Laser ion acceleration via control of the near-critical density target

Duration-controlled amplified spontaneous emission with an intensity of 10(13) W/cm(2) is used to convert a 7.5-microm -thick polyimide foil into a near-critical plasma, in which the p -polarized, 45-fs , 10(19) -Wcm (2) laser pulse generates 3.8-MeV protons, emitted at some angle between the target normal and the laser propagation direction of 45 degrees . Particle-in-cell simulations reveal that the efficient proton acceleration is due to the generation of a quasistatic magnetic field on the target rear side with magnetic pressure inducing and sustaining a charge separation electrostatic field.

Demonstration of laser-frequency upshift by electron-density modulations in a plasma wakefield

In a plasma wake wave generated by a high power laser, modulations of the electron density take the shape of paraboloidal dense shells, moving almost at the speed of light. A counterpropagating laser pulse is partially reflected from the shells, acting as relativistic flying mirrors, producing a time-compressed frequency-multiplied pulse due to the double Doppler effect. The counterpropagating laser pulse reflection from the plasma wake wave accompanied by its frequency multiplication (with a factor from 50 to 114) was detected in our experiment.

Weekly paclitaxel in Japanese women with metastatic or advanced breast cancer

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Background: Weekly administration of paclitaxel (WP) has been reported to be at least as well-tolerated and effective as conventional tri-weekly treatment (TP). The present study was to evaluate the efficacy and safety of weekly paclitaxel treatment for japanese women with metastatic or advanced breast cancer. Methods: Eligibility criteria included < 75 years of age, histologically-proven advanced or recurrent breast cancer, and performance status (PS) of 0 to 2. Patients were scheduled to receive at least one course of paclitaxel 100 mg/m2/week for 6 consecutive weeks followed by 1 week off. The present WP results were compared with the previous TP data generated by the same trial group in Japan. In the TP group, paclitaxel 210 mg/m2 was given every 3 weeks up to 3 cycles or more until tumor progression or severe toxicity was observed. Results: From December 2002 to July 2005, 69 patients were enrolled into the study of WP and 68 were eligible for evaluation. All were previously treated, and 51 of 69 patients (73.9%) had received anthracyclines prior to this study. The median age was 55 years (range 27–74), and 66 patients (95.7%) had PS of 0–1. Sixty nine patients have been analyzed for efficacy and toxicity by the evaluation committee. The median dose intensity was 81.25 mg/m2 per week. In total, 270 courses of WP were administered (median 3 courses; range 1–13). Three patients entered into complete remission (CR) and 28 achieved partial response (PR) by the WHO response criteria with a response rate (RR) of 44.9%, which is similar to RR in the historical TP group (RR of 33.9% in 62 Patients). Median duration of response was 238 days (range 91–631). Time to progression was 193 days. It is of note that grade 3–4 neutropenia was observed less frequently in WP as compared with TP (37.7 vs. 93.3%). Other major toxicities including peripheral neuropathy (PNP) appear to be similar between the two regimens through all toxicity grades of PNP (WP and TP group; 89.9% and 93.3%, respectively). Conclusion: WP appears to have similar or better efficacy with better toxicity profile as TP in patients with metastatic or advanced breast cancer.

No significant financial relationships to disclose.

Laser ion-acceleration scaling laws seen in multiparametric particle-in-cell simulations

The ion acceleration driven by a laser pulse at intensity I= 10(20)-10(22) W/cm(2) x (microm/lambda)(2) from a double layer target is investigated with multiparametric particle-in-cell simulations. For targets with a wide range of thickness l and density n(e), at a given intensity, the highest ion energy gain occurs at certain electron areal density of the target sigma = n(e)l, which is proportional to the square root of intensity. In the case of thin targets and optimal laser pulse duration, the ion maximum energy scales as the square root of the laser pulse power. When the radiation pressure of the laser field becomes dominant, the ion maximum energy becomes proportional to the laser pulse energy.

Electron, positron, and photon wakefield acceleration: trapping, wake overtaking, and ponderomotive acceleration

The electron, positron, and photon acceleration in the first cycle of a laser-driven wakefield is investigated. Separatrices between different types of the particle motion (trapped, reflected by the wakefield and ponderomotive potential, and transient) are demonstrated. The ponderomotive acceleration of electrons can be largely compensated by the wakefield action, in contrast to positrons and positively charged mesons. The electron bunch energy spectrum is analyzed. The maximum upshift of an electromagnetic wave frequency during reflection from the wakefield is obtained.

Chemotaxis of the nematode Caenorhabditis elegans toward cycloheximide and quinine hydrochloride

We investigated the chemotaxis of the nematode Caenorhabditis elegans toward cycloheximide, denatonium benzoate, 6-n-propyl-2-thiouracil, and quinine hydrochloride. Interestingly, C. elegans was strongly attracted to cycloheximide, while avoiding quinine hydrochloride. This is the first report thus far to describe the chemotactic responses of C. elegans toward bitter tastants for humans.

A rare case of Gitelman's syndrome presenting with hypocalcemia and osteopenia

Gitelman's syndrome (GS), an autosomal recessive disorder caused by a defect of the thiazide-sensitive Na-Cl cotransporter (TSC) at the distal tubule, is characterized by hyperreninemic hyperaldosteronism with normal or low blood pressure, hypokalemia, metabolic alkalosis, hypomagnesemia and hypocalciuria. An 18-yr-old Japanese man was admitted to our hospital with a history of muscle weakness and transient tetanic episodes. He showed hypocalcemia in addition to hypokalemia, severe hypomagnesemia, hypocalciuria and hyperreninemic hyperaldosteronism with normal blood pressure. Furthermore, bone mineral density at the lumbar spine revealed osteopenia. A diagnosis of GS was made on the basis of clinical features, laboratory data and renal function test. The electrolyte imbalance was corrected and bone mineral density was slightly increased with chronic treatment of magnesium and potassium salts. Genetic analysis revealed that TSC gene of the patient has a heterozygous C to A nucleotide substitution at position 545 in exon 4, which causes a threonine (Thr) to lysine (Lys) substitution at position 180. This is a rare case of GS with hypocalcemia and osteopenia which could be caused by severe hypomagnesemia.

Portal vein occlusion or stenosis in patients with hepatolithiasis: observation by multiphasic contrast-enhanced CT

AIMS

To analyze the dynamic findings of multiphasic contrast-enhanced CT in hepatolithiasis and to elucidate occlusive changes in portal veins and other associated abnormalities.

METHODS

This was a retrospective study of 25 selected patients with hepatolithiasis who underwent various imaging examinations, including multiphasic contrast-enhanced CT. The following CT findings were evaluated in each of 71 hepatic segments: visualization of a calculus; biliary dilation or focal hepatic atrophy of the affected segment; areas that were abnormally enhanced in the hepatic arterial phase; degrees (normal, stenosis, occlusion) of portal vein calibre; and linear delayed enhancement along the bile-duct walls, suggesting cholangitis.

RESULTS

On CT, calculi were depicted as a hyperdense structures in 61 of 71 segments (86%). Focal hepatic atrophy, which frequently accompanied CT findings suggesting compensatory hypertrophy of other segments, was seen in 50 of 71 segments (70%). Areas that were abnormally enhanced were recognized in 36 of 71 segments (51%). Stenosis or occlusion of portal venous branches was observed in 59 of 71 segments (83%), including 13 segments with occlusion. Findings indicating cholangitis were noted in 50 of 71 segments (70%). The degrees of portal vein calibre were significantly correlated with the presence of hepatic atrophy or cholangitis.

CONCLUSION

Hepatolithiasis is associated with significant rates of stenosis or occlusion of adjacent portal veins as well as hepatic parenchymal changes in the affected area. Chronic deterioration of portal flow may cause these morphological changes.

Electron acceleration by a nonlinear wakefield generated by ultrashort (23-fs) high-peak-power laser pulses in plasma

We study experimentally the interaction of the shortest at present (23-fs) , relativistically intense (20-TW), tightly focused laser pulses with underdense plasma. MeV electrons constitute a two-temperature distribution due to different plasma wave-breaking processes at a plasma density of 10(20) cm(-3). These two groups of electrons are shown numerically to constitute bunches with very distinctive time durations.

Dose properties of a laser accelerated electron beam and prospects for clinical application

Laser wakefield acceleration (LWFA) technology has evolved to where it should be evaluated for its potential as a future competitor to existing technology that produces electron and x-ray beams. The purpose of the present work is to investigate the dosimetric properties of an electron beam that should be achievable using existing LWFA technology, and to document the necessary improvements to make radiotherapy application for LWFA viable. This paper first qualitatively reviews the fundamental principles of LWFA and describes a potential design for a 30 cm accelerator chamber containing a gas target. Electron beam energy spectra, upon which our dose calculations are based, were obtained from a uniform energy distribution and from two-dimensional particle-in-cell (2D PIC) simulations. The 2D PIC simulation parameters are consistent with those reported by a previous LWFA experiment. According to the 2D PIC simulations, only approximately 0.3% of the LWFA electrons are emitted with an energy greater than 1 MeV. We studied only the high-energy electrons to determine their potential for clinical electron beams of central energy from 9 to 21 MeV. Each electron beam was broadened and flattened by designing a dual scattering foil system to produce a uniform beam (103%>off-axis ratio>95%) over a 25 x 25 cm2 field. An energy window (deltaE) ranging from 0.5 to 6.5 MeV was selected to study central-axis depth dose, beam flatness, and dose rate. Dose was calculated in water at a 100 cm source-to-surface distance using the EGS/BEAM Monte Carlo algorithm. Calculations showed that the beam flatness was fairly insensitive to deltaE. However, since the falloff of the depth-dose curve (R10-R90) and the dose rate both increase with deltaE, a tradeoff between minimizing (R10-R90) and maximizing dose rate is implied. If deltaE is constrained so that R10-R90 is within 0.5 cm of its value for a monoenergetic beam, the maximum practical dose rate based on 2D PIC is approximately 0.1 Gy min(-1) for a 9 MeV beam and 0.03 Gy min(-1) for a 15 MeV beam. It was concluded that current LWFA technology should allow a table-top terawatt (T3) laser to produce therapeutic electron beams that have acceptable flatness, penetration, and falloff of depth dose; however, the dose rate is still 1%-3% of that which would be acceptable, especially for higher-energy electron beams. Further progress in laser technology, e.g., increasing the pulse repetition rate or number of high energy electrons generated per pulse, is necessary to give dose rates acceptable for electron beams. Future measurements confirming dosimetric calculations are required to substantiate our results. In addition to achieving adequate dose rate, significant engineering developments are needed for this technology to compete with current electron acceleration technology. Also, the functional benefits of LWFA electron beams require further study and evaluation.

Liver lesions of visceral larva migrans due to Ascaris suum infection:

The purpose of this study was to analyze computed tomographic (CT) findings of hepatic lesions due to Ascaris suum infection. CT of the liver in three patients, all of whom had immunoserologically confirmed A. suum infection, were retrospectively reviewed. Twenty-five lesions were identified in total. Two radiologists analyzed CT findings in a consensus fashion, with particular interest in the margin, shape, and location of the lesions. Hepatic lesions were ill-defined (22 of 25), small (3-35 mm; average, 11 mm), and nodular (18 of 25) or wedge (three of 25) in shape. Most were located in periportal (16 of 25) or subcapsular (six of 25) regions. Hepatic nodules due to visceral larva migrans of A. suum were located mainly in periportal or subcapsular regions, which may represent periportal eosinophilic granuloma, its pathologic feature. The results were considered to represent the pathophysiology of this entity.

Bilateral ovarian leiomyomas: CT and MRI features

We recently treated a 21-year-old woman with leiomyomas arising from the bilateral ovaries, a very rare condition. On magnetic resonance imaging, more than half of the left adnexal mass showed low signal intensity on T2-weighted images and good enhancement by gadolinium-DTPA, and the remaining part showed high signal intensity on T2-weighted images, so the lesions initially were diagnosed as ovarian fibromas or as thecomas with a certain degree of degeneration. Pathologic examination of the excised tumors proved that they were bilateral ovarian leiomyomas; in addition, the tumor from the left side showed hemorrhagic and myxoid changes with torsion of 180 degrees.

Optical-field-ionization effects on the propagation of an ultraintense laser pulse in high- Z gas jets

Interaction of an ultraintense, a(0) >>1, laser pulse with an underdense Ar plasma is analyzed via a two-dimensional particle-in-cell simulation which self-consistently includes optical-field ionization. In spite of rapid growth of ion charge Z and, hence, electron density at the laser front, relativistic self-focusing is shown to persist owing to a reduction of the expected plasma defocusing resulting from the weak radial dependence of the ion charge on laser intensity (even for Z/gamma>1 where gamma is the electron relativistic factor).

Highly efficient relativistic-ion generation in the laser-piston regime

An intense laser-plasma interaction regime of the generation of high density ultrashort relativistic ion beams is suggested. When the radiation pressure is dominant, the laser energy is transformed efficiently into the energy of fast ions.

Energetic protons from a few-micron metallic foil evaporated by an intense laser pulse

With detailed experimental studies and hydrodynamics and particle-in-cell simulations we investigate the role of the prepulse in laser proton acceleration. The prepulse or pedestal (amplified spontaneous emission) can completely evaporate the irradiated region of a sufficiently thin foil; therefore, the main part of the laser pulse interacts with an underdense plasma. The multiparametric particle-in-cell simulations demonstrate that the main pulse generates the quasistatic magnetic field, which in its turn produces the long-lived charge separation electrostatic field, accelerating the ions.

Fat in liver metastasis from renal cell carcinoma detected by chemical shift MR imaging

A case with liver metastasis from papillary renal cell carcinoma (RCC) is presented, in which intratumoral fat was detected on dual-echo chemical shift magnetic resonance imaging (MRI). The preoperative chemical shift MR image of the primary RCC also suggested the presence of intratumoral fat. Liver metastasis from fat-containing RCC should be included in the differential diagnosis of fat-containing liver masses as observed on chemical shift MRI.

Fat detection in gallbladder carcinoma with extensive xanthogranulomatous change demonstrated by chemical shift MR imaging

We present a case of gallbladder carcinoma, in which fat was detected on dual-echo chemical shift magnetic resonance imaging (MRI). Histologic analysis showed poorly differentiated adenocarcinoma associated with massive xanthogranulomatous change. Sudan IV staining successfully confirmed the presence of fat within the interstitial histiocytes. Although rare, gallbladder carcinoma with xanthogranulomatous change should be included in the differential diagnosis of fatty tumor involving the region of the liver as observed on chemical shift MRI.

Particle selection for laser-accelerated proton therapy feasibility study

In this paper we present calculations for the design of a particle selection system for laser-accelerated proton therapy. Laser-accelerated protons coming from a thin high-density foil have broad energy and angular spectra leading to dose distributions that cannot be directly used for therapeutic applications. Our solution to this problem is a compact particle selection and collimation device that delivers small pencil beams of protons with desired energy spectra. We propose a spectrometer-like particle selection and beam modulation system in which the magnetic field will be used to spread the protons spatially according to their energies and emitting angles. Subsequently, an aperture will be used to select the protons within a therapeutic window of energy (energy modulation). It will be shown that for the effective proton spatial differentiation, the primary collimation device should be used, which will collimate protons to the desired angular distribution and limit the spatial mixing of different energy protons once they have traveled through the magnetic system. Due to the angular proton distribution, the spatial mixing of protons of different energies will always be present and it will result in a proton energy spread with the width depending on the energy. For 250 MeV protons, the width (from the maximum to the minimum energy) is found to be 50 MeV for the magnetic field configuration used in our calculations. As the proton energy decreases, its energy width decreases as well, and for 80 MeV protons it equals 9 MeV. The presence of the energy width in the proton energy distribution will modify the depth dose curves needed for the energy modulation calculation. The matching magnetic field setup will ensure the refocusing of the selected protons and the final beam will be collimated by the secondary collimator. The calculations presented in this article show that the dose rate that the selection system can yield is on the order of D=260 Gy/min for a field size of 1 x 1 cm2.

Distribution of ehrlichiae in tissues as determined by in-situ hybridization

Specific identification of ehrlichiae in the tissues and determination of their distribution is difficult. In this study, an in-situ hybridization method was developed to detect ehrlichial 16S rRNA in tissue specimens from mice experimentally infected with the HF strain. This strain is closely related to Ehrlichia chaffeensis, the agent of human monocytic ehrlichiosis. HF strain-specific 16S rRNA was detected in endothelial cells and monocyte-macrophages in the liver, lungs, bone marrow, spleen, lymph nodes, and large and small intestinal tissues. The results suggest that the in-situ hybridization method with a digoxigenin-labelled RNA probe specific to ehrlichial 16S rRNA will be useful for post-mortem diagnosis and for the histopathological investigation of ehrlichial infection.

Identification of DNA markers of tobacco linked to bacterial wilt resistance

Bacterial wilt caused by Ralstonia solanacearum is one of the most destructive soil-borne diseases in the world. Breeding resistant commercial varieties of tobacco is difficult because most donor candidates' resistance is controlled by polygenes. In this paper, we demonstrate the identification of useful DNA markers for bacterial wilt-resistant tobacco breeding. One hundred and seventeen markers were identified by the amplified fragment length polymorphism (AFLP) method between W6, a burley variety with resistance originating from a Japanese domestic variety, Hatano, and Michinoku 1, a commercial burley wilt-susceptible variety, using 3,072 primer combinations. These markers were analyzed in 125 doubled haploid lines, derived from F(1) hybrids between W6 and Michinoku 1, and a linkage map consisting of ten linkage groups was drawn. The resistance phenotype of each of these lines was investigated on the basis of the average of disease severity obtained from field trials over two growing cycles. Quantitative trait loci (QTL) analysis was performed on the marker phenotypes and the resistance phenotype of each line. One QTL for the bacterial wilt resistance of W6 and DNA markers associated with this QTL were identified on a linkage group consisting of 15 markers, 32 cM in length. This QTL explained more than 30% of the variance in resistance among these lines.

Particle in cell simulation of laser-accelerated proton beams for radiation therapy

In this article we present the results of particle in cell (PIC) simulations of laser plasma interaction for proton acceleration for radiation therapy treatments. We show that under optimal interaction conditions protons can be accelerated up to relativistic energies of 300 MeV by a petawatt laser field. The proton acceleration is due to the dragging Coulomb force arising from charge separation induced by the ponderomotive pressure (light pressure) of high-intensity laser. The proton energy and phase space distribution functions obtained from the PIC simulations are used in the calculations of dose distributions using the GEANT Monte Carlo simulation code. Because of the broad energy and angular spectra of the protons, a compact particle selection and beam collimation system will be needed to generate small beams of polyenergetic protons for intensity modulated proton therapy.

Proposed double-layer target for the generation of high-quality laser-accelerated ion beams

In order to achieve a high-quality, i.e., monoenergetic, intense ion beam, we propose the use of a double-layer target. The first layer, at the target front, consists of high-Z atoms, while the second (rear) layer is a thin coating of low-Z atoms. The generation of high-quality proton beams from the double-layer target, irradiated by an ultraintense laser pulse, is demonstrated with three-dimensional particle-in-cell simulations.