text:
Thermal fiber drawing has emerged as a novel process for the continuous manufacturing of semiconductor and polymer nanoparticles. Yet a scalable production of metal nanoparticles by thermal drawing is not reported due to the low viscosity and high surface tension of molten metals. Here, we present a generic method for the scalable nanomanufacturing of metal nanoparticles via thermal drawing based on droplet break-up emulsification of immiscible polymer/metal systems. We experimentally show the scalable manufacturing of metal Sn nanoparticles (<100 nm) in polyethersulfone (PES) fibers as a model system. The underlying mechanism for the particle formation is revealed, and a strategy for the particle diameter control is proposed. This process opens a new pathway for scalable manufacturing of metal nanoparticles from liquid state facilitated solely by the hydrodynamic forces, which may find exciting photonic, electrical, or energy applications.

## Introduction

Metal nanoparticles possess unique mechanical, physical, and chemical properties that are of great significance to both technologies and fundamental science. The making of such nanoscale entities has been an active research field for the last two decades. While bottom–up [1] and top–down [2] methods for metal nanoparticle manufacturing exist, there is always a need to produce them inexpensively at high volume.

## Materials and Methods

In this proposed method, the metal nanoparticles are formed at liquid state, as a result of the break-up of an initially slender droplet surrounded by a viscous elongational flow created by the drawing process. The material selection criteria is as follows:

1. (1)

Controllable cladding viscosity (102.5–106 Pa ·s)

2. (2)

Metal is molten at the processing temperature

3. (3)

Metal does not react with the cladding

Polyethersulfone (PES) and crystalline metal Tin (Sn) were chosen for the experimental validation of the proposed method. The glass transition temperature of the PES is 225 °C, and the melting point of Sn is 232 °C, which are close enough for the metal to be molten during the drawing process. While most metals require high glass transition point glasses such as Pyrex glass and fused silica as cladding, the selection of a thermoplastic material allows for a relatively low temperature processing.

### Preform Fabrication.

Extruded polyethersulfone (PES, BASF Ultrason E3010) rods (extruded and distributed by Port Plastics, Inc., Los Angeles, CA) with an outer diameter (OD) of 19.05 mm and length of 10 cm were first dried at 150 °C for 5 days under vacuum (2 Torr) to remove moisture. A through hole was then drilled to allow insertion of a Sn metal wire (SRA Soldering Products, Walpole, MA). The PES preform was then consolidated in a vertical tube furnace at 250 °C for 30 mins under a vacuum of 40 mTorr before the first cycle of thermal fiber drawing. The consolidation has to be conducted at a temperature higher than the melting point of the metal but lower than the softening point of the polymer to ensure seamless contact between the metal core and the cladding.

### Iterative Thermal Fiber Drawing.

During a typical fiber drawing process, as shown in Fig. 1, the metal-embedded preform is slowly lowered into a furnace, where temperature is carefully controlled and stabilized at a designated value. After the heated preform in the furnace necks down under its own weight, the bottom portion of the preform is cut away, and the fiber is pulled at a constant speed while the preform continues to be fed into the furnace. The diameter of the fiber $Df$ is controlled by varying the fiber pulling speed $vf$. The draw-down ratio $Dr$ is defined as the ratio between the fiber pulling speed and preform feeding speed $vp$. At steady-state, the law of mass conservation requires $Dr≡(vf/vp)=(Dp/Df)2$, where $Dp$ is the preform diameter, and $vp$ is the preform feeding speed.

The fibers obtained from the first-drawing cycle are cut into equal lengths and bundled, as shown in Fig. 2, to serve as the core for a new preform, which is again thermally drawn to thin fibers. All the drawings were done in a furnace with a graphite liner resistively heated. The liner has inner diameter of 36 mm and length 35 mm. The temperature of the furnace is measured with a K-type thermocouple inserted horizontally into furnace with the tip of the thermocouple aligned with the inner wall of the graphite. Table 1 lists the preform/fiber dimensions and the process parameters for each drawing cycle. The fibers achieved in one cycle (iteration) are bundled and inserted into the inner hole of a new preform for the next drawing cycle (iteration).

### Particle Formation Mechanism and Size Control.

The nanoparticles are formed at liquid state as a result of the break-up and deformation of the initially slender metal wires under the physical forces of interfacial tension and viscous stress.

Long microwires are first produced after the first and second iterations, which then start to break in the third iteration.

Various break-up events then follow. The formation of the smallest particles may be attributed to the satellites drops or a phenomenon known as tip-streaming, during which the droplet becomes slender with a pointed end, where the extremely small droplets may eject, first documented by Taylor [7]. Recent theoretical studies suggest that, at nanoscale, thermal fluctuation may dominate [8].

The largest particles are those that survive the flow without further break up after sufficient times of iterations. A theoretical estimation of the size of the largest particle is given in the discussion.

### Particle Production Rate.

The upper bound of the volume production rate of the nanoparticles can be estimated as , where $d0$ is the initial metal wire diameter in the perform, and $vp$ is the preform feeding speed, assuming the metal wire being completely converted to nanoparticles after enough number of iterations. Plugging in the preform inner diameter (ID) and feeding speed of iteration 1 from Table 1 yields a theoretical volume production rate of 0.064 mm3/s. The actual production rate is much lower than this value considering the material loss during the production and collection.

### Sample Preparation and Characterization Methods.

Samples for characterization by scanning electron microscope (SEM) are prepared by laying down multiple fibers on a silicon wafer submerged in dimethylacetamide (DMA; Sigma–Aldrich, St. Louis, MO) at room temperature for 4 h until all the polymer claddings are dissolved. Samples for characterization by transmission electron microscope (TEM) are obtained by dissolving the fibers in DMA followed by centrifuging. The sediments are dispersed in ethanol from which one drop is cast onto the TEM grid.

## Results and Discussion

Slender and long metal microwires were achieved after two drawing cycles as shown in Fig. 3. The measured diameter is close to the thinnest continuous metal wires reported that was drawn in a polymer cladding [9].

Nanoparticles were successfully produced, as shown in Fig. 4, with diameters ranging randomly from 100 nm to 500 nm. TEM image (Fig. 5) with selected area electron diffraction (SAED) patterns (Table 2) further show that the Sn nanoparticles smaller than 20 nm could be achieved. While it is confirmed that the Sn nanoparticles can be produced as shown in Fig. 5, it is possible that the particles shown in Fig. 4 are still encapsulated in polymers that are not fully dissolved away.

To the best of the author's knowledge, there is no published model yet that can satisfactorily describe the dynamics of the metal core during thermal drawing process from a preform. In an attempt to fill this gap, we start with a heuristic way and recognize that in addition to the breakup of a cylindrical thread or layers of concentric cylindrical shells with various ratios of the material properties for which a wealth of literature exist [10,11], attentions must also be brought to the deformation of the metal droplets inside an elongational flow which we believe is the main cause of the formation of the nanoparticles.

During a typical run of thermal drawing, as the preform is slowly fed into the furnace at a constant speed and uniform fibers being pulled from below, a steady-state in Eulerian frame is soon reached such that the temperature and velocity profile in the preform remains constant with time, if viewed from a fixed laboratory position. We assume the flow is one-dimensional recognizing that the length of the preform is much larger than its diameter. The molten metals embedded in different locations in the preform thus experience an almost identical flow history as they melt, deform and solidify under the influence of the energy and momentum input from the surrounding viscous cladding under thermal drawing.

A complete mathematical description of the dynamics of the shape evolution from a cylindrical metal rod to the final nanoparticle products is a formidable task, which involves multiple length scales spanning from millimeters to nanometers, and requires taking into account all the relevant physical forces from interfacial tension, viscous stresses, inertia, and gravity. Fortunately, since we focus on small droplet sizes at micro/nanoscale, gravity and inertia effects are negligible due to small Reynolds number and body force. This greatly simplifies the problem by allowing us to consider only the surface forces that are the interfacial tension, and viscous stresses in the cladding, neglecting the viscous stress of the molten metal because the viscosity ratio $(λ)$ between molten crystalline metal and the viscous cladding is close to zero (typically <10−7). The ratio of these two forces defines the dimensionless capillary number $Ca=(τa/γ)$, where $τ$ is the first normal stress difference in the cladding flow [12], $a$ is the radius of the droplet retracted to a perfect sphere, and $γ$ is the interfacial energy between the viscous cladding and the droplet. $τ$ measures the external viscous stress and ($γ/a$) scales with the interfacial-tension pressure. A low capillary number ($Ca≪1$) indicates that the dynamics of the droplet deformation is governed by the interfacial tension alone while a high capillary number ($Ca≫1$) suggests the viscous force is dominating.

Under steady-state drawing, the $τ$ increases in the direction of pulling and scales with the inverse of the area of the circular cross sections because the fiber tension (T) is the same everywhere along the axis. The corresponding capillary number increases from $Camin=(Ta/A0γ)$ to $Camax=(Ta/ALγ)$, where $A0$ is the area of the cladding on the cross section of the preform, and $AL$ the area of the cladding on the cross section of the fiber.

In the low capillary number limit, when $Camin≪1$, corresponding to the case of a small pulling force or when the metal wires or droplets just enters the heating zone and are just melted, its dynamics is governed solely by interfacial tension.

Two modes of break-up may result in this case, namely capillary break-up and end pinching. An unconstrained slender molten metal thread is inherently unstable. It flows spontaneously to minimize its surface energy by reducing its surface area. An unperturbed slender thread would shrink and eventually become one single sphere. In the presence of any disturbances from the surrounding, which is always the case, the disturbances can be decoupled into superposition of sinusoidal perturbations along its three axes as shown in Fig. 6.

Since the volume of the thread keeps constant, sinusoidal undulation of centerline does not change its surface area, the fluid thread would not break under such perturbations alone. Azimuthal modulation increases its surface area, and therefore, the thread will not grow in this direction either. However, when the radius of the thread is perturbed along its symmetric axis as shown in Fig. 6(c), one can calculate and see that its surface area is reduced if the wavelength of the perturbation is larger than a critical value [8], meaning the perturbed state has lower surface energy and thus is more stable than the unperturbed state. It is for this reason that the initial small perturbation grow spontaneously and quickly leads to breakage of the fluid thread into droplets along its centerline. In the case of end pinching, droplet break-up does not happen simultaneously but sequentially from the two ends of the slender thread as it retracts to the spherical shape to minimize its surface energy [8], which typically happens when the viscosity of the droplet is much lower than its surrounding as in the molten metal/viscous cladding case. Studies show that there exists a critical aspect ratio (ARcr) above which either end pinching or capillary break-up may happen. Experiments and numerical simulations indicate that the moderately stretched droplets with an aspect ratio can retract back to the spherical shape without fragmentation [13], and the critical aspect ratio is a function of viscosity ratio. Here, we again utilize the fact that $λ$ is close to zero, therefore, assuming that ARcr is a constant not sensitive to the viscosity changes of the metal and polymer arising from the spatial temperature and velocity profile.

As the capillary number increases along the fiber axis, the metal droplets or wires experiences stronger flow. Studies show that there exists a critical capillary number Cacr above which the droplet may disintegrate due to the viscous shearing as well, and the break-up may assume more than one mechanism, namely, center pinching, indefinite elongation, or tip streaming [14], among which indefinite elongation and tip streaming are believed to be able to produce nanoscale droplets which we do observe in this study.

With the knowledge of the possible break-up mechanisms, it is now possible to estimate the size of the largest droplet that can survive the fiber drawing flow without further break-up after multiple iterations of bundle-and-draw.

We argue that, in order for a droplet with radius $a$ to survive the fiber drawing flow without breaking up, it may neither break due to interfacial tension, nor viscous shearing. This essentially requires that the aspect ratio and the capillary number corresponding to the droplet exceeds neither the critical aspect ratio ARcr, nor the critical capillary number Cacr.

We further argue that the capillary number needed to stretch a droplet to its critical aspect ratio is always smaller than the critical capillary number that may give rise to its disintegration by shearing, which is self-evident as break-up can only happen when the shearing is too strong such that a stationary shape, which assumes a finite-aspect ratio, can no longer exist.

Now, we define a new critical capillary number $Cacrit(a)=(τa/γ)$, above which a droplet with initial radius $a$ will be stretched to an aspect ratio larger than ARcr. Equivalently, if the maximum stress $(τmax)$ in the flow is known, any droplets with radius larger than $amax=(γCacrit/τmax)$ is subject to break-up thus will not survive.

In the fiber drawing, the maximum axial stress in the flow $(τmax)$ is proportional to the fiber tension force ($T$) divided by the area of the fiber cross section ($AL$). We, therefore, reach the following expression:

The proposed functional relationship captures the key process parameters as well as the material properties that governs the metal particle size. The suggested mechanism has general implications for metal particle size design and control. The validity of this relationship should be experimentally tested in future.

Several assumptions are inherent in the above analysis which needs to be noted here:

1. (1)

The effect of temperature gradient on the interfacial tension is neglected, which can be justified when the Marangoni number is much smaller than one.

2. (2)

It is assumed that the droplets are small enough, so that the flow around it can be considered as linear, although the actual flow is nonlinear at larger length scale.

3. (3)

It is assumed that there is no interaction between droplets.

4. (4)

Continuum hypothesis is assumed to be valid, neglecting the molecular effects.

## Conclusions

In this study, a novel method for the scalable nanomanufacturing of metal nanoparticles is proposed and experimentally validated. It is proposed that the metal nanoparticles can be produced in a scalable manner by thermal fiber drawing utilizing the iterative size reduction method. Sn metal nanoparticles smaller than 100 nm were successfully produced by drawing inside a thermoplastic cladding (PES). The successful manufacturing of metal nanoparticles in liquid state from long and slender metal filaments is attributed to the physical forces of interfacial tension and viscous stress. The diameter of the particles produced is predicted to be a function of the maximum stress in the fiber and the interfacial tension between the molten metal and the viscous cladding. This proposed method is generic and can be readily extended to other material systems, following the material selection criteria given, to produce higher melting point metal nanoparticles for many exciting photonic, electrical, or energy applications.

## Acknowledgment

This work is supported by National Science Foundation.

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text:
### Application of a generalization of Darbo's fixed point theorem via Mizogochi-Takahashi mappings on mixed fractional integral equations involving $(k, s)$-Riemann-Liouville and Erd\'{e}lyi-Kober fractional integrals

Document Type : Research Paper

Authors

1 Department of Mathematics, Cotton University, Panbazar, Guwahati-781001, Assam, India

2 Department of Mathematics, Gilan-E-Gharb Branch, Islamic Azad University, Gilan-E-Gharb, Iran

3 Department of Mathematics, Rajiv Gandhi University, Rono Hills, Doimukh-791112, Arunachal Pradesh, India

We have established the solvability of fractional integral equations with both $(k,s)$-Riemann-Liouville and Erd'{e}lyi-Kober fractional integrals using a new generalized version of the Darbo's theorem using Mizogochi-Takahashi mappings and justify the validity of our results with the help of suitable examples.

format: plain


text:
# Revision history [back]

### Not able to compile packet-pkcs12-template.c

Hello all,

I am new to wireshark development. I have been able to setup build environment on Cent OS7 and compile wireshark source.

But then I proceeded to make couple of changes in packet-pkcs12-template.c. I got a compile error. I fixed it but I still get the error. Changes to other dissectors like packet-xxx.c (non-asn1 generated) were compiled successfully. I then made random changes in this file to see if the compiler is really looking at the modified file. Surprisingly I do not get other errors I was expecting before the original error. I keep getting the same first error even after fixing it.

I wonder there is something that I don't know about modifying and compiling *-template.c files.

I am badly in need of help. Let me know if you need any details.

### Not able to compile packet-pkcs12-template.c

Hello all,

I am new to wireshark development. I have been able to setup build environment on Cent OS7 and compile wireshark source.

But then I proceeded to make couple of changes in packet-pkcs12-template.c. I got a compile error. I fixed it but I still get the error. Changes to other dissectors like packet-xxx.c (non-asn1 generated) were compiled successfully. I then made random changes in this file to see if the compiler is really looking at the modified file. Surprisingly I do not get other errors I was expecting before the original error. I keep getting the same first error even after fixing it.

I wonder there is something that I don't know about modifying and compiling *-template.c files.

I am badly in need of help. Let me know if you need any details.

===================== [ 7%] Built target dissectors-corba [ 7%] Building C object epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o ./asn1/pkcs12/packet-pkcs12-template.c: In function \u2018PBE_decrypt_data\u2019: ./asn1/pkcs12/packet-pkcs12-template.c:344:2: error: passing argument 2 of \u2018tvb_new_child_real_data\u2019 discards \u2018const\u2019 qualifier from pointer target type [-Werror] In file included from /root/wireshark/epan/proto.h:35:0, from /root/wireshark/epan/packet.h:14, from ./asn1/pkcs12/packet-pkcs12-template.c:18: /root/wireshark/epan/tvbuff.h:150:25: note: expected \u2018guint8 \u2019 but argument is of type \u2018const guint8 *\u2019 WS_DLL_PUBLIC tvbuff_t *tvb_new_child_real_data(tvbuff_t *parent, ^ cc1: all warnings being treated as errors make[2]: [epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o] Error 1 make[1]: * [epan/dissectors/CMakeFiles/dissectors.dir/all] Error 2

# make: * [all] Error 2

packet-pkcs12.c does not get generated as I see the old timestamp on this.

In packet-pkcs12-template.c, I make following change in PBE_decrypt_data() to get additional compile error:

AKAKKSLD; clear_tvb = tvb_new_child_real_data(encrypted_tvb,(guint8AMIT *)clear_data, datalen, datalen);

Originally I was trying to remove the const type casting for the 2nd parameter of the function call tvb_new_child_real_data, which I fixed in function definition/declaration etc. but I kept getting the above compile error. So I edited the file to introduce more error and I suspect that those errors are not even looked at by compiler.

I cloned the source from https://github.com/wireshark/wireshark.

 3 None grahamb 23449 ●4 ●794 ●226 https://www.wireshark.org

### Not able to compile packet-pkcs12-template.c

Hello all,

I am new to wireshark development. I have been able to setup build environment on Cent OS7 and compile wireshark source.

But then I proceeded to make couple of changes in packet-pkcs12-template.c. I got a compile error. I fixed it but I still get the error. Changes to other dissectors like packet-xxx.c (non-asn1 generated) were compiled successfully. I then made random changes in this file to see if the compiler is really looking at the modified file. Surprisingly I do not get other errors I was expecting before the original error. I keep getting the same first error even after fixing it.

I wonder there is something that I don't know about modifying and compiling *-template.c files.

I am badly in need of help. Let me know if you need any details.

=====================

[  7%] Built target dissectors-corba
[  7%] Building C object epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o
./asn1/pkcs12/packet-pkcs12-template.c: In function \u2018PBE_decrypt_data\u2019:
./asn1/pkcs12/packet-pkcs12-template.c:344:2: error: passing argument 2 of \u2018tvb_new_child_real_data\u2019 discards \u2018const\u2019 qualifier from pointer target type [-Werror]
In file included from /root/wireshark/epan/proto.h:35:0,
from /root/wireshark/epan/packet.h:14,
from ./asn1/pkcs12/packet-pkcs12-template.c:18:
/root/wireshark/epan/tvbuff.h:150:25: note: expected \u2018guint8 \u2019 *\u2019 but argument is of type \u2018const guint8 *\u2019
WS_DLL_PUBLIC tvbuff_t *tvb_new_child_real_data(tvbuff_t *parent,
^
cc1: all warnings being treated as errors
make[2]:  *** [epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o] Error 1
make[1]: * *** [epan/dissectors/CMakeFiles/dissectors.dir/all] Error 2 2
make: * *** [all] Error 22

packet-pkcs12.c does not get generated as I see the old timestamp on this.

In packet-pkcs12-template.c, I make following change in PBE_decrypt_data() to get additional compile error:

AKAKKSLD; clear_tvb = tvb_new_child_real_data(encrypted_tvb,(guint8AMIT *)clear_data, datalen, datalen);

Originally I was trying to remove the const type casting for the 2nd parameter of the function call tvb_new_child_real_data, which I fixed in function definition/declaration etc. but I kept getting the above compile error. So I edited the file to introduce more error and I suspect that those errors are not even looked at by compiler.

I cloned the source from https://github.com/wireshark/wireshark.

 4 None grahamb 23449 ●4 ●794 ●226 https://www.wireshark.org

### Not able to compile packet-pkcs12-template.c

Hello all,

I am new to wireshark development. I have been able to setup build environment on Cent OS7 and compile wireshark source.

But then I proceeded to make couple of changes in packet-pkcs12-template.c. I got a compile error. I fixed it but I still get the error. Changes to other dissectors like packet-xxx.c (non-asn1 generated) were compiled successfully. I then made random changes in this file to see if the compiler is really looking at the modified file. Surprisingly I do not get other errors I was expecting before the original error. I keep getting the same first error even after fixing it.

I wonder there is something that I don't know about modifying and compiling *-template.c files.

I am badly in need of help. Let me know if you need any details.

[  7%] Built target dissectors-corba
[  7%] Building C object epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o
./asn1/pkcs12/packet-pkcs12-template.c: In function \u2018PBE_decrypt_data\u2019:
'PBE_decrypt_data':
./asn1/pkcs12/packet-pkcs12-template.c:344:2: error: passing argument 2 of \u2018tvb_new_child_real_data\u2019 'tvb_new_child_real_data' discards \u2018const\u2019 'const' qualifier from pointer target type [-Werror]
In file included from /root/wireshark/epan/proto.h:35:0,
from /root/wireshark/epan/packet.h:14,
from ./asn1/pkcs12/packet-pkcs12-template.c:18:
/root/wireshark/epan/tvbuff.h:150:25: note: expected \u2018guint8 *\u2019 'guint8 *' but argument is of type \u2018const 'const guint8 *\u2019
*'
WS_DLL_PUBLIC tvbuff_t *tvb_new_child_real_data(tvbuff_t *parent,
^
cc1: all warnings being treated as errors
make[2]: *** [epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o] Error 1
make[1]: *** [epan/dissectors/CMakeFiles/dissectors.dir/all] Error 2
make: *** [all] Error 2

packet-pkcs12.c does not get generated as I see the old timestamp on this.

In packet-pkcs12-template.c, I make following change in PBE_decrypt_data() to get additional compile error:

AKAKKSLD; clear_tvb = tvb_new_child_real_data(encrypted_tvb,(guint8AMIT *)clear_data, datalen, datalen);

Originally I was trying to remove the const type casting for the 2nd parameter of the function call tvb_new_child_real_data, which I fixed in function definition/declaration etc. but I kept getting the above compile error. So I edited the file to introduce more error and I suspect that those errors are not even looked at by compiler.

I cloned the source from https://github.com/wireshark/wireshark.

 5 None grahamb 23449 ●4 ●794 ●226 https://www.wireshark.org

### Not able to compile packet-pkcs12-template.c

Hello all,

I am new to wireshark development. I have been able to setup build environment on Cent OS7 and compile wireshark source.

But then I proceeded to make couple of changes in packet-pkcs12-template.c. I got a compile error. I fixed it but I still get the error. Changes to other dissectors like packet-xxx.c (non-asn1 generated) were compiled successfully. I then made random changes in this file to see if the compiler is really looking at the modified file. Surprisingly I do not get other errors I was expecting before the original error. I keep getting the same first error even after fixing it.

I wonder there is something that I don't know about modifying and compiling *-template.c files.

I am badly in need of help. Let me know if you need any details.

[  7%] Built target dissectors-corba
[  7%] Building C object epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o
./asn1/pkcs12/packet-pkcs12-template.c: In function 'PBE_decrypt_data':
./asn1/pkcs12/packet-pkcs12-template.c:344:2: error: passing argument 2 of 'tvb_new_child_real_data' discards 'const' qualifier from pointer target type [-Werror]
In file included from /root/wireshark/epan/proto.h:35:0,
from /root/wireshark/epan/packet.h:14,
from ./asn1/pkcs12/packet-pkcs12-template.c:18:
/root/wireshark/epan/tvbuff.h:150:25: note: expected 'guint8 *' but argument is of type 'const guint8 *'
WS_DLL_PUBLIC tvbuff_t *tvb_new_child_real_data(tvbuff_t *parent,
^
cc1: all warnings being treated as errors
make[2]: *** [epan/dissectors/CMakeFiles/dissectors.dir/packet-pkcs12.c.o] Error 1
make[1]: *** [epan/dissectors/CMakeFiles/dissectors.dir/all] Error 2
make: *** [all] Error 2

packet-pkcs12.c does not get generated as I see the old timestamp on this.

In packet-pkcs12-template.c, I make following change in PBE_decrypt_data() to get additional compile error:

AKAKKSLD;

*AKAKKSLD;
clear_tvb = tvb_new_child_real_data(encrypted_tvb,(guint8AMIT *)clear_data, datalen, datalen);datalen);*

Originally I was trying to remove the const type casting for the 2nd parameter of the function call tvb_new_child_real_data, which I fixed in function definition/declaration etc. but I kept getting the above compile error. So I edited the file to introduce more error and I suspect that those errors are not even looked at by compiler.

I cloned the source from https://github.com/wireshark/wireshark.


text:
# Topological space satisfying 2nd axiom of countability

1. Aug 16, 2010

Here's another problem which I'd like to check with you guys.

So, let X be a topological space which satisfies the second axiom of countability, i.e. there exist some basis B such that its cardinal number is less or equal to $$\aleph_{0}$$. One needs to show that such a space is Lindelöf and separable.

To show that it's separable, let B be a countable basis for X. From every element of the basis, take one element x, and we obtain a countable set S = {x1, x2, ...}. Now we only need to show that this set S is dense in X, and this is true if and only if its intersection with every open set in X is non-empty. So, let U be some open set in X. Clearly, U can be written as a union consisting of the basis sets, and its intersection with S is definitely non-empty.

To show that X is Lindelöf, let C be some open cover for X. The countable basis B is, by definition, an open cover, too. We only need to show that B is a refinement of C, which is obvious, because for every set U in C has a subset which belongs to B (since it can be written as a union of the basis sets).

I hope this works, thanks in advance.

2. Aug 17, 2010

First part looks good.

Second part: B may be a refinement of C, but what is the countable subcover of C? In other words, why is it sufficient to find a countable refinement of C? Maybe it's because it's late, but this isn't obvious to me.

3. Aug 17, 2010

Hm, it seems to be a matter of definitions. In the set of lecture notes I'm working with, a space is said to be Lindelöf if every of its open covers has a countable refinement. According to this definition, X is Lindelöf.

Then again, when speaking about compactness, in a similar manner, a topological space is defined to be compact if every of its open covers has a finite refinement. The first theorem after the definition, the one which is used frequently, states that a topological space is compact if and only if every of its open covers has a finite subcover. (Obviously, every subcover is a refinement, too.)

So, one can conclude that a space is Lindelöf if and only if every of its open cover has a countable subcover, right? But I didn't use this fact here, it seemed more straightforward to use the definition of a Lindelöf space.

4. Aug 17, 2010


text:
# Questions tagged [randomness]

Usage of randomness (i.e. non-predictable data, usually in the form of bits or numbers) for cryptographic purposes.

431 questions
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38 views

### How to generate a random string in Python for a mission-critical application

I'm trying to figure something out, but it is difficult for me. I need to generate a fully random string in Python. My current function is attached below. I just want to know whether this is secure ...
188 views

### Randomness extraction from a Santha-Vazirani (semi-random) source

In a quest to better understand randomness extractors (in the context of TRNG post-processing), I read some papers about the von Neumann Extractor and Santha-Vazirani (SV-) sources. The von Neumann ...
150 views

### Use of scrambler LFSR for randomness extraction of semi-random source

I am using a linear feedback shift register (LFSR) in a scrambler configuration as a randomness extractor for a weakly random source. This source is semi-random (aka. Santha-Vazirani source): the bits ...
63 views

### Is generalized birthday attack only suitable for the problem with multiple solutions?

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110 views

67 views

### On randomness related terminology clarification

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226 views

### What is the NIST recommended maximum bias for random number generators?

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259 views

### How to combine $n$ 'less random' bits to generate one 'more random' bit?

Suppose we have a random number generator badrand() generating 1 with probability $0.9$ and 0...
78 views

### Is there any standard present to measure strength of a generated key using true random number generator?

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117 views

### How to ensure that a cryptographic implementation is reasonably sound/robust?

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### Any famous approach for analyzing the randomness of data?

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### How to get ramdom number between 1 and 2048 from /dev/hwrng?

I am (perhaps naively) evaluating the security considerations of using the following code to create BIP39 seed phrases (on a read-only and offline Raspberry Pi). Apparently, using ...
80 views

### How big does M need to be in Blum Blum Shub?

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309 views

### Recommendation of lightweight RNG for Miller-Rabin primality test

Miller-Rabin tests the compositeness of candidate numbers (hence, input $x$) that's often used as a primality test. The M-R test requires different random numbers for accuracy and confidence in the ...
38 views

### Can disjoint distributions be Computationally indistinguishable?

As mentioned in these notes definition 2 We say that $\{Xn\}_n$ and $\{Yn\}_n$ are computationally indistinguishable if, for all $\mathsf{nuPPT}$ $D$, there exists a negligible function $ε$ such that ...
10k views

### Why do some people believe that humans are “bad at” generating random numbers/characters like this?

I'm not even sure if they are serious, but I've heard many times that some people refuse to not only trust their computer to generate a random string (which is understandable) but also don't trust ...
73 views

### How does a pseudorandom generator produce a similar distribution to $U_{n}$?

According to Wikipedia, a function ${\displaystyle G:\{0,1\}^{\ell }\to \{0,1\}^{n}}$ with ${\displaystyle \ell < n}$ is a pseudorandom generator against $\mathcal {A}$ with bias $\epsilon$ if, ...
62 views

### Nth term for Linear Congruence Generators

We can get the N+1th term for a Linear Congruence Generator like this: x[n+1] = A * x[n] (mod m) by raising the A to the exponent of n like this: ...
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### Radioactive Decay, Gaussian or Uniform?

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222 views

### NIST Statistical Test Segmentation Fault (Core dumped)

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64 views

### Min Entropy per Bit for Trevisan's Extractor/or An Extractor

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339 views

### Dieharder How can I make my input file suitable for Dieharder?

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237 views

### AES CTR: Random IV

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### is coin-tossing an instance of secure computation (MPC, 2PC, etc.)?

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### How to securely deal cards?

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33 views

### Alter signature post signing without the private key

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50 views

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54 views

### How do I retrieve a number which has been multiplied with a random number?

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79 views

### How does randomized hashing defeat collision attack?

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140 views

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52 views

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473 views

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78 views

### How can we define $\epsilon$-differential privacy for non-deterministic algorithms?

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text:
# Edexcel A Level Chemistry:复习笔记5.5.7 Rate-Determining Steps

### Deducing Rate-Determining Steps

#### Rate-determining step & intermediates

• A chemical reaction can only go as fast as the slowest part of the reaction
• So, the rate-determining step is the slowest step in the reaction

• If a reactant appears in the rate-determining step, then the concentration of that reactant will also appear in the rate equation
• For example, the rate equation for the reaction below is rate = k [CH3Br] [OH-]

CH3Br + OH- → CH3OH + Br-

• This suggests that both CH3Br and OH- take part in the slow rate-determining step

#### Predicting the reaction mechanism

• The overall reaction equation and rate equation can be used to predict a possible reaction mechanism of a reaction
• This shows the individual reaction steps which are taking place

• For example, nitrogen dioxide (NO2) and carbon monoxide (CO) react to form nitrogen monoxide (NO) and carbon dioxide (CO2)
• The overall reaction equation is:

NO2 (g) + CO (g) → NO (g) + CO2 (g)

• The rate equation is:

Rate = k [NO2]2

• From the rate equation it can be concluded that the reaction is zero order with respect to CO (g) and second order with respect to NO2 (g)
• This means that there are two molecules of NO2 (g) involved in the rate-determining step and zero molecules of CO (g)
• A possible reaction mechanism could therefore be:

Step 1:

2NO2 (g) → NO (g) + NO3 (g)                   slow (rate-determining step)

Step 2:

NO3 (g) + CO (g) → NO2 (g) + CO2 (g)     fast

Overall:

2NO2 (g) + NO3 (g) + CO (g) → NO (g) + NO3 (g) + NO2 (g) + CO2 (g)

=     NO2 (g) + CO (g) → NO (g) + CO2 (g)

#### Predicting the reaction order & deducing the rate equation

• The order of a reactant and thus the rate equation can be deduced from a reaction mechanism if the rate-determining step is known
• For example, the reaction of nitrogen oxide (NO) with hydrogen (H2) to form nitrogen (N2) and water

2NO (g) + 2H2 (g) → N2 (g) + 2H2O (l)

• The reaction mechanism for this reaction is:

Step 1:

NO (g) + NO (g) → N2O2 (g)                      fast

Step 2:

N2O2 (g) + H2 (g) → H2O (l) + N2O (g)     slow (rate-determining step)

Step 3:

N2O (g) + H2 (g) → N2 (g) + H2O (l)           fast

• The second step in this reaction mechanism is the rate-determining step
• The rate-determining step consists of:
• N2O2 which is formed from the reaction of two NO molecules
• One H2 molecule

• The reaction is, therefore, second order with respect to NO and first order with respect to H2
• So, the rate equation becomes:

Rate = k [NO]2 [H2]

• The reaction is, therefore, third order overall

#### Identifying the rate-determining step

• The rate-determining step can be identified from a rate equation given that the reaction mechanism is known
• For example, propane (CH3CH2CH3) undergoes bromination under alkaline solutions
• The overall reaction is:

CH3CH2CH3 + Br2 + OH- → CH3CH2CH2Br + H2O + Br-

• The reaction mechanism is:

Reaction mechanism for the bromination of propane under alkaline conditions

• The rate equation is:

Rate = k [CH3CH2CH3] [OH-]

• From the rate equation, it can be deduced that only CH3CH2CH3 and OH- are involved in the rate-determining step and not bromine (Br2)
• CH3CH2CH3 and OH- are only involved in the first step of the reaction mechanism, therefore the rate-determining step is:
• CH3CH2CH3 + OH- → CH3CH2CH2- + H2O


text:
# Missing genes and normalisation of RSEM output using EBSeq

Without going into too much background, I just joined up with a lab as a bioinformatics intern while I'm completing my masters degree in the field. The lab has data from an RNA-seq they outsourced, but the only problem is that the only data they have is preprocessed from the company that did the sequencing: filtering the reads, aligning them, and putting the aligned reads through RSEM. I currently have output from RSEM for each of the four samples consisting of: gene id, transcript id(s), length, expected count, and FPKM. I am attempting to get the FASTQ files from the sequencing, but for now, this is what I have, and I'm trying to get something out of it if possible.

I found this article that talks about how expected read counts can be better than raw read counts when analyzing differential expression using EBSeq; it's just one guy's opinion, and it's from 2014, so it may be wrong or outdated, but I thought I'd give it a try since I have the expected counts.

However, I have just a couple of questions about running EBSeq that I can't find the answers to:

1: In the output RSEM files I have, not all genes are represented in each, about 80% of them are, but for the ones that aren't, should I remove them before analysis with EBSeq? It runs when I do, but I'm not sure if it is correct.

2: How do I know which normalization factor to use when running EBSeq? This is more of a conceptual question rather than a technical question.

Thanks!

Yes, that blog post does represent just one guy's opinion (hi!) and it does date all the way back to 2014, which is, like, decades in genomics years. :-) By the way, there is quite a bit of literature discussing the improvements that expected read counts derived from an Expectation Maximization algorithm provide over raw read counts. I'd suggest reading the RSEM papers for a start[1][2].

But your main question is about the mechanics of running RSEM and EBSeq. First, RSEM was written explicitly to be compatible with EBSeq, so I'd be very surprised if it does not work correctly out-of-the-box. Second, EBSeq's MedianNorm function worked very well in my experience for normalizing the library counts. Along those lines, the blog you mentioned above has another post that you may find useful.

But all joking aside, these tools are indeed dated. Alignment-free RNA-Seq tools provide orders-of-magnitude improvements in runtime over the older alignment-based alternatives, with comparable accuracy. Sailfish was the first in a growing list of tools that now includes Salmon and Kallisto. When starting a new analysis from scratch (i.e. if you ever get the original FASTQ files), there's really no good reason not to estimate expression using these much faster tools, followed by a differential expression analysis with DESeq2, edgeR, or sleuth.

1<NAME>, <NAME>, <NAME>, <NAME>, <NAME> (2010) RNA-Seq gene expression estimation with read mapping uncertainty. Bioinformatics, 26(4):493–500, doi:10.1093/bioinformatics/btp692.

2Li B, <NAME> (2011) RSEM: accurate transcript quantification from RNA-Seq data with or without a reference genome. BMC Bioinformatics, 12:323, doi:10.1186/1471-2105-12-323.

• "There's really no good reason not to estimate expression using these much faster tools" -- unless you don't have the raw reads, as is the case here
– gringer
Jun 2 '17 at 1:32
• Oh wow. Big oversight on my part! Jun 2 '17 at 1:58
• Wow I never expected to get a response from the actual author! I did use R to process the data frames into a single matrix of all the expected counts for each gene of each sample. Jun 2 '17 at 17:04
• I was just as surprised to see a link to my old blog on StackExchange! :) Jun 2 '17 at 17:07
• As a small follow-up question, I'm ultimately trying to obtain the fold change and associated p-value for each gene per condition. I've found GetMultiFC() to get the fold changes, but I'm unclear about the exact difference between the fold change and the posterior fold change. I'm thinking that the posterior fold change is just the fold change for the normalized values, so it's the one I should be using, but I'm not sure about that. Also, is it possible to get associated p-values? Jun 2 '17 at 19:26
1. Include all genes/transcripts in your analysis.

A transcript that is not detected could be undetected through sampling error (i.e. the sequencer / library prep just happened to miss that transcript), or it could be because the transcript isn't generated in a particular sample. It's not uncommon for genes to be switched off in response to different biological factors, so zero-count genes shouldn't be ignored. I can't speak from experience with EBSeq, but as long as the analysis package treats a zero count as "unobserved" rather than "absent" (and makes relevant corrections), it's a good idea to keep them in.


text:
# Geometric operators on the equivariant $K$-theory of partial flag varieties

<NAME> (Kansas State University)
Seminar
Wednesday, 27 March, 2019, at 13:00-14:00, in Aud. D1 (1531-113)
Description:

<NAME> described an action of the affine Schur algebra on the equivariant $K$-theory of the cotangent vector bundle to the partial flag variety. The quantum parameter $q$ in this construction corresponds to the complex torus acting by stretching the fibers of the cotangent bundle. The goal of our project is to construct a $q=0$ degeneration of this action. We construct families of operators $E_{i,j}(p)$, $F_{i,j}(p)$, $H_{i,j}(p)$ acting on the equivariant $K$-theory of the partial flag variety and prove that they satisfy certain relations.

This is a joint work in progress with <NAME>.

Organised by: QGM
Contact person: <NAME>


text: It is well known that over-parametrized deep neural networks (DNNs) are an overly expressive class of functions that can memorize even random data with $100\%$ training accuracy. This raises the question why they do not easily overfit real data. To answer this question, we study deep networks using Fourier analysis. We show that deep networks with finite weights (or trained for finite number of steps) are inherently biased towards representing smooth functions over the input space. Specifically, the magnitude of a particular frequency component ($k$) of deep ReLU network function decays at least as fast as $\mathcal{O}(k^{-2})$, with width and depth helping polynomially and exponentially (respectively) in modeling higher frequencies. This shows for instance why DNNs cannot perfectly \textit{memorize} peaky delta-like functions. We also show that DNNs can exploit the geometry of low dimensional data manifolds to approximate complex functions that exist along the manifold with simple functions when seen with respect to the input space. As a consequence, we find that all samples (including adversarial samples) classified by a network to belong to a certain class are connected by a path such that the prediction of the network along that path does not change. Finally we find that DNN parameters corresponding to functions with higher frequency components occupy a smaller volume in the parameter. On the Spectral Bias of Deep Neural Networks


text:
Hallucinations caused by Cannabis

Discussion in 'Human Science' started by Diode-Man, Apr 18, 2011.

1. spidergoatValued Senior Member

Messages:
52,582
Feeling sorry is the mark of a moral beast.

3. Oniw17ascetic, sage, diogenes, bum?Valued Senior Member

Messages:
3,423
Not true. I've bought weed that was laced with crack when I was in Detroit, not on purpose either. People do it because retards think they're getting higher because it better weed, or just don't care it's laced, and come back. Before they know it, they're a crackhead.
No horseshit. Caffeine definitely gets you high. It's a stimulant, and it can also make you less anxious in a social environment, like alcohol. Drink 3 or 4 20oz Red Bulls and see for yourself.
It can, I started smoking tabacco because of the light headedness that it gave me. Trying to quit now though.
You know that cocaine does the same thing(among other things)? There's a large minority of cokeheads who are in it for the stimulant buzz.
What's wrong with being stoic?
Weed is illegal and much more available to kids, just saying.
Smoking raises your metabolism from what I understand. Just an example of a potential benefit. And your forgot that caffeine gives you a buzz.
Sugar? You mean that sweet stuff they take from the maize? Or the stuff they make vodka with.
Isn't tobacco a plant that literally poisons the soil it's grown in? Even if it causes no cancers,that can't be good to puit into your body.
What exactly do you mean by that(the term always seemed weird to me and I'm not sure what is the correct way to use it) . Surely it can be a gateway drug sometimes. Even if it's just that a certain crowd you smoke with does other drugs too, and after coming to the conclusion that it doesn't do so much harm to your friends you decide to try it. Or in a more malicious scenario, due to how you obtain it, what it someone laces your weed with something super addictive?

5. John99BannedBanned

Messages:
22,046
Cocaine is different than caffeine and coke changes after awhile. Takes a few years but hell i know people who go hide in a closet from coke...very creepy shit.

I would never drink red bull myself and never have but caffeine may make a person jittery but i would not apply the word "high" to it.

7. Oniw17ascetic, sage, diogenes, bum?Valued Senior Member

Messages:
3,423
Would you be accepting of the word 'buzz'; because I hardly believe you could deny that it alters the way you think, feel, and act. Or at least, have you ever done an experiment to check and see if you act different when your high on caffeine than when you're sober?

8. John99BannedBanned

Messages:
22,046
I drink coffee but have not today. No change at all, no buzz at all but if i drink too much i can get jittery. I pretty much got used to it and all i may get is a headache. A "buzz" alters perception, caffeine definitely does not do this to me.

9. Stoniphiobscurely fossiliferousValued Senior Member

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3,139
You keep circling this like a buzzard circling a road kill, so I will address it for you.

Crap Mexican brick weed retails for maybe $200 an ounce. Crap Mexican black tar heroin (an addictive substance) retails for maybe$50 a gram. Lets say it takes smoking 1/2 gram of heroin to get the average person stoned. That means that someone who wishes to improve the stone from cheap Mex schwag will need to dump what - 10 or 15 grams of that cheap heroin into an ounce of crap weed to make it strong enough to impress the buyer. That will then add $500 -$750 to the cost of each oz of scwag, bringing the retail price up to nearly $1000 an ounce? Kinda pricey for dirt weed, ain't it? There would be no way to hide that it had been dosed with black tar heroin either. Same thing if it was cocaine powder. If it was PCP or paradichlorobenzene (moth balls) word would get around very quickly and that person would be lucky if they were only out of business. Folks that do bogue things to street peeps around here get....disciplined. Please Register or Log in to view the hidden image! The same thing with adding cocaine or any other decent smokable drug - you end up with very expensive dirt weed, which is why weed dealers don't (generally) do that. There is always someone ready to do something stupid, of course, but enhancing shit weed is costly, complicated and problematic for the long term profit the dealer is looking for. Better to just sell decent weed in the first place. We have an endless train of garbage trucks crossing the border with Canada every day. 2 Have been busted at the border chock full of garbage bags full of prime Canadian bud. This is current high - grade strain cannabis grown in Canada with the best technology available. When it gets to Detroit it sells for as much as$750 an ounce. It is top quality cannabis. That is what your' hypothetical tainted schwag would be competing with. Then there are the domestic suppliers that grow in our old abandoned factory buildings. Same high quality, lower price. They are tolerated as long as they don't steal the electricity. 2 that did have been busted here in the last 2 weeks. There are plenty of others still going strong though.

No, it does not make economic sense to adulterate a bag of weed. Even Mex schwag sells briskly out there straight up, bugs and all. Like any other business, the weed business depends on repeat customers. That means there is a minimum standard for the product that the seller must guarantee or he/she will lose their client base. If they get bogue, someone will drop a dime on them and they are out of business.

Now, accidental contamination with pesticides and the like is another story alltogether. One that can only be addressed by complete legalization so the whole process can be supervised from start to finish.

10. universaldistressExtravagantly Introverted ...Valued Senior Member

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1,466
Caffeine has been to found to aid concentration but hinder wider thinking. I would consider quitting if I was you.

11. universaldistressExtravagantly Introverted ...Valued Senior Member

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1,466
Stoniphi. You may think you have a scientific basis for why small amounts of additives would not enhance the weed, but I know of dealers who do just that, and have had reasonable results. A drug that the consumer never normally takes can have a little short term hit, which can affect addiction if laced into weed.

12. Stoniphiobscurely fossiliferousValued Senior Member

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3,139
Fascinating reposte, if anecdotal. Your' understanding of that subculture and market is markedly different from mine.

Believe what you wish.

No. If it did, tobacco farmers would all be out of business. While tobacco contains nicotine, it is just one of many plants that do. Nicotine is like any other substance, it has costs and benefits. Nicotine and tobacco are not synonymous.

13. BelieveHappy mediumValued Senior Member

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1,194
Now I myself do not smoke but I am a chemist (well almost anyway) so I do feel an obligation here.

This method is going to be both ineffective and dangerous when compared with a butane extraction and here's why.

Every one knows that oil and water do not mix. The reason for this is because water is polar molecule and oil is a non-polar molecule. THC and may other canabinoids are also non-polar molecules meaning that they do not dissolve in water very well, if at all. Alcohol is also a very polar molecule.

Now boiling the mixture does increase the solubility of these molecules, but not to the extent of just using a non-polar solvent in the first place. This also introduces other issues. When you heat up a substance it becomes more reactive so boiling the alcohol would actually increase the amount of secondary reactions that you would get which will destroy some of the product. Also, alcohol is very flammable so heating it up introduces a great big fire/explosion hazard which is generally not something you want in your home. After that you have to boil away the alcohol to get the stuff you want out of it which is still a fire hazard.

The butane method would be a cold extraction with a non-polar solvent which will both increase the yield (non-polar and non-polar mix) and decrease the secondary reactions because the evaporating butane will be very cold. You also don't have to boil away the butane because it evaporates in the air very quickly. However, the butane itself is extremely flammable (at least a much as boiling alcohol anyway) do you would have to take precautions against sparks and stay away from heat sources, but the same can be said of boiling alcohol.

I hope this bit of info helps, if your going to be a deviant you can at least do it safely!

14. chimpkinC'mon, get happy!Registered Senior Member

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4,416
So, basically, for the less chemistry-experiment inclined, making marijuana-spiked salad dressing, sprinkling it on a pizza, or mushing it into your guacamole several hours prior to serving, would allow for a good extraction as well?

Edited to add: we have had a randomly growing tobacco plant come up every year...last year by the septic tank.

No telling if or where it'll come up from seed this year.

Does not poison the plants around it, nicotine's an insecticide (neurotoxin, I believe) not an herbicide.

15. BelieveHappy mediumValued Senior Member

Messages:
1,194
Only the salad dressing would technically be an extraction and you would maybe want to heat up it up with the olive oil alone a bit first (not boiling/smoking just too hot to comfortably touch). The other methods are just eating it lol (i.e. ground it up fine first till its like oregano powder).

Messages:
9,391
Probably not, no.

If you don't want to get into serious chemistry or mess with toxic chemicals, the way to go is to produce weed butter or oil. You basically grind up some weed and mix it in with melted butter or oil, and simmer it for a few hours. Then you strain the result to remove the plant matter, and stick the butter in the fridge to congeal. If you're fancy, use a double-boiler or just mix the whole thing with water directly and then skim off the cooled butter at the end. You can then use the butter/oil in any recipe that calls for them - that being how one makes proper weed brownies or cake. Simply mixing loose marijuana into a brownie mix doesn't work so well. Poke around for butter recipes on the internet - there's an entire cookbook somewhere that covers all of this in great detail, including how much ingredients to use to get what kinds of effects.

But unless you have some aversion to smoking, making butter or oil is not a very efficient use of the weed. You'll need to use quite a lot, and while the result can be very potent it won't go as far as smoking the original product would have. Most people who do this are either against smoking, or are growers who have large quantities of shake from the harvest/trimming process. I certainly wouldn't spend the money for an ounce of chronic just to make a cake with it.

Last edited: Apr 26, 2011

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9,391
No, that's an old wive's tale used to scare teenagers. Acid flashbacks are an entirely psychological phenomenon - there doesn't seem to be any pharmacological basis for them at all. It's more like a PTSD episode, and not an actual drug-induced effect. Unless it's been adulterated with something nasty, LSD doesn't exhibit much of any physiological dangers - which isn't to say that it can't cause psychological problems, especially in those predisposed to them, but psychological problems are just that: in your mind, not your body.

18. chimpkinC'mon, get happy!Registered Senior Member

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4,416
If I ever did any again it might be a special occasion thing. A treat.

But I'm not going to do that to my lungs, not even once. They're already scarred enough.

19. spidergoatValued Senior Member

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52,582
Nonsense. Oil dissolves very well in alcohol, particularly hot alcohol. You bake the herbs at a low temp to convert the precursors into orally active TCH. Then you use a double boiler on an electric range with lots of water and good ventilation, and only about a cup of alcohol. Boiled for 20 minutes then strained, what is left is a brown, highly alcoholic extract, which you drink in your beer or shot. It's very effective, perhaps too effective. 3 eyedroppers full will make you stoned for several hours, 8 eyedroppers will keep you very stoned all day long.

20. KilljoyKlownWhateverValued Senior Member

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6,493
Quad, you are quite right about the butter, makes a great spread on bread, however the green color is a bit strange. Also, not having the usual gritty brownies is a big plus.

Extracting oil with butane works great. The better the weed you use the more oil you will get per volume of weed used. Using a coffee grinder on the weed first will increase your yield, however the leftovers will be hard to sell. If you want to leave the weed in nice buds, use a slightly larger diameter PVC pipe and when you are done stripping the oil off,the buds will still look the same as what you started with and they will even still get you high.

21. Stoniphiobscurely fossiliferousValued Senior Member

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3,139
Cannabinoids will dissolve quite readily in either high - concentrate alcohol or in oils, they will not dissolve at all in water.

"Budder" is very popular with folks who wish to consume but do not smoke. It is an effective way to obtain the active ingredients as well. Grinding is not really necessary, though removing the stalks and stems first would make it less messy to strain after.

Butane honey oil - BHO - is likely the most efficient way to get all of the active ingredients out of the herb, but is very hazardous to do and you are releasing raw butane into the atmosphere. On the flip side though, it takes very little BHO to get stoned, many consumers just stir a drop into their tea or include it in a recipe. Compassionate Care in Montana sells lollipops that contain BHO and NoCal manufactures BHO chocolate truffles that are available in dispensaries.

"Green Dragon" is also very effective. The 95% ethanol Everclear likely pulls most all of the active ingredients from the bud. Boiling is not necessary. Many cannabis affectionados do a 'quick isopropal wash' extraction they call "QUISO" that obtains most all of the active ingredients as well, but one must be careful to evaporate ALL of the isopropal alcohol before consuming the product.

Another alternative extraction/concentration method is to make Bubble Hash, where the cured bud is mashed and stirred in a bucket of ice water then poured through a series of straining bags - Bubble Bags - to obtain the then - solid trichome gland heads. The result is a very high grade of hashish. Alternatively, the dried bud can be sieved through a fine screen to obtain the gland heads. There are commercial extractors available that do this very effectively, like the O'Kief, manufactured in the Netherlands. The resulting 'pollen' can then be pressed into hashish or washed with alcohol which is then evaporated to obtain a very pure grade of green oil.

Producers that take pride in the products they make do not sell the processed plant material, they compost it. The cannabis industry is like any other industry. While there are some few unscrupulous individuals, there are many more who take great pride in their product and do everything as right as they can.

The information on how to do it right is all over the Internet and the US federal government ongoing attempt to repeal the law of supply and demand with cannabis prohibition has put firm price controls on the end product assuring the investor a substantial return on their investment.

22. universaldistressExtravagantly Introverted ...Valued Senior Member

Messages:
1,466
I found out after the fact. Didn't worry me especially that it may be true. It kind of made sense because traces of drugs can be left in hair for instance, and LSD is very potent. But I have been assured by you and others that this is not true so I'll let it go. May try digging a little on the net.

23. livingin360Registered Senior Member

Messages:
182
My brother has smoked week from the time he wakes up till he goes to bed for the last 6 months and he has told me some pretty strange stuff. He told me recently that sometimes his brain will branch off into 3 streams of consciousness at once and start disputing a subject among the different consciousnesses. It reminds me of a split brain patient. He also has told me about auditory and visual hallucinations. I used to do it often but i never encountered that. It just created a anxiety disorder that has lasted for over 3 years for me even after quiting.

Last edited: Apr 26, 2011


text:
# Dividing Functions

1. Apr 1, 2007

### impendingChaos

How would one go about dividing two exponential functions.
Basically I have f(x)=k*g(x)
So to solve for k, k=f(x)/g(x)
How would one accomplish this when the functions are both within the format:
A*e^(Cx)+B

Thanks

2. Apr 1, 2007

### Eighty

There's usually no nice simplification when there's a sum in the denominator.

3. Apr 1, 2007

### Werg22

There is a way to simplify, but it's not necessarily what you are looking for. You might or might not end up with an invariant remainder. Here:

$$\frac{Ae^{Cx} + B}{Oe^{Px} + Q}$$

For example, let's say A = 1 and P = 1

$$\frac{Ae^{x} + B}{Oe^{x} + Q}$$

Make the substitution e^x = y and get

$$\frac{Ay + B}{Oy + Q}$$

Now we can write

$$\frac{A/O(Oy + Q - Q) + B}{Oy + Q}$$

$$\frac{A/O(Oy + Q ) - QA/O + B}{Oy + Q}$$

$$A/O + \frac{B - QA/O}{Oy + Q}$$

B - QA/O is the remainder here.

Last edited: Apr 1, 2007
4. Apr 3, 2007

### impendingChaos

Hmm I will try your method Werg but like you say I am not sure it is what I am looking for.
I am also trying to make both individual functions into linear expressions by taking the natural log of both sides however I run into natrual log rules which keep this from succeeding. Any ideas in the department?
Another note, I would like to clarify that I should have represented the functions as something like:
f(n)
g(v)
they are both describing different attributes of a system. What I am trying to accomplish is finding a relationship between n and v. Still working towards a solution so any help greatly appreciated.

C.N.