A General Framework for Accelerator Management Based on ISA Extension

Thanks to the promised improvements in performance and energy efficiency, hardware accelerators are taking momentum in many computing contexts, both in terms of variety and relative weight in the silicon area of many chips. Commonly, the way an application interacts with these hardware modules has many accelerator-specific traits and requires ad-hoc drivers that usually rely on potentially expensive system calls to manage accelerator resources and access orchestration. As a consequence, driver-based interfacing is far from uniform and can expose high latency, limiting the set of tasks suitable for acceleration. In this paper, we propose a uniform and low-latency interface based on Instruction Set Architecture (ISA) extension. All the previous studies that proposed extensions, were deeply tailored to address a single accelerator. One of the biggest disadvantages of those methods is their inability to scale. Adding more of these accelerators to one System-on-Chip (SoC) would result in ISA bloat, increasing power consumption and complexifying the decoding phase proportionally. Our proposed framework consists of a six-instruction ISA extension and the corresponding architectural support that implements the interface abstraction and the reservation logic at the hardware level. Our proposal allows controlling a broad class of integrated accelerators directly from the CPU. The proposed framework is ISA-independent, which means that it is applicable to all the existing ISAs. We implement it on the gem5 simulator by extending the RISC-V ISA. We evaluate it by simulating three compute-intensive accelerators and comparing our interfacing with a conventional driver-based one. The benchmarks highlight the performance benefits brought by our framework, with up to 10.38x speed up, as well as the ability to seamlessly support different accelerators with the same interface. The speed up advantage of our technique diminishes as the granularity of the workloads increases and the overhead for driver-based accelerators becomes less important. We also show that the impact of its hardware components on chip area and power consumption is limited

CuSbS2 and related chalcogenides for sustainable photovoltaics

This thesis presents a systematic investigation of some novel chalcogenides based on Earth abundant elements in order to test their suitability for sustainable photovoltaic (PV) applications. A comprehensive review of sulfo-salts in the family Cu-Sb-Bi-X (X = S, Se) is presented and indicates that CuSbS2 and Cu3BiS3 have potential as PV absorbers, showing optical band gaps in the desired range and the p-type conductivity required for PV devices. A systematic study about the formation of CuSbS2 and Cu3BiS3 thin films is presented, including of the experimental steps necessary to ensure the formation of stoichiometric films during the sulfurization of metallic precursor layers. Sulfurized CuSbS2 films (~1.2 µm thick) exhibited absorption coefficients of ~105 cm-1 and band gaps of ~1.5 eV. The films were p-type with mobilities of ~10 cm2 V-1 s-1 and resistivities in the range 10 - 1000 kΩ/□. CuSbS2 films were also deposited in a one-stage process by rf sputtering from a ternary target – they were generally more resistive than those deposited by sulfurization. Cu3BiS3 films deposited by sulfurization had band gaps of ~1.4 eV and p-type conductivity, with hole mobilities of ~3 cm2 V-1 s-1. The CuSbS2 films produced by both methods were tested in prototype CuSbS2/CdS heterojunction PV devices, and had efficiencies of ~0.1%. For these devices the dominant transport mechanism was multi-step tunnelling, suggesting that an improvement in the quality of the junction was necessary. Post-growth treatments were trialled, including impurity doping with NaF, Zn and In, and etching the absorber to remove the surface oxides identified by XPS. CuSbS2/CdS devices having efficiencies up to ~1% were achieved by doping the absorber with In and removing unwanted Sb2O3 from the layer surfaces with de-ionized water. Their Vocs and FFs were low and their Jscs were high, as reported by others. Alternative window layer materials were tested, including ZnS and ZnSe, which were expected to have an improved band alignment with CuSbS2 compared to CdS. ZnS gave Voc = 0.56 V, the highest yet reported for CuSbS2. However these alternative window layers had reduced photocurrents and their efficiencies were not greater than with CdS. Overall CuSbS2 and Cu3BiS3 films displayed the optical and electrical properties required for PV, but further developments will be essential in order to achieve high efficiency PV devices using these materials as absorbers

IXIAM: ISA EXtension for Integrated Accelerator Management

During the last few years, hardware accelerators have been gaining popularity thanks to their ability to achieve higher performance and efficiency than classic general-purpose solutions. They are fundamentally shaping the current generations of Systems-on-Chip (SoCs), which are becoming increasingly heterogeneous. However, despite their widespread use, a standard, general solution to manage them while providing speed and consistency has not yet been found. Common methodologies rely on OS mediation and a mix of user-space and kernel-space drivers, which can be inefficient, especially for fine-grained tasks. This paper addresses these sources of inefficiencies by proposing an ISA eXtension for Integrated Accelerator Management (IXIAM), a cost-effective HW-SW framework to control a wide variety of accelerators in a standard way, and directly from the cores. The proposed instructions include reservation, work offloading, data transfer, and synchronization. They can be wrapped in a high-level software API or even integrated into a compiler. IXIAM features also a user-space interrupt mechanism to signal events directly to the user process. We implement it as a RISC-V extension in the gem5 simulator and demonstrate detailed support for complex accelerators, as well as the ability to specify sequences of memory transfers and computations directly from the ISA and with significantly lower overhead than driver-based schemes. IXIAM provides a performance advantage that is more evident for small and medium workloads, reaching around 90x in the best case. This way, we enlarge the set of workloads that would benefit from hardware acceleration

A recalcitrant case of folliculitis decalvans: imaging and treatment options

Folliculitis decalvans (FD) is a rare form of scarring alopecia, presenting with tufted hairs, follicular papules or pustules. It is the most common of neutrophilic alopecia, often associated with pruritus and pain. Currently, the cause of FD is still unknown. Scalp colonization by staphylococcus aureus seems to induce a severe inflammatory reaction with consequent destruction of hair follicles. All patients with active FD should be treated because the disease destroys hair follicles and causes permanent hair loss. Multiple treatments exist, but often provide only transitory or modest improvement. For this reason FD can negatively affect patient’s quality of life. A 46-year-old man presented with 15-year history of FD characterized by recurrent purulent follicular lesion on occipital side of the scalp and consequent scarring alopecia. His medical history was unremarkable, but he was distressed by the appearance of the lesions and hair loss. He was treated with different therapies such as doxycycline, rifampicin and hydroxychloroquine with poor results. He underwent two sessions of photodynamic treatment with methyl aminolevulinate at 2-week interval. At first, he was achieved benefit, but after 2 months there was recurrence and further progression of the disease. Based on literature reports, we decided to treat with long-pulse ND:Yag laser. We started at 30 J/cm2 and then we improved dose until 80 J/cm2. A total of 7 treatments in an 8-12 weeks inter-treatment interval were performed with successfully outcome, without relapse for more than 18 months of follow up. We monitored scalp inflammation with reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) during patient’s treatment. Both technologies represent non-invasive diagnostic tool and their application on inflammatory skin diseases has increased in the last years. ND:Yag laser is useful therapy option in the treatment of recalcitrant FD. Our experience allowed us to monitor the evolution of inflammatory reaction, confirmed treatment’s efficacy over the clinical examination

Copper–antimony and copper–bismuth chalcogenides—Research opportunities and review for solar photovoltaics

The ternary Cu-Sb- and Cu-Bi-chalcogenides present a rich range of compounds of potential use for large-scale photovoltaics from Earth abundant elements. This paper reviews the state of fundamental knowledge about them, and their technological status with regard to solar cells. Research targets and missing data are highlighted, which may provide opportunities to help realize the goal of sustainable photovoltaics. The family of ternary Cu-Sb- and Cu-Bi-chalcogenides and their solid solutions present a rich selection of potential candidates for Earth-abundant low toxicity photovoltaic (PV) absorber materials. Moreover, they have some novel features imparted by the ns2 lone pair of electrons on the Sb and Bi ions. This review evaluates them as electronic materials, including experimental and theoretical evaluations of their phases, thermodynamic stability, point defects, conductivity, optical data, and PV performances. Formation of the materials in bulk, thin film, and nanoforms and the properties of the materials are critically assessed with relevance to their suitability for PV devices. There is special emphasis on CuSbS2 and CuSbSe2 which form the mainstay of the device literature and provide the most insights into the present-day limitation of the device efficiencies to 3 or 4%. Missing features of the literature are highlighted and clear statements recommending potential research pathways are made, which may help advance the technological performance from its present stuck position

Eccrine poroma: dermoscopical and confocal features of five cases

Background: Eccrine poroma (EP) is a rare benign adnexal tumor arising from the intraepidermal ductal portion of the sweat gland. It commonly occurs as a single, slowly growing, erythematous, skin-colored, cyanotic or pigmented papule, plaques or nodule. EP occurs usually at the acral sites, but it can develop in other cutaneous sites. It may occasionally mimic malignant tumors including basal cell carcinoma, squamous cell carcinoma and melanoma. Objective: The aim of this study was to describe dermoscopical and confocal features of EP. Methods: A retrospective analysis of the dermoscopical and confocal characteristics of EP was performed. All diagnosis were confirmed by histological examination. Results: A total of 5 cases of non-pigmented EP was analysed. Dermoscopic evaluation found in all lesions a polymorphous vascular pattern, including at least two type of vessels: hairpin (80%), linear (60%), leaf-like (60%), flower-like (40%) and glomerular (40%) vessels. A white-to-pink halo surrounding the vessels was found in 40% of the lesions. Multiple pink-white structureless areas were found in 4 out of 5 (80%) cases. Only in 2 cases irregular haemorrhagic and blue-white areas were also observed. Reflectance Confocal Microscopy (RCM) revealed the presence of well-demarcated hyporefractile tumor nests, dark holes corresponding to areas of ductal differentiation within the tumor and highly vascularized stroma in all 5 lesions. Conclusions: The great clinical variability of EP gives reason of the appellative of “big simulator”. Dermoscopy does not revealed univocal features except from “leaf-flower-like” vessels that have not been described in other types of skin tumors. This characteristic, when presents, may be considered an useful clue for the diagnosis. RCM examination of EP revealed features (hyporefractile tumor nests and dark holes) that relate with their histopathological findings. Dermoscopy and RCM improve the diagnostic accuracy and help for diagnosis, although they cannot replace histology that is still required

“Lambs” in wolves’ clothing: when basal cell carcinoma mimics melanoma, but it is detected by the use of reflectance confocal microscopy

Background Basal cell carcinoma (BCC) is the most frequent non-melanoma skin cancer. There are some cases in which clinical and dermoscopic examinations do not allow to formulate a unique diagnosis and in particular can be difficult the differential diagnosis with melanoma. Reflectance confocal microscopy (RCM) is a non-invasive technology, which allows an in vivo imaging of the skin with high resolution. Objectives We addressed our research to evaluate the reliability of the well-known RCM criteria for classic BCCs in a group of lesions with atypical dermoscopy presentation, possibly mimicking melanoma. Methods We retrospectively analyzed at RCM excised lesions presenting in dermoscopy ≥1 score at revisited 7-point checklist. The study population consisted of 177 cases showing no melanocytic RCM findings. Lesions were investigated for distinct non-melanocytic RCM features, while blinded from histopathology. Histopathology matching was performed before statistical analysis. Results Among the lesions classified at RCM with no-melanocytic characteristics, we recognized 34 cases, histopathological confirmed as BCCs (21 nodular BCCs and 13 superficial BCCs) and 143 cases classified as other lesions (DFs, SebKs, SCCs and others). The main features of nBCCs (with histopathological confirm) at RCM are peritumoral clefts (20/21 95,2%; p=0,037), peripheral palisading (19/21 90,5%; p=0,001), increased vascularization (20/21 95,2%; p=0,004). In sBCCs we found mild keratinocytic atypia (13/13 100%; p=<0,001), solar elastosis (12/13 92,3%; p=0,002), cords connected to epidermidis (9/13 69,2%; p=<0,001). Dendritic structures, nests of basaloid cells, inflammatory infiltrate can be seen in all tumors. Conclusions RCM classification proved high agreement with histopathology for BCCs with atypical dermoscopy presentations, allowing an early differential diagnosis and even identification of BCCs subtypes. RCM features in this group of lesions were similar to those described for typical cases of BCCs, and may drive clinicians decisions, helped them in the recognition of melanocytic and non melanocytic lesions, increasing the rate of accurate diagnoses and allowing better therapeutic management

The effect of the sterile insect technique on vibrational communication: the case of Bagrada hilaris (Hemiptera: Pentatomidae)

The painted bug, Bagrada hilaris, is an agricultural pest in its original areas (Africa, South Asia, and the Middle East), and it has recently been recorded as an invasive species in southwestern part of the US, Chile, Mexico, and two islands in the Mediterranean basin. Its polyphagous diet causes severe damage to economically important crops. The control of this pest is primarily achieved by means of synthetic pesticides, which are often expensive, ineffective, and harmful to the ecosystem. Recent physiological bioassays to assess its potential control through the sterile insect technique demonstrated that mating between untreated females and males irradiated at doses of 64 and 100 Gy, respectively, resulted in 90% and 100% sterility of the eggs produced by the females. In this study, the mating abilities of virgin males irradiated at 60 and 100 Gy with virgin females were measured through a study of short-range courtship mediated by vibrational communication. The results indicate that males irradiated at 100 Gy emit signals with lower peak frequencies, mate significantly less than unirradiated males do, and do not surpass the early stages of courtship. Conversely, males irradiated at 60 Gy present vibrational signal frequencies that are comparable to those of the control and successfully mated males. Our findings suggest that B. hilaris individuals irradiated at 60 Gy are good candidates for the control of this species, given that they retain sexual competitiveness regardless of their sterility, through an area-wide program that incorporates the sterile insect technique