Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe ...spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M
edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 10
cm
. Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first-order electron and hole decay of ∼1 ps suggests a Shockley-Read-Hall recombination mechanism. The simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.
Semiconductor
alloys containing silicon and germanium are of growing importance for compact and
highly efficient photonic devices due to their favorable properties for direct integration
into silicon
...platforms and wide tunability of optical parameters. Here, we report the simultaneous
direct and energy-resolved probing of ultrafast electron and hole dynamics in a
silicon-germanium alloy with the stoichiometry Si0.25Ge0.75 by
extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge
carriers at the germanium M4,5-edge (∼30 eV) allows the germanium atoms to be
used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons
across the direct and indirect band gap into conduction band (CB) valleys and their subsequent hot carrier
relaxation are observed and compared to pure germanium, where the Ge direct
(
Δ
E
gap
,
Ge
,
direct
=
0.8
eV
)
and Si0.25Ge0.75
indirect gaps (
Δ
E
gap
,
Si
0.25
Ge
0.75
,
indirect
=
0.95
eV
) are comparable in energy. In the alloy,
comparable carrier lifetimes are observed for the X, L, and Γ valleys in the
conduction band.
A midgap feature associated with electrons accumulating in trap states near the CB edge
following intraband thermalization is observed in the Si0.25Ge0.75 alloy.
The successful implementation of the reporter atom concept for capturing the dynamics of
the electronic bands by site-specific probing in solids opens a route to study carrier
dynamics in more complex materials with femtosecond and sub-femtosecond temporal
resolution.
Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical/NIR ...pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by attosecond transient absorption spectroscopy (ATAS) in the extreme ultraviolet at the germanium M_{4,5}-edge (~30 eV). We decompose the ATAS spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8*10^{20}cm^{-3}. Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first order electron and hole decay of ~1 ps suggests a Shockley-Read-Hall recombination mechanism. The simultaneous observation of electrons and holes with ATAS paves the way for investigating few to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.
Target product profiles: leprosy diagnostics Kukkaro, Petra; Vedithi, Sundeep Chaitanya; Blok, David J ...
Bulletin of the World Health Organization,
04/2024, Letnik:
102, Številka:
4
Journal Article
Recenzirano
L'Organisation mondiale de la Santé (OMS) vise à réduire le nombre de nouveaux cas de lèpre de 70% d'ici 2030, ce qui nécessite un meilleur diagnostic de la maladie. Dans le présent document, nous ...évoquons le développement de deux profils de produit cible établis par l'OMS à cette fin. Ces profils définissent des critères en matière d'utilisation, de conception, de performances, de configuration et de distribution du produit, en accordant une attention particulière à l'accessibilité et à l'abordabilité. Le premier profil de produit cible décrit les exigences pour les tests servant à confirmer le diagnostic de la lèpre chez les individus qui présentent des signes cliniques et des symptômes, afin d'orienter l'instauration d'un traitement à base de plusieurs médicaments. Le second profil de produit cible décrit les exigences pour les tests servant à détecter une infection à Mycobacterium leprae ou M. lepromatosis parmi les contacts asymptomatiques de patients lépreux, ce qui contribue à l'adoption de mesures prophylactiques et à la prévention. Nous avons eu recours à une modélisation statistique pour évaluer les exigences de sensibilité et de spécificité de ces tests diagnostiques. Cet article met en évidence les obstacles à l'atteinte d'un niveau élevé de spécificité en raison de l'endémicité variable de M. leprae, et à l'identification d'analytes cibles offrant de bons résultats chez les phénotypes lépreux. Nous concluons qu'un diagnostic reposant sur des caractéristiques de performance et de conception appropriées est essentiel pour détecter rapidement la maladie et intervenir en amont, et nous plaidons pour une prévention plutôt qu'une gestion de la lèpre.
Introduction:
Additional cytogenetic clonal evolution (CE) is a known risk factor for a poor prognosis in chronic myeloid leukemia (CML). However, its prognostic significance in the setting of new ...tyrosine kinase inhibitor (TKI) remains unclear. We sought to analyze the baseline characteristics and clinical outcome in chronic phase (CP) CML pts with or without CE treated on frontline TKI clinical trials in a single institution.
Methods:
Patients (pts) with Ph-positive CML in CP with or without CE at the time of diagnosis receiving initial therapy with imatinib 400 mg/d, imatinib 800 mg/d, dasatinib 100 mg/d, nilotinib 800 mg/d or ponatinib 30 or 45 mg/d in consecutive or parallel clinical trials at a single institution were analyzed. Overall survival (OS), transformation free survival (TFS), event free survival (EFS), failure free survival (FFS) were analyzed from the start of therapy by Kaplan-Meier method. Clonal evolution (CE) was defined by the presence of any cytogenetic abnormality other than a single Ph, variant Ph chromosome or loss of Y chromosome. Also we analyzed CML pts with CE with regard 'major route' abnormalities vs other. The major route abnormalities includes trisomy 8 (+8), trisomy 19 (+19), isochromosome 17q10 (i17q) and additional Ph chromosome.
Results:
A total of 603 pts were analyzed including 579 pts in CP without CE and 24 pts with CE. Pts in CP without CE received initial therapy with imatinib-400 (n=70), imatinib-800 (n=200), dasatinib (n=138), nilotinib (n=122), or ponatinib (n=49), and pts with CE received imatinib-400 (n=2), imatinib-800 (n=7), dasatinib (n=10), nilotinib (n=4), and ponatinib (n=1). Pts with CP were usually older, female and have a higher WBC (P < 0.001). There was a statistically significant higher Complete cytogenetic response (CCyR) at 6 mo in pts without CE (P = 0.012), however the cumulative and 3-month rates of complete hematologic response (CHR), and the cumulative rates of CCyR and MMR were not different (Table). Similarly, the rates of MR4.0 and MR4.5 were similar for the two groups. At 5 years, the presence of additional cytogenetic findings at diagnosis does not seem to affect the rate of transformation, failure-free, event-free and overall survival. Acknowledging the small sample size for subset analysis, response rates and survival outcomes were comparable in CP with CE irrespective of whether chromosomal abnormalities were ’major route’ or other (n=12 in each arm).
Conclusion:
Additional cytogenetic CE at the time of diagnosis among patients with CML in CP is associated with a similar favorable outcome as those without CE when treated with TKI. The type of additional CE (major route vs other) does not seem to impact outcome. Patients with CML-CP with CE at the time of diagnosis can thus be treated with TKI as all other pts with CP with no need for consideration for SCT unless there is clear evidence of failure.
Jabbour:ARIAD: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Research Funding; BMS: Consultancy. Ravandi:BMS: Research Funding; Seattle Genetics: Consultancy, Honoraria, Research Funding. DiNardo:Abbvie: Research Funding; Agios: Other: advisory board, Research Funding; Daiichi Sankyo: Other: advisory board, Research Funding; Novartis: Other: advisory board, Research Funding; Celgene: Research Funding. Daver:Ariad: Research Funding; Sunesis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Karyopharm: Honoraria, Research Funding; BMS: Research Funding; Kiromic: Research Funding; Otsuka: Consultancy, Honoraria. Cortes:ARIAD: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding.
BACKGROUND: Advanced age, AML arising from an antecedent hematologic disorder (AHD), and therapy-related AML (t-AML) are well established risk factors associated with poor outcome in AML. This ...subgroup of AML has been associated with lower rates of complete remission (CR) and shorter disease-free survival compared with de novo AML in younger patients (pts), when using standard therapy. Developing newer strategies to improve outcomes in this subgroup of pts is therefore a critical unmet need. Establishing baseline metrics from which to evaluate newer approaches is important. We sought to review our own experience with pts treated with different therapies at our institution to establish this baseline.
METHODS: We retrospectively reviewed pts aged 60-75 years with newly diagnosed AML treated at our institution from 1990-2015 with one or more of the following characteristics: history of prior MDS, CMML, MPN, or aplastic anemia, the diagnosis of t-AML, or AML with karyotypic abnormalities characteristic of MDS as defined by the WHO. The pts were grouped into 5 study cohorts based on their treatment regimen: 1) High-dose Ara-C based intensive chemotherapy (HiDAC), 2) Hypomethylating agents (HMA)/HMA combinations, 3) Low-dose Ara-C combinations (LDAC), 4) Liposomal Ara-C:Daunorubicin (CPX-351), and 5) Other investigational agents (INV). Pts’ karyotypes were divided into 4 categories: adverse karyotype (complex: defined by >2 chromosomal abnormalities, Del 5/5q, Del 7/7q, 11q, 3q abnormality); diploid karyotype, intermediate karyotype (karyotype other than adverse or diploid); and unknown/not available. Endpoints included complete response (CR) rate/CR with low platelets (CRp) and 8-week mortality rates. Both univariate and multivariate analyses were performed to examine the relationships between disease characteristics and outcomes (CR, Overall survival).
RESULTS: We evaluated a total of 931 pts with newly diagnosed AML meeting these criteria of age and secondary AML (s-AML). The baseline characteristics of pts in each group are summarized in table 1. The median age was 68 (60-75) years. Most pt characteristics were well balanced across the 5 treatment groups. Karyotyping was performed in 89% of the pts: 57.5% belonged to adverse risk profile and 31% belonged to intermediate risk profile (excluding diploid). The overall CR/CRp rates for the entire group was 39.5%. CR/CRp rates were lower in the HMA (36%) and INV (16%) groups compared to HiDAC (46%), CPX (45%) and LDAC (43%). Eight week mortality rate for the entire group was 20%: HiDAC (23%), HMA (12%), CPX (10%), LDAC (19%), and INV (27%). The median OS for the entire group was 6 months and by each treatment regimen is shown in Figure 1. There was a significant difference in OS between the 5 treatment groups. Pts receiving less intensive regimens HMA + LDAC had a superior median OS compared to those receiving HiDAC-based regimens (6.9 vs. 5.4; P=0.002, Figure 2). There was no difference in median survival in pts treated with CPX compared with conventional lower-intensity approaches (HMA + LDAC) (p=0.75). In the multivariate analysis, age >70yrs, adverse karyotype, and prior treatment for AHD were associated with a decreased OS. Similarly, use of HMA/INV treatment, adverse/intermediate risk karyotype, history of prior treatment for AHD were associated with lower CR rates.
CONCLUSIONS: The outcomes of older pts with newly diagnosed s-AML are poor and reflective of their advanced age and poor-risk karyotype. Various treatment approaches have been attempted to improve outcomes. Lower-intensity approaches such as HMA and LDAC-based regimens have response rates similar to HiDAC regimens, but are associated with lower early mortality and improved overall survival. While the investigational liposomal formulation CPX-351was associated with favorable CR rates and low early mortality, the median OS was similar to pts treated with low intensity therapy. The unsatisfactory outcomes using other investigational agents in the INV group underscores the need for more effective therapies for these patients.
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Kantarjian:BMS, Pfizer, Amgen, Novartis: Research Funding. Konopleva:Reata Pharmaceuticals: Equity Ownership; Abbvie: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Stemline: Consultancy, Research Funding; Eli Lilly: Research Funding; Cellectis: Research Funding; Calithera: Research Funding. DiNardo:Celgene: Research Funding; Abbvie: Research Funding; Novartis: Other: advisory board, Research Funding; Daiichi Sankyo: Other: advisory board, Research Funding; Agios: Other: advisory board, Research Funding. Jain:Celgene: Research Funding; Infinity: Research Funding; ADC Therapeutics: Consultancy, Honoraria, Research Funding; Novimmune: Consultancy, Honoraria; Incyte: Research Funding; Abbvie: Research Funding; Novartis: Consultancy, Honoraria; Servier: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Research Funding; Genentech: Research Funding; Pharmacyclics: Consultancy, Honoraria, Research Funding; BMS: Research Funding; Seattle Genetics: Research Funding. Wierda:Acerta: Research Funding; Novartis: Research Funding; Gilead: Research Funding; Abbvie: Research Funding; Genentech: Research Funding. Cortes:ARIAD: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding.
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