Progress in the experimental and computational methods of work function evaluation of materials: A review.

The work function, which determines the behaviour of electrons in a material, remains a crucial factor in surface science to understand the corrosion rates and interfacial engineering in making photosensitive and electron-emitting devices. The present article reviews the various experimental methods and theoretical models employed for work function measurement along with their merits and demerits are discussed. Reports from the existing methods of work function measurements that Kelvin probe force microscopy (KPFM) is the most suitable measurement technique over other experimental methods. It has been observed from the literature that the computational methods that are capable of predicting the work functions of different metals have a higher computational cost. However, the stabilized Jellium model (SJM) has the potential to predict the work function of transition metals, simple metals, rare-earth metals and inner transition metals. The metallic plasma model (MPM) can predict polycrystalline metals, while the density functional theory (DFT) is a versatile tool for predicting the lowest and highest work function of the material with higher computational cost. The high-throughput density functional theory and machine learning (HTDFTML) tools are suitable for predicting the lowest and highest work functions of extreme material surfaces with cheaper computational cost. The combined Bayesian machine learning and first principle (CBMLFP) is suitable for predicting the lowest and highest work functions of the materials with a very low computational cost. Conclusively, HTDFTML and CBMLFP should be used to explore the work functions and surface energy in complex materials.

Investigations of a high current linear aperture radial multichannel pseudospark switch.

In this paper, a high current linear aperture radial multichannel Pseudospark switch (LARM-PSS) is reported which has been analyzed for its high current characteristics. In order to enhance hold-off voltage and support hollow cathode effect for the ignition of the discharge in this configuration, the field penetration analysis through circular and linear apertures of the electrodes has been carried out. The linear apertures in the electrodes increase the current handling capacity than that of circular aperture electrodes without significant compromise of the hold-off capacity. The developed LARM-PSS switch is capable to hold voltage up to 25 kV at gas pressure between 10 and 50 Pa for hydrogen. The switch has been operated using a 800 nF capacitor bank and conducted an effective charge up to 1.5 C with peak switch current ∼20 kA at applied voltage 19 kV.

Cytomegalovirus (CMV) infections and CMV-specific cellular immune reconstitution following reduced intensity conditioning allogeneic stem cell transplantation with Alemtuzumab.

We studied the incidence and recurrence of Cytomegalovirus (CMV) infection and reactivation in 38 recipients of Alemtuzumab reduced intensity conditioning-stem cell transplantation, and used CMV-HLA tetramer studies to discover if these events correlated with recovery of circulating CMV-specific CD8+ T cells (cytotoxic T lymphocyte (CTLs)). The cumulative incidence of CMV infection was 60% at 1 year (95% CI, 45-78%) with a median reactivation time of 24 days (range 5-95 days). All patients with CMV reactivation received Ganciclovir or Foscarnet, and only one developed CMV disease. More strikingly, only 8/21 patients had relapse of CMV antigenemia. Tetramer analysis in 13 patients showed that 11 reconstituted CMV CTLs (7/11 by day 30 and 10/11 by day 90). The development of CMV infection was accompanied by a >5-fold rise of CMV CTLs. Recurrence of CMV infection occurred only in the patients who failed to generate a CTL response to the virus. Hence, recipients of SCT using Alemtuzumab-RIC are initially profoundly immunosuppressed and have a high incidence of early CMV reactivation. However, in the majority of patients, infection is transient, and antiviral T cell reconstitution is rapid. Monitoring with CMV-specific CTLs may help identify the subset of patients at risk from recurrent infection or disease.

CD52 and CD45 monoclonal antibodies for reduced intensity hemopoietic stem cell transplantation from HLA matched and one antigen mismatched unrelated donors.

Allogeneic hemopoietic stem cell transplantation (HSCT) is the only curative option for many patients with hematological malignancies. Since many of these patients lack HLA-identical sibling donors and are older or have comorbidity, a fully ablative HSCT is not feasible and an alternative approach is required. We studied 22 consecutive patients who could not have myeloablative conditioning because of comorbidity or age - 21/22 being over the age of 50 years (median 58 years range 20-70 years). A conditioning regimen consisting of fludarabine, total body radiation 450 cGy and alemtuzumab (CD52 mAb) was used for 15 patients. A second group of seven patients received CD45 monoclonal antibodies in addition. Unrelated donor stem cells were HLA matched (15 patients - 68%) or one locus mismatched (seven patients - 32%). In all, 16 patients had high-risk disease, including 12 with active malignancy at the time of transplant. With a median follow-up of 715 (216-1470) days, nonrelapse mortality, actuarial event-free and overall survival is 27, 45 and 45%, respectively. Hence the outcome of reduced intensity HSCT with lymphodepleting antibodies in older patients with intermediate/high-risk hematological malignancies appears comparable to that obtained with fully ablative transplantation in younger patients, even when these older recipients lack HLA-identical sibling donors.

Mixed hematopoietic chimerism at day 90 following allogenic myeloablative stem cell transplantation is a predictor of relapse and survival.

We retrospectively analyzed the prognostic significance of mixed chimerism and associated clinical parameters in 80 patients following unmanipulated allogenic stem cell transplantation. Chimerism studies were performed on marrow aspirates using fluorescent in situ hybridization and variable number tandem repeats techniques at day +30, day +90 and +12 months. The median overall survival (OS) was 24 months (range, 1-56 months). Mixed chimerism was found in 23, 28 and 14% of patients at day +30 (1 month), +90 (3 months), and +12 months, respectively. Day +30 chimerism studies failed to provide any prognostic information. Day +90 mixed chimeras (MC) had significantly higher relapse rates compared to day +90 complete chimeras (CC) at 6 months (P=0.03) and 18 months when compared to MC (P=0.03) following transplant. The median OS in day +90 MC and day+90 CC were, respectively (95% CI, 2-35 months), compared to 47 months (95% CI, 20-74 months) (P=0.02). In conclusion, chimerism studies on day +30 could be reserved for patients who fail to demonstrate engraftment. Day +90 MC had higher relapse rates and lower OS, and therefore may be considered for novel therapies and future studies.