Haldane gap in the quasi one-dimensional nonlinear σ\sigma-model

This work studies the appearance of a Haldane gap in quasi one-dimensional antiferromagnets in the long wavelength limit, via the nonlinear $\sigma$-model. The mapping from the three-dimensional, integer spin Heisenberg model to the nonlinear $\sigma$-model is explained, taking into account two antiferromagnetic couplings: one along the chain axis ($J$) and one along the perpendicular planes ($J_\bot$) of a cubic lattice. An implicit equation for the Haldane gap is derived, as a function of temperature and coupling ratio $J_\bot/J$. Solutions to these equations show the existence of a critical coupling ratio beyond which a gap exists only above a transition temperature $T_N$. The cut-off dependence of these results is discussed.Comment: 14 pages (RevTeX 3.0), 3 PostScript figures appended (printing instructions included

Long-term functional evaluation of the treated kidney in a prospective series of patients who underwent laparoscopic partial nephrectomy for small renal tumors.

Background: Renal scintigraphy may allow long-term monitoring of ischemic damage after partial nephrectomy (PN). Objective: Evaluate use of renal scintigraphy for evaluating long-term effects of warm ischemia on renal function in patients with a normal contralateral kidney. Design, setting, and participants: We prospectively examined kidney function of 54 patients who underwent laparoscopic PN (LPN). Minimum follow-up time was 4 yr. Intervention: LPN was performed with warm ischemia by transperitoneal or retroperitoneal approach. Measurements: Demographic, perioperative, and pathologic data and postoperative complications were registered. Split renal function (SRF) and effective renal plasma flow (ERPF) were evaluated by renal scintigraphy preoperatively, at 3 and 12 mo postoperatively, then yearly. Baseline weighted differentials (b-WDs) of both SRF and ERPF in the affected kidney were calculated between baseline condition and every time point. Multivariate linear regression was used to find independent variables for increased b-WDs at 3 and 48 mo. P values<0.05 were considered significant. Results and limitations: The SRF and ERPF of kidneys treated by LPN decreased significantly at month 3 and subsequently remained stable through the duration of follow-up. Conversely, neither serum creatinine nor estimated glomerular filtration rate changed significantly during follow-up. The regression model showed statistical significance at month 3 for warm ischemia time (WIT) and age, whereas at 48 mo, statistical significance was reached by WIT alone. No new onset of cardiovascular disease was registered. No evidence of local recurrence was recorded with computed tomography scan. Our study may be underpowered due to small sample size; however, this is one of the largest long-term prospective series using renal scintigraphy to evaluate the renal function after LPN. Conclusions: WIT contributes to irreversible kidney damage observed at month 3 that does not appear to worsen

Assessing Yield and Quality of Melon (Cucumis melo L.) Improved by Biodegradable Mulching Film

: Low-density polyethylene (LDPE) plastic mulching films have an important function, but at the end of their lifetime pose an economic and environmental problem in terms of their removal and disposal. Biodegradable mulching films represent an alternative to LDPE with the potential to avoid these environmental issues. In this preliminary study, we employed a biodegradable film based on Mater-Bi® (MB) in comparison with low-density polyethylene to assess their effect on the yield and particular quality traits (organoleptic and nutraceutical composition of the fruits) of muskmelon (cv Pregiato) grown on soils with different textures (clay-loam-CL and sandy loam-SL) in two private farms in South Italy. Soil temperature under the mulch was also measured. During the monitored periods, mean soil temperature under LDPE was higher (about 1.3 °C) than that under the biodegradable film and was higher in SL soil than in CL soil, at 25.5° and 24.2 °C, respectively. However, the biodegradable film was able to limit the daily temperature fluctuation, which was 1.7 °C in both soils compared with 2.3 °C recorded for LDPE. Fruit yields were higher with MB film than LDPE (+9.5%), irrespective of soil texture. MaterBi® also elicited increases in total soluble solids, polyphenols, flavonoids, and antioxidant activity compared with LDPE films: 13.3%, 22.4%, 27.2%, and 24.6%, respectively. Color parameters of flesh, namely brightness, chroma, and hue angle were better in fruits grown on LDPE. Our findings suggest that Mater-Bi® based biodegradable mulching film is a potentially valid alternative to traditional LDPE, particularly for obtaining the agronomical benefits outlined above and for promoting environmental sustainability due to its favourable biodegradable properties

Mixed-spin systems: coexistence of Haldane gap and antiferromagnetic long range order

Recent experiments on the quasi-1D antiferromagnets $R_{2}BaNiO_{5}$ (R = rare earth) have shown the existence of purely 1D Haldane gap excitations propagating on the Ni chains. Below an ordering temperature, the gap excitations survive and coexist with the conventional spin waves in the ordered phase. We construct a model mixed-spin system in 2D for which the ground state can be exactly specified. Using the Matrix Product Method, we show the existence of Haldane gap excitations in the ordered phase. We consider different cases of ordering to study the effect of ordering on the degeneracy of the Haldane gap excitations.Comment: 13 pages, LaTeX, 2 Postscript figures, communicated to Phys. Rev.

Magnetic excitations in coupled Haldane spin chains near the quantum critical point

Two quasi-1-dimensional S=1 quantum antiferromagnetic materials, PbNi2V2O8 and SrNi2V2O8, are studied by inelastic neutron scattering on powder samples. While magnetic interactions in the two systems are found to be very similar, subtle differences in inter-chain interaction strengths and magnetic anisotropy are detected. The latter are shown to be responsible for qualitatively different ground state properties: magnetic long-range order in SrNi2V2O8 and disordered ``spin liquid'' Haldane-gap state in PbNi2V2O8.Comment: 15 figures, Figs. 5,9, and 10 in color. Some figures in JPEG format. Complete PostScript and PDF available from http://papillon.phy.bnl.gov/publicat.ht

Spin-Vacancy-Induced Long-Range Order in a New Haldane-Gap Antiferromagnet

Magnetic susceptibility, high-field magnetization and inelastic neutron scattering experiments are used to study the magnetic properties of a new S=1 quasi-1-dimensional antiferromagnet PbNi2V2O8. Inter-chain interactions are shown to be almost, but not quite, strong enough to destroy the nonmagnetic singlet ground state and the energy gap in the magnetic excitation spectrum. Substituting nonmagnetic Mg$^{2+}$ (S=0) ions for Ni$^{2+}$ (S=1) induces a magnetically ordered state at low temperatures. To our knowledge this is the first observation of doping-induced long-range order in a Haldane-gap system.Comment: 5 pages including 4 figure

Field induced transition of the S=1 antiferromagnetic chain with anisotropy

The ground state magnetization process of the S=1 antiferromagnetic chain with the easy-axis single-ion anisotropy described by negative $D$ is investigated. It is numerically found that a phase transition between two different gapless phases occurs at an intermediate magnetic field between the starting and saturation points of the magnetization for $-1.49<D<-0.35$. The transition is similar to the spin flopping, but it is second-order and not accompanied with any significant anomalous behaviors in the magnetization curve. We also present the phase diagrams in the m-D and H-D planes which reveal a possible re-entrant transition.Comment: 6 pages, Revtex, with 6 eps figures, to appear in Phys. Rev. B (Sep. 1

How SARS-CoV-2 Infection Impacts the Management of Patients with Vulvar Cancer: Experience in a Third-Level Hospital of Southern Italy

: Background: Since February 2020, the spread of Coronavirus Disease 2019 (COVID-19) in Italy has induced the government to call for lockdown of any activity apart from primary needs, and changing the lives of each of us. All that has dramatically impacted the management of patients affected by cancer. Patients with vulvar cancer (VC) represent a particularly frail population because they are elderly and affected by multiple comorbidities. The aim of this study is to evaluate the clinical impact of the SARS-CoV-2 infection on VC patients in terms of delay or impossibility of carrying out the scheduled treatment. Methods: The medical records of patients affected by vulvar tumors, referred to "DAI Materno-Infantile" of AOU Federico II of Naples between February 2020 and January 2022 were retrospectively analyzed. The presence of a positive reverse transcription-polymerase chain reaction (RT-PCR) in nasopharyngeal swab defined the positivity to SARS-CoV-2. Results: Twenty-four patients with VC were analyzed and scheduled for treatment. The median age was 70.7 years (range: 59-80). Seven (29.2%) patients were diagnosed with SARS-CoV-2 infection: In three (42.8%) patients, the treatment was delayed with no apparent consequences, in four (57.2%), the treatment was delayed or changed due to cancer progression and, of these four, one died due to respiratory complications of COVID-19, and one died due to oncologic disease progression. Conclusion: COVID-19 caused, in most cases, significant delays in oncologic treatments and high mortality in our series of patients affected by VC

Surface-enhanced Raman spectroscopy of tears: Toward a diagnostic tool for neurodegenerative disease identification

Significance: A noninvasive method based on surface-enhanced Raman spectroscopy (SERS) of tears was proposed as a support for diagnosing neurodegenerative pathologies, including different forms of dementia and Alzheimer's disease (AD). In this field, timely and reliable discrimination and diagnosis are critical aspects for choosing a valid medical therapy, and new methods are highly required. Aim: The aim is to evince spectral differences in SERS response of human tears from AD affected, mild cognitive impaired (MCI), and healthy control (Ctr) subjects. Approach: Human tears were characterized by SERS coupled with multivariate data analysis. Thirty-one informed subjects (Ctr, MCI, and AD) were considered. Results: Average SERS spectra from Ctr, MCI, and AD subjects evidenced differences related to lactoferrin and lysozyme protein components. Quantitative changes were also observed by determining the intensity ratio between selected bands. We also constructed a classification model that discriminated among AD, MCI, and Ctr subjects. The model was built using the scores obtained by performing principal component analysis on specific spectral regions (i-PCA). Conclusions: The results are very encouraging with interesting perspectives for medical applications as support of clinical diagnosis and discrimination of AD from other forms of dementia