Dead Space Model Research Articles

Accurate Prediction of Photon Detection Probability Based on the 2-D Dead-Space Model for SPADs

In this article, we propose an accurate procedure for predicting the photon detection probability (PDP) for single-photon avalanche diodes (SPADs). The energy threshold needed for triggering impact ionization, that is, the dead space, was carefully considered and developed into a 2-D solution. The input parameters are based on the manufacturing process and device layout. The breakdown probability of each point on the 2-D profile was calculated without adding fitting parameters, which can overcome the inaccurate prediction caused by the uneven distribution of the electric field and photon generation for the device with the guard ring. Two sets of SPADs based on 180 nm for front-side illumination and 55 nm for back-side illumination were fabricated and tested. The simulation and experimental results are in accordance with each other. This procedure makes it very easy to optimize the device structure based on the simulation results. In addition, the invention can invoke graphics processing units (GPUs) in the MATLAB platform to perform parallel acceleration calculations and improve the calculation efficiency.

Wound Healing Activities of Latex of Grassleaf Spurge (<i>Euphobia </i><i>g</i><i>raminea</i><i> </i>Jacq.)

The present study evaluated the wound healing potentials of E. graminea (EG) latex. The latex of EG was screened for the presence of phytochemical constituents; in vitro antioxidant property and erythrocyte membrane stabilizing activity was used to investigate anti-inflammatory property of the latex. The wound healing potential of E. graminea latex (EGL) was investigated via incision and dead space wound models in wistar rats; eighteen wistar rats (separately for each model) were randomly divided into 3 groups (6 in each group): Group A: wound + EGL ; Group B: wound + Gentamycin (G); Group C: wound without treatment (control). Wound breaking strength (Incision model), hexuronic acid and hexosamine concentrations, activities of antioxidants biomolecules (superoxide dismutase, catalase, and reduced glutathione) as well as the levels of free radicals (nitric oxide-NO, malondialdehyde -MDA) were evaluated in the granulation tissue (dead space model) of experimental rats. The result of the study revealed that EGL tested positive for the presence of saponins, alkaloids, triterpenes, flavonoids and cardiac glycosides. Also, EGL contained an appreciable concentration of total flavonoids and phenolics. The latex exhibited mild ferric reducing power, inhibited DPPH in dose dependent manner as well as protected red blood cells against hypotonic and heat induced lyses. In wound incision model, EGL exhibited 13.6 % increase in wound breaking strength when compared to the control animals. Also, in dead space wound model, there was significant increase (p < 0.05) in hexoxamine, hexuronic acid and GSH concentrations as well as SOD activity in EGL and gentamycin treated wound compared to the control. Furthermore, there was a significant reduction (p < 0.05) in MDA concentration in EGL and gentamycin treated wound compared to the control while NO level and catalase activity showed no significant difference. This study revealed that EGL contained potentially bioactive molecules that could be employed in the treatment of wound.

A speed-optimized, low-noise APD with 0.18 μm CMOS technology for the VLC applications

A new avalanche photodiode device applied to a visible light communication (VLC) system is designed using a standard 0.18 [Formula: see text]m complementary metal oxide semiconductor process. Compared to regular CMOS APD devices, the proposed device adds a [Formula: see text]-well layer above the deep [Formula: see text]-well/[Formula: see text]-substrate structure, and an [Formula: see text]/[Formula: see text] layer is deposited upon it. The [Formula: see text]/[Formula: see text] layer acts as an avalanche breakdown layer of the device, and an STI structure is used to prevent the edge break prematurely. The simulation results shows that the avalanche breakdown voltage is as low as 9.9 V, dark current is below [Formula: see text] A under −9.5 V bias voltage, and the 3 dB bandwidth is of 5.9 GHz. It is due to the use of the 0.18 [Formula: see text]m CMOS process-specific STI protection ring and short-circuits the connection of the deep [Formula: see text]-well/[Formula: see text]-substrate, and the dark current is reduced to be lower than two orders of magnitude compared to regular CMOS APD. Gain and noise characteristics are accurately calculated from Hayat dead-space model applied to this CMOS APD. So, this device’s gain and excess noise factor are 20 and 2.5, respectively.

Wound Healing Activity of Calotropis Procera Root Bark on Diabetic Rats

Herbal therapy and herbal medicine in traditional medicine as well as in alternative medicine practiced in the developed world. There is recent most of the harbal formulation are used to cure &amp; improve the humal life. The present study Wound healing activity of Calotropis procera root bark on diabetic rats in that root bark is extracted from ethanolic extract using soxhlet method. The pharmacognostic study was done after that phytochemical characters should be studied. The root bark has alkaloids, Flavonoids, steroids and tannins active constituents. Acute toxicity study carried out with three pharmacological models Incision model, Excision model, and Dead space model. All the extract show predominant activity against selected species. Extract shows beneficial effect on diabetic wound it heals in time with standard component. Overall results of this study reveals that this is an effective extract on diabetic wound.&#x0D; Keywords: Traditional medicine, Calotropis procera, Wound Healing Activity

Temperature dependence simulation and characterization for InP/InGaAs avalanche photodiodes

Based on the newly proposed temperature dependent dead space model, the breakdown voltage and bandwidth of InP/InGaAs avalanche photodiode (APD) have been investigated in the temperature range from -50°C to 100°C. It was demonstrated that our proposed model is consistent with the experimental results. Our work may provide a guidance to the design of APDs with controllably low temperature coefficient.

In vivo models for assesment of wound healing potential: A systematic review

Abstract Introduction The wound is defined as an injury of a living tissue, arose due to either an accidental injury like cut of the cells or skin or sometime, maybe broken the tissue, which may cause the anomalies in the cellular ability to exhibit the protective mechanism. Wound healing is process of regaining the integrity of cell structure and layers of the skin. The normal healing process of wounds are categorized in 4 phases which includes hemostatic, inflammatory, fibrolastic and maturation. Purpose The present manuscript embarks on up to date information on different methods being used for wound healing assessment including incision, excision, burn wound and dead space models. The biochemical parameter which acts as wound healing markers are collagen estimation (hydroxyproline), hexosamine, DNA estimation, total protein estimation, wound Index, contraction area, epithelization period and tensile strength etc. Histologic evaluations is also an integral part of wound healing evaluation which, help in evaluating the cellular and matrix detail within the wound. Conclusion At present, molecular approaches are important to heal the wound. For assessment of potential of any herbal drug/synthetic compound, incision wound model, excision wound model, burn wound model and dead space model and their parameter are used.

Low-Noise 3-D Avalanche Photodiodes

In this paper, we present a new 3-D structure for the InP-based avalanche photodiode, aiming at decreasing the excess noise factor. To the best of our knowledge, it is the first time new device designs based on the recently developed 3-D spatial dead space model in 2014 have been proposed. In addition, we also propose a methodology, i.e., the 2-D planar absorption distribution projection technique, for further optimizing the 3-D model. According to our theoretical simulation results, by combining photonic crystal and selective area doping, the effective k values of InP and In0.52Al0.48As can be reduced to as low as ∼0.19 and as ∼0.13, respectively. Meanwhile, the optimal thickness of the multiplication region is larger than 0.45 $\mu\text{m}$ , which reduces the tunneling effect. The detailed parameter optimization process, including optics, electronics, and material, is comprehensively presented. The examples in this paper also provide a fresh idea for researchers to foretell and design new photodetectors with the 3-D structure.

Characterization and Modeling of Breakdown Probability in Sub-Micrometer CMOS SPADs

This paper presents the characterization of two different single-photon avalanche diodes fabricated in a standard 0.15 μm CMOS process and the modeling of their breakdown probability. The first device is based on a p+/nwell abrupt junction, while the second one has a pwell/n-iso diffused junction. Breakdown voltage and breakdown probability are modeled using both local and dead-space models. While the two models are in agreement for the prediction of breakdown voltage, it is shown that the local model largely underestimates the breakdown probability with respect to experimental results. On the contrary, the voltage and wavelength dependence of breakdown probability can be correctly predicted using the dead-space model.

Low-Noise Avalanche Photodiode With Graded Junction in 0.15-&lt;inline-formula&gt; &lt;tex-math notation="TeX"&gt;$\mu{\rm m}$ &lt;/tex-math&gt;&lt;/inline-formula&gt; CMOS Technology

This letter presents the experimental characterization and noise modeling of a CMOS avalanche photodiode with pwell/n-iso active junction fabricated in a 0.15-μm standard CMOS process. The device exhibits a remarkably low excess noise factor F = 6 at a gain M = 50 in the blue spectral region, and F = 12 at M = 50 in the near-infrared. Gain and noise characteristics are accurately predicted using Hayat dead-space model applied to a linearly graded junction doping profile.

Embelin accelerates cutaneous wound healing in diabetic rats

This study reports the effect of embelin (1) on cutaneous wound in streptozotocin (STZ)-induced diabetic rats. The effect was studied using excision, incision, and dead space models. In diabetic rats, topical application of embelin 5% (w/w) ointment showed a significant increase in wound contraction and better epithelialization, thereby facilitating the healing. Embelin was also active by the oral route (25 and 50 mg/kg) in the incision and dead space wound models. In incision wound model, wound granulation tissues were removed on 8th post-wounding day, and the hydroxyproline, hexosamine, total protein, and DNA contents were determined. In STZ diabetic rats, topical and oral applications of embelin showed an increase in hydroxyproline, hexosamine, total protein, and DNA contents. It also showed a significant increase in wound breaking strength. Embelin significantly increased granuloma tissue weight and breaking strength in dead space model. These results indicated that embelin accelerated wound healing in diabetic rat.

Protective effect of Lygodium flexuosum (family: Lygodiaceae) against excision, incision and dead space wounds models in experimental rats

Lygodium flexuosum (Linn) Sw. is a climbing fern, and it is the sole genus in the family Lygodiaceae. It commonly grows epiphytically on moss covered tree trunks and branches as lithophytes on shady boulders along with moss. It has been reported as a traditional folkloric medicine for a variety of ailments particularly useful for carbuncles, inflammation, ulcer, various respiratory diseases, general disorders, muscle sprains and acts as panacea for wounds. However, there are no scientific reports on wound healing activity of the plant L. flexuosum (Linn) Sw. To explore the protective effect of L. flexuosum against excision, incision and dead space wounds models in experimental rats. Wistar albino rats of either sex weighing between 180 and 220g were topically treated with extract formulated in ointment using simple ointment BP as base. Ointments, 4% and 5% (w/w), were applied once daily in excision wound model. L. flexuosum ethanolic extract was given orally at a dose of 100, 200 and 400mg/kg in incision and dead space wound healing models. Rats of standard groups were treated with 0.2% nitrofurazone ointment topically. The percentage wound contraction, epithelization time in excision wound model; breaking strength in incision wound model and wet and dry granulation weight, hydroxyproline content were measured. Topical application of L. flexuosum in excision wound model increased the percentage of wound contraction, and the epithelization time was decreased. In the incision wound model, the breaking strength of wounds increased and in dead space model the weight of dry and wet granuloma of wounds and hydroxyproline was increased. Conclusively, the data of present study indicated that the leaf extract of L. flexuosum accelerated wound healing in rats and thus supports its traditional use.

In vivo wound healing activity and phytochemical screening of the crude extract and various fractions of Kalanchoe petitiana A. Rich (Crassulaceae) leaves in mice

Ethnopharmacological relevanceThe leaves of Kalanchoe petitiana A. Rich (Crassulaceae) are used in Ethiopian folk medicine for treatment of evil eye, fractured surface for bone setting and several skin disorders including for the treatment of sores, boils, and malignant wounds. Aim of the studyIn order to scientifically prove the claimed utilization of the plant, the effects of the extracts and the fractions were investigated using in vivo excision, incision and dead space wound models. Materials and methodMice were used for wound healing study, while rats and rabbit were used for skin irritation test. For studying healing activity 80% methanolic extract and the fractions were formulated in strength of 5% and 10%, either as ointment (hydroalcoholic extract, aqueous and methanol fractions) or gel (chloroform fraction). Oral administration of the crude extract was used for dead space model. Negative controls were treated either with simple ointment or sodium carboxyl methyl cellulose xerogel, while positive controls with nitrofurazone (0.2w/v) skin ointment. Negative controls for dead space model were treated with 1% carboxy methyl cellulose. Parameters, including rate of wound contraction, period of complete epithelializtion, hydroxyproline contents and skin breaking strength were evaluated. ResultsSignificant wound healing activity was observed with ointment formulated from the crude extract at both 5% and 10% concentration (p<0.01) compared to controls in both excision and incision models. In dead space model, 600mg/kg (p<0.01) but not 300mg/kg significantly increased hydroxyproline content. Fractions showed variable effect, with the chloroform fraction lacking any significant effect. Both 5% and 10% formulations of the aqueous and methanolic fractions significantly increased wound contraction, decreased epithelializtion time and increased hydroxyproline content in excision wound model (p<0.05) as compared to controls. These fractions were also endowed with higher skin breaking strength in incision wound model (p<0.01). ConclusionsThe present study provided evidence that the leaves of Kalanchoe petitiana A. Rich possess remarkable wound healing activities supporting the folkloric assertion of the plant. Fractionation revealed that polar or semi polar compound may play vital role, as both aqueous and methanolic fractions were endowed with wound healing activity.

Biological and Clinical Availability of Adipose-Derived Stem Cells for Pelvic Dead Space Repair

Adipose-derived stem cells (ADSCs) are a very attractive cell source for regenerative and reconstructive medicine. Although ADSCs have already been used in cardiovascular disease and cosmetic surgery, they have not yet been used in gastroenterological surgery. In this study, we clarified the utility of the combined application of ADSCs and resected intraperitoneal fatty tissues as a sealant for the pelvic dead space that sometimes causes severe and fatal complications in colorectal and gynecological surgeries. In pelvic dead space model mice, mouse ADSCs efficiently maintained transplanted intraperitoneal fatty tissues without any incidence of adhesion to surrounding organs. In vivo and in vitro analyses revealed that transplanted ADSCs differentiated into endothelial cells by expressing the angiogenic factors vascular endothelial growth factor and hepatocyte growth factor. Mouse and human ADSCs contained a CD45(-)CD34(+) subset possessing high colony formation and sphere formation abilities. In addition, the CD45(-)CD34(+) subset consisted of two characteristic subsets: the CD34(+)CD90(+) angiogenic subset and the CD34(+)CD90(-) adipogenic subset. Grafts of human ADSCs with fat transplanted into mice were efficiently maintained for more than 12 months without volume reductions. A comparative study of graft maintenance efficacy between cultured human ADSCs and freshly isolated ADSCs indicated that the cultivation of ADSCs decreased their graft maintenance ability. These findings suggested that the angiogenic and adipogenic subsets act in coordination with each other and are essential for efficient graft maintenance.

Evaluation of the wound healing activity of methanol extract of Pedilanthus tithymaloides (L.) Poit leaf and its isolated active constituents in topical formulation

Ethnopharmacological relevancePedilanthus tithymaloides leaves are widely used in Indian medicine to heal wounds, burn, mouth ulcers. However, systematic evaluation of these activities is lacking. Thus, the present study aimed to assesses the wound healing activity of Pedilanthus leaves and its isolated constituents in topical ointment formulation. Materials and MethodsBioassay-guided chromatographic fractionation of the methanol extract of leaves resulted in the isolation of 2-(3,4-dihydroxy-phenyl)-5,7-dihydroxy-chromen-4-one and 1, 2-tetradecanediol, 1-(hydrogen sulfate), sodium salt. The ointment formulation of methanol extract (2.5%, 5% w/w) and isolated compounds (0.25% w/w) was prepared and evaluated on excision, incision and dead space wound models in rats. The effects of formulations on wound healing were assessed by the rate of wound closure, period of epithelialization, tensile strength, granulation tissue weight, hydroxyproline content and histopathology. ResultsSignificant wound healing activity was observed with methanol extract and isolated constituents. Topical application of isolated compound ointments caused faster epithelialization, significant wound contraction (95.41%), and better tensile strength (565.33g) on 16 post-wounding day, while 5% extract showed wound epithelialization with 95.55% contraction on 18th post-wounding day, better than the control group (76.39% on 22 day). The tensile strength of incision wound was significantly increased in extract and compound treated animals. Moreover, in dead space model the extract significantly increased granuloma tissue weight, tensile strength and hydroxyproline content. The tissue histology of ointment treated groups showed complete epithelialization with increased collagenation, compared to the povidone–iodine group. ConclusionsThe results validated the traditional use of Pedilanthus tithymaloides for cutaneous wound management.

The Polyvinyl Alcohol Sponge Model Implantation

Wound healing is a complicated, multistep process involving many cell types, growth factors and compounds1-3. Because of this complexity, wound healing studies are most comprehensive when carried out in vivo. There are many in vivo models available to study acute wound healing, including incisional, excisional, dead space, and burns. Dead space models are artificial, porous implants which are used to study tissue formation and the effects of substances on the wound. Some of the commonly used dead space models include polyvinyl alcohol (PVA) sponges, steel wire mesh cylinders, expanded polytetrafluoroethylene (ePTFE) material, and the Cellstick1,2.Each dead space model has its own limitations based on its material's composition and implantation methods. The steel wire mesh cylinder model has a lag phase of infiltration after implantation and requires a long amount of time before granulation tissue formation begins1. Later stages of wound healing are best analyzed using the ePTFE model1,4. The Cellstick is a cellulose sponge inside a silicon tube model which is typically used for studying human surgery wounds and wound fluid2. The PVA sponge is limited to acute studies because with time it begins to provoke a foreign body response which causes a giant cell reaction in the animal5. Unlike other materials, PVA sponges are easy to insert and remove, made of inert and non-biodegradable materials and yet are soft enough to be sectioned for histological analysis2,5.In wound healing the PVA sponge is very useful for analyzing granulation tissue formation, collagen deposition, wound fluid composition, and the effects of substances on the healing process1,2,5. In addition to its use in studying a wide array of attributes of wound healing, the PVA sponge has also been used in many other types of studies. It has been utilized to investigate tumor angiogenesis, drug delivery and stem cell survival and engraftment1,2,6,7. With its great alterability, prior extensive use, and reproducible results, the PVA sponge is an ideal model for many studies1,2.Here, we will describe the preparation, implantation and retrieval of PVA sponge disks (Figure 1) in a mouse model of wound healing.

The Polyvinyl Alcohol Sponge Model Implantation

Wound healing is a complicated, multistep process involving many cell types, growth factors and compounds1-3. Because of this complexity, wound healing studies are most comprehensive when carried out in vivo. There are many in vivo models available to study acute wound healing, including incisional, excisional, dead space, and burns. Dead space models are artificial, porous implants which are used to study tissue formation and the effects of substances on the wound. Some of the commonly used dead space models include polyvinyl alcohol (PVA) sponges, steel wire mesh cylinders, expanded polytetrafluoroethylene (ePTFE) material, and the Cellstick1,2. Each dead space model has its own limitations based on its material's composition and implantation methods. The steel wire mesh cylinder model has a lag phase of infiltration after implantation and requires a long amount of time before granulation tissue formation begins1. Later stages of wound healing are best analyzed using the ePTFE model1,4. The Cellstick is a cellulose sponge inside a silicon tube model which is typically used for studying human surgery wounds and wound fluid2. The PVA sponge is limited to acute studies because with time it begins to provoke a foreign body response which causes a giant cell reaction in the animal5. Unlike other materials, PVA sponges are easy to insert and remove, made of inert and non-biodegradable materials and yet are soft enough to be sectioned for histological analysis2,5. In wound healing the PVA sponge is very useful for analyzing granulation tissue formation, collagen deposition, wound fluid composition, and the effects of substances on the healing process1,2,5. In addition to its use in studying a wide array of attributes of wound healing, the PVA sponge has also been used in many other types of studies. It has been utilized to investigate tumor angiogenesis, drug delivery and stem cell survival and engraftment1,2,6,7. With its great alterability, prior extensive use, and reproducible results, the PVA sponge is an ideal model for many studies1,2. Here, we will describe the preparation, implantation and retrieval of PVA sponge disks (Figure 1) in a mouse model of wound healing.

Effect of Ficus hispida L. on normal and dexamethasone suppressed wound healing

Ethanolic extract of roots of Ficus hispida was investigated in normal and dexamethasone depressed healing conditions, using incision, excision and dead space wound models in albino rats. The root extract of Ficus hispida has shown the maximum breaking strength compared to control group. The rate of epithelialization and wound contraction in excision model was better as compared to control groups. There was significant increase in granulation tissue weight and hydroxyproline content in dead space model compared to control group. The antihealing effect of dexamethasone was also reverted by the administration of ethanolic extract of Ficus hispida in all the wound models .The results indicated that the root extract of Ficus hispida has a significant wound healing activity and also promotes healing in dexamethasone depressed healing conditions.

Comparison of different models of non‐local impact ionization for low noise avalanche photodiodes

AbstractThe dead space model of non‐local impact ionization has been developed independently by three different research groups in order to include a ‘soft’ dead space. This paper seeks to compare these models for the first time. The models are fitted to Monte Carlo simulation data (both non‐local ionization coefficients and the ionization pathlength pdf) and it is found that there are no significant differences between the models except that the Liverpool model cannot be used to fit one data set which has a very soft dead space. Likewise the models give very similar results when used to calculate the excess noise factor for low noise avalanche photodiodes. (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Catharanthus roseus flower extract has wound-healing activity in Sprague Dawley rats

BackgroundCatharanthus roseus L (C. roseus) has been used to treat a wide assortment of diseases including diabetes. The objective of our study was to evaluate the antimicrobial and wound healing activity of the flower extract of Catharanthus in rats.MethodsWound healing activity was determined in rats, after administration (100 mg kg-1 day-1) of the ethanol extract of C. roseus flower, using excision, incision and dead space wounds models. The animals were divided into two groups of 6 each in all the models. In the excision model, group 1 animals were topically treated with carboxymethyl cellulose as placebo control and group 2 received topical application of the ethanol extract of C. roseus at a dose of 100 mg/kg body weight/day. In an incision and dead space model group 1 animals were given normal saline and group 2 received the extract orally at a dose of 100 mg kg-1 day-1. Healing was assessed by the rate of wound contraction, period of epithelization, tensile strength (skin breaking strength), granulation tissue weight, and hydoxyproline content. Antimicrobial activity of the flower extract against four microorganisms was also assessedResultsThe extract of C. roseus significantly increased the wound breaking strength in the incision wound model compared with controls (P < 0.001). The extract-treated wounds were found to epithelialize faster, and the rate of wound contraction was significantly increased in comparison to control wounds (P < 0.001), Wet and dry granulation tissue weights, and hydroxyproline content in a dead space wound model increased significantly (p < 0.05). Pseudomonas aeruginosa and Staphylococcus aureus demonstrated sensitivity to C. roseusConclusionIncreased wound contraction and tensile strength, augmented hydroxyproline content along with antimicrobial activity support the use of C. roseus in the topical management of wound healing.

Effect of stochastic dead space on noise in avalanche photodiodes

A stochastic dead-space model for impact ionization is developed and used to study the effect of the soft nature of the ionization capability of carriers on the excess noise factor of avalanche photodiodes. The proposed model is based on the rationale that the gradual, or soft, transition in the probability density function (PDF) for the distance from birth to impact ionization can be viewed as that resulting from uncertainty in the dead space itself. The resulting soft PDF, which is parameterized by a tunable softness parameter, is used to establish the limitations of the existing hard-threshold ionization models in ultrathin multiplication layers. Calculations show that for a fixed operational gain and fixed average dead space, the excess noise factor tends to increase as a result of the softness in the PDF in very thin multiplication layers (viz, <70 nm), or equivalently, under high applied electric fields (viz., >800 kV/cm). A method is proposed for extracting the softness parameter from noise versus multiplication measurements.