensional reconstruction enables the visualization of individual tubules and the collagen fibrils mesh around them with an optical resolution of approximately 1 microm.

RESULTS

The images show micro-morphological details of the dentinal tubules as well as the collagen fibrils at a depth of up to about 200 microm. The data show that while collagen fibrils are organized in planes perpendicular to the tubules, close to the dentin enamel junction they lie also along the long axis of the tubules.

CONCLUSIONS

The unique 3D information opens the opportunity to study the collagen fibril arrangement in relation to the tubule orientation within the dentin matrix, and may be applied to study the micro-morphology of normal versus altered dentin.

Femtosecond pulse-shape modulation at kilohertz rates

We demonstrate a new scanning femtosecond pulse-shaping technique that allows pulse shapes to be modulated at kilohertz rates. This technique is particularly useful for lock-in measurements in which the signal is synchronized with the alternating pulse shapes. The pulse-shape lock-in technique is demonstrated in resonant coherent anti-Stokes Raman scattering, where it is shown to significantly improve the ratio of the resonant signal to both the nonresonant background and to noise.

High initial amplitude and high Mach number effects on the evolution of the single-mode Richtmyer-Meshkov instability

Effects of high-Mach numbers and high initial amplitudes on the evolution of the single-mode Richtmyer-Meshkov shock-wave induced hydrodynamic instability are studied using theoretical models, experiments, and numerical simulations. Two regimes in which there is a significant deviation from the linear dependence of the initial velocity on the initial perturbation amplitude are defined and characterized. In one, the observed reduction of the initial velocity is primarily due to large initial amplitudes. This effect is accurately modeled by a vorticity deposition model, quantifying both the effect of the initial perturbation amplitude and the exact shape of the interface. In the other, the reduction is dominated by the proximity of the shock wave to the interface. This effect is modeled by a modified incompressible model where the shock wave is mimicked by a moving bounding wall. These results are supplemented with high initial amplitude Mach 1.2 shock-tube experiments, enabling separation of the two effects. It is shown that in most of the previous experiments, the observed reduction is predominantly due to the effect of high initial amplitudes.

Stab wounds to the gluteal region: a management strategy

OBJECTIVE

To examine the utility of a protocol for treating stab wounds to the gluteal region. These are uncommon and potentially lethal, and the location of injury influences the rate and severity of associated injuries. This was a retrospective, uncontrolled study.

METHODS

Patients who sustained gluteal stab wounds and were treated according to our predetermined protocol that classifies injuries as upper or lower zone were reviewed, and associated injuries and outcome were measured.

RESULTS

Of 27 gluteal stab wounds in 17 patients, 53% were classified as upper zone and 47% as lower zone injuries. Sixty-six percent of the upper zone injuries had associated neurologic, vascular, or visceral injuries that required invasive procedures or surgery, compared with 12.5% for lower zone injuries (p < 0.05).

CONCLUSION

Upper zone gluteal stab wounds require prompt multisystem evaluation with mandatory angiography and aggressive management. Lower zone wounds need observation and repeated evaluations.

[Combined approach in management of penetrating injury of vertebral artery]

Penetrating injuries of the vertebral artery are not common. Although surgical control of this type of injury is well-documented, the combined approach (surgery and packing for temporary control of bleeding, followed by angiography and embolization for permanent control) is now recognized and practiced. We describe a 40-year-old man who was stabbed in the neck. He was rushed to the operating theater in hemorrhagic shock. A vertebral artery injury was identified and packed. Angiography and embolization permanently controlled the bleeding. The combined approach is safe and we recommend it in those in whom bleeding from the vertebral artery is initially well controlled with packing.

Adriamycin-ifosfamide induction chemotherapy for extremity soft tissue sarcoma: comparison of two non-randomized protocols

Chemotherapeutic cytoreduction of soft tissue sarcomas may permit less radical operation. In cases of large or multi-compartmental masses, deeply seated tumors or involvement of a neurovascular bundle, down-sizing of the mass is required before limb sparing surgery can be considered. We have applied a combination chemotherapy consisting of intravenous adriamycin and ifosfamide with intra-arterial cisplatin for patients with soft tissue sarcomas of the extremity as induction treatment, and switched to an intravenous-only protocol due to toxicity and management difficulties. Adjuvant chemotherapy and radiation therapy were given after limb-sparing surgery in both regimens. Fresh tumor specimens were obtained and were examined for tumor size, surgical margins, percent of necrosis, evidence of vascular or perineural invasion, and the presence of Pgp, Ki-67, p53, PCNA and bcl-2-oncoprotein. Our results in terms of percentage of tumor necrosis were comparable and even better in favor of the second regimen [38% good histological response with intravenous (i.v.)-only versus 12.5% for combined i.v. + intra-arterial (i.a.]. The clinical and radiological responses were also better for the second (i.v. only) regimen (45%) than for the first (i.v. + i.a.) regimen (12.5%). The toxicity and the inconvenience to the patients and to the treating staff were greater in the first regimen that combined intra-arterial and intravenous infusions. In the first group the failure rate is 75% within 32 months of follow-up, while it is 33% within 12 months follow-up in the second group. The immunohistochemical markers did not correlate with disease control nor with the patient outcome. Intravenous administration of ADR-IFX induction chemotherapy was more feasible than combined i.v. ADR-IFX plus i.a. cisplatin and achieved better results.

[Penetrating gluteal injuries management--the need for management protocols]

Gunshot wounds are the most common cause of penetrating injuries in the gluteal region (PIGR), while only 17.5% result from stabbing. Complications and even death have been described as resulting from stab injury in this area, which is thus a hazard that demands an algorithm for proper management. Recently, DiGiacomo et al. recommended that transpelvic bullet trajectory warrants surgery. Mercer et al., in a study of 81 patients with PIGR, recommended an algorithm based on anatomical gluteal zones and concluded that angiography is not mandatory in such injuries. We describe 9 cases of PIGR, 4 of which were from stab wound and 1 a gunshot wound, which bled from rami of the gluteal arteries. In 2 there was no apparent bleeding, and they were hemodynamically stable. Thus in this type of injury significant damage may be obscured. Our results suggest that angiography is important in the evaluation of such injuries an should be part of the protocol for management of PIGR.

Regional perfusion with hemofiltration (chemofiltration) for the treatment of patients with regionally advanced cancer

BACKGROUND

Regionally advanced cancer is a common, often unresolved problem. Effective local control with chemotherapy is limited by the toxicity following systemic administration. Chemofiltration (CF) is a form of regional perfusion that enables the administration of cytotoxic drugs into one body area while limiting systemic toxicity. The drug is infused into the artery supplying the involved area. The venous effluent of the same organ is pumped out into a hemofiltration unit at a high flow rate. The drug is then filtered away and the blood returned to systemic circulation.

METHODS

Forty-one patients underwent 45 CF. Twenty-four patients had CF of the pelvis for advanced rectal carcinoma (10), malignant melanoma (6), and cancers of the uterine cervix (3), ovary (2), vulva (1), endometrium (1), and anus (1). Seventeen patients underwent CF of the liver for metastatic colon (10), breast (4), pancreas (1), ovary (1), and unknown primary (1) cancer. 5-fluorouracil (1 g/m2) and mitomycin-C (30 mg/m2); cisplatinum (200 mg/m2) alone or combined with bleomycin (50 mg/m2) and mitomycin-C (20 mg/m2); or melphalan (1 mg/kg) were the combinations used.

RESULTS

Generally the procedure was well tolerated. Complications included transient leukopenia (18), paralytic ileus (2), hair loss (2), renal failure (1). Two patients died within 40 days following CF. Of 36 evaluable patients, 16 (44%) had partial response, 14 (38%) had stable disease, and 6 (18%) had disease progression. A decrease of at least 30% in carcinoembryonic antigen levels occurred in 12 of 24 patients (50%). Median time to progression was 7 months. Ten of 13 patients (77%) achieved good symptomatic palliation.

CONCLUSIONS

The results of CF in our study are not superior to alternative methods of drug delivery to the liver and pelvis. However, considering that previous systemic chemotherapy had failed two-thirds of the patients, some benefit may be attributed to this regional delivery modality. Furthermore, pelvic CF afforded very significant symptomatic relief which was definitely superior to other methods.

[Primary and metastatic hepatic cancer: the surgical option]

Major hepatic resection is the treatment of choice in patients with primary and secondary liver cancer. During a 22-month period 31 men and 27 women (mean age 63 years, range 14-84) with space-occupying hepatic lesions were admitted. All 15 patients with benign lesions were operated, except for 3 in whom a liver abscess was drained percutaneously. Of the 43 with malignant liver lesions, 30 had liver metastasis secondary to colorectal cancer, 15 of whom underwent major, anatomical and nonanatomical, liver resection and 1 had cryoablation of the tumor. 9 had hepatocellular carcinoma, 1 of whom had a 4-segment non-anatomical resection and 1 tumor cryoablation. 2 with metastasis from a neuroendocrine tumor had anatomical resection of liver lobes. Of 2 with liver metastasis secondary to breast cancer, 1 underwent resection. CT portography, intraoperative ultrasonography and intraarterial injection of Lipiodol were found to be very useful in selecting patients for liver resection.

Ischemic heart disease and pulmonary ventilatory function

The results of spirometric examinations on 4, 331 Israeli male civil service employees, aged 45 years or more, were analyzed according to the presence or absence of certain aspects of ischemic heart disease. Vital capacity was lower in individuals with a previously history of a heart attack, in those with definite or suspected angina pectoris and in those with ECG evidence of myocardial ischemia, probable or possible myocardial infarction, left bundle branch block or nonspecific T wave changes in subjects without these findings. The differences were small, but statistically significant. Vital capacity was lower in subjects with a recent history of a heart attack (within three years) than in those whose heart attack had occurred more than three years prior to the examination. The ratio of forced expiratory volume in the first second to forced vital capacity was not significantly different between individuals with or without a past history of heart attack, angina pectoris or ECG evidence of coronary heart disease.